JPH06123980A - Single layer type electrophotographc sensitive body - Google Patents

Abstract

PURPOSE:To provide a single layer type electrophotographic sensitive body excellent in electrifiable property and sensitivity and maintaining high stability of electrostatic characteristics even after repeated copying processes. CONSTITUTION:This single layer type electrophotographic sensitive body has a photosensitive layer 2 contg. an electric charge generating material 21, an org. positive hole transferring material and an org. acceptor-like compd. dispersed in a binder and a chalcone compd. represented by the general formula is used as the org. acceptor-like compd. In the formula, each of R1 and R2 is an optionally substd. phenyl, optionally substd. naphthyl or an arom. heterocyclic group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoconductor, and more particularly to a single-layer type electrophotographic photoconductor used in a copying machine, a printer or the like using an electrophotographic process.

[0002]

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

As a material satisfying these physical property values, a photoconductor composed of an inorganic compound such as selenium, selenium-tellurium alloy, or selenium arsenide has been conventionally adopted and used in many copying machines. However, these materials have drawbacks that they are highly toxic, are difficult to handle because they are used in an amorphous state, and are high in cost because they need to be vacuum-deposited to a thickness of several tens of μm, and are unsolved as a photoreceptor. It had a problem.

In order to improve or 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 photosensitive layer (CGL) having a charge generating function and a layer (CT) having a charge transporting function.
L) and a laminated structure, which is used exclusively in the negative charging process. The reason is that the photoconductor formed by mixing the materials to be used and simply forming it as a single layer may expose the drawback that the fatigue phenomenon of charging property, sensitivity, and electrostatic property is reduced to less than a practical level. On the other hand, in the laminated type, these drawbacks 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 the machine can be sufficiently machined in the state of being used in the process. This is because it becomes possible to maintain the photoconductor with the desired durability. In addition, organic materials exhibiting high charge mobility that does not hinder high-speed electrophotographic processes are currently limited to donor compounds having only hole-transporting properties, and the fatigue phenomenon of electrostatic properties is minimized. In order to suppress the mechanical durability of the photoconductor sufficiently while keeping it in the process, a function separation structure in which the functions of charge generation and charge transfer are separated for each layer is used, and This is because the laminated-type photoconductor disposed 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.

The first is derived from the negative charging of the photoconductor. A highly reliable charging method in the electrophotographic process is based on corona discharge, and this method is used in most copying machines and printers. However, as is well known, the negative polarity corona discharge is unstable as compared with the positive polarity, so that the charging method by the scorotron is adopted, which is one of the factors for the 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, a positive charging photoreceptor is desirable.

The second is derived from the laminated structure of the photoconductor. In the production of the photoconductor, an inexpensive solution coating method can be used as compared with the vacuum vapor deposition method. However, in order to produce such a laminated type photoconductor, at least two coating operations, usually the photoconductor is used. Since an undercoat layer is provided immediately above the substrate (between the substrate and the photosensitive layer) in order to secure the charging property of 3 times, it is necessary to perform the coating operation three times, and the plural coating operations increase the cost of the photoconductor. Leads to. Furthermore, in order to maintain a good balance between sensitivity and durability and to obtain a good image, C
Controlling the thickness of the GL in the submicron range is another factor that further raises 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 one 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 for the negative charging process, it is possible to create a photoconductor that is inexpensive and has a high degree of freedom in the usage environment. . However, there are very few examples of photoreceptors that satisfy this condition. Commercially available single-layer type organic photoconductors include charge transfer complex photoconductors composed of polyvinylcarbazole and trinitrofluorenone, eutectic complex photoconductors composed of thiapyrylium dye and polycarbonate, perylene pigments and hydrazone donors. It only counts the photoconductors, etc. dispersed in the resin. Of these, one was associated with the drawback of ozone generation because it was used in a negative charging process, and one was unsuitable for a high-speed copying process because of the low sensitivity of the photoconductor. further,
In the case where the components of the laminated-type photoconductor that have been put into practical use are simply dispersed, the charging potential and the sensitivity are low, and in particular, the drawback that they greatly fluctuate with repeated use cannot be overcome.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a single-layer type electrophotographic photosensitive member which is excellent in charging property and sensitivity, and which is stable in electrostatic characteristics even when a copying process is repeated. It is in.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that at least a charge generating substance, an organic hole transfer substance, and an organic acceptor compound are dispersed in a binder. Moreover, they have found that a photoreceptor having a photosensitive layer using a chalcone-based compound as an organic acceptor compound is effective for the above purpose, and thus completed the present invention. That is, according to the present invention, a single photosensitive layer is provided on a conductive substrate directly or via an undercoat layer, and the photosensitive layer is at least a charge generating substance, an organic hole transporting substance and an organic acceptor compound. Is dispersed in a binder, and the organic acceptor compound is a chalcone compound, and a single-layer type electrophotographic photoreceptor is provided.

Such a photoreceptor has excellent chargeability and sensitivity,
Suitable for low-speed to high-speed copying processes, the spectral sensitivity range can be controlled by changing the charge generation material, and a photoconductor for a page printer using an LD light for optical writing from a monochrome or full-color analog copying machine. It is possible to apply to. Particularly important in the photosensitive layer according to the present invention is the use of a chalcone compound as an organic acceptor compound. This makes it possible to increase the sensitivity of the photoconductor and improve the charging property and the electrostatic property. Among the conventional single-layer type electrophotographic photoconductors in which the charge-generating substance is dispersed in the resin, the charge-generating substance also has a charge transfer function, and the charge characteristics of both holes and electrons are high. However, there are some defects such as low sensitivity, small number of electric charge accumulation, and decrease in charging potential due to repetition, and an induction period in which light decay does not start immediately after light irradiation (induction effect). There were drawbacks such as the latitude of the latent image potential was narrow. Further, in order to improve the hole mobility of such a photosensitive member, it is not possible to overcome the drawbacks such as the low charging property in a photosensitive member to which a hole transfer substance is simply added, and the charging potential is remarkably lowered by repeated use. It was The present invention solves the above-mentioned drawbacks by dispersing at least a charge generating substance, an organic hole transfer substance, and an organic acceptor compound in a binder and using a chalcone compound as the organic acceptor compound. . This improvement mechanism is not clear at present, but it is estimated as follows. The charge generating substance is present in the photosensitive layer in the form of particles. Therefore, the movement of the electrons generated under the light irradiation in the photosensitive layer is extremely worse between the charge generating substance particles than in the charge generating substance particles, and this process determines the electron movement in the photosensitive layer and the lifetime. Conceivable. Therefore, when an acceptor compound excellent in electron transfer exists in the matrix that holds the charge generating substance dispersedly, electrons are injected from the charge generating substance particles into the acceptor compound, and smooth transfer through the matrix can be achieved. It is considered to be a thing. The chalcone-based compound has a high ability to attract electrons, and it is possible to move most of the electrons generated in the charge generation substance by light irradiation to the acceptor compound side.
The longevity of charging property, sensitivity, and electrostatic property that does not hinder the practical use of the photoconductor is realized. Further, in the present invention, since the hole transfer material excellent in hole transfer is also present in the resin matrix, the hole transfer in the photosensitive layer is smoother than that in the absence thereof.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 shows an example of a photoconductor according to the present invention, in which 1 is a conductive substrate, 2 is a photosensitive layer, 21 is a charge generating substance, 22 is an organic hole transfer substance and an organic acceptor compound in a binder. (Chalcone compound) represents a matrix in which (chalcone-based compound) is molecularly dispersed.

In the photosensitive layer 2 of the present invention, a chalcone compound is used as the organic acceptor compound as described above, and as the chalcone compound, a compound represented by the following general formula (I) is preferably used. To be

[Chemical 1] In the general formula (I) of the present invention, the substituent of the phenyl group and the naphthyl group in R ₁ and R ₂ is an alkyl group,
For example, methyl group, ethyl group, propyl group, butyl group, t
-Butyl group and the like, alkoxy group, for example, methoxy group, ethoxy group and the like, halogen atom, for example, fluorine atom, chlorine atom, bromine atom and the like,
Examples of the halogenated alkyl group include a trifluoromethyl group, examples of the alkoxycarbonyl group include a methoxycarbonyl group and ethoxycarbonyl group, and examples of the cyano group and nitro group. Examples of the heteroaromatic ring include a pyridine ring and quinoline. A ring etc. can be mentioned. Hereinafter, specific examples of the chalcone compound represented by the general formula (I) will be shown, but of course the present invention is not limited thereto.

[0013]

[Table 1- (1)]

[0014]

[Table 1- (2)]

[0015]

[Table 1- (3)]

[0016]

[Table 1- (4)]

[0017]

[Table 1- (5)]

[0018]

[Table 1- (6)]

[0019]

[Table 1- (7)]

[0020]

[Table 1- (8)]

The amount of the chalcone compound which is an organic acceptor compound used in the present invention in the entire photosensitive layer 2 is 1
-40% by weight, preferably 5-40% by weight.

The photosensitive layer of the present invention contains an organic hole transfer substance as an essential component. The role of the hole transfer material in the photosensitive layer is to transfer holes generated by the charge generating material in the photosensitive layer. Due to this transfer function, holes are not accumulated in the charge generating substance, and the charge generating function of the charge generating substance can be sufficiently exerted.

Examples of the organic hole transfer substance used in the present invention include compounds having a triphenylamine moiety in the molecule, hydrazone compounds, triphenylmethane compounds, pyrazoline compounds, oxadiazole compounds, compounds containing a carbazole group, and styryl. Examples thereof include donor compounds such as system compounds, butadiene compounds, polysilane compounds, and polyvinylcarbazole. The amount of the organic hole transfer material in the entire photosensitive layer 2 is 15% by weight or more, preferably 20 to
It is 40% by weight.

The role of the binder in the photosensitive layer 2 is not only the good dispersion of the charge generating substance 21 and the molecular dispersion of the organic hole transporting substance, but also the mechanical strength of the photosensitive layer required in the copying process. I am also responsible. Therefore, when the composition ratio of the binder is low, these 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. As the binder used in the present invention, polyethylene, polypropylene, acrylic resin, methacrylic resin,
Vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, addition polymerization type resin such as melamine resin, polyaddition type resin,
Polycondensation type resins and copolymer resins containing two or more of these repeating units, such as vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-vinyl acetate-maleic anhydride copolymer resins, etc. You can

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 (pigments) in the photosensitive layer 2 is 0.1 to 40% by weight, preferably 0.3 to 25% by weight.

The photosensitive layer 2 of the present invention has a thickness of 5 to 100 μm.
It is preferably about 10 to 40 μm. 5 μm
When the thickness is thinner, the charging property is lowered, and conversely, when it is thicker than 100 μm, the sensitivity is lowered.

Conductive substrate 1 that can be used in the present invention
Examples thereof include a metal plate such as aluminum, nickel, copper and stainless steel, a metal drum or a metal foil, a plastic film or glass on which a thin film such as aluminum, tin oxide and copper iodide is vapor-deposited or applied.

In the photoreceptor of the present invention, an undercoat layer may be provided between the photosensitive layer 2 and the conductive substrate 1 for the purpose of improving the charging property. As the material for the undercoat layer, polyamide resin, polyvinyl alcohol, casein, polyvinylpyrrolidone, or the like can be used in addition to the binder material. The thickness of the undercoat layer is 0.01 to 10 μm, preferably 0.1 to 5 μm.

To prepare the photoreceptor of the present invention, the above-mentioned materials are dissolved in an organic solvent or dispersed by a ball mill, ultrasonic waves or the like to prepare a photosensitive layer forming liquid, which is then dipped, blade coated or sprayed. The photosensitive layer 2 may be formed by coating the conductive substrate 1 by a coating method or the like and drying it.

[0030]

EXAMPLES The present invention will be specifically described with reference to Examples.
This does not limit the present invention.

Example 1 0.5 g of the bisazo pigment represented by the following chemical formula 2 was dissolved in a polycarbonate Z (PC-Z, Teijin Chemicals Co., Ltd.) solution 10 g (dissolved in tetrahydrofuran to a concentration of 10% by weight), After ball milling with 9 g of tetrahydrofuran, the pigment composition was 4% by weight and the PC-Z composition was 50%.
10% by weight of a polycarbonate Z solution, a chalcone-based compound, and an organic positive electrode so that the chalcone-based compound (specific example No. 5) is 23% by weight and the organic hole-transporting substance represented by the following chemical formula 3 is 23% by weight. A hole transfer substance was added, and the mixture was sufficiently stirred to prepare a photosensitive layer forming liquid. The coating solution thus prepared was vapor-deposited with aluminum to a thickness of 1000Å.
A 5 μm thick polyester film was coated with a doctor blade, and a single-layer type electrophotographic photoreceptor having a photosensitive layer with a film thickness after drying of 15 μm was produced.

[Chemical 2]

[Chemical 3]

The surface potential Vs of this photosensitive member after being charged by performing a corona discharge of +6 KV for 20 seconds using an electrostatic copying paper tester (SP-428) manufactured by Kawaguchi Electric Co., Ltd.
(V), surface potential Vo (V) after dark decay for 20 seconds
The amount of exposure E1 / 2 required for the surface potential to decay to 1/2 after irradiation with 20 lux was measured. The results are shown in Table 2.

Comparative Example 1 A photoconductor was prepared under the same conditions as in Example 1 except that the chalcone compound was omitted, and the same evaluation was carried out. The results are shown in Table 2.

Example 2 In Example 1, the chalcone compound was used as a specific example No. Four
A photoreceptor was prepared under the same conditions as in Example 1 except that the compound of Example 1 was used, and the same evaluation was performed. The results are shown in Table 2.

Example 3 In Example 1, the chalcone compound was used as a specific example No. 6
A photoconductor was prepared under the same conditions as in Example 1 except that the compound of Example 6 was used, and the same evaluation was performed. The results are shown in Table 2.

[Table 2]

[0036]

The single-layer type electrophotographic photoreceptor of the present invention is excellent in charging property and sensitivity, and is excellent in stability of electrostatic characteristics even when the copying process is repeated.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of a single-layer type electrophotographic photoconductor according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Conductive substrate 2 Photosensitive layer 21 Charge generation pigment 22 Binder layer A layer in which an organic hole transfer substance and an organic acceptor compound are molecularly dispersed

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kaoru Teramura 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Co., Ltd. (72) Akio Kojima 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh

Claims (2)

[Claims] 1. A single photosensitive layer is provided on a conductive substrate directly or via an undercoat layer, and the photosensitive layer is bound with at least a charge generating substance, an organic hole transfer substance and an organic acceptor compound. A single-layer type electrophotographic photoreceptor which is dispersed in an agent and in which the organic acceptor compound is a chalcone compound. 2. The single-layer type electrophotographic photoconductor according to claim 1, wherein the chalcone compound is a compound represented by the following general formula 1 (formula 1). [Chemical 1] (In the formula, R ₁ and R ₂ are substituted or unsubstituted phenyl groups,
It represents a substituted or unsubstituted naphthyl group or a heteroaromatic ring group. )