JPS62138262A - Thermal transfer gradation control apparatus - Google Patents

Abstract

PURPOSE:To obtain the good expression of gradation at a high speed by allowing a heat generating resistor to almost accurately generate heat in order to obtain necessary temp., by correcting the recording data of a present line corresponding to the residual quantity of heat of each heat generating resistor due to the recording data of the previous line. CONSTITUTION:A conversion table 18 converts the gradient (l) of the first recording data of a present line from a data memory apparatus 10 corresponding to the gradient (k) of the second recording data of the previous line from a memory 19 according to a formula (12) to obtain the third recording data (l') of the present line and send out said data (l') to both of a density data comprising circuit 17 and the memory 19. In the formula, alpha2 is the heat falling time constant of a heat generating resistor. The memory 19 stores the third recording data (l') of the present line from the conversion table and outputs the third recording data (l') of the present line to the conversion table 18 as the second recording data (k) of the previous line at the time of the recording of the image data of the next line. The density data comparing circuit 17 compares the third recording data with reference density data '0' showing the min. density from a data counter 15 to change the current supply time of the heating current flowing to a heat generaiting resistor.

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. The present invention relates to a thermal transfer gradation control device that controls gradation.

Conventional technology terminal printers (hard copy devices)
1. Thermal transfer type printing devices have been developed as the most promising type for printing dot type, inkjet type, etc. This thermal transfer printing device uses an ink film coated with a polyester film heat-melting ink having a diameter of 5 to 6 μm, for example, the front ink side of the ink film is brought into contact with the recording paper, and the back side is Apply a heat-sensitive head to
A current is applied to this thermal head to generate heat, melt the ink on the ink film at a position jJ 1,'i5V to the thermal head, and transfer the melted ink to the recording paper.

This thermal head has a plurality of heat-generating resistors arranged in a line, 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 onto which the molten ink is transferred 77. The area of the melting ink driver 1- is determined depending on the duration of the current applied to each heat generating body.

However, the thermal response of the heating resistor in the thermal transfer printing device is as shown in Fig. 5, and it takes a current application time of 1'a to record the minimum density, and the gradation is gradually increased. To do this, the cold/J1 time tb is also required, and the time t C - t a 41:b is required to express one gradation, so it is possible to record one gradation within the interval tc. won.

Therefore, the applicant first filed Japanese Patent Application No. Sho GO-11799G (
We have proposed a thermal transfer gradation control device that reheats only the heat generating resistors to be transferred with a trowel and controls the energization time of each heat generating resistor for 1 unit fU of print density 1a. Such a thermal transfer gradation control device converts, for example, an analog video signal into a fully digital signal (image data), sends it to a data storage device such as a semiconductor memory, determines addresses for the required number of pixels, and stores it. , read out according to the address sent from the address counter and output to the grayscale data comparison circuit.

This vi-light data comparison circuit reads the reference concentration data (data that maintains the minimum concentration value during the reheating time and increases sequentially thereafter) sent from the data counter and sequentially from the data storage device. The heating resistor and the same number of image data are sequentially compared, and the value of this image data is the standard moisture data I+iJ1. :If equal or different,
For example, a high-level output signal is supplied to the gate circuit via the shift register circuit, and if the data is smaller than the reference density data, a 1-level output signal is supplied to one input terminal of the gate circuit. The gradation data comparison circuit then compares the second standard density data from the one with the lowest temperature 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. Then, in the same manner as above, a high level or low level signal is sent to one input terminal of the gate circuit. Thereafter, the above operation is repeated in the same manner as above until the reference temperature data reaches the maximum concentration.

On the other hand, the correction table storage memory is supplied with the reference 'a 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. Next, the pulse generator 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.

Problems to be Solved by the Invention However, the conventional thermal transfer gradation control device described above does not take into consideration the temperature state of the heating resistor due to the previous line recording data that has already been recorded, but focuses only on the current line recording data. Since the energization time of the heat generating resistor was controlled, when recording the current line in a sunny period where the thermal response of the heat generating resistor was determined by the previous line recorded data, for example, the gradation of the current line recorded data could be changed. When the black level of the previous line changes from the black level to the white level, the heating resistor is heated more than necessary due to heat accumulation, and therefore, there is a problem in that it is difficult to achieve stable gradation expression of 1q.

Therefore, the present invention provides a thermal transfer gradation system that solves the above problems by correcting the current line recorded data according to the residual heat level of each heating resistor due to the previous line recorded data!
2Il device.

Means for Solving the Problems The thermal transfer gradation control device GEL according to the present invention calculates the amount of residual heat in each heating resistor from the number of gradations of the first recorded data of the current line to the second recorded data of the previous line. A complementary means outputs the number of gradations obtained by subtracting the number of gradations corresponding to the number of gradations as third recording data, and the third recording data from the correction means is stored, and the third recording data is stored in the previous line. and a memory for supplying the second recorded data to the correction means,
It is configured to control the time of each current flowing through the heating resistor in accordance with the third recorded data from the correction means.

Effect: The third recorded data outputted from the correction means is a heat-generating resistor that has already been energized and generated based on the number of gradations of the first recorded data of the current line and the second recorded data of the previous line. It is calculated by subtracting the number of gradations corresponding to the amount of residual heat in the body. Therefore, if we control the current between 01 and 100 of each current flowing through the heat generating resistor according to this third recorded data, the current line recorded data will be accurate regardless of the t'+ri line recorded data. Key expression becomes q-no.

Embodiment FIG. 1 shows a block system 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 R1 to Ro formed in a row on a ceramic substrate. The structure of this thermal head 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. 4, for example. Fourth
At J3 in the figure, an ink film 1 serving as a transfer paper has a heat-melting ink 3 coated on the surface of a poly I stellate film 2 to a predetermined thickness. The recording paper 4 has its recording surface brought into contact with the ink 3 surface of the ink film 1, and is sent together with the ink film 1 by the roller 5 in the direction of the arrow. A thermal head 6 is provided opposite the roller 5 and is in contact with the back surface of the ink film 1.

Behind the heating resistors R1 to R of the thermal head 6, the ink 3 of the ink film 1 corresponding to the energized heating resistors 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 h-dots.

One dot is formed by a negative heat generating resistor, and the size of one dot is determined by the current value or current flow time applied to the heat generating resistor. The gradation of printed figures, etc. is also 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 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 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. 2(A), and the address counter 11 and data counter 15 are reset by the start pulse a that comes in at time t1, respectively.
In addition, the control counter 14 is loaded with a preset reheating preset value from the reheating bricht source 16. This reheating preset value is a value that determines the reheating time, which will be described later. FIG. Furthermore, it is determined by the ambient temperature etc., for example "4
” will be selected. 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 14 counts the pulses b shown in FIG. 2(B) generated by the address counter 11 based on the reference clock.
As shown in Fig. 2 (C), a low level signal 8C is supplied to the data counter 15 during the period of 11.1 △T, and the m loss operation is stopped. U tighten. Therefore, the value of the standard Ci degree data d shown in FIG. Reset (direction "0", that is, held at 1direction rOJ indicating the minimum density white.The period of the pulse b mentioned above is, for example, about 1 in 10 compared to the period of the output pulse of the conventional address counter. Selected as short.

When the start pulse a is received, the address counter 11 sends the first address to the data register [8 and 10].

The data storage device 10 supplies the first recording data (the first data of the image data from the A/D converter 9) corresponding to the address of the first day and month to the conversion table 18.

The present invention is characterized in that the conversion table 18 and one memory are provided between the data storage table vi10 and the grayscale data comparison circuit 17. This conversion table 18 is Φ
The heat-generating resistor with λ is affected by the previous line recorded data1, and as a result, the amount exceeding the actually required light thermal temperature is recorded in a predetermined table between the previous line recorded data and the current line recorded data. Change 1 to increase the required gradation level by 1q, for example, change the white level to ``O''.
”.

The black level is "63", the number of gradations of the previous line recording data is r60J, and the number of gradations of the current line recording data is "10".
In this case, the number of gradations of the current line recording data is converted to, for example, "6" and output, taking into account the influence of heat accumulation in the heating resistor.

Next, to explain the operations of the conversion table 18 and the memory 19, first, when recording the first line of image data, the conversion table 18 is used as a data storage table "?llo".
The first recorded data of the first line is directly sent to the grayscale data comparison circuit 17 and the memory 19 as the third recorded data of the first line without being converted. The memory 19 has a storage capacity of one line of image data, and stores the third recording data of the first line from the conversion table 18.

When recording the image data of the second line row, the conversion table 18 converts the first recorded data of the second line from the data storage device 1o into the second recorded data of the first line row read from the memory 19 ( TJ ~, the first recorded data of the first line above) is converted to 17.
The third recorded data of the line is transferred to the grayscale data comparison circuit 17.
and the memory 19, respectively.

When recording image data on the third line, the conversion table 1B converts the first recorded data on the third line from the data storage device 10 into the second recorded data on the second line read out from the memory 19. The third recorded data of the third line (15) is converted in accordance with the third recorded data of the second line and sent to the grayscale data comparison circuit 17 and the memory 19, respectively.

In this way, the conversion table 18 has the number of gradations of the first recording data of the current line from the data storage device 10, which is 2 (however, 2
is an integer that satisfies ≧O) is converted according to the equation (12) described later according to the number of gradations k of the second recording data of the previous line from the memory 19 (where ≧an integer that satisfies O). The third recording data 2' (where 2' is an integer satisfying 2'≧0) of the current line obtained by the process is sent to the grayscale data comparison circuit 17 and the memory 19, respectively. In addition, the memory 19 stores the third recorded data 2' of the current line from the conversion table 1B, and in the next line's painting data recording poem, the third recorded data 2' of the current line is converted to the previous line. is output to the conversion table 18 as the second recorded data.

Next, a data conversion method for the conversion table 18 will be explained. Here, if one gradation recording time is Δt, then the energization time t of the heating resistor to be recorded during the previous line recording is t+=k·Δt(1). Similarly, the energization time t3 of the heating resistor to be recorded during current line recording is 1:3 = i · Δ.
■It becomes.

On the other hand, the required humidity Ta of the heating resistor at 43 during current line recording is Ta=T (1-e ``t3) -T (1-e ``fl''')G) (However,
King is the temperature at which the heat generating resistor is saturated when electricity continues to flow,
αd represents the thermal rise time constant of the heating resistor, for example,
1m5V1 degree).

Now, as shown in FIG. 3(A), based on the first recorded data of the previous line, one current is applied to the photothermal resistor for the above-mentioned energizing time, and after it is generated, it is cooled. If the next line (i.e., the current line) is recorded after the 1-line printing interval t2 (however, tz>tI) has elapsed since the current supply start time (stopping the current supply to the resistor), the current line recording time will be The 4 degree Tb of the heating resistor is Tb=T ((1-e-"' jl)-e-α2 (j
2-j+) + 1-'e'' t3) (4) (However, α2 indicates the thermal fall time constant of the heating resistor,
For example, about 2 mS). Therefore, as shown in 7I in FIG. 3 (Δ), there is a difference between the temperature Ta of the heating resistor required during current line recording and the actual temperature 4UTb, J as shown in equation (5). Temperature error (i.e., the temperature corresponding to the residual heat of the photothermal resistor of the previous line record)
er occurs.

er=Tb-Ta=T-(1-e ""), e
-α2 (tz -j+) (5)-In order to prevent the above temperature error cr from occurring, change the number of gradations 2 of the first recording data of the current line to the third recording data of the current line in the variable 1111-pull 18. i′, this third
The temperature TC of the heating resistor obtained during current line recording based on the recorded data ' is expressed as in equation (6).

TC=T ((1-e-” ”)-8-α2 (t
z −tI ) + 1−e ” ” ) (6) (However, 1
3' indicates the energization time of the heating resistor during recording of the current line by the third recording data 2', and t3'=y'·Δt. ) Here, in order to set er=o, it is necessary to select the third recording data 2' so that Ta=TC.

=αχ However, in general, the expansion of f(χ)=e is 1
When approximated by the following, f (χ ) = f (0) - χ · f'
(0) (8)〈However, 1χ1〈
<When set to 1> Therefore, when formula 0 is expanded and summarized, it becomes e-αχ=1-αχ (9). Substituting the relationship in equation e) as a function of Δt in the above equations, etc., we get T(1-(1-αIj3))=T[(1-(1-α1t+))・(1-α2 (1:2) -tI))11-(1-α+t3')] (10). Rearranging this equation (10), we get '=fl-k (1-122(Δj to tz)
), and if an approximation calculation is performed by setting tz >>kΔt, the third recorded data e' can be expressed as in equation (12).

e-''=-fl-ke-(x2t' (12) In this way, the temperature characteristics of the heat generating resistors of the previous line and the current line as shown in FIG. 3 (13>) are determined.

Returning to FIG. 1 again, the conversion table 18 is as follows:
The first data from the data storage device 10 is
2) The third recorded data obtained by conversion based on the formula is sent to the grayscale data comparison circuit 17 and the digital input signal 19, respectively. The density data comparison circuit 17 compares the third recorded data with the reference density data r indicating the minimum density obtained from the data counter 15.
Comparing the OJ, the third recorded data is the V quasi-concentration data r
If it is larger than OJ, control data “
If they are equal, control data "O" is sent to the shift register 20.

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 first recorded data corresponding to the second to nth addresses of the data storage device 10G are sent to the third recorded data via the conversion table 18. The data is sequentially sent to the grayscale data comparison circuit 17 and memory 19. Here, the data of the first recording from the 1st to nth addresses correspond to the image data printed by the heat generating resistors R1 to R of the thermal head 6, respectively. The density data comparison circuit 17 compares the third recording data corresponding to the 2-nth addresses with the reference density data "0", and calculates the 11th control data "0" in the same way as above.
Send "0" or "1" to the shift register 20. The n-stage shift register 20 sequentially takes in n-bit control data corresponding to the first to nth addresses supplied from the gray data comparison circuit 17 and sends it to the latch circuit 21 .

On the other hand, when the address counter 11 finishes counting the first to nth addresses, it sends a data transfer pulse b (not shown in FIG. 2B) to the data counter 15, latch circuit 21, and control counter 14. The period Δt of this data transfer pulse b is about 1/10 Pi compared to the conventional one! It has been shortened. When the data transfer pulse b is sent to the data counter 15, a heating pulse C (not shown in FIG. Supply to the terminal.

A reference clock signal is supplied from the terminal 12 to the other input terminal of the AND circuit 22, and the data counter 1
Simultaneously with the input of the heating pulse e from 5, the pulse is output to the shift register 20, and the 1 of the address counter 11 is
The control data of n pits corresponding to the n-th address is transferred from the shift register 20 to the latch circuit 21. The latch circuit 21 latches the control data supplied from the shift register 20 at the time when the data transfer pulse b is received, and sends it to each one of the input terminals of the gate circuit G+''-Gn. .

On the other hand, the address counter 11 is reset by the input of the heating pulse e and sequentially counts addresses 1 to n again, but during the reheating time ΔT, the address counter 11 uses the data storage S! iiδ10 is read out repeatedly from the n pieces of first data on the same line, and the reference density data is held at "0", so the n pieces of third recorded data for the same line are read as above. The density data is repeatedly compared in magnitude with reference density data having a value of "0" in the density data comparison circuit 17.

Therefore, during the interval ΔT (heating hole), the third recorded data is "
1'' or more, that is, the third recording data, a heating current is applied only to the heating resistor to be transferred by the power supply voltage +vCc, and the heat is recuperated. For this reason, the third recording 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 heating preset value for the density above the white level. I can do it.

After that, the control counter 14 sets the pulse C to high level at time 1:2 when the pulse b has been directly counted for the reheating preset, and the data counter 15 starts the jJ count operation and performs one glue operation in the same manner as above. The first line of
After doing this once for the data of The value increases to "1" indicating the th density.

Thereby, the gradation data comparison circuit 17 sequentially compares the magnitude of the first data of n1liJ for the same one line and the reference density data of the value "1". Even when the reference f1 degree data is "1", the shift register 20° latch circuit 21.
The AND circuit 22 and the like perform operations similar to those described above, and send the latched control data to one input terminal of each of the gate circuits G1 to G.

On the other hand, the correction table storage memory 24 is supplied with the reference density data rOJ shown in FIG. 2(D), and correction data is stored in advance so that the recording time and density have a linear relationship. The data corrected using the correction table is sent to the pulse generator 25. The pulse generator 25 is at a high level during a predetermined period including T during the reheating time according to the incoming correction data, and after this period the pulse width gradually changes to a smaller value as shown in Fig. 2 (F>). A pulse f shown is generated and output to the other input terminal of the AND circuit 23.

The AND circuit 23 outputs the incoming heating pulses e and J-.
The pulse 9 shown in FIG. 2 (G) is generated and sent to the other gates of the gate circuits G1 to Go.

As shown in FIG. 2 (G), the pulse Q is applied to a predetermined period from time 11 onwards, including the reheating time ΔT, that is, from time tl to 1-3 when the reference 'a degree data d is "0". ) has a predetermined pulse width, and after this period, the pulse width gradually decreases depending on the data content of the correction data sent from the correction table storage memory 24, for example.

Each of the gate circuits G1 to Go applies a gate signal obtained by gate processing the pulse 9 and the n-bit control data supplied from the latch circuit 21 to the NPN transistor T1.
~T0 is supplied to each base, and this is controlled by switching. Of the transistors T1 to T, current is passed only through the heating resistor connected to the collector side of the turned-on transistor, and heat is generated.

Further, after time t2, the reference concentration data output from the data counter 15 is rOJ in synchronization with pulses b and e.
rlJ, r2J, . . . , rmJ (where m indicates the maximum density and has a value of 1)
outputs control data "1" if the third recording data is greater than the reference density data, and outputs control data "0" if it is equal to or smaller than the reference density data. This “0”
Alternatively, depending on the control data of "1" and the pulse width of the pulse 9, the energization time of the heating current flowing through the heating resistor is changed, and gradation recording of data for one line is performed.

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, according to this embodiment, l! lji key r
Approximately linear fa degree control is possible from OJ 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.

In addition, since density control is performed by taking advantage of the influence on the temperature distribution of the heating resistor in the previous line using the conversion table 18, accurate gradation expression is possible.

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 once the recording of this one line is completed, the data counter 15 again counts from 1 to m. Start counting m times.

Note that the analog video signal supplied from the TV signal generator 8 may be an information signal 8 of images such as other characters or figures. Furthermore, although the above embodiments have been described in the case where the relationship between the recording time and the temperature is a straight line, the relationship between the recording time and the IA degree may be a predetermined curve.

Furthermore, the conversion of the first recording data of the current line into the third recording data 2' with the number of gradations of 2 using the conversion table 18 is not limited to the conversion formula shown in the above equation (12), and may be performed using other methods. It may be converted using the conversion formula.

Effects of the Invention As described above, according to the present invention, since the current line recorded data is corrected in accordance with the residual hot light of each heating resistor due to the previous line recorded data, the recording time for one line can be shortened. , the heating resistor can be made to generate heat almost accurately to the required temperature, and therefore has the advantage of being able to obtain high-speed and good gradation expression.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing an embodiment of the thermal transfer gradation control device according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the block system shown in FIG. 1, and FIGS. B) is a temperature characteristic diagram of an example of the apparatus of the present invention, FIG. 4 is a schematic perspective view of an example of the main part of a thermal transfer printing apparatus to which the apparatus of the present invention can be applied,
FIG. 5 is a diagram showing the thermal response characteristics of the heating resistor. 6...Thermal head, 10...Data storage device, 11
...Address counter, 12...Reference clock signal input terminal, 13...Start pulse No. 215 input terminal,
1/l... Control counter, 15... Data counter, 16... Reheating preset source, 17... Concentration data comparison circuit, 18... Conversion table, 19...
・Memory, 2o...Shift register, 21...Latch circuit, 22゜23...AND circuit, 24...Correction table storage mechanism L1 25...Pulse generator, G1
~G,...Gate circuit, R+''・R...Heating resistor, T1~T,...Transistor. Patent applicant: Victor Japan Co., Ltd. Figure 2, Figure 5

Claims (2)

[Claims] (1) In a thermal transfer gradation control device that controls the time of each current flowing through a plurality of heat generating resistors arranged in a line according to the number of gradations of recording data, the first recording of the current line a correction means for outputting the number of gradations obtained by subtracting the number of gradations corresponding to the amount of residual heat of each heating resistor due to the second recorded data of the previous line from the number of gradations of the data as third recorded data; , a memory for storing the third recorded data from the correcting means and supplying the third recorded data to the correcting means as second recorded data of the previous line,
A thermal transfer gradation control device characterized in that the time of each current flowing through the heating resistor is controlled in accordance with the third recording data from the correction means. (2) The correction means sets the number of gradations of the second recording data of the previous line to k (where k is an integer of k≧0), and sets the thermal fall time constant of the heating resistor to α, 1 When the line printing period is t, the number of gradations l (however, l is an integer of l≧0) of the first recording data of the current line is calculated using the conversion formula l'=l-ke^-^α^t. The thermal transfer gradation control device according to claim 1, characterized in that the data l' obtained by calculation is output as the third recording data.