JP2007183401A - Intermediate transfer belt formed of multiple layer and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an intermediate transfer belt on which the state that a cleaning blade is wound does not occur even in a high temperature and high humidity environment so that stable toner cleaning performance is exhibited with good productivity at a low cost, and to provide a high performance image forming apparatus equipped with the intermediate transfer belt. <P>SOLUTION: The belt for electrophotography comprises a base layer comprising a thermoplastic resin and a resin cured film disposed on the base layer by coating, containing conductive particles and having a thickness of 0.5-3 μm, wherein when a surface roughness of the cured film is represented by Rz, a relationship of 0.2≤Rz≤0.5 is satisfied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an intermediate transfer belt used in an image forming apparatus using an electrophotographic system or an electrostatic recording system, and an image forming apparatus using the intermediate transfer belt. The present invention relates to a transfer material carrying member for transferring a toner image on an image carrier to a transfer material, an intermediate transfer member for transferring a toner image on an image carrier, and an image forming apparatus having the transfer material carrying member or the intermediate transfer member. It is. Examples of such image forming apparatuses include black and white, mono-color or full-color electrophotographic copying machines, printers, and various other recording machines.

  Conventionally, there are various intermediate transfer belts used when transferring an image to a transfer material, such as forming a base layer material in multiple layers as disclosed in Patent Document 1. For example, in an electrophotographic apparatus having image forming means such as (charging)-(image exposure)-(toner development)-(transfer)-(cleaning), a toner image on a photosensitive member is transferred to a transfer material (for example, paper). Examples of the means for transferring include a transfer device as shown in FIG. 1 that forms an image by transferring a toner image onto a transfer material from an intermediate transfer member. Further, as disclosed in Patent Document 2 and Patent Document 3, the surface layer for improving the wear resistance and durability of the intermediate transfer member is also formed as shown in FIG. Has been done.

  On the other hand, as shown in Patent Document 4, cleaning is performed by scraping residual particles such as toner and ferrite after transfer with a blade-like member made of urethane resin or the like. In this case, in order to improve the cleaning performance of the toner, there is an example in which an upper limit value of the friction coefficient between the belt surface and the blade is defined. It is common to increase the sliding property of the blade and reduce the coefficient of friction between the coating surface and the blade. However, when the hard coat surface is excessively mirror-finished, particularly the high adhesion between the coating surface and the cleaning blade becomes a problem under high temperature and high humidity, and the cleaning blade is caught inside as the belt rotates. May occur.

In addition, as a prior art that defines the material of the multilayer belt and the surface roughness, as described in Patent Document 5, the transfer substrate is coated with a water-based emulsion paint containing a fluororesin, and the transfer member has an Rz of 10 to 10. It has been proposed to be in the range of 30 μm.
JP 2000-56585 A Japanese Patent Laid-Open No. 08-278708 JP 2000-330390 A JP 2001-042658 A JP 2002-072698 A

  In the transfer process in the image forming apparatus as described above, since various mechanical or electrical external forces such as transfer charging, static elimination, and cleaning are applied to the transfer member, durability against these external forces, that is, mechanical strength and wear resistance. Various characteristics such as property and electrical durability are required.

  However, in the above-described conventional technology, there is a big problem in durability of the transfer member unless a surface layer is provided for almost all resins except for some resins having a high Young's modulus such as polyimide. This is because when toner is transferred to the transfer member, ferrite, magnetic powder, inorganic fine particles, etc. are mixed in the toner in order to improve the charging and transportability of the toner and improve the transfer efficiency. By performing cleaning and subsequent transfer without completely recovering the particles, scratches due to residual particles occur. This is because the durability of the transfer member is lowered, and the image characteristics and cleaning properties are adversely affected. For this reason, the present condition is that the resin which can be used alone as a base material is very limited.

  Therefore, as shown in the background art, wear resistance and durability are improved by providing a hard coat surface layer on the surface of a material with poor durability.

  The toner image of the electrophotographic belt and the transfer material carrying surface should be resistant to wear so that the physical properties of the surface and the electrical characteristics of the electrophotographic belt will not change due to wear. It is required to have excellent properties. An example of a material that satisfies both of these at a high level is polyimide resin. However, polyimide resin is very expensive. Accordingly, in order to obtain a lower cost electrophotographic belt, the present inventors have an electrophotographic intermediate transfer belt having a surface layer with excellent wear resistance on a flexible base layer containing a thermoplastic resin. We have intensively studied for the purpose of providing.

  According to the present invention, in order to achieve the above-mentioned object as a transfer member, a resin layer having a thickness of 0.5 to 3 μm including a base layer containing a thermoplastic resin and conductive particles provided on the base layer by coating. An electrophotographic belt comprising a film, wherein the cured film satisfies the relationship of 0.2 ≦ Rz ≦ 0.5, where Rz is the surface roughness of the cured film, and the cured film comprises pentaerythritol hexaacrylate and conductive particles. An intermediate transfer belt, which is a cured film of a coating solution containing, was prepared.

  Further, the mass reduction rate after the Taber abrasion test (ASTM-D-1175, load 500 g, 500 revolutions) on the resin cured film surface is made 0.10% or less, and the base layer is made of polyvinylidene fluoride (PVdF) resin. An intermediate transfer belt was produced, and an image forming apparatus provided with the intermediate transfer belt was completed.

The following is achieved by the present invention.
(1) Sufficient durability against various external forces such as mechanical strength, wear resistance and electrical durability.
(2) By defining the surface roughness of the belt surface layer material, the adhesion between the belt surface layer and the cleaning blade is reduced even at high temperatures and high humidity, preventing blade entrainment due to the rotation of the belt. To achieve stable toner cleaning performance over a period of time.
(3) The cost is lower than that of an intermediate transfer belt made of polyimide, which is a transfer belt material mainly used conventionally.

  In the present invention, any film material that can be used as the base layer is suitable for use as long as it is a thermoplastic resin material. That is, polycarbonate, polyvinylidene fluoride (PVdF) resin, polyethylene, polypropylene, polymethylpentene-1, polystyrene, polyamide, polysulfone, polyarylate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyethersulfone, polyethernitrile, All thermoplastic resin materials such as thermoplastic polyimide materials, polyether ether ketone, thermotropic liquid crystal polymer, polyamic acid, and mixed resins thereof, and thermoplastic elastomers formed from the mixed resins can also be used. In the present invention, a film formed from the above thermoplastic resin material or a film reinforced by stretching at various magnifications can be used as the sheet-like film of the present invention.

In addition, at least one kind of fine powder of an organic substance or an inorganic substance is blended with the above-described various resin materials for the purpose of imparting heat resistance reinforcement, conductivity or thermal conductivity.

  Examples of fine organic powders include condensed polyimide powders and ion conductive materials, and fine inorganic powders include carbon black powder, magnesium oxide powder, magnesium fluoride powder, silicon oxide powder, and aluminum oxide powder. Inorganic spherical fine particles such as boron nitride powder, aluminum nitride powder, and titanium oxide powder can be used. Furthermore, fibrous particles such as carbon fiber and glass fiber, whisker-like powders such as potassium titanate, silicon carbide, silicon nitride, etc. Fine powders of any shape and size can be used. Particularly preferably, the fine powder has a spherical shape and a particle size of 1.0 μm or less in order to maintain the surface smoothness of the added resin material.

  The kind, particle size, and content of such fine powder are not particularly limited as long as the above-mentioned heat resistance reinforcement and conductivity can be supported on the base layer. However, the blending amount of these fine powders is preferably about 5 to 70% by mass, particularly 5 to 10% by mass with respect to the base resin in terms of the total amount in consideration of the flex resistance, strength, and thermal conductivity of the base layer. .

  On the other hand, it is proposed that a resin that is cured by heat, light, electron beam irradiation, or the like is provided on the base layer as a surface layer material. The surface layer material that can be used in the present invention can be arbitrarily selected according to required properties such as surface hardness and durability, and any material can be used as long as it falls within the category of hard coat. That is, examples of the organic material include melamine-based, urethane-based, alkyd-based, acrylic-based, and fluorine-containing resin-based materials. As the inorganic-based materials, alkoxylane / alkoxyzirconium-based materials and silicate-based materials are preferable. On the other hand, as the organic / inorganic hybrid system, inorganic fine particle acrylic radical system, inorganic fine particle dispersed organic polymer system, inorganic fine particle dispersed organoalkoxysilane system, acrylic silicon system, organoalkoxysilane system and the like can be used. However, some silicon-based and fluorine-based materials have low surface hardness, and if such a material is used as a transfer support member, the material will be scraped with use, causing problems in durability. Caution must be taken. Among these, an acrylic type containing dipentaerythritol hexaacrylate can be mentioned as a particularly preferable material because of its high surface hardness and excellent wear resistance.

  The acrylic monomer may be dipentaerythritol hexaacrylate alone or as a mixture as long as desired surface hardness and abrasion resistance can be obtained. For example, an acrylic ultraviolet curable hard coat material containing dipentaerythritol hexaacrylate (Desolite: manufactured by JSR Corporation).

  The surface layer was prepared as follows and cured.

(I) Surface layer forming coating solution In a container shielded from ultraviolet rays, zinc antimonate isopropyl alcohol sol (trade name: Celnax; manufactured by Nissan Chemical Co., Ltd.) 12 parts by mass as a conductive filler, After mixing 50 parts by mass of an acrylic UV curable hard coat material containing dipentaerythritol hexaacrylate (Desolite: trade name: manufactured by JSR Corp.), 38 parts by mass of methyl isobutyl ketone was added to the UV curable resin composition. I got a thing.

(Ii) Preparation of electrophotographic belt The surface layer forming coating solution prepared in (i) above was applied to the surface of the base layer under the environment of a temperature of 40 ° C. and a relative humidity of 10% RH by the dip coating method. After forming a thin film of the coating solution for forming the surface layer and drying the thin film for 30 seconds in the above environment, the thin film is irradiated with a UV irradiator (trade name: UE06 / 81-3; Eye Graphic Co., Ltd.) The surface layer according to the present invention having a thickness of 1 μm was formed by curing the thin film by irradiating with ultraviolet rays using an integrated light quantity of 1200 mJ / cm ² .

On the other hand, assuming that the surface roughness is Rz, the surface roughness of the surface layer material is 0.2 ≦ Rz ≦ 0.5 from the viewpoint of both prevention of blade entrainment and toner cleaning properties accompanying rotation of the intermediate transfer belt. More preferably, 0.25 ≦ Rz ≦ 0.40.
In addition, the surface roughening was performed by two kinds of methods of (1) blasting with glass beads and (2) surface polishing with a wrapping film as described in Examples.

  Furthermore, it is necessary to add a conductive filler in the surface layer material. Any conductive filler is suitable for use as long as resistance control is possible. That is, carbon black or powder such as silver, nickel, copper, zinc, iron, fiber, flaky metal system, and fine metal such as antimony-doped tin oxide, tin-doped indium oxide, aluminum-doped zinc oxide Oxide systems can be used.

Among these, in the present invention, a particulate metal oxide that can be added in a small amount and can obtain surface smoothness of the surface layer is particularly suitable. Further, the thickness of the surface layer is 0.5 μm to 10 μm, preferably 1.0 μm or more and 3.0 μm or less, and its wear resistance is ASTM-D-1175 Taber abrasion test (abrasion wheel CS-10F, (Load 500g 500 rotations) It is preferable that the rate of mass reduction after the test is 0.10% or less.
Further, the base layer is made of PVdF resin, and the resin belt can be used as an intermediate transfer belt for an image forming apparatus.

  EXAMPLES Hereinafter, although an Example is given and this invention is explained in full detail, this invention is explained in full detail, but this invention is not necessarily limited to these.

(Example-1)
(I) Preparation of base layer Including an ion conductive material having a thickness of 50 μm, volume resistivity ρv = 2.5 × 10 ⁹ (Ω · cm), and surface resistivity ρs = 1.8 × 10 ¹¹ (Ω / □) A film made of polyvinylidene fluoride resin was prepared by extrusion. A cylindrical endless belt having a thickness of 100 μm was prepared from this film according to the method described in Example 1 of JP-A No. 2002-326287.

(Ii) Coating liquid for surface layer formation In a container shielded from ultraviolet rays, a conductive filler consisting of 12 parts by mass of isopropyl alcohol sol of zinc antimonate (trade name: Celnax; Nissan Chemical Co., Ltd.) After mixing 50 parts by mass of an acrylic UV curable hard coat material (Desolite: manufactured by JSR Corporation) containing dipentaerythritol hexaacrylate, 38 parts by mass of methyl isobutyl ketone was added to the UV curable resin composition. Got. In addition, the dispersion stability of the conductive filler of the obtained composition was good.

(Iii) Preparation of electrophotographic belt The surface layer forming coating solution prepared in (ii) above was applied to the surface of the base layer prepared in (i) above in an environment of a temperature of 40 ° C. and a relative humidity of 10% RH. Then, a thin film of a coating solution for forming a surface layer is formed by applying a dip coating method, and the thin film is dried for 30 seconds in the above environment, and then a UV irradiator (trade name: UE06 / 81-3) is applied to the thin film. A surface layer according to the present invention having a thickness of 1 μm was cured by irradiating with ultraviolet rays using Igraphic Co., Ltd. (integrated light amount: 1200 mJ / cm 2).

  Thereafter, the obtained resin belt was held on a cylindrical holder, and 20 μm glass beads were sprayed while rotating to give fine polishing marks on the surface of the belt surface layer material. The surface roughness of the belt thus obtained was 0.4 μm in Rz in the width direction.

  In this measurement, a known stylus type surface roughness measuring machine (manufactured by Tokyo Seimitsu Handysurf E-35A) is used, and the measurement conditions are based on JIS B0601-1994, evaluation length = 4.0 mm, cut-off value = Measurements were taken at 0.8 mm.

  The surface abrasion of the surface layer of the electrophotographic belt according to the present invention thus obtained was evaluated by a Taber abrasion test (ASTM-D-1175, load 500 g, 500 revolutions). As a result, the mass reduction rate of the electrophotographic belt was 0.050%.

  Next, an example of the usage pattern of the obtained resin belt will be described. In this embodiment, rubber rib members (not shown) for preventing meandering are adhered to both ends in the width direction of the resin belt obtained by the above-described method, and the image forming apparatus (copying machine, laser shown in FIG. 1) is bonded. Used as a transfer belt 10 for conveying a toner carrier and transferring an image of a beam printer or the like.

The image forming apparatus shown in FIG. 1 has a rotatable photosensitive drum 1, and around the photosensitive drum 1, a charging charger 2, an optical writing device 3 using laser light, and a developing device for containing toner. 4 are arranged. Further, the transfer belt 100, which is the resin belt of the present invention described above, is stretched across four rollers (only two rollers 6 and 7 are shown in FIG. 1) and is disposed sideways. A transfer charger 11 is provided in the vicinity of a part of the belt 10.

On the other hand, the toner not transferred to the transfer paper 13 but remaining on the belt is scraped off by the cleaning blade 14, and the belt is returned to the photosensitive drum side without the toner.
In the image forming apparatus having such a configuration, the photosensitive drum 1 is rotationally driven in the arrow direction at a constant speed Vf. First, the surface of the photosensitive drum 1 is uniformly charged by the charging charger 2 and an electrostatic latent image is formed by the optical writing device 3 using laser light. Then, the toner 5 charged with charge from the developing device 4 adheres to the electrostatic latent image portion, and is visualized as a toner image.

  On the other hand, like the photosensitive drum, the transfer belt 10 circulates in the direction of the arrow at a constant speed Vf. When the transfer belt 10 reaches the transfer region, the toner 5 visualized on the photosensitive drum 1 is transferred to the transfer belt 10 by the transfer charger 11. Transcribed. Thereafter, the transferred toner is further conveyed to the downstream side (left side in FIG. 1) while being adsorbed on the belt, transferred to the transfer paper 13 by the secondary transfer roller 12, and onto the transfer paper by a fixing device (not shown). The toner image is fixed.

  In the above-described configuration, when the transfer belt 10 obtained as described above is used as the transfer belt 10 of a commercially available image forming apparatus, the contact surface area between the belt surface layer material and the clean blade is reduced due to the surface shape processing. By reducing the adhesion, the blade was not caught by the rotation of the belt even in a high temperature and high humidity environment (30 ° C./80%). On the other hand, since the sliding property between the belt and the blade was improved by reducing the contact area, the toner cleaning performance was not deteriorated even after passing 100,000 sheets, and all the remaining toner was removed from the belt by the blade. Further, in this embodiment, as a result of adjusting both the base layer material and the surface layer material of the transfer belt to the optimum resistance value, it is possible to obtain a high-definition image without causing toner scattering.

(Example-2)
In this example, the wrapping film polishing process was performed for the shape processing of the belt surface layer material instead of the blasting process using the glass beads shown in the first example. Specifically, the obtained resin belt is held by a cylindrical holder and pressed against a wrapping film (Imperal wrapping film sheet: manufactured by Sumitomo 3M Co., Ltd.) in which 12 μm aluminum oxide abrasive grains are dispersed. By rotating the belt, regular streaks were imparted to the surface material surface in the circumferential direction of the belt. Rz in the width direction of the obtained belt was 0.3 μm. In this example, all the manufacturing steps except for using the wrapping film for the belt surface shape processing are substantially the same as those in Example 1.

  In addition, the rough surface shape given by the blasting process of Example 1 was random in the belt circumferential and width directions, whereas in the present embodiment, the belt was fixed to the holder and rotated. The surface roughening direction to be applied was a constant direction only in the belt circumferential direction in that the surface shape was formed using the wrapping film. This direction coincides with the belt rotation direction, and the lapping process can form a surface shape in a uniform depth and width direction as compared with the blast process, so that the entire in-belt plane is more than in the first embodiment. The cleaning performance with the blade was improved over the entire period.

  Here, when the transfer belt obtained in the same manner as in Example 1 was used as a transfer belt of a commercially available image forming apparatus, toner scattering did not occur and a high-definition image could be obtained. Further, the cleaning performance of the residual toner on the belt in the actual machine has a slight cleaning defect after passing 100,000 sheets in the first embodiment, whereas a cleaning defect or the like occurs after passing 200,000 sheets in this embodiment. It was confirmed that by forming the belt surface rough with a wrapping film, a uniform rough shape could be given in a certain direction, and the belt durability performance in the actual machine was improved. Furthermore, as a result of obtaining a uniform rough shape as compared with Example 1, there was little damage to the cleaning blade as the counterpart member, and the blade was worn and chipped even after passing 200000 sheets as in Example 1. Compared to very few.

(Comparative Example-1)
The comparative example of a 1st Example is shown below. In this example, the material, the added amount, the coating film thickness, and the coating method are all the same as in Example 1 except that the belt surface roughening by blasting described in Example 1 is not performed. The surface roughness of the belt surface used in this comparative example was Rz = 0.05 μm. In this comparative example, since the surface of the belt was not roughened, the evaluation of the actual machine showed that the belt and the cleaning blade were poorly slidable, and as a result, all the residual toner on the belt could not be scraped off by the cleaning blade. From the initial stage of evaluation, a small amount of toner remained on the belt, resulting in poor cleaning. When 150 sheets were further passed, the blade was damaged due to the rotation of the belt due to the high adhesion between the belt and the blade, and the blade was damaged.

(Comparative Example-2)
The materials, coat film thickness, coating method, and surface shape imparting method used in this example are all in Example 2.
In this comparative example, a wrapping film in which 50 μm aluminum oxide abrasive grains were dispersed was used as the wrapping film. The surface roughness of the belt surface thus obtained was Rz = 1.0 μm. When this is used as the transfer belt in FIG. 1, the toner remaining on the belt after the transfer enters the rough groove shape, so that the toner remains on the belt over the entire surface of the belt, and an apparent cleaning failure is evaluated. Occurs from the early stages.

  As described above, in the surface layer containing a curable resin obtained by curing a composition containing dipentaerythritol hexaacrylate, extremely excellent results were obtained by adjusting the surface roughness.

  The results of Examples and Comparative Examples are shown in Table 1 below.

It is explanatory drawing of the image forming apparatus which used the tubular film in Example 1 of this invention as a transfer belt. FIG. 2 is a schematic cross-sectional view of an intermediate transfer belt having a two-layer configuration of a base layer and a surface layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging charger 3 Optical writing device 4 Developer 5 Toner 6, 7 Drive roller
8, 9 Driving roller 10 Transfer belt 11 Charger 12 Secondary transfer roller 13 Paper (transfer paper)
14 Cleaning blade 15 Transfer belt base layer 16 Transfer belt surface layer

Claims (5)

  An electrophotographic belt comprising: a base layer containing a thermoplastic resin; and a cured resin film having a thickness of 0.5 μm or more and 3 μm or less including conductive particles provided on the base layer by coating, and the cured film An intermediate transfer belt satisfying a relation of 0.2 ≦ Rz ≦ 0.5, where Rz is the surface roughness of the toner.   The intermediate transfer belt according to claim 1, wherein the cured film is a cured film of a coating liquid containing pentaerythritol hexaacrylate and conductive particles.   The intermediate transfer belt according to claim 1 or 2, wherein the mass reduction rate after the Taber abrasion test (ASTM-D-1175, load 500 g, 500 revolutions) on the surface of the cured resin film is 0.10% or less.   4. The intermediate transfer belt according to claim 1, wherein the base layer is made of polyvinylidene fluoride (PVdF) resin in the electrophotographic belt. 5. An image forming apparatus comprising the intermediate transfer belt according to claim 1.

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