JPS6012551A - Composite type electrophotographic sensitive material - Google Patents

Abstract

PURPOSE:To obtain a composite type electrophotographic sensitive material extremely excellent in durability by using >=2 layers contg. an electrostatic charge transfer substance, different from each other in the content ratio of said substance to a binder resin. CONSTITUTION:A charge generating layer is formed by finely pulverizing a charge generating substance alone or together with a binder resin, etc. in a ball mill or roll mill or the like, mixing them with a solvent to prepare a liquid coating material, and applying it. Charge transfer layers e.g., in the case of 2 layers, the first layer is formed by using a coating material having a weight ratio of a charge transfer substance to a binder resin of 1:(0.25-2), and the surface layer of the photosensitive material, i.e., the outermost layer is formed by using a coating material having said ratio of 1:(1-8) to obtain an intended photosensitive material.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a photoreceptor that is effective for image creation by electrophotography, and in particular a composite type photoreceptor comprising a highly durable charge-generating material and a charge-transporting material. This invention relates to a photoreceptor for electrophotography.

[Background of the invention]

Conventionally, as a charge generating material for a composite type electrophotographic photoreceptor, organic No.
Monoazo dyes, disazo dyes and squaric acid derivative dyes soluble in amines, quinocyanine pigments shown in JP-A-53-42830 and JP-A-53-41230, quinocyanine pigments shown in JP-A-51-11763 Many organic materials such as copper phthalocyanine pigments have been proposed.

Inorganic substances such as tellurium, arsenic, and glassy selenium as shown in Japanese Patent Publication No. 50-15137, and polymers with imide bonds and amorphous selenium as shown in Japanese Patent Publication No. 49-14272 have also been proposed.

On the other hand, as a charge transport material, Japanese Patent Application Laid-Open No. 52-77730
Poly N-vinyl carno (sol type, JP-A-49-10
Pyrazoline derivatives disclosed in Publication No. 5537, JP-A-4
6-4484 discloses lutrinitrone luorenone, and Japanese Patent Publication No. 53-301 discloses various nitro- and cyano-substituted compounds. The sensitive wavelength range of electrophotographic photoreceptors using these is 400 to 700.
Although it has high sensitivity to visible light in the nanometer range and has been put into practical use as a photoconductor for copying machines, it has the disadvantage of being significantly inferior in durability compared to photoconductors made of inorganic materials, such as selenium photoconductors. are doing. Particularly in recent years, laser beam printers that use a laser as a light source have been developed as computer terminal printers, and in this case, it is desired that the durability of conventional photoreceptors for copying machines be further improved.

[Purpose of the invention]

An object of the present invention is to overcome the drawbacks of conventional composite type electrophotographic photoreceptors and to provide a composite type electrophotographic photoreceptor with extremely excellent durability.

[Summary of the Invention] In general, factors that determine the life of a composite type electrophotographic photoreceptor include, in addition to corona discharge and deterioration of the charge transport material due to light, there is also a factor that determines the lifespan of a composite electrophotographic photoreceptor. Examples include the occurrence of scratches due to friction.

In particular, in the case of a composite type electrophotographic photoreceptor, the structure of the charge transport material layer on the surface may be mainly a charge transport material/binder resin = 1/1 (weight ratio) trenches; Compared to the selenium photoreceptor of
There is a problem that the layer material has poor corona resistance. Based on this fact, the present inventors proposed a composite electrophotographic photoreceptor consisting of a layer containing a charge-generating substance and a layer containing a charge-transporting substance, in which the charge-transporting substance is bundled in various ways. It has been discovered that the above-mentioned problems can be overcome without deteriorating the electrophotographic properties by reducing the blending ratio of the charge transport substance on the surface side of the layer, and the present invention has been achieved.

A feature of the present invention is that the layer containing the charge transporting substance is composed of two or more layers having different blending ratios of the charge transporting substance and the binder resin.

More preferably, the surface side of the layer of the charge transporting material has a smaller proportion of the charge transporting material.

The composite type electrophotographic photoreceptor of the present invention is produced by forming a layer of a charge generating substance on a conductive support, and further adding:
Sequential formation of layers of charge transport material.

Alternatively, a layer of charge generating material may be formed on a layer of charge transporting material.

To form a layer of a charge generating substance, the charge generating substance alone or mixed with a binder resin, etc., is finely milled (particle size of 5 μm or less, especially 1 μm or less) using a ball mill or roll mill.
It can be formed by grinding and mixing to prepare a coating liquid and coating it. The thickness of the charge-generating substance layer varies depending on the required electrophotographic properties, the type of charge-generating substance, and the blending ratio with the binder resin, but it is usually 10 μm or less, preferably 0.5 to 3 μm or less, and If the thickness becomes too large, not only the electrophotographic properties will deteriorate, but also the film will lose its roughness, which may cause peeling. Further, the blending ratio of the charge generating substance and the binder resin is desirably 1 part by weight of the former to 4 parts by weight or less of the latter, and if it exceeds this, there is a possibility that the electrophotographic properties tend to deteriorate.

Formation of the layer of charge transport material is also carried out by coating.

The charge transport material layer requires a binder resin to provide the film with mechanical strength. Using an organic solvent that can dissolve both the charge transport substance and the binder resin, a solution in which both are dissolved is used as a coating liquid.

For example, when the charge transporting layer according to the present invention has two layers of charge transporting material, a coating solution containing 0.25 to 2 parts of binder resin per 1 part by weight of charge transporting material is used. The layer that forms the first layer and then becomes the surface of the photoreceptor, that is, the outermost layer, is:
This can be achieved by using a coating liquid containing 1 to 8 parts by weight of the binder resin to 1 part by weight of the charge transport material. In the first layer, if the proportion of the charge transport substance increases, the charged voltage and dark decay will be poor, and if the proportion decreases, the sensitivity will deteriorate. The amount of agent resin is 0.5 to 1 part by weight.

In addition to the above-mentioned reasons, the outermost layer should also preferably contain 1 part by weight of the charge transport material, since increasing the proportion of the charge transport material lowers the mechanical strength of the coating film and deteriorates its function as a photoreceptor. , 2 to 4 parts by weight of the binder resin. In addition, when the charge transport material layer is composed of three or more layers, the blending ratio of the charge transport material and the binder resin is selected to be between the blending ratios of the first layer and the outermost layer. It is desirable to do so.

The thickness of the charge transport material layer is determined by the charging characteristics required for the photoreceptor, but is usually 5 to 1. O0μm1 is preferably 8 to 30μm. The thickness of the outermost layer is preferably 10% to 50% of the thickness of the charge transport material layer. If it is less than 10 inches, the effect of improving durability will decrease,
If it exceeds 50%, electrophotographic properties deteriorate, particularly sensitivity is adversely affected.

As the charge-generating substance in the present invention, the compounds described above are used, but phthalocyanine pigments are particularly sensitive to a wide range of wavelengths from visible light to semiconductor lasers that emit long-wavelength light, and among them, Metal-free phthalocyanine exhibits high sensitivity and is effective.

The phthalocyanine used in the present invention is described in "Phthalocyanine Compounds" by Moser and Mass.
d Tbomes “phthalocyanineC
For example, metal-free phthalocyanines are metal phthalocyanines that can be demetalized with acids such as sulfuric acid, such as lithium phthalocyanine,
Those made directly from phthalodinitrile, aminoiminoisoindolenine, alkoxyiminoisoindolenine, etc. are used by acid treatment of metal phthalocyanines including sodium phthalocyanine, calcium phthalocyanine, magnesium phthalocyanine, etc. .

In order to mix in the above-mentioned proportions, they may be simply mixed or may be mixed before acid pasting the α-type metal-free phthalocyanine. The method of stirring or milling the mixture thus mixed may be the one normally used for dispersing, emulsifying, or mixing pigments, and examples of dispersion media for stirring or kneading include glass beads, steel beads, alumina balls, flint, etc. A dispersion medium is not necessarily required, although a stone is an example.

The crushing aid, the solvent during kneading, the materials and equipment used in the crystal transition step are the same as those for the τ type and τ' type gold metal phthalocyanine described above.

The temperature range in the η type and η' type gold metal phthalocyanine crystal transition step is 30 to 220 r, preferably 60 to 1
Perform within a temperature range of 30C. At higher temperatures, it is easy to transform to the β form, and at lower temperatures, it takes time to transform to the modified η and η′ forms. It is also an effective method to use crystal nuclei as in the usual crystal transition process.

In addition to the above-mentioned compounds, charge transport substances were also
Although the hydrazone compounds shown in Japanese Patent No. 5-42380 can be used, the compounds represented by the following general formula (A) are particularly preferred because they have excellent electrophotographic properties.

One type of heterocyclic group selected from R1゜ (however, Z is O or S
and the heterocyclic group may be substituted),
n represents 0, 1 or 2, and R+ and R2 are alkyl groups having 3 or less carbon atoms.

Although it is possible to use a different compound as the charge transport material in each layer of the charge transport material layer, when forming each layer,
Compatibility becomes an issue since earlier formed layers are somewhat dissolved by solvents during later formation, and it is preferable to use the same charge transport material.

The binder resin used in the layer of charge generating material and the layer of charge transporting material includes known electrophotographic binders such as phenolic resin, urea resin, melamine resin, furan resin, epoxy resin, silicone resin, and salt pea resin. Vinyl acetate copolymers, xylene resins, toluene resins, urethane resins, vinyl acetate-methacrylic copolymers, acrylic resins, polycarbonate resins, polyester resins, cellulose derivatives, and the like are appropriately selected and used. Furthermore, the photoconductive hole IJ -N-
Carbazole rings such as vinylcarbazole and poly-IJ-9-(p-vinylphenyl)anthracene, polymers with anthracene rings in their side chains, and other heterocyclic aromatic rings such as pyrazoline rings and dibenzomoofene rings. Polymers in the chain can also be used as binder resins.

In the present invention, surfactants and plasticizers can be added to the charge-generating material layer and the charge-transporting material layer as needed, and by adding these, mechanical properties such as adhesiveness and abrasion resistance can be improved. properties, film formability.

Electrophotographic properties can be improved by improving physical properties such as flexibility and dispersibility of materials.

Brass, aluminum laminate, gold, copper, etc. are used as the conductive support, and these may be in the form of a sheet or a thin cylindrical plate having an appropriate thickness, hardness, or flexibility.
It may also be coated with a thin layer of plastic. It may also be a metal coating, a metal plastic sheet, a glass coated with a thin layer of aluminum iodide, copper iodide, indium oxide or tin oxide. It is usually desirable that the support has sufficient strength to be handled.

[Embodiments of the invention]

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 2 parts by weight of β-type copper phthalocyanine pigment (manufactured by Inu Nippon Ink Co., Ltd., First Gen Blue FGF) and butyral resin (
XYHL (manufactured by Union Carbide Co., Ltd.) was mixed in a ball mill (manufactured by Nippon Kagaku Togyo Co., Ltd., full size pot) for 5 hours to form a solution of 5 parts by weight using xylene as a solvent to obtain a charge generating substance. A layer coating solution was obtained. Apply this coating liquid to a film thickness of 1
It was applied onto a 0 μm aluminum foil using an automatic applicator (12) (manufactured by Toyo Seiki Co., Ltd.) and dried to form a layer of charge-generating material. The thickness of this layer is approximately 1 μm. next,
1 part by weight of a compound having the following structural formula as a charge transport substance, polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.)
Dissolve 1 part by weight in 15 heavy liquid parts of tetrahydrofuran,
This coating liquid was applied onto the charge-generating material layer using an automatic applicator to form a charge-transporting material layer. The thickness of this layer is 10 μm, and this sample is designated as A1. Next, 1 part by weight of the charge transport substance,
4 parts by weight of the polyester resin, 3 parts by weight of tetrahydrofuran
A solution consisting of 0 parts by weight was prepared and further coated on Sample Boiled 1 to form a second layer of charge transport material. The thickness of this layer is approximately 3 μm, and this sample was
shall be. Also, apply this solution onto the charge generating material layer.
Coating was carried out so that the layer of charge transport material was 10 μm thick.

This sample is called A3. According to this example, the configuration (1
3) The electrophotographic properties of the composite electrophotographic photoreceptor were evaluated using an electrostatic recording paper tester (manufactured by Kawaguchi Electric Co., Ltd., 5P-428). In this case, conduct a corona discharge of -5KV for 10 seconds to charge the surface (the surface potential v'o (v) immediately after charging for 10 seconds is the initial potential), and leave it in a dark place for 30 seconds (the potential at this time is set to V2O). Represented by (V),
(Vao / Vo) Sensitivity (half exposure amount + Ell. (tx-5
)) was illuminated.

As a method of examining the corona resistance of these three types of samples, they were left in the eastern atmosphere of ozone and 9-element oxides generated by corona charging, and changes in electrophotographic characteristics before and after being left were examined. The test was carried out for 6 hours under conditions of ozone concentration of 100%, NO2 concentration of 2P, temperature of 22C, and humidity of 50% RH. The results are shown in Table 1.

(14) Table 1 As shown, the lower the blending ratio of the charge transport material on the surface side of the photoreceptor, the less deterioration may occur. A2, which has a higher ratio of , has better sensitivity K (Eso). As a way to examine the abrasion resistance of these samples, we examined their hardness using the pencil hardness test method. the result,
It was determined that sample 1 was F and samples &2 and 3 were 2H, indicating that the one with less charge transporting substance added was harder and had better durability.

Example 2 A polyester film coated with aluminum (manufactured by Toshi Co., Ltd., Metal Me, thickness 50 μm) was used as a support (15), and 1 part by weight of a compound having the following structural formula and an acrylic resin (manufactured by DuPont) were placed on the support (15). A charge generating material layer was formed in the same manner as in Example 1 using 1 part by weight of 2045), 30 parts by weight of methyl ethyl ketone, and 10 parts by weight of toluene. Next, a charge transport substance having the following structural formula, a polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., Nipilon 53000), and dichloromethane/1,2 dichloroethane-7/
Using the 3 (it weight ratio), layers of charge transport materials having different blending ratios of charge transport material and binder resin as shown in Table 2 were formed.

(16) These samples were actually tested on a copying machine (manufactured by Ricoh Co., Ltd., P-
500) to produce an image, and the lifespan (number of images) of the photoreceptor was investigated from the quality of the image obtained (fogging, dirt, resolution, single color density, etc.).

The results are shown in Table 2.

Table 2 As shown, the lifespan (durability) decreases when the proportion of the charge transport material in the second layer outside the surface of the charge transport material layer decreases.
was found to be significantly superior.

However, this seems to be because when the compounding ratio of the second layer is 1/6,178, the exposure amount must be increased, and the sensitivity tends to deteriorate.

Example 3 30 parts by weight of tetrahydrofuran was added to 1 part by weight of metal-free phthalocyanine and 0.5 parts by weight of the acrylic resin of Example 2, and a layer of charge generating material was formed in the same manner as in Example 1. Next, a charge transport substance having the following structural formula and a polycarbonate resin (manufactured by Kijinsha, Panlite L1250)
, dichloromethane/1,2-dichloroethane-7/3
Composite type electrophotographic photoreceptors having different concentrations of charge transporting substances as shown in Table 3 were obtained in the same manner as in Example 1 using (weight ratio). These electrophotographic characteristics are shown in Table 3 (18
) is shown.

(19) (20) As described above, when the blending ratio of the charge transport substance in the first layer decreases, the charging voltage improves, but the sensitivity tends to deteriorate.

Example 4 A composite electrophotographic photoreceptor as shown in Table 4 was obtained using the layer of the charge generating material of Example 3, the charge transporting material of Example 3, and the binder resin. Their electrophotographic properties are shown in Table 4.

(21) As described above, the sensitivity tends to decrease as the thickness of the second layer, which forms the surface of the photoreceptor, increases.

This is considered to be because the ratio of the charge transport material in the second layer is a little low, resulting in poor charge transport properties.

〔Effect of the invention〕

As detailed above, according to the present invention, the hardness of the surface of the photoreceptor and the deterioration of the charge transport material can be minimized without deteriorating the electrophotographic characteristics, thereby improving the durability (
effective for long life).

Agent Patent Attorney Akio Takahashi (23) Procedural Amendment (B) ¥:J') 136. A1,5β1ρ719 Indication of the case of Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office 1982 Patent Application No. 118222 Name of the invention Relationship to the case of a person who corrects a photoreceptor for composite electrophotography Patent applicant name Name (5] + 1) Stock Company Hitachi "J" Column "Detailed Description of the Invention" of the specification to be amended by the agent.

Claims (1)

[Scope of Claims] 1. In a composite electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge transport layer is a combination of a charge transport substance and a binder resin. A composite electrophotographic photoreceptor characterized by comprising two or more layers having different proportions. 2. In claim 1, the proportion of the charge transporting substance in the charge transporting layer on the side of the conductive support is greater than the proportion of the charge transporting substance in the charge transporting layer on the side of the conductive support. A composite electrophotographic photoreceptor characterized by: 3. A composite electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains a phthalocyanine compound.