JPH01158467A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain a uniform image having a high image density and high quality by applying an electrostatic charge which is 400V-900V in the absolute value of a electrostatic charge potential to a specific photosensitive body, then forming an electrostatic latent image thereon by exposing, then by subjecting the image to a reversal development with the DC bias voltage having the absolute value lower than the absolute value of the electrostatic charge potential. CONSTITUTION:The photosensitive body having a carrier generating layer 6 in which the compd. having the coupler expressed by the formula I and having at least two azo groups in the molecule is incorporated as a carrier generating material and a charge blocking layer 7 in which polyvinyl butyral and/or polyvinyl formal is incorporated is used. After the electrostatic charge having 400V-900V absolute value of the electrostatic charge potential is applied to this photosensitive body, the electrostatic latent image is formed thereon by exposing and thereafter, the DC bias voltage having the absolute value lower by 0-200V than the absolute value of the charge potential is impressed thereto to execute the reversal development of the electrostatic latent image. The uniform image having the high image density and the high quality is thereby obtd.

Description

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

In the electrophotographic copying method of the prior art 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. Transfer and fix a visible image onto paper, etc. At the same time, the photoreceptor is subjected to removal of adhering 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 electrophotographic photoreceptors, inorganic photoreceptors having a photosensitive layer mainly composed of an inorganic photoconductive substance such as selenium, zinc oxide, or cadmium sulfide have 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
- Vinyl carbazole and 2.4.7-) Rietlow 9-
An organic photoreceptor having a photosensitive layer containing fluorenone is described. However, this photoreceptor is not necessarily satisfactory in sensitivity and durability. In order to improve these drawbacks, it is necessary to develop an organic photoreceptor with high sensitivity (and durability) by assigning the carrier generation function and carrier transport function to different substances in the photolayer. In such so-called function-separated type electrophotographic photoreceptors, it is possible to select substances that exhibit each function from a wide range of materials, so it is possible to create an electrophotographic photoreceptor with arbitrary characteristics. It can be produced relatively easily.Therefore, it is expected that an organic photoreceptor with high sensitivity and durability will be obtained.

FIG. 6 shows a functionally separated electrophotographic photoreceptor using such an organic photoconductive substance.

This electrophotographic photoreceptor has a structure in which a carrier generation layer 6 and a carrier transport layer 4 are sequentially laminated on a conductive substrate 1, and is used for negative charging. That is, the photosensitive layer 8 is composed of the carrier generation layer 6 and the carrier transport layer 4.

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.

On the other hand, most electron-transporting materials have excellent properties (or are carcinogenic, so they are unsuitable for use. For this reason, photoreceptors such as those mentioned above are not 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.

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. 6, and as a result, the surface charge disappears microscopically, or It will decrease. Although the cause of such local carrier injection is not clear, it is thought to be due to defects or non-uniformity on the surface of the conductive substrate, non-uniformity in the charge generation layer, or the like.

Such local carrier injection causes the following problems.

That is, recently, reversal development has been widely adopted in printers that involve digital processing, but in reversal development, 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, when 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 is developed in that area, resulting in 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 background is white, and they significantly reduce the quality of the image, and are inappropriate image defects. be.

As a way to solve these problems, the carrier transport layer 4
In this case, 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 4 to suppress carrier injection into the surface of the photoreceptor, but in this photoreceptor, there is a decrease in photosensitivity, an increase in residual potential, and an increase in IVLI. rise, 1”/Ll 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.

There is also a method of reducing the content of the carrier-generating substance in the binder resin in the carrier-generating layer 6, but this leads to a decrease in photosensitivity and an increase in IVLI.
Image density becomes insufficient.

Furthermore, it is conceivable to provide an undercoat layer between the conductive substrate 1 and the carrier generation layer 6, which has a function of shielding charge injection. Depending on the type of carrier-generating substance, the carrier-generating substance may aggregate, resulting in poor coating, resulting in an increase in black spots, a decrease in image density, and even image unevenness, resulting in significant inconvenience.

On the other hand, as a countermeasure from a process perspective, it is possible to widen the difference between the charging potential vH and the bias voltage VDC, but this does not make the difference between the potential VL of the exposed area and the bias voltage VDC
Since the difference between the two images becomes smaller, the image density decreases.

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.

In addition, in recent years, electrophotographic copying methods have become cheaper.

Semiconductor laser light sources are used, which have characteristics such as being compact and capable of direct modulation. Currently, gallium-aluminum-arsenic (G) is widely used in semiconductor lasers.
a-AA! -As) type light emitting device has an oscillation wavelength of 7
It is about 50 nm or more. In order to obtain such an electrophotographic photoreceptor with high sensitivity to long wavelength light, a number of studies have been made in the past. For example, photosensitive materials such as selenium and cadmium sulfide, which have high sensitivity in the visible light region A new method of adding a sensitizer to lengthen the wavelength was considered, but selenium and cadmium sulfide do not have sufficient environmental resistance against temperature and humidity, and are also toxic, making it difficult to put them into practical use. be.

Furthermore, the sensitivity of many known organic photoconductive materials is usually limited to the visible light region of 700 mm or less, and there are few materials that have sufficient sensitivity in longer wavelength regions.
It has been difficult to use it in laser printers that use semiconductor laser light sources, which are expected to have high reliability.

Technological systems using such laser beams and the like are expected to be applied to printers, which is why the emergence of a useful image forming method using reversal development is desired.

The object of the present invention is to provide an image forming method that can significantly reduce image defects such as black spots in the reversal development method where black spots are likely to occur, and that can obtain high-quality, uniform images with high image density. The goal is to provide the following.

20 Structure of the Invention and Its Effects The present invention provides an image forming method using a photoreceptor having a photosensitive layer provided with a carrier transport layer on a carrier generation layer, wherein (a) one molecule contains the following general formula: A carrier generation layer containing a compound having a coupler represented by [I] and having at least two azo groups in the molecule as a carrier generation substance, and a carrier generation layer provided between the carrier generation layer and the conductive substrate. (b) using a photoreceptor having a charge blocking layer containing polyvinyl butyral and/or polyvinyl formal;
After imparting a charge of 00V, an electrostatic latent image is formed by exposure, and then the voltage is 0 to 200V lower than the absolute value of the charged potential.
The present invention relates to 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.

General formula [■]: [However, in the above general formula, Ar' represents an aryl group.

Y and z represent a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted amino group, or a substituted or unsubstituted alkoxy group, S represents θ to 4, and r is represents θ~2. ] However, the charging potential and the DC bias voltage have the same sign.

In the present invention, a specific azo compound having a coupler represented by the above general formula [I] is contained as a carrier generating substance in a carrier generating layer, and the carrier generating layer is provided between the carrier generating layer and the conductive substrate. A notable feature is that the material of the charge blocking layer is specified.

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 one-reversal development. The reason for this is not clear, but -
He can be considered like a famous doctor.

That is, in the conventional photoreceptor as shown in FIG.
Carrier C holes) injected from the substrate 1 side easily pass through the carrier generation layer 6 and reach the surface of the photoreceptor via the carrier transport layer 4 having high hole transport properties. In other words, the carrier generation layer 6 cannot function as a barrier to local carrier injection.

On the other hand, 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 to local carrier injection from the conductive substrate side, and to prevent local carrier injection. It is thought that it is possible to prevent the surface charge from disappearing or decreasing due to the injection.

Therefore, when reversal development is performed, black spots do not occur on the image (and a remarkable effect can be achieved in that a high quality image without image defects can be obtained).

However, what is important here is the selection of the carrier generating substance and the material of the charge blocking layer, and the combination of the two.

That is, since the carrier generation layer is formed by coating directly on the charge blocking layer and is itself extremely thin, aggregation of the carrier generation substance may occur depending on the combination of the carrier generation substance and the material of the charge blocking layer. This is extremely inconvenient because coating defects occur, black spots increase significantly, photosensitivity decreases, and image unevenness occurs.

However, when it comes to selecting a suitable combination that will not cause coating defects from among the countless existing polymeric materials and numerous carrier-generating substances, there is no uniform selection method. The reality is that we have no choice but to determine a better combination through repeated experiments.

As a result of various studies, the present inventor has found that extremely good results can be obtained by selecting a combination of the above-mentioned specific azo compound and polyvinyl butyral and/or polyvinyl formal.

In other words, the above-mentioned specific azo compound has excellent photosensitivity, and when this compound is used as a carrier generating substance, the potential stability during repeated use of the photoreceptor is improved, there is little memory phenomenon, and there is no residual potential. Moreover, since this azo compound has high sensitivity in a long wavelength region, it is possible to provide a high-performance photoreceptor that is particularly suited to image forming methods using reversal development using a semiconductor laser as a light source. .

In addition, by containing polyvinyl butyral and/or polyvinyl formal in the charge blocking layer, the azo compound does not aggregate during the coating formation of the carrier generation layer, thereby preventing black spots and image unevenness during reversal development. , the azo compound is uniformly dispersed in the carrier generation layer, and the azo compound can exhibit its original photosensitivity without hindering it. Therefore.

High quality and uniform images can be provided, and image density can also be increased.

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 IVHI is limited to a specific range of IVH1 = 400 V to 900 V. The defects described above do not occur. That is, when IVHI < 400 V, it is difficult to obtain the required electric field strength, but IVHI) 9
If the voltage is set to 00 V, the thickness of the photosensitive layer becomes large for this purpose, which lowers the sensitivity, which is not preferable. Also,
In the present invention, the difference between IVHI and IVDcI (absolute value of DC bias voltage), IVHI - IVDCI, is calculated from θ to
It is also important that the voltage is specified as 200v. That is, IV
In the case of HI-IVDCI (OV, fogging occurs, and IVIII-IVDCI > 200
In the case of V, carrier adhesion (in the case of a two-component developer) and adhesion of toner of opposite polarity (in the case of a bipolar component developer) occur.

Therefore, based on the present invention, IVHI ~400~90
It should be 0V (preferably SOO~700V).

and 1Vl-IvDcl=0 to 200V (desired tL< is 5
0 to 150 V), and performing reversal development under these conditions is an essential condition for obtaining a good image with high quality and no black spots while maintaining high sensitivity.

Moreover, since it is based on the reversal development method, when applied to special printers, the area of one character part (black background part) is smaller than the white background part (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 specifically selecting the type of carrier-generating substance and the material of the charge blocking layer, unevenness of one black spot in the image can be prevented in reversal development.
Carrier adhesion and fogging can be prevented, and high-quality images with uniform image density can be provided.

A general configuration of a photoreceptor 1, for example, an electrophotographic photoreceptor, used in the present invention is illustrated in FIG.

In the photoreceptor shown in FIG. 1, a carrier generation layer 6 is provided on a conductive substrate 1 with a charge blocking layer 7 interposed therebetween.
A carrier transport layer 4 is provided on the carrier generation layer 6. 8 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. Further, a protective layer (protective film) may be formed on the surface of the photoreceptor in order to improve printing durability, for example, a synthetic resin film may be coated.

Generally, in the carrier generation layer, a particulate carrier generation substance and a carrier transport substance are bound together by a binder substance. That is, they are dispersed in the layer in the form of pigments.

Next, a specific azo compound used as a carrier generating substance in the present invention will be described.

This is a compound that has a coupler represented by the general formula [I] in its molecule and at least two azo groups.

Specifically, there are disazo compounds having two azo groups in the molecule, trisazo compounds having three azo groups, and compounds having four or more azo groups.

Examples of the disazo compound include those shown in the following general formula [n].

General formula [■Koni 0p-N=N-D-N=N-Cp [However, as D.

N CH.

There are CN CN, etc. ] In addition, as other azo compounds, the following general formula [■,
[IV] There are those shown in [V].

General formula [■]: N=N-cp General formula [■]: cp-1'J"N-Ar"-N = N -A r"
-N = N -Cp general formula [V]: Cp-N=N-Ar''-N=N-Ar -N=N-Ar
--N=N-cp [However, sAr", Ar", and Ar' each represent a substituted or unsubstituted carbocyclic aromatic ring group or a substituted or unsubstituted heterocyclic aromatic ring group.

Further, specific examples of Ar'', Ar'', and Ar' are given below. Examples of Cp (coupler) include the following.

[However, for A, specific trade names of polyvinyl butyral include Denka Butyral #4000, Denka Butyral: #30
00 (manufactured by Denki Kagaku Kogyo Co., Ltd.), XYHL (Union Carbide Co., Ltd.), S-LEC BM-2, S-LEC B
M-3, x, x, v-)ri BM-1, S-LEC BL-
1. S-LEC BL-3% S-LEC BL-8, S-LEC BL-7, S-LEC BX-L% S-LEC BH-
3 (manufactured by Tanezu Kagaku Kogyo Co., Ltd.) and the like.

Specific trade names of polyvinyl formal include "Denka Formal" series (manufactured by Denki Kagaku Kogyo Co., Ltd.) such as [Denka Formal #: 20J].

In the carrier generation layering, the content ratio of the carrier generation substance to the binder substance is preferably 3/1 to 1/10, more preferably 371 to 1/3. When the content ratio of the carrier-generating substance is larger than the above range, black spots etc. appear or are likely to appear.However, if the proportion of the carrier-generating substance is too small, the photosensitivity etc. are 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 30 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. In addition, 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 capacity. 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 is in the form of powder with an average particle size of 2 μm or less, preferably 1 μm or less, and more preferably 0.5 μm or less. is preferred.

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

This is because K does not cause turbidity or opacity even if the amount of binder material is increased.

The mixture ratio with the binder substance can be very wide, and the excellent compatibility ensures that the charge generation layer is uniform and stable, resulting in better sensitivity and charging characteristics. It can move around the photoreceptor, which 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.

The thickness of the charge blocking layer is preferably within the range of 0.05 to 2 μm, more preferably 0.1 to 0.5 μm.

In the present invention, it is also possible to use one or more other carrier-generating substances in combination with the above-mentioned azo compound having a coupler. Examples of carrier-generating substances that can be used in combination include anthraquinone pigments, perylene pigments, polycyclic quinone pigments, squaric acid α4L pigments, cyanine dyes, and azulenium compounds.

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 derivatives, benzothiazole derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aquinostilpene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, poly-N-vinylcarbazole, poly-1 -vinylpyrene, poly-9
- One or more compounds selected from vinylanthra7ane, etc. Specific examples of such carrier transport substances are disclosed in Japanese Patent Application No. 1983
-195881. The general formula is listed below.

The following general formula [VI] or [■
] Styryl compounds can be used.

General formula [■]: R" (However, in this general formula, R, R represents a substituted or unsubstituted alkyl group or aryl group, and substituents include an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, and a halogen group. Atom, aryl group is used.

Ar", Ar": represents a substituted or unsubstituted aryl group, 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.

R, R: Represents a substituted or unsubstituted aryl group or hydrogen atom, and the substituents include an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen atom, and an aryl group6) General formula [■]: (However, , in this general formula, R1: substituted or unsubstituted aryl group, Ro: hydrogen atom, halogen atom, substituted or unsubstituted alkyl group,
Alkoxy group, amino group, substituted amino group, hydroxyl group, R7: represents a substituted or unsubstituted oryl group, a substituted or unsubstituted heterocyclic group. ) In addition, the following general formula [■] is used as a carrier transport substance.

Hydrazone compounds of [IX], [IXa], [IXb] or [IX can also be used.

General formula [■Coni (However, in this general formula, R'' and Ro: each a hydrogen atom or a halogen atom, R and R: each a substituted or unsubstituted aryl group, Ar': a substituted or unsubstituted aryl group) (represents a group) General formula [■]: (However, in this general formula, R represents a substituted or unsubstituted aryl group, a substituted or unsubstituted carbazolyl group, or a substituted or unsubstituted heterocyclic group, , R represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aralkyl group.) General formula [IXa]: (However, in this general formula , R: methyl group, ethyl group, 2-hydroxyethyl group or 2-chloroethyl group, R11: methyl group, ethyl group, benzyl group or phenyl group, R'1: methyl group, ethyl group, benzyl group or phenyl group show.

General formula [IXbconi (However, in this general formula, R is a substituted or unsubstituted naphthyl group; R is a substituted or unsubstituted alkyl group, aralkyl group, or aryl group; R''1 is a hydrogen atom, an alkyl group, or an alkoxy Group; R'' and Ro are the same or different groups consisting of a substituted or unsubstituted alkyl group, aralkyl group, or aryl group. °: Substituted or unsubstituted oryl group, substituted or unsubstituted heterocyclic group, vinylhydrogen atom, substituted or unsubstituted alkyl group, or substituted or unsubstituted oryl group.

Q: a hydrogen atom, a 10-gen atom, an alkyl group, a substituted amino group, an alkoxy group, or a cyano group; s: an integer of 0 or 1; ) Pyrazoline compounds of the following general formula [XI] can also be used as carrier transport substances.

General formula [XI]: [However, in this general formula, l: 0 or I R and R: substituted or unsubstituted aryol group.

R: substituted or unsubstituted aryl group or heterocyclic group, R and R: hydrogen atom, alkyl group having 1 to 4 carbon atoms,
or substituted or unsubstituted) or an aralkyl group (however, both R and R are not hydrogen atoms (and when l is O, R is not a hydrogen atom) )] Furthermore, an amine derivative of the following general formula [m] can also be used as a carrier transport substance.

General formula [m]: (In this general formula, Ar', Ar' represents a substituted or unsubstituted phenyl group, and as a substituent) a 10-gen atom, an alkyl group, a nitro group, or an alkoxy group is used.

Ar: substituted or unsubstituted phenyl group, naphthyl group,
Represents an anthryl group, a fluorenyl group, or a heterocyclic group; , using an anthryl group and a substituted amino group. However, an acyl group, an alkyl group, an aralkyl group, or an aralkyl group is used as a substituent for the substituted amino group. ) Further, a compound of the following general formula [XnI] can also be used as a carrier transport substance.

General formula [XIII]: (However, in this general formula, Ar": represents a substituted or unsubstituted arylene group, R, R, R and R"': a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group, It represents a substituted aryl group or a substituted or unsubstituted aralkyl group.) Furthermore, a compound of the following general formula [XIV] can also be used as a carrier transport substance.

General formula [XIV]: RR each hydrogen atom, substituted or unsubstituted alkyl group,
Cycloalkyl group, alkenyl group, aryl group, benzyl group or aralkyl group, Rn and R4@ are each hydrogen atom, substituted or unsubstituted alkyl group having 1 to 40 carbon atoms, cycloalkyl group, alkenyl group, cycloalkenyl group, aryl group, or aralkyl group (However, R and R may jointly form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms.) R, R% R and R are each A hydrogen atom, a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a cycloalkyl group, an alkenyl group, an aral group, an aralkyl group, an alkoxy group, an amino group, an alkylamino group, or an arylamino group. . ) An antioxidant can be contained in the carrier transport layer and the carrier generation layer. This K can suppress the influence of ozone generated during discharge, and can prevent increases in residual potential and decreases 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. 61-19587
No. 8, No. 61-157644, No. 61-195879
No. 61-162867, No. 61-204469, No. 61-217493, No. 61-217492, and No. 61-221541.

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

Among these polymeric organic semiconductors, BoIJ-N-vinylcarbazole or its derivatives are highly effective and are preferably used. Such poly-N-vinylcarbazole derivatives are those in which all or part of the carbazole ring in the repeating unit is substituted with various substituents, such as an alkyl group, a nitro group, an amino group, a hydroxy group, or a halogen atom. .

Further, at least one kind of electron-accepting substance can be contained in the photosensitive layer for the purpose of improving sensitivity 1, reducing residual potential or fatigue during repeated use, etc.

Examples of electron-accepting substances that can be used in the photoreceptor of the present invention are 1
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,
L 3+ 5 ) dinitrobenzene, varanitrobenzonitrile, picryl chloride, quinone chlorimide, chloranil, pullmanil, 2-methylnaphthoquinone, dichlorodicyanovarabenzoquinone.

Anthraquinone, dinitroanthraquinone, trinitrofluorenone, 9-fluorenonethene [dicyanomethylene malonodinitrile], polynidro 9-fluorenone dene [dicyanomethylene malonodinitrile], hyfuric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, 3
．． 5-dinitrobenzoic acid, pentafluorobenzoic acid, 5
-Nitrosalicylic acid, 3,5-dinitrosalicylic acid, phthalic acid, mellitic acid, and one or more kinds of other compounds with high electron affinity can be mentioned. Among these, fluorenone type, quinone type, C1%CN, NO
Penzene derivatives having electron-withdrawing substituents such as , etc. are particularly good.

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.

Examples of binder resins that can be used for the constituent layers of the photoreceptor include polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, polyester resin, alkyd resin, polycarbonate resin, and melamine resin. , addition polymerization resins such as polyvinylidene chloride and polystyrene,
Polyaddition type resins, polycondensation type 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, vinylidene chloride-acrylonitrile copolymer resins, and polymeric organic semiconductors such as N-vinylcarbazole.

``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,
A transparent resin having a volume resistivity of 10 Ω·cm or more, preferably 10 Ω·cm or more, more preferably 10 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, epoxy resin, urethane resin, urea resin, polyester resin, alkyd resin, Examples include melamine resins, photocurable cinnamic acid resins, and copolymerized or condensed resins thereof, as well as all other photocurable or thermosetting resins used in electrophotographic materials. 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, imparting flexibility, etc.). Examples of such thermoplastic resins include polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polycarbonate resin,
Alternatively, all of these copolymer resins, polymeric organic semiconductors such as poly-N-vinylcarbazole, and other thermoplastic resins used in electrophotographic materials may be used.

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

(a) A method in which a binder solvent is added to a carrier-generating substance, etc., and a mixed solution is applied.

(b) A method in which a carrier-generating substance, etc. is made into fine particles in a dispersion medium using a ball mill, a homomixer, a sand mill, an ultrasonic disperser, an attritor, etc., and a binder is added, mixed and dispersed, and the resulting dispersion is applied.

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 a carrier transport substance is contained in the carrier generation layer, the carrier transport substance is dissolved or dispersed in the solution (a) or the dispersion liquid (b) in advance, that is, in the carrier generation layer. There is a method of adding a carrier transport substance. In this case, it is preferable that the amount of the carrier transport substance added is within the range of 1 to 100 parts by weight per 100 parts by weight 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 adopted, it is not necessary to add a carrier transport substance to the carrier generation layer as described above, but the above-mentioned Niga method may also be carried out at the same time.

As a solvent or dispersion medium used for layer formation, %n
-butylamine, diethylamine, ethylenediamine,
Isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, cuclohexanone,
Benzene, toluene, xylene, chloroform, 1.2
- Dichloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, impropatol, ethyl acetate, butyl acetate, dimethyl sulfoxide, and the like.

The photosensitive layer, undercoat layer, intermediate layer, protective layer, etc. can be provided by, for example, blade coating, dip coating, spray coating, roll coating, spiral coating, or the like.

The conductive substrate is formed by applying a conductive thin layer made of a metal plate, a metal drum, a conductive polymer, a conductive compound such as indium oxide, or a metal such as aluminum, palladium, or gold to a sheet of paper by means such as coating, vapor deposition, or lamination. , a material provided on a substrate such as a plastic film is used.

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

FIG. 2 is a schematic diagram of the configuration of an example of a recording device that implements the method of the present invention, FIG. 3 is a diagram of a schematic configuration of a laser beam scanner for image exposure, and FIG. 4 is a partial cross-section diagram of an example of a developing device. FIG. 5 is a flow chart for implementing the method of the present invention.

In the apparatus shown in FIG. 2, n is a drum-shaped image carrier having a photosensitive layer made of the above-mentioned organic photoconductive substance and rotates in the direction of the arrow, and 22 is a main charging member that uniformly charges the surface of the image carrier n. vessel,
24 is an image exposure device, and 15 is a developing device. 20 is an image carrier n
a pre-transfer exposure lamp provided as necessary to facilitate transfer of the image on which the toner image is formed to the recording material pk;
21 is a transfer device, 19 is a corona discharger for separation, and 12 is transferred to a recording medium P.

This is a fixing device that fixes the toner image. Reference numeral 13 has a static eliminator consisting of one or a combination of a static eliminator lamp and a corona discharger for static elimination, and 14 has a cleaning blade or a fur brush for removing residual toner on the surface of the image carrier n after the image has been transferred. It is a cleaning device.

When image exposure is performed using a semiconductor laser, if a drum-shaped image carrier is used as in the recording device shown in FIG. 2, the image exposure is performed using a laser beam scanner as shown in FIG. 3. The operation of the laser beam scanner shown in FIG. 3 will be described below.

The laser beam generated by the semiconductor laser 41 is rotated and scanned by a polygon mirror 43 rotated by a drive motor 42, passes through an f-theta lens, and has an optical path bent by a reflecting mirror 45 so that it is reflected onto the surface of the image carrier 23. It is projected to form a bright line 46. 47 is an index sensor for detecting the start of beam scanning.

The hammer 49 is a cylindrical lens for correcting the inclination angle. Reflecting mirrors 50a, 50b, and 50e form a beam scanning optical path and a beam detection optical path.

When scanning starts, the beam passes through the index sensor 47 &
C) [Detected, and modulation of the beam by the signal is started by a modulation unit (not shown). The modulated beam scans over the image carrier n, which is uniformly charged in advance by the charger 22. A latent image is formed on the drum surface by main scanning by the laser beam 511C and sub-scanning by the rotation of the image carrier 230.

Further, in a recording apparatus in which the image carrier can take a flat state such as a belt shape, the image exposure can be a flash exposure.

As the developing device 15, one having a structure as shown in FIG. 4 is preferably used. In FIG. 4, the developer De is conveyed in the direction of arrow G by rotation of the magnetic roll 62 in the direction of arrow F and rotation of the sleeve 61 in the direction of arrow G. Developer D
The thickness t of e is regulated by the spike control blade 63&C during transportation. The spike control blade 63 is made of an elastic metal plate and presses against the surface of the sleeve 61 to control the thickness of the developer being conveyed.

A stirring screen 5-65 is provided in the developer reservoir ω to sufficiently stir the developer De, and when the developer De in the developer reservoir 66 is consumed.

As the toner supply roller rotates, toner T is supplied from the toner hopper 67. And sleeve 6
A DC power supply 69 and a protection resistor 70 are connected in series to apply a developing bias to 1. Also.

The sleeve 61 and the image carrier 23 are arranged facing each other with a gap d in between, and the developer comes into contact with the image carrier 23 in the development area E, as shown in t) and d.

In the figure, the developing sleeve 61 and the magnet body 62 are indicated by the arrow G-
Although it is shown that the developing sleeve 61 rotates in the F direction, even if the developing sleeve 61 is fixed, the magnet body 62 is fixed, or the developing sleeve 61 and the magnet body 62 rotate in the same direction. It's a good thing. When the magnet body 62 is fixed, normally, in order to make the magnetic flux density of the magnetic pole facing the image carrier 23 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 used. The two magnetic poles may be placed close to each other.

In the above-described apparatus, based on the present invention, the electrostatic latent image t
It is charged so that vut is 400 to 900v, and IVHI-IVDcl during reversal development is set to 0 to 200v. However, VDC is a direct current bias voltage applied to the sleeve 61, which is a developer transporting carrier facing the image carrier. 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 4
kV is preferred, and 0.1 KHz to IM Hz is preferred.

The method of the present invention as shown in FIG. 5 can be carried out using the recording apparatus as described above.

Figure 5 shows that an electrostatic image is formed by an electrostatic image forming method in which the highly exposed area becomes an electrostatic image with a lower potential than the background area, and the electrostatic image is developed using toner that is charged to the same polarity as the background area potential. An example of reversal development according to the present invention, which is performed by the following methods, is shown.

The example shown in FIG. 5 when the recording apparatus shown in FIG. 2 is used will be explained.

First, the static electricity is removed by the static eliminator 13, and the cleaning device 14
The surface of the image carrier n in the initial state, which has been cleaned by the charger 22 and has a potential of 0, is uniformly charged by the charger 22, and an image exposure light is projected onto the charged surface to form an electrostatic image area. Image exposure is performed so that the potential becomes approximately 0, and the obtained electrostatic image is developed by a developing device 15 (toner T)K.

The image forming method of the present invention can be applied to various light sources such as halogen lamps, tungsten lamps, LEDs (light emitting diodes), gas lasers such as helium-neon, argon, and helium-cadmium, and semiconductor lasers.

The image forming method of the present invention has a wide variety of applications such as electrophotographic copying machines and printers.

E. Examples Below, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited thereby, and of course includes other embodiments with various modifications.

<Manufacture of Photoreceptors> First, photoreceptors A to M of Examples and photoreceptors a=d of Comparative Examples were manufactured in the following manner. That is, the manufacturing procedure for each photoreceptor is common.

[KONIcAU-Bix
Dip coating was applied to an aluminum base drum (diameter 80M) for 1550 J (manufactured by Konica) to form a charge blocking layer of a predetermined thickness.

Next, a predetermined amount of the carrier generating material CGM shown in Table 2 was pulverized in a magnetic ball mill at 4 Orpm for 18 hours, and then
20 g of polycarbonate "Panlite ni-1300" (manufactured by Yondai Kasei Co., Ltd.) was added to 1,2-dichloroethane 10001R.
1 was added and dispersed for 24 hours, and the obtained carrier generation layer coating solution was dip coated on the charge blocking layer, and the P/B ratio (carrier generation substance/binder) shown in Table 2 was applied. A carrier generation layer having a weight ratio of

However, for Photoreceptor C of Comparative Example, no charge blocking layer was provided, and a carrier generation layer was formed directly on the aluminum substrate.

Furthermore, a carrier transport substance 112.5 of the following structural formula (5)
g and polycarbonate resin “Kneepilon 2-200J (
(manufactured by Mitsubishi Gas Chemical Co., Ltd.) in 1000 g of 1,2-dichloroethane, the resulting solution was dip coated onto the carrier generation layer, and dried at a temperature of 90° C. for 1 hour to form a carrier transport layer. The photosensitive layer had a thickness of 20 μm.

As described above, each of the photoconductors A to M and a% having individual configurations and prescriptions is manufactured using a common manufacturing procedure.
d was manufactured.

That is, in each photoreceptor, the material of the charge blocking layer,
The carrier-generating substances and the like are changed from each other.

(Margin below, continued on next page) CGM (1) CGM (2) CGM (3) C*Ht CGM (4) Carrier transport substance (5) Resin C8') Polyester resin [Vylon 200j (manufactured by Toyobo Co., Ltd.) Resin ( T) Vinyl chloride vinyl acetate copolymer resin rVYHHJ (Union Carbide Co., Ltd. M) Resin (X) Polyvinyl butyral resin [XYHLJ (Union Carbide Co., Ltd.) resin (Y) Polyvinyl butyral resin [S-LEC BH-3J (Tanezu Kagaku Kogyo Co., Ltd.) manufactured by) resin (Z
) Polyvinyl formal resin [Denka Formal #304 (manufactured by Denki Kagaku Kogyo Co., Ltd.) Example 1 and Comparative Example 1 Each of the photoreceptors of the example and comparative example was treated with rKONIcA U-Bix 1550 J (manufactured by Konica Corporation) using a semiconductor laser as a light source. ) Installed on a modified aircraft, VH is 1600±10 (
Adjust the grid voltage so that the voltage becomes 480 (V), and perform reversal development with a developing bias of -480 (V) to remove black spots on the white background of the copied image and black areas (corresponding to the white background of the original image).
The image density I) max, the coatability of the carrier generation layer, and the image defects were evaluated.

In addition, the evaluation of Kuropochi was performed using the image analysis device "Omnicon 30".
00 type" (manufactured by Takasu Seisakusho Co., Ltd.) to measure the particle size and number of black spots, and 10 black spots with a diameter of φ (diameter) of 0.05 mm or more were measured.
- The number of hits was determined by K.

The criteria for evaluating black spots are as shown in Table-IK.

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

The coating properties of the carrier generation layer were evaluated as follows. In other words, the relative falling speed of the liquid level during dip coating of the carrier generation layer (CGL) is kept constant (0,5
ctn/sec) and 10 when CGL is applied.
The amount of CGM deposited per 0c111 (1 dm") was measured, and if the amount was less than 2 mg/dmF, it was determined that the coating was defective.

Further, regarding image defects, presence or absence of density unevenness in the solid black portion of the copied image was visually confirmed, and regarding agglomeration of the carrier generation layer, density unevenness of the carrier generation layer was visually confirmed.

The results of black spot evaluation on each photoreceptor are shown in Section 2 below.

(The following is a margin, continued on the next page) From the results shown in Table 2, 1. If copy images are formed based on the image forming method of the present invention, black spots will be significantly reduced, density unevenness will not occur in images, and It can be seen that the density can be increased and uniform, high-quality images can be obtained.

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 Cloth-3 below, and black spots, image density DmlLX of the black background part of the copied image, carrier adhesion, and capri I saw it.

However, regarding carrier adhesion, 0 represents no adhesion, and x represents occurrence of adhesion.

(The following margin continues on the first page) From this result, the following is clear.

For photoconductor A: IVHI (image density is insufficient at 400V.

IVHI-IVDcl) At 200V, carrier adhesion occurs.

When IVHI-IVDcI<OV, full-face cuboid IJ occurs.

For photoconductor C: Black spots occur and the image density is insufficient.

[Brief explanation of the drawing]

1 to 5 show embodiments of the present invention. Fig. 1 is a 45sθ cross-sectional view of the photoreceptor used in the present invention, Fig. 2 is a schematic diagram of the configuration of the image forming device, Fig. 3 is a schematic diagram of the configuration of the laser beam scanner for image exposure, and Fig. 4 is the development diagram. FIG. 5, which is a sectional view of the main part of the vessel, is a flowchart showing the process of image formation. FIG. 6 is a partial sectional view of a conventionally used photoreceptor. In addition, in the reference numerals shown in the drawings. 1... Conductive substrate 4... Carrier transport layer 6... Carrier generation layer 7... Charge Blocking layer 8...
...Photosensitive layer 12...Fuser 13...Static eliminator 14...Cleaning device 15...
...Developer addition......Pre-transfer exposure lamp 21...
...Transfer unit n...Charger n...Image carrier 4I...Laser 43...・Mirror scanner required・・・・
...F-θ lens for imaging, 49...
Cylindrical lens 51... Laser beam 61... Development sleeve 62... Magnet body 63... Layer thickness Regulation blade 69...
. . . Bias power supply 70 . . . Protection resistor. Agent Patent Attorney Go Aisaka Figure 1 Figure 2 Figure 5 Figure 6 (Self-produced procedure amendment dated March 11, 1985 1, Indication of the case 1988 Patent Application No. 317839 2, Title of the invention Image Forming Method 3, Relationship with the Amendment Person Case Patent Applicant Address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name
(127) Konica Co., Ltd. 4, agent address: FINE Building e, 2-4-11 Shibasaki-cho, Tachikawa-shi, Tokyo 0425-24-5411 (FT5 Specification, claims column and detailed description of the invention column 6) , The contents of the amendment (1) and the scope of the claims are corrected as shown in the attached sheet. (2) The content of the amendment is corrected on page 11, line 8 of the specification tube. (3) The same is corrected on page 22, line 4 of the same. (4), "α4L pigment" in the 7th line from the bottom of No. 26 should be changed to "
"Methine pigment" is corrected. 1 or more - (1) Claim 1, in an image forming method using a photoreceptor having a photosensitive layer comprising a carrier transport layer on a carrier generation layer, (a) within 0 molecules the following general formula [ A carrier generating layer containing a compound having a coupler represented by [1] and having at least two azo groups in the molecule as a carrier generating substance, and a carrier generating layer provided between this carrier generating layer and a conductive substrate. and a charge blocking layer containing polyvinyl butyral and/or polyvinyl formal, (b) the photoreceptor has an absolute charging potential of 400 V to 9
After applying a charge of 00 V, an electrostatic latent image is formed by exposure, and then a voltage of 0 to 20 V is lower than the absolute value of the charged potential.
Applying a DC bias voltage with a low absolute value of 0v,
An image forming method comprising performing reversal development of the electrostatic latent image. General formula [I]: [However, in the above general formula, Ar'' represents an aryl group, Y and Z are a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted amino group, or represents a substituted or unsubstituted alkoxy group, S represents O-4, and r represents 0-2.]

Claims (1)

[Scope of Claims] 1. 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 compound having the following general formula [I] in the molecule: a carrier generating layer containing a compound having a coupler and having at least two azo groups in the molecule as a carrier generating substance; (b) using a photoreceptor having a charge blocking layer containing polyvinyl formal;
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. General formula [I]: ▲ Numerical formulas, chemical formulas, tables, etc. Alkyl group, substituted or unsubstituted amino group,
or represents a substituted or unsubstituted alkoxy group, s represents 0-4, and r represents 0-2. ]