JP3521158B2 - Thermal head and driving method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a thermal recording device or the like.

[0002]

2. Description of the Related Art A conventional thermal head used in a thermal recording apparatus of this type is a heating resistor formed on a ceramic substrate in a direction orthogonal to the moving direction of a recording medium, that is, in a linear scanning direction. And contact this heating resistor,
Arranged at equal intervals in the main scanning direction,
By a plurality of lead conductors extending in the sub-scanning direction and a drive circuit that is connected to the lead conductors by wire bonding or the like and selectively drives a heating resistance element formed by two lead conductors based on a signal from the control unit. It is configured. FIG. 4 shows the configuration of a thermal head used in a thermal recording device such as a printer. The thermal head 1 shown in the figure has a heating resistor 11 provided at one end of a ceramic substrate 10 so as to extend in the main scanning direction. , A plurality of drive circuits 15 provided on the other end side of the ceramic substrate 10.
And a plurality of power supply side lead conductors 13 extending in the sub-scanning direction and arranged at equal intervals in the main scanning direction, each of which is provided so as to be connected to the heating resistor 11, and connected to the plurality of power supply side lead conductors 13. Common electrode 14 and a plurality of ground side lead conductors 12 provided in the middle of the adjacent power source side lead conductors 13 so as to extend in the sub-scanning direction and connected to the drive circuit 15 by bonding wires 16. There is. A power source 17 is connected to the common electrode 14, and energy is supplied from the power source 17 to the heating resistor 11.

The drive circuit 15 having a shift register is
Based on the control signal from the control device, the ground side lead conductor 12 is connected to the ground so that the heating resistor element connected to the ground side lead conductor 12 receives energy from the power supply side supply lead conductors 13 adjacent to each other. The heating resistor element is supplied with heat and is heated to perform desired recording on the recording medium. The drive circuit 15 is provided with a plurality of ground side lead conductor connection terminals (pads) 151 facing the connection pads 121 provided at the ends of the ground side lead conductors 12 and connected to the connection pads 121 by bonding wires 16. , Are arranged in a staggered pattern in the main scanning direction, and are provided with connection terminals 152 for data signal input, clock signal input, latch signal input, strobe signal input, data signal output, and ground connection, respectively, which are flexible. It is connected to a data signal line 181, a clock signal line 182, a latch signal line 183, a strobe signal line 184, and a ground connection line 185 formed on a printed circuit board or a printed circuit board such as glass-epoxy.

In the recording operation, the controller of the recording apparatus moves the recording medium in the sub-scanning direction by a driving mechanism (not shown) and transmits recording data to the thermal head 1 to selectively cause the heating resistance element. To drive. Since the control device drives each heating resistance element in synchronization with the shift clock signal as shown in the timing chart of FIG.
That is, a data signal indicating whether or not each ground-side lead conductor is connected to the ground is transmitted (timing a to b), and a data signal for one line, that is, the recording data of all the heating resistance elements arranged in the main scanning direction. When it is transmitted, it is latched (timing b), the heating resistance element is driven based on the strobe signal (timings c to d), and then a feed signal is transmitted to the drive mechanism to feed the recording medium by one line (timing b). d) The recording data of the following line is transmitted to the thermal head 1. Desired recording is performed by sequentially performing these recording operations.

[0005]

The thermal head constructed as described above is suitable for use in a recording device such as a printer or a facsimile, but a recording device for printing a large area with one data, for example, When used in a printer or the like for visually printing a Braille document, various problems as described below will occur. That is, in a recording device such as a printer or a facsimile, a recording resolution of 8 to 16 dots / mm or higher is required, and accordingly, the interval between the heating elements of the thermal head, that is, the arrangement of the lead conductors, is correspondingly increased. Although the spacing is formed as narrow as possible, the size of the unit print dot in the Braille printer as described above is 1 mm in diameter.
The dot shape may be on the order of mm or larger, and does not require the resolution of a conventional recording device such as a printer. Therefore, when the thermal head used in the conventional recording apparatus is used as the recording head of the Braille printer described above, one group must be formed by a plurality of heating resistance elements, and this group must be selectively driven. Therefore, even if the thermal head is formed at a high density by steps such as photolithography and etching, the performance cannot be fully utilized and the manufacturing cost cannot be matched. In addition, when the lead conductors are arranged at wide intervals in accordance with the unit print dots of the Braille printer, the heat resistance of the heating resistor element becomes large, and if the driving current is the same as in the conventional thermal head, the heating time constant becomes long. As a result, the printing speed is slowed down. Also,
If the power supply voltage for driving the heating resistor is increased in order to increase the printing speed, the drive current flowing through the ground side lead conductor connection terminal of the drive circuit of the thermal head also increases, which is specific to the drive circuit. If the maximum allowable drive current value is exceeded, a new drive circuit must be designed and manufactured again, and the drive circuit itself must be enlarged to increase the maximum allowable drive current value. However, there is a problem in that it becomes expensive and increases in size.

The present invention has been made to solve these problems and provides a thermal head capable of simplifying the manufacturing process thereof and controlling the driving by using a conventional driving circuit. With the goal.

[0007]

In order to solve the above-mentioned problems, in the thermal head of the present invention, the connection terminal of the drive circuit is connected to one drive circuit connection terminal provided at the end of the ground side lead conductor. It is configured by connecting a plurality of. The print data to be printed is stored in the memory for each print data for one line to be printed by the thermal head, the clock signal is sent to the drive circuit of the thermal head, and the clock signal is sent from the memory based on this clock signal. The recording data is sequentially shifted, and when a predetermined number of clock signals are transmitted to the thermal head drive circuit, the memory is controlled so that the recording data by the unit heating resistance element is sequentially transmitted to the thermal head drive circuit. Configured.

[0008]

When the ground side lead conductor is connected to the ground by the drive circuit, the drive current for driving the heating resistor element to generate heat is divided into the connection terminals of the plurality of drive circuits connected to the ground side lead conductor. Then flow. The control unit is 1
The same recording data is transmitted to the connection terminals of the drive circuit connected to the one ground side lead conductor.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermal head of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a thermal head of the present invention and a control unit of a recording apparatus using the thermal head. The thermal head 1 includes a substrate 10, a heating resistor 11, a ground side lead conductor 12, and a power source side lead conductor 1.
3, a common electrode 14, a drive circuit 15, a bonding wire 16, a power supply 17, and a signal line 18, and 2 is a controller 20, a memory control circuit 21, a conduction time control circuit 22,
The control unit 3 including the frequency divider 23 is a memory unit including a memory 31 and a parallel-serial conversion circuit 32.

FIG. 2 is a view showing a detailed structure of the thermal head 1 with the middle part omitted, and the thermal head of the present invention, like the conventional thermal head described above, has one end side of the substrate in the main scanning direction, that is, in the main scanning direction. A heating resistor 11 is provided so as to extend in the X direction in the figure, and a plurality of drive circuits 15 are provided on the other end side of the substrate 10 so as to face the heating resistor 11. Further, a plurality of power source side lead conductors 13 are extended in the sub-scanning direction, that is, the Y direction in the drawing so as to be connected to the heating resistor 11, and are arranged at equal intervals in the X direction in the drawing. The power source side lead conductor 13 is connected to a common electrode 14 provided so as to extend in the X direction in the figure. The ground side lead conductor 12 is provided in the middle of the power source side lead conductors 13 adjacent to each other so as to be in contact with the heating resistor 11 and to extend in the Y direction of the drawing. Pad 121 is provided. In the thermal head of the present invention, the resolution is lower than that of the conventional thermal head described above, and the widths of the power supply side lead conductor 13 and the ground side lead conductor 12 in the X direction in the figure are formed to be large. The drive circuit 15 is
The drive circuit is the same as that used in a thermal head used in a conventional thermal recording device such as a printer, and a plurality of ground side lead conductor connection terminals (pads) 151 are provided on the side close to the ground side lead conductor 12. , Are arranged in a zigzag pattern in the X direction in the figure. Further, a pad 152 for data signal input, clock signal input, latch signal input, strobe signal input, data signal output, and ground connection is provided on the signal line 18 side, and each drive circuit 15 has a flexible substrate. Alternatively, a data signal line 181, a clock signal line 182, a latch signal line 183, a strobe signal line 1 formed on a printed board 18 made of glass-epoxy or the like.
84, the ground connection line 185. The connection pad 121 of the ground side lead conductor 12 is formed wide in the X direction in the drawing, and the plurality of connection pads 151 of the drive circuit 15 are connected to the connection pad 121 by the bonding wires 16. . As a result, when the lead conductor 12 is grounded to drive the heating resistor element to generate heat, the current flowing from the common electrode 14 side is divided by the amount of the terminal on the drive circuit 15 side connected to the lead conductor 12. It will be. That is, even if the unit heating resistor element is enlarged and the energy supplied from the power source 17 is increased accordingly, the current flowing through each connection terminal 151 of the drive circuit 15 becomes sufficiently small. Therefore, the drive circuit used in the thermal head used in the conventional printer or the like can be used as the drive circuit as it is. In the thermal head of the illustrated embodiment, one ground side lead conductor 12
The four connection pads 151 of the drive circuit 15 are connected to the bonding wires 16 to the connection pads 121 of.

Next, the operation of the thermal head of the present invention and its control method will be described. The print data created by a higher-level device such as a computer is stored in the memory 31 for each line of data recorded by the thermal head in the main scanning direction. In the recording operation, the memory control circuit 21 reads the recording data stored in the memory 31 line by line, the parallel-serial conversion circuit 32 converts this to serial data, and based on the clock signal, the data is converted. It is transmitted to the drive circuit 15 via the data signal line 181 (timings a1 to b in the timing chart of FIG. 3). When the transmission of the print data for one line is completed, the controller 20 sends a latch signal to the thermal head 1 (timing c), and the drive circuit 15 latches the sent print data. Next, based on the strobe signal transmitted from the energization time control circuit 22, the ground side lead conductor 12 is connected to the ground for a predetermined time, and the heating resistance element to be recorded is energized (timing c to d). When the recording for one line is completed, the controller 20 transmits a feed signal (timing d), the driving mechanism (not shown) feeds the recording paper for one line, and the recording of the following line is performed (timing a ′).
Or later). FIG. 3 is a timing chart showing a drive control signal of the thermal head of the present invention. The shift clock signal is transmitted from the memory control circuit 21 to the drive circuit 15 via the clock signal line 182, and in the drive circuit 15, the shift clock signal is transmitted. The recording data input from the data signal line 181 is sequentially shifted based on the signal. This shift clock signal is also transmitted to the frequency divider 23, and the frequency divider 2
In 3, the shift clock signal is divided into 1/4 and the divided signal, that is, the data clock signal shown in FIG. 3 is transmitted to the parallel-serial converter 32. In the parallel-serial converter 32, based on the data clock signal, the recording data for one dot is read from the recording data for one line read from the memory 31, that is, the recording data by the unit heating resistance element, and the signal line 181. It is sequentially transmitted to the drive circuit 15 via the.

Accordingly, in the thermal head 1,
The drive circuit 15 sequentially shifts the recording data for each shift clock signal transmitted from the memory control circuit 21, and the recording data transmitted from the data signal line 181 is inputted every time the shift clock signal is inputted four times. 1
The dot recording data is updated and input to the drive circuit 15. That is, at the time of recording operation, 1
The same recording data is input to the four connection terminals of the drive circuit 15 connected to the one ground-side lead conductor 12,
These are print data for one dot.

In the thermal head of the present invention, since it is not necessary to form the lead conductors and the heating resistors in a fine pattern, it is possible to produce them at low cost only by screen printing while omitting the etching step in the production thereof. Since a large current can be applied to drive the heating resistor, high-speed driving is possible despite the large heat capacity of the heating resistor element.

Further, in this embodiment, four connection terminals of the driving circuit are connected to one ground side lead conductor, that is, the resolution is 1/4 of that of the above-mentioned conventional thermal head.
However, when the resolution is ½ that of the conventional thermal head, the two connecting terminals of the drive circuit are connected to one ground side lead conductor and the shift clock signal is supplied. The recording data may be transmitted by dividing the frequency by half. That is, the number of connection terminals of the drive circuit connected to one ground side lead conductor and the relationship between the shift clock signal and the signal for transmitting recording data may be appropriately determined depending on the resolution of the thermal head.

Further, in this embodiment, all the connection terminals 151 of the drive circuit are connected to the ground side lead conductor 12, but the heat capacity of the heating resistor 11, the current supplied by the power supply 17, or the specifications of the drive circuit. You may also set the number of connections. For example, in the above embodiment, the power source 1
The voltage of 7 is 24V, the resistance value of the heating resistor element is 200Ω
And the maximum allowable drive current of the connection terminal of the drive circuit is 60mA
In this case, two connection terminals 151 may be connected to one ground side lead conductor. In this case, among the connection terminals 151 arranged in a staggered pattern, only the connection terminals 151 close to the connection pad 121 are connected, and the connection terminals 151 on the signal line 18 side are left open. This may be done (however, the transmission of the recording data is performed in the same manner as in the above-mentioned embodiment).

[0016]

As described in detail above, in the thermal head of the present invention, a plurality of drive circuit connecting terminals are connected to one drive circuit connecting pad provided at the end of the ground side lead conductor, The control unit sends a clock signal to the drive circuit of the thermal head, sequentially shifts the print data based on the clock signal, and sends the print data to the drive circuit when a predetermined number of clock signals are sent to the drive circuit. Since it is configured by controlling, the driving current for driving the heating resistance element to generate heat is divided into the connecting terminals of the plurality of driving circuits connected to the ground side lead conductor, so that the conventional driving circuit is used as it is. In addition, it is possible to apply a large current for driving the heating resistor, and high speed driving (recording) is possible. Further, since the heating resistor, the power source side lead conductor and the ground side lead conductor can be formed by screen printing, the head can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a thermal head of the present invention and a control unit of a recording apparatus using the thermal head.

FIG. 2 is a diagram showing a configuration of a thermal head of the present invention.

FIG. 3 is a timing chart showing drive control signals for the thermal head of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional thermal head.

FIG. 5 is a timing chart showing a drive control signal of a conventional thermal head.

[Explanation of symbols]

1 thermal head 2 control unit 3 memory

Claims (3)

(57) [Claims] 1. A heating resistor formed linearly in the main scanning direction, and sub-contacts that are in contact with the heating resistor and are connected to a power source and are arranged at equal intervals in the main scanning direction. A plurality of power supply side lead conductors extending in the scanning direction and a plurality of ground side lead conductors extending in the sub-scanning direction, which are provided between the heat generating resistors and are provided between the power supply side lead conductors, and the ground side lead conductors. A thermal head comprising a drive circuit for selectively driving a heating resistance element formed by arranging a plurality of connection terminals to be connected in a longitudinal direction and dividing the lead conductor based on a signal from a control unit. A thermal head, wherein a plurality of drive circuit connection terminals are connected to one drive circuit connection pad provided at an end of the ground side lead conductor. 2. The thermal head according to claim 1, wherein the control section stores the recording data to be recorded in the memory for each recording data of one line to be recorded by the thermal head, and the clock signal is a driving circuit of the thermal head. And send this clock signal to the end of the ground side lead conductor.
Drive connected to one drive circuit connection pad
When the data is transmitted to the drive circuit of the thermal head by the number of connection terminals of the circuit, the recording data by the unit heating resistance element transmitted from the memory is sequentially shifted and controlled to be transmitted to the drive circuit of the thermal head. To
The method of driving a thermal head according to claim 1 . 3. The thermal head according to claim 1, wherein the heating resistor, the power source side lead conductor and the ground side lead conductor are formed by screen printing.