JPH0389251A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the red reproducibility of a photosensitive body by making the combination use of a specific bisazo compd. and specific perylene compd. as a charge generating material. CONSTITUTION:The photosensitive body is formed by successively or reverse- successively laminating a charge generating layer and a charge transfer layer on a conductive base body. The bisazo compd. expressed by formula I and the perylene compd. expressed by formula III are used for the charge generating material. In the formula, R1 denotes halogen, alkyl. etc., R2 denotes (substd.) alkyl; R3 denotes H, cyano,etc.; R4 denotes H, halogen, etc.; the more concrete example of the bisazo compd. of the formula includes the compd. of formula II, etc. The p-diethyl aminobenzaldehyde-diphenyl hydrazone for the charge transfer material, etc., is used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, the present invention relates to an electrophotographic photoreceptor, which includes a photoreceptor layer comprising a charge generation layer and a charge transport layer containing an organic material,
This invention relates to a laminated electrophotographic photoreceptor used in electrophotographic printers, copying machines, etc.

[Conventional technology]

Conventionally, photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors) include inorganic photoconductive substances such as selenium or selenium alloys, or inorganic photoconductive substances such as zinc oxide or cadmium sulfide in a resin binder. dispersion, organic photoconductive substances such as poly-N-vinyl carbazole or polyvinyl anthracene, organic photoconductive substances such as phthalocyanine compounds or bisazo compounds in a resin binder, and vacuum evaporation. Sasetachino and others are used. In addition, a photoreceptor must have the function of retaining surface charge in the dark, the function of receiving light and generating charge, and the function of receiving light and transporting charge, but these functions can be achieved in one layer. A so-called single-layer type photoreceptor that has both functions, and a so-called laminated type that has two functionally separated layers: a layer that mainly contributes to charge generation, a layer that contributes to surface charge in the dark, and a layer that contributes to charge transport during light reception. There is a photoreceptor. For example, the Carlson method is applied to image correction by electrophotography using these photoreceptors. Image discipline in this method involves charging the photoconductor in a dark place by corona discharge, forming electrostatic latent images such as letters and pictures on the document by exposing the surface of the charged photoconductor, and This is done by developing a latent image with toner, transferring the developed toner image to a support such as paper, and fixing it. After the toner image has been transferred, the photoreceptor is subjected to static neutralization, removal of residual toner, photostatic static elimination, etc. Subject to reuse.

When copying an original, it is desirable to be able to obtain a copied image that faithfully reproduces the image density of the original, but to achieve this, it is necessary that the photosensitivity of the photoreceptor used in the copying machine be uniform over the entire visible light range. be. However, the photosensitivity of photoconductive materials used in photoreceptors generally differs depending on the wavelength of light. For example, for phthalocyanine compounds, the wavelength is 600n.
It has an absorption maximum in the red light region of m to 700 nm, and therefore exhibits very high photosensitivity in the red light region. In addition, zinc oxide has an absorption maximum in the wavelength range of 370 nm to 390 nm.
High photosensitivity in the near-ultraviolet region.

In a copying machine equipped with a photoreceptor made of a photoconductive material that exhibits extremely high photosensitivity in a specific light wavelength range, practical problems arise when copying originals.

For example, in a copying machine equipped with a photoreceptor made of copper phthalocyanine as a photosensitive material, when the photoreceptor is charged and exposed, the maximum absorption occurs in the light wavelength range of 600 nm to 700 nm, as described above, so it has high photosensitivity to red light. show. Therefore, when exposure is performed through an original having red and blue images, the red image is less likely to be reproduced in the copied image than the blue image. This means that the photoreceptor is strongly sensitive to the red reflected light from the red image on the original, and the surface potential of that area is greatly attenuated to the same extent as the attenuation of the reflected light from the white part of the original, and toner adheres during the development process. This is because it becomes difficult to do so. In a copying machine equipped with a photoconductor that uses zinc oxide as a photosensitive material, the relationship between white light and blue light is similar to the relationship between white light and red light in copper phthalocyanine, and the blue image of the original is displayed on the copied image. becomes difficult to reproduce.

In order to eliminate this drawback, it is known to add a suitable dye to a photoconductive substance to produce a photosensitive material. For example, as an example of adding a dye to the photoconductive material of a single-layer photoconductor, β-type phthalocyanine has a light wavelength of 400 nm to 600 nm.
Japanese Unexamined Patent Publication No. 53-37423 discloses dispersing and containing a dye having an absorption maximum at m. Japanese Patent Laid-Open No. 57-14 discloses that a dye having a light absorption maximum in the red light region is dispersed and contained in a charge transport layer disposed on the light projection side of the charge generation layer.
It is disclosed in Japanese Patent No. 848. In addition, an example of dispersing fluorescein and the like in zinc oxide as a photoconductive substance is given in "Electronic Photography", edited and translated by Hide Inoue, pages 224-225 (
Published by Kyoritsu Shuppan in 1973) [Original author R, M, 5chaff
ertauthorBlectrophotography J
(published by Focal Press in 1965)].

[Problem to be solved by the invention]

However, these known methods have the disadvantage that the photoreceptor has a low surface potential because the dye, which has relatively low electrical resistance, is dispersed and contained throughout the photosensitive layer or the charge transport layer that is supposed to maintain the surface potential. there were. Furthermore, there is a drawback in that the durability of the photoreceptor is poor due to repeated use of the photoreceptor, which is inevitably carried out in copying machines, and this is mainly due to the gradual deterioration of the dye contained therein. The main cause of dye deterioration is that the dye is decomposed by ozone generated during the charging, transfer, and static elimination steps, and by light during exposure and photostatic elimination steps. As the dye decomposes over time, the effect of adding the dye to the photosensitive material decreases, and the uniformity of the light wavelength sensitivity of the photoreceptor deteriorates. Further, the decomposed dye adversely affects the photosensitive material in which it is dispersed as an impurity, causing a decrease in the surface potential and photosensitivity of the photoreceptor and an increase in the residual potential.

If the dye-containing layer is on the surface of the photoreceptor, the dye from the surface is likely to be decomposed by ozone, and if the dye is dispersed in the photosensitive material, the effects of the decomposition products of the dye may occur. This is not preferable because it directly covers the entire area of the photoreceptor material in which it is dispersed.

An object of the present invention is to eliminate the above-mentioned drawbacks in a photoreceptor containing an organic material as a charge-generating substance and a charge-transporting substance, and to provide an electrophotographic photoreceptor with excellent red reproducibility.

[Means to solve the problem]

The above problem can be solved according to the present invention in an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer made of an organic material on a conductive substrate, in which the charge generation material of the charge generation layer has the following formula [I The problem can be solved by providing an electrophotographic photoreceptor that is a mixed material of at least one of the bisazo compounds represented by the following formula [II] and a perylene compound represented by the following formula [II].

(In formula (1), R1 is a halogen atom or an alkyl group.

an alkoxy group, R2 is an optionally substituted alkyl group,
R5 is a hydrogen atom, a cyano group, or a carbamoyl group.

Carboxyl group, ester group, acyl group % R4 is a hydrogen atom, a halogen atom, a nitro group, an alkyl group.

Represents an alkoxy group. ) Specific examples of the compound represented by the general formula (1) used in this invention are as follows.

[Effect]

By using the above materials, it is possible to obtain a photoreceptor with excellent red color reproducibility.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are conceptual cross-sectional views showing different embodiments of the photoreceptor of the present invention, in which l is a conductive substrate, 2 is a charge generation layer, 3 is a charge transport layer, 4 is a photosensitive layer, and 5 is a surface coating layer, and the photosensitive layer is of a functionally separated type consisting of a charge generation layer and a charge transport layer.

The photosensitive layer in FIG. 1 has a charge generation layer and a charge transport layer laminated in this order, and the photosensitive layer in FIG. 2 has a charge transport layer and a charge generation layer laminated in that order, contrary to FIG.

The conductive substrate 1 serves as an electrode for the photoreceptor and at the same time serves as a support for the other layers, and may be cylindrical, plate-shaped, or film-shaped, and may be made of aluminum, stainless steel, nickel nanometal, etc. Alternatively, it may be made of glass, resin, or the like and subjected to conductive treatment.

The charge generating layer 2 is formed by vacuum-depositing an organic photoconductive substance or by coating a material in which particles of an organic photoconductive substance are dispersed in a resin binder, and is capable of receiving light. In addition, it is important that the charge generation efficiency is high and that the generated charges are injected into the charge transport layer 3, and it is desirable that the charge is less dependent on the electric field and can be injected even in a low electric field.

Since the charge generation layer only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance and is generally 5.
It is 1 μm or less, preferably 1 μm or less. The charge generation layer is mainly composed of a charge generation substance, and a charge transport substance or the like may be added thereto. As the resin binder, polycarbonate, polyester, polyamide, polyurethane, epoxy, silicone resin, polymers and copolymers of methacrylic acid ester, etc. can be used in appropriate combinations.

The charge transport layer 3 is a coating film made of a material in which an organic charge transport substance is dispersed in a resin binder, and in the dark, it serves as an insulating layer to retain the charge on the photoreceptor, and when receiving light, it is injected from the charge generation layer. Demonstrates the function of transporting electric charge. As a resin binder, polycarbonate, polyester,
polyamide.

Polyurethane, epoxy, silicone resin, methacrylic acid ester polymers and copolymers are used, but
In addition to mechanical, chemical and electrical stability, adhesion, etc., compatibility with the charge transport substance is important.

The thickness of the charge transport layer is preferably in the range of 3 to 30 μm in order to maintain a practically effective surface potential, and more preferably in the range of 5 to 30 μm.
~20 μm.

The surface coating layer 5 has excellent durability against mechanical stress,
Furthermore, it is composed of a chemically stable substance, has the function of accepting and retaining the charge of corona discharge in the dark, and has the ability to transmit the light to which the charge generation layer is sensitive, so that it is not exposed to light when exposed to light. It is necessary for the light to pass through, reach the charge generation layer, and receive the injection of the generated charges to neutralize and eliminate the surface charges. Further, 1. As mentioned above, it is desirable that the coating material be as transparent as possible in the wavelength range of maximum light absorption of the charge generating substance.

As the coating material for the surface coating layer, modified silicone resins include acrylic modified silicone resin, epoxy modified silicone resin, and alkyd modified silicone resin.

Polyester modified silicone resin, urethane modified silicone resin, and silicone resin as a hard coating agent can be used. These modified silicone resins can be used alone, but in order to improve durability,
,, Tin2. InaO! A mixed material with a condensate of a metal alkoxy compound that can form a coating mainly composed of 1Zr02 is suitable.

The thickness of the coating layer itself depends on the composition of the coating layer, but
It can be set arbitrarily within a range that does not cause adverse effects such as an increase in residual potential when used repeatedly and continuously.

Examples of the present invention will be described below.

Example 1 5 parts by weight of the bisazo compound represented by Compound No. I-1 as a charge generating substance, 5 parts by weight of a perylene compound represented by the formula (n), and diallyl phthalate resin (trade name DAP) as a binder resin. 10 parts by weight (made by Osaka Soda) and 1500 parts by weight of methyl ethyl ketone,
A coating solution was prepared by kneading with a mixer for 3 hours, and a coating solution for the charge generation layer was prepared. Next, p-
1 part by weight of diethylaminobenzaldehyde-diphenylhydrazone (ABPH) and 1 part by weight of polycarbonate resin (trade name: Panlite L-1225, manufactured by Teijin Chemical Co., Ltd.) as a binder resin were dissolved in 6 parts by weight of dichloromethane to form a charge transport layer. A coating liquid was prepared.

Next, a charge generation layer (1 μm) and a charge transport layer (16 μm) were coated with the prepared coating liquids in this order on a polyester film on which aluminum was vapor-deposited, and a negatively charged photoreceptor having the configuration shown in FIG. Created.

Example 2 The charge generating substance in Example 1 was changed to 1 part by weight of the bisazo compound represented by Compound No. I-1 and 9 parts by weight of the perylene compound represented by the formula [II], and the rest was the same as Example 1. A photoreceptor was produced in the same manner.

Comparative Example 1 A photoreceptor was produced in the same manner as in Example 1 except that the charge generating substance in Example 1 was changed to 10 parts by weight of the bisazo compound represented by Compound No. I-1.

The electrophotographic properties of the photoreceptor thus obtained were measured using an electrostatic recording paper tester RSP-428J manufactured by Kawaguchi Electric.

The surface potential V of the photoreceptor (volts) is -6, OkV in the dark.
This is the initial surface potential when the photoreceptor surface is negatively charged by performing corona discharge for 10 seconds, and the surface potential when the photoreceptor surface is then held in the dark for 2 seconds with corona discharge stopped, V, (
volts), and then apply an illuminance of 2L to the photoreceptor surface.
The time it takes for Vd to be halved after irradiating ux white light (
second> was determined and set as the half-attenuation exposure amount El/2 (Lux · second). In addition, the surface potential when the photoreceptor surface is irradiated with 2 Lux of white light for 10 seconds is defined as the residual potential Vr (volts).Furthermore, the half-attenuation exposure amount E of 550 nm monochromatic light is...
, (550) and half-attenuation exposure amount E of monochromatic light of 650 nm
Red color reproducibility El/2 (650) ratio. (65
0) / E I/□ (550). E 1/2
(650) /E+/2 The larger the value of (550), the better the red color reproducibility.

The measurement results are shown in Table 1.

As shown in Table 1, Example 1.2 has almost the same surface potential, residual potential, and half-attenuation exposure dose as Comparative Example 1, and the red color reproducibility is clearly improved. The advantage of mixing a perylene compound with a bisazo compound is obvious.

Example 3 5 parts by weight of the bisazo compound represented by Compound No. I-1 as the charge generating substance, 5 parts by weight of the perylene compound represented by the formula (n), and diallyl phthalate resin (trade name DAP) as the binder resin. To: Made by Osaka Soda〉20
parts by weight were mixed with 3,000 parts by weight of methyl ethyl ketone and kneaded for 3 hours using a mixer to prepare a coating solution, thereby preparing a coating solution for the charge generation layer. Next, 2 parts by weight of p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) as a charge transport substance and 3 parts by weight of polyarylate resin (trade name U-polymer U-10OA manufactured by Unitika) as a binder resin were added to 18 parts by weight of dichloromethane. A coating liquid for a charge transport layer was prepared by dissolving the mixture in the following parts. Next, a charge transport layer (
A photoreceptor for positive charging having the configuration shown in FIG. 2 was prepared by applying the prepared coating liquids in the order of 17 μm) and a charge generation layer (1 μm). However, a surface coating layer not directly related to this invention was not provided.

Example 4 The charge generating substance in Example 3 was changed to 1 part by weight of the bisazo compound represented by Compound No. T-1 and 9 parts by weight of the perylene compound represented by the formula [II], and the rest was the same as Example 3. A photoreceptor was produced in the same manner.

Comparative Example 2 The charge generating substance of Example 3 was used as the compound No. I-1.
A photoreceptor was produced in the same manner as in Example 3 except that 10 parts by weight of the bisazo compound represented by was used.

The electrophotographic properties of the photoreceptor thus obtained were measured using an electrostatic recording paper tester rSP-428J manufactured by Kawaguchi Electric.

The surface potential V, (volt) of the photoreceptor is +6.0kV in the dark.
This is the initial surface potential when corona discharge is performed for 10 seconds to positively charge the surface of the photoreceptor, and the surface potential when the photoconductor surface is then held in the dark for 2 seconds with corona discharge stopped is V, (
volts), and then apply an illuminance of 2L to the photoreceptor surface.
The time it takes for Vd to be halved after irradiating ux white light (
seconds) was determined and the half-attenuation exposure amount El, □ (Lux·seconds) was determined. Further, the surface potential when the surface of the photoreceptor was irradiated with 2 Lux of white light for 10 seconds was defined as the residual potential V (volt).

Furthermore, the half-attenuation exposure amount of monochromatic light of 550 nm E 112
(550) and half-attenuation exposure amount E l of monochromatic light of 650 nm
The ratio of /2 (650) is the red reproducibility El, □ (650)
/ E 1y-(550). E l/2 (65
0)/E 172(550), the better the red color reproducibility.

The measurement results are shown in Table 2.

Table 2 As shown in Table 2, Example 3.4 has almost the same surface potential, residual potential, and half-attenuation exposure amount as Comparative Example 2, and the red color reproducibility is clearly improved. , the advantage of mixing a perylene compound with the bisazo compound of this invention is obvious.

〔Effect of the invention〕

According to this invention, as a charge generating substance, the above-mentioned formula (1
) By mixing the perylene compound represented by formula (II) with the bisazo compound represented by formula (II), red color can be reproduced even when positively charged and negatively charged as an electrophotographic photoreceptor for printers, copiers, etc. A photoreceptor with excellent properties can be obtained.

[Brief explanation of drawings]

1 and 2 are conceptual sectional views showing different embodiments of the photoreceptor of the present invention. l conductive substrate, 2 charge generation layer, 3 charge transport layer, 4
Photosensitive layer, 5-surface coating layer. Diagram) The worst part: surface coating layer

Claims (1)

[Claims] 1) In an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer made of an organic material on a conductive substrate, the charge generation material of the charge generation layer has the following general formula [I] 1. A photoreceptor for electrophotography, characterized in that it is a mixed material of at least one bisazo compound represented by the following formula [II] and a perylene compound represented by the following formula [II]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] (In the formula [I], R_1 is a halogen atom, an alkyl group,
an alkoxy group, R_2 is an optionally substituted alkyl group,
R_3 is a hydrogen atom, cyano group, carbamoyl group, carboxyl group, ester group, acyl group, R_4 is a hydrogen atom,
Represents a halogen atom, nitro group, alkyl group, or alkoxy group. ) ▲ Contains mathematical formulas, chemical formulas, tables, etc. ▼ [II]