JP3053246B2 - Semi-conductive roller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive roller for an electrophotographic copying machine used in an electrophotographic copying machine or the like.

[0002]

2. Description of the Related Art An electrophotographic copying machine is, for example, an organic photoreceptor,
An original image is formed as an electrostatic latent image on the surface of a photosensitive drum such as selenium or CdS, toner is adhered to the image, a toner image is formed, and the toner image is transferred and fixed on a transfer paper to copy. Is performed. In this case, in order to form an electrostatic latent image on the surface of the photoconductor drum, the surface of the photoconductor drum is charged in advance, and a document image is projected through the optical system onto the charged portion, and the portion of the photo-irradiated portion is exposed to light. An electrostatic latent image is formed by removing the charge.

[0003] As a method of charging the surface of the photosensitive drum prior to the formation of the above-described electrostatic latent image, a corona discharge method has conventionally been adopted. In the corona discharge method, a photoreceptor drum surface is subjected to a corona discharge from a corona discharger to perform a charging process to impart photosensitivity. In this method, since a high voltage of 5 to 8 KV is generally applied to the metal wire, harmful ozone is generated with the discharge. In terms of electric power, the electric current flowing toward the photoreceptor is only 5 to 30% of the electric current, and most of the electric current flows to the shield plate, so that the charging means is inefficient.

In order to solve such a problem, attention has recently been paid to a contact charging system in which a semiconductive roller is rotated in contact with the surface of a photosensitive drum to charge the surface of the photosensitive member. In particular, the use of a semiconductive roller as a charging roller is disclosed in, for example, Japanese Patent Application Laid-Open No.
No. 8645, JP-A-58-194061, JP-A-Hei.
No. 142569 has been proposed.

[0005] An electrophotographic apparatus using this contact charging system is constructed, for example, as shown in FIG. 1, and the photosensitive member 1 is usually formed of an organic photosensitive member.
dS, amorphous silicon or the like may be used. The photosensitive member 1 is provided with a charging roller 2 in contact with the photosensitive member 1, and a developing device 3, a transfer roller 5, and a toner cleaner 7 are installed in a clockwise direction around the charging roller 2. Further, a fixing device 6 for fixing the transfer paper 4 sent from the transfer roller 5 in proximity to the photoconductor 1 is provided between the transfer roller 5 and the toner cleaner 7.

The copying is performed as follows.
The photosensitive drum 1 rotating in the direction of the arrow (for example, a linear velocity of 60 m
The charging roller 2, which is a semiconductive roller having elasticity, is rotated by the photosensitive drum 1 while partially elastically deforming the outer peripheral surface of the photosensitive drum 1 at m / sec). The outer surface of the photosensitive drum 1 is charged by the contact of the charging roller 2. An electrostatic latent image corresponding to the original is formed on the surface of the photoreceptor 1 charged in this way by the exposure device groove 8, and this latent image is visualized by the developing device 3 and transferred to the transfer paper 4
Is transferred using a transfer roller 5, and is fixed by a fixing device 6. Thus, a copy is obtained.

[0007] In this case, the surface of the photoreceptor 1 is filled with 85 to 85 of the toner adhered by the transfer roller 5.
Although 95% of the toner is transferred, the remaining toner after the transfer is almost completely removed by the toner cleaner 7, and is further irradiated with light from the entire surface by the eraser lamp 9 to be initialized and ready for the next charging.

[0008] Many semiconductive rollers such as a charging roller, a developing roller, and a transfer roller are used in an electrophotographic copying machine and the like. Such a semiconductive roller has a volume resistance of 10 ⁶
It is preferable that the conductive elastic body has a conductivity of about 10 to ^{12 12} Ω · cm. Usually, as shown in FIG. 2, a metallic shaft core 10 and a conductive elastic layer 11 are formed on the outer periphery thereof. A semiconductive roller having a resistance layer 12 formed along the outer periphery of the layer 11 is used.

The conductive elastic layer material has a volume resistivity of 10 ⁵ Ω · cm or less, preferably 10 ³ Ω · cm or less, and a rubber hardness (JIS A) of 20 to 50 degrees, preferably 25 to 50 degrees. A 40 degree one is used. Generally, it is formed of a composition in which conductive powder (carbon black, metal powder, etc.) is mixed in synthetic rubber such as silicone rubber, ethylene propylene rubber, nitrile rubber, urethane rubber, and the like.

The material of the resistance layer is a volume resistance of 10
⁵ to 10 ¹³ Ω · cm, preferably 10 ⁶ to 10 ¹² Ω · cm
Is used. Generally, polar rubbers such as epichlorohydrin rubber, nitrile rubber, acrylic rubber, urethane rubber, and chloroprene rubber,
Silicone rubber, ethylene propylene rubber, styrene
High resistance synthetic rubber such as butadiene rubber mixed with low resistance substances such as conductive powder (carbon black, metal powder, etc.), conductive fiber (carbon fiber, etc.), fluorine surfactant, ester plasticizer Formed by the composition.

[0011]

However, in the case of a semiconductive roller having a resistance layer as described above, when the resistance layer is formed of a polar rubber such as epichlorohydrin rubber, nitrile rubber, acrylic rubber, etc. In general, when the roller is used as a charging roller or a transfer roller, toner slightly remaining on the surface of the photoreceptor adheres and adheres to the roller surface because of poor releasability from the toner. For example, when the toner is fixed on the charging roller, the function of the roller charger is lost, and the portion where the toner is fixed cannot charge the photosensitive member. Further, when the toner is used as a developing roller, toner is more remarkably adhered to the surface of the roller, which causes image unevenness or the like, which is not preferable.

In the case where the material of the resistance layer is a system in which carbon black or the like is dispersed in synthetic rubber, there is a disadvantage that dielectric breakdown easily occurs at a high voltage. For example, in the case of a charging roller, if there is a pinhole or the like on the surface of the photoconductor, a conductive path leading to the back electrode of the photoconductor is formed, an excessive current flows from the charging roller, and the voltage applied to the charging roller is reduced. Will fall. When viewed as an image, the negative-positive development has a problem that black streaks appear in the longitudinal direction of the contact portion between the photosensitive member surface and the charging roller.

Accordingly, an object of the present invention is to provide a conductive powder, such as carbon black or the like, which is excellent in releasability (non-adhesiveness) and easily causes dielectric breakdown under a high voltage, such as carbon black, a fluorine-based surfactant, and an ester. electrophotographic double having a resistive layer made of a material containing no such low resistance substance liable to contaminate the like photoreceptor oozing over time from the roller interior, such systems plasticizer
An object of the present invention is to provide a semiconductive roller for a copying machine .

[0014]

The inventors of the present invention have made intensive studies and have found that a semiconductive roller using a tetrafluoroethylene / propylene rubber or an epichlorohydrin rubber / fluorine-based polymer mixed system as a constituent material of a resistance layer has been developed. The inventors have found that the above object is satisfied, and have completed the present invention.

That is, according to the present invention, there is provided a semiconductive roller in which a conductive elastic layer and a resistance layer are laminated on a conductive support in that order, and the resistance layer is made of ethylene tetrafluoride. propylene rubber with or is constructed, or the rubber and semi electrophotographic copying machine, characterized in that it is constituted by a semiconductive material consisting of a mixture of fluorine polymer to the epichlorohydrin rubber as a main component A sex roller is provided.

The semiconductive roller of the present invention is excellent in non-adhesion to the toner because the resistance layer is composed of a tetrafluoroethylene-propylene rubber or an epichlorohydrin rubber / fluorine-based polymer mixed system. Filming can be prevented, and a stable function as a roller can be exhibited for a long period of time.

In the semiconductive roller of the present invention, a conductive elastic layer is first formed on a conductive support. However, the material for the conductive elastic layer is not particularly limited. Formed by a composition in which conductive powder or conductive fiber (carbon black, metal powder, carbon fiber, etc.) is mixed into synthetic rubber such as rubber, ethylene propylene rubber, epichlorohydrin rubber, nitrile rubber, urethane rubber, etc. Is 10 ⁵ Ω · cm or less, preferably 10 ³ Ω · cm or less, and the rubber hardness (JIS
A) having a range of 20 to 50 degrees, preferably 25 to 40 degrees is used.

It is not preferable to use a plasticizer, an activator, or the like for the purpose of adjusting resistance or adjusting rubber hardness when mixing conductive powder or the like. This is because these chemicals ooze out over time and cause contamination of the surface of the photoreceptor and the like and toner filming on the roller surface.

In the semiconductive roller of the present invention, the resistance layer is composed of a tetrafluoroethylene-propylene rubber or an epichlorohydrin rubber / fluoropolymer mixture as described above. It is a fluororubber that has excellent non-adhesiveness to toner, has a medium resistance region with a volume resistance value, has extremely low temperature and humidity dependence of its electrical characteristics, and has mechanical strength sufficient to withstand practical use. . Therefore, maintaining the form of the resistive layer in such properties tetrafluoroethylene-propylene rubber Tona Ru polymers single system with, can prevent toner filming, yet functions as a stable roller over a long period of time Can be. Further, since it is not necessary to use a surfactant, a plasticizer, and the like for adjusting the volume resistance and the rubber hardness, the photoconductor is not contaminated.

Further, epichlorohydrin rubber has a characteristic that the volume resistance value shows a medium resistance region and the electrical characteristics have a small dependence on temperature and humidity. However, the non-adhesiveness to the toner is not sufficient, and the epichlorohydrin rubber itself is not used. In the resistance layer, the toner sticks as described above, and cannot be a roller that can withstand actual use. However, when the resistive layer is made of a mixture of the rubber containing epichlorohydrin rubber as a main component and a fluorine-based polymer, the non-adhesiveness to the toner is improved, the toner is prevented from sticking, and the function as a stable roller for a long period of time is achieved. Can be maintained. Moreover, the low-resistance material such as carbon black since they have semiconductive a polymer single system is not a distributed system in the rubber, even when used in the charging roller, the characteristics of the roller can be sufficiently exhibited.

The fluorine-based polymer used here is a solvent-soluble fluorine resin, and an amorphous polymer obtained by a copolymerization reaction between a fluoroolefin and a hydrocarbon-based vinyl ether is particularly preferable. For details of this fluorine-based polymer, see Kojima and Yamabe, “Synthetic Organic Chemistry”, 42
(8), 841 (1984), Munakata, Miyazaki, Kaya, Takayanagi, "Asahi Glass Research Report", 34 (2), 205-224.
(1984), JP-B 63-1962, 63-23
Nos. 04 and 63-2992 can be referred to.

This polymer has a relatively low fluorine content of 25 to 32% by weight, but is an alternating copolymer having a chain structure in which fluoroolefins and hydrocarbon vinyl ethers are alternately arranged, and is a chemically stable fluoroolefin. The sites are regularly arranged and the unstable hydrocarbon vinyl ether sites are protected electronically and stereochemically, so they are chemically stable and have excellent durability. Since this polymer is soluble in organic solvents, it is necessary to crosslink the polymer after coating to impart solvent resistance to the coating film.
For this purpose, a highly reactive hydroxyl group-containing vinyl ether is copolymerized and crosslinked and cured with a polyfunctional isocyanate.

Next, the method for producing the semiconductive roller of the present invention will be specifically described as follows. (I)
First, as a material for the conductive elastic layer, for example, a peroxide-based vulcanizing agent is added to a rubber compound in which carbon black is dispersed in a heat-curable silicone rubber, and the mixture is sufficiently kneaded using two rollers, and then uniformly mixed. To obtain a carbon black-dispersed rubber compound having a suitable composition. (Ii) Wrap the rubber compound around the outer periphery of the metal shaft and heat it in advance (for example,
(70 ° C.), and is subjected to primary vulcanization (for example, for 10 minutes) by applying a predetermined pressure (for example, 120 kg / cm ² ). (Iii) Next, after releasing the pressure of the mold and taking out the roller, secondary vulcanization (for example, 2
(00 ° C., 4 hours). (Iv) Then, the surface of the roller is ground to obtain the required outer diameter, and at the same time, the surface roughness is reduced to 10
μm (Rz) or less. (V) Next, as a material for the resistance layer, a tetrafluoroethylene-propylene rubber (liquid fluororubber) is applied to the outer periphery of the conductive elastic material layer obtained in (iv) using an air spray (or dipping method). After coating (coating thickness 30 to 200 μm), a predetermined condition (for example, 1
(70 ° C., 30 minutes).

In the case where an epichlorohydrin rubber / fluorine-based polymer mixed system is used as the material for the resistance layer,
A method in which the step (v) is performed as follows is employed.
(V) Next, unvulcanized epichlorohydrin rubber and solvent-soluble fluororesin (cured by isocyanate) are dissolved in a solvent (eg, toluene, xylene, etc.) as a material for a resistance layer, and adjusted to a predetermined viscosity (eg, 350 centipoise). The dipping liquid is used as a dipping liquid, and the conductive elastic layer coating roller obtained in (iv) is dipped in the dipping liquid, coated to a predetermined thickness (for example, 30 to 60 μm), dried at room temperature, and then dried at high temperature ( (For example, 150 ° C, 10 minutes)
I do.

[0025]

The present invention will be described in more detail with reference to the following examples. Parts represent parts by weight.

Example 1 As a material for a conductive elastic layer, a mixture having the following composition was kneaded to obtain a rubber compound having a uniform composition, and then a metal mold was formed (at 170 ° C. for 10 minutes, 120 kg).
/ Cm ² ), followed by secondary vulcanization (200 ° C.,
4 hours). Heat vulcanizable silicone rubber 100 parts (DY32-931U: Dow Corning Toray Silicone Co., Ltd.) Heat vulcanizable silicone rubber 100 parts (SRX-557: Dow Corning Toray Silicone Co., Ltd.) Vulcanizing agent 6 parts (RC- 4: Dow Corning Toray Silicone Co., Ltd.)

Next, the surface is polished to a surface roughness of 4 μm (R
z), finishing the outer diameter of φ12 to obtain a roller having a conductive elastic layer having a volume resistance of 3 × 10 ³ Ω · cm on the conductive shaft core.

The following uniform composition was applied on the obtained conductive elastic roller by an air spray method.
The composition was cured at 0 ° C. for 30 minutes to obtain a coating film having a thickness of 50 μm. Ethylene tetrafluoride / propylene rubber 100 parts (Eight seal main agent F20UI: manufactured by Ohira Kasei Co., Ltd.) Curing agent 4 parts (Eight seal hardener F20UI: manufactured by Ohira Kasei Co., Ltd.) 350 parts of 4-methyl-2-heptanone 350 parts A target semiconductive roller having a hardness of 35 degrees (JIS A) was obtained.

Examples 2 to 5 As a material for a resistance layer, a rubber composition having the following composition was kneaded with a two-roller, and then dissolved in 500 parts of a toluene solvent to prepare an epichlorohydrin rubber solution having a viscosity adjusted to 350 centipoise. Epichlorohydrin / ethylene oxide / allyl glycidyl ether 100 parts Epichlorohydrin rubber composed of terpolymer (Epichroma CG: manufactured by Osaka Soda Co., Ltd.) Zinc flower 5 parts Stearic acid 1 part Sulfur 1.5 parts

Similarly, as a material for the resistance layer, a mixture having the following composition was dissolved in 130 parts of a toluene / xylene = 1/1 solvent to prepare a fluororesin solution having a viscosity adjusted to 350 centipoise. 100 parts of fluororesin (Lumiflon LF-600: manufactured by Asahi Glass Co., Ltd.) 10 parts of isocyanate-based curing agent (Coronate HX: manufactured by Nippon Polyurethane Co., Ltd.)

The same conductive elastic roller as that prepared in Example 1 was immersed in a dipping solution in which the mixing ratio of the epichlorohydrin rubber solution and the fluororesin solution was changed as shown in Table 1, and coated. After drying at room temperature and then at 150 ° C. for 10 minutes, an intended semiconductive roller having a resistance layer having a thickness of 50 μm was obtained.

Comparative Example A semiconductive roller was obtained in the same manner as in Example 2 except that the simple solution of the epichlorohydrin rubber solution prepared in Example 2 was used as the material for the resistance layer.

The semiconductive roller obtained as described above is mounted as a charging roller of the electrophotographic copying machine shown in FIG. Each of the breakdown voltages was evaluated and measured. Table 1 shows the results.

The evaluation method and the measurement method were as follows. (1) Ranking of toner filming resistance Using the apparatus shown in FIG. 1, the toner adhesion state on the surface of the charging roller after 100 hours and 300 hours of operation was evaluated according to the following criteria. Rank: The toner on the roller surface can be easily wiped off with a cloth or the like.・ ・ ・: Slight toner remains after wiping.・ ・ ・: Complete wiping is not possible, and a thin layer of toner remains. 〃 ・
.. The toner is strongly adhered to the roller surface.

(2) In measuring the resistance of the volume resistance resistance layer alone, a sample in which a resistance layer material is coated on a thin aluminum plate (thickness 0.5 mm) to a thickness of 50 μm by a dipping method is measured at 20 ° C. and 60% RH. After being left in the environment for 16 hours, measurement was performed using a resistance measuring cell (16008A: manufactured by YHP) and a resistance meter (electrometer 610C: manufactured by Keithle). The resistance of the roller was measured by leaving the sample in an environment of 20 ° C. and 60% RH for 16 hours.
0 mm width copper foil tape (Scotch tape No. 124
5: 3M) as electrodes, the distance between the main electrode and the guard electrode was set to 1 mm, and a resistance meter (electrometer 61) was used.
0C: manufactured by Keithley Co., Ltd.).

(3) Two rollers for the dielectric breakdown voltage sample
After leaving in an environment of 0 ° C. and 60% RH for 16 hours, 10
A DC voltage was gradually increased and applied between the main electrode having a width of mm and the shaft core, and a minimum voltage at which dielectric breakdown occurred was obtained.

[0037]

[Table 1]

From the results shown in Table 1, it can be seen that the roller of the present invention is excellent in toner filming resistance as compared with the roller of the comparative example, and can be used as a good charging roller.

[0039]

The semiconductive roller of the present invention is a semiconductive roller in which a conductive elastic layer and a resistive layer are laminated on a conductive support in that order, and the resistive layer has four layers. Since it is made of a mixture of ethylene fluoride propylene rubber or epichlorohydrin rubber / fluorine-based polymer, it is excellent in non-adhesiveness to toner, so that toner filming hardly occurs. Surfactant for adjusting volume resistance, rubber hardness, etc.,
It is not necessary to use a plasticizer, etc., so it does not contaminate the photoreceptor and has sufficient semi-conductivity even if it does not contain a low-resistance material such as carbon black. In this case, the characteristics of the roller are sufficiently exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an electrophotographic copying apparatus using a semiconductive roller of the present invention as a charging roller.

FIG. 2 is a schematic sectional view showing a layer configuration of a semiconductive roller of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging roller 3 developing device 4 transfer paper 5 transfer roller 6 fixing device 7 toner cleaner 8 exposure mechanism 9 eraser lamp 10 shaft core 11 conductive elastic layer 12 resistance layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-145463 (JP, A) JP-A-1-204081 (JP, A) JP-A-57-176064 (JP, A) JP-A 64-64 37574 (JP, A) JP-A-63-218983 (JP, A) JP-A-63-70879 (JP, A) JP-A-64-52180 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G03G 15/02 101 G03G 15/08 501 G03G 15/16 103 G03G 21/06 F16C 13/00

Claims (3)

(57) [Claims] 1. A semiconductive roller comprising: a conductive elastic body layer and a resistance layer laminated in this order on a conductive support,
Moreover the resistive layer is semi-conductive roller for electrophotographic copying machine, characterized by being <br/> composed tetrafluoroethylene-propylene rubber. 2. A semiconductive roller comprising a conductive support, a conductive elastic layer and a resistance layer laminated in that order,
Moreover, the resistance layer is mainly composed of epichlorohydrin rubber.
Electrophotographic copying characterized by being composed of a semiconductive substance comprising a mixture of the rubber and a fluorine-based polymer.
Semi-conductive roller for machine . 3. The semiconductive material for an electrophotographic copying machine according to claim 2, wherein said fluorine-based polymer is a polymer obtained by crosslinking a fluorine-containing copolymer having fluoroolefin and hydroxyl group-containing vinyl ether as constituents with isocyanate. Sex roller.