JP2547876B2 - Method of manufacturing thermal head - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal head used in a thermal printer or a thermal transfer printer.

(B) Conventional Technology In a conventional thermal head, as shown in FIG. 3, a glass glaze layer 13 provided on a ceramic substrate 12 is used.
Via, the heating resistor 14 such as TaSiO ₂ , the common electrode 16 such as A1 or Al-Si and the lead electrode 15, after forming a predetermined pattern by photoetching method, as a protective film 17,
SiAlON, SiON, etc. are formed by sputter deposition or plasma CVD.

(C) Problems to be Solved by the Invention However, in the case of a conventional thermal head using such a glaze ceramic substrate, there are problems that the raw material cost is high and the manufacturing process is complicated due to poor workability. there were.

Therefore, a thermal head using an inexpensive and highly workable resin substrate having high heat resistance instead of the ceramic substrate is being put into practical use. That is, in this thermal head, as shown in FIG. 4, a patterned electrode layer (common electrode 29 and lead electrode 2 is formed on the high heat resistant resin substrate 22.
8) is formed, and then a varnish-shaped polyimide precursor is applied, preheating (drying / half-cure) is performed to form a layered polyimide precursor, and after etching into a predetermined pattern, an oven or infrared With irradiation device 30
By heating to a temperature of 0 ° C. or higher, the polyimide precursor is imidized to form a polyimide resin heat storage layer 23, and a heating resistor electrically bonded to the common electrode 29 and the lead electrode 28 is formed thereon. A structure in which 24 is formed and a protective film 27 is further laminated is adopted.

By the way, in the thermal head using such a high heat resistant resin substrate, when forming the electrode layer, the polyimide resin heat storage layer, the heating resistor, and the protective film,
There is a problem in that the resin substrate warps as a result of photo-etching and heat treatment, making it difficult to form a fine pattern.

Further, this thermal head has insufficient heat generation characteristics with respect to the heat generated by the heat generating resistor during operation, and the heat accumulates on the substrate, resulting in poor thermal response due to continuous pulse application. As a result, the peak temperature (maximum temperature value) and the base temperature immediately before pulse application (minimum temperature value) gradually increase, making high-speed application difficult, and the so-called tailing phenomenon easily occurs during continuous printing. There is.

The present invention has been made in consideration of such circumstances, the material cost is low, the warp of the high heat-resistant resin substrate during heat treatment is mitigated to improve the pattern accuracy, and the heat dissipation property is improved to perform high-speed printing. It is intended to provide a thermal head that enables good printing quality.

(D) Means for Solving the Problems The present invention uses a substrate in which metal foils are uniformly adhered to the upper surface and the lower surface in advance, and a common electrode and a lead electrode are formed using the metal foil on the upper surface of the substrate. A thermal process consisting of forming a heat storage layer in the area where the heating resistor layer is to be formed on the upper surface of the substrate, forming a heating resistor layer on the heat storage layer from the common electrode to the lead electrode, and forming a protective layer covering the heating resistor layer. A method for manufacturing a head is provided.

On the entire back surface of the high heat resistant resin substrate, a metal layer having better thermal conductivity than the resin substrate, for example, a copper foil or the like is provided by adhesion or sputter deposition, or a double-sided copper clad laminated substrate as a thermal head substrate. One is used as an electrode layer, the copper foil on the back side is masked with a tape or a resist, and the photoetching step of the electrode layer is performed. preferable.

(E) Action Material cost can be reduced by using a highly heat-resistant resin substrate. Further, by providing a metal layer having better thermal conductivity than the resin substrate on the back surface of the substrate, the warp of the substrate caused by the photoetching or heat treatment step can be alleviated, so that the pattern accuracy is improved. Further, as a result of promptly dissipating the heat generated by the heating resistor, the thermal response is improved, high-speed printing becomes possible, and the tailing phenomenon of printing can be eliminated.

(F) Embodiment Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

Embodiment (1) FIG. 1 is a cross-sectional view of essential parts of a thermal head of embodiment (1). This thermal head is manufactured using the double-sided copper clad laminate P as follows. 2 is 300 mm long and 4 horizontal
It is a high heat resistant resin substrate with a thickness of 00 mm and a thickness of 0.8 mm, and copper foils 1 and 1A having a thickness of 3 to 5 μm are adhered to both surfaces thereof.

First, on the copper foil 1A, N-methylpyrrodoline / (NMP)
Is applied to a predetermined thickness using a spin coater or a roll coater, and a polyimide precursor is dried at a temperature of about 120 ° C. for several minutes, and then pre-cured at a temperature of 200 ° C. for 30 minutes to form a polyimide layer. .

Next, after patterning a polyimide layer formed on one surface of the double-sided copper-clad laminated substrate P, it is heated at a temperature of about 300 ° C. to 350 ° C. for about 30 minutes by irradiation of an oven or infrared rays to store the polyimide resin heat. Form layer 3.

Then, the heating resistor layer 4 is formed on the entire surface by sputtering, and the heating resistor layer 4 is patterned by photoetching. The common electrode 6 and the lead electrode 5 are formed on the patterned resistor layer 4.
Is formed into a predetermined pattern by photoetching, and finally, a protective film 7 is formed by a sputtering method to complete the thermal head.

Embodiment (2) FIG. 2 is a sectional view of the thermal head of the embodiment (2). This thermal head is manufactured as follows.

First, as a high heat resistant resin substrate, a double-sided copper clad laminate P
By using, one of the copper foil is etched into a predetermined pattern by photolithography method, the patterned copper layer
Form 8A. At this time, the copper foil 1 on the back surface is masked with a tape or a resist and left as it is.

Next, a nickel-phosphorus plating layer 8B having a thickness of 1 μm and a thickness of 0.1 μm is formed on the copper layer 8A by an electroless plating method.
The gold-plated layers 8C are sequentially laminated to form an electrode layer, that is, the common electrode 9 and the lead electrode 8.

Next, a polyimide precursor is formed on this upper part in the same manner as in Example (1), and the photolithography method is used.
A trapezoidal polyimide layer is formed by etching in a predetermined pattern.

Next, this polyimide precursor layer is heat-treated for 30 minutes at a temperature of 300 ° C. to 400 ° C. by irradiation of an oven or infrared rays to form a trapezoidal polyimide resin heat storage layer 3. At this time, since the copper foil 1 having good thermal conductivity is provided on the back surface of the substrate, the cooling effect of the resin substrate 2 is further improved, and the deterioration and warpage of the resin substrate 2 can be prevented.

Next, the heating resistor layer 4 is formed by the sputtering method, and the protective film 7 is further formed by the sputtering method to complete the thermal head.

Applying a drive pulse between a thermal head in which this thermal head is bonded to an aluminum radiator plate 11 with an adhesive 10 (Fig. 2) and a thermal head in which the copper foil 1 is not provided on the back surface of the high heat resistant resin substrate 2 (comparative example). The heat dissipation characteristics at the time are shown in FIGS. 5 and 6.

FIG. 5 shows the temporal change of the surface temperature of the heating resistor layer when one pulse is applied, (A) shows a comparative example, and (B) shows an example. When a copper foil is provided on the back surface of the substrate, the heat storage part H (FIG. 2) is locally formed in the polyimide resin heat storage layer 3 and the heat-resistant resin substrate 2 below the heating resistor layer 4.
It can be seen that even if occurs, heat is quickly dissipated through the copper foil 1 on the back surface of the substrate, and the thermal response is improved.

Further, FIG. 6 shows the peak temperature and the base temperature with time when a continuous pulse is applied. (Ap) and (Ab) show the peak temperature and base temperature of the conventional example, and (B
p) and (Bb) show the peak temperature and base temperature of the examples. That is, since the peak temperature and the base temperature are lower when the copper foil 1 is provided on the back surface of the substrate, it is understood that the tailing phenomenon due to the residual heat of the heating resistor portion is improved. .

Further, by using an adhesive paste having good thermal conductivity as the adhesive 10 between the heat dissipation plate 11 and the thermal head substrate shown in FIG. 2, the heat dissipation characteristics can be further improved.

(G) Effect of the Invention According to the present invention, by providing a metal layer having good thermal conductivity on the back surface of the high heat-resistant resin substrate, it is possible to improve the thermal response of the resistor portion that generates heat when a drive pulse is applied. Yes, high-speed printing is possible. In addition, heat dissipation is also improved, and the tailing phenomenon can be prevented. Furthermore, since the back surface of the substrate is a metal layer, the warpage of the resin substrate itself during processing is alleviated,
The pattern processing accuracy is improved, and fine patterning is facilitated. Therefore, an inexpensive thermal head having excellent reliability is provided.

[Brief description of drawings]

1 is a sectional view showing a thermal head of an embodiment (1) of the present invention, FIG. 2 is a sectional view showing a thermal head of an embodiment (2) of the present invention, and FIG. 3 is a conventional thermal head. Sectional view, FIG. 4 is a sectional view showing the structure of a comparative example, FIG.
FIG. 6 and FIG. 6 are explanatory views showing the temperature characteristics with respect to the applied pulse. 1,1A ... Copper foil, 2 ... High heat resistant resin substrate, 3 ... Polyimide resin heat storage layer, 4 ... Heating resistor layer, 5 ... Lead electrode, 6 ... Common electrode, 7 ... Protective film .

Claims (1)

(57) [Claims] 1. A substrate in which a metal foil is uniformly adhered to the upper surface and the lower surface of the substrate in advance, a common electrode and a lead electrode are formed using the metal foil on the upper surface of the substrate, and a heating resistor layer is formed on the upper surface of the substrate. A method of manufacturing a thermal head, comprising the steps of forming a heat storage layer in a predetermined area, forming a heating resistor layer on the heat storage layer from a common electrode to a lead electrode, and forming a protective layer covering the heating resistor layer.