JP3328735B2 - Thermal print 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 print head incorporated in a printing unit such as a printer, a facsimile, a word processor, or a tape writer, and more particularly, to a means for bonding a substrate provided on the surface of a heat sink.

[0002]

2. Description of the Related Art A thermal print head of this type is generally provided with a glaze layer, a heating resistor, a common electrode pattern, and individual electrode patterns formed on a ceramic substrate, and a driving IC mounted thereon. A wiring circuit pattern for connecting the input terminal to the driving IC is formed.

In order to form or assemble all of the above-listed components over the entire surface of a single substrate, a complicated manufacturing process must be performed, and since the substrate is entirely made of ceramic, it is expensive and expensive. In addition, there is a tendency that a substrate having a mounted product in the course of manufacture tends to be large, which hinders a smooth progress of a flow operation or the like.

To cope with this, for example, Japanese Patent Application Laid-Open
JP-A-238760 discloses that a substrate is divided into two parts to constitute a thermal print head. Specifically, a glaze layer, a heating resistor, a common electrode pattern, and an individual electrode pattern are provided on one of the divided ceramic substrates, and a driving IC, a wiring circuit pattern, and an input terminal are provided on the other printed circuit board. Is arranged. The individual electrode patterns on the one ceramic substrate and the driving ICs on the other printed substrate are connected by wire bonding.

Japanese Utility Model Laid-Open Publication No. 61-60562 discloses that a substrate is divided into two for the same purpose as described above. In this case, a heating resistor and the like are formed. Driver IC is mounted on the substrate on the side where
The wiring circuit pattern on the other substrate and the driving IC are connected by wire bonding.

Since the temperature of the ceramic substrate on which the heating resistor is formed has a remarkable temperature rise, the entire back surface of the substrate is made of a metal or other heat radiating plate by using an inelastic adhesive. If the substrate is bonded to the surface, the substrate is warped due to a bimetal effect caused by a difference in the coefficient of thermal expansion between the substrate and the heat sink. For this reason, print blurring, density unevenness, and the like occur, which causes a problem that a satisfactory printing operation cannot be performed.

Therefore, conventionally, as a means for bonding the above-mentioned ceramic substrate to the heat sink, an adhesive having elasticity even after curing, such as a silicone adhesive, is used, and the difference in the coefficient of thermal expansion between the two is determined. The fact is that the substrate is prevented from warping by absorbing the elasticity of the agent.

[0008]

However, if the ceramic substrate on which the heat generating resistor and the like are formed as in the prior art is bonded to the surface of the heat sink using an elastic adhesive, There are the following problems.

That is, when printing is performed by the thermal print head, the platen for feeding the print target paper repeats normal rotation and stop, and in some cases, reverse rotation. In this case, with respect to the heater on the surface of the heating resistor formed on the ceramic substrate, the platen performs forward and reverse rotations and stops in a state where the platen is slid in contact with the printing target paper interposed therebetween. Sliding resistance or frictional force is generated between the heater and the heater.

[0010] Then, a force for moving the ceramic substrate in the width direction acts due to the frictional force and the like. At this time, the ceramic substrate and the heat radiating plate are bonded by an elastic adhesive. In such a case, there is a relative displacement between the ceramic substrate and the heat sink with respect to both sides in the width direction. Due to this displacement, a stress is repeatedly applied to the wire connecting the ceramic substrate and the printed board, and as a result, the wire is broken and the reliability of the head is reduced.

According to Japanese Patent Application Laid-Open No. 2-38058, an adhesive region is divided into three portions in the longitudinal direction of the substrate, an adhesive having no elasticity is used in a central region, and an adhesive having no elasticity is used in both side regions. It is disclosed to use an elastic adhesive.

However, in this configuration, since the central region is provided over the entire length of the substrate in the width direction, the warp due to the bimetal effect may be generated in the width direction of the substrate. Further, in the above configuration, the entire surface of the substrate is occupied by the region using one adhesive and the region using the other adhesive. For this reason, for a long time until these adhesives are cured, it is necessary to fix the substrate so as not to cause a positional shift with respect to the heat sink, and a temporary fixing means for that is required separately. There is also a problem.

The above-mentioned problems are particularly prominent on the substrate having the heating resistor in the case where the substrate is divided into two as shown in the above example. Even when all the components such as each electrode pattern are included, the same can occur.

The present invention has been made in view of the above circumstances, and has been developed in consideration of the friction between the platen and the platen when only an elastic adhesive is used as a bonding means between the substrate and the heat sink. Displacement of the board due to force and disconnection of the connection wire between other boards can be prevented, no warping occurs not only in the longitudinal direction of the board but also in the width direction, and additional fixing means is added. It is an object of the present invention to ensure that the substrate can be held at a fixed position before the adhesive is cured.

[0015]

Means for Solving the Problems To solve the above problems, the present invention takes the following technical means.

According to a first aspect of the present invention, there is provided a thermal print head in which at least a substrate on which a heating resistor and a heat generation control electrode pattern are formed is bonded to a surface of a heat radiating plate. A first adhesive region located at a longitudinal central portion within a band of a predetermined width set along the longitudinal direction, second adhesive regions located on both sides in the longitudinal direction of the first adhesive region, And a third adhesive region excluding the second adhesive region. The first adhesive region is made of an adhesive having no elasticity after being cured, and the second adhesive region is made of a cured material. Later, the third adhesive region is fixed to the substrate and the radiator plate until each of the adhesives is cured, while being bonded to the surface of the radiator plate using an adhesive having elasticity later. Using an adhesive It is characterized in that it is bonded to the surface of the heat radiating plate.

Further, the invention described in claim 2 of the present application is:
A heating substrate on which a heating resistor and a heating control electrode pattern are formed, and a wiring substrate on which a wiring circuit pattern for transmitting a signal from an input terminal to a drive circuit are formed are arranged in parallel on the surface of a heat sink. 2. The thermal print head according to claim 1, wherein the thermal print head is formed by bonding the heating substrate and the wiring substrate electrically via a signal line.
The setting of the bonding area on the back surface of the substrate and the mode of bonding with the heat sink in the thermal print head according to the above are applied to the setting of the bonding area on the back surface of the heating substrate and the bonding mode with the heat sink. is there.

Further, the invention described in claim 3 of the present application uses a double-sided pressure-sensitive adhesive sheet as the pressure-sensitive adhesive according to claim 1 or 2.

[0019]

According to the thermal print head of the present invention, the first adhesive area where the adhesive having no elasticity after curing is used is only the central portion in the longitudinal direction on the back surface of the substrate. Therefore, the board is firmly adhered to the radiator plate so that the board does not warp in the longitudinal direction due to the difference in the coefficient of thermal expansion, and does not shift. In addition, since the first adhesive region exists within a band having a predetermined width set along the longitudinal direction of the substrate, there is no possibility that the first adhesive region is warped in the width direction of the substrate. Thereby, the reliability of the head is improved.

Further, by using an adhesive having elasticity in the second bonding region located on both sides in the longitudinal direction of the first bonding region, it is possible to prevent the occurrence of warping as described above. A decrease in the adhesive strength at both ends in the longitudinal direction of the substrate due to the narrow first adhesive region is prevented.

Further, by using an adhesive in the third adhesive region excluding the first and second adhesive regions,
Until the above two types of adhesives are hardened at the time of attaching the substrate, the position of the substrate is held at a fixed position by the action of the adhesive. This eliminates the need to fix the substrate to the heat sink with clips or the like until the adhesive is cured.

If the above-described bonding means is applied to a thermal print head of the type in which the substrate is divided into two, further effects can be obtained in addition to the effects already described by dividing the substrate. . In other words, the substrate on which the heating resistor is formed has a dimension in the width direction which is shortened due to the division, so that warping is likely to occur, and this substrate is in a much higher temperature state than the other substrate. It becomes. Therefore, by applying the above-mentioned bonding means to this substrate, it is possible to prevent the occurrence of warpage due to a rise in temperature, which can be said to be a fatal drawback.

Further, if a double-sided pressure-sensitive adhesive sheet is used as the pressure-sensitive adhesive used in the third bonding area, there will be no variation in the location and amount of the two types of bonding agents. That is, a filling hole corresponding to the first and second adhesive regions is formed in advance in the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive sheet is attached to the surface of the heat radiating plate (or the back surface of the substrate). If an adhesive is poured and the substrate and the heat sink are thereafter bonded, uniform bonding is always performed at the same location with the same amount of adhesive.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a perspective view of a main part showing a typical configuration example of a thermal print head according to the present invention. As shown in FIG. 1, on the surface of the heat radiating plate 1, a ceramic substrate 2 and a printed substrate 3, which are two divided substrates, are arranged in parallel. The ceramic substrate 2 corresponds to a heating substrate, and the printed circuit board 3 corresponds to a wiring substrate.

On the ceramic substrate 2, a heating resistor 4 formed on the surface of a partial glaze (not shown), and a heating control for individually driving each region in the longitudinal direction of the heating resistor 4 to generate heat. An electrode pattern 5 is provided. The heat control electrode pattern 5 is composed of a common electrode pattern 6 and individual electrode patterns 7. A heater 4a is provided on the surface of the heating resistor 4.
(See FIG. 3) is formed.

On the other hand, a wiring circuit pattern 8 connected to an input terminal (not shown) is formed on the printed circuit board 3, and the individual electrode pattern 7 is formed based on a signal from the wiring circuit pattern 8. On ... A driving IC 9 for transmitting an off signal is mounted.

Wire bondings 10 are provided between the individual electrode patterns 7 on the ceramic substrate 2 and the driving ICs 9 on the printed circuit board 3. Wire bonding W is also provided between the wiring circuit pattern 8 on the printed circuit board 3 and the driving IC 9.

As a feature of the present invention, the bonding area on the back surface of the ceramic substrate 2 is virtually set as shown in FIG. That is, the ceramic substrate 2
A band S having a predetermined width c is provided along the longitudinal direction of the band S, and a first adhesive region 11 having a short dimension d is defined in the center of the band S in the longitudinal direction. In addition, second adhesive regions 12, 12 having a long dimension e are defined on both sides in the longitudinal direction of the first adhesive region 11 in the zone S. In this case, the first bonding region 1
A small gap f between the first and second bonding regions 12, 12.
Intervene. Further, the first and second bonding regions 1
A portion excluding 1, 12, and 12 is referred to as a third adhesive region 13.

For the first bonding area 11, an adhesive having no elasticity after curing is used, and the second bonding area 12 is used.
, An adhesive having elasticity after curing is used, and an adhesive is used for the third adhesive region 13. In this case, as the non-elastic adhesive, for example, an acrylic or epoxy resin is used, while as the elastic adhesive, for example, a silicone resin is used. The pressure-sensitive adhesive used is, for example, one containing an acrylic polymer as a main component. As the pressure-sensitive adhesive, it is preferable to use a double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive tape) having separators attached to both sides. The respective regions of the ceramic substrate 2 are adhered to the surface of the heat sink 1 by the above-mentioned two kinds of adhesives and pressure-sensitive adhesives.

An example of the procedure of this bonding operation will be described.
First, the first and second adhesive sheets are applied to a double-sided adhesive sheet as an adhesive.
A rectangular hole corresponding to the bonding areas 11, 12, 12 is formed, and the outer contour of the double-sided PSA sheet is made to correspond to the third bonding area 13. Then, this double-sided pressure-sensitive adhesive sheet is stuck on the surface of the heat sink 1, and thereafter, 2
Each kind of adhesive is filled. In such a state, the ceramic substrate 2 is placed above the double-sided pressure-sensitive adhesive sheet and the adhesive, and a pressing force is applied from above. Thereafter, the ceramic substrate 2 is held at the initial position by the action of the double-sided pressure-sensitive adhesive sheet without causing a positional shift with respect to the heat radiating plate 1 even if the adhesive is hardened until the adhesive is cured. . Note that the bonding operation is not limited to this, and the ceramic substrate 2 is radiated by using two types of adhesives and pressure-sensitive adhesives according to the bonding regions 11, 12, and 13 as shown in FIG. Any other procedure may be used as long as it can be adhered to the plate 1.

On the other hand, as a means for bonding the printed board 3 to the heat radiating plate 1, the same structure as described above may be adopted.
In this case, in consideration of the fact that it is not necessary to take the influence of heat so much into consideration, for example, an adhesive may be used on the entire surface, or only one or two kinds of adhesives may be used.

When printing is performed by mounting the thermal print head having the above-described structure on a printer or the like, as shown in FIG. With the paper 16 interposed, the platen 15 repeatedly rotates and stops. At this time, the ceramic substrate 2 is prevented from being warped due to the effect of the above-mentioned elastic adhesive due to the effect of heat, and is displaced due to the frictional force with the platen 15 due to the effect of the non-elastic adhesive. It is adhered to the heat sink 1 so as not to be present. Therefore, the wire 10 electrically connecting the ceramic substrate 2 and the printed board 3 is not subjected to the repetitive stress caused by the relative positional displacement of the two boards 2 and 3, and the wire 10 is effectively disconnected. Is prevented.

The results of an experiment conducted to prove the effect of preventing the wire 10 from breaking are shown below.

An adhesive made of epoxy resin was used as an adhesive having no elasticity, an adhesive made of silicone resin was used as an adhesive having elasticity, and an acrylic adhesive was used as a double-sided pressure-sensitive adhesive sheet. Then, in the present invention, these adhesives and pressure-sensitive adhesives were laid out in the state shown in FIG. 2, whereas in the comparative example, the adhesive having the elasticity was placed in a rectangular portion indicated by reference numeral Z1 in FIG. The double-sided pressure-sensitive adhesive sheet was used in other places Z2. The dimension g in the longitudinal direction of the portion indicated by the symbol Z1 is:
It was set to about twice the dimension d of the first adhesive region 11 in FIG. In both cases of the present invention and the comparative example, the heater portion 4a on the ceramic substrate 2 is moved from the platen 15 shown in FIG.
The platen 15 was repeatedly driven in the forward and reverse directions (ab direction) while a load P of about 2 kgf was applied to.

As a result of the above experiment, the comparative example is 100
While the wire 10 was broken in 0 cycles (one drive in each of the forward and reverse directions is defined as one cycle), the present invention did not break even in 50,000 cycles or more.
Therefore, it was confirmed that the present invention is excellent in achieving the effect of preventing the wire 10 from breaking.

In the above embodiment, the present invention is applied to a case where the driving IC 9 is mounted on the printed board 3 which is a wiring board. Apart from this, as shown in FIG. The drive I is placed on the ceramic substrate 2 which is a heating substrate.
The same applies to the case where C9 is mounted. Although the effect is slightly reduced, the case where the heating resistor 4, the heating control electrode pattern 5, the driving IC 9, the wiring circuit pattern 8, and the like are all formed or mounted on one ceramic substrate 2 is also described. The present invention can be similarly applied.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration example of a thermal print head according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing each bonding area on the back surface of a heat generating substrate which is a component of the thermal print head.

FIG. 3 is a schematic vertical sectional side view showing a use state of the thermal print head.

FIG. 4 is a schematic vertical sectional side view showing another configuration example of the thermal print head.

FIG. 5 is a schematic diagram showing each bonding region on the back surface of a heat generating substrate adopted as a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat sink 2 Heating board (ceramic board) 3 Wiring board (printed board) 4 Heating resistor 5 Heating control electrode pattern 8 Wiring circuit pattern 10 Wire bonding 11 First bonding area 12 Second bonding area 13 Third bonding area S Band

Claims (3)

(57) [Claims] 1. A thermal print head in which a substrate on which at least a heating resistor and a heating control electrode pattern are formed is adhered to a surface of a radiator plate, wherein the back surface of the substrate is set along the longitudinal direction. A first adhesive region located at a central portion in the longitudinal direction within a band of a predetermined width, second adhesive regions located on both sides in the longitudinal direction of the first adhesive region, and a second adhesive region excluding the first and second adhesive regions. The first bonding region is made of an adhesive having no elasticity after curing, and the second adhesive region is made of an adhesive having elasticity after curing. Is attached to the surface of the heat sink
On the other hand, the third adhesive area is located on the upper side until each of the adhesives is cured.
A thermal print head, wherein the thermal print head is adhered to a surface of the heat radiating plate using an adhesive capable of fixing the substrate to the heat radiating plate . 2. A heat generating board on which a heat generating resistor and a heat control electrode pattern are formed, and a wiring board on which a wiring circuit pattern for transmitting a signal from an input terminal to a driving circuit are formed on a surface of a heat radiating plate. A thermal print head, which is arranged and adhered in parallel to the substrate, and electrically connects the heat-generating substrate and the wiring substrate via signal lines. A thermal print head, wherein the setting of the bonding area on the back surface and the mode of bonding with the heat sink are applied to the setting of the bonding area on the back surface of the heat generating substrate and the mode of bonding with the heat sink. 3. The thermal print head according to claim 1, wherein a double-sided pressure-sensitive adhesive sheet is used as the pressure-sensitive adhesive.