JP2560268B2 - 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 the above situation, the present invention is directed to an electrophotographic photosensitive layer comprising an organic thin 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 ₁ and R ₂ represent different alkyl groups from each other.)

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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[0011]

[Chemical 6]

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 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 which dissolves the film-forming substance, 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 according to the present invention, the organic thin film that absorbs light energy and converts it into electric energy comprises 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, the same type of monolayers, mixed monolayers, or different types of monolayers. Cumulative membranes such as membranes and mixed monolayers 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 compounds, tripalmitic acid, and fatty acid esters such as stearic acid methyl ester 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 generating ability and charge transporting 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.

As the charge transport layer, for example, a photoconductive polymer such as polyvinylcarbazole, polyvinylpyrene, polyvinylanthracene, etc., or a triallylpyrazoline type, triphenylmethane type, trinitrofluorenone type, tetraphenylbenzidine type, etc. 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.

[0020]

EXAMPLES Next, the present invention will be described in detail with reference to Examples. Example 1 Among the squarylium dyes represented by the general formula (I), a dye in which R ₁ is a methyl group and R ₂ is an ethyl group is dissolved in chloroform. This solution was spread on the surface of water at 10 ° C, and after the evaporation of chloroform, the cumulative surface pressure was 15d.
The barrier was moved so that it became yn / cm, and the membrane area was compressed to form a monomolecular membrane . After that, an aluminum cylinder that had been hydrophobically treated with cadmium arachidate was reciprocated 30 times perpendicularly to the monomolecular film to form a charge generation layer having a thickness of about 1800 Å. 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.

Example 2 Among the squarylium dyes represented by the general formula (I), a dye in which R ₁ is a methyl group and R ₂ is an n-butyl group and stearic acid are mixed in chloroform at a molar ratio of 1: 1. Dissolved. This solution was added with CdCl ₂ at 15 ° C. 3 × 10 ⁻⁴ mol /
Liter, KHCO ₃ 3 × 10 ^-5 mol / liter It was developed on the surface of water, and after evaporation of chloroform, the barrier was moved so that the cumulative surface pressure became 20 dyn / cm, and the membrane area was compressed. Then, a monomolecular film was prepared. On the other hand, 1-phenyl-3- [p-
Dimethylaminostyryl] -5- [p-diethylaminophenyl] -pyrazoline in polycarbonate resin
The charge transport layer mixed with 0% by weight was applied and formed by an applicator so as to have a film thickness of about 15 μm. This aluminum plate was repeatedly contacted 100 times with the monolayer of square lilium by the horizontal deposition method to form a charge generation layer of about 2300 angstroms. Two +6 kV corona discharges were applied to the electrophotographic photosensitive member thus prepared.
After 2 seconds, positively charged, left in a dark place for 2 seconds, the surface potential V0 at that time is measured, and then a tungsten lamp having an illuminance of 10 lux is applied to the photosensitive layer to reduce the surface potential to 1/2 of V0. The half-exposure amount was determined by determining the time (sec) until the change. As a result, V0 = 800V, E1 / 2 =
It was 2.0 lux · sec.

Example 3 Among the squarylium dyes represented by the general formula (I), a dye in which R ₁ is a methyl group and R ₂ is an n-butyl 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 this, an aluminum plate that had been hydrophobized with cadmium arachidate in advance,
By reciprocating the monomolecular film 20 times perpendicularly, 40 layers were accumulated to form a charge generation layer. Further, on this, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4,4'-diamine was added to the polycarbonate resin in an amount of 50% by weight. The transport layer was applied by an applicator so that the film thickness was about 15 μm. The photoreceptor thus obtained is
After performing a 6 kV corona discharge for 2 seconds and negatively charging it,
Leave in the dark for 2 seconds, measure the surface potential V0 at that time, then irradiate the photoconductor with a tungsten lamp with an illuminance of 10 lux, find the time (seconds) until the surface potential becomes 1/2 of V0, and halve it. The exposure amount was determined. As a result, V0 = -830 V and E1 / 2 = 2.0 lux.sec.

Examples 4 to 9 In Table 1 , instead of the squarylium dyes represented by the general formula (I) in which R ₁ and R ₂ are n-methyl group and n-butyl group, respectively. An electrophotographic photosensitive member was prepared in the same manner as in Example 3 except that the shown square lilium dye was used, and its characteristics were evaluated. Table 1 shows the results.

[0024]

[Table 1]

[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) References JP-A-59-125735 (JP, A) JP-A-60- 130557 (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 ₁ and R ₂ represent different alkyl groups from each other.)