JPH08295044A - Thermal printer - Google Patents

Abstract

PURPOSE: To reduce the cost of a thermal head by setting the number of the logical circuits or switching elements provided in a driver IC to 1/N the number of heating elements by driving (N) heating elements constituting the heating element group of the thermal head by one logical circuit and one switching transistor. CONSTITUTION: A thermal head consists of a heating element row wherein (M) heating element groups each having a pair of electrodes connected thereto are arranged to (N) heating elements having different resistance values and a driver IC 5. A data supply means 7 supplying image data being (M×N) binary data, a signal generating means 8 counting the number of the data driving the heating elements on the basis of image data at every heating element groups and generating the printing signal corresponding thereto and a selection means 10 selecting a strobe signal on the basis of the printing signal are connected to the head 1. The driver IC 5 has (M) logical circuits based on the AND of the printing and strobe signals and (M) switching elements controlling power application.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer incorporated as a printer mechanism such as a word processor and a facsimile.

[0002]

2. Description of the Related Art Conventionally, a thermal printer incorporated as a printer mechanism such as a word processor produces a print signal (DATA) in which a thermal head 20 and image data composed of binary data are serially arranged as shown in FIG. Data supply means 26 for supplying and a predetermined strobe signal (STB)
And a control means 27 for generating.

As shown in FIG. 10, the thermal head 20 has a heating element array in which a large number of heating elements 21 are linearly arranged, and individual electrodes 22 and a common electrode 23 for supplying electric power to each heating element 21. A plurality of driver ICs 24 having a plurality of output terminals H connected to the individual electrodes 21 to selectively heat the heating element 21 based on the print signal (DATA).
Print signal (DATA), strobe signal (STB), latch signal
(LAT) and a plurality of control signal lines 25 for inputting a clock signal (CLK) are attached, and inside the driver IC 24, as shown in FIG. The same number of bits as the number of heating elements 21 connected via the electrodes 22, for example, 64-bit shift registers SR1 to SR64, latches L1 to L64, gate elements
It has G1 to G64 and switching transistors TR1 to TR64.

When the print signal (DATA) is input through the input terminal DI, the shift registers SR1 to SR64 function to serially transfer the print signal (DATA) in synchronization with the clock signal (CLK). The latches L1 to L64 are connected to the input terminal LA
When the latch signal (LAT) is input via T, the print signal (DATA) stored in the shift registers SR1 to SR64 is retained.

Further, the gate elements G1 to G64 are print signals.
(DATA) and strobe signals (STB1 to STB4) are used to output an output signal to the switching transistors TR1 to TR64 based on the logical product of the switching transistors TR1 to TR4.
Reference numeral 64 serves to control the application of electric power to each heating element 21 according to the output signals from the gate elements G1 to G64.

Further, the heating elements 21 are divided into four groups, and the heating elements 21 in each group are individually driven by four strobe signals (STB1 to STB4).

Next, using the above-mentioned thermal printer,
The operation in the case of division printing will be described based on the timing chart of FIG.

First, a print signal (DATA) composed of binary data having the same number of bits as that of the heating element 21 is serially input from the image data supply means 26 to the shift register SR via the input terminal DI of the driver IC 24 to print. The signal (DATA) is stored in the shift register SR. Next, the latch signal (LAT) is input to each latch L via the input terminal LAT, and the print signal (DATA) stored in each bit of the shift register SR is latched by the latch L.
In parallel, and the latch L holds the print signal (DATA).

Then, the strobe signal (STB1) is inverted from the high level to the low level, and the opening / closing of the switching transistor TR is controlled via the gate element G. As a result, the heating elements 21 belonging to one of the four groups described above selectively generate heat, and predetermined print dots are formed on the thermal recording medium.

Thereafter, the same operation as described above is repeated for the other three groups to sequentially form the print dots corresponding to each group, thereby forming a series of print images on the thermal recording medium.

[0011]

However, in this conventional thermal printer, the thermal head 20 is used.
Each heating element 21 of the one of the logic circuit (shift register S
Since it is driven by R, latch L, gate element G) and one switching transistor TR, the driver IC 24 of the thermal head 20 has a large number of logic circuits with the same number of bits as the heating element 21 and a large number of switching elements. Since it is necessary to provide the transistor TR, the number of driver ICs 24 mounted on one thermal head is extremely large, and the thermal head as a product has a drawback of being expensive.

[0012]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and it is an object of the present invention to realize a print quality which is almost the same as the conventional one by using a thermal head manufactured at a low cost. To provide a good thermal printer.

[0013]

A thermal printer according to the present invention has M (M) heating element groups each having a pair of electrodes connected to N (N is a natural number of 2 or more) heating elements having different resistance values.
Is a natural number of 2 or more) and the heating element rows are arranged in rows,
Data supplying means for supplying image data composed of M × N binary data, and the number of data for driving the heating elements from the image data from the data supplying means are counted for each heating element group and counted. A signal generating means for generating a print signal corresponding to the number of data and N strobe signals having different pulse widths are generated, and one strobe signal having a predetermined pulse width is selected based on the print signal from the signal generating means. The selection means, the print signal from the signal generation means and the strobe signal selected by the selection means are supplied, and an output signal is generated based on a logical product of the both.
And a driver IC having M switching elements for controlling power application to each heating element group according to an output signal from each of the logic circuits.

Further, the thermal printer of the present invention is characterized in that the N heat generating elements having different resistance values have high temperature heat generating areas of the same area.

[0015]

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

(First Embodiment) FIG. 1 is a configuration diagram showing a first embodiment of a thermal printer of the present invention, FIG. 2 is a circuit diagram of a thermal head used in the thermal printer of FIG. 1, and FIG. 3 is a thermal diagram of FIG. FIG. 4 is a partially enlarged plan view of the head, and FIG. 4 is a circuit diagram of signal generating means used in the thermal printer of FIG.
1 is a thermal head, 7 is a data supplying means, 8 is a counter, 9 is a signal generating means, and 10 is a selecting means.

The thermal head 1 is formed by arranging M (M is a natural number of 2 or more) heating element groups consisting of N (N is a natural number of 2 or more) heating elements 2a to 2d having different resistance values. An element array, a pair of electrodes 3 and 4 for applying electric power to the heating element group, a plurality of driver ICs 5 connected to the electrodes 4, various control signals (print signals (DA to DD), strobe signals). (STB), clock signal (CLK), latch signal
(LAT)) to each driver IC 5 and a plurality of control signal lines 6. In this embodiment, N is set to 4 and M is set to 512.

The heating element group is composed of four heating elements 2a to 2d, each of which is continuously arranged. The heating elements 2a to 2d have a length dimension in a direction orthogonal to the arrangement direction. The resistance value is set to a predetermined value by changing, for example, the heating element 2 has a thickness of 0.05 μm and a width of 100 μm of TaSiO ₂
2a is 90 μm, 2b is 150 μm, and 2c is
By adjusting the length of 120 μm and 2d to 180 μm
The resistance value of 2a is set to 1800Ω, the resistance value of 2b is set to 3000Ω, the resistance value of 2c is set to 2400Ω, and the resistance value of 2d is set to 3600Ω. At this time, the energy required to form the print dots is 0.38
With mJ / dot, 2a is 1.2 msec, 2b is 2.0 msec, and 2c is 1.
Each heating element by energizing 6msec, 2d for 2.4msec
It is possible to heat Joules 2a to 2d to a temperature at which print dots can be formed on the thermal recording medium.

Therefore, when the four heating elements 2a to 2d constituting the heating element group are driven to generate heat, if the energization time is set to 1.2 msec, one print dot corresponding to 2a is formed, and the energization time is 1.6 When set to msec, two print dots corresponding to 2a and 2c are formed, and when energization time is set to 2.0msec, three print dots corresponding to 2a, 2b, and 2c are formed, and energization time is 2.4. When set to msec, four print dots corresponding to 2a to 2d are formed.

The driver IC 5 has the same electrical structure as that of the conventional one shown in FIG. 10, and has M shift registers SR and latches L connected to the electrodes 4 therein. , A plurality of logic circuits composed of gate elements G, and a plurality of switching elements composed of switching transistors TR and the like.

The shift registers SR1 to SR64 are for serially transferring the print signals (DA to DD) from the signal generating means 9 described later in synchronization with the clock signal (CLK), and the latches L1 to L64 are Latch signal (L
This is to hold the print signals (DA to DD) stored in the shift registers SR1 to SR64 in synchronization with AT).
The gate elements G1 to G64 are provided to the switching transistors TR1 to TR64 based on the logical product of the print signals (DA to DD) held by the latches L1 to L64 and the strobe signal (STB) from the selecting means 10. The gate element G, the shift register SR, and the latch L described above constitute a logic circuit.

On the other hand, the switching transistors TR1 to TR
Reference numeral 64 is connected to the electrode 4 via an output terminal H, and controls the application of electric power to each heating element group according to the output signal from the gate element G.

The thermal head 1 includes a signal generating means 9 for supplying print signals (DA to DD) to a logic circuit of the driver IC 5, a selecting means 10 for supplying a strobe signal (STB) to the logic circuit, and a latch. A signal (LAT), a control means (not shown) for supplying a clock signal (CLK) and the like are connected.

The signal generating means 9 comprises a counter 8, a comparator 11 and a gate element 12, and the counter 8 is supplied with M × N supplied from the data supplying means 7.
The number of data for driving the heating elements 2 in the image data (DATA) composed of the binary data is set for each heating element group, that is, N.
Each bit (4 bits) is counted, and a predetermined output signal is issued from P1 to P3 according to the counted value.

Further, the counter 8 stores image data (DAT
Each time (A) is input by N bits (4 bits), a reset signal is input to the terminal R and an inverted signal of the reset signal is input to the terminal S, which allows the image data (DATA) to be input.
Is reset every time N bits are input.

The output signals from the terminals P1 to P3 of the counter 8 are compared with the signals from STD1 to STD3 by the comparator 11, and when P1 and STD1, P2 and STD2, P3 and STD3 all match, the CO terminal outputs. A predetermined output signal is issued to the gate element 12, and the high level (H) is maintained until the reset signal is input.

FIG. 5 shows an example of signals input as STD1 to STD3.

In this example, STD1: STD2: STD3 is L:
When L: L, the count value is 0, when H: L: L, the count value is 1, when L: H: L, the count value is 2, and when H: H: L, the count value is 3, L: L: When H, the count value is 4. At this time, if the number of data for driving the heating element 2 in the 4-bit image data (DATA) is 1, STD1: STD2: STD3 is H: L:
When L is L, the high level (H) is output from the terminal CO. When the number of data is 2, when STD1: STD2: STD3 is L: H: L, the high level is output from the terminal CO and the number of data is 3. In this case, when STD1: STD2: STD3 is H: H: L, a high level is output from the terminal CO, and when the number of data is 4, STD1: STD2:
When STD3 is L: L: H, high level is output from the terminal CO.

Further, the gate element 12 generates an output signal based on the logical product of the output signal from the comparator 11 and the clock signal, and supplies this to the thermal head 1 as a print signal (DA to DD). At this time, the clock signal
(CLK) is synchronized when the fourth data of the four image data (DATA) continuously input from the SI terminal is input.

For example, when the print signal (DC) is generated for the image data (DATA) containing three data for driving the heating element to generate heat, as shown in the timing chart of FIG. One high level (H) signal is generated from 12. At this time, if the count value is 4, since the low level (L) is output from the CO terminal when the fourth data is input, the high level (H) signal is not output from the gate element 12. .

On the other hand, the selecting means 10 is adapted to generate N signals having different lengths, and a print signal (DA to DD) corresponding to a predetermined count value is generated from the signal generating means 9 by thermal means. When input to the logic circuit of the head 1, a strobe signal (STB) having a length corresponding to the count value is selected from the N signals and supplied to each logic circuit of the thermal head 1.

The data supplying means 7 supplies to the signal generating means 9 image data (DATA) composed of M × N pieces of binary data, that is, the same number of binary data as the heating elements 2 for each scanning line. It is for doing.

In the thermal printer of the first embodiment as described above, the N heating elements 2a to 2d forming the heating element group of the thermal head 1 are combined into one logic circuit (shift register SR, latch L, gate element). Since it is driven by G) and one switching transistor TR, the number of logic circuits and switching elements provided in the driver IC 5 of the thermal head 1 may be 1 / N of the number of heating elements, which is the same as the conventional thermal head. If the driver IC of No. 1 is used, the number of driver ICs 5 mounted on the thermal head can be reduced to 1 / N, and as a result, the thermal head as a product can be made inexpensive.

Further, in the thermal printer of this embodiment, since the number of driver ICs 5 mounted on the thermal head 1 can be reduced, each driver IC 5
The area of the driver I can be made a little larger so as not to hinder the mounting on the thermal head 1. At this time, the driver I
If the arrangement interval of the output terminals H arranged along one side of C5 is widened, the connection work becomes easy when the electrodes 4 and the output terminals H are individually connected by soldering or the like. This improves the manufacturing yield of the thermal head 1.

When printing is performed by using the thermal printer of this embodiment, the positions of the print dots formed on the thermal recording medium may be slightly displaced, but such displacement is 6 mm / dot or more. 1 with a large number of printed dots
If an extremely large print quality is not required, such as when a relatively large character of 3 mm × 3 mm or more is formed or when it is used for printing with low definition such as a printer mechanism of a facsimile, This is not a problem, and when the thermal printer of the present invention is used in the above-mentioned applications, the print quality is almost the same as that of the conventional thermal printer.

Next, the driving method of the above-mentioned thermal printer will be described with reference to the timing chart shown in FIG.

First, of the four heating elements 2a to 2d forming each heating element group, only one (2a) is driven to generate heat to form a print dot.

First, the image data (DATA) having the same number of bits as that of the heating elements 2 supplied from the data supply means 7 is modulated by the signal generating means 9 into the same number of print signals (DA) as the heating element group.

Next, the print signal (DA) is serially transferred to the logic circuit (shift register SR) of the thermal head 1 in synchronization with the clock signal (CLK).

Next, the print signal (DA) stored in the shift register SR is converted into parallel data in synchronization with the latch signal (LAT) and transferred to the latch L.

Next, a strobe signal with a pulse width of 1.2 msec
STB is input to the AND gate G, and power is applied between the electrodes 3 and 4 according to the print signal (DA) held by the latch L. At this time, only the heating elements 2a among the heating elements constituting each heating element group generate heat, and only the print dots corresponding thereto are formed on the thermal recording medium.

After that, the signal generating means 9 outputs a print signal.
(DB) to (DD) are sequentially generated, and each print signal (DB) to (DD) is supplied to the logic circuit together with the strobe signal (STB) of the length corresponding to the count value, and the same as the above cycle. By repeating the operation, 2 to 4 out of the four heating elements forming each heating element group are sequentially driven to generate heat to form print dots. As a result, a series of printed images is formed on the thermal recording medium.

(Second Embodiment) Next, a second embodiment of the thermal printer of the present invention will be described. Since the thermal printer of the second embodiment is the same as the thermal printer of the first embodiment except for the configuration and driving method other than the heating element group, the description of the same parts will be omitted.

FIG. 8 is a plan view showing a heating element group of a thermal head incorporated in the thermal printer of the second embodiment of the present invention.

The thermal printer of the second embodiment is the first
The difference from the thermal printer of the embodiment is that a high-resistance high-temperature heat generating region (N) is formed in which the N heat generating elements 2a to 2d constituting the heat generating element group of the thermal head and having different resistance values are formed with an area equal to each of them. It has a width w1 and a length l1), and the resistance values of these heating elements 2a to 2d are made different by varying the length.

The high-temperature heat-generating region is a region which generates heat at a predetermined temperature or higher at which printing dots can be formed on the thermosensitive recording medium during printing. For example, all four heat-generating elements 2a to 2d are heated to a high temperature to generate 4 When forming individual print dots, the shaded area in FIG. 8 is the high temperature heat generating area.

All the heating elements 2b-2d except the heating element 2a having the smallest resistance value among the N heating elements 2a-2d.
Is wider on both sides of the high-temperature heat generation region (width w
2: 100 μm) and low resistance low temperature heat generation area (2b: 15 μm x
2, 2c: 30 μm × 2, 2d: 45 μm × 2) are provided.

The low-temperature heat-generating region generates a little heat when power is applied during printing, but does not rise to a predetermined temperature at which the print dots can be formed.

For example, when a thermal paper which develops a color at a temperature of 120 ° C. is used as the thermal recording medium, when a predetermined electric power corresponding to the pulse width of the strobe signal is applied to the heating elements 2a to 2d, the corresponding heating element The area of the surface where the temperature is 120 ° C or higher is the high temperature heat generation area, and the area which does not reach 120 ° C is the low temperature heat generation area.

When the heating elements 2a to 2d are covered with a protective film made of silicon nitride or the like, the above-mentioned regions are determined by the temperature of the surface of the protective film with which the thermal recording medium actually contacts.

The heating elements 2a to 2d have a thickness of, for example, 0.05 μm.
If made of TaSiO ₂ of m, 2a is 90 [mu] m, 2b is 15
The length of 0 μm, 2c is 120 μm, and 2d is 180 μm. The width w1 of the heating element 2a having the smallest resistance value is 70
The length l1 is set to 90 μm and the length l1 is set so as to generate heat at a temperature necessary for forming print dots on the thermal recording medium. The width w1 of the high temperature heat generation area is set to 80% or less of the width w2 of the low temperature heat generation area.

When printing is performed by driving a thermal printer incorporating such a thermal head, it is necessary to apply printing energy of about 0.38 mJ to each of the heating elements 2a to 2d, which constitutes a heating element group. Of the heating elements 2a to 2d, the pulse width of the strobe signal is 1.2 msec to heat one (only 2a), and the pulse width of the strobe signal is 1.6 to heat two (2a and 2c). The pulse width of the strobe signal is set to 2.0 msec to heat three (2a to 2c) in msec, and the pulse width of the strobe signal is set to 2.4msec to heat all four.

In such a thermal printer, the N heat generating elements 2a to 2d having different resistance values, which form the heat generating element group of the thermal head, have high temperature heat generating regions having the same area as that of the heat generating elements. All the print dots formed on the recording medium can be made uniform and approximately the same size as the heating element 2a, and the print quality is improved.

The present invention is not limited to the above-mentioned embodiment, and various modifications and improvements can be made without departing from the gist of the present invention. For example, in the above-mentioned second embodiment, high temperature heat generation is possible. Although a wide low temperature heat generating area is provided on both sides of the area, instead of this, a wide low temperature heat generating area may be provided only on one side of the high temperature heat generating area. Has the same effect.

Further, in the thermal printer of the second embodiment, the size of the heating element 2a having the smallest resistance value among the four heating elements forming the heating element group is set to the same size as the high temperature heating area. However, instead of this, while making the heating element 2a larger than its high-temperature heating area,
A low-temperature heat-generating region wider than this may be provided on one side or both sides of the high-temperature heat-generating region. Even in such a case, the size of the high-temperature heat-generating region of each heat-generating element forming the heat-generating element group is small. As long as they are all equal, the same effect as that of the second embodiment is obtained.

[0056]

According to the present invention, the N heating elements forming the heating element group of the thermal head include one logic circuit (shift register SR, latch L, gate element G) and one switching transistor TR. Since the driving is performed by using, the number of logic circuits and switching elements provided in the driver IC of the thermal head may be 1 / N of the number of heating elements, and the number of driver ICs can be reduced to 1 / N. As a result, the thermal head as a product can be inexpensively manufactured.

Further, according to the present invention, since the N heat-generating elements have high-temperature heat-generating areas of the same area, all the print dots formed on the thermal recording medium are substantially equal. The print quality can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a thermal printer of the present invention.

FIG. 2 is a circuit diagram showing an electrical configuration of a thermal head incorporated in the thermal printer of FIG.

FIG. 3 is a partially enlarged plan view of the thermal head of FIG.

FIG. 4 is a circuit diagram showing an electrical configuration of a signal generating circuit incorporated in the thermal printer of FIG.

FIG. 5 is a diagram showing an example of signals input as STD1 to STD3 and signals output from a CO terminal.

FIG. 6 is a timing chart showing the operation of the signal generating circuit.

FIG. 7 is a timing chart showing the operation of the thermal printer of the present invention.

FIG. 8 is a plan view showing a heating element group of a thermal head according to a second embodiment of the thermal printer of the present invention.

FIG. 9 is a diagram showing a configuration of a conventional thermal printer.

FIG. 10 is a circuit diagram showing an electrical configuration of a thermal head incorporated in a conventional thermal printer.

FIG. 11 is a circuit diagram showing an electrical configuration of a driver IC.

FIG. 12 is a timing chart showing the operation of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermal head 2a-2d ... Heating element 3, 4 ... Electrode 5 ... Driver IC 7 ... Data supply means 8 ... Counter 9 ... Signal generation circuit 10 ... Means of selection

Claims (2)

[Claims] 1. A group of M (M is a natural number of 2 or more) heating elements having a pair of electrodes connected to N (N is a natural number of 2 or more) heating elements having different resistance values. A heating element array, data supplying means for supplying image data composed of M × N binary data, and the number of data for driving the heating elements based on the image data from the data supplying means for each heating element group. A signal generating means for counting and generating a print signal corresponding to the counted number of data, and N strobe signals having different pulse widths, and strobes having a predetermined pulse width based on the print signal from the signal generating means. A selection means for selecting one signal, a print signal from the signal generation means and a strobe signal selected by the selection means are supplied, and M logics which output an output signal based on a logical product of the both. Thermal printer comprising a road, and a driver IC with M switching elements to control the application of power to the heating element groups in accordance with the output signal from the respective logic circuits. 2. The thermal printer according to claim 1, wherein the N heat generating elements having different resistance values have a high temperature heat generating area having the same area as each of the N heat generating elements.