JP6149547B2 - Wet image forming device - Google Patents

Description

  The present invention relates to a solvent removal apparatus and a wet image forming apparatus, and in particular, a solvent removal apparatus that volatilizes a carrier liquid contained in a toner image transferred onto a recording surface of a recording medium to remove it from the recording medium, and such a solvent. The present invention relates to a wet image forming apparatus including a removing device.

  As disclosed in Japanese Unexamined Patent Publication No. 2000-284603 (Patent Document 1), a wet image forming apparatus that forms an image using a liquid developer has been recently developed. Since the wet image forming apparatus can reproduce the details of an image using toner particles having a small particle size, application to fields such as commercial printing is expected.

  In the image forming process of the wet image forming apparatus, a liquid developer containing a carrier liquid and toner particles is used. The electrostatic latent image on the photoreceptor is developed by the liquid developer, and a toner image is formed on the photoreceptor. After the toner image is transferred onto the recording medium, the toner image is fixed on the recording medium as an output image by being pressed by a fixing unit.

  The carrier liquid remains in the toner image before being pressed by the fixing unit. If the remaining amount of the carrier liquid is large, the toner image is likely to be squeezed when the toner image is pressurized with a fixing roller or the like. Generally, a non-contact heater is installed upstream of the fixing roller. By volatilizing excess carrier liquid before the toner image is pressed by the fixing unit, the amount of carrier liquid in the toner image is reduced. It is possible to suppress the flow of the carrier liquid and the toner, and as a result, it is possible to suppress the toner image from being disturbed.

  There are carrier liquids having high volatility and those having low volatility. In recent years, use of a low-volatile carrier liquid has been studied. When a low volatile carrier liquid is used, the carrier liquid is less likely to volatilize during the image forming process. Fluctuations in the concentration of toner particles (solid component) in the liquid developer can be suppressed, and the quality of the output image can be improved. Using a low-volatile carrier liquid can also contribute to a reduction in the discharge amount of carrier liquid vapor generated by volatilization.

JP 2000-284603 A

  It may be difficult to properly remove the carrier liquid from the toner image before the recording medium enters the fixing unit. As described above, if the residual amount of the carrier liquid contained in the toner image on the recording medium is larger than necessary, the toner image is easily squeezed when the toner image is pressed by a fixing roller or the like, and the toner image after fixing is fixed. Disturbance may occur.

The present invention, wet image formation recording medium is provided with the amounts can be increased in comparison with the conventional solvent removal equipment of the carrier liquid to be removed from the toner image on the recording medium before entering the fixing unit An object is to provide an apparatus.

The wet image forming apparatus according to the present invention includes an image forming unit that forms a toner image on a recording surface of a recording medium using a liquid developer, a fixing unit that fixes the toner image on the recording medium, and the recording medium. provided with a position between said image forming portion and the fixing portion of the transport path, and the carrier liquid is volatilized contained has been the toner image transferred on the recording surface of the recording medium is removed from the recording medium A solvent removing device, and the solvent removing device is opposed to the heating unit that heats the recording medium conveyed along the conveying path, and the toner image transferred to the recording surface with a space therebetween. A solvent recovery mechanism that has a surface portion whose temperature is lower than the surface temperature of the recording surface of the recording medium, and the surface portion moves in the vicinity of the toner image transferred to the recording surface. including, above Medium recovery mechanism, the carrier liquid vapor volatilized by heating in the heating unit is brought into contact with the surface portion, to recover the carrier liquid condensed on said surface portion.

  Preferably, the apparatus further includes a cooling unit that cools the surface portion and sets the temperature of the surface portion to a value lower than the surface temperature of the recording surface of the recording medium. Preferably, when the distance between the recording surface and the surface portion is L (mm), the condition of 0 <L ≦ 2.0 is satisfied.

  Preferably, when the interval between the recording surface and the surface portion is L (mm), the average molecular weight of the carrier liquid is M, and the surface temperature of the recording surface is Tm (° C.), 0.1 < The condition of L <2 × (Tm−20) × exp (−0.02 × M) is satisfied.

  Preferably, the solvent recovery mechanism includes an endless belt, and a surface of the endless belt constitutes the surface portion.

Preferably, the heating unit is disposed so as to face the surface portion.
Preferably, the solvent recovery mechanism further includes a recovery unit that removes and recovers the carrier liquid condensed on the surface part from the surface part.

  Preferably, the cooling portion includes a fan that cools the surface portion without contacting the surface portion, and / or a cooling member that contacts the surface portion and cools the surface portion while rotating as the surface portion moves. .

  Preferably, the solvent recovery mechanism further includes a vibration suppressing member disposed so as to contact the surface portion, and the vibration suppressing member rotates in accordance with the movement of the surface portion, and the surface portion moves. The surface portion is prevented from vibrating when it is moving.

According to the present invention, wet the recording medium with the amount of can be increased in comparison with the conventional solvent removal equipment of the carrier liquid to be removed from the toner image on the recording medium before entering the fixing unit An image forming apparatus can be obtained.

It is a figure which shows the wet image forming apparatus in embodiment. It is a figure which shows the image formation part with which the wet image forming apparatus in embodiment is equipped. 1 is a diagram illustrating a solvent removal device and a fixing unit provided in a wet image forming apparatus according to an embodiment. FIG. 3 is a diagram schematically illustrating a state in which a carrier liquid contained in a toner image is volatilized. It is a figure which expands and shows the vicinity of the endless belt (surface part) with which the wet image forming apparatus in embodiment is equipped. It is a figure which shows the solvent removal apparatus in the 1st modification of embodiment. It is a figure which shows the solvent removal apparatus in the 2nd modification of embodiment. It is a figure which shows the experimental conditions of experiment example S1-S3, T1, T2, E1-E5. It is a figure which shows the experimental result of experiment example S1-S3. It is a figure which shows the experimental result of experiment example T1, T2. It is a figure showing the relation between the experimental result of interval L, and the calculation result of interval L. It is a figure which shows the experimental result of Experimental example Q1-Q3. It is a figure which shows the experimental result of Experimental example R1, R2. It is a figure which shows the experimental conditions and experimental result of Experimental example A1, A2, A3, B1, B2, B3, B4.

  Embodiments based on the present invention will be described below with reference to the drawings. In the description of the embodiments, when the number and amount are referred to, the scope of the present invention is not necessarily limited to the number and amount unless otherwise specified. In the description of the embodiments, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

[Embodiment]
(Wet image forming apparatus 100)
FIG. 1 is a diagram showing a wet image forming apparatus 100 in the present embodiment. The wet image forming apparatus 100 includes an image forming unit 10, a solvent removing device 20, and a fixing unit 60. The solvent removal device 20 includes a heating unit 30, a solvent recovery mechanism 40, and a cooling unit 50. The image forming unit 10, the solvent removing device 20, and the fixing unit 60 are accommodated in a housing (not shown).

  The image forming unit 10 is supplied with a recording medium 90 from a device (not shown) (see arrow AR90). As the recording medium 90, for example, plain paper, a resinous film made of PET or the like, or glossy paper having a coated recording surface is used. As the recording medium 90, a long continuous paper may be used, or a sheet may be used. The image forming unit 10 forms a toner image 92 on the recording surface 91 of the recording medium 90. Thereafter, the recording medium 90 is conveyed toward the solvent removal apparatus 20 along the conveyance path.

  When the recording medium 90 passes through the solvent removing device 20, a part of the carrier liquid contained in the toner image 92 is volatilized and removed from the recording medium 90. Thereafter, the recording medium 90 is further transported toward the fixing unit 60 along the transport path. The fixing unit 60 heats and pressurizes the toner image 92 on the recording medium 90 to fix the toner image 92 on the recording medium 90. The recording medium 90 that has passed through the fixing unit 60 is sent to a paper discharge unit (not shown) (see arrow AR90). As described above, the recording medium 90 having the output image formed on the recording surface 91 can be obtained. The details of each of these components will be described below.

(Image forming unit 10)
FIG. 2 is a diagram illustrating the image forming unit 10. The image forming unit 10 includes a photosensitive drum 11, an intermediate transfer roller 12, a cleaning device 13, a charging device 14, an exposure device 15, a liquid developing device 16, a secondary transfer roller 17, and a cleaning device 18. The photosensitive drum 11 rotates in the direction of the arrow AR11. The intermediate transfer roller 12, the cleaning device 13, the charging device 14, the exposure device 15, and the liquid developing device 16 are arranged around the photosensitive drum 11 in this order along the rotation direction of the photosensitive drum 11.

  The charging device 14 charges the surface of the photosensitive drum 11 to a predetermined potential. The exposure device 15 irradiates the surface of the photosensitive drum 11 with light based on predetermined image information. The surface of the photosensitive drum 11 is exposed by light from the exposure device 15. An electrostatic latent image is formed on the surface of the photosensitive drum 11.

  The liquid developing device 16 includes a liquid developer (not shown). The liquid developer has a carrier liquid and toner particles. The liquid developer is conveyed onto the surface of the photosensitive drum 11. The carrier liquid and toner particles are electrostatically adsorbed on the surface of the photosensitive drum 11. By developing the electrostatic latent image carried on the photosensitive drum 11, a toner image (not shown) corresponding to the shape of the electrostatic latent image is formed on the surface of the photosensitive drum 11.

  The intermediate transfer roller 12 rotates in the direction of the arrow AR12 while being in contact with the photosensitive drum 11. In the nip portion between the photosensitive drum 11 and the intermediate transfer roller 12, the toner image on the photosensitive drum 11 is transferred from the photosensitive drum 11 onto the surface of the intermediate transfer roller 12. The carrier liquid and toner particles remaining on the photosensitive drum 11 without being transferred are removed from the surface of the photosensitive drum 11 by the cleaning device 13.

  The secondary transfer roller 17 is disposed so as to face the intermediate transfer roller 12, and rotates in the direction of the arrow AR17. The recording medium 90 passes between the secondary transfer roller 17 and the intermediate transfer roller 12 (see arrow AR90). In the nip portion between the secondary transfer roller 17 and the intermediate transfer roller 12, the toner image is transferred from the intermediate transfer roller 12 onto the recording surface 91 of the recording medium 90. A toner image 92 is formed on the recording surface 91 of the recording medium 90.

  The carrier liquid and toner particles remaining on the intermediate transfer roller 12 without being transferred are removed from the surface of the intermediate transfer roller 12 by the cleaning device 18. The recording medium 90 on which the toner image 92 is formed is transported toward the solvent recovery mechanism 40 (see FIG. 1) by a transport device (not shown).

  The image forming unit 10 of the wet image forming apparatus 100 shown in FIGS. 1 and 2 includes a single liquid developing device 16. The wet image forming apparatus 100 may include a plurality of liquid developing devices 16 in order to form a color image. The number of installed liquid developing devices 16 is determined according to the color developing method required for the wet image forming apparatus 100. The intermediate transfer roller 12 is not an essential component and is used as necessary.

(Liquid developer)
The liquid developer used in this embodiment contains a carrier liquid that is a solvent and colored toner particles. A dispersant, a charge control agent, and the like may be added to the liquid developer. As the carrier liquid, a non-volatile solvent that has insulating properties and does not volatilize at room temperature is used. As the non-volatile solvent, for example, silicon oil, mineral oil, or paraffin oil can be used.

  The toner particles are composed of a resin and a pigment or dye for coloring. The resin has a function of uniformly dispersing the pigment or dye in the resin and a function as a binder when the toner particles are fixed to the recording medium 90. As the resin, a thermoplastic resin such as polystyrene resin, styrene-acrylic resin, acrylic resin, polyester resin, epoxy resin, polyamide resin, polyimide resin, or polyurethane resin can be used. As the resin used for the toner particles, a plurality of resins selected from these may be used in a mixed state.

  As the pigment or dye used for coloring the toner, commercially available ones can be used. As the pigment, carbon black, bengara, titanium oxide, silica, phthalocyanine blue, phthalocyanine green, sky blue, benzidine yellow, lake red D, or the like can be used. As the dye, Solvent Red 27, Acid Blue 9 or the like can be used.

  As a method for preparing the liquid developer, a commonly used one can be used. For example, the resin and the pigment are melted and kneaded at a predetermined blending ratio using a pressure kneader or a roll mill. A dispersion obtained by uniformly dispersing the resin and the pigment is finely pulverized by a jet mill or the like. Fine powder obtained by fine pulverization is classified by an air classifier or the like. A colored toner having a predetermined particle size is obtained. The obtained colored toner and an insulating liquid as a carrier liquid are mixed at a predetermined blending ratio. This mixture is uniformly dispersed by a dispersing means such as a ball mill. By the above method, a liquid developer is obtained.

  The volume average particle diameter of the toner particles in the liquid developer is preferably 0.1 μm or more and 5 μm or less. When the volume average particle diameter of the toner particles in the liquid developer is 0.1 μm or more, the toner particles easily develop the electrostatic latent image. When the volume average particle diameter of the toner particles in the liquid developer is 5 μm or less, the quality of the toner image formed from the toner particles is improved.

  The ratio of the mass of the toner particles to the mass of the liquid developer is preferably 10% or more and 50% or less. When the ratio of the mass of the toner particles to the mass of the liquid developer is 10% or more, the toner particles are less likely to settle, and the stability over time when the liquid developer is stored for a long time is improved. When the ratio of the mass of the toner particles to the mass of the liquid developer is 10% or more, it is not necessary to supply a large amount of the liquid developer in order to obtain a desired image density. Since the amount of the carrier liquid supplied onto the recording medium 90 does not increase, it is not necessary to dry much carrier liquid when fixing the toner image 92. When the carrier liquid is dried, a large amount of vapor is not generated from the carrier liquid, which is preferable.

  When the ratio of the mass of the toner particles to the mass of the liquid developer is 50% or less, the viscosity of the liquid developer becomes an appropriate value, which is convenient in manufacturing and handling. The viscosity of the liquid developer is preferably 0.1 mPa · s or more and 10,000 mPa · s or less at 25 ° C. When the viscosity of the liquid developer is 10,000 mPa · s or less, it becomes easy to handle the liquid developer when the liquid developer is stirred or the liquid developer is fed, and a uniform liquid developer is obtained. The burden on each device is reduced.

(Solvent removal device 20)
FIG. 3 is a diagram illustrating the solvent removal device 20 and the fixing unit 60. The solvent removal apparatus 20 includes a heating unit 30, a solvent recovery mechanism 40, a cooling unit 50, and transport rollers 71 and 72. The conveyance rollers 71 and 72 are members that form a conveyance path of the recording medium 90 and are arranged so that their rotation axes are parallel to each other. In the conveyance direction of the recording medium 90, the conveyance roller 71 is located on the upstream side, and the conveyance roller 72 is located on the downstream side. A conveyance belt (not shown) or the like is provided between the conveyance rollers 71 and 72.

(Heating unit 30)
The heating unit 30 includes non-contact heaters 31 and 32 and a heat insulating cover 33. The non-contact heaters 31 and 32 are provided between the transport roller 71 and the transport roller 72 and are disposed so as to face the transport path of the recording medium 90. The heat insulating cover 33 is disposed on the side opposite to the side where the conveyance path is located when viewed from the non-contact heaters 31 and 32. As the heat insulation cover 33, a member having high heat insulation and high heat resistance such as ceramic fiber may be used.

  When the recording medium 90 passes between the transport rollers 71 and 72, the non-contact heaters 31 and 32 heat these without contacting the recording medium 90 and the toner image 92 (see FIG. 1). The non-contact heaters 31 and 32 heat these from the side opposite to the recording surface 91 (surface on which the toner image 92 is formed) of the recording medium 90. A part of the carrier liquid contained in the toner image on the recording surface 91 is volatilized by the heating (heat radiation) of the heating unit 30.

  As the non-contact heaters 31 and 32, in consideration of the difference in light absorption between black toner and yellow, magenta, cyan, and non-image portions, it is preferable to use a heater that can radiate long wavelength heat such as a ceramic heater. . The surface temperatures of the non-contact heaters 31 and 32 are set to desired values (for example, about 300 ° C. to about 700 ° C.) by control means (not shown).

(Solvent recovery mechanism 40)
The solvent recovery mechanism 40 includes an endless belt 41, support rollers 42 to 45, presser rollers 46 and 47, and a recovery unit 48. The support rollers 42 to 45 are arranged so that their rotation axes are parallel to each other, and the endless belt 41 is wound around these. The endless belt 41 is a member manufactured using, for example, a metallic thin plate.

  Preferably, as the endless belt 41, a Ni belt having a thickness of 50 μm is used. The Ni belt has a high thermal conductivity. When a Ni belt is used, the temperature control is facilitated, and since the emissivity is low, it is possible to suppress the temperature rise of the belt at the portion facing the heating unit 30.

  The support rollers 42 to 45 are rotationally driven by a motor (not shown). Endless belt 41 rotates in the direction of arrow DR1. As the endless belt 41 rotates, the surface 41S of the endless belt 41 moves around. Of the surface 41 </ b> S of the endless belt 41, a portion (surface portion 41 </ b> P) located between the support roller 43 and the support roller 44 faces the recording medium 90.

  More specifically, the surface 41S of the endless belt 41 faces the recording medium 90 when passing through a portion that functions as the surface portion 41P. A surface 41S (hereinafter simply referred to as a surface portion 41P) when passing through a portion functioning as the surface portion 41P is opposed to the recording medium 90 when the recording medium 90 is heated by the heating unit 30, and this recording is performed. It is configured to move substantially parallel to the medium 90.

  Here, the case of being substantially parallel includes the case where the surface portion 41P is parallel to the recording medium 90 and the case where the surface portion 41P is substantially parallel to the recording medium 90. The phrase “substantially parallel” includes a case where the surface portion 41P moves from a state parallel to the recording medium 90 in a state of being shifted within a range of, for example, greater than 0 ° and ± 5 ° or less. Preferably, the surface portion 41P is configured to move within an angle range of −3 ° to 3 ° with respect to the recording medium 90. More preferably, the surface portion 41P is configured to move with respect to the recording medium 90 in an angle range of −1 ° to 1 °. Optimally, the surface portion 41P is configured to move parallel to the recording medium 90.

  The non-contact heaters 31 and 32 in the present embodiment are arranged to face the surface portion 41P of the endless belt 41. The surface portion 41P moves in the same direction as the conveyance direction of the recording medium 90. The presser rollers 46 and 47 (vibration suppressing members) are disposed on the back surface side of the front surface portion 41P (on the side opposite to the side where the transport path is located when viewed from the endless belt 41). The presser rollers 46 and 47 rotate in accordance with the movement of the endless belt 41 while contacting the endless belt 41. The presser rollers 46 and 47 suppress the vibration of the endless belt 41 (surface portion 41P) and guide the circumferential movement of the endless belt 41 so that the surface portion 41P can move in parallel to the recording medium 90.

  The surface portion 41P moves in the state of being close to the toner image transferred to the recording surface 91 of the recording medium 90. The movement in the close state means that the surface portion 41P passes through the carrier liquid vapor layer (particularly, the high-concentration vapor layer of the carrier liquid vapor layer) formed near the surface of the toner image. It means moving in an approaching state. The high concentration vapor layer is a layer formed by carrier liquid vapor having a concentration corresponding to the saturated vapor pressure of the carrier liquid at the temperature of the recording medium 90 or a vapor pressure close thereto. The distance from the surface of the recording medium 90 decreases, but the surface temperature 41G of the endless belt 41 passes through the surface temperature 41P of the endless belt 41. Is also expensive. When the surface portion 41P of the endless belt 41 passes through the high-concentration vapor layer, the endless belt 41 can effectively attach the carrier liquid vapor to the surface portion 41P (details will be described later).

  Since the endless belt 41 only needs to have a function of carrying a predetermined amount of heat (amount of heat for condensation) to a portion of the recording medium 90 facing the toner image, the endless belt 41 is different from the direction of the arrow DR1. It may be configured to rotate in the reverse direction. From the viewpoint of quickly carrying the necessary amount of heat and increasing the amount of condensation, it is preferable that the peripheral speed of the endless belt 41 (moving speed of the surface portion 41P) is high.

  The solvent recovery mechanism 40 of the present embodiment includes an endless belt 41, but may include the following members instead of the endless belt 41. That is, the solvent recovery mechanism 40 includes two rollers, the belt is wound around one roller, the belt is sequentially sent from the roller toward the other roller, and the belt is wound around the other roller. You may have the structure. In this case, a portion of the surface of the belt that faces the toner image 92 transferred to the recording surface 91 with a gap functions as a surface portion.

  The collection unit 48 is provided so as to face a portion of the endless belt 41 located between the support roller 44 and the support roller 45. In the rotational direction of the endless belt 41, the collection unit 48 is located on the downstream side of the surface part 41 </ b> P and on the upstream side of the cooling unit 50. The collection unit 48 includes a blade 48a and a collection tank 48b. The blade 48a is disposed so as to contact the surface 41S of the endless belt 41.

(Cooling unit 50)
The cooling unit 50 cools the endless belt 41 without contacting it. Specifically, the cooling unit 50 is provided so as to face a portion of the endless belt 41 located between the support roller 45 and the support roller 42. In the rotational direction of the endless belt 41, the cooling unit 50 is located downstream of the collection unit 48 and upstream of the surface unit 41P.

  The cooling unit 50 includes a fan 51 and a cover 52. The surface 41S of the endless belt 41 is sufficiently cooled by the blown air (cold air) from the fan 51. For example, the cooling unit 50 cools the endless belt 41 so that the temperature of the surface 41S of the endless belt 41 after passing through the cooling unit 50 is lower than the surface temperature of the recording surface 91 of the recording medium 90. By cooling the surface 41S of the endless belt 41, the condensation efficiency of the carrier liquid vapor can be increased.

(Fixing unit 60)
The fixing unit 60 heats the toner image transferred onto the recording medium 90 and fixes the toner image 92 onto the recording medium 90. The fixing unit 60 includes a fixing roller 61, a pressure roller 62, heater lamps 63 and 64, and cases 65 and 66.

  The fixing roller 61 and the pressure roller 62 are located downstream of the solvent removing device 20 in the conveyance direction of the recording medium 90. The fixing roller 61 and the pressure roller 62 are disposed inside the cases 65 and 66, respectively. The fixing roller 61 and the pressure roller 62 include a metal core, a silicon rubber layer provided on the outer periphery of the core, and a fluororesin release layer provided on the outer periphery of the silicon rubber layer, respectively. Including.

  The metal core is composed of a member having high thermal conductivity such as aluminum. The silicon rubber layer is provided as an elastic layer in order to ensure the pressure nip width. The release layer made of a fluororesin is provided in order to improve the release property on the roller surface. The thickness of the release layer made of fluororesin is, for example, 10 μm to 50 μm, and the material thereof is, for example, PTFE (polytetrafluoroethylene) or PFA (perfluoroalkoxy polymer).

  The fixing roller 61 and the pressure roller 62 are arranged so that their rotation axes are parallel to each other. Bearing members (not shown) are provided at both axial ends of the fixing roller 61 and the pressure roller 62. The fixing roller 61 and the pressure roller 62 are rotatably supported by these bearing members.

  The pressure roller 62 is further provided with a pressure mechanism (not shown) using a spring or the like. The pressure roller 62 is urged in the direction in which the fixing roller 61 is provided so as to come into pressure contact with the fixing roller 61 with a predetermined force. A pressure nip portion is formed between the fixing roller 61 and the pressure roller 62.

  The pressure roller 62 is rotationally driven at a predetermined peripheral speed by a drive mechanism (not shown). The fixing roller 61 is driven to rotate by receiving the pressure frictional force from the pressure roller 62. The fixing roller 61 may be driven to rotate, and the pressure roller 62 may be driven to rotate. The fixing roller 61 and the pressure roller 62 each include a heater lamp 63 and a heater lamp 64. The surface temperature of each of the fixing roller 61 and the pressure roller 62 is controlled to a desired temperature by a control unit (not shown).

(Operation of Wet Image Forming Apparatus 100)
The image forming unit 10 (FIGS. 1 and 2) forms a toner image 92 on the recording surface 91 of the recording medium 90. The heating unit 30 of the solvent removing device 20 heats the toner image 92 transferred onto the recording surface 91. Part of the carrier liquid contained in the toner image 92 is volatilized by the heating of the heating unit 30.

  FIG. 4 is a diagram schematically showing how the carrier liquid contained in the toner image 92 is volatilized. For convenience, FIG. 4 shows a state when the solvent recovery mechanism 40 is not used. As the carrier liquid volatilizes, carrier liquid vapor is generated around the toner image 92. When attention is paid to the vicinity of the surface of the toner image 92, a high-concentration carrier vapor layer 93 (high-concentration vapor layer) is formed in the vicinity of the surface. In particular, when a low-volatile carrier liquid is used, the concentration of the carrier liquid vapor near the gas-liquid interface is higher than the concentration of the carrier liquid vapor located in the vicinity thereof.

  When the toner image 92 on the recording surface 91 is heated in this state, a large temperature gradient is formed between the surface of the toner image 92 and the atmosphere, so that a carrier vapor layer 93 having a higher concentration is formed. The high-concentration carrier vapor layer 93 is formed so as to cover the periphery of the toner image 92. In a state in which the high-concentration carrier vapor layer 93 is formed so as to cover the periphery of the toner image 92, the toner on the recording surface 91 is caused by the presence of the high-concentration carrier vapor layer 93 even if the toner image 92 is further heated. The carrier liquid remaining in the image 92 is difficult to volatilize.

  With reference to FIG. 5, in the present embodiment, surface portion 41 </ b> P of endless belt 41 moves in a state of being close to toner image 92 transferred to recording surface 91 of recording medium 90. The surface portion 41P is not in contact with the recording surface 91 and the toner image 92 and is close to the toner image 92 to the extent that it passes through the high-concentration carrier vapor layer 93 formed in the vicinity of the surface of the toner image 92. Move with. If the distance between the surface portion 41P of the endless belt 41 and the recording surface 91 of the recording medium 90 is L, the distance L (mm) may satisfy the condition of 0 <L ≦ 2.0, for example. .

  The carrier liquid vapor generated between the surface portion 41P of the endless belt 41 and the surface of the toner image 92 is rapidly cooled by contacting the surface portion 41P of the endless belt 41. The carrier liquid vapor is condensed by the contact with the surface portion 41P, and the carrier liquid vapor adheres to the surface 41S of the endless belt 41 as a liquefied carrier liquid.

  The carrier liquid vapor condensed in contact with the surface portion 41P of the endless belt 41 becomes a carrier liquid (condensed liquid) and is conveyed toward the collection unit 48 in a state of adhering to the surface 41S of the endless belt 41. The carrier liquid is scraped off from the surface 41S by the blade 48a and collected in the collection tank 48b. The carrier liquid vapor that has not been condensed and recovered by the solvent recovery mechanism 40 is sucked through an exhaust duct (not shown) and then sent to the condenser, where it is liquefied and recovered by the condenser.

  It is assumed that the wet image forming apparatus 100 is not provided with the solvent recovery mechanism 40 and the cooling unit 50, and the carrier liquid is removed from the toner image 92 using only the heating unit 30. When plain paper is used as the recording medium 90, the carrier liquid in the toner image 92 on the recording surface 91 penetrates into the paper, so that the amount of carrier liquid remaining in the toner image 92 on the recording surface 91 is small. . Therefore, when plain paper is used as the recording medium 90, the carrier liquid can be easily removed from the toner image 92 on the recording surface 91 by heating by the heating unit 30 (non-contact heater).

  On the other hand, as the recording medium 90, a resinous film made of PET or the like, or glossy paper having a coated recording surface may be used. In this case, since the recording surface 91 of the recording medium 90 has non-penetrability, the carrier liquid in the toner image 92 on the recording surface 91 hardly penetrates into the recording medium 90. Most of the carrier liquid remains in the toner image 92 on the recording surface 91, and it is not easy to volatilize them. In particular, when a low-volatile carrier liquid is used, it is not easier to volatilize the carrier liquid in the toner image 92.

  In order to promote the volatilization of the carrier liquid, it is conceivable to raise the heating temperature by a non-contact heater or to blow hot air using a hot air device or the like. However, when plain paper is used as the recording medium 90, the moisture in the paper evaporates when subjected to high temperature heat, and deformation due to shrinkage tends to occur. When a film or the like is used as the recording medium 90, the recording medium 90 is likely to be deformed by the influence of heat when it receives high-temperature heat. When these deformations occur, a paper passing defect may occur or the fixing position accuracy of the image may decrease.

  In order to promote the volatilization of the carrier liquid, it is conceivable to use fresh hot air. However, although it is possible to promote the volatilization of the carrier liquid on the upstream side (portion where direct wind is blown) in the hot air blowing direction, the carrier liquid vapor transported from the upstream tends to accumulate in the downstream portion. In the downstream atmosphere, the concentration of the carrier liquid vapor is unlikely to decrease, and it is difficult to obtain sufficient volatilization of the carrier liquid on the downstream side.

  Furthermore, the carrier liquid vapor liquefies as the temperature decreases. When volatilization of the carrier liquid is promoted using hot air, etc., the carrier liquid vapor reaches the wall surface of the housing constituting the wet image forming apparatus, and the carrier liquid vapor recondenses on the wall surface and adheres to the wall surface. It can happen. Therefore, since it is necessary to design the apparatus with sufficient consideration of the direction of ventilation, it is not easy to promote volatilization of the carrier liquid using hot air or the like.

  In addition to using hot air or the like, a method called squeeze is also conceivable. The carrier liquid contained in the toner image on the recording surface is collected by bringing a squeeze member into contact with the toner image. However, in this method, since the squeeze member contacts the toner image before fixing, the toner may adhere to the squeeze member or the toner image may be disturbed by the squeeze member.

  With respect to these concerns, in the wet image forming apparatus 100 of the present embodiment, the surface portion 41P of the endless belt 41 moves in the state of being close to the toner image 92 transferred to the recording surface 91 of the recording medium 90. The surface portion 41P is not in contact with the recording surface 91 and the toner image 92 and is close to the toner image 92 to the extent that it passes through the high-concentration carrier vapor layer 93 formed in the vicinity of the surface of the toner image 92. Move with.

  The carrier liquid vapor generated between the surface portion 41P of the endless belt 41 and the surface of the toner image 92 is rapidly cooled by contacting the surface portion 41P of the endless belt 41. The carrier liquid vapor is condensed by the contact with the surface portion 41P, and the carrier liquid vapor adheres to the surface 41S of the endless belt 41 as a liquefied carrier liquid.

  Even when the high-concentration carrier vapor layer 93 is formed so as to cover the periphery of the toner image 92, the carrier liquid vapor is condensed by contact with the surface portion 41P. Since the high-concentration carrier vapor layer 93 generated from the toner image 92 on the recording medium 90 is removed one after another by the surface portion 41P of the endless belt 41, the toner on the recording surface 91 is continuously heated. The carrier liquid remaining in the image 92 can be continuously volatilized.

  Therefore, according to the solvent removal apparatus 20 of the present embodiment, the toner can be obtained without applying a heat amount that would deform the recording medium 90 to the recording medium 90 or bringing a squeeze member or the like into contact with the toner image. The surface portion 41P of the endless belt 41 that moves in the state of being close to the image 92 can effectively increase the amount of carrier liquid removed from the toner image. Since strong hot air is not blown onto the toner image 92, the carrier liquid is also prevented from scattering up to the wall surface of the casing constituting the wet image forming apparatus, and the carrier liquid is recondensed on the wall surface and adheres thereto. There is almost no end to it.

  In order for the solvent recovery mechanism 40 to condense the carrier liquid vapor more effectively, the circumference of the endless belt 41 is lengthened, and the area where the carrier liquid vapor can contact the endless belt 41 (that is, the endless belt 41 of the endless belt 41). It is preferable to increase the area in which the carrier liquid vapor can be condensed. In addition, it is also effective to increase the circumferential speed of the endless belt 41. A member for guiding both ends in the width direction of the recording medium 90 is separately provided so that the recording medium 90 can be transported between the transport rollers 71 and 72 when the recording medium 90 is heated by the heating unit 30. May be.

  In the present embodiment, a collection unit 48 that removes the carrier liquid adhering to the surface 41S of the endless belt 41 is used. Instead of using the collection part 48, the endless belt 41 (part constituting the surface part) may be formed of a member capable of adsorbing the carrier liquid liquefied by condensation on the surface part. For example, when the endless belt 41 includes silicon rubber or the like as a material thereof, the carrier liquid attached to the surface portion (surface 41S) is adsorbed on the surface of the endless belt 41. Also with this configuration, the same operations and effects as described above can be obtained. In addition to the configuration using the collection unit 48, this configuration may be further employed.

[First Modification]
FIG. 6 is a diagram illustrating a solvent removal device 20A according to a first modification of the embodiment. In the solvent removal apparatus 20A, a cooling unit 50A (cooling member) is used instead of the cooling unit 50 (see FIG. 3). The cooling unit 50 </ b> A has a hollow roller shape and is disposed so as to contact the surface 41 </ b> S of the endless belt 41. In the rotational direction of the endless belt 41 (arrow DR1), the cooling unit 50A is located downstream of the collection unit 48. The cooling unit 50 </ b> A rotates in accordance with the movement of the endless belt 41 while being in contact with the endless belt 41.

  Cooling air is passed through the cooling unit 50A. When a condenser (not shown) condenses and processes the carrier liquid vapor, the exhaust from the condenser may be used as the cooling air. Since the exhaust gas has undergone a condensation process, its temperature is low. The cooling unit 50A reduces the temperature of the surface 41S of the endless belt 41. As a means for cooling the surface 41S of the endless belt 41, both the cooling unit 50 in the above-described embodiment and the cooling unit 50A in the present modification may be used, or only one of them. May be used.

[Second Modification]
FIG. 7 is a diagram illustrating a solvent removal device 20B according to a second modification of the embodiment. In the solvent removal device 20B, the endless belt 41 rotates in the direction of the arrow DR2. The collection unit 48 is provided so as to face a portion of the endless belt 41 located between the support roller 43 and the support roller 42. The collection part 48 is located downstream of the surface part 41P and upstream of the cooling part 50. Also with this configuration, the same operations and effects as in the above embodiment can be obtained.

[Experimental example]
With reference to FIG. 8 to FIG. 14, a plurality of experimental examples performed on the above embodiment will be described.

(Experimental examples S1 to S3)
Experimental examples S1 to S3 will be described with reference to FIGS. These experiments were performed under the following setting conditions. As the wet image forming apparatus used in the experiment, an apparatus having the same configuration as that of the above-described embodiment was prepared. For convenience, the recovery unit 48 is removed from the solvent removal apparatus 20.

  As the recording medium 90, a PET film having a thickness of 25 μm was prepared. The toner weight ratio (TC ratio) to the liquid developer was 30%. The type of carrier liquid contained in the liquid developer was Isopar L (Isopar is a registered trademark) manufactured by ExxonMobil in Experimental Examples S1 to S3. This Isopar L has an average molecular weight of 170 and a flash point of 66 ° C. The flash point is the lowest temperature at which a substance can volatilize to produce a combustible mixture with air.

  The circumferential speed of the endless belt 41 (moving speed of the surface portion 41P) is 100 mm / sec to 300 mm / sec, and the surface portion 41P moves in the same direction as the recording medium 90 that moves while being heated by the heating unit 30. did. The heating temperature by the heating unit 30 (non-contact heaters 31 and 32) was 200 to 400 ° C. The surface temperature of the recording medium 90 after heating was 50 ° C. in Experimental Example S1, 60 ° C. in Experimental Example S2, and 80 ° C. in Experimental Example S3. The system speed of the fixing unit 60 was 100 mm / sec, and the surface temperature of the roller fixing device was 150 ° C.

  The endless belt 41 was moved around by the driving device, and the cooling unit 50 and the heating unit 30 were operated. The temperature of the endless belt 41 immediately before facing the recording medium 90 was continuously monitored using a contact thermocouple. The endless belt 41, the cooling unit 50, and the heating unit 30 were continuously operated until the surface temperature of the endless belt 41 was stabilized. When the surface temperature of the endless belt 41 was stabilized, the surface temperature of the endless belt 41 was 25 ° C.

  Thereafter, a solid image (toner image 92) was formed on the recording surface 91 of the recording medium 90 by the image forming unit 10. After passing the recording medium 90 through the solvent removal apparatus 20, these apparatuses were stopped. As described above, the solvent removal apparatus 20 used in this experimental example does not have the recovery unit 48. By doing so, the carrier liquid remains attached on the surface 41S of the endless belt 41, and by measuring this weight as the recovered amount, the recovery ability of the carrier liquid by the solvent removing device 20 is evaluated. I can do things.

Specifically, when measuring the solvent recovery amount, a certain area (10 cm ² ) on the surface 41S of the endless belt 41 was wiped with Bencot (registered trademark) manufactured by Asahi Kasei Fibers Corporation. The weight of Bencot (registered trademark) before and after wiping was measured with an electronic balance, and the solvent recovery amount was measured based on the increase in weight. The above experiment was repeated while changing the distance L between the recording medium 90 and the endless belt 41 (surface portion 41P), and the solvent recovery amounts in Experimental Examples S1 to S3 were measured.

  FIG. 9 is a graph showing the relationship between the interval L and the solvent recovery amount (g). It can be seen that, under the condition of Experimental Example S1 (the surface temperature of the recording medium after heating is 50 ° C.), when the distance L is smaller than 2 mm, the recovery amount increases sharply. Under the condition of Experimental Example S2 (the surface temperature of the recording medium after heating is 60 ° C.), it can be seen that when the distance L is smaller than about 2.4 mm, the recovery amount increases sharply. It can be seen that, under the condition of Experimental Example S3 (the surface temperature of the recording medium after heating is 80 ° C.), when the distance L is less than 4 mm, the recovery amount increases sharply.

  From these experimental results, it can be seen that the higher the surface temperature of the recording medium after heating, the greater the recovered amount. It can be seen that it is preferable that the value of the distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) varies according to the heating temperature by the heating unit 30.

(Experimental examples T1, T2)
Experimental examples T1 and T2 will be described with reference to FIGS. These experimental examples differ from the experimental examples S1 to S3 in the following points. The type of carrier liquid contained in the liquid developer was IP2028 manufactured by Idemitsu Kosan Co., Ltd. in Experimental Examples T1 and T2. This IP2028 has an average molecular weight of 210 and a flash point of 86 ° C. The temperature of the surface of the recording medium 90 after heating was 80 ° C. in Experimental Example T1, and 100 ° C. in Experimental Example T2. Other conditions are common to the experimental examples S1 to S3 and the experimental examples T1 and T2.

  FIG. 10 is a graph showing the relationship between the interval L and the solvent recovery amount (g). Under the conditions of Experimental Example T1 (the surface temperature of the recording medium after heating is 80 ° C.), it can be seen that when the distance L is smaller than about 1.6 mm, the recovery amount increases sharply. It can be seen that, under the conditions of Experimental Example T2 (the surface temperature of the recording medium after heating is 100 ° C.), when the distance L is smaller than about 2.4 mm, the recovery amount increases sharply.

  From these experimental results, it can be seen that the higher the surface temperature of the recording medium after heating, the greater the recovery amount. It can be seen that the value of the distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) is preferably different according to the surface temperature of the recording medium after heating. From the results of the experimental examples S1 to S3, T1, and T2, it can be seen that the value of the distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) is preferably different depending on the type of the carrier liquid.

(Experimental examples E1 to E5)
With reference to FIG. 8 again, Experimental Examples E1 to E5 will be described. These experimental examples differ from the experimental examples S1 to S3, T1, and T2 in the following points. The type of carrier liquid contained in the liquid developer was P-40 manufactured by MORESCO Co., Ltd. in Experimental Examples E1, E2, and E3, and P-60 manufactured by the same company in Experimental Examples E4 and E5. P-40 has an average molecular weight of 230 and a flash point of 142 ° C. P-60 has an average molecular weight of 300 and a flash point of 176 ° C.

  The surface temperature of the recording medium after heating was 90 ° C. in Experimental Example E1, 100 ° C. in Experimental Example E2, 120 ° C. in Experimental Example E3, 120 ° C. in Experimental Example E4, and 140 ° C. in Experimental Example E5. . Other conditions are common to the experimental examples E1 to E5 and the experimental examples S1 to S3, T1, and T2.

  As a result of analyzing the relationship between the interval L and the recovered amount based on the results of Experimental Examples E1 to E5 and Experimental Examples S1 to S3, T1, and T2, the recovered amount is higher when the surface temperature of the recording medium after heating is higher. It turns out that increases. When trying to obtain the same recovery amount, it has been found that the interval L can be lengthened by using a carrier liquid having a low average molecular weight and easily volatilizing.

  Furthermore, when the interval between the recording surface 91 and the surface portion 41P of the recording medium 90 is L (mm), the average molecular weight of the carrier liquid is M, and the surface temperature of the recording surface 91 is Tm (° C.), It has been found that it is preferable that the condition of approximately 0.1 <L <2 × (Tm−20) × exp (−0.02 × M) is satisfied. The average molecular weight M of the carrier liquid in the condition represented by this inequality is calculated under the following (1) and (2) using, for example, the GC-MS method (gas chromatography mass spectrometry). Value.

(1) GC (gas chromatograph) conditions Capillary gas chromatograph HP-6890 (manufactured by Hewlett Packard)
Injection part temperature: 300 ° C
Injection method: Splitless mode Sample: Stock solution (100%)
Sample injection volume: 0.1 μL
Carrier gas: helium (1 ml / min)
Interface temperature: 300 ° C
(2) MS (mass spectrometry) conditions Equipment: Time-of-flight mass spectrometer (manufactured by Micromass Ltd.)
Ionization: Electric field ionization method (extraction voltage: 12 kV)
Mass range: m / z 10-300
Ion detection: Multi Channel Plate
That is, when the distance L (mm) is smaller than the value represented by 2 × (Tm−20) × exp (−0.02 × M), a sufficient recovery amount (removal amount) of the carrier liquid can be expected. When the distance L (mm) is larger than 0.1 (mm), it is possible to sufficiently suppress the occurrence of a disorder or the like in the toner image.

  The horizontal axis of FIG. 11 shows the value of the distance L (mm) obtained from the experimental results of each of the above experimental examples S1 to S3, T1, T2, and E1 to E5. The plurality of rhombus-shaped plots shown in FIG. 11 indicate the respective experimental conditions in the above experimental examples S1 to S3, T1, T2, and E1 to E5 as L = 2 × (Tm−20) × exp. The value obtained by substituting into the calculation formula (−0.02 × M) is plotted along the vertical axis of FIG. 11. An approximate straight line LN in FIG. 11 shows an approximation of these multiple plots with straight lines.

  As indicated by the approximate straight line LN, the interval L changes substantially linearly based on the average molecular weight M of the carrier liquid and the surface temperature Tm (° C.) of the recording surface 91. Therefore, the preferable maximum value of the distance L is the average molecular weight M of the carrier liquid and the surface temperature Tm (° C.) of the recording surface 91 expressed by the above formula L = 2 × (Tm−20) × exp (−0.02). It can be seen that it is possible to estimate by substituting in × M).

  As described above, the carrier liquid used in each of the above experimental examples S1 to S3, T1, T2, and E1 to E5 includes four types having different volatility (flash points) shown in FIG. From the viewpoint of volatility, these four types of carrier liquids can be said to include approximate upper and lower limits of the flash point of carrier liquids generally used in wet electrophotographic technology. That is, for example, when a carrier liquid having higher volatility than Isopar L (Isopar is a registered trademark) (flash point 66 ° C.) is used, the concentration of the solid component in the liquid developer is likely to fluctuate during the image forming process. It becomes difficult to stabilize the TC ratio of the liquid developer. On the other hand, when a carrier liquid having a volatility lower than P-60 (flash point 176 ° C.) is used, a lot of energy is required at the time of fixing, or it is difficult to dry the carrier liquid remaining in the paper. Or

  Therefore, in a wet image forming apparatus using a general liquid developer containing a carrier liquid, the interval between the recording surface 91 and the surface portion 41P of the recording medium 90 is L (mm), and the average molecular weight of the carrier liquid is When M is M and the surface temperature of the recording surface 91 is Tm (° C.), the condition of approximately 0.1 <L <2 × (Tm−20) × exp (−0.02 × M) is satisfied. It can be said that it is preferable. However, what is described here is to explain one of preferred embodiments based on examples, and even when a carrier liquid having higher volatility than IsoparL (Isopar is a registered trademark) is used. Even when a carrier liquid having a lower volatility than P-60 is used, it does not mean that the configuration is not included in the technical scope of the present invention. That is, what is described here is that when using a carrier liquid having higher volatility than IsoparL (Isopar is a registered trademark) and when using a carrier liquid having lower volatility than P-60, the present invention It is not actively excluded from the technical scope of.

(Experimental examples Q1-Q3)
With reference to FIG. 12, Experimental Example Q1-Q3 is demonstrated. In Experimental Examples Q1 to Q3, the relationship between the circumferential speed of the endless belt 41 (the moving speed of the surface portion 41P) and the recovered amount was examined. In Experimental Example Q1, the moving speed of the surface portion 41P was set to 100 mm / sec. In Experimental Example Q2, the moving speed of the surface portion 41P was set to 200 mm / sec. In Experimental Example Q3, the moving speed of the surface portion 41P was set to 300 mm / sec. Other conditions of the experimental examples Q1 to Q3 are the same as those of the experimental examples S1 and S2.

In measuring the solvent recovery amount, in order to compare the volatilization amount (recovery amount) from the portion having the same area in the toner image 92, each of the experimental examples Q1 to Q3 according to the moving speed of the surface portion 41P. The collection areas of the carrier liquid by Bencot (registered trademark) were varied. In Experimental Example Q1 (100 mm / sec), a 10 cm ² portion on the surface 41S of the endless belt 41 was wiped off. In Experimental Example Q2 (200 mm / sec), a 20 cm ² portion on the surface 41S of the endless belt 41 was wiped off. In Experimental Example Q3 (300 mm / sec), a 30 cm ² portion on the surface 41S of the endless belt 41 was wiped off.

  FIG. 12 shows the relationship between the interval L and the recovered amount in each case of Experimental Examples Q1 to Q3. As shown in FIG. 12, it can be seen that the recovery amount of the carrier liquid increases by increasing the moving speed of the surface portion 41P. In any of the experimental examples Q1 to Q3, it can be seen that the recovery amount starts to increase when the interval L becomes smaller than 2 mm, and the recovery amount increases sharply when the interval L becomes smaller than about 1.6 mm.

(Experimental examples R1, R2)
The experimental examples R1 and R2 will be described with reference to FIG. In Experimental Examples R1 and R2, the relationship between the temperature of the surface portion 41P of the endless belt 41 and the recovered amount was examined. The circulating speed of the endless belt 41 (moving speed of the surface portion 41P) is 100 mm / sec. In order to cool the surface portion 41P (surface 41S) of the endless belt 41, the cooling unit 50 (see FIG. 3) and the cooling unit Both 50A (see FIG. 6) were used.

  The endless belt 41 was moved around by the driving device, and the cooling units 50 and 50A and the heating unit 30 were operated. The temperature of the endless belt 41 immediately before facing the recording medium 90 was continuously monitored using a contact thermocouple. The endless belt 41, the cooling units 50 and 50A, and the heating unit 30 were continuously operated until the surface temperature of the endless belt 41 was stabilized. In Experimental Example R1, when the surface temperature of the endless belt 41 was stabilized, the surface temperature was 15 ° C. In Experimental Example R2, when the surface temperature of the endless belt 41 was stabilized, the surface temperature was 25 ° C. Other conditions of the experimental examples R1 and R2 are the same as those of the experimental examples S1 and S2.

  FIG. 13 shows the relationship between the interval L and the recovery amount in each case of the experimental examples R1 and R2. As shown in FIG. 13, it can be seen that the recovery amount of the carrier liquid increases by lowering the temperature of the surface portion 41P. In any of the experimental examples R1 and R2, it can be seen that when the distance L is smaller than about 1.6 mm, the recovery amount increases sharply.

  According to the results of Experimental Examples Q1 to Q3, R1, and R2, it can be seen that the moving speed and temperature of the surface portion 41P are factors that affect the recovery amount. It can be seen that even if the moving speed of the surface portion 41P is changed or the temperature of the surface portion 41P is changed, the value of the interval L when the amount of collection increases sharply does not change.

(Experimental examples A1, A2, A3)
The experimental examples A1, A2, and A3 will be described with reference to FIG. In Experimental Examples A1, A2, and A3, the type of carrier liquid contained in the liquid developer was P-60 manufactured by MORESCO. A solid image (toner image 92) was formed on the recording surface 91 of the recording medium 90 by the image forming unit 10.

  In Experimental Example A1, both the heating unit 30 and the solvent removal device 20 were operated. In Experimental Example A1, the surface temperature of the recording medium after heating was 120 ° C., and the distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) was 0.3 mm. The temperature of the surface portion 41P of the endless belt 41 was 25 ° C. (room temperature). The state (TC ratio) of the toner image before fixing after passing through the solvent removing device 20 and the quality of the toner image (output image) actually fixed on the recording medium 90 by the fixing roller were confirmed.

  In Experimental Example A2, a device without the solvent removal device 20 was used, and the heating unit 30 was not operated. The state (TC ratio) of the toner image before fixing and the quality of the toner image (output image) actually fixed on the recording medium 90 by the fixing roller were confirmed.

  In Experimental Example A3, a device not equipped with the solvent removal device 20 was used, but the heating unit 30 was operated. The surface temperature of the recording medium after heating was 120 ° C. The state (TC ratio) of the toner image before fixing and the quality of the toner image (output image) actually fixed on the recording medium 90 by the fixing roller were confirmed. Other conditions of Experimental Examples A1, A2, and A3 are the same as those of Experimental Examples S1 and S2.

  In any of Experimental Examples A1, A2, and A3, the TC ratio of the toner image 92 at the time when the solid image was formed on the recording medium 90 by the image forming unit 10 (the time immediately after the secondary transfer) was 50%. there were. On the other hand, in Experimental Example A1, the TC ratio of the toner image before fixing after passing through the solvent removing device 20 was 80%. No image distortion occurred in the output image after fixing, and the quality evaluation was A. In Experimental Example A2, the TC ratio of the toner image before fixing was 50%, the output image after fixing was disturbed, and the quality evaluation was B. In Experimental Example A3, the TC ratio of the toner image before fixing was 53%, the output image after fixing was disturbed, and the quality evaluation was B.

  From the result of Experimental Example A1, even when P-60 having low volatility is used as the carrier liquid, the surface portion 41P of the endless belt 41 is moved in the state of being close to the toner image, so that the toner image is removed from the toner image. It can be seen that the carrier liquid can be effectively removed. Since the amount of the carrier liquid is reduced before the toner image 92 is pressed by the fixing unit 60, the carrier liquid and the toner are prevented from flowing during fixing, and the output image is also prevented from being disturbed as a result. It is thought that it was done.

  On the other hand, from the result of Experimental Example A2, it is understood that the TC ratio hardly changes when the toner image 92 is not heated between the secondary transfer and the fixing. From the result of Experimental Example A3, it can be seen that it is difficult to volatilize the carrier liquid remaining in the toner image 92 on the recording surface 91 only by heating by the heating unit 30. This is considered to be due to the fact that a high-concentration carrier vapor layer is formed so as to cover the toner image 92. When the toner image 92 is pressed by the fixing unit 60, the toner image contains a carrier liquid whose amount is not sufficiently reduced. It is thought that the image was disturbed.

(Experimental examples B1, B2, B3, B4)
The experimental examples B1, B2, B3, and B4 will be described with reference to FIG. In Experimental Examples B1, B2, B3, and B4, the type of carrier liquid contained in the liquid developer was IP2028 manufactured by Idemitsu Kosan Co., Ltd. A solid image (toner image 92) was formed on the recording surface 91 of the recording medium 90 by the image forming unit 10. In any of Experimental Examples B1, B2, B3, and B4, both the heating unit 30 and the solvent removal device 20 were operated, and the temperature of the surface portion 41P of the endless belt 41 was set to 25 ° C. (room temperature).

  In Experimental Example B1, the surface temperature of the recording medium after heating was set to 100 ° C. The distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) was 2.0 mm. When each parameter relating to the configuration of Experimental Example B1 is substituted into the formula L = 2 × (Tm−20) × exp (−0.02 × M), the calculated value of the interval L obtained thereby is 2.4 mm. It becomes. The interval L (2.0 mm) according to the implementation of Experimental Example B1 is smaller than the interval L as the calculated value. The calculated values are shown in parentheses in FIG. The other conditions in Experimental Example B1 are the same as in Experimental Examples S1 and S2. When the quality of the toner image (output image) actually fixed on the recording medium 90 by the fixing roller was confirmed, the quality of the output image was better than that of Example A3, so the quality evaluation was A It was.

  In Experimental Example B2, the surface temperature of the recording medium after heating was 80 ° C. The distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) was 1.1 mm. When each parameter related to the configuration of Experimental Example B2 is substituted into the formula L = 2 × (Tm−20) × exp (−0.02 × M), the calculated value of the interval L obtained thereby is 1.8 mm. It becomes. The interval L (1.1 mm) according to the implementation of Experimental Example B2 is smaller than the interval L as the calculated value. The calculated values are shown in parentheses in FIG. Other conditions in Experimental Example B2 are the same as in Experimental Examples S1 and S2. When the quality of the toner image (output image) actually fixed on the recording medium 90 by the fixing roller was confirmed, the quality of the output image was better than that of Example A3, so the quality evaluation was A It was.

  In Experimental Example B3, the surface temperature of the recording medium after heating was set to 100 ° C. The distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) was set to 3.0 mm. When each parameter related to the configuration of Experimental Example B3 is substituted into the formula L = 2 × (Tm−20) × exp (−0.02 × M), the calculated value of the interval L obtained thereby is 2.4 mm. It becomes. The interval L (3.0 mm) according to the implementation of Experimental Example B3 is larger than the interval L as the calculated value. The calculated values are shown in parentheses in FIG. Other conditions in Experimental Example B3 are the same as in Experimental Examples S1 and S2. The quality of the toner image (output image) actually fixed on the recording medium 90 by the fixing roller was confirmed. Since the quality of the output image was equivalent to that of Example A3, the quality evaluation was B.

  In Experimental Example B4, the surface temperature of the recording medium after heating was set to 80 ° C. The distance L between the recording medium 90 and the endless belt 41 (surface portion 41P) was 2.5 mm. When each parameter related to the configuration of Experimental Example B4 is substituted into the formula L = 2 × (Tm−20) × exp (−0.02 × M), the calculated value of the interval L obtained thereby is 1.8 mm. It becomes. The interval L (2.5 mm) according to the implementation of Experimental Example B4 is larger than the interval L as the calculated value. The calculated values are shown in parentheses in FIG. Other conditions in Experimental Example B4 are the same as in Experimental Examples S1 and S2. The quality of the toner image (output image) actually fixed on the recording medium 90 by the fixing roller was confirmed. Since the quality of the output image was equivalent to that of Example A3, the quality evaluation was B.

  According to the results of Experimental Examples B1, B2, B3, and B4, when the interval L (mm) is smaller than the value represented by 2 × (Tm−20) × exp (−0.02 × M), the carrier liquid It can be seen that a sufficient recovery amount (removal amount) can be expected.

  The embodiment, each modified example, and each experimental example based on the present invention have been described above, but the embodiment, each modified example, and each experimental example disclosed this time are illustrative and limited in all respects. It is n’t. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 10 Image forming part, 11 Photosensitive drum, 12 Intermediate transfer roller, 13, 18 Cleaning device, 14 Charging device, 15 Exposure device, 16 Liquid developing device, 17th transfer roller, 20, 20A, 20B Solvent removal device, 30 Heating Part, 31, 32 non-contact heater, 33 heat insulation cover, 40 solvent recovery mechanism, 41 endless belt, 41P surface part, 41S surface, 42, 43, 44, 45 support roller, 46, 47 presser roller (vibration suppressing member), 48 recovery unit, 48a blade, 48b recovery tank, 50 cooling unit, 50A cooling unit (cooling member), 51 fan, 52 cover, 60 fixing unit, 61 fixing roller, 62 pressure roller, 63, 64 heater lamp, 65, 66 cases, 71, 72 transport rollers, 90 recording media, 91 Surface, 92 a toner image, 93 carrier vapor layer, 100 wet-type image forming apparatus, Ar 90, DR1, DR2 arrow, L interval.

Claims (9)

An image forming unit that forms a toner image on a recording surface of a recording medium using a liquid developer;
A fixing unit for fixing the toner image on the recording medium;
The recording is provided with the image forming portion of the transport path of the medium to a position between the fixing portion, the recording medium of the transferred to the recording surface wherein the carrier liquid is volatilized contained in the toner image the recording medium A solvent removing device for removing from
The solvent removal apparatus includes:
A heating unit for heating the recording medium conveyed along the conveying path,
The toner image transferred to the recording surface is opposed to the toner image with a space, and has a surface portion whose temperature is lower than the surface temperature of the recording surface of the recording medium, and the surface portion is transferred to the recording surface. and wherein the solvent recovery mechanism for moving in close proximity to the toner image,
The solvent recovery mechanism makes the surface portion contact the carrier liquid vapor volatilized by heating of the heating unit, and recovers the carrier liquid condensed on the surface portion.
Wet image forming apparatus . A cooling unit that cools the surface part and sets the temperature of the surface part to a value lower than the surface temperature of the recording surface of the recording medium;
The wet image forming apparatus according to claim 1. When the interval between the recording surface and the surface portion is L (mm), the condition of 0 <L ≦ 2.0 is satisfied.
The wet image forming apparatus according to claim 1. The interval between the recording surface and the surface portion is L (mm),
The average molecular weight of the carrier liquid is M,
When the surface temperature of the recording surface is Tm (° C.),
0.1 <L <2 × (Tm−20) × exp (−0.02 × M) is satisfied,
The wet image forming apparatus according to claim 1. The solvent recovery mechanism includes an endless belt,
The surface of the endless belt constitutes the surface portion,
The wet image forming apparatus according to claim 1. The heating unit is disposed so as to face the surface portion.
The wet image forming apparatus according to claim 1. The solvent recovery mechanism further includes a recovery part that removes and recovers the carrier liquid condensed on the surface part from the surface part,
The wet image forming apparatus according to claim 1. The cooling unit includes a fan that cools the surface portion without contacting the surface portion, and / or a cooling member that contacts the surface portion and cools the surface portion while rotating as the surface portion moves.
The wet image forming apparatus according to claim 2. The solvent recovery mechanism further includes a vibration suppressing member arranged to contact the surface portion,
The vibration suppressing member rotates in accordance with the movement of the surface portion, and suppresses the vibration of the surface portion when the surface portion is moving.
The wet image forming apparatus according to claim 1.

Images