JP5677802B2 - Image forming apparatus and fixing device - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet and a fixing device that fixes an image on the sheet.

  As an apparatus for forming an image on a sheet, an image forming apparatus using a liquid developer is known. This type of image forming apparatus typically includes a fixing device for fixing an image on a sheet. The fixing device generates relatively high heat in order to melt the toner component in the liquid developer transferred onto the sheet (see, for example, Patent Document 1 and Patent Document 2).

JP 2008-90116 A JP 2009-98474 A

  A liquid developer in which a resin solution in which a polymer compound is dissolved in a carrier liquid and a pigment dispersion in which a pigment is dispersed in the carrier liquid is mixed, the carrier compound in the liquid developer penetrates into the sheet, so that the polymer compound is Since it is deposited on the surface of the sheet and is fixed on the surface of the sheet in a state where the pigment is embedded, heat generation from the fixing device is unnecessary. However, the present inventor has found that an image formed using a liquid developer having the above-described characteristics is easily peeled from the sheet.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a fixing apparatus that suppress peeling of an image from a sheet.

An image forming apparatus according to an aspect of the present invention includes a conveyance element that conveys a sheet, an image forming unit that forms an image on the sheet using a liquid developer, and a fixing that fixes the image on the sheet. The fixing device includes a rubbing element that rubs the image on the sheet, and the rubbing element slides the image after the upstream rubbing element and the upstream rubbing element. And a downstream rubbing element for rubbing .

  According to the above configuration, the image forming unit forms an image on the sheet conveyed by the conveying element using the liquid developer. A fixing device that fixes an image on a sheet includes a rubbing element that rubs the image on the sheet. Since the rubbing element includes an upstream rubbing element and a downstream rubbing element that rubs the image after the upstream rubbing element, the image is rubbed for a relatively long period of time. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

In the above configuration, the upstream rubbing element is a different fixing ratio from the downstream rubbing element, it is good preferable to fix the image on the sheet.

  According to the above configuration, the upstream rubbing element fixes the image on the sheet at a fixing rate different from that of the downstream rubbing element, so that rubbing suitable for the sheet and the image is performed. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

In the above configuration, the rubbing element, it is good preferable to include an elastic roller having an elastic peripheral surface.

  According to the above configuration, the rubbing element includes the elastic roller having an elastic peripheral surface. Due to the elastic deformation of the elastic roller, the image is rubbed over a relatively large area. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

In the above configuration, the rubbing element, it is good preferable including a brush roller having a brush is arranged peripheral surface.

  According to the above configuration, the rubbing element includes the brush roller having a peripheral surface on which the brush is disposed. Due to the deformation of the brush, the image is rubbed over a relatively large area. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

In the above configuration, the downstream rubbing element, it is good preferable that presses the image with a strong force than the upstream rubbing element.

  According to the above configuration, the pressing force from the rubbing element increases stepwise, so that damage to the image is suppressed.

In the above configuration, the downstream rubbing element, it is good preferable to have a greater hardness than the upstream rubbing element.

  According to the above configuration, the hardness of the rubbing element increases stepwise as well as the pressing force from the rubbing element. Therefore, fluctuation between the area where the upstream rubbing element contacts the image and the area where the downstream rubbing element contacts the image is suppressed. Therefore, management of the rubbing time for the image can be achieved relatively easily.

In the above configuration, the upstream rubbing element includes an upstream contact surface in contact with the image, the downstream rubbing element includes a downstream contact surface in contact with the image, and the upstream contact surface is the downstream contact surface. it is good preferable less than.

  According to the above configuration, the contact area between the rubbing element and the image increases stepwise, so that damage to the image is suppressed.

In the above configuration, the fixing device includes a driving source for operating the rubbing element, the rubbing element includes a rubbing roller that rotates on the image, and the rubbing roller is applied to the image. The conveying element conveys the sheet at a first speed, and the driving source moves the rubbing roller so that the contact surface moves at a second speed different from the first speed. it is good preferable to rotate.

  According to the above configuration, the drive source operates the sliding element. The sliding element includes a rubbing roller that rotates on the image. The rubbing roller includes a contact surface that contacts the image. The conveying element conveys the sheet at the first speed. The drive source rotates the rubbing roller so that the contact surface moves at a second speed different from the first speed. The difference in speed between the conveying element and the contact surface causes the image to be rubbed by the rubbing roller. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

In the above configuration, the second speed, it is good preferable greater than the first speed.

  According to the above configuration, the second speed is greater than the first speed. The difference in speed between the conveying element and the contact surface causes the image to be rubbed by the rubbing roller. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

In the above configuration, the second speed, it is good preferable smaller than the first speed.

  According to the above configuration, the second speed is smaller than the first speed. The difference in speed between the conveying element and the contact surface causes the image to be rubbed by the rubbing roller. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

In the above-described configuration, the fixing device includes a driving source for operating the rubbing element, the conveying element conveys the sheet at a first speed, and the driving source moves the upstream contact surface over the first contact surface. it is to be virtuous preferable move a large third speed than the second speed the downstream contact surface is moved in large second speed than first speed.

  According to the above configuration, the downstream contact surface rubs more images than the upstream contact surface. Since the image rubbed by the upstream contact surface and urged to be fixed on the sheet is urged to be fixed to the sheet by further rubbed by the downstream contact surface, the components in the liquid developer forming the image are Penetration into the surface layer and image peeling are suitably suppressed.

In the above configuration, the fixing device, it is good preferable containing disjunction mechanism for detaching the rubbing element from the image.

  According to the above configuration, the separation / contact mechanism separates and contacts the rubbing element from the image, so that rubbing suitable for the sheet and the image is performed. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed. Further, the separation / contact of the sliding contact element by the separation / contact mechanism suppresses unnecessary wear of the sliding friction element.

The configuration further includes a control unit that controls the separation / contact mechanism, wherein the separation / contact mechanism includes an upstream separation / contact mechanism that separates / contacts the upstream friction element from the image, and a downstream friction element from the image. It includes a lower Ryuri connection mechanism for disjunction, and the controller may good preferable to operate independently and the upper Ryuri contact mechanism and the lower Ryuri connection mechanism.

  According to the above configuration, the separation / contact mechanism includes the upstream separation / contact mechanism that separates / contacts the upstream rubbing element from the image, and the downstream separation / contact mechanism that separates / contacts the downstream rubbing element from the image. Since the control unit operates the upstream separation mechanism and the downstream separation mechanism independently, sliding suitable for the sheet and the image is performed.

In the above configuration, the conveying element is a conveyor belt that conveys the sheet, it is good preferable; and a suction device for attracting the sheet to the conveying belt.

  According to the above configuration, the suction device sucks the sheet onto the transport belt. Therefore, the rubbing of the rubbing element with respect to the image hardly affects the conveyance of the sheet on the conveying belt.

In the above configuration, the conveying belt, the through holes are formed, the suction device via the through-hole, it is good preferable including a vacuum device for sucking the sheet.

  According to the said structure, a vacuum apparatus attracts | sucks a sheet | seat through the through-hole formed in the conveyance belt. Therefore, the rubbing of the rubbing element with respect to the image hardly affects the conveyance of the sheet on the conveying belt.

In the above structure, the suction device comprises a charging device for charging the conveyor belt, the conveyor belt it is good preferable to adsorb the sheet electrostatically.

  According to the above configuration, the charging device electrostatically adsorbs the sheet to the transport belt. Therefore, the rubbing of the rubbing element with respect to the image hardly affects the conveyance of the sheet on the conveying belt.

A fixing device that fixes an image formed using a liquid developer according to another aspect of the present invention on the sheet includes a rubbing element that rubs the image on the sheet, and the rubbing element includes: And an upstream rubbing element and a downstream rubbing element for rubbing the image after the upstream rubbing element .

  According to the above configuration, the image formed using the liquid developer is rubbed by the rubbing element. Since the rubbing element includes an upstream rubbing element and a downstream rubbing element that rubs the image after the upstream rubbing element, the image is rubbed for a relatively long period of time. As a result, the component in the liquid developer that forms the image enters the surface layer of the sheet, and image peeling is suitably suppressed.

  As described above, the image forming apparatus and the fixing device according to the present invention can suppress peeling of the image from the sheet.

It is a schematic diagram which shows roughly the transfer process using a liquid developer. FIG. 2 is a schematic diagram schematically showing the principle of a fixing step after the transfer step shown in FIG. 1. 3 is a graph schematically showing a relationship between rubbing time and fixing rate. It is a graph which shows roughly the result of the screening test to various nonwoven fabric materials. FIG. 2 is a cross-sectional view schematically illustrating a fixing device and a conveyance device according to the first embodiment. FIG. 6 is a schematic plan view of the fixing device shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of a rubbing roller of the fixing device shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of a rubbing roller that rubs an image layer of a sheet conveyed by the conveying device illustrated in FIG. 5. FIG. 6 is a schematic cross-sectional view of a rubbing roller that rubs an image layer of a sheet conveyed by the conveying device illustrated in FIG. 5. FIG. 6 is a schematic cross-sectional view of a rubbing roller that rubs an image layer of a sheet conveyed by the conveying device illustrated in FIG. 5. FIG. 6 is a cross-sectional view schematically illustrating a fixing device and a conveying device according to a second embodiment. FIG. 12 is a schematic cross-sectional view of a rubbing roller that rubs an image layer of a sheet conveyed by the conveying device illustrated in FIG. 11. FIG. 9 is a cross-sectional view schematically illustrating a fixing device and a conveyance device according to a third embodiment. 1 is a cross-sectional view schematically illustrating an image forming apparatus equipped with a fixing device according to a first embodiment. 1 is a schematic cross-sectional view of an image forming apparatus excluding a portion of a circulation device. It is sectional drawing which expands and shows one of the image forming units of the image forming apparatus shown by FIG.

  Hereinafter, a fixing principle, a fixing device, an image forming apparatus equipped with the fixing device, and a liquid developer will be described with reference to the drawings. Note that the terms used in the following description, such as “up”, “down”, “left”, and “right”, are merely for the purpose of clarifying the explanation and are interpreted in a limited manner. It is not intended to be.

<Fixing principle>
FIG. 1 is a diagram schematically illustrating an image transfer process using a liquid developer. The transfer process proceeds in the order of FIG. 1 (a) to FIG. 1 (c). With reference to FIG. 1, the transfer of the image to the sheet and the image after the transfer will be described.

  FIG. 1A shows a schematic cross section of a liquid layer L of a liquid developer that forms an image transferred from the image carrier 100 to the sheet S. FIG. The image carrier 100 may be, for example, a transfer belt provided in an image forming apparatus (for example, a printer, a copier, a facsimile machine, or a multifunction machine having these functions) that forms an image using a liquid developer. The image carrier 100 conveys the liquid layer L of the liquid developer that forms an image to the transfer position to the sheet S.

  At the transfer position, the sheet S contacts the liquid layer L on the image carrier 100. The liquid layer L of the liquid developer that forms an image includes a carrier liquid C, colored particles P for coloring the image, and a polymer compound R dissolved or swollen in the carrier liquid C. The colored particles P dispersed in the carrier liquid C are electrostatically attracted to the sheet S. Thus, the colored particles P adhere on the sheet S and form an image. Note that the attracting of the colored particles P to the sheet S is achieved by, for example, an electric field across the sheet S. The principle regarding the attracting of the colored particles P to the sheet S will be described in detail in relation to an image forming apparatus described later.

  FIG. 1 (b) schematically shows the carrier liquid C that penetrates the sheet S. The carrier liquid C having a relatively low kinematic viscosity permeates the sheet S, and forms a permeation layer PL on the surface layer of the sheet S. As the carrier liquid C penetrates the sheet S, the concentration of the polymer compound R in the liquid layer L of the liquid developer increases.

  As shown in FIG. 1C, when the carrier liquid C further penetrates the sheet S, the polymer compound R in the liquid layer L is deposited. As described above, the electrostatic adhesion of the colored particles P to the sheet S occurs prior to the precipitation of the polymer compound R. Therefore, the polymer compound R deposited on the surface of the sheet S forms a coating layer laminated on the layer of the colored particles P that form an image on the sheet S.

  FIG. 2 is a diagram schematically illustrating a fixing process performed after the transfer process. FIG. 2A schematically shows the fixing process. FIG. 2B is a schematic cross-sectional view of the sheet S after the fixing process. The principle of the fixing process will be described with reference to FIGS.

  After the transfer step, the carrier liquid C is substantially permeated into the sheet S, and the image layer I including the polymer compound R and the colored particles P is formed on the sheet S. In the transfer process, almost no physical force is applied to the image layer I except for the pressure and electric field when the liquid layer L (image) is transferred from the image carrier 100 to the sheet S. For this reason, before the fixing step, the physical bond between the image layer I and the sheet S is relatively weak, and when the peeling test using a tape described later is performed, the image layer I is noticeably peeled off. It will be.

  FIG. 2A shows a rubbing plate 200 exemplified as a fixing device and / or a rubbing element. The rubbing plate 200 includes, for example, a substantially rectangular parallelepiped substrate 210 and a nonwoven fabric 220 that covers the surface of the substrate 210. In this embodiment, the layer of the nonwoven fabric 220 which forms the lower surface of the rubbing plate 200 facing the image layer I is exemplified as the contact surface. In this embodiment, a polypropylene nonwoven fabric is used as the nonwoven fabric 220. Alternatively, a non-woven fabric (hereinafter referred to as PTFE felt A) made of polytetrafluoroethylene (PTFE) having a dynamic friction coefficient of 0.10, polytetrafluoroethylene (PTFE) having a dynamic friction coefficient of 0.13. : Polytetrafluoroethylen) non-woven fabric (hereinafter referred to as PTFE felt B), polyester felt, polyethylene terephthalate felt (hereinafter referred to as PET felt), polyamide felt or wool felt may be used as the non-woven fabric 220. Good.

  The rubbing plate 200 placed on the image layer I formed on the sheet S moves on the image layer I along the upper surface of the sheet S. As a result, as shown in FIG. 2B, part of the components of the image layer I (colored particles P and / or polymer compound R) bite into the surface layer of the sheet S (anchor effect). Thus, the physical coupling between the image layer I and the sheet S is strengthened.

  As described above, the upper surface of the image layer I is covered with the polymer compound R. Therefore, the colored particles P that develop an image are covered with the film layer of the formed polymer compound R, but a stronger resin film is formed by the rubbing operation of the rubbing plate 200 and is appropriately protected. The Thus, image damage due to rubbing of the rubbing plate 200 is appropriately suppressed.

<Test example>
FIG. 3 is a graph schematically showing the relationship between the period (rubbing time) when the rubbing plate 200 is slidingly moved to the image layer I and the fixing rate of the image layer I. The relationship between the rubbing time and the fixing rate will be described with reference to FIGS.

  The rubbing time indicated on the horizontal axis of the graph of FIG. 3 represents the length of time during which a predetermined area in the image layer I is in contact with the rubbing plate 200 that is reciprocating.

The fixing rate FR shown on the vertical axis of the graph of FIG. 3 is calculated using the following mathematical formula. Here, D ₀ represents the density of the image before peeling the tape attached on the image layer I, and D ₁ is the density of the image after peeling the tape attached on the image layer I. Represents.

  The tape used for evaluation of the fixing rate FR was a mending tape manufactured by 3M. The mending tape was attached onto the image layer I using a dedicated jig. Accordingly, the adhesion strength between the image layer I and the mending tape in the test sample is kept substantially constant between the data points shown in the graph of FIG. Further, the mending tape punched on the image layer I in the test sample was peeled from the image layer I at a substantially constant peeling angle and a substantially constant peeling speed using a dedicated jig.

  The density of the image of the test sample was measured using a spectrophotometer spectroeye manufactured by Sakata Inx Engineering Co., Ltd.

  As shown in FIG. 3, when the image layer I is rubbed for 1 second or more, it can be seen that the image layer I achieves a relatively high fixing rate FR. Further, it can be seen that the fixing rate FR of the image layer I shows a rapid increase when the rubbing time is less than 1 second. It should be noted that the weight of the rubbing plate 200 is preferably determined appropriately so that generation of scratches on the surface of the image layer I is suppressed.

  FIG. 4 is a graph schematically showing the relationship between various types of nonwoven fabric 220 and the fixing rate FR. The relationship between the type of the nonwoven fabric 220 and the fixing rate FR will be described with reference to FIGS.

  The horizontal axis in FIG. 4 indicates the type of nonwoven fabric 220. In this test, PTFE felt A, PTFE felt B, polypropylene nonwoven fabric, polyester felt, PET felt, polyamide felt and wool felt are shown.

  The vertical axis on the left side of FIG. 4 indicates the above-described fixing rate FR. The fixing rate FR is represented by the bar graph of FIG. In addition, the above-mentioned all types of nonwoven fabrics 220 used in this test achieved a relatively high fixing rate FR in a rubbing time exceeding 1 second. Therefore, for the screening of a relatively advantageous type of nonwoven fabric 220, the fixing rate FR shown in FIG. 4 is calculated under a rubbing time of 0.625 seconds.

  The vertical axis on the right side of FIG. 4 indicates the dynamic friction coefficient of each type of nonwoven fabric 220 represented by the points in FIG. A low coefficient of dynamic friction is advantageous in terms of reducing the influence on the conveyance of the sheet S and reducing damage to the image layer I.

  As shown in FIG. 4, PTFE felt A has the lowest coefficient of dynamic friction and achieves the highest fixing rate FR. Thus, it can be seen that PTFE felt A is the most advantageous of the types of nonwovens 220 tested. In addition, the nonwoven fabric material which is not shown by FIG. Preferably, a nonwoven fabric material having a dynamic friction coefficient of 0.50 or less is used as the nonwoven fabric 220. The nonwoven fabric material having a dynamic friction coefficient of 0.50 or less can suitably suppress the influence on the conveyance of the sheet S and the damage to the image layer I.

<Fixing device>
(First embodiment)
FIG. 5 is a schematic diagram illustrating the fixing device and the conveyance device according to the first embodiment. The fixing device and the conveying device according to the first embodiment will be described with reference to FIG.

  The conveying device 400 that conveys the sheet S on which the image layer I is formed includes a belt unit 450, an upstream guide unit 460 disposed upstream of the belt unit 450, and a downstream guide disposed downstream of the belt unit 450. A unit 465. The sheet S is guided by the upstream guide unit 460 and sent to the belt unit 450. Thereafter, the sheet S is sent to the downstream guide unit 465 by the belt unit 450.

  The belt unit 450 includes a driving roller 451, a driven roller 452, an endless belt 453 extending between the driving roller 451 and the driven roller 452, and a tension roller 454 that applies tension to the endless belt 453. As the driving roller 451 rotates, the endless belt 453 rotates around the driving roller 451, the driven roller 452, and the tension roller 454. As a result, the sheet S sent from the upstream guide unit 460 onto the outer surface 455 of the endless belt 453 moves toward the downstream guide unit 465 as the endless belt 453 rotates. In the present embodiment, the belt unit 450 is exemplified as a transport element. The endless belt 453 is exemplified as a conveyance belt.

  The belt unit 450 further includes a charging device 456 that charges the outer surface 455 of the endless belt 453. The outer surface 455 of the endless belt 453 charged by the charging device 456 electrostatically attracts the sheet S. Accordingly, the sheet S is stably conveyed by the endless belt 453. In the present embodiment, the endless belt 453 is preferably formed from a resin such as PVDF. In the present embodiment, the charging device 456 is exemplified as an adsorption device.

  Endless belt 453 includes an inner surface 457 opposite to outer surface 455 on which sheet S is adsorbed. The belt unit 450 includes a backup roller 340 that contacts the inner surface 457 of the endless belt 453. The backup roller 340 includes an upstream backup roller 343 and a downstream backup roller 344. The downstream backup roller 344 is disposed closer to the downstream guide unit 465 than the upstream backup roller 343.

  The fixing device 300 includes a rubbing roller 310 that rubs the image layer I on the sheet S. The rubbing roller 310 includes an upstream rubbing roller 323 corresponding to the upstream backup roller 343 and a downstream rubbing roller 324 corresponding to the downstream backup roller 344. The downstream rubbing roller 324 rubs the image layer I after the upstream rubbing roller 323. In the present embodiment, the rubbing roller 310 is exemplified as a rubbing element. Further, the upstream rubbing roller 323 and the downstream rubbing roller 324 are illustrated as an upstream rubbing element and a downstream rubbing element, respectively.

  The fixing device 300 includes a housing 320 that partially accommodates the upstream rubbing roller 323 and the downstream rubbing roller 324. The housing 320 opens toward the endless belt 453. The upstream rubbing roller 323 and the downstream rubbing roller 324 protrude from the opening of the housing 320 and abut on the outer surface 455 of the endless belt 453 or the sheet S.

  The fixing device 300 includes a pressing element 355 that presses the rubbing roller 310 against the sheet S. In the present embodiment, the pressing element 355 includes an upstream coil spring 356 that presses the upstream rubbing roller 323 against the sheet S, and a downstream coil spring 357 that presses the downstream rubbing roller 324 against the sheet S. Alternatively, the pressing element 355 may be a cylinder device configured to press the rubbing roller 310 against the sheet S.

  The upper end portion of the pressing element 355 is connected to the top plate 325 of the housing 320. The lower end portion of the pressing element 355 is connected to, for example, a bearing (not shown) that rotatably supports a shaft (not shown) of the rubbing roller 310.

  FIG. 6 is a schematic plan view of the fixing device 300. The fixing device 300 is further described with reference to FIGS. 5 and 6.

  The fixing device 300 includes a drive mechanism 331 attached to the outer surface of the housing 320. The drive mechanism 331 includes an upstream gear 332 connected to the shaft 326 of the upstream rubbing roller 323, a downstream gear 333 connected to the shaft 327 of the downstream rubbing roller 324, and an upstream motor 334 connected to the upstream gear 332. A downstream motor 335 connected to the downstream gear 333. The upstream motor 334 rotates the upstream rubbing roller 323 on the image layer I. The downstream motor 335 rotates the downstream rubbing roller 324 on the image layer I. In the present embodiment, the upstream motor 334 and the downstream motor 335 are exemplified as drive sources.

  The housing 320 and the drive mechanism 331 are formed so as to allow displacement of the rubbing roller 310 accompanying expansion and contraction of the pressing element 355. Thus, the rubbing roller 310 is appropriately pressed against the image layer I on the sheet S.

  FIG. 7 is a schematic cross-sectional view of the rubbing roller 310. The rubbing roller 310 will be described with reference to FIGS. 4 and 7.

  The rubbing roller 310 includes a metal shaft 312, an elastic layer 313 that covers the peripheral surface of the shaft 312, and a nonwoven fabric layer 314 that covers the peripheral surface of the elastic layer 313. The nonwoven fabric layer 314 of the upstream rubbing roller 323 is preferably formed from a material different from that of the nonwoven fabric layer 314 of the downstream rubbing roller 324. As described with reference to FIG. 4, due to the difference in the material of the nonwoven fabric layer 314, the upstream rubbing roller 323 has the fixing rate FR different from that of the downstream rubbing roller 324 and the image layer I is applied to the sheet S. It can be fixed. In the present embodiment, since the nonwoven fabric layer 314 covers the elastic layer 313, the peripheral surface of the rubbing roller 310 has an elastic peripheral surface. Therefore, the rubbing roller 310 is exemplified as an elastic roller.

  FIG. 8 is a schematic cross-sectional view of the upstream rubbing roller 323 and the downstream rubbing roller 324 pressed on the image layer I. The rubbing roller 310 will be further described with reference to FIGS. 1, 5, 6 and 8.

  The upstream coil spring 356 urges the upstream rubbing roller 323 downward with a force F1. The downstream coil spring 357 urges the downstream rubbing roller 324 downward with a force F2 larger than the force F1. Accordingly, the downstream rubbing roller 324 presses the image layer I with a stronger force than the upstream rubbing roller 323.

  A flat upstream nip surface UN along the image layer I is formed on the peripheral surface of the upstream rubbing roller 323 pressed by the force F1. A flat downstream nip surface DN along the image layer I is formed on the peripheral surface of the downstream rubbing roller 324 pressed by the force F2. In the present embodiment, the upstream nip surface UN and the downstream nip surface DN that are in contact with the image layer I are exemplified as the upstream contact surface and the downstream contact surface, respectively.

  In the present embodiment, the downstream rubbing roller 324 has the same structure as the upstream rubbing roller 323. Therefore, the area of the upstream nip surface UN of the upstream rubbing roller 323 pressed by the force F1 smaller than the force F2 is smaller than the area of the downstream nip surface DN of the downstream rubbing roller 324. Alternatively, the elastic layer 313 of the downstream rubbing roller 324 may have a lower hardness than the elastic layer 313 of the upstream rubbing roller 323. In this case, if the force F2 is equal to or greater than the force F1, the area of the downstream nip surface DN is larger than the area of the upstream nip surface UN. Further alternatively, the elastic layer 313 of the downstream rubbing roller 324 may have a greater hardness than the elastic layer 313 of the upstream rubbing roller 323. In this case, if the force F2 is greater than the force F1, the variation in the area between the upstream nip surface UN and the downstream nip surface DN is preferably suppressed. As a result, variation between the rubbing time for the image layer I by the upstream rubbing roller 323 and the rubbing time for the image layer I by the downstream rubbing roller 324 is suppressed, and parameter management for the fixing process is relatively easy. Easily achieved.

As described above, the upper surface of the colored particles P in the image layer I is covered with the film layer formed of the polymer compound R, but a stronger resin film is formed by the rubbing operation of the rubbing roller 310, and the image is Properly protected. That is, the image layer I whose film layer is reinforced by the upstream rubbing roller 323 is less likely to be damaged as the sheet S is conveyed downstream. Accordingly, the pressing force from the upstream rubbing roller 323 (that is, the force F1) or the area of the upstream nip surface UN is larger than the pressing force from the downstream rubbing roller 324 (that is, the force F2) or the area of the downstream nip surface DN. Small is preferable. In the present embodiment, the surface pressure of the upstream nip surface UN is set to 0.02 g / cm ² , for example. The surface pressure of the downstream nip surface DN is set to 0.20 g / cm ² , for example.

  As shown in FIG. 8, the endless belt 453 conveys the sheet S at the first speed V1. The upstream motor 334 rotates the shaft 312 so that the upstream nip surface UN exemplified as the contact surface moves in the conveyance direction of the sheet S at a second speed V2 that is larger than the first speed V1. The downstream motor 335 rotates the shaft 312 so that the downstream nip surface DN exemplified as the contact surface moves in the conveyance direction of the sheet S at the second speed V2. As a result, the rubbing roller 310 rotates while rubbing the image layer I. In the present embodiment, the first speed V1 is set to 300.0 mm / second, for example. The second speed V2 is set to 301.5 mm / second or more, for example.

  9 and 10 show other controls for the rubbing roller 310 by the upstream motor 334 and the downstream motor 335. FIG. The rubbing roller 310 will be further described with reference to FIGS. 6, 9 and 10.

  If the moving speed of the upstream nip surface UN / downstream nip surface DN is different from the first speed V1, the rubbing between the upstream nip surface UN / downstream nip surface DN and the image layer I occurs. Therefore, as shown in FIG. 9, the upstream motor 334 may rotate the shaft 312 so that the upstream nip surface UN moves in the conveyance direction of the sheet S at the second speed V2 that is larger than the first speed V1. Good. Further, the downstream motor 335 may rotate the shaft 312 so that the upstream nip surface UN moves in the conveyance direction of the sheet S at a third speed V3 larger than the second speed V2. In this case, when the second speed V2 is set to 301.5 mm / second, the third speed V3 may be set to 303.0 mm / second, for example. The difference between the third speed V3 and the first speed V1 is larger than the difference between the second speed V2 and the first speed V1. Therefore, the image layer I is rubbed with a relatively small speed difference upstream, and the image layer I is rubbed with a relatively large speed difference downstream. Thus, the image layer I is fixed at a relatively high fixing rate FR with almost no damage.

  Alternatively, as shown in FIG. 10, the upstream motor 334 rotates the shaft 312 so that the upstream nip surface UN moves in the conveyance direction of the sheet S at a second speed V2 smaller than the first speed V1. May be. Further, the downstream motor 335 may rotate the shaft 312 so that the upstream nip surface UN moves in the conveyance direction of the sheet S at a third speed V3 larger than the second speed V2.

  Further alternatively, the upstream motor 334 and the downstream motor 335 may move the rubbing roller 310 on the upstream nip surface UN and the downstream nip surface DN in the direction opposite to the conveyance direction of the sheet S, respectively.

(Second Embodiment)
FIG. 11 is a schematic diagram illustrating a fixing device and a conveying device according to the second embodiment. Hereinafter, features that are different from the first embodiment will be described. Therefore, the description overlapping with the description related to the first embodiment is omitted. In the following description, the same code | symbol is assigned with respect to the element similar to 1st Embodiment. The description which concerns on 1st Embodiment is used suitably with respect to the element which is not demonstrated below. A fixing device and a conveying device according to the second embodiment will be described with reference to FIG.

  A conveying device 400A that conveys the sheet S on which the image layer I is formed includes a belt unit 450A, an upstream guide unit 460 disposed upstream of the belt unit 450A, and a downstream guide disposed downstream of the belt unit 450A. A unit 465. The sheet S is guided by the upstream guide unit 460 and sent to the belt unit 450A. Thereafter, the sheet S is sent to the downstream guide unit 465 by the belt unit 450A.

  The belt unit 450A includes a driving roller 451, a driven roller 452, an endless belt 453A extending between the driving roller 451 and the driven roller 452, and a tension roller 454 that applies tension to the endless belt 453A. As the driving roller 451 rotates, the endless belt 453A rotates around the driving roller 451, the driven roller 452, and the tension roller 454. As a result, the sheet S sent from the upstream guide unit 460 onto the outer surface 455 of the endless belt 453A travels toward the downstream guide unit 465 along the circumference of the endless belt 453A. In the present embodiment, the belt unit 450A is exemplified as a transport element. The endless belt 453A is exemplified as a transport belt.

  The belt unit 450A includes a vacuum device 456A. A plurality of through holes 458 are formed in the endless belt 453A. While the sheet S is being conveyed by the belt unit 450A, the vacuum device 456A sucks the sheet S on the endless belt 453A through the through hole 458. In the present embodiment, the vacuum device 456A is exemplified as an adsorption device.

  Endless belt 453A includes an inner surface 457 opposite to outer surface 455 on which sheet S is adsorbed. The belt unit 450A includes a backup roller 340 that contacts the inner surface 457 of the endless belt 453A. The backup roller 340 includes an upstream backup roller 343 and a downstream backup roller 344. The downstream backup roller 344 is disposed closer to the downstream guide unit 465 than the upstream backup roller 343.

  The fixing device 300A includes a rubbing roller 310A for rubbing the image layer I on the sheet S. The rubbing roller 310A includes an upstream rubbing roller 323A corresponding to the upstream backup roller 343 and a downstream rubbing roller 324A corresponding to the downstream backup roller 344. The downstream rubbing roller 324A rubs the image layer I after the upstream rubbing roller 323A. In the present embodiment, the rubbing roller 310A is exemplified as a rubbing element. Further, the upstream rubbing roller 323A and the downstream rubbing roller 324A are exemplified as an upstream rubbing element and a downstream rubbing element, respectively.

  The fixing device 300A includes a housing 320 that partially accommodates the upstream rubbing roller 323A and the downstream rubbing roller 324A. The housing 320 opens toward the endless belt 453A. The upstream rubbing roller 323A and the downstream rubbing roller 324A protrude from the opening of the housing 320 and abut on the outer surface 455 of the endless belt 453A or the sheet S.

  Unlike the first embodiment, the upstream rubbing roller 323A and the downstream rubbing roller 324A are fixedly mounted in the housing 320. Therefore, the upstream rubbing roller 323A and the downstream rubbing roller 324A do not need to be separated from and contacted with the endless belt 453A. The upstream rubbing roller 323A and the downstream rubbing roller 324A are rotated by the same drive mechanism as in the first embodiment.

  FIG. 12 is a schematic cross-sectional view of the upstream rubbing roller 323A and the downstream rubbing roller 324A that rub the image layer I. The rubbing roller 310A will be further described with reference to FIGS.

  The rubbing roller 310 </ b> A includes a metal shaft 312, a base layer 313 </ b> A that covers the peripheral surface of the shaft 312, and a brush layer 314 </ b> A that includes a brush 314 a implanted in the base layer 313 </ b> A. The brush 314a may be formed of rayon (pile fineness: 300D / 100F) or polyester (pile fineness: 75D / 12F). Thus, the rubbing roller 310A includes a peripheral surface on which the brush 314a is disposed. In the present embodiment, the rubbing roller 310A is exemplified as a brush roller.

  In the present embodiment, the brush 314a is attached to the shaft 312 via the base layer 313A. Alternatively, it may be adhered directly to the shaft 312 using an adhesive.

  In the present embodiment, the brush 314a of the upstream rubbing roller 323A is the same as the brush 314a of the downstream rubbing roller 324A. The brush 314a of the upstream rubbing roller 323A projects more greatly from the base layer 313A than the brush 314a of the downstream rubbing roller 324A. The diameter of the upstream rubbing roller 323A is equal to the diameter of the downstream rubbing roller 324A, and the protruding amount of the brush 314a is adjusted by the thickness of the base layer 313A.

  In the present embodiment, the amount of interference between the image layer I and the brush layer 314A of the upstream rubbing roller 323A is set substantially equal to the amount of interference between the image layer I and the brush layer 314A of the downstream rubbing roller 324A. Further, the upstream rubbing roller 323A is rotated at a rotational speed substantially equal to that of the downstream rubbing roller 324A.

  As described above, the brush 314a of the upstream rubbing roller 323A protrudes more greatly from the base layer 313A than the brush 314a of the downstream rubbing roller 324A. Therefore, while the rubbing roller 310A is rotating, the upstream rubbing roller 323A. The load applied to the image layer I by the brush 314a is smaller than the load applied to the image layer I by the brush 314a of the downstream rubbing roller 324A. Thus, the image layer I is fixed at a relatively high fixing rate FR with almost no damage.

  Note that there may be a difference in the bending strength, thickness, and other characteristics of the brush 314a between the upstream rubbing roller 323A and the downstream rubbing roller 324A. Depending on the difference in the characteristics of the brush 314a between the upstream rubbing roller 323A and the downstream rubbing roller 324A, the load applied to the image layer I by the brush 314a of the upstream rubbing roller 323A is the brush of the downstream rubbing roller 324A. The load applied to the image layer I by 314a may be made smaller.

(Third embodiment)
FIG. 13 is a schematic diagram illustrating a fixing device and a conveying device according to the third embodiment. Hereinafter, features that are different from the first embodiment will be described. Therefore, the description overlapping with the description related to the first embodiment is omitted. In the following description, the same code | symbol is assigned with respect to the element similar to 1st Embodiment. The description which concerns on 1st Embodiment is used suitably with respect to the element which is not demonstrated below. A fixing device and a conveying device according to the third embodiment will be described with reference to FIG.

  Similar to the first embodiment, the conveying device 400 that conveys the sheet S on which the image layer I is formed includes a belt unit 450, an upstream guide unit 460 disposed upstream of the belt unit 450, and the belt unit 450. And a downstream guide unit 465 disposed downstream. The sheet S is guided by the upstream guide unit 460 and sent to the belt unit 450. Thereafter, the sheet S is sent to the downstream guide unit 465 by the belt unit 450.

  The fixing device 300B includes a rubbing roller 310 that rubs the image layer I on the sheet S. The rubbing roller 310 includes an upstream rubbing roller 323 corresponding to the upstream backup roller 343 and a downstream rubbing roller 324 corresponding to the downstream backup roller 344. The downstream rubbing roller 324 rubs the image layer I after the upstream rubbing roller 323.

  The fixing device 300 </ b> B includes a housing 320 that partially accommodates the upstream rubbing roller 323 and the downstream rubbing roller 324. The housing 320 opens toward the endless belt 453. The upstream rubbing roller 323 and the downstream rubbing roller 324 protrude from the opening of the housing 320 and abut on the outer surface 455 of the endless belt 453 or the sheet S.

  The fixing device 300B includes a cylinder mechanism 370. The cylinder mechanism 370 brings the rubbing roller 310 into contact with the image layer I of the sheet S on the endless belt 453. In the present embodiment, the cylinder mechanism 370 is exemplified as a separation / contact mechanism. Alternatively, the separation / contact mechanism may be another structure formed so that the rubbing roller 310 is separated from / contacted to the endless belt 453. For example, the rubbing roller 310 may be separated from and contacted with the endless belt 453 using a lever arm.

  The cylinder mechanism 370 includes an upstream cylinder device 371 for bringing the upstream rubbing roller 323 into and out of contact with the image layer I of the sheet S on the endless belt 453 and an image layer of the sheet S on the endless belt 453. And a downstream cylinder device 372 that is separated from and in contact with I. In the present embodiment, the upstream cylinder device 371 is exemplified as an upstream separation / contact mechanism. The downstream cylinder device 372 is exemplified as a downstream separation / contact mechanism.

  The cylinder mechanism 370 includes an outer shell body 353 that receives and flows in the working fluid, and a rod 354 that is formed so as to be able to protrude and retract relative to the outer shell body 353. The outer shell 353 is attached to the top plate 325 of the housing 320. The rod 354 of the upstream cylinder device 371 is attached to the shaft 326 of the upstream rubbing roller 323. The rod 354 of the downstream cylinder device 372 is attached to the shaft 327 of the downstream rubbing roller 324.

  The fixing device 300 </ b> B includes a control unit 373 that controls the cylinder mechanism 370. The control unit 373 controls the flow of working fluid into and out of the outer shell 353. When the working fluid flows into the outer shell 353 under the control of the control unit 373, the rod 354 extends from the outer shell 353, and the rubbing roller 310 is pressed against the image layer I. When the working fluid flows out from the outer shell 353 under the control of the control unit 373, the rod 354 is immersed in the outer shell 353, and the rubbing roller 310 is separated from the image layer I.

  The control unit 373 controls the upstream cylinder device 371 and the downstream cylinder device 372 independently. Therefore, the control unit 373 can press one of the upstream rubbing roller 323 and the downstream rubbing roller 324 against the image layer I and separate the other from the image layer I. Alternatively, the control unit 373 can press both the upstream rubbing roller 323 and the downstream rubbing roller 324 against the image layer I. The control unit 373 can separate the upstream rubbing roller 323 and the downstream rubbing roller 324 from the image layer I as necessary. For example, the control unit 373 may separate the upstream rubbing roller 323 and the downstream rubbing roller 324 from the image layer I while the sheet S is not being conveyed. In the present embodiment, the control unit 373 is exemplified as the control unit.

  The above-described separation / contact of the rubbing roller 310 may be performed in accordance with the timing of passage of the sheet S. Alternatively, the contact / separation of the rubbing roller 310 may be determined according to the type of liquid developer or sheet S used for forming the image layer I. For example, if a liquid developer that forms the image layer I that is relatively easily damaged is used, the amount of interference between the upstream rubbing roller 323 and the endless belt 453 is the amount of interference between the downstream rubbing roller 324 and the endless belt 453. The position of the upstream rubbing roller 323 and / or the downstream rubbing roller 324 may be controlled so as to be smaller.

<Application to image forming apparatus>
FIG. 14 is a schematic configuration diagram of a color printer equipped with the fixing device 300 described in relation to the first embodiment. FIG. 15 is a schematic sectional view of the color printer excluding the portion of the circulation device. FIG. 16 is an enlarged sectional view showing one of the image forming units of the color printer. In the following description, the color printer is described as an image forming apparatus. Alternatively, the image forming apparatus may be a copier, a facsimile machine, a multifunction machine including these functions, or another apparatus capable of forming an image on the sheet S. In this embodiment, the color printer is equipped with the fixing device 300 described in relation to the first embodiment. Alternatively, the fixing devices 300A and 300B described in relation to the second embodiment or the third embodiment may be mounted on a color printer. The color printer is described with reference to FIGS. 1 and 14 to 16.

  As shown in FIG. 14, the color printer 1 includes an upper main body 1A that stores various units and parts for image formation, and a lower part of the upper main body 1A. And a lower main body 1B in which LM, LC, and LB (mixed liquid supply system) are stored. Here, the piping connecting the upper main body 1A and the lower main body 1B is not shown. The circulation devices LY, LM, LC, and LB circulate the liquid developer used in the image forming process executed in the upper main body 1A. For the configurations and principles of the circulation devices LY, LM, LC, and LB, a circulation technique for a liquid developer used in a known image forming apparatus may be used as appropriate.

  As shown in FIG. 15, the upper main body 1 </ b> A is formed of a tandem type image forming unit 2 that forms a toner image based on image data, a sheet storage unit 3 that stores a sheet S, and the image forming unit 2. A secondary transfer unit 4 for transferring the transferred toner image onto the sheet S, a fixing unit 5 for fixing the transferred toner image on the sheet S, a discharge unit 6 for discharging the sheet S after the fixing, and a sheet A sheet conveying unit 7 that conveys the sheet S from the storage unit 3 to the discharge unit 6. In the present embodiment, the principle of the fixing technique described above is applied to the fixing unit 5.

  The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22 for the intermediate transfer belt 21, and an image forming unit corresponding to each of yellow (Y), magenta (M), cyan (C), and black (Bk). FY, FM, FC, and FB. In the present embodiment, the intermediate transfer belt 21 corresponds to the image carrier 100 described with reference to FIG.

  The image forming unit 2 includes a drive roller 41 for driving the loop-shaped intermediate transfer belt 21 and a driven roller 49 that rotates as the intermediate transfer belt 21 travels. The conductive intermediate transfer belt 21 is wound around a driving roller 41 and a driven roller 49. The width of the intermediate transfer belt 21 is set larger than the maximum width sheet S allowed by the color printer 1. In the following description, the surface facing outward in the circulation drive of the intermediate transfer belt 21 is referred to as the front surface, and the other surface is referred to as the back surface.

  The image forming units FY, FM, FC, and FB connected in the vicinity of the intermediate transfer belt 21 are disposed between the cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. The image forming units FY, FM, FC, and FB include a photosensitive drum 10, a charger 11, an exposure device 12, a developing device 14, a primary transfer roller 20, a cleaning device 26, a charge removal device 13, and a removal device. And a roller 30. Note that, among the image forming units FY, FM, FC, and FB, the image forming unit FB located closest to the secondary transfer unit 4 does not include the removal roller 30, and the image forming units FY, The configuration is similar to that of FM and FC.

  Corresponding to each image forming unit FY, FM, FC, FB, circulation devices LY, LM, LC, LB are provided, respectively. The circulation devices LY, LM, LC, and LB supply and collect the liquid developer of each color.

  The circumferential surface of the cylindrical photosensitive drum 10 can carry a toner image including a charged toner (charged to a positive polarity in this embodiment). The photosensitive drum 10 that contacts the intermediate transfer belt 21 rotates along the running direction of the intermediate transfer belt 21. The charger 11 uniformly charges the surface of the photosensitive drum 10.

  The exposure device 12 has, for example, an LED light source. The light source of the exposure device 12 irradiates light onto the uniformly charged surface of the photosensitive drum 10 in accordance with image data input from an external device. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 10.

  The developing device 14 that holds the liquid developer containing the colored particles P, the carrier liquid C, and the polymer compound R so as to face the electrostatic latent image on the surface of the photoconductor drum 10 includes the colored particles P And polymer compound R is deposited. As a result, the electrostatic latent image is developed as an image colored by the colored particles P.

  As shown in FIG. 16, the developing device 14 includes a developing container 140, a developing roller 141, a supply roller 142, a support roller 143, a blade 144 pressed against the supply roller 142, a blade 145 for cleaning the developing roller 141, A collecting device 146 for collecting the liquid developer and a charger 147 for charging the developing roller 141 are included.

  The liquid developer in which the concentration of the colored particles P and the polymer compound R in the carrier liquid C has been adjusted in advance is supplied from the supply nozzle 278 to the developing container 140. The liquid developer is supplied toward the nip portion between the supply roller 142 and the support roller 143. Excess liquid developer falls below the support roller 143 and is stored at the bottom of the developing container 140. The stored liquid developer is collected through the pipe 82 using the circulation devices LY, LM, LC, and LB.

  The support roller 143 disposed substantially at the center of the developing container 140 contacts the upper supply roller 142 to form a nip portion. A groove for holding the liquid developer is formed on the peripheral surface of the supply roller 142.

  The liquid developer supplied from the supply nozzle 278 is temporarily retained at the nip portion between the support roller 143 and the supply roller 142. In the nip portion, the liquid developer held in the groove of the supply roller 142 is carried to the upper developing roller 141. The blade 144 brought into pressure contact with the peripheral surface of the supply roller 142 adjusts the amount of liquid developer held by the supply roller 142. Excess liquid developer scraped off by the blade 144 is received at the bottom of the developing container 140.

  The developing roller 141 disposed in the upper opening of the developing container 140 is in contact with the supply roller 142. The rotation direction of the developing roller 141 and the supply roller 142 is determined so that the peripheral surface of the developing roller 141 moves in the opposite direction to the supply roller 142 at the nip portion between the developing roller 141 and the supply roller 142. As a result, the liquid developer held on the peripheral surface of the supply roller 142 is delivered to the peripheral surface of the developing roller 141. Since the layer thickness of the liquid developer on the supply roller 142 is appropriately adjusted, the liquid developer layer formed on the surface of the developing roller 141 has a thickness appropriate for image formation.

  The surface of the developing roller 141 that has received the liquid developer moves above the charger 147. The charger 147 provides a charging potential having the same polarity as the charging polarity of the colored particles P. As a result, the colored particles P in the liquid developer carried on the developing roller 141 move to the surface side of the developing roller 141.

  The surface of the developing roller 141 that has passed through the charger 147 is in contact with the photosensitive drum 10. A toner image corresponding to the image data is formed on the surface of the photosensitive drum 10 by the potential difference between the electrostatic latent image potential on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 141.

  After contacting the photoconductor drum 10, the peripheral surface of the developing roller 141 contacts the blade 145. The blade 145 removes the liquid developer on the surface of the developing roller 141 that has completed the developing operation on the photosensitive drum 10.

  The collection device 146 collects the liquid developer removed by the blade 145 and sends the liquid developer to the pipe 81 of the circulation devices LY, LM, LC, and LB. The liquid developer flows down along the surface of the blade 145. If the viscosity of the liquid developer is high, the recovery device 146 may preferably include a feed roller that assists in feeding the liquid developer.

  The primary transfer roller 20 sandwiches the intermediate transfer belt 21 in cooperation with the photosensitive drum 10. A voltage having a polarity opposite to that of the colored particles P on the photosensitive drum 10 (minus in the present embodiment) is applied to the primary transfer roller 20 from a power source (not shown). The primary transfer roller 20 applies a voltage having a polarity opposite to that of the toner to the intermediate transfer belt 21. As a result, the colored particles P and the polymer compound R are attracted to the surface of the conductive intermediate transfer belt 21. Thus, the image formed on the photosensitive drum 10 is transferred to the surface of the intermediate transfer belt 21. Thereafter, the intermediate transfer belt 21 carries the toner image and conveys it to the sheet S.

  The cleaning device 26 that removes the liquid developer remaining without being transferred from the photosensitive drum 10 to the intermediate transfer belt 21 includes a conveying screw 261 and a cleaning blade 262. An end portion of the plate-like cleaning blade 262 extending in the rotation axis direction of the photosensitive drum 10 is in sliding contact with the surface of the photosensitive drum 10. The cleaning blade 262 scrapes off the liquid developer remaining on the photosensitive drum 10 as the photosensitive drum 10 rotates. The liquid developer thus scraped off is temporarily stored in the cleaning device 26. A conveying screw 261 in the cleaning device 26 conveys the residual developer to the outside.

  In order to prepare for the next round of image formation, the static elimination device 13 having a static elimination light source removes the liquid developer by the cleaning blade 262 and then neutralizes the surface of the photosensitive drum 10 with light from the light source.

  The substantially cylindrical removal roller 30 contacts the intermediate transfer belt 21. A removing roller 30 disposed between the image forming unit FY and the image forming unit FM removes the carrier liquid C from the liquid developer transferred from the image forming unit FY to the intermediate transfer belt 21. A removing roller 30 disposed between the image forming unit FM and the image forming unit FC removes the carrier liquid C from the liquid developer transferred from the image forming unit FM to the intermediate transfer belt 21. A removing roller 30 disposed between the image forming unit FC and the image forming unit FB removes the carrier liquid C from the liquid developer transferred from the image forming unit FC to the intermediate transfer belt 21. As described above, since the image forming unit FB does not include the removal roller 30, the intermediate transfer belt 21 carries a liquid developer containing the carrier liquid C, like the image carrier 100 shown in FIG.

  As shown in FIG. 15, the sheet storage unit 3 that stores the sheet S is disposed below the upper main body 1 </ b> A. The sheet storage unit 3 includes a paper feed cassette that can store the sheets S.

  The secondary transfer unit 4 that transfers the image formed on the intermediate transfer belt 21 to the sheet S includes a secondary transfer roller 42 disposed to face the drive roller 41 that drives the intermediate transfer belt 21. The secondary transfer roller 42 generates an electric field with the intermediate transfer belt 21 and draws the colored particles P toward the sheet S as described with reference to FIG.

  The fixing unit 5 disposed above the secondary transfer unit 4 fixes the toner image on the sheet S using the principle of the fixing technique described above. Therefore, the fixing unit 5 includes the fixing device 300 described in relation to the first embodiment and the belt unit 450. As described above, the fixing process is suitably performed by the rubbing of the rubbing roller 310 against the image on the sheet S. In addition, since the rubbing roller 310 has a sufficient width to rub the entire image, the gloss of the image is uniformly changed by the contact with the rubbing roller 310. As a result, even if the image on the sheet S is subsequently touched by the user, the local change in the gloss of the image is preferably suppressed.

  The sheet S on which the toner image is fixed by the fixing unit 5 is discharged to the discharge unit 6 disposed at the upper part of the color printer 1. A sheet conveyance unit 7 including a plurality of conveyance roller groups conveys the sheet S in the order of the secondary transfer unit 4, the fixing unit 5, and the discharge unit 6 from the sheet storage unit 3.

<Liquid developer>
As described above, the liquid developer includes an electrically insulating carrier liquid C and colored particles P dispersed in the carrier liquid C. The liquid developer contains the polymer compound R. Preferably, the liquid developer has a viscosity of 30 to 400 mPa · s at a measurement temperature of 25 ° C. More preferably, the viscosity (measurement temperature 25 ° C.) of the liquid developer is 40 to 300 mPa · s, and more preferably 50 to 250 mPa · s.

<Carrier liquid>
The electrically insulating carrier liquid C that functions as a liquid carrier enhances the electrical insulation of the liquid developer. As the electrically insulating carrier liquid C, for example, an electrically insulating organic solvent having a volume resistance at 25 ° C. of 10 ¹² Ω · cm or more (in other words, conductivity of 1.0 pS / cm or less) is preferable. Furthermore, in addition to the above physical properties, those capable of dissolving a polymer compound R described later (a polymer compound R having a relatively high solubility) are preferably used.

  Further, the viscosity, type, and blending amount of the carrier liquid C are appropriately adjusted and selected so that the viscosity of the entire liquid developer (measurement temperature: 25 ° C.) is 30 to 400 mPa · s. The viscosity of the liquid developer also depends on the combination of the organic solvent used as the carrier liquid C and the polymer compound R described later. Therefore, the type and blending amount of the organic solvent are appropriately determined according to the desired viscosity of the liquid developer and the type of the polymer compound R selected.

  Examples of such an electrically insulating organic solvent include aliphatic hydrocarbons and vegetable oils that are liquid at room temperature.

  As the aliphatic hydrocarbon, for example, liquid n-paraffinic hydrocarbon, iso-paraffinic hydrocarbon, halogenated aliphatic hydrocarbon, branched aliphatic hydrocarbon or a mixture thereof is preferable. For example, n-hexane, n-heptane, n-octane, nonane, decane, dodecane, hexadecane, heptadecane, cyclohexane, perchloroethylene, and trichloroethane are used as the aliphatic hydrocarbon. From the viewpoint of environmental measures (measures against VOC), non-volatile organic solvents and organic solvents with relatively low volatility (for example, those having a boiling point of 200 ° C. or higher) are preferable, for example, aliphatic carbonization having 16 or more carbon atoms. Liquid paraffin containing a relatively large amount of hydrogen is preferably used.

  Examples of vegetable oils include tall oil fatty acids (main components: oleic acid, linoleic acid), fatty acid esters derived from vegetable oils, soybean oil, safflower oil, castor oil, linseed oil, and tung oil. Of these, tall oil fatty acids are preferably used.

  As the carrier liquid C, for example, liquid paraffin “Moresco White P-55”, “Moresco White P-40”, “Moresco White P-70”, “Moresco White P-200” manufactured by Matsumura Oil Research Co., Ltd. ”; Tall oil fatty acids“ Hartol FA-1 ”,“ Hartol FA-1P ”,“ Hartol FA-3 ”manufactured by Harima Chemicals Co., Ltd .; vegetable oil-based solvent“ Vegisol MT ”,“ Vegisol CM ”manufactured by Kaneda Co., Ltd. “Vegisol MB”, “Vegisol PR”, vegetable oil “Tung oil”; “Isopar G”, “Isopar H”, “Isopar K”, “Isopar L”, “Isopar M”, “Isopar V” manufactured by ExxonMobil; Liquid paraffin “Cosmo White P-60”, “Cosmo White P-70”, “Cosmo White P-12” manufactured by Cosmo Oil Co., Ltd. ”; Vegetable oil“ soybean oil white squeezed oil S ”,“ linseed oil ”,“ saflower oil ”manufactured by Nisshin Oilio Co., Ltd .; vegetable oils“ castor oil LAV ”,“ castor oil industry ”manufactured by Ito Oil Co., Ltd. are used. Also good.

  In this embodiment, as long as the polymer compound R is dissolved in the carrier liquid C, only the carrier liquid C having a relatively high solubility of the polymer compound R (good solvent for the polymer compound R) may be used. Alternatively, a polymer compound R having a relatively low solubility (poor solvent for polymer compound R) may be used in combination. Depending on the type of carrier liquid C, the conductivity of the entire carrier liquid C (conductivity of the liquid developer) is appropriately adjusted so as not to be excessively high. For example, vegetable oils such as tall oil fatty acids generally have higher electrical conductivity than aliphatic hydrocarbons such as liquid paraffin. Therefore, in order to dissolve the polymer compound R in the carrier liquid C satisfactorily, when the oils described above are included as the carrier liquid C, it is preferable to adjust the conductivity relatively carefully.

  The carrier liquid C having a high oil content is advantageous in terms of the solubility of the polymer compound R, but disadvantageous in terms of conductivity. The carrier liquid C having a low oil content is advantageous in terms of conductivity, but is disadvantageous in terms of the solubility of the polymer compound R.

  The content of the aforementioned oils in the carrier liquid C depends on the type and content of the polymer compound R contained in the liquid developer. As content of suitable oils, 2-80 mass%, for example, More preferably, 5-60 mass% is mentioned. If it is less than 2 mass%, it will be difficult to dissolve the polymer compound R well in the carrier liquid C. On the other hand, if it exceeds 80% by mass, the conductivity of the entire carrier liquid C and thus the conductivity of the liquid developer becomes excessively high. An excessively high liquid developer conductivity, for example, causes a reduction in image density.

  In the present embodiment, the conductivity of the liquid developer is preferably 200 pS / cm or less, for example. Therefore, by mixing a high electric resistance aliphatic hydrocarbon into a solution obtained by dissolving the polymer compound R in the above-mentioned oils such as tall oil fatty acid (hereinafter referred to as “resin solution”). The conductivity of the entire carrier liquid C (the conductivity of the liquid developer) is preferably adjusted to 200 pS / cm or less, for example.

<Colored particles>
In the present embodiment, the pigment itself is used as the colored particles P. The liquid developer containing the pigment itself enables the above-described non-heating type fixing step. As a result, the pigment as the colored particles P is fixed on the recording medium with little consumption of heat energy and light energy.

  As the pigment in the present embodiment, for example, conventionally known organic pigments and inorganic pigments are used without particular limitation.

  Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. . Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK. Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B. Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include C.I. I. Pigment Blue 15: 3, cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chlorinated product, first sky blue, and indanthrene blue BC. Examples of the green pigment include chrome green, chromium oxide, pigment green B, and malachite green lake.

  The content of the pigment in the liquid developer is preferably 1 to 30% by mass. More preferably, it is 3 mass% or more, More preferably, it is 5 mass% or more. Moreover, More preferably, it is 20 mass% or less, More preferably, it is 10 mass% or less.

The average particle diameter of the pigment in the liquid developer, that is, the volume-based median diameter (D ₅₀ ) is preferably 0.1 to 1.0 μm. A pigment having an average particle size of less than 0.1 μm causes, for example, a reduction in image density. A pigment having an average particle diameter exceeding 1.0 μm causes, for example, a decrease in fixability. Here, the volume-based median diameter (D ₅₀ ) is generally 50% when the cumulative curve is obtained with the total volume of a group of particles whose particle size distribution is required as 100%. The particle diameter of a point.

<Dispersion stabilizer>
The liquid developer according to this embodiment may contain a dispersion stabilizer for promoting and stabilizing the dispersion of particles in the liquid developer. As a dispersion stabilizer that can be used in the present embodiment, for example, “BYK-116” manufactured by Big Chemie is suitable. In addition, “Solsperse 9000”, “Solsperse 11200”, “Solsparse 13940”, “Solspers 16000”, “Solspers 17000”, “Solspers 18000” manufactured by Lubrizol, and “Antaron (registered trademark) V-” manufactured by ISP 216 "," Antaron (registered trademark) V-220 "can also be preferably used.

  The content of the dispersion stabilizer in the liquid developer is about 1 to 10% by mass, preferably about 2 to 6% by mass.

<Polymer compound>
The polymer compound R contained in the liquid developer according to this embodiment is an organic polymer compound. As the organic polymer compound having solubility in the carrier liquid C, a material capable of increasing the viscosity of the liquid developer and suppressing the occurrence of bleeding in image formation is selected. Examples of the organic polymer compound include cyclic olefin copolymer, styrene elastomer, cellulose ether, and polyvinyl butyral. Preferably, a styrene elastomer is used as the organic polymer compound. As the polymer compound R, a single type of organic polymer compound may be used, or a plurality of types of organic polymer compounds may be used.

  In the liquid developer according to this embodiment, the organic polymer compound is dissolved in the carrier liquid C. The organic polymer compound dissolved in the carrier liquid C may be in a gel state. Depending on the type and molecular weight of the organic polymer compound, a gel-like organic polymer compound entangled with each other in the carrier liquid C can be obtained. Gel-like organic polymer compounds have relatively low fluidity. For example, when the concentration of the organic polymer compound is high, when the affinity between the organic polymer compound and the carrier liquid C is low, or when the temperature is low, a gel-like organic polymer compound is easily obtained. On the other hand, the organic polymer compound with little entanglement in the carrier liquid C becomes a solution having relatively high fluidity.

  The content of the organic polymer compound in the liquid developer is appropriately determined according to the type of the organic polymer compound. The content of the organic polymer compound is preferably 1 to 10% by mass, for example.

  If the content of the organic polymer compound is less than 1% by mass, sufficient viscosity in the liquid developer cannot be obtained, and there is a possibility that the occurrence of bleeding in image formation cannot be sufficiently suppressed. On the other hand, when the content of the organic polymer compound exceeds 10% by mass, the amount of the coating film formed by the organic polymer compound remaining on the surface of the sheet S is excessively increased, the drying property of the coating film is excessively decreased, and the adhesion of the coating film is decreased. (Tackiness) may be excessively increased, and the scratch resistance of the image may be excessively decreased.

  Hereinafter, organic polymer compounds that can be suitably used in the present embodiment will be further described.

(Cyclic olefin copolymer)
The cyclic olefin copolymer is a non-crystalline thermoplastic olefin resin having a cyclic olefin skeleton in the main chain and containing no environmental load substance, and is excellent in transparency, light weight, low water absorption, and the like. In the present embodiment, the cyclic olefin copolymer is an organic polymer compound having a main chain composed of a carbon-carbon bond and having a cyclic hydrocarbon structure in at least a part of the main chain. This cyclic hydrocarbon structure is introduced by using a compound (cyclic olefin) having at least one olefinic double bond in the cyclic hydrocarbon structure as represented by norbornene or tetracyclododecene as a monomer. Is done.

  Examples of the cyclic olefin copolymer that can be used in the present embodiment include (1) addition (co) polymer of cyclic olefin or hydrogenated product thereof, (2) addition copolymer of cyclic olefin and α-olefin, or The hydrogenated product, (3) a ring-opening (co) polymer of a cyclic olefin, or a hydrogenated product thereof.

Examples of the cyclic olefin include the following substances.
(A) cyclopentene, cyclohexene, cyclooctene;
(B) a monocyclic olefin such as cyclopentadiene or 1,3-cyclohexadiene;
(C) Bicyclo [2.2.1] hept-2-ene (norbornene), 5-methyl-bicyclo [2.2.1] hept-2-ene, 5,5-dimethyl-bicyclo [2.2. 1] Hept-2-ene, 5-ethyl-bicyclo [2.2.1] hept-2-ene, 5-butyl-bicyclo [2.2.1] hept-2-ene, 5-ethylidene-bicyclo [ 2.2.1] hept-2-ene, 5-hexyl-bicyclo [2.2.1] hept-2-ene, 5-octyl-bicyclo [2.2.1] hept-2-ene, 5- Octadecyl-bicyclo [2.2.1] hept-2-ene, 5-methylidene-bicyclo [2.2.1] hept-2-ene, 5-vinyl-bicyclo [2.2.1] hept-2-ene Ene, 5-propenyl-bicyclo [2.2.1] hept-2-ene 2 the ring of the cyclic olefin;
(D) tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene), tricyclo [4.3.0.12,5] dec-3-ene;
(E) Tricyclo [4.4.0.12,5] undeca-3,7-diene or tricyclo [4.4.0.12,5] undeca-3,8-diene or a partially hydrogenated product thereof ( Or an adduct of cyclopentadiene and cyclohexene), which is tricyclo [4.4.0.12,5] undec-3-ene;
(F) 5-cyclopentyl-bicyclo [2.2.1] hept-2-ene, 5-cyclohexyl-bicyclo [2.2.1] hept-2-ene, 5-cyclohexenylbicyclo [2.2.1] ] Tricyclic olefins such as hepta-2-ene and 5-phenyl-bicyclo [2.2.1] hept-2-ene;
(G) Tetracyclo [4.4.0.12,5.17,10] dodec-3-ene (tetracyclododecene), 8-methyltetracyclo [4.4.0.12,5.17,10 ] Dodec-3-ene, 8-ethyltetracyclo [4.4.0.12, 5.17,10] dodec-3-ene, 8-methylidenetetracyclo [4.4.0.12,5. 17,10] dodec-3-ene, 8-ethylidenetetracyclo [4.4.0.12,5.17,10] dodec-3-ene, 8-vinyltetracyclo [4,4.0.12. 4.17,10] dodec-3-ene, 4-cyclic olefins such as 8-propenyl-tetracyclo [4.4.0.12, 5.17,10] dodec-3-ene;
(H) 8-cyclopentyl-tetracyclo [4.4.0.12,5.17,10] dodec-3-ene, 8-cyclohexyl-tetracyclo [4.4.0.12,5.17,10] dodeca -3-ene, 8-cyclohexenyl-tetracyclo [4.4.0.12, 5.17,10] dodec-3-ene, 8-phenyl-cyclopentyl-tetracyclo [4.4.0.12,5. 17,10] dodec-3-ene;
(I) Tetracyclo [7.4.13,6.01,9.02,7] tetradeca-4,9,11,13-tetraene (1,4-methano-1,4,4a, 9a-tetrahydrofluorene) , Tetracyclo [8.4.14, 7.01, 10.03,8] pentadeca-5,10,12,14-tetraene (to 1,4-methano-1,4,4a, 5,10,10a-) Oxahydroanthracene);
(J) pentacyclo [6.6.1.13,6.02,7.09,14] -4-hexadecene, pentacyclo [6.5.1.13,6.02,7.09,13] -4 -Pentadecene, pentacyclo [7.4.0.02, 7.13, 6.110, 13] -4-pentadecene; heptacyclo [8.7.0.12, 9.14, 7.111, 17.03, 8.012,16] -5-eicosene, heptacyclo [8.7.0.12,9.03,8.14,7.012,17.113, l6] -14-eicosene;
(K) A polycyclic olefin such as a tetramer of cyclopentadiene. These cyclic olefins can be used alone or in combination of two or more.

  As the above-mentioned α-olefin, an α-olefin having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms is preferable. As α-olefin, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl- 1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, Examples include 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicocene. These α-olefins can be used alone or in combination of two or more.

  In the present embodiment, there are no particular restrictions on the polymerization method of cyclic olefin, the polymerization method of cyclic olefin and α-olefin, and the hydrogenation method of the obtained polymer, and can be carried out according to known methods. .

  In the present embodiment, the structure of the cyclic olefin copolymer is not particularly limited. The structure of the cyclic olefin copolymer may be linear, branched or cross-linked, but is preferably linear.

  In the present embodiment, as the cyclic olefin copolymer, for example, a copolymer of norbornene and ethylene or a copolymer of tetracyclododecene and ethylene is preferably used. As the cyclic olefin copolymer, a copolymer of norbornene and ethylene is particularly preferable. The content of norbornene in the copolymer is preferably 60 to 82% by mass, more preferably 60 to 79% by mass, further preferably 60 to 76% by mass, and still more preferably 60 to 65% by mass. When the norbornene content is less than 60% by mass, the glass transition temperature of the cyclic olefin copolymer film becomes too low, and the film-forming property of the cyclic olefin copolymer film may be lowered. When the norbornene content exceeds 82% by mass, the glass transition temperature of the cyclic olefin copolymer coating film becomes too high, and the fixability of the pigment, that is, the image by the cyclic olefin copolymer coating film may be lowered. Moreover, the solubility of the cyclic olefin copolymer in the carrier liquid C may become excessively low.

  In this embodiment, what is marketed may be used as a cyclic olefin copolymer. For example, as a copolymer of norbornene and ethylene, "TOPAS (registered trademark) TM" (norbornene content: about 60% by mass) and "TOPAS (registered trademark) TB" manufactured by Topas Advanced Polymers GmbH (Norbornene content: about 60 mass%), “TOPAS (registered trademark) 8007” (norbornene content: about 65 mass%), “TOPAS (registered trademark) 5013” (norbornene content: about 76 mass%), “ "TOPAS (registered trademark) 6013" (norbornene content: about 76 mass%), "TOPAS (registered trademark) 6015" (norbornene content: about 79 mass%), "TOPAS (registered trademark) 6017" (norbornene content: About 82% by mass). These may be used alone or in combination of two or more depending on the situation.

(Styrene elastomer)
As the styrene-based elastomer that can be used in the present embodiment, conventionally known styrene elastomers can be used without particular limitation. Examples of the styrene elastomer include a block copolymer composed of an aromatic vinyl compound and an olefin compound or a conjugated diene compound. As a block copolymer, for example, a block having a structure represented by Chemical Formula 1 when A is a polymer block made of an aromatic vinyl compound and B is a polymer block made of an olefinic compound or a conjugated diene compound A copolymer is mentioned.

  Examples of the aromatic vinyl compound constituting the block copolymer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,3-dimethylstyrene, 2,4- Dimethylstyrene, monochlorostyrene, dichlorostyrene, p-bromostyrene, 2,4,5-tribromostyrene, 2,4,6-tribromostyrene, o-tert-butylstyrene, m-tert-butylstyrene, p- Examples thereof include tert-butyl styrene, ethyl styrene, vinyl naphthalene, and vinyl anthracene.

  The polymer block A may be comprised from 1 type in the above-mentioned aromatic vinyl compound, and may be comprised from 2 or more types. Among these, those composed of styrene and / or α-methylstyrene give preferable physical properties to the liquid developer according to this embodiment.

  Examples of the olefin compounds constituting the block copolymer include ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, cyclopentene, 1-hexene, 2-hexene, cyclohexene, Examples include 1-heptene, 2-heptene, cycloheptene, 1-octene, 2-octene, cyclooctene, vinylcyclopentene, vinylcyclohexene, vinylcycloheptene, and vinylcyclooctene.

  Examples of the conjugated diene compound constituting the block copolymer include butadiene, isoprene, chloroprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene.

  The polymer block B may be comprised from 1 type of the above-mentioned olefinic compound and the above-mentioned conjugated diene compound, and may be comprised from 2 or more types. Among these, those composed of butadiene and / or isoprene give preferable properties to the liquid developer according to the present embodiment.

  Examples of the block copolymer include polystyrene-polybutadiene-polystyrene triblock copolymer or hydrogenated product thereof, polystyrene-polyisoprene-polystyrene triblock copolymer or hydrogenated product thereof, polystyrene-poly (isoprene / Butadiene) -polystyrene triblock copolymer or hydrogenated product thereof, poly (α-methylstyrene) -polybutadiene-poly (α-methylstyrene) triblock copolymer or hydrogenated product thereof, poly (α-methylstyrene) A polyisoprene-poly (α-methylstyrene) triblock copolymer or a hydrogenated product thereof, poly (α-methylstyrene) -poly (isoprene / butadiene) -poly (α-methylstyrene) triblock copolymer, or Its hydrogenated product, polystyrene-polyiso Ten - polystyrene triblock copolymer, poly (alpha-methylstyrene) - polyisobutene - poly (alpha-methylstyrene) triblock copolymer.

  As the styrene elastomer used in the present embodiment, a styrene-butadiene elastomer (SBS) in which the polymer block A and the polymer block B have a structure represented by the chemical formula 2 is preferable.

  The styrene-butadiene elastomer is obtained by copolymerizing a styrene monomer and butadiene which is a conjugated diene compound. Preferred styrene monomers include styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-dodecyl. Examples include styrene, p-methoxystyrene, p-phenylstyrene, and p-chlorostyrene.

  The above-mentioned styrene-butadiene elastomer has a number average molecular weight Mn in the molecular weight distribution by GPC (gel permeation chromatography), preferably in the range of 1,000 to 100,000 (see Chemical Formula 1), more preferably. Is in the range of 2,000 to 50,000. The weight average molecular weight Mw is preferably in the range of 5,000 to 1,000,000, more preferably in the range of 10,000 to 500,000. In that case, it is preferable that the weight average molecular weight Mw is in the range of 2,000 to 200,000, and preferably at least one peak is in the range of 3,000 to 150,000.

  In the above styrene-butadiene elastomer, the value of the ratio (weight average molecular weight Mw / number average molecular weight Mn) is preferably 3.0 or less, and more preferably 2.0 or less.

  The styrene content (content of polymer block A) in the styrene-butadiene elastomer described above is preferably in the range of 5 to 75% by mass (see Chemical Formula 2), more preferably 10 to 65% by mass. Is within the range. When the styrene content is less than 5% by mass, the glass transition temperature of the styrene-based elastomer film becomes too low, and the film-forming property of the styrene-based elastomer film tends to decrease. When the styrene content exceeds 75% by mass, the softening point of the styrene elastomer film becomes too high, and the fixability of the pigment, that is, the image by the styrene elastomer film tends to be lowered.

  In this embodiment, a commercially available styrene elastomer can be used. For example, as a styrene-conjugated diene block copolymer, Kuraray's “Septon” S1001, S2063, S4055, S8007 and “Hibler” 5127, 7311, Shell's “Clayton”, Asahi Kasei Chemicals' “Asuprene ( Registered trademark) "T411, T413, T437," Tufprene (registered trademark) "A, 315P, etc.," JSR TR1086 "," JSR TR2000 "," JSR TR2250 "," JSR TR2827 "manufactured by JSR; styrene-conjugated diene As a hydrogenated block copolymer, “Dynalon” 6200P, 4600P, 1320P manufactured by JSR, etc .; As a styrene-ethylene copolymer, “Index” manufactured by Dow Chemical Co., etc .; As a composition, Aron Kasei Co., Ltd. "Aron AR" made by Mitsubishi, Mitsubishi Gakusha made of "Rabalon", and the like. These may be used alone or in combination of two or more depending on the situation. “Septon” S1001, S2063, S4055, S8007 and “Hibler” 5127, 7311 manufactured by Kuraray are hydrogenated products of styrene-conjugated diene block copolymers.

(Cellulose ether)
Cellulose ether is a polymer in which a hydroxyl group in a cellulose molecule is substituted with an alkoxy group. The substitution rate is preferably 45 to 49.5%. Moreover, the alkyl part of the alkoxy group may be substituted with, for example, a hydroxyl group. The cellulose ether film is excellent in toughness and thermal stability.

  Examples of the cellulose ether that can be used in the present embodiment include alkyl celluloses such as methyl cellulose and ethyl cellulose; hydroxyalkyl celluloses such as hydroxyethyl cellulose and hydroxypropyl cellulose; hydroxyalkylalkyl celluloses such as hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl ethyl cellulose; carboxymethyl cellulose And carboxyalkyl hydroxyalkyl cellulose such as carboxymethyl hydroxyethyl cellulose. These may be used alone or in combination of two or more. Among these, alkyl cellulose is preferable, and among the alkyl celluloses, ethyl cellulose is preferable.

  In this embodiment, what is marketed can be used as a cellulose ether. Examples of the ethyl cellulose include “Etocel (registered trademark) STD4”, “Etocel (registered trademark) STD7”, “Etocel (registered trademark) STD10” manufactured by Nisshinsei Co., Ltd., and the like. These may be used alone or in combination of two or more depending on the situation.

(Polyvinyl butyral)
The polyvinyl butyral (butyral resin: alkyl acetalized polyvinyl alcohol) that can be used in the present embodiment has a hydroxyl group, a hydrophilic vinyl alcohol unit, a butyral group, and a hydrophobic vinyl as shown in Chemical Formula 3. It is a copolymer of an acetal unit and a vinyl acetate unit having an acetyl group and having intermediate properties between a vinyl alcohol unit and a vinyl acetal unit. In the liquid developer according to the exemplary embodiment, polyvinyl butyral having a degree of butyralization (determining a ratio between a hydrophilic part and a hydrophobic part) having a film forming ability (film forming property) of 60 to 85 mol% is excellent. Is preferable. Polyvinyl butyral has a vinyl acetal unit that is soluble in a nonpolar solvent and a vinyl alcohol unit that improves the binding property to a recording medium such as paper. Therefore, it is used in both the carrier liquid C and the recording medium. It has a high affinity for it.

  It does not specifically limit as polyvinyl butyral which can be used by this embodiment. Examples of polyvinyl butyral include “Mowital (registered trademark)” B20H, B30B, B30H, B60T, B60H, B60HH, and B70H manufactured by Hoechst; “ESREC (registered trademark)” BL-1 (butyralized) manufactured by Sekisui Chemical Co., Ltd. Degree: 63 ± 3 mol%), BL-2 (same: 63 ± 3 mol%), BL-S (same: 70 mol% or more), BL-L, BH-3 (same: 65 ± 3 mol%), BM-1 (Same: 65 ± 3 mol%), BM-2 (same: 68 ± 3 mol%), BM-5 (same: 63 ± 3 mol%), BM-S; “Denkabutyral” # 2000- manufactured by Denki Kagaku Kogyo Co., Ltd. L, # 3000-1, # 3000-2, # 3000-3, # 3000-4, # 3000-K, # 4000-1, # 5000-A, # 6000-C. These may be used alone or in combination of two or more.

(Production method)
The liquid developer according to the exemplary embodiment uses a carrier liquid C, a pigment, an organic polymer compound, and, if necessary, a dispersion stabilizer such as a ball mill, a sand grinder, a dyno mill, or a rocking mill (zirconia beads or the like). It can be manufactured by sufficiently dissolving or mixing and dispersing over several minutes to several tens of hours as necessary.

The pigment is finely pulverized by the mixing and dispersion described above. As described above, the mixing and dispersion time and the number of rotations are adjusted so that the average particle diameter (D ₅₀ ) of the pigment in the liquid developer is preferably 0.1 to 1.0 μm. If the dispersion time is excessively short or the rotational speed is excessively small, the average particle diameter (D ₅₀ ) of the pigment exceeds 1.0 μm, and as described above, the fixability may be lowered. If the dispersion time is excessively long or the rotational speed is excessively large, the average particle diameter (D ₅₀ ) of the pigment becomes less than 0.1 μm, and as described above, the image density is lowered due to insufficient developability. Is caused.

  In this embodiment, after dissolving the organic polymer compound in the carrier liquid C, a liquid developer may be produced by mixing and dispersing a pigment (with a dispersion stabilizer as necessary), or Resin solution (referred to a solution obtained by dissolving an organic polymer compound in carrier liquid C) and pigment dispersion (referred to a material obtained by mixing and dispersing pigment (along with a dispersion stabilizer depending on the situation) in carrier liquid C). And a liquid developer may be produced by mixing them in an appropriate mixing ratio (mass ratio).

In order to calculate the average particle diameter (D ₅₀ ) of the pigment, the particle size distribution of the pigment is measured. The particle size distribution of the pigment is measured, for example, by the following method.

  A predetermined amount of the produced liquid developer or the prepared pigment dispersion is sampled, and diluted 10 to 100 times (volume) with the same carrier liquid C as the carrier liquid C used in the liquid developer or pigment dispersion. The particle size distribution of the pigment is measured by a flow method using a laser diffraction type particle size distribution measuring device “Mastersizer 2000” manufactured by MALVERN.

  The viscosity of the manufactured liquid developer is measured using a vibration type viscometer “VISCOMATE VM-10A-L” manufactured by CBC at a measurement temperature of 25 ° C.

  The present invention can be applied to various image forming apparatuses such as a printer, a copier, a facsimile machine, and a multifunction machine having these functions.

1. Color printer (image forming device)
2... Image forming units 300, 300A, 300B... Fixing device 310... : Elastic roller)
310A ... Rubbing roller (Rubbing element: Brush roller)
323 ... Upstream rubbing roller (Upstream rubbing element: elastic roller)
323A ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Upstream rubbing roller (Upstream rubbing element: brush roller)
324 ... downstream rubbing roller (downstream rubbing element: elastic roller)
324A ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Downstream rubbing roller (downstream rubbing element: brush roller)
334 ... Upstream motor (drive source)
335 ..... Downstream motor (drive source)
370 ... Cylinder mechanism (separation mechanism)
371 ... Upstream cylinder device (upstream separation / connection mechanism)
372 ... Downstream cylinder device (downstream separation mechanism)
373 ... Control unit (control unit)
450, 450A ... belt unit (conveying element)
453, 453A ... Endless belt (conveyor belt)
456 ... ・ ・ ・ ・ ・ Charging device (adsorption device)
456A ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Vacuum device (Suction device)
458 ... Through hole DN ... Downstream nip surface (contact surface: downstream contact surface)
I: Image layer (image)
S ... sheet UN ... upstream nip surface (contact surface: upstream contact surface)
V1 ......... First speed V2 ......... Second speed V3・ 3rd speed

Claims (16)

A conveyor belt for conveying the sheet;
An adsorbing device for adsorbing the sheet to the conveying belt;
An image forming unit that forms an image on the sheet using a liquid developer;
A fixing device for fixing the image on the sheet,
The fixing device includes an upstream rubbing element for rubbing the image on the sheet, and a downstream rubbing element for rubbing the image after the upstream rubbing element. .   The image forming apparatus according to claim 1, wherein the upstream rubbing element fixes the image on the sheet at a fixing rate different from that of the downstream rubbing element.   The image forming apparatus according to claim 2, wherein the upstream rubbing element and the downstream rubbing element include an elastic roller having an elastic peripheral surface.   The image forming apparatus according to claim 2, wherein the upstream rubbing element and the downstream rubbing element include a brush roller having a peripheral surface on which a brush is disposed. A transport element for transporting the sheet;
An image forming unit that forms an image on the sheet using a liquid developer;
A fixing device for fixing the image on the sheet,
The fixing device includes an upstream rubbing element that rubs the image on the sheet, and a downstream rubbing element that rubs the image after the upstream rubbing element,
The image forming apparatus, wherein the downstream rubbing element presses the image with a stronger force than the upstream rubbing element.   The image forming apparatus according to claim 5, wherein the downstream rubbing element has a hardness greater than that of the upstream rubbing element. A transport element for transporting the sheet;
An image forming unit that forms an image on the sheet using a liquid developer;
A fixing device for fixing the image on the sheet,
The fixing device includes an upstream rubbing element that rubs the image on the sheet, and a downstream rubbing element that rubs the image after the upstream rubbing element,
The upstream rubbing element includes an upstream contact surface in contact with the image;
The downstream rubbing element includes a downstream contact surface in contact with the image;
The image forming apparatus, wherein the upstream contact surface is smaller than the downstream contact surface. The fixing device includes a drive source for operating the upstream rubbing element and the downstream rubbing element,
Each of the upstream rubbing element and the downstream rubbing element includes a rubbing roller that rotates on the image,
The rubbing roller includes a contact surface that contacts the image,
The conveying element conveys the sheet at a first speed;
The image forming apparatus according to claim 5, wherein the driving source rotates the rubbing roller so that the contact surface moves at a second speed different from the first speed.   The image forming apparatus according to claim 8, wherein the second speed is greater than the first speed.   The image forming apparatus according to claim 8, wherein the second speed is smaller than the first speed. The fixing device includes a drive source for operating the upstream rubbing element and the downstream rubbing element,
The conveying element conveys the sheet at a first speed;
The drive source moves the upstream contact surface at a second speed larger than the first speed and moves the downstream contact surface at a third speed larger than the second speed. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, wherein the fixing device includes a separation mechanism that separates and contacts the upstream rubbing element and the downstream rubbing element from the image. The fixing device includes a control unit that controls the separation / contact mechanism,
The separation / contact mechanism includes an upstream separation / contact mechanism for separating / contacting the upstream rubbing element from the image, and a downstream separation / contact mechanism for separating / contacting the downstream rubbing element from the image,
The image forming apparatus according to claim 12, wherein the control unit operates the upstream separation mechanism and the downstream separation mechanism independently. The suction device includes a charging device that charges the transport belt,
The image forming apparatus according to claim 1, wherein the conveyance belt electrostatically adsorbs the sheet. A through hole is formed in the conveyor belt,
The image forming apparatus according to claim 1, wherein the suction device includes a vacuum device that sucks the sheet through the through hole. A fixing device for fixing an image formed using a liquid developer on a sheet,
An upstream rubbing element for rubbing the image on the sheet;
A downstream rubbing element for rubbing the image after the upstream rubbing element,
The fixing device according to claim 1, wherein the downstream rubbing element presses the image with a stronger force than the upstream rubbing element.