JPH11231611A - Roller for electrophotographic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roller high in durability and capable of preventing a photoreceptor and a roller from wearing, preventing toner from deteriorating, moreover, suppressing variations of a roller resistance value and maintaining a high quality image for a long period by properly adjusting a relation between the contact pressure and the contact width. SOLUTION: In the case of a roller provided with a single or plural resin layers 4 around a conductive shaft 3 and further concentrically provided with a surface layer 5 on this resin layer, the roller 2 for an electro-photographic system comprises such a conductive elastic layer for the constitution that when a linear load of a cylindrical electrode 1 of the same shape as a photoreceptor and the surface of the roller 2 is 2.2 g wt./mm, a circumferential contact width d of the cylindrical electrode 1 with the roller 2 is 1.0 mm or longer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a roller such as a charging roller or a developing roller incorporated in an electrophotographic image forming apparatus such as a printer, a copying machine or a facsimile receiving apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus adopting an electrophotographic system, a charging roller for uniformly charging the surface of an electrostatic latent image carrier and toner carrying an electrostatic latent image are provided around the electrostatic latent image carrier. Various rollers such as a developing roller for supplying to the body and a transfer roller for transferring the toner image to the recording paper are arranged. Among these development methods, the non-magnetic development method using a non-magnetic toner has the advantage that the color of the toner is easy and a halftone image can be obtained relatively clearly even when a monochrome image is obtained. ,Attention has been paid.

FIG. 2 is a schematic diagram showing an example of an image forming apparatus in which such a non-magnetic developing type developing device 10 is incorporated. The charging roller 11 contacts and rotates the surface of the charging roller 11 with a photoreceptor 12 serving as an electrostatic latent image carrier, and uniformly forms a charge on the surface of the photoreceptor 12. A photoconductive insulator layer is formed on the surface of the photoconductor 12, and a conductor layer is formed below the photoconductive insulator layer. When 13 is applied, an electrostatic latent image is formed. The developing device 10 visualizes this electrostatic latent image. Developing device
Reference numeral 10 denotes a toner container 15 for storing toners 14, ..., a regulating blade 16 provided in the toner container 15, a developing roller 17,
And a supply roller 18 for securely carrying the toners 14 on the surface of the developing roller 17. After being carried on the surface of the developing roller 17, the nonmagnetic toners 14,... In the toner container 15 are contact-charged and friction-charged when the regulating blade 16 forms a thin toner layer. By attaching this thin toner layer to the electrostatic latent image on the surface of the photoconductor 12,
A toner image is formed on the surface of the photoconductor 12. This toner image is electrostatically attracted to the surface of the recording paper 20 by the transfer roller 19 and becomes a transfer image on the recording paper 20. This transferred image is fixed on the recording paper 20 by the heating roller 21 and the pressure roller 22. Note that a cleaning device 23 such as a blade is provided downstream of the transfer roller 19 in order to remove toner powder remaining on the surface of the photoconductor 12 without being transferred.
A brush or a roller may be used instead of the blade.

Among the various rollers described above, the charging roller 11
The basic structure of the developing roller 17 is the same. That is, these rollers are formed by forming a conductive elastic layer around a conductive shaft, and in some cases, further covering the conductive elastic layer with a surface layer. One or more layers may be interposed between the conductive elastic layer and the surface layer.
In the case of a charging roller, in order to uniformly charge the surface of the photoconductor, and also in the case of a contact type developing roller in which the surface of the roller is brought into contact with the photoconductor, a thin toner layer on the surface of the developing roller is efficiently applied to the photoconductor. In order to adhere, an appropriate contact width (hereinafter, referred to as “nip width”) is required between the surface and the photoconductor in the circumferential direction.

[0005] A contact pressure due to pressure contact with a photoconductor is constantly applied to the surface of such a charging roller or a developing roller. During operation of the image forming apparatus, the photoconductor and the roller are axially rotated. The pressure fluctuates and the nip width also fluctuates. Due to the fluctuation of the nip width, the roller resistance value also fluctuates, which causes a problem of uneven charging and uneven image. If the contact pressure is too small, the required nip width cannot be obtained, and the change in the nip width with respect to a slight change in the contact pressure becomes large, resulting in further increase in charging unevenness and image unevenness.

[0006]

The conductive elastic layer of the charging roller and the developing roller described above has an EPDM (ethylene
Propylene rubber), silicone, NBR (nitrile butadiene rubber), etc. are often used. However, since such a conductive elastic layer has high hardness, if the contact pressure is increased to obtain a required nip width, the photosensitive There is a problem that the body and the surface of the roller are easily worn and damaged, and in the case of the developing roller, a toner is cracked when a toner thin layer is formed by the regulating blade, which contributes to toner deterioration. There is also.

Accordingly, a conductive elastic layer having a low hardness is formed by adding a plasticizer or the like. However, bleeding after the formation of the conductive elastic layer is liable to occur. There has been a problem that the members are contaminated.

In view of the above problems, the present invention appropriately adjusts the relationship between the contact pressure and the contact width to prevent abrasion of the photoconductor and the roller and deterioration of the toner, and to reduce the resistance of the roller. An object of the present invention is to provide a highly durable roller capable of suppressing fluctuations and maintaining a high-quality image for a long period of time.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have focused on the relationship between the elasticity of the conductive elastic layer and the roller resistance value, and as a result, have arrived at the roller of the present invention. . That is, the roller for electrophotography of the present invention is a roller in which one or more resin layers are provided around a conductive shaft, and a surface layer is provided concentrically on the resin layer, wherein the resin layer is the same as the photoconductor. When the linear pressure at the time of contact between the cylindrical electrode having the shape and the roller surface is 2.2 gf / mm, the conductive width is such that the circumferential contact width between the cylindrical electrode and the roller surface is 1.0 mm or more. It is configured to include an elastic layer.
The linear pressure indicates a force applied per unit length in the longitudinal direction of the roller.

The resin layer has a weight of 2.2 g / mm or more.
With respect to the linear pressure that changes within the range of 0 g weight / mm or less
Between the cylindrical electrode and the conductive shaft.
The maximum value of the roller resistance value (R_max)
And the minimum value (R_min) And the ratio (R _max/ R_min) Not more than 3
It is preferable to include a conductive elastic layer.

More preferably, the resin layer does not contain a foam.

Further, it is preferable that the JIS A spring hardness of the conductive elastic layer falls within a range of 10 ° or more and 30 ° or less. The JIS A spring hardness according to the present invention is a measured value based on JIS K6301 method.

[0013] In such a roller, it is more preferable that the roller resistance value after coating the surface layer is larger than the roller resistance value before coating the surface layer.

Further, as the conductive elastic layer, in particular,
(A) containing at least one alkenyl group in the molecule,
A polymer in which the repeating units constituting the main chain are mainly oxyalkylene units or saturated hydrocarbon units, and (B)
It is desirable to use a reaction product of a curable composition containing a curing agent containing at least two hydrosilyl groups in a molecule, (C) a hydrosilylation catalyst, and (D) a conductivity-imparting agent as main components. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, various representative embodiments of the roller according to the present invention will be described. The roller according to the present invention,
SUS (stainless steel) with a diameter of about 1 mm to 12 mm,
One or more resin layers including a conductive elastic layer are provided around a conductive shaft made of an aluminum alloy, a conductive resin, or the like, and a surface layer is coated on the resin layer. The resin layer may include a single layer or a plurality of layers, such as a resistance adjusting layer for adjusting the electric resistance of the roller, and a primer layer for improving the adhesion between the layers.

FIG. 1 is a schematic diagram showing a state in which a cylindrical electrode 1 having the same shape as a photoreceptor is brought into pressure contact with a roller 2, a nip width d is provided, and roller resistance is measured. Roller 2
An example is shown in which a resin layer 4 is formed around a conductive shaft 3 and a surface layer 5 is formed around the resin layer 4. A DC voltage of 100 V is applied between the conductive shaft 3 and the cylindrical electrode 1 made of aluminum, and a current value is measured to obtain a roller resistance value. The roller resistance value of the roller according to the present invention is 10 ³ to 10 ⁹ Ω, particularly 10 ⁴ to 10 ⁷ Ω.
Is preferred in that a good image is obtained without damaging the photoreceptor.

When the roller according to the present invention has its surface pressed against the cylindrical electrode 1 with a linear pressure of 2.2 gf / mm,
A resin layer including a conductive elastic layer having appropriate hardness and flexibility so that the nip width d is 1 mm or more. When the nip width d is 1 mm or more, the fluctuation of the nip width with respect to the fluctuation of the linear pressure is suppressed,
Fluctuations in the roller resistance are also suppressed, and charging unevenness and image unevenness are extremely reduced.

In addition, 2.2 g weight / mm or more and 9.0 g weight /
When the linear resistance is changed within the range of not more than mm and the roller resistance value when the above-described DC voltage of 100 V is applied is measured, the ratio ( _Rmax / _Rmax ) between the maximum value ( _Rmax ) and the minimum value ( _Rmin ) is measured.
It is preferable to use a conductive elastic layer that suppresses R _min ) to 3 or less, because fluctuation in roller resistance can be suppressed. As the conductive elastic layer, a reactant of a curable composition described later can be used.

It is desirable that the resin layer does not contain a foam from the viewpoint of suppressing charging unevenness and image unevenness. When the resin layer contains a foam, the nip width fluctuation with respect to the linear pressure fluctuation increases, and the surface characteristics of the roller deteriorate due to bubbles and the like included in the resin layer.
This is because charging unevenness and image unevenness are likely to occur.

Further, the hardness of the conductive elastic layer is set as follows:
It is more preferable that the JIS A spring hardness according to JIS K 6301 be within a range of 10 ° to 30 °. If the hardness is less than 10 °, during operation of the image forming apparatus, the nip width greatly fluctuates in response to a slight fluctuation of the linear pressure, and the roller resistance value largely fluctuates, causing image unevenness. On the other hand, when the hardness exceeds 30 °, if the linear pressure is small, there is a problem that the nip width is not sufficiently secured, and there is a problem that the photoconductor and the roller surface are easily damaged.

Further, by adjusting the material and thickness of the surface layer to make the roller resistance after coating the surface layer larger than the roller resistance before coating the surface layer, the linear pressure and the nip width may vary. This is more preferable because the fluctuation of the roller resistance value can be suppressed to a small value. The surface layer is 10 μm to 150 μm
It is provided with a predetermined thickness in the range of m. The volume resistivity is 10 ⁸ Ω when the thickness of the surface layer is 15 μm.
cm within the range of ^10-15 Ωcm.

The above-mentioned conductive elastic layer is a polymer (A) comprising at least one alkenyl group in the molecule, wherein the repeating unit constituting the main chain is mainly composed of an oxyalkylene unit or a saturated hydrocarbon unit. And (B) a curing agent containing at least two hydrosilyl groups in the molecule;
(C) a hydrosilylation catalyst, (D) a conductivity-imparting agent,
Using a reactant of a curable composition containing as a main component,
desirable.

The polymer of the component (A) in the curable composition is a component which is cured by a hydrosilylation reaction with the component (B) and has at least one alkenyl group in the molecule. Occurs to become a polymer and harden. The number of alkenyl groups contained in the component (A) must be at least one in view of hydrosilylation reaction with the component (B), but from the viewpoint of obtaining sufficient rubber elasticity, the number of In the case of a molecule having two alkenyl groups at both ends of the molecule and having a branch,
It is desirable that two or more alkenyl groups be present at the molecular terminals. The main repeating unit constituting the main chain of the component (A) is an oxyalkylene unit or a saturated hydrocarbon unit.

First, the case where the main repeating unit constituting the main chain of the component (A) is a polymer comprising an oxyalkylene unit will be described. At this time, it is preferable to add a small amount of the conductivity-imparting agent, which is the component (D), to the cured product because the volume resistivity of the cured product is 10 ⁸ Ωcm to 10 ⁹ Ωcm. From the viewpoint of lowering the hardness of the cured product, an oxyalkylene polymer in which the repeating unit is an oxyalkylene unit, and an oxypropylene polymer in which the repeating unit is an oxypropylene unit are preferable.

Here, the oxyalkylene polymer refers to a polymer in which 30% or more, preferably 50% or more, of the units constituting the main chain are oxyalkylene units. The unit contained other than the oxyalkylene unit contains 2 units of active hydrogen used as a starting material in the production of the polymer.
Compounds having at least one compound such as ethylene glycol, bisphenol compounds, glycerin, trimethylolpropane, and pentaerythritol. When the repeating unit is an oxypropylene-based unit, it may be a copolymer (including a graft copolymer) with a unit composed of ethylene oxide, butylene oxide, or the like.

The molecular weight of such an oxyalkylene polymer is from 500 to 50,000 in terms of number average molecular weight (Mn) from the viewpoint of improving the balance between reactivity and low hardness.
0, more preferably 1,000 to 40,000. In particular, those having a number average molecular weight of 5,000 or more,
Further, those having a molecular weight of 5,000 to 40,000 are preferable. When the number average molecular weight is less than 500, it becomes difficult to obtain sufficient mechanical properties (rubber hardness, elongation) and the like when the curable composition is cured. On the other hand, if the number average molecular weight is too large, the alkenyl group 1
Because the molecular weight per unit increases or the reactivity decreases due to steric hindrance, curing often becomes insufficient,
Further, the viscosity tends to be too high and the processability tends to be poor.

The alkenyl group contained in the oxyalkylene polymer is not particularly limited, but an alkenyl group represented by the following general formula (1) is particularly preferable in terms of excellent curability.

H ₂ C ＝ C (R ¹ ) (1) (wherein R ¹ is a hydrogen atom or a methyl group)

One of the characteristics of the curable composition is that
It is easy to set the hardness to be low, and in order to exhibit this characteristic, it is preferable that the number of alkenyl groups is two or more at the molecular terminal. However, if the number of alkenyl groups is too large as compared with the molecular weight of the component (A), the composition becomes rigid and it is difficult to obtain good rubber elasticity.

Next, the case where the component (A) is a polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon unit will be described. This polymer is preferable in that it has a low water absorption and a cured product having small environmental fluctuation of electric resistance can be obtained. Further, similarly to the case of the oxyalkylene-based polymer, the component is a component which is cured by a hydrosilylation reaction with the component (B), and has at least one alkenyl group in the molecule. It becomes molecular and hardens. Further, the number of alkenyl groups contained in the component (A) is required to be at least one from the viewpoint of performing a hydrosilylation reaction with the component (B). In such a case, it is preferable that two are present at both ends of the molecule,
In the case of a molecule having a branch, it is preferable that two or more molecules exist at the molecular terminal.

Representative examples of the polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon unit include an isobutylene-based polymer, a hydrogenated isoprene-based polymer, and a hydrogenated butadiene-based polymer. These polymers may contain repeating units of other components such as copolymers, but contain at least 50% or more, preferably 70% or more, more preferably 90% or more of saturated hydrocarbon units. This is important so as not to impair the low water absorption characteristic of the saturated hydrocarbon system.

The molecular weight of the polymer of component (A) in which the main repeating unit constituting the main chain is a saturated hydrocarbon unit is about 500 to 50,000 in terms of number average molecular weight (Mn), and more preferably about 1, About 000 to 15,000,
A liquid material having fluidity at room temperature is preferable in terms of ease of handling and workability.

The alkenyl group introduced into such a saturated hydrocarbon polymer is the same as the oxyalkylene polymer.

Accordingly, a preferred specific example of the polymer having at least one alkenyl group in the molecule and the main repeating unit constituting the main chain being a saturated hydrocarbon unit as component (A) is as follows. It has two alkenyl groups at the terminals and has a linear number average molecular weight (Mn) of 2,000 to 1
Examples thereof include polyisobutylene-based, hydrogenated polybutadiene-based, and hydrogenated polyisoprene-based polymers having a molecular weight of 5,000 and an Mw / Mn of 1.1 to 1.2.

The component (B) in the curable composition is not particularly limited as long as it is a compound having at least two hydrosilyl groups in the molecule, but the number of hydrosilyl groups contained in the molecule is too large. Then, even after curing, a large amount of hydrosilyl groups tends to remain in the cured product, causing voids and cracks. Therefore, the number of hydrosilyl groups contained in the molecule is preferably 50 or less. Further, this number is from 2 to 30 in view of control of rubber elasticity of the cured product and storage stability.
, More preferably 2 to 20,
Further, from the viewpoint that foaming during curing is easily prevented, the number is preferably 20 or less, and from the viewpoint that curing failure is unlikely to occur even if the hydrosilyl group is deactivated, the number is preferably 3 and the most preferable range is 3.
~ 20.

In the present invention, the above-mentioned hydrosilyl group is
To have one means to have one H bonded to Si. In the case of SiH ₂ , it means to have two hydrosilyl groups, but H bonded to Si is preferably bonded to different Si. It is preferable in terms of curability and rubber elasticity.

The molecular weight of the component (B) is 30,000 or less in terms of the number average molecular weight (Mn) from the viewpoint of dispersibility and roller workability when the conductivity imparting agent as the component (D) is added. It is preferably 20,000 or less, more preferably 15,000 or less. In consideration of the reactivity and compatibility with the component (A), the number average molecular weight is 300 to 1
Preferably it is 000.

With respect to the component (B), since the cohesive force of the component (A) is greater than the cohesive force of the component (B), the phenyl group-containing modification is important in terms of compatibility. Styrene-modified products are preferred in terms of compatibility with the components and availability, and α-methylstyrene-modified products are preferred in terms of storage stability.

The hydrosilylation catalyst which is the component (C) is not particularly limited as long as it can be used as a hydrosilylation catalyst. Platinic acid (including complexes such as alcohols), various platinum complexes, rhodium,
Chloride of metals such as ruthenium, iron, aluminum, titanium and the like can be mentioned. Among these, chloroplatinic acid, a platinum-olefin complex, and a platinum-vinylsiloxane complex are preferable from the viewpoint of catalytic activity. These catalysts may be used alone or in combination of two or more.

The ratio of the component (B) to the component (A) in the curable composition as described above is such that the amount of the hydrosilyl group in the component (B) is 0.1 per mole of the alkenyl group in the component (A). When it is set to be 2 to 0.5 mol, more preferably 0.4 to 2.5 mol, it is preferable in that good rubber elasticity is obtained.

The amount of component (C) used is as follows:
(A) 10 ^-1 to 1 based on 1 mol of the alkenyl group in the component.
It is preferably used in the range of 0 ^-8 mol, particularly 10 ^-3 to 10 ^-6 mol. If the amount of the component (C) is less than 10 ^-8 mol, the reaction does not proceed. Use while the hydrosilylation catalysts are generally expensive and have a corrosive, and since the cured product hydrogen gas generate a large amount has a property that results in foaming exceeds 10 ^-1 mol It is preferable not to have them.

Further, by adding a conductivity-imparting agent as the component (D) to the curable composition to form a conductive composition,
It is suitable as a developing roller. Examples of the conductivity-imparting agent of the component (D) include carbon black, metal fine powder, and organic compounds having a quaternary ammonium base, a carboxylic acid group, a sulfonic acid group, a sulfate group, a phosphate group, and the like. Or a polymer, an ether ester amide, or an ether imide polymer, an ethylene oxide-epihalohydrin copolymer, a compound having a conductive unit represented by methoxypolyethylene glycol acrylate, or an antistatic agent such as a polymer compound, Examples thereof include compounds capable of imparting conductivity. These conductivity imparting agents may be used alone or in combination of two or more.

It is to be noted that the addition amount of the conductivity-imparting agent as the component (D) should be not more than 30% by weight based on the total amount of the components (A) to (C), since the rubber hardness is not increased. preferable. On the other hand, in order to obtain a uniform volume resistance, this addition amount is 1
The addition amount is preferably 0% by weight or more, and the addition amount is preferably determined so that the volume resistivity of the cured product is 10 ³ to 10 ¹⁰ Ωcm.

Further, in addition to the components (A) to (D), a storage stability improver such as a compound having an aliphatic unsaturated bond, an organic phosphorus compound, an organic sulfur compound, A nitrogen-containing compound, a tin-based compound, an organic peroxide, or the like may be added. Specific examples thereof include, for example, benzothiazole, thiazole, dimethylmalate, dimethylacetylenecarboxylate,
-Pentenenitrile, 2,3-dichloropropene, quinoline and the like, but is not limited thereto. Among these, thiazole and dimethyl malate are particularly preferred from the viewpoint of achieving both pot life and rapid curing properties. The storage stability improvers may be used alone or in combination of two or more.

Further, a filler, a storage stabilizer, a plasticizer, an ultraviolet absorber, a lubricant, a pigment, and the like may be added to the curable composition from the viewpoint of improving processability and cost.

The roller according to the present invention is obtained by casting an elastic material such as urethane rubber, chloroprene rubber, EP rubber or the like into a mold provided with the above-mentioned conductive shaft. , Injection, extrusion, etc., and by heating and curing at an appropriate temperature and time,
An elastic layer is formed around the conductive shaft, and a surface layer is formed on the elastic layer. In these formations, post-curing may be performed after semi-curing. The method for forming the surface layer is not particularly limited.
Depending on the viscosity of the resin component that constitutes the surface layer, apply it to the outer peripheral surface of the elastic layer, which is the main base layer of the roller, by dipping, spraying, roll coating, brush coating, etc., and dry and cure at a predetermined temperature Thus, the roller according to the present invention can be obtained.

[0047]

EXAMPLES Specific examples and comparative examples of the developing roller according to the present invention will be described below. The developing rollers according to the examples and the comparative examples are configured such that a conductive elastic layer is provided around a SUS shaft, and a surface layer is coated on the conductive elastic layer. Hereinafter, specific configurations of the conductive elastic layer and the surface layer will be described. These examples do not limit the present invention in any way.

The conductive elastic layer is an elastic layer 1 listed below.
3 is provided around the conductive shaft.

(Elastic layer 1) (A-1) Number average molecular weight (M
n) 10,000 parts by weight of (B-1) a polysiloxane-based curing agent (SiH value 0.97 mol / 100) with respect to 100 parts by weight of a polyisobutylene polymer having two vinyl groups at terminals.
g): 2.7 parts by weight, (C-1) a 10% solution of chloroplatinic acid in isopropyl alcohol: 0.06 parts by weight, (D-
1) Carbon black 3030B (manufactured by Mitsubishi Chemical Corporation): 1
0 parts by weight and (other) plasticizer PS-32 (manufactured by Idemitsu Kosan Co., Ltd.): 75 parts by weight.
The composition obtained by defoaming under reduced pressure for 0 minutes was coated on the conductive shaft, and allowed to stand for 30 minutes in an environment of a mold at 120 ° C. for 30 minutes to cure, thereby forming an elastic layer 1. J of the elastic layer 1
JISA spring hardness (hereinafter, simply referred to as “JIS A hardness”) according to IS K6301 is 13 °.
Met.

(Elastic layer 2) (A-2) Number average molecular weight (M
n) With respect to 100 parts by weight of the terminal allylated polyoxypropylene polymer having a molecular weight distribution of 8,000 and (B-
2) Polysiloxane-based curing agent (SiH value 0.36 mol /
100 g): 6.6 parts by weight, 1 of (C-1) chloroplatinic acid
0% isopropyl alcohol solution: 0.06 parts by weight,
(D-1) Carbon black 3030B (manufactured by Mitsubishi Chemical Corporation): 6 parts by weight, and mixed at 10 mmHg or less and 120
The composition obtained by defoaming under reduced pressure for a minute was coated on the conductive shaft, and allowed to stand for 30 minutes in a mold at 120 ° C. for 30 minutes to cure, thereby forming an elastic layer 2. JIS of elastic layer 2
The A hardness was 15 °.

(Elastic Layer 3) A silicone resin (KEI1261-U manufactured by Shin-Etsu Chemical Co., Ltd.) was coated on the conductive shaft by an extrusion molding method to form an elastic layer 3. The JISA hardness of the elastic layer 3 was 45 °.

Examples 1 to 3 using the above-described elastic layers 1 and 2 according to the present invention and Comparative Examples 1 and 2 using the conventional elastic layer 3
2), assembling these rollers as a developing roller or a charging roller in a laser printer, and performing an output test to measure and evaluate (1) image quality, (2) photoreceptor wear, (3) photoreceptor surface potential did. Before this output test,
(4) Nip width and (5) Roller resistance value of the roller were measured and evaluated using a cylindrical electrode as shown in (1).

(1) The image quality was evaluated by assembling the roller as a developing roller in a developing device employing a non-magnetic developing method, and setting the width to 1 cm × 15 cm in an environment of 20 ° C. and 60% RH (relative humidity). Was printed on 10,000 sheets, and the difference between the maximum value and the minimum value of the image density on the 10,000th sheet was measured using a Macbeth densitometer. The criterion for this evaluation is ◎, when the difference in image density is less than 0.1, 0.1 or more
When it was less than 0.3, it was set to ○, and when it was 0.3 or more, it was set to △.

(2) Regarding the wear of the photoreceptor, the roller is incorporated in a laser printer as a charging roller or a developing roller, and a black solid image having a width of 1 cm × a length of 15 cm is obtained for 10,000 hours.
The surface of the photoreceptor after printing 0 sheets was visually observed, and evaluated by the presence or absence of scraping or abrasion.

(3) The surface potential of the photoreceptor is measured using a surface potentiometer manufactured by Trek Japan, after the roller is incorporated in a laser printer as a charging roller, and the surface of the photoreceptor is charged by contact with the photoreceptor. ·evaluated. The criterion for this evaluation is that the difference between the maximum value and the minimum value of the surface potential of the photoreceptor is 5
When the voltage is less than 0 V, ◎ is set, when 50 V or more and less than 100 V, △ is set, when 100 V or more and less than 150 V is set, and when 150 V or more, × is set.

(4) The nip width is measured by pressing an aluminum cylindrical electrode having a diameter of 30 mm and a roller into pressure as shown in FIG. The nip width when the linear pressure is 2.2 gf / mm is represented by d.

(5) The roller resistance value is obtained by pressing a 30 mm-diameter aluminum cylindrical electrode against a roller as shown in FIG. 1 and applying a DC voltage of 100 volts between the cylindrical electrode and the shaft. It is measured from the flowing current value. Also,
The maximum value (R _ma) of the roller resistance value when the linear pressure was continuously increased from 2.2 g weight / mm to 9.0 g weight / mm.
_x ) and the minimum value (R _min ) were measured.

The charging roller of the first embodiment is an S roller having a diameter of 6 mm.
An elastic layer 1 having a thickness of about 3 mm was formed on the outer periphery of a US-made shaft, and an ether urethane solution (Heimlen Y-237 manufactured by Dainichi Seika) was diluted to 5% with methyl ethyl ketone on the elastic layer 1. Dipping the surface layer solution, 8
It was produced by drying at 0 ° C. for 1 hour to cover a surface layer having a thickness of 20 μm. When the linear pressure is 2.2 gf / mm, the roller resistance after coating the surface layer is 6 × 10 ⁶ Ω, and the roller resistance before coating the surface layer is 5 × 10 ⁵ Ω. Has a higher roller resistance than the latter. On the other hand, the charging roller of Comparative Example 1 is formed by forming an elastic layer 3 having a thickness of about 3 mm on the outer periphery of the shaft. The roller resistance of Comparative Example 1 when the linear pressure was 2.2 gf / mm was 5 × 10 ⁵ Ω. These rollers are incorporated in a laser printer as charging rollers, and are pressed against the surface of a photoreceptor having a diameter of 30 mm, and an AC voltage having a frequency of 400 Hz and a peak-to-peak voltage of 2,000 V is applied while being superimposed on a DC voltage of 600 V. The surface was contact charged. Table 1 shows the measurement and evaluation results at this time.

[0059]

[Table 1]

As shown in Table 1, the charging roller of Example 1 provided with the elastic layer 1 having a nip width d of 1 mm or more and a roller resistance value ratio ( _Rmax / _Rmin ) of 3 or less was used. Compared with Comparative Example 1, the difference between the maximum value and the minimum value of the surface potential was small, and no abrasion of the photosensitive member was observed. Thus, it can be seen that charging unevenness was effectively prevented. Further, the roller of Comparative Example 1 including the elastic layer 3 has a nip width d due to high hardness.
Was less than 1 mm, and abrasion of the photoreceptor was observed.

Next, the developing roller of the second embodiment has a diameter of 10
An elastic layer 2 having a thickness of 7.5 mm is formed on the outer periphery of a SUS shaft having a thickness of 7.5 mm, and a carbonate urethane solution (Resamine ME8220LP manufactured by Dainichi Seika) is formed on the elastic layer 2.
Was diluted to 5% with methyl ethyl ketone, dipped in a surface layer solution, dried at 80 ° C. for 1 hour, and dried to a thickness of 15 μm.
m. When the linear pressure is 2.2 gf / mm, the roller resistance after coating the surface layer is 7 × 10 ⁷ Ω, and the roller resistance before coating the surface layer is 7 × 10 ⁵ Ω. Has a higher roller resistance than the latter. On the other hand, Comparative Example 2 is configured by forming an elastic layer 3 having a thickness of 7.5 mm on the outer periphery of the shaft. When the linear pressure was 2.2 gf / mm, the roller resistance value of Comparative Example 2 was 2 × 10 ⁶ Ω. These rollers are incorporated in a developing device employing a non-magnetic developing method as a developing roller, and this developing device is incorporated in a laser printer,
An output test was performed. Table 2 shows the measurement and evaluation results at this time.
Shown in

[0062]

[Table 2]

As shown in Table 2, the roller resistance ratio (R
_max / R _min ) of the developing roller of Example 2 provided with the elastic layer 2 of 3 or less, compared with Comparative Example 2 provided with the elastic layer 3, showed very good image evaluation and almost no abrasion of the photoconductor. It can be seen that the image unevenness is effectively prevented and the durability of the developing roller is improved.

Next, the developing roller of the third embodiment has a diameter of 10 mm.
An elastic layer 1 having a thickness of 7.5 mm is formed on the outer circumference of a SUS shaft having a thickness of 7.5 mm, and an ether urethane solution (Heimlen Y-237 manufactured by Dainichi Seika Co., Ltd.) is formed on the elastic layer 1 with methyl ethyl ketone at a concentration of 5%. The solution was prepared by dipping a surface layer solution diluted to 80 ° C., drying at 80 ° C. for 1 hour, and coating a surface layer having a thickness of 20 μm. Linear pressure 2.2g
Weight / mm, the roller resistance after coating the surface layer is 7 ×
10 ⁶ Ω, and the roller resistance before coating the surface layer is 1 ×
Since the resistance is 10 ⁶ Ω, the roller resistance of the former is larger than that of the latter. This developing roller was incorporated into a developing device employing a non-magnetic developing system, and this developing device was incorporated into a laser printer to perform an output test. Table 3 shows the measurement and evaluation results at this time.

[0065]

[Table 3]

As shown in Table 3, since the roller resistance ratio ( _Rmax / _Rmin ) is small, the fluctuation of the roller resistance is suppressed, so that the image evaluation is good and the photoreceptor is not worn. It can be seen that image unevenness is prevented.

[0067]

As described above, the electrophotographic roller of the present invention has a resin layer including a conductive elastic layer that has a nip width of 1.0 mm or more when the linear pressure is 2.2 gf / mm. , The fluctuation of the nip width with respect to the fluctuation of the linear pressure is suppressed, and the fluctuation of the roller resistance is also suppressed.

The resin layer applies a direct current voltage of 100 V between the cylindrical electrode and the conductive shaft with respect to a linear pressure that changes within a range of 2.2 g weight / mm or more and 9.0 g weight / mm or less. Maximum value of the roller resistance measured by applying ( _Rmax )
And the minimum value (R _min ) of the conductive elastic layer having a ratio (R _max / R _min ) of 3 or less, the fluctuation of the roller resistance value is extremely reduced, and the effect of preventing the charging unevenness and image unevenness is reduced. Better.

If the resin layer is formed so as not to contain a foam, an appropriate nip width can be ensured and the surface characteristics of the roller can be improved.
Image unevenness can be suppressed more effectively.

Further, by forming a surface layer on the resin layer such that the roller resistance value after coating the surface layer is larger than that before coating the surface layer, the above-described fluctuation of the roller resistance value is more effective. Can be suppressed.

As the conductive elastic layer, (A) a polymer containing at least one alkenyl group in the molecule, wherein the repeating unit constituting the main chain mainly comprises an oxyalkylene unit or a saturated hydrocarbon unit; And (B) a curing agent containing at least two hydrosilyl groups in a molecule, (C) a hydrosilylation catalyst, and (D) a conductivity-imparting agent. Is preferable because the above-described roller can be easily configured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which a cylindrical electrode and a roller are pressed against each other to measure roller resistance.

FIG. 2 is a schematic diagram illustrating an image forming apparatus incorporating a developing device employing a non-magnetic developing method.

[Explanation of symbols]

 1 Cylindrical electrode 2 Roller 3 Conductive shaft 4 Resin layer 5 Surface layer 10 Developing device 11 Charging roller 12 Photoconductor 13 Light containing image information 14 Non-magnetic toner 15 Toner container 16 Regulator blade 17 Developing roller 18 Supply roller 19 Transfer roller 20 Recording paper 21 Heating roller 22 Pressure roller 23 Cleaner

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G03G 15/16 103 G03G 15/16 103 (72) Inventor Hiroshi Ogoshi 2-1-1 Hiei Tsuji, Otsu-shi, Shiga Pref. In company

Claims (6)

[Claims] 1. A roller in which one or more resin layers are provided around a conductive shaft and a surface layer is provided concentrically on the resin layer, wherein the resin layer has a cylindrical electrode and a roller having the same shape as a photoreceptor. When the linear pressure at the time of contact with the surface is 2.2 gf / mm, a conductive elastic layer is provided so that the circumferential contact width between the cylindrical electrode and the roller surface is 1.0 mm or more. Roller for electrophotography. 2. The method according to claim 1, wherein the resin layer has a DC voltage of 100 V between the cylindrical electrode and the conductive shaft with respect to the linear pressure that changes within a range of 2.2 g weight / mm or more and 9.0 g weight / mm or less. the ratio of the maximum value of the roller resistance value measured by applying a (R _max) and the minimum value _{(R mi n) (R max} /
2. The electrophotographic roller according to claim 1, further comprising a conductive elastic layer having R _min ) of 3 or less. 3. The resin layer according to claim 1, wherein said resin layer does not contain a foam.
Or an electrophotographic roller according to claim 2. 4. The electrophotographic roller according to claim 1, wherein the JIS A spring hardness of the conductive elastic layer is 10 ° or more and 30 ° or less. 5. The electrophotographic roller according to claim 1, wherein a roller resistance value after coating the surface layer is larger than a roller resistance value before coating the surface layer. 6. The polymer according to claim 1, wherein the conductive elastic layer contains (A) at least one alkenyl group in a molecule, and a repeating unit constituting a main chain mainly comprises an oxyalkylene unit or a saturated hydrocarbon unit. And (B) a curing agent containing at least two hydrosilyl groups in its molecule, (C) a hydrosilylation catalyst, and (D) a conductivity-imparting agent. The electrophotographic roller according to any one of claims 1 to 5, which is configured.