JP3100625B2 - Conductive roll and method of manufacturing the conductive roll - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive roll for development, charging, charge elimination, transfer and the like used in an electrophotographic recording apparatus, and more particularly to rubber or foam having a core of a good conductor metal shaft. The present invention relates to a conductive roll having a structure in which a coating film for resistance adjustment is formed on an outer peripheral surface of a material roll.

2. Description of the Related Art Electrophotographic recording devices widely used in copiers, laser beam printers, and the like generally include a photoconductor, and charge and expose the photoconductor to form an electrostatic latent image. Thereafter, the toner is attracted and developed according to the latent image on the photoconductor, and then the toner on the photoconductor is transferred and transferred to paper. The remaining toner is cleaned to prepare for the next recording. Further, the toner carried on the sheet after the transfer is finally melted and pressed and fixed on the sheet, thereby completing a series of recording operations on the sheet.

By the way, a charging means for applying a predetermined potential to the charged area of the photosensitive member of the electrophotographic recording apparatus, a transfer means for applying a predetermined potential to the sheet conveyed to the transfer area, or a photosensitive element after the transfer. As a static elimination means for uniformizing the charged area of the body to a constant potential, a corona charging method which is configured to generate a corona discharge by applying a high voltage of several hundred to several thousand volts to a small diameter wire is widely and generally used. Used in

However, in the case of using such a corona charging method, there is a possibility that active molecules such as ozone generated by the corona discharge may deteriorate the photoreceptor and other parts or may have a bad influence on the human body. There is a problem. In addition, such a method is also problematic in terms of danger of electric shock accidents due to high voltage, and further, in terms of maintenance and management of wire contamination and disconnection.

Therefore, unlike such a corona charging method, a roller-type contact charger (hereinafter referred to as a conductive roll) has been proposed in which, for example, a conductive rubber roller is brought into direct contact with a photoreceptor to apply a predetermined voltage. Have been. This conductive roll does not require a higher voltage than the corona charging type, and has excellent characteristics such as almost no generation of ozone and the like.

By the way, in this conductive roll, in order to uniformly apply a potential to the photoconductor, it is important to increase the adhesion between the roll and the photoconductor as much as possible to thereby apply a uniform potential to the photoconductor. Therefore, development of effective means is desired.

In addition, in this conductive roll, if a low molecular weight liquid compound, for example, a softening agent such as oil is mixed during the production to improve the adhesiveness, the softening agent leaches on the roll surface and contaminates the photoreceptor. There is a fear.

In the production of this conductive roll, when conductive carbon such as Ketjen Black EC or acetylene black is used as a conductive powder to impart conductivity to the roll, the amount of the powder to be added is small. In some cases, the electrical resistance value may change significantly due to a slight change or poor dispersion of the powder.

Further, in such a conductive roll, it is extremely difficult to control and adjust the electric resistance value, and it is also difficult to impart necessary charged voltage characteristics.

In addition, the electrical resistance of such conductive rolls may change significantly with changes in the external environment such as humidity and temperature, and a constant potential is always applied to the photoconductor. It can be difficult to do.

Further, such conductive rolls are fragile in material and may be easily cracked or abraded easily. Therefore, development of a roll with little aging is desired.

By the way, as a method for manufacturing such a conductive roll, a rubber or urethane foam roller 100 shown in FIG. 1 is usually coated with a liquid coating material by electrostatic coating, dipping, a wet coating method such as a roll coater, or the like. A method of applying by a dry coating method and then drying to form a coating film 101 for resistance adjustment (see FIG. 2) is employed. Then, at this time, in order to prevent the coating material from adhering to the shaft 102 and to form the end portion of the coating film 101 as shown in FIG. In general, masking is performed by covering the shaft 102 with a tube 103 having an inner diameter substantially equal to the outer diameter dimension b of the shaft 102 (FIG. 3). After masking the shaft 102 with a coating material and drying or dry coating, the coating film 101 formed as shown in FIG. 4 is cut at the portion c, and the masking tube 103 is removed. 2 are obtained.

By the way, in such masking, a considerable coating film must be exposed to prevent sparking between the photosensitive drum and a roller formed of rubber or foam having low electric resistance. However, if the coating film protrudes too much, it hits the bearing, causing problems such as tearing.

If air remains between the tube and the roll at the time of extrusion, the air expands in the extruded film, and phenomena such as blisters are likely to occur. As a result, withstand voltage characteristics of this portion may be deteriorated. In the case of such a masking, in the case of the wet coating method, air slightly existing between the masking tube 103 and the shaft 102 or between the masking tube 103 and the end face of the roller 100 during coating or drying. However, there is a problem that bubbles are generated by exuding into the coating on the end face portion of the roller 100, and the pinhole 101a is easily generated in this portion (see FIG. 5) and the coating film 101 is easily cut (see FIG. 6). .

In this way, there is a pinhole 101a, or the coating film 101 is cut, and as shown in FIG.
If the end faces have the same surface shape, spark discharge is likely to occur at the end of the roller 100, causing damage to the photosensitive drum.

The present invention has been made in view of the above-mentioned conventional drawbacks, and has high adhesion to a photoreceptor, can minimize contamination of the photoreceptor, and has an electric resistance value due to an external environmental change or the like. It is an object of the present invention to provide a conductive roll capable of minimizing the change of the conductive roller, and having less cracks and abrasion for a long period of time.

DISCLOSURE OF THE INVENTION According to the conductive roll according to claim 1 of the present invention, a shaft of a good conductor provided on a core portion, and a conductive and stretchable intermediate layer provided on the outer periphery of the shaft,
A conductive roll having a coating film having a higher specific resistance than the intermediate layer provided on the outer periphery of the intermediate layer, and applying a potential of a predetermined polarity while contacting the photosensitive member or the transfer paper;
The intermediate layer is made of silicone rubber, urethane rubber, polybutadiene urethane rubber, polynorhornene rubber, natural rubber, polybutadiene rubber, styrene butadiene rubber, acrylonitrile rubber, ethylene propylene diene rubber,
A non-foamed elastic body such as acrylic rubber, epichlorohydrin rubber, ethylene vinyl acetate rubber, fluororubber, and the like, or a mixture thereof, or a mixture of these foamed elastic bodies, and carbon black with no developed structure structure mixed therein. The outer peripheral surface of the intermediate layer is polarized.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 are process diagrams showing a conventional method for producing a conductive roll, FIGS. 5 and 6 are explanatory views showing the drawbacks of the conventional conductive roll, and FIG. FIG. 8 is a sectional view showing a conductive roll according to a first embodiment of the present invention, and FIG.
FIG. 9 is a sectional view showing a conductive roll of a third embodiment according to the present invention, and FIG. 10 is a sectional view showing a conductive roll of a fourth embodiment according to the present invention. FIG. 11 is a sectional view showing a conductive roll of a fifth embodiment according to the present invention, FIG. 12 is a sectional view showing a conductive roll of a sixth embodiment according to the present invention, and FIG. Seventh invention
FIG. 14 is a cross-sectional view showing the conductive roll of the embodiment, and FIG. 14 is a graph showing a change in resistance value with respect to each temperature and humidity change in the upper and lower layers of the coating film in the conductive roll of the seventh embodiment shown in FIG. 15 to 21 are process diagrams showing a method for manufacturing a conductive roll according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 7 shows a conductive roll according to a first embodiment of the present invention. The conductive roll according to this embodiment is designed to be used as a charger of an electronic copying machine. It is composed of a flexible intermediate layer 2 and a coating film 3.

The shaft 1 is provided along the axial direction of the core of the conductive roll, and is formed in a cylindrical shape 1 using a good conductor.

The intermediate layer 2 is formed using a mixture of solid rubber and 10 to 50 PHR of liquid rubber as a softening agent in order to improve adhesion to a drum-shaped photoreceptor (hereinafter referred to as a photosensitive drum). Is called a rubber roll). That is, the rubber roll 2 is made of a material containing, for example, solid polybutadiene rubber and liquid polyisoprene rubber (hereinafter abbreviated as IR), specifically, cis 1,4-polybutadiene 60PHR (BR02LL manufactured by Nippon Synthetic Rubber Co., Ltd.). And liquid polyisoprene 40PHR (Kuraray isoprene: LIR30) and Ketjenblack EC10PHR are used as the material.

The liquid rubber to be used preferably has a double bond in the main chain and has a number average molecular weight of 10,000 or more. With such a molecular weight, most of the liquid rubber reacts with the solid rubber at the time of vulcanization to form a bond. It does not dissolve into the paint.
In addition, the unreacted residue hardly dissolves into the paint because of its high molecular weight. Therefore, when the rubber roll 2 is made of such a rubber and a coating film 3 is formed by coating the outer peripheral surface of the rubber roll 2, the softener does not migrate to the surface of the coating film, and the rubber roll 2 is used as the photosensitive drum. When contacted, the photosensitive drum is less likely to be contaminated. As the liquid rubber, liquid IR and liquid BR can be used, and liquid IR is particularly preferable. When the solid BR and the liquid IR are used, a soft rubber is easily produced. Even if a large amount of the liquid IR is blended, the adhesion to a banbury or a roll is small.

Features include good mold release during vulcanization, fast vulcanization, and low compression set of the vulcanizate.

In order to make such a rubber roll, the electrical resistance of the rubber is usually high, so the electrical resistance of the rubber must be reduced by some method (hereinafter, this is referred to as a conductive rubber body). In the conductive rubber body, conductive powder, that is, various metal oxides whose surfaces have been subjected to conductive treatment, such as zinc oxide, titanium oxide, tin oxide, and carbon black in addition to the above Ketjen Black EC are mixed. It is configured so that the resistance can be reduced by doing things.

Also, the resistance of the rubber roll may be 10
^It is necessary to specify the semiconductor region of about ⁴ to 10 ⁷ Ω in a narrow range, but if conductive carbon such as Ketjen Black EC or acetylene black is used at this time, the amount of the conductive powder added may be slightly changed. Dispersion is large and the resistance changes greatly, making it difficult to control to a predetermined resistance. Therefore, when ordinary rubber carbon such as SAF, ISAF, HAF, MAF, FEF, GPF, SRF, etc., whose structure has not been developed and which has low conductivity, is used, the resistance becomes stable. However, in order to lower the resistance, it is necessary to mix a large amount of carbon, and the hardness of the rubber increases. Under these circumstances, in order to produce a rubber having both low hardness and low resistance value characteristics, it is necessary to use a conductive carbon such as Ketjen black, acetylene black and the like as described above for ordinary rubber carbon or paint. Merging with carbon is effective.
Although the cost is considerably higher than that of carbon black, a rubber having a low hardness and controlled to a specific resistance in a semiconductor region can be produced even by using the above-described conductive metal oxide. That is, this is because the conductive metal oxide has no reinforcing property and the conductivity is not as high as that of the conductive carbon.

The intermediate layer is not particularly limited to that of this embodiment, but may be a non-foamed elastic material such as silicone rubber, urethane rubber, BR urethane, no solex (polynorbornene rubber), or the like. It may be a foamed elastic body or the like.

The coating film 3 is made of epichlorohydrin, acrylic rubber, adhesive silicon rubber, chlorosulfonated polyethylene, fluoroolefin vinyl ether copolymer, one-pack or two-pack polyurethane, or modified nylon such as N-methoxymethyl nylon. A variety of materials can be used, which are capable of bonding to a polarized rubber surface. This coating film 3 may have a required resistance value by itself, but if not, a conductive powder may be dispersed to adjust the resistance value.

Therefore, according to the first embodiment, by using the above-described material for the intermediate layer 2, the adhesion is small,
It can be easily removed after kneading with a kneader or Banbury mixer. Further, by using this material, the mold can be easily separated after vulcanization, and can be easily removed without damaging the roll.

The conductive roll of the present invention may be manufactured by any of a wet coating method and a dry coating method. For example, even in the case of dry coating, since the liquid rubber does not migrate to the coating film, there is no need to provide the film with an action of preventing the transfer of contaminants on the photosensitive drum, and the range of film selection is widened.

Next, a conductive roll according to a second embodiment of the present invention will be described.

FIG. 8 shows a conductive roll according to a second embodiment of the present invention. The conductive roll according to the second embodiment employs a halogen gas such as a chlorine gas or an NN-diode on the surface of a rubber roll 4 constituting an intermediate layer. Chlorparatoluenesulfonic acid amide,
The rubber roll 4 is formed by halogenation using an organic halogenating agent such as trichloroisocyanurate, so that the electrical resistance of the rubber roll 4 can be increased. That is, the rubber roll 4 is, for example, 10 ³
By subjecting a roll having an electric resistance of Ω or less to a halogenation treatment, a roll having an electric resistance of about 10 ⁴ Ω can be obtained. The rubber roll 4 can be made to have a higher resistance, for example, from 10 ⁵ Ω to 10 ⁷ Ω by using together with the addition of the conductive powder for adjusting the specific resistance used in the first embodiment. Incidentally, the surface of the rubber roll 4 is made to be polarized by a halogen treatment, a polar treatment such as a corona discharge or a plasma discharge during the production.

The coating film 5 of the second embodiment includes urethane,
By using a polar material such as nylon, epichlorohydrin rubber, acrylic rubber or the like, it is possible to easily adhere to the rubber roll 4 having a polarized surface. These materials may be coated by either a wet method or a dry method. In any case, the adhesion between the rubber roll 4 and the coating film 5 causes the resistance to change with time. Can be suppressed.

Therefore, the conductive roll of the second embodiment can control the internal resistance of the rubber roll 4 as the intermediate layer,
A rubber roll 4 is used to make a conductive roll having a specific resistance.
It is possible to freely control the resistance ratio between the film and the coating film 5. Then, the voltage applied to the entire conductive roll at the time of use is applied to the intermediate layer and the coating film 5 in accordance with the resistance ratio, so that when the coating film 5 does not have a sufficient charged voltage, By increasing the ratio of the internal resistance on the intermediate layer side, the withstand voltage of the entire roll can be increased.

Next, a conductive roll according to a third embodiment of the present invention will be described with reference to FIG.

The conductive roll of the third embodiment has a first layer as an intermediate layer.
A rubber roll 6 softened by the same softening agent as in the embodiment is used, and a polymer using one-component urethane is used for the coating film 7.

The coating film 7 can be firmly adhered to the rubber roll 6 which has been subjected to the softening treatment by using one-component urethane. Particularly, an ester-based urethane or an ether whose resistance is adjusted by mixing a conductive powder. It has been found that all urethanes exhibit high withstand voltage. For example, when the volume resistivity is around 10 ⁸ to 10 ¹⁰ Ω · cm and the film thickness is 100 to 200 μm, the withstand voltage characteristic has about 1.5 to 2.5 KV.
The resistance of the coating film 7 is adjusted by dispersing a conductive powder such as a conductive metal oxide such as zinc oxide, titanium oxide, tin oxide or carbon black. And, for example, when using this carbon black,
Instead of highly conductive carbon such as Ketjen Black EC and acetylene black, use SAF, ISAF, HAF, MAF, FEF, etc.
DBP oil absorption (ASTM D2414) By using carbon for rubber or paint for structure having a structure of about 150 or less, the volume resistivity of the film is 10 ⁶ to 10 ¹⁰ Ω · cm.
It is possible to control to a specific value in the semiconductor region of the degree. As a result of research and experiments by this inventor, especially when carbon black for paint having a DBP oil absorption of about 50 to 130 is dispersed in an ester-based one-part urethane paint, the carbon for paint whose surface is treated to be acidic It has been found that black has good compatibility with urethane and has very good dispersion, so that it is possible to form a film having a stable and stable resistance.

Next, a conductive roll according to a fourth embodiment of the present invention will be described with reference to FIG.

The conductive roll of the fourth embodiment uses a coating film 8 mixed with hydrophobic silica.

Generally, the resistance value of the coating film largely depends on the humidity of the environment in which the film is placed, and in many cases, may exceed an appropriate range within the environmental conditions used.

Therefore, as a result of various attempts by the present inventor, it has been found that when hydrophobic silica (silica chemically bonded to silica) is mixed into the paint at about 5 to 50 PHR, the change in resistance is reduced. . That is, this is because the entire coating film becomes water repellent by the silicone oil. In general, when the silicone oil itself is mixed into the coating film, problems such as bleeding from the film and contaminating the photosensitive drum occur, but if the coating film is added to silica, it does not bleed. It does not happen, which is also advantageous.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

The conductive roll of the fifth embodiment uses conductive tin oxide doped with antimony oxide as a conductive powder for adjusting the resistance of the coating film 9.

Therefore, according to the conductive roll of the fifth embodiment, the particle size of the tin oxide is as small as 0.1 μm or less, and the dispersibility is very good. The resistance value of the film 9 can be easily controlled.

In addition, since the tin oxide is spherical, it is difficult for the anisotropy of the resistance of the film to appear due to the change in the shear during processing,
Therefore, good characteristics can be exhibited as a roll.

Next, a sixth embodiment of the present invention will be described with reference to FIG.

The conductive roll 6 of the embodiment shown in FIG. 12 uses a modified nylon such as N-methoxymethyl nylon as a material for forming the coating film 10.

When the inventor conducted various experiments using the conductive roll of the sixth embodiment, the coating film 10 was brought into close contact with the photosensitive drum and left for one month. It was found that there was no contamination.

Next, a conductive roll according to a seventh embodiment of the present invention will be described with reference to FIG.

In the conductive roll of the seventh embodiment, the coating film has a two-layer structure of an upper layer 11 and a lower layer 12.

The upper layer 11 is made of a material that is somewhat hard and does not contaminate the photosensitive drum at all even if the withstand voltage is low. The upper layer 11 of this embodiment has a configuration in which a modified nylon such as N-methoxymethyl nylon is used as a material for forming the same, and tin oxide doped with antimony oxide is dispersed therein. Fluctuations in the external environment such as humidity (for example, 82.5 at 32.5 ° C)
% RH to 15 ° C. and 10% RH) so as not to adversely affect the image at the time of recording. As described above, modified nylon such as N-methoxymethyl nylon is a suitable material for the upper layer, but these materials have poor adhesion to the photosensitive drum if not crosslinked at all, and the film becomes brittle if crosslinked too much. It has disadvantages such as easy abrasion, cracks on the surface to lower the electric resistance, and the tendency that the electric resistance tends to be too high even if conductive powder is added.

Therefore, by appropriately controlling the degree of cross-linking of these coating films, for example, by controlling the degree of cross-linking with an acid catalyst or heating, the above-mentioned disadvantages can be greatly improved. I have.

The lower layer 12 is made of a material that is soft, has good withstand voltage, and is thickly coated to a thickness of about 50 to 200 μm using a material that does not transmit a substance that causes contamination of the rubber or foam of the intermediate layer 2. Particularly, the material of the lower layer 12 of this embodiment is preferably one-pack or two-pack polyurethane, epichlorohydrin rubber, acrylic rubber, chlorosulfonated polyethylene, modified nylon, or the like.

As for the specific resistance between the upper layer 11 and the lower layer 12 constituting the covering layer, the resistance value of the upper layer 11 is R ₁ , and the resistance value of the lower layer 12 is
Assuming that R ₂ , it is desirable to satisfy (R ₂ / R ₁ )> 1, whereby the effect of temperature and humidity can be effectively suppressed.

Therefore, according to the conductive roll of the seventh embodiment, the lower layer 12 and the upper layer 11 having a lower resistance value than the thickness of the lower layer 12 make the resistance of the conductive roll environmentally dependent. Sex can be reduced. That is, this is the 14th
This is because, as shown in the figure, the contact resistance of the lower layer 12, which increases under low humidity conditions, can be reduced by interposing a film having a low resistance value, that is, the upper layer 11. (Note that FIG. 14 is a semi-log scale, and the roll resistance value on the vertical axis side is expressed in logarithm.)

Next, an eighth embodiment according to the present invention will be described with reference to FIG.

The conductive roll of the eighth embodiment comprises an intermediate layer 16 and a coating layer.
The specific resistance is adjusted so that the ratio of the 17 resistors is 1: 1.5.

Intermediate layer 16 is formed by mixing carbon with polybutadiene and liquid polyisoprene, and injection molding. Roll resistance (measured by winding an aluminum foil having a width of 1 cm on the outer peripheral surface and applying a voltage of 1 KV) ) Has 1 × 10 ⁸ Ω.

The coating layer 17 is formed by applying a carbon-containing polyurethane paint to a thickness of 80 μm on the outer peripheral surface of the intermediate layer 16, and similarly has a roll resistance of 1.5 × 10 ⁸ Ω.

Therefore, in the conductive roll according to the eighth embodiment,
When a high voltage of 1.5 KV was applied between the intermediate layer 16 and the coating layer 17, it was confirmed that no voltage breakdown occurred.

Next, a ninth embodiment according to the present invention will be described with reference to Table 1.

In the ninth embodiment, the conductive carbon (a) is used for both the case where the intermediate layer contains the solid rubber and the liquid rubber as the softener (a) and the case where the intermediate layer does not contain the liquid rubber (b). When the hardness and the resistance were measured when ketjen black EC (c) and non-conductive carbon (d) HAF were mixed, data as shown in the following Table 1 were obtained.

From Table 1, it can be seen that when solid rubber and liquid rubber are used together, the hardness is low and the resistance is stable, and when polybutadiene (BR) 70PHR and liquid polyisoprene (LIR) 30PHR are used as liquid rubber to be used together, carbon It has been found that a material having a low electric resistance can be obtained even if the amount is small.

Therefore, according to the ninth embodiment, a vulcanized rubber that is soft and has good conductivity can be produced.

In the ninth embodiment, when a liquid rubber is contained (a), carbon black is kneaded with polybutadiene (BR) 70PHR and liquid polyisoprene (LIR) 30PHR in a Banbury and press-vulcanized to obtain a sheet. Made and measured hardness and resistance. When no liquid rubber is contained (b), styrene butadiene rubber (SBR), natural rubber (NR)
Was kneaded with a Banbury and press vulcanized to form a sheet, and the hardness and resistance were measured.

Next, a tenth embodiment according to the present invention will be described with reference to Table 2.

The conductive roll according to the tenth embodiment has a configuration in which the surface of the intermediate layer is polarized. In this embodiment, such a structure is immersed twice in two kinds of treatment methods, that is, when immersed twice in acetone 4% of trichloroisocyanurate, and when immersed twice in ethyl acetate 4% of trichloroisocyanurate. (F) Roll resistance before and after the treatment (roll a 1 cm wide aluminum foil around the roll
KV voltage was measured).
The results shown in Table 2 were obtained.

From Table 2, it can be seen that the specific volume resistance can be increased by performing the polarization treatment, in other words, the resistance of the intermediate layer can be controlled. In other words, this is because the treatment agent impregnates the inside of the intermediate layer and forms a polarized layer of several tens of microns on the surface.

In addition, by performing the polarization treatment, dust with reduced surface tackiness is less likely to adhere, and can be easily adhered to the polarized coating film.

In this example, cis 1,4-polybutadiene 60PHR (BR02LL manufactured by Nippon Synthetic Rubber Co., Ltd.) and liquid polyisoprene 40PHR (LIR30 manufactured by Kuraray Isoprene Co., Ltd.) were used as the intermediate layer used in the case of (e). , Ketjen Black EC
(Ketjen Black International Co., Ltd.
10PHR and a vulcanizing agent were kneaded with a B-type Banbury and injection molded. The material used in (f) is a cis
1,4-polybutadiene 70PHR, liquid polyisopropylene 30
It is formed by kneading PHR, Ketjen Black EC8PHR and a vulcanizing agent with a B-type Banbury and then injection molding.

Next, an eleventh embodiment according to the present invention will be described.

In the conductive roll of the eleventh embodiment, the intermediate layer is formed by injection molding by mixing carbon black and a vulcanizing agent with polybutadiene and liquid polyisoprene. This was subjected to a polarization treatment with a 2% solution of trichloroisocyanurate in acetone, and a thermoplastic urethane paint containing carbon was applied thereto and dried to form a coating film.

The conductive roll formed in this way is placed in a laboratory.
When I left it for months, the roll resistance was 2.2 × 1
What had 0 ⁵ Ω changed to 2.3 × 10 ⁵ Ω, indicating that there was almost no change. By the way, when the roll resistance was measured by leaving the same material formed in the same way without performing the polarization treatment and leaving it for the same period, the initial 2.0 × 10 ⁵ Ω increased to 1.0 × 10 ⁶ Ω. It turned out to change.

Therefore, according to this example, it can be seen that it is possible to suppress the occurrence of aging of the resistance over time. That is, this is because the intermediate layer and the coating film are firmly adhered to each other, so that the component from the intermediate layer is prevented from changing the resistance value due to the blade from the intermediate layer in a slight gap generated at the adhesion site due to poor adhesion. It is. Further, since the displacement and wrinkling of the coating film can be prevented when the coating film is adhered to the intermediate layer, it is possible to prevent the image from being disturbed at the time of copying.

 Next, a twelfth embodiment according to the present invention will be described.

In the conductive roll of this embodiment, the coating film is formed of a polymer using one-part urethane or two-part urethane. In particular, in this embodiment, the main chain of urethane is formed of adipic acid ester.

That is, the conductive roll of this embodiment uses an intermediate layer formed by injecting carbon black and a vulcanizing agent into polybutadiene and liquid polyisoprene, kneading the mixture, and kneading the mixture. In the intermediate layer thus formed,
It is treated with a 2% solution of trichloroisocyanurate in acetone, and a thermoplastic urethane paint (trade name: P22S, manufactured by Miractran Co., Ltd.) in which carbon is dispersed is applied, dried, and dried.
m is formed.

A stress corrosion cracking experiment was performed on the photoconductor made of polycarbonate as a main material on the conductive roll formed in this manner.When the conductive roll having a urethane coating film was brought into close contact with the photoconductor, it took 20 days. No cracking was observed over the above. Further, when an intermediate layer alone was brought into close contact with the photoreceptor, cracks occurred in the intermediate layer in 8 hours.

From this experiment, it can be seen that urethane is partially crystallized to have a high strength, or that the urethane is firmly bonded to the intermediate layer subjected to the bonding treatment, that is, the rubber roll. This urethane has a high withstand voltage, and can exhibit a high withstand voltage even when the resistance is adjusted to the semiconductor region with carbon or a conductive metal oxide. Particularly, the withstand voltage of adipic acid ester is excellent. It is.

 Next, a thirteenth embodiment according to the present invention will be described.

The conductive roll of the thirteenth embodiment has a configuration in which a coating film is formed by dispersing a carbon black for paint having a DBP oil absorption of about 130 to 50 in an ester-based one-part urethane paint, and particularly having such a configuration. It has been confirmed by this inventor's research and experiment that a stable resistance film with little variation can be obtained.

That is, in this embodiment, as a coating film, a one-component polyurethane (trade name: P22S, manufactured by Nippon Milactone Co., Ltd.) obtained by chain-extending an ester of 1,4-butanediol and adipic acid with MDI (4,4-diphenylmethane diisocyanate). ) 100 PHR was dissolved in 16% dioxane / MEK, and the average particle size was 22
It is a paint made by adding 18 PHR to carbon (MA100, trade name of Mitsubishi Kasei Co., Ltd.) of μm, DBP oil absorption of 100 ml / 100 g, PH3.5. The conductive roll of this example was formed by applying this coating material to an intermediate layer that had been halogenated with a trichloroisocyanurate solution so as to have a thickness of about 200 μm, and drying at 120 ° C. for 5 hours. is there.

Note that several 100-μm-thick films were prepared from the paint used as the coating film in this example, and this was heated to 120 ° C.
After drying for 5 hours at a volume resistivity of 6.0
Experiments and measurements by the present inventor confirmed that the reproducibility was within a narrow range of × 10 ⁸ -8.0 × 10 ⁸ with good reproducibility. In addition, with respect to the conductive roll coated with the paint in this manner, a withstand voltage experiment was performed by applying a DC voltage while rotating, and it was confirmed that a voltage breakdown was not caused at 2.0 KV, and at least 2.0 KV or more. It has also been found that it has a withstand voltage characteristic.

Next, a fourteenth embodiment according to the present invention will be described.

The conductive roll of the fourteenth embodiment uses a mixture of hydrophobic silica as a coating film, and as shown in Table 3 below, it was confirmed that the resistance change in the environment was reduced. Was.

In this embodiment, a rubber roll formed by adding carbon black and a vulcanizing agent to polybutadiene and liquid polyisoprene as an intermediate layer and injection molding is used. In the conductive roll of this embodiment, the intermediate layer thus formed is treated with a 2% solution of trichloroisocyanurate in acetone, and the outer peripheral surface thereof is made of Nippon Silica Co., Ltd. Is used, and a thermoplastic urethane paint containing carbon containing 10 PHR is applied thereto and dried to form a coating film.

Next, a fifteenth embodiment according to the present invention will be described.

The conductive roll of the fifteenth embodiment has a configuration in which the coating film has tin oxide doped with antimony oxide. That is, it has been found that the conductive roll of this example uses conductive tin oxide as the coating film, and the following effects can be obtained by this.

The particle size of the tin oxide contained is as small as 0.1 μm or less,
Since the dispersibility is very good, the resistance value of the coating film can be easily controlled by appropriately changing the dispersion amount.

Further, since tin oxide is spherical, anisotropy of the film resistance due to the manner of application of the shear during processing is unlikely to appear, so that good characteristics can be exhibited as a conductive roll.

Further, the present inventor actually used the conductive roll according to this embodiment and a conductive roll having a coating film formed of various materials as a developing roll in a copying machine in order to perform various experiments. The knowledge about the image quality as shown in Table 4 was obtained.

Similarly, a case in which tin oxide is similarly applied to the upper layer of a coating film composed of two layers in modified nylon, and a case in which various other materials are applied to the upper layer of the coating film in modified nylon. Similarly, the results shown in Table 4 were obtained.

Next, a sixteenth embodiment according to the present invention will be described.

The conductive roll of this embodiment uses modified nylon as a material for forming the coating film, and the degree of crosslinking of the modified nylon is determined in consideration of high adhesion to the photosensitive drum, prevention of brittleness occurrence, high electric resistance, and the like. It has a configuration having a predetermined value.

That is, N-methoxymethyl nylon (Tresin EF30T (trade name, manufactured by Teikoku Chemical Co., Ltd.)) is used as a modified nylon for the coating film of the conductive roll of this embodiment. Polymerized nylon (trade name G550, manufactured by Teikoku Chemical Co., Ltd.), modified copolymer amide (brand name AQ nylon P-70, manufactured by Toray Industries), polyether, polyester-copolymerized nylon (brand names Pebax 2533, 3533, manufactured by Toray Industries) ).

The modified nylon such as N-methoxymethyl nylon used in this example is a suitable material for the upper layer of the coating film. However, if these materials are not crosslinked at all, they will have poor adhesion to the photosensitive drum and will be too crosslinked. And the film becomes brittle and easily wears, cracks on the surface, the electric resistance decreases, the electric resistance tends to be too high even if conductive powder is added, and it has disadvantages such as I have.

Under such circumstances, as a result of various studies conducted by the present inventor, by controlling the degree of crosslinking of the coating film, for example, by controlling the degree of crosslinking by using an acid catalyst or heating, It has been found that the disadvantages are greatly improved.

Therefore, when a film formed using the same cross-linked N-methoxymethyl nylon used for the coating film of this example was brought into close contact with the photosensitive drum and allowed to stand for one month,
It was found that there was no contamination on the photosensitive drum.

Next, a seventeenth embodiment according to the present invention will be described.

The conductive roll of the seventeenth embodiment has a coating film composed of two layers, an upper layer and a lower layer.

The upper layer is formed of a material that does not adhere to the photosensitive drum and has a thickness of 3 to 50 μm on the outer peripheral surface of the lower layer. In this embodiment, the same modified nylon as that of the seventh embodiment is used. Have been. And the upper layer of this example is
Since it is formed thinner than the lower layer, it may be somewhat hard and have a low withstand voltage.

The lower layer is made of a material that is soft and has good electric resistance as in the previous seventh embodiment, and that is made of a material that does not allow the intermediate layer rubber or the material in the foam to cause contamination of the photosensitive drum. It is so thick that it is formed on the outer peripheral surface of the intermediate layer. That is, as this lower layer, JISA hardness
Using soft thermoplastic urethane around 80 degrees,
As a result, the electric resistance is good, and the rubber or foam of the intermediate layer is not liable to pass through the photosensitive drum.

Therefore, according to the seventeenth embodiment, the functions of the upper layer and the lower layer are separately assigned to each other, so that the selection range of the material used for each of these layers is greatly expanded.

If the lower layer is covered with a one-component urethane paint in which carbon for paint is dispersed, it is easy to adjust to the predetermined resistance, but if there is a pinhole in the photosensitive drum due to the orientation of carbon in the axial direction, the It was found that poor charging was caused in the axial direction of the portion, and black lines were easily generated in the image. In particular, it has been found that this phenomenon is likely to occur when the roll resistance is lowered (3 × 10 ⁵ Ω or less) in consideration of the fluctuation of the roll resistance due to the environment, the rise due to energization, and the like.

Thus, the inventor conducted various experimental studies, and found that after coating with a one-part urethane paint, a resin having conductive tin oxide dispersed therein was coated with a resin of about 3 to 20 μm to generate a black line. Could be suppressed. This is considered to be because tin oxide has a small spherical shape and therefore has a small orientation. Conductive tin oxide is significantly more expensive than carbon, but uses a low-cost conductive material such as carbon for the lower layer, and uses a thin (5-30 μm) expensive but high-performance conductive material for the upper layer. Can be manufactured at low cost.

Further, in this embodiment, when particularly high withstand voltage characteristics are to be provided, it is necessary to increase the roll resistance value of only the lower layer (3 × 10 ⁵ Ω or more). However, at this time, the environment dependence of the roll resistance comes out, but by making the specific resistance of the upper layer film lower than the specific resistance of the lower layer film, the external environment dependence such as humidity is greatly reduced. Can be. When the roll resistance of only the lower layer is as low as 2 × 10 ⁵ Ω or less,
Even if the specific resistance of the upper film is not reduced below the specific resistance of the lower film, there is little external environment dependency. Urethane containing conductive powder has a high specific resistance under high humidity, whereas modified nylon containing conductive powder has a low specific resistance under high humidity. Therefore, it is particularly preferable to form a two-layer coating comprising urethane as a lower layer and modified nylon as an upper layer, and it is possible to reduce the environmental dependence of the conductive roll.

Next, a method of manufacturing the conductive roll according to the first embodiment of the present invention will be described with reference to FIGS.

(1) First, a conductive adhesive 13 is applied to the metal shaft 1 having an outer diameter of 8 mm (see FIG. 15). In other words, this is to firmly adhere the shaft 1 and the rubber roll 2 to improve durability during rotation, to make the contact resistance between the shaft 1 and the rubber roll 2 uniform, and to eliminate electric resistance unevenness. It is.

(2) Next, a rubber roll 2 having an outer diameter of 15 mm is formed around the shaft 1 by injection molding or extrusion molding and vulcanized (see FIG. 16).

As the rubber material used at this time, use a conductive material obtained by mixing a liquid rubber as a softening material with a solid rubber and blending a conductive material so that the filling oil does not seep into the solvent of the coating material. .

(3) Both ends of the shaft 1 are made of polypropylene,
Put a tube 14 of 6 mm and outer diameter 9 mm (see Fig. 17). The material of this tube 14 does not contaminate the coating solution,
What has elasticity and grasps a shaft is good. At this time, in order to prevent the occurrence of pinholes, the rubber roll 2
It is desirable to secure an outer diameter difference of 0.5 mm or more between the tube and the tube 14. In particular, the step S for forming a liquid pool is 0.25
It is preferable to secure mm or more.

(4) After that, in order to remove foreign substances on the surface of the rubber roll 2, it is washed with pure water, methanol, toluene or the like, and dried.

(5) Then, in order to bond the rubber roll 2 and the coating film 3, the surface of the rubber roll 2 is subjected to a polarization treatment with a halogen gas or an organic halogenating agent.

That is, if there is even a slight air layer between the comb roll 2 and the coating film 3, the withstand voltage characteristics will be inferior and the electric resistance will be uneven.
This is because it is important to firmly adhere to the substrate.

(6) Next, while holding one end of the rubber roll 2, it is set upright and dipped in a coating material solution 15 (see FIG. 18). This coating material solution is made of carbon, graphite or a conductive metal oxide. That is, electric urethane using titanium oxide, zinc oxide, tin oxide or the like as a conductive material is preferable. This urethane is a material suitable for the coating film of the conductive roll because it is soft and adheres well to the rubber roll 2 by a halogen treatment, but may be acrylic, epichrome, or nylon.

In the case of a foam, a coater system such as a roll coater or a knife coater that can use a coating material solution having a relatively high viscosity is suitable.

(7) When the rubber roll 2 and the masking tube 14 are heated and dried, the end of the roll changes from the state of FIG. 19 to the state of FIG. To form The fillet A serves to improve the withstand voltage characteristics of the end portion as described above. In addition, when the coating material solution is applied and dried while the rubber roll is set vertically, the coating material solution is excessively attached to the end face of the rubber roll and gradually falls down on the rubber roll side surface during the drying, and the thickness of the coating film 3 becomes uneven. Therefore, it is preferable that the difference between the outer diameters of the rubber roll and the tube be 2.5 mm or less.

(8) Finally, a scratch is made on the portion B of the coating film 3 with a knife over the entire circumferential direction (see FIG. 20), and the masking tube is removed (see FIG. 21).

INDUSTRIAL APPLICABILITY As described above, the conductive roll according to the present invention is useful as a conductive roll for development, charging, static elimination, transfer, and the like used in an electrophotographic recording apparatus. It is suitable for applying or removing a potential to the body.

Continuation of the front page (56) References JP-A-64-73364 (JP, A) JP-A-64-66674 (JP, A) JP-A-59-46664 (JP, A) JP-A-51-59636 (JP, A) JP-A-60-150071 (JP, A) JP-A-63-179959 (JP, A) JP-A-59-172666 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G03G 15/02 101 G03G 15/08 501 G03G 15/16 103 G03G 21/06 F16C 13/00

Claims (15)

(57) [Claims] 1. A shaft made of a good conductor provided on a core portion, a conductive and stretchable intermediate layer provided on the outer periphery of the shaft, and a specific resistance higher than that of the intermediate layer provided on the outer periphery of the intermediate layer. A conductive film for applying a potential of a predetermined polarity while being in contact with a photoreceptor or transfer paper, wherein the intermediate layer is made of silicone rubber, urethane rubber, polybutadiene urethane rubber, polynorform. Non-foamed elastic material such as nene rubber, natural rubber, polybutadiene rubber, styrene butadiene rubber, acrylonitrile rubber, ethylene propylene rubber, acrylic rubber, epichlorohydrin rubber, ethylene vinyl acetate rubber, fluorine rubber, and mixtures thereof, or a mixture thereof Constructed of foamed elastic material and mixed with carbon black with undeveloped structure A conductive roll, wherein the outer peripheral surface of the intermediate layer is polarized. 2. The conductive roll according to claim 1, wherein a polar coating material is applied to at least the adhesive surface of the intermediate layer of the coating film. 3. The conductive roll according to claim 1, wherein the coating film is formed of a polymer using one-part or two-part urethane. 4. The conductive roll according to claim 1, wherein the coating film comprises one-part urethane or two-part urethane and carbon for coating. 5. The conductive roll according to claim 1, wherein the coating film is mixed with hydrophobic silica. 6. The conductive roll according to claim 1, wherein the coating film comprises tin oxide doped with antimony oxide. 7. The conductive roll according to claim 1, wherein a modified nylon is used as a coating film forming material. 8. A coating film comprising a relatively hard and thin upper layer which does not contaminate a photoreceptor or a transfer sheet and a relatively soft and thicker lower layer having good electric resistance. The conductive roll according to claim 1, wherein the conductive roll has a two-layer structure. 9. The conductive roll according to claim 8, wherein a modified nylon is used as a material for forming the upper layer. 10. The conductive roll according to claim 8, wherein the upper layer contains tin oxide doped with antimony oxide. 11. The conductive roll according to claim 8, wherein the lower layer is formed of a polymer using one-part or two-part urethane as a material for forming the lower layer. 12. An upper layer having a thickness of 1 to 20 μm and a lower layer having a thickness of 50 to 200 μm, wherein the upper layer has a resistance value R ₁ and a lower layer has a resistance value R _1.
Conductive roll according to claim 8, the ratio of ₂ (R ₂ / R ₁₎ is equal to or is greater than 1. 13. The conductive roll according to claim 8, wherein the lower layer comprises one-component urethane and two-component urethane, and the upper layer comprises modified nylon. 14. The conductive roll according to claim 8, wherein the lower layer is more flexible and thicker than the upper layer. 15. The conductive roll according to claim 8, wherein the intermediate layer has been subjected to a halogenation treatment.