JPS63229461A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Summary] In an electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a support, the surface roughness of the support is equal to or less than the thickness of the charge generation layer, In other words, by setting the temperature to 0.5S or less, coating defects such as aggregation of charge-generating substances, which can be a problem when coating a charge-generating layer on a support, can be prevented, and the charging caused by these coating defects can be prevented. - Suppresses printing defects such as fogging due to unevenness in sensitivity, residual potential, etc.

[Industrial application field]

The present invention relates to an electrophotographic photoreceptor that can be widely applied to copying machines, printers, etc. that apply the Carlson process.

[Conventional technology]

The Carlson process consists of charging, exposure, development, transfer, and fixing steps, and by repeating these steps, printed matter is obtained. Charging applies a uniform positive or negative electrostatic charge to the surface of a photoconductive photoreceptor. In the subsequent exposure process, an electrostatic latent image corresponding to the image information is formed on the photoconductor by irradiating it with a laser beam or the like to erase the surface charge in a specific area.Next, this latent image is transferred to a powder called toner. A visible toner image is formed on the photoreceptor by electrostatic development with the body ink. Finally, this toner image is electrostatically transferred onto recording paper and fused using heat, light, pressure, etc. to obtain a printed matter.

Inorganic photoreceptors typified by selenium-based photoreceptors have been widely used as photoreceptors having photoconductivity. This inorganic photoreceptor is
Although it has the characteristics of being highly sensitive, resistant to mechanical wear, and suitable for high-speed, large-scale machines, it must be manufactured using a vacuum shrinkage method, and must be recovered because it is harmful to the human body. For these reasons, the cost is high and it is difficult to apply it to maintenance-free, small, low-cost machines.

Organic photoreceptors have been developed as an alternative to this. Organic photoreceptors can be manufactured by a coating method, which makes it easy to reduce costs through mass production.In addition, compared to inorganic photoreceptors, there is a wider range of materials to choose from, so it is possible to select non-retentive compounds, making maintenance easier due to user disposal. It has the feature that it can be made free.

Single-layer photoreceptors, such as the early developed polyvinyl carbazole photoreceptors and phthalocyanine-dispersed photoreceptors, are characterized by the presence of carrier traps due to dimer formation, and the fact that positive and negative carriers generated are in the same layer. It has been difficult to obtain high sensitivity due to factors such as disappearance due to recombination during movement. To solve this problem, a laminated photoreceptor was developed, as shown in FIG. 1, which has a charge generation layer and a charge transport layer separated into multiple layers.

Here, the charge generation layer has the function of absorbing incident light and generating electron/hole bears (carrier bears), and the charge transport layer transports one of the carriers generated in the charge generation layer to the surface of the photoreceptor. It has the function of forming an electrostatic latent image. In this case, since only one of the positive and negative carriers moves in the charge transport layer, there is no carrier disappearance due to recombination, and the surface charge can be effectively eliminated.

In addition, by separating the functions of the photoreceptor into two layers,
It has become possible to select the optimal compound for each function almost independently, and we have been able to dramatically improve basic properties such as sensitivity, spectral characteristics, charge retention, high-speed response, and mechanical abrasion resistance. .

In order to fully bring out the features of such a functionally separated laminated photoreceptor, the charge generation layer needs to be as thin as possible.

This is because if it is too thick, there is a high probability that carriers generated in the charge generation layer will recombine and disappear in the charge generation layer before being injected into the charge transport layer. Generally, a charge generation layer is formed by finely and uniformly dispersing a charge generation substance in a binder resin, so the lower limit of the film thickness is about the particle size of the charge generation substance, that is, 0.01 to 0.0.
It is about 3 μm. However, if it is too thin, the absorption efficiency of incident light will decrease, so the thickness of the charge generation layer should be 1
The thickness is preferably 0.05 to 0.5 μm, preferably 0.05 to 0.5 μm.

[Problem that the invention seeks to solve]

As shown in FIG. 2, a conductive support 2 of an electrophotographic photoreceptor
If the surface roughness 1 is 0.5s or more, that is, 0.5μm or more, when the charge generation layer 3 is applied, the particle size of the charge generation substance is relatively small, so the particles There was a problem in that the charge-generating IJ3 tended to aggregate in the concave portions of the support surface 2, resulting in uneven thickness distribution of the charge-generating IJ3. Such uneven thickness of the charge generation layer causes uneven charging and sensitivity of the photoreceptor, and causes uneven density and fog when mounted on a printer or the like for printing.

[Means for solving problems]

The above problem can be solved by controlling the surface roughness of the conductive support to 0.5s or less in a functionally separated laminated photoreceptor having at least a charge generation layer and a charge transport layer on the conductive support. be able to.

[For production]

In the electrophotographic photoreceptor of the present invention, since the surface roughness of the conductive support is made to be equal to or less than the thickness of the charge generation layer, aggregation of the charge generation substance does not occur, and therefore, the charge potential, sensitivity, etc. A photoreceptor with uniform photographic properties can be obtained, and an electrophotographic photoreceptor without fog or uneven density can be obtained.

The conductive support of the present invention can be obtained by cutting or polishing the surface of a metal cylinder made by a known method such as a drawing method with a diamond or the like.

Known charge generating substances in the charge generating layer can be used, such as bisazo compounds, trisazo compounds, perylene compounds, indigo compounds, cyanine compounds, squarylium compounds, phthalocyanine compounds, etc. can be used. The charge generating layer is formed by vapor depositing these charge generating substances on a support, or by coating and drying a mixture dispersed or dissolved in a solvent together with a binder resin. As the binder resin, polyester, polyvinyl alcohol, polyvinyl butyral, polyamide, etc. are used. The solvent is selected in consideration of the charge generating substance and binder resin used, and various organic solvents such as tetrahydrofuran, dioxane, methanol, ethanol, dichloromethane, dichloroethane, toluene, and xylene can be used alone or in combination. The coating method on the support may be dip coating, spray coating, wire barcode coating, doctor blade coating, or the like. The film thickness is generally 0.01 to 1 μm, but 0.05 to 1 μm.
It is desirable that the thickness be 0.5 μm.

The charge transport layer is made of a hydrazone compound, a pyrazoline compound,
It is formed by dissolving a charge transporting substance such as trinitrofluorenone in a binder resin. As the binder resin, known binder resins such as polycarbonate, polystyrene, polyacrylonitrile, acrylic-styrene, polyester, and polysulfone can be used. The solvent is appropriately selected depending on the binder resin used. As the coating method, the same method as in the case of the charge generation layer can be used. The film thickness is generally 5 to 50 μm, preferably 10 to 25 μm.

〔Example〕

The surface of an aluminum cylinder with a surface roughness of 5S prepared by the pultrusion method was diamond-polished to obtain a conductive support 2 with a surface roughness 1 of approximately 0.1s as shown in FIG. On top of this, 1 part by weight of aluminum chloride phthalocyanine,
A mixture of 1 part of polyvinyl butyral and 18 parts of methanol was dispersed and mixed for 24 hours using hard glass beads and a hard glass pot, which was coated by a dipping method and then dried to form a charge generation layer 3 having a thickness of about 0.3 μm.

Next, 1 part of a hydrazone compound represented by the following structural formula and 1 part of polycarbonate are dissolved in 9 parts of tetrahydrofuran in parts by weight, and the solution is coated on the charge generation layer 3 by a dipping method and heated at 90°C for 1 hour. It was dried to form a charge transport layer 4 having a thickness of about 18 μm, and a photoreceptor was obtained.

When this photoreceptor drum was installed in a semiconductor laser printer and a printing test was conducted, clear and fog-free printing was obtained.

Comparison 1: A photoreceptor was obtained in the same manner as in Example, except that a conductive support having a surface roughness of 5 s that was only subjected to drawing was used.

This photoreceptor had fog over the entire white background, and black spots appeared here and there that were thought to be caused by aggregation of charge-generating substances.

〔Effect of the invention〕

By using a functionally separated laminated photoreceptor using a conductive support with a surface roughness of 0.5 s or less, an electrophotographic photoreceptor without uneven printing such as fog can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a photoreceptor of the present invention, and FIG. 2 is a schematic sectional view of a conventional photoreceptor. 1... Surface roughness, 2... Conductive support, 3...
- Charge generation layer, 4... Charge transport layer. Cross-sectional view of the photoreceptor of the present invention Photoreceptor of the prior art Surface roughness Conductive support Charge generation layer Charge transport layer

Claims (1)

[Claims] (1) A functionally separated laminated photoreceptor having at least a charge generation layer and a charge transport layer on a cylindrical conductive support, characterized in that the conductive support has a surface roughness of 0.5s or less. An electrophotographic photoreceptor.