JPH0416068B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head for a heat-sensitive recording device capable of high-speed recording.

The thermal recording method has been increasingly used in recent years due to its ease of maintenance and low cost. In this thermosensitive recording method, recording elements (heating resistors) are arranged in a row and current is selectively passed through them to generate heat, thereby recording on thermosensitive recording paper. Conventionally, in this type of recording device, the number of lead wires,
In order to reduce the number of drive circuits, etc., a matrix circuit is used that divides the heating resistor into multiple groups, supplies image signals to these groups in parallel, and simultaneously selects the group and records the selected group. . However, even if a matrix circuit is used, image signals are supplied in parallel, so in a normal thermal head, it is necessary to draw out as many lead wires as the number of heating resistors in one group from the outside.

Therefore, it is known that in a thermal head using the above-mentioned matrix circuit, a shift register for serial-to-parallel conversion of image signals is provided on a substrate on which a heat-generating low antibody is disposed, and the number of lead wires drawn out from the thermal head is reduced. (Unexamined Japanese Patent Publication No. 54-48562,
(Japanese Patent Publication No. 54-56320). However, in this type of thermal head, recording is performed for each group of heating resistors, and recording is not performed for a plurality of groups at the same time. Therefore, the recording time increases as the number of groups increases. For example, if the number of groups is m, the number of heating resistors constituting one group is n, and the time required for thermal recording is t, then the time required for recording one line is m×t. In the case of thermal recording, since t is relatively large, the above m×t becomes a considerably long time.

On the other hand, there is also a thermal head in which each heating resistor is provided with an element having a memory function, a current holding function, etc., and image signals are sequentially supplied to these elements in parallel at high speed for each group, thereby recording all groups almost simultaneously. Known (Japanese Patent Publication No. 52-105840, Japanese Patent Application Publication No. 53-1989)
13434). However, since this type of thermal head still supplies image signals in parallel, it requires more lead wires than the number of heating resistors in one group. or,
This type of thermal head also uses a matrix circuit, so lead wires are required for group selection, and since recording is performed for each group, a control circuit is required to separate continuous image signals into group signals. be. Furthermore, the same number of elements as the heat-generating resistors are required to have a current holding function, and even if the signals to control these can be of small current, a switch for large current is required to cut off all the elements. Become.

The present invention was made in view of the problems of conventional thermal heads, and is capable of high-speed recording, has a small number of external lead-out lines, does not require a switch for large currents, and has a simple circuit configuration. The purpose is to provide thermal heads.

The thermal head according to the present invention does not use a matrix circuit, but has a driving circuit connected to each heat generating resistor on a substrate on which the lung heat resistors are arranged, and a drive circuit having the same number of bits as the number of heat generating resistors. A shift register and a latch circuit for temporarily storing an image signal output from the shift register are provided, and a plurality of drive circuits each incorporating a predetermined number of drive circuits are provided.
It is characterized in that it is composed of an IC chip, and that the shift register is divided into a plurality of groups, and an image signal input terminal is provided for each group.

According to the present invention, high-speed recording is possible because the image signal drives all the heating resistors simultaneously without using a matrix circuit. In addition, since no matrix circuit is used, there is no need for lead wires to select each group of heat generating resistors, and since image signals are supplied to all heat generating resistors at the same time during recording, elements with a current holding function can also be used. There is no need for a large current switch to cut off these elements at once.

Furthermore, since the present invention provides a shift register for converting serial image signals into parallel signals on a substrate on which heating resistors are arranged, lead wires for supplying image signals from the outside are connected to the number of shift register groups (image The number of input terminals may be the same as the number of signal input terminals, which is smaller than when using a matrix circuit. Moreover, by dividing this shift register into a plurality of groups and providing an image input terminal for each group, versatility can be provided. In other words, if the image signal transmission speed is particularly fast, the image signal input time can be shortened by inputting the image signals to the image signal input terminals of each group of the shift register at the same time, so the recording speed is limited by the image signal input time. Even image signals having such high transmission speeds can be easily recorded.

Furthermore, the drive circuits connected to each heat generating resistor are configured by IC chips incorporating a predetermined number of the drive circuits, and the shift register is divided into a plurality of groups as described above, each having an image signal input terminal. When manufacturing thermal heads of various sizes such as A4 size, B4 size, and B5 size, by providing a Since there is no need for completely separate designs depending on the size of the thermal head, production costs can be reduced.

In addition, by providing a latch circuit on the output side of the shift register, the image signal can be input to the shift register relatively slowly, so the shift register generates less heat, and there is no need for anything other than the heating resistor. There is no deterioration in recording quality due to excessive heat generation.

Examples of the present invention will be described below.

FIG. 1 is a wiring diagram of a thermal head according to an embodiment of the present invention, and FIG. 2 is a plan view thereof. In FIG. 1, reference numeral 1 denotes heating resistors, which are arranged in a row on an insulating substrate 2 as shown in FIG. 3 is an electronic circuit section consisting of a semiconductor integrated circuit;
As shown in the figure, it is arranged on a substrate 2 adjacent to a heating resistor 1.

The electronic circuit section 3 has the following configuration. 4
is a drive circuit for individually driving the heating resistor 1 according to an image signal. That is, the drive circuit 4
is mainly composed of switching elements, each one end of which is connected to each end of the heating resistor 1,
Each other end is commonly connected to a power supply terminal 5. Further, as shown in FIG. 4, which will be described later, the drive circuit 4 is
Multiple ICs each incorporating a predetermined number of drive circuits 4
It is composed of a chip 45. A power source 7 is connected from the outside between the power source terminal 5 and another power source terminal 6 to which the other ends of the heating resistor 1 are commonly connected.
is connected.

8 is the same number of bits as the number of heating resistors 1. For example,
1728-bit shift register, multiple (n)
It is divided into groups 8a to 8n, and each group has image signal input terminals 9a to 9n. Image signals (for example, facsimile demodulation signals) to be input to each group 8a to 8n of the shift register 8 are input to the image signal input terminals 9a to 9n via inverters 10a to 10n and 11a to 11n as appropriate, and the shift registers Group of 8 8a-8n
The thus inputted image transmission signals are sequentially transferred to the right in accordance with the clock signal inputted from the clock input terminal 12 and stored.

The image signal for one line stored in the shift register 8 in this manner is transferred to the latch circuit 14 at the timing of the latch signal to the latch signal input terminal 13 immediately after the storage is completed. Latch circuit 1
In this case, 4 has a gate function in the output section, and the output permission signal input terminal 15 is connected to the gate terminal.
The latched contents are output only during the period in which the output permission signal is input. Then, the image signal outputted from the latch circuit 14 is supplied to the drive circuit 4, so that the built-in switching element of the drive circuit 4 is selectively turned on in accordance with the image signal. As a result, the heating resistor 1 is selectively energized in accordance with the image signal and generates heat. The heating resistor 1 waits for a period of time determined by the output permission signal (approximately 1 to 4msec), and the power supply is stopped when the output permission signal stops. In this way, recording for one line is completed, and the recording preparation state for the next one line is entered. By performing the same operation every time one line of image signal is input to the input terminal 9,
A two-dimensional image recording is performed.

According to the configuration of this embodiment, all the heating resistors 1 are simultaneously driven in parallel according to the image signal, so the recording time for one line is equal to the recording time t by one heating resistor, and the matrix The recording speed is dramatically faster than that using circuits.

In addition, the shift register 8 is divided into n groups 8a.
.about.8n, and each group 8a.about.8n is provided with image signal input terminals 9a.about.9n. Therefore, by simultaneously inputting image signals through these input terminals 9a.about.9n, the shift register 8 can be configured to serialize all bits. The input time of the image signal per line to the thermal head is reduced to 1/n compared to the case where the thermal head is connected to the thermal head. For these reasons, when used as a facsimile recording device, the recording speed can be higher than that of the fastest conventional device.

In this case, even if there is a very fast recording capability for the time being, the capability of the transmission line may not be able to keep up. Therefore, when an image signal with a slow transmission speed is input, for example, the image signal input terminals 9a to
9n is connected externally to connect each group 8a to 8n of the shift register 8 in series, and the first group 8a
The image signal may be input from the image signal input terminal 9a of the image signal input terminal 9a. In this way, the serially transmitted image signals are transmitted to each group 8a to 8a through the external thermal head.
There is no need to perform a distribution operation corresponding to 8n.

On the other hand, if the drive circuit 4 is configured with a plurality of IC chips and the shift register 8 is further divided into a plurality of groups 8a to 8n as described above, the number of IC chips used for the drive circuit 4 can be increased or decreased. The shift register 8 can easily accommodate thermal heads of various sizes, such as A4 size, B4 size, B5 size, etc., by increasing or decreasing the number of groups n.

Further, the number of lead wires for supplying image signals from the outside may be the same number n as the number of image signal input terminals 8a to 8n, and the number of lead wires can be relatively small. Therefore, in addition to eliminating the need for lead wires for group selection of heating resistors, which is required when using a matrix circuit, the number of lead wires drawn out from the thermal head can be significantly reduced. , simplifying the connection work and improving reliability. In addition, reducing the number of lead wires means that the number of terminals provided on the integrated circuit constituting the electronic circuit section 3 can also be reduced, which leads to a reduction in the chip area of the integrated circuit and, in turn, to the head itself. can be made smaller.

Further, in the present invention, since it is not necessary to use an element having a current holding function such as a thyristor as the drive circuit 4, there is no need for a large current switch that cuts off these elements at once. Therefore, together with not using a matrix circuit, the circuit configuration becomes simple and costs can be reduced.

Furthermore, in this embodiment, by providing the latch circuit 14 on the output side of the shift register 8, the image signal for the next line can be applied to the image signal input terminal 9 even during recording. Recording speed can be further increased. That is, if there is no latch circuit 14, it is necessary to supply the contents of the shift register 8 to the drive circuit 4 and then wait for the next recording until the transfer (input) of one new line of image signals to the shift register 8 is completed. There is. In other words, it is necessary to interrupt the transfer of the image signal to the shift register 8 during recording. Taking the case where the length of the image signal for one line is 1728 bits as an example, the transfer time of the image signal to the shift register 8 is as follows: When the electronic circuit section 3 is configured with ^C2MOS , the transfer clock signal frequency is 1MHz. The transfer clock signal frequency is 1.728 msec.
Even at 3MHz, it takes 0.576msec. Although it is possible to use a high-speed TTL IC for the shift register 8, since TTL IC generates a large amount of heat, it is preferable to provide the electronic circuit section 3 on the substrate 2 on which the heat generating resistor 1 is arranged as in the present invention. When you think about it, the heat generated by the IC adversely affects recording, which is not desirable.

To deal with this, a latch circuit 14 is provided so that the image signal for the next line is input to the shift register 8 while the image signal is being supplied from the latch circuit 14 to the drive circuit 4 and recording is being performed. By doing so, the image signal can be continuously input to the shift register 8 without interruption, and the influence of the image signal transfer time in the shift register 8 on the recording time can be almost ignored.

In the above embodiment, the output section of the latch circuit 14 has a gate function, but depending on the IC used, the drive circuit 4 may have a gate function. Further, the shift register 8 is not limited to the usual one, and it goes without saying that it may be constructed of a ring counter, a memory, a CCD, or the like.

By the way, in such a thermal head, all the heating resistors 1 are driven simultaneously according to the recording signal, so if the recording signal for one line contains many "black" signals, the heating resistors 1 A large amount of current flows through the common current supply buses L ₁ and L ₂ to 1. If the number of heating resistors 1 is 1728 and the current per one is 60 mA, this current reaches approximately 104 A in the maximum case (when the recorded signal for one line is a "black" signal for all bits). . On the other hand, since the amount of heat generated by the heating resistor 1 is proportional to the square of the applied voltage,
Recording density is greatly affected by the drop in applied voltage. Now, assuming that this voltage drop must be suppressed to 0.1 V or less, the wiring resistance of the current supply buses L ₁ and L ₂ needs to be 0.9 mΩ or less for a maximum current of 104 A. however,
When considering a pattern with a width of 5 mm for the current supply buses L ₁ and L ₂ , in order to suppress the wiring resistance to 0.9 mΩ or less per 10 cm of current supply, 0.53 mm in the case of Au film and 0.53 mm in the case of Cu film.
In the case of a film, a film thickness of 0.38 mm is required, and such a thick wiring pattern cannot be formed using normal thin film technology and requires a complicated manufacturing process.

Such a problem can be solved by configuring the wiring structure of the current supply bus as follows. Third
The figure shows an example in which metal parts normally required in this type of thermal head are used as a current supply bus. In FIG. 3, 31 is a metal plate for heat dissipation, which is provided in contact with the insulating substrate 2 shown in FIG. This metal plate 31 has a width of 70 mm, for example.
It is an aluminum plate with a length of 25 mm and a thickness of 15 mm, and its electrical resistance is approximately 0.004 mΩ. Therefore, for example, a presser metal fitting 32 for holding the substrate 2 on the metal plate 31 is brought into contact with the current supply thin film wiring on the substrate 2, and the metal plate 31 is electrically connected to this wiring. That is, the metal plate 31 is used for the current supply bus _L1 or _L2 in FIG. As a result, the electrical resistance of the current supply buses L ₁ and L ₂ can be significantly reduced compared to the case of a single thin film.

On the other hand, in FIG. 3, numeral 33 is a metal cap for protecting the IC chip and the like in the electronic circuit section 3 of FIG. 2 with a hermetic seal. For example, this cap 33 has a length of 20 cm, a width of 3 cm, and a thickness.
It is about 0.5 mm and its electrical resistance is about 0.3 mΩ, which is sufficiently smaller than the thin film wiring, so it can be electrically connected to the current supply thin film wiring on the board 2 and used as the current supply bus L ₁ or L _2. However, the same effect as above can be obtained. Of course, both the metal plate 31 and the metal cap 34 may be used as the current supply buses L ₁ and L ₂ .

In FIG. 4, thick copper films 43 and 44 are deposited on current supply thin films 41 and 42 to form a current supply bus L ₁ ,
This is an example of forming _L2 . In this case, the copper film 43,
44 may be formed by plating, or a previously formed copper foil may be attached to the thin films 41 and 42 using solder, conductive epoxy, or the like. Even in this case, the electrical resistance of the current supply buses L ₁ and L ₂ can be effectively reduced. In addition, in FIG. 4, 45 is an IC incorporating a plurality of drive circuits 4 shown in FIG.
thin film wiring 4 that interconnects these chips.
A copper film may be similarly formed on 6.

As described above, according to the present invention, not only can the time required to drive all heat generating resistors be shortened, but also the provision of a latch circuit makes it possible to input image signals continuously without interruption. can. Furthermore, in the present invention, the shift register is divided into a plurality of groups, and each group is provided with an image signal input terminal for simultaneously inputting image signals to each group. can be changed, it becomes possible to support recording of image signals of various transmission speeds. Furthermore, when manufacturing various thermal heads, the drive circuit can be easily adjusted by increasing or decreasing the number of IC chips, and the shift register can be easily accommodated by increasing or decreasing the number of groups.

[Brief explanation of drawings]

Fig. 1 is a wiring diagram of a thermal head according to an embodiment of the present invention, Fig. 2 is a plan view showing an example of its appearance, and Figs. 3 and 4 are means for reducing the electrical resistance of the current supply bus. It is a perspective view for explaining. DESCRIPTION OF SYMBOLS 1... Heating resistor, 2... Board, 3... Electronic circuit section, 4... Drive circuit, 5, 6... Power terminal, 7
...Power supply, 8...Shift register, 8a to 8n...
...Shift register group, 9, 9a to 9n...
...Image signal input terminal, 10a-10n, 11a-
11n...Inverter, 12...Clock signal input terminal, 13...Latch signal input terminal, 14...
Latch circuit, 15... Output permission signal input terminal.

Claims (1)

[Claims] 1 a substrate, heating resistors arranged in a row on this substrate, each connected to these heating resistors,
A drive circuit that simultaneously drives the heating resistors according to supplied image signals, a shift register having the same number of bits as the number of heating resistors that outputs serially inputted image signals in parallel, and this shift register. and a latch circuit that temporarily stores an image signal output from the latch circuit and supplies it to the drive circuit, the drive circuit is composed of a plurality of IC chips each incorporating a predetermined number of the drive circuits, and the shift register has a plurality of IC chips each incorporating a predetermined number of the drive circuits. 1. A thermal head characterized in that the thermal head is divided into groups, each group has an image signal input terminal, and the drive circuit, shift register, and latch circuit are disposed on the substrate.