JP2000218844A - Method for controlling temperature of thermal head and thermal processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict an excessive temperature rise of a thermal head by detecting the temperature of the thermal head and the temperature of an environment where the thermal head is placed, and correcting a heating energy to be applied to the thermal head in accordance with a temperature difference. SOLUTION: An erase/printing command is issued via a serial interface 73 to a CPU 70. A printing command process is called in accordance with a program stored in a ROM 71. A temperature of an environment and a temperature of an erase head 50 as a thermal head are measured respectively by an environment temperature sensor 69 and a temperature sensor 94, and also a difference of the temperatures is obtained. A heating energy to be applied to the erase head 50 is corrected according to the obtained temperature difference. An excessive temperature rise of the erase head 50 is restricted, so that the erase head can be held at an appropriate process temperature at all times. A characteristic of a thermal process is accordingly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature of a thermal head for performing thermal treatment on a recording layer, such as a thermal erase head for thermally erasing an image printed on a rewritable layer of a rewritable card, and using the thermal head. The present invention relates to a thermal processing device.

[0002]

2. Description of the Related Art At present, various cards are used in a wide range of fields. Some of them include a telephone card, a point card and the like, and each time the card is used, variable variable information (balance, points, etc.) is used. Is updated and displayed on the card. As an information display method for this kind of card, there is a method of simply printing information by a thermal printer. However, in this method, since all the printed images remain, it is necessary to reduce the size of the printed image in order to secure the number of printing lines, or to increase the printing area, and as a result, the printed image becomes difficult to see, There is an inconvenience that an area for displaying a fixed image other than variable information such as a pattern and a name is narrowed.

Therefore, in recent years, rewritable cards have been provided in which the previous image is erased and only the latest image is printed in the same location. This rewritable card erases an image by subjecting a thermoreversible recording material laminated as a rewritable layer to a resin base material to a heating / cooling process specified for the material by a thermal head unit of a card processing device. / Printing, that is, rewriting is repeatedly performed. As a specific structure, usually, a relite layer made of the thermoreversible material is formed in a stripe shape on the surface of a rectangular resin base material constituting the main body in parallel with the longitudinal direction of the base material.

The above-described card processing apparatus generally holds the above-described rewritable card while sequentially sandwiching the rewritable card between the erasing head and the platen roller between the print head and the platen roller, and transporting the rewritable card in the direction in which the rewritable layer extends. Each head is configured to perform erasing / printing by pressing against the rewrite layer. The print head of the device has a plurality of heating elements arranged like a print head of a thermal printer.
By applying a current to a heating element corresponding to a printed portion of an image while pressing against the rewrite layer, the rewrite layer is heated to a printing temperature to thermally print an image. On the other hand, the erasing head has a configuration in which a heating element that generates heat uniformly at the erasing temperature is pressed against the rewritable layer to thermally erase the image on the rewritable layer.

FIGS. 10A, 10B, and 10C show an example of the erasing head. The erasing head has a head surface 90a of a bar-shaped substrate 90 made of ceramics or the like.
And a heating element 9 composed of electrodes 91 and 91 and an electric resistor.
2 are fixed and attached to the apparatus via U-shaped holders 93 attached to both ends of the substrate 90. The heating element 92 is supplied with a current through the electrodes 91 and 91 and generates heat uniformly according to the resistance value. The temperature of the heating element 92 is detected by a temperature sensor 94 composed of a thermistor mounted on the back side of the head surface. This erasing head is opposed to the rewritable card to be conveyed (the arrow F in FIG. 10A is the conveying direction) so that the substrate 90 and the heating element 91 cross the stripe-shaped rewritable layer, that is, orthogonally cross. It is arranged and equipped to press against the rewrite layer.

According to this erasing head, the heat energy supplied from the heating element 92 to the rewritable card during the image erasing process increases, so that the temperature and temperature of the pressure contact surface of the heating element 92 against the rewritable card are increased. A large temperature difference occurs between the temperature detected by the sensor 94 and the temperature detected by the sensor 94. For this reason, even if feedback control is performed to maintain the temperature of the heating element 92 at the erasing temperature while detecting the temperature of the heating element 92 with the temperature sensor 94, the temperature of the pressure contact surface of the heating element 92 is maintained at the predetermined erasing temperature. It is difficult.
Therefore, actually, the amount of thermal energy supplied to the rewritable card from the pressure contact surface of the heating element 92 is experimentally obtained,
By flowing a constant current (electric energy) corresponding to the heat energy amount to the heating element 92, the temperature of the press contact surface is controlled to be maintained at a predetermined erasing temperature.

[0007]

By the way, when the erasing process is started by the erasing head, the constant heating energy E applied to the heating element 92 is changed to the heating energy (heating energy) supplied from the heating element 92 to the rewritable card. (Erasing energy) Ec and heating energy Eh for heating the holder 93 at a lower temperature than the heating element 92. here,
If the temperature of the rewritable card is constant, the heating energy Ec is considered to be substantially constant accordingly, but the heating energy Eh changes mainly depending on the heat storage state of the holder 93. In other words, if the holder 93 is storing heat due to repeated erasing in a short time, the heating energy Eh becomes smaller, and the heating energy Ec is correspondingly reduced.
Increase. For this reason, the heating energy Ec supplied to the rewritable card becomes excessive, and as a result, the erasing characteristics are reduced, such as the occurrence of unerased portions. Normally, the erasing temperature of the thermoreversible recording material constituting the rewrite layer is within a certain range, while the printing temperature is not specified above the erasing temperature. Therefore, high accuracy is required for management of the erasing temperature. For this reason, an excessive rise in temperature of the erasing head is a factor that hinders proper erasing characteristics, and is a problem to be solved.

Therefore, the present invention can suppress an excessive rise in temperature of a thermal head and always maintain an appropriate processing temperature, and as a result, a thermal head temperature control method and a thermal processing apparatus in which the characteristics of thermal processing are improved. It is intended to provide.

[0009]

According to the temperature control method for a thermal head of the present invention, the temperature of a thermal head heated to a predetermined processing temperature is brought into contact with a recording layer of a record carrier to perform thermal processing. The method is characterized in that the temperature of the environment where the thermal head is placed is detected, and the heating energy applied to the thermal head is corrected according to the temperature difference between the two.

According to the above method, the heating energy applied to the thermal head is increased or decreased according to the temperature difference between the temperature of the thermal head and the environmental temperature. For this purpose, the heating energy at which the temperature of the thermal head always becomes an appropriate temperature is grasped in advance according to the temperature difference, and the heating energy is corrected based on the data.
The heating energy is a current value applied to the heating element when the thermal head is an electric resistor, and the current value is conventionally constant using a voltage, a resistance value of the heating element, a temperature characteristic of the image recording layer, and the like as a control factor. However, in the present invention,
The temperature difference between the thermal head and the ambient temperature is added to the control factor that determines the current value, and the current value is changed.

More specifically, as the temperature difference between the thermal head and the ambient temperature increases, the heating energy applied to the thermal head decreases. When the thermal head is constantly heated from the ambient temperature, the temperature difference between the two is 0, and the heating energy is maximized at this time. If the thermal head accumulates heat due to continuous processing, etc., and the thermal head is heated from a temperature higher than the ambient temperature, the temperature difference between the two will increase.
The heating energy is reduced by multiplying the maximum value of the heating energy by a correction factor of 1 or less according to the temperature difference that is grasped in advance. By reducing the heating energy, the thermal head is kept at an appropriate processing temperature by suppressing an excessive rise in temperature, and as a result, thermal processing of the recording layer of the record carrier is reliably performed.

Further, the thermal processing apparatus of the present invention relates to an apparatus suitable for carrying out the above-described thermal head temperature control method, in which a thermal head heated to a predetermined processing temperature is brought into contact with a recording layer of a record carrier. A thermal processing apparatus that performs thermal processing by using an environmental temperature detector that detects an environmental temperature in which the apparatus is placed, a thermal head temperature detector that detects a temperature of the thermal head, and a temperature detected by the environmental temperature detector. And a control means for comparing the temperature detected by the thermal head temperature detecting means with the temperature detected by the thermal head temperature detecting means, and correcting heating energy applied to the thermal head in accordance with the temperature difference.

In order to prevent the temperature of the thermal head from becoming excessively high and exceeding the processing temperature, the control means is provided for controlling the thermal head as the temperature difference between the temperature of the thermal head and the environmental temperature increases. It is desirable to take control to reduce the heating energy applied to the substrate.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an erasing head in a rewritable card processing apparatus will be described below with reference to the drawings. FIG. 1 shows a right side cross section of a rewritable card processing apparatus, and FIG.
FIG. 2 is a view taken along line II-II of FIG. In these figures, the left side is the front side of the apparatus, the right side is the rear side, and in FIG. 2, the upper side is the left side of the apparatus and the lower side is the right side. In the following description, the expression of directions such as front, rear, left and right is defined as a direction based on such a card processing device. The card processing device shown in FIG.
As shown in (1), when a rewritable card (recording carrier: hereinafter simply abbreviated to a card) C is inserted into a card insertion slot 10 provided at the front end, the card C is first conveyed to a standby position at the rear end. When an erase / print processing command is issued in this state, the image is erased and printed in this order on the rewritable layer provided on the surface of the card C while the card C is transported forward. Before describing the configuration of such a card processing device, the card C will be described first.

(1) Configuration of Rewritable Card The card C is, for example, a rectangular IC card defined by "JIS X6303", and as shown in FIG. 2, a resin base such as PVC (vinyl chloride). On the surface of the material,
A rewritable layer (recording layer) 1 formed by laminating a thermoreversible recording material and an external terminal 2 of a built-in IC are provided.
A magnetic stripe 3 is provided on the back surface. The rewrite layer 1 is laminated in a stripe pattern over the entire length of the card C on the upper side of the card C in FIG. 2, and the external terminal 2 is laminated on a predetermined position on the lower side of the rewrite layer 1 and on the right side of the card C. . Further, the magnetic stripe 3 on the back surface is stacked below.

The thermoreversible recording material constituting the rewrite layer 1 is a recording material which is reversible by heating and can easily and easily repeatedly erase / print a high-resolution image, that is, can be rewritten. As shown in FIG. 3, a resin 6a is formed on a transparent polyester film 5.
The recording layer 6 in which the organic low-molecular substance 6b is dispersed and the protective layer 7 are laminated in this order. As the organic low-molecular substance 6b, a higher fatty acid having a particle size of 1 μm or less is used. Explaining the principle of thermoreversibility with reference to FIG. 4, in the transparent state, the particles of the organic low-molecular substance 6b in the recording layer 6 form a relatively large single crystal. Therefore, the incident light passes through the interface of the crystal with a small number of times and is transmitted without being scattered, so that the light appears transparent as a whole. On the other hand, in the cloudy state, the particles of the organic low-molecular substance 6b form polycrystals. Therefore, the incident light is refracted many times at the interface of the crystal, and the light is scattered and looks white.

The thermoreversible characteristics of the thermoreversible recording material will be described with reference to FIG. First, it is assumed that it is in a cloudy state at room temperature (20 to 30 ° C.) (A). When this was heated, the transmittance began to increase from about 70 ° C. as shown by the solid line,
It becomes a maximum transparent state (B to C) at 5 to 100 ° C. Even if this is cooled to room temperature, the transparent state is maintained (D). Next, as shown by the broken line, the material in the maximum transparent state was
When reheated to 0 ° C. or higher, the state becomes an intermediate state between the maximum transparent state and the maximum turbid state (D → C → E).

(2) Configuration of Card Processing Apparatus Next, the configuration of the card processing apparatus will be described with reference to FIGS. In these figures, reference numeral 9 denotes a pair of left and right lower side frames which are spaced apart from each other and arranged to face each other in parallel. In the center between the lower side frames 9, 9, a first conveying roller pair 11 and a second conveying roller pair 1 are sequentially arranged from the front side.
Second and third transport roller pairs 13 are arranged. Each of the transport roller pairs 11, 12, and 13 is composed of a lower drive roller 14 and an upper driven roller 15, and a card C is sandwiched between the upper and lower rollers 14 and 15 in the rotation direction of the drive roller 14. , The card C is conveyed from front to back or from back to front. A printing platen roller 16 and an erasing platen roller 17 are disposed from the front side between the second conveying roller pair 12 and the third conveying roller pair 13, and a printing platen roller 16 is disposed above the printing platen roller 16. The head 40 has an erasing head (thermal head) 50 above the erasing platen roller 17.
Are arranged respectively.

The external contact 2 of the card C contacts the rear end between the lower side frames 9
An IC unit 18 for inputting / outputting information to / from the device is arranged. The card slot 10 and the IC unit 18
Between the upper and lower rollers 14 and 15 of the first to third transport roller pairs 11 to 13;
Between the print head 40 and the erasing platen roller 1
A transport path 19 for the card C is formed, which horizontally connects the card 7 with the erasing head 50. A groove-shaped card guide 9a is formed on the inner surfaces of the lower side frames 9, 9 so that the card C can be smoothly conveyed through the conveyance path 19.
When the card C is inserted into the card insertion slot 10, first, the card C is transported to the standby position at the rear end, as described above. The standby position is in the IC unit 18.

Each of the drive rollers 14 and each of the platen rollers 16 and 17 of the first to third transport roller pairs 11 to 13 are
It rotates integrally with the drive shaft 20 rotatably supported by the lower side frames 9, 9. As shown in FIG. 2, these drive shafts 20 penetrate the lower side frame 9 on the left side, and drive gears 21 are fixed to protruding ends thereof, respectively.
These drive gears 21 are connected to the main motor 22 shown in FIG. 1 through a plurality of intermediate gears (not shown) arranged outside (left side) of the lower frame 9 on the left side, and when the main motor 22 is driven, Rotational force is transmitted from each intermediate gear to each drive gear 21 so that each drive shaft 20 rotates in the same direction,
Each drive roller 1 of the first to third transport roller pairs 11 to 13
4 and the respective platen rollers 16, 17 rotate. The card C includes the drive roller 14 and the platen roller 1.
The sheet is conveyed along the conveying path 19 according to the rotation directions of 6, 17. A magnetic head 24 for reading / writing magnetic data from / to the magnetic stripe 3 of the card C is disposed on the right side of the drive roller 14 of the second transport roller pair 12.

As shown in FIG. 2, a transport path 19 includes first to fourth card sensors 3 for detecting a card C to be transported.
1, 32, 33, and 34 are provided in order from the front.
In this case, the first card sensor 31 is attached to the front end of the right lower side frame 9, and the second to fourth card sensors 32 to 34 are attached to the left lower side frame 9.

As shown in FIG. 1, a pair of left and right upper side frames 35 are attached to the lower side frames 9 and 9, respectively. The rear ends of the upper side frames 35, 35 are pin-coupled to the lower side frames 9, 9 so as to be swingable in the vertical direction, so that they can be opened and closed integrally. Arms 41, 51 extending in the front-rear direction are swingably supported by the upper side frames 35, 35, and a print head 40 and an erasing head 50 are attached to the tips of the arms 41, 51, respectively. Each arm 4
1 and 51 are urged downward by urging means such as a spring (not shown).

The erasing head 50 has the same configuration as that shown in FIG. That is, as shown in the drawing, a bar-shaped substrate 90 made of ceramics or the like is provided.
, A heating element 92 composed of electrodes 91 and 91 and an electric resistor fixed to the head surface 90a, a U-shaped holder 93 attached to both ends of the substrate 90, and a temperature of the heating element 92 attached to the substrate 90. And a temperature sensor (thermal head temperature detecting means) 94 for detecting the temperature. On the other hand, the print head 40 is a general thermal head in which a plurality of heating elements are arranged, although not shown in detail,
By applying a current to a heating element corresponding to a printed portion of an image while pressing against the rewrite layer 1, the rewrite layer 1 is heated to a printing temperature to thermally print an image.

As shown in FIG. 2, the print head 40 and the erasing head 5 are provided on the outer side (right side) of the right lower side frame 9 by swinging the respective arms 41 and 51.
Cam gear 60 for moving 0 to and away from the card C being transported
Is arranged. The cam gear 60 has a cam gear shaft 6
1, and is rotatably supported by the right lower side frame 9 and rotated counterclockwise by a cam motor 77 shown in FIG. Cam gear 60
The print head cam 64 for swinging the arm 41 on the print head 40 side and the arm 5 on the erase head 50 side
The erasing head cam 65 for swinging the cam 1 is coaxially formed with a predetermined cam profile.

The state of the printing head 40 and the erasing head 50 is determined by the rotation angle of the cam gear 60. The rotation angle of the cam gear 60 is detected by a cam sensor 66 shown in FIG. 6, and a detection signal is input to a CPU (control means) 70 shown in FIG. And CPU
70 controls the rotation of the cam motor 77 so that the cam gear 60 is positioned at a predetermined rotation angle according to the signal pattern.

As shown in FIG. 1, an environmental temperature sensor (environmental temperature detecting means) 69 is provided below the card insertion slot 10. The environmental temperature sensor 69 measures an environmental temperature in a room or the like where the device is placed. The environmental temperature sensor 69 is desirably disposed at a location that is least susceptible to a rise in temperature inside the apparatus in order to accurately measure the environmental temperature. When housed inside the apparatus, an opening communicating with the outside of the apparatus may be provided near the apparatus.

FIG. 6 is a control block diagram of the card processing device. The CPU 70 has a serial I / O, a parallel I
It is a microcontroller with built-in peripheral functions such as an O, a timer, an AD converter, and a watchdog timer. A ROM 71 storing a control program and fixed data is connected to the CPU 70.
Various controls are performed according to the program stored in.
The CPU 70 has print data, command data,
A RAM 72 that can store various set values and reference values as needed, and a serial interface 73 that receives an erase / print command or the like from a higher-level device and issues it to a CPU 70 are connected.

Detection signals from the first to fourth card sensors 31 to 34 are supplied to the CPU 70. Based on the detection signals from the card sensors 31 to 34, the CPU 70 outputs a control signal to the main motor control circuit 74. Then, operations such as the rotation speed, rotation direction, and start / stop of the main motor 22 are controlled. An FG (rotation signal generator) 75 is attached to the main motor 22. By measuring the pulse width of the pulse output from the FG 75, the rotation speed of the main motor 22 can be detected. I have.
In addition, the CPU 70 controls the second to fourth card sensors 32 to
A drive / stop signal is output to the cam motor 77 via the cam motor control circuit 76 based on the outputs of the cam sensor 34 and the cam sensor 66 to control the rotation angle of the cam gear 60. A read circuit 78 for reading magnetic data written on the magnetic stripe 3 of the card C and a write circuit 79 for writing magnetic data on the magnetic stripe 3 are connected to the magnetic head 24. The magnetic data is read / written from / to the magnetic stripe 3 via these circuits 78 and 79.

Further, the CPU 70 controls the image (bitmap)
Data is created, and the data is transferred to the print head 40 via the print head control circuit 80 while synchronizing with the transport distance of the card C. Thus, an arbitrary image is printed on the rewrite layer 1 of the card C. Further, the CPU 70
Heats the erasing head 50 to a predetermined erasing temperature via the erasing head control circuit 81. The temperature of the heating element 92 of the erase head 50 detected by the temperature sensor 94 is C
It is detected as a digital value by an A / D converter built in the PU 70. The CPU 70 detects the heating element 9
A duty is obtained based on the temperature 2 and the set value data stored in the ROM 71 or the RAM 72, and an energizing pulse having a pulse width corresponding to the duty is output to the erase head control circuit 81. Thus, the erasing head 50
Of the heating element 92 is controlled to a predetermined erasing temperature for making the thermoreversible recording material forming the rewrite layer 1 transparent.

The CPU 70 has an environmental temperature sensor 6
9 is supplied, and the detection signal is supplied to the CPU 70
And is converted into a digital value by the A / D converter. The CPU 70 executes the erasing / printing process and the print head 4 based on the measurement value of the environmental temperature sensor 69.
0 and the duty of the erase head 50 are controlled.

(3) Operation of Card Processing Apparatus Next, the operation of the card processing apparatus having the above-described configuration when erasing / printing an image on the rewrite layer 1 of the card C will be described with reference to the flowchart of FIG.
This operation is performed by the first operation for detecting the transport position of the card C.
To fourth card sensors 31 to 34 and cam sensor 6
6 is controlled by the CPU 70 to which the detection signal 6 is supplied.

First, when an erasing / printing command is issued from a higher-level device (not shown) to the CPU 70 via the serial interface 73, the CPU 70 calls a print command processing subroutine S0 according to a program stored in the ROM 71. In step S1, the print command processing subroutine S0 measures the environmental temperature and the temperature of the erasing head 50 with the environmental temperature sensor 69 and the temperature sensor 94, respectively, and obtains the temperature difference between the two. The duty of the erasing head 50 is set, and the process proceeds to step S2. In step S2, the first card sensor 31 is in a state of waiting for the insertion of the card C, and when the insertion of the card C is detected by the first card sensor 31, the main motor 22 is transmitted via the main motor control circuit 74. Drives the card C to the standby position and preheats the erasing head 50. At this time, the print head 40 and the erase head 50
Are separated upward from the transport path 19 by the action of the cam gear 60. The preheating of the erasing head 50 depends on the temperature TES detected by the temperature sensor 94 and the ROM 71 or RA
When the preheating temperature set value TER stored in M72 is used and the duty of the erase head energizing pulse is EPD, the following EPD = (TER−TES) × GAIN (however, the maximum value is 100%) (A) It is performed by energizing according to the equation. Where E
The PD is not determined once, and the energization cycle (for example, 10 m
Each time S) elapses, feedback control for performing recalculation is performed.

When the heating element 92 is rapidly heated when the heating element 92 is heated to the preheating temperature, the temperature sensor 94
The surface temperature of the heating element 92 and the temperature sensor 9 depend on the time constant of the heating element 92 and the heat conduction time from the heating element 92 to the temperature sensor 94.
There is a case where a large difference occurs between the detected value and the fourth detected value. Therefore, it is desirable that the heating element 92 be gradually heated, and the GAIN value in the above equation (A) is suitably about 1 to 2. When the preheating of the erasing head 50 is completed, the process proceeds to step S3, where the CPU 70 develops the print character string specified by the print command in the RAM 72 in the form of a bit map. Next, the process proceeds to step S4, where an image erasing / printing process is performed on the rewrite layer of the card C.

In the erasing / printing process, the card C at the standby position is transported forward at a low speed while measuring the transport distance. When the front end of the card C reaches the position of the erasing head 50, the erasing head 50 is moved downward. The heating element 92 that has been preheated as described above presses against the rewrite layer 1 of the card C. At this time, the erase head energizing pulse having the duty set in step S1 is output to the erase head 50 via the erase head control circuit 81, and the heating element 92 of the erase head 50 generates heat at a temperature corresponding to the electric energy. The rewrite layer 1 is heated by the heating element 92, and the image of the rewrite layer 1 is thermally erased by continuously moving the card C forward.

Next, the front end of the card C is
Is reached, the print head 40 swings downward and presses against the rewrite layer 1. When the print head 40 is pressed against the rewrite layer 1, the print data stored in the RAM 72 is sequentially transferred to the print head 40 every time the print head 40 is transported by a prescribed transport amount (for example, about 0.1 mm). When the transfer of one line of print data to the print head 40 is completed, a print head energizing pulse having a pulse width obtained by using a timer built in the CPU 70 is transmitted to the print head 40 via the print head control circuit 80. With the output, the heating element of the print head 40 selected by the print data is energized, and the image is thermally printed on the rewrite layer 1. In this manner, the erasing head 5
The deletion of the image by 0 and the printing of a new image by the print head 40 are performed in parallel.

Next, the rear end of the card C is
Is reached, the erasing head 50 separates upward from the card C, and thereafter only printing is performed. When the printing of all the image data is completed, the print head 40 also moves to the card C
From above, the erase / print processing is completed, and step S
Go to Card 5 In step S5, the card C is transported by a predetermined amount until the front end is ejected from the card insertion slot 10, and then the main motor 22 stops.

FIG. 8 shows a method of setting the duty of the erasing head 50 set in step S1.
This will be described with reference to FIG. Duty setting subroutine S0
Is called, in step S1, the environmental temperature sensor 6
9 is converted into a digital value by an AD converter built in the CPU 70, and the converted temperature data (T
A duty f (Ta) is obtained based on a). This duty may be a value obtained by a predetermined calculation formula or a value obtained by referring to a table. Next, in step S2, the setting state of a switch for setting the rank of the resistance value of the heating element 92 of the erasing head 50 is read, a duty correction factor f (R) corresponding to this setting state is obtained, and this is obtained in step S1. The calculated duty f (Ta) is integrated, and the process proceeds to step S3. In step S3, the output signal of the temperature sensor 94 of the erasing head 50 is converted into a digital value by an AD converter built in the CPU 70 to obtain erasing head temperature data (Te). Next, ΔT = Te−T
The calculation a is performed, and the duty correction rate f (ΔT) with respect to the determined ΔT is determined. This correction rate is added to the duty after correction obtained in step S2, and the energization duty D
Ask for. That is, the energization duty is obtained by the following (B). D = f (Ta) × f (R) × f (ΔT) (B) The duty correction rate f (ΔT) to be finally integrated
Is variably set such that, as shown in FIG. 9, when ΔT is 0, the value is 1.0, and the larger the ΔT, the smaller the value, but the lower the environmental temperature, the smaller the value. Can also.

(4) Operation and Effect of One Embodiment According to the temperature control method at the time of image erasure by the card processing apparatus of the one embodiment, the erasing head 50 stores heat by performing continuous erasing / printing processing. Even so, the heat storage state is detected when the temperature difference between the temperature of the erasing head 50 and the environmental temperature increases, and the electric energy supplied to the erasing head 50 is set low. Therefore, the erasing head 50 is kept at an appropriate erasing temperature at all times by suppressing an excessive rise in temperature. As a result, a problem such as an unerased image does not occur and the erasing process characteristics are improved.

[0039]

As described above, according to the present invention,
Since the temperature of the thermal head and the environmental temperature at which the thermal head is placed are detected, and the heating energy applied to the thermal head is corrected according to the temperature difference between them, an excessive rise in temperature of the thermal head is suppressed. The proper processing temperature is always maintained, and as a result, the characteristics of the thermal processing are improved.

[Brief description of the drawings]

FIG. 1 is a right side sectional view of a card processing apparatus provided with an erasing head according to an embodiment of the present invention.

FIG. 2 is a view taken along the line II-II in FIG.

FIG. 3 is a cross-sectional view schematically showing a thermoreversible recording material constituting a rewritable layer of the rewritable card according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating the principle of a thermoreversible recording material.

FIG. 5 is a diagram showing a change in transparency / cloudiness with heating of a thermoreversible recording material.

FIG. 6 is a control block diagram of the card processing device according to the embodiment of the present invention.

FIG. 7 is a flowchart illustrating an operation of the card processing device according to the embodiment of the present invention.

FIG. 8 is a diagram showing a conduction width (duty) supplied to an erasing head.
Is a flowchart showing the procedure of the setting method.

FIG. 9 shows a correction rate of a power supply width (duty) supplied to the erase head according to a temperature difference between the erase head and the environmental temperature.
It is a diagram showing the table for variably setting for every environmental temperature.

10A and 10B show an erasing head according to an embodiment of the present invention, wherein FIG. 10A is a side view, FIG. 10B is a front view, and FIG. 10C is a bottom view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rewrite layer (recording layer) 50 ... Erasing head (thermal head) 69 ... Environmental temperature sensor (environmental temperature detection means) 70 ... CPU (control means) 94 ... Temperature sensor (thermal head temperature detection means) C ... Rewritable card ( Record carrier)

Continued on the front page (72) Inventor Masaya Nakamura 20-10 Nakayoshida, Shizuoka City, Shizuoka Prefecture Star Precision Co., Ltd. F-term (reference) 2C066 AA03 AA18 AB09 CA05 CA11 CA14 CA15 CA19

Claims (4)

[Claims] In performing a thermal process by bringing a thermal head heated to a predetermined processing temperature into contact with a recording layer of a record carrier, a temperature of the thermal head and an environmental temperature at which the thermal head is placed are detected, respectively. A temperature control method for a thermal head, comprising: correcting heating energy applied to a thermal head according to a temperature difference between the two. 2. The temperature control method for a thermal head according to claim 1, wherein the heating energy is reduced as the temperature difference increases. 3. A thermal processing apparatus for performing thermal processing by bringing a thermal head heated to a predetermined processing temperature into contact with a recording layer of a record carrier, wherein an environmental temperature detecting means for detecting an environmental temperature at which the apparatus is placed. A thermal head temperature detecting means for detecting the temperature of the thermal head; comparing the temperature detected by the environmental temperature detecting means with the temperature detected by the thermal head temperature detecting means; A thermal processing apparatus comprising: a control unit that corrects heating energy applied to a head. 4. The thermal processing apparatus according to claim 3, wherein the control unit reduces the heating energy as the temperature difference increases.