JP5376843B2 - Multilayer elastic belt used in image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer elastic belt which has the advantages that the elasticity of rubber provided as an intermediate layer is not impaired, whatever hardness a surface layer material used therein may have, and that the frictional coefficient of the belt surface is not increased. <P>SOLUTION: There is a multilayer elastic belt for an electrophotographic device at least composed of three layers, consisting of a surface layer comprising a mold releasable material, an elastic layer comprising an elastic rubber material and a base material layer comprising a high-strength resin material, in the order starting from the surface side, and the surface layer has a rugged face which is transferred from a mold face having a rugged face. A method for manufacturing the belt is also disclosed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a multilayer elastic belt used in an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine or the like. Specifically, an electrophotographic belt such as an intermediate transfer belt, a transfer conveyance belt, or a paper conveyance belt used for transferring a toner image on an electrostatic latent image formed on a photosensitive member to a recording material such as paper. It is about.

  In order to cope with the high image quality of the intermediate transfer belt, as described in Patent Document 1, an intermediate transfer belt having a two-layer or three-layer structure having an elastic material layer has been proposed.

  Further, Patent Document 2 and the like have devised one using urethane rubber for the elastic layer, and Patent Document 3 and the like have devised one using silicone rubber for the elastic layer. These belts are usually formed by a method in which an elastic layer and a surface layer are sequentially coated on the surface of a resin belt such as polyimide as a base material layer, a method in which an elastic layer and a base material layer are sequentially molded on the inner surface of a mold, a calendar roll, etc. Manufactured by laminating sheeted sheets.

  An intermediate transfer belt made of such a rubber elastic body or provided with a rubber elastic body layer is excellent in flexibility, so that a transfer area with a photoconductor or the like that contacts the intermediate transfer belt during primary transfer can be easily and stably formed. At the same time, the stress applied to the toner between the photosensitive member and the like is reduced, which is useful for countermeasures against image dropout defects and for improving the sharpness of fine line printing.

  Further, such an intermediate transfer belt for high image quality achieves the purpose of imparting elasticity in the thickness direction of the belt, while toner releasability required for a conventional transfer belt is simultaneously required as an important factor. That is, when transferring toner from the surface of the intermediate transfer belt to a medium such as paper, releasability with respect to the toner is required. For this reason, the member constituting the surface layer is formed of a material having a low surface energy such as fluoro rubber, silicone rubber, or fluorine resin material, so that the toner can be easily released from the surface of the intermediate transfer belt, and transfer efficiency can be improved. Has been successfully used to improve.

  However, when the surface of the intermediate transfer belt is formed of a rubber elastic body made of fluorine rubber or silicone rubber, the toner releasability is not always sufficient due to the adhesiveness of the rubber, and the toner formed on the surface of the intermediate transfer belt There is a problem that the toner in the lowermost layer of the image is not transferred to a medium such as paper and remains on the surface of the intermediate transfer belt. That is, the efficiency of secondary transfer is reduced. In addition, when a cleaning blade made of silicone rubber or urethane rubber is used in the cleaning process to remove the toner remaining on the surface of the intermediate transfer belt, the surface of the intermediate transfer belt is sticky, which In the worst case, the blade will be damaged.

  Patent Document 4 describes a configuration having a surface layer made of a fluororesin such as FEP on an elastic layer.

  However, the surface layer has good releasability and cleanability, and it has been found that such a fluororesin is very preferable as the material of the surface layer, but it is more rigid than the intermediate rubber elastic layer. For this reason, the flexibility of the elastically imparted intermediate transfer belt is lowered, and the stable formation of the transfer region is hindered. As a result, image defects such as voids occur as in the case of conventional resin belts. In addition, the hard surface layer made of fluororesin cannot follow the shrinkage of the elastic rubber layer when the intermediate transfer belt is curved, causing numerous fine cracks on the surface, causing image defects and surface layer peeling. Become. In particular, when the rubber hardness constituting the rubber elastic body layer is a soft type A of 40 degrees or less, the above-mentioned lack of shrinkage following ability of the surface layer to the rubber elastic body layer is remarkable, and cracks of the surface layer are more likely to occur.

  In order to solve this problem, attempts have been made to reduce the thickness of the fluororesin surface layer (for example, Patent Document 5). However, the thin surface layer is strongly affected by the softness of the elastic layer, and the friction coefficient of the belt surface. As a result, the original releasability and cleaning properties cannot be obtained. Similarly, in order to solve this problem, there is a method of using a flexible fluorine-based material (for example, Patent Document 6), but the followability to the rubber of the surface layer is improved and the generation of cracks can be prevented. The friction coefficient of the surface is high due to the inherent softness, and particularly in the case of a thin film, it becomes noticeable due to the influence of the elastic layer. Therefore, in any case, it is difficult to ensure image defects such as voids and release or cleaning properties.

  On the other hand, dimensional accuracy is very important in the function of the intermediate transfer belt, and if there are variations in circumference or thickness, problems such as image displacement occur. The most common method for producing a multi-layer intermediate transfer belt is to coat the surface of a high-strength base material layer such as polyimide obtained by centrifugal molding or the like with an elastic layer and a surface layer in this order. However, in this method, the film thickness of each layer is not necessarily uniform due to variations in coating amount, clogging of spray nozzles, air mixing conditions, and the like. As a result, the thickness accuracy is deteriorated.

  In order to avoid this, there is a method of manufacturing a transfer belt by forming a film of each layer according to mold regulation by a method called rotational molding or centrifugal molding (for example, Patent Document 7). That is, a production method is adopted in which a surface layer is formed on the inner surface of the mold and an elastic layer is formed on the inner side. As a result, an intermediate transfer belt having a high circumferential length and thickness accuracy can be obtained.

However, in such a manufacturing method in which the film is formed on the inner surface of the mold in order from the outermost layer, the fluororesin layer as the surface layer has a uniform thickness, and when it receives local stress from the toner contacting the belt surface, Since it has a resistance to try to receive in a wider range, the effect of enveloping and receiving the toner of the elastic layer as the intermediate layer may be hindered.
Japanese Patent No. 3248455 Japanese Patent Laid-Open No. 2001-282009 JP 2002-292655 A Japanese Patent No. 3019781 JP 2005-134791 A JP 2006-178232 JP JP 2007-292851 A

  As described above, in the conventional technology, an optimal balance of primary transfer characteristics such as prevention of image dropout and secondary transfer characteristics such as releasability and cleaning is applied to a transfer belt having a multilayer structure used in an image forming apparatus. It is difficult to obtain the means to grant.

  The present invention has an optimal balance of primary transfer characteristics with excellent film thickness accuracy as a transfer belt, clear image printing and fine line printing, and secondary transfer characteristics with good releasability and cleaning properties. An object is to provide a multilayer elastic belt.

  As a result of earnest research to solve the above-mentioned problems, the present inventor can reduce the friction coefficient by giving random and fine irregularities on the belt surface, and an elastic layer necessary for primary transfer. It has been found that both the softness of mold and the releasability required for secondary transfer can be achieved. Initially, the finished belt surface was polished with a lapping film sheet (manufactured by Sumitomo 3M Limited) with a particle size of 12, 30, and 40 μm. However, in this method, it has been difficult to finish a wide range to an uneven surface having a uniform roughness due to clogging of the wrapping film sheet.

  We have also found that even with diamond-like carbon (DLC) coating, it is possible to make the surface uneven, but since coating requires additional processing steps and is expensive, industrial products Judged not suitable for use. As a result of such research and device development, the manufacturing method has been achieved by blasting the inner surface of the mold and molding the surface layer on the inner surface to transfer the unevenness of the mold to the belt surface. By doing so, the transfer efficiency was improved when the belt was incorporated in the image forming apparatus. This is because even when the surface layer is extremely thin, the phenomenon that the coefficient of friction increases due to the softness of the elastic layer, which is an intermediate layer, has been alleviated by the unevenness of the surface, and the toner surface Caused by the fact that even when subjected to local stress, the concave and convex portions of the random irregularities present on the belt surface can be locally deformed so as to envelop the toner by preferentially stretching under stress. Was guessed.

  Based on this knowledge, the optimal balance of the secondary transfer characteristics with the excellent film thickness accuracy required for the transfer belt, clear image transfer and fine line printing, and excellent releasability and cleanability. In order to realize the above, the present invention has been completed by further research on how to control the surface of the transfer belt.

  That is, the present invention provides the following elastic belt.

  Item 1. A multilayer elastic belt for an electrophotographic apparatus, comprising at least three layers of a surface layer containing a releasable material, an elastic layer containing an elastic rubber material, and a base material layer containing a high-strength resin material in order from the surface side. A multilayer elastic belt for an electrophotographic apparatus, wherein the surface layer has an uneven surface transferred from a mold surface having an uneven surface.

  Item 2: The surface layer and the elastic layer are formed on the inner surface of the same cylindrical mold by rotation molding in the order of the surface layer and the elastic layer, and the inner surface of the cylindrical mold has an uneven surface by blasting The multilayer elastic belt for an electrophotographic apparatus according to the description.

  Item 3 The multilayer elastic belt for an electrophotographic apparatus according to Item 1 or 2, wherein the surface roughness (Ra) of the uneven surface of the surface layer is in the range of 0.1 to 1.5 µm.

  Item 4 The electrophotography according to any one of Items 1 to 3, wherein the surface layer is a layer containing a fluororesin material having a Rockwell hardness (R scale) of 100 degrees or less, and the thickness of the surface layer is 5 μm or less. Multi-layer elastic belt for equipment.

  Item 5 The multilayer elastic belt for an electrophotographic apparatus according to any one of Items 1 to 4, wherein a static friction coefficient of the uneven surface of the surface layer is 0.8 or less.

  Item 6. The multilayer elastic belt for an electrophotographic apparatus according to any one of Items 1 to 5, wherein the elastic layer is a layer containing a polyurethane elastomer material.

  Item 7 The multilayer elastic belt for an electrophotographic apparatus according to any one of Items 1 to 6, wherein a material of the base material layer is polyimide or polyamideimide.

  Item 8 The multilayer elastic belt for an electrophotographic apparatus according to any one of Items 1 to 7, wherein the shape of the belt is endless.

Item 9. A method for producing a multilayer elastic belt for an electrophotographic apparatus,
(1) forming a surface layer containing a releasable material having an uneven surface by rotational molding using a cylindrical mold having an uneven surface on the inner surface;
(2) Forming an elastic layer further containing an elastic rubber material on the inner surface of the surface layer by rotational molding to produce a first belt comprising at least two layers of the surface layer and the elastic layer;
(3) The process of manufacturing the 2nd belt which consists of a base material layer containing a high-strength resin material by rotational molding using another cylindrical mold,
(4) A manufacturing method comprising a step of manufacturing a multilayer elastic belt for an electrophotographic apparatus by bonding the elastic layer side of the first belt and the second belt.

Since the multilayer elastic belt of the present invention is formed into a mold by rotational molding, good film thickness accuracy can be obtained. In addition, since the surface layer has irregularities and deforms locally, even if a hard resinous surface layer material is used, the softness of the intermediate layer rubber is not negated, so there is no image void and fine line A primary transfer characteristic with clear printing can be obtained. Furthermore, even when a surface layer material of soft resin is used or when the surface layer is thinned, the friction coefficient of the material itself usually increases or the influence of the softness of the intermediate layer rubber appears in the increase of the friction coefficient. However, since the surface of the belt of the present invention has irregularities, the friction coefficient of the surface can be lowered, and secondary transfer characteristics with good releasability and cleaning properties can be obtained. Thus, the optimum balance between primary transfer and secondary transfer can be pursued regardless of the hardness of the material constituting the surface layer.

Hereinafter, the present invention will be described in detail.
I. Processing of Inner Surface of Mold A cylindrical mold for forming a surface layer having irregularities on the surface of the multilayer elastic belt (particularly, intermediate transfer belt) of the present invention is subjected to blasting on the inner surface. The mold is usually made of a steel material having a hardness of about S20C to S55C, and the inner and outer surfaces are subjected to a plating treatment such as hard chrome plating. Either the order of plating or blasting may be first, but when plating is performed after blasting, it is important to calculate so that the roughness of the mold after plating becomes the target value.

  Types of blasting methods include shot blasting, air blasting, and wet blasting, and shot blasting or air blasting is suitable. Moreover, there are electrical discharge machining, ceramic spraying, and the like that can obtain the same effect as blasting, and these may be used alone or in combination with a plurality of methods.

  The media can be selected according to the target value of the roughness of the mold, but the unevenness transferred to the belt surface and the unevenness of the inner surface of the mold may be considered to be substantially the same value. Therefore, the roughness (Ra) of the inner surface of the mold must be 1.5 or less, and the media count should be fine # 60 or more. For example, each medium of # 200 to # 500 such as alumina, ceramic, silicon carbide, etc. is used singly or in combination of two or more. When using two or more kinds in order, it is better to finish with a fine count after first processing with a coarse count. By doing so, the inner surface roughness of the mold becomes more uniform and no sharp convex part remains. If an acute-angle convex portion remains, when a belt is formed with the mold, a pinhole is formed on the surface of the belt, and the toner is stuck and cannot be removed.

  Also, since the inner surface roughness of the finished mold will change depending on the hardness of the mold material, select an appropriate count and target value of inner surface roughness (Ra) is 0.1-1.5, preferably 0.1-1.0, more preferably It is important to set 0.1 to 0.5.

Note that (Ra) refers to the arithmetic average roughness Ra according to JIS B 0601-1994 "Surface roughness-definition and indication".
II. Formation of Surface Layer The surface layer in the multilayer elastic belt of the present invention is a layer for directly placing toner and transferring and releasing the superimposed four color toners onto paper.

  The material of the surface layer is preferably a fluororesin from the viewpoint of facilitating release of the toner. Examples of such fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride copolymer (THV), and polyvinylidene fluoride. Ride (PVDF), a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (VDF-HFP copolymer), or a mixture thereof. The copolymer of V D F and H F P preferably has a HFP ratio of about 1 to 15 mol%.

  Many fluororesin materials alone are difficult to adhere to the rubber constituting the elastic layer. In this case, urethane resin or acrylic resin may be used as the binder. Specifically, paints in which PTFE is dispersed in these binders are used.

  Also, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride copolymer (THV), polyvinylidene fluoride (PVDF), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) copolymer (VDF-HFP) When a copolymer) or a mixture thereof is selected, the inherent surface energy is large, and therefore, adhesion to rubber is relatively easy by using a primer or the like and can be used without a binder.

  Further, a fine powder of polytetrafluoroethylene (PTFE) may be added to these materials. In this case, the powder may be directly dispersed in a raw material solution to be described later, or a dispersion previously diluted with a solvent or the like may be used, and the polytetrafluoroethylene fine particle powder relative to the weight of the fluororesin raw material in the raw material solution Can be added in an amount of not more than 20% by weight, preferably not more than 10% by weight.

The volume resistivity of the surface layer is usually 10 ¹³ Ω · cm or more, more preferably 10 ¹³ to 10 ¹⁵ Ω · cm. In addition, it is possible to control the semiconductivity by adding a conductive agent such as carbon black, but since the effect is limited and uniform dispersion is difficult, the surface layer does not contain a conductive agent. May be. Since the surface layer is not affected by the change in the environment (temperature, humidity, etc.), stable primary and secondary transfer of the toner is possible, and high image quality can be realized.

  The thickness of the surface layer is preferably 5 μm or less, and more preferably 1 to 3 μm. If the thickness is too large, the rubber elasticity of the elastic layer is impaired, which is not preferable, and if the thickness is too thin, there is a problem in durability such that a hole is easily formed in the surface layer.

  The static friction coefficient of the surface layer is preferably low in view of secondary transfer properties, but it is preferable to provide a lower limit value from the viewpoint of ensuring cleaning properties and preventing blade noise. From this, the static friction coefficient is preferably 0.1 to 0.8, more preferably 0.15 to 0.35, and particularly preferably 0.2 to 0.3.

  Further, it is preferable that the surface layer has flexibility to improve the transfer efficiency of the primary transfer image, such as prevention of voids, since the effect of enveloping the toner can be expected. Specifically, the Rockwell hardness on the JIS K 7202 compliant R scale is 100 degrees or less, more preferably 80 degrees or less, particularly 40 to 80 degrees. At this time, when the surface layer is usually as thin as about 1 to 3 μm, the coefficient of static friction increases due to the influence of the elastic layer as a base, but in the present invention there is unevenness transferred from the mold on the surface, The coefficient can secure the numerical range.

  The surface state of the surface layer is transferred from the mold. The target surface roughness for obtaining the coefficient of static friction varies slightly depending on the type, blending, and hardness of the surface layer material resin, but the surface roughness (Ra) is 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm, as a result of research. More preferably, the thickness is 0.1 to 0.5 μm. When the surface roughness (Ra) exceeds 1.5 μm, the toner may fit into the irregularities on the surface, which causes image sticking (filming) and image defects such as voids, which is not preferable.

  Note that (Ra) in this case also indicates the arithmetic average roughness Ra according to JIS B 0601-1994 “Surface Roughness—Definition and Display”, in the same manner as the measurement and description method of the inner surface roughness of the mold.

  The formation of the surface layer will be described below with a typical example in which a fluororesin having a Rockwell hardness of 100 degrees or less is centrifuged using a cylindrical mold having a surface roughness (Ra) of 0.1 to 1.5 μm.

  First, the weight of the material is adjusted so that the finished surface layer has a target thickness of 1 to 5 μm. The weighed surface layer material is dissolved in a solvent to obtain a liquid raw material, which is cast on the inner surface of a cylindrical mold and centrifuged. Solvents used include water; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester solvents such as ethyl acetate and butyl acetate; amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide; Alternatively, a mixed solvent thereof or the like is used. The liquid raw material may have a solid content concentration of about 2 to 30% by weight. At this time, the target thickness of the surface layer needs to be larger than the maximum roughness (Rmax) of the inner surface of the mold. However, even when the thickness is smaller than the maximum roughness of the inner surface of the mold, a film can be formed on the whole by the surface tension of the solution.

  Centrifugal molding of the surface layer can be performed as follows using, for example, a cylindrical mold. After injecting the liquid raw material in an amount equivalent to obtaining the final thickness into the stopped cylindrical mold, the rotational speed is gradually increased to the speed at which the centrifugal force works, and the centrifugal force uniformly flows over the entire inner surface. Extend.

  The inner surface of the cylindrical mold is blasted to a predetermined surface roughness, and the inner surface state of the mold is transferred to the outer surface of the surface layer of the endless multilayer elastic belt. Therefore, by forming the irregularities on the inner surface of the mold by blasting, the belt surface layer can be adjusted to have the desired irregularities. In addition, the roughness of the inner surface of the mold to be used can be arbitrarily controlled by the count of the blast media used when the inner surface unevenness is imparted.

  Further, a release agent is applied to the inner surface of the cylindrical mold so that the film after the raw material is cured can be released from the inner surface of the mold. As the release agent, a fluorine release agent or a silicone release agent is used.

  The cylindrical mold is placed on a rotating roller, and indirectly rotated by the rotation of the roller. The size of the mold can be appropriately selected according to the desired size of the surface layer, that is, the outer diameter of the elastic belt.

For the heating, a heat source such as a far-infrared heater is disposed around the mold, and indirect heating from the outside is performed. Usually, the temperature may be gradually raised from room temperature to about 120 to 200 ° C. and heated at the temperature after the temperature raising for about 15 minutes to 2 hours. Thereby, the liquid raw material injected into the inner surface of the cylindrical mold is cured, and a seamless (seamless) tubular surface layer can be formed on the inner surface of the cylindrical mold.
III. Formation of Elastic Layer The elastic layer in the multilayer elastic belt of the present invention is made of an elastic rubber material, specifically, a cured product of liquid urethane rubber. For example, it is manufactured by applying and curing a liquid urethane rubber and, if necessary, an elastic layer material containing an electronic conductive agent or an ionic conductive agent in the liquid urethane rubber on the inner surface of the surface layer obtained in I above .

  Examples of the liquid urethane rubber include polyurethane elastomers, and those having a cured product of type A hardness (JIS K6253) of 30 to 80 degrees, more preferably 40 to 65 degrees are preferred. Specific examples include Pandex and Urehyper manufactured by Dainippon Ink and Chemicals, Takenate manufactured by Mitsui Chemicals Polyurethanes, and the like.

Usually, some of these urethane rubbers have a volume resistivity of about 10 ⁹ Ω · cm to 10 ¹¹ Ω · cm without adjusting the resistance. In many cases, the environmental variation is large when the temperature and humidity environment is shaken. Accordingly, it is desirable to select a urethane rubber having a volume resistivity of 10 ¹³ Ω · cm or more that is not originally adjusted for resistance. The resistance of this urethane rubber is adjusted with a conductive agent whose electrical characteristics are less dependent on the environment, that is, carbon black or lithium ion salt.

  The carbon black may be a conductive carbon black such as acetylene black or ketjen black. The compounding amount of carbon black is 5 to 40 parts by weight, preferably 10 to 30 parts by weight, and more preferably 10 to 25 parts by weight with respect to 100 parts by weight of the liquid urethane rubber.

Thus, by adding carbon black to the insulating urethane rubber, the elastic layer has a semi-conductivity of about 10 ⁷ to 10 ¹³ Ω · cm (preferably about 10 ⁹ to 10 ¹² Ω · cm). Thus, accurate semiconductivity suitable for the purpose can be obtained for various resistance value requirements. Further, since the obtained belt is electronically conductive by carbon black, it exhibits stable semiconductivity that is hardly affected by the external environment such as temperature and humidity.

Examples of the ionic conductive agent using a lithium salt include lithium bisimide (CF ₃ SO ₂ ) ₂ NLi and lithium trismethide (CF ₃ SO ₂ ) ₃ CLi. Specific examples include Sanconol manufactured by Sanko Chemical Co., Ltd. In the type of a normal ionic conductive agent, the conductivity is considered to be manifested by moisture absorption, which causes the ionic conductivity to depend on the environment. However, this ionic conductive agent, which is considered to exhibit conductivity when lithium ions move due to the molecular motion of oxygen, is less dependent on the environment, and is preferably used for the elastic layer constituting rubber of the transfer belt. When an ionic conductive agent is added, the addition amount is about 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the liquid urethane rubber.

  The liquid urethane material whose resistance is adjusted by any of the methods in this way is put into the inner surface of the surface layer formed on the inner side of the mold and is centrifugally molded. If the viscosity of the liquid urethane material is too high during centrifugal molding, it may be appropriately diluted with an ester solvent such as ethyl acetate or butyl acetate, or a solvent such as toluene or xylene. As the centrifugal molding method, for example, the same one as the molding equipment for the I surface layer is used. The molding temperature is gradually heated from room temperature, raised to about 120 to 150 ° C., which is below the heat resistance limit of urethane rubber, and kept in this state for about 0.5 to 1 hour to complete the curing.

  For the purpose of improving adhesion between the surface layer and the elastic layer, a method of applying a primer on the surface layer side by spraying, a method of adding a silane coupling agent to the liquid urethane material, a method of performing both, etc. You may take it.

The volume resistivity of the elastic layer is usually about 10 ⁷ to 10 ¹³ Ω · cm, preferably about 10 ⁹ to 10 ¹² Ω · cm, from the viewpoint of transferring toner as a belt by electrical control.

The thickness of the elastic layer is usually 50 to 400 μm, preferably 120 to 300 μm, in consideration of the flexibility of the belt surface and prevention of image displacement during use.
IV. Formation of Base Material Layer The base material layer in the multilayer elastic belt of the present invention is a layer for preventing deformation due to stress applied to the belt during driving. Therefore, mechanical properties are required.

  Examples of the resin for the base material layer include high-strength resin materials such as polyimide and polyamideimide.

  Polyimide is usually produced by condensation polymerization of tetracarboxylic dianhydride and diamine or diisocyanate as monomer components by a known method.

  Examples of polyimide tetracarboxylic dianhydrides include pyromellitic acid, naphthalene-1,4,5,8-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid, 2,3,5,6. -Biphenyltetracarboxylic acid, 2,2 ', 3,3'-biphenyltetracarboxylic acid, 3,3', 4,4'-biphenyltetracarboxylic acid, 3,3 ', 4,4'-diphenyl ether tetracarboxylic acid 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic acid, azobenzene-3,3 ′, 4,4′-tetracarboxylic acid, bis ( 2,3-dicarboxyphenyl) methane, bis (3,4-dicarboxyphenyl) methane, β, β-bis (3,4-dicarboxyphenyl) propane, β, β-bis (3 4-di-carboxyphenyl) dianhydride such as hexafluoropropane, and the like.

  Examples of the diamine include m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminochlorobenzene, m-xylylenediamine, p-xylylenediamine, 1,4 -Diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4'-diaminobiphenyl, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 3,4'-diamino Diphenyl ether, 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminoazobenzene, 4,4 '-Diaminodiphenylmethane, β, β-bis (4-aminophen Nyl) propane and the like.

  As said diisocyanate, the compound etc. which the amino group in the above-mentioned diamine component substituted by the isocyanate group are mentioned.

  Polyamideimide is produced by condensation polymerization of trimellitic acid and diamine or diisocyanate by a known method. In this case, the same diamine or diisocyanate as the above-mentioned polyimide raw material can be used.

  The thickness of the base material layer is usually 30 to 120 μm, preferably 50 to 100 μm, considering the stress and flexibility applied to the belt during driving.

  The base material layer may contain a conductive agent as necessary. As the conductive agent, carbon black mentioned in the elastic layer can be used. When the conductive agent is included, the amount used is usually about 5 to 25 parts by weight with respect to 100 parts by weight of the base layer resin. As a result, the base material layer can have a resistivity suitable for the intermediate transfer belt.

  When polyimide is used as the resin for the base material layer, for example, the base material layer can be formed as follows. Tetracarboxylic dianhydride, which is the raw material of the polyimide, and diamine are reacted in a solvent to obtain a polyamic acid solution once. This polyamic acid solution should just be about 10 to 40 weight% by solid content concentration.

  Examples of the solvent include N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”), N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphospho An aprotic organic polar solvent such as amide or 1,3-dimethyl-2-imidazolidinone is used. One or two or more of these solvents may be used. In particular, NMP is preferable.

  In order to impart desired semiconductivity to the base material layer, as described above, about 5 to 25 parts by weight of conductive agent such as carbon black is added to the polyamic acid solution with respect to 100 parts by weight of the base material resin as necessary. You may do it. In this case, the carbon black may be uniformly dispersed with a ball mill. Thereby, the material for base material layers containing a polyamic acid and a electrically conductive agent as needed is obtained.

  The obtained material for the base layer is subjected to centrifugal molding using a cylindrical mold or the like in the same manner as the surface layer / elastic layer. However, the inner surface of the mold in this case does not necessarily require unevenness by blasting and may be mirror finished. In the heating, the inner surface of the mold is gradually heated to reach about 100 to 190 ° C., preferably about 110 to 130 ° C. (first heating stage). The temperature raising rate may be about 1 to 2 ° C./min, for example. The belt is maintained at the above temperature for 20 minutes to 3 hours, and approximately half or more of the solvent is volatilized to form a self-supporting belt.

  Next, as the second stage heating, treatment is performed at a temperature of about 280 to 400 ° C. (preferably about 300 to 380 ° C.) to complete imidization. Also in this case, it is preferable not to reach this temperature from the first stage heating temperature all at once, but to gradually increase the temperature to reach that temperature. The second stage heating may be performed with the endless belt attached to the inner surface of the cylindrical mold, or after the first heating stage, the endless belt is peeled off from the mold and taken out and separately imidized. For heating to 280 to 400 ° C. The time required for this imidization is usually about 20 minutes to 3 hours.

  Similarly, when polyamide imide is used as the resin for the base material layer, diamine or diisocyanate derived from diamine and trimellitic acid are reacted in a solvent to directly form polyamide imide, and this is subjected to centrifugal molding to produce a joint. (Seamless) polyamideimide base material layer can be formed. In addition, in order to impart desired semiconductivity to the base material layer, a conductive agent such as carbon black as described above may be added to about 5 to 25 parts by weight with respect to 100 parts by weight of the base material layer resin as necessary. May be added.

  The base material layer formed using centrifugal molding is different from the cylindrical mold used for forming the surface layer and elastic layer described above in terms of the shrinkage rate of the raw material and the heat resistance temperature. It is preferable to use a film-dedicated mold.

  The Young's modulus of the polyimide or polyamideimide thus obtained by centrifugal molding is usually 2500 MPa or more.

  When polycarbonate, PVDF, polyamide, ethylene-tetrafluoroethylene copolymer or the like is used as the material for the base material layer, a seamless base material layer can be formed by melting and extruding these resins. You may add electrically conductive agents, such as above-mentioned carbon black, so that it may become about 5-25 weight part with respect to 100 weight part of base material layer resin.

  The resins that can be extruded are as described above. In this case, in order to maintain the performance as a substrate, a material having a Young's modulus of 1000 MPa or more, preferably 1500 MPa or more can be selected.

The volume resistivity of the base layer, from the viewpoint of performing transfer by electrical control of the toner as a belt substrate, usually 10 ⁴ ~10 ^12.5 Ω · cm approximately, - preferably 10 ⁹ to 10 ^12.5 Omega It is about cm.

As described above, a base material layer having a seamless high strength can be obtained.
V. Formation of multilayer elastic belt (three layers)
Finally, a first belt composed of two layers, ie, a surface layer and an elastic layer, which are separately formed by centrifugal molding in the above III and IV, and a base material composed of a high-strength resin material The second belt, which is a layer, is overlaid so that the inner surface (the elastic layer side surface) of the first belt and the outer surface of the second belt are in contact with each other. You may apply | coat an adhesive agent and a primer between both as needed. After the superposition of both, it is preferable that the space between the two is sealed. Thereafter, the laminate is heat-treated to obtain an endless three-layer elastic belt in which the inner surface of the elastic layer and the outer surface of the base material layer are bonded.

  Specific examples of the three-layer process will be given. A laminate adhesive is uniformly applied to the inner surface (surface on the elastic layer side) of the two-layer film composed of the surface layer and the elastic layer formed in a state regulated by the inner surface of the cylindrical mold subjected to the blasting of I above. Air dry. After applying the primer to the outer surface of the base material layer formed with another dedicated cylindrical mold in the above IV and air-drying it, it is superimposed on the inner surface of the elastic layer, so that the position does not shift on the inner surface of the base material layer. Insert the inner mold that is in close contact.

  Thereafter, heat treatment is carried out at about 100 ° C. for about 20 to 60 minutes, and interlayer adhesion is completed simultaneously with the curing of the adhesive. If necessary, the three-layer belt after demolding may be further annealed by heating at about 120 ° C. for about 3 to 5 hours. Thus, the multilayer elastic belt of the present invention is obtained.

  Examples of the laminating adhesive include Takelac A-969 manufactured by Mitsui Chemicals Polyurethane Co., Ltd. and Tyforce NT-810 manufactured by Dainippon Ink & Chemicals, Inc. In addition, although use of said primer is arbitrary, it is preferable to use from the point of an adhesive strength improvement. Examples of the primer include DY39-067 manufactured by Toray Dow Corning Co., Ltd.

  Since the multilayer elastic belt of the present invention has a surface resistivity larger than its volume resistivity, the toner does not scatter due to good transfer electrolysis, and the high-definition characteristic of the rubber elasticity imparting belt does not occur. It can be used as a semiconductive belt from which an image can be obtained.

  As described above, the multilayer elastic belt of the present invention is suitably used as an electrophotographic belt such as an intermediate transfer belt, a transfer conveyance belt, a paper conveyance belt, or a transfer fixing belt used in an image forming apparatus.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example with a comparative example, this invention is not limited to these Examples.

The following evaluation described in this specification was performed as follows.
<Base layer solid content concentration>
The sample is precisely weighed in a heat-resistant container such as a metal cup, and the weight of the sample at this time is Ag. Put the heat-resistant container containing the sample in an electric oven, heat and dry while heating up in order of 120 ℃ × 12min, 180 ℃ × 12min, 260 ℃ × 30min, and 300 ℃ × 30min. The weight of the solid content (solid content weight) is Bg. The values of A and B of five samples of the same sample were measured (n = 5) and applied to the following formula (I) to determine the solid content concentration. The average value of the five samples was adopted as the solid content concentration.

Base material layer solid content concentration = B / A x 100 (%) (I)
<Surface layer and elastic layer solids concentration>
The raw material is precisely weighed, and the weight of the solid or liquid raw material at this time is Cg. In order to dissolve the raw material in the solvent on the electronic balance, the solvent is gradually added while stirring, and the final solution weight is set to Dg. The solid content concentration is represented by the following formula (II).

Elastic layer solid content concentration = C / D x 100 (%) (II)
<Thickness>
The thickness was measured as a mean value by measuring a total of 24 points of 3 points in the width direction and 8 points in the circumferential direction using a flat probe of a contact-type film thickness measuring instrument.
<Surface resistivity, volume resistivity>
Surface resistivity (Ω / □) and volume resistivity (Ω · cm) were measured at 23 ° C and 55% RH using a resistance meter “HIRESTA UP / UR Blob” manufactured by Mitsubishi Chemical Corporation. It was measured. A belt cut to a length of 360 mm in the width direction is used as a sample, and the surface resistivity is 10 seconds after an applied voltage of 100 V at a total of 12 points in the width direction of the sample, 3 places at equal pitch and 4 places in the longitudinal (circumferential) direction. The volume resistivity was measured and the average logarithmic value was shown as a common logarithm value.
The measurement sample was measured after standing for 12 hours in an environment of 23 ° C. and 55% RH.
<Static friction coefficient>
The static friction coefficient was measured using 10 different surface parts within the same belt using Heidon 94i manufactured by Shinto Kagaku Co., Ltd., and the average value was taken as the static friction coefficient.
<Surface roughness (Ra) and (Rz)>
The surface roughness (μm) was measured according to JIS B0601-1994. As a measuring instrument, Surfcom 480A manufactured by Tokyo Seimitsu Co., Ltd. was used. The measurement conditions were CUTOFF 0.25, measurement length 2.5 mm, and T-SPEED 0.06 mm / s. Five different surface portions were measured in the same belt, and the average value was defined as the surface roughness. Ra means arithmetic average roughness, and Rz means ten-point average roughness.
<Rubber material hardness>
In accordance with JIS K6253, a durometer A was used to create and evaluate a bulk (lumb) having a thickness of 6 mm from the material constituting the elastic layer.
<Surface layer composition fluororesin material hardness>
According to JIS K7202, the measurement was performed with a Rockwell tester using an R scale.

Example 1
(1) Film formation of the base material layer Under nitrogen flow, 47.6 g of 4,4'-diaminodiphenyl ether (ODA) is added to 488 g of N-methyl-2-pyrrolidone, and kept at 50 ° C. and stirred until completely dissolved. It was. To this solution, 70 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was gradually added to obtain 605.6 g of a polyamic acid solution. This polyamic acid solution had a number average molecular weight of 17000, a viscosity of 35 poise, and a solid content concentration of 18.0% by weight.

  Next, 21 g of acidic carbon (pH 3.0) and 80 g of N-methyl-2-pyrrolidone were added to 450 g of this polyamic acid solution, and carbon black (CB) was uniformly dispersed with a ball mill. This master batch solution had a solid content concentration of 18.5% by weight and a CB concentration in the solid content of 20.6% by weight.

  And 276g was extract | collected from this solution, the cylindrical metal mold | die for base-material shaping | molding was prepared, and it shape | molded on the following conditions.

  Base mold: A cylindrical mold with an inner diameter of 301.5 mm and a width of 540 mm, with a mirror finish on the inner surface. The mold is placed on two rotating rollers and rotates with the rotation of the rollers. Arranged. For example, see FIG.

  Heating device: A device designed so that a far-infrared heater is disposed on the outer surface of the mold, and the inner surface temperature of the mold is controlled to 120 ° C.

  First, 276 g of the solution was uniformly applied to the inner surface of the mold while the cylindrical mold was rotated, and heating was started. The heating was performed at a temperature of 1 ° C./min up to 120 ° C., and heating was performed at that temperature while maintaining its rotation for 60 minutes.

After completion of the rotation and heating, the mold was removed as it was without cooling, and left in a hot air retention type oven to start heating for imidization. This heating also reached 320 ° C. while gradually raising the temperature. And after heating for 30 minutes at this temperature, it cooled to normal temperature, peeled and took out the semiconductive tubular polyimide belt formed in this metal mold | die inner surface. The belt had a thickness of 80 μm, an outer peripheral length of 944.3 mm, a surface resistivity of 12.85 (logΩ / □), and a volume resistivity of 10.68 (LogΩ · cm).
(2) Inner surface treatment of mold In the cylindrical mold used for centrifugal molding of the surface layer and the elastic layer in the present invention, the inner diameter and the outer diameter from the cylindrical body of S45C are coarsely ground with a lathe, and the inner diameter is honed and Finish grinding was applied to hard chrome plating to a thickness of 20 to 25 μm.

  Then, while rotating the mold, shot blasting # 220 silicon carbide uniformly on the inner surface of the mold by moving the gun nozzle in the mold axis direction, and then shot blasting the # 300 ceramic media again in the same way .

Thus, a cylindrical metal mold with a final inner diameter of 301.0 mm and a width of 540 mm and an internal blast finish was completed. The surface roughness (Ra) of the finished mold inner surface was 0.51 μm.
(3) Surface layer deposition
30 g of PVDF resin (KF polymer # 850, manufactured by Kureha Co., Ltd.) was dissolved in a mixed solvent of 270 g of N, N-dimethylacetamide (DMAc) and 300 g of methyl ethyl ketone (MEK) to prepare a solution having a solid content concentration of 5 w%.

  And 58g was extract | collected from this solution, and it shape | molded on the following conditions with the metal mold | die of said (2).

  Molding apparatus: The mold having an inner diameter of 301.0 mm and a width of 540 mm was placed on two rotating rollers and arranged to rotate with the rotation of the rollers. For example, see FIG.

While the mold was rotated, it was uniformly applied to the inner surface of the mold and heating was started. Heating was performed at 2 ° C./min up to 130 ° C., and heating was continued for 20 minutes while maintaining the rotation. After forming a surface layer on the inner surface of the die, the die was cooled to room temperature. The thickness of the surface layer formed on the inner surface of the mold was measured with an eddy current thickness gauge and found to be 3 μm.
(4) Formation of elastic layer Add 250 g of acidic carbon (pH 3.5) to a solution of 1000 g of polyurethane elastomer (Urehyper RUP, manufactured by Dainippon Ink & Chemicals) in 1250 g of toluene, and uniformly disperse with a ball mill. A master batch solution having a solid concentration of 50% by weight and a carbon black (CB) concentration of 20% by weight in the solid content was prepared. To 204 g of this master batch, 2.41 g of the curing agent CLH-1 and 3.26 g of CLH-5 (both curing agents are manufactured by Dainippon Ink & Chemicals, Inc.) were added and stirred.

  This solution was uniformly applied to the inner surface of the surface layer on which the film had been formed in a state where the mold was rotated, and heating was started. Heating was carried out at 2 ° C./min up to 130 ° C., and heating was continued for 30 minutes at that temperature to form an elastic layer on the inner surface of the mold.

As a preliminary test, the rubber hardness of a urethane rubber single film prepared with this urethane rubber masterbatch solution was measured and found to be 63 ° with Type A (JIS K6253).
(5) Bonding of inner surface of elastic layer and outer surface of base material layer After applying primer DY39-067 (manufactured by Dow Corning Toray Co., Ltd.) to the inner surface of the elastic layer formed in (4) above, air-drying, and then dry dry adhesive The polyimide belt (base material layer) of (1) having a thin coating on the outer surface (Takelac A-969 manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) was inserted and overlapped. Next, heating (80 to 100 ° C.) was performed in a state where the substrate was pressure-bonded from the inner surface of the substrate to complete the bonding. The laminated multilayer belt was peeled off from the mold, both ends were cut, and a multilayer belt having a width of 360 mm was collected.

  The multilayer belt had a thickness of 284 μm, an outer peripheral length of 945.0 mm, a surface resistivity of 12.49 (logΩ / □), and a volume resistivity of 11.67 (LogΩ · cm).

Example 2
VDF-HFP copolymer resin, which is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), instead of the PVDF resin (KF polymer # 850, manufactured by Kureha Co., Ltd.) in Example 1 (3) A multilayer belt was produced in the same manner as in Example 1 except that (Kayner # 2851, manufactured by Arkema: 5 mol% of HFP) was selected.

Example 3
In Example 2, only (2) the blast count of the inner surface treatment of the mold was changed. That is, the silicon carbide was changed from # 220 to # 60, the ceramic media was changed from # 300 to # 400, and shot blasting was performed in the same manner. The surface roughness (Ra) of the finished mold inner surface was 0.97 μm. Except for the above, a multilayer belt was produced in the same manner as in Example 2.

Comparative Example 1
A multilayer belt was produced in the same manner as in Example 1 except that the inner surface of the mold of Example 1 (2) was left with a mirror finish without blasting and the mold was used. The surface roughness (Ra) of the inner surface of the mirror finish mold was 0.08 μm.

Comparative Example 2
A multilayer belt was produced in the same manner as in Example 1 except that the inner surface of the mold of Example 2 (2) was left with a mirror finish without blasting and the mold was used. The surface roughness (Ra) of the inner surface of the mirror finish mold was 0.08 μm.

Table 1 shows the results of image evaluation of each sample multilayer belt incorporated in the transfer unit.
<Primary transfer properties>
The primary transferability was evaluated by observing the voids in the thin line image on the transfer belt before the secondary transfer. The thin line was observed with a laser microscope at a magnification of 300 times with solid images of two colors Y and M parallel to the transfer belt travel direction of about 0.05mm. It was evaluated according to the following criteria.

  ○: There is no void.

  (Triangle | delta): A void is 1-4 places.

X: Five or more hollows exist.
<Secondary transfer properties>
As for secondary transferability, a follow-up test of paper unevenness by observation of image omission by solid printing and the presence or absence of squeal of the cleaning blade were evaluated.
<Followability of paper unevenness>
Using “Rezak 66” (surface roughness difference 80μm, 151g / m ² ) of Fuji Xerox Office Supply Co., Ltd. as a paper with large irregularities, transfer Y, M, C color solid images to transfer secondary transfer efficiency. The toner weight on the transfer belt before and after transfer was measured and calculated from the following formula.

Transfer efficiency (%) = 100 × [(toner weight before transfer) − (toner weight after transfer)] / (toner weight before transfer)
○: Secondary transfer efficiency 95% or more △: Secondary transfer efficiency 90% or more to less than 95% ×: Secondary transfer efficiency less than 90% <blade squeal>
30,000 sheets were passed and blade squeal and damage were observed.

○: No blade squeezing until 30,000 sheets passed △: Blade squeaking occurs when 10,000 to less than 30,000 sheets are passed ×: Blade squeaking occurs when less than 10,000 sheets are passed. In the example, even if a hard R110 surface layer material is used, the thin part of the surface layer is locally deformed and can follow the toner, so there is no defect in the thin line in the primary transfer, and on the contrary, a soft R75 surface layer material is used. However, since the coefficient of friction was low due to the unevenness of the surface, toner transfer to the paper in the secondary transfer and blade squealing in the cleaning did not occur.

  In Comparative Example 1, since the surface was hard, thin line hollows occurred. In Comparative Example 2, since the surface was soft and tacky, the toner did not transfer onto the paper well, and the cleaning blade squeezed because the friction coefficient was high.

  As described above, the multilayer elastic belt of the present invention has a surface layer having irregularities and is locally deformed, so that even if a hard resinous surface layer material is used, the softness of the elastic layer can be counteracted. As a result, there was obtained a primary transfer characteristic in which fine line printing was clear without image hollowing out. Even when a surface layer material made of a soft resin is used or when the surface layer is thin, the friction coefficient increases if the normal inner surface is a mirror mold, but the belt of the present invention has an uneven surface. Thus, the surface friction coefficient can be lowered, and secondary transfer characteristics with good releasability and cleanability can be obtained. Thus, it has been proved that the optimum balance between the primary transfer and the secondary transfer can be pursued regardless of the hardness of the material constituting the surface layer, so that it can be suitably used as an intermediate transfer belt or the like.

It is a cross-sectional schematic diagram of the three-layer elastic belt of this invention. It is a schematic diagram of the apparatus used for film forming of each layer in an Example. It is a comparison schematic diagram when the surface which has an unevenness | corrugation, and the smooth surface receive stress.

Claims (7)

A multilayer elastic belt for an electrophotographic apparatus comprising at least three layers of a surface layer containing a releasable material, an elastic layer containing an elastic rubber material, and a base material layer containing a high-strength resin material in order from the surface side,
The surface layer has an uneven surface transferred from a mold surface having an uneven surface, the surface roughness (Ra) of the uneven surface is in the range of 0.1 to 1.5 μm, and Rockwell hardness (R Scale) is a layer containing a fluororesin material of 110 degrees or less, and the thickness is 1 to 3 μm .
A multilayer elastic belt for an electrophotographic apparatus. The surface layer and the elastic layer are formed on the inner surface of the same cylindrical mold by rotation molding in the order of the surface layer and the elastic layer, and the inner surface of the cylindrical mold has an uneven surface by blasting. Multilayer elastic belt for electrophotographic equipment. The multilayer elastic belt for an electrophotographic apparatus according to claim 1, wherein a static friction coefficient of the uneven surface of the surface layer is 0.8 or less. The multilayer elastic belt for an electrophotographic apparatus according to claim 1, wherein the elastic layer is a layer containing a polyurethane elastomer material. The multilayer elastic belt for an electrophotographic apparatus according to any one of claims 1 to 4, wherein a material of the base material layer is polyimide or polyamideimide. The multilayer elastic belt for an electrophotographic apparatus according to claim 1, wherein the belt has an endless shape. A method for producing a multilayer elastic belt for an electrophotographic apparatus,
(1) forming a surface layer containing a releasable material having an uneven surface by rotational molding using a cylindrical mold having an uneven surface on the inner surface;
(2) Forming an elastic layer further containing an elastic rubber material on the inner surface of the surface layer by rotational molding to produce a first belt comprising at least two layers of the surface layer and the elastic layer;
(3) The process of manufacturing the 2nd belt which consists of a base material layer containing a high-strength resin material by rotational molding using another cylindrical mold,
(4) including a step of manufacturing a multilayer elastic belt for an electrophotographic apparatus by bonding the elastic layer side of the first belt and the second belt;
The surface layer is a layer containing a fluororesin material having a surface roughness (Ra) of an uneven surface of 0.1 to 1.5 μm, a Rockwell hardness (R scale) of 110 degrees or less, and a thickness of 5 μm or less. is there,
The manufacturing method characterized by the above-mentioned.

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