JPS6358451A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain the titled body which has excellent electric chargeability, high photosensitivity, excellent printing resistance, and less residual potential and is capable of forming excellent copying image by composing an electric charge transfer substance of a specific carbazole derivative. CONSTITUTION:The titled body is provided with a layer of the electric charge transfer substance and a layer of the electric charge generating substance on a conductive substrate body. The electric charge transfer substance is composed of the carbazole derivative shown by the formula wherein R<1> and R<2> are each 1-4C alkyl group. The electric charge transfer substance contd. in the electric charge transfer layer is exemplified by 3,6-bis(dialkyl amino)-9-alkyl carbazole, and the compounding amount of said compd. is preferably a range of 10-60wt% per the weight basis of said layer. The thickness of the electric charge transfer layer is suitable to be 5-100mum. The less the sticking resin is used in the electric generating layer, the more the titled body is preferable, and the content of the sticking resin is preferably 5-50wt%. The thickness of the electric charge generating layer is usually 0.05-20mum, preferably 0.1-10mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and more particularly, a photosensitive layer comprising a layer of a charge transporting material and a layer of a charge generating material on a conductive support. The present invention relates to an electrophotographic photoreceptor.

BACKGROUND OF THE INVENTION Hitherto, various electrophotographic photoreceptors have been developed and put into practical use according to electrophotographic copying methods, but all of them have drawbacks that should be improved.

For example, selenium-based photoreceptors have poor flexibility and are difficult to handle because selenium itself is highly toxic. Furthermore, photoreceptors using zinc oxide have low sensitivity, poor charging properties, and poor rigidity. As an organic photoreceptor, a photoreceptor using a charge transfer complex of polyvinylcarbazole-trinitrofluorenone has been developed, but the sensitivity is low and trinitrofluorenone has a problem of toxicity.

Therefore, as described in Japanese Patent Publication No. 60-57588, a laminated electrophotographic photoreceptor comprising a layer of a charge-generating material and a layer of a charge-transporting material on a conductive support has recently been developed. Proposed. In this electrophotographic photoreceptor, 3,6-bis(dibenzylamino)-9-alkylcarbazole is used as a charge transport substance, and a charge transport layer containing such a charge transport substance is electrically conductive together with a charge generation layer. layered on a support. Such a charge transport layer can be prepared, for example, by forming a solution of a charge transport substance together with an appropriate organic solvent, a binder resin, and, if necessary, a plasticizer.
It is prepared by coating this on a conductive support or a charge generation layer thereon and drying it to form a film with a thickness of about 5 to 100 μm.

Generally, in an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer provided on a conductive support, the material of the charge transport layer is an important factor determining the performance of the electrophotographic photoreceptor.
In particular, in order to obtain a highly sensitive electrophotographic photoreceptor, the charge transport material is required to have as low an ionization potential as possible in order to efficiently inject the charges generated in the charge generation layer into the charge transport layer. Ru. However, in general, organic compounds with low ionization potential are easily oxidized and unstable, and the above-mentioned 3,6-bis(dibenzylamino)-9-argylcarbazole is still satisfactory in these respects. It's not a thing. Furthermore, 3.
6-bis(dibenzylamino)=9-alkylcarbazole is not easy to produce (and is expensive).

Furthermore, in addition to the above, the charge transport material is also required to have high compatibility with organic solvents and binder resins, and to be easily formed into a film as described above.

The problem to be solved by the present inventors is that the charge transport material described above is stable and has a low ionization potential, has high compatibility with binder resins, and can be easily used. Moreover, as a result of intensive research on substances that can be produced at low levels, it was found that 3,6-bis(dialkylamino)-9-alkylcarbazole particularly satisfies the above-mentioned requirements and is excellent as a charge transport material in a laminated electrophotographic photoreceptor. This discovery led to the present invention.

An electrophotographic photoreceptor according to the present invention for increasing the distance between cells is an electrophotographic photoreceptor comprising a photosensitive layer having a layer of a charge transporting material and a layer of a charge generating material on a conductive support. It is characterized in that the charge transport substance is a carbazole derivative represented by the general formula (wherein R- and R2 represent an alkyl group having 1 to 4 carbon atoms).

In the electrophotographic photoreceptor according to the present invention, the charge transport substance is a carbazole derivative represented by the above general formula, and R1 and RZ are alkyl groups having 1 to 4 carbon atoms.

Examples of R1 and Rz include a methyl group, an ethyl group, a linear or branched propyl group, and a butyl group, with a methyl group or an ethyl group being particularly preferred. Therefore, preferred specific examples of charge transport materials according to the invention include, for example, 3.6-bis(dimethylamino)-9-methylcarbazole, 3.6-bis(dimethylamino)-9
-ethylcarbazole, 3.6-bis(diethylamino)-9-ethylcarbazole, 3.6-bis(diethylamino)-9-methylcarbazole, and the like.

Such carbazole derivatives are generally produced by converting 9-alkylcarbazole into 3,6-dinitro, reducing this to obtain a 3,6-diamino compound, and then converting the 9-alkylcarbazole into a 3,6-dinitrate using an appropriate alkylating agent such as dialkyl sulfuric acid. It can be produced by alkylating an amino group.

The electrophotographic photoreceptor according to the present invention is produced by applying a solution or dispersion containing a charge generating substance, an organic solvent, a binder resin, and, if necessary, a plasticizer, etc. onto a conductive support, and drying the solution or dispersion. Obtained by forming a generation layer, applying a solution containing the carbazole derivative, an organic solvent, a binder resin, and, if necessary, a plasticizer, etc. thereon, and drying to form a charge transport layer. Can be done. However, the charge generation layer and charge transport layer on the thermoelectric support may be laminated in the reverse order to the above.

3.6- above as a charge transport substance in the charge transport layer
The content of bis(dialkylamino)-9-alkylcarbazole is usually in the range of 10 to 60% by weight, and the thickness of the charge transport layer is usually in the range of 5 to 10% by weight.
0 μm is appropriate.

Next, as the charge generating substance, any conventionally known substance can be used. Examples include, but are not limited to, bisazo pigments, trisazo pigments, malachite green, phthalocyanine, and methyl squaryrane. The content of the binder resin in the charge generation layer is preferably as small as possible, but a range of 5 to 50% by weight is usually appropriate. Further, the thickness of the charge generation layer is usually 0.05 to 20 μm, preferably 0.
．． It is in the range of 1 to 10 μm. Note that the charge generation layer may be formed from a charge generation substance alone.

The binder resin used to form the charge transport layer and charge generation layer according to the present invention must be soluble in an organic solvent and soluble in an organic solvent so that a solution or dispersion of the charge transport substance can be stably and easily prepared. Preferably, a resin is used which has high compatibility with the above-mentioned charge generating substance and charge transporting substance, and which has a low degree of mechanical strength and a coating film having high mechanical strength, and excellent transparency and insulation properties. For example, polycarbonate, polystyrene, polyester, etc. are suitable. Further, the organic solvent is not particularly limited, but for example, 1,2-dichloroethane and tetrahydrofuran are preferably used.

The carbazole derivative according to the present invention not only has high compatibility with organic solvents and binder resins, but also has very stable radical cations, and has a desirable stability as a charge transport material. We are prepared. Furthermore, the oxidation potential is also extremely low, indicating that the ionization potential is low. Charge mobility is also high.

Therefore, an electrophotographic photoreceptor having such a charge transport layer is
It has extremely high sensitivity, low residual potential, and excellent rigidity resistance.

The Great Precipice Below, examples of the production of carbazole derivatives used in the present invention will be shown as reference examples, and the present invention will be explained with reference to Examples, but the present invention is not limited in any way by these Examples.

Reference example 1 9-ethylcarbazole was dissolved in glacial acetic acid, and 2
Two times the mole of concentrated nitric acid was gradually added dropwise, and the mixture was reacted at 60°C for 12 hours to obtain 3,6-sinitro-9-ethylcarbazole as yellowish brown microcrystals. It was recrystallized from chlorobenzene. Melting point 300℃ or higher.

Next, a part of this 3,6-sinitro-9-ethylcarbazole was dissolved in ethanol, and reduced with concentrated hydrochloric acid and tin under heating to obtain 3,6-diamino-9-ethylcarbazole. It was recrystallized from a benzene/hexane mixed solvent. Melting point: 187-188°C.

3.6-Diami2-9-ethylcarbazole was dispersed in an aqueous sodium bicarbonate solution, dimethyl sulfate was added dropwise thereto, the mixture was reacted at room temperature for 2 hours, and then heated to 60°C.
The reaction was continued for an additional 2 hours. After the reaction was completed, the insoluble matter was filtered from the reaction mixture and acidified with hydrochloric acid. Potassium iodide was added thereto to precipitate a quaternary salt of amine iodide, which was separated. This quaternary salt is sublimed under reduced pressure and elevated temperature to produce 3.6
-Bis(dimethylamino)-9-ethylcarbazole was obtained as yellow crystals. After purification using a basic alumina column using benzene as an eluent, repeated sublimation was performed.
Obtained purified product. The infrared absorption spectrum is shown in Figure 1.

Temperature 120-122℃
6,89 H8,248,14 N 14.93 14.69 Red line■
Yield spectrum (cra −') 1241.1323 (
C-N expansion/contraction); 784,1480.1610 (benzene ring in-plane bone filling).

Reference Example 2 The 3,6-diamitu-9-ethylcarbazole obtained in Reference Example 1 was dispersed in an aqueous sodium bicarbonate solution, diethyl sulfate was added dropwise to this at room temperature, the reaction was allowed to proceed at room temperature for 2 hours, and then the reflux temperature was increased. The mixture was allowed to react for 6 hours. After the reaction is completed, the reaction product is extracted from the reaction mixture with benzene, and this is purified using a basic alumina column using benzene as an eluent to obtain 3゜6-bis(diethylamino)-9-ethylcarbazole as a yellow viscous liquid. Obtained. The infrared absorption spectrum is shown in Figure 2.

■ 160~b Yuhuang Ritsu value Calculated value Measured value C78,297
8,58 H9,269,35 N 12.45 12.0
6C Spectrum 1375 (CH symmetric bending), 2980 (CN stretching); 795 (benzene ring out-of-plane bending), 1490 (benzene ring in-plane bone omitted).

All of the above carbazole derivatives according to the present invention dissolve very well in many organic solvents such as tetrahydrofuran, dichloroethane, benzene, and toluene, and also have high compatibility with resins such as polycarbonate, polystyrene, and polyester.

Further, the radical cation of these carbazole derivatives according to the present invention is very stable.

That is, the graph of cyclic voltammetry of 3,6-bis(dimethylamino)-9-ethylcarbazole is shown in FIG. 3, and that of 9-ethylcarbazole as a comparative example is shown in FIG. 3,6-bis(dimethylamino)-9-ethylcarbazole has high reversibility, and the radical cation generated when positive charges are injected from the charge generation layer is more stable than 9-ethylcarbazole. It shows.

Furthermore, the oxidation potential of 9-ethylcarbazole is 0°58V.
, whereas 3,6-bis(dimethylamino)-
The oxidation potential of 9-ethylcarbazole is -0.02V, which is extremely low. Therefore, it is shown that the ionization potential of the carbazole derivative according to the present invention is low, and the charge transport material according to the present invention has a very high efficiency of charge injection from the charge generation layer.

Furthermore, a charge transport layer was prepared by dissolving 3,6-bis(dimethylamino)-9-ethylcarbazole and 9-ethylcarbazole in polycarbonate in equal weight ratios, and the relationship between electric field strength and charge mobility was determined. The relationship is shown in FIG. It is shown that the carbazole according to the invention has high charge mobility.

Example 1 1 part by weight of polycarbonate and 1 part by weight of chlorodiane blue were added to 98 parts by weight of 1,2-dichloroethane, pulverized in a ball mill, and then coated on an aluminum-deposited polyester film using a doctor blade.
It was air-dried at room temperature to form a charge generation layer with a thickness of 1 μm.

Next, 5 parts by weight of 3,6-bis(dimethylamino)-9-ethylcarbazole and 5 parts by weight of polycarbonate were dissolved in 90 parts by weight of 1,2-dichloroethane, and the resulting solution was poured onto the charge generation layer. It was applied using a doctor blade, air-dried at room temperature, and then heated and dried at 70°C for 1 hour to form a charge transport layer with a thickness of 20 μm.
In this way, a photoreceptor was manufactured.

The electrostatic charging characteristics of this photoreceptor were evaluated as follows using an electrostatic copying paper tester (Model 5P482 manufactured by Kawaguchi Electric Seisakusho ■). That is, the surface of the photoreceptor was negatively charged by -6 KV corona discharge, and the potential at that time was measured and used as the initial potential. Leave it in the dark for 5 seconds and measure the potential.
The charge retention rate was determined. Next, the surface of the photoreceptor is irradiated with light at an illuminance of 5 lux using a tungsten lamp, the time required for the surface potential to reach 2/1 or 1/6 is measured, and this is calculated as the exposure amount El/! up to that point. and El/6 (lux/second) were determined as photosensitivity. Thereafter, the potential 20 seconds after the light irradiation was measured as the residual potential. These results are shown in Table 1.

Example 2 In exactly the same manner as in Example 1, a photoreceptor containing 3,6-bis(diethylamino)-9-ethylcarbazole in the charge transport layer was manufactured. The electrostatic charging characteristics of this photoreceptor are
Shown in the table.

Comparative Example 1 A photoreceptor containing 9-ethylcarbazole in the charge transport layer was produced in exactly the same manner as in Example 1.

Table 1 shows the electrostatic charging characteristics of this photoreceptor.

From the above results, it is clear that the photoreceptor according to the present invention has excellent charging properties, high photosensitivity, and low residual potential. Further, when an electrophotographic copying test was conducted using the electrophotographic photoreceptor according to the present invention, superior copied images could be obtained compared to the electrophotographic photoreceptor according to the comparative example.
Furthermore, since no change in image quality is observed even after several hundred copies, reprintability is also excellent.

[Brief explanation of drawings]

Figure 1 shows the infrared absorption spectrum of 3.6-bis(dimethylamino)-9-ethylcarbazole, and Figure 2 shows the 3.6-bis(dimethylamino)-9-ethylcarbazole absorption spectrum.
-Infrared absorption spectrum of -bis(diethylamino)-9-ethylcarbazole, Figure 3 shows the cyclic absorption spectrum of 3.6-bis(dimethylamino)-9-ethylcarbazole.
A graph obtained by voltammetry, FIG. 4 is a graph obtained by cyclic voltammetry of 9-ethylcarbazole as a comparative example, and FIG. 5 is a graph obtained by cyclic voltammetry of 9-ethylcarbazole as a comparative example. 3 is a graph showing the relationship between electric field strength and charge mobility of a charge transport layer included in the present invention. Patent Applicant Band-Kagaku Co., Ltd. Agent Patent Attorney Ittsu Makino Department Figure 3 Kyoube Figure 4 Figure 5 2176 300 11tx) 3 (<
GE (almi)

Claims (3)

[Claims] (1) In an electrophotographic photoreceptor comprising a layer of a charge transporting substance and a layer of a charge generating substance on a conductive support, the charge transporting substance has a general formula ▲a mathematical formula, a chemical formula, a table, etc.▼ (in the formula , R^1 and R^2 represent an alkyl group having 1 to 4 carbon atoms. (2) The electrophotographic photoreceptor according to claim 1, wherein the carbazole derivative is 3,6-bis(dimethylamino)-9-ethylcarbazole. (3) The electrophotographic photoreceptor according to claim 1, wherein the carbazole derivative is 3,6-bis(diethylamino)-9-ethylcarbazole.