JP3364056B2 - Charging member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member for electrophotography, and more particularly, but not exclusively, to charging a photosensitive member for image formation in contact with or very close to the photosensitive member. The present invention relates to a charging member or a charging member that contacts or comes in close proximity to a recording paper that has been brought into contact with a photoconductor for transfer, and charges it for transfer. This type of charging member is used, for example, in a copying machine, a facsimile or a laser printer.

[0002]

2. Description of the Related Art In an electrophotographic process, recently, a contact charging device for directly bringing a charging member into direct contact with a photoreceptor is disclosed in, for example, JP-A-63-167380. It has the advantage that it can be used at a lower applied voltage and has a smaller amount of ozone than the charging method, but it is inferior to the corona charging method in terms of charging uniformity.

In order to improve the uniformity of charging, it has been proposed to superimpose an AC voltage on a DC voltage and apply the AC voltage to a charging member (JP-A-63-149668, JP-A-64).
JP-A-733364, JP-A-64-73367), for example, in JP-A-63-149668,
It has been proposed to superimpose an AC voltage having a peak-to-peak voltage that is at least twice the starting voltage when a DC voltage is applied. However, in the contact charging in which charging is performed by applying a voltage obtained by superimposing the AC voltage and the DC voltage, noise (charging noise) due to mechanical vibration due to the AC voltage of the charging device is generated, and the environment becomes unpleasant. Consumption of a large amount of the alternating current causes a problem that the effect of reducing ozone generation is impaired.

Although these problems can be solved by applying only the DC voltage of the charging device to perform charging, there has been a problem that uniformity of charging is difficult to obtain. According to the publication, the use of epichlorohydrin rubber, which can provide semiconductivity by itself, is used for the elastic layer of the charging roller to improve the uniformity of charging and the electric resistance.

[0005]

However, Japanese Patent Application Laid-Open No. 5-3
In the charging member disclosed in Japanese Patent No. 41627, a non-adhesive surface layer is formed on the semiconductive elastic layer. However, when the charging member of the copying machine is used for a long period of time, toner and paper dust are formed on the charging member surface. As a result, the electric resistance of the charging member is increased, and there is a problem that the charging performance is reduced and charging unevenness occurs. That is, residual toner particles and the like that pass through the cleaning unit and remain on the photoreceptor adhere to the surface of the charging member that is in contact with the photoreceptor, which has the above-described adverse effect.

Accordingly, a first object of the present invention is to provide a charging member to which little dirt such as toner adheres, and a second object to provide a charging member which is unlikely to deteriorate the charging function. .

[0007]

In order to solve the above problems, a charging member having an elastic layer mainly composed of a synthetic resin on a conductive support and a polymer of paraxylylene on the elastic layer are provided. A surface layer composed mainly of a resin was provided.

The above-mentioned paraxylylene polymer has a structure of polyparaxylylene, polymonochloroparaxylylene, or polydichloroparaxylylene. The surface layer is a non-adhesive material to which dirt such as toner is unlikely to adhere, has little adhesion of residual toner etc. on an image carrier such as a photoreceptor drum, and is stable over a long period of time. The charging characteristics and output image quality can be maintained.

More specifically, the charging member of the present invention has, for example, a cross section as shown in FIG. 1 and a conductive support (charging roller shaft) in the form of a cored bar.
1 and a semiconductive elastic layer 2 provided therearound and a surface layer 3 formed on the outer peripheral surface of the elastic layer 2. Alternatively, as shown in FIG. 2, the charging member of the present invention covers a flat conductive support (core plate) 1 with a semiconductive elastic layer 2 and coats the elastic layer 2 with a surface layer 3. The lower surface S1, the upper surface S2, or the right side surface (end surface) may be in contact with or very close to a charge carrier (for example, a photosensitive drum). Is preferred. Further, as shown in FIG. 3, the charging member of the present invention comprises a pair of parallel conductive supports (belt supporting rollers) 1 and a surface layer 3 on an outer peripheral surface of a semiconductive elastic layer 2.
May be stretched on an endless belt formed with.

[0010] In addition to these layers 2 and 3, a layer such as an adhesive layer for improving the adhesion between the layers may be provided.
For example, in the case of a roller shape (FIG. 1), the conductive support 1 may be a conductive primer treated with a synthetic rubber containing a conductive substance such as carbon black.

As the conductive support 1, a metal such as iron, stainless steel, aluminum or the like, or a conductive resin such as a resin dispersed in carbon black and a resin dispersed in metal particles can be used. A plate shape or the like is used. The electric resistance of the semiconductive elastic layer 2 is 10 ⁷ to
A range of 10 ¹⁰ Ω · cm is preferred. As the material,
Epichlorohydrin rubber, nitrile rubber, urethane rubber, chloroprene rubber, acrylic rubber, etc., which are elastic rubbers, can be used. Among them, epichlorohydrin rubber has relatively low electric resistance and good environmental resistance. Is preferred.

The epichlorohydrin rubber includes epichlorohydrin homopolymer (abbreviation: CO), copolymer of epichlorohydrin and ethylene oxide (abbreviation: ECO),
Copolymers of epichlorohydrin and allyl glycidyl ether (abbreviation: GCO) and terpolymers of epichlorohydrin, ethylene oxide and allyl glycidyl ether (abbreviation: GECO), among which electric resistance is relatively low GECO is preferred from the viewpoint that the electric resistance hardly changes due to environmental fluctuation. Good results are obtained when the thickness of the semiconductive elastic layer 2 is in the range of 0.5 to 10 mm. When the electric resistance of the semiconductive elastic layer 2 is lower than 10 ⁷ Ω · cm and the layer thickness is thinner than 0.5 mm, the photoreceptor may be broken down or the charging may become unstable. If a pinhole is present in the body, the current is concentrated on that portion and leakage is likely to occur, resulting in horizontal stripes appearing in the image. Further, the electric resistance of the semiconductive elastic layer is larger than 10 ¹⁰ Ω · cm,
When the layer thickness is more than 10 mm, the charging effect is reduced, and a higher voltage needs to be applied.

The surface layer 3 formed on the outer peripheral surface of the semiconductive elastic layer 2 is a non-adhesive film having a thickness of 4 to 12 μm. Due to the surface layer 3, toner on the surface of the charging member
And the like, and the good charging characteristics are maintained over a long period of time.

The surface layer 2, which is a non-stick coating,
A paraxylylene polymer resin that has excellent non-adhesiveness to dust on or around the photoreceptor, such as toner, and has a small amount of abrasion. It is valid. Paraxylylene polymer resin is available from Union Carbide, Inc. (UCC)
More product "Paris-Len" has been announced.

The structure of the paraxylylene polymer is as shown below, and the name in [] indicates a trade name of UCC.

[0016]

(Equation 1)

These paraxylylene polymers are formed by a vapor phase vapor deposition polymerization method. For example, in the case of polyparasilylene, the polymerization mechanism comprises the following three steps.

[0018]

(Equation 2)

That is, the first step in which the solid dimer diparaxylylene (i) as a raw material is vaporized, the second step in which paraxylylene radical (ii) is generated by thermal decomposition of the dimer, This is the third step of simultaneously adsorbing and polymerizing paraxylylene radicals onto the adherend (elastic layer 2) to form a high molecular weight polyparaxylylene (iii) coating. The pressure during the process is 1/10 ³ to 10 ² kpa, the first process is 70 to 160 ° C., and the second process is 150 to 300 kPa.
C., the third step is performed at room temperature. The electric resistance of the paraxylylene polymer is 2 × 10 ¹² to 1 × 10 ¹³ Ω · c.
m, especially low polydichloroparaxylylene. Since this para-xylylene polymer has excellent chemical stability, its adhesion to the adherend (elastic layer 2) is as follows:
Not always good. For the coating material (surface layer 3), the adhesion to the adherend (elastic layer 2) is the most basic and one of the important issues.

The front surface of these with respect to the improvement of the adhesion of the deposited polymer material, adherend and is semi-conductive epichlorohydrin rubber elastic layer 2 or at least the elastic layer 2
To the epichlorohydrin rubber vulcanizate (elastic layer 2) by adding one or more of a mixture of silica, calcium carbonate, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide and iron oxide It was found that the adhesion of the paraxylylene polymer (surface layer 3) was improved. The reason for this adhesion is improved as polyparaxylylene of the surface layer 3 is, the elastic layer 2 on the surface at least in the elastic layer 2, aggregate at the surface of the material such as the silica and polymerized This is probably due to

The charging member (roller-shaped member shown in FIG. 1) of the present invention can be applied to an electrophotographic apparatus, for example, as shown in FIG. The electrophotographic apparatus includes a drum-shaped electrophotographic photosensitive member (photosensitive drum) 10 on a peripheral surface thereof.
Primary charging member (charging roller) 4, image exposure means (not shown) for providing image light 5, developing means 6, transfer charging means 7, cleaning means 8 and pre-exposure means (not shown) for providing static elimination light 9 ) Is arranged. The DC power supply 12 applies a voltage (for example, −) to the core 1 (FIG. 1) of the primary charging member 4 that is placed in contact with the electrophotographic photoreceptor 10 (for example, OPC).
1.4 kv), the surface of the electrophotographic photoreceptor 10 is charged, and the image on the original is image-exposed on the photoreceptor by image exposure means (5) to form an electrostatic latent image. Next, the developer (toner) in the developing means 6 is adhered to the photoreceptor,
The electrostatic latent image on the photoreceptor is developed, and the developer (toner) on the photoreceptor is transferred to a transfer receiving member 11 such as paper by a transfer charging means 7, and the paper is transferred by a cleaning means 8 during transfer. The developer (toner) remaining on the photoreceptor without being transferred to the photosensitive member is collected. In the case where residual charges remain on the photoreceptor 10, before performing the primary charging (4), the pre-exposure means irradiates the photoreceptor with the neutralizing light 9 to remove the residual charges. FIG.
Alternatively, the charging members 4 a and 4 b shown in FIG. 3 are used instead of the primary charging member 4. Also, this type of charging member 4,
4a and 4b may be used for transfer instead of the transfer charging means 7.

The elastic layer 2 of the charging member of the present invention is preferably flame-retardant because a voltage is applied, and is particularly preferably UL.
-478 (standard for information processing and office equipment), it is preferable to have a flame resistance of 94-HB or more of UL-94 (combustion test of plastic material for parts of equipment).

Although the charging member of the present invention has been described in a somewhat more specific and somewhat detailed manner, the charging uniformity of the charging member of the present invention, which seeks to obtain uniform charging only by applying a DC voltage, depends on the superposition of the AC voltage. Conventional charging rollers (for example, those disclosed in JP-A-64-73364 and JP-A-64-73367) have their own electrical characteristics (R,
C) and the configuration of the roller layer are greatly different. That is, the AC voltage superposition type disclosed in the above publication comprises a conductive elastic layer (rubber in which conductive particles such as carbon black are dispersed) and a surface resistance layer, and the surface resistance layer serves as a capacitor. Since it functions, the capacitance is large, and the effect of uniforming the charging potential by the AC voltage superposition is large.

On the other hand, the above-mentioned charging member of the present invention is:
Only a DC voltage is applied, and the roller layer (2,
Since 3) acts as a resistor (has a small capacitance), even if an AC voltage is superimposed, it hardly contributes to uniform charging.

Other objects and features of the present invention will become apparent from the following description of embodiments.

[0026]

【Example】

Example 1 GECO-based epichlorohydrin 100.0 parts by weight (Epichroma CG-102: manufactured by Daiso) 15.0 parts by weight of calcium carbonate (whiten SO: manufactured by Shiroishi calcium) Tetramethylthiuram disulfide 1.0 part by weight (Noxera) -TT: Ouchi Shinko Chemical) Sulfur 0.3 parts by weight (Sulfax PMC: Tsurumi Chemical) Aluminum hydroxide 25.0 parts by weight (Heidilite H42S: Showa Denko) Antimony trioxide 7.0 parts by weight ( Atox S: Nippon Seimitsu) Chlorinated paraffin 15.0 parts by weight (Empara 70: Ajinomoto) The composition ratio of Epichroma CG-102 is epichlorohydrin 40 mol%, ethylene oxide 50 mol%, allyl glycidyl ether 4 mol% It is.

After sufficiently kneading the above mixture with a two-roll mill, a molding method (primary vulcanization: 150 ° C. × 15 minutes, secondary vulcanization: Fifteen
5 ° C. × 7 hours), the elastic layer 2 having an outer diameter of φ14 mm
(The embodiment shown in FIG. 1). The elastic roller (1) in this state
+2) The electric resistance is 2 × 10 ⁷ Ω · cm, and the rubber hardness of the roller, that is, the hardness of the elastic layer 2 is 38 degrees (JIS A).
Met.

In the measurement of the electric resistance of the roller (1 + 2), the roller (1 + 2) was measured at 20 ° C. and 60% R.F. After being left in an environment of H for 16 hours, a copper foil tape (manufactured by Scotch No. 1181: 3M) having a width of 25.4 mm was wound around the outer peripheral surface of the roller to form an electrode. DC 1 kv is applied between 1 and the electrode, and the current value one minute after that is measured,
The resistance between the cored bar 1 and the electrode was determined.

The hardness of the roller rubber (elastic layer 2) was measured by using a hardness meter JIS A described in JIS K6301 by applying pressure perpendicularly (radially) to the center axis of the roller. .

The elastic roller (1) manufactured as described above
+2), the surface layer 3 was formed as follows. That is, 20 g of dimer diparaxylylene was added to [2 × 1/1
0 ^3] under a reduced pressure of kpa, evaporated at 0.99 ° C., said elastic roller - was formed La (1 + 2) with a thickness of 4μm onto the surface of polyparaxylylene film. The time required for vapor deposition was 25 minutes. The electric resistance of the charging roller 4 (1 + 2 + 3) having the surface layer 3 formed on the elastic roller (1 + 2) was measured. The results are shown in the column of "Example 1" in Table 1.

[0031]

[Table 1]

[0032]

[Table 2]

The charging roller 4 produced as described above
(1 + 2 + 3) was mounted in place of the primary corona charger of the copier FT550 (manufactured by Ricoh Co., Ltd.) of the normal development system, and was brought into contact with the surface of a photoconductor (OPC) drum so as to be driven to rotate. As the primary charging voltage, a DC voltage of -1.4 kv is applied, and 24 ± 1 ° C., 50 to 55% R.V. H (continuous operation), initial (0), 5000, 10,000
The potential of the dark potential of the photoreceptor was measured for each sheet, the contamination state of the charged roller surface, and the image quality were measured and evaluated. The results are shown in the column of "Example 1" in Table 1. The state of contamination of the charged roller surface with toner was evaluated according to the following criteria: Double circle: Toner was slightly adhered, but the adhered material on the roller surface was easily removed with a cloth or the like. Can be wiped off, Single circle: Even with wiping, a slight amount of toner remains on the roller surface, Triangle: Cannot be completely wiped off, and thin film such as toner on the roller surface ×: Toner and the like are strongly adhered to the roller surface.

Example 2 GECO-based epichlorohydrin 100.0 parts by weight (Epichroma CG-102: manufactured by Daiso) Silica 15.0 parts by weight (Aerosil R972: manufactured by Nippon Aerosil Co., Ltd.) 10.0 parts by weight Stearic acid (manufactured by Asahi Denka) 0.5 part by weight Tetramethylthiuram disulfide 1.0 part by weight (NOXERA-TT: manufactured by Ouchi Shinko Chemical) Sulfur (Sulfax PMC: manufactured by Tsurumi Chemical) 0 0.3 parts by weight Antimony trioxide (Atox S: manufactured by Nippon Seimitsu) 7.0 parts by weight Chlorinated paraffin (Empara 70: manufactured by Ajinomoto) 15.0 parts by weight The above compound was prepared in the same manner as in Example 1. An elastic roller (1 + 2) was manufactured by processing. This elastic roller (1+
The electric resistance of 2) was 4 × 10 ⁷ Ω · cm, and the rubber hardness of the roller was 39 degrees (JIS A).

The elastic roller (1) manufactured as described above
+2) On the surface layer 3 was formed as follows. That is,
20 g of dimeric dimonochloroparaxylylene [8 ×
Evaporation was performed at 160 ° C. under a reduced pressure of 1/10 ⁴ ] kpa to form a 9 μm-thick polymonochloroparaxylylene film, that is, a surface layer 3 on the surface of the elastic roller (1 + 2). The time required for vapor deposition was 35 minutes. in this way,
A charging roller having a surface layer 3 formed on an elastic roller (1 + 2).
La 4 (1 + 2 + 3) was measured for electrical resistance and evaluated by an actual machine in the same manner as in Example 1. The results are shown in the column of "Example 2" in Table 1.

Example 3 GECO-based epichlorohydrin 100.0 parts by weight (Epichroma CG-102: manufactured by Daiso) Zinc oxide (manufactured by Shiroishi calcium) 5.0 parts by weight Aluminum oxide 10.0 parts by weight (alumina A-42) : Showa Denko) Sub (Pure Black Sub: Tenma Sub Kako) 10.0 parts by weight Stearic acid (Asahi Denka) 0.5 parts by weight Tetramethylthiuram disulfide 1.0 parts by weight (NOXERA-TT: Ouchi) Sulfur (Sulfax PMC: Tsurumi Chemical) 0.3 parts by weight Antimony trioxide (Atox: Nippon Seimitsu) 7.0 parts by weight Chlorinated paraffin (Empara 70: Ajinomoto) 15.0 parts by weight The above compound was processed in the same manner as in Example 1 to produce an elastic roller (1 + 2). This elastic roller (1+
The electric resistance of 2) was 2 × 10 ⁷ Ω · cm, and the rubber hardness of the roller was 38 degrees (JIS A). Next, a surface layer 3 was formed on the elastic roller (1 + 2) as follows.
That is, 20 g of dimer didichloroparaxylylene was evaporated at 160 ° C. under a reduced pressure of [8 × 1/10 ⁴ ] kpa, and the surface of the elastic roller (1 + 2) was 12 μm thick.
m of polydichloroparaxylylene, that is, a surface layer 3 was formed. The time required for the vapor deposition was 41 minutes. The electric resistance of the charging roller 4 (1 + 2 + 3) having the surface layer 3 formed on the elastic roller (1 + 2) in this manner was measured and evaluated by an actual machine in the same manner as in Example 1. Table 1 shows the results
In the column of “Example 3”.

Example 4 GECO-based epichlorohydrin 100.0 parts by weight (Epichroma CG-102: manufactured by Daiso) Titanium oxide (manufactured by Ishihara Sangyo) 10.0 parts by weight Iron oxide (manufactured by Toda Kogyo) 10.0 parts by weight Sub (Pure black sub: manufactured by Tenma Sub Kako) 12.0 parts by weight Stearic acid (manufactured by Asahi Denka) 0.7 parts by weight Tetramethylthiuram disulfide 1.2 parts by weight (Noxera-TT: manufactured by Ouchi Shinko Chemical) Sulfur (Sulfax PMC: Tsurumi Chemical) 0.3 parts by weight Antimony trioxide (Atox: Nippon Seimitsu) 7.0 parts by weight Chlorinated paraffin (Empara 70: Ajinomoto) 15.0 parts by weight An elastic roller (1 + 2) was manufactured by processing in the same manner as in Example 1. This elastic roller (1 + 2)
Had an electrical resistance of 8 × 10 ⁷ Ω · cm and a rubber hardness of 36 degrees (JIS A). Next, a surface layer 3 was formed on this elastic roller (1 + 2) in the same manner as in Example 3. That is, a polydichloroparaxylylene coating (surface layer 3) was formed. Thus, the elastic roller (1 + 2)
The electrical resistance of the charging roller 4 (1 + 2 + 3) on which the surface layer 3 was formed was measured and evaluated in the same manner as in Example 1. The results are shown in the column of "Example 4" in Table 2.

Comparative Example 1 A roller having only the elastic roller (1 + 2) of Example 1 was evaluated in the same manner as in Example 1, and the result is shown in the column of "Comparative Example 1" in Table 2. .

Comparative Example 2 An elastic roller (1 + 2) was produced in the same manner as in Example 2 except that the silica was completely removed from the elastic roller composition. The electric resistance of this elastic roller was 1 × 10 ⁷ Ω · cm, and the rubber hardness of the roller was 34 degrees (JIS A). The surface layer 3 was formed on the elastic roller thus manufactured by the method of the second embodiment.
It was formed in the same manner as described above. That is, a polymonochloroparaxylylene film (surface layer 3) was formed. The thickness of the formed film was 10 μm. This charging roller (1 + 2 + 3)
Was measured in the same manner as in Example 1. The results are shown in the column of "Comparative Example 2" in Table 2. Comparative Example 3 Elastic roller was prepared in the same manner as in Example 3 except that the total amount of zinc oxide and aluminum oxide was removed from the elastic roller formulation.
La (1 + 2) was made. The electric resistance of the elastic roller (1 + 2) was 2 × 10 ⁷ Ω · cm, and the rubber hardness of the roller was 35 degrees (JISA). The surface layer 3 was formed on the elastic roller (1 + 2) thus manufactured in the same manner as in the third embodiment. That is, a film (surface layer 3) of polydichloroparaxylylene was formed. The thickness of the formed film was 9 μm. The electrical resistance of this charging roller (1 + 2 + 3) was measured and evaluated in an actual machine in the same manner as in Example 1. The results are shown in the column of "Comparative Example 3" in Table 2.

The above results (Example 1 in Tables 1 and 2)
4 and Comparative Examples 1 to 3), it is clear that by using the charging member 4 of the present invention by applying a DC voltage,
The non-adhesiveness to the toner or the like and the charging characteristics are maintained substantially the same as the initial characteristics for a long period of time. That is, stable image quality can be obtained for a long period of time.

[0041]

Since the non-adhesiveness of the surface of the charging member is improved, toner adhesion to the surface of the charging member is suppressed, and a stable charging performance can be obtained over a long period of time. Output image quality can be maintained.

In the embodiment in which the adhesion of the surface layer to the elastic layer is improved by the additive, the surface layer is hardly peeled off and can be used for a long time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of the present invention.

FIG. 2 is a cross-sectional view of another embodiment of the present invention.

FIG. 3 is a cross-sectional view of another embodiment of the present invention.

4 is a cross-sectional view of an electrophotographic apparatus in which the charging roller 4 shown in FIG. 1 is incorporated in one mode.

[Explanation of symbols]

1: conductive support 2: semiconductive elastic layer 3: surface layer 4: primary charging member (charging roller) 5: image light for image exposure 6: developing means 7: transfer means 8: cleaning Means 9: static elimination light 10: drum-shaped photoreceptor 11: member to be transferred 12: DC power supply

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 15/08 501 G03G 15/16 103

Claims (4)

(57) [Claims] 1. A charging member having an elastic layer mainly composed of a synthetic resin on a conductive support, wherein a surface layer composed of a resin mainly composed of a paraxylylene polymer is provided on the elastic layer. Charging member. 2. The charging member according to claim 1, wherein the polymer of paraxylylene is polyparaxylylene, polymonochloroparaxylylene or polydichloroparaxylylene. 3. The method according to claim 1, wherein at least one of silica, calcium carbonate, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide and iron oxide is added to at least the surface of said elastic layer. 2. The charging member according to 2. 4. The charging member according to claim 1, wherein the synthetic resin that is the main component of the elastic layer is epichlorohydrin rubber.