JPH05188610A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body having good wear resistance and high durability while maintaining characteristics such as sensitivity even for repeated use by incorporating a disazo pigment expressed by specified formula into a charge generating layer and specifying the range of the ratio of charge transfer material to a binder resin in the charge transfer layer. CONSTITUTION:This photosensitive body consists of a conductive base body 1 and a layered photosensitive layer 4 comprising a charge generating layer 2 and a charge transfer layer 3 formed on the base body. The charge generating layer 2 contains disazo pigments expressed by formula. The ratio of the charge transfer material to the binder resin (D/R) in the charge transfer layer 3 is specified to 5/1-8/10. In formula, A is a residue the carbon atom of which couples with nitrogen atom of the azo group and Cr1 and Cr2 are coupler residues of different structures. These disazo pigments are dispersed in a resin or in an org. solvent without a resin in a ball mill or the like, applied on the conductive base body 1 by roll coating, dip coating, spray coating, blade coating, etc., and dried to form the film having specified thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated type electrophotographic photoreceptor comprising a charge generation layer and a charge transfer layer.

[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 these organic photoconductive substances dispersed in a resin binder. Things have been used.

Among these, in recent years, a large number of electrophotographic photoreceptors using organic materials have been put into practical use because of their advantages such as flexibility, thermal stability, film-forming property, and pollution-free. The mainstream of these is a multi-layer type photoreceptor in which a charge generation layer that contributes to charge generation and a charge transfer layer that contributes to holding surface charges in a dark place and transferring charges at the time of light reception are functionally separated.

Particularly in recent years, there has been a growing demand for maintaining high sensitivity and further improving mechanical strength characteristics such as abrasion resistance.
Therefore, as a photoconductor for electrophotography, it has not only electrophotographic characteristics such as good chargeability and sensitivity, and small dark decay, but also mechanical properties such as printing durability and abrasion resistance after repeated use. Strength characteristics are also required.

Various attempts have been made to meet such demands. For example, in order to improve the wear resistance of the charge transfer layer, a protective layer made of a specific resin is provided on the charge transfer layer (JP-A-62-272228 / JP-A-2-
161449), the charge transfer layer is multi-layered, and the content of the charge transfer material in the deepest charge transfer layer is made higher than that of the charge transfer layer on the surface side (JP-A-60-12551, JP-A-60-87331. JP-A-60-143346 and JP-A-2-160247) and thicker charge transfer layers (JP-A-1-267551).

However, in a conventional photoreceptor in which a charge generation layer and a charge transfer layer are sequentially laminated on a support, the charge transfer layer is formed by binding a low molecular weight charge transfer material with a polymer resin binder. Therefore, it is not always sufficient to make the electrophotographic characteristics and the mechanical strength characteristics compatible with each other. When the composition or resin binder has a high sensitivity, the surface of the photoconductor is scratched or abraded due to the friction of the cleaning brush or the cleaning blade when the photoconductor is repeatedly used. On the other hand, with a composition having a high abrasion resistance or a binder type, electrophotographic characteristics such as low sensitivity or increase in residual potential cannot be satisfied.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic photosensitive member which maintains electrophotographic characteristics such as sensitivity even after repeated use and has good abrasion resistance and high durability. Is.

[0008]

According to the present invention, in a laminated electrophotographic photoreceptor having at least a charge generation layer and a charge transfer layer on a conductive substrate, the general formula (1) is contained in the charge generation layer. ) And the ratio of the charge transfer material to the binder resin in the charge transfer layer is 5/10 to 8/10, and also in the charge generation layer in the same general formula. By containing the disazo pigment represented by (1) and setting the thickness of the charge transfer layer to 25 μm or more, high sensitivity can be maintained even after repeated use,
Further, it is possible to provide an electrophotographic photoreceptor having good wear resistance and high durability.

As shown in FIG. 2, conventionally, when the ratio (D / R) of the charge transfer material to the binder resin in the charge transfer layer is reduced, the abrasion resistance is improved, while on the other hand, as shown in FIG. As shown, decreasing D / R decreased sensitivity.
However, it has been found that by using the disazo pigment represented by the general formula (1) as the charge generating substance, the sensitivity does not decrease until D / R = 5/10 even when D / R is decreased.

If the thickness of the charge transfer layer is increased,
As shown in Fig. 4, the sensitivity increased, and the wear resistance did not change, but the change rate of the sensitivity was small, so the durability also improved, but as shown in Fig. 5, the residual potential after repeated use increased. I tended to. However, it was found that even when the film thickness of the charge transfer layer is increased by using the disazo pigment represented by the general formula (1) as the charge generating substance, the residual potential after repeated use does not increase. It was

Since the disazo pigment represented by the general formula (1), which is a charge-generating substance, has an asymmetric structure, a dense structural arrangement cannot be obtained and the distance between crystals or molecules is widened to cause charge transfer. It is considered that this is because the substance soaked into the charge-generating substance and became easy to contact.

The basic constitution of the present invention is to provide a laminated type photosensitive layer 4 comprising a charge generation layer 2 and a charge transfer layer 3 on a conductive substrate 1 as shown in FIG. Incidentally, as in the conventional one, an intermediate layer / 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 and has an electric resistance of 10 ⁸ Ωcm or less and an intermediate layer, a charge generation layer,
A material that can withstand the film forming conditions of the charge transfer layer is used. 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 insulation such as polyester, polyimide, phenol resin, nylon resin, and paper. Conductive treatment is performed by coating the surface of the conductive 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.

The charge generation layer is a layer for the purpose of generating and separating charges by imagewise exposure, and in the present invention, the disazo pigment represented by the general formula (1) is used. Examples of these disazo pigments are shown below.

[0016]

[Chemical 1]

[0017]

[Chemical 2]

[0018]

[Chemical 3]

[0019]

[Chemical 4]

[0020]

[Chemical 5]

[0021]

[Chemical 6]

[0022]

[Chemical 7]

[0023]

[Chemical 8]

[0024]

[Chemical 9]

[0025]

[Chemical 10]

[0026]

[Chemical 11]

[0027]

[Chemical 12]

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 three rolls, an attritor, or an ultrasonic method. As the resin to be dispersed, for example, polyamide
Condensation resins such as polyurethane, polyester epoxy resin, polycarbonate, polyether, and polymers such as polystyrene, polyacrylate, polymethacrylate, polyN vinylcarbazole, polyvinyl butyral, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, etc. And copolymers, which require insulation and adhesiveness.

When a charge generating layer is formed using these disazo pigments, the product obtained by the above 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, etc. To form a film and dry it to a film thickness of 0.
It may be formed in a thickness of 05 μm to several μm. The content of the disazo pigment is preferably 60% by weight to 100% by weight.

The charge transfer layer is a layer whose purpose is to retain charged charges on the surface thereof, and also to move carriers generated and separated in the charge generation layer by exposure to combine with the retained charged charges. 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 substance include pyrazoline compounds, α-phenylstilbene compounds, hydrazone compounds, diarylmethane compounds, triphenylamine compounds, divinylbenzene compounds, fluorein compounds, anthracene compounds and oxa. Examples include diazole compounds and diaminocarbazole compounds. These organic charge transfer substances are used by being blended with the resin in the same manner as those shown as the binder in the charge generation layer. In the present invention, the ratio (D / R) of the charge transfer material to the binder resin is defined as 5/10 to 8/10 in order to maintain high sensitivity and further improve abrasion resistance as described above. Further, a plasticizer is added to these as required. Examples of such plasticizers include halogen or paraffin, dimethylnaphthalene, dibutyl phthalate, dioctyl phthalate, tricresyl phthalate, dioctyl phthalate, tricresyl phosphate, and polymers such as polyesters and copolymers. The charge transfer substance, the binder resin, and silicon oil (a leveling agent at the time of film formation) are 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 to have a film thickness of 25 μm or more A charge transfer layer having a thickness of 25 to 40 μm is preferably formed. The amount of silicon oil added is 0.001 to 1% by weight with respect to the binder resin.

[0032]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. The amounts (parts) of the respective components described in Examples and Comparative Examples are parts by weight.

Examples of Claim 1 Example 1 [Coating liquid for charge generation layer] 1 in a glass pot of 15 cm in diameter
1/2 amount of φ10 mm YTZ (partially stabilized zirconia) balls and the azo pigments (A: A-20, C _p1 : C1-1,
45 g of C _p2 : C1-2) and methyl ethyl ketone (ME
K) (330 g) was added and the mixture was subjected to ball mill dispersion for 10 days. After the dispersion was completed, 750 g of cyclohexanone (anone) was added and stirred, 1000 g of the mill base was taken out, and MEK / anone / polyvinyl butyral (XYHL manufactured by Union Carbide Co., Ltd.) (493/1169/4) with stirring.
It was diluted dropwise with g) to obtain a charge generation layer coating liquid.

[Coating Liquid for Charge Transfer Layer]

[0035]

[Chemical 13]

First, the charge generation layer coating solution was dip-coated on an Al drum of φ80 mm × 340 mm, and the temperature was set to 110 ° C. 1
It was heated and dried for 0 minutes to form a 0.1 μm charge generation layer.

Further, the above-mentioned charge transfer layer coating solution was applied by dip coating, and dried by heating at 130 ° C. for 15 minutes to form a charge transfer layer of 25 μm to prepare an electrophotographic photosensitive member.

Example 2 In Example 1, the charge transfer layer coating liquid was CTM (same as in Example 1): 7 parts, polyarylate: 10 parts, dichloromethane: 68 parts (D / R = 7 / It is the same except 10).

Example 3 In Example 1, the charge generating substance was replaced by the disazo pigment (A: A-20, C _p1 : C1-12, C _p2 : C1-2).
The same applies except that the binder resin of the charge transfer layer is polycarbonate Z (Teijin Kasei).

Example 4 In Example 2, the charge transfer layer coating liquid was CTM (same as in Example 1): 7 parts, polycarbonate Z: 10 parts, dichloromethane: 68 parts (D / R = 7 / It is the same except 10).

Example 5 In Example 1, the charge generating material was the above-mentioned disazo pigment (A: A-20, C _p1 : C1-1, C _p2 : C1-3), and the coating liquid for the charge transfer layer was as follows. It is the same except that it was done.

[Coating Liquid for Charge Transfer Layer]

[0043]

[Chemical 14]

Example 6 In Example 5, the charge transfer layer coating liquid was CTM (same as in Example 5): 7 parts, polysulfone: 10 parts, dichloromethane: 68 parts (D / R = 7/10). ) Is the same except.

Example 7 In Example 1, the charge generating substance was the disazo pigment (A: A-27, C _p1 : C7-1, C _p2 : C1-1), and the coating liquid for the charge transfer layer was as follows. It is the same except that it was done.

[Coating Liquid for Charge Transfer Layer]

[0047]

[Chemical 15]

Example 8 In Example 5, the charge transfer layer coating liquid was CTM (same as in Example 5): 7 parts, polycarbonate C: 10 parts, dichloromethane: 68 parts (D / R = 7 /). It is the same except 10).

Comparative Example 1 In Example 1, the coating liquid for the charge transfer layer was CTM (same as in Example 1): 4 parts, polyarylate: 10 parts, dichloromethane: 60 parts (D / R = 4 / It is the same except 10).

Comparative Example 2 In Example 1, the coating liquid for the charge transfer layer was CTM (same as in Example 1): 9 parts, polyarylate: 10 parts, dichloromethane: 76 parts (D / R = 9 / It is the same except 10).

Comparative Example 3 In Example 3, the charge transfer layer coating liquid was CTM (same as in Example 1): 4 parts, polycarbonate Z: 10 parts, dichloromethane: 60 parts (D / R = 4 / It is the same except 10).

Comparative Example 4 In Example 3, the charge transfer layer coating liquid was CTM (same as in Example 1): 9 parts, polycarbonate Z: 10 parts, dichloromethane: 76 parts (D / R = 9 / It is the same except 10).

Comparative Example 5 In Example 5, the charge transfer layer coating liquid was CTM (same as in Example 5): 4 parts, polysulfone: 10 parts, dichloromethane: 60 parts (D / R = 4/10). ) Is the same except.

Comparative Example 6 In Example 5, the charge transfer layer coating liquid was CTM (same as in Example 5): 9 parts, polysulfone: 10 parts, dichloromethane: 76 parts (D / R = 9/10). ) Is the same except.

Comparative Example 7 In Example 7, the charge transfer layer coating liquid was CTM (same as in Example 7): 4 parts, polycarbonate C: 10 parts, dichloromethane: 60 parts (D / R = 4 / It is the same except 10).

Comparative Example 8 In Example 8, the charge transfer layer coating liquid was CTM (same as in Example 7): 9 parts, polycarbonate C: 10 parts, dichloromethane: 76 parts (D / R = 9 / It is the same except 10).

Comparative Example 9 In Example 3, as the charge generating substance, the disazo pigment (A: A-20, C _p1 : C1-2, C _p2 : C1-2) was used.
It is the same except that was used.

Comparative Example 10 The same as Example 10 except that the same charge generating substance as in Comparative Example 9 was used.

The electrophotographic photosensitive member produced as described above was measured for sensitivity to white light by using the photosensitive member potential simulation device disclosed in JP-A-60-100167.
The exposure amount E _1/10 (I) required to attenuate the initial surface potential −800 V to 1/10 was evaluated.

Further, this photosensitive drum was mounted on a Ricoh copying machine FT-4820, and a durability test was conducted.
Decreased film thickness of photoconductor after copying 100,000 sheets and E _1/10 (10
0K), and the rate of change in sensitivity (E _1/10 (100K) / E
_1/10 (I)) was _calculated and shown in Table 1.

[0061]

[Table 1]

Example of Claim 2 Example 9 The same as Example 1 except that the film thickness of the charge transfer layer was 30 μm.

Example 10 The same as Example 1 except that the thickness of the charge transfer layer was 40 μm.

Example 11 The same as Example 3 except that the film thickness of the charge transfer layer was 30 μm.

Example 12 The same as Example 3 except that the thickness of the charge transfer layer was 40 μm.

Example 13 The same as Example 5 except that the film thickness of the charge transfer layer was 30 μm.

Example 14 The same as Example 5 except that the film thickness of the charge transfer layer was 40 μm.

Example 15 The same as Example 7 except that the film thickness of the charge transfer layer was 30 μm.

Example 16 The same as Example 7 except that the thickness of the charge transfer layer was 40 μm.

Comparative Example 11 The same as Example 1 except that the film thickness of the charge transfer layer was 10 μm.

Comparative Example 12 The same as Example 1 except that the film thickness of the charge transfer layer was 20 μm.

Comparative Example 13 The same as Example 3 except that the thickness of the charge transfer layer was 10 μm.

Comparative Example 14 The same as Example 3 except that the film thickness of the charge transfer layer was 20 μm.

Comparative Example 15 The same as Example 5 except that the thickness of the charge transfer layer was 10 μm.

Comparative Example 16 The same as Example 5 except that the thickness of the charge transfer layer was 20 μm.

Comparative Example 17 The same as Example 7 except that the film thickness of the charge transfer layer was 10 μm.

Comparative Example 18 The same as Example 7 except that the film thickness of the charge transfer layer was 20 μm.

Comparative Example 19 In Example 12, the above-mentioned disazo pigments (A: A-20, C _p1 : C1-2, C _p2 : C1-) were used as the charge generating substance.
It is the same except that 2) was used.

Comparative Example 20 The same as Example 13 except that the same charge generating substance as in Comparative Example 19 was used.

The electrophotographic photosensitive member produced as described above was measured for sensitivity to white light by using the photosensitive member potential simulation device disclosed in JP-A-60-100167.
As the exposure amount E _1/10 (I) required to attenuate the initial surface potential −800 V to 1/10, and after the exposure starts, 30
The surface potential after seconds was evaluated as the residual potential V _r (I).

Further, this photosensitive drum was mounted on a Ricoh copying machine FT-4820, and a durability test was conducted.
Decreased film thickness of photoconductor after copying 100,000 sheets and E _1/10 (10
0K), and the rate of change in sensitivity (E _1/10 (100K) / E
_1/10 (I)) and the residual potential V _r (100 K) were determined and shown in Table 2.

[0082]

[Table 2]

[0083]

INDUSTRIAL APPLICABILITY As described above, in the laminated electrophotographic photoreceptor having at least the charge generation layer and the charge transfer layer on the conductive substrate, the disazo pigment represented by the general formula (1) is contained in the charge generation layer. The ratio of the charge transfer material to the binder resin in the charge transfer layer is 5/10 to 8 /
By setting the film thickness to 10 and by setting the film thickness of the charge transfer layer to 25 μm or more, it became possible to improve mechanical durability while maintaining electrophotographic characteristics such as sensitivity.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining the basic configuration of a photoconductor of the present invention,

FIG. 2 is a graph showing the relationship between the ratio (D / R) of the charge transfer material to the binder resin in the charge transfer layer and the wear film thickness;

FIG. 3 is a graph showing the relationship between the D / R and the sensitivity,

FIG. 4 is a graph showing the relationship between the thickness of the charge transfer layer and the sensitivity,

FIG. 5 is a graph showing the relationship between the thickness of the charge transfer layer and the increase in residual potential.

[Explanation of symbols]

 1 Conductive Substrate 2 Charge Generation Layer 3 Charge Transfer Layer 4 Photosensitive Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Kishi 1-3-6 Nakamagome, Ota-ku, Tokyo Reco Ltd. (72) Naoshi Mishima 1-3-6 Nakamagome, Ota-ku, Tokyo In stock company Ricoh (72) Inventor Yoshiaki Kawasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh company

Claims (2)

[Claims] 1. A laminated electrophotographic photoreceptor having at least a charge generation layer and a charge transfer layer on a conductive substrate,
The charge generation layer contains a disazo pigment represented by the following general formula (1), and the ratio (D / R) of the charge transfer material to the binder resin in the charge transfer layer is 5/10 to 8/10.
A photoconductor for electrophotography, characterized in that Formula _{(1) C P1 -N = N} -A-N = N-C P2 in formula A represents a residue bonded to the nitrogen atom of the azo group through a carbon atom. C _P1 and C _P2 are coupler residues having different structures. 2. The electrophotographic photoreceptor according to claim 1, wherein the charge transfer layer has a thickness of 25 μm or more.