JP2015145930A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent high-temperature offset and fixing failure, in forming images on both sides of a recording material with liquid developer containing toner and carrier liquid.SOLUTION: A fixing apparatus includes: a non-contact heating device which heats a liquid developer image formed on a recording material, in a non-contact manner; and a heating/pressing apparatus which heats and presses the liquid developer image formed on the recording material. A toner image is fixed both on a first side of the recording material and a second side opposite the first side, in this order. A temperature of the recording material which has passed through the non-contact heating device and has not passed through the heating/pressing apparatus is set to be higher in fixing the second side of the recording material than in fixing the first side. A temperature to be set in the heating/pressing apparatus is lower in fixing the second side of the recording material than in fixing the first side of the recording material.

Description

  The present invention relates to a fixing device and an image forming apparatus, and more specifically, heats a liquid developer image formed on a recording material such as paper and containing toner and a carrier liquid, and forms an image with the toner on the recording material. The present invention relates to a fixing device and an image forming apparatus for fixing.

  In a so-called wet electrophotographic image forming apparatus using a liquid developer containing a toner and a carrier liquid, small particles of 3 μm or less that are difficult to handle in an electrophotographic system without causing problems such as toner scattering. Diameter toner can be used. As a result, a high-quality image can be obtained.

  In such a wet electrophotographic image forming apparatus, in general, a liquid developer image formed on a recording material is heated and pressurized by a fixing device having a pair of fixing rollers, so that a carrier in the liquid developer image is obtained. The liquid was evaporated and the toner was melted and fixed on the recording material.

  However, when an image is formed on both surfaces (first surface, second surface) of the recording material, the liquid developer on the first surface of the recording material when the second surface of the recording material is fixed by a fixing device. The amount of carrier liquid in the image is smaller than the amount of carrier liquid in the liquid developer image on the second surface of the recording material because the first surface of the recording material has already been fixed by the fixing device. For this reason, if the set temperature of the fixing roller pair is set to a temperature sufficient to melt and fix the liquid developer image on the second surface of the recording material, a high temperature offset may occur on the first surface side of the recording material. . The high temperature offset is a phenomenon in which a part of the toner adheres to the fixing roller pair because the adhesion force of the melted toner is larger than the cohesive force or the adhesive force to the recording material. .

  On the other hand, if the set temperature of the fixing roller pair is set to a temperature at which high temperature offset does not occur on the first surface side of the recording material, the liquid developer image on the second surface of the recording material may be poorly fixed. Further, when a large amount of carrier liquid remains in the liquid developer image in fixing the first surface of the recording material, there is a problem that the carrier liquid adheres to the peripheral member in the recording material conveyance path after the fixing process. .

  In Patent Document 1, in a fixing device that fixes a toner image on a recording material by pressurization and heating by a pair of rollers and a first heating device, the first is positioned upstream of the pair of rollers in the conveyance direction of the recording material. Two heating devices are provided, and before the pressurization and heating by the pair of rollers and the first heating device, the recording material is heated by the second heating device to prevent toner scattering due to impact or electrostatic external force. Techniques to do this have been proposed.

  Further, in Patent Document 2, in a fixing device that fixes a recording material by sandwiching and transporting a recording material at a nip portion formed by press-contacting a heating member and a pressure member, the recording material is more than the nip portion. For example, when fixing the first surface of the coated paper on the upstream side in the conveying direction, the pretreated means is brought close to the coated paper and the coated paper is introduced into the fixing process. When fixing the second surface, a technique has been proposed in which the preprocessing means is moved backward to introduce coated paper into the fixing process to prevent toner image disturbance such as toner blistering.

  Further, in Patent Document 3, in a wet electrophotographic double-sided printing machine, a first fixing unit that heats a first surface of a recording material with a predetermined heating amount, and a second surface of the recording material are first. A technique has been proposed in which a second fixing unit that heats the surface with a heating amount larger than the heating amount is provided to prevent toner transfer failure of the recording material and to perform high-precision duplex printing.

JP 2007-93664 A JP 2006-259479 A JP 2009-163064 A

  An object of the present invention is to provide a fixing device and an image forming apparatus that do not cause high temperature offset and poor fixing when an image is formed on both surfaces of a recording material by a liquid developer containing toner and a carrier liquid. .

  According to the present invention, there is provided a fixing device that heats a liquid developer image including a toner and a carrier liquid formed on a recording material to fix an image of the toner on the recording material, A non-contact heating device that heats the liquid developer image formed on the recording material in a non-contact manner; and a non-contact heating device that is disposed downstream of the non-contact heating device in the conveyance direction of the recording material, A heating and pressurizing device for heating and pressurizing the formed liquid developer image, and images the toner image in the order of a first surface of the recording material and a second surface opposite to the first surface. When fixing on both sides of the recording material, the temperature of the recording material after passing through the non-contact heating device and before passing through the heating / pressurizing device is set to be higher when fixing the second surface than when fixing the first surface of the recording material. And the second surface of the recording material of the heating and pressurizing device is fixed. The setting temperature for the fixing device, characterized in that the lower than the set temperature for fixing the first surface of the recording material is provided.

  Here, the temperature of the recording material after passing through the non-contact heating device and before passing through the heating / pressurizing device is set higher at the time of fixing the second surface than at the time of fixing the first surface of the recording material. For this, it is preferable that the set temperature of the non-contact heating device when fixing the second surface of the recording material is higher than the set temperature when fixing the first surface of the recording material.

  In addition, as the heating and pressurizing apparatus, an apparatus including a pair of rotating members that form a nip portion that sandwiches and conveys the recording material and a heating unit that heats each of the pair of rotating members is used. When fixing the first surface of the material, the set temperature when fixing the second surface of the recording material of the rotating member in contact with the second surface is fixed to the first surface of the recording material. It is preferable that the temperature is lower than the preset temperature.

  In addition, according to the present invention, at least one first image forming unit that forms a liquid developer image including toner and carrier liquid on the first surface of the recording material, and the at least one first image formation. A first fixing device that heats the liquid developer image on the recording material formed by the section and fixes the image by the toner on the recording material; and a side surface opposite to the first surface of the recording material On the recording material formed by at least one second image forming unit and the at least one second image forming unit that forms a liquid developer image including toner and carrier liquid on the second surface. And a second fixing device that heats the liquid developer image and fixes the image of the toner on the recording material, and the fixing device according to any one of the above-described ones as the first fixing device and the second fixing device. Using the device Image forming apparatus is provided to symptoms.

  According to the fixing device and the image forming apparatus of the present invention, when an image is formed on both surfaces of a recording material with a liquid developer containing toner and carrier liquid, occurrence of high temperature offset and fixing failure is suppressed.

1 is a schematic diagram illustrating an example of a fixing device and an image forming apparatus of the present invention. FIG. 6 is a diagram showing a transition of the amount of carrier liquid in a liquid developer image in fixing processing. FIG. 6 is a diagram showing a transition of the amount of carrier liquid in a liquid developer image in fixing processing. 1 is a schematic diagram illustrating an embodiment of a fixing device of the present invention. 6 is a flowchart illustrating an example of control in the fixing device F. FIG. 6 is a schematic view showing another embodiment of the fixing device of the present invention. 1 is a schematic diagram illustrating an embodiment of an image forming apparatus according to the present invention.

  Hereinafter, the fixing device and the image forming apparatus according to the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a schematic diagram showing an example of a fixing device and an image forming apparatus according to the present invention. The image forming apparatus shown in this figure includes an image forming unit I and a fixing device F. The image forming unit I includes a rotatable intermediate transfer member 21, a developing unit 1 provided on the outer periphery of the intermediate transfer member 21, and a backup member 22. In this figure, only one developing unit 1 (for example, a black developing unit) is provided in order to make the device structure easy to understand, but normally, in addition to the developing unit 1, three developing units (for example, yellow developing unit) are provided. , Magenta and cyan color development units) are provided side by side in the rotation direction of the intermediate transfer member 21 so that a color image can be formed. The developing unit 1 includes a photoreceptor 11 and a liquid developing device 12 that develops the electrostatic latent image formed on the surface of the photoreceptor with a liquid developer.

  In the image forming unit I having such a configuration, in the developing unit 1, the electrostatic latent image formed on the surface of the photoconductor 11 is visualized by the liquid developer in the liquid developing device 12. The liquid developer image formed on the surface of the photoreceptor 11 is primarily transferred to the intermediate transfer member 21. Then, the liquid developer image primarily transferred to the intermediate transfer member 21 is conveyed to the nip portion between the intermediate transfer member 21 and the backup member 22 by the rotation of the intermediate transfer member 21, where the liquid developer image is secondarily transferred to the recording material P. Transcribed. The recording material P may be any member as long as it can form a toner image on the surface, such as paper or film, and can be transported in the image forming apparatus.

  For forming the electrostatic latent image and cleaning the surface of the photoconductor 11 in the image forming unit I, a well-known electrophotographic technique may be used here. Further, the liquid developer image formed on the photoconductor 11 may be directly transferred to the recording material P without using the intermediate transfer body 21. In this case, the image forming unit I includes the developing unit 1 and the backup member 22.

  The carrier liquid used for the liquid developer is preferably an insulating solvent, such as isoparaffinic isopar (G, H, L, M, etc.) (Exxon Mobile), IP solvent (10, 2028, 2835, etc.) (Idemitsu). Kosan) and paraffinic Moresco White (P-40, P-70, P-120) (Matsumura Oil Research Institute). Silicon oil and mineral oil can also be used.

  As the toner, a toner in which a colorant such as a pigment or a dye is dispersed in a binder resin is used. The binder resin has a function of uniformly dispersing pigments and dyes in the resin and a function as a binder when being fixed to a recording material. As the binder resin, for example, thermoplastic resins such as polystyrene resin, styrene-acrylic resin, acrylic resin, polyester resin, epoxy resin, polyamide resin, polyimide resin, and polyurethane resin are preferably used. Two or more of these binder resins may be mixed and used. Commercially available pigments and dyes used in the toner can be used. Examples of the pigment include carbon black, bengara, titanium oxide, silica, phthalocyanine blue, phthalocyanine green, sky blue, benzidine yellow, lake red D, and the like. Examples of the dye include Solvent Red 27 and Acid Blue 9.

  The volume average particle diameter of the toner is preferably in the range of 0.1 μm or more and 5 μm or less. When the volume average particle diameter of the toner is less than 0.1 μm, the developability is greatly lowered. On the other hand, when the volume average particle diameter exceeds 5 μm, the quality of the image is deteriorated.

  The mass ratio of the toner to the liquid developer is preferably about 10% to 50%. When the mass ratio of the toner is less than 10%, the toner is liable to settle, and there is a problem in stability over time during long-term storage. In addition, in order to obtain the required image density, it is necessary to supply a large amount of developer, the amount of carrier liquid adhering to the recording material increases, and the amount of carrier liquid that must be removed during fixing increases, which is necessary for fixing. Energy increases. On the other hand, when the mass ratio of the toner exceeds 50%, the viscosity of the liquid developer becomes too high, making it difficult to manufacture and handle. In this embodiment, which will be described later, the volume average particle diameter of the toner is 2 μm, and the mass ratio of the toner to the liquid developer is 30%.

  The fixing device F includes a non-contact heating device 3 and a heating and pressing device 4 provided on the downstream side of the non-contact heating device 3 in the conveyance direction of the recording material P. The non-contact heating device 3 includes a heater 31 that heats the liquid developer image in a non-contact manner, a heat insulating cover 32 that covers a portion other than the recording material side of the heater 31, and a conveyance path for the recording material P. And a sheet conveying means 5 disposed at a position facing the heater 31.

  The surface temperature of the heater 31 is controlled to a desired temperature by the control means 6. The heater 31 is preferably a long-wavelength heater (so-called far infrared) such as a ceramic heater in consideration of the difference in light absorption between the toners of black, yellow, magenta, and cyan and the non-image portion. . The surface temperature of the heater 31 is usually about 200 to 700 ° C. As a material of the heat insulating cover 32, it is preferable to use a highly heat-insulating and heat-resistant material such as ceramic fiber from the viewpoint of increasing the heat insulating effect.

  The sheet conveying means 5 includes a driving roller 51, a driven roller 52, an endless suction belt 53 spanned between these rollers, and a suction fan 54 disposed in the suction belt 53. The driving roller 51 and the driven roller 52 are preferably metal rollers made of aluminum or the like. Of course, the positional relationship between the driving roller 51 and the driven roller 52 may be opposite to the conveyance direction of the recording material P. The suction belt 53 is made of a rubber material having high heat resistance such as silicone rubber, and is provided with a plurality of suction holes. Further, in order to lower the saturated vapor pressure of the volatilized carrier liquid and improve the volatilization efficiency of the carrier liquid, air flow means (not shown) for discharging the volatilized carrier liquid (vapor) from the periphery of the heater 31 to the outside is provided. It may be provided.

  The heating and pressing device 4 includes a fixing roller 41 and a pressing roller 42. The fixing roller 41 and the pressure roller 42 are rotatably supported by a housing (not shown) via a bearing member (not shown). The pressure roller 42 is fixed to the fixing roller by a pressure mechanism (not shown) such as a spring. A nip portion is formed in pressure contact with 41. The pressurizing mechanism can switch between pressure contact and separation. The pressure roller 42 is rotationally driven clockwise at a predetermined peripheral speed in FIG. 1 by a driving mechanism (not shown), and the fixing roller 41 is pressed against the pressure roller 42 at the nip portion by the contact friction force. Rotates following rotation. Of course, the fixing roller 41 may be driven to rotate and the pressure roller 42 may be driven to rotate.

  The fixing roller 41 and the pressure roller 42 incorporate halogen lamps H1 and H2 as heating means, and the temperature is controlled independently by the control means 6. The fixing roller 41 and the pressure roller 42 are formed of a silicon rubber layer (elastic layer for securing a nip width) on the outer periphery of a hollow metal core (thickness 0.5 to 5 mm) having a good thermal conductivity such as aluminum. And a fluororesin release layer (thickness 10 to 50 μm) such as PTFE or PFA as a release layer for enhancing the release property of the surface.

  In the fixing device F having such a configuration, the recording material P to which the liquid developer image has been transferred is first heated mainly by the spraying from the heater 31 of the non-contact heating device 3. As a result, the carrier liquid in the liquid developer image volatilizes and penetrates the recording material P. At the same time, the toner melts. The non-contact heating device 3 is open around the recording material P, and the heating heater 31 can be lengthened in the conveying direction of the recording material P to increase the heating time of the recording material P. 4 can promote the volatilization of the carrier liquid and the penetration into the recording material P.

  Next, the recording material P is heated and pressed at the nip portion between the fixing roller 41 and the pressing roller 42 of the heating and pressing device 4. Thereby, the melting of the toner of the recording material P is further promoted and the surface is smoothed. Further, the volatilization of the carrier liquid and the penetration into the recording material P are further promoted, and a part of the carrier liquid is removed by the fixing roller 41. The toner image is melted and fixed on the recording material P by the heating and pressurization by the non-contact heating device 3 and the heating and pressing device 4 described above.

  Here, the transition of the carrier liquid amount in the liquid developer image in the fixing process will be described with reference to FIG. When the amount of carrier liquid in the liquid developer image before passing through the non-contact heating device when fixing the first surface of the recording material P is la, the recording material P passes through the non-contact heating device 3. The carrier liquid volatilizes and penetrates into the recording material P, and the amount of the carrier liquid in the liquid developer image after passing through the non-contact heating device is 1b, which is smaller than 1a. Next, when the recording material P passes through the heating and pressing apparatus 4, the carrier liquid further volatilizes and penetrates into the recording material P, and the amount of the carrier liquid in the liquid developer image after passing through the heating and pressing apparatus is 1b. Less than 1c. In the case of single-sided printing, the fixing is completed, and the fixing quality of the image is ensured. However, in the case of double-sided printing, image formation and fixing are further performed on the second surface of the recording material P.

  When the second surface of the recording material P is fixed, the carrier liquid amounts in the liquid developer image before passing through the non-contact heating device, after passing through the non-contact heating device, and after passing through the heating / pressurizing device are 2a, 2b, The amount of these carrier liquids is equal to la, lb, lc. On the other hand, the carrier liquid in the liquid developer image on the first surface is covered by at least several seconds until the recording material P passes through the heating and pressurizing device 4 and the liquid developer image is transferred to the second surface. Since the recording material P further penetrates, the amount of carrier liquid in the liquid developer image on the first surface before passing through the non-contact heating device when fixing the second surface is 1d which is smaller than 1c. When the recording material P passes through the non-contact heating device 3, the carrier liquid further volatilizes and penetrates into the recording material P, and the carrier in the liquid developer image on the first surface after passing through the non-contact heating device. The liquid amount is 1e which is less than 1d. Next, when the recording material P passes through the heating and pressing device 4, the carrier liquid is further volatilized and penetrates into the recording material P, and the carrier in the liquid developer image on the first surface after passing through the heating and pressing device P. The amount of liquid becomes 1f which is smaller than 1e.

The carrier liquid amount in the liquid developer image of the recording material P is summarized as follows.
la (= 2a)> lb (= 2b)> lc (= 2c)>ld>le> lf
From this equation, when fixing the second surface of the recording material P, the carrier liquid amount 1e in the liquid developer image on the first surface after passing through the non-contact heating device and before passing through the heating and pressurizing device, and the second The relationship with the carrier liquid amount 2b in the toner on the surface is “2b >> 1e”.

  Since the toner releasability is better when the amount of the carrier liquid is larger, the temperature at which the high temperature offset occurs when the second surface of the recording material P is fixed by the heating and pressing device 4 is higher than that of the second surface. One side is lower. That is, a high temperature offset is more likely to occur on the first surface than on the second surface. On the other hand, if the set temperature of the heating and pressurizing device 4 is lowered in order to prevent the high temperature offset of the first surface, a problem occurs in fixing the liquid developer image on the second surface.

  Therefore, the fixing condition of the first surface of the recording material P is set to a condition that is lighter than usual (a condition in which the amount of heat supplied is small), and the carrier liquid in the liquid developer image on the first surface is left more than usual, and the first surface is fixed. A method for suppressing the high-temperature offset of the first surface when fixing the two-side liquid developer image and securing the fixing of the second-side liquid developer image is also conceivable. However, when the second surface of the recording material P is fixed, the relationship between the amount of carrier liquid in the liquid developer image between the second surface and the first surface does not change, so that high temperature offset is prevented and fixing quality is ensured. Cannot be achieved at the same time. The reason will be described with reference to FIG.

  In FIG. 3, since the recording material P passes through the non-contact heating device, the carrier liquid in the liquid developer image is volatilized and penetrates into the recording material P. Therefore, the amount of the carrier liquid before and after passing through the non-contact heating device is 1a and 1b ′. However, since the condition is milder than the normal fixing condition, the relationship is “la> lb ′> 1b”. Next, the carrier liquid in the toner image on the first surface further penetrates into the recording material P until the recording material P passes through the heating and pressing device 4 and the liquid developer image is transferred to the second surface. Therefore, when the second surface is fixed, the carrier liquid amounts 1c ′ and 1d ′ in the toner image on the first surface after passing through the heating and pressing device 4 and before passing through the non-contact heating device are expressed as “1b ′> 1c ′> 1d ′ ”. Therefore, when the first surface of the recording material P is fixed, the carrier liquid amount 1a in the toner on the first surface before passing through the non-contact heating device and the second surface of the recording material P are fixed. The relationship with the carrier liquid amount 1d ′ in the toner on the first surface before passing through the non-contact heating device is “1a >> 1d ′”.

  Here, since the amount of the carrier liquid in the liquid developer image before passing through the non-contact heating device is equal between the first surface and the second surface of the recording material P, “2a >> ld ′” is obtained. There is a relatively large difference in the amount of carrier liquid in the liquid developer images on the first side and the second side. Further, since the amount of decrease in the carrier liquid in the liquid developer image due to passing through the non-contact heating device 3 is almost the same on the second surface and the first surface, “2b >> le ′” is obtained, and the second recording material P is recorded. A relatively large difference also occurs in the amount of carrier liquid in the liquid developer images on the first surface and the second surface before passing through the heating and pressurizing device when fixing the two surfaces. For this reason, the temperature at which the high temperature offset occurs when the second surface of the recording material P is fixed by the heating and pressing device 4 is lower on the first surface than on the second surface, and the first surface is first. High temperature offset is more likely to occur than the two surfaces. Therefore, even if the fixing condition of the first surface of the recording material P is milder than usual, the difference in temperature of occurrence of high temperature offset between the first surface and the second surface of the recording material P is reduced, but the temperature is still high. It can be seen that prevention of offset and securing of fixing quality cannot be achieved at the same time.

  Further, when the fixing condition of the first surface of the recording material P is extremely lighter than usual, and the carrier liquid in the liquid developer image on the first surface is left excessively more than usual, the first condition is The adhesion of the carrier liquid to other members of the conveyance path of the recording material P after fixing one surface becomes a problem. In addition, when the fixing strength is extremely low, the risk of image noise associated with conveyance increases.

  Therefore, in the present invention, when images are formed on both surfaces of the recording material P, the fixing conditions for fixing the first surface of the recording material P are different from the fixing conditions for fixing the second surface. The prevention of high temperature offset and the securing of fixing quality were achieved at the same time.

  Specifically, the recording material P such as paper has a front and back registerability that shrinks due to volatilization of moisture and then recovers when the moisture returns, but does not return to the original size. In this case, when the first surface is fixed, the heating and pressurizing device 4 that is relatively advantageous for paper contraction is used in preference to the non-contact heating device 3 that easily evaporates moisture, thereby securing the fixing quality. On the other hand, when fixing the second surface, a non-contact heating device was used preferentially to prevent high temperature offset of the first surface.

(Embodiment 1)

* Note: The first and second embodiments of the invention / invention manual are collectively referred to as the first embodiment.

A first embodiment of the present invention will be described with reference to FIG. When fixing the first surface of the recording material P, the recording material temperature after passing through the non-contact heating device is set to A1, and the set temperatures of the fixing roller 41 and the pressure roller 42 are set to B1. Then, when fixing the second surface, the temperature of the fixing roller 41 and the pressure roller 42 is set to B2, which is lower than B1. This prevents high temperature offset of the first surface when fixing the second surface. On the other hand, when fixing the second surface, the recording material temperature after passing through the non-contact heating device is set to A2 higher than A1, and the set temperature of the heating and pressurizing device 4 is lowered to the second surface. Eliminate the shortage of heat supply. As a result, high temperature offset prevention on the first surface of the recording material P and securing of the fixing quality on the second surface can be achieved simultaneously. The temperature of the recording material P after passing through the non-contact heating device is controlled by adjusting the set temperature of the non-contact heating device 3, the heating time, the distance between the recording material P and the non-contact heating device 3, and the like. That's fine.

  In the case of single-sided printing, the fixing conditions for fixing the first surface of the recording material P may be used as they are, and it is not necessary to consider the front and back registerability of the recording material P. You may change the ratio of the supply heat energy of the apparatus 3 and the heating-pressing apparatus 4. FIG. For example, the set temperature of the non-contact heating device 3 is set higher than in the case of duplex printing, and the set temperature of the heating and pressing device 4 is lowered than in the case of duplex printing.

  FIG. 5 is a flowchart showing an example of control in such a fixing device F. First, when a print start signal is input (step S101), printing is started (step S102). Next, it is determined whether or not duplex printing is performed (step S103). In the case of single-sided printing, the set temperature of the non-contact heating device 3 is controlled so that the temperature of the recording material after passing through the non-contact heating device is A1, and the set temperatures of the fixing roller 41 and the pressure roller 42 are set. B1 is set (step S108). Then, a fixing operation is performed (step S109). On the other hand, in the case of double-sided printing (step S103), the set temperature of the non-contact heating device 3 is controlled so that the temperature of the recording material after passing through the non-contact heating device becomes A1, and the fixing roller 41 and the pressurization are applied. The set temperature of the roller 42 is set to B1 (step S104), and the fixing operation of the first surface of the recording material P is performed (step S105). Next, the set temperature of the non-contact heating device 3 is changed and the set temperature of the fixing roller 41 and the pressure roller 42 so that the recording material temperature after passing through the non-contact heating device becomes A2 higher than A1. Is changed to B2 lower than B1 (step S106). Then, the fixing operation of the second surface of the recording material P is performed (step S107), and the control ends.

Example 1
The fixing temperature of the non-contact heating device 3 when fixing the first surface of the recording material P is set to 300 ° C. so that the temperature of the recording material after passing through the non-contact heating device is 70 ° C. The set temperature of the fixing roller 41 and the pressure roller 42 was set to 150 ° C. Next, the set temperature of the non-contact heating device 3 when fixing the second surface of the recording material P is set to 400 ° C. so that the temperature of the recording material after passing through the non-contact heating device is 90 ° C. The set temperature of the fixing roller 41 and the pressure roller 42 of the pressure device 4 was 110 ° C. Then, the fixing quality of the first surface and the second surface and the presence or absence of high temperature offset were evaluated visually. The evaluation results are shown in Table 1.

(Comparative Example 1)
The fixing temperature of the non-contact heating device 3 when fixing the second surface of the recording material P is set to 300 ° C. so that the temperature of the recording material after passing through the non-contact heating device is 70 ° C. The both surfaces of the recording material P were fixed in the same manner as in Example 1 except that the set temperature of the fixing roller 41 and the pressure roller 42 was set to 150 ° C., and the fixing quality and the presence or absence of high temperature offset were visually evaluated. The evaluation results are shown in Table 1.

(Comparative Example 2)
Example in which the set temperature of the non-contact heating device 3 when fixing the second surface of the recording material P is 300 ° C. and the temperature of the recording material after passing through the non-contact heating device is 70 ° C. In the same manner as in Example 1, both sides of the recording material P were fixed, and the fixing quality and the presence or absence of high temperature offset were visually evaluated. The evaluation results are shown in Table 1.

  As can be seen from Table 1, the temperature of the recording material after passing through the non-contact heating device is higher when fixing the second surface than when fixing the first surface. In Example 1 where the temperature was lower when the second surface was fixed than when the first surface was fixed, no high temperature offset occurred and the fixing quality was good.

  On the other hand, in Comparative Example 1 in which the fixing conditions of the first surface and the second surface of the recording material P were the same, a high temperature offset occurred on the first surface when fixing the second surface. Further, in Comparative Example 2 in which the temperature of the recording material after passing through the non-contact heating apparatus is the same when fixing the first surface and when fixing the second surface, the fixing quality is insufficient due to the insufficient amount of heat supplied to the second surface. Was bad.

(Embodiment 2)
A second embodiment of the present invention will be described based on FIG. In this embodiment, the setting temperature of the non-contact heating device 3 is set higher when fixing the second surface than when fixing the first surface, and the fixing quality is ensured as in the first embodiment. However, the second embodiment is different from the first embodiment in that the set temperature of the heating and pressing device 4 when fixing the second surface is lowered by the pressure roller 42 to prevent high temperature offset of the first surface. By setting only the pressure roller 42 to change the temperature of the heating and pressing device 4 when fixing the second surface, the set temperature of the non-contact heating device 3 can be kept lower than in the case of the first embodiment. .

  That is, when fixing the first surface of the recording material P, the set temperature of the non-contact heating device 3 is A1, the set temperature of the fixing roller 41 is B1, and the set temperature of the pressure roller 42 is C1. When the second surface is fixed, the set temperature of the non-contact heating device 3 is set to A2, which is higher than A1, and the set temperature of the fixing roller 41 is set to B1, which is the same as when the first surface is fixed. Is set to C2 lower than C1. As a result, high temperature offset prevention on the first surface of the recording material P and securing of the fixing quality on the second surface can be achieved simultaneously.

(Example 2)
When fixing the first surface of the recording material P, the set temperature of the non-contact heating device 3 was set to 300 ° C., and the set temperatures of the fixing roller 41 and the pressure roller 42 of the heating and pressing device 4 were set to 150 ° C. Next, when fixing the second surface of the recording material P, the set temperature of the non-contact heating device 3 is set to 350 ° C., the set temperature of the fixing roller 41 of the heating and pressing device 4 is set to 150 ° C., and the pressure roller 42 Was set to 110 ° C. Then, the fixing quality of the first surface and the second surface and the presence or absence of high temperature offset were evaluated visually. The evaluation results are shown in Table 1.

(Comparative Example 3)
Example 2 except that the setting temperature of the non-contact heating device 3 when fixing the second surface of the recording material P is 300 ° C. and the setting temperature of the pressure roller 42 of the heating and pressing device 4 is 150 ° C. In the same manner, both surfaces of the recording material P were fixed, and the fixing quality and the presence or absence of high temperature offset were visually evaluated. The evaluation results are shown in Table 1.

(Comparative Example 4)
Both sides of the recording material P are fixed in the same manner as in Example 2 except that the set temperature of the non-contact heating device 3 when fixing the second surface of the recording material P is 300 ° C. The presence or absence of offset was visually evaluated. The evaluation results are shown in Table 1.

  As can be seen from Table 2, the temperature of the recording material after passing through the non-contact heating device is higher when fixing the second surface than when fixing the first surface. In Example 2 where the setting temperature of the pressure roller 41 is lower when the second surface is fixed than when the first surface is fixed, no high temperature offset occurs and the fixing quality is good.

  In contrast, in Comparative Example 3 where the fixing conditions of the first surface and the second surface of the recording material were the same, a high temperature offset occurred on the first surface when fixing the second surface. Further, in Comparative Example 2 in which the set temperature of the non-contact heating device 3 is the same when fixing the first surface and when fixing the second surface, the fixing quality is not sufficient due to the lack of heat supplied to the second surface. It was.

  FIG. 7 is a schematic diagram showing an example of the image forming apparatus of the present invention provided with the fixing device F described above. The image forming apparatus shown in the figure includes a first image forming unit I1, a first fixing device F1, a recording material reversing unit 9, a second image forming unit I2, and a second fixing unit F2. The first image forming unit I1 and the second image forming unit I2 have the same configuration as the image forming unit I shown in FIG. 1, and the first fixing device F1 and the second fixing device F2 are also shown in FIG. Since the configuration is the same as that of the fixing device F, the description of the configuration is omitted here. As the recording material reversing portion 9, a conventionally known mechanism such as a switchback portion can be used.

  The first liquid developer image formed on the photoreceptor 11 by the developing unit 1 in the first image forming unit I1 is transferred to the first surface of the recording material P via the intermediate transfer member 21, and then contactless. The toner image is melted and fixed on the first surface of the recording material P by being heated and pressurized by the heating device 3 and the heating and pressing device 4. Next, the first surface and the second surface of the recording material P are reversed by the recording material reversing unit 9 so that the second surface becomes the surface (upper surface in FIG. 7). Then, the second liquid developer image formed on the photoconductor 11 by the developing unit 1 in the second image forming unit I2 is transferred to the second surface of the recording material P via the intermediate transfer body 21. Thereafter, the toner image is melted and fixed on the second surface of the recording material P by being heated and pressurized by the non-contact heating device 3 and the heating and pressing device 4.

  According to such a so-called dual engine image forming apparatus in which a plurality of image forming units I1 and I2 are serially connected, productivity of double-sided printing is remarkably increased.

  According to the fixing device and the image forming apparatus of the present invention, when an image is formed on both surfaces of a recording material with a liquid developer containing toner and a carrier liquid, occurrence of high temperature offset and fixing failure is suppressed, which is useful. .

3 Non-contact heating device 4 Heating and pressing device F Fixing device F1 First fixing device F2 Second fixing device H1, H2 Halogen lamp (heating means)
DESCRIPTION OF SYMBOLS I Image formation part I1 1st image formation part I2 2nd image formation part P Recording material 41 Fixing roller (a pair of rotation member)
42 Pressure roller (a pair of rotating members)

Claims (4)

A fixing device that heats a liquid developer image including a toner and a carrier liquid formed on a recording material and fixes an image of the toner on the recording material,
A non-contact heating device for heating the liquid developer image formed on the recording material in a non-contact manner;
A heating and pressurizing device that is arranged on the downstream side in the transport direction of the recording material than the non-contact heating device and heats and pressurizes the liquid developer image formed on the recording material;
When fixing the image by the toner on both surfaces of the recording material in the order of the first surface of the recording material and the second surface that is the opposite side of the first surface,
The temperature of the recording material after passing through the non-contact heating device and before passing through the heating / pressurizing device is set to be higher during the second surface fixing than during the first surface fixing of the recording material,
A fixing device characterized in that a set temperature when fixing the second surface of the recording material of the heating and pressing device is lower than a setting temperature when fixing the first surface of the recording material.   The fixing device according to claim 1, wherein a setting temperature of the non-contact heating device when fixing the second surface of the recording material is set higher than a setting temperature when fixing the first surface of the recording material. The heating and pressurizing device includes a pair of rotating members that form a nip portion that sandwiches and conveys the recording material, and a heating unit that heats each of the pair of rotating members,
When fixing the first surface of the recording material, the set temperature when fixing the second surface of the recording material of the rotating member in contact with the second surface is set to the first surface of the recording material. The fixing device according to claim 1, wherein the fixing device is lower than a set temperature for fixing. The recording material formed by at least one first image forming unit that forms a liquid developer image containing toner and carrier liquid on the first surface of the recording material, and the at least one first image forming unit. A first fixing device that heats the liquid developer image on the recording material and fixes the image formed by the toner on the recording material; and a toner and a carrier on a second surface that is opposite to the first surface of the recording material. Forming at least one second image forming unit that forms a liquid developer image including the liquid, and heating the liquid developer image on the recording material formed by the at least one second image forming unit, A second fixing device for fixing an image of the toner on the recording material,
An image forming apparatus using the fixing device according to claim 1 as the first fixing device and the second fixing device.