JP3132095B2 - Semiconductive roll for electrophotographic equipment - 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 roll for an electrophotographic apparatus used for a charging roll used for a copying machine, a printer and the like using an electrophotographic system, a developing roll and the like.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, an original image is formed as an electrostatic latent image on the surface of a photosensitive drum, toner is adhered to the image, and a toner image is formed, and the toner image is transferred to copy paper. Is to be copied. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, a document image is projected on the charged portion via an optical system, and a portion where light is applied is formed. It has been practiced to form an electrostatic latent image by eliminating the charging of the image. As a method for charging the surface of the photosensitive drum prior to the formation of the electrostatic latent image, a corona discharge method is generally used.
In the above-described corona discharge method, a corona discharge is applied to the surface of a photosensitive drum from a corona discharger to perform a charging process. Since this system generally uses a high-voltage power supply of 5 to 10 kV, it is necessary to take thorough safety measures, and there is a problem that harmful ozone is generated with the discharge. For this reason, recently, a roll charging system in which a semiconductive roll is brought into direct contact with the surface of the photosensitive drum to charge the surface of the photosensitive drum has attracted attention. An electrophotographic copying machine to which such a roll charging system is applied is configured as shown in FIG.
Copying is performed as follows. That is, a charging roll 2 made of a conductive roll is rotated around the outer peripheral surface of the photosensitive drum 1 rotating in the direction of the arrow about the axis 1a with the photosensitive drum 1, and is brought into sliding contact with the photosensitive drum 1 while being partially elastically deformed. Reference numeral 3 denotes an exposure mechanism through which the slit exposure 8 of the light image of the original reaches the surface of the photosensitive drum 1, and an electrostatic latent image corresponding to the original image is formed on the surface of the photosensitive drum 1. Reference numeral 4 denotes a developing device that forms a toner image by attaching toner to the electrostatic latent image. Reference numeral 6 denotes a paper feed mechanism roll, which supplies the copy paper 11 to the surface of the photosensitive drum 1 and transfers the toner image onto the copy paper 11 via the transfer device 5. Reference numeral 7 denotes a fixing roll that fixes the sheet by passing the copy paper 11 on which the toner image is formed. Thus, a copy is obtained. The cleaner 9 removes transfer residual images and residual toner from the surface of the photosensitive drum 1. Reference numeral 12 denotes a power supply for applying a voltage of about 1 to 3 kV to the charging roll 2.

[0003] In the charging roll used in the roll charging method, since the roll is in direct contact with the photosensitive drum,
If a conductive layer causes defects such as pinholes in the photosensitive layer, excessive current flows into the pinholes,
The voltage required for charging cannot be maintained, so that the entire length of the pinhole portion in the axial direction becomes defective, and the amount of current flowing through the photosensitive material is large and the life of the photosensitive drum is shortened. In order to solve such a problem, it has been studied to make the resistance value of the charging roll into a semiconductive region.
A semiconductive roll which is a charging roll in a semiconductive area has been proposed (Japanese Patent Application No. 62-301107, Japanese Patent Application No. 1-1344).
No. 30). The semiconductive roll is, as shown in FIG.
A conductive elastic layer 16 is formed on the outer periphery of the shaft body 15, and the resistance adjusting layer 1 of a semiconductive region is formed on the outer periphery of the conductive elastic layer 16.
7, and a protective layer 18 is formed on the outer periphery of the resistance adjusting layer 17. The conductive elastic layer 1
In some cases, a migration preventing layer made of a photosensitive material is formed between the resistance adjusting layer 6 and the resistance adjusting layer 17.

[0004]

However, since such a semiconductive roll uses a high dielectric elastic material for the resistance adjusting layer 17, the electric resistance is largely dependent on the environment.
There is a problem that power supply restrictions become severe.
In other words, since this roll is required to be semiconductive, to have a high dielectric breakdown voltage, and to be required to have uniform electric resistance, a system in which conductive particles are dispersed in an elastic body (electronic conductive system) However, the above requirement cannot be satisfied, and a system (high dielectric elastic body) in which the resistance value of the high dielectric elastic body itself is set to meet a required level is used for the resistance adjusting layer 17. (Ion conductive system). The semiconductive roll is provided with a protective layer for preventing interaction between the photosensitive member and the charging member.
7 uses an ion conductive system, there is a limit in suppressing a change in resistance value due to environmental fluctuations (especially humidity), and the resistance value actually changes as it exceeds 2.0 digits. In addition, the above-mentioned semiconductive roll has a problem that it cannot cope with high-speed models. That is, if the resistance value at which the amount of current required to increase the copying speed is increased under low temperature and low humidity is adjusted, the resistance value becomes too low under high temperature and high humidity, and the power supply capacity becomes insufficient, resulting in poor charging.

The present invention has been made in view of such circumstances, and provides a semiconductive roll for an electrophotographic apparatus which is excellent in environment resistance and uniformity of resistance and can be applied to high-speed models. For that purpose.

[0006]

In order to achieve the above object, a semiconductive roll for an electrophotographic apparatus according to the present invention has a conductive elastic layer formed on the outer periphery of a shaft along the circumference. A first resistance adjustment layer is formed along the circumference on the outer periphery of the conductive elastic body layer, and a second resistance adjustment layer is formed on the circumference of the first resistance adjustment layer. An electronic photograph in which a protective layer is integrally formed on the outer periphery of the resistance adjustment layer along the circumference.
A semiconductive roll for a true device , wherein the first resistance adjustment layer is made of an ionic semiconductive substance obtained by mixing an ionic conductivity control agent with a polymer composition, and the second resistance adjustment layer is made of a polymer . A hydrophobic synthetic resin as a matrix component, a conductive material dispersed in the matrix component, and a hydrophobic synthetic resin composition. The protective layer is formed of a semiconductive resin composition. Configuration.

[0007]

The present inventors have conducted a series of studies for the purpose of improving the dependence of electric resistance on the environment. as a result,
The resistance adjusting layer of the semiconductive roll is made into two layers .
The first resistance adjustment layer to be a layer is compounded with an ionic conductivity control agent
When the resistance adjustment layer (second resistance adjustment layer) which is the outer layer is made of a hydrophobic synthetic resin composition, the electrical resistance changes due to environmental conditions. And found that the present invention was achieved.

Next, the present invention will be described in detail.

A semiconductive roll for an electrophotographic apparatus according to the present invention comprises: a shaft; a conductive elastic layer formed on an outer periphery thereof;
A first resistance adjustment layer formed on the outer circumference, a second resistance adjustment layer formed on the outer circumference of the first resistance adjustment layer along the circumference, and further on the outer circumference of the second resistance adjustment layer. It is constituted by a protective layer formed along the line.

The shaft is not particularly limited, and a metal core made of a solid metal, a metal cylinder hollowed out inside, or the like is used.

The conductive elastic layer formed on the outer periphery of the shaft has a low hardness (Asker C (sponge hardness tester) 60 ° or less / 1 kg load) and an electric resistance of 10 ⁴ Ω or less. That is, it is preferable to increase the contact width with respect to the photosensitive drum. For this purpose, the hardness is desirably set to be equal to or less than the above-described hardness, and the current is passed through the first and second resistance adjusting layers formed on the outer periphery of the conductive elastic layer. Is preferably set to an electric resistance value of 10 ⁴ Ω or less. As the material for forming the conductive elastic layer, as a matrix component, ethylene-propylene-diene rubber (EPDM), polynorbornene rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR),
Silicon rubber and the like can be mentioned, and a synthetic rubber composition in which conductive powder such as carbon black is blended is used.

The first resistance adjusting layer formed on the outer periphery of the conductive elastic layer is preferably set within the range of a semiconductive region (10 ⁵ to 10 ⁸ Ω). It is set in consideration of the balance with the second resistance adjustment layer formed on the outer periphery. Further, the first resistance adjustment layer needs to have dielectric breakdown resistance, and specifically, 1500 V or more,
Preferably, it has a dielectric breakdown resistance of 2000 V or more. Then, the first resistance adjusting layer formed materials are epichlorohydrin - ethylene oxide copolymer rubber, a polymer composition based on polyurethane resins, Ru der those formulated with ionic conductivity control agent. Examples of the ionic conductivity controlling agent include quaternary ammonium compounds such as trimethyl octadecyl ammonium chloride, benzyl trimethyl ammonium chloride, trioctyl propyl ammonium bromide and trimethyl octadecyl ammonium perchlorate, and benzoates of these quaternary ammonium compounds, Nitrate, sulfate and the like can be mentioned, and they are used alone or in combination. The amount of the ionic conductivity controlling agent is preferably set to 6.0% by weight or less in the polymer composition. Since the first resistance adjusting layer is based on ionic conductivity, for example, when the environmental condition changes from low temperature and low humidity to high temperature and high humidity, the resistance value changes by about 1% due to an increase in the number of ionic carriers and an increase in mobility. .5 digits.

The second resistance adjustment layer formed on the outer periphery of the first resistance adjustment layer is formed using a hydrophobic synthetic resin composition obtained by adding a conductive powder to a hydrophobic synthetic resin as a material for forming the second resistance adjustment layer. Examples of the hydrophobic synthetic resin include a thermoplastic urethane resin and an olefin-based thermoplastic resin. Examples of the conductive powder include a carbon black and a metal double oxide, and particularly a solid solution of zinc oxide and aluminum oxide. , A solid solution of tin oxide and antimony oxide, a solid solution of indium oxide and tin oxide, etc., which are used alone or in combination. The amount of the conductive powder to be added depends on the thermal expansion and moisture absorption properties of the hydrophobic synthetic resin used. Under low temperature and low humidity, the distance between the conductive powders dispersed by heat shrinkage becomes shorter, and the resistance improvement effect is obtained. As can be seen, under high temperature and high humidity, the distance between the conductive powders becomes longer due to thermal expansion, and the resistance is not improved by the conductive powder itself, but is adjusted appropriately so as to substantially show the resistance of the synthetic resin itself. You. The amount of the conductive powder to be added is appropriately set based on the combination of the synthetic resin and the conductive powder based on the above-described phenomenon depending on the environment. For example, when using a thermoplastic urethane resin as a synthetic resin and using a metal double oxide in which titanium oxide particles are coated with a solid solution of tin oxide and antimony oxide as a conductive powder, the content of the conductive powder in the synthetic resin is It is preferably set in the range of 21 to 25% by volume, and particularly preferably 22 to 24% by volume.

As described above, when the second resistance adjusting layer is made of a hydrophobic synthetic resin and the amount of the conductive powder added is adjusted so as to exhibit the above environment dependence, the resistance of the first resistance adjusting layer depends on the environment. When the layers are stacked, the environmental dependency of the resistance is greatly improved as compared with the case where the first resistance adjustment layer and the second resistance adjustment layer are formed alone.

The outermost protective layer formed on the outer periphery of the second resistance adjusting layer preferably has a surface resistance of 10 ⁷ Ω / □ or more. That is, if the surface resistance is too low,
For example, when a defective portion such as a pinhole exists on the surface of the photosensitive drum and the roll surface and the defective portion come into contact with each other, a current flows on the roll surface, and the portion in contact with the photosensitive drum defective portion and the roll surface potential in the vicinity thereof are reduced. And the charging becomes poor. This charging failure phenomenon is a factor that causes a serious problem that an image defective portion is not limited to a defective portion and an image enlarged beyond the defective portion is formed. further,
When the surface resistance is 10 ⁵ Ω / □ or less, a defective image is enlarged and formed on the entire surface in the axial direction if there is even one defective portion in the axial direction of the photosensitive drum. For this reason, the outer periphery of the second resistance adjusting layer has semiconductivity and has a surface resistance of 1
The protective layer is formed using a layer forming material having a resistivity of × 10 ⁷ Ω / □ or more and having no adverse effect on the photosensitive drum. As the material for forming the protective layer, 8-nylon (N-methoxymethylated nylon) is preferably used. The N-methoxymethylated nylon is obtained by methoxymethylating an amide group of 6-nylon, and increasing the methoxylation rate improves solubility in alcohol. Further, a conductive powder may be added within a range that satisfies the surface resistance, and by lowering the resistance value of the protective layer by adding the conductive powder,
The effect on environmental dependency can be minimized.

The semiconductive roll for an electrophotographic apparatus of the present invention is manufactured, for example, as follows. That is, first, a conductive elastic layer forming material is prepared, and the material is filled into a molding die provided with a shaft (core bar) and vulcanized to form a conductive elastic layer. Then, a material for forming the first resistance adjusting layer is prepared, and the outer peripheral surface of the conductive elastic layer is coated by dipping or the like, and is heated and vulcanized. Next, a conductive material is added to the thermoplastic urethane resin solution, and after sufficiently dispersing using a dispersing machine so as not to cause agglomerates, the viscosity is adjusted to a predetermined value to form a second resistance adjusting layer forming material. Then, the material for forming the second resistance adjustment layer is coated on the outer peripheral surface of the first resistance adjustment layer by dipping or the like, and dried by heating. Further, a conductive material is added to a methanol solution of N-methoxymethylated nylon as a protective layer forming material,
After the dispersion is sufficiently dispersed by a dispersing machine to adjust the viscosity, the material for forming the protective layer is coated on the surface of the second resistance adjusting layer by dipping or the like, and crosslinked by heating to form a protective layer. Thus, a semiconductive roll for an electrophotographic apparatus as shown in FIG. 1 is obtained. In the figure, reference numeral 20 denotes a metal core,
21 is a conductive elastic layer, 22 is a first resistance adjustment layer, 23 is a second resistance adjustment layer, and 24 is a protective layer.

In the above-described semiconductive roll for an electrophotographic apparatus , the thickness of each layer is 3.0 mm for the conductive elastic layer 21, 120 μm for the first resistance adjustment layer 22, 20 μm for the second resistance adjustment layer 23, and 20 μm for the protective layer. 24 is preferably set in the range of 3 to 30 μm. For example, if the thickness of the protective layer 24 is 3 μm or less, the durability is poor, and if it exceeds 30 μm, the environmental dependency of the electric resistance increases.

In the semiconductive roll for an electrophotographic apparatus according to the present invention, as shown in FIG. 2, contamination between the conductive elastic material layer 21 and the first resistance adjusting layer 22 due to the photosensitive material is prevented. The migration prevention layer 25 may be formed for the purpose of preventing the migration.

[0019]

As described above, the electrophotographic apparatus according to the present invention is provided.
The semiconductive roll for use has a resistance adjustment layer formed in a two-layer structure, and the first resistance adjustment layer contains an ionic conductivity control agent.
Combined had it occurred formed in ionic semiconductive material, and a second resistance adjusting layer is by connexion formed in the hydrophobic synthetic resin composition. For this reason, the environment resistance with respect to the electric resistance is improved, and a current required for charging can be passed at a low voltage even at a low temperature and a low humidity, for example. Further, even if the drum has a defective portion, charging failure does not occur, and the present invention can be applied to a high-speed model.

Next, examples will be described together with comparative examples.

[0021]

Examples 1 to 7 A material for forming a conductive elastic layer was prepared by mixing the following components. Isoprene rubber (manufactured by Kuraray, Kuraray IR-10) 40 parts by weight Liquid isoprene rubber (manufactured by Kuraray, CIR-290) 60 parts by weight Ketjen Black EC 13 parts by weight Zinc oxide 5 parts by weight Stearic acid 1 part by weight Acceleration of vulcanization 2 parts by weight of agent [DM (dibenzothiazole disulphide), Succinol DM (manufactured by Sumitomo Chemical Co., Ltd.)] 0.6 parts by weight of vulcanization accelerator [PZ (zinc dimethyldithiocarbamate), soccinol PZ (manufactured by Sumitomo Chemical Co., Ltd.)] Part Sulfur 0.5 part by weight Then, the above-mentioned material for forming a conductive elastic layer is filled in a molding die provided with a cored bar, and heated and vulcanized to about 3.0 mm.
Of a conductive elastic layer (Asker C hardness 58 °). On the outer periphery of the conductive elastic layer, a first resistance adjusting layer forming material containing epichlorohydrin-ethylene oxide rubber as a main component and trioctylpropylammonium perchlorate (ionic conductivity controlling agent) added thereto is subjected to thickness by dipping. It was coated at 120 μm and crosslinked by heating in an oven. Next, conductive powder (ET-500, manufactured by Ishihara Sangyo Co., Ltd.) in which a solution of a thermoplastic urethane resin (manufactured by Dainippon Ink, Pandex T6990) was coated with a tin oxide-antimony oxide solid solution on the surface of titanium oxide.
W) was added at the ratio shown in Table 1 below, and the mixture was sufficiently dispersed by a disperser so as not to form an agglomerate, and then adjusted to a predetermined viscosity to form a second resistance adjusting layer having a thickness of 20 μm. Materials were made. This second resistance adjustment layer forming material was coated on the outer peripheral surface of the first resistance adjustment layer by dipping and dried by heating to form a second resistance adjustment layer. Further, N-methoxymethylated nylon (manufactured by Teikoku Chemical Co., Ltd.,
A solid solution of tin oxide-antimony oxide (T-1 manufactured by Mitsubishi Materials Corporation) was added to a methanol solution of Toresin EF30T) so as to be 14% by volume in terms of solid content, and the mixture was applied to a disperser. (Citric acid) was added to adjust the viscosity to prepare a protective layer forming material having a thickness of 5 to 30 μm. This protective layer forming material was coated on the outer peripheral surface of the second resistance adjusting layer by dipping, and dried by heating to form a protective layer. Thus, a semiconductive roll for an electrophotographic apparatus as shown in FIG. 1 was manufactured.

[0022]

[Table 1]

[0023]

Comparative Examples 1 to 3 The components shown in Table 2 below were blended in the proportions shown in the same table to prepare materials for forming the respective layers. Using these forming materials, a semiconductive roll for an electrophotographic apparatus was manufactured in the same manner as in Example 1.

[0024]

[Table 2]

Using the thus obtained semiconducting rolls for electrophotographic devices of Examples and Comparative Examples, changes in electric resistance from low temperature and low humidity to high temperature and high humidity, an image display test and The degree of contamination on the photosensitive drum surface was measured and evaluated. The results are shown in Tables 3 and 4 below.

[Method of Measuring Electric Resistance] As shown in FIG. 5, a semiconductive roll 30 for an electrophotographic apparatus is used.
An aluminum block (not shown) having a width of 10 mm was disposed at a predetermined portion (hatched portion) A of the sample so as to contact the roll surface, and the resistance value was measured.

[0027] the photosensitive drum in the [image reproduction test] laser to bracts A 404 (manufactured by Canon Inc.) to prepare a defective portion of the pre-diameter 1.0 mm, an electrophotographic
A semiconductive roll for the device was incorporated. Then, an image was actually obtained by changing the temperature and the humidity, and the image was evaluated. When the size of the image defect was the same as the size of the defective portion, the sample was rated as ○, when the size of the defective portion was 1.2 times or more, ×, and when the size of the defective portion was 1 to 1.2 times the size, Δ. .

[Contamination of Photosensitive Drum Surface] An image was taken out, and the surface of the photosensitive drum was visually observed.

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

According to the results shown in Tables 3, 4 and 5, the surface of the photosensitive drum of Comparative Example 1 was contaminated, and the electrical resistance of Comparative Example 2 varied greatly depending on environmental conditions (temperature and humidity). In Comparative Example 3, the electrical resistance was too low under high temperature and high humidity, and an image defect occurred. On the other hand, in all of the examples, the electrical resistance did not fluctuate greatly even when the environmental conditions were changed, good results were obtained in the image display test, and the surface of the photosensitive drum was not contaminated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a semiconductive roll for an electrophotographic apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the semiconductive roll for an electrophotographic apparatus of the present invention.

FIG. 3 is a configuration diagram of an electrophotographic copying machine incorporating a semiconductive roll.

FIG. 4 is a cross-sectional view showing a conventional example.

FIG. 5 is an explanatory diagram of a method for measuring an electric resistance value.

[Explanation of symbols]

 Reference Signs List 20 core metal 21 conductive elastic layer 22 first resistance adjustment layer 23 second resistance adjustment layer 24 protective layer

Continuing on the front page (72) Inventor Kazunobu Hashimoto Komaki City, Aichi Prefecture, Ogai Kitagaiyama, Gezu 3600 East Kai Rubber Industry Co., Ltd. (72) Inventor Hiroyasu Kato Komaki City, Aichi Prefecture, Ogai Kitagaiyama Character, Gezu 3600 East Sea Rubber (56) References JP-A-2-311871 (JP, A) JP-A-3-100677 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15 / 02 101 G03G 15/08 501 F16C 13/00

Claims (4)

(57) [Claims] 1. A conductive elastic layer is formed on the outer periphery of a shaft along the circumference, and a first resistance adjusting layer is formed on the outer periphery of the conductive elastic layer along the circumference. (1) For an electrophotographic apparatus, a second resistance adjustment layer is formed along the circumference on the outer circumference of the resistance adjustment layer, and a protection layer is integrally formed on the circumference of the second resistance adjustment layer . A semiconductive roll,
The first resistance adjusting layer controls the ionic conductivity of the polymer composition.
Composed of an ionic semi-conductive substance containing an agent ,
The second resistance adjusting layer is composed of a hydrophobic synthetic resin composition in which a hydrophobic synthetic resin is a matrix component, and a conductive material is dispersed and contained in the matrix component, and the protective layer is a semiconductive resin composition. A semiconductive roll for an electrophotographic apparatus , characterized by being constituted by an object. 2. The semiconductive roll for an electrophotographic apparatus according to claim 1, wherein the first resistance adjusting layer is mainly composed of epichlorohydrin-ethylene oxide copolymer rubber. 3. The second resistance adjusting layer includes at least one of a thermoplastic urethane resin and an olefin-based thermoplastic resin as a matrix component, and a solid solution of zinc oxide and aluminum oxide as a conductive material in the matrix component, and tin oxide. The electrophotographic apparatus according to claim 1, wherein the electrophotographic apparatus is composed of a resin composition containing a conductive powder containing at least one of a solid solution of antimony oxide and a solid solution of indium oxide and tin oxide as a main component. For semi-conductive rolls. 4. The semiconductive roll for an electrophotographic apparatus according to claim 1, wherein the protective layer is made of a thermoplastic resin mainly composed of N-methoxymethylated nylon. .