JPH0980866A - Electrifying member and electrifier using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the sticking of a toner, paper dust, etc., to the surface of an electrifying member and to improve the durability of the member. SOLUTION: In this electrifying member with a semiconductive elastic layer 102 and a surface layer 103 coating the surface of the elastic layer 102 on the electrically conductive substrate 101, the surface layer 103 is based on polyvinyl butyral resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used in an electrophotographic apparatus, and more particularly to a charging member in which an elastic layer mainly composed of epichlorohydrin rubber is formed on a conductive support.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a corona discharger which is a non-contact type charging apparatus has been widely used as a charging method for uniformly charging the entire surface of a photosensitive member. . Although this corona discharger is effective as a device for uniformly charging the surface of the body to be charged, it has the following problems.

1. Requires high voltage. 2. Generates a relatively large amount of ozone. 3. In order to maintain the uniform chargeability, it is necessary to provide cleaning means for the corona wire and perform cleaning procedures relatively frequently for maintenance.

On the other hand, a contact roller charging system in which a charging roller (charging member) is brought into contact with a photosensitive member and a voltage is applied while being driven to rotate to charge the surface of the photosensitive member is disclosed in Japanese Patent Laid-Open No.
It is disclosed in Japanese Patent Laid-Open No. 3-167380, "AC induction charging device". According to Japanese Patent Laid-Open No. 63-167380,
Compared to the corona discharge method, it has the advantages of lower power supply voltage and less ozone generation, but it is inferior in terms of charging uniformity.

In order to improve the uniformity of charging, for example, in the "contact charging method" disclosed in Japanese Patent Laid-Open No. 63-149668, the charging start voltage is doubled when a DC voltage is applied. It is disclosed that the uniformity of charging can be considerably improved by superimposing the AC voltage having the above peak-to-peak voltage. However, in the contact charging method of charging by applying a voltage in which the AC voltage and the DC voltage are superposed, an unpleasant environment as a charging sound due to vibration of the machine due to the AC voltage of the charging device is given, or However, the consumption of a large amount of alternating current causes a disadvantage that the reduction of ozone generation is impaired.

Although these disadvantages are solved by applying only a DC voltage to the charging device to carry out charging,
There is a problem that it is difficult to obtain uniform charging. Therefore, according to Japanese Unexamined Patent Publication No. 5-341627, by using epichlorohydrin rubber, which is semiconductive by the rubber itself, in the elastic layer of the charging member (charging roller), the uniformity of charging and the withstand voltage are improved. Has been done.

[0007]

However, according to the charging member in which the elastic layer mainly composed of epichlorohydrin rubber is formed on the above-mentioned conventional conductive support, the non-adhesive surface is formed on the semiconductive elastic layer. Although a layer is formed, when it is used as a charger for a copying machine for a long period of time, residual toner particles that have slipped through the cleaning unit and remained on the photoconductor will adhere to the surface of the charging member that is in contact with the photoconductor. However, since toner, paper powder, and the like adhere to the surface of the charging member, there is a problem that the electric resistance of the charging member increases and the charging performance decreases. In other words, there is a problem that the durability of the charging member is low.

The present invention has been made in view of the above, and it is an object of the present invention to suppress the adhesion of toner, paper dust and the like to the surface of the charging member and improve the durability of the charging member. .

[0009]

In order to achieve the above object, a charging member according to a first aspect of the present invention has a surface layer mainly composed of polyvinyl butyral resin.

Further, in the charging member according to the second aspect, the surface layer is mainly composed of polyvinyl formal resin.

Further, in the charging device according to the third aspect, the elastic layer is mainly composed of epichlorohydrin rubber.

Further, the charging member according to a fourth aspect uses a DC voltage as a voltage applied to the conductive support in a state where the charging member is in contact with the image carrier.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, regarding a charging member of the present invention and a charging device using the same, a shape and a configuration example of the charging member of the present invention. A configuration example of the charging device of the present invention. A detailed description will be given with reference to the drawings.

Shape and Configuration Example of Charging Member of the Present Invention First, a shape example of the charging member of the present invention will be described. The charging member of the present invention is, for example, in the shape of a roller as shown in FIG.
Elastic layer 102 provided around the conductive support 101
And a surface layer 103 formed on the outer peripheral surface of the elastic layer 102.
It is composed of

In the figure, the conductive support 10
1, an adhesive layer that improves the adhesiveness between the elastic layer 102 and the surface layer 103 may be provided. For example, in the case of a roller shape, the conductive support 101 may be treated with a conductive primer such as synthetic rubber containing a conductive substance such as carbon black.

As the conductive support 101, a metal such as iron, stainless steel, aluminum or the like, a conductive resin such as a carbon black dispersed resin, a metal particle dispersed resin or the like can be used, and its shape is a rod shape, a plate shape or the like. Is used.

The elastic layer 102 has an electric resistance of 10 ⁷ to
Good results can be obtained with a range of 10 ⁹ Ω · cm.
Therefore, polar rubbers such as epichlorohydrin rubber, nitrile rubber, urethane rubber, chloroprene rubber, and acrylic rubber can be used as the material, but among them, the electric resistance of the rubber itself is relatively small, and further the environment resistance is high. It uses epichlorohydrin rubber because of its good properties.

The epichlorohydrin rubber is a homopolymer of epichlorohydrin (hereinafter referred to as ECO) E
Copolymer of CO and ethylene oxide (hereinafter referred to as EO), ECO and allyl glycidyl ether (hereinafter referred to as A)
There are copolymers with GE) and terpolymers of ECO, EO, and AGE (hereinafter referred to as GECO), but among them, the electrical resistance is relatively low and the electrical resistance has little environmental dependence. GECO is preferable from the standpoint of the above.

The layer thickness of the elastic layer 102 is 0.5 to 1
Good results are obtained in the range of 0 mm. The reason for this is that when the layer thickness of the elastic layer 102 is smaller than 0.5 mm, the organic photoreceptor (hereinafter referred to as OPC) may be dielectrically broken, the charging may become unstable, and pinholes may be formed in the OPC. If there is, the current concentrates on that part and leaks easily occur,
As a result, horizontal stripes will appear in the image. If the layer thickness of the elastic layer 102 is thicker than 10 mm, the charging efficiency is lowered and a higher voltage needs to be applied, resulting in an increase in the cost of the power supply.

As the surface layer 103 covering the surface of the elastic layer 102, a non-adhesive coating having a thickness of 1 to 20 μm is formed. This is because the formation of the surface layer 103 suppresses adhesion of toner and the like to the surface of the charging member and maintains good charging characteristics for a long period of time.

For this purpose, polyvinyl butyral resin or polyvinyl formal resin is mainly used as a non-adhesive material formed on the surface of the elastic layer 102.

The polyvinyl butyral resin and polyvinyl formal resin constituting the surface layer 103 are subjected to acid saponification of polyvinyl acetate with hydrochloric acid or sulfuric acid as a catalyst, and a solution of an aldehyde is added at the initial stage of saponification to carry out the saponification and condensation reactions. It can be synthesized by a method such as once.

Since these resins have three components of vinyl acetal group, vinyl alcohol group and vinyl acetate group in the molecular chain, they are excellent in solvent solubility.

[0024]

Embedded image

Although it is crosslinkable by itself, the hydroxyl group in the vinyl alcohol group is elastic when crosslinked with various functional groups (phenol resin, melamine resin, epoxy resin, isocyanate, glyozal, etc.). Although it is possible to further improve the adhesiveness with the rubber layer and the film strength, it is preferable to crosslink the resin alone when importance is attached to the nonadhesiveness to the toner.

Configuration Example of Charging Device of the Present Invention Next, the configuration of the charging device of the present invention using the above charging member will be described with reference to FIG. In the figure, 201
Indicates the charging member of the present invention, and here, the roller-shaped charging member shown in FIG. 1 is used. Reference numeral 202 denotes a DC power source for applying a DC voltage to the core of the charging member 201. The charging member 201 and the DC power source 202 constitute the charging device of the present invention.

FIG. 2 shows an example in which the charging device of the present invention is applied to an electrophotographic device. This electrophotographic device has a primary charging member 2 on the peripheral surface of a drum-shaped electrophotographic photosensitive member 203.
01, image exposure device (not shown), developing unit 204,
A transfer charging device 205, a cleaning device 206, and a pre-exposure device (not shown) are arranged. In the figure, 207 is the exposure light emitted from the image exposure device, and 20 is the exposure light.
Reference numeral 8 indicates pre-exposure light of the pre-exposure device, and 209 indicates a transfer target member such as paper.

For example, an electrophotographic photoreceptor 20 such as OPC
Primary charging member (charging member 20
The voltage (for example, −
1400 V) is applied to charge the surface of the electrophotographic photosensitive member 203, and the image on the document is exposed to the electrophotographic photosensitive member 203 by an image exposure device to develop an electrostatic latent image.

Next, the developer in the developing unit 204 is made to adhere to the electrophotographic photosensitive member 203 to develop the electrostatic latent image on the electrophotographic photosensitive member 203, and further to develop on the electrophotographic photosensitive member 203. The transfer charging device 205 transfers the agent to a transfer target member 209 such as paper, and the cleaning device 206 recovers the developer remaining on the electrophotographic photosensitive member 203 without being transferred to the paper at the time of transfer. Further, when residual charge remains on the electrophotographic photosensitive member 203, it is preferable to remove the residual charge on the electrophotographic photosensitive member 203 by a pre-exposure device before performing the primary charging by the charging member 201.

The process leading to the present invention has been described above by explaining the shape and configuration example of the charging member of the present invention and the configuration example of the charging device of the present invention. However, uniform charging is achieved only by applying a DC voltage. The charging uniformity of the charging member 201 of the present invention, which is to be obtained, is naturally different from that of a conventional charging roller (for example, Japanese Patent Laid-Open Nos. 64-73364 and 64-73367) which is left to superimpose an AC voltage. The electrical characteristics (R, C) and the layer structure of the rollers are greatly different. That is, the AC voltage superposition type is a conductive elastic layer (rubber in which conductive particles such as carbon black are dispersed).
Since the surface resistance layer functions as a capacitor, the electrostatic capacity is large and the effect of equalizing the charging potential by superimposing an AC voltage is large.

On the other hand, in the DC voltage application only type of the present invention, the roller layer acts as a resistor (ie,
Since the electrostatic capacity is small), superimposing an AC voltage hardly contributes to uniform charging.

Embodiments 1 to 4 Hereinafter, a charging member of the present invention will be described in the order of [Embodiment 1], [Embodiment 2], [Embodiment 3], [Embodiment 4] with reference to the drawings. To do.

[Embodiment 1] In Embodiment 1, a charging member is prepared by the following method. First, as the conductive support 101, a φ8 mm stainless steel core is used. Next, the semiconductive elastic layer 102 is made of the following compound. GECO-based epichlorohydrin (Product name: Epichroma CG102, manufactured by Daiso) 100 parts by weight Light calcium carbonate 30 parts by weight Sub (Product name: GT, manufactured by Tenma Sub Chemical Co., Ltd.) 10 parts by weight Stearic acid 0.5 parts by weight Vulcanization accelerator (product) Name: Nocceller TT, manufactured by Ouchi Shinko Chemical Co., Ltd. 1.0 part by weight vulcanization accelerator (Product name: Noxceller DM, manufactured by Ouchi Shinko Chemical Co., Ltd.) 1.5 parts by weight vulcanization accelerator (Product name: Balnock R, large Uchishinko Chemical Co., Ltd.) 1.0 part by weight Vulcanizing agent (trade name: Salfax, Tsurumi Chemical Co., Ltd.) 0.25 parts by weight The composition ratio of this GECO-based epichlorohydrin is
ECO: 40 mol%, EO: 53 mol%, AGE: 7 mol%.

After the above mixture was kneaded to form a compound having a uniform composition, primary vulcanization (molding method: 150 ° C. × 1) was performed on a φ8 mm stainless steel core (conductive support 101).
5 minutes), secondary vulcanization (molding method: 155 ° C x 7 hours)
A roller-shaped semi-conductive elastic roller was provided by molding to have an outer diameter of 14 mm × 310 mm. The electric resistance of this semiconductive elastic roller is 2 × 10 ⁷ Ω · cm,
The roller rubber hardness was 38 degrees (JisA).

The volume resistance of the semiconductive elastic roller is measured by
The semi-conductive elastic roller was set to 20 ° C and 60% R.C. After left in H environment for 16 hours, a copper foil tape (product name: made by Scotch No. 1181, 3M) with a width of 25.4 mm is wrapped around the circumference of a semiconductive elastic roller to form an electrode, and a roller core metal. A direct current of 1 KV was applied between the electrode and the electrode, and the current value 1 minute later was measured to obtain the resistance value between the roller core metal and the electrode. Also, the rubber hardness of the semi-conductive elastic roller is measured by JisK6.
Using a hardness meter JisA described in No. 301, pressure was applied perpendicularly to the central axis direction of the semiconductive elastic roller for measurement.

Next, the surface layer 103 was formed on the semiconductive elastic roller as follows. First, the resin solution as the surface layer coating material was prepared as follows.

5 parts by weight of polyvinyl butyral resin (trade name: Denka Butyral # 3000-2, manufactured by Denki Kagaku Kogyo) and 95 parts by weight of a mixed solvent of ethanol: toluene = 1: 1 were added to obtain a uniform resin solution.

Then, the resin solution was spray-coated on the semiconductive elastic roller so that the film thickness was 5 μm, and then dried and cured at 150 ° C. for 60 minutes to prepare a charging roller.

The composition of the Denka butyral # 3000-2 used as the polyvinyl butyral resin (wt.
%) Is polyvinyl butyral (hereinafter referred to as PVB)
Is 75 or more, polyvinyl alcohol (hereinafter, referred to as PVA) 18 to 22, and polyvinyl acetate (hereinafter, referred to as PVAC) is 3.0 or less.

The charging roller (charging member) manufactured as described above is a regular development type copying machine FT5500 (manufactured by Ricoh).
Installed instead of the primary corona charger, the photoconductor (OP
C) The drum surface was brought into contact with the surface of the drum so as to be driven to rotate.
Apply a DC voltage of -1.3 KV as the primary charging voltage, and
Operate continuously in an environment of 4 ± 1 ℃, 50-55%, measure the potential of the dark potential of the photoconductor at the initial stage, every 5000 sheets, 10000 sheets (each A4 size), the contamination state of the charging roller surface, the image quality Was measured and evaluated.

The results of the above measurements and evaluations are shown in Table 1.
The state of contamination of the surface of the charging roller with toner etc. was evaluated according to the following criteria. Double circle: A slight amount of toner adheres, but you can easily wipe off the adhered matter on the roller surface with a cloth. ◯: A small amount of toner etc. remains on the roller surface after wiping. Δ: The film cannot be completely wiped off, and a thin film of toner or the like remains on the roller surface. X: Toner or the like is strongly adhered to the roller surface.

[0042]

[Table 1]

Example 2 The surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows. First, a resin solution as a surface layer coating material was prepared as follows.

3 parts by weight of polyvinyl butyral resin (trade name: Denka Butyral # 3000-K, manufactured by Denki Kagaku Kogyo) and 97 parts by weight of a mixed solvent of methanol: toluene = 1: 1 were added to prepare a uniform resin solution.

Then, in the same manner as in Example 1, the resin solution was spray-coated on the semiconductive elastic roller so as to have a film thickness of 5 μm, and then dried and cured at 150 ° C. for 60 minutes to prepare a charging roller.

Table 1 shows the results of measuring and evaluating the charging roller (charging member) thus prepared in the same manner as in Example 1.
The composition of Denka butyral # 3000-K used as the polyvinyl butyral resin is shown in Table 1.

Example 3 A surface layer 103 was formed on a semiconductive elastic roller similar to that of Example 1 as follows. First, a resin solution as a surface layer coating material was prepared as follows.

5 parts by weight of polyvinyl formal resin (trade name: Denka formal # 30, manufactured by Denki Kagaku Kogyo) and 95 parts by weight of a mixed solvent of methanol: toluene = 3: 7 were added to obtain a uniform resin solution.

Then, as in Example 1, the resin solution was spray-coated on the semiconductive elastic roller so as to have a film thickness of 5 μm, and then dried and cured at 150 ° C. for 120 minutes,
A charging roller was created.

Table 1 shows the results of measuring and evaluating the charging roller (charging member) prepared in the same manner as in Example 1.
The composition (wt%) of Denka formal # 30 used as the polyvinyl formal resin is 81 or more for polyvinyl formal (hereinafter referred to as PVF), 4.5 to 5.5 for PVA, and 10 to 13 for PVAC. .

Example 4 The surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows. First, a resin solution as a surface layer coating material was prepared as follows.

4 parts by weight of polyvinyl formal resin (trade name: Denka Formal # 100, manufactured by Denki Kagaku Kogyo) and 96 parts by weight of a mixed solvent of ethanol: toluene = 4: 6 were added to obtain a uniform resin solution.

Then, as in Example 1, the resin solution was spray-coated on the semiconductive elastic roller so that the film thickness was 5 μm, and then dried and cured at 160 ° C. for 120 minutes,
A charging roller was created.

Table 1 shows the results of measuring and evaluating the charging roller (charging member) thus prepared in the same manner as in Example 1.
The composition of Denka formal # 100 used as the polyvinyl formal resin is shown in Table 1.

Comparative Example 1 Here, as a comparative example, Comparative Example 1
Was created as follows. The roller having only the semiconductive elastic layer 102 of Example 1 was evaluated in the same manner as in Example 1, and the evaluation results are shown in Table 1.

COMPARATIVE EXAMPLE 2 Here, Comparative Example 2 is used as a comparative example.
Was created as follows. The surface layer 103 was formed on the same semiconductive elastic roller as in Example 1 as follows. First, the surface layer coating material was prepared as follows.

Fluoroolefin hydroxyl group-containing vinyl ether copolymer (trade name: LUMIFLON LF601C main agent,
100 parts by weight of Asahi Glass), 9 parts by weight of an isocyanate curing agent (trade name: Coronate HX, made by Nippon Polyurethane Industry Co., Ltd.), and 500 parts by weight of a mixed solvent of toluene: xylene = 1: 1 are sufficiently stirred to form a uniform solution. This is designated as solution A.

5 parts by weight of the GECO type epichlorohydrin (trade name: Epichroma CG102, manufactured by Daiso) and 95 parts by weight of a mixed solvent of toluene: 4methyl-2-pentanone = 1: 1 were added, and the mixture was sufficiently stirred to dissolve the raw rubber. To prepare a solution for adjusting electric resistance, and this solution is referred to as solution B.

Next, 100 parts by weight of the solution A and 40 parts by weight of the solution B were added and sufficiently stirred to prepare a surface layer coating material. Using this surface layer coating composition, as in Example 1, the semiconductive elastic roller was spray-coated to a film thickness of 5 μm and then dried and cured at 100 ° C. for 120 minutes to prepare a charging roller.

Table 1 shows the results of measuring and evaluating the charging roller (charging member) prepared in the same manner as in Example 1.

As described above, according to the present embodiment, by using the charging member of the present invention in the charging device for applying the DC voltage, the non-adhesiveness to the toner and the charging characteristic can be maintained almost the initial characteristic for a long period of time. It was possible to obtain stable image quality.

[0062]

As described above, according to the charging member of the present invention (claim 1), since the surface layer is mainly composed of polyvinyl butyral resin, the surface of the charging member is non-adhesive to toner. As a result, the toner adhesion on the surface of the charging member is suppressed, and stable charging characteristics can be obtained for a long period of time, so that good output image quality can be maintained.

Further, according to the charging member of the present invention (claim 2), since the surface layer is mainly composed of polyvinyl formal resin, the non-adhesiveness of the surface of the charging member to the toner is improved. Toner adhesion on the surface of the charging member is suppressed, and stable charging characteristics can be obtained for a long period of time, so that good output image quality can be maintained.

According to the charging device of the present invention (claim 3), since the elastic layer is mainly composed of epichlorohydrin rubber, that is, the elastic layer is made of a non-dispersive semiconductive material. , It is possible to improve the uniformity of charging when a DC voltage is applied and the environment resistance.

According to the charging member of the present invention (claim 4), since a DC voltage is used as the voltage applied to the conductive support while the charging member is in contact with the image carrier, a DC voltage is applied. Only with this, uniform charging is possible, and compared with the application method in which an AC voltage is superimposed on a DC voltage, the ozone generation amount can be reduced and the power supply cost can be further reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a shape and a configuration example of a charging member of the present invention.

FIG. 2 is an explanatory diagram showing an example in which the charging device of the present invention is applied to an electrophotographic device.

[Explanation of symbols]

 101 Conductive Support 102 Elastic Layer 103 Surface Layer 201 Charging Member 202 DC Power Supply

Claims (4)

[Claims] 1. A semiconductive elastic layer on a conductive support,
A charging member having two layers of a surface layer covering the surface of the elastic layer, wherein the surface layer is mainly composed of polyvinyl butyral resin. 2. A semiconductive elastic layer on a conductive support,
A charging member having two surface layers covering the surface of the elastic layer, wherein the surface layer is mainly composed of polyvinyl formal resin. 3. The charging member according to claim 1, wherein the elastic layer is mainly composed of epichlorohydrin rubber. 4. The charging member according to claim 1, wherein the charging member is in contact with an image carrier,
A charging device characterized in that a direct current voltage is used as a voltage applied to the conductive support.