JPH03184876A - Thermal head - Google Patents

Abstract

PURPOSE:To improve the heat response of a resistor part by providing a high- heat conductive metal layer on the rear surface of a high-heat resistant resin substrate. CONSTITUTION:On a copper foil 1A of a double-copper plated, laminated substrate P, a polyimide precursor dissolved in a solvent of NMP is applied with a predetermined thickness. After the solution is dried, it is precured to be a polyimide layer. After the polyimide layer is patterned, it is heated by being put in an oven or irradiated with infrared rays to be a polyimide resin heat- accumulation layer 3. Thereafter, a heating resistor layer 4 is sputtered all over the layer 3, furthermore being patterned by photoetching. Thereon, a common electrode 6 and a lead electrode 5 are photoetched into a predetermined pattern. Thereon, a protective film 7 is sputtered. With the use of a thermal head produced in this manner, a material cost is lowered, the warpage of the high-heat resistant resin substrate at the time of heat treatment is reduced, a pattern accuracy is improved, a high-speed printing can be conducted, and the printing quality is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a thermal head used in a thermal printer or a thermal transfer printer.

(B) Prior Art Conventionally, in a thermal head, a glass glaze layer 1 provided on a ceramic substrate 12 is used as shown in FIG.
After forming a heat generating resistor 14 such as Ta5iOt, a common electrode I6 and a lead electrode 15 such as AI or Al-3i into a predetermined pattern by photo-etching through the protective film I7, S1AION, S The iON and the like are formed by spar vapor deposition or plasma CVD.

(c) Problems to be solved by the invention However, in the case of conventional thermal heads using such glazed ceramic substrates, there are problems in that the cost of raw materials is high and the manufacturing process is complicated due to poor workability. there were.

Therefore, efforts are being made to put into practical use thermal heads that use highly heat-resistant resin substrates that are inexpensive and easy to process, instead of ceramic substrates. That is, in this thermal head, as shown in FIG. 4, a patterned electrode layer (common electrode 29 and lead electrode 28) is formed on a highly heat-resistant resin substrate 22, and then a varnish-like polyimide precursor is formed. A layered polyimide precursor is formed by coating the body, preheating (drying and half-curing), etching it into a predetermined pattern, and heating it to a temperature of 300°C or higher using an oven or infrared irradiation device. Then, the polyimide precursor is imidized to form a polyimide resin storage M layer 23, and a heating resistor 24 electrically connected to the common electrode 29 and the lead electrode 28 is formed thereon. Then, a structure in which a protective film 27 is further laminated is adopted.

By the way, in a thermal head using such a highly heat-resistant resin substrate, an electrode layer, a polyimide resin heat storage layer,
When forming the heating resistor and the protective film, the resin substrate warps as it goes through photo-etching and heat treatment steps, making it difficult to form fine patterns.

Furthermore, this thermal head does not have sufficient heat dissipation characteristics for the heat generated in the heating 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 (highest temperature value) and the base temperature (lowest temperature value) just before pulse application gradually rise,
It is difficult to print at high speed, and there is a problem that so-called trailing phenomenon occurs when printing continuously.

This invention was created with these circumstances in mind.The 4TF material has low material cost, reduces the warpage of a highly heat-resistant resin substrate during heat treatment, improves pattern accuracy, and improves heat dissipation characteristics to enable high-speed printing. The present invention provides a thermal head with high printing quality.

(d) Means for Solving the Problems This invention provides a heat-resistant resin substrate, a heat-storage layer made of heat-resistant resin formed on the surface of the substrate, a heat-generating resistor layer formed on the heat-storage layer, and the substrate. A thermal head comprising: an electrode layer formed on the surface of the substrate for supplying current to the heat generating resistor layer; a protective layer formed on the heat generating resistor layer and the electrode layer; and a heat dissipating metal layer formed on the back surface of the substrate. It is.

A metal layer having better thermal conductivity than the resin substrate, such as copper foil, is provided on the entire back surface of the high heat-resistant resin substrate by adhesion or sputter deposition, or a double-sided copper-clad laminate is used as a thermal head substrate. One side is used as an electrode layer, and the copper foil on the back side 4 is masked with tape or a mask, and the photo-etching process of the electrode layer is performed, leaving the copper foil as it is and forming a thermally conductive layer. It is preferable that

(e) Effect: By using a highly heat-resistant tatq=substrate, material costs can be reduced. Furthermore, by providing a metal layer with better thermal conductivity than the resin substrate on the back surface of the substrate, it is possible to alleviate the warpage of the substrate that occurs during photoetching and heat treatment steps, thereby improving pattern accuracy.

Furthermore, as the heat generated by the heating resistor is quickly dissipated, thermal responsiveness is improved, high-speed printing becomes possible, and the trailing phenomenon of printing can be eliminated.

(F) Embodiments The present invention will now be described in detail based on embodiments shown in the drawings.

Embodiment (1) FIG. 1 is a sectional view of a main part of a thermal head of embodiment (1). This thermal head is manufactured using a double-sided copper-clad laminate board P as follows. In addition, 2 is vertical 300rtt
It is a highly heat-resistant resin substrate with a diameter of 1400 mm and a thickness of 0.8 μm, with copper foil 1.5 μm thick on both sides. IA is glued.

First, N-methylpyrodrine/(NMP
) was applied as a solvent to a predetermined thickness using a spin coater or roll coater, and heated at 120°C.
After drying for several minutes at a temperature of about 100° C., preliminary curing is performed at a temperature of 200° C. for 30 minutes to form a polyimide layer.

Next, after patterning the polyimide layer formed on one side of the double-sided copper-clad laminate P, the polyimide layer is heated for 30 minutes at a temperature of approximately 300°C to 350°C in an oven or by irradiation with infrared rays.
The polyimide resin heat storage layer 3 is formed by heating for about 0 minutes.

Next, a heat generating resistor layer 4 is formed on the entire surface using a sputtering method, and the heat generating resistor layer 4 is further patterned by photoetching, and a common electrode 6 and a lead electrode 5 are formed on the top thereof in a predetermined pattern by photoetching. Finally, the medical protective film 7 is coated with an acid film by sputtering to complete the thermal head.

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

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

Next, on this copper layer 8A, a nickel plating layer 8B with a thickness of 1 μm and a nickel plating layer 8B with a thickness of 0.1 μm are formed by electroless plating.
Electrode layers, that is, a common electrode 9 and a lead electrode 8 are formed by sequentially stacking gold plating layers 8C having a thickness of .mu.m.

Next, a polyimide precursor is formed on this top in the same manner as in Example (1), and etched into a predetermined pattern using photolithography to form a trapezoidal polyimide layer.

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

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

Application of driving pulses between this thermal head bonded to an aluminum heat sink li using adhesive IO (Fig. 2) and a thermal head without copper foil 1 on the back side of the highly heat-resistant resin substrate 2 (comparative example) Figures 5 and 6 show the heat dissipation characteristics at this time.

FIG. 5 shows the temporal change in the surface temperature of the heating resistor layer during application of 1 pulse, in which (A) shows a comparative example and (B) shows an example. If a copper foil is provided on the back side of the board, even if a heat storage area H (Fig. 2) occurs locally in the polyimide resin heat storage layer 3 and the heat-resistant resin board 2 under the heating resistor layer 4, , it can be seen that heat is quickly dissipated through the copper foil 1 on the back surface of the board, and the thermal response is improved.

Furthermore, FIG. 6 shows the peak intensity and the temporal change in base concentration when continuous pulses are applied.

(Ap) and (Ab) indicate the peak temperature and base temperature of the conventional column, and (Bp) and (Bb) indicate the peak/base temperature of the example.
It shows IA degree and base temperature. In other words, since both the peak concentration and the base temperature are lower when the copper foil l is provided on the back surface of the substrate, it can be understood that the trailing phenomenon due to residual heat in the heating resistor portion is improved.

Furthermore, by using an adhesive paste with good thermal conductivity as the adhesive lO between the heat sink 11 and the thermal head substrate shown in FIG. 2, the heat dissipation characteristics can be further improved.

(G) Effects of the Invention According to this invention, by providing a metal layer with good thermal conductivity on the back surface of a highly heat-resistant resin substrate, it is possible to improve the thermal response of the resistor part that generates heat when a driving pulse is applied. This enables high-speed printing. Furthermore, heat dissipation is improved, and tailing phenomenon can be prevented. In general, since the back surface of the substrate is a metal layer, warping of the resin substrate itself during processing is alleviated, pattern processing accuracy is improved, and fine patterning is facilitated. Therefore, a highly reliable and inexpensive thermal head is provided.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a thermal head according to an embodiment (1) of the present invention, Fig. 2 is a sectional view showing a thermal head according to an embodiment (2) of the invention, and Fig. 3 is a sectional view showing a conventional thermal head. 4 is a sectional view showing the configuration of a comparative example;
This figure and FIG. 6 are explanatory diagrams showing temperature characteristics with respect to applied pulses. 1.1A...Copper foil, 2...High heat-resistant resin substrate, 3...Polyimide resin heat storage layer, 4...
... Heat generating resistor layer, 5 ... Lead electrode, 6
...Common electrode, 7...Protective film.

Claims (1)

[Claims] 1. A heat-resistant resin substrate, a heat storage layer made of heat-resistant resin formed on the surface of the substrate, a heating resistor layer formed on the heat storage layer, and a heating resistor layer formed on the surface of the substrate for energizing the heating resistor layer. A thermal head comprising: an electrode layer; a protective layer formed on the heating resistor layer and the electrode layer; and a heat dissipation metal layer formed on the back surface of the substrate.