JPH01112248A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent deterioration of sensitivity even at the time of repeated uses for a long time and to restrict rise of residual potential by incorporating a coating organic solvent specified in concentration in a photosensitive layer. CONSTITUTION:The electrophotographic sensitive body is formed by laminating on a conductive substrate a photosensitive layer containing an organic solvent in an amount of 200-8000ppm and composed of an electric charge transfer layer and a charge generating layer, and when its content is less than 200ppm, sensitivity is deteriorated and when it is more than 8,000ppm, rise of residual potential is too remarkable to attain the purpose, thus permitting sensitivity not to be deteriorated by repeated uses and rise of residual potential to be restricted by regulating said content within said range, and accordingly, a sharp copied image free from background stains to be obtained.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to improvements in electrophotographic photoreceptors.

[Prior art]

In recent years, organic photoreceptors have become popular as photoreceptors for electrophotography. The first reason for this is that organic photoreceptors, unlike inorganic photoreceptors, exhibit high sensitivity even in the wavelength range of semiconductor lasers, and also have good sensitivity in the general visible light range.

The second reason is that inorganic photoreceptors require a photosensitive layer on the substrate using methods such as vacuum evaporation or glow discharge, which increases equipment costs and requires harsh conditions such as high heat and high vacuum. In order to adopt this method, it is necessary to use a material with excellent heat resistance and volatility resistance as a support, which increases support management costs. Since the conditions are not strict, manufacturing costs are low.

By the way, although conventionally known organic photoreceptors have the above-mentioned advantages, they also have drawbacks such as a decrease in sensitivity and an increase in residual potential due to repeated use.

Although various proposals have been made to eliminate these drawbacks, they are still insufficient and further improvements have been desired.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor that has excellent durability and does not suffer from a decrease in sensitivity or an increase in residual potential even after repeated use over a long period of time.

〔composition〕

According to the present invention, in an electrophotographic photoreceptor comprising a photosensitive layer formed by laminating a charge transport layer and a charge generation layer on a conductive support, an organic solvent component is added to the photosensitive layer at a concentration of 200 to gooO
Provided is an electrophotographic photoreceptor characterized in that it contains ppm.

A feature of the electrophotographic photoreceptor of the present invention is that the photosensitive layer contains 200 to 8000 ppm of a coating organic solvent.

Generally, it is said that the presence of a coating solvent in the photosensitive layer generates a residual potential, which causes fog or background smear on copied images.

Regarding this point, as a result of intensive research by the present inventors, we found that when a specific concentration of coating organic solvent of 200 to 8000 ppm remains in the photosensitive layer, there is a surprising decrease in sensitivity and residual potential due to repeated use. It was found that the increase in

If the amount of the coating organic solvent contained in the photosensitive layer is less than 200 ppm, the sensitivity will decrease, and if it exceeds 8,000 ppm, the residual potential will increase significantly, making it impossible to achieve the object of the present invention.

Generally, the coating solvent used when coating such a photosensitive layer has good compatibility with the resin binder and film-forming resin that form the photosensitive layer.
Specific drying conditions must be employed in order to retain ~8000 ppm of the coating organic solvent.

For this reason, in the present invention, when the coating solvent is dried and distilled off after coating the photosensitive layer coating solution on the support, the drying temperature is set to the resin contained in the photosensitive layer. It is necessary to increase the specific volume of the resin and to adopt a temperature that increases the intermolecular distance of the resin, so that the necessary amount of residual solvent mixed between the molecules remains.

In this case, the drying temperature varies depending on the type of resin used and the components of the photosensitive layer, but is generally from room temperature to 150°C, preferably from 80 to 130°C.

The photosensitive layer in the present invention is a laminated photosensitive/M layer having a charge generation layer and a charge transfer layer.

The charge generation layer is formed from a charge generation substance and an organic solvent, or a resin binder and a charge generation substance.

As the charge generating substance, for example, CI Pigment Blue 25 [Color Index (CI) 21.180]
, CI Pigment Red 41 (CI 21200)
, Sea Eye Acid Red 52 (CI 45100),
CI Basic Red 3 (CI 45210), further contains a phthalocyanine pigment having a porphyrin skeleton, an azulenium salt pigment, a squalic salt pigment, an azo pigment having a carbazole skeleton (described in JP-A-53-95033), and a stilstilbene skeleton. (described in JP-A No. 53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53-132
547), an azo pigment having a dibenzothiophene skeleton (described in JP-A-54-21728),
Azo pigments having an oxadiazole skeleton
12742), an azo pigment having a fluorenone skeleton (described in JP-A No. 54-22834), an azo pigment having a bisstilbene skeleton (described in JP-A-54-17)
733), azo pigments having a distyryloxadiazole skeleton (described in JP-A-54-2129), azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-2129),
(described in JP-A No. 54-17734), triazo pigments having a carbazole skeleton (described in JP-A-57-195767)
Publication No. 57-195768), and CI Pigment Blue 16 (CI 74100).
), C.I. Butt Brown 5 (CI 73410), C.I. Butt Dye (CI
73030), Argo Scarlet B (manufactured by Violet Co., Ltd.), Indus Thread Scarlet R
Organic pigments such as perylene pigments such as (manufactured by Bayer) can be used.

The thickness of the charge generation layer is suitably about 0.05 to 2 .mu.m, preferably 0.1 to 1 .mu.m.

The charge generation layer can be formed by dispersing the charge generation substance described above in a suitable organic solvent, coating the dispersion, and drying the dispersion. As the organic solvent, benzene, toluene, xylene, methylene chloride, dichloroethane, monochlorobenzene, dichlorobenzene, ethyl acetate, butyl acetate, methyl ethyl ketone, dioxane, tetrahydrofuran, cyclohexanone, methyl cellosolve, ethyl cellosolve, etc. are used alone or in combination. be able to. Furthermore, a resin binder to be described later can be used if necessary.

The charge transfer layer can be formed by dissolving a charge transfer substance and a resin binder (described later) in a suitable organic solvent, coating the solution on the charge generation layer, and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added if necessary.

Charge transfer substances include poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives. , imidazole derivatives, triphenylamine derivatives, 9-(p-diethylaminostyryl)anthracene, 1,1-bis-(4-dibenzylaminophenyl)propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene Examples include electron-donating substances such as derivatives.

As the organic solvent at this time, tetrahydrofuran, cyclohexanone, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, etc. can be used.

The appropriate thickness of the charge transfer layer is about 5 to 100 μm.

Examples of the resin binder used in the charge generation layer or charge transfer layer include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, styrene-methyl methacrylate copolymer, polyester, and polystyrene. Vinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, polymethacrylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyltoluene, polysulfone , acrylic resin, silicone resin, epoxy resin,
Examples include thermoplastic or thermosetting resins such as melamine resins, urethane resins, phenolic resins, and alkyd resins.

In addition, the electrosensitive support as used in the present invention is intended to supply charges of opposite polarity to the charged charges to the substrate side, has an electrical resistance of 10 gΩ(1) or less, and has an intermediate layer,
Any material that can withstand the conditions for charge generation and charge transfer layer formation can be used. Examples of these are AQ,
Vacuum evaporation, By methods such as sputtering and spray painting,
AQ, Ni, Cr, Zn, stainless steel, carbon, Sn
Examples include those coated with an electrically conductive substance such as O2 or In2O3 and subjected to conductive treatment.

Furthermore, in the present invention, between the support and the photosensitive layer,
Provide an intermediate layer of polyamide, polyvinyl alcohol, polyvinyl acetal, polyacrylic acid, polyhydroxymethacrylate, epoxy resin, etc., or a white pigment layer consisting of the above resin and a white pigment such as titanium oxide, zinc oxide, magnesium oxide, barium sulfate, lithopone. You can also do it.

〔effect〕

Since the electrophotographic photoreceptor of the present invention has the above configuration,
Even after repeated use, the sensitivity does not decrease and the increase in residual potential is suppressed, giving clear copied images without background smudges.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that both parts and 2 are based on weight.

Example 1 The following charge transfer layer coating solution was applied to an aluminum cylinder on a conductive substrate by dip coating, and then dried under the drying conditions shown in Table 1 to form a charge transfer layer with a thickness of 22 μm. Samples were prepared for each.

[Charge transfer layer coating liquid]

785 parts of dichloromethane Next, a charge generation layer coating solution prepared in the following manner was applied onto the charge transfer layer of each sample using a spray coating method,
Drying was carried out at 120° C. for 10 minutes to produce an electrophotographic photoreceptor having a charge generation layer with a thickness of 2 to 3 μm.

[Charge generation layer coating liquid]

[Liquid A] 20 parts [Liquid B] 20 parts [Liquid C] 0.12
15 parts cyclohexanone [Liquid A], [Liquid B] and [Liquid C] are as follows.

[Liquid A]

Cyclohexanone 95 parts The above ingredients were dispersed in a ball mill, and 66.5 parts of cyclohexanone was added to let it down to contain 3% of the charge generating material.

[Liquid B] Polycarbonate resin (Teijin C-1,400)
10 parts Cyclohexanone 90 parts [Liquid C] Cyclohexanone 99 parts These samples were mounted on an electrostatic tester rSP-428 model (manufactured by Kawaguchi Denki Seisaku Kaisha), and the following characteristic tests were conducted.

That is, the charging potential was controlled to be 800 volts, and then the illuminance on the surface of the photoreceptor was set to 4.5L.
The color temperature of the tungsten balance is 2854 at ux.
The amount of exposure required to attenuate the surface potential of the photoreceptor to 80 volts by irradiating light at
ec) was calculated.

Furthermore, the surface potential of the photoreceptor 30 seconds after irradiation with the same light was defined as the residual potential VR.

Then, the same measurement was performed after copying 2000 sheets.

The amount of residual solvent in the photoreceptor was also measured under the following conditions. The results obtained are shown in Table-1.

[Method for measuring amount of residual solvent (dichloromethane)] The amount of residual solvent in the photoreceptor was calculated from the calibration curve of the standard solution below.

- Measurement conditions - Example 2 The dichloromethane, the solvent of the charge transfer layer coating solution used in Example 1, was replaced with tetrahydrofuran, and the film thickness was increased to 2.
Electrophotographic photoreceptors with Nα9 to 13 were prepared in the same manner as in Example 1, except that the thickness was 2 μm and the drying conditions were as shown in Table 2. The results are shown in Table-2.

Note that the amount of residual solvent was measured under the following conditions.

[Method for measuring the amount of residual solvent (tetrahydrofuran)] The amount of residual solvent in the photoreceptor was calculated from the calibration curve of the standard solution below.

1. Measurement conditions 1.

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor comprising a photosensitive layer formed by laminating a charge transport layer and a charge generation layer on a conductive support,
A photoreceptor for electrophotography, characterized in that the photosensitive layer contains 200 to 8000 ppm of an organic solvent component.