JPH01123757A - Thick film type thermal head - Google Patents

Abstract

PURPOSE:To eliminate the abnormal rise of contact resistance of a heat generating resistor with electrodes by forming the section of the resistor for forming a head in a sub-scanning direction in a special trapezoidal shape, and disposing both the edges of the upper side of the resistor at the same line as the ends of a common electrode, discrete electrodes on a substrate or outside. CONSTITUTION:A heat generating resistor 4 is formed in a trapezoidal shape having an upper side substantially parallel to a ceramic substrate 1, the taper angles of the edges E0, E0' of the upper side is theta>=90 deg., and the ends Q1, Q1' of the contacts of electrodes 2, 2' with the resistor 4 are disposed inside the edges E0, E0'. Here, when corresponding point on the substrate 1 is E1, corresponding point of E0' is E1', and the widths of the E1 and Q1, the E1' and the Q1' are W1, W1', the W1, W1' are desirably approx. 1-5mum. If the W is excessively large, the heat generated from the resistor is dissipated through the electrode having good thermal conductivity, and power consumption is increased. Eventually, a wear resistance layer 5 is formed on the resistor 4, and wired by gold wirings 7 with an IC 6 placed on the other electrode on the substrate 1, thereby completing it.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a thick-film thermal head, and in particular, in order to improve printing quality and yield, the contact area between the electrode and the heating resistor is improved. Regarding thick film type thermal head.

[Conventional technology]

Conventionally, thick-film thermal heads have been used as thermal recording devices in various printers, facsimile machines, and the like. This thick film type thermal head has usually been manufactured by screen printing a thick film paste. However, in the products manufactured using this method, there are large variations in the line width and film thickness of the heat generating resistor, resulting in variations in resistance value and variation in heat capacity, which causes deterioration in printing quality.

In order to solve these drawbacks, a photosensitive resist film having an opening at the position where the heating resistor is formed is formed on the ceramic substrate on which the electrode is formed, and a resistor paste is embedded in the opening to form the heating resistor. A method has been developed to form

However, when manufacturing with this method, the sidewalls of the openings provided in the photosensitive resist are usually tapered, so the cross section of the heating resistor formed by embedding the resistor paste in the openings is reverse tapered (reversely tapered). ).

This will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a top view of the individually opposed thick-film thermal head, and FIG. 5 is a cross-sectional view in the sub-scanning direction of the thermal head formed by the above-mentioned conventional method (for example, along line a-a' in FIG. cross-sectional view).

As is clear from FIG. 5, the taper angle of the heating resistor 40 on the left and right sides of the upper part on the side opposite to the substrate 1 is θ<9.
0'', therefore, there are edges E and E' on the left and right in this part.
has a shape that protrudes outward.

In such a shape, even if a wear-resistant layer is formed on the heating resistor 40, the edges E and E' will protrude, leading to deterioration in printing quality such as damage to the paper. If a thick wear-resistant layer is applied to completely cover this edge, the heat capacity of the heating system will be large and the power consumption will increase.

In order to solve these problems, when providing a photosensitive resist having an opening, the side wall of the opening is exposed to light at an acute angle to the substrate surface, and a cross section of the heating resistor embedded in the opening is exposed. A thermal head has been proposed that is trapezoidal in shape and has an angle (taper angle) between the upper base and the oblique side of θ>90° (Japanese Patent Application No. 175,686/1986).
(see issue).

That is, when FIG. 6 shows a cross-sectional view of this thick-film thermal head in the sub-scanning direction, the shape of the heating resistor 41 is approximately trapezoidal, and the taper angle θ of the upper edges Eo and EO' is θ>9.
0'', thereby preventing the edges E6 and EO' from protruding from the wear-resistant layer.

(Problems to be Solved by the Invention) However, as shown in FIG. 6, when the heating resistor 41 has a trapezoidal cross section and the taper angle θ of the upper edge (EO, E.') is 90'' or more, Etsuji EO, EO
' comes to enter inside the tips Q and Q' of the electrodes 2.2' on the substrate.

As a result, since the amount of the resistor near the contact portion between the heating resistor 41 and the electrode 2.2' is small, the resistance value of the heating resistor 41 near the tips Q and Q' of the electrode 2.2' is localized. As a result, the resistance value of the bit (heating resistor) increases abnormally, resulting in a problem that the variation in the resistance value of each heating resistor in the board increases.

Therefore, an object of the present invention is to provide a structure of a thermal head that stabilizes the contact between each heating resistor and an electrode and reduces variations in the resistance value of each heating resistor.

[Means and effects for solving the problem] In order to achieve the above object, the present invention has a cross-sectional shape in the sub-scanning direction of a heating resistor constituting a thick-film thermal head such that the taper angle θ of the upper edge The heating resistor is formed into a trapezoid shape such that 900≦θ, and both edges of the upper side of the heating resistor are arranged on the same line as or outside the tips of the common electrode and individual electrodes on the substrate. .

By adopting such a structure, the heating resistor of the thermal head of the present invention has sufficient contact with the electrode, and an abnormal increase in the resistance value at the contact portion between the electrode and the heating resistor can be prevented.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is an explanatory diagram of the configuration of one embodiment of the zero-blow-up device, FIG. 2 is an explanatory diagram of its manufacturing process, and FIG. 3 is an explanatory diagram of the configuration of another embodiment of the present invention.

In each of these figures, 1 is a glazed ceramic substrate, 2 and 2' are electrodes, 3 is a photosensitive resist, 4 is a heating resistor, 5 is a wear-resistant layer, 6 is an rc, and 7 is a gold wire.

As is clear from FIG. 1, in this embodiment, the heat generating resistor 4 has a trapezoidal shape with an upper side substantially parallel to the substrate 1, and an edge E of the upper side. , the taper angle of E6' is θ≧90°, and the heating resistor 4 of each electrode 2.2'
The tips QI and QI' of the contact parts with the above-mentioned edges Ell,
It is located inside E11'. In this case, the heating resistor can be formed as described above by moving the tips Q+ and Q1' of the electrodes closer to each other without changing the size of the heating resistor. Thereafter, a wear-resistant layer (not shown in FIG. 1) may be formed.

Next, FIG. 2 shows the manufacturing process. First, a conductive layer is formed on the entire surface of the glazed ceramic substrate 1, and a plurality of individually facing electrodes 2.2' are formed by photolithography. The film thickness of the electrode is about 0.4 to 4.0 μm (see FIG. 2(a)).

A negative type photosensitive resist 3 is uniformly applied onto the glazed ceramic substrate 1 including the electrodes 2.2' using a spin code method, a roll coating method, a dip method, a spray method, etc., and is dried. Thereafter, exposure and development are performed using a predetermined mask so that the position where the heating resistor is to be provided is opened. The openings at this time are separated for each bit, and the resist film thickness is about 10 to 25 μm. The photosensitive resist used at this time can control the sidewall shape of the resist pattern by adjusting the exposure amount. HC,600 (product name)
was used.

The sidewall shape of this photoresist pattern is vertical when the exposure dose is 200 to 300 mJ/cm", and 30 mJ/cm" when the exposure dose is higher than this.
0~8001IJ/cll! tapered shape, while 10
0 to 200 mJ/cm'', it has a reverse tapered shape.

In this example, the photoresist 3 is coated with a length of 100 to 300 m.
It is exposed to light at about J/c+w'' and developed to obtain a side wall with an inversely tapered shape (see FIG. 2(b)).

Next, a resistor paste 4' is embedded in this opening using a doctor blade method or screen printing, and a resistor paste 4', for example, 130
Dry at a temperature of about ℃. Note that the resistor paste that protrudes outside the opening is removed using a wrapping sheet or the like, but since the resistor is in a dry state, removal is easy (see FIG. 2(c)).

Further, baking is performed at a high temperature of 800 to 900° C., and at the same time as the heating resistor is baked, the photosensitive resist 3 is fired and vaporized to form the heating resistor 4. At this time, the heating resistor 4 is
Depending on the shape of the side wall of the photosensitive resist 3, it becomes a trapezoid with a slight taper (see FIG. 2(d)).

Here, as shown in FIG. 2(d), the edges Ell and EO' on the upper side of the heating resistor 4 are the tips Ql and Q of the electrodes 2.2'.
The opening is designed to be located outside l'.

In the present invention, as shown in FIG. 1, the corresponding point of edge E0 on the ceramic substrate 1 is El, the corresponding point of EO' is EI', the width of El and Ql, and the width of El' and Ql' is W,%. W
, ', w, , w, ' is preferably about 1 to 5 μm. This is because if W is too large, the heat generated from the heating resistor will be dissipated through the electrode with good thermal conductivity, resulting in increased power consumption.

Finally, a wear-resistant layer 5 is formed on the heating resistor 4, and the IC 6 mounted on the other electrode on the substrate is connected to the gold wire 7 to complete the thick film thermal head (see Figure 2 (+3)). ).

Another embodiment of the invention is shown in FIG. In this embodiment, the spacing between the opposing electrodes 32, 32' is the same as in the conventional one, and the length of the opening in the photoresist in the sub-scanning direction is increased to satisfy the above requirements. Can be done.

With this configuration as well, the same effects as in the first embodiment can be obtained.

In addition, in these embodiments, a trapezoid in which the taper angle θ of the edge of the heat generating resistor is θ>90° has been described, but it is also possible to
Needless to say, a similar effect can be obtained with a rectangle.

〔Effect of the invention〕

By adopting the configuration of the present invention, there is sufficient contact between the heating resistor of the thermal head and the electrode, so the resistance value does not increase abnormally in this part, and the resistance of each heating resistor (bit) Variations in values are reduced, resulting in improved print quality and improved device reliability.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the thermal head of the present invention, FIG. 2 is an explanatory diagram of the manufacturing process of one embodiment of the present invention, and FIG. FIG. 4 is a partial configuration diagram of an individual opposing type thermal head, FIG. 5 is a configuration explanatory diagram of a conventional thermal head, and FIG. 6 is a configuration explanatory diagram of another conventional thermal head. 1-glazed ceramic substrate, 2.2'--electrode, 3--photosensitive resist, 4-
・-・Heating resistor, 5-・-wear-resistant 4V layer, 6・-
・IC, 7・-Life wire. Patent applicant: Fuji Zerolux Co., Ltd. Representative Patent Attorney
Akira Yamatani Figure 1 Figure 2

Claims (2)

[Claims] (1) In a thermal head having a structure in which a common electrode and individual electrodes are connected by a heating resistor, the cross-sectional shape of the heating resistor in the sub-scanning direction is at least trapezoidal, and the taper angle θ of the upper edge of the trapezoid is A thick-film thermal head characterized in that θ≧90° and the tip of this edge is disposed on the same line as the tip of each opposing electrode or on the outside. (2) The thick film type thermal head according to claim 1, wherein the width between the corner of the upper side of the cross section of the heating resistor and the tip of the common electrode or the individual electrode is 1 to 5 μm.