JPH0594033A - Proximity electrifying device - Google Patents

Abstract

PURPOSE:To obtain the good proximity electrifying device which is hardly affected by image defects by subjecting such an aluminum base body which cannot be used as it is as a latent image holding member as many stains, projections, flaws, dents, etc., exist on the surface to an anodic oxidation treatment, thereby removing these defects. CONSTITUTION:The latent image holding member of the electrifying device which electrifies the latent image holding member by impressing a voltage between the latent image holding member and the electrifying means held in proximity to the latent image holding member is constituted by providing a photoconductive layer on the aluminum base body, the surface of which is subjected to the anodic oxidation treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device that can be used in an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, corona chargers such as corotrons and scorotrons have been widely used for charging photoreceptors in electrophotographic devices such as electrophotographic copying machines and electrophotographic printers. This corona charger requires a high voltage of 4 to 7 kV to charge the photoconductor, and has a drawback in that a large amount of ozone is generated to accelerate the deterioration of the photoconductor. In addition, due to the increasing awareness of the environment in recent years and the miniaturization and personalization of printers, etc., the amount of ozone generated that is harmful to the human body has increased due to the increased use of the device near the human body, such as on a desk. There has been a demand for a charging device with less charge.

Under these circumstances, contact charging methods such as roller charging have been reviewed in recent years, and some of them have been put to practical use. What is roller charging is that a metal-made core metal is coated with conductive rubber or the like, a roller-shaped member is brought into contact with a latent image holding member, and a voltage is applied between the metal core of the roller and the latent image holding member. Then, the surface of the latent image holding member is charged. This charging method is characterized in that the applied voltage is low and the amount of ozone generated is small (for example, see 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, both the roller and the latent image holding member are likely to be deformed, and this is liable to appear on the image as an indentation. It was Also,
Since the roller and the latent image holding member are in contact with each other, additives and the like exuding 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 the problem of being very stressful. In order to solve such a problem, as a charging method in which a roller or the like is not brought into contact with a latent image holding member, for example, as shown in JP-A-58-76851, a position 1 to 2 mm from the latent image holding member is used. 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. .. In addition, for the latent image holding member, which is the core of electrophotographic technology, inorganic photoconductive substances such as selenium, arsenic-selenium alloy, cadmium sulfide, zinc oxide, and amorphous silicon have been conventionally used as photoconductive materials. However, recently, various kinds of organic photoconductive substances have been developed which are non-polluting and are advantageous in film forming property and productivity. Among the organic latent image holding members, a charge generation layer and a charge transport layer are laminated,
A so-called function-separated type laminated latent image holding member is widely used for practical use because of its high sensitivity and long life.

[0006]

However, when a charging device for charging the latent image holding member in close proximity is used (1) In general, the photoconductive layer of the latent image holding member is provided on a conductive substrate. If the conductive layer has a defect, the current from the charging member is concentrated, the latent image holding member is unevenly charged, and a band-shaped image defect occurs. Further, at this time, the charging member itself is damaged by the concentration of the current and cannot be used. (2) If there are defects such as adhesion of foreign matter, dirt, fine holes, etc. on the surface of the substrate, image defects resulting from them 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 the copy. Especially under high-humidity environmental conditions, ground fog is extremely unusable.

In the reversal development method, the dark potential part becomes a white background and the bright potential part becomes a black background part (image area). However, in this system, there is a local charging defect due to a defect or the like on the latent image holding member. When there are many black spots on a white background or a large number of them, the development becomes a background fog, and a remarkable image defect appears. Even if such a local charging defect does not cause any problems when used in regular development, it tends to cause an image defect in reversal development, and moreover, it is a laminated latent image which has been obtained conventionally. It was found that the holding member had problems with black spots and fog to some extent.

Various causes can be considered for the cause of this problem, that is, the local charging failure. However, the injection of charges locally occurs between the conductive substrate, which is an electrode, and the photoconductive layer, and the charging potential does not rise. it is conceivable that. Therefore, as a result of various studies by the present inventors in order to solve these problems, in a device for charging a charging means in the vicinity of a latent image holding member, by using a specific latent image holding member, image defects The present invention has been achieved by knowing that a charging device that does not easily generate is obtained.

[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 the vicinity of the latent image holding member, thereby applying the latent image holding member. In the charging device, the latent image holding member comprises a photoconductive layer provided on an aluminum substrate whose surface is anodized.

Although close to close in the present invention,
A minute gap is a state in which it is maintained. The present invention will be described in detail below. Generally, materials used as the base of the latent image holding member are aluminum, iron, stainless steel, copper,
Examples thereof include zinc, nickel, electroconductive plastic, glass, and the like. Among them, aluminum is widely used because it is relatively inexpensive, lightweight, has good workability, and does not impair electrical characteristics.

When aluminum is usually used as a drum-shaped substrate, an aluminum buret is processed into an extruded tube by a porthole method, a mandrel method or the like, and then drawn out to obtain a drum having a predetermined wall thickness and outer die size. It can be made by performing processing, impact processing, ironing, etc. However, for example, since the extrusion process is usually performed under high temperature and high pressure, the surface of the aluminum drum is roughened, and the precipitation of dissimilar metals occurs during cooling.
As it is, various defects are created on the drum surface, and it is difficult to make a satisfactory product. Therefore, it is currently used by further cutting the surface, or in some cases by providing another conductive layer on the drum surface, but it still has a practically sufficient uniform surface. It can not be said.

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

The anodizing treatment is usually carried out, for example, with chromic acid,
Although it is carried out in an acid bath of sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., anodizing treatment in sulfuric acid gives the best results. For anodization in sulfuric acid,
Sulfuric acid concentration is 50-400g / l, dissolved aluminum concentration is 2-
20g / l, liquid temperature 10-40 ℃, electrolysis voltage 5-30
The V and current densities are preferably set within the range of 0.5 to ² A / dm ² .

The average thickness of the anodic oxide coating is 0.1 to
The thickness is preferably 20 μm. More preferably, it is 1 to 10 μm. The anodized film thus formed contains, for example, a low-temperature sealing treatment in which it 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 a high-temperature sealing treatment in which it is immersed in an aqueous solution, or other sealing treatment such as steam sealing or boiling water sealing.

The concentration of the nickel fluoride aqueous solution used in the low-temperature sealing treatment can be appropriately selected, but it is most effective when it is used in the range of 2 to 10 g / l. Also, in order to proceed smoothly with the sealing treatment, the treatment temperature is 15
PH of the nickel fluoride aqueous solution is 4.5 to 6.5, preferably 5.5 to 40 ° C., preferably 25 to 35 ° C.
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, etc. can be used as the pH adjusting agent. The treatment time is preferably within the range of 1 to 3 minutes per 1 μm of film thickness. In order to further improve the physical properties of the film, cobalt fluoride, cobalt acetate, nickel sulfate, a surfactant, etc. may be added to the nickel fluoride aqueous solution. Then, it is washed with water and dried to complete the low temperature sealing treatment.

As the sealing agent in the high temperature sealing treatment, an aqueous solution of a metal salt of nickel acetate, cobalt acetate, lead acetate, nickel acetate-cobalt, barium nitrate or the like can be used, but nickel acetate is particularly used. Is preferred. When using an aqueous nickel acetate solution, the concentration is 3 to 20.
It is preferably used within the range of g / l. Processing temperature is 6
The treatment is carried out at 5 to 100 ° C., preferably 80 to 98 ° C., and the pH of the nickel acetate aqueous 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 treatment time is 10 minutes or longer, preferably 20 minutes or longer. Also in this case, sodium acetate, an organic carboxylate, an anionic surfactant, a nonionic surfactant, etc. may be added to the nickel acetate aqueous solution in order to improve the physical properties of the coating. Then, after washing with water and drying, the high temperature sealing treatment is completed. Although the photoconductive layer is provided on the anodized film formed as described above, a known undercoat layer may be provided between the anodized film and the photoconductive layer. Examples of the subbing material include polyvinyl alcohol, casein, sodium caseinate, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide and phenol resin. The thickness of the undercoat layer is preferably 5 μm or less, and 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, but a laminated photoconductive layer including a charge generation layer and a charge transfer layer can be used. The layers are extremely useful. Photoconductors used for the charge generation layer include selenium and its alloys, arsenic-selenium,
Various organic pigments such as cadmium sulfide, zinc oxide and other inorganic photoconductors, phthalocyanines, azos, quinacridones, polycyclic quinones, perylenes, indigo, benzimidazoles can be used.

Among them, azo pigments such as monoazo, bisazo, trisazo, polyazos; metal-free phthalocyanine; metals such as copper, indium chloride, gallium chloride, tin, oxytitanium, zinc, vanadium, or oxides or chlorides thereof. The phthalocyanines coordinated with 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,
Examples include phenoxy resin, epoxy resin, polyester resin, acrylic resin, methacrylic resin, polyvinyl acetate, polyvinyl chloride, methyl cellulose, and polycarbonate resin. 20 to 300 parts by weight of the above-mentioned photoconductor is preferably contained in 100 parts by weight of the binder resin, and particularly preferably 30 to 150 parts by weight. 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.

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

A binder resin is blended with these charge transfer materials as needed. Preferred binder resins include polymethylmethacrylate, polystyrene,
Vinyl polymers such as polyvinyl chloride and their copolymers,
Polyarylate resin, urethane, urea, melamine polycarbonate, polyester, polysulfone, phenoxy resin, epoxy resin, silicone resin, etc.
Also, partially cross-linked cured products thereof are used. The charge transfer material is added in an amount of 30 to 2 in 100 parts by weight of the binder resin.
It is preferable that the content of the compound is 00 parts by weight, especially 50 to 150 parts by weight.

Further, 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
Used with a thickness of ~ 25 μm. As another example of the photoconductive layer, there is a dispersion type photoconductive layer obtained by dispersing the photoconductive particles as described above in a binder made of a binder resin and the 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, particularly 40 parts by weight with respect to 100 parts by weight of the binder resin.
˜150 parts by weight is preferred.

The charging means for charging the latent image holding member may have any shape such as a brush shape, a blade shape, a pin electrode shape, or a roller shape. However, a roller shape is preferable in use, and it is preferable that some kind of linkage mechanism is employed to rotate the latent image holding member in accordance with the rotation of the latent image holding member, or the rotation driving force is applied from the outside independently. By rotating the roller in this way, the surfaces used for charging are constantly replaced, so the life of the charging means is extended, and it is also possible to provide a means for cleaning the charging means on the side opposite to the surface used for charging. Therefore, 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 is usually composed of a core material and a charging member covering the periphery thereof. As the charging member, a conductor such as a metal and a semiconductor, or an electrically conductive or semiconductive rubber in which conductive particles such as carbon or other semiconductive particles are contained in an elastic body such as a rubber material is used. A roller-shaped charging member molded into a hollow cylinder can also be used. It is also possible to divide the charging member into a supporting member and a surface member, and use a charging member in which the surface member holds an appropriate electric resistance.

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

Reference numeral 3 in the figure denotes a roller-shaped support member. As the material of the supporting member, any material having conductivity or semiconductivity may be used. Examples of conductive materials include iron,
It is also possible to use a metal such as copper, brass, stainless steel, aluminum, platinum or tungsten, or a conductive organic material such as a resin molded product in which carbon or the like is kneaded.
Of course, these materials may be the same as the core material, and the core material and the supporting member may be integrally manufactured. Other elastic rubber materials, such as NBR, EPDM, silicon, neoprene, or natural rubber materials, and conductive rubber obtained by kneading conductive rubber or semiconductive particles such as carbon into these rubbers are used. ..

Further, a surface member 4 in the figure may be provided. 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, and preferably 10 ⁵ -10
¹² Ωcm, more preferably 10 ⁷ -10 ¹² Ωcm. The thickness of the surface member is preferably thicker in consideration of the durability due to abrasion as the charging member, but if it is made too thick, the chargeability to the latent image holding member is deteriorated.
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 supporting member by a dipping method, a spray method, a vacuum deposition method, a plasma coating method, etc. Among these methods, the dipping method is advantageous in terms of the 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, but it is preferable that the applied voltage is a DC voltage superposed with an AC voltage, and it is difficult to obtain uniform charging only with the DC voltage. Any alternating voltage may be used as long as it is a voltage that changes periodically. As for the voltage range, the DC voltage is preferably positive or negative 50 to 2000V, and particularly preferably 100 to 1500V. The peak-to-peak voltage (V _pp ) is usually 400 to 1800 as the superimposed AC voltage.
V, preferably 800 to 1600 V, more preferably 1
200 to 1600V is suitable. When the peak-to-peak voltage (V _pp ) of the AC voltage exceeds 1800V, the charging uniformity becomes worse than when the AC voltage is not superimposed. The frequency of the alternating 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 in the vicinity of the latent image holding member is preferably 5 to 300 μm.
To 100 μm is more preferable, and further preferably 15 to 8
0 μm is good. If the gap is too large, it becomes difficult to obtain uniform charging even if a voltage obtained by superimposing an AC voltage on a DC voltage is applied.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 An aluminum extruded tube was ironed to a thickness of 0.
An aluminum cylinder having an outer diameter of 75 mm, an outer diameter of 30 mm and a length of 246 mm was produced.

This aluminum cylinder is treated with a degreasing agent NG
6 in a 30 g / l aqueous solution of # 30 (manufactured by Kizai Co., Ltd.)
Degreasing cleaning was performed at 0 ° C. for 5 minutes. Subsequently, the plate was washed with water and then immersed in 7% nitric acid at 25 ° C. for 1 minute. After further washing with water,
180g / l sulfuric acid electrolyte (dissolved aluminum concentration 7
g / l), anodization was performed at a current density of 1.0 A / dm ² to form an anodized film having an average film thickness of 6 μm. Then, after washing with water, a high-temperature sealing agent Topseal DX-500 (manufactured by Okuno Chemical Industries Co., Ltd.) containing nickel acetate as a main component was used.
A sealing treatment was performed by immersing in a 0 g / l aqueous solution at 90 ° C. for 20 minutes. Subsequently, the plate was washed with water, immersed in a pure water hot water bath at 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.,
500 parts by weight of 1,2-dimethoxyethane was added to 5 parts by weight of S-REC BH-3), and the mixture was pulverized and dispersed by a sand grind mill. An aluminum cylinder provided with an anodized film formed previously was applied by dip coating to this dispersion liquid, 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 the following formula (2) were used for this aluminum cylinder.
14 parts by weight of the hydrazone compound shown in and 15 parts by weight of the cyano compound shown by the following formula (3)

[0033]

[Chemical 1]

[0034]

[Chemical 2]

[0035]

[Chemical 3]

Para-3,5-di (tertiary butyl)
8 parts by weight of hydroxytoluene and polycarbonate resin (Novarex (registered trademark) 702, manufactured by Mitsubishi Kasei Co., Ltd.)
5A) 100 parts by weight is applied by dip coating to a solution prepared by dissolving 1000 parts by weight of 1,4-dioxane, and the film thickness after drying is 17
The charge transfer layer was provided to have a thickness of μm.

Next, a charging member was prepared using a stainless 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 roller surface of this charging member and the latent image holding member were attached so that the gap between them was 34 μm. A voltage obtained by superimposing Vp _-p 1500V at an AC voltage frequency of 1 kHz on a DC voltage of -700V as a power supply bias is applied to the core material,
As a result of evaluating the images, good images were obtained for white background, black background, and halftone images. Further, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects which would occur when current was leaked did not occur.

Example 2 Images were evaluated in the same manner as in Example 1 except that a metal roller made of stainless steel in which a support member and a core material were integrally molded was used. As a result, white, black and halftone images were good. An image was obtained. Further, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects which would occur when current was leaked did not occur.

Example 3 On a stainless steel metal roller integrally molded with a support member and a core material, a polyamide resin was used to form a film having a thickness of 0.5 μm.
Images were 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 with halftone images. Further, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects which would occur when current was leaked did not occur.

Example 4 Images were evaluated in the same manner as in Example 1 except that 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 used. Good images were obtained with halftone images. Further, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects which would occur when current was leaked did not occur.

Example 5 Stainless steel 12 m in which a supporting member and a core material are integrally molded
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. Further, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects which would occur when current was leaked did not occur.

Example 6 Stainless steel 12 m in which a supporting member and a core material are integrally molded
Images were 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.
Further, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects which would occur when current was leaked did not occur.

Example 7-12 The gap between the roller surface of the charging member and the latent image holding member is 60 μm.
All were evaluated in the same manner as in Example 1-6 except that m was set, and 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 provided in the same manner as in Example 1 except that this aluminum cylinder was degreased and washed with trichlene and no anodized film was provided.

Next, a charging member similar to that of Example 1 was produced. Then, as in the case of Example 1, as a result of evaluating the image, many image defects were observed and a large amount of fog was observed especially in the halftone image.

Comparative Example 2 Stainless steel 12 m in which a supporting member and a core material are integrally molded
Images were evaluated in the same manner as in Comparative Example 1 except that a metal roller having a diameter of m was used, and as a result, many image defects were observed, especially in halftone images, and fog was large. In addition, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects occurred when electric charges leaked.

Comparative Example 3 An aluminum cylinder having a wall thickness of 0.75 mm, an outer diameter of 30 mm and a length of 246 mm was produced. Next, this 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 provided without providing the anodized film. Many image defects are seen in the image,
There was a lot of fog.

Comparative Example 4 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 produced. 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 coating. Many image defects were seen in the halftone image, and there were many fog.

Comparative Example 5 Stainless steel 12 m in which a supporting member and a core material are integrally molded
Images were 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, a large number of image defects were observed, especially in halftone images, and there were many fogs. Further, with respect to defects such as local recesses in the photoconductive layer, black band-shaped image defects occurred when the current leaked.

Comparative Example 6 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 produced. Next, this aluminum cylinder was degreased and washed with trichlene, and an 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 coating. Many image defects were seen in the halftone image, and there were many fog.

Comparative Example 7-12 The gap between the roller surface of the charging member and the latent image holding member is 60 μm.
All were evaluated in the same manner as in Comparative Examples 1-6 except that m was set, and the same results as in Comparative Examples 1 to 6 were obtained.

[0051]

According to the charging device of the present invention, an anodizing treatment is applied to an aluminum substrate which cannot be used as a latent image holding member as it is because of many stains, protrusions, scratches, dents, etc. on its surface. Thus, these defects can be removed. As a result, it is possible to provide a good proximity charging device that is unlikely to be affected by image defects due to image defects caused by using the proximity charging device and defects such as local depressions of the photoconductive layer.

Further, the charging device obtained by the present invention is
Even when it is used in a commercially available copying machine or an electrophotographic system including a reversal development type process in which the defects of the substrate are more severe and images are more likely to appear, the latent image holding member does not contact the charging means, so the latent image holding member ， Without giving deformation to both charging means,
No indentation appears on the image, and no additive or the like contained in the charging unit migrates to the surface of the latent image holding member to deteriorate the image. Under a wide range of environmental conditions including high humidity, a good image with extremely few fog and other image defects can be obtained.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Latent Image Holding Member 2 Core Material 3 Supporting Member 4 Surface Member

Claims (3)

[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 proximity to the latent image holding member. A charging device, wherein the image holding member comprises a photoconductive layer provided on an aluminum substrate whose surface is anodized. 2. The charging device according to claim 1, wherein the gap between the latent image holding member and the charging means held in proximity to the latent image holding member is 5 to 300 μm. 3. The average film thickness of the anodized film is 0.1 to 20.
The charging device according to claim 1, wherein the charging device has a thickness of μm.