JP2009014823A - Smoothing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a smoothing device capable of forming an image with excellent gloss on both the surface and back of a recording material without impairing the gloss on the first side. <P>SOLUTION: The smoothing device includes: a fixing belt 153 formed such that the face that comes into contact with a toner image is smoothed in order to heat the toner image on a recording material in a nip part; a pressure roller 154 forming the nip part between the fixing belt 153 and itself, thereby bringing the recording material into close contact with the fixing belt 153; and a cooling means for cooling the recording material before the separation of the recording material moved in close contact with the fixing belt 153. In the smoothing device, after one side of the recording material is smoothed, the other side is smoothed while the pressure roller 154 is kept separated from the fixing belt 153. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a smoothing device used in an image forming apparatus such as a copying machine, a printer, or a facsimile.

  2. Description of the Related Art Conventionally, image quality forming apparatuses mainly using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a multifunction machine of these are widely known. Many of these have been commercialized not only for black and white but also for full color image formation. In addition, as image quality forming apparatuses are used in various fields, the demand for image quality has become increasingly sophisticated. Here, in particular, as an element for improving the image quality of a full-color image, improvement in uniformity of glossiness is required. One factor that determines the glossiness is the smoothness of the output image. In response to such needs, Patent Documents 1 and 2 transfer a color toner made of a thermoplastic resin to a recording material (resin medium) provided with a transparent resin layer made of a thermoplastic resin as a toner receiving layer, An image forming method for forming a color image by heating and melting is disclosed.

  Such a resin medium can provide a highly glossy image even with a roller fixing device that does not use a conventionally used cooling device.

  However, when roller fixing is used, it is difficult to reduce the toner level difference that impairs smoothness. The reason for this is that sufficient heat and pressure must be applied to reduce the toner level difference, but this will cause the toner to melt sufficiently, increasing the adhesive force to the fixing roller, and winding the recording material around the fixing roller. Or toner is offset. Further, in order to melt the toner by heating for a short time passing through the fixing roller, it is preferable that the surface of the fixing roller has a low hardness so that the entire surface of the fixing roller can be wrapped and heated. In that case, the pressure cannot be applied so that the toner is embedded in the resin medium.

  For the reasons described above, a cooling peeling type fixing device (hereinafter referred to as a belt fixing device) including a fixing belt has been proposed as a smoothing device desirable for image formation using a resin medium. The belt fixing device described in Patent Documents 3 and 4 presses and heats a recording material carrying an unfixed toner image with a fixing belt made of a heat-resistant film, and cools the recording material while keeping the recording material in close contact with the fixing belt. The toner image is solidified, and the recording material on which the toner image is fixed is peeled off from the fixing belt. As a result, the toner image solidifies in accordance with the belt surface shape together with the transparent resin layer on the surface of the recording material fixed in the state of being embedded in the transparent resin layer of the recording material, and the entire surface of the recording material becomes a smooth surface. A color image having excellent properties can be obtained.

  Further, the resin media used in such an image quality forming apparatus is described in detail in Patent Document 5, and the thickness of the resin layer mainly composed of a thermoplastic resin having a glass transition temperature of 85 ° C. or less is described. An electrophotographic recording material having a coating thickness of about 10 μm has been proposed.

Japanese Patent Application Laid-Open No. 64-35542 JP 05-216322 A Japanese Patent Laid-Open No. 04-216580 Japanese Patent Laid-Open No. 04-362679 JP 2003-084477 A

  However, in the image formation using such a belt fixing device, when forming an image having excellent glossiness on both sides of the recording material, when the second surface of the double-sided image is passed through the belt fixing device, the first surface There is a problem that the glossiness of the image is lost.

  FIG. 1 is a configuration diagram of a conventional belt fixing device. As shown in FIG. The belt fixing device includes a fixing belt 13 that rotates around a fixing roller 11 and a rotating roller 12, and a pressure roller 14 that is pressed against the fixing roller 11 with the fixing belt 13 interposed therebetween. A heating source 18 is provided inside the fixing roller and the pressure roller, and a cooling device 15 is provided as a means for cooling the fixing belt 13. Reference numeral 16 denotes a transfer material, and reference numeral 17 denotes an unfixed toner image. The transfer material 16 is passed through the toner image to be given gloss to the fixing belt 13 side. In such a conventional belt fixing device, it is possible to obtain a high gloss image having a toner image on only one side of a transfer material.

  Subsequently, in order to obtain a double-sided glossy image, a transfer material on which a high-gloss image has already been formed on the first side and an unfixed image is placed on the second side as shown in FIG. Fix with belt fixing unit. On the second side, a high-gloss image can be obtained, but the high-gloss image that has already been made on the first side is once heated by the pressure roller 14 and peeled off from the second fixing roller without cooling and solidifying the toner image. It will be. For this reason, the toner is offset to the pressure roller, the toner surface is roughened, and the high glossiness of the first surface is lost.

  Accordingly, an object of the present invention is to provide a smoothing device capable of forming images having excellent glossiness on both the front and back surfaces of a recording material without impairing the glossiness of the first surface.

In order to solve the above problems, a typical structure of a smoothing device according to the present invention is that a heating rotator in which a contact surface with a toner image is smoothed in order to heat a toner image on a recording material at a nip portion. A pressure rotator that forms a nip portion with the heating rotator and closely contacts the recording material to the heating rotator, and a cooling means that cools the recording material that moves while closely contacting the heating rotator before separation. In a smoothing device having
When the one surface of the recording material is smoothed and then the other surface is smoothed, the pressure rotator is separated from the heating rotator.

  According to the present invention, it is possible to form images having excellent glossiness on both the front and back surfaces of the recording material without impairing the glossiness of the first surface.

[First embodiment]
A first embodiment of a smoothing device according to the present invention will be described with reference to the drawings.

(Image forming device)
FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment. As shown in FIG. 1, a color electrophotographic recording apparatus, which is an image forming apparatus, has developing devices 1a, 1b, 1c, and 1d, transfer chargers 24a, 24b, and 24c on the outer periphery of photosensitive drums 3a, 3b, 3c, and 3d. 24d and cleaners 4a, 4b, 4c and 4d. A light source device and a polygon mirror (not shown) are installed in the upper part of the device. The photosensitive drum 3 and the transfer charger 24 constitute an image forming unit.

  The laser light emitted from the light source device is scanned by rotating the polygon mirror, and the light beam of the scanning light is deflected by the reflection mirror. The deflected light beam is condensed on the buses of the photosensitive drums 3a to 3d by the fθ lens and exposed to form latent images corresponding to the image signals on the photosensitive drums 3a to 3d.

  The developing devices 1a, 1b, 1c, and 1d are filled with a predetermined amount of cyan, magenta, yellow, and black toners as developers, respectively, by a supply device (not shown). The developing units 1a, 1b, 1c, and 1d develop the latent images on the photosensitive drums 3a, 3b, 3c, and 3d, respectively, and visualize them as cyan toner images, magenta toner images, yellow toner images, and black toner images.

  The recording material P is accommodated in the recording material cassette 10, and is then supplied onto the transfer belt 130 via a plurality of conveyance rollers and registration rollers 12, and is opposed to the photosensitive drums 3 a, 3 b, 3 c, 3 d by conveyance by the transfer belt 130. Sequentially sent to the transfer section.

  When the transfer belt 130 is rotated by the driving roller 13 and is confirmed to be in a predetermined position, the recording material P is sent from the registration roller 12 to the transfer belt 130, and the recording material P is transferred to the first image forming unit. It is conveyed toward the transfer part. At the same time, the image writing signal is turned on, and image formation is performed on the photosensitive drum 3a of the first image forming unit at a certain timing based on the signal. The transfer charger 24a applies an electric field or electric charge at the lower transfer portion of the photosensitive drum 3a, whereby the first color toner image formed on the photosensitive drum 3a is transferred onto the recording material P. By this transfer, the recording material P is firmly held on the transfer belt 130 by an electrostatic attraction force and conveyed to the second image forming unit. The transfer charger 24 was a contact charger. Further, it is known that the transfer charging means stabilizes the image when the current contributing to the transfer is kept constant at an appropriate current. Therefore, it is common to perform constant current control so that a constant current can be obtained even when the volume resistance value changes depending on the type of recording material (thickness, material, etc.), moisture absorption conditions, and the like.

  Image formation and transfer in the second to fourth image forming units are performed in the same manner as in the first image forming unit. The recording material P onto which the four color toner images have been transferred is separated from the end of the transfer belt 130 by removing electricity by the separation charger 32 at the downstream portion in the transport direction of the transfer belt 130 to attenuate the electrostatic adsorption force. In particular, in a low humidity environment, the recording material P is also dried to increase the electrical resistance, so that the electrostatic adsorption force with the transfer belt 130 is increased, and the effect of the separation charger 32 is increased. Normally, the separation charger 32 charges the recording material P in a state where the toner image is not fixed, and therefore a non-contact charger is used.

  The separated recording material P is transported to the fixing device 9 by the transport unit 62.

  The fixing device 9 as the first image heating device includes a fixing roller 51, a pressure roller 52, heat-resistant cleaning members 54 and 55, roller heaters 56 and 57, an application roller 50, an oil reservoir 53, and a thermistor 58. have. The heat resistant cleaning members 54 and 55 clean the fixing roller 51 and the pressure roller 52, respectively. The roller heaters 56 and 57 are installed in the rollers 51 and 52. The application roller 50 applies a release agent oil such as dimethyl silicone oil to the fixing roller 51. The thermistor 58 detects the temperature of the surface of the pressure roller 52 and controls the fixing temperature.

  The fixing roller 51 has a concentric three-layer structure and has a core portion, an elastic layer, and a release layer. The core portion is composed of an aluminum hollow pipe having a diameter of 44 mm and a thickness of 5 mm. The elastic layer is made of silicon rubber having a JIS-A hardness of 50 degrees and a thickness of 2.5 mm. The release layer is made of PFA having a thickness of 50 μm. A halogen lamp as a heat source (roller heater 56) is disposed inside the hollow pipe of the core portion.

  The pressure roller 52 has the same configuration. For the elastic layer, silicon rubber having a thickness of 3 mm is used. This is to earn a fixing nip by the elastic layer. A halogen lamp as a heat source (roller heater 57) is disposed inside the hollow pipe in the core portion of the pressure roller 52.

  The fixing roller 51 and the pressure roller 52 are pressed against each other with a predetermined pressing force to form a fixing nip portion as a heating / pressure portion having a predetermined width in the recording material conveyance direction. The pressure applied by the pressure roller 52 was 30 kgf in total pressure. At this time, the width of the fixing nip portion was 7 mm.

  The recording material P to which the four color toner images are transferred is mixed with the toner image and fixed to the recording material P by fixing, and a full-color copy image is formed.

  Thereafter, the image not subjected to the glossing process is discharged out of the apparatus, and the image subjected to the glossing process is conveyed to the fixing device F1.

(Smoothing device)
FIG. 2 is a configuration diagram of the smoothing device (fixing device F1). As shown in FIG. 2, the fixing device (smoothing device) F1 is a belt fixing device. The fixing device F1 includes a first fixing roller 151, a rotating roller (separating roller) 152, a fixing belt (heating rotating body) 153, a second fixing roller (pressure roller) 154, a cooling fan 155, and a rotating roller (tension roller). 159.

  The separation roller 152 is disposed at a predetermined interval from the fixing roller 151. The tension roller 159 is disposed on the upper side of the separation roller 152. An endless (endless) fixing belt 153 is stretched around three rollers 151, 152, and 159. The pressure roller (pressure rotator) 154 is pressed against the fixing roller 151 with the fixing belt 153 interposed therebetween.

  The fixing belt 153 is obtained by coating 100 μm of fluororubber on a 100 μm polyimide base layer. As the smoothness of the surface of the fixing belt, the surface roughness Rz is 1.0 μm or less, more preferably 0.3 μm or less, and further preferably 0.1 μm or less. Further, as the gloss value (the measuring instrument is PG-1M manufactured by Nippon Denshoku Industries Co., Ltd., the measurement condition is 60 ° gloss), it is preferable to use a belt of 80 or more. In this example, a belt having a surface glossiness of 90 Is used. In this example, the above-mentioned glossiness is obtained by performing a “smoothing process (polishing process)” specially in the post-processing step on the surface of the manufactured belt. Depending on the manufacturing method, if the above glossiness can be obtained without specially performing “smoothing”, such a belt is also referred to as a “smoothed” belt.

  A cooling fan (fixing belt cooling means) 155 is disposed inside the fixing belt 153 and between the fixing roller 151 and the separation roller 152 (on the downstream side of the fixing roller 151 in the recording material conveyance direction). The cooling fan 155 blows air to the fixing belt portion between the fixing roller 151 and the separation roller 153 to cool the recording material that moves while being in close contact with the fixing belt 153 before separation.

  The fixing roller 151, the pressure roller 154, the separation roller 152, and the tension roller 159 are arranged substantially in parallel with each other.

  The fixing roller 151 has a concentric three-layer structure, and has a core portion, an elastic layer, and a release layer. The core portion is composed of an aluminum hollow pipe having a diameter of 44 mm and a thickness of 5 mm. The elastic layer is made of silicon rubber having a JIS-A hardness of 50 degrees and a thickness of 300 μm. The release layer is made of PFA having a thickness of 50 μm. A halogen lamp 158 as a heat source (roller heater) is disposed inside the hollow pipe of the core portion.

  The pressure roller 154 has the same configuration as the fixing roller 151. The elastic layer of the pressure roller 154 uses silicon rubber with a thickness of 3 mm to earn a fixing nip. The pressure roller 154 can be moved in a contact / separation direction (arrow Y direction) by a not-shown pressure roller contact / separation device (contact / separation means), and is in contact with the fixing belt 153. It can be moved to a separation position separated from the fixing belt 153.

  The pressure roller 154 is normally held at the contact position. The pressure roller 154 is connected to a drive transmission means (not shown) that transmits a driving force via a torque transmission mechanism, and is moved from the contact position to the separation position by the operation of the image forming apparatus.

  The fixing roller 151 and the pressure roller 154 are pressed against each other with a predetermined pressing force across the fixing belt 153 to form a fixing nip portion N as a heating / pressing portion having a predetermined width in the recording material conveyance direction. The pressure roller 154 brings the recording material into close contact with the fixing belt 153. The pressure applied by the pressure roller 154 was 490 N (50 kgf) in total pressure. At this time, the width of the fixing nip portion N was 5 mm.

  Since the fixing belt 153 heats the toner image on the recording material at the nip portion, the contact surface with the toner image is smoothed.

  Here, the surface hardness of the fixing roller 151 needs to be selected according to the fixing belt 153. If the surface hardness of the fixing roller 151 is soft, the fixing belt 153 is bent, and the toner is not sufficiently pushed into the receiving layer of the recording material, so that a toner step remains. When the fixing belt 153 has a soft hardness, the fixing roller 151 is sufficiently hard so that the elastic layer is thinned or eliminated, and only the surface layer of PFA is used, or only the aluminum core is used. Also good.

  The fixing roller 151 is rotationally driven at a predetermined speed in a clockwise direction indicated by an arrow by a driving mechanism (not shown). As the fixing roller 151 rotates, the fixing belt 153 rotates in the clockwise direction indicated by the arrow. The separation roller 153, tension roller 159, and pressure roller 154 rotate following the rotation of the fixing belt 57. The tension roller 159 applies a predetermined tension to the fixing belt 57.

Electric power is supplied to the halogen lamp 158 disposed inside the fixing roller 151 and the pressure roller 154, and the heat generation of the halogen lamp 158 causes the fixing roller 151 and the pressure roller 154 to be heated internally, thereby increasing the surface temperature. The surface temperatures of the fixing roller 151 and the pressure roller 154 are detected by a thermistor (not shown), and the detected temperatures of the thermistors are fed back to a control circuit (not shown). The control circuit controls the power supplied to the halogen lamp 158 so that the detected temperature input from the thermistor is maintained at a predetermined temperature set in the fixing roller 151 and the pressure roller 154. That is, the temperature of the fixing roller 151 and the pressure roller 154 are controlled to a predetermined temperature, and the temperature of the fixing nip portion N is controlled to a predetermined fixing temperature.

  The recording material P having the unfixed toner image 157 on the surface sent to the belt fixing device F side is introduced between the fixing belt 153 and the pressure roller 154 in the fixing nip portion N, and is nipped and conveyed through the fixing nip portion N. Is done. The unfixed toner image surface of the recording material P faces the surface of the fixing belt 153. The recording material P is heated and pressurized in the process of being nipped and conveyed through the fixing nip portion N to mix the color toner images and fix (fix) the recording material P on the recording material P. At the same time, the recording material P is in close contact with the surface of the fixing belt 153. Thereafter, the recording material P is conveyed in a cooling region R between the fixing nip N and the separation roller 152 as the fixing belt 153 rotates while being in close contact with the fixing belt 153. In this cooling region R, the recording material P is forcibly and efficiently cooled by the action of the airflow flowing through the cooling fan 155 and the air duct 155a surrounding it. The cooling fan 155 generates an air flow orthogonal to the paper surface.

  The recording material P that is in close contact with the surface of the fixing belt 153 is sufficiently cooled in the cooling region R, and is peeled off from the surface of the fixing belt 57 by its own rigidity (strain) in a region where the curvature of the fixing belt 153 is changed by the separation roller 152. (Curvature separation).

  The fixing belt cooling means is not limited to the cooling fan 155 but may be a contact type cooling system, or a Peltier element, a heat pipe, or a water circulation type cooling device.

  The pressure roller contact / separation device (contact / separation means) is configured to be driven by a controller (control means) when the user selects a duplex mode in which gloss is imparted to both front and back surfaces. The controller controls the contact / separation device so as to separate the pressure roller after the transfer material passes the fixing nip portion N for the first time and before passing the fixing nip portion N for the second time. That is, when one surface of the recording material is smoothed and then the other surface is smoothed, the pressure roller 154 is separated from the fixing belt 153. As the timing of the pressure roller separation, it is preferable that the transfer material is separated immediately after passing through the first fixing nip portion N.

(Recording material P)
In order to output a glossy image formed product, a recording material having a toner receiving layer (image receiving layer, glossing layer) made of resin on the surface is used as the recording material P. In this case, in the process in which the recording material is nipped and conveyed through the fixing nip portion N, the heat of the fixing nip portion N causes the temperature of the receiving layer to rise and become soft, and further the pressure of the fixing nip portion N adds to the toner. Is buried in the hot receiving layer. At the same time, the recording material is in close contact with the surface of the fixing belt 153. Thereafter, the recording material is conveyed through the cooling region R together with the rotation of the fixing belt 153 in a state of being in close contact with the fixing belt 153, and is forcibly and efficiently cooled sufficiently. Then, the separation roller 152 separates the curvature from the surface of the fixing belt 153 in a region where the curvature of the fixing belt 153 changes.

  At this time, the resin media and the toner image are solidified according to the shape of the mirror-like belt surface, and the entire surface of the recording material becomes a smooth surface, so that an image with excellent gloss can be obtained.

  The recording material P used in the present invention will be described in more detail. The most characteristic feature of this coated paper is that the outermost toner receiving layer is melted near the fixing temperature. As a result, when the toner image is fixed on the recording material, the toner image is embedded in the toner receiving layer, so that the level difference due to the toner is reduced.

  To introduce such a specific example, it is produced by providing a transparent resin layer on a coated paper having the above-mentioned pigment coating layer.

  As a result, since the lower layer has a pigment layer and a high white and smooth surface is formed, it is not necessary to add a pigment to the outermost resin layer, and the function of increasing the whiteness becomes unnecessary. For this reason, the thermoplastic transparent resin layer on the surface can be designed with priority given to the functions of increasing the glossiness and embedding the toner image. Furthermore, there is an advantage that it is not necessary to newly manufacture a coated paper.

  As such a recording material, POD super gloss coated paper manufactured by Oji Paper Co., Ltd. is marketed.

  Specifically, an example of the production method is as follows. The coated paper having the above-mentioned pigment coating layer formed on the base material is used as a base paper, and one side or both sides of the base paper is provided with a thermoplastic resin, a gravure coater or the like. The desired coated paper can be made by coating using.

As the resin constituting the transparent resin layer, a polyester resin, a styrene-acrylic ester resin, a styrene-methacrylic ester resin, or the like can be used, and it is particularly preferable to use a polyester resin. The following are illustrated as a polyhydric alcohol component and polyhydric carboxylic acid component which comprise a polyester resin.

  Polyhydric alcohol components include ethylene glycol, propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, a monomer obtained by adding olefin oxide to bisphenol A, and the like can be used.

  Examples of the polyvalent carboxylic acid component include maleic acid, maleic anhydride, fumaric acid, phthalic acid, terephthalic acid, isophthalic acid, malonic acid, succinic acid, glutaric acid, dodecyl succinic acid, n-octyl succinic acid, and n-dodecyl succinic acid. Acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxy-2 -Methyl-2-methylenecarboxypropane, tetra (methylenecarboxy) methane, 1,2,7,8-octanetetracarboxylic acid, trimellitic acid, pyromellitic acid, lower alkyl esters of these acids, and the like can be used. .

  The polyester resin constituting the transparent resin layer is synthesized by polymerization of one or more of the polyhydric alcohol components and one or more of the polyvalent carboxylic acid components. As the resin component of the toner, a polyester resin is used in color toners, and a styrene-acrylic resin is mainly used in monochrome toners. It is preferable to select a highly compatible one.

  Accordingly, one or a mixture of two or more of polyester resin, styrene-acrylic acid ester resin, styrene-methacrylic acid ester resin and the like is used depending on the purpose.

  Furthermore, the transparent resin layer can contain a pigment, a release agent, a conductive agent, and the like within a range that does not impair the transparency. In that case, it is preferable that the resin amount of the main component is 80% by weight or more based on the total weight of the resin layer. Further, the transparent resin layer preferably has a composition adjusted so that the surface electric resistance is 8.0 × 10 8 Ω or more at a temperature of 20 ° C. and a relative humidity of 85%.

  In addition, it is not limited to such a manufacturing method, as long as it is a coated paper provided with a thermoplastic resin layer having a melting characteristic whose surface melts near the fixing temperature, it is not always necessary to have a multilayer structure, such as a pigment It goes without saying that various additives may be added.

  Among such recording materials, the recording material P used in this example is a polyester (thermoplastic resin) as a receiving layer P1 on one side of a coated paper (base material) having a basis weight of 170 g / m 2 as the base material a. A transparent resin layer as a main component is provided with a thickness of 10 μm.

  Image formation was performed with the above configuration. After transfer, the maximum unfixed toner height was 12 μm.

(Operation of the fixing device F1)
First, an electrophotographic image is formed on both surfaces of the recording material P by a color electrophotographic recording apparatus. At this time, the images formed on both surfaces of the recording material P were low gloss and had a 60 ° gloss value of about 20. By passing the recording material P through the fixing device F1, it is possible to form an image having excellent glossiness of about 100 with a 60 ° gloss value.

  However, after an image having excellent glossiness is formed on the first surface by the first fixing, and the recording material P is again passed through the fixing nip portion N by the second fixing, the image surface of the first surface and the pressure roller 154 are transferred. Contact with each other and separation without being sufficiently cooled, the glossiness of the first surface is impaired.

  Therefore, in the fixing of the second surface, the pressure roller 154 and the fixing roller 151 are separated (separated position) so that the image surface of the first surface and the pressure roller 154 do not come into contact with each other. The fixing belt 153 is brought into close contact to perform image fixing.

  When the first surface is fixed, the surface temperature of both surfaces of the recording material P passing through the fixing nip N is 100 ° C. which is equal to or higher than the Tg (glass transition temperature) of the image receiving layer of the recording material P and the toner. The applied pressure was 100 kgf. It was also confirmed that the toner on both sides of the recording material P was embedded in the image receiving layer on the recording material P. Then, the recording material P is brought into close contact with the fixing belt 153 and is cooled and peeled off by the separation roller 152, whereby an image having excellent glossiness is obtained on the first surface.

  Next, after the pressure roller 154 and the fixing roller 151 are separated by using the drive transmission means and the recording material P is reversed, the second surface of the recording material P is fixed. At this time, the surface temperature of the second surface of the recording material P is 100 ° C. higher than the Tg of the image receiving layer of the recording material P and the toner, and the surface temperature of the first surface is the Tg of the image receiving layer of the recording material P and the toner. It was the following 50 ° C.

  The second surface was conveyed in close contact with the fixing belt 153, and cooled and peeled off by the separation roller 152. Here, in the fixing on the second surface, since the toner is already embedded in the image receiving layer of the recording material P in the first fixing, it is not necessary to apply pressure, and the toner is brought into close contact with the fixing belt 153 to be cooled and peeled off. By giving, an image having excellent gloss can be obtained. Accordingly, it is possible to form an image having excellent glossiness on both the first surface and the second surface without contacting the first surface and the pressure roller 154.

  The fixing temperature of the fixing device 9 was 170 ° C. and the process speed was 200 mm / s. In the fixing device F1, it is important to keep the fixing belt surface temperature at the separation roller 152 as constant as possible below the temperature at which the paper can be separated during continuous printing. In this way, it is possible to output a recording material having a certain glossiness even during continuous printing.

  FIGS. 3 and 4 are diagrams showing the results of measuring the pressure roller temperature and the belt temperature in the vicinity of the separation roller in the case of continuous printing with “with and without contact” and “without contact and separation”. “With contact and separation” means that the pressure roller 154 contacts the fixing belt 153 immediately before the recording material P enters the fixing device, and immediately after the recording material P comes out of the fixing device F1, the separation from the fixing belt 153 occurs. If you do. “No contact and separation” refers to the case where the pressure roller 154 remains in contact with the fixing belt 153.

  The fixing roller 151 and the pressure roller 154 are on standby while rotating, and the temperature adjustment temperature of the fixing roller 151 is 140 ° C., and the temperature adjustment temperature of the pressure roller 154 is 60 ° C. However, in the case of “no contact / separation”, the temperature of the pressure roller 154 increases with the temperature of the fixing roller 151 and is actually about 90 ° C. The air flow rate of the cooling fan 155 was set so that the surface temperature of the fixing belt in the vicinity of the separation roller was 50 ° C. in a steady state where no paper was passed.

  When continuous printing is started in this state, the pressure roller temperature can be stably controlled around 60 ° C. under the condition of “contact and separation”, so that the belt temperature change in the vicinity of the separation roller as shown in FIG. Also, it can be kept relatively small at about 50 ° C.

  On the other hand, under the condition of “no contact / separation”, the heat from the fixing roller 151 is transmitted to the pressure roller 154 via the fixing belt 153, and the pressure roller temperature reaches 120 ° C. near 20 prints. . As a result, as shown in FIG. 4, the fixing belt temperature near the separation roller reaches 75 ° C. When the fixing belt temperature in the vicinity of the separation roller is 55 ° C. and 75 ° C., the gloss value (measuring instrument: PG-1M 60 ° manufactured by Nippon Denshoku Industries Co., Ltd.) is different by about 5 to 10.

  As described above, the pressure roller 154 can be brought into contact with and separated from the fixing belt 153, so that the temperature on the exit side can be kept as low and constant as possible, and the recording material P can be separated without impairing the glossiness. Although it is conceivable to change the air volume of the cooling fan 155 by detecting the temperature in the vicinity of the separation roller, there is a concern about an increase in the size and cost of the apparatus.

(Experiment 1)
Next, an experiment (Experiment 1) on the contact and separation of the pressure roller 154 and the glossiness was performed. In Experiment 1, first, the fixing belt 153 is adjusted to 140 ° C., the pressure roller 154 is adjusted to 60 ° C., and the fixing roller 151 and the pressure roller 154 are turned on standby, and the fixing device F1 is heated. It is assumed that equilibrium has been reached. Then, the contact and separation of the pressure roller 154 were performed under the following conditions (Example 1, Comparative Example 1), and one double-sided image was passed. Table 1 shows the gloss value in Example 1 and Comparative Example 1 and the temperature of the pressure roller 154 immediately before the recording material P enters the belt. The gloss value is desirably 80 or more as a photographic tone high gloss, and more preferably 85 or more.

  In Example 1, the pressure roller 154 was separated from the fixing belt 153 until just before the recording material P entered the fixing device F1. In Comparative Example 1, the pressure roller 154 is kept in contact with the fixing belt 153 all the time. FIG. 5 is a diagram schematically showing the state of contact and separation of the pressure roller 154 and the state of temperature transition of the pressure roller 154 according to the first embodiment. FIG. 6 is a diagram schematically showing the state of the pressure roller 154 and the state of temperature transition of the pressure roller 154 of the first comparative example.

  From Table 1, as in Comparative Example 1, if the pressure roller 154 is kept in contact with the fixing belt 153, the temperature of the pressure roller 154 rises, and in the single-side mode, the 95th gloss of the first surface is 95. It can be seen that in double-sided mode, it falls to 60.

  This is because the high gloss image already formed on the first side is once heated by the pressure roller 154 and peeled off from the pressure roller 154 without cooling and solidifying the toner image. This is because the toner surface becomes rough.

  On the other hand, as in the first embodiment, the pressure roller 154 is normally separated and is brought into contact only immediately before the recording material P arrives. In this case, in the single-sided mode, since the temperature of the pressure roller 154 is lowered, the gloss becomes 90, which is slightly lower than 95 of the comparative example 1 that is in contact. However, since the temperature of the pressure roller 154 is suppressed to 60 ° C. in the double-sided mode, the gloss on the first side can be reduced to 90 to 85 compared to the single-sided mode, and the glossiness on both sides is excellent. Images can be formed.

[Second Embodiment]
Next, a second embodiment of the smoothing device according to the present invention will be described with reference to the drawings. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 7 is a configuration diagram of the smoothing device according to the present embodiment. As shown in FIG. 7, the fixing device (smoothing device) F2 of this embodiment is provided with an air blowing device (blowing means) W in the vicinity of the fixing roller of the fixing device F1 of the first embodiment.

The air blower W is an adsorbing unit that adsorbs the recording material to the fixing belt 153 when the other surface of the recording material is smoothed. The air blowing device W is provided on the upstream side of the pressure roller 154 in the recording material conveyance direction, and blows air from the upstream side of the recording material conveyance direction toward the portion of the fixing belt 153 that contacts the fixing roller 151. That is, the air blower W blows air in the direction in which the conveyed recording material P is in close contact with the fixing belt 153. As a result, the recording material P receives air, and the adhesion between the recording material P and the fixing roller 151 is increased.

  When the adhesion between the recording material P and the fixing belt 153 is poor, the portion in contact with the fixing belt 153 has high gloss, and the portion not in contact has low gloss. Therefore, a gloss difference occurs in the image.

  In the fixing device F1 of the first embodiment, the adhesiveness between the recording material P and the fixing belt 153 is reduced due to the separation of the pressure roller 154 and the fixing belt 153. Therefore, by blowing air to the recording material P using the air blower W, the recording material P is pressed against the fixing belt 153 to improve the adhesion and suppress the occurrence of a gloss difference.

  Specifically, in fixing (image heating) on the second surface, the wind pressure is 0.15 to 0.7 MPa toward the recording material P conveyed to the fixing belt 153 from upstream to downstream in the conveyance direction of the recording material P. Blow in. As a result, the recording material P is brought into close contact with the fixing belt 153, conveyed to the cooling fan 155, and cooled and separated from the fixing belt 153 by the separation roller 152.

  When the wind pressure is 0.15 MPa or less, good adhesion cannot be obtained, and when the wind pressure is 0.7 MPa or more, the recording material P is rolled up by the wind pressure. Good adhesion is obtained when the wind pressure is in the range of 0.15 to 0.7 MPa.

  As described above, according to the present embodiment, it is possible to form images with excellent glossiness on both the front and back surfaces of the recording material without impairing the glossiness of the first surface. Furthermore, the occurrence of a gloss difference on the second surface can also be suppressed.

[Third embodiment]
Next, a third embodiment of the smoothing device according to the present invention will be described with reference to the drawings. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 8 is a configuration diagram of the smoothing device according to the present embodiment. As shown in FIG. 8, the fixing device (smoothing device) F3 of this embodiment is obtained by providing a charging device C and a charge eliminating device D in the fixing device F1 of the first embodiment.

  The charging device (charging means) C is provided so as to sandwich the fixing belt 153 together with the fixing roller 151. The charging device C is an adsorbing unit that adsorbs the recording material to the fixing belt 153 when the other surface of the recording material is smoothed, and an adsorbing charging unit that electrostatically adsorbs the recording material to the fixing belt 153. is there. The charging device C charges the fixing belt 153 and electrostatically attracts the recording material P to the fixing belt 153, thereby improving the adhesion between the recording material P and the fixing belt 153.

  The static eliminating device (static eliminating means) D is provided so as to abut on the separation roller 152. The static eliminator D makes it possible to separate the recording material P from the fixing belt 153 by neutralizing the fixing belt 153 via the separation roller 152.

  When the adhesion between the recording material P and the fixing belt 153 is poor, the adhesion between the recording material P and the fixing belt 153 varies depending on the location, thereby causing a gloss difference in the image plane. Accordingly, the recording material P is electrostatically adsorbed and brought into close contact with the fixing belt 153 by using the charge applying device C and the charge eliminating device D to improve the adhesion.

  Specifically, in fixing (image heating) on the second surface, the fixing belt 153 is charged using the charging device C, and the recording material P is electrostatically adsorbed to and closely adhered to the fixing belt 153, and then the cooling fan. Transport to 155. Then, the fixing belt 153 is neutralized by the static eliminator D, and the separation roller 152 is cooled and separated from the fixing belt 153.

  As a result, the adhesion between the recording material P and the fixing belt 153 is enhanced, and the difference in the contact state between the recording material P and the fixing belt 153 is eliminated. Therefore, according to the present embodiment, it is possible to form images with excellent glossiness on both the front and back surfaces of the recording material without impairing the glossiness of the first surface, and further, the occurrence of a gloss difference on the second surface is also possible. Can be suppressed.

[Fourth embodiment]
Next, a fourth embodiment of the smoothing device according to the present invention will be described with reference to the drawings. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 9 is a configuration diagram of the smoothing device according to the present embodiment. As shown in FIG. 9, the fixing device (smoothing device) F4 according to this embodiment is obtained by providing a pressure roller cooling device (pressure roller cooling means) 161 to the fixing device F1 of the first embodiment. is there.

  A plurality of cooling devices 161 are used in parallel with the longitudinal direction of the pressure roller 154. The cooling device 161 uniformly cools the pressure roller 154 in the recording material width direction (direction perpendicular to the recording material conveyance direction).

(Experiment 2)
Next, an experiment (Experiment 2) on contact and separation of the pressure roller 154 and glossiness was performed. Example 1 is Example 1 of the first embodiment. In Example 4, the temperature of the pressure roller 154 is adjusted to 100 ° C., and after the recording material P on the first surface has passed through the fixing device F 4, the pressure roller 154 is separated and the pressure roller 154 is cooled by the cooling device 161. To do. After cooling, the cooled pressure roller 154 comes into contact, and the recording material P on the second surface is passed through the fixing device F4.

  Table 2 shows the gloss values in Examples 1 and 4 and the temperature of the pressure roller 154 immediately before the recording material P enters the fixing device F4.

  From Table 2, in Example 4, by adding a “cooling mechanism” to the “separation mechanism”, it is possible to change the pressure roller temperature at the time of creating the first side and the second side in the duplex mode. By doing so, compared to the first embodiment, it is possible to increase the gloss on the first surface from 85 to 90 when created in the duplex mode. Therefore, the glossiness of the first surface can be further improved as compared with Example 1.

  In order to reduce costs, the cooling fan 155 and the pressure roller cooling device 161 may be shared and used as a common cooling means. At that time, air ducts for introducing air to the respective cooling target portions (the fixing belt 153 and the pressure roller 154) are provided.

1 is a configuration diagram of an image forming apparatus according to a first embodiment. It is a block diagram of the smoothing apparatus which concerns on 1st embodiment. It is a figure which shows the result of having measured the pressure roller temperature at the time of continuous printing, and the belt temperature of the separation roller vicinity. It is a figure which shows the result of having measured the pressure roller temperature at the time of continuous printing, and the belt temperature of the separation roller vicinity. It is the figure which represented typically the mode of the contact and separation of the pressure roller of Example 1, and the mode of the temperature transition of a pressure roller. It is the figure which represented typically the mode of the pressure roller of the comparative example 1, and the mode of the temperature transition of a pressure roller. It is a block diagram of the smoothing apparatus which concerns on 2nd embodiment. It is a block diagram of the smoothing apparatus which concerns on 3rd embodiment. It is a block diagram of the smoothing apparatus which concerns on 4th embodiment.

Explanation of symbols

C: Charging device D ... static device F ... fixing device N ... fixing nip P ... recording material R ... cooling area W ... air blowing device 1 ... developing device 3 ... photosensitive drum 4 ... cleaner 9 ... fixing device 12 ... registration roller 24 ... Transfer charger 32 ... Separation charger 50 ... Coating roller 51 ... Fixing roller 52 ... Pressure roller 53 ... Reservoir 54, 55 ... Heat-resistant cleaning members 56, 57 ... Roller heater 58 ... Thermistor 62 ... Conveying unit 130 ... Transfer belt 151... Fixing roller 152 .. separation roller 153... Fixing belt 154... Pressure roller 155... Cooling fan 155a.

Claims (4)

In order to heat the toner image on the recording material at the nip portion, a heating rotator whose contact surface with the toner image is smoothed and a nip portion is formed between the heating rotator to heat the recording material. In a smoothing apparatus having a pressure rotator to be in close contact with and a cooling means for cooling the recording material moving while being in close contact with the heating rotator before separation,
A smoothing apparatus characterized in that when a smoothing process is performed on one surface of a recording material and then the other surface is smoothed, the pressure rotating body is separated from the heating rotating body. 2. The smoothing apparatus according to claim 1, further comprising an adsorbing unit configured to adsorb the recording material to the heating rotator when the other surface of the recording material is smoothed. 3. The smoothing apparatus according to claim 2, wherein the adsorption unit includes an adsorption charging unit that electrostatically adsorbs the recording material to the heating rotating body. 3. The smoothing apparatus according to claim 2, wherein the suction unit includes a blowing unit that blows air in a direction in which the recording material is sucked by the heating rotating body.

Images