JPH1195469A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which does not generate image noises such as black spots and interference fringes on an image by anodically oxidizing the surface of a substrate, dipping the substrate in a low acidic aq. soln. of a specified pH and forming at least a photosensitive layer on the resultant photoreceptor substrate. SOLUTION: The surface of an Al or Al alloy substrate is anodically oxidized, the substrate is dipped in a low acidic aq. soln. of pH 3.5-4.5 and at least a photosensitive layer is formed on the resultant photoreceptor substrate to obtain the objective electrophotographic photoreceptor capable of perfectly preventing the generation of black spots. The Al or Al alloy substrate is not especially limited if it used so far for an electrophotographic photoreceptor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic photosensitive member used in an electrophotographic apparatus.

[0002]

2. Description of the Related Art The technology of electrophotography has been developed in the field of copiers, and has recently spread rapidly due to high image quality, high speed, and quietness that are incomparable with conventional apparatuses. With the remarkable progress of the data processing system, laser beam printers, digital copiers, and the like have received special attention. The photoreceptor used in these electrophotographic devices generally has a photosensitive layer formed on a conductive photoreceptor substrate such as aluminum or an aluminum alloy,
As a layer configuration, a function-separated laminated configuration in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive substrate is widely used.

[0003] The image forming method used in the above apparatus uses a laser beam as a light source, and forms an image by adhering toner to a portion irradiated with the laser beam in order to use light effectively or increase resolution. The mainstream is to adopt a reversal development method, but there is a problem that the use of a laser beam tends to cause interference fringes on an image. To avoid this problem, it is known that roughening the surface of the photoreceptor substrate is useful.

According to this developing method, charge is injected from a defective portion on a conductive substrate into a photosensitive layer during development, so that a so-called black spot is formed at a place where a toner image should not be formed. There is a problem that image noise is generated.

Therefore, it is known that it is effective to provide an undercoat layer or a anodic oxide layer as a charge injection preventing layer on the surface of the photoreceptor substrate in order to prevent the occurrence of black spots. In providing the undercoat layer, there is a problem that it is difficult to select a material to be used because the influence on the electrostatic characteristics of the undercoat layer is large.

[0006] In providing an anodized layer, it has been general practice to first degreasing and etching a support made of aluminum or an aluminum alloy, then anodize, and optionally seal. Attempts have been made to prevent the occurrence of black spots by performing anodic oxidation treatment conditions, sealing treatment conditions, regulation of impedance or regulation of aluminum alloy material, etc. Not in.

On the other hand, there has been reported a technique in which an aluminum support is subjected to anodizing treatment, sealing treatment, and then dipping in a strongly alkaline or strongly acidic aqueous solution (Japanese Patent Laid-Open No. 1-1315).
No. 71 and JP-A-1-131572). However, in any of the techniques, the object is to remove aluminum hydroxide on the surface of the photoconductor substrate formed by elution of aluminum during anodizing treatment or sealing treatment. In addition, since a strongly alkaline or strongly acidic aqueous solution is used, the formed anodized layer is dissolved, the function as the charge injection preventing layer is not exhibited, and there is still a problem that image noise such as black spots frequently occurs. .

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photosensitive member which does not generate image noise such as black spots and interference fringes on an image.

[0009]

According to the present invention, the surface of a support made of aluminum or an aluminum alloy is anodized and then immersed in a weakly acidic aqueous solution having a pH of 3.5 to 4.5. The present invention relates to an electrophotographic photoreceptor comprising at least a photosensitive layer provided on a photoreceptor substrate to be obtained.

In the present invention, a photoreceptor is prepared by using a substrate which has been subjected to anodizing treatment of the surface of the support and then immersed in a weakly acidic aqueous solution having a pH of 3.5 to 4.5. Generation of black spots can be completely prevented. This is because the acid radicals in the processing solution such as sulfuric acid used in the anodic oxidation treatment, for example, the sulfate radicals and the phosphate radicals remain on the substrate surface, and it is difficult to remove these acid radicals in the subsequent treatment steps. It is considered that the surface of the photoreceptor substrate is activated by the acid radicals, and various contaminants are adsorbed in subsequent processing steps, for example, a sealing processing step and a transporting step, and charge injection occurs therefrom to generate black spots. It seems that the present invention can remove such acid radicals. Further, in the present invention, since the surface of the anodic oxide layer is appropriately roughened, interference fringes can be prevented. In addition, in this specification, pH is liquid temperature 20.
It shows the value measured by a pH meter (PH82: manufactured by Yokogawa Electric Corporation) at ℃, but the pH must be a value measured by the measurement model because there is no difference between the measurement models. Not at all.

The aluminum or aluminum alloy support (hereinafter simply referred to as aluminum support) used for producing the photoreceptor substrate of the present invention may be any one which can be conventionally used for an electrophotographic photoreceptor. However, there is no particular limitation. That is, any conventionally known composition and method can be employed for the aluminum composition, the forming method thereof, the surface processing method, and the like. For example, after melting and casting aluminum ingot having a purity of 99.9% or more, it is subjected to a homogenous treatment and extruded to produce a raw tube. Thereafter, as a precision finishing of the surface, the obtained base tube is subjected to ironing / drawing processing, or cutting or grinding as necessary, whereby the aluminum support used in the present invention can be manufactured.

The obtained aluminum support may be subjected to a degreasing treatment and an etching treatment prior to the anodizing treatment. The degreasing treatment is performed for the purpose of cleaning the treatment liquid applied to the surface for the purpose of rust prevention and the like during storage of the photoreceptor substrate, and the method is particularly limited as long as the purpose is achieved. Not something. For example, this is performed by immersing the substrate in an aqueous solution containing a surfactant at 45 to 65 ° C. for 2 to 5 minutes.

The etching treatment for providing the degreased aluminum support is performed for the purpose of removing a natural oxide film formed on the surface of the support in order to uniformly perform anodizing treatment. Although not particularly limited as long as the above is achieved, it is preferable to be subjected to an acid etching treatment. For example, when the substrate has a concentration of 50 to 160 g /
This is carried out by immersion in 1 l of nitric acid aqueous solution at 15 to 30 ° C for 1 to 5 minutes.

The aluminum support thus treated is subjected to a conventionally known anodizing treatment. Anodizing is generally performed, for example, with chromic acid, sulfuric acid, phosphoric acid,
It is carried out by a known method in an acidic bath of oxalic acid, boric acid, sulfamic acid or the like. In the present invention, it is most preferable for a substrate which has been subjected to anodizing treatment in sulfuric acid. In the case of anodic oxidation in sulfuric acid, the sulfuric acid concentration is usually 100 to 300.
g / l, preferably 100-200 g / l, dissolved aluminum concentration 2-15 g / l, liquid temperature 15-35 ° C, preferably 15-25 ° C, and electrolysis voltage 5-20V, preferably 10-20V. This is done by setting a range.

The thickness of the anodic oxide layer is 1 to 15 μm,
Preferably 4 to 12 μm, more preferably 4 to 10 μm
It is desirable that When the thickness is less than 1 μm, the function of the anodic oxide layer as a charge injection preventing layer is reduced.
Exceeding the above increases the cost but does not require a further film thickness.

In the present invention, the thus obtained aluminum support having an anodized layer is treated with a pH of 3.5.
Immersion treatment in a weakly acidic aqueous solution of -4.5. By doing so, the surface portion of the anodic oxide layer having a thickness from the surface of 0.1 to 2 μm, preferably 0.1 to 1 μm is dissolved. If the thickness of the anodized layer to be dissolved is less than 0.1 μm, the effect of treatment with a weakly acidic aqueous solution cannot be sufficiently obtained. If the thickness is more than 2 μm, the blocking property of the anodized layer may be reduced. By dissolving the anodized layer surface portion in this manner, the acid radicals derived from the anodized solution remaining on the support surface, which were difficult to remove in the past, are removed together with the very surface anodized layer. It is considered that since the surface is stabilized, generation of black spots due to activation of the support surface due to residual acid radicals can be completely prevented. Further, after immersion, the surface of the support in which the surface portion was dissolved is in a white mat state and is appropriately roughened, so that it is considered that interference fringes can also be prevented.

If an aqueous solution having a pH of less than 3.5 is used, the dissolution of the anodic oxide layer proceeds at a very high rate, and it becomes extremely difficult to control the thickness of the anodic oxide layer to be dissolved. The function as a charge prevention layer is likely to be reduced. On the other hand, if an acidic aqueous solution having a pH of more than 4.5 is used, the effects of the present invention cannot be obtained, that is, it is difficult to remove the acid radicals from the surface of the support and dissolve the anodic oxide layer. The effect of preventing odor is reduced.

The weakly acidic aqueous solution used in the immersion step is not particularly limited, and the pH is continuously maintained during the immersion treatment of the aluminum support.
Any aqueous solution within the H range can be used. During use, if the pH is out of the above pH range, it becomes difficult to control the thickness of the anodized layer to be dissolved as described above, or it becomes difficult to dissolve the anodized layer. This is because the effect of preventing stripes is reduced.

Specific examples of the weakly acidic aqueous solution include, for example,
An aqueous solution obtained by adding and dispersing aluminum acetate in water, a buffer solution containing potassium hydrogen phthalate and sodium hydroxide, a buffer solution containing glycine, sodium chloride and hydrochloric acid, a buffer solution containing sodium citrate and hydrochloric acid, Buffer consisting of potassium hydrogen citrate and sodium hydroxide; Buffer consisting of potassium hydrogen citrate and borax; Buffer consisting of tartaric acid and sodium tartrate; Buffer consisting of lactic acid and sodium lactate; Buffer consisting of acetic acid and sodium acetate Liquid, sodium diethyl barbiturate, a buffer consisting of sodium acetate and hydrochloric acid, a buffer consisting of disodium hydrogen phosphate and citric acid, a buffer consisting of sodium acetate and hydrochloric acid,
A buffer solution composed of acetic acid and sodium acetate, and a buffer solution composed of citric acid and disodium hydrogen phosphate, and the like.Each buffer component is added directly to water in a specified amount so that the pH falls within the above pH range. The pH may be adjusted, or the respective aqueous solutions, which have been adjusted to an appropriate concentration in advance, may be mixed at an appropriate mixing ratio and adjusted to be within the above-mentioned pH range.

Of the above weakly acidic aqueous solutions, it is preferable to use an aqueous solution obtained by adding and dispersing aluminum acetate to water. Here, the “aqueous solution obtained by dispersing” means a dispersion obtained by adding a poorly water-soluble substance such as sodium acetate to water and dispersing and mixing. Regarding the pH adjustment when aluminum acetate is used, for example, when the aluminum acetate content in the aqueous solution is 2% by weight, the pH of the aqueous solution is 4.1, and when it is 5% by weight, the pH of the aqueous solution is 4.1. 0.

The temperature of the weakly acidic aqueous solution during immersion is preferably set at 40 to 100 ° C, more preferably 50 to 80 ° C. If the temperature is lower than 40 ° C., it is difficult to obtain the effects of the present invention. Further, the immersion time may be about 10 to 60 minutes, preferably 20 to 60 minutes. When the time is less than 10 minutes, the effect of the present invention is hardly obtained, and when the time exceeds 60 minutes, the thickness of the dissolved anodic oxide layer does not remain near the surface, and the function as a charge injection preventing layer (blocking property) tends to decrease. .

The photoreceptor substrate having the anodic oxide layer immersed in this way is subjected to a sealing treatment if desired. This is because the porous part in the anodized layer is unstable,
Generally, the sealing treatment increases the resistance value of the anodic oxide layer and further improves the blocking property.

In the present invention, either low-temperature sealing or high-temperature sealing may be performed as the sealing, and high-temperature sealing is preferably performed. If desired, a two-stage sealing process for performing each process may be performed.

The low-temperature sealing treatment means a sealing treatment carried out by immersing the anodic oxide layer in a treatment solution at a temperature of 40 ° C. or lower, and other conditions are the same as those of known methods.
If desired, the treatment liquid may contain, for example, nickel fluoride, red blood salt, or the like as a low-temperature sealing agent.

Specifically, when nickel fluoride is used as the low-temperature sealing agent, the concentration of nickel fluoride is 2 to 7 g /
, preferably 3 to 6 g / l, at pH 5.
5 to 6.0, temperature 25 to 40 ° C, preferably 25 to 35
° C, and the support having the anodized layer
It is carried out by immersion for 10 to 10 minutes, preferably 2 to 5 minutes.

When red blood salt is used as the low-temperature sealing agent, the red blood salt is used at a concentration of 3 to 20 g / l, preferably 5 to 15 g / l.
At pH 5.5 to 6.0 at a temperature of 25 to 40.
C., preferably 25 to 30 ° C., and the support having the anodic oxide layer thereon is kept for 1 to 20 minutes, preferably 5 to 30 ° C.
This is performed by soaking for 10 minutes.

As the low-temperature sealing treatment, for example, a humidifying sealing treatment may be performed in addition to the case of using the low-temperature sealing agent as described above. When performing the humidifying sealing process, a relative humidity of 80
It is carried out by leaving at% RH or more and a temperature of 30 to 40 ° C. for 1 to 10 days.

The high-temperature sealing treatment means a sealing treatment carried out by immersing the anodic oxide layer in a treatment liquid at a temperature of 65 ° C. or higher, and other conditions are the same as those in known methods.
The treatment liquid optionally contains a high-temperature sealing agent, for example, a metal salt such as nickel acetate, cobalt acetate, lead acetate, nickel-cobalt acetate, and barium acetate. It is particularly preferable to use nickel acetate.

Specifically, when nickel acetate is used as the high-temperature sealing agent, nickel acetate is used at a concentration of 3 to 20 g / l.
An aqueous solution preferably containing 4 to 12 g / l, pH 5.5
~ 6.0, temperature 65 ~ 100 ° C, preferably 70 ~ 90
° C, and the support having the anodized layer
The immersion is performed for 40 minutes, preferably for 5 to 30 minutes. When a metal salt other than nickel acetate such as cobalt acetate, lead acetate, nickel-cobalt acetate, and barium acetate is used as the high-temperature sealing agent, the same operation is performed as in the case of using nickel acetate.

As the high-temperature sealing treatment, in addition to the case where the high-temperature sealing agent is used as described above, for example, hot water sealing treatment with pure water or steam sealing treatment may be performed. When performing the hot water sealing treatment, the temperature is 65 to 100 ° C., preferably 90 to 9 ° C.
It is carried out by immersing in hot water at 8 ° C. for 10 to 60 minutes, preferably 20 to 40 minutes. In the case of performing the steam sealing treatment, the steam sealing treatment is performed under a steam pressure of 3.0 to 6.0 kg / cm ^2.
It is carried out by leaving it for 0 to 30 minutes, preferably 10 to 20 minutes.

Among such sealing treatments, the sealing treatment with nickel acetate or nickel fluoride is preferred from the viewpoint of sealing efficiency.

It is preferable to provide an auxiliary processing step, such as washing with tap water or pure water, between each of the above processing steps in order to efficiently and reliably perform the processing of the next step.

A photosensitive layer is formed on the photoreceptor substrate obtained as described above by a known method. A form in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer,
The charge transport layer and the charge generation layer may be sequentially stacked, or may be any of a single layer type including a charge transport material and a charge generation material.Hereinafter, a charge generation layer and a charge transport layer are used as a photosensitive layer. A case of manufacturing the photoconductors in the form of sequentially laminated layers will be described.

The charge generation layer may be formed by vacuum deposition of the charge generation material, or by dissolving the charge generation material in a solvent such as an amine, or by coating the pigment in an appropriate solvent or, if necessary, in a solution of a binder resin. The coating liquid prepared by dispersing is applied and dried to form a charge generation layer. 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 photoreceptor of the present invention include phthalocyanine pigments, bisazo pigments, trisazo pigments, squarylium pigments, perylene pigments, polycyclic quinone pigments, triarylmethane dyes, Organic substances such as thiazine dyes, oxazine dyes, xanthene dyes, cyanine dyes, styryl dyes, pyrylium dyes, azo dyes, quinacridone dyes, indigo pigments, bisbenzimidazole pigments, and induslone pigments Is mentioned. In addition, any material that absorbs light and generates charge carriers with extremely high efficiency can be used.

The charge transporting material used in the photoreceptor of the present invention is preferably an organic substance, for example, a hydrazone compound, a pyrazoline compound, a styryl compound, a triphenylmethane compound, an oxadiazole compound, a carbazole compound, a stilbene compound, Various materials such as an enamine compound, an oxazole compound, a triphenylamine compound, a tetraphenylbenzidine compound, and an azine compound can be used.

The binder resin used in the production of the photoreceptor as described above 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 resin,
Thermoplastic resins such as vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide resin and styrene resin; epoxy resin, urethane resin, silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin, thermosetting acrylic resin, etc. Thermosetting resin; photocurable resin; polyvinyl carbazole, polyvinyl pyrene,
Examples thereof include photoconductive resins such as polyvinyl anthracene and polyvinyl pyrrole, and these binder 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 photoreceptor of the present invention can be used together with a binder resin together with a plasticizer such as halogenated paraffin, polychlorinated biphenyl, dimethylnaphthalene, dibutyl phthalate, O-terphenyl, chloranil, tetracyanoethylene, 2,4,7.
An electron withdrawing sensitizer such as trinitrofluorenone, 5,6-dicyanobenzoquinone, tetracyanoquinodimethane, tetrachlorophthalic anhydride, 3,5-dinitrobenzoic acid, methyl violet, rhodamine B, cyanine dye, pyrylium salt And sensitizers such as thiapyrylium salts.

The photoreceptor of the present invention may have a structure in which an intermediate layer is provided on the above-described anodic oxide layer. As the material used for the intermediate layer, nylon resin, polyimide resin, polyamide resin, nitrocellulose polyvinyl butyral resin, polyvinyl alcohol resin and the like are suitable. The film thickness is 0.1 to 30 μm, preferably 1 to 30 μm, more preferably 1 to 20 μm.

Further, in the photoreceptor of the present invention, a surface protective layer may be provided on the above-mentioned 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 photoreceptor thus manufactured is incorporated is not particularly limited, and may be any of a full-color, color, and single-color copying machine, printer, reader printer, and the like. Also, the shape of the photoconductor is not particularly limited,
Examples include a drum shape, a belt shape, and a plate shape. The present invention is described in more detail by the following examples.

[0042]

Example 1 JIS6063 aluminum ingot was melted and cast, homogenized, and extruded. Thereafter, the surface was cut with a cutting tool using natural diamond as a cutting blade so that the outer diameter became 80 mm, to obtain a cylindrical aluminum alloy support having a surface roughness of 0.5 S or less (length: 350 mm). ). This was washed at 60 ° C. using a surfactant (Top Alclean 161: manufactured by Okuno Pharmaceutical Co., Ltd.).
For 5 minutes and washed with running water. Next, the substrate was etched at 20 ° C. for 5 minutes with an aqueous solution of nitric acid having a concentration of 100 g / l, and washed with running pure water. Next, an anodic oxidation treatment was performed at an electrolytic voltage of 14 V and a liquid temperature of 20 ° C. for 15 minutes using 200 g / l sulfuric acid as an electrolytic solution to form an anodized layer having a thickness of 6 μm.

The support having the anodized layer was prepared at pH 4.
1. Immersion in an aqueous solution of aluminum acetate at a temperature of 55 ° C. for 1 hour to obtain a photoreceptor substrate having a milky white surface. At this time, the thickness of the anodized layer was 5.5 μm. In addition, as the aqueous solution of aluminum acetate, an aqueous solution obtained by dispersing aluminum acetate in pure water was used, and the content of aluminum acetate in the aqueous solution was 2% by weight. Thereafter, the obtained photoreceptor substrate was washed with running water with pure water while rubbing with a brush, and dried.

On the other hand, τ-type metal-free phthalocyanine (Liopho
ton TPA-909: 1 part by weight of Toyo Ink Mfg. Co., Ltd. and 1 part by weight of polyvinyl butyral resin (Eslec BX-1, manufactured by Sekisui Chemical Co., Ltd.) are mixed with tetrahydrofuran (TH)
F) It was dispersed by a sand mill together with 48 parts by weight. The obtained phthalocyanine-based dispersion is coated on the photoreceptor substrate,
Coating was performed so that the film thickness after drying was 0.3 μm to form a charge generation layer.

The following formula:

Embedded image

4 parts by weight of a styryl compound and a polycarbonate resin (PC-Z, manufactured by Teijin Chemicals Ltd.) 6
Parts by weight of methylene chloride and 44 parts by weight of methylene chloride was applied onto the charge generating layer and dried to form a film having a thickness of 25 μm.
m of the charge transport layer was formed, and an electrophotographic photosensitive member was produced.

Example 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the temperature of the aqueous solution in the immersion treatment in an aqueous solution of aluminum acetate was 70 ° C. to obtain a photoreceptor substrate whose surface turned white. Produced.

Example 3 The temperature of the aqueous solution in the immersion treatment in an aqueous solution of aluminum acetate was set to 70 ° C. to obtain a photoreceptor substrate whose surface turned white, and this photoreceptor substrate was washed with running pure water to give a concentration of 7 g /
Example 1 except that the sealing treatment was performed by immersing in a nickel acetate aqueous solution having a pH of 5.7 and a temperature of 85 ° C. for 20 minutes.
In the same manner as in the above, an electrophotographic photoreceptor was produced.

Comparative Example 1 An electrophotographic photosensitive member was prepared in the same manner as in Example 2, except that the immersion treatment in the aqueous solution of aluminum acetate was not carried out.

Comparative Example 2 An electrophotographic photosensitive member was produced in the same manner as in Example 3, except that the immersion treatment in the aqueous solution of aluminum acetate was not carried out.

(Evaluation) Examples 1-3 and Comparative Examples 1-2
Each of the electrophotographic photoreceptors obtained in the above is mounted on a digital copying machine (Di33; manufactured by Minolta Co., Ltd.) to perform image output.
Black spots and interference fringes were evaluated.

A black solid white image was copied, and the occurrence of black spots in the copied image after 10 sheets were copied was visually evaluated according to the following ranking. ：: good; Δ: slightly generated, but no problem in practical use; ×: many occurred, not suitable for practical use.

The interference fringe halftone image (ID: 0.5) was copied, and the occurrence of interference fringes in the copied image after 10 copies was visually evaluated according to the following ranking. ：: no interference fringes were generated at all; Δ: interference fringes were partially generated, but there was no practical problem; ×: interference fringes were entirely generated and were not suitable for practical use.

The results of these evaluations are shown in Table 1 below.

[Table 1]

[0055]

According to the present invention, it is possible to provide an electrophotographic photosensitive member which does not generate image noise such as black spots and interference fringes.

Claims (1)

[Claims] 1. After anodizing a surface of a support made of aluminum or an aluminum alloy, the pH of the support is adjusted to 3.5.
An electrophotographic photoreceptor comprising a photoreceptor substrate obtained by immersion in a weakly acidic aqueous solution of -4.5 and at least a photosensitive layer.