JPS6049342A - Bipolar type electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance photosensitivity and cycle stability and to reduce residual potential by interposing a layer for generating hole and electron between the electron transfer layer and the positive hole transfer layer of a functionally separated electrophotographic sensitive body. CONSTITUTION:A positive hole and electron generating layer is interposed between the electron transfer layer and the positive hole transfer layer of a functionally separated electrophotographic sensitive body. The effect of surface electron due to exposure is reduced by forming a structure capable of transferring both electron and positive hole. Since the internal electric field intensity can be always kept constant by transferring both charge of positive hole and electron, siad body is prevented from various trouble, such as decay of surface potential, lowering of the internal electric field intensity, and deterioration of efficiencies of charge generation, charge transfer, and charge injection. The positive hole and electron generating layer is made of at least one kind of phthalocynaine vapor deposited films, the eelectron transfer layer is made of an Se vapor deposited film or a polymer film contg. tetranitrofluorenone and/or tetracyanobenzoquinone, and the positive hole transfer layer is, preferably, made of a polymer contg. an org. transfer agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bipolar electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor with high sensitivity and excellent cycle stability.

Conventional photoreceptors for electrophotography have a single-layer structure made of a single material, and a laminated structure in which a charge generation layer and a charge transfer layer are made of different materials.

Single-layer electrophotographic photoreceptors have the disadvantage that suitable materials are limited because the same material must have charge generation ability, charge transfer ability, and charge acceptance based on dark resistance. there were. Furthermore, due to exposure and light, the surface potential changes and the electric field strength decreases, resulting in a significant decrease in charge generation efficiency and transfer efficiency.

On the other hand, in a laminated electrophotographic photoreceptor, since the functions are separated, there is an advantage that there is a greater degree of freedom in material selection, but on the other hand, charge injection properties at the interface between the transfer layer and the generation layer become a problem. Since this charge injection property strongly depends on the electric field strength, a decrease in surface potential due to exposure has a strong influence. For this reason, the charge injection property deteriorates as the head approaches, and the charge remains at the interface, creating a residual potential, which poses a practical problem. Furthermore, since the charge generation efficiency and transfer efficiency are greatly affected, there is a drawback that the sensitivity of the photoreceptor is significantly lowered when the exposure time is lengthened.

The present invention has been made in view of the above-mentioned points, and provides a photoreceptor for photosensitive photography having a structure in which both electron and hole carriers can move, which reduces the influence of decrease in surface potential due to exposure, has high sensitivity, The purpose of this invention is to achieve a bipolar electrophotographic photoreceptor with excellent cycle stability.

Therefore, the bipolar type electrophotographic photoreceptor according to the present invention is a function-separated type electrophotographic photoreceptor in which an electron transfer layer, a hole and electron generation layer, and a tag transfer layer are sequentially laminated. be.

According to the bipolar electrophotographic photoreceptor according to the present invention,
By moving both the charges of holes and electrons, the internal electric field strength can be kept constant at all times, so the internal electric field strength decreases due to the attenuation of the surface potential due to light irradiation, which increases the charge generation efficiency, transfer efficiency, This has the advantage that the drawback of reduced injection efficiency can be eliminated. Therefore, it is possible to improve the photosensitivity, lower the residual potential, and improve the cycle stability of the photoreceptor.

The present invention will be explained in more detail.

As described above, the bipolar electrophotographic photoreceptor according to the present invention has an electron transfer layer, a hole and electron generation layer, and a hole transfer layer laminated in this order.

The electron transfer agent that imparts electron mobility to the electron transfer layer according to the present invention may be any agent as long as it has a high electron affinity. For example, tetranitrofluorenone (TNF), tetracyanohenzoquinone (TCN)
Q), selenium, etc. can be used.

Tetranitrofluorenone and tetracyanohenzoquinone are dispersed in a polymer and applied using a spinner to form an electron transfer layer. As the polymer, one or more of polyester, vinyl chloride-vinyl acetate copolymer, acrylic resin, urethane resin, etc. can be used.

On the other hand, Se is formed into a film by vacuum evaporation or the like to form an electron transfer layer.

The thickness of these electron transfer layers is preferably 5 to 30 μm.
It is good to be. If it is less than 5 μm, the effect of the electron transfer layer will not be fully exerted, and it will be difficult to obtain the necessary potential. On the other hand, there is no need to form an electron transfer layer with a thickness exceeding 30 μm, which is not economical.

Next, as the hole transfer agent that imparts hole mobility to the hole transfer layer, an organic transfer agent having a low ionization potential can be effectively used. Examples of the organic transfer agent include one or more of birapurin derivatives and hydrazone derivatives.

These organic transfer agents can be dispersed in a polymer and applied using a spinner or the like to form a hole transfer layer in the same way as the electron transfer layer described above.

As the polymer, one or more of polyester, vinyl chloride-vinyl acetate copolymer, acrylic resin, urethane resin, etc. can be used, as in the case of the electron transfer layer described above.

The film thickness of these hole transport layers is preferably 5 to 30 μm.
It is good to be. When the thickness is less than 5 μm, the effect of the hole transport layer is not sufficiently exerted, and it is difficult to obtain the necessary potential. On the other hand, there is no need to form a hole transfer layer with a thickness exceeding 30 μm, which is not economical.

The hole and electron generation layer, ie, the charge generation layer, which are fixed in the hole transfer layer and the electron transfer layer, is preferably made of a material that generates electrons and holes at approximately the same concentration. Examples of materials that satisfy these conditions include one or more metal phthalocyanine compounds. Specific examples of such metal phthalocyanines include aluminum phthalocyanine,
Examples include one or more of various compounds such as silicon phthalocyanine, vanadyl phthalocyanine, titanyl phthalocyanine, and copper phthalocyanine. These materials are vapor-deposited or dispersed in a binder to form a film with a thickness of 0.05 to 1 μm to form a charge generation layer. If necessary, place it in a polar solvent to shift the absorption wavelength.

If the film thickness is less than 0.05 .mu.m, the effect of the charge generation layer may not be sufficient, while if it exceeds 1 .mu.m, the charge mobility may not be sufficient.

The electrophotographic photoreceptor as described above is formed on a substrate, but in the present invention, such a substrate is not fundamentally limited, and may be one that is normally used as a substrate for an electrophotographic photoreceptor. can be used effectively. For example, it can be a metal plate such as aluminum or copper, paper containing carbon powder, Nesa glass, or the like.

The stacking order of each layer formed on such a substrate is such that if the hole and electron generation layers are sandwiched, even if the electron transfer layer is on the substrate side, the hole transfer layer may be on the substrate side. There may be.

Next, a specific example of the structure of the electrophotographic photoreceptor according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an example of an electrophotographic photoreceptor according to the present invention, in which 1 is a conductive substrate, 2 is a hole transfer layer, 3 is a hole and electron generation layer (charge generation layer), 4 is an electron transfer layer.

As is clear from FIG. 1, in the electrophotographic photoreceptor according to the present invention, a hole transfer layer 2 is formed on a substrate 1, and a charge generation layer 3 is laminated on the hole transfer layer 2. Further, an electron transfer layer 4 is laminated on the charge generation layer 3, and the charge generation layer 3 is sandwiched between the hole transfer layer 2 and the electron transfer layer 4.

As described above, these layers may be stacked in the order of substrate, electron transfer layer, charge generation layer, and hole transfer layer.

Next, examples of the present invention will be described.

Example 1 A solution consisting of 10.7% by weight of P-diethylaminoaldehyde phenylhydrazine, 10.7% by weight of polycarbonate, and 78.6% by weight of chloroform was spin-coded on an aluminum substrate and dried at 40°C for 2 hours in a nitrogen stream. After that, it was vacuum dried at 40''C for 10 hours to form a hole transfer layer.The thickness of this layer was about 10 μm.

On this hole transfer layer, aluminum phthalocyanine was deposited to a thickness of 0.1 μm at a vacuum level of 10”5 torr, and the layer was left in tetrahydrofuran vapor for 60 minutes to form a charge generation layer.

Further, on this charge generating HEN, a vacuum degree of 1o-6t is applied.
Or r% evaporation rate 500 persons/mtn approximately 1
An electron transfer layer was formed by vapor deposition to a thickness of 0.17 m.

The electrophotographic photoreceptor obtained by the above method was positively charged with a 5.5 KV discharge, and the optical attenuation of its surface potential was measured to determine the amount of exposure (pJ/, ff) required to halve the surface potential.
1) was evaluated as sensitivity. Furthermore, after charging, a cycle of irradiation with a light amount 10 times the half-reduced exposure amount was repeated, and the cycle stability pressure was examined.

As a result, at 830 nm, 0.3 pJ/cn
Even when the exposure amount was reduced to half of t and the cycle was performed more than 10,000 times, the increase in residual potential was 5% or less of the initial value.

Example 2 Volustel resin 13-fold fi1%: 1-phenyl-3
-(p-diphenylaminostyryl)-5-(p-diethylaminophenyl)-pyrazoline 13% by weight: 74% by weight of tetrahydrofuran was coated onto an aluminum substrate to a thickness of iopm using a spinner.

In the same manner as in Example 1, vanadium phthalocyanine and selenium were added to this hole transfer layer at a thickness of 0.1 μm and 1O
A photoreceptor for electrophotography was manufactured by vapor-depositing to a thickness of pm.

The characteristics of this electrophotographic photoreceptor are as follows at 850 nm:
It showed a half-decreased exposure dose of 0.4 μJ/cTA, and the increase in residual potential after 10,000 cycle tests was 5% or less of the initial value.

Example 3 In Example 1, the hole transfer layer and electron transfer layer were replaced, and selenium was first vapor-deposited on the substrate, and then aluminum phthalocyanine was vapor-deposited on the substrate, and then a solvent treatment was performed with tetrahydrofuran, and a hydrazone compound was further applied. When the coating was applied using a spinner to produce an electrophotographic photoreceptor, the same results as in Example 1 were obtained.

As explained above, the bipolar type electrophotographic photoreceptor according to the present invention can always keep the internal electric field strength constant by moving both the hole and electron type planes, so it can It is possible to eliminate the drawback that the internal electric field strength decreases due to the attenuation of the surface potential due to light irradiation, which is observed in the photoreceptor for photoreceptors, and the charge generation efficiency, transfer efficiency, and injection efficiency decrease. As a result, it is possible to improve the photosensitivity, lower the residual potential, and improve the cycle stability of the electrophotographic photoreceptor.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the structure of an electrophotographic photoreceptor according to the present invention. 1... Conductive substrate, 2... Hole transfer layer, 3...
- Hole and electron generation layer (charge generation layer), 4... electron transfer layer. Applicant's agent Masaki Amemiya

Claims (1)

[Scope of Claims] (11) A bipolar type electrophotographic photoreceptor characterized in that a hole and electron generation layer is sandwiched between an electron transfer layer and a tag transfer layer in an electrophotographic photoreceptor of a separated type. (2) The hole and electron generation layer is one or more types of phthalocyanine vapor-deposited films, and the electron transfer layer is one or more selected from the group of selenium vapor-deposited films, tetranitrofluorenone and/or tetracyanobenzoquinone-containing polymers, A bipolar electrophotographic photoreceptor according to claim 1, wherein the hole transfer layer is made of one or more organic transfer agent-containing polymers. (3) The hole transfer layer is on the substrate side. A bipolar electrophotographic photoreceptor according to either Claim 1 or 2, characterized in that: (4) Claim 1, characterized in that the electron transfer layer is on the substrate side. A bipolar electrophotographic photoreceptor according to either item 1 or item 2.