JPS62214968A - Thermal head - Google Patents

Abstract

PURPOSE:To enable manufacture at low cost without sacrificing printing quality and recording speed by forming a thermal resistor on an enameled substrate using thin film technology and also forming a conductor for lead electrode with thick film technology. CONSTITUTION:A thin film 2 of thermal resistor composed of a mixture of TiB2-SiC is formed and patternized on an enameled substrate 1 using a low- alkali crystalline glass such as Mg2B2O6, BaMg2Si2O7. The resistance value of the thermal resistor is approx. 6mum thick using an Au conductive paste through application and sintering process. Next, a thick film glass layer 4 is formed into a thermal head. The enameled substrate 1 is used as an insulation substrate and a radiation substrate of a thermal head, thus radially dissipating an accumulated energy of the thermal head to the outside of the system effectively as radiation energy. Consequently a low cost thermal head which enables high-quality printing can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal head for thermal printing in facsimile machines, printers, etc., and particularly to a thermal head that is low cost and has high print quality.

BACKGROUND OF THE INVENTION Thermal heads for thermal printing are broadly classified into thin-film thermal heads and thick-film thermal heads, depending on the method of forming the heating resistor and conductor for lead electrodes.

Thin-film thermal heads are formed using so-called thin-film techniques such as vapor deposition, sputtering, and photolithography, while thick-film thermal heads use so-called thick-film techniques such as screen printing. The thin-film thermal head improves printing quality by making the resistance value of the heating resistor uniform, and enables high-speed recording due to its excellent thermal response. However, it has the disadvantage of requiring many manufacturing steps and high manufacturing cost. - Thick film thermal heads are inexpensive to manufacture and have excellent durability, but have the drawbacks of large variations in resistance, low printing quality, and high power consumption.

Problems to be Solved by the Invention The present invention solves the problems that thick-film thermal heads have, such as poor print quality and slow recording speed, that is, the large amount of waste power, and the problems that thin-film thermal heads have. The purpose is to solve the problem of high cost.

Means for Solving the Problems According to the present invention, a heating resistor is formed on a hollow substrate using a thin film technique, and a conductor for a lead electrode is formed using a thick film technique.

Function: According to the present invention, it is possible to reduce costs without impairing the high print quality and high recording speed, which are the features of thin film thermal heads.

The thermal head of the present invention is essentially different from conventional examples. Conventionally, a ceramic substrate and a heat dissipation substrate were required for the thermal head, but the hollow substrate made of low alkaline crystallized glass used in the present invention is It serves as both an insulating substrate and a heat dissipation substrate of the head, and can efficiently radiate the stored thermal energy other than the printing energy generated in the head portion as radiant energy to the outside of the system.

This low alkali glass ceramic with excellent insulation properties is L
A monovalent alkaline component selected from the group of i2O, Na2O and Ni2O is contained in an amount of 2% by weight or less, and an alkaline earth component (Ba
O, MgO, CaO, ZnO) at least 16% by weight
The thermal expansion coefficient number of glass ceramics is (
60 to 160)
Glass ceramics having a crystalline layer of g2Si207 are most suitable for the purposes of the present invention.

Glass frit that can form such a hollow layer of glass ceramics is ultrafinely pulverized, and glass frit fine particles are electrophoretically electrodeposited using an alcohol electrolyte containing a trace amount of water to form the desired material. A hollow substrate is prepared by firing at a firing temperature of .

Example The present invention will be explained in detail below.

Example 1 FIG. 1 is a sectional view of one embodiment of a thermal head.

Reference numeral 1 denotes a substrate, which is a hollow substrate made of low alkaline crystallized glass such as Mg2B2O5 or BaMg28i207. Reference numeral 2 denotes a heating resistor, which is a thin film made of a TiB2-SiC mixture, which was formed by RF sputtering and patterned by dry etching.

At this time, the resistance value of the heating resistor was approximately 3×10 −20·α. 3 is a lead electrode, and as shown in Table 1, a conductive paste of about 6 μm is coated on the entire surface of the substrate or in a pattern by screen printing using so-called thick film technology, dried and sintered. It is something. In the case of full-surface coating, a pattern was formed by a photolithography process and a wet etching process after sintering. The table shows the sintering conditions as well as the change in resistance of the heating resistor after the lead electrodes were created.

(The following is a blank space) 4 is a protective layer and wear-resistant layer, which is a thick glass layer formed by a screen printing method. Note that the pattern-formed thermal head has 8 pieces/mm.

o, oes per dot for black 1 to black 4 heads
Normal printing was possible by supplying power of 0.3W from W. In Table 1, the lower the sintering temperature of the M-U electrode, the smaller the resistance change of the heating resistor during sintering, and the smaller the desired resistance value was obtained. Further, when the MuU electrode was printed on the entire surface in advance and patterned after sintering, the increase in resistance of the resistor could be suppressed under the same sintering conditions, compared to when the pattern was printed from the beginning.

Furthermore, the resistance value within the same head is ±6% (Todoroki 1 to 3)
Thus, a highly reliable thermal head with less variation was obtained compared to a head formed using only conventional thick film technology (with variation of ±16%). Furthermore, the manufacturing process for this thermal head is about half that of a head formed using only thin film technology.

Embodiment 2 FIG. 2 is a sectional view of a second embodiment. Reference numeral 1 denotes a hollow substrate, on which thick film lead electrodes (6 to 10 μm thick) 3 are provided in advance by screen printing. No. 2 was a Ta5iO)C-based heating resistor formed by sputtering, and had a sheet resistance of 5000/hole. Patterning of the heat generating portion was performed by dry etching. 4 is a wear-resistant layer made of SiC with a thickness of 4 μm. Table 2 shows the variation in resistance values of the manufactured heads.

Table 2 From Table 2, it can be seen that the variations in resistance values of thermal heads &7 to 8 are smaller than those formed using only conventional thick film technology (variation ±16%), and those formed using only thin film technology. The number of processes can be significantly reduced compared to conventional heads.

Furthermore, by using a hollow substrate as the substrate, it was possible to improve the adhesion of the lead electrode to the substrate.

The present invention is not limited to the above embodiments, and the heating resistor may be τasiz, Tie, or ZrB.

Metal compounds such as NiCr, NbSi, and τ&2N may also be used.

Further, the lead electrode may be a thick film sintered body of a noble metal such as PT. Further, regarding the sintering conditions, an N2 gas atmosphere may be used as necessary, taking into consideration the compositional change of the heating resistor during sintering. The wear-resistant layer is diamond-like carbon,
A hard material such as glass containing Ta205 or SiC may also be used.

Effects of the Invention The present invention provides a thermal head which is low in cost and can improve printing quality by making resistors uniform.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views showing an embodiment of a thermal head according to the present invention. DESCRIPTION OF SYMBOLS 1...Hollow board, 2...Heating resistor, 3...Lead electrode, 4...Wear-resistant layer.

Claims (4)

[Claims] (1) A heating element made of a thin film resistor on a hollow substrate,
A thermal head characterized by being provided with a power supply lead electrode made of a thick film conductor. (2) The thermal head according to claim 1, wherein a heating element is provided on the hollow substrate, and a lead electrode for power supply is provided on the heating element. (3) The thermal head according to claim 1, wherein a lead electrode for power supply is provided between the hollow substrate and the heating element. (4) The thermal head according to claim 1, wherein the hollow substrate is a metal substrate whose surface is coated with low-alkaline crystallized glass.