JPS581421B2 - electrophotographic photoreceptor - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electrophotographic photoreceptor.

Electrophotographic photoreceptors have various configurations in order to obtain predetermined characteristics or depending on the type of electrophotographic process to which they are applied.

As representative electrophotographic photoreceptors, there are photoreceptors having a photoconductive layer formed on a support and photoreceptors having an insulating layer on the surface, which are widely used.

The photoreceptor, consisting of a support and a photoconductive layer, is used for imaging by the most common electrophotographic processes, ie, charging, imagewise exposure and development, and optionally transfer.

In addition, for a photoreceptor equipped with an insulating layer, this insulating layer is
Provided for purposes such as protecting the photoconductive layer, improving the mechanical strength of the photoreceptor, improving dark decay characteristics, or being applied to a specific electrophotographic process (and for pollution-free purposes). It is something that can be done.

Representative examples of photoreceptors having such insulating layers or electrophotographic processes using photoreceptors having insulating layers are, for example, U.S. Pat.
JP 16429, JP 38-15446, JP 46-3713, JP 42-23910, JP 43-24748, JP JP 1977-1
It is described in Japanese Patent Publication No. 9747, Japanese Patent Publication No. 36-4121, etc.

As a matter of course, an electrophotographic photoreceptor is required to have predetermined sensitivity, electrical properties, and optical properties depending on the electrophotographic process to which it is applied.

However, in addition to this, the durability of the photoreceptor is also an important property.

Durability is a property required when a photoreceptor is used repeatedly, and it significantly affects the formation of clear images.

The main factor determining the durability of a photoreceptor is the durability of the insulating layer in the case of a photoreceptor having a surface insulating layer.

The main object of the present invention is to provide a photoreceptor having an insulating layer with excellent durability.

The present invention is a photoreceptor having a support, a photoconductive layer, and an insulating layer, wherein the insulating layer is formed by applying and heating a thermoplastic resin and melting it.

The insulating layer formed by heating and melting a thermoplastic resin and coating it on the photoconductive layer has excellent cleaning properties and solvent resistance, and also has good adhesion to the photoconductive layer. It also has excellent charging properties and durability.

The energy of corona discharge is quite high, and the molecular chains of the resin forming the insulating layer are cut, and moisture in the air is adsorbed to this part, lowering the electrical resistance. The ozone produced by this reaction reacts with the resin, resulting in a similar decrease in electrical resistance.

This phenomenon is called corona charge deterioration and causes image blurring, especially in high humidity environments, but insulating layers formed by heating and melting thermoplastic resins are less prone to corona charge deterioration. .

Typical thermoplastic resins used include polyphenylene sulfide, polysulfone, polyacrylate, ionomer, polycarbonate, aromatic polyester, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polypropylene, polyacetal, fluororesin, and linear resins such as polyamide.

In order to make the features of the insulating layer formed by direct heat-melting application of the thermoplastic resin more prominent, the melting temperature of the resin employed as the thermoplastic resin is higher within an allowable range. things are recommended.

Usually, resins having a melting temperature in the range of 200°C to 500°C, particularly 250°C to 450°C are preferred.

The photoconductive layer that is simultaneously exposed to the melting temperature of the thermoplastic resin needs to be made of a photoconductive material with excellent heat resistance whose properties are not substantially impaired by such melting temperatures.

Therefore, conventionally widely used Se, S-Te, Se-A
Se-based photoconductors such as s or polyvinylbazole materials are not effective photoconductive materials in the present invention because they have poor heat resistance.

Amorphous silicon, cadmium sulfide or zinc oxide dispersed in a heat-resistant binder resin, etc. are effective as heat-resistant photoconductive materials.

Examples of the support constituting the photoreceptor of the present invention include stainless steel, AZICr, Mo, AurIr+NbrTa.
, V, Ti, Pt, Pd and other metals, or alloys thereof, or synthetic resin films or sheets, or electrically insulating supports such as glass and ceramics. A series of cleaning treatments are optionally performed before the a-Si layer is deposited.

In addition, in the case of an electrically insulating support, its surface is subjected to conductive treatment, if necessary.

For example, if it is glass, its surface is conductive treated, or if it is a synthetic resin film such as polyimide film, it is At, Ag, Pb, Zn.
, Ni, Au, Cr, Mo, Ir, Nb, Ta, V, T
vacuum evaporation, electron beam evaporation,
The surface is made conductive by sputtering or by laminating with the metal.

The shape of the support may be any shape, such as a cylinder or a bell plate, and the shape is determined depending on the need, but in the case of continuous high-speed copying, an endless belt or a cylinder is preferable. desirable.

The thickness of the support is determined as appropriate, but if flexibility is required, it is made as thin as possible within a range that allows the support to function satisfactorily.

However, in such cases, due to the manufacturing and handling of the support,
In terms of mechanical strength, etc., the thickness is usually 10μ or more.

As the photoconductive layer, any material may be used as long as it has excellent heat resistance, but in the present invention, amorphous silicon (hereinafter referred to as "a-Si") is particularly suitable for heat resistance (crystallization temperature = approx. 800° C.) and good electrophotographic properties, a photoconductive layer using a-Si will be explained as a representative example.

Note that since a-Si itself has not been conventionally used as an electrophotographic photoreceptor, the description will include a method for manufacturing the a-Si layer.

The a-Si layer is usually formed on a support by a deposition method such as a glow discharge method, a sputtering method, an ion plating method, or a vacuum evaporation method.

The glow discharge method, sputtering method, and ion plating method are deposition methods that utilize a discharge phenomenon, and are methods in which a gas plasma atmosphere is maintained in a deposition chamber for a predetermined period of time to form an a-Si layer of a required thickness. Particularly effective.

As the material for forming the a-Si layer, in addition to silicon itself,
A silicon compound is used that decomposes to yield silicon during deposition.

Typical examples of such silicon compounds are It is a silicon hydrogen compound such as Si2H6.

Regarding the formation of the a-Si layer, it is also effective to add hydrogen (H), oxygen, nitrogen, and/or carbon as necessary to control the dark resistance and photoelectric gain of the a-Si layer.

A typical method for incorporating H into the s-Si layer is to introduce H2 into the deposition system in the form of compounds such as SiH4, Si2H6, etc. and/or H2 when forming the layer. H2 is decomposed and incorporated into the a-Si layer as the layer grows.

When using a silicon hydride compound such as SiH4 or Si2H6 as the a-Si layer forming material, silicon in this compound can be used as the main component for forming the a-Si layer, so silicon alone or other silicon compounds are usually used. Although they do not have to be used together, these silicones alone or other silicon compounds may be used in combination, if necessary.

The amount of H contained in the a-Si layer is usually 10 to 4
0 atomic%, preferably 15-30 atomic%
It is desirable that this is done.

For example, in the glow discharge method, the inclusion of H in the a-Si layer is such that the starting material for forming a-Si is SiH4, Si2H.
Since hydrogen compounds such as 6 are used, SiH4, Si2H
When a hydrogen compound such as 6 is decomposed to form an a-Si layer, H is automatically contained in the layer. When forming the layer, H2 gas may be introduced into the apparatus system for performing glow discharge.

In the case of the sputtering method, when sputtering is performed using silicon as a target in an atmosphere of an inert gas such as Ar or a mixed gas based on this gas,
H2 gas may be introduced, or a silicon hydride gas such as SiH4 or Si2H6, or a gas such as B2H6PH3 which also serves as impurity doping may be introduced.

When oxygen, nitrogen, and carbon are contained in the a-Si layer, the same method as when hydrogen is contained can be used.

Oxygen, nitrogen, and carbon may be contained in the a-Si layer using these elements alone or in compounds of these elements.

Such oxygen compounds include SiO2, Si3N4
, CO, CO2, etc., and nitrogen compounds such as NO, NO2
, NH3, etc., include saturated hydrocarbons having 1 to 4 carbon atoms, ethylene hydrocarbons having 1 to 4 carbon atoms, acetylene hydrocarbons having 2 to 3 carbon atoms, and the like.

For example, saturated hydrocarbons include methane (CH4), ethane (C2H6), propane (C3H8), n-butane (
n-C4H10), ethylene hydrocarbons include ethylene (C2H4), propylene (C3H6), butene-1 (C4H8), butene-2 (C4H8), isobutylene (C4H8), and acetylene hydrocarbons include acetylene (C2H2). , methylacetylene (C3H4).

To form the a-Si layer, for example, gases of compounds such as oxygen, nitrogen, oxides, nitrides, carbides, etc. are introduced into a deposition chamber whose interior can be depressurized together with the raw material gas for forming the a-Si. The photoconductive layer may be formed by generating glow discharge indoors.

For example, when forming a photoconductive layer by a sputtering method, for example, (Si+C), (Si+SiO2)
, (Si+Si3N4), or use a sputtering target made of a mixture of Si wafer and C,
Sputtering is performed using two targets of SiO2 or Si3N4 wafers, or oxygen gas, nitrogen gas, or gas of a compound containing carbon oxygen or nitrogen is used together with a sputtering gas such as Ar gas. It is sufficient to introduce the a-Si layer into a deposition chamber and perform sputtering using a Si target to form an a-Si layer.

The content of oxygen, nitrogen, or carbon in the a-Si layer is set appropriately, but is usually 0.1 to 30 at.
omic%, preferably 0.1 to 20 atomic%, most preferably 0.2 to 15 atomic%.

The a-Si layer can be made intrinsic by doping with impurities during manufacture and its conductivity type can be controlled.

The impurities doped into the a-Si layer include a-
In order to make the Si layer P-type, suitable elements are those in group ⅠA of the periodic table, such as B, Al, Ga, In, Tl, etc., and in order to make the Si layer n-type, elements in group Suitable examples include elements of Group V A, such as N, P, As, Sb, Bi, and the like.

The amount of impurities doped into the a-Si layer is appropriately determined depending on the desired electrical and optical properties, but in the case of impurities in Group ⅠA of the periodic table, it is usually 10-6 to 10-6. 10
-3 atomic%, preferably 10-3 to 10-4 at
omic%, in the case of impurities in group ⅠA of the periodic table, usually 10-8 to 10-5 atomic%, preferably 10-
It is desirable that the content be 8 to 10-7 atomic%.

The layer thickness of the a-Si photoconductive layer is determined as appropriate depending on the desired electrophotographic characteristics and usage conditions, for example, whether flexibility is required, etc. 5 to 80μ, preferably 10 to 70μ, optimally 10 to 5
It is desirable to set it to 0μ.

Although a-Si has been described above, the present invention is not limited to a-Si and can be applied to other heat-resistant photoconductive materials.

Typical methods for forming the insulating layer include applying a thermoplastic resin onto the photoconductive layer and melting it by heating, and applying the heated and melted thermoplastic resin liquid directly onto the surface of the photoconductive layer. There is.

The former method is carried out by applying thermoplastic resin powder, emulsion, solution, sheet film, etc. to the surface of the photoconductive layer and heating and melting it.

The latter method is carried out by immersing the surface of the photoconductive layer in a molten thermoplastic resin liquid and spraying the molten resin onto the surface of the photoconductive layer.

Note that when forming an insulating layer by coating and drying a thermoplastic resin solution on the photoconductive layer and then heating and melting it to form an insulating layer, the solution once swollen is dried. Shrinkage strain occurs due to volume reduction during the process, but it is thought that heating and melting eases the shrinkage strain and improves various properties of the insulating layer.

In general, when an insulating layer is added for the main purpose of protecting the photoreceptor, improving its durability, dark decay characteristics, etc., the insulating layer is set relatively thin, and when the photoreceptor is used for a specific electrophotographic process, The insulating layer is set to be relatively thick.

Usually, the thickness of the insulating layer is 0.1 to 100μ, especially 0.
, 1 to 50μ.

Example 1 Using the apparatus shown in FIG. 1, a photoconductive layer was formed in the following manner, an insulating layer was further formed, and a predetermined image forming process was performed on this to form an image.

That is, the surface of a 100-mm diameter plate was cleaned using a solution of NaOH, thoroughly washed with water, and dried.
A stainless steel drum 1 having a length of 350 mm was prepared and firmly fixed at a predetermined position of a fixing member 3 located at a predetermined position in a gas discharge deposition chamber 2 at a distance of about 10 cm from a heater 4.

Next, the main valve 5 was fully opened to exhaust the air in the deposition chamber 2, resulting in a vacuum level of approximately 5×10 −5 torr.

Thereafter, the heater 4 was ignited to uniformly heat the stainless steel drum to 150° C., and the temperature was maintained at this temperature.

After that, the valve 6 is fully opened, and then the valve 8 of the cylinder 7 and the valve 10 of the cylinder 9 are fully opened, and then the flow rate adjustment valves 11 and 12 are gradually opened to supply Ar gas from the cylinder 7 and SiH4 from the cylinder 9. Gas was introduced into the deposition chamber 2.

At this time, the main valve 5 was adjusted so that the degree of vacuum in the deposition chamber 2 was maintained at approximately 0.75 torr.

Next, the switch of the high frequency power supply 13 is turned on, and a high frequency of 13.5 6 MHz is applied between the electrodes 14 and 14' to cause a glow discharge, and a-s is formed on the aluminum substrate.
An i-layer was formed.

The glow discharge power at this time was about 5W.

At this time, the growth rate of the a-Si layer was approximately 4 Å/sec, and the deposition was performed for 15 hours to form an a-Si photoconductive layer with a thickness of 20 μm on the aluminum drum.

Next, the flow rate adjustment valve 11. 12 was closed, and the switch of the high frequency power source 13 was turned off to stop the glow discharge.

Next, the stainless steel drum was taken out from the apparatus and the a-Si
A photoconductive layer was formed.

Next, an insulating layer was formed as follows.

Thermoplastic high melting point type polyphenylene sulfite (
Product name: Ryton V-2, manufactured by Phillips Petroleum) 100 parts (weight), surfactant (Product name: FC4)
31 (manufactured by Sumitomo 3M) and 150 parts of cyclohexanone were stirred and dispersed in a ball mill for 48 hours, the viscosity was further adjusted to 200 CPS with cyclohexanone, and the mixture was applied by dip coating onto a stainless steel drum on which an a-Si photoconductive layer was formed. Coat to a thickness of 6 μm, pre-dry at 100°C for 10 minutes, and then dry at 350°C for 1 hour.
Dry for 5 minutes, coat twice in the same way to a thickness of 6μ, dry and heat to a total thickness of 18μ, and finally heat 4008C for 10 minutes to coat the a-Si photoconductive layer with thermoplastic high melting point resin polyphenylene. An electrophotographic photoreceptor having a sulfide insulating layer was obtained.

Using the photoreceptor, corona charging was performed by applying 6 KV as primary charging to give a surface potential of 1,300 V.

Next, corona charging was performed by applying 5 KV as secondary charging, and at the same time image irradiation was performed at an exposure amount of 15 lux·sec, and then the entire surface was irradiated with light at 50 lux·sec to form an electrostatic latent image.

The image was further developed with a negative type dry developer and transferred to paper, resulting in a high quality image with extremely high sharpness, uniformity, and sufficient contrast.

Next, the surface was cleaned with urethane rubber tip blade cleaning (blade pressure 500 g, contact angle 150), and the same process was repeated 200,000 times. There was no sliding sound and cleaning performance was good, and the image obtained on the 200,000th cleaning was also good. A good quality image with no change compared to the initial image was obtained, no scratches were observed on the surface of the insulating layer, and no decrease in surface resistance due to corona charging was observed, which was good.

Furthermore, this durability operation was repeated 50,000 times under an environment of 35° and 85% RH, but no image blurring due to a decrease in surface resistance under high humidity was observed.

Example 2 A photoreceptor was manufactured using the following 11 types of thermoplastic resins (1) to (11) instead of polyphenylene sulfide as the resin for forming an insulating layer in Example 1.

The photoreceptors (1) to (1l) formed using each thermoplastic resin were subjected to durability tests under the same conditions as in Example 1, and the results are shown in the following table.

(1) Aromatic polyester (product name: ECONOL, manufactured by Nippon ECONOL) Melting point: Approximately 360°C (2) Polysulfone (manufactured by Union Carbide) Melting point: approximately 330°C (3) Polyarylate (product name: U Polymer, manufactured by Unitika) ) Melting point: Approximately 330°C (4) Fluororesin (Product name: Mitsui Fluorochemical) Melting point: Approximately 320°C (5) Iomer (Product name: Surlyn, manufactured by DuPont) Melting point: Approximately 2800°C (6) Polyethylene terephthalate (Product) (7) Polypropyline (Product name: Chitsuso Polypro, manufactured by Chisso) Melting point: Approximately 230°C (8) Polyamide (Product name: Nylon 66, manufactured by DuPont) Melting point: Approximately 270 ℃ (9) Polybutylene terephcrate (product name: DURANEX, manufactured by Nippon Polyplastics) Melting point: approximately 240℃ (10) Polyphenylene oxide (product name: Noryl,
Engineering plastic) melting point: approx. 240°C (11) Polyacecool (product name: Delrin, manufactured by DuPont) melting point: approx. 230°C The above melting points are based on the temperature required to heat and melt the resin to form a uniform layer. show.

In the table above, the evaluation criteria for "abrasion resistance" is to observe the surface condition of a urethane rubber chip plate after printing 100,000 times, and to indicate ◎ if it does not affect the image quality at all, and if it has almost no effect. Those that do not have an impact are marked as ○ those that do have an impact are marked as △.

The evaluation criteria for "cleanability" is that a urethane rubber chip blade is used on a photoreceptor having an insulating layer surface, and toner is interposed between the blade and the insulating layer, and the friction coefficient between the blade and the insulating layer is 1.
This is determined based on whether it is less than 0, whether there is a rubbing noise, and the degree of wear of the blade. The order of ◎>○>△ is good.

The evaluation criteria for "corona resistance" is carried out at the same time as the evaluation of "abrasion resistance", and it is observed whether there is any effect on image quality when placed in an environment of 35°C and 85% RH. It is.

Example 3 An a-Si optical guide layer was formed on a stainless steel drum in the same manner as in Example 1.

Six such drums were manufactured.

Next, an insulating layer having a thickness of 25 μm was formed on each drum a-Si photoconductive layer according to the following method, and photoreceptors (1) to (6) were manufactured.

Photoreceptor (1): A trichlorethylene solution of polysulfone resin (trade name: polysulfone) was applied onto a photoconductive layer, dried, and then heated and melted at 330° C. to form an insulating layer.

Photoreceptor (2): A trichlorethylene solution of polysulfone resin is applied onto a photoconductive layer and dried to form an insulating layer. Photoreceptor (3)
: A trichlorethylene solution of polyacrylate resin (trade name: U polymer) is applied onto the photoconductive layer and dried at 330°C.
An insulating layer formed by heating and melting.

Photoreceptor (4): A trichlorethylene solution of polyacrylate resin is applied onto a photoconductive layer and dried to form an insulating layer.

Photoreceptor (5): An insulating layer was formed by applying a trichloroethylene solution of polycarbonate resin (trade name: Panlite, manufactured by Teijin Chemicals) onto a photoconductive layer, drying it, and heating and melting it at 260°C.

Photoreceptor (6): A trichlorethylene solution of polycarbonate resin is applied onto a photoconductive layer and dried to form an insulating layer.

(Photoreceptors (2), (4), and (6) are reference examples.) The durability of photoreceptors (1) to (6) was tested in the same manner as in Example 2. The results are shown in the table below. shown.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of a photoconductive layer manufacturing apparatus used for manufacturing an electrophotographic photoreceptor according to the present invention. 1...Stainless steel drum, 2...Glow discharge deposition chamber, 3...Fixing member, 4...
・Heater, 13...High frequency power supply, 14.1
4'... Electrode.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor that basically includes a support, a photoconductive layer, and an insulating layer, characterized in that the insulating layer is formed by heating and melting a thermoplastic resin. Electrophotographic photoreceptor. 2. The electrophotographic photoreceptor according to claim 1, which is a thermoplastic resin having a melting temperature of 200° C. or higher. 3. The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer is made of amorphous silicon.