Abstract:
A thermal activating device has an activation heating apparatus for heating and activating a heat sensitive adhesive on a thermal activator layer of a thermal activation sheet. A pressing device presses the thermal activation sheet into pressure contact with the activation heating apparatus to heat and activate the heat sensitive adhesive on the thermal activator layer of the thermal activation sheet. A detector detects the presence of the thermal activation sheet at a predetermined position along its path of travel. A pressure releasing device releases the pressure contact between the thermal activation sheet and the activation heating apparatus when the detector does not detect the presence of the thermal activation sheet at the predetermined position.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a thermal activating device of a thermal activation sheet with a thermal activator layer for developing color and adhesion by heating formed on at least one surface thereof and a printer by using the thermal activating device, and more particularly to a technique of preventing a heat sensitive adhesive and a metamorphic material of the heat sensitive adhesive from attaching to the thermal activation sheet. 
   2. Description of the Related Art 
   Recently, as one kind of liner-less label, a thermal activation sheet (for example, heat sensitive adhesive label) is in a widespread use in various fields of, for example, a POS label of the foods, logistical and delivery label, label for medical care, baggage tag, display label for bottles and cans, and the like. The heat sensitive adhesive label is designed by forming a heat sensitive adhesive layer for developing the adhesion by heating, although it does not exhibit the adhesion at usual, on the back surface of a sheet-shaped label substrate (for example, base paper) and forming a printable surface on the front surface thereof. The heat sensitive adhesive mainly made from thermoplastic resin, solid elasticizer, and the like and it has a characteristic of developing the adhesion, activated through the heating by the thermal activating device, although it is non-adhesive at room temperature. Usually, the activation temperature is 50 to 150° C., and in this temperature range, a solid elasticizer within the heat sensitive adhesive is melted and the adhesion is added to the thermoplastic resin. Since the melted solid elasticizer is gradually crystallized after a supercooled state, the state of adhesion can last for predetermined hour and while maintaining this state of adhesion, the label is adhered to an object such as a glass bottle. 
   The printable surface of the heat sensitive adhesive label is formed by, for example, a heat sensitive coloring layer, and a desired letter, image and the like is printed on the printable surface by a thermal printer having a general thermal head, and after the printing, the heat sensitive adhesive layer is activated by the thermal activating device. 
   A printer is being developed in which the thermal activating device is installed in the thermal printer so as to continuously perform the thermal printing on a heat sensitive adhesive label and the activation of a heat sensitive adhesive layer. 
   This printer has the structure, for example, as illustrated in FIG.  11 . 
   In  FIG. 11 , the reference mark P 2  indicates a thermal printer unit, the reference mark C 2  indicates a cutter unit, the reference mark A 2  indicates a thermal activating unit, and the reference mark R indicates a heat sensitive adhesive label reeled like a roll. 
   The thermal printer unit P 2  comprises a printing thermal head  100 , a platen roller  101  which is pushed toward the printing thermal head  100 , and a driving system (for example, a driving motor, a gear series, and the like), not illustrated, for rotating the platen roller  101 . By rotating the platen roller  101  in the direction of D 1  (clockwise) in  FIG. 11 , the heat sensitive adhesive label R is drawn out, and after printing in a thermal method on the heat sensitive adhesive label R drawn out, the label is forwarded in the direction of D 2  (in the right direction). The platen roller  101  has pressing means (for example, a coil spring, a flat spring, and the like) not illustrated, and the elastic force is adopted to push the surface of the platen roller  101  to the thermal head  100 , serving as the pressuring means of the heat sensitive adhesive label R. The heat sensitive adhesive label R has the structure, for example, as illustrated in FIG.  12 . Namely, a thermal coat layer  501  as a heat sensitive coloring layer for forming the printable surface is provided on one surface of the base paper  500  (front surface in  FIG. 12 ) as a label substrate, and on the above layer, a color printing layer  502 , for example, with a frame of the price, characters of the unit and the like, pattern, and the like printed there, is formed. A thermal activator layer K, with the heat sensitive adhesive, mainly made from the thermoplastic resin, the solid elasticizer, and the like, applied thereto, is formed on the other surface of the base paper  500  (the back surface in FIG.  12 ). 
   The printer unit P 2  of  FIG. 11  can perform a desired printing on the thermal coat layer  501  of the heat sensitive adhesive label R by operating the printing thermal head  100  and the platen roller  101 , according to a printing signal from a printing controller, not illustrated. 
   The function of the cutter unit C 2  is to cut the heat sensitive adhesive label R that has been heat-sensitively printed by the thermal printer unit P 2 , by a proper length, and it is formed by a movable blade  200 , a fixed blade  201 , and the like operated by a driving source (not illustrated) of the electric motor and the like. The movable blade  200  is operated at a predetermined timing, according to a control of the controller, not illustrated. 
   The thermal activating unit A 2  is provided with a loading roller  300  and a discharging roller  301  for inserting and discharging the cut heat sensitive adhesive label R, which are rotated, for example, by the driving source not illustrated, and a thermal head  400  for thermal activation and a platen roller  401  pushed toward the thermal head  400  for thermal activation are arranged between the loading roller  300  and the discharging roller  301 . The platen roller  401  has a driving system (for example, an electric motor, a gear series, and the like) not illustrated, so as to rotate the platen roller  401  in the direction of D 4  (clockwise direction in  FIG. 11 ) and forward the heat sensitive adhesive label R in the direction of D 6  (in the right direction in  FIG. 11 ) by the loading roller  300  and the discharging roller  301  rotating respectively in the direction of D 3  and in the direction of D 5 . Further, the platen roller  401  has the pressing means (for example, a coil spring, a flat spring, and the like) not illustrated, and this elastic force is adopted to push the surface of the platen roller  401  toward the thermal head  400  for thermal activation with the pressure F. 
   That one indicated by the reference mark S is a discharge detecting sensor for detecting the discharge of the heat sensitive adhesive label R. According to the detection of the discharge of the heat sensitive adhesive label R by the discharge detecting sensor S, the next heat sensitive adhesive label R is printed, forwarded, and activated. The thermal head  400  for thermal activation and the platen roller  401  are operated at a predetermined timing by a controller not illustrated, the thermal activator layer K of the heat sensitive adhesive label R is activated by the heat given by the thermal head  400  for thermal activation, thereby developing the adhesion. 
   After the adhesion of the heat sensitive adhesive label R has been developed by thus constituted thermal printer unit P 2 , the display label, the price tag, and the advertisement label are stuck to a glass bottle, a plastic bottle, and the like including alcohol, chemicals, and the like. Accordingly, since a separate sheet (liner) such as a conventional general adhesive label sheet is not necessary, it is effective in reducing the cost, and since any separate sheet that will become wastes after use is not required, there is a merit from a viewpoint of the environmental concerns and resource saving. 
   In the conventional thermal activating unit A 2  of the heat sensitive adhesive label R, however, there is a problem such that a heat sensitive adhesive and a metamorphic material of the heat sensitive adhesive (chemically metamorphosed or carbonized material by heat) are attached to the forwarding means (especially, the platen roller  401 ) of the heat sensitive adhesive label R and the thermal head  400 . 
   Namely, since the platen roller  401  is always in a state of being pushed toward the thermal head  400  by the pressure F, when the heat sensitive adhesive label R is removed from the platen roller  401  after a heater element H of the thermal head  400  for thermal activation has heated and activated the thermal activator layer K of the heat sensitive adhesive label R cut by the cutter unit C 2  by a predetermined length, some of the heat sensitive adhesive of the thermal activator layer K is softened by the heating and squeezed out from the space between the platen roller  401  and the thermal head  400  for thermal activation by the pressure F, into a state of being separated from the base paper  500  of the heat sensitive adhesive label R, as illustrated in FIG.  13 ( a ). 
   The heat sensitive adhesive label R is discharged, with the platen roller  401  once in an idle running state, and the heat sensitive adhesive G 1  separated as shown in FIG.  13 ( a ) comes into a state of sticking around the surface of the platen roller  401  by the adhesion generated by activation, as illustrated in FIG.  13 ( b ). 
   By repeating the states as shown in FIGS.  13 ( a ) and ( b ) several times, it turns into a state of sticking a lot of grained heat sensitive adhesives G 1  to the surface of the platen roller  401 , as illustrated in FIG.  13 ( c ). There may occur the case where the stuck heat sensitive adhesives G 1  are chemically metamorphosed or transformed into a carbonized material G 2  by a lot of heating by the thermal head  400  for thermal activation, hence to be fixedly attached to the surface of the platen roller  401 . 
   Since the heat sensitive adhesive G 1  attached to the surface of the platen roller  401  has a stronger adhesion according to the melting through several times of heating by the thermal head  400  for thermal activation, there is a fear of attaching some to the surface of the forwarded heat sensitive adhesive label R and damaging the printing surface. 
   Further, a lot of attached heat sensitive adhesives G 1  damage the smoothness on the surface of the platen roller  401  and thermal activator layer K of the heat sensitive adhesive label R being forwarded cannot be heated uniformly, which causes a situation incapable of bringing out a full adhesion disadvantageously. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the drawbacks of the conventional art by providing a thermal activating device of a thermal activation sheet which can prevent a heat sensitive adhesive and a metamorphic material of the heat sensitive adhesive from attaching to the pressuring means and the activation heating means of the thermal activation sheet. The present invention also relates to a printer using the above thermal activating device. 
   In order to achieve the above object, the thermal activating device (the thermal activating unit A 1 ) of the thermal activation sheet according to the invention has at least activation heating means (for example, the thermal head  40  and the heater element H) for heating and activating a thermal activator layer of the thermal activation sheet (for example, the heat sensitive adhesive label R) with the thermal activator layer (for example, the thermal activator layer K) formed at least on one surface of a sheet-shaped substrate (for example, the base paper  500 ), feeding or forwarding means (platen roller  41  for thermal activation and the like) for forwarding the thermal activation sheet in a predetermined direction, and pressing or pushing means for pushing the thermal activation sheet toward the activation heating means, which is designed to comprise thermal activation sheet detecting means (heat sensitive adhesive label detecting sensor S 1 ) for detecting a presence of the thermal activation sheet at a predetermined position, and pressure releasing means (a controller  1500 , a cam mechanism  60 , and a working mallet member  50 ) for releasing a pressure working between the pushing means and the activation heating means when judging that the thermal activation sheet does not exist at the predetermined position according to the detection result of the thermal activation sheet detecting means. 
   Thus, when it is judged that the thermal activation sheet does not exist at the predetermined position, the pressure working between the pushing means and the activation heating means can be released. Accordingly, the thermal activation sheet detecting means can detect a coming of the trailing end of the thermal activation sheet in the vicinity of the activation heating means, for example, and the pressure working between the pushing means and the activation heating means is released, according to the detection signal, thereby preventing the thermal activator from attaching to the activation heating means and the pushing means. Further, the pressure releasing means can release the pressure working between the pushing means and the activation heating means by setting the activation heating means apart from the pushing means in a vertical direction. Thus, the pressure working between the pushing means and the activation heating means can be released. 
   The pressure releasing means can release the pressure working between the pushing means and the activation heating means by setting the activation heating means apart from the pushing means in a horizontal direction. Thus, the pressure working between the pushing means and the activation heating means can be released. 
   The activation heating means may be formed by an electric power source, the pushing means may be formed by a platen roller and forcing means for forcing the platen roller toward the electric power source, and the pressure releasing means may be formed by moving means for moving one of the platen roller and the electric power source in a vertical or horizontal direction. Thus, the pressure working between the pushing means and the activation heating means can be released. 
   Further, the moving means may include a working mallet member vertically movable together with the electric power source, which is provided on the bottom surface of the electric power source, and a cam mechanism attached to one portion of the working mallet member, for converting a rotation motion into a vertical movement, the forcing means may be formed by an elastic member provided on the working mallet member, for forcing the electric power source toward the platen roller, and the cam mechanism may be operated so as to lower the working mallet member against a force of the elastic member when judging that the thermal activation sheet does not exist at the predetermined position according to the detection signal from the thermal activation sheet detecting means. Thus, the thermal activation sheet detecting means can detect a coming of the trailing end of the thermal activation sheet in the vicinity of the activation heating means, for example, and the cam mechanism can be operated according to the detection signal, so to move the electric power source downwardly, thereby setting the electric power source apart from the platen roller. Therefore, the thermal activator of the thermal activation sheet can be prevented from attaching to the electric power source and the surface of the platen roller. 
   Further, the moving means may include a working mallet member vertically movable together with the electric power source, which is provided on the bottom surface of the electric power source, and an actuator attached to one portion of the working mallet member, for vertically moving the member, the forcing means may be formed by an elastic member provided on the working mallet member, for forcing the electric power source toward the platen roller, and the actuator may be operated so as to lower the working mallet member against a force of the elastic member when judging that the thermal activation sheet does not exist at the predetermined position according to the detection signal from the thermal activation sheet detecting means. Thus, the thermal activation sheet detecting means can detect a coming of the trailing end of the thermal activation sheet in the vicinity of the activation heating means, for example, and the actuator may be operated according to the detection signal, so to move the electric power source downwardly, thereby setting the electric power source apart from the platen roller. Therefore, the thermal activator of the thermal activation sheet can be prevented from attaching to the electric power source and the surface of the platen roller. 
   Further, the moving means may include a working mallet member vertically movable together with the platen roller, and a cam mechanism attached to one portion of the working mallet member, for converting a rotation motion into a vertical movement, the forcing means may be formed by an elastic member provided on the working mallet member, for forcing the platen roller toward the electric power source, and the cam mechanism may be designed so as to raise the working mallet member against a force of the elastic member when judging that the thermal activation sheet does not exist at the predetermined position according to the detection signal from the thermal activation sheet detecting means. Thus, the thermal activation sheet detecting means can detect a coming of the trailing end of the thermal activation sheet in the vicinity of the activation heating means, for example, and the cam mechanism can be operated according to the detection signal, so to move the platen roller upwardly, thereby setting the platen roller apart from the electric power source. Therefore, the thermal activator of the thermal activation sheet can be prevented from attaching to the electric power source and the surface of the platen roller. 
   Further, the moving means may include a working mallet member vertically movable together with the platen roller, and an actuator attached to one portion of the working mallet member, for vertically moving the member, the forcing means may be formed by an elastic member provided on the working mallet member, for forcing the platen roller toward the electric power source, and the actuator may be operated so as to raise the working mallet member against a force of the elastic member when judging that the thermal activation sheet does not exist at the predetermined position according to the detection signal from the thermal activation sheet detecting means. Thus, the thermal activation sheet detecting means can detect a coming of the trailing end of the thermal activation sheet in the vicinity of the activation heating means, for example, and the actuator can be operated according to the detection signal, so to move the platen roller upwardly, thereby setting the platen roller apart from the electric power source. Therefore, the thermal activator of the thermal activation sheet can be prevented from attaching to the electric power source and the surface of the platen roller. 
   Further, the actuator may be formed by one of a solenoid, a pneumatic cylinder, and a hydraulic cylinder. Thus, vertical movement of the electric power source or the platen roller can be realized at ease. 
   Further, a power supply to the electric power source may be broken in associated with an operation of the pressure releasing means. This can prevent from baking and the like of some thermal activator possible to attach to the electric power source. Further, the power consumption can be saved by cutting the power supply to the electric power source when the thermal activation is not necessary. 
   Further, the thermal activation sheet detecting means can be formed by an optical sensor or a microswitch capable of detecting a coming of a leading end or a trailing end of the thermal activation sheet. Thus, the detection of the thermal activation sheet can be surely realized at a low cost. 
   Further, one or more thermal activation sheet detecting means may be provided on a way of passage of the thermal activation sheet by the forwarding means. Thus, the presence of the thermal activation sheet at the predetermined position (for example, the position of providing the electric power source) can be surely detected. 
   It may further comprise controlling means for deciding an operation timing of the pressure releasing means, according to forwarding direction and length information of the thermal activation sheet, forwarding speed information of the thermal activation sheet by the forwarding means, distance information from the thermal activation sheet detecting means to the activation heating means, and the detection result of the thermal activation sheet detecting means. This can operate the pressure releasing means at a proper operation timing even when the length of the thermal activation sheet is changed. 
   The forwarding direction and length information of the thermal activation sheet may be obtained according to the detection result of the thermal activation sheet detecting means and the forwarding speed information of the thermal activation sheet by the forwarding means. This can obtain the length of the thermal activation sheet accurately and operate the pressure releasing means at a proper operation timing. 
   The forwarding speed information of the thermal activation sheet by the forwarding means may be obtained according to the detection result by several thermal activation sheet detecting means. This can obtain the forwarding speed information of the thermal activation sheet accurately, calculate the length of the thermal activation sheet accurately, and operate the pressure releasing means at a proper operation timing. 
   Further, the electric power source may be formed by a thermal head with a plurality of heater elements aligned there. Thus, by diverting the thermal head for use in a thermal printer, for example, the thermal activating device of the thermal activation sheet can be realized as ease. 
   Further, the electric power source may be formed by a so-called thermal bar including a single resistive element. Thus, by diverting the thermal bar for use in a thermal printer and the like, for example, the thermal activating device of the thermal activation sheet can be realized at ease. 
   Further, the electric power source may be formed by a thermal roll including a cylindrical resistive element. Thus, by diverting the thermal roll for use in a laser printer and the like, for example, the thermal activating device of the thermal activation sheet can be realized at ease. 
   Further, the thermal activator may be formed by not only the thermal activation adhesive material but also a heat sensitive recording material, an electrostatic ink toner, and the like. Thus, the heat sensitive recording material can be prevented from attaching to the electric power source and the platen roller when using heat sensitive paper and the like with the heat sensitive recording material applied thereon, for example, as the thermal activation sheet. 
   Further, the platen roller has a driving source for directly rotating the platen roller, serving as the forwarding means. 
   A printer according to another invention, is designed to comprise one of the above-mentioned thermal activating devices of the thermal activation sheets. This can realize the printer for thermal activation sheet free from damaging the thermal activation sheet. 
   Further, the printer may have a thermal head for printing while making contact with the heat sensitive coloring layer of the thermal activation sheet with a heat sensitive coloring layer formed thereon. This enables continuous printing to the thermal activation sheet and activation of the thermal activator layer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more better understanding of the present invention, reference is made of a detailed description to be read in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a schematic view showing the structure of a thermal printer according to the invention; 
       FIG. 2  is a block diagram showing the structure of a controller of the thermal printer; 
       FIG. 3  is an explanatory view showing the schematic structure of an embodiment of the pressure releasing means; 
       FIG. 4  is an explanatory view showing the position of the heat sensitive adhesive label detecting sensor of the pressure releasing means; 
       FIG. 5  is an explanatory view showing the schematic structure of another embodiment of the pressure releasing means; 
       FIG. 6  is a flow chart showing the procedure of the pressure releasing processing {circle around (1)} of the thermal activating unit; 
       FIG. 7  is a flow chart showing the continuation of the processing of  FIG. 6 ; 
       FIG. 8  is a flow chart showing the procedure of the pressure releasing processing {circle around (2)} of the thermal activating unit; 
       FIG. 9  is a flow chart showing the procedure of the pressure releasing processing {circle around (3)} of the thermal activating unit; 
       FIG. 10  is a flow chart showing the continuation of the processing of  FIG. 9 ; 
       FIG. 11  is a schematic view showing the structure of the conventional thermal printer; 
       FIG. 12  is a cross section view showing the structure of the thermal activation sheet; and 
       FIG. 13  is an explanatory view showing the attached state of the heat sensitive adhesive and the like in the conventional thermal activating device. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. 
     FIG. 1  is a schematic view showing the structure of a thermal printer according to the invention, and  FIG. 2  is a control block diagram of the thermal printer. In  FIG. 1 , the reference mark P 1  indicates a thermal printer unit, the reference mark C 1  indicates a cutter unit, the reference mark A 1  indicates a thermal activating unit as a thermal activating device, and the reference mark R indicates a heat sensitive adhesive label as the thermal activation sheet reeled like a roll. 
   The thermal printer unit P 1  has the general structure comprising a printing thermal head  10 , a platen roller  11  pushed toward the printing thermal head  10 , and a driving system (for example, a first stepping motor M 1 , a gear series, and the like), not illustrated, for rotating the platen roller  11 . 
   By rotating the platen roller  11  in the direction of D 1  (clockwise) in  FIG. 1 , the heat sensitive adhesive label R is drawn out and the heat sensitive adhesive label R drawn out is printed in a thermal method, hence to be forwarded in the direction of D 2  (in the right direction). The platen roller  11  has the pressuring means (for example, a coil spring, a flat spring, and the like) not illustrated, and the elastic force is adopted to push the surface of the platen roller  11  toward the printing thermal head  10  with the pressure F. 
   A heater element H 1  of the printing thermal head  10  is formed by a plurality of comparatively small resistive elements aligned in the width direction of the head in a way capable of dot printing. While, a heater element H 2  of the thermal head  40  for thermal activation as the electric heat source, described later, does not have to be separated by the dot unit, differently from the heater element for printing, but it may be a continuous resistive element like a thermal bar used for a laser printer and the like. Instead of the thermal head and the thermal bar, a thermal roll for rotating a cylindrical resistive element used for a laser printer and the like may be adopted. 
   By using a resistive element of the same structure respectively for the printing thermal head  10  and the thermal head  40  for thermal activation, the component can be used in common and the cost can be reduced. 
   The heat sensitive adhesive label R used in this embodiment has the structure, for example, as shown in the above-mentioned FIG.  12 . Depending on necessity, an insulating layer may be provided on the base paper  500 . 
   The printing thermal head  10  (heater element H 1 ) and the printing platen roller  11  (first stepping motor M 1 ) are operated according to a printing signal from the controller described later 1500, and hence a desired printing can be performed on the thermal coat layer  501  of the heat sensitive adhesive label R. 
   The cutter unit C 1  is to cut the heat sensitive adhesive label R that has been heat-sensitively printed by the thermal printer unit P 1 , by a proper length, and it is formed by a movable blade  20 , a fixed blade  21 , and the like operated by a driving source (not illustrated) of an electric motor and the like. A cutter driving unit  20 A, not illustrated, of the movable blade  20 , is operated at a predetermined timing according to a control of the controller described later 1500. 
   The thermal activating unit A 1  is rotated according to, for example, a driving source (a second stepping motor M 2 ) not illustrated, and it comprises a loading roller  30  and a discharging roller  31  for inserting and discharging the cut heat sensitive adhesive label R. A thermal head  40  for thermal activation and a platen roller  41  for thermal activation pushed toward the thermal head  40  for thermal activation are provided between the loading roller  30  and the discharging roller  31 . The platen roller  41  for thermal activation has a driving system (for example, the second stepping motor M 2 , a gear series, and the like), for rotating the platen roller  41  for thermal activation in the direction of D 4  (clockwise) in FIG.  1 ), so as to forward the heat sensitive adhesive label R in the direction of D 6  (right direction in FIG.  1 ), according to the loading roller  30  and the discharging roller  31  rotating respectively in the direction of D 3  and the direction of D 5 . The platen roller  41  for thermal activation is made of, for example, hard rubber and the like. 
   An L-shaped moving mallet member  50  vertically movable with the thermal head  40  for thermal activation is provided in the bottom surface of the thermal head  40  for thermal activation, and the top surface  50   a  of the moving mallet member  50  makes contact with the circumferential surface of an eccentric cam  61  of a cam mechanism  60  in a fluctuating way. The cam mechanism  60  comprises a driving source (a third stepping motor M 3 ) driven by the controller described later  1500 , and the eccentric cam  61  is fixed around a rotation axis  62  of the third stepping motor M 3 . 
   A coil spring  70  is provided on the bottom surface  50   b  of the moving mallet member  50  as forcing means, which pushes the thermal head  40  for thermal activation toward the platen roller  41  for thermal activation through the moving mallet member  50 . 
   The reference mark S 1  indicates a sensor for detecting a heat sensitive adhesive label as the thermal activation sheet detecting means for detecting the position of the heat sensitive adhesive label R, which is formed by a photo sensor, a microswitch, or the like. 
   As illustrated in FIG.  3 ( a ), the thermal head  40  for thermal activation is pushed toward the platen roller  41  for thermal activation, into a state of pinching the heat sensitive adhesive label R therebetween. When the cam mechanism  60  is operated, according to the detection of the position of the heat sensitive adhesive label R by the heat sensitive adhesive label detecting sensor S 1 , the thermal head  40  for thermal activation starts falling down, as illustrated in FIG.  3 ( b ), and the state of pushing the thermal head  40  for thermal activation toward the platen roller  41  for thermal activation is released. Thus, the heat sensitive adhesive can be prevented from attaching to the thermal head  40  for thermal activation and the platen roller  41  for thermal activation. The controller  1500  of the thermal printer comprises, as shown in  FIG. 2 , a microcomputer  1000  of one chip for managing a controlling unit, a ROM  1010  for storing a control program and the like executed by the microcomputer  1000 , a RAM  1020  for storing various printing formats and the like, an operating unit  1030  for receiving, setting, or calling the printing data, the printing format data, and the like, a display  1040  formed by a liquid crystal display panel and the like for displaying the printing data and the like, and an interface  1050  for performing the input/output of the data between the controlling unit and the driving devices. 
   The heater element H 1  of the printing thermal head  10  of the printer unit P 1 , the heater element H 2  of the thermal head  40  for thermal activation of the thermal activating unit A 1 , a cutter driving unit  20 A of the cutter unit C 1 , the first to the third stepping motors M 1  to M 3 , and the heat sensitive adhesive label detecting sensor S 1  are respectively connected to the interface  1050 . 
   A solenoid  80  may be connected there, instead of the third steeping motor M 3 , as described later. 
   When the operation of the thermal printer is started according to the control of the controller  1500 , the thermal printing is performed on the printable surface (thermal coat layer  501 ) of the heat sensitive adhesive label R by the thermal printer unit P 1 . Successively, the heat sensitive adhesive label R forwarded to the cutter unit C 1  according to the rotation of the printing platen roller  11  is cut into a predetermined length by the movable blade  20  operated by the cutter driving unit  20 A at a predetermined timing. 
   Successively, the heat sensitive adhesive label R after cut is taken into the thermal activating unit A 1  by the loading roller  30  of the thermal activating unit A 1  and a heat energy is applied to the above label R by the thermal head  40  for thermal activation (heater element H) and the platen roller  41  for thermal activation operated at a predetermined timing. Thus, the thermal activator layer K of the heat sensitive adhesive label R is activated to develop the adhesion. Successively, the label R is discharged out from the thermal printer according to the operation of the discharging roller  31 . 
   When the heat sensitive adhesive label detecting sensor S 1  detects absence of the heat sensitive adhesive label R, the third stepping motor M 3  of the cam mechanism  60  is driven according to the detection signal, the eccentric cam  61  is rotated, the thermal head  40  for thermal activation is lowered, as illustrated in FIG.  3 ( b ), and the pressed state of the thermal head  40  for thermal activation toward the platen roller  41  for thermal activation is released. 
   Thus, after the thermal activator layer K of the heat sensitive adhesive label R has been heated and activated by the heater element H of the thermal head  40  for thermal activation, when the heat sensitive adhesive label R is removed from the platen roller  41  for thermal activation, even if some of the heat sensitive adhesive of the thermal activator layer K is squeezed out between the platen roller  41  for thermal activation and the thermal head  40  for thermal activation because of heating and softening, and peeled out from the base paper  500  of the heat sensitive adhesive label R, such a situation that the heat sensitive adhesive sticks to the thermal head  40  for thermal activation and the platen roller  41  for thermal activation can be assuredly prevented because the thermal head  40  for thermal activation is away from the platen roller  41  for thermal activation. 
   Accordingly, when the thermal activating unit A 1  performs the thermal activation on the heat sensitive adhesive label R being forwarded next, it is possible to previously prevent from a situation of damaging the printing surface, depositing the heat sensitive adhesive on the peripheral surface of the platen roller  41  for thermal activation, and accordingly making uneven the contact with the thermal head  40  for thermal activation and make insufficient the thermal activation. 
   As illustrated in FIG.  3 ( b ), in a separate state of the thermal head  40  for thermal activation and the platen roller  41  for thermal activation, power supply to the thermal head  40  for thermal activation may be broken according to a control of the controller  1500 . Accordingly, the power consumption can be saved by cutting the power supply to the thermal head  40  for thermal activation when the thermal activation is not necessary. 
   In the embodiment shown in  FIG. 3 , although the description has been made in the case of providing the heat sensitive adhesive label detecting sensor S 1  on the downstream side from the platen roller  41  for thermal activation and the thermal head  40  for thermal activation in the forwarding direction of the heat sensitive adhesive label R, the position of the heat sensitive adhesive label detecting sensor is not restricted to this. 
   Namely, as illustrated in FIG.  4 ( a ), the heat sensitive adhesive label detecting sensor S 2  may be provided on the upstream side from the platen roller  41  for thermal activation and the thermal head  40  for thermal activation in the forwarding direction of the heat sensitive adhesive label R. Alternatively, as illustrated in FIG.  4 ( b ), the heat sensitive adhesive label detecting sensor S 3  may be provided in the substantially same position as that of the platen roller  41  for thermal activation and the thermal head  40  for thermal activation. 
   Alternatively, as illustrated in FIG.  4 ( c ), two heat sensitive adhesive label detecting sensors S 4  and S 5  may be provided on the upstream and downstream sides from the platen roller  41  for thermal activation and the thermal head  40  for thermal activation in the forwarding direction of the heat sensitive adhesive label R. In this case, the information about the length and the forwarding speed of the heat sensitive adhesive label R can be calculated according to the detection signals of the leading end portion and the trailing end portion of the heat sensitive adhesive label R by the heat sensitive adhesive label detecting sensors S 4  and S 5 , and based on the information, the third stepping motor M 3  of the cam mechanism  60  can be operated at a proper timing. The details of the pressure releasing processing for controlling the pressure releasing means such as the cam mechanism  60  according to the length information, the forwarding speed information, and the like of the heat sensitive adhesive label R will be described later, according to the flow charts. 
   In the embodiment shown in  FIG. 3 , although the description has been made in the case of using the cam mechanism  60  having the eccentric cam  61  as a mechanism for lowering the moving mallet member  50 , it is not restricted to this, but instead of the cam mechanism  60 , a solenoid, a pneumatic cylinder, a hydraulic cylinder, and the like may be used so as to lower the moving mallet member  50  according to the telescopic motion of the rod. Alternatively, a combination of gear series can be used in order to lower the moving mallet member  50 . 
   Next, another embodiment of the pressure releasing means in the thermal activating unit A 1  will be described with reference to FIG.  5 . 
   In this embodiment, the platen roller  41  for thermal activation is attached to the moving mallet member  51  in a rotatable way, and the telescopic rod  81  of the solenoid  80  affects the moving mallet member  51 , so as to raise the moving mallet member  51  together with the platen roller  41  for thermal activation, thereby setting the platen roller  41  for thermal activation apart from the thermal head  40  for thermal activation. 
   More specifically, as illustrated in FIG.  5 ( a ), the platen roller  41  for thermal activation is supported by an axis in a rotatable way in the lower portion of the vertical portion  51   a  of the L-shaped moving mallet member  51  and the solenoid  80  having the telescopic rod  81  is provided under the horizontal portion  51   b  of the moving mallet member  51 . The telescopic rod  81  of the solenoid  80  is usually attached to the bottom surface of the horizontal portion  51   b  of the moving mallet member  51  in a contracted state. The solenoid  80  is connected to the controller  1500  through the interface  1050 , as illustrated by a chained line in the above-mentioned  FIG. 2 , so to be operated at a predetermined timing by a control of a microcomputer  1000 . 
   Further, as the forcing means, a coil spring  71  is provided on the top surface of the horizontal portion  51   b  of the moving mallet member  51 , so as to push the platen roller  41  for thermal activation toward the thermal head  40  for thermal activation through the moving mallet member  51 , as illustrated in FIG.  5 ( a ). 
   The reference mark S 1  is the heat sensitive adhesive label detecting sensor as the thermal activation sheet detecting means for detecting the position of the heat sensitive adhesive label R, which is formed by a photo sensor, a microswitch, or the like. 
   As illustrated in FIG.  5 ( a ), the platen roller  41  for thermal activation is pushed toward the thermal head  40  for thermal activation, and from a state of pinching the heat sensitive adhesive label R therebetween, according to the detection of the position of the heat sensitive adhesive label R by the heat sensitive adhesive label detecting sensor S 1 , the solenoid  80  is operated and the telescopic rod  81 , the thermal head  40  for thermal activation starts falling down, as illustrated in FIG.  3 ( b ), and the state of pushing the thermal head  40  for thermal activation toward the platen roller  41  for thermal activation is released. Thus, the heat sensitive adhesive can be prevented from attaching to the thermal head  40  for thermal activation and the platen roller  41  for thermal activation. 
   In the embodiment shown in  FIG. 5 , although the description has been made in the case of using the solenoid  80  as the moving means for raising up the moving mallet member  51  and the platen roller  41  for thermal activation, it is not restricted to this. Instead of the solenoid, a pneumatic cylinder, a hydraulic cylinder, and the like can be used. Further, instead of the solenoid, a cam mechanism as shown in the above-mentioned  FIG. 3  may be provided so as to raise the moving mallet member  51  and the platen roller  41  for thermal activation according to the rotation of the eccentric cam. Alternatively, a combination of gear series may be considered so as to raise the moving mallet member  51 . 
   The position and the number of the heat sensitive adhesive label detecting sensor may be properly changed, similarly to the above-mentioned embodiment (refer to FIG.  4 ). 
   The pressure releasing processing performed by the controller  1500  will be described with reference to the flow charts of  FIG. 6  to  FIG. 10 , this time. 
   FIG.  6  and  FIG. 7  are flow charts showing the procedure of the pressure releasing processing {circle around (1)} of the thermal activating unit in the case of providing one heat sensitive adhesive label detecting sensor S 1  on the upstream side from the thermal head  40  for thermal activation and the platen roller  41  for thermal activation in the forwarding direction of the heat sensitive adhesive label R, as illustrated in FIG.  4 ( a ). 
   When this processing is started, in Step S 100 , first it is checked whether the heat sensitive adhesive label detecting sensor S 1  has detected the leading end of the heat sensitive adhesive label R; when it is judged that it has detected, the procedure moves to Step S 101 , where the forwarding speed information of the forwarding means (for example, the platen roller  41  for thermal activation) previously stored in the ROM  1010  or the RAM  1020  of the controller  1500  is read out, and then the procedure moves to Step S 102 . In Step S 102 , the distance information from the heat sensitive adhesive label detecting sensor S 1  to the thermal activation portion (the heater element H 2  of the thermal head  40  for thermal activation), previously stored in ROM  1010  or RAM  1020  of the controller, is read out and then, the procedure moves to Step S 103 . 
   In Step S 103 , how long it takes before the end portion of the heat sensitive adhesive label R arrives at the thermal activation portion is calculated (distance information/forwarding speed information), and then the procedure moves to Step S 104 . In Step S 104 , it is checked whether it has got to the calculated time, and when it has got to the above time, the procedure moves to Step S 105 . 
   In Step S 105 , the pressed state by the pressuring means is kept (namely, for example, in the case of using the cam mechanism, the eccentric cam  61  is attached to the moving mallet member  51  at the bottom dead center, as illustrated in FIG.  3 ( a ), and in the case of using the solenoid, the telescopic rod  81  is in a contracted state (off-state), as illustrated in FIG.  5 ( a )) and the procedure moves to Step S 106 , where the power supply to the thermal activation portion (heater element H 2 ) is started. 
   Then, the procedure moves to Step S 107 , where the forwarding of the heat sensitive adhesive label R by the platen roller  41  for thermal activation is started. Thus, the thermal activation of the heat sensitive adhesive label R is started. 
   The procedure moves to Step S 108 , where it is checked whether the heat sensitive adhesive label detecting sensor S 1  has detected the trailing end of the heat sensitive adhesive label R, and when it is judged that it has detected, the procedure moves to Step S 109 . In Step S 109 , how long it takes before the tailing end of the heat sensitive adhesive label R arrives at the thermal activation portion (heater element H 2 ) is calculated, and then the procedure moves to Step S 110 . 
   In Step S 110 , it is checked whether it has got to the calculated time, and when it has got to the above time, the procedure moves to Step S 111 , where the power supply to the heater element H 2  is cut, and then the procedure advances to Step S 112 . This can save the power consumption when the thermal activation of the heat sensitive adhesive label R is not required. In Step S 112 , the pressed state by the pressuring means is released. Namely, for example, in the case of using the cam mechanism  60  as the pressure releasing means, as illustrated in  FIG. 4 , the third stepping motor M 3  is driven so to rotate the eccentric cam  61 , and as illustrated in FIG.  3 ( b ), the moving mallet member  50  is lowered, so as to set the thermal head  40  for thermal activation apart from the platen roller  41  for thermal activation, thereby releasing the pressed state. In the case of using the solenoid  80  as the pressure releasing means, as illustrated in  FIG. 5 , the solenoid  80  is turned on, so to expand the telescopic rod  81  and raise the moving mallet member  51 , as illustrated in FIG.  5 ( b ), so as to set the thermal head  40  for thermal activation apart from the platen roller  41  for thermal activation, thereby releasing the pressed state. Then, the procedure moves to Step S 113 , where the rotation of the discharging roller  31  is stopped and returned. 
   In these ways, the pressed state of the thermal head  40  for thermal activation toward the platen roller  41  for thermal activation can be released, thereby preventing the heat sensitive adhesive from attaching to the thermal head  40  for thermal activation and the platen roller  41  for thermal activation. In the pressure releasing processing {circle around (1)}, since the system calculates how long it takes before the leading end and the trailing end of the heat sensitive adhesive label R arrive at the heater element H 2 , and so on and determines the timing for releasing the pressed state according to the calculated result, it can flexibly cope with the case where the length and the like of the heat sensitive adhesive label R varies. 
   This time, the procedure of the pressure releasing processing {circle around (2)} of the thermal activating unit in the case of providing one heat sensitive adhesive label detecting sensor S 3  at the substantially same position as that of the thermal head  40  for thermal activation and the platen roller  41  for thermal activation, as illustrated in FIG.  4 ( b ), with reference to the flow chart of FIG.  8 . 
   When this processing is started, it is checked whether the heat sensitive adhesive label detecting sensor S 3  has detected the leading end of the heat sensitive adhesive label R in Step S 200 , and when it is judged that it has detected, the procedure moves to Step S 201 , where the pressed state by the pressuring means is kept (namely, for example, in the case of using the cam mechanism, the eccentric cam  61  is attached to the moving mallet member  50  at the bottom dead center, as illustrated in FIG.  3 ( a ), and in the case of using the solenoid, the telescopic rod  81  is in a contracted state (off-state), as illustrated in FIG.  5 ( a )) and the procedure moves to Step S 202 . 
   In Step S 202 , the power supply to the thermal activation portion (heater element H 2 ) is started, and then, the procedure moves to Step S 203 , where the forwarding of the heat sensitive adhesive label R by the platen roller  41  for thermal activation is started. Thus, the thermal activation of the heat sensitive adhesive label R is started. 
   Next, in Step S 204 , it is checked whether the heat sensitive adhesive label detecting sensor S 3  has detected the trailing end of the heat sensitive adhesive label R, and when it is judged that it has detected, the procedure moves to Step S 205 . In Step S 205 , the power supply to the heater element H 2  is stopped and then the procedure moves to Step S 206 . This can save the power consumption when the thermal activation of the heat sensitive adhesive label R is not required. 
   In Step S 206 , the pressed state is released. Namely, for example, in the case of using the cam mechanism  60  as the pressure releasing means, as illustrated in  FIG. 4 , the third stepping motor M 3  is driven so to rotate the eccentric cam  61 , and as illustrated in FIG.  3 ( b ), the moving mallet member  50  is lowered, so as to set the thermal head  40  for thermal activation apart from the platen roller  41  for thermal activation, thereby releasing the pressed state. In the case of using the solenoid  80  as the pressure releasing means, as illustrated in  FIG. 5 , the solenoid  80  is turned on, so to expand the telescopic rod  81  and raise the moving mallet member  51 , as illustrated in FIG.  5 ( b ), so as to set the thermal head  40  for thermal activation apart from the platen roller  41  for thermal activation, thereby releasing the pressed state. Then, the procedure moves to Step S 207 , where the rotation of the discharging roller  31  is stopped and returned. In these ways, the pressed state of the thermal head  40  for thermal activation toward the platen roller  41  for thermal activation can be released, thereby preventing the heat sensitive adhesive from attaching to the thermal head  40  for thermal activation and the platen roller  41  for thermal activation. In the pressure releasing processing {circle around (2)}, it is not necessary to calculate how long it takes before the leading end and the trailing end of the heat sensitive adhesive label R arrive at the heater element H 2 , and so on, differently from the pressure releasing processing {circle around (1)} described before, and therefore, the procedure is simple and the device control can be simplified 
   The procedure of the pressure releasing processing {circle around (3)} of the thermal activating unit in the case of providing the heat sensitive adhesive label detecting sensors S 4  and S 5  on the upstream and downstream sides from the thermal head  40  for thermal activation and the platen roller  41  for thermal activation, as illustrated in FIG.  4 ( c ), with reference to the flow charts of FIG.  9  and FIG.  10 . 
   When this processing is started, in Step S 300 , first it is checked whether the heat sensitive adhesive label detecting sensor S 4  has detected the leading end of the heat sensitive adhesive label R, and when it is judged that it has detected, the procedure moves to Step S 301 . In Step S 301 , the forwarding speed information of the forwarding means (for example, the platen roller  41  for thermal activation) previously stored in the ROM  1010  or the RAM  1020  of the controller  1500  is read out, and then the procedure moves to Step S 302 . 
   In Step S 302 , the distance information from the heat sensitive adhesive label detecting sensor S 4  to the thermal activation portion (the heater element H 2  of the thermal head  40  for thermal activation), which has been previously stored in the ROM  1010  or the RAM  1020  of the controller  1500  is read out and then, the procedure moves to Step S 303 . 
   In Step S 303 , how long it takes before the end portion of the heat sensitive adhesive label R arrives at the heater element H 2  is calculated and then the procedure moves to Step S 304 . In Step S 304 , it is checked whether it has got to the calculated time, and when it is judged that it has got to the above time, the procedure moves to Step S 305 . 
   In Step S 305 , the pressed state by the pressuring means is kept (namely, for example, in the case of using the cam mechanism, the eccentric cam  61  is attached to the moving mallet member  51  at the bottom dead center, as illustrated in FIG.  3 ( a ), and in the case of using the solenoid, the telescopic rod  81  is in a contracted state (off-state), as illustrated in FIG.  5 ( a )) and the procedure moves to Step S 306 , where the power supply to the thermal activation portion (heater element H 2 ) is started. 
   Then, the procedure moves to Step S 307 , where the forwarding of the heat sensitive adhesive label R by the platen roller  41  for thermal activation is started. Thus, the thermal activation of the heat sensitive adhesive label R is started. 
   Continuously, in Step S 308 , a timer counter is turned on and the procedure moves to Step S 309 , where it is checked whether the heat sensitive adhesive label detecting sensor S 5  has detected the end portion of the heat sensitive adhesive label R, and when it is judged that it has detected, the procedure moves to Step S 310 . In Step S 310 , the timer counter is turned off and the procedure moves to Step S 311 , where the distance information from the heat sensitive adhesive label detecting sensor S 5  to the thermal activation portion (the heater element H 2  of the thermal head  40  for thermal activation) which has been previously stored in the ROM  1010  or the RAM  1020  of the controller  1500  is read out and the procedure moves to Step S 312 . 
   In Step S 312 , the forwarding speed of the heat sensitive adhesive label R is calculated from the time counted by the timer and the distance information (distance information/time) and the procedure moves to Step S 313 . In Step S 313 , it is checked whether the heat sensitive adhesive label detecting sensor S 4  has detected the trailing end of the heat sensitive adhesive label R, and when it is judged that it has detected, the procedure moves to Step S 314 . 
   In Step S 314 , the distance information from the thermal activation portion (heater element H 2 ) to the heat sensitive adhesive label detecting sensor S 4  which has been previously stored in the ROM  1010  or the RAM  1020  of the controller  1500  is read out, and in Step S 315 , how long it takes before the tailing end of the heat sensitive adhesive label R arrives at the heater element H 2  is calculated, and then the procedure moves to Step S 316 . 
   In Step S 316 , it is checked whether it has got to the calculated time, and when it is judged that it has got to the above time, the procedure moves to Step S 317 , where the power supply to the heater element H 2  is cut, and then the procedure advances to Step S 318 . This can save the power consumption when the thermal activation of the heat sensitive adhesive label R is not required. 
   In Step S 318 , the pressed state is released. Namely, for example, in the case of using the cam mechanism  60  as the pressure releasing means, as illustrated in  FIG. 4 , the third stepping motor M 3  is driven so to rotate the eccentric cam  61 , and as illustrated in FIG.  3 ( b ), the moving mallet member  50  is lowered, so as to set the thermal head  40  for thermal activation apart from the platen roller  41  for thermal activation, thereby releasing the pressed state. In the case of using the solenoid  80  as the pressure releasing means, as illustrated in  FIG. 5 , the solenoid  80  is turned on, so to expand the telescopic rod  81  and raise the moving mallet member  51 , as illustrated in FIG.  5 ( b ), so as to set the thermal head  40  for thermal activation apart from the platen roller  41  for thermal activation, thereby releasing the pressed state. Then, the procedure moves to Step S 319 , where the rotation of the discharging roller  31  is stopped and returned. In these ways, the pressed state of the thermal head  40  for thermal activation toward the platen roller  41  for thermal activation can be released, thereby preventing the heat sensitive adhesive from attaching to the thermal head  40  for thermal activation and the platen roller  41  for thermal activation. In the pressure releasing processing {circle around (3)}, since the system calculates how long it takes before the leading end and the trailing end of the heat sensitive adhesive label R arrive at the heater element H 2 , and so on and determines the timing for releasing the pressed state, according to the calculated results of the heat sensitive adhesive label detecting sensors S 4  and S 5 , it can flexibly cope with the case where the length and the like of the heat sensitive adhesive label R varies. 
   Although the invention made by this inventor has been described more specifically according to the embodiments, it is not restricted to the above embodiments, but various modifications may be made without departing from the spirit thereof. 
   For example, two heat sensitive adhesive label detecting sensors may be provided on the upstream side from the thermal head  40  for thermal activation and the platen roller  41  for thermal activation, in the forwarding direction of the heat sensitive adhesive label R, and the timing for the pressure release can be determined, according to the detection results of the leading end and the trailing end of the heat sensitive adhesive label R by the respective detecting sensors. 
   In the embodiments, although the description has been made in the case of using the thermal method as a printer unit, it is not restricted to this, but an ink jet method, a laser printing method, and the like may be used. In this case, each surface treatment suitable to each printing method must be performed on a printing surface of the heat sensitive adhesive sheet, instead of the thermal coat layer. 
   As set forth hereinabove, the thermal activating device of the thermal activation sheet according to the invention comprises at least activation heating means for heating and activating the thermal activator layer of the thermal activation sheet with the thermal activator layer formed at least on one surface of a sheet-shaped substrate, forwarding means for forwarding the thermal activation sheet in a predetermined direction, and pushing means for pushing the thermal activation sheet toward the activation heating means, which is designed to comprise thermal activation sheet detecting means for detecting a presence of the thermal activation sheet at a predetermined position, and pressure releasing means for releasing a pressure working between the pushing means and the activation heating means when judging that the thermal activation sheet does not exist at the predetermined position according to the detection result of the thermal activation sheet detecting means. Therefore, the thermal activation sheet detecting means can detect a coming of the trailing end of the thermal activation sheet in the vicinity of the activation heating means, for example, and the pressure working between the pushing means and the activation heating means is released, according to the detection signal, thereby it is advantageous that the thermal activator can be prevented from attaching to the activation heating means and the pushing means.