JPS6174865A - Method of manufacturing thermal head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Technical field of invention) The present invention relates to a novel method for manufacturing a thermal head.

(Background of the Invention) A method of reproducing images in the form of hard copies such as photographs from electrical image signals obtained from televisions, video cameras, video disks, electronic cameras, etc. has been actively researched. The most effective method among these is the thermal image recording method. This is a heating resistor door lined up in the main scanning direction)
While the thermal recording paper is pressed against a thermal head consisting of a group of electrodes and a pair of electrode groups for energizing each dot, the dots are selectively energized based on an electrical image signal input manually.
j1 generate electric heat, use this heat to print one line of pixels on the recording paper, then move the recording paper one line, print the next line of pixels in the same way based on the next line's signal, and do the following: , the movement and printing of each row of pixels are repeated in the same way, and finally a two-dimensional image is obtained.

In this case, the resistor dots of the thermal head (a) directly affect the image quality, so in order to obtain an image with a quality close to that of a photograph, they must generally be formed at a density of 8 dots/mm or more. (b) - If there are variations in electrical resistance between dots in a group of heating resistor dots arranged in a row, the printed 4 degrees will be uneven; (c) heating is done to speed up the thermal response characteristics. We want to make the resistor as thin as possible and reduce its heat capacity, and (d) ruthenium oxide is currently the only material for the resistor that can be applied to the thick film method. The appropriate amount of photoetching required for patterning in the process (i.e.
Due to the fact that there is currently no etching solution (that can corrode only the ruthenium oxide without corroding the underlying heat storage layer or alumina substrate), the heating resistor was formed by a thin film method, and then patterned by photoetching. Form each dot.

The "thin film method" referred to here is a method of forming a thin film by ejecting molecules, atoms, or ions in a vacuum atmosphere and depositing them on a substrate, such as vacuum evaporation, ion blating, sputtering, CVO, etc. can be given.

However, the thin film method requires a device to create a vacuum atmosphere, making the manufacturing equipment large and expensive. (c) patterning by photolithography generally involves a large number of steps and is time consuming; (d)
It has drawbacks such as poor material usage efficiency and high manufacturing costs.

On the other hand, the "thick film method" is a method in which a paste-like material is applied to a substrate and then baked to form a film.
(b) Manufacturing equipment is small and inexpensive; (b) continuous operation is easy and production efficiency is high; (c) coatings can be formed on large substrates; (d) screen printing is used during coating. Then, patterning can be performed at the coating stage, and there is no need to pattern after the film is formed.
(e) It has features such as high material usage efficiency and little waste. In particular, feature (d) is the most significant feature of the thick film method, and many people think that the thick film method equals screen printing.

On the other hand, the pair of contact electrodes for energizing each resistor dot must be made as thin as possible in order to (a) reduce the gap with the heating resistor dot and improve contact with the thermal recording paper; (b) Since the electrode spacing in the sub-scanning direction, which determines the resistance value of the resistor dots, must be formed with high precision, an RQ film is first formed on the entire surface by a thin film method, and then patterned by photoetching. Make a strip approximately the same width as the dot at the same position as each dot.

However, in general, (a) TM and Wx using the thin film method have too high electrical resistance, and (b) when forming electrodes using the thin film method, an alumina process plate with a purity of 99.5% and a high surface smoothness is used. (Because if a cheap alumina substrate with a rough surface area of 96% purity is used, a thin and uniform thin film will not be formed), and such a substrate is very expensive (c) On the other hand,
In the wafer method, an inexpensive alumina substrate with a rough surface precision of 96% purity can be used, and for reasons such as the fact that an inexpensive alumina substrate with a rough surface precision has higher adhesion, it is possible to use a pair of contact electrodes. do not form for too long,
It has been proposed to separately form a pair of lead electrodes by a thick film method and connect each contact 'gL'r5i to each lead electrode (Japanese Patent Application Laid-open No. 17853/1983).

In the method described in JP-A-54-17853, in the first step, a conductive paste is applied in a predetermined pattern by screen printing, and then baked to form a pair of leads! A group of poles is formed, and in the second step, a base paste mainly composed of glass is used in the gap between a pair of lead electrodes facing each other (a track storage layer is formed by screen printing and firing.

However, according to research by the present inventors, among the thermal heads manufactured by the method described in the above-mentioned Japanese Patent Application Laid-Open No. 54-17853, the thermal heads with a density of 8 dots/IIIm or more have (a) contact tJ (The adhesion force of i to the lead electrode is poor in durability, (b)
The position of the lead electrode and the position of the contact electrode must be consistent; (c) Pinholes are likely to form in the lead electrode;
(d) The pattern of the lead electrode is inaccurate; (e) It is impossible to achieve a density of 8 dots/mm or more unless an electrode pattern based on alternating leads is adopted; however, the alternating lead method is difficult to drive. It has been found that there are disadvantages such as the method being extremely sloppy and the circuit configuration becoming complicated.

(Object of the Invention) Therefore, the object of the present invention is to
1 by improving the manufacturing method described in Publication No. 3
1: The aim is to eliminate the various shortcomings listed in 1.

(Summary of the Invention) As a result of intensive research, the present inventors have discovered that when forming a single conductive layer using a thick film method, they can use a thick film method to form a thick conductive film on the entire surface without using screen printing. After formation, lead electrodes are formed by patterning using photoetching.
It has been discovered that the above-mentioned drawbacks can be overcome, and the present invention has been completed.

Therefore, the present invention provides a group of heating resistor dots lined up in a row in the main scanning direction, a pair of contact electrode groups for supplying current to each dot from the sub-scanning direction, and a single contact electrode at the center pole of each contact.
Dot weight 8 consisting of a group of lead electrodes for ffi electricity
In the method of manufacturing a thermal head of dots/mm or more, (1) a thick 4-electrode film is formed on a substrate using the 119-thickness method;
2) The thick conductive film is patterned by photo-etching to form a pair of glue leads to form a pole group. 3) The pair of lead electrodes are formed into a gap where they face each other, and from there, the pair of glue leads are applied to the ends of the lead electrodes by screen printing. And by firing, M
(4) forming a heating resistor layer on the heat storage layer by a thin film method; (5) patterning the heating resistor by photoetching to form a band-shaped resistor group; 6) forming a thin conductive film on the resistor group and from there to the ends of the pair of lead electrode groups by a thin film method; (7) patterning the thin conductive film by photoetching to form a pair of contacts. The present invention provides a method for manufacturing a thermal device characterized by forming an electrode group.

Hereinafter, the present invention will be explained in more detail with reference to the drawings and examples, but the present invention is not limited thereto.

(Example) In the ml process, a conductive paste mainly composed of noble metals such as gold and Ag-Pd was applied to the entire surface through a screen on an inexpensive alumina substrate (1) with a rough surface area and a purity of 96%. The film thickness can be increased by firing at 850-900℃.
A thick conductive film (2) of 5 to 6 microns is formed.

Second step: After applying photoresist on the thick conductive film (2), it is exposed through a photomask with a predetermined pattern of density 8 to 20 dots/11 to form a renost pattern, and then etching is performed to remove the resist. When the pattern is removed, a pair of lead electrode groups (2a) and (2b)
is formed (see Figure 1).

Third step - A gap where the pair of lead electrodes (2a), (2b) face each other and a pair of lead electrodes (2a), (
2b), the glass is the main component.
The heat storage layer (3) is formed using a body paste (applied by screen printing and then baked at 850-900°C (see Figure 2 and 2AUjJ).
) has a smoother surface than the alumina substrate (1), so it is convenient for the next thin film formation.

Fourth step: A film of tantalum nitride, Cr- A heating resistor thin film (4) of 3iO1NiCr or the like is formed (see FIGS. 3 and 3A).

Fifth step: After coating the resistor thin film (4) with photoresist, it is exposed through a photomask with a predetermined pattern to form a Renost pattern, and then etched.
By removing the Lenost pattern, a band-shaped resistor pattern (4) is obtained (see FIGS. 4 and 3A).

Sixth rule: The film thickness is 1 to 2
A (two-layer) thin conductive film (5) of micron Cr/Au, NiCr/Au, etc. is formed by sputtering (
(See Figures 5 and 5A).

Seventh step: After applying photorenost on the thin conductive film (5), it is exposed through a photomask with a predetermined pattern to form a renost pattern, and then etching is performed.
By removing the resist pattern, a pair of contact electrodes (5a) and (5b) are formed (see FIGS. 6 and 6A). The strip-shaped resistor (4) located in the gap between the pair of contact electrodes (5a) and (5b) thus formed becomes a resistor dot (4a).

8th step: Finally, in order to protect the resistor dot (4a) and the pair of contact electrodes (5a) and (5b), the entire surface is coated with a vacuum f coating method to protect the film thickness from 5 to 10 microns + 1A.
(6) For example, 5if2/Taxes two-layer film, Al
By laminating □0□, SiC-Si3N4, etc. (see FIG. 7), a thermal head with a density of 8 to 20 dots/mm can be obtained.

(Effects of the Invention) The thermal head manufactured by the present invention has (a) durability of adhesion of the contact electrode to the lead electrode compared to a thermal head manufactured by the conventional method with the same density of 8 dof)/m+n or more. (b) The position of the lead electrode and the position of the contact electrode must match accurately;
()・) There should be no pinholes in the lead electrode, (d) The pattern of the lead electrode should be accurate, and (e) If the Conotact electrode and the lead electrode are made to have the same width, they will overlap accurately. (On the other hand, when lead electrodes are formed using a thick film method using screen printing, the width of the lead electrodes may be locally narrow or wide.) ″
Because of this, the contact area with the contact electrode is small, and therefore the adhesion force is small.

[Brief explanation of drawings]

1, 2, 3, 4, 5, and 6 are schematic plan views at each step of the thermal head manufactured in an embodiment of the present invention6. Figure 2A is a FIG. 2 is a cross-sectional end view taken along arrows X and -X in FIG. 2; FIG. 3A is a cross-sectional end view taken along arrows X and -X2 in FIGS. 3 and 4. FIG. FIG. 5A is a cross-sectional plan view taken along arrows X and -X□ in FIG. 5. FIG. 6A is a cross-sectional end view taken along arrows X and -X in FIG. 6. FIG. 7 is a cross-sectional end view at the final step of the thermal head manufactured in the embodiment of the present invention. [Explanation of symbols of soil layer parts] 1 - Substrate 2 - - Thick film conductive films 2 a, 2 b - Pair of lead electrodes 3 - Heat storage layer 4 - Thin film resistor 4 a ---- - One shot resistance body Donodo 5 -
Thin pIJ, conductive film 5a, 5b pair of contact electrodes 6-
protective layer

Claims (1)

[Scope of Claims] Consisting of a group of heating resistor dots arranged in a line in the main scanning direction, a pair of contact electrode groups for energizing each dot from the sub-scanning direction, and a lead electrode group for energizing each contact electrode. In the method of manufacturing a thermal head with a dot density of 8 dots/mm or more, (1) a thick conductive film is formed on a substrate by a thick film method; (2)
The thick conductive film is patterned by photoetching to form a pair of lead electrode groups, and (3) the gap where the pair of lead electrodes face each other and from there to the ends of the pair of lead electrodes are patterned by screen printing and baking. , forming a heat storage layer; (4) forming a heat generating resistor on the heat storage layer by a thin film method; (5) patterning the heat generating resistor by photoetching to form a band-shaped resistor group; (6) forming a thin conductive film on the resistor group and from there to the ends of the pair of lead electrode groups by a thin film method; (7) patterning the thin conductive film by photoetching, A method of manufacturing a thermal head, comprising forming a group of contact electrodes.