JP2000211172A - Thermal print head and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a print head holding a good adhesion between a substrate with a heating resistance element array and a heat-radiating member and good thermal conduction properties by making an adhesive material thicker than a thermal conductive non-adhesive material. SOLUTION: An aluminum heat-radiating member 1 of a breadth of approximately 380 mm is used and an alumina ceramics R substrate 4 is fixed to the center of the aluminum heat-radiating member 1. A step between an area of the heat-radiating member 1 including immediately under a heating part of the R substrate 4 and an area other than the area is approximately 0.3 mm. A gel 2 of heat-radiating properties is applied by a thickness of approximately 0.1 mm to the part immediately under the heating part. A double-sided tape 3a of a thickness of approximately 0.4 mm is set to the remaining area to fix the R substrate 4 and the heat-radiating member 1. Moreover, a PCB substrate 5 and the heat-radiating member 1 are secured by a double-sided tape of a thickness of approximately 0.1 mm. The fixed substrate is left in an over of approximately 120 deg.C for about two hours to set the-gel 2. A groove of a depth of approximately 1 mm is formed as a gel reservoir to the heat-radiating member 1 between the gel 2 and the double-sided tape 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a thermal print head capable of obtaining a high-quality image even when a large amount of heat is generated due to high-speed driving, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An image recording system using a thermal print head has advantages such as low running cost, easy maintenance, and quiet image recording. It is widely used by being incorporated in various output printing devices such as information communication devices and measuring instruments.

In general, a thermal head has a configuration in which a resistance substrate on which a heating resistance element array is formed and a drive circuit substrate are attached to a heat dissipation member. That is, in the resistance substrate, a glaze glass layer mainly for improving the surface smoothness and heat storage property is arbitrarily formed on a support base such as alumina, and a heating resistor layer and aluminum or the like are formed on the glaze glass layer. After forming the conductive layer, a plurality of heating resistors and electrode patterns are formed by a photoengraving process. Further, a protective film for protecting the plurality of heating resistors and the electrode patterns is formed by a thin film forming method such as a sputtering method.

FIG. 5 is a side view schematically showing a configuration of a conventional thermal print head used for a video printer or the like. That is, an R board 4 which is a resistance board made of ceramics on which a heating resistor element array (not shown) is formed and a PCB (Print Circuit Board) board 5 which is a driving circuit board made of a glass epoxy board are made of a double-sided tape 3a and 3b are bonded to the heat dissipating member 1 made of aluminum. In order to efficiently release the heat generated from the R base 4 to the outside, a silicone gel material 2 having a high thermal conductivity is disposed in a region corresponding to a position directly below the heating element array. In other areas, a double-sided adhesive tape is arranged. Since the heat dissipating member 1 is flat (however, the gel and the double-sided adhesive tape are provided with a shallow and narrow groove as a gel reservoir), the thicknesses of the silicone gel and the double-sided adhesive tape are almost the same.

In such a thermal head, the heating resistor element array is selectively driven by an IC to generate heat, and printing is performed when the heating resistor element is brought into contact with heat-sensitive paper or the like. There is a need for printed images and higher printing speeds.

The coefficient of thermal expansion of alumina ceramic used for the R substrate and the coefficient of thermal expansion of aluminum, which is a heat dissipating member, vary. Therefore, when the conventional thermal print head shown in FIG. 5 is driven,
The heat generated in the R board 4 cannot be sufficiently released from the heat radiating member 1, and heat is accumulated inside the thermal print head. As a result, the heat radiating member 1 extends more than the R board 4. .

[0007] The difference in thermal expansion caused by heat in this way cannot be completely absorbed by the double-sided tape. As a result, peeling may occur at the end of the R substrate and the end portion of the heat dissipating member, or heat may accumulate, resulting in a density difference in printing between a part where the peeling has occurred and a part where the peeling has not occurred. This is a problem that cannot be ignored when the size of the thermal print head is increased.

When the thickness of the double-sided pressure-sensitive adhesive tape is increased in order to prevent damage due to a large difference in thermal expansion between the R substrate and the heat radiating member, the silicone gel formed to the same thickness as the double-sided pressure-sensitive adhesive tape is required. The thermal conductivity deteriorates, heat is generated, and it becomes difficult to control the print density, which causes a problem that the image quality is deteriorated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and particularly, in a large-sized thermal head, it is necessary to improve the adhesion between a substrate having a heating resistor element array and a heat radiation member. It is an object of the present invention to provide a thermal print head that has good thermal conductivity while maintaining the thermal print head, and a method for manufacturing the same.

[0010]

A thermal print head according to the present invention includes a heat radiating member and a resistor substrate on which a resistor element array having a heat generating portion closely attached to the heat radiating member is disposed. The vicinity of the portion is closely adhered to the heat radiating member via a thermally conductive non-adhesive material, and at least a part of the resistance substrate other than the vicinity of the heat generating portion is closely adhered to the heat radiating member via an adhesive material. And wherein the thickness of the adhesive material is greater than the thickness of the thermally conductive non-adhesive material.

In the present invention, the portion of the heat dissipating member to which the adhesive material is adhered has a concave shape. That is, in order to form the adhesive material thicker than the thermally conductive non-adhesive material, a groove or a step is formed in the heat dissipating member by mechanical processing such as shaving.

In the thermal print head according to the present invention, the ratio of the thickness of the adhesive material to the thickness of the thermally conductive non-adhesive material is 2 to 8. In the present invention,
The heat dissipating member is formed with a groove portion in which the heat conductive non-adhesive material is stored. The groove is formed to prevent the adhesive material from wetting before the thermally conductive non-adhesive material is cured. This groove is
It is formed at a position corresponding to the position between the adhesive material and the thermally conductive non-adhesive material. Alternatively, grooves may be formed at both ends of the thermally conductive non-adhesive material.

[0013] The thermal printhead of the present invention further includes a drive circuit board.

In the thermal print head, the resistive substrate and the drive circuit board are connected to each other in order to maintain a predetermined positional relationship between the resistive substrate on which the heating resistor element array is formed and the drive circuit board and to increase the cooling efficiency of the thermal print head. Are fixed to the heat radiating member with a space therebetween.

Further, according to the method of manufacturing a thermal print head of the present invention, a resistance substrate having a resistance element array having a heat generating portion is disposed on a portion of the resistance substrate near the heat generating portion via a thermally conductive non-adhesive material. And, when at least a part other than the vicinity of the heat generating portion of the resistance substrate is brought into close contact with the heat dissipation member through the adhesive material, the thickness of the adhesive material is larger than the thickness of the thermally conductive non-adhesive material. It is characterized by being closely adhered.

According to the thermal print head and the method of manufacturing the same of the present invention, the expansion of the resistance substrate and the heat radiating member due to the heat generated from the heat generating resistance element of the resistance substrate is absorbed, and this heat is efficiently radiated to the heat radiating member. be able to. As a result, even when high-speed printing is performed with a large-sized thermal print head, it is possible to control the residual heat on the resistive substrate and improve the printing quality.

Further, the heat conductive and non-adhesive material used in the present invention, for example, silicone gel, is only in contact with the resistance substrate and the heat radiating member, but is not adhered. Unlike the double-sided pressure-sensitive adhesive tape, which is a material, there is no need to determine the thickness by the linear expansion difference between the resistance substrate and the heat dissipation member.

[0018]

FIG. 1 is a side view of a thermal print head according to the present invention, and FIG. 2 is a plan view.

An aluminum heat dissipating member 1 having a width b of 380 mm is used, and an alumina ceramic R substrate 4 is fixed to the center of the heat dissipating member 1. When the surface temperature of the heat radiating member 1 and the surface of the R board 4 change from, for example, 25 ° C to 150 ° C,
Since the linear expansion coefficient of aluminum is 23.1 × 10 ⁻⁶ and the linear expansion coefficient of alumina is 6 × 10 ⁻⁶ , the dimension difference a in the width direction between the heat radiating member 1 and the R substrate 4 is about 0.4 mm. Becomes

In such a case, the thickness of the double-sided tape is required to be about 0.4 mm, and the thickness of the gel is desirably 0.05 to 0.2 mm, depending on the characteristics of the material used.

In FIG. 1, a step between a region of the heat dissipating member 1 including a region immediately below the heat generating portion of the R substrate 4 and a region other than the region is 0.3 mm, and the heat dissipating gel 2 is placed under the heat generating portion. The R substrate 4 and the heat radiating member 1 were fixed by applying a 0.4 mm thick double-sided tape 3a to the remaining area. In addition, the PCB substrate 5 and the heat radiation member 1
It was fixed with a double-sided tape 3b having a thickness of 0.1 mm. This one
The gel 2 was cured by leaving it in an oven at 20 ° C. for 2 hours. A groove having a depth of 1 mm is formed in the heat dissipating member 1 as a gel reservoir between the gel 2 and the double-sided tape 3a.

As the resistance substrate used in the present invention, usually,
Examples include alumina ceramics, but are not limited thereto. It is desirable to optionally form a glaze layer on the substrate in order to enhance the heat storage property of the thermal print head, smooth the surface of the substrate, and uniformly form the heating element array. Examples of the material for the glaze layer include SiO ₂ or a mixture of SiO ₂ and Ca, Ba, Al, Si, or the like. However, the glass transition point of the glaze glass layer is desirably 670 ° C. or higher in order to prevent the resistance value of the thermal print head from increasing. The thickness of the glaze glass layer is usually 40 to 200 μm.
m. Further, as a method of forming the glaze layer, a printing method or a spray method is used.

The material of the heating resistance element array is N
nitrides of highly stable metal materials such as i, Cr, Ta,
The _{Ta-SiO 2, Nb-SiO} 2, Ti-SiO 2 or the like of various cermet materials can be used as appropriate. Also,
Each electrode connected to the heating resistance element array
1, Al-Si, Al-Si-Cu or the like is used, but is not limited thereto. The thickness of the heating resistance element array is 0.1 to 1 μm, and the thickness of the electrodes is about 3 to 5 μm. The heating resistor element array and each electrode are formed by a photoengraving process using various film forming methods such as a sputtering method.

Further, in order to protect the heating resistor element array and each electrode, a protective film is formed by using an Si-ON-based film by various film forming methods such as a sputtering method.

On the other hand, as a drive circuit board, a PC
B or FPC (Flexible Print Circuit) is used, but is not particularly limited as long as a connector or the like can be mounted.

A driver IC is usually provided on a drive circuit board.
It is implemented in the form of OB (Chip On Board).

It is necessary to connect a driver IC to a common electrode connected to each heating resistor element array.
C may be connected and mounted to each common electrode by any connection method such as wire bonding, flip chip, TAB (Tape Automated Bonding). Further, when signal lines are formed on the drive circuit board, they are formed by a normal thin film forming method using Al, Cu, or the like.

FIGS. 3 and 4 show a modified embodiment of the present invention. In FIG. 3, the PCB substrate 5 is also fixed with a double-sided tape 3b thicker than the gel 2. In FIG. 4, the R substrate extends beyond the step formed on the heat radiation member 1.

[0029]

According to the thermal print head and the method of manufacturing the same according to the present invention, especially in a large-sized thermal print head, the resistance substrate having the heating resistance element array and the heat radiating member are brought into good contact with each other while at the same time having good heat conduction. Sex can be obtained.

Further, according to the thermal print head and the method of manufacturing the same of the present invention, the expansion of the resistance board and the heat radiating member due to the heat generated from the heating resistor element of the resistance board is absorbed, and this heat is efficiently transmitted to the heat radiating member. Heat can be dissipated. Thus, when high-speed printing is performed with a large-sized thermal print head, the remaining heat on the resistive substrate can be controlled to improve the printing quality.

[Brief description of the drawings]

FIG. 1 is a side view of a thermal print head according to an embodiment of the present invention.

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

FIG. 3 is a side view of a thermal print head according to another embodiment of the present invention.

FIG. 4 is a side view of a thermal print head according to another embodiment of the present invention.

FIG. 5 is a side view of a conventional thermal print head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat dissipation member, 2 ... Gel, 3a, 3b ... Double-sided tape, 4
... R board, 5 ... PCB board

Claims (7)

[Claims] 1. A thermal printhead comprising: a heat radiating member; and a resistance substrate on which a resistance element array having a heat generating portion closely attached to the heat radiating member is disposed. The heat-dissipating member is adhered through an adhesive material, and at least a part of the resistance substrate other than the vicinity of the heat-generating portion is adhered to the heat-dissipating member through an adhesive material. Is thicker than the thickness of the thermally conductive non-adhesive material. 2. The thermal printhead according to claim 1, wherein the ratio of the thickness of the adhesive material to the thickness of the thermally conductive non-adhesive material is 2-8. 3. The thermal printhead according to claim 1, wherein a portion of the heat radiating member to which the adhesive material is adhered has a concave shape. 4. The thermal printhead according to claim 1, wherein the heat dissipating member is formed with a groove portion in which the heat conductive non-adhesive material is stored. 5. The thermal printhead according to claim 4, wherein the groove-shaped portion is formed at a position between the adhesive material and the thermally conductive non-adhesive material. . 6. The thermal printhead according to claim 1, further comprising a drive circuit board. 7. A resistive substrate on which a resistive element array having a heat generating portion is arranged, wherein a portion of the resistive substrate near the heat generating portion is connected to a portion other than near the heat generating portion of the resistive substrate via a thermally conductive non-adhesive material. A thermal print, wherein at least a part of the thermal print is brought into close contact with the heat radiating member via the adhesive material such that the thickness of the adhesive material is larger than the thickness of the thermally conductive non-adhesive material. Head manufacturing method.