JP7270476B2 - COATING COMPOSITION FOR CONDUCTIVE ROLLER, DEVELOPING ROLLER USING THE SAME, AND IMAGE FORMING APPARATUS - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coating composition for a conductive roller, a developing roller using the same (hereinafter also simply referred to as "coating composition" and "roller", respectively) and an image forming apparatus, and more particularly to a use environment that is more severe than before. The present invention relates to a coating composition for a conductive roller, which can prevent filming of the roller even under the condition and improve toner leakage from the end sealing member of the developing device, and a developing roller and an image forming apparatus using the coating composition.

2. Description of the Related Art Electrophotographic image forming apparatuses such as copiers and printers are provided with a developing device. This developing device generally includes a housing having a developing roller for carrying toner, a developing blade for regulating the amount of toner, and a toner storage chamber for storing toner therein; and an end sealing member that slides on the end of the roller to prevent toner from leaking out of the housing.

Conventionally, when long-term printing is performed using an image forming apparatus in a harsh environment, the toner deteriorates due to friction between the developing roller and the developing blade in contact with the developing roller. there was a case. If this toner fusion occurs on the developing blade, development streaks will occur, and if it occurs on the developing roller, filming will occur. Therefore, there is a need for a developing roller that can minimize the deterioration of toner. Under such circumstances, Patent Document 1 discloses a coating composition that can reduce deterioration of toner during long-term printing by using it for forming a surface layer of a developing roller, a developing roller using the same, and an image forming apparatus. is proposed.

Patent No. 6276179

The coating composition proposed in Patent Document 1 contains fine particles having a low glass transition temperature Tg, that is, having a low hardness. Therefore, when the coating composition is used to form the surface layer of the roller, for example, the friction between the roller and the developing blade can be reduced, and deterioration of the toner can be reduced. As a result, it is possible to prevent the occurrence of image defects caused by the fusion of the toner to the roller and the developing blade.

However, in recent years, electrophotographic equipment is required to produce images faster (high-speed printing), longer (higher durability), and with higher image quality. In order to meet such a demand, if durability printing is performed under a harsher environment, there arises a new problem that toner easily leaks from the end seal member of the developing device.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and to prevent toner from leaking from end seal members of a developing device while preventing roller filming even under harsher usage environments than conventional ones. It is an object of the present invention to provide a coating composition for a conductive roller capable of

As a result of intensive studies aimed at solving the above problems, the present inventors have solved the above problems by using fine particles that satisfy predetermined particle diameters and physical properties for the surface layer forming the outermost surface of the developing roller. After discovering that it can be done, the present invention was completed.

That is, the coating composition for a conductive roller of the present invention is a coating composition for a conductive roller containing a resin component containing a polyol and an isocyanate, and fine particles,
The fine particles are a polyurethane resin, have a glass transition temperature of −10° C. or less, an average particle diameter of 20 μm or more, and a universal hardness of 0.8 or less at an indentation depth of 20 μm,
The content of the fine particles is 5.0 to 15.0 parts by mass with respect to 100 parts by mass of the polyol.

Here, the average particle size is a value determined by a dynamic light scattering method. Also, the universal hardness of the fine particles can be obtained by measuring the fine particle portion in the surface layer of the roller when the surface layer is formed, using a Fischer hardness tester.

In the coating composition of the present invention, the fine particles preferably have a glass transition temperature of -30°C or lower, more preferably -50°C or lower. Moreover, in the coating composition of the present invention, the content of the fine particles is preferably 7.0 to 10.0 parts by mass with respect to 100 parts by mass of the polyol. Furthermore, in the coating composition of the present invention, the glass transition temperature of the resin component is preferably −10° C. or lower.

The developing roller of the present invention includes a shaft and an elastic layer carried on the outer periphery of the shaft,
The outer periphery of the elastic layer is coated with the coating composition for a conductive roller of the present invention.

The image forming apparatus of the present invention includes a developing roller rotatably installed in a developing device, a supply roller supplying toner to the developing roller, and arranged so as to be in sliding contact with the surface of the axial end portion of the developing roller. and an image forming apparatus comprising:
The developing roller is the developing roller of the present invention.

INDUSTRIAL APPLICABILITY According to the present invention, a coating composition for a conductive roller is capable of preventing filming of the roller and improving toner leakage from the end seal member of the developing device even in a use environment that is more severe than before. , a developing roller and an image forming apparatus using the same can be provided.

1 is a longitudinal cross-sectional view of a developing roller according to one preferred embodiment of the present invention; FIG. 1 is an explanatory diagram of an image forming apparatus according to a preferred embodiment of the present invention; FIG. FIG. 2 is an enlarged view of the vicinity of the axial end of the developing roller in the image forming apparatus according to the preferred embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the coating composition for conductive rollers of the present invention will be described. The coating composition for conductive rollers of the present invention contains a resin component containing polyol and isocyanate, and fine particles, and is used to form the surface layer of the conductive roller. FIG. 1 shows a longitudinal sectional view of a developing roller according to one preferred embodiment of the present invention. The illustrated developing roller 10 includes a shaft 1, an elastic layer 2 carried on the outer periphery thereof, and a surface layer 3 covering the outer periphery thereof.

In the coating composition of the present invention, the fine particles have a glass transition temperature Tg of -10°C or lower, preferably -30°C or lower, more preferably -50°C or lower. To reduce the friction between the roller and other members, such as blades, when the surface layer 3 of the conductive roller 10 is formed using fine particles having a low Tg in the coating composition. can be done. That is, it is thought that the softer the fine particles, the softer the protrusions in the irregularities of the surface layer 3 of the roller 10 when the toner is rubbed against the blade, and thus the deterioration of the toner is reduced. . Therefore, by forming the surface layer 3 of the developing roller 10 using the coating composition of the present invention, it is possible to reduce deterioration of the toner during long-term printing, and suppress the occurrence of development streaks and filming of the roller. can. As a result, it is possible to suppress the occurrence of image defects caused by toner fusion to the roller or blade. In the coating composition of the present invention, a polyurethane resin whose Tg easily satisfies the above range is used as the material of the fine particles.

In addition, in the coating composition of the present invention, the fine particles have an average particle size of 20 μm or more, preferably 20 to 25 μm. As described above, when durable printing is performed in a harsher environment, toner leakage from the end seal member of the developing device is more likely to occur. Here, the end sealing member is a flexible member such as felt or fiber woven pile, electrostatic flocking, or the like, which rubs against the surface of the end in the axial direction (longitudinal direction) of the developing roller 10 . The flexible member is in pressure contact with the surface layer 3 of the roller 10 to exhibit sealing properties. Therefore, in order to improve the toner leakage, it is effective to improve the toner scraping ability of the end sealing member. Therefore, in the coating composition of the present invention, by using fine particles having an average particle size of 20 μm or more, the surface layer of the roller is roughened so that the end sealing member can easily scrape off the toner.

In the coating composition of the present invention, the content of such fine particles is 5.0 to 15.0 parts by mass, preferably 7.0 to 10.0 parts by mass, per 100 parts by mass of the polyol component. If the amount of the fine particles is less than 5.0 parts by mass, the effect of scraping the toner is not sufficiently obtained. becomes larger. Further, by setting the blending amount of the fine particles within the above range, it is possible to reliably obtain the effect of reducing the deterioration of the toner while ensuring the toner transportability.

Furthermore, in the coating composition of the present invention, the fine particles preferably have a universal hardness of 0.8 or less at an indentation depth of 20 μm, for example, a low hardness in the range of 0.2 to 0.8. A range of 0.4 to 0.6 is more preferred. When the hardness of the fine particles increases, the load on the toner increases, and the toner is crushed between the blade and the fine particles, which causes development streaks and filming of the roller. The hardness of fine particles is approximately proportional to the value of Tg, and the lower the Tg, the smaller the hardness.

The resin component, which is the main component of the coating composition of the present invention, is not particularly limited as long as it contains polyol and isocyanate. use. By using a coating composition that combines flexible fine particles and a flexible resin component, the friction between the formed layer and the toner is further reduced, thereby reducing deterioration of the toner and providing high-quality development. It becomes possible to obtain rollers. It is known that the softer the resin component constituting the layer, the more effective it is in reducing toner deterioration. In the coating composition of the present invention, by using soft fine particles and combining them with a soft resin component, a greater effect of reducing toner deterioration can be obtained. If the Tg of the resin component is lower than −20° C., the hardness of the surface is remarkably lowered, and blade setting marks are generated in the high-temperature and high-humidity storage test in the state assembled in the cartridge, which is not preferable.

As such a resin component, specifically, for example, a urethane resin obtained by cross-linking a lactone-modified polyol with two or more kinds of polyisocyanates including at least isophorone diisocyanate can be suitably used. Lactone-modified polyols can be produced by modifying the ends of polyols with lactones such as ε-caprolactone, and commercially available products can also be used. From the viewpoint of achieving both compression set performance and toner adhesion resistance when applied to a conductive roller, the lactone-modified polyol has a polystyrene-equivalent number-average molecular weight (Mn) measured by gel permeation chromatography. , It is preferably 1000 to 5000, more preferably 1000 to 3000, and the ratio of the polystyrene-equivalent weight average molecular weight (Mw) and number average molecular weight (Mn) measured by gel permeation chromatography The expressed molecular weight distribution (Mw/Mn) is preferably 2.5 or less, more preferably 2.0 or less.

Polyols modified with lactones include polyether polyols obtained by addition polymerization of alkylene oxides such as ethylene oxide and propylene oxide to glycerin, polytetramethylene glycol, glycerin, ethylene glycol, propylene glycol, butanediol, pentanediol, and hexane. diol, octanediol, polybutadiene polyol, polyisoprene polyol, polyester polyol, and the like.

In addition, the polyisocyanate that crosslinks the lactone-modified polyol is two or more kinds of polyisocyanates containing at least isophorone diisocyanate. Toner fusion resistance can be improved. Polyisocyanates other than isophorone diisocyanate (IPDI) among the above two or more polyisocyanates include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), hydrogenated diphenylmethane diisocyanate, and hydrogenated triphenylmethane diisocyanate. Examples include diisocyanate, hexamethylene diisocyanate (HDI), nurate-modified hexamethylene diisocyanate, and the like. From the viewpoint of achieving both low hardness and compression set performance of the layer formed by the coating composition, the two or more polyisocyanates used for cross-linking the lactone-modified polyol are isophorone diisocyanate and hexamethylene diisocyanate. More preferably, the molar ratio of isophorone diisocyanate to hexamethylene diisocyanate is from 3:1 to 1:3.

The coating composition may further contain a catalyst for promoting the cross-linking reaction between the lactone-modified polyol and two or more types of polyisocyanates. Examples of such catalysts include organic tin compounds such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, and tin octoate; organic lead compounds such as lead octoate; triethylamine; monoamines such as dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine and tetramethylhexanediamine; triamines such as pentamethyldiethylenetriamine, pentamethyldipropylenetriamine and tetramethylguanidine; triethylenediamine, dimethylpiperazine, cyclic amines such as methylethylpiperazine, methylmorpholine, dimethylaminoethylmorpholine and dimethylimidazole; alcohol amines such as dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxyethylpiperazine and hydroxyethylmorpholine; Ether amines such as (dimethylaminoethyl) ether, ethylene glycol bis(dimethyl)aminopropyl ether, and the like. Among these catalysts, organotin compounds are preferred. These catalysts may be used singly or in combination of two or more. The amount of catalyst used is preferably in the range of 0.001 to 2.0 parts by mass with respect to 100 parts by mass of polyol.

Further, the coating composition of the present invention can be mixed with a conductive agent such as an electronic conductive agent or an ionic conductive agent to adjust the conductivity. Examples of electronic conductive agents include conductive carbon such as ketjen black and acetylene black, carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, and carbon black for color that has undergone oxidation treatment. , pyrolytic carbon black, natural graphite, artificial graphite, antimony-doped tin oxide, ITO, metal oxides such as tin oxide, titanium oxide, and zinc oxide, metals such as nickel, copper, silver, and germanium, polyaniline, polypyrrole, polyacetylene, etc. conductive polymers, carbon whiskers, graphite whiskers, titanium carbide whiskers, conductive potassium titanate whiskers, conductive barium titanate whiskers, conductive titanium oxide whiskers, and conductive zinc oxide whiskers.

In addition, as ion conductive agents, perchlorates, chlorates, hydrochlorides, bromates such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, modified fatty acid dimethylethylammonium, etc. ammonium salts such as , iodate, hydroborofluorate, sulfate, ethyl sulfate, carboxylate, sulfonate; chlorate, chlorate, hydrochloride, bromate, iodate, hydroborofluorate, sulfate, trifluoromethylsulfate, sulfonate and the like. The conductive agent may be used singly or in combination of two or more, or an electronic conductive agent and an ionic conductive agent may be combined.

The amount of the conductive agent in the coating composition of the present invention is preferably 20 parts by mass or less with respect to 100 parts by mass of the resin component, more preferably 0.01 to 20 parts by mass in the case of the ion conductive agent. A range of up to 10 parts by mass is more preferable. On the other hand, in the case of the electronic conductive agent, it is preferably in the range of 1 to 70 parts by mass, more preferably in the range of 5 to 50 parts by mass, based on 100 parts by mass of the resin component. The volume resistance value of the layer formed using the coating composition is preferably adjusted to be in the range of 10 ³ to 10 ¹⁰ Ω·cm, preferably 10 ⁴ to 10 ⁸ Ω·cm, by adding a conductive agent. More preferably, it is adjusted to be in the range of cm.

Next, the developing roller of the present invention will be explained. As shown in FIG. 1, the developing roller 10 of the present invention includes a shaft 1 and an elastic layer 2 carried on its outer circumference, and has a surface layer 3 on the outer circumference of the elastic layer 2 .

In the developing roller 10 of the present invention, the surface layer 3 is formed from the coating composition of the present invention, thereby reducing friction between the roller and other members such as blades. It is possible to reduce toner deterioration during long-term printing, suppress development streaks and roller filming, and improve toner leakage from the end seal member of the developing device. Although the surface layer 3 is one layer in the illustrated example, it may be composed of two or more layers. In the developing roller of the present invention, since the surface layer 3 is arranged around the outer periphery of the elastic layer 2, it is possible to sufficiently prevent contaminants exuding from the elastic layer 2 from contaminating the photosensitive drum.

The shaft 1 is not particularly limited as long as it has good electrical conductivity. A metal shaft such as a body, a highly conductive plastic shaft, or the like can be used.

The elastic layer 2 can be formed from a foam, and specific examples include polyurethane, silicone rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), natural rubber, styrene-butadiene rubber ( SBR), butadiene rubber, isoprene rubber, polynorbornene rubber, butyl rubber, chloroprene rubber, acrylic rubber, epichlorohydrin rubber (ECO), ethylene-vinyl acetate copolymer (EVA) and mixtures thereof. Among these elastomers, it is preferable to use polyurethane. This is because the adhesiveness to the surface layer 3 is better because the surface layer 3 is composed of urethane, which is a resin component. The foam constituting the elastic layer 2 can be formed by chemically foaming the above elastomer using a foaming agent, or by mechanically entraining air to foam as in the case of polyurethane foam. . Here, the expansion ratio of the foam constituting the elastic layer 2 is preferably in the range of 1.5 to 50 times, and the density is preferably in the range of 0.05 to 0.9 g/cm ³ .

In addition, since the compression set performance is improved by making the cells of the foam constituting the elastic layer 2 closed cells, the cells in the foam are preferably closed cells. Here, in order to make the cells of the foam into closed cells, a method of foaming the raw material of the elastomer by mechanical stirring to form a foam is preferably employed.

The elastic layer 2 can be blended with a conductive agent to adjust the conductivity. Examples of the conductive agent used in the elastic layer 2 include the same electronic conductive agent and ionic conductive agent as used in the coating composition of the present invention. Among these, the amount of the electronic conductive agent to be blended is preferably in the range of 1 to 50 parts by mass, more preferably in the range of 5 to 40 parts by mass, per 100 parts by mass of the resin component constituting the elastic layer. Also, the amount of the ion conductive agent is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, per 100 parts by mass of the resin component forming the elastic layer. The elastic layer 2 preferably has a resistance value of 10 ³ to 10 ¹⁰ Ωcm, more preferably 10 ⁴ to 10 ⁸ Ωcm, by blending a conductive agent. If the resistance value of the elastic layer 2 is less than 10 ³ Ωcm, charges may leak to the photosensitive drum or the like, or the developing roller itself may be destroyed by the voltage ^.

The elastic layer 2 may optionally contain a cross-linking agent such as an organic peroxide or a vulcanizing agent such as sulfur in order to convert the elastomer into a rubber-like substance. A vulcanization accelerator, an auxiliary vulcanization accelerator, a vulcanization retarder, etc. may be contained. In addition, the elastic layer 2 contains various rubber compounding agents such as fillers, peptizers, foaming agents, plasticizers, softeners, tackifiers, anti-adhesive agents, separating agents, release agents, extenders and coloring agents. agents may be included.

The surface layer 3 is formed using the coating composition of the present invention, as described above. Although the total thickness of the surface layer 3 is not particularly limited, it is preferably 30 μm or less, more preferably in the range of 1 to 15 μm. If the total thickness of the surface layer 3 exceeds 30 μm, the surface layer 3 may become hard and lose its flexibility, resulting in deterioration in durability, cracking during use, damage to the toner, and damage to the photosensitive drum. In addition, the toner may adhere to the layering blade, resulting in an image defect.

The method of forming the surface layer 3 is not particularly limited, and the above coating composition containing each component constituting the surface layer 3 is prepared, and this coating composition is applied by a dipping method, a spray method, a roll coating method, or the like. A method of curing by heating at 100 to 120° C. for 20 to 40 minutes after coating by a known coating method is preferably used.

In the illustrated developing roller 10, the surface layer 3 is arranged on the elastic layer 2, but in the present invention, an intermediate layer may be formed between the elastic layer 2 and the surface layer 3 ( not shown). In this case, for example, by disposing an intermediate layer that is softer than the surface layer 3, damage to the toner can be greatly reduced.

The intermediate layer can be suitably formed using one or more water-based resins selected from rubber-based, urethane-based, and acrylic-based resins. Rubber-based latexes such as natural rubber (NR), chloroprene rubber (CR), nitrile rubber (NBR), and styrene-butadiene rubber (SBR); urethane-based emulsions and dispersions such as ether and ester systems; Emulsions of acrylic, acrylic styrene, etc. can be suitably used as the acrylic.

The surface roughness of the developing roller of the present invention preferably has a JIS arithmetic mean roughness (Ra) of 0.7 to 2.0 μm. When the arithmetic average roughness (Ra) of the developing roller exceeds 2.0 μm, the amount of toner conveyed tends to increase, but the amount of charge on the toner is insufficient, resulting in background fogging and gradation defects in images. . On the other hand, if the arithmetic mean roughness (Ra) is less than 0.7 μm, the toner scraping property of the end sealing member is not sufficient, and toner leakage may not be sufficiently prevented.

The resistance value of the developing roller of the present invention is not particularly limited, but in order to obtain good images, the electric resistance is preferably 10 ³ to 10 ¹⁰ Ω, and 10 ⁴ to 10 ⁸ Ω. is more preferable. If the resistance value of the developing roller is less than 10 ³ Ω, it becomes extremely difficult to control the gradation, and bias leakage may occur when the photosensitive drum has a defect. On the other hand, if the resistance value exceeds 10 ¹⁰ Ω, for example, when developing toner on a photosensitive drum, the developing bias causes a voltage drop due to the high resistance of the developing roller itself, making it impossible to secure a sufficient developing bias for development. As a result, sufficient image density cannot be obtained. The resistance value is measured, for example, by pressing the outer peripheral surface of the developing roller against a flat plate or cylindrical counter electrode with a predetermined pressure, applying a voltage of 100 V between the shaft and the counter electrode, and calculating the current value at that time. can ask. By properly and uniformly controlling the resistance value of the developing roller in this manner, the electric field intensity for toner movement can be maintained properly and uniformly.

Further, the developing roller of the present invention preferably has an Asker C hardness of 60° or less. By using a low-hardness developing roller with an Asker C hardness of 60° or less, the toner is prevented from being damaged between the developing roller, the photosensitive drum, the blade, the toner supply roller, and the like when incorporated in an image forming apparatus. can be prevented and a sufficiently good image can be formed.

Next, the image forming apparatus of the present invention will be described. FIG. 2 shows an explanatory diagram of an image forming apparatus according to a preferred embodiment of the present invention. The illustrated image forming apparatus of the present invention has an image forming body 21 such as a photoreceptor holding an electrostatic latent image. a developing roller 10 that converts an electrostatic latent image into a visible image by means of there is Image formation is performed by a series of processes in which the toner 20 is transported from the toner storage unit 23 to the image forming body 21 via the toner supply roller 22 and the developing roller 10 .

FIG. 3 shows an enlarged view of the vicinity of the end portion in the axial direction of the developing roller in the image forming apparatus according to the preferred embodiment of the present invention. The image forming apparatus of the present invention includes an end seal for preventing leakage of toner 20 to the outside of developing device 30 by sliding contact with axial end 10a of developing roller 10 rotatably supported by shaft 1. A member 24 is provided. Furthermore, the image forming apparatus of the present invention is equipped with the roller of the present invention as a developing roller. As described above, the coating composition used for forming the surface layer 3 of the roller 10 of the present invention contains fine particles having an average particle size of 20 μm or more to roughen the surface layer 3 of the roller 10, and the end seal member 24 is formed of toner. 20 is made to be easily scraped off. As a result, the image forming apparatus of the present invention can prevent filming of the roller 10 and improve toner leakage from the end seal member of the developing device. It should be noted that the image forming apparatus of the present invention can be further provided with known components that are commonly used in image forming apparatuses (not shown).

In the illustrated image forming apparatus, an electrostatic latent image is formed on the image forming body 21 by an exposure device (not shown) after the charging roller 25 charges the image forming body 21 to a constant potential. Next, the toner supply roller 22, the developing roller 10, and the image forming body 21 rotate in the directions of the arrows in the figure, so that the toner 20 on the toner supplying roller 22 passes through the developing roller 10 and is transferred to the image forming body 21. sent to The toner 20 on the developing roller 10 is formed into a uniform thin layer by the layering blade 26 , and the toner 20 is transferred from the developing roller 10 to the image forming body 21 by rotating while the developing roller 10 and the image forming body 21 are in contact with each other. adheres to the electrostatic latent image, and the latent image is visualized. The toner 20 adhering to the latent image is transferred to a recording medium such as paper by a transfer roller 27 , and the toner 20 remaining on the image forming body 21 after transfer is removed by a cleaning blade 29 of a cleaning section 28 . In the image forming apparatus of the present invention, the developing roller of the present invention is used as the developing roller 10. Therefore, it is possible to reduce the deterioration of the toner during long-term use while ensuring the transportability of the toner, thereby reducing the adhesion of the toner to the blade. It is possible to suppress the occurrence of filming of the roller and the toner leakage from the end sealing member.

The present invention will now be described in more detail using examples.
<Examples 1 and 2 and Comparative Examples 1 and 2>
100 parts by mass of a urethane prepolymer synthesized from tolylene diisocyanate (TDI) and polyether polyol and 2 parts by mass of acetylene black are mixed to prepare a urethane prepolymer in which acetylene black is dispersed, and this is used as the A component. bottom. On the other hand, 30 parts by mass of polyether polyol and 0.1 part by mass of sodium perchlorate (NaClO ₄ ) were mixed while heating to 70°C, and 4.5 parts by mass of polyether-modified silicone oil (foam stabilizer) was added. and 0.2 parts by mass of dibutyltin dilaurate (catalyst) to prepare a mixture, which was used as the B component. Next, the components A and B are foamed by a mechanical froth method, injected into a cylindrical mold set with a metal core, and RIM molded to form a roller body having an elastic layer made of foamed polyurethane. made.

A resin component (Tg: -20 ° C.) obtained by blending 100 parts by mass of polyol (Placcel 220AL, manufactured by Daicel Chemical Industries, Ltd.) with 50 parts by mass of polyisocyanate (Excel Hardener HX, manufactured by Asia Industry Co., Ltd.). A coating composition was prepared by adding 8 parts by mass of fine particles shown in the table below. The resulting coating composition was applied onto the elastic layer and cured by heating at 115° C. for 30 minutes to form a surface layer. Thus, the developing rollers of each example and comparative example were obtained.

Each of the obtained test rollers was mounted on a printer LBP5050 manufactured by Canon Inc., and durable printing was performed to check for toner leakage and filming. The results were expressed according to the following criteria.

<Toner leakage>
12K○: Not occurred until 12,000 printed sheets 9K×: Over 7,000 printed sheets, occurred up to 9,000 sheets 7K×: Over 6,000 printed sheets, occurred up to 7,000 sheets 6K×: 6,000 printed sheets if it occurs by

<Filming>
×: When toner fusion can be visually confirmed on the developing roller after printing 12,000 sheets △: When toner fusion cannot be visually confirmed, but can be confirmed with a microscope (500x) ○: Confirmed with a microscope (500x) if you can't

Ａ：アートパールＪＢ８００ＴとＪＢ４００Ｔとの１：１の混合物
Ｂ：アートパールＪＢ４００Ｔ
Ｃ：アートパールＪＢ３００Ｔ
Ｄ：アートパールＣ３００
※１：押し込み深さ２０μｍにおけるユニバーサル硬度
※２：平均粒径が異なる２種の微粒子を使用

A: 1:1 mixture of Artpearl JB800T and JB400T B: Artpearl JB400T
C: Art Pearl JB300T
D: Art Pearl C300
*1: Universal hardness at an indentation depth of 20 μm *2: Two types of fine particles with different average particle diameters are used

As shown in Table 1, it was confirmed that the developing roller of the present invention can prevent toner from leaking from the end seal member of the developing device while preventing filming of the roller.

1 shaft 2 elastic layer 3 surface layer 10 developing roller (roller)
11 End sealing member 20 Toner 21 Image forming member 22 Toner supply roller 23 Toner storage unit 24 End sealing member 25 Charging roller 26 Layering blade 27 Transfer roller 28 Cleaning unit 29 Cleaning blade 30 Developing device

Claims (5)

A coating composition for a conductive roller containing a resin component containing a polyol and an isocyanate, and fine particles,
The fine particles are a polyurethane resin, have a glass transition temperature of −50 ° C. or lower, an average particle diameter of 20 μm or higher, and a universal hardness of 0.8 or lower at an indentation depth of 20 μm,
A coating composition for a conductive roller, wherein the content of the fine particles is 5.0 to 15.0 parts by mass with respect to 100 parts by mass of the polyol. 2. The coating composition for a conductive roller according to claim 1 , wherein the content of said fine particles is 7.0 to 10.0 parts by mass with respect to 100 parts by mass of said polyol. 3. The coating composition for a conductive roller according to claim 1, wherein the resin component has a glass transition temperature of -10° C. or lower. A developing roller including a shaft and an elastic layer carried on the outer periphery of the shaft,
A developing roller, wherein the outer periphery of said elastic layer is coated with the coating composition for a conductive roller according to any one of claims 1 to 3 . a developing roller rotatably installed in a developing device; a supply roller for supplying toner to the developing roller; and an end seal member disposed so as to be in sliding contact with the surface of an axial end of the developing roller; In an image forming apparatus having
5. An image forming apparatus, wherein the developing roller is the developing roller according to claim 4 .

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