JPH02124577A - Electrophotographic sensitive body and picture forming method - Google Patents

Abstract

PURPOSE:To form a picture having uniform density by incorporating a hole- conductive charge generating pigment and a specified ketonic compd. into a binder resin of a charge generating layer. CONSTITUTION:A charge generating layer contains a hole-conductive charge generating pigment and a ketonic compd. expressed by the formula I in a binder resin. In the formula, each R1 and R2 is an H atom, alkyl group, nitro group, aryl group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, halogen atom or cyano group; each (n) and (m) is an integer zero-2. The content of the ketonic compd. is 0.01-2, pref. 0.1-1 equivalent based on the amt. of the hole-conductive charge generating pigment. The amt. of the hole-conductive charge generating pigment to be mixed is pref. 0.1-10pts.wt. per 1pt.wt. binder resin. Thus, a copy picture having stable picture density is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor and an image forming method using the same, and in particular, to an electrophotographic photoreceptor and an image forming method using the same. The present invention relates to an electrophotographic photoreceptor.

Conventional technology Conventionally, electrophotographic photoreceptors include selenium, selenium alloys,
Those using inorganic photoconductive materials such as zinc oxide and cadmium sulfide have mainly been used. However, electrophotographic photoreceptors using inorganic photoconductive materials have low manufacturability and cost i~
However, there were many problems in terms of flexibility, etc.

In recent years, in order to solve the shortcomings of inorganic photoconductive materials, research into electrophotographic photoreceptors using organic photoconductive materials has been actively conducted, and electrophotographic photoreceptors made of polyvinylcarbazole and 2,4,7-dolinitrofluorenone have been actively researched. Electrophotographic photoreceptors using a transfer complex and electrophotographic photoreceptors using a eutectic complex of pyrylium salt and alkylidene diarylene are known.

Recently, electrophotographic photoreceptors have been proposed in which the functions of absorbing light and generating electric charges and transporting the generated electric charges are divided into separate materials. A laminated type containing the same material has been proposed. (For example, see JP-A-58-16247.) Furthermore, in recent years, it has been proposed to include a cyanvinyl compound together with an electron donating charge transfer substance in the charge transport layer to prevent an increase in residual potential. There is.

(Japanese Unexamined Patent Publication No. 58-7643) Problems to be Solved by the Invention However, electrophotographic photoreceptors using these organic photoconductive materials have low photosensitivity and are not yet sufficient as photoreceptors. There wasn't. Further, a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are functionally separated has not yet been sufficiently satisfactory for practical use.

That is, even in the conventionally proposed multilayer electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are sequentially laminated on a support, the photosensitivity is still insufficient, and the photosensitivity and charging potential are insufficient. This inevitably causes problems in that the potential changes greatly due to environmental changes and that potential cycle fluctuations between exposed and non-exposed areas are large.

Such problems can also be seen in the normal process of developing unexposed areas on a photoreceptor with toner and then transferring the toner image to a transfer material such as paper, but this is especially true when the photoreceptor is uniformly negative. This is particularly noticeable in image forming methods that include the steps of charging to form an electrostatic latent image, developing to form a toner image, and applying positive charges during transfer. That is, since the electric potential of the exposed and non-exposed areas of the photoreceptor causes wide cyclical fluctuations, the density of the transferred image differs markedly between the initial image and the image obtained by copying multiple copies. If there is fog in the transferred image, or if you change the size of the transfer paper to a larger size after making multiple copies,
There were drawbacks such as high transfer density on the transfer paper corresponding to the width difference of the transfer paper and fogging.

The present invention has been made in view of the above-mentioned circumstances, and aims to solve the above-mentioned problems in the conventional technology.

That is, the object of the present invention is to have good chargeability, high photosensitivity,
The object of the present invention is to provide an electrophotographic photoreceptor whose photosensitivity and charging potential are stable against environmental changes, and whose potentials in exposed and non-exposed areas are stable even when a large number of copies are made.

Another object of the present invention is to uniformly charge a photoreceptor negatively to form an electrostatic latent image, and then apply negatively charged toner to a low potential portion of the electrostatic latent image to form a toner image. The object of the present invention is to provide an electrophotographic photoreceptor suitable for use in an image forming method that includes a step of performing transfer by applying a charge of a certain polarity.

Still another object of the present invention is to uniformly charge a photoreceptor negatively;
After forming an electrostatic latent image, negatively charged toner is attached to the low potential part of the electrostatic latent image to form a toner image, and the process is transferred by applying a charge of a certain polarity. It is an object of the present invention to provide an electrophotographic image forming method that, when applied to a photographic process, can obtain an image with uniform image density without causing large cyclical fluctuations in the potential of exposed and non-exposed areas.

Means and Effects for Solving the Problems The above-mentioned object of the present invention is to provide an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are sequentially laminated on a support, in which the charge generation layer is formed in a binder resin. This can be achieved by using a material containing a pore-transporting charge-generating pigment and a ketone compound represented by the following formula (I).

That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are sequentially laminated on a support, in which the charge generation layer contains a hole transporting charge in a binder resin. It is characterized by containing a generated pigment and a ketone compound represented by the following formula (I).

(In the formula, R1 and R2 each represent a hydrogen atom, an alkyl group, a nitro group, an aryl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, a halogen atom, and a cyano group, and n and m are (each represents an integer of O to 2) The electrophotographic photoreceptor of the present invention will be described below.

1 to 4 are schematic cross-sectional views showing the laminated structure of the electrophotographic photoreceptor 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 generating layer 1 and the charge generating layer 1 . Third
In the figure, 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 3 and the charge generation layer 1, and A protective layer 5 is provided on the surface of @2.

Next, each layer constituting the electrophotographic photoreceptor of the present invention will be explained.

As a conductive support, drums of metals such as aluminum, copper, iron, zinc, nickel, etc., and sheets, paper, plastic or glass on aluminum, copper, gold, silver, platinum, palladium, titanium, nickel-chromium , stainless steel, depositing metals such as copper-indium, depositing conductive metal compounds such as indium oxide, tin oxide, laminating metal foil, or carbon black, indium oxide, tin oxide-antimony oxide. Known materials such as drum-shaped, sheet-shaped, plate-shaped materials can be used, which are conductive-treated by dispersing powder, metal powder, etc. in a binder resin and applying the coating.

Further, if necessary, the surface of the conductive support can be subjected to various treatments as long as the image quality is not affected. for example,
For the purpose of preventing interference fringes that occur when the surface is subjected to oxidation treatment, chemical treatment, coloring treatment, or when coherent light such as laser light is used for image exposure, the surface of the conductive support is coated with
A light absorption layer may be provided or a light scattering treatment may be performed. Light scattering treatment methods include sandblasting, liquid honing, whetstone polishing, puff polishing, belt sanding,
Brush polishing method, steel wool method, acid etching method, alkali etching method, electrochemical etching method, etc. can be used.

Further, a lower arch layer may be further provided between the conductive support and the charge generation layer. This subbing layer prevents the injection of charge from the conductive support to the photosensitive layer when the photosensitive layer consisting of a laminated structure is charged, and also serves to bind the photosensitive layer to the conductive support and bond them together. It functions as an adhesive layer for holding, or in some cases functions as an antireflection function for light of the conductive support.

Binder resins used for this undercoat layer include 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, Vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, water-soluble polyester, nitrocellulose, casein,
Known resins such as gelatin can be used.

The thickness of the undercoat layer is suitably 0.01 to 10 .mu.m, preferably 0.05 to 3#2. Furthermore, the coating methods used when providing an undercoat layer include blade coating method,
Conventional methods such as Meyer bar coating, spray coating, dip coating, bead coating, air knife coating, curtain coating, etc. can be used.

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

The charge-generating pigment used together with the ketone compound must itself have hole-transporting properties.

To determine whether a charge-generating pigment has hole-transporting properties, the pigment is vapor-deposited or dispersed in a resin at a high concentration and applied to a substrate to create a multilayer, which is then positively or negatively charged. It is sufficient to use a determination method that measures optical attenuation. In the present invention, the term "hole-transporting charge-generating pigment" refers to a pigment that exhibits greater optical attenuation when positively charged than when negatively charged in the above determination method.

In the present invention, the hole-transporting charge-generating pigment includes:
Examples include square lylium pigments, cyanine pigments, and perylene pigments.

The square aryllium pigment has the following general formula % formula % (wherein A and B are each in the following formula 1, R3 and R4'+ are each a hydrogen atom, a hydroxyl group, a fluorine atom, an alkyl group, NR11R12 ( Here, R11 and R12 are each a hydrogen atom, an alkyl group,
represents an aryl group, an aralkylbonylalkoxy group, or an aryloxy group, and R5 is -
NR13R14 (here, R13 and R14 each represent an alkyl group, an aryl group, or an aralkyl group), R6 to R9 each represent a hydrogen atom, an alkyl group, an aryl group, -CONHR15 (here, R15 represents an alkyl group, aryl group or aralkyl group), halogen atom, alkoxy group or aryloxy group,
Rlo represents an alkyl group, an aryl group, or an aralkyl group, and 7 is 〉CR16R1□, -S-- -cR16=
cR1□- (where R16 and R17 each represent a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group). ]) Specifically, the following can be exemplified.

As a phthalocyanine pigment, the following general formula % formula % (wherein R18 is a hydrogen atom, an alkyl group, an aryl group,
represents an aralkyl group, a halogen atom, a cyano group, or a nitro group, M is two hydrogen atoms, or Cu, Ni
SCo, Fe, Mn, Cr, TRLI, pd, In,
Sn, Sb, Zn, MCI, Ga, Ge, As, Si
, Hg, TI, V, U, and Pd, C and D each represent a halogen atom or an oxygen atom, and X and y each represent O or 1. However, when M is a divalent metal atom, both X and y represent O, when M is a trivalent metal atom, X is 1, y is ○, and M is a tetravalent metal atom. In the case of atoms, both X and y represent 1, and when M is V, C is an oxygen atom and X is 1.
, y represents O, when M is V, C and D 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.

In addition, as perylene pigments, for example, the following formula (I
Examples include compounds represented by V).

(In the formula, R19 is an optionally substituted alkyl group,
(representing an aryl group or an aralkyl group), specifically, the following can be exemplified.

On the other hand, as specific examples of the ketone compound represented by formula (1) above, the following can be exemplified. The following margins ■ ■ ■ NO2 NO2NO□ Ni8 CH3 ■-9 As the binder resin for the above hole-transporting charge-generating pigment and the above ketone compound, polystyrene, silicone resin, polycarbonate 1 to resin, acrylic are used. Resin, methacrylic resin, polyester, vinyl resin, cellulose,
Any conventionally known resin such as alkyd resin can be used.

In the charge generation layer of the present invention, the ketone compound has a ratio of 0.01 to 2
It is contained in an equivalent amount, preferably in a range of 0.1 to 1 equivalent.

If the amount of the ketone compound is less than 0.01 equivalent, the effect on increasing photosensitivity and reducing environmental fluctuations and repetitive fluctuations in the potential of exposed/unexposed areas will be reduced, and if it is higher than 2 equivalents, In an electrophotographic process in which dark decay increases greatly, charging potential decreases, and toner is formed in non-exposed areas, the background area is likely to be fogged, so the above range is preferable.

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

Various methods can be employed to incorporate the hole-transporting charge-generating pigment and the ketone compound into the charge-generating layer. For example, it can be contained in the following manner. ■Add a hole-transporting charge-generating pigment and a ketone compound together into a binder resin solvent solution and disperse them. Dispersion methods include ball mill dispersion, attritor dispersion, sand mill dispersion, and ultrasonic dispersion. Any commonly employed method can be used. (2) 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. (2) A hole-transporting charge-generating pigment is previously treated with a ketone compound solution to be adsorbed, and then dispersed in a binder resin solvent solution. (2) A hole-transporting charge-generating pigment is dispersed in a solvent solution of a binder resin, and a film is formed by coating, and then the film is treated with a solution of a ketone compound to impregnate it.

Furthermore, during this dispersion, the charge generating pigment particles have an average particle size of 3.
It is effective to have a particle size of p or less, preferably 0.5 μm or less.

In addition, the solvents used for dispersion include methanol,
Ordinary organic solvents such as ethanol, n-propertool, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl kene, cyclohexanone, methyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, etc., alone or Two or more types can be mixed and used.

The coating method used when providing the charge generation layer may be a conventional method such as a blast 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. Can be done.

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

The charge transport layer included in the electrophotographic photoreceptor of the present invention is formed by containing a charge transport material in a suitable binder resin.

As charge transport materials, oxadiazole derivatives such as 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1-[pyridyl- (2)] Pyrazoline derivatives such as -3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, aromatic tertiary amine compounds such as triphenylamine and dibenzylaniline, N, N'- Bis(3-methylphenyl)
-[1,1'-biphenyl] Aromatic tertiary diamino compounds such as -4,4'-diamine, 3-(4'-dimethylaminophenyl)-5,6-di(4'-methoxyphenyl) 1 , 2.4-riazine derivatives such as 2.4-triazine, 4-diethylaminobenzaldehyde-1
, hydrazone derivatives such as 1'-diphenylhydrazone,
Quinazoline derivatives such as 2-phenyl-4-styrylquinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di(p-methoxyphenyl)benzofuran, p(2,
α-stilbene derivatives such as 2-diphenylvinyl)-N,N-diphenylaniline, [Journal of Imaging Sciences J
mag+ng 5science) 29: 7-10
(1985), carbazole derivatives such as N-ethylcarbazole, poly-N-
Vinyl carbazole and its derivatives, poly γ-carbazolylethyl glutamate and its derivatives, as well as pyrene, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-biphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, etc. Known charge transport materials can be used, but are not limited thereto. Further, these charge transport materials can be used alone or in combination of two or more kinds.

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, etc. 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
- Known resins such as vinyl carbazole can be used, but are not limited thereto. Further, these binder resins can be used alone or in combination of two or more types.

The blending 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 5 to 50 mm, preferably 10 to 3 mm.
It is set in the range of 0 μm.

As a coating method for forming the charge transport layer, conventional methods 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.

Furthermore, examples of solvents used when forming the charge transport layer include aromatic hydrocarbons such as benzene, 1-toluene, xylene, and chlorobenzene, ketones such as acetone and 2-butanone, methylene chloride, chloroform, and ethylene chloride. Common organic solvents such as halogenated aliphatic hydrocarbons, cyclic or linear ethers such as tetradidrofuran, and ethyl ether can 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 when the photosensitive layer having a laminated structure is charged, 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. Examples of conductive materials include metallocene compounds such as N,N'-dimedylferrocene, N,N'-diphenyl-N,N'-bis(3-methylphenyl)[1,1
Materials such as aromatic amine compounds such as "-phenyl]-4,4'-diamine, 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 this protective layer, polyamide resin, polyurethane resin, polyester resin, T-boxy resin, polyketone resin,
Known resins such as polycarbonate resin, polyvinyl ketone resin, polystyrene resin, and polyacrylamide resin can be used.

The thickness of the protective layer is 0.5-20/ffl, preferably 1-20/ffl.
It is set to a range of 10.

The electrophotographic photoreceptor of the present invention can be used in known electrophotographic image forming methods. In other words, it can be used in an image forming method that includes the steps of uniformly negatively charging the surface of a photoreceptor, performing imagewise exposure to form an electrostatic latent image, and developing it with charged toner particles. A copy image with image density can be obtained.

However, the electrophotographic photoreceptor of the present invention is particularly suitable for use in the following image forming method of forming an image by a so-called reversal development method.

That is, after the surface of the electrophotographic photoreceptor is uniformly negatively charged, an electrostatic latent image is formed by imagewise exposure, and the low potential area (exposed area) of the electrostatic latent image is negatively charged. A toner image is formed by attaching toner, a transfer material is placed on an electrophotographic photoreceptor that holds the formed toner image, and a positive charge is applied from the back side of the transfer material to transfer the toner image onto the transfer material. It is particularly suitable for an image forming method comprising:

To explain the image forming method to which the electrophotographic photoreceptor of the present invention is applied, corona dischargers such as a corotron, scorotron, dicorotron, and pincorotron, charging rollers, etc. are used as means for uniformly charging the surface of the photoreceptor. Can be used. The initial charging potential is preferably set in the range of -700 to -200V.

Image exposure means include an illumination optical system consisting of an illumination lamp and an imaging optical system, a laser exposure optical system consisting of a laser beam generation source and a laser beam deflector, an LED array, a liquid crystal light valve, a vacuum fluorescent tube array, and an optical system. Any type of light source, such as a fiber array or an optical waveguide array, can be used, but it is preferable to use a light source that emits light with a wavelength in the spectral sensitivity region of the photoreceptor.

The electrostatic latent image formed by imagewise exposure is developed using a developer to form a toner image. As the developer, a two-component developer consisting of carrier and toner or a one-component developer consisting only of toner can be used. The toner particles may be magnetic toner containing magnetic powder inside, or non-magnetic toner. During development, a developing machine having a developer carrier carrying the developer is used to bring the toner particles close to or in contact with the electrostatic latent image.
Toner particles are selectively agitated depending on the potential of the electrostatic latent image.

In this case, depending on the charging polarity of the toner, the toner either adheres to the low potential area (exposed area) of the electrostatic latent image on the photoconductor (reversal development) or to the high potential area (unexposed area) (positive development). transfer and development), but these can be carried out by selecting the charging polarity of the toner. Since the electrophotographic photoreceptor of the present invention is essentially negatively chargeable, in the case of reverse development, a toner with negative charge polarity is selected, and in the case of forward development, a toner with positive charge polarity is selected. toner is selected.

During development, a bias voltage can be applied between the support of the electrophotographic photoreceptor and the developer carrier. As the bias voltage, a DC voltage or an AC voltage superimposed on a DC voltage can be used. Particularly when performing reversal development, it is necessary to apply a bias voltage equal to or lower than the potential of the non-exposed area.

The toner image formed by development can be transferred to a transfer material by any method. As a transfer means,
In addition to the above-mentioned corona charger, a transfer roll to which a transfer voltage is applied, a pressure roll, etc. can be used, but electric field transfer, which uses a corona discharger to transfer by applying a charge from the back side of the transfer material, is particularly effective. be. For example, negatively charged toner particles formed by reverse development are suitably transferred onto the transfer material by applying positive corona discharge from the back side of the transfer material.

After the transfer is completed, if necessary, the photoreceptor is cleaned of residual toner images (toner images that were not transferred), and then static electricity is removed from the photoreceptor using an optional optical static eliminator or corona static eliminator, and the photoreceptor is cleaned for the next image forming process. will be prepared.

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

For example, after the surface of an electrophotographic photoreceptor is uniformly negatively charged, a first image exposure is performed to form a first electrostatic latent image, and the low potential portion of the first electrostatic latent image is A negatively charged toner is deposited to form a first toner image, followed by a second imagewise exposure to form a second electrostatic latent image, and a high potential of the second electrostatic latent image is applied. A second toner image is formed by attaching a positively charged second toner to the area, and then, after aligning the polarities of the first and second toner images to one polarity, the first and second toner images are formed. The transfer material is superimposed on the electrophotographic photoreceptor that holds the
Suitable for use in an image forming method comprising applying charges of polarity opposite to the polarities of the first and second toner images from the back side of the transfer material and transferring the first and second toner images onto the transfer material. Can be done.

In the above-described one-pass multicolor image forming method, as the means for uniformly negatively charging the photoreceptor, the image exposure means, the developing means, and the transfer means, the same ones as those described above can be used.

First, the surface of the photoreceptor is uniformly negatively charged, and then a first image exposure is performed. The first image exposure employs image area exposure in which a portion corresponding to the image area is exposed. The formed first electrostatic latent image is developed using a first developer to form a first toner image, but in this case, a bias voltage lower in potential than the initial charging potential is applied. Using a developer carrier, negatively charged first toner is attached to a low potential area (exposed area) of the first electrostatic latent image to form a first toner image.

Next, a second image exposure is performed, and in the second image exposure, a background portion exposure is employed in which a portion corresponding to a non-image portion is exposed. Moreover, the light source used for the second image exposure is
The light intensity is made weaker than that used for the first image exposure, and the exposure is performed so that the potential of the photoreceptor corresponding to the background part is reduced to approximately half of the initial charging potential. is preferred.

Then, the second image is exposed in the second image.
A positively charged second toner is attached to the image area in the image exposure. In this case, it is preferable to perform development by carrying the second toner on a developer carrying member to which a bias voltage higher than the potential of the photoreceptor corresponding to the background portion is applied.

Furthermore, since the second development is carried out on the photoreceptor on which the first toner has already been carried, so-called overlapping development, there may be image disturbance of the first toner image or damage caused by the second developing machine carrying the first toner. In order to prevent the toner from being mixed into the toner, it is preferable to use a two-component developer consisting of toner and a negatively chargeable low-density carrier in the second development. Also, the density of the carrier is 4. OIJ/cu
It is preferable that it is less than or equal to t.

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 to one of the polarities. In order to align the polarity, corona discharge can be performed using a pre-transfer charger. Since the electrophotographic photoreceptor of the present invention is negatively chargeable, it is preferable to adjust the polarity to i-lunar-positive. For pre-transfer charging, it is preferable to use an alternating current voltage on which a positive direct current voltage is superimposed.

Next, a transfer material is superimposed on the toner image on the photoreceptor, and the polarity opposite to that of the toner image is applied from the back side of the transfer material. A 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.

Image formation is performed as described above, and the first toner and second toner can be selected from appropriate colors. For example, if the electrophotographic photoreceptor is drum-shaped, the drum A two-color image can be obtained during one revolution.

EXAMPLES Hereinafter, the electrophotographic photoreceptor of the present invention and an image forming method using the same will be explained with reference to examples.

Example 1 The surface of a mirror-cut aluminum pipe with an outer diameter of 40 mφ and a length of 319# was polished to a surface roughness of R.
It was processed so that a=0.17 μm. Next, in order to form an undercoat layer, a mixed solution having the following composition was prepared.

Polyamide resin (Laccamite 5003 manufactured by Dainippon Ink Chemical) 1 part by weight methanol
5 parts by weight n-butanol 3 parts by weight Water 1 part by weight The above mixture was applied by dip coating,
C for 10 minutes to form a subbing layer with a thickness of 1.

A mixture of the following components was then prepared.

Type X metal-free phthalocyanine 1 part by weight ketone compound based on pigment (Example Compound 5)
A mixture of 0.3 equivalent polyvinyl butyral resin (trade name: S-LEC B) II, manufactured by Tsukisui Kagaku@), 1 part by weight, and 60 parts by weight of cyclohexanone was dispersed for 10 hours using a sand mill using 11 raφ glass beads as a dispersion medium. A temporary dispersion of pigment with an average particle size of 0.05 was prepared. The obtained dispersion was applied onto the undercoat layer by dip coating, and dried by heating at 120°C for 10 minutes to give a film thickness of 0.
．． 25 A temporary charge generation layer was formed.

Furthermore, 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 7 type) 3 parts by weight Monochlorobenzene 20 Parts by weight This mixture was coated onto the above charge generation layer by dip coating method and heated at 110'C for 60°C.
It was dried for a minute to form a charge transport layer with a thickness of 20#2.

The electrophotographic photoreceptor thus prepared was negatively charged using a scorotron (grid applied voltage: -300V), and then exposed to a semiconductor laser (780 nm emission) for optical attenuation. A surface electrometer probe was placed at the position after 0.3 seconds (corresponding to the position after 0.6 seconds after charging), and the potential during non-exposure (VH) and the potential during exposure (V L : 30er (J/ crti exposure).Furthermore, a] rotron (wire applied voltage: +5.0 KV) was placed after this probe to positively charge it, and then the charge was removed using a tungsten lamp.In this system, negative charge exposure - positive One cycle consisted of charging and removing exposure, and changes in VH and V[ were measured up to 200 cycles.

This measurement was performed at 32°C, 85% RH; 20°C, 55% R
The test was carried out under each environment of Hj, 10° C., and 15% RH. Post the results in Table 1.

In addition, the above electrophotographic photoreceptor was installed in a laser printer (product name: XP-11, manufactured by Fuji Xerox ■), and A4
After printing 500 sheets continuously on A4 size paper, print only on B4 size paper, and check the density difference between the area where A4 size paper passed and the other areas, and the background fog in each area. About, 32℃, 85%R
Evaluation was made under H environment. The results are shown in Table 2 below.

In addition, this laser printer uses negative polarity magnetic component toner as a developer, and D C++l
The toner image attached to the exposed area was transferred by a transfer corotron of +8 KV.

Examples 2 to 7 The amount of the ketone compound (Example Compound I-5) was 0.005 equivalent (Example 2), 0.01 equivalent (Example 3), and 0.1 equivalent (Example 3) relative to the pigment, respectively. Example 4), 1.0 equivalent (Example 5), 2.0 equivalent (Example 6), or 4.0 equivalent (Example 7) Photoreceptors were prepared and evaluated in the same manner.The results are shown in Tables 1 and 2.

Comparative Example 1 An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1, except that no ketone compound was added, and evaluation was performed in the same manner. The results are shown in Tables 1 and 2.

Examples 8-9 Except that the ketone compound was changed to the compound shown in Table 1,
An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1, and evaluated in the same manner. The results are shown in Tables 1 and 2.

Examples 10 to 12 Electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that the X-type metal-free phthalocyanine and ketone compound in Example 1 were replaced with the compounds shown in Table 3, and evaluated in the same manner. I did it. The results are shown in Tables 3 and 4.

Comparative Examples 2-4 Examples 10-1 except that no ketone compound was added
An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 2, and evaluated in the same manner. The results are shown in Table 3 and 4th Examples 13 to 1.
5 As a substrate, a mirror-cut aluminum pipe with an outer diameter of 84#φ and a length of 310# was used, and a perylene pigment (exemplified compound IV-1> was used as a charge-generating pigment, as shown in Table 5 as a ketone compound). An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1 except that the compound was used.

The electrophotographic photoreceptor thus prepared was negatively charged using a scorotron (grid applied voltage: -300V), and then a halogen lamp (550n
The light is attenuated by exposure using an interference filter with a central wavelength of m, and the position after 0.3 seconds (after charging,
Place the surface electrometer probe at the position (corresponding to the position after 0.6 seconds) and measure the potential during non-exposure (VH) and the potential during exposure (V L :
30erg/C/1i exposure). Furthermore, after this probe, a corotron (wire applied voltage: +
5.0 KV) was placed to positively charge the sample, and then the charge was removed using a tungsten lamp. In this system,
Negative charging - exposure - positive charging - removal exposure is one cycle, and 20
Changes in VH and VL up to cycle 0 were measured. This measurement was performed at 32°C, 85%RH; 20°C, 155%RH
; and 10° C. and 15% RH. The results are shown in Table 5.

Comparative Example 5 An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 13, except that no ketone compound was added, and evaluation was performed in the same manner. The results are shown in Table 5.

Comparative Examples 6 and 7 In Example 13, perylene pigment (exemplified compound IV-
Electrophotographic photoreceptors were prepared in exactly the same manner, except that dibromoane 1 to anthrone or a bisazo pigment represented by the following structural formula was used in place of 1>, and evaluation was performed in the same manner. The results are shown in Table 5.

Comparative Examples 8 and 9 Electrophotographic photoreceptors were prepared in exactly the same manner as in Comparative Examples 6 and 7, except that no ketone compound was added, and evaluated in the same manner. The results are not shown in Table 5.

Below are blank spaces Example 16 and Comparative Example 10 Using the electrophotographic photoreceptors prepared in Example 1 and Comparative Example 1, a scorotron (grid applied voltage: -30
0V), and then imagewise exposed to a semiconductor laser (780 nm oscillation) to attenuate the light.
A surface potential probe was placed at a position 0.3 seconds after exposure (equivalent to the position 0.6 seconds after charging), and the potential during non-exposure (VH) and the potential during exposure (V L : 20erg/
(c) scrap exposure) was measured. Furthermore, after this probe, ]
A rotron (wire applied voltage: 5.0 KV) was placed to negatively charge the sample, and then the charge was removed using a tungsten lamp. In this system, one cycle was negative charge-exposure, negative charge, and removal exposure, and changes in VH and VL were measured up to 200 cycles. This measurement was performed at 32°C, 85% R
H: 20°C 155% R[1; and 10'C, 15%
Tests were conducted under various RH environments. The results are shown in Table 6.

Example 17 and Comparative Example 11 The base material had an outer diameter of 84 mm and a length of 310 mm. The surface of the mirror-cut aluminum pipe is polished with a whetstone.
The treatment was performed so that the surface roughness was Ra=0.15 μm.

Next, an electrophotographic photoreceptor was produced in the same manner as in Example 1 or Comparative Example 1.

The electrophotographic photoreceptor produced in this way is transferred to a copying machine (
FX2700 Fuji Xerox ■) modified two-color laser printer (Charging - Primary laser exposure - Negatively charging red toner development on exposed areas - Secondary laser exposure - Positively charging black toner development on unexposed areas - DC) (consisting of superimposed AC pre-transfer charging - transfer by applying negative DC roller 1 to ron - cleaning - repetition of static electricity removal), and repeated a mixed red and black pattern 5000 times on B4 size paper.
Changes in print density in the red and black areas of the 0-sheet pudding mill were observed.

In the electrophotographic photoreceptor of Example 17, clear printing without fogging in the background area was obtained in both red and black areas, but in the electrophotographic photoreceptor of Comparative Example 11, red toner was applied to the background area as well as the number of continuous sheets. Fog started to increase, the red print started to get thicker, and the black print became thinner.

Effects of the Invention In the electrophotographic photoreceptor of the present invention, as described above, the charge generation layer contains a hole transporting charge generation pigment in a binder resin and a ketone compound represented by the above formula (I). Compared to the case where no ketone compound is added, the sensitivity is improved, the charging property is good, the photosensitivity and charging potential are stable against environmental changes, and the exposed and non-exposed areas are It has an excellent effect in that the potential remains stable without decreasing even when a large number of copies are made.

The electrophotographic photoreceptor of the present invention is particularly useful when applied to an electrophotographic image forming method that repeats the following operations: --like negatively charged image exposure, reversal development, positively charged transfer, and static elimination, for example, when used in a laser printer, etc. suitable, and in which case, the surface potential of the photoreceptor during imagewise exposure, from the first imaging operation to after a number of repeated imaging operations, undergoes a potential drop with repeated imaging operations. A stable surface potential is maintained at all times, and therefore images with stable image density can be obtained and the occurrence of fog can be suppressed.

In addition, even if the transfer paper is changed to a wider size one after repeating the image forming operation many times, the transfer density will not increase in the area corresponding to the width difference of the transfer paper, and therefore the background It is possible to obtain images with uniform density without fogging.

Note that when the above-mentioned ketone compound is not included in the charge generation layer, the potential of the exposed and non-exposed areas gradually decreases with repeated image forming operations, the image density gradually increases, and the background area becomes foggy. occurs. In addition, if you change the transfer paper to a wider size after repeating the image forming operation many times, the image may increase by 6 degrees and the background may become foggy in the area corresponding to the width difference. Can be seen.

Furthermore, the electrophotographic photoreceptor of the present invention can also be applied to a so-called one-bath multicolor image forming method.

[Brief explanation of drawings]

1 to 4 are schematic cross-sectional views for explaining the structure of the electrophotographic photoreceptor of the present invention, respectively. DESCRIPTION OF SYMBOLS 1... Charge generation layer, 2... Charge transport layer, 3... Conductive support, 4... Subbing layer, 5... Protective layer. Patent applicant Fuji Xerox Co., Ltd. Agent
Patent Attorney Tsuyoshi Horabe - One inch to one inch [F] 0 to 0 to 0

Claims (5)

[Claims] (1) In an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are sequentially laminated on a support, the charge generation layer contains a hole transportable charge generation pigment in a binder resin and the following general formula ( I
) An electrophotographic photoreceptor comprising a ketone compound represented by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the formula, R_1 and R_2 are hydrogen atoms, alkyl groups, nitro groups, aryl groups, alkoxy groups, aryloxy groups, alkoxycarbonyl groups, and aryloxycarbonyl groups, respectively) , represents a halogen atom, a cyano group, and n and m each represent an integer of 0 to 2) (2) The electrophotographic photoreceptor 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 photoreceptor according to claim 1, wherein the hole-transporting charge-generating pigment is a phthalocyanine pigment, a squareryllium pigment, or a perylene pigment. (4) After the surface of the electrophotographic photoreceptor according to claim 1 is uniformly negatively charged, imagewise exposure is performed to form an electrostatic latent image, and the low potential portions of the electrostatic latent image are negatively charged. A toner image is formed by adhering the toner, a transfer material is superimposed on an electrophotographic photoreceptor that holds the toner image, and a positive charge is applied from the back side of the transfer material to transfer the toner image onto the transfer material. An image forming method characterized by: (5) After the surface of the electrophotographic photoreceptor according to claim 1 is uniformly negatively charged, a first image exposure is performed to form a first electrostatic latent image, and the first electrostatic latent image is formed. A first toner image is formed by depositing negatively charged toner on the low potential portions of the image;
A second image exposure is performed to form a second electrostatic latent image, and a positively charged second toner is attached to a high potential portion of the second electrostatic latent image to form a second toner image. After forming and aligning the polarities of the first and second toner images to one polarity, a transfer material is superimposed on the electrophotographic photoreceptor holding the first and second toner images, and the back side of the transfer material is An image forming method characterized in that the first and second toner images are transferred onto a transfer material by applying charges having polarities opposite to those of the first and second toner images.