JP2010072371A - Fixing device and fixing method, and electrophotographic printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an image of the same size and a uniform quality on both surfaces of a printing medium in duplex electrophotographic printing. <P>SOLUTION: A fixing device 16 used for an electrophotographic printer 1 which conveys a printing medium while transferring toner to one surface of the printing medium and then transferring toner to the other surface of the printing medium, and heating the toner transferred to the printing medium to fix it on the printing medium includes: a primary heating unit 161 which is disposed in a main conveyance path P1 where the toner is transferred to one surface of the printing medium and not to transferred to the other surface of the printing medium, and heating the toner transferred to the one surface of the printing medium; and a secondary heating unit 162 disposed in the main conveyance path P1 where the toner is transferred to the other surface of the printing medium, and heating and fixing the toner transferred to both the surfaces of the printing medium. The caloric value of heating by the primary heating unit 161 is set to be lower than that of heating by the secondary heating unit 162. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device and a fixing method suitable for performing double-sided printing for electrophotographic printing, and an electrophotographic printing machine.

  A general electrophotographic printing machine that performs electrophotographic printing includes a photosensitive drum, a charging device, an exposure device, a developing device, a transfer device, and a fixing device. The peripheral surface of the photosensitive drum is charged by applying an electrostatic potential uniformly by a charging device. Further, the peripheral surface of the photosensitive drum is irradiated with a light image by an exposure device to expose the electrostatic latent image. Thereafter, a toner image in which the electrostatic latent image is visualized is formed by supplying toner charged by the developing device to a portion where the electrostatic latent image is formed on the photosensitive drum. The toner image formed on the peripheral surface of the photosensitive drum is transferred to a transfer device. Further, the toner image transferred to the transfer device is transferred to a predetermined print medium conveyed to the transfer device. Finally, the toner image transferred to the printing medium is fixed by a fixing device.

  A fixing device in such an electrophotographic printing machine is provided in a conveyance path of a printing medium to which a toner image is transferred, and the printing medium is between the heating roller that heats the toner image of the printing medium and the heating roller. And a pressure roller that applies a predetermined pressure to the print medium.

  As a conventional fixing device, the print medium and the toner image are heated to a predetermined temperature before passing through the positions of the heating roller and the pressure roller, thereby reducing the amount of heat required for heating with the heating roller. In addition, there is known one that prevents a temperature difference between a paper passing portion and a non-paper passing portion of a print medium by a heating roller from being increased to prevent the temperature of the non-paper passing portion from rising further (for example, a patent Reference 1).

  As another conventional fixing device, the liquid carrier material of the toner is evaporated and fixed by preheating the print medium and the toner image to a predetermined temperature before passing through the positions of the heating roller and the pressure roller. It is known to improve image quality (for example, see Patent Document 2).

JP 2000-305385 A JP 62-267787 A

  By the way, when performing double-sided printing, it is conceivable to transfer and fix the toner image on one side of the printing medium, and then transfer and fix the toner image on the other side of the printing medium.

  However, when duplex printing is performed in this manner, one surface of the print medium is heated twice by each fixing device. For this reason, the transfer efficiency differs due to the difference in toner absorbability between the one side and the other side of the print medium, resulting in a difference in image quality between the one side and the other side of the print medium. In addition, when the toner image is transferred and fixed on one side of the print medium, moisture is removed by heat from the fixing device and the print medium contracts, and the toner image is transferred and fixed on the other side of the print medium. Sometimes, the print medium shrinks due to the heat generated by the fixing device, so that the image on one side of the print medium is reduced as compared with the image on the other side.

  The present invention solves the above-described problems, and provides a fixing device, a fixing method, and an electrophotographic printer capable of aligning the image quality and image size of both sides of a printing medium when performing double-sided electrophotographic printing. The purpose is to do.

  In order to achieve the above-described object, in the fixing device of the present invention, an electronic device that transports the print medium in such a manner that the toner is transferred to one surface of the print medium and then the toner is transferred to the other surface of the print medium. In a fixing device used in a photographic printing machine and configured to heat and fix toner transferred to the print medium to the print medium, the print medium is located on the downstream side where the toner is transferred to one surface of the print medium. A primary heating section that is disposed in an upstream conveyance path where toner is transferred to the other surface of the printing medium, and that heats the toner transferred to one surface of the printing medium, and toner on the other surface of the printing medium. A secondary heating unit that is disposed in the downstream conveyance path to be transferred and that heats and fixes the toner transferred on both sides of the print medium, and the amount of heat to be heated by the primary heating unit is the secondary heating unit. Heat in the heating section Characterized in that it is set lower than the amount.

  According to this fixing device, the toner transferred to one surface of the print medium is semi-fixed by the primary heating unit having a heat amount lower than that of the secondary heating unit so as not to be transferred to the other side. After the toner is transferred on both sides, the toner is completely fixed by the secondary heating unit. As described above, when electrophotographic printing is performed on both sides of the print medium, the toner transferred to one side of the print medium is semi-fixed, and then the toner on both sides of the print medium is completely fixed together. For this reason, the printing medium is heated in two stages, and in the primary heating, the toner is heated with a heat amount lower than the heat amount for fixing the toner to the printing medium by the secondary heating, so that one side of the printing medium fixes the toner. It is not heated twice with the amount of heat. As a result, it is possible to suppress a situation in which the liquid absorbency of the toner and the water content of the print medium (that is, the resistance value of the print medium) are different between the one surface and the other surface of the print medium, and the transfer efficiency becomes almost equal. The image quality can be made uniform on one side and the other side of the print medium. In addition, after the toner is transferred to both sides of the print medium, the print medium contracts due to the heat of the secondary heating unit, so that the image size can be made uniform on one side and the other side of the print medium.

  In the fixing device of the present invention, the primary heating unit heats the toner of the printing medium in a non-contact manner with respect to the printing medium, and the secondary heating unit contacts the printing medium. The toner of the printing medium is heated in a form.

  According to this fixing device, since the primary heating unit heats in a non-contact manner, it is possible to prevent a situation in which dirt adheres to the surface of the print medium and the toner. In addition, since the primary heating unit does not directly apply heat in a non-contact manner, the amount of heat can be easily changed, and by controlling the total amount of heat in the primary heating unit and the secondary heating unit, the liquid toner It is possible to always maintain good print quality by using a fixing heat amount according to the amount of liquid and the water content of the print medium. On the other hand, since the secondary heating unit is a contact type, the toner to be fixed is smoothed by a pressing force to give gloss to the printing surface.

  In the fixing device of the present invention, a non-volatile liquid toner is applied as the toner.

  According to this fixing device, the non-volatile liquid toner is transferred to the print medium in a wet state. Therefore, when the liquid absorbency of the print medium is changed, the transfer state is changed to affect the print quality. Therefore, the effect of improving the print quality can be obtained more remarkably by applying the liquid toner.

  To achieve the above object, in the fixing method of the present invention, after the toner is transferred to one side of the print medium, a primary heating step of heating the toner transferred to the one side of the print medium; And a secondary heating step of heating and fixing the toner transferred to both sides of the print medium after the toner has been transferred to the other side of the print medium, and the amount of heat to be heated in the primary heating step Is set lower than the amount of heat to be heated in the secondary heating step.

  According to this fixing method, when electrophotographic printing is performed on both sides of the printing medium, the toner transferred to one side of the printing medium is semi-fixed, and then the toners on both sides of the printing medium are completely fixed together. For this reason, the printing medium is heated in two stages, and in the primary heating, the toner is heated with a heat amount lower than the heat amount for fixing the toner to the printing medium by the secondary heating, so that one side of the printing medium fixes the toner. It is not heated twice with the amount of heat. As a result, it is possible to suppress a situation in which the liquid absorbency of the toner and the water content of the print medium (that is, the resistance value of the print medium) are different between the one surface and the other surface of the print medium, and the transfer efficiency becomes almost equal. The image quality can be made uniform on one side and the other side of the print medium. In addition, after the toner is transferred to both sides of the print medium, the print medium contracts due to the heat of the secondary heating unit, so that the image size can be made uniform on one side and the other side of the print medium.

  In order to achieve the above object, in the electrophotographic printing machine of the present invention, a photosensitive drum, a charging device for charging the peripheral surface of the photosensitive drum, and exposure for exposing a latent image on the peripheral surface of the charged photosensitive drum. An apparatus, a developing device for charging a latent image on the photosensitive drum to form a toner image, and a transfer drum on which the toner image on the photosensitive drum is transferred in contact with the peripheral surface of the photosensitive drum, An electrophotographic printing machine for transferring a toner image of the transfer drum to one side of a print medium and then transferring a toner image of the transfer drum or another transfer drum to the other side of the print medium, the printing machine The fixing device according to any one of the above is applied as a fixing device that heats and fixes the toner transferred to the medium to the print medium.

  According to this electrophotographic printing machine, when electrophotographic printing is performed on both sides of a printing medium, the toner image transferred to one side of the printing medium is semi-fixed, and then the toner images on both sides of the printing medium are completely fixed together. The For this reason, the print medium is heated in two stages, and in the primary heating, the toner image is heated with a heat amount lower than the heat amount for fixing the toner image to the print medium by the secondary heating. It is not heated twice with an amount of heat sufficient to fix the image. As a result, it is possible to suppress a situation in which the liquid absorbency of the toner and the water content of the print medium (that is, the resistance value of the print medium) are different between the one surface and the other surface of the print medium, and the transfer efficiency becomes almost equal. The image quality can be made uniform on one side and the other side of the print medium. In addition, after the toner images are transferred to both sides of the print medium, the print medium shrinks due to the heat of the secondary heating unit, so that the image size can be made uniform on one side and the other side of the print medium. .

  Further, since the primary heating unit heats in a non-contact manner, it is possible to prevent a situation where dirt is attached to the surface of the print medium and the toner image. In addition, since the primary heating unit does not directly apply heat in a non-contact manner, the amount of heat can be easily changed, and by controlling the total amount of heat in the primary heating unit and the secondary heating unit, the liquid toner It is possible to always maintain good print quality by using a fixing heat amount according to the amount of liquid and the water content of the print medium. On the other hand, since the secondary heating unit is a contact type, the toner image to be fixed is smoothed by a pressing force to give gloss to the printing surface.

  Since the non-volatile liquid toner is transferred to the print medium in a wet state, if the liquid absorbency of the print medium changes, the transfer state changes and affects the print quality. Therefore, the effect of improving the print quality can be obtained more remarkably by applying the liquid toner.

  According to the present invention, when performing double-sided electrophotographic printing, the image quality and the image size of both sides of the printing medium can be made uniform.

  Embodiments of a fixing device, a fixing method, and an electrophotographic printer according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a schematic view of an electrophotographic printer according to an embodiment of the present invention. As shown in FIG. 1, the electrophotographic printing machine 1 includes a photosensitive drum 11, a charging device 12, an exposure device 13, a developing device 14, a transfer device 15, and a fixing device 16.

  The photosensitive drum 11 is provided with an organic or amorphous silicon photosensitive layer on the outer periphery of a cylindrical body made of a conductive substrate such as aluminum. The photosensitive drum 11 is supported by a frame (not shown) so as to be rotatable in a direction opposite to a rotation direction of a transfer drum 151 described later.

  The charging device 12 is disposed around the photosensitive drum 11 and applies an electrostatic potential uniformly to the surface of the photosensitive layer of the photosensitive drum 11 by corona discharge or the like. The exposure device 13 can form an electrostatic latent image on the surface of the photosensitive layer by irradiating the surface of the photosensitive layer of the photosensitive drum 11 with a light image.

  The exposure device 13 is disposed around the photosensitive drum 11 and exposes an image on the surface of the photosensitive layer of the photosensitive drum 11. The exposure device 13 receives image data from the upstream and exposes it to form an electrostatic latent image on the surface of the photosensitive layer of the photosensitive drum 11. That is, the portion exposed to light becomes conductive, so that the charge disappears, and the portion not exposed to light remains as an electrostatic latent image that is an image of the charge.

  The developing device 14 is disposed around the photosensitive drum 11 and supplies charged toner to a portion where the electrostatic latent image on the surface of the photosensitive layer of the photosensitive drum 11 is formed to reveal the electrostatic latent image as a toner image. It is to be imaged. The developing device 14 includes a supply roller 141 that is rotatably provided while being partially immersed in a predetermined concentration of liquid toner stored in a tank (not shown) and pumps up the liquid toner. Further, the developing device 14 includes a developing roller 142 that is in contact with the supply roller 141 and is rotatably provided in contact with the photosensitive drum 11 and delivers liquid toner from the supply roller 141 to the photosensitive drum 11. Although not clearly shown in the figure, a leveling blade for uniformizing the liquid toner supplied to the peripheral surface of the developing roller 142 and a voltage applying device for applying a bias voltage to the developing roller 142 are provided around the developing roller 142. And are provided.

  Here, the liquid toner as the toner is obtained by, for example, dispersing toner particles charged to a specific polarity in an insulating liquid (also referred to as a carrier or a solvent). The toner particles are formed of a resin, a pigment, a charging material, a dispersion material, and the like, and are positively (+) charged. In this embodiment, a non-volatile insulating liquid with high viscosity and high concentration is used.

  Although not clearly shown in the drawing, a static eliminator is disposed around the photosensitive drum 11 upstream of the charging device 12 and the exposure device 13 in the rotation direction of the photosensitive drum 11, and a cleaning device is further arranged upstream. The liquid toner remaining on the surface of the photosensitive layer of the drum 11 can be collected in the tank while discharging and removing.

  The photosensitive drum 11, the charging device 12, the exposure device 13, and the developing device 14 described above are configured as one unit that performs printing of one color. In this embodiment, four units that perform printing of four colors of cyan, magenta, yellow, and black are arranged so as to perform color photographic printing. In the case of single color or multicolor printing that does not perform color photo printing, the number of units corresponding to the number of colors may be provided.

  The transfer device 15 includes a transfer drum 151 and a secondary transfer roller 152. The transfer drum 151 has a photosensitive drum 11 (the photosensitive drum 11 of each unit) in contact with the peripheral surface thereof, and is supported so as to be rotatable in a clockwise direction in FIG. 1 with respect to a frame (not shown). Yes. The transfer drum 151 is to primarily transfer the toner image on the surface of the photosensitive layer of the photosensitive drum 11 to its peripheral surface due to a potential difference. The secondary transfer roller 152 is supported so as to be able to rotate counterclockwise in FIG. 1 with respect to a frame (not shown) so as to face the transfer drum 151 and make a pair. The secondary transfer roller 152 presses the print medium conveyed between the transfer drum 151 and the transfer drum 151 while sandwiching the print medium between the secondary transfer roller 152 and the transfer drum 151. Further, the secondary transfer roller 152 is configured to apply a reverse polarity voltage to the toner from the opposite surface of the print medium onto which the toner image has been transferred. Therefore, the toner image primarily transferred to the transfer drum 151 can be secondarily transferred to the printing medium.

  The fixing device 16 includes a primary heating unit 161 and a secondary heating unit 162. The primary heating unit 161 and the secondary heating unit 162 are disposed in the conveyance path P of the print medium indicated by an arrow in FIG.

  The conveyance path P includes a conveyance roller (not shown) and the like for conveying a sheet-like sheet as a print medium. The conveyance speed of the print medium is, for example, 0.5 m / s to 1.0 m / s. In the electrophotographic printer 1 of the present embodiment, electrophotographic printing is performed on the front and back surfaces of a print medium. Therefore, as shown in FIG. 1, the conveyance path P includes a main conveyance path P1 that conveys the print medium between the transfer drum 151 of the transfer device 15 and the secondary transfer roller 152, and the transfer device 15 in the main conveyance path P1. A sub-transport path P <b> 2 formed in a loop shape is provided so as to transport the print medium from the downstream side of the transfer device 15 to the upstream side of the transfer device 15, connected to the upstream side and the downstream side. A branch conveyance switching unit 171 and a merged conveyance switching unit 172 are provided at a branch portion and a junction portion where the main conveyance path P1 and the sub conveyance path P2 are connected. The branch conveyance switching unit 171 is disposed on the downstream side (branch portion) of the transfer device 15 in the main conveyance path P1, and determines whether the print medium is sent to the main conveyance path P1 or the print medium is sent to the sub conveyance path P2. Selective switching. The merging / conveying switching unit 172 is disposed on the upstream side (merging portion) of the transfer device 15 in the main conveyance path P1, and sends the print medium conveyed in the main conveyance path P1 to the transfer device 15 or the sub-conveyance path. This selectively switches whether the print medium conveyed to P2 is sent to the transfer device 15. Further, a print medium reversing unit 173 is provided in the sub-transport path P2. The print medium reversing unit 173 reverses the front and back of the print medium being transported through the sub transport path P2. The print medium reversing unit 173 has a configuration in which the front and back sides are reversed by switching the front end side and the rear end side in the transport direction of the print medium, or each side end portion in the width direction of the print medium (direction orthogonal to the transport direction). There is a configuration that reverses the front and back.

  The primary heating unit 161 is disposed between the transfer device 15 and the branch conveyance switching unit 171 in the main conveyance path P <b> 1 so as to correspond to the print medium immediately after passing through the transfer device 15. The primary heating unit 161 heats the toner image secondarily transferred to the printing medium by passing through the transfer device 15 and is configured as a non-contact type composed of, for example, a flash lamp or a warm air machine. The flash lamp irradiates the toner image of the print medium with light energy including infrared wavelengths. Although not clearly shown in the figure, the flash lamp mainly includes a xenon lamp or a heat lamp, and a reflector that reflects the light energy of the lamp. Consists of. In this case, the toner contains an infrared absorbing material, and the infrared absorbing material absorbs light energy and the temperature rises, whereby the toner image can be heated. This flash lamp can change the amount of heat for heating the toner image by changing the light quantity of the lamp. On the other hand, the warm air machine mainly includes a heater and a fan, and can heat the toner image by applying the hot air to the toner image of the printing medium. This warm air machine can change the amount of heat for heating the toner image by changing the temperature of the heater.

  The secondary heating unit 162 is disposed on the downstream side of the branch conveyance switching unit 171 in the main conveyance path P <b> 1 so as to correspond to the print medium after passing through the transfer device 15. The secondary heating unit 162 heats the toner image secondarily transferred to the printing medium by passing through the transfer device 15 and is configured as a contact type composed of a pair of fixing rollers 162a facing each other. . The fixing roller 162a has a built-in heater in a silicon sponge roller or the like, and a fixing roller 162a on the upper side of the main conveyance path P1 is supported so as to be rotatable counterclockwise in FIG. The lower fixing roller 162a of P1 is supported so as to be rotatable in the clockwise direction in FIG. The fixing roller 162a presses while sandwiching the print medium conveyed therebetween. Accordingly, the print medium sandwiched between the pair of fixing rollers 162a is heated, and the toner particle resin in the toner image is melted and fixed on the print medium.

  In the fixing device 16, the amount of heat that the primary heating unit 161 heats the toner image on the print medium is set lower than the amount of heat that the secondary heating unit 162 heats the toner image on the print medium. The heat amount of the secondary heating unit 162 is a heat amount for fixing the toner on the print medium by melting the resin of the toner particles in the toner as described above, and a heat amount for completely fixing the toner on the print medium. On the other hand, the amount of heat of the primary heating unit 161 is the amount of heat that melts the resin of the toner particles in the toner, but there is not enough heat to completely fix the toner on the print medium. When the component parts of the unit 171, the merging / conveying switching unit 172, the print medium reversing unit 173, and the transfer device 15 come into contact with the toner image transferred to the print medium, the toner particle resin does not move to such extent. The amount of heat that melts the toner, so that the toner is semi-fixed on the printing medium.

  The primary heating unit 161 is configured as a non-contact type composed of a flash lamp or a warm air machine, and is provided with a contact type composed of a fixing roller and a pressure roller, and a measure for preventing the adhesion of dirt. You may comprise as a contact type which heats using a belt. That is, the primary heating unit 161 only needs to have at least a heat amount set lower than the heat amount by which the secondary heating unit 162 heats the toner image on the print medium.

  In the electrophotographic printer 1 according to the present embodiment, the photosensitive drum 11, the supply roller 141, the developing roller 142, the transfer drum 151, the secondary transfer roller 152, and the fixing roller 162a include one drive motor (not shown). The driving force is transmitted through a plurality of gears, chains, and the like, so that synchronous rotation is possible. For example, the photosensitive drum 11, the supply roller 141, the developing roller 142, the transfer drum 151, the secondary transfer roller 152, and the fixing roller 162a may be configured to be rotated by individual driving motors. Good.

  The operation of the above-described electrophotographic printer 1 will be described.

  First, the charging device 12 performs corona discharge on the photosensitive drum 11 to charge the surface of the photosensitive drum 11 with a polarity corresponding to the toner characteristics. Next, an image is exposed on the surface of the charged photosensitive drum 11 by the exposure device 13 to form an electrostatic latent image.

  On the other hand, the electrostatic latent image on the surface of the photosensitive drum 11 is visualized by the developing device 14. That is, by rotating the supply roller 141, the liquid toner stored in the tank is pumped up by the supply roller 141, and the liquid toner of the supply roller 141 is directly supplied to the developing roller 142. A thin liquid toner layer is formed. At this time, by adjusting the bias voltage applied to the developing roller 142 by the voltage applying device, the film thickness of the liquid toner layer transferred to the photosensitive drum 11 can be adjusted by the electric field generated in the developing roller 142. Further, the liquid toner supplied to the developing roller 142 is preliminarily leveled by a leveling blade provided on the peripheral surface of the developing roller 142, whereby the film thickness can be made uniform.

  Then, the liquid toner layer on the developing roller 142 is brought close to the electrostatic latent image formed on the surface of the photosensitive drum 11, thereby moving the liquid toner charged by the potential difference onto the photosensitive drum 11. A toner image is formed on the surface. At this time, since the liquid toner layer on the developing roller 142 is in an aligned state in which the toner particles are in close contact with each other with a uniform film thickness, the liquid toner layer is close to the electrostatic latent image formed on the surface of the photosensitive drum 11. Then, the charged liquid toner layer moves to the photosensitive drum 11 with the toner particles being in an aligned state with a uniform thickness, and a toner image with a uniform thickness can be formed on the photosensitive drum 11.

  Subsequently, the toner image formed on the photosensitive drum 11 is transferred to one surface of the print medium by the transfer device 15. That is, the print medium transported to the main transport path P <b> 1 is sent to the transfer device 15 through the merge transport switching unit 172. In the transfer device 15, the toner image formed on the photosensitive drum 11 is primarily transferred onto the transfer drum 151 due to a potential difference generated between the toner image and the transfer drum 151. The toner image primarily transferred onto the transfer drum 151 is pressed between the transfer drum 151 and the secondary transfer roller 152 by applying a pressing force to the transfer drum 151 by the secondary transfer roller 152 and a reverse polarity voltage. Secondary transfer is performed on one side of the fed print medium.

  Subsequently, the toner image transferred to one surface of the print medium is heated by the primary heating unit 161 of the fixing device 16. That is, the toner image on one side of the print medium is semi-fixed on the print medium.

  Subsequently, the print medium that has passed through the position of the primary heating unit 161 is switched to the branch conveyance switching unit 171 and sent to the sub conveyance path P2. In the sub-transport path P2, the print medium reversing unit 173 reverses the front and back of the print medium. Then, the print medium with the front and back sides reversed is sent to the upstream side of the transfer device 15 via the merged conveyance switching unit 172. That is, the print medium is fed into the transfer device 15 so that the other surface opposite to the one surface to which the toner image is transferred is directed to the transfer drum 151.

  Subsequently, the toner image formed on the photosensitive drum 11 is transferred to the other surface of the print medium by the transfer device 15.

  Subsequently, the toner image transferred to the other surface of the printing medium is heated by the primary heating unit 161 of the fixing device 16. That is, the toner image on the other side of the print medium is semi-fixed on the print medium.

  Subsequently, the print medium that has passed through the position of the primary heating unit 161 is sent through the branch conveyance switching unit 171 to the secondary heating unit 162 of the fixing device 16. The secondary heating unit 162 heats the toner image transferred on both sides of the print medium. That is, the toner images on both sides of the semi-fixed print medium are completely fixed on the print medium. Note that the temperature of the surface of the print medium on which the toner images on both sides of the print medium are completely fixed through the secondary heating unit 162 reaches 100 ° C.

  As described above, in the fixing device 16 and the fixing method and the electrophotographic printing machine 1 according to the present embodiment, the downstream side where the toner is transferred to one surface of the print medium and the other surface of the print medium. The primary heating unit 161 disposed in the upstream main conveyance path P1 to which the toner is transferred performs a primary heating step of heating the toner transferred to one side of the print medium, and the other side of the print medium A secondary heating step of heating and fixing the toner transferred on both sides of the printing medium is performed by the secondary heating unit 162 disposed in the downstream main conveyance path P1 to which the toner is transferred. The amount of heat heated by the primary heating unit 161 is set lower than the amount of heat heated by the secondary heating unit 162.

  As a result, the toner image transferred to one surface of the print medium is semi-fixed by the primary heating unit 161 having a heat amount lower than that of the secondary heating unit 162 so that the toner image does not move to the other side. After the toner image is transferred, the toner image is completely fixed by the secondary heating unit 162. As described above, when electrophotographic printing is performed on both sides of the printing medium, the toner image transferred to one side of the printing medium is semi-fixed, and then the toner images on both sides of the printing medium are completely fixed together. For this reason, the printing medium is heated in two stages by the fixing device 16, and in the primary heating process, the toner image is heated with a heat quantity lower than the heat quantity for fixing the toner to the printing medium in the secondary heating process. One side is not heated twice with a quantity of heat sufficient to fix the toner image. As a result, it is possible to suppress the situation in which the liquid absorbency of the toner and the water content of the print medium (the resistance value of the print medium) are different between one side and the other side of the print medium, and the transfer efficiency becomes almost equal. The image quality can be made uniform on one side and the other side. In addition, after the toner images are transferred to both sides of the print medium, the print medium contracts due to the heat of the secondary heating unit 162, so that the image size is made uniform on one side and the other side of the print medium. be able to.

  In the present embodiment, the primary heating unit 161 is configured as a non-contact type that heats the toner of the print medium in a non-contact manner with respect to the print medium, and the secondary heating unit 162 is configured with respect to the print medium. The contact type is configured to heat and fix the toner of the printing medium in a contact form. For this reason, since the primary heating unit 161 is a non-contact type, it is possible to prevent a situation in which dirt is attached to the surface of the print medium and the toner image. In addition, since the primary heating unit 161 does not directly apply heat in a non-contact manner, the amount of heat can be easily changed, thereby controlling the total amount of heat in the primary heating unit 161 and the secondary heating unit 162. It is possible to always maintain good print quality by using a fixing heat amount according to the amount of liquid toner and the water content of the print medium. On the other hand, since the secondary heating unit 162 is a contact type, the toner image to be fixed can be smoothed by pressing force to give gloss to the printing surface.

  In this embodiment, a non-volatile liquid toner is applied as the toner. Since the non-volatile liquid toner is transferred to the print medium in a wet state, if the liquid absorbency of the print medium changes, the transfer state changes and affects the print quality. Therefore, the effect of improving the print quality can be obtained more remarkably by applying the liquid toner.

  By the way, in the above-described embodiment, an electronic apparatus in which one transfer device 15 is arranged and a print medium that is reversed upside down through the print medium reversing unit 173 of the sub-transport path P2 is cyclically transported to the transfer device 15. Although the photo printing machine 1 was applied, this is not the case.

  For example, the electrophotographic printer 2 shown in FIG. 2 or the electrophotographic printer 3 shown in FIG. 3 may be applied. 2 and 3 are schematic views of an electrophotographic printing machine according to another embodiment of the present invention. In this other embodiment, the same reference numerals are given to the same parts as those of the electrophotographic printer 1 shown in FIG.

  The electrophotographic printers 2 and 3 shown in FIGS. 2 and 3 can apply a web which is a continuous paper in addition to a sheet-like sheet as a printing medium.

  The electrophotographic printing machine 2 shown in FIG. 2 has two transfer devices 15 arranged in parallel, and a conveyance path P is formed in series so as to sequentially convey the print medium to each transfer device 15. Around the transfer drum 151 of each transfer device 15 arranged on the upstream side and downstream side of the transport path P, the photosensitive drum 11, the charging device 12, the exposure device 13, and the developing device 14 are united, and color photographic printing is performed. 4 units for printing four colors of cyan, magenta, yellow, and black are arranged. In the case of single color or multicolor printing that does not perform color photo printing, the number of units corresponding to the number of colors may be provided. A primary heating portion 161 of the fixing device 16 is disposed on the conveyance path P between the transfer devices 15. Further, a print medium reversing unit 173 is disposed in the conveyance path P between the transfer devices 15 and downstream of the primary heating unit 161. In addition, a secondary heating unit 162 of the fixing device 16 is disposed in the conveyance path P on the downstream side of the downstream transfer device 15.

  Here, when the print medium is a sheet-like sheet, the print medium reversing unit 173 can be configured similarly to the print medium reversing unit 173 in the electrophotographic printer 1 shown in FIG. On the other hand, when the print medium is a web, the print medium reversing unit 173 has a configuration in which each side end in the width direction of the print medium (direction orthogonal to the transport direction) is reversed to reverse the front and back.

  In the electrophotographic printing machine 2 shown in FIG. 2, the print medium conveyed to the conveyance path P is sent to the upstream transfer device 15, whereby the toner image formed on the photosensitive drum 11 is transferred to one of the print media. Transfer to the surface.

  Subsequently, the toner image transferred to one surface of the print medium is heated by the primary heating unit 161 of the fixing device 16. That is, the toner image on one side of the print medium is semi-fixed on the print medium.

  Subsequently, the printing medium reversing unit 173 reverses the print medium that has passed through the position of the primary heating unit 161. Then, the print medium with the front and back reversed is sent to the transfer device 15 on the downstream side, whereby the toner image formed on the photosensitive drum 11 is transferred to the other surface of the print medium.

  Subsequently, the toner image transferred on both sides of the printing medium is heated by the secondary heating unit 162 of the fixing device 16. That is, the toner images on both sides of the print medium are completely fixed on the print medium.

  The electrophotographic printing machine 3 shown in FIG. 3 has two transfer devices 15 arranged in parallel, and a conveyance path P is formed in series so as to sequentially convey the print medium to each transfer device 15. Further, one transfer device 15 is configured by inverting the arrangement of the transfer drum 151 and the secondary transfer roller 152 with respect to the other transfer device 15. Around the transfer drum 151 of each transfer device 15 arranged on the upstream side and downstream side of the transport path P, the photosensitive drum 11, the charging device 12, the exposure device 13, and the developing device 14 are united, and color photographic printing is performed. 4 units for printing four colors of cyan, magenta, yellow, and black are arranged. In the case of single color or multicolor printing that does not perform color photo printing, the number of units corresponding to the number of colors may be provided. A primary heating portion 161 of the fixing device 16 is disposed on the conveyance path P between the transfer devices 15. In addition, a secondary heating unit 162 of the fixing device 16 is disposed in the conveyance path P on the downstream side of the downstream transfer device 15.

  In the electrophotographic printing machine 3 shown in FIG. 3, the print medium conveyed to the conveyance path P is sent to the upstream transfer device 15 so that the toner image formed on the photosensitive drum 11 is transferred to one of the print media. Transfer to the surface.

  Subsequently, the toner image transferred to one surface of the print medium is heated by the primary heating unit 161 of the fixing device 16. That is, the toner image on one side of the print medium is semi-fixed on the print medium.

  Subsequently, the print medium that has passed through the position of the primary heating unit 161 is sent to the transfer device 15 on the downstream side, whereby the toner image formed on the photosensitive drum 11 is transferred to the other surface of the print medium.

  Subsequently, the toner image transferred on both sides of the printing medium is heated by the secondary heating unit 162 of the fixing device 16. That is, the toner images on both sides of the print medium are completely fixed on the print medium.

  As described above, even in the fixing device 16 and the fixing method and the electrophotographic printers 2 and 3 according to other embodiments, the toner is transferred to one surface of the print medium on the downstream side and the print medium The primary heating unit 161 disposed in the upstream conveyance path P to which the toner is transferred to the other surface performs a primary heating process of heating the toner transferred to one surface of the print medium, and the other of the print medium A secondary heating step of heating and fixing the toner transferred on both sides of the printing medium is performed by the secondary heating unit 162 disposed in the downstream conveyance path P on which the toner is transferred to the surface. The amount of heat heated by the primary heating unit 161 is set lower than the amount of heat heated by the secondary heating unit 162.

  As a result, the toner image transferred to one surface of the print medium is semi-fixed by the primary heating unit 161 having a heat amount lower than that of the secondary heating unit 162 so that the toner image does not move to the other side. After the toner image is transferred, the toner image is completely fixed by the secondary heating unit 162. As described above, when electrophotographic printing is performed on both sides of the printing medium, the toner image transferred to one side of the printing medium is semi-fixed, and then the toner images on both sides of the printing medium are completely fixed together. For this reason, the printing medium is heated in two stages by the fixing device 16, and in the primary heating process, the toner image is heated with a heat quantity lower than the heat quantity for fixing the toner to the printing medium in the secondary heating process. One side is not heated twice with a quantity of heat sufficient to fix the toner image. As a result, it is possible to suppress the situation in which the liquid absorbency of the toner and the water content of the print medium (the resistance value of the print medium) are different between one side and the other side of the print medium, and the transfer efficiency becomes almost equal. The image quality can be made uniform on one side and the other side. In addition, after the toner images are transferred to both sides of the print medium, the print medium contracts due to the heat of the secondary heating unit 162, so that the image size is made uniform on one side and the other side of the print medium. be able to.

  In other embodiments, the primary heating unit 161 is configured as a non-contact type that heats the toner of the print medium in a non-contact manner with respect to the print medium, and the secondary heating unit 162 is configured to print It is configured as a contact type in which the toner of the print medium is heated and fixed in a form in contact with the medium. For this reason, since the primary heating unit 161 is a non-contact type, it is possible to prevent a situation in which dirt is attached to the surface of the print medium and the toner image. In addition, since the primary heating unit 161 does not directly apply heat in a non-contact manner, the amount of heat can be easily changed, thereby controlling the total amount of heat in the primary heating unit 161 and the secondary heating unit 162. It is possible to always maintain good print quality by using a fixing heat amount according to the amount of liquid toner and the water content of the print medium. On the other hand, since the secondary heating unit 162 is a contact type, the toner image to be fixed can be smoothed by pressing force to give gloss to the printing surface.

  In other embodiments, a non-volatile liquid toner is applied as the toner. Since the non-volatile liquid toner is transferred to the print medium in a wet state, if the liquid absorbency of the print medium changes, the transfer state changes and affects the print quality. Therefore, the effect of improving the print quality can be obtained more remarkably by applying the liquid toner.

  In the electrophotographic printers 2 and 3 shown in FIGS. 2 and 3, when a web is applied to the printing medium, the primary heating unit and the secondary heating unit of the fixing device are not shown in the drawings, but the web is a circumferential surface. You may comprise as a heating roller wound around. In the primary heating unit and the secondary heating unit including the heating roller, the amount of heat for heating the toner transferred to the print medium can be changed by changing the winding angle.

  As described above, the fixing device, the fixing method, and the electrophotographic printer according to the present invention are suitable for aligning the image quality and the image size on both sides of the printing medium when performing double-sided electrophotographic printing.

1 is a schematic view of an electrophotographic printing machine according to an embodiment of the present invention. It is the schematic of the electrophotographic printer concerning other embodiment of this invention. It is the schematic of the electrophotographic printer concerning other embodiment of this invention.

Explanation of symbols

1, 2, 3 Electrophotographic printing machine 11 Photosensitive drum 12 Charging device 13 Exposure device 14 Developing device 141 Supply roller 142 Developing roller 15 Transfer device 151 Transfer drum 152 Secondary transfer roller 16 Fixing device 161 Primary heating unit 162 Secondary heating unit 162a Fixing roller 171 Branch conveyance switching unit 172 Junction conveyance switching unit 173 Print medium reversing unit P conveyance path P1 main conveyance path P2 sub conveyance path

Claims (5)

The toner transferred to one side of the print medium is used in an electrophotographic printing machine that transports the print medium in a mode in which the toner is transferred to the other side of the print medium, and the toner transferred to the print medium is In a fixing device that heats and fixes the print medium,
Arranged in a conveyance path on the downstream side where toner is transferred to one side of the print medium and upstream where toner is transferred to the other side of the print medium, and transferred to one side of the print medium A primary heating unit for heating the toner that has been removed;
A secondary heating unit that is disposed in a downstream conveyance path where toner is transferred to the other surface of the print medium, and that heats and fixes the toner transferred to both surfaces of the print medium;
The fixing device is characterized in that the amount of heat heated by the primary heating unit is set lower than the amount of heat heated by the secondary heating unit.   The primary heating unit heats the toner of the print medium in a non-contact form with respect to the print medium, and the secondary heating unit heats the toner of the print medium in a form of contact with the print medium. The fixing device according to claim 1, wherein:   The fixing device according to claim 1, wherein a non-volatile liquid toner is applied as the toner. A primary heating step of heating the toner transferred to one side of the print medium after the toner is transferred to one side of the print medium;
Next, after the toner is transferred to the other side of the print medium, a secondary heating step of heating and fixing the toner transferred to both sides of the print medium;
And the amount of heat heated in the primary heating step is set lower than the amount of heat heated in the secondary heating step. A photosensitive drum; a charging device that charges the circumferential surface of the photosensitive drum; an exposure device that exposes a latent image on the charged circumferential surface of the photosensitive drum; and a toner image formed by charging the latent image on the photosensitive drum with toner. A developing device to be formed, and a transfer drum to which the toner image of the photosensitive drum is transferred in contact with the peripheral surface of the photosensitive drum, the toner image on the transfer drum is transferred to one surface of the printing medium, and An electrophotographic printer that transfers a toner image of the transfer drum or another transfer drum to the other surface of the print medium,
An electrophotographic printing machine, wherein the fixing device according to claim 1 is applied as a fixing device that heats and fixes the toner transferred to the printing medium to the printing medium. .

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