JPH09325600A - Rubber roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber roll adequately used for an electrostatic recorder having various characteristics including low hardness and middle resistance as well as a high moistening property and surface smoothness by forming the rubber roll having a first layer consisting of polar rubber and a second layer consisting of a synthetic resin with which the outer periphery of the first layer is coated and which has a thickness of a specific range. SOLUTION: This rubber roll has the first layer 9 consisting of the polar rubber and the second layer 10 consisting of the synthetic resin of 10 to 100μm thickness with which the outer periphery of the first layer 9 is coated. Namely, the rubber roll is constituted by forming the first layer 9 and the second layer 10 on, for example, an arbor 7. A blank having the first layer 9 of the polar rubber material is used according to such constitution and, therefore, the additives for lowering the resistance and the hardness are not used. Then, the variations in the resistance by adding these additives are substantially eliminated. The images having no variations of the image characteristics are obtd. if the rubber roll is used for a developing roll. The high moisture resistance, the surface smoothness and the prevention of the wear characteristic of the coating layer are made possible by the second layer 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber roll, and more particularly to a developing rubber roll, a transfer rubber roll and the like used in an electrostatic recording device.

[0002]

2. Description of the Related Art Conventionally, as a developing roll and a transferring roll used in an electrostatic recording apparatus, a mandrel covered with an elastic body such as rubber has been used. In particular, as for the developing roll, as shown in FIG. 1, the so-called developing roll 2 is replenished with toner from the toner replenishing roll 3, and this toner is thinned on the surface of the developing roll 2 by the toner thinning blade 4. A contact developing method is known in which the toner 5 is formed and the thinned toner 5 is brought into pressure contact with the photoconductor 1 to obtain the developed toner 6. As the required characteristics of the developing roll 2 in such a developing method, it is particularly necessary that the developing roller 2 has a medium resistance of 10 ⁵ to 10 ¹⁰ Ωcm and a rubber hardness of 30 to 40 degrees or less. Conventionally, polar rubber such as NBR, acrylic rubber, or chloroprene rubber has been used as a member of the coating layer 8 that coats the cored bar 7 of the developing roll 2, but it is difficult to reduce the hardness and is generally used. Mixing of the plasticizer and sub (softening agent / processing aid) that is used has problems such as leaching on the roll surface and elastic recovery, and for example, toner firmly adheres to the roll surface and the surface properties change,
The toner chargeability and electric resistance fluctuate, and the toner thin layer unevenness occurs due to the deformation of the contact part of the toner thinning member such as the photoconductor, the blade, and the roll. There was an inconvenience such as being lost. Therefore, attempts have been made to use a silicone rubber or the like, which can be made harder without adding the plasticizer and the sub-substance, as a coating material, but it has a high electric resistance, so that low electric resistance particles such as metal or carbon black are dispersed. The method is adopted. But,
In this case as well, there is a problem in that there are variations in resistance due to parts due to variations in particle dispersibility after molding, resulting in variations in image quality such as image density and background stains. Therefore, the present inventor has found a polar rubber roll satisfying both low hardness and medium resistance that solves the above problems, but when this rubber roll is used as an developing roll or a transfer roll in an electrophotographic copying machine, The image quality varies due to the influence of environmental characteristics (particularly temperature characteristics) and the accumulation of unnecessary toner on the rubber roll.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a rubber roll suitable for use in an electrostatic recording apparatus having various characteristics of low hardness, medium resistance, high humidity and surface smoothness. It is a thing.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a first layer of polar rubber and the thickness of the outer periphery of the first layer.
A rubber roll disposed opposite to a photoconductor, having a second layer of synthetic resin of 10 to 100 μm.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polar rubber used as the first layer in the present invention has a volume resistance of 10 ¹⁰ Ωcm or less, particularly 10 ⁵ to 10 ¹⁰ Ωc.
It is a polar rubber having an electric resistance of m, and its rubber hardness is desirably 30 to 40 degrees or less. A typical example thereof is an alkali metal-containing urethane rubber in which an alkali metal salt is contained in a urethane rubber comparand and cured. Among various synthetic rubbers, urethane rubber is a strong rubber-like elastic body that is excellent in low hardness, abrasion resistance and compression strain resistance. By containing an alkali metal in this urethane rubber, the volume resistance can be reduced to 10 ¹⁰ Ωcm or less. The alkali metal salt added to the urethane rubber compound has a smaller dissociation energy, and the smaller the radius of the carrier ion, the greater the effect of resistance reduction due to the addition. Particularly, lithium, sodium and potassium salts are preferable, and the lithium salt is most preferable. is there. These alkali metal salts are not particularly limited as long as they are completely soluble in urethane rubber basic polymers such as polyesters and polyethers, but are not limited to halogen oxyacid salts, perhalogen oxyacid salts, tetrahalogen borate salts, and thiocyanates. Acid salts, phosphates and the like are preferable, and perhalogen oxyacid salts are most preferable. From the above, lithium perchlorate (LiC
lO ₄₎ is most preferable as the additive compound. The addition amount of these alkali metal salts is preferably 10 parts by weight or less with respect to 100 parts by weight of the urethane rubber compound. If it exceeds 10 parts by weight, the effect of lowering resistance is almost lost, and transparency, strength, moldability, etc. are lost.

Next, the characteristics of the polyurethane rubber containing the alkali metal salt will be described. (1) Liquid urethane rubber Polyester (ODX-106, Dainippon Ink and Chemicals) 100 parts by weight Isocyanate (Millionate MT, Nippon Polyurethane) 11 parts by weight Lithium perchlorate (Kanto Chemical) 0, 0.5, 1,3.5 parts by weight Polyester After dehydration under reduced pressure at 120 ° C for 30 minutes, the above amount of each lithium perchlorate (100mesh under, room temperature 24
(Time drying) is added and stirred to prepare 5 kinds of samples, and after each solution becomes transparent, it is weighed, isocyanate is further added, and this is poured into a 2 mm-thick sheet metal mold, and 100 It is cured under the condition of 3 ° C. for 3 hours. The cured sheet was left for 24 hours in an environment of room temperature and 30% humidity.
After that, the sheet was measured by a DC resistance meter (4329A High Resistanc
The volume resistance was measured with an e Meter, Yokogawa-Hewleft Packard). The results are shown by circles in FIG. Further, various rubber properties such as hardness were measured by predetermined methods. Table 1 shows the results.
Shown in

[0007]

[Table 1]

(2) Millable urethane rubber Mirasen E-34 (TSE) 100 parts by weight Zinc stearate 0.5 parts by weight Dicumyl peroxide 5 parts by weight Lithium perchlorate 0,0.05,1,3,5 parts by weight After kneading with 2 rolls, aging overnight, 15
A 2 mm thick sheet was press-molded under the conditions of 0 ° C. and 10 minutes. Then, the volume resistance was measured by the same method as in the case (1). The results are shown by triangle marks in FIG. From the measurement results of the volume resistance of each sheet shown in FIG. 2, a tendency of a decrease in resistance is clearly recognized regardless of whether it is a liquid type or a millable type as the amount of alkali metal salt added increases. Table 1
From the results, it can be seen that the strength does not change much even if the amount of the alkali metal salt added changes. The present inventors have confirmed that these results give almost the same results with alkali metal salts other than lithium perchlorate. As described above, the polyurethane rubber containing the alkali metal salt is a low-hardness and medium-resistance elastic body,
Most suitable for use as the first layer of the present invention. In the rubber roll of the present invention, the first layer made of the polar rubber as described above is formed on the mandrel with a thickness of about 1 to 20 mm, and the upper surface of the first layer is made of a synthetic resin such as fluorine-based, silicone-based or urethane-based resin. Two
A layer is formed to have a thickness of about 10 μm to 100 μm and is used as a second layer. By providing the second layer in this manner, the resistance value of the first layer changes in a high humidity environment, and when this roll is used as a developing roll, unnecessary toner is prevented from adhering to the roll surface. Properties such as toner releasability, lubricity, and toner chargeability are improved. When low-resistance particles such as metal are dispersed in the material of the second layer to form the second layer, this acts as a developing electrode, and the image quality is further improved. FIG. 3 is a schematic cross-sectional explanatory view showing each aspect of the surface of the roll of the present invention. FIG. 3A shows a roll having a first layer 9 and a second layer 10 formed on a mandrel 7, and FIG. 3B shows a roll having a first layer 9 and low-resistance particles 11 on the mandrel 7. It is the roll which formed the 2nd layer 3 containing. Next, examples of the present invention will be described.

[0009]

[Examples] 100 parts by weight of polyester (ODX-106, Dainippon Ink and Chemicals) was dehydrated under reduced pressure at 120 ° C for 30 minutes, and then 0.5 parts by weight of lithium perchlorate (Kanto Chemical) was added and stirred,
After the solution became transparent, it was weighed, 11 parts by weight of isocyanate (Millionate MT, Nippon Polyurethane) was further added, and the mixture was poured into a 2 mm-thick sheet mold and cured at 100 ° C. for 3 hours. After that, a fluorine-based resin with a thickness of 10 μm to 1
Coated within the range of 00 μm.

[0010]

As described above, since the roll of the present invention uses the material having the first layer of the polar rubber material, it does not use the additive for reducing the resistance and the hardness.
Therefore, there is almost no variation in resistance due to the addition of these additives, and when used in a developing roll, an image having no variation in image characteristics can be obtained. In addition, the presence of the second layer has an excellent effect that high moisture resistance, surface smoothness, and abrasion resistance of the coating layer can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a contact developing device.

FIG. 2 is a drawing showing the relationship between the amount of alkali metal salt added and the volume resistance of urethane rubber, which is a typical material for the first layer of the present invention.

3A and 3B are drawings showing various aspects of a roll surface of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Development roll 3 Toner supply roll 4 Toner thinning grade 5 Thinning toner 6 Developed toner 7 Core metal 8 Covering layer 9 First layer 10 Second layer 11 Low resistance particles

Claims (2)

[Claims] 1. A photosensitive material comprising a first layer made of polar rubber and a second layer made of synthetic resin having a thickness of 10 to 100 μm and coated on the outer periphery of the first layer. A rubber roll arranged facing the body. 2. The rubber roll according to claim 1, wherein the polar rubber has a rubber hardness of 40 degrees or less.