JP2000103104A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain terminal electrodes or circuit patterns of a driver IC in a good condition for a long time and to markedly improve reliability of a thermal head. SOLUTION: In this thermal head, a hole section 1a is provided to an insulation substrate 1 having a heating resistor 3 and conductive layers 4b, 4c. A driver IC 5 having terminal electrodes 5a on the top face thereof is embedded in the hole section 1a and a resin material 6 is filled in a gap between a side of the driver IC and a wall face of the hole section. One end of each conductive layers 4b, 4c is extended to a portion above the terminal electrode 5a via the top face of the resin material 6 so that the conductive layers 4b, 4c are electrically connected to the terminal electrodes 5a. Position setting is executed such that the top face is to be higher than the top face of driver IC 5 and to be equal to or lower than the heating resistor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a thermal head incorporated as a printer mechanism of a word processor, a facsimile or the like.

[0002]

2. Description of the Related Art In recent years, in order to perform thermal recording on a hard recording medium such as a plastic card which is difficult to bend using a thermal head, attempts have been made to make the surface of the thermal head in contact with the recording medium as flat as possible. ing.

In such a conventional thermal head, as shown in FIG. 4, for example, a plurality of heating resistors 13 and holes 11a are provided on an upper surface of an insulating substrate 11 made of alumina ceramics or the like. Heating resistor 13
A structure in which a driver IC 15 for controlling heat generation of the thermal head is embedded is known.
Since the thermal head does not have a large protruding part on the surface of the thermal head, even when printing on a hard recording medium such as a plastic card that is difficult to bend, The heat-sensitive recording can be performed by conveying the heat-generating resistor 13 on the heating resistor 13 while keeping the substantially flat shape.

In such a conventional thermal head, a circuit pattern (not shown) such as a terminal electrode 15a of the driver IC 15 and a switching transistor is provided on the upper surface of the driver IC 15, and is attached to the upper surface of the insulating substrate. One end of the conductive layer 14 is connected to the driver IC 15
The switching transistor and the like of the driver IC 15 are electrically connected to the heat generating resistor 13 and the external electric circuit by extending the terminal electrode 15a above.

In the thermal head, when printing is performed using, for example, an ink ribbon, the heating resistors 13 are individually driven by the driver IC 15 while sequentially transporting the ink ribbon and the recording medium onto the heating resistors 13. Function as a thermal head by selectively generating Joule heat, heating and melting the ink in the ink ribbon by the generated heat, and pressing and transferring the ink to the recording medium to form a predetermined print on the recording medium. I do.

[0006]

However, according to such a conventional thermal head, the terminal layer 15a, the switching transistor and the like are provided so that the conductive layer 14 can be easily connected to the terminal electrode 15a of the driver IC 15. Is provided on the upper surface of the driver IC 15. For this reason, when a hard recording medium such as a plastic card is conveyed along the surface of the thermal head during printing, large dust adsorbed on the recording medium by the action of static electricity or the like during the conveyance causes a large amount of dust between the upper surface of the driver IC 15 and the recording medium. If you get stuck in between,
The circuit pattern such as the terminal electrode 15a of the driver IC 15 and the switching transistor is relatively easily damaged by the pressing of dust, and has a disadvantage that the function as a thermal head is lost.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and a thermal head according to the present invention is provided with a hole in an insulating substrate having a heating resistor and a conductive layer. A driver IC having a terminal electrode on its upper surface is embedded, a resin material is filled between the driver IC side surface and the hole wall surface, and one end of the conductive layer is connected to the terminal via an upper surface of the resin material. A thermal head in which a conductive layer is electrically connected to a terminal electrode by extending over an electrode, wherein an upper surface of the resin material is higher than an upper surface of the driver IC and equal to or less than a heating resistor. Thermal head characterized by the height of.

In the thermal head according to the present invention, the upper surface of the resin material is raised so as to form a cross section between the upper surface of the insulating substrate and the upper surface of the driver IC, and the raised portion surrounds the driver IC. It is characterized by having done.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of a thermal head according to the present invention, and FIG. 2 is a cross-sectional view taken along the line XX of FIG. 1, wherein 1 is an insulating substrate, 3 is a heating resistor, 4a, 4b, and 4c.
Is a conductive layer, 5 is a driver IC, and 6 is a resin material.

The insulating substrate 1 has a thickness of 0.5 to 1.5 mm.
Alumina, silica, magnesia, and other suitable ceramic solvents are mixed with a suitable organic solvent and a solvent to form a slurry. A ceramic green sheet is obtained by employing a doctor blade method, a calendar roll method, or the like. Thereafter, the ceramic green sheet is punched into a predetermined shape, and a high temperature (about 1600) is obtained.
C).

The upper surface of the insulating substrate 1 has a mountain-like cross section (width: 0.5 mm to 2.0 mm, thickness: 40 μm to 70 μm).
μm) is deposited and formed in a strip shape.

The partial glaze layer 2 is made of a low thermal conductive material such as glass, and a heating resistor 3 attached near its top is projected upward to effectively apply a pressing force (printing pressure) to the recording medium P or the like. And these heating resistors 3
The heat generated by the thermal head is accumulated so as to have an appropriate temperature, and the function of maintaining the thermal response characteristic of the thermal head in a good condition is achieved.

The partial glaze layer 2 is formed in a band shape on the upper surface of the insulating substrate 1 by applying a predetermined glass paste obtained by adding and mixing an appropriate organic solvent and a solvent to glass powder by a conventionally known screen printing method or the like. Print and apply this to about 10
It is deposited and formed by baking at a temperature of 00C to 1200C.

In the vicinity of the top of the partial glaze layer 2, a plurality of heating resistors 3 are arranged at a predetermined pitch, for example, 62.5 μm.
It is deposited and arranged at high density with a pitch of m.

The heating resistor 3 is made of a TaN-based resistance material or T
Since it is made of an aSiO-based resistance material, a TiSiO-based resistance material, or the like, and has a predetermined electric resistivity itself, when an external power is applied through conductive layers 4a, 4b described later, Joule is applied. A predetermined temperature required to generate heat and melt the ink of the ink ribbon, for example, 15
It acts to generate heat at a temperature of 0 to 250 ° C.

On the upper surface of the insulating substrate 1, a band-shaped hole 1a is formed substantially parallel to the partial glaze layer 2.

The hole 1a has a driver I therein.
By embedding all or at least a part (lower region) of C5, the upper surface of the driver IC 5 is prevented from projecting above the heating resistor 3.
In this embodiment, the driver IC 5 is completely buried in the hole 1a so that the upper surface of the driver IC 5 is located at a height (± 10 μm) substantially equal to the upper surface of the insulating substrate 1.

Incidentally, such a hole 1a is formed by irradiating the upper surface of the insulating substrate 1 made of alumina ceramics or the like with a laser having a predetermined intensity and melting and scattering a part of the insulating substrate 1, or When the insulating substrate 1 is manufactured, it is formed by punching out a hole 1a at the same time as punching a ceramic green sheet.

On the other hand, a plurality of driver ICs 5 buried in the holes 1a are for controlling on / off of electric power applied to the heating resistor 3 via conductive layers 4a and 4b described later. A plurality of terminal electrodes 5a electrically connected to the conductive layers 4b and 4c and a circuit pattern (not shown) such as a switching transistor are formed on the upper surface thereof. Here, since the driver IC 5 is positioned so that the upper surface thereof is lower than the heating resistor 3 on the partial glaze layer 2, the driver IC 5 does not hinder the conveyance of the recording medium P or the like during printing. Absent.

A resin material 6 is filled between the side surface of the driver IC 5 and the wall surface of the hole.

The resin material 6 is made of an epoxy resin or a polyimide resin containing a predetermined amount of an inorganic filler such as alumina, silica or the like.
And acts as an adhesive for fixing each driver IC 5 at a predetermined position in the hole 1a.

The upper surface of the resin material 6 is formed so as to protrude in a mountain-like cross section between the upper surface of the insulating substrate and the upper surface of the driver IC, and the height of the top of the upper surface is higher than the upper surface of the driver IC 5. The height is set higher than that of the heating resistor 3 on the partial glaze layer 2 so that each driver IC 5 is surrounded by the raised portion 6a.

For example, the height of the partial glaze layer 2 is 55 μm.
In the case of m, the upper surface of the resin material 6 is set higher than the upper surfaces of the insulating substrate 1 and the driver IC 5 by 20 to 40 μm.

As described above, the height of the upper surface of the resin material 6 surrounding the driver IC 5 is set higher than the upper surface of the driver IC 5 and lower than the heating resistor 3 on the partial glaze layer 2. When a hard recording medium P such as a plastic card is conveyed along the surface of the thermal head in the direction of the arrow in the drawing, large dust adsorbed on the surface of the recording medium P by the action of static electricity or the like comes into contact with the upper surface of the driver IC 5. Previously, the resin material 6 and the recording medium P are sandwiched and crushed to break them into small pieces, and the pieces are effectively prevented from being strongly pressed against the upper surface of the driver IC 5 by the recording medium P or the like. Therefore, the terminal electrode 5a and the circuit pattern of the driver IC 5 can be maintained in a good state for a long period of time, whereby the reliability of the thermal head can be significantly improved.

In this case, the upper surface of the resin material 6
Since the position is set lower than the heating resistor 3 on the partial glaze layer 2, the resin material 6 does not hinder the conveyance of the recording medium P and the like, and hard recording such as a plastic card or the like which is difficult to bend. Even when printing is performed on the medium P, the recording medium P can be stably conveyed along the surface of the thermal head in a flat shape.

Since the upper surface of the resin material 6 is raised so as to form a mountain-shaped cross section between the upper surface of the insulating substrate and the upper surface of the driver IC, the upper surface of the insulating substrate 1 and the upper surface of the driver IC 5 are separated. The conductive layers 4b and 4c, which are applied from the upper surface of the insulating substrate to the upper surface of the driver IC via the upper surface of the resin material 6, are formed by a well-known thin-film method which will be described later. It can be formed as a film. Therefore, the productivity of the thermal head can be greatly improved.

The resin material 6 preferably has its Rockwell hardness set to 100 or more. By setting the hardness to such a value, even if hard dust such as sand is adsorbed on the recording medium P, Can be satisfactorily pulverized, and it is possible to more reliably prevent the driver IC 5 from being damaged by the pressing of dust. In order to set the Rockwell hardness of the resin material 6 to 100 or more, if the resin material 6 is made of an epoxy resin, the silica (SiO ₂ ) filler should be 70 to 9%.
It is realized by containing 0% by weight.

Further, if the outer shape of the silica filler contained in the resin material 6 is made substantially spherical, even if the silica filler on the surface of the resin material hits the recording medium P, the recording medium P is hardly damaged, and the printing quality is low. Can be maintained very satisfactorily. Therefore, it is preferable that the outer shape of the silica filler contained in the resin material 6 be substantially spherical.

Further, if the average particle size of the silica filler contained in the resin material 6 is set to 10 to 15 μm,
Even when the gap between the side surface of the driver IC and the wall surface of the hole is extremely narrow, the silica filler in the resin material 6 is removed by the driver I.
Good filling can be achieved between the C side surface and the hole wall surface. Accordingly, the average particle size of the silica filler contained in the resin material 6 is 1
It is preferable to set it to 0 to 15 μm.

As shown in FIG. 3, first, the insulating material 1 and the driver IC 5 are set on a jig 8 provided with a predetermined recess 8a.
The precursor 6 ′ made of liquid epoxy resin or the like is poured into the gap between the wall surface of the hole 1 a and the side surface of the driver IC using a dispenser or the like while vacuum-sucking from the vacuum suction port 8 b provided therein. Precursor 6 ′ at 100 to 180 ° C.
The resin material 6 is formed so as to form a mountain-shaped cross section between the upper surface of the insulating substrate and the upper surface of the driver IC by heat curing at the temperature of
5 is adhered and fixed at a predetermined position in the hole 1a.

Then, on the upper surface of the insulating substrate 1 on which the driver IC 5 and the like are attached, the conductive layers 4a and 4a of a predetermined pattern electrically connected to the heating resistor 3 and the terminal electrodes 5a of the driver IC 5 and the like. 4b and 4c are deposited and formed.

The conductive layers 4 a to 4 c include a conductive layer 4 a as a common electrode commonly connected to one end of the heating resistor 3,
The other end of the heating resistor 3 and the terminal electrode 5a of the driver IC 5
And a conductive layer 4c as a control signal line for supplying a printing signal and the like to the driver IC 5. The conductive layers 4a and 4b are connected to the heating resistor 3 from the outside. The conductive layer 4c transmits an external printing signal or power to the driver IC.
5 is supplied. Here, the conductive layers 4b and 4c
The one end is extended to the terminal electrode 5a of the driver IC 5 via the upper surface of the resin material 6 to be electrically connected to the terminal electrode 5a of the driver IC 5.

The conductive layers 4a to 4c are made of a metal material such as aluminum, and are formed with the above-mentioned heating resistor 3 by employing a conventionally known thin film technique, for example, a sputtering method, a photolithography technique, an etching technique, or the like. Formed at the same time. Specifically, first, a partial glaze layer 2 is formed on the upper surface, and a driver IC is provided in the hole 1a.
The TaN-based resistance material and the conductive layers 4a to 4 serving as the heating resistor 3 over the entire upper surface of the insulating substrate 1 to which the adhesive layer 5 is adhered and fixed
Al (aluminum) to be c is sequentially deposited by a conventionally known sputtering method or the like, and then a photoresist film having a predetermined pattern is deposited and formed on these sputtered films through exposure and development steps. The sputter film is finely processed by etching in accordance with the pattern of the photoresist film, the aluminum film located on the top of the partial glaze layer 2 is removed, and the TaN-based resistive material is partially exposed, thereby generating heat. Body 3 and conductive layer 4a,
4b and 4c are formed simultaneously. At this time, the upper surface of the resin material 6 filled between the upper surface of the insulating substrate and the upper surface of the driver IC has a mountain-shaped cross section, so that the surfaces to which the conductive layers 4b and 4c are applied are relatively gentle. From
The conductive layers 4b and 4c can be patterned as a good continuous film.

Further, on the upper surfaces of the conductive layers 4a to 4c, the heating resistor 3, and the driver IC 5, Si ₃ N
_{4 A} protective film 7 made of (silicon nitride) or the like is applied, and the protective film 7 prevents wear due to the sliding contact of the recording medium P and oxidative corrosion of the heating resistor 3 and the conductive layers 4a to 4c. ing.

The protective film 7 is made of, for example, Si ₃ N
₄ (silicon nitride), a substantially constant thickness (4 to 10 μm) is formed on the upper surfaces of the conductive layers 4a to 4c, the heating resistor 3, and the driver IC 5 by a conventionally known thin film method, specifically, a sputtering method, a CVD method, or the like. (± 0.1 μm). Here, since the protective film 7 is applied to a substantially constant thickness (± 0.1 μm) by a conventionally known thin film method, the upper surface of the protective film 7 has a surface state corresponding to the base. Therefore, the upper surface of the protective film protrudes between the upper surface of the insulating substrate and the upper surface of the driver IC in a shape corresponding to the raised portion 6a of the upper surface of the resin material, and the recording medium P conveyed onto the heating resistor 3 at the time of printing is placed on the raised portion 6a. Of the recording medium P and the large dust adsorbed on the recording medium P are effectively prevented from being strongly pressed by the protective film 7 on the driver IC 5, whereby the circuit pattern on the upper surface of the driver IC is formed. Etc. are kept in good condition.

Thus, when printing is performed on a hard recording medium P such as a plastic card using an ink ribbon, for example, the above-described thermal head is used to concretely move the ink ribbon and the recording medium P along the surface of the thermal head. Causes the heating resistors 3 to individually generate Joule heat as the driver ICs 5 are driven while being conveyed onto the heating resistors 3 via the driver ICs 5, and the generated heat heats and melts the ink in the ink ribbon. At the same time, this is pressed and transferred to the recording medium P to form a predetermined print on the recording medium P, thereby functioning as a thermal head.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

For example, in the above embodiment, a plurality of driver ICs 5 are buried in one elongated hole 1a.
The same number of holes as the number 5 may be formed, and one driver IC may be embedded in each of these holes.

In the above-described embodiment, the upper surface of the resin material 6 is set lower than the heating resistor 3, but the upper surface of the resin material 6 is replaced with the same height (± 10) as the heating resistor 3.
μm). In this case as well, the recording medium P can be satisfactorily conveyed along the surface of the thermal head.

[0040]

According to the thermal head of the present invention, the height of the upper surface of the resin material filled between the side surface of the driver IC and the hole wall surface of the insulating substrate is higher than the upper surface of the driver IC, and the heat generation resistance is higher. When a hard recording medium such as a plastic card is conveyed along the surface of the thermal head when printing, the large dust adsorbed on the recording medium by the action of static electricity etc. Before being brought into contact with the upper surface of the IC, it is sandwiched and crushed by the resin material and the recording medium, and crushed into small pieces, and the pieces are effectively prevented from being strongly pressed against the upper surface of the driver IC by the recording medium or the like. You.
Therefore, the terminal electrodes and the circuit patterns of the driver IC can be maintained in a good state for a long period of time, whereby the reliability of the thermal head can be significantly improved.

According to the thermal head of the present invention, since the upper surface of the resin material is positioned at a height equal to or lower than the heating resistor, the resin material hinders the conveyance of the recording medium. Even when printing is performed on a hard recording medium such as a plastic card that is difficult to bend, the recording medium can be stably conveyed along the surface of the thermal head in a flat shape. .

Further, according to the thermal head of the present invention, the upper surface of the resin material is raised so as to form a cross section between the upper surface of the insulating substrate and the upper surface of the driver IC. A sharp step is not formed between the conductive layer and the upper surface of the driver IC. The conductive layer is applied from the upper surface of the insulating substrate to the upper surface of the driver IC through the upper surface of the resin material. , And it is also possible to greatly improve the productivity of the thermal head.

[Brief description of the drawings]

FIG. 1 is a plan view of a thermal head according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of the thermal head of FIG.

FIG. 3 is a cross-sectional view for explaining a manufacturing process of the thermal head of FIG.

FIG. 4 is a sectional view of a conventional thermal head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulating board, 1a ... Hole part, 3 ... Heating resistor, 4b, 4c ... Conductive layer, 5 ... Driver I
C, 5a: terminal electrode, 6: resin material

Claims (2)

[Claims] A hole is formed in an insulating substrate having a heating resistor and a conductive layer, and a driver IC having a terminal electrode on its upper surface is buried in the hole, and a side surface of the driver IC and a wall surface of the hole are formed. A thermal head in which a conductive material and a terminal electrode are electrically connected by filling a resin material therebetween, and further extending one end of the conductive layer to above the terminal electrode via an upper surface of the resin material. A thermal head, wherein the upper surface of the resin material is higher than the upper surface of the driver IC and equal to or less than the height of the heating resistor. 2. The method according to claim 1, wherein the upper surface of the resin material is raised so as to form a cross section between the upper surface of the insulating substrate and the upper surface of the driver IC, and the raised portion surrounds the driver IC. The thermal head according to claim 1.