JP3141302B2 - Electrophotographic photoreceptor - Google Patents

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 a high-quality and high-sensitivity electrophotographic photosensitive member.

[0002]

2. Description of the Related Art Conventionally, as a photosensitive material for an electrophotographic photosensitive member, 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. Organic photoconductive substance such as poly-N-vinylcarbazole or polyvinylanthracene, an organic photoconductive substance such as a phthalocyanine compound or an azo compound, or these organic photoconductive substances are dispersed in a resin binder. What has been used has 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 formability, and no pollution. In particular, azo pigments have been widely used in the field of organic electrophotographic photoreceptors. Among them, disazo pigments having fluorenone as a central skeleton are known to exhibit good electrophotographic properties (JP-A-54-22834). Further, it has been found that an asymmetric disazo pigment having two different coupler components as shown in the general formula (1) [formula 1] has particularly excellent sensitivity. However, such an asymmetric disazo pigment shows extremely high sensitivity,
The dispersibility of the coating solution for the charge generation layer and the quality of the electrostatic characteristics of the electrophotographic photoreceptor were unstable.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly sensitive electrophotographic photosensitive member having stable quality.

[0004]

According to the present invention, the following is provided.
An invention is provided. (1) In an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, a charge generating substance represented by the following structural formula (1)-
The disazo pigment represented by (4) is used, and the disazo pigment has a monoazo component by-produced at the time of synthesis of 0.1.
An electrophotographic photoreceptor containing 1 to 0.5% by weight.

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Embedded image (2) Disazo represented by the structural formulas (1) to (4)
0.5% by weight of residual solvent used for washing and purification in pigment
The electrophotographic photoreceptor described above, wherein:

As a result of conducting various studies to achieve the above object, the novel compounds represented by the structural formulas (1) to (1)
Contained in the disazo pigment of the formula (4), it
The monoazo component produced as an intermediate during the synthesis of these compounds affects the sensitivity and dispersibility, and the residual amount of the solvent used to control the amount (washing) affects the dispersibility. This led to the completion of the present invention.

By limiting the amount of the monoazo component contained in the conventional symmetric disazo pigment having fluorenone as the central skeleton to 0.5 to 5% by weight, excellent electrophotographic properties and dispersibility of the coating liquid can be obtained. It is known that it can be obtained (JP-A-3-230168). However, the structural formula
In the disazo pigment of the non-symmetrical structure represented by (1) to (4), since it is extremely sensitive, in order to maintain its high sensitivity stably, it is necessary to further increase the purity, monoazo It has been found that the amount of the component should be less than 0.5% by weight. However, as in the case of the symmetrical disazo pigment, if the content is too small, the dispersibility of the coating liquid deteriorates. Therefore, in the case of the asymmetric disazo pigments represented by the structural formulas (1) to (4) , The lower limit of the component content is 0.1% by weight.

The disazo pigments represented by the structural formulas (1) to (4) of the present invention are synthesized by sequentially performing a coupling reaction between an azo component and two coupler components.
In the first-stage coupling reaction step, a monoazo component having only one coupled coupler is produced as an intermediate, and in the second-stage coupling reaction step, a disazo component is produced. Alternatively, a monoazo component due to decomposition remains in various forms even after completion of the reaction. Therefore, by controlling the amount of the remaining monoazo component, it is possible to provide an electrophotographic photosensitive member having stable quality, high sensitivity, and excellent dispersibility.

In order to control the amount of the monoazo component in these disazo pigments to 0.1 to 0.5% by weight, the crude disazo pigment is washed by heating (about 80 ° C.) at least three times with a solvent in which the monoazo component is dissolved. Can be achieved by doing If the number of times of washing is 3 or more, even if it is repeated several times, the amount of the monoazo component is about 0.1 to 0.2% by weight, and
Did not go below. Examples of solvents for dissolving the monoazo component include, but are not limited to, N, N-dimethylformamide, N-methylpyrrolidone, N-methylpyrrolidine, N-methylpiperidone, N-methylpiperidine, N-methylmorpholine and the like. It is not something to be done.

Further, in order to improve dispersibility, it is preferable that the solvent used for washing is also removed from the disazo pigment until the amount becomes 0.5% by weight or less. This can be achieved by washing the disazo pigment with water and alcohol and drying under reduced pressure. In addition, the monoazo component can be completely removed by the recrystallization operation. However, as described above, the monoazo component needs to be 0.1% by weight or more to maintain the dispersibility. Necessary and not very effective. The measurement of the monoazo ingredient content of the disazo pigment can be prepared by dissolving the disazo pigment of monochlorobenzene, and the absorbance is measured in a spectrophotometer, the structural formula (1)
-The monoazo component shown in (4) contained in the disazo pigment was determined from a calibration curve as a standard substance. The measurement of the residual solvent content in the disazo pigment was performed using a gas chromatograph.

The basic structure of the present invention is that a single 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. In which a laminated photosensitive layer 3 is provided. Note that, similarly to the conventional case, an intermediate layer and a protective layer may be provided as needed.

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. The conductive substrate has an electric resistance of 10 ⁸ Ωcm or less, and is formed of an intermediate layer, a charge generation layer, and a charge transfer layer. Use one that can withstand the film conditions. Examples of these include electrically conductive metals and alloys such as Al, Ni, Cr, Zn, and stainless steel; inorganic insulating substances such as glass and ceramics; and organic insulating materials such as polyester, polyimide, phenolic resin, nylon resin, and paper. The surface of the material is coated with an electrically conductive material such as Al, Ni, Cr, Zn, stainless steel, carbon, SnO ₂ , and In ₂ O ₃ by a method such as vacuum deposition, sputtering, or spray coating to conduct a conductive treatment. And others.

As shown in FIG. 1, the photosensitive layer 2 of the single-layer photoreceptor has both functions of charge generation and charge transfer in one layer, and forms a charge latent image by image exposure. It is. As described above, the photosensitive layer 2 of this type has a monoazo component content of 0.5 to 0.1% by weight as described above, and more preferably a residual amount of the solvent used for washing and purification of 0.1 to 0.1% by weight.
The disazo pigments represented by the structural formulas (1) to (4) 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 material described later, if necessary. As the binder resin, the same resin as that used in the laminated photosensitive layer 3 described later is used.
３０30 μm is appropriate. Also, as shown in FIG.
The charge generation layer 4 in the laminated photosensitive layer 3 of the laminated photoreceptor is
This layer is intended to generate and separate electric charges by image exposure. In the present invention, as described above, the content of the monoazo component is 0.5 to 0.1% by weight, and more preferably, the solvent used for washing and purification. The disazo pigments represented by the above structural formulas (1) to (4), in which the residual amount of is limited to 0.5% by weight or less, are used.

These disazo pigments are used by dispersing them by a method such as a ball mill, a three-roll mill, an attritor, an ultrasonic method or the like, with or without an organic solvent added to the resin. As the resin to be dispersed, for example, polyamide,
Polyurethane, polyester epoxy resin, polycarbonate, condensation resins such as polyether, and polystyrene, polyacrylate, polymethacrylate, poly-N-vinyl carbazole, polyvinyl butyral,
Styrene-butadiene copolymers, polymers and copolymers such as styrene-acrylonitrile copolymer,
Insulation and adhesiveness are required.

In the case of forming a charge generation layer using these disazo pigments, the one obtained by the dispersing means is coated on a conductive substrate by a roll coating method, a dip coating method, a spray coating method, a blade coating method or the like. And dried.
What is necessary is just to form it in 05 micrometers-5 micrometers. The content of the disazo pigment is preferably from 60% by weight to 100% by weight. The charge transfer layer 5 retains the charged charges on its surface and moves carriers generated and separated in the charge generation layer by exposure,
This layer is intended to be combined with the retained charged charges. High electric resistance is required to retain the charged electric charge, and further, a low dielectric constant and good charge mobility are required to obtain a high surface potential with the retained charged electric charge. To satisfy these requirements, an organic charge transfer layer containing an organic charge transfer material as an active ingredient is used.

As the charge transfer material, for example, 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 materials other than poly-N-vinylcarbazole may be used by blending with a resin, or may be used alone as in the case of the binder shown in the charge generation layer. In addition, a plasticizer is added to these as needed. Examples of such a plasticizer include halogenated paraffin, dimethylnaphthalene, dibutyl phthalate, dioctyl phthalate, tricresyl phthalate, dioctyl phthalate, tricresyl phosphate, and the like, and polymers and copolymers such as polyester. The charge transfer material, the binder resin, and, if necessary, a silicone oil (a leveling agent during film formation) is dissolved in an organic solvent, and the film is formed and dried in the same manner as in the case of the charge generation layer. A charge transfer layer having a thickness of 5 to 100 μm is formed. The ratio between the charge transfer material and the binder resin is 2/8 to 8/2 by weight, and the amount of silicone oil added is 0.001 to 1% by weight based on the binder resin.

[0016]

Example 1 A disazo pigment represented by the following structural formula (1) was synthesized (see JP-A-3-230168).

Embedded image The operation of dispersing 8.0 g of the obtained crude crystals in 800 ml of N, N-dimethylformamide (DMF) and stirring and washing at 80 ° C. for 2 hours was repeated three times. Thereafter, the crystals were washed twice with 1000 ml of ion-exchanged water, and then dried under reduced pressure at 120 ° C.
And dried. The purified crystal was dissolved in monochlorobenzene, and the absorbance at 552 nm was measured with a spectrophotometer, and the amount of the monoazo component was determined from the calibration curve. Further, the amount of residual DMF was determined by gas chromatography.

[Coating solution for charge generating layer] [0017] 1/2 amount of φ5mm YTZ in φ6cm glass pot
(Partially stabilized zirconia) A ball and 1.0 g of the disazo pigment of Chemical Formula 3, 0.1 g of polyvinyl butyral (XYHL manufactured by Union Carbide), cyclohexanone 2
2.9 g of the mixture was put into a ball mill and dispersed for 4 days. After the dispersion was completed, 24 g of cyclohexanone was added and stirred, then 30 g of the mill base was taken out and diluted dropwise with stirring with methyl ethyl ketone / cyclohexanone (27.6 / 34.8 g) to obtain a coating liquid for a charge generation layer. The average particle size of the dispersed particles in the coating solution was measured with a Horiba, Ltd. CAPA-500. (Coating liquid for charge transfer layer)

Embedded image 9 parts by weight Polycarbonate resin (Teijin Kasei Panlite C1400) 10 parts by weight Silicon oil (Shin-Etsu Silicon KF-50) 0.002 parts by weight Dichloromethane 76 parts by weight Dip coating of the above-mentioned coating solution for the charge generation layer on an Al plate as a substrate Then, it was dried by heating at 110 ° C. for 10 minutes to form a 0.1 μm charge generation layer. The film quality of the charge generation layer was visually evaluated in three stages. Further, the charge transfer layer coating solution was applied by dip coating, and heated and dried at 130 ° C. for 15 minutes to form a 25 μm
m, and a photoreceptor for electrophotography was formed.

Example 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the DMF washing of the crude crystal was performed four times.

Example 3 In Example 2, the drying conditions after the completion of the washing of the crude crystals were as follows:
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 four times with DMF, twice with ion-exchanged water, and then 800 ml of methanol.
, And dried in a reduced pressure at 75 ° C. to prepare an electrophotographic photoreceptor.

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 photoreceptor was prepared in the same manner as in Example 1, except that the DMF washing of the crude crystal was performed only once.

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

[0024] was synthesized disazo Pigments represented by Example 5 the following structural formula (2) (see JP-A-3-230168).

Embedded image Using this disazo pigment, a crude crystal was purified in the same manner as in Example 1, and this was used as a charge generating substance to prepare an electrophotographic photoreceptor.

Example 6 An electrophotographic photoreceptor was prepared in the same manner as in Example 5, except that the DMF washing of the crude crystal was performed four times.

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

Example 8 The procedure of Example 6 was repeated except that the crude crystals were washed four times with DMF, twice with ion-exchanged water, three times with 800 ml of methanol, and dried at 75 ° C. under reduced pressure. Thus, a photoconductor for electrophotography was prepared.

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

Comparative Example 5 An electrophotographic photosensitive member 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 using o-dichlorobenzene and the obtained purified crystal was used as a charge generating substance. Created.

[0031] was synthesized disazo Pigments represented by Example 9 the following structural formula (3) (see JP-A-3-230168).

Embedded image Using disazo pigments of this, in the same manner as in Example 1, crude crystals were purified, using this as a charge generating material was prepared an electrophotographic photoreceptor.

Example 10 An electrophotographic photoreceptor was prepared in the same manner as in Example 9, except that the DMF was washed four times for the crude crystals.

Example 11 An electrophotographic photosensitive member was prepared in the same manner as in Example 10 except that the drying conditions after the completion of the washing of the crude crystals were changed to 75 ° C. under reduced pressure.

Example 12 In Example 10, the crude crystals were washed four times with DMF and twice with ion-exchanged water, and then washed with 800 ml of methanol.
, And dried in a reduced pressure at 75 ° C. to prepare an electrophotographic photoreceptor.

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 DMF washing of the crude crystal was performed only once.

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

[0038] was synthesized disazo Pigments represented by Example 13 the following structural formula (4) (see JP-A-3-230168).

Embedded image Using disazo pigments of this, in the same manner as in Example 1, crude crystals were purified, using this as a charge generating material was prepared an electrophotographic photoreceptor.

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

Example 15 An electrophotographic photosensitive member was prepared in the same manner as in Example 14, except that the drying conditions after the completion of the washing of the crude crystals were changed to 75 ° C. under reduced pressure.

Example 16 In Example 14, the crude crystals were washed four times with DMF and twice with ion-exchanged water.
, And dried in a reduced pressure at 75 ° C. to prepare an electrophotographic photoreceptor.

Comparative Example 10 In Example 13, the crude crystals were washed twice with ion-exchanged water without washing with DMF, and then under reduced pressure at 120 ° C.
A photoreceptor for electrophotography was prepared in the same manner except that the photoreceptor was dried.

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

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

The electrophotographic photoreceptor prepared as described above is used in an electrostatic copying machine (EPA SP manufactured by Kawaguchi Electric Co., Ltd.)
(428 type), a corona charging of −6 kV was performed for 20 seconds, and when the surface potential became −800 V in a dark place, a 4.51 ux tungsten light was applied to irradiate with a surface potential of −80 V. Exposure E ₁ /
₁₀ (lux sec) was measured. The results are shown in Tables 8 and 9.

[0046]

[Table 8]

[0047]

[Table 9]

[0048]

As is clear from Tables 8 and 9, according to the present invention, in the electrophotographic photoreceptor having the photosensitive layer on the conductive substrate, the structural formula (1)-
Using the disazo pigment represented by (4) , the content of the monoazo component contained in the disazo pigment as an impurity is determined by:
The amount is limited to 0.1 to 0.5% by weight, and more preferably, the residual amount of the solvent used for washing and purifying the disazo pigment is also:
By limiting the amount to 0.5% by weight or less, it is possible to provide an electrophotographic photosensitive member having extremely high sensitivity, excellent dispersibility in the photosensitive layer, and which can be easily manufactured.

[Brief description of the drawings]

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

FIG. 2 is a schematic view of a laminated photoreceptor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conductive base material 2 ... Single layer type photosensitive layer 3 ... Laminated type photosensitive layer 4 ... Charge generation layer 5 ... Charge transfer layer

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroshi Adachi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-54-22834 (JP, A) JP-A-Hei 4-9859 (JP, A) JP-A-57-94046 (JP, A) JP-A-57-94048 (JP, A) JP-A-2-27362 (JP, A) JP-A-63-29461 (JP, A) A) JP-A-3-39751 (JP, A) JP-A-63-195657 (JP, A) JP-A-1-261651 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) G03G 5/00-5/16

Claims (2)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, wherein the charge generating substance has the following structural formula
(1) An electrophotographic device characterized by using a disazo pigment represented by (4) , wherein the disazo pigment contains 0.1 to 0.5% by weight of a monoazo component by-produced during synthesis. Photoconductor. Embedded image Embedded image Embedded image Embedded image 2. The residual amount of the solvent used for washing and purification in the disazo pigments represented by the structural formulas (1) to (4) is 0.1%.
2. The electrophotographic photoconductor according to claim 1, wherein the content is 5% by weight or less.