JPH01170948A - Image forming method - Google Patents

Abstract

PURPOSE:To prevent generation of black spots in reversal development by providing a charge blocking layer between a conductive base body and a carrier generating layer contg. a phthalocyanine compd. CONSTITUTION:A photosensitive body having the carrier generating layer 6 into which the phthalocyanine compd. is incorporated as a carrier generating material and the charge blocking layer which is provided between said layer and the conductive base body 1 and into which a novolak type phenolic resin is incorporated is used. An electric charge which is 400-900V absolute value of the electrostatic charge potential is applied to this photosensitive body and thereafter, an electrostatic latent image is formed by exposing thereon. The reversal development of the electrostatic latent image is then executed by applying a DC bias voltage having the absolute value lower by 0-200V than the absolute value of the above-mentioned electrostatic charge potential to the photosensitive body. The image defects such as black spots are thereby prevented in the reversal development method.

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, the electrostatic latent image is developed with toner, and then the visible image is 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 not only has electrophotographic properties such as good charging characteristics, good sensitivity, and low dark decay, but also physical properties such as stiffness resistance, abrasion resistance, and moisture resistance after repeated use. It is also required to have good 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-
Vinylcarbazole and 2.4.7- ) dinitro-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, attempts have been made to develop organic photoreceptors with high sensitivity and durability by assigning the carrier generation function and carrier transport function to different substances in the photosensitive layer. ing. 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, it is expected that organic photoreceptors with high sensitivity and durability can be obtained.

FIG. 8 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. It 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.

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. 8, 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.

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, Vt), 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 photoreceptor surface, but in this photoreceptor, there are problems such as a decrease in photosensitivity, an increase in residual potential, and an increase in IV. Increase in Ll, 1■ during repeated use, 1
This leads to a decrease in stability and also a decrease in temperature characteristics, and at low temperatures, the photoreceptor characteristics are greatly deteriorated, such as an increase in 1VLl.

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 1vLl.
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 blocking 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 increase the difference between the charging potential vH and the bias voltage vDc, but this does not mean that the potential of the exposed area is
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.

Furthermore, in recent years, semiconductor laser light sources have been used in electrophotographic copying methods, which are inexpensive, compact, and capable of direct modulation.

Gallium-aluminum-arsenic (Ga-Al-As) light emitting devices, which are currently widely used as semiconductor lasers, have an oscillation wavelength of about 750 nm or more. In order to obtain an electrophotographic photoreceptor with high sensitivity to such long wavelength light,
Many studies have been made in the past. For example, a method was considered to add a new sensitizer to a photosensitive material such as selenium or cadmium sulfide, which has high sensitivity in the visible light region, to extend the wavelength to a longer wavelength. However, there are problems in practical use due to insufficient environmental resistance and toxicity. In addition, the sensitivity of many known organic photoconductive materials is usually in the visible light region of 700 nm or less, and there are few materials that have sufficient sensitivity in longer wavelength regions, so high reliability is expected. It has been difficult to use this method in laser printers that use semiconductor laser light sources.

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, in which (a) a phthalocyanine compound is a carrier generation substance. (b) using a photoreceptor having a carrier generation layer containing a carrier-generating layer and a charge blocking layer provided between the carrier-generating layer and a conductive substrate and containing a novolac type phenolic resin; The absolute value of the charged potential on this photoreceptor is 400■~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.
(2) The present invention relates to an image forming method characterized in that the electrostatic latent image is reversely developed by applying a DC bias voltage having a low absolute value.

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

The present invention is characterized in that a phthalocyanine compound is contained in the carrier generation layer, and the material of the charge blocking layer provided between the carrier generation layer and the conductive substrate 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 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 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.

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 to local carrier injection from the electroconductive 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, no black spots are produced 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, depending on the combination of the carrier generation substance and the material of the charge blocking layer, the carrier generation substance may aggregate or This is extremely inconvenient because coating defects occur, black spots increase significantly, photosensitivity decreases, and image unevenness occurs.

However, there is no general or uniform selection method for selecting a suitable combination that will not cause coating defects from among the countless existing polymeric materials and numerous carrier-generating substances; The reality is that we have no choice but to decide on a good combination through repeated efforts.

As a result of various studies, the present inventors have found that extremely good results can be obtained by particularly selecting a combination of the above-mentioned phthalocyanine compound and novolac type phenol resin.

In other words, the above-mentioned phthalocyanine compound has excellent photosensitivity, and by using this compound as a carrier-generating substance, the potential stability during repeated use of the photoreceptor is improved, and the memory phenomenon is also reduced, making it possible to use semiconductor lasers. It is possible to provide a high-performance photoreceptor that is particularly suited to image forming methods using reversal development as a light source.

Furthermore, by incorporating the novolac type phenolic resin into the charge blocking layer, the phthalocyanine compound does not aggregate during the coating formation of the carrier generation layer, thereby preventing black spots and image unevenness during reversal development. The compound is uniformly dispersed in the carrier generation layer, allowing the phthalocyanine compound to exhibit its original photosensitivity without interfering with it.

Therefore, a high quality and uniform image can be provided, and the image density can also be increased.

Furthermore, what should be noted in the present invention is that in addition to the above-mentioned, the charge i7 expressed by 1vHl, that is, I
When VHl < 400V, it is difficult to obtain the required electric field strength, but when IVHI > 900V, the thickness of the photosensitive layer increases, which is undesirable because the sensitivity decreases. Also, (IF > t(
7) Difference IV IJ IV o cl from 0 to 2
It is also important that it is specified as 00■. That is, 1■H
1-1■ Dc1<Ov will cause fogging, and 1vH1-IVo4>, 200V (7)
tj% coalescence [Y IJ 7 fF (when using two-component developer) and adhesion of toner of opposite polarity (when using bipolar-component developer)
will occur.

According to the present invention, lv, l = 400 ~ 9
00V (preferably 500 to 700V), and IVHl -1Vncl should be 0 to 200V (preferably 50 to 150V), and performing reversal development under these conditions maintains high sensitivity. However, this is an essential condition for obtaining high-quality images without black spots.

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 specifically selecting the type of carrier-generating substance and the material of the charge blocking layer, black spots, image unevenness, etc.
Carrier adhesion and fogging can be prevented, and high-quality images with uniform image density can be provided.

FIG. 1 illustrates a general configuration of a photoreceptor, such as an electrophotographic photoreceptor, used in the present invention.

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

That is, it is known that phthalocyanine compounds, which are one type of organic photoconductive materials, have a photosensitive range extended to a long wavelength range compared to other compounds. Various crystalline forms of phthalocyanine compounds have been discovered in the process of converting α-type phthalocyanine compounds into stable crystalline β-type phthalocyanine compounds.

Examples of these phthalocyanine compounds exhibiting photoconductivity include the X-type metal-free phthalocyanine compounds described in Japanese Patent Publication No. 49-4338, and the compounds described in Japanese Patent Application Laid-open Nos. 58-182639 and 60-19151. In addition to the .tau., .tau., .eta., and .eta. type gold metal phthalocyanine compounds described in Japanese Patent Application No. 61-295784, various metal phthalocyanine compounds are exemplified. For example, a titanyl phthalocyanine compound is described in Japanese Patent Application No. 62-241938.

In addition, phthalocyanine compounds particularly suitable for semiconductor lasers are exemplified.

Phthalocyanine exemplified compounds Next, the novolak type phenolic resin will be described.

This is obtained by reacting phenols and aldehydes under an acidic catalyst.

Examples of phenols include phenol, m-cresol,
Examples of the aldehydes include 0-cresol, p-cresol, xylenol, and resorcinol, and examples of aldehydes include formaldehyde, acetaldehyde, and furfural.

Note that the term phenol resin here is a general term that also includes phenol-modified resins.

Specific product names include 5K-1, 2, 3, 4, 5, 6.
,7,8,9,10,101,102,103,104
, 105, 106, 107, 108, 109, 110,
111112.113, 114, 115, 136, 13
7, 156, 158, and 159 (manufactured by Susumu Schless Co., Ltd.).

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 carrier generation layer, the content ratio of the carrier generation substance to the binder substance is preferably 371 to 1/10, more preferably 3/1 to 1/3. When the content ratio of the carrier-generating substance is larger than the above range, black spots and the like appear markedly or easily appear. However, if the ratio of the carrier-generating substance is too small (i/), 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 small due to the thinness, and the stiffness resistance will also tend to decrease.If the film thickness is larger than the above range, the residual potential will increase on the contrary. A similar phenomenon occurs when the carrier generation layer is too thick as described above, and a sufficient transport ability tends to be difficult to obtain, so that the residual potential tends to increase during repeated use.

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

In the case where a photosensitive layer is formed by dispersing a granular carrier-generating substance, the carrier-generating substance is preferable.

Further, in the carrier transport layer, the carrier transport substance preferably has excellent compatibility with the binder substance. As a result, turbidity and opacity do not occur even if the amount of the binder substance is increased, so the mixing ratio with the binder substance can be very wide. The generation layer is uniform and stable, resulting in better sensitivity and charging characteristics, and allows for a photoreceptor that can form clear images with higher sensitivity. It is possible to achieve the effect that fatigue deterioration is less likely to occur when

In the present invention, it is also possible to use one or more other carrier-generating substances together with the phthalocyanine compound. Examples of carrier-generating substances that can be used in combination include anthraquinone pigments, perylene pigments, polycyclic quinone pigments, methine squaric acid 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, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, poly-N-vinylcarbazole, poly-1- vinylpyrene, poly-9
- It may be one or more selected from vinylanthracene and the like.

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 CI) or (n) as a carrier transport substance
styryl compounds can be used.

- maximum [■]: (However, in this maximum, R1, R2 represent substituted or unsubstituted alkyl groups, aryl groups, substituents include alkyl groups, alkoxy groups, substituted amino groups, hydroxyl groups, halogen atoms, Use an aryl group.

Ar', Ar'': represents a substituted or unsubstituted aryl group, and the substituent used is an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen atom, or an aryl group.

R3 and R4 represent a substituted or unsubstituted aryl group or a hydrogen atom, and the substituents used include an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen atom, and an aryl group. ) General formula [■]: However, in this maximum, R5: substituted or unsubstituted aryl group, Rb: hydrogen atom, hydrogen atom, substituted or unsubstituted alkyl group, alkoxy group, amino group, substituted Amino group, hydroxyl group, R? : Represents a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group. ) In addition, the following general formulas (I[), (
The hydrazone compounds of IV), [■a], (IVb) or (V) can also be used.

General formula [■]: (However, in this maximum, R8 and R9: each a hydrogen atom or a halogen atom, RIO and R■: each a substituted or unsubstituted aryl group, A r 3: a substituted or unsubstituted arylene group General formula [■]: (However, R12 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted carbazolyl group, or a substituted or unsubstituted heterocyclic group, R131R' 4 and R15: represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.) General formula (■a): Old... (However, in this maximum, Rlh: Methyl group, ethyl group, 2-hydroxyethyl group or 2-chloroethyl group, R'': methyl group, ethyl group, benzyl group or phenyl group, R111: methyl group, ethyl group, benzyl group or phenyl group.

General formula (■b): (However, in this maximum, RI9 is a substituted or unsubstituted naphthyl group, R'20 is a substituted or unsubstituted alkyl group, aralkyl group, or aryl group; R'' is a hydrogen atom, an alkyl group group or alkoxy group; R'' and R'' represent 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, RZ4. Substituted or unsubstituted aryl group or substituted or unsubstituted heterocyclic group, R2%, hydrogen atom, substituted or unsubstituted alkyl group or substituted or device-substituted aryl group, Q: hydrogen atom, (Represents a halogen atom, an alkyl group, a substituted amino group, an alkoxy group or a cyano group, S:O or an integer of 1.) Furthermore, a pyrazoline compound of the following general formula (Vl) can also be used as a carrier transport substance.

General formula [■]: [However, in this general formula, l: O or 1, R26 and R27: substituted or unsubstituted aryl group,
R28: Substituted or unsubstituted aryl group or heterocyclic group, R'' and R30: Hydrogen atom, alkyl group having 1 to 4 carbon atoms, or substituted or device-substituted aryl group or aralkyl group (However, R2! and R3 (°) are not both hydrogen atoms, and when l is 0, R29 is not a hydrogen atom.) Furthermore, an amine derivative of the following general formula [■] can also be used as a carrier transport substance.

General formula [■]: (In this general formula, Ar', Ar': 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.

Arb: 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. , nitro group, piperidino group, morpholino group, naphthyl group, anthryl group and substituted amino group. However, an acyl group, an alkyl group, an aryl group, or an aralkyl group is used as a substituent for the substituted amino group. ) Furthermore, a compound of the following general formula [■] can also be used as a carrier transport substance.

General formula [■]: (However, in this general formula, Ar': represents a substituted or unsubstituted arylene group, R"% R", R33 and R34: substituted or unsubstituted alkyl group, substituted or unsubstituted (represents a substituted aryl group, or a substituted or unsubstituted aralkyl group) Furthermore, a compound of the following general formula (IX) can also be used as a carrier transport substance.

General formula [■]: [However, this - maximum, R"% R", R" and R311
are each a hydrogen atom, a substituted or unsubstituted alkyl group, cycloalkyl group, alkenyl group, aryl group, benzyl group or aralkyl group, R39 and R40 are each a hydrogen atom, a substituted or unsubstituted carbon atom number of 1 to 40 an alkyl group, cycloalkyl group, alkenyl group, cycloalkenyl group, aryl group or aralkyl group (provided that R39 and R'' together form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms) ) R41-1R", R" and R44 each represent a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkoxy group, It is 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 can suppress the influence of ozone generated by discharge, and can be used repeatedly. It is possible to prevent an increase in residual potential and a decrease in charged potential.

Examples of the antioxidant include hindered phenol, hindered amine, paraphenylene diamine, aryl alkane, hydroquinone, spirochroman, spiroindanone, it form 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. 61-204'469
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, poly-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. .

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,
Tetrabromo phthalic anhydride, 3-nitro phthalic anhydride,
4-nitrophthalic anhydride, pyromellitic anhydride, mellitic anhydride, tetracyanoethylene, tetracyanoquinodimethane, 0-dinitrobenzene, m-dinitrobenzene, 1.3.5-) dinitrobenzene, paranitrobenzonitrile , picryl chloride, quinone chloride
Mido, chloranil, brumanil, 2-methylnaphthoquinone, dichlorodicyanoparabenzoquinone, anthraquinone, dinitroanthraquinone, trinitrofluorenone, 9-fluorenonedene-[dicyanomethylenemalonodinitrile], polynitro-9-fluorenonedene-[dicyanomethylenemalonodinitrile] Nitrile], picric acid, 0-
Nitrobenzoic acid, p-nitrobenzoic acid, 3,5-dinitrobenzoic acid, pentafluorobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, phthalic acid, mellitic acid, and other types of compounds with high electron affinity Or two or more types can be mentioned.

Among these, fluorenone type, quinone type, Cβ, C
Particularly preferred are benzene derivatives having electron-withdrawing substituents such as N and Not.

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 polymer resins such as methacrylic resins, acrylic resins, polyvinylidene chloride, and polystyrene, polyaddition resins, polycondensation resins, copolymer resins containing two or more of these repeating units, vinyl chloride-acetic acid Insulating resins such as vinyl copolymer resins, styrene-butadiene copolymer resins, vinylidene chloride-acrylonitrile copolymer resins, etc.
Further examples include 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·ω or more, preferably io"Ω·Q or more, more preferably 10 Ω·3 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, or copolymer resins thereof, polymeric organic semiconductors such as poly-N-vinylcarbazole, All other thermoplastic resins used in electrophotographic materials can be used.

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

(a) A method in which a binder and a solvent are added to a carrier-generating substance, mixed and dissolved, and a 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 transporting substance to the carrier generation layer as described above, but it is also possible to carry out the above three methods at the same time.

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.

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 can be 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 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, 23 is a drum-shaped image carrier which has a photosensitive layer made of the above-mentioned organic photoconductive substance and rotates in the direction of the arrow; 22 is a main charger that uniformly charges the surface of the image carrier 23; 24 is an image exposure device, and 15 is a developing device. 20 is a pre-transfer exposure lamp provided as necessary to facilitate the transfer of the toner image formed on the image carrier 23 onto the recording medium P; 21 is a transfer device; 19 is a separation corona discharger; 12
is a fixing device that fixes the toner image transferred to the recording medium P. 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 23 after the image has been transferred. It is a cleaning device. When performing image exposure with a semiconductor laser,
In a recording apparatus using a drum-shaped image carrier 23 like the recording apparatus shown in FIG. 2, the image exposure 24 is preferably performed by a laser beam scanner as shown in FIG.

The operation of the laser beam scanner shown in FIG. 3 will be described next.

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 44 , has its optical path bent by a reflecting mirror 45 , and is directed 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, and 48 and 49 are cylindrical lenses for correcting the inclination angle. 50a, 50b, 5
0C is a reflecting mirror that forms a beam scanning optical path and a beam detection optical path.

When scanning is started, the beam is detected by the index sensor 47, and modulation of the beam by a signal is started by a modulation section (not shown). The modulated beam is applied to an image carrier 23 that is uniformly charged in advance by a charger 22.
Scan above. A latent image is formed on the drum surface by the main scanning by the laser beam 51 and the sub-scanning by the rotation of the image carrier 23.

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 Qe is conveyed in the direction of arrow G as the magnetic roll 62 rotates in the direction of arrow F and the sleeve 61 rotates in the direction of arrow G. Developer D
The thickness t of e is regulated by the spike control blade 63 during conveyance. 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 screw 65 is provided in the developer reservoir 66 to sufficiently stir the developer De, and when the developer []e in the developer reservoir 66 is consumed, the toner supply roller 68 rotates. As a result, toner T is replenished from the toner hopper 67. A DC power supply 69 that applies a developing bias to the sleeve 61 and a protective resistor 70 are connected in series. Further, the sleeve 61 and the image carrier 23 are arranged facing each other with a gap d in between,
The developer comes into contact with the image carrier 23 in the development area E, and t>
d.

In the figure, the developing sleeve 61 and the magnet body 62 are indicated by arrows G, respectively.
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 may be something. 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 attached thereto. The two magnetic poles may be placed close to each other.

In the above-mentioned apparatus, based on the present invention, the electrostatic latent image is charged so that the voltage is 400 to 900 V, and during reverse development) lvHl -1VnJ = o to 200
Let it be V. However, (1) is a DC bias voltage applied to the sleeve 61, which is a developer transporting carrier facing the image carrier 23.

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.
5-4KV is preferable, frequency is 0.1KHz-IMH
z 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 image exposure area has 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. This shows an example of reversal development of the present invention, which is performed by adhering.

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 13 removes the static electricity. Z1
The surface of the image carrier 23 in the initial state, which has been cleaned in step 4 and has a potential of O, is uniformly charged by the charger 22, and an image exposure 24 is projected onto the charged surface to form an electrostatic image area. Image exposure is performed so that the potential of the toner becomes approximately O, and the obtained electrostatic image is developed by a developing device 15 (toner T).

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 Hereinafter, 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.

Synthesis of titanyl phthalocyanine compounds> First, prior to the examples, a synthesis example of metal-free phthalocyanine compound A having the properties shown in FIGS. 6 and 7, a synthesis example of a τ-type metal-free phthalocyanine compound, and a synthesis example of titanyl phthalocyanine. shows.

(Synthesis example of metal-free phthalocyanine compound A) 50 g of lithium phthalocyanine is added to 600 mff1 of concentrated sulfuric acid with thorough stirring at 0°C. The mixture is then stirred at this temperature for 2 hours.

The resulting solution is then filtered through a coarse sintered glass funnel and poured slowly into 4 liters of ice and water with stirring. After standing for several hours, the mixture is filtered and the resulting mass is washed with water until neutral.

The mass is then finally washed several times with methanol and dried in air. This dried powder is extracted with acetone in a 24 hour continuous extractor and dried in air to give a blue powder.

In the above the precipitation is repeated to ensure a salt residue for lithium. 30.5 g of blue powder was thus obtained. The X-ray diffraction pattern of the obtained product was consistent with the X-ray diffraction pattern of an α-type phthalocyanine compound described in previously published materials.

30 g of the metal-free α-phthalocyanine compound thus obtained was charged into a 900 ml porcelain ball mill half-grooved with 13/16 inch diameter balls and milled at about 8 Orpm for 164 hours. Thereafter, 200 ml of an organic solvent such as tetrahydrofuran or 1,2-dichloroethane was added to the ball mill, and the mixture was milled again for 24 hours. The organic solvent was removed from the milled dispersion and dried to obtain 28.2 g of metal-free phthalocyanine compound A.

(Synthesis example of τ-type metal-free phthalocyanine) α-type metal-free phthalocyanine compound (Monolite Fast Pull GS manufactured by ICI) was extracted and purified three times with heated dimethyl formaldehyde.

Through this operation, the purified product was transferred to the β form. Next, a portion of this β-type metal-free phthalocyanine compound is dissolved in concentrated sulfuric acid, and this solution is poured into ice water to cause reprecipitation.
It was transferred to α type. This reprecipitate was washed with aqueous ammonia, methanol, etc., and then dried at 10°C. Next, the α-type metal-free phthalocyanine and compound purified above were placed in a sand mill together with a grinding aid and a dispersant, and the temperature was 100±20°C.
The mixture was kneaded for 15 to 25 hours at <0>C. After confirming that the crystal form has changed to the τ type by this operation, take it out from the container, thoroughly remove the grinding aid and dispersant with water and methanol, etc., and dry it to a clear bluish color with no shape. Blue crystals of metal phthalocyanine were obtained.

(Synthesis example of titanyl phthalocyanine) 40 g of phthalodinitrile, 18 g of titanium tetrachloride and α-
A mixture of 500 ml of chloronaphthalene was heated under a stream of oxygen.
The reaction was completed by heating and stirring at 40 to 250°C for 3 hours. Thereafter, it was filtered to obtain the product dichlorotitanium phthalocyanine. A mixture of the obtained dichlorotitanium phthalocyanine and 300 mj+ of concentrated ammonia water was heated under reflux for 1 hour to obtain 18 g of the target titanyl phthalocyanine. The product was thoroughly washed with acetone using a Soxhlet extractor.

Mass spectrometry analysis of this product revealed that the main component was titanyl phthalocyanine (M''576) and a small amount of chlorinated titanyl phthalocyanine (M''610).

<Manufacture of photoreceptors> 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.

15g of the specified binder resin shown in Table 2 was mixed with acetone/
A charge blocking layer coating solution obtained by dissolving in cyclohexanone (1:1) mixed solvent 10,100O was heated to r
Dip coating was applied to an aluminum base drum (diameter 80 m) for KON I CA U Bix 1550 (manufactured by Konica) to obtain a charge blocking layer of a predetermined thickness.

Next, the predetermined carrier generating substance (CGM) shown in Table 2 is
' was ground in a magnetic ball mill at 4 rpm for 18 hours, then polycarbonate
(manufactured by Kijin Kasei Co., Ltd.) 20g to 10% of 1,2-dichloroethane
A solution dissolved in 00m It was added and dispersed for another 24 hours, and the obtained carrier generation layer coating solution was dip coated on the charge blocking layer, and the P/B shown in Table 2 was applied.
A carrier generation layer having a ratio (weight ratio of carrier generation substance/binder substance) was obtained.

However, for Photoreceptor C of Comparative Example, no charge blocking layer was provided, and a carrier generation layer was formed directly on the conductive substrate. □・Additionally, 112.5 g of a carrier transport substance having the following structural formula (5) and 150 g of polycarbonate resin “Nipilon Z-200J (manufactured by Mitsubishi Gas Chemical Co., Ltd.) were mixed with 101 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, resulting in a photosensitive layer having a thickness of about 20 μm.

As described above, each of the photoreceptors A to M and a
d was produced.

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

CGM (1) Metal-free phthalocyanine compound A CGM (2) τ-type metal-free phthalocyanine CGM (3) Said titanyl phthalocyanine CGM (4) Carrier transport substance (5) Resin (S) Polyester resin [Vylon 200J (manufactured by Toyobo Co., Ltd.) resin (T) Vinyl chloride-vinyl acetate copolymer resin rVYHHJ (manufactured by Union Carbide) Resin (X
) SK-102 (manufactured by Juman Schless Co., Ltd.) Resin (Y) SK-105 (same as above) Resin (Z) SK-9 (same as above) The rKONIcA U-Bix1550J (manufactured by Konica) was installed in a modified machine with a light source of
Reverse development at 0 (V), black spots on the white background of the copied image,
The image density D111aX of the black background area (portion corresponding to the white background area of the original image), the coatability of the carrier generation layer, and image defects were evaluated.

In addition, the evaluation of Kuropochi was performed using the image analysis device "Omnicon 30".
00 type" (manufactured by Shimadzu Corporation) to measure the particle size and number of black spots, and 1 black spot with a diameter of 0.05 m or more was measured.
Judgment was made based on the number of pieces per d.

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

Table 1 Note that if the black spot determination result is ◎, ○, or △, 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 determined as follows.

That is, the relative falling speed of the coating liquid level during dip coating of the carrier generation layer is kept constant (0.5 cm/sec).
and 100 cIi when the carrier generation layer was applied!
The amount of CGM deposited per (1 drrr) was measured, and if this was less than 2 .mu./dm, it was determined that the coating was defective. Also,
Regarding agglomeration of the carrier generation layer, presence or absence of concentration unevenness in the carrier generation layer was visually confirmed. Additionally, cases where agglomeration of the carrier generation layer was observed were also considered to be coating defects.

Furthermore, regarding image defects, presence or absence of density unevenness in solid black portions of the copied image was visually confirmed.

The results of black spot evaluation for each photoreceptor are shown in Table 2 below.

From the results shown in Table 2, if copy images are formed based on the image forming method of the present invention, black spots are significantly reduced, image density unevenness does not occur, and image density can be increased, resulting in uniform and high quality. It can be seen that an image of .

Example 1 (or Comparative Example 1) under the conditions shown in Table 3 below.
Reversal development was performed in the same manner as above, and black spots, image density DmmX of the black background portion of the copied image, carrier adhesion, and fog were observed.

However, regarding carrier adhesion, ◯ represents no adhesion, and × represents occurrence of adhesion.

(Margin below, continued on next page) Table-3 *After 10 copies, it became impossible to charge up to 950V.

From this result, the following is clear.

For photoconductor A: If IVHI<400V, image density is insufficient.

When IV Ht lv IIJ > 200 V, carrier adhesion occurs.

1 ■Il -1v ncl < OV, fogging occurs on the entire surface.

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

[Brief explanation of the drawing]

1 to 7 show embodiments of the present invention, in which FIG. 1 is a sectional view of an example of a photoreceptor used in the present invention, FIG. 2 is a schematic diagram of the configuration of an image forming apparatus, and FIG. Figure 3 is a schematic diagram of the configuration of a laser beam scanner for image exposure, Figure 4 is a sectional view of the main parts of the developing device, Figure 5 is a flowchart showing the process of image formation, and Figure 6 is an X-ray diagram of a metal-free phthalocyanine compound. Diffraction spectrum diagram. Figure 7 is a near-infrared absorption spectrum diagram of a metal-free phthalocyanine compound. FIG. 8 is a partial sectional view of a conventionally used photoreceptor. In addition, in the symbols shown in the drawings, 1... Conductive substrate 4... Carrier transport layer 6... Carrier generation layer 7... Charge blocking layer 8... Photosensitive layer 12... ... Fixing device 13 ... Static eliminator 14 ... Cleaning device 15 ... Developing device 20 ... Pre-transfer exposure lamp 21 ... Transfer device 22 ... Charger 23 ... ... Image carrier 41 ... Laser 43 ... Mirror scanner 44 ... Imaging f-theta lens 48.49 ... Cylindrical lens 51 ...
Laser beam 61...Developing sleeve 62...Magnet 63...Layer thickness regulating blade 69...Bias power supply 70...Protection resistor. Agent Patent Attorney Hiroshi Aisaka Figure 1 Figure 2 Cause Figure 5 Figure 8 Figure 7 Figure 5 Growth + WqveLengih +n ml 1 (Voluntary) Procedure (Hoshosho March 11, 1988 1, Case Display 1986 Year Patent Application No. 3290712, Name of the invention Image forming method 3, Relationship with the case of the person making the amendment Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name Name
(127) Konica Co., Ltd. 4, Agent address: FINE Building e, 2-4-11 Shibasaki-cho, Tachikawa-shi, Tokyo 0425-24-5411 (1) "One or more -" on page 18, line 1 of the specification

Claims (1)

[Claims] 1. An image forming method using a photoreceptor having a photosensitive layer having a carrier transport layer provided on a carrier generation layer, (a) a phthalocyanine compound is contained as a carrier generation substance. (b) charging the photoreceptor; Absolute value of potential is 400V~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.
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.