JPS63113466A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance light responsivity and sensitivity by using a combination of a specified bisazo type compound and specified benzidine derivative. CONSTITUTION:The electrophotographic sensitive body is provided on a conductive substrate with an electric charge generating layer containing one of the bisazo type compound represented by formula I and a charge transfer layer containing one of the benzidine derivative represented by formula II. In these formulae, X is hydrogen, halogen, or nitro group; A is a divalent aromatic hydrocarbon group or divalent heterocyclic group containing nitrogen in the ring; R1 is alkyl group or alkoxy; and each of R2 and R3 is hydrogen, alkyl group, or the like, thus permitting the obtained organic electrophotographic sensitive body to have high electrifiability characteristics, and high photosensitivity characteristics, especially, sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrophotographic photoreceptors, particularly electrophotographic organic photoreceptors.

Conventional technology An electrophotographic photoreceptor forms an electrostatic latent image by charging and image exposure, and after this electrostatic latent image is visualized with toner, it is transferred and fixed onto paper or the like to make a copy. .

Various materials have been proposed and used as electrophotographic photoreceptors. One is an inorganic material such as selenium, zinc oxide or cadmium sulfide, and the other is an organic material. Electrophotographic photoreceptors using organic materials, so-called organic photoreceptors, are constructed using a combination of materials with excellent charge generation ability and materials with excellent charge transport ability, rather than using a single material. That is, functionally separated electrophotographic photoreceptors are the mainstream. Charge-generating materials used in these electrophotographic photoreceptors include bisazo pigments 1, phthalocyanine pigments, benzopyrylium dyes, perylene pigments, etc., and charge-transporting materials include pyrazoline, hydrazone, polyvinylcarbazole, etc. These charge-generating materials and charge-transporting materials cannot simply be combined, but must be selected in consideration of various electrophotographic properties, such as injection properties.

As a functionally separated organic photoreceptor, for example, Japanese Patent Application Laid-Open No. 49-1
A number of proposals have been made, such as those described in Japanese Patent No. 05536. The organic photoreceptor described in JP-A-49-105536M uses a combination of squareium pigment as a charge-generating material and triarylpyrazoline as a charge-transporting material.

Problems to be Solved by the Invention However, conventionally proposed organic electrophotographic photoreceptors have several points that should be improved.

One of these is charging properties such as charge retention ability, dark decay, and residual potential, and the other is photosensitive properties such as sensitivity, but the conventionally proposed methods do not have enough of these properties. In particular, when compared with selenium-based photoreceptors, the performance was poor, and therefore it had to be used mainly as a low-speed photoreceptor.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an organic electrophotographic photoreceptor having excellent charging characteristics and photosensitive characteristics, particularly high sensitivity.

Means for Solving the Problems As a result of intensive research, the present inventors have found that in a laminated electrophotographic photoreceptor, the charge generation layer has the following general formula (I> (wherein, X is a hydrogen atom, a halogen atom, or a nitro group, and A is a divalent aromatic hydrocarbon group or 2 containing a nitrogen atom in the ring.
represents a valent heterocyclic group. ), and the charge transport layer contains a bisazo compound represented by the following general formula (n) (wherein, R1 represents an alkyl group or an alkoxy group,
R2 and R3 each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group, or a substituted amino group. ) The above object could be achieved by incorporating a benzidine compound represented by:

The structure of the electrophotographic photoreceptor of the present invention will be explained as follows.
A photosensitive material comprising a laminate of a charge generation layer containing a bisazo compound represented by the general formula (1) and a charge transport layer containing a benzidine compound represented by the general formula (II) on a conductive support. There are layers. The charge generation layer and the charge transport layer may be stacked in the reverse order. A protective layer may be provided on the photosensitive layer, or an intermediate layer may be provided between the photosensitive layer and the conductive support.

Next, each layer constituting the electrophotographic photoreceptor of the present invention will be explained.

The charge generation layer contains a bisazo compound represented by the general formula (1), and for example, the following compounds can be used.

These bisazo compounds can be produced by known methods. For example, it can be produced by tetrazotizing a diamine represented by the following structural formula (III) by a conventional method and coupling it with a coupling component represented by the following general formula <IV).

(In the formula, X and A have the same meanings as described above.) The charge generation layer may be formed of a bisazo compound alone, but it can also be formed using a bisazo compound in combination with a binder resin.

In the latter case, the ratio of bisazo compound to binder resin is between 10% and 90% by weight, preferably 5% by weight.
0% to 80% by weight.

When using a binder resin, examples of the binder resin include polystyrene, silicone resin, polycarbonate, acrylic resin, methacrylic resin, polyester, vinyl polymers such as polyvinyl butyral, celluloses such as cellulose ester, cellulose ether, etc. , alkyd resin, etc. are used.

The thickness of the charge generation layer is 0.05 to 3μ, preferably 0.1μ.
~1μ.

The charge generation layer is formed by a well-known method. That is, when forming a charge generation layer using a bisazo compound alone without using a binder resin, solvent coating and vacuum evaporation methods can be used.

Further, when a binder resin is used in combination, the bisazo compound is pulverized and then dispersed in the binder resin. As the pulverization method, known methods such as SPEX IILL, ball mill, RED DEVIL (trade name), etc. can be used.

The binder resin in which the bisazo compound is dispersed is applied onto the charge transport layer or the conductive support. Coating methods include a dipping method, a spray method, a bar coater method, an applicator method and the like, and a good charge generation layer can be formed by any of these methods.

On the other hand, the charge transport layer contains a benzidine compound represented by the general formula (II>), and the following benzidine compounds can be used.

In the formula, Me represents a methyl group, Ft represents an ethyl group, pr represents a propyl group, and Bu represents a butyl group.

Since these compounds do not have film-forming properties by themselves, they are used in combination with a binder resin that has good film-forming properties. Examples of binder resins that can be used include acrylic resin, methacrylic resin, polystyrene, polyester,
Examples include general-purpose resins such as polyarylate, polysal 7one, and polycarbonate.

The charge transport layer may contain additives such as plasticizers and leveling agents.

The charge transport layer is formed by dissolving the benzidine compound represented by the general formula (I [>) and the binder resin in a solvent that dissolves both, and applying the solution. weight%, preferably 30~
The content should be 70% by weight.

The thickness of the charge transport layer is set to be thicker than that of the charge generation layer, and is 5 to 50 μm, preferably 1 to 15 to 30 μm.
range is used.

Further, as the conductive support, metal, paper treated with conductivity, a polymer film having a conductive layer, glass, etc. can be used.

In the present invention, examples of the optional protective layer include those in which a metal oxide is dispersed in a resin, and those in which an electron-accepting compound is added to a resin.

Further, the intermediate layer is a layer of metal oxide such as aluminum oxide, acrylic resin, phenol resin, polyester resin, polyurethane, etc., and acts as a barrier layer or an adhesive layer.

There are various factors that determine the sensitivity of an electrophotographic photoreceptor, including the charge generation ability of the charge generation material, the charge injection efficiency from the charge generation layer to the charge transport layer, and the charge transfer efficiency of the charge transport material. If any one of them is missing, a photoreceptor with satisfactory sensitivity cannot be obtained. For example, even when a charge generation material with a high charge generation function is used, if the selection of the charge transport layer is not appropriate, the photoreceptor will have poor charge injection efficiency and charge transport efficiency, and poor photoresponsiveness. This means that the absolute sensitivity is low. Conversely, even when a charge transport material with good charge transport efficiency is used, the photoresponsiveness may be poor depending on the selection of the charge generation image.

Therefore, in the present invention, the selection of the above two compounds is extremely important in terms of charge injection properties.

In the electrophotographic photoreceptor of the present invention, whether or not the charge injection and transport functions are properly performed can be determined by measuring the amount of exposure required until the surface potential reaches 115 after initial charging. This is because the above characteristics mainly affect charge injection efficiency and transport efficiency.

Example Next, the present invention will be explained by examples.

Example 1 Polyvinyl butyral resin (Product name: BLX Sekisui Chemical ■
) was dissolved in 40 parts by weight of cyclohexanone,
Exemplified compound Nα1 is triple-mixed therein as a charge-generating material, then well dispersed using a paint shaker, and the resulting dispersion is applied onto an aluminum sheet using an applicator and dried to form a charge-generating layer. Formed.

The film thickness after drying was 0.2μ.

Exemplary compound N, which is a charge transport material, is placed on this charge generation layer.
α51 parts by weight, polycarbonate resin (trade name Nilexane 145, manufactured by GE, molecular weight 35.000-40.0
A homogeneous solution consisting of 1 part by weight of 00> and 15 parts by weight of dichloromethane was applied using an applicator and dried to form a charge transport layer. The film thickness was 20 μm.

The photoreceptor obtained as described above was subjected to the following characteristic evaluations using an electrostatic copying paper tester (Kawaguchi Denki 5P-428). First, it was negatively charged by applying corona discharge of -6 KV. After that, leave it in a dark place for 2 seconds and measure the surface potential Vpo (volt) at that time. Next, use a tungsten lamp to irradiate the surface with light at an illumination intensity of 5 lux, and check the surface potential. Find the time until the Vpo reaches 115, and calculate the exposure ME115 (I ux-se
c> was calculated. As a result, Vl)o=-980V, E
115=5.51 uX-5ec.

Examples 2 to 10 Electrophotographic photoreceptors were prepared and evaluated in the same manner as in Example 1, except that the charge generating material and transport material were changed to the combinations shown in Table 1. The results are shown in Table 1.

Table 1 Comparative Example 1 An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1, except that the charge transport material was changed to the following compound.

Comparative Example 2 An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1, except that the charge transport material was changed to the following compound.

Comparative Example 3 An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1, except that the charge transport material was changed to the following compound.

Comparative Example 4 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the charge generating material was changed to the following compound, and evaluation 1 was obtained.
I did ■.

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1, except that the charge transport material was changed to the following compound.

The results of Comparative Examples 1 to 5 are shown in Table 2.

Table 2 Effects of the Invention As is clear from the comparison of Tables 1 and 2 above, the electrophotographic photoreceptor of the present invention combines the bisazo compound represented by the general formula (1) with the general formula (1) as described above. By using a combination with a benzidine compound represented by formula (II>), high photoresponsiveness is exhibited even in a low electric field, and high sensitivity is exhibited in the visible light region.

Claims (1)

[Scope of Claims] In a laminated electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer on a conductive support, the charge generation layer has the following general formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼(I) (wherein, X represents a hydrogen atom, a halogen atom, or a nitro group, and A represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring) ), and the charge transport layer has the following general formula (II) ▲ Numerical formula, chemical formula, table, etc. ▼ (II) (wherein R_1 is an alkyl group or an alkoxy group and R_2 and R_3 each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group, or a substituted amino group. body.