JPH0596771A - Gradation control circuit in thermal transfer recorder - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer recorder reducing a recording density fluctuation, which is corresponding to a pattern of an image under printing and caused by, esp., a voltage drop of a common electrode of a thermal head, with respect to a thermal transfer recorder performing a binaryor multi- gradation recording. CONSTITUTION:When drive data of a thermal head is OFF data, a gap control means 104 controls an electric power to be applied to the thermal head by adding an OFF time to an electric signal waveform. Therefore, when the number of heating resistors to be electrically conducted is large, an applied electric power is raised; and when the number of heating resistors to be electrically conducted is small, an applied electric power is reduced. In this manner, a fluctuation of an applied electric power caused by a voltage drop in the thermal head can be reduced, and printing free from a density unevenness can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording apparatus for performing binary or multi-gradation recording, and more particularly to a thermal transfer recording apparatus capable of correcting fluctuations in recording density corresponding to an image pattern being printed. The present invention relates to the gradation control circuit.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing the outline of a conventional thermal transfer recording apparatus. In the figure, 201 is an image signal input terminal, 202 is an input interface, 203 is an image memory, 204 is a line memory, 101 is gradation control for converting gradation data into energization time for each dot and driving a thermal head. Reference numeral 205 is a thermal head, 206 is a power source for driving the thermal head, 207 is a mechanical unit of the recording apparatus, and 208 is a system controller.

First, the image signal input from the input terminal 201 is transferred to the image memory 2 via the interface 202.
Stored in 02. The stored signal is stored in the line memory 20.
Only one line transfer is stored in 4. Gradation control circuit 10
Reference numeral 1 converts the input grayscale data of one line into a time length of a drive pulse, drives the thermal head 205, and performs recording.

Further, the driving of the thermal head will be described with reference to FIGS.

FIG. 3 is an external view of the thermal head. In the figure,
301 is a common electrode manufactured by printed wiring, etc.
Reference numeral 2 is a common electrode manufactured on a ceramic substrate by a thin film process, 303 is a ceramic substrate, 304 is a plurality of heating resistor rows arranged on a line, and 305 is a wiring for connecting each resistor and a corresponding driver. And 306, a bonding wire connecting the wiring 305 and the driver,
307 is an integrated circuit such as a driver for driving a resistor, a shift register, and a latch, 308 is a connector for energizing data, and 309 is a power input connector for applying a resistor.

FIG. 4 is a circuit diagram electrically representing the thermal head. In the figure, 401 is a driver element for turning on and off corresponding to each heating resistor, 402 is an AND gate, 403 is a latch, 404 is a shift register, 4
Reference numerals 05 and 406 denote power source input terminals for resistor application, 407 a strobe signal input terminal, 408 a latch signal input terminal, 409 a shift register data input terminal, and 410.
Is a data output terminal of the shift register, and 411 is a clock input terminal. RH represents the resistance of the heating resistor. R1
Is the wiring resistance of the common electrode 301, and R2 and R3 are the common electrode 3
No. 02 wiring resistance. These wiring resistances exist in a distributed constant for each heating resistor.

Next, the driving operation of the thermal head will be described. The ON / OFF pattern of each resistor in the heating resistor array 304 is input to the shift register 404 through the input terminal 409. After the data for one line is completely input to the shift register 404, the data is transferred to the latch 403. After that,
By turning on the strobe signal from the input terminal 407, the heating resistor can be selectively heated.
The heat generation time can be controlled by controlling the on time of the strobe signal. If the above operation is performed once for one line, binary recording is performed, and if it is performed a plurality of times, density control can be performed with the number of gradations according to the number of times.

In the thermal transfer recording apparatus as described above, the current flowing through the common electrodes 301 and 302 changes depending on the number of resistors that generate heat. In the common electrodes 301 and 302, a voltage drop occurs according to the amount of flowing current, and the voltage actually supplied to the heating resistor changes. When the supply voltage changes, the heat generation amount of each heating resistor in the heating resistor array 304 changes. That is, recording density unevenness occurs depending on the number of resistors that generate heat.

For example, when a pattern having a white area in a constant density as shown in FIG. 5 is to be recorded, the density on the line AA 'in the figure is the solid line in the graph below. Like The target density for recording is shown by the dotted line in the graph.
The larger the number of resistors that generate heat, the larger the voltage drop across the common electrode and the lower the recorded density, resulting in uneven density.

As described above, as a thermal transfer recording apparatus for recording by correcting the voltage drop of the common electrode, it is disclosed in Japanese Patent Laid-Open No. Hei 1
Those described in Japanese Patent Publication No. 150557, etc. are known.

The above-mentioned prior art is to control the power source so that the voltage applied to the heating resistor becomes constant by using the power source having the remote sensing function.

[0012]

However, in the above prior art, when sensing is performed on the power connector of the thermal head, the wiring resistance from the power source to the thermal head can be corrected, but the wiring resistance on the thermal head is corrected. Minutes still remained uncorrected, and highly accurate correction was not possible. Furthermore, it is very difficult to secure the performance, such as unevenness caused by the response delay of the power supply.

As described above, as shown in FIG. 4, the wiring resistance R3 causes the wiring resistance to exist in a distributed constant with respect to each heating resistor. However, no consideration is given to this correction. Absent.

An object of the present invention is to enable correction of density unevenness due to the influence of the wiring resistance of the common wiring, and further to correct density unevenness due to the wiring resistance of the heating resistor and therefore the wiring resistance existing in a distributed constant. An object of the present invention is to provide a gradation control circuit of a thermal transfer recording device that is possible.

[0015]

In order to achieve the above object, the present invention detects the number of resistors to be energized, and when the number is large, the applied power is large, and when the number is small, the applied power is small. The duty of the strobe signal is changed according to the number of resistors to be energized so as to decrease.

Further, in order to correct the unevenness in the arrangement direction of the heating resistors, weighting is performed according to the position of each resistor when detecting the number of resistors to be energized, and the weights are accumulated and the result is obtained. The duty of the strobe signal is changed according to.

[0017]

The density unevenness due to the voltage drop of the common wiring becomes low when the number of energized resistors is large. Therefore, the duty of the strobe signal is changed so that the applied power becomes large. As a result, it is possible to prevent the recording density from decreasing due to the voltage drop of the common wiring. On the contrary, when the number of resistors to be energized is small, the duty of the strobe signal can be changed so that the applied power becomes small, and the increase in recording density can be suppressed.

[0018]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 101 is a gradation control circuit, 102 is data control means, 103 is strobe generation means, and 104.
Is a clearance control means for changing the duty by adding an off time to the strobe signal, and 105 is a line memory 20.
4 is a terminal for inputting data from 4; 106 is a terminal for connecting to the system controller 208; 107 is a terminal for inputting the output of the strobe generating means 103 to the gap control means 104; 108 is a terminal for inputting a clock;
09 is a terminal for inputting data output from the thermal head, 1
Reference numeral 10 is a terminal for inputting a control signal from the system controller, and 407 to 411 are input / output terminals of the thermal head shown in FIG.

The embodiment of the present invention shown in FIG. 1 is different from the conventional gradation control circuit in that the gap control means 104 is provided as shown in FIG. That is, the data output of the shift register 404 of the thermal head 205 and the strobe signal output by the strobe generating means 103 are
The point different from the conventional one is that after being supplied to the gap control means 104 and processed, it is output to the thermal head 205 as a new strobe signal.

The operation of the embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 6 shows drive waveforms of the thermal head 205 and the gap control means 104 when multi-gradation control is performed.
It is a figure which shows the electricity supply operation of the Nth gradation vicinity. In the figure, 601 is a shift register 404 of the thermal head 205.
, 602 is data, 603 is data output from the shift register 404, 604 is a latch pulse input to the latch 403, 605 is a strobe signal output from the strobe output means 103, 60
6 is output from the gap control means 104 and is applied to the thermal head 20.
5 shows a new strobe signal to be input to No. 5.

The data control means 102 is the heating resistor array 30.
The ON / OFF pattern data 602 of each resistor of No. 4 is input to the shift register 404 in synchronization with the clock 601. After inputting the data of the Nth gradation, waiting for the energization of the (N-1) th gradation to end, transfer the data to the latch 403 at the timing of the latch pulse 604, turn on the strobe signal, and turn on the Nth gradation. Energize. While the Nth gradation is being energized, the next N + 1th gradation data is transferred to the shift register 404.
Have been transferred to. During the transfer of the N + 1th gradation data, the Nth gradation data is being output from the shift register 404. That is, during the period of energization for the Nth gradation,
The data of the Nth gradation is output from the shift register 404.

The gap control means 104 is the shift register 40.
The output data 603 from No. 4 is detected, and when the data is off, the strobe is turned off for a predetermined period, and this operation is performed by the number of data, that is, the number of heating resistors to perform the correction processing. Output signal 606 is obtained.

As described above, by using the output data 603, the strobe of the Nth gradation can be processed by the data of the Nth gradation, and the correction can be performed at a good timing.

The construction and operation of one embodiment of the gap control means used in the embodiment of FIG. 1 will be described with reference to FIGS. 7 and 8.

In FIG. 7, 701 is a duty varying means, 702 is an OR gate, and 703 is an AND gate. It should be noted that the same reference numerals are given to those that operate in the same manner as in FIG.

FIG. 8 is a waveform diagram showing the processing operation of the data in the vicinity of the nth dot. For example, the nth dot is off, and n + 1.
This shows the case where the dot is on and the n + 2 dot is off. In FIG. 8, 801 is a clock signal input to the input terminal 108, 802 is a signal that is turned off for a predetermined period t at the rising timing of the signal 801, 803
Is a signal indicating the data input to the input terminal 109, 80
4 is a signal obtained by ORing the signals 802 and 803, 80
Reference numeral 5 denotes a strobe signal input to the input terminal 107, which continues to be on in the figure, and 806 denotes a signal 804 and a signal 80.
This is a signal obtained by ANDing 5.

Next, the operation of FIG. 7 will be described. Input terminal 1
The signal 801 input from 08 is the duty varying means 7
Is input to 01. The duty changing means 701 outputs a signal that is turned off for a predetermined period t at the rising timing of the input signal 801. Duty changing means 70
1 is, for example, a monostable multivibrator, and the off time t can be changed by a control signal from the system controller 208. Duty changing means 107
The OR gate 702 takes the OR output of the signal and the data signal 803 and outputs it as a signal 804. Furthermore O
The signal 804 output from the R gate is the AND gate 7
In 03, it is ANDed with the strobe signal 805, and the signal 8
It is output like 06. The signal 806 is sent to the thermal head 205 as a new strobe signal.

As described above, when the heating resistor with the thermal head is not energized, that is, when the drive data signal 803 of the thermal head is off, the original strobe signal 805 is turned off for a certain period t. By performing the above operation for the number of heating resistors, that is, for the number of driving data of the thermal head, the larger the number of resistors that are not energized, in other words, the smaller the number of resistors that are energized, the less power is applied. As described above, the duty of the strobe signal can be changed to suppress the unevenness of the recording density.

When multi-gradation recording is performed and the energization time (that is, the on-time of the strobe signal) differs for each gradation, the off-time t output by the duty varying means 701 is constant. Then, even if the number of resistors to be energized is the same, the ratio of the off time to the energizing time changes depending on the gradation, and the correction effect becomes uneven. In this case, the off time t output by the duty varying unit 701 may be reset for each gradation according to the energization time by a control signal from the system controller 208.

FIG. 9 shows another embodiment of the gap control means 104 of the embodiment shown in FIG. In the figure, reference numeral 901 is a delay means, and other elements that perform the same operations as in FIG. 7 are designated by the same reference numerals.

FIG. 10 is a diagram showing the operation of the gap control means 104 shown in FIG. 9, showing the operation near the nth gradation. In the figure, 1001 is a clock signal input to the terminal 108, 1002 is a signal indicating data input from the terminal 109, 1003 is an output signal of the delay unit 901, 100
4 is a strobe signal input to the terminal 107, 1005
Is a signal obtained by ANDing the signals 1003 and 1004.

The strobe signal 1004 is turned off once in order to latch the data in the latch 403 of the thermal head 205 when the energization of a certain gradation is finished and the energization of the next gradation is performed. If the OFF period and the data transfer time overlap, the correction is not performed normally. Therefore, by providing the delay means 901 as shown in the figure, it is possible to insert an off time corresponding to the data signal 1002 after the strobe signal 1004 is turned on.

For example, as shown in FIG. 10, a data signal 1002
When the strobe signal 1004 is turned on after a delay of time t1, the delay time t2 of the delay means 901 is set larger than t1 within the range where the output 1003 of the delay means 901 ends while the strobe signal 1004 is turned on. Just set it.

Another embodiment of the present invention is shown in FIG. In the figure, reference numeral 1101 is a shift register, and other elements that perform the same operations as those in FIG. 1 are denoted by the same reference numerals.

In the embodiment described with reference to FIG. 1, the output of the shift register 404 of the thermal head 205 is used as the data input to the gap control means 104, but in some cases the thermal head has a data output terminal 410. Some things may not be possible. In this embodiment, by arranging the shift register 1101 as shown in the figure, the same effect as that of the embodiment shown in FIG. 1 can be obtained without using the data output of the thermal head. The shift register 1101 has the same number of bits as the number of bits of the shift register 404 of the thermal head 205. Therefore, the output of the shift register 1101 is equal to the output of the shift register 404, so that the gradation control means 101 of this embodiment operates in the same manner as the embodiment of FIG.

Further, in FIG. 11, the shift register 11
When 01 does not exist, that is, when the data is directly input to the gap control unit 104, the data of the (n + 1) th gradation is used to correct the strobe of the nth gradation as shown in FIG. However, even in this case, some correction effect can be obtained.

In the embodiment described above, the data input to the thermal head is one, but in order to drive the thermal head at high speed, the data may be input separately. For example, FIG. 12 shows a circuit diagram of a two-input thermal head. 404a and 404b are divided shift registers, 409a and 409b are data input terminals of the shift register, and 410a and 410b are data output terminals of the shift register. As shown in FIG.
It has two shift registers a and 404b, and simultaneously transfers data by inputting data from both input terminals 409a and 409b.

FIG. 13 shows an embodiment of the gradation control means corresponding to the thermal head for divided input. In the figure, the same reference numerals are attached to the same elements as those in FIG. This drawing is different from FIG. 1 in that there are two systems of drive data for the thermal head as shown in the drawing.

FIG. 14 shows an example of the structure of the gap control means 104 used in the gradation control means 101 shown in FIG.
In the figure, 1401a and 1401b are latches and 140
Reference numeral 2 designates a doubling oscillator for transmitting at twice the frequency of the input clock, and 1403 a changeover switch. In addition, the same reference numerals are given to those that operate in the same manner as in FIG. 7.

Next, the operation of FIG. 14 will be described. The data input from the input terminals 109a and 109b is stored in the latch 1
The clocks 401a and 1401b are held until the next clock.
On the other hand, the doubling oscillator 1402 oscillates at a frequency twice that of the clock input from the terminal 108, switches the switch 1403, and drives the duty varying means 701. Duty variable means 701, OR gate 702, A
The ND gate 703 operates in the same manner as in FIG.
An off period is inserted in the strobe signal according to the ON / OFF of the data selected in 03. That is, the two input data are switched at a frequency twice as high as the data transfer frequency, and an off period is set in the strobe according to on / off of the switched data. In this way, the correction is performed even in the case of a two-input thermal head.

In this embodiment, the case of two inputs has been described, but it goes without saying that the same correction can be made in the case of three or more inputs.

FIG. 15 shows another structural example of the gap control means 104 used in the gradation control means 101 shown in FIG. In the figure, 1501a and 1501b are buffers, 1502a is a resistor, 1502b is a resistor having the same resistance value as the resistor 1502a, 1503 is a resistor, and 1504 is a terminal. In addition, the same reference numerals are given to those that operate in the same manner as in FIG. 7.

FIG. 16 shows the gap control means 1 shown in FIG.
It is a figure which shows operation | movement of 04. In the figure, 1601 is a clock signal, 1602 is a data signal input to the terminal 190a, 1603 is a data signal input to the terminal 190a, 1604 is a voltage appearing at the terminal 1504, 1605.
Is a signal output from the duty changing means 701, 1606
Is a strobe signal input to the terminal 107, and 1607 is a signal obtained by ANDing the signals 1605 and 1606.

Next, the operation will be described. Input terminal 10
When an off signal is input to both 9a and 109b,
The voltage appearing at terminal 1504 is 0v. Input terminal 10
When an ON signal is input to either one of 9a and 109b and an OFF signal is input to the other, a voltage E1 appears at the terminal 1504. Since the resistors 1502a and 1502b have the same resistance value, the voltage appearing at the terminal 1504 is the same regardless of which of the input terminals 109a and 109b is turned on. Further, when the ON signal is input to both the input terminals 109a and 109b, the voltage E2 appears at the terminal 1504.
The duty changing means 701 outputs pulses having different off periods according to the voltage so that the off period has a long period when the voltage value input to the terminal 1504 is small and the off period becomes short when the voltage value is large. That is, signals 1602 and 16 are applied to the input terminals 109a and 109b, respectively.
03 is input to the terminal 1504, a signal 160
Three different voltages 0, E1, E2 appear as shown in FIG. The duty varying means 701 uses the clock signal 16
At the rising timing of 01, a signal 1605 that is off for a period corresponding to the voltage of the signal 1604 is output. The signal 1605 and the input strobe signal 1606 are ANDed
The gate 703 is ANDed and sent to the thermal head as a strobe signal with an off period.

As described above, in the case of dividing data input, the longer the OFF data among the data transmitted at the same time, the longer the OFF period can be provided in the strobe signal. As a result, the duty of the strobe signal is changed so that the applied power decreases as the number of energized resistors decreases, and unevenness of the recording density can be suppressed.

In this embodiment, the case of two inputs has been described, but it is needless to say that the correction can be similarly performed in the case of three or more inputs only by adding a buffer and a resistor.

FIG. 17 shows another embodiment of the gradation control means according to the present invention. In the figure, 1701 is a counter for counting the number of ON data transferred to the thermal head, 17
Reference numeral 02 is a pulse generating means for generating an off pulse having a time width corresponding to the count value of the counter 1701. In addition, the same reference numerals are given to those that operate in the same manner as in FIG. FIG. 18 shows the gradation control means 1 shown in FIG.
It is an operation waveform diagram of 01. In the figure, reference numeral 1801 is a data transfer clock signal, 1802 is a heating resistor ON / OFF data signal, 1803 is a latch signal, 1804.
Is an output signal of the pulse generating means 1702, 1805 is a strobe signal generated by the strobe generating means 103, 18
Reference numeral 06 is a signal obtained by ANDing the signal 1804 and the signal 1805.

Next, the operation of the gradation control means 101 shown in FIG. 17 will be described. The counter 1701 counts the number of ON data among the data transferred to the thermal head 205. The pulse generating means 1702 generates an off pulse according to the count value of the counter 1701 when the latch signal is input. The length of the off-time is set in advance so as to be short when the count value is large and long when the count value is small. Also strobe signal 1805
Is turned off at the moment of latching, so the off pulse is set to be generated after a fixed time has elapsed after the output of the latch pulse. On the other hand, the counter 1701 is reset after inputting the latch signal and prepares for counting the data of the next gradation. The output signal of the pulse generating means 1702 and the strobe generating means 1
The output signal of 03 is ANDed by the AND gate 1703 to energize the thermal head 205.

For example, in the nth gradation of the data signal 1802, the number of conducting resistors is large, and in the n + 1th gradation, the number of conducting resistors is small. In the output signal 1804 of the pulse generation means 1702, the off pulse time t1 is short at the nth gradation and the off pulse time t2 is long at the (n + 1) th gradation. A signal 18 is obtained by ANDing the signal 1804 and the output signal of the strobe generating means 103.
06 is obtained, and the thermal head is energized as a new strobe signal. When the number of energized resistors is large as indicated by a signal 1806, the energization time is long, and when the number of energized resistors is small, the energization time is short.

In this way, it is possible to correct the unevenness of the recording density by changing the energizing time according to the number of energized resistors.

FIG. 19 shows an embodiment of the gradation control means corresponding to the thermal head for divided input. In the figure, 1
Reference numerals 701a and 1701b are counters, and 1801 is an adder that adds the count values of the counters 1701a and 1701b. In addition, the same reference numerals are given to those that operate in the same manner as in FIG.

In this embodiment, the divided and input data are respectively counted by the counters 1701a and 1701b, and the count value is added by the adder 1801. Since the pulse generating means 1702 generates an off pulse having a time width corresponding to the added value, the correction can be performed in the same manner as the embodiment shown in FIG.

In this embodiment, the case of two inputs has been described, but it is needless to say that the correction can be similarly performed in the case of three or more inputs by simply adding a counter.

By the way, as shown in FIG. 4, the wiring resistance R3
As described above, the wiring resistance exists in a distributed constant with respect to each heating resistor. For example,
When recording a pattern as shown in FIG. 20,
The density on the CC ′ line in the figure is smaller than the density on the BB ′ line. This is because the wiring resistance increases toward the center of the heating resistor array, and the recorded density decreases. In order to correct this, when detecting the number of resistors to be energized, weighting is performed according to the position of each resistor, the weights are accumulated, and the duty of the strobe signal is changed according to the result. Good.

FIG. 21 shows an embodiment of the gradation control for reducing the density fluctuation which has been described above. 2101a, 21 in the copper diagram
01b is a ROM in which the weight of each resistor is recorded, 2102
Is an adder that adds the weighting factors output from the ROMs 2101a and 2101b and accumulates over the number of all resistors.
In addition, the same reference numerals are given to those that operate in the same manner as in FIG.

The counter 1701 counts the number of clocks and outputs the counted value and the data as address signals to the ROMs 2101a and 2101b. The count value of the counter 1701 is
It indicates which heating resistor data is used. ROM
2101a and 2101b output the weighting coefficient for each heating resistor to the adder 2102 when the data is on according to the input count value. When the data is off, the weighting coefficient 0 is output. ROM 2101a, 21
The weighting coefficient stored in 01b is set to have a larger value for an address corresponding to the center of the heating resistor array. The adder 2102 is the ROM 2101a, 210
The outputs of 1b are added, and the added value is accumulated over all the heating resistors. The accumulated value is the pulse generation means 170.
In step 2, it is converted into an off pulse having a time width corresponding to the cumulative value and output. The length of the off time is set to be shorter as the cumulative value is larger, that is, as the number of heating elements to be energized is greater in the center of the heating resistor array 304. The output off-pulse is added to the strobe signal output from the strobe generating means 103 by the AND gate 1703 and sent to the thermal head.

In the present embodiment, the electric power to be applied increases as the current-carrying resistor is closer to the center of the heating resistor array.
It is possible to suppress the concentration fluctuation as shown in FIG.

[0059]

According to the present invention, the energization time can be controlled in accordance with the number of energized heating resistors, so that it is possible to reduce the density unevenness due to the voltage drop of the common electrode of the thermal head.

[Brief description of drawings]

FIG. 1 is a configuration diagram of gradation control showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an outline of a thermal transfer recording device.

FIG. 3 is an external view of a thermal head.

FIG. 4 is a circuit diagram of a thermal head.

FIG. 5 is a diagram illustrating density unevenness due to a recording pattern in a conventional apparatus.

6 is an operation waveform diagram of the gradation control circuit shown in FIG.

FIG. 7 is a configuration diagram of a gap control unit used in the embodiment shown in FIG.

8 is an operation waveform diagram of the gap control means shown in FIG.

9 is another configuration diagram of the gap control means used in the embodiment shown in FIG.

10 is an operation waveform diagram of the gap control means shown in FIG.

FIG. 11 is a configuration diagram of a gradation control unit showing another embodiment of the present invention.

FIG. 12 is a circuit diagram of a two-input thermal head.

FIG. 13 is a configuration diagram of gradation control showing an embodiment of the present invention, which corresponds to a 2-input thermal head.

14 is a configuration diagram of a gap control unit used for the gradation control shown in FIG.

15 is another configuration diagram of the gap control unit used for the gradation control shown in FIG.

16 is an operation waveform diagram of the gap control means shown in FIG.

FIG. 17 is a block diagram of a gradation control means showing another embodiment of the present invention.

18 is an operation waveform diagram of the gap control means shown in FIG.

FIG. 19 is a configuration diagram of gradation control showing another embodiment of the present invention corresponding to a two-input thermal head.

FIG. 20 is a diagram illustrating density unevenness due to a recording pattern in a conventional apparatus.

FIG. 21 is a configuration diagram of gradation control showing another embodiment of the present invention.

[Explanation of symbols]

 Reference numeral 101 ... Gradation control means, 102 ... Data control means, 103 ... Strobe generating means, 104 ... Gap control means, 205 ... Thermal head.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Mochimaru 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi Image Information Systems Co., Ltd.

Claims (5)

[Claims] 1. A thermal head comprising a plurality of heating elements arranged in a line, data control means for controlling ON / OFF of energization of individual resistors of the thermal head, and energization time of the resistors. In a thermal transfer recording apparatus composed of a strobe generating means for generating a strobe signal for controlling the ON / OFF of each resistor, the duty of the output signal generated by the strobe generating means is controlled by the detection result. A gradation control circuit for a thermal transfer recording apparatus, characterized in that the energization time of the resistor is controlled by a duty-controlled strobe signal. 2. The duty control means is configured to add an off time to the output signal of the strobe generating means when the energization of the resistor is off.
The gradation control circuit of the thermal transfer recording apparatus according to claim 1. 3. The thermal head has a plurality of data input terminals, and the data control means transfers a plurality of data for controlling ON / OFF of energization to the thermal head at the same time, and the duty control means. Is configured to add, to the output signal of the strobe generating means, a time corresponding to the number of off data of energization and off data simultaneously transferred, or a number of off times. Item 1
The gradation control circuit of the thermal transfer recording apparatus according to 1. 4. The duty control means has a counter for counting the number of resistors turned on and off from the output of the data control means, and the time corresponding to the output of the counter, or the off time of the number, The gradation control circuit of the thermal transfer recording apparatus according to claim 1, wherein the gradation control circuit is configured to be added to the output signal of the strobe generating means. 5. The duty control means is means for generating a coefficient according to the position of the resistor and ON / OFF of energization thereof, and a time or a number of OFF according to the cumulative value of the coefficient over all the resistors. Characterized in that it is arranged to add time to the output signal generated by the strobe generating means,
The gradation control circuit of the thermal transfer recording apparatus according to claim 1.