JPH04174852A - Electrophotographic sensitive material - Google Patents

Abstract

PURPOSE:To provide sensitive material high in performance and durability by making up an electric charge generating layer furnished with the thermally hardened film of mixtures containing a specifically composed polymeric compound for binder and a aromatic carboxylic acid wherein electric charge generating agent is dispersed. CONSTITUTION:An electric charge generating layer is piled up onto an electric charge transfer layer, and the electric charge generating layer is made up of the thermally hardened film of mixtures containing a polymeric compound for binder indicated by a formula (I) and aromatic carboxylic acid wherein electric charge generating agent is dispersed. In the formula, at least, either of X1 and X2 shall be Br. Namely, the benzene ring of at least, either of X1 and X2 shall contain hydrogen which has been substituted for Br (100% substitution included). This thereby allows electrophotographic sensitive material to be high in performance and durability because aromatic carboxylic acid is used together with the polymeric compound having suitable binding action to the electric charge generating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an electrophotographic photoreceptor that undergoes processes such as charging, exposure, and development.

2. Description of the Related Art Conventionally, electrophotographic photoreceptors include those using inorganic photoconductive materials and those using organic photoconductive materials as photosensitive materials. The former inorganic photoconductive substances include selenium, zinc oxide, titanium oxide, and cadmium sulfide, and the latter organic photoconductive substances include phthalocyanine pigments and disazo pigments.

The former photoreceptor using an inorganic photoconductive material has thermal stability,
There are disadvantages in that durability and the like are not sufficient, or the inorganic photoconductive substance is toxic, causing problems in manufacturing and handling.

On the other hand, the latter photoreceptor (hereinafter referred to as
Due to its features such as non-polluting, excellent productivity and economy, and the ability to adjust the photosensitive characteristics of organic photoconductive materials through molecular design, it has been developed and put into practical use. It is now becoming the mainstay of electrophotographic photoreceptors.

OPC is usually used with a double layer structure consisting of a charge generation layer (CG layer) that absorbs light and generates carriers and a charge transfer layer (CT layer) that moves the generated carriers. It is planned. Generally, in a double layer structure, the CG layer is formed to have a thickness of several μm, and the CT layer is formed to have a thickness of several tens of μm, in order to increase sensitivity. At this time, for reasons such as strength and printing durability, the CG layer is usually formed on the base side and the CT layer is formed on the surface side. As CT agents (charge transfer agents), only those that operate by the movement of holes have been put to practical use, and therefore, the electrophotographic photoreceptor is necessarily of a negative charging type.

Problems to be Solved by the Invention However, with conventional negatively charged photoreceptors, the negative charge used for charging converts oxygen in the air into ozone (this ozone is not only harmful to the human body, but also often (causing oxidation of the body and accelerating deterioration of the photoreceptor) ■Charging is incomplete ■Easy to be affected by the drum surface.

In view of the above circumstances, it is an object of the present invention to eliminate the above-mentioned drawbacks of conventional OPCs and to provide an electrophotographic photoreceptor with high performance and excellent durability.

Means to Solve the Problem In order to achieve the above object, the inventors investigated OPC from various angles and focused on a polymer compound for the binder of the charge generation layer of the charge generation layer and the charge transfer layer. After extensive research, it was discovered that a polymer compound having the structure of the following formula is suitable for solving the above problems, and was previously proposed (Japanese Patent Application No. 2-135915).

(However, Xl, X2: At least one of them must be Br, that is, there must be a small number of hydrogens in the benzene ring of both of them substituted with Br (including 100% substitution)). In order to make it more practical, we continued to study and found that the combination of aromatic carboxylic acid with the above-mentioned polymer compound was very effective, and we were able to complete this invention. .

Therefore, in the electrophotographic photoreceptor according to the present invention,
Heat generation of a mixture in which a charge generation layer and a charge transfer layer are superimposed, and the charge generation layer contains a binder polymer compound having a structure represented by the above formula and an aromatic carboxylic acid, and a charge generation agent is dispersed therein. The structure is made of a cured film.

The aromatic carboxylic acids used in this invention include, for example,
As claimed in claim 2, examples thereof include compounds having at least one aromatic ring selected from a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. The amount of aromatic carboxylic acid added is usually about 2 to 30 Wt1 per 100 wt% of the above-mentioned binder polymer compound (resin material). If the amount added is too large, there is a disadvantage that sensitivity deteriorates.

In this invention, X-type phthalocyanine, which will be described later, is suitable as the charge-generating agent. In this case, as in claim 3, molecular phthalocyanine is included in the mixture together with the particulate X-type phthalocyanine for the charge-generating agent. A form in which it is included is preferred.

Other charge generating agents include perylene compounds, phthalocyanine compounds, thiapyrylium compounds, squarylium compounds, bisazo compounds, trisazo pigments, and azulenium dyes. These charge generating agents are not limited to being used alone, but may also be used in combination.

The weight ratio of the charge generating agent to the binder polymer is usually between about 1:1 and 1:10. If the amount of the charge generating agent exceeds the above ratio (1:l), the photosensitive characteristics will improve, but the charging characteristics will deteriorate, making it difficult to apply a potential of 500 .mu.m or more. On the other hand, if the amount of the binder polymer compound exceeds the above ratio (1:10), it becomes difficult to provide sufficient photosensitivity.

Usually, a mixture is prepared by also using a solvent for the polymer compound for the binder. Suitable solvents include nitrobenzene, chlorobenzene, dichlorobenzene, dichloromethane, trichloroethylene, chlornaphthalene, methylnaphthalene, benzene, toluene, xylene, tetrahydrofuran, cyclohexanone, 1,4-dioxane, N-methylpyrrolidone, carbon tetrachloride, Examples include bromobutane, ethylene glycol, sulfolane, ethylene glycol butyl ether, acetoxyethoxyethane, and pyridine.

In this way, a mixture made using a binder polymer compound, an aromatic carboxylic acid, a charge generating agent, a solvent, etc.
percoater, calendar coater, spin coater,
Using a blade coater, dip coater, gravure coater, etc., it is applied to the surface of a substrate (drum, belt, etc.) and cured by heat treatment. The resulting thermoset film is a charge generation layer.

The heat treatment conditions are usually a temperature of about 100 to 200°C and a treatment time of about 30 to 120 minutes.

Subsequently, a charge transport layer is formed on the charge generation layer. A mixture consisting of a charge transfer agent, a binder polymer compound, a solvent, etc. is applied and heat treated to form a charge transfer layer. Since the thermosetting film serving as the charge generation layer of the OPC of the present invention has excellent solvent resistance, there is an advantage that there are few restrictions on the type of solvent used to form the charge transfer layer. Further, an insulating protective film may be formed on the charge transfer layer.

Examples of the charge transfer agent include commonly known ones, such as hydrazone compounds, oxazole compounds, triphenylmethane compounds, and arylamine compounds.

In addition to those represented by the above formula, examples of the polymer compound for the binder for the charge transfer layer and the polymer compound for the protective film include polyester, polycarbonate, polymethacrylate,
Polystyrene, polyether, polyvinyl compounds, or copolymers and blends thereof are preferred since they exhibit good bonding properties to the charge generation layer. The solvents mentioned above can also be used.

Since the charge generation layer is a thermosetting film, when forming the charge transfer layer thereon, the same binder polymer compound (having the structure shown in the above formula), aromatic carboxylic acid, and solvent as the charge generation layer are used. It is also possible. In this case, the bonding state between the charge generation layer and the charge transfer layer is extremely good and stable, the photosensitivity is improved, the mechanical strength is increased, and the printing durability is improved. There are also fewer restrictions on the solvents used for formation.

Function The charge generation layer of the electrophotographic photoreceptor of the present invention uses the binder polymer compound represented by the above formula, so it is a hard, dense film with good heat resistance. If heat treated, this film quality tendency will be further strengthened. In other words, the film becomes more durable (for example, has excellent ozone resistance).

The binder polymer compound has good compatibility with various charge generating agents and solvents (even when dispersed in a sufficient amount, a good quality and uniform film is formed, so high performance can be achieved).

Examples Examples of the electrophotographic photoreceptor of the present invention will be described below. It goes without saying that this invention is not limited to the following embodiments.

In the OPC of this invention, when X-type phthalocyanine is used for charge generation, the inventors have found that the X-type phthalocyanine has good compatibility with the binder polymer compound and is suitable. This will be explained in detail below.

Phthalocyanines include metal phthalocyanines that have a metal atom in the center and metal-free phthalocyanines that do not have a metal atom. The latter metal-free phthalocyanine (hereinafter referred to as Ht-
(abbreviated as pc), two types, α type and β type, have been known as representative types.

In response to this, Xerox has recently developed X-type NT-PC, which has excellent electrophotographic properties, and is conducting research on its synthesis method, the relationship between crystal type and electrophotographic properties, and structural analysis. (USP 3.357°989)
. X type) (t-Pc is β type Hz synthesized by a conventional method
-Pc is made into the α form by sulfuric acid treatment, and this is produced by pole milling for a long time. Its crystal structure is clearly different from the conventional α and β forms. X type H,
- According to the X-ray diffraction diagram (measured using CuKa radiation) of PC, its diffraction lines are 2θ=7.4°9.0. 15.1.
16.5. 17.2. 20.1. 20.6.
20.7°21.4. 22.2. 23.8. 27
．． 2. 28.5. Appears in 30.3 (unit 0).

The most intense diffraction line is 7.5° (planar spacing d=1
If the intensity of the diffraction line near 9.1° (corresponding to 1.8'A) is 1, then the intensity of the diffraction line near 9.1° (corresponding to d=9
．． 8A) is 066.

It is added to a solvent together with the polymer compound for the X-type H2-PC binder and dispersed by stirring and mixing (kneading).

When stirring and mixing are performed sufficiently, the X-type Ht-pc is turned into fine particles and at the same time partially solubilized (it is considered that the viscosity is increased, so it is solubilized). The mixture contains Hl in a molecular form different from the particulate X-type nz-E'c for the charge generating agent.
- It is thought that this caused PC.

It is inferred that the presence of molecular (z-Pc) provides the CT function. When X-type Ht-pc is used, the X-ray diffraction pattern is similar to that of X-type) Jt-Pc alone. It is clearly different from the diffractogram of α- and β-forms)(t-Pc, i.e., its X-ray diffraction pattern is different from the X-ray diffractogram of Compared to Around 75° (d == 11.8A) and 91
Of the two diffraction lines near 75° (d-98 people), only the diffraction line near 75° has selectively disappeared. From this, it is inferred that at least a part of the X-type H, -Pc has changed into a new one.

Degree of stirring and mixing (usually one day or more of stirring is required) time,
Temperature etc. vary depending on the solvent used. The appropriate degree of processing is X#! 7.5° of diffraction pattern
Diffraction line intensity ratio near 91° (1, , , /1.,
=) can be seen. Preferably, this ratio is between 1 and 01.

As mentioned above, the X-type metal-free phthalocyanine, binder polymer, aromatic carboxylic acid, and solvent are mixed together using a ball mill, attritor, sand mill, sand gland, etc., and then coated and heat-treated. and heat cured film.

During the mixing process, as the process progresses, part of the 7-talocyanine becomes solubilized and at the same time becomes finely dispersed, becoming properly dispersed, further increasing its viscosity and improving the light absorption rate of the formed film. . The reason why the light absorption rate of the film improves is not clear, but it is surmised that it is due to the interaction between the X-type phthalocyanine solubilized during the mixing process and the polymeric compound for the binder.

When X-type phthalocyanine is used in the charge generation layer of the OPC of this invention, it will have the following characteristics.

■ Extremely sensitive. Some reach 2 lux-sec.

(2) It has excellent photosensitivity, being sensitive over a wide wavelength range of 550 to 800 nm.

In addition, H, -P having a crystal type other than the above XmH, -PC
As C, there is a τ type 'H, -Pc. This is α, β,
Type X crystals are mixed with a grinding aid in an inert solvent at 5-10°C.
Obtained by ball milling for 20 hours. Its Xls diffraction pattern is essentially similar to that of type X. However, in this case, the ratio of the diffraction line intensity around 7.5° to the diffraction line intensity around 9.1° is 1:08. This τ type H1-PC can also be used in the same way as the X type Ht-Pc.

The electrophotographic photoreceptor of the present invention is used, for example, in recording equipment such as copying machines, printers, and facsimile machines.
It may also be used for other purposes.

This invention is not limited to the above configuration. Similar effects can be obtained even with a structure in which the charge generation layer is placed on the charge transfer layer.

More details are provided below.

Example I Type X metal-free phthalocyanine [Fastogen Blue 8120B manufactured by Inu Nippon Ink ■
)) and a polymer compound FOC-10 (manufactured by Fuji Yakuhin) having the structure shown below (however, the Br conversion rate is 25 cm) as a polymer compound for binder were dissolved in tetrahydrofuran at a weight ratio of 1:1, and 2 -naphthoic acid FOC-10
After further dispersing and mixing using a ball mill method, the resulting solution was applied to the surface of an aluminum drum plate using a dip method, and heat treated in air at 150°C for 2 hours to harden it and generate a charge with a thickness of 1 μm. formed a layer.

Next, C which is a hydrazone compound as a charge transfer agent
TC-236 (manufactured by Anan Koryo Co., Ltd.) and polyester as a binder polymer compound are dissolved and mixed in tetrahydrofuran, and the resulting solution is applied onto the charge generation layer and heat treated to form a charge transfer layer with a thickness of 15 μm. and obtained OPC.

The photosensitive characteristics of the obtained OPC were investigated. For the measurements, we used an EPA-81QQ paper analyzer manufactured by Kawaguchi Electric, and irradiated the negatively charged OPC with white light from a tungsten lamp to measure the charged voltage, photosensitivity (half-reduced exposure amount,
E,/,) and residual potential Vr were measured. Also, 10000
Similar measurements were made for those that had been subjected to repeated tests. The measurement results are shown in Table 1.

(Margins below) Table 1 Example 2 X-type metal-free phthalocyanine [Fastogen Blue 812 manufactured by Inu Nippon Ink ■
OB)) and a polymer compound FQC-12 (manufactured by Fuji Pharmaceutical) having the structure shown below (however, the Br conversion rate is 50%) as a polymer compound for binder are dissolved in cyclohexanone at a weight ratio of 1:1, After adding anthracene-2-carboxylic acid and thoroughly dispersing and mixing, the resulting solution was applied to the surface of an aluminum drum plate by the dip method, and heat treated in air at 150°C for 2 hours to form a charge generating layer with a thickness of 1 m. was formed.

Next, C which is a hydrazone compound as a charge transfer agent
Dissolve TC~236 (manufactured by Anan Koyo Co., Ltd.) and FOC-12 as a polymer compound for binder in cyclohexanone, add 2-naphthoic acid and mix thoroughly, and apply the obtained solution on the charge generation layer. A charge transfer layer having a thickness of 15 μm was formed by heat treatment to obtain an OPC.

The number of repeated tests for the obtained OPC was 200.
The same measurement as in Example 1 was performed except that the measurement was carried out 00 times. The measurement results are shown in Table 2.

(Margins below) Table 2 We also carried out measurements similar to the above under various atmospheric conditions ranging from 5 to 40 degrees Celsius and humidity from 20 to 85%, but there were still large differences in the measurement results. It didn't come out.

By repeating the manufacturing process several times, we were able to reproducibly manufacture OPCs with uniform properties.

From these results, the OPC of the example has extremely excellent characteristics such as charging voltage and photosensitivity, and the ozone resistance is improved, as the results of repeated tests using a negative charging method that involve the generation of ozone are good. It's good (I understand).

Furthermore, a copying machine (Panas) was used in the same manner as in Example 2.

n1cNP-1530), laser printer (Panas
An OPC was made to be attached to the onic L-136), and a quality evaluation test for images, etc. was conducted. Several types of OPC with different surface roughness and surface cleaning methods were made and compared for raw tubes for aluminum drums, but no major differences were found in the characteristics of the OPC. It has also been found that in the case of the OPC of the present invention, the condition of the base material surface does not affect the quality of the product as described above, and it can be manufactured with a high yield.

Printing was performed repeatedly (10,000 times) using A4 size test paper, but no image blurring or other problems were observed.

Comparative Example 1 An attempt was made to obtain OPC in the same manner as in Example 1 except that 2-naphthoic acid was not added, but the OPC of Comparative Example 1 was
Since 2-naphthoic acid was not added, the charge generation layer was dissolved in tetrahydrofuran, which was used for the charge transfer layer, and O
I couldn't get a PC.

Effects of the Invention As described above, the electrophotographic photoreceptor according to the present invention has high performance because aromatic carboxylic acid is used in the charge generation layer together with a polymeric compound having an appropriate binder action. It is highly durable and highly practical.

Claims (4)

[Claims] (1) A charge generation layer and a charge transfer layer are superimposed,
An electrophotographic photoreceptor, wherein the charge generation layer is a thermosetting film of a mixture containing a binder polymer represented by the following formula and an aromatic carboxylic acid, in which a charge generation agent is dispersed. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, X1, X2: At least one of them is Br, that is, at least one of the benzene ring hydrogens is substituted with Br (including 100% substitution) ) (2) The electrophotographic photoreceptor according to claim 1, wherein the aromatic carboxylic acid has at least one aromatic ring selected from a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. (3) The electrophotographic photoreceptor according to claim 1 or 2, wherein the mixture also contains molecular phthalocyanine together with particulate X-type phthalocyanine for charge generation agent. (4) As a charge generating agent, a perylene compound, a phthalocyanine compound, a thiapyrylium compound, a squarylium compound, a bisazo compound, a trisazo pigment,
The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein at least one of the azulenium dyes is contained in the mixture.