JPH0776838B2 - Electrophotographic photoreceptor and image forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor and an image forming method using the same, and in particular, a charge generation layer and a charge transport layer are sequentially laminated on a conductive support. And an electrophotographic photosensitive member.

Conventional Technology Conventionally, as electrophotographic photoreceptors, selenium, selenium alloys,
Those using inorganic photoconductive materials such as zinc oxide and cadmium sulfide have been mainly used. However, the electrophotographic photosensitive member using the inorganic photoconductive material, manufacturability, cost,
There was a problem in terms of flexibility.

In recent years, in order to solve the drawbacks of inorganic photoconductive materials, research on electrophotographic photoreceptors using organic photoconductive materials has been actively pursued, and a charge composed of polyvinylcarbazole and 2,4,7-trinitrofluorenone has been developed. An electrophotographic photoreceptor using a transfer complex and an electrophotographic photoreceptor using a eutectic complex of pyrylium salt and alkylidene diarylene are known.

Further, recently, an electrophotographic photosensitive member has been proposed in which the functions of absorbing light and generating electric charges and the function of transporting the generated electric charges are divided into separate materials. For example, a bisazo pigment / pyrazoline derivative is used. A laminated type and the like to be contained have been proposed. (See, for example, JP-A-58-16247) Furthermore, in recent years, it has been proposed to prevent the increase in residual potential by incorporating a cyanovinyl compound in the charge transport layer together with an electron-donating charge transfer substance. . (JP-A-58-7643
DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, electrophotographic photoreceptors using these organic photoconductive materials have low photosensitivity and have not been sufficient as photoreceptors. Further, a laminated type electrophotographic photosensitive member in which a charge generating layer and a charge transporting layer are functionally separated has not been obtained sufficiently in practical use.

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 large cycle fluctuation, the densities of transferred images may be significantly different between the initial image and the images after copying a large number of sheets, or 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 on the transfer paper corresponding to the width difference of the transfer paper is high. There were defects such as fraying 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,
It is an object of the present invention to provide an electrophotographic photosensitive member whose photosensitivity and charge potential are stable against environmental changes and whose potentials at exposed and non-exposed portions are stable even when copying a large number of sheets.

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.

Yet another object of the present invention is to uniformly negatively charge the photoreceptor,
After the electrostatic latent image is formed, a toner image is formed by attaching a negatively charged toner to the low potential portion of the electrostatic latent image to form a toner image, and the transfer is performed by applying a charge of a certain polarity. It is an object of the present invention to provide an electrophotographic image forming method capable of obtaining an image having a uniform image density without causing a large cycle variation in the potentials of an exposed portion and a non-exposed portion when applied to a photographic process.

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. This can be achieved by using a charge transporting pigment having a hole transporting property and a ketone 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 ketone compound represented by the following general formula (I).

(In the formula, A represents a substituted or unsubstituted aromatic group or a substituted or unsubstituted heterocyclic group, X represents a hydrogen atom or a halogen atom, and R ₁ represents a hydrogen atom or an alkyl group when n is 0. Represents a group or a cyano group, and when n is 1, a hydrogen atom,
It represents an alkyl group, a cyano group or an aryl group, n represents 0 or 1, and m represents 1 or 2.) The electrophotographic photoreceptor of the invention will be described below.

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

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

As the conductive support, aluminum, copper, iron, zinc,
Aluminum, copper, gold, silver, platinum on drums and sheets, paper, plastic or glass of metal such as nickel,
Deposit metal such as palladium, titanium, nickel-chromium, stainless steel, copper-indium, deposit conductive metal compound such as indium oxide, tin oxide, laminate metal foil, or carbon black, oxide A known material such as a drum-shaped, sheet-shaped, or plate-shaped material in which indium, tin oxide-antimony oxide powder, metal powder, or the like is dispersed in a binder resin and subjected to electroconductivity treatment by coating can be used.

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,
For the purpose of preventing interference fringes generated when surface oxidation treatment, chemical treatment and coloring treatment, or when coherent light such as laser light is used for image exposure, a conductive support surface is formed.
A light absorbing layer may be provided or light scattering treatment may be performed. As the method of light scattering treatment, a sand blast method, a liquid honing method, a grindstone polishing method, a buff polishing method, a belt sander method,
Brush polishing method, steel wool method, acid etching method, alkali etching method, electrochemical etching method and the like can be used.

Further, an undercoat layer may be further provided between the conductive support and the charge generation layer. This undercoat layer prevents injection of charges from the conductive support to the photosensitive layer during charging of the photosensitive layer having a laminated structure, and also integrally holds and holds the photosensitive layer to the conductive support. It exhibits an action as an adhesive layer to be applied, or in some cases, an action of preventing reflection 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 to
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 constituting the photosensitive layer on the conductive support contains a hole transporting charge generating pigment, the ketone compound represented by the general formula (I) and a binder resin.

The charge generating pigment used together with the ketone compound needs to have a hole transporting property. 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” means in the above determination method,
It means that the light attenuation during positive charging is greater than the light attenuation during negative charging.

In the present invention, the hole transporting charge generating pigment includes
Examples include square lilium pigments, phthalocyanine pigments, perylene pigments, and the like.

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

{In the formula, B and C are the following formulas, respectively. [In the formula, R ₇ and R ₈ are each a hydrogen atom, a hydroxyl group, a fluorine atom, an alkyl group, —NR ₁₅ R ₁₆ (wherein R ₁₅ and R ₁₆ ,
Each represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkylcarbonyl group or an arylcarbonyl group), an alkoxy group or an aryloxy group,
R ₉ represents —NR ₁₇ R ₈ (wherein R ₁₇ and R ₁₈ are each an alkyl group, an aryl group or an aralkyl group), and R
₁₀ to R ₁₃ each represents a hydrogen atom, an alkyl group, an aryl group, -CONHR ₁₉ (wherein R ₁₉ represents an alkyl group, an aryl group or an aralkyl group), a halogen atom, an alkoxy group or an aryloxy group, R ₁₄ represents an alkyl group, an aryl group or an aralkyl group, and Z is> CR ₂₀ R
_{21, -S -, - CR 20} = CR 21 - ( wherein, R ₂₀ and R _21,
Each represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group)]], specifically, for example, the following can be exemplified.

Examples of the phthalocyanine-based pigment include those represented by the following general formula (IV).

(In the formula, R ₂₂ represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, a halogen atom, a cyano group, or a nitro group, and M represents two hydrogen atoms, or Cu, Ni, Co, F
e, Mn, Cr, Ti, Ru, Pd, In, Sn, Sb, Zn, Mg, Ga, G
A metal atom selected from e, As, Si, Hg, Ti, V, U, and Pd is shown, D and E are each a halogen atom or an oxygen atom, and x and y are 0 or 1, respectively.
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.
Represents 0, x and y both represent 1 when M is a tetravalent metal atom, and when M is V, D represents an oxygen atom, x represents 1 and y represents 0, and M represents In the case of U, D and E are oxygen atoms, and x and y both represent 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 the perylene pigments include compounds represented by the following general formula (V).

(In the formula, R ₂₃ represents an optionally substituted alkyl group, aryl group, or aralkyl group) Specifically, the following can be exemplified.

On the other hand, as the ketone compound represented by the above general formula (I), a compound represented by the following general formula (II) is preferably used.

(In the formula, R ₁ represents a hydrogen atom, an alkyl group or a cyano group, and R _{2 to} R ₆ are each a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an aryl group, an alkenyl group,
An alkoxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyloxy group, an arylcarbonyloxy group, a halogen atom, a cyano group or a nitro group, or two adjacent groups forming an aromatic ring or a heterocycle, In the above general formula (I), specific examples of the case where A represents a substituted aromatic group include 4-chlorophenyl group, 2,
4-dichlorophenyl group, 4-nitrophenyl group, 4-
Methoxycarbonyl group, 4-cyanophenyl group, 4-phenylcarbonyloxyphenyl group, 4- (4'-nitrophenylcarbonyloxy) phenyl group, 4- (4 '
-Cyanophenylcarbonyloxy) phenyl group, 4-
Examples thereof include (4'-nitrophenyloxycarbonyl) phenyl group, 10-acetylanthracen-9-yl group, 4-acetylphenyl group and 4-cyanophenyl group.

Specific examples of the ketone compound represented by the general formula (I) include the following. As the binder resin for the hole transporting charge generating pigment and the ketone compound, polystyrene, silicone resin, polycarbonate resin, acrylic resin, methacrylic resin, polyester, vinyl resin, celluloses, alkyd resin, etc. Any conventionally known one can be used.

In the charge generation layer of the present invention, the above-mentioned ketone compound is contained in the range of 0.01 to 2 equivalents, preferably 0.1 to 1 equivalents, relative to the hole transporting charge generation pigment. If the amount of the ketone compound is less than 0.01 equivalent, the effect on the increase of the photosensitivity and the reduction of the environmental fluctuation and repetitive fluctuation of the potential of the exposed part / non-exposed part is decreased, and if it is more than 2 equivalents, the dark decay is generated. Greatly increases, the charging potential decreases,
In the electrophotographic process of forming toner on the non-exposed portion, the background portion is likely to be 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.

Various methods can be adopted as a method of incorporating the above hole transporting charge generating pigment and the above ketone compound into the charge generating layer. For example, it can be contained as follows. Both the hole transporting charge generating pigment and the ketone compound are added and dispersed in the solvent solution of the binder resin. As the dispersion method, a ball mill dispersion method, an attritor dispersion method, a sand mill dispersion method, an ultrasonic dispersion method, or the like, which is normally adopted, can be used. First, a hole transporting charge generating pigment is dispersed in a solvent solution of a binder resin, and a ketone compound is added to the resulting dispersion. The hole-transporting charge-generating pigment is previously treated with a solution of an anthraquinone compound to be adsorbed, and then dispersed in a solvent solution of a binder resin. The 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 ketone compound and impregnated.

Further, at the time of this dispersion, the particles of the charge generation pigment are mixed with an average particle size of
It is effective to make the particle size below μm, preferably below 0.5 μm.

The solvent used for dispersion is methanol,
Ordinary organic solvents such as ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform are used alone or in combination of two or more. Can be used.

As the coating method used when providing the charge generation layer, use a usual method such as a blade coating method, a Mayer 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. You can

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

The charge transport layer in the electrophotographic photoreceptor of the present invention is formed by incorporating the charge transport material in a suitable binder resin. As the charge transport material, oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1
-[Pyridyl- (2)]-3- (P-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline derivatives such as pyrazoline, triphenylamine, aromatic tertiary amino compounds such as dibenzylaniline, N , N ′
Aromatic tertiary diamino compounds such as -bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine, 3- (4'-dimethylaminophenyl) -5,6-
(4'-methoxyphenyl) -1,2,4-triazine and other 1,
2,4-triazine derivative, hydrazone derivative such as 4-diethylaminobenzaldehyde-1,1'-diphenylhydrazone, quinazoline derivative such as 2-phenyl-4-styrylquinazoline, 6-hydroxy-2,3-di (p-methoxy) Benzofuran derivatives such as (phenyl) benzofuran, α-stilbene derivatives such as p- (2,2-diphenylvinyl) -N, N-diphenylaniline, “Journal of Imaging Science”
Science) 29: 7-10 (1985), carbazole derivatives such as N-ethylcarbazole, poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethylglutamate and its derivatives, Furthermore, known charge transporting materials such as pyrene, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-biphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin can be used, but are not limited thereto. is not. 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 Polymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene alkyd resin, poly-N
-A known resin such as vinylcarbazole can be used, but is 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 preferably 10: 1 to 1: 5 (weight ratio). 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, chlorobenzene, ketones such as acetone and 2-butanone, methylene chloride, chloroform, ethylene chloride, etc. Ordinary organic solvents such as halogenated aliphatic hydrocarbons, cyclic or linear ethers such as tetrahydrofuran and ethyl ether may be used alone or in combination 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 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 containing 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 ′ -Aromatic amino compounds such as diamine, antimony oxide, tin oxide, titanium oxide, indium oxide,
Materials such as metal oxides such as tin oxide-antimony oxide can be used. As the binder resin used for this protective layer, polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin, polyvinylketone resin, polystyrene resin,
Known resins such as polyacrylamide resin can be used.

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

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 used. 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 light having 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 the 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 photosensitive member of the present invention is essentially negatively charged, a toner having a negative charging polarity is selected in the case of reversal development, and a positive charging polarity is selected in the case of forward development. Toner is selected.

At the time of development, a bias voltage can be applied between the support of the electrophotographic photosensitive member and the developer carrying member. 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, but in particular, an electric field transfer in which a corona discharger is used and transfer is performed by applying an electric charge from the back surface of the transfer material is effective. is there. For example, in the case of negatively charged toner particles formed by performing reversal development, positive corona discharge is applied from the back surface of the transfer material so that the toner particles are suitably transferred onto the transfer material.

After the completion of transfer, if necessary, the photoconductor cleans the remaining toner image (toner image that has not been transferred), and then is neutralized by any optical static eliminator or corona static eliminator.
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, It can be suitably used for an image forming method that comprises 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 to form a first toner image, but in this case, a bias voltage lower than the initial charging potential was applied. Using the developer carrier, the negatively charged first toner is made to adhere to the low potential portion (exposure portion) of the first electrostatic latent image to form the first toner image.

Next, the second image exposure is performed. In the second image exposure, the background portion exposure is used to expose the portion corresponding to the non-image portion. The light source used for the second image exposure is
The light intensity is weaker than that used in the first image exposure, and exposure is performed so that the potential of the photoconductor corresponding to the background portion is reduced to almost half the initial charging potential. Is preferred.

Then, the portion not exposed in the second image exposure (second
The positively charged second toner is attached to the image portion in the image exposure (1). 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 developing device for the first toner are performed. 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 toner from being mixed into the second development. The carrier density is
It 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 the 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 voltage.

Then, the transfer material is superposed on the toner image on the photoconductor, and a polarity opposite to the polarity of the toner image from the back surface of the transfer material, for example, when the toner image is aligned in a positive polarity, a negative polarity charging is performed. An electric potential 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 is a drum, A two-color image can be obtained during one rotation.

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-cut aluminum pipe having an outer diameter of 40 mmφ and a length of 319 mm was buffed to Ra = 0.
It was processed to have a thickness of 17 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 dried at 110 ° C. for 10 minutes to form a film. An undercoat layer having a thickness of 1 μm was formed. Then, a mixture of the following components was prepared.

x-type metal-free phthalocyanine 1 part by weight Ketone compound (Exemplary compound I-10) 0.3 equivalent to pigment Polyvinyl butyral resin (trade name: S-REC BM1,
Sekisui Chemical Co., Ltd. 1 part by weight Cyclohexanone 60 parts by weight The mixture is dispersed for 10 hours by a sand mill using 1 mmφ glass beads as a dispersion medium, and the average particle diameter of the pigment is about 0.05 μm.
m dispersion was prepared. The obtained dispersion liquid was applied onto the above-mentioned undercoat layer by a dip coating method, and dried by heating at 120 ° C. for 10 minutes to form a charge generation layer having a film thickness of 0.25 μm.

Further, a mixture of the following components was prepared.

N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1'-biphenyl) -4,4-diamine 2 parts by weight Polycarbonate resin (bisphenol Z type) 3 parts by weight Monochlorobenzene 20 Parts by weight This mixture was applied onto the above charge generation layer by a dip coating method and dried at 110 ° C. for 60 minutes to form a charge transport layer having a film thickness of 20 μm.

The electrophotographic photoreceptor thus created is negatively charged by using a scorotron (grid applied voltage: -300V), and then exposed to a semiconductor laser (780 nm oscillation) to attenuate the light. A surface electrometer probe was placed at the position after 2 seconds (corresponding to the position at 0.6 seconds after charging), and the potential during non-exposure (VH) and the potential during exposure (VL: 30 erg / 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-deexposure was set as one cycle, and changes in VH and VL up to 200 cycles were measured. This measurement is 32 ℃, 85% RH; 20 ℃, 55% RH;
The test was conducted under each environment of 10 ° C. and 15% RH. The results are shown in Table 1.

In addition, the above electrophotographic photoconductor was mounted on a laser printer (trade name: XP-11, manufactured by Fuji Xerox Co., Ltd.), and after 500 sheets of continuous A4 size paper were printed, only B4 size paper was printed. , The difference in print density between the part where A4 size paper passed and the part other than that, and the background fog in each part were evaluated under the environment of 32 ℃ and 85% RH. The results are shown in Table 2 below.

In this laser printer, a negative magnetic one-component toner was used as a developer, and the toner image adhering to the exposed portion was transferred by a DC + 4.8KV transfer corotron.

Examples 2 to 7 The amount of the ketone compound (Exemplified Compound I-10) was 0.005 equivalent (Example 2), 0.01 equivalent (Example 3), 0.1 equivalent (Example 4), 1.0 equivalent with respect to the pigment, respectively. (Example 5),
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the amount was changed to 2.0 equivalents (Example 6) or 4.0 equivalents (Example 7). The results are shown in Tables 1 and 2.

Comparative Example 1 An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the ketone compound was not added. The results are shown in Tables 1 and 2.

Examples 8 to 11, except that the ketone compound was changed to the compounds shown in Table 1,
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Tables 1 and 2.

Examples 12 to 17 Electrophotographic photoreceptors were prepared and evaluated in the same manner as in Example 1, except that the x-type metal-free phthalocyanine and ketone compounds in Example 1 were changed to the compounds shown in Table 3. I went. The results are shown in Tables 3 and 4.

Comparative Examples 2 to 7 Electrophotographic photosensitive members were prepared and evaluated in the same manner as in Examples 12 to 17 except that the ketone compound was not added. The results are shown in Tables 3 and 4.

Examples 18 to 24 As the substrate, a mirror-finished aluminum pipe having an outer diameter of 84 mmφ and a length of 310 mm was used, a perylene pigment (exemplary compound V-1) was used as the charge generating pigment, and a ketone compound is shown in Table 5. Example 1 except that the compounds shown were used
An electrophotographic photoreceptor was prepared in the same manner as in.

The electrophotographic photosensitive member thus created is negatively charged by using a scorotron (grid applied voltage: -300V), and then exposed by a halogen lamp (however, a spectrum is obtained by an interference filter having a center wavelength of 550 nm). Then, the surface electrometer probe is placed at a position 0.3 seconds after exposure (corresponding to a position 0.6 seconds after charging) after exposure, and the potential at non-exposure (VH) and the potential at exposure (VL: 30 erg / cm ² exposure) was 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-deexposure was set as one cycle, and changes in VH and VL up to 200 cycles were measured.
This measurement is 32 ℃, 85% RH; 20 ℃, 55% RH; and 10 ℃, 15
It was performed under each environment of% RH. The results are shown in Table 5.

Comparative Example 8 An electrophotographic photosensitive member was prepared in the same manner as in Example 18 except that the ketone compound was not added, and the same evaluation was performed. The results are shown in Table 5.

Comparative Examples 9 and 10 In Example 18, the perylene pigment (Exemplified Compound V-1)
Instead of dibromoanthanthrone or a bisazo pigment represented by the following structural formula An electrophotographic photosensitive member was prepared in the same manner except that was used, and the same evaluation was performed. The results are shown in Table 5.

Comparative Examples 11 and 12 In Comparative Examples 9 and 10, an electrophotographic photosensitive member was prepared in the same manner except that the ketone compound was not added, and evaluated in the same manner. The results are shown in Table 5.

Example 25 and Comparative Example 13 Using the electrophotographic photosensitive members prepared in Example 1 and Comparative Example 1, a scorotron (grid applied voltage: -300V) was used.
Negatively, and then a semiconductor laser (780n
m oscillation) to image-expose and attenuate the light, and place the surface electrometer probe at the position 0.3 seconds after exposure (corresponding to the position 0.6 seconds after charging) to obtain the potential (VH) during non-exposure. The potential (VL) during exposure: 20 erg / cm ² exposure) was measured. Furthermore, after this probe, a corotron (wire applied voltage: −
(5.0 KV), placed negatively charged, and then discharged with a tungsten lamp. In this system, negative charge-exposure-negative charge-removal exposure was set as one cycle, and changes in VH and VL up to 200 cycles were measured. This measurement is 32
C., 85% RH; 20 ° C., 55% RH; and 10 ° C., 15% RH. The results are shown in Table 6.

Example 26 and Comparative Example 14 As a substrate, the surface of an aluminum pipe having an outer diameter of 84 mmφ and a length of 310 mm, which was mirror-cut, was treated with a grindstone so that the surface roughness was Ra = 0.15 μm. Then, an electrophotographic photosensitive member was produced in the same manner as in Example 1 or Comparative Example 1.

A two-color laser printer (charging-primary laser exposure-development of negatively-chargeable red toner on exposed area-2) obtained by modifying a copying machine (FX2700, manufactured by Fuji Xerox Co., Ltd.) was used for the electrophotographic photosensitive member thus produced. Next laser exposure-development of positively charged black toner to unexposed area-charging before AC transfer with superimposed DC-transfer by negative DC corotron application-cleaning-repetition of charge removal. Then, 500 sheets of a mixed pattern of red and black were printed repeatedly, and the change in the print density of the red part and the black part was observed.

With the electrophotographic photosensitive member of Example 26, clear printing without fog in the background portion was obtained in both the red and black portions, but Comparative Example 14
In the electrophotographic photosensitive member of No. 3, the fog of the red toner began to increase on the background portion as the number of continuous sheets increased, the red printing started to thicken, and the black printing became thin.

EFFECTS OF THE INVENTION The electrophotographic photoreceptor of the present invention contains the hole transporting charge generating pigment in the binder resin and the ketone compound represented by the general formula (I) in the charge generating layer as described above. Compared to the case where no ketone compound is added, the sensitivity is improved, the chargeability is good, the photosensitivity and the charging potential are stable against environmental changes, and the exposed area and the unexposed area are It has an excellent effect that the potential is stable and does not decrease even when copying a large number of sheets.

The electrophotographic photosensitive member of the present invention is applied to an electrophotographic image forming method in which the operations of uniform negative charging, image exposure, reversal development, positive charging transfer, and static elimination are repeated, particularly when used in a laser printer or the like. In that case, the surface potential of the photoconductor during imagewise exposure shows a decrease in potential due to repeated image forming operations from the first image forming operation to after repeating a large number of image forming operations. It does not occur and always maintains a stable surface potential. Therefore, an image having a stable image density can be obtained, and the occurrence of fog can be suppressed.

In addition, even after the image forming operation is repeated a large number of times, even when the transfer paper is changed to a wide size, 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.

When the above-mentioned ketone compound is not contained in the charge generation layer, the potentials of the exposed portion and the non-exposed portion gradually decrease with repeated image forming operations, the image density gradually increases, and the background portion is fogged. 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 ... Charge generation layer, 2 ... Charge transport layer, 3 ... Conductive support, 4 ... Undercoat layer, 5 ... Protective layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiro Sato 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd. Takematsu Plant (72) Inventor Katsumi Nukata 1600 Takematsu, Minamiashigara, Kanagawa Fuji Xerox Co., Ltd. Takematsu Business In-house (72) Inventor Kosei Marumo 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu Plant

Claims (6)

[Claims] 1. An electrophotographic photosensitive member comprising a support, on which a charge generation layer and a charge transport layer are sequentially laminated, wherein the charge generation layer contains a hole transporting charge generation pigment in a binder resin, and An electrophotographic photoreceptor containing a ketone compound represented by the formula (I). (In the formula, A represents a substituted or unsubstituted aromatic group or a substituted or unsubstituted heterocyclic group, X represents a hydrogen atom or a halogen atom, and R ₁ represents a hydrogen atom or an alkyl group when n is 0. Represents a group or a cyano group, and when n is 1, a hydrogen atom,
Represents an alkyl group, a cyano group or an aryl group, n represents 0 or 1, and m represents 1 or 2) 2. The electrophotographic photosensitive member according to claim 1, wherein the ketone compound is contained in an amount of 0.01 to 2 equivalents based on the hole transporting charge generating pigment. 3. The electrophotographic photosensitive member according to claim 1, wherein the hole-transporting charge generating pigment is a phthalocyanine pigment, a squarylium pigment or a perylene pigment. 4. The electrophotographic photoreceptor according to claim 1, wherein the ketone compound is a compound represented by the following general formula (II). (In the formula, R ₁ represents a hydrogen atom, an alkyl group or a cyano group, and R _{2 to} R ₆ are each a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an aryl group, an alkenyl group,
An alkoxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyloxy group, an arylcarbonyloxy group, a halogen atom, a cyano group or a nitro group, or two adjacent groups forming an aromatic ring or a heterocycle, Show) 5. 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, which is negatively applied to a low potential portion of the electrostatic latent image. A charged toner is attached to form a toner image, the transfer material is superposed on the electrophotographic photosensitive member that holds the toner image, positive charge is applied from the back surface of the transfer material, and the toner image is transferred onto the transfer material. An image forming method characterized by transferring. 6. The surface of the electrophotographic photosensitive member according to claim 1 is uniformly negatively charged, and then subjected to a first image exposure to form a first electrostatic latent image, and the first electrostatic latent image is formed. A negatively charged toner is attached to the low-potential portion of the latent image to form a first toner image, and then a second image exposure is performed to form a second electrostatic latent image. Second positively charged toner is attached to the high potential portion of the electrostatic latent image to form a second toner image, and the polarities of the first and second toner images are aligned to one polarity. , A 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. And an image forming method comprising transferring the second toner image onto a transfer material.