JP2001117348A - Developing roller, developing device and developing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roller having excellent uniformity and durability of triboelectrification to a developer, a developing device having the developing roller and a developing method utilizing the developing roller. SOLUTION: The developing roller which is the developing roller having at least a surface layer and elastic layer and contains at least olefin-vinyl alcohol copolymer in the binder resin of the surface layer, the developing device having the developing roller and the developing method utilizing the developing roller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller for carrying a developer used in an electrophotographic apparatus, a developing device provided with the developing roller, and a developing method using the developing roller.

[0002]

2. Description of the Related Art Conventionally, as a developing method in an electrophotographic apparatus such as a copying machine or a laser beam printer, a one-component developer is used, and the one-component developer is carried on a developer carrier to form an image on an image carrier. 2. Description of the Related Art A contact developing method is known in which a developer is transferred from a developer carrier to a surface of an image carrier, thereby developing an electrostatic latent image on the image carrier. As a developer carrying member used in such a contact developing method, a roller-shaped developer having an elastic body provided around a metal shaft (core bar) and a surface layer provided thereon as necessary is known. ing.

[0003]

However, in the contact developing method, the developing efficiency is improved, and a high density, clear and suppressed fog can be obtained, and a uniform developed image can be obtained in any use environment (low temperature / low humidity to high temperature / high temperature). (Humidity), the problems such as uniformity of triboelectric charging to the developer and stabilization of durability, which are important for obtaining a stable image, have not been completely solved. In particular, while the developing roller is rotating repeatedly, the charge amount of the toner coated on the developing roller becomes too high due to the contact with the developing roller, and the toner attracts due to the mirror force with the developing roller surface. A so-called charge-up phenomenon, in which the developing roller does not move to the latent image on the electrostatic latent image holding member (drum) on the surface of the developing roller and does not move from the developing roller to the latent image, tends to occur particularly under low humidity. When such a charge-up phenomenon occurs, the toner in the upper layer of the toner adhered to the developing roller is difficult to be charged, and the amount of developed toner is reduced. The following problems occur.

Further, since the toner layer formation state of the image area (toner consuming section) and the non-image area changes, and the charging state changes, for example, the position where a solid image having a high image density is developed is When a halftone image is developed at the developing position at the next rotation of the roller, a so-called ghost phenomenon that a trace of a solid image appears on the image is likely to occur. In recent years, in order to further improve the image quality of electrophotography, toner has been reduced in particle size and particle size. For example, to improve the resolution and sharpness and faithfully reproduce a latent image,
Generally, a toner having a weight average particle size of about 6 to 9 μm is used. Further, there is a tendency that the fixing temperature of the toner is lowered for the purpose of shortening the first copy time and saving power. Under such circumstances, the toner is more likely to electrostatically adhere to the developing roller, and the external force exerts a physical force on the developing roller, so that the surface of the developing roller is easily contaminated and the toner is easily fused. ing.

As a method for solving such a phenomenon, there is a method in which a developing roller provided with a surface layer in which a conductive lubricant such as a solid lubricant and carbon is dispersed in a resin is provided in a developing device. By using this method, it is recognized that the above-mentioned phenomenon is reduced, but at present it is not enough, and from the viewpoint of uniformity of frictional charging with the developer and durability stability, the developing roller is Further improvements in suitable surface layers are desired. Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a developing roller excellent in uniformity and durability stability of triboelectric charging to a developer, a developing device having the developing roller, and a developing method using the developing roller. It is to be.

[0006]

The above object is achieved by the present invention described below. That is, the present invention provides a developing roller having at least a surface layer and an elastic layer, wherein the binder resin of the surface layer contains at least an olefin-vinyl alcohol copolymer. And a developing method using the developing roller.

A preferred embodiment of the present invention is as follows. 1. The above-mentioned developing roller, wherein the olefin content in the olefin-vinyl alcohol copolymer is 20 to 60 mol% based on all monomers constituting the olefin-vinyl alcohol copolymer. 2. The above developing roller, wherein the olefin is ethylene. 3. The above developing roller, wherein the olefin-vinyl alcohol copolymer has a degree of saponification of 70 mol% or more. 4. The surface layer has an average particle size of 0.3 to 30 μm and a true density of 3
The above-mentioned developing roller containing g / cm ³ or less of spherical particles. 5. The above developing roller, wherein the ratio of the major axis / minor axis of the spherical particles is 1.0 to 1.5. 6. The above developing roller, wherein the surface layer contains a charge control agent. 7. The above-mentioned developing roller, wherein the charge control agent is a nitrogen-containing heterocyclic compound. 8. The above developing roller, wherein the nitrogen-containing heterocyclic compound is an imidazole compound. 9. A developing device including the above developing roller and a developing method using the above developing roller.

[0008]

Next, the present invention will be described in more detail with reference to preferred embodiments. The developing roller of the present invention includes:
As shown in FIG. 1, a cross section of the core layer 114a has at least a surface layer 114c and an elastic layer 114b around the core bar 114a.
It is characterized by containing a vinyl alcohol copolymer.

[0009] The binder resin of the surface layer provided on the developing roller of the present invention contains at least an olefin-vinyl alcohol copolymer. The olefin-vinyl alcohol copolymer is an olefin-vinyl acetate binary copolymer or a terpolymer obtained by copolymerizing olefin-vinyl acetate and one of other polymerizable third components (or a terpolymer obtained by copolymerizing the olefin-vinyl acetate binary copolymer). The above) is produced by saponifying a copolymer,
It has an appropriate amount of olefin and vinyl alcohol as monomer components. By having appropriate amounts of olefin and vinyl alcohol as monomer components, the uniformity of triboelectric charging and the durability stability with respect to the developer are improved.

The olefin content of all the monomer components in the olefin-vinyl alcohol copolymer is preferably 20 to 60 mol%, more preferably 25 to 55 mol%.
Mol%, most preferably 30 to 50 mol%. When the olefin content is less than 20 mol%,
The vinyl alcohol-based copolymer comes to exhibit properties and physical properties similar to polyvinyl alcohol (PVA), and the following phenomena may occur.

That is, since PVA has a high dielectric constant and is a material on the positive side in the triboelectric series, when it is used as a binder resin for the surface layer, it imparts a high negative charge to the negatively chargeable developer. can do. However, on the other hand, since the hardness of the surface layer is increased, the followability to the elastic layer is poor, and the elastic layer of the surface layer is easily cracked or peeled during use. In addition, the material itself has high water absorption, so that the developing characteristics become unstable. Also, in general,
In a high-humidity environment, problems such as a decrease in charge imparting properties occur.

When the olefin content exceeds 60 mol%, the environmental stability of the surface layer is maintained due to the hydrophobic effect of the olefin. Also, the hardness of the surface layer is appropriate, and there is no problem in following the elastic layer. However, since the vinyl alcohol content is low, an appropriate negative charge may not be imparted to the negatively chargeable developer in some cases.

The olefin constituting the olefin-vinyl alcohol copolymer includes, for example, ethylene, propylene, butene and the like. Considering the followability, ethylene is suitable.

The saponification degree of the olefin-vinyl alcohol copolymer is preferably at least 70 mol%, more preferably at least 90%, further preferably at least 98%. If the degree of saponification is less than 70 mol%, the content of unsaponified vinyl acetate units increases, and the water resistance becomes poor.
The mechanical and electrical properties of the surface layer may change. In addition, since the releasability of the surface layer is insufficient, there is a case where the developer is easily attached or fused. Along with this, the development characteristics also change, so that it is not possible to stably obtain a clear and fog-suppressed developed image. This phenomenon is particularly remarkable when used in a high temperature and high humidity environment.

It is preferable that the developing roller of the present invention contains spherical particles having the following physical properties in the surface layer. That is, as the physical property values of the spherical particles, the average particle size is preferably 0.3 to 30 μm, more preferably 2 to 20 μm.
m, the true density is preferably 3 g / cm ³ or less, more preferably 2.7 g / cm ³ or less, and still more preferably 0.9 to 0.9 g / cm ^3.
2.5 g / cm ³ .

That is, when the average particle diameter of the spherical particles is less than 0.3 μm, the surface layer has an appropriate and uniform roughness (Rz = 5 to 20).
μm), and it may be difficult to obtain sufficient developer transportability. If the average particle size is larger than 30 μm, the roughness of the surface layer becomes too large, and the charging of the developer may be insufficient. On the other hand, when the true density of the spherical particles exceeds ³ g / cm ³ , the dispersibility of the spherical particles in the surface layer becomes insufficient, so that it becomes difficult to impart uniform roughness to the surface of the surface layer. In some cases, the toner is charged quickly and uniformly and the strength of the surface layer is insufficient.
When the true density of the spherical particles is too low, the dispersibility of the spherical particles in the surface layer may be insufficient.

As the spherical particles, for example, EPDM, N
Rubber particles such as BR, SBR, CR, and silicone rubber; elastomer particles such as polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyester, and polyamide-based thermoplastic elastomer (TPE);
Resin particles such as silicone resin, phenol resin, naphthalene resin, furan resin, xylene resin, divinylbenzene polymer, styrene-divinylbenzene copolymer, polyacrylonitrile resin, and such resin-based spherical particles and mesocarbon microbeads Low-density and good-conductive spherical carbon particles obtained by firing to carbonize and / or graphitize, and the like. The mesocarbon microbeads can be usually produced by washing spherical crystals generated in the process of heating and firing the medium pitch with a large amount of a solvent such as tar, medium oil and quinoline.

As a method for obtaining the above conductive spherical particles, for example, spherical resin such as phenol resin, naphthalene resin, furan resin, xylene resin, divinylbenzene polymer, styrene-divinylbenzene copolymer, polyacrylonitrile, etc. By coating the particle surface with a bulk mesophase pitch by a mechanochemical method, heating the coated particles under an oxidizing atmosphere, and then firing under an inert atmosphere or vacuum to carbonize and / or graphitize, There is a method of obtaining conductive spherical carbon particles in which the inside is carbonized and the outside is graphitized. When the spherical carbon particles obtained by this method are graphitized, the coating portion of the obtained spherical carbon particles becomes more crystallized, so that the conductivity is improved.

The term "spherical" in the above spherical particles means a substantially spherical particle, preferably having a ratio of major axis / minor axis of 1.0 to 1.5, more preferably major axis / minor axis. Of spherical particles having a ratio of 1.0 to 1.2 are used. When the ratio of the major axis / minor axis of the spherical particles exceeds 1.5, the dispersibility of the spherical particles in the surface layer decreases, and the surface roughness becomes nonuniform. In some cases, it is not preferable from the viewpoints of charging and the strength of the surface layer.

The methods for measuring the above physical properties are as follows. (1) Measurement of Particle Size of Spherical Particle The particle diameter of the spherical particle is measured by using an electron microscope. The photographing magnification is set at 60,000 times. If it is difficult, the photograph is photographed at a low magnification and then the photograph is enlarged and printed so as to have a magnification of 60,000 times. Measure the particle size of the primary particles on the photograph. At this time, the major axis and the minor axis are measured, and the average value is defined as the particle diameter. This is measured for 100 samples, and the 50% value is defined as the average particle size. (2) Measurement of True Density of Spherical Particles The true density of spherical particles was measured using a dry densimeter Acupic 1330.
(Manufactured by Shimadzu Corporation).

The developing roller of the present invention preferably contains a charge control agent in the binder resin of the surface layer. The most preferred charge control agent is a nitrogen-containing heterocyclic compound. By including the nitrogen-containing heterocyclic compound in the binder resin, the charging performance of the surface layer is remarkably improved. That is, since the nitrogen-containing heterocyclic compound is easily dispersed uniformly in the binder resin (ethylene-vinyl alcohol copolymer) of the surface layer,
The charge controllability of the nitrogen-containing heterocyclic compound is effectively exhibited, and the toner can be charged quickly and uniformly, and the sharpness of the character line is excellent and the image with high image density is stable under different environmental conditions. Can be obtained.

Examples of the nitrogen-containing heterocyclic compound include, for example, imidazole, imidaline, imidazolone, pyrazoline,
Pyrazole, pyrazolone, oxazoline, oxazole, oxazolone, thiazoline, thiazole, thiazolone, selenazoline, selenazole, selenazolone, oxadiazole, thiadiazole, tetrazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, benzoselenazole, pyrazine, pyrimidine, Pyridazine, triazine, oxazine, thiazine, tetrazine, polyazain, pyridazine, pyrimidine, pyrazine, indole, isoindole, indazole, carbazole, quinoline, pyridine, isoquinoline, cinnoline, quinazoline, quinoxaline, phthalazine, purine, pyrrole, triazole,
Phenazine and the like. In the present invention, an imidazole compound is particularly preferred because it promotes the effect of the developer carrier of the present invention.

The above-mentioned nitrogen-containing heterocyclic compound has a number average particle diameter of preferably 20 μm or less, more preferably 0.1 μm or less.
の も の 15 μm is used. When the number average particle diameter of the nitrogen-containing heterocyclic compound exceeds 20 μm, it may be difficult to sufficiently obtain the effect of improving the charging performance due to poor dispersibility of the nitrogen-containing heterocyclic compound in the coating layer. The number average particle size was measured using a Coulter LS-13 of a laser diffraction type particle size distribution meter.
It is a value measured using a type 0 particle size distribution meter (manufactured by Coulter) and calculated from the number distribution.

Next, the developing roller of the present invention will be described more specifically with reference to the drawings. FIG. 1 shows the basic configuration of the developing roller of the present invention. The developing roller 114 has an elastic layer 114 on a cored bar 114a made of a cylindrical conductive substrate.
b, surface layer 114c is formed. As a material of the developing roller, a general known material can be used. As the conductive base 114a, for example, a metal such as iron, copper, aluminum, or stainless steel, a metal alloy, a conductive resin, or the like can be used. The elastic layer 114b includes, for example, EP
Rubber materials such as DM, NBR, SBR, CR, and silicone rubber; and any of polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyester, and polyamide-based thermoplastic elastomer (TPE) can be used. It is desirable that the elastic layer has heat resistance. As the resistance (relative dielectric constant) controlling agent added to the elastic layer, carbon black, conductive metal oxide, metal powder,
A charge control agent or the like may be appropriately selected and used alone or in combination of two or more. The layer thickness of the elastic layer is preferably 0.5
It is 10 to 10 mm, more preferably 2 to 6 mm, but is not particularly limited to this layer thickness.

The surface layer 114c of the developing roller has a roughness of 1
The zero point average roughness (hereinafter referred to as “Rz”) is preferably in the range of 1 to 30 μm, more preferably 3 μm.
２０20 μm. If the surface layer has an Rz of less than 1 μm, the toner transportability may be reduced, and a sufficient image density may not be obtained. In addition, R of the surface layer
If z exceeds 30 μm, the toner transport amount may be too large and the toner may not be sufficiently charged. The thickness of the surface layer of the developing roller is preferably 5 to 50.
When the thickness is 0 μm, more preferably 10 to 200 μm, a uniform layer thickness can be obtained, but the thickness is not particularly limited.

The image carrier that can be used in combination with the developing roller of the present invention includes OPC (organic photoconductor),
Examples include a photosensitive drum using various photosensitive members such as amorphous-Si, Se, and ZnO. Examples of the developing device that can use the developing roller of the present invention include a developing device of an electrophotographic application device such as a copying machine, a laser beam printer, an LED printer, or an electrophotographic plate making system.

Next, the developing device and the developing method of the present invention will be described. A developing device and a developing method according to the present invention include and use the developing roller according to the present invention. FIG. 2 shows a schematic configuration of a laser beam printer having a developing device having the developing roller of the present invention. In FIG. 2, a developing device 10 of a laser beam printer uses a non-magnetic one-component developing system. A developer 11 (non-magnetic toner) is stored in the developer container 12, and a developing roller 24 is placed in an opening of the container 12 facing the photosensitive drum 1 so as to be in contact with the photosensitive drum 1. is set up. As described above, the developing roller 24 is
a, an elastic layer 24b and a surface layer 24c are formed thereon.

When the developing roller 24 rotates in the direction of the arrow, the developer 11 in the developer container 12 is carried on the developing roller 24. The developer 11 is regulated by the blade 16 to form a thin layer 11 a of the developer on the developing roller 24, and only the non-magnetic toner is conveyed to the developing area 13 facing the photosensitive drum 1. A developing bias is applied between the developing roller 24 and the photosensitive drum 1 by the constant voltage power supply 18, and the electrostatic latent image on the photosensitive drum 1 is developed. In FIG. 2, reference numeral 19 denotes a charging roller for primary charging the photosensitive drum 1, and L denotes a laser beam for forming an electrostatic latent image on the photosensitive drum 1.

[0029]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples. In the Examples and Comparative Examples, “parts” are based on weight unless otherwise specified.

Embodiment 1 An example in which the developing roller of the present invention is applied to a laser beam printer will be described. The developing roller was prepared by the following method. [Preparation of elastic layer] A semi-conductive rubber containing acrylic rubber as a dispersion medium polymer, various additives such as a vulcanization accelerator, and conductive carbon black as a resistance control agent was used using two rolls. And homogeneously dispersed and kneaded. This is wrapped around an iron core coated with a primer, placed in a mold, and
Heat vulcanization was performed at 0 ° C. for 25 minutes to form a semiconductive elastic layer on the cored bar.

[Preparation of surface layer paint] 20 parts of ethylene-vinyl alcohol copolymer (degree of saponification 99.8 mol%, ethylene content 35 mol%), 40 parts of n-propyl alcohol, 40 parts of ion-exchanged water , 1 part of conductive carbon black and PMMA particles [average particle size 7.5 μm, true density 1.19 g / cm ³ , spherical shape (major axis / minor axis = 1.06)]
Two parts were mixed and dispersed to prepare a coating for the surface layer.

[Preparation of Developing Roller] The above-mentioned coating material for a surface layer was spray-coated on the elastic layer (discharge amount: 12 mL / mi).
n, atomization pressure 1.75 kg / cm ² , work rotation speed 1,0
(00 rpm, gun moving speed: 1,000 mm / sec), and then heated and dried at 100 ° C. for 1 hour and further at 160 ° C. for 1 minute to prepare a developing roller of the present invention. The obtained developing roller had a core metal diameter of 6 mm and an outer diameter of the elastic layer of 16 m.
m, the length of the elastic layer in the longitudinal direction was 240 mm.

This developing roller is used as a laser beam printer (manufactured by Canon, trade name: Color Laser Shot LBP).
-2040) in a developing device (a non-contact developing device was converted into a contact developing device), and the temperature was 15 ° C. and the humidity was 10%.
And an image was formed up to 20,000 sheets in an environment of a temperature of 32.5 ° C. and a humidity of 80%, and the obtained image was evaluated. The results are shown in Tables 2 and 3.

Example 2 The procedure of Example 1 was repeated except that the development roller was prepared as described below. [Preparation of Elastic Layer] Same as Example 1. [Preparation of Surface Layer Coating] A coating was prepared in the same manner as in Example 1 except that an ethylene-vinyl alcohol copolymer (degree of saponification: 90 mol%, ethylene content: 35 mol%) was used. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 3 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Preparation of Surface Layer Coating] A coating was prepared in the same manner as in Example 1 except that an ethylene-vinyl alcohol-based copolymer (degree of saponification: 70 mol%, ethylene content: 35 mol%) was used. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 4 The procedure of Example 1 was repeated except that the development roller was prepared as described below. [Preparation of Elastic Layer] Same as Example 1. [Preparation of Surface Layer Coating] Ethylene-vinyl alcohol copolymer (degree of saponification 99.8 mol%, ethylene content 20
(Mol%) was used in the same manner as in Example 1. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 5 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Preparation of Surface Layer Coating] Ethylene-vinyl alcohol copolymer (degree of saponification 99.8 mol%, ethylene content 60
(Mol%) was used in the same manner as in Example 1. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 6 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Preparation of surface layer paint] PMMA particles were prepared with an average particle size of 0.3.
μm, true density 1.19 g / cm ³ , spherical (major axis / minor axis =
1.06), except that it was manufactured in the same manner as in Example 1. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 7 The procedure of Example 1 was repeated except that the development roller was prepared as described below. [Preparation of Elastic Layer] Same as Example 1. [Preparation of surface layer paint] PMMA particles were prepared to have an average particle size of 30 μm.
m, true density 1.19 g / cm ³ , spherical (major axis / minor axis =
1.06), except that it was manufactured in the same manner as in Example 1. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 8 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Preparation of Surface Layer Coating] Instead of PMMA particles, silver fine particle-dispersed resin particles [average particle size 5 μm, true density 3 g / cm ³ ,
Except for using a spherical shape (major axis / minor axis = 1.21)], it was manufactured in the same manner as in Example 1. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 9 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Preparation of surface layer paint] PMMA particles were prepared with an average particle size of 5 μm.
m, true density 1.19 g / cm ³ , spherical (major axis / minor axis =
The same procedure as in Example 1 was carried out except that 1.5) was adopted. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 10 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Preparation of Surface Layer Coating] A coating was prepared in the same manner as in Example 1 except that 4 parts of an imidazole-based charge control agent represented by the following formula I (number average particle size: 3 μm) was added.

[0043]

Embedded image

[Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Example 11 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Production of Surface Layer Coating] Example 9 was repeated except that the imidazole-based charge control agent was replaced by a quaternary ammonium salt (containing no nitrogen-containing heterocyclic ring; number average particle size of 2.2 μm) represented by the following formula II. It was produced similarly.

[0046]

Embedded image

[Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Production of surface layer] 100 parts of polyethylene, 15 parts of conductive carbon black and PMMA particles [average particle diameter of 7.5 µm]
m, true density 1.19 g / cm ³ , spherical (major axis / minor axis =
1.06)] A semiconductive tube having a thickness of 150 μm and an outer diameter of 16φ was prepared by mixing and kneading 10 parts with an extruder. [Production of developing roller] Under normal temperature and normal humidity (23 ° C, 55%)
Then, the above-mentioned semiconductive tube was coated on the elastic layer to prepare a developing roller for comparison. The obtained developing roller had a core metal diameter of 6 mm, an outer diameter of the elastic layer of 16 mm, and a length of the elastic layer portion of 220 mm. Tables 2 and 3 show the results of evaluation using this in the same manner as in Example 1.

Comparative Example 2 The procedure of Example 1 was repeated except that the development roller was prepared as follows. [Preparation of Elastic Layer] Same as Example 1. [Preparation of Surface Layer Coating] Instead of ethylene-vinyl alcohol copolymer, polyvinyl alcohol (degree of saponification 99.
(8 mol%) was used in the same manner as in Example 1. [Production of Developing Roller] Tables 2 and 3 show the results of production and evaluation in the same manner as in Example 1.

Each of the evaluation items in Tables 2 and 3 was measured by the following method. (1) Image Density (Durable Density) Using a reflection densitometer RD918 (manufactured by Macbeth), the density of a solid black portion at the time of solid printing was measured at five points, and the average value was defined as the image density.

(2) Fog density (durable fog) The reflectance (D1) of the solid white portion of the recording paper on which an image was formed was measured, and the reflection of an unused recording paper having the same cut as the recording paper used for the image formation was measured. The ratio (D2) was measured, the value of D1-D2 was determined at five points, and the average value was defined as the fog density. The reflectance is T
It was measured by C-6DS (manufactured by Tokyo Denshoku).

(3) Ghost (durable ghost) The position of the developing sleeve which has developed the image in which the solid white portion and the solid black portion are adjacent comes to the developing position at the next rotation of the developing sleeve, and develops the halftone image. Then, the difference in shading appearing on the halftone image was visually evaluated based on the following criteria. ：: No difference in shade was observed. △: A slight difference in shading is observed. Δ: A slight difference in shading is observed. X: The contrast is remarkably observed.

(4) Stain Resistance of Surface Layer The surface of the developing roller after the endurance was observed by SEM, and the degree of toner contamination was evaluated based on the following criteria. ：: Only slight contamination is observed. ○ △: Slight contamination is observed. Δ: Contamination is partially observed. X: Remarkable contamination is observed.

(5) Change in Surface Layer The surface of the developing roller after the endurance was observed with an optical microscope, and the change in the surface layer was evaluated based on the following criteria. ：: No crack occurred. Δ: Cracks are partially observed. X: A remarkable crack is observed.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

As described above, the effect of the present invention is as follows.
It is another object of the present invention to provide a developing roller having at least a surface layer and an elastic layer, wherein the binder resin of the surface layer contains at least an ethylene-vinyl alcohol copolymer. ADVANTAGE OF THE INVENTION According to this invention, high developing efficiency can be attained, and it is possible to obtain a clear, high-density developed image with reduced fog over a long period of time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a developing roller of the present invention.

FIG. 2 is a schematic configuration diagram showing a laser beam printer provided with a developing roller of the present invention.

[Explanation of symbols]

 1: photosensitive drum 10: developing device 11: developer (non-magnetic toner) 11a: developer thin film 12: developer container 13: developing area 16: blade 18: constant voltage power supply 19: charging roller 24: developing roller 24a: Core bar 24b: Elastic layer 24c: Surface layer 25: Supply roller 25a: Core bar 25b: Elastic layer 25c: Surface layer 114: Developing roller 114a: Core bar 114b: Elastic layer 114c: Surface layer L: Laser beam

Claims (11)

[Claims] 1. A developing roller having at least a surface layer and an elastic layer, wherein the binder resin of the surface layer contains at least an olefin-vinyl alcohol copolymer. 2. The olefin content in the olefin-vinyl alcohol copolymer is from 20 to 60, based on all monomers constituting the olefin-vinyl alcohol copolymer.
The developing roller according to claim 1, which is mol%. 3. The method according to claim 1, wherein the olefin is ethylene.
Or the developing roller according to 2. 4. The developing roller according to claim 1, wherein the olefin-vinyl alcohol copolymer has a saponification degree of 70 mol% or more. 5. The developing roller according to claim 1, wherein the surface layer contains spherical particles having an average particle diameter of 0.3 to 30 μm and a true density of 3 g / cm ³ or less. 6. The ratio of the major axis / minor axis of the spherical particles is 1.0 to 1.0.
The developing roller according to claim 5, wherein the ratio is 1.5. 7. The developing roller according to claim 1, wherein the surface layer contains a charge control agent. 8. The developing roller according to claim 7, wherein the charge control agent is a nitrogen-containing heterocyclic compound. 9. The developing roller according to claim 8, wherein the nitrogen-containing heterocyclic compound is an imidazole compound. 10. A developer contained in a developer container is carried on a developing roller, and while a thin layer of the developer is formed on the developing roller by a developer layer thickness regulating member, the developing roller and a latent image are formed. In a developing device that transports a developer to a development area where the carrier contacts, and develops the latent image on the latent image carrier with the developer into a visible image, the developing roller includes a developing roller.
A developing device comprising the developing roller according to any one of claims 9 to 13. 11. A developing device in which a developer contained in a developer container is carried on a developing roller, and a thin layer of the developer is formed on the developing roller by a developer layer thickness regulating member. In a developing method in which a developer is transported to a development area where the carrier is in contact with the developer, and the latent image on the latent image carrier is developed by the developer into a visible image, the developing roller includes:
A developing method comprising the developing roller according to any one of claims 9 to 13.