JP3405724B2 - Thermal head - 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.

[0002]

2. Description of the Related Art As an example of a conventional thermal head, for example, a thermal head proposed in Japanese Patent Application Laid-Open No. 5-84952 discloses a rectangular insulating substrate having a surface parallel to one long side of the insulating substrate. A print medium, for example, a heat generating resistor is arranged, and a plurality of drive ICs for driving the heat generating resistor by a predetermined number of dots are arranged and mounted along a straight line parallel to the arrangement direction of the heat generating resistor.

On the other hand, a plurality of external connection terminals for connecting to an external control circuit are formed on the other long side of the insulating substrate, and the plurality of drive ICs are shorter than the arrangement length of the heating resistors. The external connection terminals are arranged centrally at both ends in the longitudinal direction of the insulating substrate where a space is provided by the arrangement in the area.

Further, one end or both ends of the external connection terminal are electrically connected to a part of the external connection terminal in a strip-shaped region extending from the mounting portion of the drive IC on the insulating substrate to the other long side of the insulating substrate in the longitudinal direction of the insulating substrate. A signal wiring pattern extending to the above is formed, and a predetermined signal input pad of each drive IC is commonly connected to this signal wiring pattern.

In the above thermal head, since the external connection terminals are centrally arranged at both ends in the longitudinal direction of the insulating substrate, the length from the connection terminal of the common wiring to the supply portion to each heating resistor can be shortened, so that the voltage drop. Can be reduced and the printing quality can be improved. This means that the ground wiring is also commonly connected to each drive IC that drives the dots of the heating resistor from the external connection terminals, like the common wiring, so if the external connection terminals are arranged at both ends of the insulating substrate, The wiring length of both the common wiring and the ground wiring can be shortened, and the voltage drop can be reduced.

Further, as another example of the conventionally proposed thermal head, for example, in the thermal head proposed in Japanese Patent Laid-Open No. 177863/1993, a heating resistor and a driving IC are longitudinally mounted on a rectangular insulating substrate. Signal wirings that are arranged in parallel to each other and that commonly connect individual electrodes for connecting the heating resistors and the driving ICs, ground electrodes, and control signal pads of each driving IC on the insulating substrate. A pattern is formed.

Then, a ground electrode is formed along an edge of a long side opposite to the side where the heating resistor is arranged based on the mounting portion of the drive IC, and the ground electrode and the drive IC are connected to each other. The signal wiring pattern is arranged between them.

In the thermal head, the width of the ground electrode can be wide or thick by forming the ground electrode along one long side edge of the rectangular insulating substrate. A large electric current can be passed.

Further, as another example of the conventionally proposed thermal head, for example, a thermal head proposed in Japanese Examined Patent Publication No. 7-12702 has a rectangular insulating substrate on which one side of the insulating substrate is long. A heating resistor is arranged in parallel with the side, and a plurality of drive ICs for driving the heating resistor by a predetermined number of dots are arranged and mounted along a straight line parallel to the arrangement direction of the heating resistor.

Then, a plurality of signal wirings provided on the insulating substrate, for example, each input of each drive IC such as a signal-in terminal, a power supply terminal, a clock signal terminal, a ground terminal, a latch terminal, a strobe terminal, and a signal-out terminal. The signal wiring terminal is connected to the common signal line by wire bonding.

These common signal lines are arranged between the ground electrode pattern formed along the other long side and the plurality of drive IC rows, and the common electrode is formed at the other long side end of the insulating substrate. The pattern and the ground electrode pattern are formed along the tip portion, and only the strobe pattern in the pattern is linearly arranged so as to pass through the lower side of each drive IC.

[0012]

However, the thermal head proposed in Japanese Unexamined Patent Publication No. 5-177863 is
Forming a wide ground electrode on an insulating substrate
Inevitably, the short side width of the insulating substrate itself becomes large, which is an obstacle to miniaturization. Furthermore, the ground electrode is formed along the long edge of the insulating substrate opposite to the side where the heating resistor is arranged. is there. In such a configuration, for example, even if the signal wiring pattern and the ground electrode are arranged so as to overlap each other, only a space between the drive IC and the ground electrode and under the drive IC is left, so that it does not contribute to space saving. .

As described above, Japanese Patent Laid-Open No. 177863/1993
In the thermal head proposed in the publication, a part of the space on the insulating substrate is allocated only to the ground electrode, which causes the width of the insulating substrate itself to increase. Therefore, in view of the above problems, the present invention is to provide a thermal head that can increase the width of the pattern of the ground electrode, suppress the increase of the width of the insulating substrate, and reduce the size.

When the thermal head having the external connection terminals arranged at both ends of the insulating substrate proposed in Japanese Patent Laid-Open No. 5-84952 is incorporated in a set such as a facsimile, a signal for driving the thermal head is output. It is necessary to connect the control board on the set side, the power supply board for supplying a power supply voltage for driving, for example, 24 V, and the thermal head board.

Generally, on the set side, the power supply board or the control board is commonly used for several kinds of facsimile set models, and it is possible to incorporate the power supply board and the control board as independent boards in order to reduce the manufacturing cost due to the same specifications. Has been done. For this reason, the power supply board and the control board are independently provided with connection terminals for connecting the thermal head board.

When the thermal head substrate having the above structure is electrically connected to the set, connection cables are attached to the external connection terminals on both sides of the thermal head, and the power supply terminal and the control signal terminal are provided inside the external connection terminals on both sides. Therefore, it is necessary to further branch to the set side end of the connection cable for the power supply board connection terminal and the control board connection terminal, and to attach two connectors to the tip. Therefore, in the thermal head substrate having the above-mentioned structure, when the thermal head substrate is assembled into the set, two cables having the ends branched into two systems are required.

Further, the cable having the branched end has a special specification, which increases the manufacturing cost of the cable and affects the price of the printer set. Therefore, when using a standard specification cable with a non-branched tip, there is no choice but to centrally place the power board connection terminal and control board connection terminal for connecting to the thermal head board on the set side in one place. It also becomes a factor to increase the manufacturing cost on the set side.

Further, when the external connection terminals are centrally arranged as in the prior art, the ground electrode commonly connected to the ground terminal of each drive IC from the ground terminal of the external connection terminal is opposite to the drive IC row with respect to the heating resistor. It becomes necessary to dispose along the long side end portion of the side insulating substrate. Furthermore, the ground electrode needs to have a current capacity corresponding to the number of dots of the heating resistor to be printed at the same time.
A current capacity of about 6 A is required.

In order to obtain a ground electrode pattern having such a current capacity, the pattern width needs to be about 1 mm. When such a ground electrode is newly added on the insulating substrate, the short length of the insulating substrate is obtained. The hand size will be that much larger.

Further, in the thermal head proposed in Japanese Patent Publication No. 7-12702, a plurality of signal wirings other than the strobe pattern are arranged between the drive IC row and the ground electrode to input the drive IC. It is connected to each signal terminal. In such a configuration, in order to wire-bond the input signal terminal of the driving IC and each signal wiring, a distance between the driving IC and the signal wiring pad is required, and an arrangement area for a plurality of signal wirings is required. From that,
It is difficult to reduce the size of the insulating substrate in the short side direction.

Further, in view of the above problems, the present invention reduces the number of electrical connection points between the thermal head and the set side,
Moreover, even when independently connected to the connection terminals of the power supply board and the control board on the set side, the cables can be easily separated and divided, and the problem of the arrangement of the plurality of signal wirings is solved,
The present invention proposes a thermal head that shortens the insulating substrate.

[0022]

The present invention is derived from the heating resistor in a thermal head in which a heating resistor and a plurality of drive ICs are provided on a rectangular insulating substrate in the longitudinal direction of the insulating substrate. An insulating film provided on the individual electrode, a first ground electrode provided on the insulating film along the longitudinal direction of the insulating substrate, and on a side opposite to the first ground electrode with respect to the plurality of drive ICs. A second ground electrode, which is provided along the longitudinal direction of the insulating substrate and is connected to each ground pad of the plurality of drive ICs, and adjacent drive ICs of the plurality of drive ICs are crossed,
A connection means for electrically connecting the ground electrode and the second ground electrode is provided.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an overall plane of an embodiment of a thermal head of the present invention will be described with reference to FIG. Figure 1
As shown in FIG. 3, a heating resistor 6 is formed on the first long side 2 of the glaze layer provided on the rectangular insulating substrate 1 (not shown) in parallel with the first long side. A second heat generating resistor 6 is provided between the heat generating resistor 6 and the first long side 2 in parallel with the heat generating resistor 6.
The common electrode 7 is formed. The first common electrode will be described later. At one end of the second common electrode 7, a common electrode extension portion 7a is provided at an end portion of the first long side 2 along the first short side 4 in a direction orthogonal to the heating resistor 6. There is.

A driving IC 9 for driving each dot of the heating resistor 6 is mounted at the end of each individual electrode 8 extended from each dot of the heating resistor 6 to the second long side 3 side, It is connected to each individual electrode. Further, as will be described later with reference to FIGS. 2 and 3, signal wirings 13 are arranged below the driving ICs 9 and between the driving IC row and the individual electrode pads. The signal wirings 13 are long sides of the insulating substrate 1. And extends in the same direction as the external connection terminal group 14 on the first short side 4 side. The external connection terminal group 14 is connected to the main body set side by a connector, a flexible cable, or the like.

The first ground electrode 15 commonly connected to each driving IC 9 is arranged in the same direction as the heating resistor 6 between the mounting row of the driving IC 9 and the heating resistor 6. From the first ground electrode 15, a connection electrode 22 for connecting to a second ground electrode described below is extended toward the second long side 3. Further, the mounting portion of the drive IC 9 is sealed with the sealing resin 16 to form the thermal head substrate 28.

Next, the detailed pattern arrangement of the thermal head will be described with reference to the pattern arrangement diagrams of FIGS. 1, 2 and 3. First, gold on the upper surface of the rectangular insulating substrate 1,
First in metal material with low conductor resistance such as aluminum
The common electrode 17, the individual electrode 8, the second ground electrode 18, and the signal wiring 13 are formed by photoetching. Among them, the first common electrode 17 is an electrode for supplying a heating current to each heating resistor dot, and is formed in a comb-shaped pattern (not shown) in the heating resistor 6 part. There is.

A comb tooth-shaped pattern (not shown) is formed at one end of the individual electrode 8 at the portion where the heating resistor 6 is formed, and the comb tooth-shaped pattern of the first common electrode 17 is alternately formed. Will be placed. Further, the other end of the individual electrode 8 is extended to the side of the second long side 3 away from the heating resistor 6, and supplies a current for heating to each dot of the heating resistor 6.

The second ground electrode 18 is connected to the drive I
This is a ground pattern for a heating current that is bonded to the ground pad 19 of C9 and the wire 30.
The signal wiring 13 is a wiring for sending a signal for controlling the drive IC 9 for supplying a heating current to each dot of the heating resistor 6. After the wiring patterns are formed, the heating resistor 6 is formed by electrically connecting the first common electrode 17 and the individual electrode 8 on which the toothed patterns of the comb are alternately formed.

Then, the second common electrode 7 is formed of a metal material having a low conductor resistance value such as gold or silver so as to overlap a part or all of the first common electrode 17, and the conductor resistance value of the entire common electrode is set. To increase the current capacity. As a result, the voltage drop due to the common electrode can be suppressed to a low level even when a plurality of dots are simultaneously energized and printed.

Further, the first ground electrode 15 is arranged between the mounting row of the driving IC 9 and the heating resistor 6. An insulating film 21 is formed below the first ground electrode 15 with a width wider than the pattern width of the first ground electrode 15. Here, the first ground electrode 15 serves as a reinforcing pattern for increasing the current capacity of the entire ground electrode.

Further, below the first ground electrode 15, a protective film 20 made of amorphous glass (FIGS. 3 and 4).
Is provided, and the individual electrode 8 and the signal wiring 13 are arranged below the protective film 20, and particularly the signal wiring 13 is provided.
Is under the driving IC 9 and the driving IC 9 row and the individual electrode pad 11
It is located in between.

In this portion, it is preferable that the insulating film 21 is an upper layer and the protective film 20 is formed as a lower layer thereof to form a two-layer structure insulating film. This is because a silver-based metal material having a low conductor resistance value is used as the first ground electrode 15. At this time, the silver-based metal material is sintered at a firing temperature of about 800 ° C., but when fired at such a high temperature, the protective film 2 is formed as a lower layer.
This is because if there is a layer of amorphous glass that constitutes 0, silver will diffuse from the silver film to the protective film 20 during firing.

As a factor causing the diffusion of silver, the softening point of the layer in which the protective film 20 is mainly composed of amorphous glass is as low as 750 ° C., and therefore the upper silver-based material is used. When fired at a high temperature of 800 ° C, the amorphous glass in the lower layer melts during firing, and silver easily penetrates into the amorphous glass,
It will spread. In addition, the diffusion prevents the protective film 20.
Diffusion to the lower electrode, for example, a gold electrode, and an alloy layer of gold and silver is formed, which increases the conductor resistance value of the individual electrode 8 and causes uneven printing density, and in the worst case, the individual electrode. May cause a disconnection failure.

Therefore, it is effective to provide a layer containing crystallized glass as a main component as the diffusion preventing layer as the insulating film 21 so that the diffusion of silver does not proceed to the lower layer. The crystallized glass has a softening point temperature of 800 ° C. or higher, which is higher than that of the amorphous glass, and the diffusion of silver can be prevented without melting even when silver is baked at around 800 ° C.

As another method of preventing diffusion, if the first ground electrode 15 is made of gold, which hardly causes diffusion, it is not necessary to have a two-layer structure, and it is sufficient to provide the protective film 20 of amorphous glass. Is. As another diffusion prevention method, the first ground electrode may be formed by using a silver paste for low temperature firing at a temperature lower than or close to the softening point of amorphous glass, for example, a firing temperature of 600 ° C. or lower. In this case, since the diffusion of silver is reduced, it is not necessary to have a two-layer structure in this case, but this does not prevent the adoption of the two-layer structure. However, in this case, the conductor resistance value of silver becomes higher than that obtained by firing at around 800 ° C., which is the high temperature.

Next, the external connection terminal group 14 of the thermal head substrate 28 will be described in detail with reference to FIGS. 1 and 2. As shown in FIG. 1, the mounting pitch P of each drive IC 9 is set shorter than the heating resistor dot number length E corresponding to the number of output bits of the drive IC 9. That is, a plurality of drive I
By arranging the wiring length of C in a region shorter than the effective print width length of the heating resistor 6, a vacant space is formed at one end of the insulating substrate 1.

An external connection terminal group 14 is provided in this empty space so as not to overlap the mounting row of the drive ICs 9. As a result, the width of the short side of the insulating substrate 1 can be reduced, which leads to downsizing of the thermal head substrate.

As shown in FIG. 2, the external connection terminal group 14 has 24 outermost terminals in the outer connection terminal group 14.
A drive voltage supply terminal (COM) 24 for V is arranged, the second common electrode 7 is connected to the drive voltage supply terminal 24, and the number of terminals is arbitrarily formed according to the required current capacity. A ground (GND) terminal 25 is provided inside the drive voltage supply terminal 24.
Are arranged and the first ground electrode 15 is connected.

Further, a signal terminal group 26 for sequentially controlling the driving IC is arranged toward the inside of the ground terminal 25,
The signal terminal group 26 includes signal in (SI), strobe 1 to strobe 4 (STR1 to STR4), latch (L).
Terminals such as AT), clock (CLK), thermistor (TM), and logic power supply (VDD) are arranged. A signal wiring 13 (FIG. 2) is connected to each of these signal terminals. It is preferable to arrange the signal wiring 13 below the driving IC 9 and between the driving IC and the connection pad 11 of the individual electrode 8. It is suitable. With such wiring, since there is no signal wiring between the drive IC and the second ground electrode 18, the size of the insulating substrate 1 in the short side direction can be shortened. At this time, if necessary, a single component such as the thermistor 30 is arranged in the space near the second short side 5.

As shown in FIG. 2, since the second common electrode 7 is taken out from the short side 4 on one side of the insulating substrate 1, one end of the effective printing width of the heating resistor 6 is set to the long side of the insulating substrate 1. By arranging them close to the edge vicinity, an empty space where the effective print width portion is not arranged is generated at the opposite long side end. If a necessary pattern is arranged in this portion, the insulating substrate, that is, the thermal head substrate can be further downsized. As an example, the thermistor 30 can be arranged in this space.

Further, the drive IC 9 is mounted on the extension line of the row of the external connection terminal group 14, but in this case, from the leftmost dot 32 of the effective printing width of the heating resistor 6 to the leftmost end for driving it. The wiring of the individual electrodes 8 to the drive IC is arranged with an inclination. The mounting position of this drive IC is set on an extension line inside the portion where the external connection terminal group 14 is arranged.

That is, the dimension from the short sides 4 and 5 of the insulating substrate 1 near the both end dots of the right and left most end dots in the effective print width area of the heating resistor 6 and the dimension on the one dot side are the other. Is larger than the size on the dot side, and the groups of the external connection terminals 14 are centrally arranged at the long side ends of the insulating substrate on the side where the size is increased.

When the effective print width portion of the conventional heating resistor is symmetrically arranged on the long side of the insulating substrate, the leftmost dot 32 moves to the left side of the insulating substrate on the extension line of the heating resistor. Will be done. On the other hand, the arrangement position of the leftmost drive IC cannot be moved to the left side so as not to overlap the row of the external connection terminal group 14. Therefore, the inclination of the individual electrode connecting the leftmost dot and the driving IC becomes an acute angle. If the inclination of the individual electrodes becomes acute,
Although the adjacent electrode pattern pitch of the individual electrodes becomes narrower and it becomes difficult to form the individual electrode patterns, according to the present invention, since the inclination of the individual electrodes does not become an acute angle, the pattern formation of the individual electrodes can be easily performed. .

Next, the detailed pattern arrangement and wire bonding in the vicinity of the mounting portion of the drive IC 9 will be described with reference to FIG. The first ground electrode 15 and the second
In order to connect the ground electrode 18, the connection electrode 22 is extended between the drive ICs 9 and extends from the first ground electrode 15 toward the second ground electrode 18. This connection electrode 2
Since 2 is orthogonal to the signal wiring 13 in the lower layer, the insulating film 21 is formed in a place where the connection electrode is formed to be wider than the connection electrode 22. This connection electrode 22 has at least a plurality of drive I
It is provided between C, but it is preferable to provide it between all the drive ICs.

Since the first ground electrode 15 is formed of a thin film such as gold or silver, the connection from one side of the insulating substrate 1 has a high conductor resistance and a small current capacity. The voltage drop occurs as it goes to the end of the insulating substrate farther from the printer, and the print density varies.
If it is provided between them, this variation can be eliminated.

According to the ground electrode of the wiring pattern, the first ground electrode 15 can be formed on the insulating film 21 in a multi-layered pattern having a sufficient width, while the second ground electrode 18 is formed by one driving IC. The pattern width may be as small as 0.3 mm because the current capacity corresponding to the driving dot is required. Therefore, the dimension from the driving IC of the thermal head substrate to the second long side 3 can be reduced.

As described above, the width of the thermal head substrate can be reduced and at the same time the driving voltage drop due to the ground electrode can be reduced to prevent the occurrence of variations in the print density, and the external connection terminal group 14 can be provided only on one side of the insulating substrate 1. It is possible to provide a thermal head that can be centrally arranged.

Further, when the above wiring pattern arrangement is adopted, the pads 12 provided on the short side of the driving IC 9 and the signal wiring pad 23 can be wire-bonded between the driving ICs, and the driving IC 9 row and the first row. Between the two ground electrodes 18, only the wire bonding connection between the ground pad 19 arranged near the long side of the drive IC 9 and the second ground electrode 18 is made, and the distance between the drive IC row and the second ground electrode 18 can be shortened. It will be possible.

The multi-layer wiring structure portion of the head substrate having the above wiring structure will be described below with reference to the sectional views of FIGS. FIG. 4 is a detailed cross section of the AA ′ portion of FIG. The first common electrode 17, the individual electrode 8, the signal line 13, and the second ground electrode 18 are simultaneously formed on the insulating substrate 1 at once. Then, the heating resistor 6 is formed on the individual electrode 8, and the second common electrode 7 for reducing the resistance value is laminated on the first common electrode 17. Further, a protective film 20 is formed on each of the electrodes, and the insulating film 2 made of crystallized glass is formed on the protective film 20 made of amorphous glass between the mounting position of the driving IC 9 and the heating resistor 6.
1 is formed, and the first ground electrode 15 is further formed thereon.

Then, the protective film 20 on the signal wiring 13 is formed.
The drive IC 9 is mounted on the upper part, and each individual electrode pad 11 and the output pad 10 of the drive IC are wire-bonded with a gold wire 29. Further, the control signal pad 12 and the signal wiring pad 23 (FIG. 3) of the drive IC 9 are further driven by the drive I.
The ground pad 19 of C9 and the second ground electrode 18 are wire-bonded to each other.

Then, the 9 rows of the driving ICs and the wire-bonded portions are sealed with the sealing resin 16 (FIG. 5). At this time, the sealing portion may cover all or part of the first ground electrode 15 in the width direction.

FIG. 5 shows a cross section taken along the line BB 'of FIG. The structure up to the formation of the protective film 20 is the same as that of FIG. This cross-sectional view shows a portion between the drive ICs 9, and the connection electrode 22 extending from the first ground electrode 15 extends over the signal wiring 13 and reaches the second ground electrode 18, and the first ground electrode 15 is formed. And the second ground electrode 18 are connected.

In the above embodiment, as shown in FIG. 1, the mounting rows of the drive ICs 9 and the rows of the external connection terminal groups 14 are arranged in a row, and both rows are arranged in a row in the lateral direction of the insulating substrate 1. As another embodiment, as shown in FIG. 6, the mounting row of the drive ICs 9 and the external connection terminal group 14 are used.
The rows may be arranged in two rows with some rows adjacent to each other in the lateral direction of the insulating substrate 1.

This is a case where the external connection terminal group 14 is long in the lateral direction and the row for mounting the drive IC 9 and the row for the insulating substrate 1 are arranged so as to be partially adjacent to each other in the lateral direction, so that they cannot be accommodated in the thermal head substrate. This is an effective arrangement. As a case where the external connection terminal group 14 has to be lengthened, there are cases in which the number of control signals is large and it is necessary to increase the number of ground terminals and common terminals due to the current capacity.

With such an arrangement, an empty space is created between the row of the external connection terminal group 14 and the heating resistor 6, so that it can be effectively used for mounting a single component such as the thermistor 30. Further, in the embodiment shown in FIG. 6, the external connection terminal group 14 is divided into the left and right in the center and the external connection terminal group 14 is divided.
It shows a case where a and 14b are provided and the connection is made by dividing into two connectors. When the connector is divided into two, the thickness of the connector cable is in the central part, so a long horizontal space is required The horizontal length of the connection terminal group is long.

In the case of this embodiment, the short side dimension of the insulating substrate is slightly larger than that of the embodiment of FIG. 2, but instead, an empty space is formed under the drive IC 9 mounting row. In this empty space, the second common electrode 7 is provided with the second short side 5
From the part along the end of the second long side 3, the external connection terminal group 1
It can be extended and arranged toward 4.

By doing so, the second common electrode 7 of FIG.
As described above, the conductor resistance value of the common electrode provided from the common electrode terminal 24 of the external connection terminal group 14 to the right end of the insulating substrate 1 can be made smaller. As a result, the difference in conductor resistance value between the left and right short portions of the second common electrode 7 is reduced, and the difference in print density can be reduced when printing is performed. As described above, although the short side dimension of the thermal head substrate is slightly increased, the print density difference can be reduced.

[0058]

According to the present invention, since the ground electrode is arranged on the insulating film on the individual electrode, the thermal head can be constructed without increasing the width of the insulating substrate even if the width of the ground electrode is widened. This leads to downsizing of the thermal head. Further, since the group of external connection terminals is centrally arranged at one location on one side of the insulating substrate, the vacant space created thereby can be effectively utilized for mounting other wirings and components.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a thermal head of the present invention.

FIG. 2 is a detailed plan view of the thermal head of the present invention.

FIG. 3 is a detailed plan view of a drive IC mounting portion of the thermal head of the present invention.

FIG. 4 is a cross-sectional view taken along the line AA ′ of FIG.

5 is a sectional view taken along line B-B 'of FIG.

FIG. 6 is another detailed plan view of the thermal head of the present invention.

[Explanation of symbols]

1-Insulating substrate 6-Heating resistor 7, 17-Common electrode 8-Individual electrode 9-Drive IC 14-External connection terminal group 15-First ground electrode 18-Second ground electrode 21 ..Insulating film 22 ..
Connection electrode for connecting the first ground electrode 15 and the second ground electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Yamaji 1 Aoi Electronics Co., Ltd. 1 at 455, Kosainanmachi, Takamatsu City, Kagawa Prefecture (56) References JP-A-7-276691 (JP, A) JP-A-8 -125335 (JP, A) JP 62-7568 (JP, A) JP 6-171133 (JP, A) JP 63-216760 (JP, A) JP 6-297745 (JP, A) ) JP-A-8-78626 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/345 B41J 2/335

Claims (3)

(57) [Claims] 1. A thermal head comprising a rectangular insulating substrate on which a heating resistor and a plurality of drive ICs are provided in a longitudinal direction of the insulating substrate. Insulation provided on an individual electrode led from the heating resistor. A film, a first ground electrode provided on the insulating film along the longitudinal direction of the insulating substrate, and on the opposite side of the first ground electrode to the plurality of drive ICs along the longitudinal direction of the insulating substrate. And a second ground electrode connected to each ground pad of the plurality of drive ICs and between adjacent drive ICs of the plurality of drive ICs to cross the first ground electrode and the second ground electrode.
A thermal head comprising: a connecting unit that electrically connects to a ground electrode. 2. The thermal head according to claim 1, wherein the first ground electrode is formed of a metal material containing silver as a main component. 3. The thermal head according to claim 1, wherein the insulating film has a two-layer structure, one insulating film is a crystallized glass layer, and the other insulating film is an amorphous glass layer.