JPH0514271B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, the present invention relates to an electrophotographic photoreceptor, and more specifically, a charge generation layer containing a charge generation substance, and a charge generation layer containing a charge transport substance that receives and transports carriers generated by the charge generation substance. This invention relates to an electrophotographic photoreceptor with a laminated transport layer. [Prior Art] Such an organic photoreceptor is formed from a photoconductive polymer typified by poly-N-vinylcarbazole and a Lewis acid such as 2,4,7-trinitro-9-fluorenone. All electrophotographic photoreceptors having a photosensitive layer containing a charge transfer complex as a main component have been put to practical use. However, this photoreceptor is not necessarily satisfactory in sensitivity and durability. On the other hand, functionally separated electrophotographic photoreceptors in which charge generation and charge transport functions are shared by separate materials have brought about significant improvements in sensitivity and durability, which were considered to be shortcomings of conventional organic photoreceptors. Such a functionally separated photoreceptor has the advantage that there is a wide selection range of materials for each of the charge-generating substance and the charge-transporting substance, and that an electrophotographic photoreceptor having arbitrary characteristics can be produced relatively easily. . In particular, as electrophotographic photoreceptors have come to be used not only in copying machines but also in laser beam printers, LED printers, etc. in recent years, functionally separated type is suitable. As charge generating substances, various azo pigments, phthalocyanine pigments, polycyclic quinone pigments, cyanine dyes, squaric acid dyes, pyrylium salt dyes, etc. are known. Among them, azo pigments are highly durable.
Many structures have been proposed due to their high charge generation ability and ease of material synthesis. For example, dizuazo pigments similar to the present invention are disclosed in JP-A-56-116040, JP-A-57-182747, and JP-A-58-49952.
Publication No. 115447, Japanese Patent Publication No. 115447, Japanese Patent Application Publication No. 1983-
Publication No. 72448, Japanese Unexamined Patent Publication No. 155848, Japanese Unexamined Patent Publication No. Sho 59-155848,
58-115445, JP-A-58-115446, JP-A-59-7365, etc. are already known. The azo pigment used here as a charge-generating substance is required to (i) be stable against heat and light;
() For those that exhibit charge generation ability in a separated state, dispersion is easy and the dispersion liquid does not change over time; () charge generation ability does not change with temperature; () characteristics change during repeated use. () It has an effective spectral sensitivity range for the light source used; () The charge transport material is not limited. Practically speaking, it is most important to satisfy these requirements at a high level on average. Although some of the above-mentioned known pigments satisfy some of the above requirements, none satisfy all of them to a high level. On the other hand, as charge transport substances, hydrazone compounds, pyrazoline compounds, stilbene compounds, triarylmethane compounds, arylamine compounds, etc. are known. These compounds are required to have (i) stability against light and heat, () stability against ozone, _NOx , nitric acid, etc. generated by corona discharge, and () high transport ability. and () high compatibility with organic solvent binders. Examples of combinations of the above-mentioned known azo pigments and charge transport substances include JP-A-58-18636, JP-A-57-204551, JP-A-59-44050,
JP-A-59-44051, JP-A-59-157644, JP-A-60-24549, JP-A-60-24550, JP-A-60-24551, JP-A-60- 24552
Publications, etc. can be cited. Although photoreceptors made with these combinations have little potential fluctuation during repeated use, many of them have major drawbacks in image characteristics, such as image deterioration due to changes in the usage environment, which poses problems in actual use. It's summery. [Problems to be Solved by the Invention] An object of the present invention is to provide a functionally separated photoreceptor having a charge generation layer and a charge transport layer, which has high sensitivity and which maintains a stable potential during repeated use. An object of the present invention is to provide an electrophotographic photoreceptor that can exhibit stable sensitivity and image characteristics regardless of the environment in which it is used (temperature, humidity). Another object of the present invention is to provide an azo pigment which can be easily dispersed and whose dispersion liquid changes little over time. Another object of the present invention is to provide an electrophotographic photoreceptor that exhibits sufficiently high sensitivity to light sources in the range of 600 to 700 nm. Another object of the present invention is to provide a photoreceptor that is stable against ozone, NO _x , nitric acid, etc. generated by corona discharge. [Means for Solving the Problems] As a result of studies conducted by the present inventors, a multilayer electrophotographic photosensitive material having a charge generation layer containing a disazo pigment having a specific structure and a charge transporting layer containing a styryl compound having a specific structure was developed. It has been found that the above-mentioned problems can be solved and the body exhibits excellent electrophotographic properties. That is, the present invention provides a laminated electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive support, in which the charge generation layer has a charge generation substance represented by the general formula (1). The charge transport layer contains a disazo pigment represented by the general formula (2) as a charge transport substance. Or general formula (3) This is an electrophotographic photoreceptor characterized by containing a styryl compound represented by: In the general formula (1), R ₁ and R ₂ represent an alkyl group, an aralkyl group, an aromatic ring group, or a heterocyclic group, specifically, an alkyl group such as methyl, ethyl, propyl, butyl, benzyl, phenethyl, Aralkyl groups such as naphthylmethyl, phenyl, diphenyl,
Examples include aromatic ring groups such as naphthyl and anthryl, and heterocyclic groups such as carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. In addition, these alkyl groups, aralkyl groups, aryl groups, aromatic ring groups, and heterocyclic groups include, for example, alkyl groups such as methyl, ethyl, and propyl, or alkoxy groups such as methoxy, ethoxy, and propoxy, fluorine, chlorine, bromine, etc. may have a halogen atom or a substituent such as a nitro group, a cyano group, or a trifluoromethyl group. Ar ₁ and Ar ₂ represent an aromatic ring group or a heterocyclic group, and specific examples of these aromatic ring groups and heterocyclic groups are the same as above. Also,
These aromatic ring groups and heterocyclic groups may have a substituent, such as an alkyl group, an alkoxy group, a halogen atom, or a cyano group as described above. X ₁ , X ₂ , X ₃ and X ₄ are hydrogen atoms, alkyl groups such as methyl, ethyl and propyl, alkoxy groups such as methoxy, ethoxy and propoxy, halogen atoms, nitro groups, cyano groups, or trifluoromethyl groups. and not all are hydrogen atoms. In general formula (2) and general formula (3), R ₃ and R ₄ are
Indicates an alkyl group, an aralkyl group, an aromatic ring group, or a heterocyclic group, specifically, an alkyl group such as methyl, ethyl, propyl, butyl, an aralkyl group such as benzyl, phenethyl, naphthylmethyl, phenyl, diphenyl, naphthyl, Indicates an aromatic ring group such as anthryl or a heterocyclic group such as pyridyl, quinolyl, thienyl, furyl. Further, these alkyl groups, aralkyl groups, aromatic ring groups and heterocyclic groups may have a substituent, and examples of the substituent include alkyl groups such as methyl, ethyl, and propyl, and methoxy, ethoxy, and propoxy groups. Examples include alkoxy groups, halogen electrons such as fluorine, chlorine, and bromine, and nitro groups. R ₅ and R ₆ represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. Specific examples of the alkyl group and alkoxy group are the same as above.
Further, the alkyl group and alkoxy group may have the above-mentioned substituents. Ar ₃ represents an aromatic ring group or a heterocyclic group, specifically an aromatic ring group such as phenyl, naphthyl, or a heterocyclic group such as pyridyl, quinolyl, thienyl, furyl. The aromatic ring group and the heterocyclic group may have a substituent. Examples of substituents that Ar ₃ may have include alkyl groups such as methyl, ethyl, and propyl, alkoxy groups such as methoxy, ethoxy, and propoxy, halogen atoms such as fluorine, chlorine, and bromine, or nitro groups. Can be mentioned. In general formula (3), Y represents a single bond, -CH ₂ CH ₂ - or -CH=CH-. Furthermore, among the charge-generating substances, the disazo pigment having the structure represented by the general formula (4) is particularly excellent in terms of electrophotographic properties. General formula (4) In general formula (4), R ₇ and R ₈ are hydrogen electrons, methyl,
Alkyl groups such as ethyl and propyl, aralkyl groups such as benzyl, phenethyl and naphthylmethyl, aromatic ring groups such as phenyl, naphthyl and anthranyl,
Indicates alkoxy groups such as methoxy, ethoxy, and propoxy, halogen atoms such as fluorine, chlorine, and bromine, nitro groups, cyano groups, and trifluoromethyl groups. R ₉ and R ₁₀ are hydrogen atoms, alkyl groups such as methyl, ethyl, propyl, benzyl, phenethyl,
Aralkyl groups such as naphthylmethyl, aromatic ring groups such as phenyl, naphthyl, anthranyl, methoxy,
Indicates an alkoxy group such as ethoxy or propoxy, a halogen atom such as fluorine, chlorine, or bromine, a cyano group or a trifluoromethyl group, and an alkyl group, aromatic ring group, or aralkyl group for R ₇ , R ₈ , R ₉ and R ₁₀ , and the alkoxy group may have a substituent, such as an alkyl group such as methyl, ethyl, or propyl, an alkoxy group such as methoxy, ethoxy, or propoxy, a halogen atom such as fluorine, chlorine, or bromine, a nitro group, Examples include cyano group and trifluoromethyl group. Z, X ₁ , X ₂ , X ₃ and X ₄ have the same meaning as in general formula (1). Representative examples of charge generating substances and charge transporting substances used in the present invention are listed below. charge generating material The electrophotographic photoreceptor of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing the layer structure of the electrophotographic photoreceptor of the present invention. The charge generation layer 2 containing the disazo pigment represented by the general formula (1) contains as much of the above-mentioned photoconductive compound as possible in order to obtain sufficient absorbance, and also contains as much of the above-mentioned photoconductive compound as possible to prevent the generated charge carriers from flying. A thin film layer, e.g. less than 5 μm, preferably
A thin film layer having a thickness of 0.01 μm to 1 μm is preferable. The charge generation layer 2 can be formed by dispersing the above-mentioned disazo pigment in a suitable binder and coating it on a support, or by forming a vapor deposited film using a vacuum vapor deposition device. be able to. The binder that can be used when forming the charge generation layer by coating can be selected from a wide range of insulating resins, including poly-N-vinylcarbazole,
It can be selected from organic photoconductive polymers such as polyvinylanthracene and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.),
Examples include insulating resins such as polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. . The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer or undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, N,N-dimethylformamide,
Amines such as N,N-dimethylacetamide,
Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, etc. Aliphatic halogenated hydrocarbons or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. Coating can be performed using a coating method such as a dip coating method, a spray coating method, a Meyer bar coating method, or a blade coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying is
It can be carried out at a temperature of 30° C. to 200° C. for a time ranging from 5 minutes to 2 hours, either stationary or under a draft. The charge transport layer 3 is electrically connected to the charge generation layer 2 described above, receives charge carriers injected from the charge generation layer in the presence of an electric field, and
It has the function of transporting these charge carriers to the surface. At this time, the charge transport layer 3 is preferably laminated on the charge generation layer 2, but the charge transport layer 3 may be laminated below the charge generation layer 2. The charge transport layer 3 can be formed by dissolving and coating the charge transport material described above together with a suitable binder. Examples of resins that can be used as binders include acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, etc. insulating resin or poly-N-vinylcarbazole,
Mention may be made of organic photoconductive polymers such as polyvinylanthracene and polyvinylpyrene. Since the charge transport layer 3 has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5μm to 35μm,
The preferred range is 8 μm to 30 μm. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer 4 having such a laminated structure of the charge generation layer 2 and the charge transport layer 3 is provided on the conductive support 1 . As the conductive support 1, materials whose support itself is conductive, such as aluminum, aluminum alloy, stainless steel, etc., can be used.In addition, aluminum, aluminum alloy,
Plastics, conductive particles (e.g.,
Supports such as carbon black, silver particles, etc.) coated on a plastic or metal support with a suitable binder, supports in which plastic or paper is impregnated with conductive particles, or plastics containing conductive polymers can be used. can. A subbing layer having a barrier function and an adhesive function can also be provided between the conductive support 1 and the photosensitive layer 4. The subbing layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon
66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the undercoat layer is 0.1 μm to 5 μm, preferably
0.5 μm to 3 μm is suitable. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines but also for a wide range of electrophotographic application fields such as laser printers, LED printers, liquid crystal printers, and laser plate making, but especially for LED
By using it in a printer, it can fully demonstrate its performance. [Example] The present invention will be explained below using examples. Example 1 A 0.1 μm undercoat layer made of vinyl chloride-maleic anhydride-vinyl acetate copolymer resin was provided on an aluminum plate. Next, 135 g of the above-exemplified disazo pigment G-1 was added to a solution prepared by dissolving 2 g of butyral resin (degree of briralization 63 mol%, number average molecular weight 20,000) in 95 ml of cyclohexanone, and dispersed in a sand mill for 20 hours. This dispersion was applied onto the previously formed undercoat layer using a Mayer bar so that the film thickness after drying was 0.5 μm, and dried to form a charge generation layer. Next, the exemplified styryl compound T-39
5g and 5g of bisphenol Z-type polycarbonate resin (viscosity average molecular weight 30000) and 70% chlorobenzene
ml and coated on the charge generation layer with a Mayer bar so that the film thickness after drying was 22 μm and dried to form a charge transport layer, thereby producing photoreceptor No. 1. The electrophotographic photoreceptor thus prepared was statically charged with a corona charge of -5.5 KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., and held in a dark place for 1 hour. The charging characteristics were investigated by exposing to a halogen lamp with an illuminance of 2 lux. As for the charging characteristics, the surface potential (V ₀ ) and the exposure amount (E1/2) required to attenuate the potential (V _D ) by 1/2 when dark decayed for 1 second were measured. The results are shown below. V ₀ : -720V V _D : -700V E1/2: 0.99lux・sec Next, first set the light intensity to the light source of the electrostatic copying paper tester.
Spectral sensitivity was measured using monochromatic light of 1 μW/cm ² .
Sensitivity is given by the amount of exposure required for the surface potential (V _D ) to be -700V and the surface potential to be -200V = _500V (μJ/cm ² )
Measure E (V・cm ² / μJ) = 500 (V) / E〓 _500V (μJ / cm ²
) is calculated and plotted against wavelength, and the results are shown in Figure 2. Furthermore, this photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with a -5.6 KV corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner, and the image characteristics were investigated. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Evaluation of image characteristics using this copying machine was as follows: Humidity: 10% Temperature: 5℃; Humidity: 50% Temperature: 18℃
The experiments were conducted in three environments: ℃, humidity 80%, and temperature 35℃. Good images faithful to the original were obtained in both environments. Even after the 10,000th print, no blurring or blurring of the image was observed, indicating that the present photoreceptor exhibited good image characteristics. Example 2 A photoreceptor was produced in exactly the same manner as in Example 1, except that disazo pigments G-10, G-11, G-19, and G-14 were used in place of disazo pigment G-13 in Example 1. The charging characteristics and spectral sensitivity were measured. The charging characteristics are shown in Table 1, and the spectral sensitivity is shown in Table 3.
As shown in the figure.

[Table] Comparative Examples 1 and 2 The following comparative disazo pigment (1) described in JP-A-59-157644 A photoreceptor was prepared in exactly the same manner as in Example 1, except that a photoconductor was used, and the charging characteristics were examined as Comparative Sample 1 in the same manner as in Example 1. Furthermore, a similar evaluation was performed on a comparative pigment (2) having the following structure. Table 2 shows the results.

[Table] Tables 1 and 2 show that the electrophotographic photoreceptor according to the present invention has high sensitivity. Examples 6 to 10 The photoreceptors used in Examples 1 to 5 and Comparative Examples 1 and 2 were used in an electrophotographic machine equipped with a corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner. A photoreceptor was attached to the cylinder.
This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copying machine, the initial light area potential (V _L ) and dark area potential (V _D ) are
were set to −200 V and −700 V, respectively, and the fluctuation amounts ΔV _L and ΔV _D in the light potential (V _10000/L ) and the dark potential (V _10000/D ) were measured after 10,000 uses. The results are shown in Table 3. Note that a negative sign in ΔV _D and ΔV _L represents a decrease in potential, and a positive sign represents an increase in potential.

【table】

[Table] From Table 3, it can be seen that the photoreceptor using the disazo pigment of the present invention has little potential fluctuation during repeated use. Comparative Examples 5 to 11 Photoreceptors were prepared in the same manner as in Examples 1 to 5, except that the styryl compound T-39 used in Examples 1 to 5 and Comparative Examples 1 and 2 was replaced with a humanazone compound having the following structure. The charging characteristics were measured. Further, the amount of potential fluctuation was measured in exactly the same manner as in Examples 6 to 10. The results are shown in Table 4.

【table】

[Table] From Table 4, a photoreceptor having excellent properties can be obtained by combining the disazo pigment of the present invention and a styryl compound. Furthermore, it can be seen that the disazo pigment of the present invention shows little deterioration in properties even when the charge transport substance is changed, and a wide range of charge transport substances can be selected. Example 11 455 g of the above-exemplified disazo pigment G-4 was mixed with 100 ml of cyclohexanone and dispersed in a ball mill for 10 minutes. This dispersion was applied onto an aluminum plate so that the film thickness after drying was 0.5 μm to form a carrier generation layer. Next, the exemplary charge transport material T-60
10 g of bisphenol A type polycarbonate resin (viscosity average molecular weight 28000) was dissolved in 70 ml of 1,2-dichloroethane, and this solution was applied onto the carrier generation layer so that the film thickness after drying was 18 μm. A carrier transport layer was formed to produce an electrophotographic photoreceptor of the present invention. The electrophotographic properties of the photoreceptor obtained as described above were measured in the same manner as in Example 1. Furthermore, similar measurements were repeated 1000 times. Furthermore, after the dispersion used in this example was allowed to stand for one month, a photoreceptor was prepared in the same manner as above, and its electrophotographic properties were measured. The results are shown in Table 5.

[Table] Comparative Example 12 A comparative photoreceptor was prepared in the same manner as in Example 11 using the following bisazo pigment described in JP-A-59-7365 as a carrier generating substance. When this comparative photoreceptor was measured in the same manner as in Example 11, the results shown in Table 6 were obtained.

〔Effect of the invention〕

The combination of a disazo pigment and a styryl compound according to the present invention improves carrier generation efficiency and carrier transport efficiency within the photosensitive layer, resulting in high sensitivity, durability, and particularly excellent potential stability. An electrophotographic photoreceptor can be obtained.
Further, the disazo pigment of the present invention has good stability in its dispersed state and exhibits excellent properties in practical use. Further, the photoreceptor of the present invention exhibits high electrophotographic sensitivity in the LED emission wavelength range by selecting the substituents of the azo pigment.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the layer structure of an electrophotographic photoreceptor, and FIGS. 2 and 3 are diagrams showing the spectral sensitivity of Examples.

Claims (1)

[Claims] 1. In a laminated electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive support, the charge generation layer has a charge generation substance represented by the general formula (1). (In the formula, R ₁ and R ₂ represent an alkyl group, an aralkyl group, an aromatic ring group, or a heterocyclic group, Ar ₁ and Ar ₂ represent an aromatic ring group or a heterocyclic group, and X ₁ ,
X ₂ , X ₃ and X ₄ represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a nitro group, a cyano group or a trifluoromethyl group, and not all of them are hydrogen atoms. Z represents an oxygen atom or a sulfur atom. ), and the charge transport layer contains a disazo pigment represented by general formula (2) as a charge transport substance. Or general formula (3) (In the formula, R ₃ and R ₄ represent an alkyl group, an aralkyl group, an aromatic ring group, or a heterocyclic group, R ₅ and R ₆ represent a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom, and Ar ₃ represents an aromatic ring group. (representing a cyclic group or a heterocyclic group; Y represents a single bond, _-CH2 - _CH2- , or -CH=CH-) An electrophotographic photoreceptor comprising a styryl compound represented by the following formula. 2 The charge generating substance has the general formula (4) (In the formula, R ₇ and R ₈ are hydrogen atoms, alkyl groups,
Represents an aralkyl group, aromatic ring group, alkoxy group, halogen atom, nitro group, cyano group, or trifluoromethyl group, and R ₉ and R ₁₀ are hydrogen atoms, alkyl groups, aralkyl groups, aromatic ring groups, alkoxy groups, and halogen atoms. , cyano group or trifluoromethyl group. Z ₁ , X ₁ , X ₂ , X ₃ and X ₄ have the same meanings as in general formula (1). ) The electrophotographic photoreceptor according to claim 1, which is a disazo pigment represented by: