JP2930001B2 - Developing roller and developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a copying machine or a printer, an electrostatic recording apparatus, or the like, in which a developer is supplied to a surface of a latent image holding member having an electrostatic latent image held on the surface. More specifically, a developing roller for visualizing an electrostatic latent image and a developing device using the developing roller are excellent in abrasion resistance, triboelectrification and toner separation, and stably perform good development over a long period of time. The present invention relates to a developing roller capable of performing the developing and a developing device using the developing roller.

[0002]

2. Description of the Related Art
In an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus, a developer (toner) is supplied to the surface of a latent image holding member such as a photosensitive drum holding an electrostatic latent image, and the surface of the latent image holding member is charged. As a developing method for visualizing an electrostatic latent image, a contact developing method is known (U.S. Pat.
According to this method, a magnetic material is not required, so that the apparatus can be simplified and downsized easily.
There are advantages such as easy colorization of toner.

In this contact developing method, a developing roller carrying a toner (usually, a non-magnetic one-component developer) is brought into direct contact with or close to the surface of a latent image holding member such as a photosensitive drum. Is developed on the surface of the latent image holding member, so that the developing roller needs to be formed of an elastic body.

In the contact developing method, for example, as shown in FIG. 2, a developing roller is provided between a toner applying roller 5 for supplying toner and a photosensitive drum 6 holding an electrostatic latent image. The developing roller 1, the photosensitive drum 6, and the toner applying roller 5 are disposed in a state in which the developing roller 1 is in contact with the photosensitive drum 6 and is slightly separated from the toner applying roller 5.
Are rotated in the directions indicated by arrows in the drawing, so that the toner 7 is supplied to the surface of the developing roller 1 by the toner applying roller 5, and the toner is arranged in a uniform thin layer by the layering blade 8. 1 is a photosensitive drum 6
The toner formed in a thin layer is electrostatically attached to the latent image on the photosensitive drum 6 from the developing roller 1 by rotating while contacting with the photosensitive drum 6, and the latent image is visualized. In the drawing, reference numeral 9 denotes a transfer unit, which transfers a toner image onto a recording medium such as paper. Reference numeral 10 denotes a cleaning unit, and the surface of the photosensitive drum 6 is transferred by a cleaning blade 11 after the transfer. The remaining toner is removed.

In this case, the developing roller 1 must rotate while reliably maintaining a state in which the developing roller 1 is in close contact with the photosensitive drum 6, and therefore, as shown in FIG. The shaft 2 has a structure in which an elastic layer 3 made of an elastic body provided with conductivity by blending a conductive agent with an elastic rubber such as urethane rubber, silicone rubber, NBR, EPDM, polyurethane foam, or the like is formed on the outer periphery of the shaft 2. . Further, it has been proposed to provide a skin layer 4 on the elastic layer 3.

Here, since the elastic body such as rubber or polyurethane which forms the elastic layer 3 is soft and has good deformation characteristics, it does not give a shock to a contacting object such as the photosensitive drum 6 or the like. On the other hand, the surface is easily damaged,
Poor wear resistance. In particular, when the elastic layer 3 is formed of polyurethane, there is a problem that the abrasion resistance is insufficient, the toner easily adheres, and the durability life is inferior. In this case, it has been proposed to coat a polyamide, a fluororesin or the like as the skin layer 4 on the elastic layer 3 made of polyurethane, but it has not yet completely solved the problems of abrasion resistance and toner adhesion. .

There is also known a developing roller in which a skin layer made of phenolic resin is formed on the surface of a metal shaft or sleeve, but such a developing roller performs development in a non-contact state with a photosensitive drum. Since it is used in the jumping development method and has no elasticity, it will damage the photosensitive drum surface or damage the toner when it comes in contact with the photosensitive drum, and cannot be used in the contact development method. is there.

The present invention has been made in view of the above circumstances, and has a low hardness and sufficient elasticity as a whole roller, has excellent abrasion resistance and is hardly damaged, and can be applied to a contact partner member such as a photosensitive drum. A developing roller and a developing device using the developing roller capable of reliably performing good and stable development for a long time without causing damage, further excellent in toner separation, and without inconvenience due to toner adhesion. The purpose is to provide.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a thickness of 1 to 4 having a phenol resin as a main component on an elastic layer made of polyurethane.
By forming a 50 μm thin film as a skin layer, it can be softly deformed as a whole, has excellent abrasion resistance and is hardly damaged, has good triboelectric charging property to toner, has excellent toner separation, and has good contact with toner. It has been found that a developing roller suitably used for the developing method can be obtained.

[0010] That is, if a phenolic resin is coated on a polyurethane in a thin film form, it is considered that the two layers are well adapted to each other. However, a roller capable of following the deformation of the polyurethane satisfactorily and being soft and deformable as a whole is considered. As well as being obtained, the surface is covered with a hard phenol resin coating layer and has excellent abrasion resistance, and furthermore, this coating layer has good triboelectric charging property and toner releasability to toner. Good and stable development can be reliably performed over a long period of time by the contact development method using a positively chargeable toner. In this case, by using a resole type or a resorcinol-containing phenol resin, more reliable development is possible. It has been found that the above-mentioned effects can be exhibited, and the present invention has been completed.

Therefore, the present invention comprises forming an elastic layer based on polyurethane on the outer periphery of a good conductive shaft,
A developer is carried on the surface to form a thin layer of the developer, and in this state, the electrostatic latent image is brought into contact with the latent image holding member holding the surface, and the developer carried on the surface is charged with the latent image holding member. A developing roller for supplying a developer to the surface of the latent image holding member to visualize the electrostatic latent image by directly contacting the surface with the surface;
Provided is a developing roller having a μm skin layer formed thereon. In this case, the present invention, as a preferred embodiment,
The present invention provides the developing roller, wherein the phenol resin as a main component of the skin layer is a resol type or a resin containing resorcin.

Further, according to the present invention, there is provided a latent image holding member for holding an electrostatic latent image on a surface thereof, wherein the latent image holding member is brought into contact with the surface of the latent image holding member with a positively charged developer carried on an outer peripheral surface thereof, and A developing roller that supplies an agent to the surface of the latent image holding member to visualize the electrostatic latent image, wherein the developing roller according to claim 1 is used as the developing roller. And a developing device using the same.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. As shown in FIG. 1, the developing roller of the present invention
An elastic layer 3 made of polyurethane is formed on the outer periphery of a good conductive shaft 2, and a thin skin layer 4 mainly composed of a phenol resin is formed on the elastic layer 3.

Here, as the shaft 2, any shaft having good conductivity can be used, but it is usually a core made of a solid body or a cylindrical body having a hollow inside. The metal or resin shaft of the above is used.

An elastic layer 3 formed on the outer periphery of the shaft 2
Is formed of a conductive elastic body based on a polyurethane foam or a polyurethane elastomer. These polyurethane foams and polyurethane elastomers may be any of those produced by various methods, for example, a method in which a conductive material such as carbon black is blended in a polyurethane prepolymer to cause a cross-linking reaction of the prepolymer, and a conductive material is added to a polyol. It can be obtained by a method of blending and reacting this polyol with polyisocyanate by a one-shot method.

Examples of the polyhydroxyl compound for obtaining polyurethane used as the base material of the elastic layer 3 include polyols used for producing general flexible polyurethane foams and urethane elastomers, for example, polyether polyols having a polyhydroxyl group at a terminal. , Polyester polyols, and polyether polyester polyols which are copolymers of both, and polyolefin polyols such as polybutadiene polyols and polyisoprene polyols, so-called polymers obtained by polymerizing ethylenically unsaturated monomers in polyols General polyols such as polyols can be used. Examples of the isocyanate compound include polyisocyanates used in the production of general flexible polyurethane foams and urethane elastomers, that is, tolylene diisocyanate (TDI), composition TDI, and 4,4 ′.
-Diphenylmethane diisocyanate (MDI), composition MDI, aliphatic polyisocyanate having 2 to 18 carbon atoms,
An alicyclic polyisocyanate having 4 to 15 carbon atoms and a mixture or modified product of these polyisocyanates, for example, a prepolymer obtained by partially reacting with a polyol or the like is used.

In this case, the mixing ratio of the polyol and the polyisocyanate is generally about polyisocyanate / polyol = 1 to 1.3. In particular, the mixing ratio is set to less than 1 for the purpose of lowering the hardness of the elastic layer 3. Is also good. Furthermore,
As a base material of the elastic layer 3, any polyurethane such as the above-mentioned polyether-based, polyester-based, polyolefin-based, and polymer polyol-based may be used, but the affinity with the phenol resin forming the skin layer 4 is particularly good. ,
It is preferable to use a polyether-based polyurethane for the reason that low hardness is achieved, it is easy to mix an ion conductive substance described later, and when a low hardness is required, it is formed as a foam material. Is preferred.

In the polyurethane base material, a conductive material is usually blended to give an appropriate conductivity so that the conductivity of the elastic layer 3 is 10 ³ to 10 ¹⁰ Ωcm ² , particularly 10 ⁴ to 1 Ωcm ² .
It is carried out to adjust the 0 ⁸ [Omega] cm about ^2. in this case,
As the conductive material, conductive powder or particles such as carbon, metal, metal oxide, and conductive polymer, or an ionic conductive material is preferably used.

More specifically, the conductive powder or particles include conductive carbon such as Ketjen Black EC and acetylene black, SAF, ISAF, HAF and FE.
Rubber carbon such as F, GPF, SRF, FT, MT, etc.
Metals and metal oxides such as color (ink) carbon, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium, etc.
Examples include conductive polymers such as polyanine, polypyrrole, and polyacetylene. Among these, the carbon-based conductive material is advantageous in that the resistance is less dependent on the environment, is relatively inexpensive, and the conductivity can be controlled with a small amount. In addition,
These conductive powders and particles are not particularly limited, but usually 0.5 to 5 parts by weight based on 100 parts by weight of urethane.
It is used in an amount of 0 parts by weight, particularly 1 to 30 parts by weight.

Specific examples of the ionic conductive material include inorganic ionic conductive materials such as sodium perchlorate, calcium perchlorate, and lithium chloride; denatured aliphatic dimethylammonium salfort, stearylammonium acetate, and laurylammonium acetate. And organic ionic conductive substances such as octadecyltrimethylammonium perchlorate and tetrabutylammonium borate. These ionic conductive substances are advantageous in that they have uniform resistance and low voltage dependency. The ionic conductive material is not particularly limited, but is usually used in an amount of 0.01 to 30 parts by weight, particularly 0.01 to 5 parts by weight, based on 100 parts by weight of urethane.

Further, on the elastic layer 3 made of polyurethane, various charge control agents such as nigrosine, triaminophenylmethane and cationic dye, silicone resin, Fine powders such as silicone rubber and nylon can be added. In this case, the amount of these additives is preferably 1 to 5 parts by weight, and the fine powder is preferably 1 to 10 parts by weight, based on 100 parts by weight of the polyurethane.

Although the hardness of the elastic layer 3 is not particularly limited, it is important to lower the hardness of the roller, and the Asker C hardness should be 30 to 90 °, particularly 60 to 80 °. preferable. In this case, if the Asker C hardness of the elastic layer 3 exceeds 90 °, the contact area with the photosensitive drum or the like becomes small, so that good development may not be performed. If the developing roller becomes deformed or eccentric for some reason, the density unevenness of the image occurs. For this reason,
Even when the hardness of the elastic layer 3 is set to a low hardness, it is preferable to reduce the compression set as much as possible. Specifically, it is preferable to set the compression set to 20% or less.

The method of forming the elastic layer 3 on the outer periphery of the shaft 2 is not limited. For example, the shaft 2 is set in a mold, and a polyol which is a raw material of polyurethane,
A mixture of polyisocyanate, conductive material, catalyst, etc.
Alternatively, a method in which the prepolymer is cast and cured by heating can be adopted. The obtained elastic layer 3 can be appropriately polished and adjusted to an appropriate surface roughness.

Next, the skin layer 4 formed on the elastic layer 3 is mainly composed of a phenol resin.
In this case, as the phenol resin, any of a resole type and a novolak type can be used.More specifically, a simple phenol resin obtained by reacting phenol and formalin, a resorcin resin using resorcin in place of phenol, Resins using a combination of phenol and resorcin, and various modified phenol resins such as melamine-modified, xylene-modified, and epoxy-modified can also be used. Among them, a simple phenol resin, a resorcin resin, and a mixture thereof are preferably used. Further, the resol type phenol resin is advantageous in that a good cured film can be formed on the urethane elastic body only by heating without requiring a crosslinking agent.

Here, the reason why the phenol resin is used as the main component of the skin layer 4 is that the phenol resin has a high dielectric effect. That is, the phenolic resin exhibits a high relative dielectric constant due to the effect of the hydroxyl group coordinated to the benzene ring. For example, the relative dielectric constant of the fluororesin is about 2, while the relative dielectric constant is about 4 or more. The modified resin exhibits a higher relative dielectric constant.
In this case, as a factor that determines the charge amount of the toner carried on the surface of the developing roller, the work function difference between the electrically charged material and the material to be electrically charged and the relative dielectric constant of each are approximately the same ratio. The higher the work function difference or the higher the relative dielectric constant, the higher the charge amount. Therefore, the phenolic resin having a high relative dielectric constant is applied to the skin layer 4.
It is preferably used as

The skin layer 4 can be mixed with a conductive material as necessary to reduce the resistance. As a conductive material,
A conductive material similar to the conductive material used for the elastic layer 3, such as powder or particles having electron conductivity, such as carbon, metal, metal oxide, or conductive polymer, or an ionic conductive material can be used. Among these conductive materials, although not particularly limited, carbon is preferably used, and by using carbon, the chargeability of the toner can be improved. In this case, the conductivity of the roller surface of the skin layer 4 is formed, 10 ⁰ to 10 ¹⁰ [Omega] cm ^2, in particular 10
^It is preferably ¹ to 10 ⁷ Ωcm ² . In addition, as long as such conductivity is achieved without blending a conductive material, it is not necessary to blend a conductive material into the skin layer 4.

The skin layer 4 is formed as a thin film having a thickness of 1 to 50 μm, preferably 3 to 30 μm. In this case, if the thickness of the skin layer 4 is less than 1 μm, the abrasion resistance of the roller surface may be insufficient and the roller surface may not be able to withstand long-term use. When it is damaged and cannot contact the deformation of the elastic layer 3 and comes into contact with a latent image holding member such as a photosensitive drum, a crack or the like may occur, and the surface of the latent image holding member may be damaged.

The surface roughness of the roller on which the skin layer 4 is formed is an important factor for obtaining good toner transportability.
Although not particularly limited, it is usually preferable to adjust the JIS 10-point average roughness Rz to 1 to 30 μm, particularly preferably 3 to 20 μm. In this case, JIS 10-point average roughness Rz
Is less than 1 μm, the toner conveyance amount may be insufficient and the image density may be reduced.
If it exceeds, the toner may be conveyed to an uncharged toner and fog may occur in the image. The surface roughness of the roller can be adjusted by polishing the surface of the elastic layer 3. In this case, if the skin layer 4 formed on the surface of the elastic layer 3 is too thick, the roller surface is smoothed by the skin layer 4. In some cases, sufficient roughness cannot be obtained, and it is necessary to select the roughness of the elastic layer 3 and the thickness of the skin layer 4 in consideration of this point.
The skin layer 4 is mixed with polymer fine particles such as fluororesin, silicone resin and phenol resin, inorganic fine particles such as silica and graphite, and metal oxides such as titanium oxide and zinc oxide to obtain an appropriate roughness. You can also.
The hardness of the entire roller on which the skin layer 4 is formed is not particularly limited, but may be 30 to 30 in Asker C hardness.
It is preferably 90 °, particularly preferably 60 to 80 °.

The skin layer 4 is formed on the elastic layer 3 by dissolving the phenolic resin in a solvent and dispersing or dissolving a necessary additive such as a conductive material in the solvent. The method of coating the surface of the elastic layer 3 is preferably employed. The resin component concentration in this coating solution is
Although not particularly limited, the thickness of the skin layer 4 is preferably set to about 2 to 20% in order to keep the thickness in the above preferable range. As a solvent for preparing the coating solution, any solvent can be used as long as it can dissolve the phenolic resin, and lower alcohols such as methanol, ethanol, and isopropanol are preferably used. In order to obtain good film properties by the drying step, it is preferable to use a mixed solvent in which ketones such as methyl ethyl ketone and cyclohexane, toluene, xylene and the like are appropriately mixed. In addition, a dispersant may be added to the coating solution for the purpose of improving the dispersion stability of a conductive material such as carbon.

After the solution is prepared, the coating solution can be applied by a spray method, a roll coater method, a dipping method, or the like. For example, in the application by dipping, a roller composed of the shaft 2 and the elastic layer 3 is immersed in a coating solution having the above-mentioned resin concentration at a normal room temperature for about 5 seconds to 5 minutes, preferably for about 10 seconds to 1 minute. Can be adopted. When the spray method is adopted, the resin concentration in the coating solution can be set higher than that in the dipping method. For example, a coating solution adjusted to a concentration of 30 to 60% can be used. In any case, the coating may be performed by appropriately selecting an optimum resin concentration, a coating method, and a coating condition so as to obtain a desired film thickness.

The developing roller of the present invention can be used by being incorporated in a normal developing device which performs development by a contact developing method. Specifically, as shown in FIG. The developing roller 1 of the present invention is provided between the roller 5 and a latent image holding member 6 such as a photosensitive drum holding an electrostatic latent image.
Is disposed in contact with the latent image holding member 6, and the toner 7 is supplied to the developing roller 1 by the toner applying roller 5.
This is formed into a uniform thin layer by the layering blade 8, and toner is supplied from the thin layer to the latent image holding member 6, and the toner is adhered to the electrostatic latent image on the latent image holding member 6 to visualize the latent image. Is what you do. Since the details of FIG. 2 have already been described in the related art, the description thereof will be omitted.

In this case, the developing roller and the developing device of the present invention are suitably used for both the case where the developer is positively charged and the development is performed, and the case where the developer is negatively charged and the development is performed. However, it is particularly preferably used when a non-magnetic one-component developer is used and the developer is positively charged to perform development. The reason is as follows.

When the toner is positively charged, negative charges, that is, electrons are induced on the surface of the developing roller. In this case, when the surface of the roller is a resin having no electron conductivity, the resin is usually a hole-transferring conductive material, so that the dielectric electrons are difficult to escape and remain as they are. Therefore, the roller rotates after development, and the contact charging efficiency becomes extremely low due to the charge remaining on the roller surface when the next toner is charged.Specifically, for example, when a solid black image is printed during image printing, An image having a large difference between the front and rear end densities is obtained. In contrast, when an electron conductive layer containing carbon, metal oxide, or the like is formed on the roller surface, the induced charges, that is, the electrons, are easily dissipated, and the next time the toner is charged, the charge is charged on the new roller surface. As a result, the charging efficiency is good and a good image can be obtained. As described above, the charge amount is improved because the phenol resin has a high dielectric effect. However, contact charge is caused due to the electron-withdrawing property (-I effect) of the hydroxyl group coordinated to the benzene ring. It has a function of positively charging the other party, that is, the toner. Therefore, when a positively chargeable toner is used, a high charge amount can be efficiently expressed.

[0034]

The developing roller of the present invention has low hardness and sufficient elasticity as a whole, has excellent abrasion resistance, is hardly damaged, and damages a contact partner such as a photosensitive drum. In addition, excellent and stable development can be reliably performed over a long period of time without causing toner inconvenience due to excellent toner separation. Therefore, the developing device using the developing roller of the present invention can surely perform good and stable development over a long period of time.

[0035]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. [Example 1] Urethane-modified MD was added to 100 parts by weight of a polyether polyol having a molecular weight of 5,000 by adding propylene oxide and ethylene oxide to glycerin.
I 25.0 parts (parts by weight, the same applies hereinafter), 1,4-butanediol 2.5 parts, dibutyltin laurate 0.01 parts,
2.0 parts of Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.) is blended, and the mixture is poured into a mold heated to 110 ° C. and cured for 2 hours. A layer was formed to produce a conductive member. The surface of the obtained conductive member was dried and polished to form a roller, and the surface roughness was measured according to JIS 10-point roughness Rz =
It was adjusted to 15 μm (Asker C hardness = 75 °).

On the other hand, PR50781 (manufactured by Sumitomo Durez) was used as a resole type phenol resin, and XE2 (manufactured by Degussa) was used as a carbon in a solution obtained by dissolving this in an ethanol solvent so that the resin concentration was 10%.
Was mixed for 15 hours with respect to the resin concentration, and dispersed for 1 hour with a sand grinder to obtain a coating solution.

The above coating solution is placed in a cylindrical glass container,
The roller-shaped conductive member was immersed therein at a speed of 1 cm / sec and pulled up at the same speed to provide a skin layer on the surface of the conductive member, and then heated at 110 ° C. for 3 hours to crosslink the surface layer, A developing roller was obtained. In this case, the film forming property of the skin layer was extremely good.

When the surface conductivity of the obtained developing roller was measured, it was 10 ² Ωcm ² , and a sufficiently low resistance was achieved. The hardness of this developing roller was 75 degrees in Asker C hardness, and the surface roughness was 15 μm in JIS 10-point roughness Rz. Further, the obtained roller was cut along the axial direction and observed with an optical microscope. As a result, it was confirmed that the skin layer was a uniform thin film having a thickness of about 6 μm. Furthermore, when a predetermined stress was applied to the roller surface to compress the roller surface, the surface skin layer satisfactorily followed the deformation of the roller surface, and no inconvenience such as cracking occurred.

Next, the developing roller is incorporated into the developing device of FIG. 1 as a developing roller 1, and this developing device is incorporated in a developing unit of a commercially available laser beam printer.
An image was formed using a polyester-based positive charging toner, and the image was evaluated. The obtained image was a good image having no image defects such as fog and density unevenness.

When the charge amount of the toner carried on the developing roller surface was measured using a Faraday gauge,
It had a sufficient charge amount of 15 μC / g. Further, when a continuous paper passing test was performed using the laser beam printer using the developing roller of the present example for 10,000 sheets, an initial good image was maintained to the end, and there was no change on the developing roller surface. I was not able to admit. Next, the developing roller of this embodiment was pressed against the photoreceptor of the developing unit at a pressure of 500 g, and left in an atmosphere of 50 ° C. and 85% for 5 days. No change was observed on the photoreceptor after standing.

As the conductive paint resin, resol type
Resorcinol-modified phenol (MD3 manufactured by Dainippon Ink and Chemicals, Inc.)
100, H, MD3200D), except that a developing roller was obtained in the same manner as in Example 1. When the surface conductivity of the surface of the obtained developing roller was measured, it was 10 ² Ωcm ² , indicating that the resistance was sufficiently reduced. In addition, a thin film (about 6 μm) having good film forming properties and good followability is formed, and has a Asker C hardness of 75 degrees and a surface roughness of JIS.
The 10-point roughness Rz was 15 μm.

When this developing roller was evaluated in the same manner as in Example 1, the toner charge amount was particularly 20 μC / g.
And a good image free of image defects such as fog and density unevenness was obtained. Further, when a continuous paper passing test was performed on 10,000 sheets, an initial good image was maintained to the end, and no change was recognized on the surface of the developing roller. Further, the developing roller of the present embodiment is attached to the photosensitive member of the developing unit by 50.
It was press-contacted with a pressure of 0 g and left for 5 days in an atmosphere of 50 ° C. and 90%, but no change was observed on the photoreceptor after leaving.

Comparative Example 1 A developing roller was obtained in the same manner as in Example 1 except that soluble nylon (CM8000 manufactured by Toray Industries, Inc.) was used as the main resin for forming the skin layer. When the performance of the obtained developing roller was evaluated by performing the same test as in Example 1, the image obtained by the obtained developing roller was very good at the initial stage. A decrease in concentration occurred. Observation of the roller surface after the paper passing test revealed that the surface of the roller was smoothed due to friction with the blade (reference numeral 8 in FIG. 1). It was considered.

Comparative Example 2 A developing roller was obtained in the same manner as in Example 1 except that the resin concentration of the resin in the coating solution was changed to 30%, and the same evaluation was performed by the same test as in Example 1. The obtained roller had a surface skin layer thickness of about 100
It was confirmed that the skin layer completely covered the polished surface of the roller surface with a JIS 10-point roughness Rz of 3 μm when it was at least μm. Further, it was confirmed that when the roller surface was deformed by compression, a crack was generated on the surface, and the skin layer could not follow the deformation of the roller surface. Further, in the image obtained by this developing roller, an image defect occurred due to insufficient density even in the initial stage.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a developing roller of the present invention.

FIG. 2 is a schematic sectional view showing an example of the developing device of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing roller 2 shaft 3 elastic layer 4 skin layer 5 toner coating roller 6 photosensitive drum (latent image holder) 7 toner (developer) 8 layering blade 9 transfer unit 10 cleaning unit 11 cleaning blade

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Harashima 43-1-206, Sachigaoka, Asahi-ku, Yokohama-shi, Kanagawa Prefecture (72) Takahiro Kawagoe 1302-57, Aobadai, Tokorozawa-shi, Saitama (56) References JP-A-7 -56434 (JP, A) JP-A-5-249809 (JP, A) JP-A-4-103672 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08 501 F16C 13/00

Claims (7)

(57) [Claims] An elastic layer made of polyurethane as a base material is formed on the outer periphery of a good conductive shaft, and a developer is carried on the surface to form a thin layer of the developer. By contacting the latent image holding member holding the image on the surface and bringing the developer carried on the surface into direct contact with the latent image holding member surface,
A developing roller that supplies a developer to the surface of the latent image holding member to visualize the electrostatic latent image;
A developing roller having a 50 μm skin layer formed thereon. 2. The developing roller according to claim 1, wherein the phenol resin as a main component of the skin layer is a resol type. 3. The developing roller according to claim 1, wherein the phenol resin as a main component of the skin layer contains resorcin. 4. The developing roller according to claim 1, wherein the skin layer is made conductive by compounding powder or particles having electron conductivity. 5. The electric conductivity of the roller surface is from 10 ⁰ to 10 ¹⁰ Ω.
The developing roller according to any one of claims 1 to 4, wherein the developing roller has a size of cm ² . 6. The JIS 10-point average roughness Rz of the roller surface
The developing roller according to any one of claims 1 to 5, wherein the particle diameter is 1 to 30 µm. 7. A latent image holding member for holding an electrostatic latent image on a surface thereof and a surface of the latent image holding member having a positively charged developer carried on an outer peripheral surface thereof, and the developer is brought into contact with the latent image holding member. 7. A developing device comprising: a developing roller that supplies the electrostatic latent image to the surface of the holding member to visualize the electrostatic latent image, wherein the developing roller according to claim 1 is used as the developing roller. A developing device.