JP3195126B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member containing an azo compound subjected to a specific treatment.

[0002]

2. Description of the Related Art Heretofore, inorganic photoconductive materials such as selenium, cadmium sulfide, zinc oxide, and silicon have been known for electrophotographic photoreceptors, and have been widely studied and put to practical use. . While these inorganic materials have many advantages, they also have various disadvantages. For example, selenium has disadvantages in that production conditions are difficult, and crystallization is easily caused by heat or mechanical impact, and cadmium sulfide and zinc oxide have poor moisture resistance and durability. It has been pointed out that silicon is insufficient in chargeability and difficult to manufacture. In addition, selenium and cadmium sulfide have toxicity problems.

On the other hand, organic photoconductive materials have good film-forming properties, excellent flexibility, are lightweight, have good transparency, and are sensitive to a wide wavelength range by an appropriate sensitization method. Due to its advantages such as easy design of the body, its practical use is gradually attracting attention.

Incidentally, the photoreceptor used in the electrophotographic technology is generally required to have the following basic properties. That is, (1) high chargeability against corona discharge in a dark place, (2) little leakage (dark decay) of the obtained charge in a dark place, and (3) charge charge by light irradiation. (4) The residual charge after light irradiation is small.

However, many studies have been made on photoconductive polymers such as polyvinyl carbazole as organic photoconductive substances to date, but these have not always had sufficient film-forming properties, flexibility and adhesiveness. Also, it is difficult to say that the above-mentioned basic properties of the photoreceptor are sufficiently provided.

On the other hand, as for the organic low-molecular-weight photoconductive compound, a photoreceptor having excellent mechanical strength such as film property, adhesion and flexibility can be obtained by selecting a binder or the like used for photoreceptor formation. Although it can be obtained, it is difficult to find a compound that is suitable for retaining high-sensitivity properties.

In order to improve such a point, the carrier generation function and the carrier transport function are shared by different substances,
Organic photoreceptors having higher sensitivity characteristics have been developed. The feature of such a photoreceptor, which is called a function-separated type, is that a material suitable for each function can be selected from a wide range. Has been advanced.

[0008]

As described above, various improvements have been made in the preparation of an electrophotographic photoreceptor, but the basic properties and high durability required for the above-mentioned photoreceptor have been proposed. The one that satisfies such requirements has not yet been obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity, high durability, a high charging potential, and almost no reduction in sensitivity even when used repeatedly, and having a stable charging potential. It is.

[0009]

Means for Solving the Problems As a result of research on a photoconductive substance having high sensitivity and high durability, the present inventors conducted a heat treatment or a wet pulverization treatment in a specific solvent, and then recovered and dried. The inventors have found that the azo compound represented by Chemical Formula 1 is effective, and have reached the present invention.

In formula 1, m and n are 0 or 1, A is a coupler residue, B is a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group, an aryl group, or a heterocyclic group. .

Specific examples of A include, for example, those shown in Tables 1 to 7.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

[Table 4]

[0016]

[Table 5]

[0017]

[Table 6]

[0018]

[Table 7]

Specific examples of B include a hydrogen atom, an alkyl group such as a methyl group, a trifluoromethyl group, an ethyl group, a hydroxyethyl group, an isopropyl group and an n-octyl group, a benzyl group, a p-methylbenzyl group, and a p-methylbenzyl group. Aralkyl groups such as -trifluoromethylbenzyl group, 2-phenylethyl group, 2-naphthylmethyl group, phenyl group, p-methylphenyl group, pn-propylphenyl group, p-isobutylphenyl group, p-methoxyphenyl Group, 3,5
Aryl groups such as -dichlorophenyl group, 2-naphthyl group and 9-anthryl group; and heterocyclic groups such as furyl group, thienyl group, pyridyl group and chloropyridyl group.

Examples of the cyclic ether used in the present invention include tetrahydrofuran (THF), 2-methyltetrahydrofuran, tetrahydropyran, 1,4-dioxane and the like. Examples of polar aprotic solvents include dimethylformamide (DMF), dimethylsulfoxide (DMSO), and N-methylpyrrolidone (N
MP), hexamethylphosphoric triamide (HMP
A), 1,3-dimethyl-2-imidazolidone (DM
I) and the like.

The heat treatment in the solvent of the present invention is desirably carried out with stirring in order to keep the temperature distribution in the solvent uniform and to bring the pigment particles and the solvent into sufficient contact. The conditions such as the heating temperature and time are set in consideration of the characteristics of the electrophotographic photosensitive member.

For the wet pulverization in the solvent of the present invention, for example, a sand mill, a colloid mill, an attritor, a ball mill or the like can be used. The amount of the solvent, the pulverizing time, and the like are set in consideration of the processing amount, the capacity of the pulverizer, and the characteristics of the electrophotographic photosensitive member.

The electrophotographic photoreceptor of the present invention can be obtained by containing one or more azo compounds represented by Chemical Formula 1 which have been heated or wet-pulverized in a specific solvent. Various types of photoconductors are known, and any of them can be used. For example, an azo compound, a charge transport material, and a photosensitive layer made of a film-forming binder resin provided on a conductive support,
There is a laminated photoreceptor in which a charge generation layer composed of an azo compound and a binder resin and a charge transport layer composed of a charge transport substance and a binder resin are provided on a conductive support. Either of the charge generation layer and the charge transport layer may be an upper layer. As a support for preparing a photoreceptor using the compound of the present invention, a metal drum, a metal plate, a paper subjected to conductive processing, a sheet of a plastic film, a drum or a belt, and the like are used. .

As the film-forming binder resin used for forming the photosensitive layer on the support, there are various resins depending on the field of use. For example, for photoreceptors for copying, polystyrene resins, polyvinyl acetal resins, polysulfone resins, polycarbonate resins, polyester resins, polyphenylene oxide resins, polyarylate resins, acrylic resins, methacrylic resins, phenoxy resins and the like can be mentioned. Among these, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, polyarylate resin, and the like are excellent in potential characteristics as a photoconductor. These resins can be used alone or as a mixture of two or more of them as a copolymer.

These resins contained in the photosensitive layer are preferably from 10 to 500% by weight based on the azo compound,
150% by weight is more preferred. If the ratio of the resin is too high, the charge generation efficiency is lowered, and if the ratio of the resin is too low, there is a problem in film formability.

Some of these resins include tension, bending,
Some have weak mechanical strength such as compression. To improve this property, substances which impart plasticity can be added. Specifically, phthalic acid esters (eg, DOP, DOP
BP, etc.), phosphate esters (eg, TCP, TOP, etc.)
And so on. If these substances are added unnecessarily, they adversely affect the electrophotographic properties. Therefore, the ratio is preferably 20% or less based on the binder resin.

In addition, an antioxidant, an anti-curl agent and the like can be added as necessary to the photosensitive member.

The charge transport material includes a hole transport material and an electron transport material. An example of the former is, for example, Japanese Patent Publication No. 34-5
Oxadiazoles disclosed in JP-B-466-466, triphenylmethanes disclosed in JP-B-45-555, pyrazolines described in JP-B-52-4188, and JP-B-55-42380. And oxadiazoles described in JP-A-56-123544, and JP-B-58-3237.
And the stilbenes disclosed in JP-A-58-198043. On the other hand, as the electron transporting substance, for example, chloranil, tetracyanoethylene, 2,2
4,7-trinitro-9-fluorenone, 2,4,5
Examples include 7-tetranitroxanthone and 1,3,7-trinitrodibenzothiophene. These charge transport materials can be used alone or in combination of two or more.

[0029]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 2 g of Compound 2 shown in Table 8 and 20 ml of THF were refluxed for 1 hour. After leaving to cool for 1 hour, the solution was filtered and dried at 80 ° C. for 2 hours to obtain 1.72 g of a treated pigment. 1 part by weight of this product and phenoxy resin (P from Union Carbide)
KHJ) (1 part by weight) was mixed with 100 parts by weight of dimethoxyethane, and dispersed together with glass beads by a paint conditioner for 2 hours. The obtained dispersion was applied on an aluminum-evaporated polyester film (Metal Me, manufactured by Toray Industries, Inc.) using an applicator to form a charge generation layer having a thickness of about 0.2 μm. Next, p-dibenzylaminobenzaldehyde = diphenylhydrazone was mixed with a polyarylate resin (U-polymer manufactured by Unitika) at a weight ratio of 1: 1 to prepare a 10% solution using dichloromethane as a solvent. On the surface with an applicator.
A 0 μm charge transport layer was formed.

The laminated photoreceptor thus prepared is
Electrophotographic characteristics were evaluated using an electrostatic recording tester (SP-428, manufactured by Kawaguchi Electric Co., Ltd.). Measurement condition is applied voltage -6k
V, static No. 3 (turntable rotation speed mode: 10 m / min), irradiation light (white light) illuminance 2
lux. As a result, the charged potential was -770 V, and the half-life exposure amount was 1.4 lux · sec, which was a high sensitivity value.

Next, this photoreceptor was attached to an aluminum drum base tube, and the repetition characteristics of charging and exposure were evaluated by a drum photoreceptor evaluation device (Cynthia 90 manufactured by Gentec). The measurement conditions were as follows: corona applied voltage -6.5 kV, process speed 160 mm / sec, 500 in TCDD2 mode.
There were zero charges and light elimination. Light elimination was performed using a tungsten lamp array. As a result, the charge potential was −740 V and the residual potential was −15 V after the repetition of 5000 times against the initial charge potential of −750 V and the residual potential of −10 V.
It was found that the change was extremely small.

Example 2 The processing conditions in Example 1 (THF reflux for 1 hour) were changed to the same amount of DMF and heated at 60 ° C., filtered, washed with acetone, and dried. Using 1.84 g of the treated pigment thus obtained, a photoreceptor was produced in the same manner as in Example 1, and the electrophotographic characteristics were evaluated using an electrostatic recording test apparatus. as a result,
As a result, a high-sensitivity value was obtained with a charging potential of -750 V and a half-life exposure amount of 1.5 lux · sec. In the evaluation of the repetition characteristics using the same photoreceptor, even after the initial charging potential of −740 V and the residual potential of −15 V, the change was extremely small, that is, the charging potential of −720 V and the residual potential of −20 V after 5,000 times of repetition. Do you get it.

Example 3 2 g of Compound 2 shown in Table 8 and 20 ml of THF were dispersed together with glass beads by a paint conditioner (PC) at room temperature for 2 hours. The dispersion was centrifuged to obtain a treated pigment having a dry weight of 1.51 g. Thereafter, a photoreceptor was prepared in the same manner as in Example 1, and the electrophotographic characteristics were evaluated using an electrostatic recording test apparatus. As a result, a high-sensitivity value was obtained with a charging potential of -780 V and a half-life exposure amount of 1.4 lux · sec. In the evaluation of the repetition characteristics using the same photoconductor, it was found that the charge potential was −760 V and the residual potential was −15 V, which was extremely small even after 5,000 repetitions, compared to the initial charge potential of −770 V and the residual potential of −10 V. Do you get it.

Comparative Examples 1 and 2 Compound 2 was not subjected to the solvent treatment shown in Example 1 (Comparative Example 1), and 2 g of the same compound and 20 ml of 2-butanone were heated under reflux for 1 hour. After allowing to cool for 1 hour, the product was collected by filtration, and dried at 80 ° C. for 2 hours (Comparative Example 2; recovered amount after treatment: 1.91 g). Electrophotographic characteristics were evaluated using an electrostatic recording test apparatus. As a result, the charging potential is -720, respectively.
V, -710 V, half-exposure amount is 2.4 lux.sec.
The sensitivity was inferior to 5 lux · sec. Also in the evaluation of the repetition characteristics, in Comparative Example 1, the initial charging potential-
After 5,000 repetitions, the charging potential was −660 V and the residual potential was −45 V with respect to 720 V and the residual potential of −10 V.
It turned out that the change was large. In Comparative Example 2, the initial charging potential was −710 V and the residual potential was −15 V.
After 5,000 repetitions, the charge potential was −640 V and the residual potential was −50 V, which was a large change.

Examples 4 to 11 The compounds shown in Table 8 were subjected to the treatments described above, and the electrophotographic characteristics were evaluated in the same manner as in Example 1. Table 9 shows the results.

Comparative Examples 3 to 7 The compounds shown in Table 10 were subjected to the treatments described above, and the electrophotographic characteristics were evaluated in the same manner as in Example 1. Table 11 shows the results.

[0038]

[Table 8]

[0039]

[Table 9]

[0040]

[Table 10]

[0041]

[Table 11]

[0042]

As is apparent from the above, according to the present invention, an electrophotographic photosensitive member having high sensitivity and high durability can be provided.

Continuation of the front page (56) References JP-A-1-22757 (JP, A) JP-A-1-200267 (JP, A) JP-A-63-89866 (JP, A) JP-A-6-130698 (JP, A) JP-A-7-120950 (JP, A) JP-A-3-278053 (JP, A) JP-A-63-309964 (JP, A) JP-A-1-120562 (JP, A) JP-A JP-A-63-18354 (JP, A) JP-A-4-362654 (JP, A) JP-A-63-301955 (JP, A) JP-A-6-43672 (JP, A) JP-A-4-45162 (JP, A A) JP-A-4-235964 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/06

Claims (1)

(57) [Claims] 1. A photoconductive substance on a conductive support,
An electrophotographic photoreceptor comprising an azo compound represented by Chemical Formula 1, which is recovered and dried after heat treatment or wet pulverization treatment in a cyclic ether or a polar aprotic solvent. Embedded image (In formula 1, m and n are 0 or 1, A is a coupler residue, B is a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group, an aryl group, or a heterocyclic group.)