JPH10104938A - Semiconductor roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep excellent printing characteristic even by long-term use by forming an elastic semiconductor formed of semiconductor silicone rubber on the circumferential surface of a conductive shaft body, and hardened the surface by electron beam irradiation. SOLUTION: A semiconductive roll has a conductive shaft body 1, a non- foamed elastic semiconductive layer 2a formed of semiconductive silicone rubber which is formed on the circumferential surface of the conductive shaft body 1, and a surface treatment layer 3 by electron beam irradiation to the layer 2a provided on the outermost circumference. In such a semiconductive roll, a core metal is used as the conductive shaft body 1, and one end or both ends of the shaft body are grounded, or a bias voltage is applied thereto, whereby a function such as development of an electrostatic latent image by carrying of toner to an electrostatic latent image carrier is exhibited. The elastic semiconductive layer 2a formed of semiconductive silicone rubber is formed by heating and hardening it in combination with polyorganosiloxane crude rubber. The surface treatment layer 3 is made irregular by electron beam irradiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a copier, an LBP
The present invention relates to a semiconductive roll which is useful as a developing roll used in (laser beam printers), facsimile machines, etc., and has improved printing characteristics at initial and after long use.

[0002]

2. Description of the Related Art As an example of a use of a semiconductive roll composed of a conductive shaft and an elastic semiconductive layer provided on the outer peripheral surface thereof, a triboelectric toner is carried on the outer peripheral surface in a thin layer state. An electrophotographic printer having a structure as shown in FIG. 2 is a developing device for visualizing an electrostatic latent image formed on a latent image carrier. In the drawing, 10 is a photosensitive drum, 11 is a charging roll, 12 is a developing roll, 13 is a toner transport roll, 14 is a transfer roll, 15 is a cleaning roll, 16
Is a stirrer, 17 is a triboelectric charging blade, 18 is an LED array,
19 is a body and 20 is a recording paper. Semi-conductive rolls for such applications are required to have various properties such as conductivity, environmental resistance, low hardness, and triboelectric charging properties, and impart conductivity to materials such as urethane rubber, NBR, and silicone rubber. A semiconductive roll prepared by adding and blending an ion conductive additive or an electron conductive filler as an agent has been used.

[0003]

The urethane rubber, N
In semiconductive rolls made of an elastic material such as BR, the hardness was reduced by adding various process oils and liquid agents such as softeners to the elastic material. Protective layers made of various resins are provided to prevent bleeding.However, for example, when left under high temperature and high humidity for a long time, the resin component may be hydrolyzed and fixed to the latent image carrier. For example, these environmental resistance characteristics were not always satisfactory.
Further, as the printing speed is increased, there is an inconvenience that scratches due to abrasion of the surface of the semiconductive roll and printing characteristics due to so-called filming due to sticking of toner are reduced. Further, when used as a developing roll for some printers, the toner cleaning effect is insufficient, which is considered to be due to insufficient toner adhesion. As a solution to these problems, a semiconductive roll using silicone rubber as an elastic material has been studied.This semiconductive roll has extremely stable environmental resistance and a high toner cleaning effect. During the printing durability test, there are disadvantages such as a decrease in printing characteristics and a decrease in density due to a decrease in toner conveyance force, and an increase in printing speed promotes abrasion of the surface of the semiconductive roll, and a printing characteristic due to scratches or the like. And the printing characteristics deteriorated due to surface wear when used for a long time. This is considered to be due to the low abrasion resistance of the silicone rubber. Therefore, an object of the present invention is to provide a semiconductive roll capable of maintaining excellent printing characteristics even after long-term use.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that irradiating the surface of silicone rubber with an electron beam improves the wear resistance of the surface, and the electron beam generated by the irradiation of the electron beam. Find out that the fine irregularities on the roll surface are involved in improving the toner transportability,
The present invention has been completed. That is, the semiconductive roll according to the present invention has an elastic semiconductive layer made of semiconductive silicone rubber formed on the outer peripheral surface of the conductive shaft body, and the surface thereof is cured by electron beam irradiation and has a fine It is a surface treatment layer in which irregularities are generated at a high density. The surface treatment layer has an acceleration voltage of 100 to 300 kV and an absorbed dose of 1
It is cured by electron beam irradiation in the range of 0 to 150 Mrad.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductive roll according to the present invention will be described below in detail with reference to FIGS. 1 (a) and 1 (b). FIG. 1A shows a semiconductive roll according to a first embodiment, in which reference numeral 1 denotes a conductive shaft, and reference numeral 2a denotes a semiconductive silicone rubber formed on an outer peripheral surface of the conductive shaft 1. The non-foamed elastic semiconductive layer 3 is a surface treatment layer by irradiating the elastic semiconductive layer with an electron beam. FIG. 1 (b)
Relates to the second embodiment of the semiconductive roll, in which a foamed elastic semiconductive layer 2b is provided on the outer periphery of the conductive shaft 1, and a surface treatment layer 3 provided by electron beam irradiation is provided on the outermost periphery. It is.

[0006] In the above semiconductive roll, the conductive shaft 1 has a so-called "core" made of iron, aluminum, SUS, brass, etc., as well as a thermoplastic resin and / or
Alternatively, a conductive body obtained by plating a surface of a core body made of a thermosetting resin to make it conductive, a conductive resin obtained by blending a conductive resin such as a conductive carbon black or a metal powder with a thermoplastic resin and / or a thermosetting resin. Such as a core formed of a conductive resin molded product, or a core formed of a combination thereof,
As long as the material is conductive, a material made of any material selected from plastic, metal, and ceramic is used. The semiconductive roll is configured such that one end or both ends of the conductive shaft body 1 is grounded or a bias voltage is applied thereto, thereby injecting charge into the toner and transporting the toner to the electrostatic latent image carrier, thereby forming an electrostatic latent image. Demonstrates functions such as development.

The elastic semiconductive layer 2a made of semiconductive silicone rubber is composed of a polyorganosiloxane raw rubber, for example, dimethyl silicone raw rubber, methyl vinyl silicone raw rubber, methylphenyl silicone raw rubber, or a combination of two or more thereof. To a silicone rubber compound by adding a reinforcing filler such as fumed silica or precipitated silica, to which conductive carbon black; metal powder such as nickel, aluminum, and copper;
One or more selected from metal oxides such as zinc oxide and tin oxide; insulating core materials such as barium sulfate, titanium oxide and potassium titanate coated with a conductive substance such as tin oxide; A conductivity-imparting agent combined with a desired ratio is blended, a vulcanizing agent such as hydrogen peroxide in the presence of a peroxide or a platinum catalyst is added, and kneaded together, followed by press molding, extrusion molding, By heating and curing the outer peripheral surface of the conductive shaft body by a method such as injection molding, a non-foamable elastic semiconductive layer is formed.

As shown in FIG. 1 (b), when the foamed elastic semiconductive layer 2b is provided on the outer periphery of the conductive shaft, azobisisobutyronitrile (AIBN), azodicarbonamide A foaming agent such as (ADCA) may be added, followed by heat curing and foaming. Note that the desired ratio of the conductivity-imparting agent is that the volume resistivity of the semiconductive silicone rubber is 10 ¹
It is in the range of ~ 10 ⁹ Ω · cm. If the volume resistivity is outside the above range, the toner is liable to be scattered to portions other than the latent image forming portion, so-called fogging, abnormal print density, and the like, which is not preferable. The elastic semiconductive layers 2a and 2b
Acts as an electrode in the development process, an electrode for contact charging and charge injection to the toner, and carries the toner on the surface of the semiconductive roll due to the surface irregularities and van der Waals force, mirror image force, Coulomb force, etc. , To be transported. In addition, since the elastic semiconductive layer 2 is made of silicone rubber, it has excellent environmental resistance to temperature and humidity. In addition, since it uses an electron conductive conductivity imparting agent, the electric resistance value depends on the environment. There is also the advantage that the property is very low.

In the molding, the conductive shaft and the silicone rubber composition are extruded integrally using a crosshead by an extruder, and then primary vulcanized in a gear oven or an IR furnace. After the conductive shaft is set in the mold, the above silicone rubber composition is injected and primary vulcanization is performed at room temperature or under heating. An injection molding method, the conductive shaft and the silicone rubber composition are simultaneously heated in the mold. And a compression molding method of applying pressure. Thereafter, the physical properties can be stabilized by performing secondary vulcanization for a certain period of time in a gear oven or the like. This roll-shaped molded product may be subjected to electron beam irradiation as it is, but is usually irradiated with an electron beam after finishing to a predetermined outer diameter with a cylindrical grinder. The surface state can be changed by a shot blaster, a sand blaster, a lapping machine, a buff, or the like, and then the electron beam can be irradiated. Then, on the surface of the roll-shaped molded product, using a curtain-type electron beam irradiation device or the like,
By performing the electron beam irradiation, the vulcanization of the silicone rubber is accelerated, and the hardness of the roll surface becomes higher. In addition, fine unevenness is generated on the roll surface by the energy of the electron beam acting on the structure of the rubber surface. Therefore, the semiconductive roll having the surface treatment layer of the present invention can be obtained by irradiation with these electron beams.

In this electron beam irradiation, it is desirable to have a mechanism in which the semiconductive roll itself is rotated so that only a part of the surface layer of the elastic semiconductive layer is not concentratedly irradiated. When irradiating the electron beam, the accelerating voltage is 1
100 to 300 kV and the absorbed dose is 10 to 150 kV.
By performing the process within the range of Mrad, the print durability characteristics can be further improved. This acceleration voltage is 100 kV
When it is larger, the penetration depth of the electron beam becomes deeper, and the wear resistance of the surface is further improved. When it is smaller than 300 kV, the penetration depth of the electron beam does not become too deep. The possibility of an excessively high hardness increase is reduced, resulting in a more appropriate hardness setting. When the value of the absorbed dose is larger than 10 Mrad, fine irregularities on the surface become high, and the effect of improving the wear resistance becomes more remarkable.
If it is less than 0 Mrad, the possibility of excessively hardening is reduced, and the decrease in print density due to an increase in the resistance value is less likely to occur.

The fine and high-density irregularities formed on the surface treatment layer 3 obtained by electron beam irradiation in the semiconductive roll of the present invention will be described. First of all, fine irregularities
For example, a ten-point average roughness in the outer circumferential direction of the semiconductive roll was measured by a universal roughness tester, and this value was 3
Any irregularities within a range of about 25 μm may be used.
If it is less than m, there is a disadvantage that the toner conveying force is small, and if it is more than 25 μm, it is not preferable because undulation on the surface affects printing and there is a disadvantage that density unevenness occurs. The high-density unevenness is defined as, for example, the average spatial frequency of surface roughness using the number of peaks and peaks per unit length (1 mm) of a cross-sectional curve (roll outer peripheral direction) by a roughness tester, It means that this value is 20 or more. Therefore, if this value is smaller than 20, high-density unevenness cannot be obtained, and the toner is less likely to be caught by the unevenness on the surface. Unstable and not preferred.

[0012]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the description of these examples. (Examples 1 to 3, Comparative Examples 1 to 4) As a conductive shaft, S
Electroless nickel plated UM22, diameter 10mm, length 250
mm shaft with silicone primer and
Primer No. 16 (Shin-Etsu Chemical Co., Ltd., trade name) was applied and baked at 150 ° C. for 10 minutes in a gear oven. As a semiconductive silicone rubber composition, 100 parts by weight of organic peroxide-reactive silicone raw rubber, KE-78VBS (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), carbon black and thermal black (trade name, manufactured by Asahi Carbon Co., Ltd.) ) 10 parts by weight, 25 parts by weight of fumed silica-based filler, Aerosil 200 (trade name, manufactured by Nippon Aerosil Co., Ltd.), kneaded with a pressure kneader, and further an organic peroxide-based vulcanizing agent, C- 8 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name) was prepared by adding 2.0 parts by weight.

This was vulcanized and bonded to the shaft at 175 ° C. for 10 minutes in a compression mold having a cylindrical cavity having an inner diameter of 20 mm. Then in a gear oven 200
After 7 hours of secondary vulcanization at ℃, polished with cylindrical grinder, diameter 18mm, rubber part length 210mm, surface roughness 8.2μm (R _Z )
Was obtained. Next, while rotating the core of the roll-shaped molded product around the rotation axis, the acceleration voltage was set to 100 kV and the absorbed dose was set to 1 using a curtain-type electron beam irradiation apparatus.
A developing roll (semiconductive roll) of a developing device for irradiating an electron beam under the condition of 0 Mrad to visualize an electrostatic latent image was produced (Example 1). Subsequently, semiconductive rolls were produced in the same manner as in Example 1 while changing the irradiation conditions (Examples 2 and 3 and Comparative Examples 2 to 4). Next, each semiconductive roll was mounted as a developing roll on an electrophotographic printer as shown in FIG. 2, and a continuous printing test was performed assuming long-term use, and the following measurements were performed. Next, the surface of the developing roll was observed under a microscope, and the adhesion of the toner was also examined. Further, as a comparative example, the same test was performed by using the above-mentioned roll-shaped molded product as a developing roll without irradiation with an electron beam. The above results are also shown in Table 1 (Comparative Example 1).

(Measurement items) Roll resistance: A semiconductive roll before electron beam irradiation is placed on a gold-plated electrode 5 mm longer than its entire length, and a 500 g weight is applied to both ends of the roll, and a voltage of 10 V is applied. Was applied to measure the resistance value between the conductive shaft and the roll surface. Surface roughness: Using a universal roughness tester, the ten-point average roughness in the outer circumferential direction of the semiconductive roll was measured.・ Average spatial frequency of surface roughness (referred to as average spatial frequency in the table): Cross-sectional curve by a roughness tester (toward the outer circumference of roll)
And the number of peaks and pole peaks per unit length was defined as the average spatial frequency of surface roughness. Roll weight change before and after the durability test (in the table, the roll weight change): The roll weight before and after the durability test was measured with an electronic balance, and the difference was taken as the roll weight change (= abrasion amount).・ Fog: Each of the above semiconductive rolls was subjected to a continuous printing test with an electrophotographic printer to obtain a solid black, a halftone dot,
5% duty, white background printing, and the like were repeated, and the Macbeth density of the white background portion of the 5% duty image was measured using a Macbeth densitometer. -Initial print density: The Macbeth density of a black solid print portion printed by the same method as that for fog was measured using a Macbeth densitometer.

(Pass / Fail Judgment) Fog: Both initial and post-durability fog exceeding 0.015 are rejected.・ Print density: Both initial and post-durability densities less than 1.3 are rejected. -Toner sticking: The surface of the semiconductive roll after the durability test was observed with a microscope. -Comprehensive printing characteristics after endurance: Density unevenness (black solid), vertical black streaks, vertical white streaks, image flow, etc., were rejected.・ Comprehensive evaluation ◎: All evaluations are excellent. …: Most evaluations are excellent. ×: Poor evaluation.

[0016]

[Table 1]

[0017]

According to the semiconductive roll of the present invention, the surface of the elastic semiconductive layer is cured by electron beam irradiation,
Since the surface treatment layer is formed with fine and high-density irregularities, the abrasion resistance of the surface is improved, and the printing characteristics and image density after the printing durability test can be maintained. In addition, the density of the solid black at that time depends on the state of irregularities on the surface of the semiconductive roll, the coefficient of friction, and the electric resistance value, so that the density of the initial print is sufficiently secured, and the density after the durability test is sufficient. Obtainable. Furthermore, since the elastic semiconductive layer of this semiconductive roll is made of silicone rubber, there is no hydrolysis due to moisture in the air, and there is no sticking to the latent image carrier or toner sticking. Can be provided.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional explanatory views illustrating different embodiments of a semiconductive roll of the present invention.

FIG. 2 is an explanatory cross-sectional view of an electrophotographic printer used in Examples.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductive shaft body, 2a ... Non-foamable elastic semiconductive layer, 2b
... foamed elastic semiconductive layer, 3 ... surface treatment layer, 10 ... photosensitive drum, 11 ... charging roll, 12 ... developing roll, 13 ... toner transport roll, 14 ... transfer roll, 15 ... cleaning roll,
16: stirrer, 17: triboelectric charging blade, 18: LED array, 19: container, 20: recording paper.

Claims (2)

[Claims] 1. An elastic semiconductive layer made of semiconductive silicone rubber is formed on the outer peripheral surface of a conductive shaft body, and the surface thereof is cured by electron beam irradiation, and fine irregularities are generated at high density. A semiconductive roll, characterized in that the roll is a surface treated layer. 2. The method according to claim 1, wherein the surface treatment layer has an acceleration voltage of 100 to 300 k.
The semiconductive roll according to claim 1, wherein the semiconductive roll is cured by electron beam irradiation at V and an absorbed dose in the range of 10 to 150 Mrad.