JPH0271274A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide the photosensitive body which is not deteriorated in the characteristics even when the body is exposed in an oxidation atmosphere by incorporating at least one kind selected from a charge transfer material and specific compd. into a photosensitive layer. CONSTITUTION:At least one kind selected from the charge transfer material, more preferably the transfer material expressed by the formula I and the compds. expressed by formulas II to IV are incorporated into the photosensitive layer. In the formulas I to IV, R<1> to R<4> denote a hydrogen atom, alkyl group, alkoxy group, halogen atom or substd. amino group; R<2> and R<3> denote a hydrogen atom, alkyl group or substd. or unsubstd. phenyl group. The formula V denotes a benzene ring, naphthalene ring, anthracene ring, indole ring or carbazole ring; n denotes 0 or 1; m denotes 0, 1, 2 or 3 integer. The photosensitive body which is free from the degradation of sensitivity, the degradation of electrostatic charge potential, etc., and is not deteriorated in the characteristic even when the body is exposed in the oxidation atmosphere is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor that has excellent charging stability even when used repeatedly over a long period of time. .

[Conventional technology]

Inorganic materials such as selenium, cadmium sulfide, and zinc oxide have been conventionally known as photoconductive materials for electrophotographic photoreceptors. However, these inorganic materials do not necessarily satisfy the characteristics such as photosensitivity, thermal stability, and durability required for electrophotographic photoreceptors, as well as manufacturing conditions. For example, selenium tends to crystallize due to heat, dirt, etc., and its properties tend to deteriorate. In addition, it has drawbacks such as manufacturing cost, impact resistance, toxicity, and other issues that require careful handling.

Photoreceptors using cadmium sulfide have poor moisture resistance and durability, and also have problems such as toxicity. Zinc oxide also has the disadvantage of poor moisture resistance and durability.

For electrophotographic photoreceptors using these inorganic photoconductive materials,
Photoreceptors using organic photoconductive materials are being actively researched and developed because of their lightness, ease of film formation, manufacturing cost, and wide variation as organic compounds. For example, in the early stage, polyvinylcarbazole and 2.4.7-t-
A photoreceptor containing lintro-9-fluorenone, a photoreceptor in which polyvinylcarbazole is sensitized with a pyrylium salt dye as described in Japanese Patent Publication No. 48-25658, or a photoreceptor having a eutectic complex as a main component has been proposed. however,
These photoreceptors do not have sufficient sensitivity and durability.

Therefore, in recent years, the charge generation layer and charge transport layer have been separated.
A functionally separated photoreceptor was proposed, published in Japanese Patent Publication No. 55-4238.
A photoreceptor comprising a combination of chlordiane blue described in No. 0 and a hydrazone compound, the charge generating substance being a bisazo compound as described in JP-A-53-133445, JP-A-54-21728, and JP-A-54-228.
34, as a charge transport material, JP-A-58-1
98043 and those described in JP-A-58-199352 are known. However, these function-separated photoconductors are not particularly satisfactory in terms of durability, and in recent years, as demands for durability have been increasing,
Ensuring charging stability has become a problem that cannot be ignored. That is, if the charging property decreases, it causes a decrease in the image density of the copy in a copying machine, and in the case of a laser printer using a reversal development method, it causes a decrease in image quality such as background staining. In order to solve these problems, it has been proposed to provide an intermediate layer between the conductive substrate and the photosensitive layer. However, if a high-resistance material with high barrier properties is used for the intermediate layer in order to stabilize the charging property, although the charging property will improve, the photosensitivity will decrease.
The disadvantage is that the residual potential increases. Furthermore, if a material with relatively low resistance that does not increase the residual potential is used, charging stability will be insufficient.

On the other hand, when a photoreceptor is actually used in a copying machine, the photoreceptor is exposed to ozone generated by a charger and is therefore subject to strong oxidation. Particularly in the case of organic photoreceptors, this effect is significant, and the materials constituting the photosensitive layer gradually oxidize and decompose, resulting in deterioration in the performance and durability of the photoreceptor. As a countermeasure, JP-A No. 57-122444,
JP-A-61-156052, JP-A-62-39863
The addition of an antioxidant to the photosensitive layer has been proposed, as shown in the above issue. However, in order to prevent brushing or to form a uniform photosensitive layer, a high boiling point organic solvent with a boiling point of 130°C or higher is generally used as a coating solvent, and its drying requires a high temperature of 130°C or higher. When dried at such high temperatures, ordinary antioxidants undergo thermal deterioration and do not lose their functionality, and therefore, when a photoreceptor is exposed to an oxidizing atmosphere such as ozone, its photoreceptor properties deteriorate.

[Problem to be solved by the invention]

The present invention has been made in view of the above-mentioned state of the prior art, and its purpose is to be able to easily produce the product by a coating method using a high boiling point organic solvent, and to be able to easily produce the product even when exposed to an oxidizing atmosphere. An object of the present invention is to provide an electrophotographic photoreceptor whose photoreceptor characteristics do not deteriorate.

[Means to solve the problem]

The present inventors formed a photosensitive layer using a coating method using a high-boiling organic solvent, and then dried it at high temperatures without losing its oxidation-preventing function. As a result of intensive research into the following agents, it was discovered that the specific phenolic antioxidant shown below satisfies the above-mentioned properties, and the present invention was completed.

That is, according to the present invention, in an electrophotographic photoreceptor having a photosensitive layer provided on a conductive support, the photosensitive layer contains a charge transporting substance, preferably a transporting substance represented by the following general formula (II), and a transporting substance represented by the following general formula (II). ), formula (1-8), and formula (1-C).

(In the formula, R1 and R4 are hydrogen atoms, alkyl groups, alkoxy groups, halogen atoms, or substituted amino groups, R2 and R
3 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted phenyl group.

]Co is a benzene ring, a naphthalene ring, anthraC-x
-' represents a sen ring, an indole ring or a carbazole ring.

n is 0 or 1, m is 0, 1, 2. or an integer of 3.

) The electrophotographic photoreceptor of the present invention has the formula (I-
A), because it contains at least one compound selected from formula (1-B) and formula (1-C), it has excellent oxidation resistance, especially ozone resistance, and can be stored for a long time. Also, the photoreceptor characteristics do not deteriorate and the storage stability is extremely excellent.

The compounds represented by the formula (1-A), formula (1-B) and formula (I-C) used in the present invention are known compounds, but even if the photosensitive layer is dried at high temperature, other antioxidants It is a suitable antioxidant that does not lose its antioxidant function, unlike other substances, and does not have an adverse effect on other substances contained in the photosensitive layer.

Further, according to studies conducted by the present inventors, it has been found that the above-mentioned effects are even more pronounced when a compound represented by the general formula (II) is used as a charge transporting substance.

Specific examples of the charge transport substance represented by the general formula (II) that can be used in the present invention include the following compounds.

10-32~ As charge generating substances that can be used in the present invention, there are the following: (1) Perylene pigments such as perylene acid anhydride and perylene acid imide.

■Indigo pigment.

■Quinacridone pigment.

■Polycyclic quinones such as anthraquinones, birequinones, anthoanthros, and flavanthrones.

■Bisbenzimidazole pigment.

■Squaric methine pigment.

■Indathlon pigment.

■Phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine.

■ Azo pigments such as monoazo pigments, disazo pigments, and triazo pigments. Examples of monoazo pigments include monoazo pigments having a central skeleton of anthraquinone, N-phenylcarbazole, etc.; examples of disazo pigments include benzidine pigments such as Diane Blue and Chlordiane Blue, or N-ethylcarbazole, stilbene, etc.
Distylbenzene, naphthalene, fluorenone, fluorene, anthraquinone, 2,5-diphenyl-1,3,
There are disazo pigments having a central skeleton such as 4-oxadiazole, dibenzothiophene, dibenzothiophene dioxide, acridone, and phenanthrenequinone. Examples of trisazo pigments include trisazo pigments having a central skeleton such as triphenylamine or N-phenylcarbazole. Examples include pigments.

[Phase] Azulenium salt compound etc.

The photosensitive layer of the electrophotographic photoreceptor of the present invention can be in either a dispersed type or a functionally separated type by combining a charge generating substance and a charge transporting substance.

In the case of a dispersed layer structure, a photosensitive layer in which a charge generating substance and a charge transporting substance are dispersed in a binder is provided on a conductive support.

In the case of a functionally separated type, a charge generating layer containing a charge generating substance and a binder is placed on a support, a charge transporting substance is placed on the charge generating layer, and the above (1)
-A) to form a charge transport layer containing one of the compounds shown in (1-C) and a binder, but in the case of a positively charged type, a charge generation layer and a charge transport layer are formed. Conversely, they may be laminated. In the case of a functionally separated type, a charge transport substance may be contained in the charge generation layer. In particular, in the case of a positively charged structure, the sensitivity is improved.

Furthermore, an intermediate layer may be provided between the photosensitive layer and the substrate in order to improve adhesion and charge blocking properties. Furthermore, a protective layer may be provided on the photosensitive layer in order to improve mechanical durability such as abrasion resistance. Binders used when forming dispersed and separated photosensitive layers include polycarbonate (bisphenol A type, bisphenol 2 type), polyester, methacrylic resin, acrylic resin, polyethylene, vinyl chloride, vinyl acetate, polystyrene, phenol resin, and epoxy resin. , polyurethane, vinylidene chloride, alkyd resin, silicone resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyarylate, polyacrylamide, polyamide, phenoxy resin, etc. are used. These binders can be used alone or as a mixture of two or more.

When producing a photoreceptor using the layer structure and materials described above, there is a preferable range for the film thickness and the ratio of the materials.

In the case of a negatively charged type (laminated substrate/charge generation layer/charge transport layer), the ratio of the charge generation substance to the binder in the charge generation layer is 20 to 500% by weight2, and the film thickness is 0.1 to 5%. preferable. In the charge transport layer, the ratio of the charge transport material to the binder is preferably 20 to 200 parts by weight, and the film thickness is preferably 5 to 50 parts by weight.

In the case of a positively charged type (laminated base/charge transport layer/charge generation layer), the ratio of the charge transport material to the binder in the charge transport layer is 20 to 200% by weight, and the film thickness is 5 to 50 μm.
It is preferable that In the charge generation layer, the charge generation substance is preferably contained in an amount of 10 to 100% by weight based on the binder. Furthermore, it is preferable to include a charge transporting substance in the charge generation layer, which has the effect of suppressing residual potential and improving sensitivity. In this case, the charge transport material is preferably contained in an amount of 20 to 200 parts by weight based on the binder.

In addition, the amount of the compound represented by the formula (1-A), formula (1-B), or formula (I-C) used in the present invention to be added to the photosensitive layer is determined based on the amount added to the charge transport layer in the case of a functionally separated type. When added, the amount is 0.001 to 4.0% by weight, preferably 0.01 to 2% by weight, based on the charge transport material. In the case of a dispersed type, □ is preferably added in an amount of 0.001 to 4.0% by weight based on the charge transport material.

If the amount added is less than the lower limit, no ozone resistance effect can be obtained, and if it is more than the upper limit, adverse effects such as a decrease in sensitivity may occur.

The intermediate layer provided as needed is generally made of resin as its main component, but considering that the photosensitive layer is coated on top of it with a solvent, these resins have poor solvent resistance to common organic solvents. It is desirable that the resin has a high Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, copolymerized nylon,
Alcohol-soluble resins such as methoxymethylated nylon,
Examples include curable resins that form a three-dimensional network structure, such as polyurethane, melamine resin, phenol resin, and epoxy resin.

Further, fine powder pigments of metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide may be added to the intermediate layer to prevent moire and reduce residual potential.

Dip coating and spray coating are generally used to coat these layers, but it is desirable to use a high boiling point solvent to prevent brushing and obtain a uniform coating.

The method for forming the photosensitive layer will be described below.

First, the binder resin used in the charge generation layer and the charge transport layer is mixed with a common solvent such as tetrahydrofuran.
Dichloromethane, 1,2-dichloroethane, chloroform, toluene, benzene, methyl ethyl ketone, etc., and a solvent with a boiling point of 130°C or higher, namely cyclohexanone (b
, P, 155.6°C), xylene (b+p, 140°C)
, monochlorobenzene (b, p, 131.6° C.), etc., and then a charge generating substance and a charge transporting substance are added and dispersed or dissolved to prepare a coating liquid. This coating solution is applied to a support by dipping or spraying, and after application, it is dried at a temperature higher than the boiling point of the high-boiling solvent added. In this case, if drying is carried out below the boiling point, the amount of residual solvent in the photosensitive layer will be large, causing adverse effects such as a decrease in sensitivity. Drying at a temperature above the boiling point makes it possible to reduce the amount of residual solvent in a short time, leading to improved productivity. If the amount of the high boiling point solvent remaining in the photosensitive layer is 5°O weight ppm or less, it will not cause any adverse effects such as a decrease in sensitivity. The amount of residual solvent in the photosensitive layer can be measured using a pyrolysis gas chromatograph or the like.

The support used in the electrophotographic photoreceptor of the present invention includes:
Aluminum, metal drums and sheets made of aluminum, brass, stainless steel, nickel, etc., materials such as polyethylene terephthalate, polypropylene, nylon, paper, etc.
Examples include sheet-like or cylindrical substrates made of plastic, paper, etc., which are treated to be conductive by vapor-depositing metals such as nickel, or by coating conductive substances such as titanium oxide, tin oxide, or carbon black together with a suitable binder.

〔effect〕

The electrophotographic photoreceptor of the present invention has the above-mentioned structure, and since the photoreceptor layer contains a specific antioxidant, there is no decrease in sensitivity or charge potential even when exposed to an oxidizing atmosphere, and the photoreceptor characteristics are maintained. Since it does not deteriorate, its practical value is extremely high.

Further, even if a coating method using a high boiling point organic solvent, which is effective as a means for preventing brushing and forming a uniform photosensitive layer, is used, the photosensitive layer does not deteriorate, so it has the advantage of increasing production efficiency.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 10 parts of alcohol-soluble copolymerized nylon CM-8000 [manufactured by Toshi ■] was dissolved in 100 parts of methanol, and titanium oxide powder TA-100 (manufactured by Fuji Titanium Industry ■) was dissolved in this 8 parts.
After dispersing in a ball mill for 10 hours, the mixture was diluted with 50 parts of n-butanol to prepare an intermediate layer coating solution.

This solution was sprayed onto the surface of an Affi board with a thickness of 0.2IIIl, dried at 100°C for 10 minutes, and the film thickness was 3.
．． A middle layer of 0 voices was formed.

Next, polyester resin Byron 200 [manufactured by Toyobo ■]
5 parts of cyclohexanone was dissolved in 150 parts of cyclohexanone, 10 parts of trisazo pigment represented by the following formula (A-1) was added thereto, and dispersed for 48 hours in a ball mill.
10 parts were added and dispersion was carried out for 3 hours. This was taken out into a container and diluted with cyclohexanone while stirring so that the solid content was 1.0% by weight.

The charge generation layer coating liquid thus obtained was spray coated onto the intermediate layer and dried at 100° C. for 10 minutes to form a charge generation layer having a thickness of about 0.2 tones.

6. Next, prepare a charge transport layer coating solution having the following composition,
The charge transport layer was spray coated onto the charge generation layer and dried at 160° C. for 20 minutes to form a charge transport layer having a thickness of 27 mm, thereby producing an electrophotographic photoreceptor of the present invention.

[Coating liquid for charge transport layer]

Charge transport layer material represented by the following formula (II-A) 8 parts Compound represented by the following formula (IA) (Inganox 1
330; manufactured by Ciba Geigy)
O, Oa part Tetrahydrofuran 1
00 parts cyclohexanone ioo
Note that the amount of residual cyclohexane in the photosensitive layer of the photoreceptor thus obtained was 200 ppm by weight.

Example 2 In Example 1, the formula (1-
A) Compound shown (SANOL, LS-2626;
An electrophotographic photoreceptor of the present invention was produced in the same manner as in Example 1, except that a compound represented by the following formula (1-B) was used in place of Sankyo ■).

Example 3 In Example 1, the formula (I
-^) Instead of the compound represented by the following formula (1C) (Ma
An electrophotographic photoreceptor of the present invention was produced in the same manner as in Example 1, except that a compound represented by rk AO-20 (Adeka Argus, Inc.) was used.

After dissolving 10 parts of [manufactured by] in 170 parts of methanol,
A coating solution for an intermediate layer was prepared by adding 80 parts of n-butanol. This liquid was dip-coated onto an AQ plate with a thickness of 0.2 mm, and dried at 100° C. for 5 minutes to form an intermediate layer with a thickness of 0.3 μm.

Next, 20 parts of bisazo pigment shown below (A-2).

400 parts of cyclohexanone was dispersed in a ball mill for 48 hours, and a mixed solvent consisting of 400 parts of methyl isobutyl ketone and 200 parts of cyclohexanone was added to this dispersion.
The mixture was dispersed again for 2 hours. Thereafter, the mixture was further diluted with 1000 parts of methyl isobutyl ketone to prepare a charge generation layer coating solution.

This was dip-coated onto the intermediate layer and dried at 120° C. for 5 minutes to form a charge generation layer with a thickness of 0.2/a.

Example 4 Alcohol-soluble copolymerized nylon CM-8000 (Higashi) Next, a charge transport coating solution having the following composition was prepared and spray coated on the charge generation layer to form a charge transport layer with a thickness of 20 μm. , an electrophotographic photoreceptor of the present invention was produced.

[Coating liquid for charge transport layer]

Charge transport layer material represented by the following formula (IT-B) 8 parts Compound represented by the following formula (IA) (Inganox
1330; manufactured by Ciba Geigy) 0.0
03 parts cyclohexanone 100
Note that the amount of residual cyclohexane in the photosensitive layer of the photoreceptor thus obtained was 200 ppm by weight.

Example 5 In Example 4, the formula (I-
An electrophotographic photoreceptor of the present invention was produced in the same manner as in Example 4, except that a compound represented by the following formula (1-B) was used in place of the compound represented by A).

100 parts of tetrahydrofuran Example 6 In Example 4, the formula (1
An electrophotographic photoreceptor of the present invention was produced in the same manner as in Example 4, except that a compound represented by the following formula (IC) was used instead of the compound represented by -A).

Comparative Example 3 In Example 1, the formula (1-
A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the following compound was used instead of the compound shown in A).

Comparative Example 1 A comparative electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the compound represented by formula (IA) was removed from the charge transporting coating solution.

Comparative Example 2 In Example 1, the formula (1-
A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the following compound was used instead of the compound shown in A).

Comparative Example 4 In Example 1, the formula (I-
A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the following compound was used instead of the compound shown in A).

Acclimatization Comparative Example 5 In Example 1, the drying conditions of the charge transport layer were changed to 120°C;
A comparative electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the heating time was 20 minutes. The residual cyclohexanone concentration in the photosensitive layer of this photoreceptor was 5000 ppm by weight.

Next, the initial photoreceptor characteristics of the photoreceptor obtained above were measured using an electrostatic paper analyzer 5P-428 [manufactured by Kawaguchi Electric Seisakusho Co., Ltd.] under the following conditions.

After being charged for 10 seconds at an applied voltage of -6, OKV, it was allowed to decay in the dark for 10 seconds. At this time, the surface potential v1 (
V) and dark decay rate DDR (%) were measured. In addition, the exposure amount E 1/10 (Lux-sec) required to attenuate light from the surface potential of 800 V to 80 V was also measured (exposure intensity 5], ux).

Thereafter, the photoreceptor characteristics were evaluated under the same conditions after being exposed to an oxidizing atmosphere with an ozone concentration of 5 ppm for 200 hours. The results are shown in Table-1.

Table-1 Patent applicant Rico Co., Ltd.

Claims (3)

[Claims] (1) In an electrophotographic photoreceptor having a photosensitive layer provided on a conductive support, the photosensitive layer contains a charge transporting substance and the following formula (I-A
), formula (I-B), and formula (I-C). ▲There are mathematical formulas, chemical formulas, tables, etc.▼( I -A) ▲There are mathematical formulas, chemical formulas, tables, etc.▼( I -B) ▲There are mathematical formulas, chemical formulas, tables, etc.▼( I -C) (2) The electrophotographic photoreceptor according to claim 1, wherein the charge transport material is a compound represented by the following general formula (II). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R^1 and R^4 are hydrogen atoms, alkyl groups, alkoxy groups, halogen atoms, or substituted amino groups, R^2
and R^3 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted phenyl group. ▲There are mathematical formulas, chemical formulas, tables, etc. ▼ indicates a benzene ring, naphthalene ring, anthracene ring, indole ring, or carbazole ring. n represents 0 or 1; m represents an integer of 0, 1, 2, or 3; ) (3) The electrophotographic photoreceptor according to claim 1, wherein the residual amount of the organic solvent having a boiling point of 130° C. or higher contained in the photosensitive layer is 500 ppm by weight or less.