JPS6140170A - Thermal head - Google Patents

Abstract

PURPOSE:To eliminate causes of oxidation of a heating resistor layer in a thermal head, thereby reduce variations in resistance and enhance reliability, by constituting a quenchant-resistant undercoat layer of a Ta oxide having a low degree of oxidation and being deficient in oxygen, when providing the layer on a glaze by reactive sputtering. CONSTITUTION:On a glazed insulating substrate obtained by covering the surface of an insulating substrate 1 with a glaze layer 2, a TaOx (2<=x<=2.5) undercoat layer 3 with a low degree of oxidation is provided by Ar-O2 gas reactive sputtering of Ta. Next, a Ta2N heating resistor layer 4 is provided thereon by Ar- N2 gas reactive sputtering of Ta. Then, an Al conductor layer 5 and an Ni conductor layer 6 are provided, and photo-etching is conducted to sequentially provide an Ni conductor pattern, an Al conductor pattern and a Ta2N resistor pattern, thereby providing the patterns of the thermal head. After covering terminal parts by a metallic mask, an oxidation-resistant layer 7 consisting of an SiO2 film and an abrasion-resistant layer 8 consisting of Ta2O5 are provided by sputtering.

Description

[Detailed Description of the Invention] [Technical Public Expenditure of the Invention] The present invention provides, for example, a plurality of heating resistance elements arranged linearly on the same substrate, and heating the heating elements with electricity according to information to be recorded. This invention relates to a thermal head that performs color recording on thermal recording paper or transfer recording onto plain paper via an ink ribbon.

[Prior art and its problems]

Generally, as shown in FIG. 1, for example, a conventional thermal head is made of an insulating substrate 1 made of ceramic or the like whose surface is covered with a glaze layer 2 with a thickness of approximately 0.2 μm as a glaze etchant. , 02 excess and sufficient oxidation of T
An undercoat layer 3 such as A2011 is formed on top of the undercoat layer 3 made of Ta2N etc., which generates heat and coats thermal recording paper etc.
A heating resistor layer 4 for providing coloring energy, and a conductor layer 5 made of Al+Ns or the like that is connected to the heating resistor layer 4 and conducts current depending on the information to be recorded.
, an oxidation-resistant layer 7 made of 5i02, etc., which protects the heating resistor layer 4 from deterioration due to oxidation, and a Ta205
It has a structure in which a wear-resistant layer 8 for protecting the heat-generating resistor layer 4, conductor layer 5, and oxidation-resistant layer 7 from wear due to contact with heat-sensitive recording paper, etc., are laminated in this order.

When a current is passed through the conductor layer 5, the heat-generating portion 9 generates heat to provide color recording energy to the heat-sensitive recording paper or the like.

As shown in FIG. 2, the thermal head has a heat generating section 99.
A common electrode line 10 and individual electrode lines 11A to 11G are provided on both sides, and the head surface 13 other than the terminal portion 12 connected to an external circuit by soldering is covered with the anti-oxidation layer 7 and the wear-resistant layer. covered and protected by 8.

Note that the thermal head shown in FIG. 1 is
FIG. 3 is a cross-sectional view taken along a line.

In such a conventional thermal head, a sufficiently oxidized Ta2O layer with a thickness of approximately 0.2μ is deposited on the glaze layer 2.
s To provide the undercoat layer 3, for example, Ta2N
When patterning the heating resistor layer 4 using photopropylene, a mixed solution of hydrogen fluoride fluoride and nitric acid is generally used. This 7-nitric acid strongly attacks the glaze, making manufacturing control difficult.
is often used.

However, in such a conventional thermal head, according to an accelerated test called Step, Stress, Test (8S T) to evaluate the thermal characteristics of the thermal head, the curve (4) in Figure 4 is reproduced. It shows a phenomenon in which the resistance value increases, which is considered to be due to oxidation of the heat generating resistive layer 4, from a low applied power.

See you in 5th v! As shown in curve (4) of J, even in a pulse life test using a practical applied power, the resistance value changes in the direction of increasing with the number of pulses. When a thermal head with such characteristics is mounted on a printer and printed, coloring energy decreases due to an increase in resistance value, resulting in deterioration of printing quality. Generally, for example, Ta2
The N heating resistance layer 4 has the property of being rapidly oxidized at temperatures above 300°C, and this type of thermal head
! Prevention of intrusion is an important technical point.

[Purpose of the invention]

In view of the problems of the prior art, an object of the present invention is to reduce the oxidation of oxygen-deficient Ta by adjusting the oxygen gas partial pressure when forming an etchant-resistant undercoat layer of a glaze by reactive and sputtering of Ta. The object of the present invention is to provide a highly reliable thermal head with little change in resistance value over a long period of time by eliminating the oxidation factor of the heat generating resistive layer existing inside the thermal head.

[Embodiments of the invention]

As shown in FIG.
2 gas, reactive, sputtering, 0.2
Tact with low oxidation degree due to the thickness of μcoastal (2≦2≦2.5)
An undercoat layer 3 is formed. Next, Ta is mixed with Ar and N2
0.05~ by gas adhesive and sputtering
A T-type N heating resistance layer 4 is formed with a thickness of 0.2 μm, then a mulch conductor 5 is formed with a thickness of about 2 μm, and a Ni conductor layer 6 is formed with a thickness of 0.5 to 1 μm. Then, photoetching is performed in the order of the Nj and Al conductor patterns and the Tag N resistor pattern to form a thermal head pattern.

Next, after covering the terminal portion with a metal mask, an oxidation-resistant layer 7 made of an 8402 film with a thickness of about 2 μm and a wear-resistant layer 8 made of TaxOs with a thickness of about 5 μm are formed by sputtering. Next, after preliminary soldering is performed on the surface of the N1 conductor layer 6 which will become the terminal portion, connection to an external circuit is made.

As mentioned above, a step, stress, test (SST) is generally used to evaluate the thermal characteristics of a thermal head.
Accelerated testing is used. This involves applying pulse-like power to the heating resistor for a certain period of time, measuring the change in resistance from the initial resistance value, and gradually increasing the applied power until the heating resistor is burned out. This is a test to evaluate the thermal stability of a heating resistor, which is a test to measure the rate of change in the resistance value of a heating resistor. It is said to be stable.

4th v! The curve (6) of J indicates that the thermal head of the above embodiment has a pulse li1.1 inert 8#C1 pulse period 6 inert 8#c
This is the result of blank printing SST performed under the condition that one application time is 10 minutes. Compared to the conventional curve (4) in the same figure, the destructive applied power when the resistance suddenly increases is the same, but there is a difference in the rate of resistance change at the applied power midway, and the Ta of the present invention The Os undercoat layer is the conventional 03
It can be said that this is superior to that of the Tag Os undercoat layer formed in excess.

Curve (6) in FIG. 5 is the result of the pulse life test of the present invention, and as is clear from this figure, it has better characteristics than the conventional one.

〔Effect of the invention〕

As described above, according to the present invention, in order to prevent damage to the glaze caused by fluoronitric acid in photopuressing, the etchant-resistant undercoat layer is
By forming a low 02-deficient oxide Tαoz (2≦2≦2.5) by glue active and sputtering, all the 02 gas reacts with Tα and is consumed, so the excess contained in the undercoat layer is reduced. The 02 gas will be gone. When such an undercoat layer is used, Tα2
Even if the N heating resistance layer is rapidly oxidized, and even if the temperature exceeds 300°C, 02 gas is not generated from inside the thermal head, and the 8402 oxidation-resistant layer blocks the penetration of 02 gas from the outside, so oxidation does not occur. The increase in resistance caused by this is extremely small.

When such a thermal head was mounted on a printer and a printing life test was conducted using actual applied power, the printing quality remained stable with little change.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional thermal head taken along line A' in FIG. 2, FIG. 2 is a plan view of the same thermal head, and FIG. 3 is a plan view of the present invention. FIG. 4 is a cross-sectional view showing one embodiment of the thermal head, and FIG. 4 is a graph showing the steps, stress, and test results of each thermal head.
FIG. 5 is a graph showing the results of a pulse life test of each thermal head. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Glaze layer, 3... Undercoat layer, 4... Heat generating resistance layer, 5, 6... Conductor layer, 7... Oxidation-resistant layer, 8... ...Abrasion resistant layer. Fig. 1 Fig. 2 Fig. 3 Shafted bone 2

Claims (1)

[Claims] In a thermal head having a structure in which a glazed etchant-resistant undercoat layer, a heat-generating resistor layer, a conductor layer, and a protective layer are sequentially laminated on a glazed arsina substrate, the undercoat layer contains an oxygen-deficient low oxide of tantalum. A thermal head characterized by containing: