JP2008225350A - Image forming method, image forming apparatus and process cartridge for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method by which degradation in cleaning property on a spherical toner of a small particle size due to wear of the cleaning blade can be suppressed by a simple means, preferable cleaning property can be kept without causing cleaning failure, and a stable and excellent image can be obtained in a high-definition electrophotographic process, and to provide an image forming apparatus and a process cartridge for an image forming apparatus. <P>SOLUTION: The image forming method, the image forming apparatus and the process cartridge are characterized in that: at least a photoreceptor 19 is subjected to processes of charging, image-wise exposure, development, transfer, fixing and cleaning; a cleaning unit performing the cleaning process has a rectangular elastic material blade 20; the contact angle of the elastic material blade 20 on the photoreceptor 19 is changed in a single stage in accordance with the operation time; and simultaneously, changes in the contact pressure to the photoreceptor 19 caused by changes in the angle are corrected to keep a constant contact pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming method, an image forming apparatus, and a process cartridge for an image forming apparatus. More specifically, the present invention can suppress the occurrence of poor cleaning in a cleaning portion in an image forming process, and can also be applied to a spherical toner having a small particle diameter. Image forming method, image forming apparatus, and image forming apparatus capable of obtaining good cleaning characteristics and capable of suppressing deterioration of cleaning property against blade wear during use over time and obtaining a stable image The present invention relates to a process cartridge.

An electrophotographic method using the Carlson process and various modifications of this process is widely used in the electrophotographic field such as a copying machine, a facsimile machine, and a printer.
As an electrophotographic photosensitive member used in this electrophotographic method (hereinafter sometimes simply referred to as a photosensitive member), organic photosensitive materials have been widely used in recent years because of advantages such as low cost, mass productivity, and non-pollution. In addition, various measures have been taken for durability, such as addition of a protective layer.
Further, as a toner used in this electrophotographic method, in addition to stabilization of charging, there is an increasing demand for a reduction in particle size and spheroidization, in addition to stabilization of charging.
In order to improve the functions of such an electrophotographic supply, it has become necessary to improve the functions and optimization of the components related to them to achieve high durability and high image quality. In particular, the technique related to cleaning is closely related to each element of the electrophotographic process and has a great influence on the output image.

  As the durability of photoconductors, mechanical durability, mainly wear resistance, has been strongly demanded. However, in conventional organic photoconductors (OPC) and electrophotographic processes using the photoconductor, Due to the low wear resistance, it is clear that sufficient durability has not been obtained, and on the other hand, it has become clear that the thinning of the photosensitive layer is essential for high definition of the output image, The margin for wear is becoming stricter.

Here, since these wear phenomena are mainly caused by the cleaning process, the cleaning unit as a contact member to the photosensitive member and the toner related to the cleaning are greatly affected. And optimization are essential.
More importantly, the reduction in particle size and spheroidization of the toner used clearly reduces the cleaning margin, and cannot be handled by simply changing the setting conditions of a conventional cleaning device. Therefore, it is necessary to develop a new cleaning method and apparatus. The small particle size and spherical toner referred to here is a toner having an average particle size of 5.5 μm or less and a circularity of 0.97 or more for the purpose of improving the image quality, and it is a problem to ensure a sufficient cleaning capability. ing.

  As a manufacturing method for reducing the toner particle size, the polymerization method is effective rather than the conventional pulverization method from the viewpoint of manufacturing cost, and the small particle size toner manufactured by the polymerization method has a nearly spherical shape and a particle size distribution. Since it is sharp, it has excellent reproducibility of fine lines and dot reproducibility of digital images, and can achieve high image quality.

With respect to the above-mentioned problems related to cleaning, the occurrence of cleaning failure due to wear of the contact portion of the blade has become a major problem, particularly in the case of small particle size and spherical toner. In this situation, it is important to maintain and control the contact state of the blade in accordance with the disturbance. For example, a means for detecting the surface state of the image carrier that contacts the blade is provided and cleaning is performed. The mechanism that controls the contact pressure and contact angle of the member changes the contact pressure and contact angle according to the surface state of the image carrier, thereby suppressing the occurrence of defective cleaning due to an increase in the coefficient of friction over time. Is disclosed (for example, see Patent Document 1).
In addition, there is a configuration in which guide means and urging means are configured so that the contact load of the blade can be automatically adjusted according to a change in the frictional force between the photosensitive drum and the blade, and a stable cleaning state is maintained. It is disclosed (for example, see Patent Document 2).
Further, the blade is configured to abut against the photosensitive drum with two rollers, and the blade is supported by a shaft provided on a frame body integrally formed with the roller receiving portion so that the blade can be bent. A device that controls the contact state with the drum surface with high accuracy and exhibits a stable cleaning function at all times is disclosed (see, for example, Patent Document 3).

However, all the cleaning methods related to the cleaning blade described above are complicated in mechanism and inevitable in cost increase, and it is not possible to effectively avoid deterioration in cleaning performance against the irreversible phenomenon of blade wear. . The fact is that it is still not sufficient in terms of extending a stable cleaning property by a simple means for a small particle size and spherical toner.
JP 2000-172026 A JP 200384637 A JP 2003-307984 A

  The object of the present invention is to solve such disadvantages of the prior art, and in particular, can be applied to a high-endurance digital high-speed electrophotographic process using a laser beam as a writing light source that has become mainstream in recent years. Image forming method, image forming apparatus, and image forming apparatus capable of suppressing deterioration of cleaning property due to wear of cleaning blade with respect to particle size and spherical toner and obtaining excellent image by stable cleaning device that does not cause defective cleaning It is an object to provide a process cartridge for use.

  In order to solve the above-mentioned problems, the present inventors have intensively studied with a particular focus on a cleaning unit that performs a cleaning process. As a result, the present invention has been completed. The present invention is as follows.

1. In an image forming method in which charging, image exposure, development, transfer, fixing, and cleaning processes are performed on at least a photoconductor, a cleaning unit that performs the cleaning process includes a strip-shaped elastic blade, An image characterized in that the contact angle to the photoconductor is changed by one step according to the operation time, and at the same time, the change in the contact pressure to the photoconductor due to the change in angle is corrected to keep the contact pressure constant. Forming method.
2. The elastic blade is brought into contact with the photosensitive member by a constant displacement method, and the angle formed between the tip cut surface and the photosensitive member contacting surface is increased by one step according to the operation time, and at the same time, the photosensitive member at the tip of the elastic blade. 2. The image forming method as described in 1 above, wherein the amount of biting into the surface is increased to keep the contact pressure constant.
3. 3. The image forming method as described in 1 or 2 above, wherein the elastic blade is made of urethane rubber and has a hardness of 70 to 78 degrees (JIS A) at 25 ° C. and a rebound resilience of 17 to 68%. .
4). 4. The image forming method according to any one of 1 to 3, wherein the photoreceptor has a protective layer, and the protective layer contains inorganic fine particles made of alumina or titanium oxide.
5. 5. The image forming method as described in 4 above, wherein the protective layer contains a charge transport material.
6). 6. The image forming method as described in any one of 1 to 5 above, wherein the toner used for the development processing has a volume average particle size of 5.5 μm or less and a circularity of 0.97 or more.
7). At least the photosensitive member includes a charging unit that performs a charging process, an image exposure unit that performs an image exposure process, a developing unit that performs a developing process, a transfer unit that performs a transferring process, a fixing unit that performs a fixing process, and a cleaning unit that performs a cleaning process. In the image forming apparatus, the cleaning unit in the cleaning unit has a strip-shaped elastic blade, the contact angle of the elastic blade to the photosensitive member is changed by one step according to the operation time, and the angle is changed simultaneously. An image forming apparatus, wherein the contact pressure is kept constant by correcting a change in contact pressure on the photosensitive member due to the above.
8). The strip-shaped elastic blade is brought into contact with the photosensitive member by a constant displacement method, and the angle formed between the tip cut surface and the photosensitive member contacting surface is increased by one step according to the operation time, and at the same time, 8. The image forming apparatus as described in 7 above, wherein the amount of biting into the photosensitive member is increased to keep the contact pressure constant.
9. The image forming apparatus according to 7 or 8 above, wherein the elastic blade is made of urethane rubber, and has a hardness of 70 to 78 degrees (JIS A) and a rebound resilience of 17 to 68% at 25 ° C. .
10. 10. The image forming apparatus according to any one of 7 to 9, wherein the photoreceptor has a protective layer, and the protective layer contains inorganic fine particles made of alumina or titanium oxide.
11. 11. The image forming apparatus as described in 10 above, wherein the protective layer contains a charge transport material.
12 12. The image forming apparatus as described in any one of 7 to 11 above, wherein the toner used in the developing unit has a volume average particle size of 5.5 μm or less and a circularity of 0.97 or more.
13. The contact angle to the photosensitive member is changed by one step according to at least the operation time used in the image forming method according to any one of 1 to 6 or the image forming apparatus according to any one of 7 to 12. A process cartridge for an image forming apparatus, comprising a cleaning unit comprising an elastic blade that simultaneously maintains a constant contact pressure by correcting a change in contact pressure against the photosensitive member due to a change in angle.

  As will be apparent from the following detailed and specific description, according to the present invention, it can be preferably applied to a highly durable digital high-speed electrophotographic process using a laser beam that has become a mainstream in recent years as a writing light source. Deterioration of cleaning performance due to wear of the cleaning blade for small particle size and spherical toner is suppressed, good cleaning performance can be secured without causing defective cleaning, and stable and excellent image for high-definition electrophotographic process The image forming method, the image forming apparatus, and the process cartridge for the image forming apparatus can be provided.

The present invention is described in detail below.
The present inventors examined a cleaning method that can suppress the occurrence of defective cleaning. In particular, with respect to small particle size and spherical toner typified by polymerized toner, it was examined in detail how the cleaning can be performed stably.
When a small particle size and spherical toner is used, the cleaning toner that is blocked at the blade tip (edge) is slipped off, resulting in a problem of poor cleaning. As for the particle size, of course, these toner particles have a distribution, but can be almost discussed by the average particle size. When the circularity is 0.94 or less, the particle size is 5 μm. Cleaning is possible even before and after, whereas when the sphere has a circularity of 0.97 or more, the cleaning margin is drastically reduced, and when the particle size is around 5 μm, the conventional blade cleaning device is almost Cleaning is impossible, and the cleaning state varies greatly depending on the characteristics of the toner to be cleaned.
In addition, an external additive is added to the toner in order to improve its fluidity and adjust the chargeability, but the external additive is partly removed from the toner and enters the cleaning section with the external additive alone. To do. This external additive has a very small particle size compared to the toner, and easily passes through the cleaning blade. Accordingly, the external additive is present between the blade edge and the surface of the photosensitive member in the cleaning operation, whereby both the photosensitive member and the cleaning blade are subjected to wear. In addition to abrasion, filming may occur due to the continued pressing of these external additives against the surface of the photoreceptor, and it is not easy to deal with them. In addition to the commonly used external additives, a large particle size external additive may be further added. This large particle size external additive is considered to have an effect of hindering the rotational motility of the spherical toner cleaning, and the cleaning performance margin is improved.

  The use ratio of the external additive may be 0.01 to 5% by weight of the toner, and preferably 0.01 to 2.0% by weight. Examples of external additives include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, Examples thereof include chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.

  On the other hand, when the abrasion state of the blade tip in contact with the photosensitive member was examined in more detail, it was found that the wear amount with time was very large in the small particle size and spherical toner as compared with the conventional pulverized toner. The cause of this is not clear, but it is presumed that the decrease in the cleaning margin due to the small particle size and the spherical shape was affected, and the increase in the amount of toner passing through the blade is considered to be one factor. Further, it is confirmed from the detailed observation of the wear state that the wear often occurs from the cut surface of the blade, which is considered to be a result of the wear action while the blade edge is drawn in the photosensitive member operating direction. The present invention was obtained as a result of intensive studies aimed at suppressing the deterioration of the cleaning performance as much as possible even when subjected to such wear action, and it is one of the reasons to extend the use limit of the blade due to wear. Is the purpose.

  Here, the deterioration of the cleaning property due to wear of the blade edge will be considered. First, when there is no wear, an edge portion formed by cutting is clearly present, and the toner is blocked or scraped at that portion, and the toner does not enter downstream from the blade. This is because the contact surface is narrow and the contact surface pressure is high, so that the toner cannot be caught between the blade and the photosensitive member. On the other hand, when the blade edge is worn, the clear edge portion disappears, and in the micro contact area at the contact is enlarged and the contact surface pressure is reduced, so that the toner easily moves between the blade and the photoconductor. It will be overgrown. As a result, the amount of toner that passes through the blade increases, resulting in poor cleaning. Although it is possible to recover the contact surface pressure by increasing the contact pressure against the expansion of the contact surface due to wear, the blade deformation increases due to the increase in applied pressure, and the drive torque There is a problem such as an increase of

In the present invention, it has become clear that the following measures are effective for the above-described problems. The wear blade is brought into contact with an angle formed by the tip cut surface and the photosensitive member contact surface, which is increased from the initial angle.
Here, as shown in FIG. 6, the angle formed by the tip cut surface and the photosensitive member abutting surface is that of the blade 61 with respect to the tangent 63 on the surface of the photosensitive member 60 at the contact 62 between the photosensitive member 60 and the blade 61. This is the angle θ of the cut surface 611. Note that the arrow indicates the rotation direction of the photoconductor 60.

  The initial blade edge disappears due to wear, but a second obtuse angled edge is newly generated at both ends of the wear portion, so that the contact condition is changed to use the edge portion. In the new edge part that occurs secondary due to wear, the one on the cut surface side is less likely to have an edge shape due to the influence of erosion wear, and in order to use this edge, the angle formed with the contact surface of the photoconductor is reduced. In this case, it is not preferable because the blade is likely to be twisted. Therefore, a new contact state is formed by using the edge portion on the contact surface side, but the contact pressure is reduced because the blade is in a positional relationship with respect to the surface of the photoconductor than the initial state. Therefore, it is preferable to increase the amount of biting of the blade into the photoreceptor. As a result, the contact pressure drop in the constant displacement method can be corrected.

  However, as a result of the examination, it has become clear that sufficient cleaning performance can be obtained with the same pressure as the initial contact pressure. The increase in the contact angle is suitably 3 to 5 degrees. If the angle is larger than 5 degrees, the blade tends to hit against the surface of the photosensitive member, resulting in a decrease in cleaning performance. It is difficult to obtain the effect of recovering the influence of wear. Further, in the present invention, the increase setting of the angle is set to one stage because the angle setting range is narrow. Further, “one-step change” as used in the present invention means that the contact angle is changed sequentially instead of continuously, so that the new edge portion caused by the above-mentioned wear can be effectively used. Can do.

The blade contact condition change can be easily performed, for example, as follows. FIG. 3 is a schematic view of a blade positioning structure used in the present invention. In FIG. 3, components and driving mechanisms other than the photoreceptor and the blade are omitted.
In FIG. 3, the blade is a strip-shaped elastic blade 20, extending over the entire width direction of the photoconductor 19, and its blade edge is in contact with the surface of the photoconductor 19. A part of the elastic blade is supported by a blade sheet metal holder 21, and the blade sheet metal holder 21 is fixed to the photosensitive cartridge side plate 22. The fixing location of the blade sheet metal holder 21 is determined by a blade positioning fixing portion 23 provided on the photosensitive member cartridge side plate 22. As a result, depending on the installation location of the blade positioning fixing portion 23, the tip cut surface of the elastic blade 20 and the photosensitive member are fixed. The angle formed by the contact surface with 19 is determined. When the elastic blade 20 is worn due to the lapse of the operating time of the elastic blade 20, the photosensitive cartridge side plate 22 is removed, and another photosensitive cartridge side plate in which the installation position of the blade positioning fixing portion 23 is changed is newly attached. . The timing of replacement depends on the shape and material of the toner to be used, the properties of the surface of the photoreceptor, etc., and the relationship between them may be determined in advance through preliminary experiments or the like. In this other photoconductor cartridge side plate, the installation location of the blade positioning and fixing portion 23 is changed so that the above-described one-stage change is made. In this way, it is possible to easily change the contact condition of the blade.

As a material of urethane applied to the elastic blade, a material having a hardness of 70 to 78 degrees (JIS A) at 25 ° C. and a rebound resilience of 17 to 68% can be used. High impact resilience urethane has the best properties for small particle size and spherical toner, but it is actually inferior in abrasion resistance, while low resilience urethane has good abrasion resistance but small particle size The spherical toner is inferior in cleaning property, and particularly, when there is a large amount of toner input, poor cleaning tends to occur. By reducing the coefficient of friction on the surface of the photoconductor, it is possible to improve the cleaning margin even for small particle size and spherical toner. The coefficient of friction is reduced to 0.2 or less by a method such as externally supplying a lubricant. If maintained, any blade belonging to the above characteristic range can be used. Since the degree of wear resistance varies depending on the blade material, grasp the progress of wear in advance, and change the contact condition of the blade with the usage limit estimated from the wear information as a target in actual use. . Specifically, the wear width occurring on the abutting surface side with respect to the cut surface of the blade is about 10 μm, which is the limit that can maintain the cleaning performance. At that time, the blade contact setting is switched.
In addition, about the wear condition of the edge front-end | tip, the shape can be expanded and observed with the ultra deep shape measurement microscope VK8500 etc. by Keyence, for example, and it can evaluate including a wear dimension.

Next, the photoconductor used in the present invention will be described.
The photosensitive member may be either a single layer or a stacked layer, but a function separation type stacked type will be described as an example.
FIG. 1 is a schematic cross-sectional view of a multilayer electrophotographic photosensitive member used in the present invention.
FIG. 2 is a schematic cross-sectional view of another laminated electrophotographic photosensitive member used in the present invention.
The electrophotographic photosensitive member used in the present invention is provided with a photosensitive layer (2) on a conductive support (conductive substrate) (1), and this photosensitive layer (2) is mainly composed of a charge generating material. And a charge transport layer (4) mainly composed of a charge transport material.
And a protective layer (5) is formed as a surface layer of such an electrophotographic photoreceptor. This protective layer (5) will be described later.

The conductive support (1) is one having a volume resistance of 10 ¹⁰ Ωcm or less, such as a metal such as aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum, tin oxide, indium oxide, etc. Metal oxide film or cylindrical plastic or paper coated by vapor deposition or sputtering, aluminum, aluminum alloy, nickel, stainless steel plate or the like, and then cutting, superfinishing, polishing, etc. It consists of a tube surface treated with

The charge generation layer (3) is a layer mainly composed of a charge generation material.
As the charge generation material, an inorganic or organic material is used, and typical examples include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squarics. Examples include acid dyes, phthalocyanine pigments, naphthalocyanine pigments, azulenium salt dyes, selenium, selenium-tellurium alloys, selenium-arsenic alloys, and amorphous silicon.
These charge generation materials may be used alone or in combination of two or more.
In the charge generation layer (3), the charge generation material is dispersed by a ball mill, attritor, sand mill or the like using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, 2-butanone or dichloroethane together with a binder resin, and a dispersion is applied. Can be formed. The application is performed by a dip coating method, a spray coating method, a bead coating method, or the like.
Examples of the binder resin used as appropriate include polyamide resins, polyurethane resins, polyester resins, epoxy resins, polyketone resins, polycarbonate resins, silicone resins, acrylic resins, polyvinyl butyral resins, polyvinyl formal resins, polyvinyl ketone resins, polystyrene resins, poly resins. An acrylic resin, a polyamide resin, etc. can be mentioned.
The amount of the binder resin is suitably 0 to 2 parts with respect to 1 part of the charge generating material on a weight basis.
The charge generation layer (3) can also be formed by a known vacuum thin film production method.
The film thickness of the charge generation layer (3) is usually 0.01 to 5 μm, preferably 0.1 to 2 μm.

The charge transport layer (4) can be formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent, and applying and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added as needed.
Among charge transport materials, low molecular charge transport materials include electron transport materials and hole transport materials.
Examples of the electron transport material include chloroanil, bromanyl, 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-one, 1,3,7-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide.
These electron transport materials may be used alone or as a mixture of two or more.
Examples of hole transport materials include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane. , Styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like.
These hole transport materials may be used alone or as a mixture of two or more.
When a polymer charge transport material is used as the charge transport material, it may be dissolved or dispersed in an appropriate solvent, and coated and dried to form a charge transport layer.
The polymer charge transport material may be a material having a charge transporting substituent in the main chain or side chain in the low molecular charge transport material.
Particularly preferred polymer charge transport materials are polycarbonate, polyurethane, polyester, polyether, etc. Among them, use of a polycarbonate having a triarylamine structure is advantageous.
If necessary, an appropriate amount of a binder resin, a low molecular charge transport material, a plasticizer, a leveling agent, a lubricant and the like can be added to the polymer charge transport material.
The binder resin used in the charge transport layer (4) together with the charge transport material includes polystyrene resin, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester resin, polychlorinated resin. Vinyl resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate resin, polyvinylidene chloride resin, polyarylate resin, phenoxy resin, polycarbonate resin, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral resin, polyvinyl formal resin, polyvinyl toluene resin And thermoplastic or thermosetting resins such as acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, and alkyd resin.
If necessary, examples of the plasticizer added to the charge transport layer (4) include general-purpose plasticizers such as dibutyl phthalate and dioctyl phthalate, and the amount used is based on the weight of the binder resin. About 0 to 30% is appropriate.
Examples of leveling agents added to the charge transport layer (4) include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in the side chain. The amount is suitably about 0 to 1% based on the weight of the binder resin.
Examples of the solvent include tetrahydrofuran, dioxane, toluene, 2-butanone, monochlorobenzene, dichloroethane, methylene chloride and the like.
The thickness of the charge transport layer (4) may be appropriately selected in the range of 5 to 30 μm according to desired photoreceptor characteristics.
In the present invention, the content of the charge transport material contained in the photosensitive layer is preferably 40% by weight or more of the charge transport layer.
If it is less than 40% by weight, a sufficient light decay time in a high-speed electrophotographic process cannot be obtained in pulsed light exposure in laser writing on a photoreceptor, which is not preferable.
The charge transport layer mobility in the photoreceptor is 3 × 10 ⁻⁵ cm ² / V · s under conditions of the charge transport layer electric field strength in the range of 2.5 × 10 ^{5 to} 5.5 × 10 ⁵ V / cm. It is preferable that it is above, and it is more preferable that it is 7 × 10 ⁻⁵ cm ² / V · s or more.
This mobility can be adjusted as appropriate to achieve this under each use condition.
This mobility may be obtained by a conventionally known (Time Of Flight) method.

In the laminated electrophotographic photoreceptor used in the present invention, an undercoat layer can be formed between the conductive support (1) and the photosensitive layer.
This subbing layer generally comprises a resin as a main component, but these resins are resins that are highly soluble in general organic solvents in consideration of applying a photosensitive layer thereon using a solvent. It is desirable.
Examples of such resins include polyvinyl alcohol resins, caseins, water-soluble resins such as sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane resins, melamine resins, alkyd-melamine resins, and epoxy resins. Examples thereof include curable resins that form an equal three-dimensional network structure.
Further, fine powder of metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide may be added to the undercoat layer in order to prevent moire and reduce residual potential.
This undercoat layer can be formed by using an appropriate solvent and coating method as in the case of the photosensitive layer.
Furthermore, it is also useful to use a metal oxide layer formed by, for example, a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like as the undercoat layer.
In addition, the undercoat layer is formed by anodizing Al ₂ O ₃ , organic materials such as polyparaxylylene (parylene), inorganic materials such as SiO, SnO ₂ , TiO ₂ , ITO, and CeO _2. It is also effective to form the film by a vacuum thin film manufacturing method.
The thickness of the undercoat layer is suitably from 0 to 5 μm.

In the multilayer electrophotographic photoreceptor, a protective layer (5) containing a filler is formed on the photosensitive layer (2) as a surface layer for the purpose of protecting the photosensitive layer and improving durability.
Materials used for the protective layer (5) include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether resin, allyl resin, phenol resin, polyacetal resin, polyamide resin, polyamideimide resin, Polyacrylate resin, polyallylsulfone resin, polybutylene resin, polybutylene terephthalate resin, polycarbonate resin, polyethersulfone resin, polyether resin, polyethylene terephthalate resin, polyimide resin, acrylic resin, polymethylpentene resin, polypropylene resin, polyphenylene oxide resin, Examples of the resin include polysulfone resin, AS resin, AB resin, BS resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, and epoxy resin.
A filler is added to the protective layer (5) for the purpose of improving the wear resistance.
As the filler, it is preferable to use a fine powder made of an inorganic material of alumina or titanium oxide in the present invention. In some cases, these fillers are used together or inorganic fine particles such as silica are added.
The amount of filler added to the protective layer (5) is usually 10 to 40%, preferably 20 to 30% on a weight basis.
If the amount of the filler is less than 10%, the wear is large and the durability is inferior. If it exceeds 40%, the bright portion potential at the time of exposure increases remarkably, and the sensitivity reduction cannot be ignored.
Furthermore, a dispersion aid can be added to the protective layer (5) in order to improve the dispersibility of the filler.
As the added dispersion aid, those used in coatings and the like (for example, modified epoxy resin condensates, unsaturated polycarboxylic acid low molecular weight polymers, etc.) can be used as appropriate, and the amount is usually a filler based on weight. The amount is 0.5 to 4%, preferably 1 to 2%.
Moreover, it is very effective to add the above-mentioned charge transport material to the protective layer (5), and the addition amount may be the same, and the characteristics for exposure can be improved.
Further, an antioxidant can be added as necessary. The antioxidant will be described later.
As a method for forming the protective layer (5), a normal coating method such as a spray method is adopted, and the thickness of the protective layer (5) is suitably about 0.5 to 10 μm, preferably about 4 to 6 μm.

In the present invention, another intermediate layer can be formed between the photosensitive layer and the protective layer.
In the intermediate layer, a binder resin is generally used as a main component.
Examples of the binder resin include polyamide resin, alcohol-soluble nylon, water-soluble polyvinyl butyral resin, polyvinyl butyral resin, and polyvinyl alcohol resin.
As the method for forming the intermediate layer, the above-described normal coating method is adopted, and the thickness of the intermediate layer is suitably about 0.05 to 2 μm.

In the present invention, in order to improve environmental resistance, for the purpose of preventing a decrease in sensitivity and an increase in residual potential, an antioxidant, a plasticizer, a lubricant, an ultraviolet absorber, and a low molecular charge transport material are used for each layer. And leveling agents can be added.
Antioxidants that can be added to each layer include phenol compounds such as 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, n -Octadecyl-3- (4-hydroxy-3,5-di-tert-butylphenol), 2,2-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2-methylene-bis- ( 4-ethyl-6-tert-butylphenol), 4,4-thiobis- (3-methyl-6-tert-butylphenol), 4,4-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1 , 3-Tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4 − Droxybenzyl) benzene, tetrakis- [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, bis [3,3-bis (4-hydroxy-3-tert-butyl) Phenyl) butyric acid] glycol ester, tocopherols and the like.
As paraphenylenediamines, N-phenyl-N-isopropyl-p-phenylenediamine, N, N-di-sec-butyl-p-phenylenediamine, N-phenyl-Nsec-butyl-p-phenylenediamine, N, N -Di-isopropyl-p-phenylenediamine, N, N-dimethyl-N, N-di-t-butyl-p-phenylenediamine and the like.
As hydroquinones, 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2-octadecenyl) -5-methylhydroquinone and the like.
Examples of organic sulfur compounds include dilauryl-3,3-thiodipropionate, distearyl-3,3-thiodipropionate, and ditetradecyl-3,3-thiodipropionate.
Examples of the organic phosphorus compounds include triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, and tri (2,4-dibutylphenoxy) phosphine.

Plasticizers that can be added to each layer include phosphate ester plasticizers such as triphenyl phosphate, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, trichlorethyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, Examples include tri-2-ethylhexyl phosphate and triphenyl phosphate.
As phthalate ester plasticizers, dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, di-n-octyl phthalate, phthalic acid Dinonyl, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, butyl lauryl phthalate, methyl oleyl phthalate, octyl decyl phthalate, dibutyl fumarate, dioctyl fumarate, etc. Is mentioned.
Examples of the aromatic carboxylate plasticizer include trioctyl trimellitic acid, tri-n-octyl trimellitic acid, octyl oxybenzoate, and the like.
As an aliphatic dibasic ester plasticizer, dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n-octyl adipate, adipate-n-octyl-n-decyl, Diisodecyl adipate, dicapryl adipate, di-2-ethylhexyl azelate, dimethyl sebacate, diethyl sebacate, dibutyl sebacate, di-n-octyl sebacate, di-2-ethylhexyl sebacate, di-2-sebacate Examples thereof include ethoxyethyl, dioctyl succinate, diisodecyl succinate, dioctyl tetrahydrophthalate, and di-n-octyl tetrahydrophthalate.
Examples of the fatty acid ester derivative plasticizer include butyl oleate, glycerin monooleate, methyl acetylricinoleate, pentaerythritol ester, dipentaerythritol hexaester, triacetin, and tributyrin.
Examples of the oxyester plasticizer include methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, and tributyl acetyl citrate.
Epoxy plasticizers such as epoxidized soybean oil, epoxidized linseed oil, butyl epoxy stearate, decyl epoxy stearate, octyl epoxy stearate, benzyl epoxy stearate, dioctyl epoxy hexahydrophthalate, didecyl epoxy hexahydrophthalate, etc. Is mentioned.
Examples of the dihydric alcohol ester plasticizer include diethylene glycol dibenzoate and triethylene glycol di-2-ethylbutyrate.
Examples of the chlorine-containing plasticizer include chlorinated paraffin, chlorinated diphenyl, chlorinated fatty acid methyl, and methoxychlorinated fatty acid methyl.
Examples of the polyester plasticizer include polypropylene adipate, polypropylene sebacate, polyester, and acetylated polyester.
As sulfonic acid derivative plasticizers, p-toluenesulfonamide, o-toluenesulfonamide, p-toluenesulfoneethylamide, o-toluenesulfoneethylamide, toluenesulfone-N-ethylamide, p-toluenesulfone-N-cyclohexylamide Etc.
Examples of the citric acid derivative plasticizer include triethyl citrate, triethyl acetyl citrate, tributyl citrate, tributyl acetyl citrate, tri-2-ethylhexyl acetyl citrate, and acetyl citrate-n-octyldecyl.
Other examples include terphenyl, partially hydrogenated terphenyl, camphor, 2-nitrodiphenyl, dinonylnaphthalene, methyl abietic acid, and the like.

Examples of ultraviolet absorbers that can be added to each layer include 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2,4-trihydroxybenzophenone, 2,2,4,4-tetrahydroxybenzophenone as benzophenone-based ultraviolet absorbers. 2,2-dihydroxy 4-methoxybenzophenone and the like.
Examples of the salicylate ultraviolet absorber include phenyl salicylate, 2,4 di-t-butylphenyl 3,5-di-t-butyl 4-hydroxybenzoate, and the like.
As a benzotriazole ultraviolet absorber, (2-hydroxyphenyl) benzotriazole, (2-hydroxy5-methylphenyl) benzotriazole, (2-hydroxy5-methylphenyl) benzotriazole, (2-hydroxy-3-tert-butyl) 5-methylphenyl) 5-chlorobenzotriazole and the like.
Examples of the cyanoacrylate ultraviolet absorber include ethyl-2-cyano-3,3-diphenyl acrylate, methyl 2-carbomethoxy 3 (paramethoxy) acrylate, and the like.
Examples of the quencher (metal complex salt) ultraviolet absorber include nickel (2,2thiobis (4-t-octyl) phenolate) normal butylamine, nickel dibutyldithiocarbamate, nickel dibutyldithiocarbamate, cobalt dicyclohexyldithiophosphate and the like.
As HALS (hindered amine) -based ultraviolet absorbers, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1 -[2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionyloxy] -2,2,6,6-tetramethylpyridine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2 , 4-dione, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine and the like.
The photoreceptor of the present invention is thus resistant to abrasion by forming a photosensitive layer and a protective layer on a conductive substrate, and optionally forming an undercoat layer and an intermediate layer, and adding a filler to the protective layer. And improved durability.

Subsequently, an image forming method and an image forming apparatus of the present invention will be described.
FIG. 4 is a schematic view showing an image forming method and an image forming apparatus of the present invention.
The photoconductor (6) has a drum shape, but may be a sheet or an endless belt.
Around the photoreceptor (6), a pre-transfer charger (7), a transfer charger, a separation charger, and a pre-cleaning charger (8) are arranged as necessary, and corotron, scorotron, solid state charger (solid state Charger) and known means such as a charging roller are arranged.
The charging member (9) may be in contact with the photosensitive member. However, by providing an adjacent gap with an appropriate gap (about 10 to 200 μm) between them, the wear amount of both can be reduced and the charging member Toner filming can be suppressed and can be preferably used.
The voltage applied to the charging member (9) is effective when the AC component is superimposed on the DC component in order to stabilize charging and suppress charging unevenness.
As the transfer means, the above charger can be generally used. However, as shown in FIG. 4, a transfer belt (10) is effective.
Further, light sources such as the image exposure unit (11) and the charge removal lamp (12) include fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium lamps, light emitting diodes (LEDs), semiconductor lasers (LD), electroluminescence (EL). ) And other luminescent materials can be used.
Various types of filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range.
These light sources are used not only for the process shown in FIG. 4 but also for a transfer process, a static elimination process, a cleaning process, a pre-exposure process and the like using light irradiation, and irradiate the photoreceptor (6) with light.
The toner developed on the photosensitive member (6) by the developing unit (13) is transferred to the transfer paper (14), but not all is transferred, and the toner remaining on the photosensitive member (6) is also transferred. The toner is removed from the photoreceptor (6) by the fur brush (15) and the cleaning blade (16).
Although cleaning may be performed only with a cleaning blade, a cleaning brush such as a fur brush may be used in combination with the cleaning blade of the present invention.
When the electrophotographic photosensitive member is positively (negatively) charged and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member.
If this is developed with negative (positive) polarity toner (electrodetection fine particles), a positive image can be obtained, and if developed with positive (negative) polarity toner, a negative image can be obtained.
A known method is applied to the developing unit, and a known method is also used as the charge eliminating unit.
In FIG. 4, (17) is a registration roller, and (18) is a separation claw.
The present invention is an image forming method and an image forming apparatus using an electrophotographic photosensitive member for such image forming means.

The image forming unit may be fixedly incorporated in a copying apparatus, a facsimile machine, or a printer, but may be incorporated in these apparatuses and made detachable in the form of a process cartridge.
Here, the process cartridge is a single device (part) that contains a photoconductor and further includes a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit.
Accordingly, the present invention also provides a process cartridge for an image forming apparatus having at least charging, image exposure, development, transfer, fixing, and cleaning means, comprising the electrophotographic photosensitive member and a cleaning blade. A process cartridge for a forming apparatus is also provided.
FIG. 5 is a schematic view showing an example of a process cartridge for an image forming apparatus according to the present invention. In FIG. 5, 101 is a photosensitive drum, 102 is a contact charging device, 103 is image exposure, 104 is a developing device, 105 is a transfer body, 106 is a contact transfer device, 107 is a cleaning blade, 108 is a static elimination lamp, and 109 is fixing. Device.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited at all by these Examples.

Urethane rubber blade for evaluation The urethane rubber blade for evaluation was prepared with the following physical properties.
The urethane rubber strip was 2 mm thick and the free length was 7.3 mm.
In addition, hardness (JISK6301) and impact resilience (JISK6301) are values at 25 ° C.
(Blade 1)
Hardness: 72 degrees Rebound resilience: 17%
(Blade 2)
Hardness: 70 degrees Rebound resilience: 68%
(Blade 3)
Hardness: 78 degrees Rebound resilience: 27%
(Blade 4)
Hardness: 70 degrees Rebound resilience: 37%
(Blade 5)
Hardness: 80 degrees Rebound resilience: 34%
(Blade 6)
Hardness: 64 degrees Rebound resilience: 31%

When evaluating the blade, a urethane strip was bonded to a predetermined sheet metal holder to complete an evaluation cleaning blade.
The evaluation of the cleaning property was performed by mounting the blades on Ricoh's color multifunction machine, image Neo Neo C455 (the blades were manufactured in the same shape and size as the standard blades).
However, the blade pressing method is changed to the constant displacement method, and the initial contact condition of each blade is that the cleaning angle, which is the angle θ between the blade cut surface and the photoreceptor surface, is 75 degrees, and the linear pressure is 25 g / cm. It was. Also, when changing the contact condition, it was changed after passing 100k sheets, and the blade bracket was replaced with a separately prepared one according to the change amount of the contact condition.

Toner for evaluation A toner prepared by a polymerization method was used.
Toner base: circularity 0.97, average particle size 5.8 μm
External additive: 1.5 parts by weight of small particle size silica (H2000 manufactured by Clariant)
0.75 part by weight of small particle size titanium oxide (MT-150AI manufactured by Teika)
0.5 parts by weight of large particle size silica (UFP-30H manufactured by Denki Kagaku Kogyo)
Evaluation environment 20 ° C 65% RH
Paper-feeding conditions Yield 5% chart 100,000 sheets + 50,000 sheets at 3 prints / job (A4 landscape)
Change of contact condition Predetermined change after passing 100,000 sheets Evaluation item Toner slipping amount: Captures the toner passing through the blade for driving A4 paper with a felt cloth and measures its density (after passing the blade) Sampling by pressing on the surface of the photoconductor)
Occurrence of cleaning failure: Existence (visual observation of 5% chart output)

Evaluation results (Example 1)
Evaluation blade: Blade 3 (hardness 78 degrees, rebound resilience 27%)
Contact condition change at 100k: Available (cleaning angle +5 degrees, linear pressure +0 g / cm)
Toner slip-through density at 150 k: 0.25
Occurrence of cleaning failure: None

(Example 2)
Evaluation blade: Blade 4 (hardness 70 degrees, rebound resilience 37%)
Contact condition change at 100k: Yes (cleaning angle +3 degrees, linear pressure +0 g / cm)
Toner slip-through density at 150 k: 0.21
Occurrence of cleaning failure: None

(Example 3)
Evaluation blade: Blade 2 (hardness 70 degrees, rebound resilience 68%)
Contact condition change at 100k: Available (cleaning angle +5 degrees, linear pressure +0 g / cm)
Toner slip-through density at 150k: 0.28
Occurrence of cleaning failure: None

Example 4
Evaluation blade: Blade 1 (hardness 72 degrees, rebound resilience 17%)
Contact condition change at 100k: Available (cleaning angle +5 degrees, linear pressure +0 g / cm)
Toner slip-through density at 150k: 0.27
Occurrence of cleaning failure: None

(Comparative Example 1)
Evaluation blade: Blade 2 (hardness 70 degrees, rebound resilience 68%)
Contact condition change at 100k: None Toner slipping density at 150k: 0.41
Cleaning failure occurred: Yes

(Example 5)
Evaluation blade: Blade 4 (hardness 70 degrees, rebound resilience 37%)
Contact condition change at 100k: Available (cleaning angle +5 degrees, linear pressure +0 g / cm)
Toner slip-through density at 150 k: 0.25
Occurrence of cleaning failure: None

(Comparative Example 2)
Evaluation blade: Blade 1 (hardness 72 degrees, rebound resilience 17%)
Contact condition change at 100k: Available (cleaning angle +0 degree, linear pressure + 20g / cm)
Toner slip-through density at 150 k: 0.35
Cleaning failure occurred: Yes

(Example 6)
Evaluation blade: Blade 1 (hardness 72 degrees, rebound resilience 17%)
Contact condition change at 100k: Yes (cleaning angle +3 degrees, linear pressure +0 g / cm)
Toner slip-through density at 150 k: 0.26
Occurrence of cleaning failure: None

(Comparative Example 3)
Evaluation blade: Blade 4 (hardness 70 degrees, rebound resilience 37%)
Contact condition change at 100k: Available (cleaning angle +5 degrees, linear pressure -10g / cm)
Toner slip-through density at 150k: 0.38
Cleaning failure occurred: Yes

(Comparative Example 4)
Evaluation blade: Blade 4 (hardness 70 degrees, rebound resilience 37%)
Contact condition change at 100k: Yes (cleaning angle +3 degrees, linear pressure + 20g / cm)
Toner slip-through density at 150 k: 0.32
Cleaning failure occurred: Yes

(Comparative Example 5)
Evaluation blade: Blade 6 (hardness 64 degrees, rebound resilience 31%)
Contact condition change at 100k: None Toner slip-through density at 150k: 0.43
Cleaning failure occurred: Yes

  According to the present invention, in a simple means, it is possible to suppress the deterioration of the cleaning property due to the abrasion of the cleaning blade with respect to the small particle size and spherical toner, and to ensure a good cleaning property without causing a cleaning failure, and to achieve high definition. Since it is possible to provide an image forming method, an image forming apparatus, and a process cartridge for an image forming apparatus capable of providing a stable and excellent image for an electrophotographic process, a highly durable high speed digital system using a laser beam as a writing light source It can be preferably applied to an electrophotographic process.

1 is a schematic cross-sectional view of a multilayer electrophotographic photosensitive member used in the present invention. It is a schematic sectional drawing of the other laminated electrophotographic photosensitive member used for this invention. It is the schematic of the positioning structure of the blade used for this invention. 1 is a schematic view showing an image forming method and an image forming apparatus of the present invention. FIG. 2 is a schematic diagram illustrating an example of a process cartridge for an image forming apparatus according to the present invention. FIG. 6 is a schematic diagram illustrating an angle θ formed by a front end cut surface of a cleaning blade and a photoreceptor contact surface in the image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Photosensitive layer 3 Charge generation layer 4 Charge transport layer 5 Protective layer 6 Photoconductor 7 Charger before transfer 8 Charger before cleaning 9 Charging member 10 Transfer belt 11 Image exposure part 12 Static elimination lamp 13 Developing unit 14 Transfer paper 15 Fur Brush 16 Cleaning Blade 17 Registration Roller 18 Separation Claw 19 Photosensitive Drum 20 Elastic Blade 21 Blade Sheet Metal Holder 22 Photosensitive Cartridge Side Plate 23 Blade Positioning Fixing Unit 101 Photosensitive Drum 102 Contact Charging Device 103 Image Exposure 104 Developing Device 105 Transfer Body 106 Contact transfer device 107 Cleaning blade 108 Static elimination lamp 109 Fixing device 60 Photoconductor 61 Blade 611 Cut surface

Claims (13)

  In an image forming method in which charging, image exposure, development, transfer, fixing, and cleaning processes are performed on at least a photoconductor, a cleaning unit that performs the cleaning process includes a strip-shaped elastic blade, An image characterized in that the contact angle to the photoconductor is changed by one step according to the operation time, and at the same time, the change in the contact pressure to the photoconductor due to the change in angle is corrected to keep the contact pressure constant. Forming method.   The elastic blade is brought into contact with the photosensitive member by a constant displacement method, and the angle formed between the tip cut surface and the photosensitive member contacting surface is increased by one step according to the operation time, and at the same time, the photosensitive member at the tip of the elastic blade. The image forming method according to claim 1, wherein the amount of biting into the surface is increased to keep the contact pressure constant.   3. The image formation according to claim 1, wherein the elastic blade is made of urethane rubber and has a hardness of 70 to 78 degrees (JIS A) at 25 ° C. and a rebound resilience of 17 to 68%. Method.   The image forming method according to claim 1, wherein the photosensitive member has a protective layer, and the protective layer contains inorganic fine particles made of alumina or titanium oxide.   The image forming method according to claim 4, wherein the protective layer contains a charge transport material.   The image forming method according to claim 1, wherein the toner used for the development processing has a volume average particle size of 5.5 μm or less and a circularity of 0.97 or more.   At least the photosensitive member includes a charging unit that performs a charging process, an image exposure unit that performs an image exposure process, a developing unit that performs a developing process, a transfer unit that performs a transferring process, a fixing unit that performs a fixing process, and a cleaning unit that performs a cleaning process. In the image forming apparatus, the cleaning unit in the cleaning unit has a strip-shaped elastic blade, the contact angle of the elastic blade to the photosensitive member is changed by one step according to the operation time, and the angle is changed simultaneously. An image forming apparatus, wherein the contact pressure is kept constant by correcting a change in contact pressure on the photosensitive member due to the above.   The strip-shaped elastic blade is brought into contact with the photosensitive member by a constant displacement method, and the angle formed between the tip cut surface and the photosensitive member contacting surface is increased by one step according to the operation time, and at the same time, The image forming apparatus according to claim 7, wherein the contact pressure is kept constant by increasing an amount of biting into the photosensitive member.   The image forming apparatus according to claim 7 or 8, wherein the elastic blade is made of urethane rubber, and has a hardness of 70 to 78 degrees (JIS A) at 25 ° C and a rebound resilience of 17 to 68%. apparatus.   The image forming apparatus according to claim 7, wherein the photoconductor has a protective layer, and the protective layer contains inorganic fine particles made of alumina or titanium oxide.   The image forming apparatus according to claim 10, wherein the protective layer contains a charge transport material.   The image forming apparatus according to claim 7, wherein the toner used in the developing unit has a volume average particle size of 5.5 μm or less and a circularity of 0.97 or more.   The contact angle to the photosensitive member is changed in one step according to at least the operation time used in the image forming method according to claim 1 or the image forming apparatus according to any one of claims 7 to 12. And a process for an image forming apparatus, comprising a cleaning unit comprising an elastic blade that simultaneously corrects a contact pressure change to the photosensitive member due to an angle change and keeps the contact pressure constant. cartridge.

Images