JP2012179737A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent detachment of particles adhering to an image forming face of a recording medium and to prevent occurrence of stacker blocking.SOLUTION: A particle applying device 200 that loads a recording face of a paper sheet 122 with matting agent particles and a pressing roller 220 that presses the recording face of the paper sheet 122 after the matting agent particles are applied thereon by the particle applying device 200 are provided at portions where they are in contact with the paper sheet 122 which is conveyed by a fixing drum 184. The particle applying device 200 is provided with a fixing roller 188 which is brought into contact with the recording face of the paper sheet 122 placed on the fixing drum 184, and a web 204 which is brought into contact with the fixing roller 188 by being supported by a first rod 206 and a second rod 208 and is impregnated with a particle dispersion liquid 210L containing many matting agent particles dispersed therein. Matting agent particles 210P loaded on the recording face of the paper sheet 122 via the fixing roller 188 from the web 204 are pressed into the paper sheet 122 by being pressed by the pressing roller 220.

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus that ejects ink droplets onto a recording medium such as paper using an ink jet recording head is known.

  In this image forming apparatus, ink droplets are ejected onto a recording medium, and further, the ink droplets on the recording medium are dried and fixed by heating, and then the recording medium is sequentially discharged and stacked on a paper discharge unit. In such an image forming apparatus, when a recording medium is stacked on a paper discharge unit, a phenomenon called blocking in which ink adheres between recording media that overlap vertically (this phenomenon is referred to as stacker blocking hereinafter) occurs. There is a case. In particular, in a high-productivity ink jet recording apparatus, ink is insufficiently dried or insufficiently fixed, and stacker blocking is likely to occur.

  Patent Document 1 listed below discloses a powder coating method in which powder is applied onto ink of a printed material immediately after printing and before drying. In this method, the powder is supplied to the outer peripheral surface of the rotating roller, the powder is adsorbed and held on the outer peripheral surface of the rotating roller, and the printed material immediately after printing is fed into the rotating roller on which the powder is adsorbed and held. The powder is transferred to the printed image surface due to the viscosity of the ink.

  Patent Document 2 below discloses a configuration in which a matting agent is held in a plurality of concave portions formed on a surface of a coating roller at predetermined intervals, and the matting agent is applied to a printed matter in spots.

Japanese Patent Laid-Open No. 9-011654 Japanese Patent No. 4010577

  However, in Patent Document 1, since the rotary roller wipes off the powder once transferred to the printed matter, the transfer efficiency of the powder is low and sufficient performance cannot be obtained. In addition, after the powder is transferred onto the ink on the printed image surface of the printed matter, the powder may be detached when the recording medium is sprinkled or the seasoning wind is blown against the recording medium. There is.

  In Patent Document 2, ink is likely to gradually accumulate in the recesses of the application roller, and it is difficult to maintain good application properties (transferability of a required amount of matting agent applied). Further, after applying the matting agent to the printed matter, the matting agent may be detached when the recording medium is scratched or a seasoning wind is blown onto the recording medium.

  In view of the above facts, an object of the present invention is to provide an image forming apparatus capable of suppressing the detachment of particles attached to the image forming surface of a recording medium and suppressing the occurrence of stacker blocking.

  The image forming apparatus according to claim 1, wherein a liquid droplet ejecting apparatus that ejects liquid droplets onto a recording medium to form an image, a carrier that transports the recording medium, and an image of the recording medium include a number of particles. A particle applying unit for applying to the formed surface; and after applying the particles by the particle applying unit, applying pressure to the particles applied to the surface on which the image of the recording medium is formed A pushing roller for pushing particles into the recording medium.

  According to the above invention, the droplet discharge device discharges droplets onto the recording medium to form an image, and the particle applying unit applies a large number of particles to the surface on which the image of the recording medium is formed. Further, after a large number of particles are applied by the particle applying means, the particles are pressed into the recording medium by applying pressure to the particles applied to the surface of the recording medium on which the image is formed by the pressing roller. As a result, the positions of the particles on the surface on which the image of the recording medium is formed are fixed. For this reason, when the recording medium is sprinkled in the subsequent process or when a wind for seasoning is blown to the recording medium, detachment of particles attached to the image forming surface of the recording medium is suppressed, and stacker blocking is prevented. Occurrence can be suppressed.

  According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the particle applying unit is disposed so as to be in contact with the recording medium on the conveyance body and is supplied with the particles. A roller is provided, and the particles are applied to the surface on which the image of the recording medium is formed via the applying roller.

  According to the above invention, the particle applying unit includes the applying roller disposed so as to come into contact with the recording medium on the conveyance body, and the particles are supplied to the applying roller, and the particles attached to the surface of the applying roller are By contacting the surface of the recording medium on which the image is formed, particles are applied to the surface of the recording medium on which the image is formed. That is, by applying the particles to the surface on which the image of the recording medium is formed via the applying roller, contamination in the apparatus due to the particles can be minimized.

  According to a third aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect of the present invention, wherein the pressing roller is configured to transfer the particles from the surface of the recording medium to 20 to 80% of an average particle diameter of the particles. It pushes into depth.

  According to the above invention, the pressing roller presses the particles from the surface of the recording medium to a depth of 20 to 80% of the average particle diameter of the particles, whereby the position of the particles on the surface on which the image of the recording medium is formed. Is more reliably established. For this reason, when the recording medium is scratched or a seasoning wind is blown onto the recording medium, the detachment of the particles attached to the image forming surface of the recording medium is more reliably suppressed.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the surface layer of the pressing roller has an Asker C hardness of 70 ° or less and a thickness of 1 mm or more. A rubber layer and a surface film layer wound around the rubber layer and having a thickness of 50 μm or more and 200 μm or less.

  According to the above invention, the surface layer of the pressing roller has the rubber layer and the surface film layer wound around the rubber layer, whereby the particles on the surface on which the image of the recording medium is formed by the pressing roller. On the other hand, when pressure is applied, the particles are more effectively pushed into the recording medium, and the transfer of the particles from the recording medium to the pushing roller is suppressed.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the pressure P ₁ applied by the application roller to the recording medium and the push roller are The relationship with the pressure P ₂ applied to the recording medium satisfies P ₂ ≧ P ₁ .

According to the above invention, the relationship between the pressure P ₁ applied by the applying roller to the recording medium and the pressure P ₂ applied by the pressing roller to the recording medium satisfies P ₂ ≧ P _1. By applying an equal or stronger pressure to the particles that have not been sufficiently pressed into the surface on which the image of the recording medium is formed by the pressing roller, the particles are sufficiently pressed into the surface on which the image of the recording medium is formed. be able to.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the contact area S ₁ generated when the application roller applies pressure to the recording medium. And the contact area S ₂ generated when the pressing roller applies pressure to the recording medium satisfies S ₂ ≧ S ₁ .

According to the above invention, the relationship between the contact area S ₁ generated when the applying roller applies pressure to the recording medium and the contact area S ₂ generated when the pressing roller applies pressure to the recording medium is By satisfying S ₂ ≧ S ₁ , by applying pressure to the particles that have not been sufficiently pressed into the surface on which the image of the recording medium is formed by the applying roller with an equal or wider contact width by the pressing roller, The particles can be sufficiently pushed into the surface of the recording medium on which the image is formed.

  Since the present invention has the above-described configuration, it is possible to suppress the detachment of particles attached to the image forming surface of the recording medium and to suppress the occurrence of stacker blocking.

1 is a conceptual diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment of the present invention. It is a block diagram which shows the particle | grain provision apparatus and pushing roller which are used for the image forming apparatus shown in FIG. It is a schematic block diagram which shows the particle | grain provision apparatus used for the image forming apparatus shown in FIG. It is a block diagram which shows the particle | grain provision apparatus used for the image forming apparatus which concerns on 2nd Embodiment of this invention. (A) is a figure which shows the state of the mat agent particle pressed into the image forming surface of the thin paper using only the applying roller, and (B) is the image forming surface of the thin paper using the applying roller and the pressing roller. It is a figure which shows the state of the mat | matte agent particle | grains pushed in. (A) is a diagram showing the state of the matting agent particles pressed into the cardboard image forming surface using only the applying roller, and (B) is the cardboard image forming surface using the applying roller and the pressing roller. It is a figure which shows the state of the mat | matte agent particle | grains pushed in. Graph showing the embedding depth of matting agent particles on the image forming surface of thin paper when only the applying roller is used, and the embedding depth of matting agent particles on the image forming surface of thin paper when using the applying roller and the pressing roller It is. Graph showing the embedding depth of matting agent particles on the image forming surface of thick paper when only the applying roller is used and the embedding depth of matting agent particles on the image forming surface of thick paper when using the applying roller and the pressing roller It is. It is a graph which shows the relationship between the Asker C hardness of the rubber layer of a pressing roller, and the ratio of the mat agent particle | grains embedded in the image formation surface of the recording medium. 3 is a graph showing the relationship between the thickness of a rubber layer of a pressing roller and the ratio of matting agent particles embedded in an image forming surface of a recording medium. It is a block diagram which shows the particle | grain provision apparatus used for the image forming apparatus which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the particle | grain provision apparatus used for the image forming apparatus which concerns on 4th Embodiment of this invention.

  Hereinafter, an exemplary embodiment according to the present invention will be described with reference to the drawings.

<Overall configuration>
A configuration example of an ink jet image forming apparatus for carrying out the image forming apparatus according to the first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a conceptual diagram (side view) showing the entire image forming apparatus.

  The ink jet recording apparatus 1 uses a plurality of colors of ink (droplets) from an ink jet head 172C, 172M, 172Y, 172K as an example of a droplet discharge device on a sheet 122 held on a pressure drum (drawing drum 170) of the drawing unit 114. Is a pressure-cylinder direct drawing type ink jet recording apparatus that forms a desired color image by applying a processing liquid (ink aggregation processing liquid) onto a sheet 122 as a recording medium before ink discharge. Is an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method for forming an image on a sheet 122 by reacting with the ink is applied.

  The ink jet recording apparatus 1 mainly includes a paper feeding unit 110, a processing liquid application unit 112, a drawing unit 114, a drying unit 116, a fixing unit 118, and a paper discharge unit 120.

  The paper supply unit 110 is a mechanism that supplies the paper 122 to the treatment liquid application unit 112, and the paper 122 that is a sheet is stacked on the paper supply unit 110. The sheet feeding unit 110 is provided with a sheet feeding tray 150, and the sheets 122 are fed one by one from the sheet feeding tray 150 to the processing liquid applying unit 112. In the inkjet recording apparatus 1, a plurality of types of paper 122 having different paper types and sizes (medium sizes) can be used as the paper 122. In the present embodiment, a case where a sheet (cut sheet) is used as the sheet 122 will be described.

  The processing liquid application unit 112 is a mechanism that applies the processing liquid to the recording surface (image forming surface) of the paper 122. The treatment liquid contains a color material aggregating agent that agglomerates the color material in the ink applied by the drawing unit 114. When the treatment liquid and the ink come into contact with each other, the ink is separated from the color material and the solvent. Promoted.

  As shown in FIG. 1, the treatment liquid application unit 112 includes a paper feed cylinder 152, a treatment liquid drum 154, and a treatment liquid application device 156. The treatment liquid drum 154 is a drum that holds the sheet 122 and rotates and conveys the sheet 122. The processing liquid drum 154 includes a claw-shaped holding means (gripper) on the outer peripheral surface thereof, and the front end of the paper 122 can be held by sandwiching the paper 122 between the claw of the holding means and the peripheral surface of the processing liquid drum 154. It is like that.

  The treatment liquid drum 154 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the sheet 122 can be held in close contact with the peripheral surface of the treatment liquid drum 154.

  A treatment liquid coating device 156 is provided outside the treatment liquid drum 154 so as to face the peripheral surface thereof. The processing liquid coating device 156 is pressed against the processing liquid container in which the processing liquid is stored, the anilox roller partially immersed in the processing liquid in the processing liquid container, and the sheet 122 on the anilox roller and the processing liquid drum 154. And a rubber roller for transferring the measured processing liquid to the paper 122. According to this processing liquid application device 156, the processing liquid can be applied to the sheet 122 while being measured. A hot air heater 158 and an IR heater 160 for drying the processing liquid applied to the paper 122 are provided downstream of the processing liquid coating device 156 in the conveyance direction of the paper 122.

  The sheet 122 to which the processing liquid is applied by the processing liquid applying unit 112 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 114 via the intermediate transport unit 124 (transfer cylinder 130). The drawing unit 114 includes a drawing drum 170 and ink jet heads 172C, 172M, 172Y, and 172K. Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) on its outer peripheral surface. The sheet 122 fixed to the drawing drum 170 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the inkjet heads 172C, 172M, 172Y, 172K.

  Inkjet heads 172C, 172M, 172Y, and 172K are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the sheet 122, and the ink ejection surfaces thereof are A nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area is formed. Each of the inkjet heads 172C, 172M, 172Y, and 172K is installed so as to extend in a direction orthogonal to the conveyance direction of the paper 122 (the rotation direction of the drawing drum 170).

  The liquid droplets of the corresponding color ink are ejected from the respective inkjet heads 172C, 172M, 172Y, 172K toward the recording surface of the paper 122 held in close contact with the drawing drum 170, so that the processing liquid application unit 112 in advance. The ink comes into contact with the treatment liquid applied to the recording surface, and the pigment and resin particles dispersed in the ink are aggregated to form an aggregate. As a result, pigment flow on the sheet 122 is prevented, and an image is formed on the recording surface of the sheet 122.

  The sheet 122 on which an image is formed by the drawing unit 114 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 116 via the intermediate conveyance unit 126. The drying unit 116 is a mechanism for drying moisture contained in the solvent separated by the aggregating action. As shown in FIG. 1, the drying unit 116 is provided between the drying drum 176, a plurality of IR (infrared) heaters 178, and each IR heater 178. And a hot air heater 180 disposed in the.

  Similar to the treatment liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) on its outer peripheral surface, and the holding unit can hold the leading end of the sheet 122. The temperature and amount of warm air blown from the warm air heater 180 toward the paper 122 and the temperature of each IR heater are detected by a temperature sensor and sent to a control unit (not shown) as temperature information. Based on the temperature information, the controller appropriately adjusts the temperature and air volume of the warm air and the temperature of each IR heater, thereby realizing various drying conditions.

  The surface temperature of the drying drum 176 may be set to 50 ° C. or higher. Drying is promoted by heating from the back surface of the sheet 122, and image destruction during fixing can be prevented. The upper limit of the surface temperature of the drying drum 176 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 176 (preventing burns due to high temperatures). It is preferably set to 75 ° C. or lower (more preferably 60 ° C. or lower).

  Further, it has been found that the higher the drying drum temperature (the surface temperature of the drying drum 176) (the stronger the drying temperature), the less the expansion and contraction of the paper 122, so that the surface of the drying drum 176 does not impair the safety. Higher temperatures can reduce the effects of cockle.

  Holding on the outer peripheral surface of the drying drum 176 so that the recording surface of the paper 122 faces outward (that is, in a state where the recording surface of the paper 122 is convex), and drying while rotating and transporting. Thus, it is possible to prevent the paper 122 from being wrinkled or lifted, and to prevent uneven drying due to these.

  The sheet 122 that has been dried by the drying unit 116 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 118 via the intermediate conveyance unit 128. The transfer drum 130 of the intermediate transport unit 128 may be provided with a hot air heater (not shown) that blows hot air on the recording surface of the paper 122. By providing a warm air heater in the transfer drum 130 of the intermediate conveyance unit 128, immediately after ink is ejected onto the paper 122 by the ink jet heads 172C, 172M, 172Y, and 172K, moisture contained in the solvent separated by the aggregating action is dried. Can be made.

  The fixing unit 118 includes a fixing drum 184 as an example of a conveyance body that holds and conveys the sheet 122, a fixing roller (heating roller) 188 as an example of an application roller, a pressing roller 220, and an inline sensor 190.

  Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) on its outer peripheral surface, and the holding unit can hold the leading end of the sheet 122. By the rotation of the fixing drum 184, the sheet 122 is conveyed with the recording surface facing outward, and the recording surface is subjected to fixing processing by the fixing roller 188 and inspection by the inline sensor 190.

  The fixing roller 188 is a roller member that heats and pressurizes the ink to weld resin particles (particularly self-dispersing polymer particles) in the ink to form a film of the ink. Composed.

  Specifically, the fixing roller 188 is disposed so as to be in pressure contact with the fixing drum 184 and constitutes a nip roller with the fixing drum 184. The fixing roller 188 is configured to rotate following the rotation of the fixing drum 184 holding the sheet 122. As a result, the sheet 122 is sandwiched between the fixing roller 188 and the fixing drum 184 and nipped at a predetermined nip pressure (for example, 0.15 MPa), and a fixing process is performed.

  The fixing roller 188 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and is controlled to a predetermined temperature (for example, 60 to 80 ° C.).

  By heating the paper 122 with these heating rollers, thermal energy equal to or higher than the Tg (glass transition temperature) of the resin particles contained in the ink is applied, and the resin particles are melted to be pressed into the unevenness of the paper 122 and fixed. And the unevenness of the image surface is leveled to obtain gloss.

  Further, at a position facing the fixing drum 184, a particle applying device 200 as an example of particle applying means for applying matting agent particles as an example of a large number of particles is disposed. The particle applying device 200 includes a fixing roller 188 as an example of an applying roller that contacts the recording surface (image forming surface) of the paper 122 that is held and conveyed by the fixing drum 184, and a position at which the fixing roller 188 contacts the paper 122. And a supply unit 202 that is disposed upstream of the fixing roller 188 in the rotational direction and supplies matting agent particles to the fixing roller 188. In the particle applying device 200, the matting agent particles are supplied from the supply unit 202 to the surface of the fixing roller 188, and the fixing roller 188 rotates to apply the matting agent particles to the recording surface (image forming surface) of the paper 122. It has become so. The particle applying device 200 will be described later.

  A pressing roller 220 that presses the recording surface (image forming surface) of the sheet 122 is disposed downstream of the fixing roller 188 in the sheet conveying direction, and the matting agent applied to the recording surface (image forming surface) of the sheet 122. The particles are pushed into the sheet 122 by the pushing roller 220. The pushing roller 220 will also be described later.

  The in-line sensor 190 is a measuring unit for measuring a check pattern, a water content, a surface temperature, a glossiness, and the like for an image fixed on the paper 122, and a CCD line sensor or the like is applied.

  According to the fixing unit 118, the resin particles in the thin image layer formed by the drying unit 116 are heated and pressurized by the fixing roller 188 and melted, and can be fixed on the paper 122. Further, the surface temperature of the fixing drum 184 is set to 50 ° C. or more, and drying is promoted by heating the sheet 122 held on the outer peripheral surface of the fixing drum 184 from the back surface, thereby preventing image destruction during fixing. In addition, the image intensity can be increased by the effect of increasing the image temperature.

  As shown in FIG. 1, a paper discharge unit 120 is provided downstream of the fixing unit 118 in the recording medium conveyance direction. The paper discharge unit 120 includes a discharge tray 192. Between the discharge tray 192 and the fixing drum 184 of the fixing unit 118, a transfer drum 194, a conveying belt 196, and a stretching roller 198 are in contact with each other. Is provided. The sheet 122 is sent to the transport belt 196 by the transfer drum 194 and discharged to the discharge tray 192.

  The discharge tray 192 is also provided with a cold air jet nozzle 199, and the paper 122 can be cooled by blowing cold air from the cold air jet nozzle 199.

  Although not shown in FIG. 1, in addition to the above-described configuration, the ink jet recording apparatus 1 performs processing on the ink storage tank that supplies ink to the ink jet heads 172C, 172M, 172Y, and 172K, and the treatment liquid application unit 112. In addition to providing means for supplying liquid, the head maintenance unit for cleaning each ink jet head 172C, 172M, 172Y, 172K (wiping, purging, nozzle suction, etc. of the nozzle surface) and the position of the paper 122 on the medium conveyance path are detected. A position detection sensor that detects the temperature of each part of the apparatus, and the like.

  The ink jet recording apparatus 1 shown in FIG. 1 may include a plurality of seasoning devices used for the discharge tray 192, and each seasoning device may be movable between the paper discharge unit 120 and the paper supply unit 110.

<Details of Particle Applying Device 200 and Pushing Roller 220>
FIG. 2 shows details of the particle applying device 200.
As described above, the particle applying device 200 includes the fixing roller 188 as an example of the applying roller, and the supply unit 202 disposed on the upstream side in the rotation direction of the fixing roller 188 from the position where the fixing roller 188 contacts the sheet 122. It is equipped with. The supply unit 202 has a belt-like web 204 impregnated with a particle dispersion in which a number of matting agent particles are dispersed in a liquid, and a first rod that supports the web 204 so as to contact the surface of the fixing roller 188 from the back side. 206 and a second rod 208 on which the back side of the web 204 is wound and for applying tension to the web 204.

  The web 204 is supported by the first rod 206 from the back side and comes into contact with the fixing roller 188 and is tensioned by the second rod 208 that does not come into contact with the fixing roller 188. It is in surface contact with a width. The web 204 is disposed almost the entire length in the width direction of the sheet contact surface of the fixing roller 188.

  The web 204 is configured to move in a direction orthogonal to the width direction. For example, as shown in FIG. 3, a feed roller 212 that is disposed upstream of the first rod 206 in the moving direction of the web 204 and feeds the web 204, and downstream of the second rod 208 in the moving direction of the web 204. And a winding roller 214 that winds the web 204. As a result, the web 204 moves in the direction (arrow direction) opposite to the rotation direction of the fixing roller 188 at a position where the web 204 comes into contact with the fixing roller 188. In the present embodiment, the web 204 is moved by a predetermined amount in the direction of the arrow for every predetermined number of sheets passed, and the contact surface between the web 204 and the fixing roller 188 is updated.

  At that time, a bead of particle dispersion 210L is formed between the web 204 on the upstream side of the rotation direction of the fixing roller 188 relative to the first rod 206 and the fixing roller 188, and the matting agent particles 210P are stably transferred to the fixing roller 188. Can be supplied.

  As the web 204, a cloth material that can be impregnated with a particle dispersion (a liquid in which a number of matting agent particles are dispersed) is used. A non-woven fabric or the like is used as the cloth material.

  As the particles (mat agent particles) used in the particle dispersion, for example, plastic (for example, polymethyl methacrylate, polystyrene) and the like are preferable. As the liquid used for the particle dispersion, for example, a release agent such as silicone oil is preferable. As a particle size of particle | grains, 10-50 micrometers is preferable, 10-30 micrometers is more preferable, 15-30 micrometers is still more preferable. Further, by using silicone oil as the liquid, it is possible to ensure the glossiness of the image when applied to the recording surface (image forming surface) of the sheet 122 and to offset the image to the fixing roller 188. Can be suppressed.

  By using a particle dispersion liquid in which a large number of matting agent particles are dispersed, powder particles (powder) are contained in the ink jet recording apparatus 1 as compared with a case where powder particles (powder) are directly supplied to the fixing roller 188 and the recording surface of the paper 122. Since particles do not fly, contamination in the inkjet recording apparatus 1 is reduced.

  Further, if a dispersion medium such as oil is excessively applied to the recording surface of the paper 122 as the particle dispersion, gloss unevenness and density unevenness (due to processing agent and ink repelling) become a problem. By supplying the web 204 impregnated with the toner to the fixing roller 188, the particles can be supplied to the fixing roller 188 in a concentrated state. The amount of the dispersion medium can be reduced as compared with the supply by other application rollers or blades. Further, when the particle dispersion liquid is applied directly, the liquid is repelled on the fixing roller 188 and uniform application is difficult. However, the amount of the dispersion medium can be reduced by contacting the web 204 impregnated with the particle dispersion liquid. Combined with the effect of concentrating the particles, the matting agent particles can be applied to the fixing roller 188 almost uniformly.

  In this particle applying device 200, the web 204 impregnated with a particle dispersion 210L in which matting agent particles are dispersed in a liquid is brought into contact with the fixing roller 188, whereby the matting agent particles 210P are applied from the web 204 to the fixing roller 188. Then, the matting agent particles 210P supplied to the fixing roller 188 are transferred to the recording surface (image forming surface) of the sheet 122 on the fixing drum 184 by the rotation of the fixing roller 188 (second forming). Transferred).

  Since the matting agent particles 210P are easily transferred from the fixing roller 188 to the image portion of the paper 122 due to the adhesive force of the ink film, the matting agent particles 210P are not easily transferred from the fixing roller 188 to the non-image portion of the paper 122. The matting agent particles 210P are selectively applied to the image portion 122.

  As shown in FIG. 4, the particle applying device 230 according to the second embodiment of the present invention may be used instead of the particle applying device 200. The particle applying device 230 is a side opposite to the fixing roller 188 on the back side of the web 204 for the purpose of reducing the replacement frequency of the web 204 by reducing the feed amount of the web 204 by the winding roller 214 (see FIG. 3). A dispersion supply head 232 that supplies the particle dispersion to the web 204 may be disposed between the first rod 206 and the second rod 208. The dispersion liquid supply head 232 includes an ejection surface in which a plurality of ejection holes for ejecting the particle dispersion liquid are formed. By disposing the ejection surface in the vicinity of or in contact with the back surface of the web 204, a plurality of The particle dispersion is supplied to the web 204 from the discharge hole.

  Although not shown, the dispersion liquid supply head 232 is disposed so as to face the fixing roller 188 without the web 204, and the matting agent particle dispersion liquid is directly supplied from the dispersion liquid supply head 232 to the fixing roller 188. Also good.

  In the case of the system using these dispersion liquid supply heads 232, the number of matting agent particles required differs depending on the paper type or ink application amount of the paper (printing paper) 122. Therefore, the particle dispersion liquid depends on the paper type and ink application amount. Control may be made to vary the amount of liquid to be fed. Since it is located at the lower part of the stack of sheets 122 as the print job starts, stacker blocking is likely to deteriorate due to the influence of the weight of the upper sheet 122. Therefore, since the number of matting agent particles required increases as the printing job starts, it is preferable to control the amount of the particle dispersion to be increased at the beginning of the printing job.

  In the system in which the matting agent particles are applied to the sheet 122 through the fixing roller 188 in the form of a particle dispersion, the surface of the fixing roller (applying roller) 188 is roughened in order to efficiently perform transfer application. Need to be. First, by increasing the surface area by roughening the surface of the fixing roller 188 and improving the wettability of the particle dispersion, a large amount of matting agent particles can be supplied to the surface of the fixing roller 188.

That is, with respect to the surface tension γ _{L of} the particle dispersion, the surface tension γ _{S of} the fixing roller 188, the interfacial tension γ _SL of the particle dispersion and the fixing roller 188, Young's equation is used for the contact angle θ of the particle dispersion on the smooth roller. γ _S = γ _SL + γ _L cos θ or cos θ = (γ _S −γ _SL ) / γ _L
Where but satisfied, the surface area by a fine uneven structure on the surface of the fixing roller 188 is R times (R> 1) and increased, the contact angle theta _R and surface tension gamma _S of the fixing roller in the formula Young particle expression Wenzel multiplied by R in interfacial tension _{gamma SL} of the dispersion and the fixing roller _{Rγ S = Rγ SL + γ L} cosθ R or cosθ _R = Rcosθ
Is established, and the roller surface (θ <90 °) on which the dispersion liquid gets wet becomes more wet.

  Second, in the system in which the particle dispersion is applied to the fixing roller 188 via the web 204, the surface of the fixing roller 188 is roughened so that the web 204 has a width along the circumferential direction of the roughening roller. The transfer imparting performance to the surface of the fixing roller 188 can be improved by the effect of scraping and holding the matting agent particles when brought into contact.

  Further, in the roughened fixing roller 188, the matting agent particles can pass through the recesses on the surface of the fixing roller 188 and preferably remain on the surface of the paper 122, thereby improving the transfer performance to the surface of the paper 122. I can expect. The fixing roller 188 preferably has a configuration in which a rubber layer made of silicone rubber or the like and a surface film made of a resin such as PFA that has been roughened are wound around it.

  The moving direction of the web 204 and the rotating direction of the fixing roller 188 are preferably reversed. Thereby, the effect that the fixing roller 188 scrapes the matting agent particles from the web 204 is obtained. The moving direction of the web 204 and the rotation direction of the fixing roller 188 may be the same direction.

Next, the pushing roller 220 will be described.
Since the stacker blocking is a phenomenon that occurs remarkably in the paper 122 having a coat layer, it is assumed here that the paper 122 is a coated paper.
As shown in FIG. 2, a pressing roller 220 is disposed on the downstream side of the fixing roller 188 that contacts the sheet 122 on the fixing drum 184 in the sheet transport direction so as to contact the sheet 122 on the fixing drum 184. . The pushing roller 220 is pressed against the paper 122 on the fixing drum 184 with a predetermined pressure, and rotates in the same direction as the paper 122 on the fixing drum 184 moves. The width (length in the axial direction) of the pressing roller 220 is set to be equal to or larger than the maximum width of the paper 122 held on the fixing drum 184.

  The matting agent particles 210P applied to the recording surface (image forming surface) of the sheet 122 by the fixing roller 188 are pressed by the pressing roller 220, thereby embedding the matting agent particles 210P in the coat layer (not shown) of the sheet 122. Further, the degree of adhesion between the matting agent particles 210P and the paper 122 is strengthened. This suppresses the detachment of the matting agent particles when the printed paper 122 is spread or seasoned (conditioning by air blowing).

  It is preferable that a part of the matting agent particle 210P is embedded in the coating layer of the paper 122 by the pressing roller 220 and is held by the rigidity of the coating layer and the frictional force between the matting agent particle and the coating layer. The film thickness of the surface ink layer of the paper 122 is about 1 to 2 μm on average, and the thickness of the coat layer is 5 to 20 μm although it depends on the paper type. For example, in the case of matting agent particles having a particle size of 10 to 30 μm, the coating layer is reliably reached by embedding 20% or more.

  If the embedding depth of the matting agent particles is shallower than this, the matting agent particles will be detached from the paper 122 in the process of spreading the paper 122, applying seasoning, or processing after printing. When performing double-sided printing, if the matting agent particles applied to the first recording surface (image forming surface) are detached, it is necessary to make up for the extra amount when printing the last recording surface. It becomes complicated and the running cost increases. Further, when the last recording surface is printed, there is a concern that the matting agent particles adhering to the first recording surface may be detached and cause contamination in the apparatus.

  In the case of matting agent particles having a particle size of 10 to 30 μm, the stacking agent blocking effect is obtained by embedding 80% or more of the matting agent particles between the paper 122 and the paper 122 stacked thereon, thereby stacker blocking. The effect of deterring is weakened. The amount of the matting agent particles pushed into the paper 122 is preferably 20 to 80%, more preferably 20 to 50%, and still more preferably 30 to 50%.

  The pushing of the matting agent particles by the pushing roller 220 is effective when the recording surface of the paper 122 is softened with ink. Therefore, the pushing roller 220 is disposed immediately after the particle applying device 200. It is preferable.

  It is preferable that the pressing roller 220 be appropriately deformed with respect to the size of the matting agent particles applied to the recording surface of the paper 122. In the present embodiment, the surface layer of the pressing roller 220 includes a rubber layer provided near the surface and a surface film layer wound around the rubber layer. The surface film layer is formed of a resin (for example, PFA) that is harder than the rubber layer. The pushing roller 220 is provided with a core portion formed around the rotation shaft inside the surface layer. The thickness of the surface film layer is preferably 50 μm or more and 200 μm or less. When the thickness of the surface film layer is smaller than 50 μm, the surface film layer is deformed and scrapes off particles on the paper 122. When the thickness of the surface film layer is larger than 200 μm, the surface of the pressing roller 220 is This is because it is difficult to deform and it is difficult to push the matting agent particles.

  Further, if the surface of the pressing roller 220 is roughened, the surface of the pressing roller 220 is smooth because the particles on the sheet 122 are scraped off or the particles pass through the unevenness and are not pressed firmly. Good. However, the surface of the pressing roller 220 may be roughened.

FIG. 9 shows that the matting agent particles applied to the paper 122 by the particle applying device 200 were successfully pressed when the matting agent particles were pressed by the pressing roller 220 after the number density n ₁ per mm ² (= The ratio n ₂ / n ₁ of the number density of n ₂ particles / mm ² of the matting agent particles that were removed from the paper sheet 122 by the pressing roller 220 and not detached, and the Asker C hardness of the rubber layer of the pressing roller 220 was 30 to 70 °. It is the graph plotted by changing. The thickness of the rubber layer of the pressing roller 220 is set to 4 mm. Here, the measurement of Asker C hardness is a value when the rubber layer of the pressing roller 220 is measured under a load of 1 kg using an Asker C hardness meter manufactured by Kobunshi Keiki Co., Ltd. As shown in this graph, the smaller the Asker C hardness of the rubber layer of the pressing roller 220 (= the smaller the elastic modulus), the larger the ratio of the number of particles that can be pressed by the pressing roller 220.

  In particular, when a fixing roller (applying roller) 188 is used as the particle applying device 200, the pressure between the fixing roller 188 and the paper 122 is increased or the contact area is increased for the purpose of applying the matting agent particles at the same time. As a result, the image on the sheet 122 is transferred (offset) to the fixing roller 188, and curls and cockles generated on the sheet 122 are brought close to cause wrinkles. This defect can be overcome by embedding the matting agent particles with another push roller 220 after the fuser roller 188 is in contact with the paper 122.

  When the elastic modulus of the pressing roller 220 is small, the contact area between the pressing roller 220 and the paper 122 increases, and offset and wrinkles are likely to occur. From this point of view, it is preferable to use a rubber roller having an Asker C hardness of 30 ° or more as the pressing roller 220.

  In order to improve the efficiency of the number of applied matting agent particles and reduce the contamination in the apparatus, it is better to reduce the rate at which the matting agent particles are removed from the paper 122 by the pushing roller 220 and detached. From this point of view, the push roller 220 is preferably a rubber roller having an Asker C hardness of 70 ° or less.

  The thickness of the rubber layer of the pressing roller 220 should be easily deformed with respect to the size of the matting agent particles, and should be thicker.

10, to the number density n ₁ piece / mm ² of matting agent particles applied to the sheet 122 by the particle application device 200, and succeeded in pushing the matting agent particles during I pushed by a subsequent pushing roller 220 (= The ratio n ₂ / n ₁ of the number density n ₂ particles / mm ² of the matting agent particles that have been removed from the paper 122 by the pressing roller 220 and not detached is changed, and the thickness of the rubber layer of the pressing roller 220 is changed to ₁ to 8 mm. This is a graph plotted. Here, the Asker C hardness of the rubber layer of the pressing roller 220 is set to 70 ° and 30 °. As shown in this graph, the greater the thickness of the rubber layer of the pressing roller 220, the larger the ratio of the number of matting agent particles that could be pressed. The thickness of the rubber layer of the pressing roller 220 is preferably 1 mm or more. This is because if the thickness of the rubber layer of the pressing roller 220 is smaller than 1 mm, the ratio of the number of matting agent particles that can be pressed decreases.

When the effect of embedding the matting agent particles is enhanced by increasing the pressure P ₁ applied to the sheet 122 by the fixing roller 188, image transfer (image offset) on the sheet 122 to the fixing roller 188 is likely to occur. However, this risk can be reduced by using the pushing roller 220.

5 and 6, the pressure P ₂ that the pressing roller 220 applies to the paper 122 without increasing the pressure P ₁ (for example, about 0.15 MPa) that the fixing roller 188 applies to the paper 122 is the pressure P. ₁ (P ₁ = P ₂ ), the matting agent particles having an average particle diameter of 20 μm, measured with a Keyence Corporation laser microscope VK-9600, are applied to the surface of the paper 122 and pushed. Has been. In FIG. 5A, when the thin paper (OK top coat 157 gsm in this example) is used as the paper 122 and only the application roller (fixing roller 188) is used, the matting agent particles are pushed into the surface of the paper 122. In FIG. 5B, when a thin paper is used as the paper 122 and the application roller (fixing roller 188) and the pressing roller 220 are used, the matting agent particles are pushed into the surface of the paper 122. The situation is shown. In FIG. 6A, when the thick paper (in this example, eye vest 310 gsm) is used as the paper 122 and only the application roller (fixing roller 188) is used, the matting agent particles are pushed into the surface of the paper 122. In FIG. 6B, when thick paper is used as the paper 122 and the application roller (fixing roller 188) and the pressing roller 220 are used, the matting agent particles are pressed onto the surface of the paper 122. The situation is shown. 5 and 6, the coat layer and the surface ink layer of the paper 122 are omitted.

  FIG. 7 shows an average value of the embedding depth of the matting agent particles (three times of measurement) when thin paper (OK topcoat 157 gsm in this example) is used as the paper 122. FIG. Shows an average value of the embedding depth of the matting agent particles when using thick paper (in this example, eye vest 310 gsm) as the paper 122 (three times of measurement).

As shown in FIGS. 5 to 8, the pressure P ₂ applied to the paper 122 by the pressing roller 220 is the same as the pressure P ₁ without increasing the pressure P ₁ (for example, about 0.15 MPa) (P ₁ = Even in the case of P ₂ ), it is confirmed that the matting agent particles are surely pushed in by obtaining a total time for applying pressure from the application of the matting agent particles to the pushing. Therefore, it is preferable to satisfy the relationship of P ₂ ≧ P ₁ .

Similarly, the relationship between the contact area S ₁ generated when the application roller (fixing roller 188) applies pressure to the sheet 122 and the contact area S ₂ generated when the pressing roller 220 applies pressure to the sheet 122. However, by satisfying S ₂ ≧ S ₁ , more time can be taken from application to indentation, and particles can be indented.
This relationship of S ₂ ≧ S ₁ may be achieved by setting the diameters of the fixing roller 188 and the pressing roller 220 to be substantially the same and satisfying P ₂ ≧ P _1. However, the diameter of the pressing roller 220 is set to the fixing roller. by greater than 188 diameter of, it may be to increase the contact area S _2.

<Action and effect>
As shown in FIG. 1, the sheet 122 fed from the sheet feeding unit 110 is conveyed along the outer peripheral surfaces of the rotating sheet feeding cylinder 152 and the processing liquid drum 154. In the treatment liquid application unit 112, the treatment liquid application device 156 applies the treatment liquid to the recording surface (image forming surface) of the sheet 122 conveyed along the outer peripheral surface of the treatment liquid drum 154.

  Further, the sheet 122 coated with the treatment liquid is transported along the outer peripheral surface of the drawing drum 170 via the intermediate transport unit 124. In the drawing unit 114, the ink jet heads 172 </ b> C, 172 </ b> M, 172 </ b> Y, and 172 </ b> K for each color eject droplets (ink) onto the recording surface of the paper 122 conveyed by the drawing drum 170 to form an image on the paper 122. At that time, the ink comes into contact with the processing liquid previously applied to the recording surface by the processing liquid applying unit 112, and the pigment and resin particles dispersed in the ink are aggregated to form an aggregate. As a result, pigment flow on the sheet 122 is prevented, and an image is formed on the recording surface of the sheet 122.

  Further, the sheet 122 having an image formed on the recording surface is conveyed along the outer peripheral surface of the drying drum 176 via the intermediate conveying unit 126. In the drying unit 116, moisture contained in the paper 122 conveyed by the drying drum 176 after ink discharge is dried by the heat of the IR heater 178 and the warm air blown from the warm air heater 180 (the solvent separated by the aggregating action). To reduce the water content in

  Further, the sheet 122 is conveyed along the outer peripheral surface of the fixing drum 184 via the intermediate conveyance unit 128. In the intermediate conveyance unit 128, warm air is blown from a warm air heater (not shown) to the recording surface of the paper 122, so that moisture contained in the paper 122 is dried after ink discharge (included in the solvent separated by the aggregating action). Reduced water).

  In the fixing unit 118, the image formed on the paper 122 is fixed on the paper 122 by being pressed against the fixing drum 184 and the fixing roller 188.

  The fixing unit 118 is provided with a particle applying device 200. As shown in FIGS. 2 and 3, the web 204 is supported by the first rod 206 so as to come into contact with the fixing roller 188, and the second unit A tension is applied to the web 204 by the rod 208. In this state, the web 204 is fed by the feed roller 212 and taken up by the take-up roller 214, whereby the web 204 is moved in the direction of the arrow.

  In this particle applying device 200, the matting agent particles 210 </ b> P are applied from the web 204 to the fixing roller 188 by bringing the web 204 impregnated with the particle dispersion 210 </ b> L in which the matting agent particles are dispersed in the liquid into contact with the fixing roller 188. Then, the matting agent particles 210P supplied to the fixing roller 188 are transferred to the recording surface (image forming surface) of the sheet 122 on the fixing drum 184 by the rotation of the fixing roller 188 (second forming). Transferred).

  Since the matting agent particles 210P are easily transferred from the fixing roller 188 to the image portion of the paper 122 due to the adhesive force of the ink film, the matting agent particles 210P are not easily transferred from the fixing roller 188 to the non-image portion of the paper 122. The matting agent particles 210P are selectively applied to the image portion 122. In FIG. 2, the matting agent particles 210 </ b> P are applied to the image portion of the paper 122, but the matting agent particles 210 </ b> P are not matting agent particles composed only of powder particles but also liquid.

  Thereafter, the matting agent particles 210 </ b> P applied to the recording surface of the paper 122 on the fixing drum 184 are pressed by the pressing roller 220 so that the matting agent particles are embedded in the coating layer of the paper 122.

  Further, as shown in FIG. 1, in the fixing unit 118, the sheet 122 held on the fixing drum 184 passes through the opposite part of the in-line sensor 190, and the check pattern, moisture amount, surface temperature, surface temperature, Glossiness etc. are measured.

  Further, the sheet 122 measured by the inline sensor 190 is conveyed by the transfer drum 194 and the conveyor belt 196 and is discharged to the discharge tray 192.

  In such an ink jet recording apparatus 1, after the matting agent particles are attached to the recording surface of the paper 122 held on the fixing drum 184 by the particle applying device 200, the recording surface of the paper 122 is pressed by the pressing roller 220. Thus, the matting agent particles are embedded in the coat layer of the paper 122, and the degree of adhesion between the matting agent particles and the paper 122 is enhanced. Accordingly, the matting agent particles are prevented from being detached when the printed paper 122 is spread or seasoned (humidified by air blowing). For this reason, it is possible to suppress the occurrence of stacker blocking when the sheet 122 is stacked on a stacking unit such as the discharge tray 192.

  In the particle applying device 200, the number of parts can be reduced and the number of parts can be reduced by applying the matting agent particles to the recording surface of the paper 122 using the fixing roller 188 originally used in the ink jet recording device 1. Fixing performance can be ensured.

  FIG. 11 shows a particle applying device 250 used in an ink jet recording apparatus according to the third embodiment of the present invention. In addition, about the same component as 1st Embodiment and 2nd Embodiment mentioned above, the same number is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 11, the particle applying device 250 does not use an applying roller, but directly applies a web 204 impregnated with a particle dispersion in which matting agent particles are dispersed in a liquid onto a sheet 122 on a fixing drum 184. By bringing them into contact, the matting agent particles are applied to the recording surface (image forming surface) of the sheet 122. In the particle applying device 250, the web 204 is brought into contact with the sheet 122 on the fixing drum 184 with a width in the circumferential direction of the fixing drum 184 by the first rod 206 and the second rod 208. Further, the moving direction of the web 204 is set to be opposite to the conveying direction of the paper 122 on the fixing drum 184 at the contact portion with the paper 122 on the fixing drum 184.

  The matting agent particles applied to the recording surface (image forming surface) of the sheet 122 are pressed by the pressing roller 220, so that the matting agent particles are embedded in the coating layer of the sheet 122. Accordingly, the matting agent particles are prevented from being detached when the printed paper 122 is spread or seasoned (conditioning by air blowing), and the occurrence of stacker blocking can be suppressed.

  FIG. 12 shows a particle applying device 260 used in the ink jet recording apparatus according to the fourth embodiment of the present invention. In addition, about the same component as 1st Embodiment-3rd Embodiment mentioned above, the same number is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 12, the particle applying device 260 does not use an applying roller, and the web 204 impregnated with the particle dispersion is directly applied to the paper 122 on the fixing drum 184 by the first rod 206 and the second rod 208. In addition, the dispersion liquid supply head 232 is disposed between the first rod 206 and the second rod 208. The dispersion liquid supply head 232 supplies the particle dispersion liquid to the back surface side of the web 204 by discharging the particle dispersion liquid from a plurality of discharge holes formed on the discharge surface.

  Even in such a configuration, matting agent particles are applied to the recording surface (image forming surface) of the paper 122 by bringing the web 204 into direct contact with the paper 122 on the fixing drum 184 and then pressed by the pressing roller 220. Thus, the matting agent particles are embedded in the coat layer of the paper 122. Accordingly, the matting agent particles are prevented from being detached when the printed paper 122 is spread or seasoned (conditioning by air blowing), and the occurrence of stacker blocking can be suppressed.

<Others>
As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to said embodiment at all, and can be implemented with a various aspect in the range which does not deviate from the summary of this invention.

  In the particle applying device of the above-described embodiment, the fixing roller 188 is used as an example of the applying roller, but the present invention is not limited to this, and a dedicated applying roller may be used. Further, the feed roller 212 that feeds out the web 204, the take-up roller 214 that winds up the web 204, and the like are not limited to the configuration of the above-described embodiment, and can be changed.

  Further, for example, in the above embodiment, an inkjet image forming apparatus using water-based ink using water as a solvent has been described as an example, but the liquid to be discharged is not limited to ink for image recording / character printing, Any liquid that uses a solvent or a dispersion medium that permeates the recording medium can be applied to various ejection liquids.

1 Inkjet recording device (image forming device)
122 paper (recording medium)
172C, 172M, 172Y, 172K Inkjet head (droplet ejection device)
184 Fixing drum (conveyor)
188 Fixing roller (applying roller)
200 Particle imparting device (particle imparting means)
204 Web 210P Matting agent particle 210L Particle dispersion 220 Push roller 230 Particle applying device (particle applying means)
232 Dispersion supply head 250 Particle applying device (particle applying means)
260 Particle applying device (particle applying means)

Claims (6)

A droplet discharge device that forms an image by discharging droplets onto a recording medium;
A transport body for transporting the recording medium;
A particle applying means for applying a large number of particles to the image-formed surface of the recording medium;
A pressing roller for pressing the particles into the recording medium by applying pressure to the particles applied to the surface on which the image of the recording medium is formed after the particles are applied by the particle applying means;
An image forming apparatus.   The particle applying means includes an applying roller that is disposed so as to contact the recording medium on the carrier and to which the particles are supplied, and a surface on which an image of the recording medium is formed via the applying roller. The image forming apparatus according to claim 1, wherein the particles are applied to the image forming apparatus.   The image forming apparatus according to claim 1, wherein the push roller pushes the particles from the surface of the recording medium to a depth of 20 to 80% of an average particle diameter of the particles. The surface layer of the pressing roller is
A rubber layer having an Asker C hardness of 70 ° or less and a thickness of 1 mm or more;
A surface film layer wound around the rubber layer and having a thickness of 50 μm to 200 μm;
The image forming apparatus according to any one of claims 1 to 3, further comprising: The relationship between the pressure P ₁ applied by the application roller to the recording medium and the pressure P ₂ applied by the push roller to the recording medium is as follows:
The image forming apparatus according to claim 2, wherein P ₂ ≧ P ₁ is satisfied. The relationship between the contact area S ₁ generated when the application roller applies pressure to the recording medium and the contact area S ₂ generated when the pressing roller applies pressure to the recording medium
The image forming apparatus according to claim 2, wherein S ₂ ≧ S ₁ is satisfied.

Images