JPS61287769A - Thermal transfer gradation controller - Google Patents

Abstract

PURPOSE:To enable recording speed to be enhanced and gradation characteristics to be optimized and stabilized, by a method wherein correction data obtained each time by calculations according to external conditions are stored into a memory, and are read from the memory at the time of recording. CONSTITUTION:Each time the external condition data such as the ambient temperature, the kinds of a transfer paper and a recording paper and melting characteristics of an ink are changed, the correction data indicating an energization time for heating resistors are outputted from a calculating part 21. The correction data comprise gradation number versus energization time characteristics varied for every one or several units of density to give an optimum recorded density characteristic according to the external condition data. Therefore, the width of a pulse outputted from a comparator 23 for comparing the level of the correction data with the level of a signal of one gradation data time period is gradually varied for every one or several units of density. An electric current is passed to the heating resistors R1-Rn for a period of time equivalent to the pulse duration, whereby gradation density control is performed. Accordingly, it is possible to contrive a higher recording speed and optimal and stable gradation characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal transfer gradation control device, which controls the size of printed dots by 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.

2. Description of the Related Art In addition to conventional printers (hard copy devices) for terminals, such as wire dot printers 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 microns, for example, and the front ink side of this ink film is placed in contact with the recording paper, and the back side is heat-sensitive. A head is applied to the thermal head, and an electric current is applied to the thermal head to generate heat, thereby melting the ink on the ink film at a position corresponding to the thermal head and transferring the ink to the recording paper.

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 the current applied to each heating resistor.

The thermal transfer printing device described above 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 and stores addresses for the required number of pixels, and then converts an analog video signal into a digital signal (image data). It is read out according to the address sent from the counter and output to the grayscale data comparison circuit.

This density data comparison circuit uses the standard density data (initially data indicating the minimum density) sent from the data counter.
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.

A heating pulse is supplied from the data counter to the other input terminal of the gate circuit, and the heating pulse passes through only the gate circuit to which the above-mentioned high-level signal is input to one input terminal, causing the corresponding heating resistor to pass through. cause fever. In this way, a heating pulse is applied to the plurality of heating resistors for a time corresponding to the concentration, and a pulsed current is caused to flow, thereby controlling the gradation.

However, in order to express gradation with sufficient print density using the thermal transfer printing apparatus, sufficient cooling time and energization time are required for the heating resistor for each gradation. Furthermore, when the recording time is shortened in this apparatus, the above conditions are no longer satisfied, and there are drawbacks such as the inability to achieve necessary gradation characteristics.

Conventionally, in order to solve the above-mentioned drawbacks, there has been a method of connecting a correction circuit between the data storage device and the grayscale data comparison circuit to correct the data from the data storage device.
The recording time vs. density characteristic in this case is as shown in Figure 7. For example, if the number of gradations is 64, the recording time will be controlled in increments of 1764 of the maximum recording time, but if the number of gradations is 32, for example, If the corrected recording time is 32.5, the recording time must be selected from either 32 or 33.
There was a problem in that a concentration error e'' was produced.

Therefore, the present applicant previously proposed in Japanese Patent Application No. 60-49121 or No. 60-66083 that the pulse width can be adjusted depending on external conditions such as external temperature, type of recording paper, melting characteristics of ink, etc. A thermal transfer gradation control device has been proposed which solves the above-mentioned problems by generating a changing pulse and performing recording by passing a current through a heating resistor for a time corresponding to the pulse width.

The heat-sensitive transfer gradation control device (hereinafter referred to as the "first heat-sensitive transfer gradation control device") disclosed in Japanese Patent Application No. 60-49121M is a. An analog signal generator generates an analog signal whose time versus level characteristics change depending on the external conditions, and generates and outputs a heating pulse whose pulse width changes depending on the level of the analog signal.

Further, the thermal transfer gradation control device disclosed in the above-mentioned Japanese Patent Application No. 60-66083 (hereinafter referred to as the "second thermal transfer gradation control device") adjusts the recording time and density according to the external conditions. Correction data set so that the relationship is a straight line or a predetermined curve is stored in advance in read-only memory (ROM), and the heating pulse whose pulse width changes according to the correction data read from this ROM. was generated and output.

Problems to be Solved by the Invention The first and second thermal transfer gradation control devices described above make it possible to correct the recording density according to rough external conditions.

However, the first thermal transfer gradation control device requires an A/D converter or a D/A converter for the analog signal generator, resulting in high cost. Furthermore, the stability or reliability of the analog signal generator itself has been a problem.

In addition, in the second thermal transfer gradation control device, since the correction data is stored in the ROM, when the correction conditions are diverse, the ROM needs to have a large capacity, which causes problems such as high cost. There was a point.

Therefore, the present invention provides a thermal transfer gradation control device that solves the above problems by storing correction data calculated each time according to external conditions in a memory, and reading the correction data from this memory during recording. The purpose is to provide

Means for Solving the Problems The thermal transfer gradation control device according to the present invention compares the input capacitor to be transferred, and applies current to a plurality of heating resistors in a row for each unit of density. A means for generating control data indicating the heating resistor to be used, and data on external conditions such as ambient temperature, types of transfer paper and recording paper, and melting characteristics of ink are input, and the heating resistor is calculated by calculating from the external condition data. A calculation unit that generates correction data indicating the energization time of the body, and a memory that stores the correction data when the recording device is stopped, and then reads out the stored correction data for each unit of concentration while the recording device is in operation. and a comparison means for comparing the levels of the correction data read from the memory and the signal of one gradation data time period to generate a pulse whose pulse width indicates the time of the current flowing for each unit of density; The output pulse and the control data are supplied to the heating resistor for a time corresponding to the pulse width of the pulse.

Effect: The calculation section calculates and outputs correction data each time the external condition data is changed.

Such correction data has a gradation number vs. energization time characteristic that changes in units of - or several units of density so that the recording density characteristic is optimized according to external condition data.

Therefore, the pulse width of the pulse outputted from the comparison means gradually changes by - or several units of density based on the correction data. A current is passed through the heating resistor for a time corresponding to the pulse width period of this output pulse, and gradation density control is performed.

In this specification, thermal transfer recording refers to thermal recording in which recording is performed by chemically changing the recording paper itself due to heat generation, or thermal recording using heat-melting transfer paper.
This includes all types of thermal sublimation recording using sublimation transfer paper and recording by applying geothermal 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, the thermal head 6 includes n heating resistors R1 to Rn formed in a row on a ceramic substrate. The configuration of this heat-sensitive pad 6 is the same as that of a conventional thermal transfer printing device, and extends in the width direction of the ink film 1, as shown in FIG. In the same figure,
An ink film 1 serving as a transfer paper has a heat-melting ink 3 coated on the surface of a polyester film 2 to a predetermined thickness. The recording surface of the recording paper 4 is coated with the ink 3 of the ink film 1.
The ink film 1 and the ink film 1 are sent in the direction of the arrow by the roller 5 so as to be brought into contact with the surface of the ink film 1 .

A thermal head 6 is provided opposite the roller 5 and 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 Rn 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, the transferred ink 3a is shown as having a large area, but it actually consists of a collection of small dots.

One dot is formed by a - heating resistor element,
The size of the -dot is determined by the value of the current or the duration of the current flowing through the heating resistor element.

Depending on the size of each dot, the 1m lightness, or gradation, of the printed figure, etc., is determined.

The present invention is a gradation control device that can be applied to such a thermal transfer printing device.
The analog video 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 the reference clock signal shown in FIG. 4 (B) from the terminal 12 and the start pulse a shown in FIG. Send it to the storage device 1o. The data storage device 10 stores first data (A/D converter M9) corresponding to this first address.
(first data of the image data) is sent to the grayscale data comparison circuit 14.

At this time, the count of the data counter 15 is set to rOJ, for example.
Then, reference density data (hereinafter referred to as "second data") that increases sequentially in accordance with this count number is supplied from the data counter 15 to the density data comparison circuit 14. The gradation data comparison circuit 14 compares the first data with the second data rOJ indicating the minimum density, and if the first data is thicker than the second data "0", the control data is sent to the shift register 16. "1" is sent, and if they are equal, control data rOJ 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 R1 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. shift register 1
Send to 6. The n-stage shift register 16 is! N-bit control data corresponding to the first to nth addresses supplied from the light data comparison circuit 14 are sequentially taken in and sent to the latch circuit 17.

When the address counter 11 finishes counting the 1st to nth addresses, it sends a data transfer pulse C shown in FIG. 4(C) to the data counter 15 and latch circuit 17. At the same time as this data transfer pulse C is sent, the data counter 15 sends a heating pulse to the correction circuit 18 via the terminal 19.
．． The data is supplied to the address counter 11 and the AND circuit 20, and the second data, which was previously "0", is increased to "1", the value indicating the second smallest density. on the other hand,
A reference clock signal is supplied from the terminal 12 to one end of the AND circuit 20, and simultaneously with the input of the heating pulse, the pulse is output to the shift register 16, and the pulse is outputted to the 1st to nth addresses of the address counter 11. The corresponding n-bit control data is transferred from the shift register 16 to the latch circuit 1.
Transfer to 7. The latch circuit 17 latches the control data supplied from the shift register 16 when the data transfer pulse C is received, and gate circuits G1 to Qn
are sent to each one of the input terminals.

Next, the address counter 11 is reset by the input of the heating pulse and sequentially counts 1 to n addresses again, and the n first data becomes the second data with the value "1". and are sequentially compared in magnitude in the grayscale data comparison circuit 14. Even when the second data is "1", the data counter 15° shift register 16. Latch circuit 17.
The AND circuit 20 and the like perform operations similar to those described above, and send latched control data to each of the gate circuits G1 to Gn. A heating pulse is applied to the other input terminal of each of the gate circuits G+ to Gn by a terminal 29 of a correction circuit 18, which will be described later, and each output signal is applied to the base of the corresponding NPN transistor T1 to Tn, which is used for switching. Control. Current flows only through the heating resistor connected to the collector side of the turned-on transistor among the transistors T+ to Tn, and heat is generated.

This embodiment is characterized in that a correction circuit 18 is provided in the gradation control device shown in FIG. 1, and one embodiment thereof will be described below. In FIG. 2, the correction circuit 18
is the calculation unit 21. Static random access memory (SRAM) 22° comparator 23 and AND circuit 24
It is composed of. As the arithmetic unit 21, for example, a microcomputer can be used.

Now, the external temperature, the type of recording paper and transfer paper.

A pulse P shown in FIG. 3(A), which notifies a change in external conditions from a device (not shown) for selecting and inputting external conditions such as the melting characteristics of ink, is sent to the calculation unit 2 via a terminal 25.
1, the arithmetic unit 21 switches the high level to the low level at the rise time t1 of the pulse P, and thereafter maintains this low level for a predetermined period of time, as shown in FIG. The pulse Q is supplied via terminal 26 to an indicator (not shown), for example as an indicator signal. This indicator externally displays the inoperative state of the recording device while the pulse Q is at a low level, and externally displays the operational state while the pulse Q is at a high level. Therefore, the recording apparatus is stopped for a predetermined period from time t+ to t4 when the pulse Q becomes low level.

In such a state, the calculation unit 2.1 receives the incoming pulse P.
Based on this, external conditions are input, calculations are performed, and correction data corresponding to the external conditions is generated and sent to the SRAM 22. Furthermore, at the falling time t2 of the pulse P, the arithmetic unit 21 calculates
A pulse R shown in FIG. 3(C) in which the low level becomes high level is generated and supplied to the SRAM 22.

This pulse R is maintained at a high level for a predetermined period from time t2 to t3, and the correction data is written in the SRAM 22 during this period. Moreover, after time t3, the pulse R
When becomes low level, the SRAM 22 becomes in a state where the written correction data can be read. After that, time t
When the pulse Q becomes high level at step 4, the recording device becomes ready for operation and waits for the start of device startup. Therefore, the timings of the above-mentioned times t1 to t4 are set so that the relationship tl<t2<t3<ta is satisfied. .

Next, the operation during recording will be explained with reference to the signal waveform diagram shown in FIG. Here, the address counter 11 and data counter 15 shown in FIG. 1 are reset at the rising time t5 of the incoming start pulse a (FIG. 4(A)). On the other hand, the address counter 11 increases sequentially from rOJ, for example, every time the reference clock signal b (FIG. 4(B)) is received from the pulse rise time t5 of the data transfer pulse C (FIG. 4(C)). Comparison data Da is generated and sent via terminal 27 to comparator 23 in correction circuit 1'8 shown in FIG. Note that this comparison data [)a is reset when the next pulse of the data transfer pulse C arrives and returns to "O" again.

On the other hand, the data counter 15 receives the number n of heating resistors based on the incoming reference clock signal ga and the data transfer pulse C supplied from the address counter 11, and uses the data transfer pulse C. Address data is generated and supplied to the arithmetic unit 21 and SRAM 22 in the correction circuit 18 via a terminal 28, respectively. As a result, S
The RAM 22 reads out the already written correction data Db based on the address data and sends it to the comparator 23.

As a result, the comparator 23 compares the incoming comparison data Da and the correction data Db for each pulse section of the data transfer pulse C, and when the level of the correction data Db is large,
It outputs a pulse d shown in FIG. 4(D) which is at a high level and becomes a low level when it becomes smaller. This pulse d becomes high level at the rising edge of the data transfer pulse C, and its pulse width gradually decreases, for example, as the gradation level becomes higher. This pulse d is shown in Fig. 4 (E
), the pulse width may be set to a low level at the rising edge of the data transfer pulse C, and the pulse width may be set to gradually become smaller as the gradation level becomes higher.

In addition, the correction data Db has, for example, the number of gradation levels vs. energization time characteristic as shown in FIG. By calculating the characteristics, storing them in the SRAM 22, and setting the optimum characteristics each time, delicate gradation expression becomes possible. Therefore, the pulse width of the pulse d gradually changes by - or several units of concentration based on the characteristics shown in FIG.

On the other hand, one end of the AND circuit 24 shown in FIG.
A high-level heating pulse (strope signal) is supplied through the terminal 9, and the pulse d supplied to the other terminal passes through the AND circuit 24 and is connected to the gate circuits 01 to Gn via the terminal 29. Each of the other input terminals is supplied as a heating pulse. Each of the gate circuits 01-Qn supplies a gate signal obtained by gate processing the pulse d and the control data supplied from the latch circuit 17 to the bases of the NPN transistors T1-Tn, respectively. The transistors T+-Tn are turned on while the gate signal supplied to their base is at a high level, and the heating current is connected to the collector of the turned-on transistor among the heating resistors R1 to Rn by the power supply voltage 10 Vcc. The current flows only through the heating resistor.

In this way, a heating current whose conduction time varies depending on the concentration is passed through some of the heat generating resistors R1 to Rn corresponding to the portion to be recorded, and the data is Each time the counter 15 finishes counting 1 to m times (m is the maximum density value), one line is recorded on the recording paper 4, and after the recording of this one line is completed, the next start pulse a is started. Data counter 15 again due to arrival
starts counting 1 to m times.

Note that the analog video signal supplied from the TV signal generator 8 may be an information signal of an image of another character or figure.

Effects of the Invention As described above, according to the present invention, the density can be changed every - or several units in response to changes in various external conditions such as the ambient temperature, the type of recording paper or transfer paper, and the melting characteristics of ink. By changing the energization time of the heat-generating resistor, it is possible to increase the recording speed, optimize and stabilize the gradation characteristics, and furthermore, it is possible to increase the recording speed by changing the energization time of the heating resistor. Since the configuration is configured such that the optimum correction data according to the input external conditions is written in the memory such as the SRAM each time and read out as necessary, the correction data corresponding to some external conditions assumed in advance can be stored in the ROM. Compared to the apparatus previously proposed by the present applicant in which the device is stored as a table, concentration control corresponding to more external conditions is possible, and the cost can be reduced.

[Brief explanation of drawings]

1 is a circuit system diagram showing an embodiment of the thermal transfer gradation control device according to the present invention; FIG. 2 is a circuit system diagram showing an embodiment of the correction circuit in the circuit system shown in FIG. 1; 4 and 4 are signal waveform diagrams for explaining the operation of the circuit system shown in FIG. 2, respectively. FIG. 5 is a graph of tone number vs. energization time characteristic of an example of correction data. FIG. 6 is a thermal transfer stage according to the present invention. FIG. 7 is a schematic perspective view of an example of a main part of a thermal transfer printing apparatus to which the tone control device can be applied, and FIG. 7 is a recording time vs. density characteristic diagram of a conventional thermal transfer tone control device. 10...Data storage device, 11...Address counter, 12-...Reference clock signal input terminal, 13...
Start pulse signal input terminal, 14... Grayscale data comparison circuit, 15... Data counter, 16... Shift register, 17... Latch circuit, 18... Correction circuit, 19... Heating pulse input Terminal, 20.24...A
ND circuit, 21... Arithmetic unit, 22... Static random access memory (SRAM), 23.
...Comparator, 27...Comparison data input terminal, 28...
・Address data input terminal, G1-Qn...gate circuit, R1-Rn...heating resistor, ■1-Tn...
transistor. Patent Applicant: Victor Company of Japan Co., Ltd. Figure 3 Figure 4 (A) Hanichi ----------------------- Figure 6 Figure 1

Claims (1)

[Claims] In a thermal transfer gradation control device that individually controls the time of each current flowing through a plurality of heat generating resistors arranged in a row according to the density, a comparison is made with the input data to be transferred, and the density is determined. Means for generating control data indicating which heating resistor to which current should flow among the heating resistors in a row of plural heat generating resistors for each unit, ambient temperature, types of transfer paper and recording paper, melting characteristics of ink, etc. an arithmetic unit that receives data on external conditions and generates correction data indicating the energization time of the heating resistor by calculation from the data on the external conditions; and a calculation unit that stores the correction data while the recording device is in a stopped state; Thereafter, in the operating state of the recording device, a memory is used to read out the stored correction data for each unit of density, and a level comparison is made between the correction data read from the memory and the signal of one gradation data time period. a comparison means for generating a pulse whose pulse width indicates the time of the current flowing for each unit of concentration; and a heat generating resistor which is supplied with the output pulse and control data of the comparison means and whose time corresponds to the pulse width of the pulse. A thermal transfer gradation control device characterized by comprising means for passing an electric current through the body.