JPH07191472A - Electrophotographic photoreceptor for liquid development and production of the photoreceptor - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic photoreceptor for liquid development having an org. photoconductive layer on a conductive supporting body comprising aluminum or an aluminum alloy with which good picture image qualities can be always obtd. in a liquid developing process in which high-quality picture images are obtd. by normal or reversal development, by heat treating the photoconductive layer after the layer is formed by coating and drying. CONSTITUTION:The photoconductive layer is formed on a conductive supporting body which preferably consists of aluminum or an aluminum alloy. It is preferable to use an anodically oxidized film of aluminum as a barrier layer between the conductive supporting body and the photoconductive layer. The anodically oxidized film formed is subjected to low temp. sealing treatment or high temp. sealing treatment, then successively, sufficiently washed with water and dried. Then the org. photoconductive body for liquid development thus formed is heat treated. The heat treatment is done at >=40 deg.C, preferably >=60 deg.C for >=30min, more preferably >=60min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member for liquid development and a method for manufacturing the same. More specifically, the present invention relates to an electrophotographic photosensitive member used in a copying machine, an optical printer or the like that forms an image by an electrophotographic process utilizing a liquid developing method, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Electrophotographic technology has been widely used and applied not only in the field of copying machines but also in the field of various printers in recent years because of its ability to obtain images of instant quality and high quality. Photoreceptors, which are the core of electrophotographic technology, have recently been formed as pollution-free inorganic photoconductors such as selenium, arsenic-selenium alloy, cadmium sulfide, and zinc oxide. A photoreceptor using an organic photoconductive material, which has advantages such as easy and easy manufacture, has been developed.

Among organic photoconductors, a so-called laminated type photoconductor in which a charge generation layer and a charge transport layer are laminated has been devised and is the mainstream of development. The multi-layered photoconductor is a high-sensitivity photoconductor obtained by combining a highly efficient charge-generating substance and a charge-transporting substance, and a photoconductor having a wide selection range of materials and high safety, Further, since the coating productivity is high and the cost is comparatively advantageous, the possibility of becoming the mainstream of the photoreceptor is high and the coating has been earnestly developed.

On the other hand, in recent years, with the aim of improving image quality such as resolution and halftone reproducibility, in terms of hardware, electrophotographic technology,
That is, although digitization of reading elements, writing elements, image processing devices, etc. is rapidly progressing, it is well known to use liquid development as a means for achieving higher image quality than before. In liquid development, the toner particles can be made extremely fine compared to normal dry development, so that high resolution and good image reproducibility can be obtained. The liquid developer is usually one in which a dye / pigment and polymer particles are dispersed in a highly electrically insulating medium (solvent) for coloring, and a charge control agent is added to this to impart a predetermined charge. However, while high resolution can be obtained by performing liquid development, it becomes easier to reproduce a non-uniform portion due to defects in the photoconductor on the image more faithfully than in dry development. Therefore, a higher quality photoreceptor is required for the liquid development. In particular, when a laminated organic photoconductor, which is currently the mainstream as a photoconductor, is used, the charge generation layer is formed with a relatively thin film thickness, so that dirt or defects on the surface of the substrate, such as cutting scratches or impurities. It is easily affected by those derived from metals.
The charge generation layer is generally formed by dispersing pigment particles in a binder in many cases.
Coating defects such as repellency and agglomerates are likely to occur, and these also tend to appear as image defects in liquid development.

On the other hand, as an image forming method in an optical printer, for the purpose of effectively utilizing light or enhancing the resolution, a so-called reversal development method in which toner is attached to a portion irradiated with light to form an image is adopted. Many. In the reversal development process, the dark potential part becomes a white background and the bright potential part becomes a black background part (image area). However, in this system, if there is a local charging failure due to a defect on the photoconductor, When there are many black spots or a large number of them, a phenomenon called background fog occurs, which causes a remarkable image defect.

Such a local charging failure is likely to cause an image failure in reversal development even if it is at a level where there is no problem when used in regular development. There are various possible causes for this problem, namely, local charging failure. However, due to the local injection of charges between the conductive support that is an electrode and the photosensitive layer, the charging potential does not rise. It is thought that the main cause is.

As an organic photoreceptor which can be used for liquid development, a binder obtained by mixing an acrylic resin and a vinyl resin, which are substantially insoluble in a paraffinic petroleum solvent, has been used (Japanese Patent Publication No. 53-11856). , An example of using an insoluble resin in a liquid developer as an overcoat layer (JP-A-52-89328), and an example of using a thermotropic liquid crystalline resin (JP-A-4-213460).
Etc. have been reported. These are all types of photoreceptors formed by binding with a binder resin. It is intended to improve deterioration (solvent resistance), and almost no mention is made of images when these photoreceptors are used in a liquid development process.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic photoconductor that always obtains good image quality in a liquid development process in which a very high quality image is obtained in regular or reversal development. To provide.

[0009]

[Means for Solving the Problems] Various investigations have been made to solve such problems. As a result, the organic photoconductor prepared by coating and drying is subjected to heat treatment again so that the image quality, particularly liquid development, can be effectively improved. The inventors have found that it is possible to improve minute black dot defects on a white background image in the reversal process, and have reached the present invention.

Although it is not clear why such improvement is observed by the heat treatment, the contact interface state between the surface of the conductive support (electrode) and the photosensitive layer probably depends on the carrier from the electrode to the photosensitive layer. Is estimated to have changed so as to be smaller. That is, the gist of the present invention is an electrophotographic photoreceptor for liquid development having at least an organic photoconductive layer on a conductive support made of aluminum or an aluminum alloy, the photoconductive layer being formed by coating and drying. The present invention also relates to an electrophotographic photosensitive member for liquid development, characterized by being heat-treated later, and a method for producing the photosensitive member.

[0011]

The present invention will be described in detail below. The photoconductive layer of the present invention is provided on a conductive support. As the conductive support, a metal material such as aluminum, stainless steel, copper or nickel, a polyester film having a conductive layer such as aluminum, copper, palladium, tin oxide or indium oxide on the surface thereof, an insulating support such as paper Any body sheet, belt, drum or the like can be used, but it is preferable to use aluminum or aluminum alloy. As a material of aluminum, for example, A1050, A300
3, A6063 or the like can be used.

A known barrier layer, which is commonly used, may be provided between the conductive support and the photoconductive layer. Examples of the barrier layer include inorganic layers such as aluminum anodic oxide coating, aluminum oxide, and aluminum hydroxide, polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, and other organic layers. Is used. Above all, it is preferable to use an aluminum anodic oxide coating.

When an anodic oxide coating is provided, the conductive support is previously provided with an acid, an alkali, an organic solvent, a surfactant,
Degreasing treatment is preferably performed by various degreasing cleaning methods such as emulsion and electrolysis. The anodized film is usually formed by anodizing in an acidic bath of chromic acid, sulfuric acid, oxalic acid, boric acid, sulfamic acid, etc., but anodizing in sulfuric acid gives the best results. give.

In the case of anodization in sulfuric acid, the sulfuric acid concentration is 1
00-300g / l, dissolved aluminum concentration is 2-15g /
1, the liquid temperature is 10 to 30 ° C., the electrolysis voltage is 5 to 20 V, and the current density is preferably 0.5 to ² A / dm ² . The average thickness of the anodized film is usually 15 μm or less and preferably 5 μm or more. If the film thickness is too thin, the effect as a blocking layer decreases,
Fogging tends to occur particularly when used in the reversal liquid development process. On the other hand, if the thickness is too large, the cost for forming the anodic oxide coating becomes high, and the anodic oxide coating is prone to cracks, and the cracks are likely to appear on the image.

The anodic oxide coating thus formed is
For example, a low-temperature sealing treatment of immersing in an aqueous solution containing nickel fluoride as a main component or a high-temperature sealing treatment of immersing in an aqueous solution containing nickel acetate as a main component is performed. The concentration of the nickel fluoride aqueous solution used in the case of the low temperature sealing treatment can be appropriately selected, but it is 3 to 6 g / l.
It is most effective when used within the range.

In order to smoothly carry out the sealing treatment,
The treatment temperature is 25 to 50 ° C., preferably 30 to 35
And the pH of the nickel fluoride aqueous solution is 4.5 to 6.
It is good to treat in the range of 5, preferably 5.5 to 6.0. As the pH adjuster, oxalic acid, boric acid, formic acid, acetic acid, caustic soda, sodium acetate, aqueous ammonia, etc. can be used.

The processing time is preferably within the range of 1 to 3 minutes per 1 μm of the average film thickness of the coating. In order to further improve the physical properties of the coating, nickel fluoride, cobalt acetate, nickel sulfate, a surfactant, etc. may be added to the nickel fluoride aqueous solution. As the sealing agent for 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 preferably used.

When the nickel acetate aqueous solution is used, the concentration is preferably within the range of 3 to 20 g / l.
Treatment temperature is 65 to 100 ° C, preferably 80 to 98 ° C
The pH of the aqueous nickel acetate solution is preferably in the range of 5.0 to 6.0. Here, as the pH adjusting agent,
Ammonia water, sodium acetate, etc. can be used. Also in this case, sodium acetate, an organic carboxylate, an anionic surfactant, a nonionic surfactant and the like may be added to the nickel acetate aqueous solution in order to improve the physical properties of the coating.

It is preferable that the sealing-processed anodic oxide film formed as described above is subsequently thoroughly washed with water and dried. Further, various surface contaminations occur in the steps of anodic oxidation, sealing, and washing with water. Therefore, it is desirable to perform a physical contact rubbing washing treatment to finally obtain a clean surface. In this rubbing cleaning, it is preferable to use the following rubbing materials in a brush shape, a foam shape, or a cloth shape.

As the rubbing material, cotton, rayon, cellulose, natural fibers such as wool, polyester, nylon,
Synthetic fibers such as acrylic and acetate, thermoplastic foam such as polystyrene, polyethylene and polypropylene, and thermosetting plastic foam such as polyurethane and polyurea can be used. As the rubbing cleaning method, these rubbing materials are brought into contact with the anodized film, and while supplying a solvent such as water, methanol, isopropanol, etc., the rubbing material is mechanically or manually rotated while cleaning, or reciprocating. How to scrub and wash,
A method of reciprocating while rotating and cleaning can be used.

The photoconductive layer may be formed by stacking a charge generation layer and a charge transport layer in this order, or by stacking them in the opposite order, or by using a so-called dispersion type in which charge generation material particles are dispersed in a charge transport medium. You can In the case of a laminated photoconductive layer, the charge generating material used in the charge generating layer includes selenium and its alloys, arsenic-selenium, cadmium sulfide, zinc oxide, other inorganic photoconductive materials, phthalocyanines, azo dyes, quinacridones, and many other materials. Various organic pigments and dyes such as ring quinone, pyrylium salt, thiapyrylium salt, indigo, thioindigo, anthanthrone, pyranthrone and cyanine can be used. Among them, metal-free phthalocyanines, copper, indium chloride, gallium chloride, tin, oxytitanium, zinc, vanadium, and other metals or oxides thereof, chloride-coordinated phthalocyanines, monoazo, bisazo, trisazo, polyazo, etc. Azo pigments are preferred.

Particularly, oxytitanium phthalocyanine, for example, JP-A-63-218768, 62-134651.
JP-A No. 2-111955 and the like showing an X-ray diffraction pattern, x-type or τ-type metal-free phthalocyanines, bisazo pigments and the like are preferable. The charge generation layer contains fine particles of these substances, such as polyester resin, polyvinyl acetate, polyacrylate,
Polymethacrylic acid ester, polyester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin,
You may use it in the dispersion layer of the form bound by various binder resins, such as an epoxy resin, a urethane resin, a cellulose ester, and a cellulose ether. Among them, polyvinyl acetals such as polyvinyl acetoacetal and polyvinyl butyral, phenoxy resin, vinyl chloride resin and the like are particularly preferable. The usage ratio in this case is 10% binder resin.
It is usually used in the range of 30 to 500 parts by weight with respect to 0 parts by weight, and the film thickness is usually 0.1 μm to 2 μm, preferably 0.15 μm to 0.8 μm. Further, the charge generation layer may contain various additives such as a leveling agent, an antioxidant and a sensitizer for improving the coating property, if necessary. The charge generation layer may be a vapor deposition film of the above charge generation substance.

The charge transport layer may be of any type, such as a type in which a low molecular weight charge transport material is dispersed in a binder resin, a polymer type charge transport layer, or the like. As the low molecular weight charge transporting substance, there are known electron withdrawing substances such as 2,4,7-trinitrofluorenone and tetracyanoquinodimethane.
Heterocyclic compounds such as carbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, and thiadiazole; electron-donating substances such as aniline derivatives, hydrazone compounds, aromatic amine derivatives, and stilbene derivatives; Can be selected from electron withdrawing substances or electron donating substances such as polymers having groups consisting of these compounds in the main chain or side chains. Among them, hydrazone compounds having excellent sensitivity and responsiveness, such as (No. 1 to 16), stilbene compounds such as (No. 17 to 22), aromatic amine compounds such as (No. 23 to 30) are used. Preferably.

[0024]

[Chemical 1]

[0025]

[Chemical 2]

[0026]

[Chemical 3]

[0027]

[Chemical 4]

[0028]

[Chemical 5]

[0029]

[Chemical 6]

Among them, in order to have sufficient solvent resistance in liquid development, for example, a charge transporting substance having a relatively small solubility in a specific solvent, as described in Japanese Patent Application No. 5-70089, or a Japanese Patent Application. Flat 5-87380
Glass transition temperature as described in Japanese Patent Publication No.
It is preferable to use a charge transport material having a temperature of not less than ° C.

As the binder resin used in the charge transport layer, for example, vinyl polymers such as polymethylmethacrylate, polystyrene and polyvinyl chloride, and copolymers thereof, polycarbonate, polyester, polyester carbonate, polysulfone, polyimide, phenoxy,
Examples thereof include epoxy resins and silicone resins, and partially cross-linked cured products thereof can also be used. Above all, it is preferable to use polycarbonates such as homopolymers and copolymers having the following structures, or blends thereof.

The ratio of the binder resin to the charge transport material is usually 30 to 100 parts by weight of the binder resin.
It is used in an amount of 200 parts by weight, preferably 40 to 150 parts by weight, more preferably 40 to 120 parts by weight. Further, the charge transport layer may contain various additives such as an antioxidant and a sensitizer, if necessary. The thickness of the charge transport layer is 1
It is preferable to use it with a thickness of 0 μm or more, preferably 15 μm or more and 45 μm or less. As the outermost surface layer, a conventionally known overcoat layer mainly composed of a thermoplastic or thermosetting polymer may be provided. Usually, the charge transport layer is formed on the charge generation layer, but the reverse is also possible. As a method of forming each layer, a known method such as sequentially coating and drying a coating liquid obtained by dissolving or dispersing a substance contained in the layer in a solvent can be applied.

In the case of the dispersion type photoconductive layer, the above-mentioned charge generating substance is dispersed in the matrix containing the charge transporting substance having the above-mentioned compounding ratio as a main component. In that case, the particle size needs to be sufficiently small, and the particle size is preferably 1 μm or less, more preferably 0.5 μm or less. If the amount of the charge generating substance dispersed in the photosensitive layer is too small, sufficient sensitivity cannot be obtained, and if the amount is too large, there are adverse effects such as a decrease in charging property and a decrease in sensitivity. For example, preferably 0.5 to 50% by weight. %, More preferably 1 to 20% by weight. The thickness of the photosensitive layer is 10 μm or more, preferably 15 μm or more and 45 μm or less. Also in this case, known plasticizers for improving film-forming properties, flexibility, mechanical strength, etc., additives for suppressing residual potential, dispersion aids for improving dispersion stability, and coating properties are used. Leveling agents and surface active agents such as silicone oil, fluorine-based oil and other additives may be added for improvement. Similarly, as a method of forming the dispersion type photoconductive layer, a known method such as sequentially coating and drying a coating solution obtained by dissolving or dispersing a substance contained in the layer in a solvent can be applied.

The organic photoconductor for liquid development thus formed is then subjected to the heat treatment according to the present invention.
The heat treatment condition is usually 40 ° C. or higher, preferably 5
It is desirable to carry out at a temperature of 0 ° C. or higher, more preferably 60 ° C. or higher, for 30 minutes or longer, preferably 60 minutes or longer. The temperature and time of the heat treatment conditions are not particularly limited, but when the temperature is too high (for example, 100
(° C or more) or when performing for a long time (for example, 100 hours or more)
However, this is not preferable because the photoreceptor may deteriorate. A usual method can be used as the heat treatment method. For example, hot air heating in a chamber or a continuous hot air oven, heating by infrared rays or far infrared rays, and the like can be used.

[0035]

EFFECT OF THE INVENTION Even when the electrophotographic photosensitive member for liquid development, which is obtained by subjecting the organic photoconductive layer according to the present invention to heat treatment, is used in either regular or reversal liquid development process, it has very few image defects. It is possible to obtain a clear image. Further, even when it is repeatedly used, the image quality hardly deteriorates, and a stable image can be always obtained.
Therefore, it can be widely used in black and white and color copiers and printers using liquid development without any problem.

[0036]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the invention is not limited thereto. Example 1 An aluminum cylinder having a mirror-finished surface and a thickness of 1 mm was used as a degreasing agent, NG- # 30 [manufactured by Kizai Co., Ltd.].
Degreasing was performed for 5 minutes at 60 ° C. in a g / l aqueous solution.
Then, after washing with water, it was immersed in 7% nitric acid at 25 ° C. for 1 minute. After further washing with water, anodic oxidation was performed at a current density of 1.2 A / dm ^{2 in} a 180 g / l sulfuric acid electrolytic solution (dissolved aluminum concentration 7 g / l) to form an anodized film having an average film thickness of 6 μm. Then, after washing with water, a sealing treatment was performed by immersing in a 10 g / l aqueous solution of a high temperature sealing agent Topseal DX-500 [made by Okuno Chemical Industries Co., Ltd.] containing nickel acetate as a main component at 95 ° C. for 30 minutes. After washing with water,
Using a polyester sponge, the entire surface of the coating film was reciprocated three times for rubbing and cleaning. Then, it was washed with water and dried.

1,2-dimethoxy was added to 10 parts by weight of oxytitanium phthalocyanine having a powder X-ray spectrum pattern by CuKa line shown in FIG. 1 and 5 parts by weight of polyvinyl butyral (S-REC BH-3 manufactured by Sekisui Chemical Co., Ltd.). 500 parts by weight of ethane was added, and the mixture was pulverized and dispersed by a sand grind mill. An aluminum cylinder provided with an anodic oxide coating 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, this aluminum cylinder was mixed with 60 parts by weight of the following hydrazone compound,

[0038]

[Chemical 7]

And 1.5 parts by weight of cyano compound

[0040]

[Chemical 8]

Also, 100 parts by weight of a polycarbonate resin [viscosity average molecular weight 30,000] shown below was immersed in a solution prepared by dissolving 1000 parts by weight of 1,4-dioxane, and was applied.
The charge transport layer was provided so that the film thickness after drying would be 17 μm. The drum thus obtained is placed in a chamber 70
A heat treatment was performed at 60 ° C. for 60 minutes to obtain a photoconductor A.

[0042]

[Chemical 9]

Example-2 A photoconductor B was prepared in the same manner as in Example-1, except that the heat treatment conditions in Example-1 were 70 ° C. and 2 hours. Example-3 A photoconductor C was prepared in the same manner as in Example-1, except that the heat treatment conditions in Example-1 were 70 ° C. and 48 hours. Example-4 A photoreceptor D was prepared in the same manner as in Example-1, except that the heat treatment conditions were 70 ° C. and 72 hours. Example-5 A photoreceptor E was prepared in the same manner as in Example-1 except that the heat treatment conditions were 50 ° C. and 24 hours. Example-6 A photoreceptor F was prepared in the same manner as in Example-1, except that the heat treatment conditions were 90 ° C. and 24 hours.

Comparative Example-1 The procedure of Example-1 was repeated, except that no heat treatment was performed.
A comparative photoconductor G was prepared. Each of the photoconductors prepared as described above was mounted on a prototype of a laser printer including an inversion liquid development process, and the development contrast potential was set to 4
The image was evaluated by changing the voltage from 00 to 600V. Table 1 shows the evaluation results of the stains (fogging) on the obtained white background image portion. It can be seen that the comparative photoconductor G that has not been heat-treated gives a good image with no particular problem when the development contrast potential is low, but the image quality sharply decreases as the development contrast potential increases. On the other hand, it can be seen that when the photoconductor according to the present invention is used, a very good image can be obtained even when the development contrast potential is high.

[0045]

[Table 1] Explanation of symbols ○: Good image △: Fogging is seen in some areas, but is reasonably good image ×: Fogging over the whole XX: Fogging over the entire surface and contrast with the black background is very small .

[Brief description of drawings]

FIG. 1 is an X-ray spectrum diagram of oxytitanium phthalocyanine used in Example 1, taken with CuKa line.

Claims (5)

[Claims] 1. A liquid developing electrophotographic photoreceptor having at least an organic photoconductive layer on a conductive support made of aluminum or an aluminum alloy, the photoconductive layer being formed by coating and drying. An electrophotographic photosensitive member for liquid development, which is heat-treated. 2. The electrophotographic photoreceptor for liquid development according to claim 1, wherein the organic photoconductive layer comprises at least a charge generation layer and a charge transport layer. 3. The electrophotographic photoreceptor for liquid development according to claim 1, wherein the conductive support has an anodized film. 4. A method for producing an electrophotographic photosensitive member for liquid development, which has at least an organic photoconductive layer on a conductive support made of aluminum or an aluminum alloy,
A method for producing an electrophotographic photoreceptor for liquid development, which comprises heat-treating after forming a photoconductive layer by coating and drying. 5. The method for producing a photoconductor for liquid development according to claim 4, wherein the condition of the heat treatment is a temperature of 40 ° C. or higher for 30 minutes or longer.