JPH10272798A - Thermal head - Google Patents

Abstract

(57) [Problem] To continuously form a printing pattern including a ruled line, the life of a specific heating element frequently used has been destroyed in an extremely short time. A plurality of heating elements (R1) arranged linearly.
Rn and the same number of shift register cells S1,..., Sn as the heating elements R1 to Rn are connected in series, and one line of the print data is stored in one of these shift register cells.
By sequentially inputting the print data bit by bit and serially transferring the print data among the shift register cells S1,.
Shift registers S1 to Sn stored in 1,..., Sn,
A plurality of switching elements A1 to An for controlling energization to the respective heating elements R1 to Rn based on the print data in the shift register cells S1,..., Sn; A thermal head is constituted by a selection circuit B for selecting a shift register cell for inputting print data for a line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a thermal head incorporated as a printer mechanism such as a point-of-sale information system (POS), a cash register (ECR), a barcode printer, and a ticketing machine.

[0002]

2. Description of the Related Art A conventional thermal head comprises a plurality of heating elements arranged in a straight line and a driver IC for controlling the heat generation of these heating elements. A platen roller is opposed to such a thermal head. By causing the plurality of heating elements to selectively generate Joule heat while transporting the recording medium sequentially in a direction orthogonal to the heating element row of the thermal head by the rotation of the platen roller, and transmitting this to the recording medium. I try to do thermal recording.

A driver IC for the thermal head
A plurality of shift register cells and switching elements corresponding one-to-one with the heating elements are provided therein, and one line supplied from the printer main body by a shift register in which the shift register cells are connected in series. The print data is sequentially input one bit at a time to the first shift register cell, and serially transferred between the shift register cells to store the print data in each cell, and the switching element stores the print data in the shift register cell. The power supply to each heating element is controlled based on the stored print data.

When the above-described thermal head is incorporated as a printer mechanism such as a POS or an ECR, the thermal head may be used to form a print pattern including a ruled line in a conveying direction of a recording medium such as a table or a graph. Many,
When such a printing operation is repeatedly performed, a specific heating element must be heated each time to print a ruled line, and there is a large difference in the frequency of use between such a heating element and other heating elements. I can do it. For this reason, some of the frequently used heating elements are destroyed in a very short time, and the thermal head has to be replaced even though many usable heating elements remain.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and a thermal head according to the present invention comprises a plurality of linearly arranged heating elements and the same number of shift elements as the heating elements. Register cells are connected in series, and one line of print data is stored in one of these shift register cells.
A shift register that sequentially inputs the print data bit by bit and serially transfers the print data between shift register cells to store each print data in a predetermined shift register cell; and generates a heat based on the print data in the shift register cell. A plurality of switching elements for controlling energization of the elements;
A selection circuit for selecting a shift register cell for inputting print data for a line, and transporting the recording medium by selectively heating the heating elements while transporting the recording medium in a direction orthogonal to the row of heating elements. When a print pattern including ruled lines in a direction is formed, a shift register cell selected by the selection circuit is periodically switched.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing one embodiment of a thermal head according to the present invention, wherein R1 to Rn are heating elements, S1
Sn is a shift register, A1 to An are switching elements, and B is a selection circuit.

The thermal head shown in FIG. 1 has a plurality of heating elements R1 to Rn and a plurality of switching elements A1 to An.
, A plurality of latch circuits L1 to Ln, and a shift register S
1 to Sn and a selection circuit B.

The heating elements R1 to Rn are linearly attached and arranged at a linear density of 160 to 600 dpi on the upper surface of an insulating substrate made of, for example, alumina or the like. The switching element A1 is made of an electric resistance material such as tantalum nitride.
When power from an external power supply is applied through ~ An or the like,
The temperature required to form a print on the recording medium, for example, 15
It acts to generate heat at a temperature of 0 to 350 ° C.

On the other hand, the switching elements A1 to An,
The latch circuits L1 to Ln, the shift registers S1 to Sn, and the selection circuit B are provided in a predetermined driver IC and mounted on the above-mentioned insulating substrate.

The switching elements A1 to An are provided in one-to-one correspondence with the heating elements R1 to Rn, and each of the heating elements R1, R2, based on print data in shift registers S1 to Sn described later. .., Rn is controlled. Note that such switching elements A1 to A1
An is composed of an AND gate and a NAND gate.

The shift registers S1 to Sn in the driver IC are formed by serially connecting the same number of shift register cells S1, S2,..., Sn as the heating elements R1 to Rn. S2, ..., S
n, one line of print data supplied from the printer main body is input to one of the n bits in order in synchronization with a clock signal, and the print data is serially transferred between shift register cells. The data is stored in predetermined shift register cells S1, S2,..., Sn. In the present embodiment, latch circuits L1, L2,... For temporarily storing print data are provided between the shift register cells S1, S2,. , Ln, and when a latch signal from the printer body is supplied to each of the latch circuits L1, L2,..., Ln, the print data in the shift register cells S1, S2,. To the switching elements A1, A2,..., An.

The driver IC further has a selection circuit B at a stage preceding the shift registers S1 to Sn for selecting a shift register cell to which one line of print data is inputted.

The selection circuit B includes, for example, an AND gate,
An OR gate, an inverter, and the like are combined, and the heating elements R1 to Rn are selectively individually heated while transporting the recording medium in a direction orthogonal to the row of heating elements, and include ruled lines in the transport direction of the recording medium. When forming a print pattern, a shift register cell to be selected is periodically switched based on a selection signal from the printer body. For example, as shown in FIG. 2, when a ruled line in a print pattern is formed by two adjacent print dots, print data for one line is stored in the shift register cell S.
The switching operation is performed such that one or two shift registers S1 subsequent to S1 are input from the shift register cell S3.

As described above, in the thermal head of the present embodiment, the selection circuit B for selecting a shift register cell to which one line of print data is to be input is provided at a stage preceding the shift registers S1 to Sn. The shift register cell selected by the printer is switched periodically based on a selection signal from the printer body, etc., so that thermal patterns can be used to form print patterns including ruled lines in the transport direction of recording media such as tables and graphs. When the head is used, the heating elements used to print the ruled lines are changed every page or every several pages, so that the Joule heat can be prevented from being concentrated on a specific heating element. As a result, the frequency of use of the heating elements can be leveled, and the life of the thermal head can be extended.

Next, using the above-described thermal head, FIG.
The printing operation for forming such a printing pattern will be described with reference to the timing chart of FIG.
Note that, in the present embodiment, a case where three printing patterns (first to third pages) are continuously formed on a recording medium while the heating elements used for printing ruled lines are changed every page. Will be described.

First, the first recording medium is conveyed to a position above the row of heating elements, and printing of the first line of the first page is performed. First page first
In the line printing operation, first, a high-level selection signal is supplied from the printer body to the selection circuit B, and the shift register cell for inputting the print data for one line is set to S1. Next, the print data of the first line of the first page is input to the shift register cell S1 in synchronization with the clock signal, and the input print data is serially transferred between the shift register cells. Stores the print data of the line.

Next, a latch signal is supplied from the printer body to the latch circuits L1, L2,..., Ln, and the print data in the shift register cells S1, S2,.
1, L2,..., Ln, the outputs from the latch circuits L1 to Ln and the strobe signal from the printer main body are supplied to the switching elements A1 to An, respectively. During the supply, printing of the first line of the first page is performed by selectively generating Joule heat individually.

Subsequently, the printing medium is conveyed by one line in a direction orthogonal to the row of heating elements, and printing is performed on the second line of the first page. The printing operation of the second line is basically performed in the same procedure as the printing of the first line described above, and thereafter, the same printing operation is repeated up to the k-th line (k is the number of lines of one page). First print pattern (page 1)
Is formed. Here, the print data for one line used for forming the print pattern is, when these are arranged in the order of input to the shift registers S1 to Sn, the j-th and j + 1-th (j is a natural number of 3 or more) of each line. ) Is data indicating that the heating element is energized, so that the heating element R1
When printing is performed by transporting the recording medium in a direction perpendicular to the row of heating elements while sequentially generating heat for each line, a ruled line is printed in the transport direction of the recording medium.

After completing the first printing operation period for forming the first printing pattern in this way, a printing suspension period comes next. During this printing suspension period, all the heating elements R
1 to Rn are not heated, and only the conveyance of the recording medium is performed. During this time, the selection signal is inverted from the high level to the low level, and the shift register cell to which the print data for one line is input is changed. Switch from S1 to S3.

Next, the second recording medium is conveyed to a position above the row of heating elements to print the first line of the second page. The printing operation of the first line of the second page is different from that of the first page in that the printing data of one line is input to the shift register cell S3. A part of the shift register (S3 to S3) is input to the shift register cell S3 in synchronization with the clock signal and serially transferred between the shift register cells S3 to Sn.
Sn). At this time, of the print data for one line, the first and second data are not erased, and the (n-1) -th and n-th data are stored in the shift register cells S3, S4 and S1. , S2 are overlapped, but usually, an area of about 3 mm on both sides is a blank area, so that unnecessary prints are not formed or necessary prints are not formed. .

Next, the print data in the shift registers S1 to Sn is taken into the latch circuits L1 to Ln in accordance with the latch signal from the printer main body, and the first line of the second page and the first line of the second page are processed in the same manner as the print operation of the first page. Perform printing. Here, the heating elements used to print the ruled lines of the print pattern of the second page are different from those used in the printing of the first page, and the same heat generating element is used to print the ruled lines over two pages. It is not used continuously.

Thereafter, the above-described printing operation for the first line of the second page is sequentially repeated until the k-th line, thereby completing a second printing operation period for forming a printing pattern for the second page. After the pause period, the operation proceeds to the printing operation period for the third page. Note that the printing operation of the third page is basically performed in the same manner as the printing operation of the first page, and thus the description thereof is omitted.

When three print patterns are successively formed as described above, the odd-numbered print patterns (first
Page, page 3) and the even-numbered print pattern (page 2) have slightly different positions of the ruled lines.
In the case of a thermal head of dpi, the deviation is about 0.3 mm, and the entire print pattern is shifted sideways, so that the contents of tables and graphs formed as print patterns are particularly difficult to see. However, it can be said that there is no problem in checking the contents.

The above-described thermal head of the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.
For example, in the thermal head of the above embodiment, the print data is shifted by 2 bits, but the number of bits to be shifted may be set according to the width of the ruled line.
As long as the same heating element is not used for printing ruled lines when the printing data is shifted, it may be 1 bit or 3 bits or more.

In the thermal head of the above-described embodiment, the shift register cell for inputting print data is switched for each page by using the selection circuit B in the description of the print operation. The switching may be performed for each page.

Further, in the thermal head of the above embodiment, a latch circuit is provided between the shift register cell and the switching element, and the latch circuit temporarily holds the print data in the shift register cell. Such a latch circuit is not always necessary. For example, the output of the shift register cell may be directly supplied to the switching element without providing the latch circuit.

[0027]

According to the thermal head of the present invention, a selection circuit for selecting a shift register cell for inputting one line of print data is provided at a stage preceding the shift register, and the shift register selected by the selection circuit is provided. Since the cells are switched periodically, a heating element used to print the ruled lines when using a thermal head to form a print pattern that includes the ruled lines in the transport direction of the recording medium, such as a table or graph. Can be changed every page or every few pages to prevent Joule heat from being concentrated on a specific heating element. As a result, the frequency of use of the heating elements can be leveled, and the life of the thermal head can be extended.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a thermal head according to the present invention.

FIG. 2 is an example of a print pattern by the thermal head of the present invention.

FIG. 3 is a timing chart when a printing operation is performed using the thermal head of the present invention.

[Explanation of symbols]

 R1 to Rn: heating elements S1 to Sn: shift registers A1 to An: switching elements B: selection circuit

Claims (1)

[Claims] 1. A plurality of heating elements arranged in a straight line and the same number of shift register cells as the heating elements are connected in series, and one line of print data is transferred to one of the shift register cells. A shift register that stores each print data in a predetermined shift register cell by sequentially inputting the print data one bit at a time and serially transferring the print data between the shift register cells; A plurality of switching elements for controlling energization of the heating elements, and a selection circuit provided at a preceding stage of the shift register to select a shift register cell for inputting print data for one line. Printing with ruled lines in the transport direction of the recording medium by selectively heating the heating elements while transporting in the direction orthogonal to the row of heating elements A thermal head, wherein a shift register cell selected by the selection circuit is periodically switched when a pattern is formed.