JPH05188606A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body having high sensitivity which enables fast printing and causes no deterioration of characteristics even for repeated use by incorporating an enamine deriv. expressed by specified formula into a charge transfer layer. CONSTITUTION:This electrophotographic sensitive body is a layered type having at least a charge generating layer and a charge transfer layer on a conductive supporting body. The charge transfer layer contains an enamine deriv. expressed by formula. In formula, R1-R3 are independently lower alkyl groups, R4 and R5 are independently lower alkyl, lower alkoxy, phenyl or naphthyl groups with substitution of lower alkyl or lower alkoxy groups. This charge transfer layer is formed by dissolving a compd. expressed by the formula with a binder resin in a solvent, applying the liquid on the charge generating layer, and drying. As for the charge generating material which constitutes the charge generating layer or is included in the charge generating layer, dyes or pigments such as azo, phthalocyanine, indigo, perylene, etc., are used.

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, and more particularly to an electrophotographic photosensitive member exhibiting high sensitivity and excellent continuous stability.

[0002]

2. Description of the Related Art Electrophotographic photoreceptors are widely applied to copying machines, printers and the like to which an electrophotographic method is applied. As an example of electrophotography, it is common to obtain a printed matter by repeating the steps of charging, exposing, developing, transferring, and fixing. The charging applies a uniform positive or negative electrostatic charge to the surface of the photoconductor having photoconductivity. In the subsequent exposure process, a laser beam or the like is irradiated to erase the surface charge of a specific portion, thereby forming an electrostatic latent image corresponding to image information on the photoconductor. Next, this latent image is electrostatically developed with powder ink called toner to form a visible image with toner on the photoconductor. Finally, this toner image is electrostatically transferred onto a recording paper and fused by heat, light, pressure or the like to obtain a printed matter.

Conventionally, inorganic photoconductors represented by selenium have been widely used as the photoconductors having photoconductivity. Although this inorganic photoconductor has high sensitivity and resistance to mechanical abrasion and is suitable for high-speed and large-scale machines, it has to be manufactured by the vacuum deposition method, and it is harmful to the human body, so it needs to be recovered. However, there is a problem in that it is difficult to apply to maintenance-free small-sized and low-priced machines because of high cost due to such reasons.

The organic photoconductor has been developed as an alternative to the inorganic photoconductor. This is because it can be manufactured by the coating method, so it is easy to reduce the cost by mass production, and since the material selection range is wider than the inorganic photoconductor that uses an inorganic substance such as selenium, it is possible to select a compound that is not harmful. It has the feature that it can be maintenance-free.

In particular, the function-separated laminated type photoreceptor (FIG. 1) in which a charge generation layer and a charge transport layer are laminated has attracted attention. In the figure, 1 is a photosensitive layer, 2 is a charge transport layer, 3 is a charge generation layer, 4
Indicates a support, respectively. Here, the charge generation layer has a function of absorbing incident light to generate an electron-hole pair (carrier pair), and the charge transport layer holds charge on its surface and also generates carriers generated in the charge generation layer. Has the function of transporting one of them to the surface of the photoconductor to form an electrostatic latent image. The charge generation layer is formed by depositing a charge generation substance that absorbs light to generate a carrier pair or by dispersing it in a binder resin. Azo pigments and phthalocyanines are known as charge generating substances, and polyester, polyvinyl butyral and the like are used as binder resins. The charge transport layer is formed by making a binder resin compatible with a charge transport material having a carrier transport ability. As the charge-transporting substance, there are electron-transporting charge-transporting substances such as trinitrofluorenone and chloranil, which have an electron-transporting property, and hole-transporting charge-transporting substances such as hydrazone and pyrazoline, which have a hole-transporting property.
As binder resin, polycarbonate or styrene-
Acrylic is used.

By separating the function of the photoconductor into two layers in this way, it is possible to select the compounds most suitable for each function almost independently, and to obtain various properties such as sensitivity, spectral characteristics and mechanical abrasion resistance. The characteristics can be improved.

[0007]

However, the sensitivity is still lower than that of conventional inorganic photoconductors such as selenium, and it is difficult to apply it to high-speed printers. Therefore, there has been a demand for the development of an electrophotographic photosensitive member that has high sensitivity and enables high-speed printing.

[0008]

The present invention has as its object to solve the above-mentioned conventional problems, and in order to achieve this object, the electrophotographic photosensitive member of the present invention is at least on a conductive support. In a laminated electrophotographic photoreceptor having a charge generation layer and a charge transport layer, the following structural formula (I) is contained in the charge transport layer:

[0009]

[Chemical 2]

(In the above formula, R ₁ , R ₂ and R ₃ each independently represent lower alkyl, R ₄ and R 3
_5's each independently represent phenyl or naphthyl substituted with lower alkyl, lower alkoxy or lower alkyl or lower alkoxy. ) It is characterized by containing an enamine derivative represented by.

As described above, in the present invention, the conductive support may be of any type as long as it can ground the photoreceptor, and various metal cylinders, cylinders of conductive resin or paper, insulating cylinders, etc. A metal vapor-deposited or laminated surface, a conductive organic thin film formed on an insulating cylinder, and a film having the same structure as described above can be preferably used.

As the charge generating substance constituting the charge generating layer or contained in the charge generating layer, azo type, phthalocyanine type, indigo type, perylene type, squarylium type, quinone type dyes or pigments can be used. Particularly when a phthalocyanine pigment is used, good sensitivity can be obtained. As the phthalocyanine, various metal phthalocyanines such as metal-free phthalocyanine, copper phthalocyanine, aluminum chloride phthalocyanine, titanyl phthalocyanine, vanadyl phthalocyanine and indium phthalocyanine can be used. The charge generation layer is formed by vapor-depositing these charge generation substances on a support or by coating and drying a dispersion of the charge generation substance together with a binder resin in a solvent. As the binder resin, various resins such as polyester, polyvinyl alcohol, polyvinyl acetal, polyamide, epoxy, and silicone, or various organic compounds having a film-forming property such as casein can be used. Select in consideration of dispersibility. The solvent is selected according to the charge generating substance and the binder resin used, but tetrahydrofuran, dioxane, methanol, ethanol, hexane, ether, dichloromethane, dichloroethane, benzene, toluene, chlorobenzene, xylene, methyl cellosolve, ethyl cellosolve, ethyl acetate, etc. Various organic solvents can be used alone or as a mixture. Examples of the method for applying to the support include dip coating, spray coating, wire bar coating and doctor blade coating. The film thickness is about 0.01 to 3 μm, but it is desirable to set it to 1 μm or less.

The charge transport layer is formed by dissolving the compound represented by the structural formula I in a solvent together with a binder resin, and coating and drying the solution on the charge generating layer. The compound represented by Structural Formula I can be synthesized from an aldehyde II and a diamine III represented by the following structural formulas by a known dehydration condensation reaction. Representative examples of the compounds are shown in Table 1 below.

[0014]

[Chemical 3]

In the formula, R ₁ , R ₂ and R ₃ each independently represent lower alkyl.

[0016]

[Chemical 4]

In the formula, R ₄ and R ₅ each independently represent lower alkyl, lower alkoxy or phenyl or naphthyl substituted with lower alkyl or lower alkoxy. In the present invention, lower alkyl and lower alkoxy represent alkyl and alkoxy having 1 to 3 carbon atoms, respectively.

As the binder resin for the charge transport layer, known resins such as polyester, polycarbonate, polystyrene, polyacrylonitrile, acryl-styrene and polysulfone can be used. The solvent is appropriately selected from the same materials as those used for coating the charge generation layer, depending on the binder resin used. As the coating method, the same method as in the case of the charge generation layer can be used. The film thickness is 5-50 μm
However, it is desirable that the thickness is 10 to 30 μm.

In the charge transport layer, the enamine derivative I
In addition, other hole transporting charge transporting substances such as other hydrazone derivatives and pyrazoline derivatives may be added.
At this time, the mixing ratio of the other charge transport material to the hydrazone derivative is preferably in the range of 100: 1 to 100: 500. Further, the order of stacking the charge generation layer and the charge transport layer may be reversed.

Between the conductive support and the charge generating layer, the adhesion is improved, the surface of the support is flattened, the surface of the support is covered with defects, hot carriers are controlled to be injected, and the charge acceptance and the charge retention are improved. An undercoat layer may be provided for the purpose such as. As a constituent material of the undercoat layer, a material having film-forming property such as various binder resins or casein used in the charge generation layer or the charge transport layer, or a resistance value by containing a conductive substance in them. It is possible to use the one having a value of 10 ¹⁴ Ω · cm or less. As the conductive substance for adjusting the resistance value of the undercoat layer, any conductive substance such as various metal powders, conductive metal oxide powders and carbon may be used.

[0021]

The photoreceptor of the present invention, which uses a novel enamine derivative in the charge transport layer, exhibits high sensitivity and excellent continuous stability. The reason why the photoconductor of the present invention exhibits high sensitivity is considered as follows. Generally, in the case of a laminated type photoreceptor as in the present invention, its sensitivity is determined by the carrier generation efficiency ξ in the charge generation layer, the carrier injection efficiency η from the charge generation layer to the charge transport layer, and the carrier transport efficiency ζ in the charge transport layer. It is said that the higher each efficiency is, and the product thereof is closer to 1, the higher the sensitivity is. Since Example 1 and the comparative example have the same charge generation layer, both ξ are the same. Therefore, it can be said that the embodiment has higher sensitivity because η and ζ are larger.

In the carrier injection from the charge generation layer to the charge transport layer, electron-hole pairs generated in the charge generation material in the charge generation layer are separated, and independent holes are charged from the charge generation material by electric field energy. It is believed to be achieved by migrating to the charge transport material in the transport layer. At this time, it is said that the closer the respective energy levels involved in the movement of holes, the higher the transfer efficiency (that is, injection efficiency). From this, the hydrazone derivative of the present invention shows that the molecular orbital (highest occupied molecular orbital, HOMO) related to its hole transporting.
Is close to the energy level of the holes generated in the charge generating substance, and it is considered that this shows high sensitivity.

Further, it is considered that the reason why the sensitivity is particularly good with phthalocyanine is that the energy levels of the phthalocyanine and the enamine derivative of the present invention are close to each other. It is considered that the hole transport in the charge transport layer is achieved by the holes injected from the charge generation layer performing hopping conduction between the charge transport materials toward the surface.
Therefore, it can be said that the transport efficiency ζ is higher as the hole hopping is more likely to occur. Further, it is considered that hopping is more likely to occur as the charge transport material more easily emits electrons (smaller ionization energy). The reason why the hydrazone derivative of the present invention is superior to ζ is that it has a benzene ring to which three donors (—OR) are bonded.
It is considered that the energy level of MO becomes higher than that of the conventional charge transport material, and electrons are more easily emitted.

For the above reasons, the photoconductor of the present invention is considered to exhibit higher sensitivity than those using the conventional charge transport material. Hereinafter, the present invention will be described with reference to Examples.
It goes without saying that the invention is not limited by these examples.

[0025]

【Example】

Synthesis Examples 1-4: Synthesis of Enamine Derivatives Enamine Synthesis Example 3,4,5 Trimethoxybenzaldehyde 0.01 mol, diphenylamine 0.01 mol and benzene 40 ml were put into a 200 ml flask, and H ₂ O produced under N ₂ gas stream. While heating, the mixture was heated and refluxed for 8 hours.

The obtained fine crystals were collected by suction filtration, washed with methanol three times, and then purified by recrystallizing with ethanol to obtain 3,4,5-trimethoxyphenyl 1,3.
1-Diphenylenamine (No. 1 compound in Table 1) (melting point 112-115 ° C) was obtained with a yield of 55%. The same operations as in Synthesis 1 were carried out to synthesize the compounds No. 2 to No. 4 shown in Table 1.

[0027]

[Table 1]

Example 1 Titanium oxide phthalocyanine (1 part by weight), polyester (1 part), dichloromethane (9 parts) and dichloroethane (9 parts) were dispersed and mixed for 24 hours in a hard glass ball and a hard glass pot to prepare an aluminum vapor-deposited polyester film. It was applied onto an aluminum surface with a doctor blade and dried at 100 ° C. for 1 hour to form a charge generation layer having a film thickness of about 0.3 μm.

Next, the enamine derivative No. 1 shown in Table 1
1 part, polycarbonate 1 part tetrahydrofuran 1
It was dissolved in 0 part, coated on the charge generation layer with a doctor blade, and dried at 70 ° C. for 2 hours to form a charge transport layer having a film thickness of about 17 μm, and a photoreceptor of Example 1 was obtained. Comparative Example 1 In Example 1, an enamine derivative that is a charge transport material
Comparative Example 1 was carried out in the same manner as in Example 1 except that a hydrazone derivative represented by the following structural formula (V) was used instead of No. 1.
To obtain a photoconductor.

[0030]

[Chemical 5]

The following measurements were performed on the above two types of photoreceptors. First, the corona is charged at -5 kV, and the surface potential after 1 second is V
o (V). From that moment, the exposure is performed with incident light of 780 nm until the surface potential becomes half of Vo, t1 /
2 is calculated and the half-exposure amount E1 / 2 (μJ / cm ² ) is calculated. Furthermore, the surface potential Vr of 10t1 / 2 after the start of exposure
(V) is recorded, and the process is completed by finally removing the charge with a 630 nm LED. The results of repeating this process 5000 times are shown in Table 2.

As can be seen from Table 2, the photoconductor of the present invention has an E1 / 2 value of 40 to 50% smaller than that of the comparative example, and therefore has high sensitivity. Furthermore, it is considered that the sensitivity did not decrease and the residual potential Vr did not increase even after the continuous test of 5000 times, and that the characteristics did not deteriorate. On the other hand, although the photoconductor of the comparative example shows relatively good characteristics at the initial stage, the photoconductor is deteriorated (or fatigued) after the continuous test due to a decrease in sensitivity and an increase in residual potential. I understand.

Examples 2 to 4 Photoconductors 2 to 4 of Examples were manufactured in exactly the same manner as Example 1 except that the enamine derivative shown in Table 1 was used as the enamine derivative of the charge transport layer. Table 2 shows the results of the same tests as in Example 1 performed on this photoreceptor.

[0034]

[Table 2]

[0035]

INDUSTRIAL APPLICABILITY As described above, the present invention is configured so that the charge transport layer contains the enamine derivative I of the present invention. Therefore, high sensitivity and low residual potential can be obtained, and repeated use is possible. Also in the case, there is an effect of obtaining an electrophotographic photosensitive member without deterioration of characteristics.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of the configuration of a photoconductor of the present invention. DESCRIPTION OF SYMBOLS 1 ... Photosensitive layer 2 ... Charge transport layer 3 ... Charge generation layer 4 ... Support

Claims (2)

[Claims] 1. A laminate type electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge transport layer contains an enamine derivative represented by the following structural formula (I). An electrophotographic photosensitive member characterized by the above. [Chemical 1] In the above formula, R ₁ , R ₂ and R ₃ each independently represent lower alkyl, and R ₄ and R ₅ each independently represent lower alkyl, lower alkoxy or phenyl or naphthyl substituted with lower alkyl or lower alkoxy. Represents. 2. The charge transport layer according to claim 1, and a charge generation layer containing at least one of an azo-based, phthalocyanine-based, indigo-based, perylene-based, squarylium-based, quinone-based dye and pigment. The electrophotographic photosensitive member according to claim 1.