JP2015004768A - Image forming apparatus, process cartridge, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to stabilize the amount of image carrier protective agent to be supplied, for a long time, and to maintain high image quality under any environment.SOLUTION: An image forming apparatus includes: an image carrier; a protective agent supply member which comes into contact with a surface of the image carrier in a rotatable manner; and protective layer forming means including at least an image carrier protective agent formed of a granulated material containing fatty acid metal salt at least. The protective agent supply member is formed of a foam roller. A median size (D50) of the granulated material of the image carrier protective agent from a volume particle size distribution obtained by laser diffraction/scattering particle size distribution measurement is larger than an average cell diameter of the foam roller.

Description

  The present invention relates to an image forming apparatus, a process cartridge, and an image forming method.

Conventionally, in electrophotographic image formation, a latent image is formed on an image carrier such as a photoconductive substance by electrostatic charge, and charged toner particles are attached to the electrostatic latent image to form a visible image. Is forming. The visible image formed by the toner is finally transferred to a recording medium such as paper, and then fixed on the recording medium by heat, pressure, solvent gas, or the like, and becomes an output image.
In these electrophotographic image forming apparatuses, a drum-shaped or belt-shaped image carrier is uniformly charged while rotating, and a latent image pattern is formed on the image carrier by laser light or the like. Is visualized by a developing device and further transferred onto a recording medium.

  Further, the toner component that has not been transferred remains on the image carrier after the toner image is transferred to the recording medium. When these residues are conveyed to the charging process as they are, it is often the case that the uniform charging of the image carrier is hindered. The components and the like are removed in a cleaning process to make the surface of the image carrier sufficiently clean, and then charging is performed.

As described above, the surface of the image carrier is subjected to various physical stresses and electrical stresses in various processes such as charging, development, transfer, and cleaning, and the surface state changes as the usage time elapses.
Of these stresses, stress due to friction in the cleaning process not only wears the image carrier, but also reduces the life of the cleaning member.
The longevity of the image forming apparatus and the members used therefor is of great interest in the market from the viewpoint of protecting the global environment by reducing running costs and waste. From such a flow, in recent years, not only the image carrier but also the life of peripheral members has been demanded, and the reduction of stress in the cleaning process has become a major issue.

In recent years, the contact charging method and the proximity charging method have been used more and more for the purpose of reducing the size and cost of the apparatus. Among these, the proximity charging method makes the surface of the image carrier uniform by a slight contact non-uniformity between the charging member and the surface of the image carrier or non-contact due to a gap variation between the charging member and the surface of the image carrier. Since it is difficult to charge, in recent years, an AC superposition charging method in which an alternating current (AC) component is superimposed on a direct current (DC) component is often used.
Such a proximity charging method in which the AC component is superposed can realize downsizing and high image quality of the apparatus, and at the same time, the charging member and the image carrier can be brought into non-contact while maintaining charging uniformity. Therefore, it can be said that this is a very advantageous technology for downsizing, high image quality, and high durability of the apparatus.

However, when the image carrier is an organic photoconductor (OPC), the AC superimposed charging energy cuts the resin chain on the surface of the image carrier and lowers the mechanical strength. It has become clear that it will be significantly accelerated.
Further, since AC superimposed charging activates the surface of the image carrier, the adhesion force between the surface of the image carrier and the toner is increased, which is a disadvantageous cleaning property.
Further, in recent years, toner diameters and spheres have been reduced from the viewpoint of high image quality, and the margin for cleaning performance is becoming lower.
In order to solve the above-mentioned problems, various kinds of various methods have been developed so far in order to reduce the frictional force between the image carrier and the cleaning member, protect both the image carrier and the cleaning member, and improve the cleaning property. Many proposals have been made on lubricants (protective agents) and lubricant component supply / film formation methods.

For example, Patent Document 1 proposes to supply a solid lubricant mainly composed of zinc stearate to the surface of the photoreceptor to form a lubricating film on the surface of the photoreceptor in order to extend the life of the photoreceptor and the cleaning blade. Yes.
In Patent Document 2, the surface of the image bearing member is supplied with various lubricants added with boron nitride, which is one of inorganic lubricants, to a solid lubricant mainly composed of zinc stearate. Even when an electrical stress is applied to the surface of the image carrier, the lubricity is hardly lowered, and a lubricant film can be formed over the entire surface of the image carrier to maintain a high lubricity.

On the other hand, in Patent Document 3, as a general lubricant application mechanism, a lubricant supply device (application member) is in contact with a brush-like rotation member (brush portion) that is in sliding contact with an image carrier, and the brush-like rotation member. It comprises a solid lubricant, a pressurizing mechanism for urging the solid lubricant toward the brush-like rotating member, and the like. Then, the lubricant is gradually scraped off from the solid lubricant by the brush-like rotating member rotating in a predetermined direction, and the lubricant scraped off by the brush-like rotating member is applied (supplied) to the surface of the image carrier.
However, in the proposed technique, in the configuration in which the spring contacts and is pressed against the brush-like rotating member, the spring expands as the solid lubricant is scraped, and thus the pressing force inevitably decreases. As a result, the amount of solid lubricant is reduced, and the amount of solid lubricant supplied to the photoreceptor and intermediate transfer belt is also reduced, making it impossible to sufficiently protect the photoreceptor and intermediate transfer belt. There is a problem.

With respect to these problems, for example, in Patent Document 4, a movable pressing member is provided on a member that holds a solid lubricant, and the solid lubricant is scraped by pressing it with a spring member. The same pressure can be maintained.
Further, in Patent Document 5, the use of a foam roller having a foam layer as a protective agent supply member makes it possible to uniformly form a solid lubricant film on the surface of the image carrier with a relatively small consumption.

  However, as a method of supplying a protective agent block represented by Patent Document 1 and Patent Document 2, the brush-shaped rotating member shown in Patent Document 3 is protected by rotating the brush-shaped rotating member. A large amount of the protective agent powder rubbed from the block flies, and a large amount of the protective agent is wasted. In addition, the brush fibers are severely fallen and deteriorated over time. For this reason, even when a protective agent pressurizing mechanism that can maintain the same applied pressure over time as in Patent Document 4 is used, the amount of protective agent consumption is not stable over time, and the protective agent is kept in a constant amount over a long period of time. Cannot supply. In particular, when the protective agent block is manufactured by compression molding, there is a problem that the degree is severe.

On the other hand, by using a foam roller having a foam layer as the protective agent supply member as in Patent Document 5, almost no flying of the protective agent powder due to rubbing occurs. In addition, there is no effect of brush fall or deterioration of the brush-like rotating member, it is possible to supply a constant amount of protective agent over a long period of time, and a solid lubricant film is uniformly formed on the surface of the image carrier with relatively little consumption it can. Moreover, since it can be manufactured at a relatively low cost compared to the brush-like rotating member, it can also contribute to the cost reduction of the unit.
However, in the foam roller of Patent Document 5, when the protective agent particles adhering to the cell portion of the foam layer have entered the cell, the protective agent particle does not appear again on the roller surface, It will stay. For this reason, when these are accumulated, the cell part of the foam layer is filled with the protective agent particles, and the state is the same as when the number of cells apparently decreases. Then, the grinding force with respect to the protective agent block of the foam roller decreases, and the supply amount of the protective agent to the image carrier gradually decreases. A decrease in the supply amount of the protective agent causes filming of the image carrier, and there is a problem that the image is detected as white streaks in a halftone image particularly in a high humidity environment.

  Therefore, even when a foam roller is used as the protective agent supply member, the problem with the brush-like rotating member has not necessarily been completely solved, and the solution is desired at present.

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide an image forming apparatus capable of stabilizing the supply amount of the image carrier protecting agent for a long period of time and maintaining high image quality in any environment.

An image forming apparatus according to the present invention as means for solving the above-described problems includes an image carrier, a protective agent supply member that rotatably contacts the surface of the image carrier, and a granulated material containing at least a fatty acid metal salt. An image forming apparatus having a protective layer forming means having at least an image carrier protective agent comprising:
A median diameter (D50) based on a volume-based particle size distribution obtained by measuring the protective agent supplying member with a foam roller and measuring the granulated product of the image carrier protective agent by a laser diffraction / scattering particle size distribution measurement method is obtained. It is larger than the average cell diameter of the foam roller.

  According to the present invention, the conventional problems can be solved, the object can be achieved, the supply amount of the image carrier protecting agent can be stabilized over a long period of time, and high image quality can be achieved in any environment. An image forming apparatus that can be maintained can be provided.

FIG. 1A is a schematic cross section showing an example of an open-cell foam layer. FIG. 1B is a schematic cross-sectional view showing an example of a closed cell foam layer. FIG. 2A is a side view showing an example of the protective agent supply member. FIG. 2B is an enlarged schematic view showing an example of an exposed surface of the continuous foam type foam layer. FIG. 3 is a schematic sectional view showing an example of the protective layer forming means. FIG. 4 is a schematic sectional view showing an example of the image forming apparatus of the present invention. FIG. 5 is a schematic sectional view showing an example of the process cartridge of the present invention.

(Image forming apparatus and image forming method)
The image forming apparatus of the present invention comprises at least an image carrier (hereinafter sometimes referred to as “electrostatic latent image carrier”, “electrophotographic photosensitive member”, “photosensitive member”, etc.) and protective layer forming means. And other means as required.
The image forming method of the present invention includes at least a protective layer forming step, and further includes other steps as necessary.
The image forming method can be suitably performed by the image forming apparatus, the protective layer forming step can be performed by the protective layer forming unit, and the other steps can be performed by the other unit. it can.

<Protective layer forming means and protective layer forming step>
The protective layer forming means includes at least a protective agent supply member that rotatably contacts the surface of the image carrier and an image carrier protective agent (hereinafter sometimes simply referred to as “protective agent”), and further. It has other members as needed.
The protective layer forming step is not particularly limited as long as it is a step of forming a protective layer by applying a protective agent to the surface of the image carrier after transfer, and can be appropriately selected according to the purpose. This can be done by the protective increase forming means.

<< Protective agent supply member >>
The protective agent supply member is means for scraping off the protective agent and supplying the protective agent to the surface of the image carrier.
A foam roller is used as the protective agent supply member.
The foam roller has at least a core material and a foam layer formed on the outer periphery of the core material and having a plurality of bubbles, and further includes other members as necessary.

−Core material−
There is no restriction | limiting in particular as a material of the said core material, a shape, a magnitude | size, and a structure, According to the objective, it can select suitably.
Examples of the material of the core material include resins such as epoxy resins and phenol resins; metals such as iron, aluminum, and stainless steel.
Examples of the shape of the core material include a columnar shape and a cylindrical shape.

-Foam layer-
The foam layer is a layer formed on the outer periphery of the core material, and has a plurality of bubbles (sometimes referred to as “cell”, “hole”, “void”, etc.).
There is no restriction | limiting in particular as a shape of the said foam layer, According to the objective, it can select suitably, For example, cylindrical shape etc. are mentioned.

--Foamed polyurethane--
There is no restriction | limiting in particular as a material of the said foam layer, According to the objective, it can select suitably, For example, foaming polyurethane etc. are mentioned.
There is no restriction | limiting in particular as said foaming polyurethane, According to the objective, it can select suitably, For example, a polyol, polyisocyanate, a catalyst, and a foaming agent are mixed at least, and also if necessary, foam control Examples thereof include foamed polyurethane obtained by mixing and reacting other components such as an agent.

--- Polyol ---
There is no restriction | limiting in particular as said polyol, According to the objective, it can select suitably from conventionally well-known various polyols, For example, polyether polyol, polyester polyol, etc. are mentioned. Among these, polyether polyol is preferable from the viewpoint of easy adjustment of processability and foam layer hardness.

As the polyether polyol, for example, at least one of a low molecular polyol and a low molecular polyamine having 2 to 8 active hydrogen groups is used as an initiator, and at least one of ethylene oxide and propylene oxide is opened. Examples thereof include polyether polyols obtained by addition polymerization.
Examples of the polyether polyol include polyether polyether polyols, polyester polyether polyols, and polymer polyether polyols that are generally used in the production of flexible polyurethane foams.
The polyether polyol is preferably a polyether polyether polyol in which ethylene oxide is bonded to the terminal at 5 mol% or more from the viewpoint of moldability.

Examples of the polyester polyol include dibasic acids such as adipic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and maleic anhydride, and anhydrides thereof, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, Examples thereof include polyester polyols obtained by polymerizing glycols and triols such as propylene glycol, 1,4-butanediol, glycerin and trimethylolpropane.
Further, as the polyester polyol, those obtained by depolymerizing a waste material of polyethylene terephthalate resin with the above-mentioned glycol can also be used.
The said polyol may be used individually by 1 type, and may use 2 or more types together.

--- Polyisocyanate ---
There is no restriction | limiting in particular as said polyisocyanate, According to the objective, it can select suitably from conventionally well-known various polyisocyanate, For example, 2, 4- tolylene diisocyanate (2, 4-TDI), 2 , 6-tolylene diisocyanate (2,6-TDI), tolidine diisocyanate (TODI), naphthylene diisocyanate (NDI), xylylene diisocyanate (XDI), 4,4'-diphenylmethane diisocyanate (MDI), carbodiimide-modified MDI, poly Examples include methylene polyphenyl polyisocyanate and polymeric polyisocyanate. These may be used alone or in combination of two or more.

  There is no restriction | limiting in particular as a compounding quantity of the said polyisocyanate, According to the objective, it can select suitably, For example, as equivalent ratio (NCO / OH) of the isocyanate group of the said polyisocyanate with respect to the hydroxyl group of the said polyol, 1. The range of 0-3.0 is mentioned.

---- Catalyst ---
There is no restriction | limiting in particular as said catalyst, According to the objective, it can select suitably from the catalysts used for a conventionally well-known urethanation reaction, For example, an amine catalyst, an organometallic catalyst, etc. are mentioned. .
Examples of the amine catalyst include triethylenediamine, dimethylethanolamine, and bis (dimethylamino) ethyl ether.
Examples of the organometallic catalyst include dioctyltin and distearyltin dibutyrate.
The catalyst may be a reactive catalyst such as dimethylaminoethanol having active hydrogen.
These may be used individually by 1 type and may use 2 or more types together.

There is no restriction | limiting in particular as a compounding quantity of the said catalyst, According to the objective, it can select suitably, For example, 0.01 mass part-20 mass parts are mentioned with respect to 100 mass parts of said polyols.
By appropriately selecting the type of the catalyst and controlling the amount of the catalyst used, it is possible to adjust the cell wall width, open cell diameter, hardness, air flow rate, and the like of the foam layer.

---- Foaming agent ---
There is no restriction | limiting in particular as said foaming agent, According to the objective, it can select suitably, For example, water, a fluorocarbon compound, a low boiling point hydrocarbon type compound etc. are mentioned. These may be used alone or in combination of two or more.
Examples of the fluorocarbon compounds include HCFC-141b, HFC-134a, HFC-245fa, HFC-365mfc, and the like.
Examples of the low-boiling hydrocarbon compound include cyclopentane, n-pentane, iso-pentane, and n-butane.
There is no restriction | limiting in particular as a compounding quantity of the said foaming agent, According to the objective, it can select suitably, For example, 5 mass parts-50 mass parts are mentioned with respect to 100 mass parts of said polyols.
By appropriately selecting the type of the foaming agent and controlling the amount of the foaming agent used, the cell wall width, the open cell diameter, the hardness, the air flow rate, and the like of the foam layer can be adjusted.

--- Other ingredients ---
The other components are not particularly limited and may be appropriately selected depending on the purpose. For example, foam stabilizers, crosslinking agents, foam breakers, conductive agents, antistatic agents, flame retardants, viscosity reducers, Examples include pigments, stabilizers, colorants, anti-aging agents, ultraviolet absorbers, and antioxidants. These may be used alone or in combination of two or more.

There is no restriction | limiting in particular as said foam stabilizer, According to the objective, it can select suitably, For example, silicone type surfactant etc. are mentioned.
Commercially available products can be used as the silicone surfactant. Specific examples of the commercially available products include dimethylsiloxane foam stabilizers (for example, “SRX-253” manufactured by Toray Dow Corning Silicone, Shin-Etsu). "F-122" manufactured by Chemical Industry Co., Ltd.), a polyether-modified dimethylsiloxane foam stabilizer (for example, "L-5309", "SZ-1311" manufactured by Nippon Unicar Co., Ltd.) and the like. These may be used alone or in combination of two or more.
There is no restriction | limiting in particular as a compounding quantity of the said foam stabilizer, According to the objective, it can select suitably, For example, 0.2 mass part-10 mass parts etc. are mentioned with respect to 100 mass parts of said polyols. .

The crosslinking agent and foam breaker are blended for the purpose of controlling the closed cell property and open cell property of the foam of the foam layer.
There is no restriction | limiting in particular as said crosslinking agent, Although it can select suitably according to the objective, Triethanolamine, diethanolamine, etc. are mentioned.
There is no restriction | limiting in particular as said foam breaker, According to the objective, it can select suitably, For example, the thing with high foam breakability is mentioned in the said foam stabilizer.
There is no restriction | limiting in particular as a compounding quantity of the said crosslinking agent and a foam breaker, According to the objective, it can select suitably.

  Usually, components other than the polyisocyanate are mixed in advance and mixed with the polyisocyanate component immediately before molding.

  A commercially available product can be used as the polyurethane foam. Examples of the commercially available products include HR20, HR30, QM60, QZK50, and QZK70 (all manufactured by Bridgestone Kasei Co., Ltd.).

  There is no restriction | limiting in particular as a structure of the said foam layer, According to the objective, it can select suitably, For example, a closed cell type, an open cell type, these mixed types etc. are mentioned.

  FIG. 1A is a schematic cross-section showing an example of the open-cell foam layer. The open-cell foam layer is a foam layer having a structure in which air and water are allowed to pass through since adjacent bubbles are connected to each other. FIG. 1B is a schematic cross section showing an example of the closed cell foam layer. The closed cell foam layer is a foam layer having a structure in which bubbles are independent and air and water are not allowed to pass through.

  Among these, the foam layer is preferable in that the open-cell type has a small compressive residual strain and is easy to return to its original shape even when compressed, so that it hardly deforms even in long-term use. In addition, the open cell type is less costly than the closed cell type, and it is advantageous in terms of cost, and the amount of protective agent supplied (protective agent block shaving amount) is uniform. Since the image carrier can be sufficiently protected, filming of the image carrier can be prevented, a smaller protective agent block can be obtained, and the apparatus can be downsized.

  The average cell diameter of the foam roller is not particularly limited as long as it is equal to or less than the median diameter (D50) of the image carrier protective agent described later, and the grinding performance for the protective agent and the protective agent are uniformly supplied to the surface of the image carrier. In view of this, the average cell diameter is preferably 400 μm to 850 μm, and more preferably 500 μm to 700 μm. When the average cell diameter is less than 400 μm, it becomes difficult to grind the protective agent. Therefore, when the molded body on the block is used as the protective agent, the supply amount of the protective agent tends to be unstable. On the other hand, when the average cell diameter exceeds 850 μm, a region where the contact area between the protective agent and the image carrier is partially reduced appears, so that it is difficult to supply the protective agent uniformly. Any of these effects may appear as filming of the image carrier.

The average cell diameter of the foam roller can be obtained, for example, from a value obtained by dividing 1 inch (= 25.4 mm) by the number of cells measured by the following method.
On the surface of the foam layer 10 of the foam roller 22, three measurement points are arbitrarily selected between the axial end portions and the central portion (here, in FIG. 2A, 20 is the end measurement portion and 21 is the center). Part of measurement.). Next, two more points are selected in the circumferential direction at each measurement point, and a total of nine measurement points are determined. Next, the photograph screen of each measurement location is observed using a microscope. Then, as shown in FIG. 2B, a line X having a length corresponding to an actual size of 1 inch is drawn at the center of the photo screen, the number of cells in the line is counted, and an average value of 9 points is obtained. Ask. A cell that touches even a 1-inch line is counted as one. For example, in the case shown in FIG. 2B, since the number of cells is 12, the average cell diameter is 25.4 (mm) ÷ 12 (cells) = 2.117 (mm) = 2,117 (μm). .

There is no restriction | limiting in particular as average thickness of the said foam layer, Although it can select suitably according to the objective, 1 mm-4 mm are preferable. When the average thickness is less than 1 mm, the influence of the shaft (core material) is easily picked up, and when it exceeds 4 mm, the amount of the protective agent scraped may be reduced.
When the foam layer is cylindrical, the thickness is defined as the distance between the cylindrical inner peripheral surface and the outer peripheral surface. Here, the average thickness is an average value when the thickness of the foam layer is arbitrarily measured at three points.

There is no restriction | limiting in particular as hardness of the said foam layer, Although it can select suitably according to the objective, 40N-430N are preferable and 40N-300N are more preferable. If the hardness is less than 40N, it may be difficult to suppress contamination of the image carrier, and if it exceeds 430N, it may be difficult to suppress contamination of the image carrier. When the hardness is in the more preferable range, it is advantageous in that the suppression of contamination of the image carrier is more excellent.
The hardness is an average value of values measured based on JIS K 6400 at arbitrary three points on the surface of the foam layer.

  In the foam layer, the form of the bubbles (open-cell type or closed-cell type), the number of the bubbles, the hardness of the foam layer, and the like are the types of the polyurethane foam raw material when producing the foam layer, It can be controlled by appropriately adjusting the amount of the foaming agent, reaction conditions, and the like.

-Manufacturing method of protective agent supply member-
There is no restriction | limiting in particular as a manufacturing method of the said protective agent supply member, According to the objective, it can select suitably.
As an example of the method for producing the protective agent supply member, a production example in which the foamed polyurethane is used as the material of the foam layer will be described.
First, a foamed polyurethane raw material is foam-cured by a known method to form a block-shaped foamed polyurethane. Then, after cutting into a required shape, polishing the surface, processing into a cylindrical shape having bubbles opened on the surface, the core material is inserted into the cylindrical shape. Thereafter, a polishing blade or the like is applied while rotating the polyurethane foam using a polishing machine and a cutting machine, and the blade is moved parallel to the axial direction of the protective agent supply member to cut to a predetermined thickness (traverse grinding). Thereby, the cylindrical protective agent supply member which has the bubble opened on the surface is obtained. Furthermore, irregular unevenness | corrugation can also be formed in the foam layer surface by changing the rotational speed of the protective agent supply member, or the moving speed.
An adhesive may be applied to the core material in order to improve the adhesiveness with the foam layer. By these steps, the protective agent supply member is manufactured.

Moreover, another example of the manufacturing method of the said protective agent supply member is also demonstrated.
A foamed polyurethane raw material is injected into a mold for molding the protective agent supply member containing the core material, and foamed and cured. Thus, the protective agent supply member is manufactured.

Among these production methods, the method using a mold is preferable because the formation of the foam layer and the opening of the foam layer can be simultaneously performed and the processing accuracy is good.
The manufacturing method using the mold does not require complicated processing, and the foam layer having a suitable opening property can be formed. Therefore, the inner surface of the mold is separated by a fluororesin coating agent, a release agent, or the like. It is preferable to provide a mold layer.

<< Image carrier protecting agent >>
The image carrier protective agent is composed of a granulated product containing at least a fatty acid metal salt, preferably a granulated product containing a fatty acid metal salt and an inorganic lubricant, and the granulated product is compression molded in a mold. A block-shaped molded body is preferable.
The granulated product means a product obtained by adhering and agglomerating fine powder or by compressing to form particles of a predetermined size.
As the form of the protective agent, either powder or molded product can be used, but in the present invention, it is easy to adjust the supply amount, and the device can be downsized. It is preferable.
As molding methods, methods such as melt molding in which a material is melted and poured into a mold and then cooled and solidified, and compression molding in which a powder material is directly compressed to obtain a molded product are known.

In the present invention, it is necessary to make the median diameter (D50) of the granulated product of the protective agent larger than the average cell diameter of the foam roller.
Control of the median diameter (D50) of the granulated product of the protective agent is not particularly limited, and a known method may be used. For example, the particle diameter is controlled to a desired particle size by optimizing the conditions for grinding the protective agent. However, since it is technically simpler, the method of compression molding a granulated product of the protective agent is most preferably used in the present invention.
Here, granulation refers to attaching and agglomerating fine powder, or compressing to form particles. In the present invention, the fatty acid metal salt and the inorganic lubricant are preferably mixed and granulated.
There is no restriction | limiting in particular as the said granulation method, According to the objective, it can select suitably, For example, well-known methods, such as a dry type, a wet, and a melt-pulverization system, can be used.
As an apparatus used for granulation, for example, a roller compactor (RC-MINI, manufactured by Freund Corporation) can be used as a dry granulator.
Of course, the granulator is not limited to this, and for example, a wet or melt-pulverized granulator may be used. The granulation is performed by pulverizing or classifying the aggregate once aggregated, and the particle size can be controlled in the pulverization or classification process.

The median diameter (D50) of the granulated product is not particularly limited as long as it is larger than the average cell diameter of the foam roller, and can be appropriately selected according to the purpose. 000 μm or less is preferable, 500 μm to 1,000 μm is more preferable, and 600 μm to 800 μm is still more preferable. When the median diameter (D50) exceeds 1,000 μm, the protective agent becomes difficult to be spread by the protective layer forming member, and the protective agent particles adhere to the charging member or adhere to the surface of the image carrier. It tends to cause images.
The particle size of the granulated product can be measured using, for example, a laser diffraction particle size distribution measuring device (SALD-2300, manufactured by Shimadzu Corporation).

  In the present invention, it is preferable to compression-mold the granulated material produced as described above. In this case, the structure of the molded body is maintained by a binding force mainly composed of cohesive force between particles while maintaining a discontinuous state at the boundary (grain boundary) between the protective agent particles. Since a compact formed by such agglomeration of particles easily breaks down to a powder having the original particle diameter with a relatively gentle force, the desired median diameter (D50) can be obtained by grinding them with a foam roller. It becomes possible to supply the protective agent powder. Therefore, the median diameter (D50) of the protective agent ground by the foam roller is not changed (same as) the median diameter (D50) of the granulated product of the protective agent.

In the present invention, since the median diameter (D50) of the protective agent powder is set larger than the average cell diameter of the foam roller, the protective agent powder is contained inside the cell of the foam roller even during long-term use. Since the body does not enter and the grinding force against the protective agent block of the foam roller does not decrease, it is possible to supply the protective agent stably over time.
In this case, it is preferable that the median diameter (D50) of the protective agent powder is larger than the average cell diameter of the foam roller by 5% (1.05 times) or more.

-Fatty acid metal salt-
The fatty acid metal salt is not particularly limited and may be appropriately selected depending on the purpose.For example, stearic acid metal salt, oleic acid metal salt, palmitic acid metal salt, caprylic acid metal salt, linolenic acid metal salt, Examples include ricinoleic acid metal salts. These may be used alone or in combination of two or more.

  Examples of the metal stearate include, for example, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, stearin Examples include zinc acid.

  Examples of the metal oleate include zinc oleate, magnesium oleate, iron oleate, cobalt oleate, copper oleate, lead oleate, and manganese oleate.

  Examples of the metal palmitate include zinc palmitate, cobalt palmitate, lead palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, and the like.

  Examples of the caprylic acid metal salt include lead caprylate.

  Examples of the linolenic acid metal salt include zinc linolenate, cobalt linolenate, and calcium linolenate.

  Examples of the ricinoleic acid metal salt include zinc ricinoleate and cadmium ricinoleate.

  Among these, as the fatty acid metal salt, the substance having a lamellar crystal has a layered structure in which amphiphilic molecules are self-organized, and when shearing force is applied, the crystal breaks along the interlayer and is slippery. A metal stearate salt is preferable in that it is excellent in lubricity, covers the surface of the image carrier relatively evenly, protects well from electrical stress in the charging process, and is excellent in suppressing contamination of the image carrier, and stearic acid metal salt. Zinc acid is more preferred.

  There is no restriction | limiting in particular as content of the said fatty-acid metal salt in the said protective agent, According to the objective, it can select suitably.

-Inorganic lubricant-
The inorganic lubricant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, mica, boron nitride, molybdenum disulfide, tungsten disulfide, talc, kaolin, montmorillonite, calcium fluoride, graphite, etc. Is mentioned. These may be used alone or in combination of two or more. Among these, as the inorganic lubricant, boron nitride, mica, and talc are preferable, and boron nitride is more preferable because it is excellent in suppressing contamination of the charging member.

There is no restriction | limiting in particular as content of the said inorganic lubricant in the said protective agent, According to the objective, it can select suitably.
The protective agent can also contain organic fine particles such as PMMA.

  The content ratio between the fatty acid metal salt and the inorganic lubricant in the protective agent is not particularly limited and may be appropriately selected depending on the intended purpose, but the fatty acid metal salt: the inorganic lubricant is in a mass ratio. 100: 0 to 50:50 is preferable, and 90:10 to 60:40 is more preferable. If the content ratio of the fatty acid metal salt is less than 50:50, it may be difficult to form a protective layer on the image carrier. When the content ratio is in the more preferable range, it is advantageous in that it is excellent in suppressing contamination of the image carrier and contamination of the charging member.

  There is no restriction | limiting in particular as a magnitude | size and a shape of the said protective agent, According to the objective, it can select suitably. Examples of the shape include block shapes such as a quadrangular prism shape and a cylindrical shape. Among these, the shape of the protective agent is preferably a square columnar shape.

<< Other parts >>
There is no restriction | limiting in particular as said other member in the said protective layer formation means, According to the objective, it can select suitably, For example, a pressing force provision member, a protective layer formation member, etc. are mentioned.

-Pressure applying member-
The pressing force applying member is not particularly limited as long as it is a member that presses the protective agent block and causes the protective agent supply member to contact the protective agent block, and can be appropriately selected according to the purpose. For example, a pressure spring is mentioned.

-Protective layer forming member-
The protective layer forming member is not particularly limited as long as it can form a protective layer by thinning the protective agent supplied to the surface of the image carrier, and can be appropriately selected according to the purpose. For example, a blade etc. are mentioned.

There is no restriction | limiting in particular as a material of the said blade, According to the objective, it can select suitably, For example, urethane rubber, hydrin rubber, silicone rubber, fluororubber etc. are mentioned.
These may be used individually by 1 type and may use 2 or more types together.
In these blades, the contact portion with the image carrier may be coated or impregnated with a low coefficient of friction material. Further, in order to adjust the hardness of the blade, a filler such as an organic filler or an inorganic filler may be dispersed.

The blade is fixed to the blade support by any method such as adhesion or fusion so that the tip can be pressed against the surface of the image carrier. The thickness of the blade cannot be uniquely defined in view of the force applied by pressing, but is preferably 0.5 mm to 5 mm, and more preferably 1 mm to 3 mm.
Also, the length of the blade that protrudes from the blade support and can be deflected, that is, the so-called free length is not uniquely defined in consideration of the force applied by pressing in the same manner. Preferably, 2 mm to 10 mm is more preferable.

  As another configuration of the protective layer forming member, a coating layer of resin, rubber, elastomer or the like is coated or dipped on the surface of an elastic metal blade such as a spring plate via a coupling agent or a primer component as necessary. For example, the film may be formed by a method such as heat curing if necessary, and surface polishing if necessary.

The coating layer contains at least a binder resin and a filler, and further contains other components as necessary.
The binder resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), fluororesin such as polyvinylidene chloride (PVdF); fluoroelastomer, silicone elastomer such as methylphenyl silicone elastomer, and the like.

  There is no restriction | limiting in particular as average thickness of the said elastic metal braid | blade, Although it can select suitably according to the objective, 0.05 mm-3 mm are preferable and 0.1 mm-1 mm are more preferable. In the elastic metal blade, in order to suppress twisting of the blade, a process such as bending may be performed in a direction substantially parallel to the support shaft after the attachment.

  The force that presses the image carrier with the protective layer forming member is sufficient to spread the protective agent for the image carrier to form a protective layer, and the linear pressure is preferably 5 gf / cm to 80 gf / cm, preferably 10 gf. / Cm to 60 gf / cm is more preferable.

  The protective layer forming member may also serve as a cleaning member. However, in order to more reliably form the protective layer, the cleaning material is used to remove in advance the residue mainly composed of toner on the image carrier, and then the residue. It is preferable not to mix in the protective layer.

The protective layer forming means will be described with reference to the drawings. FIG. 3 is a schematic sectional view showing an example of the protective layer forming means.
The protective layer forming means 2 disposed facing the image carrier 1 includes a protective agent block 21, a foam roller 22 as a protective agent supply member having a foam layer, a pressing force applying member 20, and a support 42. It is mainly formed from the fixed protective layer forming member 41 or the like.

The protective agent block 21 contacts the foam roller 22 by the pressing force of the pressing force applying member 20. The protective agent supply member 22 is preferably rotated and rubbed with the image carrier 1 with a linear velocity difference, thereby supplying the protective agent held on the surface of the foam roller 22 to the surface of the image carrier 1.
Since the protective agent supplied to the surface of the image carrier 1 may not be a sufficient protective layer at the time of supply depending on the selection of the material type, for example, a blade-like member is used to form a more uniform protective layer. The protective agent supply member 41 has a thin layer to form a protective layer.

  The image carrier 1 on which the protective layer is formed is, for example, brought into contact or proximity with a charging roller (charging member) 3 to which a DC voltage or a voltage obtained by superimposing an AC voltage is applied by a high voltage power source (not shown). The image carrier is charged by discharge in a minute gap. At this time, a part of the protective layer is decomposed or oxidized due to electrical stress, and air discharge products adhere to the surface of the protective layer.

  The deteriorated image carrier protecting agent is removed by a cleaning mechanism together with components such as toner remaining on the image carrier by a normal cleaning means. As such a cleaning means, the protective layer forming member 41 may also be used. However, the function of removing the residue on the surface of the image carrier and the function of forming the protective layer are based on the state of rubbing of an appropriate member. Therefore, it is preferable to separate the functions in order to form the protective layer more reliably. As such an embodiment, as shown in FIG. 3, a cleaning unit 4 including a cleaning member 43, a cleaning pressing member 44, and the like is provided upstream of the protective agent supply member 22 with respect to the rotation direction of the image carrier 1. It is preferable to remove the residue such as toner on the surface of the image carrier 1 with the cleaning member 43 in advance so that the residue does not enter the protective layer.

<Image carrier>
The material, shape, structure, size and the like of the image carrier are not particularly limited and can be appropriately selected from known ones. A preferable example of the shape of the image carrier is a drum shape. Examples of the material of the image carrier include inorganic image carriers such as amorphous silicon and selenium; organic image carriers such as polysilane and phthalopolymethine. These may be used alone or in combination of two or more.

The image carrier preferably comprises a conductive support and at least a photosensitive layer on the conductive support, and further comprises other layers such as an undercoat layer and an outermost surface layer as necessary. Have.
An appropriate amount of a plasticizer, an antioxidant, a leveling agent or the like can be added to each layer as necessary.

<< Photosensitive layer >>
The photosensitive layer is not particularly limited and may be appropriately selected depending on the intended purpose. However, the photosensitive layer preferably contains a charge generation material, a charge transport material, and a binder resin. Contains ingredients.
The photosensitive layer may be a single layer type in which the charge generation material and the charge transport material are mixed, a forward layer type in which a charge transport layer is provided on the charge generation layer, or a charge generation layer on the charge transport layer. There is a reverse layer type provided.

-Charge generation material-
The charge generating material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include azo pigments such as monoazo pigments, bisazo pigments, trisazo pigments, tetrakisazo pigments, and triarylmethane dyes. , Thiazine dyes, oxazine dyes, xanthene dyes, cyanine dyes, styryl dyes, pyrylium dyes, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indus Organic pigments or dyes such as Ron-based pigments, squarylium-based pigments, phthalocyanine-based pigments; inorganic materials such as selenium, selenium-arsenic, selenium-tellurium, cadmium sulfide, zinc oxide, titanium oxide, and amorphous silicon. These may be used individually by 1 type and may use 2 or more types together.

-Charge transport material-
Examples of the charge transport material include anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, phenothiazine derivatives, pyrazoline compounds, hydrazone compounds, styryl compounds, styrylhydrazone compounds, enamine compounds, butadiene compounds, distyryl compounds, oxazoles. Examples thereof include compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, and triphenylmethane derivatives. These may be used individually by 1 type and may use 2 or more types together.

-Binder resin-
The binder resin is electrically insulating and may be a known thermoplastic resin, thermosetting resin, photocurable resin, photoconductive resin, or the like. Examples of the binder resin include polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, polyvinyl butyral, Polyvinyl acetal, polyester, phenoxy resin, (meth) acrylic resin, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, ABS resin and other thermoplastic resins, phenol resin, epoxy resin, urethane resin, melamine resin, isocyanate Examples thereof include thermosetting resins such as resins, alkyd resins, silicone resins, and thermosetting acrylic resins, polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene. These may be used individually by 1 type and may use 2 or more types together.

<< Conductive support >>
There is no restriction | limiting in particular as said electroconductive support body, Although it can select suitably according to the objective, What shows electroconductivity whose volume resistance value is 1.0 * 10 < ¹⁰ > (omega | ohm) * cm or less is preferable.
As such a conductive support, for example, a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, or a metal oxide such as tin oxide or indium oxide is deposited or sputtered to form a film. Shaped or cylindrical plastic, paper-coated, or aluminum, aluminum alloy, nickel, stainless steel, etc., and after making them into drums by extrusion, drawing, etc., cutting, superfinishing, polishing A surface-treated tube or the like can be used.

There is no restriction | limiting in particular as said drum-shaped support body, Although it can select suitably according to the objective, A diameter is preferable 20 mm-150 mm, 24 mm-100 mm are more preferable, 28 mm-70 mm are especially preferable. If the diameter of the drum-shaped support is less than 20 mm, it is physically difficult to arrange each means such as a charging member, exposure means, developing means, transfer means, and cleaning means around the drum. If it exceeds 150 mm, the image forming apparatus may become large. In particular, when the image forming apparatus is a tandem type, since it is necessary to mount a plurality of image carriers, the diameter is preferably 70 mm or less, and more preferably 60 mm or less.
Further, an endless nickel belt or an endless stainless steel belt as disclosed in JP-A-52-36016 can also be used as the conductive support.

<< undercoat layer >>
The image carrier may be provided with an undercoat layer between the photosensitive layer and the conductive support.
The undercoat layer may be a single layer or a plurality of layers. For example, (1) a resin-based component, (2) a white pigment and a resin-based component, and (3) a metal oxide film obtained by chemically or electrochemically oxidizing the surface of a conductive substrate. Can be mentioned. Among these, those containing a white pigment and a resin as main components are preferable.

  The white pigment is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include metal oxides such as titanium oxide, aluminum oxide, zirconium oxide and zinc oxide. These may be used alone or in combination of two or more. Among these, titanium oxide is particularly preferable in terms of excellent charge injection preventing properties from the conductive support.

  There is no restriction | limiting in particular as said resin, According to the objective, it can select suitably, For example, thermoplastic resins, such as polyamide, polyvinyl alcohol, casein, methylcellulose; Acrylic, phenol, melamine, alkyd, unsaturated polyester, epoxy And thermosetting resins. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as thickness of the said undercoat layer, Although it can select suitably according to the objective, 0.1 micrometer-10 micrometers are preferable, and 1 micrometer-5 micrometers are more preferable.

-Outermost surface layer-
The image carrier may be provided with an outermost surface layer on the photosensitive layer in order to improve mechanical strength, abrasion resistance, gas resistance, cleaning properties, and the like.
The outermost surface layer is not particularly limited and may be appropriately selected depending on the intended purpose. However, the outermost layer preferably contains an inorganic filler, and is a polymer compound having higher mechanical strength than the material of the photosensitive layer, A polymer compound in which an inorganic filler is dispersed is more preferable.

  The polymer compound is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably a thermoplastic resin, a thermosetting resin or the like, has high mechanical strength, and wear due to friction with the cleaning means. A thermosetting resin is more preferable in that it can be greatly reduced, and a thermosetting resin cross-linked by a cross-linking agent having a polyfunctional acryloyl group, carboxyl group, hydroxyl group, amino group or the like is particularly preferable.

  The resin used for the outermost surface layer is preferably one that is transparent to the writing light at the time of image formation and excellent in insulation, mechanical strength, and adhesiveness. For example, ABS resin, ACS resin, olefin-vinyl Monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic Resin, polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride, epoxy resin Etc., and the like. These may be used alone or in combination of two or more.

  If the outermost surface layer has a small thickness, there is no problem even if it does not have the charge transport capability, but if the outermost surface layer without the charge transport capability is formed thick, the sensitivity of the image carrier decreases. It is preferable to include the above-described charge transport material in the outermost surface layer or to use a polymer resin having a charge transport capability as the polymer resin used in the surface layer because it is likely to cause an increase in potential after exposure and an increase in residual potential. .

Since the mechanical strength of the photosensitive layer and the outermost surface layer generally differs greatly, when the outermost surface layer is worn away due to friction with the cleaning means, the photosensitive layer is worn away immediately. When providing a layer, it is important to have a sufficient thickness.
The specific thickness of the outermost surface layer is preferably 0.1 μm to 12 μm, more preferably 1 μm to 10 μm, and particularly preferably 2 μm to 8 μm. When the thickness is less than 0.1 μm, it is too thin and is likely to be partially lost due to friction with the cleaning blade, and wear of the photosensitive layer may proceed from the lost portion. Decrease in sensitivity, increase in potential after exposure, and increase in residual potential are likely to occur. Particularly when a polymer having charge transport ability is used, the cost of the polymer having charge transport ability may be increased.

  The outermost surface layer preferably has a charge transporting capability. In order to provide the outermost surface layer with a charge transporting capability, the polymer used for the outermost surface layer and the above-described charge transporting material are mixed and used. A method using a polymer having a charge transporting capability for the outermost surface layer is conceivable, and the latter method is preferable because an image carrier having high sensitivity and little increase in potential after exposure and little increase in residual potential can be obtained.

  The outermost surface layer may contain a filler in order to increase the mechanical strength of the outermost surface layer. Examples of the filler include inorganic fillers and organic fillers. Among these, an inorganic filler is preferable. Examples of the inorganic filler include aluminum oxide (alumina), titanium oxide, tin oxide, potassium titanate, titanium nitride, zinc oxide, indium oxide, and antimony oxide. Examples of the organic filler include fluororesins such as polytetrafluoroethylene, silicone resins, and the like.

  When the image carrier has the outermost surface layer, the change in the surface state of the image carrier can be made extremely small. Even a toner having a large degree and a toner having a small average particle diameter are advantageous in that stable cleaning can be performed over a long period of time. Further, since the water contact angle on the surface of the image carrier is improved and water repellency can be imparted to the surface of the image carrier, it is advantageous in that it prevents water absorption on the surface of the image carrier and suppresses image blur. is there.

<Other means and other processes>
The other means in the image forming apparatus is not particularly limited and may be appropriately selected depending on the purpose. For example, the electrostatic latent image forming means, the developing means, the transferring means, the fixing means, the static eliminating means, and the cleaning Means, recycling means, control means and the like.
The other steps in the image forming method are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include an electrostatic latent image forming step, a developing step, a transferring step, a fixing step, a static eliminating step, and a cleaning. A process, a recycling process, a control process, etc. are mentioned.

<< Electrostatic latent image forming means and electrostatic latent image forming process >>
The electrostatic latent image forming means is not particularly limited as long as it is a means for forming an electrostatic latent image on the image carrier, and can be appropriately selected according to the purpose. For example, the image carrier A means for charging the surface of the image bearing member and an exposure device for exposing the surface of the image carrier imagewise.
The electrostatic latent image forming step is not particularly limited as long as it is a step of forming an electrostatic latent image on the image carrier, and can be appropriately selected according to the purpose. This can be done using image forming means.

The charging can be performed, for example, by applying a voltage to the surface of the image carrier using the charger.
The charger is not particularly limited and may be appropriately selected depending on the purpose. For example, a known contact charging device including a conductive or semiconductive roll, brush, film, rubber blade, etc. And non-contact chargers utilizing corona discharge such as corotrons and corotrons.
The charger preferably has voltage applying means for applying a voltage having an AC component.

The exposure can be performed, for example, by exposing the surface of the image carrier imagewise using the exposure device.
The exposure device is not particularly limited as long as it can perform image-like exposure on the surface of the image carrier charged by the charger, and can be appropriately selected according to the purpose. Examples include various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system.
In the present invention, an optical back side system in which imagewise exposure is performed from the back side of the image carrier may be adopted.

<< Developing means and development process >>
The developing means is means for developing the electrostatic latent image using toner or developer to form a visible image.
The developing unit is not particularly limited as long as it can be developed using the toner or the developer, and can be appropriately selected from known ones. For example, the toner or the developer is contained, Preferable examples include those having at least a developing unit capable of bringing the toner or the developer into contact or non-contact with the electrostatic latent image.
The development step is not particularly limited as long as it is a step of developing the electrostatic latent image using a toner or a developer to form a visible image, and can be appropriately selected according to the purpose. The developing unit can be used.

  The developing unit may be a dry developing type, a wet developing type, a single color developing unit, or a multi-color developing unit. For example, a toner or a developer having a stirrer for charging the toner or developer by frictional stirring and a rotatable magnet roller is preferable.

In the developing device, for example, the toner and the carrier are mixed and agitated, and the toner is charged by friction at that time, and held on the surface of the rotating magnet roller in a raised state to form a magnetic brush. . Since the magnet roller is disposed in the vicinity of the image bearing member (photosensitive member), a part of the toner constituting the magnetic brush formed on the surface of the magnet roller is caused by the electric attractive force. It moves to the surface of the image carrier (photoreceptor). As a result, the electrostatic latent image is developed with the toner, and a visible image is formed with the toner on the surface of the image carrier (photoconductor).
The developer accommodated in the developing device is a developer containing the toner, but the developer may be a one-component developer or a two-component developer.

-Toner-
The toner is not particularly limited and may be appropriately selected depending on the intended purpose.For example, a polyester prepolymer having a functional group containing a nitrogen atom, a compound that extends or crosslinks with the prepolymer, a polyester, a colorant, Examples thereof include a toner prepared by a polymerization method in which a toner composition containing a release agent or the like is crosslinked and / or extended in the presence of resin fine particles in an aqueous medium. The toner can reduce the hot offset by curing the toner surface, and can prevent the fixing unit from becoming dirty and appearing on the image.

--Polyester prepolymer--
Examples of the polyester prepolymer having a functional group containing a nitrogen atom include a polyester prepolymer having an isocyanate group.
Examples of the polyester prepolymer having an isocyanate group include a product obtained by further reacting a polyester having an active hydrogen group with a polyisocyanate, which is a condensate of a polyol and a polycarboxylic acid.
The active hydrogen group possessed by the polyester is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a hydroxyl group (alcoholic hydroxyl group and phenolic hydroxyl group), amino group, carboxyl group, mercapto group and the like. It is done. Among these, alcoholic hydroxyl groups are particularly preferable.

  There is no restriction | limiting in particular as said polyol, According to the objective, it can select suitably, For example, diol, a trivalent or more polyol, etc. are mentioned. Among these, a diol alone or a mixture of a diol and a small amount of a trivalent or higher polyol is preferable.

  There is no restriction | limiting in particular as said polycarboxylic acid, According to the objective, it can select suitably, For example, dicarboxylic acid and trivalent or more polycarboxylic acid are mentioned. Among these, dicarboxylic acid alone or a mixture of dicarboxylic acid and a small amount of trivalent or higher polycarboxylic acid is preferable.

  The ratio of the polyol and the polycarboxylic acid is not particularly limited and may be appropriately selected depending on the intended purpose. The equivalent ratio of hydroxyl group [OH] and carboxyl group [COOH] ([OH] / [COOH] ) Is preferably 2/1 to 1/1, more preferably 1.5 / 1 to 1/1, and particularly preferably 1.3 / 1 to 1.02 / 1.

  Examples of the polyisocyanate include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.); Diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanurates; Or something blocked. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as a ratio of the said polyisocyanate, Although it can select suitably according to the objective, Equivalent ratio ([NCO] / [NCO] of an isocyanate group [NCO] and the hydroxyl group [OH] of the polyester which has a hydroxyl group. OH]), preferably 5/1 to 1/1, more preferably 4/1 to 1.2 / 1, and particularly preferably 2.5 / 1 to 1.5 / 1. When the equivalent ratio of [NCO] to [OH] exceeds 5, low-temperature fixability may be deteriorated. When the equivalent ratio of [NCO] to [OH] is less than 1, the polyester pre- The urea content in the polymer is lowered, and the hot offset resistance is deteriorated.

  Furthermore, if necessary, the molecular weight of the urea-modified polyester can be adjusted using an elongation terminator. Examples of the elongation terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), or those obtained by blocking them (ketimine compounds).

--Compound that extends or crosslinks with prepolymer--
Examples of the compound that extends or crosslinks with the prepolymer include amines.
Examples of the amines include diamines, trivalent or higher polyamines, amino alcohols, amino mercaptans, amino acids, and those obtained by blocking these amino groups. Among these amines, preferred are diamine and a mixture of a diamine and a small amount of a triamine or higher polyamine.

The circularity of the toner is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.93 to 1.00. The circularity of the toner can be calculated from the following equation.
Toner circularity = perimeter of a circle having the same area as the particle projection area / perimeter of the particle projection image

  In the present invention, the present invention can be applied not only to a polymerization toner having a configuration suitable for obtaining a high-quality image, but also to an irregularly shaped toner by a pulverization method. In this case, the life of the apparatus is greatly extended. This is advantageous in that it can. The material constituting the toner of such a pulverization method can be appropriately selected from those usually used as an electrophotographic toner according to the purpose.

  The ratio (D4 / D1) of the weight average particle diameter (D4) to the number average particle diameter (D1) of the toner is not particularly limited and may be appropriately selected depending on the intended purpose. .40 is preferred.

<< Transfer means and transfer process >>
The transfer means is means for transferring the visible image to a recording medium. The transfer means includes a primary transfer means for transferring the visible image onto an intermediate transfer member to form a composite transfer image, and a secondary transfer means for transferring the composite transfer image onto a recording medium. The aspect which has is preferable.
The transfer step is not particularly limited as long as it is a step of transferring the visible image to a recording medium, and can be appropriately selected according to the purpose. For example, the transfer step can be performed using the transfer unit.

The transfer unit (the primary transfer unit and the secondary transfer unit) includes at least a transfer unit that peels and charges the visible image formed on the image carrier to the recording medium side. preferable. There may be one transfer means or two or more transfer means. Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.
The recording medium is not particularly limited and can be appropriately selected from known recording media (recording paper).

  The image carrier is used to perform image transfer by a so-called intermediate transfer method in which a toner image formed on the image carrier is primarily transferred to perform color superposition and then transferred to a recording medium. It may be a body.

  There is no restriction | limiting in particular as said intermediate transfer body, According to the objective, it can select suitably from well-known transfer bodies, For example, a transfer belt etc. are mentioned suitably.

The intermediate transfer member is not particularly limited and may be appropriately selected depending on the intended purpose. However, it has a volume resistance value of 1.0 × 10 ⁵ Ω · cm to 1.0 × 10 ¹¹ Ω · cm. Is preferable. When the volume resistance is less than 1.0 × 10 ⁵ Ω · cm, when transferring a toner image from an image carrier onto an intermediate transfer member, so-called transfer dust is generated in which the toner image is disturbed due to discharge. If it exceeds 1.0 × 10 ¹¹ Ω · cm, the counter charge of the toner image remains on the intermediate transfer member after the toner image is transferred from the intermediate transfer member to a recording medium such as paper. It may appear as an afterimage on the top.

As the intermediate transfer member, for example, a metal oxide such as tin oxide or indium oxide, conductive particles such as carbon black, or a conductive polymer may be used alone or in combination with a thermoplastic resin, and then extruded. A belt-like or cylindrical plastic can be used. In addition, it is also possible to add conductive particles or conductive polymer to a resin solution containing a thermal crosslinking reactive monomer or oligomer, if necessary, and perform centrifugal molding while heating to obtain an intermediate transfer member on an endless belt. it can.
When providing a surface layer on the intermediate transfer member, the resistance is adjusted by appropriately using a conductive material in combination with the composition excluding the charge transport material among the surface layer materials used for the outermost surface layer. be able to.

<< Fixing means and fixing process >>
The fixing means is means for fixing the visible image transferred to the recording medium. It may be performed each time the toner of each color is transferred to the recording medium, or may be performed at the same time in a state where the toner of each color is laminated.
The fixing unit is not particularly limited and may be appropriately selected depending on the intended purpose, but a known heating and pressing unit is preferable. Examples of the heating and pressing unit include a combination of a heating roller and a pressure roller, and a combination of a heating roller, a pressure roller, and an endless belt.
The heating in the heating and pressing means is usually preferably 80 ° C to 200 ° C.
In the present invention, for example, a known optical fixing device may be used together with or in place of the fixing unit depending on the purpose.
The fixing step is a step of fixing the visible image transferred to the recording medium using the fixing unit, and may be performed each time the toner of each color is transferred to the recording medium, or may be applied to the toner of each color. On the other hand, it may be carried out simultaneously at the same time in a state of being laminated.

<< Static elimination means and static elimination process >>
The neutralization means is not particularly limited and may be appropriately selected from known neutralizers as long as it can apply a neutralization bias to the image carrier. It is done.
The neutralization step is a step of performing neutralization by applying a neutralization bias to the image carrier, and can be suitably performed by the neutralization unit.

<< Cleaning means and cleaning process >>
The cleaning unit is preferably provided downstream of the transfer unit and upstream of the protective layer forming unit.
The cleaning means is not particularly limited, and may be selected from known cleaners as long as it can remove the electrophotographic toner remaining on the image carrier. For example, a magnetic brush cleaner, Suitable examples include electrostatic brush cleaners, magnetic roller cleaners, blade cleaners, brush cleaners, web cleaners, and the like.
The cleaning step is a step of removing the electrophotographic toner remaining on the image carrier, and can be suitably performed by the cleaning unit.

<< Recycling means and recycling process >>
There is no restriction | limiting in particular as said recycling means, A well-known conveyance means etc. are mentioned.
The recycling step is a step of recycling the toner removed by the cleaning step to the developing unit, and can be suitably performed by the recycling unit.

<< Control means and control process >>
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as sequencers and computers.
The control step is a step of controlling each step, and can be suitably performed by the control means.

Hereinafter, an example of the image forming apparatus of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to this. FIG. 4 is a schematic cross-sectional view showing an example of the image forming apparatus 100 of the present invention.
Around the drum-shaped image carrier (1Y, 1M, 1C, 1K), a protective layer forming unit 2, a charging unit 3, an exposure unit 8, a developing unit 5, a transfer unit 6, and a cleaning unit 4 are arranged, respectively. Yes.

Next, a series of processes for image formation will be described using a negative-positive process.
An image carrier represented by an image carrier (OPC) having an organic photoconductive layer is neutralized by a static elimination lamp (not shown) or the like, and is uniformly negatively charged by the charging means 3.
When the image carrier is charged by the charging unit 3, the image carrier (1Y, 1M, 1C, 1K) is charged to a desired potential from the voltage application mechanism (not shown) to the charging unit 3. A suitable and appropriate voltage or a charging voltage obtained by superimposing an AC voltage thereon is applied.

The charged image carrier (1Y, 1M, 1C, 1K) forms a latent image with laser light irradiated by the exposure means 8 such as a laser optical system (the absolute value of the exposed portion potential is the absolute value of the non-exposed portion potential). Is lower than the value).
Laser light is emitted from a semiconductor laser, and the surface of the image carrier (1Y, 1M, 1C, 1K) is scanned in the direction of the rotation axis of the image carrier by a polygonal polygonal mirror (polygon) that rotates at high speed. .

The latent image formed in this manner is developed with a developer made of toner particles or a mixture of toner particles and carrier particles supplied on a developing sleeve which is a developer carrying member in the developing means 5, and toner can be transferred. A visual image is formed.
At the time of developing the latent image, a voltage of an appropriate magnitude between the exposed portion and the non-exposed portion of the image carrier (1Y, 1M, 1C, 1K) is applied from the voltage applying mechanism (not shown) to the developing sleeve. A developing bias with an alternating voltage superimposed thereon is applied thereto.

The toner image formed on the image carrier (1Y, 1M, 1C, 1K) corresponding to each color is transferred onto the intermediate transfer body 60 by the transfer means 6 and fed from the paper feed mechanism 200. The toner image is transferred onto a recording medium such as
At this time, it is preferable that a potential having a polarity opposite to the polarity of toner charging is applied to the transfer unit 6 as a transfer bias. Thereafter, the intermediate transfer member 60 is separated from the image carrier to obtain a transfer image.

Further, the toner particles remaining on the image carrier are collected by the cleaning member into the toner collecting chamber in the cleaning unit 4.
The transferred recording medium is heated by the fixing means 7 and the toner is fixed to the recording medium.
As the image forming apparatus, a plurality of developing units 5 are used, and a plurality of toner images with different colors sequentially produced by the plurality of developing units 5 are sequentially transferred onto a transfer material, and then sent to a fixing unit. The toner fixing device may be used, or a plurality of similarly produced toner images may be sequentially transferred onto the intermediate transfer member 60 and then transferred to a recording medium such as paper. An apparatus for fixing in the same manner may be used later.

(Process cartridge)
The process cartridge of the present invention includes an image carrier, a protective agent supplying member that rotatably contacts the surface of the image carrier, and a protective layer having at least an image carrier protective agent made of a granulated material containing at least a fatty acid metal salt. Forming means, and further, if necessary, other means such as charging means, exposure means, developing means, transfer means, cleaning means, and static elimination means.
In this case, the protective agent supply member is a foam roller, and the median diameter (by volume-based particle size distribution obtained by measuring the particle size distribution measurement method of the granulated product of the image carrier protective agent by a laser diffraction scattering type particle size distribution ( D50) needs to be larger than the average cell diameter of the foam roller.
The process cartridge can be detachably provided in various electrophotographic image forming apparatuses, and is preferably provided detachably in the image forming apparatus of the present invention described above.

Here, FIG. 5 is a schematic sectional view showing an example of a process cartridge used in the present invention.
In the process cartridge, the protective layer forming apparatus 2 disposed opposite to the photosensitive drum 1 as an image carrier includes a protective agent block 21, a foam roller 14, and a protective layer forming member 24.
The photosensitive drum 1 as the image carrier has a surface on which the image carrier protective agent and the toner component partially deteriorated after the transfer process remain, but the surface residue is cleaned by the cleaning device 4. To be cleaned.
In FIG. 5, the cleaning device 4 is abutted at an angle similar to a so-called counter type (leading type).
The protective agent is supplied from the foam roller 22 to the surface of the image carrier from which the residual toner and the deteriorated image carrier protective agent on the surface have been removed by the cleaning device 4, and the protective layer forming member 24 protects the film. A layer is formed.
The image carrier having the protective layer formed in this manner is charged, and then an electrostatic latent image is formed by exposure L such as a laser, developed by the developing device 5 to be visualized, and transferred outside the process cartridge. The image is transferred to the recording medium 7 by the apparatus 6 or the like.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example of production of image carrier protecting agent)
-Preparation of image carrier protecting agents 1-8-
The image carrier protective agent component was mixed and granulated so as to have the composition and mixing ratio shown in Table 1.
The granulation is performed using a roller compactor RC-MINI (manufactured by Freund Sangyo Co., Ltd.), so that the median diameter (D50) of the granulated product shown in Table 1 is reached: 2 rpm to 10 rpm, molding pressure: Granulation was performed under conditions of 1,000 kg to 5,000 kg.
The median diameter (D50) of the obtained granulated product is measured by a laser diffraction scattering particle size distribution measuring method using a laser diffraction particle size distribution measuring device (SALD-2300, manufactured by Shimadzu Corporation). The median diameter (D50) according to the volume-based particle size distribution obtained in the above was measured.

Next, after each of the granulated materials is put into an aluminum mold having a depth of 20 mm, a width of 8 mm, and a length of 350 mm, and the surface is leveled with a spatula, the height of the packing is 8 mm. The powder compacted body was molded by pressing with a pressing die. At this time, the weight of the powder put into the mold was adjusted so that the filling ratio of the powder compacted body was 90%. That is, the weight of the powder to be charged = the volume of the mold × the true specific gravity of the powder × 0.9.
After molding, the solid was removed from the mold, shaped into 8 mm × 8 mm × 320 mm, and attached to a metal support with double-sided tape to produce image carrier protective agents 1-8.

Each material shown in Table 1 is as follows.
・ Zinc stearate (fatty acid metal salt): GF-200, manufactured by NOF Corporation ・ Zinc laurate (fatty acid metal salt): reagent, manufactured by Wako Pure Chemical Industries, Ltd. ・ Boron nitride (inorganic lubricant): NX5, Momentive・ Performance Materials ・ Mica (inorganic lubricant): SA mica, manufactured by Miyoshi Kasei Co., Ltd. ・ PMMA (organic fine particles): MP-1000, manufactured by Soken Chemical Co., Ltd.

(Production example of foam roller)
-Production of foam rollers AE-
Commercially available urethane foam rollers A to E shown in Table 2 were prepared. The core of the urethane foam roller was (material SUS, outer diameter 6 mm product), and the thickness of the urethane foam layer was adjusted so that the outer diameter of the urethane foam roller was (12 mm).
Next, for the foam rollers A to E, the average cell diameter and hardness were measured as follows. The results are shown in Table 2.

<Measurement of average cell diameter>
The average cell diameter of the foam roller was determined as a value obtained by dividing 1 inch (= 25.4 mm) by the number of cells measured by the following method.
On the surface of the foam layer of the foam roller 32, three measurement points were arbitrarily selected between the axial end portions and the central portion (here, in FIG. 2A, 30 is the end measurement portion, and 31 is the central portion). Is the measurement point.) Next, two further points were selected in the circumferential direction at each measurement point, and a total of nine measurement points were determined. Next, the photograph screen of each measurement location was observed using a microscope. Then, as shown in FIG. 2B, a line X having a length corresponding to an actual size of 1 inch is drawn at the center of the photo screen, the number of cells in the line is counted, and an average value of 9 points is obtained. Asked. A cell that touches even a 1-inch line is counted as one. For example, in the case shown in FIG. 2B, since the number of cells is 12, the average cell diameter is 25.4 (mm) ÷ 12 (cells) = 2.117 (mm) = 2,117 (μm). .

<Hardness>
Hardness (unit: N) was measured based on JIS K 6400 at any three points on the surface of the foam layer, and the values were averaged.

Example 1
A photoconductor unit was taken out from the black station of a color MFP image MP MP5000 manufactured by Ricoh Co., Ltd., which is an image forming apparatus having a protective agent layer forming means, and the protective agent 1 shown in Table 1 was used as the image carrier protective agent. Furthermore, instead of the brush roller as a protective agent supply member, roller A in Table 2 was attached. The photoreceptor unit thus produced was mounted on the black station of imgio MP C5000.

  Next, using the color MFP image MP MP5000 manufactured by Ricoh Co., Ltd., modified as described above, a total of 60,000 sheets of A4 size plate and 5% image area ratio chart were continuously sent in an 80% RH environment at 27 ° C. Paper was then evaluated for contamination of the member as follows. In addition, the consumption of the image carrier protecting agent is measured between the initial 1,000 sheets and 1,000 sheets (59,000 to 60,000 sheets) before the end of the run as follows. went. The results are shown in Table 4. In addition, the median diameter (D50) of the protective agent ground by the foam roller as the protective agent supply member is separately measured by the above-mentioned laser diffraction particle size distribution measuring device, and the median diameter of the granulated product of the protective agent is measured. (D50) and it was confirmed that there was no change.

<Evaluation of contamination status of components after run>
Regarding the photoreceptor at the end of the 60,000 sheet run, the degree of contamination of the photoreceptor surface and the charging roller was visually observed and evaluated according to the following criteria.
〔Evaluation criteria〕
◎: No dirt on the member ○: The member is dirty but does not appear in the image △: The dirt on the member appears in the image, but the tolerance level ×: The level of the member that appears in the image is a problem Abnormal If there is, we checked whether abnormal images occurred at the corresponding locations. When the surface of the photoconductor is stained, white stripes are more likely to occur in a high temperature and high humidity environment. In addition, when the charging member is contaminated, black streaks are more likely to occur in a low temperature and low humidity environment. Therefore, for samples in which the charging member is visually observed, the sample is separately treated at 10 ° C. in a 15% RH environment. Image confirmation was performed.

<Measurement of protective agent consumption per 1,000 sheets>
The protective agent bar pressure was adjusted beforehand in advance so that the initial consumption of protective agent (weight reduction of protective agent / photoreceptor driving distance) was about 0.18 g / km under each condition. In addition, in the imgio MP C5000, a technique described in Japanese Patent Application Laid-Open No. 2007-293240 is adopted as a mechanism for pressurizing the protective agent, and the pressure is almost constant over time. Therefore, the change in the consumption of the protective agent accompanying the run is not affected by the pressurizing mechanism of the protective agent.

(Examples 2 to 10 and Comparative Examples 1 to 7)
In Example 1, instead of the protective agent 1 and the roller A, the combination of the image carrier protective agent and the foam roller shown in Table 3 was used in the same manner as in Example 1, except that the members after the run were completed. The contamination state and the protective agent consumption per 1,000 sheets were evaluated. The results are shown in Table 4.

From the results of Table 3 and Table 4, in Examples 1 to 10, the median diameter (D50) of the granulated product of the protective agent is larger than the average cell diameter of the foam roller, so the consumption of the protective agent is stable over time. ing. Furthermore, it was found that there was little photoconductor contamination and charging roller contamination after evaluation, and good quality could be maintained over a long period of time.
Further, from comparison between Examples 1 and 6 and Examples 2 to 5, the average cell diameter of the foam roller used in the present invention is set to 400 μm or more and 850 μm or less, and the median diameter of the granulated product of the protective agent (D50). It was found that by setting the thickness to 1,000 μm or less, a result with particularly less photoconductor contamination can be obtained.
Further, from comparison between Examples 3, 7, 8 and Examples 9, 10, it was found that charging roller contamination can be significantly reduced by including a fatty acid metal salt and an inorganic lubricant in the protective agent.
Further, from the comparison between Example 3 and Examples 7 and 8, by using zinc stearate as the fatty acid metal salt and boron nitride as the inorganic lubricant, particularly good results can be obtained for both the photosensitive member stain and the charging roller stain. I understood it.
Further, in Comparative Examples 1 to 7, the median diameter (D50) of the granulated product of the protective agent is smaller than the average cell diameter of the foam roller. It was found that it would occur as an abnormal image.

As an aspect of this invention, it is as follows, for example.
<1> An image carrier, a protective agent supplying member that rotatably contacts the surface of the image carrier, and a protective layer forming unit having at least an image carrier protective agent made of a granulated material containing at least a fatty acid metal salt. An image forming apparatus having
A median diameter (D50) based on a volume-based particle size distribution obtained by measuring the protective agent supplying member with a foam roller and measuring the granulated product of the image carrier protective agent by a laser diffraction / scattering particle size distribution measurement method is obtained. The image forming apparatus is characterized by being larger than an average cell diameter of the foam roller.
In the image forming apparatus described in <1>, since the protective agent powder does not accumulate in the cell of the foam roller, the consumption of the protective agent over time is stable.
<2> Median diameter by volume-based particle size distribution obtained by measuring the average cell diameter of the foam roller from 400 μm to 850 μm and measuring by a laser diffraction scattering particle size distribution measurement method of the granule of the image carrier protective agent The image forming apparatus according to <1>, wherein (D50) is 1,000 μm or less.
In the image forming apparatus described in <2>, since the consumption of the protective agent is stable, the photosensitive member is hardly contaminated, and the charging roller can be prevented from being stained.
<3> The image forming apparatus according to any one of <1> to <2>, wherein the foam roller includes open-cell foamed polyurethane.
<4> The image carrier protecting agent according to any one of <1> to <3>, wherein the image carrier protective agent is a block-shaped molded body obtained by compression molding a granulated product containing a fatty acid metal salt and an inorganic lubricant. This is an image forming apparatus.
In the image forming apparatus described in <4>, the charging roller contamination can be particularly reduced.
<5> The image forming apparatus according to <4>, wherein the fatty acid metal salt contains zinc stearate.
In the image forming apparatus described in <5>, good photoconductor protection property of zinc stearate is exhibited, and particularly, photoconductor contamination is small.
<6> The image forming apparatus according to any one of <4> to <5>, wherein the inorganic lubricant is boron nitride.
In the image forming apparatus described in <5>, good lubricity of boron nitride is exhibited, and charging roller contamination is particularly small.
<7> An image carrier, a protective agent supplying member that rotatably contacts the surface of the image carrier, and a protective layer forming unit having at least an image carrier protective agent made of a granulated material containing at least a fatty acid metal salt. A process cartridge comprising:
A median diameter (D50) based on a volume-based particle size distribution obtained by measuring the protective agent supplying member with a foam roller and measuring the granulated product of the image carrier protective agent by a laser diffraction / scattering particle size distribution measurement method is obtained. The process cartridge is larger than the average cell diameter of the foam roller.
In the process cartridge according to <7>, the life of parts around the photosensitive member can be extended.
<8> The surface of the image carrier using a protective layer forming means having at least a protective agent supplying member that rotatably contacts the surface of the image carrier and an image carrier protective agent composed of a granulated material containing at least a fatty acid metal salt. An image forming method including at least a protective layer forming step of forming a protective layer on the substrate,
A median diameter (D50) based on a volume-based particle size distribution obtained by measuring the protective agent supplying member with a foam roller and measuring the granulated product of the image carrier protective agent by a laser diffraction / scattering particle size distribution measurement method is obtained. The image forming method is characterized by being larger than the average cell diameter of the foam roller.

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Protection layer formation means 21 Protection agent block 22 Protection agent supply member (foam roller)
100 Image forming apparatus 200 Paper feed mechanism

Japanese Patent Publication No.51-22380 JP 2006-350240 A JP 2007-65100 A JP 2007-293240 A JP 2009-150986 A

Claims (8)

Image forming comprising: an image carrier; a protective agent supplying member that rotatably contacts the surface of the image carrier; and a protective layer forming unit having at least an image carrier protective agent made of a granulated material containing at least a fatty acid metal salt. A device,
A median diameter (D50) based on a volume-based particle size distribution obtained by measuring the protective agent supplying member with a foam roller and measuring the granulated product of the image carrier protective agent by a laser diffraction / scattering particle size distribution measurement method is obtained. An image forming apparatus having an average cell diameter larger than that of the foam roller.   The average cell diameter of the foam roller is 400 μm to 850 μm, and the median diameter (D50) based on the volume-based particle size distribution obtained by measuring the granulated product of the image carrier protective agent by the laser diffraction scattering type particle size distribution measuring method. The image forming apparatus according to claim 1, wherein the thickness is 1,000 μm or less.   The image forming apparatus according to claim 1, wherein the foam roller contains open-cell foamed polyurethane.   The image forming apparatus according to any one of claims 1 to 3, wherein the image carrier protective agent is a block-shaped molded body obtained by compression molding a granulated product containing a fatty acid metal salt and an inorganic lubricant in a mold.   The image forming apparatus according to claim 4, wherein the fatty acid metal salt contains zinc stearate.   The image forming apparatus according to claim 4, wherein the inorganic lubricant is boron nitride. A process cartridge having an image carrier, a protective agent supplying member that rotatably contacts the surface of the image carrier, and a protective layer forming unit having at least an image carrier protective agent comprising a granulated material containing at least a fatty acid metal salt Because
A median diameter (D50) based on a volume-based particle size distribution obtained by measuring the protective agent supplying member with a foam roller and measuring the granulated product of the image carrier protective agent by a laser diffraction / scattering particle size distribution measurement method is obtained. A process cartridge having an average cell diameter larger than that of the foam roller. A protective layer is formed on the surface of the image carrier using a protective layer forming means having at least a protective agent supplying member that rotatably contacts the surface of the image carrier and an image carrier protective agent made of a granulated material containing at least a fatty acid metal salt. An image forming method including at least a protective layer forming step for forming
A median diameter (D50) based on a volume-based particle size distribution obtained by measuring the protective agent supplying member with a foam roller and measuring the granulated product of the image carrier protective agent by a laser diffraction / scattering particle size distribution measurement method is obtained. An image forming method characterized by being larger than an average cell diameter of the foam roller.