JPS6317630B2 - - Google Patents

Description

Detailed Description of the Invention The present invention has a structure in which a heat generating resistor layer is formed on a substrate via a heat storage layer, and a metal electrode is ohmicly attached to the heat generating resistor layer. The present invention relates to an improvement in a thermal head having a heat head.

A thermal head has a configuration in which a heat generating resistor layer is formed on a substrate via a heat storage layer, and a metal electrode is attached to the heat generating resistor layer on the heat generating resistor layer. Applicable to cases where a layer is heated by passing electricity through a metal electrode, the heat is applied to thermal paper, the thermal paper develops color, and a record is obtained by the color development. .

Such a conventional thermal head, when applied to a printing thermal head, usually has the following configuration.

That is, as shown in FIG. 1, on the substrate 1,
A heat generating resistor layer 3 is formed through the heat storage layer 2, and a pair of metal electrodes 4 and 5 are attached to an ohmic on this heat generating resistor layer 3 with a required spacing therebetween. There is.

Further, a protective layer 6 is provided on the area between the metal electrodes 4 and 5 of the heat generating resistor layer 3. In this case, the protective layer 6 also extends over the metal electrodes 4 and 5.

The above is a common configuration of a conventional thermal head that is applied to a printing thermal head.

In the thermal head having such a configuration, when electricity is applied to the heat generating resistor layer 3 through the metal electrodes 4 and 5, the heat generating resistor layer 3 is connected to the area between the metal electrodes 4 and 5. can generate heat. The heat can then be applied via the protective layer 6 to the thermal paper 7 that is in relative sliding contact with the protective layer 6.

By the way, in the thermal head described above in FIG. 1, conventionally, the heating resistor layer 3 itself generates heat continuously or intermittently at a required high temperature of, for example, 300 to 500°C. Considering that the resistance value will not change from the expected value and that the heat generating resistor layer 3 itself can be easily formed as having the desired heat generating characteristics, The resistor layer 3 is usually formed of, for example, tantalum nitride formed by sputtering, nichrome formed by vacuum evaporation, or sintered ruthenium oxide.

In addition, it must be able to sufficiently withstand the heat from the heat generating resistor layer 3, and when electricity is applied to the heat generating resistor layer 3 via the metal electrodes 4 and 5, it should be possible to avoid unnecessary heat generation due to the energization. The metal electrodes 4 and 5 are made of a high-melting point metal such as tungsten or molybdenum, in order to prevent the heat-generating resistor layer 3 from forming and to ensure a good ohmic connection with the heat-generating resistor layer 3. is normal.

In the case of such a printing thermal head, the heating resistor layer 3 is made of, for example, tantalum nitride formed by sputtering, nichrome formed by vacuum evaporation, or ruthenium oxide sintered. However, if the heat generating resistor layer 3 is formed of tantalum nitride formed by a sputtering method, the heat generating resistor layer 3 may be formed of a material having a desired resistance value. It is difficult to form as such. The reason is that a layer of tantalum nitride is generally formed by sputtering.
This is because it is difficult to uniformly form the film to the required thickness.

For this reason, it is difficult to form the heat generating resistor layer 3 to have the desired heat generating characteristics, and when the heat generating resistor layer 3 is heated by energizing, the heat generating resistor layer 3 is difficult to form. The surface of the resistor layer 3 is oxidized, and therefore the resistance value of the heat generating resistor layer 3 changes from the intended value. As a result, there is a possibility that the heat generating resistor layer 3 may change from its expected heat generating characteristics.

In addition, when the heat generating resistor layer 3 is formed of nichrome formed by a vacuum evaporation method, the heat generating resistor layer 3 is made of a material having a desired resistance value, and therefore a material having the desired heat generating characteristics. It is difficult to form something that has. The reason is that nichrome is generally
This is because, since its specific resistance is relatively small, the thickness of the heat generating resistor layer 3 must be extremely thin.

Furthermore, when the heat generating resistor layer 3 is formed of a ruthenium oxide sintered body, the heat generating resistor layer 3
However, it is difficult to form a material having a desired resistance value and therefore a desired heat generation characteristic without occupying a large area. This is because, in general, it is difficult to form a ruthenium oxide sintered body into a fine shape with high precision.

In this way, in conventional thermal heads, the heat generating resistor layer prevents the resistance value from changing from its initial value due to heat generated by continuous or intermittent high temperature heat generation. Even if the heat-generating resistor layer itself is formed to have the desired heat-generating characteristics and is easily formed, as described above, the heat-generating resistor layer can be formed to have the desired resistance. value and therefore have the desired heat generating properties, without occupying a large area, and which is difficult to form;
There is a risk that the resistance value of the heat generating resistor layer, and thus the heat generating characteristics, may change from the intended value due to oxidation of the surface of the heat generating resistor layer due to heat generation of the heat generating resistor layer itself. It had the disadvantage of being overly heated.

In view of the above, the inventors of the present invention have decided to propose a new thermal head which is based on the thermal head described above but does not have the above-mentioned drawbacks.

The thermal head will be described below with reference to FIG. 2 as an example of the thermal head for printing when applied to the thermal head for printing.

In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

An example of the printing thermal head shown in FIG. 2 has the configuration described above in FIG.
It has the same structure as the case of FIG. 1, except that it is replaced by a heat generating resistor layer 13 formed of polycrystalline silicon.

In this case, the heating resistor layer 13 has a required specific resistance by introducing, for example, a required amount of phosphorus as an impurity that provides conductivity, and also has a required resistivity between the metal electrodes 4 and 5. It has the required thickness to obtain the desired resistance value.

The above is an example of the configuration of a printing thermal head proposed by the present inventors and to which a novel thermal head is applied.

Such a printing thermal head is constructed by replacing the heating resistor layer 3 of the printing thermal head described above in FIG. 1 with a heating resistor layer 13 formed of polycrystalline silicon. This is the same as in FIG. 1, except that

Therefore, as in the case of FIG.
When electricity is applied to the heat generating resistor layer 13 through the heat generating resistor layer 13 and the heat generating resistor layer 13, heat is generated in the area between the metal electrodes 4 and 5 of the heat generating resistor layer 13, and the heat is transferred to the heat generating resistor layer 13 through the protective layer 6. It can be applied to the thermal paper 7 that comes into sliding contact with the paper. Therefore, the function as a printing thermal head is obtained.

However, since the heat generating resistor layer 13 is formed of polycrystalline silicon, even if the heat generating resistor layer 13 is continuously or intermittently heated at a high temperature, the resistance value remains unchanged. There is almost no change from the initial value, and the heating resistor layer 13 itself can be easily formed to have the desired heating characteristics.

That is, since the heat generating resistor layer 13 is formed of polycrystalline silicon, the heat generating resistor layer 13 is formed to the required thickness and thickness by sputtering, CVD, vacuum evaporation, etc. It can be easily formed into a shape having the desired specific resistance.

For example, when forming the heat generating resistor layer 13 by the CVD method, using a normal vapor phase growth apparatus,
Then, the substrate 1 in which the heating resistor layer 13, the metal electrodes 4 and 5, and the protective layer 6 are not present, and only the heat storage layer 2 is formed thereon is arranged in the device, and , the temperature of the substrate 1 is 700℃~
At 1000℃, silane SiH ₄ was added to the device using a carrier gas of hydrogen or helium
The heating resistor layer 13 can be formed by supplying silane SiH 4 and thermally decomposing the silane SiH ₄ in the apparatus. In this case, the formation (growth) of polycrystalline silicon relative to the feed rate (mol/min) of silane _SiH4
The relationship between speed (μm/min) is as shown in Figure 3.
Because it has linearity (however, in Figure 3, the substrate 1
), the heating resistor layer 13 can be easily formed to the required precise thickness and in a short time.

By the way, heat storage layer 2 is made of 82% feldspar and 12.5% SiO ₂
%, _CaCO3 2.9%, Kaolin 2.6%
When the substrate 1 is made of high melting point craze glass with a softening point of 1000°C or higher, the temperature of the substrate 1 is set to 900°C or higher.
℃, the heating resistor layer 13 can be formed to a desired thickness in the range of several 100 Å to several μm in a short time of about 10 to 15 minutes with an error of 2% or less.

Further, as described above, when forming the heat generating resistor layer 13 by the CVD method using a normal vapor phase growth apparatus, silane is added in the vapor phase growth apparatus.
Along with _SiH4 , phosphorus as an impurity gives conductivity,
If a component such as arsenic or boron is included, the heating resistor layer ₁₃ is formed with an impurity that imparts conductivity introduced therein. If carrier gas is used to supply the impurities into the apparatus, the amount of components that become impurities within the apparatus can be easily controlled by controlling the supply amount of the impurities. Therefore, the amount of impurities introduced into the heating resistor layer 13 can be easily controlled. Therefore, the heat-generating resistor layer 13 can be easily obtained as having a required specific resistance, and thus a desired resistance value.

By the way, if the impurity component is supplied into the device using a carrier gas like SiH ₄ , then the impurity component will be phosphorus.
When phosphine PH ₃ is supplied into the device, the relationship between the supply amount (mol/min) of phosphine PH ₃ and the specific resistance (Ω cm) of polycrystalline silicon is obtained as shown in Figure 4. Heat generating resistor layer 13
can be easily obtained with the required resistivity in the range of 10 ^-3 Ω·cm to 1 Ω·cm.

Furthermore, since the heat generating resistor layer 13 is formed of polycrystalline silicon, the heat generating resistor layer 13 is made of polycrystalline silicon.
There is no fear that the resistance value of No. 3, and hence the heat generation characteristics, will change from the expected heat generation characteristics based on the heat generation of the heat generating resistor layer 13 itself.

By the way, the substrate 1 is made of alumina with a thickness of 700 μm, and the heat storage layer 2 is made of a high melting point material consisting of, for example, 82% feldspar, 12.5% SiO ₂ , 2.9% CaCO ₃ , and 2.6% kaolin, as described above. The heating resistor layer 13 is made of glazed glass, and as described above, is made of polycrystalline silicon into which phosphorus is introduced by the CVD method, and has a specific resistance of 3×10 ^-3 Ω·cm. and 200Ω between metal electrodes 4 and 5
Furthermore, the metal electrodes 4 and 5 are formed of tungsten formed by vacuum evaporation to a thickness of 1.5 μm, and the protective layer 6 is formed by CVD. Depending on the phosphorus
The metal electrode of the heat generating resistor layer 13 when the heat generating resistor layer 13 is repeatedly and intermittently heated when the heat generating resistor layer 13 is formed of a boron compound and has a thickness of 1.5 to 2.0 μm. When the rate of change in resistance value between 4 and 5 is considered as the heat generation characteristic of the heat generating resistor layer ¹³ , as shown in FIG. on, approx.
Even if the current is applied for 2 msec to obtain a temperature of 450°C, the rate of change in the resistance value of the heat generating resistor layer 13 is 5% of that in the case where no heat is generated. It was below average.

Since the heat generating resistor layer 13 is formed of polycrystalline silicon, the heat generating resistor layer 13 is freed from phosphorus impurities by the CVD method using phosphine DH ₃ as described above. However, in this case, the amount of phosphorus impurity introduced must be large enough to obtain a sufficiently low resistivity of 5 x 10 ^-1 Ωcm or less. For example, the heat generating resistor layer 13 is 300 ppm/
Since it is obtained as having a positive temperature coefficient of approximately ℃, when the heating resistor layer 13 generates heat,
This prevents the heating characteristics of the heat generating resistor layer 13 from deteriorating due to the heat, and makes the thickness of the heat generating resistor layer 13 relatively thin to obtain the same resistance value. Therefore, the heating resistor layer 13
can be obtained in a fine manner and less prone to thermal distortion.

As described above, the configuration of a printing thermal head to which a new thermal head is applied, proposed by the present inventors, etc.
and its excellent characteristics have become clear.

As proposed by the present inventor and others,
In the printing thermal head to which the new thermal head is applied, the metal electrodes 4 and 5 are as described above.
The metal electrodes 4 and 5 must themselves be able to sufficiently withstand the heat from the heat generating resistor layer 13, and the metal electrodes 4 and 5
When electricity is applied to the heat generating resistor layer 13 via the heat generating resistor layer 13, it is ensured that no unnecessary heat is generated due to the energization and that a good ohmic connection to the heat generating resistor layer 13 is achieved. In consideration, it is made of a high melting point metal such as tungsten or molybdenum.

However, since the metal electrodes 4 and 5 are attached to the heating resistor layer 13, the metal electrodes 4 and 5 are
and 5 are heated by the heat generated by the heat generating resistor layer 13, whereby the tungsten or molybdenum forming the metal electrodes 4 and 5 are heated by the polycrystalline silicon forming the heat generating resistor layer 13. A tungsten/semiconductor compound or a molybdenum/semiconductor compound is generated in the area under the metal electrodes 4 and 5 of the heat generating resistor layer 13 by reacting with the semiconductor formed by the tungsten/semiconductor compound. For this reason, the configuration in which the metal electrodes 4 and 5 are attached to the heat generating resistor layer 13 in an ohmic manner collapses, and the metal electrodes 4 and 5 are attached to the heat generating resistor layer 13.
However, if it is attached to a non-ohmic, it will have a similar configuration.

As a result, the metal electrodes 4 and 5 deteriorate, and as a result, the heat generation characteristics of the heat generating resistor layer 13 viewed between the metal electrodes 4 and 5 may change from the expected one.

Moreover, the protective layer 6 is
The metal electrodes 4 and 5 are formed after the metal electrodes 4 and 5 are formed. For this reason, when the protective layer 6 is formed of tantalum pentoxide, for example, and the protective layer 6 is formed in such a manner that the metal electrodes 4 and 5 are heated, the metal electrodes 4 and 5 are heated. As described above, when the metal electrodes 4 and 5 are made of tungsten or molybdenum in a single layer, the tungsten or molybdenum forming the metal electrodes 4 and 5 becomes the heating resistor layer. It reacts with the polycrystalline silicon that constitutes 13.

As a result, the metal electrodes 4 and 5 deteriorate, and therefore, the heat generation characteristics of the heat generating resistor layer 13 viewed from the metal electrodes 4 and 5 may change from the expected heat generation characteristics.

Therefore, the present invention provides a novel thermal head that can effectively avoid the above-mentioned concerns when applied to a printing thermal head to which a novel thermal head is applied, as proposed by the inventors of the present invention and others. This will become clear from the detailed explanation below.

FIG. 6 shows an example of a thermal printing head according to the invention.

In FIG. 6, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

An example of a printing thermal head according to the present invention shown in FIG. 6 has a similar construction to the thermal head described above in FIG. 2 with the following exceptions.

That is, the metal electrodes 4 and 5 are formed of a layer 21a made of aluminum of the heating resistor layer 13 formed of polycrystalline silicon, and a layer 21b made of kungsten or molybdenum on the layer 21a.
and has.

Further, the metal electrode 4 is attached to the heat generating resistor layer 13.
and 5 under the metal electrodes 4 and 5 side, layer 21
A region 22 is formed in which the aluminum constituting the layer 21a is diffused, and the aluminum constituting the layer 21a is diffused into the layer 21b of the metal electrodes 4 and 5 on the heating resistor layer 13 side. A region 23 is formed.

The above is an example of the configuration of the printing thermal head according to the present invention.

The thermal head for printing according to the present invention has the same structure as the thermal head described above in FIG.
When electricity is applied to the metal electrodes 4 and 5 through the metal electrodes 4 and 5, the area between the metal electrodes 4 and 5 of the heating resistor layer 13 generates heat, and the heat is transferred through the protective layer 6 relative to the area between the metal electrodes 4 and 5. It can be applied to the thermal paper 7 that comes into sliding contact.
Therefore, the function as a printing thermal head is obtained.

Further, according to the thermal head according to the present invention shown in FIG. 6, the heat generating resistor layer 13 is made of polycrystalline silicon, so that it has the same characteristics as described above in FIG. 2 regarding the heat generating resistor layer 13. .

However, in this case, metal electrodes 4 and 5
has a layer 21a made of aluminum on the heat generating resistor layer 13 side, and a layer 21b made of tungsten or molybdenum on the layer 21a, and also has a layer 21b made of tungsten or molybdenum on the heat generating resistor layer 13, and metal electrodes 4 and 5 below the heat generating resistor layer 13. A region 22 in which aluminum constituting the layer 21a is diffused is formed on the side of the metal electrodes 4 and 5, and a layer 21b of the metal electrodes 4 and 5 is formed.
On the heating resistor layer 13 side, there is a region 2 in which aluminum constituting the layer 21a is diffused.
3 is formed.

Therefore, since the metal electrodes 4 and 5 are attached to the heat generating resistor layer 13, the heat generating resistor layer 13
Even if the protective layer 6 is formed in such a manner that the metal electrodes 4 and 5 are heated after they are formed, the protective layer 6 is heated by the heat generated by the metal electrodes 4 and 5. The polycrystalline silicon constituting the resistor layer 13 is the layer 21b of the metal electrodes 4 and 5.
does not react with the tungsten or molybdenum that constitutes the metal electrodes 4 and 5.
The tungsten or molybdenum forming the layer 21b does not react with the polycrystalline silicon forming the heating resistor layer 13.
As described above with reference to FIG. 2, no tungsten/semiconductor compound or molybdenum/semiconductor compound is produced.

This means that when looking at the relationship between the voltage V applied between the metal electrodes 4 and 5 and the current I flowing through these metal electrodes 4 and 5, the voltage V vs. the current I
It was confirmed that the characteristic was obtained in a straight line over a large range of current I, as shown in FIG. However, the characteristics of voltage V vs. current I shown in FIG. 7 are obtained when the heating resistor layer 13 made of polycrystalline silicon has a specific resistance of 10 ^-2 to ^{10 -3} Ωcm. These are the actual measurement results.

Therefore, in the case of the thermal head according to the present invention, the metal electrodes 4 and 5 will not have the same structure as if they were non-ohmicly attached to the heating resistor layer 13.

Furthermore, for this reason, there is a risk that the metal electrodes 4 and 5 may deteriorate or that the heat generation characteristics of the heat generating resistor layer 13 viewed between the metal electrodes 4 and 5 may change from the expected ones. do not have.

As described above, the structural and effective features of an example of the thermal head according to the present invention have been clarified.

Next, an example of a method for manufacturing a thermal head according to the present invention having such characteristics will be described.

The thermal head according to the present invention is manufactured through the steps described below.

That is, a substrate 1 made of, for example, alumina, which has a relatively high thermal conductivity, is prepared in advance,
A heat storage layer 2 made of, for example, so-called gray glass having a lower thermal conductivity than the substrate 1 is formed on the substrate 1 by various methods known per se.

Next, on the heat storage layer 2 formed on the substrate 1, a heat generating resistor layer 13 made of polycrystalline silicon is placed. In the same way as described in the specific example of forming by CVD method, for example, silane is
It is formed using SiH ₄ , phosphine PH ₃ and a carrier gas of hydrogen or helium.

Next, on the heat generating resistor layer 13 formed on the heat storage layer 2, a layer 21a made of aluminum having a thin thickness of 100 Å to 2000 Å and the layer 21
A pair of electrodes 4 and 5 having a layer 21b made of tungsten or molybdenum having a thickness of 1000 Å or more on the surface of the electrode a is formed using a sputtering method or a vacuum evaporation method which is known per se.

Next, the layer 2 of the electrodes 4 and 5 is placed on the heating resistor layer 13 on the electrode 4 and 5 side below the electrodes 4 and 5.
In addition to forming a region 22 in which the aluminum forming the electrodes 4 and 5 is diffused, the aluminum forming the layer 21a of the electrodes 4 and 5 is formed on the heat generating resistor layer 13 side in the layer 21b of the electrodes 4 and 5. A region 23 is formed in which .

Furthermore, on the area between the electrodes 4 and 5 of the heating resistor layer 13, a protective layer 6 extending also onto the electrodes 4 and 5 is formed by various methods known per se.

In addition, in the step of forming the electrodes 4 and 5 described above, the electrodes 4 and 5 are formed by heating the layer that will become the layer 21a through subsequent etching to a high temperature on the substrate 1, and therefore on the heating resistor layer 13. The aluminum formed on the heat generating resistor layer 13 and forming the layer 21a at this time is diffused into the heat generating resistor layer 13, and then,
A layer that will become the layer 21b is formed by subsequent etching on the layer that will become the layer 21a, and at this time, aluminum constituting the layer that will become the layer 21a is diffused again into the heating resistor layer 13. The regions 22 and 23 described above can be formed by etching the laminate of the layer 21a and the layer 21b. Therefore, in the step of forming the electrodes 4 and 5, when forming the electrodes 4 and 5 as just described,
The process of forming the regions 22 and 23 described above also serves as the process of forming the electrodes 4 and 5 described above.

Furthermore, in the step of forming the protective layer 6 described above, if the protective layer 6 is formed while the substrate 1, therefore the heating resistor layer 13, and the electrodes 4 and 5 are heated to a high temperature, Areas 2 and 23 mentioned above
is formed. Therefore, in the step of forming the protective layer 6, if the protective layer 6 is formed as just described, the step of forming the regions 22 and 23 described above is the same as that of the protective layer 6. This is also part of the process.

The above is an example of a method for manufacturing a thermal head according to the present invention.

According to such a method, although detailed explanation is omitted, it is possible to easily manufacture the thermal head according to the present invention having the excellent features described above in FIG. 6.

Note that the layer made of aluminum of the heat generating resistor layer included in the pair of electrodes attached to the heat generating resistor layer does not have the limited meaning of being made only of aluminum; The layer includes polycrystalline silicon from the heating resistor layer.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a printing thermal head to which a conventional thermal head is applied. Figure 2 shows
1 is a schematic cross-sectional view showing an example of a printing thermal head to which a thermal head proposed by the present inventors is applied. Figure 3 shows the relationship between the supply amount of silane and the growth rate of polycrystalline silicon when the heating resistor layer of the printing thermal head shown in Figure 2 is formed of polycrystalline silicon. It is a curve diagram. FIG. 4 is a curve diagram showing the relationship between the specific resistance of polycrystalline silicon and the amount of phosphine supplied for the same purpose. FIG. 5 is a curve diagram showing the heat generation characteristics of the heat generating resistor layer of the printing thermal head shown in FIG. 2. FIG. FIG. 6 is a schematic cross-sectional view showing an example of a thermal head for printing when the thermal head according to the present invention is applied to the thermal head for printing. FIG. 7 is a curve diagram showing the voltage versus current characteristics of the printing thermal head shown in FIG. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Heat storage layer, 3... Heat generating resistor layer, 4, 5... Metal electrode, 6... Protective layer,
7...Thermal paper, 13...Heating resistor layer, 21
a, 21b... layer, 22, 23... area.

Claims (1)

[Scope of Claims] 1. A thermal head having a structure in which a heat generating resistor layer is formed on a substrate via a heat storage layer, and a metal electrode is ohmicly attached to the heat generating resistor layer. The heat generating resistor layer is formed of polycrystalline silicon, and the metal electrode is formed of a first layer of aluminum on the side of the heat generating resistor layer and tungsten or molybdenum on the first layer. and a region in which aluminum constituting the first layer is diffused is formed in the heating resistor layer on the metal electrode side below the metal electrode. and a region in which aluminum constituting the first layer is diffused is formed in the second layer of the metal electrode on the side of the heating resistor layer. heat head.