JPS61276479A - Gradation control device for thermal transfer - Google Patents

Abstract

PURPOSE:To obtain optimum density characteristic in highlight parts and shorten recording time by making concurrent heating only to a resistance for heat generation to be transferred. CONSTITUTION:Reference density data are kept at a value that indicates minimum density during concurrent heating by a control counter 18. Accordingly, input data larger in value than the minimum density is given only to resistances for heat generation (R1-Rn) to be transferred by a density data comparator circuit 14 and concurrent heating is made. Reference density data from a data counter 15 changes from minimum to maximum density value in a short time after lapse of concurrent heating time, and current is applied by the comparator circuit 14 to a resistance Ri that transfers input data for each unit of density. Current is applied to the resistance Ri for a time set to make the relation between the recording density and reference density data to a straight line or specified curve basing on a correction data generating circuits 22, 23, and heat is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal transfer@tone control device, which controls the size of printed dots by controlling the duration of a constant current flowing through a heating resistor of a thermal head, thereby controlling the gradation. The present invention relates to a thermal transfer gradation control device for controlling.

In addition to conventional technology terminal printers (hard copy min!), such as wire dot and inkjet printers, thermal transfer printers have been developed as the most promising printer.

This thermal transfer printing device uses an ink film in which heat-melting ink is coated on one side of a polyester film with a thickness of 5 to 6 μm, for example, and the front ink side of this ink film is brought into contact with recording paper, and the back side is heat-sensitive. Apply the head,
The structure is such that an electric current is passed through this thermal head to generate heat, thereby melting the ink on the ink film at a position corresponding to the thermal head and transferring it onto a recording sheet.

This thermal head has a plurality of heat-generating resistors arranged in a row, and a current is sequentially applied to each heat-generating resistor.

The density, which determines the gradation of printed characters, figures, pictures, etc., is determined according to the area of each dot on the recording paper to which the molten ink has been transferred. The area of the molten ink dot is determined depending on the duration of current II applied to each heating resistor.

However, the relationship between the print density and the time (recording time) in which a current is passed through the heating resistor in the thermal transfer printing device is not linear, and there may be a density error between the originally desired density and the density actually obtained. There was a drawback that this could occur.

Therefore, in Japanese Patent Application No. 60-49119, the present applicant previously proposed a thermal transfer gradation control device that controls printing density by correcting the relationship between density and recording time to be a straight line or a predetermined curve. proposed. Such a thermal transfer gradation control device converts, for example, an analog video signal into a digital signal (image data), sends this to a data storage device such as a semiconductor memory, determines addresses for the required number of pixels, and then stores it. , read out according to the address sent from the address counter, and output it to the grayscale data comparison circuit.

This density data comparison circuit uses the reference density data sent from the data counter (data indicating the minimum density at the beginning of R).
and image data of the same number as the number of heating resistors read out from the data storage device sequentially, and if the value of this image data is equal to or larger than the value of the reference density data, the data is transferred through the shift register circuit. For example, a high level output signal is supplied to the gate circuit, and if the density data is smaller than the reference density data, a low level output signal is supplied to one input terminal of the gate circuit. The density data comparison circuit then compares the second standard density data from the one with the lowest density with the same number of image data as the number of heating resistors sequentially read out from the data storage device in the same manner as above. , sends a high level or low level signal to one input terminal of the gate circuit in the same manner as above. Thereafter, the above operation is repeated in the same manner as above until the reference density data reaches the maximum density.

On the other hand, the correction circuit is supplied with the reference density data and corrects it using a correction table in which correction data is stored in advance so that there is a linear relationship between recording time and density. As a result, the correction circuit supplies to the other input terminal of the gate circuit a heating pulse whose pulse width changes for each unit of the reference concentration data based on the correction data.

Therefore, the heating pulse passes through only the gate circuit to which the high level signal is input to one input terminal.
Make the corresponding heating resistor generate heat. In this way,
A heating pulse is applied to the plurality of heating resistors for a time corresponding to the concentration, causing a pulsed current to flow, thereby controlling the gradation.

However, the problems that the invention attempts to solve are: 1. In the thermal transfer printing device, the density is increased approximately linearly at the minimum density and a density level close to it (hereinafter referred to as "white level"), and at the maximum density and a density level close to it (hereinafter referred to as "black level"). cannot be reproduced, resulting in blown-out highlights and blown-out shadows.

As a method of correcting the above-mentioned mill skipping, there is a method in which electricity is supplied in advance only to the heating resistor to be transferred to reheat it.

According to this method, it was possible to reproduce the density linearly from the white level to the halftone level, but the range from the halftone level to the black level was easily distorted to black due to heat accumulation in the heating resistor (
, linear concentration reproduction was not possible.

Further, as a method for correcting the blackout, there is a method of controlling the amount of current applied to the heating resistor for each density, such as in the thermal transfer gradation control device proposed by the applicant of the present invention. According to this method, linear density reproduction was obtained for almost every density, but there were problems such as that linear density reproduction was impossible at the white level.

Therefore, the present invention provides a thermal transfer gradation control device that solves the above problems by reheating only the heat generating resistor to be transferred and controlling the energization time of each heat generating resistor for each unit of print density. The purpose is to provide

Means for Solving the Problems The thermal transfer gradation control device according to the present invention includes a control counter that generates and outputs a signal corresponding to a preset reheating time, and a control counter that generates and outputs a signal corresponding to a preset reheating time. means for generating reference density data that holds a value indicating the minimum density (minimum density printed) during the reheating time and sequentially changes from the minimum density to the value indicating the maximum density in a short time after the elapse of the reheating time; The reference concentration data that compliments the reference concentration data during the reheating time is compared with the input data to be transferred, and the heat generating resistor to which the IIl flow should flow is determined from among the plurality of heat generating resistors in a row for each unit of concentration. Means for generating control data indicating the body and reference density data are supplied, and correction data set so that the relationship between the recorded density stored in advance and the reference density data becomes a straight line or a predetermined curve is inputted. Consisting of a correction data generation circuit that outputs according to reference concentration data, and a means for supplying correction data and control data, respectively, and passing current through a heating resistor indicated by time control data according to the value of the correction data. .

Operation: The reference concentration data is maintained at a value indicating the minimum concentration during the reheating time by the control counter.

Therefore, the control data generating means causes current to flow only through the heating resistor to which input data having a value greater than the minimum density is to be transferred, thereby reheating the heat generating resistor.

In addition, since the reference concentration data changes sequentially from the minimum concentration to the maximum concentration in a short time after the reheating time has elapsed, the control data generation means generates a heat-generating resistor to which the input data should be transferred for each concentration level. Electric current is passed through the body. A current is passed through the heating resistor for a time set so that the relationship between the recorded density and the reference density data becomes a straight line or a predetermined curve based on the correction data supplied from the correction data generation circuit. I get a fever.

In addition, in Honkawa IS, thermal transfer recording refers to thermal recording in which recording is performed by chemically changing the recording paper itself due to heat generation, thermal recording using heat-melting transfer paper, and thermal sublimation using sublimation transfer paper. This shall include all forms of thermal recording and other devices that perform recording by applying heat.

Embodiment FIG. 1 shows a circuit diagram of an embodiment of a thermal transfer gradation control device according to the present invention. In the figure, a thermal head 6 includes n heating resistors RI''RO formed in a row on a ceramic substrate.The configuration of this thermal head 6 is the same as that of a conventional thermal transfer printing device, and for example, As shown in Fig. 4, the ink film 1 extends in the width direction. The recording paper 4 is sent in the direction of the arrow along with the ink film 1 by the roller 5 with its recording surface facing the ink 3 surface of the ink film 1.A thermal head 6 is provided opposite the row 55. It is in contact with the back surface of the ink film 1.

The ink 3 of the ink film 1 corresponding to the energized heat generating resistor among the heat generating resistors R1 to Ro of the thermal head 6 is melted and transferred onto the recording paper 4. After passing through the thermal head 6, the ink film 1 is guided by a roller 7 and separated from the recording paper 4, and then placed on a take-up spool (not shown).
The ink film is wound up as a used ink film 1a. The transferred ink 3a remains on the printed recording paper 4a. For convenience of illustration - F1 The transferred ink 3a is shown as having a large area, but actually consists of a collection of small dots.

One dot is formed by a negative heat generating resistor, and the size of the negative dot is determined by the current value or current flow time applied to the heat generating resistor. The shading, or gradation, of the printed figure is determined according to the size of each dot.

The present invention is a gradation control device that can be applied to such a thermal transfer printing device.
The analog movie signal supplied from the V signal generator 8 is A.
The signal is converted into a digital signal by the /D converter 9, and sent to the data storage device 10 for storage. On the other hand, the address counter 11 is supplied with a reference clock signal from a terminal 12 and a start pulse from a terminal 13. The start pulse is a pulse as shown by a in FIG.
In addition, a preset reheating preset value from the reheating preset source 20 is loaded into the control counter 18 . This reheating preset value is a value that determines the reheating time, which will be described later, and includes the period of pulse b shown in FIG. Determined by pressure, ambient temperature, etc., for example r4
It is selected to be around J. Further, the heating time is selected to be a time during which pixel data for one line is read out repeatedly an integer number of times.

The control counter 18 counts the pulse b shown in the second IJ (B) generated by the address counter 11 based on the reference clock, and counts this pulse b by the reheating preset value in the interval Δt between rJ8. Middle, Figure 2 (
As shown in C), a low level signal C is supplied to the data counter 15 to stop its counting operation. Therefore,
The value of the reference density data d shown in FIG.
0", that is, the value "0" indicating the minimum concentration. Note that the period of the pulse b is selected to be shorter, for example, about 1710, than the period of the output pulse of a conventional address counter.

The address counter 11 sends the first address to the data storage device W10 upon receipt of the start pulse a.

The data storage device 10 sends first data (the first data of the image data from the A/D converter 9) corresponding to this first address to the grayscale data comparison circuit 14. The density data comparison circuit 14 compares the first data with reference density data (lower J and C, referred to as "second data") "0" indicating the minimum density from the data counter 15, and
If the data is larger than the second data "0", control data "1" is sent to the shift register 16, and if it is smaller, control data "0" is sent to the shift register 16.

In this way, when the processing at the first address is completed, the address counter 11 is sequentially updated to 2°3, . . . +,
The nth address is sent to the data storage device 10, and the data storage device 10 sequentially sends first data corresponding to the second to nth addresses to the grayscale data comparison circuit 14 each time. Here, the first data from the 1st to nth addresses correspond to image data printed by each of the heating resistors R+ to Rn of the thermal head 6, respectively. The gray data comparison circuit 14 compares the first data and second data "0" corresponding to the 2nd to nth addresses, respectively, and sets the control data "0" or "1" in the same manner as above. Send to shift register 16. The n-stage shift register 16 sequentially takes in n-bit control data corresponding to the 1st to n@th addresses supplied from the grayscale data comparison circuit 14 and sends it to the latch circuit 17.

When the address counter 11 finishes counting the 1st to nth addresses, it sends a data transfer pulse b shown in FIG. 2(B) to the data counter 15, latch circuit 17, and control counter 18.

The period Δt of this data transfer pulse b is about 1 compared to the conventional one.
It has been shortened to about /10. At the same time as this data transfer pulse b is sent, the data counter 15 is activated as shown in FIG.
) is applied to the address counter 11 and AN
It is supplied to one input terminal of the D circuit 19 and the AND circuit 21.

On the other hand, a reference clock signal is supplied from the terminal 12 to one end of the AND circuit 19, and simultaneously with the input of the heating pulse e from the data counter 15, the pulse is output to the shift register 16, and the pulse is outputted to the shift register 16. 1~n
flilltll of n bits corresponding to the th address
Data is transferred from the shift register 16 to the latch circuit 17. When the data transfer pulse b is received, the latch circuit 17 latches the control data supplied from the shift register 16 and sends it to one input terminal of each of the gate circuits 01 to Go.

On the other hand, the address counter 11 is reset by the input of the heating pulse e and sequentially counts 1 to n addresses again. During the reheating time ΔT, the address counter 11 allows the data storage device 10 to n pieces of first data are read out repeatedly, and the second data is held at "0", so the n pieces of first data for the same line have the above value "0". and the second data of
The grayscale data comparison circuit 14 repeatedly compares the magnitude.

Therefore, during the reheating time ΔT, a heating current is applied to only the heating resistor to be transferred when the first data is "1" or more, that is, the heat generating resistor is to be transferred according to the first data, and the heat is reheated. For this reason, the first data of the white level is held as white and is not transferred, and the rise of the transfer density is optimized by optimizing the above-mentioned reheat precera 1-value for the density above the level from white. be able to.

After that, when the pulse C becomes high level at time t2 when the control counter 18 has finished counting the pulses b for the reheating preset value, the data counter 15 starts counting operation and repeats the same operation as above for one line. After doing this once for the first data of
The second data shown in is increased to the value "1" indicating the second density from the smallest one.

As a result, the gray data comparison circuit 14 sequentially compares the n pieces of first data for the same line with the second data having the value "1". If the second data is "1", the shift register 16. Latch circuit 17. AND circuit 1
9 etc. performs the same operation as above, and the gate circuit G +
"'-G The latched control data is sent to each one input terminal of n.

On the other hand, the correction table storage memory 22 is supplied with the second data "0" shown in FIG. The data corrected using the corrected correction table is sent to the pulse generator 23. The pulse generator 23 is at a high level during a predetermined period including the reheating time 6 according to the incoming correction data, and after this period, the pulse f as shown in FIG. Generate and AND
It is output to the other input terminal of the circuit 21. AND circuit 21
is due to the incoming heating pulse e and pulse f, the second
The gate circuit 01 generates a pulse Q shown in FIG.
~G, to each other input terminal.

As shown in FIG. 2 (G), the pulse q is a predetermined pulse during a predetermined period including the reheating time Δt after time t1 (i.e., the period from time t1 to t3 when the second data d is rOJ). After this period, the pulse width gradually decreases depending on the data content of the correction data sent from the correction table storage memory 22.

Each of the gate circuits 01 to Gn applies a gate signal obtained by gate processing the pulse q and n-bit control data supplied from the latch circuit 17 to an NPN transistor T.
It is supplied to each base of 1 to To, and the switching is controlled. Among the transistors T+ to T, a current is passed only through the heating resistor connected to the collector side of the turned-on transistor, and heat is generated.

Moreover, after time t2, the second data output from the data counter 15 is rOJ, NJ in synchronization with pulses b and e.
, r2J, .
If it is equal to or smaller than the second data, control data "0" is output. Depending on the control data of "0" or "1" and the pulse width of the pulse q, the energization time of the heating current flowing through the heating resistor changes, and data for one line is recorded between stories.

After that, when the next start pulse a comes in, the address counter 11 and the data counter 15 are each reset, and the data counter 15 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 the gradation recording of the first data for the next one line is performed.

In this way, as shown in FIG. 3, the number of gradations vs. density characteristic (■) according to this embodiment is better than the number of gradations vs. density characteristic (■) in the case where only the blackout correction is performed in the highlight area. It is possible to perform linear density control from halftone to black level, compared to the gradation number vs. density characteristic (2) when only the above-mentioned mill skipping correction is performed. Therefore, according to this embodiment, it is possible to perform approximately linear density control from the number of gradations "0" to rmJ, that is, from the white level to the black level. Also, the period of pulse b is about 1/10 of the conventional one, so
The interval between records i can be shortened.

In this way, each time the data counter 15 finishes counting 1 to m times, one line is recorded on the recording paper 4, and after the recording of this one line is completed, the data counter 1 to m counts again. Start counting.

Note that the analog video signal supplied from the TV signal generator 8 may be an information signal of images such as other characters and figures. In addition, although the above embodiment describes the case where the relationship between the recording time and the density is a straight line, the relationship between the 28 hours and the density may be a predetermined curve.

Effects of the Invention As described above, according to the present invention, only the heat generating resistor to be transferred is heated, so it is possible to obtain the optimum density characteristic in the highlight part, and the period of the data transfer pulse can be changed from the conventional one. Since it was made considerably shorter than that, it was possible to shorten the recording time, and furthermore, the energization time of each heating resistor was controlled for each degree so that the recording time and density had a substantially linear relationship. Therefore, the density can be controlled almost linearly from the highlight area to the maximum number of gradations without causing the black-out problem described above even at high density areas, and high-quality printing can be achieved. has.

[Brief explanation of drawings]

FIG. 1 is a circuit system diagram showing an embodiment of the thermal transfer gradation control device d according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the circuit system shown in FIG. FIG. 4 is a schematic perspective view of an example of a main part of a thermal transfer printing device to which the thermal transfer gradation control device of the present invention can be applied. . 6...Thermal head, 10...Data storage device, 11
...Address counter, 12...Reference clock signal input terminal, 13...Start pulse signal input terminal, 1
4... Grayscale data comparison circuit, 15... Data counter, 16... Shift register, 17... Latch circuit, 18... Control counter, 19.21-...
AND circuit, 20... Reheating preset source, 22...
Correction table storage memory, 23...Pulse generator, 0
1-G...Gate circuit, R1-Ro...Heating resistor, T1-Tn...Transistor. Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A signal corresponding to a preset reheating time is generated in a thermal transfer gradation control device that individually controls the time of each current flowing through a plurality of heating resistors arranged in a row according to the concentration. Depending on the output control counter and the signal supplied from the control counter, the value indicating the minimum concentration is held during the reheating time, and after the elapse of the reheating time, the value is changed from the minimum concentration to the value indicating the maximum concentration in a short time. means for generating reference concentration data that sequentially changes in the reheating time, and comparing the reference concentration data including the reference concentration data during the reheating time with the input data to be transferred, and generating a plurality of data in one row for each unit of concentration. means for generating control data indicating which heat generating resistor is to be passed a current among the heat generating resistors; A correction data generation circuit outputs correction data set to be a straight line or a predetermined curve according to the input reference density data, and the correction data and control data are respectively supplied, and the correction data is adjusted to the value of the correction data. 1. A thermal transfer gradation control device comprising: means for causing a current to flow through the heating resistor for a corresponding time indicated by the control data.