JP2884812B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member that can be widely used in fields such as a CRT printer, a laser beam printer, an electrophotographic copying machine, and an electrophotographic plate making system.

[0002]

2. Description of the Related Art In general, an electrophotographic photosensitive member obtained by providing a photosensitive layer comprising a charge generating substance and a charge transporting substance on a base material such as an aluminum cylinder,
From the viewpoint of its use, it is necessary to have excellent sensitivity, electrical characteristics, optical characteristics, and the like. However, in the conventional electrophotographic photoreceptor, there has been a problem that the surface is deteriorated due to ozone generated by corona discharge due to repeated use for a long period of time, which causes a decrease in sensitivity and an increase in residual potential. In addition, if paper dust adheres to the photosensitive layer due to contact with paper, image deletion occurs. Even if toner adheres due to toner filming or poor cleaning, a similar problem occurs. Desirably, it is desirable to have a characteristic that is difficult to remove or a substance that can easily remove attached matter, but there is still room for improvement in this regard.

In order to solve the above problems, it has been proposed to use a resin having excellent abrasion resistance, such as polycarbonate, as a binder for the photosensitive layer. In this case, however, cleaning of adhering paper powder and residual toner is performed. And the image quality is degraded. For the purpose of improving the cleaning properties, it has been proposed to use a polycarbonate as a binder and to add a surface modifier such as silicone oil or Teflon. Poor compatibility,
There is a problem that the photosensitive layer is removed from the photosensitive layer within a relatively short time.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, the present invention, on the top of the photosensitive layer,
It is obtained by copolymerizing (a) a macromonomer having a (meth) acryloyl group at one end of silicone, (b) an α, β-ethylenically unsaturated carboxylic acid and (c) other radically polymerizable monomers. Has an acid value of 30 to 260 mg KOH /
It is an electrophotographic photoreceptor having a film made of a graft copolymer of g resin.

Hereinafter, the present invention will be described in more detail. Constituting the graft copolymer in the present invention,
(A) A macromonomer having a (meth) acryloyl group at one end of silicone (hereinafter referred to as silicone-based macromonomer) is a high molecular weight monomer having a silicone skeleton, and its preferred number average molecular weight is gel permeation. The number average molecular weight is 1,000 to 50,000 in terms of polystyrene as measured by chromatography. When the number average molecular weight of the macromonomer is less than 1,000, properties derived from silicone, that is, lubricity,
Properties such as releasability and weather resistance are hardly exhibited, while when the number average molecular weight is 50,000 or more, the copolymerizability of the macromonomer is inferior.

The preferred amount of the silicone-based macromonomer is 0.5 to 60% by weight, based on the total amount of all radically polymerizable components to be copolymerized, that is, all the monomers including the macromonomer. Is 2 to 50
% By weight. If the amount of the silicone-based macromonomer is less than 0.5% by weight, the properties of the silicone such as lubricity and releasability will not be sufficiently exhibited. Phase separation easily occurs during storage of the polymer, and a stable solution cannot be obtained.

The silicone-based macromonomer can be synthesized by anionically polymerizing a cyclic siloxane with lithium trialkylsilanolate as an initiator to obtain a living polymer and reacting it with γ-methacryloxypropyldimethylmonochlorosilane. (For example, JP-A-59-78236). Further, Japanese Patent Application Laid-Open Nos. Sho 58-167606 and
The production method disclosed in JP-A-123518, that is, a method of obtaining a silicone-based macromonomer as a condensation reaction product of a silicone having a terminal silanol group and an organosilicon compound may be employed.

Next, (b) α, β-ethylenically unsaturated carboxylic acid used together with the silicone-based macromonomer will be described. Examples of the α, β-ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and citraconic acid, and preferably acrylic acid and methacrylic acid. The amount of the α, β-ethylenically unsaturated carboxylic acid used in the present invention is such that the acid value of the obtained graft copolymer is from 30 to 260 mg KOH / g resin. % By weight based on total amount
Although it depends on the type of unsaturated carboxylic acid used, it is usually about 3 to 40% by weight. When the acid value of the graft copolymer is less than 30 mg KOH / g resin, the ionicity of the graft copolymer is low, and the residual charge is liable to accumulate when the electrophotographic process is repeatedly performed, so that the quality of the image deteriorates quickly. . On the other hand, if it exceeds 260 mg KOH / g resin, the water resistance is poor.

(C) Other radically polymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. Isobutyl, (meth)
Tert-butyl acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Lauryl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate,
Phenyl (meth) acrylate, 2- (meth) acrylic acid
Examples of (meth) such as hydroxyethyl, 2-hydroxybutyl (meth) acrylate, polyalkylene glycol (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and perfluoroalkyl (meth) acrylate ) Acrylic esters, styrene, vinyltoluene, aromatic vinyl compounds such as α-methylstyrene, (meth) acrylonitrile, vinyl acetate,
Vinyl propionate, N-methylol (meth) acrylamide, vinyl chloride, vinyl fluoride, vinylidene chloride,
Examples include vinylidene fluoride and trichloroethylene. Preferred monomers are methyl (meth) acrylate,
Butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, behenyl (meth) acrylate, styrene, N-methylol (meth) acrylamide, 2-hydroxyethyl (meth) acrylate and Glycidyl (meth) acrylate is used in a preferred amount of 10 to 96% by weight.

The above radical polymerizable component is copolymerized by a radiation irradiation method, a method using a radical polymerization initiator, or the like. A solution polymerization method using a radical polymerization initiator and using an organic solvent is preferred from the viewpoint of easy polymerization operation and easy control of the molecular weight of the resulting graft copolymer. Preferred organic solvents used for solution polymerization include acetone,
Ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; acetate solvents such as ethyl acetate and butyl acetate; aromatic hydrocarbon solvents such as benzene, toluene and xylene; methanol, ethanol, isopropanol, ethyl cellosolve, and butyrosolve; Propylene glycol monomethyl ether, tetrahydrofuran and methylene chloride. Excellent solubility of silicone-based graft copolymer, and good volatility after application,
Isopropanol is particularly preferred because of its low toxicity.

Examples of the radical polymerization initiator include ammonium persulfate, hydrogen peroxide, peroxyketals such as 2,2-bis (tert-butylperoxy) octane, hydroperoxides such as cumene hydroperoxide, and tert.
Dialkyl peroxide such as -butylcumyl peroxide, diacyl peroxide such as benzoyl peroxide, peroxydicarbonate, peroxyester and 2,2′-azobis (2-methylbutyronitrile);
Azobis-4-cyanovaleric acid, azobis (2,4-
Azo compounds such as dimethylvaleronitrile) and 2,2′-azobisisobutyronitrile. To adjust the molecular weight of the graft copolymer, if necessary,
A serial transfer agent such as mercaptoacetic acid, mercaptopropionic acid, 2-propanethiol, 1-butanethiol, 2-methyl-2-propanethiol and ethylmercaptoacetate may be used.

An alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, ammonia or a primary, secondary or tertiary amine compound is added to the graft copolymer solution obtained by the above polymerization to form a carboxyl group. It is also possible to use a graft copolymer in which a part or the whole is neutralized. The neutralized graft copolymer is well miscible with water.

The electrophotographic photoreceptor of the present invention is obtained by forming a film of the above graft copolymer on the surface of a photosensitive layer of an electrophotographic photoreceptor manufactured by a known method. It is as follows. That is, as the substrate, a cylindrical cylinder or a film made of metal such as aluminum or stainless steel can be used. An undercoating layer having a barrier function and an undercoating function is provided on such a base material, and a photosensitive layer containing a charge generating substance and a charge transporting substance is further provided thereon. As a material of the undercoat layer, polyvinyl alcohol, poly-N-
Examples include vinyl imidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, casein, polyamide, copolymerized nylon, glue, gelatin and the like. These are dissolved in a suitable solvent and applied onto a substrate. The preferred film thickness is about 0.2 to 2 μm.

The charge generating material dispersed in the photosensitive layer includes phthalocyanine pigments such as ε-copper phthalocyanine pigment, pyrylium, thiopyrylium dye, anthantrone pigment, dibenzpyrenequinone pigment, pyranthrone pigment, trisazo pigment, disazo pigment. , Azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanines,
Quinocyanine and the like.

As the charge transporting substance, pyrene, N
Hydrazones such as -alkylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, -Phenyl-3- (p-diethylaminostyryl) -5- (p-
Pyrazolines such as diethylaminophenyl) pyrazolin and spiropyrazolin; oxazole compounds such as 2- (p-diethylaminostyryl) -6-diethylaminobenzoxazole; thiazole compounds such as 2- (p-diethylaminostyryl) -6-diethylaminobenzothiazole. And triarylmethane compounds such as bis (4-diethylamino-2-methylphenyl) -phenylmethane; 1,1-bis (4-N, N-diethylamino-
And polyarylalkanes such as 2-methylphenyl) heptane.

The charge generating material and the charge transporting material include:
The photosensitive layer is processed by the following operation together with a binder composed of a dispersing resin such as polycarbonate or polyvinyl butyral. That is, the above-mentioned charge generating material is well dispersed together with a polyvinyl butyral and a solvent in an amount of 0.3 to 10 times by a method such as a homogenizer, an ultrasonic wave, a ball mill, a vibration ball mill, a sand mill, an attritor, and a roll mill. Next, a charge transport material is dissolved in the dispersion to obtain a photosensitive layer forming liquid, which is then subjected to a dip coating method, a spray coating method, a spinner coating method, a beat coating method, a blade coating method, a curtain coating method, or the like. A photosensitive layer is formed by coating on the undercoat layer by a coating method and then drying. The thickness of the photosensitive layer is 1 to 50
About μ is appropriate.

In the present invention, as described above, a film of a silicone-based graft copolymer is further formed on the photosensitive layer. As a method of forming the film, a method of applying an organic solvent solution or an aqueous solution of the silicone-based graft copolymer so that the film thickness after drying is 0.5 to 1 μm is preferable. When the thickness of the film made of the silicone-based graft copolymer is less than 0.5 μm, the cleaning properties are poor.

The silicone-based graft copolymer may be used in combination with a melamine resin such as methylol group-type methylated melamine, imino group-type methylated melamine, imino group-type etherified melamine, a glycol urea resin, a carboxy-modified amino resin, or Crosslinking and curing may be performed at the time of film formation by a chelation reaction between a carboxyl group and a transition metal salt and a reaction with a blocked isocyanate. Further, an acrylic resin, an epoxy resin, an unsaturated polyester resin, a polycarbonate resin, a fluorine resin, or the like may be used together with the silicone graft copolymer in an amount of 50% by weight or less.

[0019]

EXAMPLES The present invention will be described more specifically with reference to the following examples. Parts in the following examples are parts by weight. Example 1 (Synthesis of silicone-based macromonomer) α, ω-dihydroxypolydimethylsilicone (average degree of polymerization 300) 111 was placed in a flask equipped with a stirrer, a condenser and a thermometer.
g (0.005 mol), p-toluenesulfonic acid 0.1
2 g, toluene 74 g, and methyl ethyl ketone 37
g, γ-methacryloyloxypropyltrimethoxysilane, 2.48 g (0.01 mol),
Heated for hours. After cooling, 30 g of a basic anion exchange resin (A-21 manufactured by Organo) was added to the reaction solution, and the mixture was neutralized by stirring at 40 ° C. for 2 hours. The above ion exchange resin was removed by filtration, the filtrate was distilled under reduced pressure, and the solvent was removed to obtain 110 g of a colorless and transparent oily macromonomer. The number average molecular weight in terms of polystyrene of the silicone-based macromonomer as determined by gel permeation chromatography was 35,000.

(Synthesis of Silicone Graft Copolymer)
30 parts of silicone macromonomer, 20 parts of methyl methacrylate, 20 parts of butyl methacrylate, 2 parts of methacrylic acid
-Hydroxyethyl 20 parts, methacrylic acid 10 parts, n-
Dodecyl mercaptan 1.0 part, 2,2 ′ of polymerization initiator
-1.0 part of azobisisobutyronitrile and 100 parts of isopropanol were added to a stirrer, a condenser, a thermometer,
A flask equipped with a nitrogen inlet tube was charged, heated at 80 ° C. for 4 hours while bubbling with nitrogen, further charged with 0.5 part of a polymerization initiator, and the reaction was continued at the same temperature for 4 hours to obtain an acid value. Synthesized a graft copolymer solution (solid content: 50% by weight) of 65 mg KOH / g resin.

(Formation of Undercoat Layer) Lactic Casein 1
After 0 parts were dispersed in 90 parts of water, 1 part of aqueous ammonia was added and dissolved. On the other hand, hydroxypropylcellulose resin (trade name: Metroose 60SH50, manufactured by Shin-Etsu Chemical)
3 parts were dissolved in 20 parts of water, and both solutions were mixed to obtain a coating solution for an undercoat layer. This solution was applied to an aluminum cylinder of 80 mm x 300 mm by the dipping method.
After drying for 0 minutes, an undercoat layer of 2 μm was provided.

(Formation of photosensitive layer and formation of silicone-based graft copolymer film) ε-copper phthalocyanine pigment 2
Of a pigment dispersion obtained by adding 50 parts of commercially available polyvinyl butyral to 50 parts of tetrahydrofuran and further adding glass beads thereto, was subjected to a sand mill for 20 hours in order to uniformly disperse the pigment dispersion. A solution obtained by dissolving 10 parts of a charge transporting substance N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole in the obtained dispersion liquid,
In the same manner as in the case of the undercoat layer, a dip coating was performed on the same layer, followed by drying at 80 ° C. for 10 minutes to form an 18 μm photosensitive layer.

On the photosensitive layer, the above graft copolymer solution was applied by dip coating and dried at 80 ° C. for 10 minutes to form a film having a thickness of 1 μm, thereby obtaining an electrophotographic photosensitive member. The obtained photoreceptor was subjected to a durability test of an electrophotographic process including a cleaning operation using a urethane rubber blade. As a result, a stable high-quality image was obtained up to 20,000 sheets. In addition, when an endurance test of 20,000 sheets was conducted at room temperature and normal pressure with an electrophotographic copying machine having a -5.5 Kv corona charger, the VD potential and the VL current exposed for 7.5 lux seconds were not longer. VD before test = -6
93; VL = -178, after test VD = -67
8; VL = -192, fluctuation was small and stable.

Example 2 Using the isopropanol solution of the silicone-based graft copolymer used in Example 1, 100 parts of a 5% aqueous solution of diethanolamine was gradually added with stirring to adjust the pH to 7.
A clear aqueous solution of 7 was obtained. The aqueous solution was dip-coated on the photosensitive layer of the photosensitive member formed in the same manner as in Example 1, and then dried to form a silicone-based graft copolymer film having a thickness of 1 μm. The electrophotographic photoreceptor thus obtained was subjected to the same durability test as in the previous example. As a result, a stable high-quality image was obtained up to 20,000 sheets.

[0025]

According to the electrophotographic photoreceptor of the present invention, a silicone-based graft copolymer having a specific acid value is formed on the surface of the photosensitive layer. In addition, it has a characteristic that accumulation of residual charges hardly occurs even when the electrophotographic process is repeatedly performed, and a high-quality image can be obtained even when used for a long time.

Continuation of the front page (56) References JP-A-3-33752 (JP, A) JP-A-4-278959 (JP, A) JP-A-63-227670 (JP, A) JP-A-2-163177 (JP) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 5/00-5/16

Claims (1)

(57) [Claims] 1. A macromonomer having (a) a (meth) acryloyl group at one end of silicone, on the photosensitive layer,
(B) a film comprising a graft copolymer of an acid value of 30 to 260 mg KOH / g resin, obtained by copolymerizing (b) α, β-ethylenically unsaturated carboxylic acid and (c) other radical polymerizable monomers An electrophotographic photosensitive member having: