JP2508810B2 - Thermal head - Google Patents

Description

The present invention relates to improvements in thermal heads, and more particularly to a thermal head capable of obtaining high-quality printing during high-speed printing, thermal transfer recording and the like.

[Conventional technology]

The thermal recording method has been widely used in recent years because it is simple. In this method, a heating resistor formed on a substrate is selectively energized to color the recording paper, and various driving methods are known. Of these, JP-A-59-13
There is a conventional direct drive type thermal head disclosed in Japanese Patent No. 3081, and a circuit block diagram used for this is shown in FIG. This connects the switching elements to the heating resistors (11) arranged linearly,
It is mounted in a thermal head and sends recording data to a shift register (33) or a latch circuit (34) for one printing line. That is, for example, data for one line is serially input to the shift register (33), and then the content of the shift register (33) is transferred to the latch circuit (34) by a latch signal.

With the contents of this latch circuit (34), switching ON / O
When the strobe signal (9) is turned on, the FF state is stabilized, and the heating resistor (11) is energized to generate heat to record an image. Since the strobe signal (9) is commonly connected to all bits or arbitrary plural bits, it is not possible to change the energization time to each heating resistor (11), that is, the print pulse width, at the same timing. . Further, since the energization time for one line is as short as several milliseconds, the heat of the previous line remains during recording of the next line, and the influence of the heat storage of the heating resistor cannot be avoided.

Therefore, Japanese Patent Publication Nos. 60-22629 and 61-12790 disclose methods for preventing deterioration of printing quality due to the effect of heat storage of the thermal head heating resistor (11) during high-speed printing and thermal transfer printing. It is shown in these documents that the energizing pulse time to the heating resistor is varied with reference to the recording history of the heating resistor, the printing cycle, and the like. When these methods are used for the direct drive type thermal head described above, an external circuit having a circuit block diagram as shown in FIG. 7 is required for the apparatus. In FIG. 7, (39) is the direct drive type thermal head shown in FIG.
7) is a memory circuit for recording history, (35) is a recording controller, (3)
6) is an energizing pulse time determining unit, (40) is print data for one line, and (38) is an external circuit for driving the thermal head. When the previous line print data using this external circuit (38) is referred to, the print timing of the input signal timing chart to the direct drive type thermal head and the print history of the heating resistor (11) and the energizing pulse time Shown in the figure. In FIG. 8, D1 indicates data with or without preceding line printing, and D2 indicates data transfer with or without this line printing. For example, regarding the heating resistor,
In n-line printing, D1 has no printing, and D2 has data transfer with printing, resulting in a wide drive signal. In the case of (n + 1) line printing, since D1 is printed and D2 is data transferred with printing, the drive signal has a narrow width. Therefore, when printing with reference to previous history such as the previous two lines, data transfer D1, D2, D3 ...
The number of data transfers and the number of data increases, and the external circuit configuration becomes complicated.

[Problems to be Solved by the Invention]

Since the conventional thermal head is configured with an external circuit as described above, it is necessary to increase the number of memories or external memory to control the complicated driving of the heating resistor during high-speed printing or thermal transfer recording. Required, the external circuit becomes complicated, the use of the thermal head becomes difficult, and the apparatus for using the thermal head becomes large and expensive, and the wiring of the external circuit is also large, and the mixing of noise into the connection wiring or However, there was a problem such as a decrease in reliability of the connection contact portion.

The present invention has been made to solve the above problems, and is used in the past, when performing high-speed printing control using the direct drive type thermal head driving method that is a simple structure as it is, The drive control of the heating resistor is controlled by a simple signal to eliminate the complexity of data transfer during high-speed printing, thermal transfer, and higher-quality printing, and the cost and size of the thermal head device can be reduced. It is possible to reduce the number of connection wiring such as external circuits,
The purpose is to improve the reliability of the device using the thermal head.

[Means for solving the problem]

The thermal head according to the present invention has a storage unit that reads and stores print data of a plurality of lines and a data comparison unit that compares the print data of the plurality of lines with each other.
A data conversion circuit that creates and outputs conversion data that determines the energization time to a plurality of heating resistors based on the comparison, a shift register that is serially input in the same number as the plurality of heating elements, and a parallel output of this shift register. A memory circuit for storing, and the output of the memory circuit causes the plurality of heating resistors to
With a switching element that controls ON / OFF, and with a drive circuit that drives the plurality of heating resistors based on the conversion data, the conversion data output from the data conversion circuit is stored in the shift register. Converted input data, a converted clock signal that determines the timing of inputting this converted input data, a latch signal that determines the parallel output timing from the shift register to the memory circuit, and energization of the heating resistor together with the output of the memory circuit. A strobe signal for determining the time, and the reading of the print data into the storage section and the output of the converted data from the data conversion circuit are synchronized by a start signal input to the data conversion circuit for each line of the print data. It is designed to be taken.

Further, the plurality of heating resistors, the drive circuit, and the data conversion circuit are integrally mounted on the same heat dissipation plate.

[Action]

The thermal head according to the present invention has a data conversion circuit integrated therein, and the data conversion circuit, the drive circuit and the heating resistor are integrally mounted on the thermal head radiator plate to reduce the size of the apparatus and to transfer the basic clock signal to the data conversion circuit inside. Is counted to determine the drive pulse time of the heating resistor and read the print data of one line by inputting the start signal, and then drive the heating resistor with the print conversion data before the line for each line. By doing so, it is possible to prevent the print quality from deteriorating due to the accumulation of heat in the heating resistor.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit block diagram of the present invention, in which (1) is a basic clock signal input terminal (OSC) and (2) is a print data signal input terminal (RDAT).
A) and (3) are data reading clock signal input terminals (R
CLOCK), (4) are start signal input terminals (START),
(5) is composed of a chip integrated with a data conversion circuit. (6) to (9) are signals generated by the data conversion circuit (5), (6) is a conversion data signal (XDATA),
(7) is used for the conversion clock signal (XCLOCK) for the conversion data signal (6), (8) is used for the latch signal (LATCH), (9) is used for the strobe signal (STROBE), and (10) is used for the conventional thermal head. A heating resistor drive circuit consisting of a switching element having a shift register function, (11) a plurality of heating resistors arranged on the substrate, (12) a common end of a plurality of heating resistors (11) Common electrode terminal connected to
Reference numerals (13) and (14) respectively denote a data conversion circuit (5) and a circuit power supply terminal of the heating resistor drive circuit (10), and (15) denotes a thermal head in which these are integrated.

Further, FIG. 2 (a) is a plan view showing an embodiment of the present invention, and FIG. 2 (b) is a sectional view. In the figure, (16) is a substrate such as alumina ceramic, (17) is a flexible printed circuit board (hereinafter referred to as FPC), (18) is a reinforcing plate of FPC (17), and (19) is for connecting a thermal head. Connector, (20) is IC encapsulation resin for heating element drive circuit (10) and data conversion circuit (5), (21)
Is a surface protection film on the heating resistor (11), (22) is a heat sink of iron, alumina, etc., (23) is a cover for fixing the substrate (16) and FPC (17) and protecting the IC, ( 24 is a screw for fixing the cover (23), (25) is a board (16) and an FPC (1
The pressure contact rubber 7), the platen roller 26, and the thermal paper or the transfer paper 27 are shown. In FIG. 2, the data conversion circuit (5) is composed of an integrated chip, is miniaturized by double-sided wiring, and is electrically connected to the FPC (17) by wire bonding or the like. The FPC (17), the heating resistor (11), and the substrate (16) on which the heating resistor drive circuit (10) composed of an integrated chip is mounted is
After the positions of the patterns are aligned, the screw (24) is tightened, and the cover (23) and the rubber (25) are electrically connected by pressure contact force. In this way, the FPC (17) having the data conversion circuit (5) and the substrate (16) having the heating resistor (11) and the drive circuit (10) mounted thereon can be mechanically separated from each other. As shown below, it is possible to flexibly change the design of the thermal head in response to changes in specifications. That is, for example, the data conversion circuit (5) is mounted.
If the FPC (17) is replaced with an FPC that does not have a data conversion circuit, it can be used as the conventional direct drive type thermal head of the drive circuit (10) and the heating resistor (11). In addition, when the required specifications of the device (for example, thermal recording device) in which the thermal head is used are changed, only the FPC (17) equipped with the data conversion circuit (5) can generate patterns based on the required specifications. It can be handled by changing the design, and the part of the board (16) can be used as it is.

FIG. 3 shows the timing chart in the case of referring to the print data of the previous line of the thermal head, and its operation will be described.

The drive circuit (10) for the heating resistor (11) shown in FIG. 1 is the same as that of the conventional direct drive system of the thermal head, and therefore its explanation is omitted. As shown in Figs. 1 to 3, the input signals to the thermal head (15) are basic clock signal (OSC), print data (RDATA), data read clock signal (RCLOCK), start signal (START).
Only the data conversion circuit (5), drive circuit (1
0) converted data signal (XDATA) (6), converted clock signal (XCLOCK) (7), and latch signal (LATC)
H) (8) and strobe signal (STROBE) (9) are generated.

Here, the data conversion circuit (5) has a structure as shown in FIG. That is, the memory section (31) has a line (n)
-1) A print data memory (31a), a print line (n) data memory (31b), and a next line (n + 1) print data memory (31c), which have three stages and can be sequentially switched. Data conversion circuit (5)
Is a pulse width determining unit (28) that determines the energizing pulse time to the memory unit (31) and the heating resistor (11) by counting the basic clock signal (OSC), and XDATA, XCLOCK, LATCH, STR
It consists of a signal generator (30) that generates OBE output signals and a controller (29) that controls them. Each part is synchronized with the basic clock signal (OSC) and start signal (START), and print input The data and the actual print line are controlled to be delayed by one line. That is, input RDATA, RCLOCK and output data XDAT
A and XCLOCK are shifted by one line at a time, and if the thermal head user side considers the printing deviation of one line, it is as if the same thermal head as the conventional thermal head is used. It becomes like

In the case of considering the configuration of shifting by one line, considering the line memory of three stages, one stage is used for storing input data and the other two stages are used.
The conversion data XD2 is used for storing the data of the previous line and the line before the second line in the row, comparing the data of the two rows, that is, determining whether the dot to be printed was printed in the previous line. Output is possible.

The front line information that can be created by conversion is determined in advance in the circuit of the data comparison unit (32), and various combinations are possible. For example, XD1 is the original print data, XD2 is the front line print Determined by data and logic circuit. (It may be decided by the program etc.). In addition, the output timing of LATCH and STROBE has a ROM of the counter in the signal creation section (30), and the timing is created by matching the count value of this ROM with the clock count of OSC. Therefore, when the OSC frequency is changed, the STROBE signal time changes. OS
If the STROBE signal is 1 ms for C 4 MHZ, 2 for OSC 2 MHZ
It becomes ms.

The condition setting for outputting 1 ms at 4 MHz is to put a numerical value such as "FF" in the ROM.

As described above, the print data of the heating resistor is
Since it is determined by referring to the next line data, the influence of heat storage on the heating resistor is reduced. In the operation of recording with thermal paper, first the paper is not conveyed by the platen roller (26) at the first print line, but the paper is conveyed from the print data input of the second line, and the last print line is the last. After the input data is input, extra paper is conveyed by one print line.

In the above embodiment, since the strobe signal (STROBE) determines the energizing pulse time within the printing cycle of the heating resistor (11) by counting the basic clock signal (OSC), a plurality of short pulse energizing can be performed. It will be possible.

Therefore, as can be seen from the diagram showing the relationship between the energizing pulse to the heating resistor and the surface temperature illustrated in FIG. 5, the effect of heat storage of the heating resistor (11) can be made smaller than that of the single-shot long pulse. Therefore, it improves the printing quality and also helps prevent thermal destruction of the heating resistor (11).

Further, in the above embodiment, the case of referring to the previous line print data is shown, but in the case of the reference such as the line before the line print, the print input data and the actual print line are delayed by the reference history. Becomes Furthermore, it is possible to create conversion data not only by referring to the previous line print data but also by referring to the adjacent print data, and the number of data transfer of print conversion data XDATA XD1, XD2 ... If it does not enter within one printing cycle, the number of XDATA transfer bits may be reduced and the number of XDATA signals may be increased.

Further, in the above embodiment, XDATA, XCLOCK, LATCH, STROBE
Although the case where each signal is output one by one has been shown, the signal may be further increased to control the driving circuit (10) by several blocks. In this case, the power source capacity of the thermal head using device can be reduced, and higher speed printing control can be performed.

Also, a plurality of integrated circuits having the function of the data conversion circuit (5) may be mounted in the thermal head (15).

In addition, the basic clock generation circuit has a thermal head (15).
It is possible to further prevent malfunctions due to the inclusion of noise and the like by integrally mounting it inside and providing a basic clock start signal terminal.

Further, the method of integrating the thermal head (15) is not particularly limited, and it goes without saying that reducing the number of wires and making the wire length as short as possible eliminates problems such as noise contamination.

〔The invention's effect〕

As described above, the thermal head according to the present invention has a storage unit that reads and stores print data of a plurality of lines and a data comparison unit that compares print data of the plurality of lines with each other, A data conversion circuit that creates and outputs conversion data that determines the energization time to the heating resistor, a shift register that is serially input in the same number as the plurality of heating elements, a memory circuit that stores the parallel output of this shift register, A switching circuit that controls ON / OFF of the plurality of heating resistors by a memory circuit output, and a drive circuit that drives the plurality of heating resistors based on the conversion data, and output from the data conversion circuit The conversion data to be converted is the conversion input data to the shift register and the conversion clock that determines the timing of inputting this conversion input data. A clock signal, a latch signal that determines the parallel output timing from the shift register to the memory circuit, and a strobe signal that determines the energization time of the heating resistor together with the output of the memory circuit. Since the reading of data and the output of the converted data from the data conversion circuit are synchronized by the start signal input to the data conversion circuit for each line of print data, a simple and small number of signals are used. Since the heating resistor can be driven so that the effect of heat accumulation on the heating resistor is reduced, high-quality printing can be obtained especially during high-speed printing control, and the complexity of data transfer to the thermal head is eliminated, and the thermal head The internal circuit can be easily configured and integrated, and the thermal head and its equipment can be made smaller, less expensive, and more reliable. Improvement, there is an effect that attained is flexible design changes to further specification change.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a thermal head according to an embodiment of the present invention, FIG. 2 is a plan view and a sectional view of a thermal head according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a timing chart of the thermal head when referring to the preceding line, FIG. 4 is a circuit block diagram showing a data conversion circuit of the thermal head according to one embodiment of the present invention, and FIG. FIG. 6 is a circuit block diagram showing a conventional direct drive type thermal head, FIG. 7 is a circuit block diagram showing a conventional thermal head control circuit for high-speed printing, and FIG. The drawing is a diagram showing a timing chart using a direct drive type thermal head, a current-carrying time of a heating resistor, and a printing state in the case of referring to the preceding line printing. (1) is a basic clock signal input terminal, (2) is a print data signal input terminal, (3) is a data reading clock signal input terminal, (4) is a start signal input terminal, (5) is a data conversion circuit, and (10) ) Is a heating resistor drive circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-62-264972 (JP, A) JP-A-56-106883 (JP, A) JP-A-57-116665 (JP, A)

Claims (2)

(57) [Claims] 1. A storage unit for reading and storing print data of a plurality of lines, and a data comparison unit for comparing print data of the plurality of lines with each other, and an energization time to a plurality of heating resistors based on the comparison. Create conversion data to determine
A data conversion circuit for outputting, a shift register that is serially input in the same number as the plurality of heating elements, a memory circuit that stores the parallel output of the shift register, and ON / OFF of the plurality of heating resistors by the memory circuit output. In a thermal head having a switching element for controlling and a drive circuit for driving the plurality of heating resistors based on the conversion data, conversion data output from the data conversion circuit is converted to the shift register. Input data, a conversion clock signal that determines the timing of inputting this conversion input data, a latch signal that determines the parallel output timing from the shift register to the memory circuit, and the energization time to the heating resistor together with the output of the memory circuit And a strobe signal that determines the The output of the conversion data from the data conversion circuit, a thermal head is characterized in that synchronization is taken by a start signal input to each line of print data to the data conversion circuit. 2. The thermal head according to claim 1, wherein a plurality of heating resistors, a drive circuit, and a data conversion circuit are integrally mounted on the same radiator plate.