JPH05297616A - Electrophotographic sensitive body - Google Patents

Abstract

(57) [Summary] [Object] To provide an electrophotographic photoreceptor having high sensitivity, excellent dispersibility of a charge generating substance in a photosensitive layer, and easy to manufacture. A disazo pigment represented by the following general formula (1) [Chemical formula 1] is used as a charge generating substance, and the pigment contains 0.1 to 0.5% by weight of a monoazo component produced as a by-product during synthesis.
More preferably, the residual amount of the cleaning and purifying solvent is 0.5% by weight or less, and the electrophotographic photoreceptor. [Chemical 1]

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to a high quality and highly sensitive electrophotographic photoreceptor.

[0002]

2. Description of the Related Art Conventionally, as a photosensitive material for an electrophotographic photoreceptor, an inorganic photoconductive substance such as selenium or a selenium alloy and an inorganic photoconductive substance such as zinc oxide or cadmium sulfide are dispersed in a resin binder. The organic photoconductive substance such as poly-N-vinylcarbazole or polyvinylanthracene, the organic photoconductive substance such as a phthalocyanine compound or an azo compound, or the organic photoconductive substance dispersed in a resin binder. What was made to have been used. Among these, in recent years, many electrophotographic photoreceptors using an organic material have been put into practical use due to advantages such as flexibility, thermal stability, film-forming property, and pollution-free. In particular, azo pigments have been widely used in the field of organic electrophotographic photoreceptors. Among them, disazo pigments having fluorenone as the central skeleton are known to exhibit excellent electrophotographic characteristics (Japanese Patent Laid-Open No. 54-22834). Further, it has been found that the asymmetric disazo pigments represented by the general formula (1) [Chemical formula 1] having two different coupler components have particularly excellent sensitivity. However, while such an asymmetric disazo pigment shows extremely high sensitivity,
The dispersibility of the coating liquid for the charge generation layer and the quality of electrostatic characteristics of the electrophotographic photoreceptor were unstable.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photosensitive member having stable quality and extremely high sensitivity.

[0004]

According to the present invention, in an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, a disazo pigment represented by the following general formula (1) [Chemical formula 1] as a charge generating substance. And the disazo pigment contains 0.1 to 0.5% by weight of a monoazo component produced as a by-product during synthesis.
An electrophotographic photosensitive member characterized by containing a residual amount of a solvent used for washing and purification in the disazo pigment represented by the general formula (1) [Chemical formula 1] is 0.5% by weight. There is provided the electrophotographic photoreceptor as described below.

[Chemical 1]

As a result of various studies to achieve the above-mentioned object, a monoazo which is contained in the disazo pigment represented by the general formula (1) [Chemical formula 1] and which is produced as an intermediate during the synthesis is obtained. The ingredients affect sensitivity and dispersibility,
Furthermore, it was found that the residual amount of the solvent used for controlling (washing) the amount thereof affects the dispersibility, and the present invention has been completed.

By controlling the amount of the monoazo component contained in the conventional symmetrical disazo pigment having fluorenone as the central skeleton to 0.5 to 5% by weight, excellent electrophotographic characteristics and coating liquid dispersibility can be obtained. It is known to be obtained (JP-A-3-230168). However, the disazo pigment having an asymmetric structure represented by the general formula (1) [Chemical formula 1] has extremely high sensitivity, and therefore, in order to stably maintain the high sensitivity characteristics, further increase in purity is required. It was found that the amount of monoazo component should be 0.5% by weight or less. However, as in the case of the symmetric disazo pigment, when the content is too small, the dispersibility of the coating solution becomes poor. Therefore, in the case of the asymmetric disazo pigment represented by the general formula (1) The lower limit of the component content is 0.1% by weight.

The disazo pigment represented by the general formula (1) [Chemical formula 1] of the present invention is synthesized by sequentially coupling the azo component and two coupler components.
In the coupling reaction step of the first step, a monoazo component having only one coupler bonded as an intermediate is produced, and in the coupling reaction step of the second step, a disazo component is produced. Alternatively, the monoazo component due to decomposition remains in various forms even after the completion of the reaction (the following general formula (2-1) [Chemical formula 2- (1)] and general formula (2-2) [Chemical formula 2- (2 )] Is an example of the monoazo component, but is not limited to this form).
Therefore, by controlling the amount of the remaining monoazo component, it is possible to provide a high-sensitivity electrophotographic photoreceptor having stable quality and excellent dispersibility.

[Chemical 2- (1)]

[Chemical 2- (2)]

In order to control the amount of monoazo component in these disazo pigments to 0.1 to 0.5% by weight, the crude disazo pigment is washed with a solvent that dissolves the monoazo component three times or more by heating (about 80 ° C.). Can be achieved by If the number of washings is three or more, the amount of monoazo component will be about 0.1 to 0.2% by weight even if it is repeated several times.
It did not go below. Examples of the solvent that dissolves the monoazo component include, but are not limited to, N, N-dimethylformamide, N-methylpyrrolidone, N-methylpyrrolidine, N-methylpiperidone, N-methylpiperidine, and N-methylmorpholine. It is not something that will be done.

Further, in order to improve the dispersibility, it is preferable to remove the solvent used for these washings from the disazo pigment until the amount becomes 0.5% by weight or less. This is after adjusting the amount of monoazo component. This can be achieved by washing the disazo pigment with water and alcohol and drying under reduced pressure. Further, the monoazo component can be completely removed by the recrystallization operation, but as described above, the monoazo component is required to be 0.1% by weight or more in order to maintain the dispersibility. Therefore, it is necessary to add an appropriate amount of the monoazo component. Required and not very effective. The content of the monoazo component in the disazo pigment is measured by dissolving the disazo pigment in monochlorobenzene and measuring the absorbance with a spectrophotometer to obtain the formula (2-
1) [Chemical 2- (1)] and general formula (2-2) [Chemical 2-
The monoazo component shown in (2)] was used as a standard substance and determined from a calibration curve. The residual solvent content in the disazo pigment was measured by using a gas chromatograph.

The basic constitution of the present invention is that a single-layer photosensitive layer 2 is provided on a conductive substrate 1 as shown in FIG. 1, or a charge generation layer 4 and a charge transfer layer 5 are formed on a conductive substrate. The laminated photosensitive layer 3 is formed. In addition, as in the conventional case, an intermediate layer and a protective layer may be appropriately provided if necessary.

The constituent materials used in the present invention are as follows. The conductive substrate is intended to supply a charge having a polarity opposite to that of the charged charge to the substrate side, has an electric resistance of 10 ⁸ Ωcm or less, and includes an intermediate layer, a charge generation layer, and a charge transfer layer. Use one that can withstand the membrane conditions. Examples of these are electrically conductive metals and alloys such as Al, Ni, Cr, Zn and stainless steel, inorganic insulating materials such as glass and ceramics, and organic insulating materials such as polyester, polyimide, phenol resin, nylon resin and paper. Conductive treatment is performed by coating the surface of the physical material with an electrically conductive material such as Al, Ni, Cr, Zn, stainless steel, carbon, SnO ₂ , In ₂ O ₃ by a method such as vacuum deposition, sputtering and spray coating. There are things such as things.

As shown in FIG. 1, the photosensitive layer 2 of the single-layer photoconductor has a single layer having both functions of charge generation and charge transfer, and is a layer for forming a latent charge image by imagewise exposure. Is. In the present invention, the photosensitive layer 2 of this type has a monoazo component content of 0.5 to 0.1% by weight, more preferably a residual amount of the solvent used for cleaning and purification of 0.5.
The disazo pigment represented by the general formula (1) [Chemical formula 1] and the binder resin, which are limited to 5% by weight or less, are formed on the conductive substrate 1 together with a charge transfer substance described later, if necessary. The same binder resin as that used in the laminated photosensitive layer 3 described later is used, and the thickness of the photosensitive layer 2 is 5
-30 μm is suitable. Also, as shown in FIG.
The charge generation layer 4 in the laminated photosensitive layer 3 of the laminated photoreceptor is
It is a layer for the purpose of generating and separating charges by imagewise exposure, and in the present invention, as described above, the monoazo component content is 0.5 to 0.1% by weight, and more preferably the solvent used for washing and purification. The disazo pigment represented by the general formula (1) [Chemical formula 1] is used in which the residual amount of the above is limited to 0.5% by weight or less. Examples of these disazo pigments are given in Table 1 below.
The results are shown in Table 7.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

[Table 5]

[0018]

[Table 6]

[0019]

[Table 7]

These disazo pigments are used by adding an organic solvent in a resin or without a resin and dispersing them by a method such as a ball mill, a sand mill triple roll, an attritor or an ultrasonic method. As the resin to be dispersed, for example, polyamide,
Condensation resins such as polyurethane, polyester epoxy resin, polycarbonate, and polyether, as well as polystyrene, polyacrylate, polymethacrylate, poly-N-vinylcarbazole, polyvinyl butyral,
Styrene-butadiene copolymer, styrene-polymers and copolymers such as acrylonitrile copolymer, and the like,
Insulation and adhesion are required.

When a charge generating layer is formed using these disazo pigments, the product obtained by the dispersing means is applied onto a conductive substrate by a roll coating method, a dip coating method, a spray coating method, a blade coating method or the like. To form a film and dry it to a film thickness of 0.
It may be formed in a thickness of 05 μm to 5 μm. The content of the disazo pigment is preferably 60% by weight to 100% by weight. The charge transfer layer 5 holds charged charges on its surface, and moves carriers generated and separated in the charge generation layer by exposure,
It is a layer whose purpose is to combine with the retained electrostatic charge. A high electric resistance is required to retain the charged electric charge, and a low dielectric constant and good charge mobility are required to obtain a high surface potential with the retained charged electric charge. In order to satisfy these requirements, an organic charge transfer layer containing an organic charge transfer substance as an active ingredient is used.

Examples of the charge transfer material include poly-N.
-Vinylcarbazole, pyrazoline compounds, α-phenylstilbene compounds, hydrazone compounds, diarylmethane compounds, triphenylamine compounds, divinylbenzene compounds, fluorene compounds, anthracene compounds, oxadiazole compounds, benzidine Compounds, diaminocarbazole compounds, and the like. These organic charge transfer substances other than poly-N-vinylcarbazole may be blended with the resin or may be used alone, similar to those shown as the binder in the charge generation layer. Further, a plasticizer is added to these as required. Examples of such a plasticizer include halogenated paraffin, dimethyl naphthalene, dibutyl phthalate, dioctyl phthalate, tricresyl phthalate, dioctyl phthalate, tricresyl phosphate and the like, and polymers and copolymers of polyester and the like. The charge transfer material, the binder resin, and optionally silicon oil (a leveling agent at the time of film formation) are dissolved in an organic solvent, and the film is formed and dried by the same method as in the case of the charge generation layer to form a film. A charge transfer layer having a thickness of 5 to 100 μm is formed. The ratio of the charge transfer material to the binder resin is 2/8 to 8/2 weight ratio, and the addition amount of silicone oil is 0.001 to 1 weight% with respect to the binder resin.

[0023]

【Example】

Example 1 Among the disazo pigments represented by the general formula (1) [Chemical formula 1], one having a structure of the following chemical formula 3 was synthesized (JP-A-3-
230168).

[Chemical 3] The operation of dispersing 8.0 g of the obtained crude crystals in 800 ml of N, N-dimethylformamide (DMF) and washing with stirring at 80 ° C. for 2 hours was repeated 3 times. Then, the crystals are washed twice with 1000 ml of ion-exchanged water, and the pressure is reduced to 120 ° C.
Dried in. The purified crystals were dissolved in monochlorobenzene, the absorbance at 552 nm was measured with a spectrophotometer, and the amount of monoazo component was determined from the calibration curve. In addition, the amount of residual DMF was determined by gas chromatography.

[Coating Liquid for Charge Generation Layer] 1/2 volume of φ5 mm YTZ (partially stabilized zirconia) balls and 1.0 g of the disazo pigment of the above chemical formula 3 in a 6 cm glass pot, polyvinyl butyral (XYH manufactured by Union Carbide Co., Ltd.)
L) 0.1 g and cyclohexanone 22.9 g were added to obtain 4
Ball mill dispersed for days. After the dispersion was completed, 24 g of cyclohexanone was added and stirred, and then 30 g of the mill base was taken out and diluted with methyl ethyl ketone / cyclohexanone (27.6 / 34.8 g) while stirring to obtain a coating liquid for the charge generation layer. The average particle size of the dispersed particles in this coating liquid was measured by CAPA-500 manufactured by Horiba Ltd. [Coating liquid for charge transfer layer]

[Chemical 4] 9 parts by weight Polycarbonate resin (Teijin Kasei Panlite C1400) 10 parts by weight Silicone oil (Shin-Etsu Silicon KF-50) 0.002 parts by weight Dichloromethane 76 parts by weight The above charge generation layer coating solution is applied by dipping on an Al plate as a base. Then, it was heated and dried at 110 ° C. for 10 minutes to form a 0.1 μm charge generation layer. The film quality of this charge generation layer was visually evaluated in three levels. Furthermore, the charge transfer layer coating solution is applied by dip coating, and dried by heating at 130 ° C. for 15 minutes to 25 μm.
A charge transfer layer of m was formed to prepare a photoconductor for electrophotography.

Example 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the crude crystals were washed with DMF four times.

Example 3 In Example 2, the drying conditions after the washing of the crude crystals were
An electrophotographic photoreceptor was prepared in the same manner except that the temperature was reduced to 75 ° C.

Example 4 In Example 2, the crude crystals were washed 4 times with DMF and 2 times with ion-exchanged water, and then 800 ml of methanol was added.
A photoreceptor for electrophotography was prepared in the same manner except that it was washed 3 times with and dried at 75 ° C. under reduced pressure.

Comparative Example 1 In Example 1, the crude crystals were not washed with DMF.
An electrophotographic photoreceptor was prepared in the same manner except that it was washed twice with ion-exchanged water and then dried at 120 ° C. under reduced pressure.

Comparative Example 2 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the crude crystals were washed only once with DMF.

Comparative Example 3 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the crude crystal was recrystallized from o-dichlorobenzene to obtain a purified crystal.

Example 5 Among the disazo pigments represented by the general formula (1) [Chemical formula 1], those having a structure of the following [Chemical formula 5] were synthesized (see JP-A-3-230168).

[Chemical 5] Crude crystals were purified in the same manner as in Example 1 using the disazo pigment of the above [Chemical Formula 5], and this was used as a charge generating substance to prepare a photoconductor for electrophotography.

Example 6 An electrophotographic photoreceptor was prepared in the same manner as in Example 5, except that the coarse crystals were washed with DMF four times.

Example 7 In Example 6, the drying conditions after the completion of washing the crude crystals were
An electrophotographic photoreceptor was prepared in the same manner except that the temperature was reduced to 75 ° C.

Example 8 The same as Example 6 except that the crude crystals were washed 4 times with DMF, 2 times with ion-exchanged water, then 3 times with 800 ml of methanol, and dried at 75 ° C. under reduced pressure. Then, a photoconductor for electrophotography was prepared.

Comparative Example 4 In Example 5, the crude crystals were not washed with DMF.
An electrophotographic photoreceptor was prepared in the same manner except that it was washed twice with ion-exchanged water and then dried under reduced pressure at 120.

Comparative Example 5 An electrophotographic photoreceptor was prepared in the same manner as in Example 5, except that the DMF washing of the crude crystals was performed only once.

Comparative Example 6 An electrophotographic photoreceptor was prepared in the same manner as in Example 5, except that the crude crystal was recrystallized from o-dichlorobenzene and the obtained purified crystal was used as a charge generating substance. Created.

Example 9 Among the disazo pigments represented by the general formula (1) [Chemical formula 1], those having the following [Chemical formula 6] structure were synthesized (Japanese Unexamined Patent Publication No. Hei 3 (1999)).
-230168).

[Chemical 6] Using the above disazo pigment, in the same manner as in Example 1,
The crude crystal was purified and used as a charge generating substance to prepare a photoconductor for electrophotography.

Example 10 An electrophotographic photoreceptor was prepared in the same manner as in Example 9, except that the DMF washing of the crude crystals was carried out 4 times.

Example 11 An electrophotographic photoreceptor was prepared in the same manner as in Example 10, except that the drying condition after the washing of the crude crystals was set to 75 ° C. under reduced pressure.

Example 12 In Example 10, the crude crystals were washed 4 times with DMF and 2 times with ion-exchanged water, and then 800 ml of methanol was added.
A photoreceptor for electrophotography was prepared in the same manner except that it was washed 3 times with and dried at 75 ° C. under reduced pressure.

Comparative Example 7 In Example 9, the crude crystals were not washed with DMF,
An electrophotographic photoreceptor was prepared in the same manner except that it was washed twice with ion-exchanged water and then dried at 120 ° C. under reduced pressure.

Comparative Example 8 An electrophotographic photoreceptor was prepared in the same manner as in Example 9 except that the crude crystals were washed only once with DMF.

Comparative Example 9 An electrophotographic photoreceptor was prepared in the same manner as in Example 9, except that the crude crystal was recrystallized from o-dichlorobenzene and the obtained purified crystal was used as a charge generating substance. Created.

Example 13 Among the disazo pigments represented by the general formula (1) [Chemical formula 1], those having the following [Chemical formula 7] structure were synthesized (Japanese Patent Application Laid-Open No. HEI 3).
-230168).

[Chemical 7] Crude crystals were purified in the same manner as in Example 1 using the disazo pigment of the above [Chemical formula 7], and this was used as a charge generating substance to prepare an electrophotographic photoreceptor.

Example 14 An electrophotographic photoreceptor was prepared in the same manner as in Example 13, except that the crude crystals were washed with DMF four times.

Example 15 An electrophotographic photoreceptor was prepared in the same manner as in Example 14, except that the drying condition after the washing of the crude crystals was set to 75 ° C. under reduced pressure.

Example 16 In Example 14, the crude crystals were washed 4 times with DMF and 2 times with ion-exchanged water, and then 800 ml of methanol was added.
A photoreceptor for electrophotography was prepared in the same manner except that it was washed 3 times with and dried at 75 ° C. under reduced pressure.

Comparative Example 10 In Example 13, the crude crystals were not washed with DMF but washed with ion-exchanged water twice, and then at 120 ° C. under reduced pressure.
An electrophotographic photoreceptor was prepared in the same manner except that it was dried in.

Comparative Example 11 An electrophotographic photoreceptor was prepared in the same manner as in Example 13, except that the DMF washing of the crude crystals was performed only once.

Comparative Example 12 An electrophotographic photoreceptor was prepared in the same manner as in Example 13, except that the crude crystal was recrystallized from o-dichlorobenzene and the obtained purified crystal was used as a charge generating substance. did.

The electrophotographic photosensitive member produced as described above is applied to an electrostatic copying apparatus (Kawaguchi Electric Co., Ltd. EPA SP
428 type), corona charging of −6 kV was performed for 20 seconds, and when left in the dark where the surface potential became −800 V, 4.51 ux of tungsten light was irradiated, and the surface potential was −80 V. required to become an exposure amount E _1/10
(Lux sec) was measured. The results are shown in Tables 8 and 9.

[0053]

[Table 8]

[0054]

[Table 9]

[0055]

As is apparent from Tables 8 and 9, according to the present invention, in the electrophotographic photosensitive member having a photosensitive layer on a conductive substrate, the above-mentioned general formula (1) is used as a charge generating substance.
Using the disazo pigment represented by [Chemical Formula 1], the content of the monoazo component contained as an impurity in the disazo pigment is limited to 0.1 to 0.5% by weight, and more preferably, the disazo pigment is washed and purified. To provide an electrophotographic photoreceptor having extremely high sensitivity, excellent dispersibility in a photosensitive layer, and easily produced by limiting the residual amount of the solvent used in the above to 0.5% by weight or less. You can

[Brief description of drawings]

FIG. 1 is a schematic diagram of a single-layer photoconductor.

FIG. 2 is a schematic diagram of a laminated photoconductor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conductive substrate 2 ... Single layer type photosensitive layer 3 ... Laminated type photosensitive layer 4 ... Charge generating layer 5 ... Charge transfer layer

Front Page Continuation (72) Inventor Hiroshi Adachi 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd.

Claims (2)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, wherein a disazo pigment represented by the following general formula (1) [Chemical formula 1] is used as a charge generating substance, and the disazo pigment is An electrophotographic photosensitive member comprising a monoazo component produced as a by-product during synthesis in an amount of 0.1 to 0.5% by weight. [Chemical 1] 2. The residual amount of the solvent used for washing and purification in the disazo pigment represented by the general formula (1) [Chemical formula 1] is 0.1.
The electrophotographic photoreceptor according to claim 1, wherein the content is 5% by weight or less.