JP3279167B2 - Electrophotographic photoreceptor - Google Patents

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 requiring a long time from charging to development.

[0002]

2. Description of the Related Art The technology of electrophotography has been developed in the field of copying machines in the past, but recently, it has rapidly spread due to high image quality, high speed, and quietness that are incomparable with conventional devices, and digital cameras are particularly popular. With remarkable progress in signal data processing systems, laser beam printers, digital copiers, and the like have received special attention. As an image forming method used in these apparatuses, a reversal developing method of forming an image by adhering toner to a portion irradiated with light has been adopted for the purpose of effectively utilizing light or increasing resolution. As a result, the photoreceptor has been required to have high reliability during reversal development. The photoreceptor used in these electrophotographic apparatuses generally has a photosensitive layer formed on a conductive support such as aluminum. As a layer configuration, a function-separated laminated structure in which a photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support is formed.

However, such a photoreceptor does not have a sufficient blocking effect for preventing injection of charges from the conductive support into the charge generation layer, and is disadvantageous in that a toner image should not be formed during reversal development. Image noise, which is a so-called black spot, in which a toner image is formed, occurs. For this reason, a technique has been proposed in which an anodized film is provided on a conductive support containing aluminum or an aluminum alloy to prevent charge injection from the support into the charge generation layer.

For example, in Japanese Patent Application Laid-Open No. 7-84391, the surface of aluminum or an aluminum alloy, which is a conductive substrate, is treated with a sulfuric acid solution of about 18 ° C. to about 21 ° C. as an electrolyte at a current density of 5 A / dm ² for 24 minutes. The substrate is oxidized to form an anodic oxide film, and then subjected to sealing treatment using a nickel acetate solution to obtain a support having an anodic oxide film formed thereon, and a photoreceptor is prepared using the support. Japanese Patent Application Laid-Open No. 7-26143
In No. 9, the surface of a conductive substrate made of an aluminum-based material is degreased and washed by etching with a weak acid, and then subjected to an anodic oxidation treatment at 5 A / dm ² using a sulfuric acid solution as an electrolyte for 24 minutes to form an undercoat layer of an anodic oxide film. Is formed. However, the photoreceptor as described above requires a time from exposure to development of 4 times.
If the method is simply applied to an image forming process exceeding 00 msec or more, the amount of charge leaking through a defective portion increases, causing a local potential drop, and 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 in which the generation of black spots is prevented as much as possible even in the above-mentioned long-time process, and high image quality is obtained. .

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for charging, exposing,
An electrophotographic photoreceptor for reversal development used in an image forming process for forming an image through each step of development and transfer, wherein the photoreceptor is a conductive support made of aluminum or an aluminum alloy, and an intermediate made of an aluminum anodic oxide film. layer,
A resistance value R (where R is 1 MΩ or less) when the intermediate layer is composed of a charge generation layer and a charge transport layer and the intermediate layer is measured at a frequency of 100 Hz.
The product of the capacitance C when measured at a frequency 100Hz and except in the case of below) 2～5Msec, preferably reversal development electrophotographic photosensitive characterized the 3~5msec der Turkey <br/> About the body.

The electrophotographic photoreceptor of the present invention comprises a conductive support,
A laminated electrophotographic photoreceptor comprising an intermediate layer, a charge generation layer and a charge transport layer, wherein the electric conductivity of the intermediate layer provided between the conductive support and the photosensitive layer thereon is set to a specific range. It is obtained by this.

The CR value of the intermediate layer (the product of the resistance value R (Ω) at a frequency of 100 Hz and the capacitance C (F) at a frequency of 100 Hz) is 2 mse
By setting the range of c ≦ CR ≦ 5 msec (except when R is 1 MΩ or less) , good blocking properties and rectification properties can be obtained. The CR value is a time constant representing the relaxation time of the electric field. In the case of the intermediate layer, the CR value is the time from when the potential sharing due to the electric charge provided by the charger is reduced and the electric field is concentrated on the photosensitive layer.
If the CR value is too small, a sudden electric field concentration occurs, causing charge injection from an inhomogeneous portion at the interface between the charge generation layer and the intermediate layer, or causing discharge in voids, thereby causing a local decrease in surface potential. become. If the CR value is too large,
Charges accumulate in the intermediate layer during repeated use, leading to an increase in residual potential, a decrease in half-life exposure energy, and the like.

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

By performing the anodic oxidation treatment for a long time at a low current density, an intermediate layer of the anodic oxide film 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 , preferably
0.3~0.8A / dm ^2, more preferably 0.6~0.8A / dm ² 30~60
Minutes, preferably 30 to 40 minutes of anodizing. The average thickness of the obtained anodic oxide film is adjusted to 1 to 15 μm, preferably 2 to 10 μm, and more preferably 4 to 8 μm.

The material of the aluminum alloy support used for the photoreceptor of the present invention is not particularly limited. However, when the crystal grain size of the mixed dissimilar metals in the aluminum alloy is large, a thin portion of the oxide film is formed, and the resistance value tends to decrease. Therefore, as the aluminum alloy used for the conductive support, for example, a material having a small crystal grain size of the mixed heterogeneous metal such as the A6063 material is used as compared with using an aluminum alloy having a relatively large mixed crystal size of the mixed dissimilar metal such as the A3003 material. The use of is easier to obtain an intermediate layer having fewer surface defects and effective against black spot noise.

The anodic oxidation 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
g / l, the liquid temperature is preferably set to 15 to 30 ° C., and the electrolysis voltage is preferably set to 5 to 20 V.

The obtained anodic oxide film is subjected to a treatment for sealing the pores, that is, a sealing treatment, since the porous portion is unstable. Generally, the resistance value of the anodic oxide film increases by the sealing treatment. As such a sealing treatment, for example, a low-temperature sealing treatment in which an anodized film is immersed in an aqueous solution containing nickel fluoride as a main component, or a high-temperature sealing treatment in which it is immersed in an aqueous solution containing nickel acetate as a main component Processing and the like. The concentration of the nickel fluoride aqueous solution used in the case of the low-temperature sealing treatment can be appropriately selected.
It is most effective when used in the range of ６6 g / l.

In order to smoothly perform the sealing process,
The treatment temperature is 25-30 ° C, preferably 30-35.
° C, and the pH of the aqueous nickel fluoride solution is 4.5 to 6.5.
5, and preferably in the range of 5.5 to 6.0. Oxalic acid, boric acid, formic acid, acetic acid, sodium hydroxide, sodium acetate, aqueous ammonia and the like can be used as the pH adjuster. The time for the sealing treatment is preferably in the range of 1 to 3 minutes per 1 μm of the average film thickness. To further improve the film properties, nickel fluoride, cobalt acetate, nickel sulfate, a surfactant and the like may be added to the nickel fluoride aqueous solution.

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

On the intermediate layer formed as described above, a charge generation layer and a charge transport layer, which are photosensitive layers, are laminated. The charge generation layer may be formed by vacuum deposition of the charge generation material, or by dissolving in a solvent such as amine or the like, or by dispersing the pigment in an appropriate solvent or a solution in which a binder resin is dissolved if necessary. The charge generation layer is formed by applying and drying the coating solution prepared as described above. A solution containing a charge transport material and a binder resin is further applied thereon 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, and pyrylium dyes. And organic substances such as azo dyes, chiacdrine dyes, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indathrone pigments, squarylium pigments, and phthalocyanine pigments. In addition, any material that absorbs light and generates charge carriers with extremely high efficiency can be used.

As the charge transporting material used in the photosensitive layer of the present invention, an organic substance is used, for example, hydrazone compound, pyrazoline compound, styryl compound, triphenylmethane compound, oxadiazole compound, carbazole compound, 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 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 resin, xylene resin, alkyd resin, and thermosetting acrylic resin; photocurable resins; photoconductive resins such as polyvinylcarbazole, polyvinylpyrene, polyvinylanthracene, and polyvinylpyrrole; and binders thereof. The resins are used alone or in combination of two or more. When the charge transporting material is a polymer charge transporting material that can be used as a binder, it is not necessary to use another binder resin.

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

In the above description, the photoreceptor in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on the intermediate layer has been specifically described. A configuration in which a charge generation layer and a charge generation layer are sequentially laminated may be employed. In addition, organic photoconductive materials such as polyvinyl carbazole, anthracene, phthalocyanine, etc.
Alternatively, it may be of a single-layer structure formed by mixing and applying 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 into which the electrophotographic photoreceptor of the present invention is incorporated is not particularly limited, and full-color, color, and single-color copying can be performed as long as the time from charging to development includes an image forming process of 400 msec or more. Machine, a printer, a reader printer, or the like. The shape of the photoreceptor is not particularly limited, and examples thereof include a drum shape, a belt shape, and a plate shape. Of these, in an apparatus in which a plurality of developing devices are arranged around the photoreceptor, the time from charging to development differs for each developing device, and from charging to developing as the charging position and the position of the developing device become farther apart. Time is inevitably longer. The photoreceptor of the present invention is particularly suitably used for such an apparatus. The time from charging to development refers to the time from charging to the end of development in an actual machine.For example, when a plurality of developing units are used and development is performed in several stages as in a full-color copying machine, It means the time from charging to the end of 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 form an outer diameter of 80 mmφ and an inner diameter of 78 mmφ (length 35 mm).
0 mm), and this was used as a conductive substrate.

[Pretreatment] This was treated with a degreasing agent (surfactant) at 60 ± 5 ° C. for 5 minutes to perform degreasing, and washed with running water to remove the degreasing agent. Then, it is etched with 10% by weight / volume nitric acid for 1 minute to perform degreasing and washing sufficiently,
The surface was cleaned with running water cleaning with pure water. [Anodizing treatment] The substrate was anodized as follows. Anodizing treatment was performed at a current density of 0.7 A / dm ^{2 at} a liquid temperature of 20 ° C. for 30 minutes using 15% by weight / volume 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 was 5 to 10%.
Using a nickel acetate aqueous solution of g / l, sealing treatment was performed at 70 ° C. for 15 minutes, followed by 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 was applied on 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 Characteristics of Intermediate Layer] The capacitance, resistance and impedance of the intermediate layer were measured as follows. An intermediate layer was formed on a conductive substrate, and an aluminum deposition film having an area of 1 cm ² was formed thereon. A potential of 100 Hz is applied from both sides, and the capacitance C, the resistance value R and the impedance between the aluminum vapor-deposited film and the base are measured by LCR METER-AG- manufactured by Ando Electric Co., Ltd.
4311.

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

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 performed in the same manner.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that the anodic oxidation 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.
Table 1 shows the resistance value R of the intermediate layer measured at 100 Hz.
The capacitance C and the product CR are also shown.

[0033]

[Table 1]

[0034]

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

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-19515 (JP, A) JP-A-64-56453 (JP, A) JP-A-2-181159 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 5/00

Claims (2)

(57) [Claims] An electrophotographic photoreceptor for reversal development used in an image forming process for forming an image through respective steps of charging, exposing, developing and transferring, wherein the photoreceptor is a conductive support made of aluminum or an aluminum alloy. Body, an intermediate layer consisting of an aluminum anodic oxide film, a charge generation layer, and a charge transport layer, and a resistance value (R) when the above-mentioned intermediate layer is measured at a frequency of 100 Hz (except when R is 1 MΩ or less) . Week
Product der of the capacitance (C) when measured at a wave number 100Hz
Reversal developing electrophotographic photoconductor CR value and wherein the 2~5msec der Turkey that. 2. A reversal developing electrophotographic photoconductor according to claim 1, wherein the electrostatic capacitance C is characterized this <br/> and is 1000～3000PF.