JPH04103367A - Thermal printer - Google Patents

Abstract

PURPOSE:To make it possible to use a printer in a short time for preparation by providing a controller for controlling electric power of a heater and deciding print start permission in accordance with a detected output of a temperature sensor for detecting the temperature of a thermal head which is to be heated by the heater directly. CONSTITUTION:According as a thermal print head 21 is heated by a heater 29, a detecting temperature rises rapidly. A controller 35 cuts off the current being supplied to the heater 29 when the controller detects a control temperature. However, the temperature of a temperature sensor 30 of the thermal print head 21 further rises slightly due to a time lag of heat conduction. Thereafter, the temperature begins to decrease due to radiation. When the detecting temperature decreases to the control temperature, the controller 35 starts to energize the heater 29 again and the current is cut off again at the time that the detecting temperature exceeds a control temperature L. After this, the charging of the current to the heater 29 is controlled in accordance with the detecting temperature. Although the temperature of the thermal print head 21 changes up and down slightly with the control temperature as a middle temperature, it is maintained in a nearly constant temperature without changing largely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thermal print having current-carrying heating resistors segmented into print pixel units and arranged in rows along the width direction of a recording medium. The present invention relates to a thermal printer that prints by bringing a head into pressure contact with a heat-sensitive recording medium and selectively energizing the current-carrying heating resistor according to a recording image signal.

[Prior Art] A thermal print head includes a heat-sensitive recording medium and a thermal print head having current-carrying heating resistors that are segmented into print pixels and arranged along the width direction of the recording medium over an area approximately equal to the width of the recording medium. Thermal printers that print in combination are well known and have been widely put into practical use.

A thermal print head generally has a heat insulating glaze layer made of glass or the like formed on a ceramic substrate, an electrode layer and a resistance layer on top of the glaze layer, and a wear-resistant layer on the outermost surface. The electrode layer is segmented and can be selectively energized according to the print image signal. Driver elements and the like are mounted on the ceramic substrate. The ceramic substrate is held on a thermoelectric heat dissipation substrate made of aluminum or the like to prevent heat accumulation.

Thermal recording media include those that are printed directly on a sheet coated with a heat-sensitive coloring agent, and those that are printed by placing an ink sheet coated with a heat-melting colorant in close contact with image-receiving paper and transferring the colorant onto the image-receiving paper by melting and adhesive. There are some that use an ink sheet coated with a thermal sublimation transfer dye and an image-receiving paper that are pressed together, and then print by thermally diffusing the dye onto the image-receiving paper.

In printers using these thermal print heads, changes in environmental temperature and temperature changes due to heat accumulation in the thermal print head directly affect print characteristics, causing problems such as changes in print dot diameter and fluctuations in image density. Ta.

Furthermore, the energy applied for printing is large, which is an obstacle to realizing high-speed printing.

Various proposals have been made to solve this problem. For example, Japanese Patent Application Laid-Open No. 49-37720 discloses a means for increasing the temperature of the recording medium sheet and the thermal print head by heating a pad provided for pressing the recording medium sheet against the print head. .

FIG. 8 is a diagram quoted from the above-mentioned publication.

The thermosensitive recording medium 2 is carried by a conveyance roller 6 and is pressed against the thermal head 1 by a pad 7 to perform printing. A heating resistor such as a nichrome wire is incorporated in the pad 7, and power is supplied from the terminal 8. pad 7
The temperature of is sensed by a temperature sensor and read via sensor leads 12.13. The temperature of the pad 7 is controlled so that the heat is conducted to the thermosensitive recording medium 2 and the thermal head 1 and heated to a temperature at which printing is not performed.

[Problem to be solved by the invention] In order to print with less energy and enable high-speed printing in a thermal printer, it is quite effective to keep the temperature of the thermal print head high. This was experimentally confirmed by the present inventor. However, in the configuration shown in the example shown in FIG. 8, in which the pad 7 is heated and the heat is transferred to the thermal print head 1 for heating, it is difficult to preheat the thermal print head at high speed while satisfying the condition that no printing is performed. , heating the thermal head to a sufficiently high temperature to be effective, and continuing to maintain that temperature during printing, etc., is extremely difficult. In addition, in thermal printers, in order to maintain the print head temperature at a predetermined temperature and stabilize printing, complicated controls and additional devices are required because the print head itself has a heat storage effect due to its own heat generation. There were some problems.

Therefore, the present invention can raise the temperature of the thermal print head to a predetermined temperature extremely quickly, making it possible to complete preparations for use within a short time, and also making it possible to maintain the thermal print head at a predetermined temperature even during the printing process. It is an object of the present invention to provide a thermal printer that can maintain stable print image density and realize high-speed printing with less printing energy.

[Means for Solving the Problems] In order to solve the above problems and achieve the objectives, the present invention takes the following measures as basic means.

A thermal print head having energized heating resistors segmented into print pixel units and arranged in rows along the width direction of the recording medium is brought into pressure contact with the thermosensitive recording medium,
In a thermal printer that prints by selectively energizing the current-carrying heat-generating resistors according to a recording image signal, there is provided a heater provided along the arrangement direction of the current-carrying heat-generating resistors of the thermal print head; a temperature sensor that detects the temperature of the thermal print head, and a controller that controls the power of the heater and determines permission to start printing based on the detection output of the temperature sensor; A control command is issued based on a specified control temperature value within a temperature range that is equal to or lower than a printing threshold temperature.

[Effect] As a result of taking the above measures, the following effects occur.

Because the thermal head is directly heated by the heater,
It is possible to heat the thermal print head to a predetermined temperature extremely quickly. As a result, it can be used in a short preparation time. Furthermore, since sufficient heat can be supplied even during the printing process, a predetermined temperature can be stably maintained. Furthermore, since the set temperature is set to 50° C. or higher and lower than the printing threshold, high-speed printing can be achieved with less printing energy. Furthermore, in the function of removing heat generated by the thermal head itself, since the temperature of the print head is sufficiently higher than the temperature of the air inside the apparatus, it is possible to use natural cooling or a simple air blowing means. In this way, the temperature of the print head can be maintained with high accuracy, and the print image density can be stabilized.

[Embodiment] FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention. In the figure, 21 is a thermal print head, 22 is a ceramic substrate, 23 is a heating line, and 24 is a wiring cover 2
5 is a driver circuit, 26 is a support plate, 27 is a connector,
28 is a radiation fin, 29 is a sheath heater, 30 is a temperature sensor, 31 is a platen roller, 32 is an ink sheet,
33a is an ink sheet supply roll, 33b is an ink sheet take-up roll, 34 is an image receiving paper, 35 is a controller, 3
Reference numeral 6 indicates a cooling fan, and reference numeral 35g indicates a print start permission signal terminal.

The thermal print head 21 has a ceramic substrate 22
A heating line 23 having a length approximately equal to the width of the image receiving paper 34 is provided near the end of the image receiving sheet 34 along the main scanning direction.

The heat generating line 23 is formed by providing a glass glaze layer with a heat insulating effect on the ceramic substrate 23, further forming an electrode layer divided into corresponding to the printed pixels, and depositing a thin film layer of a current-carrying heat generating resistor on top of the electrode layer. , the outermost surface is coated with a wear-resistant layer.

The electrode wire is drawn out to the left in the figure on the ceramic substrate 22, connected to the driver circuit 25, and further connected to the outside via the connector 27. Further, the surface of the electrode layer is protected by a cover 24.

The ceramic substrate 22 is attached to a support plate 26 made of aluminum or the like for reinforcement and heat radiation.

Furthermore, a heat radiation fin 28 is attached on the opposite surface of the support plate 26 with the heat generation line 23 in the center. A sheath heater 29 is installed in the radiation fin 28 with a length that covers at least the length of the heat generation line 23 in the main scanning direction. At the upper part near the center of the heat generation line 23, there is a temperature sensor 3.
0 is installation.

The platen roller 31 is pressed so that a nip is formed approximately around the heat generation line 23, and the ink sheet 32 and the image receiving paper 34 are conveyed through the nip portion so as to move in the sub-scanning direction.

The controller 35 operates using the detection output from the temperature sensor 30 as input, and controls the supply of electricity to the heater 29 . Further, when the thermal head 21 reaches a predetermined temperature and is ready to start printing, a signal indicating this is sent from the terminal 35a. Further, the power supply to the cooling fan 36 is controlled.

FIG. 2 is a diagram showing the state of control by the controller 35. In the figure, A indicates ON-OFF of the power supply, B indicates ON-OFF of the heater 29, and C indicates the temperature sensor 3.
Indicates a detection signal of 0. Note that the temperature controlled by the controller 35 is set to a temperature of 50° C. or higher and lower than the printing threshold temperature.

When the power is turned on at time 10, power supply to the heater 29 starts. The temperature sensor 30 initially indicates the room temperature, but as the thermal print head 21 is heated by the heater 29, the detected temperature rapidly rises. Time t1
When the controller 35 detects that the control temperature is low, the controller 35 cuts off the power to the heater 29. However, the temperature of the temperature sensor 30 of the thermal print head 21 further increases slightly due to the time lag of heat conduction. After that, it starts to fall due to heat radiation. When the detected temperature drops to the control temperature at time t2, the controller 29 starts energizing the heater 29 again, and cuts off the energization again at time t3 when the detected temperature exceeds the control temperature.

Thereafter, energization to the heater 29 is controlled based on the detected temperature,
Although the temperature of the thermal print head 21 changes slightly upward and downward around the control temperature, it is maintained almost constant without major changes.

The effects of this embodiment configured in this way will be explained using FIG. 3.

Figure 3 uses a thermal print head 21 that prints at a pixel density of 10 dots per millimeter, an ink sheet 32 coated with a thermal sublimation transfer dye as a thermal recording medium, and an image-receiving layer coated with a synthetic paper base. 120 per dot using receiver paper 34
A pulse with a microsensor width is applied 64 times to produce a solid C.
,M.

This figure shows how the temperature of the thermal print head changes when seven images are printed one after another.

FIG. 3 is also a diagram for explaining the temperature change situation of the thermal print head 21 when this printer is implemented.

The horizontal axis in FIG. 3 indicates the passage of time, and the numbers indicate the number of prints. Note that it takes about 150 seconds to print one sheet, including the access time associated with conveying the image receiving paper 34 and the ink sheet 32. Also, the vertical axis indicates the temperature of the support plate of the thermal print head 21. Curve 8 shows the case when the thermal head 21 is cooled by blowing air, curve 5 shows the case when natural heat radiation is performed without blowing air, and curve C shows the case when heater energization control is performed according to the present invention.

Although the outside temperature is 25°C, the thermal print head 21
The temperature was started at 35°C due to the influence of previous experiments. In the case of air cooling, as shown in curve 8, there is a rapid temperature change until the end of printing the fourth sheet, but after that the temperature changes gradually and reaches a saturation temperature around 45°C.

In the case of natural heat dissipation, as shown in curve 5, there is a rapid temperature rise until the end of printing the 6th sheet, and the rise thereafter becomes gradual. The curve shows the average temperature change during printing, and X and y show the temperature change (variation) of the thermal print head 21 during the creation of one print. 8
As can be seen from the curve and curve 5, the temperature change due to self-heating of the thermal print head 21 is significant, and although forced cooling is effective in preventing heat accumulation, the thermal print head 21
It is not effective enough to sufficiently prevent temperature changes. Therefore, in this case, it is necessary to take measures to detect the temperature of the print head 21 and control the print pulse width and number of pulses to stabilize the print image density and the like. However, the known methods have problems such as impeding the speeding up of printing and causing unstable changes in print density in low image density areas.

Next, as shown by curve C, in the case of the printer configured according to the present invention, the head is heated at high speed by the heater mounted on the print head prior to printing. In the conventional configuration shown in Fig. 8, the print head 1 is preheated from the pad 7, so the heating efficiency is poor, it is not possible to preheat to a sufficiently high temperature at a high speed, and the temperature drops due to heat dissipation during printing. Even when it happened, I couldn't prevent it. In contrast, with the configuration of this printer, a large amount of heat can be applied directly to the thermal print head 21. Moreover, heating can be performed at appropriate times as necessary even during the printing process. Therefore, within a very short period of time, the control temperature L is higher than 50℃ and lower than the printing threshold temperature.
(65° C. in the illustrated example) and can shorten the preparation time. Note that during printing, the temperature of the print head 21 fluctuates due to heat radiation and self-heating of the print head 21, but it can be easily heated by the heater 29. Also, the control temperature is sufficiently higher than the outside temperature. Therefore, it can be efficiently cooled by natural heat radiation or weak ventilation.
It is extremely easy to maintain the temperature of the thermal print head 21 at a predetermined temperature.

When the print head 21 reaches the control temperature at time T prior to printing, the controller 35 turns on the heater 2.
9 is cut off, and a signal S for permission to start printing is issued.

As explained in FIG. 2, after the heater 29 is turned off, there is a slight temperature drift due to heating overshoot and heat radiation, but the temperature of the print head 21 is maintained around the control temperature, and the image signal is Even if there is a change in the amount of heat generated due to a change in print pulses or a change in heat dissipation efficiency due to a change in outside temperature, the temperature of the print head 21 is maintained stably with the configuration of this embodiment.

Note that if the power supply to the heater 29 is not cut off due to some kind of accident, it is preferable to set a higher temperature detection level to forcibly turn off the power, or to provide a temperature phase in the print head to cut off the power supply. The temperature change in this case is shown by the dotted line in FIG.

Note that if a high-power heater 29 is used to shorten the start-up preparation time, the amount of overheating after the heater 29 is turned off also increases. For this reason, density unevenness may occur during printing of one screen. In order to shorten the preparation time and prevent the occurrence of image density unevenness, the power supply to the heater 29 can be switched between 11 and 11 low power.The heater 29 is energized at high power during preparation, and the heater 29 is switched on during printing.
It is preferable to energize with low power.

FIG. 4 is a diagram illustrating the effect of the power switchable configuration, where A indicates ON-OFF of the power supply, B indicates changes in the energization level of the heater 29, and C indicates the detection signal of the temperature sensor 30. It shows change. Heater 2 as shown in B
The level of energization to 9 can be selected from high power HP during preparation and low power LP during printing, and the power is increased during preparation and lowered during printing.

At the temperature detected by the temperature sensor 30 shown in C, Ll is the heater power switching level during preparation, and L2 is the heater control level during printing.

Switch on at time to and apply high power HP to heater 29
The heater 2 is energized at the time t1 when the control level L1 is reached.
Switch 9 to low power. At time t2 when the temperature reaches the control level L2, power to the heater 29 is cut off. After a slight overshoot occurs, the control level becomes L2 again at time t3 due to temperature drop due to heat radiation. At this point, low power LP energization is started, and energization is cut off at time t4. After that, printing is continued by repeatedly turning on and off the low power LP. Since the heater is energized at low power during printing, there is little overshoot and the print head 21 can be maintained in a state with very little temperature drift. Note that without providing the first control level L1, high power HP operation is performed until reaching L2 at startup, and after that, low power L
It is also possible to energize at P. In this case, it is preferable that the print start permission signal S is generated at the time when the temperature L2 is reached, goes through overshoot, and reaches the temperature L2 again due to heat radiation.

Next, other effects obtained by the configuration of this embodiment will be explained using FIG. 5. In the figure, the horizontal axis shows the print pulse width, and the vertical axis shows the image density. ■■■■ The temperature of the thermal print head 21 is 10℃, 30℃, 5℃.
This is a curve showing the gradation characteristics of a printed image when changing the temperature to 0°C and 70°C. The gradation curves at each temperature have the same shape and are shifted in parallel in the lateral direction.

For example, when obtaining an image density of 2.0, the print head 21
When the temperature is 10° C., a pulse width of 158 μs is required, but at 70° C., a signal with a pulse width of 120 μs may be applied. When actually constructing a printer, the maximum pulse width or number of pulses is determined so that printing is possible even at low temperatures, which requires a wide pulse width, and this determines the printing speed. As the environmental temperature increases,
The pulse width or number of pulses may be smaller, but it will not speed up the print and will only introduce additional latency.

However, in this embodiment, since the print head 21 is preheated to a high temperature at the start of printing, the print speed can be set based on a short pulse width or a small number of pulses regardless of the environmental temperature process. Therefore, a high-speed printer can be realized, and the load on the print head driver circuit can be reduced.

In addition, in the curve (■) in Fig. 5, the density is 0.0 in the low density part of the image.
The pulse width required to obtain 1 is 7oμS, and the concentration 2
．． It takes 168 μs to obtain 0, and the pulse of 70 μs or less acts as a bias for the recording threshold. As the pulse width for this bias becomes larger than the pulse width for original printing, the influence on the degree of image when the pulse voltage and pulse width vary at a constant rate increases. In particular, the concentration in the low concentration portion fluctuates greatly. On the other hand, when the temperature of the print head 21 is raised, the VPO ratio of the bias portion of the pulse width becomes smaller, so that even if the pulse voltage and width change at the same ratio, the influence on the print image density is small.

That is, according to the configuration of this embodiment, the print head 2
1 at a high temperature of 50''C or higher, it is possible to reduce the bias action component of the pulse width and stabilize the print density.

As described above, the effects obtained by the configuration of this embodiment include a stabilizing print density effect by stabilizing the temperature of the thermal print head 21, an effect of simplifying the heat dissipation assisting means, an effect of reducing print energy and speeding up printing, and a bias component of the print pulse. The effect of stabilizing print density in low-density areas of images due to reduction has been explained. In order to make this effect effective, the heating temperature of the print head 21 needs to be sufficiently higher than room temperature or the internal temperature of the printer. Therefore, it should be set to at least 50''C or higher.The set temperature must also be below the threshold level for starting printing, and the temperature varies depending on the thermosensitive recording medium.

When applying the thermal sublimation transfer method that utilizes the thermal diffusion phenomenon of dyes, the paper "Japan Hardcopy '90" states that the print start temperature mainly depends on the glass transition temperature of the image receiving layer coated on the image receiving paper 34. He is known for his publications such as Collected Works (pages 183-186). Therefore, considering that the temperature of the image receiving paper 34 during printing is slightly lower than the temperature of the thermal print head 21, the heating temperature of the thermal print head 21 is set to T of the image receiving layer of the image receiving paper 34.
It is preferable to set it to less than g.

Incidentally, in the apparatus configured as shown in FIG. 1, it is preferable to provide the temperature sensor 30 at a position close to the heat generation line 23, but if the temperature sensor 30 is located extremely close, the sensor 30 will cause temperature unevenness. Therefore, the sensor 30 is provided near the center of the support plate 26 in the thickness direction, and the heater 29 is provided on the opposite side of the heat generation line 23 with respect to the sensor 30. With this configuration, temperature information suitable for control purposes can be detected without being directly affected by the temperature of the heater 29, which changes rapidly, and without causing temperature unevenness in the heat generating line 23.

As mentioned above, the heating temperature of the thermal print head 21 is below the printing threshold, and it is preferable in terms of operation and effect to set it to a temperature as high as possible. However, in a print head configuration in which a latch circuit, a driver circuit, etc. are integrated with the thermal print head 21,
There is an inconvenience that a high temperature cannot be set because the heat resistance temperature of such circuits is a constraint.

In order to eliminate the above disadvantages, the thermal brinato head 2
It is convenient to provide a groove in the center of one support plate 26 in the direction along the heat generating line 23 to thermally separate the heat generating line 23 and the circuit section.

FIG. 6 is a diagram showing a main part of a second embodiment constructed in consideration of the above points. In the figure, 21' is an improved thermal print head, 26' is a support plate, 37 is a groove, 38 is a heat radiation section, 29' is a planar heater, and 28' and 39 are radiation fins. The other members are the same as those in FIG.

By providing a groove 37 in the center of the support plate 26' in a direction parallel to the heat generation line 23, a high temperature section including the heat generation line 23 and the heater 29' and a low temperature section including the circuit section 25 on which semiconductor circuit elements are mounted are formed. are thermally separated. This effect occurs because the heat conduction area, that is, the longitudinal cross-sectional area of the remaining portion of the support plate 26' after the grooves 37 have been processed, becomes smaller, making it difficult for heat to transfer. As shown in the figure, since a plurality of grooves 37 (two in this example) are provided and a protrusion 38 is provided between them, the groove serves as a radiation fin, which is more convenient. Further, since the heat dissipation fins 39 are provided on the low-temperature side of the groove 37, a significant effect of lowering the temperature of the circuit section 25 is added.

On the other hand, on the high temperature side, the volume of the part thermally separated by the groove 37 is reduced, so it can be heated with a heater with less power, and the high temperature area is small, so that it can be heated inside the printer. The amount of heat dissipated is also reduced, resulting in the effect of reducing the cooling load of the entire device. Heater 2
Although a planar heater is illustrated as 9', any shape of the heater can be applied.

In the embodiment shown in FIG. 6 above, in order to enhance the thermal isolation effect, the depth of the groove 37 is increased and the cross-sectional area of the support plate 26' at the connecting portion between the low-temperature section and the high-temperature section is reduced. It is effective to do so. However, in that case, a problem arises in that the strength of the support plate 26' is reduced. In order to thermally separate the low temperature section and the high temperature section without reducing the strength of the support plate 26', a heat insulating material may be embedded in the central separation groove.

FIGS. 7(a) and 7(b) are views showing essential parts of two different embodiments that take this point into consideration, and show an improved support plate 46°56. 47.57 is a separation groove, and a heat insulating material 40.50 is filled in this groove. As the heat insulating material, a material with high heat insulating properties and rigidity such as thermosetting heat-resistant plastic such as Bakelite or porous ceramics is used. These heat insulating materials 40.degree. 50 are inserted and joined into the grooves 47.57 and integrated. Note that 51 and 52 in FIG. 7(b) are connecting screws.

Note that the present invention is not limited to the embodiments described above, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects] According to the present invention, it is possible to raise the temperature of the thermal print head to a predetermined temperature extremely quickly, and it is possible to complete preparations for use within a short period of time. It is possible to provide a thermal printer that can stably maintain a predetermined temperature, keep print image density stable, and realize high-speed printing with less printing energy.

[Brief explanation of drawings]

Figures 1 to 5 are diagrams showing a first embodiment of the present invention.
Figure 2 is a waveform diagram showing the configuration, Figure 2 is a waveform diagram showing the control state by the controller, Figure 3 is a diagram explaining the action, and Figure 4 is a waveform diagram showing the control state when a means for switching power input to the heater is adopted. , FIG. 5 is an explanatory diagram of other effects. FIG. 6 is a side view showing the main parts of the second embodiment of the present invention, and FIG.
Figures (a) and (b) are side views showing main parts of a third embodiment of the present invention. FIG. 8 is a perspective view showing the prior art. 21... Thermal print head, 22... Ceramic substrate, 23... Heat generating line, 24... Wiring cover 25... Driver circuit, 26... Support plate, 27
... Connector, 28 ... Radiation fin, 29 ... Sheath heater, 30 ... Temperature sensor 31 ... Platen roller, 32 ... Ink sheet, 33a ... Ink sheet supply roll, 33b ... - Ink sheet winding roll, 34... image receiving paper, 35... controller,
36...Cooling fan. Applicant's representative Patent attorney Atsushi Tsuboi Figure 2 Figure 6

Claims (5)

[Claims] (1) A thermal print head having current-carrying heat-generating resistors segmented into printing pixels and arranged in rows along the width direction of the recording medium is brought into pressure contact with the thermal recording medium, and the current-carrying heat is generated according to the recording image signal. In a thermal printer that performs printing by selectively energizing resistors, there is a heater provided along the arrangement direction of the energized heating resistors of the thermal print head, and a heater that heats the thermal print head by the heater. The controller includes a temperature sensor that detects temperature, and a controller that controls the power of the heater and determines permission to start printing based on the detection output of the temperature sensor, and the controller is configured to control the temperature when the temperature is 50° C. or higher and the print threshold is reached. 1. A thermal printer characterized in that the printer is configured to issue a control command based on a specified control temperature value within a temperature range below a temperature. (2) The thermal printer according to claim 1, wherein the recording medium is composed of an ink sheet coated with a thermal sublimation transfer dye and an image receiving paper coated with a receptor layer for the dye, and the recording medium is controlled at a temperature controlled by a controller. The value is 50
A thermal printer characterized in that the temperature range is specified to be above .degree. C. and below the Tg of the dye-receiving layer of the image-receiving paper. (3) The thermal printer according to claim 1, wherein a temperature sensor is provided between a heat generating line of the print head and a heater. (4) The thermal printer according to claim 1, wherein the support plate constituting the thermal print head has a support plate parallel to the heat generation line in the center between the area corresponding to the heat generation line and the area where the semiconductor circuit element is mounted. A thermal printer characterized by having grooves in one direction. (5) The thermal printer according to claim 1, wherein the power supplied to the heater attached to the thermal print head can be switched between high and low, and the power is supplied at high power during a preparation period prior to printing, and during printing. A thermal printer that is characterized by low power energization.