JPH06266206A - Charging roller - Google Patents

Abstract

(57) [Abstract] [Purpose] The photoreceptor can be uniformly charged simply by applying a high voltage DC voltage to the charging roller, and a large amount of AC current is consumed without superimposing an AC voltage on the charging roller. And a charging roller that does not generate ozone. A charging roller for charging a photoreceptor of an image forming apparatus has an elastic layer and a surface layer, and the elastic layer is made of an electrically medium resistance material in which conductive particles are not dispersed, and the surface layer is made of the above material. It is made of non-sticky material with high non-stickiness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roller used in a charging device of an image forming apparatus.

[0002]

2. Description of the Related Art In a charging device 1 for charging a photosensitive member 3 of a conventional image forming apparatus, (1) a high-voltage DC voltage is applied to a charging roller 2 as shown in FIG. The charging roller 2 has a conductive elastic layer 15 in which NBR or conductive particles are dispersed on the core metal 4, and the surface of the elastic layer 15 is rotated by driven rotation. A non-adhesive coating 10 made of a conductive fluorine type is coated. Such a material has a problem that the nonuniformity of the electric characteristics is large and uneven charging of the photoconductor 3 occurs via the conductive elastic layer 15, and the background stain occurs in the same cycle as the roller cycle. As a charging roller that solves this problem, (2) the surface layer 11 in which a conductive material is dispersed as shown in FIG.
An elastic layer 25 made of urethane, EPDM, or the like is provided so as to cover the core metal 4, and the conductive surface layer 11 is applied to the core metal 4 by superimposing an AC voltage on a DC voltage. Has been. In this case, the AC voltage that is superimposed to obtain the uniform charging has a peak-to-peak voltage that is at least twice the charging start voltage when the DC voltage is applied. 7
Is a DC power supply, and 8 is an AC power supply.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The charging of the photoconductor by the charging roller as in (2) requires an AC power supply in addition to the DC power supply, which increases the cost and consumes a large amount of unnecessary AC current that does not contribute to the charging potential of the photoconductor. In addition, there is a problem that ozone is generated with it.

Therefore, an object of the present invention is to solve the problems of the conventional charging roller as described above, and to uniformly charge the photosensitive member by simply applying a high voltage DC voltage to the charging roller. An object of the present invention is to provide a charging roller that does not consume a large amount of alternating current and does not generate ozone without superimposing an alternating voltage on a direct current voltage and applying it.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a charging roller for charging a photoreceptor of an image forming apparatus having an elastic layer and a surface layer. However, the elastic layer is made of an electrically medium resistance substance in which conductive particles are not dispersed, and the surface layer is made of a non-adhesive substance having a higher non-adhesiveness than the substance. According to a second aspect of the invention, in the first aspect of the invention, the surface layer has a thickness of 5 to 10 μm. According to a third aspect of the present invention, in the first aspect of the present invention, the medium electrical resistance substance is epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer or epichlorohydrin-
It is mainly composed of a homopolymer of ethylene oxide binary copolymer or a mixture thereof. According to the invention of claim 4, in the invention of claim 1, the non-adhesive substance is a fluorine-containing cross-linked copolymer obtained by cross-linking a fluorine-containing copolymer having fluoro olefin and vinyl ether having a hydroxyl group as a constituent with isocyanate. It will be.

[0006]

According to the invention of claim 1, the elastic layer of the charging roller is made of an electrically medium resistance material in which conductive particles are not dispersed, and a high voltage DC voltage is applied to the photoconductor. Uniform charging is performed, and the surface layer is made of a non-adhesive substance having a higher non-adhesiveness than the above substances, so that the toner does not adhere to the surface layer and the photoreceptor is not contaminated. The invention of claim 2 is
The thickness of the surface layer is 5 to 10 μm, and the photoreceptor is uniformly charged. In the invention of claim 3, the medium electric resistance substance is epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer or epichlorohydrin-
Mainly composed of ethylene oxide binary copolymer homopolymer or a mixture thereof epichlorohydrin rubber,
Even if it contacts the pinhole portion of the photoconductor, the photoconductor will not be damaged by energization. According to the invention of claim 4, the non-adhesive substance comprises a fluorine-containing cross-linked copolymer obtained by cross-linking a fluorine-containing copolymer having a fluoroolefin and a hydroxyl group-containing vinyl ether as a constituent with isocyanate.
A uniform non-stick surface layer is formed on the elastic layer.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In this embodiment shown in the drawings, the same parts as those of the conventional one are referred to by the same reference numerals, and the description thereof will be omitted.

The charging roller 2 of the present invention is as shown in FIG. 1, in which an elastic layer 5 is provided on a cored bar 4 and a surface layer 6 is provided on the elastic layer 5, and the cored bar 4 has a voltage of 1.3 KV to 1.6 KV. A negative DC high voltage of K volt is applied to charge the photoconductor 2. The elastic layer 5 is made of epichlorohydrin rubber made of an epichlorohydrin / ethylene oxide binary copolymer or an epichlorohydrin / ethylene oxide / allyl glycidyl ether ternary copolymer in which electrically conductive particles are not dispersed.

The surface layer 6 is provided in order to improve the non-adhesiveness of the surface of the charging roller 2 to toner without lowering the charging efficiency.
Is a mixture of the epichlorohydrin rubber used for the elastic layer 5 and a non-adhesive fluorine-based resin. The fluororesin is a solvent-soluble fluororesin and is an amorphous polymer obtained by a copolymerization reaction of a fluoroolefin and a hydrocarbon vinyl ether. For details, see “Organic Synthetic Chemistry, 42 (8), p. 841 (1984), Kojima, Yamabe,”
Asahi Glass Research Report 34 (2), pages 205-224 (1984), Munakata, Miyazaki, Kaya, Takayanagi. Although this resin has a relatively low fluorine content of 25 to 32 wt%, it is an alternating copolymer with a chain structure in which fluoroolefins and hydrocarbon vinyl ethers are arranged alternately, and it is a fluoroolefin that is thermally and chemically stable. Since the sites are regularly arranged and the unstable hydrocarbon vinyl ether site is protected electronically and sterically, it is chemically stable and has good durability.
Also, 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, but for this purpose copolymerize a highly reactive vinyl ether containing hydroxyl groups and The resin structure allows easy cross-linking.

With such a structure, the elastic layer 5 functions as an electric resistor with stability and uniformity, and has a small electrostatic capacity and a large improvement in charging uniformity even when AC is superposed. It is not seen, and it is not necessary to superimpose alternating current, and high voltage direct current voltage may be applied.

The elastic layer 5 of the first embodiment of the present invention comprises 100 parts by weight of epichlorohydrin rubber (trade name: Epichroma CG, manufactured by Daiso Co., Ltd.), which is a terpolymer of epichlorohydrin / ethylene oxide / allyl glycidyl ether. 30 parts by weight of light calcium carbonate, Sub [Product name: G
T, manufactured by Tenma Sub Chemical Co., Ltd.] 10 parts by weight, zinc white 5 parts by weight, stearic acid 0.5 part by weight, vulcanization accelerator [trade name:
Nox Cellar TT, manufactured by Ouchi Shinko Kagaku Co., Ltd.] 1 part by weight, [trade name: Nox Cellar DM, manufactured by Ouchi Shinko Kagaku Co., Ltd.] 1.5 parts by weight,
[Product name: Salfax H, manufactured by Tsurumi Chemical Industry Co., Ltd.]
After kneading 25 parts by weight into a compound having a uniform composition, it was molded on the outer circumference of a 6φ stainless steel shaft, and primary vulcanization: 17
Secondary vulcanization: 200 ° C./2 was performed at 0 ° C. for 10 minutes, and the surface of the roller thus formed was ground to have a roller outer diameter of φ12, which had electrical medium resistance. Its physical characteristics are volume resistance 2 × 10 ⁸ Ω · cm, rubber hardness 33 ° (JIS A),
The surface roughness is 3 μm · Rz.

The surface layer 6 of the first embodiment is 100 parts by weight of a terpolymer of epichlorohydrin rubber [trade name: Epichroma CG, manufactured by Daiso Co., Ltd.], 0.5 part by weight of stearic acid, 5 parts by weight of zinc white, 1 part by weight of vulcanization accelerator [Product name: Nocceller TT, manufactured by Ouchi Shinko Chemical Co., Ltd.], [Product name: Noxceller D
M, manufactured by Ouchi Shinko Chemical Co., Ltd.], 1.5 parts by weight, and [trade name: SALFAX H, manufactured by Tsurumi Chemical Industry Co., Ltd.], 0.25 parts by weight to form a compound having a uniform composition. Parts by weight toluene 48.8 parts by weight 4-methyl-2-
Pentanone was dissolved in 48.8 parts by weight to make an epichlorohydrin rubber solution (paint A-1) with a solid content of 2.5%, and a solvent-soluble fluororesin [brand name: Lumifun LF-601C main agent, Asahi Glass Co., Ltd. )) 22 parts by weight, isocyanate-based curing agent (trade name: Lumifun LF-601C curing agent,
Asahi Glass Co., Ltd.] 4.4 parts by weight is dissolved in 36.8 parts by weight of toluene and 36.8 parts by weight of xylene to prepare a fluororesin solution (paint B) having a solid content of 10%, and 40 parts by weight of paint B and paint A-
1 100 parts by weight (solid content ratio: (paint A-1) /
Paint B = 1.0 / 1.6), this paint was coated on the elastic layer 5 by the dipping method, dried at a temperature of 160 ° C. for 30 minutes, and molded to a thickness of 20 μm. The volume resistance of the surface layer 6 is 8 × 10 ⁹ Ω · cm.

This charging roller 2 is attached in place of the primary corona charger of the positive / positive developing type copying machine FT3300 (manufactured by Ricoh) and driven by the photoconductor 3 to rotate, and the DC voltage of the primary charging voltage is -1.4 kV as a core metal. The results of examining the potential of the dark potential of the photoconductor 3 and the image were shown in the column of Example 1 in Table 1. Furthermore, no abnormality occurred in the electric potential measurement and the image after the repeated preparation of 5000 images. The volume resistance of the elastic layer 5 was measured by leaving the sample in an environment of 20 ° C. and 60% RH for 16 hours and then using an Electrometer 610C manufactured by Keithley Co., Ltd., and measuring electrodes were 10 mm wide copper foil tape (3M). Company, No. 1245). Also, the volume resistance of the surface layer alone is measured with a thin aluminum plate (thickness 0.2 m
m) A sample coated with surface layer material to a thickness of about 50 μm
After being left in an environment of 20 ° C. and 60% RH for 16 hours, it was measured by an electrometer 610C manufactured by Keithle Co. using a resistance measuring cell (16008A manufactured by YHP).

[0014]

[Table 1]

The second embodiment is the same as the first embodiment except that the surface layer 6 has a thickness of 90 μm. The properties were good and are shown in the column of Example 2 in Table 1.

The elastic layer 5 of the third embodiment is made of epichlorohydrin rubber which is a binary copolymer of epichlorohydrin / ethylene oxide [trade name: Epichroma C, manufactured by Daiso Co., Ltd.].
Made] 100 parts by weight, light calcium carbonate 30 parts by weight, Sub [trade name: GT, manufactured by Tenma Sub Chemical Co., Ltd.] 10 parts by weight, zinc white 5 parts by weight, stearic acid 0.5 parts by weight, vulcanization accelerator [product Name: NOXCELLER TT, manufactured by Ouchi Shinko Kagaku Co., Ltd.] 1 part by weight, [Brand name: NOXCELLER DM, manufactured by Ouchi Shinko Kagaku Co., Ltd.] 1.
5 parts by weight [Product name: Salfax H, Tsurumi Chemical Industry
Co., Ltd.] 0.25 parts by weight was kneaded to form a compound having a uniform composition, which was then molded on the outer circumference of a 6φ stainless steel shaft, primary vulcanization: 170 ° C / 10 minutes, secondary vulcanization: 200 ° C / 2 Do time,
The surface of the roller thus formed is ground to have a roller outer diameter of φ12 and has an electrical medium resistance. Its physical characteristics are volume resistance 7 × 10 ⁷ Ω · cm, rubber hardness 32 ° (JI
SA) and surface roughness 3 μm · Rz.

The surface layer 6 of the third embodiment is 100 parts by weight of a binary copolymer epichlorohydrin rubber [trade name: Epichroma C, manufactured by Daiso Co., Ltd.], 0.5 parts by weight of stearic acid, 5 parts by weight of zinc white, 1 part by weight of vulcanization accelerator [Product name: Nocceller TT, manufactured by Ouchi Shinko Chemical Co., Ltd.], [Product name: Noxceller D
M, manufactured by Ouchi Shinko Chemical Co., Ltd.], 1.5 parts by weight, and [trade name: SALFAX H, manufactured by Tsurumi Chemical Industry Co., Ltd.], 0.25 parts by weight to form a compound having a uniform composition. Parts by weight toluene 48.8 parts by weight 4-methyl-2-
Pentanone was dissolved in 48.8 parts by weight to prepare an epichlorohydrin rubber solution (paint A-2) having a solid content of 2.5%, and 100 parts by weight of paint A-2 and 40 parts by weight of paint B were mixed (solid content ratio: ( A paint A-2) / paint B = 1.0 / 1.6) was prepared, and this paint was coated on the elastic layer 5 by the dipping method, and then dried at a temperature of 160 ° C. for 30 minutes and molded to a thickness of 20 μm. The characteristics of the charging roller 2 are shown in Table 3 as Example 3
Is shown in the column.

The elastic layer 5 of the fourth embodiment is a compound of the first embodiment (epichlorohydrin / ethylene oxide / allyl glycidyl ether terpolymer) and the third embodiment (epichlorohydrin / ethylene oxide terpolymer). Was mixed in a ratio of 1: 1 and molded in the same manner as in the first embodiment, and has an electric medium resistance of a roller diameter φ12. Its volume resistance is 1 × 10 ⁸ Ω · cm, rubber hardness is 33 ° (JIS A), and surface roughness is 3 μm · Rz. The surface layer 6 was prepared by mixing 100 parts by weight of the paint A-1 and 50 parts by weight of the paint B (solid content ratio: (paint A-1) / paint B = 1/2) and dipping this paint on the elastic layer 5. Method, and then dried at a temperature of 160 ° C. for 30 minutes and molded to a thickness of 6 μm. The volume resistance of this surface layer was 1 × 10 ¹⁰ Ω · cm. Various characteristics of this charging roller 2 are shown in the column of Example 4 in Table 1.

In the fifth embodiment, after the coating material B alone is coated on the elastic layer 5 of the first embodiment by the dipping method, 10
The surface layer 6 having a thickness of 8 μm was formed by drying at a temperature of 0 ° C. for 30 minutes. The volume resistance of this surface layer 6 is 2 × 10 ¹⁴ Ω ・
cm, and the characteristics of this charging roller 2 are shown in Table 5 as Example 5
Is shown in the column.

In the sixth embodiment, the coating B alone is coated on the elastic layer 5 of the third embodiment by the dipping method, and then 10
The surface layer 6 having a thickness of 5 μm was formed by drying at a temperature of 0 ° C. for 30 minutes. Various characteristics of the charging roller 2 are shown in the column of Example 6 in Table 1.

Comparative Example 1 shown in Table 1 shows various characteristics of the elastic layer 5 of the first embodiment without the surface layer 6.
This shows that when 5,000 images are formed, uneven density and toner filming occur in the image.

Comparative Example 2 has no difference except that the thickness of the surface layer 6 of the first embodiment was 230 μm.
The hardness of this charging roller 2 is 48 ° (JIS A).

In Comparative Example 3, after coating the coating material B only on the elastic layer 5 of the fourth embodiment by the dipping method, 100
The surface layer 6 having a thickness of 30 μm was formed by drying at a temperature of 30 ° C. for 30 minutes, which shows that uneven density and toner filming occur in the image.

Comparative Example 4 has no difference except that the thickness of the surface layer 6 of the sixth embodiment was 11 μm.
As a result, as shown in Table 1, the charging potential became slightly low,
It is shown that the image density becomes slightly lower accordingly.

Comparative Example 5 has no difference except that the thickness of the surface layer 6 of the sixth embodiment was increased to 15 μm, and the result is that the charging potential is further lowered as shown in Table 1, and This shows that the decrease in image density is further increased.

[0026]

The present invention is as described above. According to the invention of claim 1, the charging roller for charging the photoreceptor of the image forming apparatus has an elastic layer and a surface layer, and the elastic layer is made of conductive particles. Is composed of a non-dispersed electric medium resistance material, and the surface layer is composed of a non-adhesive material having a higher non-adhesiveness than the above-mentioned materials. It is obtained, does not superpose AC voltage on the charging roller, does not consume a large amount of AC current, does not generate ozone, and the surface is non-adhesive, so that toner adheres over a long period of time. There is no effect. According to the second aspect of the invention, since the thickness of the surface layer is 5 to 10 μm, there is an effect that the filming of the toner on the surface layer can be prevented and the photoreceptor can be uniformly charged. In the invention of claim 3, the medium electrical resistance substance is mainly composed of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, epichlorohydrin-ethylene oxide binary copolymer alone, or a mixture thereof epichlorohydrin rubber. Therefore, even if the pinhole portion of the photoconductor and the charging roller come into contact with each other, it is possible to prevent damage due to energization. According to the invention of claim 4, the non-adhesive substance comprises a fluorine-containing cross-linked copolymer obtained by cross-linking a fluorine-containing copolymer having a fluoroolefin and a vinyl ether having a hydroxyl group as constituents with an isocyanate. Easy to form non-adhesive layer on top,
The effect is that the toner does not adhere to the surface for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional view of a conventional charging device.

FIG. 3 is a schematic vertical sectional view of another conventional charging device.

[Explanation of symbols]

 1 Charging Device 2 Charging Roller 3 Photoreceptor 4 Core Bar 5 Elastic Layer 6 Surface Layer 7 DC Power Supply 8 AC Power Supply 9 Blade

Claims (4)

[Claims] 1. A charging roller for charging a photoreceptor of an image forming apparatus has an elastic layer and a surface layer, and the elastic layer is made of an electric medium resistance material in which conductive particles are not dispersed, and the surface layer is A charging roller comprising a non-adhesive substance having a higher non-adhesiveness than a substance. 2. The charging roller according to claim 1, wherein the surface layer has a thickness of 5 to 10 μm. 3. The medium electrical resistance substance is epichlorohydrin.
2. The charging roller according to claim 1, which is mainly composed of an epichlorohydrin rubber of an ethylene oxide-allyl glycidyl ether terpolymer or an epichlorohydrin-ethylene oxide binary copolymer, or a mixture thereof. 4. The charging roller according to claim 1, wherein the non-adhesive substance is a fluorine-containing cross-linked copolymer obtained by cross-linking a fluorine-containing copolymer having fluoro-olefin and vinyl ether having a hydroxyl group as constituents with isocyanate.