JP2001034088A - Conductive silicone rubber roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a conductive silicone roller used for an electro- photographic device by using singly silicone rubber which is not used singly as usual because a photoreceptor drum is contaminated. SOLUTION: This conductive silicone rubber roller which does not contaminate the photoreceptor drum is obtained by bringing conductive silicone rubber 5a into contact with a roller core bar 5b centering the core bar 5b, and cylindrically molding it so as to envelop the core bar 5b, then performing heating processing to the rubber 5a at 150 to 220 deg.C and for 1 to 48 hours after vulcanizing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer or an electrostatic recording apparatus, and an image forming means such as an electrophotographic process or an electrostatic recording process on an image carrier such as a photosensitive member. The present invention relates to a transfer member of an apparatus for transferring a transferable image (toner image) formed and carried on a recording medium such as paper.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a schematic view of a conventional electrophotographic recording apparatus.

In electrophotography, a photoreceptor having an insulative photoconductor formed on a conductive substrate is used, and an image is formed by the following steps.

First, the surface of the photosensitive drum 1 is uniformly charged by a charging roller 2 in a dark place (charging step).
Next, an image is exposed on the uniformly charged surface of the photosensitive drum 1 by exposure means 3 such as a laser. Then, a hole-electron pair is generated in the exposed portion of the photosensitive drum 1, neutralizing the charge in that portion, and forming a distribution of electrostatic charges corresponding to the exposed image, that is, a so-called electrostatic latent image (exposure step).

Next, when a colored powder (toner) (not shown) is brought into contact with the surface of the photosensitive drum 1 on which the electrostatic latent image is formed, the toner is charged according to the electrostatic charge of the electrostatic latent image. The electrostatic latent image is electrostatically attached to one surface, and the electrostatic latent image is visualized as a toner image in the developing unit 4 (developing step). Next, when an electric field is applied from the back surface of the recording medium P by the transfer roller 5 while the recording medium P such as paper is in contact with the toner image, the toner image is transferred to the surface of the recording medium P (transfer step).

Thereafter, if the residual charge on the surface of the photoreceptor is removed (static elimination step) and the toner remaining on the surface is removed in the cleaning unit 6 (cleaning step), the cycle of image formation by electrophotography is completed. .

Further, the toner image transferred to the surface of the recording medium is heat-treated by a heat roller or the like, and is fixed on the surface of the recording medium (fixing step).

Next, the transfer step will be described. Conventionally, in the steps of charging, transferring, and discharging, corona discharge by a discharge wire stretched near the photosensitive drum has been used to apply a voltage to the photosensitive drum. However, corona discharge generates a large amount of ozone, not only contaminating air but also causing deterioration of the surface of the photoreceptor.
In view of this, attempts have been made to use a roller-type conductive elastic transfer roller that is in contact with a photoreceptor and that can suppress the generation of harmful ozone.

[0009] The transfer roller, ozone characteristics, but it is a matter of course that the heat resistance is required, in order to obtain a good transferred image, a certain degree of conductivity (1 × 10 ⁷ ~
5 × 10 ⁹ Ω).

The transfer roller applies a voltage to the toner image formed on the photosensitive drum from the back surface of the recording medium P,
It has the function of transferring. If the electric resistance of the transfer roller is low, an excessive current flows through the recording medium P (paper or the like), and the paper is excessively charged and wraps around the photosensitive drum.
An arc discharge is generated, which disturbs the toner image and deteriorates the photoconductor. This phenomenon is particularly remarkable when a small-sized sheet in which the photosensitive drum and the transfer roller are in contact with each other over a wide area is used.

When the electric resistance of the transfer roller is high, the transfer efficiency is deteriorated, and a defect occurs. To increase the transfer efficiency, the voltage applied to the transfer roller should be 3 kV
This must be done as described above, resulting in an increase in the size of the apparatus and an increase in cost.

From the above, the transfer roller needs to have an electric resistance in an appropriate range. A rubber material is generally used for the transfer roller, and there are roughly two methods for imparting conductivity to the rubber material. A method of adding a conductivity-imparting agent utilizing an electronic conduction mechanism This is a method of adding a conductivity-imparting agent utilizing an ionic conduction mechanism.

Conductivity-imparting Agent Utilizing Electronic Conduction Mechanism This method is a method of imparting conductivity to rubber by adding a substance exhibiting conductivity based on free electrons or π electrons to rubber. Examples of the electronic conductivity imparting agent include carbon black. However, the electric resistance range (1 × 10 ^{7 to} 5 × 10 ⁹ Ω) required for the transfer roller is a region where the electric resistance of the rubber changes sensitively to the amount of carbon black added. Further, in order to achieve this electric resistance range, a large amount of carbon black must be added, so that the viscosity of the rubber increases, the dispersion of the carbon black particles in the rubber becomes uneven, and the electric resistance is reduced. Causes unevenness. This unevenness in electric resistance may cause unevenness in image density.

In particular, in an image forming apparatus employing the reversal developing method, a photosensitive member as an image carrier is locally charged, so that the portion becomes a transfer charging memory and becomes insufficiently charged in the next charging step. When developed, black fog is formed, resulting in remarkable deterioration of image quality.

Conductivity imparting agent utilizing ionic conduction mechanism This is a method of imparting conductivity to rubber by adding a substance exhibiting conductivity based on anions or cations to rubber. However, when an ionic conduction mechanism is used, there is a disadvantage that electric resistance greatly changes due to environmental factors such as ambient humidity and temperature. The temperature in the electrophotographic apparatus varies widely from a room temperature level immediately after power-on to a maximum of 60 ° C.
Among them, resistance to changes in temperature and humidity is required to exhibit constant performance. In an attempt, a transfer roller made of silicone rubber was prepared using only a complex of LiClO ₄ and 1,4-butanediol as an ionic conductivity-imparting agent, and was obtained at a temperature of 15 ° C. and a humidity of 10% (hereinafter, L / L).
It is described as environment. ) And a temperature of 32.5 ° C. and a humidity of 90% (hereinafter referred to as an H / H environment).

Further, the transfer roller must have low hardness. However, if the hardness is too low (too soft), a problem occurs. In this case, since the rubber is greatly deformed when a load is applied to the transfer roller, the distribution of the conductivity imparting agent such as carbon graphite dispersed in the rubber in the rubber temporarily changes, and the conductivity is imparted. The contact state of the agent particles greatly changes, causing unevenness in electric resistance depending on the location. This unevenness in electric resistance may affect a transferred image.

On the other hand, if the hardness is too high, the width (nip width) of the portion where the photosensitive drum and the transfer roller are in contact decreases, and it becomes difficult to stably fix a recording medium such as paper, and , The paper slips and the image shifts.
When the transfer roller is pressed against the photosensitive drum with a stronger force to prevent the roller from spinning and correct the image misalignment, the center part of the transferred figure (especially characters) is not transferred. appear. This is particularly likely to occur when thick paper is used, and is caused by the fact that the toner image is strongly pressed against the photosensitive drum and the transfer efficiency of the portion where the potential of the electrostatic image is relatively low decreases.

Further, an electrophotographic apparatus such as a copying machine or a facsimile is often in a standby state. During that time, the transfer roller often remains partially pressed against the photosensitive drum.
Resistance to permanent compression set is required.

As the material of the conductive rubber roller, silicone rubber, ethylene-propylene-non-conjugated diene rubber, acrylonitrile-butadiene rubber, urethane rubber and the like are used, and they are used in a transfer step in an image forming apparatus such as an electrophotographic apparatus. Conductive rubber rollers are required to have excellent environmental change stability, ozone resistance, and heat resistance stability. Consider using a physically and chemically stable silicone rubber as a material that meets these requirements. Have been. However, in the case of a conductive roller using silicone rubber, there has been a problem that a low molecular weight component precipitates on the surface of the conductive roller due to long-term use, adheres to the photosensitive drum, and marks the roller on an image. Here, the low molecular weight refers to those having a molecular weight of about 30,000 or less, and examples thereof include cyclic siloxanes having a low degree of polymerization.

[0020]

SUMMARY OF THE INVENTION The present invention relates to a transfer member provided with a conductive silicone rubber in which a conductivity-imparting agent is dispersed. Prevents image density unevenness and fogging due to the local transfer memory of the drum, and provides stable electrical resistance even when temperature, humidity, etc. change, and at the same time,
Provided is a conductive silicone rubber roller used in an electrophotographic apparatus which has a low hardness, a small compression set, and does not contaminate a photosensitive drum for a long time by reducing bleeding from the inside of the conductive silicone rubber roller. With the goal.

Another object of the present invention is to provide an image forming apparatus using the conductive silicone rubber roller as a constituent member.

[0022]

DISCLOSURE OF THE INVENTION In view of the above problems, the present invention provides a conductive material in which a conductivity imparting agent utilizing an ionic conduction mechanism and a conductivity imparting agent utilizing an electronic conduction mechanism are dispersed in silicone rubber. Provided is a conductive silicone rubber roller used in an electrophotographic apparatus, which is formed into a cylindrical shape so as to wrap a roller core by contacting a conductive silicone rubber with the roller core.

In the present invention, since the conductivity imparting agent utilizing the electronic conduction mechanism and the conductivity imparting agent utilizing the ionic conduction mechanism are used in combination, the conductivity imparting utilizing the electron conduction mechanism such as carbon black is employed. As compared with the case where only the agent is used, the additive can be suppressed to a small amount, and it is possible to secure sufficient conductivity while keeping the hardness of the silicone rubber low.

When the toluene-insoluble content of the conductive silicone rubber of the conductive silicone rubber roller is 95% or more,
Bleeding of low molecular weight components from silicone rubber can be suppressed for a long time. Further, if the toluene-insoluble content is 97% or more, bleed can be further suppressed. Thereby, contamination of the photosensitive drum can be suppressed.

Here, the toluene-insoluble content in the polymer is
It is an index of the amount of a component having a high molecular weight and not dissolving in toluene.
It is calculated from the change in weight of the conductive silicone rubber roller before and after immersion for a time.

The conductive silicone rubber is brought into contact with the roller core metal around the roller core metal to form a cylindrical shape so as to wrap the roller core metal, and then the conductive silicone rubber is vulcanized. After 150-220 ° C,
In addition, it is desirable that the heat treatment be performed for 1 to 48 hours.

This heat treatment is performed in order to remove unreacted low molecular weight components from the conductive silicone rubber and to increase the above-mentioned toluene-insoluble content.

By performing this heat treatment, the toluene-insoluble content of the conductive silicone rubber roller having a toluene-insoluble content of 90% or less can be increased to 95% or more at which the effect of the present invention appears.

In Japanese Patent Application Laid-Open No. 06-025431, there is a report that heat treatment is performed under vacuum in order to remove low-polymerization degree siloxane in silicone rubber. It has been found that, in a conductive silicone rubber in which a imparting agent and a conductivity imparting agent by an electron conduction mechanism are dispersed, low molecular weight components in the silicone rubber can be removed even by heating at atmospheric pressure.

In addition, at least one of carbon black and an inorganic conductive filler is preferably used as a conductivity imparting agent utilizing the above-described electron conduction mechanism. Here, the inorganic conductive filler refers to an inorganic filler having conductivity.

If the hardness of the above-mentioned conductive silicone rubber roller is in the range of 5 to 70 ° as evaluated by an Asker C hardness tester, the defect of “hollowing out” caused by too high hardness and the hardness is too low. And an image of good quality without "transferred image unevenness" occurring at the same time. More preferably, it is 15 to 60 ° (Asker C). Further, it is even more preferable that the hardness is 24 to 40 ° (Asker C).

Here, the Asker C hardness tester is a hardness tester based on SRIS 0101 (physical test method for expanded rubber) of the Japan Rubber Association standard, and is mainly used to measure the hardness of sponge rubber such as foam rubber. It is.

The electric resistance of the conductive silicone rubber roller is preferably in the range of 1 × 10 ^{4 to} 5 × 10 ⁹ Ω. This is for transferring the toner image on the photosensitive drum to a recording medium (paper or the like) with good quality. Furthermore, 1 ×
An electric resistance of 10 ^{7 to} 5 × 10 ⁹ Ω is even more preferable.

Here, the electric resistance of the silicone rubber roller is measured by a method as shown in FIGS. That is, a load of 500 g is applied to both ends of the roller core 5b, and a voltage of 2 kV is applied between the roller core 5b and the metal drum 7 while rotating the metal drum 7 so that the electric resistance of the conductive silicone rubber 5a of the transfer roller 5 and the peripheral resistance are reduced. The unevenness of the electrical resistance in the direction is measured. Subsequently, a method of measuring the electric resistance unevenness in the longitudinal direction of the conductive silicone rubber 5a of the transfer roller 5 using the metal drum 8 divided as shown in FIG.

Further, the conductive silicone rubber roller obtained by the above means is suitably used as one member of an electrophotographic apparatus, but is particularly suitably used as a transfer roller.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The molding material of the conductive silicone rubber roller may be either liquid or millable. In the present invention, the filler, dispersant, etc. are based on a gel-like silicone raw rubber having a polymerization degree of about 5,000 to 10,000. Vulcanizing agents, vulcanization accelerators, catalysts, extenders,
Various additives such as a conductivity-imparting agent were blended and kneaded by a roll mill, a Banbury mixer or the like to obtain a forming material. Further, in the present invention, a two-liquid type addition type liquid silicone rubber can also be used.

Specific examples of the raw silicone rubber used as the raw material of the silicone rubber used in the conductive silicone rubber include polydimethylsiloxane, polymethylvinylsiloxane, polymethylphenylvinylsiloxane, polymethylp-vinylphenylsiloxane, and polymethylsiloxane. • Trifluoropropyl vinyl siloxane and modified silicone rubbers thereof. These silicone raw rubbers may be the above-mentioned homopolymers or copolymers, or may be mixtures of these polymers.

The inorganic vulcanizing agents include sulfur vulcanizing agents, organic peroxides, quinoid vulcanizing agents, resin crosslinking agents,
A metal oxide crosslinking agent, an amine crosslinking agent, a triazine-based crosslinking agent, a polyol crosslinking agent, a metal soap crosslinking agent, a maleimide-based crosslinking agent, and the like are appropriately selected and used. As the organic peroxide vulcanization, for example, benzoyl peroxide, 2,4
Dichlorobenzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, parachlorobenzoyl peroxide, di-tert-butyl peroxide, dialkyl peroxide, For example, tert-butyl perbenzoate, 1,1-di (tert-butyl peroxy) 3,3,5-trimethylcyclohexane or the like is used.

Examples of the extender include reinforcing fillers, inorganic fillers such as calcium carbonate, hard clay, barium sulfate, talc, mica, asbestos, graphite, etc., recycled rubber, powdered rubber, asphalts, styrene resin, glue, etc. Organic fillers are used.

As the conductivity imparting agent utilizing the ionic conduction mechanism, a complex or a surfactant is used. Here, the complex refers to a complex of a salt of Group 1 of the periodic table, a salt or ammonium salt of Group 2 of the periodic table with a polyhydric alcohol, a derivative or monol thereof.

Here, the salt of Group 1 of the periodic table is Li
CF ₃ SO ₃ , NaClO ₄ , LiClO ₄ , LiAs
F ₆ , LiBF ₄ , NaSCN, KSCN, NaCl and the like. Further, as the salt of the second group of the periodic table, Ca
(ClO ₄ ) ₂ , Ba (ClO ₄ ) _{2 and the} like. As ammonium salts, NH ₄ Cl, NH ₄ S
O ₄ and NH ₄ NO ₃ are exemplified.

As the polyhydric alcohol, 1,4-
Butanediol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol and the like.

Examples of the monool include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, polyethylene glycol monomethyl ether, and polyethylene glycol monoethyl ether.

Examples of the surfactant include cationic surfactants such as quaternary ammonium salts, anionic surfactants such as aliphatic sulfonates, alkyl sulfates, and alkyl phosphates; Examples include nonionic surfactants such as polyethylene glycol adducts of higher alcohols and polyethylene glycol fatty acid esters, betaines, and the like.

These conductivity imparting agents utilizing the ionic conduction mechanism can be used alone or in combination of two or more in the form of powder or fibrous.

On the other hand, as the conductivity-imparting agent utilizing the electronic conduction mechanism, a carbon-based substance, a metal or an alloy, a metal oxide, a substance obtained by plating various fillers with a metal, a polymer substance, or the like is suitably used.

Here, examples of the carbon-based material include carbon black, graphite and the like. Aluminum, silver, gold, tin-lead alloy, copper-
Nickel alloys and the like can be mentioned.

Examples of the metal oxide include zinc oxide, titanium oxide, aluminum oxide, tin oxide, antimony oxide, indium oxide, silver oxide and the like.

Examples of fillers plated with metal include fillers plated with copper, nickel, silver or the like.

Examples of the polymer substance include polyacetylene, polypyrrole, polyaniline, polyaniline, poly (p-
Phenylene), poly (p-phenylene-vinylene), poly (pyridinopyridine) and the like.

These conductivity imparting agents utilizing the electronic conduction mechanism can be used alone or as a mixture of two or more in the form of powder or fiber.

Raw silicone rubber as a raw material of the conductive silicone rubber, an ionic conductivity imparting agent, an electronic conductivity imparting agent,
Various additives and various fillers are kneaded by a known method to form a material for forming a conductive silicone rubber roller.
Then, the forming material is poured into a pipe-shaped mold in which the core metal 5b coated with the primer is set, and then vulcanized at a predetermined temperature, and after cooling, the pipe mold is released.
Furthermore, a conductive silicone rubber roller is obtained by secondary vulcanization.

Here, when the proportion of the low molecular weight component in the conductive silicone rubber roller is to be further reduced, it is preferable to continue the heat treatment at 150 to 220 ° C. and 1 to 48 hours. This heat treatment can be performed under atmospheric pressure.

In some examples and comparative examples shown below, more specific production conditions and properties of the conductive silicone rubber roller will be described. Incidentally, the electrical resistance measurement method of the conductive silicone rubber roller of the present invention, all the comparative examples,
The method described in "Means for solving the problem" was used in common in the examples.

[0055]

Embodiment (Transfer Roller 5-A) FIG. 1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. The image forming apparatus according to the present embodiment is a rotary drum type / transfer type electrophotographic apparatus, and a photosensitive drum 1 is an electrophotographic photosensitive member and carries an electrophotographic image. For this purpose, it is driven to rotate at a predetermined peripheral speed (process speed) in the clockwise direction indicated by the arrow. The peripheral surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential (-600 V in this embodiment) by a charging roller 2 to which a charging bias is applied from a power source E1 as a charging unit during the rotation process. In the exposure step 3, a negative image exposure (analog exposure of the original image, digital scanning exposure) corresponding to the target image is performed, and an electrostatic latent image of the target image information is formed on the peripheral surface.

Next, the electrostatic latent image is developed as a toner image in a developing section 4 of a reversal developing system using minus toner. Then, the recording medium P is fed from a paper feeding unit (not shown) at a predetermined timing to a transfer section between the photosensitive drum 1 and a transfer roller as the transfer roller 5 with the toner image, and a power supply E2 is supplied to the transfer roller 5. From about +2
A transfer bias of 3 kV is applied, and the reversal-developed toner image on the surface of the photosensitive drum 1 is sequentially transferred to the recording medium P.

The recording medium P to which the toner image has been transferred is
It is separated from the surface of the photosensitive drum 1 and is introduced into a fixing unit (not shown) to undergo an image fixing process. The surface of the photosensitive drum 1 after the transfer of the toner image is cleaned by the cleaning unit 6 to remove adhered contaminants such as untransferred toner, and is repeatedly used for image formation.

In this embodiment, as the transfer roller 5, the conductive silicone rubber roller shown in FIG.

Polydimethylsiloxa having vinyl terminal
Ion conductivity imparting agent (LiClO_FourAnd 1,4-butanegio
100 parts of the carbon nanotubes
Rack 30 parts, 2,5-dimethyl-2,5-di (tarsi
(Butyl peroxy) hexane (50% paste)
Knead the two parts with a roll until they are evenly dispersed.
Of a pipe-shaped metal core 5b
Rubber was injected into the mold by transfer molding. So
After that, 170 ° C, 30 minutes, 200kg / cm^TwoVulcanized at
After cooling, remove the mold from the pipe.
Vulcanized in a hot-air drying oven to produce conductive silicone
A rubber roller 5-A was obtained. As shown in FIG.
The hardness of the transfer roller 5-A is measured with an Asker C hardness tester.
28-32 ° (Asker C)
Was. The conductive silicone rubber roller (transfer roller)
Was measured by the above-mentioned method,
10 ⁹Ω. Also, the direction of the transfer roller at this time
The non-uniformity of the electrical resistance in the
The air resistance unevenness was about 1.3 times.

When the transfer roller 5-A was used by incorporating it into the above-described image forming apparatus, the transfer roller 5 applied a predetermined pressing force to the photosensitive drum 1 (a load of 500 g was applied to both ends of the roller core). ), And rotates in the forward direction of the rotation of the photosensitive drum 1 at substantially the same peripheral speed as the rotational speed of the drum. In the present embodiment, the solid image is transferred uniformly, and no excessive positive charge is locally applied to the photosensitive drum, so that, at the next image formation, local spot-shaped density unevenness occurs, of course. There was no spotty fog.

(Transfer Roller 5-B) On the other hand, as the transfer roller 5-B, a conductive silicone rubber roller using only a conventional electronic conductive mechanism was prepared as follows. Polydimethylsiloxane 100 having vinyl terminals
30 parts of carbon black, 2,5-dimethyl-2,
5-di (tert-butylperoxy) hexane (5
(0% paste) 2 parts were kneaded by a roll until uniformly dispersed, and rubber was injected by transfer molding into a pipe-shaped mold in which a core metal 5b coated with a primer was set. Then 170 ° C, 30 minutes, 200kg / c
vulcanized at m ^2, after cooling pipe mold and demolding 200 ° C.,
The conductive silicone rubber roller 5-B was obtained by performing secondary vulcanization in a hot air drying furnace under the condition of 4 hours. The hardness of the transfer roller 5-B shown in FIG.
28-32 ° (Aske
rC). When the electrical resistance of the conductive silicone rubber roller (transfer roller) was measured by the same method as that of the transfer roller 5-A, it was 5 × 10 ⁹ Ω. About 1.8
It was twice. Furthermore, the electric resistance unevenness in the longitudinal direction is about 2.5
It was twice.

When the transfer roller 5-B was used by being incorporated in the above-mentioned image forming apparatus, the electric resistance unevenness in the circumferential direction and the longitudinal direction was large, the solid image was not transferred uniformly, and an excessively large positive charge was locally generated. Was applied to the photosensitive drum, causing local spot-like density unevenness or spot-like fog during the next image formation.

(Transfer Roller 5-C) On the other hand, as the transfer roller 5-C, a conductive silicone rubber roller using only a conventional ionic conductive mechanism was prepared as follows. 100 parts of polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) is added, and 100 parts of 2,5-dimethyl-2,5-di (tertiary) 2 parts of butylperoxy) hexane (50% paste) were kneaded by a roll until uniformly dispersed, and rubber was injected by transfer molding into a pipe-shaped mold in which a core metal 5b coated with a primer was set. Then 170 ° C, 30 minutes, 200k
g / cm ² , and after cooling, the pipe mold was removed from the mold.
Conductive silicone rubber roller 5-C was obtained by secondary vulcanization in a hot air drying oven at 0 ° C. for 4 hours. When the hardness of the transfer roller 5-C shown here and shown in FIG. 2 was measured with an Asker C hardness meter, it was 28 to 32 ° (A
kerC). When the electrical resistance of this conductive silicone rubber roller was measured by the same method as that of the transfer roller 5-A, it was 4 × 10 ⁹ Ω, and the unevenness of the electrical resistance in the circumferential direction of the transfer roller at this time was about 1.2. It was twice. Further, the electric resistance unevenness in the longitudinal direction was about 1.3 times.

When the transfer roller 5-C is used by incorporating it into the above-mentioned image forming apparatus, a solid image is transferred uniformly and no excessive positive charge is locally applied to the photosensitive drum. During image formation, local spot-shaped density unevenness did not occur, and spot-shaped fog did not occur.

However, when conductivity is imparted using only the ionic conduction mechanism, there is a disadvantage that the environmental fluctuation of the electric resistance of the elastic body is very large (about between the L / L environment and the H / H environment). Electrical resistance fluctuation of two digits). Transfer roller 5-C, temperature: 23.5 ° C, humidity: 50% (hereinafter, N /
Described as N environment. Under the environment of ()), the electric resistance is 4 × 10 ⁹ Ω
In the L / L environment, 3 × 10 ¹⁰ Ω,
It was 5 × 10 ⁸ Ω under an H / H environment. When the transfer roller 5-C is used by being incorporated in the above-described image forming apparatus, a solid image is uniformly transferred under an H / H and N / N environment, and an excessively large positive charge is locally applied to the photosensitive drum. Since there was no occurrence of such a phenomenon, not only the occurrence of local spot-shaped density unevenness but also the occurrence of spot-shaped fog did not occur during the next image formation. However, in the L / L environment, the electrical resistance of the transfer roller 5-C was too high, and the transfer efficiency was poor, resulting in poor transfer.

On the other hand, each environment in the case of the transfer roller 5-A
The electrical resistance at the bottom is 3 × 10 under N / N environment.
⁹Ω, 6 × 10 under L / L environment⁹Ω, under H / H environment
1 × 10 ⁹Ω. This transfer roller 5-A is
When used in each environment by incorporating it into the image forming device of
Solid images are transferred uniformly in any environment, and
No extra positive charge is applied to the photosensitive drum
Therefore, local spot-like density unevenness may occur during the next image formation.
Not only raw but also fogged fog.

(Transfer Roller 5-D) Transfer Roller 5-
The conductive silicone rubber roller shown in FIG.

100 parts of polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) has been added, 60 parts of carbon black and 60 parts of silicon-bonded hydrogen atoms 100 parts of the polydimethylsiloxane was kneaded with a roll until it was uniformly dispersed, and rubber was injected into a pipe-shaped mold in which a cored bar 5b coated with a primer was set. After that, it was vulcanized at 150 ° C. for 20 minutes. After cooling, the pipe mold was demolded and subjected to secondary vulcanization in a hot air drying furnace at 200 ° C. for 4 hours to obtain a conductive silicone rubber roller 5-D. Was. The hardness of the transfer roller 5-D shown here and shown in FIG.
2 ° (Asker C). When the electric resistance of the conductive silicone rubber roller (transfer roller) was measured by the same method as that of the transfer roller 5-A, 2 × 10 ⁹
Ω, and the unevenness of the electric resistance in the circumferential direction of the transfer roller at this time was about 1.2 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.3 times.

Here, polydimethylsiloxane having a silicon atom-bonded hydrogen atom means a repeating unit of --Si
(CH ₃ ) ₂ refers to polydimethylsiloxane in which part of —O— is replaced by —SiH (CH ₃ ) —O—. The same applies hereinafter.

When the transfer roller 5-D was used by being incorporated in the above-described image forming apparatus, the transfer roller 5-A was used.
Similarly, also in the transfer roller 5-D, the solid image is uniformly transferred, and no local excessive positive charge is applied to the photosensitive drum. There was no occurrence, of course, and no fog-like fog.

(Transfer Roller 5-E) Transfer Roller 5-
As E, a conductive silicone rubber roller shown in FIG.

100 parts of polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) is added 80 parts of zinc oxide as an inorganic conductive filler, , 5-dimethyl-
2 parts of 2,5-di (tert-butylperoxy) hexane (50% paste) are kneaded by a roll until uniformly dispersed, and placed in a pipe-shaped mold in which a core metal 5b coated with a primer is set. Rubber was injected by transfer molding. Then 170 ° C, 30 minutes, 200kg
/ Cm ² , and after cooling, the pipe mold was removed from the mold.
Conductive silicone rubber roller 5-E was obtained by secondary vulcanization in a hot air drying furnace at 4 ° C. for 4 hours. When the hardness of the transfer roller 5-E shown here and shown in FIG. 2 was measured with an Asker C hardness meter, it was 32 to 36 ° (As).
kerC). Further, the electric resistance of the conductive silicone rubber roller (transfer roller) is determined by the transfer roller 5-
When measured by the same method as in A, it was 3 × 10 ⁹ Ω,
At this time, the unevenness of the electric resistance in the circumferential direction of the transfer roller was about 1.2 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.3 times.

When the transfer roller 5-E was incorporated into the above-mentioned image forming apparatus and used, the transfer roller 5-A was used.
Similarly, since a solid image is uniformly transferred and a local excessive positive charge is not applied to the photosensitive drum, local spot-shaped density unevenness occurs in the next image formation, as well as a spot-shaped spot. There was no fog.

(Transfer Roller 5-F) Transfer Roller 5-
As the F, the conductive silicone rubber roller shown in FIG.

100 parts of polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) is added, 80 parts of zinc oxide as an inorganic conductive filler, and 100 parts of carbon Black 1
0 parts, 2 parts of 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane (50% paste) are kneaded by a roll until uniformly dispersed, and a cored bar 5b coated with a primer is set. Rubber was injected into the pipe-shaped mold by transfer molding. Then 17
The conductive silicone rubber roller 5 was vulcanized at 0 ° C. for 30 minutes at 200 kg / cm ² , cooled, demolded and subjected to secondary vulcanization in a hot air drying furnace at 200 ° C. for 4 hours. -F was obtained. When the hardness of the transfer roller 5-F shown here and shown in FIG. 2 was measured by an Asker C hardness meter, it was 32-36 ° (Asker C). When the electrical resistance of this conductive silicone rubber roller (transfer roller) was measured by the same method as that of the transfer roller 5-A, it was 3 × 10 ⁹ Ω. It was about 1.2 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.3 times.

When the transfer roller 5-F was incorporated in the above-described image forming apparatus and used, the transfer roller 5-A was used.
Similarly, since a solid image is uniformly transferred and a local excessive positive charge is not applied to the photosensitive drum, local spot-shaped density unevenness occurs in the next image formation, as well as a spot-shaped spot. There was no fog.

(Transfer Roller 5-G) Transfer Roller 5-
The conductive silicone rubber roller shown in FIG.

100 parts of a polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) is added, 40 parts of carbon black, and 2,5-dimethyl- 2 parts of 2,5-di (tert-butylperoxy) hexane (50% paste) are kneaded by a roll until uniformly dispersed, and placed in a pipe-shaped mold in which a core metal 5b coated with a primer is set. Rubber was injected by transfer molding. Then, vulcanization was performed at 170 ° C. for 30 minutes at 200 kg / cm ² , and after cooling, the pipe mold was demolded and subjected to secondary vulcanization in a hot air drying furnace at 200 ° C. for 4 hours to form a conductive silicone rubber roller. 5-G was obtained. Fig. 2 obtained here
The hardness of the transfer roller 5-G shown in (1) was measured by an Asker C hardness meter and found to be 29 to 33 ° (Asker C). When the electrical resistance of the conductive silicone rubber roller (transfer roller) was measured by the same method as that of the transfer roller 5-A, it was 7 × 10 ⁸ Ω. It was about 1.2 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.3 times.

When this transfer roller 5-G was used by being incorporated in the above-mentioned image forming apparatus, the transfer roller 5-A was used.
Similarly, since a solid image is uniformly transferred and a local excessive positive charge is not applied to the photosensitive drum, local spot-shaped density unevenness occurs in the next image formation, as well as a spot-shaped spot. There was no fog.

(Transfer Roller 5-H) A transfer roller 5-H having low hardness was prepared as follows.

100 parts of polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) is added, 10 parts of carbon black, and 2,5-dimethyl- 2 parts of 2,5-di (tert-butylperoxy) hexane (50% paste) are kneaded by a roll until uniformly dispersed, and placed in a pipe-shaped mold in which a core metal 5b coated with a primer is set. Rubber was injected by transfer molding. Then, vulcanization was performed at 170 ° C. for 30 minutes at 200 kg / cm ² , and after cooling, the pipe mold was demolded and subjected to secondary vulcanization in a hot air drying furnace at 200 ° C. for 4 hours to form a conductive silicone rubber roller. 5-H was obtained. Fig. 2 obtained here
The hardness of the transfer roller 5-H shown in (1) was 4 ° (Asker C) as measured with an Asker C hardness meter.
When the electrical resistance of the conductive silicone rubber roller (transfer roller) was measured by the same method as that of the transfer roller 5-A, it was 5 × 10 ⁹ Ω. It was about 1.1 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.2 times.

In the case of the transfer roller 5-H, since the hardness is low, the influence of the electric resistance unevenness on the load of the conductive silicone rubber roller is larger than that of a normal hardness product (20 to 45 °). The electric resistance unevenness of the contacting part is particularly large. For this reason, when this transfer roller 5-H was used by being incorporated in the above-described image forming apparatus, the electric resistance unevenness in the circumferential direction and the longitudinal direction of the conductive silicone rubber roller of the transfer roller 5-H was large, and the solid image was not formed. It is not transferred uniformly, and an excessive positive charge is locally applied to the photosensitive drum, and a local spot-like density unevenness occurs at the next image formation,
Spot-like fog has occurred.

(Transfer Roller 5-I) A transfer roller 5-I having high hardness was prepared as follows.

100 parts of a polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) is added, 80 parts of carbon black, 2,5-dimethyl- 2 parts of 2,5-di (tert-butylperoxy) hexane (50% paste) are kneaded by a roll until uniformly dispersed, and placed in a pipe-shaped mold in which a core metal 5b coated with a primer is set. Rubber was injected by transfer molding. Then, vulcanization was performed at 170 ° C. for 30 minutes at 200 kg / cm ² , and after cooling, the pipe mold was demolded and subjected to secondary vulcanization in a hot air drying furnace at 200 ° C. for 4 hours to form a conductive silicone rubber roller. 5-I was obtained. Fig. 2 obtained here
The hardness of the transfer roller 5-I shown in (1) was 72 ° (Asker C) as measured with an Asker C hardness meter. The electric resistance of the conductive silicone rubber roller (transfer roller) was 3 × 10 ⁷ Ω, and the unevenness of the electric resistance in the circumferential direction of the transfer roller at this time was 1.1 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.2 times.

High hardness (70 ° or more) transfer roller 5-
In the case of I, the width of the nip where the photosensitive drum and the transfer roller are in contact is reduced, and it becomes difficult to stably hold a recording medium such as paper between the photosensitive drum and the transfer roller. The medium is not synchronized with the movement of the photosensitive drum, and an image shift occurs. In order to eliminate this image shift, the width of the nip may be increased, but in the case of a high hardness product, the spring pressure supporting the conductive silicone rubber roller must be increased. However, when the spring pressure is increased, a "centered-out" phenomenon occurs in which the transferred image, particularly the central portion of the line width of the character, becomes white. This is particularly likely to occur when a thick recording medium is used, and is caused by the fact that the toner image is strongly pressed against the photosensitive drum and the transfer efficiency of a portion where the transfer electric field is relatively weak is reduced.

From the transfer rollers G, H and I, the hardness of the conductive silicone rubber roller used for the transfer roller is within the above set range of 5 to 70 ° (Asker C).
, More specifically, 24 to 40 °
(AskerC) is desirable.

(Transfer Roller 5-J) Transfer Roller 5-
As J, the conductive silicone rubber roller shown in FIG.

100 parts of polydimethylsiloxane having vinyl terminals to which an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol) has been added, 100 parts of carbon black and 60 parts of silicon-bonded hydrogen atoms 100 parts of the polydimethylsiloxane was kneaded with a roll until it was uniformly dispersed, and rubber was injected into a pipe-shaped mold in which a cored bar 5b coated with a primer was set. Thereafter, the mixture was vulcanized at 150 ° C. for 20 minutes, and after cooling, the pipe mold was removed and subjected to secondary vulcanization in a hot air drying furnace at 200 ° C. for 4 hours to obtain a conductive silicone rubber roller 5-J. Was. The hardness of the transfer roller 5-J shown here and shown in FIG.
2 ° (Asker C). The electric resistance of this conductive silicone rubber roller (transfer roller) is 2 ×
It was 10 ⁹ Ω, and the unevenness of the electric resistance in the circumferential direction was about 1.2 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.3 times. The measurement of the toluene insoluble matter of the transfer roller 5-J was 97%.

When the transfer roller 5-J was incorporated into the above-mentioned image forming apparatus and used, the transfer roller 5-A was used.
Similarly, since a solid image is uniformly transferred and a local excessive positive charge is not applied to the photosensitive drum, local spot-shaped density unevenness occurs in the next image formation, as well as a spot-shaped spot. There was no fog. further,
The transfer roller 5-J is directly pressed against the photosensitive drum (200 g / cm ² ) and left under pressure (temperature: 40 ° C., humidity:
80%, leaving time: 2 weeks), the transfer roller 5-J was removed from the photosensitive drum, and the photosensitive drum
When an image was evaluated using a transfer roller, no drum pressure contact was observed in the image.

(Transfer Roller 5-K) On the other hand, when the transfer roller 5-K prepared in the same manner as the transfer roller 5-J and having a toluene insoluble content of 88% was incorporated into the above-described image forming apparatus and used, As in the case of -A, since a solid image is uniformly transferred and a local excessive positive charge is not applied to the photosensitive drum, not only the occurrence of local spot-shaped density unevenness but also There was no fogging. The transfer roller 5-K is pressed directly onto the photosensitive drum (200 g / cm ² ) under pressure (temperature: 40 ° C., humidity: 80%, standing time: 2 weeks).
After that, remove the transfer roller 5-K from the photosensitive drum,
When the image was evaluated using the photosensitive drum and the transfer roller used here, a drum pressure contact mark was observed in the image.
This is because a low molecular weight (molecular weight of about 2,000 to 50,000) is removed from the elastic body of the transfer roller 5-K at the time of pressing the drum.
It is considered that the unreacted components and the like migrated to and adhered to the photosensitive drum side and appeared on the image.

Transfer Roller 5-J and Transfer Roller 5-
From K, it is preferable to use a silicone rubber having a toluene insoluble content of 95% or more as the conductive silicone rubber roller, and more preferably 97% or more.

(Transfer Roller 5-L) Transfer Roller 5-
L was prepared as follows.

100 parts of polydimethylsiloxane having a vinyl terminal and provided with an ionic conductivity-imparting agent (complex of LiClO ₄ and 1,4-butanediol), 60 parts of carbon black and 60 parts of silicon-bonded hydrogen atoms 100 parts of the polydimethylsiloxane was kneaded with a roll until it was uniformly dispersed, and rubber was injected into a pipe-shaped mold in which a cored bar 5b coated with a primer was set. Thereafter, it was vulcanized at 150 ° C. for 20 minutes. After cooling, the pipe mold was demolded and subjected to secondary vulcanization in a hot air drying furnace at 180 ° C. for 4 hours. At this stage, the toluene insoluble content of the roller was measured and found to be 88%. The roller not used for the measurement of the toluene insoluble content was further heated at 200 ° C. for 12 hours to obtain a conductive silicone rubber roller 5-L. When the hardness of the transfer roller 5-L shown here and shown in FIG. 2 was measured by an Asker C hardness meter, it was 28 to 32 °.
(Asker C). The electric resistance of this conductive silicone rubber roller (transfer roller) is 2 × 10 ⁹
And the unevenness of the electric resistance in the circumferential direction of the transfer roller was about 1.2 times. Further, the electric resistance unevenness in the longitudinal direction was about 1.3 times. Further, the formed transfer roller 5-
It was 97% when the toluene insoluble matter of L was measured.

When the transfer roller 5-L is used by incorporating it into the above-described image forming apparatus, a solid image is uniformly transferred and an excessively positive charge is locally applied to the photosensitive drum similarly to the transfer roller 5-A. Since there was no occurrence of such a phenomenon, not only the occurrence of local spot-shaped density unevenness but also the occurrence of spot-shaped fog did not occur during the next image formation. Further, a load is directly applied to the transfer roller 5-L on the photosensitive drum (2
00g / cm ² ) Pressure contact (temperature: 40 ° C, humidity: 80)
%, Leaving time: 2 weeks), the transfer roller 5-I was removed from the photosensitive drum, and the image was evaluated using the photosensitive drum and the transfer roller used here. No drum pressure contact was observed in the image. Was. Even if the toluene insoluble content is 90% or less, the low molecular weight component on the surface of the conductive silicone rubber roller is scattered by heating at a temperature of about 200 ° C. for a long time, and it is considered that a good image is obtained.

[0095]

According to the present invention, a conductive silicone rubber for an electrophotographic apparatus capable of overcoming the problem of drum contamination by a bleed material, which was a problem when silicone rubber was used alone, and which can withstand long-term use. Provide rollers.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a side view of a transfer roller according to the embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating measurement of electric resistance of a transfer roller according to the embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a partial electric resistance measurement of a transfer roller according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Exposure means 4 Developing part 5 Transfer roller 5a Conductive silicone rubber 5b Core 6 Cleaning part 7 Metal drum 8 Divided metal drum E1, E2 Power supply for bias application

Claims (8)

[Claims] An electroconductive silicone rubber in which a conductivity imparting agent utilizing an ionic conduction mechanism and a conductivity imparting agent utilizing an electronic conduction mechanism are dispersed in a silicone rubber is brought into contact with a roller core to form a roller core. A conductive silicone rubber roller for electrophotographic devices that is molded into a cylindrical shape so as to enclose gold. 2. The conductive silicone rubber roller for an electrophotographic apparatus according to claim 1, wherein the toluene-insoluble content of the conductive silicone rubber of the conductive silicone rubber roller is 95% or more. 3. The conductive silicone rubber is brought into contact with the roller core metal around the roller core metal to form a cylindrical shape so as to surround the roller core metal, and then added to the conductive silicone rubber. At 150-220 ° C after the sulfurizing treatment,
3. A heat treatment for 1 to 48 hours.
A conductive silicone rubber roller for an electrophotographic apparatus according to the above. 4. The method according to claim 1, wherein at least one of carbon black and an inorganic conductive filler is used as the conductivity imparting agent utilizing the electron conduction mechanism.
The conductive silicone rubber roller for an electrophotographic apparatus according to any one of the above. 5. The conductive silicone rubber roller has a hardness of 5 to 70 ° (Aske C hardness meter) as measured by an Asker C hardness tester.
The conductive silicone rubber roller for an electrophotographic apparatus according to any one of claims 1 to 4, wherein rC). 6. The electrophotographic apparatus according to claim 1, wherein the conductive silicone rubber roller has an electric resistance of 1 × 10 ^{4 to} 5 × 10 ⁹ Ω. Conductive silicone rubber roller. 7. An electrophotographic apparatus comprising the conductive silicone rubber roller for an electrophotographic apparatus according to claim 1 as one of the constituent elements. 8. An electrophotographic apparatus, wherein the electroconductive silicone rubber roller for an electrophotographic apparatus according to claim 1 is used as a transfer roller.