JP3462056B2 - Thermal head and method of manufacturing the same - 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 incorporated as a printer mechanism for video printers, facsimiles and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Recently, in order to perform thermal recording on a hard recording medium such as a plastic card which is difficult to bend, it has been attempted to make the surface of a thermal head in contact with the recording medium as flat as possible. .

As such a conventional thermal head, for example, as shown in FIG. 5, an insulating substrate 11 made of alumina ceramic having a plurality of heating resistors 12 is provided with a plurality of holes 11a each having a rectangular shape. The driver ICs 14 are individually embedded in the holes 11a, and the adhesive 15 such as epoxy resin is filled between the side surface of each IC 14 and the inner wall of each hole 11a. There is known a structure in which the driver IC 14 is fixed at a predetermined position in the hole 11a.

According to such a thermal head, by embedding the driver IC 14 in the hole 11a of the insulating substrate 11, there is no one projecting more than the surface of the thermal head, so that a hard recording medium such as a plastic card is used. Even when performing heat-sensitive recording, the recording medium should be conveyed on the heating resistor 12 in a flat shape.
That is, the flat path of the recording medium is possible.

Incidentally, the heating resistor 12 and the driver IC 14
Electrical connection with the driver I is made by extending the individual electrode wiring connected to one end of the heating resistor 12 up to the terminals on the upper surface of the driver IC.
The output from the terminal of C14 is applied to the corresponding heating resistor 12 to selectively cause the heating resistor 12 to generate Joule heat.

[0006]

However, in such a conventional thermal head, the four corners of the hole 11a on the upper surface of the insulating substrate are square at right angles.
Hole 1 for fixing the driver IC 14 in a
When the adhesive 15 is filled between the inner wall of 1a and the side surface of the driver IC 14, the insulating substrate 11 and the adhesive 1 near the corners
A large stress is applied to No. 5. Therefore, when heat is applied to the insulating substrate 11 and the adhesive 15 during the manufacturing process or use of the thermal head, the insulating substrate 11 may be cracked at the corners where stress is most concentrated, or The thermal head cannot be used because the adhesive 15 is peeled off from the insulating substrate 11.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above drawbacks, and a thermal head of the present invention has a substantially rectangular shape on an insulating substrate having a plurality of heating resistors and thin film conductors on its upper surface. And a driver IC for controlling heat generation of the heating resistor is fixed in the hole with a resin adhesive, and each of the substantially rectangular corners has an R surface. Forming a counterbore part around the hole part that forms the above, and filling the counterbore part with a resin adhesive to form a smooth surface from the upper surface of the insulating substrate to the upper surface of the driver IC, and through the smooth surface. The driver IC and the heating resistor are connected by the thin film conductor.

Further, in the method of manufacturing a thermal head of the present invention, a recess is provided on the upper surface of the insulating substrate by blasting or water jet processing, and the recess is provided in the recess.
A first step of forming a substantially rectangular hole having an opening smaller than the recess by laser processing and providing a counterbore around the hole, and controlling the heat generation of the heating resistor provided on the insulating substrate A second step of fixing the driver IC in the hole with a resin adhesive.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of the thermal head of the present invention, where 1 is an insulating substrate, 1a is a hole,
1b is a counterbore part, 3 is a heating resistor, and 5 is a driver I.
C and 5a are terminals, and 6 is an adhesive.

The insulating substrate 1 has a thickness of 0.5 to 1.5 mm.
Made of alumina ceramics, glass, etc., and acts as a support base material for supporting the glaze layer 2, the heating resistor 3, the thin film conductor, etc., which will be described later, on the upper surface thereof.

When the insulating substrate 1 is made of, for example, alumina ceramics, it is formed into a sludge by adding a suitable organic solvent and a solvent to a ceramic material powder such as Al ₂ O ₃ , SiO ₂ , MgO and the like to form a slurry. Ceramic green sheets are formed by adopting the well-known doctor blade method, and then the ceramic green sheets are punched into a predetermined shape and subjected to high temperature (about 1600
It is manufactured by firing at (° C).

On the upper surface of the insulating substrate 1, a band-shaped glaze layer 2 having a mountain-shaped cross section, a plurality of heating resistors 3 and a thin film conductor having a predetermined pattern are respectively deposited.

The glaze layer 2 is made of a low heat conductive material such as glass, and a plurality of heating resistors 3 attached to the top of the glaze layer 2 are projected upward to press the heating resistor 3 against the recording medium (printing pressure). 2) is effectively increased, and the heat generated by the heat generating resistor 3 is accumulated and dissipated to an appropriate temperature to maintain the thermal response characteristics of the thermal head in good condition.

The heating resistors 3 are attached and arranged near the top of the glaze layer 2 at a constant pitch along the length direction of the glaze layer 2. Since each of the heating resistors 3 is formed of an electric resistance material such as TaSiO, TiSiO, TaN, etc., when the electric power from the external power source is applied through the thin film conductors 4a and 4b described later, the heating resistors 3 are selectively selected. Joule heat is generated in the recording medium to generate heat at a temperature required to form a print on a recording medium, for example, a temperature of 150 to 250 ° C.

The thin film conductor is a thin film conductor 4a serving as a common electrode wiring commonly connected to each end of the heating resistor 3.
And each other end of the heating resistor 3 and a driver IC 5 described later.
Thin film conductor 4b as an individual electrode wiring for connecting the output terminal 5a of the same and a thin film as a signal wiring connected to an input terminal (not shown) of the driver IC 5 and led out to the vicinity of the rear end edge of the insulating substrate 1. It is composed of a conductor.
These thin film conductors are made of a metal such as aluminum, copper, silver, etc., and the thin film conductor has a function of applying electric power from the external power source to the heating resistor 3 described above, and the thin film conductor has a driver IC 5 for receiving a print signal from the outside. To supply to.

The glaze layer 2 is formed by applying a suitable organic solvent to a predetermined glass powder and a glass paste obtained by mixing and mixing an appropriate organic solvent in a strip shape by a conventionally known screen printing method. By baking at a temperature of about 1000 ° C. to 1200 ° C., it is deposited and formed in a strip shape on the upper surface of the insulating substrate 1 so as to have a mountain-shaped cross section.
The thin film conductor and the thin film conductor are deposited and formed to have a predetermined thickness and a predetermined pattern on the upper surface of the insulating substrate 1 by adopting a conventionally known thin film forming technique, for example, a sputtering method and a photolithography technique.

In addition, in the thickness direction of such an insulating substrate 1, a substantially rectangular hole portion 1a is provided substantially parallel to the arrangement of the heating resistors 3 described above, and the opening portion of the hole portion 1a is surrounded. The counterbore part 1b is provided. By embedding a plurality of driver ICs 5 therein, the hole 1a acts so as to prevent the upper surface of the driver IC 5 from projecting above the surface of the thermal head to a large extent. That is, the recording medium can be conveyed on the heating resistor 3 in a flat shape.

The driver IC 5 in the hole 1a is for controlling the on / off of the electric power applied to each heating resistor 3 based on a print signal from the outside, and outputs the output from the output terminal 5a. The heating resistors 3 are applied to the corresponding heating resistors 3 via the above-mentioned thin film conductors 4b to selectively and selectively generate Joule heat.

These driver ICs 5 are fixed at predetermined positions in the hole 1a by an adhesive 6 made of a resin such as epoxy resin, polyimide resin, polyetheramide or the like.

The electrical connection between the thin-film conductor 4b and the output terminal 5a is made by applying the thin-film conductor 4b to the upper surface of the insulating substrate 1 by the above-mentioned thin-film forming technique.
This is performed by extending one end of b to the output terminal 5a on the upper surface of the driver IC.

The hole 1a of the insulating substrate 1 in which the driver IC 5 is embedded is, as shown in FIG.
Each corner between the adjacent inner walls A and B has a radius of curvature of 0.2 mm to 1.
It has a 0 mm R-face, and this R-face makes the hole 1a
The stress concentration on the insulating substrate 1 and the adhesive 6 at the four corners is relaxed.

Therefore, even if heat is applied to the insulating substrate 1 or the adhesive 6 during the manufacturing process or use of the thermal head, a large stress is locally concentrated on the insulating substrate 1 or the adhesive 6. Instead, the insulating substrate 1 is effectively prevented from cracking at the four corners of the hole 1a, and the adhesive 6 can be firmly adhered to the R surface of the hole 1a. The reliability of is greatly improved.

In addition, such a hole 1a is provided with a countersunk portion 1b around the opening by blasting or water jet processing, and the hole 1a is drilled by laser processing. By doing so, hole 1
Since the periphery of a is once melted by the heat of the laser beam, the surface condition of the corner formed by the upper surface of the insulating substrate 1 and the inner wall of the hole 1a becomes smooth, and the thin film conductor 4b is insulated by the above-mentioned thin film forming technique. From the top surface of the board 1, the driver IC 5
Can be formed as a good continuous film over the upper surface of the. Further, when the hole 1a is formed by laser processing, the substrate material scattered around the hole 1a adheres to the countersunk portion 1b. Therefore, it is preferable that the counterbore 1b is provided around the opening of the hole 1a, and the hole 1a is drilled by laser processing. Further, the driver IC 5 is fixed to the insulating substrate 1 by temporarily fixing the driver IC 5 to a predetermined position in the hole 1a using an adhesive tape or the like, and the side surface of the driver IC 5 and the inner wall of the hole 1a and the counterbore 1b. In between, a varnish such as an epoxy resin is filled using a dispenser or the like, and then the varnish is thermally cured to form the resin adhesive 6. By doing so, the surface of the insulating substrate 1 can be made smooth, and the driver IC 5 can be formed from the upper surface of the insulating substrate 1.
The thin-film conductor 4b to be deposited on the upper surface of the can be formed as a good continuous film.

Then, a protective film 7 made of silicon nitride or the like is further deposited on the upper surfaces of the heating resistor 3, the thin film conductor, the resin adhesive 6 and the like on the insulating substrate 1 as described above. The heating resistor 3 and the thin film conductors are protected by 7 to prevent abrasion due to sliding contact of the recording medium and corrosion due to contact with moisture contained in the atmosphere.

Thus, the thermal head of the present invention described above conveys the recording medium along the surface of the thermal head (on the heating resistor 3 via the driver IC 5),
As the driver IC 5 is driven, electric power is applied to the heating resistors 3 through the thin film conductors 4a and 4b to selectively cause Joule heating of the heating resistors 3 and conduct the generated heat to a recording medium or the like. , Functions as a thermal head by forming a predetermined print on a recording medium.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention. For example, in the above-described embodiment, one large hole 1a is provided in the insulating substrate 1, and this hole 1
Although all the driver ICs 5 are embedded in the a, instead of this, a plurality of holes may be provided in the insulating substrate and one driver IC may be embedded in each hole. Also in this case, the radius of curvature at the corner of each hole
An R surface of 0.2 mm to 1.0 mm is formed.

Further, in the above-described embodiment, the holes 1a are formed on both sides longer than the effective printing width by 0.1 mm or more, and the distance between the edge of the hole on the heating resistor 3 side and the driver IC 5 is Lcm, and the resin IC is made of resin. The thermal conductivity of the adhesive 6 is K cal / cm · sec.
The value of L × K when measured in ° C is 2.0 × 10 ^-5 cal / sec ・
If the temperature is set to 0 ° C., the temperature distribution of the insulating substrate 1 can be made substantially uniform and the uneven density of the print can be effectively prevented. For example, L is 2 × 10 ⁻² cm and K is 1 × 10 ⁻³ cal / cm.
By setting sec · ° C., the temperature distribution of the insulating substrate 1 can be made substantially uniform, and uneven density of the print can be prevented.

[0028]

According to the thermal head of the present invention, a counterbore is formed around the substantially rectangular hole, and
The counterbore portion is filled with a resin adhesive to form a smooth surface from the upper surface of the insulating substrate to the upper surface of the driver IC, and a thin film conductor for connecting the driver IC and the heating resistor is formed on the smooth surface. Therefore, if the counterbore portion 1b is provided around the opening of the hole 1a by blasting or water jet processing, the substrate scattered around the hole 1a when the hole 1a is formed by laser processing. Since the material adheres to the countersunk portion 1b, the surface of the insulating substrate 1 can be made smooth by covering this portion with the resin adhesive 6, and the driver IC 5 can be removed from the upper surface of the insulating substrate 1. Thin film conductor 4b to be applied over the upper surface
Can be formed as a good continuous film. This greatly improves the reliability of the thermal head.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one form of a thermal head of the present invention.

FIG. 2 is a sectional view of a conventional thermal head.

[Explanation of symbols]

1 ... Insulating substrate 1a ... hole 1b ... counterbore part 3 ... Heating resistor 5: Driver IC 5a ... Output terminal 6 ... Resin adhesive

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-5-221004 (JP, A) JP-A-9-174905 (JP, A) JP-A-9-174904 (JP, A) JP-A-63- 251256 (JP, A) Actual Kaihei 4-132958 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/335 B41J 2/345

Claims (2)

(57) [Claims] 1. An insulating substrate having a plurality of heating resistors and a thin film conductor on the upper surface thereof is provided with a substantially rectangular hole, and heat generation of the heating resistor is controlled in the hole. A thermal head in which a driver IC is fixed via a resin adhesive, wherein each of the substantially rectangular corners has a counterbore around a hole forming an R surface.
Part, and fill the counterbore part with a resin adhesive.
The upper surface of the insulating substrate to the upper surface of the driver IC.
To form a smooth surface.
A thermal head characterized in that a liver IC and a heating resistor are connected by the thin film conductor . 2. The upper surface of the insulating substrate is blasted or wrought.
-By forming a recess by turbine jet processing,
An approximately rectangular hole with an opening smaller than the recess inside the part
Are formed by laser processing, and the counterbore part is around the hole.
The first step of providing the heat-generating resistor and the step of controlling the heat generation of the heat-generating resistor provided on the insulating substrate.
Fix the Liver IC in the hole with resin adhesive
And a second step of manufacturing the thermal head.