JPH01130961A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a low cost thermal head by setting the second potential to a value which is 0.7 time or less the first potential, the third potential to a value as an intermediate potential between! the first and second potentials, and the fourth potential to a value which is less than the second potential. CONSTITUTION:When two common electrodes are provided, the common elec trode 9-1 can select either one of voltages Vo or (2<1/2>-1)Vo by means of a switch 10-1, and the common electrode 9-2 by means of a switch 10-2. The selected either one of the third potential 2<1/2> Vo/2 and the fourth potential 0 V is applied to discrete electrodes 8-1, 8-2,...selected by a drive IC 11. The electric power generated in each thermal resistor 1-1, 1-2,... is such that while the power of a thermal resistor for printing is 1, those of other thermal resistors are 0.17 or 0.085. In this way, the power of the non-selected thermal resistor is 0.5 or less against an effective color developing power. Therefore, a printing error due to a roundabout current can be prevented and therefore, no diode need be provided. Subsequently, a thermal head can be realized at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a thermal head used in printers, facsimile machines, and the like.

(Prior art) In a thermal head, a plurality of heating resistors are arranged in a row on an insulating substrate or a substrate in which a conductor is coated with an insulating material, and the heating resistors are arranged as required according to input data. The drive is controlled so that the heating resistor generates heat when energized.

There are two drive methods: the diode matrix method shown in Fig. 11 and the one-to-one drive method shown in Fig. 12.
There are different types.

In FIG. 11, 1-1.1-2. . . . is a heat generating resistor, and a plurality of them are divided into groups. In the case shown in the figure, six heating resistors form one group. The heating resistors (for example, 1-1 to 1-6) belonging to the same group have one end commonly connected to the electrode 2-1, and the other end connected to different t-poles 3-1 to 3-6.

In the diode matrix method, diodes 30-1, 30-2. ·····is necessary.

In the case of the one-to-one drive system in Fig. 12, the heating resistor 1-1
．． 1-2. . . . One end is connected to the common electrode 2a, and the other end is connected to the driving ICs 4-1, 4-2, . Therefore, the number of driving ICs increases and the cost increases.

Although FIG. 13 shows a matrix type, it is a driving method that does not use a diode (see Japanese Patent Laid-Open No. 119946/1983).

In Figure 13, heating resistors 5-1.5 connected in series
-2. A voltage Vo or Vo/3 is selected and applied to one end of each of the heating resistors 5-1.
5-2. . . . 2Vo/3 or 0 volt is selected and applied to the other end. As a result, a voltage Vo is applied to the heating resistor to be printed.
A voltage of Vo/3 is applied to the other heating resistors. Since there is a nine-fold difference in power, it is possible to distinguish between a heating element intended for printing and a heating element for which printing is not intended.

However, in the method shown in FIG. 13, since current also flows through the heating resistors that are not printed, the reactive power increases on average, and as the number of heating resistors to be printed decreases, the reactive power increases. Therefore, it is disadvantageous in terms of power when transmitting a facsimile document that generally has many blank areas.

(Objective) It is an object of the present invention to provide a low-cost thermal head that reduces the number of driving ICs and does not include a diode for preventing sneak current.

(Structure) The thermal head of the present invention includes a plurality of heating resistors arranged in a row, a common electrode in which one end of each heating resistor is connected to one of the plurality of heating resistors, and a different common electrode. Select one of the individual electrodes connected to the other end of the adjacent heating resistor and the common electrode according to a predetermined order and set it to the first potential, and set the other electrode to the first potential. a common electrode selection means for setting the common electrode to a second potential; and an individual electrode selection means for setting the individual electrode to a third potential or a fourth potential according to input data; is 0.7 times or less than the first potential, the third potential is an intermediate potential between the first potential and the second potential, and the fourth potential is the second potential.
The potential is set below the potential of

Examples will be specifically described below.

FIG. 1 shows an embodiment in which the present invention is applied to a case where there are two common electrodes.

Heating resistors arranged in a row 1-1.1-2°...
... are alternately connected to the first common electrode 9-1 and the second common electrode 9-2. The lower ends of the adjacent heating resistors are commonly connected to individual electrodes 8-1, 8-2, . . . and led to the driving ICI 1, and each two adjacent heating resistors are connected to the driving ICI 1. They are selected simultaneously by ICI 1.

The common electrode 9-1 can select either the first potential Vo or the second potential (2'/2-1) Vo by the switch 10-1, and the common electrode 9-2 can select the first potential Vo or the second potential (2'/2-1) Vo by the switch 10-1. -2 by voltage vO or (21/2-1)V
You can select either o. Switches 10-1 and 10-2 correspond to common electrode selection means.

Individual electrode 8-1 selected by driving ICI 1.
8-2. . . . has a third potential 2 ”2Vo/
A second or fourth potential of 0 volts is selectively applied.

The driving ICI 1 corresponds to individual electrode selection means.

In this embodiment, each heating resistor 1-1. l-2゜...
Figure 2 shows the power generated in... If the power of the heating resistor for printing is 1, the power of the other heating resistors is 0.17 or 0.085. In this way, since the power of the non-selective heat generating resistor is 0.5 or less with respect to the effective coloring power, it is possible to prevent incorrect printing due to a bypass current, and there is no need to provide a diode.

Comparing the case of Fig. 1 and the conventional case shown in Fig. 13 for a B4 size thermal head with 2048 bits, in Fig. 13, the reactive power when printing n bits is Vo'' /R (R is the resistance of one heating resistor) is (2048-n)/9.In the example shown in Figure 13, printing must be done four times in order to print one row. This corresponds to four divisions, and therefore the reactive power is also four times that amount, which is −0.44n+910.2.The symbol 12 in FIG. 3 is the reactive power in the case of FIG.

On the other hand, the reactive power of the embodiment shown in FIG. 1 is 348, and the 3rd
As shown by symbol 13 in the figure, the reactive power in the conventional case is smaller than that in the conventional case, and in particular, the smaller the number n of black bits is, the larger the reactive power in the conventional case is.

FIG. 4 shows an embodiment in which there are four common electrodes.

One of the common electrodes 15-1 to 15-4 is selected and the first potential Vo is applied to it, and the second potential Vo/3 is applied to the other common electrodes. Further, four adjacent heat generating resistors connected to different common electrodes 15-1 to 15-4 are simultaneously selected by the driving ICI 1, and the third potential Vo/2 or the fourth potential 0 volt is selected. applied.

As a result, if the power of the heating resistor to be printed is 1, the power of the other heating resistors is 1/4.1/9 or 1/3.
It is 6.

When the reactive power of the embodiment shown in FIG. 4 is calculated in units of Vo2/R, it is 683, which is indicated by the symbol 14 in FIG. In this case as well, the reactive power is smaller than in the conventional case, especially in a region where the number n of black bits is small.

As can be seen from these embodiments, the reactive power is generally lower than that of the conventional method when transmitting a facsimile document with many blank areas. and 2 common electrodes, 4
The number of driving ICs 11, which account for a considerable part of the direct material cost, can be reduced to 1/2 or 1/4 by
．． . . . and also eliminates the need for a diode array for preventing wraparound, which reduces the cost of the thermal head.

FIG. 5 shows a third embodiment.

Heat generating resistor 1-1.1-2. ... One end is connected to either of the two common electrodes 9-1.9-2, and the adjacent heating resistor is connected to a different common electrode 9-1.9-2. I for driving by respective common individual electrodes
Connected to C17.

The common electrode 9-1 is connected to (21/
2-1) Vo or 0 volts is applied and the switch 16-
2, Vo or 0.7 Vo is applied. The other common electrode 9-2 is connected to (21/2) by a switch 16-3.
-1) Vo or 0 volts is applied and switch 16-4
Vo or 0.7 Vo is applied. On the other hand, drive ICI 7 is off (undefined state), 0 volts, 2'/2
Four states can be selected: Vo/2 or 0.15VO. In this way, the common electrode 9-1, 9-2 can select any of the four potentials, and the individual electrodes can also have four potentials.
One of two potentials can be selected.

In this embodiment, the potentials of the common electrode and the individual electrodes are determined by the number n of heating elements printed at one time.

FIG. 6 shows a circuit configuration for realizing the embodiment of FIG. 5.

In the embodiment of FIG. 5, the heating resistors 1-1.1-2. ... is divided into two groups, so the input data is divided into odd and even numbers, and the number of blacks to be printed in each is counted by the counter 18.
Count by Input data is input to the shift register 19 in the driving ICI 7 and stored in the latch circuit 20. The input data in the latch circuit 20 is selected depending on whether it is an odd number or an even number by a switch 21 that selects an odd number or an even number.
1.1-2. Power is applied to... At this time, the voltage of the power supply 24 is selected via the power supply controller 23 according to the count value of the counter 18.

Divide the range of the black number n into three as shown in Figure 7 (A) to Figure 7 (C), and set the voltage applied to the common electrode and individual electrode in each case as shown in Figure 7. do. This voltage setting is automatically performed according to the count value of the counter 18.

In either case, assuming that the power of the heating resistor that performs printing is 1, the reactive power of the non-selected heating resistor is 0.5 or less, and printing by thermal paper or thermal transfer paper can be suppressed.

The reactive power in cases from Figure 7 (A) to Figure 7 (C) is Vo2
Expressed in units of /R, in order: (A) 0.888n+9
4.2 (B)348 (C)-n+1024. These are represented in FIG. 8 as 25A, 25B, and 25C. Both are smaller than the reactive power (symbol 12) in the conventional case shown in FIG.

FIGS. 9(A) to 9(C) show an embodiment in which the number of common electrodes is four.

Depending on the range of n, the voltage applied to the four common electrodes is Vo,
Either 0.7Vo, Vo/3 or O, and the voltage applied to the individual electrodes is 0.8Vo, 0.7Vo, Vo/2.0.
Either. Depending on which of the three ranges n is in between 0 and 512, the reactive power in each case is (A) 5.6 n+143.4 (B) 683 (C) −6,24n+3194.8. These are shown in FIG. 10 as 26A, 26B, and 26C.

In this case as well, the reactive power is smaller than the conventional reactive power (symbol 12) in FIG.

In the embodiments shown in FIGS. 7 and 9, the reactive power is smaller than that of the conventional example, especially at both ends of the region where the number n of heating elements to be printed is small and the region where it is large. This means that the present invention is more advantageous when transmitting a facsimile document with many blank spaces, for example, and is also advantageous when transmitting all-black documents, such as when drawing lines on a table.

(Effects) The thermal head of the present invention divides the heating resistor array by a common electrode and individual electrodes, sets the common electrode to the first potential or the second potential, and sets the individual electrodes to the third potential or the fourth potential. In addition, since the relationship between the first potential and the fourth potential is maintained at a predetermined relationship, reactive power can be reduced compared to the conventional one, which is advantageous in reducing power consumption.

In addition, by providing a plurality of common electrodes, the number of driving ICs can be reduced in inverse proportion to the number of common electrodes, and the cost of driving ICs, which directly occupy a considerable portion of the materials, can be reduced. Moreover, since a diode for preventing a sneak current is not required, the thermal head can be realized at a low cost.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment, Fig. 2 is a diagram showing power of the same embodiment, Fig. 3 is a diagram showing reactive power in the embodiment and the conventional case, and Fig. 4 is another embodiment. Figure 5 shows the power consumption of
The figure is a circuit diagram showing still another embodiment, FIG. 6 is a block diagram showing a control circuit in the embodiment of FIG. 5, and FIG. 7 (A)
(C) is a diagram showing the power consumption of the embodiment of FIG.
FIG. 8 is a diagram showing the reactive power in the embodiment shown in FIG. 5 and the conventional case, FIGS. FIG. 9 is a diagram showing reactive power in the embodiment and the conventional case, and FIGS. 11, 12, and 13 are circuit diagrams showing conventional thermal heads, respectively. 1-1.1-2...; heating resistor, 8-1.8
-2...Individual electrode, 9-1.9-2.15-1
~15-4・Old・・Common electrode, 10-1.10-2.16-1～16-4・・・・
a common electrode selection means switch;

Claims (1)

[Claims] (1) A plurality of heating resistors arranged in a row, a common electrode in which one end of each heating resistor is connected to one of the plurality of heating resistors, and adjacent heating resistors connected to different common electrodes. Select one of the individual electrodes connected together to the other end of the resistor and the common electrode according to a predetermined order, and
common electrode selection means for setting the potential of the individual electrode to a third potential or a fourth potential according to input data; and individual electrode selection means for setting the individual electrode to a third potential or a fourth potential according to input data. the second potential is 0.7 times or less than the first potential, the third potential is an intermediate potential between the first potential and the second potential, and the fourth potential is A thermal head that is at or below a second potential.