JPH01204762A - Thermal head - Google Patents

Abstract

PURPOSE:To achieve prevention of a printing concentration characteristic from deterioration caused by a gather of paper refuse, and damage and wear of a protective film by smoothly feeding thermosensible paper in printing and recording, by a method wherein an end surface in contact with a heating resistant band part of a conductive layer is formed in a tapered state to have a smooth surface. CONSTITUTION:For instance, a TaSiO resistor layer 2 of 0.1mum and an Al conductor layer of 1mum are formed by coating on a surface of a ceramic substrate 5 to which a heat accumulating layer 4 is attached, and then, they are successively processed by chemical etching so as to become a pattern corresponding to a heating resistant band part 6. Then, positive type photoresist is used as an etching mask. An etchant where a mixed solution of 5:3:1:1 in phosphoric acid, acetic acid, nitric acid, and water is mixed with 1% NH4F is heated at 45 deg.C and aluminum is etched. By mixing of above-mentioned NH4F, a penetration speed to an adhesive surface between the resist and Al of the etchant can be adjusted, a taper angle alpha of conductive tapered parts 7a and 7b can be controlled, and said angle alpha is preferably 20-40 degrees. Then, when a protective film 3 is formed by using Si3N4 of 5mm, since the heating resistor part is smoothly formed, pulse life can be prolonged.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a thermal head.

[Conventional technology]

With the spread of print recording devices having thermal heads, there has been a demand for improvements in the print quality and lifespan of thermal heads.

FIGS. 3(a) and 3(b) are pattern diagrams of a heating resistor band portion and a conductor layer of an example of a conventional thermal head, and a corresponding sectional view taken along the line AA'.

The thermal head includes a convex heat storage layer 4 provided on a part of the surface of a ceramic substrate 5, a resistor layer 2 covering these two surfaces, and a heating resistor corresponding to the center of the top of the convex portion of the heat storage layer 4. Common conductor layer 116 formed on both sides of band 6
, an individual conductor layer 11b, and a protective film 3b covering the surface.

On the surface of the convex portion of the resistor layer 2, conductor end portions 7 are provided on both sides except for the heating resistor band portion 6, so that portion of the resistor layer 2 is electrically short-circuited.

Therefore, only the heating resistor band portion 6 generates heat due to the drive IC current flowing from the individual conductor layer 11b to the common conductor layer 11°.

As the material of the resistor layer 2, Ti5iO (titanium silicide), Ta5iO (tantalum silicide), etc. are used, and the conductor layer is made of Ae'? ? Ae-based alloys are mainly used.

Further, Ta203 (tantalum pentoxide) or 5i3N4 (silicon nitride) is used for the protective film 3b.

Generally, the angle β of the conductor end 7 is between 50 and 90 degrees.

[Problem to be solved by the invention]

In the conventional thermal head described above, the conductor layer requires a thickness of approximately 1 μm, which creates a steep step on both sides of the heating resistor band, which also forms a large step on the protective film. This has disadvantages in that during long-term printing, paper can accumulate at the stepped portions and edges of the slits, causing uneven print density and damage and wear of the protective film.

In addition, the stress that the resistor layer receives from the protective film is particularly large at the stepped portions, which leads to a deterioration in power resistance such as the printing life of the heat-generating resistor band portion, resulting in a decrease in reliability.

An object of the present invention is to provide a thermal head with good print quality and long life.

[Means to solve the problem]

The thermal head of the present invention includes a heat storage layer provided on the surface of an insulating substrate, a common conductor layer provided on the heat storage layer with a heat generating resistor band between them, and connected to each side of the heat generating resistor band. In the thermal head having individual conductor layers, respective connection portions where the common conductor layer and the individual conductor layer connect to the heating resistor band portion are formed in a tapered shape.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the invention.

The thermal head is the same as the conventional thermal head shown in FIG. 3, except that the common conductor tapered portion 7& and the individual conductor tapered portion 7b are different from the conductor end portion 7, and therefore the protective film 3 is also different from the protective film 3b. be.

0.1 μm on the surface of the ceramic substrate 5 with the heat storage layer 4 attached
A T a Si ○ resistor layer 2 of 1 μm and an Ae conductor layer of 1 μm are deposited.

Next, Ae and Ta5iO are selected and chemically etched in order so as to form a pattern corresponding to the heating resistor band 6.

Here, the etching mask is positive photoresist)-(O
Phosphoric acid, acetic acid,
A mixed solution of nitric acid and water in a ratio of 5:3:1:1 was used.

In this case, the conductor end portion of Aff is formed substantially perpendicular to the substrate surface as in the conventional example.

Next, mask the area other than the heating resistor band with 0FPR, and
E Etchant mixed with 1% N84F at 1% and heated to 45℃ A! ! etching was carried out.

By mixing NH4F, the etchant resist and Aj? It is possible to adjust the rate of penetration into the bonding surface between the conductor parts, and to control the taper angle α of the conductor tapered portions 71 and 7b.

In the case of this example, the taper angle α was 30 degrees.

For the protective film 3, 5L3N4 with a thickness of 5 μm was used.

AI of the heating resistor band using the thermal head of this example and an etchant that does not contain NH4F! A pulse was applied to a conventional thermal head formed by etching and the resistance was compared.

As a result, the thermal head of this embodiment has a lifespan of about 1 when the same pulse is continuously applied, compared to the conventional thermal head.
．． A five-fold improvement was confirmed.

In this way, in the conventional thermal head, the edge of the heating resistor pattern has a steep step and is under the stress of the protective film, so the power resistance of this part is weak and wire breakage easily occurs. In this case, since the heating resistor portion is formed smoothly, the pulse life can be improved.

Further, when a continuous printing test was conducted and compared, the thermal head of this embodiment was far less likely to cause unevenness or change in print density after a long period of time than the conventional thermal head.

This is because in conventional thermal heads, paper crumbs that stick to the step at the end of the heating resistor pattern gradually accumulate, making the contact between the thermal paper and the head poor, and dust adhering to it, which tends to cause damage and abrasion of the protective film. On the other hand, the thermal head according to this embodiment has a smooth surface, so the above-mentioned problems are less likely to occur.

Note that the taper angle α can be further reduced by increasing the mixing ratio of NH4F in the Ae etchant.

However, if α is made too small, it becomes difficult to control pattern accuracy and the resistance value of the heating resistor band portion varies, resulting in poor print density uniformity.

A suitable taper angle α is 20 to 40 degrees.

FIG. 2 is a sectional view of a second embodiment of the invention.

The thermal head forms a flat heat storage layer 4a and A/layer on the surface of the ceramic substrate 5, and then etches away the A47 layer corresponding to the heating resistor band 6a to form conductor tapered parts 7A and 7B at the ends. are doing.

A Ta5iO resistor layer 21 is deposited on the surface and plasma etched to form the tapered parts 7A, 7B and the heating resistor band part 6.
．． Leave only the surface.

Protective film 3. Also in L, the level difference on the surface of the side conductor tapered portions 7A and 7B becomes flat, and the effect of preventing paper residue from adhering during print recording becomes even greater.

〔Effect of the invention〕

As explained above, in the present invention, the end surface of the conductor layer in contact with the heating resistance band is formed into a tapered shape and has a smooth surface, so that the thermal paper is smoothly fed during print recording, and paper waste is removed. It is possible to prevent deterioration of print density characteristics due to damage or abrasion of the protective film or the protective film, and also to prevent deterioration of power resistance due to stress received from the protective film, thereby increasing the reliability of the thermal head.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a first embodiment of the present invention, Fig. 2 is a sectional view of a second embodiment of the invention, and Figs. 3(a) and (b) are an example of a conventional thermal head. FIG. 2 is a pattern diagram of a heating resistor band portion and a conductor layer, and a corresponding cross-sectional view taken along the line AA'. IA, 1a... Common conductor layer, ln, lb... Individual conductor layer, 2... Resistor layer, 3... Protective film, 4... Heat storage layer, 5... Ceramic substrate, 6 ...Heating resistance band, 7A. 7, . . . common conductor taper portion, 7a, 7b . . . individual conductor taper portions.

Claims (1)

[Claims] Thermal has a heat storage layer provided on the surface of an insulating substrate, and a common conductor layer and individual conductor layers provided on the heat storage layer with a heat generating resistor band between them and connected to each one side of the heat generating resistor band. A thermal head characterized in that respective connection portions where the common conductor layer and the individual conductor layer connect to the heat generating resistor band portion are formed in a tapered shape.