JP2012071487A - Thermal transfer printer, multicolor thermal transfer printer, and control program of thermal transfer printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the change of an image density thermally transferred in the screen or between the screens in a thermal transfer printer.SOLUTION: The thermal transfer printer is provided, wherein an image of a predetermined color ink is thermally transferred to a continuous transferring object 7 because the object is sandwiched together with an ink ribbon 14 having the color ink, between a thermal head 13 and a platen roll 12, and because the thermal head 13 produces heat, in thermal transfer units I, II, III and IV, each equipped with the thermal head 13, and the platen roll 12 facing the thermal head 13. Here, thermal transfer prevention bodies 51 and 55 are made to run between the platen roll 12 of the thermal transfer unit and the continuous transferring object 7, so that a temperature of the platen roll 12 is controlled.

Description

  The present invention relates to a thermal transfer printer that thermally transfers a fine image to a continuous transfer target such as a resin film.

  The image is thermally transferred onto the surface by injecting the molten synthetic resin into the mold after the transfer foil, on which the image has been thermally transferred with the thermoplastic resin ink, is pasted into the mold. Injection molded products can be manufactured. After the injection molded product is taken out from the mold, the base material of the transfer foil is removed to complete the injection molded product with an image displayed on the surface.

  For the production of the transfer foil, it is considered desirable to use a thermal transfer printer that uses a thermoplastic resin ink for thermal transfer of an image. Wax-based thermoplastic inks used in thermal transfer printers melt at high temperatures, but thermoplastic resin inks exhibit moderate plasticity at higher temperatures than wax-based thermoplastic inks, so they are transferred to injection molded products. This is because the image is hardly distorted by heat.

  In this thermal transfer printer, a plurality of thermal transfer units each thermally transferring an image of a predetermined color ink are arranged in a tandem type, and a continuous transfer object such as a resin film is transferred from an upstream thermal transfer unit to a downstream thermal transfer unit. While running, a continuous transfer target is sandwiched between a thermal head and a platen roll together with an ink ribbon provided with a predetermined color ink in each thermal transfer unit, so that images of the respective color inks are sequentially superimposed and thermally transferred. ing.

  A thermal head is usually formed by arranging a large number of heating elements in a dot shape, and the amount of heat generated is controlled by the length of application time of the current flowing through the heating element. As described above, in a thermal transfer printer that controls gradation according to the amount of heat generated by the thermal head, density unevenness occurs or printing differs from the desired gradation unless the temperature of the heating element is strictly managed. Conventionally, the temperature of the heating element of the thermal head is strictly controlled, but in order to further reduce the difference between the initial thermal transfer density at the start of thermal transfer and the final thermal transfer density at the end of thermal transfer due to heat storage during continuous thermal transfer. For example, Patent Literature 1 and Patent Literature 2 describe a temperature control technique for a platen roll that directly heats or cools the platen roll.

Japanese Patent Laid-Open No. 5-155075 JP 2007-253405 A

  As described above, in order to reduce image density fluctuation due to thermally transferred ink and maintain density stability in an image or between images thermally transferred to a continuous transfer material, Changes in the surface temperature of the platen roll due to heat generated by the head and heat absorbed by the ink ribbon and the continuous transfer medium are canceled each time the platen roll rotates once. It is necessary to control the surface temperature of the platen roll to be constant.

  In particular, in high-definition halftone thermal transfer that requires high definition, a large density difference occurs even in a portion that should have the same density due to minute heat fluctuation during thermal transfer.

  In addition, when the thermal transfer speed increases, the speed at which the platen roll makes one revolution also increases, and the time for the platen roll to make one revolution is shortened. It becomes difficult.

  That is, in the conventional thermal transfer printer, if the thermal transfer is continued for a long time at a high speed, it is impossible to prevent the surface temperature of the platen roll facing the thermal head in the thermal transfer unit from changing. Therefore, the surface temperature of the platen roll fluctuated, resulting in uneven density of the image, which was thermally transferred different from the desired gradation. When such a thermal transfer failure occurs, it cannot be used as a transfer foil for painting an injection molded product.

  The present invention has been made to solve the above-described problems. Even when continuous thermal transfer is performed at a high speed for a long time, an image is transferred onto a continuous transfer body with a thermoplastic resin ink with high definition. It is intended to provide a thermal transfer printer that can do this.

  In order to solve the above problems, the present invention employs the following configuration.

  In addition, although the code | symbol with a parenthesis is attached | subjected in order to make an understanding of this invention easy, this invention is not limited to this.

  That is, in order to solve the above problems, the invention according to claim 1 is directed to a thermal transfer unit (I, II, III) comprising a thermal head (13) and a platen roll (12) facing the thermal head (13). , IV) and an ink ribbon (14) provided with a predetermined color ink and sandwiched between the thermal head (13) and the platen roll (12) and the thermal head (13) generates heat, In the thermal transfer printer in which the color ink image is thermally transferred to the continuous transfer target (7), heat transfer is performed between the platen roll (12) of the thermal transfer unit and the continuous transfer target (7). A thermal transfer printer characterized in that the prevention body (51, 55) is made to travel so that the temperature of the platen roll (12) is controlled. .

  According to a second aspect of the present invention, there is provided the thermal transfer printer according to the first aspect, wherein the continuous transfer target passing between the platen roll (12) and the thermal head (13) is provided. A nip roller (15) for pressing the body (7) and the heat transfer prevention body (51, 55) against the platen roll (12) before and after the thermal head (13) is provided. Adopt a thermal transfer printer.

  In order to solve the above problem, the invention according to claim 3 is the thermal transfer printer according to claim 1 or 2, wherein the heat transfer prevention body (51) is moved from the rotating body (50a) to the thermal transfer unit (I). , II, III, IV), and is discharged from the thermal transfer unit (I, II, III, IV) and then wound around another rotating body (50b). Is adopted.

  In order to solve the above-mentioned problem, the invention according to claim 4 is the thermal transfer printer according to claim 1 or 2, wherein the heat transfer prevention body (55) is an endless belt, and the endless belt is the endless belt. A thermal transfer printer is employed, which is wound around a platen roll (12) and at least one roller (50) and travels between the plates.

  Further, in order to solve the above-mentioned problem, the invention according to claim 5 is the thermal transfer printer according to claim 4, wherein the length of the endless belt (55) is thermally transferred in the rotation direction of the platen roll (12). A thermal transfer printer characterized by being longer than the length of one image to be used is adopted.

  In order to solve the above problem, an invention according to claim 6 is the thermal transfer printer according to any one of claims 1 to 5, wherein the platen roll (12) of the thermal transfer unit (I, II, III, IV) is provided. The heat transfer printer is provided with a heat quantity transmission part (54) for transmitting heat to the heat transfer prevention body before the heat transfer prevention body travels.

  In order to solve the above-mentioned problem, the invention according to claim 7 is characterized in that a plurality of thermal transfer printers according to any one of claims 1 to 6 each printing an image of a predetermined color ink are arranged in series, A multicolor thermal transfer printer, wherein an image of each color ink is overprinted while the continuous transfer target (7) travels from an upstream thermal transfer printer to a downstream thermal transfer printer.

  In order to solve the above problems, the invention according to claim 8 is directed to a thermal transfer unit (I, II, III) comprising a thermal head (13) and a platen roll (12) facing the thermal head (13). , IV) and an ink ribbon (14) provided with a predetermined color ink and sandwiched between the thermal head (13) and the platen roll (12) and the thermal head (13) generates heat, In the thermal transfer printer in which the color ink image is thermally transferred to the continuous transfer target (7), heat transfer is performed between the platen roll (12) of the thermal transfer unit and the continuous transfer target (7). The thermal transfer pre is characterized in that the prevention body (51, 55) is caused to function so that the temperature of the platen roll (12) is controlled. To adopt a data control program.

  According to the present invention, the platen roll (51, 55) is wound around the platen roll (12) of the thermal transfer unit (I, II, III, IV) and the platen roll (12) rotating together. The temperature of 12) can be controlled. That is, since the temperature of the platen roll (12) at the start of the thermal transfer can be maintained, the image density variation due to the thermally transferred ink is reduced in the image to be transferred to the continuous transfer body 7 or between the images. It became possible to maintain a stable thermal transfer image.

  High-definition halftone dot density can be kept constant even with high-definition halftone thermal transfer, and even during high-speed thermal transfer, fluctuations in image density can be reduced to keep high-definition halftone dot density constant. became.

  As described above, since the high-definition halftone dot density can be kept constant in each thermal transfer unit, after passing through the plurality of thermal transfer units I, II, III, and IV, fine and beautiful with no color unevenness and density unevenness. The image is thermally transferred.

  Moreover, when the heat-transfer prevention body (51) is used as a film, the heat-transfer prevention body (51) once used can be collected and sufficiently cooled and then used repeatedly.

1 is a schematic front view of an embodiment of a thermal transfer printer according to the present invention. It is a schematic front view of one thermal transfer unit in the thermal transfer printer. It is a schematic front view which shows the other example of one thermal transfer unit in a thermal transfer printer. It is a schematic front view which shows the other example of one thermal transfer unit in a thermal transfer printer.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

<Embodiment 1>
Details of the thermal transfer printer will be described below.

  As shown in FIG. 1, in this thermal transfer printer, a plurality of thermal transfer units I, II, III, and IV, each of which thermally transfers an image of a predetermined color ink to a continuous transfer target 7, are arranged in tandem, that is, in series. It is constituted by.

  As viewed in the direction of flow of the continuous transfer body 7 in the thermal transfer printer, a feed roll 7a for feeding the untransferred continuous transfer body 7 is installed on the upstream side, and the continuous transfer of preheated transfer is on the downstream side. A winding roll 7b for winding the body 7 is installed. The rotation shafts of the pulse motors 10 and 11 are connected to the cores of the feeding roll 7a and the winding roll 7b, respectively. The rotations of both rolls 7a and 7b are controlled by pulse motors 10 and 11 so that continuous transfer body 7 travels between both rolls 7a and 7b at a predetermined speed.

  The thermal transfer units I, II, III, and IV are indigo, red, yellow, and white between the feeding roll 7a and the take-up roll 7b from the upstream side to the downstream side of the continuous transfer body 7. They are arranged to print each color ink. Of course, the arrangement of the thermal transfer units I, II, III, and IV is not limited to the order of indigo, red, yellow, and white. Also, it is not limited to four units, it may be three units of three color printing or two units of two color printing, or additional units may be added from four units so that other color inks can be further thermally transferred. Also good.

  As shown in FIG. 2, the thermal transfer unit I for indigo color ink is provided with guide rollers 10 and 11 for detouring the continuous transfer body 7 traveling in the horizontal direction upward. Above these guide rollers 10 and 11, a platen roll 12 for running a detoured continuous transfer body 7 is disposed. Above the platen roll 12, the thermal head 13 is disposed so as to face the platen roll 12. An indigo ink ribbon 14 is disposed between the platen roll 12 and the thermal head 13.

  The platen roll 12 is a roll whose surface is covered with rubber. The platen roll 12 is directly connected to the rotating shaft of a constant speed control servo motor Ma.

  Further, nip rollers 15 and 15 for pressing the continuous transfer target 7 passing between the platen roll 12 and the thermal head 13 against the platen roll 12 before and after the thermal head 13 are provided as necessary. The continuous transfer body 7 is pressed against the surface of the platen roll 12 by the nip rollers 15 and 15, thereby preventing slippage between the continuous transfer body 7 and the platen roll 12. As a result, the image is thermally transferred more precisely and beautifully.

  Further, below the platen roll 12, when viewed in the flow direction of the continuous transfer body 7 in the thermal transfer printer, the feeding roll 50a for feeding out the heat transfer prevention body 51 on the upstream side, and the heat transfer prevention body on the downstream side. A take-up roll 50b for taking up 51 is installed. The rotation shafts of the pulse motors 10 and 11 are connected to the winding cores of the feeding roll 50a and the winding roll 50b, respectively. Or you may comprise so that it can rotate freely according to rotation of the platen roll 12, without connecting the rotating shaft of the pulse motors 10 and 11 to each winding core of the delivery roll 50a and the winding roll 50b, respectively. .

  The thermal head 13 can be pivoted up and down with the pivot 13a as a fulcrum. When the image is thermally transferred, the thermal head 13 is pivoted downward from above with the pivot 13a as a fulcrum, and the ink ribbon 14 is moved to the platen roll 12 as shown in FIG. It is designed to be pushed toward.

  The ink ribbon 14 in the indigo ink thermal transfer unit I is formed by applying indigo ink on the surface of a continuous metal foil or the like, and its feeding roll 14 a and take-up roll 14 b are composed of a platen roll 12 and a thermal head 13. Are arranged so as to be sandwiched between the upstream side and the downstream side of the continuous transfer body 7. The feeding roll 14a and the winding roll 14b of the ink ribbon 14 are controlled so that the ink ribbon 14 travels around the platen roll 12 at the same speed as the continuous transfer body 7 during the thermal transfer shown in FIG.

  When the platen roll 12 is rotated at a constant speed by the constant speed control servo motor 22, the continuous transfer target 7 is moved between the platen roll 12 and the thermal head 13 at a constant speed equal to the peripheral speed of the platen roll 12. The image of indigo color ink is thermally transferred to the surface while passing in a state where it overlaps with the image 14.

  The thermal transfer unit I for indigo color ink is configured as described above, but the thermal transfer units II, III, and IV for other color inks are also configured in the same manner. However, only the ink color of the ink ribbon 14 is different. Therefore, detailed description of the thermal transfer units II, III, and IV of other color inks is omitted.

  The constant speed control servomotors 22 that drive the platen rolls 12 of the thermal transfer units I, II, III, and IV of the above-described colors all control the control unit 17 so that the continuous transfer body 7 runs at the same constant speed. Controlled by. Specifically, the constant speed controlled servo motor 22 for driving the platen roll 12 is provided in the same number of four as the thermal transfer color number, and the other three rotation speeds are based on the desired rotation speed. Are controlled to have the same rotational speed. As a result, the continuous transfer body 7 is fed in one direction by the platen roll 12 of each color, and the image of each color is superimposed and thermally transferred onto the surface without causing a color shift.

  As described above, the continuous transfer object 7 is moved under the thermal head 13 in each unit I, II, III, IV at the same constant speed by the platen roll 12 of each color thermal transfer unit I, II, III, IV. Although it travels, if the rotational speed of the platen roll 12 is increased and the thermal transfer speed from the ink ribbon 14 to the continuous transfer body 7 is increased, the time for the platen roll 12 to rotate once is shortened and generated in the thermal head 13. The heat thus stored in the platen roll 12 makes it difficult to control the surface temperature of the platen roll 12 to a desired temperature, that is, to maintain the temperature at the start of thermal transfer.

  In order to prevent this, as shown in FIG. 2, the sheet is wound between the platen roll 12 and the continuous transfer body 7 from the upstream feeding roll 50a toward the downstream winding roll 50b. The heat transfer prevention body 51 is caused to travel.

  The heat transfer prevention body 51 has a function to prevent heat generated by the thermal head 13 from being transmitted to the platen roll 12. Accordingly, the heat transfer prevention body 51 is made of a material having a large heat capacity and hardly transferring heat, that is, a low thermal conductivity. As an example, a structure containing a large amount of air in an air layer or the like can be given. An example of a structure containing a large amount of air includes paper, a porous film, a film containing a micro void inside, and the like. Moreover, a polyethylene film is mentioned as the example. Furthermore, although the thickness of the heat transfer prevention body 51 can be set to an arbitrary thickness, as an example, it can be configured with a thickness of 10 microns or less. In this case, an example of the thickness of the ink ribbon 14 is about 4 microns, and an example of the thickness of the continuous transfer body 7 is about 50 microns.

  Moreover, the heat transfer prevention body 51 does not need to be comprised with one type of substance, and may be comprised with many types of substances. Moreover, the heat transfer prevention body 51 does not need to be comprised by one layer, and may be comprised by the multilayer. As an example, the heat transfer prevention body 51 may have a multilayer structure in which a layer close to the thermal head 13 has endothermic characteristics and a layer close to the platen roll 12 has heat insulating characteristics.

  Furthermore, the heat transfer prevention body 51 may have heat reflection characteristics. According to this configuration, the amount of heat generated by the thermal head 13 is reflected by the heat transfer prevention body 51, so that the amount of heat generated by the thermal head 13 is not transmitted to the platen roll 12, and the temperature of the platen roll 12 starts thermal transfer. The initial temperature of the time can be maintained.

  Since the surface of the platen roll 12 is made of rubber, the platen roll 12 accumulates heat by continuing the thermal transfer, and the diameter fluctuates, and the traveling speed of the continuous transfer body 7 changes accordingly. The amount of heat generated in the thermal head 13 by the prevention body 51 is not transmitted to the platen roll 12, and such inconvenience can be solved.

  Further, since it is desirable that the temperature of the platen roll 12 does not change from the start of thermal transfer, as an example, the temperature of the platen roll 12 is maintained at a temperature near the ambient temperature at the start of thermal transfer during continuous thermal transfer.

  Furthermore, the heat transfer prevention body 51 wound around the winding core of the winding roll 50b may be collected, remounted on the feeding roll 50a core, and reused. By adopting such a configuration, it is not necessary to discard the heat transfer prevention body 51, the cost can be reduced, and an environment-friendly system can be obtained. Furthermore, the heat transfer prevention body 51 can also have an endless structure (described later in FIGS. 3 and 4).

  The continuous transfer body 7 wound up as the winding roll 7b is cut into a predetermined length and used as a transfer foil.

  Also, each of the thermal transfer units I, II, III, and IV can be employed as a single thermal transfer printer that thermally transfers a single color ink.

(Modification 1)
FIG. 3 shows an endless heat transfer prevention body 55 instead of the heat transfer prevention body 51 wound toward the downstream take-up roll 50b from the upstream supply roll 50a of FIG. 12 and is configured to reciprocate around the roller 50. The characteristics such as the material of the heat transfer prevention body 55 are the same as those of the heat transfer prevention body 51.

  At the start of thermal transfer, the winding roll 7a and the feeding roll 7b of the continuous transfer body 7 are rotated by driving of the respective stepping motors 10 and 11, so that the continuous transfer body 7 is the thermal transfer units I, II, Drive in III and IV.

  Further, in each color thermal transfer unit I, II, III, IV, the platen roll 12 is rotated at a constant speed by the drive of a constant speed control type servo motor Ma, and the continuous transfer object 7 is moved from the upstream side to the downstream side. And send. At that time, the thermal head 13 presses the ink ribbon 14 against the continuous transfer body 7 on the platen roll 12, and the corresponding color ink is thermally transferred to the continuous transfer body 7 as an image.

  A part of the amount of heat generated in the thermal head 13 is stored in the heat transfer prevention body 55, but the heat stored in the heat transfer prevention body 55 is again transferred from the thermal head 13 via the roller 50 by the heat transfer prevention body 55. The heat is radiated into the air before facing the thermal head 13.

  As described above, when the thermal transfer is performed by the thermal head 13 in large quantities at high speed, the temperature of the platen roll 12 is changed from the initial temperature at which the thermal transfer is started by the heat stored in the platen roll 12 when there is no heat transfer prevention body 55. Gradually rises. Therefore, in the case of high-definition halftone thermal transfer, a large density difference occurs between halftone dots to be thermally transferred to the same density due to temperature fluctuations of the platen roll 12, and image quality deteriorates.

  However, most of the heat generated in the thermal head 13 is radiated to the ink ribbon 12 and the continuous transfer body 7 pressed between the thermal head 13 and the platen roll 12, but the ink ribbon 12 and the continuous transfer target The remaining heat that has not been radiated by the transfer body 7 is radiated by the heat transfer prevention body 55.

  Thus, before the heat transfer prevention body 55 again faces the thermal head 13 from the thermal head 13 via the roller 50, the heat conducted to the heat transfer prevention body 55 is radiated into the air. Therefore, since the temperature of the heat transfer prevention body 55 pressed between the thermal head 13 and the platen roll 12 is constant, that is, almost the ambient temperature, the temperature fluctuation does not occur in the platen roll 12, and the high-definition halftone dot Even in the case of thermal transfer, there is no difference in density between halftone dots to be thermally transferred to the same density, and a fine image is beautifully thermally transferred, and image quality is not deteriorated.

  The heat transfer prevention body 52 may intersect between the platen roll 12 and the roller 50.

(Modification 2)
Next, when the rotational speed of the platen roll 12 is increased and the thermal transfer speed from the ink ribbon 14 to the continuous transfer body 7 is increased, the time for the platen roll 12 to rotate once is shortened. A modification 2 that is another modification of the embodiment for preventing the difficulty of controlling the surface temperature to a desired temperature, that is, maintaining the temperature at the start of thermal transfer will be described.

  In the second modification, the endless heat transfer prevention body 55 described in the first modification is wound around the platen roll 12 so as to reciprocate between the roller 50 and the heat transfer prevention body 55. A temperature detector 52 as a temperature detection unit for detecting temperature, a calorimeter (not shown) for calculating the amount of heat transmitted to the heat transfer prevention body 55 based on the output of the temperature detector 52, and heat transfer prevention And a heat source 54 as a heat transfer section for transferring to the body 55. In addition, it is also possible to provide only the heat source 54 without providing the temperature detector 52 and the calorific value calculator.

  As the heat source 54, any means capable of cooling the heat transfer prevention body 55 can be used. As an example, it is possible to use a cooler by blowing cold air or blowing ambient air.

  The temperature detector 52 can be any temperature detecting means such as an infrared radiation thermometer.

  In addition, a control device such as a microcomputer having a CPU that is a central processing unit can be used as the calorific value calculator.

  As described above, the heat transfer preventing body 55 changes in temperature between the start of contact with the platen roll 12 and the end of contact due to heat generated from the thermal head 13 and heat absorption by the continuous transfer target 7 and the ink ribbon 14. To do.

  In this case, if high-definition halftone dot thermal transfer is attempted, a large density difference occurs between the halftone dots to be thermally transferred to the same density due to temperature fluctuations of the platen roll 12, and image quality deteriorates.

  Further, when high-speed thermal transfer for rotating the platen roll 12 at a high speed is required, the time for the platen roll 12 to rotate once is shortened, so that the surface temperature of the platen roll 12 rotating at high speed is controlled to a desired temperature. Becomes difficult.

  As described above, in order to reduce the fluctuation of the image density due to the thermally transferred ink and maintain the high image quality within the image or between the images thermally transferred to the continuous transfer body 7, the temperature of the platen roll 12 is transmitted. It is necessary to control with the heat prevention body 55.

  Therefore, a temperature detector 52, a calorific value calculator, and a heat source 54 are provided in the middle of the path of the heat transfer prevention body 55 that is separated from the platen roll 12 and contacts the platen roll 12 again after passing through the roller 50.

  As an example of the installation position of the temperature detector 52, the temperature detector 52 is provided in the vicinity of the roller 50 in FIG. 4.

  The temperature calculator 52 receives the temperature of the heat transfer prevention body 55 in the vicinity of the roller 50 detected by the temperature detector 52.

  The temperature at which the heat transfer prevention body 55 comes into contact with the platen roll 12 is input to the calorific value calculator as a preset set temperature. Examples of the set temperature include the temperature of the platen roll 12 of the thermal transfer units I, II, III, and IV of each color at the start of thermal transfer or the ambient temperature of the platen roll 12.

  Further, the distance from the temperature detector 52 to the platen roll 12, the heat capacity of the heat transfer prevention body 55, and the distance from the heat source 54 to the heat transfer prevention body 55 are also input to the heat quantity calculator in advance.

  Therefore, the calorific value calculator can calculate the amount of heat to be applied to the heat transfer preventing body 55 before the heat transfer preventing body 55 near the roller 50 comes into contact with the platen roll 12 again.

  The heat source 54 adds the amount of heat calculated by the heat amount calculator to the heat transfer prevention body 55, that is, cools the heat transfer prevention body 55.

  In this way, after the heat transfer prevention body 55 comes into contact with the platen roll 12, the heat generated from the thermal head 13, which varies depending on the image portion, and the heat generated by the thermal head 13 are transferred to the continuous transfer target 7 and the ink ribbon 14. Even after being exposed to the heat absorption by the heat transfer preventive body 55 before the heat transfer preventive body 55 comes into contact with the platen roll 12 again, the heat transfer preventive body 55 can always be controlled at a constant temperature.

  Further, the heat transfer prevention body 55 may intersect between the platen roll 12 and the roller 50.

  Further, since the heat source 54 can be provided at an arbitrary position around the heat transfer prevention body 55, restrictions on the installation position of the heat source 54 are reduced, and the heat source 54 can be freely installed according to the installation space of the manufacturing site. Can do.

  In addition, the calorific value calculator need only be connected to the temperature detector 52 and the heat source 54 with an electric cable, and it is not necessary to place the calorific value calculator close to the heat transfer prevention body 55. Therefore, the degree of freedom to install the calorific value calculator is great.

  Moreover, the heat transfer prevention body 55 does not need to be installed directly under the platen roll 12, and may be installed obliquely below (not shown). It is also possible to provide at least one idler roller (not shown) between the platen roll 12 and the roller 50 and freely change the position where the heat transfer prevention body 55 travels.

  Furthermore, as an example of another installation position of the temperature detector 52, the temperature detector 52 may be installed at a position immediately before the heat transfer prevention body 55 is caught in the platen roll 12.

  In this case, since the temperature detector 52 detects a temperature close to a predetermined set temperature, the amount of heat to be applied from the heat source 54 to the heat transfer prevention body 55 can be calculated more accurately. . Even if the ambient temperature changes suddenly, the temperature of the heat transfer prevention body 55 immediately before being wound around the platen roll 12 can be stably controlled.

  As described above, since the high-definition halftone dot density can be kept constant in each thermal transfer unit, after passing through the plurality of thermal transfer units I, II, III, and IV, fineness without color misregistration, color unevenness, and density unevenness. And beautiful images are thermally transferred.

  In addition, when using ambient air as it is as the heat source 54 and spraying it on the heat transfer prevention body 55, the temperature detector 52 is set at a predetermined temperature, for example, the initial temperature of the platen roll 12 without providing a calorific value calculator. It is also possible to provide a detection means (not shown) for detecting that the temperature has risen from the heat source 54 and to blow ambient air from the heat source 54 to the heat transfer prevention body 52 under the control of the detection means for detecting the temperature rise of the platen roll 12. Is possible. In this case, the amount of air blown to the heat transfer prevention body 52 can be controlled by the detection means or the heat source 54.

  Furthermore, without providing the temperature detector 52 and the calorific value calculator, it is also possible to adopt a configuration in which a gas such as ambient air is continuously blown from the heat source 54 to the heat transfer prevention body 52.

  The present invention is not limited to the melting type thermal transfer printer described above, but can also be applied to a sublimation type thermal transfer printer. In this case, the halftone density can be made constant.

  In addition, this invention is not limited to the said embodiment, A various change is possible.

I, II, III, IV ... thermal transfer unit 7 ... continuous transfer target 12 ... platen roll 13 ... thermal head 14 ... ink ribbon 15 ... nip roller 20a, 20b ... feed roller 22 ... speed controlled servo motor 23 ... motor 50 ... Rollers 51, 55 ... Heat transfer prevention body 52 ... Temperature detector 54 ... Heat source

Claims (8)

  A thermal transfer unit including a thermal head and a platen roll opposite to the thermal head is provided, and the thermal head generates heat while being sandwiched between the thermal head and the platen roll together with an ink ribbon provided with a predetermined color ink. In this way, in the thermal transfer printer in which the color ink image is thermally transferred to the continuous transfer target, the heat transfer prevention member runs between the platen roll of the thermal transfer unit and the continuous transfer target, A thermal transfer printer characterized in that the temperature of the platen roll is controlled.   2. The thermal transfer printer according to claim 1, wherein the continuous transfer target body and the heat transfer prevention body that pass between the platen roll and the thermal head are pressed against the platen roll before and after the thermal head, respectively. A thermal transfer printer characterized in that a nip roller is provided. The thermal transfer printer according to claim 1 or 2,
The thermal transfer printer, wherein the heat transfer prevention body is in a sheet form that is supplied from a rotating body to the thermal transfer unit, discharged from the thermal transfer unit, and wound around another rotating body. The thermal transfer printer according to claim 1 or 2,
The thermal transfer printer, wherein the heat transfer prevention body is an endless belt, and the endless belt runs around the platen roll and at least one roller. The thermal transfer printer according to claim 4.
The length of the endless belt is longer than the length of one image that is thermally transferred in the rotation direction of the platen roll. The thermal transfer printer according to any one of claims 1 to 5,
A thermal transfer printer, comprising: a heat quantity transfer unit for transferring heat to the heat transfer prevention body before the heat transfer prevention body travels on the platen roll of the thermal transfer unit.   7. A plurality of thermal transfer printers according to any one of claims 1 to 6, each of which prints an image of a predetermined color ink, wherein the continuous transfer object is arranged from an upstream thermal transfer printer to a downstream thermal transfer printer. A multi-color thermal transfer printer in which images of respective color inks are overprinted while traveling to the head.   A thermal transfer unit including a thermal head and a platen roll opposite to the thermal head is provided, and the thermal head generates heat while being sandwiched between the thermal head and the platen roll together with an ink ribbon provided with a predetermined color ink. Accordingly, a computer included in the thermal transfer printer in which the color ink image is thermally transferred to the continuous transfer target is provided between the platen roll of the thermal transfer unit and the continuous transfer target. A control program for a thermal transfer printer, wherein the temperature of the platen roll is controlled so as to function.

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