JPS60166469A - Thermal head - Google Patents

Abstract

PURPOSE:To prevent useful life from being reduced, by a construction wherein a laminate of at least one layer of silicon nitride and at least one layer comprising silicon oxide as a main constituent is provided between a heating element layer and an uppermost protective layer, in proximity to an end part on the heating part side of at least one lead layer. CONSTITUTION:A glaze layer 3 is provided on a substrate 2. Thereafter, the heating element layer 4 consisting of a thin film of polycrystalline silicon and the lead layers 51, 53 are provided. Then, the laminate 7 of the layer 71 of silicon nitride and the layer 75 comprising silicon oxide as a main constituent is provided on a predetermined shape, followed by providing the protective layer 6 to obtain the thermal head 1. Accordingly, deterioration of resistance of the heating element layer and delamination, breakage or the like of the laminate structure are reduced, and the useful life of the head is prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention Technical Field The present invention relates to a heat generating head. More specifically, the present invention relates to an improvement of a heat generating head having a polycrystalline silicon thin film heat generating layer as a heat generating resistor.

Prior art and its problems In recent years, recording devices have improved in performance, become maintenance-free,
Thermal recording is attracting attention due to demands for smaller size, higher reliability, and silence. This heat-sensitive recording uses a heat-generating head that has one or more minute heat-generating resistors installed on a substrate, and generates heat by passing an electric current through the minute heat-generating resistors. ” Second, letters, shapes,
It is used as an output method for drawing symbols, facsimiles, computer terminals, printing devices, recorders, etc.

Conventionally, one type of heat-generating head for heat-sensitive recording has been one in which a heat-generating resistor is formed from a heat-generating layer made of a polycrystalline silicon thin film. ). in this case,
Such a heat generating end usually has a structure as shown in FIG. In other words, a substrate 2 made of alumina, etc.
Secondly, a glaze layer 3 is provided to accumulate heat generated by the heating element layer. On this glaze layer 3, a polycrystalline silicon thin film heating element layer 4 is provided in a predetermined arrangement, and on this heating element layer 4, a pair of lead layers 51 and 53 are provided. 51° 53, it is possible to conduct electricity to the heating element layer 4, and the heating element layer 4 is connected to the interlayer gap and the vicinity thereof.
is configured to function as a heat generating section.

Furthermore, a protective layer 6 is usually provided on the polycrystalline silicon thin heating layer 4 and the REIT layers 51 and 53.

The heat generating head 10 having such a polycrystalline silicon thin film heat generating layer 4 has good heat generating characteristics and also has good manufacturability. However, as the heat generating layer is used, the resistance of the heat generating layer fluctuates, resulting in fluctuations in image reproducibility, damage to the heat generating head, and a short lifespan.

The present invention has been made to eliminate such inconveniences. The present inventor conducted research to find out the cause of such inconvenience, and obtained the following findings.

To heat generation with conventional polycrystalline silicon thin film heating element layer
10 has a laminated structure as described above, the ends of the Lee I layers 51 and 53 on the side of the heat generating part form a step. For this reason, the heat generating head IO is brought into sliding contact with the thermal paper. When used over a long period of time, excessive external stress is repeatedly applied to the step at the end of the lead layer 51, 53 on the side of the heat generating part from the thermal paper through the uppermost protective layer 6, which causes damage to the laminated structure in the vicinity. The adhesion will deteriorate and the life of the head itself will be shortened.

Furthermore, since the heating resistor is made of a polycrystalline silicon thin film, the following phenomenon occurs due to its special characteristics. That is, the thermal paper that comes into sliding contact with the head contains an alkali metal or an alkaline earth metal. Therefore, when the heat generating head is used and the heat generating part is repeatedly heated over a long period of time by passing between the lead layers 51 and 53,
The lower surface of the protective layer 63 located on one side of the heat generating part side end of the REET layer (for example 51) used as a negative side with respect to the applied voltage is coated with alkali metal or The alkaline earth metal cations migrate, forming a cation-rich layer with a thickness of about 10 gm. When such a cation-excessive layer is formed, internal stress is generated between the protective layer 6 and the thin polycrystalline silicon heating element layer 4, and the silicon and alkali metal etc. that constitute the heating element layer are This reaction occurs, and the adhesion between the first heating element layer 4 and the protective layer 6 decreases, especially directly under and around the end of the negative lead layer on the heating section side.
In addition, cracks occur in the heating element layer 4 and/or the protective layer 6, resulting in resistance deterioration of the heating element layer 4 and between the heating element layer 4 and the protective layer 6.
This may lead to breakage of the heat generating head, reducing the lifespan of the heat generating head.

As described above, when a polycrystalline silicon thin film is used as a heat generating resistor, an excessive cation layer is formed over a long period of use, resulting in various adverse effects. and,
This, combined with the effect of external stress due to the presence of the step at the end of the lead layer described above, causes damage to the laminated structure due to long-term use of the head, especially near the end of the lead layer on the heat generating part side, which is used as the negative side. This causes destruction, etc., increases resistance deterioration, and becomes a factor that further reduces the service life of the metal.

11. Object of the Invention The object of the present invention is to prevent the above-mentioned reduction in the life of the heat generating head.

These objects are achieved by the invention described below.

That is, the present invention provides a heating head having a polycrystalline silicon thin film heating element layer on a substrate on which a glaze layer is formed, in which the heating element layer is located near the end of at least one glue layer on the heating part side. 1 each between and the most-1-protective layer.
The object is to interpose a laminate of a layer made of silicon nitride and a layer mainly composed of silicon oxide.

In the present invention, a silicon nitride layer is used as one of the constituent layers of the intermediate layer laminate, and the effects of the present invention are brought about by this silicon nitride.

For this reason, when silicon nitride is replaced with silicon oxide, silicon carbide, etc., which are equivalently used as a protective layer of a heat generating end, for example, the desired effects of the present invention cannot be achieved.

Also, JP-A-55-154186, JP-A-55-77
Publication No. 584 describes an example in which a silicon nitride layer is interposed between the heat generating layer and the protective layer, although a heat generating layer other than polycrystalline silicon thin +1fi is used.
However, when only a silicon nitride layer is interposed without laminating a layer containing silicon oxide as a main component, the effect of improving head life is insufficient.

These matters will become clear in the experimental examples described later.

■Specific structure of the invention The heat generating head of the present invention will be explained in detail below.

In the heat generating head of the present invention, the substrate may be made of ceramic such as alumina, and usually has a shape such as a flat plate or a column.

The glaze layer provided on such a substrate may be formed from a normal glass material. Note that the glaze layer is provided over almost the entire area of the substrate as in the usual case, and its thickness may be 15 to 200 μm. It may be formed by a screen printing method, a dipping method, or the like.

- On the other hand, a heating element layer is arranged on the glaze layer. The heating element layer may be a polycrystalline silicon thin film formed by various methods, but its characteristics J-G indicate that it is a silicon polycrystalline thin film formed according to a known chemical vapor deposition method. preferable. In addition, impurities such as P, As, B, and Sb are contained in this polycrystalline silicon 7X1 film by 10%.
It may be contained in a range of about 0% by weight or less. And its resistance is 2 X I O-'~5X10-3Ωc
It may be about m. Furthermore, although only one polycrystalline silicon thin film heating element layer may be provided on the substrate in a predetermined shape, it is usually separated into multiple layers and provided in a predetermined arrangement, for example, in the form of parallel strips. The thickness is generally 0.91 to 5 gm.

A pair of REET layers are connected to this polycrystalline silicon thin film heating element layer having a predetermined shape and a predetermined arrangement. The lead layer may be formed as a thin film from various high-melting point metals according to various methods, but it is preferably formed from tungsten, molybdenum, or alloys thereof, tungsten silicide, molybdenum silicide, or the like. In this case, the lead layer may be located below the polycrystalline silicon thin film heating element layer, but it is usually preferable that it be laminated above the polycrystalline silicon thin film heating element layer. Further, the thickness of the lead layer may be approximately 0.5 to 2 μm.

Furthermore, a protective layer is provided as the first layer over almost the entire upper surface of such a laminate. This protective layer prevents the heat-generating resistance layer and the lead layer from abrasion caused by contact with thermal paper, and is usually composed of phosphorus boride, silicon nitride, silicon chloride, silicon carbide, etc. or a silicon oxide layer as an underlying layer,
A two-layer structure having a phosphorus boride layer as the eleventh layer is preferable. In addition, the thickness of the protective layer is approximately 0.5 to -
It may be expressed as μm.

Under such a premise, in the present invention, as shown in FIG.
In the vicinity of the end of the silicon heating element layer 4 on the heating part side,
Most J-layer protective layer 6 and polycrystalline silicon? 1 Membrane heating element layer 4
A laminate 7 consisting of at least one layer each of a layer 71 made of silicon nitride and a layer 75 mainly made of silicon oxide is interposed between the two.

In this case, the layer 71 made of silicon nitride is typically Si3
It has a composition of N4, but this Si2N3, S
It may have a composition of iN, or it may have a composition that deviates from these stoichiometric compositions, or it may have a mixed composition of these. The thickness of this silicon nitride layer is 100 to 8000, especially 500 to 30.
00 people is enough.

On the other hand, if the layer 75 mainly composed of silicon oxide is formed of a material having a coefficient of thermal expansion similar to that of the glaze layer 3 and the silicon heating element layer 6, the effects of the present invention will be even greater.
As such a component, a silicon oxide layer or a phosphorus-containing silicon oxide layer is particularly preferable.

As described above, it is preferable that the total thickness of the laminate 7 of one or more of the layers 75 mainly composed of silicon oxide and the layer 71 made of silicon nitride is about 3 m or less.

Such a laminate 7 is present between the protective layer 6 and the heat generating layer 4 in a predetermined region located above the heat generating part side end of the polycrystalline silicon thin film heat generating layer 4 in at least one lead layer. Therefore, when the heating element layer is provided in qi rows of strips on the glaze layer, for example, as shown in FIG. The laminate 7 may be provided over the entire direction, or the laminate 7 may be provided partially only in the vicinity of the region corresponding to the end of one lead layer 51. Note that in the width direction of the strip-shaped heating element layer 4, the laminates 7 may be provided separated from each other by a width corresponding to the width thereof, but usually they are continuous and sink.

In addition, in section 4-, one REIT layer is referred to as
As is clear from the above, the lead layer is usually used as a negative side with respect to the applied voltage. but,
The present invention is not limited to such cases, but can also achieve certain effects when high-frequency current is applied between lead layers.
It is something that appears.

Note that, as shown in FIG. 2, such a laminate 7 is interposed so as to be in direct contact with the lower surface of the protective layer 6 and the upper surface of the polycrystalline silicon thin film heating element layer 4, and is a layer made of silicon nitride. 71 and a layer 75 mainly composed of silicon oxide
It is sufficient that each layer has one or more layers, and there are no restrictions on the number or the order of lamination. However, as shown in FIGS. 3(a) to (C), the -1 layer of the layer 71 made of silicon nitride and/or
Alternatively, a layer 75 mainly composed of silicon oxide is laminated as a lower layer, and the silicon nitride layer 71 is applied to the lower surface of the protective layer 6 and/or the heating element layer 4 via the layer 8 mainly composed of silicon oxide.
Usually, it is in contact with the h-plane, etc.

The heat generating head 1 of the present invention having such a structure is usually manufactured in the following manner. For example, in a first embodiment, a glaze layer 3 is formed on a substrate 2 according to a known method. Thereafter, polycrystalline silicon thin film heating element layer 4 and REIT layers 51 and 53 are formed according to a known method.

Next, a laminate 7 of a layer 71 made of silicon nitride and a layer 75 mainly made of silicon oxide is formed in a predetermined shape.

In this case, the formation of the layer 71 made of silicon nitride is usually
RF sputtering targeting silicon nitride, silicon chloride, or silane and ammonia as a source, N2 + H21f? This may be carried out based on a known chemical vapor deposition method using a z mixture gas as a carrier.
Further, the layer 8 containing silicon oxide as a main component may be formed by any known method. After this, the protective layer 6 is formed, and the heat generating head 1 of the present invention is manufactured.

IV. Specific Effects of the Invention The heat generating end of the present invention has a nitride layer between the protective layer and the polycrystalline silicon thin film heat generating layer in a predetermined region above or below the end of at least one lead layer on the heat generating part side. Since the laminated body 7 of the layer 71 made of silicon and the layer 75 mainly composed of silicon fertilized is provided, the intrusion of alkali components due to contact with thermal paper during long-term use of the head as described above is prevented by υ1.
The negative effects caused by the formation of an excessive cation layer are significantly reduced, and the external stress applied near the end of the lead layer when bonding with thermal paper due to the presence of the step mentioned above is alleviated, and as a result, the heating element The resistance deterioration of the layers, peeling and destruction of the laminated structure are significantly reduced, and the lifespan of the heat sink is extremely long.

The inventor conducted various experiments to confirm the effects of the present invention. An example is shown below.

Experimental example board 2: 300mm x 300mm, thickness 2II1
Using 98% alumina of m, Na, K, and C are placed on the -
A glassy glaze layer 3 containing a total of 0.1% by weight and having a thickness of 80 gm was formed.

Next, a 1 μm thick polycrystalline silicon thin film containing 1% by weight of poron was corrugated using silane and diporane as sources and hydrogen as a carrier gas, using the chemical vapor phase growth method while holding the substrate at 850°C. , by photoetching, the interval 3
At 0 pLm, a plurality of thin polycrystalline silicon heating element layers 4 were formed in the form of a thousand rows of strips each having a width of 1100 p. After this,
A 1.5 m thick W thin film was applied to this, and a window of 100 x 230 m was formed in the center of each of the four strip-shaped heating element layers by photolithography. Then, W lead layers 51 and 53 were formed. After that, according to the chemical vapor deposition method, diborane and bosphin were used as sources, hydrogen was used as a carrier, and the reaction temperature was 1 m 850
A thin boron phosphide pattern 1 (B13P2) with a thickness of 2 gm was formed over the entire upper surface at °C to form the protective layer 6, and a heat generating head (head A) belonging to the prior art shown in FIG. 1 was created.

Next, for comparison, a comparative head B was prepared in exactly the same manner as above, except that a 1 tm thick Si3N4 thin film was formed over the entire surface of the heating element layer 4-F by chemical vapor deposition. It was created.

On the other hand, silicon nitride layer 71. as shown in Table 1 below. Heads C and D of the present invention were produced in the same manner as the above head 1 except that silicon oxide 75 was interposed between the heating element layer 4 and the protective layer 6.

The silicon nitride layer was formed by chemical vapor phase growth at a reaction temperature of 850° C. using silane and ammonia as a source and hydrogen as a carrier, and the silicon oxide layer was formed by spatter.

Pulse energization of 3 m5ec was repeated at intervals of 20 m5ec while the thermal paper was in sliding contact with each head.

Table 1 shows the 0 resistance value change rate after 106 times of energization.

From the results shown in Table 1, the effects of the present invention are clear.

Table 1 Intervening Layer Main Resistance Value Change Above Glaze Layer Below Protective Layer (%) B 5j3N4 5 (0.2 m) When there are multiple interposed layers, the layer described in 7] ;
Located as a layer.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a heat generating head having a conventional polycrystalline silicon thin film heating element layer, FIG. 2 is a sectional view showing an embodiment of the heat generating head of the present invention, and FIGS. c) is a sectional view showing an example of stacking a layer made of silicon nitride and a layer made of silicon oxide in the present invention. Explanation of symbols 1, to...Heating head, 2...Substrate, 3...Glaze layer, 4...Polycrystalline silicon thin film heating element layer, 51.53...
・Lead layer, 6... Protective layer, 7... Laminate, 71... Layer made of silicon nitride, 75... Slipper whose main component includes silicon oxide Applicant TDC Co., Ltd. FIG, 1 0 FIG, 2

Claims (1)

[Claims] (1) Substrate] having a glaze layer on the second side, the glaze layer
Second, it has a polycrystalline silicon thin film heating element layer and a lead layer of 4 parts for supplying electricity to the silicon thin film heating element layer,
A heat generating part is formed in the heat generating layer including the pair of 1,1-V layers] 141 gap + 141, and furthermore, the heat generating body layer has a protective layer as the last layer, and has at least one force. The heat generating part of the lead layer (near the end of +111,
A heat generating device comprising at least one layer made of silicon nitride and a layer mainly composed of silicon nitride between the heat generating layer and the manipulating layer.