JP2994943B2 - Method and apparatus for fixing liquid developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for fixing a liquid developer applied to a copying machine, a printing machine, a printer plotter and the like.

[0002]

2. Description of the Related Art A conventional liquid developer fixing device is shown in FIGS. First, the fixing device of the liquid developer shown in FIG. 9 will be described. 1 is a heating roller for fixing, 4 is paper, 5 is a liquid toner (liquid developer), and the surface of the paper 4 is heated by the heat roller 1 for fixing. Thus, the liquid toner 5 attached to the surface of the paper 4 is heated and fixed to the paper 4.

Next, a fixing device for a liquid developer shown in FIG. 10 will be described. The identification fixing device shows an example of double-side fixing, wherein 1a and 1b are heat rollers for fixing, and 1a 'and 1b' are fixing rollers. Nip rollers facing the heat rollers 1a and 1b, 4
Is paper, 5a and 5b are liquid toners. First, as shown in FIG. 10A, a fixing heat roller 1a and a nip roller 1a '
While the fixing heat roller 1b and the nip roller 1b 'are separated from each other, the paper 4 is fed between the fixing heat roller 1a and the nip roller 1a',
The liquid toner 5a adhering to the surface (first surface) of the paper 4 is heat-fixed to the surface of the paper 4.

Next, as shown in FIG. 10 (b), the fixing heat roller 1a and the nip roller 1a 'are separated from each other, while the fixing heat roller 1b and the nip roller 1b' are approached, while the paper 4 is moved. The sheet is fed upside down, fed between the fixing heat roller 1b and the nip roller 1b ', and heat-fixes the liquid toner 5b attached to the back surface (second surface) of the paper 4 to the back surface of the paper 4.

[0005]

In the conventional liquid developer fixing device shown in FIGS. 9 and 10, the surface of the paper to which the liquid toner 5 is adhered is heated by the fixing heat roller 1, so that the liquid The toner 5 adheres to the fixing heat roller 1, and the fixing heat roller 1 and the image become dirty. Therefore, a device or the like for applying a release agent such as silicone oil to the fixing heat roller 1 is required, so that the fixing device becomes complicated and the running cost increases.

The present invention has been made in view of the above problems, and has as its object to simplify the fixing device, reduce the running cost, and to contaminate the heat roller for fixing and the image. It can improve contact heat transfer, achieve energy savings, can respond to changes in toner concentration and the amount of solvent per sheet, and can fix both sides without fouling the heat roller for fixing and the image. There is no need to worry about the heat roller for fixing or contamination of the image, and there is no need to select the type of toner, and it is possible to heat and fix by the near-infrared heating means for fixing. It is an object of the present invention to provide a method and an apparatus for fixing a liquid developer which can obtain a beautiful image as compared with a liquid developer.

[0007]

In order to achieve the above-mentioned object, a method for fixing a liquid developer according to the present invention comprises heating a back surface of an image carrier with a heat roller for fixing to adhere to the surface of the image carrier. The liquid developer is heated and fixed on the image carrier, and the tension of the image carrier or the holding angle between the image carrier and the fixing heat roller is controlled.

Further, the method for fixing a liquid developer according to the present invention
Liquid liquid wetted by insulating low dielectric constant hydrocarbon solvent
Fixing temperature T of image liquid₁Is the heating and melting of the dried liquid toner
Temperature T_TwoUse a lower liquid developer than the surface of the image carrier.
Surface temperature T_RTo T₁<T_R<T _TwoHeat for fixing
Heating the back side of the image carrier while controlling the temperature of the roller,
Fixes the liquid developer adhering to the surface of the image carrier to the image carrier
It is characterized by having

The fixing device for a liquid developer according to the present invention further comprises a fixing heat roller for heating the back surface of the image carrier to heat and fix the liquid developer adhering to the surface of the image carrier to the image carrier; And a fixing near-infrared heating means for heating and fixing the liquid developer adhering to the surface of the image carrier to the image carrier. In the liquid developer fixing device, a fixing heat roller and a fixing near-infrared heating means may be arranged in series.

In the liquid developer fixing device, the fixing heat roller and the fixing near-infrared ray heating means may be arranged in parallel.

[0011]

The fixing method of the liquid developer according to the present invention is constituted as described above, and the back surface of the image carrier is heated by the heat roller for fixing so that the liquid developer adhering to the surface of the image carrier is imaged. In addition to heat fixing on the carrier, the tension of the image carrier or the holding angle between the image carrier and the fixing heat roller is controlled to improve the contact heat transfer rate from the fixing heat roller to the image carrier. At this time, using a liquid developer in which the fixing temperature T ₁ of the liquid developer wetted with a hydrocarbon solvent having a high insulating property and a low dielectric constant is lower than the heating and melting temperature T ₂ of a dried product of the liquid developer. while controlling the temperature of the fixing heat roller to the surface temperature T _R of the image carrier to _{T 1 <T R <T 2} , heating the rear surface of the image carrier, adhering to the surface of the image carrier The liquid developer is fixed on the image carrier, or the image carrier is sent to a system of a fixing heating roller, and then the image carrier is reversed and sent to a system of a near-infrared heating means for fixing, and adheres to both surfaces of the image carrier. The liquid toner is sequentially heated and fixed by the fixing heat roller and the fixing near-infrared heating means.

[0012]

【Example】

(First Embodiment) Next, an example of the configuration of a fixing device applied to the method of fixing a liquid developer according to the present invention will be described with reference to FIGS. 1 and 2. Reference numeral 1 denotes a fixing heat roller, 2 denotes a tension roller, 3a, 3b are nip rollers, 4 is paper (image carrier), 5
Is a liquid toner (liquid developer).

Next, the operation of the liquid developer fixing device will be specifically described. The back surface of the paper 4 is heated by the fixing heat roller 1 so that the liquid toner 5 adhering to the surface of the paper 4 is heated and fixed to the front surface of the paper 4, and then the paper 4 passes between the nip rollers 3a and 3b. Let me run further.
When the back surface of the paper 4 is heated by the fixing heat roller 1, the temperature of the paper 4 at the exit side of the fixing heat roller 1 is determined by the following equation.

[0014]

(Equation 1)

The above equations will be briefly described. Equation α
_c indicates the contact heat transfer coefficient, which is the thermal conductivity of air λ
_a , roll diameter D, air viscosity resistance μ, web speed V _S ,
A function of the paper tension T _e, the alpha _c, proportional to the tension, is inversely proportional to the roll diameter and velocity V, especially in the case of controlling the alpha _c, a method of changing the tension T _e is convenient .

In the equation, V is the overall heat transfer coefficient, t _h is the paper thickness, and λ _P is the thermal conductivity of the paper. The equation is a logarithmic average temperature difference, Δt ₁ is the difference between the inlet-side roll temperature _trz and the inlet-side paper temperature t _PI, and Δt ₂ is the outlet-side roll temperature _tr.
The difference between φ and the paper temperature t _P φ on the outlet side is shown. A in the formula is
This is the contact area between the paper and the heat roller for fixing.

Usually, since the heat capacity of the fixing heat roll is large, the roll temperature t _rI on the inlet side and the roll temperature t _rI on the outlet side are determined.
_r is equal to Q in the equation is the amount of heat transferred from the fixing heat roller to the paper, which is (1) the temperature rise of the paper, (2) the latent heat of evaporation of the solvent, (3) the temperature rise of the solvent,
(4) The sum of the temperature rise of the toner is obtained.

If the exit side paper temperature t _P φ required for fixing is determined, the amount of heat Q to be transferred to the paper is determined. α _c is
Although there are various parameters as in the equation, α _c = f (T _e ) because the factor of the tension changes freely. Substituting these into the equation gives the following equation.

[0019]

(Equation 2)

In the above equation, tb / λ _P , Q, t _P φ, t
_PI is a constant. Therefore the temperature of the fixing hot roll, i.e., in order to reduce the energy for heating the fixing hot roll is tension T _e the contact area A, i.e., may be controlled contact length. FIG. 1 shows a case where the tension of the paper 4 is controlled by pressing the tension roller 2 in the direction of the arrow.

[0021] Figure 2 is a case of moving the tension roller 2 to a pre-2 'position, the contact length with respect to the fixing heat roller 1 paper 4, i.e., to increase the embracing angle from theta ₁ to the theta _2. Alternatively, the tension roll 2 may be moved from the state where the tension roll 2 has moved to the 2 ′ position to control the tension of the paper 4. Dimensionless number on the horizontal axis as shown in FIG. 3 (μV _S / T _e), the contact heat transfer coefficient on the vertical axis, taking respectively, as T _e is large, the contact heat transfer coefficient increases. Then, the overall heat transfer coefficient V becomes relatively large. Therefore, even if the temperature of the heat roll is lowered, a predetermined amount of heat can be transferred to the paper.

The above is the case where the tension is controlled. However, when the holding angle is changed, A in the following equation is changed. Q = V · A · Δt That is, since the holding angle is changed, and A increases, Δt decreases with respect to a fixed amount of Q, and the temperature of the fixing heat roller can be reduced.

The adjustment of the liquid toner is as follows. Aliphatic hydrocarbon isoper G (Exxon): 216 in a vessel equipped with a stirrer, thermometer, reflux condenser and vacuum deaerator.
Parts, aromatic hydrocarbon toluene (Katayama Chemical): 144 parts,
Aliphatic alcohol ethanol (Katayama Chemical): 90 parts, modified ethylene-vinyl acetate copolymer dumilan C-2
280 (Takeda Pharmaceutical): 6 parts, coloring material Brilliant Carmine 6B (Dainichi Seika): 1.2 parts were added, and the mixture was stirred at 70 ° C. for 60 minutes to completely dissolve Dumilan.
While maintaining the temperature at 0 ° C. (at this time, the dumilane is in a dissolved state), the container is evacuated by vacuum, and toluene and ethanol are removed from the solvent, so that red toner particles having a 50% particle size based on the deposition of 1.95 μm are obtained. A dispersion was obtained.

A conventional additive such as a charge controlling agent is added to the toner particle dispersion to form a liquid developer for electrophotography (solid content of 2%).
%). The fixing temperature of the toner in a solvent wet state is 80 ° C., and the re-melting temperature of the dried product is 130 ° C. Next, a fixing test example of the fixing method of the liquid toner will be described.

(Fixing Test Example 1) A case where the tension of the paper is controlled will be described. Paper (web) speed 100
mm / sec, high-quality paper having a width of 1 m and a thickness of 80 μm was used, and the average amount of the adhered solvent was 6.324 kg / Hr and the amount of adhered toner was 0.812 kg / Hr. A heat roller having a diameter of 40 mm and a surface coated with a fluororesin was used. The temperature of the heat roller at the time of tension control when the paper inlet temperature was 25 ° C. and the paper outlet temperature was 110 ° C. was determined. The holding angle was 90 °.

First, the tension measured by the tension roller 2 was 5 kgf / m. The temperature of the heat roller satisfying the above condition at this time was 225 ° C. However, when tension was applied to 25 kgf / m, the heat roller temperature was 208 ° C.
As a result, the paper exit temperature reached 110 ° C., and a printed matter having excellent fixing characteristics could be obtained on both sides. That is, by applying tension, the temperature of the heat roller could be lowered from 225 ° C to 208 ° C.

In this case, the bearing load of the fixing heat roller 1 was measured by a load cell to determine the tension of the paper, and the tension roll 2 was moved to control the tension. (Fixing Test 2) Tension of 5 kgf /
and the holding angle is 9 when the temperature of the heat roller is 225 ° C.
0 °. Therefore, the holding angle was set to 120 ° as shown in FIG. In this case, the temperature of the fixing heat roller was 183 ° C. in order to set the roll exit temperature to 110 ° C. However, in this case, only the holding angle was changed without changing the tension to 5 kgf / m. Also in this case, both-side fixing was possible.

In each of the above embodiments, the tension of the paper and the angle of holding the fixing heat roller are separately controlled.
If these controls are performed in parallel, a greater effect can be obtained. The first embodiment has the following advantages. That is, the back surface of the paper (image carrier) is heated by a fixing heat roller to heat and fix the liquid developer adhering to the surface of the image carrier to the image carrier. There is no need to apply a release agent such as
In addition to simplifying the fixing device and reducing running costs, the fixing heat roller and the image are not stained. In addition, the tension of the image carrier or the holding angle between the image carrier and the fixing heat roller is controlled, and the contact heat transfer is improved,
Energy saving becomes possible. Further, as described above, the tension roller controls the tension of the image carrier or the holding angle between the image carrier and the heat roller for fixing, so that even if the toner concentration or the amount of solvent per sheet varies, it can be handled.

(Second Embodiment) Next, another configuration example of a fixing device applied to the implementation of the liquid developer fixing method of the present invention will be described with reference to FIGS. Is a tension roller, 3a and 3b are nip rollers, 4 is paper (image carrier), 5 is liquid toner (liquid developer), and 6 is fixed toner.

Next, the operation of the fixing device for the liquid developer will be described in detail. The toner particles in the liquid developer contain some hydrocarbon solvent in the toner particles due to the binder resin being wetted by the solvent. The heating solvent temperature T ₁ of the resin particles wetted by the hydrocarbon solvent as described above is:
The temperature becomes lower than the heating re-melting temperature T ₂ of the dried resin particles.

Therefore, first, a toner image is formed on one side of the paper 4.
After the transfer, the toner image is transferred to the back surface by the fixing heat roll 1.
To fix the paper 4 and then apply the toner image to the other side.
After the transfer, the toner image is already
The sheet is heated from the fixed back side and fixed on the paper 4. this
In this case, the surface temperature T of the paper 4 contacting the fixing heat roll 1_R
To T₁<T_R<T _TwoTemperature of the fixing heat roller 1
While controlling the degree, heat the back side of the paper 4 and
Since the liquid toner adhering to the sheet 4 is fixed on the paper 4,
Without heat melting the toner on the back side
That is, both-side fixing without fouling the fixing heat roller 1 and the image.
Becomes possible.

The adjustment of the toner is as described above. Next, a fixing test example of the fixing method of the liquid toner will be described. (Example of Fixing Test) A fixing device of a commercially available wet electrophotographic copying machine was modified into a fixing device of the present invention (a fixing device for heating paper from the back side by a fixing heat roll), and the paper surface temperature in contact with the fixing heat roll 1 was reduced. At a temperature of 112 to 115 ° C., an image formed on a commercially available high-quality paper with a liquid developer was heat-fixed from the back side by a fixing heat roll 1 (see FIG. 4).

Next, an image was formed again on the opposite surface of the paper with a liquid developer, and this was heated and fixed from the back surface (the back surface on which the toner was already fixed on the paper surface) by the fixing heat roll 1 (see FIG. 5). ). On both surfaces, an excellent fixed image with image density of 1.2 ^D and background smear of 0.01 ^D or less without soil on the paper was obtained. Further, no toner adhered to the apparatus from the fixing heat roll 1 or the like. Note that a Macbeth densitometer was used for measuring the density and the background contamination.

The second embodiment has the following advantages in addition to the advantages of the first embodiment. That is, by using highly insulating low-permittivity hydrocarbon low liquid developer than the heat-melting temperature T ₂ of the fixing temperature T ₁ of the liquid toner wetted dry solid of the liquid toner by a solvent, the image carrier Surface temperature T _R of T ₁ <T
While controlling the temperature of the fixing heat roller 1 so as to _R <T _2, heating the rear surface of the image carrier, so as to fix the liquid salted solution adhering to the surface of the image carrier to the image carrier Thus, double-sided fixing can be performed without thermally fixing the liquid developer on the back surface that has already been fixed, that is, without fouling the fixing heat roller and the image.

(Third Embodiment) Next, the liquid toner fixing device of the present invention will be described with reference to the configuration examples shown in FIGS.
Reference numeral 1 denotes a fixing heat roller, and reference numerals 3a and 3b denote nip rollers. A tension roller 2 is provided between the fixing heat roller 1 and the nip rollers 3a and 3b, although not shown.

4a is a first printing surface of paper (image carrier), 4b is a second printing surface of paper (image carrier), 5 is a liquid toner (liquid developer), 6 is a fixed toner, and 12 is a near infrared heater. (Fixing near-infrared heating means), 13 is a sensor, 14a is a printing roller (yellow), 14b is a printing roller (red), 14c is a printing roller (blue), 14d is a printing roller (black), 1
Reference numeral 5 denotes a paper feed unit, 22 denotes a nip roller of the printing unit rollers 14a to 14d, 23 denotes a paper feed roller, and 25 denotes a paper discharge roller.

Next, the operation of the liquid developing solution fixing device shown in FIGS. 6 and 7 will be specifically described. As shown in FIG. 7, the back surface of the first printing surface 4 a of the paper 4 is heated by the fixing heat roller 1 to fix the liquid toner 5 adhered to the first printing surface 4 a of the paper 4 and then fixed. The heat roller 1 is stopped, and then the liquid toner 5 adhering to the second printing surface 4b of the paper 4 is heated and fixed by a near-infrared heater (fixing near-infrared heating means) 12 as shown in FIG. . That is, when heat-fixing is performed by the fixing heat roller 1, the paper 4 passes through a path a in FIG. 6, and when heat-fixing is performed by the near-infrared heater 7, the paper 4 passes through a path b in FIG.

The reason for changing the path of the paper 4 is that, after using the heat roller 1 for fixing, it takes a considerable time for the heat roller 1 for fixing to cool down to room temperature, and This is because if the paper surface on which the toner has been fixed once comes into contact, the toner dissolves and the image becomes dirty. The operation of the liquid toner fixing device will be described more specifically. The paper sent from the paper supply unit 15 shown in FIG. 6 is a four-color printing unit roller (yellow) 14 a → a printing unit roller (red) 14.
b → printing roller (blue) 14c → printing roller (black) 1
Printed through 4d. In addition, each printing unit roller 14a ~
14d, the paper is sandwiched by the nip roller 22. When the liquid toner adhering to the first surface 4a of the paper 4 is fixed, the paper 4 is heated from the back surface by the fixing heat roller 1. After the liquid toner is heated and fixed, it is discharged between the nip rollers 3a and 3b → through the paper discharge roller 25 (see route a).

When the liquid toner 5 adhering to the second printing surface 4b of the paper 4 is fixed by heating, the reversed paper 4
Is sent to the near-infrared heater 12 via the paper feed roller 23 between the printing unit roller (black) 14 d and the nip roller 22, where the liquid toner 5 adhering to the second printing surface 4 b of the paper 4
Is heated and fixed, and then discharged via a paper discharge roller 25 (see route b).

If the printed paper 4 is left under near-infrared rays due to an operational trouble, the temperature may rise too much and cause a fire. A sensor 13 is provided upstream of the near-infrared heater 12 to prevent this fire. For this sensor, a laser speedometer or a laser displacement sensor is used. The laser speedometer irradiates a laser beam onto the paper surface, monitors the speed, and stops the near-infrared heater 12 when the speed falls below a predetermined speed. Also, the laser displacement sensor catches the reflected light of the running object, but the object stops,
If it deviates from a predetermined position, abnormal reflected light is caught and the near infrared heater 1
Stop 2

In the above embodiment, the fixing heat roller 1 and the near-infrared heater 12 are installed in parallel. However, they may be installed in series. (Fixing Test Example 1) The toner described above was used. The web speed is 100 mm / sec, and the paper width is 1
m, a high-quality paper of 80 μm in thickness, the average amount of solvent attached is 6.324 kg / Hr, and the amount of attached toner is 0.8
It was 12 kg / Hr. For the heat roller, a fluorine-based roll having a diameter of 40 mm and a surface was used. The temperature of the hot roll was 215 ° and the paper tension at that time was 15 kgf / cm. When using a near-infrared heater, 2.5 KW
Was used. Under these conditions, it was possible to obtain a print having excellent fixing characteristics on both sides.

(Fixing Test Example 2) The toner described above was used. Further, both sides were heated and fixed by a near infrared heater. That is, the paper 4 sent from the paper supply unit 15 is printed via the printing unit rollers 14a to 14d, and sent to the near-infrared heater 12 via the path b, where the liquid adhering to the first surface of the paper 4 The toner was heat-fixed. The second surface of the paper 4 was similarly sent to the near-infrared heater 12 via the path b, where the liquid toner adhering to the second surface of the paper 4 was heated and fixed. The near-infrared heater 12 has 2.5K on both sides.
W was used. Under these conditions, it was possible to obtain a print having excellent fixing characteristics on both sides. in this case,
Although it requires more energy than the fixing test example 1, the apparatus is simpler.

The third embodiment has the following advantages in addition to the advantages of the above embodiments. That is, a fixing near-infrared heating means for heating and fixing the liquid developer adhering to the surface of the image carrier to the image carrier is provided, and the liquid developer adhering to the surface of the image carrier is heat-fixed in a non-contact manner. Yes, no need to worry about dirt. If an abnormality detection sensor is installed upstream of the fixing near-infrared heating means, safe operation becomes possible.
Also, there is no need to select the type of toner. Further, in the system of the near-infrared heating means for fixing, a beautiful image can be obtained as compared with the heat roller in close contact with the surface and the film type.

[0044]

According to the fixing method of the liquid developer of the present invention, the back surface of the image carrier is heated by the fixing heat roller as described above.
The liquid toner adhering to the surface of the paper is heated and fixed on the paper, eliminating the need to apply a release agent such as silicone oil to the heat roller for fixing.
The running cost can be reduced, and the fixing heat roller and the image are not stained. Further, the tension of the image carrier or the holding angle between the image carrier and the fixing heat roller is controlled, so that contact heat transfer can be improved and energy saving can be achieved. Further, as described above, the tension roller controls the tension of the image carrier or the holding angle between the image carrier and the fixing heat roller, so that even if the toner concentration or the amount of the solvent per paper surface changes, it can be coped with.

The fixing method of the liquid developer of the present invention is as described above.
Wet with high insulating low dielectric constant hydrocarbon solvent
Fixing temperature T of liquid toner₁Is the same
Thermal melting temperature T_TwoUse a lower liquid developer
Body surface temperature T_RTo T₁<T _R<T_TwoFix like
While controlling the temperature of the heat roller 1, the back surface of the image carrier is heated.
Heats the image to remove the liquid salt solution adhering to the surface of the image carrier.
Back side that has been settled on the body and is already fixed
Without heat melting the liquid developer of
Both sides can be fixed without fouling the heat roller and the image.

Further, the fixing device for a liquid developer according to the present invention comprises near-infrared heating means for fixing for heating and fixing the liquid developer adhering to the surface of the image carrier to the image carrier as described above. The liquid developer adhering to the surface can be heated and fixed without contact, so that there is no need to worry about contamination and there is no need to select the type of toner. Further, in the system of the near-infrared heating means for fixing, a beautiful image can be obtained as compared with a film-type one in which the heat roller is in close contact with the surface.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of a configuration of a fixing device used for carrying out a liquid toner fixing method of the present invention.

FIG. 2 is an explanatory diagram of an operation of the identification attachment device.

FIG. 3 is an explanatory diagram showing an effect of the identification landing device.

FIG. 4 is a side view showing a state at the time of single-side fixing of another configuration example of the identification attaching device.

FIG. 5 is a side view showing a state in which the identification and fixing device is fixed on both sides.

FIG. 6 is a side view showing still another configuration example of the identification attachment device.

FIG. 7 is a side view showing a heat fixing state in a fixing heat roller system of the identification fixing device.

FIG. 8 is a side view illustrating a heating and fixing state in a system of a fixing near-infrared heating unit of the identification attaching device.

FIG. 9 is a side view illustrating an example of a conventional liquid toner fixing device.

FIG. 10A is a side view illustrating a state of one-side fixing of another example of the conventional liquid toner fixing device, and FIG. 10B is a side view illustrating a state of two-side fixing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat roller for fixing 2 Tension roller 3a, 3b Nip roller 4 Image carrier (paper) 5 Liquid toner

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-148441 (JP, A) JP-A-64-42676 (JP, A) Fully open Showa 50-16939 (JP, U) Really open show 56- 96459 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/20 102 G03G 15/10 G03G 9/12

Claims (5)

(57) [Claims] An image carrier is heated by a fixing heat roller to heat and fix the liquid toner adhering to the surface of the image carrier to the image carrier. A fixing method of a liquid developer, wherein a holding angle with a roller is controlled. 2. A use highly insulating low-permittivity low liquid developer than the heat-melting temperature T ₂ of the fixing temperature T ₁ of the wetting liquid developer a hydrocarbon solvent dried product of the same liquid developer and, while controlling the temperature of the fixing heat roller to the surface temperature T _R of the image carrier to _{T 1 <T R <T 2} , heating the rear surface of the image carrier, attached to the surface of the image carrier And fixing the liquid developer to the image carrier. 3. A fixing heat roller for heating the back surface of the image carrier to heat and fix the liquid toner adhering to the surface of the image carrier to the image carrier, and a liquid developer adhering to the surface of the image carrier. A fixing device for a liquid developer, comprising: a fixing near-infrared heating means for heating and fixing to an image carrier. 4. The fixing device for a liquid developer according to claim 3, wherein the heat roller for fixing and the near-infrared heating means for fixing are arranged in series. 5. The fixing device for a liquid developer according to claim 3, wherein the heat roller for fixing and the near-infrared heating means for fixing are arranged in parallel.