JP3714740B2 - Semi-conductive roll - Google Patents

Description

【００１７】
【発明の効果】
本発明の半導電性ロールは、弾性半導電体層の表面が電子線照射によって硬化されるとともに、微細で高密度な凹凸で形成された表面処理層であるので、表面の耐摩耗性が向上し、印字耐久試験後の印字特性及び画像濃度を維持することができる。また、そのときの黒ベタの濃度は、半導電性ロール表面の凹凸の状態、摩擦係数、電気抵抗値に依存するため、初期印字の濃度が十分に確保され、耐久試験後も十分な濃度を得ることができる。さらに、この半導電性ロールは弾性半導電体層がシリコーンゴムであるため、空気中の水分による加水分解がなく、潜像担持体への固着やトナーの固着がないので、品質の良い製品を提供することができる。
【図面の簡単な説明】
【図１】（ａ）、（ｂ）はそれぞれ本発明の半導電性ロールの異なる態様を例示する断面説明図である。
【図２】実施例で使用した電子写真式プリンターの断面説明図である。
【符号の説明】
１…導電性軸体、２ａ…非発泡性弾性半導電体層、
２ｂ…発泡の弾性半導電体層、３…表面処理層、
10…感光ドラム、11…帯電ロール、12…現像ロール、13…トナー搬送ロール、
14…転写ロール、15…クリーニングロール、16…撹拌機、
17…摩擦帯電ブレード、18…ＬＥＤアレイ、19…容体、20…記録紙。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductive roll that is useful as a developing roll used in copying machines, LBPs (laser beam printers), facsimiles, and the like and has improved printing characteristics after initial and long-term use.
[0002]
[Prior art]
As an example of the use of a semiconductive roll comprising a conductive shaft and an elastic semiconductive layer provided on the outer peripheral surface, a latent image is supported by supporting a triboelectric toner in a thin layer state on the outer peripheral surface. As a developing device for visualizing an electrostatic latent image formed on a body, there is an electrophotographic printer having a structure as shown in FIG.
In the figure, 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 friction charging blade, and 18 is an LED. An array, 19 is a container, and 20 is a recording paper.
Semiconductive rolls for such applications are required to have various properties such as conductivity, environmental resistance, low hardness, and tribo-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 and an electronic conductive filler as a sizing agent has been used.
[0003]
[Problems to be solved by the invention]
In the semiconductive roll made of an elastic material such as urethane rubber and NBR, since the hardness is reduced by adding various process oils and softeners to the elastic material, urethane or nylon is applied to the surface of the semiconductive roll. In order to prevent bleeding, the resin component hydrolyzes into the latent image carrier when left at high temperature and high humidity for a long time. These environmental resistance characteristics such as sticking may not always be satisfied. Further, as the printing speed is increased, there is a disadvantage that printing characteristics due to so-called filming or the like due to scratches due to abrasion of the surface of the semiconductive roll or fixing of toner are deteriorated. Further, when used as a developing roll of 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 a very stable environment resistance and a high toner cleaning effect. During the printing durability test, there are inconveniences such as a decrease in printing characteristics and density due to a decrease in toner conveyance force, and an increase in printing speed promotes wear on the surface of the semiconductive roll, and printing characteristics due to scratches, etc. In addition, the printing characteristics deteriorated due to surface wear when used for a long time. This is considered due to the low wear resistance of silicone rubber.
Accordingly, an object of the present invention is to provide a semiconductive roll that can maintain excellent printing characteristics even after long-term use.
[0004]
[Means for Solving the Problems]
As a result of diligent research, the present inventors have found that the surface wear resistance is improved by irradiating the surface of the silicone rubber with an electron beam. The present invention has been completed by ascertaining that it is involved in improving the transportability.
That is, in the semiconductive roll according to the present invention, an elastic semiconductive layer made of semiconductive silicone rubber is formed on the outer peripheral surface of the conductive shaft body, the surface thereof has an acceleration voltage of 100 to 300 kV and an absorbed dose of 60 It is a surface treatment layer that is cured by electron beam irradiation in a range of ˜150 Mrad and fine irregularities are generated at a high density.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the semiconductive roll of the present invention will be described in detail with reference to FIGS. 1 (a) and 1 (b).
FIG. 1A relates to a first embodiment of a semiconductive roll, wherein 1 is a conductive shaft body, 2a is a semiconductive silicone rubber formed on the outer peripheral surface of the conductive shaft body 1. FIG. The non-foamed elastic semiconductive layer 3 is a surface treatment layer by electron beam irradiation to the elastic semiconductive layer.
FIG. 1 (b) relates to a 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 the surface treatment layer 3 by electron beam irradiation is further removed. It is provided on the outer periphery.
[0006]
In the semiconductive roll, the conductive shaft 1 includes a core made of a thermoplastic resin and / or a thermosetting resin in addition to a so-called “core metal” made of iron, aluminum, SUS, brass, or the like. Core made of conductive resin molded product in which conductive surface is plated and made conductive, thermoplastic resin and / or thermosetting resin is mixed with conductive carbon black as conductive agent, metal powder, etc. As long as it is conductive, such as a core made of a combination of these materials, 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 1 is grounded or a bias voltage is applied to inject an electric charge into the toner and convey the toner to the electrostatic latent image carrier. Demonstrate functions such as development.
[0007]
The elastic semiconductive layer 2a made of a semiconductive silicone rubber is a polyorganosiloxane raw rubber, such as a dimethyl silicone raw rubber, a methyl vinyl silicone raw rubber, a methylphenyl silicone raw rubber, or a combination of two or more. Further, reinforcing rubber filler such as fumed silica and precipitated silica is added to form a silicone rubber compound, and conductive carbon black; metal powder such as nickel, aluminum and copper; metal oxide such as zinc oxide and tin oxide; A desired ratio of a conductivity-imparting agent that is a combination of one or more selected from an insulating core material such as barium sulfate, titanium oxide, and potassium titanate coated with a conductive material such as tin oxide; Hydrogen polysiloxax in the presence of peroxide or platinum catalyst A non-foaming elastic semiconductive layer is obtained by adding a vulcanizing agent and kneading together and then heat-curing the outer peripheral surface of the conductive shaft body by a method such as press molding, extrusion molding or injection molding. Is formed.
[0008]
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 (ADCA) is added to the above composition. What is necessary is just to heat-harden and foam by adding foaming agents.
The desired proportion of the conductivity-imparting agent means that the volume specific resistance of the semiconductive silicone rubber is in the range of 10 ¹ to 10 ⁹ Ω · cm. If the volume resistivity is out of the above range, it is not preferable because toner scattering other than the latent image forming portion, so-called fogging, print density abnormality, etc. are likely to occur.
The elastic semiconductive layers 2a and 2b act as electrodes for the development process, electrodes for contact charging and charge injection to the toner, and surface irregularities and van der Waals force, mirror image force, Coulomb force, etc. The toner is carried and conveyed on the surface of the semiconductive roll. In addition, since the elastic semiconductive layer 2 uses silicone rubber, it has excellent environmental resistance against temperature and humidity, and also uses an electron conductive conductivity imparting agent, so that the electrical resistance value depends on the environment. There is also an advantage that the property is very low.
[0009]
In molding, the conductive shaft body and the silicone rubber composition are integrally dispensed using a crosshead with an extruder, and then subjected to primary vulcanization in a gear oven or IR furnace. After the body is set in a mold, the silicone rubber composition is injected, and an injection molding method in which primary vulcanization is performed at room temperature or under heating, the conductive shaft body and the silicone rubber composition are simultaneously heated and pressurized in the mold. A compression molding method or the like is used. Thereafter, the physical properties can be stabilized by performing secondary vulcanization for a certain period of time in a gear oven or the like.
The roll-shaped molded product may be subjected to electron beam irradiation as it is, but is usually irradiated with an electron beam after being finished to a predetermined outer diameter by a cylindrical grinder. Further, the electron beam can be irradiated after the surface state is changed by a shot blaster, a sand blaster, a wrapping machine, a buff or the like.
Thereafter, by irradiating the surface of the roll-shaped molded product with an electron beam using a curtain type electron beam irradiation device or the like, the vulcanization of the silicone rubber is promoted and the hardness of the roll surface becomes higher. Further, when the energy of the electron beam acts on the structure of the rubber surface, fine irregularities are generated on the roll surface. Therefore, the semiconductive roll having the surface treatment layer of the present invention can be obtained by irradiation with these electron beams.
[0010]
In this electron beam irradiation, it is desirable that the semiconductive roll itself be rotated so that only a part of the surface layer portion of the elastic semiconductive layer is not concentratedly irradiated.
Further, when the electron beam irradiation is performed within the range of the acceleration voltage of 100 to 300 kV and the absorbed dose of 10 to 150 Mrad, the printing durability characteristics can be further improved.
If this acceleration voltage is higher than 100 kV, the penetration depth of the electron beam will be deeper and the surface wear resistance will be further improved. If it is less than 300 kV, the penetration depth of the electron beam will not be too deep. The possibility that the rubber roll surface hardness is too high will be reduced, and the hardness will be set more appropriately. Also, if the absorbed dose value is greater than 10 Mrad, fine irregularities on the surface become higher, and the effect of improving the wear resistance becomes more prominent. If the absorbed dose value is less than 150 Mrad, the possibility of excessive curing is reduced, and the resistance value increases. A decrease in print density is less likely to occur.
[0011]
In the semiconductive roll of the present invention, the fine and high-density unevenness formed on the surface treatment layer 3 obtained by electron beam irradiation will be described.
First, the fine unevenness is, for example, a 10-point average roughness in the outer peripheral direction of the semiconductive roll measured by a universal roughness tester, and if this value is unevenness within a range of 3 to 25 μm. Well, if this value is smaller than 3 μm, there is a disadvantage that the toner conveying force is small, and if it is larger than 25 μm, it is not preferable because the surface waviness affects printing and causes density unevenness.
In addition, the high-density unevenness is, for example, the average spatial frequency of the surface roughness, with the number of peaks and pole peaks per unit length (1 mm) of the cross-sectional curve (roll outer circumferential direction) by a roughness tester, This means that this value is 20 or more. Therefore, if this value is less than 20, high density unevenness cannot be obtained, and the toner does not easily get caught on the surface unevenness, so the toner conveyance amount and conveyance force change over time, and the printing characteristics are deteriorated. It is not preferable because it is not stable.
[0012]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited by description of these Examples.
(Examples 1-2 , Comparative Examples 1-4 , Reference Example 1 )
As a conductive shaft, a SUM22 electroless nickel-plated shaft with a diameter of 10 mm and a length of 250 mm was used. 16 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name) was applied and baked at 150 ° C. for 10 minutes in a gear oven.
Semi-conductive silicone rubber composition, organic peroxide reaction type silicone raw rubber KE-78VBS (made by Shin-Etsu Chemical Co., Ltd., trade name) 100 parts by weight, carbon black thermal black (Asahi Carbon Co., trade name) ) Add 10 parts by weight, 25 parts by weight of fumed silica filler, Aerosil 200 (product name, manufactured by Nippon Aerosil Co., Ltd.), knead with a pressure kneader, and then add organic peroxide vulcanizing agent, C- 8 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) A product with 2.0 parts by weight added was prepared.
[0013]
This was vulcanized and bonded to the shaft at 175 ° C. for 10 minutes in a compression mold comprising a cylindrical cavity having an inner diameter of 20 mm. After that, secondary vulcanization is performed in a gear oven at 200 ° C for 7 hours, polished with a cylindrical grinder, and a roll-shaped product with a diameter of 18mm, a rubber part length of 210mm, and a surface roughness of 8.2μm (R _Z ). Got.
Next, while rotating the cored bar of the roll-shaped product with the rotation axis, using a curtain type electron beam irradiation apparatus, the electron beam is irradiated under the conditions of an acceleration voltage of 100 kV and an absorbed dose of 10 Mrad, A developing roll (semiconductive roll) of a developing device for visualizing an image was prepared ( Reference Example 1).
Then, the semiconductive roll was produced by changing the irradiation conditions by the same method as in Reference Example 1 (Examples 1 and 2 and Comparative Examples 2 to 4).
Next, each semiconductive roll was mounted on an electrophotographic printer as shown in FIG. 2 as a developing roll, a continuous printing test was conducted assuming long-term use, and the following measurements were performed. Next, the surface of the developing roll was observed with a microscope, and toner adhesion was also examined.
Further, as a comparative example, the same test was performed using the roll-shaped molded product as it was as a developing roll without being irradiated with an electron beam. The above results are also shown in Table 1 (Comparative Example 1).
[0014]
(Measurement item)
・ Roll resistance:
Place the semi-conductive roll before electron beam irradiation on a gold-plated electrode that is 5 mm longer than its total length, apply 500 g of weight to each end of the roll, apply a voltage of 10 V, and place the conductive shaft and roll surface. The resistance value between was measured.
·Surface roughness:
The ten-point average roughness in the outer peripheral direction of the semiconductive roll was measured using a universal roughness tester.
・ Average spatial frequency of surface roughness (referred to as average spatial frequency in the table):
The average spatial frequency of the surface roughness was determined by the number of peaks and pole peaks per unit length in the cross-sectional curve (roll outer circumferential direction) measured by a roughness tester.
-Roll weight change before and after the endurance test (referred to as roll weight change in the table):
The roll weight before and after the durability test was measured with an electronic balance, and the difference was defined as the roll weight change (= wear amount).
・ Fog:
The above semiconductive rolls were repeatedly printed with black, halftone dots, 5% duty, white background, etc., by a continuous printing test with an electrophotographic printer, and the Macbeth density of the white background portion of the 5% duty image was determined as the Macbeth density. Measured using a meter.
・ Initial print density:
The Macbeth density of the black solid print portion printed by the same method as that for fogging was measured using a Macbeth densitometer.
[0015]
(Admission decision)
・ Fog:
Both initial and post-end foggings exceeding 0.015 failed.
・ Print density:
Both initial and post-endurance concentrations are below 1.3.
-Toner adhesion:
The surface of the semiconductive roll after the endurance test was observed with a microscope.
・ Total printing characteristics after durability:
Density of density unevenness (solid black), vertical black streaks, vertical white streaks, and image flow were rejected.
・ Comprehensive evaluation ◎… All evaluations are excellent.
○: Most evaluations are excellent.
X: Evaluation is inferior.
[0016]
[Table 1]

[0017]
【The invention's effect】
In the semiconductive roll of the present invention, the surface of the elastic semiconductive layer is hardened by electron beam irradiation and is a surface treatment layer formed with fine and high-density unevenness, so that the wear resistance of the surface is improved. In addition, the printing characteristics and image density after the printing durability test can be maintained. In addition, since the density of the black solid at that time depends on the unevenness of the surface of the semiconductive roll, the friction coefficient, and the electric resistance value, the density of the initial printing 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 adhesion to the latent image carrier and no toner adhesion. Can be provided.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional explanatory views illustrating different aspects of a semiconductive roll of the present invention.
FIG. 2 is an explanatory sectional view of an electrophotographic printer used in Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Conductive shaft body, 2a ... Non-foaming elastic semiconductor layer,
2b ... elastic semiconductive layer of foam, 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 ... friction charging blade, 18 ... LED array, 19 ... container, 20 ... recording paper.

Claims (1)

An elastic semiconductive layer made of semiconductive silicone rubber is formed on the outer peripheral surface of the conductive shaft, and its surface is cured by electron beam irradiation with an acceleration voltage of 100 to 300 kV and an absorbed dose of 60 to 150 Mrad. And a semi-conductive roll characterized in that it is a surface treatment layer in which fine irregularities are formed at a high density.

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