JPH11338245A - Developing roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roll provided with excellent pressure withstanding performance and constituted so that the density irregularity of a copied image is not caused. SOLUTION: This developing roll is constituted so that a base rubber layer 2 is formed at the outside circumferential surface of a shaft body 1, an intermediate layer 3 is formed at the outside circumference of the layer 2 and a surface layer 4 is formed at the outside circumference of the layer 3. Then, the volume electrical resistivity of the layer 2 is set to be within 1×10<3> to 1×10<7> Ω.cm and the surface electrical resistivity is set to be within 1×10<4> to 1×10<6> Ω. Besides, the volume electrical resistivity of the layer 4 is set to be within 1×10<5> to 1×10<9> Ω.cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roll used in an electrophotographic apparatus such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art Generally, copying by an electrophotographic apparatus such as a copying machine or a printer is performed as follows. That is, a document image is formed as an electrostatic latent image on a photosensitive drum rotating about an axis, and toner is adhered to the image to form a toner image. Next, copying is performed by transferring the toner image to copy paper. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, and a document image is projected on the charged portion through an optical system and irradiated with light. 2. Description of the Related Art An electrostatic latent image is formed by canceling the charge of a part.
As a developing method of developing an electrostatic latent image on a photosensitive drum to form a visible image, various methods have conventionally been proposed according to the type of developer used. As one example, a one-component developing system using only toner as a developer is known.

As a developing device in the one-component developing system, for example, a developing device as shown in FIG. 9 is used. In this developing device, a developing roll 72 carrying a one-component developer (toner) 71 is pressed against a photosensitive drum 73,
Further, it is accommodated in a toner box 74 opened to the photosensitive drum 73 side. Further, an elastic roll 75 using a foam made of polyurethane foam, sponge, or the like is brought into contact with the developing roll 72.
5, the toner 71 is supplied. On the other hand, one end of the support holder 77 to which the layer forming blade 76 is bonded (the side opposite to the bonding portion of the layer forming blade 76) is fixed to the upper end of the opening edge of the toner box 74.
The layer forming blade 76 at the other end has a configuration in which the tip end (the portion extending from the bonding portion with the support holder 77) is pressed against the outer peripheral surface of the developing roll 72.

In the developing device having such a configuration, a toner image is formed on the outer peripheral surface of the photosensitive drum 73 as follows. That is, first, the developing roller 72 and the photosensitive drum 73 rotate as shown in the drawing, and the toner 71 is frictionally charged by the friction between the layer forming blade 76 and the outer peripheral surface of the developing roller 72. A uniform toner layer is formed. Then, due to the toner 71 of the toner layer, the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 73 becomes visible as a toner image. Thus, a toner image is formed on the outer peripheral surface of the photosensitive drum 73. For this reason, the toner 7
1 is required to have a function of forming a uniform toner layer on the outer peripheral surface of the developing roll 72 while frictionally charging the developing roller 1. Therefore, as satisfying such demands,
A metal material such as stainless steel is used.

On the other hand, as a material for forming the developing roll 72, a urethane resin has been conventionally used. In recent years, low-torque motors are often used due to demands for miniaturization and the like, and if the hardness of the urethane resin is too high, the roll does not rotate smoothly at the start,
Problems such as generation of a click sound due to stick-slip occur. For this reason, a developing roll using a low-hardness urethane resin has been proposed (JP-A-5-323777).
JP-A-3-187732).

[0006]

In the developing device having the above structure, a bias is applied to each of the developing roller 72, the photosensitive drum 73, the elastic roll 75, and the layer forming blade 76, and a bias difference is generated between the respective components. Has occurred.
Therefore, when the photosensitive drum 73 and the layer forming blade 76 are used while being pressed against the developing roll 72, it is necessary to use a developing roll 72 having excellent withstand voltage (hereinafter, abbreviated as “withstand voltage”) performance. However, the conventional developing roller 72 generally has a two-layer structure in which a surface layer made of urethane resin is formed on the surface of a urethane base rubber layer, so that the pressure resistance is inferior, and the resistance of each layer is increased to increase the pressure resistance. In this case, there is a problem that uneven resistance is likely to occur, and uneven density occurs in a copied image.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a developing roll having excellent pressure resistance performance and having no density unevenness in a copied image.

[0008]

In order to achieve the above object, a developing roll of the present invention has a base rubber layer formed on the outer peripheral surface of a shaft, and an intermediate layer formed on the outer periphery of the base rubber layer. A developing roller having a surface layer formed on the outer periphery of the intermediate layer, wherein the volume electric resistance of the base rubber layer is 1 × 1
0 ³ to 1 × 10 ⁷ Ω · cm, the surface electric resistance of the intermediate layer is set to 1 × 10 ⁴ to 1 × 10 ⁶ Ω, and the volume electric resistance of the surface layer is 1 × 10 ⁵
構成 1 × 10 ⁹ Ω · cm.

In general, the electric power of each layer constituting the developing roll
Increasing the resistance improves withstand voltage performance, but on the contrary
And the variation also increases, so that the gradation
Or the resistance of the base rubber layer is uneven.
Problems such as uneven density occur. Therefore, the present invention
Do not affect the gradation of the density, causing uneven density.
To obtain a developing roll with excellent pressure resistance performance
To this end, research was repeated mainly on the electrical characteristics of the developing roll. So
As a result, the developing roll is transferred to the base rubber layer, intermediate layer and surface layer.
And the electrical resistance of the entire developing roll
To the medium resistance region (1 × 10^Five~ 1 × 10⁸Ω)
It was found that it was desirable. And electricity of each layer
After extensive research on resistance, the body of the base rubber layer
The product electric resistance is 1 × 10^Three~ 1 × 10⁷Ω · cm range,
The surface electric resistance of the intermediate layer is 1 × 10 ^Four~ 1 × 10⁶Ω range
In the figure, the volume electric resistance of the surface layer is 1 × 10^Five~ 1 × 10⁹Ω
・ If each is set in the range of cm, the entire developing roll
Electric resistance is medium resistance (1 × 10^Five~ 1 × 10⁸Ω)
It was found that the intended purpose could be achieved, and the present invention was reached.
Reached.

[0010]

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

FIG. 1 shows an example of the developing roll of the present invention.
The developing roll includes a base rubber layer 2 formed along an outer peripheral surface of a shaft body 1, an intermediate layer 3 formed on the outer peripheral surface, and a surface layer 4 formed on the outer peripheral surface.

The shaft 1 is not particularly limited.
For example, a metal core made of a solid metal body, a metal cylindrical body hollowed out inside, or the like is used. Examples of the material include stainless steel, aluminum, and iron plated. Also, if necessary, the shaft 1
An adhesive, a primer and the like can be applied thereon. The adhesive, the primer and the like may be made conductive as needed.

The material for forming the base rubber layer 2 formed on the outer peripheral surface of the shaft 1 is not particularly limited. For example, silicone rubber, ethylene-propylene-diene rubber (EP)
DM), styrene-butadiene rubber (SBR), polyurethane elastomer and the like. Among them, silicone rubber is particularly preferable because of its low hardness and little set. When silicone rubber is used as the material for forming the base rubber layer 2, a step of activating the surface of the silicone rubber by corona discharge, plasma, or the like, or a step of applying a primer thereafter may be performed.

A conductive agent may be appropriately added to the material for forming the base rubber layer 2. Examples of the conductive agent include carbon black, graphite, potassium titanate, iron oxide, c-TiO ₂ , c-ZnO, c
—SnO ₂ , ionic conductive agents (quaternary ammonium salts, borates, surfactants, etc.) and the like. Note that the above “c”
"-" Means having conductivity.

The material for forming the intermediate layer 3 formed on the outer periphery of the base rubber layer 2 is not particularly limited. For example, acrylonitrile-butadiene rubber (nitrile rubber) (hereinafter abbreviated as “NBR”), hydrogenated acrylonitrile-butadiene Rubber (hydrogenated nitrile rubber) (hereinafter "H-NB
R "), polyurethane elastomer, chloroprene rubber (CR), natural rubber, butadiene rubber (B
R), butyl rubber (IIR), hydrin rubber, nylon and the like. Among them, H-NBR is particularly preferred from the viewpoints of adhesiveness and stability of the coating solution.

The H-NBR has an acrylonitrile content of 40 to 50% and an iodine value of 18%.
The amount set in the range of ~ 56 mg / 100 mg is preferable, and the amount of acrylonitrile is particularly preferably 45-50.
% And an iodine value of 18 to 45 mg / 100
mg range. Such an H-NBR can be manufactured, for example, as follows. That is, first, emulsion polymerization of acrylonitrile and butadiene is performed to produce NBR as a raw material. Then, the raw material NBR
Is dissolved in a solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and Rh, P
The desired H-NBR can be produced by performing a hydrogenation reaction in the presence of a noble metal catalyst such as d or Pt (by subjecting NBR to hydrogenation treatment) and desolvation. The amount of acrylonitrile can be set in the above range depending on NBR as a raw material, and the iodine value (the amount of hydrogen added) can be set in the above range depending on the concentration of hydrogen to be reacted.

Examples of the material for forming the intermediate layer 3 include a vulcanizing agent such as a conductive agent and sulfur, and a vulcanization accelerator such as guanidine, thiazole, sulfenamide, dithiocarbamate, and thiuram.
Stearic acid, zinc white (ZnO), a softener, and the like may be appropriately added. Note that, as the conductive agent, the same as described above is used.

The surface layer 4 formed on the outer periphery of the intermediate layer 3 is not particularly limited. For example, a silicone graft acrylic polymer, an acrylic graft silicone polymer,
Acrylic rubber, urethane and the like. These may be used alone or in combination of two or more.

The silicone-grafted acrylic polymer is preferably a polymer obtained by grafting a side chain composed of a siloxane-derived structural part to a main chain composed of a linear structural part derived from an acrylic monomer. . Specifically, those represented by the following general formula (1) are particularly preferred.

[0020]

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In the general formula (1), the number of repetitions k
Is a positive number of 1 to 3000, preferably a positive number of 1 to 300. The number of repetitions n is a positive number from 1 to 3000, and preferably a positive number from 1 to 300.

In the above general formula (1), Y is a linear structural part derived from an acrylic monomer. As the acrylic monomer, specifically, acrylic acid,
Methyl acrylate, ethyl acrylate, octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, acrylic acid 2,2-dimethylpropyl, cyclohexyl acrylate, acrylic acid-2
-Tert-butylphenyl, 2-naphthyl acrylate, phenyl acrylate, 4-methoxyphenyl acrylate, 2-methoxycarbonylphenyl acrylate, 2-ethoxycarbonylphenyl acrylate, 2-chlorophenyl acrylate, 4-chlorophenyl acrylate ,
Benzyl acrylate, 2-cyanobenzyl acrylate,
4-cyanophenyl acrylate, p-tolyl acrylate, isononyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-cyanoethyl acrylate, 3-oxabutyl acrylate, Methacrylic acid, methyl methacrylate, ethyl methacrylate, octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, propyl methacrylate, n-methacrylic acid
Butyl, isobutyl methacrylate, sec methacrylate
-Butyl, tert-butyl methacrylate, 2,2-dimethylpropyl methacrylate, cyclohexyl methacrylate, 2-tert-butylphenyl methacrylate,
2-naphthyl methacrylate, phenyl methacrylate, 4-methoxyphenyl methacrylate, 2-methoxycarbonyl methacrylate, 2-ethoxycarbonylphenyl methacrylate, 2-chlorophenyl methacrylate, 4-chlorophenyl methacrylate, benzyl methacrylate, methacrylic 2-cyanobenzyl acid, 4-cyanophenyl methacrylate, p-tolyl methacrylate, isononyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-cyanoethyl methacrylate, 3-oxabutyl methacrylate, γ-methacryloyloxypropyltrimethoxysilane, acrylamide, butylacrylamide, N, N-dimethylacrylamide, piperidylua Riruamido, methacrylamide, 4-carboxyphenyl methacrylamide, 4-methoxy-carboxyphenyl methacrylamide, methyl chloro acrylate, ethyl -α- chloro acrylate,
Propyl-α-chloroacrylate, isopropyl-α
Radical polymerizable monomers such as -chloroacrylate, methyl-α-fluoroacrylate, butyl-α-butoxycarbonyl methacrylate, butyl-α-cyanoacrylate, methyl-α-phenyl acrylate, isobonyl acrylate, isobonyl methacrylate, and diethylaminoethyl methacrylate. Mers. And
One type of these acrylic monomers is polymerized or two or more types are copolymerized to form a linear structural portion represented by Y.

In the above general formula (1), Z is a structural part derived from an acrylic monomer and has a structural part derived from siloxane. this is,
It is derived from those represented by the following general formula (2) or (3).

[0024]

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[0025]

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As a preferred specific example of the above general formula (3) or (4), the following structural formula (a)
To (r).

[0027]

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[0028]

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[0029]

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[0030]

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The silicone-grafted acrylic polymer having the structure represented by the general formula (1) has a glass transition temperature of an acrylic polymer portion [main chain] excluding a structural portion [side chain] derived from siloxane. It is preferably in the range of −35 to 30 ° C., particularly preferably −30 to 0 ° C.
It is in the range of ° C. That is, when the glass transition temperature of the acrylic polymer portion (main chain) is lower than −35 ° C., the adhesiveness is increased and the friction coefficient is increased, so that toner filming occurs, and the copied image is deteriorated. This is because the roll becomes too hard, causing problems such as the roll not rotating smoothly at the start and a click sound. There is also a problem that traces are likely to remain on the roll when pressed against other parts.

The glass transition temperature of the acrylic polymer portion [main chain] excluding the structural portion [side chain] derived from the siloxane can be set as follows, for example. That is, the acrylic polymer portion (main chain)
Is carried out by setting the weight ratio of each acrylic polymer according to the following Fox formula so that the glass transition temperature of the polymer falls within the range of −35 to 30 ° C.

[0033]

1 / Tg = (W ₁ / Tg ₁ ) + (W ₂ / T
_{g 2) + ... + (W} m / Tg m) W 1 + W in ₂ + ... + W _m = 1 [Equation, Tg represents the glass transition temperature of the acrylic polymer _{portion, Tg 1, Tg 2, ...} , Tg m is The glass transition temperature of each acrylic monomer is shown. W ₁ , W ₂ , ...,
W _m denotes a weight ratio of each acrylic monomer. ]

The above glass transition temperature (Tg) is determined by DSC
(Differential scanning calorimetry) or a dynamic viscoelasticity tan δ peak.

The number average molecular weight of the silicone-grafted acrylic polymer having the structure represented by the general formula (1) is preferably set in the range of 10,000 to 300,000, and particularly preferably 30,000 to 300,000. 100,
000. That is, if the number average molecular weight of the silicone graft acrylic polymer is less than 10,000, the strength of the surface layer tends to be inferior, and 300,000
This is because, if it exceeds, formation of the surface layer becomes difficult.

(Z) _n in a silicone-grafted acrylic polymer having a structure represented by the above general formula (1)
The number average molecular weight of the portion is preferably set in the range of 260 to 100,000, particularly preferably 2,000.
It is in the range of ５０50,000. That is, (Z) _n
When the number average molecular weight of the portion is less than 260, the effects of silicone such as flexibility, low friction coefficient, and releasability are reduced,
If it exceeds 100,000, stickiness occurs.

The content of the (Z) _n part is 5 to 60% by weight based on the total weight of the silicone-grafted acrylic polymer.
It is preferable to set the range. That is,
When the content of the (Z) _n portion is less than 5% by weight, the effects of the silicone such as flexibility, low friction coefficient, and releasability are reduced. When the content exceeds 60% by weight, stickiness peculiar to the silicone occurs. It is.

The specific silicone-grafted acrylic polymer can be produced, for example, as follows. That is, it can be produced by subjecting the above (Y) _k portion and (Z) _n portion to radical copolymerization in the presence of an azo polymerization initiator. Such polymerization is preferably performed by a solution polymerization method using a solvent, a bulk polymerization method, an emulsion polymerization method, or the like, and particularly preferably a solution polymerization method.

Examples of the azo polymerization initiator include azobisisobutyronitrile (AIBN), azobis-4-cyanovaleric acid, azobis (2,4-dimethylvaleronitrile), azobis (4-methoxy-2,4- Dimethylvaleronitrile), dimethyl-2,2'-azobisisobutyrate, azobis-1-cyclohexacarbonitrile and the like, with AIBN being particularly preferred. Further, the polymerization temperature at the time of the radical copolymerization is preferably set in the range of 50 to 150 ° C, particularly preferably 60 to 100 ° C.
° C. Further, the polymerization time is preferably in the range of 3 to 100 hours, particularly preferably 5 to 10 hours.

As the silicone-grafted acrylic polymer, those having a structure represented by the general formula (1) are preferable, and a linear linear polymer derived from another acrylic monomer is preferable. Having a structure represented by the following general formula (4), in which the structural portion [(X) _m portion] is linked.

[0041]

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In the above general formula (4), X is a linear structural part derived from an acrylic monomer, and the acrylic monomer includes those exemplified in the above general formula (1). And similar ones.

The acrylic graft silicone polymer which is a material for forming the surface layer 4 is not particularly limited.
It is preferable that a side chain composed of a structural part derived from an acrylic monomer is grafted to a main chain composed of a linear structural part derived from siloxane. In particular,
Those represented by the following general formulas (5) to (7) are particularly preferred.

[0044]

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Preferred specific examples of the structural portion represented by the above general formula (5) include those represented by the following structural formulas.

[0046]

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X in the general formulas (6) and (7) represents hydrogen or a carbon functional group such as a halogenated hydrocarbon group or a cyanated hydrocarbon group. Examples of the halogenated hydrocarbon group include a halogenated alkyl group, a halogenated aryl group, a halogenated aralkyl group, and a halogenated alkenyl group. Examples of the cyanated hydrocarbon group include a cyano group and an aralkyl cyanide group. Group, aryl cyanide group, aralkyl cyanide group, alkenyl cyanide group and the like.

The acrylic graft silicone polymer has a structural part [side chain] derived from an acrylic monomer.
Is preferably set in the range of 30 to 150 ° C., particularly preferably 60 to 150 ° C.
It is in the range of 120 ° C. That is, when the glass transition temperature (Tg) is less than 30 ° C., the effects of lowering the coefficient of friction, releasability, and non-stickiness tend to be reduced.
If the temperature exceeds ℃, the solubility in a solvent is reduced and the toner releasability tends to be inferior. The glass transition temperature (Tg) of the structural portion [side chain] derived from the acrylic monomer can be measured according to the above-mentioned Fox formula.

In the acryl-grafted silicone polymer, the molecular weight of the main chain composed of a linear structural portion derived from siloxane is preferably set in the range of 1,500 to 20,000, particularly preferably 3,500. 0
The range is from 00 to 10,000. That is, if the molecular weight is less than 1,500, it is difficult to obtain the effects of silicone such as appropriate chargeability, low friction coefficient and releasability.
If it exceeds 000, the compatibility will be reduced, the effect will be reduced, and stickiness of the silicone will tend to occur.

The structural portion derived from the acrylic monomer in the acrylic graft silicone polymer is not particularly limited, and examples thereof include those represented by the following general formula (8). Examples of the acrylic monomer include the same ones as described above. A structure derived from an acrylic monomer by polymerization of one of these acrylic monomers or copolymerization of two or more thereof. The part is composed.

[0051]

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Preferred specific examples of the structural portion represented by the general formula (8) include those represented by the following structural formulas.

[0053]

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In the acrylic graft silicone polymer, the molecular weight of the side chain comprising the structural portion derived from an acrylic monomer is preferably set in the range of 200 to 20,000, particularly preferably 1,000 to 20,000.
It is in the range of 10,000. That is, when the molecular weight is 2
If the molecular weight is less than 00, it is difficult to obtain an appropriate chargeability, so that the above-mentioned effects are hardly obtained. If the molecular weight exceeds 20,000, the above-mentioned effects are hardly obtained.

The acryl-grafted silicone polymer comprises, for example, a structural portion derived from the siloxane,
It can be produced by subjecting a structural part derived from an acrylic monomer to the above-mentioned radical copolymerization in the presence of the above-mentioned azo-based polymerization initiator. Further, the acrylic graft silicone polymer may be produced, for example, by subjecting a structural part derived from the siloxane and a structural part derived from an acrylic monomer to an anionic polymerization reaction in the presence of an anionic polymerization catalyst. Can also. Examples of the anion polymerization catalyst include lithium, alkali metals such as sodium, aliphatic hydrocarbons such as methyl, ethyl, propyl, and butyl, naphthalene, anthracene,
Examples thereof include aromatic hydrocarbons such as phenanthrene, triphenylene, naphthacene, acenaphthylene, transstilbene, biphenyl, styrene, methylstyrene, divinylbenzene, benzonitrile, diphenylethylene, and diphenylbutadiene. These may be used alone or in combination of two or more.

The acrylic graft silicone polymer thus obtained has a molecular weight of 3,000 to 300,
It is preferably set in the range of 000, and particularly preferably in the range of 10,000 to 100,000. That is, if the molecular weight is less than 3,000, it is difficult to obtain the above-mentioned effects, and bleeding tends to contaminate the photoreceptor. If it exceeds 300,000, the compatibility with other materials decreases. This is because it is difficult to obtain effects such as low friction due to separation.

In the acrylic graft silicone polymer, the weight ratio of the main chain consisting of the linear structural part derived from the siloxane to the side chain consisting of the structural part derived from the acrylic monomer is a weight ratio. The main chain / side chain is preferably set in the range of 5/95 to 60/40, particularly preferably the main chain / side chain = 10/90 to 40 /.
The range is 60. That is, when the ratio of the main chain exceeds 60 (the ratio of the side chains is lower than 40), the silicone component tends to increase too much and the compatibility with other materials tends to be deteriorated. If it is lower (the ratio of the side chains exceeds 95), the silicone component is reduced, so that a suitable chargeability can be obtained.
This is because releasability is difficult to obtain, and the effect on strength tends to decrease.

The material for forming the surface layer 4 includes a conductive agent, a charge controlling agent, a stabilizer, an ultraviolet absorber, an antistatic agent, a reinforcing agent, a lubricant, a release agent, a dye, a pigment, a flame retardant, an oil, a crosslinking agent, and the like. Can also be added as appropriate. Examples of the conductive agent include the same ones as described above. Examples of the charge control agent include a quaternary ammonium salt, a borate, and a conventionally used quaternary ammonium salt.
Examples thereof include azine-based (nigrosine-based) compounds, azo compounds, metal complexes of oxynaphthoic acid, and surfactants (anionic, cationic, and nonionic). Examples of the crosslinking agent include isocyanate group-containing substances, amino groups, Examples of the curing agent include an epoxy group, a carboxyl group, and a -SH group.

The material for forming the surface layer 4 can be produced, for example, as follows. That is, first, a silicone-grafted acrylic polymer, an acrylic-grafted silicone polymer, and the like are prepared according to the method described above, and these are dissolved in an organic solvent. Then, if necessary, a conductive agent,
A coating liquid for coating is prepared by dispersing the mixture containing the charge control agent and the like in a sand mill or the like. Examples of the organic solvent include methyl ethyl ketone, toluene, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, methyl isobutyl ketone, cyclohexane,
Methanol, isopropyl alcohol and the like can be mentioned.
These may be used alone or in combination of two or more.

Alternatively, the above-mentioned silicone-grafted acrylic polymer, acrylic-grafted silicone polymer, conductive agent and the like are dispersed by a twin-screw kneader or the like, and these are dissolved in the organic solvent to prepare a coating liquid for coating. Is also good.

The developing roll of the present invention can be produced, for example, as follows. That is, first, each component for the base rubber layer 2 forming material is kneaded using a kneading machine such as a kneader to prepare a base rubber layer 2 forming material. Further, the components for the intermediate layer 3 forming material are kneaded using a kneading machine such as a roll, and the organic solvent is added to the mixture, followed by mixing and stirring, whereby the intermediate layer 3 forming material (coating liquid) is obtained. Make it. Further, according to the method described above, the material for forming the surface layer 4 (coating liquid)
Is prepared.

Next, as shown in FIG. 2, the shaft body 1 is prepared, an adhesive, a primer and the like are applied to the outer peripheral surface thereof as necessary, and then the shaft body 1 is placed in a cylindrical mold 6 in which the lower lid 5 is fitted. Shaft 1
Is set. Next, after the base rubber layer 2 forming material is cast or the like, the upper lid 7 is fitted over the cylindrical mold 6. Subsequently, the entire roll mold is heated to vulcanize the material for forming the base rubber layer 2 (150 to 220 ° C. × 30 minutes) to form the base rubber layer 2. Subsequently, the shaft 1 on which the base rubber layer 2 is formed is removed from the mold, and the reaction is completed as required (200 ° C. × 4 hours). Next, a corona discharge treatment is performed on the roll surface as needed. Further, a coupling agent is applied to the roll surface as needed. Then, a coating liquid serving as a material for forming the intermediate layer 3 is applied to the outer periphery of the base rubber layer 2, or the roll on which the base rubber layer 2 has been formed is dipped in the coating liquid and pulled up, followed by drying and heat treatment. Is performed, the intermediate layer 3 is formed on the outer periphery of the base rubber layer 2. Further, a coating liquid as a material for forming the surface layer 4 is applied to the outer periphery of the intermediate layer 3, or a roll on which the intermediate layer 3 has been formed is immersed in the coating liquid and pulled up, followed by drying and heat treatment. Thereby, the surface layer 4 is formed on the outer periphery of the intermediate layer 3.
The method of applying the coating liquid is not particularly limited, and includes a conventionally known dipping method, spray coating method, roll coating method, and the like. In this way, a three-layer developing roll in which the base rubber layer 2 is formed along the outer peripheral surface of the shaft body 1, the intermediate layer 3 is formed on the outer periphery, and the surface layer 4 is further formed on the outer periphery. can do.

The developing roll of the present invention needs to be manufactured such that the electric resistance of each layer is in the following range. The volume electrical resistance of the base rubber layer 2 is 1 × 10 ³ to 1 × 10 ⁷ Ω.
・ It is necessary to set in the range of cm, preferably 1 × 1
0 is in the range of ^{4 ~1 × 10 6 Ω · cm} . That is, the volume electric resistance of the base rubber layer 2 is 1 × 10 ³ Ω · cm.
If it is less than 1, the pressure resistance is inferior, and if it exceeds 1 × 10 ⁷ Ω · cm, density unevenness occurs, and the reproducibility of the gradation of the density is lost. The surface electric resistance of the intermediate layer 3 needs to be set in the range of 1 × 10 ⁴ to 1 × 10 ⁶ Ω, and preferably in the range of 5 × 10 ⁴ to 2 × 10 ⁵ Ω. That is, the surface electric resistance of the intermediate layer 3 is 1 × 10
^If it is less than ⁴ Ω, the withstand voltage performance is poor, and if it exceeds 1 × 10 ⁶ Ω, concentration unevenness occurs. And the above-mentioned surface layer 4
Must be set in the range of 1 × 10 ⁵ to 1 × 10 ⁹ Ω · cm, and preferably 1 × 10 ⁶ to 1 ×.
The range is 10 ⁸ Ω · cm. That is, when the volume electric resistance of the surface layer 4 is less than 1 × 10 ⁵ Ω · cm, the pressure resistance is inferior, and when it exceeds 1 × 10 ⁹ Ω · cm, charges easily accumulate and an afterimage appears or the base rubber layer This is because resistance unevenness is easily spread and unevenness in density occurs.

The electric resistance of each layer is measured as follows.

[Volume Electric Resistance of Base Rubber Layer] As shown in FIG. 3, a sheet 32 (thickness: 2 mm) made of the above-mentioned base rubber layer forming material is placed on a stainless steel plate 31 and then placed on the stainless steel plate 31. A voltage of 10 V is applied, and the volume electric resistance of the sheet 32 is measured.

[Surface Electric Resistance of Intermediate Layer] As shown in FIG. 4, the above-mentioned intermediate layer forming material is applied on a polyethylene terephthalate film 41 to form a coating film 42 (having a thickness of 50 to 60).
μm). On the other hand, a rectangular casing 43 is prepared, and two copper tapes 44 (10 × 50
mm) at 10 mm intervals. Then, one of the copper tapes 44 to which a voltage of 1000 V is applied is pressed onto the coating film 42 with a load of 3000 g, and the surface electric resistance of the coating film 42 is measured.

[Volume Electric Resistance of Surface Layer] As shown in FIG. 5, the surface layer forming material is applied on a conductive polyethylene terephthalate film (mylar sheet) 21 to form a coating film 22 (50 to 60 μm in thickness). . Then, this is sandwiched between SME-8311 electrodes 23 (manufactured by Toa Denpasha Co., Ltd.), and the current when a voltage of 1 V is applied is measured by an ammeter 24 (KE
(ITHLEY-6517, manufactured by Kesley Co., Ltd.), and this is converted into volume electric resistance. In the drawing, reference numeral 25 denotes an aluminum foil, which is fixed to the conductive polyethylene terephthalate film (mylar sheet) 21 with a clip (not shown).

In the developing roll of the present invention, the thickness of the base rubber layer 2 is usually preferably set in the range of 1 to 15 mm, particularly preferably in the range of 1 to 5 mm.
In addition, the thickness of the intermediate layer 3 is preferably set in the range of usually 5 to 40 μm, particularly preferably 10 to 20 μm.
Range. And the thickness of the surface layer 4 is usually 5 to 30 μm.
m, particularly preferably 5
２０20 μm.

The hardness of the developing roll of the present invention is determined by JI
The hardness measured by SA is 70 (Hs: JIS).
A) Those having the following range are preferred, and particularly preferably 60 (Hs: JIS A) or less.

Next, examples will be described together with comparative examples.

First, prior to Examples and Comparative Examples, a silicone-grafted acrylic polymer composed of the following repeating units was prepared according to the method described above.

[0072]

Embedded image

[0073]

Examples 1 to 5 and Comparative Examples 1 to 6 First, the components shown in the following Tables 1 to 3 were blended in the proportions shown in the same table, and the material for forming each layer was adjusted according to the above-mentioned method. Then, a core (diameter: 10 mm, made of SUS304) serving as a shaft was prepared, and a base rubber layer was formed on the core according to the method described above. Then, after performing a corona discharge treatment on the surface of the base rubber layer, a coupling agent was further applied. Then, an intermediate layer and a surface layer were sequentially formed on the outer periphery of the base rubber layer to obtain a developing roll having a three-layer structure.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

With respect to the developing rolls of the example product and the comparative example product thus obtained, the residual charge, the residual charge unevenness, the electric resistance of the roll, the withstand voltage, the density unevenness at the time of image formation, and the image formation were determined according to the following criteria. A comparative evaluation was made on the time density gradation. These results are also shown in Tables 4 to 6 below.

[Residual Charge] As shown in FIG. 6, while the developing roll 51 is rotated in the direction of the arrow at a rotation speed of 60 rpm, 100 μm is applied using a corona discharge wire (corotron) 52.
A corona current of A was applied to charge the surface of the developing roll 51. Then, the developing roll 51 is measured by a surface voltmeter 53.
The residual charge on the surface was measured. The residual charge of each layer was measured in the same manner as described above.

[Residual Charge Unevenness] The difference between the maximum value and the average value of the residual charges on the developing roll was expressed as residual charge unevenness.

[Electric Resistance of Roll] The electric resistance was measured by a metal roll method using an apparatus as shown in FIG. That is, the developing roll 62 was brought into contact with the metal roll 61 made of stainless steel, and both ends of the developing roll were pressed with a load of 700 g. Next, a voltage of 100 V was applied to one end of the developing roll 62, and the electrical resistance of the roll was measured.

[Withstand voltage] The measurement was performed using the apparatus shown in FIGS. 8 (A) and 8 (B). That is, the developing roll 62 is placed on the two stainless steel metal rolls 61 that are not in contact with each other.
Was placed, and both ends of the developing roll 62 were pressed with a load of 500 g. Next, a current value when a voltage of 300 V was applied to one of the metal rolls 61 was measured. And the current value is 1
The case where the current value was less than 0 μA was indicated by ○, and the case where the current value was 10 μA or more was indicated by x.

[Density Unevenness at Image Output] A halftone image was output by incorporating a developing roll into an electrophotographic copying machine. Then, the concentration is measured with a Macbeth densitometer, and the case where the difference between the maximum value and the minimum value is within 0.05 is displayed as ○, the case between 0.05 and 0.10 as Δ, and the case where it is 0.1 or more as ×. did.

[Density Gradation at Image Output] A developing roll was incorporated in an electrophotographic copying machine, and a gray scale image was output. Then, those with a color gradation of 10 or more were displayed as ○, those with 7 to 9 as Δ, and those with 6 or less as X.

[0084]

[Table 4]

[0085]

[Table 5]

[0086]

[Table 6]

From the results shown in Tables 4 to 6, it can be seen that the developing rolls of the examples have excellent pressure resistance, do not cause density unevenness, and have excellent density gradation. On the other hand, it can be seen that the developing roll of the comparative example is inferior in at least one of the characteristics such as the withstand voltage, the density unevenness at the time of image output, and the density gradation at the time of image output.

[0088]

As described above, the developing roll of the present invention
It has a three-layer structure consisting of a base rubber layer, an intermediate layer, and a surface layer.
Also, the volume electric resistance of the base rubber layer is 1 × 10^Three~ 1 ×
10⁷Ω · cm, the surface voltage of the intermediate layer
Air resistance is 1 × 10^Four~ 1 × 10 ⁶Ω range,
And the volume electric resistance of the surface layer is 1 × 10⁶~ 1 × 10
⁹It is set in the range of Ω · cm. As a result,
The electrical resistance of the entire rule is medium resistance (1 × 10^Five~ 1 × 10⁸
Ω) to have excellent pressure resistance performance
In addition, density unevenness does not occur.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a developing roll of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a method for manufacturing a developing roll of the present invention.

FIG. 3 is an explanatory view showing a method of measuring a volume electrical resistance of a base rubber layer.

FIG. 4 is an explanatory diagram showing a method for measuring the surface electric resistance of the intermediate layer.

FIG. 5 is an explanatory view showing a method of measuring the volume electric resistance of the surface layer.

FIG. 6 is an explanatory diagram showing a method for measuring a residual charge.

FIG. 7 is an explanatory diagram showing a method for measuring the electric resistance of a roll.

FIG. 8A is an explanatory view showing a method for measuring a withstand voltage, and FIG.
FIG. 3 is a cross-sectional view showing a method for measuring a withstand voltage.

FIG. 9 is a schematic diagram illustrating a configuration of a conventional developing device.

[Explanation of symbols]

 1 Shaft 2 Base rubber layer 3 Intermediate layer 4 Surface layer

Continuation of the front page (72) Inventor Shoji Arimura Komaki City, Aichi Prefecture Oita Kita-gaiyama character Gezu 3600 Tokai Rubber Industries Co., Ltd.

Claims (2)

[Claims] 1. A developing roll having a base rubber layer formed on an outer peripheral surface of a shaft body, an intermediate layer formed on an outer periphery of the base rubber layer, and a surface layer formed on an outer periphery of the intermediate layer.
The volume electrical resistance of the base rubber layer is 1 × 10 ³ to 1 × 1
0 ⁷ Ω · cm, the surface electric resistance of the intermediate layer is set in the range of 1 × 10 ⁴ -1 × 10 ⁶ Ω, and the volume electric resistance of the surface layer is 1 × 10 ⁵ -1. × 10 ⁹
A developing roll characterized by being set in the range of Ω · cm. 2. The developing roll according to claim 1, wherein the surface layer is in contact with a metal layer forming blade, and a potential difference is generated between the surface layer and the metal layer forming blade.