JP2536154B2 - Electrophotographic photoreceptor and image forming method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor having a charge generating layer and a charge transporting layer sequentially laminated on a conductive support, and an image forming method using the same.

2. Description of the Related Art Conventionally, as an electrophotographic photoreceptor, those using an inorganic photoconductive material such as selenium, a selenium alloy, zinc oxide, and cadmium sulfide have been mainly used. However, electrophotographic photoreceptors using an inorganic photoconductive material have problems in terms of manufacturability, cost, flexibility, and the like.

In recent years, in order to solve the drawbacks of inorganic photoconductive materials, electrophotographic photoreceptors using organic photoconductive materials represented by polyvinylcarbazole-2,4,7-trinitrofluorenone (TNF) have been known. ing. Recently, as charge generating materials, perylene-based, perinone-based, phthalocyanine-based, azo-based pigments, and others, cyanine dyes, pyrylium salt and thiapyrylium salt dyes, dye dyes such as squarylium dyes, and pyrazoline as a charge-transporting material, 1 material such as hydrazone, triallylamine, stilbene
There is provided a laminated electrophotographic photosensitive member formed by combining two or more kinds.

(For example, JP-A-58-16247) However, electrophotographic photoreceptors using these organic photoconductive materials have low photosensitivity and have not been sufficient as photoreceptors. In addition, a laminated electrophotographic photosensitive member having a charge-generating layer and a charge-transporting layer whose functions are separated has not been practically satisfactory.

That is, the photosensitivity is not yet sufficient even in the laminated electrophotographic photoconductor in which the charge generation layer and the charge transport layer are sequentially laminated on the support as has been conventionally proposed, and the photosensitivity and the charging potential are not sufficient. However, there is a problem in that it changes greatly with environmental changes, and the potential cycle fluctuations of the exposed and non-exposed parts are large.

This kind of problem is also seen in the normal process of transferring the toner image onto a transfer material such as paper after developing the non-exposed area on the photoreceptor with toner. This is remarkably observed in an image forming method including a step of forming an electrostatic latent image by charging, forming a toner image by development, and imparting a positive charge during transfer. That is, since the potentials of the exposed portion and the non-exposed portion of the photosensitive member cause a wide cycle variation, the density of the transferred image may be significantly different between the initial image and the image after copying a large number of images, or the transferred image may be different. If the image is fogged or if the size of the transfer paper is changed to a large size after copying a large number of sheets, the transfer density of the portion on the transfer paper corresponding to the width difference of the transfer paper becomes high. There were defects such as fogging and fogging.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above problems in the conventional art.

That is, the object of the present invention is that the charging property is good, the photosensitivity is high, the photosensitivity and the charging potential are stable against environmental changes, and the potentials of the exposed portion and the non-exposed portion are stable even when copying a large number of sheets. An object is to provide an electrophotographic photoreceptor.

Another object of the present invention is to uniformly negatively charge a photoconductor to form an electrostatic latent image, and then attach the negatively charged toner to a low potential portion of the electrostatic latent image to form a toner image. However, it is another object of the present invention to provide an electrophotographic photosensitive member suitable for use in an image forming method including a step of performing transfer by applying an electric charge having a certain polarity.

Still another object of the present invention is to apply the electrophotographic photoreceptor to the electrophotographic process to form an image having a uniform image density without causing a large cycle variation in the potentials of the exposed portion and the non-exposed portion. An object is to provide an electrophotographic image forming method that can be obtained.

Means and Actions for Solving the Problems The above-mentioned object of the present invention is to provide an electrophotographic photosensitive member comprising a support and a charge generation layer and a charge transport layer which are sequentially laminated, wherein the charge generation layer is positive in the binder resin. A hole transporting charge generating pigment,
This can be achieved by using a compound containing a dicyanovinyl compound represented by the following general formula (I).

That is, the electrophotographic photosensitive member of the present invention is an electrophotographic photosensitive member in which a charge generating layer and a charge transporting layer are sequentially laminated on a support, and the charge generating layer generates a hole transporting charge in a binder resin. It is characterized by containing a pigment and a didianovinyl compound represented by the following general formula (I).

[In the formula, R ₁ represents a hydrogen atom, an alkyl group, -CN, -COOH,-
COOR ₆ (R ₆ is an alkyl group), allyl group, (A is an oxygen atom or a sulfur atom) or (R ₇ is an alkyl group) a, R ₂ is an alkyl group or a hydrogen atom, a halogenated alkyl group, R ₃ represents a hydrogen atom or an alkyl group, R ₄ is a hydrogen atom, an alkyl group, -OH, - NH ₂ , -NHR ₈ (R ₈ is an alkyl group) or -NR ₉ R ₁₀ (R ₉ and R ₁₀ are each an alkyl group), R ₅ is a hydrogen atom or an alkyl group, and R ₁ and R ₂ may combine with each other to form a ring, and
Two or three members of R ₃ , R ₄ and R ₅ may combine with each other to form a ring] Hereinafter, the electrophotographic photosensitive member of the present invention will be described.

1 to 4 are schematic cross-sectional views showing the laminated structure of the electrophotographic photosensitive member of the present invention. In FIG. 1,
The charge generation layer 2 and the charge transport layer 3 are sequentially provided on the conductive support 1. In FIG. 2, an undercoat layer 4 is provided between the conductive support 1 and the charge generation layer 2. In FIG. 3, a protective layer 5 is provided on the surface of the charge transport layer 3, and in FIG. 4, an undercoat layer 4 is provided between the conductive support 1 and the charge generation layer 2 to reduce the charge. A protective layer 5 is provided on the surface of the transport layer 3.

Next, each layer constituting the electrophotographic photosensitive member of the present invention will be described.

As the conductive support, aluminum, copper, iron, zinc, a drum of metal such as nickel, and sheet, paper, plastic, or glass on aluminum, copper, gold, silver, platinum, palladium, titanium, nickel-chromium, Metals such as stainless steel and copper-indium are deposited, conductive metal compounds such as indium oxide and tin oxide are deposited, metal foil is laminated, or carbon black, indium oxide, tin oxide-antimony oxide powder It is possible to use a known material such as a drum-shaped, sheet-shaped, or plate-shaped material which is conductively treated by dispersing metal powder or the like in a binder resin and applying the resin.

Further, if necessary, the surface of the conductive support can be subjected to various treatments within a range that does not affect the image quality. For example, is a light absorption layer provided on the surface of the conductive support for the purpose of preventing oxidation fringes, chemical treatments and coloring treatments on the surface, or preventing interference fringes that occur when coherent light such as laser light is used for image exposure? Alternatively, light scattering treatment may be performed.
As the light scattering method, sand blasting method, liquid honing method, grindstone polishing method, buff polishing method, belt sander method, brush polishing method, steel wool method, acid etching method, alkali etching method, electrochemical etching method, etc. are used. it can.

Further, an undercoat layer may be further provided between the conductive support and the charge generation layer. This undercoat layer prevents the injection of charges from the conductive support to the photosensitive layer during charging of the photosensitive layer having a laminated structure, and the photosensitive layer to the conductive support.
Acts as an adhesive layer that holds and holds them together, or
In some cases, it shows the antireflection function of light of the conductive support.

The binder resin used for this undercoat layer is polyethylene, polypropylene, acrylic resin, methacrylic resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, polycarbonate, polyurethane, polyimide resin, vinylidene chloride resin, polyvinyl acetal resin. ,
Known resins such as vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, water-soluble polyester, nitrocellulose, casein, and gelatin can be used.

The thickness of the undercoat layer is 0.01 to 10 μm, preferably 0.05.
-3 μm is suitable. Further, as a coating method used when providing the undercoat layer, a usual method such as a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method is used. be able to.

In the present invention, the charge generating layer forming the photosensitive layer on the conductive support contains a hole transporting charge generating pigment, the dicyanovinyl compound represented by the general formula (I) and a binder resin.

The charge generation pigment used together with the dicyanovinyl compound needs to have a hole transporting property itself.
To determine whether the charge generating pigment has hole transporting properties, the pigment is vapor-deposited or dispersed in a high concentration in a resin and applied to a substrate to form a multilayer, which is charged positively or negatively. The determination method of measuring the optical attenuation may be used. In the present invention, the “hole-transporting charge generating pigment” refers to a pigment having a large light attenuation during positive charging as compared with the light attenuation during negative charging in the above determination method.

In the present invention, the charge generating pigment has a hole transporting property for the following reason. That is, the hole-transporting charge-generating pigment forms a combination of the electron-transporting dicyanovinyl compound and the so-called donor-acceptor relationship, which enhances the charge-generating efficiency and improves the sensitivity. In addition, in this combination, both the charge-generating pigment having a hole-transporting property and the ginanovinyl compound having an electron-transporting property can transport the charge, so that among the generated charges, the charge having the opposite polarity to the charging polarity is charged. It is possible to smoothly transfer from the generation region to the charge transport layer and transfer charges of the same polarity to the substrate side, and it is possible to prevent an adverse effect on potential repetitive stability due to charge trapping. Furthermore, when the specific dicyanovinyl compound represented by the above general formula (I) of the present invention is added, there is little environmental fluctuation of the potential that tends to occur when an ordinary acceptor is added, and stable electric characteristics are obtained. To be

In the present invention, the hole transporting charge generating pigments include squarylium pigments, phthalocyanine pigments,
Perylene pigments and the like can be mentioned.

The following general formula (II) is used as a square lilium pigment.
You can list the ones shown in.

Ｂwhere B and C are the following formulas [In the formula, R ₁₁ and R ₁₂ are each a hydrogen atom, a hydroxyl group, a fluorine atom, an alkyl group, —NR ₁₉ R ₂₀ (wherein R ₁₉ and
R _{20 represents} a hydrogen atom, an alkyl group, an aryl group, an alkylcarbonyl group or an arylcarbonyl group), an alkoxy group or an aryloxy group, and R ₁₃
Represents -NR ₂₁ R ₂₂ (wherein R ₂₁ and R ₂₂ each represent an alkyl group or an aryl group), and R ₁₄ to R ₁₇ each represent a hydrogen atom, an alkyl group, an aryl group, -CONHR ₂₃
(Here, R ₂₃ represents an alkyl group or an aryl group),
Represents a halogen atom, an alkoxy group or an aryloxy group, R ₁₈ represents an alkyl group or an aryl group, and Z represents CR
_{24 R 25, -S -, -} CR 24 = CR 25 - ( wherein, R ₂₄ and R ₂₅
Each represents a hydrogen atom, an alkyl group or an aryl group)]], and specifically, for example, the following can be exemplified.

As the phthalocyanine pigment, the following general formula (III)
You can list the ones shown in.

(In the formula, R ₂₆ represents a hydrogen atom, an alkyl group, an aryl group, a halogen atom, a cyano group, or a nitro group, and M represents
2 hydrogen atoms or Cu, Ni, Co, Fe, Mn, Cr, Ti, R
u, Pd, In, Sn, Sb, Zn, Mg, Ga, Ge, As, Si, Hg, T
represents a metal atom selected from i, V, U, and Pd, D and E each represent a halogen atom or an oxygen atom, x
And y each represent 0 or 1. However, when M is a divalent metal atom, both x and y are 0, and when M is a trivalent metal atom, x is 1 and y is 0, and M is a tetravalent metal. In the case of atoms, x and y both represent 1, and M
When V is V, D is an oxygen atom, x is 1 and y is 0, and when M is U, D and E are oxygen atoms, and x and y are
Are both 1) Specifically, for example, metal-free phthalocyanine, copper phthalocyanine, vanadyl phthalocyanine, titanyl phthalocyanine, aluminum phthalocyanine, gallium phthalocyanine, indium phthalocyanine, thallium phthalocyanine, silicon phthalocyanine, germanium phthalocyanine, tin phthalocyanine, lead phthalocyanine, And halides of the above phthalocyanines.

Examples of perylene pigments include compounds represented by the following general formula (IV).

(In the formula, R ₂₇ represents an optionally substituted alkyl group or aryl group) Specifically, the following can be exemplified.

On the other hand, as specific examples of the dicyanovinyl compound represented by the general formula (I), the following can be exemplified.

The binder resin for the hole transporting charge generating pigment and the dicyanovinyl compound, polystyrene, polycarbonate resin, acrylic resin, methacrylic resin,
Polyester, vinyl resin, silicone resin, celluloses, alkyd resin, etc.
Anything can be used.

In the charge generation layer according to the present invention, the dicyanovinyl compound has a hole-transporting charge generation pigment content of 0.
It is contained in the range of 01 to 2 equivalents, preferably 0.1 to 1 equivalent. If the amount of the dicyanovinyl compound is less than 0.01 equivalent, the effect on the increase in the above-described photosensitivity and the reduction of the environmental fluctuation and the repetition fluctuation of the potential of the exposed / unexposed area is reduced. The damping is greatly increased,
In the electrophotographic process in which the charging potential is lowered and the toner is formed on the non-exposed portion, the background portion is easily fogged, so the above range is preferable.

Further, the hole transporting charge generating pigment is preferably blended in the range of 0.1 to 10 parts by weight with respect to 1 part by weight of the binder resin.

As a method of including the above-described hole transporting charge generating pigment and the above dicyanovinyl compound in the charge generating layer,
Various methods can be adopted. As one of them, a hole transporting charge generating pigment and a dicyanovinyl compound are both added and dispersed in a solution of a binder resin. As another method, first, a hole transporting charge generating pigment is dispersed in a solvent solution of a binder resin, and then a dicyanovinyl compound is added to the dispersion. As another method, a hole transporting charge generating pigment is treated with a solution of a dicyanovinyl compound in advance to be adsorbed, and then dispersed in a solvent solution of a binder resin. As still another method, a hole transporting charge generating pigment is dispersed in a solvent solution of a binder resin to form a film by coating, and then the film is treated with a solution of a dicyanovinyl compound and impregnated.

As a dispersion method, a commonly employed method such as a ball mill, a roll mill, an attritor, or a sand mill can be used. At the time of this dispersion, it is preferable that the particles of the hole transporting charge generating pigment have an average particle size of 3 μm or less, particularly 0.5 μm or less.

As the solvent used for dispersion, any solvent can be used as long as it has solubility, but it is preferable to select a solvent having good pigment dispersibility. A plurality of solvents may be used in combination.

As a coating method used when providing the charge generation layer, a blade coating method, a Mayer bar coating method,
A usual method such as a spray coating method, a dip coating method, a bead coating method, an air knife coating method and a curtain coating method can be used.

The thickness of the charge generation layer is generally set in the range of 0.05 to 5 μm, preferably 0.1 to 2.0 μm.

The charge transport layer in the electrophotographic photoreceptor of the present invention is formed by including a charge transport material in a suitable binder resin.
Examples of the charge transport material include oxadiazole derivatives such as 2,5-bis (p-cyethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline,
Pyrazoline derivatives such as 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline; aromatic tertiary amino compounds such as triphenylamine and dibenzylaniline; N,
Aromatic tertiary diamino compounds such as N'-bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine, 3- (4'-dimethylaminophenyl) -5, 6−
1,24-Triazine derivatives such as di- (4'-methoxyphenyl) -1,2,4-triazine, hydrazone derivatives such as 4-diethylaminobenzaldehyde-1,1'-diphenylhydrazone, 2-phenyl-4-styryl Quinazoline derivatives such as quinazoline, 6-hydroxy-2,3-di (p
-Methoxyphenyl) benzofuran and other benzofuran derivatives, p- (2,2-diphenylvinyl) -N, N-diphenylaniline and other α-stilbene derivatives, "Journal
Of Imaging Science "(Journal of Imagi
ng Science) 29: 7-10 (1985), enamine derivatives, carbazole derivatives such as N-ethylcarbazole, poly-N-vinylcarbazole and its derivatives,
Known charge transport materials such as poly-γ-carbazolyl ethyl glutamate and its derivatives, as well as pyrene, polyvinyl pyrene, polyvinyl anthracene, polyvinyl acridine, poly-9-biphenyl anthracene, pyrene-formaldehyde resin and ethylcarbazole-formaldehyde resin. Can be used, but is not limited thereto. These charge transport materials can be used alone or in combination of two or more.

Further, as the binder resin, polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin,
Acrylic resin, vinyl chloride resin, vinylidene chloride resin,
Polystyrene resin, polyvinyl acetal resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicon-alkyd Resin, phenol-formaldehyde resin, styrene alkyd resin, poly-
Known resins such as N-vinylcarbazole can be used, but are not limited thereto. Further, these binder resins can be used alone or as a mixture of two or more kinds.

The compounding ratio of the charge transport material and the binder resin is 10: 1 to 1: 5
(Weight ratio) is preferable. The thickness of the charge transport layer used in the present invention is generally set in the range of 5 to 50 μm, preferably 10 to 30 μm.

As a coating method for forming the charge transport layer, a usual method such as a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, and a curtain coating method can be used.

Further, as the solvent used when providing the charge transport layer,
Aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and ethylene chloride, tetrahydrofuran and ethyl ether. Ordinary organic solvents such as cyclic or linear ethers can be used alone or in admixture of two or more.

In the electrophotographic photoreceptor of the present invention, a protective layer may be provided on the charge transport layer, if necessary. This protective layer is
It is used to prevent chemical deterioration of the charge transport layer during charging of the photosensitive layer having a laminated structure and to improve the mechanical strength of the photosensitive layer.

This protective layer is formed by including a conductive material in a suitable binder resin. As the conductive material, a metallocene compound such as N, N′-dimethylferrocene, N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1′-phenyl] -4,4 ′ An aromatic amino compound such as diamine,
Materials such as metal oxides such as antimony oxide, tin oxide, titanium oxide, indium oxide, and tin oxide-antimony oxide can be used. As the binder resin used for the protective layer, known resins such as polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin, polyvinylketone resin, polystyrene resin, and polyacrylamide resin may be used. it can.

The thickness of the protective layer is 0.5 to 20 μm, preferably 1 to 10 μm
It is set to the range of.

The electrophotographic photoreceptor of the present invention can be used in a known electrophotographic image forming method. That is, it can be used in an image forming method including a step of uniformly negatively charging the surface of a photoconductor, performing image exposure to form an electrostatic latent image, and developing with electrostatically charged toner particles, and it is always stable. A copy image having an image density can be obtained.

However, the electrophotographic photoreceptor of the present invention is particularly suitable for use in the following image forming method for forming an image by the so-called reversal development method. That is, after uniformly negatively charging the surface of the electrophotographic photosensitive member, imagewise exposure is performed to form an electrostatic latent image, and the low potential portion (exposed portion) of the electrostatic latent image is negatively charged. A toner image is formed by adhering toner, a transfer material is superposed on an electrophotographic photosensitive member that holds the formed toner image, a positive charge is applied from the back surface of the transfer material, and the toner image is transferred onto the transfer material. It is particularly suitable for the image forming method comprising

Explaining the image forming method to which the electrophotographic photoreceptor of the present invention is applied, as a means for uniformly charging the surface of the photoreceptor, a corona discharger such as a corotron, a scorotron, a die corotron, a pin corotron, and a charging roller are Can be used. The initial charging potential is preferably set in the range of -700 to -200V.

As the image exposure means, an illumination optical system including an illumination lamp and an imaging optical system, a laser exposure optical system including a laser light source and a laser light deflector, an LED array, a liquid crystal light valve, a vacuum fluorescent tube array, an optical fiber array. Any optical waveguide array or the like can be used, but it is preferable to use a light source that emits a wavelength in the spectral sensitivity region of the photoconductor.

The electrostatic latent image formed by imagewise exposure is developed with a developer to form a toner image. As a developer,
A two-component developer including a carrier and a toner or a one-component developer including only a toner can be used. The toner particles may be magnetic toner containing magnetic powder inside or non-magnetic toner. At the time of development, a developing machine having a developer carrying member carrying these developers is used to bring the toner particles close to or in contact with the electrostatic latent image, and the toner particles are selectively selected according to the potential of the electrostatic latent image. Attach it.

In this case, depending on the charging polarity of the toner, the toner adheres to the low potential portion (exposed portion) of the electrostatic latent image on the photoconductor (reverse development) or the high potential portion (non-exposed portion) (positive portion). Transfer development) can be performed by selecting the charging polarity of the toner. Since the electrophotographic photoreceptor of the present invention is inherently negatively chargeable, a toner having a negative charge polarity is selected in the case of reversal development, and a positive polarity in the case of forward rotation development. Is selected.

During development, a bias voltage can be applied between the support of the electrophotographic photosensitive member and the developer carrier. As the bias voltage, a DC voltage or an AC voltage superposed with a DC voltage can be used. In particular, when performing reversal development, it is necessary to apply a bias voltage equal to or lower than the non-exposed portion potential.

The toner image formed by development can be transferred to a transfer material by any method. As the transfer means, in addition to the corona charger described above, a transfer roll to which a transfer voltage is applied, a pressure contact roll, or the like can be used. In particular, a corona discharger is used to perform transfer by applying an electric charge from the back surface of the transfer material Electric field transfer is effective. For example, negatively charged toner particles formed by reversal development are preferably transferred onto the transfer material by applying positive corona discharge from the back surface of the transfer material.

After the transfer is completed, the photoreceptor cleans the remaining toner image (toner image that has not been transferred), if necessary.
Then, the light is neutralized by any optical static eliminator or corona static eliminator and prepared for the next image forming step.

Further, the electrophotographic photosensitive member of the present invention can be suitably used in a so-called one-pass multicolor color image forming method.

For example, after uniformly negatively charging the surface of the electrophotographic photosensitive member, a first image exposure is performed to form a first electrostatic latent image,
Negatively charged toner is attached to the low potential portion of the first electrostatic latent image to form a first toner image, and then second image exposure is performed to form a second electrostatic latent image. Then, the positively charged second toner is adhered to the high potential portion of the second electrostatic latent image to form a second toner image, and then the polarities of the first and second toner images are set to one. After aligning the polarities, the transfer material is superposed on the electrophotographic photosensitive member holding the first and second toner images, and a charge having a polarity opposite to the polarities of the first and second toner images is applied from the back surface of the transfer material. However, it can be suitably used for an image forming method including transferring the first and second toner images onto a transfer material.

In the above-described one-pass multicolor image forming method, as the means for uniformly negatively charging the photoconductor, the image exposing means, the developing means and the transferring means, the same ones as described above can be used.

First, the surface of the photoconductor is uniformly negatively charged, and then the first
Image exposure is performed. As the first image exposure, image portion exposure for exposing a portion corresponding to the image portion is adopted. The formed first electrostatic latent image is developed with a first developer,
A first toner image is formed. In this case, a developer carrying member to which a bias voltage lower than the initial charging potential is applied is used, and a low potential portion (exposure portion) of the first electrostatic latent image is formed. , And attaches the negatively charged first toner to form a first toner image.

Next, a second image exposure is performed. In the second image exposure, a background portion exposure for exposing a portion corresponding to a non-image portion is employed. The light source used for the second image exposure has a light intensity lower than that used for the first image exposure so that the potential of the photoconductor corresponding to the background portion is almost half the initial charging potential. It is preferable to adopt such a type that the exposure is performed so as to decrease.

Next, the positively charged second toner is attached to the portion not exposed by the second image exposure (image portion in the second image exposure). In this case, it is preferable to carry out the development by carrying the second toner on the developer carrying body to which a bias voltage higher than the potential of the photoconductor corresponding to the background portion is applied. Further, the second development is so-called overlapping development, which is performed on the photoconductor on which the first toner is already carried. Therefore, the image disturbance of the first toner image and the second development of the first toner image occur.
It is preferable to use a two-component developer composed of a toner and a negatively chargeable low-density carrier in the second development in order to prevent the mixing of the toner into the developing machine. The carrier density is preferably 4.0 g / cm ³ or less.

After forming the first and second toner images on the photoreceptor, these toner images are transferred onto a transfer material. In this case, since these toners are charged with opposite polarities, it is necessary to align them with one of the polarities. In order to make the polarities uniform, corona discharge by a pre-transfer charger can be used. Since the electrophotographic photosensitive member of the present invention is negatively charged, it is preferable that the toner has a positive polarity. For the pre-transfer charging, it is preferable to use an AC voltage superimposed with a positive DC current.

Next, overlay the transfer material on the toner image on the photoreceptor,
A polarity opposite to the polarity of the toner image from the back surface of the transfer material, for example, when the toner image has a positive polarity, a charging potential of negative polarity is applied to transfer the toner image onto the transfer material. In this case, it is preferable to use a negative DC voltage as the transfer potential.

Although image formation is performed as described above, the first toner and the second toner can be selected in appropriate colors. For example, when the electrophotographic photosensitive member has a drum shape, A two-color image can be obtained during one rotation of the drum.

Examples Hereinafter, the electrophotographic photosensitive member of the present invention and the image forming method using the same will be described with reference to Examples.

Example 1 The surface roughness of a mirror-finished aluminum pipe with an outer diameter of 40 mmφ and a length of 319 mm was measured by liquid honing.
It was processed so that Ra = 0.18 μm. Then, in order to form an undercoat layer, a mixed solution having the following composition was prepared.

Polyamide resin (Laccamide 5003, manufactured by Dainippon Ink and Chemicals, Inc. 1 part by weight methanol 5 parts by weight n-butanol 3 parts by weight water 1 part by weight The above mixture is applied by dip coating, and at 115 ° C. 10
After drying for a minute, an undercoat layer having a film thickness of 1 μm was formed.

 Then, a mixture of the following components was prepared.

x-type metal-free phthalocyanine 1 part by weight Polyvinyl butyral resin (Brand name: S-REC BM1, manufactured by Sekisui Chemical Co., Ltd.) 1 part by weight Dicyanovinyl compound (Exemplified Compound I-5) 0.3 equivalents Cyclohexanone 60 parts by weight Based on the above mixture Was dispersed for 6 hours with a sand mill using 1 mmφ glass beads as the dispersion medium, and the average particle diameter of the pigment was about
A 0.05 μm dispersion was prepared. The obtained dispersion was applied onto the above-mentioned undercoat layer by a dip coating method, and dried by heating at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.2 μm.

 Further, a mixture of the following components was prepared.

2 parts by weight of N, N'-diphenyl-N, '-bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine Polycarbonate resin (bisphenol Z type) 3 parts by weight Monochlorobenzene 20 parts by weight This mixture is applied onto the above charge generation layer by a dip coating method and dried at 115 ° C. for 60 minutes to form a charge transport layer having a thickness of 20 μm. Formed.

The electrophotographic photosensitive member thus prepared is negatively charged by using a scorotron (grid applied voltage: −340V), and then exposed to a semiconductor laser (780 nm oscillation) to attenuate the light. Position in seconds (0.6 after charging
A surface electrometer probe was placed at a position after 2 seconds), and the potential during non-exposure (VH) and the potential during exposure (VL: 30erg / cm ² exposure) were measured. Furthermore, a corotron (voltage applied to the wire: +5.0 KV) was placed after this probe to be positively charged, and then discharged by a tungsten lamp. In this system, negative charge-exposure-positive charge-removal exposure was set as one cycle, and changes in VH and VL up to 1000 cycles were measured. The results are shown in Table 1.

Further, the above electrophotographic photosensitive member was mounted on a laser printer (trade name: XP-11, manufactured by Fuji Xerox Co., Ltd.).
This laser printer uses a negative polarity magnetic component toner, and transfers the toner image adhering to the exposed portion with a DC + 4.8 kV transfer corotron. Using this laser printer, after continuously printing 500 sheets of A4 size paper, only B4 size paper was printed, and the difference in print density between the part where the A4 size paper passed and the other part was evaluated. The results are shown in Table 1.

Examples 2 to 7, except that the addition amount of the dicyanovinyl compound (Exemplified Compound I-5) to the pigment was changed to the addition amount shown in Table 1.
An electrophotographic photosensitive member was produced in exactly the same manner as in Example 1, and the same measurement was performed. The results are shown in Table 1.

Examples 8 to 10 Electrophotographic photoreceptors were prepared in the same manner as in Example 1 except that the dicyanovinyl compound was changed to the compounds shown in Table 1, and the same measurements were performed. The results are shown in Table 1.

Comparative Example 1 An electrophotographic photosensitive member was prepared and measured in the same manner as in Example 1 except that the dicyanovinyl compound was not added. The results are shown in Table 1.

Examples 11 to 15 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the x-type metal-free phthalocyanine and dicyanovinyl compound in Example 1 were changed to the compounds shown in Table 2. The measurement was performed. The results are shown in Table 2.

Comparative Examples 2 to 6 Electrophotographic photoreceptors were prepared and measured in the same manner as in Examples 11 to 15 except that the dicyanovinyl compound was not added. Table 2 shows the results.

Examples 16 to 20 Perylene pigments (exemplified compound IV-
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 1) was used and the compounds shown in Table 3 were used as the dicyanovinyl compound. Then, using the electrophotographic photosensitive member thus manufactured as a light source, a halogen lamp (however, 55
The measurement was performed in the same manner as in Example 1 except that the light was separated by an interference filter having a center wavelength of 0 nm and the exposure amount was set to ²⁰ erg / cm ² . The results are shown in Table 3.

Comparative Example 7 An electrophotographic photosensitive member was prepared in the same manner as in Example 16 except that the dicyanovinyl compound was not added, and the same measurement was performed. The results are shown in Table 3.

Example 21 and Comparative Example 8 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 and Comparative Example 1 except that a mirror-finished aluminum pipe having an outer diameter of 84 mmφ and a length of 340 mm was used as the substrate.

The electrophotographic photosensitive member thus prepared is a two-color laser printer obtained by modifying a copying machine'F50303 Fuji Xerox Co., Ltd.) Charging-Primary laser exposure-Negative charging red toner development on exposed area-2 Next laser exposure-Positive black toner development on unexposed area-AC pre-transfer charging with positive DC superimposed-Transfer by negative DC corotron application-Cleaning-Repeating static electricity removal) B4 size paper A pattern of a mixture of red and black was repeatedly printed on 500 sheets, and changes in print density in the red and black portions were observed.

With the electrophotographic photosensitive member of Example 21, clear printing without background fog was obtained in both the red and black portions, but Comparative Example 8
In the electrophotographic photosensitive member of No. 2, as the number of continuous sheets increased, the fog of the red toner started to increase on the background portion, the red printing started to thicken, and the black printing became thin.

EFFECTS OF THE INVENTION The electrophotographic photosensitive member of the present invention comprises, as described above, the charge generation layer having the hole transporting charge generation pigment and the dicyanovinyl compound represented by the general formula (I) in the charge generation layer. An excellent effect that the sensitivity is improved and the potentials of the exposed and non-exposed areas are stable and do not decrease even when copying a large number of sheets, as compared with the case where no dicyanovinyl compound is added. Have.

The electrophotographic photoreceptor of the present invention is particularly applicable to an electrophotographic image forming method in which each operation of uniform negative charge-image exposure-reverse development-positive charge transfer-discharge is repeated, for example, when used in a laser printer or the like. In such a case, the surface potential of the photoreceptor during image exposure is such that a decrease in potential due to the image forming operation is repeated from the first image forming operation to after the image forming operation is repeated many times. It does not occur and maintains a stable surface potential at all times, so that an image with a stable image density can be obtained,
Further, the generation of fog can be suppressed.

In addition, even when the transfer paper is changed to a wide size after repeating the image forming operation many times, the transfer density does not increase in the portion corresponding to the width difference of the transfer paper. It is possible to obtain an image having a uniform density with no fog in the area.

In the case where the dicyanovinyl compound is not contained in the charge generation layer, the potential of the exposed part and the non-exposed part gradually decreases with repeated image forming operations, the image density gradually increases, and the background part is Fog occurs. Also, after the image forming operation is repeated many times, when the transfer paper is changed to a wide size, the increase in the image density and the background fog are observed in the area corresponding to the width difference. To be

Further, the electrophotographic photoreceptor of the present invention can be applied to a so-called one-pass multicolor color image forming method.

[Brief description of drawings]

1 to 4 are schematic cross-sectional views for explaining the structure of the electrophotographic photosensitive member of the present invention. 1 ... Conductive support, 2 ... Charge generation layer, 3 ... Charge transport layer, 4 ... Undercoat layer, 5 ... Protective layer.

Claims (5)

(57) [Claims] 1. An electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer sequentially laminated on a support, wherein the charge generation layer has a hole transporting charge generating pigment in a binder resin, and An electrophotographic photoreceptor comprising a dicyanovinyl compound represented by the formula (I). [In the formula, R ₁ represents a hydrogen atom, an alkyl group, -CN, -COOH,-
COOR ₆ (R ₆ is an alkyl group), allyl group, (A is an oxygen atom or a sulfur atom) or (R ₇ is an alkyl group) a, R ₂ represents a hydrogen atom, an alkyl group or a halogenated alkyl group, R ₃ represents a hydrogen atom or an alkyl group, R ₄ is a hydrogen atom, an alkyl group, -OH, - NH ₂ , -NHR ₈ (R ₈ is an alkyl group) or -NR ₉ R ₁₀ (R ₉ and R ₁₀ are each an alkyl group), R ₅ is a hydrogen atom or an alkyl group, and R ₁ and R ₂ may combine with each other to form a ring, and
Two or three members of R ₃ , R ₄ and R ₅ may combine with each other to form a ring. 2. The electrophotographic photosensitive member according to claim 1, wherein the dicyanovinyl compound is contained in an amount of 0.01 to 2 equivalents relative to the hole transporting charge generating pigment. 3. The electrophotographic photoreceptor according to claim 1, wherein the hole-transporting charge generating pigment is a phthalocyanine pigment, a squarylium pigment or a perylene pigment. 4. The surface of the electrophotographic photosensitive member according to claim 1 is uniformly negatively charged, and then imagewise exposed to form an electrostatic latent image, and a low potential portion of the electrostatic latent image is formed. A toner image is formed by attaching negatively charged toner to the electrophotographic photosensitive member that holds the toner image, and a positive charge is applied from the back surface of the transfer material to transfer the toner image to the transfer material. An image forming method, characterized in that the image is transferred onto the upper surface. 5. The surface of the electrophotographic photosensitive member according to claim 1 is uniformly negatively charged, and then subjected to a first image exposure to obtain a first image.
To form a first toner image by attaching a negatively charged toner to a low potential portion of the first electrostatic latent image, and then performing a second image exposure. A second electrostatic latent image is formed, and a positively charged second toner is adhered to the high potential portion of the electrostatic latent image of FIG. 2 to form a second toner image, and the first and second electrostatic latent images are formed. After aligning the polarity of the second toner image to one polarity, a transfer material is superposed on the electrophotographic photosensitive member holding the first and second toner images, and the first and second transfer materials are arranged from the back surface of the transfer material. The charge having a polarity opposite to that of the toner image of No. 2 is applied,
And an image forming method comprising transferring the second toner image onto a transfer material.