JP3943742B2 - Image forming apparatus and intermediate transfer belt - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an image forming apparatus using an electrophotographic system.And intermediate transfer beltIn particular, a copying machine, a printer, and a fax machine, in which a toner image formed on a first image carrier is once transferred onto an intermediate transfer member and then further transferred onto a second image carrier to obtain an image formed product. Image forming apparatus such asAnd intermediate transfer beltAbout.
[0002]
[Prior art]
  An image forming apparatus that uses an intermediate transfer member is a color image forming device that sequentially stacks and transfers a plurality of component color images of color image information and multicolor image information, and outputs an image formed product in which color images and multicolor images are synthesized and reproduced. It is effective as an apparatus, a multicolor image forming apparatus, or an image forming apparatus having a color image forming function and a multicolor image forming function.
[0003]
  In a color electrophotographic apparatus having an image forming apparatus using an intermediate transfer member, a second image support is pasted or adsorbed on a transfer drum, which is a conventional technique, and an image is transferred from the first image support to the second image support. A color electrophotographic apparatus having an image forming apparatus for transferring is superior to the transferring method described in, for example, Japanese Patent Laid-Open No. 63-301960 in the following points. That is, there is little color misregistration when the toner images of the respective colors are superimposed.
[0004]
  Next, as shown in a schematic diagram of an example of an image forming apparatus using an intermediate transfer belt as the intermediate transfer member in FIG. 1, the second image carrier is processed and controlled (for example, gripped by a gripper, adsorbed). The image can be transferred from the intermediate transfer member without the need for curvature, etc., so that the second image carrier can be selected from a wide variety.
[0005]
  For example, thin paper (40 g / m²Paper) to thick paper (200g / m²Paper), and transfer is possible regardless of whether the second image carrier is wide or short. Furthermore, it is possible to deal with envelopes, postcards, label paper, and the like.
[0006]
  In addition, since the intermediate transfer member is excellent in rigidity, it is difficult for dimensional accuracy such as dents, distortions and deformations to occur due to repeated use, and therefore the frequency of replacement of the intermediate transfer member can be reduced.
[0007]
  As described above, because of the advantage of using the intermediate transfer member, color copiers, color printers and the like using this image forming apparatus have already started to operate in the market.
[0008]
  However, when the image forming apparatus using the intermediate transfer member is actually repeatedly used, there are still the following problems.
[0009]
  In order to increase the transfer efficiency from the first image carrier, for example, the photosensitive drum to the intermediate transfer member, and the transfer efficiency from the intermediate transfer member to the second image carrier, for example, paper or an OHP sheet, When a mixture of a large amount of high-lubricating powder is used in the binder of the outermost layer of the intermediate transfer body using only a combination of the outer layer and the elastic layer, the transfer efficiency is improved, but a binder with high adhesiveness is used. However, the adhesion with the elastic layer may not be good. For this reason, the durability of about 3 to 40,000 sheets is maintained even in this state, but if the durability is further extended, the surface layer may be peeled off or cracked from the elastic layer. In some cases, the image is not sufficiently transferred, causing unevenness of the image due to insufficient transfer, or the cracked surface is transferred as it is without sufficiently transferring the cracked portion. As a result, the intermediate transfer member has to be replaced every 3 to 40,000 sheets, and the running cost may be high.
[0010]
  In addition, when a high-lubricant powder mixed in the outermost layer binder is used, the bleed material from the elastic layer passes through the interface between the binder and the highly-lubricated powder and contaminates the photoreceptor. An image defect may occur.
[0011]
  On the other hand, there has been a considerable disclosure of an invention using fluorine and silicone as a material for the surface layer of an intermediate transfer member, which has excellent releasability. For example, JP-A-57-869 discloses an intermediate transfer material treated with a fluorine-containing polymer compound, JP-A-57-163264, JP-A-59-91465, JP-A-6-301223. There are many disclosures such as an intermediate transfer member using a fluorine-based rubber and an elastomer, and an intermediate transfer member using a fluorine-based resin on the surface in Japanese Patent Application Laid-Open Nos. 58-90654 and 5-40417. In the case of silicone, in JP-A-57-23975, JP-A-57-164773, and JP-A-59-50473, an intermediate transfer member composed of a silicone rubber surface layer is disclosed in JP-A-5-46035. An intermediate transfer member coated with a liquid silicone compound has been disclosed. The present inventors conducted additional experiments on some of these inventions and confirmed their performance, but were unable to obtain the effects that the invention claimed and described.
[0012]
  If these fluorine-based or silicone-based compounds are used for the surface layer, they are low surface energy compounds. Therefore, they have better transferability and releasability than other surface layer materials. It also has an effect on toner contamination, toner filming, and the like. However, as intended by the present inventors, the final design purpose of an intermediate transfer body having a life equivalent to that of the main body provided with the intermediate transfer body, in other words, a replacement-free long-life intermediate transfer body, is described above. The intermediate transfer member is insufficient for the transferability after endurance and the surface contamination resistance.
[0013]
  However, the present invention proposes an image forming apparatus using a novel intermediate transfer member that solves the above-described problems.
[0014]
[Problems to be solved by the invention]
  An object of the present invention is to provide an image forming apparatus having extremely high transfer efficiency from a first image carrier to an intermediate transfer member, and transfer efficiency from an intermediate transfer member to a second image carrier.And intermediate transfer beltIs to provide.
[0015]
  Another object of the present invention is that a transfer defect of a minute part of an image does not occur, a so-called hollow image, and a uniform and homogeneous image quality depends on the type of paper or OHP sheet as the second image carrier. Image forming apparatus achieved without having toAnd intermediate transfer beltIs to provide.
[0016]
  Still another object of the present invention is to maintain the same characteristics as the initial stage while maintaining the same characteristics as in the initial stage even when severe endurance using repeated use of the intermediate transfer body is performed, and to construct an intermediate transfer body. Image forming apparatus that realizes uniform conductivity and transferability without peeling or cracking between layersAnd intermediate transfer beltIs to provide.
[0017]
  Another object of the present invention is to provide an image forming apparatus which does not cause filming due to toner adhesion to the surface of an intermediate transfer member and does not adversely affect the organic photosensitive member and has a long photosensitive member lifetime. .
[0018]
  Another object is to set a transfer bias that increases transfer efficiency when transferring from the first image carrier to the intermediate transfer member and from the intermediate transfer member to the second image carrier. An object of the present invention is to provide an image forming apparatus in which leakage does not occur.
[0019]
[Means for Solving the Problems]
  According to the present invention, in an image forming apparatus for transferring an image formed on a first image carrier onto an intermediate transfer member and further transferring the image onto a second image carrier.
The intermediate transfer member has an inorganic coating layer,
The inorganic coating layer is
  Colloidal silica,
  A partially hydrolyzed organosilane,
  Silanol group-containing polyorganosiloxaAnd
It is a layer obtained by applying and curing paint containing
An image forming apparatus is provided.
[0020]
  The intermediate transfer belt used in the image forming apparatus according to the present invention has an outermost layer containing a condensate of partially hydrolyzed organosilane and silanol group-containing polyorganosiloxane. Is provided.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described in detail.
[0022]
  In order to form the inorganic coating layer of the present invention, at least colloidal silica and organosilane are contained as components in the paint to be blended and prepared..
[0023]
  In the paint, a necessary amount of water in addition to the organic solvent is added depending on the reaction rate, and the organosilane is partially hydrolyzed by heating and stirring the above components together with the solvent. An inorganic coating layer is obtained by applying this paint so as to be a surface layer of the intermediate transfer member.
[0024]
  This partially hydrolyzed organosilane dominates the adhesion of the surface layer to the lower layer, the flexibility, the binding property of colloidal silica, and the releasability of the surface layer. For this reason, it is important to appropriately select the material of the organosilane and consider the amount ratio of colloidal silica.
[0025]
  The organosilane used in the present invention is represented by the general formula (1) as shown below. In order to obtain good dispersibility and high partial hydrolyzability of colloidal silica, alkoxysilane is particularly preferred in the present invention.
[0026]
      R_nSiX_4-n        (1)
In the formula, R represents a hydrocarbon group having 1 to 8 carbon atoms, X represents a hydrolyzable group, and n represents an integer of 0 to 3.
[0027]
  Examples of the triorganoalkoxysilane with n = 3 include trimethylmethoxysilane, trimethylethoxysilane, trimethylisopropoxysilane, and dimethylisobutylmethoxysilane.
[0028]
  Examples of the diorganodialkoxysilane with n = 2 include dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, and methylphenyldimethoxysilane.
[0029]
  Examples of the organotrialkoxysilane with n = 1 include methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane.
[0030]
  Examples of the tetraalkoxysilane with n = 0 include tetramethoxysilane and tetraethoxysilane.
[0031]
  In the present invention, methyltrimethoxysilane, dimethyldimethoxysilane, and trimethylmethoxysilane are more preferably used.
[0032]
  The colloidal silica used in the present invention effectively acts as an intermediate transfer member for releasing the surface layer, that is, preventing toner filming and improving transfer efficiency. When a large amount is added to the inorganic coating layer, although the releasability and the toner contamination resistance are increased, the hardness of the coating layer is increased, and when the lower layer is an elastic body or elastomer, these elastic deformation and flexibility are reduced. The surface layer cannot follow and cracks occur. On the other hand, if the amount is too small, the originally expected release property cannot be obtained.
[0033]
  Therefore, the amount added in the present invention is in the range of 2.5 to 80% by weight, more preferably 5 to 70% by weight, based on the total solid content in the paint. If it is less than 2.5% by weight, the surface releasability and the appropriate hardness of the coating layer cannot be obtained. On the other hand, if it exceeds 80% by weight, the dispersibility of the colloidal silica becomes difficult. Furthermore, the hardness of the layer is too high, so that the layer cannot withstand deformation and is liable to crack.
[0034]
  The colloidal silica used in the present invention is an aggregate of fine particles having a primary particle size of 0.005 to 0.1 μm, and several hundred to several thousand particles of these primary particle sizes are aggregated to form secondary particles. However, it normally exists in this state.
[0035]
  The surface of the colloidal silica fine particles can be modified to be hydrophilic or hydrophobic depending on the required characteristics of the inorganic coating layer. In the present invention, it is necessary to select a solvent in consideration of the compatibility of the alkoxysilane, the partial hydrolyzability, and the dispersibility of the colloidal silica. Is an essential component, and therefore, it is preferable to use an organic solvent having an affinity for water.
[0036]
  Therefore, examples of the organic solvent include alcohols, ie, methanol, ethanol, isopropanol diacetone alcohol, and the like, and glycols, ie, ethylene glycol, ethylene glycol monobutyl ether, diethylene glycol, diethylene glycol monobutyl ether, and the like. Other organic solvents such as methyl ethyl ketone, ethyl acetate, toluene, xylene and the like can be added and mixed in a timely manner as long as the affinity with water is not disturbed.
[0037]
  The required amount of water in the solvent is preferably 0.01 to 1.0 mole per mole of alkoxysilane. When the amount is less than 0.01 mol, a sufficient hydrolyzate cannot be obtained, and when the amount exceeds 1.0 mol, the stability of the hydrolyzate deteriorates. As a partial hydrolysis method, the reaction proceeds by stirring and mixing the organosilane and colloidal silica in a water mixed solvent. In order to increase the reaction rate, it is preferable to heat in the range of about 40 to 100 ° C.
[0038]
  In addition to the above organosilane and colloidal silica, silanol group-containing polyorganosiloxaneas well asOne or both of the curing agents are included in the paint for forming the inorganic coating layer.It is necessary to.
[0039]
  This silanol group-containing polyorganosiloxane has a function of imparting flexibility to the coating layer. In particular, use of a mixture of a silanol group-containing polyorganosiloxane (A) containing a phenyl group and a silanol group-containing polyorganosiloxane (B) containing an alkyl group gives more favorable results with respect to bending and flexibility. . The ratio of (A) and (B) is preferably in the range of 0.5 mol% <(A) <50 mol% and 95.5 mol% <(B) <50 mol%. When (A) is 0.5 mol% or less, bending flexibility cannot be obtained, and when it is 50 mol% or more, curing delay occurs, and the surface layer has a sticky feeling or tack.
[0040]
  In order to contain the silanol group-containing polyorganosiloxane in the inorganic coating layer of the present invention, for example, methyltrichlorosilane, dimethyldichlorosilane, It can be obtained by adding at least one mixture of phenyltrichlorosilane, diphenyldichlorosilane and the like, and hydrolyzing with water contained in the paint to obtain a silanol group-containing polyorganosiloxane.
[0041]
  As another method, the above-mentioned halogenated alkoxysilane is added to a previously prepared water-organic mixed solvent to cause hydrolysis, and this solution is added to a solution containing colloidal silica and partially hydrolyzed organosilane to form a coating. It can also be used as a paint.
[0042]
  At this time, a curing agent may be added to condense the partially hydrolyzed organosilane and the silanol group-containing polyorganosiloxane to obtain a tough inorganic coating layer.
[0043]
  At this time, examples of the curing agent used includeIf, Tin octylate, dibutyltin dilaurate, dioctyltin dimaleate, dibutylamine-2-hexoate, dimethylamine acetate, ethanol-amine acetate, tetraethylpentamine, phthalic acid, hydrochloric acid, aluminum alkoxide, tetraisopropyl titanate, tetrabutyl titanate, etc. Can be mentioned.
[0044]
  The amount of the partially hydrolyzed organosilane, colloidal silica, silanol group-containing polyorganosiloxane, and curing agent is added to the material under the inorganic coating layer, elasticity, flexibility, surface smoothness, and addition to the coating layer. Depending on the type and amount of the agent, it is necessary to determine the formulation that best suits the characteristics in a timely manner.
[0045]
  In addition, for the purpose of improving toner stain resistance and transferability, the inorganic coating layer of the present invention may contain, for example, additives such as the following materials, powders, and particles.
[0046]
  However, it is not necessarily limited to these. Fluoro rubber, fluoroelastomer, fluorocarbon with fluorine bonded to graphite and graphite, and fluorine compound powder such as PTFE, PVDF, ETFE, PFA, etc., silicone resin particles, silicone rubber, silicone elastomer such as silicone elastomer Powder, polyethylene, polypropylene, polystyrene, acrylic resin, polyamide resin, phenol resin, epoxy resin, etc. and their compounds, powder of mixture, granular carbon such as spherical graphite, silica, alumina, titanium oxide, magnesium oxide Inorganic powders such as tin oxide and iron oxide, which are surface-treated, or can be used alone or in combination.
[0047]
  In addition, the shape and particle size of the additive particles are not particularly limited, and any shape such as a spherical shape, a fiber shape, a plate shape, or an indefinite shape can be used. Is preferably 0.02 to 50 μm. These powders may be subjected to a surface treatment as needed within a range not impairing the lubricity. Moreover, a dispersing agent can also be used in the range which does not cause a problem in various characteristics.
[0048]
  In order for the present invention to exhibit a desired effect, the additive can occupy 0 to 50% by weight, preferably 0 to 40%, based on the total solid content of the inorganic coating layer constituting the surface layer of the intermediate transfer member. % By weight.
[0049]
  The thickness of the inorganic coating layer can be used in the range of 0.1 to 70 μm. Within this range, the coating layer is stably in close contact with the lower layer, and even if the lower layer has flexibility, it can follow it sufficiently, and no peeling, cracking, cracking, etc. will occur. Over 70μmRuAs a result, the coating layer becomes stiff, is easily cracked, and lacks flexibility. If it is less than 0.1 μm, the substantial effect of the present invention cannot be obtained.
[0050]
  The inorganic coating layer of the present invention is most effective when used as the uppermost layer of the intermediate transfer member. On the other hand, it is also possible to use it as an intermediate layer to maintain the flexibility between layers or to maintain flexibility. At this time, when an inorganic coating layer is used as an intermediate layer between the inorganic coating layer and the lower layer, a surface treating agent such as a primer may be applied between the upper layer and the lower layer.
[0051]
  Surface treatment agents include those that use silane compounds, those that use titanate compounds, those that use isocyanate resins, those that use epoxy resins, and those that use thermoplastic resins. Absent.
[0052]
  Moreover, in order to further improve the effect of preventing bleeding from the lower layer, a bleeding preventing layer may be provided between the layers. Examples of the bleed prevention layer include resins having high barrier properties, such as polyamide, vinylidene chloride, polyethylene terephthalate, polyvinyl alcohol, and ethylene vinyl alcohol, but are not limited thereto.
[0053]
  Furthermore, in order to further improve the leak prevention effect, a leak prevention layer may be provided. Examples of the leak preventing layer include resins having high leak resistance, such as polyamide, polystyrene, polyethylene, vinylidene chloride, polyethylene terephthalate, polyvinyl alcohol, and ethylene vinyl alcohol, but are not limited thereto.
[0054]
  The inorganic coating layer, bleed prevention layer, leak prevention layer and surface protective layer of the present invention may be imparted with conductivity, and examples of a method for imparting conductivity include conductive fillers and additives. Specifically, examples of the conductive filler include carbon, conductive titanium oxide, aluminum, and nickel, and examples of the additive include a surfactant and a perchlorate. Moreover, the electrically conductive agent used for these is not restricted to the above.
[0055]
  The intermediate transfer member used in the present invention has, for example, a roller shape having an elastic layer made of at least rubber, elastomer, or resin on a cylindrical conductive support, and further has one or more coating layers on the elastic layer. The shape of the roller having the belt shape as shown in FIG. 2 and various modes can be selected according to the purpose and necessity. Examples of the configuration are shown in FIGS.
[0056]
  Considering the color misalignment of images, durability due to repeated use, and the cost of the intermediate transfer member and the apparatus, a more preferable aspect of the present invention is a belt shape. 5 to 6 show an example of the intermediate transfer drum. Reference numeral 100 denotes a rigid cylindrical conductive support, 101 denotes an elastic layer, 102 denotes an intermediate layer, and 103 denotes an inorganic coating layer. 2 to 4 show examples of the intermediate transfer belt, where 101 is an elastic layer, 102 is an intermediate layer, and 103 is an inorganic coating layer. Further, reference numeral 104 in FIG. 4 denotes a belt reinforcing layer. In these examples, the intermediate layer is one layer, but it is of course possible to have one or more layers as shown in FIG.
[0057]
  As the cylindrical conductive support, metals or alloys such as aluminum, iron, copper and stainless steel, conductive resins in which carbon, metal particles, etc. are dispersed can be used. The shape and the center of the cylinder penetrate the shaft, and the inside of the cylinder is reinforced.
[0058]
  Examples of the rubber and elastomer used in the elastic layer of the intermediate transfer member used in the present invention include, for example, styrene-butadiene rubber, high styrene rubber, butadiene rubber, isoprene rubber, ethylene-propylene copolymer, nitrile butadiene rubber, chloroprene rubber, Examples thereof include butyl rubber, silicone rubber, fluorine rubber, nitrile rubber, urethane rubber, acrylic rubber, epichlorohydrin rubber, and norbornene rubber.
[0059]
  As a more preferred embodiment, for example, ethylene-propylene copolymer nitrile butadiene rubber, urethane rubber, nitrile rubber, acrylonitrile-containing acrylic rubber, polyamide elastomer, etc., alone or in combination with other rubbers and elastomers as described above are used. It is.
[0060]
  The thickness of the elastic layer is preferably 0.1 mm or more, more preferably 0.15 mm or more, and particularly preferably 0.15 mm to 10 mm. The thickness of the upper layer is preferably a thin layer for further transmitting the flexibility of the lower elastic layer to the upper layer or the surface of the photoreceptor, and the thickness of each layer is specifically 1 mm or less, more preferably 100 μm or less. In particular, the thickness is preferably 70 μm to 0.1 μm.
[0061]
  The volume resistivity of the intermediate transfer member used in the present invention is 10¹-10¹⁶It is preferably Ω · cm, particularly 10²-10¹³It is preferably Ω · cm.
[0062]
【Example】
  The present invention will be further described below with reference to examples. In addition, "part" in an Example shows a weight part.
[0063]
  (Production example of paint A)
  70 parts of ethanol is added to a flask equipped with a stirrer and a heating device, and colloidal silica (average particle size 15 μm, manufactured by Nippon Aerosil Co., Ltd.) is added to the flask in small portions, and the total is added to 30 parts. Stir well until all the colloidal silica is immersed and dispersed in ethanol. Next, 12 parts of pure water was added, 70 parts of methyltrimethoxysilane was further added, and partial hydrolysis was carried out while stirring at a temperature of 60 to 70 ° C. to obtain paint A. The solid content of the paint after removing the solvent was 75 parts.
[0064]
  (paintBProduction example)
  A mixed solvent of pure water 1100 parts / acetone 50 parts was placed in a flask equipped with a stirrer and a heating device, and about 1 part was added dropwise thereto by adding 60 parts of methyltrichlorosilane and 45 parts of phenyltrichlorosilane dissolved in 200 parts of xylene. The reaction was allowed to proceed for hydrolysis.
[0065]
  Then, only the upper layer of the solution which was allowed to stand and separated into two layers was taken out, the excess pure water, hydrochloric acid and excess xylene were removed, and the silanol group-containing polyorganosiloxane xylene solution paintBGot.
[0066]
  (paintCProduction example)
  70 parts of paint A, paintB30 parts, and dioctyltin dimaleate 0.9 part as a curing agent, and the paint by stirringCGot.
[0067]
  Example 1
    Elastic layer: 10 parts of conductive carbon black
            20 parts of paraffin oil
            Zinc oxide 5 parts
            Vulcanizing agent 2 parts
            Higher fatty acid 1.5 parts
            Nitrile butadiene rubber (NBR) 40 parts
            EPDM 60 parts
The mixture was mixed for 30 minutes while being cooled with two rolls to form a compound to obtain an elastic layer.
[0068]
    Intermediate layer: 100 parts of polyester urethane
            50 parts of conductive tin oxide
            1000 parts of DMF (solvent)
Were mixed to obtain an intermediate layer paint (1) to obtain an intermediate layer.
[0069]
  {Manufacture of intermediate transfer member}
  A rubber compound having the above composition was uniformly wound around a cylindrical mold with a thickness of 0.4 mm. Next, a polyethylene terephthalate yarn (twist, diameter: 100 μm) coated with an adhesive was spirally wound on the compound so that the distance between adjacent fibers was 0.05 mm. On top of that, a rubber compound of the above-mentioned composition extruded in a tube shape is covered, and vulcanization and polishing are performed, so that a core body having a thickness of 0.8 mm, a length of 250 mm, and an outer peripheral length (expandable free length) of 435 mm is obtained. An elastic rubber belt was obtained.
[0070]
  Next, the intermediate layer is formed by spray coating with the intermediate layer coating material, and then the coating material A is further formed thereon.70 parts / 30 parts paint B mixed reaction productWas spray-coated to form the inorganic coating layer of the present invention, and an intermediate transfer body having a three-layer structure of an elastic layer, an intermediate layer and an inorganic coating layer was obtained.
[0071]
  This intermediate transfer belt was mounted on the full-color electrophotographic apparatus shown in FIG. 1, and color misregistration, transferability and durability were evaluated.
[0072]
  Note that the cleaning method for the intermediate transfer belt is 1 × 10 6 for the cleaning charging member 7.⁸The primary transfer simultaneous cleaning method using an elastic roller having a resistance of (Ω) was used, and continuous printing of 10,000 full-color images was performed. At this time, the current value applied from the bias power source 26 to the cleaning charging member 7 is +40 μA.
[0073]
  The electrophotographic apparatus of the present invention will be described with reference to FIG.
[0074]
  Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) that is repeatedly used as a first image bearing member, and is rotated at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. The As the first image carrier, it is preferable to use a photosensitive drum containing fine powder of tetrafluoroethylene resin (PTFE) in at least the outermost layer because higher transfer efficiency can be obtained. This is considered to be because the surface energy of the outermost layer of the photosensitive drum is lowered and the toner releasability is improved by containing the fine powder of PTFE.
[0075]
  The photosensitive drum 1 is uniformly charged to a predetermined polarity / potential by a primary charger 2 in the course of rotation, and then exposed to exposure means 3 (color separation / imaging exposure optical system for color document image, image information). A first color component image (for example, yellow color) of the target color image is obtained by receiving image exposure by a scanning exposure system using a laser scanner that outputs a laser beam modulated in accordance with the time-series electrical digital pixel signal. An electrostatic latent image corresponding to the component image) is formed.
[0076]
  Next, the electrostatic latent image is developed with yellow toner Y as the first color by the first developing device (yellow color developing device 41). At this time, the developing units of the second to fourth developing units (magenta color developing unit 42, cyan color developing unit 43, and black color developing unit 44) are turned off and do not act on the photosensitive drum 1. The first color yellow toner image is not affected by the second to fourth developing units.
[0077]
  The intermediate transfer member 20 is supported by rollers 64, 65, and 66, and is driven to rotate in the clockwise direction at the same peripheral speed as that of the photosensitive drum 1.
[0078]
  The yellow toner image of the first color formed and supported on the photosensitive drum 1 is applied from the primary transfer roller 62 to the intermediate transfer belt 20 in the process of passing through the nip portion between the photosensitive drum 1 and the intermediate transfer body 20. Intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer belt 20 by an electric field formed by the primary transfer bias.
[0079]
  The surface of the photosensitive drum 100 after the transfer of the first color yellow toner image corresponding to the intermediate transfer member 20 is cleaned by the cleaning device 13.
[0080]
  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black toner image are sequentially superimposed and transferred onto the intermediate transfer body 20, and a composite color corresponding to the target color image is obtained. A toner image is formed.
[0081]
  Reference numeral 63 denotes a secondary transfer roller, which is supported in parallel with the secondary transfer counter roller 64 and arranged so as to be separated from the lower surface portion of the intermediate transfer body 20.
[0082]
  A primary transfer bias for sequentially superimposing and transferring the first to fourth color toner images from the photosensitive drum 1 to the intermediate transfer member 20 is applied from a bias power source 29 with a polarity (+) opposite to that of the toner. The applied voltage is preferably in the range of +100 V to +2 kV, for example.
[0083]
  In the primary transfer process of the first to third color toner images from the photosensitive drum 1 to the intermediate transfer member 20, the secondary transfer roller 63 can be separated from the intermediate transfer member 20.
[0084]
  When the composite color toner image transferred onto the intermediate transfer body 20 is transferred to a transfer material P such as a recording sheet as a second image carrier, the secondary transfer roller 63 is brought into contact with the intermediate transfer body 20. The transfer material P is fed from the paper feed roller 11 through the transfer material guide 10 to the contact nip between the intermediate transfer body 20 and the secondary transfer roller 63 at a predetermined timing, and the secondary transfer bias is supplied from the power supply 28. Applied to the secondary transfer roller 63. By this secondary transfer bias, the composite color toner image is transferred (secondary transfer) from the intermediate transfer member 20 to the transfer material P that is the second image carrier. The transfer material P that has received the transfer of the toner image is introduced into the fixing device 15 and heated and fixed.
[0085]
  After the image transfer to the transfer material P is completed, the charging member 7 for cleaning is brought into contact with the intermediate transfer body 20, and a bias having a polarity opposite to that of the photosensitive drum 1 is applied, so that the intermediate transfer body 20 is not transferred to the transfer material P. Electric charge having a polarity opposite to that of the photosensitive drum 1 is applied to the toner (transfer residual toner) remaining on the transfer body 20. Reference numeral 26 denotes a bias power source.
[0086]
  The transfer residual toner is electrostatically transferred to the photosensitive drum 1 at and near the nip portion with the photosensitive drum 1 to clean the intermediate transfer member.
[0087]
  As shown in FIG. 1, the cleaning of the intermediate transfer member is a method of cleaning the intermediate transfer member by electrostatically transferring the transfer residual developer to the photosensitive drum 1.
[0088]
  In the image forming apparatus shown in FIG. 1, the developer is primarily transferred from the photosensitive drum 1 to the intermediate transfer body 20, and at the same time, the transfer residual developer on the intermediate transfer belt 20 generated in the previous image forming step is transferred to the photosensitive drum 1. (Hereinafter referred to as a primary transfer simultaneous cleaning method). The primary transfer simultaneous cleaning method has an advantage that there is no reduction in throughput because a cleaning step is not particularly required.
[0089]
  Further, as shown in FIG. 7, a transfer residual developer collecting member 8 may be provided. The residual transfer developer collecting member 8 can take various forms such as a metal roll, a conductive elastic roll, a conductive fur brush, and a conductive blade. Reference numeral 27 denotes a bias power source.
[0090]
  A voltage having a polarity opposite to that applied to the cleaning charging member 7 is applied to the transfer residual developer collecting member 8, so that the transfer residual developer can be electrostatically cleaned.
[0091]
  In the apparatus of FIG. 7, for example, when the power is turned on, a bias having a polarity opposite to that of the photosensitive drum 1 is applied to the transfer residual developer recovery member 8 to remove the transfer residual developer in the transfer residual developer recovery container 9. It is also possible to charge the toner and collect it in the photosensitive drum cleaning device 13. This method has an advantage that the transfer residual developer collecting container 9 can be reduced in size.
[0092]
  Although the belt-shaped intermediate transfer member has been described above, the intermediate transfer member of the present invention can be formed in a drum shape as shown in FIG.
[0093]
  As an evaluation, it was possible to perform electrostatic transfer better than the initial stage, and it was possible to obtain a good image with no transfer failure and no image flow due to toner contamination on the surface layer of the belt even after 60,000 full-color sheets were used. Tables 1 and 2 show the structures and results of the intermediate transfer member of this example.
[0094]
  The image forming conditions of this embodiment are shown below.
[0095]
  Non-image area surface potential: -550V
  Image part surface potential: -150V
  Color developer (both four colors): Non-magnetic single component toner
  Primary transfer voltage: + 500V
  Secondary transfer voltage: + 1500V
  Process speed: 120mm / sec
  Development bias: Vdc = −400V
  Vac = 1600Vpp Frequency 1800Hz
[0096]
  (Example2)
  Example2Then, an intermediate transfer belt was prepared in the same manner as in Example 1 except that the conditions shown in Table 1 were changed, and image evaluation was performed. The results are shown in Table 2.
[0097]
  (Comparative Example 1)
  In Example 1, except that only the intermediate layer was used, it was prepared in the same manner as in Example 1, and durability was evaluated. The results are shown in Table 2.
[0098]
  (Comparative Example 2)
  In the blending of the intermediate layer of Example 1, 4 parts of conductive carbon and 70 parts of silicone resin particles (average particle size 1.5 μm) were added in place of the conductive tin oxide, and dispersed and mixed to obtain paint (2). This was spray-coated on the elastic layer to obtain an intermediate transfer belt, and durability was evaluated in the same manner as in Example 1. The configuration and results are shown in Tables 1 and 2.
[0099]
[Table 1]
[0100]
[Table 2]
[0101]
  The secondary transfer efficiency in Table 2 was determined according to the following equation by measuring the reflection density on the intermediate transfer body after the secondary transfer on the intermediate transfer body and the reflection density on the paper for cyan.
[0102]
  Secondary transfer efficiency (%) = (reflection density on paper) / (reflection density on paper + reflection density on intermediate transfer body after secondary transfer) × 100
[0103]
  Furthermore, the surface state of the intermediate transfer member was observed visually and with a microscope after durability. The image was judged from the transferred image after endurance.
[0104]
【The invention's effect】
  According to the present inventionIfSince the intermediate transfer member has an inorganic coating layer, toner contamination and filming do not occur even when severely used repeatedly, and the same transfer efficiency as in the initial stage can be maintained. Excellent image forming device that does not occur even after repeated useAnd intermediate transfer beltIt became possible to provide.
[Brief description of the drawings]
FIG. 1 is a schematic view of an example of an image forming apparatus using an intermediate transfer belt as an intermediate transfer member.
FIG. 2 is a schematic configuration diagram illustrating an entire intermediate transfer belt.
FIG. 3 is a schematic configuration diagram showing a part of an intermediate transfer belt having two intermediate layers.
FIG. 4 is a schematic configuration diagram showing a part of an intermediate transfer belt having a belt reinforcing layer.
FIG. 5 is a schematic configuration diagram illustrating an entire intermediate transfer drum.
FIG. 6 is a schematic configuration diagram illustrating a cross section of an intermediate transfer drum.
FIG. 7 is a schematic view of an example of another image forming apparatus using an intermediate transfer belt as an intermediate transfer member.
[Explanation of symbols]
  1 Photosensitive drum
  2 Primary charger
  3 Image exposure means
  7 Charging member for cleaning
  8 Transfer residual development development recovery member
  9 Transfer residual development development collection container
  10 Transfer guide
  11 Paper feed roller
  13 Cleaning means
  15 Fixing means
  20 Intermediate transfer belt
  26, 27, 28, 29 Bias power supply
  41 yellow toner
  42 Magenta Toner
  43 Cyan Toner
  44 Black Toner
  62 Primary transfer roller
  63 Secondary transfer roller
  64 Secondary transfer counter roller
  65, 66 support roller
  100 Support
  101 Elastic layer
  102 Middle layer
  103 Inorganic coating layer
  104 Belt reinforcement layer
  P transfer material

Claims (8)

In the image forming apparatus for transferring the image formed on the first image carrier onto the intermediate transfer member and further transferring the image onto the second image carrier.
The intermediate transfer member has an inorganic coating layer,
The inorganic coating layer is
Colloidal silica,
A partially hydrolyzed organosilane,
Image forming apparatus, characterized in that the silanol group-containing polyorganosiloxane ting paint containing the <br/> a layer obtained by coating and curing. The image forming apparatus according to claim 1, wherein the paint further contains a curing agent. The inorganic coating layer, the image forming apparatus according to claim 1 or 2 which is the outermost layer of the intermediate transfer body. The image forming apparatus according to any one of claims 1 to 3 , wherein a content of the colloidal silica is 2.5 to 80% by weight with respect to a total solid content of the paint. The organosilane, an image forming apparatus according to any one of claims 1-4 alkoxysilanes.   An intermediate transfer belt for use in an image forming apparatus, comprising an outermost layer containing a condensate of partially hydrolyzed organosilane and silanol group-containing polyorganosiloxane. The intermediate transfer belt according to claim 6 , wherein the outermost layer further contains silica particles. The intermediate transfer belt according to claim 6 or 7 , wherein the organosilane is an alkoxysilane.