JP5160726B2 - Conductive rubber roller - Google Patents

Description

  The present invention relates to a conductive rubber roller, and in particular, has good charging characteristics and extremely low surface roughness, and is particularly suitable as a developing roller for attaching toner to a photoreceptor in an image forming mechanism such as a laser beam printer. The present invention relates to a conductive rubber roller used.

  In recent years, electrophotographic apparatuses such as laser printers are rapidly increasing in speed and image quality. The toner particle size tends to be small in order to cope with high image quality. Currently, toners having a particle size of 10 μm or less are mainly used, but toners having a particle size of about 5 to 8 μm are also widely used. . Therefore, an extremely low surface roughness is required for the developing roller that supplies toner to the latent image drawn on the photoreceptor.

As electrophotographic apparatuses such as laser printers have become widespread, not only high speed and high image quality but also low prices have been advanced. In order to satisfy these requirements, a one-component toner composed only of a non-magnetic polymerized toner is widely used instead of a two-component toner composed of two types of carrier and toner composed of ferrite powder or iron powder. It has become like this. Along with this, the developing roller is also shifting from the conventional magnet type to a semiconductive roll having rubber elasticity. As such a semiconductive roll, a roll having a resistance value of 10 ⁵ to 10 ⁸ Ω is widely used in consideration of the balance between the voltage drop generated when the toner is conveyed to the photoreceptor and the voltage applied to the developing roll. It has been.

There are roughly two types of developing methods in the electrophotographic apparatus depending on the relationship between the photoreceptor and the developing roll. That is, a non-contact type in which the toner is jumped from the developing roll to the photoconductor while having a gap of about 200 μm, and a direct type in which the toner on the developing roll and the photoconductor are conveyed to the photoconductor while being in contact with each other.
Regardless of the method, the developing roll
(1) conveying a uniform amount of toner;
(2) Uniformly charging the toner to be conveyed;
(3) The toner is required to be uniformly transferred to the photoreceptor.

  When using a two-component toner using a carrier, it is relatively easy to charge the toner and transport it to the photoreceptor due to electrical and magnetic action. However, when using a one-component toner, the toner is magnetic. Cannot be used. Therefore, in order to satisfy the above three requirements imposed on the developing roll, high surface accuracy is required that the surface of the developing roller as the electrode end surface is uniformly formed, and a bias potential is applied to the developing roller. In some cases, electrical characteristics such as a resistance value are required to be extremely uniform in the roller so as to obtain a very uniform potential distribution.

  In addition, since the one-component toner does not include a carrier, the developing roller is required to have a function of controlling the charging property of the toner. If the charge amount of the toner is insufficient, the electrostatic force is insufficient and the toner cannot be faithfully conveyed to the latent image on the photoreceptor. For this reason, for example, various image defects such as density change due to the rotation of the developing roller, development ghost, and fogging occur.

  Various proposals have been made for solving such problems. For example, in Japanese Patent Laid-Open No. 2002-194203 (Patent Document 1), in order to obtain uniformity of electrical resistance, calcium carbonate, which is controlled by ionic conduction instead of electronic conduction by a conductive filler and has a prescribed particle size, is ionic conductive. A rubber material dispersed in epichlorohydrin rubber, which is a rubber, has been proposed. Japanese Patent Laid-Open No. 2001-357735 (Patent Document 2) proposes to treat the surface of a conductive member with a treating agent having an amine compound in order to control the chargeability of the toner.

  In Patent Document 1, it is possible to reduce the surface roughness at the time of polishing, and it is possible to uniformly convey toner having a particle size of less than 10 μm. Furthermore, the electric resistance of the rubber layer can be made uniform to some extent. However, the adhesiveness of epichlorohydrin rubber on the roll surface obtained by polishing causes a problem of an increase in the coefficient of friction. Furthermore, the addition of calcium carbonate may have an adverse effect. For example, the tackiness of the rubber surface may be markedly increased compared to when calcium carbonate is not added, resulting in a high friction coefficient. In addition, there are very few factors that lower the coefficient of friction. In addition, there is a problem that the chargeability to the toner and the sustainability of the charging performance are not good, and a good print image cannot be obtained when used as a developing roller.

  In Patent Document 2, since the surface layer material is formed by coating, the material can be appropriately selected, and the toner chargeability and the friction coefficient can be easily adjusted. However, uneven coating at the time of coating the surface material becomes a problem. That is, if the thickness of the surface layer is too thick, the coating material will sag and it will be difficult to obtain the outer diameter accuracy. The chargeability becomes non-uniform and a good image cannot be obtained. As a result, the manufacturing yield is extremely poor and the cost is high. Further, since the base material and the surface treatment coating agent are made of different materials, there is a problem in that the coating agent is peeled off during production and use. In particular, in the seal portion for preventing toner leakage, the coating material may be cracked due to the difference in hardness from the base material, and as a result, there is a problem that high durability cannot be obtained.

  As described above, it is difficult to achieve both control of toner transportability and toner chargeability. Accordingly, the present inventor has eagerly studied to solve such conventional problems, and can make the electrical resistance uniform and is excellent in the chargeability to the deposit such as toner, and can maintain the chargeability. A rubber roller has been developed and provided in Japanese Patent Application No. 2002-338968 (Patent Document 3).

When the conductive rubber roller is used, a very good image can be obtained at the initial stage. However, there is room for further improvement in terms of maintaining a good image.
That is, the toner continues to be used until the image life of about several thousand sheets is exhausted while receiving a force such as a shearing force between the toner supply roll or the amount regulating blade and the developing roll. In addition, since toner is conveyed from the developing roll to the photosensitive member only in the latent image portion, there are many toners that return to the cartridge again without being transferred to the paper even on the developing roll. After a long period of use with such a great deal of stress, the external additives added to prevent toner adhesion and the paper components transported from the photoreceptor sink into the toner particles, and the toner itself Cause cracking and deformation. As described above, the surface of the toner is greatly changed from the surface which is easily charged during the long-term use. As a result, the charge amount of the toner is decreased, and as a result, an image failure such as so-called fogging in which the toner is originally deposited on a white print surface may occur.

JP 2002-194203 A JP 2001-357735 A Japanese Patent Application No. 2002-338968

  It is an object of the present invention to provide a conductive rubber roll that can make the electrical resistance uniform, has excellent chargeability to deposits such as toner, can sustain the chargeability, and has extremely low surface roughness. It is said.

To solve the above problems, the present invention is e Pikuroruhidorin (EP) - comprises a mixture of ethylene oxide (EO) copolymer and acrylonitrile-butadiene rubber as a rubber component, a primary particle diameter with respect to the rubber component 100 parts by weight A conductive rubber roller containing 5 to 70 parts by weight of weakly conductive carbon black of 80 nm or more and 500 nm or less and having a conductive rubber layer not containing an ionic conductive additive in at least the outermost layer. And
The surface portion of the conductive rubber layer is an oxide film, the surface roughness Rz is 5 μm or less, and the dielectric loss tangent when an AC voltage is applied at a voltage of 5 V and a frequency of 100 Hz is 0.1 to 1. 5. A conductive rubber roller having a friction coefficient of 0.1 to 1.5 and a roll resistance value of 10 ⁵ to 10 ⁸ Ω is provided.

In the present invention, the dielectric loss tangent of the roller is reduced to the above range in view of the fact that the dielectric loss tangent has a great influence on the charging characteristics in the conductive rubber roller suitably used for the developing roller for attaching the toner to the photosensitive member. As a result, it has been found that it is possible to achieve both uniform electrical resistance and control of the chargeability of the toner, and as a result, excellent charging characteristics are exhibited. Therefore, when the conductive rubber roller of the present invention is used as a developing roller or the like, the charge amount of toner existing on the surface of the developing roller before contact with the photoreceptor can be maintained at a high level.
Further, if the roller friction coefficient is reduced to the above range, the stress applied to the toner can be reduced, and as a result, the deterioration of the toner can be delayed, so that a good image can be maintained over a long period of use. In addition, there is an advantage that the toner can be reduced in diameter.

As described above, the conductive rubber roller of the present invention has a dielectric loss tangent measured under the above conditions of about 0.1 to 1.5.
In the electrical characteristics of a rubber roller, the dielectric loss tangent is an index indicating the degree of influence of electric flow (conductivity) and the capacitor component (capacitance), and is also a parameter indicating the phase delay when an alternating current is applied. The size of the capacitor component ratio when a voltage is applied is shown. That is, the dielectric loss tangent is expressed by the amount of charge generated when the toner contacts the developing roller at a high pressure by the amount regulating blade, and the amount of charge that escapes onto the roller before being conveyed to the photosensitive member. This is an index indicating the amount of charge. If the dielectric loss tangent is large, it is easy to pass electricity (charge) and the polarization is difficult to proceed. Conversely, if the dielectric loss tangent is small, the polarization is difficult to pass electricity (charge).
Therefore, the smaller the dielectric loss tangent, the higher the capacitor-like characteristics of the roll, and the toner charge generated by frictional charging can be maintained without escaping from the roll. That is, chargeability can be added to the toner, and the added chargeability can be maintained. In order to obtain such an effect, the dielectric loss tangent is set to 1.5 or less.
Further, the dielectric loss tangent is set to about 0.1 or more in order to prevent the amount of filler from increasing and becoming hard, or to prevent the surface from deteriorating due to the formation of an excessive oxide film. The dielectric loss tangent is more preferably 0.2 to 1.0.
The reason why the voltage is set to a minute voltage of 5 V under the dielectric tangent measurement condition is that a very small voltage fluctuation occurs when the rubber roller holds the toner or when the toner is conveyed to the photoreceptor. is there. Further, the reason why the frequency is set to 100 Hz is that a low frequency of about 100 Hz matches the event very much in consideration of the rotation speed of the developing roller, the fitting body, the blade, and the nip with the toner supply roller.

Further, the conductive rubber roller of the present invention has a friction coefficient of about 0.1 to 1.5. As described above, the toner is subjected to stress such as shearing force between the toner supply roll or the amount regulating blade and the developing roll. In order to reduce such stress, the friction coefficient of the conductive rubber roller is preferably about 1.5 or less. In order to convey a sufficient amount of toner without slipping, the conductive rubber roller preferably has a friction coefficient of about 0.1 or more. The lower limit of the friction coefficient is more preferably 0.25 or more. On the other hand, the upper limit is preferably 0.9 or less, more preferably 0.8 or less, and particularly preferably 0.55 or less.
The coefficient of friction here is a coefficient of friction on the surface of the conductive rubber roller. A commercially available polyester OHP film is brought into contact with a width of 50 mm and brought into contact with a part of the surface of the conductive rubber roller, and the dynamic friction during constant speed movement. The friction coefficient was obtained by measuring the force and calculating this dynamic friction force by introducing it into Euler's equation. The purpose of the commercially available polyester OHP film is that it is a resin product close to the material of the toner and that the surface is flat and uniform.

Conductive rubber roller of the present invention, in addition to the above physical properties, the surface roughness Rz Ru der about 5μm or less. By reducing the surface roughness Rz of the conductive rubber roller in this way, the surface of the conductive rubber roller has only irregularities smaller than the particle size of the toner, so that not only the toner can be conveyed uniformly but also the toner. The fluidity is improved, and as a result, the efficiency of imparting chargeability to the toner becomes extremely high. The surface roughness Rz is measured according to JIS B 0601 (1994).
The resistance value of the roller Ru about 10 ⁵ to 10 ⁸ Omega der in conductive rubber roller of the present invention.

The conductive rubber layer forming the outermost layer of the conductive rubber roll may have any component as long as it has conductivity, but a rubber component, a filler, or a conductive agent, a vulcanizing agent, Contains additives such as plasticizers or acid acceptors.
Conductivity in the conductive rubber layer as an ion conductive using an ion-conductive rubber such as e Pi chlorohydrin rubber, also, it is preferable to use an electron conductivity obtained by blending carbon black and ion conductivity.

  In order to reduce the dielectric loss tangent, ion conductive rubber is preferably used and carbon black is preferably blended. The weakly conductive carbon black having a primary particle size of 80 nm or more and 500 nm or less is 100 parts by weight of the rubber component. -70 weight part is mix | blended.

The weakly conductive carbon black is a carbon black that has a large particle size, a small structure development, and a small contribution to conductivity. By blending this, it acts as a capacitor by polarization without increasing conductivity. Therefore, it is possible to control the charging without impairing the uniformity of electric resistance.
If the weak conductive carbon black has a primary particle size of about 80 nm or more, preferably about 100 nm or more, the above effect can be obtained more effectively. Moreover, surface roughness can be made very small in it being 250 nm or less.
The blending amount of the weakly conductive carbon black is about 5 to 70 parts by weight with respect to 100 parts by weight of the rubber component. If it is less than 5 parts by weight, the curing to reduce the dielectric loss tangent is poor, and exceeds 70 parts by weight. This is because the hardness increases and other members that come into contact with it are damaged.
Various types of weakly conductive carbon black can be selected. Among them, carbon black produced by a furnace method or a thermal method that easily obtains a large particle size is preferable, and thermal carbon black with few impurities is most preferable. In terms of carbon classification, SRF, FT, and MT are preferable. Carbon black used as a pigment may also be used.

The conductive agent is not limited to carbon black, and a known inorganic conductive material or organic conductive material can be used. However, an ion conductive additive is not blended.
Examples of the inorganic conductive material include known conductive carbon blacks such as ketjen black, furnace black or acetylene black; conductive metal oxides such as zinc oxide, potassium titanate, antimony-doped titanium oxide, tin oxide or graphite; LiClO ₄ , metal salts such as LiCF ₃ SO ₃ , NaC 1 O ₄ , LiAsF ₆ , LiBF ₄ , NaSCN, KSCN, and NaC 1.
The organic conductive material, high-grade alcohol ethylene oxide, polyethylene glycol fatty acid esters, antistatic agents such as nonionic surface active agents such as polyhydric alcohol fatty acid esters. These may be used alone or in combination.

And min rubber component of the conductive rubber layer is used by blending the error peak chlorohydrin rubber and acrylonitrile-butadiene rubber.

Specifically, an epichlorohydrin-ethylene oxide (EO) copolymer is used as the epichlorohydrin rubber. Epichlorohydrin rubber is preferably blended in a proportion of less than about 20 wt% to 100 wt% based on the total rubber components when Ru combination with other rubber components.

The filler to be blended in the conductive rubber layer contains a vulcanizing agent, a processing aid, a plasticizer, an acid acceptor, a deterioration preventing agent and the like in addition to the conductive agent, and the total amount of these fillers is the rubber component 100. About 30-70 weight part is preferable with respect to a weight part.
The amount of 30 to 70 parts by weight is preferably about 30 parts by weight or more in order to efficiently adjust the dielectric loss tangent, improve the grindability (workability) and improve the processing accuracy. On the other hand, the total amount of the filler is preferably about 70 parts by weight or less in order to prevent the hardness from rising and damaging other members that come into contact.

As the vulcanizing agent to be blended, sulfur, triazine derivative, thiourea, various monomers and the like can be used. These may be used alone or in combination of two or more. Examples of the sulfur-based vulcanizing agent include powdered sulfur, organic sulfur-containing compounds such as tetramethylthiuram disulfide or N, N-dithiobismorpholine. The thiourea vulcanizing agent is selected from the group consisting of tetramethylthiourea, trimethylthiourea, ethylenethiourea, and (CnH2n + 1NH) 2C = S (wherein n represents an integer of 1 to 10). One or more thioureas can be used.
The addition amount of the vulcanizing agent is about 0.5 to about 5 parts by weight, preferably about 1 to about 3 parts by weight, based on 100 parts by weight of the rubber component.

  A rubber obtained by vulcanizing an epichlorohydrin rubber or epichlorohydrin polymer with a thiourea-based vulcanizing agent, especially ethylene thiourea, has a compression set of about 15% or less and good durability, and it is easy to ensure accuracy during polishing. Furthermore, since the effect of forming an oxide film by ultraviolet rays can be enhanced, it can be used particularly preferably in the present invention. In this case, the thiourea vulcanizing agent may be blended at a ratio of about 0.2 parts by weight to about 3 parts by weight, preferably about 1 part by weight to about 2 parts by weight with respect to 100 parts by weight of the rubber component. .

In addition to various plasticizers such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), and tricresyl phosphate, the above various processing aids and plasticizers include substances used as conductive agents and processing aids. Many also have plastic components. For example, fatty acids such as stearic acid or the like used as a processing aid. These plastic components are preferably blended in a proportion of about 5 parts by weight or less with respect to 100 parts by weight of the rubber component of the conductive rubber layer. This is to prevent bleeding when forming the oxide film and contamination of the photoconductor when the printer is mounted or operated.

In addition, various anti-aging agents can be blended to prevent deterioration of the conductive rubber layer as long as the oxide film formation is not affected.
When a halogen-based rubber, particularly epichlorohydrin rubber or epichlorohydrin polymer is used as the rubber component, the acid acceptor is blended at a ratio of about 1 wt% to about 10 wt%, preferably about 3 wt%, based on the weight of the rubber component. Is preferred. The amount of the acid acceptor is preferably about 1% by weight or more in order to effectively exhibit the effects of preventing vulcanization inhibition and photoreceptor contamination, and the amount of the acid acceptor is about 10 in order to prevent the hardness from increasing. It is preferable that it is below wt%. As the acid-accepting agent, hydrotalcites and magsarat are particularly preferable because of excellent dispersibility. In addition, as the acid acceptor, various substances that act as acid acceptors can be used.

Further, in addition to the above-mentioned additives, in order to adjust the dielectric loss tangent to the range specified in the present invention, fatty acid-treated calcium carbonate, clay, organic / inorganic pigments and the like may be blended.
The fatty acid-treated calcium carbonate has higher activity than ordinary calcium carbonate due to the presence of the fatty acid at the interface of calcium carbonate, and is easily slippery, so that high dispersion can be realized easily and stably. Further, when the polarization action is promoted by the treatment, the action of the capacitor in the rubber is strengthened by both actions, so that the dielectric loss tangent can be efficiently reduced.

  The surface layer portion of the conductive rubber layer of the present invention is an oxide film. As the oxide film, an oxide film having many C═O groups or C—O groups is preferable. Such an oxide film is effective by reducing the friction coefficient and adjusting the dielectric loss tangent in the conductive rubber roll of the present invention. The oxide film can be formed on the surface portion of the rubber layer by subjecting the surface of the rubber layer to ultraviolet irradiation or / and ozone irradiation to oxidize the rubber layer. In particular, it is preferable to form an oxide film by ultraviolet irradiation because the processing time is fast and the cost is low. The treatment for forming the oxide film can be performed according to a known method. For example, in the case of performing ultraviolet irradiation, although depending on the distance between the surface of the rubber layer and the ultraviolet lamp, the type of rubber, and the like, the wavelength of about 100 nm to 400 nm, more preferably about 100 nm to 200 nm is applied for 30 seconds to 30 minutes. The irradiation is preferably performed for about 1 to 10 minutes. In addition, the intensity | strength of ultraviolet rays and irradiation conditions (time, the temperature in a tank, distance) are selected in the range used as the dielectric loss tangent and friction coefficient in this invention.

  When the roller resistance when the voltage 50V is applied to the conductive rubber roller before forming the oxide film is R50, and the roller resistance at the applied voltage 50V after forming the oxide film is R50a, logR50a-logR50 = about 0.2 to 1.. A value of about 5 is preferable from the viewpoints of improving durability, reducing stress on the toner, and measures against collapse of the photoreceptor.

  The conductive rubber roller of the present invention having the above-described physical properties is not particularly limited as long as it has at least the conductive rubber layer in the outermost layer, and may have a plurality of structures such as two layers according to the required performance. A structure in which the conductive rubber layer having the above-described physical properties is provided on the outer peripheral surface of the core metal is preferable because variations in physical properties are small and manufacturing can be performed at low cost.

  A cored bar is attached to the conductive rubber roller, and a cored bar made of metal such as aluminum, aluminum alloy, SUS or iron, or ceramic is used as the cored bar.

  The thickness of the conductive rubber layer is preferably about 0.5 mm to 10 mm, more preferably about 1 mm to 7 mm. In order to obtain an appropriate nip, the wall thickness is preferably about 0.5 mm or more, and in order to reduce the size and weight, the wall thickness is preferably about 10 mm or less.

The conductive roller of the present invention can be suitably used for an image forming mechanism of an electrophotographic apparatus in OA equipment such as a laser beam printer, an ink jet printer, a copying machine, a facsimile machine, and an ATM. Specifically, it is suitably used as a developing roller for adhering non-magnetic one-component toner to the photoreceptor.
The developing method in the image forming mechanism of the electrophotographic apparatus is roughly classified into a contact type or a non-contact type when classified according to the relationship between the photosensitive member and the developing roll, but the conductive roller of the present invention can be used in any method. In particular, it is preferable that the developing roller of the present invention is almost in contact with the photoreceptor. The conductive roller of the present invention includes a charging roll for uniformly charging a photosensitive drum, a transfer roll for transferring a toner image from a photosensitive member to a transfer belt or paper, and a toner supply roll for conveying toner. Also, it can be used as a drive roll for driving the transfer belt from the inside.

  In the conductive rubber roll of the present invention, the surface layer portion of the outermost conductive rubber layer is an oxide film, and has a dielectric loss tangent and a friction coefficient within a predetermined range, so that electric resistance is uniformized and toner chargeability is increased. Control can be achieved at the same time, good charging characteristics can be obtained, and stress applied to a deposit such as toner can be reduced. Therefore, when the conductive rubber roller of the present invention is used as a developing roller or the like, the charge amount of toner existing on the surface of the developing roller before contact with the photoreceptor can be maintained at a high level, and a good initial image can be obtained. It is possible to maintain a good image over a long period of use by delaying the deterioration of the image.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the conductive rubber roller 10 includes a cylindrical rubber layer 1 having a thickness of 10 mm, and a cylindrical cored bar (shaft) 2 having a diameter of 10 mm that is press-fitted into the hollow portion.
The rubber layer 1 and the core metal 2 are joined with a conductive adhesive. The surface layer portion of the rubber layer 1 is an oxide film in which rubber is oxidized by ultraviolet irradiation.

The rubber layer 1 having a surface layer portion as the oxide film contains 20 parts by weight or more and less than 100 parts by weight of epichlorohydrin rubber as a rubber component, and is blended with acrylonitrile butadiene rubber . Moreover, 5-70 weight part of weakly conductive carbon black is mix | blended with respect to 100 weight part of rubber components. The weakly conductive carbon black has a primary particle size of 80 nm to 500 nm.
Furthermore, in addition to the conductive agent, the filler containing additives such as a vulcanizing agent, a plasticizer, and an acid acceptor, and the conductive agent composed of the weakly conductive carbon black and the vulcanizing agent is a rubber component. 30 parts by weight or more and 70 parts by weight or less are blended with respect to 100 parts by weight.

The conductive rubber roller 10 has a dielectric loss tangent of 0.1 to 1.5 and a friction coefficient of 0.1 to 1.5 when applied to the surface layer portion of the oxide film with an AC voltage of 5 V and a frequency of 100 Hz. The surface roughness Rz is 5 μm or less. Further, the resistance value of the roller is set to 10 ⁵ to 10 ⁸ Ω.

  The rubber roller 10 having the above-described configuration is used as a developing roller for adhering non-magnetic single component toner to the photoreceptor in the image forming apparatus.

The following components were used as constituent components in the conductive rubber rolls of the examples and comparative examples.
In Reference Examples 1 to 7, epichlorohydrin rubber (GECO) (“Epichromer CG102” manufactured by Daiso Corporation) was used as the rubber component. Such a rubber component is an epichlorohydrin polymer in which the copolymerization ratio of ethylene oxide (EO) / epichlorohydrin (EP) / allyl glycidyl ether (AGE) is 56 mol% / 40 mol% / 4 mol%. In Example 1 , 75 parts by weight of epichlorohydrin rubber (ECO) (“Epichromer D” manufactured by Daiso Corporation) and 25 parts by weight of acrylonitrile butadiene rubber (NBR) (“Nippol 401LL” manufactured by Nippon Zeon Co., Ltd.) were used. .

In Reference Example 1, fatty acid-treated calcium carbonate was used as the filler, and in Examples 1 and Reference Examples 2 to 7 , weak electric carbon black (“Asahi # 15” manufactured by Asahi Carbon Co., Ltd.) was used. Used calcium carbonate that was not treated with fatty acids. The blending amounts are as shown in Table 1.
As the vulcanizing agent, 0.5 parts by weight of sulfur was used with respect to 100 parts by weight of the rubber component, and 1.4 parts by weight of ethylenethiourea (Axel 22-S manufactured by Kawaguchi Chemical) was used with respect to 100 parts by weight of the rubber component.
Ginseng In Remarks Example 1-6 using 3 parts by weight hydrotalcite (DHT-4A-2) relative to the epichlorohydrin rubber (GECO) 100 parts by weight of acid acceptor.

The manufacturing method of the conductive rubber roll of each Example and a comparative example is described below.
The blended materials described above and in Table 1 were kneaded with a Banbury mixer, and then extruded into a tube shape having an outer diameter of φ21 mm and an inner diameter of φ9.5 mm using an extruder. The tube is attached to a vulcanizing shaft, vulcanized in a vulcanizing can at 160 ° C. for 1 hour, and then attached to a φ10 mm shaft coated with a conductive adhesive and adhered in an oven at 160 ° C. did. Thereafter, the end portions were molded, traverse polishing was performed with a cylindrical polishing machine, and mirror polishing was performed as final polishing, and each was finished to a predetermined surface roughness of φ20 mm (tolerance 0.05). Table 1 shows the surface roughness Rz of the conductive rubber rolls of Examples and Comparative Examples.

After washing the roller surface with water, in Example 1, Reference Examples 1 to 7 and Comparative Example 2, an ultraviolet ray was irradiated to form an oxide layer on the surface layer. This uses an ultraviolet irradiator (“PL21-200” manufactured by Sen Special Light Source Co., Ltd.), and the distance between the roller and the ultraviolet lamp is 10 cm, and ultraviolet rays (wavelengths 184.9 nm and 253.7 nm) are emitted every 90 degrees in the circumferential direction. The irradiation was performed for a predetermined time, and the roller was rotated four times to form an oxide film on the entire circumference of the roller (360 degrees). The irradiation time in Table 1 refers to the irradiation time per surface (90-degree range).

  The following characteristic measurements were performed on the conductive rubber rollers of Examples and Comparative Examples produced as described above. The results are shown in Table 1.

(Measurement of roller electrical resistance)
As shown in FIG. 2, the rubber layer 1 through the metal core 2 is abutted and mounted on the aluminum drum 3, and the tip of the lead wire of the internal resistance r (100Ω) connected to the + side of the power source 4 is connected to the aluminum drum 3 Measurement was performed by connecting the end of the conductive wire connected to the end face and connected to the negative side of the power source 4 to the other end face of the conductive roller 1.
The voltage applied to the internal resistance r of the wire was detected and used as the detection voltage V.
Assuming that the applied voltage is E in this apparatus, the roller resistance R is R = r × E / (V−r), but this time the term −r is regarded as very small and R = r × E / V.
In a state where a load F of 500 g is applied to both ends of the core metal 2 and rotated at 30 rpm, 100 detection voltages V when the applied voltage E is 500 V are measured for 4 seconds, and R is calculated by the above formula. The above measurement was performed under constant temperature and humidity conditions of a temperature of 23 ° C. and a relative humidity of 55%.

(Measurement of dielectric loss tangent)
As shown in FIG. 3, the metal plate 53 on which the rubber roller 51 is placed and the shaft 52 are used as electrodes, and an AC voltage is applied to the rubber roller 51 at a voltage of 5 V and a frequency of 100 Hz. 4311B "), the R (resistance) component and the C (capacitor) component were separated and measured. From the values of R and C, the dielectric loss tangent, impedance, phase angle, and the like were obtained by the following formula. The measurement temperature was 23 ° C. to 24 ° C. (room temperature).
Dissipation factor (tan δ) = G / (ωC)
G = 1 / R
Thus, the dielectric loss tangent is a value obtained as G / ωC when the electrical characteristics of one roller are modeled as two parallel equivalent circuits of a roller resistance component and a capacitor component.

(Measurement of friction coefficient)
As shown in FIG. 4, a digital force gauge ("Model PPX-2T" manufactured by Imada Co., Ltd.) 41, a friction piece (a commercially available polyester OHP film, contact width with the roll longitudinal direction; 50 mm) 42, The numerical value measured by the digital force gauge 41 in the apparatus shown in FIG. 4 including the weight 44 of 20 g and the conductive rubber roller 43 was substituted into Euler's formula to calculate the friction coefficient.

(Measurement of surface roughness Rz)
The surface roughness Rz was measured according to JIS B 0601 (1994).

(Image evaluation during durable use)
The conductive rubber roll of each example and comparative example was mounted as a developing roller on a printer (a commercially available printer using a non-magnetic one-component plus-charged toner), and the number of sheets until fogging occurred was measured.

In the conductive rubber roll of Comparative Example 1, no oxide film is formed on the surface layer of the rubber layer, and the dielectric loss tangent and friction coefficient are also larger than the range of the present invention. In this case, when 4000 sheets were printed, the seal portion was broken before fogging occurred.
In the conductive rubber roll of Comparative Example 2, an oxide film is formed on the surface layer of the rubber layer, but the dielectric loss tangent and friction coefficient are larger than the range of the present invention. In this case, fogging occurred on 4000 sheets.
The conductive rubber roll of Example 1 has a use durability of 2.75 times that of the conductive rubber roll of Comparative Example 2, which is 11000 sheets until fogging occurs.
The overall evaluation in the lower part of Table 1 shows that ◎ indicates extremely excellent durability in practical use and that high image quality has been maintained for a long time, and ○ indicates excellent durability in practical use and high image quality is maintained. X indicates that it is not suitable for practical use.

It is the schematic of the conductive rubber roller of this invention. It is a figure which shows the measuring method of the electrical resistance of a conductive rubber roller. It is a figure which shows the measuring method of the dielectric loss tangent of a conductive rubber roller. It is a figure which shows the measuring method of the friction coefficient of an electroconductive rubber roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive rubber layer 2 Core metal 10 Conductive rubber roller

Claims (3)

Et Pikuroruhidorin (EP) - comprises a mixture of ethylene oxide (EO) copolymer and acrylonitrile-butadiene rubber as a rubber component, 500 nm or less weak conductive carbon black primary particle diameter 80nm or more with respect to the rubber component 100 parts by weight 5 to 70 parts by weight of a conductive rubber roller having at least an outermost layer of a conductive rubber layer that does not contain an ionic conductive additive,
The surface portion of the conductive rubber layer is an oxide film, the surface roughness Rz is 5 μm or less, and the dielectric loss tangent when an AC voltage is applied at a voltage of 5 V and a frequency of 100 Hz is 0.1 to 1. 5. A conductive rubber roller having a friction coefficient of 0.1 to 1.5 and a roll resistance value of 10 ⁵ to 10 ⁸ Ω.   The conductive rubber roller according to claim 1, wherein the oxide film is formed by ultraviolet irradiation or / and ozone irradiation.   The core according to claim 1 or 2, wherein a cored bar is attached to the conductive rubber roller, and used as a developing roller for adhering non-magnetic single component toner to a photoconductor in an image forming mechanism of an electrophotographic apparatus. Conductive rubber roller.

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