JPH02269064A - Thermal head - Google Patents

Abstract

PURPOSE:To suppress the effects of thermal interference between adjacent heat generating elements by controlling a driving means so that a driving time for one of a plurality of heat generating elements does not overlap with that for the adjacent heat generating element. CONSTITUTION:Strobe gates Gno with output values brought to a level 1 drive drivers DRno corresponding respectively to the strobe gates Gno, whereby heat generating elements Hno corresponding respectively to the drivers DRno are driven to generate heat. Printing is conducted by controlling a driving IC 4 by a controlling circuit so that a strobe signal B at the level 1 is not inputted to a strobe signal input terminal SB while a strobe signal A at the level 1 is inputted to a strobe signal input terminal SA. When the inputting of the strobe signal A to the input terminal SA is finished, strobe gates Gne with output values brought to the level 1 drive drivers DRne corresponding respectively to the strobe gates Gne, whereby heat generating elements Hne corresponding respectively to the drivers DRno are driven to generate heat. It is thereby possible to suppress the effects of thermal interference.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a thermal head, and particularly to a thermal head equipped with a drive circuit that can minimize the influence of thermal interference between adjacent heating elements. It is.

[Conventional technology]

FIG. 2 is a block diagram of a conventional thermal head.

In the figure, 1 is a shift register composed of 64 bit cells, and power is supplied through a power supply terminal Vt1D.

A latch 2 reads the print information in the shift register 1 in parallel, and has a capacity of 64 bits, which is the same as that of the shift register 1.

61 to G64 (hereinafter collectively referred to as rG and J. However,
n=1, 2.3...64° or less, the same. ) is a strobe gate that performs an AND operation between the print information value read into the latch 2 and the strobe signal value.

DR1 to DRo (hereinafter collectively referred to as "DRfi").

) is a driver that drives a heating element, which will be described later, according to the output value of the strobe gate G, and generally uses a transistor. A strobe signal for controlling the driver DRII is supplied to the strobe signal input terminal S.
is input through one strobe line.

Reference numeral 3 designates a driving IC in which the driver DR, strobe gate G, latch 2, and shift register 1 described above are integrated into one.

H1 to H64 (hereinafter collectively referred to as rH, J) are heating elements driven by drivers DR, .

The main components of the thermal head are the driving IC 3 and the heating element H. A plurality of drive ICs 3 are mounted in parallel on the thermal head corresponding to the plurality of heat generating elements Hn arranged (here, one for 64 heat generating elements).

Next, the printing operation of the thermal head having the above configuration will be explained.

The 64-bit print information is serially input into the shift register 1 bit by bit through the print information input terminal in synchronization with a clock signal input from the clock signal input terminal C. (After printing is completed, the print information in shift register 1 is serially output from print information output terminal 0.) After 64 bits of print information is input into shift register 1, a load signal is output from load signal input terminal. , the print information in shift register 1 is read into latch 2 at once in parallel.

Then, the strobe signal is input to the strobe signal input terminal S, and the strobe gates G, . . . perform an AND operation between the print information value in the latch 2 and the strobe signal value.

For example, when the print information value in latch 2 corresponding to strobe gate G1 is level 1 and the strobe signal value is level 1, the output value of strobe gate G is level 1 and driver D R1 is in the ON state. Become. At this time, a current flows through the heating element H1 from a power source (not shown) to generate heat and print. Further, even when the strobe signal value is level 1, when the print information value in latch 2 corresponding to strobe gate G is level O, the output value of strobe gate G becomes level O, and driver DR1
is in an OFF state, and no current flows through the heating element H1. At this time, the heating element H□ does not generate heat and no printing is performed.

[Problem to be solved by the invention]

However, in the conventional thermal head described above, depending on the value of the print information, a certain heating element and an adjacent heating element may generate heat at the same time to perform printing.

For example, if we look at adjacent bit cells in a shift register, if the printed information values input to these adjacent bit cells are all level 1, then the adjacent bit cells that are driven corresponding to the adjacent bit cells in the shift register will The heating element generates heat at the same time as printing. In this case, the heat generated by adjacent heating elements interferes with each other, resulting in a higher temperature than when each heating element generates heat individually.

As a result, the print density may become darker in some areas, causing uneven print density, or the temperature may become too high, causing bleeding between adjacent print dots and making the boundaries between print dots unclear. There were problems that degraded quality.

In other words, even though a certain amount of printing energy is applied to each heating element, the printing density and printing resolution of each heating element fluctuate, making it difficult to obtain stable printing quality, especially for photographs that require high printing quality. When applied to transmission, imprint transmission, gradation printers, etc., there is a problem in that a sufficiently satisfactory density expression cannot be obtained.

Therefore, the present invention has been made to solve the problems of the prior art as described above, and its purpose is to:
It is an object of the present invention to provide a thermal head that can stabilize print density by suppressing the influence of thermal interference between adjacent heating elements as much as possible, and can obtain excellent print quality such as high print resolution.

[Means to solve the problem]

A thermal head according to the present invention includes a plurality of heating elements arranged adjacent to each other in a line, and a driving means for independently driving the plurality of heating elements.
The driving means is controlled so that the driving time of one of the plurality of heating elements does not overlap with the driving time of at least one of the heating elements adjacent to the heating element.

[Effect]

In the thermal head of the present invention, among the plurality of heating elements arranged in adjacent rows, for example, the even-numbered heating elements and the odd-numbered heating elements are separately driven so that they do not generate heat at the same time.

In this way, since one heating element and at least the adjacent heating element are controlled not to be driven within the same time,
The influence of thermal interference generated between adjacent heating elements can be suppressed to a small level.

〔Example〕

The present invention will be explained below with reference to the drawings.

FIG. 1 is a block diagram of a thermal head according to an embodiment of the present invention. Components that are the same as those of the conventional example are designated by the same reference numerals as those of the conventional example, and the description thereof will be omitted, and the characteristic portions of the present invention will be described below.

In FIG. 1, 4 is a driving means (hereinafter referred to as "driving ICJ") in which a driver DR, a strobe gate G, a latch 2, and a shift register 1 are integrated into one.

Further, in this embodiment, two strobe wires are provided, and each strobe wire is connected to an odd-numbered heating element H1° (no is an odd number).

same as below. ) for driving the driver DRf1. and a driver DR, which drives an even-numbered heating element H7, (ne is an even number. The same applies hereinafter).

Therefore, the heating element Has is driven by the strobe signal A input from the strobe signal input terminal SA which is the terminal of one strobe line, and the heating element H7 is driven by the eight strobe signal input terminals which are the terminals of the other strobe line. It is driven by strobe signal B input from

Next, the operation of the thermal head of this embodiment will be explained.

FIG. 3 is a time chart for explaining the operation of the driving IC 4. FIG.

In the figure, T indicates the period of strobe signal A and strobe signal B. Further, the numbers 1 and O given in the figure mean the level values of the signals.

As in the case of the conventional example, 64 bits of print information is serially input into the shift register 1 through the print information input terminal while being synchronized with the clock signal. Thereafter, when a level 1 load signal is input into the latch 2 through the load signal input terminal, the print information in the shift register 1 is read into the latch 2 at once in parallel.

Next, the strobe signal A at level 1 is input to the strobe signal input terminal SA, and each strobe gate G7° outputs the print information value in the latch 2 corresponding to these strobe gates G7° and the value to the strobe signal. Performs a logical AND operation.

As a result, the output value of the strobe gate G becomes level 1. are drivers DR, corresponding to these strobe gates G7°. to drive. The heating elements H7° corresponding to these drivers DR, . generate heat.

In this embodiment, as shown in FIG. 3, the level 1 strobe signal A is sent to the strobe signal input terminal SA.
While the strobe signal B at level 1 is input to the strobe signal input terminal S, the driving IC 4 is controlled by a control circuit (not shown) so that printing is performed.

When the level 1 strobe signal A is input to the strobe signal input terminal Sλ, the strobe signal input terminal S,
Strobe signal B at level 1 is input to each strobe gate G1. are these strobe gates Gf
The print information value in the latch 2 corresponding to i and the strobe signal B are ANDed. As a result, the strobe gate Gas whose output value becomes level 1 drives the drivers DR, , corresponding to them, and the heating elements Hn, corresponding to these drivers DRfi, start generating heat.

Then, while the level 1 strobe signal B is input to the strobe signal input terminal SR, the drive IC 4 is controlled by a control circuit (not shown) so that the level 1 strobe signal A is not input to the strobe signal input terminal SA. Then, printing is performed.

Strobe signal A and strobe signal B at level 1 are repeatedly input to strobe signal input terminal SA and strobe signal input terminal SB at period T, and printing for 64 bits in shift register 1 is performed by inputting this - period. .

A plurality of driving ICs 4 are mounted in parallel on the thermal head in correspondence with a plurality of arranged heating elements Hl (in this case, one for 64 heating elements), so each driving IC 4 is mounted in parallel on the thermal head. The strobe signal A at level 1 is simultaneously input to the strobe signal input terminal SA in each of the driving ICs 4 and 4, respectively.
At the same time, a strobe signal B of level 1 is input to perform printing.

In this way, in this embodiment, in the plurality of heating elements H1 arranged in a row adjacent to each other, the adjacent heating elements H7 are controlled so as not to generate heat at the same time. To improve printing quality without causing uneven printing density due to mutual interference of heat generated when printing dots generate heat at the same time, or blurring between adjacent printing dots and making the boundaries between printing dots unclear. was completed.

FIG. 4 is a block diagram of a thermal head according to another embodiment of the present invention.

In this figure, the same components as those in the embodiment shown in FIG. 1 described above will be described with the same reference numerals.

In the embodiment shown in FIG. 4, the driving IC 5 connects the strobe line to
This arrangement differs from the embodiment shown in FIG. 1 in that separate strobe signals can be input to each.

That is, in the embodiment shown in FIG. 4, each of the four strobe lines receives a strobe signal) G4- (where m=1.2
．． 3-・-・16° and below are the same. ), Ga5-t, 04
m-2 and Gaza-s are connected, and each strobe gate is connected to a driver DR, , DR4-1, D
R4m-2 and DR4m-1, and each driver also has four heating element groups H4+m, 84m-
1,84m-2 and H, , are connected.

Each strobe line has a strobe signal w, x.
SySz is the strobe signal input terminal SW%S,,5YS
are input separately through S.

A control circuit (not shown) controls other heating element groups not to be driven while the - heating element group is being driven.

For example, while the level 1 strobe signal W is being input to the strobe signal input terminal Sv, the level 1 strobe signal is controlled not to be input to the other three strobe signal input terminals 5x1SY and G2, and the level While one strobe signal X is input to the strobe signal input terminal Sx, the other three strobe signal input terminals 5
The level 1 strobe signal is controlled not to be input to WSSY and G2, and the level 1 strobe signal Y
is input to the strobe signal input terminal SY,
The other three strobe signal input terminals S'sSx and G
2 is controlled so that the level 1 strobe signal is not input to the strobe signal Z, and while the level 1 strobe signal Z is input to the strobe signal input terminal S2, the other three strobe signal input terminals S'91 and SX and level 1 for SY
Input the strobe signal and control it accordingly.

In this way, each strobe signal w, xSy and Z
The heating element H41, -1, H4, -
, and H4a- are driven at different times.

As a result, not only the heating elements on both sides but also the heating elements connected to the heating elements on both sides are prevented from overlapping in drive time, which further reduces the mutual interference of heat generated by adjacent heating elements. can.

It should be noted that the configuration and functions other than those described above are the same as those of the present embodiment shown in FIG. 1, so their explanation will be omitted.

Further, in the above embodiment, the case where the number of heating element groups driven simultaneously is 2 or 4 has been described, but the present invention is not limited to this, and the number of heating element groups driven simultaneously is The optimum number may be determined based on the printing speed required of the thermal printer, the power supply capacity for supplying power to the heating element, etc.

〔Effect of the invention〕

As explained above, according to the present invention, among a plurality of heating elements arranged adjacently in a line, one heating element and at least the adjacent heating element are controlled so as not to generate heat within the same time. , it is possible to minimize the effects of thermal interference that occurs between adjacent heating elements, and the boundaries between prints are unclear due to uneven print density and bleeding between adjacent print dots that occur in the past. We were able to improve the print quality without any problems.

Further, according to the present invention, since stable printing quality can be obtained, it is possible to fully satisfactorily apply the invention to photo transmission, imprint transmission, gradation printers, etc., which particularly require high printing quality.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the thermal head of this embodiment, Fig. 2 is a block diagram of a conventional thermal head, Fig. 3 is a time chart showing the operation of the driving IC 4, and Fig. 4 is another embodiment. FIG. 2 is a block diagram of a thermal head of FIG. 1...Shift register, 2...Latch, DR, ~DRaa...Driver 01-G64...Strobe gate, H1-H64.
・Heating element,

Claims (1)

[Scope of Claims] A thermal head having a plurality of heating elements arranged adjacent to each other in a line and driving means for independently driving the plurality of heating elements, wherein one of the plurality of heating elements The thermal head is characterized in that the driving means is controlled so that the driving time of one heating element and the driving time of at least one heating element adjacent to the one heating element do not overlap.