JPH0727264B2 - Multilayer photoconductor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate type photoconductor in which at least a charge generation layer and a charge transport layer are provided on a substrate.

2. Description of the Related Art Conventionally, selenium, zinc oxide, titanium oxide, selenium, as a photosensitive material for forming a photosensitive layer of a photoreceptor used in electrophotography,
Inorganic photoconductive materials such as cadmium sulfide have been used. However, these have a number of drawbacks, and in general, many of them are highly toxic, and there are also problems with moisture resistance and the like.

On the other hand, the photoreceptor using the organic photoconductive material has
Although it is excellent in terms of lightness and price, it still has problems in terms of sufficient sensitivity, durability and stability due to environmental changes.

In recent years, a multi-layer type photoconductor in which the functions of charge generation and transport are separated has been proposed, and the drawbacks of conventional photoconductors using organic photoconductive materials have been greatly improved, resulting in the practical use of organic photoconductors. , Is making rapid progress.

The laminated photoreceptor has a structure in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive substrate such as metal aluminum or copper.

These laminated type photoreceptors have charge retention, high sensitivity, repeated stability, dielectric breakdown resistance, abrasion resistance, durability, moisture resistance,
It is required to satisfy the basic conditions such as transferability, cleaning property and storage stability.

Further, the laminated type photoconductor is also used for a laser printer, and high image reliability and repetitive stability at the time of reversal development are required.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a conventional laminated type photoreceptor, particularly when the charge generation layer is a dispersion film in which a pigment is dispersed in a resin, adhesiveness to a substrate, coating property, charge transport layer from the substrate There were various problems such as charge injection into the. These have a serious problem of the conductive substrate, and it is necessary to improve defects on the substrate, charge injection property and adhesive property.
As measures against these problems, JP-A-58-30757 and JP-A-58-957 have been adopted.
No. 44 proposes a photoreceptor using an undercoat layer. Further, in JP-A-58-14841, JP-A-59-41360, and JP-A-61-140947, there have been proposed photoreceptors obtained by subjecting an aluminum support to an alumite treatment.

However, the electric resistance of the undercoat layer disclosed in JP-A-58-30757 and JP-A-58-95744 is greatly affected by changes in the external environment, particularly humidity in the atmosphere.
Fog may occur at low humidity. Further, when the electric resistance is high, a charging potential is applied to the undercoat layer, causing fog in the image as a so-called residual potential. The undercoating layer is required to have such various characteristics, but it is difficult to obtain a good one when only a single resin is used. Therefore, the film thickness of the resin film is made extremely thin, or conductive powder (metal powder or the like) is dispersed in the resin as needed. However, reducing the film thickness of the resin layer has a drawback that the performance as an undercoat layer is not sufficient, while in the undercoat layer in which the metal powder is dispersed, the metal particles are coarse, There is a drawback that the surface property of the pulling layer is lowered.

In particular, even if the conventional laminated type photoreceptor is applied to a laser printer, it is not so effective for the minute black spots generated on the white paper portion during the reversal development.

On the other hand, JP-A-58-14841 discloses that an aluminum support is
Disclosed is a photoreceptor including a step of immersing in water having a specific resistance of 10 ⁶ Ω · cm or more and a temperature of 60 ° C. or more. JP 59-
No. 41360 uses a phthalocyanine vapor deposition film as a charge generation layer,
Disclosed is a photoreceptor in which an aluminum support is treated to form a non-sealing anodized film of at least 4 μm. JP-A-61-140947 discloses a photoconductor in which a barrier layer and a porous layer are provided by previously subjecting the aluminum support to an alumite treatment when forming a-Si on the surface of the aluminum support. . However, in the technologies disclosed in these documents, when the charge generation layer is a dispersion film, no improvement is shown for black spots generated during reversal development, and no description is made conditionally.

An object of the present invention is to provide a photoconductor in which the above drawbacks are eliminated, and specifically to provide a photoconductor having excellent electrophotographic properties by using a specific conductive substrate. .

Means for Solving the Problems The present invention relates to a photoreceptor having at least a charge generation layer and a charge transport layer on an aluminum substrate, wherein the charge generation layer comprises an organic pigment dispersed in a binder resin. The substrate has an alumite layer, the thickness of the barrier layer of the alumite layer is 100 ~ 1000Å, the thickness of the porous layer is 1 ~ 15μ
The present invention relates to a reversal development type laminated photoreceptor for a laser printer having m and an impedance of 1 to 200 KΩ.

The photoconductor composed of the substrate having the alumite layer of the present invention is a good one in which the generation of black spots, which is a problem in a laser printer for reversal development, is suppressed.

The alumite-treated aluminum substrate is effective for improving the adhesiveness and the like, but in particular, it needs to be manufactured under the condition that good characteristics can be obtained in terms of photosensitivity.

Generally, the alumite layer consists of two layers, a barrier layer and a porous layer, on the substrate. As the role of the alumite layer,
Adhesiveness, charge injection prevention, and rectification are required.

In order for the alumite layer to have the property of preventing charge injection, it is necessary to make the barrier layer thick. However, if the barrier layer is made too thick, the residual potential will increase, which will cause a decrease in sensitivity and cause a Caribbean or the like to occur during repetition.

Therefore, the thickness of the barrier layer is 100 to 1000Å, preferably 100 to 500Å.

The porous layer needs to have a certain thickness, not only to impart adhesiveness, but if it is too thick, it causes an increase in residual potential and an increase in dark current. Therefore, the thickness of the porous layer is 1 to 15 μm, preferably 2 to 10 μm, more preferably 2
˜8 μm is desirable.

More preferably, the alumite layer of the present invention is partially sealed. Partially means that only the surface of the porous layer is sealed with the voids remaining in the porous layer. The sealing degree can be adjusted by the sealing treatment time, the concentration of nickel acetate, the temperature of the solution, and the like.
Impurities such as Ni that entered the alumite layer by the partial sealing treatment allow electrons to flow smoothly, while the barrier property of the alumite layer prevents the injection of holes themselves, resulting in good rectification. can get.

The photoreceptor of the present invention uses an aluminum support, which is processed into a suitable shape such as a cylindrical shape, as a support of the photoreceptor as an anode, and performs electrolytic treatment using sulfuric acid or oxalic acid as an electrolytic solution. An alumite layer is formed on the surface. The thickness of the barrier layer can be adjusted by adjusting the electrolysis voltage, and the thickness of the porous layer can be adjusted by adjusting the electrolysis time.

The sealing treatment is performed by treating with an aqueous solution of nickel acetate. The concentration of nickel acetate is preferably 1 to 15 wt%, preferably 5 to 10 wt%, and the temperature of the aqueous solution is preferably 50 to 80 ° C.

The alumite layer of the photoreceptor of the present invention contains crystalline aluminum oxide (Al ₂ O ₃ ) and amorphous Al ₂ O ₃ . Crystalline Al ₂ O ₃ is effective for preventing charge injection, and amorphous Al ₂ O ₃ is effective for adhesion and adhesion to the photosensitive layer. If the amount of crystalline Al ₂ O ₃ that has the effect of preventing charge injection increases, the residual potential rises, causing a decrease in sensitivity and the occurrence of fog during repeated use.Also, the amount of amorphous Al ₂ O ₃ is too large. However, the same result will be brought about.

From the above, the amount and amorphous amount of Al ₂ O ₃ crystalline Al ₂ O ₃ of alumite layer, the molar ratio of amorphous Al ₂ O ₃ on crystalline Al ₂ O ₃ is 50 to 1500, preferably When it is 100 to 1200, the photosensitivity characteristic, the image characteristic and the adhesiveness are the best.

The amounts of crystalline Al ₂ O ₃ and amorphous Al ₂ O ₃ can be adjusted by adjusting the electrolysis voltage, electrolysis time, electrolysis density, and electrolytic bath composition.

The charge injection prevention property is also greatly affected by impurities in the alumite layer. If a large amount of iron, copper, silicon, or the like is contained as an impurity, the charge injection prevention and the rectifying property are greatly affected. In the present invention, it is particularly preferable to suppress impurities such as silicon, copper and iron which are considered to be the cause of charge injection as much as possible. In addition, when magnesium and silicon are contained, it is extremely harmful magnesium-
A silicon alloy is formed. For this reason, it is desirable that the amount of the metal is as small as possible, but if it is too small, the machinability and workability of the aluminum substrate deteriorate.

From this viewpoint, magnesium is contained in the alumite layer as impurities in an amount of less than 10% by weight, iron in an amount less than 200 ppm, copper in an amount less than 1% by weight, silicon in an amount less than 1% by weight, and other metals in a total amount of less than 1% by weight. . By doing so, the injection preventive property is not adversely affected, and the one having excellent photoconductor characteristics, image characteristics, adhesiveness and the like can be obtained.

The amount of impurities in the alumite layer in the present invention can be adjusted by the material of the aluminum alloy and the alumite treatment conditions.

In the alumite layer of the present invention, magnesium, iron, copper,
Metals other than silicon, such as manganese, chromium, zinc, and titanium, may be contained unless they cause charge injection, but the amount is preferably 0.1% by weight or less.

The amount of metal in the alumite layer can be quantified by Auger electron spectroscopy analysis and emission spectroscopy analysis.

Furthermore, the impedance of the alumite layer is 1 to 200K.
By adjusting the range of Ω, preferably in the range of 1 to 100 KΩ, it is possible to improve the characteristics of the photoconductor, which are said to be deteriorated by the alumite treatment, such as an increase in residual potential and deterioration of repetitive characteristics.

The impedance can be adjusted by adjusting the electrolysis time or the electrolysis voltage, or by performing a sealing treatment. If the impedance of the alumite layer is too low, it will not serve as an injection preventing layer,
The charge retention ability is low, and many black spots occur during reversal development. On the contrary, if the impedance of the alumite layer is too high, the initial residual potential becomes high, leading to a decrease in sensitivity,
Further, the repetitive copying causes an increase in residual potential, causing fog in the image.

The impedance can be measured by the standard method according to ASTM-B457-67. That is, the method is a method of measuring using an AC impedance bridge, using 35% saline as an electrolyte, measuring at 1000 Hz, and repeatedly measuring the test several times at other places. It is an average.

The impedance of the coating is proportional to the thickness of the coating, inversely proportional to the measurement area, and affected by the measurement temperature. In the present invention, the impedance of the alumite layer coating is a measurement area of 0.129 cm ² ,
It is converted into impedance value under the condition of measurement temperature of 25 ° C.

Examples of the organic pigment used in the charge generation layer of the present invention include various azo pigments, perylene pigments, phthalocyanine pigments,
Examples thereof include polycyclic quinone pigments, indico pigments, and quinacridone pigments.

The charge generation layer is prepared by dissolving a binder resin using a suitable solvent and adding the above pigment to the binder resin in an amount of 10 parts by weight based on 100 parts by weight of the binder resin.
~ 200 parts by weight, and 0.1 ~ 1μ of the solution dispersed by ball mill, vibration mill, sand mill, roll mill, etc.
It is obtained by applying to m.

The charge transport layer includes pyrazoline, triphenylmethane, oxadiazole, carbazole, hydrazone, styryl,
Dissolving electron-donating substances consisting of derivatives such as imidazole and substances with charge-transporting properties such as electron-accepting substances such as trinitrofluorenone, tetranitroxanthone, tetracyanoethylene, tetracyanoquinodimethane in film-forming resins It can be obtained by coating and coating to 5 to 30 μm.
Examples of the binder resin used in the charge generation layer and the charge transport layer include polyester, polycarbonate, polymethacrylic acid ester, polyvinyl butyral, silicone resin, epoxy resin, melamine resin, urethane resin, polystyrene and the like.

The photoreceptor of the present invention may have a structure in which a charge generation layer and then a charge transport layer are laminated on an alumite-treated aluminum substrate, or a structure in which a charge transport layer and then a charge generation layer are laminated. Further, those photoreceptors may have a surface protective layer or an intermediate layer, if necessary.

Hereinafter, the present invention will be described with reference to examples. In the examples, all "parts" are "parts by weight" unless otherwise specified.

Example 1 As a conductive substrate, aluminum subjected to surface treatment by lathing was used, and an alumite layer was formed on the surface of the conductive substrate by an electrolytic bath containing sulfuric acid 15 vol% at a liquid temperature of 20 ° C. ± 1 ° C. . The impedance was measured by the method of ASTM-B457-67 using a Z-Scope manufactured by Twin City.

The characteristics of the alumite layer are shown below.

Film thickness: 6μ Barrier layer thickness: 300Å Porous layer thickness: 6μ Amorphous Al ₂ O ₃ / Crystalline Al ₂ O ₃ : 190 Impedance: 60KΩ Impurity concentration in alumite layer: Mg: 0.4% by weight, copper: 0.01% by weight, iron: trace amount, silicon: 0.
05% by weight Next, 1 part of a bisazo pigment represented by the following general formula as a charge generation layer thereon, a polyester resin (Toyobo Co., Ltd.)
(Byron 200) (1 part) and cyclohexane (90 parts) were dispersed by a sand grinder, and then a charge generation layer having a thickness of 0.5 μm was formed.

A hydrazone compound is formed on this charge generation layer. And 10 parts of a polycarbonate resin (manufactured by Teijin Kasei Co., Ltd .; Panlite K1300) dissolved in 100 parts of tetrahydrofuran to form a charge transport layer by applying a coating solution to a film thickness of 15 μm after drying. Then, an electrophotographic photosensitive member was produced.

Examples 2 to 4 In the same manner as in Example 1, an alumite layer having the following characteristics, the impedance of which is 10 KΩ, 112 KΩ, and 174 KΩ, is formed, and the charge generation layer and the charge are formed thereon in the same manner as in Example 1. A transport layer was formed to prepare an electrophotographic photosensitive member.

Comparative Example 1 An electrophotographic photosensitive member was produced in exactly the same manner as in Example 1 except that an alumite layer having the following characteristics was provided. The characteristics of the alumite layer are shown below.

Film thickness: 0.5μ Barrier layer thickness: 80Å Porous layer thickness: 0.5μ Amorphous Al ₂ O ₃ / Crystalline Al ₂ O ₃ : 60 Impedance: 0.4KΩ Impurity concentration in alumite: Mg: 0.5wt% Copper: 0.01 wt%, Iron: 150 PPM, Si: 0.2 wt% Comparative Example 2 An electrophotographic photosensitive member was produced in exactly the same manner as in Example 1 except that an alumite layer having the following characteristics was provided. The characteristics of the alumite layer are shown below.

Film thickness: 21μ Barrier layer thickness: 1500Å Porous layer thickness: 21μ Amorphous Al ₂ O ₃ / Crystalline Al ₂ O ₃ : 120 Impedance: 300KΩ Impurity concentration in alumite: Mg: 1% by weight, copper: 0.1% by weight, iron: 100 PPM, Si: 0.3% by weight Example 5 Aluminum which has been subjected to surface treatment by lathing is used as a conductive substrate, and the surface thereof has a liquid temperature of 20 ° C. ± 1 ° C. sulfuric acid.
An alumite layer was formed on the surface in an electrolytic bath containing 15 vol% to obtain an alumite layer having the following characteristics.

The characteristics of the alumite layer are shown below.

Film thickness: 8μ Barrier layer thickness: 180Å Porous layer thickness: 8μ Amorphous Al ₂ O ₃ / Crystalline Al ₂ O ₃ : 400 Impedance: 24KΩ Impurity concentration in alumite: Mg: 0.5% by weight, copper: 0.04% by weight, iron: 100PPM, Si: 0.1% by weight Next, 1 part of metal-free phthalocyanine (manufactured by Toyo Ink Co., Ltd.), 1 part of polystyrene and 50 parts of cyclohexanone were placed in a ball mill pot and dispersed for 24 hours. , A photosensitive coating solution was obtained, which was coated and dried to a thickness of 0.
A 5 μm charge generation layer is formed. On this charge generation layer, 10 parts of polycarbonate resin 10 parts of tetrahydrofuran
A coating solution dissolved in 100 parts was applied so that the film thickness after drying was 15 μm to form a charge transport layer, and an electrophotographic photosensitive member was produced.

Comparative Example 3 A photoconductor was prepared in exactly the same manner as in Example 1 except that an aluminum substrate that had not been subjected to alumite treatment was used. The impedance of this product was 0.01 KΩ.

The obtained photoreceptor was corona charged using a powder image transfer type copying machine (Ep407Z manufactured by Minolta Camera Co., Ltd.), and the initial potential was reduced to 1/2 when the initial surface potential (V ₀ ) was set to −750V. Exposure dose E1 / 2 (lux · sec) required for 5 seconds, decay rate of initial potential when left in the dark for 5 seconds DDR ₅ (%) and residual potential Vr
(V) was measured. The results are shown in Table-1.

Further, the black spots on the white paper portion on the image when the reversal development was carried out at V ₀ = −750V and the developing bias Vb = −500V were measured. The results are shown in Table-2. In Table 2, ○ means good
X means that there is a problem, and XX means that it is very bad.

It has no effect if the impedance is low. If the impedance is too high, the residual potential increases and fogging occurs.

EFFECTS OF THE INVENTION According to the laminated type photoreceptor of the present invention, the adhesiveness between the charge generating layer and the aluminum support can be dramatically improved, and the rectifying function of the alumite layer can prevent charge injection. When the reversal development is performed, black spots, which are a problem on a white paper portion, are suppressed during reversal development, the coatability of the pigment-dispersed coating liquid for the charge generation layer is improved, and good electrophotographic characteristics are obtained.

Claims (1)

[Claims] 1. A laminate type photoreceptor having at least a charge generation layer and a charge transport layer on an aluminum substrate, wherein the charge generation layer comprises an organic pigment dispersed in a binder resin, and the aluminum substrate has an alumite layer. The barrier layer of the alumite layer has a thickness of 100 to 1000Å and the porous layer has a thickness of 1 to 1
Laminate type photoreceptor for reversal development type laser printer with 5 μm and impedance of 1 to 200 KΩ.