Patent Publication Number: US-6219078-B1

Title: Printer with preheating of sheet

Description:
This is a divisional of application Ser. No. 08/997,533 filed Dec. 23, 1997, U.S. Pat. No. 6,144,395, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printer with sheet preheating in which a thin film heat transfer toner ribbon material is heat-transferred onto a recording sheet by a thermal head or a laser. 
     2. Description of the Related Art 
     Conventionally, for example, as shown in FIG. 8, a printer  1  using a line thermal head includes as main structural members: a thermal head  3 ; a platen roller  5  which opposes a resistance heat generating body  3   a  of the thermal head  3 ; a toner ribbon  7  which is disposed between the thermal head  3  and the platen roller  5  and which is supplied from a conveying side  7   a  and is taken up onto a winding side  7   b ; a guide roller  9  which guides the toner ribbon  7 ; a pinch roller  11  and a capstan roller  13  which are provided at the downstream side of the thermal head  3  in the feeding direction of a recording sheet; and a back-up roller  15  which abuts the pinch roller  11 . 
     As shown in FIGS. 9A through 9C, in order to effect heat recording onto a recording sheet in the printer  1  structured as described above, firstly, a heat adhesive recording sheet (a recording sheet)  17  which has a heat adhesive layer  17   a  on the surface is fed (see FIG.  9 A). The toner ribbon  7  is superposed on the recording sheet  17 , and the toner ribbon  7  and the recording sheet  17  are inserted between the thermal head  3  and the platen roller  5 . Next, when a portion of the resistance heat generating body dots corresponding to an image to be printed is selectively heated, adhesive strength of the surface of the recording sheet is increased and toner adheres onto the recording sheet  17  from the toner ribbon  7  (see FIG.  9 B). Subsequently, when the toner ribbon  7  separates from the recording sheet  17  while the recording sheet  17  is conveyed, only the toner portion t adhered to the surface of the recording sheet is remained and fixed onto the recording sheet  17  (see FIG.  9 C). In this way, the image information is recorded onto an image receiving surface of the recording sheet  17 . 
     However, in the aforementioned conventional heat transfer type printer  1 , a predetermined amount of thermal energy is supplied to the toner ribbon  7  from the thermal head or laser, and the toner and the surface of the recording sheet are heated for transfer. Accordingly, the heat adhesiveness of the surface of the recording sheet is changed by environment to be used (in particular, temperature) and sensitivity (the degree of amount of transfer relative to the amount of heat to be supplied) varies. Thus, there is a drawback in that recording densities become different. 
     Namely, in the recording sheet  17  shown in FIG. 10A, a surface polymer which forms the heat adhesive layer  17   a  tends to harden at low temperature. As a result, the adhesive strength of the recording sheet  17  lowers in low-temperature environment. On the other hand, if the heat adhesive layer  17   a  is heated in advance, the adhesive strength of the recording sheet remains high even if the recording takes place several hours later. 
     Therefore, as shown in FIG. 10B, when a plurality of colors are superposed and recorded onto the recording sheet  17 , a first color  19   a  is directly recorded onto the surface of the recording sheet  17  and a second color  19   b  is superposed and recorded onto the toner of a first color  19  which has been recorded onto the recording sheet  17 . In this case, the head adhesive strength of the second color  19   b , which is heated again, is higher than that of the first color  19   a . As a result, the sensitivities become different and a drawback arises in that the recording densities become different. 
     SUMMARY OF THE INVENTION 
     The present invention was developed in light of the above circumstances, and the object thereof is to provide a printer with sheet preheating in which sensitivity does not vary due to the difference in environment and difference in the order of transfer. 
     In order to achieve the above-described object, a first aspect of the present invention is a printer with sheet preheating in which toner applied to a toner ribbon is heat-transferred onto a heat adhesive recording sheet, wherein: heating means which heats the recording sheet at a temperature within a range of predetermined temperatures before the heat transfer is provided. 
     It is preferable that said heating means is a pinch roller in which a heater is built. 
     Further, said heating means may be a heat roller provided at the upstream side of said heat transfer means in the feeding direction of the recording sheet. 
     Moreover, said heating means can be a radiation heater provided at the upstream side of said heat transfer means in the feeding direction of the recording sheet. 
     Furthermore, it is preferable that the range of predetermined temperatures is from 70° C. to 120° C. 
     Because the above-structured printer includes the heating means which heats the recording sheet at a temperature before the heat transfer, the adhesiveness of the heat adhesive recording sheet can be substantially constant regardless of the environment of circumferential temperature and the like. 
     In the printer with sheet preheating in which the pinch roller serves as heating means, it is not necessary to provide a new member independently, such that the number of parts of the device does not increase. 
     Further, in the printer with sheet preheating in which the heat roller provided at the upstream side of the heat transfer means in the feeding direction of the recording sheet serves as heating means, there is no need to convey the recording sheet reciprocally for heating. 
     Moreover, in the printer with sheet preheating in which the radiation heater provided at the upstream side of the heat transfer means at the feeding direction of the recording sheet serves as heating means, because the recording sheet is heated by radiation, the contact between the heating means and the recording sheet is prevented. 
     Furthermore, in the printer with sheet preheating which uses the heating means for heating the surface of the recording sheet at the side opposite the transferred surface thereof, the adhesion of toner to the heating means, which occurs in a case in which the heating means contacts and heats the transferred surface of the recording sheet, is prevented. 
     Still further, in the printer with sheet preheating in which the heat source and the heat roller for transferring the toner on the recording sheet to the main paper are used as heating means, there is no need to provide separate heating means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic structural view of a printer with sheet preheating relating to a first embodiment of the present invention. 
     FIG. 2 is a schematic structural view of a printer with sheet preheating relating to a second embodiment of the present invention. 
     FIG. 3 is a schematic structural view of a printer with sheet preheating relating to a third embodiment of the present invention. 
     FIG. 4 is a schematic structural view of a printer with sheet preheating relating to a fourth embodiment of the resent invention. 
     FIG. 5 is a schematic structural view of a printer with sheet preheating relating to a fifth embodiment of the present invention. 
     FIG. 6 is a schematic structural view of a printer with sheet preheating relating to a sixth embodiment of the present invention. 
     FIG. 7 is a schematic structural view of a printer with sheet preheating relating to a seventh embodiment of the present invention. 
     FIG. 8 a schematic structural view of a conventional printer. 
     FIG. 9A is an explanatory view which shows a process for heat transfer using a heat transfer toner ribbon. 
     FIG. 9B is an explanatory view which shows a process for heat transfer using a heat transfer toner ribbon. 
     FIG. 9C is an explanatory view which shows a process for heat transfer using a heat transfer toner ribbon. 
     FIG. 10A is an explanatory view of a case in which toners are superposed and recorded onto a recording sheet. 
     FIG. 10B is an explanatory view of a case in which toners are superposed Ad recorded onto a recording sheet. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A printer with sheet preheating relating to the preferred embodiments of the present invention will be explained in detail hereinafter with reference to the drawings. 
     FIG. 1 is a schematic structural view of a printer with sheet preheating of sheet relating to a first embodiment of the present invention. 
     A heat transfer color printer (e.g., a line thermal printer)  21  serving as a printer with sheet preheating includes as main structural members: a thermal head  23  serving as heat transfer means; a platen roller  25  which opposes a resistance heat generating body  23   a  of the thermal head  23 ; a toner ribbon  27  which is disposed between the thermal head  23  and the platen roller  25  and which is supplied from a conveying side  27   a  and is taken up onto a winding side  27   b ; a guide roller  29  which guides the toner ribbon  27 ; a pinch roller  31  and a capstan roller  33  which are provided at the downstream side of the thermal head  23  in the feeding direction of a recording sheet; and a back-up roller  35  which abuts the pinch roller  31 . 
     For example, a halogen heater  37 , which is elongated in the axial direction of the pinch roller  31 , is built in the center of the pinch roller  31 . The halogen heater  37  is connected to an unillustrated power supply line and generates heat at predetermined temperature. A silicon rubber  39  is formed in the cylindrical shape at the outer circumference of the halogen heater  37 , and the outer circumference of the silicon rubber  39  closely contacts the capstan roller  33 . Namely, the pinch roller  31  forms heating means in which the halogen heater  37  serves as a heat source, and a predetermined amount of heat can be supplied to a recording sheet  41  which is inserted between the pinch roller  31  and the capstan roller  33 . 
     The operation of the heat transfer color printer  21  structured as described above will be explained. 
     In advance of the heat recording by the thermal head  23 , firstly, the recording sheet  41  is fed from the right-hand side in FIG.  1  and is conveyed in the left direction in FIG. 1 until the proximal end of the recording sheet  41  reaches the pinch roller  31 . In this way, the recording sheet  41  is heated by the high-temperature pinch roller  31  which has been heated by the halogen heater  37  serving as a heat source. 
     Next, when the proximal end of the recording sheet  41  reaches the pinch roller  31 , the capstan roller  33  is reversely rotated and the recording sheet  41  is rewound in the right direction in FIG.  1 . In this way, the recording sheet  41  is heated again by the pinch roller  31  and is raised to predetermined temperature. 
     When the distal end of the recording sheet  41  returns to the position of the capstan roller  33 , the capstan roller  33  is switched to the normal rotation and printing is started by the thermal head  23 . 
     The printing by the thermal head  23  is effected in the same manner as the conventional printing. The toner ribbon  27  is superposed on the recording sheet  41  and the toner ribbon  27  and the recording sheet  41  are inserted between the thermal head  23  and the platen roller  25 . A portion of the resistance heat generating body dots corresponding to an image to be printed is selectively heated. In this way, the toner applied to the toner ribbon  27  and the recording sheet  41  are heated for transfer. 
     At this time, the recording sheet  41  reaches predetermined temperature by the pinch roller  31  serving as heating means and the heat adhesiveness of the surface of the recording sheet is stabilized. 
     Further, in a case in which a plurality of colors is superposed and recorded onto the recording sheet  41 , since the recording sheet  41  is heated at predetermined temperature, the heat adhesiveness of the surface of the recording sheet becomes high. In this way, the heat adhesiveness of a first color which is directly recorded onto the surface of the recording sheet  41  and that of a second color which is superposed and recorded onto the toner of a first color, which has already been recorded onto the recording sheet  41 , are the same. Thus, the recording can be carried out at the same sensitivity. 
     In this way, in accordance with the aforementioned heat transfer color printer  21 , the pinch roller  31  serves as heating means, the recording sheet  41  is heated before the heat recording by the thermal head  23 , and heat recording is effected on the recording sheet  41  which has been heated at predetermined temperature. Therefore, the variation in sensitivities due to the difference in environment to be used and difference in the order of transfer can be reduced, and the difference in recording densities can be minimized. 
     Further, in accordance with the heat transfer color printer  21 , because the halogen heater  37  is built in the pinch roller  31 , the recording sheet  41  can be heated without increasing the number of parts of the device. 
     Moreover, in this embodiment, since the heating can take place twice as the recording sheet  41  moves reciprocally, the temperature of the halogen heater  37  can be set low. 
     In addition to the aforementioned procedure of heating the recording sheet  41  in the heat transfer color printer  21 , it is possible that the recording sheet  41  is fed, for example, from the left-hand side in FIG.  1  and is conveyed in the right direction in FIG.  1 . When the left end of the recording sheet  41  reaches the position of the capstan roller  33 , the capstan roller  33  is stopped, and thereafter, the feeding direction of the recording sheet  41  is changed to the left in FIG.  1  and printing is started. In this procedure, the number of conveyances can be reduced at the time of heating of the recording sheet  41 . 
     Next, a heat transfer color printer with preheating of sheet relating to a second embodiment of the present invention will be explained. FIG. 2 is a schematic structural view of a printer with sheet preheating relating to the second embodiment of the present invention. Members which are the same as those shown in FIG. 1 are denoted by the same reference numerals, and repetitive descriptions thereof are omitted. 
     A heat transfer color printer  51  uses an ordinary pinch roller  53  in which the aforementioned halogen heater  37  is not built. 
     A roller  55 , which rotates around a rotational shaft in a direction which is the reverse of that of the pinch roller  53 , and a heat roller  57 , which rotates around a rotational shaft parallel to that of the roller  55 , are provided at the upstream side of the thermal head  23  in the feeding direction of a recording sheet. As the rotational shaft of the heat roller  57  is moved in parallel by an unillustrated raising and lowering mechanism, the heat roller  57  is movable from the upper side in FIG. 2 in the directions of moving close to and away from the roller  55 . For example, a halogen heater  37 , which is elongated in the axial direction of the heat roller  57 , is provided at the center of the h eat roller  57 . The halogen heater  37  is connected to an unillustrated power supply line and generates heat at predetermined temperature. For example, a silicon rubber  39  is formed in the cylindrical shape at the outer circumference of the halogen heater  37 . Namely, the heat roller  57  forms heating means in which the halogen heater  37  serves as a heat source, and a predetermined amount of heat can be supplied to a recording sheet  41  which is inserted between the roller  55  and the heat roller  57 . The other structures are the same as those in the aforementioned heat transfer color printer  21 . 
     In the heat transfer color printer  51  structured as described above, the recording sheet  41  is fed from the right-hand side in FIG.  2 . In advance of the heat re cording by the thermal head  23 , the recording sheet  41  contacts the high-temperature heat roller  57  which has been heated by the halogen heater  37  serving as a heat source. The recording sheet  41  is thereby heated. 
     Next, when the distal end of the recording sheet  41  reaches the position of the pinch roller  53 , printing is started by the thermal head  23 . 
     When the printing progresses and the proximal end of the recording sheet  41  passes between the heat roller  57  and the roller  55 , the heat roller  57  is raised several millimeters (mm) from the roller  55  by the unillustrated raising and lowering mechanism and separated from the roller  55 . 
     In accordance with the heat transfer color printer  51 , heat recording can be effected on the recording sheet  41  which has been heated at predetermined temperature in the same way as the aforementioned heat transfer color printer  21 . Therefore, the variation in sensitivities due to the difference in environment to be used and the difference in order of transfer can be reduced, and the difference in recording densities can be minimized. Additionally, because the heat roller  57  is provided in the feeding direction upstream side of the recording sheet  41 , the recording sheet  41  need not be conveyed reciprocally for heating and the recording sheet  41  can be heated while the ordinary feeding operation is effected. The time required for heating can be reduced compared to the case of the first embodiment. 
     Next, a heat transfer color printer with sheet preheating relating to a third embodiment of the present invention will be explained. FIG. 3 is a schematic structural view of a printer with sheet preheating relating to the third embodiment of the present invention. Members which are the same as those shown in FIG. 1 are denoted by the same reference numerals, and repetitive descriptions thereof are omitted. 
     A heat transfer color printer  61  uses an ordinary pinch roller  53  in which the aforementioned halogen heater  37  is not built. 
     A radiation heater (a halogen heater)  37  is provided at the right-hand side of a thermal head  23  in FIG. 3 so as to oppose the recording surface of a recording sheet  41 . A heat reflector  63  is provided on the opposite side of the halogen heater  37  with respect to the recording sheet  41 . The heat reflector  63  can efficiently supply the heat of the halogen heater  37  to the recording sheet  41  by radiation. The other structures are the same as those of the aforementioned heat transfer color printer  21 . 
     In the heat transfer color printer  61  structured as described above, the recording sheet  41  is fed from the right-hand side in FIG.  3 . In advance of the heat recording by the thermal head  23 , the recording sheet  41  is heated at predetermined temperature by the radiation from the halogen heater  37 . 
     When the distal end of the recording sheet  41  reaches the position of a capstan roller  53 , printing is started by the thermal head  23 . When the proximal end of the recording sheet  41  passes the halogen heater  37 , the power supply to the halogen heater  37  is stopped. 
     In accordance with the heat transfer color printer  61 , heat recording can be effected on the recording sheet  41  which has been heated at predetermined temperature in the same way as the aforementioned heat transfer color printer  21 . Therefore, the variation in sensitivities due to the difference in environment to be used and order of transfer can be reduced, and the difference in recording densities can be minimized. Similarly to the heat transfer color printer  51 , the recording sheet  41  can be heated without being conveyed reversely and the time required for heat recording can be reduced. Additionally, since the recording sheet  41  is heated by the radiation from the halogen heater  37 , damages, contaminates, and the like to the recording sheet  41  due to the contact with the roller and the like can be prevented. 
     Next, a heat transfer color printer with sheet preheating relating to a fourth embodiment of the present invention will be explained. FIG. 4 is a schematic structural view of a printer with sheet preheating of sheet relating to the fourth embodiment of the present invention. Members which are the same as those shown in FIG. 1 are denoted by the same reference numerals, and repetitive descriptions thereof are omitted. 
     A heat transfer color printer  71  uses an ordinary pinch roller  53  in which the aforementioned halogen heater  37  is not built. 
     A radiation heater (a halogen heater)  37  is provided so as to oppose a capstan roller  33 . A heat reflector  63  is provided on the opposite side of the halogen heater  37  with respect to the recording sheet  41 . The heat reflector  63  can efficiently supply the heat of the halogen heater  37  to the capstan roller  33  by radiation. The other structures are the same as those of the aforementioned heat transfer color printer  21 . 
     In the heat transfer color printer  71  structured as described above, as in the same manner as the heat transfer color printer  21 , the recording sheet  41  is fed from the right-hand side in FIG. 4 in advance of the heat recording by the thermal head  23 . The recording sheet  41  is conveyed in the left direction in FIG. 4 until the proximal end of the recording sheet  41  reaches the pinch roller  53 . In this way, the surface (reverse surface) of the recording sheet  41  at the side opposite the heat-transferred surface thereof is heated by the high-temperature capstan roller  33  which has been heated by the halogen heater  37  serving as a heat source. Thereafter, in the same manner as the heat transfer color printer  21 , the capstan roller  33  is reversely rotated and the recording sheet  41  is rewound in the right direction in FIG.  4 . Then, the capstan roller  33  is again switched to the normal rotation and printing is started by the thermal head  23 . 
     In accordance with the heat transfer color printer  71 , heat recording can be effected on the recording sheet  41  which has been heated at predetermined temperature in the same way as the aforementioned heat transfer color printer  21 . Therefore, the variation in sensitivities due to the difference in environment to be used and the difference in order of transfer can be reduced, and the difference in recording densities can be minimized. Additionally, because the reverse surface of the recording sheet  41  is heated, the adhesion of image receiving material (toner), which occurs when the heat roller contacts and heats the transferred surface of the recording sheet, to the heat roller can be prevented. 
     Next, a heat transfer color printer with sheet preheating relating to a fifth embodiment of the present invention will be explained. FIG. 5 is a schematic structural view of a printer with sheet preheating relating to the fifth embodiment of the present invention. Members which are the same as those shown in FIG. 1 are denoted by the same reference numerals, and repetitive descriptions thereof are omitted. 
     A heat transfer color printer  81  uses an ordinary pinch roller  53  in which the aforementioned halogen heater  37  is not built. 
     A heat roller  83 , which rotates around a rotational shaft in the direction which is the reverse of that of the pinch roller  53 , is provided at the upstream side of a thermal head  23  in the feeding direction of a recording sheet. A halogen heater  37 , which is elongated in the axial direction of the heat roller  83 , is provided at the center of the heat roller  83 . The halogen heater  37  is connected to an unillustrated power supply line and generates heat at predetermined temperature. For example, a silicon rubber  39  is formed in the cylindrical shape at the outer circumference of the halogen heater  37 . Namely, the heat roller  83  forms heating means in which the halogen heater  37  serves as a heat source and, as the heat roller  83  contacts the reverse surface of a recording sheet  41 , a predetermined amount of heat can be supplied to the recording sheet  41 . The other structures are the same as those in the aforementioned heat transfer color printer  21 . 
     In the heat transfer color printer  81  structured as described above, the recording sheet  41  is fed from the right-hand side in FIG.  5 . In advance of the heat recording by the thermal head  23 , the reverse surface of the recording sheet  41  contacts the high-temperature heat roller  83  which has been heated by the halogen heater  37  serving as a heat source. The recording sheet  41  is thereby heated. 
     Next, when the distal end of the recording sheet  41  reaches the position of the capstan roller  33 , printing is started by the thermal head  23 . 
     In accordance with the heat transfer color printer  81 , heat recording can be effected on the recording sheet  41  which has been heated at predetermined temperature. Therefore, the variation in sensitivities due to the difference in environment to be used and order of transfer can be reduced, and the difference in recording densities can be minimized. Similarly to the heat transfer color printers  51  and  61 , the time required for heat recording can be reduced. Additionally, since the reverse surface of the recording sheet  41  is heated, the adhesion of toner to the heat roller  83  can be prevented. Further, since the heat roller  83  is provided independently, the pinch roller  53  which contacts the surface of the recording sheet  41  is not heated indirectly as in the case of the heat transfer color printer  71 . Moreover, because the recording sheet  41  can contact the heat roller  83  at a certain winding angle, the recording sheet  41  can be heated sufficiently even at high conveying speed. 
     Next, a heat transfer color printer with sheet preheating relating to a sixth embodiment of the present invention will be explained. FIG. 6 is a schematic structural view of a printer with sheet preheating relating to the sixth embodiment of the present invention. Members which are the same as those shown in FIG. 1 are denoted by the same reference numerals, and repetitive descriptions thereof are omitted. 
     A heat transfer color printer  91  uses an ordinary pinch roller  53  in which the aforementioned halogen heater  37  is not built. 
     A laminater  95 , which transfers toner on a recording sheet  41  to a main paper  93 , is provided at the upstream side of the thermal head  23  in the feeding direction of the recording sheet. The laminater  95  is formed by a pair of heat rollers  97   a ,  97   b . The heat rollers  97   a ,  97   b  rotate around a rotational shaft in the direction which is the same as that of the pinch roller  53  and capstan roller  33  while the outer circumferences of the heat rollers  97   a ,  97   b  contact with each other. For example, a halogen heater  37 , which is elongated in the axial direction of each of the heat rollers  97   a ,  97   b , is provided at the center of each of the heat rollers  97   a ,  97   b . The halogen heater  37  is connected to an unillustrated power supply line and generates heat at predetermined temperature. For example, a silicon rubber  39  is formed in the cylindrical shape at the outer circumference of the halogen heater  37 . Namely, the heat rollers  97   a ,  97   b  form heating means in which the halogen heater  37  serves as a heat source, and a predetermined amount of heat can be supplied to the recording sheet  41  and the main paper  93  which are superposed and inserted between the heat rollers  97   a ,  97   b . Thereby, toner on the recording sheet  41  is transferred to the main paper  93 . The other structures are the same as those in the aforementioned heat transfer color printer  21 . 
     In the heat transfer color printer  91  structured as described above, the recording sheet  41  is fed from the right-hand side in FIG.  6 . In advance of the heat recording by the thermal head  23 , the reverse surface of the recording sheet  41  contacts the high-temperature heat roller  97   a  which has been heated by the halogen heater  37  serving as a heat source. The recording sheet  41  is thereby heated. 
     Next, when the distal end of the recording sheet  41  reaches the position of the capstan roller  33 , printing is started by the thermal head  23 . 
     The distal end of the printed recording sheet  41  is returned to the position at which the heat rollers  97   a ,  97   b  pressing-contact and rotate. The recording sheet  41  and the main paper  93  are superposed and inserted between the heat rollers  97   a ,  97   b  from the distal end sides of the recording sheet  41  and the main paper  93 . The toner is thereby transferred on the main paper  93 . 
     In accordance with the heat transfer color printer  91 , heat transfer recording can be effected on the recording sheet  41  which has been heated at a predetermined temperature. Therefore, the variation in sensitivities due to the difference in environment to be used and the difference in order of transfer can be reduced, and the difference in recording densities can be minimized. Additionally, because the recording sheet  41  is heated by the heat roller  97   a  of the laminater  95  provided at the feeding direction upstream side of the recording sheet  41 , the time required for heat recording can be reduced similarly to the heat transfer color printers  51 ,  61 ,  81 . Additionally, since the reverse surface of the recording sheet  41  is heated, the adhesion of toner to the heat roller  97   a  can be prevented. Further, since the heat roller  97   a  which does not contact the pinch roller  53  is used, the pinch roller  53  which contacts the surface of the recording sheet  41  is not heated indirectly. Moreover, because the recording sheet  41  can contact the heat roller  97   a  at a certain winding angle, the recording sheet  41  can be heated sufficiently even at high conveying speed. Furthermore, because the heat roller  97   a  of the laminater  95  can be used, the recording sheet  41  can be preheated without providing new heating means in the heat transfer color printer having the laminater  95 . 
     Next, a heat transfer color printer with sheet preheating relating to a seventh embodiment of the present invention will be explained. FIG. 7 is a schematic structural view of a printer with sheet preheating relating to the seventh embodiment of the present invention. Members which are the same as those shown in FIG. 1 are denoted by the same reference numerals, and repetitive descriptions thereof are omitted. 
     A heat transfer color printer  101  uses an ordinary pinch roller  53  in which the aforementioned halogen heater  37  is not built. 
     In the same way as the heat transfer color printer  91 , a laminater  95 , which transfers toner on a recording sheet  41  to a main paper  93 , is provided at the upstream side of a thermal head  23  in the feeding direction of the recording sheet. A metal roller  103  for heating (hereinafter, “heating metal roller  103 ”), which rotates around a rotational shaft in the direction which is the reverse of that of a heat roller  97   a , contacts the heat roller  97   a  of the laminater  95 . The other structures are the same as those in the aforementioned heat transfer color printer  21 . 
     In the heat transfer color printer  101  structured as described above, the recording sheet  41  is fed from the right-hand side in FIG.  7 . In advance of the heat recording by the thermal head  23 , the reverse surface of the recording sheet  41  contacts the high-temperature heating metal roller  103  which has been heated by contacting the heat roller  97   a . The recording sheet  41  is thereby heated. 
     Next, when the distal end of the recording sheet  41  reaches the position of a capstan roller  33 , printing is started by the thermal head  23 . 
     Since the heating metal roller  103  is used in the heat transfer color printer  101 , the recording sheet  41  conveyed to the thermal head  23  side can be preheated due to the rotation of the laminater  95  at the time in which a main paper  93  and the recording sheet  41  are passed between the laminater  95 . Namely, one recording sheet  41   a  can be preheated at the same time that the toner on another recording sheet  41   b  is transferred to the main paper  93 . 
     In accordance with the heat transfer color printer  101 , heat transfer recording can be effected on the recording sheet  41  which has been heated at predetermined temperature. Therefore, the variation in sensitivities due to the difference in environment to be used and the difference in order of transfer can be reduced, and the difference in recording densities can be minimized. Additionally, because the recording sheet  41  is heated by the heating metal roller  103  provided at the feeding direction upstream side of the recording sheet  41 , the time required for heat recording can be reduced similarly to the heat transfer color printers  51 ,  61 ,  81 ,  91 . Additionally, since the reverse surface of the recording sheet  41  is heated, the adhesion of toner to the heating metal roller  103  can be prevented. Further, since the heating metal roller  103  which does not contact the pinch roller  53  is used, the pinch roller  53  which contacts the surface of the recording sheet  41  is not heated indirectly. Moreover, because the recording sheet  41  can contact the heat metal roller  103  at a certain winding angle, the recording sheet  41  can be heated sufficiently even at high conveying speed. Furthermore, because the laminater  95  can be used, the recording sheet  41  is preheated without providing new heating means in the heat transfer color printer having the laminater  95 . Still further, since the heating metal roller  103  is provided, the one recording sheet  41   a  can be preheated at the same time that the toner on the other recording sheet  41   b  is transferred to the main paper  93 . Thus, the productivity is increased. 
     EXAMPLES 
     Heat recording was actually carried out by a heat transfer color printer having a conventional structure (a structure having no heating means) and the aforementioned heat transfer color printers  21 ,  51 ,  61 ,  71 ,  81 ,  91 ,  101  corresponding to structural examples 1, 2, 3, 4, 5, 6, 7. The results of comparison of densities are shown in Table 1. 
     A thermal head  23  having 300 dpi (a heater size main direction 75 m, a heater size sub direction 80 μm) was used. Under the conditions of electric power of 80 mW, strobing of 3 ms, cycle of 12.6 ms, paper conveying speed of 12.5 mm/s, Color of M (Magenta) of Proof Ribbon J of Digital Color Proofer First Proof manufactured by Fuji Photo Film Co., Ltd. was recorded onto a receiver sheet A3W. A dot percentage recorded in this way was measured by a densitometer X-Rite 938 sold by Nippon Lithograph, Inc. 
     The measurement was carried out in a case in which the other color is not recorded at all and in a case in which 100% of Color C was printed before the printing of Color M. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Temperature 
                   
                   
               
               
                   
                 Temper- 
                 of heated 
                   
                   
               
               
                   
                 ature 
                 portion on 
                 Dot % 
                 Dot % 
               
               
                 Measuring 
                 Environ- 
                 recording 
                 (first 
                 (on  
               
               
                 object 
                 ment 
                 sheet 
                 color) 
                 Color C) 
               
               
                   
               
             
            
               
                 Conventional 
                 23° C. 
                 25° C. 
                 40% 
                 45% 
               
               
                 structure 
                 10° C. 
                 13° C. 
                 25% 
                 35% 
               
               
                 Structural 
                 23° C. 
                 95° C. 
                 45% 
                 45% 
               
               
                 Example 1 
                 10° C. 
                 95° C. 
                 40% 
                 40% 
               
               
                 Structural 
                 23° C. 
                 60° C. 
                 42% 
                 45% 
               
               
                 Example 2 
                 10° C. 
                 60° C. 
                 28% 
                 36% 
               
               
                   
                 23° C. 
                 80° C. 
                 45% 
                 45% 
               
               
                   
                 10° C. 
                 80° C. 
                 40% 
                 40% 
               
               
                   
                 23° C. 
                 95° C. 
                 45% 
                 45% 
               
               
                   
                 10° C. 
                 95° C. 
                 40% 
                 40% 
               
               
                 Structural 
                 23° C. 
                 120° C. 
                 45% 
                 45% 
               
               
                 Example 3 
                 10° C. 
                 120° C. 
                 40% 
                 40% 
               
            
           
           
               
               
               
               
            
               
                 Structural 
                 23° C. 
                 140° C. 
                 cannot be conveyed 
               
               
                 Example 4 
                 10° C. 
                 140° C. 
                 due to adhesion 
               
            
           
           
               
               
               
               
               
            
               
                 Structural 
                 23° C. 
                 95° C. 
                 45% 
                 45% 
               
               
                 Example 5 
                 10° C. 
                 95° C. 
                 40% 
                 40% 
               
               
                 Structural 
                 23° C. 
                 95° C. 
                 45% 
                 45% 
               
               
                 Example 6 
                 10° C. 
                 95° C. 
                 40% 
                 40% 
               
               
                 Structural 
                 23° C. 
                 95° C. 
                 45% 
                 45% 
               
               
                 Example 7 
                 10° C. 
                 95° C. 
                 40% 
                 40% 
               
               
                   
               
            
           
         
       
     
     As can be seen from Table 1, in Structural Example 1, both the difference in dot % due to the temperature environment and the difference between the case in which Color M is the first color and the case in which Color M is printed on Color C were able to be reduced as compared to the conventional structure by setting the temperature of the heated portion on the recording sheet from 60° C. or more to 140° C. or less. Further, in any of Structural Examples 2, 3, 4, 5, 6, 7, the differences were able to be reduced in common at a substantially intermediate value (95° C.) of the aforementioned temperature range. 
     Further, in Structural Examples 1, 2, 3, 4, 5, 6, 7, the defects such as a mark with a conveying roller and a mark with a fingerprint copied onto the recording sheet were able to be decreased. 
     In the aforementioned embodiments, an example is described of a case in which the printer of the present invention was applied to a line thermal printer. However, the printer of the present invention having the same recording material structure can be applied in the same way to a printer in which a serial thermal head undergoes recording and peeling and to a printer in which a heat mode laser undergoes heat recording, pealing, and developing. 
     As described in detail hereinbefore, in accordance with a printer with sheet preheating relating to the present invention, since the heating means is provided which heats the recording sheet at temperature within predetermined temperatures before the heat transfer, the heat adhesiveness of the recording sheet can be substantially constant regardless of the environment of circumferential temperature, the variation in sensitivities due to the difference in environment to be used and the difference in the order of transfer can be reduced, and the difference in recording densities can be minimized. 
     In the printer with preheating of sheet in which the pinch roller serves as heating means, the recording sheet can be heated without increasing the number of parts of the device. 
     Further, in the printer with preheating of sheet in which the heat roller provided at the upstream side of the heat transfer means in the feeding direction of the recording sheet serves as heating means, the recording sheet need not be conveyed reciprocally for heating, the heating can be effected while the ordinary feeding operation is carried out, and the time required for heat recording can be minimized. 
     Moreover, in the printer with preheating of sheet in which the radiation heater provided at the upstream side of the heat transfer means in the feeding direction of the recording sheet serves as heating means, because the recording sheet is heated by radiation, the damages, contaminates, and the like onto the recording sheet due to the contact with the roller and the like can be prevented. 
     Furthermore, in the printer with preheating of sheet which uses heating means for heating the surface of the recording sheet at the side opposite the transferred surface thereof, the adhesion of toner to the heating means, which occurs in a case in which the heating means contacts and heats the transferred surface of the recording sheet, can be prevented. 
     Still further, in the printer with preheating of sheet in which the heat source and the heat roller for transferring the toner on the recording sheet to the main paper are used as heating means, the recording sheet can be preheated without providing separate heating means.