JP2000305289A - Electrophotographic photoreceptor, image forming method and device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having satisfactory response to light attenuation even in very short-time pulse exposure by laser exposure and having high-speed responsiveness adaptable to the shortening of electrophotographic process time due to decrease in the diameter of a drum. SOLUTION: At least, an electric charge generating layer and an electric charge transferring layer are laminated on an electrically conductive substrate to obtain the objective electrophotographic photoreceptor. The ratio of the thickness of the electric charge transferring layer to the mobility of the electric charge transferring layer is <=1.5×103 V.s/m when the field intensity of the electric charge transferring layer is in the range of 2.5×105-5.5×105 V/cm. The electric charge transferring layer preferably contains an electric charge transferring material and a lubricant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor for electrophotography, and an image forming method and apparatus (electrophotographic process cartridge) using the same.

[0002]

2. Description of the Related Art Electrophotographic methods using the Carlson process and other various deformation processes are widely used in copiers and printers. Among the photoreceptors used in such an electrophotographic method, those using an organic photosensitive material have been used in recent years because of their advantages of low cost, mass productivity and no pollution. The mechanism of the formation of the electrostatic latent image on the photoreceptor is as follows. When light is irradiated after charging the photoreceptor, the light is absorbed by the charge generating material, and the charge generating material that has absorbed the light generates charge carriers.
The charge carriers are injected into the charge transport material, move in the charge transport layer (or the photosensitive layer) according to the electric field generated by the charge, and neutralize the charge on the surface of the photoreceptor. As a result, an electrostatic latent image is formed. Organic electrophotographic photoreceptors include a photoconductive resin represented by polyvinyl carbazole (PVK), a charge transfer complex represented by PVK-TNF (2,4,7-trinitrofluorenone), and a phthalocyanine-binder. And a function-separated type photoreceptor using a combination of a charge generating substance and a charge transporting substance, and a function-separated type photoreceptor has attracted attention and has been put to practical use.

Conventionally, various organic materials for photoreceptors have been developed. To make these electrophotographic photoreceptors which can be practically used, sensitivity, receptive potential, potential holding property, potential stability, residual Electrophotographic characteristics represented by potential and spectral characteristics,
Various characteristics are required, such as mechanical durability such as abrasion resistance, and chemical stability against heat, light, and discharge products. In particular, the demand for smaller electrophotographic systems
The diameter of the photoreceptor has to be reduced, the process time between exposure and development has been shortened, and high-speed response of the photoreceptor has become important. For high-sensitivity characteristics, it is necessary to first select an appropriate material, but in addition to this, an appropriate design in terms of formulation is indispensable. However, conventionally, the prescription design on the condition of the high-speed response has not been sufficiently performed, and no high-speed response evaluation method satisfying the requirements has been obtained. further,
Mechanical durability, mainly abrasion resistance, is required as an important property, and in conventional organic photoreceptor constructions and electrophotographic processes, sufficient durability is required due to the low abrasion resistance of organic substances. Had not been obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photosensitive member capable of realizing a stable and high-speed electrophotographic process which has not been achieved conventionally. That is, an object of the present invention is to provide an electrophotographic photosensitive member that can be suitably used in a digital high-speed electrophotographic process using a laser as a writing light source, which has become mainstream in recent years. In other words, its main purpose is to achieve a high-speed response that has a sufficient light attenuation response even in an extremely short pulse exposure by a laser exposure and that can cope with a reduction in the electrophotographic process time due to the aforementioned small-diameter drum. It is an issue. Another object of the present invention is to provide a photoconductor having excellent mechanical durability, which is a problem in making the photoconductor thinner in order to increase the definition of an output image. Still another object is to provide an image forming method and apparatus having excellent mechanical durability.

[0005]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that the thickness of the photosensitive layer or the charge transport layer and the mobility of the photosensitive layer or the charge transport layer are constant. Has been found to be able to provide a photoreceptor having a good light decay time even in light decay by short-time pulsed light, and can respond to a stable high-speed electrophotographic process, and completed the present invention. I came to. Further, they have found that a photoreceptor excellent in mechanical durability can be obtained by adding a lubricant as a constituent material of the photoreceptor and allowing the lubricant to be present in the surface layer portion of the photoreceptor layer. Furthermore, a highly durable image forming apparatus having excellent mechanical durability by providing a step (means) for controlling the surface friction coefficient of the photoreceptor as an image forming apparatus using the photoreceptor (electrophotographic process) Was obtained.

That is, according to the present invention, the following photoreceptor is provided. (1) In a laminate type electrophotographic photoreceptor in which at least a charge generation layer and a charge transport layer are laminated on a conductive substrate, the electric field intensity of the charge transport layer is 2.5 × 10 ^{5 to} 5.5 × 10 ⁵ V /. c
An electrophotographic photoreceptor, wherein the charge transport layer thickness / charge transport layer mobility ratio in the range of m is 1.5 × 10 ³ V · s / m or less. (2) The electrophotographic photoreceptor according to the above (1), wherein the charge transport layer contains a charge transport material and a lubricant. (3) The photoconductor for electrophotography according to the above (1) or (2), wherein the charge transporting material contained in the charge transporting layer contains a polymer charge transporting material. (4) The electrophotographic photoreceptor according to the above (2) or (3), further comprising a lubricant having a lubricating action for maintaining a surface friction coefficient of 0.5 or less.

Further, according to the present invention, the following image forming method and electrophotographic process cartridge are provided. (5) (i) charging step, (ii) image exposure step, (iii)
In an image forming method in which an image is formed in a series of steps including a developing step, (iv) a transferring step, and (v) a fixing step, any one of the above-mentioned (1) to (4) is used as a photosensitive member used for the image forming. An image forming method, comprising using the photosensitive member described above and having a step of controlling a friction coefficient of the surface of the photosensitive member. (6) The image forming method as described in (5) above, wherein the coefficient of friction of the photosensitive member surface is controlled to be 0.5 or less. (7) (i) charging step, (ii) image exposure step, (iii)
A process cartridge used in an image forming apparatus that forms an image in a series of steps including a development step, (iv) a transfer step, and (v) a fixing step, wherein the process cartridge is described in any one of (1) to (4) above. An electrophotographic process cartridge comprising a photoreceptor. (8) The electrophotographic process cartridge according to (7), further comprising means for controlling a surface friction coefficient of the photosensitive member.

As a high-speed electrophotographic photoreceptor, for example, JP-A-8-6450 and JP-A-8-62862 each disclose a photosensitive material having a specific range of mobility of an organic charge transporting material. However, it has not been found that a photosensitive member having a constant relationship between the charge transport layer thickness and the charge transport layer mobility as in the present invention can respond to a stable high-speed electrophotographic process. Was. Further, for example, Japanese Patent Laid-Open No.
As described in JP-A-287052 and JP-A-5-165384, those in which a component for reducing the friction coefficient is contained in the surface layer of the photoreceptor are further disclosed in JP-A-6-3422.
No. 36 and JP-A-9-81001, it has been proposed to externally add a component for lowering the coefficient of friction to the surface layer of a photoreceptor. It has not been applied to photoconductors that can be handled as a process. Further, in Japanese Patent Application Laid-Open No. 8-272198, a latent relationship is established by giving a constant relationship between the mobility of the photosensitive layer, the thickness of the photosensitive layer, the moving speed of the image carrier arranged opposite to the photosensitive member, and the electric field intensity of the photosensitive layer. An image forming apparatus that prevents image flow due to image disturbance and enables uniform image formation has been disclosed.However, this image forming apparatus is disadvantageous for further speeding up due to its configuration. In addition, this apparatus is intended to prevent image deletion due to a time lag between the photosensitive layer and the image carrier, and is different from the present invention. The present invention provides a photosensitive member having a constant relationship between the photosensitive layer thickness and the photosensitive layer mobility or the charge transport layer thickness and the charge transport mobility, and by using this photosensitive member, a stable high-speed electrophotographic process. However, in this case, the thickness of the photosensitive layer or the thickness of the charge transport layer has a particularly large effect on the enhancement of the definition of the output image.
For example, in the case of a stack type negatively charged OPC, electrons of the positive and negative carriers generated in the charge generation layer by the exposure light are absorbed by the substrate, but holes move through the charge transport layer and re-combine with the electrons on the photoreceptor surface. Combine and disappear. With this annihilation,
The electric field that pulls up the hole to the photoreceptor surface gradually weakens, and the hole moves toward an unlit area. This is called a diffusion phenomenon of the carrier in the direction of the surface of the photoreceptor, which hinders the formation of a latent image faithful to the exposure light, and causes image deterioration such as a reduction in resolution.
The charge transport thickness has a large effect on this diffusion phenomenon,
Reducing the layer thickness is very effective for maintaining the resolution. Furthermore, unlike the exposure exposure, such as a conventional halogen lamp in the laser exposure that has recently become mainstream, the incident photon flux in relation to the exposure, as compared with the case of the halogen lamp, about ¹⁰⁷ times larger. As a result, the generated carrier density becomes extremely large, and the electric charge flowing into the charge transport layer weakens the electric field of the charge generation layer, which affects the carrier movement speed and delays the carrier generated near the center of the laser beam from reaching the photoconductor surface. It will also be.
The space charge distribution thus generated tends to cause carrier diffusion in the direction parallel to the surface of the photoreceptor, and has a greater effect on resolution reduction. It is important to note that the use of a charge transport material having high mobility is effective in suppressing the diffusion of carriers in a direction parallel to the surface of the photoreceptor.

[0009]

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 and FIG. 2 are explanatory cross-sectional views of the laminated photoreceptor of the present invention, and show a charge generation layer 17 mainly composed of a charge generation material and a charge transport layer 1 mainly composed of a charge transport material.
9 has a laminated configuration.

The conductive support 11 has a volume resistance of 10
Those exhibiting a conductivity of ¹⁰ Ωcm or less, for example, aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum and other metals, tin oxide, indium oxide and other metal oxides, by vapor deposition or sputtering, in the form of a film. Or a cylindrical plastic, one coated with paper, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc.
A tube or the like surface-treated by polishing or the like can be used.

The charge generation layer 17 is a layer containing a charge generation material as a main component. Inorganic and organic materials are used for the charge generating material, and representative examples thereof include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, and squaric acid dyes. Phthalocyanine pigments, naphthalocyanine pigments, azulhenium salt dyes, selenium, selenium-tellurium, selenium-arsenic alloys, amorphous silicon, and the like. The charge generating material may be used alone or
Two or more kinds are used in combination.

The charge generation layer 17 is prepared by dispersing a charge generation material together with a suitable binder resin using a suitable solvent such as tetrahydrofuran, cyclohexanone, dioxane, 2-butanone, or dichloroethane using a ball mill, an attritor, a sand mill, or the like. Can be formed. Application is dip coating, spray coating,
It can be performed using a bead coating method or the like. As the binder resin appropriately used, polyamide, polyurethane, polyester, epoxy resin, polyketone,
Examples thereof include polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, and polyacrylamide. An appropriate amount of the binder resin is appropriately 0 to 2 parts by weight based on 1 part by weight of the charge generating material. The charge generation layer 17 can also be provided by a known vacuum thin film manufacturing method. The thickness of the charge generation layer 17 is 0.01 to
About 5 μm is appropriate, and preferably 0.1 to 2 μm.

The charge transport layer 19 can be formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent, and applying and drying this. If necessary, a plasticizer or a leveling agent can be added. Among the charge transport materials, low-molecular charge transport materials include a hole transport material and an electron transport material.

Examples of the electron transporting material include chloranil, bromanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,
4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4
ON, 1,3,7-trinitrodibenzothiophene-
Electron accepting substances such as 5,5-dioxide are exemplified. These electron transport materials can be used alone or as a mixture of two or more.

As the hole transporting material, the following electron donating substances can be mentioned, and they are preferably used. For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9-
(P-diethylaminostyrylanthracene), 1,1
-Bis- (4-dibenzylaminophenyl) propane,
Styryl anthracene, styryl pyrazoline, phenylhydrazone, α-phenylstilbene derivative, thiazole derivative, triazole derivative, phenazine derivative,
Examples include acridine derivatives, benzofuran derivatives, benzimidazole derivatives, and thiophene derivatives. These hole transport materials can be used alone or as a mixture of two or more.

Further, as the charge transporting material, a polymer charge transporting material is dissolved or dispersed in an appropriate solvent,
The charge transport layer may be formed by drying. As the polymer charge transporting material, a known material having a charge transporting substituent described in the aforementioned low molecular weight charge transporting material in a main chain or a side chain can be used. Also, if necessary, a suitable binder resin other than the polymer charge transport material, a low molecular charge transport material,
An appropriate amount of a plasticizer, a leveling agent, a lubricant or the like can be added.

As the binder resin used in the charge transport layer 19 together with the charge transport material, polystyrene, styrene-acrylonitrile copolymer, styrene butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride , Vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene,
Thermoplastic or thermosetting resins such as acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, and alkyd resin are exemplified. As the solvent, tetrahydrofuran, dioxane, toluene, 2-butanone, monochlorobenzene, dichloroethane, methylene chloride and the like are used. The thickness of the charge transport layer 19 may be appropriately formed in the range of 5 to 30 μm according to desired characteristics of the photoconductor.

In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer 19. As a plasticizer,
Dibutyl phthalate, dioctyl phthalate and the like, which are frequently used as plasticizers for general resins, can be used as they are, and the amount of the plasticizer is 0 to 30 with respect to the binder resin.
A suitable amount is about weight%. As the leveling agent, silicone oils such as dimethyl silicone oil and methyl phenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in a side chain are used. % Is appropriate.

In the present invention, the electric charge contained in the photosensitive layer
The content of the charge transporting material is 40% by weight or more of the charge transporting layer.
Is preferred. Preferably it is 45 to 50%. 4
If the amount is less than 0% by weight, pulse light exposure of 5 μs or less
In light, the amount of light used in high-speed electrophotographic processes
Sufficient light decay time is not achievable. Photoreceptor of the present invention
Has a mobility of 2.5 × 10^Five~ 5.5
× 10^FiveCondition of electric field strength of charge transport layer in the range of V / cm
And 3 × 10^-Fivecm^Two/ V · s or more
7 × 10^-Fivecm^Two/ V · s or more
Good. This mobility achieves this under each use condition
The configuration can be appropriately adjusted as described above. This mobility is conventionally known
Can be obtained by the TOF method, and a sample for measurement is separately provided.
Polyester having translucent aluminum electrode of similar composition
A film is formed on a tellurium film to a thickness of about 7.5 μm, and
A 50 ° gold electrode is formed and used as a sample. The mobility measurement is
Using a pulsed nitrogen laser as the light source and an aluminum electrode
Irradiate light from the side and calculate the mobility from the transient photocurrent waveform
You. The measurement is performed at room temperature (25 ° C.). In addition, the charge generation layer
Xerography for laminated photoreceptor with charge transport layer
The charge transport layer mobility by the time-of-flight method
You can ask. In this case, the photoconductor is charged and
Pulse light from a non-flash lamp (pulse half width ≤
5μs) and the surface potential change at that time
It measures with an electrometer (TREK362A). Light pulse
The mobility is calculated from the surface potential decay characteristics immediately after the irradiation.
Charge transport layer thickness / charge transport layer movement in photoreceptor of the present invention
The degree ratio is 1.5 × 10 ^ThreeV · s / m or less, preferably
1.0 × 10^ThreeV · s / m or less. Note that charge transport
When the material is a polymer charge transport material, the charge transport function
Each having at least 40% by weight of the charge transport layer
It is preferred that

In the electrophotographic photoreceptor of the present invention, an undercoat layer can be provided between the conductive support 11 and the photosensitive layer. The undercoat layer generally contains a resin as a main component. However, considering that the photosensitive layer is coated thereon with a solvent, these resins are resins having high solubility resistance to general organic solvents. desirable. Such resins include polyvinyl alcohol, casein, water-soluble resins such as sodium polyacrylate, copolymerized nylon, alcohol-soluble resins such as methoxymethylated nylon, polyurethane, melamine resin, alkyd-melamine resin, epoxy resin, and the like. Curable resins that form a three-dimensional network structure are exemplified.

In order to prevent moiré and reduce residual potential, fine powder of a metal oxide exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide, etc. may be added to the undercoat layer. Good. These undercoat layers can be formed using an appropriate solvent and a coating method as in the above-described photosensitive layer. Further, as an undercoat layer of the present invention, a silane coupling agent, a titanium coupling agent,
A metal oxide layer formed by, for example, a sol-gel method using a chromium coupling agent or the like is also useful. In addition, the undercoat layer of the present invention is provided with Al ₂ O ₃ by anodic oxidation, an organic substance such as polyparaxylylene (parylene), SiO, SnO ₂ , TiO ₂ , ITO, CeO ₂ And the like provided with an inorganic substance by a vacuum thin film production method can also be used favorably. The thickness of the undercoat layer is suitably from 0 to 5 μm.

In the electrophotographic photosensitive member of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. Materials used for this are ABS resin, A
CS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallyl sulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyether sulfone, polyethylene, Polyethylene terephthalate, polyimide, acrylic resin, polymethylpentene,
Resins such as polypropylene, polyphenylene oxide, polysulfone, AS resin, AB resin, BS resin, polyurethane, polyvinyl chloride, polyvinylidene chloride, and epoxy resin. For the purpose of improving abrasion resistance, the protective layer may be made of a fluororesin such as polytetrafluoroethylene, a silicone resin, or a material in which an inorganic material such as titanium oxide, tin oxide or potassium titanate is dispersed in these resins. Can be added. As a method of forming the protective layer,
A normal coating method is employed. The thickness of the protective layer is
About 0.5 to 10 μm is appropriate. In addition to the above, known materials such as iC and a-SiC formed by a vacuum thin film manufacturing method can also be used as the protective layer.

In the present invention, another intermediate layer may be provided between the photosensitive layer and the protective layer. In the middle layer,
Generally, a binder resin is used as a main component. These resins include polyamide, alcohol-soluble nylon,
Water-soluble polyvinyl butyral, polyvinyl butyral,
Polyvinyl alcohol and the like. As a method for forming the intermediate layer, a normal coating method is employed as described above.
The thickness of the intermediate layer is suitably about 0.05 to 2 μm.

In the second, third or fourth electrophotographic photoreceptor of the present invention, at least one layer from the surface farthest away from the conductive substrate contains a charge transporting material, and the outermost surface of the photoreceptor A lubricant that improves the coefficient of friction, water repellency, and releasability is used. Examples of the lubricant include fluorine oil, and examples of the fluorine oil include perfluoropolyether oil having a linear structure, and those having an average molecular weight of 2,000 to 9000 can be used. Alternatively, more than that is appropriately selected. When fluorine oil is used, the amount of addition is 0.1 to 5 since it can maintain good binding force in the photoreceptor surface layer when it is contained together with the charge transporting substance and does not hinder film formation. % By weight is preferred. Other lubricants include silicone oils, metal soaps,
Fluororesin and the like can be mentioned.

The inventors of the present invention have studied to realize higher durability of the electrophotographic process. As a result, at least (i) the charging step (means), (ii) the image exposure step (means), (iii) ) In a process (apparatus) for forming an image in a series of steps (means) including a development step (means), (iv) a transfer step (means) and (v) a fixing step (means), It has been found that the provision of a process for controlling the surface friction coefficient on the surface of the photoconductor farthest from the substrate can reduce the wear of the photoconductor. In this case, the surface of the photoconductor farthest from the substrate can be a thin layer of a lubricant supplied and transferred from the outside.

By the way, when the photosensitive layer is scraped,
The electrical characteristics (e.g., charging performance and light attenuation performance) of the photoconductor change, making it impossible to perform a predetermined image forming process, and making it difficult to maintain the quality of the final output hard copy. This film abrasion occurs in the electrophotographic process in all areas where the photoconductor and other imaging units come into contact,
The most problematic unit is the cleaning unit (blade or brush) that mechanically removes the toner remaining on the photoconductor. Although there is wear by other units,
It does not affect the real life. Wear generated in the cleaning unit is mainly divided into two forms. One is abrasion caused by the shearing force generated on the photoconductor and the blade (brush), and the other is abrasion wear in which the toner acts like a grindstone when the toner is sandwiched between the blade (brush) and the photoconductor. It is.

Factors that determine these factors include the structural strength of the photosensitive member, the contact pressure of the cleaning blade (brush), the composition of the toner particles, and the surface friction coefficient (μ) of the photosensitive member. In particular, there is a large correlation between the shearing force at the contact portion between the photoconductor and the cleaning blade (brush), the surface friction coefficient of the photoconductor, and the wear amount thereof. It turns out that you can.

In the present invention, as a method (means) for controlling the friction coefficient of the photoreceptor surface, conventionally known methods and means can be used. In this case, it is preferable to supply a lubricant to the surface of the photoconductor. In order to uniformly supply the lubricant, a brush-like roller, an elastic roller, an elastic blade, a brush, a belt, or the like is used as a contact charging or transfer member or simply as a member for supplying a substance for controlling a surface friction coefficient. be able to.

For the purpose of controlling the surface friction coefficient of the photoreceptor surface characteristics, the lubricant supplied to the photoreceptor surface via contact charging or a transfer member has various lubricating actions such as liquid, solid, and powder. Can be used, and in the case of a solid, it can itself be a functional member. That is, lubricating liquids such as silicone oil and fluorine oil, PTFE / PF
Various types of fluorine-containing resins such as A and PVDF, silicone resins, polyolefin resins, silicone grease, fluorine grease, paraffin wax, fatty acid metal salts such as zinc stearate, graphite, and lubricating solids and powders such as molybdenum disulfide. The object is achieved by supplying the photoreceptor surface in an appropriate manner.

Next, the control method of the friction coefficient of the photosensitive member and its necessity will be described. As described above, when the photoreceptor has a low friction coefficient by the above method, the photoreceptor abrasion amount can be reduced.However, the photoreceptor surface friction coefficient is reduced to 0.5 or less by the Euler belt method. The effect is significant when maintained. On the other hand, when the coefficient of friction is reduced more than necessary, as a problem, when the latent image is visualized by the developing unit, the adhesion between the toner and the photoconductor is reduced, and the toner is not intended to be on the photoconductor. A phenomenon occurs in which transfer cannot be performed. These may occur particularly in a system in which a developer is developed while being in contact with a photoreceptor, such as two-component development. That is, when the developer spike, which is a feature of two-component development, comes into contact with the surface of the photoreceptor, a mechanical force is generated by the spike at the time of contact, and the toner transferred to the photoreceptor may be scraped off again. Phenomenon such as the image being deviated from the normal position is the cause of this problem.

These phenomena hardly occur when the friction coefficient of the surface layer of the photoreceptor is high, and remarkably occur when the surface friction coefficient becomes smaller than 0.1, for example, about 0.05 as measured by the Euler belt method. I will be.
This problem is a fatal problem in hard copy quality, and in order to prevent the occurrence, it is necessary to control the application of the additive so as not to lower the friction coefficient of the photoconductor surface layer more than necessary.

The Euler belt method employed in the present invention as a method for quantifying the photoreceptor surface friction coefficient will be described below. A belt-shaped measuring member, which is obtained by cutting medium-thick high-quality paper so that the paper cutting direction is the longitudinal direction, is brought into contact with a quarter of the outer periphery of the surface of the cylindrical photoreceptor.
0g), and a force gauge is connected to the other side. Then, the force gauge is moved at a constant speed, and the value of the force gauge when the belt starts moving is read and calculated by the following equation. μs = 2 / π × 1n (F / W) where μS: coefficient of static friction F: force gauge reading (g) W: load (100 g)

The necessity of controlling the friction coefficient of the photosensitive member has been described above. ADVANTAGE OF THE INVENTION According to this invention, a low-wear photoreceptor system is provided, and it becomes possible to suppress an abnormal image for a long term and to keep the image normal. The photoreceptor and the image forming means described above may be fixedly incorporated in a copying machine, a facsimile, or a printer, or may be incorporated in the apparatus in the form of a process cartridge. The process cartridge is one device (part) that includes a photoconductor and further includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a charge removing unit. Although there are many shapes and the like of the process cartridge, a general example is shown in FIG. in this case,
The photoreceptor has at least a photosensitive layer on a drum-shaped conductive support.

[0034]

The present invention will now be described in more detail with reference to the following Examples, which are provided only for illustrating the present invention in detail and do not limit the present invention. First, in order to confirm the high-speed response of the photoconductor, a method of measuring the light attenuation response to short pulse exposure will be described. The light decay response to the pulse exposure can be measured, for example, by mounting a Hamamatsu photonic xixenon flash lamp module C5604 (half-width at exposure pulse: 3 μs) as an exposure light source to Kawaguchi Electric EPA8200. At this time, the amount of light is changed using an ND filter to adjust the amount of light attenuation in each sample. The sample was corona-charged to about -500 V and charged to about -1.
The measurement can be performed by giving a pulse exposure that attenuates the light to 00V and taking the response at that time into a storage scope. In the following examples, the half-life of light decay in the above measurement method is shown as a pulse exposure response time. The thickness of the charge transport layer is sloan DEKT.
Using AKIIA, it is measured as a step from the reference plane. The electric field intensity of the charge transport layer is calculated from the charge potential in the electrophotographic process and the thickness of this layer.

Example 1 A charge generation material represented by the following structural formula (a) and polyvinyl butyral (XYC: XY) were placed on an aluminum substrate.
HL) is 0.16 μm in a charge generation layer having a weight ratio of 10: 4.
m was formed. On this, a charge transporting layer represented by the following structural formula (b) and bisphenol A polycarbonate (manufactured by Teijin Chemicals Ltd., Panlite K-1300) having a 1: 1 weight ratio to form a 10 μm charge transporting layer, and a laminated photoreceptor was prepared. Produced.

[0036]

Embedded image

Embedded image

The pulse exposure response time of the photoreceptor manufactured as described above was 0.08 ms. The operation characteristics of the photoconductor of this configuration were examined at a linear speed of 200 mm / s using an in-house electrophotographic process simulator.
It has been found that this linear velocity can be stably handled. Further, a similar photoreceptor was prepared on an aluminum substrate having a diameter of 60 mm, and this photoreceptor was mounted on a modified machine of a copier Imagio MF4550 manufactured by Ricoh Co., Ltd. to perform a copy test.
The time required between the image exposure and the development process of the copying machine is about 1
00 ms. The resolution of the output image was good, showing a resolution of 7.1 lines / mm. At the actual copying speed, no abnormal image due to an increase in the light portion potential due to insufficient sensitivity was not recognized. The mobility of the charge transport layer of the present photoconductor at 4.5 × 10 ⁵ V / cm was 1 × 10 ⁻⁴ cm ^2.
/ V · s, charge transport layer thickness / charge transport layer mobility = 1
× 10 ³ V · s / m.

Example 2 A charge generation layer comprising a charge generation material (a) used in Example 1 and a charge transport material represented by the following structural formula (c) in a weight ratio of 1: 1 on an aluminum substrate 0.21 μm Was formed. A charge transport layer 11 μm of the same charge transport material represented by the following structural formula (c) was formed thereon to produce a laminated photoreceptor.

[0039]

Embedded image

The pulse exposure response time of the photosensitive member manufactured as described above was 0.03 ms. The operation characteristics of the photoconductor of this configuration were examined at a linear speed of 200 mm / s using an in-house electrophotographic process simulator.
It has been found that this linear velocity can be stably handled. Further, the same photoreceptor was attached to a modified machine of a copier IMAGIO MF4550 manufactured by Ricoh Co., Ltd. in the same manner as in Example 1, and a copying test was performed. The resolution of the output image was good, showing a resolution of 6.3 lines / mm, and no abnormal image was observed even at the actual copying speed due to an increase in the light portion potential due to insufficient sensitivity. The mobility of the charge transport layer of the present photoconductor at 4.0 × 10 ⁵ V / cm was 5 × 10 ⁻⁴ c.
m ² / V · s, and charge transport layer thickness / charge transport layer mobility = 2.2 × 10 ² V · s / m.

Example 3 The same charge generation layer as in Example 1 having a thickness of 0.16 μm was formed on an aluminum substrate. A charge transporting layer (9 μm) having a 1: 1 weight ratio of the charge transporting material (b) used in Example 1 and the charge transporting material (c) used in Example 2 was formed thereon, thereby producing a laminated photoreceptor. .

The pulse exposure response time of the photoreceptor manufactured as described above was 0.03 ms. The operation characteristics of the photoconductor of this configuration were examined at a linear speed of 200 mm / s using an in-house electrophotographic process simulator.
It has been found that this linear velocity can be stably handled. Further, the same photoreceptor was attached to a modified machine of a copier IMAGIO MF4550 manufactured by Ricoh Co., Ltd. in the same manner as in Example 1, and a copying test was performed. The resolution of the output image was good, showing a resolution of 6.3 lines / mm, and no abnormal image was observed even at the actual copying speed due to an increase in the light portion potential due to insufficient sensitivity. The mobility of the charge transport layer of the photoreceptor at 4.5 × 10 ⁵ V / cm is 2 × 10 ⁻⁴ c.
m ² / V · s, and charge transport layer thickness / charge transport layer mobility = 4.5 × 10 ² V · s / m.

Comparative Example 1 A charge generating material represented by the following structural formula (d) and polyvinyl butyral (XYC: XY) were placed on an aluminum substrate.
HL) having a weight ratio of 3: 1 to form a charge generation layer of 0.2 μm. A charge transporting layer (20 μm) was formed on the charge transporting material (c) used in Example 2 and bisphenol A polycarbonate (manufactured by Teijin Chemicals Limited, Panlite K-1300) in a weight ratio of 1: 1. Was prepared.

[0044]

Embedded image

The pulse exposure response time of the photoreceptor manufactured as described above was 1.2 ms. In addition, the photoconductor of this configuration is used for the internal electrophotographic process simulator.
When the operating characteristics were examined at a linear speed of 00 mm / s, it was found that the response speed was insufficient, and the linear velocity could not be accommodated. In addition, 4.5 × 10 ⁵ of the charge transport layer of the present photoreceptor.
The mobility at V / cm is 3 × 10 ⁻⁵ cm ² / V · s, and the charge transport layer thickness / charge transport layer mobility = 6.7 × 10 ³
V · s / m.

Comparative Example 2 The charge transporting layer of Example 1 was composed of a charge transporting material represented by the structural formula (b) and bisphenol A polycarbonate (manufactured by Teijin Chemicals Ltd., Panlite K-1300) in a weight ratio of 3: 7. A laminated photoconductor was prepared in the same manner as in Example 1, except that the charge transport layer was set to 19 μm.

The pulse exposure response time of the photosensitive member manufactured as described above was 2.5 ms. In addition, the photoconductor of this configuration is used for the internal electrophotographic process simulator.
When the operating characteristics were examined at a linear speed of 00 mm / s, it was found that the response speed was insufficient, and the linear velocity could not be accommodated. In addition, 4.5 × 10 ⁵ of the charge transport layer of the present photoreceptor.
The mobility at V / cm is 2 × 10 ⁻⁵ cm ² / V · s, and the charge transport layer thickness / charge transport layer mobility = 9.5 × 10 ³
V · s / m.

Example 4 A charge generating layer of 0.2 μm in which a charge generating material composed of an oxotitanium phthalocyanine pigment and polyvinylbutyral (XYHL, manufactured by UCC) at a weight ratio of 10: 1 was formed on an aluminum substrate. A 11 μm charge transport layer made of a polymer charge transport material represented by the following structural formula (e) was formed thereon, and a laminated photoreceptor was produced.

[0049]

Embedded image

The pulse exposure response time of the photosensitive member manufactured as described above was 0.7 ms. In addition, the photoconductor of this configuration is used for the internal electrophotographic process simulator.
The operation characteristics were examined at a linear velocity of 00 mm / s, and it was found that the linear velocity could be stably accommodated. Further, the same photoreceptor was mounted on a copying machine IMAGIO MF4550 manufactured by Ricoh Co., Ltd. in the same manner as in Example 1, and a copying test was performed. The resolution of the output image was good, showing a resolution of 6.3 lines / mm, and no abnormal image was observed even at the actual copying speed due to an increase in the light portion potential due to insufficient sensitivity. The charge transport layer of the present photoconductor was 4.5 ×
The mobility at 10 ⁵ V / cm is 1 × 10 ⁻⁴ cm ² / V · s
And the thickness of the charge transport layer / the mobility of the charge transport layer = 1.1 × 1
0 ³ V · s / m.

Example 5 In Example 1, the charge transport layer was further provided with a fluorine oil (perfluoropolyether oil: Demnum S-10).
0 / manufactured by Daikin Industries, Ltd.) was prepared in the same manner as in Example 1 except that 0.2% by weight was contained.

The obtained photoreceptor pulse exposure response time was 0.5.
It was 25 ms. The operation characteristics of the photoreceptor of this configuration were examined at a linear speed of 200 mm / s using an in-house electrophotographic process simulator. As a result, it was found that the photoreceptor could stably cope with this linear speed. Furthermore, when the characteristics of the same photoconductor were examined using an in-house wear tester,
Even after a copying load of 100,000 sheets was applied to the copying machine, the coefficient of friction against paper was 0.5 or less.

Example 6 In Example 2, a fluorine oil (perfluoropolyether oil: Demnum S-10) was further added to the charge transport layer.
0 / manufactured by Daikin Industries, Ltd.) was prepared in the same manner as in Example 2 except that 0.2% by weight was contained.

The pulse exposure response time of the obtained photoreceptor was 0.19 ms. Further, the photoconductor of this configuration was manufactured at 200 mm / s using an in-house electrophotographic process simulator.
When the operating characteristics were examined at the linear velocity, it was found that the linear velocity could be stably supported. Furthermore, the characteristics of the same photoreceptor were examined using an in-house abrasion tester. The coefficient of friction against paper was 0.5 or less even after a copying load of 100,000 sheets was given to the copier. Was.

Example 7 A laminated photoreceptor was produced in the same manner as in Example 3, except that the charge transport layer further contained 0.3% by weight of zinc stearate.

The pulse exposure response time of the obtained photoreceptor was 0.22 ms. Further, the photoconductor of this configuration was manufactured at 200 mm / s using an in-house electrophotographic process simulator.
When the operating characteristics were examined at the linear velocity, it was found that the linear velocity could be stably supported. Further, when the characteristics of the same photoreceptor were examined using an in-house abrasion tester, the coefficient of friction against paper was 0.5 or less even after a copying load of 100,000 sheets was given by a copying machine. there were.

Comparative Example 3 The characteristics of a photoreceptor having the same structure as in Comparative Example 1 were examined using an in-house abrasion tester. Coefficient of friction is 0.6
That was all.

Comparative Example 4 The characteristics of a photoreceptor having the same structure as in Comparative Example 2 were examined using an in-house abrasion tester. Coefficient of friction is 0.6
That was all.

Example 8 A laminated photoreceptor was produced in the same manner as in Example 4, except that the charge transport layer further contained 0.2% by weight of lead stearate.

The pulse exposure response time of the obtained photoreceptor was 0.83 ms. Further, the photoconductor of this configuration was manufactured at 200 mm / s using an in-house electrophotographic process simulator.
When the operating characteristics were examined at the linear velocity, it was found that the linear velocity could be stably supported. Further, when the characteristics of the same photoreceptor were examined using an in-house abrasion tester, the coefficient of friction against paper was 0.5 or less even after a copying load of 100,000 sheets was given by a copying machine. there were.

Example 9 A photoreceptor drum having the same configuration as that of Example 1 was manufactured and mounted on an internal copy tester. The copying tester was provided with a friction coefficient reducing member between cleaning and charging so as to be always in contact with the photosensitive member. As a friction coefficient reducing member, urethane foam L manufactured by INOAC Co., Ltd. on a stainless steel support
Nichias PTFE sheet T / # 90 via E20
01 was attached. 10
Even after a copying load equivalent to 10,000 sheets was applied, the friction coefficient against paper was 0.5 or less.

Example 10 A photoreceptor drum having the same structure as in Example 2 was manufactured and its characteristics were examined using the same copying tester as in Example 9.
Even after a copying load of 100,000 sheets was applied on a copying test machine, the friction coefficient against paper was 0.5 or less.

Example 11 A photosensitive drum having the same structure as in Example 3 was manufactured, and its characteristics were examined using the same copying test machine as in Example 9. In addition,
In this case, a cleaning brush is diverted as a friction coefficient reducing member, and a PTFE powder Lubron L manufactured by Daikin is used.
While supplying 2, the same portion as in Example 9 was rotated and contacted in the opposite direction to the photosensitive member. Also in this case, 1
The friction coefficient against paper after applying a copying load equivalent to 100,000 sheets was 0.5 or less.

Example 12 A photoreceptor drum having the same structure as that of Example 4 was manufactured and its characteristics were examined by using the same copying test machine as in Example 11. Even after application of the load, the coefficient of friction on the paper was 0.5 or less.

[0065]

The photoreceptor for electrophotography of the present invention has a constant relationship between the thickness of the charge transport layer and the mobility of the charge transport layer, so that the photoreceptor has good light attenuation by short-time pulsed light. It is a photoreceptor having a light decay time, and is suitable as a high-sensitivity electrophotographic photoreceptor capable of coping with a stable high-speed electrophotographic process.

Further, according to the present invention, by including a lubricant in the surface layer of the photoreceptor, mechanical durability and abrasion resistance, which are problems in thinning the photoreceptor for the purpose of achieving higher definition of an output image, are provided. It is possible to provide a highly durable electrophotographic photoreceptor having excellent durability.

According to the image forming apparatus of the present invention, a highly durable image forming method having high mechanical durability is provided by using the above-mentioned photoreceptor and further providing a step of controlling the surface friction coefficient of the photoreceptor. , Device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a layer configuration of a laminated electrophotographic photoconductor of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating another example of the layer configuration of the laminated electrophotographic photosensitive member of the present invention.

FIG. 3 is an explanatory view of an electrophotographic process cartridge.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 conductive support 15 single-layer photosensitive layer 17 charge generation layer 19 charge transport layer 101 photosensitive drum 102 charging device 103 exposure 104 developing device 105 transfer member 106 transfer device 107 cleaning blade 108 static elimination lamp 109 fixing device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Minoru Umeda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Masao Yoshikawa 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Inside Ricoh Company (72) Inventor Hiroshi Nagame 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh (72) Inventor Ryuta Takeichi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Akiyo Nakajima 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (8)

[Claims] 1. A laminated electrophotographic photosensitive member comprising at least a charge generation layer and a charge transport layer laminated on a conductive substrate, wherein the electric field intensity of the charge transport layer is 2.5 × 10 ^{5 to} 5.5 × 1.
0 charge in a range of ⁵ V / cm transport layer thickness / charge transporting layer electrophotographic photoreceptor, wherein the mobility ratio is less ^{1.5 × 10 3 V · s /} m. 2. The electrophotographic photosensitive member according to claim 1, wherein the charge transport layer contains a charge transport material and a lubricant. 3. The electrophotographic photoreceptor according to claim 1, wherein the charge transporting material contained in the charge transporting layer contains a polymer charge transporting material. 4. The electrophotographic photoconductor according to claim 2, further comprising a lubricant having a lubricating action for maintaining a surface friction coefficient of 0.5 or less. 5. An (i) charging step, (ii) an image exposing step,
5. An image forming method in which an image is formed in a series of steps including (iii) a developing step, (iv) a transferring step, and (v) a fixing step, wherein the photosensitive member used for the image forming is used.
An image forming method, comprising using the photoconductor of any one of the above, and controlling a friction coefficient of the surface of the photoconductor. 6. The image forming method according to claim 5, wherein the coefficient of friction of the surface of the photoconductor is controlled to be 0.5 or less. 7. An (i) charging step, (ii) an image exposure step,
A process cartridge used in an image forming apparatus in a series of steps including (iii) a developing step, (iv) a transferring step, and (v) a fixing step, comprising a photoconductor according to any one of claims 1 to 4. Electrophotographic process cartridge. 8. The electrophotographic process cartridge according to claim 7, further comprising means for controlling a surface friction coefficient of the photosensitive member.