Roll or roller – Concentric layered annulus – Specific composition
Reexamination Certificate
1999-12-14
2001-09-04
Cuda Rosenbaum, I (Department: 3726)
Roll or roller
Concentric layered annulus
Specific composition
C492S053000, C492S054000
Reexamination Certificate
active
06283903
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a conductive roll used in an image forming apparatus of an electrophotographic system such as a copying machine or a printer and to a method of manufacturing the same. To be more specific, the present invention relates to a conductive roller used as a charging roll for charging a surface of an image carrier, as a developing roll for coating an image carrier with a toner, and as a transfer roll for transferring the toner from the image carrier onto a paper sheet, and to a method of manufacturing the same.
FIG. 2
shows how various rolls are used. As shown in the drawing, a transfer roll
1
and an image carrier roll
2
serve to collectively transfer the toner from the image carrier onto a paper sheet
3
. A charging roll
4
for charging a surface of the image carrier and a developing roll
5
for coating the image carrier with the toner are arranged in the vicinity of the image carrier roll
2
. Further, a pair of fixing rolls
6
are arranged downstream of the transfer roll
1
.
Known is a conductive member formed of a high molecular weight elastomer or a high molecular weight cellular elastomer (sponge body) mixed with an electron conducting agent such as a metal powder, a metal oxide powder, whiskers or a conductive carbon black to allow the conductive member to exhibit a predetermined electric resistance. The conventional conductive member of this type is defective in that the conductive member is greatly dependent on voltage, that the electric resistance is rendered nonuniform depending on portions of the roll product, and that the electric resistance of the conductive member is gradually increased during a continuous power supply. However, the conventional electron conductive member is advantageous in that a difference in electric resistance as measured under a voltage of 1 kV is small between a low temperature-low humidity environment (temperature of 10° C. and a relative humidity of 10%) and a high temperature-high humidity environment (temperature of 30° C. and a relative humidity of 80%).
Also known is a conductive member formed of a high molecular weight elastomer or a high molecular weight cellular elastomer (sponge body) mixed with an ionic conducting agent such as inorganic ionic substances including lithium perchlorate, sodium perchlorate or calcium perchlorate, a cationic surfactant, an amphoteric ionic surfactant, or an organic ionic substance such as tetraethyl ammonium perchlorate (or butyl ammonium) to control the electric resistance of the conductive member at a predetermined value. The ionic conductive member of this type is defective in that there is a large difference in electric resistance as measured under a voltage of 1 kV between a low temperature-low humidity environment (temperature of 10° C. and a relative humidity of 10%) and a high temperature-high humidity environment (temperature of 30° C. and a relative humidity of 80%). However, the ionic conductive member of this type produces a merit, which is not produced by the electron conducting conductive member, that the voltage dependence, i.e., difference in electrical resistance produced when the voltage is changed, is low.
As described above, the conventional electron conducting conductive member containing an electron conducting agent such as a conductive carbon black or a metal oxide powder exhibits a high voltage dependence (i.e., the change in electric resistance caused by the change in voltage is large), resulting in failure to obtain a constant electric resistance. Therefore, when applied to, for example, a developing roll, the electron conductive member fails to obtain a predetermined amount of charge. As a result, the toner attached to the developing roll is rendered nonuniform in density, resulting in failure to obtain a high quality image.
Likewise, when the conventional electron conductive member is applied to a transfer roll, the nonuniformity in the resistance value of the electron conductive member causes the toner transferred onto the paper sheet to be nonuniform in density. It is impossible to obtain a high quality image in this case, too.
On the other hand, the ionic conductive member containing ionic conducting agent such as lithium perchlorate or a cationic ionic surfactant gives rise to a large difference in the electric resistance between a low temperature-low humidity environment and a high temperature-high humidity environment, making it difficult to obtain a constant electric resistance throughout the four seasons of a year. It follows that, when applied to, for example, a developing roll, a stable electric resistance cannot be obtained. To be more specific, the amount of charging is rendered highly nonuniform depending on the change in the environment. As a result, the developed toner is rendered unstable, leading to failure to obtain a high quality image.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a conductive rubber roller, which permits exhibiting a stable resistance regardless of changes in voltage, and which permits diminishing the difference in electric resistance between a low temperature-low humidity environment and a high temperature-high humidity environment so as to form stably a high quality image constantly. The present invention is intended to overcome the above-noted defects inherent in the conventional conductive roll used in an image forming apparatus and utilizes in combination the merit of the electron conducting conductive member obtained by mixing an electron conducting agent and the merit of the ionic conductive member obtained by mixing an ionic conducting agent.
According to a first aspect of the present invention, there is provided a conductive rubber roller, comprising a metal core connected to a power source, an ionic conductive layer containing an ionic conducting agent and formed to surround the outer surface of the metal core, and an electron conductive layer formed to surround the outer surface of the ionic conductive layer and consisting of a high molecular weight elastomer containing an electron conducting agent or a cellular elastomer of a high molecular weight elastomer containing an electron conducting agent, wherein the ionic conductive layer consists of a high molecular weight elastomer, a polymer alloy thereof, a high molecular weight cellular elastomer, or a polymer alloy, and an electric resistance R
1
of the ionic conductive layer is higher than an electric resistance R
2
of the electron conductive layer (R
1
>R
2
).
According to a second aspect of the present invention, there is provided a conductive rubber roller, comprising a metal core connected to a power source, an ionic conductive layer containing an ionic conducting agent and formed to surround the outer surface of the metal core, an electron conductive layer formed to surround the outer surface of the ionic conductive layer and consisting of a high molecular weight elastomer containing an electron conducting agent or a high molecular weight cellular elastomer containing an electron conducting agent, and an insulating annular sealing member mounted to each of both edges of the ionic conductive layer and the electron conductive layer both extending in a longitudinal direction of the metal core, wherein the ionic conductive layer consists of a high molecular weight elastomer, a polymer alloy thereof, a high molecular weight cellular elastomer, or a polymer alloy thereof, an electric resistance R
1
of the ionic conductive layer is higher than an electric resistance R
2
of the electric conductive layer (R
1
>R
2
), and the annular sealing member exhibits an electric resistance of at least 10
13
&OHgr;·cm.
According to a third aspect of the present invention, there is provided a method of manufacturing a conductive rubber roller, comprising the steps of extruding a high molecular weight elastomer containing an ionic conducting agent or a cellular material prepared by adding a blowing agent to the high molecular weight elastomer onto an outer surface of a metal core co
Ishikura Sadayuki
Onuki Akio
Sonobe Saburo
Tani Satoru
Cuda Rosenbaum I
Kinoyosha Co., Ltd.
Lackenbach Siegel Marzullo Aronson & Greenspan P.C.
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