JPH0915885A - Photoreceptor - Google Patents

Abstract

PURPOSE: To provide a photoreceptor manufactured easily while suppressing the cost by forming a transparent base body of thermoplastic plastic, and coating the transparent base body with a solvent resistant conductive layer. CONSTITUTION: In a photoreceptor 14 with a photosensitive layer 14g formed on a transparent base body 14a, the transparent base body 14a is formed of carbonate, and the transparent base body 14a is coated with a solvent resistant conductive layer. This transparent base body 14a is formed into cylindrical shape by extrusion-molding carbonate. In the photoreceptor 14, a transparent solvent resistant layer 14b is formed on the whole surface of the transparent base body 14a, and a transparent conductive layer 14c, an under coating layer (transparent insulating layer) 14d, a charge generating layer 14e and a charge transport layer 14f are formed in the laminated state at the periphery of the solvent resistant layer 14b. Out of these layers, the charge generating layer 14e and the charge transport layer 14f form the photosensitive layer 14g. Since the transparent base body 14a is thus coated with the solvent resistant conductive layer, the transparent base body 14a is not deformed at the time of washing, and the photoreceptor 14 can be manufactured easily while suppressing the cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor, and more particularly to a photoconductor used in, for example, a back exposure type electrophotographic apparatus and having a photosensitive layer formed on a transparent substrate.

[0002]

2. Description of the Related Art In a conventional back exposure type electrophotographic apparatus,
Since it is necessary to provide an LED head on the back surface (inner surface) of the photoconductor for exposure, the substrate is made of glass.

[0003]

In the back exposure type, the substrate is ideally transparent in order to properly expose the surface of the photoreceptor. Therefore, in addition to the method of forming the substrate with glass, a method of forming the substrate with polycarbonate and forming a conductive layer on its surface is also conceivable. However, if it is made of glass, there is a problem that the cost is high, and if it is made of polycarbonate, the substrate is deformed when it is washed with a solvent such as dichloromethane, so that there is a problem that manufacturing becomes difficult. If the cleaning of the substrate is omitted, a slight amount of dust or oil adhering to the surface of the substrate causes deterioration of image quality and a decrease in yield. Therefore, cleaning of the substrate is indispensable.

Therefore, a main object of the present invention is to provide a photoreceptor which can be manufactured at low cost and is easy to manufacture.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a photoreceptor having a photosensitive layer formed on a transparent substrate, wherein the transparent substrate is made of thermoplastic resin and the transparent substrate is coated with a solvent-resistant conductive layer. The characteristic is a photoconductor.

[0006]

The transparent substrate is made of polycarbonate, and the transparent substrate is covered with the solvent resistant conductive layer. For example, the entire surface of the transparent substrate is coated with a solvent resistant layer having a thickness of 2 μm, and the surface of the solvent resistant layer is coated with a conductive layer. An insulating layer is formed on the surface of the conductive layer, and a photosensitive layer is formed on the surface of the insulating layer. The photosensitive layer includes, for example, a charge generation layer made of a combination of phthalocyanine and titanyl and a charge transport layer made of a binder resin.

[0007]

According to the present invention, since the transparent substrate composed of polycarbonate is coated with the solvent resistant conductive layer,
The transparent substrate does not deform during cleaning, and the photoreceptor can be easily manufactured while suppressing the cost. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an image forming apparatus 1 of this embodiment.
Reference numeral 0 includes a developing device 12 and an organic photoconductor 14. In the developing device 12, a magnetic roller 18 having S poles and N poles alternately formed on the peripheral surface is arranged in the opening at the lower end of the toner box 16, and a developing sleeve 20 is rotatably covered on the outer periphery of the magnetic roller 18. A bias voltage of −400 V is applied to the developing sleeve 20 by the bias power source 22.

The photoreceptor 14 is a transparent substrate 1 as shown in FIG.
A transparent solvent resistant layer 14b is formed on the entire surface of 4a. Then, a transparent conductive layer 14c, an undercoat layer (transparent insulating layer) 14d, a charge generation layer 14e, and a charge transport layer 14f are laminated on the outer periphery of the solvent resistant layer 14b. Of these, the charge generation layer 14e and the charge transport layer 14f form the photosensitive layer 14g. The photoconductor 14 thus configured is charged within the range of -1.5 kV to -800 V by the cleaning / charging blade 26 to which the bias power source 24 is applied.

The developer is contained in the toner box 16 in a state where the magnetic toner 30a and the magnetic carrier 30b are mixed, and the magnetic toner 30a is charged with a negative charge. Therefore, when the developing sleeve 20 is rotated under the same negative bias voltage, the magnetic carrier magnetically attracted to the S pole and the N pole of the magnetic roller 18 moves as the developing sleeve 20 rotates. Further, the magnetic toner 3 which is coupled to the magnetic carrier 30b by Coulomb force.
Similarly, 0a is also pulled out from the toner box 16 by the developing sleeve 20 and moves toward the side facing the surface of the photoconductor 14. More specifically, the magnetic roller 1
N poles and S which are alternately formed on the circumferential surface of 8 in the circumferential direction.
A magnetic brush 28, which is a developer of a magnetic carrier and a magnetic toner, is formed along the line of magnetic force between the poles.

A conductive path is formed by the magnetic carrier 30b on the magnetic brush 28, and charges are injected onto the surface of the photoconductor 14 until the potential becomes the same as the developing bias voltage while being in contact with the magnetic brush. That is, the photoconductor 14 is sufficiently charged by this charge injection. As a result, the photoconductor 1
The surface of 4 and the developing sleeve 20 have the same potential and the same polarity, and the Coulomb force acting on the magnetic carrier 30b becomes 0,
There is no electric force to attach the magnetic carrier 30b to the photoconductor 14. On the other hand, since a strong local Coulomb force acts on the magnetic toner 30a with the magnetic carrier 30b, the force of moving the magnetic toner 30a toward the photoconductor 14 is also zero. Moreover, since the charging polarity of the photoconductor 14 and the charging polarity of the magnetic toner 30a are the same,
A repulsive force acts on the surface of the photoconductor 14.

When the LED array head 32 is used to perform exposure from the inner surface side of the photoconductor 14 in such a charged state of the photoconductor 14, the surface potential of the photoconductor 14 becomes 0 only in the exposed portion and the well type is formed. A potential is formed.
Therefore, the Coulomb force on the magnetic carrier 30b is 0
Is broken, and a weak Coulomb force due to the transient charge injection acts around the closest portion of the magnetic carrier 30b to the photoconductor 14, and the magnetic carrier 3 is transferred to the electrostatic latent image on the surface of the photoconductor 14.
0b moves at a constant potential. At the same time, the magnetic carrier 30b
The magnetic Coulomb force between the magnetic toner 30a and the magnetic toner 30a also moves, and the electrostatic latent image on the surface of the photoconductor 14 is developed.

What should be noted is the structure of the photoconductor 14. The transparent substrate 14a becomes a cylinder having a thickness of 1 mm and an outer diameter of 30 mm by extruding polycarbonate. Examples of transparent thermoplastic materials include vinyl chloride resin, styrene resin, and methacrylic resin. Polycarbonate was used in this example because these materials have problems such as moldability and heat resistance. Acrylic UV curable resin having good adhesion is applied to the transparent substrate 14a by a dipping method, so that the entire surface of the transparent substrate 14a is covered with the solvent resistant layer 14b. The performance of the solvent resistant layer 14b improves as the thickness increases. However, as the thickness increases, it becomes difficult to make the film uniform, which leads to deterioration in quality due to uneven coating. Especially,
If it is 10 μm or more, coating unevenness becomes extremely large. The film thickness is 1 μm from the viewpoint of less unevenness after coating and solvent resistance.
However, the uniformity of the film after coating tends to be relatively poor in the vicinity of 10 μm as compared with the case where the coating is thin. Further, the solvent resistance is improved as it approaches 10 μm as compared with the case where the film thickness is thin, but an increase in cost cannot be avoided. Therefore, the film thickness should be set in the range of 1 μm to 5 μm in consideration of reliability, uniformity of film thickness, and cost.
However, the more preferable thickness is 2 μm.

A UV curable ITO conductive paint is used for the conductive layer 14c formed on the surface of the solvent resistant layer 14b.
This paint is a highly transparent coating material having solvent resistance and permanent electrical characteristics, and is mainly used for preventing static electricity of a transparent plastic film and adjusting the electrostatic capacity. The reason why ITO also has solvent resistance is that dichloromethane is used as a solvent for the polycarbonate used in the photosensitive layer material in the step of coating the photoreceptor. In addition, low surface resistance (10 ⁵ ~
10 ⁶ Ω / sq) and a visible light transmittance of 85% or more, and the solid content is about 40%. By forming the conductive layer 14b having such properties, the solvent resistance is further improved.

The undercoat layer 14d is made of a binder resin, and its thickness is set within the range of 0.6 μm to 5.0 μm. The minimum value of this thickness is set in consideration that the breakdown voltage is locally reduced due to the generation of pinholes due to the dielectric breakdown of the charge transport layer 14f. In addition, the maximum value of the thickness is set in consideration that the transparency (visible light transmittance) changes due to the unevenness of the film thickness, which causes unevenness in the sensitivity characteristics of the photoconductor 14. Photoconductor 14 in which the thickness of the undercoat layer 14d is set in the range of 0.6 μm to 5.0 μm
FIG. 6 shows the sensitivity characteristics of. This is the LED array head 3
2 shows the surface potential of the photoconductor 14 with respect to the duty ratio of 2, the curve A shows the characteristics when the film thickness is 0.6 μm, and the curve B shows the film thickness of 1 μm, 3 μm and 5 μm.
This is the characteristic when m is set. From this, 0.6 μm-5
It can be seen that the characteristics hardly change in the range of μm. The more preferable range of the film thickness is considered to be 1.0 μm to 3.0 μm in consideration of the manufacturing cost and the breakdown voltage.

As the material of the undercoat layer 14d, a material containing 10% by weight to 40% by weight of alcohol-soluble polyamide and styrene-myrensan resin is used. Such a material is produced, for example, by dissolving a polyamide resin (“CM8000” manufactured by Toray Industries, Inc.) in methanol, dip-coating this on the surface of the conductive layer 14c, and drying it at a temperature of 90 ° C. for 20 minutes. The undercoat layer 14d is formed.

As the material of the charge generation layer 14e, a combination of a phthalocyanine-based material and a titanyl-based material is used in order to improve sensitivity.
A charge generation layer 14e having a film thickness of 2 μm to 0.5 μm is formed on the surface of the undercoat layer 14d. FIG. 7 shows the sensitivity characteristics of the standard-sensitivity type charge generation layer in which the high-sensitivity type charge generation layer 14e and the X-type metal-free phthalocyanine are combined. This represents the surface potential of the photoconductor with respect to the duty ratio of the LED array head,
A curve C is a high sensitivity type characteristic, and a curve D is a standard sensitivity type characteristic. From this, it can be seen that the charge generation layer 14e of this example has improved sensitivity. In addition,
Both film thicknesses are set to the same value.

The charge transport layer 14f is damaged by the pressure contact of the magnetic roller 18 and the cleaning / charging blade 26. According to experiments, in the conventional material having a molecular number of about 2000, pinholes were generated due to dielectric breakdown after printing several thousand sheets. Therefore, a binder resin having a molecular number of about 5,000 is used as the material of the charge transport layer 14f. According to the experiment on the charge generation layer 14f, pinholes due to dielectric breakdown did not occur even after printing 15,000 sheets. The film thickness is 20 μm.

The operation process of the photosensitive member 14 from the charging of the photosensitive member 14 to the exposure by the LED array head 26 and the subsequent charging will be described with reference to FIG. For convenience of description, the discharge charging by the corona charger 34 will be used instead of the contact charging. First,
As shown in (A), the corona charger 34 is used to
When No. 4 is charged, a negative charge is applied to the surface of the photosensitive layer 14g. At this time, conventionally, electrons were injected into the conductive substrate, but in this embodiment, since the undercoat layer 14d is formed, the injection of electrons from the conductive layer 14c to the photosensitive layer 14g is blocked. As a result, no leakage current is generated, and as a result, the potential on the surface of the photoconductor 14 is not attenuated and kept constant.

Next, when the light is exposed from the inner surface of the photoconductor 14, the carrier 36 among the charge pairs generated in the charge generation layer 14e moves toward the surface through the charge transport layer 14f, and the negative charge is underdrawn. It is carried towards layer 14d. At this time, since electrons are not injected from the conductive layer 14c, the negatively charged charges in the region A are canceled by only the carriers 36 generated by the exposure. Therefore, there is no carrier 36 drifting in the charge transport layer 14f, and the potential after exposure is stable as shown in FIG.

After that, as shown in FIG.
When charging No. 4, since there is no electron injection, there is no unevenness in the surface potential at the time of charging, and it is not necessary to input extra charging energy. FIG. 5 shows changes in the surface potential with respect to the number of printed sheets when the undercoat layer 14d is formed inside the photoreceptor 14 and when it is not formed. The straight line X is the characteristic when the photoreceptor 14 having the undercoat layer 14d is not exposed,
The curve Y represents the characteristics when the photoreceptor having no undercoat layer 14d is not exposed. Further, the straight line Z is the characteristic when both the photoconductors are exposed. From this, it can be seen that the surface potential change is small when the undercoat layer 14d is applied.

Next, FIG. 6 shows the difference in fog density between the case where the undercoat layer 14d is formed and the case where it is not formed. From this, it can be seen that the fog density becomes less than the allowable value when the undercoat layer 14d is formed. According to this embodiment, by forming the undercoat layer 14d in the photoconductor 14, the electron injection and the drift of the carrier 36 in the charge transport layer 14f are eliminated, so that the surface potential of the photoconductive layer 14g is not lowered. It is possible to prevent fogging of a formed image. Further, since the transparent substrate 14a made of polycarbonate is covered with the solvent resistant layer 14b, the transparent substrate 14a is not deformed during cleaning, and the photoreceptor 14 can be easily manufactured while suppressing the cost. Furthermore, since the film thickness of the undercoat layer 14d is set within the above range, it is possible to avoid a local decrease in breakdown voltage caused by pinholes in the charge transport layer 14f, and also to cause unevenness in the photoconductor characteristics due to the uneven film thickness. Can be prevented. Furthermore, since the phthalocyanine-based material combined with the titanyl-based material is used as the material of the charge generation layer 14e, the sensitivity can be improved. Also,
Since the binder resin is used as the material of the charge transport layer 14f, it is possible to prevent generation of pinholes due to dielectric breakdown.

In this embodiment, the solvent resistant layer and the conductive layer are formed separately, but the solvent resistance and conductivity can be improved by mixing the acrylic UV curable paint with the UV curable ITO conductive paint. You may make it form the layer which has. Further, in order to avoid unevenness in the characteristics of the photoconductor in a state where the thickness of the undercoat layer is 5.0 μm or more, titanium oxide is removed from a conventionally used undercoat layer material, and its transparency is improved. It is necessary to improve (visible light transmittance).

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention;

FIG. 2 is an illustrative view showing one portion of an operation of the embodiment in FIG. 1;

FIG. 3 is an illustrative view showing one portion of an operation of the embodiment in FIG. 1;

FIG. 4A is an illustrative view showing a charging process,
(B) is an illustration showing an exposure process, (C) is an illustration showing a process after exposure, and (D) is an illustration showing a recharging process.

FIG. 5 is a graph showing the relationship between the number of printed sheets and the surface potential.

FIG. 6 is a graph showing sensitivity characteristics.

FIG. 7 is a graph showing sensitivity characteristics.

[Explanation of symbols]

 10 ... Image forming device 12 ... Developing device 14 ... Photosensitive member 14a ... Transparent substrate 14b ... Solvent resistant layer 14c ... Conductive layer 14d ... Undercoat layer 14e ... Charge generation layer 14f ... Charge transport layer 32 ... LED array head

Claims (7)

[Claims] 1. A photoconductor in which a photosensitive layer is formed on a transparent substrate, wherein the transparent substrate is made of a thermoplastic and the transparent substrate is coated with a solvent resistant conductive layer. . 2. The photoreceptor according to claim 1, wherein the solvent-resistant conductive layer includes a transparent solvent-resistant layer coated on the entire surface of the transparent substrate and a transparent conductive layer coated on the surface of the solvent-resistant layer. . 3. The photoreceptor according to claim 1, wherein the solvent resistant layer has a thickness of 1 μm to 10 μm. 4. The photoreceptor according to claim 1, further comprising a transparent insulating layer formed on the surface of the solvent resistant conductive layer or the conductive layer. 5. The photoreceptor according to claim 1, wherein the photosensitive layer includes a charge generation layer and a charge transport layer formed on the surface of the charge generation layer. 6. The photoconductor according to claim 5, wherein the charge generation layer is formed of a material in which a phthalocyanine material is combined with a titanyl material. 7. The photoreceptor according to claim 5, wherein the charge transport layer is made of a binder resin.