JPH08286407A - Image forming method and device - Google Patents

Abstract

PURPOSE: To form a stable image while suppressing the reduction of the film thickness of a photoreceptor and defective cleaning even at the time of repetitive use by using an electrophotographic photoreceptor contg. specified hydrophobic inorg. fine particles and subjecting the photoreceptor to digital exposure at a specified spot diameter. CONSTITUTION: Inorg. fine particles having 0.05-1μm particle diameter and >=10<8> Ω.cm volume resistivity are incorporated into the surface layer of an electrophotographic photoreceptor with a photosensitive layer on the electrically conductive substrate and the resultant electrophotographic photoreceptor is used. The inorg. fine particles are preferably particles having a Mohs hardness of >=5, e.g. particles of titanium oxide, silica, zirconium oxide, alumina, carbon nitride, aluminum nitride or silicon carbide. When the particles are hygroscopic, they are made hydrophobic by treatment with a titanium coupling agent, a silane coupling agent, a high molecular fatty acid, etc. An image having high image quality is formed by subjecting the photoreceptor to digital image exposure at <=80μm spot diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and apparatus for visualizing an electrostatic charge image with a developer for forming an image such as electrophotography, and more particularly to an OPC containing inorganic fine particles in a surface layer in an electrophotographic process. The present invention relates to an image forming method and apparatus using the photoconductor.

[0002]

2. Description of the Related Art In an electrophotographic copying machine of the Carlson method, after uniformly charging the surface of a photoconductor, the charge is erased for an image by exposure to form an electrostatic latent image. Is developed with toner, and then the toner image is transferred and fixed on paper or the like. On the other hand, the photoreceptor is subjected to removal of adhered toner, charge removal, and surface cleaning, and is repeatedly used for a long period of time. Therefore, as an electrophotographic photoreceptor, not only the electrophotographic characteristics such as good charging characteristics and sensitivity and small dark decay, but also physical properties such as printing durability after repeated use, abrasion resistance, moisture resistance, etc. Also, it is required to have good resistance (environmental resistance) to ozone generated during corona discharge and ultraviolet rays during exposure. Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having an inorganic photoconductive substance such as selenium, zinc oxide, or cadmium sulfide as a photosensitive layer main component has been widely used. Recently, as a photosensitive layer of an electrophotographic photoreceptor, a carrier generation function and a carrier transport function are shared by different substances,
There is a trend to put into practical use an organic photoconductor having high sensitivity and high durability, which is selected from a wide range of substances exhibiting each function in accordance with desired characteristics.

Such a function-separated type organic photoreceptor is conventionally used mainly for negative charging, and is disclosed in JP-A-60-247.
As described in Japanese Patent No. 647, a structure is adopted in which a thin carrier generation layer is provided on a support and a relatively thick carrier transport layer is provided thereon.

[0004]

However, since this carrier transporting layer is composed of a polymer binder, a carrier transporting substance, etc., as it is used, it is rubbed against the developing sleeve, transfer paper, cleaning member, etc. and gradually wears down. However, there is a problem that the initial charging characteristics and light attenuation characteristics cannot be obtained. Further, these organic compounds are easily oxidized by discharge active species such as ozone and become hygroscopic, and especially when foreign matter such as paper powder adheres, the surface resistance of the photosensitive layer is lowered and the image is blurred, or in a severe case,
The phenomenon that the image flows may occur.

In order to solve such problems, as a binder resin for the charge transport layer, which is the outermost surface layer of the photoreceptor, electrophotographic characteristics,
Polycarbonate resin is preferred and used from the viewpoint of mechanical strength, but when compared with selenium photoreceptors,
At present, the scratch resistance and wear resistance are inferior and sufficient performance is not yet obtained. Further, introduction of a substituent having a fluorine atom at a carbon between phenylene rings into a polycarbonate resin (JP-A-63-65444), substitution of an alkyl group or a halogen atom into a phenylene ring (JP-A-62-14).
8263), or a copolymer of monomers in which both phenylene rings are substituted with phenyl groups or cyclohexyl groups (JP-A-1-269942, JP-A-1-269).
No. 943) has been proposed, but there are problems such as insufficient surface strength, weakness against abrasion and scratches, deterioration of image quality during repeated use, and deterioration of sensitivity due to reduction of film thickness due to abrasion. are doing.

On the other hand, in recent years, laser beam printers and LED printers have become widespread as computer output devices, and the demand for higher image quality has increased accordingly. Various methods are conceivable for achieving high image quality, but among others, reducing the particle size of the toner and increasing the exposure density are being actively carried out. However, especially when the exposure spot diameter is reduced and the exposure density is increased, there is a demand for a photoreceptor that does not easily deteriorate when the surface of the photoreceptor deteriorates, such as defects such as image blurring.

An object of the present invention is to provide an image forming method and apparatus which are highly sensitive, have less wear of the photosensitive layer, and are excellent in image stability by using a photoconductor with less deterioration of image quality and deterioration of sensitivity.

[0008]

According to the image forming method and apparatus of the present invention, the surface layer of an electrophotographic photosensitive member having a photosensitive layer on a conductive substrate has a particle size of 0.05 to 1 μm and a volume resistivity of 10. It is characterized in that an electrophotographic photosensitive member containing inorganic fine particles of ⁸ Ω · cm or more, which has been subjected to a hydrophobic treatment as required, is used, and the electrophotographic photosensitive member is digitally exposed with a spot diameter of 80 μm or less.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the drawings, but these are representative examples and the present invention is not limited thereto.

FIG. 1 is an explanatory view of a conventionally known image forming apparatus, in which 1 is an electrophotographic photosensitive member (photosensitive drum or photosensitive belt) capable of carrying an electrostatic latent image on its outer periphery, and 2 is the photosensitive member. A charger 3 for charging the outer periphery of the photoconductor 1 which is arranged so as to face the outer periphery of the body 1 is also the image exposure 4
Developing devices 5 of different colors for developing the electrostatic latent image formed on the photoconductor 1 into a toner image by electrostatically transferring the toner image on the photoconductor 1 onto the transfer material 6. Transfer means such as a transfer roller for collectively transferring the image onto the photosensitive member 1, 7 is a separator for separating the transfer material 6 from the photosensitive member 1, and 8 is a cleaning blade for removing the toner remaining on the photosensitive member 1. Reference numeral 9 is a pre-charging exposure means (PCL), 10 is an upstream registration roller for transporting the transfer material 6, and 11
Similarly, reference numeral 12 denotes a downstream side registration roller, and 12 denotes a transfer power source.

FIG. 2 shows a case where the intermediate transfer member 1a is used. When the intermediate transfer member 1a is used, the electrostatic latent image formed on the rotated photosensitive member 1 is developed by the developing device 3. To form a toner image by transferring the toner image from the image carrier 1 to the intermediate transfer body 1a, and further, at the transfer portion where the intermediate transfer body 1a and the transfer roller 5 are in pressure contact with each other. After the electrostatic transfer is performed on the transfer material 6 which is fed from the section and energized, the transfer material 6 is carried out.

In the present invention, a photosensitive member having a charge generating layer and a charge transporting layer laminated on a conductive substrate, a photosensitive member having a photosensitive layer containing a mixture of a charge generating substance and a charge transporting substance, or these photosensitive members At least the outermost surface layer of the photoreceptor on which a protective layer is further provided contains inorganic fine particles having a particle diameter of 0.05 to 1 μm and a volume resistivity of 10 ⁸ Ω · cm or more.

If desired, an undercoat layer may be provided between the conductive substrate and the photosensitive layer.

As the conductive substrate, a metal plate of aluminum, stainless steel, iron or the like, a metal layer of aluminum, palladium, gold or the like is provided on the surface of a flexible support such as paper or plastic film by laminating or vapor deposition. It is possible to use a material having a layer containing a conductive compound such as a conductive polymer, indium oxide or tin oxide applied or vapor-deposited on the surface of a flexible support such as paper or plastic film.

The subbing layer used as required includes casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, polyamides (nylon 6, nylon 66, alkoxymethylated). Nylon etc.), polyurethane, gelatin and aluminum oxide are used. The thickness of the undercoat layer is preferably 0.1 to 10 μm, and particularly preferably 0.1 to 5 μm.

The charge generating layer is a layer containing a charge generating substance, and the charge generating substance is not particularly limited, and examples thereof include a phthalocyanine pigment, a polycyclic quinone pigment, an azo pigment, a perylene pigment and an indigo pigment. , A quinacridone pigment, an azurenium pigment, a squarylium dye, a cyanine dye, a pyrylium dye, a thiopyrylium dye, a triphenylmethane dye, a styryl dye, and the like, which may be used alone or dispersed in a resin. As the resin used here, styrene-acrylic resin, polycarbonate resin, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, styrene resin, polyvinyl acetate, styrene-butadiene resin, vinylidene chloride-acrylonitrile resin, Examples thereof include vinyl chloride-vinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin and the like.

The charge-transporting layer is a layer containing a charge-transporting substance, and the charge-transporting substance is not particularly limited. For example, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives,
Triazole derivative, imidazole derivative, imidazolone derivative, imidazoline derivative, bisimidazolidine derivative, styryl compound, hydrazone compound, benzidine compound, pyrazoline derivative, stilbene compound, amine derivative, oxazolone derivative, benzothiazole derivative, benzimidazole derivative, Quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, poly-N-vinylcarbazoles, poly-1-vinylpyrenes, poly-
9-vinyl anthracenes and the like can be mentioned. It is formed by dispersing or dissolving these in a resin alone or in combination. As the resin used here, styrene-acrylic resin, polycarbonate resin, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, styrene resin, polyvinyl acetate, styrene-butadiene resin, vinylidene chloride-acrylonitrile resin, Vinyl chloride-vinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin,
Examples thereof include silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin and the like. The thickness of the charge transport layer is 5 to 50 μm, preferably 10 to 40 μm.
Is.

In the case of a photosensitive layer composed of a mixture of a charge-transporting substance and a charge-generating substance, the above-mentioned charge-transporting substance and charge-generating substance are appropriately mixed and dispersed in the above-mentioned resin, and then the layer is formed. Obtained by forming. In this case, the layer thickness is from 5 to 50 μm, preferably from 10 to 40 μm.

The inorganic fine particles used in the surface layer in the present invention are not particularly limited, but those having a Mohs hardness of 5 or more are preferable. Specifically, oxides such as titanium oxide, silica, zirconium oxide and alumina, carbon nitride, aluminum nitride, nitrides such as silicon nitride, carbides such as silicon carbide, strontium titanate and titanate compounds such as barium titanate. And so on. Of these, silica is particularly preferable.

When organic fine particles are used as the fine particles, the hardness is not as high as that of the inorganic fine particles, so that the wear resistance and scratch resistance are not improved so much. In addition, many organic fine particles have higher hygroscopicity than inorganic fine particles, and in that case, the surface resistance is lowered and the image is likely to be blurred in a high humidity environment.

The Mohs hardness of the inorganic fine particles means the Mohs hardness of the substance having the material. The Mohs hardness is a relative hardness evaluated by the presence or absence of scratches using a standard substance in which talc is 1 and diamond is 10 in sequence.

These fine particles preferably have a volume average primary fine particle diameter of 0.01 to 5 μm. More preferably, it is 0.05 to 2 μm. When the particle size is large, the surface layer itself becomes brittle, the desired improvement in durability cannot be exhibited, and the presence of fine particles causes damage to the cleaning mechanism. Further, when the particle size is small, the hardness does not improve due to the presence of fine particles, and the durability does not improve.

Further, when the inorganic fine particles are hygroscopic, it is preferable that they are hydrophobic because the electric resistance of the surface of the photosensitive member may be lowered in a high humidity environment to cause image defects such as image blurring. In the case of hydrophilic inorganic fine particles, it is preferable to perform hydrophobic treatment by a known method. As a method for hydrophobizing, for example, a well-known hydrophobizing agent such as a titanium coupling agent, a silane coupling agent, a polymeric fatty acid or a metal salt thereof can be used for treatment.

Examples of the titanium coupling agent include tetrabutyl titanate, tetraoctyl titanate, isopropyl isostearoyl titanate, isopropyl tridecylbenzene sulfonyl titanate, bis (dioctyl pyrophosphate) oxyacetate titanate and the like. Further, as the silane coupling agent,
γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) γ -Aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyl Trimethoxysilane, o
-Methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane and the like can be mentioned. In addition, fatty acids and metal salts thereof include undecyl acid, lauric acid,
Tondecanoic acid, myristic acid, palmitic acid, pentadecanoic acid, stearic acid, heptadecanoic acid, arachidic acid,
Long-chain fatty acids such as montanic acid, oleic acid, linoleic acid, and arachidonic acid are listed, and their metal salts are zinc,
Examples thereof include salts with metals such as iron, magnesium, aluminum, calcium, sodium and lithium. These compounds are 1 to 10% by weight with respect to the inorganic fine particles,
It is preferable to add 3 to 7% by weight for coating. Further, these materials can be used in combination, and they are usually formed on the surface of the inorganic fine particles as a monomolecular layer or a layer close thereto.

Further, the volume resistivity of the fine particles themselves is preferably 10 ⁸ Ω · cm or more. If this resistance is lower than this range, the resistance of the surface is lowered, the charge retaining function is lowered, and the problem of causing image defects is induced.

The surface layer can be formed by dispersing the above fine particles in a resin and applying the resin. Although the resin to be formed is not particularly limited, for example,
Styrene-acrylic resin, polycarbonate resin, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, styrene resin, polyvinyl acetate, styrene-butadiene resin, vinylidene chloride-
Acrylonitrile resin, vinyl chloride-vinyl acetate resin,
Examples thereof include vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin and the like. The content of fine particles in these resins is 1 with respect to 100 parts of the resin.
It is ˜200 parts, preferably 5 to 100 parts. If the amount is less than 1 part, the amount of the fine particles is too small to exert the effect of improving the hardness. If the amount is more than 200 parts, the hardness is improved. Scattering occurs, which causes image defects.

Further, the thickness of the surface layer in the present invention is 0.2 to 10 μm, preferably 0.4 to 5 μm.
When this layer is thin, the effect of improving durability of the present invention is not exhibited, and when the film thickness is thick, the effect of improving durability is exhibited, but occurrence of image defects due to light scattering and , Causes a problem of reduced sensitivity.

The layer containing fine particles in the present invention preferably contains a charge transporting substance. That is, since the specific surface layer is not formed by containing the charge transport substance, the charge is uniformly transported, and the charge distribution according to the image can be stably formed. The content ratio of this charge transport substance in the surface layer is 30 to 30 with respect to 100 parts of the resin constituting the protective layer.
It is 0 part, preferably 50 to 200 parts.

On the other hand, the spot diameter of digital exposure is 80 μm.
When the spot diameter is larger than 80 .mu.m, the exposure density of the electrostatic latent image is low so that image defects are less likely to occur, but it is difficult to improve the image quality.
On the other hand, when the spot diameter is 80 μm or less, high image quality can be achieved, but on the other hand, image defects are likely to occur when the surface resistance of the photoconductor is reduced and the surface resistance is lowered. The spot diameter of digital exposure refers to the width of the exposure intensity which becomes 13.5% of the maximum intensity when the intensity distribution of digital exposure is shown. When the irradiation shape is not circular, it is the value of the shortest part of the width.

In the present invention, by containing the inorganic fine particles in the outermost surface layer, the electrophotographic characteristics such as charge retention, sensitivity and residual potential are excellent, the thickness loss is small even when repeatedly used, and the thickness is 80 μm or less. Even in an electrophotographic apparatus which performs image exposure with an exposure spot diameter of 1, the image defect does not occur and stable image quality can be obtained.

The photoconductors (1) to (1) in the present invention will be described below.
The method of creating 1) will be described.

Photoreceptor (1)

30 g of polyamide resin CM-8000 (Toray Industries, Ltd.) was placed in a mixed solvent of 900 ml of methanol and 100 ml of 1-butanol and heated and dissolved at 50.degree. After cooling to room temperature, use this solution to obtain an outer diameter of 40 m.
An intermediate layer having a thickness of 0.5 μm was formed by dip coating on an aluminum drum having a length of m and a length of 270 mm.

Next, 5 g of polyvinyl butyral resin S-REC BX-1 (Sekisui Chemical Co., Ltd.) was added to MEK1000.
Dissolved in ml, and further Y-type titanyl phthalocyanine 10
After mixing g, dispersion was performed for 20 hours using a sand mill. Using this solution, a charge generation layer having a thickness of 0.3 μm was formed by dip coating on the intermediate layer.

Then, 100 g of Exemplified Compound T and 150 g of BPZ type polycarbonate resin Panlite TS-2050 (Teijin Kasei Co., Ltd.) were dissolved in 1000 ml of dichloromethane. Using this solution, a charge transport layer having a thickness of 20 μm was formed on the charge generation layer by dip coating.

Then, a solution prepared by dissolving 20 g of Exemplified compound T and 30 g of BPZ type polycarbonate resin Panlite TS-2050 (Teijin Kasei Co., Ltd.) in 1000 ml of dichloromethane was treated with a silane coupling agent to 0.2 μm.
10 g of silica fine particles (Mohs hardness 7.0) of
Disperse for 20 minutes in an ultrasonic bath. Using this solution, a ring-coated surface protection layer having a thickness of 3 μm was formed on the charge transport layer.

Finally, it was heated and dried at 100 ° C. for 1 hour, and an intermediate layer, a charge generating layer, a charge transporting layer and a surface protective layer were sequentially laminated to prepare a photoreceptor. The exemplified compound T is shown in Chemical formula 1.

[0038]

Embedded image

Photoreceptor (2)

0.2 μm silica fine particles are added to 0.05 μm
A photoconductor was prepared in the same manner as the photoconductor (1) except that the silica fine particles (Mohs hardness 7.0) were changed.

Photoreceptor (3)

A photoreceptor was prepared in the same manner as the photoreceptor (1) except that the silica fine particles of 0.2 μm were changed to the silica fine particles of 2.0 μm (Mohs hardness 7.0).

Photoreceptor (4)

A photoreceptor was prepared in the same manner as the photoreceptor (1) except that the silica fine particles of 0.2 μm were changed to the silica fine particles of 2.5 μm (Mohs hardness 7.0).

Photoreceptor (5)

A photoconductor was prepared in the same manner as the photoconductor (1) except that 0.2 μm silica fine particles were changed to 0.2 μm zirconia (Mohs hardness 7.5) fine particles.

Photoreceptor (6)

A photoreceptor was prepared in the same manner as the photoreceptor (1) except that the silica fine particles of 0.2 μm were changed to the silica fine particles of 0.1 μm (Mohs hardness 7.0).

Photoreceptor (7)

A photoconductor was prepared in the same manner as the photoconductor (1) except that the 0.2 μm silica fine particles were changed to 0.5 μm titanium oxide fine particles (Mohs hardness 6.0).

Photoreceptor (8)

A photoconductor was prepared in the same manner as the photoconductor (1) except that the silica fine particles of 0.2 μm were changed to the alumina fine particles of 0.5 μm (Mohs hardness 9.0).

Photoreceptor (9)

A photoconductor was prepared in the same manner as the photoconductor (1) except that the 0.2 μm silica fine particles were changed to 0.5 μm organic silicone fine particles (Toshiba Silicone Co., Ltd.).

Photoreceptor (10)

A photoconductor was prepared in the same manner as the photoconductor (1) except that the 0.2 μm silica fine particles were changed to the 0.1 μm tin oxide fine particles.

Photoreceptor (11)

Photoconductor (1) except that fine particles were not added
A photoconductor was prepared in the same manner as in.

The photoconductors (1) to (9) were mounted on a modified laser beam printer LP-3110 manufactured by Konica Co., Ltd., and 10,000 prints were made under the conditions of 33 ° C. and 80% RH by changing the conditions as shown in Table 1. The durability test was performed. Evaluation,
It was performed depending on whether or not there was an image defect during actual shooting.

[0060]

[Table 1]

The lower four columns in Table 1 show comparative examples.

[0062]

As shown in Table 1 above, according to the image forming method and apparatus of the present invention, even when repeatedly used, the film thickness of the photoconductor is less worn, and a stable image can be obtained without causing cleaning failure. You will get it.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram of an image forming apparatus of the present invention using an intermediate transfer member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 1a Intermediate transfer body 2 Charging device 3 Developing device 4 Image exposure 5 Transfer means 6 Transfer material 7 Separator 8 Cleaning blade 9 Pre-charging exposure means 10 Upstream registration roller 11 Downstream registration roller 12 Transfer power source

Claims (3)

[Claims] 1. An image forming method for exposing a digital image on an electrophotographic photosensitive member with a spot diameter of 80 μm or less, wherein the surface layer of the electrophotographic photosensitive member has a particle diameter of 0.05 to 1 μm and a volume resistivity of 10 ⁸ Ω · cm. An image forming method comprising the above-mentioned inorganic fine particles. 2. An image forming unit having an electrophotographic photosensitive member and a digital exposure unit for image-exposing the electrophotographic photosensitive member with a spot diameter of 80 μm or less, wherein the surface layer of the electrophotographic photosensitive member has a particle size of 0. An image forming unit containing inorganic fine particles having a volume resistivity of 10 ⁸ Ω · cm or more and a diameter of 0.05 to 1 μm. 3. An image forming apparatus having an electrophotographic photosensitive member and a digital exposure unit for image-exposing the electrophotographic photosensitive member with a spot diameter of 80 μm or less, wherein the surface layer of the electrophotographic photosensitive member has a particle size of 0. An image forming apparatus characterized by containing inorganic fine particles having a volume resistivity of 10 ⁸ Ω · cm or more and a diameter of 0.05 to 1 μm.