JP2010181505A - Transfer fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer fixing device and an image forming device that reduces consumption of energy, preventing a recording medium from being wound firmly around a transfer fixing belt, even when various recording mediums such as a paper having recessed and projecting parts, a coated paper, or the like, pass through it, preventing the occurrence of defect such as reduction of dot reproducibility, and forming an image having satisfactory fixing performance and high quality. <P>SOLUTION: This transfer fixing device 66 transfers and fixes a toner image T on a transfer fixing surface of the recording medium P and is provided with a heating means 67 for heating the transfer fixing surface of the recording medium P to be conveyed toward a nip part of the transfer fixing belt 27 and a pressurizing member 68. The transfer fixing belt 27 is provided with a surface layer, formed by an elastic material and a porous fluororesin material and having electrical conductivity, on a side where it comes into contact with the recording medium P. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer fixing device for transferring and fixing a toner image on a recording medium, and an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a composite machine including the same. , About.

2. Description of the Related Art Conventionally, in image forming apparatuses such as copiers and printers, a technique using a transfer fixing device that simultaneously performs a transfer process and a fixing process is known (see, for example, Patent Document 1 and Patent Document 2).
An image forming apparatus provided with such a transfer fixing device is less likely to cause a decrease in image quality even when a recording medium having a rough surface is used, compared to an image forming apparatus that performs a transfer process and a fixing process separately. There are advantages.

Specifically, in an image forming apparatus that performs a transfer process and a fixing process separately, when a recording medium with a rough surface is used, an intermediate transfer body such as an intermediate transfer belt cannot follow the surface characteristics of the recording medium. A small gap is formed between the recording medium and the recording medium. For this reason, abnormal discharge occurs in the portion where the minute gap is formed, and the image carried on the intermediate transfer member is not normally transferred onto the recording medium, and the image becomes rough as a whole.
On the other hand, in an image forming apparatus provided with a transfer and fixing device, heat is applied to a toner image simultaneously with transfer, so that the toner is softened and melted to form a block-like lump having viscoelasticity. Therefore, even if a minute gap is formed between the fixing member and the recording medium using a recording medium having a rough surface, the image is transferred as a lump to that portion. Therefore, the image is good and has a high image quality without being distorted.

  Further, the image forming apparatus provided with the transfer fixing device is not fixed on the recording medium conveyed to the nip portion (the contact position between the transfer fixing belt and the pressure member) where the transfer / fixing process is performed. Since the toner image is not carried, restrictions on the transport path of the recording medium are reduced as compared with an image forming apparatus that performs the transfer process and the fixing process separately. That is, an image forming apparatus that performs a transfer process and a fixing process separately is not fixed on a recording medium conveyed to a nip portion (a contact position between a fixing member and a pressure member) in which the fixing process is performed. Since the toner image is carried, restrictions are imposed on the conveyance path from the transfer unit to the fixing unit so as not to contact the unfixed toner image. Therefore, the image forming apparatus provided with the transfer fixing device has a high degree of design freedom with respect to the recording medium conveyance path, and can improve the conveyance of the recording medium.

The conventional transfer fixing apparatus described above heats and melts the toner image by heating the transfer fixing belt carrying the toner image, so that the transfer fixing belt becomes thicker for a longer life or a large tandem. When the circumference of the transfer / fixing belt becomes long because it is installed in the image forming apparatus of the mold, the thermal efficiency of the transfer / fixing belt is lowered. For this reason, the energy consumption in the transfer fixing apparatus has been increased.
Further, in addition to the above-described heating process of the transfer fixing belt, the conventional transfer fixing apparatus is provided with a cooling process for cooling the transfer fixing belt after the transfer / fixing process in order to reduce thermal damage of the image forming unit. There were many cases. Since such a heating / cooling cycle is repeated, energy consumption in the transfer and fixing device is large.

  The inventor of the present application has conducted research to solve such problems, and as a result, the heating of the transfer fixing belt is minimized, and the amount of heat necessary for heating and melting the toner is immediately transferred to the nip portion. In addition, they learned how to supplement the recording medium by heating it efficiently. In order to realize such a measure, it is conceivable to provide a heating unit that heats the transfer fixing surface of the recording medium on the upstream side of the nip portion in the conveyance direction of the recording medium and in the vicinity of the nip portion. .

  On the other hand, in an image forming apparatus for commercial printing, in addition to plain paper as a recording medium, various paper types such as uneven paper having a large surface unevenness, coated paper having a high surface smoothness, etc. On the other hand, it is required to form a high-quality image. However, in order to form a high-quality image on uneven paper, the surface layer of the transfer and fixing belt is formed of a rubber material, and measures are taken to increase the adhesion of the transfer and fixing belt to the uneven surface of the uneven paper. In this case, when the coated paper having a high surface smoothness is passed and the surface layer of the transfer and fixing belt is high, the coated paper after the transfer and fixing process is transferred without being separated from the transfer and fixing belt. There is a possibility that a problem of winding around the fixing belt may occur. On the other hand, if the surface layer of the transfer and fixing belt is formed of a resin material such as a fluororesin in order to reduce the tackiness of the surface layer of the transfer and fixing belt, the transfer and fixing to the uneven surface of the uneven paper The belt adhesion could not be improved, and there was a possibility that a high-quality image could not be formed due to a problem such as a drop in the dot reproducibility of the image when the concavo-convex paper was passed. .

  The present invention has been made to solve the above-described problems, and has low energy consumption. Even when various recording media such as concavo-convex paper and coated paper are passed through the transfer fixing belt, To provide a transfer fixing device and an image forming apparatus capable of forming a high-quality image with good fixability without causing a problem such as winding of a recording medium and lowering of dot reproducibility. It is in.

  The transfer fixing device according to the first aspect of the present invention is a transfer fixing device that transfers and fixes a toner image onto a transfer fixing surface of a recording medium, and carries the toner image and travels in a predetermined direction. A transfer fixing belt; a pressure member that forms a nip portion that is pressed against the transfer fixing belt to convey the recording medium; and a heating unit that heats the transfer fixing surface of the recording medium conveyed toward the nip portion. The transfer fixing belt is provided with a conductive surface layer made of an elastic material and a porous fluororesin material on the side in contact with the recording medium.

  According to a second aspect of the present invention, there is provided the transfer fixing device according to the first aspect, wherein the surface layer of the transfer fixing belt is made of an elastic material and a conductive and porous fluorine. And a resin material.

  According to a third aspect of the present invention, there is provided the transfer fixing device according to the second aspect of the present invention, wherein the transfer fixing belt is stretched during processing in the fluororesin material having conductivity and being made porous. The direction and the traveling direction of the transfer and fixing belt coincide with each other.

  According to a fourth aspect of the present invention, in the transfer fixing device according to any one of the first to third aspects, the transfer fixing belt has an elastic layer on a conductive base material layer. The surface layer is formed through.

  According to a fifth aspect of the present invention, in the transfer fixing device according to the fourth aspect of the present invention, the elastic layer is formed so as to have a higher volume resistivity than the surface layer.

  The transfer fixing device according to a sixth aspect of the present invention is the transfer fixing device according to any one of the first to fifth aspects, wherein the elastic material is silicone rubber, and the porous fluorine material. The resin material is polytetrafluoroethylene.

  According to a seventh aspect of the present invention, in the transfer fixing device according to the first to sixth aspects, the heating means is heated by a heating body and directed toward the nip portion. A heat transfer plate that heats the transfer and fixing surface of the recording medium while guiding the recording medium that is conveyed, and a biasing member that biases the recording medium guided by the heat transfer plate toward the heat transfer plate And.

  According to an eighth aspect of the present invention, there is provided the transfer fixing device according to any one of the first to seventh aspects, further comprising a cooling means for cooling the transfer fixing belt after passing through the nip portion. In addition.

  An image forming apparatus according to a ninth aspect of the present invention includes the transfer fixing apparatus according to any one of the first to eighth aspects.

  The present invention provides a heating means for heating the transfer fixing surface of the recording medium conveyed to the nip portion between the transfer fixing belt and the pressure member, and optimizes the material of the surface layer of the transfer fixing belt, thereby reducing the energy consumption. Even when various recording media such as concavo-convex paper and coated paper are passed, the recording medium does not wrap around the transfer and fixing belt, and the dot reproducibility is reduced. In addition, it is possible to provide a transfer fixing device and an image forming apparatus in which a high-quality image with good fixability is formed.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. It is an enlarged view showing a part of the transfer fixing device. It is the figure which looked at the heating apparatus installed in a transfer fixing apparatus in the width direction. It is an expanded sectional view showing a transfer fixing belt. It is a table | surface figure which shows the conditions and results of experiment. It is an enlarged view which shows the dot formed in the image. FIG. 6 is an enlarged view showing the vicinity of a transfer fixing device according to Embodiment 2 of the present invention. It is an enlarged view which shows the vicinity of the transfer fixing apparatus in Embodiment 3 of this invention. It is a block diagram which shows a part of image forming apparatus in Embodiment 4 of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is an apparatus main body of a color copying machine as an image forming apparatus, 2 is a writing section (exposure section) that emits laser light based on input image information, and 20Y, 20M, 20C, and 20BK are colors (yellow, magenta). , Cyan, black), 21 is a photosensitive drum (image carrier) accommodated in each of the process cartridges 20Y, 20M, 20C, and 20BK, 22 is a charging unit that charges the photosensitive drum 21, 23Y, 23M, 23C, and 23BK are developing devices that develop the electrostatic latent image formed on the photosensitive drum 21, and 24 is a transfer bias that transfers the toner image formed on the photosensitive drum 21 to the transfer fixing belt 27. A roller 25 indicates a cleaning device that collects untransferred toner on the photosensitive drum 21.

  Reference numeral 27 denotes a transfer fixing belt as a transfer fixing member onto which a plurality of color toner images are transferred, 29 denotes a cleaning device (belt cleaning device) for cleaning the transfer fixing belt 27 after the transfer / fixing process, and 32Y, 32M. , 32C, 32BK are toner replenishing units for replenishing the developing devices 23Y, 23M, 23C, 23BK with toner of each color, 51 is a document conveying unit for conveying the document D to the document reading unit 55, and 55 is image information of the document D. A document reading section to be read, 61 is a paper feed section for storing a recording medium P such as transfer paper, 66 is a transfer fixing device for transferring and fixing a toner image on the recording medium P, and 67 is a recording medium immediately before the transfer / fixing process. A heating device as a heating means for heating P, a pressure roller 68 as a pressure member that presses against the transfer fixing belt 27 to form a nip portion, and 70 is a transfer fixing belt 27. A heater 85 for heating, uniformizing the temperature distribution in the width direction of the transfer and fixing belt 27 and a leveling roller as a cooling means for cooling the transfer and fixing belt 27, 91 biasing the recording medium toward the heating device 67. The brush-like member as a biasing member to perform is shown.

The transfer fixing device 66 includes a transfer fixing belt 27 (transfer fixing member), a heating device 67 as a heating unit, a pressure roller 68 as a pressure member, a heater 70, and a leveling roller 85 as a cooling unit. It is composed of a brush-like member 91 as a biasing member.
The process cartridges 20Y, 20M, 20C, and 20BK are obtained by integrating the photosensitive drum 21, the charging unit 22, and the cleaning device 25, respectively. Then, image formation of each color (yellow, magenta, cyan, black) is performed on the photosensitive drum 21 in each of the process cartridges 20Y, 20M, 20C, and 20BK.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport roller of the document transport unit 51 and placed on the contact glass 53 of the document reading unit 55. Then, the document reading unit 55 optically reads the image information of the document D placed on the contact glass 53.

  Specifically, the document reading unit 55 scans the image of the document D on the contact glass 53 while irradiating light emitted from the illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, an image processing unit (not shown) performs color conversion processing, color correction processing, spatial frequency correction processing, and the like on the basis of RGB color separation image signals, so that yellow, magenta, cyan, and black are processed. Get color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. Then, laser light (exposure light) based on the image information of each color is emitted from the writing unit 2 toward the photosensitive drums 21 of the corresponding process cartridges 20Y, 20M, 20C, and 20BK.

On the other hand, the four photosensitive drums 21 rotate in the clockwise direction in FIG. First, the surface of the photosensitive drum 21 is uniformly charged at a position facing the charging unit 22 (a charging process). Thus, a charged potential is formed on the photosensitive drum 21. Thereafter, the surface of the charged photosensitive drum 21 reaches the irradiation position of each laser beam.
In the writing unit 2, laser light corresponding to the image signal is emitted from the light source corresponding to each color. The laser light is incident on the polygon mirror 3 and reflected, and then passes through the lenses 4 and 5. The laser light after passing through the lenses 4 and 5 passes through different optical paths for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  The laser beam corresponding to the yellow component is reflected by the mirrors 6 to 8 and then irradiated onto the surface of the photosensitive drum 21 of the first process cartridge 20Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 21 by the polygon mirror 3 that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 21 charged by the charging unit 22.

  Similarly, the laser beam corresponding to the magenta component is reflected by the mirrors 9 to 11 and then irradiated to the surface of the photosensitive drum 21 of the second process cartridge 20M from the left side of the paper, thereby causing an electrostatic latent image corresponding to the magenta component. An image is formed. The cyan component laser light is reflected by the mirrors 12 to 14 and then irradiated onto the surface of the photosensitive drum 212 of the third process cartridge 20C from the left side of the drawing to form a cyan component electrostatic latent image. The black component laser light is reflected by the mirror 15 and then irradiated on the surface of the photosensitive drum 21 of the fourth process cartridge 20BK from the left side of the paper, thereby forming an electrostatic latent image of black component.

Thereafter, the surface of the photosensitive drum 21 on which the electrostatic latent images of the respective colors are formed reaches positions facing the developing devices 23Y, 23M, 23C, and 23BK, respectively. Then, the respective color toners are supplied from the developing devices 23Y, 23M, 23C, and 23BK onto the photosensitive drum 21, and the latent image on the photosensitive drum 21 is developed (this is a developing step).
Thereafter, the surface of the photosensitive drum 21 after the development process reaches a position facing the transfer and fixing belt 27 stretched and supported by the plurality of roller members 28A to 28C and 85, respectively. Here, a transfer bias roller 24 is installed at each facing position so as to contact the inner peripheral surface of the transfer fixing belt 27. Then, at the position of the transfer bias roller 24, the images (toner images) of the respective colors formed on the photosensitive drum 21 are sequentially superimposed and transferred onto the transfer and fixing belt 27 (first transfer step). .

Then, the surface of the photosensitive drum 21 after the first transfer process reaches a position facing the cleaning device 25. Then, the untransferred toner remaining on the photosensitive drum 21 is collected by the cleaning device 25 (this is a cleaning process).
Thereafter, the surface of the photosensitive drum 21 passes through a static elimination unit (not shown), and a series of image forming processes on the photosensitive drum 21 is completed.

On the other hand, the surface of the transfer and fixing belt 27 on which the toner images of the respective colors on the photosensitive drum 21 are transferred and carried are run in the direction of the arrow in the figure and contacted with the pressure roller 68 (pressure member). The contact position (the nip part) is reached. Here, the transfer fixing device 66 according to the first exemplary embodiment is provided with a heater 70 that heats the transfer fixing belt 27 (or the toner image carried on the transfer fixing belt 27) on the upstream side of the nip portion. However, the heating amount by the heater 70 is set to be considerably smaller than the conventional one.
The toner image carried on the transfer fixing belt 27 is transferred and fixed to the transfer fixing surface (front surface) of the recording medium P at the nip portion between the transfer fixing belt 27 and the pressure roller 68 ( Transfer / fixing process). More specifically, the transfer fixing surface of the recording medium P is heated by a heating device 67 (heating means) immediately before the nip portion, and the heat of the transfer fixing surface and the transfer preliminarily heated by the heater 70 at the nip portion. The toner image is heated and melted by the heat of the fixing belt 27, and the toner image is fixed to the transfer and fixing surface by the pressure of the nip portion. The configuration and operation of the transfer fixing device 66 will be described in more detail later with reference to FIGS.
Thereafter, the surface of the transfer fixing belt 27 reaches the position of the belt cleaning unit 29. Then, deposits such as residual toner on the transfer fixing belt 27 are collected by the belt cleaning device 29, and a series of transfer fixing processes on the transfer fixing belt 27 is completed.

Here, the recording medium P transported to the nip portion of the transfer fixing device 66 is transported from the paper feed unit 61 via the transport guide 63, the registration roller 64, the heating device 67, and the like.
Specifically, the transfer paper P fed by the paper feed roller 62 from the paper feed unit 61 that stores the recording medium P passes through the conveyance guide 63 and is guided to the registration roller 64. The recording medium P that has reached the registration roller 64 is conveyed toward the nip portion between the transfer fixing belt 27 and the pressure roller 68 in synchronization with the toner image on the transfer fixing belt 27. At this time, the recording medium P conveyed toward the nip portion is guided to the heat transfer plate 67b (see FIG. 2) of the heating device 67 and attached to the heat transfer plate 67b by the brush-like member 91. While being energized, only the transfer and fixing surface of the recording medium P is heated by the heating device 67 (heat transfer plate 67b).
Thereafter, the recording medium P on which the full-color image has been transferred and fixed passes through the paper discharge conveyance path, and is discharged as an output image outside the apparatus main body 1 by the paper discharge roller 80, and a series of image forming processes is completed. In the image forming apparatus according to the first embodiment, the conveyance speed (or process linear speed) of the recording medium P is set to about 300 mm / second.

The toner used in Embodiment 1 is preferably suitable for low-temperature fixing. Specifically, the softening point (1/2 outflow temperature) of the toner is preferably about 100 ° C.
As the toner binder resin, one having the following composition can be used.
For example, homopolymers of styrene such as polyester, polystyrene, poly p-chlorostyrene, polyvinyltoluene and the like; and styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers. Styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate Copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Examples thereof include styrenic copolymers such as polymers.
Moreover, the following resin can also be mixed and used. Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or fat Examples thereof include cyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffin, and paraffin wax. Among these, those containing a polyester resin are preferred in order to obtain sufficient fixing properties. In particular, the crystalline polyester resin is sufficiently softened and melted at the time of paper contact, and can form an image with high color reproducibility as well as fixing strength. The polyester resin is obtained by condensation polymerization of alcohol and carboxylic acid, and the alcohol used is polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butane. Diols such as diol, neopentyl glycol, 1,4-butenediol, 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyexethylenated bisphenol A, polyoxypropylenated bisphenol A, etc. And a divalent alcohol simple substance obtained by substituting these with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, and other divalent alcohol simple substance.
Examples of the carboxylic acid used to obtain the polyester resin include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, Adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, acid anhydrides thereof, lower alkyl esters and linolenic acid Dimers and other divalent organic acid monomers can be mentioned.
In order to obtain a polyester resin to be used as a binder resin, it is also preferable to use not only a polymer with only the above bifunctional monomer but also a polymer containing a component with a trifunctional or higher polyfunctional monomer. It is. Examples of the polyhydric alcohol monomer having three or more valences that are such polyfunctional monomers include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sarbitane, pentaesitol, dipenta. Esitol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol , Trimethylolethane, trimethylolpropane, 1.3.5-trihydroxymethylbenzene, and others.
Examples of the trivalent or higher polyvalent carboxylic acid monomer include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2 -Methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, embol trimer acid, acid anhydrides thereof, and the like.

Further, the toner used in the first exemplary embodiment can contain a release agent for the purpose of improving the release property of the toner on the surface of the transfer fixing belt 27 in the transfer fixing step. As the release agent, all known ones can be used, and in particular, defree fatty acid type carnauba wax, montan wax, oxidized rice wax, and ester wax can be used alone or in combination. As the carnauba wax, those having fine crystallinity, an acid value of 5 or less, and a particle diameter of 1 μm or less when dispersed in a toner binder are preferable. The montan wax generally refers to a montan wax refined from minerals, and like a carnauba wax, it is microcrystalline and preferably has an acid value of 5 to 14. The oxidized rice wax is obtained by air-oxidizing rice bran wax, and the acid value is preferably 10-30. When the acid value of each wax is less than the respective range, the low temperature fixing temperature rises and the low temperature fixing becomes insufficient. On the contrary, when the acid value exceeds each range, the cold offset temperature rises and the low-temperature fixing becomes insufficient. The added amount of the wax is 1 to 15 parts by weight, preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder resin. If it is less than 1 part by weight, the releasing effect is thin and the desired effect is difficult to obtain. On the other hand, if the amount exceeds 15 parts by weight, problems such as significant spent on the carrier occur.
Further, as an external additive, for the purpose of improving the fluidity of the toner, silica, titanium oxide, alumina, and the like, and if necessary, fatty acid metal salts, polyvinylidene fluoride, and the like may be added.
In particular, since the transfer fixing device 66 can sufficiently heat the toner, even if a relatively large amount of an additive such as submicron large particle size silica is used, the fixing property and the fixing temperature are not affected. Therefore, an external additive prescription considering fluidity and transferability is possible.

Next, with reference to FIGS. 2 to 4, the characteristic transfer fixing device 66 in the first embodiment will be described in detail.
FIG. 2 is an enlarged view showing a part of the transfer fixing device 66. FIG. 3 is a view of the heating device 67 as the heating means when viewed from the X direction in FIG. 2 in the width direction. FIG. 4 is an enlarged sectional view showing the transfer fixing belt 27.
As shown in FIG. 2, the transfer fixing device 66 includes a transfer fixing belt 27 (transfer fixing member), a heating device 67 (heating means), a heater 70, a pressure roller 68 as a pressure member, and a brush as a biasing member. And a leveling roller 85 as a cooling means.

  Here, referring to FIG. 4, the transfer fixing belt 27 has a multilayer structure in which an elastic layer 27b and a surface layer 27a (covering layer) are sequentially formed on a base material layer 27c formed on the inner peripheral surface side. Endless belt. The base material layer 27c (base film) of the transfer fixing belt 27 may have any flexibility and strength suitable for winding around the roller members 28A to 28C. For example, a polymer film, a metal film, Alternatively, a composite film obtained by combining these can be used. Specifically, examples of the polymer film include sheet-shaped or cloth-shaped molded products such as polyimides, polyamideimides, polyesters, and polycarbonates. Further, such a polymer film may be one in which additives such as a conductive agent such as carbon black and graphite, an antistatic agent, a magnetic material, a release agent, and a reinforcing material are added. In the first embodiment, polyimide is used as the base material layer 27c, and silicone rubber is used as the elastic layer 27b.

Here, in the transfer fixing belt 27 in the first embodiment, the surface layer 27a formed on the side in contact with the recording medium P (on the outer peripheral surface side) has heat resistance (about 200 ° C. larger than the fixing temperature). It is formed of a composite material composed of an elastic material having a physical property value such as strength and elastic modulus and the like, and a porous fluororesin material, and further has conductivity. It is formed as follows.
Specifically, as a porous fluororesin material, a shear force is applied to PTFE (polytetrafluoroethylene) by means of rolling, extruding, kneading, stretching, etc. so that these resins have continuous pores. Examples thereof include fibrillated resins obtained by making them porous. The elastic material combined with such a porous fluororesin material is important for imparting elasticity to the surface layer 27a in addition to releasability (anti-tackiness), (RTV) or low temperature curing (LTV) rubber material can be used. Specifically, examples of the elastic material for the surface layer 27a include RTV silicone rubber, LTV silicone rubber, fluorine rubber, fluorinated silicone rubber, and fluorocarbon siloxane rubber. Further, in these rubbers, silicone oil or the like is added in order to further improve the releasability of the surface layer 27a, or carbon black, graphite, boron nitride, alumina in order to improve performance such as thermal conductivity. Inorganic powders such as silica may be added.
In this way, by forming the surface layer 27a of the transfer fixing belt 27, the transfer fixing belt onto the uneven surface of the uneven paper at the nip portion even when the uneven paper having a large surface unevenness is passed. Therefore, it is possible to form a high-quality image without reducing the dot reproducibility of the image on the uneven paper. Further, even when a coated paper having a high surface smoothness is passed, the coated paper after the transfer and fixing process is transferred without being separated from the transfer and fixing belt 27 because the tackiness of the surface layer 27a is relatively low. The problem of winding around the fixing belt 27 can be suppressed. Note that the “porous” fluororesin material in the present application is a fluororesin material having a substantially mesh structure with a porosity of approximately 50% or more (volume ratio is 50% or less).

The thickness of the transfer fixing belt 27 is preferably set to 300 μm or less (preferably 100 μm or less). If the thickness of the transfer and fixing belt 27 is too thin, the desired strength cannot be achieved, and it becomes difficult to impart desired performance to the surface layer 27a, which is important for imparting releasability and elasticity. At least a thickness of about 80 μm is required. Further, if the belt thickness exceeds 300 μm, the curvature when the belt is stretched cannot be increased, so that it is impossible to reduce the size of the apparatus while ensuring the durability of the belt.
In the transfer fixing belt 27, the base layer 27c has a layer thickness of 15 to 200 μm (preferably 50 to 75 μm), and the elastic layer 27b (intermediate layer) has a layer thickness of 50 to 200 μm (preferably 80 to 160 μm). The layer thickness of the surface layer 27a is preferably set to 10 to 40 μm.
Further, it is preferable that the friction coefficient between the surface of the transfer fixing belt 27 and the recording medium P is set in a range of 0.1 to 0.5. If the friction coefficient exceeds 0.5, the adhesion between the recording medium P and the transfer fixing belt 27 becomes too large, and the recording medium P becomes difficult to separate from the transfer fixing belt 27. Furthermore, the transfer fixing belt Insoluble matter such as paper dust and dust adheres to the surface of 27 and the cleaning property is deteriorated.
The transfer and fixing belt 27 has a high degree of quality that does not affect the image quality by laminating the elastic layer 27b and the surface layer 27a on the base material layer 27c even if the base material layer 27c does not have a completely seamless structure. If an accurate seam is formed, there is no problem in use as it is substantially the same as the seamless structure.

The transfer fixing belt 27 having the surface layer 27a containing the fluororesin material made porous with the fibrillated resin as described above is manufactured as follows.
First, a fluororesin is fibrillated in advance to form a porous body of the fibrillated resin, and a rubber material (elastic material) is impregnated in the voids of the porous body. Thereafter, this is bonded to the surface of the base material layer 27c (or the elastic layer 27b) whose adhesiveness has been improved, and then heat-treated to cure the rubber material. At that time, the surface layer 27a may be laminated on the base material layer 27c (or the elastic layer 27b) after applying an adhesive to one surface of the porous body, or rubber may be formed in the voids of the porous body. The material may be impregnated and heat-cured, and then an adhesive may be applied to one surface of the material, and this may be laminated on the surface of the base material layer 27c (or the elastic layer 27b). Furthermore, after laminating the above-mentioned porous body on the surface of the base material layer 27c (or the elastic layer 27b) with an adhesive, the voids of the laminated porous body are impregnated with rubber, and then Heat curing may be performed.

Here, the transfer and fixing belt 27 in the first embodiment has a length in the width direction (in the direction perpendicular to the paper surface in FIG. 2) of 300 mm and a circumferential length (in the running direction) of 1150 mm. Is set. Further, in the transfer and fixing belt 27, the base material layer 27c is made of polyimide having a layer thickness of about 70 μm, the elastic layer 27b is made of silicone rubber having a layer thickness of about 110 μm, and the surface layer 27a has a thickness of 10 μm and a gap. It is formed by impregnating an addition-polymerization type silicone rubber in a conductive expanded porous PTFE having a rate of 80% and curing by heating at 120 ° C. for 1 hour. The transfer fixing belt 27 formed in this way has a volume resistivity of about 10 ⁸ Ω · cm.

The pressure roller 68 as a pressure member has a surface layer (release layer) formed on a cylindrical metal core made of aluminum or the like, and rotates in the clockwise direction in FIG. The pressure roller 68 is brought into pressure contact with the roller member 28A via the transfer fixing belt 27 by a pressure mechanism (not shown). In this way, a desired nip portion is formed between the pressure roller 68 and the transfer fixing belt 27. In the first embodiment, the pressure applied to the nip portion by the pressure roller 68 is set to about 0.3 to 0.5 MPa, and the nip width in the nip portion is set to about 12 mm.
As the surface layer of the pressure roller 68, PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), or the like is used. be able to.

A heating device 67 as a heating unit is disposed in the vicinity of the entrance side of the nip portion in the transfer fixing device 66. The heating device 67 includes a heating body 67a, a heat transfer plate 67b, an electrode 67c, and the like.
The heating element 67a is sandwiched between the heat transfer plate 67b and the electrode 67c. In the first embodiment, as the heating element 67a, a resistance heating element whose resistance rapidly increases when a predetermined Curie point is reached is used. Specifically, a positive temperature coefficient thermistor made of a barium titanate semiconductor ceramic body is used as the heating body 67a. In the first embodiment, as shown in FIG. 3, ten heating elements 67a (positive characteristic thermistors) are arranged in parallel in the width direction.
The heat transfer plate 67b (heat transfer member) is a stainless steel plate having a plate thickness of 0.2 mm. The heat transfer plate 67b extends from the vicinity of the registration roller 64 to the vicinity of the nip portion, and functions as a guide plate (guide plate) that guides the recording medium P conveyed toward the nip portion. Further, the heat transfer plate 67b contacts the transfer fixing surface (front surface) of the recording medium P conveyed toward the nip portion, and heat generated by the heating body 67a is recorded on the recording medium P (transfer fixing surface). It has the function of transferring heat to Furthermore, the AC power supply 71 is connected to the heat transfer plate 67b, and functions as one of the electrodes.

An AC power supply 71 is connected to the electrode 67c and the heat transfer plate 67b that sandwich the heating body 67a, and a voltage of AC 100 volts is applied to both ends of the heating body 67a when the switch 72 is connected. Thereby, an electric current flows in the heating body 67a, and the heating body 67a generates heat. Further, the heat of the heating body 67a is transmitted from the heat transfer plate 67b to the transfer fixing surface of the recording medium P.
In the first embodiment, as the material of the heat transfer plate 67b, heat conductivity is high, heat capacity in the same volume is low, and relatively inexpensive copper is used. Therefore, heating efficiency is high and relatively inexpensive. A heating device 67 can be provided.

Here, it is preferable to use a heating body 67a having a Curie point lower than the ignition point of the recording medium P. As a result, the heating body 67a is prevented from malfunctioning due to its self-temperature control function, causing the temperature to rise above the ignition point of the recording medium P.
Specifically, in the first embodiment, the Curie point of the heating body 67a is set to 200 ° C. Thereby, when the temperature of the heating body 67a exceeds 200 ° C., the resistance between the electrode 67c and the heat transfer plate 67b rapidly increases, and the current flowing in the heating body 67a decreases. Specifically, when the temperature of the heating body 67a is 210 ° C., the current flowing in the heating body 67a decreases to ½, and when the temperature of the heating body 67a is 220 ° C., the current flowing in the heating body 67a is ¼. To drop.
The heating element 67a configured in this manner is heated to 190 to 200 ° C. after 6 seconds with 1200 watts of power, and thereafter does not increase to 210 ° C. or more by the self-temperature control function. When the heating body 67a is controlled at 210 ° C. or lower, it is controlled to a desired temperature by PID control or the like using a temperature sensor (not shown). Even if the control circuit fails, safety cannot be ensured because it cannot exceed 210 ° C. as described above. Moreover, in this Embodiment 1, since the several heating body 67a is arranged in parallel in the width direction, each self-temperature control is performed by the several heating body 67a, and the temperature nonuniformity of the width direction is 10 degreeC. It can be:

  As described above, the heating device 67 configured in this way heats only the transfer fixing surface (front surface) of the recording medium P immediately before the transfer / fixing process. In other words, the heating device 67 causes the recording medium P to nip before the temperature of the back surface of the recording medium P (the back surface with respect to the transfer fixing surface) rises (before heat is transferred from the front surface to the back surface). The transfer fixing surface is heated so as to be conveyed to the section.

The inventor of the present application made a recording when the recording medium P (thick paper 300 g paper) was brought into contact with a copper plate (thickness 1 mm) heated to 160 ° C. for 60 msec and then conveyed (running) in the air at an ambient temperature of 40 ° C. The temperature fluctuation of the transfer fixing surface of the medium P was simulated. As a result, the recording medium P heated to about 140 ° C. by the copper plate is only 110 m. For 10 msec (corresponding to a conveying distance of 3 mm when the conveying speed is 300 mm / sec.) In the air at an atmospheric temperature of 40 ° C. It was found that the temperature decreased until. Therefore, in order to increase the heating efficiency of the recording medium P before the transfer and fixing step, it is necessary to place a heat transfer member (heat transfer plate) for heating the recording medium as close to the nip as possible.
In the first embodiment, the heat transfer plate 67b is formed in a plate shape, the tip thereof is as close as possible to the nip portion, and the length in the transport direction is set as long as possible. The heating efficiency of the previous recording medium P can be improved.

Here, the heat transfer plate 67b in Embodiment 1 has a guide surface (a surface in contact with the recording medium P) for guiding the recording medium P covered with nickel plating containing fluororesin particles. Yes. Specifically, 30 vol% PTFE (polytetrafluoroethylene) is dispersed in a nickel plating film. Such a coating has a hardness in a precipitated state of about Hv300, is harder than a normal resin coating, and is excellent in slipping property, wear resistance, and releasability. Therefore, it is possible to reduce the problem of toner and paper powder adhering to the heat transfer plate 67b and to improve the durability of the heat transfer plate 67b.
The guide surface of the heat transfer plate 67b (the surface that contacts the recording medium P) can be covered with diamond-like carbon (DLC) or graphite-like carbon (GLC) having high wear resistance.

The heating device 67 in the first embodiment heats the transfer and fixing surface so that the temperature of the transfer and fixing surface of the recording medium P is higher than the surface temperature of the transfer and fixing belt 27. That is, the toner image T carried on the transfer fixing belt 27 is heated and melted by heat mainly received from the recording medium P at the nip portion.
In the first embodiment, the transfer and fixing surface of the recording medium P is heated, and the temperature for obtaining sufficient gloss on the output image can be set independently. Therefore, the transfer and fixing belt heated by the heater 70 is used. 27 (fixing set temperature) can be lowered. Further, since the recording medium P is heated immediately before the transfer / fixing process, the adhesion between the toner T and the recording medium P is not increased more than necessary without being heated excessively.
That is, according to the configuration of the first embodiment, it is possible to perform low-temperature fixing, reduce the warm-up time of the apparatus, and improve energy saving. In addition, since heat transfer to the transfer fixing belt 27 can be suppressed, durability of the transfer fixing belt 27 can be improved. Furthermore, since the heating temperature of the transfer fixing belt 27 is reduced, thermal deterioration of the transfer fixing belt 27 can be suppressed.

  Further, the transfer fixing device 66 according to the first embodiment presses (biases) the recording medium P guided to the nip portion by the heat transfer plate 67b against the heat transfer plate 67b by the brush-like member 91 (biasing member). ) Is configured as follows. With this configuration, in order to improve the adhesion force and the adhesion time of the recording medium P to the heat transfer plate 67b, the surface of the recording medium P is reliably raised to the target temperature by the heat transfer plate 67b and fixed. Defects can be suppressed.

Here, the brush-like member 91 is a recording medium P on which brush bristles 91 a made of heat-resistant polyimide fibers (diameter 0.2 mm) and planted at a density of 50 fibers / cm ² are guided to the heat transfer plate 67 ^b . Are configured to be in point contact or line contact at a plurality of locations. By reducing the contact area with the recording medium P as much as possible and pressing the recording medium P against the heat transfer plate 67b, the heat is transferred to the brush-like member 91 side, thereby preventing the heating efficiency of the recording medium P from being reduced. In addition, it is possible to suppress a problem that the transportability of the recording medium P is lowered.

As described above, the transfer fixing device 66 according to the first embodiment minimizes the heating of the transfer fixing belt 27, and the recording medium immediately before the amount of heat necessary for heating and melting the toner is conveyed to the nip portion. It supplements by heating P efficiently. However, in this case, the transfer and fixing belt 27 receives a large amount of heat from the heated recording medium P and has a non-uniform distribution, and is the width direction of the transfer and fixing belt 27 (the direction orthogonal to the recording medium conveyance direction). ) Causes temperature unevenness, and it becomes easy to generate defective fixing images such as uneven fixing and offset.
In contrast, in the first embodiment, as shown in FIG. 2, the temperature distribution in the width direction of the surface of the transfer and fixing belt 27 after passing through the nip portion is made uniform, and the transfer after the transfer and fixing step is performed. A leveling roller 85 is installed as a cooling means for cooling the fixing belt 27.
The leveling roller 85 is a roller member disposed on the downstream side in the running direction of the transfer fixing belt 27 with respect to the nip portion, and stretches and supports the transfer fixing belt 27 together with the three roller members 28A to 28C. The leveling roller 85 as a cooling means is a heat pipe, and cools the transfer fixing belt 27 and efficiently distributes the temperature distribution in the width direction of the surface of the transfer fixing belt 27 by efficiently convection heat inside the heat pipe. Turn into. Accordingly, even when the recording medium P immediately before being conveyed to the nip portion is heated by the heating device 67 with the heating of the transfer fixing belt 27 being minimized, fixing defects such as uneven fixing and offset occur. Can be suppressed.

  As described above, the transfer fixing belt 27 according to the first embodiment has the surface layer 27a formed on the outer peripheral surface side in contact with the recording medium P, the heat-resistant elastic material, the porous fluororesin material, and the like. , The adhesiveness of the transfer fixing belt 27 to the uneven surface of the recording medium P (follow-up property), and the recording medium P The releasability (anti-tack property) of the transfer fixing belt 27 with respect to the smooth surface can be made compatible. Specifically, even when the type of the recording medium P is different and the Ry (maximum height) of the surface thereof changes in the range of 0.5 to 40 μm, the above-described adhesion and releasability can be made compatible. it can.

Here, the conductivity of the surface layer 27a of the transfer and fixing belt 27 is necessary to prevent transfer dust from being generated in the toner image transferred onto the recording medium P due to abnormal discharge near the entrance of the nip portion. It is necessary to have a volume resistivity of about 10 ⁸ to 10 ¹¹ Ω · cm.
As a method for imparting conductivity to the surface layer 27a of the transfer fixing belt 27, carbon black or the like may be added to a rubber material (elastic material) to impart conductivity. It is preferable to add conductivity by adding carbon black or the like. This is because, when carbon black or the like is added to rubber material (elastic material) to give conductivity, the linear expansion of the rubber material is as large as 200 to 300 ppm / ° C, so the heating / cooling cycle is repeated. This is because the conductive path in the rubber material may be blocked by this, and the conductivity of the material may decrease over time. On the other hand, when conductivity is imparted to the porous fluororesin material, the linear expansion of the fluororesin material is relatively small at 100 to 120 ppm / ° C., so the heating / cooling cycle is repeated. However, the expansion and contraction is small, and the change in conductivity is less likely to occur.
In addition, as a method of imparting conductivity to the surface layer 27a, a method of filling a porous mesh-like fluororesin with carbon or the like by kneading or the like, or a method of imparting nanocarbon or the like to a porous mesh-like fluororesin There are a method of adsorbing and a method of filling carbon or the like into a rubber material (elastic material) present in a porous mesh-like fluororesin by kneading or the like.

  In addition, as described above, when a conductive filler such as carbon black is added to the porous fluororesin material to impart conductivity, the stretching direction during processing of the porous fluororesin material And the traveling direction of the transfer and fixing belt 27 are preferably matched. The stretching direction at the time of processing in the porous fluororesin material is a direction in which the interval between the conductive fillers contained in the material is larger than the direction orthogonal thereto. Therefore, by making the stretching direction coincide with the traveling direction of the transfer fixing belt 27, the resistance in the traveling direction of the transfer fixing belt 27 can be increased, so that the bias effect at the entrance of the nip portion is reduced, The discharge in the space near the entrance is reduced, and transfer dust is less likely to occur in the toner image transferred onto the recording medium P.

Further, as described above, the transfer fixing belt 27 in the first embodiment has the surface layer 27c formed on the base material layer 27c via the elastic layer 27b. As described above, by providing the elastic layer 27b between the base material layer 27c and the surface layer 27c, the elasticity of the transfer fixing belt 27 as a whole can be secured, and the surface of the recording medium P can be adhered to the unevenness. (Trackability) will be improved.
The elastic layer 27b is formed to have a higher volume resistivity than the surface layer 27a. In this way, by setting the volume resistivity of the elastic layer 27b inscribed in the surface layer 27a to be high, the surface resistance of the transfer fixing belt 27 is increased, so that the bias effect at the entrance of the nip portion is reduced, The discharge in the space near the entrance is reduced, and transfer dust is less likely to occur in the toner image transferred onto the recording medium P.

FIG. 5 is a table showing the conditions and results of an experiment conducted by the inventors of the present application in order to confirm the effect of using the transfer fixing device 66 according to the first embodiment.
In the experiment, using the image forming apparatus according to the first embodiment, 12 kinds of materials of the surface layer 27a of the transfer fixing belt 27 (Examples 1 to 7 and Comparative Examples 1 to 5) were shaken, and various recording media P were used. The paper passing property (wrapping of the recording medium P around the transfer fixing belt 27) and the image quality (dot reproducibility) are confirmed.
In Comparative Example 1, the surface layer 27a of the transfer and fixing belt 27 is formed only of silicone rubber (JIS-A hardness is 20Hs). In Examples 1 to 3, the surface layer 27a of the transfer and fixing belt 27 is formed of silicone. Rubber (JIS-A hardness is 20Hs) and volume ratio (100% -porosity) was made of porous PTFE with 10, 20, 30%. In Comparative Example 2, the surface layer 27a of the transfer fixing belt 27 is formed only of silicone rubber (JIS-A hardness is 40Hs), and in Examples 4 to 5, the surface layer 27a of the transfer fixing belt 27 is formed of silicone rubber (JIS-A). And a porous PTFE having a volume ratio of 10, 20%. In Comparative Example 3, the surface layer 27a of the transfer fixing belt 27 is formed only by “SIFEL” manufactured by Shin-Etsu Chemical Co., Ltd. (JIS-A hardness is 30 Hs). In Examples 6-7, the surface layer 27a of the transfer fixing belt 27 is formed by Shin-Etsu. It was formed with “SIFEL” (JIS-A hardness 30Hs) manufactured by Kagaku Kogyo and porous PTFE with a volume ratio of 10, 20%. In Comparative Example 4, the surface layer 27a of the transfer and fixing belt 27 was formed only of fluororubber (JIS-A hardness 50Hs). In Comparative Example 5, the surface layer 27a of the transfer / fixing belt 27 was formed only of PTFE (not porous).

In FIG. 5, symbols A to F correspond to the following recording media.
A is “Oji Paper POD gloss coated paper” (basis weight 80 g / m ² , Ry 0.5 μm), B is “Oji Paper Mirror Coat Platinum” (basis weight 104 g / m ² , Ry 0.4 μm), C Is “NBS Ricoh type 6200” (basis weight 80 g / m ² , Ry 5.2 μm), D is “NBS Ricoh type CF135W” (basis weight 155 g / m ² , Ry 6.3 μm), and E is “special papermaking” Mermaid ”(basis weight 105 g / m ² , Ry 30 μm), and F is“ special papermaking Rezak 66 ”(basis weight 116 g / m ² , Ry 36 μm). The “Ry” is the surface property (maximum height) of the recording medium when the measurement length is set to 25 mm and λc is set to 8 mm. The recording media A and B are coated paper, the recording media C and D are plain paper, and the recording media E and F are uneven paper.
With respect to all of these six types of recording media A to F, a predetermined number of sheets are passed, whether or not the recording medium is wound around the transfer and fixing belt 27, and dot reproducibility in a 600 × 2 2 × 2 image (dots) The presence or absence of deficiency) was confirmed. The quality of dot reproducibility was evaluated by changing the pressure conditions of the pressure roller 68 by two types (pressure 0.5 MPa and pressure 0.3 MPa). In addition, the dot reproducibility is determined by observing an enlarged photograph of a 2 × 2 image, and assuming that there is no dot PD defect at all as shown in FIG. 6 (A), as shown in FIG. 6 (B). In the case where a dot PD defect occurred, “No” was determined.
For example, in Comparative Example 1, the dot reproducibility was good for all the paper types A to F regardless of the pressurizing conditions, whereas two paper types A and B (both coated papers) Thus, the recording medium is wound around the transfer fixing belt 27.

Further, in FIG. 5, a result of performing a ball tack test in order to investigate the tack property (release property) of the transfer fixing belt 27 as a substitute characteristic relating to the presence or absence of the recording medium wound around the transfer fixing belt 27 (one). Part of the examples and comparative examples only.).
The ball tack test was based on “JIS Z 0237” and was performed by changing only the inclination angle to 20 degrees. The results shown in FIG. 5 are the ball numbers measured in the test (for example, ball number 2 is a ball having a diameter of 1.59 mm). The smaller the ball number, the lower the tackiness and the lower the transfer fixing belt. It will be difficult for winding to occur.

Further, in FIG. 5, the result of measuring and calculating the universal hardness (HU) in order to examine the adhesion (following property) of the transfer fixing belt 27 to the uneven surface of the recording medium as a substitute characteristic relating to the quality of dot reproducibility. Is shown.
The universal hardness (HU) is obtained by measuring the repulsive force at the indentation depth of 30 μm of the Vickers indenter and dividing it by the area to obtain a stress. Specifically, a micro hardness tester “Fischer Scope H100” (manufactured by Helmut Fischer) was used for the measurement. The transfer fixing belt is heated by a heating source such as a heater, and measurement is performed while the transfer fixing belt is held at an actual fixing temperature. For the measurement, a Vickers indenter which is a regular quadrangular diamond indenter is used. The Vickers indenter is pushed vertically into the sample, and the universal hardness (HU) is calculated from the indenter penetration depth (h) and load (F). Since the facing angle of the regular quadrangular pyramid is 136 °, the universal hardness (HU) is defined by the following equation.
HU (N / mm ² ) = F (mN) × 10 ³ /(26.43×h (μm) ² )
If this value falls below the pressure at the nip portion, the transfer and fixing belt follows the uneven paper such as the recording media E and F.

The transfer fixing apparatus used in this experiment is set such that the transfer fixing belt traveling speed is set to 300 mm / second, the surface temperature of the transfer fixing belt is set to 60 ° C., and the nip entry temperature of the recording medium is set to 100 to 120 ° C. . Further, the printing speed in the image forming apparatus was set to 60 sheets / minute (A4 size recording medium), and a predetermined number of continuous sheets were passed.
The toner used in this experiment is “P × P toner for imagio MP C6000” (manufactured by Ricoh). As an additional experiment, the same test was performed using “EA Toner” (Fuji Xerox Co., Ltd.) and “S Toner” (Canon Co.). As a result, almost the same result as the experimental result of FIG. 5 was obtained. I was able to. Note that the nip entry temperature of the recording medium was within a range of ± 1 ° C. when any of the above-described toners was used.

In the experimental results of FIG. 5, the same results are obtained from the comparison between Comparative Example 1 and Examples 1 to 3, the comparison between Comparative Example 2 and Examples 4 to 5, the comparison between Comparative Example 3 and Examples 6 to 7, and the like. By combining porous PTFE with a rubber material (elastic material) to reduce tackiness, winding of a recording medium (particularly coated paper such as A or B) around a transfer and fixing belt may be reduced. Recognize. Further, from the comparison between Comparative Example 5 and Examples 1 to 7, the PTFE is made porous and the rubber material is combined to greatly reduce the universal hardness of the transfer and fixing belt, and the recording medium (in particular, E, It can be seen that the adhesiveness to uneven paper such as F is improved and the dot reproducibility is greatly improved.
Further, from the overall experimental results, the surface layer 27a of the transfer fixing belt 27 is formed of silicone rubber as a rubber material (elastic material) and porous PTFE as a porous fluororesin material. Thus, it can be seen that various recording media can be balanced with both prevention of winding of the recording medium around the transfer fixing belt and improvement of dot reproducibility. In particular, the conditions of Example 2 (silicone rubber 20Hs + porous PTFE with a porosity of 80%) can achieve both high levels of prevention of wrapping and improvement of dot reproducibility regardless of the pressurization conditions at the nip portion. I understand. In addition, with regard to the conditions of Examples 3, 4, and 6, by setting the pressurizing condition at the nip portion to be high (about 0.5 MPa), it is possible to achieve both high levels of prevention of wrapping and improvement of dot reproducibility. You can see that Under these conditions, even when a continuous paper feeding test of 50,000 sheets is performed, the releasability of the recording medium from the transfer fixing belt is good, and the image quality such as density stability and color developability in the output image is also good. there were.

In the experiment relating to FIG. 5, a surface layer made of conductive PTFE and an insulating rubber material is formed, and the volume resistance is about 10 ⁸ Ω · cm and the surface resistance is 10 ¹¹ Ω / □. This is performed using a set transfer fixing belt.
In contrast, when a continuous sheet passing test was performed using a transfer fixing belt having a surface layer made of PTFE having an insulating property and a conductive rubber material, the number of passing sheets exceeded 10,000. Further, it was confirmed that the surface resistance of the transfer fixing belt increased by an order of magnitude or more, and blurring due to poor image transfer occurred.
In addition, the transfer fixing belt traveling direction and the stretching direction at the time of processing the porous PTFE having conductivity coincide with the width direction of the transfer fixing belt (the direction perpendicular to the traveling direction) and the conductivity. When the image quality of the output image was compared using the one in which the stretching direction at the time of processing the porous PTFE having the same was used, the standard deviation of the dot area of the former was about 30 compared to the latter. % Small image quality with small transfer dust was obtained. Further, when the polyimide used as the base material layer was replaced with one having a volume resistance of 10 ⁹ Ω · cm, dot transfer dust was further reduced.

  As described above, according to the first embodiment, the heating device 67 that heats the transfer fixing surface of the recording medium P conveyed to the nip portion between the transfer fixing belt 27 and the pressure roller 68 (pressure member). (Heating means) and the material of the surface layer 27a of the transfer-fixing belt 27 is optimized, so that energy consumption is low and even when various recording media P such as concavo-convex paper and coated paper are passed. In addition, the recording medium P is not wound around the transfer fixing belt 27, and a defect such as a decrease in dot reproducibility does not occur, and a high-quality image with good fixability can be formed.

In the first embodiment, a resistance heating element (positive characteristic thermistor) is used as the heating element 67a of the heating device 67 so that the heat transfer plate 67b is heated by the heating element 67a. However, the heating device 67 as the heating means is not limited to such a configuration. For example, the heat transfer plate 67b may be formed of a metal material whose magnetic permeability decreases when reaching a predetermined Curie point, and the heat transfer plate 67b can be heated by electromagnetic induction. In such a case, the same effect as in the first embodiment can be obtained.
In the first embodiment, the brush-like member 91 is used as an urging member that urges the recording medium P toward the heat transfer plate 67b. However, a spring material may be used as the urging member. In that case, in order to reduce the friction with the recording medium P, it is preferable to coat the sliding surface of the spring material with a low friction material such as a fluororesin.

  In the first embodiment, the leveling roller 85 is used as a cooling means for cooling the transfer fixing belt 27 after the transfer fixing process, but a cooling fan facing the surface of the transfer fixing belt may be used as the cooling means. it can.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is an enlarged view showing the vicinity of the transfer fixing device in the second embodiment, and corresponds to FIG. 2 in the first embodiment. In the transfer fixing apparatus according to the second embodiment, the toner images formed on the photosensitive drums 21 of the respective colors are primarily transferred to the intermediate transfer belt 95 and then secondarily transferred to the transfer fixing belt 27 and then onto the recording medium P. The third transfer is different from that of the first embodiment in which the toner image formed on the photosensitive drum 21 of each color is primarily transferred to the transfer fixing belt 27 and secondarily transferred to the recording medium P. To do.

In the image forming apparatus according to the second embodiment, the toner images formed on the photosensitive drums for each color (not shown, but arranged in parallel so as to face the intermediate transfer belt 95) are intermediate transfer belts 95. Then, the toner image is secondarily transferred to the transfer and fixing belt 27 between the intermediate transfer belt 95 and the transfer and fixing belt 27. Further, the toner image T transferred to the transfer fixing belt 27 is tertiary transferred and fixed (transfer-fixed) to the recording medium P at the position of the nip portion with the pressure roller 68.
Here, also in the second embodiment, a heating device 67 (heating means) for heating the recording medium P immediately before the transfer fixing process is installed in the vicinity of the nip portion between the transfer fixing belt 27 and the pressure roller 68. Yes. The transfer fixing belt 27 is stretched and supported by three roller members 97a to 97c, and a heater 70 is disposed at a position on the upstream side of the nip portion and facing the transfer fixing belt 27.
In the transfer fixing belt 27 in the second embodiment, the surface layer 27a formed on the outer peripheral surface side in contact with the recording medium P is made of a heat resistant elastic material, a porous material, as in the first embodiment. It is formed with the composite material which consists of the fluorinated fluororesin material, and is formed so that it may further have electroconductivity.

  As described above, also in the second embodiment, similarly to the first embodiment, the transfer of the recording medium P conveyed to the nip portion between the transfer fixing belt 27 and the pressure roller 68 (pressure member). Since the heating device 67 (heating means) for heating the fixing surface is provided and the material of the surface layer 27a of the transfer fixing belt 27 is optimized, the energy consumption is low, and various recording media P such as uneven paper and coated paper can be used. Even when the paper is passed, the recording medium P does not wrap around the transfer and fixing belt 27, and defects such as a decrease in dot reproducibility do not occur. can do.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is an enlarged view showing the vicinity of the transfer fixing device in the third embodiment, and corresponds to FIG. 2 in the first embodiment. The image forming apparatus according to the third embodiment is different from that according to the first embodiment in that a fixing device 98 is installed separately from the transfer fixing device 66.

Unlike the first embodiment, the image forming apparatus according to the third embodiment is provided with a fixing device 98 for auxiliary refixing of the recording medium after the transfer and fixing process. The fixing device 98 includes a fixing roller in which a heater is provided, a pressure roller that presses the fixing roller to form a nip, and the like. Unlike the fixing device installed in the conventional image forming apparatus that performs the transfer process and the fixing process separately, the fixing apparatus 98 assists and re-fixes the toner image on the recording medium after the transfer fixing process. Therefore, the heating amount and the applied pressure are set lower than the conventional one.
Here, also in the third embodiment, a heating device 67 (heating means) for heating the recording medium P immediately before the transfer fixing process is installed in the vicinity of the nip portion between the transfer fixing belt 27 and the pressure roller 68. Yes. In the third embodiment, unlike the first embodiment, the heater 70 facing the transfer fixing belt 27 is not provided.
Also, in the transfer fixing belt 27 in the third embodiment, the surface layer 27a formed on the outer peripheral surface side in contact with the recording medium P is made of a heat resistant elastic material, a porous material, as in the above embodiments. It is formed with the composite material which consists of the fluorinated fluororesin material, and is formed so that it may further have electroconductivity.

  As described above, also in the third embodiment, the transfer of the recording medium P conveyed to the nip portion between the transfer fixing belt 27 and the pressure roller 68 (pressure member) as in the above-described embodiments. Since the heating device 67 (heating means) for heating the fixing surface is provided and the material of the surface layer 27a of the transfer fixing belt 27 is optimized, the energy consumption is low, and various recording media P such as uneven paper and coated paper can be used. Even when the paper is passed, the recording medium P does not wrap around the transfer and fixing belt 27, and defects such as a decrease in dot reproducibility do not occur. can do.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 9 is a configuration diagram illustrating a part of the image forming apparatus according to the fourth embodiment. The image forming apparatus according to the fourth embodiment is different from that of the first embodiment in which four photosensitive drums 21 are installed in that one photosensitive drum 21 is installed.

As shown in FIG. 9, the image forming apparatus according to the fourth embodiment has a writing unit (not shown) corresponding to each color (yellow, magenta, cyan, black) around one photosensitive drum 21. , A charging unit (not shown), developing devices 23Y, 23M, 23C, 23BK, a cleaning device 25, and the like are disposed. Then, images (toner images) of the respective colors are formed on the photosensitive drum 21 so as to overlap each other, and the color image is transferred onto the transfer fixing belt 27 at a position facing the transfer bias roller 24.
After that, the toner image T carried on the transfer fixing belt 27 is transferred onto the recording medium P heated by the heating device 67 at the position of the nip portion with the pressure roller 68 as in the above embodiments.・ Fixed.

  In the transfer fixing belt 27 in the fourth embodiment, the surface layer 27a formed on the outer peripheral surface side in contact with the recording medium P is formed of a heat-resistant elastic material, a porous material, as in the above embodiments. It is formed with the composite material which consists of the fluorinated fluororesin material, and is formed so that it may further have electroconductivity.

  As described above, also in the fourth embodiment, the transfer of the recording medium P conveyed to the nip portion between the transfer fixing belt 27 and the pressure roller 68 (pressure member) as in the above-described embodiments. Since the heating device 67 (heating means) for heating the fixing surface is provided and the material of the surface layer 27a of the transfer fixing belt 27 is optimized, the energy consumption is low, and various recording media P such as uneven paper and coated paper can be used. Even when the paper is passed, the recording medium P does not wrap around the transfer and fixing belt 27, and defects such as a decrease in dot reproducibility do not occur. can do.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 image forming apparatus body (apparatus body),
27 transfer fixing belt (transfer fixing member),
27a surface layer, 27b elastic layer, 27c base material layer,
28A-28C roller member,
66 transfer fixing device,
67 Heating device (heating means),
67a heating element,
67b heat transfer plate,
67c electrode,
68 Pressure roller (pressure member),
85 Leveling roller (cooling means),
91 brush-like member (biasing member),
95 Intermediate transfer belt, P recording medium.

JP-A-2005-37879 JP 2002-99159 A

Claims (9)

A transfer fixing device for transferring and fixing a toner image to a transfer fixing surface of a recording medium,
A transfer fixing belt that carries a toner image and travels in a predetermined direction;
A pressure member that forms a nip portion to which the recording medium is conveyed in pressure contact with the transfer fixing belt;
Heating means for heating the transfer fixing surface of the recording medium conveyed toward the nip portion;
With
The transfer-fixing apparatus, wherein the transfer-fixing belt comprises a conductive surface layer made of an elastic material and a porous fluororesin material on the side in contact with the recording medium.   2. The transfer fixing device according to claim 1, wherein the surface layer of the transfer fixing belt is made of an elastic material and a conductive and porous fluororesin material.   The transfer fixing belt is formed so that a stretching direction at the time of processing in the fluororesin material having conductivity and being made porous coincides with a running direction of the transfer fixing belt. The transfer fixing device according to claim 2.   4. The transfer fixing device according to claim 1, wherein the transfer fixing belt is formed by forming the surface layer through an elastic layer on a conductive base material layer. .   The transfer fixing apparatus according to claim 4, wherein the elastic layer is formed to have a higher volume resistivity than the surface layer. The elastic material is silicone rubber,
The transfer fixing device according to claim 1, wherein the porous fluororesin material is polytetrafluoroethylene. The heating means includes
A heat transfer plate that is heated by a heating body and that heats the transfer-fixing surface of the recording medium while guiding the recording medium conveyed toward the nip portion;
A biasing member that biases the recording medium guided by the heat transfer plate toward the heat transfer plate;
The transfer fixing device according to claim 1, wherein the transfer fixing device is provided.   The transfer fixing device according to claim 1, further comprising a cooling unit that cools the transfer fixing belt after passing through the nip portion.   An image forming apparatus comprising the transfer fixing device according to claim 1.

Images