JP2009186639A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method which can exhibit satisfactory fixing intensity, does not allow a formed image to produce strong gloss and, even if the image has a gloss, can form a toner image having even gloss without irregularity. <P>SOLUTION: In the image forming method, image formation is performed by using a fixing device provided with: a core-shell structure toner of which the average roundness is 0.895 to 0.980; and a heating roller with an elastic layer having a resilient modulus of 30% to 70% and a thickness of 0.2 mm to 0.4 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming method in which fixing can be performed at a lower temperature than before and a good toner image without gloss unevenness can be obtained.

  In an electrophotographic image forming apparatus, a so-called low-temperature fixing technique for fixing a toner image at a temperature lower than that in the past has been recently studied in order to reduce power consumption and produce a print at high speed. . The performance required of the toner for realizing the low-temperature fixing includes an improvement of the melting property at a low temperature. For example, the glass transition temperature and the softening point of the toner constituting resin are reduced. Technology.

  However, if the glass transition temperature and softening point are reduced based on the viewpoint of conventional resin composition and molecular weight control, the viscoelasticity of the resin is lowered, and the fixing strength of the formed toner image is low. As the glossiness increased, gloss unevenness was likely to occur. In particular, when the print was folded, a decrease in fixing strength called crease fixing strength, at which the image at the fold position easily peeled off from the paper, was noticeable. From such a background, it has been studied to improve the crease fixing strength by adding a crosslinkable monomer to form a high molecular weight toner constituent resin (for example, see Patent Document 1).

However, although the above-mentioned technique has ensured the crease fixing strength, it has not been able to successfully form a toner image having an appropriate glossiness and no gloss unevenness that does not place a burden on the user's eyes. An image having a high glossiness is difficult to read due to the influence of reflected light, and in particular, places a burden on the eyes of a user who reads a character image. Therefore, the development of a toner compatible with low-temperature fixing that achieves both securing of crease fixing strength and improvement of image glossiness by forming resin particles by dissolving or dispersing polybutadiene in a polymerizable monomer at the time of toner production. (For example, refer to Patent Document 2).
JP 2003-173044 A JP 2007-133308 A

  With the toner disclosed in Patent Document 2, an appropriate crease strength is expressed even when fixing at a low temperature, and it is possible to realize toner image formation with good image quality without gloss unevenness. However, the toner requires a process of dissolving polybutadiene in the polymerizable monomer when forming the core resin, and requires a lot of production. In addition, there was a tendency that the amount of polybutadiene added was limited from the viewpoint of solubility and dispersibility in the polymerizable monomer.

  Under these circumstances, the present inventor replaced the technique for achieving both low-temperature fixability and improvement in glossiness by adding polybutadiene, and instead of adding polybutadiene or the like, the core-shell toner produced without adding polybutadiene has good gloss image quality. I wanted to find a technology that could form an image.

  The present invention can firmly fix a toner image at a low temperature, and the formed image does not have a strong gloss, and if it is a glossy image, it can form a uniform gloss image without unevenness. Another object of the present invention is to provide an electrophotographic image forming method. Specifically, even when the surface temperature of the heating roller is set to 90 ° C. to 140 ° C. and the toner image on the transfer material is fixed, the toner is peeled off from the bent portion when the fixed transfer material is bent. It is an object to obtain a good crease fixing strength without any problems. At the same time, an object of the present invention is to provide an image forming method in which a formed toner image does not have strong gloss or gloss unevenness and can be easily read without causing a burden on the eyes of the user.

  It has been found that the above problems can be solved by the configuration described below.

The invention described in claim 1
“In an image forming method including a step of fixing a toner image transferred onto a transfer body using a fixing device composed of a heating roller and a roller-like pressure body,
The toner forming the toner image has a core-shell structure in which a shell is coated around a core containing at least a resin and a colorant, and has an average circularity of 0.895 to 0.980. Yes,
The heating roller constituting the fixing device has an elastic layer having a rebound resilience of 30% to 70% and a thickness of 0.2 mm to 0.4 mm. Method. ].

  According to the present invention, it becomes possible to firmly fix a toner image at a lower temperature than before, and the toner image obtained at the same time has a finish in which the occurrence of gloss is suppressed, and the gloss is temporarily generated. The result was a uniform gloss with no unevenness. Specifically, the toner image obtained by fixing the toner image on the transfer material with the surface temperature of the heating roller of 90 ° C. to 140 ° C. may be peeled off from the bent portion even if the transfer material is folded. And good crease fixing strength can be obtained. Further, the formed toner image does not have strong gloss or uneven gloss and does not give a burden to the user's eyes, and can provide a print that is easy to read for a user who has many opportunities to output a character image. It became like.

  The present invention uses a fixing device having a heating roller having an elastic layer having a rebound resilience of 30% to 70% and a thickness of 0.2 mm to 0.4 mm, and an average circularity of 0.895 to 0.00. The present invention relates to an image forming method for fixing a toner image formed with toner having a core-shell structure of 980.

  With the image forming method according to the present invention, the fixed toner image has a stable strength that does not peel off even when it is bent, and has good image quality that is free of unevenness and burdens the eyes of the user, that is, glossy A toner image that solves the problem can be obtained.

  As described above, one of the reasons that a toner image having stable fixing strength and good glossiness can be produced is that fixing can be performed without applying excessive pressure to the toner. . In other words, it is considered that the heating roller having the elastic layer thickness and the rebound resilience specified does not make the toner image smooth and easily glossy even when a pressing force is applied from the heating roller during fixing. In other words, since the toner image is not crushed by the pressing force from the heating roller, the surface of the toner image after fixing maintains minute irregularities that diffusely reflect light, and as a result, the occurrence of gloss is suppressed, and the gloss is temporarily reduced. Even if there is, it seems that the thing with no unevenness has come to be obtained.

  In addition, by using a toner having an average circularity of 0.895 to 0.980 and a shape close to a circle, fixing can be performed with the contact area between the toner particles and the heating roller being minimized. This is considered to be one of the factors that cause excessive pressing force to be applied to the toner.

  In addition, by using a core-shell structure compatible with low-temperature fixing, the toner melts sufficiently with a small amount of heat, and the toner can adhere firmly to the transfer paper without applying a strong force. It is thought that it is one of.

  In this way, the present invention combines the surface characteristics of the heating roller and the shape characteristics of the toner that can be fixed at low temperature, so that it can be peeled even when the image is folded, with good gloss performance that does not impose a burden on the eyes of the user. It is considered that the stable fixing strength without any problem can be achieved at the same time.

  Hereinafter, the present invention will be described in detail.

  An image forming apparatus capable of performing the image forming method according to the present invention will be described. FIG. 1 is a schematic diagram showing an example of an image forming apparatus 10 equipped with a fixing device having a heating roller.

  In FIG. 1, reference numeral 50 denotes a photosensitive drum (photosensitive member) which is an image carrier, which has a structure in which an organic photosensitive layer is coated on a drum and a resin layer is coated thereon. Driven and rotated. Reference numeral 52 denotes a scorotron charging device (charging means) that uniformly charges the circumferential surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charging device 52, the peripheral surface of the photosensitive member can be discharged by performing exposure by the pre-charging exposure unit 51 using a light emitting diode or the like in order to eliminate the history of the photosensitive member in the previous image formation.

  After uniform charging of the photoreceptor, image exposure based on the image signal is performed by an image exposure device 53 that is an image exposure unit. The image exposure apparatus 53 in this figure uses a laser diode (not shown) as an exposure light source. An electrostatic latent image is formed by scanning on the photosensitive drum with the light whose optical path is bent by the reflecting mirror 532 through the rotating polygon mirror 531 and the fθ lens.

  Next, the electrostatic latent image is developed by a developing device 54 as developing means. In the image forming apparatus of FIG. 1, a developing device 54 containing toner specified in the present invention as a developer is disposed on the periphery of the photosensitive drum 50. In the developing device 54, a developing sleeve (developing roller) 541 also called a developer carrying member that rotates while holding toner as a developer is provided, and the developer held on the developing sleeve 541 is the photosensitive drum 50. Supplied on top. In addition to supplying the toner on the developing sleeve 541 in contact with the surface of the photosensitive drum 50, the developer can be supplied to the photosensitive drum 50 by flying the developer from the developing sleeve 541. In this way, by supplying the developer on the developing sleeve 541 onto the photosensitive drum 50, the electrostatic latent image on the photosensitive drum 50 can be developed into a toner image.

In addition to the developing sleeve 541 in the developing device 54, a supply roller 543 that supplies the developer to the developing sleeve 541, a developer agitating / conveying member 544 that stirs and conveys the developer in the device, and a conveyance amount regulation (not shown). A member 542 and the like are included. By these constituent members, the developer is stirred and transported in the developing device, and the charged developer is supplied onto the developing sleeve 541. The developer supply amount to the developing sleeve 541 is controlled by a conveyance amount regulating member 542 (not shown). The developer transport amount varies depending on the linear velocity of the photoreceptor used and the specific gravity of the developer, but is generally in the range of ²⁰ to 200 mg / cm ² . The diameter of the developing sleeve (developing roller) is 5 to 20 mm, preferably 18 to 7 mm to 18 mm, and the linear velocity of the developing sleeve is preferably 200 to 1800 mm / sec.

  Reference numeral 70 in the figure denotes a process cartridge having a structure in which the photosensitive member 50, the charging device 52, the transfer device 58, the separation device 59, and the cleaning device 62 are integrated. The process cartridge 70 is attached to and detached from the image forming apparatus. It has a possible structure.

  As described above, the electrostatic latent image formed on the photoconductive drum 50 is developed with the toner supplied from the developing sleeve 541 in the developing device 54 disposed in the vicinity of the photoconductive drum 50 to be a toner image. It becomes.

  After the toner image is formed on the photoconductive drum 50, the charge on the photoconductive drum 50 is discharged by a neutralizing unit (not shown), and the toner image on the photoconductive drum 50 is transferred onto the transfer paper P by the transfer device 58. Is done. The transfer paper P is transported by the transport roller 57 from the paper feed cassette, and a charge having a polarity opposite to that of the toner is applied by the transfer device 58, and the toner is transferred onto the transfer paper P by the electrostatic action of the charge having the reverse polarity. The image is transferred.

  The transfer paper P onto which the toner image has been transferred is separated from the photosensitive drum 50 via the separation device 59 and then conveyed to the fixing device 60 by the conveyance belt 71. The fixing device 60 includes a heating roller, a pressure roller, and the like.

  By such a procedure, the electrostatic latent image formed on the photosensitive drum 50 of the image forming apparatus 1 is visualized as a toner image, and the formed toner image is transferred and fixed onto the transfer paper P. As a result, a printed matter is produced.

  The fixing device used in the present invention will be further described. The fixing device used in the present invention includes a heating roller and a roller-shaped pressure member, and the heating roller has a rebound resilience of 30% to 70% and a thickness of 0.2 mm to 0.4 mm. Having an elastic layer. Thus, the fixing device used in the present invention is a so-called heat roller fixing type fixing device. In the present invention, a heating roller having a roller-shaped pressure member and an elastic layer having a rebound resilience of 30% to 70% and a thickness of 0.2 mm to 0.4 mm is used. The formed toner image is melted and fixed.

  In the present invention, by specifying the impact resilience and thickness of the elastic layer constituting the heating roller, the toner image formed with the core-shell structure toner compatible with low-temperature fixing is firmly fixed, and good gloss performance is exhibited. I was able to do it. In other words, the heating roller having the above-described configuration enables fixing of a toner image having a strength that does not detach from the transfer paper and having an appropriate glossiness without unevenness. As described above, by using the fixing device having the above-described configuration, fixing can be performed while uniformly applying an appropriate pressure to the toner image formed with the core-shell toner.

  In the present invention, the thickness of the elastic layer constituting the heating roller is set to 0.2 mm or more and 0.4 mm or less, so that the toner image after the fixing is not detached from the transfer paper and the user can have an appropriate fixing strength. It seems to give moderate glossiness that does not impose a burden on the eyes. That is, if the thickness of the elastic layer constituting the heating roller is less than 0.2 mm, the pressure applied to the toner image becomes too strong, and there is a concern that a strong glossiness is generated in the toner image after fixing. . On the other hand, when the thickness of the elastic layer exceeds 0.4 mm, it is expected that sufficient pressure cannot be applied to the toner image, and sufficient fixing strength cannot be applied to the toner image.

  Further, in the present invention, by setting the rebound resilience of the elastic layer constituting the heating roller to be 30% or more and 70% or less, the applied pressure during fixing is uneven with respect to the transfer material on which the toner image is transferred via the elastic layer. The fixing strength is evenly distributed over the transfer material. As a result, it is considered that uniform fixing without unevenness can be realized on the transfer material. That is, when the rebound resilience is less than 30%, the fixing roller cannot absorb excessive pressure, so that a state in which strong pressure is locally applied to the transfer material is formed, and uniform fixing cannot be performed, and gloss is not achieved. It is thought that unevenness is likely to occur. On the other hand, if the rebound resilience exceeds 70%, the fixing roller absorbs an unnecessarily large pressure, making it impossible to fix the transfer paper with sufficient strength at the nip, and the image after fixing is easily detached. It is considered to be.

  Here, the rebound resilience will be described. In the image forming method according to the present invention, the heating roller constituting the fixing device is specified by the rebound resilience. The rebound resilience referred to in the present invention is an index representing energy absorbed by a material at the time of so-called object collision. Specifically, by observing that an object with a predetermined mass falls from a predetermined height and collides with a test piece and the object bounces, the energy ratio of the object at the time of collision and bounce is calculated and calculated. This ratio is called the rebound resilience.

  The rebound resilience referred to in the present invention can be measured and calculated by applying the method defined by JIS K 6255, which is a rebound resilience test method for vulcanized rubber and thermoplastic rubber. As a rebound resilience test method standardized by JIS K 6255, the measurement by the Lüpke rebound resilience test or the trypso rebound resilience test is mentioned. Here, the Rüpke-type rebound resilience test is a test method for calculating the rebound resilience from the height obtained at the time of drop and rebound using a pendulum, and the Trypso rebound resilience test is performed at the time of dropping using a solid disk and This is a test method for calculating the rebound resilience from the angle obtained at the time of rebound.

  The rebound resilience defined by JIS K 6255 can be calculated from the following equation. That is, when an object with a load W is dropped from the height of h1, collides with the test piece, and bounces back to the height of h2, the energy E absorbed in the test piece and the rebound resilience R (%) of the test piece Is expressed by the following equation.

Energy; E = W (h1-h2)
Rebound resilience: R (%) = (h2 / h1) × 100
From the above formula, the resilience modulus R can be calculated by measuring the heights h1 and h2 at the time of dropping and at the time of rebounding. Here, when the resilience elastic modulus R = 0 (%), the falling object is stationary without rebounding, and when R = 100 (%), the falling object rebounds to the same position as the falling position. It means to come. Moreover, (100-R) (%) represents the rate converted into thermal energy by the internal friction of the test piece.

  An outline of the Lübke-type rebound resilience test method capable of measuring the rebound resilience of the heating roller used in the present invention will be described. FIG. 2 is a schematic view of a Lübke type test apparatus.

  In the Lüpke-type test apparatus, a steel rod having a diameter of 12.5 mm and a length of 356 mm (mass 350 g) is suspended horizontally with four threads. The length of the thread for hanging the rod is 2 m. In this state, the iron bar is caused to collide with the heating roller, which is the test object, installed vertically from the lateral direction. Specifically, the collision speed of the iron bar is set to 1.4 m / s, and the drop height h1 is set to 100 mm for collision. Then, the rebound resilience can be measured by measuring the stationary position (rebound height) h2 of the iron bar bounced back by the collision. The test is performed at a temperature of 23 ° C.

  Next, the fixing device that can be used in the present invention will be described in detail. As described above, the fixing device that can be used in the present invention includes a heating roller and a roller-shaped pressure member, and has a rebound elastic modulus of 30% to 70% and a thickness of 0.2 mm to 0.4 mm. If it can mount the heating roller which has an elastic layer which has thickness, it will not be limited in particular.

  FIG. 3 is a sectional view of a type having a heating roller and a pressure roller as an example of a fixing device usable in the present invention. The fixing device 60 shown in FIG. 3 has a heating roller 71 and a pressure roller 72 in contact with the heating roller 71. In FIG. 3, T is a toner image formed on a transfer material (transfer paper) P.

  In the heating roller 71, a coating layer 82 corresponding to the elastic layer in the present invention is formed on the surface of the cored bar 81, and a heating member 75 made of a linear heater is disposed in the cored bar 81. As the heating member 75, for example, a halogen heater or the like is a suitable one.

  The cored bar 81 is made of metal and has an inner diameter of 10 to 70 mm. Although the metal material which comprises the metal core 81 is not specifically limited, For example, metals, such as iron, aluminum, copper, and these alloys can be mentioned. The thickness (thickness) of the cored bar 81 is preferably 0.1 to 15 mm, and the material and thickness are set from the viewpoint of balancing the reduction in thickness accompanying the demand for energy saving and the securing of strength as a heating roller in a balanced manner. be able to. For example, in order to achieve the same strength as that of an iron cored bar having a thickness of 0.57 mm with an aluminum cored bar, the thickness needs to be 0.8 mm.

  The covering layer 82 corresponding to the elastic layer in the present invention can be formed of a known elastic body. The elastic body that constitutes the covering layer 82 is not particularly limited as long as it has a rebound resilience of 30% or more and 70% or less when it is an elastic layer having a thickness of 0.2 mm or more and 0.4 mm or less that constitutes a heating roller. It is not something. Specifically, silicone rubber and silicone sponge rubber are one of the representative examples. That is, the silicone rubber can have a rebound resilience in the above range when it is formed into an elastic layer having a thickness of 0.2 mm or more and 0.4 mm or less, and can exhibit good heat resistance.

  Silicone rubber is formed by polymerizing a monomer by an addition reaction with a platinum catalyst. Since a polymer can be formed without generating a by-product, impurities are present in the polymer. Since it is not included, an elastic layer having excellent dimensional stability can be formed.

Specific examples of the silicone rubber (silicone sponge rubber) include the following.
(1) RTV (Room Temperature Vulcanization; room temperature curing type) silicone rubber: It has a liquid or paste-like form, and is cast into a mold and undergoes a curing reaction at a temperature of 50 ° C. or less to obtain a molded product (2) HTV (High Temperature Vulcanization; high temperature curing type) Silicone rubber: Also called millable silicone, composed of a high viscosity compound, compounded with a vulcanizing agent (catalyst) and molded at a temperature of 130 ° C or higher. Is obtained. Conventionally existing type (3) LTV (Low Temperature Vulcanization) silicone rubber: a liquid or paste form located between room temperature vulcanization type (RTV) and high temperature vulcanization type (HTV) The molded product is obtained by pouring into a mold and performing a curing reaction at a temperature of 50 ° C to 130 ° C.

  The covering layer 82 can be formed by forming a known fluororesin layer on the elastic body surface. Specific examples of the fluororesin include polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). In this way, by providing a fluororesin layer on the surface of the coating layer 82, it becomes difficult for scratches due to paper dust or the like to adhere to the surface of the coating layer 82, so the problem of image contamination caused by toner adhering to the scratched portion is avoided. can do.

  The generation of scratches can be avoided by setting the thickness of the fluororesin layer formed on the surface of the covering layer 82 to 5 μm to 30 μm. Examples of the method of forming the fluororesin layer include a known fluororesin coating method or a method of covering the fluororesin tube from above the elastic body.

  Next, the pressure roller 72 is formed by forming a coating layer 84 made of an elastic body on the surface of the cored bar 83. The elastic body constituting the covering layer 84 is not particularly limited, and examples thereof include various soft rubbers such as polyurethane rubber and silicone rubber, and sponge rubber. Among these, the above-described silicone rubber and silicone sponge rubber are preferable. The thickness of the coating layer 84 is preferably 0.1 to 30 mm, and more preferably 0.1 to 20 mm.

  Moreover, in this invention, it is preferable to set the surface temperature of the heating roller 71 to 90-150 degreeC, and 90-130 degreeC is more preferable. The nip width of the heating roller 71 is preferably 8 to 40 mm, and more preferably 11 to 30 mm. Further, the fixing linear velocity of the fixing device 60 is preferably set to 80 to 640 mm / sec.

  Next, another embodiment of the fixing device that can be used in the present invention will be described.

  The fixing device shown in FIG. 4 uses a type of pressure roller called a soft roller, and a soft rubber member having a rubber hardness of 30 to 50 Hs (JIS, A rubber hardness) is used for the pressure roller. ing.

  4 has a heating roller 71 and a pressure roller 72 as in the fixing device shown in FIG. 3, and has a halogen lamp 75 as a heating member inside the heating roller 71. In the fixing device 60 shown in FIG. 4, since the pressure roller 72 is soft, a nip portion N is formed between the heating roller 71 and the pressure roller (hereinafter also referred to as a soft roller) 72, and the nip portion N is interposed therebetween. Thus, heat and pressure are applied to the transfer material, and the toner image on the transfer material P can be fixed.

  The heating roller 71 constituting the fixing device 60 of FIG. 4 has basically the same specifications as the heating roller constituting the fixing device 60 of FIG. That is, the covering layer 82 corresponding to the elastic layer in the present invention is formed on the surface of the cored bar 81, and the cored bar 81 has a structure in which a halogen heater 75 as a heating member is disposed. The covering layer 82 is composed of an elastic layer having a thickness of 0.2 mm or more and 0.4 mm or less and a rebound resilience of 30% or more and 70% or less. It is also possible to make it.

  The pressure roller 72 has a cylindrical cored bar 83 made of iron or the like and having a thickness of 5 mm to 10 mm, and a coating layer 84 that imparts a certain thickness and elasticity to the outer peripheral surface of the cored bar 83. The covering layer 84 is made of, for example, a soft material having a thickness of 3 mm to 15 mm and a rubber hardness of 30 to 50 Hs (JIS, A rubber hardness).

  The elastic material constituting the covering layer 84 is not particularly limited as long as it can form a sufficient nip with the heating roller 71. Specifically, known rubber materials such as polyurethane rubber and the like, including the silicone rubber described in the coating layer 82 of the heating roller 71, can be used.

  A porous rubber material called sponge rubber, foamed rubber, or foam rubber is preferable as an elastic material constituting the coating layer 84 from the viewpoint of more reliably developing the curing of the present invention. Since these porous rubber materials have continuous or discontinuous gaps, the elasticity of the pressure roller is improved by the presence of the gaps, so that a larger nip width can be secured. Furthermore, by forming the coating layer 84 with a porous rubber material, the heat insulation property of air can be applied to the coating layer 84, so that the heat capacity of the pressure roller is improved and the efficiency is improved. Fixing can be realized. Examples of porous rubber materials including sponge rubber include silicone sponge rubber, neoprene sponge rubber, urethane foam, ethylene propylene sponge rubber, and nitrile sponge rubber.

  The fixing device 60 in FIG. 4 can fix the toner image in a state where a wide fixing nip formed between the pressure roller 72 and the heating roller 71 is secured. In other words, since a wide fixing nip can be secured, a wide contact area can be obtained between the fixing device and the transfer material, a long contact time can be secured, and the amount of heat provided during fixing can be used efficiently. The toner image can be fixed in a ready state. In particular, the effect is more prominently exhibited in a pressure roller in which the covering layer 84 is made of a porous rubber material or the like having continuous or discontinuous bubbles.

  That is, since the fixing device 60 in FIG. 4 has a large contact area between the transfer material and the fixing device, it can uniformly apply a uniform pressing force to the transfer material. It is preferable for producing a finished printed product with reduced gloss. Further, since the pressing force is uniformly applied to the transfer material without unevenness, a glossy image without unevenness can be formed. Further, since the contact time between the transfer material and the fixing device can be increased, it is advantageous for high-speed print production. Further, since it is difficult to apply a strong pressing force, the toner image is not easily collapsed at the time of fixing, and the resolution is maintained, which is advantageous for forming a high-resolution image such as a photographic image. Further, since the pressure roller 72 is made of a soft material, the transfer material is less likely to be wound during fixing, which is advantageous for stable continuous printing.

  According to the present invention, a toner image with improved gloss characteristics can be obtained by combining a fixing device having a heating roller having the above-described characteristics with a core-shell structure toner having an average circularity of 0.895 to 0.980. It is a thing. As described above, according to the present invention, fixing can be performed while leaving minute irregularities on the surface of the toner image, and light can be irregularly reflected on the minute irregularities on the surface of the toner image. It is thought that it came to be able to. Further, the pressing force applied from the fixing device is also suppressed, and it is considered that unevenness does not occur even if gloss is generated. With such a mechanism, it is presumed that in the present invention, the gloss of the toner image after fixing can be suppressed.

  The “glossiness of the toner image” as used in the present invention is a quantification of the degree of reflection of the toner image surface obtained when the toner image surface is irradiated with light under a predetermined condition. For example, the following procedure is used. Can be quantified. That is, an image portion in which an area area of 90% or more of the transfer material is covered with toner is measured according to “JIS Z8741 1983 Method 2” at an incident angle of 75 ° with a gloss measuring device (gross meter) “GMX-203”. The value measured by “Murakami Color Research Laboratory Co., Ltd.)” is the glossiness.

  In FIG. 5, the conceptual diagram of a glossiness measuring apparatus (gross meter) is shown. In the glossiness measuring apparatus, light is irradiated to the sample 72 from the light source 70 via the optical system 71. The reflected light from the sample 72 is received by the light receiver 74 through the optical system 73. S1 and S2 in the figure are slits. Α1 is the opening angle of the optical image, β1 is the opening angle in the vertical plane, α2 is the opening angle of the light receiver, and β2 is the opening angle in the vertical plane. The glossiness G is expressed by the following equation, where the specular reflected light beam from the surface of the sample 72 is φ and the reflected light beam from the standard surface is φs for the specified incident angle θ shown in the figure.

Glossiness G = (φ / φs) × (Glossiness of standard surface used)
Here, the glossiness of the standard surface used is 100.0. Accordingly, the glossiness is represented by a numerical value of 100 or less. That is, as the amount of reflected light increases, the value of the glossiness G becomes closer to 100. In the present invention, a toner image having a glossiness of 25 or less is maintained in a low glossy state. .

  Next, a toner having a core-shell structure with an average circularity of 0.895 to 0.980 used in the present invention will be described.

  The toner used in the present invention has an average circularity of 0.895 or more and 0.980 or less, and more preferably 0.920 or more and 0.970 or less. In the present invention, by setting the average circularity value of the toner to 0.895 to 0.980, fixing is performed without applying an excessive pressing force to the toner, and the toner image surface is not crushed. It is thought that the smoothing of can be avoided. That is, by using toner particles close to a circular shape having an average circularity in the above range, fixing is performed under a state where the contact area between the toner particles and the heating roller is close to the minimum. The closer the contact area between the two, the more difficult it is to apply an extra force to the toner, and the toner image is expected to be melted and fixed to the transfer paper without being crushed.

  In addition, toner having an average circularity in the above range exhibits appropriate fluidity, and even if the state of being subjected to a mechanical load for a long time in the image forming apparatus continues to be deformed or deteriorated. Can be prevented. As a result, a high-definition toner image can be stably formed over a long period.

  The average circularity of the toner is a value calculated by dividing the sum of the circularity of the toner defined by the following formula by the total number of toners.

Circularity = (perimeter of a circle having the same projection area as the toner image) / (perimeter of the toner projection image)
The average circularity of the toner can be calculated using, for example, a flow particle image analyzer represented by “FPIA-2100 (manufactured by Sysmex)”.

  Specifically, the toner is blended with an aqueous solution containing a surfactant, dispersed by ultrasonic dispersion for 1 minute, and then “FPIA-2100” is used to detect the HPF in the measurement condition HPF (high magnification imaging) mode. Measurement is performed at appropriate concentrations of several thousand to 10,000. Within this range, reproducible identical measurement values can be obtained.

  The average circularity of the toner having a core-shell structure can be set by the following procedure, for example, when the toner is prepared by an emulsion association method. That is, in the ripening step performed after agglomerating and fusing resin fine particles, etc., aging was performed while observing the average circularity of the particles using the flow type particle image analyzer described above, and the desired average circularity was obtained. This can be set by performing an operation to stop ripening.

  Next, the structure of the core-shell toner used in the present invention will be described. The toner according to the present invention has a core-shell structure in which a shell is formed by coating a resin on the surface of a core made of a resin containing at least a colorant. An example of the core-shell structure of the toner is shown in FIG. The toner T shown in FIG. 6 includes a core A made of a resin 2 containing a colorant 1 and a shell B formed by coating the resin 3 on the surface of the core A. In the toner T shown in FIG. 6, the description of rubber elastic particles having a breaking elongation of 100% or more and 800% or less, which is an essential constituent element of the present invention, is omitted in the core A.

  The toner T shown in FIG. 6A has a structure in which the shell B completely covers the surface of the core A. The toner used in the present invention is not limited to one having a structure in which the shell B completely covers the core A as shown in FIG. 6A. For example, as shown in FIG. A structure in which the shell B does not completely cover the core A and the core A is exposed in some places is also included.

  That is, the core-shell toner in the present invention refers to a toner having a structure in which 30% or more of the core surface is covered with the shell B. Further, in the present invention, the term “shell formation” is also used, but making the surface of the core A covered with 30% or more of the resin 3 which is a shell forming resin is called “shell formation”. Is.

  For example, the toner T shown in FIG. 6B shows a state in which the shell B covers 30% or more and less than 100%, preferably 50% or more and 95% or less of the surface of the core A. In addition, although the toner T in FIG. 6C has some unevenness on the surface of the core A, the average circularity of the toner T after the shell formation is increased due to a part of the shell B entering the core A. It becomes 0.895 or more and 0.980 or less. Further, the difference between the average circularity of the core A before the shell formation and the average circularity of the toner T is preferably 0.005 or more and 0.090 or less, and the toner T shown in FIG. The difference in average circularity is within the above range.

  The cross-sectional structure of the toner according to the present invention and the shell coverage on the core surface can be confirmed, for example, by observing with a transmission electron microscope (TEM), a scanning probe microscope (SPM), or the like. The scanning probe microscope (SPM) can evaluate the physical properties such as the hardness of the resin constituting the toner in addition to the observation of the sectional shape of the toner.

  A method for observing the cross-sectional structure of the toner with a transmission electron microscope (TEM) will be described. Regarding the cross-sectional structure of the toner, the method for observing the cross-sectional structure of the toner with a transmission electron microscope can observe the prepared sample from a photographed image, for example, by the following procedure.

  First, after sufficiently dispersing the toner in a room temperature curable epoxy resin, embedding and dispersing in a fine styrene powder having a particle size of about 100 nm, and then performing pressure molding to form a block containing the toner. Make it. If necessary, the prepared block is dyed with ruthenium tetroxide or osmium tetroxide if necessary, and then a microtome having diamond teeth is used to form a flake shape having a thickness of 80 to 200 nm. The sample for a measurement is produced.

  The measurement sample thus thinned is set on a transmission electron microscope (TEM), and the cross-sectional structure of the toner is photographed. At this time, the magnification of the electron microscope is preferably a magnification that allows the cross section of one toner to enter the field of view, and specifically about 10,000 times. Further, it is preferable that the number of toners to be photographed with a transmission electron microscope is at least 10 or more.

  Observation of the cross-sectional structure of the toner with a transmission electron microscope can be sufficiently handled by a model that is generally well known among those skilled in the art. For example, “LEM-2000 type (manufactured by Topcon)” And “JEM-2000FX (manufactured by JEOL Ltd.)”.

  The toner according to the present invention has a core-shell structure. When a photograph of the photographed cross-sectional structure is observed, a region where a colorant or the like is present and a region where these are not present are confirmed, and a boundary serving as an interface between the core and the shell. Can be confirmed.

  The coverage of the shell on the core surface is calculated by processing the captured image information with an image processing apparatus “Luzex F” (manufactured by Nireco) using a transmission electron microscope (TEM). That is, the area of the core region and the shell region of the photographed toner is calculated by the arithmetic processing using “Luzex F”, and the average coverage of the shell on the core surface is calculated from the cross-sectional structure photograph of at least 10 toners. Is possible.

  Next, a method for producing the toner used in the present invention will be described.

  The colored particles constituting the toner used in the present invention (toner particles before external addition treatment) have a core-shell structure in which a shell is formed by coating a resin on the surface of a core made of a resin containing at least a colorant. I have it. The method for producing the toner used in the present invention is not particularly limited, and can be produced by a conventional toner production method. That is, it can be produced by a so-called pulverization method in which a toner is produced through a kneading, pulverization, and classification process, or a so-called polymerization method in which a polymerizable monomer is polymerized and particles are formed while simultaneously controlling the shape and size. .

  Among them, the toner production by the polymerization method is a small-diameter toner that can form a desired toner while controlling the shape and size of the particles in the production process, and can faithfully reproduce a minute dot image. It is most suitable for making. From this point of view, it is preferable to prepare a toner by a polymerization method. Among them, resin particles of about 120 nm are formed in advance by an emulsion polymerization method or a suspension polymerization method, and particle formation is performed through a process of aggregating the resin particles. The emulsification association method to be performed can be said to be one of effective production methods.

Hereinafter, an example of preparing a toner having a core-shell structure by the emulsion association method will be described. In the emulsification association method, a toner is generally prepared through the following procedure. That is,
(1) Preparation process of resin fine particle dispersion for core formation (2) Preparation process of fine colorant particle dispersion (3) Aggregation / fusion process of resin particles for core (4) First aging process (5) Shelling process (6) Second aging step (7) Cooling step (8) Cleaning step (9) Drying step (10) External additive treatment step Hereinafter, each step will be described.

(1) Production process of resin fine particle dispersion In this process, a polymerizable monomer that forms the resin particles for the core is put into an aqueous medium and polymerized to form resin fine particles having a size of about 120 nm. It is a process. In this step, it is possible to form a resin fine particle containing a wax. In this case, the wax is dissolved or dispersed in a polymerizable monomer, and this is polymerized in an aqueous medium. Resin fine particles containing wax are formed.

(2) Colorant fine particle dispersion preparation step In this step, a colorant is dispersed in an aqueous medium to prepare a colorant fine particle dispersion having a size of about 110 nm.

(3) Aggregation and fusion process of core particles (core formation)
This step is a step of aggregating the aforementioned resin fine particles, colorant fine particles, and fine particles expressing rubber elasticity in an aqueous medium, and fusing these agglomerated particles to produce core particles. . In this step, after adding an alkali metal salt or an alkaline earth metal salt as an aggregating agent to an aqueous medium in which resin particles and colorant particles are mixed, the mixture is melted at a temperature equal to or higher than the glass transition temperature of the resin particles. Heating below the peak temperature causes the agglomeration to proceed and simultaneously fuses the resin particles.

  Specifically, the resin particles and the colorant particles produced by the above-described procedure are added to the reaction system, and a coagulant such as magnesium chloride is added to agglomerate the resin particles and the colorant particles at the same time. Particles are formed by fusing together. Then, when the particle size reaches the target size, a salt such as saline is added to stop aggregation.

(4) First aging step This step is a step of aging until the shape of the core becomes a desired shape by heat-treating the reaction system following the above-described aggregation / fusion step.

(5) Shelling step This step is a step of adding shell-forming resin particles to the core dispersion formed in the first aging step to form a shell on the core surface.

(6) Second aging step In this step, following the shelling step, the reaction system is heat-treated to strengthen the coating of the shell on the core surface, and until the colored particles have a desired shape. This is the process of aging.

(7) Cooling step This step is a step of cooling (rapid cooling) the dispersion of the colored particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

(8) Washing step This step includes a step of solid-liquid separation of the particles from the particle dispersion cooled to a predetermined temperature in the above step, and a surfactant or the like from the particles solid-liquid separated into wet cake-like aggregates. It consists of a cleaning process for removing deposits such as aggregating agents.

  In the washing treatment, the filtrate is washed with water until the electric conductivity of the filtrate reaches 10 μS / cm. Examples of the filtration method include a centrifugal separation method, a vacuum filtration method using Nutsche and the like, and a filtration method using a filter press and the like, and are not particularly limited.

(9) Drying step This step is a step of drying the washed particles to obtain dried particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like.

  The moisture of the dried particles is preferably 5% by mass or less, more preferably 2% by mass or less. In addition, when the dried particles are aggregated with weak interparticle attractive force, the aggregate may be crushed. Here, as the crushing treatment apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

(10) External additive treatment step This step is a step of preparing a toner by mixing the dried particles with an external additive as necessary. As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  The toner production method by the emulsion association method is one in which the toner is produced through the above-described steps. For the reasons described above, the core-shell structure toner according to the present invention is preferably produced by the emulsion association method.

  The method for producing the core-shell structure toner by the emulsion association method is carried out through the above steps, and as described above, the core-shell structure toner used in the present invention is preferably produced by the emulsion association method.

  Next, components such as resin, colorant, and wax that can be used in the toner used in the present invention will be described with specific examples.

  First, as a resin that can be used in the toner according to the present invention, in addition to the polymerizable monomer described above, a vinyl monomer shown in the following (1) to (10) can be used. is there. That is, examples of the resin that can be used in the toner according to the present invention include those obtained by polymerizing the following vinyl monomers alone or in combination.

(1) Styrene or styrene derivatives Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert- Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, etc. (2) Methacrylate derivatives Methyl methacrylate, methacryl Ethyl acetate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethyl methacrylate Aminoethyl, dimethylaminoethyl methacrylate, etc. (3) Acrylic acid ester derivatives Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, and the like.

(4) Olefins Ethylene, propylene, isobutylene, etc. (5) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate, etc. (6) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, etc. (7) Vinyl ketones Vinyl methyl ketone, Vinyl ethyl ketone, vinyl hexyl ketone, etc. (8) N-vinyl compounds N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, etc. (9) Vinyl compounds Vinyl naphthalene, vinyl pyridine, etc. (10) Acrylic acid or methacrylic acid Derivatives Acrylonitrile, methacrylonitrile, acrylamide, etc.

  Moreover, it is also possible to use combining the polymerizable monomer which has an ionic dissociation group as a polymerizable monomer which comprises resin. Examples of the ionic dissociation group include substituents such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group. The polymerizable monomer having an ionic dissociation group has these substituents.

  Specific examples of the polymerizable monomer having an ionic dissociation group are given below.

  Acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfone Acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate and the like.

  Furthermore, it is also possible to use a polyfunctional vinyl as a polymerizable monomer constituting the resin to obtain a resin having a crosslinked structure. Specific examples of the polyfunctional vinyls are listed below.

  Divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, and the like.

  Further, in the present invention, as the colorant that can be used in the toner, the following black colorants can be said to be representative colorants, but known colorants other than the black colorant can also be used. . Specific colorants are shown below.

  Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, and magnetic powder such as magnetite and ferrite.

  Examples of the colorant for magenta or red include C.I. I. Pigment red 1 to 23, C.I. I. Pigment red 30, C.I. I. Pigment red 31, C.I. I. Pigment red 32, C.I. I. Pigment red 37-41, C.I. I. Pigment red 48-58, C.I. I. Pigment red 60, C.I. I. Pigment red 63, C.I. I. Pigment red 64, C.I. I. Pigment red 68, C.I. I. Pigment red 81, C.I. I. Pigment red 83, C.I. I. Pigment red 87-90, C.I. I. Pigment red 112, C.I. I. Pigment red 114, C.I. Pigment Red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 150, C.I. I. Pigment red 163, C.I. I. Pigment red 166, C.I. I. Pigment red 170, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 184, C.I. I. Pigment red 202, C.I. I. Pigment red 206, C.I. I. Pigment red 207, C.I. I. Pigment red 209, C.I. I. Pigment red 222, C.I. I. Pigment red 238, C.I. I pigment red 269 etc. are mentioned.

  Examples of the colorant for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 162, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Further, as a colorant for green or cyan, C.I. I. Pigment blue 2, C.I. I. Pigment blue 3, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15; 2, C.I. I. Pigment blue 15; 3, C.I. I. Pigment blue 15; 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 17, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

  Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 2, 6, 14, 15, 16, 19, 21, 21, 33, 44, 56, 61, 77, 79, 80, 81, 82, the same 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc. can be used.

  These colorants can be used alone or in combination of two or more as required. The addition amount of the colorant is set in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

Next, the wax that can be used for the toner according to the present invention will be described. Examples of the wax that can be used in the toner according to the present invention include conventionally known waxes, and specific examples include the following.
(1) Long-chain hydrocarbon wax Polyolefin wax such as polyethylene wax and polypropylene wax, paraffin wax, sazole wax, etc. (2) Ester wax Trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrasteare Rate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitic acid, distearyl maleate, etc. (3) Amide wax Ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. (4) Dialkyl ketone waxes, distearyl ketone, etc. (5) Others Carnaubawack , Montan waxes, and the like.

  The melting point of the wax is usually 40 to 130 ° C, preferably 50 to 100 ° C, more preferably 60 to 90 ° C. By keeping the melting point of the wax within the above range, the heat-resistant storage stability of the toner is ensured, and at the same time, stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

  Next, the toner according to the present invention is prepared by adding particles such as inorganic fine particles and organic fine particles having a number average primary particle size of 40 to 800 nm as external additives (= external additives) in the production process. It is preferable.

  By adding the external additive, the fluidity and chargeability of the toner are improved, and the cleaning property is improved. The type of the external additive is not particularly limited, and examples thereof include the following inorganic fine particles, organic fine particles, and lubricants.

  A conventionally well-known thing can be used as an inorganic fine particle. Specifically, silica, titania, alumina, strontium titanate fine particles and the like can be preferably used. These inorganic fine particles may be hydrophobized if necessary. Specific examples of the silica fine particles include commercially available products R-805, R-976, R-974, R-972, R-812, R-809 manufactured by Nippon Aerosil Co., Ltd., HVK-2150, H- manufactured by Hoechst. 200, commercial products TS-720, TS-530, TS-610, H-5, MS-5 and the like manufactured by Cabot Corporation.

  As titania fine particles, for example, commercially available products T-805 and T-604 manufactured by Nippon Aerosil Co., Ltd., commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, JA- 1. Commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium Co., Ltd. Commercial products IT-S, IT-OA, IT-OB, IT- manufactured by Idemitsu Kosan Co., Ltd. OC etc. are mentioned.

  Examples of the alumina fine particles include commercial products RFY-C and C-604 manufactured by Nippon Aerosil Co., Ltd. and commercial products TTO-55 manufactured by Ishihara Sangyo Co., Ltd.

  As the organic fine particles, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. Specifically, homopolymers such as styrene and methyl methacrylate and copolymers thereof can be used.

  Further, it is possible to use a lubricant to further improve the cleaning property and the transfer property. Examples of the lubricant include metal salts of higher fatty acids such as the following. That is, salts of zinc stearate, aluminum, copper, magnesium, calcium, etc., zinc oleate, salts of manganese, iron, copper, magnesium, etc., zinc palmitate, salts of copper, magnesium, calcium, etc., linoleic acid And salts of zinc and calcium of ricinoleic acid.

  The addition amount of these external additives and lubricants is preferably 0.1 to 10.0% by mass with respect to the whole toner. Examples of the method for adding external additives and lubricants include methods using various known mixing devices such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer.

  The toner according to the present invention can be used as a two-component developer composed of a carrier and a toner, or as a non-magnetic one-component developer composed only of a toner.

  When the toner constituting the full-color toner kit according to the present invention is used as a two-component developer, for example, a full-color print can be created at a high speed using a tandem image forming apparatus described later. In addition, by selecting a resin or wax constituting the toner, it is possible to produce a full color print by so-called low-temperature fixing in which the paper temperature during fixing is about 100 ° C.

  In addition, carriers that are magnetic particles used when used as a two-component developer are conventionally known, for example, metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead. It is possible to use materials. Among these, ferrite particles are preferable. The carrier has a volume average particle size of preferably 15 to 100 μm, more preferably 25 to 80 μm.

  The toner image formed using the toner according to the present invention is transferred onto the transfer paper P and fixed on the transfer paper P by a fixing process. The transfer paper P here is a support for holding the toner image transferred from the image carrier, and is usually called an image support, a recording material, transfer paper, or paper. Specifically, various types of transfer such as plain paper and high-quality paper from thin paper to heavy paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. Materials.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to this.

1. 1. Preparation of “two-component developer (toner) 1-8” 1-1. Production of “Toner 1” (1) Production of “Core Forming Resin Fine Particle 1” “Core Forming Resin Fine Particle 1” was produced by the following procedure. That is,
(A) First-stage polymerization Anionic surfactant polyoxy (2) dodecyl ether sulfate sodium salt 4.0 parts by mass and ion-exchanged water in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction device 3000 parts by mass was added to prepare a surfactant solution. The surfactant solution was heated to 80 ° C. while stirring under a nitrogen stream. After raising the temperature to 80 ° C., an initiator aqueous solution in which 10 parts by mass of potassium persulfate (KPS) is dissolved in 400 parts by mass of ion-exchanged water is added to bring the liquid temperature to 75 ° C. Body mixed solution 1 "was added dropwise over 1 hour.

Styrene 532 parts by weight n-butyl acrylate 200 parts by weight Methacrylic acid 68 parts by weight n-octyl mercaptan 16 parts by weight After adding “monomer mixed solution 1” dropwise to the surfactant solution, the system is heated at 75 ° C. Polymerization (first stage polymerization) was carried out by heating and stirring for 2 hours to produce “resin fine particle dispersion a1”.

(B) Second-stage polymerization In a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction device, 3.0 parts by weight of anionic surfactant polyoxy (2) dodecyl ether sulfate sodium salt and ion-exchanged water A surfactant solution was prepared by charging 3060 parts by mass. The surfactant solution was heated to 80 ° C. while stirring under a nitrogen stream.

  After the temperature rise, 35 parts by mass of the resin fine particles a1 (in terms of solid content) and a mixed liquid containing the following compound are added, and a mechanical dispersion device “CLEAMIX (M Technique Co., Ltd.)” having a circulation path is added. Was mixed and dispersed for 30 minutes to prepare an emulsified particle (oil droplet) dispersion.

Styrene 100 parts by weight n-butyl acrylate 62 parts by weight Methacrylic acid 12 parts by weight n-octyl mercaptan 1.75 parts by weight Paraffin wax “HNP-57 (manufactured by Nippon Wax Co., Ltd.)” 96 parts by weight Next, the emulsified particle dispersion An initiator aqueous solution prepared by dissolving 5 parts by mass of potassium persulfate (KPS) in 100 parts by mass of ion-exchanged water was added to the system, and the system was heated and stirred at 80 ° C. for 1 hour to perform polymerization (first reaction). Two-stage polymerization) was performed.

(C) Third-stage polymerization After the second-stage polymerization, an initiator aqueous solution prepared by dissolving 5.45 parts by mass of potassium persulfate (KPS) in 220 parts by mass of ion-exchanged water is added, and the reaction system is added. At 80 ° C., and a mixture of the following compounds was added dropwise over 1 hour.

Styrene 294 parts by mass n-butyl acrylate 155 parts by mass n-octyl mercaptan 7.1 parts by mass After completion of dropping, the mixture was heated and stirred for 2 hours to conduct polymerization (third stage polymerization), and then the reaction system was 28 ° C. The resin fine particles were produced by cooling to a low temperature. The obtained resin fine particles are referred to as “core-forming resin fine particles 1”.

(2) Production of “shell forming resin fine particle dispersion” Prepared at the time of the first stage polymerization of “core forming resin fine particles 1” in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device. The same surfactant solution was prepared. While this surfactant solution was stirred at a stirring speed of 230 rpm under a nitrogen stream, the internal temperature was raised to 80 ° C. Thereafter, an initiator solution prepared by dissolving 10 parts by mass of potassium persulfate (KPS) in 400 parts by mass of ion-exchanged water is added to the surfactant solution, and the liquid temperature is set to 80 ° C. The body mixed solution "was added dropwise over 2 hours.

And it superposed | polymerized by heating and stirring process at 80 degreeC over 2 hours, and produced "resin fine particle 1 dispersion liquid for shell formation." The monomer mixed solution is
Styrene 624 parts by mass 2-ethylhexyl acrylate 120 parts by mass Methacrylic acid 56 parts by mass n-octyl mercaptan (NOM) 16.4 parts by mass.

(3) Preparation of “Colorant Dispersion 1” A solution prepared by stirring and dissolving 90 parts by mass of sodium dodecyl sulfate in 1600 parts by mass of ion-exchanged water was stirred, and carbon black “Regal 330R ( 420 parts by mass of “Cabot Corporation” was gradually added. Subsequently, a dispersion process was performed using a stirrer “CLEARMIX (M Technique Co., Ltd.)” to prepare “Colorant Dispersion Liquid 1”.

(4) Formation of core particles In a reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen introducing device,
"Core-forming resin fine particles 1" 360.6 parts by mass (solid content conversion)
Ion-exchanged water 1100 parts by mass “Colorant Dispersion 1” 200 parts by mass (in terms of solid content)
The liquid temperature was adjusted to 30 ° C. Thereafter, a 5 mol / liter aqueous sodium hydroxide solution was added to adjust the pH to 10.0.

  The reaction system was allowed to stir, and in this state, an aqueous solution prepared by dissolving 60 parts by mass of magnesium chloride hexahydrate in 60 parts by mass of ion-exchanged water was added to the reaction system over 10 minutes. After the addition, the mixture was allowed to stand for 3 minutes, and then the temperature increase was started. The system was heated to 80 ° C. over 60 minutes, and the particles were agglomerated while maintaining the temperature at 80 ° C. to grow the particles. In this state, the particle size of the aggregated particles was measured using “Multisizer 3 (manufactured by Beckman Coulter)”. When the volume-based median system (D50) reached 6.5 μm, an aqueous solution obtained by dissolving 40 parts by mass of sodium chloride in 160 parts by mass of ion-exchanged water was added to the reaction system to stop particle growth. Furthermore, the temperature of the reaction system was set to 70 ° C., and the mixture was heated and stirred to continue the fusion of the particles and perform the aging treatment. In this state, using a flow type particle image analyzer “FPIA-2100 (manufactured by Sysmex)”, aging treatment was performed while observing the average circularity of the particles, and when the average circularity reached 0.905, the mixture was heated and stirred. Core particles were produced by stopping.

(5) “Shelling process”
Next, to the dispersion of “core 1”,
"Shell-forming resin fine particles 1" 44 parts by mass (solid content conversion)
Further, an aqueous solution prepared by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water was added over 10 minutes.

  Subsequently, the temperature of the system was raised to 80 ° C., and stirring was continued for 1 hour to start fusion (shell formation) of “shell forming resin fine particles 1” to the surface of “core 1”. Thereafter, the system was heated to 75 ° C. and stirred for 20 minutes. Further, an aqueous solution in which 150 parts by mass of sodium chloride was dissolved in 600 parts by mass of ion-exchanged water was added to stop the shelling. Subsequently, the maturation treatment was continued while observing the average circularity of the particles using the flow type particle image analyzer “FPIA-2100 (manufactured by Sysmex)” at the temperature, and the average circularity reached 0.940. Then, the aging treatment was stopped by cooling to 30 ° C. under the condition of 8 ° C./min.

(6) “Washing process”
The produced colored particles are subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40 (manufactured by Matsumoto Kikai Co., Ltd.)” to produce a wet cake of “colored particles 1”. The ion-exchanged water was added for washing. The solid-liquid separation and washing by the basket type centrifugal separator were repeated until the electric conductivity of the filtrate reached 5 μS / cm or less.

(7) "Drying process"
The wet cake prepared when the electrical conductivity of the filtrate was 5 μS / cm or less was crushed, and the water content was reduced to 0.5 mass% using “flash jet dryer (manufactured by Seishin Enterprise Co., Ltd.)”. Drying treatment was performed to obtain “colored particles 1” having a core-shell structure. The shell coverage on the “colored particle 1” surface was evaluated and found to be 98%.

(8) “External additive treatment process”
By adding 1% by mass of hydrophobic silica (number average particle size = 12 nm, hydrophobization degree = 68) to the “colored particle 1”, and processing with “Henschel mixer (Mitsui Miike Chemical Co., Ltd.)”, “Toner 1” having an average circularity of 0.940 was produced.

1-2. Preparation of “Toners 2 to 8” (1) Preparation of “Toner 2” In the core formation of “Toner 1”, the aging treatment after addition of the sodium chloride aqueous solution is performed until the average circularity of the core particles becomes 0.925. “Toner 2” was prepared in the same procedure except that the aging treatment after the shelling step was performed until the average circularity of the particles reached 0.960.

(2) Production of “Toner 3” In the core formation of “Toner 1”, the aging treatment after addition of the sodium chloride aqueous solution is performed until the average circularity of the core particles reaches 0.890, and the aging treatment after the shelling step. The “Toner 3” was prepared in the same procedure except that the average circularity of the particles was 0.920.

(3) Preparation of “Toner 4” In the core formation of “Toner 1”, the aging treatment after adding the sodium chloride aqueous solution is performed until the average circularity of the core particles reaches 0.940, and the aging treatment after the shelling step. “Toner 4” was prepared in the same procedure except that the average circularity of the particles was 0.970.

(4) Production of “Toner 5” In the core formation of “Toner 1”, the aging treatment after adding the sodium chloride aqueous solution is performed until the average circularity of the core particles becomes 0.872, and the aging treatment after the shelling step. A “toner 5” was prepared in the same procedure except that the average circularity of the particles was 0.895.

(5) Preparation of “Toner 6” In the preparation of “Toner 4”, “Toner 6” was prepared in the same procedure except that the aging treatment after the shelling step was performed until the average circularity of the particles reached 0.980. Produced.

(6) Preparation of “Toner 7” In the preparation of “Toner 4”, “Toner 7” was prepared in the same procedure except that the aging treatment after the shelling step was performed until the average circularity of the particles reached 0.990. Produced.

(7) Preparation of “Toner 8” In the preparation of “Toner 5”, “Toner 8” was prepared in the same procedure except that the aging treatment after the shelling step was performed until the average circularity of the particles reached 0.885. Produced.

(8) Production of “two-component developer 1-8” “toner 1-8” produced by the above procedure was mixed with a ferrite carrier having a volume average particle diameter of 60 μm coated with a silicone resin, so that the toner concentration was 6. %, “Two-component developers 1 to 8” were produced.

2. Production of “Fixing devices 1 to 13” “Heat rollers 1 to 10” of a fixing device specification of a commercially available monochrome digital printer “bizhub Pro 1050 (manufactured by Konica Minolta Business Technologies, Inc.)” are produced by the following procedure. Fixing devices equipped with the heated rollers were designated as “fixing devices 1 to 10”. As shown in Table 1, the fixing device uses a pressure roller having a structure shown in FIG. 3 that is originally mounted on the printer, and a device using a pressure roller having a structure shown in FIG. Prepared. That is, the pressure roller shown in FIG. 4 has a coating layer 84 formed using a commercially available silicone sponge rubber, which is a porous rubber material, and a nip is formed between the heating roller and the width that can be confirmed with the naked eye. It is a thing. On the other hand, the pressure roller having the structure shown in FIG. 3 is one in which the coating layer 84 is formed using a commercially available silicone rubber having no gap, and forms a nip in contact with the heating roller in a line.

(1) Production of “heating rollers 1 to 4” A commercially available sponge having a rebound elastic modulus defined by JIS K 6255 of 30% on the surface of an aluminum alloy core for a heating roller that is originally mounted on the printer. An elastic layer having a thickness of 1 mm was formed from a silicone rubber, and the elastic layer was polished by a known method to produce “heating rollers 1 to 3” having a thickness of 0.2 mm, 0.4 mm, and 0.6 mm. In addition, when the rebound resilience of the produced “heating rollers 1 to 3” was measured, all were 30%.

(2) Manufacture of “heating rollers 4-6” In the manufacture of “heating rollers 1-3,” a commercially available sponge-like silicone rubber having a rebound resilience of 70% was used. A 1 mm elastic layer was formed. Next, the elastic layer was polished by a known method, and “heating rollers 4 to 6” having thicknesses of 0.1 mm, 0.2 mm, and 0.4 mm were manufactured in the same procedure except that. The rebound resilience of the produced “heating rollers 4 to 6” was measured and found to be 70%.

(3) Production of “heating roller 7” A commercially available sponge-like silicone having a rebound elastic modulus defined by JIS K 6255 of 40% on the surface of an aluminum alloy core for heating roller that is originally mounted on the printer. An elastic layer having a thickness of 1 mm was formed from rubber, and the elastic layer was polished by a known method to produce “heating roller 7” having a thickness of 0.4 mm. The rebound resilience of the produced “heating roller 7” was measured and found to be 40%.

(4) Production of “heating roller 8” A commercially available sponge-like silicone having a rebound elastic modulus defined by JIS K 6255 of 60% on the surface of an aluminum alloy core for a heating roller originally mounted on the printer. An elastic layer having a thickness of 1 mm was formed from rubber, and the elastic layer was polished by a known method to produce “heating roller 8” having a thickness of 0.2 mm. The rebound resilience of the produced “heating roller 8” was measured and found to be 60%.

(5) Production of “heating roller 9” A commercially available sponge-like silicone having a rebound elastic modulus defined by JIS K 6255 of 25% on the surface of an aluminum alloy core for heating roller that is originally mounted on the printer. An elastic layer having a thickness of 1 mm was formed from rubber, and the elastic layer was polished by a known method to produce a “heating roller 9” having a thickness of 0.4 mm. The rebound resilience of the manufactured “heating roller 9” was measured and found to be 25%.

(6) Production of “heating roller 10” A commercially available sponge-like silicone having a rebound elastic modulus defined by JIS K 6255 of 80% on the surface of an aluminum alloy core for heating roller that is originally mounted on the printer. An elastic layer having a thickness of 1 mm was formed from rubber, and the elastic layer was polished by a known method to produce “heating roller 10” having a thickness of 0.2 mm. The rebound resilience of the produced “heating roller 10” was measured and found to be 80%.

  Table 1 shows “fixing devices 1 to 13” formed by combining the produced “heating rollers 1 to 10” and the pressure roller having the structure shown in FIG.

3. Evaluation Experiment A developing device filled with each of the above-mentioned “two-component developers 1 to 8” and a fixing device loaded with the above “heating rollers 1 to” were combined with a commercially available monochrome digital printer “bizhub Pro 1050 (Konica Minolta Business Technologies, Inc.). ))). As shown in Table 2, the evaluation was performed by combining “two-component developers 1 to 8” and “fixing devices 1 to 13”.

  A heating roller having an average circularity of 0.895 to 0.980 and a heating roller constituting the fixing device having an elastic layer thickness of 0.2 to 0.4 mm and a rebound resilience of 30 to 70% m The combination with the fixing device used was Examples 1 to 10, and the others were Comparative Examples 1 to 7. The evaluation was performed for low temperature fixing property, crease fixing strength, document offset property, glossiness of toner image and occurrence of gloss unevenness.

<Low temperature fixability>
The fixable temperature was calculated by the following procedure to evaluate the low temperature fixability. The fixable temperature is a fixing temperature at which the fixing rate is 90% or more.

Specifically, in a normal temperature and normal humidity (20 ° C., 50% RH) environment, the surface temperature of the fixing belt was changed from 100 to 160 ° C. in increments of 5 ° C., and a solid image of 2.5 cm square (toner adhesion amount 0). .3 mg / m ² ) print was produced. The fixing rate of each produced solid image was measured by a mending tape peeling method, a fixing temperature at which the fixing rate was 90% or more was determined, and the temperature was evaluated as a fixable temperature.

Hereinafter, the mending tape peeling method will be described.
(A) The absolute reflection density D ₀ of the toner image produced under the setting condition in which the toner adhesion amount of the solid black image of 2.5 cm square on the transfer paper is 0.3 mg / m ² is measured.
(B) “Mending tape (manufactured by Sumitomo 3M: No.810-3-12)” is lightly applied to the toner image.
(C) Rub the tape over 3.5 times with a pressure of 1 kPa.
(D) The tape is peeled off under the conditions of a peel angle of 180 ° and a peel strength of 2N.
(E) The absolute reflection density D ₁ after peeling is measured.
(F) The fixing rate is calculated from the absolute reflection densities D ₀ and D ₁ . The fixing rate is the following formula: fixing rate (%) = (D ₁ / D ₀ ) × 100
It is calculated from. The absolute reflection density was measured using a reflection densitometer “RD-918 (manufactured by Macbeth)”. Those having a fixable temperature of less than 150 ° C. were accepted, and particularly those having a fixable temperature of less than 130 ° C. were evaluated as excellent.

<Fold crease strength>
After the printing of 30,000 sheets after the replacement of the toner storage portion, the heating roller surface temperature was changed to 90 ° C., 105 ° C., and 125 ° C., and the fixing rate of the toner image at the crease on the print was evaluated. Specifically, when the solid image portion of the print was bent toward the inner surface, the degree of toner peeling at the bent portion was evaluated as the fixing rate.

  The measurement method is to fold the solid image part (image density is 0.8) with the image side inward, rub it with a finger 3 times, open the image, and wipe it 3 times with “JK Wiper (Cresia Co., Ltd.)” The value calculated from the following equation from the image density before and after folding the crease portion of the solid image.

Fixing rate (%) = (image density after folding) / (image density before folding) × 100
From the obtained fixing rate, the crease fixing strength was evaluated as follows, and a crease fixing rate of 80% or more was determined to be acceptable.

<Document offset>
The document offset property is evaluated by setting the temperature of the heating belt to 130 ° C., and printing two sheets of the same test image as described above, and superimposing the image surface (print surface) and the non-image surface (back surface) on a glass plate. And a weight equivalent to 7.8 kPa was placed on the overlapped portion and left standing in an environment of 60 ° C. and 50% RH for one week. After standing, the two overlapped sheets were peeled off, and the degree of image defect of the printed images peeled off by visual observation was ranked in the following four grades “R1” to “R4” and evaluated. Ranks “R3” and “R4” are accepted.

“R1”: Level where two sheets stick together and difficult to peel off “R2”: Level where image transfer is seen on the back side when two sheets are peeled off “R3”: Although gloss reduction in the image area is seen, Acceptable level with almost no image defects (image transfer on the back side) “R4”: a good level where no image defects or image transfer are seen in both the image area and the non-image area.

<Glossiness of toner image>
Evaluation was performed using printed materials prepared at the fixing temperature. Ten A4 plate samples each having an area of 90% or more of the image support covered with toner were prepared and bound in a booklet form. After repeating the work of flipping the sample bound in a booklet shape five times, the glossiness of the fifth sheet was measured. The glossiness was measured using a gloss meter “GMX-203 (Murakami Color Research Laboratory Co., Ltd.)” based on the above-mentioned “JIS Z8741 1983 Method 2”. The thing of 20 or more and 50 or less was set as the pass, and the thing of 30-40 was especially excellent.

<Gloss unevenness>
Using art paper (manufactured by Mitsubishi Paper Industries Co., Ltd., Tokishi Art) as a recording medium, the printed solid image was evaluated visually or with a loupe as follows, and ま た は or ○ was accepted. That is,
A: Gloss unevenness cannot be detected at all. ○: Gloss unevenness cannot be detected at all unless magnified with a loupe. X: Streaky gloss unevenness can be detected visually.

  The results are shown in Table 2.

  As shown in Table 2, in Examples 1 to 10 satisfying the configuration of the present invention, the formed toner images had good fixing strength and suppressed generation of glossiness. Further, no gloss unevenness was observed when an image having gloss was formed. As described above, it is confirmed from the results of Examples 1 to 10 that the image forming method having the configuration of the present invention exhibits the effects of the present invention, and the effects of the present invention are not sufficiently exhibited. It was confirmed that there was a clear difference in performance between Comparative Examples 1 to 7.

1 is a schematic view of an image forming apparatus in which a fixing device having a heating roller can be mounted. It is the schematic of a Lübke type testing apparatus. FIG. 3 is a cross-sectional view of a fixing device having a heating roller and a pressure roller. It is sectional drawing of other embodiment of the fixing device which has a heating roller and a pressure roller. It is a conceptual diagram of a glossiness measuring device (gross meter). FIG. 4 is a schematic diagram illustrating an example of a toner having a core-shell structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Colorant 2, 3 Resin 10 Image forming apparatus 50 Photosensitive drum 54 Developing apparatus 541 Developing sleeve (developing roller)
60 fixing device 71 heating roller 82 coating layer (elastic layer)
72 Pressure roller T Toner A Core B Shell

Claims (1)

In an image forming method including a step of fixing a toner image transferred onto a transfer body using a fixing device composed of a heating roller and a roller-like pressure body,
The toner forming the toner image has a core-shell structure in which a shell is coated around a core containing at least a resin and a colorant, and has an average circularity of 0.895 to 0.980. Yes,
The heating roller constituting the fixing device has an elastic layer having a rebound resilience of 30% to 70% and a thickness of 0.2 mm to 0.4 mm. Method.

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