JPH01297674A - Image forming method - Google Patents

Abstract

PURPOSE:To reduce the faults of an image such as a black spot, etc., by electrostatically charging a photosensitive body which has a charge blocking layer containing a binder material and an organic pigment, then forming an electrostatic latent image and performing reversal development. CONSTITUTION:After electrostatic charging in which the absolute value of an electrostatic charging potential is 400-900V is performed to the photosensitive body which has the charge blocking layer 5 containing the binder material and the organic pigment, the electrostatic latent image is formed with exposure. Then the reversal development of the electrostatic latent image is performed by impressing a DC bias voltage whose absolute value is 0-200V lower than that of the electrostatic charging potential. The charge blocking layer 5 is provided between a carrier generation layer 2 and a conductive substrate 1. Thus, the black spot can be prevented from occurring in the reversal development.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an image forming method, and particularly to an electrophotographic copying method.

[Prior Art] In the electrophotographic copying method of the Carlson method, after the surface of a photoreceptor is charged, an electrostatic latent image is formed by exposure, and the electrostatic latent image is developed with toner, and then the visible image is formed. Transfer and fix onto paper, etc. At the same time, the photoreceptor is subjected to removal of adhered toner, neutralization of static electricity, and surface cleaning, and is used repeatedly over a long period of time.

Therefore, as an electrophotographic photoreceptor, it is important to not only have electrophotographic properties such as good charging characteristics, good sensitivity, and low dark decay, but also physical properties such as printing durability, abrasion resistance, and moisture resistance after repeated use. It is also required to have good physical properties and resistance to ozone generated during corona discharge, ultraviolet rays during exposure, etc. (environmental resistance).

Conventionally, as an electrophotographic photoreceptor, a non-81 photoreceptor having a photosensitive layer containing an inorganic photoconductive substance such as selenium, zinc oxide, or cadmium sulfide as a main component has been widely used.

On the other hand, the use of various organic photoconductive substances as materials for photosensitive layers of electrophotographic photoreceptors has been actively developed and researched in recent years.

For example, in Japanese Patent Publication No. 50-10496, poly-N-
An organic photoreceptor having a photosensitive layer containing vinylcarbazole and 2,4,7-dolinitro-9-fluorenone is described. However, this photoreceptor is not necessarily satisfactory in sensitivity and durability. In order to improve these drawbacks, attempts have been made to develop a leading photoreceptor with high sensitivity and great durability by assigning carrier generation freezing ability and carrier transport function to different substances in the photosensitive layer. being done. In such so-called function-separated type electrophotographic photoreceptors, substances that exhibit each function can be selected from a wide range of materials, so it is relatively easy to produce electrophotographic photoreceptors with arbitrary characteristics. Is possible. Therefore, the sensitivity is high,
It is expected that organic photoreceptors with high durability will be obtained.

FIG. 5 shows an example of a functionally separated type electrophotographic photoreceptor using such an organic photoconductive substance. This electrophotographic photoreceptor includes a carrier generation layer 2 on a conductive substrate 1,
It has a structure in which kyrelia transport layers 3 are sequentially laminated, and is used for negative charging. That is, the photosensitive layer 4 is composed of a carrier generation layer 2 and a carrier transport layer 3.

In an electrophotographic photoreceptor having the above-mentioned layer structure, since the mobility of holes is higher than that of electrons when used with negative charging, it is possible to use photoconductive materials with hole transport properties that have good properties. This is advantageous in terms of sensitivity, etc.

In contrast, few electron-transporting materials have excellent properties or are carcinogenic, making them unsuitable for use. For this reason, the above-mentioned photoreceptor is used for negative charging. In this case, it is advantageous to use a material with a high hole transport ability in order to achieve high sensitivity.

[Problems to be Solved by the Invention] However, in the above-mentioned photoreceptor, carrier injection from the conductive substrate or lower layer side tends to occur when negatively charged, as shown in FIG. microscopically disappears or decreases. The cause of such local carrier injection is not clear, but it is thought to be caused by defects or non-uniformity on the surface of the conductive substrate, non-uniformity in the carrier generation layer, or the like.

Such local carrier injection causes the following problems.

In other words, recently, reversal development has been widely adopted in printers that involve digital processing, but in the reversal development method, a toner image is formed in the exposed area (the area where the surface charge has disappeared, VL), and the toner image is formed in the unexposed area. No toner image is formed on (portion where surface charge is retained, VH).

However, in the reversal development method, if the surface charge microscopically disappears or decreases in the unexposed area due to carrier injection from the substrate or lower layer as described above, toner will appear in that area, causing so-called fog. It becomes an image. This kind of fog is different from normal fog, and is a phenomenon that occurs when the surface charge on the photoreceptor microscopically disappears or decreases during reversal development, as described above, and is called "black spots." There is. These black spots are caused by toner locally adhering to the white background, so they are much more noticeable than when the black areas are left blank, and they significantly reduce the quality of the image, indicating that they are inappropriate image defects. be.

As a way to solve these problems, carrier transportation JI
In No. 3, it is conceivable to reduce the content of carrier transport material (hereinafter sometimes referred to as CTM) or change the type of CTM or binder resin. All of these are intended to reduce the hole transport ability of the carrier transport layer 3 to suppress carrier injection into the photoreceptor surface, but in this photoreceptor, there are problems such as a decrease in photosensitivity, an increase in residual potential, and an increase in IVLI. increase in IVLI during repeated use.
This results in a decrease in stability and also a decrease in temperature characteristics, and at low temperatures, photoreceptor characteristics are significantly deteriorated, such as an increase in IVLI.

It is also possible to provide an undercoat layer between the conductive substrate 1 and the carrier generation layer 2 that has the function of shielding charge injection, but if the thickness of such an undercoat layer is small, the charge injection may be insufficient. could not be prevented, and black spots occurred during reversal development. On the other hand, when the thickness of the undercoat layer is increased, it is effective in blocking charge injection, but photocarriers generated in the carrier generation layer provided on the upper layer side are transferred to the conductive substrate side. Since movement becomes difficult, photosensitivity decreases, residual potential increases, and image density decreases, resulting in poor photoreceptor characteristics.

As described above, there has been no known photoreceptor that eliminates image defects such as black spots and has good photoreceptor characteristics, and a technical solution to these mutually contradictory problems has been desired.

An object of the present invention is to provide an image forming method that can significantly reduce image defects such as black spots and provide high-quality images with high image density in a reversal development method in which black spots are likely to occur.

[Means for solving the problem] The present invention provides a carrier transport layer on the carrier generation layer.
In the image forming method using a photoreceptor having a separate photosensitive layer, (a) a charge blocking layer provided between the carrier generation layer and the conductive substrate and containing a binder substance and an organic pigment; (b) The absolute value of the charged potential on this photoreceptor is 400V to 9.
After applying a charge of 00 V, an electrostatic latent image is formed by exposure, and then the voltage is 0 to 200 V lower than the absolute value of the charged potential.
The present invention relates to an image forming method characterized in that reverse development of the electrostatic latent image is performed by applying a DC bias voltage having a low absolute value.

However, the charging potential and the DC bias voltage have the same sign.

[Functions and Effects] In the present invention, in an image forming method using reversal development, a remarkable feature is that a charge blocking layer containing a binder substance and an organic pigment is provided between a carrier generation layer and a conductive substrate. Has characteristics.

That is, by providing a charge blocking layer between the conductive substrate and the carrier generation layer, it is possible to prevent the occurrence of black spots during reversal development. The reason for this is not clear, but it is thought to be as follows.

That is, in the conventional photoreceptor as shown in FIG.
Carriers (holes) injected from the substrate 1 side easily pass through the carrier generation H2 and reach the surface of the photoreceptor via the carrier transport layer 3 having high hole transport properties. In other words, the carrier generation layer 2 cannot function as a barrier to local carrier injection.

In contrast, in the present invention, by providing a charge blocking layer between the substrate and the carrier generation layer, it is possible to provide a barrier against local carrier injection from the conductive substrate side. It is possible to prevent the loss and decrease of surface charge caused by

However, when only a charge blocking layer is provided, it becomes difficult for the photocarriers generated in the carrier generation layer to move toward the conductive substrate, resulting in a decrease in photosensitivity, an increase in residual potential, and a decrease in image density. I was invited.

In contrast, in the present invention, it is important to specify the material of the charge blocking layer, and this solves the technical problem of preventing black spots and providing an image with high image density.

That is, it seems that the electric resistance of the charge blocking layer itself is kept high due to the action of the binder substance and the organic pigment, and therefore, carrier injection from the conductive substrate side can be effectively blocked.

On the other hand, negative photocarriers generated within the carrier generation layer during light irradiation are transported within the charge blocking layer by the organic pigment and transferred to the conductive substrate. That is, the organic pigment is a substance that has electron conductivity, and its action will impart electron conductivity to the charge blocking layer itself.

Therefore, the movement of photocarriers becomes smooth, making it possible to increase photosensitivity, reduce residual potential during repeated use, and increase image density, making it possible to provide high-quality images.

Furthermore, what should be noted in the present invention is that in addition to the above, the absolute value of the charging potential represented by IVHl as described above is limited to a specific range of l VHl = 400V to 900V, so that the above-mentioned Such defects will not occur. That is, when l VHl < 400V, it is difficult to obtain the required electric field strength, but when l VHl > 900V, it is difficult to obtain the required electric field strength.
For this purpose, the WA thickness of the photosensitive layer becomes large,
This reduces sensitivity, which is undesirable. In addition, in the present invention, the difference between 1VHl and 1Vocl (absolute value of DC bias voltage), IVHI IVDcI, is set to O~200.
v and a specific location are also important. [a] #5.1V
In the case of hl-IVpcl < O■, fogging occurs, and l V) l l I Voc l >
In the case of 200V (7), carrier adhesion (when using a two-component developer) and toner adhesion of opposite polarity (when using a bipolar component developer) occur.

Therefore, according to the invention, l VHl = 400-9
00V (preferably 500 to 700V), and l VHl −1vDc l =O to 200
V (preferably 50 to 150 V>)
Performing reversal development under these conditions is an indispensable condition for obtaining a good image with high image quality and no black spots while maintaining high sensitivity.

Moreover, since it is based on the reversal development method, especially when applied to a printer, the area of the text area (black background area) is smaller than the white background area (that is, the exposed area is smaller).
This method is advantageous in terms of preventing deterioration of the photoreceptor, etc., compared to the regular development method.

As described above, according to the present invention, by uniquely configuring the charge blocking layer during reversal development, it is possible to provide a high-quality image in which black spots and the like are significantly suppressed and the image density is high.

[Specific Structure of the Invention] A general structure of a photoreceptor, such as an electrophotographic photoreceptor, used in the present invention is illustrated in FIG.

In the photoreceptor shown in FIG. 1, a carrier generation layer 2 is provided on a conductive substrate 1 with a charge blocking layer 5 interposed therebetween.
A carrier transport layer 3 is provided on the carrier generation layer 2. 4 indicates a photosensitive layer.

In the photoreceptor shown in FIG. 1, an intermediate layer having a blocking function or the like may be provided between the carrier generation layer and the carrier transport layer. Furthermore, a protective ff1 layer (protection m>) may be formed on the surface of the photoreceptor in order to improve printing durability, for example, by coating with a synthetic resin film.

Examples of organic pigments used in the present invention include red (
400-500nm>, green (500-600nI1
1), blue (600 to 700 nm), etc., have high transmittance for each color, are heat resistant, and do not cause bleeding.

Examples of blue organic pigments include ε-type copper phthalocyanine blue and Victoria Blue Lake (C,1, Pig
a+ent Blue 1) (7) One type also has two types of Shikuha as its main components, and methyl violet lake (C, 1
, Piament Violet 3) and dioxazine violet (C, I, Pigment V
Examples include those using one or two types of 1olet 1) as a spectral property adjusting agent. Incidentally, ε-type copper phthalocyanine blue is a clear blue pigment with a strong reddish tinge, which is known from Japanese Patent Application Laid-Open No. 52-6301, etc., and is, for example, L 1onol Blue E (Toyo Ink Seisakusho (trade name)). available.

The spectral characteristics (visible absorption spectra) of the most widely used phthalocyanine pigments in various crystal forms such as α and β are that their dominant wavelength is 490 to 500 nm, and for ε-type copper phthalocyanine blue, it is on the short wavelength side of 470 to 480 nm. Yes, and the dominant wavelength of Victoria Blue Lake is 430n.
It is m.

Further, as a red organic pigment, for example, a naphthol-based orange pigment (C, 1, Pioment Orange 24)
, pyrazolone orange pigment (C,1,・pigment
Q range 13, same 1) and disazo orange pigment (C,I, Pigment Orange
The main component is one or more selected from e13), and if necessary, a naphthol red pigment (C1゜P
igment Red 22. Same 8. Same 5. Same 4.
3゜31. Same 112. 114) and pyrazolone red pigments (C, I, Pigment Red
Examples include those using one or more selected from 38) as a spectral property adjusting agent.

Examples of green organic pigments include polychloropolybromophthalocyanine green (C, I).

The main component is P1gll1ent Green 38), and disazo yellow pigment (C,1,Pipme
nt Yellow 12゜Same 13. 14) and isoindolinone yellow pigment <C,I, Pigme
1f selected from the group of nt Yellow 109, 100)! ! Alternatively, examples include those using two or more types as spectral property modifiers. Polychlorophthalocyanine green (C,1
, Pigment Green37) has a dominant wavelength of 51
0 nm, while that of polychloroboribromophthalocyanine green is at 535 r+m.

Charge blocking layer Il! The thickness is preferably 0.1 to 5 μm, more preferably 0.5 to 2 μm. Further, in the charge blocking layer, the content ratio (weight ratio) of the organic pigment and the binder substance is (1:
10) to (10:1) is preferable.

In the carrier generation layer, the foot pressure of the carrier generation substance to the binder substance is preferably 3/1 to 1/10, more preferably 2/1 to 1/3. When the content of the carrier-generating substance is greater than the above range, black spots and the like appear significantly or tend to appear. However, if the proportion of the carrier-generating substance is too small, the photosensitivity and the like will be rather reduced.

The thickness of the carrier generation layer is preferably 0.1 μm or more, and more preferably within the range of 0.2 to 5 μm.

The thickness of the carrier transport layer is preferably 10 μm or more.

The thickness of the entire photosensitive layer is preferably within the range of 10 to 40 μm, and more preferably within the range of 15 to 30 μm. If the film thickness is smaller than the above range, the charging potential will be low due to the thinness, and the printing durability will also tend to decrease. Furthermore, if the film thickness is larger than the above range, the residual potential will increase on the contrary, and the same phenomenon as described above will occur when the carrier generation layer is too thick, making it difficult to obtain sufficient transport performance. Therefore, the residual potential tends to increase during repeated use.

It is also possible to include a carrier transport substance in the carrier generation layer.

When a photosensitive layer is formed by dispersing a granular carrier-generating substance, the carrier-generating substance has a particle size of 2 μm or less, preferably 1 μm or less, and more preferably 0.5 μI.
It is preferable that the particles have an average particle size of 11 or less.

Furthermore, in the carrier transport layer, the carrier transport substance is
Those having excellent compatibility with the binder substance are preferred.

As a result, turbidity and opacity do not occur even if m is increased with respect to the binder material, so the mixing ratio with the binder material can be set at a very wide range.Furthermore, due to the excellent compatibility, charge generation The layer is uniform and stable, resulting in better sensitivity and charging characteristics.
Furthermore, it is possible to use a photoreceptor that can form clear images with high sensitivity.

Furthermore, especially when used in repeated transfer type electrophotography, it is possible to achieve the effect that fatigue deterioration is less likely to occur.

Binder substances that can be used in the charge blocking layer and photosensitive layer include, for example, polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, polyester resin, alkyd resin, polycarbonate resin, and melamine. Addition polymer resins such as resins, methacrylic resins, acrylic resins, polyvinylidene chloride, and polystyrene, polyaddition resins, polycondensation resins, copolymer resins containing two or more of these repeating units, vinyl chloride- Examples include insulating resins such as vinyl acetate copolymer resins, styrene-butadiene copolymer resins, nylidene chloride, acrylonitrile copolymer resins, and polymeric organic semiconductors such as N-vinylcarbazole.

In addition to the above-mentioned binder resin, the charge blocking layer may also contain, for example, polyvinyl alcohol, ethyl cellulose, carboxymethyl cellulose casein, N-alkoxymethylated nylon, starch, or the like.

The above binders can be used alone or as a mixture of two or more.

As a binder for the protective layer provided as necessary,
Volume resistance 108Ω・cm or more, preferably 1010Ω・
A transparent resin having a resistance of C16 or more, more preferably 10 13 Ω·cm or more is used. Further, the binder may be a resin that is cured by light or heat, and examples of the resin that is cured by light or heat include thermosetting acrylic resin,
silicone resin, epoxy resin, urethane resin, urea resin, polyester resin, alkyd resin, melamine resin,
Photocurable cinnamic acid resins, copolymerized or condensed resins thereof, and all other photocurable or thermosetting resins used in electrophotographic materials can be used. If necessary, the protective layer may contain less than 50% by weight of a thermoplastic resin for the purpose of improving processability and physical properties (preventing cracks, adding flexibility, etc.). Examples of such thermoplastic resins include polymers such as polypropylene, acrylic resins, methacrylic resins, vinyl chloride resins, vinyl acetate resins, epoxy resins, polycarbonate resins, silicone resins, copolymer resins thereof, and poly-N-vinylcarbazole. All thermoplastic resins used in organic semiconductors and other electrophotographic materials can be used.

As the carrier generating substance (CGM), any inorganic substance or organic substance can be used as long as it absorbs electromagnetic waves and generates free carriers.

Examples of CGM include the following.

(1) Amorphous selenium, trigonal selenium, selenium-arsenic alloy, selenium-tellurium alloy, cadmium sulfide, cadmium selenide, cadmium selenide sulfide, mercury sulfide, lead sulfide,
Non-m pigments such as zinc oxide and amorphous silicone (2) Azo pigments such as monoazo pigments, polyazo pigments, gold complex azo pigments, pyrazolone azo pigments, stilbene azo and thiazole azo pigments (3) Anthraquinone derivatives, anthorone derivatives , dibenzpyrenequinone derivatives, pyrantrone derivatives,
Anthraquinone or polycyclic quinone pigments such as violanthrone derivatives and isoviolanthrone derivatives (4) Indigo-de pigments such as indigo derivatives and thioindigo derivatives (5) Diphenylmethane pigments, triphenylmethane pigments, xanthine pigments and acridine pigments carbonium pigments such as (6) quinone imine pigments such as azine pigments, oxazine pigments and thiazine pigments (a) methine pigments such as cyanine pigments and azomethine pigments (8) quinoline pigments (9) nitro pigments (10) nitroso Pigments (11) Benzoquinone and naphthoquinone pigments (12)
Naphthalimide pigments (13) Perinone pigments such as bisbenzimidazole derivatives (14) Fluorenone pigments (15) Squarylium pigments (16) Azulenium compounds (11) Perylene pigments such as perylenic anhydride and perylenic acid imide, Examples of preferred azo compounds and polycyclic quinone pigments will be shown.

([-4) A-N=N Ar'-CH=CHAr''-N=N
AN-6) A-N=N-Ar'-CH=CH-Ar''-CH=CH
-Ar Co N=N-A(T-7) (T-8) A-N-"N-Ar'-N=N-Ar2-N=N-A(
I-9) A-N"N-Ar'-N=N-Ar"-N=N-Ar'
-N=N-A(T-11) K'K" [However, in each of the above general formulas, Ac1, A'2 and Ar3: each substituted or unsubstituted carbocyclic aromatic ring group, R+, R2 , R3 and R+: each is an electron-withdrawing group or a hydrogen atom, and at least one of R1-R4 is an electron-withdrawing group such as a cyano group, atom or a substituted or unsubstituted alkyl group, R8 is a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group>, Y is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group, a carboxyl group group, sulfo group, substituted or unsubstituted carbamoyl group, or substituted or unsubstituted sulfamoyl group (however, when there are two or more groups, they may be different groups), 2 is a substituted or unsubstituted Atom group necessary to constitute a carbocyclic aromatic ring or a substituted or unsubstituted heterocyclic aromatic ring, R5 is a hydrogen atom, a substituted or unsubstituted amino group, a substituted or unsubstituted carbamoyl group, carboxyl group or its ester group, Ar4 is a substituted or unsubstituted aryl group, n is an integer of 1 or 2, and m is an integer of O to 4.)] In addition, the following general formula [polycyclic quinone of the IF5 group Pigments are also CGM
Can be used as

General formula [■]: (However, in this general formula, X' is a halogen atom, a nitro group,
Represents a cyan group, acyl group or carboxyl group, p is O
An integer of ~4, q represents an integer of O~6. ) For squarylium pigments, see JP-A-60-25855.
There is a description in Publication No. 0, etc.

Regarding azulenium compounds, patent application No. 62-2511
It is described in the specification of No. 88.

The carrier transport substances used in the present invention include carbazole derivatives, oxazole derivatives, oxadiazole derivatives,
Thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidasilone derivatives,
imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline derivatives,
Oxacilone derivative, benzothiazole 171, benzimidazole derivative, quinazoline derivative, benzofuran derivative, acridine derivative, phenazine derivative, aminostilbene derivative, triarylamine derivative, phenylenediamine derivative, stilbene derivative, poly-N-
Vinyl carbazole, poly-1-vinylpyrene, poly-
It may be one or more selected from 9-vinylanthracene and the like.

Specific examples of such carrier transport substances are disclosed in Japanese Patent Application No. 1983.
It is described in the book Ill.-195881. The general formula is given below.

The following general formula [I [I] or [
rV] styryl compounds can be used.

General formula [■]: (However, in this general formula, R9, R10 represent substituted or unsubstituted alkyl groups, aryl groups, and substituents include alkyl groups, alkoxy groups, substituted amino groups, hydroxyl groups, halogen atoms, Use an aryl group.

Ar5. Ar6: represents a substituted or unsubstituted aryl group, and the substituent used is an alkyl group, an alkoxy group, a substituted amine L* acid group, a halogen atom, or an aryl group.

R++, R12: @represents a substituted or unsubstituted aryl group or hydrogen atom, and as a substituent, an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen atom, or an aryl group is used. ) General formula [■]: Shin (However, in this general formula, R13: substituted or unsubstituted aryl group, RH: hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, alkoxy group, amino group, substituted (Amyl LL hydroxyl group, R+5: @represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group.) In addition, a hydrazone compound of the following general formula % formula % [ ] can also be used as a carrier transport substance. .

General formula [V]: (However, in this general formula, R16 and R17: each a hydrogen atom or a halogen atom, R18 and R19: each a substituted or unsubstituted aryl group, Ar7: a substituted or unsubstituted arylene group.

) General formula [■]: (However, in this general formula, R20 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted carbazolyl group, or a substituted or unsubstituted heterocyclic group, R21, R22 and R23 : Represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.) General formula [VIal: h... (However, in this general formula, R24 dimethyl group, ethyl group, 2-hydroxyethyl group or 2-chloroethyl group, R25: methyl group, ethyl group, benzyl group, or phenyl group, R26: methyl group, ethyl group, benzyl group, or phenyl group.

General formula [VI bl: (In this general formula, R27 is a substituted or unsubstituted naphthyl group; R28 is a substituted or unsubstituted alkyl group,
Aralkyl group or aryl I; R29 is a hydrogen atom, an alkyl group, or an alkoxy group, and R30 and R31 are the same or different groups consisting of a substituted or unsubstituted alkyl group, aralkyl group, or aryl group. ) General formula [■]: (However, in this general formula, R32 = substituted or unsubstituted aryl group or substituted or unsubstituted heterocyclic group, R33: hydrogen atom, substituted or unsubstituted alkyl group, or substituted or unsubstituted Substituted aryl group, Q: hydrogen atom, halogen atom, alkyl group, substituted amine L alkoxy group, or siam L S: represents an integer of 0 or 1.) In addition, as a carrier transport substance, the following general formula [■] Pyrazoline compounds can also be used.

General formula [■]: [However, in this general formula, R34 and R35: substituted or unsubstituted aryl group, R36: substituted or unsubstituted aryl group or heterocyclic group, R37 and R38: hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group or aralkyl group (however, both R37 and R38 are not hydrogen atoms, and if the above ! is O, R37 is hydrogen Furthermore, an amine derivative of the following general formula [rX] can also be used as a carrier transport substance.

General formula [IX]: (However, in this general formula, Ar8.Ar9 represents a substituted or unsubstituted phenyl group, and a halogen atom, an alkyl group, a nitro group, or an alkoxy group is used as a substituent.

A "10: Represents a substituted or unsubstituted phenyl group, naphthyl group, anthryl group, fluorenyl group, or heterocyclic group, and substituents include an alkyl group, an alkoxy group, a halogen atom, a hydroxyl group, an aryloxy group, an aryl group, and an amino group. In addition, the following are used: A compound of the general formula [X] can also be used as a carrier transport substance.

General formula [X]: (However, in this general formula, Ar": represents an fa-substituted or unsubstituted arylene group, and R3
9, R40, R4+ and R42: represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group. ) Furthermore, a compound of the following general formula [XI] can also be used as a carrier transport substance.

General formula [XI]: [However, in this general formula, R43, R44, R45 and R4
6 is a hydrogen atom, a substituted or unsubstituted alkyl group, a cycloalkyl group, an alkenyl group, an aryl group,
Benzyl group or aralkyl group, R47 and R48 each have a hydrogen atom, a substituted or unsubstituted carbon atom number of 1 to
40 alkyl groups, cycloalkyl groups, alkenyl groups,
Cycloalkenyl group, aryl group, or aralkyl group (However, R47 and R48 may jointly form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms.)R
49, R50, R and R are each a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a cycloalkyl group, an alkenyl group, an aryl group,
They are an aralkyl group, an alkoxy group, an amiLL alkylamino group, or an arylamino group. ] An antioxidant can be contained in the carrier transport layer and the carrier generation layer. This can suppress the influence of ozone generated during discharge, and can prevent an increase in residual potential and a decrease in charged potential during repeated use.

Examples of the antioxidant include hindered phenol, hindered amine, paraphenylene diamine, aryl alkane, hydroquinone, spirochroman, spiroindanone and derivatives thereof, organic sulfur compounds, organic phosphorus compounds, and the like.

These specific compounds are disclosed in Japanese Patent Application No. 61-1628.
No. 66, No. 61-188975, No. 61-195
No. 878, No. 61-157644, No. 61-195
No. 879, No. 61-162867, No. 61-204
No. 469, No. 61-217493, No. 61-2174
It is described in No. 92 and No. 61-221541.

A polymeric organic semiconductor can also be included in the photosensitive layer.

Among these polymeric organic semiconductors, poly-N-vinylcarbazole or its derivatives are highly effective and are preferably used. Such poly N-vinylcarbazole derivatives have various substituents such as alkyl groups, nitro groups, and ami/W on all or part of the carbazole rings in their repeating units.

It is substituted with a hydroxy group or a halogen atom.

Furthermore, at least one type of electron-accepting substance can be contained in the photosensitive layer for the purpose of improving sensitivity, reducing residual potential or fatigue during repeated use, and the like.

Electron-accepting substances that can be used in the photoreceptor of the present invention include:
For example, succinic anhydride, maleic anhydride, dibromaleic anhydride, phthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, 3-nitrophthalic anhydride, 4
-Nitrophthalic anhydride, pyromellitic anhydride, mellitic anhydride, tetracyanoethylene, tetracyanoquinodimethane, O-dinitrobenzene, m-dinitrobenzene,
1.3.5-trinitrobenzene, varanitrobenzonitrile, picryl chloride, quinone chlorimide,
Chloranil, brumanil, 2-methylnaphthoquinone, dichlorodicyanobarabenzoquinone, anthraquinone, dinitroanthraquinone, trinitrofluorenone, 9-
Fluorenylidene = [dicyanomethylenemalonodinitrile], polynitro-9-fluorenylidene-[dicyanomethylenemalonodinitrile], picric acid, 0-nitrobenzoic acid, p-nitrobenzoic acid, 3.5-dinitrobenzoic acid, pentafluorobenzoic acid Acids, 5-nitrosalicylic acid, 3.5-dinitrosalicylic acid, phthalic acid, mellitic acid, and other compounds with high electron affinity can be used. Among these, fluorenone series, quinone series, and Cj! , CNSNO2 and other benzene derivatives having electron-withdrawing substituents are particularly preferred.

Furthermore, silicone oil or a fluorine-based surfactant may be present as a surface modifier. Further, an ammonium compound may be contained as a durability improver.

Furthermore, an ultraviolet absorber may be used.

Preferred ultraviolet absorbers include nitrogen-containing compounds such as benzoic acid, stilbene compounds and derivatives thereof, triazole compounds, imidazole compounds, triazine compounds, coumarin compounds, oxadiazole compounds, thiazole compounds and derivatives thereof.

The charge blocking layer and carrier generation layer can be provided by the following method.

(a) A method in which a binder and a solvent are added to organic pigments or carrier-generating substances, and a mixed solution is applied.

(b) Grind organic pigments or carrier-generating substances into fine particles in a dispersion medium using a ball mill, homomixer, sand mill, ultrasonic disperser, attritor, etc., add a binder, mix and disperse, and apply the resulting dispersion. Method.

Dispersing the particles under the action of ultrasound in these methods allows for homogeneous dispersion.

Further, the carrier transport layer can be formed by applying and drying the above-mentioned carrier transport substance alone or by dissolving and dispersing it together with the above-mentioned binder resin.

In this case, when the carrier-generating layer contains a chyrelia-transporting substance, a method of dissolving or dispersing the carrier-transporting substance in the solution (a) or the dispersion liquid of (b) in advance, that is, in the carrier-generating layer. There is a method of adding a carrier transport substance. In this case, it is preferable that the carrier transport substance is added in an amount of 1 to 100 parts by weight based on 100 mm parts of the binder. Alternatively, there is a method in which a solution containing a carrier transport substance is applied onto the carrier generation layer, and the carrier generation layer is swollen or partially dissolved to diffuse the carrier transport substance into the carrier generation layer. When this method is employed, it is not necessary to add a carrier transporting substance to the carrier generation layer as described above, but the two methods described above may be carried out simultaneously.

As the solvent or dispersion medium used for forming the layer, n
-butylamine, diethylamine, ethylenediamine,
Isopropanolamine, triethanolamine, triethylenediamine, N,N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, 1,2-dichloroethane, dichloromethane, tetrahydrofuran,
Dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide and the like can be mentioned.

The charge blocking layer, photosensitive layer, undercoat layer, intermediate layer,
The protective layer etc. can be provided by, for example, blade coating, dip coating, spray coating, roll coating, spiral coating, or the like. For example, blade coating is suitable for providing layers of a few μm.

The S conductive substrate is prepared by coating, vapor depositing, laminating, etc. a conductive A layer made of a metal plate, a metal drum, or a conductive polymer, an eleventh compound such as indium oxide, or a metal such as aluminum, palladium, or gold. Those provided on a substrate such as paper or plastic film are used.

Next, preferred embodiments of the present invention will be described.

FIG. 2 is a schematic configuration diagram showing an example of a recording apparatus that implements the method of the present invention, and FIG. 3 is a partial sectional view showing an example of a developing device.
FIG. 4 is a flowchart for implementing the method of the present invention.

In the apparatus shown in FIG. 2, 10 is a drum-shaped image carrier that has a photosensitive layer made of the above-mentioned organic photoconductive substance and rotates in the direction of the arrow, and 9 is a charger that uniformly charges the surface of the image carrier 10. ,
12 is an image exposure device, and 13 is a developing device. 14 is the image carrier 1
15 is a transfer device, 16 is a corona discharger for separation, and 19 is a recording medium P. This is a fixing device that fixes the toner image transferred to the printer. Reference numeral 17 has a static eliminator consisting of one or a combination of a static eliminator lamp and a corona discharger for static elimination, and 18 has a cleaning blade or a fur brush for removing residual toner on the surface of the image carrier 10 after the image has been transferred. It is a cleaning device.

As the developing device 13, one having a structure as shown in FIG. 3 is preferably used. In FIG. 3, the developer material is conveyed in the direction of arrow G as the magnetic roll 21 rotates in the direction of arrow F and the sleeve 20 rotates in the direction of arrow G. The thickness t of the developer layer is regulated by a spike regulating blade 22 during transportation. The spike control blade 22 is made of an elastic metal plate and presses against the surface of the sleeve 20 to control the thickness of the developing agent being conveyed. A stirring screw 23 is provided in the developer reservoir 25 to sufficiently stir the developer reservoir.
When the developer in the developer reservoir 25 is consumed, the toner T is replenished from the toner hopper 26 by the rotation of the toner supply roller 24. And sleeve 20
A DC power supply 27 and a protective resistor 2 that apply a developing bias to
8 are connected in series. Further, the sleeve 20 and the image carrier 10 are arranged facing each other with an interval d, and the developing area E
The developer comes into contact with the image carrier 10 at .degree. C.>d.

In the figure, the developing sleeve 20 and the magnet body 21 are respectively indicated by the arrow G-
Although it is shown that the developing sleeve 20 rotates in the F direction, even if the developing sleeve 20 is fixed, the magnet body 21 is fixed, or the developing sleeve 20 and the magnet body 21 rotate in the same direction. It may be something. When the magnet body 21 is fixed, normally, in order to make the magnetic flux density of the magnetic pole facing the image carrier 10 larger than the magnetic flux density of other magnetic poles, the magnetization is strengthened or a magnetic pole of the same or different polarity is attached thereto. In some cases, two magnetic poles are placed close to each other.

In the above-described apparatus, based on the present invention, the I of the electrostatic latent image is
Charged so that VHI was 400 to 900v, and IVHI during reversal development (IVI) Gl-0 to 200
■. However, Vpc is a DC bias voltage applied to the sleeve 20 as a developer transport carrier facing the image carrier 10.

It is preferable to superimpose an AC bias voltage on the DC bias voltage. At this time, the effective value of the AC bias voltage is 0.5
KV to 4KV is preferred, and 0.1KHz to 1MH7 is preferred.

With the recording apparatus as described above, the method of the present invention as shown in FIG. 4 can be carried out.

Figure 4 shows that an electrostatic image is formed by an electrostatic image forming method in which the image exposure area is an electrostatic image with a lower potential than the background area, and the development is nN.
This figure shows an example of reversal development of the present invention, which is performed by adhering to the image toner that is charged to the same polarity as the background potential.

The example shown in FIG. 4 when the recording apparatus shown in FIG. 2 is used will be explained.

First, the static electricity is removed by the static eliminator 17, and the cleaning device 18
The surface of the image carrier 10 in the initial state, which has been cleaned by the electrifier 11 and has a potential of O, is uniformly charged by the charger 11, and an image exposure 12 is projected onto the charged surface to form an electrostatic image area. Image exposure is performed so that the potential is approximately O, and the obtained electrostatic image is developed by a developing device 13 (toner T).

Note that the image forming method of the present invention can be applied to light sources such as halogen lamps, tungsten lamps, and LEDs (light emitting diodes).

The image forming method of the present invention has a wide variety of uses.

[Examples] Examples of the present invention will be described in more detail below.
The present invention is not limited thereby.

Production of Photoreceptors> Photoreceptors A-1 of the present invention and comparative photoreceptors a-g were produced in the following manner. That is, the manufacturing procedure for each photoreceptor is common.

Binder resin (Y) or (Z) shown in Table 2 was mixed with acetone/cyclohexanone-1/1 mixed solvent (for resin (Y)) or 1,2-dichloroethane (for resin (Z)) 10 ( A freshly dissolved solution in h12 was used as a coating solution for forming a charge blocking layer (comparative photoreceptors a-C)
. In addition, a carrier transport substance (2) or an electron-accepting substance shown in Table 2 is dissolved in this solution to prepare a charge blocking layer coating solution for comparative photoreceptors d and e).
. Furthermore, an organic pigment rTNC-113J (manufactured by Sumitomo Chemical Co., Ltd.) or titanium oxide treated with conductivity was added to the charge blocking layer coating solution consisting of the above binder resin and solvent, and the mixture was dispersed in a ball mill for 48 hours to determine the respective charges. A blocking layer coating solution (photoreceptor A-1 of the present invention,
Comparative photoreceptor f).

Each of these coating solutions was coated with aluminum to a thickness of approximately 7 mm.
A charge blocking layer having a predetermined thickness was formed by coating on a conductive substrate made of polyethylene terephthalate with a thickness of 5 μm using a doctor blade.

Next, the carrier-generating substance 20 (+) shown below in (1) was ground in a ball mill at 240 rpm for 18 hours, and then 20 g of polycarbonate resin [Panlite L-1250J (manufactured by Yojin Kasei Co., Ltd.) was mixed with 1.2-dichloroethane 10001R.
A solution dissolved in II. l Thickness approx. 0
．． A carrier generation layer of 5 μm was obtained.

However, for comparative photoreceptor 9, no charge blocking layer was provided, and a carrier generation layer was formed directly on the conductive substrate.

Furthermore, 11.25 (l) of the carrier transport substance in (2) below and 15 g of polycarbonate resin "Nipiron Z-200J (manufactured by Mitsubishi Gas Chemical Co., Ltd.) were mixed with 10 g of 1,2-dichloroethane.
The resulting solution was applied onto the carrier generation layer using a doctor blade and dried at a temperature of 90° C. for 1 hour to form a carrier transport layer having a thickness of 25 μm.

As described above, photoreceptors A-1 and a-9 having individual configurations and prescriptions as shown in Table 2 were manufactured using a common manufacturing procedure.

That is, in each photoreceptor, the material of the charge blocking layer,
Contents, film thickness, etc. are varied from each other.

In Table 2, the P/B ratio indicates the weight of the contained material and the resin ff1jt (weight of the contained material (6)/weight of the resin).

Carrier generating substance (1) Carrier transporting substance (2) Conductively treated titanium oxide [500WJ (tin Mide, antimony oxide treatment; 6
(manufactured by Hara Sangyo Co., Ltd.) Electron-accepting substance TCNB (2,4,6-dolinitrochlorobenzene) Resin (Y) Polyvinyl butyral resin rXYHLJ (Union Carbide Co., Ltd.) Resin (Z) Polyester resin "Vylon-200" (Toyobo Co., Ltd.) Example 1 and Comparative Example 1 Each of the photoreceptors of the present invention and comparison was prepared by rKON I CAIJ -
B ix 1550M RJ (:I manufactured by Nika Corporation,
Equipped with an LED light source with a wavelength of 660 nm) installed on a modified machine,
Adjust the grid voltage so that H is -600 ± 10 [V], and set the developing bias DC -480 [V] + AC7
00 [V] (1 KHz), and the image density Dmax of the black spots on the white background part of the copied image and the black spot (the part corresponding to the white background part of the original image) was evaluated.

In addition, the evaluation of Kuropochi was performed using the image analysis device "Omnicon 30".
The particle size and number of black spots were measured using a "Type 00" (manufactured by Shimadzu Corporation), and the number of black spots with a diameter of 0.05 mo or more was determined based on the number of black spots per cm2.

The criteria for black spot evaluation are as shown in Table-1.

Table 1 Note that if the black spot determination result is ◎, ○, or Δ, it is practical, but if it is ×, it is not suitable for practical use.

The results of black spot evaluation on each photoreceptor are shown in Table 2 below.The umbrella potential did not exceed 200V, and the entire image was solid black.

From the results shown in Table 2, it can be seen that when copying images are formed according to the present invention, black spots are significantly reduced in reversal development, and high-quality images with high image density can be formed.

Example 2 and Comparative Example 2 Reverse development was performed in the same manner as in Example 1 (or Comparative Example 1) under the conditions shown in Table 3 below, and black spots, image density Dmax of the black background part of the copied image, carrier adhesion, and fog were I saw it. However, regarding carrier adhesion, ◯ represents no carrier adhesion, and X represents occurrence of carrier adhesion.

From this result, the following is clear.

For photoconductor A: l　V) When I　1　<　400V, the image density is insufficient.

IV) I I IVcIc l > 200V causes carrier adhesion.

IVHI-IV9゜l　Fog occurred on the entire surface with OV.

For photoconductor: Black spots occur, image density is insufficient

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the photoreceptor used in the present invention, FIG. 2 is a schematic diagram of the configuration of a recording apparatus that implements the method of the present invention, FIG. A flowchart showing the process of image formation according to the invention, and FIG. 5 is a sectional view of a conventionally used photoreceptor.

Claims (1)

[Scope of Claims] In an image forming method using a photoreceptor having a photosensitive layer having a carrier transport layer provided on a carrier generation layer, (a) a carrier transport layer provided between the carrier generation layer and the conductive substrate; (b) using a photoreceptor having a charge blocking layer containing a binder substance and an organic pigment;
After applying a charge of 00 V, an electrostatic latent image is formed by exposure, and then the voltage is 0 to 200 V lower than the absolute value of the charged potential.
An image forming method characterized in that reversal development of the electrostatic latent image is performed by applying a DC bias voltage having a low absolute value of V.