JPS6076360A - Heat-sensitive recording device - Google Patents

Abstract

PURPOSE:To enable the prevention of heat accumulation in heating resistors, by providing a larger number of recording signal information storage circuits than the number of heating bodies, by comparing recording signal informations at the current time point with those before the number of the heating bodies, and by controlling a time of electrification based on the result of comparison. CONSTITUTION:Heating resistors 31 in the number of 1728, for instance, are connected, half and half, to an external power source 32 through terminals (a) and (b). A recording signal input from a terminal 35 is inputted in series alternately for each of the terminals (a) and (b), enters an 864-bit shift register 38, and is read out through an inverter 40. Meanwhile, the content holding recording signals for half a line is outputted in parallel and transferred to latch circuits 41, 43 and 45 sequentially. The content of the latch circuit 45 is passed through a NAND circuit 48 controlled by a printing signal E and is compared with the content of the latch circuit 41 in an AND circuit 49, and the result of comparison enters a driving circuit 33. A time of electrification of the heating resistors is controlled according to the result of comparison. In this way, the number of LSI can be halved, and a printing density can be controlled to be uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head that is highly reliable, inexpensive, and capable of high-speed recording.

The f--r head has a large number of heat-generating resistors, which are recording elements, arranged in a row, and selectively energizes these heat-generating resistors to generate heat to print and record on thermal recording paper. Facsimile machines using this thermal head have rapidly become popular over the past few years because they are inexpensive, require low maintenance and operation costs, and can print and record image information with high quality.

This thermal head is formed according to the configuration diagram shown in FIG. 1, for example. Here, 1 is a heating resistor for thermal recording. For example, in the case of a thermal head equivalent to A4 size in which 8 resistors are arranged at a density of 1fi, a total of 1728 resistors are arranged in a row on the head substrate. will be established. One end of each of these heating resistors 1 is commonly connected to one end of a power source 2 for each section, and each other end is connected to the other end of the power source 2 via the same number of drive circuits 3 as the heating resistors 1.

The drive circuit 3 is mainly composed of switching elements,
When the recording signal supplied in parallel via the latch circuit and the output permission signal input via the output control signal 4 coincide with each other, each switching element is turned on, and each switching element is individually connected to the heating resistor 1. Turn on electricity.

Reference numeral 5 denotes a recording signal input terminal, into which a series of recording signals such as words (for example, one line IJ), a 1728-bit black and white binary factor B) image signal, etc. is input in series. This recording signal is a tie-on signal 8. input from the timing control terminal 6. AND gate 7 and OR controlled by
The signals are inputted sequentially through gates 8 to a shift register 9, which is a first storage circuit. This shift register 9 is 172
It has an 8-bit capacity, and according to the clock signal Cp input from the clock input terminal 10, the input recording signal is sequentially transferred to the right and stored for one line. The contents of the shift register 9 are output in parallel, and the latch signal to the latch control terminal 12 is sent to the 1728 latch circuits 11 by the signal Tt,
It will be moved at the timing of.

However, in the thermal head using this method, if the recording signal corresponding to the same exploding resistor is significant information (black information) for two or more consecutive lines, the same heating resistor is energized several times in succession. If this is done, there is a risk that the heating resistor may become overheated due to heat accumulation, causing the density of the recorded print to become abnormally high, or that the heating resistor itself may be destroyed.

Therefore, various measures have been considered to prevent abnormal printing or destruction of the resistor. One of them is to compare the information between the current series of recording signals supplied to the drive circuit and the recorded signal one time ago for each corresponding bit, and depending on the comparison result, the heat generation resistance by the drive circuit is There is a method to control the time that electricity is applied to the body. This can be achieved by the following method.

That is, the contents of the shift register 9 are read out in series from the rightmost final stage, and the AND gate 14 is controlled by the timing signal S input from the timing control terminal 13.
is input to another shift register 15, which is a second storage circuit.

This shift register 15 is the same as shift register 9.
It has a capacity of 28 bits and is sequentially transferred to the right to store the inputted recording signals by a clock signal inputted through an AND gate 21 controlled by a timing signal Sm.

The contents of the shift register 15 are serially read out from the rightmost final stage, and compared with the recording signal serially read out from the shift register 9 in a comparator circuit 16.

This comparison circuit 16 includes an inverter 17 that inverts the serial output of the shift register 15 and an A that obtains a coincidence signal between the output of the inverter 17 and the serial output of the shift register 9.
It is composed of an ND gate 18.

The output of this comparison circuit 16 is the tireing signal S,
The data is input to the shift register 9 as replacement data through an AND gate 20 and an OR gate 8 which are controlled by an inverted signal from an inverter 19.

5- When each heat generating resistor is energized continuously in this manner, it is possible to control the energization time to be shorter than when the energization is performed non-continuously.

However, this method requires drive circuits or switching elements corresponding to the number of heating resistors.

These switching elements have 32 elements to form one L
formed on the SI, and by means such as wire bonding,
Each element is connected to a corresponding heating resistor. Therefore,
In the case of a thermal head in which 1728 heating resistors are formed, 54 LSIs and at least 1728 wire bondings are required. Since the reliability of a manufactured thermal head is inversely proportional to the number of wire bondings, it was inevitable that conventional thermal heads with a large number of wire bondings would have low reliability. The large quantity of 54 pieces of L8I, which requires nine pieces, has been an obstacle to reducing the price of thermal heads.

These points became more noticeable when higher resolution images were required. In other words, if the current resolution of 8 wires/mu or 16 wires/mu is increased, the required number of wire bonding will be A.
2560 or 345 pieces each for 4-size equivalent
There were six pieces. Further, the required number of LSIs was 80 or 108, respectively. Therefore, it is virtually impossible to guarantee the reliability of the manufactured thermal heads, and they have to be expensive.

Therefore, it is an object of the present invention to provide a thermal head that can reduce the required number of LSIs and wire bonding to less than half of the conventional number, and can uniformly control printing density. The company also claims to provide highly reliable thermal heads.

The present invention provides a plurality of heating resistors connected to a drive circuit, a memory circuit for storing recording signal information that is one or more more than the number of heating elements, and recording signal information to be recorded at the present time, A VC feature is that a comparison circuit is provided to compare the recorded signal information with the number of heating elements before.

The present invention will be described in detail below with reference to FIG.

31 is a heating resistor, and one example is A with a resolution of 8 wires/drink.
In the case of a thermal head equivalent to the 4th edition, 1728 thermal heads are arranged in a row on the head substrate. Half of these, 864, are a
The remaining half of the resistors are commonly connected to the b terminal. The a terminal and the b terminal are alternately connected to one end of the external power supply 32 through a switch mechanism SW. The other ends of the pair of heating resistors connected to the a and b terminals are commonly connected to a single drive circuit. Therefore, the number of drive circuits 33 required is 864, which is half of the conventional number, and the number of required wire bondings is obviously reduced. The other ends of the heating resistors via these drive circuits are commonly connected to the other end of the source 32.

Reference numeral 35 denotes a recording signal input terminal, into which a series of recording signals, such as an 864-bit image signal corresponding to a heating resistor connected to the a terminal, is input in series. Next, after a predetermined time, 86 corresponding to the heating resistor connected to the b terminal
A 4-bit recording signal is input in series. This process is repeated from now on. These recording signals are input to the shift register 38 via an AND gate 37 controlled by a timing signal S input from a timing control signal terminal 36. This shift register has a capacity of 864 bits, and sequentially transfers the input recording signal to the right according to the clock signal cP input from the input terminal 39, and transfers the recording signal via the inverter 40. and read externally.

The contents of the shift register 38, which accommodates half of the recording signal of one line (for example, the recording signal corresponding to the heating resistor connected to the a terminal), are output in parallel, and the contents of the shift register 38, which accommodates the recording signal of half of one line (for example, the recording signal corresponding to the heating resistor connected to the a terminal), are output in parallel to the first shift register, which is composed of a circuit corresponding to 864 bits. Two transfers of the latch control terminal 42 are transferred to the latch circuit 41 at timing T.

The contents of the latch circuit 41 are such that the latch signal of the latch control terminal 44 is T.

The signals are transferred in parallel to the second latch circuit 43 at the timing of . Similarly, the contents of the latch circuit 43 are transferred to the third latch circuit 45 at the timing of one latch entry of the latch control terminal 46. All nine latch circuits have a capacity of 864 bits.

The contents of the third latch circuit 45 are output in parallel and are controlled by the print signal E of the print time control terminal 47.
It is applied to an AND gate 49 together with the parallel output of the first latch circuit 41 via a D gate 48, and recorded information is compared for each corresponding pit. The output of the AND gate is transferred in parallel to the drive circuit 33, and each switching element is turned on by a coincidence output with the output permission signal inputted via the output control signal 34, and each switching element is individually connected to the heating resistor 31. Turn on electricity.

Accordingly, the present invention compares the current series of recording signals supplied to the heating resistor drive circuit 33 with the recording signal of the two-time tune for each corresponding bit, and according to the comparison result. Since the driving circuit can control the time during which the heating resistor is energized, the thermal head can be driven at high speed.

Next, the operation of the interpolation example with time chart 10- This will be explained with reference to

First, as an initial state, the contents of the latch circuits 41, 43, and 45 are all set to "O". In this state, it is assumed that a recording signal equivalent to half a line (a recording signal corresponding to the heating resistor connected to the a terminal) is input in series to the recording signal input terminal 35. At this time, the timing control terminal 36
As shown in FIG. 3(a), while the 864-bit recording signal is input to the terminal 35, the timing signal island of 1" level is continuously input. Therefore, the recording signal is input to the gate 37. The signal is energized and read into the shift register 38 by the clock signal CP.

When all the recording signals for half 247 minutes (corresponding to the heating resistor connected to the a terminal) are read into the shift register 38, the latch signal shown in FIG. 3(b) is sent to the third latch circuit 45 via the terminal 46. Ts is supplied.

Therefore, the contents of the ICC notch path 43, ie, IIOII, are latched in the latch circuit 45 in parallel until that time. Next, a latch signal T shown in FIG. 3(e) is supplied to the second latch circuit 43 via the terminal 44. For this purpose, the contents of the latch circuit 41, ie 'O', are latched as they are in the latch circuit 43 in parallel.Finally, the first latch circuit 41
IJ via the terminal 42 (the latch shown in FIG. 3(d))
is supplied with a signal T. For this reason, the distribution signal read into the shift register 38 (recording signal corresponding to the heating resistor connected to the a terminal) is latched in parallel to the latch circuit 41 as it is.

At this time, the print signal E of the print time control terminal 47 is set to 10", and the 8W of the power supply 32 is connected to the aIIC. Therefore, the output of the NAND gate 48 of the comparator circuit 50 is always 51".
Otherwise, the recording signals read out in parallel from the latch circuit 41 pass through the AND gate 50 as they are.

Immediately after the latch signal T1, an output enable signal with a pulse width of t is supplied to the drive circuit 33 via the terminal 34, as shown in FIG. 3(e). As a result, the drive circuit 33 turns on the switching element only for the time t to which the latch circuit 41 has given the recording signal 1'' black information, and the heating resistor 3 connected to the a terminal
1 is energized. After the energization ends, the SW terminal of the power supply is switched to the b terminal side.

On the other hand, the contents of the shift register 38 are stored in the latch circuit 4.
After being latched to 1, b
Recording signals corresponding to the terminal connection resistance are serially transferred. During this time, the timing signal 8. 1" is continuously input as 1". When all the recording signals are read, the same operation as before is performed, and the latch circuit 45 is all "on", and the latch circuit 43 is set to "a terminal connected resistance phase." Minute recording signal”
, the latch circuit 41 latches the ``record signal of the proportion of the resistance connected to the b terminal''. The recording signal corresponding to the resistance connected to the b terminal is sent via the drive circuit 34 to an output permission signal with a pulse width of t, which operates the switching element, and prints and records only on the heating resistor to which black information is given. Thereafter, the SW terminal of the power supply is switched to the a terminal side, and by this series of operations, the print recording for the 12-inch phase is completed.

Next, for recording the second line, a recording signal corresponding to the resistance connected to the a terminal is read into the shift register 38 using the timing signals S, &C. After that, the latch circuit 45 receives ``'' due to the latch trigger Ts, T snow, and TI.
A recording signal equivalent to the resistance connected to the a terminal of the first line is read into the latch circuit 43, a recording signal corresponding to the resistance connected to the b terminal of the first line is read into the latch circuit 43, and a recording signal corresponding to the resistance connected to the b terminal of the first line is read into the latch circuit 41. The recording signal '° corresponding to the resistance connected to the a terminal of the two lines is read. Therefore, the comparison circuit 50 can compare the contents of the latch circuit 4B and the contents of the latch circuit 41. That is, it is possible to compare the recording signal No. 1B of the first line and the recording signal of the 25th line corresponding to the resistance connected to the a terminal for each corresponding bit.

The recording signal of the 22nd input latched by the latch circuit 41 can pass through the AND gate 49 as it is only when the printing time control signal ``of the NANLI gate terminal 47 of the comparison circuit 50 is 0'', and output is permitted. The switching element of the drive circuit 33 is operated by the signal E, and printing is performed only on the heating resistor to which the black information, that is, '1'' is given. = 14-, then K means that the output of the NAND gate 48 is 1'' only when the first line recording signal is 60'', that is, white information, and the second line recording signal passes through the AND gate 49. I can do it.

Therefore, the switching element of the drive circuit 33 to which the output enable signal D3 of time t is applied is given 12 levels of on-operation time. That is, when the image signal of the first line is white, the heating resistor is energized and heated for one hour. However, when the picture signal of the first line is black, VC1'! , 1. =1
-1. The heating resistor is energized and heated for a time (1, < 1).

As described above, according to the present invention, when @l 1 m appears consecutively in the same bit of the recording signal and the same heating resistor is energized for two or more lines in succession, the heating resistor is energized once. The energization time of t! is shorter than the normal time of t from the second time onwards. 1. By appropriately determining the value of , it is possible to prevent heat from accumulating in the heating resistor.

Furthermore, compared to a method in which the energization time is always constant, overheating of the heating resistor can be prevented with a shorter energization stop time, so the thermal head according to the present invention can perform high-speed recording. .

Further, according to the present invention, the recording signal of the current line and the recording signal of the corresponding previous line are compared for each corresponding bit, and the time of energization of the heating resistor is controlled based on the comparison result. The energization time t when the resistor is energized non-continuously and the energization time t when the resistor is energized continuously can be selected by independent VCs. For this reason, t
, it is possible to select an optimal time that prevents overheating of the heating resistor and does not cause uneven yield.

In addition, when comparing the recording signal of the current line and the corresponding recording signal of the previous line for each corresponding bit in the previous comparison circuit, for example, two heating resistors are attached to the drive circuit. Sometimes, the nth recorded signal! l-2
It is only necessary to compare the recorded signal of the second time, that is, the recorded signal of two stages before. Therefore, if rn mutually independent heating resistors are connected to the drive circuit, the n-th recording signal and n-m
It goes without saying that it is only necessary to compare the recorded signal for the first time.

In this case, the IC requires a function such as a latch circuit or a shift register for recording at least (m+i) stages of recording signals.

1. Furthermore, since the present invention exhibits the above-mentioned effects, it can be implemented with various modifications. That is, in the above embodiment,
Although the time of conduction to each heating resistor was controlled by comparing the fI & signal information of the corresponding current line and the previous line, the method of changing the number of energized rgl depending on the comparison result would not work. good.

Moreover, it is also a problem to set a plurality of types of energization time in advance. Furthermore, signals such as 'l', 'i', 'T', etc. can be supplied from a single terminal through a separation circuit. Further, for example, printing corresponding to the a terminal connection resistance can be divided into a plurality of blocks to increase the depth.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional thermal recording device, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a diagram explaining the operation of the device shown in FIG. 2. 31... Heating resistor, 32... Power supply,
33...17- Drive circuit, 38...Shift register, 41...
...first latch circuit (first storage circuit), 43.
...Second latch circuit (second storage circuit), 45
...Third latch circuit (third storage circuit), 5
0... Comparison circuit. 18-

Claims (1)

[Claims] Heat-generating resistors are divided into at least two groups and arranged in a row, and a plurality of heat-generating resistors extracted from each group are connected to a single drive circuit. a drive circuit that selectively energizes the heat-generating resistors belonging to the group in accordance with the recording signal of the group; and a drive circuit that stores a series of recording signal information to be supplied to these drive circuits, the number of divisions plus one or more. a storage circuit; a comparison circuit that compares the recorded signal information stored in the first storage circuit with the recorded signal information before the time corresponding to the number of groups for each corresponding bit;
Depending on the comparison result of this comparison circuit, the time or number of times of energization to the heat generating resistor will be shorter when the heat generating resistor is energized continuously than when energized non-continuously. Alternatively, the thermal recording device is equipped with an energization time control means to control the amount of mold.