JPH04284475A - Electrical conductive roll - Google Patents

Abstract

PURPOSE:To provide high toner electrostatic chargeability by forming a an electrical conductive layer made of a coating film of an electrical conductive coating material containing a phenolic resin binder, an electrical conductive metal oxide powder, either of a phenolic resin cured powder and a polyethylene fluoride based powder having specific particle diameter or a phenolic resin cured powder as a filler. CONSTITUTION:The electrical conductive layer formed on an outer circumference of the core metal 16 is made by using the electric conductive coating material dispersing and containing the phenolic resin cured powder having <=20mum particle diameter or/with the polyethylene fluoride based powder having <=20mum particle diameter. This is, the electrical conductive layer 15 is made by curing the phenolic resin binder 21, and the phenolic resin cured powder and the polyethylene fluoride based powder or only the phenolic resin cured powder is dispersed as the filler 20 to form a rugged coarse surface on the surface layer. Since charge induced electricity by allowing the toner to contact with the surface of the electrical conductive layer is accumulated around the filler 20, electrostatic chargeability of the toner is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll used as a developing roll of an electrophotographic copying machine.

0002

2. Description of the Related Art Generally, an electrophotographic copying machine is constructed as shown in FIG. 3, and in the case of copying using an analog method, copying is performed as follows. That is, the photosensitive drum 1 rotating in the direction of the arrow about the shaft 1a is uniformly charged by the corotron 2. 3 is an exposure mechanism section through which slit exposure 8 of the original optical image reaches the surface of the photosensitive drum 1, and an electrostatic latent image (minus portion) corresponding to the original image is formed on the surface of the photosensitive drum 1. Reference numeral 4 denotes a developing roll built into the case 4a, which is frictionally charged (
plus), and the toner inside the case 4a is attached. Then, the electrostatic latent image (minus part) on the surface of the photosensitive drum 1
The positively charged toner flies toward the photosensitive drum 1, forming a toner image on the surface of the photosensitive drum 1. This toner image is transported in the direction of the arrow by the paper feed roller 6, transferred to the copy paper 11 via the transfer device 5, and fixed onto the copy paper 11 by the fixing roll 7. Copying is performed in this manner. Note that 9 is a cleaner that removes transfer afterimages and residual toner on the surface of the photosensitive drum 1, and 10 is an eraser lamp that zeroes the photosensitive drum 1 and prepares it for the next charging.

When the toner is non-magnetic, this type of developing roll 4 generally has a metal shaft (as shown in FIG. 4).
When the toner is magnetic, as shown in FIG.
A metal sleeve (core metal) 41b, end caps 41c at both ends thereof, and a magshaft 4 inside the metal sleeve 41b.
1d and a conductive layer 42 on the outer periphery of the metal sleeve 41b.
It is composed of b. In the figure, 43 is a bearing.

The conductive layers 42a, 42 of these developing rolls 4
From the viewpoint of cost reduction, etc., recently, the conductive material made by mixing a conductive material such as carbon powder into a synthetic resin matrix is formed into a cylindrical molded body. , 41b). The surface thereof is formed into an uneven surface so that the attached toner can be conveyed in the circumferential direction.

[0005]

[Problems to be Solved by the Invention] However, with such a developing roll 4, although a copied image with uniform density can be ensured by controlling the electrical resistance of the conductive layers 42a and 42b, the toner may be insufficiently charged. This causes problems such as insufficient density of the copied image and large fluctuations in density due to environmental conditions.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a conductive roll having high toner charging property and capable of stably obtaining a sufficient density of a copied image.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the conductive roll of the present invention is a conductive roll having a conductive layer formed on the outer periphery of the shaft, the conductive layer being a phenol-based roll. It is formed of a conductive paint containing at least component (A) of the following components (A) and (B) and conductive metal oxide powder dispersed in a resin binder. (A) Phenol resin hardened powder with a particle size of 20 μm or less. (B) Polyfluorinated ethylene powder with a particle size of 20 μm or less.

[0008]

[Operation] That is, the present inventors have conducted a series of studies in order to improve the toner charging property of the conductive layer formed on the outer peripheral surface of a conductive roll such as a developing roll. As a result, a conductive paint containing a phenolic resin binder, a conductive metal oxide powder, and both a phenolic resin hardened powder and a polyfluorinated ethylene-based powder of a specific particle size as a filler, or only the above-mentioned phenolic resin hardened powder. The inventors have discovered that when a conductive layer is formed by a coating film, the toner has a high charging property, and as a result, a sufficient density of a copied image can be stably obtained, and the present invention has been achieved.

Next, the present invention will be explained in detail.

The conductive roll of the present invention is composed of a shaft and a conductive layer formed on the outer periphery of the shaft.

The shaft body is not particularly limited, and a metal core made of a solid metal body or a metal cylindrical body with a hollow interior can be used.

[0012] The conductive layer formed along the outer periphery of the shaft includes a specific phenolic resin hardened powder (component A) and a specific polyfluorinated ethylene powder (component B) in a phenolic resin binder. It is formed by a coating film of conductive paint containing both or only a specific phenol resin cured powder (component A) and conductive metal oxide powder dispersed therein, and its thickness can be set to 50 to 300 μm. suitable.

[0013] The above-mentioned phenolic resin binder is not particularly limited, and various phenolic resins can be mentioned, but among them, it is preferable to use resol type phenolic resin from the viewpoint of hardness, abrasion resistance, etc. .

The above-mentioned specific phenolic resin cured powder (component A) is obtained by curing a phenolic resin and pulverizing it into a powder by a known method. As such a phenolic resin, a novolak type phenolic resin is suitably used. The phenol hardened powder (component A) needs to have a particle size of 20 μm or less. That is, if the particle size of the phenol hardened powder (component A) exceeds 20 μm, spots (white spots in solid black) will occur in the copied image.

[0015] The above-mentioned specific polyfluorinated ethylene powder (B
Component) is a powdered polyfluorinated ethylene resin. Examples of the polyfluoroethylene resin include tetrafluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, and specific examples include Teflon manufactured by DuPont. The polyfluoroethylene powder (component B) needs to have a particle size of 20 μm or less. That is, if the particle size of the polyfluoroethylene powder (component B) exceeds 20 μm, spots (white spots in solid black) will occur in the copied image.

In the present invention, the specific phenolic resin cured powder (component A) and the specific polyfluorinated ethylene powder (component B) are combined with both the A component and the B component or the specific phenolic resin cured powder (component A). The blending ratio is that whether both A and B components are used or only A component is used, the powder component is mixed with one part of the phenolic resin binder.
It can be blended at a ratio of 5 to 100 parts per 00 parts by weight (hereinafter abbreviated as "parts"). That is, if the blending ratio is less than 5 parts, the effect of improving toner chargeability cannot be obtained, and on the other hand, if it exceeds 100 parts, the thixotropy of the conductive paint increases,
This is because coating defects tend to occur more easily.

[0017] As the conductive metal oxide powder, c-
Examples include ZnO and c-SnO2. In addition, the above “
"c-" means having electrical conductivity.

[0018] The conductive paint used as the material for forming the conductive layer includes the above-mentioned phenolic resin binder, conductive metal oxide powder, both a specific phenolic resin hardened powder and polyfluorinated ethylene powder, or a specific phenolic resin. In addition to the hardened powder, a dispersant and the like may be appropriately blended as needed.

The conductive roll of the present invention is produced using the above-mentioned raw materials, for example, in the following manner. That is, first, a phenolic resin binder, a conductive metal oxide powder, both a specific phenolic resin hardened powder (component A) and a polyfluorinated ethylene powder (component B), or a specific hardened phenolic resin powder (component A). ), and by mixing and stirring this mixture using a ball mill or the like, a conductive paint is produced. Then, this conductive paint is applied to the surface of the metal shaft (core metal) to a uniform thickness by a dip method, roll coating method, spray coating method, etc., dried, and heated to harden. The conductive layer 15 of the conductive roll has a structure as shown in FIG. In the figure, 16 is a core metal.

As shown in FIG. 2, the conductive layer 15 is made of fillers (hardened phenolic resin powder and polyfluorinated ethylene powder) so that the phenolic resin binder 21 hardens and forms an uneven surface on its surface layer. (both or only the phenolic resin cured powder) 20 are dispersed. In the figure, 22 is a conductive metal oxide powder. Therefore, a large amount of electric charge generated by contact between the toner and the surface of the conductive layer 15 is accumulated around the filler 20,
The charging properties of toner are improved. Furthermore, by dispersing and containing the polyfluoroethylene powder, more positive charges appear on the surface of the conductive layer 15, making it ideal as a conductive roll for analog type electrophotographic copying machines.

The conductive roll of the present invention is widely used not only for the electrophotographic copying machine described above, but also for various conductive rolls such as facsimile machines and printers.

[0022]

As described above, in the conductive roll of the present invention, the conductive layer is composed of a phenolic resin binder, a phenolic resin cured powder (component A) of a specific particle size, and a polyfluoride resin of a specific particle size. Both ethylene powder (component B) or hardened phenolic resin powder with a specific particle size (component A)
The toner has high charging properties because it is formed of a special conductive paint film containing dispersed conductive metal oxide powder. Therefore, for example, when the conductive roll of the present invention is incorporated into an electrophotographic copying machine and used, a copy image with sufficient density can be obtained without causing insufficient density of the copy image.

Next, examples will be explained together with comparative examples.

[0024]

[Examples 1 to 6] As a conductive layer forming material, the raw materials shown in Table 1 below were blended in the proportions shown in the same table, mixed and stirred in a ball mill, and the viscosity was adjusted to 300 cps, and a dip liquid (conductive paint) was added. Tsukutsuta. In this liquid,
A conductive layer was formed by immersing and coating a core metal of mm in length, then pulling it up and drying it, and then heat-treating it. Then, a conductive roll as shown in FIG. 1 was produced.

[0025]

[Table 1]

*1: Manufactured by Sumitomo Durez, PR-51923 *2: Manufactured by Toshiba Chemical, TVB-2014 *3: Manufactured by Hakusui Chemical Co., Ltd.
23K *4: Manufactured by Asahi Carbon Co., Ltd., Asahi Thermal *5: Manufactured by Daikin Industries, Ltd., Lubron L-5 (particle size 0.5 μm) *6: Manufactured by Kanebo Co., Ltd., Bell Pearl (particle size 10 μm) *7: Manufactured by Nippon Silica Co., Ltd. ,E-75

[0027]

[Comparative Examples 1 to 3] The raw materials shown in Table 2 below were blended in the proportions shown in the same table. Other than that, a conductive roll as shown in FIG. 1 was produced in the same manner as in Example 1.

[0028]

[Table 2]

*1: Manufactured by Sumitomo Durez, PR-51923 *2: Manufactured by Toshiba Chemical, TVB-2014 *3: Manufactured by Hakusui Chemical Co., Ltd.
23K *4: Manufactured by Asahi Carbon Co., Ltd., Asahi Thermal *5: Manufactured by Daikin Industries, Ltd., Lubron L-5 (particle size 0.5 μm) *6: Manufactured by Kanebo Co., Ltd., Bell Pearl (particle size 10 μm) *7: Manufactured by Nippon Silica Co., Ltd. ,E-75

[0030]

[Comparative Example 4] Instead of Bell Pearl (manufactured by Kanebo Co., Ltd., particle size 10 μm), which is a phenolic resin hardened powder, one having a particle size of 50 μm (manufactured by Unitika Co., Ltd., Univex C-50) was used. Other than that, a conductive roll as shown in FIG. 1 was obtained in the same manner as in Example 2.

For each of the conductive rolls thus obtained, the density of the copied image and the amount of toner charge were measured and evaluated using the following methods. The results are shown in Tables 3 and 4 below.

[Copied image density] A conductive roll was used as a developing roll and installed in an electrophotographic copying machine under two different conditions (25°C x 55% RH, 35°C x 80% RH).
Images were taken at. Then, select a solid black image with sufficient density and no image unevenness or missing white spots.
If any of the following occurred: insufficient density, image unevenness, or white spots, it was evaluated as ×.

[Toner charge amount] The charge amount of the toner on the conductive roll was determined under two different conditions (25°C x 55%
RH, 35° C. x 80% RH) as follows. That is, as shown in FIG. 6, 32 layers of developer (toner) are formed on the surface of the conductive roll 30, and the developer 32 is sucked by the suction pump 33, and the faraday gauge 3
4 (Faraday gauge method). In the figure, 35 is a filter, 36 is an insulator pipe, and 37 is an electrometer.

[0034]

[Table 3]

[0035]

[Table 4]

*: White spots appeared on the solid black image obtained.

From the results in Tables 3 and 4 above, the comparative example products had a low evaluation of the copied image and a low toner charge amount. On the other hand, it was found that the example products had good properties in all respects and could be used as an excellent developing roll.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a conductive roll of the present invention.

FIG. 2 is a schematic diagram of a cross section of the conductive layer of the conductive roll of the present invention.

FIG. 3 is a configuration diagram of an electrophotographic copying machine incorporating a conductive roll.

FIG. 4 is a longitudinal cross-sectional view of a conventional conductive roll.

FIG. 5 is a longitudinal cross-sectional view of another conventional conductive roll.

FIG. 6 is a configuration diagram showing a measurement state of a Faraday gauge method for evaluating toner chargeability.

[Explanation of symbols]

15 Conductive layer 16 Core metal 20 Filling material 21 Phenol resin binder 22 Conductive metal oxide powder

Claims (1)

[Claims] 1. A conductive roll having a conductive layer formed on the outer periphery of a shaft, the conductive layer comprising at least (A) of the following components (A) and (B) in a phenolic resin binder. ) and a conductive paint containing conductive metal oxide powder dispersed therein. (A) Phenol resin hardened powder with a particle size of 20 μm or less. (B) Polyfluorinated ethylene powder with a particle size of 20 μm or less.