JP3486697B2 - Single-layer 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 photoreceptor comprising a single photosensitive layer containing a charge generating substance, an organic acceptor compound and a hole transporting substance.

[0002]

2. Description of the Related Art Since the electrophotographic process is based on the principle of visualizing a latent image by electrostatic force, the electrophotographic photosensitive member used for carrying out the process has a good charging property in a dark place and light Rapid surface potential decay by irradiation is required. The characteristics required for the electrophotographic photosensitive member in such a process are translated into high dark resistance, which is a specific physical property value, good charge generation quantum efficiency, and high charge mobility.

In order to satisfy these physical property values, a photoconductor composed of an inorganic compound such as selenium, selenium-tellurium alloy, selenium arsenide or the like has been adopted and has been used in many copying machines. However, these materials have strong toxicity, are difficult to handle because they are used in an amorphous state, and have the drawback of being costly because they need to be vacuum-deposited to a thickness of several tens of μm. Have a solution problem.

In order to improve and eliminate these drawbacks, electrophotographic photoreceptors (OPC) using organic materials have been actively developed and put into practical use. Most of the practically used OPCs have a laminated structure in which the photosensitive layer is composed of a layer having a charge generating function (CGL) and a layer having a charge transporting function (CTL), and is mainly used for a negative charging process. There is.

The reason for this is that the photosensitive member formed by mixing the materials to be used and simply forming it as a single layer has a drawback that the fatigue phenomenon of charging property, sensitivity, and electrostatic property is reduced to a level less than practical. On the other hand, in the case of the laminated type, these defects are suppressed as much as possible, and the CTLs, which are rich in mechanical strength and capable of designing the film thickness, are arranged on the surface, so that they can be used in the process. This is because it becomes possible for the photoreceptor to retain sufficient mechanical durability. In addition, organic materials exhibiting a high charge mobility that does not hinder the high-speed electrophotographic process are currently limited to donor compounds having only hole-transporting properties. In order to minimize the mechanical durability of the photoconductor in the state of being subjected to the process, the function separation structure in which the functions of charge generation and charge transfer are separated for each layer is used in order to maintain the hole mobility. This is because the laminated-type photoconductor in which the CTL is placed on the surface is the most rational in terms of electrostatic characteristics.

However, the electrophotographic photoconductor having such a function-separated structure actually causes a new problem. First, it is derived from the negative charging of the photoconductor. The most reliable charging method in the electrophotographic process is corona discharge.
This method is adopted in the printer. However, as is well known, negative-polarity corona discharge is more unstable than positive-polarity, and therefore, the charging method using a scorotron is adopted, which is one of the causes of cost increase. Further, since negative corona discharge is accompanied by more generation of ozone, an ozone filter is used in a negative charging type copying machine or printer in order to prevent external discharge thereof. With the positive charging method, the ozone generation amount can be suppressed to a very small amount. Further, at present, the toner of the two-component type developer, which is capable of obtaining a stable image with little environmental change, is for positive charging, and from this aspect as well, a photoconductor for positive charging is desirable.

Secondly, it is derived from the laminated structure of the photoconductor. Although a solution coating method, which is less expensive than the vacuum deposition method, can be used in the production of the photoconductor, in order to produce such a laminated type photoconductor, at least two coating operations are usually performed. Since an undercoat layer is provided immediately above the substrate (between the substrate and the photosensitive layer) in order to ensure the charging property of 3 times, it is necessary to perform the coating operation three times, and the coating operation for plural times increases the cost of the photoconductor. Leads to. Further, maintaining the balance between sensitivity and durability and controlling the thickness of CGL in the submicron range in order to obtain a good image are factors that further increase the manufacturing cost.

In view of these problems, it is understood that the electrophotographic photosensitive member using an organic material preferably has a single layer type (type having a single photosensitive layer) structure for a positive charging process. Further, it is also understood that if the photoconductor can be used as it is or with a slight modification in the negative charging process, a photoconductor can be created which is inexpensive and has a high degree of freedom in use environment.

As a commercially available monolayer type organic photoconductor, a charge transfer complex photoconductor comprising polyvinylcarbazole and trinitrofluorenone described in JP-B-50-10496, JP-B-48-38430.
Only the eutectic complex photosensitive material comprising a thiapyrylium dye and a polycarbonate described in JP-A No. 3-37354, the photosensitive material in which a perylene pigment and a hydrazone donor described in JP-A-2-37354 are dispersed in a resin are counted. Among these, since the one used for the negative charging process has a drawback of ozone generation, and the one having a low sensitivity of the photoconductor has a drawback unsuitable for a high speed copying process.

Recently, Japanese Unexamined Patent Publication (Kokai) No. 2-165158 proposes a photoconductor containing organic polygermane as a hole transport material. This organic polygermane can be formed into a film from a solution, and has a high hole drift mobility (~ 10 ^-4 cm ² / V · se in an amorphous polymer material).
It is also known that the dependence of the hole mobility on the electrolytic strength is smaller than that of the organic polysilane (Synthetic Metals, 49-50 (1).
992) 395-405).

As a photoreceptor using this organic polygermane compound, Japanese Patent Application Laid-Open No. 2-165158 in which an organic polygermane compound is used in a charge transport layer without a binder, or an organic polygermane compound in a charge transport layer or a charge is used. There is JP-A-5-188604 used for the generating layer. But,
These are all used as the charge transport layer or additive of the laminated photoreceptor, and there has been no example used as the charge transport material for the single-layer photoreceptor. Further, although these photoreceptors are excellent in terms of electrostatic properties, they have a drawback that they have insufficient mechanical strength during repeated use.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and is excellent in charging property and sensitivity, and is also excellent in stability of electrostatic characteristics even when a copying process is repeated. An object is to provide a layered electrophotographic photoreceptor.

[0013]

According to the present invention, a single layer type electrophotographic photosensitive member is provided with a photosensitive layer containing at least a charge generating substance, an organic acceptor compound and a hole transporting substance on a conductive substrate. In the above, there is provided an electrophotographic photosensitive member characterized by using a low molecular weight organic hole transporting substance and an organic polygermane compound as the hole transporting substance. Further, the organic polygermane compound has the following general formula (I):
The single-layer type electrophotographic photosensitive member is provided which is a compound represented by:

[Chemical 1] (In the formula, R and R ′ are an alkyl group, a cycloalkyl group,
It represents an aryl group and may be the same or different from each other. n represents the degree of polymerization. )

Specific examples of the organic polygermane compound used in the present invention include, for example, the following structural formula (I
Examples thereof include compounds represented by I), (III), (IV) or (V).

[Chemical 2]

[Chemical 3]

[Chemical 4]

[Chemical 5] (In the formulas (II) to (V), n represents the degree of polymerization.) Among these, polymethylphenyl germane represented by the general formula (II) is preferable.

In the single-layer type electrophotographic photoreceptor of the present invention,
The weight ratio of the low molecular weight organic hole transport material to the organic polygermane compound is 1:99 to 99: 1, preferably 29 :.
It is preferable to use 1 to 1: 1.

As described above, the single-layer type electrophotographic photoreceptor of the present invention is characterized in that a low molecular weight organic hole transporting material and an organic polygermane compound are used in combination as the hole transporting material, and the chargeability is improved. It has excellent sensitivity and is suitable for low-speed to high-speed copying processes. Also, the spectral sensitivity range can be controlled by changing the charge generation material, and LD light is used for optical writing from analog copying machines for monochrome or full color. It is possible to apply it to the photoconductor of the page printer. Further, the charging property of the photoconductor and the stability of electrostatic properties during repeated use are also excellent.

The present invention will be described in more detail below with reference to the drawings. FIG. 1 shows an example of a photoconductor according to the present invention, where 1 is a conductive substrate, 2 is a photosensitive layer, 21 is a charge generating substance, 22 is an organic acceptor compound in a binder, and a low molecular weight organic hole. It represents a matrix in which a transport material and an organic polygermane compound are dispersed. In the photosensitive layer 2 of the present invention, the organic polygermane compound is preferably the following structural formulas (II) to (V) as described above.
The compound shown by is used.

[Chemical 2]

[Chemical 3]

[Chemical 4]

[Chemical 5] (In the formulas (II) to (V), n represents the degree of polymerization.)

The low molecular weight organic hole transport material used in the present invention and the organic polygermane compound account for 15% by weight or more, preferably 20 to 40% by weight of the entire photosensitive layer (2 in the figure). As described above, the ratio of the organic hole transport material to the organic polygermane compound is 1:99 to 99: 1.
(Weight ratio), preferably 29: 1 to 1: 1. If the ratio of the organic polygermane compound to the low molecular weight organic hole transporting substance is less than this range, the charging property becomes poor, and if it is more than this range, sufficient sensitivity cannot be obtained.

The low molecular weight organic hole transporting material used in the present invention is 9-ethylcapazole-3-aldehyde 1
-Methyl-1-phenylhydrazone, 9-ethylcarbazole-3-aldehyde 1,1-diphenylhydrazone, 4-diethylaminostyrene-β-aldehyde 1-
Methyl-1-phenylhydrazone, 4-methoxynaphthalene-1-aldehyde 1-benzyl-1-phenylhydrazone, 4-methoxybenzaldehyde 1-methyl-1
-Phenylhydrazone, 2,4-dimethoxybenzaldehyde 1-benzyl-1-phenylhydrazone, 4-diethylaminobenzaldehyde 1,1-diphenylhydrazone, 4-methoxybenzaldehyde 1-benzyl-
Hydrazone compounds such as 1- (4-methoxyphenyl) hydrazone, 4-diphenylaminobenzaldehyde 1-benzyl-1-phenylhydrazone, 4-dibenzylaminobenzaldehyde 1,1-diphenylhydrazone,
1,1-bis (4-dibenzylaminophenyl) propane, tris (4-diethylaminophenyl) methane,
Triphenylmethane compounds such as 2,2'-dimethyl-4,4'-bis (diethylamino) -triphenylmethane or diphenylmethane compounds, 9- (4-diethylaminostyryl) anthracene, 9-bromo-10-
(4-Diethylaminostyryl) anthracene, 9-
(4-Dimethylaminostyryl) fluorene, 3- (9
-Fluorenylidene) -9-ethylcarbazole, 1,
2-bis (2,4-diethylaminostyryl) benzene, 1,2-bis (2,4-dimethoxystyryl) benzene, 3-styryl-9-ethylcarbazole, 3-
(4-methoxystyryl) -9-ethylcarbazole,
4-diphenylaminostilbene, 4-dibenzylaminostilbene, 4-ditolylaminostilbene, 1-
(4-diphenylaminostyryl) naphthalene, 1-
(4-Diethylaminostyryl) naphthalene, 4′-diphenylamino-α-phenylstilbene, 4′-methylphenylamino-α-phenylstilbene and other stilbene compounds, or aryl vinyl compounds, 1-phenyl-3- (4-diethylamino) Styryl) -5- (4-
Diethylaminophenyl) pyrazoline, 1-phenyl-
Pyrazoline compounds such as 3- (4-dimethylaminostyryl) -5- (4-dimethylaminophenyl) pyrazoline, 2,5-bis (4-diethylaminophenyl)-
1.3,4-oxadiazole, 2,5-bis [4-
(4-Diethylaminostyryl) phenyl] -1,3,
4-oxadiazole, 2- (9-ethylcarbazolyl-3-)-5- (4-dieylaminophenyl) 1,
3,4-oxadiazole, 2-vinyl-4- (2-chlorophenyl) -5- (4-diethylaminophenyl)
Oxazole, 2- (4-diethylaminophenyl)-
Heterocyclic compounds such as 4-phenyloxazole, triphenylamine, tri-p-tolylamine, 4,4'-dimethoxytriphenylamine, N, N'-bis (3-methylphenyl) -N, N'-diphenylbenzidine , 1,
1-bis (4-di-p-triphenylaminophenyl)
Cyclohexane, N, N, N ', N'-tetra (p-tolyl) benzidine, N, N, N', N'-tetra (p-
There are triphenylamine compounds such as tolyl) -o-phenylenediamine and N, N'-bis (4-methoxyphenyl) -1-aminopyrene, or low molecular compounds such as triarylamine compounds.

Examples of the organic acceptor compound used in the photosensitive layer of the present invention include chloranil,
Bromanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, diphenoquinone, 2,4,5,7-tetranitro Xanthone, 2,4,8-trinitrothioxanthone,
2,6,8-Trinitro-4H-indeno [1,2-
b] thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, succinic anhydride, maleic anhydride, phthalic acid, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, 4-nitro Phthalic anhydride, 3-nitrophthalic anhydride, pyromellitic dianhydride,
Picric acid, o-nitrobenzoic acid, 3,5-dinitrobenzoic acid, pentafluorobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, o-dinitrobenzene, m-dinitrobenzene, 1,3,5- Trinitrobenzene, p-nitrobenzonitrile, picryl chloride, dichlorodicyano-p-benzoquinone, anthraquinone, chloroanthraquinone, dichloroanthraquinone, dinitroanthraquinone, 9-fluorenylidene [dicyanomethylene malonodinitrile], 2,4,7-
Trinitro-fluorenylideneaniline, 3,5-dimethyl-3 ′, 5′-di-t-butyldiphenoquinone, etc.,
Examples include compounds having a high electron affinity. The amount of the organic acceptor compound in the entire photosensitive layer (2 in the figure) is
It is 1 to 40% by weight, preferably 5 to 40% by weight. These low molecular weight organic hole transport materials or organic acceptor compounds may be used alone or in admixture of two or more.

The role of the binder in the photosensitive layer 2 is required not only in the good dispersion of the charge generating material 21 and the molecular dispersion of the low molecular weight organic hole transporting material and the organic acceptor compound, but also in the copying process. It also bears the mechanical strength of the photosensitive layer. Therefore, when the composition ratio of the binder is low,
These various properties will be impaired. Therefore, the amount of the binder in the photosensitive layer cannot be unnecessarily low. The proportion of these binders in the entire photosensitive layer is 30 to 90% by weight, preferably 40 to 70% by weight.

The binder which can be used in the present invention includes polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate. resin,
Addition polymerization resins such as silicone resins and melamine resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more of these repeating units, such as vinyl chloride-vinyl acetate copolymer, chloride Mention may be made of vinyl-vinyl acetate-maleic anhydride copolymer resins.

In the single-layer type electrophotographic photoreceptor of the present invention, the charge generating substance is also an essential component. Examples of the charge generating substance that can be used in the present invention include bisazo pigments, trisazo pigments, phthalocyanine pigments, perylene pigments, quinacridone pigments, indigo pigments, and polycyclic quinone pigments.
Among these, as the central skeleton of the azo pigment, an electron donating property such as a carbazole group, a styryl group, a diphenylamine group or a triphenylamine group is preferable. The amount of these charge generating substances in the photosensitive layer 2 is 0.1 to 40% by weight,
It is preferably 0.3 to 25% by weight.

The thickness of the photosensitive layer of the present invention is 5 to 100 μm,
It is preferably about 10 to 40 μm. If it is thinner than 5 μm, the charging property is lowered, and conversely, if it is thicker than 100 μm, the sensitivity is lowered.

As the conductive substrate which can be used in the present invention, a metal plate such as aluminum, nickel, copper or stainless steel, a metal drum or a metal foil, a plastic film coated with a thin film of aluminum, tin oxide or copper iodide, or Examples thereof include glass.

In the photoreceptor of the present invention, an undercoat layer may be provided between the photosensitive layer and the conductive substrate for the purpose of improving charging property. As these materials, in addition to the binder material, polyamide resin, polyvinyl alcohol, casein, polyvinylpyrrolidone or the like can be used. The thickness of the undercoat layer is 0.01 to 10 μm, preferably 0.1.
It is suitable to be about 5 μm.

The photoconductor of the present invention is prepared by dissolving a predetermined material in an organic solvent or dispersing a coating solution prepared by a ball mill, ultrasonic wave, homomixer or the like on a conductive substrate by dipping, blade, spraying or the like. It is made.

[0028]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the embodiments of the present invention are not limited thereby.

Example 1 1.0 g of x-type metal-free phthalocyanine was dissolved in a ball together with 10 g of a solution of polycarbonate Z (PC-Z manufactured by Teijin Chemicals Co., Ltd.) (dissolved in tetrahydrofuran so as to have a concentration of 10% by weight) and 9 g of tetrahydrofuran. After milling and adding 20 g of a 10 wt% PC-Z solution,
The pigment composition is 2% by weight, the PC-Z composition is 50% by weight, and the organic acceptor compound represented by the following structural formula (VI) is 1% by weight.
8% by weight, 25% by weight of a low molecular weight organic hole transporting material represented by the following structural formula (VII), and 10% by weight of a PC-Z solution containing 5% by weight of polyphenylmethylgermane, an organic acceptor property. A compound, a low molecular weight organic hole transporting substance, polyphenylmethylgermane, and tetrahydrofuran were added and sufficiently stirred to prepare a photosensitive layer forming liquid. The coating solution prepared in this way was applied by a doctor blade onto a 75 μm-thick Polyester film with aluminum deposited to a thickness of 1000 Å, and the film thickness after drying was 17 μm.
A single-layer type electrophotographic photoreceptor having the photosensitive layer of was prepared.

[Chemical 6]

[Chemical 7]

Example 2 A photoconductor was prepared under the same conditions as in Example 1 except that the low molecular weight organic hole transport material was 15% by weight and the polyphenylmethylgermane was 15% by weight.

Example 3 8% by weight of a low molecular weight organic hole transport material was used in Example 1,
A photoconductor was prepared under the same conditions as in Example 1 except that the amount of polyphenylmethylgermane was 22% by weight.

Comparative Example 1 30% by weight of a low molecular weight organic hole transport material was used in Example 1.
Then, a photoreceptor was prepared under the same conditions as in Example 1 except that polyphenylmethylgermane was not added.

Comparative Example 2 A photoconductor was prepared under the same conditions as in Example 1 except that polyphenylmethylgermane was set to 30% by weight in Example 1 and a low molecular weight organic hole transport material was not added.

Example 4 A photoconductor was prepared under the same conditions as in Example 1 except that polydiethylgermane was used in place of polyphenylmethylgermane.

Example 5 A photoconductor was prepared under the same conditions as in Example 4 except that the low molecular weight organic hole transport material was 15% by weight and the polydiethylgermane was 15% by weight.

Example 6 In Example 4, 8% by weight of a low molecular weight organic hole transport material,
A photoconductor was prepared under the same conditions as in Example 4 except that polydiethylgermane was 22% by weight.

Comparative Example 3 A photoconductor was prepared under the same conditions as in Example 4 except that polydiethylgermane was set to 30% by weight in Example 4 and a low molecular weight organic hole transport material was not added.

Example 7 A photoconductor was prepared under the same conditions as in Example 1 except that polydiphenylgermane was used in place of polyphenylmethylgermane.

Example 8 A photoconductor was prepared under the same conditions as in Example 7 except that the low molecular weight organic hole transport material was 15% by weight and the polydibutylgermane was 15% by weight.

Example 9 In Example 7, 8% by weight of a low molecular weight organic hole transport material,
A photoconductor was prepared under the same conditions as in Example 7, except that the amount of polydibutylgermane was 22% by weight.

Comparative Example 4 A photoconductor was prepared under the same conditions as in Example 7 except that polydibutylgermane was 30% by weight in Example 7 and no low molecular weight organic hole transport material was added.

Example 10 A photoconductor was prepared under the same conditions as in Example 1 except that polyphenylmethylgermane was replaced with polydihexylgermane.

Example 11 A photoconductor was prepared under the same conditions as in Example 10 except that the low molecular weight organic hole transport material was 15% by weight and the polydihexylgermane was 15% by weight.

Example 12 A photoconductor was prepared under the same conditions as in Example 10 except that the low molecular weight organic hole transporting material was 8% by weight and the polydihexylgermane was 22% by weight.

Comparative Example 5 A photoconductor was prepared under the same conditions as in Example 10 except that polydihexyl germane was adjusted to 30% by weight in Example 10 and no low molecular weight organic hole transport material was added.

The electrophotographic photosensitive member manufactured as described above was used as an electrostatic copying paper tester (SP-42) manufactured by Kawaguchi Electric Co., Ltd.
It evaluated using 8). For the evaluation, first, corona charging was carried out for 20 seconds under the condition of +16 μA (at this time, the surface potential V
s), the surface potential Vo after standing for 20 seconds was determined. Dark decay was evaluated by Vo / Vs. Next, the surface illuminance is 20 lu
The exposure (tungsten lamp) for x is performed for 30 seconds, the surface potential V ₃₀ at that time is taken as the residual potential, and the exposure amount (E _1/2 ) necessary for the surface potential to be attenuated to _1/2 is set. It was measured. Further, under the +16 μA corona charge, a 9000 lux tungsten lamp was continuously irradiated for a predetermined time to forcibly subject the electrophotographic photoconductor to photocurrent fatigue (the total amount of charge passing through the photoconductor was approximately 25 μQ).
/ Cm ² ), the same measurement as above is performed, and the charging potential V
o ′, dark decay (Vo / Vs) ′, residual potential V ₃₀ ′, and sensitivity E _1/2 ′ were determined. The results are shown in Table 1.

[0047]

[Table 1]

[0048]

INDUSTRIAL APPLICABILITY The single-layer type electrophotographic photosensitive member of the present invention is excellent in charging property and sensitivity, and is excellent in stability of electrostatic property even after repeating copying process.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a single-layer type electrophotographic photosensitive member according to the present invention. DESCRIPTION OF SYMBOLS 1 Conductive substrate 2 Photosensitive layer 21 Charge generating substance 22 Matrix in which an organic acceptor compound, a low molecular weight organic hole transporting substance and an organic polygermane compound are dispersed in a binder

Continuation of front page (56) Reference JP-A-6-295079 (JP, A) JP-A-5-241362 (JP, A) JP-A-5-188604 (JP, A) JP-A-4-164924 (JP , A) JP-A-2-165158 (JP, A) U.S. Pat. No. 4,822,703 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/00-5/16 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. A single-layer type electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer containing at least a charge generating substance, an organic acceptor compound and a hole transporting substance provided on the conductive substrate.
An electrophotographic photoreceptor comprising a low molecular weight organic hole transporting material and an organic polygermane compound as the hole transporting material. 2. The single-layer type electrophotographic photosensitive member according to claim 1, wherein the organic polygermane compound is a compound represented by the following general formula (I). [Chemical 1] (In the formula, R and R ′ are an alkyl group, a cycloalkyl group,
It represents an aryl group and may be the same or different from each other. n represents the degree of polymerization. ) 3. The single-layer electron according to claim 2, wherein the organic polygermane compound represented by the general formula is polymethylphenylgermane in which R is a methyl group and R ′ is a phenyl group. Photoreceptor.