JPS63304265A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the sensitivity of an electrophotographic sensitive body without changing the kinds of materials, proportions of the components, thickness of each layer, etc. by forming a charge generating layer by coating a liquid dispersion obtd. by adding an acid to a soln. of a binder resin on a charge generating material. CONSTITUTION:A charge generating layer 2 and a charge transfer layer 3 are formed on a substrate 1 wherein the charge generating layer 2 is formed by coating a liquid dispersion obtd. by adding an acid to a soln. contg. a binder resin on a charge generating material 4. In order to obtain better effect of the acid, it is preferred to carry out acid treatment previously by dispersing the charge generating material in a soln. of an acid, then dispersing the binder resin by adding the soln. of the binder resin thereto. Suitable amt. of the acid to be added is about 0.1-2mol.% basing on the amt. of the charge generating material. If the amt. of the acid is less, the sensitizing effect is less. The sensitivity of an electrophotographic sensitive body is improved by carrying out a simple treatment, namely, by adding an acid in a stage of dispersion of a charge generating material.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laminated electrophotographic photoreceptor having improved sensitivity.

Conventional electrophotographic photoreceptors include those using inorganic photoconductors and those using organic photoconductors.

Among these, photoreceptors using organic photoconductors have come into widespread use in recent years because they have advantages such as fewer environmental pollution problems, high productivity, and low cost.

However, among organic photoconductors, substances that absorb visible light and generate electric charge have poor charge retention ability, whereas materials that have good charge retention ability and excellent film forming properties generally The drawback is that there is almost no photoconductivity due to light. As a method for solving this drawback, there is a method of functionally separating the photosensitive layer into a charge generation layer that absorbs visible light to generate charges and a charge transport layer that transports the charges, and then forming a laminated structure.

By adopting such a laminated structure, the charge generation material and the charge transport material can be selected individually, and the selection criteria for each material can be widened. Examples of charge-generating materials include polycyclic quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, quinacridone pigments, phthalocyanine pigments, monoazo pigments, disazo pigments,
Tris or higher polyazo pigments are known, and as charge transport materials, amine compounds, hydrazone compounds, pyrazoline compounds, oxazole compounds, oxadiazole compounds, stilbene compounds, carbazole compounds, etc. are known.

In order to produce an electrophotographic photoreceptor using these materials, electrophotographic properties such as sensitivity, acceptance potential, potential retention, potential stability, residual potential, and spectral properties, as well as strength, durability,
It is necessary to select materials that are satisfactory in all respects of usage properties, such as stain resistance.

Among these characteristics, the sensitivity of an electrophotographic photoreceptor is the most important, and improvement in sensitivity is always desired.

Sensitivity is mainly determined by the combination of the charge generating material and the charge transporting material, but it also changes depending on the conditions for forming the charge generating layer and the charge transporting layer, the adjustment of the components, etc.

Problems to be Solved by the Invention Sensitivity can be increased to some extent by, for example, increasing the thickness of the charge generation layer and/or the charge transport layer. However, there are limits due to changes in physical properties other than sensitivity or constraints on manufacturing technology. Increasing the proportion of the charge-generating material in the charge-generating layer is also effective for improving sensitivity, but this also has limits due to changes in physical properties other than sensitivity and constraints on manufacturing technology. Therefore, there has been a desire for a means to further improve sensitivity by selecting specific types of charge-generating material and charge-transporting material.

Therefore, an object of the present invention is to provide an electrophotographic photoreceptor in which only the sensitivity is improved without changing the type of material, the ratio of components, the thickness of each layer, etc.

Means for Solving the Problems As a result of extensive research, the present inventors have discovered that sensitivity can be improved by adding and dispersing a charge generating material together with an acid in a binder resin solution, and have developed the present invention. I was able to complete it.

That is, the laminated electrophotographic photoreceptor of the present invention has at least a charge generation layer and a charge transport layer provided on a substrate, and the charge generation layer is obtained by adding a charge generation material to a binder resin solution together with an acid. It is characterized in that it is formed by applying a dispersion liquid obtained by

The present invention will be explained in detail below.

FIG. 1 is a schematic diagram showing a cross section of the electrophotographic photoreceptor of the present invention, showing an enlarged view of the charge generation layer. A charge generation layer 2 and a charge transport layer 3 are provided on the substrate 1, and the charge generation layer 2 includes a charge generation material 4 and a charge transport layer 3.
5 is included. FIG. 2 is a schematic diagram of another embodiment of the present invention, in which a barrier layer 6 is provided between the base 1 and the charge generator 112.

As the substrate for the electrophotographic photoreceptor of the present invention, those conventionally used in electrophotographic photoreceptors can be used.

A charge generation layer is formed on the substrate by applying a dispersion of a powder charge generation material dispersed in a binder resin solution, but in the present invention, an acid is added together with the charge generation material. It is characterized in that it uses a dispersion obtained by

As described above, the C sensitivity can be improved simply by adding an acid during dispersion of the charge generating material.

The types of acids used include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, and phosphoric acid; organic acids such as formic acid, acetic acid, propionic acid, acetic acid, lactic acid, benzoic acid, and sulfonic acid; Examples include halogen-substituted products, nitro-substituted products, and alkyl-substituted products.

Among these, organic acids that are easily compatible with organic solvents are preferred, and mono-, di-, or trifluoroacetic acid is particularly preferred since it has a remarkable effect of improving sensitivity.

As the charge generating material, known pigments can be used. For example, polycyclic quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, quinacridone pigments, phthalocyanine pigments, monoazo pigments, disazo pigments, tris or higher polyazo pigments, etc. can be used.

As a dispersing means for dispersing these charge generating materials, those used in conventional methods such as a ball mill, roll mill, sand mill, attritor, etc. can be used.

As the binder resin, for example, polycarbonate, polystyrene, polyester, polyvinyl butyral, methacrylic acid ester polymer or copolymer, vinyl acetate polymer or copolymer, cellulose ester or ether, polybutadiene, polyurethane, epoxy resin, etc. are used. It will be done.

The acid may be added when dispersing the charge generating material in the binder resin solution, but in order to bring out the effect of the acid even more, the charge generating material is dispersed in an acid solution in advance and subjected to acid treatment. Preferably, a resin solution is then added thereto for dispersion.

The amount of acid added is approximately 0.1 to 2 mol % based on the charge generating material. When the amount of acid is small, the sensitizing effect is small, and when the amount of acid is too large, physical properties other than sensitivity tend to occur, such as a decrease in charging potential and a decrease in repeat stability. In the case of acids that contain water, such as hydrochloric acid and nitric acid, it is necessary to exclude the water content in the calculation. Although water will be mixed into the dispersion, it will not be a problem since it is extremely small compared to the total amount of the dispersion.

Note that when dispersing the charge-generating material in a solvent, it is better to add an acid and then disperse it together with the binder resin solution. The sensitizing effect is greater than when mixed and dispersed.

On the other hand, the charge transport layer is made of the charge transport material described above and a resin having film-forming properties. As such resins, general binding resins such as polycarbonate, polyarylate, polyester, polystyrene, styrene-acrylonitrile copolymer, polysulfone, polymethacrylic acid esters, and styrene-methacrylic acid ester copolymer are used.

The blending ratio of the charge transport material and the resin is about 5:1 to 1:5, preferably about 3:1 to 1:3. If the former is too large, the mechanical strength of the charge transport layer will be reduced, and if it is too small, the sensitivity will be reduced. The thickness of the charge generation layer is 0.05 to 5.
μ, the thickness of the charge transport layer is approximately 5 to 50 μ.

Further, as shown in FIG. 2, a barrier layer 6 may be formed between the charge generation layer and the substrate. The barrier layer is effective in preventing unnecessary charge injection from the substrate, and can increase the chargeability of the photosensitive layer.

In addition, it is also possible to improve the adhesion between the photosensitive layer and the substrate. Materials for the barrier layer include polyvinyl alcohol,
Polyvinylpyrrolidone, polyvinylpyridine, cellulose ethers, cellulose esters, polyamide, polyurethane, casein, gelatin, polyglutamic acid,
Examples include starch acetate, amine starch, polyacrylate, polyacrylamide, and the like. The resistivity of the material is preferably about 10'' to 1014 Ω·cm. The thickness of the barrier layer is about 0.05 to 2 μm.

The reason why the sensitivity is improved when an acid is included in the charge generation layer is not known in detail, but it is believed that the acid changes the surface properties of the charge generation material and that the acid have the property of forming a charge transfer complex with all electron-donating compounds).

Also, acids tend to collect around charge generating materials.

At the interface between the charge generation layer and the charge transport layer, a charge transfer complex is formed by contact between the acid and the charge transport material, resulting in a low resistance region with reduced electrical resistance. Since acid is originally a substance with low resistance compared to the binder resin, when the charge generation layer is irradiated with light, the photoelectric charge is injected directly from the charge generation material into the charge transport layer. From charge-generating materials, acids,
When photocharge is injected through a low-resistance part called a charge transfer complex, the charge flows more easily, improving the injection property.
It is thought that the sensitivity will be improved.

Example Hereinafter, the present invention will be explained by examples.

Example 1 and Comparative Example 1 1 part (by weight, the same hereinafter) of polyvinyl butyral resin (trade name: BHl, manufactured by Tsukisui Kagaku ■) was mixed with 1 part of cyclohexanone.
It was dissolved in 9 parts. To this solution were mixed 8 parts of dibromanthanthrone pigment (C, 1, Pigment Red 168) and 0.02 part of trifluoroacetic acid. in this case,
The acid is 1 mole percent of the pigment.

Next, dispersion was performed using a sand mill using 11It11φ glass beads as a dispersion medium. Cyclohexanone was further added to the dispersion liquid to prepare a coating liquid having a solid content concentration of about 10%.

On the other hand, 84 parts of a methanol/butanol mixed solution of nylon 8 resin (trade name Niratsukamite, manufactured by Dainippon Ink) was applied to an aluminum pipe of mφ x 310#I.
．． A barrier layer with a thickness of 8 μm was formed, and the coating solution was applied thereon using a ring coater, and the layer was dried by heating at 100° C. for 10 minutes to form a charge generation layer with a thickness of 0.8 μm. .

On the other hand, N,N--diphenyl-N,N--bis(3-methylphenyl)-[1,1-biphenyl]-4,4"
- 5 parts of diamine was used as a charge transport material and dissolved in 40 parts of monochlorobenzene along with 6 parts of polycarbonate 2 resin. The obtained solution was applied by dip coating method, and 110
It was dried at ℃ for 1 hour to form a 20 μm charge transport layer.

For comparison, an electrophotographic photoreceptor was prepared in the same manner except that trifluoroacetic acid was not added when dispersing the pigment. (Comparative Example 1) These electrophotographic photoreceptors were charged to -800 Vk, and then white light was irradiated to attenuate the light, and the exposure amount E (erg
/Cl7K) and potential attenuation V, and the sensitivity dV/d
I asked for E. After repeating the above-mentioned charging and white light irradiation operations 20 times, the sensitivity was determined in the same manner. The results are shown in the table.

As is clear from this result, Example 1 in which acid was added had higher sensitivity.

Example 2 8 parts of pigment (same as Example 1) and 0.0 part of trifluoroacetic acid
2 parts of cyclohexanone and 12 parts of cyclohexanone were mixed, and then ultrasonic waves were applied for 30 minutes to stir well. A solution consisting of 1 part of polygonyral resin (same as in Example 1) and 7 parts of cyclohexanone was added to this, and sand mill dispersion was performed. Cyclohexanone was further added to the dispersion liquid to obtain a coating liquid having a solid content concentration of about 10%.

Other than using this coating liquid! An electrophotographic photoreceptor was produced in the same manner as in Example 1. When the sensitivity was measured, it was 90 (v-Cd/ergS) for the first time and 90 (v-Cd/ergS) for the 200th time.
-cd/ergS) Tea ivy.

Example 3 Instead of trifluoroacetic acid in Example 1, 0.036 parts of 35% hydrochloric acid was used. In this case the acid (hydrogen chloride) is 2 mol% of the pigment. Otherwise, an electrophotographic photoreceptor was produced in the same manner as in Example 1. When I measured the sensitivity, it was 89 (v・d/ergs) for the first time, and 8 for the 20th time.
8 (v-7/ergS). Also, add 0.01 hydrochloric acid
8 parts (acid is 1 mol% of the pigment), the sensitivity is 85 (v ci/ergS) for the first time and 85 (v ci/ergS) for the 200th time.
-CIi/ergs), and the sensitivity was slightly lower.

Effects of the Invention As described above, in the electrophotographic photoreceptor of the present invention, since the charge generation layer is formed by adding an acid when dispersing the charge generation material, no acid is added. It has increased sensitivity compared to those formed with.

The electrophotographic photoreceptor according to the present invention is effectively used in electrophotographic copying machines, but can also be applied to various printers, microfilm readers, electrophotographic engraving systems, etc. that apply xerography technology.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cross section of an electrophotographic photoreceptor of the present invention, and FIG. 2 is a schematic diagram of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Charge generation layer, 3... Charge transport layer, 4... Charge generation material, 5... Acid, 6... Barrier layer. Patent applicant Fuji Pilots Co., Ltd. Agent
Patent Attorney Tsuyoshi Horabe 1...Substrate 2...Charge generating layer 3...Charge transporting layer 4...Charge generating material 5...Acid 6...Barrier layer Fig. 2

Claims (3)

[Claims] (1) In a laminated electrophotographic photoreceptor in which at least a charge generation layer and a charge transport layer are provided on a substrate, the charge generation layer is a dispersion obtained by adding a charge generation material to a binder resin solution together with an acid. An electrophotographic photoreceptor characterized in that it is formed by coating. (2) A patent claim in which the charge-generating layer is formed by coating a dispersion obtained by dispersing the charge-generating material in advance in an acid solution and then adding it to a binder resin solution. The electrophotographic photoreceptor according to item 1. (3) The electrophotographic photoreceptor according to claim 1 or 2, wherein the acid is an organic acid.