JPH01186343A - Thermal transfer type printing apparatus - Google Patents

Abstract

PURPOSE:To effectively prevent a change of printing density by providing a control counter, a data counter for outputting a reference density signal and a heating signal, a reference signal counter, a correction table memory for a value constituting a time sharing signal and a density data comparing circuit. CONSTITUTION:The reference clock signal from a terminal 14 and the current supply start pulse from a terminal 15 are supplied to an address counter 13. A control counter 17 is loaded with the preset concurrent heating value from a concurrent heating presetting source 18 in response to the current supply start pulse. A counter 19 counts the reference clock signal during a cooling period to a thermal head and the count value thereof is supplied to a correction table memory 21. This memory 21 preliminarily stores the optimum current supply pulse duty corresponding to the variation of the length of the cooling period caused by the variation of the transfer speed of recording paper. The current supply pulse duty-to-gradation characteristic read on the basis of the output count value of the counter 19 is supplied to a pulse generator 27.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Applications) The present invention relates to a thermal transfer printing device, and particularly to a thermal transfer printing device that prevents print density unevenness that becomes noticeable when printing with a constant density signal.

(Prior Art) A thermal transfer printing device used as a terminal printing device (hard copy device) is a device in which thermal sublimation ink is applied to the negative side of a polyester film (or ribbon) with a thickness of 15 to 6 μm, for example. Using an ink film (or ink ribbon), the front ink side of the ink film is placed in contact with the recording paper, a thermal head is applied to the back side, and a current is passed through the thermal head to generate heat. The structure is such that the ink on the ink film at the position corresponding to the prevention of heat generation is sublimated and transferred to the recording paper.

In order to print with constant print data, use a print start signal with an accurate cycle and keep the rotational speed of the outer platen as constant as possible. It is well known that it is possible to obtain unit print dots with uniform widths and uniform density.

However, in actual printing using the thermal transfer printing apparatus, although it is possible to align the pitch between printing lines using a very precise encoder, it is not possible to control linear velocity unevenness around the outer periphery of the platen.

FIG. 7(a) shows the energization control pulse for controlling the energization to the thermal head, FIG. 7(b) shows the energization start pulse for instructing the start and end of energization to the thermal head, and FIG.
, ) show the heat generation temperature vs. time characteristics of the thermal head in correspondence with FIGS. 3(a) and 3(b). As is clear from FIG. 7(C), when the immediate cooling time is shortened, the thermal head is not completely cooled down at the end of the cooling period, causing it to generate more heat than necessary during the next reheating period.

Furthermore, if the cooling time becomes longer, the thermal head will be overcooled at the end of the cooling period, resulting in insufficient heat generation during the next reheating period.

Figure 8 <a> shows an example of printing with a uniform pitch between lines, Figure 8 (b) shows an example of printing with an uneven pitch between lines, and (c) shows an example of printing with a uniform pitch between lines. An example of printing is shown in which the prints are uniform, but each drum remains uneven in density.゛ □ As is clear from Fig. 8(a), in the conventional thermal transfer printing device, the pitch between lines printed on the recording paper can be controlled to be constant even if the transport speed of the recording paper changes; As shown in (b), the length of the cooling period of the thermal head changes due to fluctuations in the transfer speed, and as shown in (c) of the same figure, insufficient cooling or overcooling of the thermal head causes the next reheating to occur. There is a problem in that the thermal head generates more heat than necessary (overheating) or insufficient heat during the period, resulting in uneven density of printed dots.

Therefore, the present applicant has proposed a thermal transfer printing device (patent application No. 62) that eliminates the amount of heat generated in accordance with the fluctuations in the cooling period by controlling the reheating period and suppresses uneven printing density.
-77106), or detect insufficient cooling or overcooling of the thermal head by measuring the cooling period or η] uniform cycle period using a reference pulse, and adjust the energizing pulse duty optimally based on the detection result. We have proposed a thermal transfer printing bag (described in Japanese Patent Application No. 62-94032) that suppresses uneven printing density by controlling the temperature.

(Problems to be Solved by the Invention) However, in the above-mentioned thermal transfer printing device, it is not possible to use a single correction table to correct uneven printing density caused by fluctuations in the cooling period of the thermal head and fluctuations in the power supply voltage. Therefore, there is a problem in that it is not possible to effectively prevent changes in printing density due to fluctuations in the power supply voltage of the thermal head by energizing the heating resistor.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention uses a thermal transfer printing device to apply an electric current to each of a plurality of heating resistors arranged in a line forming a thermal head. A heating period in which the current application time is individually controlled according to the print density, and the heat is reheated by energizing the corresponding heat generating resistor of the thermal head, and energizing the corresponding heat generating resistor. A thermal transfer type printing device that prints each dot on a recording paper during a printing period consisting of a thermal transfer period in which the dot is cooled, and a cooling period in which the corresponding heat-generating resistor is cooled. a platen that sandwiches the recording paper and transports the recording paper at a predetermined speed; an encoder that detects the rotation of the platen and generates a energization start signal according to the transport speed of the recording paper; and an incoming video signal. a data storage device that stores image data corresponding to the energization start signal; and after outputting to the data storage device an address that corresponds to the image data printed by the heating resistor in response to the energization start signal, a transfer signal is sent. an address counter for outputting, a reheating preset source storing a reheating preset value that determines the reheating interval, and a control counter to which the energization start signal and the transfer signal are supplied and counts the reheating preset value. , a data counter that stops counting during the counting period of this control counter and outputs a reference concentration signal and a heating signal; is a counter that counts the reference signal during one cycle period from the generation of the energization start signal to immediately before the next energization start signal, the output count value of this counter, and the energization to the heat generating resistor of the thermal head. a time division circuit that outputs as a time division signal a value corresponding to power supply voltage fluctuations of the thermal head caused by the above, and the output count value to which the time division signal and the reference density signal are supplied and constitute the time division signal; and a correction table storage memory in which correction data for values corresponding to power supply voltage fluctuations of the thermal head are stored as correction data, and the image data supplied from the data storage device and the reference density signal are compared; Image data> When the reference is low density No. 6, the first control data is sent, and the image data is the reference, quasi-concentration signal, i.

having a predetermined pulse width for a predetermined period including the reheating period according to the correction data value supplied from the grayscale data comparison circuit that sends out the second control data and the correction temperature pool storage memory; a pulse generator that outputs a signal whose pulse width is varied after this period;

a shift register to which control data is supplied and which transfers control data corresponding to the address of the address counter;
a latch circuit that latches the control data of the shift register in synchronization with the transfer signal; an AND circuit that outputs a logical product of the output from the pulse generator and the heating signal; a gate circuit for intermittent output from the latch circuit; and energizing means for energizing each of the plurality of heat generating resistors arranged in a row constituting the thermal head in accordance with the output from the gate circuit. and eliminates print density changes in each line of one line due to time axis fluctuations during one line printing of the platen and print density changes due to power supply voltage fluctuations caused by energization to the heating resistor of the thermal head. The device is configured to obtain a predetermined gradation density characteristic for the input video signal.

(Example) The thermal transfer printing device according to the present invention has the following configuration.

That is, the application time of the current applied to each of the heat-generating resistors R1 to Rn arranged in a row constituting the thermal head 1 is individually controlled according to the print density, and the corresponding current of the thermal head 1 is controlled. Each printing period consists of a heat replenishment period in which heat is supplied to the heat generating resistor by energizing it, a thermal transfer period in which the corresponding heat generating resistor is energized, and a cooling period in which the corresponding heat generating resistor is cooled down. This is a thermal transfer type printing machine that prints dots on recording paper 5, and includes a platen 6 that sandwiches recording paper 5 with an ink film 4 between it and a thermal head 1, and transports this recording paper 5 at a predetermined speed. , an encoder 8 that detects the rotation of the platen 6 and generates an energization start signal a corresponding to the transport speed of the recording paper 5, and a data storage device 12 that stores image data corresponding to an incoming video signal. Heat generating resistors R1 to R according to the energization start signal a
An address counter 13 that outputs a transfer signal after outputting an address corresponding to the image data to be printed by n to the data storage device 12, and a reheating preset in which values are stored such as a reheating preseller 1 that determines a reheating period. source 18, a control counter 17 which is supplied with the energization start signal a and the transfer signal S and counts the values of the reheating preseller 1, and which stops counting during the counting period of the control counter 17 and also receives the reference concentration signals d and d. A data counter 16 that outputs the heating signal e, and a counter 1 that counts the reference signal during the cooling period or one cycle of printing until immediately before the energization start signal.
9, and the output count value of this counter 19 and a value corresponding to the fluctuation of the power supply voltage Vcc of the thermal head 1 caused by energization to the heating resistors R1 to R'n of the thermal head 1 are outputted as a time division signal. The time division circuit 29 is supplied with this time division signal and the reference density signal, and the output count value and the power supply voltage +Vcc of the thermal head 1 which constitute this time division signal are supplied.
A correction data storage memory 21 stores correction data for values corresponding to fluctuations as correction data, and compares the image data supplied from this data storage device 12 with a reference density signal d, and determines that image data>reference density signal d. At this time, the gradation data comparison circuit 22 sends out the first control data, and at the time of the image data reference density signal d, it sends out the '2nd control data. A pulse generator 27 that outputs a signal having a predetermined pulse width for a predetermined period including a reheating period and varying the pulse width after this period according to A shift register 23 to which data is supplied transfers control data corresponding to the address of the address counter 13, a latch circuit 24 that latches the control data of the shift register 23 in synchronization with the transfer signal, and a pulse generator 27. output and heating signal e
an AND circuit 26 that outputs a logical product of
It has an energizing means for energizing each of the heating resistors R1 to Rn arranged in a row that constitute the thermal head 1 according to the output from the thermal head 1, and the time axis during one line printing of the platen 6. By eliminating the print density changes of each dot in one line due to fluctuations and the print density changes due to fluctuations in the power supply voltage +Vcc of the thermal head 1 caused by energization to the heating resistors R1 to Rn of the thermal head 1, the input video signal is This is a thermal transfer printing device characterized in that it is configured to obtain predetermined gradation density characteristics.

FIG. 1 shows a circuit diagram of an embodiment of a thermal transfer printing apparatus according to the present invention.

In the figure, a thermal head 1 includes n heating resistors R1 to Rn formed in a row on a ceramic substrate. The configuration of this thermal head 1 is the same as that of a conventional thermal transfer type device, and extends in the width direction of the ink film 2, as shown in FIG. 3, for example.

In FIG. 3, an ink film 2 serving as a transfer paper has a heat sublimable ink 4 coated on the surface of a polyester film 30 to a predetermined thickness. The recording paper 5 is conveyed together with the ink film 2 by the platen 6 in the six directions of the arrows, with its recording surface facing the ink 4 surface of the ink film 2. A thermal head 1 is provided facing the platen 6 and is in contact with the back surface of the ink film 2.

The ink 4 of the ink film 2 in the portion corresponding to the energized heat generating resistor among the heat generating resistors R1 to Rn of the thermal head 1 is sublimated and transferred onto the recording paper 5. After passing through the thermal head 1, the ink film 2 is guided by a roller 7 and separated from the recording paper 5, and is placed on a take-up spool (not shown).
The ink is wound up as a used ink film 2a. The transferred ink 4a remains on the printed recording paper 5a. For convenience of illustration, the transferred ink 4a is shown as having a large area, but it actually consists of a collection of small dots.

8 is a high-precision encoder, and by detecting the rotation angle of the encoder 80, the transport speed (transfer amount) of the recording paper 5 is determined.
and outputs the energization synchronization pulse.

Therefore, even if there is a fluctuation in the transport speed of the recording paper 5, a well-known circuit (not shown) generates an energization start pulse as shown in FIG. By controlling the energization period, it is possible to keep the pitch between lines printed on the recording paper 5 constant.

One dot is formed by a negative heating resistor, and the size of the negative dot is determined by the time for which electricity is applied to the heating resistor (or the level of voltage applied). The shading, or gradation, of the printed figure is determined according to the size and density of each dot.

Returning to FIG. 1 again, the TV signal generator 10
An analog video signal supplied from the controller is converted into a digital signal by an analog/digital (A/D) converter 11, and sent to a data storage device 12 for storage.

On the other hand, the address counter 13 receives the constant frequency reference clock signal from the terminal 14 and the reference clock signal shown in FIG. 2 (A) from the terminal 15.
An energization start pulse a as shown in FIG. The address counter 13 and the data counter 16 are each started by the energization start pulse a that arrives at time t1. The control counter 17 is loaded with a preset reheating preset value from the reheating preset source 18 in response to the energization start pulse a. This reheating reset value is a value that determines the reheating period (time), which will be described later. It is determined by the pressing force of , the ambient temperature, etc., and is selected to be about "4", for example.

Further, the heating period is selected to be a time during which pixel data for one line is read out repeatedly an integer number of times.

On the other hand, the reference clock signal from terminal 14 is sent to counter 19.
is also supplied and counted. This counter 19 is reset by a pulse a obtained by inverting the energization start pulse a from the terminal 15 using an inverter 20 . That is, the counter 19 counts the reference clock signal during the cooling period for the thermal head 1 in FIG. 7(b). counter 1
The output count value of 9 is supplied to the correction table storage memory 21. The correction table storage memory 21 is stored in the correction table storage memory 21 as shown in FIG.
) The optimum energization pulse duty corresponding to the variation in the length of the cooling period caused by the variation in the transport speed (transfer amount) of the recording paper 5 is stored in advance as a correction table. The energization pulse duty vs. gradation characteristic read from the output count value of the counter 19 is supplied to the pulse generator 27. The reheating preset source 18 supplies the reheating preset value set in advance to the control counter 17 as an initial value.

The control counter 17 is generated based on the reference clock signal from the address counter 13 as shown in FIG. 2(B).
The pulse b shown in Fig. 2 (
As shown in C), a low level signal C is supplied to the data counter 16 to stop its counting operation.

Therefore, the value of the reference density data d shown in FIG.
During the reheating period), it is held at the reset value "O", that is, the value "0" indicating the minimum density white.

The period of the pulse b is selected to be shorter, for example, about 1/10, than the period of the output pulse of a conventional address counter.

The address counter 13 sends the first address to the data storage device 12 upon reception of the energization start pulse a.

The data storage device 12 sends first data (the first data of the image data from the A/D conversion device 11) corresponding to this first address to the grayscale data comparison circuit 22. The density data comparison circuit 22 compares the first data with reference density data (hereinafter referred to as
If the first data is larger than the second data "O", control data "1" is sent to the shift register 23, and if they are equal, the control data "1" is sent to the shift register 23. Send data “O”.

In this way, when the processing at the first address is completed, the address counter 13 is sequentially updated to 2°3, . . .
The nth address is sent to the data storage device 12, and the data storage device 12 sequentially sends first data corresponding to the second to nth addresses to the grayscale data comparison circuit 22 each time.

Here, the first data from the 1st to nth addresses correspond to the image data printed by the heating resistors R1 to -19=Rn of the thermal head 1, respectively. The gray data comparison circuit 22 compares the first data and second data "O" corresponding to the second to nth addresses, respectively, and transfers the control data rOJ or "1" to the shift register in the same manner as above. Send to 23.

The n-stage shift register 23 includes the grayscale data comparison circuit 22
n corresponding to the 1st to nth addresses supplied by
Bit control data is taken in sequentially and sent to the latch circuit 24.

When the address counter 13 finishes counting the 1st to nth addresses, the data counter 16 and the latch circuit 2 use the pulse b shown in FIG. 2 CB) as a data transfer pulse.
4 and the control counter 17. At the same time that the data counter 16 receives this transfer pulse b,
The heating pulse e shown in Fig. 2 (E) is applied to the address counter 1.
3 and one input terminal of an AND circuit 25 and an AI'J[) circuit 26, respectively.

On the other hand, a reference clock signal is supplied from the terminal 14 to one end of the AND circuit 25, and simultaneously with the input of the heating pulse e from the data counter 16, the pulse is output to the shift register 23, and the pulse is outputted to the shift register 23. 1~n
The n-bit control data corresponding to the second address is transferred from shift 1 to register 23 to latch circuit 24. When the data transfer pulse b is received, the latch circuit 24 latches the control data supplied from the shift register 23 and sends it to each input terminal of the gate circuits G1 to Gn.

The address counter 13 is reset by the arrival of the heating pulse e and sequentially counts addresses 1 to n again in response to the energization start pulse a, but during the reheating period Δ
During T, the address counter 13 controls the data storage device 12.
repeatedly reads n pieces of first data on the same line, and the second data is held at "0", so the n pieces of first data for the same line have the above value "0". ”
The grayscale data comparison circuit 22 repeatedly compares the magnitude of the second data with the second data.

Therefore, during the heating period T, when the first data is "1" or more, a heating current is applied to only the heat generating resistor to be transferred according to the first data, and the heat is reheated. Therefore, the first data of the white level is held as white and is not transferred, and the rise of the transfer density can be optimized for the density above the white level by the preset heating preset value.

Thereafter, when the pulse C becomes high level at time t2 when the control counter 17 has finished counting the pulses b by the reheating preset value, the data counter 16 starts counting l~, and repeats the same operation as above. After counting the first data for the line once, the next incoming pulse b is counted at time t3, and the value shown in Fig. 2 (D
) is increased to the value "1" indicating the second smallest density.

From this, the gray data comparison circuit 22 sequentially compares the n pieces of first data for the same one line with the second data having the value "1". Even when the second data is "1", the shift register 23, latch circuit 24, AND circuit 25
etc. perform the same operation as above, and the gate circuits G1 to Gn
The latched control data is sent to one input terminal of each.

On the other hand, the heating resistors R1 to Rn forming the thermal head 1
A signal corresponding to a variation in the power supply voltage +ycc caused by energization is converted into a digital signal by the A/D converter 28 and then supplied to the time division circuit 29 . Time division circuit 2
9 is inserted between the counter 19 and the correction table memory 21, and the output count value of the counter 19 and the A/
The power supply voltage of the thermal head 1 supplied from the D converter 28 + a digital signal corresponding to the VCC fluctuation is supplied to the correction table memory 21 as a time-division signal.

The correction table 21 is a correction table that outputs a signal that takes into account each correction and 8-character correction for each of the output count value that constitutes the time-sharing signal supplied from the time-sharing circuit 29 and the value that corresponds to the power supply voltage fluctuation of the thermal head 1. Table storage memory 2
1 to t until the above second data "0" shown in Figure 2 (1))
is supplied, and the data is corrected using a correction table in which correction data is stored in advance so that there is a linear relationship between recording time and density, and the data is sent to the pulse generator 27. The pulse generator 27 generates a pulse f as shown in FIG. 2(F), which is at a high level during a predetermined period including the reheating period ΔT according to the incoming correction data, and whose pulse width gradually changes after this period. is generated and output to the other input terminal of the AND circuit 26. The A N,D circuit 26 generates a pulse q shown in FIG. 2(G) by the incoming heating pulse e and pulse f.
is generated and sent to the other input terminal of each of the gate circuits G1 to Qn.

As shown in FIG. 2 (G), the pulse q is applied during a predetermined period including the reheating period Δt after time t1 (i.e., the period from time t1 to t3 when the second data d is 10). has a predetermined pulse width, and after this period □, the pulse width gradually decreases, for example, in accordance with the data content of the correction data read out from the correction table storage memory 27.

Each of the gate circuits G1 to Qn applies a gate signal obtained by gate processing the pulse q and n-bit control data supplied from the latch circuit 24 to an NPN transistor T1.
~Tn to the bases of each of them and performs switching control. 1- of transistors T1 to Tn that are turned on
Current is passed only through the heating resistor connected to the collector side of the transistor, causing it to generate heat.

Also, after time t2, the second data output from the data count 16 becomes "O" in synchronization with the pulse b+'e.
"1", "2", ..., 4 mJ (where m is the value indicating the maximum density), and if the first data is larger than the second data, the control data "
If the control data is equal to or smaller than the second data, control data "0" is output. Depending on the control data of "O" or "1" and the pulse width of the pulse q, the energization time of the heating current flowing through the heating resistor changes, and the gradation recording of the data for the - line is performed.

After that, when the next start pulse a comes in, the address counter 13 and the data counter 16 are each reset, and the data counter 16 again changes the second data sequentially as shown from time t1 onward in FIG. 2(D). Then, the same operation as above is performed, and gradation recording of the first data for the next line is performed.

FIGS. 4(a) to 4(C) are diagrams for explaining the 8-character correction.

In figure-8 correction, when gradations are recorded using a data signal with a constant duty ratio, the number of gradations versus density becomes non-linear, as shown in (a) of the same figure, and this is changed to the same characteristic as shown in (b) of the same figure. This is a correction to provide linearity.

Specifically, the duty ratio of the data signal of each output of the gate circuits G1 to Qn is configured to form a time division signal obtained from the time division circuit 29 centered around the reference correction curve as shown in FIG. The gradations shown in FIG. 2(a) are determined by selecting a plurality of correction curves for each of the output count value and the value corresponding to the power supply voltage fluctuation of the thermal head 1. The number-to-density characteristic is corrected to provide a linear number-to-density characteristic as shown in FIG. 2(b).

In addition, the present invention also provides the following, as shown in FIG.
This is an attempt to correct density unevenness due to cooling time fluctuations, such as in the cooling time fluctuation vs. concentration fluctuation characteristic, which has non-linearity.

In other words, the density fluctuations caused by the cooling time fluctuations as shown in Figure (a) are compared to the cooling time fluctuations versus the duty of the energizing pulses as shown in Figure (b) for each gradation recording period and the heating resistor. By taking into account the ratio fluctuation width characteristic, the above-mentioned fourth
The duty ratio characteristic of the number of gradations versus the energizing pulse shown in FIG. By changing the correction curve b according to the power supply voltage fluctuation at any time with a predetermined time division ratio, it is possible to maintain the linearity versus density characteristic of the number of gradations shown in FIG. This is an attempt to improve unevenness.

Therefore, according to this embodiment, substantially linear density control can be performed from the number of gradations rOJ to rmJ, that is, from the white level to the black level. Furthermore, since the period of pulse b is about 1/10 that of the conventional one, the recording time can be shortened. Furthermore, even if the power supply voltage of the thermal head 1 fluctuates due to fluctuations in the cooling period and energization of the thermal head 1, the energization pulse duty versus gradation characteristic is corrected by the data value in the correction table storage memory 21, so that the energization pulse duty Since this is variably controlled at a predetermined time division ratio, uneven printing density will not occur.

In this way, each time the data counter 16 finishes counting from 1 to m times, one line is recorded on the recording paper 5, and after the recording of this one line is completed, the data counter 16 counts from 1 to m again. Start counting.

Incidentally, the structure of the thermal head 1 may be as shown in FIG. 6. In the same figure, the same parts as No. 3- are given the same symbols,
The explanation will be omitted. The recording paper 5 is wound and fixed around the outer periphery of the platen 31 by a clamper 30. The encoder 8a detects the rotational speed (rotation angle) of the platen 31 via the belt 32, and generates the energization synchronization pulse.

In the example of FIG. 3, the recording paper 5 may be continuous paper, but the 6th
In the illustrated example, the recording paper 5 is fixed to the platen 31 one by one.

It goes without saying that the present invention can also be applied to color printers.

Note that the analog video signal supplied from the TV signal generator 10 may be an information signal of images such as other characters and figures.

Also, in the above embodiment, the relationship between the recording time and the density is a straight line, but the relationship between the recording time and the density may be a predetermined curve.

Moreover, it is natural that the same effect can be obtained even if the fluctuation in one period of energization is measured in order to measure the fluctuation in the cooling time.

(Effects of the Invention) As described above, the thermal transfer printing apparatus according to the present invention detects insufficient cooling or overcooling of the thermal head, and detects thermal overcooling by measuring the length of the cooling period of the thermal head.

The variation in the power supply voltage of the thermal head due to the energization of the heat generating resistor of the heat generating resistor is detected, and the duty of the energization pulse is variably controlled based on the detection result, so it is possible to prevent fluctuations in the cooling period and the power supply voltage of the thermal head. It has features such as being able to effectively prevent print density unevenness caused by fluctuations with a single correction table, and effectively preventing print density changes due to power supply voltage fluctuations of the thermal head by energizing the heating resistor.

[Brief explanation of the drawing]

FIG. 1 is a circuit system diagram showing an embodiment of the thermal transfer printing apparatus according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the circuit system shown in FIG. A schematic perspective view of an example of a main part of a liquid thermal transfer printing device, FIG. 4(a)-
(C) is a diagram showing an example of the number of gradation levels vs. density characteristic and the number of gradation levels vs. duty ratio characteristic of energizing pulse; Figures 5(a) and (b)
6 is a diagram showing an example of the cooling time variation vs. density variation characteristic and the due-eye variation width characteristic of the energizing pulse; FIG. Figure 7 is a diagram for explaining the dot printing period, and Figure 8 is a diagram for explaining the dot printing period.
Figures (a) to (C) are diagrams for explaining the unevenness of print density that occurs in the conventional apparatus-31=. 1... Thermal head, 4... Ink film, 5...
・Recording paper, 6...platen, 8...encoder,
12...Data recording device, 13...Address counter, 14.15...Terminal, 16...Data counter, 17...] control counter, 18...Heat supplementary sensor l-source, 19 ...Counter, 21...Correction table memory,
22... Grayscale data comparison circuit, 23... Shift register, 24... Latch circuit, 2
6...AND circuit, 27...Pulse generator, 29.
...Time division circuit, a...Electrification start signal, b...Transfer signal, d...Reference concentration signal, e...Heating signal, 01-Gn...Gate circuit, R1-Rn... - Heat generating resistor. ＼≧ Shiki, Eaves □ 82 ゛ Procedural amendment writing method) May 72, 1986

Claims (1)

[Claims] The application time of a current applied to each of a plurality of heating resistors arranged in a line constituting a thermal head is individually controlled according to print density, and the corresponding heating of the thermal head is controlled individually. a reheating period in which the resistor is reheated by energizing it;
A thermal transfer printing device that prints each dot on recording paper during a printing period consisting of a thermal transfer period in which the corresponding heat generating resistor is energized and a cooling period in which the corresponding heat generating resistor is cooled. , a platen that sandwiches a recording paper with an ink film between it and the thermal head and transports the recording paper at a predetermined speed; and a platen that detects the rotation of the platen and generates an energization start signal in accordance with the transport speed of the recording paper. a data storage device that stores image data corresponding to the incoming video signal; and a data storage device that stores an address corresponding to the image data printed by the heating resistor in response to the energization start signal. an address counter that outputs a transfer signal after being output to the device; a reheat preset source that stores a reheat preset value that determines the reheat period; and a reheat preset source that is supplied with the energization start signal and the transfer signal and that outputs the reheat preset value. a control counter that counts values; a data counter that stops counting during the counting period of this control counter and outputs a reference concentration signal and a heating signal; and a data counter that is reset by the inverted energization start signal and that is reset during the cooling period or A counter that counts the reference signal during one printing cycle from generation of the energization start signal to immediately before the next energization start signal, and a count value generated by the output count value of this counter and the energization to the heat generating resistor of the thermal head. a time division circuit that outputs a value according to power supply voltage fluctuations of the thermal head as a time division signal; and the output count value and the thermal head to which the time division signal and the reference density signal are supplied and constitute the time division signal. A correction table storage memory stores correction data for values corresponding to power supply voltage fluctuations as a correction table, and the image data supplied from the data storage device and the reference density signal are compared, and the image data>the a grayscale data comparison circuit that sends out first control data when the reference density signal is present, and sends out second control data when the image data = the reference density signal; a pulse generator that outputs a signal having a predetermined pulse width for a predetermined period including the reheating period and varying the pulse width after this period according to the correction data value; a shift register to which second control data is supplied and which transfers the control data corresponding to the address of the address counter; a latch circuit which latches the control data of the shift register in synchronization with the transfer signal; and the pulse generator. an AND circuit that outputs the logical product of the output from the device and the heating signal; a gate circuit that connects and disconnects the output from the latch circuit according to the output of the AND circuit; and energizing means for energizing each of the plural heat generating resistors arranged in a line constituting the head, and the print density of each dot of one line changes due to time axis fluctuations during printing of one line of the platen. and a structure that eliminates print density changes due to power supply voltage fluctuations caused by energization of the heating resistor of the thermal head, and obtains predetermined gradation density characteristics for input video signals. Thermal transfer printing equipment.