JPH03109557A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance red color reproduction performance by using a material of a mixture of a specified compound and another specified compound. CONSTITUTION:The electrophotographic sensitive body is formed by laminating on a conductive substrate 1 a photosensitive layer 4 composed of an electric charge generating layer 2 and a charge transfer layer 3. The red color reproduction performance can be enhanced by incorporating a mixture of at least one of the bisazo compounds represented by formula I in which R1 is halogen, alkyl, or alkoxy; R2 is optionally substituted alkyl; R3 is H, cyano, carbamoyl, or and R4 is H, halogen, nitro, alkyl, or alkoxy, and at least one of the bisazo compound represented by formula II.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, it is equipped with a charge generation layer and a charge transport layer containing an organic material, and is suitable for use in electrophotographic copying machines, etc. The present invention relates to a laminated electrophotographic photoreceptor that is used.

[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. Dispersed, Po I
Organic photoconductive substances such as JN-vinylcarbazole or polyvinylanthracene, phthalocyanine compounds, or bisazo compounds dispersed in a resin binder or vacuum-deposited are used. .

The photoreceptor also needs to 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 three layers. The so-called single-layer type photoreceptor has both a so-called single-layer type photoreceptor, and the so-called laminated type photoreceptor 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. I have a body.

For example, the Carlson method is applied to image formation by electrophotography using these photoreceptors.

Image formation 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 is transferred, the photoreceptor is charged.

After residual toner is removed and static electricity is removed, it is reused.

When copying an original, it is desirable to obtain a copied image that faithfully reproduces the image density of the original, but in order to achieve this, it is essential that the photosensitivity of the photoreceptor used in the copying machine be uniform over the entire visible light range. It is.

However, the photosensitivity of photoconductive materials used in photoreceptors generally differs depending on the wavelength of light. For example, phthalocyanine compounds have an absorption maximum in the red light region with a wavelength of 600 nm to 700 nm, and therefore exhibit extremely high photosensitivity in the red light region. Also, for zinc oxide, the wavelength is 370n++~39
It has an absorption maximum in the 0 nm region and has 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 gold-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 the photoreceptor has high photosensitivity to red light. shows. Therefore, when exposure is performed through an original having red and blue images, the red image is less likely to be reproduced than the blue image in the resulting copied 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 this 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 60 nm.
JP-A No. 53-37423 discloses that a dye having an absorption maximum of 0 nm l is dispersed and contained, and examples of adding a dye to the charge transport layer of a laminated photoreceptor include phthalocyanine compounds. It was disclosed in Japanese Patent Application Laid-Open No. 5 (1973) 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 a charge generation layer containing
It is disclosed in Japanese Patent No. 7-14848. Another example of dispersing and containing fluorescein etc. in zinc oxide as a photoconductive substance is "Electronic Photography" 224-2, edited and translated by Hide Inoue.
25 pages (published by Kyoritsu Shuppan in 1973) [Original author R, M, 5c
rB1 electrophotograph by haffert
hy” (published by Focal Press in 1965)].

[Problem to be solved by the invention]

However, in these known methods, because a dye with relatively low electrical resistance is dispersed and contained throughout the photoconductive layer or the charge transport layer that is supposed to maintain a surface potential, the surface potential of the photoreceptor is low. There was a drawback. moreover,
Although it has the disadvantage that the photoreceptor has poor durability due to the repeated use of the photoreceptor that is inevitably carried out in copying machines,
The main reason for this is that the pigment contained gradually deteriorates. 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. In a structure in which the dye-containing layer is on the surface of the photoreceptor, the dye from the surface is easily decomposed by ozone.
Further, if the dye is dispersed and contained in the photosensitive material, this is not preferable because the effects of the decomposition products of the dye will directly affect the entire area of the photosensitive material in which the dye is dispersed.

The present invention provides an electrophotographic photoreceptor for copying machines that eliminates the above-mentioned drawbacks and has excellent red reproducibility in a photoreceptor equipped with a photoreceptor layer containing an organic material as a charge-generating substance and a charge-transporting substance. That is the issue.

[Means to solve the problem]

According to the present invention, the above problem can be solved by using the following general formula (I) as a charge generation substance in an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer comprising an organic material on a conductive substrate. The problem can be solved by preparing an electrophotographic photoreceptor using a bisazo compound represented by the following formula (II) mixed with at least one of the bisazo compounds shown below.

[In formula (I), R4 is a halogen atom or an alkyl group.

Represents any alkoxy group, R2 represents an optionally substituted alkyl group, R3 represents any one of a hydrogen atom, a cyano group, a carbamoyl group, a carboxyl group, an ester group, and an acyl group, R4 are hydrogen atoms, halogen atoms, and nitro groups.

Represents either an alkyl group or an alkoxy group. ] Specific examples of the compound represented by the general formula (I) used in this invention are as follows.

[Effect]

By using a material containing a mixture of at least one of the compounds represented by the above general formula (I) and the compound of the above formula (former formula) as a charge generating substance, it is possible to obtain a photoreceptor with excellent red reproducibility. becomes.

〔Example〕

Embodiments of the present invention will be described below 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 is a charge generation layer,
A charge transport layer is laminated in this order, and the photosensitive layer shown in FIG. 2 has a charge transport layer and a charge generation layer laminated in that order, contrary to FIG. 1. In the case of a photoreceptor having the structure shown in FIG. 2, a surface coating layer 5 is generally provided to protect the charge generation layer.

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, etc. Metal or glass! ! It may also be made of fat or the like with conductive treatment applied.

The charge generation layer 2 is formed by applying a material in which at least one of the compounds represented by the general formula (I) and the compound represented by the formula (TI) are mixed and dispersed in a resin binder (binder). It is formed by absorbing light and generating an electric charge. The charge generation efficiency is high, and the injection property of the generated charges into the charge transport layer 3 or the surface coating layer 5 is less dependent on the electric field and is good 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.

In order to maintain a practically effective surface potential, the thickness of the charge transport layer is preferably in the range of 3 μm to 30 μm, more preferably 5 μm to 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. Furthermore, as described above, it is desirable that the coating material of the surface coating layer 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. Although these modified silicone resins can be used alone, 310%
2. T+Ot, In, 0. A mixed material with a condensate of a metal alkoxy compound that can form a film containing ZrOi as a main component is suitable.

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

Examples of the present invention will be described below.

Example 1 5 parts by weight of a bisazo compound represented by the above compound Ha I-1 as a charge generating substance, 5 parts by weight of a bisazo compound represented by the above formula (II), and diallyl phthalate resin (trade name) as a binder resin. For the needlefish: Made by Osaka Soda)
10 parts by weight of methyl ethyl ketone were mixed with 1 part by weight of 1,500 parts by weight of methyl ethyl ketone, and kneaded for 3 hours using a mixer to prepare a coating solution.A coating solution for the charge generation layer was prepared. Next, 1 part by weight of p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) as a charge transport substance, 11 parts of polycarbonate resin (trade name Panlite L-1225, manufactured by Teijin Kasei) as a binder resin, and was dissolved in 6 parts by weight of dichloromethane to prepare a coating liquid for a charge transport layer.

Next, a charge generation layer (I μm) and a charge transport layer (I 6 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 of Example 1 was converted into the compound N[l I −1
1 part by weight of a bisazo compound represented by the above formula (TI)
A photoreceptor was produced in the same manner as in Example 1 except that 9 parts by weight of the bisazo compound represented by was used.

Comparative Example 1 The charge generating substance of Example 1 was converted into the compound N (L I -1
A photoreceptor was produced in the same manner as in Example 1 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 VS (volt) of the photoreceptor is -5,QkV 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 Va (
volts), and then apply an illuminance of 2 to the surface of the photoreceptor.
The time (seconds) required for Vd to be halved after irradiation with white light of lux was determined, and the half-attenuation exposure amount E 1/2 (IIIX·seconds) was determined. Further, the surface potential when the surface of the photoreceptor was irradiated with 21 u× white light for 10 seconds was defined as the residual potential V (volt). Furthermore, the half-attenuation exposure amount E 1/2 (550) of monochromatic light of 550 nm and the half-attenuation exposure amount E 1yz (650) of monochromatic light of 650 nm are measured, and the ratio is calculated as the red color reproducibility E 1/2 (650) / E1/2 (
550).

The larger the value of El/□(650)/E1/-(550), the better the red color reproducibility.

The measured results are shown in Table 1.

As seen in Table 1, Examples 1 and 2 are compared to Comparative Example 1.
The surface potential, residual potential, and half-attenuation exposure amount are almost the same, and the red color reproducibility is clearly improved. ) The advantage of mixing the bisazo compound shown in ) as a charge generating substance is obvious.

Example 3 5 parts by weight of the bisazo compound represented by the above compound No. I-1 as a charge generating substance, 5 parts by weight of the bisazo compound shown by the above formula (II), and diallyl phthalate resin ( 20 parts by weight of Datsutsu (trade name: manufactured by Osaka Soda) 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.A coating solution for the charge generation layer was prepared. 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-100A, manufactured by Unitika) as a binder resin. was dissolved in 18 parts by weight of dichloromethane to prepare a coating liquid for a charge transport layer.

Next, a charge transport layer (I 7 μm) and a charge generation layer (I μm) were coated on the polyester film on which aluminum had been vapor-deposited, respectively, with the prepared coating liquids in that order, and a surface coating layer was further formed, as shown in Figure 2. A photoconductor for positive charging with the following configuration was fabricated.

Example 4 The charge generating substance of Example 3 was used as the compound No. I-1.
1 part by weight of a bisazo compound represented by the above formula (II)
A photoreceptor was produced in the same manner as in Example 3 except that 9 parts by weight of the bisazo compound represented by was used.

Comparative Example 2 A photoreceptor was produced in the same manner as in Example 3 except that the charge generating substance in Example 3 was changed to 10 parts by weight of the bisazo compound represented by the compound NαI-1.

The electrophotographic properties of the photoreceptor thus obtained were evaluated using an electrostatic recording paper tester RSP-428J manufactured by Kawaguchi Electric, and the corona discharge voltage was +5. Other than setting it to QkV,
Measurements were made in the same manner as in Examples 1 and 2 and Comparative Example 1.

The measurement results are shown in Table 2.

As seen in Table 2, Examples 3 and 4 are compared to Comparative Example 2.
The surface potential, residual potential, and half-attenuation exposure amount are almost the same, and the red color reproducibility is clearly improved. ) The advantage of mixing the bisazo compound shown in ) as a charge generating substance is obvious.

〔Effect of the invention〕

According to this invention, the charge generating substance is of the general formula (I
By mixing the bisazo compound represented by the above formula with the bisazo compound represented by formula You can get a body.

[Brief explanation of drawings]

1 and 2 are conceptual sectional views showing different embodiments of the photoreceptor of the present invention. 19. conductive substrate, 2 charge generation layer, 3 charge transport layer,
4 photosensitive layer, 5 surface coating layer. ] Figure Figure 5 Surface coating layer

Claims (1)

[Scope of Claims] 1) In an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer comprising an organic material on a conductive substrate, a bisazo compound represented by the following general formula (I) is used as a charge generation substance. An electrophotographic photoreceptor characterized in that at least one of the compounds is mixed with a bisazo compound represented by the following formula (II). ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・( I
) [In formula (I), R_1 is a halogen atom, an alkyl group,
Represents any alkoxy group, R_2 represents an optionally substituted alkyl group, R_3 is a hydrogen atom, a cyano group, a carbamoyl group, a carboxyl group, an ester group,
Represents any of the acyl groups, R_4 is a hydrogen atom,
Represents any one of a halogen atom, nitro group, alkyl group, and alkoxy group. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(II)