JP2560269B2 - Method for manufacturing electrophotographic photosensitive layer - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for manufacturing an electrophotographic photosensitive layer can effectively convert light energy into electrical energy.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic photosensitive member as a photoelectric conversion element is an inorganic photosensitive material such as amorphous selenium, selenium alloy, cadmium sulfide or zinc oxide, or an organic material represented by polyvinylcarbazole and polyvinylcarbazole derivatives. System light-sensitive materials are widely known. It is also known that an organic dispersion type photosensitive layer is used as a charge generating layer of a function-separated type electrophotographic photosensitive member.

[0003]

Amorphous selenium or selenium alloy has excellent characteristics as an electrophotographic photoreceptor,
It is well known that it is put to practical use. However, there is a drawback in that its production requires a complicated process of vapor deposition, and the vapor deposition film produced is not flexible. When zinc oxide is used, it is used as a dispersion type photosensitive material in which zinc oxide is dispersed in a resin. However, such a photosensitive material has difficulty in mechanical strength and cannot withstand repeated use as it is. Polyvinylcarbazole, which is widely known as an organic photoconductive material, has advantages such as transparency, film-forming property, and flexibility, but polyvinylcarbazole itself has no sensitivity in the visible light range. It cannot be put to practical use as it is, and therefore various sensitizing methods have been proposed. However, when polyvinylcarbazole is spectrally sensitized by using a dye sensitizer, the spectral sensitivity range is extended to the visible light range, but the electrophotographic photoconductor has a drawback that fatigue is serious. . Further, when chemically sensitized with an electron-accepting compound, a photosensitive member having good sensitivity can be obtained as a photosensitive member for electrophotography, and some of them have been put into practical use There are problems in strength and life.

Despite active research on organic dispersion type photosensitive materials and numerous reports, a photosensitive body having excellent electric characteristics and sufficient reliability as a photosensitive body for electrophotography has not yet been obtained. Not. One of the reasons is that the dispersed pigment as the photoelectric conversion substance is randomly dispersed in the matrix polymer, and the orientation and the dispersed state are not controlled. Another reason is that reliability is deteriorated due to the presence of deep trapping sites for holes or electrons formed at the interface between the dispersed pigment as the photoelectric conversion substance and the matrix polymer.

When an organic dispersion type photosensitive layer is used as a charge generating layer of a function-separated type electrophotographic photosensitive member, it is necessary to make the layer as thin as possible have sufficient absorption of light energy for high sensitivity and reliability. Desirable to maintain. To that end, it is desirable that the dispersed pigment be present in the thin charge generation layer in the highest possible concentration. However, in general, a dispersed pigment as a photoelectric conversion substance has a high cohesive property, so that it is difficult to disperse it in a matrix polymer at a certain concentration or more. Also, conventionally known dip coating method, spray coating method, spinner coating method, bead coating method, blade coating method,
With a coating method such as a wire bar coating method, it is not easy to form a very thin layer with uniform and controlled dispersion.

In view of such a situation, the present invention is directed to an electrophotographic photosensitive layer comprising a monomolecular film whose orientation is highly controlled.
It aims at providing the manufacturing method of. Furthermore, the present invention has a high conversion efficiency, and to provide a manufacturing method of an electrophotographic photosensitive layer having good reliability and resolution of repetition stability.

[0007]

The electrophotographic photosensitive layer of the present invention
The manufacturing method of , on the surface of water, to form a monomolecular film containing a squarylium dye represented by the following general formula,
It is characterized in that an organic thin film made of a squarylium dye is formed on the surface of the substrate by bringing the monomolecular film into contact with a suitable substrate.

Embedded image (In the formula, R represents an alkyl group)

Next, typical examples of the squarylium dye used in the present invention will be given.

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[0009]

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[0010]

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The above square lilium dye is HESpre
nger and W.Ziegenbein; Angew.Chem.internat.Edit., V
It can be produced by a method similar to the method described in ol. 5, p894 (1966). An electrophotographic photosensitive layer made of the organic thin film, to be formed on the substrate by uniformly and form a film forming molecules are highly oriented control, to form a monomolecular film on the water surface as described below, appropriate The method of transferring onto the substrate is adopted
It By this method, a highly oriented monomolecular film containing one or more squarylium dyes represented by the above general formula is formed on the surface of water, and the monomolecular film is repeatedly contacted with an appropriate substrate. As a result, the electrophotographic photosensitive layer made of a thin film containing a square lilium dye can be formed on the surface of the substrate.

As a method for accumulating a highly oriented controlled monomolecular film containing a squarylium dye of the present invention, a liquid in which a film substance is dissolved is spread on a water surface, and the spread film is compressed at a constant surface pressure. Then, the Langmuir-Blodgett (Langmua-Blodgett
The ir-Blodgett) method, horizontal attachment method, rotating cylinder method, etc. are used. For example, in the Langmuir-Blodgett method, first, a squarylium dye and other substances, if necessary, are dissolved in an organic solvent, and this is spread on a water surface to deposit the squarylium dye in a film form. Next, a partition plate is provided to prevent this precipitate from freely diffusing on the water surface and spreading too much, and controlling the spreading area to control the aggregated state of the film substances, gradually increasing the surface pressure, and increasing the cumulative film. It is possible to set a surface pressure (π) suitable for manufacturing In the case of the squarylium dye used in the present invention, the type of dye, the ratio of matrix molecules, the set temperature, the type and concentration of metal ions, and the pH.
The surface pressure suitable for the production of the cumulative film varies depending on
π = 5 to 50 dyn / cm, preferably π = 10
˜30 dyn / cm. When the clean substrate is gently moved vertically in water while maintaining this surface pressure, the monomolecular film is transferred onto the substrate, and by repeating this, the cumulative film is uniformly formed on the substrate.

As the solvent for the film-forming substance used in the present invention, any solvent can be used as long as it is a volatile organic solvent that dissolves the film-forming substance and is incompatible with water. However, for example, halogenated hydrocarbons such as dichloromethane, chloroform and trichloroethane, aromatic hydrocarbons such as benzene, toluene and xylene, alcohols such as isopropanol and butanol, ketones such as methyl ethyl ketone and cyclohexanone, tetrahydrofuran and dioxane. Ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate and butyl acetate can be used.

In the present invention , the accumulator used for producing the electrophotographic photosensitive layer is preferably equipped with a controller capable of constantly monitoring the surface pressure and automatically maintaining a constant surface pressure. . Specifically, a Kyowa Interface Science accumulator, a Lauda accumulator, and a Joyce-Loebel accumulator can be used.

In the electrophotographic photosensitive layer produced by the present invention, the organic thin film that absorbs light energy and converts it into electric energy is composed of one or more kinds of film-forming molecules that absorb light. In the electrophotographic photosensitive layer composed of the above organic thin film, not only a monomolecular film composed of only one kind of the square lilium dye but also two or more kinds of dye molecules having different characteristics are mixed in the same monomolecular film. Mixed monolayers can also be used, and in a multi-layered film in which two or more monolayers are accumulated, monolayers of the same type, mixed monolayers, or different types of monolayers. Cumulative films of molecular films and mixed monomolecular films can also be used. Film forming materials for improving the stability of a monomolecular film include fatty acids such as arachidic acid and stearic acid, paraffin hydrocarbons such as hexadecane and octadecane, 10,12-pentacosadiynoic acid, 10,12-tricosadiynoic acid and the like. The diacetylene-based compound can be used.

An electrophotographic photosensitive member having an electrophotographic photosensitive layer produced by the present invention has a structure as shown in FIGS . 1 to 3 . That is, as shown in FIG. 1 , an electrophotographic photosensitive member provided with a photoconductive layer 2 having a single layer structure having two functions of charge generation ability and charge transport ability on a conductive support 1, and FIG. and as shown in Figure 3, the electrophotographic photosensitive member of function separation type remembering separately the functions of the both, i.e., a charge transport layer and charge generating layer 3 on the conductive substrate 1 as shown in FIG. 2 4 those having a photoconductive layer 2 are laminated in this order, and a charge generation layer 3 and a charge transport layer 4 in contrast to FIG. 2 on a conductive support 1 as shown in FIG. 3 in this order One having a photoconductive layer 2 laminated is given.
The square lilium dye in the present invention can be used in any of them, but in view of the dye existing in a high concentration and the formability of a uniform thin film having a highly controlled orientation state, a charge separation layer of a function separation type is particularly preferable. When used as, it can best exhibit its characteristics.

The charge transport layer may be, for example, a photoconductive polymer such as polyvinylcarbazole, polyvinylpyrene, polyvinylanthracene, etc., or a triallylpyrazoline type, triphenylmethane type, trinitrofluorenone type, tetraphenylbenzidine type. By providing a layer containing a binder resin containing a photoconductive substance such as a hydrazone type, it is possible to improve the charging property, reduce the residual potential, and achieve higher sensitivity and reliability.

The substrate used in the present invention is not particularly limited, but a conductive one or an electrically insulating one can be used. If the surface of the substrate is contaminated with a surfactant or the like, the monomolecular film is disturbed during accumulation, and a good monolayer film or a multilayer film cannot be obtained. Therefore, the substrate surface needs to be particularly clean. As the conductive substrate, a metal such as silver, aluminum, or chromium, a paper subjected to a conductive treatment, a polymer film having a conductive layer, glass, or the like can be used. Further, as the electrically insulating substrate, a polymer film such as glass, polyester, polyethylene, polycarbonate or polyimide can be used. The shape of the substrate is not particularly limited, and any shape according to the purpose of use, for example, a sheet shape, a plate shape, or a cylindrical shape can be used. Further, in the structure of the photoreceptor shown in FIG. 2 , an undercoat layer having a barrier function and an adhesive function can be provided between the conductive support 1 and the charge generation layer 3. Further, a protective layer may be provided on the surface of the photosensitive layer in order to improve ozone resistance, mechanical strength and abrasion resistance.

[0019]

EXAMPLES The present invention will be described below with reference to examples. Example 1 In the structural formula of the squarylium dye represented by the general formula (I), the dye in which R is a methyl group is dissolved in chloroform. Spread this solution on the surface of water at 15 ° C,
After evaporation of chloroform, the barrier was moved so that the cumulative surface pressure was 15 dyn / cm, and the membrane area was compressed to form a monomolecular membrane . Then, an aluminum cylinder that had been subjected to a hydrophobic treatment with cadmium arachidate was reciprocated vertically 20 times with respect to the monolayer to form a charge generation layer. Furthermore, N, N'-diphenyl-N,
A charge transport layer obtained by adding 50% by weight of N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine to a polycarbonate resin is formed by a dip coating method so that the film thickness becomes about 15μ. Applied. The electrophotographic photosensitive member thus prepared was mounted on a copying machine for electrophotography, and well-known processes such as charging, exposure, development, transfer, and fixing were repeated to perform image evaluation.
It was confirmed that high image quality was maintained despite the image formation of more than 0,000 sheets.

Comparative Example Instead of the charge generation layer in Example 1, a charge generation layer was formed by applying a coating liquid dispersed and prepared in a binder resin. That is, 30% by weight of the above-mentioned squarylium dye was mixed with a polyester resin and pulverized and dispersed in methylene chloride. The resulting coating liquid was applied by the dip coating method so as to have a thickness of about 0.5 μm to form a charge generation layer. An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except for the above.

For the electrophotographic photoreceptors of Example 1 and Comparative Example, the image quality was evaluated by examining the relationship between the gray line having a density of 0.7 and the number of background copies. The results are shown in Table 1.
Shown in

[Table 1]

Example 2 Among the squarylium dyes represented by the general formula (I), a dye in which R is an n-butyl group and stearic acid were dissolved in chloroform at a molar ratio of 1: 1. This solution 15
℃ CdCl ₂ 3 × 10 ^-4 mol / liter, KHC
O ₃ It spreads on the surface of water adjusted to a concentration of 3 × 10 ^-5 mol / liter, and after evaporation of chloroform, the barrier is moved so that the cumulative surface pressure becomes 20 dyn / cm, and the membrane area is compressed to form a single molecule. The membrane was created. On the other hand, a film thickness of a charge transport layer obtained by adding and mixing 50% by weight of 1-phenyl-3- [p-dimethylaminostyryl] -5- [p-diethylaminophenyl] -pyrazoline into a polycarbonate resin is formed on an aluminum plate. It was formed by coating with an applicator so as to have a size of about 15 μm. This aluminum plate was attached to the above monolayer of square lilium by the horizontal attachment method.
The contact was repeated 00 times to form a charge generation layer of about 2300 angstroms. Corona discharge of +6 kV was carried out for 2 seconds on the photoreceptor thus adjusted, and after positively charged, it was left in the dark for 2 seconds, the surface potential V0 at that time was measured, and then a tungsten lamp with an illuminance of 10 Lux was exposed. The half-exposure amount was determined by irradiating the layer and determining the time (seconds) until the surface potential became 1/2 of V0. As a result, V0 = 800V, E1 / 2 = 1.8 lux.
It was seconds.

Example 3 Among the squarylium dyes represented by the general formula (I), the dye in which R is an n-amyl group was dissolved in chloroform. This solution was spread on the surface of water at 15 ° C., and after evaporation of chloroform, the barrier was moved so that the cumulative surface pressure was 15 dyn / cm, and the film area was compressed to form a monomolecular film. After that, an aluminum plate which had been subjected to a hydrophobic treatment with cadmium arachidate was reciprocated vertically 20 times with respect to the monomolecular film to accumulate 40 layers to form a charge generation layer. Furthermore, on this, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1 '
A charge transport layer obtained by adding 50% by weight of diphenyl-4,4′-diamine to a polycarbonate resin has a film thickness of about 15
It was formed by coating with an applicator so that the thickness becomes μ. The photoreceptor thus obtained was subjected to a corona discharge of -6 kV for 2 seconds, negatively charged, and then left in the dark for 2 seconds, the surface potential V0 at that time was measured, and then a tungsten lamp having an illuminance of 10 lux was exposed. The half-exposure amount was determined by irradiating the layer and determining the time (seconds) until the surface potential became 1/2 of V0. As a result, V0 = 830V, E1 / 2 = 1.5 looks.
It was seconds.

Examples 4 to 8 Examples other than using the squarerium dyes shown in Table 2 in place of the squarerium dyes represented by the general formula (I) in which R is an n-amyl group, An electrophotographic photosensitive member was prepared by the same method as in Example 3, and its characteristics were evaluated. Table 2 shows the results.

[Table 2]

[0025]

According to the manufacturing method of the present invention, the above-mentioned general formula
By using the squarylium dye represented by (I), a photosensitive layer can be formed as a very thin film on a substrate in a state in which film-forming molecules are highly controlled in orientation, and a photosensitive aggregate in a homogeneous state is formed. The layers can be manufactured very simply and inexpensively. Electrophotographic having the obtained electrophotographic photosensitive layer
Photoreceptor shows excellent photoelectric conversion characteristics and is a photosensitive material for electrophotography.
It shows high conversion efficiency as a body, good repeatability and
It has high reliability and resolution.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of an electrophotographic photosensitive member having an electrophotographic photosensitive layer of the present invention.

FIG. 2 is a schematic view of an example of a function-separated electrophotographic photosensitive member having an electrophotographic photosensitive layer of the present invention.

FIG. 3 is a schematic view of another example of the function-separated electrophotographic photosensitive member having the electrophotographic photosensitive layer of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductive support, 2 ... Photoconductive layer, 3 ... Charge generation layer, 4
… Charge transport layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoko Sato 2274 Hongo, Ebina City, Kanagawa Fuji Zerox Co., Ltd. Ebina Works (56) Reference JP-A-57-144558 (JP, A) JP-A-60- 131537 (JP, A) "Iwanami Physics and Chemistry Dictionary 3rd Edition", pages 1188 to 1189, "Project Law" column

Claims (1)

(57) [Claims] 1. A substrate surface by forming a monomolecular film containing a squarylium dye represented by the following general formula (I) on the surface of water and bringing the monomolecular film into contact with a suitable substrate. A method for producing an electrophotographic photosensitive layer, comprising forming an organic thin film made of square lilium dye on the top. Embedded image (In the formula, R represents an alkyl group.)