JP4443203B2 - Electrophoretic display device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrophoretic device, and more particularly to an electrophoretic display device in which a liquid phase dispersion medium and electrophoretic particles are accommodated between opposing electrodes and a method for manufacturing the same.

  An electrophoretic display device utilizing an electrophoretic phenomenon is known. In the electrophoretic display device, medium and electrophoretic particles having a positive or negative charge are enclosed, and by applying an electric field to the electrophoretic particles, they are collected on the display surface side of the display panel, Alternatively, it is possible to display a desired image by moving away from the display surface side of the display panel. JP-A-64-86116 (Patent Document 1) and JP-A-10-149118 (Patent Document 2) disclose an invention of an electrophoretic display device using microcapsules. FIG. 1 is a cross-sectional view of an essential part for explaining an example of a conventional electrophoretic display device using microcapsules.

A first substrate 2, a transparent second substrate 3 having a transparent electrode 4, the transparent electrode 4 and the transparent electrode 5 ₁ to 5 ₃ facing having an electrophoretic display device 1, the transparent electrode 5 ₁ to 5 ₃ Are arranged at a predetermined interval. The first substrate 2 and the second substrate 3 are formed using, for example, an insulating synthetic resin such as PET (polyethylene terephthalate). The transparent electrode 4 and the transparent electrode ₅ 1 to 5 _3, for example, have a transparent electrode film (ITO (indium oxide) film) is formed, respectively. A large number of microcapsules 6 are arranged between the first substrate 2 and the second substrate 3. The microcapsule 6 is obtained by individually encapsulating a dispersion liquid (dispersion system) in which electrophoretic particles 7 are dispersed in a liquid phase dispersion medium 9 in advance by a microencapsulation technique, and has a spherical shape in its natural shape. The electrophoretic particles 7 are composed of charged particles such as a white pigment. The dispersion medium 11 is composed of, for example, a colored dispersion medium colored black. Hereinafter, the liquid mixture of the electrophoretic particles 7 enclosed in the microcapsules 6 and the liquid phase dispersion medium 9 is also referred to as an electrophoretic display dispersion. Between the first substrate 2 and the second substrate 3, a binder material 8 for fixing the large number of microcapsules 6 is contained together with the large number of microcapsules 6. The binder material 8 is transparent and has good adhesiveness with the transparent electrodes 4, 5 _{1 to} 5 ₃ .

In such a configuration, for example, the transparent electrode 4 and the ground potential, when the transparent electrode 5 _1, 5 ₃ applying a negative voltage, between the transparent electrode 4 and the transparent electrode 5 _1, 5 ₃ microcapsules 6 Electrophoretic particles 7 which are charged particles inside move toward the transparent electrode 4. As a result, the microcapsule 6 between the transparent electrode 4 and the transparent electrodes 5 ₁ , 5 ₃ exhibits a black color with respect to the direction of the second substrate 3. Further, the transparent electrode 4 and the ground potential, when a positive voltage is applied to the transparent electrode 5 _2, the electrophoretic particles 7 is inside the charged particles of the microcapsules 6 between the transparent electrode 4 and the transparent electrode 5 ₂ is transparent moves toward the electrode _{5 2.} As a result, the microcapsules 6 between the transparent electrode 4 and the transparent electrode 5 ₂ Teisu white to the direction of the first substrate 2.

JP-A 64-86116 JP-A-10-149118

However, the electrophoretic display device 1 is extremely inferior in display characteristics and storability at high temperatures (for example, about 60 ° C.) and high humidity (for example, about 90%), and further changes (discolors) the microcapsules. There was a problem.
In view of the above-described circumstances, the present invention provides an electrophoretic display device capable of improving an excellent contrast ratio and display stability without deterioration in display state even under high temperature and high humidity, and a method for manufacturing the same. There is to do.

An electrophoretic display device of the present invention is provided between a first electrode and a second electrode, at least one of which is made of a transparent material, and between the first electrode and the second electrode. In an electrophoretic display device having a microcapsule layer containing a plurality of microcapsules formed by enclosing a dispersion system containing, on at least one of the first electrode and the second electrode on the surface of the microcapsule layer In addition, a silicon nitride film having an insulating property and having a thickness of 100 nm to 400 nm is provided . “Insulating” means that, for example, a current of several nA / cm ² or less is generated when a voltage of 15 V is applied between the electrodes, and the specific film thickness is about 100 nm or more. By providing such a configuration, cuts off the direct current of the first and second electrodeposition machining gap arising from the DC voltage applied, the electrophoretic dispersion liquid for display caused by transfer of charge between the dispersion for electrophoretic display electrode Has the effect of preventing the deterioration of Further, under such a configuration, when the silicon nitride film has an optimal silicon nitride film thickness that is sufficiently larger than the capacitance value of the electrophoretic display dispersion liquid, the liquid phase dispersion medium and the electrophoretic particles are obtained. A strong electric field can be applied between the contained electrodes, and excellent display characteristics are exhibited.

The present invention provides a dispersion system including a first electrode and a second electrode , at least one of which is made of a transparent material, and a liquid phase dispersion medium and electrophoretic particles provided between the first electrode and the second electrode. In the manufacturing method of an electrophoretic display device having a microcapsule layer containing a plurality of encapsulated microcapsules , an insulating property is provided on a surface of at least one of the first electrode and the second electrode on the microcapsule layer side look including the step of forming a silicon nitride film from the liquid phase using an organic solvent having a film thickness of the silicon nitride film is characterized in that at 100nm or 400nm or less. The silicon nitride film is formed by a spin coating method, a dip method, a screen printing method, a casting method, or the like. Such a manufacturing method can easily form a silicon nitride film , and further eliminates the need for a vacuum apparatus, and thus has an effect of reducing the manufacturing cost.

The present invention provides a dispersion system including a first electrode and a second electrode , at least one of which is made of a transparent material, and a liquid phase dispersion medium and electrophoretic particles provided between the first electrode and the second electrode. In the manufacturing method of an electrophoretic display device having a microcapsule layer containing a plurality of encapsulated microcapsules , an insulating property is provided on a surface of at least one of the first electrode and the second electrode on the microcapsule layer side comprising the step of film formation by using a chemical vapor deposition silicon nitride film having a film thickness of the silicon nitride film is characterized in that at 100nm or 400nm or less. When a silicon nitride film is formed by plasma enhanced chemical vapor deposition (PECVD), a high-quality insulating film can be easily formed, and the display performance of the electrophoretic display device is significantly improved and the life is further extended. Excellent effect.

According to the electrophoretic display device of the present invention, the electrode and the microcapsule wall or the electrophoretic display dispersion liquid can be electrically cut off, and charge transfer between the electrode and the microcapsule wall or the electrophoretic display dispersion liquid. It is possible to prevent the deterioration of the microcapsule wall caused by the above, and to maintain an excellent contrast ratio and display stability without deterioration of the display state even under high temperature and high humidity.
In addition, according to the method for manufacturing an electrophoretic display of the present invention, the above-described excellent electrophoretic display device can be easily realized.

The conventional electrophoretic display device having a spherical microcapsule in which a dispersion for electrophoretic display is encapsulated has the above-mentioned problems. However, the following (1) and (2) have been investigated as factors by the applicant's research. This has led to the present invention.
(1): The microcapsule was in close contact with the electrode, and current was generated in the microcapsule. Therefore, an electrochemical reaction was caused between the microcapsule wall and the electrode, and the microcapsule wall material was altered.
(2): Due to the moisture absorption of the microcapsules, the electrical conductivity of the microcapsules was increased, and the amount of direct current passing through the microcapsule surface layer was increased. For this reason, an electric field was not applied to the electrophoretic particles, and electrophoresis was hindered.

The present invention eliminates these deterioration factors and realizes an excellent electrophoretic display device.
Hereinafter, the electrophoretic display device of the present invention will be described in detail.
FIG. 2 is a cross-sectional view of an essential part for explaining the present invention. The electrophoretic display device 2 includes a first substrate 2, a first electrode 5 formed on the first substrate 2, and an insulating coating 11 typified by a silicon nitride film formed on the first electrode 5. A microcapsule layer 12 containing a plurality of microcapsules 6 formed on an insulating coating 11 and encapsulating a dispersion system including a liquid phase dispersion medium 9 and electrophoretic particles 7, and formed on the microcapsule layer 12. And a substrate 13 with a conductive film. The substrate 13 with conductive film shown here shows the second substrate 3 and the second electrode 4 formed on the second substrate 3. Either one of the first substrate 2 and the first electrode 5 or the second substrate 3 and the second electrode 4 needs to be transparent. In FIG. 2, the first electrode 5 and the second electrode 4 form a pair of electrodes, but the number of electrodes is not limited and may be composed of a plurality of drive electrodes.

  In the electrophoretic display device 2, one electrode (for example, the first electrode 5) is grounded, and a predetermined voltage such as 15 V is applied to the other electrode (for example, the second electrode 4). An electric field is generated between the films, and the electrophoretic particles 7 move in response to the electric field. As a result, the distribution state of the electrophoretic particles 7 in the dispersion system changes, and the optical reflection characteristics change. Thus, the required display is performed.

The first substrate 2 and the second substrate 3 of the electrophoretic display device 2 of the present invention are made of a material that can carry (or can support or hold) the first electrode 5 and the second electrode 4 and has an insulating property. If it becomes, a various base material will be used without a restriction | limiting in particular. As such a substrate, for example, a substrate made of a glass substrate, a ceramic substrate, a paper substrate, an insulating synthetic resin substrate, a flexible circuit board, a glass epoxy resin, or the like can be used. Silicate glass (quartz glass), alkali silicate glass, soda lime glass, potash lime glass, lead glass, barium glass, borosilicate glass, etc. can be used as the glass substrate, and ceramic plates etc. can be used as the ceramic substrate. As the paper, high-quality paper, Japanese paper, high filler-containing paper, non-woven fabric, and the like can be used. Moreover, what is illustrated below can be used as an insulating synthetic resin base material.
(A) Polyethylene, chlorinated polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polypropylene, ABS resin, methyl methacrylate resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, chloride Vinyl-vinylidene chloride copolymer, vinyl chloride acrylate copolymer, vinyl chloride-methacrylic acid copolymer, vinyl chloride-acrylonitrile copolymer, ethylene-vinyl alcohol-vinyl chloride copolymer, propylene-vinyl chloride copolymer Thermoplastic resins such as polymers, vinylidene chloride resins, vinyl acetate resins, polyvinyl alcohol, polyvinyl formal, and cellulose resins.
(B) Polyamide-based resin, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyamideimide, polyaminobismaleimide, polyethersulfone, polyphenylenesulfone, polyarylate, grafted polyfinylene ether, polyetherether Polymers with excellent heat resistance and mechanical strength such as ketones and polyetherimides.
(C) Polytetrafluoroethylene, polyfluorinated ethylene propylene, ethylene tetrafluoride-perfluoroalkoxyethylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polytrifluoroethylene chloride, fluororubber Fluorine resin such as
(D) Silicon resins such as silicone resin and silicon rubber.
As other insulating synthetic resin base materials, methacrylic acid-styrene copolymer, polybutylene, methyl methacrylate-butadiene-styrene copolymer, and the like can be used.

  In the electrophoretic display device 2 of the present invention, the first electrode 5 is formed on the first substrate 2 and the second electrode 4 is formed on the second substrate 3. Examples of the first electrode 5 and the second electrode 4 include a tin-doped indium oxide film (ITO film), a fluorine-doped tin oxide film (FTO film), an antimony-doped zinc oxide film, and indium. Preferred examples include zinc oxide films doped with aluminum, zinc oxide films doped with aluminum, and the like. The method for forming the first electrode 5 and the second electrode 4 is not particularly limited. For example, sputtering, electron beam, ion plating, vacuum deposition, chemical vapor deposition (CVD), etc. Can be formed. The first electrode 5 and the second electrode 4 can be formed on the entire surface of the first substrate or the second substrate.

  In the electrophoretic display device 2 of the present invention, the insulating film 11 is formed on the first electrode 5 or the second electrode 4. Examples of the insulating film 11 include polyethylene, polycarbonate, polyimide, vinyl chloride resin, acrylate copolymer, epoxy resin, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl butyral, urethane resin, phenol resin, polyamide resin, urea resin, Insulating organic substances such as urea resin, silicone resin, polysilazane, polymethyl methacrylate, insulating metal oxides such as aluminum oxide, silicon oxide, silicon nitride, barium titanate, titanium oxide, sulfide, halide, etc. are used. it can.

  Although there is no restriction | limiting in particular in the method of forming the insulating film 11, It forms by the spin coat method from the organic solvent containing an insulating organic substance, or the dip method, the screen printing method, the casting method, the coating method by a roll etc. I can do it. Further, it can be formed by a spin coating method, a dip method, a screen printing method, a casting method, a coating method using a roll, or the like from an organic solvent containing an insulating metal oxide, sulfide, or halide. Whichever formation method is used, a sheet or roll can be formed from a unit of one wafer or substrate by roll-to-roll. When a silicon nitride film is used as an insulating film, it can be formed by using a chemical vapor deposition (CVD) method from a source gas such as silane, ammonia, or nitrogen.

In the electrophoretic display device 2 of the present invention, a microcapsule layer 12 in which a plurality of microcapsules 6 are arranged is formed on an insulating film 11. The microcapsule 6 is formed by enclosing a dispersion system in which electrophoretic particles 7 are dispersed in a liquid phase dispersion medium 9.
Examples of the liquid phase dispersion medium 9 used in the dispersion system include alcohol solvents such as water, methanol, ethanol, isopropanol, butanol, octanol and methyl cellosolve, various esters such as ethyl acetate and butyl acetate, acetone, methyl ethyl ketone, Ketones such as methyl isobutyl ketone, aliphatic hydrocarbons such as pentane, hexane and octane, cycloaliphatic hydrocarbons such as cyclohexane and methylcyclohexane, aromatic hydrocarbons such as benzene, toluene, xylene and hexylbenzene, methylene chloride, A compound obtained by blending a surfactant or the like with a halogenated hydrocarbon such as chloroform, carbon tetrachloride, 1,2-dichloroethane, a carboxylate or other various oils alone or a mixture thereof can be used.

  In the present specification, the electrophoretic particle 7 refers to a particle (polymer or colloid) having a property of performing electrophoresis by a potential difference in the liquid phase dispersion medium 9 and moving to a desired electrode side. For example, black pigments such as aniline black and carbon black, white pigments such as titanium dioxide, zinc white, antimony trioxide, aluminum oxide, azo pigments such as monoazo, disazo, polyazo, isoindolinone, yellow lead, yellow iron oxide , Yellow pigments such as cadmium yellow, titanium yellow and antimony, red pigments such as quinacridone red and chrome vermillion, phthalocyanine blue and indanthrene blue, anthraquinone dyes, blue pigments such as bitumen, ultramarine blue and cobalt blue, phthalocyanine green, etc. It is a green pigment. These particles may be used alone or in combination of two or more. Furthermore, these pigments include electrolytes, surfactants, metal soaps, resins, rubbers, oils, varnishes, charge control agents composed of particles such as compounds, or dispersing agents such as titanium coupling agents, lubricants, as necessary. Stabilizers and the like can be added. The dispersion system configured as described above is a well-known microcapsule such as an interfacial polymerization method, an insolubilization reaction method, a phase separation method, or an interfacial precipitation method after sufficiently mixed by an appropriate means such as a ball mill, a sand mill, or a bainto shaker. The dispersion system can be microencapsulated by the conversion method.

  As a material constituting the microcapsule 6, it is preferable to use a flexible material such as a gum arabic / gelatin compound or a urethane compound. In addition, it is preferable that the microcapsules have a substantially uniform size in order to exhibit an excellent display function. Microcapsules having a substantially uniform size can be obtained by using, for example, filtration or a specific gravity differential class. The size of the microcapsules is usually about 30 to 60 μm.

The microcapsule layer 12 is a method in which the above-described microcapsule 6 is mixed with a desired dielectric constant adjusting agent in a binder resin 8 and the resulting resin composition (emulsion or organic solvent solution) is used on a substrate using a roll coater. Or a method using a roll laminator, a screen printing method, or a known coating method such as a spray method.
The binder resin 8 that can be used is not particularly limited as long as the binder resin 8 has good affinity with the microcapsules 6, has excellent adhesion to the electrode, and has insulating properties. As this binder resin 8, the thing illustrated below can be used similarly to the insulating synthetic resin base material mentioned above.

  Polyethylene, chlorinated polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polypropylene, ABS resin, methyl methacrylate resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-chloride Vinylidene copolymer, vinyl chloride acrylate copolymer, vinyl chloride-methacrylic acid copolymer, vinyl chloride-acrylonitrile copolymer, ethylene-vinyl alcohol-vinyl chloride copolymer, propylene-vinyl chloride copolymer, Thermoplastic resins such as vinylidene chloride resin, vinyl acetate resin, polyvinyl alcohol, polyvinyl formal, and cellulose resin. Polyamide resin, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyamideimide, polyaminobismaleimide, polyethersulfone, polyphenylenesulfone, polyarylate, grafted polyfinylene ether, polyetheretherketone, poly Polymers such as etherimide. Fluorine such as polytetrafluoroethylene, polyfluoroethylenepropylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polytrifluoroethylene chloride, fluororubber Resin. Silicon resins such as silicone resin and silicon rubber. As the other binder material 8, methacrylic acid-styrene copolymer, polybutylene, methyl methacrylate-butadiene-styrene copolymer, or the like can be used. Further, as described in JP-A-10-149118, the binder material 8 preferably has substantially the same dielectric constant as that of the electrophoretic display liquid 14 and that of the dispersant. Here, the electrophoretic display liquid 14 includes a liquid phase dispersion medium 9 and charged electrophoretic particles 7 dispersed in the dispersion medium. Therefore, it is preferable to further add, for example, alcohols, ketones, carboxylates and the like to the binder resin composition. As such alcohols, 1,2-butanediol, 1,4-butanediol and the like are used.

  In the electrophoretic display device 2 of the present invention, a substrate 13 with a transparent conductive film is formed on the microcapsule layer 12. The base material 13 with a transparent conductive film includes a second substrate in the figure and a second electrode formed on the second substrate. The substrate 13 with a transparent conductive film protects the microcapsule layer 12 and also plays a role as a counter electrode. The base material 13 with a transparent conductive film is brought into close contact with the microcapsule layer 12 using a method such as a roll laminator method or a vacuum laminator method.

従って絶縁性被膜の容量C_ISがマイクロカプセルの容量C_mcよりも十分に大きければ（約１０倍以上で有れば）、
C_IS >> C_mc
C_IS > 10C_mc
マイクロカプセルには略電源電圧が印可されることになり、

電気泳動粒子には有効に電界が加わる。この結果電気泳動表示装置は良好な表示性能を有することになる。 In order for the electrophoretic display device according to the present invention to operate satisfactorily, the dielectric constant and thickness of the insulating film 11 must be appropriately determined. This will be described using an electric equivalent circuit (FIG. 4). Capacitance value C _mc of microcapsule and voltage V _mc applied to microcapsule, capacitance value C _IS of insulating film, voltage V _IS applied to insulating film such as silicon nitride film, power supply voltage the following relationship between the V ₀ is true.

Therefore, if the capacity C _IS of the insulating coating is sufficiently larger than the capacity C _{mc of the} microcapsule (if it is about 10 times or more),
C _IS >> C _mc
C _IS > 10C _mc
The power supply voltage is applied to the microcapsule,

An electric field is effectively applied to the electrophoretic particles. As a result, the electrophoretic display device has good display performance.

Although the capacitance value C _IS insulating film of the silicon nitride film or the like is required to have a sufficiently larger value than the capacitance value C _mc microcapsule (see Comparative Example 2) As described in detail later insulation If the film is extremely thin, the electrical insulation is poor, and the display characteristics deteriorate after leaving at high temperature and high humidity. In order to show excellent display performance without deterioration even after leaving at high temperature and high humidity, the insulating coating has insulating properties, and the capacitance value C _{IS of the} insulating coating is the capacitance value C _{mc of the} microcapsule. It is necessary to be 10 times larger than that. If the capacitance C _IS opposite to the insulating coating be sufficiently larger than the capacitance C _mc microcapsules, the voltage is applied to the microcapsules does not function as a small becomes electrophoretic display device. As will be described later in Comparative Example 3, when the insulating film is a silicon nitride film, the thickness must be less than 500 nm, and the thickness is 400 nm or less for the electrophoretic display device to function reliably. Since the relative dielectric constant of the silicon nitride film is 7.9, when the insulating film is formed of a material other than the silicon nitride film, the dielectric constant ε and the film thickness d (nm) of the insulating film are 7.9. / 400 (nm) ≦ ε / d
If the relationship is satisfied, the electrophoretic display device functions, and an excellent electrophoretic display device that is resistant to environmental tests such as high temperature and high humidity is realized.

  Next, the present invention will be described in more detail with reference to examples. Note that the following description is only one embodiment of the present invention, and the types of the electrophoretic particles enclosed in the base material, the conductive film, the insulating film, and the microcapsules without departing from the gist of the present invention, etc. Can be changed freely.

An electrophoretic display device and a manufacturing method thereof according to the present invention will be described with reference to FIG. First, a first substrate 2 having a first electrode 5 was prepared by forming an ITO film having a thickness of 1 to 2 μm on a PET (polyethylene terephthalate) film. Next, as an electrophoretic display liquid to be enclosed inside, 12 parts of titanium oxide, 1.5 parts by weight of a surfactant, 0.5 parts by weight of a titanium coupling agent, 1 part by weight of a blue anthraquinone dye, a liquid phase dispersion medium 9 And 85 parts by weight of dodecylbenzene were mixed by ultrasonic dispersion. The thus obtained electrophoretic display liquid was sealed in microcapsules 6 having an average particle size of 50 microns prepared by a gum arabic-gelatin composite coacervation method. Next, the obtained microcapsule 6 and the emulsion type silicone coating agent (made by Shin-Etsu Silicone Co., Ltd., trade name: POLON-MF-40) as a binder material 8 are mixed at a weight ratio of 2: 1. Thus, a resin emulsion was formed, and this was coated on the ITO film-coated PET film 13 to form the microcapsule layer 12.
As the second substrate 3 having the second electrode 4, a PET film with ITO was used, and a silicon nitride film serving as the insulating film 11 was formed on the second electrode 4 by the CVD method. The electrophoretic display device was manufactured by setting the thickness of the silicon nitride film to four conditions of 100 nm, 200 nm, 300 nm, and 400 nm.

  The PET film with an ITO film coated with the microcapsule layer 12 and the PET film with an ITO film formed with an insulating film are closely adhered by a roll laminator method so that the microcapsule layer 12 is sandwiched, An electrophoretic display device 3 shown in FIG. In order to operate the electrophoretic display device 3, a drive voltage generator 17 is connected between the first electrode 5 and the second electrode 4.

Next, the operation state of the electrophoretic display device thus created will be described. In the following explanation, it is assumed that the electrophoretic particles are negatively charged. However, the positively charged particles are exactly the same except that the moving direction of the electrophoretic particles is reversed. The operating status can be obtained.
First, in the electrophoretic display device of Example 1, the thickness of the insulating coating 11 made of a silicon nitride film was 100 nm to 400 nm. Such an insulating coating can apply a sufficiently strong electric field to the electrophoretic display liquid while blocking the current between the electrodes. Therefore, the electrophoretic apparatus of this example showed excellent display characteristics. Further, even when the electrophoretic device thus obtained was left under high temperature and high humidity, good display characteristics were maintained. Specifically, the following display stability test was performed under the influence of the external environment. First, the display state when a voltage of ± 15 V was applied between the electrodes of the electrophoretic display device was measured using a reflection densitometer, and the initial display performance (contrast) was examined. Next, this electrophoretic display device was subjected to a display stability test in a high temperature and high humidity environment. That is, the electrophoretic display device of this example was placed at a high temperature and high humidity of 60 ° C. and 90% RH, taken out after 6 hours, a voltage of ± 15 V was applied, and the display state was examined with a reflection densitometer. . Table 1 shows the relationship between the characteristics of the electrophoretic display device prepared in this example and the thickness of the silicon nitride film. In the electrophoresis apparatus of this example, the leakage current amount between the two electrodes was suppressed to a few nA / cm ^{−2 on the} order of several nA / cm ⁻² even when 15 V was applied, and the effect of blocking the current was recognized. For this reason, no discoloration and deterioration of the microcapsules 6 were observed. In addition, a good contrast ratio was exhibited even after display in a high-temperature and high-humidity environment, and the contrast value only decreased about 10% after the high-temperature and high-humidity environment test compared to the initial value. When left in a room temperature environment, good display characteristics similar to the initial values were maintained even after 50 days.

(Comparative Example 1)
The electrophoretic display device of Comparative Example 1 shown in FIG. 3B was produced in the same manner as in Example 1 except that the insulating film 11 was not formed on the electrophoretic display device.
The electrophoretic display device produced in Comparative Example 1 does not have an insulating film. The electrophoretic display device of Comparative Example 1 exhibited good display characteristics in a room temperature environment. However, the results of the display stability test under high temperature and high humidity were disastrous. These results are shown in Table 1. After 6 hours of standing at 60 ° C. and 90% RH under high humidity, the leakage current between the two electrodes increased to the order of several hundred μA / cm ⁻² when 15 V was applied. Furthermore, the contrast ratio was significantly reduced in the display state when ± 15 V voltage was applied after maintaining high temperature and high humidity. It was confirmed that the contrast was degraded by about 95% compared to the initial value. In addition, the microcapsule 6 also turned brown and deteriorated.

(Comparative Example 2)
The same electrophoretic display device as that of Example 1 was manufactured except that the thickness of the silicon nitride film as the insulating film 11 was set to 50 nm.
In the electrophoretic display device having a thickness of 50 nm of the silicon nitride film manufactured in Comparative Example 2, the silicon nitride film does not have sufficient insulation and does not have the insulating film shown in Comparative Example 1. It showed the same display characteristics as the electrophoretic display device. Table 1 shows these results.

(Comparative Example 3)
The same electrophoretic display device as in Example 1 was manufactured except that the thickness of the silicon nitride film as the insulating film 11 was changed to 500 nm.
The electrophoretic display device having the thickness of 500 nm of the silicon nitride film manufactured in Comparative Example 3 can sufficiently electrically cut off the electrode and the capsule. However, even in the initial state, a sufficient contrast ratio was not obtained when 15V was applied. This is because when the thickness of the silicon nitride film increases, the capacitance value of the insulating film decreases, and therefore the voltage applied between the electrodes greatly drops at the insulating film. As a result, the effective voltage applied to the microcapsule layer 12 is drastically reduced, and an electric field that causes electrophoresis particles to migrate is not generated. For the electrophoretic display device to function as a display device, the thickness of the insulating film must be less than 500 nm. These results are also shown in Table 1.

  The electrophoretic display device of the present invention is used as a display device in a public display field such as a rewritable card, a rewritable sheet, and a rewritable paper, and in an information communication field such as a display of information equipment such as a digital paper, a computer, and a portable information terminal. Can do.

It is sectional drawing which shows the electrophoretic display apparatus in background art. It is sectional drawing which shows the electrophoretic display apparatus in this invention. 1A and 1B are diagrams showing an electrophoretic display device according to the present invention, in which FIG. 1A is a cross-sectional view showing an electrophoretic display device of Example 1, and FIG. 2B is a cross-sectional view showing an electrophoretic display device of Comparative Example 1; It is a figure which shows the electrical equivalent circuit of Example 1 in this invention.

Explanation of symbols

1 electrophoresis device 1
2 First substrate 3 Second substrate 4 First electrode 5, 5 _{1 to} 5 ₃ Second electrode 6 Microcapsule 7 Electrophoretic particle 8 Binder material (binder resin)
9 liquid phase dispersion medium 10 electrophoresis apparatus 2
11 Insulating film 12 Microcapsule layer 13 Substrate with transparent conductive film 14 Dispersion liquid 15 for electrophoretic display 3 Electrophoretic display device 3
16 electrophoretic display 4
17 Drive voltage generator

Claims (9)

A first electrode and a second electrode, at least one of which is made of a transparent material, and provided between the first electrode and the second electrode and encapsulating a dispersion system including a liquid phase dispersion medium and electrophoretic particles. In an electrophoretic display device having a microcapsule layer containing a plurality of microcapsules ,
Wherein the first electrode and the second electrodes of at least one of the microcapsule layer side on the surface, an insulating property, and that the film thickness is 400nm or less of the silicon nitride film is provided above 100nm An electrophoretic display device.   2. The electrophoretic display device according to claim 1, wherein the silicon nitride film is provided only on a surface of the second electrode on the microcapsule layer side. In the electrophoretic display device according to claim 1 or 2, wherein the silicon nitride film is an electrophoretic display device, characterized in that the function as an adhesive layer between the front Symbol microcapsule layer. A first electrode and a second electrode, at least one of which is made of a transparent material, and provided between the first electrode and the second electrode and encapsulating a dispersion system including a liquid phase dispersion medium and electrophoretic particles. In a method of manufacturing an electrophoretic display device having a microcapsule layer containing a plurality of microcapsules ,
Look including the step of forming from the liquid phase using an organic solvent at least one of the microcapsule layer side silicon nitride film having an insulating property on the surface of the first electrode and the second electrode, the silicon nitride film The method of manufacturing an electrophoretic display device, wherein the film pressure is 100 nm or more and 400 nm or less . 5. The method for manufacturing an electrophoretic display device according to claim 4 , wherein the silicon nitride film is formed by a spin coating method. 5. The method for manufacturing an electrophoretic display device according to claim 4 , wherein the silicon nitride film is formed by a dipping method. 5. The method for manufacturing an electrophoretic display device according to claim 4 , wherein the silicon nitride film is formed by a screen printing method. A first electrode and a second electrode, at least one of which is made of a transparent material, and provided between the first electrode and the second electrode and encapsulating a dispersion system including a liquid phase dispersion medium and electrophoretic particles. In a method of manufacturing an electrophoretic display device having a microcapsule layer containing a plurality of microcapsules ,
Forming a silicon nitride film having an insulating property on a surface of at least one of the first electrode and the second electrode on the microcapsule layer side using a chemical vapor deposition method , The method of manufacturing an electrophoretic display device, wherein the film pressure is 100 nm or more and 400 nm or less . 9. The method for manufacturing an electrophoretic display device according to claim 8 , wherein the silicon nitride film is formed by a plasma chemical vapor deposition method (PECVD method).

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