JP5637810B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image on a 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 the image on the sheet is rubbed. A fixing device for fixing the image, the fixing device having a rotation center, and a rubbing surface for rubbing the image while rotating around the rotation center in a state of surface contact with the sheet; And a drive source for rotating the rubbing surface about the rotation center.

  According to the image forming apparatus of the present invention, the rubbing surface rubs the image while rotating around the center of rotation while being in surface contact with the sheet by the driving source. Therefore, as compared with the configuration in which the image is rubbed with a roller, the time for the image to be rubbed by the rubbing surface becomes longer. This makes it easier for components in the liquid developer that forms an image to enter the surface layer of the sheet. As a result, the fixing time of the image is shortened and peeling of the image is suitably suppressed, that is, the fixing strength of the image is improved.

  In a preferred embodiment of the present invention, the transport element transports the sheet at a predetermined transport speed, and the drive source applies the rubbing surface so that the rubbing surface has a predetermined linear velocity in a tangential direction. The linear velocity is set to be larger than the conveying speed.

  According to this configuration, the linear velocity of the rubbing surface is set to be larger than the sheet conveyance speed. As a result, the time during which the image is rubbed by the rubbing surface becomes longer. As a result, the components in the liquid developer forming the image are likely to enter the surface layer of the sheet.

  In another preferred embodiment of the present invention, the liquid developer includes a carrier liquid, the image is a color image, and the rubbing surface is disposed in a direction orthogonal to the sheet conveyance direction. Includes one rubbing surface and a second rubbing surface.

  According to this configuration, a plurality of rubbing surfaces are arranged. Thereby, even when a color image in which the amount of the carrier liquid increases is fixed, the carrier liquid easily enters the surface layer of the sheet.

  In still another preferred embodiment of the present invention, the drive source rotates the first rubbing surface in a first rotation direction and the second rubbing surface in a first direction opposite to the first rotation direction. Rotate in two rotation directions.

  According to this configuration, the first rubbing surface and the second rubbing surface rub the image while rotating in opposite directions. Therefore, the sheet is rubbed while being stretched. As a result, the occurrence of wrinkles on the sheet is suppressed.

  In still another preferred embodiment of the present invention, the rubbing surface is made of a non-woven fabric and is formed of a non-woven fabric layer that rubs the image, and the non-woven fabric layer has a surface contact between the layer surface and the image. In this state, the image is rubbed.

  According to this structure, the nonwoven fabric layer which consists of a nonwoven fabric is used as a rubbing surface. This makes it easy to bring the rubbing surface into surface contact with the image.

  In still another preferred embodiment of the present invention, the nonwoven fabric has a dynamic friction coefficient of 0.50 or less.

  According to this configuration, since the nonwoven fabric having a low dynamic friction coefficient is used, it is possible to reduce the influence on the conveyance of the sheet and to suppress image damage due to the rubbing operation.

  In still another preferred embodiment of the present invention, the fixing device includes a plurality of brush bristles and includes a rubbing brush that rubs the image with the bristles, and the rubbing surface includes the plurality of brushes. It is formed at the tip of the hair.

  According to this configuration, the image is rubbed with a rubbing brush having a large number of brush hairs. By appropriately adjusting the material, fineness, density, length, and the like of the bristle, the influence on sheet conveyance can be reduced and image damage due to the rubbing operation can be suppressed.

  In still another preferred embodiment of the present invention, the fixing device includes a first rubbing brush and a second rubbing brush that have a plurality of brush bristles and rub the image with the bristles. One rubbing surface is formed by tips of the plurality of brush bristles of the first rubbing brush, and the second rubbing surface is formed by tips of the plurality of bristles of the second rubbing brush. The brush bristles of the first rubbing brush and the bristles of the second rubbing brush are disposed so as to contact each other in the orthogonal direction.

  According to this configuration, the bristles of the first rubbing brush and the bristles of the second rubbing brush are in contact with each other in a direction orthogonal to the sheet conveying direction. Thereby, generation | occurrence | production of the non-rubbing area | region where an image is not rubbed is suppressed.

  In still another preferred embodiment of the present invention, the fixing device further controls a contact area changing mechanism that changes a contact area of a contact surface between the rubbing brush and the image, and the contact area changing mechanism. And a control unit. The contact area changing mechanism switches the contact area between a first contact area and a second contact area larger than the first contact area. The sheet includes a first sheet having a first thickness dimension and a second sheet having a second thickness dimension larger than the first thickness dimension. The control unit controls the contact area changing mechanism to switch the contact area to the first contact area when the first sheet is conveyed, and changes the contact area when the second sheet is conveyed. A mechanism is controlled to switch the contact area to the second contact area.

  According to this configuration, the control unit changes the contact area of the contact surface between the rubbing brush and the image according to the thickness dimension of the sheet. Specifically, when the first sheet has the first thickness dimension, the control unit controls the contact area changing mechanism to switch the contact area to the first contact area, and sets the second thickness dimension larger than the first thickness dimension. When the second sheet has, the contact area changing mechanism is controlled to switch the contact area to a second contact area larger than the first contact area. Thereby, the time for which the image is rubbed is appropriately changed according to the thickness dimension of the sheet. As a result, even if the thickness dimension of the sheet is different, the components in the liquid developer that forms an image can easily penetrate into the surface layer of the sheet.

  In still another preferred embodiment of the present invention, the fixing device further includes a brush support member having a brush mounting surface to which the rubbing brush is mounted, one end connected to the drive source, and the brush support. And a shaft that extends in a direction perpendicular to the brush mounting surface and that is rotated by the drive source. The contact area changing mechanism may switch an intersection angle between a virtual line extending the shaft and a virtual surface extending the contact surface between a first angle and a second angle larger than the first angle. The contact area is switched to the first angle by switching the intersection angle to the first angle, and the contact area is changed to the second angle by switching the intersection angle to the second angle. Switch to 2 contact area. The controller controls the contact area changing mechanism when the first sheet has been conveyed to switch the crossing angle to the first angle, and when the second sheet has been conveyed, the contact area. A change mechanism is controlled to switch the intersection angle to the second angle.

  According to this configuration, the intersection angle between the virtual line extending the shaft and the virtual surface extending the contact surface is switched between the first angle and the second angle, so that the contact area is the first contact area. It is switched between the second contact areas. In this configuration, since a rubbing brush having brush bristles is used, it is easy to switch the crossing angle and thus the contact area.

  According to the image forming apparatus of the present invention, it takes a long time for the image to be rubbed by the rubbing surface. This makes it easier for components in the liquid developer that forms an image to enter the surface layer of the sheet. As a result, the fixing time of the image is shortened and peeling of the image is suitably suppressed, that is, the fixing strength of the image is improved.

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 schematic diagram illustrating a fixing device and a conveying device according to the first embodiment. It is an external appearance perspective view of a rubbing member. It is a top view of a rubbing member and an endless belt. FIG. 6 is a schematic diagram illustrating a fixing device and a conveying device according to a second embodiment. It is an external appearance perspective view of a rubbing member. It is a top view of a rubbing member and an endless belt. FIG. 2 is a schematic diagram of the fixing device, showing a state where the area of the rubbing area is switched to the first area. FIG. 2 is a schematic diagram of a fixing device, showing a state in which a region area of a rubbing region is switched to a second region area. It is a top view of a rubbing member and an endless belt, and shows a modification of a 2nd embodiment. FIG. 6 is a schematic diagram illustrating a fixing device and a conveyance device according to a modification of the first 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. FIG. 16 is an enlarged cross-sectional view illustrating one of the image forming units of the image forming apparatus illustrated in FIG. 15.

  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 rubbing 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 50 and the transport device CV according to the first embodiment. The sheet S on which the image layer I is formed is conveyed to the fixing device 50 by the conveying device CV. The transport device CV includes a belt unit 70, an upstream guide unit 76 disposed upstream of the belt unit 70, and a downstream guide unit 77 disposed downstream of the belt unit 70. The sheet S is guided by the upstream guide unit 76 and sent to the belt unit 70. Thereafter, the sheet S is sent to the downstream guide unit 77 by the belt unit 70.

  The belt unit 70 includes a driving roller 72, a driven roller 73, an endless belt 71 that extends between the driving roller 72 and the driven roller 73, and a tension roller 75 that applies tension to the endless belt 71. Due to the rotation of the driving roller 72, the endless belt 71 circulates around the driving roller 72, the driven roller 73 and the tension roller 75. The driven roller 73 and the tension roller 75 rotate as the endless belt 71 turns. As a result, the sheet S sent out from the upstream guide unit 76 onto the endless belt 71 moves toward the downstream guide unit 77 as the endless belt 71 circulates. The sheet S is conveyed from the upstream guide unit 76 to the downstream guide unit 77 at the conveyance speed V. A symbol T indicates a direction in which the sheet S travels from the upstream guide unit 76 to the downstream guide unit 77 by the belt unit 70. The belt unit 70 is illustrated as a conveyance element.

  The belt unit 70 further includes a backup roller 74 disposed inside the endless belt 71. The backup roller 74 is in contact with the inner surface of the endless belt 71 at a position between the driving roller 72 and the driven roller 73 and at a position opposite to the tension roller 75.

  The fixing device 50 rubs the image layer I on the sheet S to fix the image layer I. The fixing device 50 includes a rubbing member 51 disposed on the opposite side of the backup roller 74 with the endless belt 71 interposed therebetween, and a drive source 52 that drives the rubbing member 51.

  The rubbing member 51 includes a support member 53, a nonwoven fabric layer 54, and a shaft 55.

  FIG. 6 is an external perspective view of the rubbing member 51. The support member 53 is a member having a cylindrical shape. The support member 53 includes a first support surface 53a that is an end surface facing the endless belt 71, and a second support surface 53b that is an end surface located on the opposite side of the first support surface 53a in the axial direction. The first support surface 53a and the second support surface 53b are substantially circular.

The nonwoven fabric layer 54 rubs the image layer I on the sheet S. The non-woven fabric layer 54 is made of non-woven fabric, is attached over the entire first support surface 53a, and has a circular shape in plan view. As the non-woven fabric, the non-woven fabric listed in connection with FIG. 4 is used. The dynamic friction coefficient of the nonwoven fabric is 0.50 or less. The backup roller 74 of the belt unit 70 is disposed so that the surface pressure between the non-woven fabric layer 54 and the layer surface 54a is, for example, 0.2 g / mm ^2. It is maintained in surface contact. The layer surface 54a in contact with the endless belt 71 in the nonwoven fabric layer 54 forms a rubbing surface. The layer thickness of the nonwoven fabric layer 54 is appropriately set so that smooth contact is obtained between the nonwoven fabric layer 54 and the image layer I.

  The nonwoven fabric layer 54 has a rubbing region CR that rubs the image layer I while being in surface contact with the image layer I. The rubbing region CR will be described with reference to FIG. 7 in addition to FIG. 5 and FIG. FIG. 7 is a plan view of the rubbing member 51 and the endless belt 71. The shaft 55 is fixed to the second support surface 53 b of the support member 53 at a position where one end coincides with the center axis of the support member 53. The drive source 52 is, for example, a motor connected to the other end of the shaft 55, and rotates the shaft 55 clockwise in FIG. The nonwoven fabric layer 54 has a rotation center O that coincides with the center axis of the support member 53 and the rotation axis of the shaft 55. When the shaft 55 rotates, the support member 53 rotates around the central axis, and the nonwoven fabric layer 54 attached to the first support surface 53a of the support member 53 rotates around the rotation center O while being in contact with the endless belt 71.

  The rubbing region CR is a region set on the downstream side of the rotation center O of the nonwoven fabric layer 54 when viewed from the conveyance direction T of the sheet S, and has a substantially semicircular shape in plan view. The nonwoven fabric layer 54 contacts the endless belt 71 only in the rubbing region CR, and forms a nip portion N with the endless belt 71 in the rubbing region CR. The nonwoven fabric layer 54 is in surface contact with the sheet S over the entire rubbing region CR at the nip portion N. The contact position of the backup roller 74 with respect to the endless belt 71 and the inclination angle of the shaft 55 of the rubbing member 51 are adjusted as appropriate so that the rubbing region CR has a semicircular shape.

  Therefore, when the sheet S is conveyed to the nip portion N, the nonwoven fabric layer 54 rubs the image layer I while rotating around the rotation center O in a state of surface contact with the sheet S in the rub area CR. FIG. 7 shows a state in which the leading end of the sheet S in the transport direction T is in surface contact with the rubbing region CR.

  In the first embodiment, the linear velocity in the tangential direction of the support member 53 rotated by the shaft 55, that is, the linear velocity LV of the nonwoven fabric layer 54 can be set larger than the conveyance velocity V of the sheet S. The diameter of the support member 53, that is, the diameter D of the nonwoven fabric layer 54 is set to be larger than the sheet width dimension W orthogonal to the sheet S conveyance direction T. Thereby, the entire image layer I is rubbed.

  According to the fixing device 50 according to the first embodiment described above, the nonwoven fabric layer 54 rubs the image layer I while rotating around the rotation center O in a state of surface contact with the sheet S in the rubbing region CR. . In addition, the linear velocity LV of the nonwoven fabric layer 54 can be set larger than the conveyance speed V of the sheet S. Therefore, as compared with a configuration using a roller that rubs the image layer I while being in line contact with the sheet S, the time during which the image layer I is rubbed by the nonwoven fabric layer 54 becomes longer. As a result, the components in the liquid developer forming the image layer I can easily enter the surface layer of the sheet S. As a result, the fixing time of the image layer I is shortened, and peeling of the image layer I is preferably suppressed, that is, the fixing strength of the image layer I is improved.

  In the first embodiment, since the nonwoven fabric layer 54 made of a nonwoven fabric is used as the rubbing surface, a configuration in which the sheet S is brought into surface contact can be easily achieved.

  Further, since the nonwoven fabric forming the nonwoven fabric layer 54 has a dynamic friction coefficient of 0.50 or less, the influence on the conveyance of the sheet S can be reduced, and damage to the image layer I due to the rubbing operation can be suppressed. be able to.

  In addition, although 1st Embodiment demonstrated about the case where the planar shape of the nonwoven fabric layer 54 was made into circular shape, the planar shape of the nonwoven fabric layer 54 is not specifically limited. The planar shape of the nonwoven fabric layer 54 may be, for example, a ring shape in which the central portion where the rubbing region CR is not set in the nonwoven fabric layer 54 is omitted.

(Second Embodiment)
FIG. 8 is a schematic diagram showing a fixing device 500 and a conveying device CV according to the second embodiment. The sheet S on which the image layer I is formed is conveyed to the fixing device 500 by the conveying device CV. The configuration of the transport device CV is as described with reference to FIG. The fixing device 500 rubs the image layer I on the sheet S to fix the image layer I. The fixing device 500 includes a rubbing member 510 disposed on the opposite side of the backup roller 74 with the endless belt 71 interposed therebetween, and a drive source 52 that drives the rubbing member 510.

  The rubbing member 510 includes a support member 53 (brush support member), a rubbing brush 60, and a shaft 55.

  The support member 53 is a member having a cylindrical shape, similar to that shown in FIGS. 5 and 6. The support member 53 includes a first support surface 53a that is an end surface facing the endless belt 71, and a second support surface 53b that is an end surface located on the opposite side of the first support surface 53a in the axial direction. The first support surface 53a and the second support surface 53b are substantially circular.

  The rubbing brush 60 rubs the image layer I on the sheet S. The rubbing brush 60 is attached so as to cover the entire first support surface 53 a (brush mounting surface) of the support member 53. The rubbing brush 60 has a circular shape in plan view. The rubbing brush 60 has a brush surface 60a facing the endless belt 71, and a large number of brush hairs 61 are implanted on the brush surface 60a. The brush bristles 61 are implanted at the periphery of the brush surface 60a. Examples of the material for the brush bristles 61 include a textile made of conductive rayon or polyester in a pile shape. When conductive rayon is used, the pile fineness is 300D / 100F, and when polyester is used, the pile fineness is 75D / 12F.

The tip of the bristle 61 of the rubbing brush 60 is in contact with the endless belt 71 while being pressed against the endless belt 71 and bent. Therefore, the rubbing brush 60 is in surface contact with the endless belt 71 in a state where a large number of the bristles 61 are bent. The bent tip of the brush bristles 61 forms a rubbing surface. The brush bristles 61 of the rubbing brush 60 are pressed against the endless belt 71 so that the surface pressure against the endless belt 71 is, for example, 0.2 g / mm ² . The brush bristles 61 are appropriately set not only with the above-mentioned pile fineness but also with a density, length, etc. so that a predetermined surface pressure can be obtained.

  The rubbing brush 60 has a rubbing region CR that rubs the image layer I while being in surface contact with the image layer I. The rubbing region CR will be described with reference to FIG. 10 in addition to FIGS. FIG. 10 is a plan view of the rubbing member 510 and the endless belt 71. The shaft 55 is fixed to the second support surface 53b of the support member 53 at a position coinciding with the central axis of the support member 53, and the drive source 52 is connected to the shaft 55, for example, a motor. Rotating the shaft 55 clockwise is the same as that described with reference to FIGS. The rubbing brush 60 has a rotation center O that coincides with the center axis of the support member 53 and the rotation axis of the shaft 55. When the shaft 55 rotates, the support member 53 rotates about the central axis, and the rubbing brush 60 attached to the first support surface 53a of the support member 53 is bent with a large number of brush bristles 61 coming into contact with the endless belt 71. Rotate around the rotation center O in a bent state.

  The rubbing area CR is an area set on the downstream side of the rotation center O of the rubbing brush 60 when viewed from the conveyance direction T of the sheet S, and has an arc shape in plan view. The bristle 61 of the rubbing brush 60 contacts the endless belt 71 only in the rubbing region CR, and forms a nip portion N with the endless belt 71 while being bent in the rubbing region CR. The brush bristles 61 of the rubbing brush 60 are in surface contact with the sheet S in a bent state over the entire rubbing region CR in the nip portion N.

  Accordingly, when the sheet S is conveyed to the nip portion N, the rubbing brush 60 rotates the image layer I with the bristles 61 while rotating around the rotation center O in a state where the bristles 61 are in surface contact with the sheet S. Rub. FIG. 10 shows a state in which the leading end portion of the sheet S in the transport direction T has entered the rubbing region CR.

  In the second embodiment, the linear velocity in the tangential direction of the support member 53 rotated by the shaft 55, that is, the linear velocity LV of the rubbing brush 60 can be set larger than the conveying velocity V of the sheet S. Further, the diameter of the support member 53, that is, the diameter D1 of the rubbing brush 60 is set larger than the sheet width dimension W orthogonal to the sheet conveying direction T. Thereby, the entire image layer I is rubbed.

  Furthermore, in the second embodiment, the contact area of the contact surface between the brush bristles 61 of the rubbing brush 60 and the image layer I, in other words, the bristles 61 of the rubbing brush 60 are in surface contact with the image layer I. The region area of the rubbing region CR that rubs the image layer I is switched between a first region area (first contact area) and a second region area (second contact area) larger than the first region area. Can do. The fixing device 500 according to the second embodiment includes a region area changing mechanism (contact area changing mechanism) 80 and a control unit U that controls the region area changing mechanism 80 in order to switch the region area of the rubbing region CR. Further included.

  The area area changing mechanism 80 will be described with reference to FIGS. 11 and 12 in addition to FIG. FIG. 11 shows a state where the region area of the rubbing region CR is switched to the first region area, and FIG. 12 shows a state where the region area of the rubbing region CR is switched to the second region area. The driving source 52 of the fixing device 500 is accommodated in the housing 83. The shaft 55 of the rubbing member 510 is connected to the drive source 52 through a hole penetrating the housing 83. The housing 83 is configured to be rotatable within a predetermined range. As the housing 83 rotates, the rubbing member 510 rotates about the drive source 52.

  The area area changing mechanism 80 includes, for example, a cam 81 and an urging member 82. The biasing member 82 is, for example, a spring member, and applies a biasing force in the direction of arrow B to the housing 83 so as to rotate the housing 83 in a predetermined direction (counterclockwise direction in FIG. 8). The cam 81 contacts the housing 83 and rotates the housing 83 clockwise in FIG. 8 against the urging force of the urging member 82.

  In the second embodiment, an imaginary line VL obtained by extending the shaft 55 of the rubbing member 510 and an imaginary plane VS obtained by extending the contact surface between the brush bristles 61 of the rubbing brush 60 and the image layer I intersect. By switching the angle α between the first angle and the second angle larger than the first angle, the region area of the rubbing region CR is switched between the first region area and the second region area. As the crossing angle α increases, the area of the rubbing region CR increases. Specifically, when the intersection angle α is switched to the first angle, the region area of the rubbing region CR is switched to the first region area, and when the intersection angle α is switched to the second angle, the rubbing region The CR area is switched to the second area. The first angle is set to 60 °, for example, and the second angle is set to 90 °, for example.

  The control unit U controls the area area changing mechanism 80 to switch the area area of the rubbing area CR between the first area area and the second area area. Next, the control operation of the area area changing mechanism 80 by the control unit U will be described. The control unit U rotates the cam 81 in a predetermined first direction when the region area of the rubbing region CR is switched from the state switched to the first region area to the second region area as shown in FIG. Thus, the urging member 82 urges the housing 83 in the direction of the arrow B to allow the housing 83 to rotate counterclockwise in FIG. As the housing 83 rotates counterclockwise, the rubbing member 510 also rotates counterclockwise about the drive source 52. At this time, the rotation range of the cam 81 and thus the rotation range of the rubbing member 510 are set so that the crossing angle α is 90 °. Thereby, the area area of the rubbing area CR is switched to the second area area larger than the first area area.

  On the other hand, when the control unit U switches the region area of the rubbing region CR from the state switched to the second region area to the first region area as shown in FIG. 12, the cam 81 is opposite to the first direction. Turn in the second direction. As a result, the cam 81 rotates against the urging force of the urging member 82, so that the housing 83 rotates clockwise. Along with this, the rubbing member 510 also rotates clockwise around the drive source 52. At this time, the rotation range of the cam 81 and thus the rotation range of the rubbing member 510 are set so that the crossing angle α is 60 °. Thereby, the area area of the rubbing area CR is switched to the first area area smaller than the second area area.

  Further, the sheet S has a first sheet S having a first thickness dimension (for example, a normal A4 size thin paper) and a second sheet S having a second thickness dimension larger than the first thickness dimension (for example, a postcard or coated paper). ), When the first sheet S is conveyed to the nip portion N, the control unit U controls the region area changing mechanism 80 to set the region area of the rubbing region CR to the first region area (that is, , The intersection angle α is switched to 60 °. On the other hand, when the second sheet S is conveyed to the nip portion N, the control unit U controls the region area changing mechanism 80 to change the region area of the rubbing region CR to the second region area (that is, the intersection angle α is 90 °). As described above, since the area of the second region is larger than the area of the first region, it takes a long time for the rubbing brush 60 to rub the image layer I in the rubbing region CR. Thus, the control unit U appropriately changes the rubbing time of the image layer I by the rubbing brush 60 according to the thickness dimension of the sheet S (the type of the sheet S).

  According to the fixing device 500 according to the second embodiment described above, the rubbing brush 60 rotates around the rotation center O while the bristles 61 are in surface contact with the sheet S in the rubbing region CR, and the image layer I is rubbed with the bristle 61. In addition, the linear velocity LV of the rubbing brush 60 can be set larger than the conveying velocity V of the sheet S. Therefore, as compared with the configuration using a roller that rubs the image layer I while making line contact with the sheet S, the time during which the image layer I is rubbed by the bristles 61 of the rubbing brush 60 becomes longer. As a result, the components in the liquid developer forming the image layer I can easily enter the surface layer of the sheet S. As a result, the fixing time of the image layer I is shortened, and peeling of the image layer I is preferably suppressed, that is, the fixing strength of the image layer I is improved.

  In the fixing device 500 according to the second embodiment, the image layer I is rubbed with the rubbing brush 60 having a large number of brush bristles 61. By appropriately adjusting the material, pile fineness, density, length, and the like of the brush bristles 61, the influence on the conveyance of the sheet S can be reduced, and image damage due to the rubbing operation can be suppressed. it can.

  Furthermore, in the fixing device 500 according to the second embodiment, the control unit U switches the area area of the rubbing area CR between the first area area and the second area area according to the thickness dimension of the sheet S. Thus, the rubbing time of the image layer I corresponding to the thickness dimension of the sheet S is appropriately changed. As a result, even if the thickness dimension of the sheet S is different, the components in the liquid developer that forms an image can easily penetrate into the surface layer of the sheet S.

  Further, in the fixing device 500 according to the second embodiment, the image layer I is rubbed using the rubbing brush 60 having the brush bristles 61. Thereby, switching between the first angle and the second angle of the crossing angle α, and thus switching between the first region area and the second region area of the area of the rubbing region CR can be easily performed.

  Next, a modification of the second embodiment will be described with reference to FIG. FIG. 13 is a plan view of the rubbing member 510 and the endless belt 71. In the modification of the second embodiment, two first rubbing members 510A and second rubbing members 510B are used. The first rubbing member 510A and the second rubbing member 510B are arranged side by side in a direction orthogonal to the conveyance direction T of the sheet S. That is, the first rubbing surface (the tip of the bristle 61A) formed by the first rubbing brush 60A of the first rubbing member 510A and the second rubbing brush 60B formed by the second rubbing member 510B. The rubbing surface (the tip of the brush bristles 61 </ b> B) is arranged side by side in a direction (width dimension direction W of the sheet S) orthogonal to the conveyance direction T of the sheet S. Thereby, even when the color image layer I in which the amount of the carrier liquid increases is fixed, the carrier liquid easily enters the surface layer of the sheet S.

  The first shaft 55A of the first rubbing member 510A is rotated in the first rotation direction R1 (the clockwise direction in FIG. 13) by the driving source 52, and the second shaft 55B of the second rubbing member 510B is driven by the driving source. 52 is rotated in the second rotation direction R2 (the counterclockwise direction in FIG. 13) opposite to the first rotation direction R1. Therefore, the first rubbing brush 60A rubs the image layer I while rotating in the first rotation direction R1, and the second rubbing brush 60B rotates the image layer I while rotating in the second rotation direction R2. Rub. Therefore, the sheet S is rubbed while being stretched. As a result, the occurrence of wrinkles on the sheet S is suppressed.

  In the modification of the second embodiment, the first rubbing member 510A and the second rubbing member 510B include the first brush bristles 61A of the first rubbing brush 60A and the second brush of the second rubbing brush 60B. The bristles 61B are arranged so as to contact each other in a direction orthogonal to the conveyance direction T of the sheet S. Therefore, a contact area OA where the first brush bristles 61A and the second brush bristles 61B are in contact with each other is formed between the first rubbing member 510A and the second rubbing member 510B. Thereby, generation | occurrence | production of the non-rubbing area | region where the image layer I is not rubbed is suppressed.

  In FIG. 13, the configuration using the two first rubbing brushes 60 </ b> A and the second rubbing brush 60 </ b> B has been described. However, instead of this configuration, two non-woven fabric layers, for example, the first non-woven fabric layer and the second non-woven fabric are used. The layers may be arranged side by side in a direction orthogonal to the conveyance direction T of the sheet S.

  Next, a modification of the first embodiment will be described with reference to FIG. In the first embodiment described with reference to FIGS. 5 to 7, the configuration in which only a part of the nonwoven fabric layer 54 is in surface contact with the endless belt 71 has been described. Alternatively, the entire nonwoven fabric layer 54 may be brought into contact with the endless belt 71 and the image layer I may be rubbed. In this case, a support plate 85 that supports the non-woven fabric layer 54 is disposed over the entire surface of the non-woven fabric layer 54 on the opposite side of the non-woven fabric layer 54 across the endless belt 71. In the case of the configuration shown in FIG. 14, the surface pressure of the nonwoven fabric layer 54 against the endless belt 71 is appropriately adjusted in order to prevent the nonwoven fabric layer 54 from rubbing the image layer I too much. In the modification shown in FIG. 14, a rubbing brush 60 may be used instead of the nonwoven fabric layer 54. In that case, all of the brushes of the rubbing brush 60 come into contact with the endless belt 71.

<Application to image forming apparatus>
FIG. 15 is a schematic configuration diagram of a color printer equipped with the fixing device 300 described in relation to the first embodiment. FIG. 16 is a schematic sectional view of the color printer excluding the portion of the circulation device. FIG. 17 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 the present embodiment, the color printer is equipped with the fixing device 50 described in relation to the first embodiment. Alternatively, the fixing device 500 described in connection with the second embodiment may be installed in a color printer. The color printer will be described with reference to FIGS. 1 and 15 to 17.

  As shown in FIG. 15, the color printer 1 includes an upper main body 1A that stores various units and parts for image formation, and a lower portion of the upper main body 1A, and a circulation device LY for each color. 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. 16, the upper main body 1 </ b> A is formed of a tandem 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 on the electrostatic latent image. 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. 17, 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. 16, 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. Accordingly, the fixing unit 5 includes the fixing device 50 described in relation to the first embodiment and the belt unit CV. As described above, the fixing process is suitably performed by rubbing the nonwoven fabric layer 54 against the image on the sheet S. In addition, since the nonwoven fabric layer 54 has a width sufficient to rub the entire image, the gloss of the image is uniformly changed by contact with the nonwoven fabric layer 54. 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. 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.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 50,500 Fixing apparatus 51,510 Sliding member 52 Driving source 53 Support member 54 Nonwoven fabric layer (rubbing surface)
55 Shaft 60 Rub brush 61 Brush bristles 71 Endless belt 80 Area change mechanism (contact area change mechanism)
CR Rubbing area CV Conveying device I Image layer N Nip part LV Nonlinear layer linear velocity O Rotation center S Sheet T Sheet conveying direction V Sheet conveying speed

Claims (6)

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 having a plurality of brush bristles, including a rubbing brush that rubs the image with the bristles, and rubbing the image on the sheet to fix the image;
A contact area changing mechanism for changing a contact area of a contact surface between the rubbing brush and the image;
A control unit for controlling the contact area changing mechanism;
With
The fixing device includes:
A rubbing surface having a center of rotation and rubbing the image while rotating around the center of rotation in surface contact with the sheet;
A drive source for rotating the rubbing surface about the rotation center;
Including
The rubbing surface is formed by tips of the numerous brush hairs,
The contact area changing mechanism switches the contact area between a first contact area and a second contact area larger than the first contact area,
The sheet includes a first sheet having a first thickness dimension, and a second sheet having a second thickness dimension larger than the first thickness dimension,
The control unit controls the contact area changing mechanism to switch the contact area to the first contact area when the first sheet is conveyed, and changes the contact area when the second sheet is conveyed. An image forming apparatus that controls a mechanism to switch the contact area to the second contact area. The image forming apparatus according to claim 1.
The transport element transports the sheet at a predetermined transport speed;
The drive source rotates the rubbing surface so that the rubbing surface has a predetermined linear velocity in the tangential direction,
The image forming apparatus in which the linear velocity is set to be larger than the conveyance speed. The image forming apparatus according to claim 1, wherein
The liquid developer includes a carrier liquid,
The image is a color image;
The image forming apparatus includes a first rubbing surface and a second rubbing surface arranged in a direction orthogonal to the sheet conveying direction. The image forming apparatus according to claim 3.
The drive source rotates the first rubbing surface in a first rotation direction, and rotates the second rubbing surface in a second rotation direction opposite to the first rotation direction. The image forming apparatus according to claim 1.
The fixing device further includes:
A brush support member having a brush mounting surface to which the rubbing brush is mounted;
A shaft having one end connected to the drive source and the other end connected to the brush support member, and extending in a direction perpendicular to the brush mounting surface and rotated by the drive source. ,
The contact area changing mechanism may switch an intersection angle between a virtual line extending the shaft and a virtual surface extending the contact surface between a first angle and a second angle larger than the first angle. The contact area is switched to the first angle by switching the intersection angle to the first angle, and the contact area is changed to the second angle by switching the intersection angle to the second angle. Switch to 2 contact area,
The controller controls the contact area changing mechanism when the first sheet has been conveyed to switch the crossing angle to the first angle, and when the second sheet has been conveyed, the contact area. An image forming apparatus that controls a change mechanism to switch the crossing angle to the second angle. The image forming apparatus according to claim 3 or 4, wherein:
The fixing device includes a first rubbing brush and a second rubbing brush that rub the image with the brush bristles,
The first rubbing surface is formed by tips of the plurality of brush bristles of the first rubbing brush,
The second rubbing surface is formed by tips of the plurality of brush bristles of the second rubbing brush,
The image forming apparatus, wherein the bristles of the first rubbing brush and the bristles of the second rubbing brush are arranged to contact each other in the orthogonal direction.