JPS5882251A - Electrophotographic receptor - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic receptor free from deterioration of an image, especially, lack of density and bleeding, and superior in durability, by forming on a photosensitive layer a protective layer contg. an electron donor in the binder resin, higher in content near the photosensitive layer than near the surface. CONSTITUTION:A protective layer is provided on the surface of a photosensitive layer formed on a conductive substrate. The protective layer contains 1-50wt% electron donor based on the total layer, such as alkyl-substd. ferrocene, e.g., methylferrocene, or triphenylmethane, in a binder resin, such as polystyrene or polyester, its content being <=15wt% near the surface and higher near the side of the photosensitive layer, thus permitting deterioration of the protective layer due to charging, exposure, developing, image transfer, destaticization, and cleaning of the photosensitive layer to be prevented, especially, deterioration due to high humidity in the environment and ozone produced by corona discharge to be avoided, and consequently, a photoreceptor excellent in durability to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor having a surface protective layer.

Conventionally used electrophotographic photoreceptors are those formed by vapor-depositing S, Ss-T@ alloy, 5e-As alloy, etc. as a photosensitive layer on a conductive substrate, or those formed by vapor-depositing S. A typical example is one coated with an organic photoconductor such as 2t4°7-dolinitrofluorenone.

However, when the photoreceptor is repeatedly used, it is difficult to damage it due to peeling of the transfer paper or cleaning/drying of residual toner, and the photosensitive layer is easily worn out at a relatively early stage before the characteristics deteriorate. The photoreceptor had to be replaced. In order to improve this point, it is known to provide a surface layer on the surface of the photoreceptor. One of the surface layers is an insulating layer made of a material with relatively high electrical insulation.

This insulating layer has the advantage of being able to be made thick and having a high mechanical strength.However, in order to use this type of photoreceptor repeatedly, for example, first long-term charging → reverse polarity secondary charging is required. →Special latent image forming processes such as image exposure or first Teiden →secondary charging simultaneous image exposure →uniform exposure are required, and these processes are carried out twice or more in one copying process. This necessitates a charging process of 100 volts, which complicates the device, resulting in unstable characteristics and increased costs.

In addition, there is no need for the special latent image formation process mentioned above, and charging→
There is a protective layer as a surface layer that can be used in the so-called Carlson process of imagewise exposure. This protective layer needs to have low insulation to prevent charge from accumulating on the surface or inside the protective layer.

The method that has been adopted so far is to add quaternary ammonium salts, etc. to the protective layer, but the conductivity of these materials generally fluctuates widely due to moisture absorption, and the conductivity of the protective layer decreases when dry. When the humidity is high, the conductivity increases more than necessary, causing charge to move laterally, causing blur in the image.

Furthermore, since the conventional protective layer is used in the Carlson process, it must be relatively thin, with a thickness of several microns or less, which is difficult to satisfy in terms of mechanical strength, and in order to achieve low insulation. The protective layer is colored by the substances added to it,
This had an unfavorable effect on the spectral sensitivity of the photoreceptor. Attempts have also been made to add electron-donating substances to the protective layer, and in this case, compared to the case of adding quaternary ammonium salts, it is possible to obtain a protective layer with a relatively thick layer. Although it is possible to obtain a protective layer with little change in electrical conductivity due to changes in humidity, etc., when copying
Do you have white spots or blurred images? have.

The present invention relates to a surface protective layer of an electrophotographic photoreceptor used in the above-mentioned Carlson process, and an object of the present invention is to provide a surface protective layer that does not cause white spots or bleeding.

An object of the present invention is to provide an electrophotographic photoreceptor in which a substrate, a photosensitive layer, and a protective layer containing an electron-donating substance in a binder resin are successively laminated. This can be achieved by using an electrophotographic photoreceptor having a protective layer that is lower on the surface side than on the photosensitive layer side.

In the protective layer used in the present invention, the content of the electron donating substance is different between the surface side of the protective layer and the substrate side, that is, the photosensitive layer side, and the content on the surface side is lower than that on the photosensitive layer side.
have a slight

The content of the electron-donating substance in the protective layer may decrease continuously from the photosensitive layer side to the surface side of the protective layer, or may decrease only on the surface side of the protective layer, It is sufficient that the content of the electron donating substance in the surface side portion is low.

The surface side portion of the protective layer as used herein refers to a portion extending from the surface of the protective layer to 1 μm, preferably 0.5 μm. The content of the electron-donating substance in the surface side portion is lower than the content of the entire protective layer, and the average content in the surface side portion is 15% by weight or less.

Further, the electron donating substance may be uniformly dispersed on the surface, or may be dispersed in a state where the area near the interface with the free surface contains no or almost no electron donating substance. , as long as the surface side portion satisfies the content as described above.

Such a protective layer having a low content of electron-donating substance in the surface side portion can be created by various methods. For example, after applying a uniform mixed solution of a binder resin and an electron-donating substance onto the photosensitive layer and drying it to form a coating M7 with a uniform concentration distribution, electron-donating material can be applied without dissolving the binder resin. Either the surface of this film is washed with a solvent that dissolves the electron-donating substance and the electron-donating substance on the surface side of the protective layer is eluted, or two solutions with different contents of the electron-donating substance are prepared, and the initial content is By applying a solution with a high content to the photosensitive layer and then further applying a solution with a low content to form a protective layer with a two-layer structure, it is possible to obtain a protective layer with a low content of electron-donating substances on the surface side. can.

As the electron-donating substance used in the protective layer of the present invention,
Triphenylmethane, triphenylamine, pyrazoli/
, oxadiazole, hydrazo/, carbazole, phenazine, na7tase/, fena/tre/, violantre/
, anthracene, naphtali/, billet/, quinoxaline,
Acridine, bire/, cuproine, zena/droline,
neofugloin, triazole, tetrazole, thiadiazole, bathocguloin, bathophenandroline, bikinori/, triazine, nigrosi/, pyrrole, ferrocene, titanose/, dibenzenechromium, and their multimeric derivatives, such as fatty acids in these electron-donating molecules. family,
Examples include those with substituents such as aromatics, and those with nitrogen content quaternized to form salts.

Among them, ferrocephs, especially 7-erocenes substituted with alkyl groups such as methylferrocene, ethylferrocene, butylferroce/, propylferrocene, amylferroce/, dimethyl 7-ero7/, and decamethylferro-7/, are relatively effective when used as a protective layer. This is preferred because it provides high transparency and stable electrical conductivity. These electron-donating substances may be used alone or in a mixture of two or more, and are used in an amount of 1 to 50% by weight based on the entire protective layer.

The binder resin used together with the electron-donating substance in the protective layer is substantially transparent to the wavelength of light used for exposure,
Examples include resins that have relatively high electrical insulation, high mechanical strength such as abrasion resistance, and good adhesion to the photosensitive layer.

Examples of such binder resins include polystyrene/, polyacrylate, polymethacrylate, styrene-acrylic ester copolymer, styrene-methacrylic ester copolymer, polyamide, polyester, polyurethane, polycarbonate, polyvinyl acetal, and polyvinyl butyral. , ethylcellulose, nitrocellulose,
Alternatively, use cellulose acetate, etc.

Among these, it is more preferable to use a binder resin capable of forming a charge transfer complex with an electron donating substance because a protective layer with stable electrical conductivity can be obtained. As the binder resin, for example, poly-
Mention may be made of esters, polyurethanes/polycarbonates.

%, the polyester is represented by the general formula [where n is an integer of 20 to 200, R1 and R8
are each independent of each other, and include a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a substituted alkyl group,
or represents an aryl group such as phenyl or naphthyl group, or a substituent of such aryl group with a halogen atom or an alkyl group having 1 to 5 carbon atoms, R3, R4 and R6 are each independent of each other, and a hydrogen atom , represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogen-substituted product of these alkyl groups. ] is preferred.

These binder resins may be used alone or in a mixture of two or more, and are used in an amount of 50 to 99% by weight based on the entire protective layer.

Various additives may be added to the protective layer, such as adhesives to improve adhesion, leveling agents to smooth the surface, or electron-accepting substances to improve electrical properties.

The protective layer used in the present invention is formed directly on the photosensitive layer or via an intermediate layer. The thickness of the protective layer is 1 to 20μ, preferably 3 to 157g,
It is less durable than lj, and if it is thicker than 20μ, the resolution decreases and background stains increase.

The photosensitive layer is a layer that has both charge generation ability and charge transport ability by light irradiation, and may be a single layer or a stack of two or more layers. Examples of photoconductive substances forming the photosensitive layer include selenium, Selenium/-tellurium, selenium-arsenic, -k V 7- f
# Inorganic substances such as h-arsenic, zinc oxide, titanium oxide, cadmium sulfide, cadmium selenide, zinc sulfide, amorphous clico/, polyvinyl carbazole and its derivatives, aromatic amines, azo pigments, 7-talocyanide/, oxazole , triazole, imidazole, brompyrene, and other organic substances. This photosensitive layer is formed by a known method.

An intermediate layer may be provided between the protective layer and the photosensitive layer. This intermediate layer may include an adhesive layer that improves the adhesion between the protective layer and the photosensitive layer, or a charge injection blocking layer that prevents charges on the surface of the protective layer from being injected into the photosensitive layer.

The substrate used in the present invention may be a conductive material such as aluminum, zinc, brass, copper, tin, nickel, stainless steel, or polyvinyl alcohol, or a combination of the above-mentioned conductive materials such as paper, plastic, glass, etc. Materials such as composites can be used, and are used in the form of sheets, belts, or drums. A barrier layer, such as a thin layer of aluminum oxide or a thin layer of glass, may be provided between the photosensitive layer and the substrate.

In the electrophotographic photoreceptor of the present invention, a substrate, a photosensitive layer, an intermediate layer and a protective layer are sequentially laminated as necessary, and the protective layer contains an electron-donating substance and a binder resin, and the content of the electron-donating substance is low. The surface area of the protective layer is configured to be lower than the photosensitive layer side, and this configuration prevents white spots in the image or blurring of the image that occur during copying. .

The detailed reason for this effect is not clear.
However, if the electron-donating substance is exposed on the surface of the protective layer and its amount is large, the electron-donating substance undergoes chemical and physical alteration during the copying process, and the electrical properties of that part change. This is thought to be due to the fact that in the photoreceptor of the present invention, the amount of electron-donating substance present on the surface portion of the protective layer is small, making it less susceptible to such deterioration.

Furthermore, the photoreceptor of the present invention has significantly improved durability. Compared to a protective layer that uniformly contains an electron-donating substance, the protective layer according to the present invention contains a large amount of binder resin component in the surface portion, so it is difficult to take advantage of the mechanical properties of the binder resin itself. I can do it,
The book can be highly durable against the various mechanical abrasions that occur during the copying process.

Furthermore, the electrical conductivity required as a protective layer is transparent, etc.
Needless to say, I am satisfied.

In particular, when conventional photoreceptors with a protective layer are used repeatedly, the residual potential increases, and background stains increase.
However, with the photoreceptor of the present invention, such development does not occur and clear copies without background stains or blurred images can be obtained.

In the electrophotographic photoreceptor of the present invention constructed in this manner, electrostatic latent*V is formed by uniform charging and image exposure, and this latent image is developed by a magnetic brush developing device or the like to obtain a toner image. After the image is transferred to transfer paper, it is fixed to obtain a copy.

On the other hand, the photoreceptor after the transfer is charged and cleaned and used for new copying.

The present invention will be explained below using comparative examples and examples.

Example l Vacuum deposition of selenium on an Al2 Pig substrate to a thickness of 60μ
A photosensitive layer was formed. A solution of 7elose/2αt and polycarbonate 809′ dissolved in chloroform was applied onto the photosensitive layer by a dipping method and air-dried to form a protective layer with a thickness of 15 μm.

Then, the surface of the protective layer was washed with ingropanol.

The surface of the protective layer of the photoreceptor thus formed had a content of 13.6% by weight, which was lower than that on the substrate side of the protective layer.

In order to test the electrostatic properties, image properties and durability of this photoreceptor, the copying machine t'I@h uniform charging, image exposure, development, transfer,
By repeating static electricity removal and cleaning/cleaning, the initial charging potential,
Residual potential, resolving power, white areas in the image, artist's error 2. Durability was determined. The results are shown in Table 1. Comparative Example l For comparison, after the protective layer was formed, the protective layer was exposed in the same manner as in Example 1, except that it was formed without cleaning the surface of the protective layer with a solvent. created a body. The ferrocef content was uniform throughout the thickness of this photoreceptor+i protective layer. As in Example 1, this photoreceptor VEAL,! ! The results shown in 1 were obtained.

Example 2 Example 1 except that a solution of dimethylferrocene 209 and polycarbonate 80f dissolved in chloroform was used.
A photoreceptor was prepared and tested in the same manner as described above. The results are shown in Table 1.

Example 3 A solution of decamethylferrocene 229 and U polymer (manufactured by Unideka) 78t dissolved in tetrachloroethane VC was applied onto the photosensitive layer by a spray method and air-dried to form a protective layer with a thickness of 10 μm. A photoreceptor was prepared and tested in the same manner as in Example 1, except that it was washed with methyl alcohol. The results are shown in Table 1.

Example 4 n-butylferrocene 20f and polycarbonate 80f
A photoreceptor was prepared and tested in the same manner as in Example 3, except that the surface of the protective layer was washed with methyl alcohol using a solution dissolved in tetrachloroethane. The results are shown in Table 1.

Example 5 Sere 7ya-vacuum deposition on aluminum pipe substrate to thickness 6
A photosensitive layer of 0 μm was formed. A solution dissolved in 80fY tetrachloroethane (ferro 5c/20f and polycarbonate) was applied to the photosensitive layer by spraying and air-dried to a thickness of 10
Next, a solution of 7 Elose 713f and polycarbonate 87f' dissolved in tetrachloroethane was applied onto the film by spraying and air-dried to a thickness of 0.
．． A film of 5μ was formed.

The protective layer formed in this way has a two-layer structure, the lower layer (substrate side) 10 μ is the weight percentage, the upper layer (surface side) 0.5 μ is 1
It had a ferrocene content of 3% by weight. A test was conducted in the same manner as in Example 1 using this photoreceptor. Results 7 are shown in Table 1.

As is clear from the results in Table 1, when an electron-donating substance is added to a binder and applied to the surface of the photosensitive layer so that the concentration is 15 weight or less on the surface of the protective layer, the surface concentration becomes 15 weight - It is possible to completely prevent image deterioration, especially white spots and blurring in images, which occur when the above conditions exist. Furthermore, the durability of the protective layer is clearly improved. Such an effect is particularly noticeable in a humid environment or an environment where the ozone concentration is increased due to corona discharge or the like.

According to the present invention, the practical life of a photoreceptor having a protective layer in which an electron-donating substance is added to a binder is significantly extended.

Claims (1)

[Claims] 1) In an electrophotographic photoreceptor having a protective layer on the photosensitive layer containing an electron-donating substance in a binder resin, the content of the electron-donating substance in the protective layer is It was made to be lower on the surface side than on the photosensitive layer side! -Characteristic electrophotographic photoreceptor. 2) The content of electron donating substance is 15 on the surface side of the protective layer.
Claim 1 characterized in that it is less than % by weight.
The electrophotographic photoreceptor described in . 3) The electron-donating substance is at least one compound selected from 7-elose/and 7-rose/S conductors Y4
The electrophotographic photoreceptor according to claim 1, which is defined as I.