JP2010128080A - Elastic developing roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller that forms a uniform-density image by decreasing uneven surface roughness of the developing roller, suppresses an image stripe by suppressing deformation and local reduction of the surface roughness caused by long-term press-contact, and maintains a high-quality image over a long term, in a contact-developing type image forming apparatus and a cartridge for electrophotography. <P>SOLUTION: Elastic resin particles of core shell structure are dispersed in a surface layer of the developing roller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing roller used in an image forming apparatus, an electrophotographic process cartridge using the same, and an image forming apparatus.

  In recent years, in electrophotographic image forming apparatuses (hereinafter referred to as image forming apparatuses) such as copying machines and laser beam printers, colorization and high image quality have progressed. Accordingly, in the development process, a contact development method has been proposed in which development is performed by uniformly pressing an elastic developing roller (hereinafter referred to as a developing roller) to which a developer is attached to a photosensitive member. In order to obtain a uniform and high-density image in the contact development method, the developing roller must be made of a low-elastic material and ensure a uniform pressure contact width to the photosensitive member. Furthermore, a uniform rough surface is formed on the surface of the developing roller, and a uniform gap is secured between the developer amount regulating member (hereinafter referred to as a developing blade), and a uniform and thin layer developer is formed on the surface of the developing roller. It is necessary to form an adhesion layer. Therefore, a method is used in which resin particles for roughening are dispersed on the surface of the developing roller to form a surface having a uniform roughness.

However, in a contact development type image forming apparatus, the developing roller is stationary for a long period of time due to the developing blade, the photoconductor, etc. during the period from manufacture to use for image formation, or during the period when image output is suspended. Continue to be pressed in the state. As a result, a dent is generated on the surface of the pressure contact portion of the developing roller, and further, the surface roughness of the pressure contact portion is reduced, the developer adhesion state is locally changed, and an image defect (image streak) of the developing roller cycle on the image. There is concern about the problem of For this reason, Patent Document 1 discloses a developing roller in which a material having a low compression set, such as a silicone resin or a urethane resin, is used for the developing roller resin layer, the surface layer binder resin, and the resin particles for roughening.
JP 09-269648 A

  However, if a material with low elasticity and low compression set is selected for both the binder resin on the developing roller surface layer and the particles for roughening, the particles for roughening will aggregate and not be uniformly dispersed. was there. In particular, when silicone resin particles are selected as the particles for roughening, the particles are likely to aggregate and may not be uniformly dispersed.

  If the particles for roughening are aggregated, a surface with a uniform surface roughness is not formed on the surface of the developing roller, the developer film is not uniformly formed, and a uniform and high-density image cannot be obtained. there is a possibility.

  Accordingly, an object of the present invention is to form a uniform surface roughness surface on the developing roller of a contact developing type image forming apparatus to obtain a uniform and high-density image, and also to provide a surface of the pressure contact portion even in long-term pressure welding. Roughness does not change and the generation of image streaks is suppressed.

In order to achieve the above object, in a developing roller having a core, a resin layer formed around the core, and a surface layer formed around the resin layer,
The surface layer includes elastic resin particles having a core / shell structure, and a binder resin in which the elastic resin particles are dispersed, and
A developing roller that satisfies the following conditions a) to e):
a) The core portion of the elastic resin particles is made of a silicone resin, and the shell portion is at least one resin selected from the group consisting of a polyurethane resin, an epoxy resin, and a silicone resin,
b) 10% compression hardness E of the elastic resin fine particles is 3 MPa or more and 10 MPa or less,
c) The volume average particle diameter A of the elastic resin particles is 1.0 μm or more and 15.0 μm or less, and the average interparticle distance B μm of the elastic resin particles in the cross section of the surface layer is 0.1 A or more and 2.0 A or less. And the coefficient of variation C of the average interparticle distance B is 150% or less,
d) When the film thickness of the surface layer is D μm, A / D is 0.30 or more and 3.0 or less,
e) The elastic recovery rate of the elastic resin particles is 90% or more.

  The present invention also relates to an electrophotographic process cartridge configured to be detachable from an electrophotographic image forming apparatus, comprising the developing roller.

  The present invention also relates to an electrophotographic image forming apparatus comprising the developing roller of the present invention.

  The developing roller of the present invention can improve the uniformity of the surface roughness of the developing roller in a contact developing type image forming apparatus and an electrophotographic cartridge, and an image having a uniform density can be obtained. In addition, it is possible to suppress deformation due to long-term pressure contact and local decrease in surface roughness in the developing roller, and it is possible to suppress the occurrence of image streaks. In addition, it is possible to maintain a high-quality image even after long-term storage of an image forming apparatus of a contact development type and an electrophotographic cartridge and long-term image output suspension.

  Hereinafter, embodiments of the present invention will be described in detail.

  A feature of the present invention is a developing roller having a surface layer in which elastic resin particles having a core / shell structure are dispersed in a surface layer binder resin.

  First, a brief description will be given with respect to a series of figures for describing an embodiment of the present invention.

  FIG. 1 shows a configuration example of a developing roller to which the present invention can be applied. FIG. 1 is a cross-sectional view of a plane parallel to the longitudinal direction of the developing roller 101 and a cross section of a vertical plane passing through the center of the cylinder of the developing roller in the longitudinal direction. As shown in FIG. 1, the developing roller 101 has at least one resin layer 103 formed around the shaft core body 102 and a surface layer 104 formed around the resin layer 103.

  FIG. 2 is an enlarged view of a cross section of a developing roller surface layer applicable to the present invention. In the surface layer 104, core / shell particles 202 are dispersed in a surface layer binder resin 201. The surface layer 104 is adjusted to the required surface roughness by forming the irregularities 204 on the surface layer surface 203 by the core-shell particles 202.

  FIG. 3 shows a structural example of the core / shell particle 202 applicable to the present invention. The core / shell particle 202 includes a core portion 301 and a shell portion 302.

  FIG. 4 illustrates a method for measuring the elastic recovery rate of the core-shell structure elastic resin particles applicable to the present invention.

  FIG. 5 shows a schematic diagram of an electrophotographic process cartridge and an image forming apparatus on which a developing roller 101 applicable to the present invention is mounted. The developing roller 101 is supplied with the developer 405 from the developer storage tank 414 by the developer supply roller 413 in contact with the surface of the developing roller 101. Further, a developing blade 415 is brought into contact with the developing roller 101 so that the thickness of the developer adhesion layer formed on the surface becomes uniform. In the contact development method, the photosensitive drum 401 is in contact with the developing roller 101.

  The core-shell particles 202 applicable to the present invention are particles having a two-layer structure in which a core portion 301 made of a first resin occupying the center of the particle is wrapped with a shell portion 302 made of a second resin.

  By using different types of resin for each of the core part 301 and the shell part 302, the core part 301 and the shell part 302 are provided with different functions, and resin particles exhibiting functions unique to the core / shell structure are obtained. Is possible. Also, by selecting the same type of resin and having different physical properties such as elasticity, molecular weight, and crosslink density, the core part 301 and the shell part 302 have different functions, and are specific to the core / shell structure. It becomes possible to obtain resin particles that exhibit their functions.

  Specifically, by selecting a material having a small compression set for the core 301, the unevenness 204 formed on the surface layer surface 203 is prevented from being locally lowered due to long-term pressure contact, and the developer adhesion layer It reduces local changes in state.

  In addition, by selecting a material that disperses well with respect to the surface layer binder resin 201 as the material of the shell portion 302, it is possible to form the unevenness 204 uniformly on the surface layer surface 203 and make the surface roughness uniform. .

  In the core-shell particles 202 applicable to the present invention, a low-elasticity silicone resin elastic body (elastic silicone resin) having a 10% compression hardness E of 3 MPa or more and 10 MPa or less is used for the core portion 301. The silicone resin elastic body is an organosilicon polymer whose main chain is composed of siloxane bonds. Examples of the silicone resin elastic body include dimethyl silicone rubber, vinyl methyl silicone rubber, phenyl methyl silicone rubber, vinyl phenyl methyl silicone rubber, and fluoro silicone rubber.

  It is also possible to select a material combined with an elastic material other than the silicone resin elastic body so long as the 10% compression hardness E is 3 MPa or more and 10 MPa or less and the elastic recovery rate does not deteriorate 90% or more. In that case, the resin particles made of the composite material preferably include 10% compression hardness E of 3 MPa or more and 10 MPa or less and a silicone resin elastic body of 70% by mass or more.

  When a general elastic body is stretched, the molecular chains of the elastic body approach each other, and are arranged in a certain direction and crystallize. It is believed that if the elongation is loosened, most of the crystals melt and return to their original state, but some molecular chains remain in the crystalline state and become compression set. However, it is known that the silicone resin elastic body has a higher mobility of the main chain and side chain than other elastic bodies, the molecular chains are rarely crystallized, and the residual compression set is particularly small.

  In the present invention, the compression elastic recovery rate is used as an index representing the magnitude of compression set.

  A method for measuring the compression elastic recovery rate will be described with reference to FIG. The measurement is performed in an environment with a room temperature of 23 ° C. and a relative humidity of 60%. 1) The initial diameter F (μm) of the diameter 501 of the core / shell particle 202 is measured with a digital microscope attached to an ultra-micro hardness measuring device (trade name ENT-2100, manufactured by Elionix Co., Ltd.). 2) A flat indenter 503 having a 20 μm square tip is attached to the ultra-small hardness measuring device, and a load of 1 mN is added per second, and the particle diameter in the applied direction is compressed by 25% of the initial diameter F (μm). (State 502). 3) Then, after holding the load for 1 second, releasing the load by 1 mN per second and immediately after releasing the load, the measured particle diameter in the direction 401 immediately after the load is taken as G (μm), and the elastic recovery rate (%) is It is defined as Equation 1.

(G / F) × 100 Formula 1
The larger the value of the elastic recovery rate, the smaller the compression set. By using a silicone resin elastic body for the core portion 301 of the core-shell particle 202, it is possible to obtain the core-shell particle 202 having an elastic recovery rate of 90% or more.

  In the developing roller 101 applicable to the present invention, it is preferable to disperse the core / shell particles 202 having an elastic recovery rate larger than 95% in the surface layer 104. A more preferable elastic recovery rate is between 96 and 99%. By dispersing the core / shell particles 202 having an elastic recovery rate of 95% or more in the surface layer 104, it is possible to reduce the change in the surface roughness of the press contact portion even in the long-term press contact.

  The core-shell particle 202 to which the present invention can be applied needs to have low elasticity. The silicone resin elastic body can make an elastic material in which the distance between the molecular chains is larger than that of other elastic material, and a material having a high degree of freedom of molecular chains and a low elasticity can be obtained. By using a silicone resin elastic body for the core portion 301 of the core-shell particle 202 of the present invention, the core-shell particle 202 having a 10% compression hardness of 3 MPa or more and 10 MPa or less is obtained.

  The 10% compression hardness E of the core-shell particles 202 applicable to the present invention is defined as follows. The measurement is performed in an environment where the room temperature is 23 ° C. and the relative humidity is 60%. 1) The particle diameter d (mm) of the core-shell particle 202 is measured with a digital microscope attached to an ultra-micro hardness measuring apparatus (trade name ENT-2100, manufactured by Elionix Co., Ltd.). 2) A flat indenter with a 20 μm square tip is attached to the ultra-micro hardness measuring device, and a 0.001N load is added per second, and the particle diameter in the applied direction is compressed by 10% of the diameter d (mm). . 3) Measure the load P (N) applied to the planar indenter when the diameter of the core-shell particle 202 is compressed by 10%. 4) The load P (N) applied to the planar indenter is put into the following formula 2 and defined as 10% compression hardness (MPa) of the core-shell particle 202.

E = 2.8P / πd ² Formula 2
The core-shell particles 202 applicable to the present invention preferably have a 10% compression hardness of 3 MPa or more and 10 MPa or less. By setting the 10% compression hardness E within the above numerical range, it is possible to suppress the unevenness 204 of the developing roller surface 101 from being crushed by the pressure contact of the developing blade 415. As a result, an appropriate gap can be secured between the developing blade 415 and a developer adhesion layer having an appropriate thickness can be formed on the surface of the developing roller 101. Further, it is possible to suppress the deterioration of the developer 405 in the repeated electrophotographic process. That is, the unevenness 204 forms a developer adhesion layer with an appropriate thickness on the surface of the developing roller 101 and at the same time sandwiches the developer 405 in the gap with the developing blade 415. When the developer is repeatedly sandwiched, the external additive may be peeled off from the developer surface and the developer base may be deformed. When the developer 405 from which the external additive has been peeled off and the developer base has been deformed is used in an electrophotographic process, density unevenness may occur due to a decrease in developer fluidity. Further, development fogging due to non-uniform charging characteristics of the developer 405 (for example, a phenomenon in which a non-exposed portion is developed in a reversal development type electrophotographic process) may occur.

  The glass transition point of the core portion 301 of the core-shell particle 202 applicable to the present invention is preferably −120 ° C. or higher and −110 ° C. or lower. In an elastic material, the glass transition point is closely related to the degree of freedom between molecular chains and the ease of crystallization. Therefore, in a silicone resin elastic body having a high glass transition point of −110 ° C. or less, the degree of freedom between the molecular chains is ensured, so that the low elasticity 10% compression hardness can be 10 MPa or less.

  The condition of the surface layer binder resin 201 in the developing roller 101 that can be applied to the present invention is primarily composed of a low-elastic material, but on the other hand, to the extent that a uniform pressure contact width to the photoreceptor can be secured. It is preferable to maintain elasticity and not to cause deterioration of the developer. Secondly, a material having a small compression set is preferable so that permanent deformation does not occur in the press contact portion. Thirdly, it is preferable to use a material that has an action of stably triboelectrically charging the developer 405 and appropriately performing an electrostatic latent image on the photoreceptor 401. Examples of materials that can be used for the binder resin for the surface layer having the above three conditions are given below. Epoxy resin, diallyl phthalate resin, polycarbonate resin, fluororesin, polypropylene resin, urea resin, melamine resin, silicon resin, polyester resin, styrene resin, vinyl acetate resin, phenol resin, polyamide resin, fiber resin, polyurethane resin, Silicone resin, acrylic urethane resin, etc. It is also possible to use a combination of two or more of these.

  Among the above materials, polyurethane resin is particularly preferable as the material that can maintain the most stable triboelectric charge.

  The polyurethane resin is obtained from an isocyanate compound and a polyol. Examples of the isocyanate compound are listed below. Diphenylmethane-4,4′-diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, Carbodiimide-modified MDI, xylylene diisocyanate, trimethylhexamethylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, paraphenylene diisocyanate, hexamethylene diisocyanate, or polymethylene polyphenyl polyisocyanate. Moreover, these mixtures can also be used and the mixing ratio may be any ratio.

  Examples of the polyol are given below. As a divalent polyol (diol), ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, hexanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, Xylene glycol and triethylene glycol can be mentioned, and trivalent or higher polyols include 1,1,1-trimethylolpropane, glycerin, pentaerythritol, sorbitol and the like. Furthermore, high molecular weight polyethylene glycol, polypropylene glycol, or ethylene oxide-propylene oxide block glycol polyol obtained by adding ethylene oxide or propylene oxide to diol or triol can be used. Moreover, these mixtures can also be used and the mixing ratio may be any ratio.

  Even when the polyurethane resin is selected as the surface layer binder resin 201, when resin particles having no core / shell structure are used, the dispersibility is not good and the resin particles aggregate in the surface layer 104. May end up. As a result, the surface roughness of the developing roller may not be uniform.

  However, when the shell portion is at least one resin selected from a polyurethane resin, an epoxy resin, and a silicone resin having a high degree of polymerization, the binder resin 201 is easily compatible with the polyurethane resin, and the dispersion of the resin particles is good, so that the developing roller is obtained. In some cases, the surface roughness becomes more uniform. When both the surface layer binder resin 201 and the shell portion 302 are polyurethane resins, they are the same type of resin and have high affinity and are well dispersed. Polyurethane resin and epoxy resin are close to each other in solubility parameter and have high affinity and are well dispersed. A silicone resin having a high molecular weight and a high degree of polymerization has a high affinity with a polyurethane resin and is well dispersed. Moreover, since it does not swell in the dispersion solvent, the dispersibility is good.

  Further, as a surface layer forming method of the developing roller, a surface layer binder resin 201, resin particles, and other materials are dissolved and dispersed in an appropriate solvent to prepare a coating liquid, which is applied to the surface of the molded resin layer 103 to be surface layer Methods for forming 104 are known. When a polyurethane resin suitable for the surface layer binder resin 201 as described above is selected in such a method for forming the surface layer 104, it is necessary to use a solvent that is highly soluble in the resin particle material as the dispersion solvent. .

  Examples of solvents that are highly soluble in the resin particle material include ketone solvents such as 2-butanone and acetone, and aromatic solvents such as toluene and xylene.

  General low-elasticity resin particles have high swellability and swell when dispersed in a coating solution using a solvent having high solubility as described above. When the resin particles swell, viscosity is generated on the surface of the resin particles, and the resin particles may adhere to each other in the coating solution to generate aggregated particles. When aggregated particles are generated in the coating solution, the surface roughness may become non-uniform when coated as a developing roller surface layer.

  However, in the case of core / shell particles in which the shell portion 302 is a polyurethane resin, an epoxy resin, or a silicone resin having a high degree of polymerization, the shell portion 302 protects the core portion 301 even in a solvent coating solution having a high solubility as described above. Resin particles hardly swell. Therefore, a developing roller having a uniform surface roughness can be obtained. When the shell portion 302 is a polymer such as an acrylic resin or a vinyl resin, the shell portion 302 does not sufficiently protect the core portion 301, and the resin particles swell when a highly soluble solvent is used. Sometimes.

  In the core-shell particles that can be applied to the present invention, by selecting a resin that does not have a glass transition point in the temperature region of less than −60 ° C. for the shell portion 302, the dispersion with respect to the surface binder resin 201 becomes good. I found out.

  Some resins start thermal decomposition before reaching the glass transition point, and the glass transition point is substantially impossible to measure. However, if the resin does not have a glass transition point in a temperature range lower than −60 ° C., it is dispersible. Is good. When a resin having a glass transition point in a temperature region lower than −60 ° C. is used as the shell material, the shell portion 302 is not sufficient in protecting the core portion 301, and the resin particles are contained in the solvent as described above. May swell. In such a case, aggregation of particles occurs, and a surface layer having a uniform surface roughness may not be obtained.

  As for the surface roughness of the developing roller surface applicable to the present invention, Ra is preferably 0.5 μm or more and 3.0 μm or less. When Ra is smaller than 0.5 μm, the surface roughness of the surface layer surface becomes too small, the developer adhesion layer becomes thin, and the image density may become thin. When Ra is larger than 3.0 μm, the surface roughness of the developing roller surface is too large, the developer adhesion layer becomes too thick, and development fogging may occur. The definition of the surface roughness Ra is JIS-B0601: 2001, the measurement method is JIS-B0651: 2001, the feed rate is 0.1 mm / second, the cutoff is 0.8 mm or more, and the tip of the measuring needle is JIS-B0651. : R10 μm 60 ° conical needle designated by 2001 was used.

  The volume average particle diameter A of the core / shell particles 202 applicable to the present invention is 1.0 μm or more and 15.0 μm or less. When the volume average particle diameter A is smaller than 1.0 μm, the effect of adding resin particles is small, the developer adhesion layer becomes thin, and the image density may become thin. When the volume average particle diameter A is larger than 15.0 μm, the surface roughness of the developing roller surface becomes too large, the developer adhesion layer becomes too thick, and development fogging may occur.

A method for measuring the volume average particle diameter of the core-shell particles 202 to which the present invention can be applied will be described below. 1) An enlarged image is displayed on a display, and a digital microscope (VHX-600, manufactured by Keyence Corporation) capable of measuring the distance between two points on the image is prepared. 2) 100 core / shell particles 202 were enlarged and observed, and the interval (Feret diameter) between parallel lines sandwiching the outer periphery of the particles was measured to obtain the particle diameter of the particles. 3) If each particle diameter of the measured core-shell particles 202 is d _i (μm) (i is an integer from 1 to 100), d _i (μm) is substituted into the following equation 3 to obtain a volume average particle diameter: A (μm). The core / shell particles 202 were calculated as spheres.

  Examples of the method for producing the core / shell particles 202 applicable to the present invention include the following method. First, various polymerizable compounds are combined to form a core portion 301 by a polymerization reaction, and then a polymerizable monomer for forming a shell portion 302 is added, and a polymerization reaction is performed to form composite particles. . Next, there is a method for obtaining composite particles by removing water from the suspension containing the composite particles. The particle diameter of the core part 301 and the thickness of the shell part 302 can be adjusted by changing the temperature in the reaction vessel and the stirring conditions.

  The example of the manufacturing method of the core shell particle 202 which has the silicone resin core part 301 and the shell part 302 is given to the following.

  A method in which a polyorganosiloxane containing a vinyl group in the molecule and a polyorganohydrogensiloxane as a crosslinking agent are emulsified with a surfactant, and a catalyst such as a platinum compound is added to perform a hydrosilylation reaction. Examples of the surfactant include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, and glycerin fatty acid ester.

  A method of emulsifying a polyorganosiloxane containing a silanol group and a polyorganohydrogensiloxane or an alkoxy group-containing polysiloxane with a surfactant and adding ammonia or amines to carry out a condensation reaction.

  The core particle 301 made of a silicone resin elastic body preferably has 50 mol% or more of silicon atoms in its molecular structure is a dimethylsiloxane unit, and the number of repeating dimethylsiloxane units is 5 or more and 3000 or less. This is because the flexibility of the silicone resin is excellent and the production of the particles is stable.

  Next, the following method is mentioned as an example of the manufacturing method of the shell part 302 which consists of silicone resins. The shell part 302 made of a silicone resin can be formed by adding a hydrolyzable group-containing compound of an alkaline aqueous solution and organotrialkoxysilane, organodialkoxysilane, monoalkoxysilane, or alkoxy group-containing siloxane, and performing hydrolysis and condensation reactions.

  Examples of the organotrialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, and phenyltrimethoxysilane. Examples of the organodialkoxysilane include dimethyldimethoxysilane and diethyldiethoxysilane. Examples of the monoalkoxysilane include trimethylmethoxysilane and trimethylethoxysilane.

  Examples of preferable materials for the core / shell particles on the market are listed below.

  Composite silicon powder (trade name: KMP-600; manufactured by Shin-Etsu Chemical Co., Ltd.).

  Composite silicon powder (trade name: KMP-601; manufactured by Shin-Etsu Chemical Co., Ltd.).

  Composite silicon powder (trade name: KMP-602; manufactured by Shin-Etsu Chemical Co., Ltd.).

  Composite silicon powder (trade name: KMP-605; manufactured by Shin-Etsu Chemical Co., Ltd.).

  The core 301 of the above composite silicon powder is a silicone resin and is an elastic body having a low glass transition point of −120 ° C. Although the shell 302 is also a silicone resin, the degree of polymerization is high, and thermal decomposition starts before reaching the glass transition point, and the shell 302 has substantially no glass transition point.

  Product name: Albidur PU5640, manufactured by Nano Resins (core is silicone resin, shell is polyurethane resin) Product name: Albidur EP2240, manufactured by Nano Resins (core is silicone resin, shell is polyurethane resin).

  Further, in the developing roller 101 applicable to the present invention, the core / shell particles 202 need to be appropriately uniformly dispersed in the surface layer.

The dispersion evaluation method was measured and evaluated by the following method.
1) A device capable of displaying an enlarged image on a display and measuring a distance between two points on the image, for example, a digital microscope (VHX-600, manufactured by Keyence Corporation) is prepared.
2) The cross section of the surface layer of the developing roller 101 is observed, and the interparticle distance between a certain core / shell particle 202 and the closest core / shell particle is measured. For example, if attention is paid to the core-shell particle 205 in FIG. 2, the distance 210 to the closest core-shell particle 206 is measured.
3) Similarly, 50 inter-particle distances between a certain core-shell particle and the closest core-shell particle are measured. For example, in FIG. 2, the distance 211 from the closest core / shell particle 206 is measured when attention is paid to the core / shell particle 207, and the distance 212 from the closest core / shell particle 209 is measured when attention is paid to the core / shell particle 208.

The interparticle distance was measured between the outer periphery of the core / shell particle and the closest core / shell particle 202.
4) An arithmetic average value of 50 interparticle distances b _i (μm) (i is an integer of 1 to 50) was defined as an average interparticle distance B (μm). Furthermore, b _i (μm) was substituted into the following equation 4 to obtain the coefficient of variation C (%).

When the average interparticle distance Bμm is smaller than 0.1 times the volume average particle diameter Aμm, the core / shell particles 202 are too dense, the developer adhesion layer becomes too thick, and development fogging may occur. . When the average interparticle distance Bμm is larger than 2.0 times the volume average particle diameter Aμm, the effect of adding the resin particles is not sufficient, and the developer adhesion layer may become thin and the image density may become thin. Therefore, the average interparticle distance (B) is 0.1 A or more and 2.0 A or less.
When the coefficient of variation C is larger than 150%, the core / shell particles 202 are aggregated in the surface layer 104, the surface roughness uniformity is insufficient, and density unevenness may occur. Therefore, the coefficient of variation C is preferably 150% or less.

  When the film thickness of the developing roller surface layer 104 of the present invention is D μm, A / D is preferably in the range of 0.30 to 3.0. When A / D is smaller than 0.30, the effect of adding resin particles is not sufficient, and the developer adhesion layer may become thin and the image density may become thin. When A / D is larger than 3.0, the core / shell particles 202 are too clogged, the developer adhesion layer becomes too thick, and development fogging may occur.

  The content of the core / shell particles 202 in the surface layer 104 is preferably 22 parts by mass or more and 81 parts by mass or less. When the content of the core-shell structure elastic resin fine particles is larger than 81 parts by mass, the core-shell particles 202 are too clogged, the developer adhesion layer becomes too thick, and development fogging may occur. When the content of the core / shell particles 202 is smaller than 22 parts by mass, the amount of the core / shell particles 202 is small, and the effect of adding the resin particles is not sufficient, and the developer adhesion layer may become thin and the image density may become thin.

  In the present invention, as a means for making the elastic material used for the resin layer 103 and the surface layer 104 conductive, there is widely known a method of making the material conductive by adding a conductivity imparting agent based on an ionic conduction mechanism or an electronic conduction mechanism to the material. It has been.

Examples of the conductivity-imparting agent based on the ion conduction mechanism include the following. LiCF ₃ SO ₃ , NaClO ₄ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , NaSCN, KSCN, NaCl Group 1 metal salt, NH ₄ Cl, (NH ₄ ) ₂ SO ₄ , NH ₄ NO ₃ Ammonium salt, Ca (ClO ₄ ) ₂ , Ba (ClO ₄ ) ₂ periodic table group 2 metal salt, these salts and 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol Complexes of polyhydric alcohols and their derivatives, complexes of these salts with ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether monool, and quaternary ammonium salt Ionic surfactant, aliphatic sulfur Anionic surfactants such as phonates, alkyl sulfates and alkyl phosphates, and amphoteric surfactants of betaine.

  Moreover, the following can be mentioned as an electroconductivity imparting agent by an electronic conduction mechanism. Carbon black, carbonaceous material of graphite, aluminum, silver, gold, tin-lead alloy, copper-nickel alloy metal or alloy, zinc oxide, titanium oxide, aluminum oxide, tin oxide, antimony oxide, indium oxide, silver oxide Metal oxides, materials with various metal fillers plated with conductive metal such as copper, nickel, silver, etc. These conductivity-imparting agents based on the ion conduction mechanism and the electron conduction mechanism can be used alone or in a mixture of two or more in the form of powder or fiber. Among these, carbon black is often used from the viewpoint of easy control of conductivity and economy, and in the present invention, a method using an electronic conduction mechanism is used.

  Examples of materials used for the resin layer 103 to which the present invention can be applied include natural rubber, isoprene rubber, styrene rubber, butyl rubber, butadiene rubber, fluorine rubber, urethane rubber, and silicone resin. These materials can be used alone or in combination of two or more. Further, a foam of these materials may be used for the resin layer.

  Among these, a silicone resin elastic body is particularly preferable. As described above, the silicone resin elastic body is less susceptible to crystallization of molecular chains than other elastic body materials, and the residual compression set is particularly small. When an elastic material other than silicone resin is mainly used for the resin layer 103, a dent may be generated on the surface of the pressure contact portion of the developing roller 101.

  As described above, the developer 405 deteriorates due to repeated pressure. Therefore, it is necessary to set the developing roller 101 applicable to the present invention to a low surface hardness so that the developer is not deformed even when the developer 405 is sandwiched and is absorbed by the deformation of the developing roller surface layer 104.

  The surface hardness of the developing roller 101 is preferably 20 to 60 degrees as measured and defined by an MD-1 surface hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) for the above reasons. The surface hardness is evaluated by fixing the developing roller 101 and measuring the load required for pressing by pressing the push needle (height 0.50 mmφ0.16 mm cone) perpendicularly to the surface of the developing roller. The surface hardness is a value when measured with the developing roller 101 at 23 ° C. When the developing roller surface hardness is lower than 20 degrees, the unevenness 204 on the developing roller surface 101 is crushed when pressed by the developing blade 415, and an appropriate gap cannot be secured between the developing roller and the developing blade. In some cases, the developer 405 cannot be formed with an appropriate thickness of the developer 405.

  Further, when the surface hardness of the developing roller 101 is higher than 60 degrees, the developer may be damaged when contacting the developer 405 in the image forming process, and the image quality of the output image may deteriorate due to durability. There is.

The developing roller 101 needs to have an electric resistance value of the semiconductor region. Therefore, the resin layer 103 preferably contains a conductive agent and is formed from a rubber material having a volume resistivity of 1 × 10 ⁴ Ω · cm to 1 × 10 ¹⁰ Ω · cm. Here, if the volume resistivity of the material of the resin layer 103 is 1 × 10 ⁴ Ω · cm to 1 × 10 ¹⁰ Ω · cm, it is possible to obtain uniform charge controllability with respect to the developer. The volume resistivity is more preferably 1 × 10 ⁴ Ω · cm to 1 × 10 ⁹ Ω · cm.

In addition, the value calculated | required with the following method is employable as the volume resistivity of the resin layer 2. FIG. As the resistance meter, an ultrahigh resistance meter R8340A (manufactured by Advantest) is used for measurement under the following conditions.
Measurement mode: Program mode 5
(Charge and major 30 seconds, discharge 10 seconds)
Applied voltage: 100 (V)
Sample box: Sample box TR42 (manufactured by Advantest) for measuring ultrahigh resistance meter, the main electrode is a metal having a diameter of 10 mm and a thickness of 10 mm, and the guard ring electrode is a metal having an inner diameter of 20 mm and an outer diameter of 26 mm and a thickness of 10 mm.
Test piece: First, a flat test piece is produced by curing the material of the resin layer 2 to the same thickness as that of the resin layer 2 under the same conditions as those for molding the resin layer 2. Next, a test piece having a diameter of 30 mm is cut out from the test piece. On one side of the cut-out test piece, a vapor deposition film electrode (back surface electrode) is provided by performing Pt—Pd vapor deposition on the entire surface, and a main electrode film having a diameter of 15 mm is formed on the other surface by the same Pt—Pd vapor deposition film. A guard ring electrode film having an inner diameter of 18 mm and an outer diameter of 28 mm is provided concentrically. The Pt—Pd vapor-deposited film is obtained by performing a vapor deposition operation for 2 minutes at a current value of 15 mA using mild sputter E1030 (manufactured by Hitachi, Ltd.). The sample after the vapor deposition operation is used as a measurement sample.

  At the time of measurement, the main electrode having a diameter of 10 mm is placed so as not to protrude from the main electrode film having a diameter of 15 mm. Further, measurement is performed by placing a guard ring electrode having an inner diameter of 20 mm on the electrode film so as not to protrude from the guard ring electrode film having an inner diameter of 18 mm. The measurement is performed in an environment where the temperature is 23 ° C. and the relative humidity is 50%. Prior to the measurement, the measurement sample is left in the environment for 12 hours or more.

  In the above state, the volume resistance (Ω) of the test piece is measured. Next, when the measured volume resistance value is RM (Ω) and the thickness of the test piece is t (cm), the volume resistivity RR (Ωcm) of the test piece is obtained by the following Equation 5.

RR (Ωcm) = π × 0.75 × 0.75 × RM (Ω) ÷ (4 × t (cm)) Equation 5
<Developing roller shaft core according to the present invention>
The shaft core body 102 of the developing roller needs to be conductive, and can be selected and used from carbon steel, alloy steel and cast iron, conductive resin, etc., but metal is preferable from the viewpoint of strength. Examples of alloy steel include stainless steel, nickel chromium steel, nickel chromium molybdenum steel, chromium steel, chromium molybdenum steel, nitriding steel to which Al, Cr, Mo and V are added. When the shaft core material is a metal material, it is preferable to perform plating and oxidation treatment as a rust prevention measure.

<Developer according to the present invention>
As a developer suitable for an electrophotographic process using the developing roller of the present invention, a development dry developer using styrene-acrylic resin as a binder resin is particularly preferable. The following are mentioned as an example of a styrene-acrylic resin.

  Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methacrylic acid Acid methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer Polymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-maleic acid copolymers, styrene copolymers of styrene-maleic acid ester copolymers, and the like.

  The following wax may be added to the developer used in the present invention. For example, hydrocarbon waxes include the following. Low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, aliphatic hydrocarbon wax such as Fischer-Tropsch wax, and the like.

<Image Forming Apparatus According to the Present Invention>
Next, an outline of an electrophotographic process cartridge and an image forming apparatus equipped with a developing roller applicable to the present invention will be described with reference to FIG.

  The surface of the electrophotographic photosensitive drum 401 is subjected to exposure processing 403 of target image information after being charged by the charging roller 402 so that the surface has a predetermined polarity and a uniform potential. An electrostatic latent image corresponding to the target image is formed. This electrostatic latent image is visualized as a developer image by the developer 405 supplied by the developing roller 101 of the present invention. The visualized developer image is transferred to the recording material 407 by applying a voltage from the back surface of the recording material 407 conveyed by the paper supply roller 406 by the transfer roller 408. Further, the toner is conveyed to a fixing unit constituted by a fixing roller 409 and a pressure roller 410, undergoes image fixing, and is output as an image formed product. The electrophotographic photosensitive drum 401 is cleaned by a cleaning unit 411 in order to remove the developer, dust, and the like remaining on the electrophotographic photosensitive drum 401, is discharged by a discharging member (not shown), and proceeds to the charging process again. Note that the developer removed by the cleaning unit 411 is collected in a waste developer container 412. In addition, a cleaning roller can be used as a member of the cleaning unit 411.

  On the other hand, the developing roller 101 is in contact with the developing blade 415 so that the developer is supplied from the developer storage tank 414 by the developer supplying roller 413 and the developing blade 415 has a uniform thickness. The developer not used when developing the electrostatic latent image with the photosensitive drum 401 on the developing roller 101 is scraped off from the developing roller 101 once by the developer supply roller 413. The charging roller 402, the developing roller 101, and the transfer roller 408 are applied with a necessary voltage by a bias application power source. In the electrophotographic process cartridge, all or some of the members excluding the paper feeding unit, transfer roller, fixing unit, and exposure unit are selected and integrated into a single unit and separated from the main body.

  In addition, by arranging four color electrophotographic process cartridges of black, magenta, cyan, and yellow, transferring each toner to a recording material, and performing image fixing, it becomes possible to output a color image formed product. .

  As described above, the electrophotographic image forming apparatus includes at least an electrophotographic photosensitive member for forming an electrostatic latent image, and an electrophotographic developing member disposed in contact with the electrophotographic photosensitive member. The developing roller according to the present invention is used as a developing member. The electrophotographic process cartridge includes at least an electrophotographic photosensitive member for forming an electrostatic latent image, and an electrophotographic developing member disposed in contact with the electrophotographic photosensitive member, and includes an electrophotographic image forming apparatus. It is configured to be removable. The developing roller according to the present invention is used as an electrophotographic developing member.

  Hereinafter, the present invention will be described in detail based on examples and comparative examples.

  The following examples are examples of the best mode of the present invention, but the present invention is not limited to these examples.

(Example 1-1)
<Measurement of physical properties of resin particles>
(Glass transition point measurement method)
A scanning calorimeter DSC8230L (manufactured by Rigaku Corporation) was used, and the measuring method was measured from JIS-K7121.

<Production of developing roller>
As the shaft core body 102, a SUS304 cored bar having a diameter of 6 mm and a length of 270 mm is coated and baked with a two-component primer (Dow Corning DY39-051: Toray Dow Corning) as an adhesive layer. It was.

Next, the shaft core was placed in a mold, and liquid silicone having a composition in which the following first liquid silicone and second liquid silicone were mixed at the following weight ratio was injected.
(First liquid silicone)
・ Organopolysiloxane: 100 parts by weight (dimethylpolysiloxane having a viscosity of 100 Pa · s with both ends substituted with vinyl groups)
・ Quartz powder ・ ・ ・ ・ ・ ・ 7 parts by weight (Min-USil, manufactured by Pennsylvania Glass Sands)
・ Carbon black ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 8 parts by weight (Denka Black powder grade, manufactured by Denki Kagaku Kogyo Co., Ltd.)
・ Platinum compound (as a curing catalyst) ・ ・ ・ ・ ・ ・ Trace amount (second liquid silicone)
・ Organic hydrogen polysiloxane 3 parts by weight (amount of SiH group 1.1 moles per mole of vinyl group contained in the dimethylpolysiloxane substituted with the vinyl group)
Subsequently, the liquid silicone injected into the heating mold was heated at 130 ° C. for 5 minutes to be cured. After cooling, demolding, and further heat treatment at 180 ° C. for 3 hours, a resin layer 103 mainly composed of a silicone resin with a thickness of 2.990 mm was provided on the outer peripheral surface of the shaft core body 102.

As a material for the surface layer 104, polytetramethylene glycol with the following composition was mixed with isocyanate in a MEK solvent stepwise and reacted at 80 ° C. for 6 hours in a nitrogen atmosphere.
・ 100 parts by mass of polytetramethylene glycol (trade name: PTG1000SN; manufactured by Hodogaya Chemical Co., Ltd.)
・ Isocyanate 21.2 parts by mass (trade name: Millionate MT; manufactured by Nippon Polyurethane Industry Co., Ltd.)
A bifunctional polyurethane polyol prepolymer having a molecular weight Mw = 48000, a hydroxyl value of 5.6, a molecular weight dispersity Mw / Mn = 2.9, and Mz / Mw = 2.5 was obtained. The hydroxyl value was measured by the method of ISO 15063.

  Add 100 parts by mass of the above polyurethane polyol prepolymer and 7.2 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3; manufactured by Mitsui Takeda Chemical Co., Ltd.) It was set to 1.2. Further, an appropriate amount of carbon black (# 1000; pH 3.0; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. An organic solvent was added to the raw material mixture to obtain a solid content of 20%. (Composite silicon powder KMP-601; volume average particle diameter 15 μm; manufactured by Shin-Etsu Chemical Co., Ltd.) was added as core-shell particles 202. The core / shell particle 202 content was 30 parts by mass with respect to 70 parts by weight of the solid content, and the mixture obtained by stirring and dispersing and mixing with propeller blades was used as the coating solution for the surface layer 104.

  The shaft core body 102 after the formation of the elastic layer 103 was immersed in the resin layer raw material liquid, pulled up, and naturally dried to form a surface layer 104 coating film. Next, the coating film was cured by heat treatment at 140 ° C. for 150 minutes to form a surface layer 104 having a thickness of 10 μm and a surface roughness Ra of 1.5 μm. Through the above steps, the developing roller 101 having an outer diameter of 12.00 mm was obtained.

  In addition, the measuring method of the molecular weight of a polyurethane polyol prepolymer and molecular weight distribution is described below. The molecular weight (Mn, Mw, Mz) of the chromatogram by gel permeation chromatography (GPC) is measured under the following conditions. The column was stabilized in a heat chamber at a temperature of 40 ° C., and tetrahydrofuran (THF) as a solvent was passed through the column at this temperature at a flow rate of 1 ml / min. Approximately 100 μl is injected and measured. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts (retention time). An RI (refractive index) detector is used as the detector.

As the molecular weight dispersion of the polyurethane polyol prepolymer, Mn: number average molecular weight, Mw: weight average molecular weight, and Mz: Z average molecular weight are used. The Z average molecular weight is most important for the contribution of the high molecular weight compound to the average molecular weight, and is defined as follows.
When Ni molecules having a molecular weight Mi exist in the polymer, it is expressed by the following formula 6.

Mz = (ΣMi ³ · Ni) / (ΣMi ² · Ni) Equation 6
(Surface layer thickness measurement)
The developing roller surface layer cross section was observed with a digital microscope (VHX-600, manufactured by Keyence Corporation), the surface layer film thickness was measured at three locations, and an arithmetic average value was adopted. The measurement was performed in an environment where the room temperature was 23 ° C. and the relative humidity was 60%.

(Surface layer surface roughness measurement)
A surface roughness meter (SE3500, manufactured by Kosaka Laboratory Ltd.) was used, and the surface roughness Ra was measured by the method described above.

  After measuring the central part of the developing roller at 10 mm intervals in the longitudinal direction, shift 3 points in the circumferential direction by 4.7 mm, 3 points in the same way, and 3 points in the same direction by shifting 4.7 mm in the circumferential direction. It was measured. That is, three areas of a total area of 30 mm × 9.4 mm were measured in three rows and nine points, and the arithmetic average value of the surface roughness was obtained to obtain the surface roughness Ra of the surface layer. Further, the difference between the maximum value and the minimum value of the surface roughness measured at the nine points was defined as the value of the unevenness of the surface roughness.

<Image evaluation method>
(Evaluation of initial image density / initial image density uniformity)
As the image forming apparatus, Color Laser Jet 4700dn manufactured by Hewlett-Packard Co., and a dedicated cartridge were used. The developing roller of the present invention was incorporated in an unused cartridge and mounted on an image forming apparatus main body installed in a temperature 23 ° C. and humidity 60% environment. Five solid images were continuously output with the cyan developer, and the image density uniformity was evaluated on the fifth sheet. A rectangular area of 30 mm in the sheet passing direction × 9.4 mm in the direction perpendicular to the sheet passing direction was set at the center of the image area, and the reflection density was measured at three points in three rows and nine points at regular intervals. As the reflection densitometer, an RD-918 reflection densitometer (manufactured by Kurekuma Kubes) was used. The maximum and minimum reflection density at a total of 9 points was defined as image density uniformity. The smaller the maximum and minimum difference, the better the image density uniformity.
The image density uniformity was evaluated according to the following criteria.
“A”: the difference between the maximum and the minimum is 0.10 or less.
“B”: greater than 0.10 and 0.15 or less.
“C”: greater than 0.15 and less than or equal to 0.20.
“D”: Greater than 0.20.

The initial image density was evaluated according to the following criteria.
“A”: The average density of the solid image is 1.3 or more.
“B”: Less than 1.3 and 1.1 or more.
“C”: Less than 1.1 and 0.9 or more.
“D”: Less than 0.9.

  A and B evaluations are within an allowable range as an output image of the image forming apparatus for high image quality. C evaluation is an allowable range as an output image of a normal image forming apparatus. D rating is out of acceptable range.

(Evaluation of initial image fog)
After outputting five solid images in succession, one solid white image was output, and the degree of fogging (image fogging value) was measured by the following method as the first method, and used as an index of the surface contamination of the developing roller. . The fog value is measured using a reflection densitometer TC-6DS / A (manufactured by Tokyo Denshoku Technology Center Co., Ltd.) and the reflection density of transfer paper, which is a transfer material before image formation by the image forming apparatus, and image formation of a solid white image. The reflection density of the transfer paper after the measurement was measured, and the difference was taken as the image fog value of the developing roller. The reflection density was measured by scanning the entire image printing area of the transfer paper to measure the reflection density, and setting the minimum value as the reflection density of the transfer paper.
The smaller the image fog value, the better. The evaluation was based on the following criteria.
“A”: Less than 1.0.
“B”: 1.0 or more and less than 3.0.
“C”: 3.0 or more and less than 5.0.
“D”: 5.0 or more.

  A and B evaluations are within an allowable range as an output image of the image forming apparatus for high image quality. C evaluation is an allowable range as an output image of a normal image forming apparatus. D rating is out of acceptable range.

(Image streak evaluation after long-term storage)
As the image forming apparatus, Color Laser Jet 4700dn manufactured by Hewlett-Packard Co., and a dedicated cartridge were used. The developing roller of the present invention was assembled in an unused cartridge and left in an environment of a temperature of 40 ° C. and a humidity of 90% for 28 days. At this time, the developing roller was in contact with the photosensitive drum and the developing blade.

After that, the image forming apparatus was installed in a temperature 23 ° C. and humidity 60% environment and left for 2 hours to output an image. A solid image (exposed to all dots in reversal development) and a halftone image (exposed on the photosensitive drum every other dot) are output one by one, and the image is visually evaluated for image streaks of the developing roller cycle. did.
Image streaks were evaluated according to the following criteria.
“A”: Even a solid image or a halftone image cannot be visually confirmed.
“B”: A slight image streak is confirmed only with a solid image.
“C”: Slight image streaks are confirmed in both solid images and halftone images.
“D”: An image streak clearly visible in both solid images and halftone images is confirmed.

  A and B evaluations are within an allowable range as an output image of the high-quality image forming apparatus. C evaluation is an allowable range as an output image of a normal image forming apparatus. D rating is out of acceptable range.

(Evaluation of image fog after endurance)
As the image forming apparatus, Color Laser Jet 4700dn manufactured by Hewlett-Packard Co., and a dedicated cartridge were used. The developing roller 101 of the present invention was incorporated in an unused cartridge and mounted on an image forming apparatus main body installed in a temperature 23 ° C. and humidity 60% environment. 15000 images with a printing rate of 1% were output continuously.

Thereafter, one solid white image was output, and the degree of fogging (image fogging value) on the first sheet was measured by the following method, and used as an index of the surface contamination of the developing roller. The fog value is determined by using a reflection densitometer TC-6DS / A (manufactured by Tokyo Denshoku Technology Center Co., Ltd.) and the reflection density of transfer paper, which is a transfer material before image formation by the image forming apparatus, and image formation of a solid white image. The reflection density of the transfer paper after the measurement was measured, and the difference was taken as the image fog value of the developing roller. The reflection density was measured by scanning the entire image printing area of the transfer paper to measure the reflection density, and setting the minimum value as the reflection density of the transfer paper.
The smaller the image fog value, the better. The evaluation was based on the following criteria.
“A”: Less than 1.0.
[B]: 1.0 or more and less than 3.0.
“C”: 3.0 or more and less than 5.0.
“D”: 5.0 or more.

  In the repeated image forming process, the developer 405 that is contacted by the developing roller 101 may be damaged, and the image quality of the output image may deteriorate (image fogging) due to durability. A and B evaluations are within an allowable range as an output image of the high-quality image forming apparatus. C evaluation is an allowable range as an output image of a normal image forming apparatus. D rating is out of acceptable range.

  Image evaluation is performed on the aforementioned evaluation items, and the evaluation results are shown in Table 1-1.

(Examples 1-2 to 3)
A developing roller was produced under the same conditions as in Example 1-1, except that the amount of resin particles dispersed on the surface of the developing roller in Example 1-1 was changed as shown in Table 1-1. The physical properties of the produced developing roller are as shown in Table 1. Evaluation was performed in the same manner as in Example 1, and the evaluation results are shown in Table 1-1.

(Examples 1-4 to 6)
The resin particles dispersed on the surface of the developing roller of Example 1-1 were replaced with core / shell particles (composite silicon powder KMP-600; volume average particle diameter 5 μm; manufactured by Shin-Etsu Chemical Co., Ltd.), and the amount added was shown in Table 1-1. A developing roller was produced under the same conditions as in Example 1-1 except as described above. The physical properties of the developing roller are as shown in Table 1. Evaluation was performed in the same manner as in Example 1-1, and the evaluation results are shown in Table 1-1. The composite silicon powder KMP-600 has a structure similar to that of the composite silicon powder KMP-601 and has a difference in volume average particle diameter.

(Examples 1-7 to 8)
The resin particles dispersed on the surface of the developing roller in Example 1-1 were changed to core / shell particles (composite silicon powder X-52-7030; volume average particle size 1.0 μm; manufactured by Shin-Etsu Chemical Co., Ltd.), and the addition amount was changed. As shown in Table 1-2. Other than that, a developing roller was produced under the same conditions as in Example 1-1. The physical properties of the developing roller are as shown in Table 1. Evaluation was carried out in the same manner as in Example 1-1, and the evaluation results are shown in Table 1-2. The composite silicon powder X-52-7030 has the same structure as the composite silicon powder KMP-601, but has a difference in volume average particle diameter.

(Comparative Example 1)
Example 1-1 except that the resin particles added to the surface layer are resin particles made only of a silicone resin elastic body having no core / shell structure (trade name: silicone rubber powder KMP-598, manufactured by Shin-Etsu Chemical Co., Ltd.) A developing roller was produced in the same manner as described above. Table 2-1 shows the physical properties of the resin particles and the developing roller manufacturing conditions.

  Evaluation is performed by the image forming apparatus in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-1. As a result of microscopic observation of the cross section of the surface layer of the developing roller, many aggregated particles were observed.

(Comparative Example 2)
A developing roller was produced in the same manner as in Example 1-1 except that the particles added to the surface layer were resin particles having a core made of an acrylic resin (trade name: Metablen W-450A, manufactured by Mitsubishi Rayon Co., Ltd.). The physical properties of the resin particles and the conditions for producing the developing roller are shown in Table 2-1.

  Evaluation is performed by the image forming apparatus in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-1. METABLEN W-450A has a core-shell structure, but the core is an acrylic resin elastic body and has a glass transition point of -60 ° C, and the shell is an acrylic resin and has a glass transition point of -20 ° C.

(Comparative Example 3)
A developing roller was produced in the same manner as in Example 1-1 except that the particles added to the surface layer were resin particles whose core was made of an acrylic resin (trade name: Metablen SX005, manufactured by Mitsubishi Rayon Co., Ltd.). The physical properties of the resin particles and the conditions for producing the developing roller are shown in Table 2-1.

  Evaluation is performed by the image forming apparatus in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-1. METABLEN SX005 has a core-shell structure, but the core is an acrylic silicon resin elastic body and has a glass transition point of −100 ° C., and the shell is an acrylic silicon resin and has a glass transition point of −20 ° C.

(Comparative Example 4)
The resin particles dispersed on the developing roller surface of Example 1-1 were the same as those of Example 1-1 except that the core / shell particles (composite silicon powder KMP-603; volume average particle diameter 30 μm; manufactured by Shin-Etsu Chemical Co., Ltd.) were used. A developing roller was produced by this method. Table 2-2 shows the physical properties of the resin particles and developing roller manufacturing conditions.

  Evaluation is performed by the image forming apparatus in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-2.

(Comparative Example 5)
A developing roller was produced in the same manner as in Example 1-1 except that the particles added to the surface layer were core / shell particles (trade name: Genio Pearl, manufactured by Asahi Kasei Co., Ltd.) whose core is made of silicone resin. The physical properties of the resin particles and the conditions for producing the developing roller are shown in Table 2-2.

  Evaluation is performed by the image forming apparatus in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-2. Geniopearl volume average particle diameter is 0.15 μm.

(Comparative Example 6)
[Preparation of core / shell particles 1]
The following materials were placed in a 20 liter glass container and heated to 45 ° C. with stirring at 10 m / S.

・ Water: 1000g
-Sodium dodecyl sulfate: 30 g
Α, ω-dihydroxypolydimethylsiloxane having a viscosity of 40 mPa · s: 250 g,
-Methyltrimethoxysilane: 15g.

  Next, 10 g of 10% tetrapropoxyoxytitanium isopropyl alcohol solution was added and reacted for 20 hours to polymerize the core particles of the composite particles. The obtained suspension was dispersed at a peripheral speed of 5 m / s for 40 hours using a Viscomill disperser filled with φ0.5 zircon beads. Subsequently, water was evaporated to obtain silicone resin particles.

  Next, as a secondary step, 120 g of the above silicone resin particles are added to a mixed solution of 25 g of polyoxyethylene octylphenyl ether having an addition mole number of 9 mol and 5000 g of water, and the dispersion is stirred at 5.0 m / S. Obtained. Next, aqueous ammonia was added to adjust the pH to 11. 51 g of methyltrimethoxysilane, 95 g of phenyltrimethoxysilane, and 27 g of α, ω-dihydroxypolydimethylsiloxane having a viscosity of 40 mPa · s were dropped, and the mixture was heated to 70 ° C. and stirred for 1 hour. Next, the mixed solution was filtered with a pressure filter and dried at 100 degrees to obtain core / shell particles.

  The obtained core-shell particle 202 had a core part 301 having a glass transition point of −120 ° C. and a silicone resin elastic body of shell part 302 having a glass transition point of −60 ° C.

  The developing roller surface layer of Example 1-1 was prepared as the core / shell particles prepared above, and the developing conditions were the same as in Example 1-1 except that the addition conditions were as shown in Table 2-3. . The physical properties of the developing roller are as shown in Table 2-3. Evaluation was carried out in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-3.

(Comparative Example 7)
Core-shell particles 202 were produced in the same manner as in Comparative Example 6 except that α, ω-dihydroxypolydimethylsiloxane having a viscosity of 5 mPa · s was used instead of the viscosity of 40 mPa · s. The developing roller surface layer of Example 1-1 was prepared as the core / shell particles prepared above, and the developing conditions were the same as in Example 1-1 except that the addition conditions were as shown in Table 2-3. . The physical properties of the developing roller are as shown in Table 2-3. Evaluation was carried out in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-3.

(Comparative Example 8)
A developing roller was produced under the same conditions as in Example 1-1 except that the film thickness of the surface layer of the developing roller in Example 1-1 was changed as shown in Table 2-4. The physical properties of the produced developing roller were as shown in Table 2-4. Evaluation was performed in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-4.

(Comparative Example 9)
A developing roller was produced under the same conditions as in Example 1-7, except that the film thickness of the surface layer of the developing roller in Example 1-7 was changed as shown in Table 2-4. The physical properties of the produced developing roller were as shown in Table 2-4. Evaluation was performed in the same manner as in Example 1-1, and the evaluation results are shown in Table 2-4.

  (Note 1) Although the shell 302 is also a silicone resin, the degree of polymerization is high and thermal decomposition starts before reaching the glass transition point, and the shell 302 has substantially no glass transition point. Therefore, no glass transition point is observed in the temperature region below -60 ° C.

  As shown in Table 1, the developing roller 101 in which the core / shell particles 202 of the present invention were added to the surface layer 104 showed high uniformity in solid image density as a result of image evaluation. Further, no image streaks were observed even after the image was stored for a long time with the photosensitive drum or developing blade in contact with the developing roller. Further, the uniformity of the surface roughness of the developing roller 101 was high. As a result of observing the cross section, the dispersion uniformity of the resin particles was high. However, as shown in Table 2 Comparative Example 1, in the developing roller in which resin particles having no core / shell structure were added to the surface layer, the solid image density was non-uniform as a result of image evaluation. Furthermore, the surface roughness of the developing roller was not uniform, and as a result of observing the cross section, the resin particles were not uniformly dispersed.

  As shown in Table 2, in the developing roller 101 in which resin particles whose core is not silicone resin are dispersed in the surface layer 104 even when having a core-shell structure, the photosensitive drum and the developing blade are brought into contact with the developing roller. Image streaks were seen in the image after long-term storage.

  As shown in Table 2 Comparative Example 3, even with a core / shell structure, solid image density is non-uniform in the developing roller 101 in which resin particles whose shell is not polyurethane resin, epoxy resin, or silicone resin are dispersed in the surface layer 104 It was sex. Further, the surface roughness of the developing roller was not uniform, and the cross section was observed. As a result, the resin particles were not uniformly dispersed.

  As shown in Table 2 Comparative Example 4, image fogging occurred when the particle diameter A of the core-shell particles 202 was larger than 15.0 μm.

  As shown in Table 2 Comparative Example 5, when the particle diameter A of the core / shell particles 202 was smaller than 1.0 μm, the image density was insufficient.

  As shown in Table 2 Comparative Example 6, when the 10% compression hardness E of the core-shell particles 202 was larger than 10 MPa, image fogging after durability occurred.

  As shown in Table 2 Comparative Example 7, when the 10% compression hardness E of the core-shell particles 202 was smaller than 3 MPa, the image density was insufficient.

  As shown in Table 2 Comparative Example 8, when the film thickness of the surface layer of the core / shell particles 202 was D μm, image fogging occurred when A / D was larger than 3.0.

  As shown in Table 2 Comparative Example 9, when the film thickness of the surface layer of the core-shell particle 202 was D μm, the image density was insufficient when A / D was smaller than 0.30.

(Examples 2-1 to 3)
Example 1 except that resin particles dispersed on the surface of the developing roller of Example 1-1 were Alvidur PU5640, manufactured by Nano Resins (core is silicone resin, shell is polyurethane resin), and the addition amount is as shown in Table 3. A developing roller was produced under the same conditions. Table 3 shows the physical properties of the developing roller. Evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 3.

(Examples 3-1 to 3)
Example 1 except that resin particles dispersed on the developing roller surface of Example 1-1 were Albidur EP2240, manufactured by Nano Resins (core is silicone resin, shell is epoxy resin), and the addition amount is as shown in Table 3. A developing roller was produced under the same conditions. Table 3 shows the physical properties of the developing roller. Evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 3.

  As shown in Table 3, when the elastic recovery rate of the resin particles is 95% or more with the developing roller in which the resin particles having the core / shell structure of the present invention are added to the surface layer, the photosensitive drum or the developing blade is kept in contact for a long time. The image streaks were not seen even in the image after. When the elastic recovery rate of the resin particles was 90%, image streaks were observed, but the product was acceptable.

(Examples 4-1 to 3)
[Preparation of core / shell particles 2]
In a 20-liter glass container, add 1000 g of water and 30 g of sodium dodecyl sulfate, mix 250 g of α, ω-dihydroxypolydimethylsiloxane with a viscosity of 10 mPa · s and 15 g of methyltrimethoxysilane at 10 m / s. Warm to 45 ° C. with stirring. Next, 10 g of 10% tetrapropoxyoxytitanium isopropyl alcohol solution was added and reacted for 20 hours to polymerize the core particles of the composite particles. The obtained suspension was dispersed at a peripheral speed of 5 m / s for 40 hours using a Viscomill disperser filled with φ0.5 zircon beads. Subsequently, water was evaporated to obtain silicone resin particles.

  Next, as a secondary step, 120 g of the above silicone resin particles are added to a mixed solution of 25 g of polyoxyethylene octylphenyl ether having an addition mole number of 9 mol and 5000 g of water, and the dispersion is stirred at 5.0 m / S. Obtained. Next, aqueous ammonia was added to adjust the pH to 11. 51 g of methyltrimethoxysilane, 95 g of phenyltrimethoxysilane, and 27 g of α, ω-dihydroxypolydimethylsiloxane having a viscosity of 20 mPa · s were dropped, and the mixture was heated to 70 ° C. and stirred for 1 hour. Next, the mixed solution was filtered with a pressure filter and dried at 100 degrees to obtain core / shell particles.

The obtained core / shell particles 202 had a core part 301 with a silicone resin elastic body having a glass transition point of −120 ° C., and a glass transition point of the silicone resin of the shell part 302 of −60 ° C. Development roller of Example 1-1 A developing roller was produced under the same conditions as in Example 1-1 except that the surface layer resin particles were the core / shell particles produced above and the addition conditions were as shown in Table 4. Table 4 shows the physical properties of the developing roller. Evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 4.

(Examples 4-4 to 6)
[Preparation of core-shell particles 3]
Core-shell particles were produced in the same manner as the core-shell particles 1 except that the viscomill disperser conditions of the obtained suspension were changed to dispersion for 60 hours at a peripheral speed of 15 m / s.

  The obtained core-shell particle 202 had a core part 301 having a glass transition point of −120 ° C. and a shell resin 302 having a glass transition point of −120 ° C. and a glass transition point of −60 ° C.

  The developing roller was produced under the same conditions as in Example 1-1 except that the resin particles on the surface layer of the developing roller of Example 1-1 were the core / shell particles prepared above and the addition conditions were as shown in Table 4. Table 4 shows the physical properties of the developing roller. Evaluation was carried out in the same manner as in Example 1-1, and the evaluation results are shown in Table 4.

(Example 5-1)
A developing roller was produced under the same conditions as in Example 1 except that the amount of resin particles added to the surface layer of the developing roller in Example 1-2 was as shown in Table 5. Table 5 shows the physical properties of the developing roller. The surface roughness Ra was 3.5 μm. Evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 5. Image streaks were good, but development fog was observed. The cause was that the surface roughness of the developing roller was too large and the developer adhered film thickness was too large.

(Example 5-2)
A developing roller was produced under the same conditions as in Example 1 except that the amount of resin particles added to the surface layer of the developing roller in Example 1-6 was as shown in Table 4. Table 4 shows the physical properties of the developing roller. The surface roughness Ra was 0.3 μm. Evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 4. The image streak was good, but the density of the whole image was insufficient in the solid image. The cause was that the surface roughness of the developing roller was small and the developer adhesion film thickness was too thin.

1 shows an example of a cross-sectional view of a developing roller according to the present invention in a longitudinal section and a plane perpendicular to an axis. It is the figure which expanded the cross section of the developing roller surface layer which can apply this invention. It is a block diagram which shows an example of the core-shell structure elastic resin particle concerning this invention. It is a figure explaining the measuring method of the elastic recovery factor of the core-shell structure elastic resin particle concerning this invention. 1 is a schematic configuration diagram illustrating an example of an electrophotographic process cartridge and an image forming apparatus according to the present invention.

Explanation of symbols

101 Development Roller 102 Shaft Core 103 Elastic Layer 104 Surface Layer 201 Surface Binder Resin 202 Core Shell Particle 203 Surface Layer Surface 204 Concavity and Concavity on Surface Layer 205-209 Core Shell Particle 210-212 Between Core Shell Particle Distance 301 Core portion 302 Shell portion 401 Photosensitive drum 402 Charging roller 403 Exposure 405 Developer 406 Feed roller 407 Recording material 408 Transfer roller 409 Fixing roller 410 Pressure roller 411 Cleaning unit 412 Waste developer container 413 Developer supply roller 414 Developer storage tank 415 Development blade 501 Core / shell particle diameter 502 25% compression state 503 Flat indenter

Claims (9)

In a developing roller having a core, a resin layer formed around the core, and a surface layer formed around the resin layer,
The surface layer includes elastic resin particles having a core / shell structure, and a binder resin in which the elastic resin particles are dispersed, and
A developing roller that satisfies the following conditions a) to e):
a) The core portion of the elastic resin particles is made of a silicone resin, and the shell portion is at least one resin selected from the group consisting of a polyurethane resin, an epoxy resin, and a silicone resin,
b) 10% compression hardness E of the elastic resin fine particles is 3 MPa or more and 10 MPa or less,
c) The volume average particle diameter A of the elastic resin particles is 1.0 μm or more and 15.0 μm or less, and the average interparticle distance B μm of the elastic resin particles in the cross section of the surface layer is 0.1 A or more and 2.0 A or less. And the coefficient of variation C of the average interparticle distance B is 150% or less,
d) When the film thickness of the surface layer is D μm, A / D is 0.30 or more and 3.0 or less,
e) The elastic recovery rate of the elastic resin particles is 90% or more.   The developing roller according to claim 1, wherein the elastic recovery rate of the core-shell structure elastic resin particles is 95% or more.   The glass transition point of the core portion of the core-shell structure elastic resin particles is -120 ° C or higher and -110 ° C or lower, and the shell portion does not have a glass transition point in a temperature region lower than -60 ° C. 3. The developing roller according to 1 or 2.   The developing roller according to claim 1, wherein the binder resin of the surface layer is a polyurethane resin.   The developing roller according to claim 1, wherein the surface layer has a surface roughness Ra of 0.5 μm or more and 3.0 μm or less.   The developing roller according to claim 1, wherein the resin forming the resin layer is a silicone resin.   7. The developing roller according to claim 1, wherein a content of the core-shell structure elastic resin fine particles with respect to the surface layer is 22 parts by mass or more and 81 parts by mass or less.   An electronic apparatus comprising at least an electrophotographic photosensitive member for forming an electrostatic latent image and an electrophotographic developing member disposed in contact with the electrophotographic photosensitive member, and configured to be detachable from an electrophotographic image forming apparatus 8. An electrophotographic process cartridge according to claim 1, wherein the developing member is a developing roller according to any one of claims 1 to 7.   8. An electrophotographic image forming apparatus comprising: an electrophotographic photosensitive member for forming at least an electrostatic latent image; and an electrophotographic developing member disposed in contact with the electrophotographic photosensitive member. An electrophotographic image forming apparatus comprising at least the developing roller described above.

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