JP2666492B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly, to a photoreceptor for electrophotography, comprising a charge generation layer and a charge transport layer containing an organic material.
The present invention relates to a laminated electrophotographic photosensitive member used in an electrophotographic copying machine or the like.

[Conventional technology]

Conventionally, photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors) include inorganic photoconductive substances such as selenium or selenium alloys and inorganic photoconductive substances such as zinc oxide or cadmium sulfide in a resin binder. , An organic photoconductive substance such as poly-N-vinylcarbazole or polyvinylanthracene, an organic photoconductive substance such as a phthalocyanine compound or a bisazo compound dispersed in a resin binder, or vacuum evaporation. Is used.

The photoreceptor must have the function of retaining surface charges in the dark, the function of receiving light to generate charges, and the function of receiving light and transporting charges. A so-called single-layer type photoreceptor that combines functions, a layer that mainly contributes to charge generation, and a layer that separates functions into a layer that contributes to the retention of surface charges in a dark place and the charge transport during photoreception. There is a laminated photoreceptor.

For image formation by electrophotography using these photoconductors, for example, the Carlson method is applied. Image formation by this method is performed by charging the photoconductor in a dark place by corona discharge,
Forming an electrostatic latent image such as a character or picture on a document by exposing the charged photoreceptor surface, developing the formed electrostatic latent image with toner, and applying the developed toner image to a support such as paper. The transfer is performed by transfer and fixing. After the toner image is transferred, the photoreceptor is subjected to charge removal, removal of residual toner, light charge removal, and the like, and then reused.

In recent years, electrophotographic photoreceptors using organic materials have been put to practical use due to advantages such as flexibility, thermal stability, and film forming properties. A typical example is a photoreceptor using a phthalocyanine compound as a charge generating substance (US Pat. No. 3,816,118).
And a photoreceptor using an azo compound (JP-A
47-37543), a photoreceptor using a perylene compound (described in JP-A-63-271461), and a photoreceptor using a polycyclic quinone compound (described in JP-B-60-59588)
And so on.

In applying such an organic photoreceptor to a copying machine, one of the important conditions that must be satisfied is the reproducibility of a red image.

When copying an original, it is desirable to obtain a copied image that faithfully reproduces the image density of the original, but for that purpose, the photosensitivity of the photoconductor used in the copying machine must be uniform over the entire visible light range. is there. However, among the organic photoconductive substances used for the organic photoreceptor, many substances having high sensitivity generally have photosensitivity in a long wavelength light region. For example, a phthalocyanine compound has a wavelength of 600n.
There is an absorption maximum in the red light region from m to 700 nm, and therefore shows very high light sensitivity in the red light region.

For this reason, in a copier equipped with a photoreceptor using copper phthalocyanine as a photosensitive material, when the photoreceptor is charged and exposed, as described above, it has a maximum absorption in a light wavelength range of 600 nm to 700 nm, and thus has a high red light. Indicates light sensitivity. Therefore, when exposure is performed through a document having red and blue images, a red image is less likely to be reproduced in a resulting copy image than a blue image. This means that the photoreceptor is strongly sensitive to the red reflected light from the red image on the original, and the surface potential of this part is attenuated as much as the attenuation for the reflected light from the white part of the original, and toner adheres in the development process This is because it becomes difficult to do so.

It is known that a photosensitive material is prepared by adding an appropriate dye to a photoconductive substance in order to eliminate this defect. For example, as an example in which a dye is added to the photoconductive substance of a single-layer type photoreceptor, it is disclosed in JP-A No. 11-163873 that a dye having an absorption maximum at a light wavelength of 400 nm to 600 nm is dispersed and contained in β-phthalocyanine.
No. 53-37423, and examples of adding a dye to the charge transport layer of the laminated photoreceptor include a charge transport layer disposed on the light projection side of a charge generation layer containing a phthalocyanine compound. JP-A-57-14848 discloses that a dye having a maximum light absorption is dispersed and contained in a red light region.

[Problems to be solved by the invention]

However, these known methods have the drawback that the charge transport ability is deteriorated by adding a dye to the charge transport layer, and the dye having a relatively low electric resistance should maintain the entire surface of the photoconductive layer or the surface potential. Since the photoreceptor is dispersed and contained in the entire area of the charge transport layer, there is a disadvantage that the surface potential of the photoreceptor is lowered. Further, there is a disadvantage that the durability of the photoreceptor is inferior when the photoreceptor is used repeatedly in a copying machine, which is mainly caused by the gradual deterioration of the contained dye. The main cause of the dye deterioration is that the dye is decomposed by ozone generated in each of the steps of charging, transferring, and discharging, and light in the exposure and light discharging steps. As the dye decomposes with time, the effect of adding the dye to the photosensitive material decreases, and the uniformity of the light wavelength sensitivity of the photoconductor deteriorates.
Further, the decomposed dye has an adverse effect as an impurity on the photosensitive material dispersed and contained, causing a decrease in the surface potential and photosensitivity of the photosensitive member and an increase in the residual potential. In the structure where the dye-containing layer comes to the surface of the photoreceptor, the dye is easily decomposed by ozone from the surface, and when the dye is dispersed in the photosensitive material, the effect of the decomposition products of the dye Is undesirably applied directly to the entire region of the dispersed photosensitive material. Therefore, development of azo compounds, perylene compounds, and polycyclic quinone compounds which are insensitive to the reflected light of a red image is being promoted, but a photoreceptor using these materials is required for a copying machine. The photographic characteristics are not sufficiently satisfied, and problems remain in environmental resistance, sensitivity, printing durability, and the like. Among them, polycyclic quinones such as dibromance anthrone are particularly excellent in environmental resistance and printing durability, but have problems in sensitivity, and high sensitivity is strongly desired.

The present invention eliminates the above-mentioned disadvantages in a photoreceptor provided with a charge generation layer and a charge transport layer containing an organic material,
An object of the present invention is to provide an electrophotographic photoreceptor for a copying machine having excellent red reproducibility, high sensitivity, and excellent electrophotographic characteristics.

[Means for solving the problem]

According to the present invention, the present invention provides an electrophotographic photoreceptor having a charge generation layer and a charge transport layer each containing an organic material on a conductive substrate. An electrophotographic photoreceptor using at least one of the polycyclic quinone compounds represented by (I) and at least one of hydrazone compounds represented by the following general (II) as a charge transporting substance of a charge transporting layer: It is solved by doing.

[In the formula (I), A represents any one of a halogen atom, a nitro group, a cyano group, an acyl group, and a carboxyl group, and n represents an integer of 0 to 4. ] [In the formula (II), B represents an optionally substituted aryl group, heterocyclic group or R ₁ represents any of an alkyl group and an aryl group each of which may be substituted, and R ₂ represents a hydrogen atom, a halogen atom, Represents either an alkyl group or an aryl group, and m represents 0 or 1. The above general formula (I) and general formula (I
Specific examples of the compound represented by I) are as follows.

[Function] By using a charge generating substance and a charge transporting substance in combination as described above, high sensitivity and good red reproducibility,
In addition, it becomes possible to obtain a photoconductor having excellent repetition characteristics.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are conceptual cross-sectional views showing different embodiments of the photoreceptor of the present invention.
Is a charge generation layer, 3 is a charge transport layer, 4 is a photosensitive layer, 5 is a surface coating layer, and the photosensitive layer is a function-separated type which is separated into a charge generation layer and a charge transport layer. The photosensitive layer in FIG. 1 is laminated in the order of a charge generation layer and a charge transport layer, and the photosensitive layer in FIG.
Conversely, the charge transport layer and the charge generation layer are stacked in this order. In the case of the photoreceptor having the structure shown in FIG. 2, a surface coating layer is generally provided to protect the charge generation layer.

The conductive substrate 1 serves not only as an electrode of the photoreceptor but also as another multi-layered support, and may be cylindrical, plate-like or film-like, and may be made of aluminum, stainless steel, nickel or the like. A conductive material may be applied to metal, glass, resin, or the like.

The charge generation layer 2 is formed by applying a material in which at least one of the polycyclic quinone compounds represented by the general formula (I) is dispersed in a resin binder (binder), and receives light to generate a charge. Occurs. The charge generation efficiency is high, and the injection of the generated charges into the charge transport layer 3 and the surface coating layer 5 has little dependence on the electric field and is good even at a low electric field.

Since the charge generation layer only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance and is generally 5 μm or less, preferably 1 μm or less. The charge generation layer may be mainly composed of a charge generation substance, to which a charge transport substance or the like is added. As the resin binder, it is possible to use a suitable combination of polycarbonate, polyester, polyamide, polyurethane, epoxy, silicone resin, methacrylate polymer and copolymer, and the like.

The charge transport layer 3 is formed in a resin binder by the general formula (II)
Is a coating film made of a material in which at least one of the hydrazone compounds shown in the above is dispersed.It retains the charge of the photoreceptor as an insulator layer in a dark place, and transports the charge injected from the charge generation layer when receiving light. Demonstrate the function of. As resin binder, polycarbonate, polyester,
Polyamide, polyurethane, epoxy, silicone resin,
Polymers and copolymers of methacrylic acid esters are used, but the compatibility with a charge transport material is important in addition to mechanical, chemical and electrical stability, adhesion and the like.

The thickness of the charge transport layer is preferably in the range of 3 μm to 30 μm, more preferably 5 μm to 20 μm, in order to maintain a practically effective surface potential.

The surface coating layer 5 is excellent in durability against mechanical stress and is made of a chemically stable substance, and has a function of receiving and holding a charge of corona discharge in a dark place.
In addition, it is necessary that the charge generation layer has a performance of transmitting light that is sensitive to the light, and that the light is transmitted during exposure, reaches the charge generation layer, and receives the injected charge to neutralize and eliminate the surface charge. . As described above, it is desirable that the coating material is as transparent as possible in the wavelength region where the light absorption of the charge generating substance is maximum.

As the modified silicone resin, acrylic modified silicone resin, epoxy modified silicone resin, alkyd modified silicone resin, polyester modified silicone resin, urethane modified silicone resin, etc.
Silicon resin or the like as a hard coat agent can be applied. These modified silicone resins can be used alone, but SiO ₂ , TiO ₂ , In ₂ O ₃ , Zr
A mixed material with a condensate of a metal alkoxy compound capable of forming a film containing O ₂ as a main component is preferable.

Although the thickness of the surface coating layer itself depends on the composition of the coating material, it can be arbitrarily set within a range where adverse effects such as an increase in residual potential do not occur when used repeatedly and continuously.

 Hereinafter, embodiments of the present invention will be described.

Example 1 1 part by weight of a polycyclic quinone compound represented by the above-mentioned compound No. I-1 as a charge generating substance, and a vinyl chloride copolymer resin (trade name: MR-110: manufactured by Zeon Corporation) 1 as a binder resin Parts by weight, and 100 parts by weight of methyl ethyl ketone.
The mixture was kneaded with a mixer for an hour to prepare a coating solution to prepare a coating solution for the charge generation layer. Next, 1 part by weight of a hydrazone compound represented by the above compound No. II-2 as a charge transporting substance and 1 part by weight of a polycarbonate resin (trade name Panlite L-1225: manufactured by Teijin Chemicals Ltd.) as a binder resin were used. And dissolved in 6 parts by weight of dichloromethane to prepare a coating solution for the charge transport layer. Next, a charge generation layer (1 μm) and a charge transport layer (16 μm) are formed on a polyester film on which aluminum is deposited.
The coating solutions prepared respectively were applied in this order to produce a photosensitive member for negative charging having the structure shown in FIG.

Example 2 A photoconductor was prepared by the same way as that of Example 1 except that the charge transport material of Example 1 was changed to the hydrazone compound represented by the above compound No. II-3.

Example 3 A photoconductor was prepared by the same way as that of Example 1 except that the charge transport material of Example 1 was changed to the hydrazone compound represented by the above compound No. II-5.

Example 4 A photoconductor was prepared by the same way as that of Example 1 except that the charge transport material of Example 1 was changed to the hydrazone compound represented by the above compound No. II-8.

Example 5 A photoconductor was prepared by the same way as that of Example 1 except that the charge transport material of Example 1 was changed to the hydrazone compound represented by the above compound No. II-9.

Comparative Example 1 The charge transport material of Example 1 was replaced with 1-phenyl-3- (p-
A photoconductor was prepared by the same way as that of Example 1 except that diethylaminostyryl) -5- (p-diethylaminophenyl) -2-pyrazolin (ASPP) was used.

Comparative Example 2 A photoconductor was prepared by the same way as that of Example 1 except that the charge transport material of Example 1 was changed to p-dimethylaminobenzaldehyde-diphenylhydrazone (ABPH).

Comparative Example 3 A photoconductor was prepared by the same way as that of Comparative Example 1 except that the charge generating substance of Comparative Example 1 was changed to ε-type copper phthalocyanine.

Comparative Example 4 A photoconductor was prepared by the same way as that of Comparative Example 3 except that the charge transporting material of Comparative Example 3 was changed to p-diethylaminobenzoaldehyde-diphenylhydrazone (ABPH).

The electrophotographic characteristics of the photoreceptor thus obtained were measured using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric. Table 1 shows the results.

The photoreceptor surface potential V _s (volts) is the initial surface potential when the surface of the photoreceptor is negatively charged by performing a corona discharge of −6.0 kV for 10 seconds in a dark place, and then stopping the corona discharge. Surface potential V _d (volts) when kept in the dark for 2 seconds at
It was measured, V _d and the illuminance on the surface of the photosensitive member and white light illumination of 2lux is the time to half the half decay exposure amount E _1/2 determined (in seconds) (lux · sec) Further subsequently. Further, the surface potential when the surface of the photoconductor was irradiated with 2 lux white light for 10 seconds was defined as residual potential V _r (volt).

As can be seen in Table 1, Examples 1 to 5 are Comparative Examples 1 to 5.
Although the surface potential is equivalent to that of Comparative Example No. 4, the residual potential and the half-attenuation exposure amount are clearly improved, and the superiority of the combination of the polycyclic quinone compound and the hydrazone compound of the present invention is apparent.

Example 6 1 part by weight of the polycyclic quinone compound represented by the compound No. I-1 as a charge generating substance and 2 parts by weight of a diallyl phthalate resin (trade name: DAP K: manufactured by Osaka Soda) as a binder resin were The mixture was mixed with 150 parts by weight of methyl ethyl ketone and kneaded with a mixer for 3 hours to prepare a coating solution, thereby preparing a coating solution for a charge generation layer. Next, 1 part by weight of a hydrazone compound represented by the aforementioned compound No. II-2 as a charge transporting substance,
1.5 parts by weight of a polyarylate resin (trade name: U Polymer U-100A: manufactured by Unitika) as a binder resin was dissolved in 9 parts by weight of dichloromethane to prepare a coating liquid for a charge transport layer. Next, a coating solution prepared in the order of a charge transport layer (17 μm) and a charge generation layer (1 μm) was applied on a polyester film on which aluminum was deposited, and a surface coating layer was further formed, as shown in FIG. A positively charged photoconductor having the above configuration was produced.

Example 7 A photoconductor was prepared by the same way as that of Example 6 except that the charge transport material of Example 6 was changed to the hydrazone compound represented by the above compound No. II-3.

Example 8 A photoconductor was prepared by the same way as that of Example 6 except that the charge transport material of Example 6 was changed to the hydrazone compound represented by the above compound No. II-5.

Example 9 A photoconductor was prepared by the same way as that of Example 6 except that the charge transport material of Example 6 was changed to the hydrazone compound represented by the above compound No. II-8.

Example 10 A photoconductor was prepared by the same way as that of Example 6 except that the charge transport material of Example 6 was changed to the hydrazone compound represented by the above compound No. II-9.

Comparative Example 5 The charge transport material of Example 6 was replaced with 1-phenyl-3- (p-
A photoconductor was prepared by the same way as that of Example 6 except that diethylaminostyryl) -5- (p-diethylaminophenyl) -2-pyrazolin (ASPP) was used.

Comparative Example 6 A photoconductor was prepared by the same way as that of Example 6 except that the charge transporting substance of Example 6 was changed to p-diethylaminobezaldehyde-diphenylhydrazone (ABPH).

Comparative Example 7 A photoconductor was prepared by the same way as that of Comparative Example 5 except that the charge generating substance of Comparative Example 5 was changed to ε-type copper phthalocyanine.

Comparative Example 8 A photoconductor was prepared by the same way as that of Comparative Example 7 except that the charge transporting material of Comparative Example 7 was changed to p-diethylaminobenzoaldehyde-diphenylhydrazone (ABPH).

The electrophotographic characteristics of the photoreceptor thus obtained were the same as in Example 1 except that the electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric Co., Ltd. was used, and the corona discharge voltage was +6.0 kV. Was measured in the same manner as described above. Table 2 shows the results.

As can be seen from Table 2, Examples 6 to 10 are Comparative Examples 5 to
Although the surface potential is equivalent to that of No. 8, the residual potential and the half-attenuated exposure amount are clearly improved, and the superiority of the combination of the polycyclic quinone compound and the hydrazone compound of the present invention is apparent.

〔The invention's effect〕

According to the present invention, a polycyclic quinone compound represented by the general formula (I) is used as a charge generating substance, and a hydrazone compound represented by the general formula (II) is used as a charge transporting substance. As a photoreceptor for electrophotography, it is possible to obtain a photoreceptor having high sensitivity under positive charging and negative charging, good red color reproducibility, and excellent repetition characteristics.

[Brief description of the drawings]

1 and 2 are conceptual sectional views showing different embodiments of the photoconductor of the present invention. DESCRIPTION OF SYMBOLS 1 ... Conductive substrate, 2 ... Charge generation layer, 3 ... Charge transport layer, 4 ... Photosensitive layer, 5 ... Surface coating layer.

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor having a charge generation layer comprising an organic material and a charge transport layer on a conductive substrate, wherein the charge generation material of the charge generation layer is represented by the following general formula (I). An electrophotographic photoreceptor comprising at least one polycyclic quinone compound and using at least one hydrazone compound represented by the following general formula (II) as a charge transporting substance for a charge transporting layer. . [In the formula (I), A represents any one of a halogen atom, a nitro group, a cyano group, an acyl group, and a carboxyl group, and n represents an integer of 0 to 4. ] [In the formula (II), B represents an optionally substituted aryl group, heterocyclic group or Represents any of the groups represented by, R ₁ represents an optionally substituted alkyl group, an aryl group, R ₂ represents a hydrogen atom, a halogen atom, each of the following substituted Represents either an alkyl group or an aryl group, and m represents 0 or 1. ]