JPH09127711A - Electrophotographic method and electrophotographic photoreceptor used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoreceptor which can enough electrified from the first rotation by incorporating a phthalocyanine compd. as a charge generating material and further incorporating an azo compd. into a photosensitive layer. SOLUTION: The photosensitive layer essentially consists of a charge generating layer and a charge transfer layer, and the charge generating material used is a phthalocyanine compd. For example, nonmetal phthalocyanines or phthalocyanines with coordination of copper, indium, tin, titanium, zinc, vanadium or oxides or chlorides of these can be used. Further, an azo compd. is used in the same layer that contains the phthalocyanine compd. As for the azo compd., monoazo, bisazo, trisazo, or polyazo can be used. The compounding ratio of the phthalocyanine compd. to the azo compd. is 1:(0.1 to 2), and preferably 1: 0.1 to 1. The ratio of a binder resin to these compd. (weight ratio) is specified to (0.2 to 5):1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic method used in copying machines, printers and the like, and an electrophotographic photosensitive member used in the method.

[0002]

2. Description of the Related Art C.I. F. The electrophotographic technology according to the invention of Carlsson has been widely used not only in the field of copying machines but also in the fields of various printers and facsimiles in recent years because of its ability to obtain images with instantness, high quality and high storability. Is showing. This electrophotographic process is basically performed by uniformly charging a photoreceptor, forming an electrostatic latent image by image exposure, developing the latent image with toner, and transferring the toner image to paper (intermediately through a transfer member). In some cases) and an image forming process by fixing.

[0003] Photoconductors, which are the core of the electrophotographic technology, have been developed from conventional inorganic photoconductors such as selenium, arsenic-selenium alloys, cadmium sulfide, and zinc oxide as photoconductive materials. A photoreceptor using an organic photoconductive material, which has advantages such as easy film formation and easy production, has been developed. Among them, a so-called laminated photoreceptor in which a charge generation layer and a charge transport layer are laminated, a photoreceptor with higher sensitivity can be obtained, a photoreceptor with a wide selection range of materials can be obtained, and coating can be performed. Due to its high productivity and relatively low cost, photoconductors are now the mainstream and are produced in large quantities.

On the other hand, digitization for image formation has been rapidly progressing recently in order to obtain higher quality images and to store and freely edit input images. Until now, digital image formation was limited to laser printers, LED printers, and some color laser copiers, which are output devices for word processors and personal computers. Digitization is progressing in the field of ordinary copiers.

When performing such digital image formation,
When directly using computer information, the electrical signal is converted into an optical signal. In the case of information input from an original, the original information is read as optical information, then converted into a digital electrical signal, and then the optical signal is read again. Is converted into and input to the photoconductor. In any case, an optical signal is input to the photoconductor, and laser light or LED light is mainly used for the optical input of such a digital signal.
The most commonly used wavelength of input light at present is 78
It is near-infrared light of 0 nm or 660 nm or long-wavelength light of a single wavelength close to it. The first requirement for a photoreceptor used for digital image formation is to have sensitivity to these long-wavelength light, and various materials have been studied so far. Among them, phthalocyanine compounds have been widely studied and put to practical use because they are relatively easy to synthesize and many have sensitivity to long-wavelength light.

For example, Japanese Patent Publication No. 55860/1993 discloses a photoconductor using titanyl phthalocyanine.
JP-A No. 155851 discloses a photoreceptor using β-type indium phthalocyanine, and JP-A-2-233769 discloses a photoreceptor using x-type metal-free phthalocyanine.
JP-A 1-28557 discloses a photoconductor using vanadyl phthalocyanine.

However, although the photoconductor using such a phthalocyanine compound as a charge generating substance has high sensitivity at a long wavelength, it has a drawback that the electrification voltage at the first rotation is low and the electrification voltage is stable at the second rotation. There was. This phenomenon is related to the standing time after the image forming process such as charging and exposure, and the longer the standing time is 30 minutes, 1 hour, etc., the lower the charged voltage at the first rotation tends to be. From this fact, this phenomenon is related to the generation of dark charges by the phthalocyanine compound that has been allowed to stand and the accumulation thereof in the charge generation layer, or the phenomenon that the charges are injected and accumulated from the conductive support into the charge generation layer. It is considered that

On the other hand, in the case of digitally forming an image, for the purpose of effectively using light or enhancing the resolution,
Toner is attached to the light-exposed area to form an image,
A so-called reversal development method is often adopted. In the reversal development process, the unexposed area (dark area potential) becomes a white background, and the exposed area (light area potential) becomes a black background area (image area). Therefore, in the reversal development process, fog (a phenomenon in which black spots occur in a white background portion) does not occur even when the potential of the bright portion rises as in the normal development process, but fog occurs when the potential of the dark portion decreases. Therefore, a scorotron charger is often used as a charger so that the dark part potential is always kept constant.

[0009]

Conventionally, an electrophotographic apparatus using a reversal developing method using a photoconductor using a phthalocyanine compound as a charge generating substance has a low electrification voltage at the first rotation and is easily fogged as described above. As a warm-up, I always had to put in one or more pre-rotations. This means that it takes a lot of time from the start of driving the electrophotographic apparatus to the actual image formation. However, conventionally, the data transfer from the computer to the printer is slow, and the image processing takes time even in a digital copying machine. Therefore, the time required for the pre-rotation is not a particular problem.

However, in recent years, the performance of microcomputers has been remarkably improved, and the data transfer time and image processing time have become sufficiently fast. Therefore, it is desired to use the photoconductor from the first rotation for image formation and to speed up the copying and printing of the first sheet. Request came out. However, when a conventional photoconductor using phthalocyanine as a charge generating substance is used in the process of forming an image from the first rotation, as described above, the electrification voltage of the first rotation is low, which causes a change in density or a terrible change. In some cases, I found that I had to wear a front rev to avoid wearing it. This means that the first copy or print does not become faster. Further, the photoconductor using an azo compound as disclosed in JP-A-57-196244 shows relatively good charging property after the first rotation, and the image forming process can be performed from the first rotation. However, it has a drawback that it cannot be speeded up because of its low sensitivity, and that the first copy is not fast.
Japanese Patent Application Laid-Open No. 3-37667 discloses a technique for producing a panchromatic photoconductor containing titanium phthalocyanine and an azo compound as a charge generating substance. However, titanium phthalocyanine is used in image formation by light of a single wavelength. It is not described that an excellent image can be formed from the first rotation by using it as a charge generating substance and using an azo compound together as in the present invention.

[0011]

Means for Solving the Problems The present inventors have investigated a photoconductor which is highly sensitive to long-wavelength light and which is sufficiently charged from the first rotation. We examined the electrophotographic method of the first copy and fast print. As a result, it was found that in order to have sufficiently high sensitivity to long-wavelength light, phthalocyanine is contained as a charge generating substance, and in order to be sufficiently charged from the first rotation, it is desirable to further use an azo compound. Invented an electrophotographic method.

That is, the gist of the present invention is an electrophotographic method in which each process of at least charging, exposure with light of a single wavelength, reversal development, and transfer is performed on a photoconductor, and the photoconductor is provided on a conductive support. An electrophotographic method comprising a photosensitive layer, the photosensitive layer containing a phthalocyanine compound as a charge generating substance, the photosensitive layer further containing an azo compound, and performing image formation from the first rotation of the photoreceptor. It is in. Further, the gist of the present invention is, in the electrophotographic method,
The electrophotographic method is characterized in that the photosensitive layer has a charge generation layer and a charge transport layer, and the charge generation layer contains a phthalocyanine compound and an azo compound.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, the photosensitive layer is provided on the conductive support.
As the conductive support, for example, a metal material such as aluminum, aluminum alloy, stainless steel, copper, nickel or the like, a polyester film deposited with aluminum, paper or the like is mainly used.

A known barrier layer, which is usually used, may be provided between such a conductive support and the photosensitive layer. Examples of the barrier layer include an anodized aluminum film, an inorganic layer such as aluminum oxide and aluminum hydroxide, and an organic layer such as polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, and polyamide. Is used. Further, these barrier layers may contain metal such as aluminum, copper, tin, zinc and titanium, or conductive or semi-conductive fine particles such as metal oxide.

The photosensitive layer of the present invention is preferably a laminated type which basically comprises a charge generation layer and a charge transport layer, but may be a so-called single layer dispersion type which is composed of a single photosensitive layer. Hereinafter, the laminated type will be mainly described. A phthalocyanine compound is used as the charge generating substance. Specifically, metal-free phthalocyanines, metals such as copper, indium, gallium, tin, titanium, zinc, and vanadium, or phthalocyanines coordinated with oxides or chlorides thereof are used. Particularly preferred are highly sensitive X-type and τ-type metal-free phthalocyanines, titanyl phthalocyanines such as A-type, B-type and D-type, vanadyl phthalocyanine, and chloroindium phthalocyanine.

In the present invention, it is preferable to use the azo compound in the same layer as the phthalocyanine compound. As the azo compound, azo compounds such as monoazo, bisazo, trisazo and polyazo can be used. These azo compounds may have absorption in laser light or LED light used for exposure, but it is preferable not to have absorption because the amount of light absorbed in phthalocyanine decreases and the sensitivity is lowered. Particularly preferred azo compounds include compounds represented by the following formula [I].

[0017]

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(A and B each represent a coupler residue having a phenolic hydroxyl group.) Preferred examples of the coupler residue of A and B are those of the formula [II] or [III].
]

[0019]

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[0020]

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And the like. In the formula [II], Q represents a divalent group of an aromatic hydrocarbon which may have a substituent, or a divalent group of a heterocyclic ring which may have a substituent. O-phenylene group, O-naphthylene group, 1,8-
Naphthylene group, 1,2-anthraquinonylene group, 9,1
0-phenanthrylene group, 3,4-pyrazolediyl group, 2,3-pyridinediyl group, 3,4-pyridinediyl group, 4,5-pyrimidinediyl group, 6,7-indazolediyl group, 5,6-benz An imidazolediyl group,
5,6-quinolinediyl group and the like can be mentioned.

In the formula [III], R ₁ and R ₂ are each a hydrogen atom, a lower alkyl group which may have a substituent, an aryl group or a heterocyclic group, and R ₁ and R ₂ are They may be bonded to each other to form a ring. Z represents a divalent group required to be condensed with a benzene ring to form an aromatic hydrocarbon ring or a heterocyclic ring. For example, Z is condensed with a benzene ring to form a naphthalene ring, anthracene ring, carbazole ring, benzocarbazole ring, The group which becomes a dibenzofuran ring is mentioned.

The charge generation layer comprises fine particles of these phthalocyanine compounds and azo compounds (preferably an average particle size of 1 μm).
m or less, more preferably 0.5 μm or less, further preferably 0.3 μm or less), for example, polyester resin, polyvinyl acetate, polyacrylic acid ester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin,
You may use it in the dispersion layer of the form bound by various binder resins, such as an epoxy resin, a urethane resin, a cellulose ester, and a cellulose ether.

The ratio (weight ratio) of the phthalocyanine compound to the azo compound is preferably 0.1 based on 1 phthalocyanine.
˜2, more preferably 0.1 to 1 ratio. The ratio (weight ratio) of the binder resin to these compounds was 0.
Used in the range of 2-5. The film thickness is usually 0.1 to 2
μm, preferably 0.1 to 0.8 μm is suitable. Further, the charge generation layer may contain various additives such as a leveling agent, an antioxidant and a sensitizer for improving the coating property, if necessary.

The charge transport layer is mainly composed of a charge transport material and a binder resin, and the charge transport material is 2, 4, 7-
Electron withdrawing substances such as trinitrofluorenone and tetracyanoquinodimethane, heterocyclic compounds such as carbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, aniline derivatives, hydrazone compounds, aromatic amine derivatives , An electron-donating substance such as a stilbene derivative, or a polymer having a group composed of these compounds in its main chain or side chain. The charge transport layer is formed in a state where these charge transport materials are bound to the binder resin.

As the binder resin used in the charge transport layer, for example, vinyl polymers such as polymethylmethacrylate, polystyrene and polyvinyl chloride, and copolymers thereof, polycarbonate, polyester, polyester carbonate, polysulfone, polyimide, phenoxy,
Epoxy, silicone resin and the like can be mentioned, and their partially crosslinked and cured products can also be used.

The ratio of the binder resin to the charge transport material is
Usually, 30 to 20 relative to 100 parts by weight of binder resin
It is used in an amount of 0 parts by weight, preferably 40 to 150 parts by weight. The film thickness is generally 5 to 50 μm, preferably 1
0 to 45 μm is preferable. The charge transport layer contains a well-known plasticizer in order to improve film-forming properties, flexibility, coating properties, and the like.
You may contain additives, such as an antioxidant, a ultraviolet absorber, and a leveling agent.

These photosensitive layers are formed on the conductive substrate by dip coating, spray coating, nozzle coating or the like. The photoreceptor obtained as described above has a long wavelength single wavelength, for example, 600 nm to 850 nm, preferably 660 nm to
Since it has high sensitivity to 800 nm light and is sufficiently charged from the first rotation, an electrophotographic process for forming an image from the first rotation of the photoreceptor can be configured by using this photoreceptor, and the first copy or It is possible to construct an electrophotographic device with fast printing.

This electrophotographic method uses at least charging, exposure,
Although each process of reversal development and transfer is included, any of commonly used methods may be used. As a charging method, for example, any of corotron or scorotron charging using corona discharge, contact charging with a conductive roller or a brush, and the like may be used. In the charging method using corona discharge, scorotron charging is often used to keep the dark part potential constant. As a developing method, a general method of developing by contacting or non-contacting a magnetic or non-magnetic one-component developer, a two-component developer, etc. is used, but both are used in reversal development for developing a bright part potential. . The transfer method may be corona discharge, a method using a transfer roller, or the like. Usually, a fixing process for fixing the developer to paper or the like is used, and as a fixing unit, generally used heat fixing and pressure fixing can be used. In addition to these processes, processes such as cleaning and charge removal may be included.

In the present electrophotographic method, image formation is performed from the first rotation of the photoconductor, but in the electrophotographic method used in the present electrophotographic method, image formation is performed from the second rotation of the photoconductor and thereafter. Is also useful. That is, in the conventional photoreceptor containing phthalocyanine as the charge generating substance, the charged voltage at the first rotation is too low,
When it is used in the reversal development, the development is performed even if the image formation is not performed, which sometimes adversely affects the image formation performed after the second rotation.
Since the photoconductor used in the present electrophotographic method is sufficiently charged from the first rotation, such a phenomenon can be avoided.

[0031]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 Cutting outer diameter 65 mm, length 348 mm, wall thickness 1 m
m aluminum cylinder, degreasing agent NG- # 30
(Kizai Co., Ltd.) in a 30 g / l aqueous solution at 60 ° C. for 5
Degreasing was performed for a minute. Then, after washing with water, it was immersed in 7% nitric acid at 25 ° C. for 1 minute.

After further washing with water, 1.2 A / dm ^{2 in} a 180 g / l sulfuric acid electrolytic solution (dissolved aluminum concentration 7 g / l).
Anodization was performed at a current density of 1 to form an anodized film having an average film thickness of 6 μm. Then, after washing with water, a sealing treatment was performed by immersing in a 10 g / l aqueous solution of a high-temperature sealing agent Topseal DX-500 (manufactured by Okuno Chemical Industries Co., Ltd.) containing nickel acetate as a main component at 95 ° C. for 30 minutes. Subsequently, after washing with water, the entire surface of the coating film was reciprocated three times using a polyester sponge to perform rubbing cleaning. Then, it was washed with water and dried.

On the other hand, in the powder X-ray diffraction spectrum,
10 parts by weight of a crystalline oxytitanium phthalocyanine showing a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° and a diffraction peak at 7.4 °, 9.7 ° and 24.2 °, An azo compound having the following structure (azo-
1) 5 parts by weight of 4-methoxy-4-methylpentanone-
In addition to 2200 parts by weight, pulverization and dispersion treatment was performed with a sand grind mill.

[0034]

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Further, polyvinyl butyral (Sekisui Chemical Co., Ltd., trade name S-REC BH-3) 4% 1,2
-4 parts by weight of 100 parts by weight of dimethoxyethane solution and phenoxy resin (union carbide, trade name PKHH)
% 1,2-dimethoxyethane solution was mixed to prepare a binder solution. To 215 parts by weight of the pigment dispersion liquid prepared above, 375 parts by weight of the binder solution, 1, 2
-160 parts by weight of dimethoxyethane was added to finally prepare a dispersion liquid having a solid content concentration of 4.0%. An aluminum cylinder provided with an anodized film formed previously was applied by dip coating to this dispersion, and a charge generation layer was formed so that the film thickness after drying was 0.5 μm. Next, 70 parts by weight of the following hydrazone compound was added to the aluminum cylinder.

[0036]

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Also, 100 parts by weight of a polycarbonate resin (Novalex 7030A manufactured by Mitsubishi Chemical Co., Ltd.) is applied by dipping in a solution prepared by dissolving 1000 parts by weight of 1,4-dioxane so that the film thickness after drying becomes 25 μm. Was provided with a charge transport layer. The drum thus obtained is referred to as a photoconductor A. Example 2 As an azo compound, a compound having the following structure (azo-
A photoconductor B was produced in the same manner as in Example 1 except that 2) was used.

[0038]

[Chemical 6]

Comparative Example 1 15 parts by weight of the same oxytitanium phthalocyanine used in Example 1 was added to 200 parts by weight of 4-methoxy-4-methylpentanone-2, and pulverized and dispersed by a sand grind mill. . On the other hand, polyvinyl butyral (Sekisui Chemical Co., Ltd., trade name S-REC BH-3)
100% by weight of 4% 1,2-dimethoxyethane solution and phenoxy resin (trade name P manufactured by Union Carbide Co., Ltd.
A binder solution was prepared by mixing 100 parts by weight of a 4% 1,2-dimethoxyethane solution of KHH).

To 215 parts by weight of the pigment dispersion liquid prepared above,
375 parts by weight of the binder solution and 160 parts by weight of 1,2-dimethoxyethane were added to finally give a solid content of 4.0%.
A dispersion liquid of was prepared. Anodizing aluminum cylinder was applied by dip coating to the dispersion liquid obtained here.
A photoconductor C was prepared in the same manner as in Example 1 except that the charge generation layer having a thickness of 5 μm was formed.

Comparative Example 2 10 parts by weight of the same oxytitanium phthalocyanine used in Example 1 was added to 200 parts by weight of 4-methoxy-4-methylpentanone-2, and pulverized and dispersed by a sand grind mill. . On the other hand, polyvinyl butyral (Sekisui Chemical Co., Ltd., trade name S-REC BH-3)
100% by weight of 4% 1,2-dimethoxyethane solution and phenoxy resin (trade name P manufactured by Union Carbide Co., Ltd.
A binder solution was prepared by mixing 100 parts by weight of a 4% 1,2-dimethoxyethane solution of KHH).

To 210 parts by weight of the pigment dispersion liquid prepared above,
500 parts by weight of the binder solution and 40 parts by weight of 1,2-dimethoxyethane were added to finally prepare a dispersion liquid having a solid content concentration of 4.0%. Anodizing aluminum cylinder was applied by dip coating to the dispersion liquid obtained here to 0.5
A photoconductor D was obtained in the same manner as in Example 1 except that a charge generation layer having a thickness of μm was formed.

These photoconductors A, B, C, and D were mounted on a copier having a process speed of 190 mm / sec, which was modified for reversal development and in which the copying process was performed from the first rotation of the photoconductor. A surface potential measuring device was attached, and a process of charging, exposing, and removing charge was repeated 50,000 copying processes (equivalent to copying 50,000 sheets by A4 transverse feeding). Since the warm-up operation (pre-rotation of the photoconductor prior to image formation, etc.) is not performed, the power of the copying machine is turned on 1
After standing for a period of time, the copy button was pressed to perform a copy process, and the surface potential of the unexposed portion of the photoreceptor at this time was measured. Table 1 shows the results.

[0044]

[Table 1]

Next, after 1,000 sheets of these photoconductors were actually photographed by a copying machine modified for reversal development, the photoconductor was left for 1 hour with the power on, and after 1 hour, an original having a black background portion and a halftone portion. Was copied (because it is reverse development, the black background of the original becomes a white background when copied). As a result, a good image was obtained in both the white background portion and the halftone portion of the photoconductor A, and a density change was observed in the middle of the halftone portion of the photoconductor B.
The white background was good. On the other hand, in the photoconductors C and D, fogging was observed in the first half of the white background portion, and a clear density change was observed in the halftone portion.

[0046]

As described above, according to the present invention, since the photosensitive layer contains a phthalocyanine compound as a charge generating substance, it is highly sensitive to long wavelengths, and the photosensitive layer contains an azo compound. A photosensitive member that is sufficiently charged from the first rotation is obtained, and by using this photosensitive member, an electrophotographic process for forming an image from the first rotation of the photosensitive member can be configured, and an electrophotographic apparatus that can quickly copy or print the first sheet. Can be configured.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Lingo 1060 Narita, Odawara-shi, Kanagawa Mitsubishi Chemical Co., Ltd.Odawara Works (72) Inventor, Satoshi Ogawa 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi Kanagawa Mitsubishi Chemical Corporation Yokohama (72) Inventor Hiroaki Takamura 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Mitsubishi Chemical Corporation Yokohama Research Institute

Claims (8)

[Claims] 1. In an electrophotographic method in which at least charging, exposure with light of a single wavelength, reversal development, and transfer are performed on a photoconductor, the photoconductor has a photosensitive layer on a conductive support. The electrophotographic method, wherein the photosensitive layer contains a phthalocyanine compound as a charge generating substance, the photosensitive layer further contains an azo compound, and image formation is performed from the first rotation of the photoreceptor. 2. The electrophotographic method according to claim 1, wherein an image is formed with light having a single wavelength of 600 nm to 850 nm. 3. The electrophotographic method according to claim 1, wherein an image is formed with light having a single wavelength of 660 nm to 800 nm. 4. The electrophotographic method according to claim 1, wherein the photosensitive layer has a charge generation layer and a charge transport layer, and the charge generation layer contains a phthalocyanine compound and an azo compound. 5. At least each process of charging, exposure with light of a single wavelength, reversal development, and transfer is performed on the photoconductor, and image formation is performed from the first rotation of the photoconductor. An electrophotographic photoreceptor used in an electrophotographic method, comprising a phthalocyanine compound as a charge generating substance and a photosensitive layer further containing an azo compound on a conductive support. 6. The electrophotographic photosensitive member according to claim 5, wherein the electrophotographic photosensitive member is used in an electrophotographic method which forms an image with light having a single wavelength of 600 nm to 850 nm. 7. The electrophotographic photosensitive member according to claim 5, wherein the electrophotographic photosensitive member is used in an electrophotographic method which forms an image with light having a single wavelength of 660 nm to 800 nm. 8. The electrophotographic photoreceptor according to claim 5, wherein the photosensitive layer has a charge generation layer and a charge transport layer, and the charge generation layer contains a phthalocyanine compound and an azo compound.