JP2001142244A - Electrophotographic photoreceptor and its producing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a tough silicone hard coat layer having a certain thickness or above by coating and to produce a positive charge electrophotographic photoreceptor which withstands repetitive use over a long period of time. SOLUTION: In the production of the electrophotographic photoreceptor, a coating solution containing an organosilanol compound and titanium dioxide having <=30 nm average particle diameter is applied on an electric charge generating layer and cured to form a silicone hard coat layer having >=1.5 μm thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic photosensitive member. More specifically, the present invention relates to a positively charged electrophotographic photosensitive member that generates less ozone.

[0002]

2. Description of the Related Art In recent years, offices using so-called electrophotographic processes such as copiers and printers have overflowed into offices.
Moreover, they tend to be faster.

[0003] Currently, negatively charged organic photoreceptors are mainly used as electrophotographic photoreceptors used for these. However, the problem of ozone generated at the time of charging is becoming a serious problem as the speed is increased. Since the amount of ozone generated is greatly reduced only by making the photosensitive member positively charged, it is desirable to use a positively charged photosensitive member.

[0004] Conventionally, negatively charged organic photoreceptors have been the main reason that, in order to make the organic photoreceptor positively chargeable while maintaining the current layer structure, an electron transporting charge transporting material is required. Development was required, and this development was not easy.

[0005] Therefore, at present, a charge transport layer, a charge transport layer, a charge transport function, and a charge transfer function are formed on the same layer without separating the charge generation function and the charge transport function.
Photoreceptors coated with a charge generation layer in sequence were considered to be realistic. The reverse layer photoreceptor imparts a sufficient surface potential because charge generation and charge transport are separated in function, and is highly sensitive but easy to design. However, since there is a pigment-containing layer as the uppermost layer (as is the case with a single-layer photoreceptor), it is easily scraped and cannot be used for a long time.

Therefore, it is conceivable to provide a vitreous hard protective layer (silicon hard coat film) on the surface. The silicon hard coat film is formed by applying a silanol compound and then curing, and is currently used as a protective film for plastic lenses and the like. However, the silicon hard coat agent has a defect that the flow of photocurrent is poor as usual as an insulator, the sensitivity is lowered, and the residual potential is increased upon repeated use. This tendency is particularly remarkable in a relatively thick hard coat layer of 1.5 μm or more. On the other hand, when the film thickness is reduced, the film is fragile and easily scraped. Therefore, it has been desired to develop a positively charged photoreceptor that is coated with a strong silicon hard coat film having a film thickness of a certain level or more and can withstand repeated use for a long time.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems.

An object of the present invention is to provide a method of manufacturing a positively charged photoreceptor which is provided with a strong silicon hard coat layer having a film thickness of a certain degree or more and which can withstand repeated use for a long period of time. An object of the present invention is to provide an electrophotographic photosensitive member.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve this problem. As a result, a positively charged photoreceptor that can withstand the above-mentioned long-term repetition is formed with an organic silanol on a charge generation layer (CGL). A silicon hard coat layer having a thickness of 1.5 μm or more containing titanium oxide having a particle size of 30 nm or less,
The inventors of the present invention have found out what can be obtained by coating and curing, and have reached the present invention.

That is, the object of the present invention is achieved by adopting one of the following constitutions. [1] A coating liquid containing an organic silanol compound and titanium oxide having an average particle diameter of 30 nm or less is applied on the charge generation layer, and cured to form a silicon hard coat layer having a thickness of 1.5 μm or more. A method for producing an electrophotographic photoreceptor.

[2] The method for producing an electrophotographic photosensitive member according to [1], wherein a coating liquid containing both a bifunctional silanol compound and a trifunctional silanol compound is used as the organic silanol compound.

[3] The method for producing an electrophotographic photosensitive member according to [1] or [2], wherein the coating solution for the silicon hard coat layer further contains an alcohol-soluble polymer.

[4] An electrophotographic photoreceptor characterized in that the titanium oxide produced by the production method according to [1], [2] or [3] is anatase type having a particle size of 10 nm or less.

[5] The alcohol-soluble polymer contained in the silicon hard coat layer is selected from acetal resin, polyamide resin, cellulose resin, polyvinyl acetate, polyvinyl pyridine and poly (meth) acrylic resin [3]. The method for producing the electrophotographic photosensitive member according to the above.

[6] An electrophotographic photosensitive member manufactured by the method according to [1], [2], [3] or [5].

In the present invention, the thickness of the silicon hard coat layer is an important factor, and this point will be described in Examples and Comparative Examples described later. In the case of a thin film having a large thickness, not only the time required for erosion differs in proportion to the thickness, but also the erosion speed itself greatly varies depending on the film thickness.

Although the cause is not always clear, if it is thin, it will be hard coat layer (hereinafter sometimes referred to as a protective layer) when it receives an external force such as contact with a blade or a charging roller.
Distortion and deformation always occur, including the soft underlayer (photosensitive layer), which cannot withstand itself. It becomes fatigue and brittle over a long period of time. On the contrary, it is considered that if the film is thick, the hard film of the hard coat itself can withstand the deformation pressure due to the external force, so that the amount of strain deformation is small, and as a result, the film is less susceptible to fatigue and is less likely to be brittle. The film thickness is 1.5
μm or more is preferable, and 2.0 μm or more is more preferable.
The upper limit is not particularly limited, but is preferably 15 μm or less in order to maintain the potential characteristics of the photoconductor.

The organic silanol is a compound comprising R _n Si (OH) _m , wherein R represents an alkyl group or an aryl group,
+ M is 4. Those having m of 3 are called trifunctional silanols, and those of m being 2 are bifunctional silanols. In many hard coat agents, trifunctional is the main material, but in the present invention which is an electrophotographic photosensitive member, it is preferable to add bifunctional silanol in order to increase the hydrophobicity of the film. With only three functions, the image may be blurred under high humidity. The ratio of the trifunctional silanol to the bifunctional silanol is 9: 1 by mass ratio of the solid content after curing.
~ 4: 6 is preferred.

The silanol form of ordinary alkoxysilane _{[R n Si (OR ')} m] in added to the coating liquid, solution preparation, is hydrolyzed (R' is an alkyl group). Therefore, although only partially hydrolyzed substances and oligomers are present in the coating solution, they are all referred to as the silanol of the present invention.

As an example of a typical alkoxysilane,
Examples of trifunctional compounds include methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, and methyltriethoxysilane. Examples of bifunctional compounds include dimethyldimethoxysilane and methylphenyldimethoxysilane.

Other than these essential components, tetrafunctional ones such as tetramethoxysilane and monofunctional ones such as trimethylmethoxysilane may be added.

The hard coat layer of the present invention further contains titanium oxide having a particle size of 30 nm or less. These titanium oxide fine particles are N-type semiconductors, and when a charge generation layer is irradiated with light and photoelectrons are emitted, charges are transferred to the surface. This is particularly important when the film thickness is set to 1.5 μm or more with emphasis on durability as in the present invention. Naturally, titanium oxide is preferably an anatase type which has a strong property as an N-type semiconductor. Since it is used in a layer above the photosensitive layer, it is a fine particle so as to transmit light quickly and is called a titania sol on a colloid, preferably 10 nm or less. Is preferable. The lower limit of the particle size is not particularly limited, but may be about 1 nm in the sense that particles are formed.

The hard coat layer of the present invention preferably further contains an alcohol-soluble polymer. We believe that alcohol-soluble polymers act as reinforcing bars when compared to concrete, a building material, to increase film strength and adhesion. In this analogy, the titanium oxide fine particles of the present invention play a role of gravel in addition to carrying the above-mentioned electric charge. In addition, it is more preferable to add colloidal silica in order to increase the hardness.

Colloidal silica is an aqueous or alcoholic sol having a particle size of 100 nm or less, preferably 30 nm.
In the following, those which do not greatly scatter light are preferable. The amount of colloidal silica to be added is not particularly limited, but is preferably 1 to 100 when the mass of the solid content after curing of the organic silanol is 100.
200, more preferably 10 to 100.

The present invention does not exclude colloids other than silane such as metal oxides (eg, aluminum oxide, titanium oxide, zirconium oxide, etc.). These metal oxides can also be easily prepared by hydrolyzing the corresponding metal alkoxide.

Colloidal silica imparts rigidity to the film, and transports a small amount of charge, and reduces the rise in residual potential, which is a side effect of attaching a silicon hard coat film that is essentially an insulator. Work to make it work. On the other hand, when the amount is too large, there are disadvantages such as the film being easily scraped and the moisture resistance being lowered.

The alcohol-soluble polymer in the present invention is a polymer which contains at least 0.1% by mass of methanol or ethanol and contains an ester group or a polymer containing an alcoholic OH group.

For example, acetal resin, polyamide resin,
Cellulose resin, polyvinyl acetate, polyvinyl pyridine, and those soluble in alcohol among acrylic resins,
Examples include oligomers of hydroxymethyl methacrylate and its copolymer, acrylic acid, methacrylic acid and its ester, and the like.

The amount of the silanol added after curing is 10
0 is preferably 0.01 to 30, more preferably 0.1 to 20.

Further, the coating solution for a hard coat layer of the present invention may contain a curing catalyst. As the catalyst, a known curing catalyst such as an acid, a metal chelate, a metal oxide, a metal salt, and an alkylaminosilane compound which has been conventionally used for a silicon hard coat material can be used. Particularly preferred are metal chelate compounds. The metal chelate compound may be added to the coating solution in its completed form, but in another form, for example, using acetylacetone as a solvent in part and adding aluminum chloride to it to form the chelate compound in the coating solution You may do it.

In addition, the coating liquid of the present invention may further contain various materials known as materials for electrophotography, for example, antioxidants such as hindered amine and hindered phenol, leveling agents such as silicone oil, amine compounds and the like. And an electron transporting agent such as a quinone.

The binder for the charge generation layer is not particularly limited, but a resin having a certain degree of polarity is preferable.
For example, phenoxy resin, polymethyl methacrylate, ethyl acrylate, vinyl acetate and the like can be mentioned.
Of course, copolymers of styrene and the like and mixtures with other resins such as polycarbonate resins and polyester resins can also be used in the present invention.

These resins have a polar group, and some OH groups may react with silanol, which is considered to contribute to the adhesion between the charge generation layer and the hard coat layer. The ratio of these polar polymers to the total binder of the charge generation layer is 5% or more, preferably 10% or more, and the ratio of the total binder of the charge generation layer to the pigment is preferably 5/1 to 1/20 by mass, Preferably 3 /
It is 1/10.

When these polar polymers are used as a binder for the charge generation layer, the layer structure is preferably a photoreceptor having a function-separated reverse layer structure rather than a single layer photoreceptor also having a charge transport function. This is because these polymers have a polar group compared to the commonly used polycarbonate, which has good adhesion to the silicon hard coat layer. 15-25μ
In m), this is a problem. In a photoreceptor having a function-separated reverse layer structure, a relatively thin (usually 0.5 to 10 μm) charge generation layer is formed under the hard coat layer, so that charge transport is not a major problem and even a relatively polar polymer can be used as a binder. It can be.

The charge generating substance in the charge generating layer is not particularly limited, and conventionally known pigments can be used.
Specifically, azo pigments such as fluorenone disazo pigment,
Many examples include phthalocyanine pigments such as titanyl phthalocyanine and gallium phthalocyanine, and condensed polycyclic pigments such as anthranthrone and perylene bisimidazole.

The residual potential can be reduced by adding a small amount of a hole transporting substance or an electron transporting substance to the charge generation layer of the present invention.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For the charge transport layer, the technique known for the charge transport layer of a known negatively charged photoreceptor can be applied as it is. Examples of the charge transport material include the following. 1. Triarylamine compounds

[0038]

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2. Hydrazine compounds

[0040]

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3. Stilbene compounds

[0042]

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4. Benzidine compound

[0044]

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5. Butadiene compound

[0046]

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6 Other compounds

[0048]

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As the binder resin contained in the charge transport layer, any resin such as a polycarbonate resin, a polyester resin, a polystyrene resin, an acrylic resin, a polyvinyl chloride resin, a polyvinyl butyral resin, and a polyamide resin can be selected.

In the present invention, the ratio between the charge generating substance and the binder resin in the charge generating layer is from 1: 5 to 5: 1 by mass.
Is preferred. The thickness of the charge generation layer is preferably 10 μm or less. The ratio between the charge transporting material and the binder resin in the charge transporting layer is preferably from 3: 1 to 1: 3 by mass ratio. The thickness of the charge transport layer is preferably 5 to 50 μm, more preferably 10 to 50 μm.
40 μm.

The solvent or dispersion medium used in the present invention includes n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, Benzene, toluene,
Xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2
-Trichloroethane, 1,1,1-trichloroethane,
Examples include trichloroethylene, tetrachloroethane, tetrahydrofuran, dioxolan, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve and the like. Although the present invention is not limited to these, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone and the like are preferably used. In addition, these solvents can be used alone or as a mixed solvent of two or more kinds.

Next, the electroconductive support of the electrophotographic photoreceptor of the present invention includes: 1) a metal plate such as an aluminum plate or a stainless steel plate; 2) a support such as paper or a plastic film;
A thin metal layer such as aluminum, palladium, or gold provided by lamination or vapor deposition. 3) On a support such as paper or plastic film,
Examples thereof include those in which a layer of a conductive compound such as a conductive polymer, indium oxide, or tin oxide is provided by coating or vapor deposition.

Next, the coating method for producing the electrophotographic photosensitive member of the present invention includes dip coating, spray coating,
Coating methods such as circular amount control type coating are used, but the coating process on the surface layer side of the photosensitive layer is spray coating or circular amount control type in order to minimize dissolution of the lower layer film and to achieve uniform coating processing. (A typical example is the circular slide hopper type.)
It is preferable to use a coating method such as coating. The spray coating is described in detail in, for example, JP-A-3-90250 and JP-A-3-269238,
The circular amount control type coating is described in, for example, JP-A-58-1.
It is described in detail in JP-A-89061.

In the present invention, an intermediate layer having a barrier function may be provided between the conductive support and the photosensitive layer.

Examples of the material for the intermediate layer include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, and phenol resin polyamides (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethyl). And an intermediate layer using polyurethane, gelatin, and aluminum oxide, or a hardening intermediate layer using a metal alkoxide, an organic metal chelate, or a silane coupling agent as described in JP-A-9-68870. The thickness of the intermediate layer is preferably from 0.1 to 10 μm, particularly preferably from 0.1 to 10 μm.
5 μm is preferred.

In the present invention, a coating for compensating for surface defects of the support is provided between the support and the intermediate layer, and interference fringes, which is a problem particularly when image input is performed by laser light, are performed. A conductive layer for the purpose of preventing the generation can be provided. This conductive layer is made of carbon black,
It can be formed by applying and drying a solution in which conductive powder such as metal particles or metal oxide particles is dispersed in a suitable binder resin. The thickness of the conductive layer is preferably 5 to 40 μm, particularly preferably 10 to 30 μm.

The shape of the support may be a drum shape, a sheet shape or a belt shape, and may be any shape suitable for the electrophotographic apparatus to be applied.

The electrophotographic photoreceptor of the present invention is applicable to general electrophotographic devices such as copiers, laser printers, LED printers, and liquid crystal shutter printers. It can be widely applied to devices such as light printing, plate making, and facsimile.

[0059]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the invention are not limited thereto.

Example 1 A photoreceptor was produced as follows. <Intermediate layer> polyvinyl butyral resin (S-lec BM
S, manufactured by Sekisui Chemical Co., Ltd.) and a charge transport material (S-3)
1.0 g was dissolved in a mixture of 85 ml of methyl ethyl ketone and 15 ml of cyclohexanone, and PET was deposited on aluminum.
The base was applied with a wire bar so as to have a thickness of 0.2 μm. <Charge Transport Layer> 15 g of a polycarbonate resin (bisphenol Z300, manufactured by Mitsubishi Gas Chemical Company) and 10 g of a charge transport material (S-3) were added to 100 ml of 1,2-dichloroethane.
And applied to the above-mentioned intermediate layer with a doctor blade to form a charge transporting layer having a thickness of 20 μm. <Charge generation layer> Phenoxy resin (PKHJ Pheno)
(xy Associate, Tomoe Kogyo Co., Ltd.) (1.0 g) was dissolved in tetrahydrofuran (50 ml), Y-type titanyl phthalocyanine (1.0 g) was added, and the mixture was ultrasonically dispersed. This dispersion was applied onto the above-mentioned charge transport layer so as to have a thickness of 1.5 μm to form a charge generation layer. <Protective layer (overcoat layer)> 15 g of butanol was added with 4.9 g of methyltrimethoxysilane (2.4 g in terms of solids after curing) and 2.6 g of dimethyldimethoxysilane (1.6 g in terms of solids after curing). Diluted with 2%
2.5 ml of an acetic acid aqueous solution is added, and the mixture is heated and stirred at 60 ° C. for 2 hours.

After standing at room temperature overnight, 4.0 g of methanol silica sol (concentration 30%, manufactured by Nissan Chemical Industries, Ltd.) and titanium oxide sol for photocatalyst (ST-02 concentration 30%, manufactured by Ishihara Sangyo Co., Ltd.)
1.0 g was further added thereto, and 40 mg of butyral resin (Denka butyral 3000 k, manufactured by Denki Kagaku) was added, and 0.2 g of aluminum trisacetylacetonate (manufactured by Tokyo Chemical Industry) was added as a curing catalyst, followed by stirring and dissolution to apply. The liquid was made.

This coating solution was applied as a protective layer having a dry film thickness of 2.7 μm on the above-mentioned charge generating layer, and dried at 120 ° C. for 1 hour to prepare a photoreceptor.

Example 2 A photoconductor was prepared by the same way as that of Example 1 except that the thickness of the protective layer was changed to 1.9 μm.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that the thickness of the protective layer was changed to 1.2 μm.

Comparative Example 2 The titanium oxide sol for photocatalyst in the protective layer of Example 1 (ST-
02) A photoreceptor was prepared in the same manner as in Example 1, except that 1.0 g of methanol silica sol was used instead of 1.0 g (total amount of methanol silica sol was 4.0 g).

Comparative Example 3 A photoconductor was prepared in the same manner as in Example 1, except that both the titanium oxide sol for photocatalyst and the methanol silica sol in the protective layer in Example 1 were omitted.

Evaluation 1 Taber abrasion test 500 g in an environment of a temperature of 20 ° C. and a humidity of 50% RH.
1000 under the condition of worn wheel CS-5 and rotation speed of 70 rpm
The surface was turned by turning it up to three times.

It is confirmed by visual inspection that the ground has not been removed,
The mass loss was measured. The results are shown in Table 1 below.

[0069]

[Table 1]

According to Table 1, the present invention is hard to be scraped. On the other hand, Comparative Example 1 in which the film thickness was reduced was large. Since all of the wear was within the hard coat layer, the wear amount did not necessarily increase after the hard coat layer of the comparative example was lost. The hard coat layer itself may have been weakened.

Evaluation 2 The above photoreceptor was subjected to a paper analyzer (EPA 810).
0, manufactured by Kawaguchi Electric Co., Ltd.).
The corona charging was performed for 5 seconds under the condition of +80 μA, and the surface potential Va (V) immediately after the charging and the surface potential V after leaving for 5 seconds were measured.
i (V) is determined, and then exposure is performed for 10 seconds so that the surface illuminance becomes 2.0 lux, and the exposure amount E1 / 2 at which the surface potential is 1 / 2Vi and the surface potential are changed from 600V to 100V.
The exposure amount E600 / 100 required to reduce the voltage to V and the surface potential Vr after exposure were determined.

The dark decay rate, DD = (Va-Vi) / Va%, was determined as a measure of the decrease in surface charge in a dark place.

Table 2 shows the results.

[0074]

[Table 2]

Those having a hard coat layer containing the anatase type titanium oxide fine particles of the present invention have good sensitivity and low residual potential Vi. In contrast, Comparative Example 2 using only colloidal silica has a high residual potential and a large dark decay. Comparative Example 3, which contains neither colloidal silica nor titanium oxide, has a low dark decay rate but has an excessively high residual potential.

This is thought to be because the titanium oxide fine particles strongly exhibit the properties as an N-type semiconductor and transfer charges to negative charges but strongly block positive charges.

Evaluation 3 The coating solution of the composition of Example 1 was applied to an aluminum drum to prepare a photosensitive drum.

This was mounted on a machine obtained by modifying Konica 7050 (a digital copying machine manufactured by Konica) for positive charging.
The evaluation was performed. A sufficiently good image is obtained and 1
No scratches were seen on the photoreceptor drum after printing 0000 times.

[0079]

According to the present invention, a method of manufacturing a positively charged photoreceptor which is coated with a strong silicon hard coat layer having a film thickness of a certain degree or more and which can withstand repeated use for a long time, and manufactured using the same. An electrophotographic photosensitive member can be provided.

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Claims (6)

[Claims] 1. A silicon hard coat layer having a thickness of 1.5 μm or more is provided by applying a coating solution containing an organic silanol compound and titanium oxide having an average particle size of 30 nm or less on the charge generation layer and curing the coating solution. A method for producing an electrophotographic photoreceptor. 2. The method according to claim 1, wherein a coating solution containing both a bifunctional silanol compound and a trifunctional silanol compound is used as the organic silanol compound. 3. The method for producing an electrophotographic photoreceptor according to claim 1, wherein the coating solution for the silicon hard coat layer further contains an alcohol-soluble polymer. 4. An electrophotographic photoreceptor produced by the method according to claim 1, wherein the titanium oxide is an anatase type having a particle size of 10 nm or less. 5. The method according to claim 3, wherein the alcohol-soluble polymer contained in the silicon hard coat layer is selected from acetal resin, polyamide resin, cellulose resin, polyvinyl acetate, polyvinyl pyridine, and poly (meth) acrylic resin. A method for producing an electrophotographic photoreceptor. 6. An electrophotographic photoreceptor produced by the method according to claim 1, 2, 3, or 5.