JPH05119491A - Electrophotographic sensitive material - Google Patents

Abstract

PURPOSE:To effectively suppress photofatigue and to obtain stability by providing a photosensitive layer containing an azo compd. and a hydrazone compd. expressed by specified formulae as essential components. CONSTITUTION:The photosensitive material has a photosensitive layer containing an azo compd. expressed by formula I having high efficiency of generating charges as a charge producing agent, and a hydrazone compd. expressed by formula II having high hole transfer efficiency as a charge transfer agent as essential components. In formula I, X is hydrogen, halogen atom, alkyl group or alkoxy group. In formula II, X and R1-R4 are hydrogen atoms, alkyl groups, alkoxy groups, halogen atoms, or substd. amino groups, or substd. or unsubstd. allyl group. In this case, a charge generating layer 2 essentially comprising the disazo compd. is provided on a photoconductive substrate 1, and a charge transfer layer 3 essentially comprising the hydrazone compd. is provided thereon to form a negative charge function separating two-layer structure.

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 provided with a photosensitive layer containing, as an essential component, two kinds of organic materials of a specific disazo compound and a specific hydrazone compound.

[0002]

2. Description of the Related Art Conventionally, inorganic materials such as selenium, selenium tellurium, diarsenic triselenide, cadmium sulfide, zinc oxide, and amorphous silicon have been generally used as photoconductive materials for electrophotographic photoreceptors. However, these photoreceptors have drawbacks such as poor flexibility in practical use, sensitivity to heat and mechanical shock, and high manufacturing cost. In recent years, a photoreceptor using an organic material that eliminates these drawbacks has been proposed and put into practical use. This organic photoreceptor is a so-called function-separated type in which a charge generation layer and a charge transfer layer are generally laminated on a conductive substrate, and a function-combined type in which a photosensitive layer also serving as two layers is laminated on a substrate. Is widely known.

As the function-separated type, for example, a photosensitive layer in which a charge generation layer containing a cyanine pigment or the like as an active ingredient and a charge transfer layer containing an organic compound such as hydrazone type, pyrazoline type or oxadiazole type are laminated. The body is well known, and it is known that many compounds are effective as both the charge generating agent and the charge transfer agent.

In such a function-separated type photoreceptor, the charge generator absorbs light in the charge generation layer to generate carriers, and the generated carriers are injected into the charge transfer layer and move in the charge transfer layer. However, it is important to select a material that allows the charge generator to move to the surface without being trapped by impurities in the transfer layer. The electrophotographic characteristics of the above-mentioned function-separated type electrophotographic photosensitive member are greatly influenced by the combination of the charge generating agent and the charge transfer agent.

However, when many compounds are used as a photosensitive layer in combination with a charge generation layer and a charge transfer layer, it has been experimentally found that very few compounds satisfy the various characteristics and conditions of the photoreceptor required for practical use. Known as a result. In particular, there are few that satisfy the repeating characteristics of charging and exposure by the known electrophotographic process, and repeated charging and exposure causes an increase in residual potential, which is considered to be caused by accumulation of traps of charge generators in the charge transfer layer. Fogging is likely to occur in the image. It is assumed that these are due to light fatigue. The above-mentioned problems also occur in a single-layer photoreceptor having a function and a function in which a phthalocyanine pigment, a disazo pigment and the like are dispersed and coated on a binder resin.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have earnestly studied and conducted experiments on a method for preventing light fatigue of a photoconductor due to repeated use and a rise in residual potential accompanying it. As a result, it was found that a combination of a specific azo compound and a specific hydrazone compound represented by the general formula [IV] has extremely excellent characteristics as an electrophotographic photoreceptor, and the above-mentioned problems have been solved. It was

[0007]

The present invention provides an azo compound represented by the following general formula [I] having a high charge generation efficiency as a charge generating agent and a general formula [I] having a high hole transfer efficiency as a charge transfer agent. IV] is provided with a photosensitive layer containing a hydrazone compound as an essential component.

[Chemical 3] (In the formula, X represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group. Y represents a group consisting of -CONH-Ar [II] -CONHN = CH-Ar [III], and Ar has a substituent. Which may be an aromatic carbocyclic group or an aromatic heterocyclic group)

[Chemical 4] (In the formula, X and R _{1 to} R ₄ are each a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a substituted amino group,
A substituted or unsubstituted allyl group is shown. )

That is, by containing the above two components, efficient generation of electric charges and migration of holes with respect to incident light occur, and it has been confirmed that the organic photoconductor has excellent characteristics, and it has been completed. Is.

The charge generating layer used in the present invention has a first characteristic in that it contains a disazo pigment represented by the following general formula [I].

[Chemical 5] (In the formula, X represents a hydrogen atom, a halogen atom, an alkyl group, or an alkoxy group. Y represents a group consisting of -CONH-Ar [II] -CONHN = CH-Ar [III], and Ar has a substituent. Which may be an aromatic carbocyclic group or an aromatic heterocyclic group)

Specific examples of the disazo compound used in the present invention are shown in Table 1.

[Table 1]

This charge generation layer can be formed by means of coating or the like with a dispersion liquid in which the aforementioned pigment is dispersed in a binder solution. As the binder, for example, polyvinyl butyral, polyvinyl acetal, polyester, polycarbonate, polyamide, polyurethane, phenol resin or the like can be used. The resin forming these binders accounts for 8% in the charge generation layer.
It is preferably 0% or less, preferably 50% or less, and particularly preferably 40% or less. As the solvent, alcohols, ethers such as dioxane, cyclohexanone and tetrahydrofuran, ketones such as acetone and methyl ethyl ketone, and chlorine hydrocarbons such as dichloromethane, chloroform and carbon tetrachloride can be used. The solid content concentration of the azo compound and the binder in the solvent is preferably 0.5 to 5%, particularly preferably 1 to 3%. The ratio of the azo compound to the binder is 0.5 / 1 to 5/1, preferably 1/1 to 3/1.

When the above-mentioned pigment is dispersed, the azo compound and the binder are dried, kneaded and pulverized by a known method using a ball mill, an attritor or the like, and then continuously mixed with a solvent by using a dispersing device such as a sand mill. It is obtained by dispersing. Examples of the dispersion method in which the pigment is dispersed and the coating method used when the charge transfer layer described below are provided include a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a curtain coating method, and a bead coating method. It is applied by a coating method such as. The thickness of the charge generation layer is
It is 5 μm or less, preferably 0.1 to 2 μm.

Another feature of the present invention is a hydrazone compound specific to a charge generation layer using a disazo pigment,
That is, a charge transfer layer containing a hydrazone compound represented by the following general formula [IV] is used.

[Chemical 6] (In the formula, X and R _{1 to} R ₄ are each a hydrogen atom, an alkyl group,
An alkoxy group, a halogen atom, a substituted amino group, or an unsubstituted allyl group is shown. )

Specific examples of the hydrazone compound represented by the general formula [IV] used in the present invention are shown in Table 2 below.

[Table 2]

The charge transfer layer used in the present invention has the general formula [I
V] is preferably formed by coating a solution of a hydrazone compound represented by V] and a binder dissolved in a suitable solvent and drying.

The binder and solvent can be selected in the same manner as the above-mentioned coating liquid for the azo compound. The ratio of the hydrazone compound to the binder in the solvent is 0.3 / 1 to 2/1, preferably 0.5 / 1 to 1.5 / 1. The thickness of the charge transfer layer is 5 to 30 μm, preferably 15 to 25 μm.
Is desirable.

The charge transfer layer of the present invention may contain various additives. For example, 2-tert-butyl-4-methoxyphenol, 2,6-di-tert-
Butylphenol, 2,6-di-tert-butyl-4
-Methylphenol, 2,6-di-tert-butyl-
Examples include phenolic antioxidants such as 4-ethylphenol and 2,6-di-tert-butyl-4-phenol. These phenolic antioxidants suppress the occurrence of cracks due to the adhesion of oil, fingerprints, etc. to the surface of the photoconductor without impairing the basic characteristics of the photoconductor, and have ozone resistance and stability of the coating liquid. At the same time, the repetitive characteristics and light fatigue characteristics of the electrophotographic photosensitive member are improved. Particularly, a phenolic antioxidant having a molecular weight of 200 to 1000 is effective, and is 1 to 20 with respect to the hydrazone compound in the coating solution.
It is desirable to dissolve the weight percent antioxidant. When the content is 1% by weight or less, cracks occur, and when the content is 20% by weight or more, the residual potential increases.

Various forms of the laminated structure of the electrophotographic photosensitive member are known, and the electrophotographic photosensitive member of the present invention can take any of these forms. 1, 2 and 3 are cross-sectional views of an electrophotographic photoreceptor applied to the present invention, in which FIG. 1 mainly shows the above-mentioned disazo compound on the side of the conductive substrate 1. 2 shows a negative charge type function separation type two-layer structure in which a charge generation layer 2 as a component and a charge transfer layer 3 having a hydrazone compound as a main component are formed thereover.
3 shows a positively charged function-separated two-layer structure having an inverse layer structure of FIG. 1, and FIG. 3 shows a bipolar single layer having a photosensitive layer 6 in which a charge generating agent 4 and a charge transfer agent 5 are mixed and dispersed. It shows the structure.

Further, in the photoreceptor of the present invention, the injection of free charges from the conductive support to the photosensitive layer is prevented when the photosensitive layer is charged, and the photosensitive layer is integrally bonded to the conductive support. To obtain the function as an adhesive layer to hold it,
If desired, an intermediate layer may be provided on the conductive support. For this intermediate layer, aluminum oxide, indium oxide, tin oxide, polyethylene, acrylic resin, epoxy resin, polycarbonate, polyurethane, vinyl chloride resin, vinyl acetate resin, polyvinyl alcohol, or the like can be used. The thickness of the intermediate layer or the adhesive layer is 0.
1 to 5 μm, preferably 0.5 to 3 μm is suitable.

The support used for the electrophotographic photosensitive member of the present invention may be any support as long as it has conductivity. Specific examples include metals such as aluminum, copper, stainless steel and brass, and plastics obtained by vapor deposition or lamination of tin oxide and the like. The shape thereof may be a sheet shape, a belt shape, a drum shape, or any other shape.

[0021]

EFFECT OF THE INVENTION The electrophotographic photoreceptor of the present invention has the constitution as described above, and as will be apparent from the examples described later, it effectively suppresses light fatigue and stabilizes the repeating characteristics. It has high photosensitivity. That is, it can be said that the present invention is extremely useful because it has excellent charging characteristics, sensitivity characteristics, and image characteristics, and has little fatigue deterioration even after repeated use, and excellent durability.

[0022]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention.

Example 1 Disazo compound [I]-(3) exemplified in Table 1 and polyvinyl butyral were dry-kneaded at a ratio of 2/1 on an aluminum drum substrate, and then dioxane and acetone 8/2 were mixed in a sand mill. Was used as a solvent and was dispersed at a solid content of 10% for 10 hours to obtain a coating liquid A, which was applied by a dip coating method and dried to form a charge generation layer. The film thickness at this time was 0.3 μm. Next, the hydrazone compound [IV]-(1) and the polycarbonate exemplified in Table 2 above were dissolved in dichlormethane at a ratio of 1/1 to obtain a solid content of 25%,
Furthermore, 10 wt% of antioxidant butyl hydroxytoluene as an additive, (2,6-di-tert-butyl)
-4-methylphenol) was dissolved in a hydrazone compound in an amount of 1 wt%, and the resulting solution was applied as a coating liquid B on the charge generation layer by a dip coating method and dried to form a charge transfer layer. The film thickness at this time was 21 μm.

The photoreceptor thus produced was subjected to corona discharge of -5 kv. The surface potential at this time was measured (initial potential V ₀ ). Further, the surface potential of this photosensitive member after being left for 10 seconds in a dark place was measured, and (V ₁₀ ) V ₁₀ / V ₀ was obtained, which was defined as dark decay DDR. Sensitivity is surface potential -700V 1 /
Exposure required to attenuate to 2 (T / 2, lux.s
It was evaluated by measuring ec). At this time, a halogen lamp (wavelength 780 nm) was used as a light source. The results are shown in Table 3.

Example 2 In place of the disazo compound [I] formula- (1) used in Example 1, [I]-(2) shown in Table 1 was used.
A photoconductor was prepared in the same manner as in Example 1 except that the above was used, and the photographic characteristics were measured in the same manner as in Example 1.

Example 3 Except that the hydrazone compound [IV]-(1) shown in Table 2 was used in place of the hydrazone compound [IV]-(1) shown above used in Example 1, there was no difference. A photoconductor was prepared by the same method, and the photographic characteristics were measured by the same method as in Example 1.

Comparative Example 1 In place of the hydrazone compound [IV]-(1) used in Example 1, the known charge transfer agent compound NO. A photoconductor was prepared in exactly the same manner except that 1 was used.

Comparative Example 2 In place of the hydrazone compound [IV]-(1) used in Example 1, the known charge transfer agent compound NO. A photoconductor was prepared by the same method except that No. 3 was used.

Comparative Example 3 In place of the hydrazone compound [IV]-(1) used in Example 1, the known charge transfer agent compound NO. A photoconductor was prepared in exactly the same manner except that 5 was used.

Comparative Example 4 In place of the hydrazone compound [IV]-(1) used in Example 1, the known charge transfer agent compound NO. A photoconductor was prepared in exactly the same manner except that No. 7 was used.

[Comparative Example 5] A photoconductor was prepared in the same manner except that the additive butylhydroxytoluene used in Example 1 was omitted. As described above, Examples 1 to 3 and Comparative Example 1
Photographic properties of .about.5 are shown in Table 3.

[0032]

[Table 3] V ₀ : Surface potential (−5 kv) DDR: Dark decay (surface potential measurement value after leaving the photoconductor for 10 seconds in a dark place) VR: Residual potential (charging / erasing was repeated while irradiating white light of 300 Lux, 100 cycles). The potential after the subsequent neutralization.) E1 / 2: Half-exposure amount (exposure amount required to attenuate surface potential -700V to 1/2.) Crack: Oil, fingerprints, etc. adhered to the photoreceptor surface, 48
Visually observe after a lapse of time. )

As shown in Table 3, it was found that the electrophotographic photosensitive members of Comparative Examples 1 to 5 had low sensitivity and high residual potential. On the other hand, it was found that the electrophotographic photoreceptors of Examples 1 to 3 have high sensitivity and low residual potential. The high sensitivity of the electrophotographic photosensitive members of Examples 1 to 3 is considered to be due to the following reasons.

Generally, the organic electrophotographic photosensitive members can be classified into a single layer type and a laminated type as described above.
In the case of the single-layer type, light is absorbed throughout the photosensitive layer, carrier pairs (holes and electrons) are generated, and they are separated under the electric field and reach the opposing electrodes, thereby attenuating the charges. In the case of the laminated type of this embodiment, the functions of the charge generation layer and the charge transfer layer are separated. When light is absorbed in the charge generation layer, a carrier pair is generated, and under negative electric charge, holes are injected into the charge transfer layer in the case of negative charging and move in the charge transfer layer to attenuate the charge. Therefore, it is considered that the interface (energy barrier) with the charge generation layer when holes are injected into the charge transfer agent [IV] of Examples 1 to 3 is extremely small, and therefore the hole injection efficiency is good. ..

[0035]

[Table 4]

[Table 5]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an electrophotographic photosensitive member applied to the present invention, showing a negative charging type function separation type two-layer structure.

FIG. 2 is a cross-sectional view showing another example of a photoconductor for electrophotography applied to the present invention, showing a positive charging type function separation type two-layer structure.

FIG. 3 is a cross-sectional view showing still another example of an electrophotographic photoreceptor applied to the present invention, showing a bipolar single layer structure.

[Explanation of symbols]

 1. Conductive substrate 2. Charge generation layer 3. Charge transfer layer 4. Charge generating agent 5. Charge transfer agent 6. Photosensitive layer (photoconductive layer)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Shiozawa 486 Nishihiromonda, Shioyama City, Yamanashi Prefecture

Claims (2)

[Claims] 1. In an organic electrophotographic photoreceptor, an azo compound represented by the following general formula [I] and a general formula [I]
V] and a hydrazone compound represented by the formula V) in the photosensitive layer. [Chemical 1] (In the formula, X represents a hydrogen atom, a halogen atom, an alkyl group, or an alkoxy group. Y represents a group consisting of -CONH-Ar [II] -CONHN = CH-Ar [III], and Ar has a substituent. And optionally represents an aromatic carbocyclic group or an aromatic heterocyclic group.) (In the formula, X and R _{1 to} R ₄ each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a substituted amino group, and a substituted or unsubstituted allyl group.) 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains a phenolic antioxidant in an amount of 1 to 20% by weight based on the hydrazone compound represented by the general formula [IV].