JPH08179543A - Electrophotographic photoreceptor and its manufacture - Google Patents

Abstract

PURPOSE: To reduce the particle diameters of a fluororesin and to stabilize it and to prevent drop of electrophotographic characteristics due to the use of a dispersing agent and the like by using the fluororesin particles for a surface layer dispersed by passing through a narrow nozzle by high pressure and dispersing them with a sand mill using a medium. CONSTITUTION: The electrophotographic photoreceptor contains in the surface layer the fluororesin particles dispersed by passing them through a narrow nozzle by high pressure and dispersing them with a sand mill using a medium. The fluororesin particles are dispersed in a proper dispersing medium, and introduced into the nozzle or a chamber by the pressure of an air pump or a mechanical pump, and the introduced dispersion is subjected to impacts at the time of passing at high speed in the inside of the chamber and cavitation due to vacuum action and the like and the particles are finely pulverized, and dispersed with the sand mill using the medium in order to allow a surfactant added to stabilize the size-reduced particles to function efficiently.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor and a method for producing the same.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member is required to have sensitivity, electrical characteristics and optical characteristics according to an electrophotographic process to be applied. Includes charging, toner development, transfer to paper,
Since electrical and mechanical external forces are directly applied by a process such as cleaning, durability against these is required. Specifically, it is required to have durability against abrasion of the surface due to friction, generation of scratches, and deterioration of the surface under high humidity. Further, there is a problem that the toner adheres to the surface layer due to repeated development and cleaning by the toner. To this end, improvement of the cleaning property of the surface layer is required. Various methods have been investigated for eyes satisfying the properties required for the surface layer as described above. Among them, the means for providing the resin layer in which the fluorine-based resin particles are dispersed on the surface is
It is effective to some extent.

In order to add the fluororesin particles to the surface layer of the electrophotographic photoreceptor, the fluororesin particles are uniformly dispersed in the surface layer coating material, and a film is formed by a method such as dip coating or spray coating. Is common. However, it is not easy to uniformly disperse it in the paint or coating film. That is,
In order to provide high image quality as a photoreceptor, it is necessary to make the particles as small as possible, but as the diameter becomes smaller, the total surface area increases and the cohesive force between the particles increases. The cohesive force not only impairs image quality improvement due to particle size increase, but also causes non-uniformity and sedimentation of particles in the paint.

Conventionally, a roll mill, a sand mill, ultrasonic dispersion, etc. have been known as a means for dispersing powder and the like, but they have advantages and disadvantages in terms of dispersion efficiency, dispersion capacity, etc. The method was less than optimal. As described above, it was not easy to produce an electrophotographic photoreceptor containing the fluorine-based resin particles in the surface layer.

That is, when the fluororesin particles agglomerate or settle in the coating material for the photoconductor, they become non-uniform in the surface layer of the photoconductor, resulting in a difference in the amount of abrasion due to the formation of agglomerates or a difference in wear resistance and a clearing. -Difference in tunability occurs, which causes image defects. As a countermeasure, it is possible to add a surfactant or the like as a dispersion aid in order to improve the dispersion stability of the fluorine-based resin particles, but when the amount exceeds a certain amount, the potential characteristics of the electrophotographic photoreceptor deteriorate. Will be accompanied.

[0006]

The object of the electrophotographic photosensitive member and the method for producing the same of the present invention is to reduce the diameter and stabilization of the fluorine-based resin particles to be applied to the surface layer of the electrophotographic photosensitive member, and to further disperse the particles. This is to prevent deterioration of electrophotographic properties due to the use of auxiliary agents and the like.

[0007]

The present invention relates to an electrophotographic photoreceptor containing fluororesin particles in the surface layer, wherein the fluororesin particles used in the surface layer are dispersed by passing through a narrow nozzle at high pressure. And an electrophotographic photosensitive member characterized by being dispersed by a sand mill using medium.

Further, in the present invention, the fluororesin particles used in the surface layer in the production of the electrophotographic photosensitive member containing the fluororesin particles in the surface layer are dispersed by passing through a narrow nozzle at high pressure. And a method of manufacturing an electrophotographic photosensitive member characterized by being dispersed by a sand mill using medium.

The layer structure of the electrophotographic photosensitive member of the present invention is a so-called single layer type in which the charge generating substance and the charge transporting substance are contained in the same layer, but the charge generating layer containing the charge generating substance and the charge transporting substance are contained. A so-called laminated type having an electric charge transport layer contained therein may be used. Further, a protective layer may be provided on the single-layer type and the laminated type for the purpose of protecting the photosensitive layer.

In the present invention, in any layer constitution, the outermost layer is defined as a surface layer, that is,
In the single layer type, it refers to its own layer, in the laminated type for negative charging, it refers to the charge transport layer, and in the type provided with a protective layer,
Refers to the protective layer.

In the present invention, it is necessary that the diameter of the fluororesin particles is reduced and uniformly dispersed in the surface layer of the electrophotographic photosensitive member. Therefore, first, the diameter of the fluorine-based resin particles is reduced, and the particles are efficiently passed through a narrow nozzle at high pressure to disperse the particles. In this dispersion, fluororesin particles are dispersed in an appropriate dispersion medium and introduced into a narrow nozzle (chamber) by a pressure of an air pump or a mechanical pump. The particles are atomized by the impact force when passing or cavitation by vacuum action.

The schematic diagram of the dispersion method is shown in FIG. Fluorine-based resin particles (dispersion liquid 1 before dispersion) dispersed in an appropriate dispersion medium are pressurized by a high-pressure pump 2 and introduced into a chamber-3 to be dispersed fluorine-based resin particles (dispersion liquid 4 after dispersion).
As the shape of the chamber, the curved shape shown in FIGS. 2 and 3 is effective, but if the pressure can be secured even with a linear shape, the effect of impact force and cavitation is similar to that of the curved shape. It can be used by. The liquid inlet is indicated by 4 and the liquid outlet is indicated by 6. The inner diameter of the chamber is preferably about 1000 μm or less, although it varies depending on the conditions such as the ability of the pump used and the type of fluororesin particles.

Although the pressure applied varies depending on the conditions, dispersion is possible at 50 kg / cm ² or more.
Good results are obtained at kg / cm ² or more. On the other hand, the upper limit of the pressure depends on the limit of the device, but it is 2000 kg / cm ²
In the above, the dispersibility of reducing the particle diameter is saturated.

The velocity at the time of passage through the chamber is
30 m / sec or more is preferable.

Further, at the time of dispersion, a polymer resin may coexist as a binder, or a surfactant may be added to improve dispersibility.

Fluorine-based resin particles whose diameter has been reduced by passing them through a narrow nozzle at high pressure as described above are likely to re-aggregate due to the enlarged surface area, so that they are uniform when applied to the surface layer of a photoreceptor. Is easily damaged. Therefore, in order to prevent reaggregation of particles, it is effective to reduce interparticle cohesion force with a surfactant. However, in general, the addition of a surfactant or the like to the photoreceptor may deteriorate the electrophotographic characteristics, so it is preferable that the amount be as small as possible. Therefore, it is necessary to make the surfactant act as efficiently as possible. Therefore, in the present invention, a sand mill method using medium is adopted and good results are obtained.

The sand mill device employed in the present invention includes a continuous dispersion method having a mechanism for circulating the liquid to be dispersed and a batch dispersion method having no mechanism, but the invention is not particularly limited thereto. With such a sand mill device,
As a pretreatment, a dispersion liquid of fluorine-based resin particles, which has been passed through a narrow nozzle at high pressure and dispersed, is dispersed together with a surfactant.
As for the dispersion condition, a strong shear is not required, and a dispersion disk peripheral speed of about 1 to 10 m / sec is sufficient. The amount of the surfactant depends on the kind used, but the fluororesin particles 100
0.5 to 15 parts by weight, preferably 1 to 10 parts by weight
Parts by weight.

As a means for reducing the diameter of the fluororesin particles in this way, a method of passing a narrow nozzle at high pressure is used,
And, in order to stabilize the particles whose diameter has been reduced, in order to effectively act the surfactant added in advance or at the time of dispersion, it is dispersed by a sand mill using a medium to form a surface layer of the photoreceptor. Suitable.

[0019]

【Example】

Example 1 A 30 mmφ × 357 mm aluminum cylinder was used as a support, and a polyamide (trade name Amilan CM8
000, manufactured by Toray Industries, Inc., was dip-coated with a 5% methanol solution to form an undercoat layer having a thickness of 0.5 μm.

Next, 5 parts by weight of a disazo pigment having the following structural formula (weight part, the same applies hereinafter)

Embedded image 2 parts of polyvinyl butyral (trade name: S-REC BL-S, manufactured by Sekisui Chemical Co., Ltd.) and 150 parts of cyclohexanone were dispersed in a sand mill using a 1 mmφ glass bead for 20 hours. 150 parts of tetrahydrofuran was added to this dispersion. This dispersion was applied onto the undercoat layer by dip coating to form a charge generation layer having a thickness of 0.2 μm.

Next, 10 parts of a styryl compound having the following structural formula

Embedded image And bisphenol Z type polycarbonate (trade name Z2
00, manufactured by Mitsubishi Gas Chemical Co., Inc.) was dissolved in 30 parts of chlorobenzene to prepare a charge transport layer coating material.

Further, 5 parts of polytetrafluoroethylene powder (trade name: Lubron L2, manufactured by Daikin Chemical Co., Ltd.) and 20 parts of chloronebenzene were mixed, and a surfactant (trade name: G
A dispersion liquid to which 0.1 part of F-300, manufactured by Toagosei Kagaku Co., Ltd. was added was prepared. This liquid was passed through the apparatus shown in FIG. 1 at a pressure of 500 kg / cm ² to disperse the polytetrafluoroethylene powder under high pressure. Further, this high-pressure dispersed liquid was dispersed for 1 hour in a sand mill using 1 mmφ glass beads. The disk peripheral speed at this time was 5 m / sec.

The polytetrafluoroethylene dispersion thus prepared was added to the charge transport layer coating material. The amount of polytetrafluoroethylene added was 5% based on the total solid content (charge transport material, resin, polytetrafluoroethylene) in the paint.
It became a part. This coating material was applied onto the charge generation layer by dip coating to form a charge transport layer having a film thickness of 25 μm, to prepare an electrophotographic photoreceptor. The photoconductor 1-1.

Furthermore, except that the charge transport layer coating material prepared as described above was used after being stored at room temperature for 1 week.
An electrophotographic photoreceptor was prepared in the same manner as described above. Photoconductor 1
-2.

Comparative Example 1 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the sand mill dispersion step in the polytetrafluoroethylene powder dispersion step was not carried out. Photoconductor 2-
Set to 1.

Furthermore, except that the charge transport layer coating material prepared as described above was used after being stored at room temperature for 1 week.
An electrophotographic photoreceptor was prepared in the same manner as described above. Photoconductor 2
-2.

Photoreceptors 1-1, 1-2, 2-1 and 2-2
Each of them was mounted on a copying machine (trade name: NP-6030, manufactured by Canon Inc.) and a halftone density image was copied. Photoconductors 1-1 and 1-2 showed uniform density images. was gotten. On the other hand, an image having a uniform density was obtained with the photoconductor 2-1. However, in the photoconductor 2-2, since the polytetrafluoroethylene powder was not uniformly dispersed in the charge transport layer, a non-uniform image was formed at intervals of about 95 mm of the photoconductor cycle.

Example 2 Example 1 was repeated except that the amount of the surfactant coexisted at the time of dispersing the polytetrafluoroethylene powder added to the charge transport layer coating composition was 0.05 part. An electrophotographic photoreceptor was prepared in the same manner as in. Let it be a photoconductor 3-1.

Further, except that the charge transport layer coating material prepared as described above was used after being stored at room temperature for 1 week.
An electrophotographic photoreceptor was prepared in the same manner as described above. Photoconductor 3
-2.

Comparative Example 2 An electrophotographic photosensitive member was prepared in the same manner as in Example 2 except that the sand mill dispersion step in the polytetrafluoroethylene powder dispersion step was not performed. Photoconductor 4-
Set to 1.

Furthermore, except that the charge transport layer coating material prepared as described above was used after being stored at room temperature for 1 week.
An electrophotographic photoreceptor was prepared in the same manner as described above. Photoconductor 4
-2.

Photoreceptors 3-1, 3-2, 4-1 and 4-2
Each of them was mounted on a copying machine in the same manner as described above to copy a halftone density image.
For -2, an image having a uniform density was obtained. On the other hand, the photoconductor 4-1
And 4-2, images with non-uniform density were obtained. This is because the polytetrafluoroethylene powder in the charge transport layer coating was not uniformly dispersed from the time of preparation, and therefore the polytetrafluoroethylene powder in the charge transport layer became non-uniform, which was excellent. No image was obtained.

Example 3 In the same manner as in Example 1, the layers up to the charge generation layer were formed.

Next, 10 parts of a styryl compound (supra) as a charge transport material and a bisphenol Z type polycarbonate are used.
10 parts of the above (described above) was dissolved in 30 parts of chlorobenzene to prepare a coating material for the charge transport layer, which was dip-coated on the charge generation layer to form a charge transport layer having a thickness of 20 μm.

Next, polytetrafluoroethylene powder (supra)
5 parts and 20 parts of chlorobenzene were mixed. Furthermore, 5 parts of bisphenol Z type polycarbonate (trade name Z400, manufactured by Mitsubishi Gas Chemical Co., Inc.) and 0.5 part of a surfactant (trade name Modiper, manufactured by Nippon Yuka Co., Ltd.) are dissolved. did. This liquid was dispersed by the same high pressure dispersion device as in Example 1. Further, it was similarly dispersed by a sand mill using glass beads. Chlorobenzene was added to this dispersion to dilute it, and this solution was applied on the charge transport layer by spray coating to form a protective layer having a film thickness of 3 μm to prepare an electrophotographic photoreceptor. Let it be a photoconductor 5-1.

Further, an electrophotographic photosensitive member was prepared in the same manner as described above except that the protective layer coating material prepared as described above was used after being stored at room temperature for 1 week. Photoconductor 5-2
And

Comparative Example 3 An electrophotographic photosensitive member was prepared in the same manner as in Example 3 except that the sand mill step was not performed. Let it be a photoconductor 6-1.

Further, an electrophotographic photosensitive member was prepared in the same manner as described above except that the protective layer coating material prepared as described above was used after being left standing at room temperature for 1 week. Photoconductor 6-2
And

Comparative Example 4 An electrophotographic photosensitive member was prepared in the same manner as in Example 3 except that the sand mill step in Example 3 was not performed and the high pressure dispersion step was performed twice. The photoconductor 7-1.

The photoconductors 5-1, 5-2, 6-1, 6-2 and 7-1 were mounted on the copying machine in the same manner as described above,
The halftone density image was copied. Photoconductors 5-1 and 5
-2 and 6-1 gave good images with uniform density. On the other hand, in the case of the photoconductors 6-2 and 7-1, the uniformity of the overall density was maintained, but the image quality was unclear.

The above results are summarized in Table 1.

[Table 1]

[0042]

INDUSTRIAL APPLICABILITY The electrophotographic photosensitive member of the present invention has a remarkable effect that a high quality copied image or printed image can be obtained by containing the fluorine-based resin particles having the surface layer subjected to the specific treatment. Further, according to the method for producing an electrophotographic photosensitive member of the present invention, it is possible to disperse the fluorine-based resin particles in a minute diameter, by the sand mill dispersion at that time,
A remarkable effect is obtained in that a good coating material for a surface layer can be obtained and a good electrophotographic photoreceptor can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic view of a method for dispersing fluororesin particles in the present invention.

FIG. 2 is an enlarged view of a chamber.

FIG. 3 is an enlarged view of a chamber.

[Explanation of symbols]

 1 Dispersion liquid before dispersion 2 Pump 3 Chamber-4 Dispersion liquid after dispersion 5 Liquid inlet 6 Liquid outlet

Claims (2)

[Claims] 1. An electrophotographic photosensitive member containing fluororesin particles in a surface layer, wherein the fluororesin particles used in the surface layer are dispersed by passing through a narrow nozzle at high pressure, and An electrophotographic photosensitive member characterized by being dispersed by a sand mill using medium. 2. The fluororesin particles used in the surface layer in the production of an electrophotographic photosensitive member containing fluororesin particles in the surface layer, the fluororesin particles being dispersed by passing through a narrow nozzle at high pressure, A method for producing an electrophotographic photosensitive member, characterized by being dispersed by a sand mill using medium. [0001]