JPS61191164A - Thermal head driving method - Google Patents

Abstract

PURPOSE:To drive selectively respective unit heating bodies by executing the on and off control in accordance with the picture data for one side element group only out of the first and second switching element groups connected to the lead wire in the mutually reverse direction of the heating resistance body group. CONSTITUTION:Unit heating bodies 321-32N form a thermal head 12, and to lead wires 13 and 14 pulled out in the reverse direction, switching element groups 331-33M and 341-34M are respectively connected. A common terminal 49 connected with an element 34 is grounded, an impressing pulse is supplied to a common terminal 41 connected with an element 33, a picture signal 54 is supplied to a signal input terminal 52, and to a signal input terminal 44, a unit heating body selecting signal 45 is supplied. Signals 45 and 54 are S/P-converted respectively by shift registers 37 and 38 and respectively, latched to latch circuits 35 and 36 by control signals 48 and 53. By the output signal 42 of the circuit 35, the element 33 is turned on, a unit heating body 32 is selected, the element 34 is on and off-controlled in accordance with the picture signal 54 by the output signal 59 of the circuit 36, and by the impressing pulse from the terminal 41, the voltage is supplied to a selected unit heating body 32 and heating is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for driving a thermal head in an image display device that performs thermal recording or display.

``Prior Art'' For example, in a thermal recording device using a thermal transfer recording method, a thermal head is used to apply a heat pulse to a thermal transfer recording medium called an ink donor sheet, and the ink in the applied area is fluidized or sublimated and transferred to recording paper. I am transcribing it. The thermal head used in such a recording device is
So-called thick film type and thin film type are commonly used.

Among these, thick-film thermal heads have become widely used because they are relatively inexpensive and have high power durability.

FIG. 11 shows such a thick-film thermal head and part of its drive circuit.

In the thermal head 11, two types of lead wires 13 and 14, first and second, are alternately arranged on a single elongated heating resistor 12. The power supply 15 is connected to the first
and second common electrodes c1 and C2, and pulses are alternately applied to odd and even numbers of the first lead wires 13 via a diode 17 for preventing backflow. (Japanese Unexamined Patent Application Publication No. 1973)
-94940).

On the other hand, the image signal 18 is supplied to a shift register 19 disposed on the same substrate as the heating resistor 12 in synchronization with a clock (not shown), and the output after serial-to-parallel conversion is latched by a latch circuit 20. Each latch output is supplied to the corresponding switching element of the switching circuit 21, which is also arranged on the same substrate as the heating resistor 12, and controls these on and off.These switching elements are grounded in the on state. Therefore, when an applied pulse is supplied from the power source 15 to the first lead wire 13, the part of the heating resistor (hereinafter referred to as a unit) that sandwiches the first lead wire 13 and the second lead wire 14 which is grounded. (referred to as a heating element) is energized and its heating is controlled.

That is, as a result, the heating resistor 12 selectively generates heat in units of heating elements, and the individual dots forming the display image are formed.

"Problems to be Solved by the Invention" Incidentally, in such a thick film type thermal head, operations such as recording are performed by alternately driving the odd and even lead wires 13. For this reason, not only is the switch circuit 16 required, but it is also necessary to connect a diode 17 to each of the first lead wires 13 (approximately several thousand wires), which requires a large number of man-hours for connecting components, leading to high costs. was there.

Therefore, the present inventors devised a thermal head that can use common parts and reduce the number of connection steps. 12th
The figure schematically shows the structure of such a thermal head. This proposed thermal head 21 is
It is similar to the previous thermal conductor 11 in that two types of lead wires 13 and 14 are drawn out alternately in opposite directions from one heating resistor 12 at a predetermined interval. However, in this proposed thermal head 21, a first switching element group 22 is arranged, one for each of the lead wires 13 on one side, for electrically connecting and disconnecting these, and Lead wire 1 on the side of
4, a second switching element group 23 is arranged corresponding to each of them to electrically connect and disconnect from them. Although not shown in FIG. 11, in addition to the respective switching element groups 22 and 23, a shift register and a latch circuit may be arranged on the same substrate as the heating resistor 12.

The present invention provides a new method for driving a thermal head.

"Means for Solving the Problem" That is, in the present invention, each unit heating element is selectively driven by performing on/off control in accordance with image data of only one switching element group of this thermal head. . At this time, the switching element group on the side that is not controlled to be turned on or off by the image data may be set and held in a state in which the on state and off state are repeated one element at a time, or all may be held in the on state. . In addition, the switching elements that are controlled on and off by image data are
All lines need not be fixed, and may be switched line by line. In this case, as will be explained in detail later, it is possible to obtain a good image when performing halftone recording or the like.

"Example" The present invention will be described in detail with reference to Examples below.

FIG. 1 shows a specific configuration of a thermal head used in an embodiment of the present invention. Thermal head 3
1, a plurality of unit heating elements 32.1 are mounted on a substrate (not shown). ~3
2N.

First and second switching elements 331-33. ．． 3
4, ~34M, first and second latch circuits 3 and 5.3
6 and the first and second shift registers 37, 38 are also arranged on the same substrate. A plurality of unit heating elements 32.
32N is actually a long and narrow heating resistor 12 having a width of about 120 μm and a height of about 10 μm, which is electrically divided by the two types of lead wires 13 and 14 described above. The lead wires 13 and 14 are made of a conductor made of gold or the like and having a width of 25 μm and a thickness of 5 μm, for example, formed on a substrate. Heat generating resistor 12
are formed on these lead wires 13, 14, and a protective layer having a thickness of, for example, 7 μm is covered thereon.

The heating resistor 12 may be formed in such a manner that one end of the lead wires 13 and 14 protrudes above the substrate, or may be formed in such a manner that one end thereof is covered.

The other ends of the lead wires 13 are connected to one ends of first switching elements 33, . These switching elements 33. The other end of ~33° is the first common terminal 41
It is connected to the.

Switching element 33. -33. The on/off control is performed from the first latch circuit 35 to each switching element 33. ~3
3. depending on the signal state of the latch output 42 provided to the. For example, the switching element 33 whose latch output 42 is the signal LL 1 +1 is turned on, and the first common terminal 41 and the corresponding lead wire 13 are electrically connected. On the other hand, the switching element 33 whose output 42 is the signal "0"
is turned off, and the lead wire 13 is insulated from the first common terminal 41. The first shift register 37 and the first latch circuit 35 have the same functions as the shift register 19 and the latch circuit 20 shown in FIG. Signal 45 is serial-parallel converted. The parallel output data 46 thus obtained is latched by the latch control signal 48 supplied to the latch control signal input terminal 47, and the above-mentioned latch output is obtained.

The second latch circuit 36 and the second shift register 38, which have one end connected to the lead wire 14, receive a latch control signal 53 or a serial input signal 54 from a latch control signal input terminal 51 or a signal input terminal 52, respectively.
is supplied, and the first latch circuit 35
Alternatively, it performs the same operation as the shift register 37.

First Driving Method First, as a first thermal head driving method, a driving method similar to a normal driving method in a conventional thick-film thermal head will be described.

FIG. 2 shows the connection state of the thermal conductor 31 when performing this first driving method.

When this driving method is adopted, the second common terminal 49 commonly connected to the second switching element 34 is grounded, and the first common terminal 41 is supplied with an applied pulse 56 from a pulse applying power source (not shown). be done. The image signal is input signal 5
4 is supplied to the signal input terminal 52, and a unit heating element selection signal is supplied to the other signal input terminal 44 as an input signal 45.

This thermal head driving method will be explained with reference to FIG.

11a is an input signal 45 supplied to the signal input terminal 44.
2 types of human input signals 45.145□ are supplied once in this order for each line of recording. Of these, the first human signal 45 is a signal"
The second input signal 452 is the inverted serial signal "1010...10" in which the signal 1fL11 and the signal 1fL11 are alternately repeated.
0101...01''. The first shift register 37 first sets the first input signal 451, converts it from serial to parallel, and outputs it as output data 46.

This output data 46 is the latch control signal 4 shown in FIG.
8 and the first switching element 33, to 3 as a latched output for the first input signal 45,
3. supplied to As a result, the odd-numbered switching elements 33. ．． 333, . . . are turned on, and their first lead wires 13 are connected to the first common terminal.

On the other hand, an image signal is supplied as an input signal 54 from the input terminal 52 at the timing shown in FIG. 3C, and is set in the second shift register 38. The second latch circuit 36 latches this parallel output data using a latch control signal 53 (FIG. 3d), and uses these latch outputs 59 to
switching element 34. On/off control of ~34i is performed. At this time, the applied pulse 6 as shown in FIG.
1□ is supplied to the first common terminal 41, the odd-numbered switching elements 33. ．． 333... through corresponding unit heating elements 320.322.325326...
A voltage is applied to ..., and their energization is controlled to be turned on or off according to the image signal. This means that the 11th
The same printing operation as the printing operation using the common electrode C1 shown in the figure is performed.

After printing half of one line by two dots as described above, the second manual signal 452 causes the first switching element 33. The on/off operation of ~33M is reversed. Further, the second switching elements 34, - 34
c) Human input signal (image signal) input in the second half of one line
54, their on/off states are reset.

In this state, the application pulse 612 is applied to the first common terminal 41, and the printing operation for the latter half of one line is performed.

Thereafter, the printing operation proceeds line by line in the same manner. Fourth
The figure shows, as an example, the arrangement of each printing dot 62 when all the dots are printed continuously in one line in this first operation example. The print position moves up and down in the sub-scanning direction every two dots at a time because the recording paper is continuously moving, and is similar to when using a conventional thick-film thermal head. be. Of course 1
If the recording paper is kept stationary until recording of a line is completed, the printed dots 62 can be lined up in a straight line.

Next, a thermal head driving method in a state where the resolution has been switched to 1/2 will be described as an effective method for an image display device capable of switching the resolution, such as a facsimile machine.

FIG. 5 shows the wiring state of the thermal head 31 when performing this second driving method. Comparing with FIG. 2, the input signal 64 for batch drive is input to the signal input terminal
The difference is that it is supplied with

In addition, in the first driving method described above, the image signal for one line was supplied in two parts, the first half and the second half.
Since the resolution is 1/2 in the driving method, it is supplied only once.

This second driving method will be explained with reference to FIG.

Input signal 64 supplied to signal input terminal 44 (Fig. 6a)
) is a continuous signal "1" and is set in the first shift register 37.The first shift register 37
The output data 46 of is latched by a latch control signal 48 (FIG. 6b), and this latch output 42 turns on all the first switching elements 331 to 33M.

On the other hand, an image signal is supplied as an input signal 54 from the input terminal 52 at the timing shown in FIG. 6C, and is set in the second shift register 38. The second latch circuit 36 latches this parallel output data using a latch control signal 53 (FIG. 6d), and these latch outputs cause the second switching elements 341 to 34 . On/off control is performed.

At this time, the applied pulse 61° as shown in Fig. 6e is the first
When supplied to the common terminal 41 of all unit heating elements 32. ~
A voltage is applied to 32N, and these are controlled on and off in units of two adjacent dots in accordance with the image signal. This completes printing for one line. Thereafter, each line is printed in the same manner.

FIG. 7 shows a printing example corresponding to FIG. 4. In this case, since one line is printed in one printing operation, the printing dots 62 can be lined up in a straight line even if the recording paper does not stop during the printing operation.

Third Driving Method Finally, a thermal head driving method effective for reproducing halftone images will be described. In this driving method, printing is performed by alternating the functions of the switching elements 33 and 34 for each line.

FIG. 8 shows the wiring state of the thermal head 31 when performing this third driving method.

' In this case, the first to third switching devices 71 to 73 are used, and two signal lines (74, 742), (751, 75°), and (76 ,
, 762) and that on the output side are alternately switched line by line of recording. The two types of input signals 45. used in the first driving method are connected to the signal line 741. ．． 452 are alternately supplied to the first half and the second half of one line, and the image signal is supplied to the signal line 742. The signal line 751 is connected to a power source for generating applied pulses, and the signal line 752 is grounded. signal line 76,
A latch control signal for latching the aforementioned selection signal is supplied to the signal line 762, and a latch control signal for latching the image signal is supplied to the signal line 762.

In this third thermal head driving method, the first
Connections between each signal line and the input terminal are made in the lines as shown below.

As a result, exactly the same printing operation for one line is performed by the same operation as shown in FIG.

In printing the next second line, the first to third switching devices 71 to 73 reverse the signal connection relationship between the input side and the output side. As a result, the image signal is now set in the first shift register 37, and printing of the ■ line is performed.

At this time, the switching elements for selecting the unit heating element that performs the energization control are the first switching elements 33 to 3.
3. to the second switching elements 34□ to 34M. Therefore, the printing on this second line is performed with a difference of one dot in the main scanning direction (the length direction of the heating resistor) from the printing on the previous first line.

For printing on the third line, the first to third switching devices 71 to 73
Further, the signal connection relationship between the input side and the output side is reversed, and printing is performed in the same way as the printing operation for the first line. In printing on the fourth line, the same printing operation as on the second line is performed. The same applies below.

In this third driving method, the printing operations that are performed twice each on odd-numbered lines and even-numbered lines are shifted by one dot from each other, so that the printed dots are not aligned on the recording surface or The particles are dispersed on the display screen, making it possible to make the image density uniform. FIG. 9 corresponds to FIGS. 4 and 7, and shows the arrangement of the printing dots 62 when all dots are printed in two consecutive lines in this second driving method. .

FIG. 1O shows for reference an example of the configuration of a recording apparatus that employs the various driving methods exemplarily described above.

This recording apparatus is designed to correct heat accumulation in the thermal head 31. For this reason, the image signal memory 81 receives the clock signal 83 supplied from the timing control circuit 8.2 or 3.
The image signal 5 is captured in synchronization with the image signal 5, and is accumulated for several lines. The pixel is located around a specific gate or pixel (hereinafter referred to as the pixel of interest) for which heat storage calculation is currently being performed. The density of the pixel, the past ρ of the surface of interest, the element, or the surrounding pixels.

The state is extracted and supplied to the application pulse calculation circuit 85 as heat storage calculation data 84. When the pixel of interest is a printed dot (black dot), the applied pulse calculation circuit 85 determines the applied energy based on the heat storage calculation data 84 in consideration of the influence of heat storage.

At this time, the calculation and content of applied energy determination are changed according to the drive method identification signal 87 supplied from the drive method control circuit 86. This is because, depending on the method of driving the thermal head, two dots may be printed per pixel, or the process speed or printing cycle of one line may vary, and the optimal applied energy will change accordingly. It is.

The applied energy data 88 outputted from the applied pulse calculation circuit 85 is information representing the applied energy to the unit heating element for the pixel of interest in terms of the time width of the applied pulse. This time width is expressed, for example, as the number of unit pulses having a time length of 0.1 mS. For example, when the applied energy for a certain pixel of interest corresponds to an applied pulse of 1 mS, a signal "1" corresponding to 10 unit pulses is output, and this becomes the applied energy data 88. On the other hand, when the applied energy for another pixel of interest corresponds to 0.8 mS, a signal "1" corresponding to eight unit pulses is output as the applied energy data 88.

The transfer signal buffer 89 is composed of multi-stage line buffers, and each time it receives one pixel's worth of applied energy data 88, it transfers the applied energy data 88 to each line buffer.
Distributed and stored bit by bit. When one line of applied energy data 88 has been stored in this way, one line of data is read out in sequence using the in-buffer as a unit, and this becomes the two signals 54 supplied to the thermal head 31. . At this time, the input terminal switch 91 determines which terminal of the thermal head 31 the image signal 54 is supplied to. The drive method control circuit 86 supplies the input unit switch 91 with control signals 92 such as an identification signal for making this determination, the aforementioned selection signal, and a batch drive signal.

In this recording device, the thermal head 31 repeats data reception and printing operations as many times as the number of line buffers constituting the transfer signal buffer 89, and generates a unit heating element depending on how many times it is energized by a unit pulse of 0.1 mS. Adjust the applied energy each time. In connection with the printing operation of the thermal head 31, the drive method control circuit is connected to the recording paper transport device 9.
3 to control the conveyance of recording paper (not shown).

"Effects of the Invention" As explained above, according to the present invention, various driving modes of the thermal head can be realized by supplying image data to only one switching element group in a new thermal head that does not require connection of a diode. This makes it possible to perform printing or display suitable for various uses.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram showing an example of a thermal head used in the present invention, Fig. 2 is a circuit diagram showing a wiring state of the thermal head in the first driving method of the invention, and Fig. 3 is a circuit diagram showing this driving method. Various timing diagrams for explaining the 4th
The figure is an enlarged plan view showing a printing example in this driving method, FIG. 5 is a circuit diagram showing the connection state of the thermal head in the second driving method, and FIG. 6 is a diagram for explaining the second driving method. Various timing charts, FIG. 7 is an enlarged plan view showing an example of printing in this second driving method, and FIG.
9 is an enlarged plan view showing an example of printing in this third driving method, and FIG. 10 is a schematic diagram showing an example of a recording device to which the present invention is applied. Fig. 11 is a circuit diagram showing a part of the thick-film thermal head and its drive circuit used in the conventional thermal head driving method, and Fig. 12 is the basic configuration of the thermal head proposed this time. It is a diagram. I2... Heating resistor, 13.14... Lead wire, 22.23... Switching element group, 45...
...Human signal (selection signal), 54...Input signal (image signal), 64...Input signal (collective drive signal), 92...Control signal. Applicant: Fuji Xerox Co., Ltd. Representative
Person Patent Attorney Ume Yu Yamauchi ＾ Convex ha ρ ha (g f: J Q 'CI Φ-v'-/'''
−″′

Claims (1)

[Claims] 1. One elongated heating resistor, a plurality of lead wires drawn out alternately in directions substantially perpendicular to the length direction of the heating resistor, one by one in opposite directions, and these lead wires. a first switching element group connected one by one to each of the lead wires drawn out to one side of the lead wires for electrical connection and disconnection thereto; In an image display device using a thermal head, the thermal head is equipped with a second switching element group, which is connected to each of the lead wires and electrically connects and disconnects them. A thermal head driving method characterized in that only one switching element group is controlled on and off according to image data. 2. The switching element group on the side that is not controlled to be turned on or off by the image data is set and held in a state in which the on state and off state are repeated one element at a time. Thermal head driving method. 3. The thermal head driving method according to claim 1, wherein all of the switching element groups on the side that are not controlled to be turned on or off by the image data are kept in the on state. 4. The thermal head driving method according to claim 1, characterized in that a group of switching elements controlled on/off by image data is switched line by line.