JP2572219B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor excellent in electrostatic characteristics and moisture resistance. In particular, it relates to a CPC photosensitive member having excellent performance.

(Prior Art) An electrophotographic photosensitive member has various configurations in order to obtain predetermined characteristics or according to the type of an applied electrophotographic process.

Representative electrophotographic photoreceptors include a photoreceptor having a photoconductive layer formed on a support and a photoreceptor having an insulating layer on the surface, and are widely used.

Photoreceptors composed of a support and at least one photoconductive layer are used for image formation by the most common electrophotographic processes, i.e. charging, image exposure and development, and, if necessary, transfer.

Further, a method using an electrophotographic photosensitive member as an offset original plate for direct plate making has been widely used. In particular, in recent years, direct electrophotographic lithographic printing has become important as a method for printing high-quality printed matter with about hundreds to thousands of printed sheets.

The binder used to form the photoconductive layer of the electrophotographic photoreceptor has excellent film forming properties of itself and the ability to disperse the photoconductive powder in the binder, and the formed recording medium layer The adhesion to the substrate is good, and the photoconductive layer of the recording layer has excellent charging ability, low dark decay, large light decay, low pre-exposure fatigue, and changes in humidity during imaging. In addition, it is necessary to provide various electrostatic characteristics, such as a need to stably maintain these characteristics, and excellent imaging properties.

For example, silicone resins (Japanese Patent Publication No. 34-6670), styrene-butadiene resins (Japanese Patent Publication No. 35-1960), alkyd resins, maleic acid resins,
Polyamide (JP-B-35-11219), vinyl acetate resin (JP-B-41-2425), vinyl acetate copolymer (JP-B-41
No. 2426), an acrylic resin (Japanese Patent Publication No. 35-11216), and an acrylate copolymer (for example, Japanese Patent Publication No. 35-11219).
Nos. JP-B-36-8510, JP-B-41-13946, etc.) are known.

However, in the electrophotographic photosensitive material using these resins, 1) the affinity with the photoconductive powder is insufficient, and the dispersibility of the coating liquid is poor. 2) The chargeability of the photoconductive layer is poor. Low,
3) Poor quality of the image portion (particularly halftone dot reproducibility / resolution) of the copied image; 4) The image quality is easily affected by the environment (for example, high temperature, high humidity, low temperature, low humidity, etc.) at the time of creating the copied image. There was a problem.

Various methods have been proposed as a method for improving the electrostatic properties of the photoconductive layer. One of the methods is, for example, a compound containing a carboxyl group or a nitro group on an aromatic ring or a furan ring, or a dicarboxylic acid anhydride. Methods of further combining the materials to coexist in the photoconductive layer are disclosed in JP-B-42-6878 and JP-B-45-3073. However, even a photosensitive material improved by these methods does not have sufficient electrostatic characteristics, and a material having particularly excellent light attenuation characteristics has not been obtained. Therefore, in order to improve the sensitivity shortage of this photosensitive material,
Conventionally, a method of adding a large amount of a sensitizing dye to the photoconductive layer has been adopted. However, the light-sensitive material produced by such a method significantly deteriorates whiteness and deteriorates the quality of a recording medium. In some cases, the dark decay of the photosensitive material is deteriorated, and a sufficient copied image cannot be obtained.

On the other hand, Japanese Patent Application Laid-Open No. 60-10254 discloses a method in which the average molecular weight of the resin is adjusted and used as the binder resin used in the photoconductive layer. That is, by using an acrylic resin having an acid value of 4 to 50 and a component having a distribution having an average molecular weight of 10 ³ to 10 ⁴ and a component having a distribution having a distribution of 10 ⁴ to 2 × 10 ⁵ , the electrostatic properties ( In particular, there is described a technique for improving the reproducibility of the PPC photoreceptor), moisture resistance and the like.

Furthermore, research on a lithographic printing original plate using an electrophotographic photoreceptor has been earnestly conducted, and a binder resin for a photoconductive layer having both electrostatic characteristics as an electrophotographic photoreceptor and printing characteristics as a printing original plate. For example, in Japanese Patent Publication No. 50-31011,
Copolymerized with (meth) acrylate monomer and other monomers in the presence of fumaric acid, Tg 10-80 at Mw 1.8-10 × 10 ⁴
C. and a copolymer comprising a (meth) acrylate monomer and a monomer other than fumaric acid. JP-A-53-54027 discloses that a carboxylic acid group is formed by forming at least an atom from an ester bond. Those using a terpolymer containing a (meth) acrylic ester having a substituent which is located at a distance of several sevens, and those disclosed in JP-A-54-20735 and JP-A-57-20254.
No. 4 uses a quaternary or pentameric copolymer containing acrylic acid and hydroxyethyl (meth) acrylate,
JP-A-58-68046 discloses a method using a terpolymer containing a (meth) acrylate ester having an alkyl group having 6 to 12 carbon atoms as a substituent and a carboxylic acid-containing vinyl monomer. It is described that it is effective in improving the desensitizing property of the layer.

(Problems to be Solved by the Invention) However, even if a resin is considered to be effective in the above-mentioned electrostatic properties and moisture resistance properties, particularly when it is actually evaluated, it is particularly chargeability, dark charge retention, light There are problems in electrostatic characteristics such as sensitivity, smoothness of the photoconductive layer, and the like, and these have not been practically satisfactory.

Further, even in the case of a binder resin which was developed as an electrophotographic lithographic printing plate precursor, when actually evaluated, there were problems with the above-described electrostatic characteristics, background contamination of printed matter, and the like.

The present invention is to improve the above-mentioned problems of the conventional electrophotographic photosensitive member.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-quality electrophotographic photoreceptor having improved electrostatic characteristics (particularly dark charge retention and photosensitivity) and reproducing a copied image faithful to an original image.

Another object of the present invention is to provide an electrophotographic photoreceptor having a clear and high-quality image even when the environment at the time of forming a copy image fluctuates such as low temperature and low humidity or high temperature and high humidity.

Another object of the present invention is to provide a CPC electrophotographic photoreceptor having excellent electrostatic characteristics and low environmental dependency.

It is another object of the present invention to provide a lithographic printing plate that provides a printed matter that does not cause background stain at all as an electrophotographic lithographic printing original plate.

Another object of the present invention is to provide an electrophotographic photoreceptor that is hardly affected by the type of sensitizing dye that can be used in combination.

(Means for Solving the Problems) The above-mentioned problem is caused by the fact that in an electrophotographic photosensitive member having a photoconductive layer containing at least a photoconductive zinc oxide, a binder resin and a spectral sensitizing dye, the binder resin is A copolymer component having a weight average molecular weight of 10 ³ to 10 ⁴ and containing at least one acidic group selected from a —PO ₃ H ₂ group and a —SO ₃ H group.
The problem is solved by an electrophotographic photoreceptor characterized in that it is a copolymer containing at least 30% by weight of a copolymer component corresponding to a monomer represented by the following general formula (I): .

General formula (I) In the formula (I), X represents a hydrogen atom, a halogen atom, a cyano group or an alkyl group having 1 to 4 carbon atoms. R ′ is an alkyl group having 1 to 18 carbon atoms which may be substituted, an alkenyl group having 2 to 18 carbon atoms which may be substituted,
12 to 12 optionally substituted aralkyl groups, 5 to 5 carbon atoms
And 8 represents an optionally substituted cycloalkyl group or an optionally substituted aryl group.

That is, the binder resin used in the present invention is a resin having a weight average molecular weight of 10,000 or less containing the above-mentioned acidic group and the monomer represented by the above general formula (I).

Preferably, the resin has a weight average molecular weight of 5 × 10 ^{3 to} 9
× 10 ³ , and the content of the copolymer component containing the acidic group is preferably 0.1 to 8% by weight.

Conventionally known acidic group-containing binder resins as described above are mainly used for offset masters, and have a large molecular weight (for example, 5 × 10 ⁴ or more) in order to improve printing durability by maintaining film strength.

On the other hand, in the present invention, the binder resin has an acidic group contained in the resin adsorbed on a stoichiometric defect of the inorganic photoconductor, and is a low molecular weight substance. It has been found that while improving the surface coverage, the trapping of the photoconductor is compensated and the humidity characteristics are improved, while the photoconductor is sufficiently dispersed and aggregation is suppressed.

 Accordingly, the smoothness of the photoconductive surface becomes smooth.

On the other hand, when a photoconductor having a rough surface of the photoconductive layer is used as the electrophotographic lithographic printing plate precursor, the dispersion state of the zinc oxide particles as the photoconductor and the binder resin is not appropriate, and an aggregate exists. Since the photoconductive layer is formed in the state, even if the desensitizing treatment with the desensitizing solution is performed, the non-image portion is not sufficiently and sufficiently hydrophilized, causing adhesion of the printing ink during printing, and as a result, The background stain on the non-image portion of the printed matter occurs.

On the other hand, by reducing the molecular weight of the binder resin according to the present invention,
There was concern that the film strength was weakened, but the photoconductor was sufficiently dispersed and adsorbed and coated on the surface of the particles to maintain the film properties, and the CPC photoreceptor or an offset master with thousands of printed sheets It was found that the film had sufficient film strength.

If the molecular weight of the binder resin is smaller than 10 ³ , the film-forming ability is reduced and sufficient film strength cannot be maintained. On the other hand, the molecular weight is 10 ⁴
If it is larger, the electrophotographic characteristics (particularly, initial potential and dark decay retention) deteriorate, which is not preferable. In particular, in the case of such a high molecular weight product, when the content of the acidic group exceeds 3%, such deterioration of the electrophotographic characteristics is remarkable, and background fouling becomes remarkable when used as an osset master.

If the content of the acidic group in the binder resin is less than 0.05% by weight, the initial potential is too low to obtain a sufficient image density. On the other hand, when the acidic group content is more than 10% by weight,
The dispersibility is reduced, the film smoothness and the high-humidity characteristics of the electrophotographic properties are reduced, and the background fouling is increased when used as an offset master.

The glass transition point of the resin is preferably in the range of -10 ° C to 100 ° C, more preferably -5 ° C to 80 ° C.

The binder resin according to the present invention contains a monomer represented by the following general formula (I) as a copolymer component in a total amount of 30% by weight.
It contains above.

General formula (I) In the general formula (I), X represents a hydrogen atom, a halogen atom (for example, a chloro atom or a bromo atom), a cyano group or an alkyl group having 1 to 4 carbon atoms. R 'has 1 to 1 carbon atoms
18 alkyl groups which may be substituted (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, 2-methoxyethyl group , 2-
An ethoxyethyl group and the like; an optionally substituted alkenyl group having 2 to 18 carbon atoms (for example, a vinyl group, an allyl group, an isopropenyl group, a butenyl group, a hexenyl group, a heptenyl group, an octenyl group, etc.), and a carbon number of 7 to 18; 12 optionally substituted aralkyl groups (eg, benzyl group, phenethyl group, methoxybenzyl group, ethoxybenzyl group, methylbenzyl group, etc.), and optionally substituted cycloalkyl groups having 5 to 8 carbon atoms (eg, cyclopentyl) Group, cyclohexyl group, cycloheptyl group, etc.), and optionally substituted aryl group (for example, phenyl group, tolyl group, xylyl group,
Mesyl group, naphthyl group, methoxyphenyl group, ethoxyphenyl group, chlorophenyl group, dichlorophenyl group, etc.).

The “copolymer component containing an acidic group” of the present invention may be any vinyl compound containing the acidic group that can be copolymerized with, for example, the general formula (I). Polymer Data Handbook [Basic Edition], Baifukan (1986). Specific examples include vinylbenzene sulfonic acid, vinyl sulfonic acid, vinyl phosphonic acid, and compounds containing the sulfonic acid ester derivative or amide derivative containing the acidic group in the substituent.

Further, the resin of the present invention may contain other monomers as copolymerization components together with the monomer of the general formula (I) and the monomer containing the acidic group.

For example, α-olefins, vinyl alkanoates or allyl esters, acrylonitrile, methacrylonitrile, vinyl ethers, acrylamides, methacrylamides, styrenes, heterocyclic vinyls (eg, vinylpyrrolidone, vinylpyridine, vinylimidazole, vinylthiophene) , Vinyl imidazoline, vinyl pyrazole, vinyl dioxane, vinyl quinoline, vinyl thiazole, vinyl oxazine, etc.). Particularly, vinyl acetate, allyl acetate, acrylonitrile, methacrylonitrile, styrenes and the like are preferable components from the viewpoint of improving the film strength.

Examples of the inorganic photoconductive material used in the present invention include zinc oxide.

The total amount of the binder resin used for the inorganic photoconductive material is 10 to 100 parts by weight, preferably 15 to 50 parts by weight, based on 100 parts by weight of the photoconductor.

In the present invention, various dyes can be used in combination as a spectral sensitizer. For example, Harumiya Miyamoto: Hidehiko Takei; Imaging 1973 (No.8), page 12, CJ Young, RCA Review 1
5 , 469 (1954), Kohei Kiyota, IEICE Transactions J63
-C (No.2), 97 (1980), Yuji Harasaki, etc., Industrial Chemistry Magazine
66 , 78 and 188 (1963), Tadaaki Tani, Journal of the Photographic Society of Japan 35 , 2
08 (1972), such as carbonium dyes, diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, phthalein dyes, and polymethine dyes (eg, oxonol dyes, merocyanine dyes, cyanine dyes, rhodacyanine dyes, styryl dyes), and the like. And phthalocyanine dyes (which may contain a metal).

More specifically, those using mainly carbonium dyes, triphenylmethane dyes, xanthene dyes, and phthalein dyes are described in JP-B-51-452,
0-90334, JP-A-50-114227, JP-A-53-39130
And JP-A-53-82353, U.S. Pat. No. 3,052,540, U.S. Pat. No. 4,054,450, and JP-A-57-16456.

Oxonol dyes, merocyanine dyes, cyanine dyes, polymethine dyes such as rhodacyanine dyes, F.
M. Hamer, `` The Cyanine Dyes and Related Compound
s '' can be used, and more specifically, U.S. Pat.No. 3,047,384, U.S. Pat.No. 3,110,591, U.S. Pat.No. 3,121,008, U.S. Pat.
No. 28179, U.S. Pat.No. 3,313,942, U.S. Pat.No. 3,622,317
No., British Patent No. 1226892, British Patent No. 1309274, British Patent No. 1405898, JP-B-48-7814, JP-B-55-18892
And the like.

Further, as a polymethine dye for spectrally sensitizing the near infrared to infrared light region having a long wavelength of 700 nm or more, JP-A-47-840, JP-A-47-44180, JP-B-51-41061, 1949-5034
No., JP-A-49-45122, JP-A-57-46245, JP-A-56
No. -35141, JP-A-57-157254, JP-A-61-26044,
JP-A-61-27551, U.S. Pat.No. 3,619,154, U.S. Pat.
4175956, "Research Disclosure", 1982, 216, No. 1
And those described on pages 17 to 118 and the like.

The photoreceptor of the present invention is also excellent in that even when various sensitizing dyes are used in combination, the performance is not easily changed by the sensitizing dye.

Furthermore, various conventionally known additives for an electrophotographic photosensitive layer such as a chemical sensitizer can be used in combination, if necessary. For example, the review mentioned above: Imaging 1973 (No. 8)
"Recent development and commercialization of photoconductive materials and photoreceptors", e.g., electron accepting compounds (eg, halogen, benzoquinone, cranyl, acid anhydride, organic carboxylic acid, etc.) described in the reviews on page 12, etc. Chapters 4 to 6: Polyarylalkane compounds, which are reviewed in Japanese Science Information Publishing Co., Ltd. (1986)
Hindered phenol compounds, p-phenylenediamine compounds and the like.

The amount of these various additives is not particularly limited,
Usually, it is 0.0001 to 2.0 parts by weight based on 100 parts by weight of the photoconductor.

The thickness of the photoconductive layer is preferably from 1 to 100 μm, particularly preferably from 10 to 50 μm.

When a photoconductive layer is used as the charge generation layer of the photoreceptor having the charge generation layer and the charge transport layer, the thickness of the charge generation layer is preferably 0.01 to 1 μm, particularly preferably 0.05 to 0.5 μm.

Examples of the charge transporting material for the laminated photoreceptor include polyvinyl carbazole, oxazole dyes, pyrazin dyes, and triphenylmethane dyes. The thickness of the charge transport layer is preferably 5 to 40 μm, particularly preferably 10 to 30 μm.

As the resin used for forming the insulating layer or the charge transport layer, typical ones are polystyrene resin, polyester resin, cellulose resin, polyether resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride-copolymer resin, A thermoplastic resin and a curable resin such as a polyacryl resin, a polyolefin resin, a urethane resin, an epoxy resin, a melamine resin, and a silicone resin are appropriately used.

The photoconductive layer according to the present invention can be provided on a conventionally known support. Generally speaking, the support of the electrophotographic photosensitive layer is preferably conductive. As the conductive support, a base material such as metal, paper, plastic sheet or the like is impregnated with a low-resistance substance in the same manner as in the related art. A substrate that has been subjected to a conductive treatment, for example, by applying a conductivity to the back surface of the substrate (the surface opposite to the surface on which the photosensitive layer is provided), and further coated with at least one layer for the purpose of preventing curling and the like. A substrate provided with a water-resistant adhesive layer on its surface, a substrate provided with at least one or more pre-coat layers as required on the surface layer of the support, and a substrate-conductive plastic on which Al or the like is deposited is laminated on paper. Can be used.

Specifically, as an example of a conductive substrate or a conductive material, Yukio Sakamoto, Electrophotography, 14, (No. 1), pp. 2-11 (1975), Hiroyuki Moriga, "Chemistry of Introductory Specialty Paper," Molecular Publishing Association (1975), MFHoover, J. Macromol. Sci. Chem. A-4
(6), and those described in pages 1327 to 1417 (1970) and the like are used.

(Examples) Embodiments of the present invention will be illustrated below, but the contents of the present invention are not limited thereto.

Synthesis Example 1 A mixed solution of 95 g of ethyl methacrylate, 5 g of acrylic acid, and 200 g of toluene was heated to a temperature of 90 ° C. under a nitrogen stream, and then heated to 2,2′-azobis (2,4-dimethylvaleronitrile).
6 g was added and reacted for 10 hours. Obtained copolymer (I)
Had a weight average molecular weight of 7,800 and a glass transition point of 45 ° C.

Synthesis Example 2 A mixed solution of 95 g of ethyl methacrylate, 5 g of methacrylic acid, and 200 g of toluene was heated to a temperature of 75 ° C. under a nitrogen stream, and 1.0 g of azobisisobutyronitrile was added to react for 8 hours. The weight average molecular weight of the obtained copolymer (II) is 45.
000, the glass transition point was 48 ° C.

Synthesis Example 3 A mixed solution of 100 g of ethyl methacrylate and 200 g of toluene was heated to a temperature of 90 ° C. in a nitrogen stream, 6 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added, and the mixture was reacted for 10 hours. . The weight average molecular weight of the obtained copolymer (III) was 7,500 and the glass transition point was 45 ° C.

Reference Example 1 A mixture of 40 g (as solid content) of the copolymer (I) produced in Synthesis Example 1, 200 g of zinc oxide, 0.05 g of rose bengal and 300 g of toluene was dispersed in a ball mill for 2 hours to prepare a photosensitive layer-formed product. This was applied to a conductive-treated paper with a wire bar so that the dry adhesion amount was 22 g / m ^2, and dried at 110 ° C. for 1 minute. Then, in the dark, at 20 ° C and 65% RH
An electrophotographic photoreceptor was prepared by being left for 24 hours.

Comparative Example A Synthesis Example 2 in place of the copolymer (I) used in Reference Example 1
A comparative electrophotographic photosensitive member A was produced in the same manner as in Reference Example 1 except that 40 g (as solid content) of the copolymer (II) produced in (1) was used.

Comparative Example B Copolymer (I) produced in Synthesis Example 1 as a binder resin
An electrophotographic photosensitive member B for comparison was produced in the same manner as in Reference Example 1 except that 20 g (as solid content) and 20 g (as solid content) of the copolymer (II) produced in Synthesis Example 2 were used.

Comparative Example C Synthesis Example 3 in place of the copolymer (I) used in Reference Example 1
Comparative electrophotographic photoreceptor C was produced in the same manner as in Reference Example 1 except that 40 g (as solid content) of copolymer (III) produced in the above was used.

The film properties (surface smoothness), electrostatic properties, imaging properties, and imaging properties of these photosensitive materials when the environmental conditions were 30 ° C. and 80% RH were examined. Furthermore, when these photosensitive materials are used as masters for offset masters, the photoconductive layer is desensitized (expressed by the contact angle with water of the photoconductive layer after desensitization treatment) and printable (ground contamination). , Printing durability, etc.).

The image-capturing property and printability were measured using a fully automatic plate-making machine ELP404V (manufactured by Fuji Photo Film Co., Ltd.) using a developer ELP-T.
An image was formed by development processing, and examined using a lithographic printing plate obtained by etching with a desensitizing liquid ELP-E using an etching processor (note that the printing machine was Hamadastar Co., Ltd.) Hamadastar 800SX type).

 Table 1 summarizes the above results.

The embodiments of the evaluation items described in Table 1 are as follows.

Note 1) Smoothness of photoconductive layer: The obtained photosensitive material was measured for its smoothness (sec / cc) using a Bekk smoothness tester (manufactured by Kumagaya Riko Co., Ltd.) under the condition of an air capacity of 1 cc. It was measured.

Note 2) Electrostatic property: Paper analyzer (Kawaguchi Electric Co., Ltd. paper analyzer) in a dark room at a temperature of 20 ° C and 65% RH.
After the 20 seconds corona discharge 6kV with SP-428 type), allowed to stand for 10 seconds to measure the surface potential V ₁₀ at this time.
Then, the potential V ₇₀ after standing still in the dark for 60 seconds was measured, and the retention of the potential after dark decay for 60 seconds, that is, the dark decay retention rate [DRR (%)] was calculated as (V ₇₀ / V ₁₀ ) x 100 (%)
I asked for it. Also, the surface of the photoconductive layer is -400 V by corona discharge.
After that, the surface of the photoconductive layer was irradiated with visible light having an illuminance of 2.0 lux, and the time required for the surface potential (V ₁₀ ) to attenuate to 1/10 was determined. From this, the exposure amount E _1/10 (lux) was obtained.・
Second).

Note 3) Imageability: Copy images (fog, image) obtained by leaving each photosensitive material for one day and night under the following environmental conditions, and then making a plate using a fully automatic plate-making machine ELP-404V (Fuji Photo Film Co., Ltd.) Image quality) was visually evaluated. Environmental conditions at the time of imaging are 20 ° C and 65% RH (I).
The test was performed at 30 ° C. and 80% RH (II).

Note 4) Contact angle with water: Each photosensitive material was treated with an desensitizing solution ELP-E (manufactured by Fuji Photo Film Co., Ltd.) for 1 hour in an etching processor.
After passing through the photoconductive layer to desensitize the surface of the photoconductive layer, a drop of 2 μm of distilled water is placed thereon, and the contact angle with the formed water is measured by a goniometer.

Note 5) Smearing of printed matter: Each photosensitive material is made into a plate by full-plate making machine ELP404V (manufactured by Fuji Photo Film Co., Ltd.) to form a toner image, and desensitized under the same conditions as above (Note 3). Using this as an offset master, an offset printing machine (Hamaduster 800SX, manufactured by Hamadastar Co., Ltd.) is used to print 500 sheets on high-quality paper, and the soiling of all printed matter is visually determined. This is referred to as background smear I of the printed matter.

The background smear II of the printed matter is tested in the same manner as the background smear I except that the desensitizing solution is diluted 5 times and the dampening solution for printing is diluted 2 times. The case of II corresponds to printing under more severe conditions than I.

Note 6) Printing durability: Indicates the number of sheets that can be printed without causing any problem in background stain on the non-image area and image quality of the image area when each photosensitive material is processed under the evaluation conditions of print smear I described in Note 5). (The greater the number of prints, the better the printing durability.) Note 7) DM (Image Density): Indicates the maximum value of the solid toner image density (measured with a Macbeth reflection densitometer).

As shown in Table 1, the photosensitive material of Reference Example 1 had good photoconductive layer smoothness and electrostatic properties, and the actual copied image had no background fog and the copied image quality was clear. This is presumed to be due to the photoconductor and the binder resin being sufficiently adsorbed and covering the particle surface. For the same reason, even when used as an offset master master, the desensitizing treatment with the desensitizing solution proceeds sufficiently, the contact angle with water of the non-image area is as small as 15 degrees or less, and it is sufficiently hydrophilic. You can see that it is. Even when the printed material was actually printed and the background stain was observed, no background stain was observed. In Comparative Example A, which is a copolymer having the same composition as the resin of Reference Example 1 and has a large weight average molecular weight, the smoothness of the photoconductive layer is remarkably deteriorated, and further, the electrostatic properties, particularly the DRR, are poor. It got worse. Even when used as an offset master, the contact angle with water of the non-image area after desensitization treatment was as large as 35 degrees, and even when printing was actually performed, background stains were generated from printing. This is presumed to be caused by an increase in the molecular weight of the binder resin, causing aggregation between the particles and adsorption to the photoconductor particles, resulting in an adverse effect.

Comparative Example B is a combination of copolymers having the same composition but different molecular weights. However, aggregation of the high molecular weight occurs, and as a result, the performance is reduced to the same level as the photoreceptor having only the high molecular weight. I got it.

In Comparative Example C using a resin containing no acidic group, the smoothness of the photoconductive layer was good, and the degree of hydrophilicity of the non-image area after the desensitization treatment was sufficiently advanced. However, the electrophotographic properties, particularly the initial potential and the dark charge retention were extremely poor, and the image density of the copied image was significantly reduced. Therefore, when printing as an offset master, the non-image area is sufficiently hydrophilized and no background smearing occurs, but the density of the image area is low and the toner area is small, so the printing ink receptivity decreases and the printing starts. After about 500 sheets, the ink on the image area became insufficient, and the image area was cut off and the solid image was whitened (insufficient inlay). This means that low-molecular-weight resins that do not contain acidic groups have an interaction that disperses the photoconductor, but the adsorption with the photoconductor is insufficient, which is not sufficient to satisfy the electrostatic properties. It is estimated to be. On the other hand, a binder resin was prepared in the same manner as in Synthesis Example 1 except that the acrylic acid content was 12% by weight, and a photosensitive layer-formed product was prepared in the same manner as in Reference Example 1. It could not be liquid.

As described above, when the resin of Reference Example 1 containing a specific amount of an acidic group and having a weight average molecular weight in a specific range is used, an electrophotographic photosensitive member satisfying electrostatic characteristics and printability is obtained. You can see that.

Examples 1 to 3 As resins, copolymers shown in Table 2 were produced in the same manner as in the production conditions of Synthesis Example 1.

Each photoconductor was prepared in the same manner as in Reference Example 1 except that 40 g (as solid content) of each resin shown in Table 2 was used instead of the copolymer (I) used in Reference Example 1. Each characteristic was measured in the same manner as in Example 1. The surface of the photoconductive layer of each photoreceptor was smooth at 80 (sec / cc) or more. Table 3 shows the results of the electrostatic characteristics and the imaging performance.

All photosensitive materials of the present invention are chargeable, dark charge retention,
Excellent light sensitivity, real copy image is high temperature and humidity (30 ℃, 80%
Even under severe conditions (RH), a clear image was obtained without occurrence of ground fogging or fine line skipping.

(Effects of the Invention) According to the present invention, it is possible to obtain an electrophotographic photoreceptor having excellent photoconductive layer smoothness, electrostatic properties, image-capturing property, desensitizing property and background contamination.

Furthermore, the photosensitive material of the present invention has a sufficiently high printing durability of about several thousand sheets.

Furthermore, the electrophotographic photoreceptor of the present invention can have excellent photoconductive layer smoothness, electrostatic properties and the like even when used in combination with various sensitizing dyes.

Continuation of the front page (56) References JP-A-53-54027 (JP, A) JP-A-54-12741 (JP, A) JP-A-58-127931 (JP, A) JP-A-58-127930 (JP, A) , A) JP-B-44-6394 (JP, B1) JP-B-46-11636 (JP, B1) JP-B-48-34183 (JP, B1)

Claims (1)

(57) [Claims] An electrophotographic photosensitive member having a photoconductive layer containing at least a photoconductive zinc oxide, a binder resin and a spectral sensitizing dye, wherein the binder resin has a weight average molecular weight of 10 ³ to 10 ^4. and, and a copolymer component containing at least one acidic group selected from -PO ₃ H ₂ group and -SO ₃ H group 0.05
An electrophotographic photoreceptor characterized in that it is a copolymer containing 30% by weight or more of a copolymer component corresponding to a monomer represented by the following general formula (I) by weight. General formula (I) In the formula (I), X represents a hydrogen atom, a halogen atom, a cyano group or an alkyl group having 1 to 4 carbon atoms. R 'is an optionally substituted alkyl group having 1 to 18 carbon atoms, 2 carbon atoms.
-18 optionally substituted alkenyl groups, having 7-carbon atoms
12 aralkyl groups which may be substituted, having 5 to 8 carbon atoms
Represents an optionally substituted cycloalkyl group or an optionally substituted aryl group.