JP2012163817A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of generating a foamy fixing liquid layer of a two-layer structure in a simple configuration and achieving the miniaturization of the whole device.SOLUTION: A foamy fixing liquid 45 generated by foamy fixing liquid generating means 30 is applied on a roller surface of a foam application roller 41 from a foam discharging head 43, and is adjusted to a predetermined film thickness by a thickness adjustment blade 42. The surface of the foamy fixing liquid 45 on the foam application roller 41 is heated by a heater 52 serving as foam breaking means, and the foamy fixing liquid 45 of the surface side is broken. A liquid-like fixing liquid which is broken and liquefied flows into a film of the adjacent foamy fixing liquid, thereby increasing the film thickness of the foamy fixing liquid. As a result, a foam density of the foamy fixing liquid in which liquid-like fixing liquid flows onto the film thereof is increased. Thus, through the use of the small heater 52, the miniaturization of a whole device can be achieved by forming the foamy fixing liquid of the two layer structure having a layer of a foamy fixing liquid 45b of a high foam density and a layer of a foamy fixing liquid 45a of a low foam density which is not broken and does not flow into a foam film of the liquid-like fixing liquid so as to reduce a disposal quantity of the fixing liquid.

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Image forming apparatuses such as printers, facsimile machines, and copying machines are apparatuses that form images including characters and symbols on recording media such as paper, cloth, and OHP sheets based on image information. In particular, electrophotographic image forming apparatuses are widely used because they can form high-definition images on plain paper at high speed. In such an electrophotographic image forming apparatus, a heat fixing method is widely used in which toner on a recording medium is heated and melted, and the molten toner is pressurized to fix the toner on the recording medium. Yes. This thermal fixing method is preferably used because it can provide a high fixing speed and high fixed image quality. However, about half or more of the power consumption in such an electrophotographic image forming apparatus is consumed in heating the toner in the heat fixing method.

  On the other hand, a low power consumption (energy saving) fixing device is desired from the viewpoint of countermeasures for environmental problems in recent years. That is, there is a demand for a fixing method in which the temperature for heating the toner for fixing the toner is extremely lowered than before, or the toner does not need to be heated. In particular, the non-heat fixing method in which the toner is fixed to the recording medium without heating the toner at all is ideal in terms of low power consumption.

  As such a non-heating fixing method, an oil-in-water fixing solution in which an organic compound that can dissolve or swell toner and is insoluble or hardly soluble in water is dispersed and mixed in water is made into a foam, and a roller or the like is used. A film is formed on top. Then, after the unfixed toner contacts and penetrates the surface of the fixing object (recording medium) disposed at a predetermined position to dissolve or swell the toner, the fixing object is dried to fix the toner. A fixing method has been proposed and already known.

  As such a non-heat fixing method, the one described in Patent Document 1 is known. In the fixing method of Patent Document 1, a foam-like fixing solution produced by containing a large amount of bubbles in a liquid fixing solution containing at least a softening agent that dissolves or swells at least a part of a resin by a foam-like fixing solution producing means is obtained. This fixing method focuses on the extremely low bubble density. According to this fixing method, the foamy fixing solution is applied from the fixing solution supply port onto the foam application roller, which is the foam application unit, and the film thickness of the foamed fixing solution is adjusted. Then, a foam application roller to which a foam-type fixing liquid having an adjusted film thickness is applied is brought into contact with the recording medium, and the foam-type fixing liquid on the foam application roller is applied to an unfixed toner image on the recording medium. The toner is fixed on the recording medium. In this way, since the foam density of the fixing solution can be reduced by making the fixing solution foam, fixing with a smaller amount of fixing solution than before is possible, thus suppressing the residual liquid feeling on the recording medium. be able to.

  However, according to the above-mentioned Patent Document 1, when the foam-like fixing liquid whose film thickness is adjusted is brought into contact with the unfixed toner on the recording medium by the foam-applying roller, as described above, the foam-like fixing on the foam-applying roller is performed. There was a problem that the liquid was separated and the foamy fixing solution remained on the foam application roller. The foam-like fixing liquid remaining on the foam application roller after fixing may be collected from the foam application roller and discarded because unfixed toner on the recording medium may be mixed. For this reason, it is desired to reduce the amount of wasted fixing solution that is discarded by reducing the amount of fixing solution remaining on the foam application roller after fixing.

  In response to such a demand, the inventors of the present invention have made use of two foam fixing solution generating means for generating foam fixing solutions having different densities in Japanese Patent Application No. 2010-054060 (hereinafter referred to as the prior application). A fixing device that forms a two-layered foam fixing solution layer on a coating roller and contacts and penetrates the unfixed toner for fixing the second foam fixing solution layer to a medium. is suggesting. In the fixing device of this prior application, as described above, the discarding foam that is pulled by the surface tension of the foam application roller and remains on the surface of the foam application roller and is discarded by the first foam-fixing liquid generator. A foam-like fixer is produced, and this discarding foam-like fixer is applied as a first layer onto the foam application roller. This discarding foam fixing solution is generated with a lower bubble density than the second-layer fixing foam fixing solution used for fixing because the amount of useless fixing solution is reduced. Then, the fixing foam fixing solution generated by the second foam fixing solution generating means is formed as a second layer on the upper layer of the discarding foam fixing solution. The two-layer foam fixing solution thus formed is applied to the unfixed toner on the recording medium, and only the second-layer fixing foam fixing solution is transferred to the unfixed toner and comes into contact with and penetrates. The foam fixing solution for discarding the first layer remains on the foam application roller, and is recovered and discarded from the foam application roller by a residual foam fixing solution recovery means such as a recovery blade. As a result, the discarding foam fixing solution has a lower bubble density and the same volume as the fixing foam fixing solution, and its weight is small. Therefore, the amount of the fixing solution discarded is small.

  The fixing device of the prior application generates the first and second foam-like fixing liquids that generate foam-like fixing liquids having different foam densities in order to form a two-layer foam-like fixing liquid on the foam application roller. Means. Each of the first and second foamy fixing solution generating means has gas-liquid mixing means for causing the liquid fixing solution to contain a gas. Further, the first and second foamy fixing solution generating means include, in addition to the gas-liquid mixing means, a liquid fixing solution supply means for supplying a liquid fixing solution to the gas-liquid mixing means, and a gas-liquid mixing means. Gas supply means for supplying a gas to each. The gas supply means supplies a gas at a high pressure to the liquid fixer conveyed from the container for storing the liquid fixer to the gas-liquid mixing means to generate bubbles, so that a pump with a large output is required. The larger the output of the pump, the larger the size of the pump, and the larger the foam fixing liquid generating means including the gas supply means that requires a pump with a large output becomes large. For this reason, since it leads to the enlargement of the fixing device and the image forming apparatus of the above-mentioned prior application provided with two foamy fixing liquid generating means, it is desired that the fixing device is small.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device that can be miniaturized while forming a two-layer foam fixing solution to reduce the amount of fixing solution discarded, and An image forming apparatus is provided.

In order to achieve the above object, the invention of claim 1 is characterized in that a gas is mixed with a liquid fixing solution containing at least a softening agent that softens fine particles containing a resin by dissolving or swelling at least a part of the resin. The foam-like fixer generating means for generating a foam-like fixer, and the foam-like form generated by the foam-like fixer generating means on the coating surface of the foam applying means for applying to the unfixed resin fine particles formed on the medium. A fixing device for applying a fixing solution for applying a fixing solution, and applying the foaming fixing solution to unfixed resin fine particles on a medium by the application means to fix the resin fine particles to the medium. The foam fixing solution is broken to be liquefied, and the liquid fixing solution flows on a foam film of another foam fixing solution to increase the foam density of the foam fixing solution, and the foam-like fixing means Foam generated by fixer generator A layer of a high-foam-density foam-like fixer that is generated by increasing the foam density of the landing liquid by the high-bubble density-improving means and applied to unfixed resin fine particles on the medium; And a two-layer structure forming means for forming a two-layer foam fixing solution with a layer of the foam fixing solution in which the liquid fixing solution does not flow into the foam film.
According to a second aspect of the present invention, there is provided the fixing device according to the first aspect, wherein the high-bubble density means is a foam-type fixing on the surface side of the layer of the foam-type fixing liquid applied to the application surface of the foam-applying means. It is characterized by breaking the liquid.
Further, the invention of claim 3 is the fixing device according to claim 1 or 2, wherein the high-bubble density increasing means is a heater for heating the surface of the foam-like fixing liquid layer. .
According to a fourth aspect of the present invention, there is provided the fixing device according to the third aspect, further comprising temperature detecting means for detecting an environmental temperature, wherein the set temperature of the heater is changed based on the environmental temperature detected by the temperature detecting means. It is characterized by.
Further, the invention of claim 5 is the fixing device according to claim 3 or 4, wherein the heater heats unfixed resin fine particles formed on the medium.
According to a sixth aspect of the present invention, in the fixing device according to the first aspect, the high-bubble density increasing means is a roller that rubs the surface of the foam-like fixing liquid layer with a roller surface. .
Further, the invention of claim 7 is the fixing device according to claim 6, wherein the liquid fixing solution is applied to the surface of the foamy fixing solution layer using the roller surface of the roller.
According to an eighth aspect of the present invention, in the fixing device according to the first aspect, the high bubble density increasing means is a belt that rubs the surface of the foam-like fixing liquid layer with a belt surface.
Further, the invention of claim 9 is characterized in that, in the fixing device of claim 8, the liquid fixing solution is applied to the surface of the foamy fixing solution layer by using the belt surface of the belt.
The tenth aspect of the present invention is the fixing device according to the first aspect, wherein the high-bubble-density increasing means is the bubble-shaped fixing before being applied to the application surface of the bubble-applying means by the foam-like fixing liquid applying means. A part of the liquid is broken.
Further, the invention according to claim 11 is the fixing device according to claim 10, wherein the foam-like fixing liquid applying means includes a foam discharge head having a flow path through which the foam-like fixing liquid discharged from the discharge port flows. The high-bubble density increasing means is provided in the flow path of the discharge head.
According to a twelfth aspect of the present invention, in the fixing device according to the eleventh aspect, the high bubble density increasing means is provided on a part of an inner wall or an outer wall constituting the flow path.
Further, the invention of claim 13 is an image forming means for forming an unfixed toner image on a medium by performing an electrostatic recording process with toner in which resin-containing fine particles contain a colorant, and any one of claims 1 to 12. And fixing means for fixing the unfixed toner image on a medium by the fixing device described in the above item.

  In the present invention, a part of the foam fixer generated by the foam fixer generating means breaks down into a liquid by the high bubble density increasing means, and this liquid fixer is formed on the foam film of the nearby foam fixer. The foam density of a part of the foam-like fixer in which the liquid fixer has flowed onto the foam film increases. By the two-layer structure forming means, the foam fixing solution layer having a high foam density and the foam fixing solution layer in which the foam density is not broken and the liquid fixing solution does not flow into the foam film and the foam density is not changed. A two-layer foam fixing solution having different foam densities is formed. The layer of the foam-like fixing solution having a high foam density is applied to the resin fine particles on the medium. It is possible to reduce the amount of the fixing solution discarded by previously reducing the bubble density of the foam-like fixing solution foam in which the bubble density has not changed. The high-bubble density increasing means has only a configuration for breaking the foam-like fixing liquid, and includes a gas-liquid mixing means, a gas supply means having a large pump, and a liquid fixing liquid supply means. Compared to the foam-like fixer generating means, it is small. As a result, the fixing device provided with one foam-like fixing liquid generating means and one high-bubble density increasing means becomes smaller than the fixing apparatus provided with two foam-like fixing liquid generating means.

  As described above, according to the present invention, there is an excellent effect that it is possible to reduce the size of the fixing solution while forming a two-layered foamy fixing solution to reduce the amount of the fixing solution discarded.

1 is an overall schematic configuration diagram of an image forming apparatus according to an exemplary embodiment. FIG. 2 is a schematic configuration diagram illustrating an enlarged main part of an image forming unit. It is explanatory drawing about the fixing principle by a foamy fixing liquid. FIG. 3 is a schematic configuration diagram of a foamy fixing solution generating unit. 1 is a schematic configuration diagram of a fixing device having a foamy fixing solution generating unit of the present embodiment. It is a schematic block diagram which shows the mode of the film thickness adjustment with the blade for film thickness adjustment. It is a schematic sectional drawing which shows the mode of the high foam density by a broken bubble. It is a schematic block diagram of the fixing apparatus which has another foamy fixing liquid production | generation means of this embodiment. It is a schematic block diagram of the fixing apparatus which has another foamy fixing liquid production | generation means of this embodiment. It is a schematic block diagram of the fixing apparatus which has another foamy fixing liquid production | generation means of this embodiment. It is a schematic block diagram of the fixing apparatus which has another foamy fixing liquid production | generation means of this embodiment. It is a schematic block diagram of the fixing apparatus which has another foamy fixing liquid production | generation means of this embodiment. It is a schematic block diagram which shows another structure of a bubble breaker. It is a schematic block diagram of the fixing apparatus which has another foamy fixing liquid production | generation means of this embodiment.

Hereinafter, an embodiment of an image forming apparatus to which the present invention is applied will be described in detail with reference to the drawings.
FIG. 1 is an overall schematic configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus shown in FIG. 1 includes an image forming unit 1 that is an image forming unit in the center, a sheet feeding unit 2 below the image forming unit 1, an image reading unit 3 above the image forming unit 1, and an image forming unit. A color image forming apparatus having a configuration of an in-body sheet discharge unit 4 between the unit 1 and the image reading unit 3, and has functions of a printer, a copying machine, a facsimile machine, and a scanner. Although not shown, an automatic document feeder (ADF) is provided above the image reading unit 3.

  In FIG. 1, an image reading unit 3 includes a contact glass 3a, a document illumination light source 3b mounted on a reading traveling body, a first mirror 3c, a second mirror 3d, a third mirror 3e, an imaging lens 3f, and an image sensor 3g. The image of the document placed on the contact glass 3a by ADF or manual feeding is read by the image sensor 3g, and image information for writing (for example, yellow (Y), cyan (C), Image data corresponding to each color of magenta (M) and black (Bk), and is transmitted to the image forming unit 1.

  The image forming unit 1 includes a plurality of image carriers 5Y, 5C, 5M, and 5BK configured by drum-shaped photosensitive members, and toner images of different colors are formed on the respective image carriers. Is done. In the illustrated example, yellow toner images, cyan toner images, and magenta toner images are formed on the surfaces of three image carriers 5Y, 5C, and 5M, respectively, and black toner is formed on the image carrier 5BK. An image is formed. The image carriers 5Y to 5BK are arranged in parallel with each other at a predetermined interval. An intermediate transfer member 6 is disposed opposite to the image carriers 5Y to 5BK, and a drum may be used as the intermediate transfer member 6. In the illustrated example, a plurality of support rollers 7, 8, An endless belt that is wound around 9 and driven in the direction of arrow A is used.

  FIG. 2 is a schematic configuration diagram illustrating an enlarged main part (image forming unit of each color) of the image forming unit 1 illustrated in FIG. Since the four image forming units 20 of yellow (Y), cyan (C), magenta (M), and black (Bk) shown in FIG. 1 have the same configuration, FIG. 2 focuses on one image forming unit 20. Symbols representing colors are omitted.

  In the image forming unit 20 of FIG. 2, there are a charging device 10 that performs charging processing on the surface of the image carrier 5, and an exposure device 11 that irradiates the image surface with laser light L on the surface of the photoreceptor. 1), a developing device 12 that visualizes an electrostatic latent image formed on the surface of the image carrier 5 by exposure, and a transfer device that is disposed to face the image carrier 5 via an intermediate transfer member 6. 13. A cleaning device 14 that removes and collects toner remaining on the surface of the image carrier after being transferred to the intermediate transfer member 6, and a lubricant application device 25 that lowers the friction coefficient of the surface of the image carrier 5 are provided.

  The charging device 10 includes a charging roller 10a as a charging member and a spring 10b as an urging member that presses the charging roller 10a to the image carrier 5 with a predetermined pressure. Although not shown, the charging roller 10a has a conductive elastic layer around the conductive shaft, and the conductive elastic layer, the image carrier 5 and the like are connected via the conductive shaft by a voltage application device (not shown). A predetermined voltage is applied to the gap to impart an electric charge to the surface of the image carrier. Further, the developing device 12 sufficiently stirs the developer with the stirring screw 12a and magnetically adheres it to the developing roller 12b. The attached developer is thinned on the developing roller 12b by the developing doctor 12c, and the electrostatic latent image on the image carrier 5 is visualized by the developer. The transfer device 13 has a transfer bias roller, and electrically attaches the toner image on the image carrier 5 onto the intermediate transfer member 6 by the roller. The cleaning device 14 has a cleaning sheet made of urethane rubber or the like, and removes residual toner on the image carrier 5 by scraping with the sheet.

  In this embodiment, each color image forming unit 20 is configured as a process cartridge (PC) in which the image carrier 5, the charging device 10, the developing device 12, the cleaning device 14, and the lubricant applying device 25 are unitized. ing. The form of the process cartridge (PC) is arbitrary, but the process cartridge (PC) of the present invention is at least one constituent member of the lubricant applying device 25, the image carrier 5, the charging device 10, the developing device 12, and the cleaning device 14. Is a combination.

  When image formation is started in such an image forming apparatus, in each color image forming unit, the image carrier 5 is rotationally driven in the clockwise direction in FIG. 2, and at this time, the surface of the image carrier 5 is charged by the charging device 10. Is charged to a predetermined polarity. Next, the charged surface is irradiated with laser light L based on image information from the exposure device 11 shown in FIG. 1, whereby an electrostatic latent image is formed on the image carrier 5. Note that the image information is image data read by the image reading unit 3 described above, data sent from an external computer via a LAN, data received by facsimile, and the like. When the image reading unit 3 is used, an original (not shown) placed on the contact glass 3a is reciprocated by a reading traveling body including the original illumination light source 3b and the first mirror 3c. Image information scanned by the reading traveling body is passed through the second mirror 3d, the third mirror 3e, and the imaging lens 3f as an image signal to an image pickup device (eg, CCD) 3g installed behind the imaging lens 3f. Is read. The read image signal is digitized, image-processed, and written on the surface of the image carrier 5 by light emission of a laser diode (not shown) of the exposure device 11. The electrostatic latent image formed on the surface of the image carrier 5 includes a dry developer (resin fine particles containing resin and color material (hereinafter referred to as toner)) carried on the developing roller 8 of the developing device 12. The developer is visualized as a toner image.

  The image forming operation described above is performed on all the image carriers 5Y to 5Bk shown in FIG. 1, and thereby the yellow toner image, cyan toner image, magenta toner image, and black formed on the image carriers 5Y to 5BK, respectively. The toner images are sequentially transferred onto the intermediate transfer body 6 in a superimposed manner. In the image forming apparatus shown in FIG. 1, a secondary transfer device (for example, a secondary transfer roller) 16 is disposed facing the support roller 7 with the intermediate transfer member 6 interposed therebetween.

  On the other hand, a recording medium made of transfer paper (standard plain paper, continuous paper, letter paper, postcard, cardboard, etc.) or a resin film (OHP sheet, etc.), etc., from a paper feed unit 2 disposed below the image forming unit 1 P is fed out by the paper feed roller 2a as indicated by an arrow B, and the recording medium P is fed between the secondary transfer device 16 and the intermediate transfer body 6 at a predetermined timing by the rotation of the registration roller pair 2b. . In this way, when the recording medium P passes through the secondary transfer device 16, the superimposed toner images on the intermediate transfer body 6 are collectively transferred onto the recording medium P by the action of the secondary transfer device 16. Then, after the toner image is fixed on the recording medium P by the fixing device 18, the toner image is discharged to the in-body discharge unit 4 by the discharge roller 19. Further, the transfer residual toner adhering to the surface of the intermediate transfer body 6 after the toner image transfer is removed by the belt cleaning device 15. Further, toner, paper dust, and the like adhering to the roller surface of the secondary transfer device 16 are removed by a roller cleaning device. The belt cleaning device 15 and the roller cleaning device are also provided with a lubricant application device as required.

Next, a basic fixing device and fixing method using a foamy fixing solution will be described in detail.
FIG. 3 is an explanatory diagram of the principle of fixing with a foamy fixing solution. In the fixing device and the fixing method according to the present embodiment, as shown in FIG. 3, a foamy fixing solution 45 containing a softening agent that softens fine particles containing a resin by dissolving or swelling at least a part of the resin is used. It is applied to resin fine particles (unfixed toner T) on the recording medium P to fix the resin fine particles to the recording medium P. Specifically, the foam density of the fixer can be lowered by changing the fixer into a foam-like fixer 45 composed of foam by a foam-like fixer generating unit to be described later, as shown in FIG. As described above, since the fixing liquid layer (foam-like fixing liquid film) 45 on the foam application roller 41, which is a foam-type fixing liquid application member, can be thickened, and further, the influence of the surface tension of the fixing liquid can be suppressed. The offset of resin fine particles to the application roller 41 can be prevented.

  The foam-like fixing liquid 45 permeates and transfers to the recording medium P and the unfixed toner T on the recording medium P by bringing the foam application roller 41 and the recording medium P into contact with each other during the conveyance process of the recording medium P. At that time, it is known that not all of the foam-like fixing liquid 45 is transferred onto the recording medium P, but some remains on the foam application roller 41 as shown in FIG. As a result of this experiment, the ratio is a volume ratio, and it has been found that the fixing solution on the recording medium: the fixing solution on the foam application roller = 7: 3.

  Next, a basic configuration of the foamy fixing solution generating unit will be described. FIG. 4 is a schematic configuration diagram of the foamy fixing solution generating means. The foam fixing solution generating means 30 shown in FIG. 4 generates a foam fixing solution with a large bubble from the liquid fixing solution, and then separates the large bubbles to generate a foam fixing solution with a fine prescription. It is. As shown in FIG. 4, as the large bubble generating unit in the foam-like fixing solution generating unit 30, the liquid fixing solution 32 in the fixing solution container 31 is supplied to the liquid transport pump 33 by a pump drive control signal from the control unit 50. It is driven and supplied to the gas-liquid mixing unit 35 through the liquid transport pipe 34 and the like. Further, the gas transport pump 39 is driven by a pump drive control signal from the control unit 50 and air is supplied from the air port 40 to the gas-liquid mixing unit 35 through the gas transport pipe 36 and the like. A method using compressed air is also conceivable.

  In the gas-liquid mixing unit 35, the liquid and the gas conveyed as described above are mixed and further passed through the microporous sheet 37, whereby a large bubble having a uniform bubble diameter can be generated. The hole diameter of the microporous sheet 37 is desirably about 30 [μm] to 100 [μm]. Further, the porous member is not limited to the microporous sheet 37 in FIG. 4, and may be a porous member having an open cell structure, such as a sintered ceramic plate, a nonwoven fabric, or a foamed resin sheet having a pore diameter of about 30 [μm] to 100 [μm]. May be. As another method for generating large bubbles, the liquid fixing solution and air supplied from the liquid transfer pump 33 and the gas transfer pump 39 are agitated with a blade-shaped stirrer and bubbles are entrained in the liquid. It is also desirable to generate a large bubble by bubbling the liquid fixer supplied from the liquid transport pump 33 with an air supply pump or the like.

  Next, in the foam-like fixing liquid generating means 30 shown in FIG. 4, in order to divide the large bubbles generated in the gas-liquid mixing unit 35 and divide them into two or more, a shear force is applied to the large bubbles. The micro-bubble generating part 38 is provided. As shown in FIG. 4, the microbubble generating unit 38 is configured by a closed double cylinder, and the inner cylinder 38-1 is rotatable. Then, a large foamy fixing solution generated in the gas-liquid mixing unit 35 is supplied from a part of the outer cylinder 38-2, and a gap between the inner cylinder 38-1 and the outer cylinder 38-2 that rotate inside (this is The foamy fixing solution having a large bubble is subjected to a shearing force by the inner cylinder 38-1 by rotating the motor 51 by a motor drive control signal from the control unit 50. Due to this shearing force, the large bubbles are changed into minute bubbles, and a foam-like fixing solution having a desired minute bubble diameter can be obtained from the bubble outlet provided in the outer cylinder 38-2.

  As described above, in the foam-like fixing liquid generating means 30 shown in FIG. 4, a large-diameter foam generating part (gas-liquid mixing part 35) that changes the liquid fixing liquid 32 into a liquid having a large foam diameter, and shearing into large bubbles. By combining the microbubble generator 38 that generates microbubbles by applying force, the foam-like fixing having a microbubble diameter of about 5 [μm] to 50 [μm] from the liquid fixing liquid 32 in a very short time. A liquid can be generated.

The foam density of the foam-like fixing solution is preferably in the range of about 0.04 [g / cm ³ ] to 0.02 [g / cm ³ ]. The bubble density can be controlled by changing the liquid / gas flow rate ratio per unit time by changing the outputs of the liquid transfer pump 33 and the gas transfer pump 39. For example, in order to obtain a foam-like fixing solution having a foam density in the above range, the ratio between the liquid fixing solution and air may be controlled from about 1:25 to about 1:50.

Here, a method for measuring the bubble density of the foam-like fixing solution will be described.
A container whose volume and mass are known in advance is filled to the extent that it exceeds the volume of the foam-like fixer to be measured and overflows from the container. Immediately after filling, the foamy fixer overflowing from the container is worn away. After grinding, the weight mass of the container filled with foam is measured. By subtracting the mass of only the container previously known from the mass of the container filled with the foamed fixing solution measured at this time, the mass of only the foamed fixing solution filled in the container can be calculated. Then, by dividing the calculated mass of only the foam-like fixing solution by the volume of the container known in advance, the bubble density of the foam-like fixing solution to be measured can be calculated. Since it is necessary to perform such a process in order to accurately measure the bubble density of the foam-like fixing solution, it is difficult to calculate the bubble density of the foam-like fixing solution generated by the fixing device 50 in real time. .

  Further, when the bubble density of the foam-like fixing solution is higher than the above-described desirable range, the state becomes close to that of the liquid fixing solution, so that the toner is caught in the liquid and moves to be fixed on the recording medium P, so-called image flow. Is likely to occur, and image degradation is likely to occur. Furthermore, since the amount of the fixing solution contained in a certain volume of the foam-like fixing solution is excessive, an unnecessarily large amount of the fixing solution is used, and the use efficiency is lowered. On the other hand, if the foam density of the foam-like fixing solution is too lower than the above-described desirable range, the amount of the fixing solution contained in a certain volume of the foam-like fixing solution is insufficient. Failure to fix will occur.

  The present inventors have obtained from various experiments that the average bubble diameter of the foam-like fixing solution applied to the recording medium P is desirably about 20 [μm]. Since there is no fixing solution in the air part of the bubbles constituting the foam-like fixing solution, if the bubble diameter is too large, the toner in the air part is not softened and fixed. In other words, uneven fixing occurs. On the other hand, if the bubble diameter is too small, it becomes a dry foam state in which the wettability with respect to the foam application roller 41 is extremely reduced, and even if the film is adjusted by the film thickness adjusting blade 42, a uniform foam film is formed on the foam application roller 41. Because it does not become, after all it becomes uneven. In the fixing device 50, the initial bubble-shaped fixing solution having a large bubble diameter generated in the gas-liquid mixing unit 35 is subjected to shearing force by the bubble reducing device 38 to separate the bubbles, whereby the average bubble diameter is 20 [ [mu] m] is produced.

  For the reasons described above, the bubble density and bubble diameter of the foam-like fixing solution have a good range for the fixing performance. Of course, good portions differ depending on the type of fixing solution, the type of toner, and the like, but there is basically such a range in the method of fixing with foaming fixing solution.

  In the foam-like fixing liquid generating device 30, the air pressure in the gas-liquid mixing unit 35 is increased by sending air with the gas transport pump 39, and the pressure is increased between the gas-liquid mixing unit 35 and the container of the bubble reducing device 38. It makes a difference. Due to this pressure difference, pressure is applied to the foam-like fixing solution, and the initial foam-like fixing solution is conveyed from the gas-liquid mixing unit 35 to the bubble reducing device 38. In the fixing device 50, the atmospheric pressure in the gas-liquid mixing unit 35 is set to be about 150 [kPa] higher than the atmospheric pressure, but the setting of the atmospheric pressure in the gas-liquid mixing unit 35 is not limited to this. is not. When transporting the inside of a tubular member by applying pressure to the foam-like fixing solution as in the foam transportation in the fixing device 50, it is easy to send if the foam density of the foam-like fixing solution is high, and difficult to send if the foam density is low. Become.

  When the control device 50 receives a signal for starting a printing operation from the printer control device, the control device 50 operates the gas transport pump 39 and the motor 51. By the operation of the gas transport pump 39, air in the atmosphere is sucked into the gas transport pump 39, air is blown into the liquid fixer 32 in the gas / liquid mixing unit 35, and the initial foamy fixer is transferred into the gas / liquid mixing unit 35. Is generated.

  In addition to the above-described configuration, the configuration for generating the initial foam-like fixing solution having a large bubble diameter includes a configuration using bubbling in which air is fed into the liquid fixing solution 32 by an air pump, or a microporous sheet. Alternatively, a configuration in which the liquid fixing solution 32 and air are passed to generate an initial foamy fixing solution is also applicable.

Next, the cleaning blade will be described.
The foam-like fixing liquid that has not been transferred from the foam application roller 41 to the recording medium P at the application nip and a small amount of offset toner that has been transferred from the recording medium P are scraped off by the cleaning blade 46 from the surface of the foam application roller 41. Removed. The foamy fixing solution scraped off by the cleaning blade 46 accumulates in the vicinity of contact between the cleaning blade 46 and the foam application roller 41. The accumulated foam fixing solution is recovered in a foam recovery container (not shown).

  FIG. 5 is a schematic configuration diagram of a fixing device having a foamy fixing liquid generating unit of the present embodiment. The control unit 50 shown in FIG. 2 is a main part of the image forming unit having the configuration shown in FIG. 2 (each color image forming unit, intermediate transfer body, secondary transfer device, etc.) and the bubble fixing unit having the configuration shown in FIG. The fixing device 18 provided with the liquid generating means 30 is controlled. As described above, images of the respective colors are formed on the image carriers 5Y, 5C, 5M, and 5BK by the image forming units 20Y, 20C, 20M, and 20BK of the respective main colors of the image forming unit illustrated in FIG. The unfixed toner image transferred onto the transfer body 6 and formed on the intermediate transfer body 6 is transferred onto the recording medium P by the secondary transfer device 16 at the secondary transfer section. In the embodiment, the bubble breaking means 52 having a heater extending in the axial direction of the foam application roller 41 so as to face the roller surface of the foam application roller 41 downstream from the installation position of the film thickness adjusting blade 42. Is provided. The surface of the layer of the low-density foam-like fixing liquid 45 applied on the foam application roller 41 is heated by the heater of the foam breaking means 52.

  The control unit 50 controls the main part of the image forming unit to supply the foam-like fixing liquid generated by the foam-like fixing liquid generating unit 30 according to the image mode of the unfixed toner image formed on the recording medium P. The amount and bubble density are controlled to be appropriate values. In this embodiment, a two-layer foam fixing solution layer is formed on a foam application roller, and the second layer of foam fixing solution 45b is brought into contact with and penetrates unfixed toner for fixing. Is fixed on the medium. Then, a layer of the foam fixing solution 45a for discarding which is pulled by the surface tension and remains on the surface of the foam application roller and discarded is applied as a first layer on the foam application roller. The discarding foam fixing solution 45a has a lower bubble density than the second-layer fixing foam fixing solution 45b used for fixing because the amount of useless fixing solution is reduced. In order to form such a two-layer foam fixing solution, in this embodiment, a foam fixing solution having a low foam density is first generated by the foam fixing solution generating means 30 and applied to the coating roller. At the same time, the film thickness adjusting blade 42 is adjusted so that the film thickness of the foam-like fixing solution on the foam application roller 41 of the fixing device 18 becomes an optimum value corresponding to the supply amount. In the present embodiment, the film thickness is adjusted to take into consideration that the film thickness is optimized even if the film thickness is reduced by the bubble breaking means described later.

  The foam fixer generated by the foam fixer generating means 30 as described above is sent to the foam discharge head 43 by a foam transport pipe connected to the foam outlet provided in the outer cylinder of the microbubble generator 38. It is done. Then, after the foam is ejected onto the foam application roller 41 by the foam ejection head 43, it is shaped to a desired film thickness via the film thickness adjusting blade 42, and formed as a foam-like fixing liquid 45 on the foam application roller 41. The The film of the foam-like fixing liquid 45 is brought into contact with and applied to an unfixed toner image on the recording medium P at a contact portion between the foam application roller 41 and the pressure roller 44, thereby performing a fixing process.

  As shown in FIG. 6, the film thickness adjustment of the foam fixing solution on the foam application roller 41 is performed by using a rotatable film thickness adjusting blade 42 having a gap with the foam application roller 41 to reduce the film thickness. When the gap between the foam application roller 41 and the film thickness adjusting blade 42 is narrowed as shown in FIG. 6 (a), and when the film thickness is increased, the foam application roller 41 as shown in FIG. 6 (b). And the gap between the film thickness adjusting blades 42 is widened. As an example of controlling the gap, a rotating shaft 42a having a rotation driving means (stepping motor, solenoid, etc.) is provided at the end of the film thickness adjusting blade 42, and the driving of the rotating shaft 42a is controlled by the control unit 50. The gap amount is controlled according to the thickness of the toner layer, the ambient temperature, the size of the bubbles of the foam-like fixing liquid 45, the foam viscosity, the applied pressure of the foam, the layer thickness of the unfixed toner, etc. The film thickness is adjusted to take into consideration that the film thickness is optimized even if the film thickness is reduced due to bubble breaking.

  Then, the foam application roller 41 is rotated, and the surface of the layer of the low-foam-density foam-like fixing liquid 45 applied on the foam application roller 41 as shown in FIG. The vicinity of the heater 52 which is a bubble breaking means arranged downstream from the installation position is passed. Thereby, the surface of the layer of the foam-like fixing liquid 45 applied on the application roller 41 is heated by the heater 52 of the foam breaking means. The heating temperature of the heater 52 of the bubble breaking means is controlled by the control unit 50. As shown in FIG. 7B, the bubbles of the foam-like fixing solution 45 present on the surface of the heated low-density foam-fixing solution 45 are broken and liquefied. Then, as shown in FIG. 7C, the liquefied fixing solution flows on the foam fixing solution film immediately below. As shown in FIG. 7D, the film thickness of the foamy fixing solution through which the liquid fixing solution has flowed increases. Such a bubble breaking phenomenon occurs on the surface side of the foam-like fixing liquid 45. As a result, the weight of the foam-like fixing solution in which the film thickness of the foam is increased is increased by the amount of the liquefied liquid fixing solution that has broken bubbles. Therefore, the bubble density of the foam-like fixing solution is higher than the bubble density of the foam-like fixing solution in which the liquid fixing solution does not flow. For example, a two-layer foam fixing solution having a different foam density as shown in FIG. 7D is formed. In this manner, a two-layer foam fixing solution can be formed on the foam application roller 41 by the heater 52 of the foam breaking means. Using the formation of the two-layer foam fixing solution, a two-layer structure having a first layer of foam fixing solution 45a for discarding and a second layer of fixing foam fixing solution 45b. Form a layer of foamy fixer of structure. In addition, since the foamed fixing solution contains air, the thermal conductivity is poor. For this reason, the heating amount at the set temperature of the heater 52 of the bubble breaking means breaks the bubbles in order from the bubbles of the bubble-like fixing solution located on the surface of the bubble-like fixing solution. Accordingly, the appropriate film thickness of the fixing foam-like fixing solution can be controlled by the heating amount of the heater 52 of the bubble breaking means, the speed of passing through the heater 52 of the bubble breaking means, that is, the rotation speed of the application roller 41. it can. Alternatively, it can also be controlled by controlling the distance between the heater 52 of the bubble breaking means and the foam-like fixing liquid 41.

  FIG. 8 is a schematic configuration diagram of a fixing device having another foamy fixing solution generating unit of the present embodiment. In the figure, the same reference numerals as those in FIG. 5 denote the same components. The heater 52 of the bubble breaking means shown in the figure is arranged in the vicinity of the nip portion between the bubble applying roller 41 and the pressure roller 44. For this reason, the heat from the heater 52 of the bubble breaking means reaches the surface of the foam-like fixing liquid 45 applied on the foam application roller 41 and the unfixed toner layer on the recording medium P. As a result, a foam fixing liquid layer 45b for fixing of the second layer can be generated, and the unfixed toner image on the recording medium P can be heated and softened to improve the fixability.

  FIG. 9 is a schematic configuration diagram of a fixing device having another foamy fixing solution generating unit of the present embodiment. In the figure, the same reference numerals as those in FIG. 5 denote the same components. The fixing device shown in the figure is provided with a heater 53 in addition to the heater 52 of the bubble breaking means shown in FIG. The heater 53 is provided to heat the unfixed toner image on the recording medium P, and heat is supplied from the heater 53 to soften the unfixed toner by the supply current from the control unit 50, thereby fixing the fixing property. It is improving.

  FIG. 10 is a schematic configuration diagram of a fixing device having another foamy fixing solution generating unit of the present embodiment. In the figure, the same reference numerals as those in FIG. 9 denote the same components. The fixing device shown in the figure is provided with a temperature sensor 54 for measuring the environmental temperature. Based on the environmental temperature measured by the temperature sensor 54, the control unit 50 controls the heating operation or the heating temperature of the heater 52 or the heater 53 of the bubble breaking means. For example, when the environmental temperature is not low, it is not necessary to heat the unfixed toner on the recording medium P, so that unnecessary power consumption can be suppressed by automatically turning off the heating. In addition, by automatically changing the set temperature, even when the environmental temperature is low compared to the case where the set temperature is fixed, the fluidity of the foam-like fixer due to the temperature drop can be prevented and optimal fluidity can be obtained. it can. Thereby, the film of the foam-like fixing solution can be applied to the recording medium P more efficiently.

  FIG. 11 is a schematic configuration diagram of a fixing device having another foamy fixing solution generating unit of the present embodiment. In the figure, the same reference numerals as those in FIG. 5 denote the same components. The fixing device shown in the figure is disposed at a position facing the roller surface of the foam application roller 41 and includes a bubble breaker roller 55 which is a bubble breaker. The roller surface of the bubble breaking roller 55 of the bubble breaking means rubs against the surface of the layer of the foam-like fixing liquid 45 on the foam application roller 41, so that the bubbles of the foam-like fixing liquid are broken and liquefied. The liquefied fixing solution flows on the film of the foam-like fixing solution directly below. The film thickness of the foamy fixing solution through which the liquid fixing solution has flowed increases. Such a bubble breaking phenomenon occurs on the surface side of the foam-like fixing liquid 45. As a result, the weight of the foam-like fixing solution in which the film thickness of the foam is increased is increased by the amount of the liquefied liquid fixing solution that has broken bubbles. Therefore, the bubble density of the foam-like fixing solution is higher than the bubble density of the low-density foam-like fixing solution in which the liquid fixing solution does not flow. Thereby, a foam-like fixing solution having a two-layer structure with different foam densities is formed. As described above, the foam fixing liquid having a two-layer structure can be formed on the foam application roller 41 by the foam breaking roller 55 of the foam breaking means.

FIG. 12 is a schematic configuration diagram of a fixing apparatus having another foamy fixing liquid generating unit of the present embodiment. In the figure, the same reference numerals as those in FIG. 11 denote the same components. The fixing device shown in the figure is disposed at a position facing the roller surface of the foam application roller 41, and serves as a bubble breaker that applies liquid fixer to the surface of the foam-like fixer 45 applied on the foam application roller 41. The liquid fixing liquid application roller 56 is provided. The liquid fixing liquid application roller 56 is provided with a pumping roller 56-1 in a container in which the liquid fixing liquid is stored, and the liquid fixing liquid application roller 56-2 is provided via the pumping roller 56-1. The scooping roller 56-1 and the liquid fixing solution roller 65-2 are rollers that extend in the axial direction of the foam application roller 41, and are wider than the width of the foam fixing solution applied to the roller surface of the foam application roller 41. The roller surface length is as follows. The liquid fixing solution is applied to the surface of the foam fixing solution layer on the foam application roller 41 by the liquid fixing solution application roller 56. This prevents the dried roller from peeling off the foamy fixing solution from the foam application roller 41 and changing the film thickness adjusted by the film thickness adjusting blade 42, and the liquid fixing solution is removed from the foam fixing solution. By applying the liquid as it is on the surface film, a layer of a high-density foam-like fixing solution can be generated.
Although the bubble breaking means in FIGS. 11 and 12 is constituted by a roller, the present invention is not limited to this. As shown in FIG. 13, the bubble breaking belt 57 suspended by the driving roller 57-1 and the driven roller 57-2. You may comprise the bubble breaking means using. The foam-breaking belt shown in FIG. 13 is in a form in which the liquid adhering liquid is applied while being rubbed on the belt surface, and may be in a form in which the surface of the layer of the foam-like fixing liquid 45 is rubbed with a dry belt surface.

  FIG. 14 is a schematic configuration diagram of a fixing device having another foamy fixing solution generating unit of the present embodiment. In the figure, the same reference numerals as those in FIG. 5 denote the same components. The fixing device shown in the figure has a foam discharge head 43 provided with a heater 58 as a bubble breaking means. Then, the foamy fixer generated by the foamy fixer generating unit 30 passes through the flow path in the foam discharge head 43. A heater 58 for foam breaking means is installed on one side of the inner wall or outer wall of the flow path. Due to the heating of the heater 58, bubbles of the foam-like fixer that have passed through the heater installation side in the layer of foam-like fixer that passes through the bubble discharge head 43 break and liquefy. Then, the liquefied liquid fixer flows into the foam fixer film nearby. The film thickness of the foamy fixing solution through which the liquid fixing solution has flowed increases. As a result, the weight of the foam-like fixing solution having a thick film thickness is increased by the amount of the liquid fixing solution that has broken and liquefied. Therefore, the bubble density of the foam-like fixing solution is higher than the bubble density of the low-density foam-like fixing solution in which the liquid fixing solution did not flow. As a result, a two-layer foam fixing solution having a different foam density is formed in the foam discharge head 43. A two-layer foam fixing liquid 45 discharged from the foam discharge head 43 is applied onto the foam application roller 41. As described above, the two-layer foam fixing liquid can be formed on the foam application roller 41 by the heater 58 of the foam breaking means provided in the foam discharge head 43. In this embodiment, a heater is used as the bubble breaker, but a bubble breaker roller, a bubble breaker belt, and a liquid fixer application unit may be provided on the inner wall of the flow path in the bubble discharge head.

  Next, the fixing solution composition used in the fixing device of this embodiment will be described. In the fixing device of the present embodiment, a liquid fixing solution containing at least a softening agent and a foaming agent is used as described above using a foam-like fixing solution containing a large amount of bubbles by dispersing bubbles from a liquid state into the liquid. Fixing is in progress.

First, the softener will be described.
The softening agent has a function of softening the resin fine particles by dissolving or swelling at least a part of the resin contained in the toner.
The softener is preferably an ester compound. The ester compound is excellent in solubility or swelling property that dissolves or swells at least a part of the resin contained in resin fine particles such as toner. Among the ester compounds, aliphatic esters and carbonates are particularly preferable because of their excellent resin softening ability. Moreover, it is preferable also from the point which does not inhibit the foaming property by the anionic surfactant as a foaming agent mentioned later.

  Further, the fixing of the toner as the resin fine particles to the recording medium is performed by an apparatus frequently used in a sealed environment, and the softening agent remains in the toner even after the toner is fixed on the recording medium. It is preferable that the fixing of the toner with respect to the toner does not involve generation of a volatile organic compound (VOC) and an unpleasant odor. That is, the softener preferably does not contain volatile organic compounds (VOC) and substances that cause unpleasant odors. Aliphatic esters have a high boiling point and low volatility and have no irritating odor as compared to generally used organic solvents (toluene, xylene, methyl ethyl ketone, ethyl acetate, etc.).

  As a practical odor measurement scale that can measure odors in office environments with high accuracy, the odor index [10 × log (until the substance odor is no longer felt) by the three-point comparison odor bag method, which is a sensory measurement Can be used as an indicator of odor. The odor index of the aliphatic ester contained in the softener is preferably 10 or less. In this case, an unpleasant odor is not felt in a normal office environment. Furthermore, it is preferable that not only the softening agent but also other liquid agents contained in the fixing solution have no unpleasant odor and irritating odor.

  The aliphatic ester includes a saturated aliphatic ester. When the aliphatic ester contains a saturated aliphatic ester, the storage stability (resistance to oxidation, hydrolysis, etc.) of the softener can be improved. Further, many saturated aliphatic esters can dissolve or swell the resin contained in the toner within 1 [second]. Furthermore, saturated aliphatic esters can reduce the tackiness of the toner provided on the recording medium. This is considered to be because the saturated aliphatic ester forms an oil film on the surface of the dissolved or swollen toner.

  Therefore, as the fixing solution, it is desirable to use a solution in which the saturated aliphatic ester contains a compound represented by the general formula “R1COOR2”. R1 in the general formula of this compound represents an alkyl group having 11 to 14 carbon atoms, and R2 represents a linear or branched alkyl group having 1 to 6 carbon atoms. If the number of carbon atoms in R1 and R2 is less than the desired range, odor is generated, and if it is greater than the desired range, the resin softening ability is lowered. As the fixing solution, the saturated aliphatic ester containing a compound represented by the general formula “R1COOR2” can improve the solubility or swelling property with respect to the resin contained in the toner. In addition, the odor index of the compound represented by the general formula “R1COOR2” is 10 or less, and does not have an unpleasant odor or an irritating odor.

  Examples of the aliphatic monocarboxylic acid ester that is the saturated aliphatic ester containing the above compound include ethyl laurate, hexyl laurate, ethyl tridecylate, isopropyl tridecylate, ethyl myristate, isopropyl myristate, and the like. Many of these aliphatic monocarboxylic esters containing the above compounds are soluble in oily solvents but not in water. Therefore, for many of the aliphatic monocarboxylic acid esters which are the above compounds, in an aqueous solvent, glycols are contained in the fixing solution as a dissolution aid and are in the form of dissolution or microemulsion.

  Further, as the fixing solution, it is desirable to use a solution in which the aliphatic ester contains an aliphatic dicarboxylic acid ester. When the aliphatic ester contains an aliphatic dicarboxylic acid ester, the resin contained in the toner can be dissolved or swollen in a shorter time. For example, in high-speed printing of about 60 [ppm], it is preferable that the time until the toner is fixed on the recording medium after applying the fixing liquid to the unfixed toner on the recording medium is within 1 [second]. When the aliphatic ester contains an aliphatic dicarboxylic acid ester, a time required for fixing the toner on the recording medium by applying a fixing solution to the unfixed toner or the like on the recording medium is 0.1 [second. ] Within. Furthermore, since the resin contained in the toner can be dissolved or swollen by adding a smaller amount of the softening agent, the content of the softening agent contained in the fixing solution can be reduced.

Therefore, as the fixing solution, it is desirable to use a fixing liquid containing the compound represented by the general formula “R3 (COOR4) ₂ ”. R3 in the general formula of this compound represents an alkylene group having 3 to 8 carbon atoms, and R4 represents a linear or branched alkyl group having 3 to 5 carbon atoms. If the number of carbon atoms in R3 and R4 is less than the desired range, odor is generated, and if it is greater than the desired range, the resin softening ability decreases. As the fixing solution, the aliphatic dicarboxylic acid ester containing a compound represented by the general formula “R3 (COOR4) ₂ ” is used to improve the solubility or swellability of the resin contained in the toner. Can do. Further, the odor index of the compound represented by the above general formula “R3 (COOR4) ₂ ” is 10 or less, and does not have an unpleasant odor or an irritating odor.

  Examples of the aliphatic dicarboxylic acid ester containing the above compound include 2-ethylhexyl succinate, dibutyl adipate, diisobutyl adipate, diisopropyl adipate, diisodecyl adipate, diethyl sebacate, dibutyl sebacate and the like. Many of these aliphatic dicarboxylic acid esters containing the above compounds are soluble in oily solvents but not in water. Therefore, in an aqueous solvent, glycols are contained in the fixing solution as a dissolution aid and are dissolved or in the form of a microemulsion.

  Further, in the fixing solution in the present embodiment, the aliphatic ester preferably contains a dialkoxyalkyl aliphatic dicarboxylate. When the aliphatic ester contains an aliphatic dicarboxylate dialkoxyalkyl, the fixability of the toner to the recording medium can be improved.

As the fixing solution, it is preferable to use a fixing solution containing a compound represented by the general formula “R5 (COOR 6 —O—R 7) ₂ ” as described above. R5 in the general formula of this compound represents an alkylene group having 2 to 8 carbon atoms, R6 represents an alkylene group having 2 to 4 carbon atoms, and R7 represents 1 to 4 carbon atoms. The alkyl group is shown. If the number of carbon atoms in R5, R6, and R7 is less than the desired range, odor is generated, and if it is greater than the desired range, the resin softening ability decreases. As the fixing solution, a solution in which the aliphatic dicarboxylate dialkoxyalkyl contains a compound represented by the general formula “R5 (COOR6-O-R7) ₂ ” is used. Swellability can be improved. Moreover, the odor index of the compound represented by the general formula “R5 (COOR6-O-R7) ₂ ” is 10 or less, and does not have an unpleasant odor or an irritating odor.

  Examples of the aliphatic dicarboxylate dialkoxyalkyl containing the above compound include diethoxyethyl succinate, dibutoxyethyl succinate, dicarbitol succinate, dimethoxyethyl adipate, diethoxyethyl adipate, dibutoxyethyl adipate, sebacin Examples include diethoxyethyl acid. When these aliphatic dicarboxylic acid dialkoxyalkyls containing the above compounds are used in an aqueous solvent, glycols are included in the fixing solution as a solubilizing agent, if necessary, to form a solution or microemulsion.

  Examples of the carbonate ester include ethylene carbonate, propylene carbonate (propylene carbonate), glycerol 1,2-carbonate, 4-methoxymethyl-1,3-dioxolan-2-one, and the like.

  Examples of ester compounds other than the above include citric acid esters such as triethyl citrate, acetyl triethyl citrate, tributyl citrate and tributyl acetyl citrate; ethylene glycol diacetate, diethylene glycol diacetate, triethylene glycol diacetate And compounds obtained by esterifying glycols such as monoacetin; compounds obtained by esterifying glycerol such as monoacetin, diacetin, and triacetin.

Next, the foaming agent will be described.
As described above, the fixing solution contains a softening agent, but generally the softening agent has a strong defoaming action. For this reason, when the liquid fixing solution is used as the foamy fixing solution as in the fixing device of the present embodiment, the higher the concentration of the softening agent in the fixing solution, the worse the foaming property and foam stability of the fixing solution. Therefore, there is a possibility that foaming is difficult to occur or the foam-like fixing solution is easily broken. If it is difficult to foam, it is impossible to obtain a foam fixer having a low foam density. Even if a foam fixer having a desired foam density is obtained, if the foam fixer easily breaks, This causes the same problem as the configuration in which the liquid fixer is applied.

  In addition, as a foaming agent, an anionic surfactant can achieve excellent foaming properties and foam stability, and is excellent as a foaming agent. Among anionic surfactants, fatty acid salts are most excellent in foam stability and are most suitable as a foaming agent for fixing solutions. Here, foam stability refers to the property that the fixing solution in the form of foam is difficult to become liquid. As the foam-type fixing solution to be applied to the unfixed toner by the fixing device of the present embodiment, it is desirable that the foam does not disappear even if left in a foam state for 1 minute, and has foam stability enough to maintain the foam state. .

  In order to solve the problem of deterioration of foamability and foam stability when the softener concentration in the fixing solution is increased, the present inventors have made various prototypes based on the type and concentration of the anionic surfactant. It was. Further, a prototype was made by paying attention to a technique called “super fat” described in Non-Patent Document 1, that is, a free fatty acid contained in a solid detergent (soap). Here, to outline the technology called super fat, it is a method of adding a small amount of free fatty acids that are difficult to oxidize to increase the excess fat and oil, leaving a small amount of fat and oil that is not saponified, for example, to enhance the moisturizing action, etc. It is said to be effective. In Non-Patent Document 1, it is known that when a very small amount of fatty acid is added to a soap water-based system, the foaming performance is improved and the foam quality becomes more creamy, which is called super fat soap. It is described. Similar to this super fat, an attempt was made to foam by adding a very small amount of fatty acid to a fixing solution having a softening agent, but both foamability and foam stability were poor.

  On the other hand, the present inventors use a fatty acid salt having 12 to 18 carbon atoms as a foaming agent, and further contain a fatty acid having 12 to 18 carbon atoms in the fixing solution, thereby increasing the concentration of the softening agent. The present inventors have found that it is possible to provide a foamy fixing solution that does not deteriorate the foamability of the fixing solution. In the fixing solution containing the softening agent, the number of carbon atoms of the fatty acid salt is excellent in foaming property as compared with the case where water is simply foamed. Specifically, laurate (12 carbon atoms), myristate (14 carbon atoms), palmitate (16 carbon atoms), and stearate (18 carbon atoms) are suitable. Further, pentadecylic acid (carbon number 15), margaric acid (carbon number 17), and the like are also suitable.

  Here, the action of the fatty acid and the softening agent will be described. The softening agent has an ester group in the chemical structure, and the fatty acid has a carbonyl group in the chemical structure. From this point, the ester group of the softener and the carbonyl group of the fatty acid show an electrical action in the fixing solution system, and this causes a binding action between molecules, and the fixing solution is characterized by foaming properties and Improves foam stability.

  Even in the range of 12 to 18 carbon atoms, the smaller the number of carbons, the better the foaming property, but the foam stability is poor, and the larger the number of carbons, the less foaming properties, but the foam stability is extremely excellent. ing. For this reason, a single fatty acid salt may be contained in the fixing solution, but it is more excellent to mix and contain a fatty acid salt having 12 to 18 carbon atoms. As a mixing ratio, it is desirable to contain the most myristic acid salt (14 carbon atoms) and to lower the ratio of lauric acid salt (12 carbon atoms) and stearic acid salt. More specific fatty acid salt ratios are 0: 6: 3: 1, 1: 5: 3: 1, 1: 4 by weight ratio of laurate: myristate: palmitate: stearate. : 4: 1 is suitable.

  By the way, by containing the fatty acid having the same carbon number as the fatty acid salt as the foaming agent in the fixing solution, the foaming property and foam stability can be maintained even when the concentration of the softening agent is increased. If the concentration of the softening agent is less than 10 [wt%], there is no problem in foaming properties even if no fatty acid is contained. However, when the concentration of the softening agent is 10 [wt%] or more, particularly when the concentration of the softening agent is 30 [wt%] or more, only the fatty acid salt is hardly foamed and the foamability is deteriorated. In the fixing solution in which the concentration of the softening agent is 30 [wt%], when the fatty acid having the same carbon number as the fatty acid salt is contained, the foaming property can be maintained.

  However, if the fatty acid content is too high, the ratio of the fatty acid salt, which is a foaming agent, decreases, and the foamability deteriorates again. Therefore, it is better to make the number of moles of fatty acid salt the same as or larger than the number of moles of fatty acid. Or when the ratio of a fatty acid and a fatty acid salt is in the range of 5: 5 to 1: 9, the foamability is excellent.

  In addition to the combination of fatty acid and fatty acid salt having the same carbon number, for example, the fatty acid salt is amine myristate, the fatty acid is stearic acid, the fatty acid salt is potassium palmitate, and the fatty acid is stearic acid. Different combinations in the range of 12 to 18 may be used. In short, by containing a fatty acid having 12 to 18 carbon atoms in the fixing solution, even if a high concentration softener is contained, the foaming property is not deteriorated, the foam stability is excellent, and the foam density is extremely high. Allows low foaming.

  In addition, even if the fixing solution contains a fatty acid having 12 to 18 carbon atoms using other anionic surfactants such as alkyl ether sulfate (AES) as a foaming agent, the foaming property due to an increase in the concentration of the softener It turns out that it is effective in preventing it from getting worse. However, the best combination is a combination with a fatty acid salt.

  Furthermore, fatty acid sodium, fatty acid potassium, and fatty acid amine are suitable as the fatty acid salt. Furthermore, the most suitable fatty acid amine is specifically prepared by heating water, adding a fatty acid, and then adding triethanolamine, followed by heating and stirring for a certain period of time for a saponification reaction. be able to. At this time, by increasing the molar ratio of fatty acid to triethanolamine in the range of 1: 0.5 to 1: 0.9 and the fatty acid ratio, unreacted fatty acid remains after saponification, and the fixing solution Fatty acid and fatty acid amine can be mixed therein. The same is possible with sodium and potassium salts.

  By the way, when the concentration of the softening agent in the fixing solution increases, the softening agent becomes difficult to dissolve in water as a dilution solvent. Therefore, as a result of investigation, by adding polyhydric alcohols, specifically ethylene glycol, diethylene glycol, propylene glycol, 1,3 butylene glycol, glycerin, etc., in the fixing solution, the softener can be dissolved even at a high concentration. And it was found that the foaming property by the fatty acid salt was not deteriorated, but rather the foaming property was improved. The content of the polyhydric alcohol is suitably in the range of 1 [wt%] to 30 [wt%]. If the content is more than 30 [wt%], the foamability is rather deteriorated, which is not suitable.

  In this embodiment, the foam application roller 41 is used as the foam fixing liquid application member. However, the foam application member may be a foam application belt stretched around a plurality of rollers. Further, the pressure member disposed to face the foam-like fixing liquid application member is not limited to the pressure roller 44, and may be a pressure belt stretched around a plurality of rollers.

  As described above, according to the present embodiment, as shown in FIG. 5, the foam-like fixing liquid 45 generated by the foam-like fixing liquid generating unit 30 is transferred from the foam discharge head 43 to the roller surface of the foam application roller 41. To be granted. Then, the film thickness is adjusted to a predetermined film thickness by the film thickness adjusting blade 42. The surface of the foam-like fixing liquid 45 on the foam application roller 41 is heated by the heater 52 which is a foam breaking means, and the foam-like fixing liquid 45 on the surface side is broken. The liquid fixer that has broken and liquefied flows into the film of the nearby foam fixer, the film thickness of the foam fixer increases, and the foam density of the foam fixer that has flowed over the film Becomes higher. A foam fixing solution having a two-layer structure is formed of a foam fixing solution layer having a high foam density and a foam fixing solution layer that is not broken and does not flow into the foam film of the liquid fixing solution. As a result, the bubble density of the foam-like fixer other than the fixing foam-type fixer transferred in contact with the unfixed toner is made lower than that of the fixer-like foam-fixing solution. The amount can be reduced. The foam-like fixing liquid generating unit includes a gas-liquid mixing unit 35, a liquid transport pump 33, and a gas transport pump 39. The gas transport pump 39 is a large-sized pump having a large output because the gas is supplied to the liquid fixing solution carried up to the gas-liquid mixing unit 35 with a large pressure to generate bubbles. The heater 52 is composed of a heating wire and a lamp, and is extremely smaller than the foamy fixing solution generating means 30. Therefore, the fixing device according to the present embodiment including one foamy fixing solution generating unit 30 and the heater 52 is smaller than the fixing device including two foaming fixing solution generating units. Therefore, it is possible to reduce the size of the fixing solution while reducing the amount of fixing solution discarded by forming a two-layer foam fixing solution.

  Further, according to the embodiment, as shown in FIG. 10, a temperature sensor 54 that detects the environmental temperature is provided. Then, the temperature is changed to the set temperature of the heater 52 that is optimum for the environmental temperature detected by the temperature sensor 54. Since the amount of foam breakage changes according to the environmental temperature, when the foam breaks even at a low temperature in relation to the environmental temperature, the power consumption can be suppressed by lowering the set temperature.

  Furthermore, according to the embodiment, as shown in FIG. 8, the heater 52 that is a bubble breaker is disposed at a position close to the recording medium P side to heat the unfixed resin fine particles T formed on the medium. To do. This makes it possible to soften unfixed resin fine particles and improve fixability while forming a foamy fixing solution having a two-layer structure.

  Further, according to the embodiment, as shown in FIG. 11, the foam breaking means 55 is constituted by a roller, and the surface of the foam-like fixing liquid layer is rubbed with the roller surface of the foam breaking roller. Low power consumption of roller drive is sufficient compared to a heater with high power consumption.

  Furthermore, according to the embodiment, as shown in FIG. 12, the liquid fixing solution is applied to the surface of the foam-like fixing solution layer by using the roller surface of the roller as the bubble breaking means 56, so Not only the foam density but also the foam density can be increased by applying a liquid fixer to further increase the foam density. Further, as shown in FIG. 13, the bubble breaking means 57 is constituted by a belt, and the surface of the foam-like fixing liquid layer is rubbed with the belt surface of the belt. The liquid fixing solution is applied to the surface of the foamy fixing solution layer using the belt surface of the belt. Similar to the roller, the power consumption is lower than that of the heater, and a higher bubble density can be achieved.

  Further, according to the embodiment, as shown in FIG. 14, the two-layer foam fixing solution formed by providing the heater 58 on a part of the inner wall or the outer wall constituting the flow path of the foam discharge head 43. Can be applied directly onto the roller surface of the foam application roller 41. Thereby, it is possible to form a two-layer foam fixing solution on the foam application roller with a simpler configuration.

1: Image forming unit 2: Paper feeding unit 3: Image reading unit 4: In-body paper discharge unit 5 (5Y, 5C, 5M, 5Bk): Image carrier 6: Intermediate transfer member 10: Charging device 11: Exposure device 12 : Developing device 13: Transfer device 18: Fixing device 20 (20Y, 20C, 20M, 20Bk): Image forming unit 25: Lubricant coating device 30: Foamed fixing solution generating means 31: Fixing solution container 32: Liquid fixing solution 33 : Liquid transport pump 34: liquid transport tube 35: gas-liquid mixing unit 36: gas transport pipe 37: microporous sheet 38: microbubble generating unit 39: gas transport pump 40: air port 41: foam application roller 42: film thickness adjustment Blade 43: Foam discharge head 44: Pressure roller 45: Foam fixer 45a: Foam fixer with low foam density 45b: Foam fixer with high foam density 50: Control unit 51: Motor 52: Bubble breaker 5 3: Heater 54: Temperature sensor 55: Bubble breaking means 56: Bubble breaking means 57: Bubble breaking means 58: Heater P: Recording medium T: Unfixed toner (resin-containing fine particles)

Japanese Patent No. 4486160

"Foam Engineering" first edition (written by Ishii Ikuo, Techno System, Inc., published on March 25, 2005, P.489)

Claims (13)

A foam-like fixing solution generating means for generating a foam-like fixing solution by mixing a gas with a liquid fixing solution containing at least a softening agent that softens fine particles containing a resin by dissolving or swelling at least a part of the resin; A foam fixing solution applying unit that applies the foam fixing solution generated by the foam fixing solution generating unit to an application surface of a foam applying unit that applies to unfixed resin fine particles formed on the medium. In the fixing device, the foaming fixer is applied to unfixed resin fine particles on the medium by the application means, and the resin fine particles are fixed on the medium.
A foam-improving means for breaking and foaming the foam-like fixing solution, the liquid fixing solution flowing on the foam film of the other foam-like fixing solution, and increasing the foam density of the foam-like fixing solution;
A high foam density applied to unfixed resin fine particles on a medium produced by increasing the foam density of a part of the foam fixer generated by the foam fixer generating means by the high foam density increasing means. A two-layer structure forming means for forming a two-layer foam fixing solution of a foam fixing solution layer and a foam fixing solution layer in which the liquid fixing solution is not broken and the liquid fixing solution does not flow into the foam film;
A fixing device. The fixing device according to claim 1.
The fixing device according to claim 1, wherein the high-bubble density increasing means breaks off the foam-like fixing liquid on the surface side of the foam-type fixing liquid layer applied to the application surface of the foam applying means. The fixing device according to claim 1 or 2,
The fixing device according to claim 1, wherein the high-bubble density increasing means is a heater for heating the surface of the foam-like fixing liquid layer. The fixing device according to claim 3.
A fixing device comprising temperature detecting means for detecting an environmental temperature, and changing the set temperature of the heater based on the environmental temperature detected by the temperature detecting means. In the fixing device according to claim 3 or 4,
The fixing device is characterized in that the heater heats unfixed resin fine particles formed on a medium. The fixing device according to claim 1.
The fixing device according to claim 1, wherein the high-density foaming means is a roller that rubs the surface of the foam-like fixing liquid layer with a roller surface. The fixing device according to claim 6.
A fixing device, wherein a liquid fixing solution is applied to a surface of a foamy fixing solution layer using a roller surface of the roller. The fixing device according to claim 1.
The fixing device is characterized in that the high-bubble density increasing means is a belt that rubs the surface of the foam-like fixing liquid layer with a belt surface. The fixing device according to claim 8.
A fixing device, wherein a liquid fixing solution is applied to a surface of a foamy fixing solution layer using a belt surface of the belt. The fixing device according to claim 1.
The fixing device characterized in that the high-bubble density increasing means breaks a part of the foam-like fixing liquid before being applied to the application surface of the foam-applying means by the foam-like fixing liquid applying means. The fixing device according to claim 10.
The foam-like fixing liquid applying means includes a foam discharge head having a flow path for flowing a foam-like fixing liquid discharged from a discharge port, and the high-bubble density increasing means is provided in the flow path of the foam discharge head. A fixing device. The fixing device according to claim 11.
The fixing device according to claim 1, wherein the high-bubble density increasing means is provided on a part of an inner wall or an outer wall constituting the flow path.   An image forming unit that forms an unfixed toner image on a medium by performing an electrostatic recording process with a toner in which resin-containing fine particles contain a colorant, and the undetermined state by the fixing device according to claim 1. An image forming apparatus comprising: a fixing unit that fixes a toner image onto a medium.

Images