JP3276095B2 - Thermal printer and heating element driving method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer and a heating element driving method, and more particularly to a thermal printer and a heating element driving method capable of rapidly increasing the temperature when a thermal head is cold. .

[0002]

2. Description of the Related Art Thermal printers include a thermal type and a thermal transfer type. A thermal-type thermal printer uses a thermal head in which a plurality of heating elements are formed in a line, presses this thermal head against thermal recording paper and heats it, and records the dots by coloring the thermal recording paper with each heating element. I do. Thermal transfer type thermal printers include a fusion type and a sublimation type. In these, an ink ribbon or an ink film is superimposed on recording paper (image receiving paper), and a thermal head presses and heats the recording paper from behind the ink ribbon or ink film to thereby transfer the ink to the recording paper. Is transferred to

When recording one pixel, bias heating and gradation heating are performed. This bias heating is to heat the heating element to a state immediately before coloring or immediately before the start of ink transfer, and one bias heating drive pulse having a long pulse width of several milliseconds to several tens of milliseconds generates heat. Supplied to the device. The gradation heating is for controlling color development or transfer density, and the number of gradation heating drive pulses corresponding to image data is as short as a pulse width of several μsec to several tens μsec and corresponding to image data. Supplied to the device. In the sublimation type, the ink density changes in accordance with the heat energy, but in the fusion type, the ink density does not change. Therefore, the recording paper is moved simultaneously with the gradation heating to change the ink transfer area within one pixel. Express halftones. A method of performing bias heating using a plurality of bias heating drive pulses has also been recently proposed (Japanese Patent Application No. 5-147591).

Each of the bias heating drive pulse and the gradation heating drive pulse includes a strobe signal for determining ON time and OFF time of the heating element, and ON / OF of the heating element.
It is created from the logical product with the driving data for determining F.

[0005]

A pause time is provided between each drive pulse, the heating element is intermittently energized, and the temperature rises while repeating heating and heat radiation. This prevents an excessive rise in the temperature of the heating element and enables heating according to the γ characteristics of the recording material. However, when the thermal head is cold, for example, immediately after the start of printing, the heat generation element does not rise to a predetermined temperature due to heat radiation during the pause time. In this case, since the color density is low in the heat-sensitive type and the ink area is small in the thermal transfer type, so-called shading occurs in which the density at the beginning of the recording area is low.

When a binary image such as a character is recorded, high-precision temperature control is not necessary. However, since the heating element is conventionally driven in the same manner as a full-color image, it takes a long time to print. There was a problem that it took.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal printer and a heating element driving method capable of eliminating unnecessary cooling of the heating elements and shortening the printing time.

[0008]

According to a first aspect of the present invention, there is provided a heating element driving method according to the first aspect of the present invention. The heating element is driven by the pulse, and each drive pulse is created from driving data for determining ON / OFF of the heating element and a strobe signal for determining ON time and OFF time of the heating element. When the thermal head is cold or when a binary image such as a character is recorded, a plurality of drive pulses are made continuous by setting the OFF time setting data to zero. This continuous driving may be one of the bias heating and the gradation heating, or both.

In the thermal printer according to the second aspect, 1
A line memory for bias data for storing bias data for one line, a line memory for image data for storing image data for one line, and a comparison data M corresponding to the lowest gradation level for bias heating and gradation heating. Comparison data generating means for generating comparison data sequentially changing up to comparison data N corresponding to a gradation level; first, bias data is read from the bias data line memory when recording one line, and then image data line memory A memory controller for reading image data from the memory, a comparator for comparing read bias data or image data with comparison data and outputting drive data for determining ON / OFF of the heating element, bias heating and gradation heating For each comparison data. A strobe signal having a predetermined pulse width and a pause time is generated based on a table memory in which ON time setting data and OFF time setting data are written and time setting data read from the table memory using comparison data as an address. And a driving pulse generating means for generating a driving pulse from the strobe signal and the driving data.

In the thermal printer according to the third aspect, the bias heating table includes a plurality of sub-tables selected according to the position of a print line to be recorded.
The sub-table used at the beginning of printing when the thermal head is cold stores zero OFF time setting data so that a part or all of the bias heating drive pulses are made continuous.

In the thermal printer according to the present invention, the table for bias heating includes a plurality of sub-tables selected according to the temperature of the thermal head. , Zero OFF time setting data, so that a part or all of the bias heating drive pulses are made continuous.

[0012]

[Function] When the thermal head is cold, such as at the beginning of printing, or when recording a binary image such as a character,
The strobe pulse is made continuous by setting the OFF time setting data to zero. Since the continuous strobe pulse drives the heating elements continuously, unnecessary cooling of the heating elements is eliminated, and each heating element can be raised to a desired temperature. Further, since the pause time of the strobe pulse is eliminated, the print time is reduced.

When bias heating is performed by a plurality of drive pulses, the bias heating drive pulse is made continuous.
In particular, in the case of a binary image such as a character, if the density is uniform, there is no problem even if the value is different. Therefore, all the drive pulses for bias heating and gradation heating are continuously connected to form one drive pulse. To form This further reduces the printing time.

When the thermal head is cold, such as at the beginning of printing, it is preferable to continue bias heating to eliminate unnecessary heat radiation. Therefore, in the thermal printer according to the third aspect, a sub-table storing ON time setting data and OFF time setting data for continuously performing bias heating, and ON time setting data for performing bias heating intermittently are provided. And a sub-table storing OFF time setting data. These two types of sub-tables are selected according to the position of the print line on the thermal recording paper.

In the thermal printer according to the present invention, the temperature of the thermal head is directly measured, and one of the two sub-tables is selected according to the temperature, and the heating element is driven continuously or intermittently.

[0016]

FIG. 3 shows a thermal printer of the heat-sensitive type. In FIG. 3, a platen drum 2 is intermittently rotated in the direction of an arrow about a rotary shaft 3 by a pulse motor (not shown). A color thermosensitive recording paper 4 is wound around the outer periphery of the platen drum 2, and the leading end thereof is fixed by a clamper 5. A thermal head 6, a magenta fixing ultraviolet lamp 7, and a yellow fixing ultraviolet lamp 8 are arranged on the outer periphery of the platen drum 2.

A heating element array 10 is provided on the lower surface of the thermal head 6. The heating element array 10 has a large number of heating elements formed in a line in the axial direction of the platen drum 2. Each of the heating elements presses and heats the color thermosensitive recording paper 4 to cause dots to be formed in the square pixels. The magenta fixing ultraviolet lamp 7 has an emission peak of 3
The UV lamp 8 emits ultraviolet light having a light emission peak of around 420 nm.

As shown in FIG. 4, the color thermosensitive recording paper 4
Are formed on the support 12 by a cyan thermosensitive coloring layer 13, a magenta thermosensitive coloring layer 14, a yellow thermosensitive coloring layer 15, and a protective layer 16.
Are sequentially layered. The cyan thermosensitive coloring layer 13 has the lowest thermal sensitivity and develops cyan when a large amount of thermal energy is applied. The magenta thermosensitive coloring layer 14 has a medium heat sensitivity and develops magenta when heated. Further, this magenta thermosensitive coloring layer 14 has approximately 365
It has a light fixing property by ultraviolet light of nm. The yellow thermosensitive coloring layer 15 has the highest thermal sensitivity and develops yellow when relatively small heat energy is applied. The yellow thermosensitive coloring layer 15 has a light fixing property with ultraviolet light of approximately 420 nm. These thermosensitive coloring layers 13 to 15
Are arranged in the order in which they are thermally recorded. Although not shown in the drawings, an intermediate layer for adjusting the thermal sensitivity is formed between the thermosensitive coloring layers.

FIG. 5 shows the coloring characteristics of each thermosensitive coloring layer. When thermal recording is performed on yellow (Y) pixels,
The heating element gives the color thermosensitive recording paper 4 coloring heat energy obtained by adding the gradation heat energy GY _I to the bias heat energy BY. The bias thermal energy BY is thermal energy immediately before the yellow thermosensitive coloring layer 15 develops a color, and is a constant value. Gradation heat energy GY
_I is determined according to the image data representing the gradation level I. Since the same applies to magenta M and cyan C, only symbols are given.

The bias thermal energy is generated by repeatedly driving the heating element with a fixed number of bias heating drive pulses. However, when the thermal head 6 is cold or when recording a binary image, the thermal head 6 is driven by one continuous pulse of a plurality of bias heating driving pulses. The gradation heat energy is generated by driving the heating elements with the number of gradation heating drive pulses corresponding to the image data. In the recording of a binary image, the driving pulse for gradation heating may also be continuous, whereby bias heating and gradation heating may be performed by one pulse.

In this embodiment, in order to print a full-color image close to a photograph, 256 gradations can be expressed. Therefore, the gradation thermal energy is divided into 256 steps, and each color develops the highest density with 256 gradation heating drive pulses. In addition, bias heating is performed by 256 bias heating driving pulses so that comparison of bias data and comparison of image data can be performed in the same manner.

In FIG. 6, the system controller 20
Writes yellow image data, magenta image data, and cyan image data into the frame memory 21 at the time of data capture. The three-color image data is obtained by, for example, color correction and color conversion of one frame of image data captured by an electronic still camera. At the time of printing, the system controller 20 designates a line within one frame based on the count value of the counter 20a, reads out one color image data to be printed from the frame memory 21 and writes it into the image data line memory 22. . Since this image data represents the gradation level of the pixel, the number of gradation heating drive pulses is determined based on this image data.

The system controller 20 stores bias data indicating the number of bias heating drive pulses. This bias data is written to the bias data line memory 23. This bias data is the same for each color, and is “255” for all pixels for one line. Since the bias heat energy differs depending on the color, the bias data may be changed depending on the color, or may be changed depending on the coloring characteristics of the color thermosensitive recording paper. Further, in order to correct a thermal energy error caused by a resistance value error of each heating element, the bias data “255” may be used as a reference value, and the reference value may be corrected according to the resistance value error.

The system controller 20 sends a system 1 line start signal to the memory controller 24 when printing one line. When the system one-line start signal is input, the memory controller 24 sends a switching signal to the selector 25 to switch to the bias data line memory 23 side, and then the bias data for one line from the bias data line memory 23. The data is sequentially read out for each pixel and sent to the comparator 26.

When the one-line end signal is input from the print control unit 27 after the bias heating is completed, the memory controller 24 switches the selector 25 to the image data line memory 22 and then switches the image data line memory. From line 22, one line of image data is sequentially read out for each pixel and sent to the comparator 26. When the gradation heating is completed, the print control unit 27 sends a one-line end signal to the memory controller 24. Memory controller 24
Receives the one line end signal twice, sends a system 1 line end signal to the system controller 20 indicating that printing of one line has been completed. After rotating the platen drum 2 by one print line, the system controller 20 sends a system 1 line start signal to the memory controller 24 again to start recording of the next print line.

Upon receiving the one-line start signal from the memory controller 24, the print controller 27 counts the clock of the system controller 20 and
The comparison data whose numerical value increases in order from “0” to “255” is generated and sent to the comparator 26. In the bias heating, the comparator 26 sequentially compares one line of bias data with respect to one piece of comparison data, and outputs “H” drive data when the bias data is larger. Occasionally, “L” drive data is output. Therefore, the bias data for one line is compared 256 times, whereby one bias data is converted into 256 drive data. Similarly, in gradation heating, the image data for one line is changed from “0” to “25”.
5), and one image data is converted into 256 drive data.

The print controller 27 generates a latch signal and a strobe signal in synchronization with the generation of the comparison data. The latch signal is sent to the latch array 30, and the strobe signal is sent to the AND gate array 31.

The drive data for one line is output from the comparator 26 as a serial signal and sent to the shift register 32. The shift register 32 is operated by a clock from the system controller 20 and converts one line of drive data into a parallel signal. The parallel-converted drive data is latched in the latch array 20 by a latch signal.

The drive data for one line latched by the latch array 20 is sent to an AND gate array 31,
The logical product with the strobe signal is obtained. Therefore,
When the drive data is "H", a drive pulse having the same width as the pulse of the strobe signal is generated. The strobe pulse width and the pulse interval (pause time) differ depending on the type of heating, the color of printing, the temperature of the thermal head or the position of the print line and the drive pulse.

The drive pulse for one line is supplied to a drive IC
33. The drive IC 33 includes transistors 33a to 33n, and the transistor to which the drive pulse is input is turned on. The heating element array 10 includes a plurality of heating elements 10a to 10n arranged in a line, and each of the heating elements 10a to 10n includes a transistor 33a to 33a.
33n. For example, the transistor 33a
Is turned on, the heating element 10a connected to the transistor 33a is energized and generates heat.

FIG. 7 shows a print control unit.
The comparison data counter 36 is reset by a one-line start signal, and when a count permission signal is input,
Count only one clock. The obtained count value is sent to the comparator 26 and the look-up table memory 37 as comparison data. When counting from "0" to "255", a one-line end signal is generated.

A table is prepared for each color in the look-up table memory 37, and the system controller 2
A color table to be printed is selected by a table selection signal from 0. There are two types of colors, bias and image, which are selected by a selection signal from the memory controller 24 in accordance with the type of heating. In the drawings, only a table for one color is shown.

Generally, at the start of printing, the thermal head 6 is cold, so that even if a predetermined drive pulse is given, the temperature does not rise to the expected temperature. For this reason, so-called shading occurs in which the density of the recording start portion becomes low.
Therefore, two sub-tables 37a and 37b are prepared for the bias table in order to perform the high-speed printing while preventing the shading and increasing the thermal efficiency. The sub-table 37a is used for a print line belonging to the beginning of printing, and the other sub-table 37b is used for other print lines. The system controller 20 checks the position of the print line using the counter 20a, and selects a sub-table according to this position. Similarly, the image table also has two sub-tables 37c and 37d.

Each sub-table is provided with ON time setting data for setting the energizing time of the heating element and OFF time setting data for setting the pause time of the heating element for each gradation level. I have. In each sub-table, ON time setting data and OFF time setting data are read using the comparison data output from the comparison data counter 36 as an address, and the strobe signal generation circuit 3
8 When a RAM is used as the lookup table memory, the system controller 20
The data is stored in the lookup table memory 37 when the power of the thermal printer is turned on.

The strobe signal generation circuit 38 generates a strobe signal for determining the ON time and the OFF time of the heating element. The strobe signal includes a strobe pulse created from a set of ON time setting data and a pause time determined by the OFF time setting data. When this pause time has elapsed, the strobe signal generation circuit 38
Generates a count enable signal and a latch signal. This count permission signal is sent to the comparison data counter 36,
Then, the latch signal is sent to the latch array 30. The strobe signal generation circuit 38 receives a one-line start signal.

FIG. 8 shows an example of a strobe signal generation circuit. The ON time setting data output from the lookup table memory 37 is stored in the preset counter 4
It is set to 0, and the OFF time setting data is set in the preset counter 41. The preset counter 40 counts the clock from the system controller 20 after the ON time setting data is set, and resets the flip-flop 42 when the count value matches the ON time setting data, and resets the count of the preset counter 41. Enable operation.

When set by a signal from the timing controller 43, the flip-flop 42 sets the strobe signal to "H" and outputs a strobe pulse. Then, when reset by the output signal of the preset counter 40, the strobe signal is set to “L”. Only during the generation of this strobe pulse, the heating elements 10a to 10a
10 n of electricity can be supplied.

The preset counter 41 counts the clock from the system controller 20 when the counting operation is permitted by the preset counter 40. When the count value matches the OFF time setting data, the output signal is output to the timing controller 4.
Send to 3.

When the timing controller 43 receives a signal from the preset counter 41 during recording of one print line, it generates a latch signal, a read request signal, a count permission signal, and a set signal of the flip-flop 38. During the recording of the print line, after receiving the one-line start signal, the preset counter 4
The determination can be made by counting the number of times of the signal from 1. Also, when receiving the one-line start signal,
The flip-flop 42 is set.

Next, the operation of the above embodiment will be described with reference to FIGS. When a freeze key (not shown) is operated after an input device such as an electronic still camera is connected to the thermal printer, the capture of image data is started. When capturing the image data, a blue signal, a green signal, and a red signal are separated from the composite video signal as is well known, and then digital conversion and color conversion are performed to obtain yellow image data, magenta image data, and cyan image data. Convert to data. The image data of these three colors is “0”
Represents the gradation level within the range of "255" to "255", and is written in the frame memory 21 in a state of being separated for each color.

When a print key (not shown) is operated,
A color thermal recording paper 4 is fed, and the leading end thereof is a clamper 5.
Is clamped by After this clamping, the platen drum 2 winds the color thermosensitive recording paper 4 while
Rotate intermittently by print line. While the platen drum 2 is rotating, the system controller 20 prepares for recording of the first print line. First, the counter 20a for designating the position of the print line is set to "1".
Set to. Next, the first line of the frame memory 21 is designated based on the count value “1”, and the yellow image data of the first line is sequentially read from the frame memory 21 and written to the image data line memory 22.

After writing the yellow image data of the first line, the bias data set in advance, for example, “25”
"5" is repeatedly written into the bias data line memory 23. Thus, the bias data for one line in which all the bias data is “255” is written in the bias data line memory 23.

When the leading end of the recording area of the color thermal recording paper 4 reaches the thermal head 6 due to the rotation of the platen drum 2, the system controller 20 sends a system 1 line start signal to the memory controller 24. The memory controller 24 outputs the switching signal to the selector 25.
To connect the bias data line memory 23 to the comparator 26.

Further, the memory controller 24 sends a one-line start signal to the print controller 27. The one-line start signal sets the comparison data counter 36 to zero, and the timing controller 43
A read request signal is sent to the memory controller 24. The memory controller 24 reads out the bias data for one line from the bias data line memory 23 in order from the first and sends it to the comparator 26. On the other hand, since the comparison data counter 36 of the print control unit 27 is zero in the initial state, it outputs comparison data of “0”,
It is sent to the comparator 26 and the look-up table memory 37.

The comparator 26 compares the bias data for one line with the comparison data "0", and outputs "H" drive data when the bias data is larger than the comparison data.
In this embodiment, since the bias data for one line is all "255", the drive data in which all the lines for one line have become "H" are serial signals as the shift register 3.
Sent to 2. The shift register 32 shifts one line of drive data by a clock signal and converts the drive data into parallel drive data.

After setting one line of drive data in the shift register 32, the timing controller 43 outputs a latch signal. With this latch signal, the drive data for one line converted into a parallel signal is latched in the latch array 30. The latched drive data for one line is sent to the AND gate array 31.

Immediately after the generation of the latch signal, the timing controller 43 sends a read request signal to the memory controller 24 to generate the next drive data, and reads the bias data for one line for the second time. And sends a count permission signal to the comparison data counter 36.

On the other hand, look-up table memory 37
Is the first line on which the bias table is selected by the switching signal and is printed in a state where the thermal head 6 is cold.
Is selected. The sub-table 37a reads ON time setting data and OFF time setting data using the comparison data as an address, and sends the data to the strobe signal generation circuit 38.

As shown in FIG. 8, ON time setting data is set in a preset counter 40, and OFF time setting data is set in a preset counter 41. Almost simultaneously with this set, the timing controller 43
The flip-flop 42 is set, and a count permission signal is sent to the preset counter 40.

When the flip-flop 42 is set,
The “H” strobe signal is sent to the AND gate array 31. Since the drive data of “H” created based on the bias data is input to the AND gate array 31, a drive pulse is generated from each AND gate. These driving pulses cause the transistors 33a to 33a to
33n is turned on, and the heating elements 10a to 10n are energized.

During the generation of the strobe signal, the preset counter 40 counts the clock. If the count value reaches the ON-time setting data during the counting of the preset counter 40, the output signal is output to the flip-flop 4.
2 and the preset counter 41. When the flip-flop 42 is reset by the output signal of the preset counter 40, the strobe signal becomes "L" and the generation of the strobe pulse stops. AND gate array 31
Stops the generation of the drive pulse when the strobe pulse is no longer input. Thereby, each transistor 33
a to 33n are turned off, and the energization of each of the heating elements 10a to 10n is stopped.

The preset counter 41 starts counting when an output signal of the preset counter 40 is input. However, since the OFF time setting data is zero at the beginning of printing, a signal is sent to the timing controller 43 immediately. This timing controller 43
Receives the signal of the preset counter 41, sets the flip-flop 42 and generates an "H" strobe signal. Therefore, the flip-flop 42
Is instantaneously reset, so that two strobe pulses are substantially continuous.

To completely connect the two strobe pulses, instead of inputting the output signal of the preset counter 40 to the flip-flop 42, the signal is input to the timing controller 43, and the flip-flop 42 is reset by the timing controller 43. Good. In this case, when an output signal is generated from the preset counter 41 simultaneously with the start of counting of the preset counter 41, the flip-flop 42 is not reset, and when no output signal is output from the preset counter 41, the OFF time setting data is output. Judging that it is not zero, the flip-flop 42 is reset.

Since the preparation for the second energization is completed during the first energization, each time the second strobe pulse is output in a state following the first strobe pulse, each The energization of the heating elements 10a to 10n is started, and the heating elements 10a to 10n are substantially continuously driven.

That is, the timing controller 43
When the first drive data is latched in the latch array 30, a read request signal is sent to the memory controller 24. Therefore, the memory controller 24 reads out one line of bias data from the bias data line memory 23 again. The comparison data counter 36 counts one clock by the count permission signal from the timing controller 43, and the count value is “1”. The comparator 26 compares the bias data for one line with the comparison data “1” to generate drive data for one line. Also in this case, all the drive data for one line is “H”, and these drive data are set in the shift register 32. The comparison data “1” is sent to the look-up table memory 37 as address data, and the ON time setting data and the OFF time setting data stored therein are read.

As described above, the flip-flop 42 is set to generate the second strobe signal, and at the same time, the ON time setting data and the OFF time setting data are set in the preset counters 40 and 41. At the same time, a count permission signal is sent to the preset counter 40, and the counting operation is started.

After generating the second strobe pulse for the time determined by the ON time setting data,
The generation of the strobe pulse is stopped for a time corresponding to the time setting data. Also in this case, since the OFF time setting data is zero, the pause time is eliminated and the third "H" strobe signal is immediately generated. As a result, FIG.
As shown in (1), each strobe pulse is connected, and the heating elements 10a to 10n are continuously energized. Therefore, since there is no heat radiation during the idle time, the temperature of each of the heating elements 10a to 10n rises quickly, and bias heating can be performed efficiently.

According to the above procedure, the bias data for one line is read out 256 times.
55 ”and is converted into drive data. Therefore, each of the heating elements 10a to 10n
Are energized by 256 drive pulses. In this embodiment, the drive pulses “0” to “252” are continuously energized by setting the OFF time setting data to zero, and the drive pulses “253” to “255” are
By setting the FF time setting data to a value other than zero, a pause time is inserted between each drive pulse.

When the count value of the comparison data 36 becomes "255", a one-line end signal is generated and sent to the memory controller 24. The memory controller 24 determines that the bias heating has ended, switches the selector 25, and connects the image data line memory 22 to the comparator 26. At the same time, a switching signal is sent to the look-up table memory 37,
Select a table for the image. Further, since the printing is for the first print line, the system controller 20 selects a sub-table 37c used when the thermal head 6 is cold, from the two sub-tables 37c and 37d for images.

Further, the memory controller 24 sends a one-line start signal to the print controller 27. The one-line start signal sets the comparison data counter 36 to zero, and the timing controller 43
A read request signal is sent to the memory controller 24. The memory controller 24 sequentially reads out one line of image data one by one from the image data line memory 22 and sends it to the comparator 26. On the other hand, since the comparison data counter 36 of the print control unit 27 is zero in the initial state, it outputs comparison data of “0” and sends it to the comparator 26 and the lookup table memory 37.

The comparator 26 compares each of the image data for one line with the comparison data “0”, and outputs driving data of “H” when the data is larger than the comparison data, and outputs driving data of “L” when the driving data is the same or smaller. Output drive data. The drive data for one line obtained by this comparison is sent to the shift register 32 as a serial signal. Shift register 32
Shifts the drive data for one line with a clock signal and converts it into parallel drive data. The drive data of the shift register 32 is sent to the AND gate array 31 after being latched by the latch array 30.

During the transfer of the drive data, the comparison data "0"
The ON time setting data and the OFF time setting data are read from the sub-table 37c of the look-up table memory 37 using the
Send to 8. Almost at the same time, the timing controller 4
3 sets the flip-flop 42 and sends a strobe pulse to the AND gate array 31. The strobe pulse has a width determined by the ON time setting data, and has a pause time determined by the OFF time setting data.

When "H" drive data is input, each AND gate generates a drive pulse for gradation heating having the same width as the strobe pulse to generate transistors 10a to 10a.
10n is selectively turned on. ON of this transistor
As a result, the heating element is energized, and the gradation heating is started.

The second reading of the image data line memory 22 is performed while the heating elements 10a to 10n are selectively driven by the first gradation heating driving pulse. The read image data for one line is compared with the comparison data “1” by the comparator 26, converted into drive data, and set in the shift register 32.

When the heat generation by the first gradation heating drive pulse is completed, the lookup table memory 37 is read out using the comparison data "1" as an address, and a strobe pulse is created. Thus, a second gradation heating drive pulse is generated, and the heating pulses drive the heating elements 10a to 10n again.

In this manner, the first line of yellow image data is read out 256 times, and every time the readout is performed, "0" to "2"
55 ".
As a result, each yellow image data is converted into 256 drive data. The number of gradation heating drive pulses is determined by the value of the yellow image data,
The heating element is energized a plurality of times. Here, the width of the driving pulse for gradation heating and the pause period are based on the ON time setting data read from the sub-table 37c based on the comparison data and the OF time.
It is determined by the F time setting data. Of course, by setting the OFF time setting data to zero, a plurality of gradation heating drive pulses may be continued.

For example, if the image data is "100" in decimal system
, 256 bias heating drive pulses,
One hundred gradation heating drive pulses are generated, and the heating element is energized 356 times. Thus, each heating element gives thermal energy according to the yellow image data to each pixel virtually divided into squares on the color thermosensitive recording paper 4. As a result, the yellow thermosensitive coloring layer 15 of the color thermosensitive recording paper 4 develops a color, and a dot having a density corresponding to the yellow image data is formed.

As described above, when the count value of the comparison data counter 36 becomes “255” during the gradation heating, 1
A line end signal is generated and sent to the memory controller 24. When the memory controller 24 receives two one-line end signals, it determines that printing of one line has been completed, and sends a system one-line end signal to the system controller 20. This system controller causes the counter 20a to count from "1" to "2". At the same time, the pulse motor is driven to rotate the platen drum 2 to feed the color thermosensitive recording paper 4 by one print line.

Next, the system controller 20 sets the frame memory 2 based on the count value of the counter 20a.
The image data of the first to second lines is read and written to the image data line memory 22. After this writing, the system controller 20 sends a system 1 line start signal to the memory controller 24 to start recording of the second print line.

As shown in FIG. 1, one pixel recording cycle includes a bias heating period and a gradation heating period cooling period. This cooling period is a period from the end of the gradation heating of the first print line to the start of the bias heating of the second print line. During this cooling period, the thermal head 6 is allowed to cool naturally or blow air. Forced cooling is performed. The system controller 20 generates a system 1 line start signal and starts recording of the second print line so as to secure an appropriate cooling period. If the period of one pixel recording cycle is the same for all three colors, the printing speed of each color can be kept constant.

When the recording of the second print line is started, as described above, each heating element performs bias heating and gradation heating. As the yellow image is recorded line by line in this manner, the thermal head 6 becomes warm. Therefore, after the Nth print line, the sub table 37b is selected for bias heating, and the sub table 37d is selected for gradation heating. In this case, as shown in FIG. 2, a pause time is given to each bias heating drive pulse so that each of the heating elements 10a to 10n does not excessively increase in temperature. It is energized. Further, even during the gradation heating, the current is repeatedly supplied while maintaining an appropriate pause time.

While the platen drum 2 rotates intermittently, a yellow image is recorded on the color thermosensitive recording paper 4 line by line. When the portion on which the yellow image is recorded reaches the yellow fixing ultraviolet lamp 8, 4
Irradiation with 20 nm UV light. As a result, the diazonium salt compound in the yellow thermosensitive coloring layer 15 remaining without undergoing the color development reaction is decomposed, and the coloring ability of the yellow thermosensitive coloring layer 15 is lost. When the color thermosensitive recording paper 4 passes through the yellow fixing ultraviolet lamp 8, the yellow fixing ultraviolet lamp 8 is turned off.

After the recording of the yellow image and the light fixing are completed, when the platen drum 2 enters the second rotation, the recording of the magenta image is started. In the recording of this magenta image,
Magenta image data is read line by line from the frame memory 21 and set in the image data line memory 22. Since the bias data is common to the three colors,
The bias data written in the bias data line memory 23 when the yellow image is recorded is used as it is.

Also in the case of recording the magenta image, each heating element is driven by 256 bias heating drive pulses and a maximum of 256 gradation heating drive pulses in the same manner as in the above-described yellow image. . As shown in FIG.
Since the thermal sensitivity of the magenta coloring layer 14 is smaller than that of the yellow coloring layer 15, the ON time setting data is determined so that the pulse width of the driving pulse becomes longer. Further, depending on the γ characteristic of the magenta thermosensitive coloring layer 14, O
FF time setting data is determined. When this large thermal energy is applied to the color thermosensitive recording paper 4, the magenta thermosensitive coloring layer 14 develops a color and one line of the magenta image is recorded. Since the yellow thermosensitive coloring layer 15 is light-fixed, no color is formed again when a magenta image is recorded. In recording a magenta image, since the thermal head 6 is already warm, it is preferable to provide a pause between each drive pulse.

During recording of the magenta image, the magenta fixing ultraviolet lamp 7 is on, so that the magenta image
When the portion recorded line by line reaches the magenta fixing ultraviolet lamp 7, ultraviolet light emitted from the portion is irradiated with 365 nm, and the magenta thermosensitive coloring layer 14 is optically fixed.

When the platen drum 2 enters the third rotation, the thermal head 6 is driven based on the cyan image data read from the frame memory 21, and the cyan image is recorded on the cyan thermosensitive coloring layer 13 line by line. The cyan heat-sensitive coloring layer 13 does not have light fixing property because its coloring heat energy BC is a large value that is not given in a normal storage state. Therefore, in recording a cyan image, both the magenta fixing ultraviolet lamp 7 and the yellow fixing ultraviolet lamp 8 are turned off.

When the recording of the cyan image is completed by rotating the platen drum 2 three times, a yellow image, a magenta image and a cyan image are recorded on the color thermosensitive recording paper 4, and a full-color image is formed by these three colors. . After recording the full-color image, the platen drum 2 stops. Then, after the clamper 5 releases the clamp of the color thermal recording paper 4, only the platen drum 2 rotates to discharge the recorded color thermal recording paper 4 pressed by the thermal head 6.

In the above embodiment, the temperature state of the thermal head is estimated from the print line. However, as shown by the two-dot chain line in FIG. The sub-table of the look-up table memory 37 may be selected according to the temperature measured by the sensor 45.

The present invention can also be used for recording binary images such as characters. In the case of this binary image, as long as the coloring density is constant, there is no problem even if the density differs from the original value. Therefore, in the case of a binary image, the driving pulse for bias heating and the driving pulse for gradation heating may be made continuous, and one driving pulse having a long pulse width may be generated to continuously drive each heating element. In this case, the thermal energy can be efficiently used, and the printing time can be reduced. The drive pulse having a long pulse width can be obtained by setting all the OFF time setting data to zero. Alternatively, the bias heating may be performed by one pulse having a long pulse width, and the gradation heating may be performed by a plurality of pulses having a short pulse width. In this case, the gradation heating OF
Zero the F-time gator. Further, the present invention can be applied to a thermal transfer type thermal printer using an ink ribbon or an ink film.

[0080]

As described above in detail, according to the method of the present invention, the OFF time setting data for determining the rest time of the strobe pulse is set to zero, and a part of the plurality of driving pulses is set. Alternatively, the heating elements are driven by this drive pulse in a state where they are all continuous, so unnecessary cooling is necessary when the thermal head is cold or when the fine control of the recording density is not necessary such as characters. Can be eliminated. Further, since the heating elements are driven continuously, the printing time can be reduced.

In the thermal printer according to the present invention, the ON time for setting the ON time of the heating element is set for each comparison data to be compared with the bias data or the image data.
Since the table memory storing the time setting data and the OFF time setting data for setting the OFF time of the heating element is used, the width of the strobe pulse and the pause time can be set for each gradation level. Heat generation control according to the γ characteristic of the thermosensitive recording paper can be performed.

In the thermal printer according to the third aspect, at least two types of sub-tables which are selectively used according to the position of the print line at the time of bias heating are provided, and the print line at which the thermal head is presumed to be cold is provided. The sub-table used for
Since the F time setting data is set, the desired bias thermal energy can be applied to the thermal recording paper even when the thermal head is cold.

In the thermal printer according to the fourth aspect, since the sub-table is selected according to the temperature of the thermal head, the desired bias thermal energy can be applied even when the thermal head is cold.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing a driving pulse and a temperature of a heating element in an initial stage of printing.

FIG. 2 is a waveform diagram showing a drive pulse and a temperature of a heating element during printing.

FIG. 3 is a schematic view of a color thermal printer.

FIG. 4 is an explanatory diagram showing a layer structure of a color thermosensitive recording paper.

FIG. 5 is a graph showing the color development characteristics of a color thermosensitive recording paper.

FIG. 6 is a block diagram showing an electrical configuration of the color thermal printer.

FIG. 7 is a block diagram of a print control unit.

FIG. 8 is a block diagram of a strobe signal generation circuit.

[Explanation of symbols]

 2 Platen Drum 4 Color Thermal Recording Paper 6 Thermal Head 7 Ultraviolet Lamp for Magenta Fixing 8 Ultraviolet Lamp for Yellow Fixing 10 Heating Element Array 10a to 10n Heating Element 37 Look Up Table Memory 38 Strobe Signal Generation Circuit

Claims (4)

(57) [Claims] When recording one pixel, a heating element is driven by a number of driving pulses corresponding to a gradation level of the pixel, and each driving pulse is turned on / off of the heating element.
In a heating element driving method created from drive data for determining F and a strobe signal for determining the ON time and OFF time of the heating element, the strobe signal is used to control the heating element according to ON time setting data. the width of the strobe pulse are determined for turned ON, and are determined pause time of the strobe pulse by OFF time setting data, temperature and printing of the heat generating element
A method for driving a heating element, comprising: setting the OFF time setting data to zero in accordance with the type of an image to be performed, thereby making a part or all of the driving pulses continuous. 2. When printing one pixel, a heating element is driven by a fixed number of drive pulses for bias heating to heat the thermosensitive recording paper almost immediately before coloring, and then to a gradation level. One line of bias data in a thermal printer that drives the heating elements with the corresponding number of gradation heating drive pulses to heat the thermal recording paper gradation and records dots with the desired density with each heating element , A line memory for bias data for storing image data, a line memory for image data for storing image data for one line, and a comparison data M corresponding to the lowest gradation level for bias heating and gradation heating corresponding to the highest gradation level Comparison data generating means for generating comparison data sequentially changing up to the comparison data N, and a buffer from a bias data line memory when recording one line. Memory data for reading out the image data from the image data line memory, and driving data for determining ON / OFF of the heating element by comparing the read bias data or the image data with the comparison data. And two tables for bias heating and gradation heating. Each table has ON time setting data and OFF for each comparison data.
A table memory in which the time setting data is written, and a strobe signal generating means for generating a strobe signal having a predetermined pulse width and a pause based on the time setting data read from the table memory using the comparison data as an address. A driving pulse generating means for generating a driving pulse from the strobe signal and the driving data. 3. The table for bias heating includes a plurality of sub-tables selected according to the position of a print line to be recorded. 3. The thermal printer according to claim 2, wherein a part or all of the bias heating drive pulses are made continuous by storing the OFF time setting data. 4. The table for bias heating includes a plurality of sub-tables selected according to the temperature of the thermal head, and a sub-table used when the thermal head is cold has an OFF time setting of zero. 3. The thermal printer according to claim 2, wherein a part or all of the drive pulses for bias heating are made continuous by storing data.