JP5378115B2 - Semi-conductive endless belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductive endless belt including an ion conductive material, which does not have a risk of contaminating the surface of a photoreceptor, because even when the semiconductive endless belt is left, as it is, under high temperature and high humidity environment for a long time, a bleed-out material is not generated and can be used for an electrophotographic image forming apparatus. <P>SOLUTION: The semiconductive endless belt in which the ion conductive material is compounded in a thermoplastic resin includes the thermoplastic resin, the ion conductive material and porous silica whose oil absorption measured according to JIS K5101-13 is 50 to 350 ml/100g. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a semiconductive endless belt used in an electrophotographic image forming apparatus, and more particularly to a semiconductive endless belt provided with semiconductivity by adding an ion conductive material.

  Electrophotographic image forming apparatuses are increasing in speed, image quality, and color. In these image forming apparatuses, semiconductive endless belts are frequently used as transfer conveyance belts and intermediate transfer belts. Since the transfer and conveyance belt conveys the recording medium and simultaneously transfers the toner image on the photosensitive member directly to the recording medium, the recording medium is interposed between the photosensitive member and the transfer and conveyance belt during image formation. There is no. However, there is also an image forming apparatus that stops in a state where the photosensitive member and the transfer conveyance belt are in direct contact with each other because no recording medium is interposed during non-image formation. On the other hand, since the intermediate transfer belt receives the toner image on the photosensitive member directly in contact with the photosensitive member, the intermediate transfer belt is frequently in direct contact with the photosensitive member.

Endless belts used in these image forming apparatuses are required to have electrical resistance and uniformity in a semiconductive region having a volume resistivity of 1 × 10 ⁵ to 1 × 10 ¹³ Ω · cm. In order to give the endless belt electrical resistance in the semiconductive region, a method of blending an electron conductive material such as carbon black or a conductive filler or an ion conductive material into a thermoplastic resin is known. A semiconductive endless belt can be obtained by molding the compound.

  A semiconductive endless belt using an ion conductive material is characterized in that variation in electric resistance in the endless belt surface and variation between lots are small, and that electric resistance can be easily controlled. However, an image forming apparatus equipped with a semiconductive endless belt containing an ion conductive material can be printed after being left in a high temperature and high humidity condition for a long time with the semiconductive endless belt in contact with the photoreceptor. When this is done, there is a problem in that white spots due to transfer defects occur in the portions that are in contact with the photoreceptor. This phenomenon is due to the fact that the toner image formed on the surface of the photosensitive member is not transferred to the recording medium on the intermediate transfer belt or the transfer conveying belt, and the photosensitive member surface is contaminated. It has been found.

  As a method for preventing a decrease in light response characteristics due to photoconductor contamination, Patent Document 1 proposes an image forming apparatus equipped with an intermediate transfer medium having a structure containing an ionic conductive agent and having an abrasive dispersed in a surface layer. Yes. In this proposal, the surface of the photosensitive member contaminated with the ionic conductive agent is polished by the abrasive dispersed in the surface layer of the intermediate transfer medium, and the contaminant on the surface of the photosensitive member is removed. However, this method has a problem that the surface of the photoconductor is always polished and the durability of the photoconductor is reduced.

  Further, Patent Document 2 discloses that an image forming apparatus using an intermediate transfer belt in which the hard particle concentration in the outer peripheral surface portion is higher than that in the inner peripheral surface portion obtained by centrifugal molding is a photoconductor even when printing is performed under high temperature and high humidity conditions. The toner image formed on the recording medium can be transferred to the recording medium at a high transfer rate, and the toner image can be formed on the recording medium without causing white spots in the solid image, voids in the character image, and toner scattering in the character portion. It is described that can be. This is because hard particles are present in a high concentration near the surface of the intermediate transfer belt to increase the surface hardness, so that the surface of the intermediate transfer belt is not deformed by toner, and even a toner image formed with a small particle size toner can be recorded. It is assumed that it can be transferred to a medium at a high transfer rate. Therefore, the intermediate transfer belt is not intended to prevent the photoreceptor contamination.

  On the other hand, Patent Document 3 has a base fabric formed from a fiber material, a polyvinyl chloride resin layer, a plasticizer migration prevention layer, and a photocatalyst antifouling layer, and the plasticizer migration prevention layer is specified. An antifouling sheet comprising a flexible polymer resin layer containing synthetic silica and an additional flexible polymer resin layer not containing synthetic silica has been proposed. In this antifouling sheet, the specific synthetic silica holds the plasticizer that has migrated from the polyvinyl chloride resin layer in the plasticizer migration preventing layer, and prevents the plasticizer from migrating to the surface of the antifouling sheet. It has the effect of suppressing the deterioration of antifouling property and light resistance. However, the present invention relates to an antifouling sheet useful for industrial materials such as medium and large tents, tent warehouses, truck hoods, signboard backlits, etc., and is a semiconductive endless belt for electrophotography. Is completely different in both the application field and the technical field.

JP 2004-258444 A JP 2007-57924 A JP 2004-58673 A

Conventionally, an image forming apparatus equipped with a semiconductive endless belt containing an ion conductive material has a problem that an image defect considered to be caused by contamination of the surface of the photoreceptor occurs. As a result of analyzing the surface of the photoreceptor in order to investigate the cause, it was found that the components of the ion conductive material added to the semiconductive endless belt adhered to the surface of the photoreceptor. As a result of further detailed investigation, in the process of forming the semiconductive endless belt at a high temperature, that is, in the compounding process, the extrusion molding process, and the circumferential length regulating process, the ion conductive material is subjected to a thermal decomposition reaction. It was estimated that a small amount of a low molecular weight component was produced, which bleeded out to the surface of the semiconductive endless belt and contaminated the surface of the photoreceptor.
Based on this estimation, the present inventors have earnestly studied a semiconductive endless belt that does not contaminate the photoreceptor even when a low molecular weight component is produced in the production process of the semiconductive endless belt, and reached the present invention. .
That is, the present invention solves the above-described problem, and in a semiconductive endless belt containing an ion conductive material, particularly when left in high temperature and high humidity for a long time, the semiconductive endless belt processing It is an object of the present invention to provide a semiconductive endless belt that suppresses bleeding out of a low molecular weight component sometimes generated from the semiconductive endless belt and does not contaminate the photoreceptor.

According to the present invention,
(1) In a semiconductive endless belt in which an ion conductive material is blended with a thermoplastic resin, the semiconductive endless belt is a thermoplastic resin, an ion conductive material, and JIS.
A semiconductive endless belt comprising porous silica having an oil absorption measured according to K5101-13 of 50 to 350 ml / 100 g and an average particle size of 0.5 to 15 μm ;
(2) The semiconductive endless belt according to (1), wherein the thermoplastic resin is a fluororesin having a melting point of 190 ° C. or lower;
(3) The semiconductive endless belt according to (1) or (2), wherein the ion conductive material is a polymer type antistatic agent;
Is a summary.

  Although the semiconductive endless belt of the present invention contains an ion conductive material, the specific porous silica compounded in the semiconductive endless belt is compounded in the semiconductive endless belt. A small amount of thermal decomposition product derived from the ion conductive material is adsorbed, and the low molecular weight component which is the thermal decomposition product is prevented from bleeding out to the surface of the semiconductive endless belt. As a result, the semiconductive endless belt of the present invention has an effect of not contaminating the surface of the photosensitive member in contact with the image forming apparatus. In addition, since the semiconductive endless belt of the present invention uses an ion conductive material, there is little in-plane variation or lot-to-lot variation in electrical resistance, which is a feature of the semiconductive endless belt using the ion conductive material. Also, the electric resistance can be easily controlled, and a semiconductive endless belt having a desired electric resistance can be stably manufactured. Further, when printing is performed with an image forming apparatus equipped with the semiconductive endless belt of the present invention, there is an effect that a uniform and high quality image without white spots can be obtained.

Hereinafter, the present invention will be described in detail.
Examples of the thermoplastic resin used in the present invention include olefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene and ABS resin, acrylic resins, polyvinylidene fluoride, vinylidene fluoride copolymers, ethylene and tetrafluoroethylene, Fluorine resins such as copolymers, polyesters such as polylactic acid, polyethylene terephthalate and polybutylene terephthalate, polycarbonates, aliphatic polyamides and the like.

  Of these, the thermoplastic resin is preferably a fluororesin having a flame resistance and a melting point of 190 ° C. or lower that can be processed at a relatively low temperature in order to suppress the thermal decomposition reaction of the ion conductive material. Examples of the fluorine-based resin having a melting point of 190 ° C. or lower include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-tetrafluoroethylene copolymer.

  As the ion conductive material used in the present invention, a polymer type antistatic agent is preferable, polyether ester amide, polyether ester, polyether amide, polyethylene oxide, a copolymer of ethylene oxide and propylene oxide, polyepichlorohydrin, Examples thereof include a polymer having a polyethylene oxide chain, such as a copolymer of ethylene oxide and epichlorohydrin, a polymer having a quaternary ammonium salt in the side chain, and a polymer having a sulfonate in the side chain. Among these, since the environmental dependence of the electrical resistance of the obtained semiconductive endless belt (change in electrical resistance due to fluctuations in temperature and humidity) is small, polyethylene oxide or ethylene oxide and propylene oxide can be used as an ion conductive material. These copolymers are preferred.

The polymer antistatic agent used as the ion conductive material preferably has a weight average molecular weight of 100,000 or more. Moreover, since a low molecular weight component may cause a bleed-out phenomenon, an ion conductive material containing no low molecular weight component having a molecular weight of 3000 or less is preferable. More preferably, an ion conductive material containing no low molecular weight component having a molecular weight of 8000 or less is preferable. The weight average molecular weight is a value measured using GPC (gel permeation chromatography) using distilled water as an eluent and polyethylene oxide as a standard sample.
The amount of these additives depends on the electrical resistance required for the semiconductive endless belt, but if the amount of ion-conductive material added is large, the amount of low molecular weight components generated by thermal decomposition during molding increases, The amount is preferably 10 parts by weight or less with respect to 100 parts by weight of the plastic resin. In order to impart semiconductivity to the endless belt, it is preferable to blend 0.3 parts by weight or more of the ion conductive material with respect to 100 parts by weight of the thermoplastic resin.

  As described above, it is preferable that the polymer antistatic agent used as the ion conductive material does not contain a low molecular weight component having a molecular weight of 3000 or less. However, even if such an ion conductive material is used, a compound process for adding and mixing the ion conductive material to the thermoplastic resin, a molding process for extruding the obtained compound into a tube shape, and the obtained tube are predetermined. When the ion conductive material is exposed to a high temperature in the heating process for making the circumference uniform after cutting into length, the ion conductive material may cause a thermal decomposition reaction to generate a low molecular weight component having a molecular weight of 3000 or less. Therefore, these processing temperatures are preferably 240 ° C. or lower.

  In addition to the ion conductive material, an ion electrolyte can be used in combination with the semiconductive endless belt of the present invention for the purpose of lowering electric resistance. Examples of ion electrolytes include lithium perchlorate, sodium perchlorate, potassium perchlorate, ammonium perchlorate, tetrabutylammonium hydrogen sulfate, tetraethylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, lithium chloride Alkali metal salts such as lithium thiocyanate, sodium thiocyanate, potassium thiocyanate, ammonium salts, borates and the like can be used.

  The porous silica that can be used in the present invention is obtained by mixing sodium silicate and sulfuric acid to form a silicate sol, gradually polymerizing and gelling it to form colloidal silica, and then pulverizing it. be able to. Among these, those having an oil absorption of 50 to 350 ml / 100 g, further 80 to 350 ml / 100 g as defined in JIS K5101-13 can be suitably used as the porous silica. Silica having an oil absorption of less than 50 ml / 100 g is not preferable because the effect of suppressing bleed out of low molecular weight components due to the ion conductive material is insufficient.

The average particle size of the porous silica is preferably 0.5 to 15 μm. When the average particle size of the porous silica is less than 0.5 μm, it is not preferable because when the porous silica and the thermoplastic resin are heat-kneaded, secondary aggregates of the porous silica are easily formed, and the average particle size is 15 μm. In the case of exceeding the semi-conductive endless belt, the surface roughness of the endless belt obtained because the average particle diameter of the porous silica is large is not preferable.
Furthermore, the specific surface area of the porous silica is preferably 100 to 1000 m ² / g. When the specific surface area of the porous silica is less than 100 m ² / g, the specific surface area is small, which is not preferable because the oil absorption is small, and the porous silica having a specific surface area exceeding 1000 m ² / g has an average pore diameter that is too small. This is not preferable because the ability to adsorb low molecular weight components generated by the thermal decomposition reaction of the ion conductive material is reduced.

  The amount of the porous silica added is preferably 0.05 to 2.0 parts by weight with respect to 100 parts by weight of the thermoplastic resin. Furthermore, 0.1-1.0 weight part is preferable. When the addition amount of the porous silica is less than 0.05 parts by weight, the effect is small because the addition amount of the porous silica is small, which is not preferable. When the addition amount exceeds 2.0 parts by weight, the obtained semiconductive endless is obtained. This is not preferable because the surface roughness of the belt increases.

  Furthermore, in addition to the above, the semiconductive endless belt of the present invention contains various additives such as a heat stabilizer, a reinforcing agent, a lubricant, a compatibilizer, a colorant, and a modifier for various purposes. Also good.

Below, the manufacturing method of the semiconductive endless belt of this invention is demonstrated.
The compound for a semiconductive endless belt according to the present invention is a conventional kneader, roll, Banbury mixer, biaxial kneader containing various additives such as a thermoplastic resin, an ion conductive material, porous silica and, if necessary, an ionic electrolyte. It can be produced by kneading and pelletizing with a machine or the like.

The compound thus obtained is supplied to an extruder equipped with an annular die and formed into a tube having a predetermined circumference, whereby a semiconductive endless belt original fabric can be obtained. Alternatively, the compound can be supplied and co-extruded to at least one extruder equipped with a multilayer annular die to obtain a multilayer semi-conductive endless belt raw material.
The obtained semi-conductive endless belt material is cut into a predetermined length, and then heated over a cylindrical mold slightly larger than the original material circumference to increase the accuracy of the circumference, so that the circumference is uniform. The intended semiconductive endless belt can be obtained.

  In the case of a multilayer semiconductive endless belt, 0.05 to 2.0 parts by weight of porous silica is added to a layer containing an ion conductive material with respect to 100 parts by weight of the thermoplastic resin of the layer. It is preferable to do this. Alternatively, the amount of porous silica described above can be added to the other layer on the surface layer side of the layer containing the ion conductive material.

  In order to impart properties such as releasability, slipperiness, and wear resistance to the semiconductive endless belt thus obtained, a coating agent that imparts these properties is applied to the endless belt surface. It can also be crafted.

  As described above, in order to obtain the semiconductive endless belt of the present invention, a compounding step of kneading a thermoplastic resin, an ion conductive material, porous silica and the like, and a tube-shaped semiconductive from the obtained compound. There are extruding process to obtain the raw material for the conductive endless belt, heating process for covering the endless belt raw material on the mold to increase the circumference accuracy, and the raw material for the semiconductive endless belt is heated in each process, but the ionic conductivity In order to suppress the production of low molecular weight components due to thermal decomposition of the material, the temperature of each step is preferably 240 ° C. or lower.

  Next, the present invention will be described specifically by way of examples. The evaluation method of the obtained semiconductive endless belt is as follows. Table 1 shows the characteristics of the porous silica used in the examples and comparative examples.

<Characteristics of porous silica>
The average particle diameter, specific surface area, and oil absorption of the porous silica were determined as follows.
[Average particle size (Laser method)]
The average particle diameter of the porous silica was determined by irradiating the porous silica particles with laser light and determining the average particle diameter of the porous silica from the scattering pattern obtained therefrom.
[Specific surface area]
The specific surface area of the porous silica was measured by a simple BET method.
That is, first, the weight of the degassed porous silica is measured, nitrogen gas is blown into the porous silica, and nitrogen gas is adsorbed on the sample surface. Then, the amount of adsorption of nitrogen gas molecules adsorbed only on the surface of the porous silica was determined from the BET adsorption isotherm by plotting the variation of the amount of adsorption against the pressure change of nitrogen gas.
[Oil absorption]
The amount of oil absorption of the porous silica was represented by the volume (ml) of refined sesame oil absorbed by 100 g of porous silica in accordance with JIS K5101-13.

<Volume resistivity, surface resistivity>
The volume resistivity was measured using a Hiresta URS probe manufactured by Mitsubishi Chemical Corporation under an applied voltage of 250 V, 23 ° C., and 50% RH.
The surface resistivity was measured using a Hiresta URS probe manufactured by Mitsubishi Chemical Corporation under an applied voltage of 500 V, 23 ° C., and 50% RH.
The volume resistivity and the surface resistivity are average values obtained by measuring 10 arbitrary points, and the variation is represented by a value obtained by dividing the maximum value by the minimum value.

<Tensile strength and elongation at break>
Using Autograph AGS-100 (manufactured by Shimadzu Corporation), No. 2 test piece was prepared according to JIS K7127, and the maximum load and tensile elongation at break when measured at a tensile speed of 30 mm / min were measured.

<Surface roughness>
Centerline average roughness Ra was measured using a contact type surface roughness meter Surfcom 575A (manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with JIS B0601-1982.

<Evaluation of bleed-out>
Bleed out by placing a metal roller with a diameter of 12 mm on a strip-shaped sample, leaving it in a normal state for 30 days in 50 ° C. and 90% relative humidity, and observing the state of the sample surface on which the metal roller was placed. The presence or absence of was determined. That is, the surface of the sample on which the metal roller was placed was visually observed. A case where no foreign matter was observed on the surface of the sample was indicated as ◯, and a case where foreign matter was observed was indicated as ×.

  100 parts by weight of polyvinylidene fluoride, 3 parts by weight of a copolymer of ethylene oxide and propylene oxide (propylene oxide content 10%, weight average molecular weight when using distilled water as an eluent and polyethylene oxide as a standard sample), Supplying 0.2 parts by weight of lithium perchlorate, 0.2 parts by weight of a phenol-based heat stabilizer, and 0.2 parts by weight of porous silica A to a biaxial kneader at a set temperature of 180 ° C., a compound for a semiconductive endless belt Got. Next, this compound was supplied to an extruder (set temperature 210 ° C.) equipped with an annular die to obtain a tube having a diameter of 180 mm. This tube was cut into a length of 320 mm, covered with a cylindrical mold having an outer diameter of 183 mm, and heated at 150 ° C. for 60 minutes to obtain a semiconductive endless belt. Table 2 shows the characteristics of the obtained semiconductive endless belt.

  A semiconductive endless belt was obtained in the same manner as in Example 1 except that porous silica B was used as the porous silica. Table 2 shows the characteristics of the obtained semiconductive endless belt.

  A semiconductive endless belt was obtained in the same manner as in Example 1 except that the amount of the copolymer of ethylene oxide and propylene oxide was changed to 4 parts by weight. Table 2 shows the characteristics of the obtained semiconductive endless belt.

  A semiconductive endless belt was obtained in the same manner as in Example 1 except that 0.3 part by weight of porous silica A was used as the porous silica. Table 2 shows the characteristics of the obtained semiconductive endless belt.

[Comparative Example 1]
A semiconductive endless belt was obtained in the same manner as in Example 1 except that porous silica was not used. Table 2 shows the characteristics of the obtained semiconductive endless belt.

[Comparative Example 2]
A semiconductive endless belt was obtained in the same manner as in Example 1 except that porous silica C was used as the porous silica. Table 2 shows the characteristics of the obtained semiconductive endless belt.

[Comparative Example 3]
A semiconductive endless belt was obtained in the same manner as in Comparative Example 2 except that the copolymer of ethylene oxide and propylene oxide was changed to 4 parts by weight. Table 2 shows the characteristics of the obtained semiconductive endless belt.

  From the above results, the semiconductive endless belts of Examples 1, 2, 3 and 4 to which porous silica having an oil absorption of 50 ml / 100 g or more was added were semiconductive even when left for a long time under high temperature and high humidity. No blade-outs were found on the endless belt surface, and it was confirmed that there was no fear of contaminating the photoreceptor. Moreover, the influence on volume resistivity, surface resistivity, tensile strength, tensile elongation at break, and surface roughness due to the addition of porous silica was not observed. On the other hand, Comparative Example 1 in which no porous silica was added, Comparative Example 2 in which porous silica having an oil absorption of less than 50 ml / 100 g was added, and the semiconductive endless belts in 3 were used for a long time under high temperature and high humidity. When left untreated, a bleed-out was observed.

  Although the semiconductive endless belt obtained by the present invention uses an ion conductive material, it does not bleed out even if left in a high temperature and high humidity for a long time, so it contaminates the surface of the photoreceptor. There is no fear, and it can be suitably used as a transfer conveyance belt or an intermediate transfer belt of an electrophotographic image forming apparatus.

Claims (3)

In a semiconductive endless belt in which an ion conductive material is blended with a thermoplastic resin, the semiconductive endless belt has an oil absorption amount of 50 to 50 measured according to the thermoplastic resin, the ion conductive material, and JIS K5101-13. A semiconductive endless belt comprising 350 ml / 100 g of porous silica having an average particle size of 0.5 to 15 μm .   The semiconductive endless belt according to claim 1, wherein the thermoplastic resin is a fluorine resin having a melting point of 190 ° C or lower. 3. The semiconductive endless belt according to claim 1, wherein the ion conductive material is a polymer type antistatic agent.