JPS6128953A - Electrostatic charge image forming method - Google Patents

Abstract

PURPOSE:To improve the number of durable times by applying positive electrostatic charge to the surface of an electrophotographic sensitive body having a conductive substrate and the laminated layers formed with an electric charge generating layer specified with the ratio of a binder resin with respect to a charge generating pigment within a specific range on a charge transfer layer then subjecting the surface to image exposing. CONSTITUTION:An electroreceptive material such as aliphat. cyclic compd., arom. compd. or heterocyclic compd. having a nitro group, nitroso group or cyano group is made into a soln. with a resin such as polyester, polymethyl methacrylate or polystyrene or the copolymer resin thereof as a binder and such soln. is coated on the substrate consisting of metal, paper, plastic, etc. and is dried to form the charge transfer layer. Methyl ethyl ketone, ethyl acetoacetate or butyl acetate are used for the solvent. The charge generating layer is formed by dispersing a charge generating pigment such as sudan red or dian blue together with a binder. The ratio of the charge generating layer and the binder resin in this case is about (5:1)-(1:5). The conveyance of a charge carrier from the charge generating layer to the charge transfer layer is thus executed without loss and the photosensitive body having high sensitivity with less dark attenuation is obtd.

Description

[Detailed description of the invention] TECHNICAL FIELD The present invention relates to a method of electrostatic charge formation.

Since organic photoconductive materials have lower sensitivity than inorganic photoconductive materials, several sensitization methods have been devised, and effective methods include a charge generation layer that generates charge carriers upon exposure to light, and a charge carrier transport method. In combination with a charge transport layer that has the ability to

゛A laminated electrophotographic photoreceptor made by such a method includes, for example, a conductive support such as an aluminum vapor-deposited film, a β-type copper phthalocyanine pigment, a styrene-butadiene resin dispersion layer, and an oxadiazole dissolved in a polyester resin. A device in which a layered charge transport layer is laminated is known. Similar to a general single-layer photoreceptor, an image can be formed on such a laminated photoreceptor by the Carlson process in which charging, one-imagewise exposure, and development are the base steps.

The laminated photoreceptor may have a structure in which a charge generation layer is laminated on a charge transport layer, or vice versa. It is an object of the present invention to provide an electrostatic image forming method that improves the number of durability when the process is used repeatedly and the charging potential during repeated use.

Such an object of the present invention is to provide a positive charge to the surface of an electrophotographic photoreceptor having a stacked layer in which a charge generation layer is formed on a conductive substrate and a charge transport layer, and an image exposure step. This is accomplished by electrostatic imaging, which forms a positive electrostatic image on the surface of the body.

That is, a photoreceptor having a structure in which a charge generation layer is formed on a charge transport layer tends to have poor sensitivity because the injection of charge carriers from the charge generation layer to the transport layer decreases. As a result of conducting various experiments regarding charge carrier injectability, it was found that it is best to use a solvent that causes the surface of the charge transport layer to swell with or be compatible with the charge generation layer solvent when the charge generation layer is applied. Therefore, the charge generation layer is formed using a solvent that is soluble in the charge transport layer, for example, a solvent that is the same as or different from the charge transport layer forming solvent, but that dissolves the charge transport layer. Also, when a charge generation layer is coated on a charge transport layer using such a solvent.

If the charge transport layer elutes, the properties will be significantly reduced. Therefore, it is important to apply the coating in a manner that prevents it from eluting, and a spray coating method is suitable for this purpose, which is a feature of the present invention. In the spray method, the coating liquid is sprayed with air, and the solvent adheres to the object to be coated and then evaporates in a relatively short period of time, so the solvent does not affect the substrate and has the effect of improving sensitivity. brought about.

Examples of charge-generating substances include azo pigments such as Sudan Red and Guianpuru, quinone pigments such as alcohol yellow and pinone quinone, indigo pigments such as indigo and thioindico, dithalocyanine pigments such as copper phthalocyanine, bisbenzimidazole pigments, and quinacridone pigments. etc.

In addition, the electron transport layer generally contains a polycyclic aromatic compound such as anthracene, pyrene, phenanthrene, coronene, or indole, carbazole, oxazole, inoxazole, thiazole, imidazole, pyrazole, or oxazole in the main chain or side chain. A compound having a nitrogen-containing cyclic compound such as diazole is used. These are electron-donating substances, and a photoreceptor in which a charge generation layer is formed on a charge transport layer is used with positive charging. Compared to negative charging, positive charging has more stable corona discharge, less ozone generation, and easier production of compatible developers.
Positive charging is more convenient.

Examples of electron-accepting substances forming the charge transport layer include aliphatic cyclic compounds, aromatic compounds, and heterocyclic compounds having electron-accepting substituents such as nitro group, nitroso group, and cyan group. Tetracyanoethylene, trinitrobenzene, ~ dinitrofluorenone, trinitroanisole, tetranitronaphthalene, terephdalonitrile, inphthalonitrile, henzoyl cyanide, quinoline cyanide, cyanopyridine, nitroanthracene, dinitrofluorenone, trinitrofluorenone, tetranitro Examples include fluorenone, tetracyanopyrene, etc. Electron-donating substances are more suitable for the charge transport layer.

To explain the present invention in more detail, first, the substrate may be metal, paper,
Plastic etc. are subjected to conductive treatment, subbing treatment, etc. as necessary, and used in an appropriate shape.

Charge transport materials on this substrate include polyester, polymethyl methacrylate, and polystyrene.

A charge transport layer is formed by making a solution of polyvinyl chloride, polyvinyl acetate, polyarylate, or a copolymer resin thereof as a binder, applying it, and drying it. The ratio (weight) of charge transport material and binding agent is 5:1 to 1
; It is about 2. The solvent must be able to dissolve both, and generally includes ketones such as methyl ethyl ketone and acetone, esters such as ethyl acetate and butyl acetate, aromatic hydrocarbons such as toluene and xylene, and monochloromethane. Chlorinated hydrocarbons such as benzene, dichlorobenzene, and chlorotoluene are used. Film thickness is 3-20
It is formed to the extent of 1.

The charge generating layer is then prepared by dispersing the charge generating pigment described above together with a binder. The binder resin may be the same as that used in the charge transport layer, or may be different, or two or more types may be mixed.

The resin has electrical properties, mechanical properties, and pigment dispersibility.

Selected taking into consideration stability, etc. The solvent used is the same as that used for forming the charge transport layer, or a different solvent that dissolves the charge transport layer. The ratio of charge generating pigment to binder resin is 5:
The ratio is about 1 to 1:5, particularly about 2:1 to 1:4. If the binder resin contains 5 parts or more to 1 part of the charge generating pigment, sufficient sensitivity cannot be obtained, and if the charge generating pigment contains 5 parts or more to 1 part of the binder resin, the lower example As clarified in the above, the charging characteristics deteriorate during repeated use. For dispersion, methods such as a ball mill, vibratory ball mill, attritor, sand mill, homogenizer, colloid mill, etc. are used. The dispersion is further diluted appropriately and applied onto the charge transport layer by spraying.

When spraying, the type of gun, air pressure, amount of application, spray distance, etc. are set appropriately. The film thickness is 0.1 to 1μ,
If it is thin, the sensitivity will be low, and if it is thick, the charging potential will decrease.

When the solvent is selected according to the present invention, the interface between the charge transport layer and the charge generation layer becomes compatible with each other to some extent. This allows charge carriers to be transported from the charge generation layer to the charge transport layer without loss, resulting in a photoreceptor with higher sensitivity and less dark decay than would otherwise be possible.

Example 1 An aluminum cylinder of 80 φ x 300 mm was treated with casein to form a substrate.

Next, 1 part of the pyrazoline compound of the structure, polycarbonate resin (
Prepare a coating solution consisting of 1 part (trade name: Tijin Panlite) and 10 parts of monochlorobenzene, apply it onto the above substrate by dipping method, and dry for 100"010 minutes to form a charge transport layer with a thickness of 13". did.

On the other hand, a mixed solution consisting of 1 part of copper phthalocyanine pigment (manufactured by Dainippon Ink), 1 part of linear polyester resin (trade name: Vylon 200, manufactured by Toyobo Co., Ltd.), and 4 parts of cyclohexanone was processed in a sand mill for 1 hour to obtain a pigment. was dispersed.

Further, 10 parts of methyl ethyl ketone was added to this solution to make a total of 6 parts, and the solution was applied by spraying onto the charge transport layer.

Cyclohexanone and methyl ethyl ketone are solvents that dissolve the charge transport layer. The coating conditions were as follows: Using a spray gun manufactured by Binks, the air pressure was 1.5 kg/cm 2 , the distance between the gun and the substrate was 3 cm, and the coating amount was 8 m. Spraying was carried out for 17 minutes while rotating the substrate and moving the gun in the longitudinal direction of the substrate. Thereafter, it was thoroughly dried at 80° C. to form a charge generation layer, thereby producing an electrophotographic photoreceptor.

Using this photoreceptor, the image was viewed in an electrophotographic copying machine consisting of +6.2 KV charging, image exposure, dry toner development, transfer to plain paper, and fur brush cleaning, and it was found that a good copy was obtained. Obtained. In addition, when measuring the characteristics, the charging potential is 560V, and the exposure intensity is 6, which reduces the potential by half.
．． The sensitivity was 8 lux·sec (this is considered the sensitivity).

Furthermore, the electrophotographic process consisting of the above-mentioned steps was performed for 500 times.
When copies were made 0 times, the images were as faithful to the original as the first copy, with no background stains. Also, when the charging characteristics were measured for the 5000th time,
The charging potential was 610 V, and the exposure intensity was 7.4 lux·sec to reduce the potential by half.

In order to compare with this photoreceptor, the same as in the above example was used except that the amounts of the copper phthalocyanine pigment and the linear polyester resin in the charge generation layer of the above example were 6 parts of the copper phthalocyanine pigment and 1 part of the linear polyester resin. An electrophotographic photoreceptor was prepared using the method described above, and its characteristics were then evaluated. As a result, a good copy was obtained at first, but gradually as the number of repetitions increased, the background smudge became more noticeable, and the background smear on the 5000th copy was more significant compared to the first copy obtained. It has been found.

In addition, when we measured the charging characteristics at the initial stage and at the 5000th time,
Initially, the charging potential is 510V, and the exposure intensity at which the potential is halved is 4. Flux seconds (but 500
At the 0th time, the charging potential was 970 V, and the exposure intensity at which the potential was reduced by half was 6.2 Lux·sec.

As described above, the copies obtained by the electrostatic image forming method other than the present invention were significantly less favorable than those of the present invention because of the occurrence of scumming during repeated use.

Example 2 The fabrication process up to the charge transport layer was carried out in the same manner as in Example 1.

Next, add 1 part of the following disazo pigment, 1 part of acrylic resin (trade name = 7 Kuribase, manufactured by Fujikura Kasei) as a binder, 10 parts of toluene, and 1 part of ethyl acetate.
0 part was dispersed in a vibrating ball mill for 1 hour using glass beads. In addition, t.

Luene and ethyl acetate partially dissolve the charge transport layer. This dispersion was spray coated onto the charge transport layer in the same manner as in Example 1.

When the characteristics of this photoreceptor were measured, the charging potential was 550 V, the sensitivity was 5.9 lux Φ seconds, and a good image could be obtained.

Furthermore, the electrophotographic process consisting of the above-mentioned steps was performed for 500 times.
When copies were made 0 times, the images were faithful to the originals and had no background stains to the same degree as the first copy. Further, when the charging characteristics were measured for the 5000th time, the charging potential was 600 V, and the exposure intensity was 6.9 lux per second, which halved the potential.

In order to compare with this photoreceptor, electrophotography was carried out in the same manner as in the above example except that the disazo pigment and acrylic resin in the charge generation layer of the above example were changed to 6 parts of the disazo pigment and 1 part of the acrylic resin. After the photoreceptor was prepared, its characteristics were evaluated.

As a result, good copies were obtained at first, but as the number of repetitions increased, the background smudges became more noticeable.
It was found that the background stain of the 00th copy was more significant than that of the first copy obtained.

In addition, 1. When we measured the charging characteristics at the initial stage and at the 5000th time, the charging potential was 480 V at the initial stage, and the exposure intensity at which the potential was halved was 3.8 lux seconds, but at the 5000th time, the charging potential was 880 V. The exposure intensity at which the potential is halved is 5
．． It was 8 lux·sec.

As described above, the copies obtained by the electrostatic image forming method other than the present invention were significantly less favorable than those of the present invention because of the occurrence of scumming during repeated use.

Examples 3 to 5 In Example 1, even when the following binder resin and solvent for the charge generation layer were used, a highly sensitive photoreceptor could be manufactured in the same manner as in Example 1.

3 Resin: Polyester (Product name: Pylon 50
0, Toyobo Button Solvent: Methyl ethyl ketone, methyl imbutyl ketone 4 Resin: Acrylic (Dainippon Ink Young Solvent: Toluene 5 Resin: Vinyl chloride-acetate copolymer (product name: VYHH, Union Carbide Co., Ltd. 1υ Solvent:
Methyl ethyl ketone, toluene Example 6 Same as Example 1 except that the amount of copper phthalocyanine pigment and linear polyester resin in the charge generation layer in Example 1 was changed to 3 parts of copper phthalocyanine pigment and 1 part of linear polyester resin. When an electrophotographic photoreceptor was prepared by the method described above and its characteristics were evaluated, the same results as in Example 1 were obtained.

Example 7 An electrophotographic photoreceptor was prepared in the same manner as in Example 2, except that the disazo pigment and acrylic resin in the charge generation layer were changed to 143 parts of disazo and 1 part of acrylic resin. When the characteristics were evaluated after that, the same results as in Example 2 were obtained.

Claims (10)

[Claims] (1) Positive charging on the surface of an electrophotographic photoreceptor having a laminate in which a charge generation layer is formed on a conductive substrate and a charge transport layer with a ratio of binder resin to charge generation pigment of 5:1 to 1:5. An electrostatic image forming method, characterized in that a positive electrostatic image is formed on the surface of the electrophotographic photoreceptor by a step of applying and an image exposure step. (2) The electrostatic charge image forming method according to claim 1, wherein the charge transport layer contains an electron donating substance. (3) The electrostatic image forming method according to claim 2, wherein the electron donating substance is a polycyclic aromatic compound or a nitrogen-containing cyclic compound. (4) The polycyclic aromatic compound is anthracene, pyrene,
The electrostatic image forming method according to claim 3, which is a compound containing phenanthrene or coronene. (5) The electrostatic image forming method according to claim 3, wherein the nitrogen-containing cyclic compound is a compound containing indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, or pyrazoline. (6) The electrostatic image forming method according to claim 1, wherein the charge-generating pigment contains an azo pigment, a quinone pigment, an indigo pigment, a phthalocyanine pigment, a bisbenzimidazole pigment, or a quinacridone pigment. (7) The electrostatic image forming method according to claim 6, wherein the azo pigment is a disazo pigment. (8) The electrostatic image forming method according to claim 7, wherein the phthalocyanine pigment is a copper phthalocyanine pigment. (9) The electrostatic image forming method according to claim 1, wherein the conductive substrate is a substrate subjected to undercoating treatment. (10) The electrostatic image forming method according to claim 1, wherein the conductive substrate is a substrate subjected to conductive treatment.