JP2803799B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member containing a disazo pigment having a specific structure, and an electrophotographic apparatus using the photosensitive member. , Facsimile.

[Conventional technology]

Conventionally, inorganic photoconductive substances such as selenium, cadmium sulfide, and zinc oxide have been widely used as electrophotographic photoreceptors.

On the other hand, electrophotographic photoreceptors made of organic photoconductive materials include photoconductive polymers represented by poly-N-vinylcarbazole and 2,5-bis (p-diethylaminophenyl) -1,3,4- There are known those using a low-molecular organic photoconductive substance such as oxadiazole, and those combining such an organic photoconductive substance with various dyes and pigments.

An electrophotographic photoreceptor using an organic photoconductive substance has a good film-forming property and cannot be produced by coating, and thus has an advantage that an inexpensive photoreceptor with extremely high productivity can be provided. Further, there is an advantage that the color sensitivity can be freely controlled by selecting a dye or a pigment to be used, and wide studies have been made so far. Particularly recently, the development of a function-separated photoreceptor in which a charge generation layer containing an organic photoconductive dye or pigment and a charge transport layer containing the aforementioned photoconductive polymer or low molecular organic photoconductive low substance are laminated. As a result, remarkable improvements have been made in sensitivity and durability, which have been regarded as disadvantages of conventional organic electrophotographic photosensitive members.

Azo pigments exhibit excellent photoconductivity, and since compounds having various properties can be easily obtained by combining an amine component and a coupler component, many compounds have been proposed so far. JP-A-54-22834, JP-A-58-70232, JP-A-60-11539, JP-A-61-117553, JP-A-61-51063, JP-A-61-121061 JP, JP-A-61-215556, JP-A-61-241763 and JP-A-63-158561 are already known.

[Problems to be solved by the invention]

However, conventional electrophotographic photoreceptors using disazo pigments are not always sufficient in terms of sensitivity and potential stability during repeated use, and only a few materials have been put to practical use. .

Accordingly, an object of the present invention is to provide a novel photoconductive material.

Another object of the present invention is to provide an electrophotographic photoreceptor having practical high sensitivity characteristics and stable potential characteristics when used repeatedly.

[Means for solving the problem]

An object of the present invention is to provide an electrophotographic photoreceptor characterized in that a photosensitive layer containing a disazo pigment represented by the following general formula [1] is provided on a conductive support. Wherein A ₁ and A ₂ represent the same or different coupler residues having a phenolic hydroxyl group.

In the general formula [1], A ₁ and A ₂ represent the same or different coupler residues having a phenolic hydroxyl group, and preferred examples include compounds represented by the general formulas [2] to [7].

X in the general formulas [2], [3], [4], and [5] is a naphthalene ring, an anthracene ring, a carbazole ring, a benzocarbazole ring, or a dibenzofuran which may have a substituent by condensing with a benzene ring. Represents a residue necessary for forming a polycyclic aromatic ring such as a ring or a heterocyclic ring.

Y in the general formula [7] represents a divalent aromatic hydrocarbon group which may have a substitution value or a divalent heterocyclic group containing a nitrogen atom in the ring. Specifically, o-phenylene, o-
Naretylene, perinaphthylene, 1,2-anthrylene, 3,4
Divalent groups such as -pyrazoldiyl, 2,3-pyridinediyl, 4,5-pyridinediyl, 6,7-indazolediyl, and 6,7-quinolinediyl.

R ₁ and R ₂ in the general formulas [2], [3] and [4] represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, an aroyl group and a heterocyclic group. , Also R ₁ , R
₂ may combine with a nitrogen atom to form a cyclic amino group containing a nitrogen atom in the ring. R ₃ in the general formula [5] represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, or a heterocyclic group, and R ₄ in the general formula [6] represents a substituent. It represents an alkyl group, an aryl group, an aralkyl group, and a heterocyclic group which may be possessed.

In the above expression, the alkyl group is a group such as methyl, ethyl, or propyl; the aralkyl group is a group such as benzyl or phenethyl; the aroyl group is a group such as benzoyl; the aryl group is a group such as phenyl, naphthyl or allysyl. Examples of the cyclic group include pyridyl, thienyl, thiazolyl, carbazolyl, benzimidazolyl, and benzothiazolyl.Examples of the cyclic amino group containing a nitrogen atom in the ring include pyrrole, pyrroline, pyrrolidine, pyrrolidone, indole, indoline, carbazole, imidazole, and the like. Pyrazole, pyrazoline, oxazine, phenoxazine and the like can be mentioned.

Examples of the substituent include an alkyl group such as methyl, ethyl, and propyl; an alkoxy group such as methoxy and ethoxy; a halogen atom such as fluorine, chlorine and bromine; an alkylamino group such as cimethylamino and diethylamino; a phenylcarbamoyl group; and a nitro group. , Cyano group, halomethyl group such as trifluoromethyl and the like.

Z in the general formula [2] represents an oxygen atom or a sulfur atom, and 1 represents 0 or 1.

In the general formula [1], A ₁ and A ₂ are the same as those in the general formula [2],
[3], [4] or [5], wherein a pigment using a coupler in which X in the formula is condensed with a benzene ring to form a benzocarbazole ring has an absorption range near the near infrared region. Since it spreads, it is also suitable as a charge generation material for a semiconductor laser.

Hereinafter, typical examples of the disazo pigment used in the present invention are listed, but the disazo pigment used in the present invention is not limited thereto.

The disazo pigment used in the present invention is a method in which a corresponding diamine is tetrazotized by an ordinary method and coupled with an aqueous system of a coupler in the presence of an alkali, or after converting a tetrazonium salt to a borofluoride or a zinc chloride double salt, N, It can be easily synthesized by coupling with a coupler in an organic solvent such as N-cimethylformamide or dimethyl sulfoxide in the presence of a base such as sodium acetate, triethylamine or N-methylmorpholine.

When synthesizing a disazo pigment in which A ₁ and A ₂ in the general formula [1] are different couplers, the above-mentioned tetrazonium salt is used.
First, 1 mol of one coupler is coupled to 1 mol, and then 1 mol of the other coupler is coupled, and then synthesized, or one amino group of diamine is protected with an acetyl group or the like, and this is diazotized. After coupling one of the couplers, the protecting group is hydrolyzed with hydrochloric acid or the like, and this is diazotized again to be synthesized by coupling the other coupler.

 Next, a synthesis example of the disazo pigment used in the present invention will be described.

Synthesis Example (Synthesis of Disazo Pigment No. 1 as Exemplified) In a 300 ml beaker, add 150 ml of water and 20 ml (0.23 mol) of concentrated hydrochloric acid. (0.032 mol) and cooled to 0 ° C, 4.6 g of sodium nitrite
(0.067 mol) in 10 ml of water was added dropwise to the solution over 10 minutes while maintaining the temperature at 5 ° C. or lower. After stirring for 15 minutes, the mixture was filtered with carbon, and into this solution was added sodium borofluoride (10.5 g).
(0.096 mol) in 90 ml of water was added dropwise with stirring, and the precipitated borofluoride was collected by filtration, washed with cold water, washed with isopropyl ether, and dried at room temperature under reduced pressure. Yield 14.3
g, yield 92% Next, N, N-dimethylformamide (DM
F) 500ml Was dissolved and the temperature of the solution was cooled to 5 ° C. Then, 9.7 g (0.020 mol) of the borofluoride salt obtained above was dissolved, and then triethylamine was dissolved.
5.1 g (0.050 mol) was added dropwise over 5 minutes. After stirring for 2 hours, the precipitated pigment was collected by filtration, washed four times with DMF and three times with water, and then freeze-dried. Yield: 17.6 g, 97% Yield Elemental analysis Calculated value (%) Actual value (%) C 70.28 70.31 H 3.78 3.76 N 9.28 9.27 The electrophotographic photoreceptor of the present invention has the above-mentioned general formula [1] on a conductive support. And a photosensitive layer containing a disazo pigment represented by The form of the photosensitive layer may be any known form, but the photosensitive layer containing the disazo pigment represented by the general formula [1] is used as a charge generation layer, and the charge transport layer contains a charge transport material. Is particularly preferred.

The charge generation layer can be formed by applying a coating solution obtained by dispersing the above disazo pigment together with a binder resin in an appropriate solvent onto a conductive support by a known method, and has a thickness of, for example, 5 μm. Preferably 0.1-1μ
It is desirable to use a thin film layer of m.

The binder resin used at this time is selected from a wide range of insulating resins or organic photoconductive polymers, but polyvinyl butyral, polyvinyl benzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulose resin, acrylic resin, urethane resin ,
And the like, and the amount used is determined by the content in the charge generation layer
It is at most 80% by weight, preferably at most 40% by weight.

The solvent used is preferably selected from those which dissolve the resin and do not dissolve the charge transport layer and the undercoat layer described below. Specifically, ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as cyclohexane and methyl ethyl ketone; amides such as N, N-dimethylformamide; esters such as methyl acetate and ethyl acetate; toluene, xylene; Aromatics such as monochlorobenzene; alcohols such as methanol, ethanol, and 2-propanol; and aliphatic halogenated hydrocarbons such as chloroform and methylene chloride.

The charge transport layer is stacked on or below the charge generation layer and has a function of receiving charge carriers from the charge generation layer in the presence of electrolysis and transporting the carriers. The charge transporting layer is formed by dissolving a charge transporting substance in a solvent together with a suitable binder resin if necessary, and applying the solution. The film thickness is generally 5 to 40 μm, but preferably 15 to 30 μm.

The charge transport material includes an electron transport material and a hole transport material.Examples of the electron transport material include 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, and tetracyanoquinodimethane. And electron-withdrawing substances, and those obtained by polymerizing these electron-withdrawing substances.

Examples of the hole transporting substance include polycyclic aromatic compounds such as pyrene and anthracene; heterocyclic compounds such as carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, thiadiazole, and triazole; p-diethylaminobenzaldehyde- Hydrazone-based compounds such as N, N-diphenylhydrazone and N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole: α-phenyl-4′-N,
N-diphenylaminostilbene, 5- [4- (di-p
-Tolylamino) benzylidene] -5H-dibenzo [a,
b] styryl compounds such as cycloheptene; benzidine compounds; triarylmethane compounds; triphenylamine or polymers having a group consisting of these compounds in the main or side chain (for example, poly-N-vinylcarbazole, polyvinylanthracene Etc.).

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can be used.

These charge transport materials can be used alone or in combination of two or more.

When the charge transport material does not have a film-forming property, an appropriate binder resin can be used, and specifically, an acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-sterene copolymer, polysulfone, polyacrylamide Insulating resin such as polyamide, chlorinated rubber, or poly-N-
Organic photoconductive polymers such as vinyl carbazole, polyvinyl anthracene and the like can be mentioned.

As the conductive support on which the photosensitive layer is formed, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, titanium, nickel, indium, gold, platinum, and the like can be used. In addition, such metal or alloy,
Plastics (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, etc.) coated with a vacuum deposition method, or conductive particles (for example, carbon black, silver particles, etc.) with a suitable binder on a plastic or metal substrate Or conductive particles impregnated with plastic or paper can be used.

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer. The thickness of the undercoat layer is 5 μm or less, preferably 0.1 to 3 μm. The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66,
Nylon 610, copolymerized nylon, N-alkoxymethylated nylon, etc.), polyurethane, aluminum oxide and the like.

As another specific example of the present invention, an electrophotographic photosensitive member in which the above-mentioned disazo pigment and a charge transporting substance are contained in the same layer can be mentioned. In this case, a charge transfer complex composed of poly-N-vinylcarbazole and trinitrofluorenone can be used as the above-mentioned charge transport material.

The electrophotographic photoreceptor of this example can be formed by applying and drying a liquid in which the above-mentioned disazo pigment and the charge transporting substance are dispersed in an appropriate resin solution.

The crystal form of the disazo pigment represented by the general formula [1] used in any of the electrophotographic photoreceptors may be either crystalline or amorphous, and if necessary, the general formula [1] It is also possible to use a combination of two or more types of disazo pigments represented by the formula (1) or a combination with a known charge generating substance.

FIG. 1 shows a schematic configuration example of a general transfer type electrophotographic apparatus using the electrophotographic photosensitive member of the present invention.

In the figure, reference numeral 1 denotes a drum type photosensitive member of the present invention as an image carrier, which is driven to rotate around an axis 1a in a direction indicated by an arrow at a predetermined peripheral speed. The photosensitive member 1 is charged by charging means 2 during its rotation.
Receives a uniform charge of a predetermined positive or negative potential on the peripheral surface thereof, and then, in the exposure section 3, a light image exposure L (slit exposure, laser beam scanning exposure, etc.) by an image exposure means (not shown).
Receive. As a result, an electrostatic latent image corresponding to the exposure image is sequentially formed on the peripheral surface of the photoconductor.

The electrostatic latent image is then developed with toner by developing means 4 and the developed toner image is synchronized with the rotation of photoconductor 1 between photoconductor 1 and transfer means 5 from a feeding unit (not shown) by transfer means 5. The transfer material P is sequentially transferred onto the surface of the transferred transfer material P.

The transfer material P having undergone the image transfer is separated from the photoreceptor surface, introduced into the image fixing means 8 and subjected to image fixing, and is printed out as a copy (copy) outside the machine.

The surface of the photoreceptor 1 after the image transfer is cleaned and cleaned by removing the untransferred toner by the cleaning means 6, and further subjected to a charge removal treatment by the pre-exposure means 7 to be used repeatedly for image formation.

As the uniform charging means 2 for the photoreceptor 1, a corona charging device is generally widely used. The transfer device 5 also generally uses a corona transfer unit. As an electrophotographic apparatus, a plurality of components such as the above-described photoreceptor, developing means, and cleaning means are integrally connected as an apparatus unit, and this unit is configured to be detachable from the apparatus body. May be. For example, the photoconductor 1 and the cleaning means 6 are integrated into one device unit,
It may be configured to be detachable using a guide means such as a rail of the apparatus body. At this time, the charging unit and / or the developing unit may be configured to be understood in the device unit.

When the electrophotographic apparatus is used as a copying machine or a printer, the light image exposure L is a signal reflected from or transmitted from an original, or a signal is read from the original, and the signal is used to scan a laser beam and drive an LED array. Or by driving a liquid crystal shutter array.

When using as a facsimile printer,
The light image exposure L is an exposure for printing received data. FIG. 2 is a block diagram showing one example of this case.

The controller 11 controls the image reading unit 10 and the printer 19. The entire controller 11 is controlled by the CPU 17. The read data from the image reading unit 10 is transmitted to the partner station through the transmission circuit 13. Data received from the partner station is sent to the printer 19 through the receiving circuit 12. The image memory 16 stores predetermined image data. The printer controller 18 controls the printer 19. 14 is a telephone.

The image information (image information from a remote terminal connected via a line) received from the circuit 15 is demodulated by the receiving circuit 12, and then subjected to decoding processing by the CPU 17 and stored in the image memory 16 sequentially. You. When the image information of at least one page is stored in the memory 16, the image of the page is recorded. The CPU 17 reads out one page of image information from the memory 16, and
Send out the image information of the page. Printer controller 18
Receives the image information of one page from the CPU 17, and controls the printer 19 to record the image information of the page.

Note that the CPU 17 is receiving the next page during recording by the printer 19.

 Image reception and recording are performed as described above.

The electrophotographic photoreceptor of the present invention can be widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

EXAMPLES Hereinafter, the present invention will be described with reference to examples.

Examples 1 to 15 A solution prepared by dissolving 5 g of methoxymethylated nylon resin (average molecular weight: 45,000) and 10 g of alcohol-soluble copolymerized nylon resin (average molecular weight: 65,000) in 95 g of methanol was applied to an aluminum substrate with a Meyer bar, and dried. Was provided with an undercoat layer having a thickness of 1 μm.

Next, 5 g of the disazo pigment No. 25 exemplified above was mixed with 95 g of cyclohexanone in butyral resin (butyralization degree: 65 mol%).
g was dissolved in the solution and dispersed in a sand mill for 10 hours.
The dispersion was applied on a previously formed undercoat layer with a Meyer bar so that the film thickness after drying was 0.18 μm, to form a charge generation layer.

Next, a hydrazone compound represented by the following structural formula 5g and polymethyl methacrylate resin (number average molecular weight 80
000) 5 g was dissolved in monochlorobenzene 80 g, and this was coated on the charge generation layer with a Meyer bar and dried to form a 16 μm charge transport layer. Thus, the photoreceptor of Example 1 was prepared.

Photoconductors corresponding to Examples 2 to 15 were similarly prepared using the exemplified pigments shown in Table 1 in addition to Disazo Pigment No. 2.

The electrophotographic photoreceptor thus prepared is negatively charged by a corona discharge of -5 kV using an electrostatic copying paper tester (Model SP-428) manufactured by Kawaguchi Electric Co., Ltd. It was exposed to light having an illuminance of 17 lux using a lamp, and the charging characteristics were evaluated. And surface potential V _o as charging characteristics, the surface potential after standing dark was measured exposure E1 / 2 required to decay to 1/2. Table 1 shows the results.

Comparative Examples 1 to 3 Except that the disazo pigment used in Example 1 was replaced with a disazo pigment represented by the following structural formula, exactly the same electrophotographic photoreceptor was prepared, and the charging characteristics were similarly evaluated. Table 2 shows the results.

From these results, it can be seen that all the electrophotographic photoreceptors of the present invention have sufficient charging ability and excellent sensitivity.

Examples 16 to 30 An electrophotographic copying machine equipped with a -6.5 kV corona charger, an exposure optical system, a developing device, a transfer charger, a charge-removal exposure optical system, and a cleaner was prepared by applying the electrophotographic photosensitive member prepared in Example 1 to -6.5 kV. Pasted on the cylinder.

Initial dark potential V _D and the light portion potential V _L respectively -700 V, -2
The fluctuation amount of the dark area potential (ΔV _D ) and the fluctuation amount of the light area potential (ΔV _L ) were measured when the voltage was set at around 00 V and the filter was used 5,000 times.

The same evaluation was performed for the photoconductors prepared in Examples 2 to 15, and the results are shown in Table 3. Note that a negative sign in the fluctuation amount of the potential indicates a decrease in the absolute value of the potential,
A positive sign indicates an increase in the absolute value of the potential.

Comparative Examples 4 to 6 The amount of potential fluctuation when the photoconductors prepared in Comparative Examples 1 to 3 were repeatedly used was measured in the same manner as in Example 16. Table 4 shows the results.

Examples 16 to 30 and Comparative Examples 4 to 6 show that the electrophotographic photoreceptor of the present invention has a small potential fluctuation upon repeated use.

Example 31 An undercoat layer of polyvinyl alcohol having a thickness of 0.5 μm was formed on the amino surface of an aluminum-deposited polyethylene terephthalate film. The dispersion liquid of the disazo pigment used in Example 3 was coated thereon with a Meyer bar and dried to form a film having a thickness of 0.2 μm.
m of the charge generation layer was formed.

Then, a styryl compound represented by the following structural formula A solution prepared by dissolving 10 g and 8 g of a polycarbonate resin (number average molecular weight: 65,000) in 70 g of tetrahydrofuran was applied on the charge generation layer and dried to form a charge transport layer having a thickness of 17 μm. The charging characteristics and durability of the photoreceptor thus prepared were measured in the same manner as in Examples 1 and 16. The results are shown below.

Vo: 700 (−V) E1 / 2: 0.85 (1 ux.sec) ΔV _D : +3 (V) ΔV _L : −1 (V) Example 32 The charge generation layer and the charge transport of the photoreceptor prepared in Example 13 A photoreceptor having the layers applied in reverse order was prepared, and the charging characteristics were evaluated in the same manner as in Example 1. However, the charging was positive.

Vo: 697 (-V) E1 / 2: 1.07 (1 ux.sec) Example 33 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-4,4 were formed on the charge generation layer prepared in Example 15. '-Dioxydiphenyl-2,2'-propane carbonate (molecular weight 300000)
A solution in which 5 g was dissolved in 50 g of tetrahydrofuran was applied by a Meyer bar and dried to form a charge transport layer having a thickness of 18 μm.

The electrophotographic photosensitive member thus produced was evaluated for charging characteristics in the same manner as in Example 1. However, the charging was a raw charging.

Vo: 697 (+ V) E1 / 2: 1.5 (1 ux.sec) Example 34 0.5 g of the disazo pigment No. 6 exemplified above was dispersed together with 9.5 g of cyclohexanone for 50 hours using a paint shaker. A solution prepared by dissolving 5 g of the charge transport material used in Example 1 and 5 g of a polycarbonate resin in 40 g of tetrahydrofuran was added thereto, and the mixture was further shaken for 1 hour. The coating solution thus adjusted is applied to an aluminum substrate with a Meyer bar and dried to a thickness of 15 μm.
m of the photosensitive layer was formed.

The electrophotographic photosensitive member thus produced was evaluated for charging characteristics in the same manner as in Example 1. However, the charging was positive.

Vo: 698 (+ V) E1 / 2: 5.3 (1 ux.sec) [Effects of the Invention] As described above, the electrophotographic photoreceptor of the present invention uses a disazo pigment having a specific structure in the photosensitive layer to provide a photosensitive layer. Either or both of the generation efficiency and the injection efficiency of charge carriers in the layer are improved, and characteristics excellent in sensitivity and potential stability during repeated use are obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a general transfer type electrophotographic apparatus. FIG. 2 is a block diagram of a facsimile using the electrophotographic apparatus as a printer. 1: photoreceptor, 2: charging means, 3: exposure unit, 4: developing means, 5: transfer means, 6: cleaning means, 7: pre-exposure means, 8: image fixing means.

Claims (4)

(57) [Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a disazo pigment represented by the following general formula [1] on a conductive support: (Wherein A ₁ and A ₂ represent the same or different coupler residues having a phenolic hydroxyl group). 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer comprises at least two layers of a charge generation layer containing a disazo pigment represented by the general formula [1] and a charge transport layer. 3. An electrophotographic apparatus comprising the electrophotographic photoreceptor according to claim 1. 4. A facsimile comprising the electrophotographic photosensitive member according to claim 1, and having a receiving means for receiving image information from a remote terminal.