JP2006293169A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent distortion of a toner image due to flow of a fixing solution during imparting the fixing solution to the toner image and insufficient fixing of a toner image having a large toner amount on a recording medium, to stably obtain images of high image quality over a prolonged period of time, and to reduce the consumption of the fixing solution, in an image forming apparatus by a wet fixing system using the fixing solution. <P>SOLUTION: In the image forming apparatus 1 comprising a toner image forming device 2, an intermediate transfer device 3 including an intermediate transfer belt 21, an intermediate transfer medium heating device 4, a fixing solution imparting device 5, a transfer fixing device 6, a recording medium feeding device 7 and a discharge device 8, a coating roller 32 which comes in pressure contact under rotation with a toner image on the intermediate transfer belt 21 to impart the fixing solution 35 has an elastically deformable porous layer capable of holding the fixing solution 35 on a surface thereof. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  In an electrophotographic image forming apparatus that is widely used in copying machines, printers, facsimiles, etc., a photoconductor having a photosensitive layer containing a photoconductive material formed on the surface is used, and a uniform charge is applied to the photoconductor surface. After the toner is charged, an electrostatic latent image corresponding to image information is formed by various image forming processes, and a developer containing toner is supplied to the electrostatic latent image from a developing unit and developed, thereby developing a toner image. The toner image is transferred directly or via an intermediate transfer medium to a recording medium such as paper, and the toner image transferred to the recording medium is fixed on the recording medium, whereby an image is formed on the recording medium.

  For fixing a toner image to a recording medium, a thermal fixing method for heating the toner image, a wet fixing method for applying a fixing solution for softening and / or swelling the toner to the toner image, and the like are known. Among these, in the wet fixing method, a toner image softened and / or swollen by applying a fixing solution is attached to a recording medium and pressed to fix the toner image on the recording medium. The wet fixing method has an advantage that it consumes much less power than the thermal fixing method, and many proposals have been made.

  For example, a toner image forming unit that forms a toner image, an intermediate transfer medium that carries the toner image formed by the toner image forming unit, and a fixer that dissolves or swells the toner are applied to the toner image carrying region of the intermediate transfer medium. An image forming apparatus is proposed that includes a fixing solution applying unit that contacts and applies a fixing solution applying roller and a transfer unit that transfers a toner image dissolved or swollen by the fixing solution applying unit onto a recording medium (for example, Patent Literature 1). 1). In this image forming apparatus, utilizing the affinity between the fixing solution and the toner, the contact-fixing fixing solution is applied only to the image portion that is the toner adhesion portion in the toner image carrying region of the intermediate transfer medium, and the toner It is configured not to be applied to a non-image portion to which no adhesion occurs. This reduces the consumption of the fixing solution.

  However, according to the image forming apparatus of Patent Document 2, since the interval between the intermediate transfer medium and the fixing liquid application roller is constant, when the toner image carrying portion of the intermediate transfer medium and the surface of the fixing liquid application roller meet, There is a problem that the fixing liquid adhering to the surface of the fixing liquid application roller is pushed away by the toner image, and a sufficient amount of fixing liquid for dissolving or swelling the toner image cannot be applied to the toner image. This is particularly noticeable when a plurality of toner images of different colors are overlapped to form a color image by destructive color mixing, because the toner image becomes bulky.

  In addition, a squeegee roller is provided in which a toner image made of toner that absorbs water and softens is carried on an intermediate transfer medium made of a hydrophobic material, and the intermediate transfer medium carrying the toner image is pressed against the intermediate transfer medium. A method has been proposed in which water is applied by a (coating roller) and water is selectively applied to the toner image to soften the toner image, and the softened toner image is pressure-transferred to a recording medium (for example, see Patent Document 2). In this method, when water is applied to the intermediate transfer medium by the squeegee roller, the intermediate transfer medium is made of a hydrophobic material, so that there is no water on the intermediate transfer medium, and only the toner image is wet. However, the water imparted to the toner image on the intermediate transfer medium by the squeegee roller is squeezed at the nip portion (contact portion) between the intermediate transfer medium and the squeegee roller, forms a meniscus at the entrance of the nip portion, and stays there. Since the excess is reattached to the squeegee roller and returned, a strong water flow is generated at the entrance to the nip, and the toner image forming dot is very weak in combination with the toner image. Flows, the toner image is disturbed, and the desired image is not formed. In addition, the dots of the toner image may be partially crushed to cause image deterioration. Furthermore, toner may adhere to the squeegee roller, causing image deterioration and image contamination.

JP 2004-109747 A JP 58-40570 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus of a wet fixing type in which problems such as toner image disturbance due to the flow of a fixing liquid and insufficient fixing of a toner image having a large amount of toner onto a recording medium do not occur.

The present invention relates to an intermediate transfer including a toner image forming means for forming a toner image made of a chargeable toner containing a binder resin, and an intermediate transfer medium that has a smooth surface and carries a toner image on the surface and is driven to rotate. A fixing liquid applying means for applying a fixing liquid having a function of softening the toner image to the toner image on the intermediate transfer medium in contact; and a transfer for transferring the softened toner image applied with the fixing liquid to the recording medium. An image forming apparatus including:
Fixing liquid application means
Including a coating member that is elastically deformable at least on the surface, has a porous layer that holds a fixing solution, and is provided so as to be rotatable around its axis;
An image forming apparatus characterized in that a fixing liquid held in a porous layer of an application member is applied in contact with the toner image carrying surface while rotating the application member while being pressed against the toner image carrying surface of the intermediate transfer medium. is there.

In the image forming apparatus of the present invention, the application member described above is
A porous layer;
And a fixing solution holding layer which is provided as an inner layer of the porous layer and has a larger thickness than the porous layer and can permeate and hold the fixing solution.

In the image forming apparatus of the present invention, the application member described above is
A fixing solution storage layer for holding and storing the fixing solution;
A penetration control layer made of a material provided on the surface of the fixing solution storage layer so as to be elastically deformable and capable of penetrating and holding the fixing solution;
It is provided on the surface of the permeation control layer so as to be elastically deformable, and includes a porous layer that holds a fixing solution, and is formed in a roller shape.

  Furthermore, in the image forming apparatus of the present invention, the porous layer has a pore diameter of 0.1 μm to 2 μm (0.1 μm or more and 2 μm or less), and a porosity of 60% to 90% (60% or more and 90% or less). And a layer thickness of 10 μm to 200 μm (10 μm or more and 200 μm or less).

  Further, the image forming apparatus of the present invention is characterized in that the contact angle of the porous layer with the fixing solution is smaller than the contact angle with the fixing solution on the surface of the intermediate transfer medium and larger than the contact angle with the fixing solution on the toner surface. To do.

Furthermore, in the image forming apparatus of the present invention, the fixing solution applying unit described above further includes a pressing unit that presses the coating member against the intermediate transfer medium,
The pressure contact means presses the coating member against the intermediate transfer medium with a pressing force that allows the fixing liquid held in the porous layer of the coating member to pass through the pressure contact portion between the coating member and the toner image carrying surface of the intermediate transfer medium. It is characterized by.

  Furthermore, in the image forming apparatus of the present invention, the pressing force by which the above-mentioned pressing means presses the coating member against the intermediate transfer medium is 0.05 N / cm to 1.0 N / cm (0.05 N / cm or more, 1 0.0 N / cm or less).

Furthermore, in the image forming apparatus of the present invention, the above-described fixing liquid applying unit is
Along with the application member
Furthermore, a fixing solution storage means for storing a fixing solution;
Fixing solution supply means for supplying the fixing solution stored in the fixing solution storage means to the outer peripheral surface of the coating member;
Fixing liquid regulating means for adjusting the amount of the fixing liquid that is provided so as to contact the outer peripheral surface of the coating member and that is held in the porous layer of the coating member.

  Furthermore, the image forming apparatus of the present invention is characterized in that the elastic modulus of the binder resin contained in the toner is larger than the elastic modulus of the surface of the application member.

The image forming apparatus of the present invention includes a toner image forming unit that forms a toner image made of a chargeable toner containing a binder resin, and a smooth surface that carries the toner image on the surface and is held at a constant potential. Intermediate transfer means including an intermediate transfer medium that is rotationally driven, a fixing liquid applying means that applies a non-contact fixing solution having a function of softening the toner image to the toner image on the intermediate transfer medium, and a fixing liquid applied And an image forming apparatus including a transfer unit that transfers the softened toner image to a recording medium.
Fixing liquid application means
Fixing liquid atomizing means for making the fixing liquid into mist-like droplets;
Fixing liquid charging means for charging the fixing liquid droplets formed by the fixing liquid atomizing means to a polarity opposite to the charging polarity of the toner;
An image forming apparatus including: a toner image on an intermediate transfer medium and droplet supply means for supplying droplets of a fixing solution in a charged state to the vicinity thereof.

  Furthermore, the image forming apparatus of the present invention is characterized in that the above-described fixing liquid atomizing unit forms droplets of the fixing liquid having a diameter equal to or smaller than the average particle diameter of the toner.

Furthermore, the image forming apparatus of the present invention includes an intermediate transfer medium heating unit provided upstream of the fixing liquid applying unit in the rotational driving direction of the intermediate transfer medium,
The intermediate transfer medium heating means
The toner image on the intermediate transfer medium is heated to a temperature equal to or higher than the glass transition point of the binder resin contained in the toner.

Furthermore, the image forming apparatus of the present invention includes an intermediate transfer medium heating unit provided upstream of the fixing liquid applying unit in the rotational driving direction of the intermediate transfer medium,
The intermediate transfer medium heating means
The toner image includes a toner containing a binder resin and a wax having a softening point lower than that of the binder resin, and the toner image carried on the intermediate transfer medium is heated to a temperature equal to or higher than the softening point of the wax.

  The image forming apparatus according to the present invention further includes a toner image forming unit that forms a toner image including a plurality of chargeable toners including a binder resin, and superimposes the plurality of color toner images on an intermediate transfer medium. A color image is formed by the above.

  According to the present invention, an image includes a toner image forming unit, an intermediate transfer unit including an intermediate transfer medium, a fixing liquid applying unit that applies a fixing liquid to the toner image on the intermediate transfer medium in contact, and a transfer unit. In the forming apparatus, at least the surface of the coating member having a porous layer that can be elastically deformed and capable of holding the fixing liquid is held on the porous layer while being pressed against the toner image carrying surface of the intermediate transfer medium and rotated. There is provided a wet-fixing type image forming apparatus having a configuration in which a fixing solution is applied in contact with a toner image carrying surface.

  In the porous layer of the coating member, there are a large number of pores that can hold the fixing solution. The fixing solution held in the porous layer stays in the porous layer at a portion where a large pressure is applied from the outside to the porous layer, such as a nip portion (pressure contact portion) between the coating member and the intermediate transfer medium. In a portion where the pressure applied from the outside is small, such as a portion in contact with the toner image, it oozes out from the porous layer. Therefore, in a portion where pressure is applied from the outside, such as the nip portion (pressure contact portion) between the coating member and the intermediate transfer medium, the fixer is present in the porous layer, so the nip portion between the coating member and the intermediate transfer member The fixing liquid hardly forms a meniscus at the entrance and stays there, and the flow of the fixing liquid that disturbs the toner image hardly occurs.

  Further, the amount of the fixing solution that oozes out from the porous layer varies depending on the surface area of the portion of the intermediate transfer medium with which the porous layer contacts. Since the toner image is formed by aggregating fine toner particles, the surface area per macroscopic area is large. In a portion having a large surface area, a large amount of the fixing solution oozes out and the amount of fixing solution applied per macroscopic area increases. Furthermore, when a plurality of toner images of different colors are stacked to form a color toner image, the surface area is further increased by the stacking of the plurality of toner images, and the amount of fixing liquid applied is further increased accordingly. . On the other hand, the portion of the intermediate transfer medium where the toner does not adhere is smooth, and therefore the surface area per macroscopic area is small. In a portion having a small surface area, the amount of the fixing solution leached out from the porous layer is small, and the amount of fixing solution applied is small. Further, the porous layer is configured to be elastically deformable, and the porous layer is deformed following the unevenness of the toner image. Therefore, even if the toner amount is partially different and the height of the toner image is partially raised, Also, the fixing solution can be applied uniformly. Further, even when the toner image is locally supported on the intermediate transfer medium, the porous layer is deformed accordingly and the fixing liquid is applied to the toner image. For this reason, a large amount of fixing liquid is applied to the image portion on which the toner image is carried, and the amount of fixing liquid applied is reduced in the non-image portion on which the toner image is not carried. As a result, the fixing liquid is almost selectively applied only to the image portion. Is granted.

  Thus, by using the image forming apparatus of the present invention, a high-quality and high-definition image can be stably formed over a long period of time.

  According to the present invention, there is used an application member that includes a porous layer and a fixing solution holding layer that is provided as an inner layer of the porous layer and has a larger thickness than the porous layer and is capable of penetrating and holding the fixing solution. As a result, even when the amount of the fixing solution retained by the porous layer is small, a sufficient amount of fixing solution can be applied to the toner image on the intermediate transfer medium. That is, if the fixing solution holding layer as described above is provided, the porous layer can be formed of a porous film having a small film thickness. For example, only the surface layer is an expensive and fine porous film, and the inside is an inexpensive felt. If constituted by a member made of continuous foam rubber or the like, the coating member can be manufactured at a low cost without deteriorating the applicability of the fixing liquid to the toner image. According to the present invention, there is provided an application member formed in a roller shape, including a fixing solution storage layer, a penetration control layer provided on the surface of the fixing solution storage layer, and a porous layer provided on the surface of the penetration control layer. By using it, the coating member can be a cartridge system, and the fixing solution can be replenished by replacing the coating member. As a result, since the liquid fixing solution exists only in the closed space inside the coating member, the fixing solution does not overflow or scatter in the image forming apparatus.

  In addition, since the permeation control layer is interposed between the holding storage layer and the porous layer, and excessive supply of the fixing solution to the porous layer is prevented, excessive fixing solution oozes out on the surface of the coating member. This further prevents the fixing liquid from forming a meniscus at the entrance of the nip portion between the coating member and the intermediate transfer medium. Accordingly, the flow of the fixing liquid does not occur in the state where the fixing liquid and the toner image are in contact with each other, and the toner image is not disturbed, so that a high-quality and high-definition image can be obtained. Further, since the fixing solution is stably supplied from the permeation control layer in contact with the holding storage layer to the porous layer, even if a solid image having a large amount of toner is continuously output, the solid image is necessary and sufficient for fixing. An amount of fixing solution is applied, and a high-quality and high-definition fixed image is always obtained.

  According to the present invention, the aforementioned effect is maximized by setting the pore diameter of the porous layer in the coating member to 0.1 to 2 μm, the porosity to 60 to 90%, and the layer thickness to 10 to 200 μm. Demonstrated. If the pore diameter is less than 0.1 μm, the amount of fixing liquid applied to the toner image is insufficient, and the fixing strength is insufficient at a portion where the toner amount is large. On the other hand, if it exceeds 2 μm, the toner particles are fitted into the pores. It adheres firmly and clogs the porous membrane. If the porosity is less than 60%, the amount of fixing solution retained and the amount applied to the toner image will be insufficient, and the fixing strength will be insufficient in areas where the amount of toner is large. In addition, it is difficult to form a porous layer having elasticity. If the thickness is less than 10 μm, it is difficult to form a porous layer. On the other hand, if the thickness exceeds 200 μm, the amount of fixing solution applied to the toner image becomes insufficient. Run short.

  According to the present invention, the contact angle between the porous layer and the intermediate transfer medium is reduced when the contact angle of the porous layer with respect to the fixer is smaller than the contact angle with respect to the fixer on the surface of the intermediate transfer medium. Becomes easier to adhere to the porous layer than the intermediate transfer medium. As a result, it is possible to reduce the application of the fixing solution from the porous layer to the intermediate transfer medium in the non-image area where the toner image does not adhere as much as possible, thereby reducing the amount of the fixing solution used and the number of replenishments. In addition, the contact angle of the porous layer with the fixing solution is larger than the contact angle of the toner with the fixing solution, so that when the porous layer and the toner image are in contact with each other, the fixing solution has more toner image than the porous layer. It becomes easy to adhere to. As a result, a sufficient amount of fixing liquid can be applied to the image portion to which the toner image adheres according to the toner amount.

  According to the present invention, the fixing liquid applying means further includes a pressure contact means, and the fixing liquid held by the pressure contact means on the porous layer of the application member forms a nip portion (pressure contact portion) between the application member and the intermediate transfer medium. The coating member is pressed against the intermediate transfer medium so that it can pass through. With this configuration, since the fixing liquid held on the coating member always passes through the nip portion between the coating member and the intermediate transfer medium, the coating member is pressed against the intermediate transfer medium with a constant pressing force through a thin layer of the fixing liquid. Will do. As a result, a toner image (solid image) with a large area and a large amount of toner enters the nip portion, so that a sufficient amount of fixing solution is applied to the toner image even when the distance between the coating member and the intermediate transfer medium is increased. it can. In addition, at the entrance of the nip portion between the coating member and the intermediate transfer medium, it is further prevented that the fixing liquid forms a meniscus and stays therein, thereby enabling more stable formation of a high-quality and high-definition image. . Further, the application member and the toner image are in contact with each other through the thin layer of the fixing solution, and the toner image is not in direct contact with the application member, so that adhesion of the toner to the application member is prevented.

  According to the present invention, the above-described effects are conspicuously exhibited by setting the pressure and pressing force of the application member to the intermediate transfer medium by the pressure contact member to be 0.05 to 1.0 N / cm in terms of linear pressure. If it is less than 0.05 N / cm, the contact state between the coating member and the intermediate transfer medium becomes unstable, and the fixer may not be uniformly applied to the toner image on the intermediate transfer medium. Further, the coating member cannot be elastically deformed following the subtle unevenness of the intermediate transfer medium and the unevenness of the toner image, and a sufficient amount of the fixing liquid cannot be applied to the concave portion of the toner image. There may be unevenness and uneven color. On the other hand, if it exceeds 1.0 N / cm, the fixing solution on the surface of the coating member cannot pass through the coating member, the intermediate transfer medium, and the nip portion, and the squeezing solution is squeezed at the nip portion. Forming and surplus fixer returns to the upstream side of the rotation direction of the coating member; The fixer may flow violently at the entrance of the nip, and the toner image may be disturbed.

  According to the present invention, the fixing liquid is applied to the outer peripheral surface of the coating member by using the fixing liquid applying means including the applying member, the fixing liquid containing means, the fixing liquid supplying means, and the fixing liquid regulating means. As a result, it is not necessary to hold the fixing liquid inside the application member, and the application member can be downsized. In addition, by providing the fixing solution storage means outside the coating member, it becomes possible to store a large amount of the fixing solution and to reduce the number of times the fixing solution is replenished. Further, by adjusting the amount of the fixing liquid on the surface of the coating member by the fixing liquid regulating means, an excessive amount of the fixing liquid adheres to the surface of the coating member, and the meniscus is fixed at the entrance of the nip portion between the coating member and the intermediate transfer medium. Can be prevented, and the flow of the fixing liquid does not occur in the state where the fixing liquid and the toner image are in contact with each other, and the toner image is not disturbed, so that a high-quality and high-definition image can be obtained. According to the present invention, by making the elastic modulus of the binder resin contained in the toner larger than the elastic modulus of the coating member surface, the coating member surface can be reliably elastically deformed following the unevenness of the toner image. As a result, the fixer can be applied uniformly regardless of the relative height of the toner image, regardless of the relative height of the toner image, even in a portion with a large amount of toner or a portion with a small amount of toner surrounded by a portion with a large amount of toner. Is obtained.

  According to the present invention, in an image forming apparatus including a toner image forming unit, an intermediate transfer unit including an intermediate transfer medium, a fixer applying unit, and a transfer unit, a fixer atomizing unit, a fixer charging unit, A fixing liquid applying means including a droplet supplying means, forming a fixing liquid droplet, charging the fixing liquid droplet to a polarity opposite to that of the toner image, and supplying the toner image in the vicinity of the toner image. The fixing solution can be selectively applied only in accordance with the toner amount of the toner image, and the fixing solution hardly adheres to the intermediate transfer medium, so that the amount of the fixing solution used can be reduced and the number of replenishments of the fixing solution can be reduced.

  According to the present invention, the fixing liquid atomizing means is configured to form fixing liquid droplets having a diameter that is the same as or smaller than the average particle diameter of the toner. When droplets adhere, it is possible to suppress aggregation of toner particles, and a uniform and high-quality fixed image can be obtained. When the fixing liquid droplets are larger than the average particle diameter of the toner, the toner particles around the toner image are aggregated at the moment when the fixing liquid droplets adhere to the toner image, and unevenness that can be visually confirmed in the toner image occurs.

  According to the present invention, the image forming apparatus of the present invention includes the intermediate transfer medium heating unit upstream of the fixing liquid applying unit in the rotational driving direction of the intermediate transfer medium. By adopting a configuration in which the toner image is heated to a temperature equal to or higher than the glass transition point of the binder resin contained in the toner, the binder resin in the toner is appropriately softened, and the adhesion between the intermediate transfer medium and the toner particles is increased. To do. As a result, it is possible to further prevent the toner particles from adhering to the coating member and the toner image from being disturbed when the fixing liquid is applied. Therefore, it is particularly suitable when an application member is used.

  According to the present invention, the image forming apparatus of the present invention includes the intermediate transfer medium heating unit upstream of the fixing liquid applying unit in the rotational driving direction of the intermediate transfer medium, and has a softening point that is higher than that of the binder resin together with the binder resin. By using a toner containing a low wax and heating the toner image on the intermediate transfer medium to a temperature equal to or higher than the softening point of the wax contained in the toner by the intermediate transfer medium heating means, the wax in the toner is appropriately Softening increases the adhesion between the intermediate transfer medium and the toner particles. As a result, it is possible to further prevent the toner particles from adhering to the coating member and the toner image from being disturbed when the fixing liquid is applied. Therefore, it is particularly suitable when an application member is used. Further, since the wax in the toner particles is softened, the fixing liquid enters the inside of the toner particles, and the softened state suitable for transfer to the recording medium can be obtained in a short time. As a result, the time from applying the fixing solution to transferring to the recording medium can be shortened, the interval between the fixing solution applying position and the transfer position to the recording paper can be set short, and the apparatus can be easily downsized. is there.

  According to the present invention, in the above-described image forming apparatus, when a color image is formed by destructive color mixing that superimposes a plurality of color toner images on the intermediate transfer medium, a necessary and sufficient amount of fixing liquid is applied according to the amount of toner. Therefore, a high-quality color fixed image can be formed. As described above, the image forming apparatus of the present invention is particularly suitable for forming a color image.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus 1 according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a configuration of a main part (a toner image forming unit 2 described later) of the image forming apparatus 1 shown in FIG. FIG. 3 is an enlarged cross-sectional view showing a configuration of a main part (mainly fixing solution applying unit 5) of the image forming apparatus 1 shown in FIG. The image forming apparatus 1 is an image forming apparatus having a so-called tandem configuration in which toner images of four colors of yellow, magenta, cyan, and black are sequentially superimposed and transferred.

  The image forming apparatus 1 includes a toner image forming unit 2, an intermediate transfer unit 3, an intermediate transfer medium heating unit 4, a fixing liquid applying unit 5, a transfer fixing unit 6, a recording medium supply unit 7, and a discharge unit 8. It is comprised including.

  The toner image forming unit 2 includes image forming units 10y, 10m, 10c, and 10b, which form an electrostatic latent image corresponding to image information of each hue, develop the electrostatic latent image, and develop each electrostatic color image. A toner image is formed. That is, the image forming unit 10y forms a toner image corresponding to yellow image information, the image forming unit 10m forms a toner image corresponding to magenta image information, and the image forming unit 10c uses cyan image information. The image forming unit 10b forms a toner image corresponding to black image information.

  The image forming unit 10y includes a photosensitive drum 11y, a charging roller 12y, an optical scanning unit 13, a developing device 14y, and a drum cleaner 15y.

  The photosensitive drum 11y is supported by a driving unit (not shown) so as to be rotatable around an axis, and includes a cylindrical, columnar, or thin film sheet (preferably cylindrical) conductive substrate (not shown) and the surface of the conductive substrate. And a photosensitive layer formed thereon. As the photosensitive drum 11y, those commonly used in this field can be used. For example, the photosensitive drum 11y is connected to a GND potential including an aluminum base tube as a conductive substrate and an organic photosensitive layer formed on the surface of the aluminum base tube. And a photosensitive drum having a diameter of 30 mm. The organic photosensitive layer is formed by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. The organic photosensitive layer may include a charge generation material and a charge transport material in one layer. The layer thickness of the organic photosensitive layer is, for example, 20 μm. An underlayer may be provided between the organic photosensitive layer and the conductive substrate. Further, a protective layer may be provided on the surface of the organic photosensitive layer. Instead of the organic photosensitive layer, a photosensitive layer made of zinc oxide, selenium, amorphous silicon or the like can be used. The photosensitive drum 11y is rotationally driven in a clockwise direction, for example, at a peripheral speed of 100 mm / s.

  The charging roller 12y charges the surface of the photosensitive drum 11y to a predetermined polarity and potential. Instead of the charging roller 12y, a brush type charger, a charger type charger, a corona charger such as a scorotron, or the like can be used. In the present embodiment, the photosensitive drum 11y is charged to −600 V by the charging roller 12y.

  The optical scanning unit 13 irradiates the surface of the photosensitive drum 11y to be charged with laser light 13y corresponding to yellow image information, and electrostatically corresponds to the yellow image information on the surface of the photosensitive drum 11y. A latent image is formed. A semiconductor laser or the like is used as the light source of the laser beam 13y. In the present embodiment, an electrostatic latent image having an exposure potential of −70 V is formed.

  The developing device 14y is in pressure contact with the surface of the photosensitive drum 11y, includes a fixed magnetic pole (not shown), and is rotatably driven around an axis, and supplies yellow toner 16y to the electrostatic latent image on the surface of the photosensitive drum 11y. A developing roller 17y, a developing blade 18y that is provided so as to be in contact with the surface of the developing roller 17y, uniformizes the layer of yellow toner on the surface of the developing roller 17y (layer regulation), and a toner storage container that stores the yellow toner 16y. 19y and a stirring roller 20a, 20b provided in the toner storage container 19y so as to be in pressure contact with each other and rotatably driven around the axis, the stirring roller 20a being in pressure contact with the surface of the developing roller 17y and the surface of the developing roller 17y And stirring rollers 20a and 20b for supplying yellow toner 16y. The developing roller 17y is rotationally driven in the same direction as the rotational driving direction of the photosensitive drum 11y at a developing nip portion that is in pressure contact (contact) with the photosensitive drum 11y. Therefore, the rotational drive direction around the axis is the opposite direction. In the present embodiment, the peripheral speed of the developing roller 17y is, for example, 150 mm / s, which is 1.5 times the peripheral speed of the photosensitive drum 11y. In the present embodiment, a DC voltage of −240 V is applied to the developing roller 11y as the developing potential. The yellow toner 16y in the toner storage container 19y is mixed with a magnetic carrier (not shown) by the stirring rollers 20a and 20b, then supplied to the surface of the developing roller 17y, and the layer thickness is made uniform by the developing blade 18y. The toner image corresponding to the yellow image information is formed by selectively supplying the electrostatic latent image on the surface of the photosensitive drum 11y almost selectively.

  As will be described later, the drum cleaner 15y removes and collects the yellow toner remaining on the surface after the yellow toner image on the surface of the photosensitive drum 11y is transferred to the intermediate transfer belt 21.

  According to the image forming unit 10y, the surface of the photosensitive drum 11y is first charged to, for example, -600V by the charging roller 12y while the photosensitive drum 11y is rotated about its axis. Next, the surface of the charged photosensitive drum 11y is irradiated with signal light corresponding to yellow image information from the optical scanning unit 13, and an electrostatic latent having an exposure potential of −70 V corresponding to the yellow image information. Form an image. Next, the yellow toner layer carried on the surface of the developing roller 16y comes into contact with the surface of the photosensitive drum 11y. A DC voltage of −240 V is applied to the developing roller 16y as a developing potential. Due to the potential difference, the yellow toner 16y adheres to the electrostatic latent image and is developed, and a yellow toner image is formed on the surface of the photosensitive drum 11y. Is formed. As will be described later, this yellow toner image is intermediately transferred to an intermediate transfer belt 21 in contact with the surface of the photosensitive drum 11y. The yellow toner 16y remaining on the surface of the photosensitive drum 11y is removed and collected by the drum cleaner 15y. Thereafter, the same yellow toner image forming operation is repeatedly executed.

  The image forming units 10m, 10c, and 10b have the same structure as the image forming unit 10y except that magenta toner 16m, cyan toner 16c, and black toner 16b are used. Further, “m” indicating magenta color, “c” indicating cyan color, or “b” indicating black color is added to the end of each reference symbol, and the description is omitted. The image forming units 10y, 10m, 10c, and 10b are arranged in a line in this order from the upstream side in the moving direction (sub operation direction) of the intermediate transfer belt 21, that is, the direction of the arrow 30.

  Each of the color toners 16y, 16m, 16c, and 16b contains a binder resin, a colorant, and, if necessary, a release agent. Hereinafter, the toners 16y, 16m, 16c, and 16b are collectively referred to as the toner 16 unless otherwise specified.

  The binder resin is not particularly limited as long as it is a resin that is softened and / or swollen by the fixing liquid 35 described later. For example, polystyrene, a homopolymer of a substituted styrene, a styrene copolymer, polyvinyl chloride, Examples thereof include polyvinyl acetate, polyethylene, polypropylene, polyester, and polyurethane. Binder resins can be used alone or in combination of two or more. Among these, the softening point is 100 to 150 ° C. and the glass transition point is 50 to 80 ° C. from the viewpoints of storage stability and durability of the toner 16 itself, and softening and / or swelling control of the toner 16 by application of the fixing liquid 35. A resin having a Young's modulus of 0.5 to 5 GPa is preferable, and a polyester is particularly preferable. Polyesters are easily swelled and / or softened and made transparent by readily available and inexpensive organic solvents. Thus, when a color toner image obtained by superimposing a plurality of different single color toner images is fixed on a recording medium, sufficient color development can be obtained by subtractive color mixing. In addition, when a resin having a softening point (or molecular weight) higher than that in the above-mentioned softening point range is used, deterioration of the toner 16 due to a load during development is prevented, and the developed toner image that is stable over a long period of time and thus stable at a high level. The obtained image is obtained.

  As the colorant, toner pigments and dyes conventionally used in electrophotographic image forming technology can be used, but in order to prevent bleeding due to the fixing solution 35, a pigment that does not dissolve in the fixing solution 35 is preferable, and a nigrosine dye Dyes such as are not preferred. Specific examples of the pigment include, for example, azo pigments, benzimidazolone pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, isoindoline pigments, dioxazine pigments, anthraquinone pigments, perylene pigments, Organic pigments such as perinone pigments, thioindigo pigments, quinophthalone pigments, metal complex pigments, inorganic pigments such as carbon black, titanium oxide, molybdenum red, chromium yellow, titanium yellow, chromium oxide, Berlin blue, aluminum powder And metal powders.

  The release agent is not particularly limited as long as it is softened and / or swollen by the fixing solution 35 described later, and examples thereof include waxes such as polyethylene wax, polypropylene wax, and paraffin wax. Among these waxes, it is preferable to use a wax having a glass transition point lower than that of the binder resin depending on the binder resin to be used. Wax having a glass transition point lower than that of the binder resin is easily softened by heating. Therefore, even at a temperature lower than the softening point of the toner 16 itself, the binding force between the toners 16 and the toner image carrier of the toner 16, the recording medium, etc. Since the adhesion force of the toner increases, it is possible to reduce the occurrence of the flow and aggregation of the toner 16 when the fixing solution is applied. Further, the softening of the wax causes the fixing liquid 35 to permeate into the toner particles from the wax-existing portion of the toner particles. Therefore, the entire toner 16 softens and / or swells in a short time after the fixing liquid 35 is applied. As a result, at the time of transfer and fixing to a recording medium, sufficient fixing strength can be obtained, and sufficient color development can be obtained by superimposing toner images.

  The toner 16 may contain one or more general toner additives such as a charge control agent, a fluidity improver, a fixing accelerator, and a conductive agent as necessary.

  The volume average particle diameter of the toner 16 is not particularly limited, but is preferably 2 to 7 μm. When such a small particle size toner is used, the surface area of the toner 16 per unit weight is increased, the contact area with the fixing liquid 35 is increased, and fixing is facilitated. As a result, the amount of the fixing liquid 35 used can be reduced, and the fixing of the toner image onto the recording medium and the drying after the fixing can be performed in a short time. Further, the smaller the volume average particle diameter of the toner 16 is, the higher the coverage with respect to the recording medium 9 is. Therefore, it is possible to achieve a high image quality with a low adhesion amount and a reduction in the consumption amount of the toner 16. Further reduction in consumption can be achieved.

  When the volume average particle size of the toner 16 is less than 2 μm, the fluidity of the toner 16 is lowered, and during the developing operation, the supply, stirring and charging of the toner 16 are insufficient, the toner 16 is insufficient, the reverse polarity toner There is a possibility that high quality images cannot be obtained. On the other hand, if the volume average particle size exceeds 7 μm, the toner particles having a large particle size that is difficult to soften and / or swell to the center of the toner particles increase, so that the fixability of the image to the recording medium is reduced and the image Color development deteriorates, and the image becomes dark particularly when fixing to an OP film.

  The softening point and glass transition point of the toner 16 itself are not particularly limited, but the softening point is preferably 100 to 150 ° C. and the glass transition point is preferably 50 to 100 ° C. Such a toner having a high softening point has high durability against a load during development, but does not sufficiently fix and develop color in the heat fixing method. However, in the present invention, since the toner 16 is chemically swollen and softened using the fixing liquid 35, fixing and color development are sufficient, and a high-quality image can be obtained.

  The toner 16 can be manufactured according to a known method. For example, a method of dispersing and pulverizing a colorant and a release agent in a binder resin, a method of dispersing a colorant and a release agent in a binder resin monomer solution, and then polymerizing the binder resin monomer Etc. In any of the methods, in order to increase the surface area of the toner 16, it is preferable to adjust the shape of the toner 16 to be indefinite rather than spherical. This facilitates contact with the fixing solution 35, so that the amount of the fixing solution 35 used can be reduced, and the toner image can be fixed and dried in a short time.

Each color toner 16y, 16m, 16c, and 16b used in the present embodiment has the same configuration as described below except for the pigment. This toner contains a binder resin, a colorant and a release agent, and has a volume average particle size of 6 μm, a pigment content of 12% by weight of the total amount of toner, a wax content as a release agent of 7% by weight of the total amount of toner, and the balance Is a negatively chargeable insulating non-magnetic toner which is a binder resin. The binder resin is a polyester having a glass transition point of 60 ° C., a softening point of 120 ° C., and a Young's modulus of 2 GPa. The wax is a low molecular weight polyethylene wax having a softening point of 70 ° C. Using this toner, the amount of toner per unit area required to obtain a predetermined image density (the measured value of reflection density by X-Rite 310 is 1.4) is 5 g / m ² . Further, the contact angle with respect to the fixing liquid 35 is 47 °.

  The intermediate transfer unit 3 includes an intermediate transfer belt 21, intermediate transfer rollers 22y, 22m, 22c, and 22b, support rollers 26, 27, and 28, a belt cleaner 29, and a temperature sensor 31.

  The intermediate transfer belt 21 is a toner image carrier, and is an endless belt that is stretched between support rollers 26, 27, and 28 to form a loop-shaped movement path, and the photosensitive drums 11y, 11m, 11c, and 11b. Rotate in the direction of the arrow 30 at approximately the same speed. As the intermediate transfer belt 21, a material that does not allow the fixing liquid 35 to permeate is selected from those commonly used in this field. Among them, those containing one or more of fluororesins such as polytetrafluoroethylene (PTFE), a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA), and synthetic resins such as polycarbonate and polyimide are preferable. . In the present embodiment, on a polyimide substrate surface having a thickness of 100 μm, 1) a silicone rubber layer having a thickness of 300 μm, and 2) polytetrafluoroethylene (PTFE) and a copolymer weight of tetrafluoroethylene and perfluoroalkyl vinyl ether A laminate in which a surface coat layer having a thickness of 20 μm made of a fluororesin composition in which coalescence (PFA) is mixed at 8: 2 (weight ratio) is laminated in this order is used. The polyimide base material and the surface coat layer can be mixed with a conductive material such as furnace black, thermal black, channel black, and graphite carbon in order to adjust the electric resistance value as an intermediate transfer belt. Note that it is preferable to select each material so that the contact angle of the intermediate transfer belt 21 with respect to the fixing liquid 35 is larger than the contact angle with respect to the porous layer 36 in the application roller 32 described later. As a result, the fixing liquid 35 is difficult to adhere to the non-image portion where the toner image on the intermediate transfer belt 21 is not carried, the contamination of the intermediate transfer belt 21 with the fixing liquid 35 is prevented, and the amount of the fixing liquid 35 used is also increased. Can be reduced. In the present embodiment, the contact angle of the intermediate transfer belt 21 with respect to the fixing liquid 35 is 70 °.

  The toner image carrying surface 21a of the intermediate transfer belt 21 is in pressure contact with the photosensitive drums 11y, 11m, 11c, and 11b in this order. The positions where the intermediate transfer belt 21 is in pressure contact with the photosensitive drums 11y, 11m, 11c, and 11b are the intermediate transfer positions of the toner images of the respective hues. Intermediate transfer rollers 22y, 22m, 22c, and 22b are disposed at positions facing the photosensitive drums 11y, 11m, 11c, and 11b via the intermediate transfer belt 21 that is a toner image carrier.

  The intermediate transfer rollers 22y, 22m, 22c, and 22b are respectively provided in pressure contact with the surface opposite to the toner image carrying surface 21a of the intermediate transfer belt 21 and rotatably driven around its axis by a driving unit (not shown). A metal shaft body and a conductive layer coated on the surface of the metal shaft body are configured. The shaft body is formed of a metal such as stainless steel, for example. The diameter of the shaft body is not particularly limited, but is preferably 8 to 10 mm. The conductive layer is formed of a conductive elastic body or the like. As the conductive elastic body, those commonly used in this field can be used, and examples thereof include EPDM, foamed EPDM, foamed urethane and the like containing a conductive material such as carbon black. A high voltage is uniformly applied to the intermediate transfer belt 21 by the conductive layer.

  The intermediate transfer rollers 22y, 22m, 22c, and 22b are opposite to the charging polarity of the toner in order to transfer the toner images formed on the surfaces of the photosensitive drums 11y, 11m, 11c, and 11b onto the intermediate transfer belt 21. A polar intermediate transfer bias is applied by constant voltage control. As a result, the yellow, magenta, cyan, and black toner images formed on the photosensitive drums 11y, 11m, 11c, and 11b are sequentially superimposed on the toner image carrying surface 21a of the intermediate transfer belt 21. Transferred to form a multicolor toner image.

  For the support rollers 26, 27, and 28, for example, an aluminum cylinder having a diameter of 30 mm and a thickness of 1 mm is used. The heating support roller 26 is supported by a driving unit (not shown) so as to be rotatable in the axial direction thereof, and the intermediate transfer medium heating unit 4 is provided therein. The intermediate transfer medium heating unit 4 has an effect of increasing the adhesion force of the toner image to the intermediate transfer belt 21 and the binding force between the toners constituting the toner image. For the intermediate transfer medium heating means 4, for example, a heater such as a halogen lamp is used. The support roller 27 also functions as a backup roller that comes into pressure contact with a transfer fixing roller 44 (to be described later) via the intermediate transfer belt 21, and is thus electrically grounded. The support roller 28 is a tension roller that applies tension to the intermediate transfer belt 21.

  The belt cleaner 29 is a member for removing the toner remaining on the toner image carrying surface 21a after the toner image on the toner image carrying surface 21a of the intermediate transfer belt 21 is transferred to the recording medium 9 by the transfer fixing unit 6 described later. And is provided so as to face the support roller 28 via the intermediate transfer belt 21, and is pressed against the toner image carrying surface 21a of the intermediate transfer belt 21 by a pressing means (not shown), so that residual toner on the toner image carrying surface 21a. A cleaning blade 29a that scrapes off the toner, and a toner storage container 29b that stores toner scraped off by the cleaning blade 29a. As the cleaning blade 29a, for example, a blade made of an elastic rubber material (for example, urethane rubber) can be used.

  In order to detect the temperature of the intermediate transfer belt 21, the temperature sensor 31 contacts the intermediate transfer belt 21 at a position downstream of the heating support roller 26 in the rotation direction of the intermediate transfer belt 21, that is, in the direction of the arrow 30. Or in close proximity. The detection result by the temperature sensor 31 is stored in a CPU (not shown) that controls the entire operation of the image forming apparatus 1, and the CPU sends a control signal to the intermediate transfer medium heating unit 4 based on the stored detection result to perform intermediate transfer. The heating of the belt 21 is controlled, and the surface temperature of the intermediate transfer belt 21 is controlled. In the present embodiment, the surface temperature of the intermediate transfer belt 21 is heated to 65 ° C. and held. This heating temperature is higher than the glass transition point (60 ° C.) of the binder resin contained in the toner 16 used in the present embodiment. When the toner image is heated above the glass transition point of the binder resin in the toner 16, the binder resin is softened and the adhesion between the toners 16 and between the intermediate transfer belt 21 and the toner 16 is increased. As a result, it is possible to more reliably prevent the toner 16 from adhering to the application roller 32 and the toner image from being disturbed by the application of the fixing liquid 35 in the fixing liquid applying means 5 described later. Contact coating can be easily performed.

  According to the intermediate transfer means 3, the toner images of the respective colors formed on the photosensitive drums 11 y, 11 m, 11 c, and 11 b are superimposed and transferred onto predetermined positions on the toner image carrying surface 21 a of the intermediate transfer belt 21. A color toner image is formed, the intermediate transfer belt 21 passes over the heating support roller 26, and the toner image on the intermediate transfer belt 21 is heated to substantially the same temperature as the intermediate transfer belt 21. The fixer 35 is applied by the above.

  In this embodiment, although the heating temperature of the intermediate transfer belt 21 by the heating support roller 26 is 65 ° C., the heating temperature can be appropriately changed according to the components contained in the toner 16. For example, when the toner 16 contains a wax having a softening point of 70 ° C., the heating temperature is 75 ° C., and the temperature of the intermediate transfer belt 21 and the toner image at the nip portion between the intermediate transfer belt 21 and the application roller 32 is the wax in the toner. The temperature may be set to be higher than the softening point.

  With this configuration, the wax in the toner 16 is softened immediately before the fixing liquid 35 is applied, and the adhesion between the toners 16 and between the toner 16 and the intermediate transfer belt 21 is further increased. It is possible to further prevent the toner image from being disturbed and the toner 16 from adhering to the application roller 32. Further, since the amount of heat that compensates for the temperature drop of the intermediate transfer belt 21 and the toner image due to the application of the fixing liquid 35 can be supplied on the spot, the temperature drop of the intermediate transfer belt 21, the toner image, and the fixing liquid 35 immediately after the application can be prevented. The fixing liquid 35 can be quickly diffused and penetrated. Furthermore, the wax in the toner particles is softened, so that the fixing liquid 35 penetrates into the toner particles. As a result, the toner 16 is swollen and softened instantaneously over a wide range. Thereby, when the toner image is pressed against the recording medium 9 by the transfer fixing means 6 described later, sufficient fixing strength to the recording medium 9 can be obtained. Furthermore, since the temperature of the fixing solution 35 after application is increased, the fixing solution 35 can be dried in a short time after application. Thereby, the throughput which is the number of output sheets per unit time of the image forming apparatus can be further improved. In addition, since the toner 16 instantaneously swells and softens, the time from the application of the fixing liquid 35 to the transfer to the recording medium 9 can be shortened, so that the application position of the fixing liquid 35 and the transfer position to the recording medium 9 can be reduced. Can be set to be short, and the apparatus can be reduced in size.

  The fixing liquid applying unit 5 applies a fixing liquid 35 that softens and / or swells the toner image carried on the intermediate transfer belt 21 in contact.

  The fixing liquid applying unit 5 includes an application roller 32, a casing 33, an opening / closing door 34, a pivot 39, a guide groove 40, and a pressing spring 42.

  The application roller 32 is formed in a roller shape and includes a cored bar 36, a penetration control layer 37 formed on the surface of the cored bar 36, and a porous layer 38 formed on the surface of the penetration control layer 37. A rotating shaft integral with a flange (not shown) provided at both ends in the longitudinal direction of the core metal 35 is rotatably supported by a bearing (not shown) provided in the casing 33, and is rotated by the rotation of the intermediate transfer belt 21. To do.

  The application roller 32 is provided such that the porous layer 38 on the surface thereof is lightly pressed against the heating support roller 26 via the intermediate transfer belt 21. With this configuration, even if a solid image with a large area and a large amount of toner enters the nip portion between the intermediate transfer belt 21 and the coating roller 32, the pressing force is not so high, and the coating roller 32 is pushed up by the solid image. The gap between the application roller 32 and the intermediate transfer belt 21 is increased, and a thin layer of the fixing liquid 35 on the surface of the application roller 32 passes through the nip portion together with the toner image, and is sufficiently applied to the toner image at that time. Further, since the fixing liquid 35 does not form a large meniscus and stay in the nip portion, the toner image is not disturbed, and a high-quality and high-definition image can be obtained. Further, since the application roller 32 and the toner 16 come into contact with each other through the fixing liquid 35, the adhesion of the toner 16 to the application roller 32 is prevented.

  The pressing force of the application roller 32 against the intermediate transfer belt 21 is preferably 0.05 to 1.0 N / cm in terms of linear pressure. If it is less than 0.05 N / cm, the contact state between the coating roller 32 and the intermediate transfer belt 21 becomes unstable, and the fixing liquid 35 cannot be uniformly applied to the toner image. Furthermore, the application roller 32 does not sufficiently elastically follow the subtle unevenness of the intermediate transfer roller 21 and the unevenness of the toner image, so that it becomes insufficient to apply the fixing liquid 35 to the concave portion of the toner image. As a result, uneven application of the fixing liquid 35, uneven fixing, uneven gloss, uneven color, and the like are caused. If it exceeds 1.0 N / cm, the fixing liquid 35 on the surface of the application roller 32 cannot pass through the nip portion while the application roller 32 and the intermediate transfer belt 21 rotate under pressure. As a result, the fixer 35 is squeezed at the nip, the fixer 35 forms a meniscus at the entrance of the nip, the excess fixer 35 returns to the upstream side in the rotation direction of the application roller 32, and the solution is removed at the entrance of the nip. The toner flows violently and the toner image is disturbed. When a color image is obtained by superimposing a plurality of single color toner images of different colors, the absolute amount of toner increases, and the locations where much toner adheres and where the toner adheres are finely mixed and distributed. To do. For example, when three color toner images are superimposed, the height of the high density portion is three times higher than that of a single color toner image. For this reason, it is particularly important to apply the fixing liquid 35 in accordance with the amount of toner by the application roller 32 that contacts with a constant pressing force and has elasticity. In the present embodiment, the pressing force of the application roller 32 against the heating support roller 26 is 0.1 N / cm.

  The elastic modulus of the application roller 32 is desirably smaller than the elastic modulus of the toner 16, preferably 1/10 or less, more preferably 1/100 or less of the elastic modulus of the toner 16.

  As the core bar 36 included in the coating roller 32, a core bar commonly used in this field can be used. In the present embodiment, an aluminum core bar having an outer diameter of 30 mm and a wall thickness of 0.5 mm is used. The cored bar 36 is provided with a plurality of passage holes 36a through which the fixing liquid 35 passes. In the present embodiment, passage holes 36a having a diameter of 0.1 mm are provided at 16 equiangular positions in the circumferential direction of the cored bar 36 and at intervals of 5 mm with a half phase shift in the axial direction. A fixing liquid 35 is held and stored inside the cored bar 36. Therefore, the cored bar 36 functions as a fixing liquid storage layer as well as the original function of increasing the rigidity of the application roller 32.

  The permeation control layer 37 is capable of permeating and holding the fixing solution 35 and is elastic in order to prevent the fixing solution 35 supplied through the passage hole 36 a of the core metal 36 from being excessively supplied to the porous layer 38. A deformation is provided. Since the permeation control layer 37 is in contact with the cored bar 36 that holds and stores the fixing solution 35, a sufficient supply of the fixing solution 35 can be received. The permeation control layer 37 can hold the fixing solution 35 in the fine pores existing therein, and the porous layer 38 that is the outer layer of the permeation control layer 37 is a toner image. When an object having a large surface area is contacted, a large amount of fixing solution 35 is applied from the porous layer 38 to the object, and the amount of the fixing solution 35 retained in the porous layer 38 is reduced, and the porous layer 38 is fixed. Liquid 35 is supplied. When the porous layer 38 comes into contact with an object having a large change in unevenness such as a toner image partially supported on the smooth intermediate transfer belt 21, the permeation control layer 37 is elastic together with the porous layer 38. The fixing solution 35 is replenished to the porous layer 38 so as to deform and help the application of the local fixing solution 35 by the porous layer 38. Further, since the fixing liquid 35 inside the cored bar 36 does not directly contact the porous layer 38 due to the presence of the permeation control layer 37, excessive fixing liquid 35 leaks to the surface of the coating roller 32, and the coating roller 32 and the intermediate transfer belt 21. It is possible to prevent the fixing liquid 35 from forming a meniscus at the entrance to the nip. Therefore, the toner image is not disturbed by the flow of the fixing liquid 35, and a high-quality and high-definition image can be obtained. For the permeation control layer 37, for example, felt, an open cell foam (sponge) of rubber, or the like is used. In the present embodiment, a felt having a thickness of 5 mm is used. In the present embodiment, the Young's modulus serving as an elastic body of the permeation control layer 37 is 3 MPa, which is 1/100 or less compared to the toner 16.

  The porous layer 38 is in pressure contact with the intermediate transfer belt 21 and applies the fixing liquid 35 appropriately supplied from the permeation control layer 37 to the toner image on the toner image carrying surface 21a of the intermediate transfer belt 21 in contact. As with the permeation control layer 37, the porous layer 38 can hold the fixing solution 35 in fine pores existing therein, and the amount of the fixing solution 35 applied according to the surface state of the contacting object. Can be changed. When contacted with an object having a large surface area such as a toner image, a large amount of the fixing solution 35 oozes out from the porous layer 38, and the applied amount per macroscopic area increases. On the other hand, when the surface of the intermediate transfer belt 21 is brought into contact with an object having a small surface area such as a surface that does not carry a toner image, the amount of leaching of the fixing liquid 35 is relatively reduced and the applied amount per macroscopic area is reduced. . Further, elastic deformation is locally generated in a portion where the unevenness is greatly changed, and a necessary and sufficient amount of the fixing liquid 35 can be supplied to the portion. Therefore, the fixing liquid 35 can be uniformly applied to the entire toner image regardless of the unevenness (level) of the toner image. Even if the fixing liquid 35 in the porous layer 38 is applied to the toner image and the amount of the fixing liquid 35 held in the porous layer 38 decreases, the fixing liquid 35 is immediately replenished from the permeation control layer 37. Even if a solid image having a large amount is continuously output, a high-quality fixed image can be stably obtained. The porous layer 38 has a function of applying the fixing solution 35 to the toner image, and also has a function of absorbing the fixing solution 35 when a large amount of the fixing solution 35 is present in the vicinity of the surface of the porous layer 38. Demonstrate.

  The material of the porous layer 38 is not particularly limited as long as it is a material that can be elastically deformed and made porous, and examples thereof include PTFE, polyurethane, and polyimide. In the present embodiment, a porous layer 38 made of PTFE and having a thickness of 50 μm is provided, and the pore diameter in the layer 38 is 0.5 μm and the porosity is 80%. In the present embodiment, the contact angle of the porous layer 38 with respect to the fixing liquid 33 is 65 °.

  The pore diameter in the porous layer 38 is preferably 0.1 to 2 μm. If the thickness is less than 0.1 μm, the leaching amount of the fixing liquid 35 becomes insufficient, and the fixing strength is insufficient in a portion where the toner amount is large. On the other hand, if the thickness exceeds 2 μm, the toner particles fit into the pores and clog the porous layer 38. The porosity is preferably 60 to 90%. If it is less than 60%, both the holding amount and the leaching amount of the fixing liquid 35 are insufficient, and the fixing strength is insufficient in a portion where the toner amount is large. If it exceeds 90%, it is difficult to form a porous layer having elasticity to restore. Furthermore, the layer thickness is preferably 10 to 200 μm. If it is less than 10 μm, it is difficult to form a porous layer. On the other hand, if it exceeds 200 μm, the amount of leaching of the fixing solution becomes insufficient, and the fixing strength is insufficient in a portion where the amount of toner is large. The layer thickness of the porous layer 38 is preferably smaller than the layer thickness of the permeation control layer 37. Felt, sponge, or the like used as the material for the permeation control layer 37 has a function as a fixing solution holding layer for holding the fixing solution 35. Therefore, even if the amount of fixing solution 35 retained is reduced by reducing the layer thickness of the porous layer, a sufficient amount of fixing solution 35 is retained in the permeation control layer 37 and the fixing solution 35 is sequentially deposited on the porous layer 38. Since the toner is supplied, the application of the fixing liquid 35 to the toner image is performed without any trouble. As a result, the amount of expensive porous membrane used for the porous layer is reduced, and the permeation control layer 37 is made of an inexpensive member such as felt or continuous foamed rubber (sponge), thereby reducing the manufacturing cost of the application roller 32. Can be realized.

  It is preferable that the contact angle of the porous layer 38 with respect to the fixing solution 35 is smaller than the contact angle of the toner image carrying surface 21 a of the intermediate transfer belt 21 with respect to the fixing solution 35. As a result, when the porous layer 38 and the intermediate transfer belt 21 come into contact with each other, the fixing solution 35 is more likely to adhere to the porous layer 38 than to the intermediate transfer belt 21 and is applied to the non-image portion of the intermediate transfer belt 21. The amount of the fixing solution 35 to be reduced can be reduced, and the usage amount of the fixing solution 35 and the number of replenishments can be reduced. The difference in contact angle between the two is desirably 5 degrees or more.

  Further, it is preferable that the contact angle of the porous layer 38 with the fixing solution 35 is larger than the contact angle of the surface of the toner 16 with the fixing solution 35. As a result, when the porous layer 38 and the toner image come into contact with each other, the fixing liquid 35 is more likely to adhere to the toner image than the porous layer 38, and the toner image that is the image portion is transferred from the porous layer 38 to the fixing liquid 35. And a toner image having a large amount of toner per area can be reliably fixed. The difference in contact angle between the two is desirably 10 degrees or more. When the application roller 32 having the above-described configuration is used, the fixing liquid 35 does not form a meniscus and stay at the entrance of the nip portion between the application roller 32 and the intermediate transfer belt 21. For this reason, when the toner image and the fixing liquid 35 are in contact with each other, no flow of the fixing liquid 35 occurs and the toner image is not disturbed, so that a high-quality and high-definition image can be stably formed. Further, by forming the coating member in a roller shape, a closed space can be formed inside the coating member, and the fixing liquid can be easily held by using the closed space.

  FIG. 4 is a view for explaining the application of the fixing liquid 35 to the toner image on the intermediate transfer belt 21 by the application roller 32. When the application roller 32 comes into contact with a toner image (image portion) that is an aggregate of the toner 16 carried on the intermediate transfer belt 21, the permeation control layer 37 and the porous layer 38 of the application roller 32 are elastically deformed and recessed. . Since there are many gaps around the toner particles 16 and the surface area per macroscopic area is large, the fixing liquid 35 oozes out from the porous film 38 to fill the gaps around the toner particles 16, and the toner particles 16. Swells and softens. On the other hand, in the smooth portion (non-image portion) where the toner image is not carried on the intermediate transfer belt 21, the permeation control layer 37 and the porous layer 38 are not elastically deformed, the surface area per macroscopic area is small, and the porous Since the leaching amount of the fixing solution 35 from the film 38 is small, the fixing solution 35 is selectively applied only to the image portion, and contamination of the intermediate transfer belt 21 by the fixing solution 35 is prevented. The amount can be reduced.

  According to the application roller 32, the fixing liquid 35 stored in the core metal 36 is supplied to the permeation control layer 37 from the passage hole 36 a, and the permeation control layer 37 appropriately supplies the fixing liquid 35 to the porous layer 38. The porous layer 38 applies the fixing liquid 35 to the toner image on the intermediate transfer belt 21 under contact. The application roller 32 also applies the fixing liquid 35 to the fog toner adhering to the non-image portion, so that the fog toner can also be fixed to the recording medium 9. Thus, fog toner can be prevented from adhering to and contaminating hands and clothes.

  In the present embodiment, the fixing liquid 35 is filled in the metal core 36 inside the coating roller 32 and the fixing liquid 35 is replenished by replacing the coating roller 32. However, the present invention is not limited thereto, and the image forming apparatus 1 is not limited thereto. Alternatively, a separate fixing solution storage tank may be provided, and the fixing solution 35 may be replenished to the application roller 32 from the tank.

  The casing 33 accommodates the coating roller 32 while rotatably supporting the coating roller 32, and the coating roller 32 and the heating support roller 26 are pressed against the side surface 33 a facing the heating support roller 26 via the intermediate transfer belt 21. An opening 33b is provided. In addition, pivots 39a and 39b are provided at both ends of the casing 33 in the longitudinal direction. The pivots 39a and 39b are slidably inserted into U-shaped guide grooves 40a and 40b provided on the side surface of the open / close door 34 facing the casing 33. As the pivots 39a and 39b slide in the guide grooves 40a and 40b, the casing 33 moves in the direction of the arrow 41, and the application roller 32 is attached to and detached from the operating position where it contacts the intermediate transfer belt 21. When the pivots 39a and 39b are positioned at the tips of the guide grooves 40a and 40b, the application roller 32 is in the operating position. The casing 33 is formed in a detachable cartridge system, and a sensor (not shown) detects that the fixing liquid in the coating roller 32 has run out, stores the detection result in the CPU, and the CPU is shown in accordance with the detection result. A message indicating that it is time to replace the casing 33 is displayed on the operation panel. Based on this, the casing 33 is replaced. With this configuration, the possibility that the fixing liquid 35 is scattered or leaked into the image forming apparatus 1 is extremely reduced, and internal contamination by the fixing liquid 35 is prevented.

  The open / close door 34 is provided on a part of the side surface 1 a of the image forming apparatus 1 so as to be openable and closable in the direction of the arrow 43. Thereby, replacement | exchange of the casing 33 is easy. The guide grooves 40 a and 40 b and the pressing spring 42 are provided on the side surface facing the casing 33. When the open / close door 34 is closed, the pressing spring 42 presses the lower side of the casing 33. At this time, the casing 33 is supported rotatably about the pivots 39a and 39b. As a result, the application roller 32 in the casing 33 is pressed against the intermediate transfer belt 21 with a predetermined pressing force. The pressing force of the pressure contact can be adjusted by changing the type of the pressing spring 42 or the like. For the pressing spring 42, for example, a coil spring, a leaf spring, a torsion spring, or the like can be used.

  The fixing solution 35 used here is a liquid that softens and / or swells the toner. For example, the fixing solution 35 is a composition containing water and an auxiliary solvent and does not penetrate into the intermediate transfer belt 21. A co-solvent is an organic compound that can be dissolved or dispersed in water. Specific examples of the auxiliary solvent include, for example, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, octyl alcohol, decyl alcohol, diethylene glycol, glycerin, polyethylene glycol, phenols, benzyl alcohol, methylbenzyl alcohol and other alcohols, acetone, Ketones such as methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, methyl ethyl ether, diethyl ether, methyl butyl ether, methyl isobutyl ether, dimethyl ether, diisopropyl ether, octyl phenyl ether and other ethers, methyl acetate, ethyl acetate , Ethyl oleate, ethyl acrylate, methyl methacrylate, dibutyl succinate, phthalic acid Ethyl, diethyl tartrate, ethyl palmitate, and the like esters such as dioctyl phthalate. Among these, ethers and esters are preferable, and esters are most preferable. These auxiliary solvents are excellent in the action of swelling and softening the binder resin of the toner 16. The auxiliary solvent can be used alone or in combination of two or more.

  The content of the auxiliary solvent in the fixing solution 35 is not particularly limited, but is preferably 5 to 80% by weight, more preferably 10 to 70% by weight, based on the total amount of the fixing solution 35. If it is less than 5% by weight, the action of swelling and softening the binder resin in the toner 16 becomes weak, and sufficient fixing strength may not be obtained. On the other hand, if it exceeds 80% by weight, the permeability to the toner image is reduced, and particularly when the amount of toner is large, only the toner on the surface of the toner image swells and softens, so that the toner inside the toner image is fixed to the recording medium. Insufficient toner may be removed.

  For the purpose of improving the wettability of the fixing solution 35 with respect to the toner 16 and improving the dispersibility of the auxiliary solvent in the fixing solution 35, for example, a surfactant or a dispersion aid can be added to the fixing solution 35. Examples of the surfactant include an anionic surfactant such as a higher alcohol sulfate such as lauryl sulfate sodium salt, a higher fatty acid metal salt such as sodium oleate, a fatty acid derivative sulfate, and a phosphate ester. , Quaternary ammonium salts, cationic surfactants such as heterocyclic amines, amino acid esters, zwitterionic surfactants such as amino acids, nonionic surfactants, polyoxyalkylene alkyl ethers, polyoxy An ethylene alkylamine etc. are mentioned. Examples of the dispersion aid include coupling agents such as diethylene glycol, triethylene glycol, polyethylene glycol, monobutyl ether, and diethylene glycol monomethyl ether.

  The fixing solution 35 is a low-viscosity aqueous solution, and quickly penetrates between the particles of the toner 16 and between the intermediate transfer belt 21 and the toner 16. The auxiliary solvent contained in the fixing solution 35 instantly swells the toner 16. Soften. Further, since the fixing liquid 35 is applied to the intermediate transfer belt 21 heated by the heating support roller 26, the toner image is dried in a short time after swelling and softening.

  According to the fixing liquid applying unit 5, the toner image on the intermediate transfer belt 21 is heated to almost the same temperature as the intermediate transfer belt 21 by the heating support roller 26, and at the same time, the fixing liquid 35 is applied by contact with the application roller 32. The toner 16 is swollen and softened. The toner image swollen and softened on the intermediate transfer belt 21 is carried to the transfer fixing unit 6 by the rotational drive of the intermediate transfer belt 21. Note that the heating by the heating support roller 26 also has a meaning of correcting the temperature drop of the toner image due to the application of the fixing liquid 35.

  The transfer fixing unit 6 includes a support roller 27 and a transfer fixing roller 44 that is in pressure contact with the support roller 27 via the intermediate transfer belt 21 and is rotatably driven in the axial direction. As the transfer and fixing roller 44, one commonly used in this field can be used. However, in this embodiment, the outer diameter is 30 mm, the core metal and the elastic layer provided on the surface of the core metal are 3 mm thick, and the hardness is 50 degrees. A laminate including a (JIS-A) silicone rubber layer and a PFA layer having a thickness of 20 μm as a surface layer provided on the surface of the silicone rubber layer is used. Further, the transfer fixing roller 44 is disposed so as to be in pressure contact with the support roller 27 via the intermediate transfer belt 21 with a linear pressure of 8 N / cm, for example, and no voltage is applied.

  The toner image on the intermediate transfer belt 21 is heated by the intermediate transfer medium heating unit 4 in the heating support roller 26 and applied with the fixing solution 35 by the fixing solution applying unit 5 to be in a swelling and softened state. By rotation, it is conveyed to the pressure contact portion between the support roller 27 and the transfer fixing roller 44, and in synchronization therewith, the recording medium 9 is fed from the recording medium supply means 7 described later, and the toner image on the intermediate transfer belt 21 is recorded. It is transferred and fixed to the surface of the medium 9 by pressing.

  When the fluororesin layer is formed on the surface of the intermediate transfer belt 21, since the adhesive force with the toner 16 is low, almost the entire toner image is transferred to the recording medium 9. Further, when the intermediate transfer belt 21 has a rubber layer, the surface layer is deformed following the unevenness of the recording medium 9, and the toner image can be brought into contact with the concave portion of the recording medium 9, so that a uniform transfer-fixed image is obtained. It is done.

  Further, since the intermediate transfer belt 21 is formed of a material that does not penetrate the fixing liquid 35 and further has a configuration in which the fixing liquid 35 is selectively applied only to the toner image, the penetration of the fixing liquid 35 into the recording medium 9 is prevented. Further, it is possible to prevent the recording medium 9 from being wrinkled and curled, and to reduce the amount of the fixing liquid 35 used.

  In addition, since the application roller 32 for applying the fixing liquid 35 and the recording medium 9 are not in direct contact with each other, when the recording medium 9 is paper, paper powder such as cellulose fiber is applied to the surface of the application roller 32. There is no clogging caused by adhesion. Therefore, nonuniform application of the fixing solution 35 due to clogging does not occur, and a high-quality image can be stably obtained over a long period of time.

  In the transfer and fixing unit 6, the toner image is pressed against the recording medium 9, and strongly enters the paper fiber. At the same time, the particles of the toner 16 are fused together, and the surface of the toner image becomes smooth. As a result, a high-quality color image excellent in color developability and surface gloss due to subtractive color mixing can be obtained.

  According to the transfer fixing unit 6, the toner image in a softened and / or swollen state is transferred and fixed to the recording medium 9 by pressing by the intermediate transfer medium heating unit 4 and the fixing liquid applying unit 5.

  The recording medium supply means 7 includes a recording medium cassette 50 that stores the recording medium 9, a pickup roller 51 that feeds the recording medium 9 one by one to the conveyance path P, and a toner image on the intermediate transfer belt 21 that is a transfer fixing roller. A pair of registration rollers 52a and 52b for feeding the recording medium 9 to the pressure contact portion in synchronism with being conveyed to the pressure contact portion between 44 and the support roller 27.

  According to the recording medium supply means 7, the recording medium 9 stored in the recording medium cassette 50 is fed to the conveyance path P one by one by the pickup roller 51, and further, the transfer fixing roller by the registration rollers 52 a and 52 b. Supplied to the press-contact portion between 44 and the support roller 27.

  The discharge unit 8 includes a conveyance belt 45, a drive roller 46, a tension roller 47, and a discharge roller 48.

  The conveyance belt 45 is an endless belt that is stretched between a driving roller 46 and a tension roller 47 to form a loop-shaped conveyance path. The recording medium 9 on which an image is formed by the transfer fixing unit 6 is discharged from the discharge roller. 48. As the transport belt 45, for example, a polyimide film having a thickness of 100 μm to which conductivity is imparted by adding a conductive agent and having a coating layer having a thickness of 10 μm made of PTFE on at least a recording medium transport surface 45a can be used. .

  The driving roller 46 is provided so as to be rotatable around an axis by a driving means (not shown). As the driving roller 46, for example, a hollow roller made of a metal such as aluminum can be used.

  The tension roller 47 applies a predetermined tension to the conveyor belt 45 so that the conveyor belt 45 does not loosen. The tension roller 47 includes, for example, a metal shaft body and a coating layer formed on the surface of the metal shaft body. Moreover, what consists only of metal shaft bodies may be sufficient. For example, stainless steel is used as the material of the metal shaft, and fluororubber is used as the material of the coating layer.

  The paper discharge roller 48 is a member that discharges the recording medium 9 conveyed by the conveyance belt 45 to a paper discharge tray 49 provided on the outer side surface of the image forming apparatus 1, and includes a pair of rollers provided so as to be in pressure contact with each other. Each roller is supported so as to be able to rotate in the respective axial directions.

  According to the image forming apparatus 1, the toner image formed on the intermediate transfer belt 21 that is a toner image carrier by the toner image forming unit 2 is heated by the intermediate transfer medium heating unit 4 and contacted by the fixing liquid applying unit 5. The fixing solution 35 is applied below to soften and / or swell the toner image, and this is transferred and fixed to the recording medium 9 by the transfer fixing means 6 to form an image.

  FIG. 5 is a cross-sectional view schematically showing the configuration of the main part of the image forming apparatus 55 according to the second embodiment of the present invention.

  The image forming apparatus 55 is similar to the image forming apparatus 1, and corresponding parts are not shown and described. In addition, among the portions shown in FIG. 5, portions corresponding to the image forming apparatus 1 are denoted by the same reference numerals and description thereof is omitted.

The image forming apparatus 55 includes a fixing liquid applying unit 56.
The fixing liquid applying unit 56 is supported by a driving unit (not shown) so as to be rotationally driven in the direction of an arrow 61, and an application roller 57 provided so as to be in pressure contact with the heating support roller 26 via the intermediate transfer belt 21. It is supported by the driving means so as to be rotatable in the direction of the arrow 63, and is supported so as to be rotatable in the direction of the arrow 66 by the fixing liquid supply roller 62 provided so as to be in pressure contact with the application roller 57 and a driving means (not shown). The fixing liquid regulating roller 64 provided so as to be in pressure contact with the application roller 57, the first seal member 65 provided so as to be in pressure contact with the surface of the fixing liquid regulating roller 64, and the surface of the application roller 57 are provided in pressure contact with each other. The second seal member 67, the application roller 57, the fixing liquid supply roller 62, the fixing liquid regulating roller 64, the first sealing member 65, and the second seal member. Accommodating the seal member 67 therein, further configured to include a casing 68 for storing the fixer 35 therein.

  The application roller 57 is a member that applies the fixing liquid 35 to the toner image on the toner image carrying surface 21 a of the intermediate transfer belt 21 in contact with the core roller 58 and a fixing liquid holding layer provided on the surface of the core metal 58. 59 and a porous layer 60 provided on the surface of the fixing solution holding layer 59.

  The fixing solution holding layer 59 receives and holds the fixing solution 35 supplied from the fixing solution supply roller 62 through the porous layer 60, and the holding amount of the fixing solution 35 in the porous layer 60 decreases. Then, the fixing liquid 35 is supplied to the porous layer 60. The fixing liquid holding layer 59 is made of a material having liquid absorbency and elasticity such as felt and continuous foam rubber. By providing the fixing liquid holding layer 59, the fixing liquid 35 can be sufficiently held as the entire coating roller 57 even if the fixing liquid 35 held by the porous layer 60 is small, so that the toner image on the intermediate transfer belt 21 is sufficient. An amount of fixer 35 can be applied. For this reason, the porous layer 60 can be formed with a thin porous film, as will be described later. That is, only the surface layer can be an expensive and fine porous film, and the inside can be constituted by a member such as inexpensive felt or continuous foam rubber.

  The porous layer 60 has a large number of fine holes therein, holds a part of the fixing solution 35 supplied from the fixing solution supply roller 62 in the holes, and fixes the remaining fixing solution 35. Supply to the liquid holding layer 59. The fixing liquid 35 held in the porous layer 60 is applied to the toner image on the intermediate transfer belt 21 at the nip portion between the coating roller 57 and the intermediate transfer belt 21. The contact angle of the porous layer 60 with respect to the fixing liquid 35 is preferably 80 degrees or less. If it exceeds 80 degrees, the fixing solution 35 is difficult to permeate the porous layer 60, and the fixing solution 35 cannot be supplied to the fixing solution holding layer 59, and the fixing solution 35 cannot be sufficiently applied to the toner image.

  In the present embodiment, a 3 mm thick felt layer (elastic modulus: 3 MPa) is laminated on the surface of the core metal 58 having a diameter of 14 mm as the fixing solution holding layer 59 to obtain a roller having an outer diameter of 20 mm. As the porous layer 60, a coating roller 57 formed by laminating a urethane resin porous film having a thickness of 0.1 mm is used. The pressing force of the application roller 57 against the intermediate transfer belt 21 is 0.5 N / cm in terms of linear pressure. The application roller 57 rotates at the same speed as the surface speed of the intermediate transfer belt 21.

  A part of the fixing liquid supply roller 62 is provided so as to be immersed in the fixing liquid 35 in the fixing liquid reservoir formed in the lower part of the casing 68, and adheres to the surface by rotation in the direction of the arrow 63. The fixing liquid 35 to be supplied is supplied to the surface of the application roller 57 at the pressure contact portion with the application roller 57. Thus, by adopting a configuration in which the fixing liquid 35 is supplied to the outer peripheral surface of the application roller 57, it is not necessary to hold and store the fixing liquid 35 in the application roller 57, and the application roller 57 can be downsized. For the fixing liquid supply roller 62, for example, a roller member in which a resin foam layer is laminated on the surface of a core metal is used. In the present embodiment, a sponge roller is used in which an open cell foam of urethane resin having a thickness of 5 mm is laminated on the surface of a core metal having a diameter of 10 mm.

  The fixing liquid regulating roller 64 is a roller member that adjusts the holding amount of the fixing liquid 35 in the porous layer 60 on the surface of the coating roller 57 to an appropriate amount. For example, a metal roller is used. In the present embodiment, a stainless steel roller having an outer diameter of 12 mm is used. By providing the fixing liquid regulating roller 64, the fixing liquid 35 is excessively adhered to the surface of the application roller 57, and the fixing liquid 35 forms a meniscus at the entrance of the nip portion between the application roller 57 and the intermediate transfer belt 21. Since the flow of the liquid 35 is prevented and the toner image is prevented from being disturbed, a high-quality and high-definition image can be obtained.

The first seal member 65 is a plate-like member provided so that one end abuts on the surface of the fixing liquid regulating roller 64 and the other end is supported by the casing 68, and the fixing liquid 35 on the surface of the fixing liquid regulating roller 64 is removed. to recover. Specifically, the fixing liquid 35 removed from the surface of the fixing liquid regulating roller 64 by the first seal member 65 travels through the first seal member 65 and falls into a fixing liquid reservoir provided at the lower part in the casing 68. To do. At the same time, a closed space is formed in the casing 68 by the linkage of the application roller 57, the fixing liquid regulating roller 64, and the second seal member 67 to prevent the fixing liquid 35 from being dried and leaking out of the casing 68. .
In the present embodiment, a urethane rubber sheet having a thickness of 40 μm is used.

  The second seal member 67 is a plate-like member provided so that one end is in pressure contact with the surface of the application roller 57 and the other end is supported by the casing 68, and collects the fixing liquid 35 on the surface of the application roller 57. The operation is the same as that of the first seal member 65. In the present embodiment, a urethane rubber sheet having a thickness of 40 μm is used.

  Similar to the casing 33, the casing 68 has an opening 68 b on a side surface 68 a that faces the intermediate transfer belt 21. In the opening 68 b, a part of the application roller 57 protrudes toward the outside of the casing 68 and presses against the heating support roller 26 via the intermediate transfer belt 21. A fixing liquid reservoir is formed in the lower part of the casing 68, and the fixing liquid 35 is stored. As with the casing 33, the casing 68 is provided with pivots 39a and 39b at the upper end thereof at both ends in the longitudinal direction. The pivots 39a and 39b are slidably inserted into U-shaped guide grooves 40a and 40b provided on the side surface of the open / close door 34 facing the casing 56. Further, the casing 68 is biased by the pressing spring 42 provided on the open / close door 34, whereby the application roller 57 is pressed against the heating support roller 26 via the intermediate transfer belt 21. In this case, the casing 68 is detachably provided and can be replaced when the fixing liquid 35 runs out.

  According to the fixing liquid application unit 56, the application roller 57 is supplied with the fixing liquid 35 from the fixing liquid supply roller 62 to the porous layer 60, and further the fixing liquid 35 in the porous layer 60 is fixed by the fixing liquid regulating roller 64. After the holding amount is adjusted, the fixing liquid 35 is applied to the toner image on the toner image carrying surface 21a of the intermediate transfer belt 21 in a contact state.

  In the present embodiment, the casing 68 is formed in a cartridge system, but is not limited thereto. For example, a fixing liquid tank that contains the fixing liquid 35 in the image forming apparatus 55 and a fixing liquid replenishing unit that replenishes the casing 68 with the fixing liquid 35 from the fixing liquid tank are provided, and the liquid of the fixing liquid 35 in the fixing liquid reservoir of the casing 68 is provided. A configuration may be employed in which the fixing solution 35 is replenished from the fixing solution tank in accordance with the consumption amount of the fixing solution 35 so that the surface height is constant. In this way, by providing the storage means for the fixing liquid 35 outside the application roller 57, it becomes possible to store a large amount of the fixing liquid 35 and reduce the number of times the fixing liquid 35 is replenished.

  Further, in the present embodiment, although it is supplied to the application roller 57 via the fixing liquid supply roller 62, a part of the application roller 57 is always immersed in the fixing liquid 35 without providing the fixing liquid supply roller 62. A configuration in which the fixing liquid 35 is directly supplied to the application roller 57 can be adopted. In this case, since the fixing liquid supply roller 62 is not provided, the configuration can be simplified and the manufacturing cost can be reduced.

  FIG. 6 is a cross-sectional view schematically showing a configuration of an image forming apparatus 70 according to the third embodiment of the present invention. FIG. 7 is an enlarged cross-sectional view showing a configuration of a main part of the image forming apparatus 70 shown in FIG.

  The image forming apparatus 70 is similar to the image forming apparatus 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  The image forming apparatus 70 is different from the image forming apparatus 1 in that an intermediate transfer unit 3a, a fixing liquid applying unit 71, a transfer fixing unit 72, a recording medium supply unit 7a, and a discharge unit 73 are different. More specifically, in the image forming apparatus 70, a fixing liquid applying unit 71 including a secondary transfer roller 74 is interposed between the intermediate transfer unit 3 a and the transfer fixing unit 72, and the toner is formed on the surface of the secondary transfer roller 74. The fixing liquid 35 is applied in contact while heating the image. In the image forming apparatus 70, the fixing liquid 35 is applied to the toner image on the secondary transfer roller 74 different from the intermediate transfer belt 21, so that the fixing liquid 35 does not adhere to the intermediate transfer belt 21. Further, since the secondary transfer roller 74 different from the intermediate transfer belt 21 is heated, the temperature of the intermediate transfer belt 21 does not rise. For this reason, the toner 16 can be prevented from being deteriorated during the toner image formation process due to a rise in temperature of each member constituting the toner image forming means 2 such as the photosensitive member 20 and adhesion of the fixing liquid 35 to each member. A high-quality image can be obtained stably over a period of time.

  The intermediate transfer unit 3a includes an intermediate transfer belt 21, intermediate transfer rollers 22y, 22m, 22c, and 22b, support rollers 26a and 28, and a belt cleaner 29. In the intermediate transfer means 3a, a support roller 26a having no heating means is disposed downstream of the intermediate transfer roller 22b in the rotational drive direction of the intermediate transfer belt 21 (the direction of the arrow 30). That is, the intermediate transfer unit 3a is configured not to heat the intermediate transfer belt 21 and the toner image, and therefore, a temperature sensor may or may not be provided. The intermediate transfer belt 21 is supported at two points by support rollers 26 a and 28 instead of the three-point support in the image forming apparatus 1. In this embodiment, the intermediate transfer belt 21 has a thickness of 20 μm made of a fluororesin composition in which PTFE and PFA are mixed at a weight ratio of 8: 2 on the surface of a polyimide substrate having a thickness of 100 μm. A laminated surface coat layer is used.

  The fixing liquid applying unit 71 is supported by a driving unit (not shown) so as to be rotationally driven in the direction of an arrow 75 and is provided so as to be in pressure contact with the support roller 26a via the intermediate transfer belt 21, and The application roller 76 is supported so as to be rotationally driven in the direction of an arrow 77 by a non-driving means and is pressed against the secondary transfer roller 74, and is supported so as to be rotationally driven in the direction of an arrow 79 by a driving means (not shown). And a fixing liquid supply roller 78 provided so as to be in pressure contact with the application roller 76 and a fixing liquid regulation provided so as to be rotationally driven in the direction of an arrow 81 by a driving means (not shown) and provided in pressure contact with the application roller 76. A roller 80, a coating roller 76, a fixing liquid supply roller 78, a casing 82 that accommodates the fixing liquid regulating roller 80, and a fixing liquid tank Including 90, and the fixing solution supply means 91, and a roller cleaner 87 disposed in pressure-contact with the secondary transfer roller 74.

The secondary transfer roller 74 applies the fixing liquid 35 to the toner image while heating the toner image transferred from the intermediate transfer belt 21, and swells and softens the toner image to an extent suitable for fixing to the recording medium 9. . The toner image on the intermediate transfer belt 21 is electrostatically transferred to the secondary transfer roller 74 by applying a transfer electric field between the secondary transfer roller 74 and the intermediate transfer belt 21, for example. The secondary transfer roller 74 includes, for example, a roller member in which a conductive elastic layer is formed on the surface of a core metal and a surface layer made of a material having excellent toner releasability such as a fluororesin is formed on the surface. Can be used. Inside the secondary transfer roller 74, an intermediate transfer medium heating unit 4 for heating the toner image is provided. For the intermediate transfer medium heating means 4, for example, a general heater such as a halogen lamp is used. The heating temperature of the secondary transfer roller 74 is preferably as low as possible from the viewpoint of energy saving. If the temperature of the secondary transfer roller 74 is 100 ° C. or less, loss of heat energy due to heat radiation can be reduced. Furthermore, since the amount of energy required for the temperature rise after startup is small and reaches a predetermined temperature in a short time, the warm-up time can be shortened. This eliminates the need for a heat retaining operation during the standby time, thereby realizing energy saving as the entire apparatus. In this embodiment, the secondary transfer roller 74 is configured to apply a voltage of +1 kV opposite to the charging potential of the toner 16 and to attract and transfer the toner 16 electrostatically. In this embodiment, a silicone rubber layer having a volume resistance of 10 ⁻⁸ to 10 ⁻⁹ Ω · cm and a thickness of 3 mm is provided on the surface of a core metal made of carbon steel and having a thickness of 1 mm, and a PFA having a thickness of 20 μm is further provided on the surface. A roller member having a laminated structure in which layers are provided and having an outer diameter of 30 mm is used as the secondary transfer roller 74.

  The application roller 76 brings the fixing liquid 35 into contact with the toner image on the surface of the secondary transfer roller 74. When the application roller 76 comes into contact with the surface of the secondary transfer roller 74, the fixing liquid 35 held on the surface of the application roller 76 and the surface layer oozes out, and the fixing liquid 35 is applied to the toner image. As the coating roller 76, a roller member in which a surface layer made of an elastic material that can be impregnated and held with the fixing solution 35 or has wettability with respect to the fixing solution 35 can be suitably used. Examples of the elastic material include metal materials such as aluminum, resin materials such as hydrophilic resins, and rubber materials such as ethylene propylene rubber and urethane rubber. The elastic modulus of the elastic material in the radial direction in the application roller 76 is preferably 1/10 or less, more preferably 1/100 or less, of the elastic modulus of the toner 16. Further, when the lyophilicity of the elastic material is expressed as a contact angle with respect to the fixing liquid 35, it is preferably 50 degrees or less. Such a lyophilic elastic material has a high affinity with the fixing liquid 35 and can hold the fixing liquid 35 as a thin layer on the surface thereof. Therefore, a small amount of the fixing liquid 35 can be applied over a wide range, and the consumption of the fixing liquid 35 can be reduced, and the toner image can be prevented from being disturbed by the excessive fixing liquid 35. In the present embodiment, a roller member having a diameter of 20 mm in which an elastic layer made of ethylene propylene rubber having a Young's modulus of 2 MPa is provided on the surface of a core metal having a diameter of 12 mm is used as the application roller 76.

  FIG. 8 is a cross-sectional view for explaining the application of the fixing liquid 35 to the toner image on the surface of the secondary transfer roller 74 by the application roller 76. Since the surface of the application roller 76 is formed of an elastic material, the surface of the application roller 76 is deformed following the fine unevenness of the surface of the secondary transfer roller 74 and the unevenness of the toner image. The toner image is uniformly pressed through the thin layer. At this time, since the portion where the toner image does not exist (non-image portion) is the smooth surface of the secondary transfer roller 74, the surface area per macroscopic area is small, and thus the application of the fixing liquid 35 from the application roller 76. The amount is small. On the other hand, in the portion where the toner image exists (image portion), the toner 16 that is powder gathers to form a toner image, so that the surface area per macroscopic area is larger than that of the non-image portion. For this reason, a larger amount of the fixing liquid 35 is applied to the image portion than to the non-image portion. In particular, a portion having a large amount of toner per area obtained by laminating a plurality of single color toner images such as a color toner image has a larger surface area per area, so that the amount of fixing liquid 35 applied is further increased. With such characteristics, it is possible to selectively apply the fixing liquid 35 to the image portion by changing the application amount of the fixing liquid 35 between the image portion and the non-image portion. In the image portion, the fixing liquid 35 is uniformly applied to the entire toner image regardless of the partial height of the toner image due to a partial change in the toner amount. Accordingly, the fixing liquid 35 is also applied to a toner image such as a color toner image in which the toner amount partially changes greatly, or a toner image having a portion with a small amount of toner surrounded by a portion with a large amount of toner. A uniform image can be applied to the entire surface, and a high-quality fixed image can be obtained.

  The application roller 76 is preferably in pressure contact with the secondary transfer roller 74 with a pressing force of 0.05 to 1.0 N / cm (linear pressure). If it is less than 0.05 N / cm, the contact state between the application roller 76 and the secondary transfer roller 74 becomes insufficient, and the fixer 35 may not be uniformly applied to the toner image on the secondary transfer roller 74. Furthermore, the elastic deformation of the coating roller 76 that follows the fine unevenness on the surface of the secondary transfer roller 74 and the unevenness of the toner image becomes insufficient, and there is a possibility that a sufficient amount of the fixing liquid 35 cannot be applied to the toner image in the recess. . As a result, uneven application of the fixing solution 35, uneven fixing, gloss unevenness, and color unevenness may occur. On the other hand, when it exceeds 1.0 N / cm, the fixing liquid 35 on the surface of the application roller 76 is transferred between the application roller 76 and the secondary transfer roller 74 in a state where the application roller 76 and the secondary transfer roller 74 rotate under pressure. The nip may not pass. If it cannot pass, the fixing solution 35 is squeezed at the nip portion, the fixing solution 35 forms a meniscus at the entrance of the nip portion, and the excess fixing solution 35 returns to the upstream side in the rotation direction of the coating roller 76 so that the fixing solution 35 is The toner flows violently and the toner image is disturbed. In the present embodiment, the pressing force of the application roller 76 against the secondary transfer roller 74 is 0.5 N / cm as a linear pressure.

  The application roller 76 is rotatably supported by a bearing provided on the casing 63 with a rotation shaft integrated with a flange (not shown) provided at both ends of the core metal.

  The application roller 76 carries the fixing liquid 35 on its surface and is pressed against the secondary transfer roller 74, and is rotated at a speed equal to the surface speed of the secondary transfer roller 74 by a driving unit (not shown).

  The fixing liquid supply roller 78 supplies the fixing liquid 35 held on the surface of the fixing liquid supply roller 78 to the application roller 76 when being pressed against the application roller 76. A part of the fixing liquid supply roller 78 is provided so as to be immersed in the fixing liquid 35 stored in the fixing liquid reservoir 84 provided in the lower part of the casing 82, and the surface thereof is driven by rotation in the direction of the arrow 77. The fixing solution 35 is adhered to the coating roller 35, and the fixing solution 35 is supplied to the application roller 76. For the fixing liquid supply roller 78, for example, a roller member in which a porous layer is provided on the surface of a core metal can be used. In the present embodiment, a sponge roller is used in which a core layer having a diameter of 10 mm is formed with a porous layer having a thickness of 5 mm made of urethane open cell foam.

  The fixing liquid regulating roller 80 is a roller member that adjusts the amount of fixing liquid on the surface of the application roller 76 to an appropriate amount. A thin layer of the fixing liquid 35 having a uniform layer thickness is formed on the application roller 76 by the fixing liquid regulating roller 80. For the fixing liquid regulating roller 80, for example, a metal hollow roller is used. In the present embodiment, a stainless steel roller having an outer diameter of 12 mm is used.

  The casing 82 has an opening 82 b at a portion of the side surface 82 a facing the intermediate transfer belt 21 and the secondary transfer roller 75 in the vicinity of the secondary transfer roller 74, and the opening 82 b faces the outside of the casing 82. The fixing liquid supply roller 78 is disposed so that a part thereof protrudes. As a result, the fixing liquid supply roller 78 and the secondary transfer roller 74 can be pressed against each other.

  A fixing liquid reservoir 84 that stores the fixing liquid 35 is provided in the lower part of the casing 82. The height of the fixing liquid surface of the fixing liquid reservoir 84 is kept constant within a range where, for example, a part of the fixing liquid supply roller 78 is immersed in the fixing liquid 35 and the application roller 76 is not immersed in the fixing liquid 35. In order to keep the liquid level of the fixing solution 35 constant, the fixing solution 35 is supplied from the fixing solution tank 90 storing and storing the fixing solution 35 via the fixing solution supply means 91 according to the consumption amount of the fixing solution 35. Is supplied.

  In the upper part of the fixing liquid reservoir 84, the application roller 76, the fixing liquid supply roller 78, and the fixing liquid regulating roller 80 are integrally arranged. At the end opposite to the end, a pivot 83 is provided in the longitudinal direction of the casing 82 ( (In a direction perpendicular to the paper surface) is provided so as to penetrate the casing 82, and is rotatably supported by the main body of the image forming apparatus 1. As a result, the casing 82 is supported so as to be rotatable about the pivot 83. Furthermore, a pressing spring 85 that is supported by the main body of the image forming apparatus 1 and presses the casing 82 is provided on the bottom 82c of the casing 82 in a direction opposite to the diagonal line with respect to the installation position of the pivot 83. By the action of the pivot 83 and the pressing spring 85, the application roller 76 is pressed against the secondary transfer roller 74 with a predetermined low pressing force. For the pressing spring 85, for example, a coil spring, a leaf spring, a torsion spring or the like can be used.

  The fixer tank 90 stores and stores the fixer 35. The fixer tank 90 can be formed in a cartridge type, for example. When the fixing liquid 35 in the fixing liquid tank 90 runs out, a sensor (not shown) detects it and stores the detection result in a CPU (not shown). The CPU sends a control signal to an operation panel (not shown) according to the detection result, and displays on the operation panel that it is time to replace the fixing liquid tank 90.

  The fixer supply unit 91 supplies the fixer 35 in the fixer tank 90 to the fixer reservoir 84 of the casing 82 by a driving unit (not shown). The height of the fixing liquid 35 in the fixing liquid reservoir 84 is detected by a sensor (not shown) provided in the casing 82, and the detection result is stored in a CPU (not shown). The CPU sends a control signal to the driving means (not shown) according to the detection result, and sends the fixing liquid 35 to the fixing liquid reservoir 84 according to the consumption status of the fixing liquid 35 in the fixing liquid reservoir 84.

  In order to detect the surface temperature of the secondary transfer roller 74, the temperature sensor 86 is upstream of the nip portion between the secondary transfer roller 74 and the support roller 26a in the rotational direction of the secondary transfer roller 74, that is, in the direction of the arrow 75. The secondary transfer roller 74 is provided in contact with or close to the secondary transfer roller 74. The detection result by the temperature sensor 86 is stored in a CPU (not shown) that controls the entire operation of the image forming apparatus 1, and the CPU sends a control signal to the intermediate transfer medium heating unit 4 based on the stored detection result to perform secondary operation. The heating of the transfer roller 74 is controlled, and the surface of the secondary transfer roller 74 is heated to a uniform temperature over the entire circumference. In the present embodiment, the surface temperature of the secondary transfer roller 74 is heated and held at 65 ° C., which is higher than the glass transition point (60 ° C.) of the binder resin contained in the toner 16. As a result, the binder resin is softened, and the adhesion between the surface of the secondary transfer roller 74 and the toner particles 16 is appropriately increased. Therefore, it is possible to prevent the toner 16 from being offset to the application roller 76 or the toner image from being disturbed when the application liquid 16 is contacted with the fixing liquid 35.

  The roller cleaner 87 removes the toner 16 and / or the fixing liquid 35 remaining on the secondary transfer roller 74 after the toner image on the secondary transfer roller 74 is transferred to the recording medium 9 by a transfer fixing unit 72 described later. A cleaning blade 87a that is pressed against the secondary transfer roller 74 by a pressure unit (not shown) and scrapes off the residual toner 16 and the like on the secondary transfer roller 74; a toner 16 that is scraped off by the cleaning blade 87a; And a storage container 87b for storing 35 and the like.

  According to the fixing liquid applying unit 71, the toner image formed on the toner image carrying surface 21a of the intermediate transfer belt 21 in the toner image forming unit 2 is electrostatically applied to the surface of the secondary transfer roller 74 by applying a transfer voltage. Transcript. The toner image on the secondary transfer roller 74 is subjected to uniform heating by the intermediate transfer medium heating means 4 built in the secondary transfer roller 74, and further receives the fixing liquid 35 by contact with the coating roller 76, and is recorded. Swells and softens to an extent suitable for fixing to the medium 9. The toner image is conveyed to the transfer fixing unit 72 by the rotational drive of the secondary transfer roller 74. After the transfer of the toner image onto the recording medium 9 by the transfer and fixing means 72, the toner 16 and the fixing liquid 35 remaining on the secondary transfer roller 74 are removed by the roller cleaner 87, and the surface of the secondary transfer roller 74 is cleaned. The toner image is again transferred from the intermediate transfer medium 21. This process is repeated.

  As in the fixing liquid applying means 71, heating is performed from one surface in the thickness direction of the toner image, and further, the fixing liquid 35 is applied from the other surface, so that it is suitable for transfer and fixing to the recording medium 9. The toner image is appropriately swollen and softened, and an image having a higher fixing strength can be formed than when only one of heating and applying the fixing liquid 35 is performed.

  The transfer fixing unit 72 includes a secondary transfer roller 74 and a transfer fixing roller 44 that is rotatably supported by a driving unit (not shown) and is provided in pressure contact with the secondary transfer roller 74.

  In this embodiment, as the transfer fixing roller 44, an elastic layer having a thickness of 2 mm made of silicone rubber having a hardness of 50 degrees (JIS-A) is formed on the surface of the core metal, and further, a thickness made of PFA is formed on the surface of the elastic layer. A roller member having an outer diameter of 40 mm on which a surface layer of 20 μm is formed is used. In this embodiment, the pressing force of the transfer fixing roller 44 against the secondary transfer roller 74 is 10 N / cm.

  According to the transfer fixing unit 72, a toner image heated on the surface of the secondary transfer roller 74 and being in an appropriate swollen / softened state upon application of the fixing liquid 35 is subjected to secondary transfer by rotational driving of the secondary transfer roller 74. It is conveyed to a pressure contact portion between the roller 74 and the transfer fixing roller 44. In synchronization with this, the recording medium 9 is conveyed from the recording medium supply means 7, and the toner image and the recording medium 9 are overlapped at the press contact portion and pressed (pressed) by the transfer fixing roller 44, and the toner image is applied to the recording medium 9. Transfer fixed.

  The recording medium 9 on which the toner image is transferred and fixed is transported by a transport roller 92 in a discharge unit 73, further discharged to the outside of the image forming apparatus 70 by a paper discharge roller 93, and discharged from the upper surface of the image forming apparatus 70. Accumulated in the tray 94.

  In the present embodiment, the heating temperature of the secondary transfer roller 74 is 65 ° C., but the heating temperature can be changed as appropriate according to the components contained in the toner 16. For example, when the toner 16 includes a wax having a softening point of 70 ° C., the heating temperature is set to 75 ° C., and the surface temperature of the secondary transfer roller 74 is set to be higher than the softening point of the wax in the toner. Good.

  With this configuration, the wax in the toner 16 is softened immediately before the fixing solution 35 is applied, and the adhesion between the toners 16 and between the toner 16 and the secondary transfer roller 74 is further increased. It is possible to further prevent disturbance of the toner image at the time, adhesion of the toner 16 to the application roller 76, and the like. Further, since the amount of heat to compensate for the temperature drop of the secondary transfer roller 74 and the toner image due to the application of the fixing liquid 35 can be supplied on the spot, the temperature drop of the secondary transfer roller 74, the toner image and the fixing liquid 35 immediately after the application is prevented. The fixing solution 35 can be quickly diffused and penetrated. Furthermore, the wax in the toner particles is softened, so that the fixing liquid 35 penetrates into the toner particles. As a result, the toner 16 is swollen and softened instantaneously over a wide range. As a result, when the toner image is pressed against the recording medium 9 by the transfer fixing means 72 described later, sufficient fixing strength to the recording medium 9 can be obtained. Furthermore, since the temperature of the fixing solution 35 after application is increased, the fixing solution 35 can be dried in a short time after application. Thereby, the throughput which is the number of output sheets per unit time of the image forming apparatus can be further improved. In addition, since the toner 16 instantaneously swells and softens, the time from the application of the fixing liquid 35 to the transfer to the recording medium 9 can be shortened, so that the application position of the fixing liquid 35 and the transfer position to the recording medium 9 can be reduced. Can be set to be short, and the apparatus can be reduced in size.

  FIG. 9 is a cross-sectional view schematically showing a configuration of a main part of an image forming apparatus 95 according to the fourth embodiment of the present invention. The image forming apparatus 95 is similar to the image forming apparatus 70, and corresponding parts are not shown and described. Also, of the portions shown in FIG. 9, the portions corresponding to the image forming apparatus 70 are given the same reference numerals, and the description thereof is omitted.

The image forming apparatus 95 includes a fixing liquid applying unit 96.
The fixing liquid applying unit 96 includes a secondary transfer roller 74, a fixing liquid atomizing unit 100, a temperature sensor 86, and a roller cleaner 87.

  The fixing liquid atomizing unit 100 is provided so that the opening 107 faces the surface of the secondary transfer roller 74, and is provided in the lower part of the main body 101 and the fixing liquid atomizing unit main body 101 made of a conductive material. , A fixing solution reservoir 102 for storing the fixing solution 35, an ultrasonic vibrator 103 provided so as to be in contact with or immersed in the fixing solution 35 stored in the fixing solution storage unit 102, and a mesh for atomizing the fixing solution 35. 104, a spray duct 105 that recirculates the atomized droplets of the fixing liquid 35, a fan 106 that generates an air stream of the atomized droplets of the fixing liquid 35 in the spray duct 105, and an atomized droplet of the fixing liquid 35. An opening 107 that discharges outward, an internal space 108 for forming the spray duct 105, and a power source 109 that applies a voltage to the main body 101 are configured. Further, although not shown, a corona charger and a fan may be provided in the vicinity of the opening 107 in the internal space 108 so that the atomized droplets of the fixing liquid 35 can be discharged from the opening 107.

  According to the fixer atomizing unit 100, a high frequency (2.4 MHz high frequency in the present embodiment) is applied to the fixer 35 stored in the fixer storage unit 102 by the ultrasonic vibrator 103, and the vibration is generated. The fixing liquid 35 becomes droplets of about 3 μm and scatters in the spray duct 105. Among the droplets, there are also large droplets having a diameter of 1 mm or more. These droplets are guided by the fan 106 to the mesh 104 (in this embodiment, a stainless steel mesh having a pitch of 0.5 mm), and pass through the mesh 104 to form fine mist droplets. The mist droplets ride on the airflow generated by the fan 106 and circulate in the spray duct 105 to reach the vicinity of the opening 107. Here, a potential difference is generated in the main body 101 with respect to the secondary transfer roller 74 by the power source 109, and the mist droplets are charged to a positive polarity that is opposite to the charging polarity of the toner image on the secondary transfer roller 74. A voltage is applied as shown. In this embodiment, a voltage is applied so that a potential difference of + 250V is generated. Thus, since the mist-like droplet is charged with a polarity opposite to that of the toner image, and there is a potential difference of +250 V between the opening 107 and the secondary transfer roller 74, the mist-like droplet is opened by the electric field force. To the secondary transfer roller 74. The toner adheres to a region including the toner image on the secondary transfer roller 74. Note that the amount of the fixing liquid 35 attached to the non-image portion can be controlled by appropriately adjusting the potential difference between the secondary transfer roller 74 and the fixing liquid atomizing unit 78. The potential difference can be appropriately adjusted according to characteristics such as the thickness and water absorption of the recording medium 9.

  On the other hand, since the toner that forms the toner image is negatively charged, the mist droplets that are charged positively are attracted. For this reason, since the amount of the fixing liquid 35 applied to the image portion where the toner image exists is larger than that of the non-image portion, the fixing liquid 35 can be applied almost selectively to the image portion, and the fixing liquid 35 can be applied. The amount of use of 35 can be reduced.

  The droplet diameter of the atomized droplet of the fixing liquid 35 is preferably set to be equal to or smaller than the average particle diameter of the toner 16. Thereby, it is possible to prevent the toner image from being disturbed due to the flow or aggregation of the toner at the moment when the atomized droplets of the fixing liquid 35 adhere to the toner image. Further, when the droplet diameter is small, the traveling path of the droplet can be appropriately changed by electric field force, electric charge and the like. Here, the droplet diameter can be adjusted by appropriately adjusting the high-frequency output of the ultrasonic transducer 103, the pitch of the mesh 104, and the like. When the droplets of the fixing liquid 35 are large, the surrounding toner is agglomerated at the moment when the droplets adhere to the toner image, so that minute unevenness occurs in the uniform toner image. When the diameter of the droplets of the atomized fixing liquid 35 is larger than the average particle diameter of the toner, the amount of toner to be agglomerated increases so that the unevenness can be confirmed visually. This is considered to be defined by the relative relationship between the amount of liquid contained in the toner particles and the droplets. When the liquid amount is large, the toner particles are pushed away, but when the toner particles are relatively large, it is considered that the toner particles are not pushed away. That is, by setting the diameter of the fine droplets of the fixing liquid formed by the atomizing means to be equal to or less than the average particle diameter of the toner, it is possible to suppress aggregation of the toner particles when the fixing droplets adhere to the toner image. A high-quality fixed image can be obtained.

  In the fixer storage unit 102 of the fixer atomizing unit 100, the fixer 35 is supplied from the fixer tank 90 via the fixer supply means 91 so that the amount of the fixer 35 is constant according to the consumption state of the fixer 35. 35 is replenished.

  In the present embodiment, the ultrasonic vibrator 103 is used to atomize the fixing liquid 35, but the invention is not limited to this. For example, a method in which the fixing liquid 35 is sprayed by a high-speed air flow (for example, an air flow), etc. A well-known atomization method may be adopted.

  In the present embodiment, the atomized droplets of the fixing liquid 35 are applied to the heated toner image on the secondary transfer roller 74, but the present invention is not limited thereto. An atomized droplet of the fixing liquid 35 may be applied.

  According to the fixing liquid applying unit 96, the toner image on the intermediate transfer belt 21 is transferred to the secondary transfer roller 74, and the fixing liquid 35 is applied to the toner image as atomized droplets while being heated on the secondary transfer roller 74. Thus, the toner 16 is softened and / or swelled.

  In the image forming apparatus of the present invention, the fixing solution 35 that swells and softens the toner is used. However, the fixing solution 35 is not limited thereto, and a fixing solution containing a known adhesive component, adhesive component, or the like can also be used. Specific examples of the adhesive component include, for example, a rubber-based adhesive mainly composed of a polymer elastomer such as chloroprene rubber, nitrile rubber, and SBR rubber, vinyl acetate, ethylene-vinyl acetate copolymer (EVA), acrylic resin, and the like. And an emulsion adhesive obtained by dispersing a hydrophilic synthetic resin in water. By adopting this configuration, the adhesive force between the toner and the recording medium 9 is applied not only by the swelling / softening of the toner but also by an adhesive component or an adhesive component. Fixing strength can be improved. Furthermore, as the fixing solution, any conventionally used and known ones can be used.

  In the image forming apparatus of the present invention, materials, layer structures, dimensions, and the like used for the intermediate transfer belt, the conveyance belt, each roller, and the like are not limited to those described above, and are commonly used in the field of electrophotographic image formation. Those can be used as they are or after being appropriately changed.

  Further, an endless member such as a belt can be used instead of the roller. Further, although the intermediate transfer belt, the conveyance belt, and the like are endless members, they may be in the form of rollers.

  The image forming apparatus according to the present invention is shown as a tandem color image forming apparatus in each embodiment, but is not limited thereto. For example, each time the intermediate transfer belt rotates once, one color image is superimposed. A so-called four-rotation color image forming apparatus can also be used. Further, the present invention is not limited to a color image forming apparatus, and may be a single color image forming apparatus.

  Such an image forming apparatus of the present invention is used as, for example, a copying machine, a printer, a facsimile machine, or a combination of two or more of these.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view illustrating a configuration of a main part of the image forming apparatus illustrated in FIG. 1. FIG. 2 is an enlarged cross-sectional view illustrating a configuration of a main part of the image forming apparatus illustrated in FIG. 1. 6 is a diagram illustrating application of a fixing liquid to a toner image on an intermediate transfer medium by an application member. It is sectional drawing which shows schematically the structure of the principal part in the image forming apparatus which is the 2nd Embodiment of this invention. It is sectional drawing which shows schematically the structure of the image forming apparatus which is 3rd Embodiment of this invention. FIG. 7 is an enlarged cross-sectional view illustrating a configuration of a main part of the image forming apparatus illustrated in FIG. 6. FIG. 6 is a cross-sectional view illustrating application of a fixing liquid to a toner image on an intermediate transfer medium by an application member. It is sectional drawing which shows schematically the structure of the principal part in the image forming apparatus which is 4th Embodiment of this invention.

Explanation of symbols

1, 55, 70, 95 Image forming apparatus 2 Toner image forming means 3, 3a Intermediate transfer means 4 Intermediate transfer medium heating means 5, 56, 71, 96 Fixing liquid applying means 6, 72 Transfer fixing means 7, 7a Recording medium supply Means 8, 73 Ejecting means 9 Recording medium 10y, 10m, 10c, 10b Image forming unit 11y, 11m, 11c, 11b Photosensitive drum 12y, 12m, 12c, 12b Charging roller 13 Optical scanning unit 14y, 14m, 14c, 14b Development Device 15y, 15m, 15c, 15b Drum cleaner 16 Toner 17y, 17m, 17c, 17b Developing roller 18y, 18m, 18c, 18b Developing blade 19y, 19m, 19c, 19b Toner storage container 20a, 20b Stirring roller 21 Intermediate transfer belt 22y 22m, 22c, 22b Intermediate transfer Roller 26, 27, 28 Support roller 29 Belt cleaner 31, 86 Temperature sensor 32, 57, 76 Application roller 35 Fixing liquid 44 Transfer fixing roller 45 Conveying belt 46 Drive roller 47 Tension roller 48, 93 Paper discharge roller 49, 94 Paper tray 50 Recording medium cassette 51 Pickup roller 52a, 52b Registration roller 62, 78 Fixing liquid supply roller 64, 80 Fixing liquid regulating roller 74 Secondary transfer roller 87 Roller cleaner 91 Fixing liquid supply means 92 Conveying roller 100 Fixing liquid atomizing unit

Claims (14)

A toner image forming means for forming a toner image made of a chargeable toner containing a binder resin, an intermediate transfer means including an intermediate transfer medium having a smooth surface and carrying a toner image on the surface and rotationally driven; and toner A fixing solution applying unit that applies a fixing solution having an action of softening an image to a toner image on an intermediate transfer medium in contact; and a transfer unit that transfers the softened toner image applied with the fixing solution to a recording medium. In the image forming apparatus,
Fixing liquid application means
An application member that is elastically deformable at least on the surface, has a porous layer that holds the fixing solution, and is provided so as to be rotatable around its axis;
An image forming apparatus, wherein a fixing liquid held in a porous layer of an application member is applied in contact with the toner image carrying surface while rotating the application member in pressure contact with the toner image carrying surface of the intermediate transfer medium. Application member
A porous layer;
2. The image forming apparatus according to claim 1, further comprising a fixing solution holding layer which is provided as an inner layer of the porous layer and has a thickness larger than that of the porous layer and capable of penetrating and holding the fixing solution. Application member
A fixing solution storage layer for holding and storing the fixing solution;
A penetration control layer made of a material provided on the surface of the fixing solution storage layer so as to be elastically deformable and capable of penetrating and holding the fixing solution;
3. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a porous layer provided on the surface of the permeation control layer so as to be elastically deformable and holding a fixing solution, and is formed in a roller shape.   The image forming apparatus according to claim 1, wherein the porous layer has a pore diameter of 0.1 μm to 2 μm, a porosity of 60% to 90%, and a layer thickness of 10 μm to 200 μm. .   5. The image forming apparatus according to claim 4, wherein the contact angle of the porous layer with respect to the fixing solution is smaller than the contact angle with respect to the fixing solution on the surface of the intermediate transfer medium and is larger than the contact angle with respect to the fixing solution on the toner surface. . The fixing solution applying means further includes a pressure contact means for pressing the application member against the intermediate transfer medium,
The pressure contact means presses the coating member against the intermediate transfer medium with a pressing force that allows the fixing liquid held in the porous layer of the coating member to pass through the pressure contact portion between the coating member and the toner image carrying surface of the intermediate transfer medium. The image forming apparatus according to claim 1, wherein:   3. The image forming apparatus according to claim 1, wherein the pressing force with which the pressing member presses the coating member against the intermediate transfer medium is 0.05 N / cm to 1.0 N / cm in terms of linear pressure. Fixing liquid application means
Along with the application member
Furthermore, a fixing solution storage means for storing a fixing solution;
Fixing solution supply means for supplying the fixing solution stored in the fixing solution storage means to the outer peripheral surface of the coating member;
8. A fixing liquid regulating means that adjusts the amount of the fixing liquid that is provided in contact with the outer peripheral surface of the coating member and that is held in the porous layer of the coating member. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, wherein the elastic modulus of the binder resin contained in the toner is larger than the elastic modulus of the application member surface. A toner image forming unit that forms a toner image including a chargeable toner including a binder resin, and an intermediate transfer medium that has a smooth surface, carries the toner image on the surface, and is rotated at a constant potential. Intermediate transfer means, fixing liquid applying means for applying a non-contact fixing solution having a function of softening the toner image to the toner image on the intermediate transfer medium, and a softened toner image applied with the fixing liquid on the recording medium In an image forming apparatus including a transfer means for transferring,
Fixing liquid application means
Fixing liquid atomizing means for making the fixing liquid into mist-like droplets;
Fixing liquid charging means for charging the fixing liquid droplets formed by the fixing liquid atomizing means to a polarity opposite to the charging polarity of the toner;
An image forming apparatus comprising: a droplet supply unit that supplies droplets of a fixing solution in a charged state to a toner image on an intermediate transfer medium and the vicinity thereof. Fixer atomizing means
The image forming apparatus according to claim 10, wherein droplets of the fixing liquid having a diameter equal to or smaller than the average particle diameter of the toner are formed. Including an intermediate transfer medium heating means provided upstream of the fixing liquid applying means in the rotational drive direction of the intermediate transfer medium,
The intermediate transfer medium heating means
The image forming apparatus according to claim 1, wherein the toner image on the intermediate transfer medium is heated to a temperature equal to or higher than a glass transition point of a binder resin contained in the toner. Including an intermediate transfer medium heating means provided upstream of the fixing liquid applying means in the rotational drive direction of the intermediate transfer medium,
The intermediate transfer medium heating means
2. A toner comprising a binder resin and a wax containing a wax having a softening point lower than that of the binder resin, and heating a toner image carried on the intermediate transfer medium to a temperature not lower than the softening point of the wax. The image forming apparatus according to any one of ˜11.   A toner image is formed by a toner image forming unit that forms a toner image composed of a plurality of chargeable toners including a binder resin, and a color image is formed by subtractive color mixing in which the toner images of a plurality of colors are superimposed on an intermediate transfer medium. The image forming apparatus according to claim 1.

Images