JP2002287482A - Developing roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the occurrence of an image stripe in the case of forming an image by using a developing roller used in an electrophotographic device and developing an image to a visible image with developer while coming into press-contact with a photoreceptor. SOLUTION: This developing roller for developing an electrostatic latent image by rotating while coming into press-contact with the photoreceptor is equipped with a shaft body, a conductive elastic layer provided on the shaft body, and a surface covering layer provided on the elastic layer. The elastic layer incorporates oil whose kinematic viscosity at 25 deg.C is 10 to 500 mm<2> /s by 5 to 15 mass %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller for visualizing a developer by pressing a photosensitive member in an electrophotographic apparatus.

[0002]

2. Description of the Related Art In recent years, OA equipment such as copiers and printers have been improved in image quality, and accordingly, a contact developing method has been proposed in which an elastic body is used as a developing roller and development is performed by uniformly pressing against a photosensitive body. Have been.

For example, in a printer using an electrophotographic system, a photoconductor 4 which is configured as shown in FIG. 2 and rotates in the direction of an arrow is uniformly charged by a charging roller 2 and an electrostatic latent image is formed by a laser 3 or the like. Form. Next, the developing container 7
The developer inside is a developer application roller 6 and a developer regulating member 5
Thus, the developer is uniformly applied onto the developing roller 1 with an appropriate charge, and transfer (development) of the developer is performed at a contact portion between the photoconductor 4 and the developing roller 1. Thereafter, the developer on the photoreceptor is transferred to the recording paper 9 by the transfer roller 8 and fixed by heat and pressure. The developer remaining on the photoreceptor is removed by the cleaning blade 10 to complete a series of processes.

In this case, the developing roller is always in pressure contact with the photosensitive member and the developer regulating member, and is in contact with the photosensitive member for a long time when stopped, when not in use, and the like. When permanent deformation occurs, a problem such as occurrence of streaks on an image occurs. For this reason, Japanese Patent Application Laid-Open
Japanese Patent Publication No. -21699 proposes a developing roller using a rubber material having a permanent compression set (70 ° C. × 22 hours, 25% compression) of 15% or less as an elastic body.

However, the image streaks after being pressed against the photosensitive drum are not due to only the compression set caused by the pressing. For example, conductive silicone rubber having a permanent deformation of 3% at 25% compression at 70 ° C. for 22 hours. Is used as the elastic layer, a layer in which nylon beads and carbon black are added and dispersed in urethane resin is provided on the surface layer, and the layer is left under pressure contact. Even when the roller compression deformation amount is 5 μm or less, streaks occur on the image. There are cases.

[0006]

As a result of the inventor's intensive study on the cause of the streak generation phenomenon on the image, the electric resistance partially changed at the photosensitive member pressure contact portion of the elastic layer conductive rubber material. And that this change in electrical resistance affects image streaks.

An object of the present invention is to suppress the occurrence of image streaks when an image is formed by using a developing roller which is used in an electrophotographic apparatus and which presses a photosensitive member to visualize a developer. An object of the present invention is to improve the recoverability of the resistance change of the elastic layer rubber material at the pressure contact portion of the developing roller and suppress the occurrence of image streaks.

[0008]

According to the present invention, there is provided a developing roller for developing an electrostatic latent image by pressing against a photosensitive member and rotating the developing roller, wherein the developing roller comprises a shaft, and a conductive member provided on the shaft. An elastic layer having a property, and a surface coating layer provided on the elastic layer, wherein the elastic layer has a kinematic viscosity at 25 ° C. of 1
A developing roller containing 5 to 15% by mass of an oil of 0 to 500 mm ² / s.

In the present invention, it is preferable that the elastic layer has a silicone rubber as a main component, and the oil is a silicone oil.

[0010] It is also preferable that the elastic layer contains dimethyl silicone rubber as a main component and the oil is dimethyl silicone oil.

According to the present invention, the elastic layer has a kinematic viscosity of 10-5.
By adding 5 parts by mass to 15 parts by mass of oil of 00 mm ² / s, it is possible to recover in a short time the roller resistance whose resistance value has been partially shifted by compression. This is because polymer oils, etc., which are difficult to move through the molecular network in rubber, are caused to move by long-term compression deformation and change in resistance. This is considered to be because it is possible to relax with time and recover the resistance change.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the developing roller of the present invention comprises a shaft, a conductive elastic layer provided directly or indirectly on another shaft via another layer, and a direct or other conductive layer. A surface coating layer provided on the elastic layer indirectly via a layer. Kinematic viscosity at 25 ° C. is 10 to 500 mm ²
There is no particular limitation according to the present invention except that the elastic layer contains 5 to 15% by mass of the oil, and any developing roller having the shaft, the elastic layer and the surface coating layer can be used. .

The preferred form of the elastic layer in the present invention is:
A rubber material is a main component (a component having the highest mass content ratio), and oil is added to this. In addition to rubber materials and oils, additives commonly used as rubber compounding agents, such as conductive agents, reinforcing agents, extenders, antioxidants, ultraviolet absorbers, reaction catalysts, reaction retarders, and foaming agents are appropriately included. You can go out.

The oil to be added to the elastic layer is 25 ° C.
Kinematic viscosity at 10 to 500 mm ^Two/ S is effective
But more preferably 10 to 300 mm^Two/ S,
More preferably 10 to 150 mm^Two/ S kinematic viscosity
Oil. Kinematic viscosity is 10mm^Two/ S,
The oil volatilizes during the roller thermoforming process and contains
Kinetic viscosity is 500mm^Two
/ S, it is difficult for the oil to move through the rubber molecular network.
And the time to alleviate the resistance change becomes longer, and the effect of the present invention
The fruits are not practically sufficient.

The kinematic viscosity is measured according to JIS Z88.
03.

The amount of the oil added to the elastic layer is preferably 5% by mass to 15% by mass, more preferably 5% by mass to 10% by mass. When the addition amount is less than 5%, it is disadvantageous in that the resistance relaxation effect tends to decrease,
On the other hand, if it exceeds 15% by mass, the permanent change amount (Set amount) of the pressure contact of the roller is deteriorated, which is disadvantageous in that image streaks tend to occur due to the permanent change.

The type of the oil contained in the elastic layer is selected from those having good compatibility with the rubber material as the main component of the elastic layer, and more specifically, the solubility parameter (SP
(Value) is preferable because it is uniformly present in the rubber, and the effect of reducing the resistance change works well. For example, non-polar rubber such as EPDM having an SP value of 7.9 has SP
A low-viscosity process oil having a value of about 6 to 9 is preferable, for example, a paraffin-based oil having an SP value of about 7.9 is preferable, and a silicone-based oil is preferable for the silicone rubber. In particular, dimethyl silicone oil is most preferable for dimethyl silicone rubber widely used as a material for a developing roller.

The rubber material used as the elastic layer has a hardness of 10 to 8 in order to uniformly contact the photosensitive drum.
0 degree (Asker C) is preferable, and more preferably, 20 to 50 degrees.
The degree (Asker C) is more preferable.

The electric resistance of the elastic layer forming material is preferably in the range of 10 ³ Ωcm to ^{10 10} Ωcm in order to properly develop the charged developer on the latent image on the photosensitive drum by utilizing the potential difference.

Here, ordinary silicone rubber contains about 2 to 8% by mass of unreacted oligomer components, and the molecular weight distribution of the oligomer is almost normal within the range of several hundreds to several tens of thousands. In this oil, the kinematic viscosity is 10 to 5
The range of 00 mm ² / s is considered to be about 1 to 4% by mass, and the effect of reducing the resistance is insufficient with this amount of oil, and it is necessary to add low-viscosity silicone oil to silicone rubber as in the present invention. is there.

FIG. 1 schematically shows one embodiment of the developing roller of the present invention. In the figure, 1a indicates a shaft body, 1b indicates an elastic layer, and 1c indicates a surface coating layer.

The shaft body 1a only needs to have strength enough to withstand molding or actual use, and for example, a metal core can be used. The outer diameter of the shaft body is preferably 4 to 10 mm from the viewpoint of minimizing the roller deflection at the time of contact to a practically usable range.

The thickness of the elastic layer 1b is 1 to 6 m from the viewpoint of exhibiting sufficient rubber elasticity and uniformly contacting the photosensitive drum or the like.
m is preferred.

The surface coating layer 1c is for directly applying a charge to the developer and for preventing the photosensitive drum from being contaminated by oil or the like oozing out of the elastic layer. Etc. are required. To form the surface coating layer, for example, urethane resin, nylon resin,
Acrylic resin, fluororesin, etc. are appropriately diluted with a solvent such as methyl ethyl ketone, toluene, alcohol, water, and the like, and carbon black is dispersed as a conductive agent, and a surface roughening material is dispersed as necessary. In this case, a paint obtained by adding a curing catalyst or a reaction retarder and stirring may be applied by a method such as spraying or dipping.

The electric resistance of the surface coating layer is preferably in the range of 10 ³ Ωcm to ^{10 10} Ωcm in order to properly develop the charged developer on the latent image on the photosensitive drum by utilizing the potential difference. Is preferably in the range of 3 to 12 μm in ten-point average roughness (Rz) in order to convey an appropriate amount of developer.

The thickness of the surface coating layer is preferably 3 to 100 μm in consideration of abrasion without impairing the flexibility of the elastic layer.

[0027]

EXAMPLE 1 A steel cored bar (SUM22) having an outer diameter of 8 mm was used with an inner diameter of 16 m.
m in a cylindrical mold.

A two-component addition type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd.), Asker C hardness of 50 degrees, volume resistivity of 10 ⁷ Ωcm), and a kinematic viscosity at 25 ° C. of 1
10 mm ² / s dimethyl silicone oil (manufactured by Toray Dow Corning, trade name: SH200-100)
% Of the mixture, injected into the mold, heated in a 130 ° C. oven for 60 minutes, demolded, and subjected to secondary vulcanization in a 200 ° C. oven for 4 hours to obtain an elastic layer having a thickness of 4 mm. Roller was obtained.

Next, a urethane paint (manufactured by Nippon Polyurethane Co., Ltd., trade name: Nipporan N5033) was added with a solid content of 1%.
It was diluted with methyl ethyl ketone so as to be 0%, and carbon black (manufactured by Asahi Carbon Co., Ltd., trade name:
# 7360F) was added to 16 parts by weight based on 100 parts by weight of the solid content of the urethane paint, and 10 parts by weight of nylon beads (trade name: SP500, manufactured by Toray Co., Ltd.) as a surface roughening material were added to 100 parts by weight of the solid content of the urethane paint. After that, a well-dispersed hardening agent (manufactured by Nippon Polyurethane Co., trade name:
Coronate L) is added to 10 parts by mass of the urethane paint.
The parts by mass added and agitated paint is applied on a previously molded roller so as to have a film thickness of 15 μm by dipping,
After drying in an oven at 80 ° C. for 15 minutes, it was cured in an oven at 120 ° C. for 4 hours to obtain a developing roller of Example 1.

Example 2 A two-component addition type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., AskerC hardness 50 degrees, volume specific resistance 10 ⁷ Ωcm) was used as an elastic layer.
15 mm of dimethyl silicone oil (manufactured by Toray Dow Corning Co., Ltd., trade name: SH200-100) having a thickness of 00 mm ² / s.
A developing roller of Example 2 was obtained in the same manner as in Example 1 except that a material in which a mass% was mixed was used.

Example 3 A two-component addition-type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., AskerC hardness: 50 degrees, volume specific resistance: 10 ⁷ Ωcm) as an elastic layer was added with a kinematic viscosity of 10 at 25 ° C.
A developing roller of Example 3 was obtained in the same manner as in Example 1 except that a material containing 5% by mass of 0 mm ² / s dimethyl silicone oil (manufactured by Toray Dow Corning Co., Ltd., trade name: SH200-100) was used. .

Example 4 A two-component addition type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., AskerC hardness 50 degrees, volume specific resistance 10 ⁷ Ωcm) as an elastic layer was added to a kinematic viscosity of 20 at 25 ° C.
A developing roller of Example 4 was obtained in the same manner as in Example 1 except that a material in which 5% by mass of dimethyl silicone oil (trade name: SH200-20, manufactured by Dow Corning Toray Co., Ltd.) of 5 mm ² / s was used. .

Example 5 A two-component addition-type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., AskerC hardness: 50 degrees, volume resistivity: 10 ⁷ Ωcm) as an elastic layer was added to a kinematic viscosity of 50 at 25 ° C.
A developing roller of Example 5 was obtained in the same manner as in Example 1 except that a material in which 5% by mass of 0 mm ² / s dimethyl silicone oil (trade name: SH200-500, manufactured by Dow Corning Toray Co., Ltd.) was used. .

Comparative Example 1 Example 1 was repeated except that the material of the two-component addition type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., AskerC hardness 50 degrees, volume resistivity 10 ⁷ Ωcm) was used as the elastic layer.
A developing roller of Comparative Example 1 was obtained in the same manner as described above.

Comparative Example 2 Example 1 except that the material of the two-component addition type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., AskerC hardness 35 degrees, volume resistivity 10 ⁷ Ωcm) was used as the elastic layer.
A developing roller of Comparative Example 2 was obtained in the same manner as described above.

COMPARATIVE EXAMPLE 3 A two-component addition type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., Asker C hardness: 50 degrees, volume resistivity: 10 ⁷ Ωcm) as an elastic layer was added to a kinematic viscosity of 10 at 25 ° C.
A developing roller of Comparative Example 3 was obtained in the same manner as in Example 1, except that a material containing 20% by mass of 0 mm ² / s dimethyl silicone oil (manufactured by Toray Dow Corning Co., Ltd., trade name: SH200-100) was used. .

COMPARATIVE EXAMPLE 4 A two-component addition type conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., having an Asker C hardness of 50 degrees and a volume resistivity of 10 ⁷ Ωcm) having a kinematic viscosity of 100 mm ² / s dimethyl silicone oil (elastic layer) was used as the elastic layer. A developing roller of Comparative Example 4 was obtained in the same manner as in Example 1 except that a material in which 2% by mass of Toray Dow Corning Co., Ltd., trade name: SH200-100) was used.

The rollers in the above Examples and Comparative Examples were pressed into contact with the photosensitive member so as to have a deformation amount of 100 μm.
After being left for 30 days in a high-temperature and high-humidity environment (35 ° C., 90% relative humidity), a solid image is output using a color laser printer, and the presence or absence of image streaks and the roller rotation time until recovery are 180 minutes per minute. The image was evaluated every time idle rotation was performed for 30 seconds at the rotation speed, and the time until the image streak disappeared was evaluated. Table 1 shows the results.

Here, the rubber hardness and the roller hardness are Aske
Using a spring hardness tester of rC scale, load 500
g. The volume resistivity of the rubber material was primarily cured at 100 ° C. for 30 minutes using a sheet molding die and a hot press, then taken out of the die, and subjected to secondary curing at 200 ° C. for 4 hours to mold a rubber sheet having a thickness of 2 mm. . The volume resistivity of this sheet was calculated from the resistance obtained with a resistance meter.

The amount of compressive deformation is JIS K6301 (180
C., 22 hours).

As is apparent from Table 1, in Examples 1 to 5, the streak disappears at a constant rotation speed on the image because the relaxation rate of the resistance change of the elastic layer in the press contact portion is increased. On the other hand, in Comparative Examples 1, 2, and 4, it took time for the change in resistance of the elastic layer to relax, so that image streaks could be confirmed even after the completion of the idle rotation for 10 minutes. In Comparative Example 3, the amount of deformation in a high-temperature and high-humidity environment was too large, and the image was not stable.

[0042]

[Table 1]

[0043]

According to the roller according to the present invention, the addition of low-viscosity oil increases the speed of relaxation of the change in the electric resistance of the press-contact portion, so that the image streak cannot be confirmed even if the roller runs idle within 5 minutes. And high image quality can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a developing roller of the present invention.

FIG. 2 is a schematic diagram illustrating an electrophotographic image forming mechanism.

[Explanation of symbols]

 1a shaft body 1b elastic layer 1c surface coating layer 1 developing roller 2 charging roller 3 exposure light 4 photosensitive drum 5 developer regulating member 6 developer applying roller 7 developing container 8 transfer roller 9 recording medium 10 cleaning blade

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 13/00 F16C 13/00 E // C08L 83:04 C08L 83:04 C10N 20:02 C10N 20:02 40:06 40:06 (72) Inventor Yuhiro Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term within Canon Inc. (reference) 2H077 AC04 AD02 AD06 AD13 AD23 FA13 FA16 FA22 FA27 GA03 3J103 AA02 AA14 AA21 AA32 AA51 BA41 CA03 EA02 FA18 GA02 GA57 GA58 HA03 HA04 HA12 HA41 HA43 HA46 HA48 HA53 4F006 AA42 AB19 AB24 AB37 AB38 AB54 AB72 BA02 BA07 BA11 CA00 DA04 4H104 CJ02A CJ03C EA02A PA04 QA23

Claims (3)

[Claims] 1. A developing roller for developing an electrostatic latent image by pressing against a photoreceptor and rotating the developing roller, wherein the developing roller has a shaft, a conductive elastic layer provided on the shaft, and A developing roller having a surface coating layer provided on an elastic layer, wherein the elastic layer contains 5 to 15% by mass of an oil having a kinematic viscosity at 25 ° C of 10 to 500 mm ² / s. 2. The developing roller according to claim 1, wherein said elastic layer contains silicone rubber as a main component, and said oil is silicone oil. 3. The developing roller according to claim 1, wherein the elastic layer has dimethyl silicone rubber as a main component, and the oil is dimethyl silicone oil.