JP2001142234A - Electrophotographic photoreceptor and method for producing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a silicone hard coat layer which does not peel or lower sensitivity 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 for a silicone hard coat containing an organosilanol compound of the formula Rn-Si-(OH)m (where R is alkyl or aryl; (n) is an integer of 1 or 2, (m) is an integer of 2 or 3 and n+m=4) is applied on an electric charge generating layer containing a slightly alcohol-soluble polymer containing an alcoholic OH group or an ester group as a binder and the coating solution is cured.

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.
It has been considered that a photoconductor in which a charge generation layer (hereinafter, sometimes referred to as CGL) is sequentially applied is 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, existing silicon hard coat agents often use a silanol compound with a polar group such as a glycidyl group partially introduced in consideration of the adhesion to the underlayer. There is a drawback that the image is blurred under humidity. Nevertheless, without a functional group such as a glycidyl group, the film is liable to peel off and is not practical. Until now, no good method for solving this problem has been found, and at present, positively chargeable organic electrophotographic photoreceptors have hardly been put to practical use.

[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 for producing a positively charged photoreceptor which is capable of producing a silicon hard coat layer which does not cause film peeling and does not lower the sensitivity, 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, even if an attempt is made to improve the adhesiveness by devising the underlayer (CGL) of the silicon hard coat film, for example, such as butyral may be used. The use of alcohol-soluble ones improves the adhesion, but greatly reduces the sensitivity. Probably because most of the solvent of the hard coat layer (also referred to as a protective layer) is mainly composed of alcohol, the underlying CGL is dissolved or swelled at the time of coating, and as a result, the binder flows into the CGL unnecessarily and the CGM concentration decreases. It is thought that it is the cause. The present invention has been completed by solving this point.

The object of the present invention is attained by adopting one of the following constitutions. [1] A coating liquid for a silicon hard coat containing an organic silanol compound represented by the following general formula on a charge generation layer using a polymer that is poorly soluble in alcohol and contains an alcoholic OH group or an ester group as a binder. A method for producing an electrophotographic photoreceptor, comprising coating and curing. In the general formula R _n -Si- (OH) _m , R represents an alkyl group or an aryl group;
Or, represents an integer of 2, and m represents an integer of 2 or 3.
However, n + m is 4.

[2] Bifunctional organic silanol compound (m
(2) and a trifunctional organic silanol compound (m = 3) at the same time, and a coating solution for silicon hard coat is applied and cured.

[3] The method for producing an electrophotographic photosensitive member according to [1] or [2], wherein the coating solution contains colloidal silica.

[4] The electrophotographic photosensitive material according to [1], [2] or [3], wherein the binder of the coating solution for the charge generation layer contains a phenoxy resin or a poly (meth) acrylic ester resin. How to make the body.

[5] The method for producing an electrophotographic photosensitive member according to any one of [1] to [4], wherein a phthalocyanine pigment is used as a pigment for the charge generation layer.

[6] An electrophotographic photosensitive member obtained by the production method according to any one of [1] to [5].

As described above, a positively charged photoreceptor which can withstand repeated use for a long period of time contains a polymer which is hardly soluble in alcohol and has an alcoholic OH group or ester group as a binder for the charge generation layer. It is obtained by applying and curing a coating liquid for a silicon hard coat containing an organic silanol compound represented by the general formula.

In the present invention, the term "poorly soluble in alcohol" refers to those having a solubility of 2% by mass or less in methanol or ethanol at room temperature.

Alcohol-soluble polymers, such as butyral resin, are not practical because of the disadvantage that the sensitivity of the photoreceptor is reduced even if the adhesiveness is improved. As mentioned above, probably because most of the hard coat layer solvent is mainly composed of alcohol, dissolve or swell the underlying CGL when applied,
As a result, the material of the protective layer unnecessarily flows into the CGL and C
This is probably because the GM concentration has decreased.

Preferred specific examples of the resin for CGL of the present invention include a phenoxy resin and a poly (meth) acrylic ester resin. Needless to say, the charge generation layer in the present invention is a charge generation material (hereinafter referred to as CGM).
In addition to the so-called reverse-layer photoconductor in which charge generation and charge transport are separated in function, a single-layer photoconductor containing a charge-transporting substance at the same time is included. A photoconductor having a layer configuration is more preferable. Although the resin of the present invention belongs to the category of high polarity, generally, when a binder of an electrophotographic photosensitive member has a polar group, the binder tends to trap and slow the charge mobility. Although the resin of the present invention has good adhesiveness to the silicon hard coat layer, it has a low charge mobility as compared with commonly used polycarbonate, and this is a problem for thick films (typically 15 to 30 μm). This is because On the other hand, in the reverse layer configuration, a relatively thin (10 μm or less) charge generation layer is formed under the hard coat layer, so that the charge transport property hardly causes a serious problem, and a polymer having relatively strong polarity can be used as a binder. It is.

With respect to the CGL binder having a polar group of the present invention, these resins may be used alone,
In consideration of the mobility, it may be used as a mixture with polycarbonate, polyarylate, or the like. It is not necessary to use the binder alone to provide the adhesive property, and it is sufficient if the binder is at least 1%, preferably at least 5% of the total CGL binder. Also CG
The mass ratio of M to the total binder of CGL is 10/1 to 1
About / 10 is common.

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

Of these, phthalocyanine pigments are particularly excellent because they have a photosensitive range of 700 to 830 nm and can be applied to printers and digital copiers compatible with semiconductor laser writing. However, compared to condensed polycyclic pigments such as perylene, the resistance to ozone and nitrogen oxides is weak, and it has been difficult to commercialize a photoreceptor having a layer structure in which a charge generation layer is coated on the surface of a positively charged photoreceptor. It can be said that the use of phthalocyanines became easier by providing a protective layer as in the present invention. Further, a preferable silicon hard coat layer which can reduce the residual potential by adding a small amount of a hole transporting substance or an electron transporting substance to the charge generation layer of the present invention contains both trifunctional silanol and bifunctional silanol simultaneously. Silanol has the general formula: R
It is a compound consisting of _n Si (OH) _m. put it here,
R represents an alkyl group or an aryl group, and n + m is 4. Those having m of 3 are called trifunctional silanols and m is 2
Are called bifunctional silanols.

In many hard coat agents, trifunctional is the main material, but in the present invention used for an electrophotographic photosensitive member, it is more 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 preferably from 9: 1 to 4: 6 in mass ratio of the solid content after curing.

Silanol is usually added to a coating solution in the form of an alkoxysilane [R _n Si (OR ') _m ], prepared and hydrolyzed (where R' represents an alkyl group). Therefore, a part of the coating solution which is not hydrolyzed is also present in the coating solution, and a part which is oligomerized is also included in the scope 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. it can.

In addition, tetrafunctional silanes such as tetramethoxysilane and monofunctional ones such as trimethylmethoxysilane, which are not essential components, may be added. Further, it is more preferable to add colloidal silica from the viewpoint of increasing the hardness. The colloidal silica is preferably an aqueous or alcoholic sol having a particle size of 100 nm or less, preferably 30 nm or less and does not greatly scatter light. The amount of colloidal silica to be added is not particularly limited, but is preferably 5 to 100 when the mass of the solid content after curing of the organic silanol is 100.

In the present invention, a metal hydroxide (for example, a hydrolyzate of each alkoxide of aluminum, titanium and zirconium) other than silane may be contained. Colloidal silica imparts rigidity to the film, transports a small amount of charge, and serves to reduce the increase in residual potential as a side effect of the application of the silicon hard coat film, which is essentially an insulator. 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.

Further, it is preferable that the coating solution for a hard coat film of the present invention contains 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, acetylacetone is used in part as a solvent, and aluminum chloride is added thereto to form a chelate compound in the coating solution. You may do it.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrophotographic photoreceptor of the present invention may further include various materials known as materials for electrophotography, for example, antioxidants such as hindered amine and hindered phenol, and smoothing agents such as silicone oil. Further, a hole transport material such as an amine compound and an electron transport material such as a quinone may be added.

An alcohol-soluble resin such as a polyamide or an acetal resin may be added to the hard coat layer in order to further increase the adhesiveness and the strength of the film.

For the charge transport layer, a technique known for a charge transport layer of a known negatively charged photosensitive member can be applied as it is. Examples of the charge transport material include the following. 1. Triarylamine compounds

[0032]

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2. Hydrazine compounds

[0034]

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3. Stilbene compounds

[0036]

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4. Benzidine compound

[0038]

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5. Butadiene compound

[0040]

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6. Other compounds

[0042]

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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 conductive 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. A conductive layer for the purpose of preventing generation and the like 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 can be applied 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.

[0053]

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 Sekisui Chemical Co., Ltd.) 1.0 g and 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)> 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) were added to 15 ml of butanol. 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.) was added thereto.
Further acetal resin (Denka Butyral 3000k,
40 mg of aluminum trisacetylacetonate (manufactured by Tokyo Chemical Industry) as a curing catalyst
0.2 g was added and dissolved by stirring to prepare a coating solution.

This coating solution was applied as a protective layer having a dry film thickness of 2 μm on the above-mentioned charge generating layer, and dried at 120 ° C. for 1 hour to prepare a photoreceptor.

Example 2 The binder of the charge generation layer was changed from PKHJ alone to PKHJ.
A photoconductor was prepared by the same way as that of Example 1 except that the mixture of J and polycarbonate resin (Z200) was 1: 3.

Example 3 A photoconductor was prepared in the same manner as in Example 1, except that the binder of the charge generation layer was changed to 60 mg of polymethacrylate resin (Acrypet MF, manufactured by Mitsubishi Rayon Co., Ltd.).

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that the binder in the charge generation layer was replaced by a polycarbonate resin (TS2050 manufactured by Teijin Chemicals Limited) having a lower polarity than the resin of the present invention. did.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 1, except that the binder in the charge generation layer was replaced with an alcohol-soluble butyral resin (Slec BL-2 manufactured by Sekisui Chemical Co., Ltd.).

Comparative Example 3 A photoconductor was prepared in the same manner as in Example 1, except that the binder in the charge generation layer was replaced by alcohol-soluble methoxymethylolated nylon (Toresin EF30T, Teikoku Chemicals).

Further, photoreceptors without a hard coat layer were prepared for Examples 1 to 3 and Comparative Examples 1 to 3, which were referred to as Reference Examples 1 to 3 and Reference Comparative Examples 1 to 3, respectively.

Evaluation 1 Film Peeling Test (1) A mending tape was attached to the photoreceptor, and the film was peeled off and the adhesion of the film was observed.

○: No peeling of film ×: Peeling of film

[0065]

[Table 1]

Evaluation 2 The above photoreceptor was subjected to a paper analyzer (EPA 8100).
The following test was performed using Kawaguchi Electric Co., Ltd.). +
The corona charging was performed for 5 seconds under the condition of 80 μA, and the surface potential Va immediately after charging and the surface potential Vi after standing for 5 seconds were obtained. Subsequently, exposure was performed for 10 seconds so that the surface illuminance became 2.0 lux. Exposure E1 to make 1 / 2Vi
/ 2 and the exposure amount E600 / 100 required to reduce the surface potential from 600 V to 100 V, and the surface potential Vr after exposure were determined.

[0067]

[Table 2]

[0068]

[Table 3]

In Comparative Examples 2 and 3, Vr was increased and the sensitivity was significantly reduced with the application of the overcoat layer.

On the other hand, Embodiments 1 to 3 have large Vr
No increase or decrease in sensitivity is observed. Note that Comparative Example 1 (polycarbonate binder) has the best change in potential, but has extremely poor adhesion as seen in Evaluation 1.

Looking at the characteristics of Reference Examples 1 to 3 and Reference Comparative Examples 1 to 3 shown in Table 3, the potential characteristics at the stage where the overcoat layer is not applied are all good. This indicates that the binder of the comparative example causes some change in the application of the hard coat layer, whereas the CGL using the binder of the present invention maintains the original performance even after the application of the hard coat layer. I understand.

Example 4 A coating liquid having the composition of Example 1 was applied to an aluminum drum to prepare a photosensitive drum. This is Konica 70
50 (digital copying machine manufactured by Konica Corp.) was mounted on an image forming apparatus modified for positive charging, and image evaluation was performed. A sufficient image was obtained, and no defects were found in the image even after printing 10,000 times.

However, the evaluations of Reference Examples 1 to 3 and Reference Comparative Examples 1 to 3 similarly caused a problem after about 100 prints, and a good image could not be obtained thereafter.

[0074]

According to the present invention, a method for producing a positively charged photoreceptor which is capable of withstanding a long-term repeated use by producing a silicon hard coat layer which does not cause film peeling and does not lower the sensitivity, and which has been produced by using the same. An electrophotographic photosensitive member can be provided.

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Claims (6)

[Claims] 1. A silicon hard coat containing an organic silanol compound represented by the following general formula on a charge generation layer using a polymer that is poorly soluble in alcohol and contains an alcoholic OH group or ester group as a binder. A method for producing an electrophotographic photosensitive member, comprising applying and curing a coating liquid. In the general formula R _n -Si- (OH) _m (wherein, R represents an alkyl group or an aryl group, n represents an integer of 1 or 2, m represents an integer of 2 or 3. However n + m is 4 is there.) 2. Bifunctional organic silanol compound (m = 2)
2. The method for producing an electrophotographic photoreceptor according to claim 1, wherein a coating liquid for silicon hard coat, which simultaneously contains and a trifunctional organic silanol compound (m = 3), is applied and cured. 3. The method according to claim 1, wherein the coating liquid contains colloidal silica. 4. The method for producing an electrophotographic photoreceptor according to claim 1, wherein the binder of the coating solution for the charge generation layer contains a phenoxy resin or a poly (meth) acrylic ester resin. 5. The method according to claim 1, wherein a phthalocyanine pigment is used as a pigment for the charge generation layer.
The method for producing an electrophotographic photoreceptor according to the above item. 6. An electrophotographic photosensitive member obtained by the production method according to claim 1. Description: