JP3003263B2 - Dielectric roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a facsimile,
Furthermore, the present invention relates to a developing roll used in an electrophotographic developing device such as a laser printer, and particularly to a dielectric material suitable for a direct contact type electrophotographic developing method in which a developer is directly contacted with the surface of the developing roll without using a metal sleeve. About roles.

2. Description of the Related Art In one type of electrophotographic developing apparatus such as a copying machine and a facsimile machine, a rubber magnet layer is disposed as a magnetic dielectric on a cylindrical or cylindrical metal substrate, and the surface thereof is made fine. A developing method in which toner is directly magnetized on the surface of the magnet roll using a dielectric developing roll (hereinafter referred to as a dielectric roll) finished in
There is a so-called direct contact developing method.

[0001]

In the dielectric roll used in this developing method, the electric characteristics based on the constituent members affect the development. In other words, it is difficult to stabilize the electrical characteristics unless it is manufactured with extremely high precision using carefully selected resin ferrite materials and conductive base shafts, and the stability of image quality of products incorporating the dielectric roll is reduced. There is no guarantee. For example, if the resin ferrite material contains foreign matter or uneven distribution of constituent materials, variations in the electrical characteristics of the dielectric roll cannot be ignored. Similarly, when the adhesive layer interposed between the resin ferrite layer and the conductive substrate has an uncured portion or a hardener residue, or when there is an oil layer or the like on the surface of the substrate shaft, the electrical characteristics of the dielectric roll vary. This causes image defects. In addition, if the adhesion between the resin ferrite layer and the conductive substrate is incomplete, there is a problem that the electrical characteristics are largely fluctuated as a whole due to the presence of the gap. Poor and problematic. In addition, even if careful attention is paid to the quality control of the resin ferrite and the adhesive in order to solve these problems, it is not possible to eliminate variations in the electrical characteristics, and an effective solution that can eliminate such inconveniences is desired. I was The present invention has been made in view of such a situation, and an object of the present invention is to provide a dielectric roll which has a small variation in electric resistance and can obtain a good developed image.

[0002]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems in the prior art, intensive studies have been made on the lamination state of a resin ferrite layer and a conductive substrate, which is considered to affect the quality of a dielectric roll having magnetism. As a result, the inventors have found that unevenness in the thickness of the adhesive layer is the largest factor as a cause of the variation in electric resistance, and arrived at the present invention. That is, the present invention
A dielectric roll used for direct contact electrophotographic development
The resin ferrite layer, the adhesive layer, and the conductive substrate, and the unevenness of the thickness of the adhesive layer is one of the thickness of the resin ferrite layer.
0% or less , and the thickness of this adhesive layer is 100 μm or less
The subject matter is a dielectric roll characterized in that:

[0003]

The electrical resistance of the adhesive is much higher than that of the resin ferrite, and the unevenness of the thickness of the adhesive layer greatly affects the electrical resistance of the whole magnet roll. The thickness unevenness of the layer is not more than 10% of the thickness of the resin ferrite layer , and the adhesive layer
Is less than 100 μm , the effect of uneven thickness of the adhesive layer on the electric resistance of the entire dielectric roll can be reduced, and the electric characteristics of the dielectric roll can be made uniform throughout. Can be.

[0004]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on embodiments. FIG. 1 is an explanatory sectional view showing one embodiment of the dielectric roll of the present invention, in which 1 is a conductive base constituting a shaft, 2 is a resin ferrite layer, and 3 is an adhesive layer.

The conductive substrate 1 used in the present invention is a material having a high elastic modulus such as a metal. It is preferable that this surface has no notch or step. If there are notches or steps, the thickness of the adhesive layer tends to vary, and if the degree cannot be ignored, when coated with resin ferrite, the knitting change of the lamination state cannot be tolerated and the dielectric roll surface The behavior of the toner at each position is not uniform, which causes soiling and image defects.
The adhesive applied to the conductive substrate surface is appropriately selected from thermoplastic, thermosetting and other general-purpose adhesives according to the purpose and the production method. If a sufficient adhesive strength is obtained, a pressure-sensitive adhesive can be used. Coating method is painting method, spray spray method,
Conventional methods such as an immersion method and a transfer method can be used.

The most important electrical property of the dielectric roll of the present invention is the presence of the resin ferrite layer. Therefore, the electrical properties defined by the resin ferrite layer are not significantly affected by the presence or state of the adhesive layer. It is preferable to do so. For this purpose, the thickness of the adhesive layer is preferably thin. In order to easily realize a thin layer state, the adhesive is preferably applied in a state diluted with a solvent. Emulsion type is not preferable because of existence of contaminants such as dispersant and emulsifier and pinhole. The average thickness of the adhesive is preferably about 100 μm or less. The average thickness of the adhesive is 1
If it exceeds 00 μm, the influence on other electric characteristics such as relative permittivity other than the electric resistance value of the dielectric roll becomes excessive,
Further, it is not preferable because the adhesive strength is weakened, the application process is troublesome, and the coating tends to be uneven.
The thickness unevenness of the adhesive layer is 1% of the thickness of the resin ferrite layer.
It needs to be 0% or less. From the viewpoint of electric resistance, the dielectric roll is equivalent to a configuration in which resistors corresponding to the resin ferrite layer 2, the adhesive layer 3, and the conductive substrate 1 are connected in series as shown in FIG. Can be considered. Since the volume resistivity of the adhesive is at least 10 times the volume resistivity of the resin ferrite material, if the dielectric roll is regarded as a circuit in which the electric resistance is connected in series as described above, a high electric resistance is obtained. If the thickness unevenness of the adhesive layer having a value is 10% or more of the resin ferrite layer, a variation in the same order as the resistance value of the resin ferrite layer occurs, and the resin ferrite layer, the adhesive layer, and the conductive substrate are connected in series. The variation of the electric resistivity in the entire electric equivalent circuit becomes not negligible. And in such a case,
The behavior of the toner at each position on the surface of the dielectric roll is not uniform, and background contamination and image defects are likely to occur. From such a viewpoint, the thickness unevenness of the adhesive layer needs to be 10% or less of the thickness of the resin ferrite layer.

It is preferable that the thickness unevenness of the adhesive is minimized. For example, when the average thickness of the adhesive layer is about several tens μm or more, the average thickness of the adhesive layer is suppressed to about 10% or less. Is industrially preferable. However, when the thickness of the adhesive layer is about several μm and the electrical resistance value of the adhesive layer is sufficiently smaller than the electrical resistance value of the resin ferrite layer, the thickness unevenness of the adhesive layer is an average of the adhesive layer. Even if it exceeds 10% of the thickness, there is no industrial problem.

[0008] The resin ferrite of the present invention means a permanent magnet ferrite powder filled in a thermoplastic resin, a thermosetting resin or rubber. Barium ferrite, strontium ferrite, or the like can be used as the magnet powder used for the resin ferrite used in the present invention. These may be isotropic or anisotropic. This may be subjected to a surface treatment using a silane-based or titanate-based coupling agent.
As the binder, a thermoplastic resin, unvulcanized rubber, vulcanized rubber, or the like as a main component and containing a plasticizer, a stabilizer, a lubricant, a vulcanizing agent or a crosslinking agent, a filler, and the like can be used. Preferably, a thermoplastic resin is used. Those requiring a bridging step or a cross-linking step are not preferred because the electrical properties of the molded article vary depending on the degree of reaction.

As a method for forming a dielectric layer having magnetism on the conductive substrate, various conventional methods are appropriately selected.
For example, there is a method in which a rubber magnet sheet is wound around a base and pressure-fused, and a preferable method is a method in which a thermoplastic resin magnet material is coated by injection molding or extrusion molding.

Next, specific examples performed to confirm the effects of the present invention will be described. Example 1 70% by weight of vinyl chloride monomer, vinyl acetate monomer 3
A thermoplastic resin having a radical copolymerization of 0% by weight was dissolved in methyl ethyl ketone at a concentration of 5% by weight to prepare an adhesive solution. This is sprayed onto a stainless steel shaft with no notch, dried at 50 ° C. for 20 minutes, and an adhesive layer having a thickness of 3 μm from the center of the shaft to one end and a 5 μm thickness from the center of the shaft to the other end is formed. Each was formed, and the thickness difference of the adhesive layer was intentionally formed. The resin ferrite is a mixer composed of 40% by volume of a resin mixture composed of 70% by weight of chlorinated polyethylene, 29.5% by weight of an ethylene / vinyl acetate copolymer, and 0.5% by weight of a phenolic antioxidant, and 60% by volume of Ba ferrite. And kneaded with a hot roll mill at 120 ° C. to obtain a kneaded product of a plastic resin ferrite for molding. This was coated and formed at 140 ° C. so as to have a thickness of 1 mm from the surface of the shaft by an extruder having a crosshead die mounted on the shaft. Measurement points were taken at regions where the adhesive thickness of the molded product was different, the apparent volume resistivity was measured at each value, and the difference was calculated. The roll thus obtained was mounted on a copying machine, and the copied image was evaluated. In addition, the evaluation of the adhesiveness was made by placing 20
After the poles are magnetized and the roll surface is cut with a lathe to finish the surface, the stainless steel plate is pressed against the roll with a load of 200 g and the roll is pressed at 100 rpm at 40 ° C.
A check was made to determine whether or not there was a deviation in the magnetization pattern before and after rotation for 0 hour. Table 1 shows the results.

Examples 2 to 4 The thickness was 3 μm from the center of the shaft to one end, and the thickness was 10 μm and 50 μm from the center of the shaft to the other end.
A molded article was obtained under the same conditions as in Example 1 except that an adhesive layer of m and 100 μm was formed, and the apparent volume resistivity difference was measured, and the quality of the copied image and the evaluation of the adhesion were evaluated. Performed similarly to 1. Table 1 shows the results.

Example 5 An adhesive layer having a thickness of 3 μm from the center of the shaft to one end and a 200 μm thickness from the center of the shaft to the other end was formed so that the ferrite kneaded material had a thickness of 2 mm. A molded article was obtained under the same conditions as in Example 1 except that the coating was performed, and the apparent volume resistivity difference was measured, and the quality of the copied image and the evaluation of the adhesion were evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 A molded product was obtained under the same conditions as in Example 1 except that an adhesive layer having a thickness of 3 μm was formed from the center of the shaft to one end and a 120 μm thickness was formed from the center of the shaft to the other end. The apparent volume resistivity difference was measured, and the quality of the copied image and the evaluation of the adhesion were evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 A molded product was obtained under the same conditions as in Example 5 except that an adhesive layer having a thickness of 3 μm was formed from the center of the shaft to one end and a 220 μm thickness was formed from the center of the shaft to the other end. The apparent volume resistivity difference was measured, and the quality of the copied image and the evaluation of the adhesion were evaluated in the same manner as in Example 1. Table 1 shows the results.

[0015]

[Table 1]

In Examples 1 to 3, no difference in image was observed at the portions where the thickness of the adhesive was different. Example 4
In Examples 5 and 5, there was a strict difference, but there was virtually no difference as a practical image. In Comparative Examples 1 and 2, there was a clear difference in image density, which was not preferable. The adhesive properties were all good except for Comparative Example 1. From these results, by controlling the thickness unevenness of the adhesive layer to be within 10% of the thickness of the resin ferrite layer, there is no problem in the adhesiveness, and the electrical characteristics such as apparent volume resistivity are satisfied. As a result, it is understood that a dielectric roll from which a good copy image can be obtained can be obtained.

[0017]

According to the present invention, it is possible to suppress variations in the electrical characteristics which have been inevitably generated even if the quality control of the resin ferrite alone and the adhesive alone was strictly performed, and a good copy image was obtained. It has become possible to stably mass-produce dielectric rolls suitable for a direct contact developing method capable of obtaining the following.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a dielectric roll of the present invention.

FIG. 2 is an explanatory diagram showing an outline of the present invention.

[Explanation of symbols]

 Reference Signs List 1 conductive substrate 2 resin ferrite layer 3 adhesive layer

Continuation of front page (72) Inventor Yasushi Kakehashi 14 Kinuigaoka, Moka-shi, Tochigi Pref. Kanebuchi Chemical Industry Co., Ltd. JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/08

Claims (1)

(57) [Claims] 1. A dielectric used in a direct contact type electrophotographic developing method.
A body roll comprising a resin ferrite layer, an adhesive layer and a conductive substrate, wherein the thickness unevenness of the adhesive layer is 10% or less of the thickness of the resin ferrite layer, and the thickness of the adhesive layer is
A dielectric roll having a thickness of 100 μm or less .