JP2661435B2 - Proximity charging device - 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 device which can be used in an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, a corona charger such as a corotron or a scorotron has been widely used for charging a photosensitive member in an electrophotographic apparatus such as an electrophotographic copying machine and an electrophotographic printer. This corona charger requires a high voltage of 4 to 7 kV in order to charge the photoreceptor, and has a drawback that a large amount of ozone is generated and the deterioration of the photoreceptor is accelerated. In addition, as the awareness of the environment has increased in recent years and printers and other devices have become smaller and more personalized, the amount of ozone generated, which is harmful to the human body, has increased due to the increased use of such devices near desks and other human bodies. There has been a demand for a charging device having a small number of charges.

Under these circumstances, contact charging methods such as roller charging have recently been reviewed, and some of them have been put to practical use. Roller charging is a process in which a metal core is coated with conductive rubber or the like, and a roller-shaped member is brought into contact with a latent image holding member, and a voltage is applied between the core metal of the roller and the latent image holding member. Then, the surface of the latent image holding member is charged. This charging method has the characteristics that the applied voltage is low and the amount of generated ozone is small (see, for example, JP-A-63-149669).

However, in this roller charging method, since the roller and the latent image holding member are always in contact with each other, there is a disadvantage that both the roller and the latent image holding member are easily deformed, and this is likely to appear as an indentation on the image. Was. Also,
Since the roller and the latent image holding member are in contact, additives and the like that exude from the rubber of the roller move to the latent image holding member,
There is also a problem that the surface of the latent image holding member is contaminated.

Further, although the voltage applied to the roller is relatively low, the voltage applied to the roller is directly applied to the latent image holding member at the contact surface between the roller and the latent image holding member. There was also a problem that it became strong stress. In order to solve such a problem, as a charging method that does not bring a roller or the like into contact with the latent image holding member, as shown in, for example, Japanese Patent Application Laid-Open No. 58-76851, The surface is 1
A method has been proposed in which a conductor coated with a substance having a specific resistance of 0 ⁴ -10 ¹⁰ Ωcm is provided, and a DC voltage is applied between the conductor and the latent image holding member to charge the latent image holding member. . As for the latent image holding member which is the core of the electrophotographic technology, an inorganic photoconductive substance such as selenium, arsenic-selenium alloy, cadmium sulfide, zinc oxide, amorphous silicon or the like has been conventionally used as the photoconductive material. However, recently, various organic photoconductive substances which are non-polluting and advantageous in film forming property and productivity have been developed. Among the organic latent image holding members, a charge generation layer and a charge transport layer were laminated,
A so-called function-separated type latent image holding member is widely used in practice because of its high sensitivity and long life.

[0006]

However, in the case where a charging device is used for charging in the vicinity of the latent image holding member (1) In general, the photoconductive layer of the latent image holding member is provided on a conductive substrate. If there is a defect in the conductive layer, current from the charging member is concentrated, the latent image holding member is charged unevenly, and a band-like image defect occurs. Also, at this time, the charging member itself is damaged by the concentration of the current and cannot be used. (2) If defects such as adhesion of foreign matter, dirt, and fine holes are present on the surface of the base, image defects caused by the defects may appear on the copy. (3) In the case of the reversal development method, image defects such as minute black spots and background fog may appear on a copy. In particular, under high humidity environmental conditions, ground fog is extremely unpractical.

In the reversal developing method, a dark potential portion becomes a white background and a bright potential portion becomes a black background (image area). However, in this system, if a local charging defect due to a defect or the like exists on the latent image holding member. If there are a large number of black spots on a white background, development such as background fogging will occur, resulting in a remarkable image defect. Even if such a local charging failure does not cause any problem when used in regular development, it is easy to cause an image failure in reversal development, and furthermore, a conventionally obtained laminated latent image It was found that the holding member had problems with black spots and fogging to some extent.

Although various causes can be considered as the cause of this problem, that is, local charging failure, there is a case where charge injection occurs locally between the conductive substrate as the electrode and the photoconductive layer and the charging potential does not rise. it is conceivable that. Accordingly, the present inventors have conducted various studies to solve these problems, and as a result, in a device in which a charging unit is brought into proximity with a latent image holding member to perform charging, an image defect is caused by using a specific latent image holding member. The present inventors have learned that a charging device is less likely to occur, and the present invention has been achieved.

[0009]

That is, the gist of the present invention is to apply a voltage between a latent image holding member and a charging means held in close proximity to the latent image holding member so that the latent image holding member is charged. The latent image holding member is provided with a photoconductive layer on an aluminum substrate whose surface is anodized.

In the present invention, the proximity is close,
The minute gap refers to a situation where the gap is maintained. Hereinafter, the present invention will be described in detail. In general, materials used as a base of the latent image holding member include aluminum, iron, stainless steel, copper,
Examples include zinc, nickel, conductive plastic, and glass. Among them, aluminum, which is relatively inexpensive, lightweight, has good workability, and does not impair the electrical characteristics, is widely used.

Usually, when aluminum is used as a drum-shaped substrate, the aluminum buret is formed into an extruded tube by a porthole method, a mandrel method, or the like, and then drawn to obtain a drum having a predetermined thickness and outer dimensions. It can be made by performing processing, impact processing, ironing, and the like. However, for example, extrusion processing is usually performed under high temperature and high pressure, so that the surface of the aluminum drum is rough, and the precipitation of dissimilar metals occurs during cooling,
In this state, various defects are formed on the drum surface, and it is difficult to produce a satisfactory product. For this reason, the surface is further cut or, in some cases, another conductive layer is provided on the drum surface and used, but it still has a uniform enough surface for practical use. It can not be said.

The aluminum substrate used in the present invention can be obtained in a desired shape by a process such as drawing, impact, or ironing as described above. Further, mirror finishing by cutting is performed as necessary. The aluminum substrate is preferably degreased by various degreasing methods such as acid, alkali, organic solvent, surfactant, emulsion, and electrolysis before the anodic oxidation treatment is performed.

The anodizing treatment is usually carried out, for example, with chromic acid,
It is carried out in an acidic bath of sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the best results. In the case of anodic oxidation in sulfuric acid,
Sulfuric acid concentration is 50-400g / l, dissolved aluminum concentration is 2-
20 g / l, liquid temperature 10-40 ° C, electrolysis voltage 5-30
V and the current density are preferably set in the range of 0.5 to ² A / dm ² .

The average thickness of the anodic oxide film is 0.1 to
Preferably, it is formed to have a thickness of 20 μm. More preferably, it is 1 to 10 μm. The anodic oxide film formed in this manner is, for example, a low-temperature sealing treatment in which the film is immersed in an aqueous solution containing nickel fluoride as a main component, or contains nickel acetate as a main component in order to enhance the stability of the film. It is preferable to perform high-temperature sealing treatment immersed in an aqueous solution and other sealing treatments such as steam sealing and boiling water sealing.

The concentration of the aqueous nickel fluoride solution used in the case of the low-temperature sealing treatment can be appropriately selected, but is most effective when used in the range of 2 to 10 g / l. In order to smoothly proceed with the sealing process, the processing temperature is set to 15
-40 ° C, preferably 25-35 ° C, and the pH of the aqueous nickel fluoride solution is 4.5-6.5, preferably 5.5-5.5.
It is better to process within the range of 6.0. In this case, oxalic acid, boric acid, formic acid, acetic acid, sodium hydroxide, sodium acetate, aqueous ammonia or the like can be used as the pH adjuster. The processing time is preferably within a range of 1 to 3 minutes per 1 μm of the film thickness. In order to further improve the physical properties of the film, cobalt fluoride, cobalt acetate, nickel sulfate, a surfactant and the like may be added to the nickel fluoride aqueous solution. Next, it is washed with water and dried to complete the low-temperature sealing treatment.

As the sealing agent for the high-temperature sealing treatment, an aqueous solution of a metal salt such as nickel acetate, cobalt acetate, lead acetate, nickel-cobalt acetate, barium nitrate, etc. can be used. In particular, nickel acetate is used. Is preferred. The concentration when using an aqueous nickel acetate solution is 3 to 20.
It is preferably used within the range of g / l. Processing temperature is 6
The treatment is preferably performed at 5 to 100 ° C., preferably 80 to 98 ° C., and the pH of the aqueous nickel acetate solution is in the range of 5.0 to 6.5. Here, ammonia water, sodium acetate, or the like can be used as the pH adjuster.

The processing time is 10 minutes or more, preferably 20 minutes or more. Also in this case, sodium acetate, an organic carboxylate, an anionic or nonionic surfactant may be added to the nickel acetate aqueous solution in order to improve the film properties. Then, after washing with water and drying, the high-temperature sealing treatment is completed. Although the photoconductive layer is provided on the anodic oxide film formed as described above, a known undercoat may be provided between the anodic oxide film and the photoconductive layer. Examples of the undercoating material include polyvinyl alcohol, casein, casein sodium, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, and phenol resin. The thickness of the undercoat layer is preferably 5 μm or less, particularly preferably 2 μm or less.

As the photoconductive layer provided on the substrate formed as described above, various inorganic and organic photoconductive layers can be used, and a laminated photoconductive layer comprising a charge generation layer and a charge transfer layer can be used. Layers are very useful. Selenium and its alloys, arsenic-selenium,
Various organic pigments such as cadmium sulfide, zinc oxide and other inorganic photoconductors, phthalocyanine, azo, quinacridone, polycyclic quinone, perylene, indigo, and benzimidazole can be used.

Above all, azo pigments such as monoazo, bisazo, trisazo and polyazo; metal-free phthalocyanine; metals such as copper, indium chloride, gallium chloride, tin, oxytitanium, zinc and vanadium, or oxides and chlorides thereof Are preferred.
The charge generation layer is formed as a uniform layer of these substances or in a state where fine particles are dispersed in a binder. The binder resin used here is polyvinyl butyral,
Phenoxy resin, epoxy resin, polyester resin, acrylic resin, methacrylic resin, polyvinyl acetate, polyvinyl chloride, methyl cellulose, polycarbonate resin, and the like. The photoconductor is preferably contained in an amount of 20 to 300 parts by weight, more preferably 30 to 150 parts by weight, based on 100 parts by weight of the binder resin. The thickness of such a charge generation layer is usually 5 μm or less, preferably 0.01 to
1 μm, more preferably 0.15 to 0.6 μm, is suitable.

As the charge transfer material used in the charge transfer layer, various known materials can be used. Examples thereof include hydrazone derivatives, pyrazoline derivatives, heterocyclic derivatives such as carbazole, indole and oxadiazole, derivatives of arylamines such as triphenylamine, stilbene derivatives, and high molecular compounds having the above compound in the side chain or main chain. . Among them, hydrazone derivatives, arylamines and stilbene derivatives are more preferred charge transfer materials.

A binder resin is blended with these charge transfer materials as needed. Preferred binder resins include polymethyl methacrylate, polystyrene,
Vinyl polymers such as polyvinyl chloride and copolymers thereof,
Polyarylate resin, urethane, urea, melamine polycarbonate, polyester, polysulfone, phenoxy resin, epoxy resin, silicone resin, etc.
These partially crosslinked cured products are also used. 30 to 2 parts by weight of the charge transfer material in 100 parts by weight of the binder resin.
It is preferably contained in an amount of 00 parts by weight, particularly 50 to 150 parts by weight.

The charge transfer layer may contain various additives such as an antioxidant and a sensitizer, if necessary. The thickness of the charge transfer layer is usually 10 to 40 μm, preferably 10 to 40 μm.
Used with a thickness of ２５25 μm. As another example of the photoconductive layer, there is a dispersion type photoconductive layer obtained by dispersing the above-described photoconductor particles in a binder made of a binder resin and the above-mentioned charge transfer material. In this case, the total content of the photoconductor and the charge transfer material is preferably 20 to 200 parts by weight, more preferably 40 to 200 parts by weight, based on 100 parts by weight of the binder resin.
~ 150 parts by weight are preferred.

The shape of the charging means for charging the latent image holding member may be brush, blade, pin electrode, roller or the like. However, a roller shape is preferable for use, and it is preferable to employ some kind of linkage mechanism to rotate the latent image holding member in accordance with the rotation of the latent image holding member, or to rotate the latent image holding member by independently applying a driving force for rotation from outside. When the roller is rotated in this way, the surface used for charging is always changed, so the life of the charging means is prolonged, and a means for cleaning the charging means on the side opposite to the surface used for charging can be provided. Thus, the charged surface can always be kept clean, and the uniformity of charging can be maintained.

When the charging means is in the form of a roller, it usually comprises a core material and a charging member which covers the periphery of the core material. As the charging member, a conductor such as a metal and a semiconductor, or a conductive or semiconductive rubber obtained by adding conductive particles such as carbon or other semiconductive particles to an elastic body such as a rubber material is used. A roller-shaped charging member molded into a hollow cylinder can also be used. Further, the charging member may be divided into a supporting member and a surface member, and a charging member having an appropriate electric resistance held by the surface member may be used.

Hereinafter, the roller-shaped charging member will be described with reference to FIG. 1 showing an example of the charging device of the present invention. In the drawing, reference numeral 1 denotes a latent image holding member of the present invention. It is an inorganic and organic latent image holding member, and any shape such as a drum shape or a sheet shape can be used. In the figure, reference numeral 2 denotes a core material supporting the charging member. A bias potential is applied using this core bearing or other electrical contact means. Any material may be used as the material of the core as long as it has conductivity, and usually, metal is often used. Examples of metals include iron, copper, brass, stainless steel,
Aluminum, platinum, tungsten, etc. are available. In addition, a resin molded product in which a conductive organic material such as carbon is kneaded can be used.

In the drawing, reference numeral 3 denotes a roller-shaped support member. Any material may be used as the material of the support member as long as it has conductivity or semi-conductivity. Examples of conductive materials include iron,
Metals such as copper, brass, stainless steel, aluminum, platinum, and tungsten, and resin molded products in which a conductive organic material such as carbon is kneaded can also be used.
Of course, these materials may be manufactured and processed integrally with the core material and the support member using the same material as the core material. Other rubber materials such as NBR, EPDM, silicon, neoprene, or natural rubber materials and conductive rubber obtained by kneading conductive particles such as carbon or semiconductive particles into these rubbers are used. .

Further, a surface member 4 in the figure can be provided. The material is polyamide resin, cellulose resin,
Polyvinyl butyral resin, fluororesin, vinyl chloride resin, acrylic resin, and other various polyester resins are used as main components. As the resistivity of the surface member,
10 ³ -10 ¹⁴ Ωcm is good, preferably 10 ⁵ -10
^It is preferably ¹² Ωcm, more preferably 10 ⁷ -10 ¹² Ωcm. The thickness of the surface member is preferably large in consideration of the durability due to abrasion as the charging member. However, if the thickness is too large, the charging ability of the latent image holding member deteriorates.
000μ, preferably 0.1μ-500μ, more preferably 0.5μ-100μ. As a method of manufacturing the surface member, the surface member is formed on the support member by a dipping method, a spray method, a vacuum evaporation method, a plasma coating method, or the like. In these methods, the dip method is advantageous in terms of a manufacturing process. .

In order to charge the latent image holding member, a voltage is applied between the latent image holding member and the charging means. Normally, the voltage is applied to the charging member, that is, the core material. However, it is preferable that the applied voltage is obtained by superimposing an AC voltage on a DC voltage, and it is difficult to obtain a uniform charge by using only the DC voltage. Any alternating voltage may be used as long as it varies periodically. As the voltage range, the DC voltage is preferably positive or negative 50 to 2000 V, and particularly preferably 100 to 1500 V. As a superimposed AC voltage, a peak-to-peak voltage (V _pp ) is usually 400 to 1800.
V, preferably 800-1600 V, more preferably 1
200-1600V is suitable. When the peak-to-peak voltage (V _pp ) of the AC voltage exceeds 1800 V, the charging uniformity becomes worse than when no AC voltage is superimposed. The frequency of the AC voltage is preferably 100 to 2000 Hz. The gap between the surface of the latent image holding member and the surface of the charging means provided close to the latent image holding member is preferably 5 to 300 μm,
To 100 μm, more preferably 15 to 8
0 μm is good. If the gap is too large, it is difficult to obtain uniform charging even when a voltage obtained by superimposing an AC voltage on a DC voltage is applied.

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited to the following Examples without departing from the scope of the invention. Example 1 An aluminum extruded tube was ironed to a wall thickness of 0.
An aluminum cylinder having a length of 75 mm, an outer diameter of 30 mm and a length of 246 mm was prepared.

The aluminum cylinder was replaced with a degreasing agent NG.
6 in a 30 g / l aqueous solution of # 30 (Kizai Co., Ltd.)
Degreasing washing was performed at 0 ° C. for 5 minutes. Subsequently, after washing with water, it was immersed in 7% nitric acid at 25 ° C. for 1 minute. After further washing with water,
180 g / l sulfuric acid electrolyte (dissolved aluminum concentration 7
g / l) at an electric current density of 1.0 A / dm ² to form an anodic oxide film having an average film thickness of 6 μm. Then, after washing with water, a high temperature sealing agent Top Seal DX-500 (manufactured by Okuno Pharmaceutical Co., Ltd.) containing nickel acetate as a main component was used.
It was immersed in an aqueous solution of 0 g / l at 90 ° C. for 20 minutes to perform a sealing treatment. Subsequently, after washing with water, it was immersed in a hot water bath of 95 ° C. for 10 minutes, taken out and dried.

On the other hand, oxytitanium phthalocyanine 1
0 parts by weight, polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd.
To 5 parts by weight of Esrec BH-3) was added 500 parts by weight of 1,2-dimethoxyethane, and the mixture was pulverized and dispersed by a sand grind mill. An aluminum cylinder provided with the previously formed anodic oxide film was dip-coated on this dispersion, and a charge generation layer was provided so that the film thickness after drying was 0.4 μm.

Next, 56 parts by weight of the hydrazone compound represented by the following formula (1) and this aluminum cylinder were combined with the following formula (2).
14 parts by weight of a hydrazone compound represented by the following formula and 15 parts by weight of a cyano compound represented by the following formula (3):

[0033]

Embedded image

[0034]

Embedded image

[0035]

Embedded image

Para-3,5-di (tert-butyl)
8 parts by weight of hydroxytoluene and a polycarbonate resin (NOVAREX (registered trademark) 702, manufactured by Mitsubishi Kasei Corporation)
5A) Dip-coating in a solution in which 100 parts by weight of 1,4-dioxane was dissolved in 1000 parts by weight, and the film thickness after drying was 17
The charge transfer layer was provided to have a thickness of μm.

Next, a charging member was prepared using a stainless steel rod having a diameter of 6 mm as a core material and a roller having a diameter of 12 mm using a conductive EPDM rubber having a resistivity of 10 ⁸ Ωcm as a supporting member. Then, instead of the corona charger of a commercially available printer (PR406LM manufactured by NEC Corporation), the charging member was attached so that the gap between the roller surface of the charging member and the latent image holding member was 34 μm. A voltage obtained by superimposing Vp _-p 1500 V at a frequency of 1 kHz of an AC voltage on a DC voltage -700 V as a power supply bias is applied to the core material.
As a result of evaluation of the images, good images were obtained for white, black, and halftone images. Also, for a defect such as a local concave portion of the photoconductive layer, a black band-like image defect generated when current leaked did not occur.

Example 2 An image was evaluated in the same manner as in Example 1 except that a stainless steel metal roller in which a support member and a core material were integrally molded was used. As a result, images of white background, black background, and halftone were good. Image was obtained. Also, for a defect such as a local concave portion of the photoconductive layer, a black band-like image defect generated when current leaked did not occur.

Example 3 A 0.5 μm-thick film made of a polyamide resin was placed on a stainless steel metal roller in which a support member and a core material were integrally molded.
The image was evaluated in the same manner as in Example 1 except that a surface member having a resistivity of 10 ¹¹ Ωcm was provided.
Good images were obtained for both halftone images. Also, for a defect such as a local concave portion of the photoconductive layer, a black band-like image defect generated when current leaked did not occur.

Example 4 An image was evaluated in the same manner as in Example 1 except that an aluminum cylinder having a mirror-finished surface, a thickness of 1.0 mm, an outer diameter of 30 mm, and a length of 246 mm was used. Good images were obtained for both halftone images. Also, for a defect such as a local concave portion of the photoconductive layer, a black band-like image defect generated when current leaked did not occur.

Example 5 A stainless steel 12 m molded integrally with a support member and a core material
The images were evaluated in the same manner as in Example 4 except that a metal roller having a diameter of m was used. As a result, good images were obtained for white background, black background, and halftone images. Also, for a defect such as a local concave portion of the photoconductive layer, a black band-like image defect generated when current leaked did not occur.

Example 6 A stainless steel 12 m molded integrally with a supporting member and a core material
An image was evaluated in the same manner as in Example 4, except that a surface member having a film thickness of 0.5 μm and a resistivity of 10 ¹¹ Ωcm using a polyamide resin was provided on a metal roller having a diameter of m.
Good images were obtained for white, black, and halftone images.
Also, for a defect such as a local concave portion of the photoconductive layer, a black band-like image defect generated when current leaked did not occur.

Example 7-12 The gap between the roller surface of the charging member and the latent image holding member was 60 μm.
The evaluation was performed in the same manner as in Example 1-6, except that the value was changed to m. As a result, the same good results were obtained. Comparative Example 1 An aluminum cylinder was produced in the same manner as in Example 1.
Next, a charge generation layer and a charge transfer layer were sequentially formed in the same manner as in Example 1 except that the aluminum cylinder was degreased and washed with trichlene and an anodic oxide film was not provided.

Next, the same charging member as in Example 1 was manufactured. As in Example 1, as a result of evaluating the image, many image defects were observed especially in the halftone image, and the fog was large.

Comparative Example 2 A stainless steel 12 m molded integrally with a supporting member and a core material
The image was evaluated in the same manner as in Comparative Example 1 except that a metal roller having a diameter of m was used. As a result, many image defects were observed particularly in a halftone image, and fog was large. In addition, black band-like image defects generated when electric charge leaked also occurred for defects such as local concave portions of the photoconductive layer.

Comparative Example 3 An aluminum cylinder having a thickness of 0.75 mm, an outer diameter of 30 mm and a length of 246 mm was prepared. Next, the aluminum cylinder was degreased and washed with trichlene, and the image was evaluated in the same manner as in Example 3 except that the charge generation layer and the charge transfer layer were sequentially formed without providing the anodized film. Many image defects are seen in the image,
There were many fog.

Comparative Example 4 An aluminum cylinder having a mirror-finished surface and a thickness of 1.0 mm, an outer diameter of 30 mm and a length of 246 mm was prepared. Next, the aluminum cylinder was degreased and washed with trichlene, and the image was evaluated in the same manner as in Example 4 except that the charge generation layer and the charge transfer layer were sequentially provided without providing the anodic oxide film. Many image defects were found in the halftone image, and there were many fogs.

COMPARATIVE EXAMPLE 5 A stainless steel 12 m molded integrally with a support member and a core material
The image was evaluated in the same manner as in Comparative Example 4 except that a metal roller having a diameter of m was used. As a result, many image defects were observed particularly in a halftone image, and fog was large. In addition, a black band-like image defect that occurs when current leaks also occurs for a defect such as a local concave portion of the photoconductive layer.

Comparative Example 6 An aluminum cylinder having a mirror-finished surface with a thickness of 1.0 mm, an outer diameter of 30 mm and a length of 246 mm was prepared. Next, the aluminum cylinder was degreased and washed with trichlene, and the image was evaluated in the same manner as in Example 6 except that the charge generation layer and the charge transfer layer were sequentially provided without providing the anodic oxide film. Many image defects were found in the halftone image, and there were many fogs.

Comparative Example 7-12 The gap between the roller surface of the charging member and the latent image holding member was 60 μm.
As a result of evaluation in the same manner as in Comparative Examples 1 to 6 except that the value was changed to m, the same results as in Comparative Examples 1 to 6 were all obtained.

[0051]

According to the charging device obtained by the present invention, anodizing treatment is performed on an aluminum substrate which cannot be used as it is as a latent image holding member because the surface has many dirt, projections, scratches, dents and the like. Thereby, these defects can be removed. This makes it possible to provide a good proximity charging device that is less susceptible to image defects caused by image defects and defects such as local dents in the photoconductive layer when the proximity charging device is used.

Further, the charging device obtained by the present invention is
Even when used in a commercially available copying machine or an electrophotographic system including a reversal developing system process in which the defects in the substrate are more severe and an image is likely to appear, the latent image holding member does not come into contact with the charging means. , Without giving any deformation to both charging means
Indentations do not appear on the image, and additives and the like contained in the charging means do not migrate to the surface of the latent image holding member to deteriorate the image. Then, under a wide range of environmental conditions including high humidity, a good image with very little fog and other image defects can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of an example of a charging device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image holding member 2 Core material 3 Support member 4 Surface member

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-242264 (JP, A) JP-A-63-298250 (JP, A) JP-A-4-1944891 (JP, A)

Claims (2)

(57) [Claims] 1. A charging device for charging a latent image holding member by applying a voltage between the latent image holding member and a charging means held in close proximity to the latent image holding member, the latent image holding member comprising: Holding member
And the charging means held in proximity to the latent image holding member
A charging device , wherein the distance is 5 to 300 μm, and the latent image holding member is provided with a photoconductive layer on an aluminum substrate whose surface is anodized. 2. An anodic oxide film having an average thickness of 0.1 to 20.
The charging device according to claim 1, wherein the charging device has a thickness of μm.