JPH09230617A - Electrophotigraphic photosensitive member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-sensitive member for electrophotography which can produce a high picture quality even in an electrophotographic process requiring a long time from electrostatic charge to the development. SOLUTION: A photo-sensitive member for electrophotography of inverted development type is to be used in an image forming process including electrostatic charge, photo-exposure, development, and transcription and is composed of an electroconductive support made of aluminum or its alloy, an intermediate layer consisting of an aluminum anode oxidated film, an electric charge genarating layer, and an electric charge conveying layer. The intermediate layer is used in an image forming process in which the product of the resistance value (R) measured at a frequency of 100Hz and the electrostatic capacity (C) ranges between 2 and 5msec and the time from charging on the photo-sensitive member to the development is more than 400msec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member suitable for an electrophotographic process that requires a long time from charging to development.

[0002]

2. Description of the Related Art Electrophotographic technology has been developed in the field of copying machines, but recently it has rapidly spread due to its high image quality, high speed, and quietness, which are incomparable to those of conventional machines. With remarkable progress in signal data processing systems, laser beam printers, digital copiers, etc., have received particular attention. As an image forming method used in these apparatuses, a reversal developing method is used in which toner is attached to a portion irradiated with light to form an image for the purpose of effectively utilizing light or increasing resolution. As a result, it has become necessary for the photosensitive member to have high reliability during reversal development. The photoconductor used in these electrophotographic apparatuses is generally formed by forming a photoconductive layer on a conductive support such as aluminum. The layer structure is generally a function-separated laminated structure in which a photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated is formed on a conductive support.

However, in such a photoreceptor, the so-called blocking function for preventing the injection of charges from the conductive support to the charge generation layer is insufficient, and a toner image should not be formed at the time of reversal development. Image noise, which is a so-called black spot, is generated in which a toner image is formed. Therefore, a technique has been proposed in which an anodized film is provided on a conductive support containing aluminum or an aluminum alloy to prevent injection of charges from the support into the charge generation layer.

For example, in Japanese Unexamined Patent Publication No. 7-84391, the surface of aluminum or aluminum alloy which is a conductive substrate is anodized at a current density of 5 A / dm ² for 24 minutes by using a sulfuric acid solution of about 18 ° C. to about 21 ° C. as an electrolytic solution. Oxidation is performed to form an anodized film, and then a sealing treatment is performed using a nickel acetate solution to obtain a support having an anodized film formed thereon, which is used to prepare a photoreceptor. In addition, JP-A-7-26143
In No. 9, the surface of the conductive substrate made of an aluminum-based material was degreased and washed by etching with a weak acid, and then anodizing treatment was performed for 24 minutes at 5 A / dm ² using a sulfuric acid solution as an electrolytic solution to form an undercoat layer for the anodized film. Is formed. However, the time from exposure to development is 4
If it is simply applied to an image forming process for more than 00 msec, the amount of electric charge leaking through the defect portion increases and a local potential drop occurs, so that a high quality image cannot be obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic photoreceptor for reversal development, which can obtain high image quality by preventing black spots from occurring as much as possible even in the above-mentioned long-time process. .

[0006]

The present invention is an electrophotographic photoreceptor for reversal development used in an image forming process in which an image is formed through the steps of charging, exposure, development and transfer. The photoreceptor is aluminum or A conductive support made of an aluminum alloy, an intermediate layer made of an aluminum anodic oxide film, a charge generation layer, a charge transport layer, and the intermediate layer having a resistance value (R) and a capacitance (C) measured at a frequency of 100 Hz. ) Is 2 to 5 msec, preferably 3 to 5 ms
ec, the electrophotographic photosensitive member for reversal development, which is used in an image forming process in which the time from the charging of the photosensitive member to the development is 400 to 1500 msec, preferably 600 to 1200 msec. Regarding

The electrophotographic photoreceptor of the present invention is a conductive support,
A laminated electrophotographic photosensitive member including an intermediate layer, a charge generation layer, and a charge transport layer, which sets an electric conductivity characteristic of an intermediate layer provided between a conductive support and a photosensitive layer thereabove in a specific range. It is obtained by doing so.

CR value of the intermediate layer (frequency 100H above)
The product of the resistance value R (Ω) and the capacitance C (F) at z) is
Good blocking and rectifying properties can be obtained by setting the range of 2 msec ≦ CR ≦ 5 msec. The CR value is a time constant representing the relaxation time of the electric field, and in the case of the intermediate layer, it is the time until the potential sharing due to the charges applied by the charger is relaxed and the electric field is concentrated on the photosensitive layer. If the CR value is too small, a sudden electric field concentration may occur, causing charge injection from the inhomogeneous portion at the charge generation layer / intermediate layer interface or discharge in the voids, resulting in a local decrease in surface potential. become. If the CR value is too large, electric charges will be accumulated in the intermediate layer during repeated use, leading to an increase in residual potential and a decrease in half-exposure energy.

As the intermediate layer of the electrophotographic photosensitive member of the present invention, an anodized film and a resin film obtained by anodizing aluminum or an aluminum alloy are used. The capacitance C of the intermediate layer is considered to be proportional to the surface area, and this value tends to increase in the case of an anodic oxide film with many surface defects or an anodic oxide film with insufficient sealing. On the contrary, if this value is too small, it is considered that the anodic oxide film is not sufficiently formed and the blocking property is deteriorated. 10
The value of the capacitance when measured at 0 Hz is 1,000 to 3,
It is preferably 000 pF, preferably in the range of 1,500 to 2,000 pF. Also, the resistance value R of the anodized film
If this is too small, the blocking property becomes poor, and if it is too large, the rectifying property becomes poor and the residual potential becomes high.
If the anodic oxidation time is too short to form a sufficient anodic oxide film, or if the sealing is insufficient, it tends to be low.

By performing anodizing treatment for a long time at a low current density, an anodized film intermediate layer satisfying the CR value of the present invention can be obtained. That is, the current density is 0.3 to 1.0 A / dm ² ,
It is preferably achieved by anodizing treatment at 0.6 to 0.8 A / dm ² for 30 to 60 minutes, preferably 30 to 40 minutes. The average film thickness of the obtained anodized film is 1 to 15 μm,
The thickness is preferably adjusted to 2 to 10 μm, more preferably 4 to 8 μm.

The material of the aluminum alloy support used in the photoreceptor of the present invention is not particularly limited. However, when the crystal grain size of the mixed dissimilar metal in the aluminum alloy is large, a thin oxide film is formed and the resistance value tends to be low. Therefore, as the aluminum alloy used for the conductive support, a material having a smaller crystal grain size of the mixed dissimilar metal such as the A6063 material than that of an aluminum alloy having a relatively large crystal grain size of the dissimilar metal such as the A3003 material is used. It is easier to obtain an intermediate layer effective against black spot noise with less surface defects.

The anodizing treatment is usually carried out, for example, with chromic acid,
Although it is carried out in an acidic bath such as sulfuric acid, oxalic acid, boric acid, sulfamic acid, etc., anodizing treatment in sulfuric acid gives the best results. In the case of anodic oxidation in sulfuric acid, the sulfuric acid concentration is 1
00-300 g / l, dissolved aluminum concentration 2-15
It is preferable to set g / l, the liquid temperature to 15 to 30 ° C., and the electrolysis voltage to 5 to 20V.

Since the obtained anodic oxide film is unstable in the porous portion, it is subjected to a treatment for sealing those pores, that is, a sealing treatment. Generally, the sealing treatment increases the resistance value of the anodized film. Examples of such a sealing treatment include a low temperature sealing treatment in which the anodized film is immersed in an aqueous solution containing nickel fluoride as a main component, or a high temperature sealing treatment in which the anodized film is immersed in an aqueous solution containing nickel acetate as a main component. Treatment etc. are mentioned. The concentration of the nickel fluoride aqueous solution used in the low-temperature sealing treatment can be appropriately selected,
It is most effective when used within a range of ˜6 g / l.

In order to smoothly carry out the sealing treatment,
The treatment temperature is 25 to 30 ° C., preferably 30 to 35
In addition, the pH of the nickel fluoride aqueous solution is 4.5 to 6.
It is good to treat it in the range of 5, preferably 5.5 to 6.0. As the pH adjuster, oxalic acid, boric acid, formic acid, acetic acid, sodium hydroxide, sodium acetate, aqueous ammonia, etc. can be used. The sealing treatment is preferably performed within a range of 1 to 3 minutes per 1 μm of the average film thickness. In order to further improve the physical properties of the film, nickel fluoride, cobalt acetate, nickel sulfate, a surfactant, etc. may be added to the nickel fluoride aqueous solution.

As the sealing agent for the high temperature sealing treatment, an aqueous solution of a metal salt of nickel acetate, cobalt acetate, lead acetate, nickel acetate-cobalt, barium nitrate or the like can be used, but nickel acetate is particularly preferably used. Is preferred. When using an aqueous solution of nickel acetate, the concentration is 3 to 20 g /
It is preferably used within the range of 1. The processing temperature is 65-
It is preferable to use at 100 ° C., preferably 80 to 98 ° C., and the pH of the nickel acetate aqueous solution in the range of 5.0 to 6.0. Ammonia water, sodium acetate or the like can be used as the pH adjusting agent. Also in this case, sodium acetate, an organic carboxylate, an anionic surfactant, a nonionic surfactant, etc. may be added to the nickel acetate aqueous solution in order to improve the physical properties of the film.

A charge generation layer and a charge transport layer, which are photosensitive layers, are laminated on the intermediate layer formed as described above. The charge generation layer is formed by vacuum-depositing the charge generation material, or applying it by dissolving it in a solvent such as amine, or dispersing the pigment in an appropriate solvent or a solution in which a binder resin is dissolved if necessary. The coating liquid thus prepared is applied and dried to form a charge generation layer. On top of this, a solution containing a charge transport material and a binder resin is applied and dried to form a charge transport layer.

Examples of the charge generating material used in the photosensitive layer of the present invention include bisazo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, cyanine dyes, styryl dyes, pyrylium dyes. Examples include organic substances such as azo dyes, quinacdrine dyes, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indathlon pigments, squarylium pigments, and phthalocyanine pigments. In addition, any material that absorbs light and generates charge carriers with extremely high efficiency can be used.

An organic substance is used as the charge transporting material used in the photosensitive layer of the present invention. For example, a hydrazone compound, a pyrazoline compound, a styryl compound, a triphenylmethane compound, an oxadiazole compound, a carbazole compound, a stilbene compound, Enamine compounds,
Various compounds such as oxazole compounds, triphenylamine compounds, tetraphenylbenzidine compounds and azine compounds can be used.

The binder resin used in the production of the above-mentioned photoreceptor is electrically insulating, and is measured by itself to be 1 × 10 ¹²
It is desirable to have a volume resistance of Ω · cm or more. For example, a binder such as a thermoplastic resin, a thermosetting resin, a photocurable resin, or a photoconductive resin known per se can be used. Specifically, polyester resin, polyamide resin, acrylic resin, ethylene-vinyl acetate resin, ion-crosslinked olefin copolymer (ionomer), styrene-butadiene block copolymer, polycarbonate, vinyl chloride-vinyl acetate copolymer, cellulose Thermoplastic resin such as ester, polyimide, styrene resin; epoxy resin, urethane resin, silicone resin, phenol resin,
Thermosetting resins such as melamine resins, xylene resins, alkyd resins, and thermosetting acrylic resins; photocurable resins; photoconductive resins such as polyvinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylpyrrole, etc., and binders thereof. The resins are used alone or in combination of two or more. When the charge transport material is a polymer charge transport material that can be used as a binder itself, other binder resin may not be used.

The photosensitive layer of the present invention comprises a binder resin, a plasticizer such as halogenated paraffin, polyvinyl chloride phenyl, dimethylnaphthalene, dibutyl phthalate and O-terphenyl, chloranil, tetracyanoethylene, 2, and the like.
Electron-withdrawing sensitizers such as 4,7-trinitrofluorenone, 5,6-dicyanobenzoquinone, tetracyanoquinodimethane, tetrachlorophthalic anhydride and 3.5-dinitrobenzoic acid, methyl violet, rhodamine B, cyanine dye A sensitizer such as a pyrylium salt or a thiapyrylium salt may be used.

In the above description, the photosensitive member in which the charge generating layer and the charge transporting layer are sequentially laminated as the photosensitive layer on the intermediate layer has been specifically described. However, in the present invention, the photosensitive layer is the charge transporting layer. A structure in which a charge generation layer and a charge generation layer are sequentially stacked may be used. Furthermore, organic photoconductive materials such as polyvinylcarbazole, anthracene, and phthalocyanine can be used as they are,
Alternatively, it may have a single-layer structure formed by mixing and coating with an insulating binder resin.

Further, the photoreceptor of the present invention may have a surface protective layer provided on the photosensitive layer. As a material used for the surface protective layer, a polymer such as an acrylic resin, a polyarylate resin, a polycarbonate resin or a urethane resin as it is, or a material in which a low resistance compound such as tin oxide or indium oxide is dispersed is suitable. Further, an organic plasma polymerized film can be used as the surface protective layer. The organic plasma polymerized film may optionally contain oxygen, nitrogen, halogen, and atoms of groups 3 and 5 of the periodic table.

The apparatus in which the electrophotographic photosensitive member of the present invention is incorporated is not particularly limited, and full-color, color, or single-color copying may be used as long as it includes an image forming process of 400 msec or more from charging to development. It may be a machine, a printer, a reader printer, or the like. The shape of the photoconductor is not particularly limited, and examples thereof include a drum shape, a belt shape, and a plate shape. Among them, in the apparatus in which a plurality of developing devices are arranged around the photoconductor, the time from charging to developing is different for each developing device, and from charging to developing as the charging position and the position of the developing device are separated. Will inevitably become longer. The photoconductor of the present invention is particularly preferably used in such a device. The time from charging to development means the time from charging to the end of development in an actual machine.For example, when the development is carried out in several stages having a plurality of developing devices like a full-color copying machine, It means the time from the charging to the end of the final development.

[0024]

The present invention will be described below in detail with reference to examples. Example 1 A cylinder made of an aluminum alloy (JIS 6063 material) was cut to have an outer diameter of 80 mmφ and an inner diameter of 78 mmφ (length 35 mm).
0 mm) drum was prepared and used as a conductive substrate.

[Pretreatment] This was treated with a degreasing agent (surfactant) at 60 ± 5 ° C for 5 minutes for degreasing, and washed with running water to remove the degreasing agent. Then, etching with 10% by weight / volume% nitric acid for 1 minute to sufficiently degrease and clean,
The surface was cleaned by flushing with pure water. [Anodizing Treatment] This substrate was subjected to anodizing treatment as follows. Anodizing treatment was performed for 30 minutes at a current density of 0.7 A / dm ² and a solution temperature of 20 ° C. using 15 wt / vol% sulfuric acid as an electrolytic solution to form an anodized film having a thickness of about 7 μm. [Sealing treatment] After washing the substrate with pure water, the concentration is 5 to 10
Using a g / l aqueous solution of nickel acetate, sealing treatment was performed at 70 ° C. for 15 minutes, washing with water, and then washing with warm pure water.

[Formation of Photosensitive Layer] A photosensitive layer was formed on the obtained substrate as follows. 1 part by weight of a τ-type metal-free phthalocyanine and 0.5 part by weight of polyvinyl butyral were dispersed together with 50 parts by weight of tetrahydrofuran by a sand mill. The obtained phthalocyanine-based dispersion liquid was applied onto an aluminum drum substrate so that the film thickness after drying was 0.3 μm to form a charge generation layer. Benzyldiphenyl compound represented by the following formula

[0027]

Embedded image 10 parts by weight and polycarbonate resin ("Panlite K-
1300 "(manufactured by Teijin Chemicals Limited) in 10 parts by weight of dichloromethane was dispersed in 180 parts by weight of dichloromethane to form a charge transporting layer having a thickness of 24 μm. Thus, the photoreceptor of the present invention was produced.

[Evaluation of Electrical Properties of Intermediate Layer] The capacitance, resistance and impedance of the intermediate layer were measured as follows. An intermediate layer was formed on the conductive substrate, and an aluminum vapor deposition film having an area of 1 cm ² was formed on the intermediate layer. A potential of frequency 100 Hz is applied from both sides, and electrostatic capacitance C, resistance value R and impedance between the aluminum vapor deposition film and the substrate are measured by Ando Electric Co., Ltd. LCR METER-AG-
It was measured using 4311.

[Image Evaluation] Using the CF-80 full color copying machine manufactured by Minolta Co., Ltd. for the obtained photoreceptor,
System speed is 109mm / sec, 218mm / se
c, 436 mm / sec, 654 mm / sec, and the time from charging to development is 165 msec, 330
Image evaluation was performed with msec, 660 msec, and 990 msec. [Criteria for image evaluation] Copy a solid white image to 25 mm ²
Count the number of black spots inside. 0 to less than 15: ○ 15 to less than 30: △ 30 or more: ×

Example 2 A photosensitive layer was prepared in the same manner as in Example 1 except that the sealing treatment was performed at 95 ° C. for 25 minutes, and image evaluation was performed in the same manner.

Example 3 A photosensitive layer was prepared in the same manner as in Example 1 except that JIS A5005 was used as the aluminum alloy, and image evaluation was carried out in the same manner.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that the anodizing treatment was performed at a current density of 1.5 A / dm ² for 15 minutes. Image evaluation of the photoreceptor of Comparative Example 1 was performed in the same manner as described in Example 1. Table 1 shows the results of image evaluation performed on the photoconductors of Examples 1 to 3 and Comparative Example 1.
Further, in Table 1, the resistance value R of the intermediate layer measured at 100 Hz,
The capacitance C and its product CR are also shown.

[0033]

[Table 1]

[0034]

It has been shown that the photoconductor of the present invention can obtain a good image even in the process in which the time from charging to development exceeds 400 msec.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor for reversal development used in an image forming process in which an image is formed through each step of charging, exposure, development and transfer, wherein the photoreceptor is a conductive support made of aluminum or aluminum alloy. Body, an intermediate layer composed of an aluminum anodic oxide film, a charge generation layer, a charge transport layer, and the intermediate layer has a product of a resistance value (R) and a capacitance (C) of 2 to 2 when measured at a frequency of 100 Hz. 5 ms
An electrophotographic photosensitive member for reversal development, which is ec, and is used in an image forming process in which the time from the charging of the photosensitive member to the development is 400 msec or more.