JP4942363B2 - Developing roller and image forming apparatus - Google Patents

Description

  The present invention includes a conductive shaft body and a conductive elastic layer positioned outside the conductive shaft body, and further, a toner formed in a thin film state on a toner carrying layer provided on the outer peripheral portion of the conductive elastic layer. The present invention relates to a developing roller used in an image forming apparatus that visualizes an electrostatic latent image formed on a latent image carrier after the toner layer is formed to a predetermined toner layer thickness and an image forming apparatus using the same.

  Conventionally, in an image forming apparatus such as an electrophotographic system such as a copying machine or a printer or an electrostatic recording system, contact development is used as a developing method for visualizing a latent image by attaching toner to an electrostatic latent image on a latent image carrier. The law is known.

  In addition, a developing roller is known in which a conductive elastic layer made of an elastic body and a toner carrying layer made of resin are concentrically stacked in this order around a conductive shaft.

  As described above, the latent image is developed by the developing roller including the conductive shaft, the conductive elastic layer positioned outside the conductive shaft, and the toner carrying layer, and the toner carried in a thin film state on the toner carrying layer of the developing roller. In an image forming apparatus that visualizes an electrostatic latent image formed on a carrier, the developing roller must rotate while maintaining a close contact with the latent image carrier. Therefore, the toner carrying layer that covers the surface of the developing roller has control of chargeability and adhesion to the toner, control of the frictional force between the latent image carrier and the layer forming member, or prevention of contamination of the latent image carrier. Required.

  Furthermore, in recent years, demands for higher speed, finer image formation, color image formation, etc. for printers and the like have become very severe, and problems that cannot be handled by conventional toner carriers have become apparent. That is, when a toner carrier is incorporated in an image forming apparatus and used for a long time, an increase in the number of printed sheets may cause image defects such as white image fogging, halftone image roughness, or black image shading. There is a problem (see, for example, Patent Document 1).

  This is because when a toner carrier such as a developing roller is used for a long time by an image forming apparatus, the toner carrier layer on the surface of the toner carrier is worn by friction with toner, a toner application roller or a stratification blade. When the toner component filming occurs, the properties of the toner carrying layer change, the toner charge amount and transport amount change, white image fogging, halftone image roughness, black image shading unevenness, etc. It is known that this is caused by image defects.

  In order to solve the above problems, it has been proposed to provide a coating layer made of a polyurea resin cured by reacting a polyamine compound and a polyisocyanate compound on a conductive elastic layer (see Patent Document 1). .

However, when a polyamine compound and a polyisocyanate compound are mixed to form a one-component coating material, the pot life is short and disadvantageous.
Japanese Patent Laid-Open No. 11-352770

  Accordingly, in order to solve the conventional problems as described above, the toner carrying layer on the surface of the developing roller reduces the frictional force and / or frictional heat against the toner, thereby preventing the filming of the toner component. Prevents the occurrence of image defects such as fogging of white images, roughness of halftone images, or unevenness of black images, and lengthens and stabilizes the pot life during the compound reaction that forms the toner-carrying layer. It is an object of the present invention to provide a developing roller capable of obtaining a high-definition and high-quality printed image that can be produced, and an image forming apparatus using such a developing roller with improved surface durability.

  The present invention employs the following means in order to realize the above-described problems.

The invention according to claim 1 is a developing roller having a conductive shaft, a conductive elastic layer positioned outside the conductive shaft, and a toner carrying layer provided on an outer periphery of the conductive elastic layer. The toner carrying layer contains a reaction product of a polyurea compound and a polyurethane compound, and the reaction product is generated by a reaction of an MDI isocyanate, an ether polyol, and an amine. Yes.

The invention according to claim 2 is the structure according to claim 1 , and the reactant reacts with an amine after pre-reacting an MDI isocyanate and an ether polyol in advance to form a prepolymer. It is characterized by being.

According to a third aspect of the present invention, in addition to the constitution of the first or second aspect , the JIS (B0601) ten-point average roughness (Rz) of the surface of the toner carrying layer is 2 to 15 μm. .

According to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, an electric resistance value between the conductive shaft body and the surface of the toner carrying layer is DC 100V. It is characterized by being 1 × 10 ⁴ to 10 ⁹ Ω.

According to a fifth aspect of the present invention, there is provided the developing device according to any one of the first to fourth aspects, wherein the toner is carried on the surface of the toner carrying layer of the developing roller and the toner thin film is formed. The toner is attached to the surface of the latent image carrier, and a visible image is formed on the surface of the latent image carrier.

  Since the present invention employs the configuration as described above, according to the first aspect of the present invention, the toner carrying layer provided on the outer peripheral portion of the conductive elastic layer of the developing roller is composed of a polyurea compound and a polyurethane compound. Therefore, the toner-carrying layer on the surface of the developing roller reduces the frictional force and / or frictional heat against the toner, thereby preventing the occurrence of filming of the toner component and the white image. High definition that can prevent the occurrence of image defects such as fogging, halftone image roughness, black image shading, and the like, and can increase and stabilize the pot life during the reaction of the compound that forms the toner carrying layer. A developing roller capable of obtaining a high-quality printed image can be provided.

Further, according to the invention described in claim 1, the reaction product of a polyurea compound and a polyurethane compound, MDI-based isocyanate, since those produced by the reaction of the ether-based polyols, and amine, the wear of the surface of the developing roller Thus, a developing roller having further improved durability against the above can be obtained.

According to the second aspect of the present invention, a reaction product of a polyurea compound and a polyurethane compound is pre-reacted with an MDI isocyanate and an ether polyol to form a prepolymer, and then reacted with an amine. Therefore, in addition to the effect of the invention of claim 1 , a developing roller with more stable quality can be obtained.

According to the invention of claim 3 , since the JIS (B0601) ten-point average roughness (Rz) of the surface of the toner carrying layer is 2 to 15 μm, in addition to the effects of the invention of claim 1 or 2 , Higher-definition and high-quality printed images can be obtained.

According to the fourth aspect of the present invention, by setting the electric resistance value between the conductive shaft and the surface of the toner carrying layer to 1 × 10 ⁴ to 10 ⁹ Ω, an appropriate development bias can be obtained. Therefore, in addition to the effects of any one of the first to third aspects, a clear printed matter can be obtained without causing toner fog or blur.

According to the fifth aspect of the present invention, after the toner is carried on the surface of the toner carrying layer of the developing roller according to any one of the first to fourth aspects to form the toner thin film, the toner is Since a visible image is formed on the surface of the latent image holding member by being attached to the surface of the latent image holding member, an image forming apparatus capable of obtaining a high-definition and high-quality printed image can be provided.

  The developing roller and the image forming apparatus using the developing roller according to the embodiment of the present invention will be described below. However, the present invention is not limited to this embodiment.

  FIG. 1 is a cross-sectional view of a developing roller according to an embodiment of the present invention.

  As shown in FIG. 1, the developing roller 1 includes a columnar conductive shaft body 2 and a cylindrical conductive elastic layer 3 that covers the surface of the conductive shaft body 2. A toner carrying layer 4 that can carry toner in a thin film state is provided on the outer periphery of the conductive elastic layer 3.

  The conductive shaft body 2 includes, for example, (1) a metal shaft body made of iron, aluminum, stainless steel, brass, etc., and (2) a metal on the surface of a thermoplastic resin or thermosetting resin core body. Shaft body plated with film, (3) Shaft body with metal film deposited on the surface of thermoplastic resin or thermosetting resin core, (4) Conductivity imparting agent on thermoplastic resin or thermosetting resin What is necessary is just the shaft etc. which were integrally formed with the resin composition which mix | blended carbon black, metal powder, etc.

  The conductive elastic layer 3 is made of silicone rubber, ethylene-propylene-butadiene rubber, polyurethane rubber, chloroprene rubber, natural rubber, butyl rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, nitrile rubber, ethylene-propylene rubber, acrylic rubber. Etc., and a mixture thereof, so-called rubber or elastomer is used as a main component.

  These rubbers or elastomers include fillers such as fumed silica, precipitated silica and reinforcing carbon, metal powders such as nickel, aluminum and copper, metal oxides such as zinc oxide and tin oxide, and barium sulfate. , Conductive filler with tin oxide coated on core material such as titanium oxide, potassium titanate, etc. was blended and kneaded with vulcanizing agents such as peroxide, hydrogen siloxane in the presence of platinum catalyst, isocyanate, etc. Things are used.

  As a material for forming the toner carrying layer 4, a reaction product of a polyurea compound and a polyurethane compound is used. In order to form the toner carrying layer 4 by the reaction product of the polyurea compound and the polyurethane compound, a method of coating these reaction products on the surface of the conductive elastic layer 3 is employed. That is, the developing roller 1 according to the embodiment of the present invention has the conductive elastic layer 3 on the conductive shaft 2 and the toner carrying layer 4 formed by coating on the outer peripheral portion of the conductive elastic layer 3. It is preferable to have it.

  Examples of the polyurea compound include MDI, TDI, XDI, NDI, TMXDI, IPDI, H6XDI, H12MDI, HDI, DDI, NBDI, TMDI, and 1,3-PDO. Isocyanate, ether, PPG, PTMG, ester, POP, PCL, PCD, 1,4-BD, 1.5-PD, 1.6-HD, PBP, TMP And a reaction product with polyols such as NPG, NPG and MPD. Of these, a reaction product comprising an MDI isocyanate and a polyether polyol is preferred from the viewpoints of contamination and durability on the photoreceptor and abrasion resistance, heat resistance, moisture resistance and electrical properties.

  Examples of the polyurethane compound include MDI, TDI, XDI, NDI, TMXDI, IPDI, H6XDI, H12MDI, HDI, DDI, NBDI, TMDI, and 1,3-PDO. And a reaction product of an isocyanate such as an amine and an amine. Among these, a reaction product composed of an MDI isocyanate and an amine is preferable from the viewpoint of contamination and durability to the photoreceptor.

  Further, in the developing roller 1 according to the embodiment of the present invention, the surface roughness (JIS (B0601) ten-point average roughness (Rz) of the toner carrying layer 4. It is confirmed that a good image can be obtained by defining the expression in a predetermined range.

  That is, when the surface roughness Rz of the toner carrying layer 4 is less than 2 μm, the image density of the black solid print sample is low, and when the surface roughness Rz exceeds 15 μm, the image density of the black solid print sample is too high. Toner fog is likely to occur, and the resolution also decreases. Therefore, it can be said that a good image can be obtained by setting the surface roughness Rz of the toner carrying layer 4 to 2 to 15 μm.

  In order to adjust the surface roughness Rz of the toner carrying layer 4 on the surface of the developing roller 1 to a predetermined range as described above, (1) In addition to a method of forming a resin coat layer on the conductive elastic layer 3 ( 2) A method of selecting the type of rubber material or additive component constituting the conductive elastic layer 3, and (3) a method of changing polishing conditions at the time of final polishing of the conductive elastic layer 3.

  Further, in the developing roller 1 according to the embodiment of the present invention, an electrical resistance value between the conductive shaft body 2 of the developing roller 1 and the toner carrying layer 4 on the surface of the developing roller 1 is set to a predetermined value by an experimental example described later. It was confirmed that a good image can be obtained by defining the above range.

That is, when the electrical resistance value between the conductive shaft body 2 of the developing roller 1 and the toner carrying layer 4 on the surface of the developing roller 1 is less than 1 × 10 ⁴ Ω, the development bias is applied too much, so the black solid print sample The image density of the toner becomes too high, so that the toner is liable to be fogged and the resolution is also lowered. Further, if this electrical resistance value exceeds 1 × 10 ⁹ Ω, the developing bias is not applied and the developability is lowered, the image density of the black solid print sample is low, and the paper as the printing medium can be seen through, It becomes difficult to obtain a good image. Therefore, it can be said that a good image can be obtained if the electrical resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 is in the range of 1 × 10 ⁴ to 10 ⁹ Ω.

  A developing roller according to an embodiment of the present invention is used in an image forming apparatus in an electrophotographic system, and FIG. 2 shows an embodiment of an image forming apparatus incorporating a developing roller.

  As shown in FIG. 2, the image forming apparatus 12 includes a developing roller 1 disposed between a toner supply roller 5 for supplying toner and a latent image carrier 6 holding an electrostatic latent image. When the developing roller 1, the latent image carrier 6 and the toner supply roller 5 rotate in the direction of the arrow in the figure, the toner 7 is supplied to the surface of the developing roller 1 by the toner supply roller 5, and this toner is layered. 8, the developing roller 1 rotates in contact with the latent image carrier 6 in this state, whereby the toner formed in the thin layer is transferred from the developing roller 1 to the latent image carrier 6. The electrostatic latent image is made visible by adhering to the image. In the figure, reference numeral 9 denotes a transfer unit, which transfers a toner image onto a recording medium such as paper. Reference numeral 10 denotes a cleaning unit, and the latent image carrier 6 is transferred by the cleaning blade 11 after being transferred. The toner remaining on the surface is removed.

  Since the image forming apparatus 12 according to the embodiment of the present invention is the same as the conventional one except for the developing roller 1, the details thereof are omitted.

Hereinafter, manufacturing methods and evaluation results of Examples and Comparative Examples of the developing roller 1 according to the present invention will be described.
[Example 1]

  As the conductive shaft 2, a metal shaft having a diameter of 10 mm and a length of 250 mm obtained by electroless nickel plating on SUM22 is used, and a silicone primer (trade name: Primer No. 16, Shin-Etsu Chemical Co., Ltd.) is used for this metal shaft. (Made by Co., Ltd.) was applied, and baked in a gear oven at 150 ° C. for 10 minutes.

  As a material for the conductive elastic layer 3, 100 parts by mass of methyl vinyl silicone raw rubber (trade name: KE-78VBS, manufactured by Shin-Etsu Chemical Co., Ltd.), dimethyl silicone raw rubber (trade name: KE-76VBS, Shin-Etsu Chemical Co., Ltd.) 20 parts by mass, carbon black (trade name: Asahi Thermal, Asahi Carbon Co., Ltd.) 10 parts by mass, fumed silica-based filler (trade name: AEROSIL 200, manufactured by Nippon Aerosil Co., Ltd.), 0.5 parts by mass of a platinum catalyst (trade name: C-19A, manufactured by Shin-Etsu Chemical Co., Ltd.), 2 parts by mass of hydrogen siloxane (trade name: C-19B, manufactured by Shin-Etsu Chemical Co., Ltd.) were added, A silicone rubber composition was prepared by kneading with a pressure kneader.

  Next, this silicone rubber composition is dispensed with an extruder through a crosshead and integrated with the conductive shaft body 2, and is heated and vulcanized in a gear oven at 150 ° C. for 30 minutes to form the conductive shaft body 2. Vulcanization adhesion molding was carried out so that it might become a cylindrical shape with an outer diameter of 18 mm. Further, secondary vulcanization was performed in a gear oven at 200 ° C. for 4 hours to form the conductive elastic layer 3.

  After the secondary vulcanization, the outer peripheral surface of the conductive elastic layer 3 was polished with a cylindrical grinder equipped with a GC # 400 grindstone to prepare a roller base material having a diameter of 16 mm and a length of 230 mm of the conductive elastic layer 3. The surface roughness Rz of the finish-polished roller surface was 4.7 μm.

Next, MDI isocyanate (trade name: MC-C31, manufactured by Nippon Polyurethane Industry Co., Ltd.) and ether polyol (trade name: ON-F29, Nippon Polyurethane Industry Co., Ltd.) are formed on the surface of the conductive elastic layer 3 in advance. The toner carrier layer 3 was formed by reacting an amine (trade name: KBP-40, manufactured by Shin-Etsu Chemical Co., Ltd.) with a pre-reacted product (prepolymer). The blending ratio was R = 1.05 [R: NCO equivalent / (OH + NH ₂ ) equivalent], and the surface of the conductive elastic layer 3 was spray-coated so as to have a thickness of 2.0 μm, at 120 ° C. for 90 minutes. Heat-cured under conditions. The pot life when cured was about 1 hour. The surface roughness Rz of the toner carrying layer 4 of the developing roller 1 thus completed was 4.0 μm. The electric resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 was 1 × 10 ⁶ Ω.
[Example 2]

In Example 2, the carbon black addition amount of the material of the conductive elastic layer 3 of Example 1 was changed from 10 parts by mass to 7 parts by mass, and the surface roughness Rz was changed by changing the finish polishing conditions of the conductive elastic layer 3. The developing roller 1 was manufactured by the same method as in Example 1 except that the surface roughness Rz of the developing roller 1 was 2.0 μm. The electric resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 was 1 × 10 ⁸ Ω.
[Example 3]

Example 3 was the same as Example 1 except that the surface roughness Rz was changed to 16.0 μm by changing the finish polishing conditions of the conductive elastic layer 3 of Example 1, and then the toner carrying layer 4 was applied several times. The developing roller 1 was manufactured by the same method, and the surface roughness Rz of the toner carrying layer 4 of the developing roller 1 was 15.0 μm. The electric resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 was 1 × 10 ⁶ Ω.
[Example 4]

In Example 4, the amount of carbon black added to the material of the conductive elastic layer 3 of Example 1 was changed from 10 parts by mass to 15 parts by mass, and the thickness of the toner carrying layer 4 was changed to 4.0 μm. The developing roller 1 was manufactured by the same method as in Example 1, and the surface roughness Rz of the toner carrying layer 4 of the developing roller 1 was 8.0 μm. The electric resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 was 1 × 10 ⁴ Ω.
[Comparative Example 1]

In Comparative Example 1, the toner carrying layer 4 is made of polyurethane (MDI isocyanate (trade name: MC-C31, manufactured by Nippon Polyurethane Industry Co., Ltd.)) and ether polyol (trade name: ON-F29, manufactured by Nippon Polyurethane Industry Co., Ltd.). The developing roller 1 was manufactured in the same manner as in Example 1, except that the surface roughness Rz of the toner carrying layer 4 of the developing roller 1 was 4.0 μm. The electrical resistance value between the sex shaft 2 and the surface of the toner carrying layer 4 was 1 × 10 ⁶ Ω.
[Comparative Example 2]

In Comparative Example 2, the toner carrying layer 4 is made of polyurea (MDI isocyanate (trade name: MC-C31, manufactured by Nippon Polyurethane Industry Co., Ltd.) and amine (trade name: KBP-40, manufactured by Shin-Etsu Chemical Co., Ltd.). The developing roller 1 was prepared by the same method as in Example 1, except that the pot life was about 5 minutes when cured at 120 ° C. for 90 minutes. The surface roughness Rz of the toner carrying layer 4 of the developing roller 1 was 4.0 μm, and the electric resistance value between the conductive shaft 2 and the surface of the toner carrying layer 4 was 1 × 10 ^6. Ω.

[Comparative Example 3]
In Comparative Example 3, the amount of carbon black added to the material of the conductive elastic layer 3 of Example 1 was changed from 10 parts by mass to 5 parts by mass, and the surface roughness was changed by changing the finish polishing conditions of the conductive elastic layer 3. The developing roller 1 was manufactured in the same manner as in Example 1 except that Rz was set to 2.0 μm. The surface roughness Rz of the toner carrying layer 4 of the developing roller 1 was 1.5 μm. The electric resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 was 3 × 10 ⁹ Ω.
[Comparative Example 4]

In Comparative Example 4, the amount of carbon black added to the material of the conductive elastic layer 3 of Example 1 was changed from 10 parts by mass to 8.5 parts by mass, and the finish polishing condition of the conductive elastic layer 3 was changed to The developing roller 1 was manufactured by the same method as in Example 1 except that the roughness Rz was 17.0 μm. The surface roughness Rz of the toner carrying layer 4 of the developing roller 1 of Comparative Example 4 was 16.0 μm. Further, the electric resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 was 3 × 10 ⁷ Ω.
[Comparative Example 5]

In Comparative Example 5, the amount of carbon black added to the material of the conductive elastic layer 3 of Example 1 was changed from 10 parts by weight to 18 parts by weight, and the thickness of the toner carrying layer 4 was changed to 0.7 μm. The developing roller 1 was manufactured by the same method as in Example 1, and the surface roughness Rz of the toner carrying layer 4 of the developing roller 1 was 4.5 μm. The electrical resistance value between the conductive shaft body 2 and the surface of the toner carrying layer 4 was 8 × 10 ³ Ω.
[Test method]

The surface roughness Rz and the electrical resistance value for the examples and comparative examples were obtained by the following measurement methods, and the following tests were performed for durability and image evaluation.
(1) Surface roughness Rz

The developing roller 1 is set on a surface roughness meter (trade name: 590A, manufactured by Tokyo Seimitsu Co., Ltd.) equipped with a measurement probe having a tip radius of 2 μm, a measurement length of 2.4 mm, a cutoff wavelength of 0.8 mm, and a cutoff type. The surface roughness Rz was measured with Gaussian. The measurement frequency was set at three locations for the toner carrying layer 4 of one developing roller 1, and the average value was defined as the surface roughness Rz.
(2) Electric resistance value

Using an electric resistance meter (trade name: ULTRA HIGH RESISTANCE METER R8340A) manufactured by Advantest Corporation, the developing roller 1 is placed horizontally, the thickness is 5 mm, the width is 30 mm, and the length is the entire rubber part (conductive elastic layer 3). An aluminum plate that can be used is used as an electrode, and a load of 500 g is supported at both ends of the conductive shaft 2 of the developing roller 1, and DC 100V is applied between the conductive shaft 2 and the electrode. The value of the electric resistance meter after 2 seconds was defined as the electric resistance value.
(3) Printing durability

  As a test for confirming the durability of the toner carrying layer 4 on the surface of the developing roller 1, a continuous printing test using a printing tester was performed, and the presence or absence of streaks in the printed image was visually determined. Here, when filming occurs, streaks appear in the printed image.

Specifically, a test cartridge incorporating the developing roller produced in the example and the comparative example is attached to the position of a black toner cartridge of a commercially available printer (manufactured by HL-1850 Brother Industries, Ltd.), and the room temperature is 23 ±. After being left overnight at 2 ° C. and a humidity of 50 ± 5% at room temperature and normal humidity, black solid printing was performed, and the images were observed every 500 sheets to evaluate the durability.
(4) Image evaluation

After incorporating the developing roller produced in the example and the comparative example at the position of the black toner cartridge of a commercially available printer (HL-1850 Brother Industries, Ltd.), black solid, halftone dot, 5% duty, white background printing 4 An image pattern for evaluation of items was printed and used as initial evaluation data. Thereafter, 20,000 sheets of 5% duty images were printed, and thereafter, four evaluation image pattern items were printed in the same manner as in the initial stage to obtain evaluation data after printing.
・ Print density

The Macbeth density of black solid printing was measured using a Macbeth densitometer. In both the initial stage and after printing, the Macbeth density of 1.3 or more is “◯”, and less than 1.3 is “X”.
・ Cover of white image

The Macbeth density of the white background of the 5% duty image was measured with a Macbeth densitometer. Initially and after printing, the Macbeth density of less than 0.015 is “◯”, and 0.015 or more is “x”.
[Test results]

  Table 1 shows the results of surface roughness Rz, electrical resistance value, printing durability, and image evaluation for Examples and Comparative Examples.

（注）１．印字耐久性
○：印字画像に筋が発生し始めた印刷枚数が１５，０００枚以上のも の。
×：印字画像に筋が発生し始めた印刷枚数が１５，０００枚未満のも の。
２．画像評価
○：「印字濃度」，「白画像のかぶり」の評価結果が共に「○」のもの。
×：「印字濃度」，「白画像のかぶり」の評価結果で少なくとも一つが 「×」のもの。

(Note) Durability of printing ○: The number of printed sheets on which streaks began to appear in the printed image is 15,000 sheets or more.
×: The number of printed sheets on which streaks began to appear in the printed image is less than 15,000 sheets.
2. Image evaluation ○: Evaluation results for “print density” and “white image fog” are both “○”.
×: At least one of the evaluation results of “print density” and “white image fog” is “×”.

  As in Examples 1 to 4, the surface of the conductive elastic layer 3 was spray-coated with a reaction product obtained by reacting an amine with a pre-reaction product (prepolymer) of MDI isocyanate and ether polyol in advance. When heat-cured at 90 ° C. for 90 minutes and the surface roughness Rz of the surface of the toner carrying layer 4 of the developing roller 1 is adjusted in the range of 2 to 15 μm, the printing durability is improved. Therefore, even in an environment where the development process is speeded up and lengthened, the cleaning performance using the cleaning blade is maintained well. In the image forming apparatus using such a developing roller 1, it was confirmed that the filming resistance was good (print durability: ◯) and a high-definition and high-quality print image was obtained ( Image evaluation: ○).

In Comparative Example 1 in which the toner carrying layer 4 of the developing roller 1 is polyurethane (reaction product of MDI isocyanate and ether polyol) and in Comparative Example 2 in which polyurea (reaction product of MDI isocyanate and amine) is used, development is performed. Although the surface roughness Rz of the toner carrying layer 4 on the surface of the roller 1 is adjusted to 4.0 μm and the electric resistance value is adjusted to 1 × 10 ⁶ Ω, the printing durability is inferior. Before the 15,000th sheet, the streaks were confirmed by black solid printing (print durability x).

  Further, the developing roller 1 of Comparative Examples 3 to 5 in which the carbon black blending amount and finish polishing conditions of the conductive elastic layer 3 of Example 1 were changed had good printing durability, but the printing density was affected. However, a good image could not be obtained.

It is a cross-sectional view of the developing roller according to the embodiment of the present invention. 1 is a schematic view showing an embodiment of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing roller 2 Conductive shaft 3 Conductive elastic layer 4 Toner carrying layer 5 Toner supply roller 6 Latent image carrier 7 Toner 8 Layer forming member 9 Transfer unit 10 Cleaning unit 11 Cleaning blade 12 Image forming apparatus

Claims (5)

In a developing roller having a conductive shaft, a conductive elastic layer located outside the conductive shaft, and a toner carrying layer provided on the outer periphery of the conductive elastic layer, the toner carrying layer is a polyurea compound. And a polyurethane compound, and the reaction product is a product of a reaction between an MDI isocyanate, an ether polyol, and an amine . The developing roller according to claim 1, wherein the reaction product is obtained by pre- reacting an MDI isocyanate and an ether polyol to form a prepolymer and then reacting with an amine . The developing roller according to claim 1, wherein a JIS (B0601) ten-point average roughness (Rz) of the surface of the toner carrying layer is 2 to 15 μm . 4. The electric resistance value between the conductive shaft and the surface of the toner carrying layer is 1 × 10 ⁴ to 10 ⁹ Ω at DC 100 V. 5. Development roller. The toner is carried on the surface of the toner carrying layer of the developing roller according to claim 1 to form a thin film of the toner, and then the toner is attached to the surface of the latent image carrying body. An image forming apparatus for forming a visible image on a surface of a latent image carrier.

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