JPH0630890B2 - Thermal head drive - Google Patents

Description

The present invention relates to a thermal head driving device used in an apparatus for thermal recording or display.

"Prior Art" A recording apparatus that performs thermal recording using a thermal recording paper or a transfer type thermal recording medium is widely used in facsimiles, printers and the like. Usually, in such a recording apparatus, a thermal head in which unit heating elements (heating elements) are arranged one-dimensionally or two-dimensionally is used as a recording head. The same applies to a type of display device that displays an image by utilizing a latent magnetic image. Since the thermal head generates heat energy for recording or displaying, there is a problem of image quality deterioration due to this energy. Among these, the deterioration of image quality due to the thermal storage phenomenon of the thermal head has come to be particularly noticed with the improvement of image resolution and the speeding up of recording or display operation.
Research is being conducted in various fields.

FIG. 12 shows an outline of a thermal head driving device disclosed in Japanese Patent Application No. 245420/1983 as an example of a technique for preventing the image quality deterioration due to the heat storage phenomenon. This apparatus is employed in a recording or display apparatus of a type in which one or more unit heating elements of a thermal head are repeatedly and selectively driven for each printing unit process to record or display image data. The thermal head driving device stores the image data 11 sequentially in a storage unit 12 for a plurality of printing unit processes, and a thermal head printing state in a future printing unit process in the storage unit 12 with a time delay. Image data 1
3, future information determining means 14, a past information determining means 16 for determining the printing state of the thermal head in the past printing unit process from the image data 15 stored in the storage means 12 with a time delay, and storage. The future information discriminating means 14 and the past information discriminating means 16 determine the applied energy of the unit heating element in the present printing unit process, which should be obtained based on the present image data 17 stored in the means 12 temporally. The apparatus includes an applied energy setting unit 18 that sets the determined future and past printing states in consideration, and a thermal head drive unit 21 that drives the unit heating element with the set applied energy 19. The "printing state" taken into consideration by this device is not only a two-dimensional arrangement state of image data at the time of printing, but also a state of information obtained by processing these image data, for example, thermal energy is adjusted. It also contains the state of pulse width information for

As described above, in the proposed apparatus, thermal energy is calculated with reference to past image data and future image data. Therefore, for example, when the future information discriminating unit 14 detects the start or end of a solid black portion, that is, a solid portion, the applied energy in the future can be adjusted together with the heat storage energy in the past, and the printing speed can be sufficiently increased. be able to.

By the way, in this conventionally proposed thermal head drive device, only the respective unit heating elements have been considered as targets for heat storage correction. That is, for example, as shown in FIG. 13, it is assumed that the recording pixels 23 corresponding to the recording positions of the respective unit heating elements are present on the recording image, the line on which the current printing is performed is the i line, and the lines before this are i lines. -1, ...
i-4 line. Is the target dot to be subjected to calculation of applied energy of consideration to the unit heat generation body blow the current heat storage state D ₀ to D ₁₀ is given a weight according to the heat storage contribution, the heat storage contribution to target dot D ₀ The applied energy to the target dot is calculated according to the sum.
When the dots D _{1 to} D ₁₀ are print dots (black dots), the weights of the dots D _{1 to} D ₁₀ are, for example, values shown in Table 1 below.

However, in the heat storage calculation targeting only such a unit heating element, it is not possible to accurately infer the actual heat storage phenomenon of the thermal head. In order to understand this, the structure of the thermal head will be outlined next.

FIG. 14 shows a general structure of the thermal head. The heat generating resistor 25 of the thermal head is made of ruthenium (RuO ₂ ) or the like, and is formed by screen printing or the like on a heat insulating layer 27 having a thickness of about 45 μm covering the ceramic substrate 26. The heating resistor 25 and the heat insulating layer 27 are wear resistant layers 28 such as tantalum (Ta ₂ O ₅ ).
Is covered with. The ceramic substrate 26 is attached to a heat dissipation substrate 29 made of aluminum so that heat dissipation is promoted and local heat accumulation in the thermal head is suppressed as much as possible.

On the other hand, a material having a small thermal conductivity, such as glaze, is used for the heat insulating layer 27, which is generally called a glaze layer, so that the thermal energy generated in a unit of the heating element can be effectively used for printing or displaying. . Needless to say, the time constants of heat storage and heat dissipation of the heat insulating layer 27 are sufficiently shorter than the thermal excitation cycle of repeated heating and heat dissipation of the heating resistor 25 that constitutes the unit heat generating element, and this will cause heat storage depending on the state of recording. It accelerates and causes the substrate temperature of the thermal head to rise.

Now, the heat storage state of each unit heating element cannot be accurately grasped because the existence of the layer structure such as the heat insulating layer 27 and the heat radiation and heating effects by these layers complicate the heat storage state. Therefore, a technique is disclosed in which a temperature detecting element is attached to the heat dissipating board 29 to correct the energy applied to each unit heating element (Japanese Patent Application No. 59-088438, etc.).

"Problems to be solved by the invention" However, as already described, the thermal excitation cycle of the heating resistor is shorter than the time constant of heating and heat dissipation of the heat insulating layer,
The temperature of the unit heating element in the heat storage state is higher than the measured temperature of the heat dissipation board. That is, unless temperature correction is performed in consideration of the heat storage phenomenon such as the heat insulating layer or the ceramic substrate existing between the heat dissipation board to which the temperature detecting element is attached and the unit heating element, the measured temperature and the actual temperature of the unit heating element are There is a temperature difference between them, and the presence of this uncertain temperature difference adversely affects the image quality, especially when recording or displaying at high speed.

In view of such circumstances, an object of the present invention is to provide a thermal head drive device capable of calculating a heat storage amount of a thermal head in consideration of a layer structure such as a heat insulating layer and performing accurate thermal energy control. And

[Means for Solving Problems] In the present invention, as shown in principle in FIG. 1, heat generation of a thermal head is performed using image data of pixels around a target pixel as a pixel for which applied energy is to be calculated. Exothermic resistors other than the exothermic resistors of the thermal head are based on the exothermic resistor accumulated heat information calculating means 32 for calculating the exothermic resistor accumulated heat information X _i representing the accumulated heat state of the resistor portion and the calculated exothermic resistor accumulated heat information X ₁ . Adiabatic layer heat storage information calculating means 33 for calculating heat storage layer heat storage information B _i representing the heat storage state in the heat insulating layer and the like, and two types of heat storage information X _i , B obtained by these means 32, 33. It is provided with a applied energy calculating means 34 for calculating the applied energy E _i for each unit heating element as the minimum unit of the heating resistor of the thermal head using an _i to thermal head drive unit

Here, the heat storage layer heat storage information calculation means 33 roughly divides the respective stages of the heat storage state represented by the calculated heat generation resistor heat storage information into more than this, and obtains information representing these divided stages. A heat storage contribution information calculating means that is heat storage contribution information indicating the degree of heat energy spread from the heating resistor to the heat insulating layer as the other part, and is initialized to "0" immediately before the start of recording by the thermal head. The heat storage information calculation means for adding and subtracting a predetermined value for each pixel according to the heat storage contribution information calculated by the heat storage contribution information calculation means.

The heat generating resistor heat storage information calculation means 32 calculates the heat generating resistor heat storage information X _i using the past image data already used for image creation and the temperature data representing the temperature of the thermal head at the present time. Is effective. Of course, other data may be used in addition to the temperature data. The applied energy calculation means 34 may calculate the applied energy E _i as the time width of the applied pulse, that is, the energization time.

According to the present invention, to create a derivative occurring heat insulating layer such as the heat storage information from the thermal energy B _i to the output of the unit heating element from the heating resistor thermal storage information X _i, these two heat storage information X _i, based on B _i Since the energy to be applied to each unit heating element is calculated, accurate thermal energy control in the thermal head becomes possible.

[Examples] The present invention will be described in detail below with reference to Examples.

FIG. 2 shows the configuration of the thermal head drive device in the embodiment of the present invention. The image data 41 input to this device incorporated as a part of the recording device is
This is serial data in which an original image is scanned by an original reading device (not shown) and the read analog image signal is binarized for each pixel. Based on the image data 41, the peripheral pattern extraction circuit 42 extracts image data for a pixel group around a pixel (hereinafter referred to as a pixel of interest) whose applied energy is to be calculated at the present time. The extracted reference data 43 and 44 are supplied to the first and second ROMs (read only memories) 45 and 46 as address information.

FIG. 3 specifically shows the peripheral pattern extraction circuit 42 and the first and second ROMs 45 and 46. The image data 41 is a binarized bit-serial signal sequence, which is sequentially latched bit by bit by the latch circuit 48 and then written in the i + 1 line memory 49 _{i + 1} in the line memory group 49. i + 1 line memory 4
9 _{i + 1} is a memory for storing future image data for one line. I in synchronization with a video clock (not shown)
The image data of 1 bit pushed out from the +1 line memory 49 _{i + 1} is latched by the latch circuit 51 and input to the i line memory 49 _i and the i + 1 line shift register 52 _{i + 1} in the line memory group. It The i-line memory 49 _i is a memory for storing the image data of the line currently to be recorded. The 1-bit by 1-bit image data pushed out from this memory is latched by the latch circuit 51, and the i-1 line memory 49 in the line memory group is
It is input to the shift register 52 _i for _i-1 and i line.
Similarly, the image data pushed out from the i-3 line memory 49 _i-3 in the line memory group is latched by the latch circuit 51 and input to the i-3 line shift register 52 _i-3. It

On the other hand, the image data latched by the latch circuit 48 is also input to the i + 2 line shift register 42 _{i + 2} . Therefore, each shift register 42 _{i + 2 to} 42 _i-3 receives 6 bits of image data of _{i + 2 to i-} 3 lines in synchronization with the video clock. Each of the shift registers 42 _{i + 2 to} 42 _i-3 is a five-stage shift register, and the reference data 43 output from the third-stage flip-flop circuit of the i + 2 line shift register 42 _{i + 2} is the first It is supplied to the input terminal A3 of the ROM 45. The 3-bit parallel reference data 43 output from the second to fourth flip-flop circuits of the i + 1 line shift register 52 _{i + 1} is similarly supplied to the input terminals A2 to A0 of the first ROM 45. To be done. On the other hand, the 4-bit parallel reference data 44 output from the flip-flop circuits of the stages 1, 2, 4, 5 of the i-line shift register 52 _i is the second R
The parallel reference data supplied to the input terminals A0 to A3 of the OM 46 and output from the i-1 line shift register 52 _i-1 are supplied to the input terminals A4 to A8 of the second ROM 46. Further, the shift register 52 for i-2 line
_The reference data 44 output from the third-stage flip-flop circuits of the _i-2 and i-3 line shift registers 52 _i-3 are input terminals A9 and A10 of the second ROM 46.
Will be supplied to.

The correspondence between the reference data 43 and 44 output from each of the shift registers 52 _{i + 2 to} 52 _{i -3} on the recorded image is as shown in FIG. It shows the correspondence. The dots indicated by crosses in FIG. 4 are target data corresponding to the target pixel. This data is taken out from the third-stage flip-flop circuit of the i-line shift register 52 _i shown in FIG. 3 and supplied as the print data 54 to the subsequent circuit.

Calculation of heat-generating resistor heat storage information X _i First, in the second ROM 46, its input terminals A0 to A10.
The heat storage state (heat-generating resistor heat storage information X _i ) in the unit heating element corresponding to the target pixel is calculated based on the 11-bit reference data 44 supplied to the. FIG. 5 shows the contents of the second ROM 46 for this purpose. Ie the second
In the ROM 46 of, each reference data is weighted and added,
The heating resistor heat storage information X _i is determined based on this added value. FIG. 5 corresponds to FIG. 4, and shows the weight of the reference bit at this time. When all of the reference data 44 are in the printing state, the influence of the heat storage on the data of interest indicated by X is the largest, and the added value at this time is 4
55. At this time, the heat-generating resistor heat storage information X _i becomes the maximum “10”. On the other hand, when only the reference data on both sides of the data of interest on the i-line is in the printing state, the added value is 140, and the heat-generating-resist heat storage information X _i is “3”. Each reference data 44 is stored in the second ROM 46.
The heat generating resistor heat storage information X _i corresponding to the added value is written as the address information, and the read heat generating resistor heat storage information X _i is 4-bit data as the T _iA calculator 55.
It becomes an address input of the lower 4 bits of.

Calculation of future discrimination information F _i One-way, in the first ROM 45, its input terminals A0 to A3
The future print state is predicted based on the 4-bit reference data 43 supplied to, and the future discrimination information F _i is output. The relationship between the future discrimination information F _i and the 4-bit reference data is as shown in Table 2 below.

The future discrimination information F _i becomes 2-bit data and is input to the upper 2-bit address of the T _iA calculator 55.

Calculation of heat storage information such as heat insulation layer B _i The heat generation resistor heat storage information X _i calculated by the second ROM 46 is supplied to the third ROM 56, which is, for example, the heat insulation layer 27 of the thermal head shown in FIG. The degree of contribution to heat storage of the substrate 26 and the like is calculated.
The calculated heat storage contribution information X _i ′ has the relationship shown in Table 3 below with the heat generating resistor heat storage information X _i .

The B _i calculator 57 that calculates the heat storage information of the heat insulating layer or the like calculates the heat storage information B _i of the heat insulating layer using the heat storage contribution information X _i ′ and the heat history information of the heat insulating layer B _i-1 . Here, the heat insulating layer such as a thermal history information B _i-1, by the heat insulating layer such as the heat storage information B _i a RAM (random access memory) 58 for outputting the B _i calculator 57, the recording process i.e. by one line delay This is the information. The heat storage layer heat storage information B _i is composed of 10-bit data so as to follow the slow change of the heat storage state of the heat insulation layer, etc., and is in the state of all “0” in the initial state immediately before the start of recording. . The following Table 4 shows heat history information B _i-1 and heat storage contribution information X
_The heat storage layer etc. heat storage information B _i calculated by _i ′ is represented as the amount of adjustment with respect to the heat insulation layer etc. heat history information B _i-1 at the present time.

That is, for example, if the heat history information B _{i-1 of the} heat insulating layer is “001” in hexadecimal notation and the heat storage contribution information X _i ′ at this time is “0” or “1”, the adjustment amount is “0”. ”
Therefore, the heat insulation layer isothermal history information B _i calculated by the B _i calculator 57 is also “001”. On the other hand, a state in which the degree of progress of heat storage of the unit heating element is large and heat storage of the heat insulating layer or the like relatively progresses, that is, the heat storage contribution information X
_{When i'is} "2" or "3", the adjustment amount is "1".
In this case, the heat insulation layer heat history information B _i is “002”.

The heat insulation layer isothermal history information B _i calculated by the B _i calculator 57 is supplied to the fourth ROM 59 as address information. The fourth ROM 59 is a kind of converter for giving a heat storage state such as an adiabatic layer as processing data to the T _iB calculator 61 which determines the applied energy in the form of pulse width,
For the heat insulation layer isotherm history information B _i , heat insulation layer isotherm history information B _i ′ is output based on the following Table 5.

That is, in the example described above, the heat insulation layer isotherm history information B _i is “002”, and thus the converted heat insulation layer isotherm history information B _i ′ is “0”.

Next, before describing the calculation of the T _iB computing unit 61, the operation of the T _iA computing unit 55 for tentatively determining the energization time of the applied pulse to each unit heating element will be described.

Calculation of _Applied Pulse Width T _{iA In} the T _iA calculator 55, the first ROM 45 and the second RO
The applied pulse width T _{iA using the} heating resistor heat storage information X _i and future discrimination information F _i supplied from M46 as address information.
To decide. This is provisional because the _TiB calculator 61 described below corrects the applied pulse width by taking into consideration the substrate temperature of the thermal head and the resistance value information of the unit heating element.

FIG. 7 shows T _iA that determines this provisional applied pulse width T _iA.
The contents of the calculator 55 are shown. In this figure, the horizontal axis is the heat-generating resistor heat storage information X _i , and the vertical axis is the applied pulse width T _iA (msec). Applied pulse width T _iA is 0.05
It is output as hexadecimal output data (H) that represents how many pulses the msec pulse is composed of. For example, when the heating resistor heat storage information X _i is the highest “10” and the future discrimination information F _i is “11” at this time, the applied pulse width T _iA is 0.45 msec, which is 9 pulses of 0.05 msec. It can be achieved by continuing.

From FIG. 7, the heat-generating resistor heat storage information X _i is “10”.
At this time, if the future discrimination information F _i is “11”, the applied pulse width T _iA becomes maximum. This is to apply a relatively large amount of heat energy so that a white gap does not occur between the print dots, because a solid black print state will be obtained for at least two lines in the future from the line currently being printed. Under the same condition, the future discrimination information F _i is “01”, “00”, “10”
The reason why the applied pulse width T _iA becomes short in this case is that the solid black portion will end in the near future, so that the edge portion must be reproduced sharply. Further, the dot of the i + 2th line is added as a criterion for the future discrimination information F _i , in order to prevent the image quality from being deteriorated by gradually reducing the application of heat energy and suppressing the “blurring” of the edge portion. . The applied pulse width T _iA for each unit heating element read from the T _iA calculator 55 in this way is supplied to the T _iB calculator 61 for determining the print energy information.

Calculation of _Applied Pulse Width T _iB The T _iB calculator 61 is used to modify the calculated applied pulse width T _iA and determine the applied pulse width T _iB at a predetermined applied voltage. That is, the applied energy to each unit heating element is finally determined by this T _iB calculator 61. A so-called voltage compensating circuit may be provided in the subsequent stage of the arithmetic unit 61 in order to increase or decrease the applied pulse width T _iB according to the variation of the applied voltage, but this does not increase or decrease the printing energy.

Now, in the T _iB calculator 61, the applied pulse width T _iA is corrected based on the resistance value information R _i and the heat insulation layer isothermal history information B _i ′. Among them, the resistance value information R _i may be an average resistance value of all the unit heating elements that form the thermal head,
The information may individually represent the resistance value. When using the unit heating element discrete resistance value as the resistance value information R _i may be to create a resistance value information R _i within the device by measuring the current amount of the respective unit heating element, device shipments It may be measured in advance, for example.

FIG. 8 shows the output portion of the resistance value information R _i in this embodiment. This circuit portion includes a thermal head resistance value measuring circuit 71 having an A / D converter built therein. The thermal head resistance value measuring circuit 71 measures the resistance values of the unit heating elements of the thermal head one by one while the write address counter 72 is selected by the selector 73. These measurement results are 8 bits (maximum 256
Bit conversion ROM 7 as resistance value measurement result 74
5 is supplied. In the bit conversion ROM 75, the resistance value measurement result 74 is converted into 3-bit resistance value information R based on the following Table 6.
Convert to _i .

The resistance value information R _i thus obtained is stored in the RAM 76.
Input data. At this time, the address information 77 designated by the write address counter 72 is supplied to the RAM 76, and the resistance value information R _i is written in the address corresponding to the unit heating element. Similarly, the write address counter 72 counts up and the resistance value information R _i of the unit heating element is sequentially written in the RAM 76. The writing of the resistance value information R _i may be performed each time the recording device or the display device is powered on, or the RAM 76 is backed up by a battery and the resistance value information R _i measured once is stored. It may be stored for a period.

The resistance value information R _i stored in the RAM 76 is read when the applied pulse width T _iB is determined. When reading, the selector 73 causes the read address counter 78.
Is selected, the address information 79 corresponding to the unit heating element for which the applied pulse width T _iB is determined is sequentially output, and the RAM 7 is output.
6 is supplied. In the RAM 76, the desired resistance value information R _i of the unit heating element is sequentially read out by this, and the Ti _B calculator 61 is read.
Will be supplied to.

'In (operation Well T _iB calculator 61, applied pulse width T _iA based on first application pulse width T _iA and the resistance value information R _i applied pulse width T _iA)' performs operations. Then, the applied pulse width T _iA ′ and the already-obtained heat insulation layer isothermal history information B _i ′ are used to calculate the applied pulse width T _iB .

FIG. 9 shows the relationship between the applied pulse width T _iA and the applied pulse width T _iA ′. For example, the applied pulse width T _iA is 0.
When the resistance value information R _i is 010 in 7 msec, the applied pulse width T _iA ′ is 0.6 msec. From this figure, it can be seen that the larger the resistance value of the unit heating element, the longer the applied pulse width T _iA ′.

(Calculation of _Applied Pulse Width T _iB ) FIG. 10 shows the relationship between the applied pulse width T _iA ′ and the applied pulse width T _iA . Such information can be stored as a table in another ROM in the _TiB computing unit 61, for example. In the previous example, the applied pulse width T
_{When iA} ′ is 0.6 msec and the heat insulating layer isothermal history information B _i ′ is “7”, that is, the highest level of heat storage, the applied pulse width T _iB is 0.4 msec and “0”, that is, the lowest level of heat storage. Then, the applied pulse width T _iB is 0.
It will be 6 msec. This is, of course, because the energy applied to the unit heating element needs to be kept low as the thermal head portion other than the heating resistor accumulates heat.

The applied pulse width T _iB is not information indicating the length of the pulse width itself, but is indicated as the number of unit pulses of 0.05 msec. For example, the applied pulse width T _iB is 0.4 msec.
In the case of, the unit pulse is output as information in which four consecutive pulses are output, and when the applied pulse width T _iB is 0.6 msec, the unit pulse is output as information in which twelve consecutive pulses.

The applied pulse width T _iB is supplied to a thermal head drive circuit (not shown) in the _subsequent stage. In the thermal head drive circuit, the number of applied unit pulses of 0.05 msec is controlled for each unit heating element, and the energization time given by the applied pulse width T _iB is realized for each unit heating element.

In the thermal head drive device of this embodiment described above, the applied energy is determined by combining the future determination information F _i , so that it is possible to obtain a high-quality recorded image before and after the solid (solid black) region.

“Modification” By the way, the heat storage of the heating resistor, the heat insulating layer, and the like varies depending on the outside air temperature when the thermal head is driven, the temperature condition of the aluminum heat dissipation substrate, and the like. Regarding the heating resistor, the temperature change occurs in the range of several hundred degrees during the energization control, so when the heat storage information is divided into that of the heating resistor and the heat insulating layer as in the present invention, the influence on the heat storage needs to be considered so much. Absent. However, with respect to the heat insulation layer and the like, the heat storage state is considerably affected.

In consideration of such circumstances, FIG. 11 shows the substrate temperature information K obtained from the aluminum heat dissipation substrate 29 (FIG. 14).
2 shows a thermal head driving device that determines the applied energy (applied pulse width) by combining the above. In this device, the same parts as those in FIG. 2 are designated by the same reference numerals,
Description of these parts will be omitted as appropriate.

Now, in the thermal head drive device of this modification, (i)
Heat storage contribution information X _i ′, (ii) Heat history information of heat insulation layer B _i-1
In addition to (iii) the substrate temperature information K is used to calculate the heat storage layer heat storage information B _i . B _i calculator 8 for performing such calculation
1 is an R having a memory area corresponding to the substrate temperature information K
OM is arranged. Then, the heat storage layer heat storage information B _i is read out using a table partially shown in the following Table 7 corresponding to Table 4 of the previous embodiment.

That is, as the measured temperature indicated by the substrate temperature information K is higher, the heat storage amount is corrected to be higher than the heat storage amount calculated purely from the image data 41, and the energy applied to the unit heating element is set smaller by the T _iB calculator 61. Will be.

Although the energy applied to the unit heating element is adjusted by the time width of the applied pulse in the embodiments and the modifications described above, it is also possible to adjust it by the voltage value or a combination of both.

[Advantages of the Invention] As described above, according to the present invention, the control of the energy applied to the thermal head is performed in consideration of the heat storage of the heat insulating layer and the like, so that the thermal energy can be corrected to a sufficiently high level, and the recording Alternatively, even if the display operation is speeded up, fine gradation expression such as halftone can be properly performed.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the principle of the present invention, and FIGS. 2 to 10 are for explaining one embodiment of the present invention. Of these, FIG. 2 shows the structure of a thermal head driving device. FIG. 3 is a block diagram specifically showing the peripheral pattern extraction circuit and the first and second ROMs, FIG. 4 is an explanatory diagram showing the arrangement of reference data, and FIG. 2 is an explanatory diagram showing the contents of the ROM, FIG. 6 is an explanatory diagram showing the weight of each reference bit for heat storage calculation,
FIG. 7 is an explanatory diagram showing the contents of calculation of the T _iA calculator, FIG. 8 is a block diagram showing a portion where the resistance value information R _i is created, and FIG. 9 is an applied pulse width T _iA ′ in the T _iA calculator. explanatory view showing contents of operation of FIG. 10 is an explanatory diagram also shows the operation contents of the applied pulse width T _iB in T _iB calculator, 11
FIG. 12 is a schematic block diagram showing a modified example of the present invention, FIG. 12 is a block diagram showing an example of a conventionally proposed thermal head driving device, and FIG. 13 is an arrangement example of pixels used for conventional heat storage calculation. FIG. 14 is a sectional view showing a general structure of the thermal head. 25 ... Heating resistor, 27 ... Insulation layer, 29 ... Heat dissipation substrate, 31 ... Image data, 32 ... Heating resistor heat storage information calculation means, 33 ... Heat storage information calculation means for heat insulation layer, 34 ... Applied energy computing means, 55 ... T _iA computing unit, 56 ... Third ROM, 57,81 ... B _i computing unit, 58 ... RAM, 61 ... T _iB computing unit, B _i ... Adiabatic layer etc. heat storage information, K ...... substrate temperature data, X i _...... heating resistors heat storage information.

Claims (3)

[Claims] 1. A heat-generating resistor heat storage that represents a heat storage state of a heat-generating resistor portion corresponding to the target pixel of the thermal head by using image data of pixels around the target pixel as a pixel whose applied energy is to be calculated. The heat-generating resistor heat storage information calculating means for calculating information and the heat storage state stages represented by the calculated heat-generating resistor heat storage information are roughly divided, and the information showing each divided stage is displayed. A heat storage contribution information calculating means that is heat storage contribution information indicating the degree of thermal energy spread from the heating resistor to the heat insulating layer as the other part, and is initialized to "0" in the state immediately before the start of recording of the thermal head. The heat storage information calculator for a heat insulation layer or the like that adds or subtracts a predetermined value for each pixel according to the heat storage contribution information calculated by the heat storage contribution information calculation means. And two types of heat storage information obtained by the heat storage resistor heat storage information calculation means and the heat insulation layer heat storage information calculation means are applied to each unit heating element as the minimum unit of the heating resistor of the thermal head. An applied energy calculation means for calculating energy, the thermal head driving device. 2. The heat storage layer heat storage information calculation means calculates heat storage layer heat storage information by using a combination of heat generating resistor heat storage information and temperature data representing the temperature of the thermal head at the present time. The first claim
The thermal head drive device according to the paragraph. 3. The thermal head drive device according to claim 1, wherein the applied energy calculation means calculates the applied energy as a time width of the applied pulse.