JPS5938113B2 - Silicon semiconductor thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a silicon semiconductor type thermal head.

The thermal recording method uses heat-generating dots that utilize the Joule heat generated by a small resistor to generate primary color on thermal paper.It does not require development (primary color development), is simple and suitable for miniaturization, is maintenance-free, and is low-priced, making it popular among terminals. This is becoming the mainstream recording method for devices.

However, there are three types of thermal heads, which are the heart of this heat-sensitive recording method: thin film type, thick film type, and semiconductor type, each of which has advantages and disadvantages.The present invention relates to this semiconductor type thermal head. Therefore, the advantages and disadvantages of the conventional semiconductor type will be explained using the structure as an example.
FIG. 1 is a schematic perspective view of a conventional semiconductor thermal head. As shown in the figure, heat-generating dots b, also made from silicon semiconductor, are provided on the top surface of a horizontally long rectangular head a made of silicon semiconductor, and heat-sensitive dots b, which are also made from silicon semiconductor, move in the direction of the arrow in the figure. The above dot b on paper p...
・Receives a signal pulse from a power supply circuit (not shown) and generates instantaneous and selective heat generation necessary to form the required print, and this heat generation causes the thermal paper corresponding part to develop a primary color. It has a mechanism to form an image of the printed characters. The advantages of such semiconductor-type thermal heads include...fast thermal response, the ability to create even elaborate patterns in principle, and the ability to
The active elements can be formed on the same head, and (d) there is little deterioration of the heat-generating resistor (dots), but the drawbacks are C)) the manufacturing process is complicated and the large head is It is pointed out that it is difficult to make, (a) high cost, e) has poor thermal efficiency, and (o) it is difficult to accumulate heat. To explain the reason for this defect in a little more detail, the silicon head a in Fig. 1 is created by cutting out bulk silicon (silicon slab), and since this bulk silicon inherently has limited dimensions, It is not possible to obtain large rectangular shapes [Disadvantages (c)]; small silicon dots b are formed with minute gaps in the head a obtained by a troublesome cutting process; The cost is high [disadvantage (ro)], silicon itself has a small heat capacity, so dot b
The heat generated by ... is taken away from the head a at the back, resulting in poor thermal efficiency and difficulty in accumulating heat [Defect O Co., Ltd.]
〕,It turns out that.

In view of the above, the present inventors arranged an SOS (silicon on sapphire) composite in which a silicon layer is fixed on an α-alumina ceramic single crystal (sapphire) substrate to be compatible with this thermal head. A patent application filed in 1972-141 was first filed in which the above-mentioned problems were eliminated.
022 (Japanese Unexamined Patent Publication No. 53-65741) (filed on November 22, 1975), later research experiments revealed that in addition to sapphire substrates, α-SiO2, spinel (M
gO・Al2O3. ), silicon carbide (SiC), and titania (TiO2) single crystal substrates can be equally applied to the sapphire substrate of the prior invention, which led to the filing of the present invention. , these α-S
The object of the present invention is to provide a thermal head that uses a substrate selected from iO2, spinel, silicon carbide, or titania, is thermally and structurally reasonable, and can be manufactured by a simple method. Preferred embodiments of the present invention will be explained in detail below with reference to the drawings. FIG. 2 is a plan view showing an example of the pattern of the thermal head of the present invention, and FIG.
Figure 4 is an enlarged plan view of the thermal dot part in Figure 4. Figure 4 is a schematic perspective view of the head in Figure 2, partially enlarged.
The figure shows an enlarged sectional view taken along the line V-V in FIG.

Further, FIG. 6 is a sectional view corresponding to FIG. 5 showing another embodiment of the thermal head of the present invention. From the above embodiment figures, the thermal head of the present invention comprises a single crystal substrate 1 made of α-SiO2, spinel, silicon carbide, or titania, a silicon layer fixed on this supporting substrate 1, and heat generating dots (3 )... A silicon layer 2 made of high resistance so as to prevent heat from escaping and at the same time accumulate heat, and low-resistance silicon heat-generating dots 3 integrally protruded on this silicon layer 2.・It consists of

In the patterning shown in the example diagrams, such heating dots 3 are arranged one at a time in the middle of the conductive path 6 of the electrode 4 (Figures 2 and 3). This generates heat instantaneously and selectively on the thermal paper (not shown) which runs in a fused manner to cause the corresponding portion to develop a primary color, thereby obtaining a print. The substrate 1, high-resistance silicon layer 2, and silicon heating dots 3 in the present invention are preferably created in the following manner. A high-resistance silicon layer 2 is grown by an epitaxial method on a single crystal substrate 1 of α-SiO2, spinel, silicon carbide, and titania obtained by a conventional method. As will be described later, by appropriately selecting the thickness of the silicon layer 2, it can be used as a medium to prevent heat dissipation from the heat generating dots 3 on the silicon layer 2 and at the same time to accumulate heat appropriately. This is an extremely important bead controller, and its thickness is appropriately selected from a range of about 1 to 100 μm, taking into consideration the amount of heat generated by the heat generating dots 3 and the thickness of the substrate 1.

This silicon layer 2 also has a doping amount of 1014 to 101
It has a high purity of 5 pieces/Cc and a resistivity of approximately 10Ω/solder. The heat-generating dots 3 of low-resistance silicon integrally provided on the silicon layer 2 are formed by forming a silicon layer (not shown) on the silicon layer 2 by the same epitaxial method.
It is obtained by growing dots 3... and removing the others by etching, leaving a section of predetermined dots 3..., and the doping amount is about 1018 dots/Cc, which is relatively low resistance silicon. The rate is tenon 0.01Ω・? The thickness is 0.1 to 3μ. As already clear from the above, the dots 3 obtained from the upper silicon layer are the Joule heating elements themselves, while the lower silicon layer 2 is combined with the substrate 1 to prevent and moderate the dissipation of the heat. functions as a heat storage medium, and is not electrically involved in any way.

The thermal head of the present invention mainly has the above configuration, but the diodes electrically connected to the dots 3... can be easily separated from the silicon layer and produced without mounting a separate semiconductor chip as in the past. It is something that

That is, this diode 5... connects the silicon layer 2 to the substrate 1.
This diode can be easily obtained by etching the necessary diode formation area and separating it from the silicon layer 2 of the main body after forming it uniformly over the entire surface of the diode. It is provided with a PN junction 51 (see FIG. 5). The conductive path 6 connects the heating dot 3 and the diode 5 directly as shown in the figure, and the means for forming this path 6 is made of Al,
Au or other conductive metal is provided in the path shape by vapor deposition. When using Au, a chromium layer is vapor-deposited as a base layer (not shown) in consideration of adhesion to the silicon surface.

Thermal head dot 3...Since thermal paper always runs in contact with the surface, it is desirable to apply a wear-resistant coating that does not inhibit heat conduction. For example, SlC coating 8 (Figure 6) is used. good. In this case, since SiC has electrical conductivity, an insulating film 7 made of SiO2 is coated on the bottom of the SiC in advance. As configured above, the thermal head of the present invention has a silicon layer 2 of an appropriate thickness that takes into account heat conduction and heat storage at the same time under the heat generating dots 3, and a layer of α-SiO2 with a large heat capacity, spinel, etc. , silicon carbide or titania, the heat of the dots 3 is transferred to the silicon layer 2.
Even if the heat is transmitted to the layer 2, the heat in the layer 2 is rapidly taken away by the substrate 1. In other words, the heat in the layer 2 is not unnecessarily escaped to the side opposite to the thermal paper, and the heat in the layer 2 is removed from the substrate 1 and the dots 3...
A certain amount of heat can be accumulated by the silicon layer 2 interposed between the dots 3 and 2, and due to these, in the present invention, the thermal efficiency of the dots 3... with respect to the thermal paper is improved and the heat is easily accumulated. It shows instantaneous high thermal reactivity.

In particular, in the present invention, the substrate 1 selected from α-SiO2, Nupinel, silicon carbide, and titania has a crystal lattice constant similar to that of the sapphire substrate, and therefore has extremely high chemical affinity with silicon. good (e.g.
Spinel has a better affinity than single-crystal sapphire), and since both have similar coefficients of thermal expansion and contraction, when placed in the heat cycle of heat accumulation and heat release during thermal recording, No thermal stress remains inside the high-resistance silicon layer 2, so cracks due to thermal strain do not occur, and a thermal head that is thermally reasonable and robust can be manufactured. Furthermore, since the only difference between high-resistance silicon and low-resistance silicon is whether or not there are impurities inside, when growing the high-resistance silicon layer 2 on the substrate 1 by the epitaxial method, the low-resistance silicon By growing the high-resistance silicon layer to a thickness equivalent to layer 3 and adding impurities to it, it is possible to form a low-resistance silicon layer 3 continuously following the high-resistance silicon layer 2, thus increasing the resistance. It is possible to form the silicon layer 2 and the low resistance silicon layer 3 in a single epitaxial growth step.

This, combined with the above-described affinity between the substrate 1 and the silicon layers 2 and 3, has the advantage that a thermal head can be manufactured easily and robustly. As described above, the present invention can produce excellent effects that can eliminate the drawbacks of known semiconductor type thermal heads.

[Brief explanation of drawings]

Figure 1 is a schematic perspective view of a conventional semiconductor thermal head.
2 is a plan view showing an example of the pattern of the thermal head of the present invention, FIG. 3 is an enlarged plan view of the thermal dot portion in FIG. 2, and FIG. 4 is a schematic diagram of the head in FIG. 2. FIG. 5 shows an enlarged sectional view taken along the line V in FIG. 4. Further, FIG. 6 is a sectional view corresponding to FIG. 5 showing another embodiment of the thermal head of the present invention. Explanation of symbols, 1...
・・Single crystal substrate of α-SiO2, spinel, silicon oxide, or titania, 2 ・・High resistance silicon layer, 3 ・・Heating dots (low resistance silicon), 4
...Electrode, 5...Diode, 6...
...Conductive path, 7...α-SiO2, 8.
...Wear-resistant coating SiC. p...Thermal paper.

Claims (1)

[Scope of Claims] 1 A single crystal substrate of α-SiO_2, spinel, silicon carbide, or titania, and a silicon layer fixed on this substrate, which prevents heat dissipation of heat generating dots and at the same time dissipates heat. A silicon layer with high resistance that accumulates,
This silicon semiconductor thermal head consists of heat-generating dots made of low-resistance silicon that are integrally protruded onto this silicon layer. 2. A patent claim in which a high-resistance silicon layer is epitaxially grown on the substrate, and low-resistance silicon heating dots are left by etching from the low-resistance silicon layer epitaxially grown on the high-resistance silicon layer. The thermal head according to item 1. 3 A high-resistance silicon layer is epitaxially grown on the substrate, and heating dots of low-resistance silicon are left behind by etching from the low-resistance silicon layer epitaxially grown on the high-resistance silicon layer, and a silicon diode is formed. 2. The thermal head according to claim 1, wherein said high-resistance silicon layer is formed of said high-resistance silicon layer.