JPH04328565A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body having high sensitivity and low residual potential as an electrophotographic sensitive body widely used for a copying machine, a printer, etc., applying an electrophotographic system. CONSTITUTION:A hydrazone deriv. using a 2,4,5-trialkoxyphenyl group in the molecular skeleton and represented by structural formula I is incorporated into an electric charge transferring layer. In the formula I, each of R1-R3 is lower alkyl and each of R4 and R5 is lower alkyl, phenyl or naphthyl which may be substd. with lower alkyl or lower alkoxy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor that is widely applied to copying machines, printers, etc. that utilize electrophotography. A common electrophotographic method is to obtain printed matter by repeating the steps of charging, exposing, developing, transferring, and fixing.

Charging applies a uniform positive or negative electrostatic charge to the surface of a photoreceptor having photoconductivity. In the subsequent exposure process, an electrostatic latent image corresponding to the image information is formed on the photoreceptor by irradiating it with laser light or the like to erase the surface charge on a specific portion. Next, this latent image is electrostatically developed with powder ink called toner, thereby forming a visible image of the toner on the photoreceptor. Finally, this toner image is electrostatically transferred onto recording paper and fused using heat, light, pressure, etc. to obtain a printed matter.

0003

[Prior Art] As the above-mentioned photoconductor having photoconductivity,
Inorganic photoreceptors typified by selenium-based photoreceptors were widely used. This inorganic photoreceptor has high sensitivity and is resistant to mechanical wear.
Although it has the advantage of being suitable for high-speed, large-scale machines, it is expensive because it must be manufactured using a vacuum evaporation method, and it must be recovered because it is harmful to the human body. The problem was that it was difficult to apply to low-cost machines.

Organic photoreceptors have been developed as an alternative to inorganic photoreceptors. This material can be manufactured by a coating method, which makes it easy to reduce costs through mass production, and because it has a wider range of materials to choose from than inorganic photoreceptors that use inorganic materials such as selenium, non-hazardous compounds can be selected. It has the advantage of being maintenance-free.

In particular, as shown in FIG. 1, a functionally separated laminated photoreceptor in which a charge generation layer 1 and a charge transport layer 2 are laminated has attracted attention. Here, the charge generation layer 1 has a function of absorbing incident light and generating electron-hole pairs (carrier pairs), and the charge transport layer 2 retains a charge on its surface, and
It has a function of transporting one of the carriers generated in the charge generation layer 1 to the surface of the photoreceptor to form an electrostatic latent image. The charge generation layer 1 is formed by forming a charge generation substance that absorbs light and generates carrier pairs into a vapor deposited film or by dispersing it in a binder resin. Azo pigments, phthalocyanine, and the like are known as charge-generating substances, and polyester, polyvinyl butyral, and the like are used as binder resins. The charge transport layer 2 is formed by dissolving a charge transport material having carrier transport ability into a binder resin. Charge transport materials include electron transport charge transport materials such as trinitrofluorenone and chloranil, which have the property of transporting electrons, and hole transport charge transport materials such as hydrazone and pyrazoline, which have the property of transporting holes. Polycarbonate, styrene-acrylic, etc. are used as the binder resin.

[0006] By separating the functions of the photoreceptor into two layers in this way, it is possible to select the most suitable compound for each function almost independently, and various factors such as sensitivity, spectral characteristics, and mechanical abrasion resistance can be selected. Characteristics can be improved. In addition,
In the figure, 3 is a photosensitive layer and 4 is a conductive support.

[0007]

[Problem to be solved by the invention] However, such conventional organic photoreceptors still have lower sensitivity than conventional inorganic photoreceptors such as selenium, making it difficult to apply them to high-speed printers. . The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an electrophotographic photoreceptor that can obtain high sensitivity and low residual potential.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, in which the charge transport layer contains the following: It contains a hydrazone derivative represented by structural formula (1).

[0009]

[Case 2]

(In the formula, R1 to R3 represent a lower alkyl group, and R4 and R5 represent a lower alkyl group, or a phenyl group or a naphthyl group which may be substituted with a lower alkyl group or a lower alkoxy group.) The invention will now be described in more detail. Generally, in the case of a laminated photoreceptor like the present invention, its sensitivity depends on (1) carrier generation efficiency in the charge generation layer, (2) carrier injection efficiency from the charge generation layer to the charge transport layer, and (3) charge transport. It is said that the higher the carrier transport efficiency in the layer and the closer the product of these efficiencies to 1, the higher the sensitivity.

[0011] Carrier injection from the charge generation layer to the charge transport layer involves separation of electron-hole pairs generated in the charge generation material in the charge generation layer, and the isolated holes are transferred from the charge generation material by electric field energy. It is believed that this is achieved by transfer 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 movement efficiency (that is, the injection efficiency). From this, the hydrazone derivative of the present invention has a molecular orbital (highest occupied molecular orbital, HOMO) involved in hole transport.
is close to the energy level of holes generated within the charge-generating material, which is thought to be the reason for its high sensitivity.

[0012] It is also believed that the reason why the sensitivity is particularly good with phthalocyanine is that the energy levels of phthalocyanine and the hydrazone derivative of the present invention are close to each other. It is believed that hole transport in the charge transport layer is achieved by hopping conduction of holes injected from the charge generation layer toward the surface between charge transport materials. Therefore, it can be said that the easier hole hopping occurs, the higher the carrier transport efficiency. Furthermore, it is thought that the easier a charge transport material is to emit electrons (the lower its ionization energy), the more likely hopping will occur. The reason why the hydrazone derivative of the present invention has excellent carrier transport efficiency is that because it has a benzene ring with three donors (-OR) bonded to it, the HOMO energy level is higher than that of conventional charge transport materials, and it transfers electrons. This is thought to be because it is easier to release.

For the above reasons, it is believed that the photoreceptor of the present invention exhibits higher sensitivity than those using conventional charge transport materials. The conductive support may be anything that can ground the photoreceptor, such as various metal cylinders, conductive resin or paper cylinders, insulating cylinders with metal vapor-deposited or laminated on the surface, and insulating ones. A cylinder having a conductive organic thin film applied thereto, a film having the same structure as above, etc. can be used.

Various dyes and pigments such as azo-based, phthalocyanine-based, indigo-based, perylene-based, squarylium-based, and quinone-based dyes and pigments are used as charge-generating substances constituting or contained in the charge-generating layer. You can, but
In particular, good sensitivity can be obtained by using phthalocyanine pigments. 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 generating layer is formed by vapor depositing these charge generating substances on the support, or by coating and drying a mixture dispersed in a solvent together with a binder resin. Binder resins include polyester, polyvinyl alcohol, polyvinyl acetal,
Various resins such as polyamide, epoxy, silicone, etc., and various organic compounds having film-forming properties such as casein can be used, and are selected in consideration of adhesion to the base, dispersibility of the charge generating substance, etc. The solvent is selected according to the charge generating substance and binder resin used, but examples include 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 in combination. Application methods to the support include dip coating, spray coating,
There are wire bar coats, doctor blade coats, etc. The film thickness is approximately 0.01 to 3 μm, but preferably 1 μm or less.

The charge transport layer is formed by dissolving the compound represented by the structural formula (1) in a solvent together with a binder resin, coating the solution on the charge generating layer, and drying the solution. The compound represented by the structural formula (1) can be synthesized from aldehydes represented by the following structural formulas (2) and (3), respectively, and hydrazine by a known dehydration condensation reaction. Examples of compounds are shown in Table 1.

[0016]

[Chemical formula 3]

[0017]

[C4]

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

In addition to the hydrazone derivative of formula (1), other hole-transporting charge transport substances such as other hydrazone derivatives and pyrazoline derivatives may be added to the charge transport layer. At that time, the mixing ratio of the other charge transport substance to the hydrazone derivative is 100:1 to 100:500.
range is desirable. Further, the stacking order of the charge generation layer and the charge transport layer may be reversed.

Between the conductive support and the charge generation layer, improvements in adhesion, flattening of the surface of the support, covering of defects on the surface of the support, control of hot carrier injection, and improvement of charge acceptance and charge retention are provided. A subbing layer may be provided for purposes such as the following. The constituent material of the undercoat layer may be a film-forming material alone such as various binder resins or casein used in the charge generation layer or charge transport layer, or a conductive material may be added therein to increase the resistance value. It is possible to use a material whose resistance is adjusted to 1014 Ω·cm or less. As the conductive substance for adjusting the resistance value of the undercoat layer, any substance having conductivity may be used, such as various metal powders, conductive metal oxide powders, and carbon.

[0021]

[Function] The photoreceptor of the present invention uses a novel hydrazone derivative in the charge transport layer, and therefore exhibits high sensitivity and excellent continuous stability.

[0022]

EXAMPLES The present invention will now be explained in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 1 part (by weight) of titanium oxide phthalocyanine, 1 part of polyester, 9 parts of dichloromethane, and 9 parts of dichloroethane were dispersed and mixed for 24 hours using a hard glass ball and a hard glass pot, and a mixture was mixed on the aluminum surface of an aluminum-deposited polyester film. The charge generation layer was coated with a doctor blade and dried at 100° C. for 1 hour to form a charge generation layer with a thickness of about 0.3 μm.

Next, hydrazone derivative No. shown in Table 1
．． 1 part of polycarbonate and 1 part of polycarbonate were dissolved in 10 parts of tetrahydrofuran, and the solution was applied onto the charge generation layer using a doctor blade and dried at 70°C for 2 hours to form a film with a thickness of about 17 μm.
A charge transport layer of m was formed to obtain a photoreceptor of Example 1. Comparative Example 1 In Example 1, the charge transport material hydrazone derivative No. A photoreceptor of Comparative Example 1 was obtained in the same manner as in Example 1 except that a hydrazone derivative represented by the following structural formula (4) was used instead of 1.

[0024]

[C5]

The following measurements were carried out on the above two types of photoreceptors. First, corona charging is performed at -5 kV, and the surface potential after 1 second is set to Vo (V). From that moment, exposure is performed with 780 nm incident light, and the time t until the surface potential becomes half of Vo.
1/2 and the half-decreased exposure amount E1/2 (μJ/cm2
). Furthermore, the surface potential Vr (V) of 10t1/2 after the start of exposure was recorded, and finally the 630nm LED
The process was completed by removing the static electricity.

From Table 2, it can be seen that the photoreceptor of Example 1 has an E1/2 value 40 to 50% smaller than that of Comparative Example 1, and therefore has high sensitivity. Examples 2 to 4 Photoreceptors of Examples 2 to 4 were prototyped in exactly the same manner as in Example 1, except that the hydrazone derivatives shown in Table 1 (No. 2 to No. 4) in the charge transport layer were used. did.

[0027] This photoreceptor was subjected to the same tests as in Example 1, and the results are shown in Table 2.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

As described above, according to the present invention, a photoreceptor with high sensitivity and low residual potential can be obtained.

[Brief explanation of the drawing]

[Figure 1] Configuration diagram of a conventional laminated photoreceptor

[Explanation of symbols]

1: Charge generation layer 2: Charge transport layer 3: Photosensitive layer 4: Conductive support

Claims (1)

[Claims] 1. An electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge transport layer contains a hydrazone derivative represented by the following structural formula (1). Characteristic electrophotographic photoreceptor. [Formula 1] (wherein, R1 to R3 are lower alkyl groups, R4, R
5 represents a lower alkyl group, a phenyl group or a naphthyl group which may be substituted with a lower alkyl group or a lower alkoxy group. )