JPH06167821A - Single layer type electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide a single layer type electrophotographic sensitive body excellent in electrification ability and sensitivity, capable of electrification to both positive and negative polarities and maintaining high stability of electrostatic characteristics even after repetition of copying processes. CONSTITUTION:This single layer type electrophotographic sensitive body has a photosensitive layer contg. at least an electric charge generating material, an org. positive hole transferring material and an org. acceptor-like compd. in a dispersed state and using a disazo compd. represented by the formula as the electric charge generating material. In the formula, Cp is a residual group of a coupler.

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 that the charging polarity is derived from negative charging. 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 corona discharge of the negative polarity is more unstable than that of the positive polarity. Therefore, 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 that causes chemical damage, ozone filters are used in negative charging type copying machines and printers to prevent the discharge of ozone to the outside. Has become a factor of cost increase. With the positive charging method, the amount of ozone generated is originally very small. Further, the two-component toner which is widely used in the present situation is more preferable when the photoconductor is positively charged, since a stable image can be obtained with less environmental fluctuation, and from this viewpoint, the photoconductor which can be used by the positive charge is desirable. Further, since the charging polarity is limited to negative charging, the process is limited, and there is a drawback that it cannot be applied to an electrophotographic image forming process having higher expandability. For example, if there is a photoconductor that can be charged with both positive and negative charges, one photoconductor can handle positive or negative processes, and it is also possible to realize a process using positive and negative charges.

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 An object of the present invention is to provide a single-layer type electrophotographic which is excellent in chargeability and sensitivity, can be charged in both positive and negative polarities, and is stable in electrostatic characteristics even when a copying process is repeated. To provide a photoreceptor for use.

[0009]

The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and as a result, at least a charge-generating substance, an organic hole-transporting substance, and an organic acceptor compound are contained, and as a charge-generating substance. The inventors have found that a photoreceptor having a photosensitive layer using a material containing a specific disazo compound is effective for the above purpose, and thus arrived at 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. And a charge-generating substance containing a disazo compound represented by the following general formula (I) (Chemical formula 1).

[Chemical 1] (In the formula, Cp represents a coupler residue.) The coupler residue in the disazo compound represented by the general formula (I) can be selected from known coupler components. 2)

[Chemical 2] (In the formula, X represents a hydrocarbon ring or a heterocycle which may have a substituent or may have, Y represents -CON (R ₁ ) (R ₂ ), R ₁ and R ₂ are each independently Represents a hydrogen atom, a hydrocarbon ring or a heterocycle which may have a substituent, and R ₁ and R ₂ may form a ring with each other.) Are preferred. Specific examples of R ₁ and R ₂ in the coupler residue of the above general formula (II) include an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, an aromatic carbon group such as a phenyl group and a naphthyl group. Examples thereof include a hydrogen group, a pyridyl group, a carbazolyl group, and an aromatic heterocyclic group such as a benzotriazole group. R ₁
And R ₂ is a substituted aromatic hydrocarbon group or a substituted aromatic heterocyclic group, examples of the substituent include a methyl group, an ethyl group,
Alkyl group such as propyl group or butyl group, halogenated alkyl group such as trifluoromethyl group, halogen atom such as chlorine atom, bromine atom or iodine atom, methoxy group, ethoxy group, propoxy group, butoxy group or phenyl group Substituted hydroxy groups such as, methylamino group, ethylamino group, dimethylamino group, diethylamino group, phenylamino group, substituted amino groups such as diphenylamino group, nitro group, cyano group, hydroxy group, amino group, etc. . The disazo compound represented by the general formula (I) (Formula 1) according to the present invention can be produced by a conventionally known method. For example, the general formula (II
I) The diamino compound represented by (Chemical Formula 3) is diazotized by a conventional method and coupled with a coupler (Cp) in the presence of an alkali, or the diamine compound represented by the general formula (III) (Chemical Formula 3) is diazotized. After that, the tetrazonium salt is once isolated as a borofluoride salt or a zinc salt, and then the coupler (in the presence of an alkali in a suitable solvent, for example, an inert organic solvent such as N, N-dimethylformamide or dimethyl sulfoxide) ( The disazo compound represented by the general formula (I) (formula 1) can be easily produced by coupling with Cp).

[Chemical 3]

Such a photoreceptor has excellent chargeability and sensitivity,
It can be used for both positive and negative charging and is suitable for low to high speed copying processes. 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 has improved the above-mentioned drawbacks by combining a charge generating substance containing a specific azo compound, a hole transfer substance and an acceptor compound. Specific examples of the disazo compound represented by the general formula (I) used in the present invention are shown below, but the present invention is not limited to these.

[Table 1- (1)]

[Table 1- (2)]

[Table 2- (1)]

[Table 2- (2)]

[Table 3- (1)]

[Table 3- (2)]

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. And represent a molecularly dispersed matrix.

In the photosensitive layer 2 of the present invention, as described above, the disazo compound represented by the general formula (I) is used as the charge generating substance, and the amount of this charge generating substance in the photosensitive layer is 0.1. -40% by weight, preferably 0.3-
It is 25% by weight. The present invention uses the azo compound represented by the above general formula (I) as the charge generating substance. However, if necessary, a conventionally known inorganic substance or organic substance that absorbs visible light to generate a free charge is used. Can be used together. As such an example, for example, amorphous selenium, trigonal selenium, selenium-
Inorganic substances such as arsenic alloys, selenium-tellurium alloys, cadmium sulfide, cadmium selenium cadmium, mercury sulfide, lead oxide, lead sulfide, and amorphous silicon, or bisazo dyes, polyazo dyes, cyanine dyes, citryl dyes, pyrylium dyes Organic substances such as dyes, quinacridone dyes, indigo dyes, pyrylene dyes, polycyclic quinone dyes, bisbenzimidazole dyes, indusulon dyes, squarylium dyes, anthraquinone dyes, and phthalocyanine dyes. .

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 of the donor compound include a system compound, a butadiene compound, and a polysilane compound having a linear main chain made of Si. The amount of the organic hole transfer material in the entire photosensitive layer 2 is 15% by weight or more, preferably 2
It is 0 to 40% by weight.

In the present invention, a binder is used if necessary. 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. There is. 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 preferably 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 resins such as melamine resins, polyaddition resins, polycondensation 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 resin etc. can be mentioned.

The role of the organic acceptor compound in the single-layer type organic photoconductor of the present invention is to lower the residual potential and to prolong the electrostatic property of the photoconductor. The reason why these are improved is not necessarily clear, but one of them is to prevent the reduction of the internal electric field of the charge generating substance by extracting the electrons out of the holes and electrons generated in the charge generating substance by light irradiation. It can be considered to prevent a decrease in electric resistance. The role of another organic acceptor compound is to increase the charging potential.

In the usual copying process, the photosensitive member is not charged up to the potential receiving capacity of the photosensitive member determined by the capacity of the charging unit during the charging process, and the charging is terminated at a transient potential level. In such a situation, the change in the charging speed of the photoconductor greatly affects the charging potential of the photoconductor.
Even with a photoreceptor having a high potential receiving ability, the repeated charging potential changes when the charging speed changes.

When the organic acceptor compound is added, the charging potential can be further stabilized by repeating as compared with the case where the photoreceptor is not added. This is also presumed to be related to the above-mentioned electron extraction. As described above, the organic acceptor compound is an essential component in the organic single-layer type electrophotographic photoreceptor according to the present invention.

Examples of the organic acceptor compound used in the present invention include a quinone compound, a π-electron compound having a nitrile group, and a π-electron compound having a nitro group. The amount of these organic acceptor compounds in the entire photosensitive layer 2 is 1 to 40% by weight, preferably 5 to 40% by weight.
Is.

The thickness of the photosensitive layer 2 of the present invention is 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 photoconductor of the present invention, the above-mentioned materials are dissolved in an organic solvent or dispersed by a ball mill, an ultrasonic wave or the like to prepare a photosensitive layer forming liquid, which is immersed, 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.

[0024]

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

Example 1 10 g of a solution of 0.5 g of an azo compound (Exemplified Compound No. 19) in polycarbonate Z (PC-Z, manufactured by Teijin Chemicals Ltd.)
(Dissolved in tetrahydrofuran so as to have a concentration of 10% by weight), ball-milled with 9 g of tetrahydrofuran, and then the composition of the charge generating substance is 2% by weight, PC
A 10% by weight polycarbonate Z solution such that the Z composition is 50% by weight, the organic acceptor compound represented by the following chemical formula 4 is 20% by weight, and the organic hole transporting substance represented by the following chemical formula 5 is 28%. An organic acceptor compound and an organic hole transfer substance were added and sufficiently stirred to prepare a photosensitive layer forming liquid. The coating solution thus prepared is applied to a 75 μm-thick polyester film on which aluminum is vapor-deposited to a thickness of 1000 Å with a doctor blade, and a single-layer type electrophotographic having a photosensitive layer with a film thickness of 15 μm after drying. A photoconductor was prepared.

[Chemical 4]

[Chemical 5]

Examples 2 to 13 The azo compound of Example 1 (compound No. 1 in the exemplified compounds)
Compound No. in the exemplified compounds instead of 9). 1, compound No. 3, compound No. 5, compound No. 8, compound N
o. 12, compound No. 13, compound No. 17, compound No. 18, compound No. 20, compound No. 60,
Compound No. 64, Compound No. A single-layer type photoreceptor was prepared in the same manner as in Example 1 except that 69 was used.

Example 14 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the compound shown in Chemical formula 5 below was used as the organic hole transporting material in place of the compound shown in Chemical formula 5 below. Was produced.

[Chemical 6]

Example 15 In Example 1, as the organic acceptor compound,
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the compound represented by the following chemical formula 7 was used in place of the compound represented by the chemical formula 4.

[Chemical 7]

Example 16 In Example 1, as the organic acceptor compound,
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the compound shown in Chemical formula 4 below was used instead of the compound shown in Chemical formula 4.

[Chemical 8]

With respect to the photoreceptor obtained as described above, an electrostatic copying paper test apparatus (SP-428) manufactured by Kawaguchi Electric Co., Ltd.
Then, the charging potential Vs (surface potential 20 seconds after the start of charging) and the exposure amount (E1 / 2) required for the surface potential after light irradiation to decrease to 1/2 were measured. The results are shown in Table 4.

Further, the photosensitive member of Example 16 was changed to a linear velocity of 260 m.
It is attached to an m / s drum, and positive charging, white light exposure, and light quenching are repeated, and the charging potential (Vd) and post-exposure potential (V
1) was measured. The results are shown in Table 5. From Table 5, it was confirmed that sufficient repeatability was obtained.

[0032]

[Table 4]

[Table 5]

[0033]

INDUSTRIAL APPLICABILITY The single-layer type electrophotographic photosensitive member of the present invention has excellent chargeability and sensitivity, can be charged both positively and negatively, and has excellent 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 generating substance 22 Binder layer A layer in which an organic hole transfer substance and an organic acceptor compound are molecularly dispersed

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Emi Kawamura 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Kaoru Teramura 1-3-6 Nakamagome, Ota-ku, Tokyo Shares In Ricoh Company (72) Inventor Masaomi Sasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh (72) Inventor Masafumi Ota 1-3-6 Nakamagome, Tokyo Ota-ku Stock Company, Ricoh Company

Claims (2)

[Claims] 1. A single photosensitive layer is provided on a conductive substrate directly or via an undercoat layer, and the photosensitive layer contains at least a charge generating substance, an organic hole transfer substance and an organic acceptor compound. A single-layer type electrophotographic photoreceptor, wherein the charge generating substance contains a disazo compound represented by the following general formula (I) (Formula 1). [Chemical 1] (In the formula, Cp represents a coupler residue.) 2. The coupler residue Cp has the general formula (II) (Chemical Formula 2): (In the formula, X represents a hydrocarbon ring or a heterocyclic ring which may have a substituent, Y represents —CON (R ₁ ) (R ₂ ), R ₁ and R ₂ are each independently A hydrogen atom, a hydrocarbon group which may have a substituent or a heterocyclic group, wherein R ₁ and R ₂ may form a ring with each other). Photoconductor.