JP2008276037A - Image fixing unit and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the possibility of the recording material being curled by applying an appropriate amount of fixing solution without disturbing the toner images on the recording material in a fixing unit using a toner fixing liquid consisting of a softener and a solvent dissolving or dispersing it and fixing the unfixed toner on the recording material by applying this fixing liquid to soften it with the softener. <P>SOLUTION: This image fixing unit has a sprayer 33 to spray the toner fixing liquid droplets with a diameter of 15 μm or smaller, a droplet static charger 34 such as an ionizer to charge the droplets sprayed by the sprayer in the same polarity as the unfixed toner 42, a medium carrier 35 to carry a paper sheet (recording material) 17 having unfixed toner through the atmosphere of the fixing liquid droplets charged by the droplet static charger, and a recording material static charger 36 to charge the paper sheet carried by the medium carrier in the polarity reverse to the unfixed toner and the fixing liquid droplets. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof. In particular, charging, writing, and developing are performed to form a toner image on the image carrier, and the toner image is transferred directly or indirectly through an intermediate transfer member, and the transferred toner image is fixed by a fixing device. The present invention relates to an electrophotographic image forming apparatus that records an image on a recording material such as paper. The present invention also relates to a fixing device that fixes unfixed toner after toner image transfer onto a recording material in such an image forming apparatus. In particular, the present invention relates to a fixing device that fixes a toner image on a recording material by applying a fixing liquid while conveying the recording material.

  Image forming apparatuses such as printers, facsimiles, and copiers record images including characters, symbols, and the like on recording materials such as paper, cloth, and OHP films based on image information. There are various types of such image forming apparatuses. Among them, the electrophotographic image forming apparatus can record high-definition images on plain paper at a high speed. Widely used.

  In an electrophotographic image forming apparatus, a charging device, a writing device, a developing device, a transfer device, a cleaning device, a charge eliminating device, and the like are arranged around a drum-shaped or belt-shaped image bearing member, and charged with the rotation of the image bearing member. After that, writing is performed to form an electrostatic latent image on the surface of the image carrier, and the electrostatic latent image is developed by attaching toner to form a toner image on the image carrier. Is transferred directly or indirectly through an intermediate transfer member such as a belt to record an image on a recording material. The recording material after transfer of the toner image is guided to a fixing device, and the unfixed toner is fixed on the recording material. On the other hand, the surface of the image carrier after image transfer is cleaned by a cleaning device and discharged to prepare for image formation again. It was.

  In this type of electrophotographic image forming apparatus, since the fixing speed is fast and the fixed image quality is good as a fixing device, the toner on the recording material is heated by a heating element such as a halogen heater or a ceramic heater. A thermal fixing method in which the toner is fixed on a recording material by being melted and pressurized is widely used. However, in an image forming apparatus using such a heat fixing type fixing device, a large amount of electric power is consumed because the toner is heated. Adoption of a low power consumption fixing device is strongly desired. Further, the fixing device of the thermal fixing type has a problem that the startup time until the start of fixing is long.

  In view of this, some conventional fixing devices adopt a vapor fixing method as described in, for example, Patent Document 1 below. In the vapor fixing method, a recording paper on which unfixed toner is placed is inserted into a solvent vapor that dissolves toner, and this method certainly consumes less energy than the thermal method. However, there was a concern that the liquid had an odor or harmed the human body, and it was not widely spread. However, recently, liquids that can swell and dissolve odorlessly and harmlessly and fix the toner have been developed, and the fixing method using the liquid has been reviewed again.

  In a fixing device that uses an odorless and harmless fixing solution, for example, as described in Patent Document 2 below, a fixing device that includes a softening material that softens toner and a solvent that disperses or dissolves the softening material. Unfixed toner is recorded by spraying or dripping the fixer, or applying it with a roller, etc. and adhering to the recording material after image transfer, softening the toner, and then drying the fixer. A method of fixing on a material has been proposed.

  Since this type of fixing device does not require toner heat treatment unlike the case of the thermal fixing method, it can be said to be a fixing method suitable for energy saving measures with low power consumption. On the other hand, there are various problems that arise when a large amount of fixing solution is applied to the recording material.

  That is, 1) When water is used as the solvent of the fixing solution, this large amount of water swells the paper fibers as the recording material. As a result, the melted toner reaches the back surface of the recording material, causing image back-through and degrading image quality. 2) Absorption of a large amount of moisture causes wrinkles and curls in the recording material, which significantly impairs stable and high-speed recording material conveyance as an image forming apparatus. 3) If this large amount of water is removed by evaporation using a drying device, power consumption comparable to that of the thermal fixing method is required. 4) In order to use a large amount of fixing solution, it is necessary to change the fixing solution frequently. If a large-capacity fixing solution tank is used, the size of the fixing device increases, and the size of the image forming apparatus decreases. There were problems such as obstructing.

  For this reason, in order to solve such problems 1) to 4), among the conventional fixing methods, for example, as described in Patent Documents 3 and 6 below, an ink jet method is used, and a recording material is used. It has been proposed to apply the fixing liquid only to the toner image based on the positional information of the upper toner image or the positional information of the toner image on the image carrier before being transferred to the recording material. However, this method has been difficult to realize because the application along the image data must be accurately performed in units of toner.

  Further, in the fixing device described in Patent Document 2, when the droplet hits the toner violently, the toner that is only electrostatically adhered to the recording material is moved by force to move the toner on the recording material. Problems that disturb the image occur. Therefore, in the conventional fixing device, as in the transfer fixing device shown in Patent Documents 4 and 5 below, the fixing solution formed into droplets is charged and attached to the secondary transfer roller, and the fixing solution is applied by the Coulomb force. A technique has been proposed in which the toner is attached to the toner on the next transfer roller and then transferred to a recording material together with fixing droplets to be fixed. When this method is employed, small droplets hit the toner at a relatively slow speed, so that the kinetic energy is small and the movement of the toner can be suppressed.

  However, in such a conventional fixing device, the fixing droplet adhered on the secondary transfer roller is transferred to the recording material as it is together with the toner for fixing. When adhered, there is a basic problem that the surface of the recording material is wetted and the recording material is curled.

Japanese Patent Publication No. 40-10867 Japanese Patent No. 3290513 JP 2004-109747 A JP 2006-163083 A JP 2006-293169 A JP 2006-350099 A

  Accordingly, a first object of the present invention is to use a toner fixing solution comprising a softening material that is energy-saving, odorless and harmless, and a solvent that dissolves or disperses the softening material, and adheres the fixing solution. Therefore, in a fixing device in which unfixed toner is softened by a softening material and fixed on the recording material, the toner image on the recording material may not be disturbed, and an appropriate amount of fixing solution may be applied to cause curling of the recording material. It is an object of the present invention to provide a fixing device with a small amount.

  A second object of the present invention is to provide an appropriate amount of fixing solution for effective use of the fixing solution and to uniformly apply the fixing solution to the toner image to eliminate occurrence of fixing unevenness.

  A third object of the present invention is to reliably and stably convey a recording material on which unfixed toner is placed to perform good fixing.

  A fourth object of the present invention is to even more reliably eliminate curling of the recording material by equalizing the liquid concentrations on the front and back sides of the recording material.

  A fifth object of the present invention is to reliably attract unfixed toner and fixed droplets to a recording material.

  A sixth object of the present invention is to increase the fixing efficiency and to effectively use the fixing solution.

  A seventh object of the present invention is to provide an image forming apparatus provided with a fixing device which does not disturb the toner image on the recording material and which is less likely to cause curling of the recording material by applying an appropriate amount of fixing liquid. There is.

For this reason, the invention described in claim 1 is to achieve the first object described above.
A toner fixing liquid composed of a softening material and a solvent that dissolves or disperses the softening material is used. By attaching the fixing liquid, unfixed toner is softened by the softening material, and recording material such as paper or an OHP film is used. In the fixing device fixed to
Spray means for spraying toner fixing liquid as fixing droplets, droplet charging means such as an ionizer for imparting charges of the same polarity as the unfixed toner to fixing droplets sprayed by the spray means, and charging the droplets A medium conveying means for conveying the recording material on which the unfixed toner is placed, through the atmosphere of the fixing droplet to which the charge is applied by the means, and the recording material conveyed by the medium conveying means with the unfixed toner and the fixing droplet Is provided with a recording material charging means for charging to a reverse polarity.

  The fixing droplets sprayed by the spraying means are charged with the same polarity as the unfixed toner on the recording material by the droplet charging means, while the medium is conveyed through the atmosphere of the fixing droplets to which the charge has been applied. The recording material on which the unfixed toner is placed is transported by the means, and the transported recording material is charged to a polarity opposite to that of the unfixed toner and the fixing droplet by the recording material charging means, and is forcibly attracted by the Coulomb force. Then, the unfixed toner and the fixing droplets are adsorbed on the recording material, and the unfixed toner is softened and fixed on the recording material by the softening material of the fixing liquid.

  According to a second aspect of the present invention, in order to achieve the second object described above, in the fixing device of the first aspect, the toner fixing liquid is sprayed by the fixing means, and the fixing liquid having a mode droplet diameter of 15 μm or less. It is sprayed as a drop.

  The sprayed small fixing droplets uniformly float in the space as dry mist and adhere to the recording material without waste and without unevenness.

  According to a third aspect of the present invention, in order to achieve the third object described above, in the fixing device according to the first or second aspect, the medium conveying means is wound around a plurality of rollers and these rollers. And a conveying belt that conveys the recording material through the atmosphere of the fixing droplets by electrostatic adsorption.

  Then, the conveyance belt is conveyed by driving the roller, electrostatically attracted to the conveyance belt and placed on the conveyance belt, and the recording material on which the unfixed toner is loaded is conveyed.

  According to a fourth aspect of the present invention, in order to achieve the fourth object described above, in the fixing device according to the third aspect, the recording material charging means is disposed inside the conveyance belt that is wound around the roller. And an electric power source connected to the electrode.

  Then, a voltage is applied to the electrodes disposed inside the conveyor belt by the power source, and the recording material conveyed by the conveyor belt is charged with a polarity opposite to that of the unfixed toner and the fixed droplets.

  According to a fifth aspect of the present invention, in order to achieve the fifth object described above, in the fixing device according to the third aspect, the recording material charging means is a conveyor belt wound around a roller, and the conveyor belt. In addition, it is characterized in that it comprises an application means for applying a reverse polarity to the unfixed toner and the fixed droplets.

  Then, an electric charge is applied to the conveying belt by the applying means, and the recording material conveyed by the conveying belt is charged with a polarity opposite to that of the unfixed toner and the fixing droplet.

  According to a sixth aspect of the present invention, in order to achieve the sixth object described above, in the fixing device according to any one of the first to fifth aspects, a spraying chamber is provided, and spraying means toward the spraying chamber is provided. The fixing droplets are sprayed by the liquid droplets, and the fixing droplets are charged by the droplet charging means, so that the spray chamber is filled with the fixing droplets charged to the same polarity as the unfixed toner, and the spray chamber is fixed. The recording material is conveyed by the medium conveying means through the droplet atmosphere.

  Then, the fixing droplet is sprayed by the spraying means toward the spraying chamber, and the fixing droplet is charged with the same polarity as that of the unfixed toner by applying the electric charge to the fixing droplet by the droplet charging means. The recording material is conveyed by the medium conveying means in the fixing droplet atmosphere in the spray chamber.

According to a seventh aspect of the present invention, in order to achieve the second object described above, in the image forming apparatus according to any one of the first to sixth aspects, the required application area of the recording material is S [cm ² ], When the amount of fixing liquid applied to the recording material is Q [g], the average diameter of the fixing droplets is d [μm],
30,000 × (Q / S) ≦ d ≦ 15 μm
It is characterized by that.

  Then, an appropriate amount of small fixing droplets are sprayed in accordance with the required application area of the recording material, and the sprayed fixing droplets are uniformly floated in the space as dry mist and adhere to the recording material without waste.

  In order to achieve the seventh object described above, the invention described in claim 8 is formed by an image forming means for forming a toner image on an image carrier such as a photosensitive member or an intermediate transfer member, and the image forming means. A transfer unit that transfers a toner image on an image carrier to a recording material, and a fixing device according to any one of claims 1 to 7 that fixes the unfixed toner on the recording material by transferring with the transfer unit. An image forming apparatus, such as a copying machine, a printer, a facsimile, or a composite machine thereof, is provided.

  Then, a toner image is formed on the image carrier by the image forming means, the toner image on the image carrier is transferred to the recording material by the transfer means, and the recording material on which the unfixed toner is placed is sent to the fixing device. The recording material is charged with the opposite polarity to the non-fixed toner and the fixing droplets by the recording material charging means in the fixing device through the atmosphere of the fixing droplets to which electric charges are applied while being conveyed by the medium conveying means, and the recording material Unfixed toner is adsorbed, and fixed droplets that are sprayed by the spraying unit and charged to the same polarity as the unfixed toner by the droplet charging unit are adsorbed.

  In order to achieve the seventh object described above, the invention according to claim 9 is formed by an image forming means for forming a toner image on an image carrier such as a photosensitive member or an intermediate transfer member, and the image forming means. A primary transfer means for primary transfer of the toner image on the image carrier to an intermediate transfer body; and a secondary transfer means for secondary transfer of the toner image on the intermediate transfer body primarily transferred by the primary transfer means to a recording material; A copier and printer comprising: a fixing device according to claim 1 for fixing unfixed toner on a recording material secondarily transferred by the secondary transfer means. An image forming apparatus such as a facsimile or a multifunction machine thereof.

  Then, a toner image is formed on the image carrier by the image forming unit, and the toner image on the image carrier is primarily transferred to the intermediate transfer member by the primary transfer unit, and is transferred to the intermediate transfer member by the primary transfer unit. The toner image is secondarily transferred to the recording material by the secondary transfer unit, and the recording material on which the unfixed toner is transferred, which is secondarily transferred by the secondary transfer unit, is sent to the fixing device and is conveyed by the medium conveying unit. However, through the atmosphere of the charged fixing droplet, the recording material is charged by the recording material charging means in the fixing device with a polarity opposite to that of the unfixed toner and the fixing droplet, and the unfixed toner is adsorbed to the recording material. At the same time, the fixing droplets sprayed by the spraying means and charged to the same polarity as the unfixed toner by the droplet charging means are adsorbed.

  According to the first aspect of the present invention, the unfixed toner on the recording material is electrostatically attracted to the recording material applied with the opposite polarity, and the scattering of the unfixed toner on the recording material is prevented to prevent the toner image from being scattered. Disturbance can be eliminated and good fixing without deterioration of image quality can be performed. In addition, the fixing droplets are electrostatically attracted to the recording material applied with the reverse polarity, and uniformly adhered to the recording material without waste, thereby eliminating the fixing unevenness and effectively using the fixing solution. Consumption can be reduced. In addition, fixing droplets adhering to the recording material are further electrostatically attracted and penetrated to the back side of the recording material, and the liquid density is made uniform on the front and back of the recording material to reduce curling of the recording material. Can do.

  According to the second aspect of the present invention, the toner fixing liquid is sprayed as fixing droplets having a mode droplet diameter of 15 μm or less by the spraying means, and the sprayed fixing droplets are uniformly distributed in the space as dry mist. Since it floats and adheres to the recording material without waste, it is possible to adhere the fixing droplets to the recording material without waste to effectively use the fixing liquid and to eliminate fixing unevenness.

  According to the third aspect of the present invention, the conveying belt is conveyed by driving the roller, electrostatically attracted to the conveying belt, and placed on the conveying belt to convey the recording material. Through the droplet atmosphere, the recording material on which the unfixed toner is placed can be reliably and stably conveyed.

  According to the fourth aspect of the present invention, a voltage is applied to the electrode disposed inside the conveyor belt by the power source, so that the recording material conveyed by the conveyor belt is opposite in polarity to the unfixed toner and the fixed droplets. Therefore, by attracting from the back side of the recording material, the fixed droplets adhering to the recording material penetrate further to the back side of the recording material, and the liquid concentration is evenly recorded on both sides of the recording material. The curl of the material can be reduced.

  According to the invention described in claim 5, since the charge is applied to the conveying belt by being applied by the applying means, and the recording material conveyed by the conveying belt is charged with a polarity opposite to that of the unfixed toner and the fixing droplet, Unfixed toner and fixing droplets can be electrostatically and reliably attracted to a recording material charged to a reverse polarity.

  According to the sixth aspect of the present invention, the fixing droplets are sprayed by the spraying means toward the spraying chamber, and the fixing droplets are charged by the droplet charging means, whereby the spraying chamber becomes unfixed toner. Since the recording material is conveyed by the medium conveying means in the fixing droplet atmosphere in the spray chamber filled with the fixing droplets charged to the same polarity, the fixing droplets are divided by dividing the area where the fixing droplets are sprayed. Can be prevented, and the fixing efficiency can be increased to effectively use the fixing solution.

  According to the seventh aspect of the present invention, an appropriate amount of small fixing droplets are sprayed according to the required application area of the recording material, and the sprayed fixing droplets are uniformly floated in the space as dry mist, which is wasted on the recording material. Therefore, the fixing unevenness can be eliminated and the fixing liquid can be adhered to the recording material without waste, so that the fixing liquid can be used effectively and the consumption of the fixing liquid can be reduced.

  According to the eighth aspect of the present invention, in the fixing device, the unfixed toner on the recording material is electrostatically attracted to the recording material applied with the reverse polarity, and the scattering of the unfixed toner on the recording material is prevented. Thus, the toner image can be prevented from being disturbed and good fixing can be performed without deteriorating the image quality. In the fixing device, the fixing droplets are electrostatically attracted to the recording material applied with the reverse polarity, and uniformly adhered to the recording material without waste, thereby eliminating uneven fixing and effectively using the fixing liquid. The consumption of the fixing solution can be reduced. In addition, with the fixing device, the fixing droplets adhering to the recording material are further electrostatically attracted and penetrated to the back side of the recording material, and the water concentration is made uniform between the front and back of the recording material. Curling can be reduced.

  According to the ninth aspect of the present invention, similarly, in the fixing device, the unfixed toner on the recording material is electrostatically attracted to the recording material applied with the reverse polarity, and the unfixed toner on the recording material is It is possible to prevent the toner image from being disturbed by preventing scattering and to perform good fixing without deteriorating the image quality. In the fixing device, the fixing droplets are electrostatically attracted to the recording material applied with the reverse polarity, and uniformly adhered to the recording material without waste, thereby eliminating uneven fixing and effectively using the fixing liquid. The consumption of the fixing solution can be reduced. In addition, with the fixing device, the fixing droplets adhering to the recording material are further electrostatically attracted and penetrated to the back side of the recording material, and the water concentration is made uniform between the front and back of the recording material. Curling can be reduced.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 shows a main configuration of an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof. The illustrated one is an electrophotographic tandem color image forming apparatus that directly transfers a toner image on an image carrier onto a recording material sheet without using an intermediate transfer member. It is.

  Reference numeral 10 in the figure denotes an endless belt-like transport belt. In the illustrated example, the conveyor belt 10 is provided so as to be able to rotate around the driving roller 12 and the driven roller 13 in a counterclockwise direction in the drawing. Of course, the number of rollers that wrap around the conveyor belt 10 is not limited to two, and a roller that adjusts the deviation of the conveyor belt 10 or a tension roller may be provided to hang around three or more rollers. .

  Around the conveyor belt 10, four image forming means 15K, black, magenta, cyan, and yellow are sequentially arranged along the traveling direction of the conveyor belt 10 on a horizontal stretched portion between the driving roller 12 and the driven roller 13. 15M, 15C, and 15Y are installed side by side to constitute the tandem image forming device 16. Although not shown in the drawing, an exposure device and the like are further provided on the tandem image forming device 16.

  Between the transport belt 10 and the tandem image forming device 16, a paper transport path for transporting the paper 17 is formed from right to left in the drawing as the transport belt 10 travels counterclockwise. A registration roller (not shown) is disposed upstream along the sheet conveyance path, and a fixing device 18 is disposed downstream.

FIG. 2 shows a schematic configuration of one image forming unit 15 provided in the image forming apparatus shown in FIG.
The four image forming means 15K, 15M, 15C, and 15Y have the same configuration as shown in FIG.

  Reference numeral 20 in the drawing denotes a photosensitive member which is a drum-shaped image carrier. Around the photosensitive member 20, a developing device 22, a transfer device 23, a cleaning device 24, a static elimination device 25, and the like are arranged in order from the charging device 21 arranged at the upper left in the rotational direction indicated by the arrow in the drawing.

  Here, in the illustrated example, the charging device 21 employs a non-contact charging method that gives uniform negative charging using a charging charger, but a contact charging method using a charging roller may of course be employed. In this example, the developing device 22 uses a two-component developer composed of a positively charged carrier 26 and a negatively charged toner 27, which is carried by a developing sleeve 28 and attaches only the toner 27 to the photosensitive member 20. The electrostatic latent image on the body 20 is visualized.

  In the illustrated example, the transfer device 23 employs a non-contact plus transfer corona charger system and is disposed so as to face the photoconductor 20 with the conveyance belt 10 interposed therebetween. However, in addition to the non-contact corona charger system, the transfer device 23 is electrically conductive. A property brush or a transfer roller can also be used. The cleaning device 24 is provided with a cleaning brush 30 and a cleaning blade 31 as cleaning members. As a result, the toner scraped off by the cleaning brush 30 and the cleaning blade 31 can be recovered and reused by the developing device 22 using a recovery screw (not shown) or a toner recycling device. Moreover, as the static elimination apparatus 25, a static elimination lamp is used, for example.

  Then, along with the clockwise rotation of the photosensitive member 20, the surface of the photosensitive member 20 is uniformly charged by the charging device 21, and writing light L (Lk, Lm, Lc, Ly in FIG. 1) is emitted by an exposure device (not shown). After irradiation, an electrostatic latent image is formed on each photoconductor 20, and each color toner is attached by a developing device 22 to visualize the electrostatic latent image, and each color monochromatic toner is formed on each photoconductor 20. Form an image.

  The paper 17 is transported through a paper transport path, and is sent onto the transport belt 10 by a registration roller in time with each color toner image formed on the photoreceptor 20. Then, as the conveyor belt 10 travels, the sheet 17 is further conveyed, and the monochromatic toner images on the respective photoreceptors 20 are sequentially transferred to the conveyed sheet 17 by the transfer device 23, and each color monochromatic toner is transferred onto the sheet 17. The images are superimposed to form a composite color image. After the toner image has been transferred, the surface of the photoconductor 20 is cleaned by the cleaning device 24, and then is neutralized by the neutralizing device 25 to be initialized, and is prepared for another image formation starting from the charging device 21 again.

  The negatively charged toner 27 on the paper 17 that forms the composite color image is only electrically attached to the paper 17 at this time, and is separated from the paper 17 when subjected to a strong impact or rubbing. The sheet 17 on which the composite color image is formed is conveyed by the conveying belt 10 and guided to the fixing device 18, where the transferred image is fixed by the fixing device 18 and then discharged to a paper discharge stack unit (not shown).

  As shown in FIG. 1, the fixing device 18 includes a spraying means 33 for spraying a toner fixing liquid as fixing droplets, and a negative voltage having the same polarity as that of unfixed toner on the fixing droplets sprayed by the spraying means 33. A droplet charging unit 34 for applying electric charge, a medium conveying unit 35 for conveying the paper 17 on which unfixed toner is placed, through the atmosphere of the fixing droplet to which electric charge is applied by the droplet charging unit 34, and A recording material charging unit 36 that charges the sheet 17 conveyed by the medium conveying unit 35 to a positive polarity opposite to that of the unfixed toner and the fixed droplets is provided.

FIG. 3 shows an enlarged view of the fixing device 18 shown in FIG.
As can be seen from FIG. 3, the spraying means 33 is installed in the spray chamber 38 partitioned by the casing 37, and the toner fixing liquid stored in a fixing liquid storage section (not shown) has the mode value. Spraying is performed as fixing droplets having a droplet diameter of 15 μm or less, and the spray chamber 38 is filled with the fixing droplets.

  The toner fixing liquid includes a softening material that softens the toner by dissolving or semi-dissolving the toner, and a solvent that disperses or dissolves the softening material. Since it is easy to use and can be used safely, it is preferable that it is odorless and harmless to the human body. From this point of view, softening materials include fatty acid esters, specifically linear saturated fatty acid esters, aliphatic nitric acid. It is preferable to use a basic acid ester or an aliphatic dibasic acid dialkoxydialkyl ester. In addition, it is preferable to use water since the solvent is environmentally friendly, inexpensive, odorless and harmless, and can be used conveniently and safely. A surfactant may be added for the purpose of controlling the wettability of the fixing solution containing the softening material having a predetermined concentration to the unfixed toner and the penetration rate into the paper 17.

  As the droplet charging unit 34, an ionizer or the like is used, air ions are sprayed into the spray chamber 38, mixed with the fixing droplet sprayed by the spraying unit 33, and the fixing droplet has the same polarity as the unfixed toner. Charge negatively. Unlike the illustrated example, when the unfixed toner is positively charged, the fixing droplet is also positively charged.

  The medium transport unit 35 includes a plurality of rollers 40 and a transport belt 41 that is wound around the rollers 40 and electrostatically attracts and transports the paper 17. Then, the sheet 17 transferred by the transfer device 23 and carrying the unfixed toner 42 having a negative residual charge as shown in the figure is transported by the transport belt 10 and sent to the fixing device 18, and the medium transport of the fixing device 18 is performed. Subsequently, the toner is conveyed from the right to the left in the drawing through the atmosphere of the fixing droplets to which the charge is applied by the droplet charging unit 34 by the conveying belt 41 of the unit 35.

  The recording material charging unit 36 includes an electrode 44 disposed on the inner side of the conveyance belt 41 that is wound around the roller 40, and a power supply 45 connected to the electrode 44. A voltage is applied from the power source 45 to the electrode 44 disposed on the inner side of the transport belt 41 to charge the paper 17 transported by the transport belt 41 to a positive polarity opposite in polarity to the unfixed toner 42 and the fixed droplets. . At this time, of course, the transport belt 41 is formed of a material that does not prevent the paper 17 from being charged. As a result, by sucking from the back side of the sheet 17 by Coulomb force, the fixing droplets adhering to the sheet 17 penetrate further to the back side of the sheet 17, and the liquid concentration is made even more uniform on the front and back sides of the sheet 17. Curling of the sheet 17 can be reduced.

  Reference numeral 46 in the figure denotes a static elimination roller as a static elimination member that neutralizes the paper 17 coming out of the fixing device 18 and of course may be a brush instead of the roller.

  As described above, according to the illustrated example, the fixing droplet sprayed by the spraying unit 33 is applied with the charge having the same polarity as the unfixed toner 42 on the paper 17 by the droplet charging unit 34, while the charge is applied. The sheet 17 on which the unfixed toner 42 is placed is conveyed by the medium conveying unit 35 through the atmosphere of the fixed droplets, and the conveyed sheet 17 is transferred to the unfixed toner 42 and the fixed droplets by the recording material charging unit 36. As shown in FIG. 7B, which will be described later, the toner is forcibly attracted by the Coulomb force, and the unfixed toner 42 and the fixing droplets 53 are adsorbed on the sheet 17, and the fixing liquid softening material is used. The unfixed toner 42 is softened and fixed on the paper 17.

  As a result, the unfixed toner 42 on the paper 17 is electrostatically attracted to the paper 17 applied with the reverse polarity, preventing the unfixed toner 42 on the paper 17 from being scattered and preventing the toner image from being disturbed. It is possible to perform good fixing without lowering of the thickness. Further, the fixing droplet 53 is electrostatically attracted to the paper 17 applied with the reverse polarity and uniformly adhered to the paper 17 without waste, thereby eliminating the fixing unevenness and effectively using the fixing liquid. Consumption can be reduced. In addition, the fixing droplet 53 attached to the paper 17 is further electrostatically attracted and penetrates to the back side of the paper 17, and the liquid concentration is made uniform on the front and back of the paper 17 to reduce curling of the paper 17. be able to.

  When the toner fixing liquid is sprayed by the spraying means 33 as the fixing droplet 53 having a mode droplet diameter of 15 μm or less, the sprayed fixing droplet 53 is uniformly floated in the space as a dry mist, and the paper 17 Therefore, the fixing droplet 53 can be adhered to the sheet 17 without waste, and the fixing liquid can be effectively used and the uneven fixing can be eliminated.

4A and 4B show the size of the electrode 44 compared to the paper 17. FIG.
As shown in (A), the length L1 of the electrode 44 may be shorter than the length L of the paper 17, and the width B1 of the electrode 44 is also smaller than the width B of the paper 17 as shown in (B). May be. According to the experiment, the entire sheet 17 could be charged even when the length and width were small as in (B).

FIG. 5 shows a modification of the fixing device 18.
In this example, a counter electrode 47 is disposed in the spray chamber 38 so as to face the electrode 44. In this way, an electric field 48 can be formed in the spray chamber 38 to further increase the suction force of the unfixed toner 42 and the fixed droplets 53 with respect to the paper 17. In FIG. 5, the other symbols used in FIG. 3 are used as they are.

FIG. 6 shows another example of the fixing device 18.
In this example, the recording material charging unit 36 imparts a charge to the transport belt 41 around the roller 40 and charges the transport belt 41 so that the paper 17 is opposite in polarity to the unfixed toner 42 and the fixing droplet 53. And an application means 50 such as a charging charger for charging the Then, an electric charge is applied to the conveying belt 41 by being applied by the applying means 50, and the sheet 17 conveyed by the conveying belt 41 is charged with a polarity opposite to that of the unfixed toner 42 and the fixing droplet 53. As a result, the unfixed toner 42 and the fixed droplets 53 can be reliably and electrostatically attracted to the sheet 17 charged with the reverse polarity. In FIG. 6 as well, the other reference numerals are the same as those used in FIG.

7A and 7B show how the fixing droplets 52 and 53 adhere to the paper 17. FIG.
(A) shows a state in which the fixing droplet 52 having a relatively large diameter, specifically, a mode value of about 40 μm to 80 μm is attached to the unfixed toner 42 on the paper 17. With such a size, the fixing droplet 52 falls by its own weight, or is landed on the sheet 17 as it is by giving an initial velocity in the horizontal and upward directions. On the other hand, (B) shows a state in which a relatively small fixing droplet 53, specifically 15 μm or less, adheres to the unfixed toner 42 on the paper 17.

  By the way, in the case of the fixing method using the fixing liquid, the amount of the fixing liquid applied to the paper 17 is preferably small in consideration of the curling and sticky feeling and the fixing liquid amount tank capacity of the fixing liquid reservoir. For example, when coating on A4 size paper 17 (210 × 297 mm), it is desirable that the coating amount be 0.2 g / A4 at the maximum, preferably 0.1 g / A4 or less, and preferably 0.05 g / A4. Although there is a difference in fixability depending on the composition of the fixing solution, it cannot be generally stated. However, any composition is not limited to the above amount, and the merchantability of the sheet 17 after fixing remains adversely affected.

Here, it is assumed that the necessary application amount of the fixing liquid is 0.1 g / A4, and the droplet diameter of the fixing droplet 52 of (A) is 60 μm. Since the volume of the 60 μm droplet is 113,040 μm ³ , if the specific gravity is 1, the weight is 1.13 × 10 ⁻⁷ g. Therefore, to apply 0.1 g, 884,643 fixing droplets 52 are required. Assuming that this number of fixed droplets 52 are neatly arranged on the A4 size paper 17, the distance between the droplets is calculated to be 265 μm. The droplets usually have a larger diameter when landing, and the landing diameter is about 1.5 to 2.5 times the diameter of the droplet. However, even if this is taken into consideration, the paper 17 is not completely filled, and coating unevenness as shown in FIG. become. This becomes fixing unevenness as it is. In this way, it can be seen that a droplet having a certain drop diameter d has landed, and the sum of the applied areas must be at least the required application area of the paper 17.

  As shown in FIG. 7B, if the droplet is a small fixed droplet 53 of 8 μm, for example, compared to the fixed droplet 52, it does not permeate in the depth direction of the paper 17 and is thin and uniform. It can be performed. FIG. 9 shows the state of application, and it can be seen that even if the same amount of application as in FIG. That is, the required number N of droplets is calculated from the droplet diameter d and the sheet area. If the droplet diameter d and the appropriate number N are known, the amount of coating liquid can also be known. In other words, when applying a certain area without unevenness, the required droplet diameter is automatically determined when the coating amount is determined.

A calculation example is given below. The droplet diameter of the fixer is d [μm], the required application area of the sheet 17 is S [cm ² ], the application amount to the recording paper is Q [g], and the number of droplets is N [pieces]. Assuming that the diameter expansion is zero in the worst case,
Landing area of one drop π · (d × 10 ⁻⁴ / 2) ² [cm ² ]
Volume of one drop (4π / 3) · (d × 10 ⁻⁴ / 2) ³ [cm ³ ]
It becomes.

As described above, the area that can be applied by droplets must be at least equal to the required application area S of the paper 17.
N · π · (d × 10 ⁻⁴ / 2) ² = S ……………………………… (1)
It becomes.

Also, from the total volume of the drop, if the specific gravity is 1, 1 cm ³ = 1 g,
N · (4π / 3) · (d × 10 ⁻⁴ / 2) ³ = Q ………………… (2)
It becomes.

If (1) and (2) are transformed into the formula of N = and both are equal,
N = (4S / d ² × 10 ⁻⁸ ) = (6Q / d ³ × 10 ⁻¹² )
And
d = 30,000 ・ (Q / S) ……………………………………… (3)
And can be transformed.

As a trial, if the required application area S is A4, 21 cm × 29.7 cm = 623.7 cm ² , and if the coating amount Q is 0.1 g / A4, d = 4.8 μm from the above formula, which is larger than this diameter It can be seen that the coating is uneven.

  Now, in this system, since it is a condition that the sprayed mist floats uniformly in the housing | casing 37, it is necessary to be what is called a dry mist that a droplet does not get wet. Otherwise, the sprayed drops fall as they are and wet the objects below, so that the paper 17 cannot be applied uniformly. In order to be dry mist, it is a necessary condition that the droplet diameter is 15 μm or less. FIG. 10 is a diagram showing the range because the minimum application amount was 0.05 g / A4 in the droplet diameter condition and dry mist condition of the above formula (3) and in our experiment. Of course, if the composition of the fixing solution is different, the minimum required amount of 0.05 g / A4 varies.

  Further, it has been found that, when the liquid is pulled by the Coulomb force from the back side of the sheet 17 with this configuration, the curl is extremely reduced. In the experiment, although depending on the type of paper, the result is that the amount of warping of the paper 17 after application has been reduced from about 1/6 to about 1/10. FIG. 11 shows the results of curl experiments. The graph shows the amount of warping when water is uniformly applied by 0.1 g / A4 with a roller. Although it depends on the type of paper, a large item warps 50 mm, is very difficult to handle, and its commercial value is drastically reduced. FIG. 12 shows the same amount of water applied by this method. It can be seen that the amount of warping has decreased drastically. Curling occurs because the fibers on the liquid adhesion side of the paper 17 swell and make a difference from the back surface. In this case, the water adhering from the back surface of the paper 17 by the recording material charging means 36 due to the Cron force. It is considered that the liquid permeates to the back surface of the paper 17 and the curl is reduced because the water concentration is uniform on both sides.

  By the way, in a conventional copier or the like of the heat fixing method, the recording material finally enters a fixing device using heat. However, in the heat fixing method, the recording material is heated and consumes very much electric power. In addition, when the copying machine or the like is not in use, the heater temperature needs to be kept fairly high so that it takes no time to start up, and a considerable amount of power is consumed during operation including the standby state. On the other hand, the fixing method using the fixing liquid of the present invention as described above has an advantage that the power is low even when the fixing device 18 is operated, and little power is consumed during standby.

FIG. 13 shows another example of an image forming apparatus including the fixing device 18 according to the present invention.
The illustrated one is an electrophotographic tandem type color image forming apparatus, which uses an intermediate transfer member to temporarily transfer the toner image on the image carrier to the intermediate transfer member, and then on the intermediate transfer member. This is an indirect transfer type in which a toner image is secondarily transferred to a recording material.

  Reference numeral 60 in the drawing denotes an image forming apparatus main body that is placed on the paper feeding device 61, forms the in-body paper discharge unit 62, and places the image reading device 63 thereon. In the image forming apparatus main body 60, a belt-like intermediate transfer member 64 is provided so as to run around a plurality of rollers. Four image forming means 15K, 15M, 15C, and 15Y are arranged side by side below the horizontal stretched portion of the intermediate transfer body 64, and a tandem image forming device 16 is provided.

  In the paper feeding device 61, recording material containers 65 are provided in a plurality of stages. From the upper right of these recording material containers 65, a vertical recording material conveyance path 66 is formed from the paper feeding device 61 through the image forming apparatus main body 60 to the in-body paper discharge unit 62. A secondary transfer unit 67 is disposed in the recording material conveyance path 66 so as to face the intermediate transfer member 64, and the fixing device 18 is installed downstream thereof. Next to the fixing device 18, a fixing liquid storage unit 68 is provided.

  The toner images formed by the image forming means 15K, 15M, 15C, and 15Y are primarily transferred to the intermediate transfer body 64 by the primary transfer means 69, while the recording material fed from the recording material container 65 is the recording material conveyance path. 66, the toner image on the intermediate transfer body 64 is secondarily transferred by the secondary transfer means 67. The recording material after the image transfer passes through the fixing device 18, fixes the transferred image, and is then discharged to the in-body discharge unit 62.

FIG. 14 shows a fixing device 18 provided in the image forming apparatus shown in FIG.
Similarly, the fixing device 18 sprays the toner fixing liquid as a fixing droplet, and applies a negative charge having the same polarity as the unfixed toner to the fixing droplet sprayed by the spraying device 33. A droplet charging unit 34, a medium conveying unit 35 that conveys a recording material on which unfixed toner is placed, through the atmosphere of a fixing droplet to which electric charges are applied by the droplet charging unit 34, and the medium conveying unit 35 And a recording material charging means 36 for charging the recording material to be conveyed to a positive polarity opposite to that of the unfixed toner and the fixing droplets.

  The spraying means 33 sprays the fixer stored in the fixer storing tank 70 as dry mist of 15 μm or less using ultrasonic waves in the illustrated example to fill the spray chamber 38 with the fixing droplets. The fixer storage tank 70 is supplied with fixer from the fixer reservoir 68. As the droplet charging means 34, an ionizer that charges the fixing droplet floating in the spray chamber 38 is used.

  The medium transport unit 35 includes a plurality of rollers 40 and a transport belt 41 that is wound around the rollers 40 and electrostatically attracts a recording material to transport upward against gravity. Further, a pressure roller pair 71 is provided downstream to improve the fixing force and color reproducibility by applying pressure.

  The recording material charging unit 36 includes an electrode 44 disposed on the inner side of the conveyance belt 41 that is wound around the roller 40, and a power supply 45 connected to the electrode 44. Then, the fixing droplet 53 is attached to the toner 42 and the recording material 17 as shown in FIG. 7B by sucking the fixing droplet toward the recording material by the Coulomb force. Further, in this example, surplus droplets in the spray chamber 38 are sucked out by the fan 72 through the collection pipe 73, collected by filtering with a filter 74, and returned to the fixer storage tank 70 for reuse.

  Also in this example, the fixing droplet sprayed by the spraying means 33 is given a charge having the same polarity as the unfixed toner on the recording material by the droplet charging means 34, and the atmosphere of the fixing droplet to which the charge has been given. Through the medium, the recording material on which the unfixed toner is placed is conveyed by the medium conveying means 35, and the conveyed recording material is charged by the recording material charging means 36 to a polarity opposite to that of the unfixed toner and the fixing droplets. The toner is forcibly attracted by the Coulomb force, and the unfixed toner and the fixing droplet are adsorbed on the recording material, and the unfixed toner is softened by the softening material of the fixing liquid and fixed on the recording material.

  As a result, also in this example, the unfixed toner on the recording material is electrostatically attracted to the recording material applied with the reverse polarity, and the toner image is prevented from being disturbed by preventing the unfixed toner on the recording material from scattering. Therefore, it is possible to perform good fixing without deterioration in image quality. In addition, the fixing droplets are electrostatically attracted to the recording material applied with the reverse polarity, and uniformly adhered to the recording material without waste, thereby eliminating the fixing unevenness and effectively using the fixing solution. Consumption can be reduced. In addition, fixing droplets adhering to the recording material are further electrostatically attracted and penetrated to the back side of the recording material, and the liquid density is made uniform on the front and back of the recording material to reduce curling of the recording material. Can do.

1 is a configuration diagram of a main part of an image forming apparatus. FIG. 2 is a schematic enlarged configuration diagram of one image forming unit provided in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a schematic enlarged configuration diagram of a fixing device provided in the image forming apparatus shown in FIG. 1. (A) And (B) is a perspective view which shows the relationship of the magnitude | size of a paper and an electrode, respectively. FIG. 6 is a schematic enlarged configuration diagram of a modified example of the fixing device. FIG. 6 is a schematic enlarged configuration diagram of another example of the fixing device. (A) shows a state in which relatively large fixing droplets are attached to unfixed toner on the paper, and (B) shows relatively small fixing droplets on unfixed toner on the paper according to the present invention. It is a figure which shows a mode that it adheres. It is a top view of the recording material which shows the adhesion state in the case of FIG. It is a top view of the recording material which shows the adhesion state in the case of FIG. 7 (B). It is a figure which shows the relationship between the application quantity of a fixing liquid, and the required droplet diameter of a fixing droplet. It is a figure which shows the relationship between a paper and a curl amount. FIG. 6 is a diagram illustrating a relationship between a sheet and a curl amount in the case of the fixing device of the present invention. FIG. 6 is an overall schematic configuration diagram of another example of an image forming apparatus including a fixing device according to the present invention. FIG. 14 is an overall schematic configuration diagram of a fixing device provided in the image forming apparatus illustrated in FIG. 13.

Explanation of symbols

15K, 15M, 15C, 15Y Image forming means 17 Paper (recording material)
DESCRIPTION OF SYMBOLS 18 Fixing device 23 Transfer means 33 Spray means 34 Droplet charging means 35 Medium conveying means 36 Recording material charging means 38 Spray chamber 40 Roller 41 Conveying belt 42 Unfixed toner 44 Electrode 45 Power supply 50 Applying means 53 Fixing droplet 64 Intermediate transfer body 67 Secondary transfer means 69 Primary transfer means

Claims (9)

A fixing device in which a toner fixing liquid composed of a softening material and a solvent for dissolving or dispersing the softening material is used, and unfixed toner is softened by the softening material and fixed on the recording material by attaching the fixing liquid. In
A spraying means for spraying the toner fixing liquid as fixing droplets; a droplet charging means for imparting a charge of the same polarity as the unfixed toner to the fixing droplets sprayed by the spraying means; and the droplet charging means. The medium conveying means for conveying the recording material on which the unfixed toner is placed through the atmosphere of the fixing droplet to which the electric charge is applied, and the unfixed toner and the fixing droplet for the recording material conveyed by the medium conveying means. A fixing device comprising: a recording material charging means for charging to a reverse polarity.   The fixing device according to claim 1, wherein the toner fixing liquid is sprayed by the spraying unit as fixing droplets having a mode droplet diameter of 15 μm or less.   3. The medium conveyance unit according to claim 1, wherein the medium conveyance unit includes a plurality of rollers and a conveyance belt that is wound around the rollers and electrostatically attracts and conveys the recording material. Fixing device.   4. The recording material charging unit according to claim 3, wherein the recording material charging unit includes an electrode disposed inside a conveyance belt wound around the roller and a power source connected to the electrode. Fixing device.   The recording material charging unit includes a conveyance belt wound around the roller, and an application unit that applies a charge to the conveyance belt to charge the recording material with a polarity opposite to that of unfixed toner and fixing droplets. The fixing device according to claim 3, wherein the fixing device is provided.   A spraying chamber is provided, and the fixing droplet is sprayed by the spraying unit toward the spraying chamber, and the fixing droplet is charged by the droplet charging unit, whereby the spraying chamber is the same as the unfixed toner. 6. The recording medium according to claim 1, wherein the recording material is conveyed by the medium conveying means through the fixing droplet atmosphere charged in the polarity and through the fixing droplet atmosphere in the spray chamber. The fixing device described. When the required application area of the recording material is S [cm ² ] and the application amount of the fixing liquid to the recording material is Q [g], the average diameter of the fixing droplet is d [μm],
30,000 × (Q / S) ≦ d ≦ 15 μm
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   An image forming means for forming a toner image on the image carrier, a transfer means for transferring the toner image on the image carrier formed by the image forming means to a recording material, and a transfer means for transferring the toner image on the recording material. An image forming apparatus comprising: the fixing device according to claim 1 that fixes the unfixed toner.   Image forming means for forming a toner image on the image carrier, primary transfer means for primary transfer of the toner image formed on the image carrier on the image carrier to an intermediate transfer member, and primary transfer by the primary transfer means 8. A secondary transfer means for secondary transfer of the toner image on the intermediate transfer member to a recording material, and an unfixed toner on the recording material secondarily transferred by the secondary transfer means is fixed. An image forming apparatus comprising the fixing device according to claim 1.

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