JP5339080B2 - Transfer fixing device, and image forming apparatus and image forming method using the transfer fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer fixing device which can obtain high definition special color images, and to provide an image forming apparatus using the transfer fixing device, and an image forming method. <P>SOLUTION: The transfer fixing device includes: an intermediate transfer belt 2 for carrying toner images on the surface; a transfer fixing belt 13 for carrying the toner images transferred from the intermediate transfer belt 2 on the surface; a transfer roller 21 for transferring the toner images from the intermediate transfer belt 2; a belt heating means 36 for heating the transfer fixing belt 13; a transfer fixing member 9 and a pressurization member 24 for sandwiching the transfer fixing belt 13 to form a transfer fixing nip N; a process color image formation part arranged on the surface side of the intermediate transfer belt 2 and for forming process color toner images T1 of YMCK; a special color toner image formation part arranged on the side of the surface of the transfer fixing belt and forming special color toner images T2 in one or more kinds. The transfer fixing belt 2 uses a material having viscosity on a surface layer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

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

  2. Description of the Related Art Conventional image forming apparatuses such as electrophotographic copying machines, printers, and facsimiles can obtain a copy or a recorded material by heat-fixing an unfixed image transferred from an image carrier to a recording medium. During fixing, the unfixed image is heated while nipping and pressing the recording medium carrying the unfixed image to thereby melt and soften the developer contained in the unfixed image, in particular, toner, and penetrate into the recording medium. By doing so, the toner is fixed to the recording medium. In view of this, there has been proposed a transfer and fixing device that integrally transfers and fixes an unfixed image formed on an image carrier onto a recording medium.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 10-63121) proposes a secondary transfer fixing type transfer fixing device that performs fixing from an intermediate transfer member to a transfer material (recording medium) together with secondary transfer.
Further, for example, in Patent Document 2 (Japanese Patent Laid-Open No. 2004-145260), after secondary transfer from an intermediate transfer member to a transfer fixing member, fixing is performed together with tertiary transfer from the transfer fixing member to a transfer material (recording medium) 3. A transfer fixing device of the next transfer fixing type has been proposed.

In the techniques described in Patent Documents 1 and 2, it is common to use a chargeable powder mainly composed of a resin called toner as a member constituting an image.
These toners have higher hot offset generation temperatures (good hot offset resistance) and lower fixing temperatures (low temperature fixing properties) as energy savings and miniaturization of devices such as copying machines are studied. Is good) toner is desired. In particular, when the fixing temperature (belt temperature) rises in transfer fixing, heat is transferred to the drum (photoconductor) in contact with the transfer fixing belt, and further to the developing unit (developing device), and image defects due to belt deformation, and Since problems such as solidification of the toner are more likely to occur, a toner having a lower temperature fixability is required.

  Conventionally, wax is added to the toner in order to add releasability to the toner. In general, release agents such as waxes often have a low melting point, which causes contamination of the developing member due to seepage, and may cause turbidity due to formation of an interface with the resin at the time of melting, thereby impairing color reproducibility. In addition, there is a problem in compatibility with the resin, developability deteriorates as the addition amount increases, and spent with the carrier also occurs, so the charge amount is insufficient and charging instability occurs, so it is not used or the use amount is reduced Preferably it can be done.

  In a conventional electrophotographic image forming apparatus, a process that easily deteriorates image quality is a transfer process to a transfer material (recording medium). Paper is mainly used as the transfer material, but there are papers with various thicknesses ranging from plain paper to cardboard, and the surface properties also vary from fine (nearly smooth) to rough. . Conventional electrostatic transfer to paper is very susceptible to such paper surface effects, so image defects such as transfer dust are likely to occur.

  On the other hand, in the image forming apparatus described in Patent Documents 1 and 2 having the transfer fixing process, since the transfer and fixing are performed simultaneously with non-electrostatic force (heat, pressure, etc.), the above-described image is used. It has the advantage that quality degradation is unlikely to occur. Since heat is applied simultaneously with the transfer, the toner is softened and melted by the heat and transferred as a block-like lump having viscoelasticity, so that an image without transfer dust is obtained. Because of such advantages, the image forming apparatus having the transfer fixing unit can be said to be an optimal unit for achieving high image quality.

  On the other hand, various utilization methods have been considered for full-color image forming apparatuses such as copying machines and printers. For example, a home party guide letter with a full-color printer, a small-scale store flyer, and advertisement creation. Therefore, in addition to the conventional yellow, magenta, cyan, and black color toners, the transparent toner for the purpose of obtaining a high gloss image, the fluorescent toner for the purpose of obtaining a fluorescent image, and the expansion of the color reproduction area. For the purpose, colored toners such as red and green, so-called “special color toners (spot color toners)” are beginning to be adopted.

  Among them, in fields where decorativeness is required (for example, certificate frames, printed paper, celebration bags, etc.), there may be a demand for gold-silver-colored electrophotographic copies or printed materials. It has been demanded. This is because a normal color printer overlays yellow, magenta, and cyan colors to express metallic luster, but the image quality obtained is gold with low reflectivity, and is not of a quality that satisfies customer requirements. .

  For example, Patent Document 3 (Japanese Patent Publication No. 6-73028) relates to a gold toner having such a special color, coloring a pigment obtained by coating scaly mica (mica) with titanium dioxide and iron oxide in a thin film shape. It is described to be used as an agent. Patent Document 4 (Japanese Patent Laid-Open No. 9-160298) describes that reproduction of a golden color can be obtained by using fine powder of an alloy mainly composed of copper, zinc and aluminum as a colorant. Yes.

  However, since such a pigment is generally conductive, its electric resistance value is low, so electrostatic transfer is difficult, and as a result, the transfer rate is low and sufficient image density, that is, metallic gloss is expressed. I could not.

  Accordingly, an object of the present invention is to provide a high-quality special color image (particularly, a glossy and gorgeous color image having a glossy and distinctive weight with a glossiness) and a high-quality image. It is an object of the present invention to provide an image forming apparatus and an image forming method using the above-described transfer fixing device.

In order to solve the above problems, a transfer fixing device according to the present invention, and an image forming apparatus and an image forming method using the transfer fixing device are specifically described in the technical aspects described in (1) to (5) below. Has characteristics.
(1): an intermediate transfer belt carrying a toner image on the surface, a transfer fixing belt carrying a toner image transferred from the intermediate transfer belt on the surface, and the intermediate transfer belt provided on the back surface of the transfer fixing belt; A transfer roller for transferring the toner image to the transfer fixing belt, a belt heating means for heating the transfer fixing belt, a transfer fixing member and a pressure member for sandwiching the transfer fixing belt to form a transfer fixing nip N A process color image forming portion for forming yellow, magenta, cyan and black process color toner images, respectively, and a transfer fixing belt surface side. It includes a spot color toner image forming unit for forming a process color toner image other than the special color toner image of one or more, and the spot color toner A toner having metallic luster, wherein the transfer-fixing belt is transfer fixing apparatus characterized by comprising material is used having an adhesive property to the surface layer.
(2) The transfer fixing apparatus according to (1) above, further comprising recording medium heating means for heating the surface of the recording medium conveyed to the transfer fixing nip N.
(3): After the toner image carried on the surface of the intermediate transfer belt is transferred to the transfer and fixing belt, the first cooling means for cooling the intermediate transfer belt and the surface of the transfer and fixing belt are carried. And (2) a second cooling means for cooling the transfer and fixing belt after the toner image is transferred and fixed to the recording medium conveyed to the transfer and fixing nip N. Alternatively, the transfer fixing device according to (2) .
(4) : An electrophotographic image forming apparatus comprising the transfer fixing device according to any one of (1) to (3) above.
(5) : An electrophotographic image forming method using the transfer fixing apparatus according to any one of (1) to (3) above.

In a normal color printer, yellow, magenta, and cyan colors are superimposed to express metallic luster, but the resulting image quality is gold or silver with low reflectivity, and the quality is not sufficient to satisfy customer requirements. In particular, in fields where decorativeness is required (for example, certificate frames, printed paper, celebration bags, etc.), there may be demands for gold and silver electrophotographic copies and printed materials. It has been demanded. In general, the electrical properties of these special color toners vary greatly depending on the pigment used. For example, pigments such as gold and silver toners are conductive and have low electrical resistance, so electrostatic transfer is difficult, resulting in low transfer rate and sufficient image density, ie, metallic luster I could not.
Therefore, according to the configuration described in (1) above, even such a toner is not an electrostatic transfer as long as it is an adhesive transfer, so a high image can be obtained with a very high transfer rate regardless of the electrical characteristics of the toner. Transfer with which density can be obtained is possible.

Further, when the temperature of the transfer fixing belt rises, heat is transmitted to the drum (photosensitive member as a latent image carrier) in contact with the transfer fixing belt, and further to the developing unit (developing device), and image defects and toner Problems such as solidification are more likely to occur.
Therefore, according to the configuration described in (2) above, since the recording medium heating unit heats the paper as the recording medium, the set temperature of the transfer fixing belt heating can be lowered, and the transfer fixing belt temperature can be increased. It can be suppressed, and the transfer fixing belt can be easily cooled. Further, by controlling the temperature of the paper and the transfer fixing belt separately, a good image without offset can be provided.

Furthermore, in the transfer fixing device, heat is transferred to the drum that is in contact with the transfer fixing belt, and further to the developing unit, and it is easy for image defects and toner solidification to occur. It is preferable to cool the transfer fixing belt.
Therefore, according to the configuration described in (3) above, it is possible to suppress problems caused by the temperature increase of the transfer fixing belt.

  According to the configurations described in the above (4) to (8), a desired image can be obtained, that is, a golden silver toner can obtain a metallic gloss image, a transparent toner can obtain a high gloss image, and a light toner can have a granularity. There is an improvement effect, and the colored toner (RGB) has an effect of widening the color gamut, and the fluorescent toner can obtain a fluorescent color image.

  According to the configurations described in the above (9) to (10), an electrophotographic image forming apparatus such as a facsimile apparatus, a copying machine, or a printer can be used as a transfer fixing apparatus capable of using a special color that can be used for various applications. In addition, by applying to the image forming method, it is possible to deal with various uses.

  According to the present invention, it is possible to provide a transfer fixing device capable of obtaining a high-quality spot color image, and an image forming apparatus and an image forming method using the transfer fixing device optimal for achieving high image quality.

1 is a side view showing an internal essential part of an electrophotographic color copying machine which is an embodiment of an image forming apparatus according to the present invention. It is a graph which shows an example of the spectral radiant intensity of a carbon heater and the halogen heater (tungsten wire heater) of the power consumption equivalent to this carbon heater. (A) It is a schematic diagram which shows the relationship between F1, F2, and F3. (B) It is a schematic diagram which shows the relationship between F1, F2, and F3 in case offset generate | occur | produces. (C) It is a schematic diagram which shows the relationship between F1, F2, and F3 when an offset does not generate | occur | produce. (A) It is a graph which shows the flow curve of the flow tester for demonstrating Ts and Tfb. (B) It is a graph which shows the flow curve of the flow tester for demonstrating the melting temperature in a 1/2 method. It is the figure which showed the fixing property on Tt-Tp coordinate in Tfb = 90 degreeC. It is the figure which showed the fixing property on Tt-Tp coordinate in Tfb = 110 degreeC. 1 is a side view showing a part of an electrophotographic color copying machine that is an embodiment of an image forming apparatus according to the present invention, and is a schematic view showing a contact state of a heating guide plate 120, a conveyance roller 121, and conveyance paper.

The transfer and fixing device according to the present invention includes an intermediate transfer belt 2 that carries a toner image on its surface, a transfer and fixing belt 13 that carries a toner image transferred from the intermediate transfer belt 2 on its surface, and a transfer and fixing belt 13. A transfer roller 21 provided on the back surface for transferring a toner image from the intermediate transfer belt 2 to the transfer fixing belt 13, a belt heating means 36 for heating the transfer fixing belt 13, and the transfer fixing belt 13 are sandwiched. The transfer fixing member 9 and the pressure member 24 that form the transfer fixing nip N, and the process for forming yellow, magenta, cyan, and black process color toner images T1 are disposed on the surface side of the intermediate transfer belt 2 respectively. A special color toner image other than the process color toner image, which is disposed on the surface side of the color image forming portion and the transfer and fixing belt The transfer-fixing belt 2 includes a spot color toner image forming unit, the forming 2 one or more are characterized by comprising material is used having an adhesive property to the surface layer.
Next, the transfer fixing device, the image forming apparatus, and the image forming method according to the present invention will be described in more detail.

(Image forming device)
Hereinafter, the present invention will be described with reference to the drawings, taking an embodiment adapted to a tandem type electrophotographic color copying machine as an image forming apparatus.
Although the embodiments described below are preferred embodiments of the present invention, various technically preferred limitations are given, but the scope of the present invention is intended to limit the present invention in the following description. As long as there is no description, it is not restricted to these aspects.

  FIG. 1 is a side view showing an essential part of an electrophotographic color copying machine which is an embodiment of an image forming apparatus according to the present invention. An outline of the configuration and operation of a tandem type color copier as an image forming apparatus in the present embodiment will be described with reference to FIG.

The color copying machine includes an image forming unit 1A positioned at the center of the apparatus main body, a paper feeding unit 1B positioned below the image forming unit 1A, and an image reading unit (not shown) positioned above the image forming unit 1A. Have.
The transfer fixing device according to the present invention includes a process color toner image forming unit (4-8Y, 4-8M, 4-8C, 4-8K), a special color toner image forming unit (4-8S), and an intermediate transfer belt 2. , A transfer fixing belt 13, a transfer roller 21, a belt heating means 36, a transfer fixing roller 9 as a transfer fixing member, and a pressure roller 24 as a pressure member. Prepare.

  This device can form images at a linear speed of 300 mm / s. An intermediate transfer belt 2 as an intermediate transfer body having a transfer surface extending in the horizontal direction is disposed in the image forming unit 1A. The upper surface of the intermediate transfer belt 2 has a color complementary to the color separation color. A configuration for forming an image is provided. That is, the photoreceptors 3Y, 3M, 3C, and 3K as image carriers capable of carrying images of complementary color toners (yellow, magenta, cyan, and black) are provided along the transfer surface of the intermediate transfer belt 2. It is juxtaposed. A typical structure of the intermediate transfer belt 2 is a polyimide resin of 80 μm serving as a base material. A fluororesin (about 10 μm) may be provided on the surface (on the side facing the photoconductor 3) in order to improve releasability with respect to toner and paper dust.

  Each of the photoreceptors 3Y, 3M, 3C, and 3K is configured by a drum that can rotate in the same direction (clockwise direction in FIG. 1; arrow direction), and an image forming process is performed around the drum. A charging device 4, a writing device 5 as an optical writing means, a developing device 6, a primary transfer device 7, and a cleaning device 8 are arranged. The alphabet added to each symbol corresponds to the color of the toner as in the photosensitive member 3. Each developing device 6 stores color toners corresponding to the respective colors. The intermediate transfer belt 2 is configured to be wound around the belt driving roller 10 and the driven roller 11 so as to be movable in the same direction at a position (primary transfer portion) facing the photoreceptors 3Y, 3M, 3C, and 3K. . A cleaning device 12 for removing normal secondary transfer residual toner is provided at a position facing the driving roller 10, and an image correction pattern cleaning for removing an image adjustment pattern at a position facing the driven roller 11. A member 19 is provided.

  The adjustment pattern is used to obtain data for various adjustments (density correction, color misregistration correction, etc.). As long as the toner detection sensor 15 performs reading, the adjustment pattern is normally applied to a recording medium such as transfer paper. No transcription is necessary. In this configuration, since heat and pressure are applied to the transfer fixing unit described later, if the image adjustment pattern is cleaned after the transfer fixing, the image is fixed to the transfer fixing belt and the pressure roller, which makes cleaning very difficult. The image adjustment pattern must be cleaned before transfer and fixing. Therefore, an image correction pattern cleaning member 19 is installed at a position downstream of the primary transfer portion (a position where the intermediate transfer belt 2 and the photosensitive member 3 face each other) and upstream of the transfer fixing portion.

  The surface of the photoreceptor 3Y is uniformly charged by the charging device 4Y, and an electrostatic latent image is formed on the photoreceptor 3Y based on image information from the image reading unit. The electrostatic latent image is visualized as a toner image by a developing device 6Y containing yellow toner, and the toner image is primary-transferred onto the intermediate transfer belt 2 by a primary transfer device 7Y to which a predetermined bias is applied. Transcribed. The other photoreceptors 3M, 3C, and 3K also form similar images only with different toner colors. The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 2 and superimposed, and the process color toner image T1. Is formed. The toner remaining on the photoreceptor 3 after the transfer is removed by the cleaning device 8, and after the transfer, the electric potential of the photoreceptor 3 is initialized by a charge-removing lamp (not shown) to prepare for the next image forming process.

  On the other hand, a transfer fixing portion is provided in the vicinity of the driven roller 11. The transfer fixing unit is a transfer fixing unit between a transfer fixing belt 13 to which an unfixed toner image on the intermediate transfer belt 2 is transferred and a transfer fixing roller (transfer fixing member) 9 via the transfer fixing belt 13. And a pressure roller 24 as a pressure member for forming the transfer fixing nip N. The transfer and fixing belt 13 is made of a material having adhesiveness on the surface. In this embodiment, a polyimide resin of 80 μm is used as a base material, and 200 μm of silicone rubber is laminated as a surface layer on the side facing the intermediate transfer belt 2 of the base material. It has been configured. The pressure roller 24 is formed in a pipe shape from a metal such as aluminum, and a release layer is coated on the surface. The pressure member is not limited to the pressure roller, and may be a non-rotating member. In the present embodiment, silicone rubber is used for the surface layer of the transfer and fixing belt 13 as an adhesive material.

  A special color toner image forming unit for forming a special color toner image (gold or silver toner) is provided on the transfer and fixing unit. In this special color toner image forming process, the surface of the photoconductor 3S is uniformly charged by the charging device 4S in the same manner as the above yellow, magenta, cyan, and black, and the surface of the photoconductor 3S is statically charged on the photoconductor 3S based on image information from the image reading unit. An electrostatic latent image is formed. The electrostatic latent image is visualized as a toner image by the developing device 6S containing special color toner. Thereafter, the toner image T2 on the photosensitive member 3S is adhesively transferred onto the above-described transfer and fixing belt 13 having adhesiveness on the surface. In general, the electrical properties of special color toners vary greatly depending on the pigment used. For example, pigments such as gold and silver toners are conductive and have low electrical resistance, so electrostatic transfer is difficult, resulting in low transfer rate and sufficient image density, ie, metallic luster I could not. However, even with such toner, if it is the above-mentioned adhesive transfer, it is not electrostatic transfer, and therefore, transfer capable of obtaining a high image density at a very high transfer rate is possible regardless of the electrical characteristics of the toner. As with the yellow, magenta, cyan, and black, the photosensitive member 3S after the adhesive transfer has the toner remaining on the surface removed by the cleaning device 8S, and further, the electric potential of the photosensitive member 3S is initialized by a neutralization lamp (not shown). And prepared for the next image forming step.

  The toner image T1 primarily transferred onto the intermediate transfer belt 2 from the above-described photoreceptors 3Y, 3M, 3C, and 3K includes a bias (AC, pulse, etc.) applied to the driven roller 11 by a bias applying unit (not shown). ), The transfer roller 21 and the driven roller 11 are secondarily transferred by electrostatic force onto the transfer fixing belt 13 onto which the special color toner image T2 has been transferred (secondary transfer).

  Here, in this image forming apparatus, after the special color toner image is transferred onto the transfer fixing belt 13, the process color toner image T1 is electrostatically transferred to the same location on the transfer fixing belt 13 as the special color toner image. As a result, in the formed image, the special color toner is present at the top of the final image (on the paper) (the side farthest from the contact surface between the paper surface and the toner), and it is brilliant and gorgeous without dullness. A special color image can be formed.

The toner image T1 + T2 transferred to the transfer fixing belt 13 is heated by the belt heating means 36. The belt heating means 36 is constituted by a heat source and a reflection plate, and is spaced apart from the outer side (toner image carrying side) of the transfer fixing belt 13. Although a halogen heater may be used as the heat source, a carbon heater having a high radiant heating efficiency is used here. FIG. 2 shows an example of the spectral radiation intensity of a carbon heater and a halogen heater (tungsten wire heater) with power consumption equivalent to that of the carbon heater. As shown in FIG. 2, the wavelength of the maximum radiation intensity of the halogen heater is in the range of 1 to 2 μm, and the maximum radiation intensity of the carbon heater is in the range of 2 to 4 μm. The infrared absorption spectrum of the surface layer of the transfer and fixing belt 13 used in this embodiment is about 2800 to 3100 (cm ⁻¹ ), that is, the wavelength is about 3.2 to 3.6 (μm). Is good. In addition, the resin used in the intermediate layer and surface layer of transfer members and fixing members that are generally used has a wavelength range of 2 to 4 (μm) with good infrared absorption efficiency, and the carbon heater is a halogen heater. Compared to resin-based heating. Carbon heaters are also excellent in having resistance to inrush current and rapid heat.

  As the belt heating means, heating from the inside of the transfer fixing belt 13 can be considered, but as described above, the structure of the transfer fixing belt 13 is a base material + elastic layer (+ surface layer), and heating from the inside is not necessarily performed. The thermal efficiency is not good from the viewpoint of heat conduction and heat capacity (if the entire belt is heated, the cooling load in the subsequent process increases). Therefore, radiant heating from the outside of the belt is the most efficient method as the belt heating means. (Because a toner image is placed on the belt, contact heating outside the belt is impossible.)

  The reflection plate is installed to collect light (heat) from the heat source toward the transfer fixing belt 13. That is, the surface on the side including the heating source is a mirror surface having a particularly high reflectivity with respect to infrared light, and is configured to efficiently apply radiant heat to the outer peripheral surface of the transfer and fixing belt 13. The shape of the reflecting surface of the reflecting plate is not particularly limited, but may be a box shape, a hemisphere shape or an ellipsoid shape, but the reflecting plate is formed in a parabolic curved plate shape having a parabolic cross section, and the focal point of the parabola. It is preferable to install a line heat source on the line connecting the wires. Thereby, the reflection efficiency of the reflecting plate is further increased.

  Examples of the material of the reflecting plate include metals such as stainless steel, gold, silver, copper, nickel, and aluminum (high brightness aluminum), and heat-resistant resin. Moreover, what coated these metals may be used. Furthermore, in order to increase the reflection efficiency, it is preferable to mirror-polish the reflecting surface of the reflecting plate.

  The paper feed unit 1B includes a paper feed tray 14 that stacks and stores paper P as a recording medium, and a paper feed roller 16 that feeds paper P in the paper feed tray 14 one by one from the top in order. A pair of transport rollers 17 for transporting the fed paper P, and after the paper P is temporarily stopped and the oblique shift is corrected, the leading edge of the image on the transfer fixing belt 2 coincides with a predetermined position in the transport direction. And a registration roller pair 18 fed toward the nip N at timing.

A recording medium heating unit 120 for heating the paper surface is provided immediately before the transfer fixing unit. In the present embodiment, belt heating means 36 for heating the image (toner image T1 + T2) on the transfer / fixing belt 13 is provided, and the toner image T1 + T2 on the transfer / fixing belt 13 is heated. Heat is also transmitted to the photosensitive member 3S in contact with the belt 13 and further to the developing device 6S, and problems such as image defects and toner solidification are more likely to occur. Further, heat is transferred to the photoreceptors 3Y, 3M, 3C, and 3K and the developing devices 6Y, 6M, 6C, and 6K through the intermediate transfer belt 2, and similarly, further problems such as image defects and toner solidification occur. It becomes easy to do.
Therefore, if the paper is heated by the recording medium (paper) heating means 120, the set temperature for heating the transfer fixing belt 13 can be lowered, and the temperature rise of the transfer fixing belt 13 can be suppressed. Cooling is also easy.

  Furthermore, the temperature of the paper and the transfer and fixing belt 13 can be controlled separately. For example, by making the temperature of the paper higher than the temperature of the transfer and fixing belt 13, the difference in viscoelasticity at the interface with each toner causes hot Offset can be prevented. That is, by increasing the temperature on the paper side of the toner layer and decreasing the temperature on the transfer and fixing belt 13 side, the adhesive force between the paper and the toner becomes higher than the adhesion force between the transfer and fixing belt 13 and the toner. By improving the toner releasability, a good image with no offset in the transfer and fixing belt 13 can be obtained. Further, in order to add releasability to the conventional toner, wax has been added to the toner, but this can be minimized or eliminated by improving the hot offset resistance. If the wax can be reduced or eliminated, color reproducibility, developability and chargeability can be improved.

  In this regard, the inventors observed the separation behavior in an experiment using a high-speed video camera. As an experimental method, a high-speed video camera system capable of photographing 40,000 frames per second was used to confirm the toner offset phenomenon on a micrometer scale. Since the obtained image was dark, a probe with a sufficient amount of light and a lens with a high magnification rigid mirror optical magnification of 120 times having a super focal length was used as a probe. As a result, it is possible to observe a phenomenon in which the toner coming out of the fixing nip and the toner are offset at a magnification of 400 times on the monitor. First, observation was performed with a conventional general fixing device. As the fixing roller / pressure roller, a silicon rubber roller covered with a PFA (polytetrafluoroethylene) tube was used. As a result of observation, it was found that the toner extended like rubber between the fixing roller and the paper. The rubber is cut from the vicinity of the fixing roller when it is fully extended, and the toner is separated into the fixing roller side and the paper side. As described above, it was confirmed that the yarn pulling phenomenon occurred at the fixing nip exit in the normal fixing device. Accordingly, the same observation was made in the paper heating transfer fixing in which the paper temperature and the toner temperature are “paper temperature> belt temperature”, which is a preferable embodiment in the present invention. It was confirmed that the stringing phenomenon hardly occurred. This indicates that the transfer fixing system of the present embodiment is superior in offset property, that is, release property, compared to a normal fixing system.

  The offset property will be described with reference to FIG. The offset phenomenon is caused by the three force relationships shown in FIG. 3A: the adhesion force between the fixing member and the toner (F1), the toner cohesion force (F2), and the adhesion force between the toner and paper (F3). It becomes. An offset occurs when F1 is the largest as shown in FIG. 3B, and to suppress the offset, F1 may be reduced as shown in FIG. 3C. In normal fixing, oil application, wax addition, stress due to roller distortion, etc. are mainly performed to reduce F1. However, in the transfer fixing device according to the present embodiment, improvement in releasability is achieved without such oil application. In normal fixing, heat is applied to the toner only from the fixing member, and the temperature gradient of the toner layer is extreme such that the fixing roller side> the paper side, whereas in this embodiment, the temperature gradient of the toner layer is It is considered that F1 is very small because the fixing member side <the paper side.

  Here, the present inventors have clarified through experiments that it is a case where all of the following formulas (1) to (3) are satisfied for an appropriate temperature balance.

  When the surface temperature Tt of the toner layer before fixing, the surface temperature Tp of the recording medium before fixing, the temperature Tb of the pressure member 24, the outflow start temperature Tfb of the toner, and the softening point temperature Ts of the toner, the following formulas (1) to ( It is preferable to satisfy all 3).

(Tt + Tp) / 2> Tfb (1)
Tt <Tfb (2)
Tb <Ts Formula (3)

  The above formula (3) is more preferably the following formula (3 ′), more preferably the following formula (3 ″).

Tt <Tfb−20 ° C., Formula (3 ′)
Tt <Tfb−30 ° C. Formula (3 ″)

Here, the softening point temperature Ts and the outflow start temperature Tfb of the toner can be measured using a flow tester. A flow tester is a capillary rheometer that measures the viscous resistance when a melt (toner) passes through a capillary. First, a sample (toner) filled in a cylinder is heated and melted from the surroundings, and a certain pressure is applied from above by a piston. The melted toner is extruded through a die having a narrow hole, and the flowability of the sample, that is, the melt viscosity is determined from the flow rate (cm ³ / s). An example of the flow tester is a Koka flow tester CFT500D manufactured by Shimadzu Corporation. The flow curve of this flow tester becomes the data shown in FIG. 4A and FIG. 4B, from which each temperature can be read. In FIG. 4A, point B is the softening point temperature Ts that moves from the solid region to the transition region, and point C is the outflow start temperature Tfb at which the sample (toner) flows out. The melting temperature in the 1/2 method in FIG. 4 (b) is obtained by calculating 1/2 of the difference between the outflow end point Smax and the minimum value Smin (X = (Smax−Smin) / 2), and X and Smin. It is the temperature at the position of the point A to which is added. Measurement conditions are, for example, a load: 5 kgf / cm ² , a temperature rising rate: 3.0 ° C./min, a die diameter: 1.00 mm, and a die length: 10.0 mm.

5 and 6 are diagrams showing the fixing property in this configuration. The conditions are as follows: paper is Casablanca X (coated paper made by Oji Paper, basis weight 100 g / m ² ), nip time is 50 ms, surface pressure is 2 kgf / cm ² , and FIG. 5 shows that the toner outflow start temperature Tfb is 90 ° C. FIG. 6 shows a toner (toner A) having a toner outflow start temperature Tfb of 110 ° C. (toner B). Each temperature Tt (horizontal axis) and Tp (vertical axis) described here will be described. The surface temperature Tt of the toner layer before fixing indicates the temperature immediately before the transfer fixing nip N, and is detected and controlled by a non-contact temperature sensor. Further, the surface temperature of the transfer fixing belt and the surface temperature of the toner layer are substantially equal and can be regarded as the same. The surface temperature Tp of the recording medium before fixing also indicates the temperature immediately before the transfer fixing nip N, and is detected and controlled by a contact temperature sensor or a non-contact temperature sensor. The lower limit of fixing is a rubbing test or the like, and indicates a lower limit temperature showing good fixability. The upper part of the fixing lower limit line in the figure indicates good fixability. The minimum fixing temperature is determined by nip time, paper type, surface pressure, and toner. Tfb indicates the toner outflow start temperature, and the condition described in the above formula (1), (Tt + Tp) / 2> Tfb is equal to or higher than the toner outflow start temperature by averaging the heat applied to the toner from the belt and the paper, respectively. The lower limit of fixing (no cold offset) is specified.

  Another condition described in the above equation (2), the range of Tt <Tfb, indicates the left side of the Tfb line on the vertical axis. Further, the range of Tt <Tfb−20 ° C. shows the left side of the Tt = Tfb−20 ° C. line in the drawing, and the range of Tt <Tfb−30 ° C. shows the left side of the Tt = Tfb−30 ° C. line in the drawing. Now, referring to FIG. 5, when the temperature of the toner layer before fixing is higher than the fixing lower limit temperature and higher than the toner outflow start temperature, that is, even when the temperature is higher than the lower limit of fixing, a hot offset occurs in the range of Tfb <Tt. Therefore, a good image cannot be obtained. Similarly, in FIG. 6 in which the outflow start temperature Tfb is different, a hot offset occurs in the range of Tfb <Tt even at a temperature equal to or higher than the lower limit of fixing, so that a good image cannot be obtained. Therefore, by controlling the temperature so that the above conditions (Tt + Tp) / 2> Tfb and Tt <Tfb are satisfied, a good image with almost no offset can be obtained. When (Tfb−Tt> 20 ° C.), the amount of hot offset is further reduced, and almost completely disappears when (Tfb−Tt> 30 ° C.).

  The hot offset here refers to the toner remaining on the belt side after the transfer and fixing, and a good image with almost no offset is a transfer image that is slightly left on the belt after the transfer and fixing. 20 can be easily removed. The fact that the hot offset is not completely means a transfer rate of 100%. Although not shown, similar results are obtained with toner outflow temperatures of 82 ° C., 101 ° C., and 118 ° C., and it is good to satisfy both the conditions described in the above formulas (1) and (2). A good image was obtained. The upper limit of the paper temperature is preferably 200 ° C. or lower in consideration of safety.

  Another condition Tb <Ts described in the above formula (3) is that the temperature of the pressure member 24 forming the transfer fixing nip N is regulated to be equal to or lower than the toner softening point temperature Ts. Image deterioration of the back surface (first surface) of the first surface after printing on the first surface can be prevented. In particular, in the past, the difference in gloss between the front and back surfaces due to the formation of the second image on the back surface on which the image was formed on one surface appeared. However, under the conditions described in the above formula (3), the image deteriorates even during duplex printing. It is possible to provide a good image without any problem.

  The surface of the recording medium (paper) P conveyed by the registration roller pair 18 is heated to a desired temperature by contacting with a recording medium heating means (hereinafter also referred to as “heating guide plate”) 120. In order to ensure contact between the paper P and the heating guide plate 120, the transport roller 121 made of a heat-resistant brush, foamed urethane, felt, or the like forms a nip width (pressing width) of about 3 to 10 mm. It is driven at substantially the same speed in the P conveying direction. Moreover, although it is set as the conveyance roller 121 in this embodiment, the plate-shaped pressing member which planted the fiber may be sufficient.

As a heating source for the heating guide plate 120, a heating element 134 having PTC characteristics is attached to the opposite side of the surface in contact with the paper. The PTC characteristic is a characteristic that the electric resistance increases and the current stops flowing as the temperature increases, and converges to a constant temperature. The heating element 134 having such a characteristic does not require temperature control and maintains a constant temperature. be able to. The heating guide plate 120 is made of a metal plate having a high thermal conductivity and suppresses the thermal resistance of the heating element 134. Since the heating element 134 is a resistance heating element whose resistance rapidly increases when a predetermined Curie point is reached, the self-temperature control function prevents an accident in which the temperature of the sheet abnormally rises, and constitutes a highly safe apparatus. it can. The heating guide plate 120 is controlled in a range of 140 to 220 ° C. to heat the paper surface to be conveyed. At this time, when an experiment was performed with a thermocouple fixed to the back side of the paper, it was confirmed that the temperature on the back side of the paper fell within 15 ° C. within 0 to 60 ms after contact with the heating guide plate 120 (measurement was equivalent to 60 k paper). Ricoh copy paper 6200 (paper thickness 87 μm, 70 g / m ² ) was used).

  FIG. 7 shows a contact state of the heating guide plate 120, the conveyance roller 121, and the conveyance paper (recording medium). A conveying roller 121 made of a brush, urethane foam, or the like is driven to rotate in the same direction as the pressure roller 24 at a position where the outer periphery contacts and deforms the cylindrical guide plate 140. The cylindrical guide plate 140 is fixed concentrically with the pressure roller 24 while maintaining a small gap, and preferably has a low friction surface treatment such as a fluororesin coat or diamond graphite to reduce the sliding resistance with the transport roller 121. ing. In this configuration, since the distance L from the conveying roller 121 to the pressure roller 24 is arranged to be smaller than the sum of the radii of both rollers, the idle running distance, that is, L2 (conveying roller 121-transferring shown in FIG. The distance between the fixing nips N) can be made as close as possible to maximize the heating efficiency. In the heating nip N1 formed by the heating guide plate 120 and the conveyance roller 121, it is desirable that the deformation of the conveyance roller 121 is large in order to increase the heating time. Therefore, a heat-resistant brush, a urethane foam, or a roller wrapped with a felt material is used. Further, an acting force of about 3 to 5 kgf is applied in the direction of the heating guide plate 120.

  The transport roller 121 reduces the idle running distance by deformation of the side surface and secures the heating nip distance by deformation of the upper surface. Due to the change, pressure unevenness occurs in the rotation direction of the conveying roller 121, and a portion where heating is insufficient occurs. For this reason, when the sheet is not conveyed, the conveyance roller 121 is controlled to be separated from the heating guide plate 120 and the cylindrical guide plate 140.

  On the other hand, when a jam occurs during the conveyance of the sheet, especially when the sheet stays in the lower part of the heating guide plate 120, there is a risk of ignition depending on the sheet even if the power to the heating element 134 is cut off. For this reason, when jamming, the heating guide plate 120 is prevented from rotating upward.

  As described above, the toner image T1 + T2 heated by the belt heating unit 36 is fixed to the paper P heated by the recording medium heating unit 120 at the nip N.

  After the transfer and fixing, the transfer and fixing belt 13 is cooled by the second cooling unit 23 between the transfer and fixing portion for the transfer and fixing belt 13 and the primary transfer portion for the photosensitive member 3S. As a result, the temperature increase of the transfer fixing belt 13 can be suppressed, and the thermal influence on the photosensitive member 3S is eliminated. Further, a leveling roller 210 is provided as shown in FIG. The leveling roller 210 is formed of a material such as a heat pipe or graphite having high thermal conductivity, and rotates in contact with the transfer fixing belt 13. By providing the temperature leveling roller 210, the temperature of the transfer and fixing belt 13 can be leveled while being uniformly cooled. Then, the residue (attached matter such as residual toner) on the cooled transfer fixing belt is collected by the transfer fixing belt cleaning device 20, and the transfer fixing process is completed. Further, the cooling structure of the transfer fixing belt 13 can also be applied to the intermediate transfer belt 2, and the temperature increase of the intermediate transfer belt 2 can be suppressed. Specifically, the temperature of the intermediate transfer belt 2 is leveled by the leveling roller 211, and the intermediate transfer belt 2 is cooled by the first cooling means 22. Although the cooling means 22 and 23 of this embodiment use a fan (an axial flow fan, a cross flow fan, etc.), they may be cooled by ion wind or a heat exchanger.

  In the conventional color image forming apparatus, in order to obtain a sufficient gloss, the heat amount of about 1.5 times that of the black and white image forming apparatus is given in consideration of the temperature drop due to the paper. For this reason, the paper is heated more than necessary, and the adhesion between the toner and the paper is increased more than necessary. In this embodiment, the temperature for obtaining sufficient gloss can be heated to the transfer fixing belt temperature and the paper temperature, respectively, so that the temperature (fixing set temperature) of the transfer fixing belt 13 can be lowered. Further, since the paper P is heated immediately before, it is not excessively heated, and the adhesion between the toner T1 + T2 and the paper is not increased more than necessary. According to the present embodiment, since heat transfer to the intermediate transfer member (intermediate transfer belt) can be suppressed, durability can be improved. Further, the temperature of the intermediate transfer member can be reduced, and thermal deterioration on the intermediate transfer member side can be suppressed. As described above, the image forming apparatus according to the present embodiment is positioned as a “paper heating transfer fixing apparatus” with respect to a conventional fixing apparatus that simply heats and pressurizes a sheet holding an unfixed toner image.

(toner)
In addition, as the toner binder resin used in the present invention, those having the following composition can be used as long as the characteristics are satisfied. 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 acetate Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Examples thereof include styrene copolymers such as copolymers.

  Also, the following resins can be mixed and used. Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or Examples thereof include alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffin, and paraffin wax.

  Among these, it is particularly preferable to contain a polyester resin in order to obtain sufficient fixability. In particular, the crystalline polyester resin is sufficiently softened and melted at the time of paper contact, and image formation with high color reproducibility as well as fixing strength becomes possible. The polyester resin is obtained by condensation polymerization of alcohol and carboxylic acid.

  Examples of the alcohol used to obtain the polyester resin include polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1, Diols such as 4-butenediol, etherified bisphenols such as 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyexethylenated bisphenol A, polyoxypropylenated bisphenol A, Examples thereof include a divalent alcohol simple substance in which these are substituted 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, lower alkyl esters and linolenic acid Dimers and other divalent organic acid monomers can be mentioned.

  In order to obtain a polyester resin used as a binder resin, it is also preferable to use not only a polymer based on the above bifunctional monomer but also a polymer containing a component based on a trifunctional or higher functional 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, 7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylene Examples thereof include carboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, embol trimer acid, acid anhydrides thereof, and the like.

  The toner used in the present invention may contain a release agent for the purpose of improving the releasability of the toner on the surface of the transfer and fixing belt during transfer and fixing. 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. The carnauba wax is preferably a microcrystalline one, having an acid value of 5 or less and a particle size of 1 μm or less when dispersed in a toner binder. 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 amount of the wax added is generally in the range of 1 to 15 parts by weight, preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder-resin. Therefore, it is possible to reduce the amount of the toner added and to improve the developability and chargeability of the toner. Incidentally, when 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, a fatty acid metal salt, polyvinylidene fluoride, or the like, such as silica, titanium oxide, or alumina, may be added as necessary.

<Process Color Toner>
The process color toner used in the present invention is composed of four colors, yellow, magenta, cyan, and black, and conventionally known colorants can be used for each.

<Special Color Toner>
Next, the special color toners (RGB toner, light color toner, transparent toner, metallic gloss toner and fluorescent toner) used in the present invention will be described.

  In the case of a transparent toner, the transparent toner can be constituted by not adding a colorant to the toner. Various additives can be used for the transparent toner, and any additive that can maintain transparency in the state of the toner is used so as not to disturb the properties (transparency) of the transparent toner.

  The RGB toner, light color toner, and fluorescent toner can be configured in the same manner as the process color toner by changing the pigment type and amount.

  As for the metallic glossy toner, the flake-like substance that reflects light is not particularly limited as long as it achieves sufficient glossiness, but metal powder, alloy powder, flake-like metal powder, flake-like alloy powder are not particularly limited. , Inorganic powder coated with metal, organic powder coated with metal, inorganic flaky powder coated with metal, organic flaky powder coated with metal, etc. Can be used alone or in combination of two or more as required.

  Specifically, platinum powder, gold powder, silver powder, copper powder, aluminum powder, bronze powder (such as pale gold and rich gold), chromium powder, titanium powder, zinc powder, nickel powder, tin powder, and other metal powders and alloy powders Etc. Some gold itself is gold like gold, but it appears gold by providing a yellow-orange layer on the material that reflects light. However, if the yellow-orange color layer becomes too thick, the reflected light will be absorbed by the outer color layer, resulting in a yellow-orange color. It is necessary to make it thinner.

  The substance that reflects light can develop a gold color even if it is a fine powder, but since it becomes a flat color, it is flake-like and has a shape that can increase the amount of reflected light. A brilliant and brilliant golden image can be formed.

The flake-like substance that reflects light may be in the form of flakes. For example, flake-like fluorine resin, silicone resin, ester resin, phenol resin, epoxy resin, styrene resin, acrylic resin, amide resin, urethane Resin, carbonate resin, vinyl chloride resin, vinyl chloride vinyl acetate copolymer resin, urea resin, melamine resin and other materials that reflect light, such as dry methods such as vapor deposition and sputtering, and electroless plating The use of a flaky material produced by a wet method is preferable from the viewpoints of productivity, uniformity and economy.

  Since most of the flake-like substances that reflect light are conductive when they are metals or alloys, if they are brought into the electrophotographic process as they are, discharge occurs during development, charging, and transfer, resulting in destruction of the photoreceptor and members. Since the possibility is high, it is preferable that the substance that reflects light is coated with the above-described resin that transmits yellow to orange light, a transparent resin, or an inorganic substance.

  Specifically, flaky metal powder and alloy powder coated with inorganic substances such as silica, alumina, titania, magnesium fluoride; fluorine resin, silicone resin, ester resin, phenol resin, epoxy resin, di-tertiary butyl salicylic acid Metal complexes, styrene resins, acrylic resins, amide resins, polyvinyl butyral, nigrosine, aminoacrylate resins, urethane resins, carbonate resins, vinyl chloride resins, vinyl chloride vinyl acetate copolymer resins, urea resins, melamine resins, basic dyes Further, flaky metal powder and alloy powder coated with an organic substance such as a basic dye lake are used.

  Also, flaky metal powder and flaky alloy powder coated with inorganic substances such as silica, alumina, titania, magnesium fluoride; fluorine resin, silicone resin, ester resin, phenol resin, epoxy resin, ditertiary butyl salicylic acid Metal complexes, styrene resins, acrylic resins, amide resins, polyvinyl butyral, nigrosine, amino acrylate resins, urethane resins, carbonate resins, vinyl chloride resins, vinyl chloride vinyl acetate copolymer resins, urea resins, melamine resins, basic dyes, A flaky metal powder and a flaky alloy powder coated with an organic substance such as a basic dye lake are used.

  Further, powders and flakes coated with an inorganic material coated with a metal and an alloy, and the coating layer further coated with an inorganic material such as silica, alumina, titania, magnesium fluoride, etc .; coated with an inorganic material coated with a metal and an alloy Layer is further fluorine resin, silicone resin, ester resin, phenol resin, epoxy resin, metal complex of di-tertiary butylsalicylic acid, styrene resin, acrylic resin, amide resin, polyvinyl butyral, nigrosine, aminoacrylate resin, urethane resin, carbonate Resins, vinyl chloride resins, vinyl chloride vinyl acetate copolymer resins, urea resins, melamine resins, basic dyes, powders and flakes coated with organic substances such as basic dye lakes; resins coated with metals and alloys The coating layer is further made of silica, alumina, titani Powders and flakes coated with inorganic substances such as magnesium fluoride; resin coated with metals and alloys, and the coating layer is further made of fluorine resin, silicone resin, ester resin, phenol resin, epoxy resin, ditertiary Butylsalicylic acid metal complex, styrene resin, acrylic resin, amide resin, polyvinyl butyral, nigrosine, aminoacrylate resin, urethane resin, carbonate resin, vinyl chloride resin, vinyl chloride vinyl acetate copolymer resin, urea resin, melamine resin, base Powders and flakes coated with organic substances such as basic dyes and lakes of basic dyes can be used.

  The average particle diameter of the light reflecting material (flaky substance that reflects light) as described above is 1 μm or more in order to realize sufficient gloss of the image without impairing the fixing property and releasability of the toner. Preferably, it is 5 μm or more, more preferably 10 μm or more, on the other hand, 500 μm or less is preferable, 200 μm or less is more preferable, 100 μm or less is more preferable, and 50 μm or less is also possible. If necessary, two or more kinds of light reflecting materials can be used in combination.

  Further, the ratio of the light reflecting material to the entire toner is preferably 0.1% by weight or more, more preferably 0.5% by weight or more in order to realize sufficient gloss of the image, while the toner fixing property and From the viewpoint of not deteriorating the releasability, 40% by weight or less is preferable, and 20% by weight or less is more preferable.

  In such a case, the ratio of the light reflecting material to the entire developer is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, in order to realize sufficient gloss of the image, From the viewpoint of not impairing the fixing property and releasability of the toner, the content is preferably 40% by weight or less, and more preferably 20% by weight or less.

DESCRIPTION OF SYMBOLS 1A Image forming part 2 Intermediate transfer belt 3 Photoconductor 4 Charging device 5 Writing device 7 Primary transfer device 8 Cleaning device 9 Transfer fixing roller (transfer fixing member)
13 Transfer fixing belt 12 Transfer roller 22 First cooling unit 23 Second cooling unit 24 Pressure roller (pressure member)
36 Belt heating means 120 Recording medium heating means N Transfer fixing nip T1 Process color toner image T2 Special color toner image

Japanese Patent Laid-Open No. 10-63121 JP 2004-145260 A Japanese Patent Publication No. 6-73028 JP-A-9-160298

Claims (5)

An intermediate transfer belt carrying a toner image on the surface;
A transfer-fixing belt carrying a toner image transferred from the intermediate transfer belt on its surface;
A transfer roller provided on the back surface of the transfer fixing belt and transferring a toner image from the intermediate transfer belt to the transfer fixing belt;
Belt heating means for heating the transfer fixing belt;
A transfer fixing member and a pressure member that sandwich the transfer fixing belt to form a transfer fixing nip N;
A process color image forming portion which is disposed on the surface side of the intermediate transfer belt and forms process color toner images of yellow, magenta, cyan and black, respectively;
A special color toner image forming unit that is disposed on the transfer fixing belt surface side and forms one or more special color toner images other than the process color toner image ;
The special color toner is a metallic glossy toner,
The transfer-fixing apparatus, wherein the transfer-fixing belt is made of a material having adhesiveness on the surface layer.   The transfer fixing apparatus according to claim 1, further comprising a recording medium heating unit that heats a surface of the recording medium conveyed to the transfer fixing nip. A first cooling means for cooling the intermediate transfer belt after the toner image carried on the surface of the intermediate transfer belt is transferred to the transfer fixing belt;
And a second cooling means for cooling the transfer and fixing belt after the toner image carried on the surface of the transfer and fixing belt is transferred and fixed to the recording medium conveyed to the transfer and fixing nip N. The transfer fixing device according to claim 1, wherein: An electrophotographic image forming apparatus characterized by comprising a transfer-fixing device according to any one of claims 1-3. The image forming method of an electrophotographic system, which comprises using a transfer-fixing device according to any one of claims 1-3.

Images