JP2011248236A - Display particles, production method thereof and image display medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide display particles for realizing high contrast while reducing a drive voltage when an image display medium displays an image.SOLUTION: Display particles used for an image display medium 10 which performs an image display by applying an electric field between substrates 11 and 21, at least one of which has translucency, and thereby moving a display particle group 5. The display particles comprise negatively charged white particles, positively charged black particles, and silicone fine particles in which the average particle diameter is 0.8 μm-4.5 μm and the variation coefficient of the particle diameter is equal to or lower than 14.

Description

  The present invention relates to display particles used for displaying an image, a method for manufacturing the same, and an image display medium using the display particles.

  Conventionally, regarding image display media applied to electronic paper or the like, a plurality of types of display particles having different colors and charging characteristics are encapsulated between a pair of substrates to which an electric field is applied, and between the substrates according to the electric field. A configuration for displaying an image by moving is known (see Patent Document 1). In this type of image display medium, as a writing method using electricity / magnetism, a wet display method (electrophoresis method or the like) in which display particles are dispersed in a solvent filled between substrates, or a gap between substrates. Dry display systems (charged toner type display system, electronic powder fluid system, etc.) in which display particles are dispersed (in air, nitrogen, argon, etc.) have been developed.

  With regard to the dry display method, for example, in an image display medium that displays an image by enclosing display particles between opposing substrates at least one of which is transparent and applying an electric field between these substrates to move the display particles, Using composite particles composed of particles and at least one kind of child particle as display particles, and managing particle size ratio, particle size distribution, etc., improving stability and driving during repeated image display and storage A technique for achieving both reduction in voltage is known (see Patent Document 2).

  For example, the 1st board | substrate which has translucency, the 2nd board | substrate arrange | positioned facing the 1st board | substrate, and the particle group enclosed between the 1st board | substrate and the 2nd board | substrate And an image display medium having a partition wall that keeps the distance between the first substrate and the second substrate constant. The particle group includes a first particle and a second color different from the first particle. And a third particle that positively charges the second particle and negatively charges the second particle, thereby improving the display performance and reducing the driving voltage. (See Patent Document 3).

  In addition, there is a technique for improving contrast when white is used as the display color of an image of this type of image display medium, and for preventing a decrease in contrast over time even when an image is repeatedly displayed. For example, display particles having a property that can be positively or negatively charged and containing titanium oxide have been known to have an average dispersion diameter of titanium oxide of 1 μm or less and the surface of the titanium oxide is subjected to lipophilic treatment. (See Patent Document 4).

JP 2001-31225 A JP 2003-233092 A JP 2007-240876 A JP 2005-107395 A

  However, in the conventional image display media described in Patent Documents 2 to 4, when the image display is repeatedly performed, a part of the display particles stays in a state of adhering to the substrate or the like, and the image display operation is performed. There has been a problem that the image becomes unstable and the contrast of the monochrome image is lowered. As a result, it is necessary to increase the driving voltage in order to move the display particles appropriately. On the other hand, attempts have been made to mechanically or thermally spheroidize display particles. However, improvement of powder flowability of display particles is expected by simply spheroidizing display particles. Can not.

  Further, in the conventional image display medium, when the display particles are encapsulated between the substrates, the cohesive force between the particles becomes strong, the encapsulated amount varies, and the image on the image display medium is uneven. There was also.

  The present invention has been devised in view of such problems of the prior art, and at the time of image display of an image display medium, by suppressing aggregation of display particles, the drive voltage is reduced and high. The main object is to provide display particles capable of realizing contrast, a method for producing the same, and an image display medium using the display particles.

  The display particles of the present invention include a pair of substrates that are arranged so that at least one of them is translucent and a group of display particles having a predetermined charging property enclosed between the substrates, and an electric field is generated between the substrates. Display particles used in an image display medium that displays an image by applying and moving the display particle group, wherein the negatively chargeable first display particles and the first display particles have a color different from that of the first display particles. It is characterized by comprising chargeable second display particles and silicone fine particles having an average particle diameter of 0.8 μm to 4.5 μm and a coefficient of variation of the particle diameter of 14 or less.

  As described above, according to the present invention, when displaying an image on an image display medium, by suppressing aggregation of display particles, an excellent effect is achieved in that high contrast can be realized while driving voltage is reduced. .

Schematic sectional view of an image display device according to an embodiment Schematic plan view of an image display medium according to an embodiment Schematic sectional view showing one process (dry film laminating process) in partition formation Schematic sectional view showing one process (exposure process) in partition formation Schematic sectional view showing one process (development process) in partition formation Schematic perspective view showing the main part of a roll melt kneader Schematic plan view showing the main parts of a roll melt kneader Configuration diagram of micronization processing equipment Configuration diagram of surface modification processing equipment Detailed view showing an X portion in FIG. 9 in an enlarged manner

  A first invention made to solve the above problems includes a pair of substrates, at least one of which is disposed facing each other, having translucency, and a group of display particles having a predetermined charging property enclosed between the substrates. Display particles used for an image display medium that displays an image by applying an electric field between the substrates and moving the display particle group, the first display particles having negative chargeability, and the first display A positively chargeable second display particle having a color different from that of the particle, and a silicone fine particle having an average particle diameter of 0.8 μm to 4.5 μm and a coefficient of variation of the particle diameter of 14 or less. .

  According to this, since the display particles are configured to include silicone fine particles having an average particle diameter of 0.8 μm to 4.5 μm and a coefficient of variation of the particle diameter of 14 or less, when displaying an image on the image display medium, , Aggregation of display particles is suppressed. In addition, the generation of display particles that are charged to the opposite polarity is also suppressed. As a result, the display particles can easily move between the substrates, and a high contrast can be realized while reducing the driving voltage. In addition, since the aggregation of the display particles is suppressed during the production of the image display medium, the display particles can be easily enclosed between the substrates, and the variation in the amount of display particles enclosed between the cells is reduced. There is an advantage that the display image can be made uniform.

  The second invention may be configured such that, in the first invention, the negatively chargeable silicone fine particles are adhered to the second display particles.

  According to this, by adhering negatively chargeable silicone fine particles to the positively chargeable second display particles, aggregation can be mitigated by utilizing electrostatic repulsion with the negatively chargeable first display particles.

  According to a third aspect of the present invention, in the first aspect of the invention, the silicone fine particles treated with positively charged aminosilane may be attached to the first display particles.

  According to this, by adhering positively chargeable silicone fine particles to the negatively chargeable first display particles, aggregation can be mitigated by utilizing electrostatic repulsion with the positively chargeable second display particles. .

  In addition, according to a fourth aspect of the present invention, in any one of the first to third aspects, the silicone fine particles hydrolyze an alkyltrialkoxysilane, and the spherical silicone fine particles generated by a condensation reaction of the hydrolysis products. It can be set as the structure which is.

  According to this, by using the spherical silicone fine particles, aggregation of the display particles can be more effectively suppressed during the image display of the image display medium.

  Further, a fifth invention is the method according to any one of the first to fourth inventions, wherein the first display particles are colored resin particles generated from at least a binder resin and titanium oxide treated with silicone oil. And inorganic fine particles having an average particle size of 3 nm to 14 nm fixed to the surface of the colored resin particles, and the inorganic fine particles were surface-treated with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms. It can be configured.

  According to this, since the titanium oxide is uniformly dispersed in the colored resin particles and the powder fluidity of the display particles is increased, the driving voltage is reduced at least during the image display of the image display medium that performs white display. In addition, a high contrast can be realized, and a stable image display operation can be maintained even when repeated display is performed.

  According to a sixth invention, in any one of the first to fifth inventions, the second display particle is a colored resin produced from at least a binder resin and carbon black treated with an amino-modified silicone oil. Particles and inorganic fine particles having an average particle diameter of 3 nm to 14 nm fixed to the surface of the colored resin particles, the inorganic fine particles having an alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms, an amine It can be set as the structure surface-treated with the system coupling agent.

  According to this, since the carbon black in the colored resin particles is uniformly dispersed and the powder fluidity of the display particles is increased, the driving voltage is reduced at least during the image display of the image display medium that performs black display. In addition, a high contrast can be realized, and a stable image display operation can be maintained even when repeated display is performed.

  In addition, according to a seventh invention, in the fifth or sixth invention, the colored resin particles may have a shape factor of 125 or less and a variation coefficient of the shape factor of 16 or less.

  According to this, it becomes possible to stabilize the repeated display characteristics in the image display medium by bringing the shape of the colored resin particles close to a true sphere.

  According to an eighth aspect of the present invention, there is provided a pair of substrates, at least one of which is disposed facing each other, having a light-transmitting property, and a display particle group having a predetermined charging property enclosed between the substrates, and an electric field between the substrates. Display particles used in an image display medium that displays an image by moving the display particle group, wherein the display particles are negatively charged first display particles and the first display. Forming positively chargeable second display particles having a color different from the particles, and generating colored resin particles containing at least a binder resin and a colorant with respect to the first display particles; and a surface of the colored resin particles A step of adhering inorganic fine particles having an average particle diameter of 3 nm to 14 nm, which is surface-treated with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having at least 6 to 18 carbon atoms, The inorganic fine particles are fixed to the surface of the colored resin particles by subjecting the colored resin particles to which the fine particles are adhered to the surface of the colored resin particles by subjecting the colored resin particles to a surface treatment with hot air having a temperature 180 to 300 ° C. higher than the softening point of the binder resin. And fine particles treated with aminosilane having an average particle size of 0.8 to 4.5 μm and a coefficient of variation of the particle size of 14 or less on the surface of the colored resin particles to which the inorganic fine particles are fixed And a step of adhering.

  The ninth invention comprises a pair of substrates, at least one of which is disposed facing each other, having a light-transmitting property, and a display particle group having a predetermined charging property enclosed between the substrates, and an electric field between the substrates. Display particles used in an image display medium that displays an image by moving the display particle group, wherein the display particles are negatively charged first display particles and the first display. Forming positively chargeable second display particles having a color different from that of the particles, and generating colored resin particles containing at least a binder resin and a colorant with respect to the second display particles; and a surface of the colored resin particles And an average trial particle size of 3 nm to 14 nm surface-treated with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms and an amine coupling agent. The colored resin particles are subjected to a surface treatment with hot air having a temperature higher by 180 to 300 ° C. than the softening point of the binder resin on the colored resin particles to which the inorganic fine particles are adhered A step of fixing the inorganic fine particles to the surface, and a surface of the colored resin particles fixed with the inorganic fine particles having an average particle size of 0.8 to 4.5 μm and a coefficient of variation of the particle size of 14 or less. And a step of attaching the silicone fine particles.

  The tenth invention may be configured to further include a step of fixing the silicone fine particles to the surface of the colored resin particles in the eighth or ninth invention.

  According to this, by adhering the silicone fine particles to the surface of the colored resin particles, aggregation of the display particles can be more effectively suppressed during image display on the image display medium.

  In an eleventh aspect based on any one of the eighth to tenth aspects, the binder resin has a softening point of 110 ° C. to 180 ° C. and a glass transition point of 70 ° C. to 100 ° C. It can be set as the structure which consists of a plastic resin.

  According to this, the surface of the colored resin particles can be rapidly melted, the spheroidization can be promoted by the surface tension, and the fixing of the inorganic fine particles to the surface of the molten colored resin particles can be promoted.

  A twelfth aspect of the invention is an image display medium using the display particles according to any one of the first to seventh aspects of the invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Configuration of image display medium>
FIG. 1 is a schematic cross-sectional view of the image display apparatus according to the present embodiment. As shown in FIG. 1, the image display device 1 includes two types of display particle groups having different colors and charging characteristics in a gap 4 between a top sheet 2 and a back sheet 3 that are opposed to each other at a predetermined interval. Voltage application as an electric field applying means for applying an electric field between the image display medium 10 in which 5A and 5B (hereinafter collectively referred to as the display particle group 5) are sealed, and the top sheet 2 and the back sheet 3. The apparatus 6 is mainly configured. The image display medium 10 is used as an electronic paper or the like, and an electric field is applied between the top sheet 2 and the back sheet 3 by a voltage applying device 6 having a known configuration to dispose the display particle group 5 on both sheets. By moving in a direction substantially perpendicular to the second and third images, it is possible to display an image made up of characters, figures and the like and to hold the image display without power.

  FIG. 2 is a schematic plan view of the image display medium according to the present embodiment. As shown also in FIG. 2, between the top sheet 2 and the back sheet 3, a grid-like partition wall 7 is disposed so as to be orthogonal to each other as a member for maintaining a gap. Thus, the size of the gap 4 between the sheets 2 and 3 is kept constant. A plurality of cells 8 are defined in the gap 4 in plan view by the partition walls 7, and two kinds of display particle groups 5A and 5B are provided in each cell filled with gas (air, nitrogen, argon, etc.). Is enclosed. Here, the display particle group 5A includes negatively charged white first display particles (hereinafter referred to as white particles), and the display particle group 5B includes positively charged black second display particles (hereinafter referred to as white particles). It is composed of black particles.)

(Surface sheet)
As shown in FIG. 1, the surface sheet 2 is formed of a transparent substrate (polyethylene terephthalate) and a transparent substrate (indium tin oxide) formed on one side (inside) of the surface substrate 11. And a plurality of strip-like column electrodes 12 and a dielectric film 13 formed of polycarbonate that covers and protects the column electrodes 12 and stabilizes the charging characteristics of the display particle group 5. ing.

  As the surface substrate 11, for example, in addition to the above PET, a flexible sheet such as a transparent resin film or a transparent resin sheet made of polyethersulfone, polyethylene, polycarbonate, polyimide, polyethylene naphthalate, acrylic, or the like is used. It can be used suitably. Further, as the surface substrate 11, a non-flexible sheet made of an inorganic material such as glass or quartz may be used.

  The thickness of the surface substrate 11 is 1 to 10000 μm, preferably 5 to 5000 μm. When the thickness of the surface substrate 11 is less than 1 μm, it is difficult to maintain the strength of the surface sheet 2 and the uniformity of the gap 4 between the surface sheet 2 and the surface substrate 11 when the thickness exceeds 10,000 μm. In addition to the decrease, the weight increases and the size of the partition wall 7 needs to be increased, or the strength of the partition wall 7 is insufficient.

  Each column electrode 12 extends in a predetermined direction and is made of a conductive material that is transparent and can be patterned. As the conductive material, in addition to the above ITO, metals such as aluminum, gold, silver and copper, metal oxide materials such as ITO, indium oxide, zinc oxide and tin oxide, polyaniline, polypyrrole, polythiophene, etc. These conductive polymers can be used.

  Each column electrode 12 can be formed as a conductive film by vapor deposition, sputtering, coating, or the like. For example, a coated metal oxide conductive film can be patterned by screen printing with an acid etching material on an electrode substrate on which an electrode material (for example, ITO) is applied or deposited on the entire surface.

  The pattern formation of each column electrode 12 can be performed by a laser etching method, a screen printing method, a patterning method by vapor deposition using a mask, an ink jet method, or the like. The laser etching method is a method of patterning a transparent conductive film by laser processing. In the screen printing method, a screen (for example, 200 to 500 mesh) on which an opening pattern is formed is placed on a substrate to be printed, and the conductive polymer is applied only to the opening pattern portion using the opening pattern. And a paste material (electrode material) in which inorganic transparent conductive particles are dispersed is attached and printed to perform patterning. A known technique can be used as such a screen printing method. If a more detailed explanation is necessary, refer to, for example, Japanese Patent Application Laid-Open No. 2004-287011.

  The width of each column electrode 12 is 30 to 5000 μm, preferably 100 to 2000 μm. If the width of each column electrode 12 is less than 30 μm, the possibility of disconnection or the like increases, while if it exceeds 5000 μm, the size of one pixel increases and the display becomes rough. The space between adjacent column electrodes is preferably 20 to 500 μm, more preferably 40 to 300 μm. If the space between the electrodes is less than 20 μm, there is a possibility of short-circuiting with the adjacent column electrode due to variations in manufacturing accuracy. On the other hand, if it exceeds 500 μm, the area where no image is displayed becomes large and the display quality deteriorates.

  The surface resistance of the column electrode 12 is preferably 1000Ω / □ or less, and more preferably 500Ω / □ or less. If the surface resistance of the column electrode 12 exceeds 1000 Ω / □, waveform rounding occurs during rewriting of the image display, and the rewriting speed becomes slow. In addition, there is a problem that display quality is deteriorated due to a decrease in the voltage at the end of the image display unit.

  In addition to the polycarbonate, polyester, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymerized nylon, ultraviolet curable acrylic resin, or the like can be used for the dielectric film 13.

(Back sheet)
As shown in FIG. 1, the back sheet 3 includes a back substrate 21 made of transparent PET, a plurality of strip-like row electrodes 22 made of copper or the like formed inside the back substrate 21, and row electrodes 22. An adhesive layer 23 that covers and protects the row electrodes 22 and the partition walls 7 is laminated. Each row electrode 22 extends in a direction perpendicular to the column electrode 12 and is arranged at a predetermined interval from each other. The adhesive layer 23 is formed of a low temperature thermosetting polyester resin adhesive.

  The back substrate 21 can be made of the same material as that of the top substrate 11 of the top sheet 2 described above. The row electrode 22 can be configured in the same manner as the column electrode 12, but the conductive material of the row electrode 22 is not necessarily required to display an image from the back substrate 21 side. Aluminum, silver paste, or silver paste with carbon added can also be used.

(Partition wall)
The partition wall 7 is made of an insulating material such as a thermosetting resin. The shape of the partition wall 7 can be appropriately set depending on the characteristics of the display particle group 5 used. The width | variety of the partition 7 is 10-100 micrometers, Preferably it is 20-60 micrometers. Moreover, the height of the partition 7 is 20-100 micrometers, Preferably it is 30-70 micrometers.

  The partition walls 7 can be formed by using a method in which ribs are formed on each of the facing top sheet 2 and the back sheet 3 and then bonded to each other, a method in which ribs are formed only on one substrate, or the like. In the present embodiment, one cell includes a plurality of pixels, but one cell may include one pixel. Here, each pixel is formed in a region where each column electrode 12 and row electrode 22 intersect.

  The shape of each cell can be, for example, a square shape, a line shape, a circular shape or a hexagonal shape, depending on the shape of the partition walls 7 that define them. It can arrange | position at mesh shape. The area of the cell frame corresponding to the cross-sectional portion of the partition wall 7 as viewed from the display surface side (here, the surface sheet 2 side) should be as small as possible in order to improve the sharpness of the display image. good.

  For the formation of the partition walls 7, for example, a photoresist method, a screen printing method, a sand blast method, an additive method, or a mold transfer method can be used. Among these, a photoresist method using a resist film and a screen printing method can be more suitably used.

  In the photoresist method, the partition wall can be formed by the steps of attaching a dry film on one of the transparent substrate and the counter substrate, exposing to a predetermined pattern, developing, and washing. A known technique can be used as such a photoresist method. If a more detailed explanation is necessary, refer to, for example, JP-A-2005-003892. In the screen printing method, a paste serving as a partition wall material is applied and transferred onto a substrate on which the above electrode pattern is formed via a plate making made of stainless mesh or the like. This is cured by heating, ultraviolet irradiation or the like. Such a process is repeated until a partition wall having a desired height is formed. A known technique can be used as such a screen printing method. If a more detailed explanation is necessary, refer to, for example, JP-A-2004-341018.

  Each cell is filled with display particles by mixing the display particle group 5A made of white particles and the display particle group 5B made of black particles in a weight ratio of, for example, 2: 1 to 1: 2. This can be done by shaking the particles by the desired amount through the screen and into the cell. At this time, unnecessary display particles remaining on the top of the partition wall 7 are removed by a method of scraping with a rubber blade or a metal blade, a method of scraping with a brush or the like, a method using an adhesive roller or sheet, and the like. Thereafter, the front substrate 11 and the rear substrate 21 are brought into intimate contact with each other through the partition wall 7, and the two substrates are pressed and held to bond the partition wall 7 and both the substrates 11 and 21, respectively. The filling rate of the display particle group 5 with respect to each cell is preferably 20 to 70%, more preferably 30 to 70%, and still more preferably 40 to 60%.

  For filling the display particles, a method can be used in which the display particles are placed on the cells separated by the partition walls 7 and the display particles are filled into the cells using a brush, a brush, or a metal or a resin blade. . In addition, by placing display particles on the cell and applying vibration to the cell, a method of pushing the display particles into the cell or a method of spraying the display particles filled in the powder spray can be used. Furthermore, it is possible to use a method in which a counter electrode is disposed on the back surface of the cell and the display particles are filled into the cell using an electric field. Furthermore, unnecessary display particles on the partition wall 7 can be removed by previously forming a thin film-shaped release member on the partition wall 7 and removing the release member after filling the display particles into the cell.

<Configuration of display particles>
Each of white particles and black particles as display particles which are powder particles constituting the display particle group 5 is mainly composed of colored resin particles constituting the base and inorganic fine particles externally added to the colored resin particles. Is done.

  The white particles (first display particles) include colored resin particles having a desired particle size distribution and inorganic fine particles having an average particle size of 3 nm to 14 nm fixed to the surface of the colored resin particles. It is the structure surface-treated with alkyltrialkoxysilane or alkylsilazane having an alkyl group of several 6-18. As will be described later, it is preferable to use titanium oxide treated with silicone oil as a colorant for the colored resin particles of the white particles.

  On the other hand, the black particles (second display particles) include colored resin particles having a desired particle size distribution and inorganic fine particles having an average particle diameter of 3 nm to 14 nm fixed to the surface of the colored resin particles. The surface treatment with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms and an amine coupling agent is preferred. As described later, it is preferable to use carbon black treated with amino-modified silicone oil as a colorant for the colored resin particles of the black particles.

  The display particles in the present invention include silicone fine particles having an average particle diameter of 0.8 to 4.5 μm and a coefficient of variation of the particle diameter of 14 or less. Thereby, regarding the white particles and the black particles, aggregation of the particles can be alleviated, and movement of each particle between the substrates is facilitated when displaying an image on the image display medium. Here, when the average particle size of the silicone fine particles is less than 0.8 μm, it is difficult to obtain an effect of alleviating the aggregation of the display particles. On the other hand, when the average particle diameter is larger than 4.5 μm, the powder fluidity of the display particles tends to be lowered. Moreover, by setting the coefficient of variation of the particle size to 14 or less, the powder fluidity of the display particles is improved, and the effect of alleviating aggregation is further increased.

  Silicone fine particles are hydrolyzable alkyltrialkoxysilanes such as methyl, ethyl or propyl as a starting material with a large amount of water, and in water while forming siloxane bonds by condensation reaction of the hydrolysis products. It is obtained by growing into fine particles. The silicone fine particles produced are preferably spherical (substantially spherical) and have a narrow particle size distribution.

  The silicone fine particles are preferably added in an amount of 0.5 to 10 parts by weight with respect to 100 parts by weight of the colored resin particles. Preferably it is 1-8 weight part, More preferably, it is 1-4 weight part. When the addition amount of the silicone fine particles is less than 0.5 parts by weight, it is difficult to obtain the effect of relaxing the aggregation of the particles. On the other hand, when the addition amount is larger than 10 parts by weight, floating particles of silicone fine particles tend to be generated.

  Further, it is preferable that the silicone fine particles are adhered to the surface of the display particles by mixing them with colored resin particles to which inorganic fine particles are fixed at a certain ratio. Furthermore, a configuration in which the silicone fine particles are fixed by applying surface modification treatment with hot air to the display particles to which the silicone fine particles are attached is also preferable. Thus, by fixing the silicone fine particles to the display particles, the effect of alleviating the aggregation of the display particles is enhanced.

(Colored resin particles)
The colored resin particles are formed so as to include at least a binder resin as a binder and a colorant, and optionally include additives such as a charge control agent.

(Binder resin)
As the binder resin, for example, urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin Styrene / acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin, etc. can be used. It can also be used as a mixture.

  In this embodiment, a polyester resin obtained by polycondensation of an alcohol component and a carboxylic acid component such as a carboxylic acid, a carboxylic acid ester, or a carboxylic acid anhydride is used as a material suitable for the binder resin.

  Here, examples of the divalent carboxylic acid or lower alkyl ester include aliphatic dibasic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, hexahydrophthalic anhydride, maleic acid, maleic anhydride, and fumaric acid. It is possible to use aliphatic unsaturated dibasic acids such as itaconic acid and citraconic acid, aromatic dibasic acids such as phthalic anhydride, phthalic acid, terephthalic acid and isophthalic acid, and methyl esters and ethyl esters thereof. it can. Of these, aromatic dibasic acids such as succinic acid, phthalic acid, terephthalic acid, and isophthalic acid, and lower alkyl esters thereof are more preferable. Further, it is more preferable to use a combination of succinic acid and terephthalic acid or phthalic acid and terephthalic acid.

  Examples of the trivalent or higher carboxylic acid component include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 2,5,7-naphthalenetricarboxylic acid. Acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexatricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarbopropane, tetra (Methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, emporic trimer acid and acid anhydrides thereof, alkyl (C1-12) ester, and the like can be used. .

  Examples of the dihydric alcohol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, neopentyl glycol, Diols such as diethylene glycol, dipropylene glycol, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct, triols such as glycerin, trimethylolpropane, and trimethylolethane, and mixtures thereof can be used.

  Examples of the trivalent or higher alcohol component include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol. 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, etc. Can be used. For the polymerization, known polycondensation, solution polycondensation or the like can be used. Thereby, the color of favorable black-and-white and color coloring material can be expressed.

  In addition, about the usage rate of polyhydric carboxylic acid and polyhydric alcohol, it is common to make the ratio (OH / COOH) of the number of hydroxyl groups with respect to the number of carboxyl groups 0.8-1.4.

  Further, as thermoplastic binder resins, styrenes such as styrene, parachlorostyrene, α-methylstyrene, methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, etc. Acrylic monomers, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, methacrylic monomers such as 2-ethylhexyl methacrylate, acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. A homopolymer such as an unsaturated polyvalent carboxylic acid monomer having a carboxyl group as a dissociating group, a copolymer obtained by combining two or more of these monomers, or a mixture thereof can be used.

  Here, a styrene / acrylic copolymer is preferably used as the copolymer. In particular, a styrene / butyl acrylate copolymer is preferable, and those containing 75 to 90% by weight of styrene and 10 to 25% by weight of butyl acrylate are preferably used. Styrene monomers include styrene, O-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pnbutylstyrene, p-tert-butylstyrene, p Styrene and its derivatives such as -n-hexyl styrene, pn-octyl styrene, pn-hexyl styrene and P-chlorostyrene can be used, and styrene is particularly preferable.

  Examples of the acrylic monomer include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, acrylate-2-ethylhexyl, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate, butyl α-hydroxyacrylate, ethyl β-hydroxymethacrylate, propyl γ-aminoacrylate, γ-N, N-diethylaminoacrylic Acid propyl, ethylene glycol dimethacrylic acid ester, tetraethylene glycol dimethacrylic acid ester and the like can be used.

  The binder resin has a weight average molecular weight of 50,000 to 350,000 and a ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) of 3 to 100 in terms of molecular weight by GPC (Gel permeation Chromatography). is there. Further, the binder resin has a melting temperature (hereinafter referred to as a softening point) by a 1/2 method using a constant load extrusion capillary rheometer flow tester of 110 to 180 ° C., an outflow start temperature of 90 to 160 ° C., and a resin glass. The transition point is in the range of 70-100 ° C.

  Preferably, the binder resin has a weight average molecular weight of 50,000 to 300,000, a weight average molecular weight / number average molecular weight of 3 to 50, a softening point of 115 to 170 ° C., an outflow start temperature of 95 to 150 ° C., and a glass transition point. Is in the range of 75-95 ° C.

  More preferably, the binder resin has a weight average molecular weight of 100,000 to 250,000, a weight average molecular weight / number average molecular weight of 3 to 15, a softening point of 120 to 140 ° C., an outflow start temperature of 95 to 145 ° C., and a glass transition. The point is in the range of 75-85 ° C.

  If the weight average molecular weight of the binder resin is less than 50,000, the weight average molecular weight / number average molecular weight is less than 3, the softening point is less than 110 ° C., and the outflow start temperature is less than 90 ° C., the dispersibility during kneading decreases. However, the vivid color expression is reduced. This leads to a decrease in durability of the display particles.

  When the weight average molecular weight of the binder resin is greater than 350,000, the weight average molecular weight / number average molecular weight is greater than 100, the softening point is greater than 180 ° C., and the outflow start temperature is greater than 160 ° C., the spherical shape of the colored resin particles in the heat treatment For example, the interchangeability of white particles and black particles during an image display operation deteriorates, leading to a decrease in contrast.

  In forming the binder resin, it is also preferable to mix two or more resins having different thermal properties (low softening or low molecular weight resin particles, high softening or high molecular weight resin particles) as follows.

  In the case of low softening or low molecular weight resin particles, the weight average molecular weight is 10,000 to 60,000, the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) is 1.5 to 6, and the softening point is 90. -140 degreeC, outflow start temperature shall be 80-120 degreeC, and glass transition point shall be the range of 75-100 degreeC.

  Preferably, the weight average molecular weight is 20,000 to 50,000, the weight average molecular weight / number average molecular weight is 1.5 to 3.9, the softening point is 95 to 135 ° C., the outflow start temperature is 85 to 115 ° C., and the glass transition point is The range is 78 to 98 ° C.

  More preferably, the weight average molecular weight is 20,000 to 45,000, the weight average molecular weight / number average molecular weight is 1.5 to 3, the softening point is 100 to 130 ° C., the outflow start temperature is 90 to 110 ° C., and the glass transition point. Is in the range of 80 to 88 ° C.

  The purpose of blending the low softening or low molecular weight resin particles is to secure the spheres of the colored resin particles and to promote melting and fixing with the inorganic fine particles. The weight average molecular weight is less than 10,000, the weight average molecular weight / number average molecular weight is less than 1.5, the softening point is less than 90 ° C., the outflow start temperature is less than 80 ° C., and the glass transition point is 75 ° C. If it is smaller than that, secondary agglomeration tends to occur in the heat treatment for spheroidization, and the particle size tends to increase. On the other hand, the weight average molecular weight is greater than 60,000, the weight average molecular weight / number average molecular weight is greater than 6, the softening point is greater than 140 ° C., the outflow start temperature is greater than 120 ° C., and the glass transition point is 100 ° C. If it is larger than the range, the spheroidization tends to hardly progress in the heat treatment for spheroidization.

  In addition, relatively high softening or high molecular weight resin particles have a weight average molecular weight of 60,000 to 600,000, a ratio of weight average molecular weight to number average molecular weight (weight average molecular weight / number average molecular weight) of 2 to 10, softening The point is 150 to 190 ° C, the outflow start temperature is 120 to 170 ° C, and the glass transition point is 65 to 95 ° C.

  Preferably, the weight average molecular weight is 80,000 to 580,000, the weight average molecular weight / number average molecular weight is 2 to 7, the softening point is 155 to 185 ° C., the outflow start temperature is 125 to 165 ° C., and the glass transition point is 65 to 90 ° C. The range.

  More preferably, the weight average molecular weight is 100,000 to 550,000, the weight average molecular weight / number average molecular weight is 2 to 5, the softening point is 160 to 180 ° C., the outflow start temperature is 130 to 160 ° C., and the glass transition point is 65 to 80. The range is ° C.

  The purpose of blending the high softening or high molecular weight resin particles is to maintain durability for maintaining stable and repeatable display characteristics of the display particles. That is, it is for improving the durability with respect to collision between particles, a board | substrate, and a partition. It is also for making the dispersibility of the additive uniform in the melt-kneading process and stabilizing high chargeability.

  The weight average molecular weight is less than 60,000, the weight average molecular weight / number average molecular weight is less than 2, the softening point is less than 150 ° C, the outflow start temperature is less than 120 ° C, and the glass transition point is more than 65 ° C. If it is small, the durability for maintaining the repeated display characteristics tends to decrease.

  The weight average molecular weight is greater than 600,000, the weight average molecular weight / number average molecular weight is greater than 10, the softening point is greater than 190 ° C., the outflow start temperature is greater than 170 ° C., or the glass transition point is greater than 95 ° C. Is too large, the spheroidization tends to hardly progress in the heat treatment for spheroidization. Moreover, the smoothness of the colored resin particle surface is inferior, and unevenness tends to remain on the surface.

  The blending ratio of the low softening or low molecular weight resin particles to the high softening or high molecular weight resin particles is in the range of 5: 5 to 9: 1. This is to ensure a good balance between the durability and the progress of spheroidization. Preferably, the range is 6: 4 to 9: 1. More preferably, the range is 7: 3 to 9: 1.

(Coloring agent)
As the colorant, various organic or inorganic pigments and dyes as shown below can be used.

  As the white colorant, particles containing white pigments such as zinc oxide, tin oxide, rutile type titanium oxide, anatase type titanium oxide, lead white, zinc sulfide, aluminum oxide, silicon oxide and zirconium oxide can be used.

  Here, the titanium oxide is preferably treated with silicone oil. Thereby, the dispersion state of titanium oxide in the colored resin particles is made uniform, and the whiteness is improved. Furthermore, the powder fluidity of the display particles is improved by using together the inorganic fine particles having an average particle diameter of 3 nm to 14 nm which are surface-treated with alkyltrialkoxysilane having 6 to 18 carbon atoms or alkylsilazane. . As a result, in the image display device, the contrast is improved and the deterioration of the image quality with time in repeated image display is reduced. In addition, when the display particles are filled and sealed in the image display device, it is possible to obtain an effect that variation in the filling amount of the display particles between the cells is suppressed.

  Silicone oils include methylhydrogen silicone oil, methylphenyl silicone oil, cyclic dimethyl silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, methacryl-modified silicone oil, mercapto-modified silicone oil, and polyether-modified. Silicone oil, methylstyryl-modified silicone oil, alkyl-modified silicone oil, fluorine-modified silicone oil, α-methylsulfone-modified silicone oil, chlorophenyl silicone oil, and the like are preferable. In particular, dimethyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil or methacryl-modified silicone oil is preferably used. For example, SH200, SH510, SF230, SH203, BY16-823, BY16-855B, etc. manufactured by Toray Dow Corning Silicone can be used.

  The treatment of titanium oxide with silicone oil can be carried out as follows. First, silicone oil and titanium oxide are added to an organic solvent such as toluene and sufficiently stirred while applying ultrasonic waves. Next, unnecessary solvent components are removed by heating and drying the titanium oxide having the surface coated with silicone oil.

  The amount of silicone oil added is preferably in the range of 0.5 to 30 parts by weight with respect to 100 parts by weight of titanium oxide. More preferably, it exists in the range of 1-20 weight part, More preferably, it exists in the range of 2-10 weight part. When the addition amount of the silicone oil is less than 0.5 parts by weight, the surface of the titanium oxide is not sufficiently coated, and the dispersion state of the titanium oxide in the colored resin particles is difficult to be uniformed. I cannot expect improvement. On the other hand, when the addition amount exceeds 30 parts by weight, the silicone oil that remains and does not contribute to the surface treatment increases, and conversely, the powder fluidity of the display particles decreases.

  Moreover, it is preferable that the addition amount of a titanium oxide exists in the range of 10-50 weight part with respect to 100 weight part of binder resin. More preferably, it is in the range of 15 to 35 parts by weight, and still more preferably in the range of 20 to 30 parts by weight. When the addition amount of titanium oxide is less than 10 parts by weight, sufficient whiteness cannot be obtained. On the other hand, when the addition amount exceeds 50 parts by weight, the powder fluidity of the display particles is lowered. .

  As the black colorant, particles containing organic or inorganic dye / pigment black pigments such as carbon black, aniline black, manganese ferrite black, titanium black, magnetic powder, oil black and the like can be used.

  The black pigment carbon black is preferably treated with an amino-modified silicone oil, as in the case of the titanium oxide. Thereby, the dispersion state of carbon black in the colored resin particles is made uniform, and the blackness is improved. Furthermore, by using together with inorganic fine particles having an average particle diameter of 3 nm to 14 nm, which is surface-treated with alkyltrialkoxysilane having an alkyl group having 6 to 18 carbon atoms or alkylsilazane, powder flowability of display particles Will improve. As a result, black particles having a narrow charge amount distribution and sharp positive chargeability can be obtained. The combined use with the white particles using the titanium oxide further enhances the effect of improving contrast and reducing deterioration with time in repeated image display.

  As the amino-modified silicone oil, KF857, KF858, KF859, KF861, KF864 and KF880 manufactured by Shin-Etsu Chemical Co., Ltd., DF8417 manufactured by Toray Dow Corning Co., etc. can be used. It is also preferable to use nitrile-modified silicone oil or isocyanate-based silicone oil instead of or in combination with aminosilicone oil.

  The amount of amino-modified silicone oil added is preferably in the range of 0.2 to 30 parts by weight with respect to 100 parts by weight of carbon black. More preferably, it exists in the range of 1-20 weight part, More preferably, it exists in the range of 2-10 weight part. When the addition amount of the amino-modified silicone oil is less than 0.2 parts by weight, the surface of the carbon black is not sufficiently coated, and the dispersion state of the carbon black in the colored resin particles is difficult to be uniformed. It is impossible to improve. On the other hand, when the addition amount exceeds 30 parts by weight, the amount of silicone oil that remains and does not contribute to the surface treatment increases, and on the contrary, the powder fluidity of the display particles decreases.

  The amount of carbon black added is preferably in the range of 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. More preferably, it is in the range of 2 to 8 parts by weight, and further preferably in the range of 3 to 6 parts by weight. When the addition amount is less than 1 part by weight, sufficient blackness cannot be obtained, while when it exceeds 10 parts by weight, the powder fluidity of the display particles is lowered.

  Here, the DBP oil absorption (ml / 100 g) of carbon black is preferably 45 to 70. Specifically, for example, # 52 (particle size 27 nm, DBP oil absorption 63 ml / 100 g), # 50 (28 nm, 65 ml / 100 g), # 47 (23 nm, 64 ml / 100 g) manufactured by Mitsubishi Chemical Co., Ltd. , # 45 (24 nm, 53 ml / 100 g), # 45 L (24 nm, 45 ml / 100 g), REGAL250R (35 nm, 46 ml / 100 g), REGAL330R (25 nm, 65 ml / 100 g) manufactured by Cabot. ), MOGULL (24 nm, 60 ml / 100 g). More preferably, # 45, # 45L, and REGAL250R are used. By using carbon black having a relatively low DBP oil absorption, there is an effect of obtaining high contrast. This is considered to be an effect due to dispersibility and colorability in the resin.

  The DBP oil absorption is a quantitative representation of the chain assembly state (structure) of the particles, and is expressed by a primary structure by chemical bonding and a secondary structure by physical bonding by van der Waals force.

DBP oil absorption (JISK6217) was measured by putting 20 g (Ag) of sample dried at 150 ° C. ± 1 ° C. for 1 hour into a mixing chamber of an absorber meter (manufactured by Brabender, spring tension 2.68 kg / cm), After setting the limit switch to about 70% of the maximum torque in advance, the mixer is rotated. At the same time, DBP (specific gravity 1.045 to 1.050 g / cm ³ ) is added from the automatic burette at a rate of 4 ml / min. As the end point is approached, the torque increases rapidly and the limit switch is turned off. The DBP oil absorption (= Bx100 / A) (ml / 100 g) per 100 g of the sample is determined from the DBP amount (Bml) added so far and the sample weight.

  In addition, the arithmetic mean diameter by SEM is used for a particle size. The particle size of carbon black is preferably 20 to 40 nm, more preferably 20 to 35 nm. If the particle size is larger than the preferred range, the coloring power tends to decrease. Moreover, when the particle diameter is smaller than the preferred range, dispersion in the resin tends to be difficult.

  Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, First Sky Blue, Indanthrene Blue BC and the like can be used. The addition amount is preferably 3 to 12 parts by weight with respect to 100 parts by weight of the binder resin.

  Red colorants include brilliant carmine 6B, eosin lake, rhodamine lake B, brilliant carmine 3B, C.I. I. Red pigments such as CI Pigment Red 48, 49: 1, 53: 1, 57, 57: 1, 81, 122, 5; I. Red dyes such as Solvent Red 49, 52, 58, 8 can be used.

  Examples of yellow colorants include naphthol yellow S, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, C.I. I. Acetoacetic acid arylamide monoazo yellow pigments such as C.I. Pigment Yellow 1, 3, 74, 97 or 98; I. Acetoacetic acid arylamide disazo yellow pigments such as C.I. Pigment Yellow 12, 13, 14, and 17; I. Solven Yellow 19, 77, 79 or C.I. I. Disperse Yellow 164 is blended, and C.I. I. Benzimidazolone pigments of CI Pigment Yellow 93, 180 and 185 are preferred.

  The above pigments and inorganic additives can be used alone or in combination. Carbon black is particularly preferable as the black pigment, and titanium oxide is particularly preferable as the white pigment.

(Charge control agent)
Examples of the negative charge control agent include salicylic acid metal complexes, metal-containing azo dyes, metal-containing oil-soluble dyes (including metal ions and metal atoms), calixarene compounds, boron-containing compounds (for example, benzyl acid boron complexes), Nitroimidazole derivatives, acrylic sulfonic acid polymers (vinyl copolymers of styrene monomers and acrylic acid monomers having a sulfonic acid group as a polar group, particularly preferably a copolymer of acrylamido-2-methylpropane sulfonic acid) Polymer) and the like.

  In the salicylic acid metal complex, the functional group bonded to the benzene ring is preferably independently a hydrogen atom, a linear or molecular chain alkyl group having 1 to 10 carbon atoms, or an aryl group, a methyl group, an ethyl group, n- A propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, or the like can be used. Moreover, as a metal, zinc, nickel, cobalt, copper, and chromium can be used, and zinc and chromium are particularly preferable.

  As the metal salt of the benzylic acid derivative, lithium, sodium, potassium, or the like can be used as the alkali metal, and potassium is particularly preferable.

  On the other hand, as the positive charge control agent, for example, a nigrosine dye, a triphenylmethane compound, a quaternary ammonium salt compound, a polyamine resin, an imidazole derivative, or the like can be used.

  The addition amount of the charge control agent is 0.5 to 8 parts by weight, preferably 1 to 6 parts by weight, and more preferably 2 to 5 parts by weight with respect to 100 parts by weight of the binder resin. When the addition amount of the charge control agent is less than 0.5 parts by weight, the charging effect is lost. On the other hand, when the addition amount exceeds 8 parts by weight, the charge amount becomes excessively high and tends to be overcharged.

(Inorganic fine particles)
Examples of inorganic fine particles used for display particles include fine metal oxide powders such as silica, alumina, titanium oxide, zirconia, magnesia, ferrite, and magnetite, and titanates such as barium titanate, calcium titanate, and strontium titanate. Alternatively, a zirconate salt such as barium zirconate, calcium zirconate or strontium zirconate, or a mixture thereof can be used. As the inorganic fine particles, metal oxide fine powders of hydrophobic silica, titanium oxide or alumina are particularly preferable. Thereby, in the display particles, overcharge during long-term use can be prevented, and the effect of improving the fluidity while maintaining the chargeability can be obtained.

  The inorganic fine particles have an average particle diameter of 3 nm to 14 nm and are surface-treated with alkyltrialkoxysilane or alkylsilazane having an alkyl group having at least 6 to 18 carbon atoms. This surface treatment is performed by reacting OH groups present on the surface of the inorganic fine particles with alkyltrialkoxysilane.

  More specific surface treatment methods include, for example, an inert gas (for example, an inorganic gas such as titanium oxide and silica fine particles, an alkyltrialkoxysilane, and water vapor in a fluidized bed reactor heated to about 400 ° C. The surface of the inorganic fine particles is hydrophobized with alkyltrialkoxysilane.

  The average particle diameter of the inorganic fine particles is preferably 3 to 7 nm, and more preferably 5 to 7 nm. If the average particle size of the inorganic fine particles is less than 3 nm, its production becomes difficult. On the other hand, when the average particle size of the inorganic fine particles exceeds 14 nm, it is difficult to obtain the effect of improving the powder fluidity of the display particles.

  The alkyltrialkoxysilane or alkylsilazane preferably has an alkyl group having 8 to 16 carbon atoms, and more preferably has an alkyl group having 8 to 12 carbon atoms. When the number of carbon atoms of the alkyl group is less than 6, the effect of increasing powder fluidity is reduced. On the other hand, if the alkyl group has more than 18 carbon atoms, the cohesiveness of the inorganic fine particles increases, making it difficult to uniformly adhere the inorganic fine particles to the surface of the colored resin particles, making it difficult to improve the powder fluidity of the display particles. .

The alkyltrialkoxysilane or alkylsilazane used is preferably an alkoxysilane or alkylsilazane represented by the following (Chemical Formula 1) to (Chemical Formula 16). Further, chlorosilanes represented by the following (Chemical Formula 17) to (Chemical Formula 23) can be preferably used.
(Chemical Formula 1) C ₆ H ₁₃ Si (OCH ₃ ) ₃
(Chemical Formula 2) C ₆ H ₁₃ Si (OC ₂ H ₅ ) ₃
(Chemical Formula 3) C ₈ H ₁₇ Si (OCH ₃ ) ₃
(Chemical Formula 4) C ₈ H ₁₇ Si (OC ₂ H ₅ ) ₃
(Chemical Formula 5) C ₁₀ H ₂₁ Si (OCH ₃ ) ₃
(Chemical Formula 6) C ₁₀ H ₂₁ Si (OC ₂ H ₅ ) ₃
(Chemical Formula 7) C ₁₂ H ₂₅ Si (OCH ₃ ) ₃
(Chemical Formula 8) C ₁₂ H ₂₅ Si (OC ₂ H ₅ ) ₃
(Chemical 9) C ₁₄ H ₂₉ Si (OCH ₃ ) ₃
(Chemical Formula 10) C ₁₄ H ₂₉ Si (OC ₂ H ₅ ) ₃
(Chemical Formula 11) C ₁₆ H ₃₃ Si (OCH ₃ ) ₃
(Chemical Formula 12) C ₁₆ H ₃₃ Si (OC ₂ H ₅ ) ₃
(Chemical 13) C ₁₈ H ₃₇ Si (OCH ₃ ) ₃
(Chemical Formula 14) C ₁₈ H ₃₇ Si (OC ₂ H ₅ ) ₃
(Chemical formula 15) (CH ₃ ) ₃ SiNHSi (CH ₃ ) ₃
(Chemical Formula 16) (C ₂ H ₅ ) ₃ SiNHSi (C ₂ H ₅ ) ₃
(Chemical Formula 17) C ₆ H ₁₃ SiCl ₃ (OCH ₃ ) ₃
(Chemical Formula 18) C ₈ H ₁₇ SiCl ₃
Embedded image C ₁₀ H ₂₁ SiCl ₃
(Chemical Formula 20) C ₁₂ H ₂₅ SiCl ₃
Embedded image C ₁₄ H ₂₉ SiCl ₃
(Chemical Formula 22) C ₁₆ H ₃₃ SiCl ₃
(Chemical Formula 23) C ₁₈ H ₃₇ SiCl ₃

  The positively charged inorganic fine particles have an average particle diameter of 3 nm to 14 nm and are subjected to a surface treatment with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having at least 6 to 18 carbon atoms and an amine coupling agent. Is done.

  As the amine-based silane coupling agent, for example, those represented by the following (Chemical 24) to (Chemical 27) are preferably used.

Embedded image H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
(Chemical Formula 25) H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃
(Chemical Formula 26) H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃
Embedded image H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃

  These treatment agents are preferably added in an amount of 0.1 to 15 parts by weight with respect to 100 parts by weight of the inorganic fine particles. More preferably, it is 0.5-10 weight part, More preferably, it is 1-5 weight part.

  The average particle size of the inorganic fine particles and silicone fine particles is taken with an SEM (scanning electron microscope), and the long axis length (the longest diameter of one particle) and the short axis of about 100 particles are taken. It is the value which calculated | required the average value of length (the shortest diameter in one particle | grain).

For loss on drying (% by weight), about 1 g of a sample is placed in a container that has been dried, allowed to cool, and precisely weighed in advance and weighed accurately. Dry in a hot air dryer (105 ° C ± 1 ° C) for 2 hours. After cooling in a desiccator for 30 minutes, the weight is precisely weighed and calculated from the following formula.
Loss on drying (% by weight) = [Loss on drying (g) / Sample amount (g)] × 100

For ignition loss, about 1 g of a sample is placed in a magnetic crucible that has been dried, allowed to cool, and precisely weighed in advance, and weighed accurately. Ignite for 2 hours in an electric furnace set to 500 ° C. After standing to cool in a desiccator for 1 hour, its weight is precisely weighed and calculated from the following formula.
Loss on ignition (% by weight) = [Loss on ignition (g) / Sample amount (g)] × 100

  Further, the moisture absorption amount of the treated external additive is preferably 1% by weight or less. Preferably it is 0.5 weight% or less, More preferably, it is 0.1 weight% or less, More preferably, it is 0.05 weight% or less. When the moisture adsorption amount is more than 1% by weight, the chargeability and filming resistance are lowered. The moisture adsorption amount was measured with a continuous vapor adsorption apparatus (BELSORP18: Nippon Bell Co., Ltd.).

The degree of hydrophobicity is determined by methanol titration, weighing 0.2 g of the product to be tested in 50 ml of distilled water charged in a 250 ml beaker. At the tip, methanol is dropped from a burette immersed in the liquid until the total amount of the external additive is wet. In that case, it stirs slowly slowly with an electromagnetic stirrer. The degree of hydrophobicity is calculated by the following equation from the amount of methanol a (ml) essential for complete wetting.
Hydrophobic degree = (a / (50 + a)) × 100 (%)

(Physical properties of display particles)
The display particles preferably have a volume average particle size of 3 to 15 μm and a volume-based variation coefficient of 10 to 25% from the viewpoints of productivity and image quality (resolution) improvement. More preferably, the display particles have a volume average particle diameter of 5 to 10 μm and a volume-based variation coefficient of 12 to 20%, and more preferably a volume average particle diameter of 6 to 9 μm and a volume-based variation coefficient of 14. ~ 18%.

  Here, the variation coefficient is obtained by dividing the standard deviation in the particle size distribution of the display particles by the average particle size, and represents the extent of the particle size distribution. The particle size was measured using a Coulter counter (Coulter). If the variation coefficient of the volume particle size distribution is less than 10%, production becomes difficult, which causes a cost increase. On the other hand, if the coefficient of variation of the volume particle size distribution exceeds 20%, the particle size distribution becomes broad and the contrast tends not to be improved.

  Further, the shape factor (SF) of the colored resin particles is preferably 125 or less, and the coefficient of variation of the shape factor is preferably 16% or less.

  In this case, by setting the shape factor to 125 or less, the shape of the colored resin particles becomes closer to a sphere, and it is possible to stabilize the repeated display characteristics. For the shape factor, a real surface view microscope (VE7800) manufactured by Keyence Corporation was used, about 100 toner base particles magnified 1000 times were taken, the maximum length and the projected area were measured, and the following (formula 1) Determined (d: maximum long axis length corresponding to the longest diameter of the colored resin particles, A: projected area of the colored resin particles).

Shape factor (SF) = 100 × π × d ² / (4 × A) (Formula 1)

  Further, when the measured BET specific surface area of the display particles is BTr and the specific surface area value calculated from the particle size distribution of the display particles is BSr, BTr / BSr is preferably 2.5 to 10.

  This is because the colored resin particles are processed into a spherical shape or a more spherical shape to stabilize repeated display characteristics, and fine particles having a small radius of curvature are attached to the surface of the colored resin particles. The purpose is to reduce the presence of particles that increase in the BET specific surface area and stick to the partition walls and become inoperable.

  By specifying the specific surface area ratio (BTr / BSr), the state of adhesion of fine particles to the surface of the colored resin particles can be quantified. When the specific surface area ratio is less than 2.5, the contact between the display particles and the partition walls is so dominated by so-called point contact to surface contact, and it is easy to stick to the partition walls. In addition, the charge retention is also reduced. On the other hand, when the specific surface area ratio exceeds 10, it is assumed that the fine particles are not adhered to the surface of the colored resin particles, or the surface of the display particles is too rough, and the contrast in display characteristics tends to be lowered.

  The specific surface area measured value (BTr) was measured using Flowsorb II2300 manufactured by Shimadzu Corporation. The calculated specific surface area (BSr) was calculated from BSr = 6 / (ρ · r). Here, ρ is the true specific gravity of the display particles, and r is the volume particle diameter of the display particles.

  That is, by satisfying the relationship of the following (Expression 2) and (Expression 3), more preferably, by satisfying the relationship of (Expression 4) and (Expression 5), more preferably, (Expression 6) and (Expression 7). ), The above-described characteristics can be achieved with good reproducibility.

100 ≦ SF ≦ 125 (Equation 2)
2.5 ≦ BTr / BSr ≦ 10 (Expression 3)

100 ≦ SF ≦ 122 (Equation 4)
3 ≦ BTr / BSr ≦ 8 (Formula 5)

100 ≦ SF ≦ 118 (6)
5 ≦ BTr / BSr ≦ 8 (Expression 7)

  The particle size distribution of the colored resin particles is measured by using a Coulter Counter TA-II type (Coulter Counter Co., Ltd.) and connecting an interface (manufactured by Nikkiki) that outputs the number distribution and volume distribution and a personal computer. A known method can be used for the measurement of the particle size distribution. If a more detailed explanation is necessary, refer to JP-A-2005-284269.

  By narrowing the particle size distribution of the display particles and making the shape more spherical, the powder fluidity increases. In addition, making the particle size and amount of the external additive appropriate also determines the fluidity. For example, when the particle size of the external additive is small, the degree of compression is small and the powder fluidity is high. The degree of compression is preferably 5 to 40%. More preferably, it is 10 to 30%. It is well known to use a powder tester (for example, PT-E type) manufactured by Hosokawa Micron Corporation for measurement of static bulk density and dynamic bulk density. Here, the degree of compression is one of the indicators of the fluidity of the display particles, and is calculated from the static bulk density and the dynamic bulk density.

  The molecular weight of the resin is a value measured by gel permeation chromatography (GPC) using several types of monodisperse polystyrene as a standard sample. The measuring device is HLC8120GPC series manufactured by Tosoh Corporation, the column is TSKgel superHM-H H4000 / H3000 / H2000 (6.0 mm ID-150 mm × 3), eluent THF (tetrahydrofuran), flow rate 0.6 mL / min, sample concentration 0.1%, injection amount 20 μL, detector RI, measurement temperature 40 ° C. As a pretreatment for measurement, the sample is dissolved in THF and allowed to stand overnight, and then filtered through a 0.45 μm membrane filter to measure a resin component from which an additive such as silica has been removed. The measurement condition is that the molecular weight distribution of the target sample is included in a range in which the logarithm of the molecular weight and the count number in a calibration curve obtained from several types of monodisperse polystyrene standard samples are linear.

  The softening point of the binder resin is measured by a constant-load extrusion type capillary rheometer flow tester (CFT500) manufactured by Shimadzu Corporation. A known method can be used to measure the softening point. If a more detailed explanation is necessary, refer to JP 2009-077554. From the flow curve in this known method, the outflow start temperature (Tfb) described later and the melting temperature (softening point Tm ° C.) in the 1/2 method are defined.

  The glass transition point of the binder resin is measured with a differential scanning calorimeter (TA Instruments, Q100 type (a genuine electric refrigerator is used for cooling)). A known method can be used for measuring the glass transition point. If a more detailed explanation is necessary, refer to JP 2009-077554.

The charge amount of the inorganic fine particles was measured by a blow-off method of frictional charge with an uncoated ferrite carrier. Specifically, in an environment of 25 ° C. and 45 RH%, 100 g of a polyethylene container is mixed with 50 g of carrier and 0.1 g of inorganic fine particles such as silica, and 5 minutes at a speed of 100 min ⁻¹ by longitudinal rotation. After stirring for 30 minutes, 0.3 g was collected and measured by blowing with nitrogen gas 1.96 × 10 ⁴ [Pa] for 1 minute. As charging characteristics, it is preferable that the ratio (30 minute value / 5 minute value) of the charge amount when stirred for 30 minutes and the charge amount when stirred for 5 minutes is 0.5 or more. The chargeability of the display particles can be maintained, and a stable image display can be output.

<Method for producing display particles>
In producing the colored resin particles, the binder resin and the colorant and, if necessary, an additive such as a charge control agent are uniformly mixed and dispersed by a mixer equipped with a stirring blade. As the mixer, a known mixer such as a super mixer (manufactured by Kawada Manufacturing Co., Ltd.), a Henschel mixer (manufactured by Mitsui Miike Kogyo Co., Ltd.), a PS mixer (manufactured by Shinko Pantech Co., Ltd.) or a Ladige mixer can be used.

(Melt kneading process)
Next, in the melt-kneading process, the binder resin in the mixture is melted by a heating action or a shearing action, and the additive is dispersed in the binder resin. For the melt-kneading treatment, a split segment type twin-screw kneading extruder in which a cylinder and a kneading shaft are divided into a plurality of segments can be suitably used. An example is a kneading extruder (trade name PCM30) manufactured by Ikegai.

  For the melt-kneading treatment, a two-roll kneader that melts and kneads the material between two rotating rolls can also be suitably used. For example, a two-roll kneader (trade name KNEADEX140-800) manufactured by Mitsui Mining Co., Ltd. may be mentioned. The melt-kneading process using the two-roll kneader can be performed in the same manner as the known toner melt-kneading process. If a more detailed explanation is necessary, refer to Japanese Patent Application Laid-Open No. 2004-013049.

  In the melt-kneading process using a two-roll kneader, the surface temperature of the roll to be heated is set lower than the softening point of the binder resin. More specifically, it is necessary to lower the surface temperature of the roll by 10 ° C. or more than the softening point of the binder resin. When the temperature is increased in order to quickly melt the resin and wrap it around the roll when the material is charged (that is, the difference between the resin softening point and the roll surface temperature is less than 10 ° C.), shear force is applied during kneading. This is because non-uniform dispersion occurs. On the other hand, if the temperature difference exceeds 70 ° C., the resin is transported without being completely melted, which also causes a decrease in dispersibility. Further, by setting the temperature difference between the two rolls to be equal to or higher than half the glass transition point of the resin, ultrahigh molecular weight molecular cutting during kneading can be kneaded and dispersed in an appropriate state, and contrast can be increased. It is possible to achieve both improvement of the above and improvement of repeatability. Furthermore, by providing a temperature gradient between the first half and the second half of one roll and setting the temperature difference to be 40 ° C. lower than the glass transition point of the resin, an effect of improving display characteristics can be obtained.

(Crushing process)
The kneaded mass obtained by melt-kneading treatment and cooling is roughly pulverized by a cutter mill or the like, and then jet mill pulverized (for example, trade name IDS pulverizer, manufactured by Nippon Pneumatic Kogyo Co., Ltd.) or fixed stator. Finely pulverized by rotating rotor type pulverization (for example, trade name Kryptron pulverizer, manufactured by Earth Technica Co., Ltd.) that pulverizes by putting the material to be pulverized into a minute gap with the rotating roller. Colored resin particles having a desired particle size distribution can be obtained by an airflow classifier (for example, a trade name Elbow Jet classifier, manufactured by Nittetsu Mining Co., Ltd.).
(Emulsion aggregation method)

  In producing colored resin particles, an emulsion aggregation method can be used as a suitable alternative method. In the emulsion aggregation method, first, a dispersion obtained by dispersing resin particles of a vinyl monomer homopolymer or copolymer (vinyl resin) in an ionic surfactant is prepared, and then a polymerization initiator or Using a chain transfer agent, emulsion polymerization is performed to prepare a resin particle dispersion having a fine particle size. Further, a colorant particle dispersion is prepared by adding colorant particles in water to which a polar surfactant is added and dispersing the particles using a known dispersing means.

  Then, in the aqueous medium, at least the resin particle dispersion in which the resin particles are dispersed and the colorant particle dispersion in which the colorant particles are dispersed are mixed, and the pH of the aqueous medium is set to a certain value (for example, pH 8 to 13), and in the presence of an inorganic salt, colored resin particles can be generated by heating the temperature of the aqueous medium to a temperature equal to or higher than the glass transition point of the resin particles for a certain time (1 to 5 hours). it can.

  Also, a resin particle dispersion containing an ionic surfactant and a colorant particle dispersion are prepared, mixed, and agglomerated by an ionic surfactant having a polarity opposite to that of the ionic surfactant. Then, the aggregated particles can be formed by forming the resin particles, and then heated to a temperature equal to or higher than the glass transition point of the resin particles to fuse the aggregated particles, and the colored resin particles can be produced by washing and drying.

(Suspension polymerization method)
Furthermore, in the production of colored resin particles, a suspension polymerization method can be used as a suitable alternative method. This suspension polymerization method can be carried out in the same manner as a known method for producing a small particle toner. If a more detailed explanation is necessary, refer to Japanese Patent Application Laid-Open No. 2004-191598.

(Fixed fine particles)
First, the positively charged colored resin particles formed to have a desired particle size distribution and the inorganic fine particles are mixed by a known mixer such as the Henschel mixer or the supermixer described above, thereby attaching the inorganic fine particles to the colored resin particles. Thereafter, the colored resin particles to which the negatively charged inorganic fine particles are attached are put into hot air, whereby the surface of the colored resin particles is melted by heat to fix the inorganic fine particles.

  The inorganic fine particles to be fixed to the surface of the colored resin particles are added in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the colored resin particles. The addition ratio of the inorganic fine particles is preferably 4 to 9 parts by weight, more preferably 4 to 8 parts by weight. When the amount of inorganic fine particles is less than 2 parts by weight, the fluidity tends not to improve. On the other hand, when the amount of inorganic fine particles exceeds 10 parts by weight, floating particles of inorganic fine particles are likely to be generated.

  The surface treatment using hot air is preferably performed with hot air having a temperature 180 to 300 ° C. higher than the softening point (° C.) of the binder resin. More preferably, the temperature is 200 to 260 ° C. higher than the softening point of the binder resin, and more preferably 220 to 240 ° C. higher than the softening point of the binder resin. By performing the treatment at a temperature 180 ° C. or higher than the softening point of the binder resin, the colored resin particles and the inorganic fine particles can be sufficiently melt-fixed and the spheroidization can be promoted. On the other hand, when the temperature is lower than 180 ° C. from the softening point, it is difficult to obtain the effect of improving fluidity. Further, when the treatment is carried out at a high temperature exceeding the range of 300 ° C. from the softening point of the binder resin, the secondary aggregation of the colored resin particles often occurs, the particles become coarse and the particle size distribution tends to be widened.

  The binder resin is preferably formed from a thermoplastic resin having a softening point in the range of 110 to 180 ° C and a glass transition point in the range of 70 to 100 ° C. Thereby, the surface of the colored resin particles is rapidly melted, whereby the spheroidization can be promoted by the surface tension, and the fixing (fixing) of the fine particles to the surface of the molten colored resin particles can be promoted. Further, the colored resin particles and the inorganic fine particles can be sufficiently fixed, and the occurrence of secondary aggregation between the colored resin particles can be suppressed.

(Function of display particles)
The display particles produced by fixing the inorganic fine particles to the surface of the colored resin particles as described above may be a case where the surface treatment is performed with the colored resin particles alone as in the past, or a silane coupling agent having a lower alkyl group. Compared with the case where the treated inorganic fine particles are used, the powder fluidity of the display particles is increased, and it is possible to realize a reduction in driving voltage and high contrast during image display. Further, such display particles are easily separated even when they come into contact with the partition walls, and the display particles can be prevented from staying in the four corners of the cell without performing a display operation. Such an effect seems to be due to a synergistic effect of the surface treatment agent for inorganic fine particles and the melting of the resin by the surface treatment with hot hot air.

<Operation of image display medium>
The image display medium 10 having the above configuration displays an image by being driven by the image display device 1. In the image display device 1, the voltage application device 6 includes a power source, a control circuit, and the like (not shown), stores image information to be displayed on the image display medium 10 in a memory or the like, and based on the image information, the image display medium 10. The timing and voltage value of voltage application to the are controlled. As a driving method of the image display medium 10 by the voltage application device 6, a passive matrix driving method, an active matrix driving method, or the like can be appropriately employed as in the driving of a known liquid crystal display device.

 In the image display medium 10, as shown in FIG. 1, at least two or more kinds of display particle groups 5 (here, the display particle group 5A and the display particle group 5B) having different optical reflectance and charging characteristics are encapsulated. In each cell, a voltage is applied between the column electrode 12 provided on the top sheet 2 and the row electrode 22 provided on the back sheet 3. The display particle groups 5A and 5B can be moved between the top sheet 2 and the back sheet 3 in accordance with the electric field generated thereby to display a white or black image. Here, each of the display particle groups 5A and 5B is composed of one kind of display particle, but may be composed of two or more kinds of display particles having different colors.

  In displaying an image, it is preferable to apply an alternating voltage in advance between the electrodes of the top sheet 2 and the back sheet 3. The alternating voltage is applied for a predetermined time (for example, about 0.1 to 1 s) with a frequency of 100 to 400 Hz and a voltage between the peak and peak of the waveform of ± 150 to 300 V. As the waveform of the alternating voltage, a sine wave is preferable, but a rectangular wave or a triangular wave may be applied depending on the characteristics of the display particles.

  In this way, by applying an alternating voltage to rapidly move the display particles between the top sheet 2 and the back sheet 3, charging is stabilized and aggregation between the display particle groups 5A and 5B is reduced. Can be made.

  When displaying an image after applying the alternating voltage, a DC voltage is applied according to the image display pattern stored in the image storage unit. Since the black particles and the white particles are positively charged and negatively charged, respectively, in the case of a simple matrix configuration of the row electrodes 22 and the column electrodes 12, first, all the row electrodes 22 have a negative potential (for example, −50V), all It is preferable to apply a positive potential (for example, +50 V) to the column electrode 12 to temporarily display the entire screen in white.

  Then, a positive selection voltage (for example, +50 V) is applied only to the row electrode that performs display switching from white to black from the DC voltage generation circuit of the voltage application unit to perform row selection (other rows that do not perform display switching). The electrode is 0V).

  Further, a negative image voltage (for example, −50 V) is applied to each column electrode orthogonal to the selected row electrode when switching from white to black is performed, and 0 V is applied when switching is not performed.

  An image is displayed by sequentially performing these operations on all the row electrodes and column electrodes. By setting each voltage application time to a time longer than the response speed of the display particles (for example, 30 ms), sufficient contrast can be obtained. Note that the voltage applied to each electrode may be set to any value as long as the magnitude and direction of the electric field are the same.

  By performing the image display operation as described above, in the region (pixel) between the substrates to which the positive voltage is applied to the column electrode 12, the negatively charged white particles are on the side of the column electrode 12 to which the positive voltage is applied. And the positively charged black particles move to the opposite side of the row electrode 22 and adhere to the inner surface of the back sheet 3.

  On the other hand, in a region where a negative voltage is applied to the column electrode 12, the positively charged black particles move to the column electrode 12 side where the negative voltage is applied and adhere to the inner surface of the topsheet 2. The white particles move to the opposite side of the row electrode 22 and adhere to the inner surface of the back sheet 3. In this way, a black and white image is displayed through the top sheet 2.

  Once the image is displayed, the electrostatic adhesion between the display particles and the dielectric films 13 and 23 is maintained even when the application of voltage between the electrodes is stopped. It can be held for a long time while being attached and displaying a black and white image. In addition, what is necessary is just to reverse the direction of each electric field, when reversing the inversion order of white and black. In addition, when the drive voltage value of the display particles is different, the magnitude of the electric field may be adjusted according to the drive voltage value.

  Hereinafter, the image display medium and display particles according to the present invention will be described with reference to more specific examples.

<Configuration of image display medium>
The configuration of the image display medium 10 is the same as that shown in FIG. Here, both the front substrate 11 and the rear substrate 21 having translucency are made of transparent PET having a thickness of 175 μm. The height H of the partition 7 corresponding to the size of the gap 4 was 40 μm, and the width W of the partition 7 was about 50 μm. The distance D between adjacent partition walls 7 was 1000 μm.
<Method for producing image display medium>

  In the production of the surface sheet 2, first, an A4-sized transparent PET film (that is, the surface substrate 11) having a thickness of 175 μm obtained by depositing ITO having a thickness of 50 nm on the entire surface is prepared. Next, a column electrode 12 having a width of each electrode of 900 μm and a space between the electrodes of 100 μm was formed on the surface substrate 11 by laser etching. The resistance of the column electrode 12 was 150Ω / □. Next, a coating film having a thickness of 12 μm is formed on the column electrode 12 by a pulling dipping method in a solution in which polycarbonate is dissolved in a THF solution at a weight ratio of 10%. The dielectric film 13 having a thickness of 3 μm was laminated by drying at 80 ° C. for 5 minutes.

  FIG. 3 is a schematic cross-sectional view showing one step (dry film laminating step) in the partition wall formation. Subsequent to the formation of the laminated dielectric film 13, as shown in FIG. 3, the surface sheet 2 having the column electrodes 12 and the dielectric film 13 formed on the surface substrate 11, and an epoxy resin and an acrylic resin, using a dry film laminator. A UV curable resin dry film 31 having a thickness of 50 μm made of a mixed system is adhered and bonded together. At this time, the roll temperature was 60 ° C. and the feed rate was 0.4 m / min.

FIG. 4 is a schematic cross-sectional view showing one process (exposure process) in the partition formation. In the subsequent exposure step, as shown in FIG. 4, an exposure mask 32 was placed on the surface sheet 2 and the resin dry film 31 bonded together, and exposure was performed with an exposure amount of 100 mJ / cm ² . The exposure mask 32 defines an ultraviolet-irradiated portion for forming a partition wall having a vertical line width and a horizontal line width of 50 μm and a pitch of 1000 μm.

  FIG. 5 is a schematic cross-sectional view showing one step (development step) in the partition formation. In the subsequent development step, the ultraviolet curable resin dry film 31 that has been exposed is fed by an alkali developing machine using a 1% sodium carbonate developer at a feed rate of 0.6 m / min, a liquid temperature of 35 ° C., a shower pressure of 0. Development was performed under the condition of 15 MPa. As a result, as shown in FIG. 5, the ultraviolet curable resin dry film 31 was removed by the developer except for the ultraviolet irradiation portion in the exposure process, and only the cured portion 7 'that later became the partition remained.

Then, after sufficiently washing with ion-exchanged water, draining and drying at room temperature were performed for 1 hour. Further, after curing at 1000 mJ / cm ² with an ultraviolet curing device, after baking was performed in a drying furnace at 130 ° C. for 30 minutes.

  The partition walls formed had a height of 48 μm, a partition wall width of 45 μm, and a pitch of 1000 μm, both vertically and horizontally, as measured by a step measuring instrument using a microscope.

  For the production of the back sheet 3, a film with copper foil having a thickness of 18 μm was used on an A4 size PET film having a thickness of 175 μm (that is, the back substrate 21).

  In the laminating process, an acrylic UV-curable resin dry film having a thickness of 20 μm was closely adhered to and bonded to a PET film with a copper foil using a dry film laminator. At this time, the roll temperature was 110 ° C. and the feed rate was 0.4 m / min.

Next, an exposure mask was prepared in which the width of each electrode was 900 μm and the space was 1 mm. In the subsequent exposure process, an exposure mask was placed on a PET film with copper foil laminated with an ultraviolet curable resin dry film, and exposure was performed at an exposure amount of 100 mJ / cm ² .

  Further, in the subsequent development process, the ultraviolet curable resin dry film that has been exposed is fed by an alkali developing machine using a 1% sodium carbonate developer at a feed rate of 0.6 m / min, a liquid temperature of 35 ° C., and a shower pressure of 0. Development was performed under the condition of 15 MPa. The pattern of the electrode part was formed by the ultraviolet curable resin dry film remaining without being removed by this development. Thereafter, using an etching apparatus using a ferric chloride solution, copper was etched and developed under the conditions of a feed rate of 0.5 m / min, a liquid temperature of 45 ° C., and a shower pressure of 0.13 MPa. Thus, unnecessary portions of the copper foil corresponding to the spaces between the electrodes were removed.

  Subsequently, the ultraviolet curable resin dry film remaining on the electrode part was subjected to an alkali developing machine using a 3% aqueous solution of sodium hydroxide under the conditions of a feed rate of 0.6 m / min, a liquid temperature of 45 ° C., and a shower pressure of 0.12 MPa. Peeling was performed. This confirmed that unnecessary portions could be removed. Finally, it was thoroughly washed with ion-exchanged water, and then immediately drained by air blow.

  Through the above steps, it was confirmed that the row electrodes 22 having the width of each electrode of 895 μm, the space of 105 μm, and the pitch of 1 mm were formed. Each row electrode 22 is formed with the same width and space as the column electrode 12, and is arranged so as to be orthogonal to each column electrode 12 at a predetermined interval, and has a so-called passive matrix configuration.

  Next, the display particle filling step will be described. A cell in which the ratio of the filling and blending ratio of two types of display particle groups (white particles HW 40 g and black particles HB 20 g) having different colors and charging characteristics is mixed by a partition on the display substrate. The desired amount is filled by a method of shaking through a screen. The injection into the cell was adjusted and sealed so that the volume occupation ratio was about 50%. Thereafter, the particles on the top of the partition walls were removed using a silicone rubber squeegee having a width of 5 mm, a length of 30 mm, and a width of 300 mm.

  In this case, the silicone fine particles and the positively charged black particles are mixed in advance and adhered to the surface of the colored resin particles, and the black particles and the white particles to which the silicone fine particles are adhered are mixed at a constant weight ratio, It is also preferable to enclose in a cell between substrates. In this way, by adhering the negatively chargeable silicone fine particles to the positively chargeable black particles, the aggregation of the particles is relieved by utilizing electrostatic repulsion with the negatively chargeable white particles, and an electric field is applied. The display particles can be smoothly moved between the substrates, and a high contrast can be realized while reducing the driving voltage.

  Alternatively, the silicone fine particles treated with aminosilane and the negatively charged white particles are mixed in advance and adhered to the surface of the colored resin particles, and the white particles and the black particles to which the silicone fine particles are adhered are in a certain weight ratio. After mixing, it is also preferable to enclose in a cell between the substrates. As described above, by attaching the silicone fine particles treated with the positively charged aminosilane to the negatively charged white particles, aggregation can be reduced by utilizing electrostatic repulsion with the positively charged black particles. .

  Next, a thermosetting polyester adhesive was applied to the back sheet 3 and cured at 110 ° C. for 5 minutes. Thereafter, the partition wall 7 is formed, and the top sheet 2 in which the display particles are filled in the cells 8 and the back sheet 3 to which the thermosetting polyester resin adhesive is applied are bonded together. Then, a pressure of 1 MPa was applied at a temperature of 65 ° C. for 3 minutes to bond the top sheet 2 and the back back sheet 3 to produce the image display medium 10.

  This thermosetting polyester resin adhesive tends to have a low adhesive force with the particles, and is applied to the entire inner surface of the back sheet. Therefore, an alkyltrialkoxysilane or alkyl having at least an alkyl group having 6 to 18 carbon atoms. When inorganic fine particles that have been surface-treated with silazane are used in combination with display particles made of colored resin particles fixed to the surface, the display particles are easily detached from the back sheet. As a result, the drive voltage can be reduced.

<Configuration of display particles>
(Binder resin)
Table 1 shows the characteristics of the binder resin used in the examples. The binder resin is a polyester resin composed mainly of alcohol of bisphenol A propyl oxide adduct and divalent carboxylic acid of terephthalic acid, succinic acid or fumaric acid, or trivalent carboxylic acid of trimellitic acid. Then, a resin whose thermal characteristics were changed depending on the blending ratio and polymerization conditions was used.

  In Table 1, Mnf is the number average molecular weight of the binder resin, Mwf is the weight average molecular weight of the binder resin, Mzf is the Z average molecular weight of the binder resin, Wmf is the ratio Mwf of the weight average molecular weight Mwf to the number average molecular weight Mnf / Mnf and Wzf are the ratio Mzf / Mnf of the Z-average molecular weight Mzf and the number-average molecular weight Mnf of the binder resin, Tmr (° C.) is the softening point, Tfb (° C.) is the outflow start temperature, and Tgr (° C.) is the glass transition point. .

(Pigment)
Table 2 shows the composition of the pigments used in the examples.

  In Table 2, the titanium oxide particles PW1 are rutile titanium oxide (SJR-405S) having an average particle diameter of 0.21 nm and surface-treated with silicone oil. This titanium oxide surface treatment is performed by stirring 100 parts by weight of a raw material of titanium oxide (JR-405), 10.5 parts by weight of silicone oil (Toray Dow Corning Silicone SF230) and 300 parts by weight of toluene at room temperature for 2 hours. After removing the supernatant by decantation, it was performed by heating and vacuum drying in a vacuum dryer set at 80 ° C. for 4 hours.

  Carbon black is a pigment having a particle size of 24 nm, a DBP oil absorption of 53 ml / 100 g and a low DBP oil absorption, and is treated with an amino-modified silicone oil (KF857 manufactured by Shin-Etsu Chemical Co., Ltd.). The amount of amino-modified silicone oil added was 8.5 parts by weight with respect to 100 parts by weight of carbon black. The particle diameter is about 100 arithmetic average diameters by SEM.

(Charge control agent)
Table 3 shows the structure of the charge control agent used in the examples. CAW1 and CAW2 are negatively chargeable charge control agents, and CAB1 is a positively chargeable charge control agent.

(Colored resin particles)
Table 4 shows the composition of the colored resin particles used in the examples. In the parentheses, the blending parts by weight with respect to 100 parts by weight of the binder resin are shown.

(Inorganic fine particles)
Table 5 shows the constitution and characteristics of the inorganic fine particles used in the examples.

[SN1]
25 g of colloidal silica (AEROSIL (registered trademark) 380 (average particle size 5 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles was placed in a magnetic stirrer and stirred with 10 g of tetrahydrofuran. A mixed solution in which 7 g was dissolved was gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. It was crushed with a pin mill to obtain inorganic fine particles SN1.

[SN2]
25 g of colloidal silica (AEROSIL 380 (average particle size 5 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles was placed in a magnetic stirrer, and 1.2 g of alkylsilane represented by the above (Chemical Formula 3) was dissolved in 10 g of tetrahydrofuran while stirring. The solution was gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. It was crushed with a pin mill to obtain inorganic fine particles SN2.

[SN3]
25 g of colloidal silica (AEROSIL 300 (average particle size: 7 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles was put in a magnetic stirrer, and 0.7 g of alkylsilane represented by the above (Chemical Formula 7) was dissolved in 10 g of tetrahydrofuran while stirring. The solution was gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. It was crushed with a pin mill to obtain inorganic fine particles SN3.

[SN4]
25 g of colloidal silica (AEROSIL 200 (average particle size: 12 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles was placed in a magnetic stirrer and mixed with 10 g of tetrahydrofuran dissolved in 0.5 g of alkylsilane represented by the above (Chemical Formula 11) while stirring. The solution was gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. It was crushed with a pin mill to obtain inorganic fine particles SN4.

[SN5]
25 g of titanium oxide (AEROXIDE (registered trademark) P90 (average particle size: 14 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles was placed in a magnetic stirrer and stirred with 10 g of tetrahydrofuran. A mixed solution in which 5 g was dissolved was gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. It was crushed with a pin mill to obtain inorganic fine particles SN5.

[AP1]
25 g of colloidal silica (AEROSIL 380 (average particle size 5 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles is placed in a magnetic stirrer and stirred with 10 g of tetrahydrofuran, and γ-aminopropyltriethoxysilane 0 as a coupling agent having an amine group. 0.8 g and a mixed solution in which 0.5 g of alkylsilane represented by the above (Chemical Formula 15) was dissolved were gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. This was crushed with a pin mill to obtain inorganic fine particles AP1.

[AP2]
25 g of colloidal silica (AEROSIL 380 (average particle size 5 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles was placed in a magnetic stirrer and stirred with 10 g of tetrahydrofuran, 0.5 g of γ-aminopropyltriethoxysilane, and the above (Chemical Formula 3). A mixed solution in which 0.6 g of alkylsilane represented by the formula was dissolved was gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. This was crushed with a pin mill to obtain inorganic fine particles AP2.

[AP3]
25 g of colloidal silica (AEROSIL 300 (average particle size: 7 nm), manufactured by Nippon Aerosil Co., Ltd.) as inorganic fine particles was placed in a magnetic stirrer, and γ-aminopropyltriethoxysilane as a coupling agent having an amine group in 10 g of tetrahydrofuran was stirred. 9 g and a mixed solution in which 0.6 g of alkylsilane represented by the above (Chemical Formula 13) was dissolved were gradually added and stirred for 30 minutes. Then, it filtered and dried at 120 degreeC for 2 hours. This was crushed with a pin mill to obtain inorganic fine particles AP3.

In Table 5, “5-minute value” and “30-minute value” represent the charge amount ([μC / g]), and these were measured by a blow-off method by frictional charging with an uncoated ferrite carrier. Specifically, in an environment of 25 ° C. and 45 RH%, 50 g of a carrier is mixed with 100 g of a polyethylene container with 0.1 g of inorganic fine particles such as silica or 0.1 g of silicon fine particles, and 5 times at a speed of 100 min ⁻¹ by longitudinal rotation. After stirring for 30 minutes or 30 minutes, 0.3 g was collected and measured by blowing with nitrogen gas at 1.96 × 10 ⁴ [Pa] for 1 minute.

  As charging characteristics, it is preferable that the ratio (30 minute value / 5 minute value) of the charge amount when stirred for 30 minutes and the charge amount when stirred for 5 minutes is 0.5 or more. Thereby, it is possible to maintain the chargeability of the display particles and output a stable image display.

<Method for producing display particles>
(Preparation of colored resin particles)
In producing the colored resin particles, first, the binder resin, the colorant, and the charge control agent are about 4 kg using a Henschel mixer FM20B (manufactured by Mitsui Miike Kogyo Co., Ltd.) equipped with a stirring blade, the rotation speed is 800 min ⁻¹ , and the time is 5 min. The mixing was performed with the blade Z0S0 under the conditions of:

  FIG. 6 is a schematic perspective view showing the main part of the roll melt kneader, and FIG. 7 is a schematic plan view showing the main part of the roll melt kneader. Following mixing of the binder resin, the colorant, and the charge control agent, a kneading process was performed in a two-roll melt kneader. In the kneading process, as shown in FIG. 6, the colored resin particle raw material charged toward the end of the first roll 51 from the quantitative feeder 50 is wound around the first roll 51 and colored resin particles. The molten film 53 is formed. Here, as shown in FIG. 7, the first roll 51 and the second roll 52 are configured by front half parts 51A and 52A and latter half parts 51B and 52B, respectively, with a broken line part as a boundary. More specifically, the raw material is wound around the first half 51 </ b> A of the first roll 51 when the resin is melted by the heat of the first roll 51 and the compressive shear force of the second roll 52. Thereafter, the melted raw material spreads to the end of the second half 51B of the first roll 51, and from the second half 52B of the second roll 52 heated at a lower temperature than the first half 51A of the first roll 51. It is peeled off.

Here, both the diameter of the 1st roll 51 and the 2nd roll 52 is 140 mm, and length is 800 mm. The rotation speed of the first roll 51 is 75 min ⁻¹ , and the rotation speed of the second roll 52 is 55 min ⁻¹ . The temperature of the heat medium that heats the first half 51A of the first roll 51 is 140 ° C., and the temperature of the heat medium that heats the second half 51B of the first roll 51 is 70 ° C. Moreover, the 2nd roll 52 is 15 degreeC. Further, the clearance between the first roll 51 and the second roll 52 is 0.1 mm, and the raw material supply amount is 5 kg / h.

  The kneaded mass obtained by cooling after the kneading treatment was coarsely pulverized by a cutter mill.

  FIG. 8 is a configuration diagram of the fine pulverization processing apparatus. Then, it refined | miniaturized to about 6 micrometers of volume average particle diameters with the refinement | pulverization grinding | pulverization apparatus 60 shown in FIG. The fine pulverizing apparatus 60 is fitted with a cylindrical rotating body 61 having irregularities on the surface and rotating at a high speed, and a gap of 0.5 mm to 40 mm on the outside of the rotating body 61. A crushing processing unit 63 including a cylindrical fixed body 62 having irregularities on the surface sharing the same is provided.

  In the refinement process by the refinement and pulverization apparatus 60, the pulverized product 71 that has passed the mesh diameter of about 5 mm by coarse pulverization is input from the quantitative supply device 72, and then the cooling air 74 that is supplied from the cooler 73. Is sent to the supply port 75 of the pulverization processing unit 63. The object to be crushed 71 is conveyed to the gap between the rotator 61 and the fixed body 62 in the pulverization processing unit 63, and is exchanged with the flow of the high-speed air current generated between the rotator 61 and the fixed body 62 that rotates at high speed. It is crushed by repeating strong collisions. The obtained pulverized product 80 is discharged from the discharge port 76 of the pulverization processing unit 63, sent to the cyclone 82 through the coarse powder classifier 81, and finally collected in the collection container 83. In the coarse powder classifier 81, coarse particles are sent again to the supply port 75 of the pulverization processing unit 63 by the cooling air 74 via the reprocessing path 84.

  In the pulverization process, the peripheral speed of the rotating body 61 is 130 m / s, the gap between the rotating body 61 and the fixed body 62 is 1.5 mm, the raw material supply rate is 3 kg / h, the temperature of the cooling air 74 is 0.5 ° C., and the discharge is performed. The part temperature was 40 ° C.

(Addition of fine particles to colored resin particles)
The colored resin particles, the display particles, and the inorganic fine particles or the silicone fine particles were mixed, and an external addition treatment for electrostatically attaching the inorganic fine particles or the silicone fine particles to the colored resin particles was performed. The external addition process was performed using a Henschel mixer (FM20B manufactured by Mitsui Mining Co., Ltd.) under the conditions of a stirring blade Z0S0 type, a rotational speed of 2200 min ⁻¹ , a processing time of 4 min, and an input amount of 1 kg.

(Surface modification treatment)
FIG. 9 is a configuration diagram of the surface modification treatment apparatus. The surface modification treatment with hot air on the colored resin particles to which the inorganic fine particles are electrostatically attached was performed using a surface modification treatment apparatus 90 shown in FIG. In the surface modification treatment, the colored resin particles 91 to which the fine particles are attached are introduced from a fixed amount feeder 92 and sent to a dispersion nozzle 94 (see FIG. 10) which is a particle dispersion means by compressed air 93 through a particle pipe 111. . The colored resin particles 91 discharged from the dispersion nozzle 94 are introduced into the hot air 96 discharged from the hot air generator 95 through the hot air pipe 112. The colored resin particles 91 pass through the hot air 96 while being dispersed, whereby the surface modification treatment is performed, and the inorganic fine particles are firmly fixed to the colored resin particles. Thereafter, the surface-modified display particles are taken into the hood 97, sent to the cyclone 98, and then collected and collected in the collection box 99.

  FIG. 10 shows the details of the state of the colored resin particles introduced into the hot air in FIG. The particle pipe 111 and the hot air pipe 112 have a coaxial double pipe structure. In addition, a gap (not shown) is provided between the hot air pipe 112 and the dispersion nozzle 94, and it is difficult for heat of the hot air to be transmitted to the particles by circulating cold water or cold air through the gap. The dispersion nozzle 94 has a tapering shape that gradually decreases toward the tip. A dispersion impingement plate 113 is provided in front of the dispersion nozzle 94 to be used for rectification of the discharged colored resin particles.

  The colored resin particles discharged from the tip of the dispersion nozzle 94 collide with the dispersion collision plate 113 and flow in the lateral direction along the collision surface (curved surface). Thereafter, the colored resin particles enter the hot air discharged from the hot air pipe 112 located outside the particle pipe 111 and are subjected to surface modification treatment. The hot air temperature is a temperature in a region where the radiated hot air first collides with the colored resin particles, and the temperature of the hot air radiated by a thermometer is measured in advance in that region.

  The dispersion impingement plate 113 serves to make the flow of the colored resin particles into a laminar flow, thereby enabling uniform surface modification treatment and reducing the variation coefficient of the shape factor. On the other hand, since the dispersion collision plate 113 is located near the hot air, there is a concern that the colored resin particles are fused. However, by adding inorganic fine particles having an average particle size of 3 nm to 14 nm, which has been surface-treated with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms, to such colored resin particles, Wearing can be avoided.

  In the surface modification process, it is preferable that the surface-modified display particles taken into the hood 97 are cooled by the cooling air 102 generated from the cooler 101. The rapid cooling by the cooling air 102 can stabilize the processing state. The air volume of the cooling air 102 can be appropriately set according to the processing volume. The distance from the position where the display particles are treated with hot air to the point where the cooling air is applied is determined by the amount of treatment, but is generally 10 to 100 cm, preferably 20 to 80 cm. The temperature of the cooling air 102 is not particularly limited, but is preferably 10 ° C. or lower. As another method, a method using water cooling, a method of arranging a solid object (dry ice or the like) cooled around the pipe, and the like can also be used.

  In the surface modification treatment, the hot air flow rate is 1.0 Nm 3 / min (wind pressure 5 × 104 Pa), the raw material supply dispersion air flow rate of the dispersion nozzle 94 is 0.5 Nm 3 / min (wind pressure 3 × 104 Pa), and the supply rate is 1 kg / h. Processed. This treatment with hot air aims to promote the spheroidization of the colored resin particles. In the treatment with hot air, hot air having a temperature 180 to 300 ° C. higher than the softening point of the binder resin was used.

Hot air volume, 0.35~1.0Nm ³ / min in air pressure 3 to 5 × ¹⁰ 4 Pa is the preferred range, also the raw material supply dispersed air volume, wind pressure 1~3 × ¹⁰ 4 Pa, 0. A suitable range is from 05 to 0.5 Nm ³ / min. Further, the ratio of the hot air flow rate to the raw material supply dispersion air flow rate is preferably in the range of 10: 1 to 4: 1. If the air volume of the hot air 96 relative to the raw material supply dispersion air volume is too large, the particles to be treated are repelled and uniform processing becomes difficult. Moreover, when the raw material supply dispersion | distribution air volume with respect to a hot air volume is too large, it will become difficult for the to-be-processed particle to cross | intersect a hot air and to perform a uniform process.

  In addition, although the heater heated with propane gas etc. was used as the hot air generator 95, it is not restricted to this, What is necessary is just to be able to generate a hot air.

<Evaluation of image display media>
(Initial characteristics)

  Evaluation of drive voltage (voltage applied between electrodes when white and black particles are switched to perform black and white display) characteristics (evaluation of relationship between drive voltage and contrast) was performed on the image display medium having the above configuration. .

  Prior to the evaluation, an alternating voltage was applied in advance between the electrodes of the front substrate and the rear substrate to initialize the image display medium. The alternating voltage has a rectangular waveform, a frequency of 100 Hz, a voltage between the peak and peak of the waveform of 200 V, and an application time of 500 ms. After that, a constant DC voltage is applied between the electrodes on the front substrate and the rear substrate, and the drive voltage characteristics are evaluated by measuring the reflected image density during black / white display when the polarity is reversed at the voltage value. Went.

  Specifically, the potential of the column electrode on the front substrate side is set to 0 V, the potential of the row electrode on the rear substrate side is set to +250 V, black is displayed, and the reflected image density is measured using a Macbeth densitometer. Next, the potential of the column electrode is kept at 0 V, the potential of the row electrode is set to −250 V, white is displayed, and the reflected image density is measured using a Macbeth densitometer.

  Next, the reflection image density is measured when black is displayed with the potential of the row electrode being + 225V and when white is displayed with the potential of the row electrode being −225V.

  Thereafter, the reflected image density measurement is similarly performed while reducing the voltage value in 25V steps, and these measurements are continued until the black / white inversion display is not performed.

  Based on the above measurement, the drive voltage characteristics of the image display medium are grasped, and ± 100 V is applied to the row electrode to display black or white, and using the reflected image densities IDb and IDw, the following (Expression 8) The contrast C at the represented drive voltage 100V is calculated.

C = 10 ^(−IDw) / 10 ^(−IDb) (Equation 8)

(Repetitive display characteristics)
A repeated display test was performed on the image display medium having the above configuration. In the repeated display test, black display is performed by setting the potential of the column electrode on the front substrate side to 0 V and the potential of the row electrode on the rear substrate side to +100 V, and then the potential of the row electrode is set to −100 V with the column electrode potential kept at 0 V. As a white display.

  After such display switching operation was repeated 200,000 times, the reflection image densities IDb and IDw when black and white were displayed at a driving voltage of 100 V were measured, and the contrast C was evaluated. Repeated display 200,000 times was performed by applying a rectangular wave alternating electric field having a frequency of 10 Hz and a voltage of 200 V between the peak and peak of the waveform to the row electrode for 340 minutes.

<Evaluation of display particles>
Tables 6, 7 and 8 show the characteristics of the display particle samples subjected to the above-described surface modification treatment. The values in parentheses indicate the weight parts of inorganic fine particles based on 100 parts by weight of colored resin particles. In Table 6, the display particle matrix No, the colored resin particles No included in the display particle matrix, the glass transition point (Tgr (° C)) of the resin used by the colored resin particles, the softening point (Tmr (° C)), and The inorganic fine particles and the average particle diameter are shown. Table 7 shows the hot air temperature (° C.), the softening point Tmr (° C.) and Tsmr (° C.) of the binder resin (temperature difference between the hot air temperature (° C.) and the softening point Tmr (° C.) of the binder resin). Table 8 shows the shape factor (SF) of the colored resin particles, the variation coefficient of the shape factor, the volume average particle diameter of the colored resin particles and the variation coefficient thereof.

  Table 9 shows the characteristics of the silicone fine particles.

  As the silicone fine particles, silicone fine particles of Momentive Performance Materials can be suitably used. TSP5, TSP6, and tsp7 are obtained by treating silicone fine particles with aminosilane. The silicone fine particles are adhered to the display particle matrix by mixing with the display particle matrix having the inorganic fine particles fixed on the surface of the colored resin particles. The conditions are the same as when using the above-described FM 20B.

  Table 10 shows the composition of the display particles obtained by mixing the display particle matrix and the silicone fine particles. For each display particle, the silicone fine particle No and its blending amount, the inorganic fine particle No and its blending amount, and the static bulk density of the display particle are shown.

  Table 11 shows the results of evaluating the image display characteristics by the above-described method after the sample is sealed in an image display medium. The transition of contrast C for 340 minutes was observed.

  In the display particles DHW1, DHW2, DHW3, DHW4, DHW5, DHB9, DHB10, and DHB11, spheroidization progressed, and the shape factor and its variation coefficient also showed small values. Also, there is almost no fusion to the dispersion impingement plate.

  Also, in the display characteristics, DHW1 and DHB8, DHW2 and DHB9, DHW3 and DHB8, DHW4 and DHB9, and DHW5 and DHB10, which are a combination of white particles and black particles, are not adhered to the periphery of the partition wall in repeated image display. The contrast of black and white was maintained at 9 or more, and the decrease was small. Regarding the initial characteristics, the driving voltage when white particles and black particles started to move and image formation was possible was as low as 50V. Further, when the display particles are filled in the cells of the display element, the cells can be filled in a short time, and there is little variation in filling between the cells.

  However, the contrast between dhw6 and dhb12 is slightly reduced, and it takes some time to fill the cells in the display element when filling the display particles, and the amount of filling between the cells varies slightly. was there.

  In dhw7 and dhb13 and dhw8 and dhb14, the driving voltage when white particles and black particles start to move and image formation is possible shows a high value of 100 to 125 V, and the contrast is low, so that Degradation occurred quickly. Further, when filling the display particles into the cells, it takes time to fill the cells, and there are many variations in the filling amount between the cells.

  Although this invention was demonstrated based on specific embodiment containing an Example, these embodiment is an illustration to the last and this invention is not limited by these embodiment. Not all of the components of the display particles according to the present invention, the manufacturing method thereof, and the image display medium using the display particles shown in the above embodiments are necessarily essential, and at least as long as they do not depart from the scope of the present invention. It is possible to select.

  The display particles according to the present invention, the manufacturing method thereof, and the image display medium using the display particles include information transmission media such as electronic books and electronic newspapers, messenger boards such as digital signage and electronic blackboards, and display units on IC cards and the like. Is preferably used.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Top sheet 3 Back sheet 4 Gap 5 Display particle group 7 Partition 8 Cell 10 Image display medium 11 Surface substrate 12 Column electrode 13 Dielectric film 21 Back substrate 22 Row electrode 23 Dielectric film 31 Resin dry film 32 Exposure Mask 50 Constant supply machine 51 First roll 52 Second roll 60 Fine pulverization apparatus 63 Crushing processing section 81 Coarse powder classifier 90 Surface modification processing apparatus

Claims (12)

The display particle group includes a pair of substrates having translucency, at least one of which is disposed so as to face each other, and a display particle group having a predetermined charging characteristic sealed between the substrates, and applying an electric field between the substrates. Display particles used in an image display medium that displays an image by moving
Negatively chargeable first display particles;
Positively chargeable second display particles having a color different from that of the first display particles;
A display particle comprising: silicone fine particles having an average particle size of 0.8 μm to 4.5 μm and a coefficient of variation of the particle size of 14 or less.   The display particles according to claim 1, wherein the second display particles have the negatively chargeable silicone fine particles attached thereto.   The display particles according to claim 1, wherein the silicone fine particles treated with positively charged aminosilane are attached to the first display particles.   The display according to any one of claims 1 to 3, wherein the silicone fine particles are spherical silicone fine particles produced by hydrolysis of an alkyltrialkoxysilane and a condensation reaction of the hydrolysis product. particle.   The first display particles include colored resin particles generated from at least a binder resin and titanium oxide treated with silicone oil, and inorganic fine particles having an average particle size of 3 nm to 14 nm fixed to the surface of the colored resin particles. The display particles according to any one of claims 1 to 4, wherein the inorganic fine particles are surface-treated with alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms.   The second display particles are inorganic particles having a colored resin particle produced from at least a binder resin and carbon black treated with an amino-modified silicone oil, and an average particle size fixed to the surface of the colored resin particle of 3 nm to 14 nm. The inorganic fine particles are subjected to surface treatment with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms and an amine-based coupling agent. The display particle according to any one of 5.   The display particles according to claim 5 or 6, wherein the colored resin particles have a shape factor of 125 or less and a variation coefficient of the shape factor of 16 or less. The display particle group includes a pair of substrates having translucency, at least one of which is disposed so as to face each other, and a display particle group having a predetermined charging characteristic sealed between the substrates, and applying an electric field between the substrates. A method for producing display particles used in an image display medium that displays an image by moving
The display particles include negatively chargeable first display particles and positively chargeable second display particles having a color different from that of the first display particles.
Regarding the first display particles,
Producing colored resin particles containing at least a binder resin and a colorant;
Attaching inorganic fine particles having an average particle diameter of 3 nm to 14 nm, which is surface-treated with alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms, on the surface of the colored resin particles;
The inorganic resin particles adhere to the surface of the colored resin particles by subjecting the colored resin particles to which the inorganic particles have adhered to the surface of the colored resin particles by subjecting the colored resin particles to surface treatment with hot air at a temperature 180 to 300 ° C. higher than the softening point of the binder resin. A process of
Silicone fine particles treated with aminosilane having an average particle size of 0.8 to 4.5 μm and a variation coefficient of the particle size of 14 or less are attached to the surface of the colored resin particles to which the inorganic fine particles are fixed. And a process for producing display particles. The display particle group includes a pair of substrates having translucency, at least one of which is disposed so as to face each other, and a display particle group having a predetermined charging characteristic sealed between the substrates, and applying an electric field between the substrates. A method for producing display particles used in an image display medium that displays an image by moving
The display particles include negatively chargeable first display particles and positively chargeable second display particles having a color different from that of the first display particles.
Regarding the second display particles,
Producing colored resin particles containing at least a binder resin and a colorant;
On the surface of the colored resin particles, inorganic fine particles having an average particle diameter of 3 nm to 14 nm which are surface-treated with an alkyltrialkoxysilane or alkylsilazane having an alkyl group having 6 to 18 carbon atoms and an amine coupling agent are attached. A process of
The inorganic resin particles adhere to the surface of the colored resin particles by subjecting the colored resin particles to which the inorganic particles have adhered to the surface of the colored resin particles by subjecting the colored resin particles to surface treatment with hot air at a temperature 180 to 300 ° C. higher than the softening point of the binder resin. A process of
A step of attaching silicone fine particles having an average particle diameter of 0.8 to 4.5 μm and a coefficient of variation of the particle diameter of 14 or less to the surface of the colored resin particles to which the inorganic fine particles are fixed. A method for producing display particles characterized by the above.   The method for producing display particles according to claim 8, further comprising a step of fixing the silicone fine particles to the surface of the colored resin particles.   The said binder resin consists of a thermoplastic resin whose softening point is 110 to 180 degreeC, and whose glass transition point is 70 to 100 degreeC, It is any one of Claims 8-10 characterized by the above-mentioned. A method for producing display particles.   An image display medium using the display particles according to claim 1.

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