JPH06983A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head which is capable of using an electric power energy supplied to a thermal resistor effectively and forming a printed image on a thermosensitive sheet. CONSTITUTION:The subject thermal head consists of a heat accumulation layer 2 coated on the upper surface of an insulating substrate 1, and a thermal resistor 3 and paired electroconductive layers 4 coated on the heat accumulation layer 2. The heat accumulation layer 2 contains an inorganic material which absorbs radiant heat emitted by the thermal resistor 3. Thus, the temperature of the thermal head is increased to a specified level required for printing in an extremely short time due to the conductive heat and radiant heat emitted by the thermal resistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a thermal head incorporated in a printer mechanism such as a word processor and a facsimile.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a thermal head incorporated in a printer mechanism such as a word processor has an insulating substrate 1 made of alumina ceramics or the like.
The heat storage layer 12 made of glass or the like is provided on the upper surface of the plate 1 at 50-80
A heat-generating resistor 13 made of Ta—SiO ₂ or the like and Al are formed on the heat storage layer 12 while being deposited to a thickness of μm.
Has a structure in which a pair of conductive layers 14 made of, for example, are sequentially deposited, and a predetermined electric power is applied between the pair of conductive layers 14 to heat the heating resistor 13 to a predetermined temperature necessary for printing. It functions as a thermal head by generating heat and conducting the generated heat to thermal paper or the like to form a printed image on the thermal paper or the like.

The heating resistor 13 and the pair of conductive layers 1 are used.
On the upper surface of 4, the heating resistor 13 is formed due to oxidative corrosion due to contact with moisture contained in the atmosphere and abrasion due to sliding of thermal paper or the like.
A protective layer 15 is applied to protect the conductive layer 14 and the conductive layer 14.

However, in this conventional thermal head, when a predetermined electric power energy is supplied to the heating resistor 13 at the time of printing, the heating resistor 13 causes Joule heat generation and converts this into conduction heat and radiant heat. The conductive heat is once stored in the heat storage layer 12, and then transferred to the thermal paper or the like to contribute to printing, but the radiant heat passes through the heat storage layer 12 or the like and hardly contributes to printing. 1
3 had a drawback that the electric power energy supplied to No. 3 could not be used efficiently.

Therefore, in order to solve the above-mentioned drawback, as shown in FIG. 6, a thermal resistance layer 16 made of SiC or the like is interposed between the heat storage layer 12 and the heating resistor 13 with a thickness of about 1 μm, and the thermal resistance layer 16 is formed. It has been proposed to efficiently use the electric power energy supplied to the heating resistor 13 by absorbing the radiant heat (Japanese Patent Laid-Open No. 3-297663).
Issue).

However, the heat storage layer 12 and the heating resistor 1
When the heat resistance layer 16 is interposed between the heat resistance layer 1 and the heat resistance layer 1, the heat resistance layer 1 increases as the temperature of the heat storage layer 12 increases during printing.
6 causes secondary radiation (a phenomenon in which radiant heat is radiated from the thermal resistance layer 16 itself), and the radiant heat radiated by this secondary radiation is because the thermal resistance layer 16 is extremely thin, about 1 μm. There is a drawback in that the radiant heat radiated from the heat resistance layer 16 after passing through 16 and escaping cannot sufficiently contribute to printing.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to more effectively utilize electric power energy supplied to a heating resistor to efficiently form a print on a thermal paper or the like. It is to provide a thermal head capable of performing.

[0008]

A thermal head according to the present invention comprises a heat storage layer deposited on an upper surface of an insulating substrate, and a heating resistor and a pair of conductive layers deposited on the heat storage layer. In the above, the heat storage layer contains an inorganic substance that absorbs radiant heat radiated from the heating resistor inside.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a sectional view showing an embodiment of a thermal head of the present invention, in which 1 is an insulating substrate, 2 is a heat storage layer, 3 is a heating resistor, 4 is a pair of conductive layers, 5 is a protective layer.

The insulating substrate 1 is made of an electrically insulating material such as alumina ceramics, and a heat storage layer 2, a heating resistor 3 and a pair of conductive layers 4 are attached to the upper surface of the insulating substrate 1, the heat storage layer 2, the heating resistor 3 and a pair of layers. It functions as a support member that supports the conductive layer 4 of.

The insulating substrate 1 made of an electrically insulating material such as alumina ceramics is made of, for example, alumina (Al
₂ O ₃ ), silica (SiO ₂ ), magnesia (Mg
O), calcia (CaO) and other raw material powders are mixed with an appropriate organic solvent and solvent to form a slurry and this is formed into a sheet by using the conventionally known doctor blade method, calendar roll method, etc. A ceramic green sheet (ceramic green sheet) is obtained by the above method, and thereafter, the ceramic green sheet is punched into a predetermined shape by a punching method and is fired at a high temperature (about 1600 ° C.).

A heat storage layer 2 made of glass is formed on the upper surface of the insulating substrate 1 so as to have a thickness of 20 to 40 μm. The heat storage layer 2 applies predetermined power energy to a heating resistor 3 described later. The supplied Joule heat accumulates and dissipates the Joule heat to maintain the thermal response characteristics of the thermal head.

The heat storage layer 2 also absorbs the radiant heat radiated from the heat generating resistor 3 inside the heat storage layer 2, SiC, WC, T.
_{aSiO 2, AlN X, SiC-} N, SiC-O, Ta
_{O X, TiO X, SiN X} , and inorganic substances such as CrO _X is contained, the inorganic material, when to cause a Joule heat by supplying a predetermined electrical energy to the heating resistor 3, the heating resistor The radiant heat radiated from the heat storage layer 3 is efficiently absorbed by the inorganic substance near the surface of the heat storage layer 2, and as a result, the heat storage layer 2 is instantaneously heated to a predetermined temperature required for printing by the conduction heat and the radiant heat generated by the heating resistor 3. As a result, the thermal head rises extremely rapidly during printing.

Further, the heat storage layer 2 causes secondary radiation (a phenomenon in which radiant heat is radiated from the heat storage layer 2 itself) as the temperature of the heat storage layer 2 itself rises. Since it is extremely thick at about 40 μm, the radiant heat radiated by the secondary radiation is absorbed in the heat storage layer 2,
As a result, the temperature rise during printing by the thermal head can be made faster.

The volume ratio of the inorganic substance such as SiC contained in the heat storage layer 2 is 1 with respect to the total volume of the heat storage layer 2.
If it is less than%, it becomes difficult for the radiant heat radiated from the heating resistor 3 to be efficiently absorbed in the heat storage layer 2, and 1
If it exceeds 0%, the thermal conductivity of the entire heat storage layer 2 becomes large, and the heat storage action in the heat storage layer 2 may deteriorate. Therefore, the volume ratio of the inorganic substance such as SiC contained in the heat storage layer 2 is 1 to the total volume of the heat storage layer 2.
It is preferable to make it 10%.

The heat storage layer 2 containing an inorganic substance such as SiC on the insulating substrate 1 is made of, for example, SiO ₂ --BaO--C.
aO—Al ₂ O ₃ —B ₂ O ₃ -based powder such as glass and Si
A glass paste obtained by adding and mixing an inorganic substance powder such as C and a suitable organic solvent, a solvent, etc., is applied to the upper surface of the insulating substrate 1 by a conventionally known screen printing method or the like to 20 to 40 μm
Is applied by printing and is baked at a temperature of about 1200 ° C. to form a film on the upper surface of the insulating substrate 1. In this case, when the particle diameter of the inorganic substance powder such as SiC contained in the glass paste is set to 0.5 μm or less, the glass paste is baked on the insulating substrate 1 and the heat storage layer 2 is applied. By making the surface of the heat storage layer 2 extremely smooth, it is possible to form the heating resistor 3 having a predetermined pattern extremely accurately on the surface thereof, and at the time of printing, the contact of the heat sensitive paper or the like becomes uniform, and the heat sensitive paper or the like. It is possible to form an excellent printed image. Therefore, in the glass paste, it is preferable that the particle diameter of the inorganic substance powder such as SiC contained in the glass paste is 0.5 μm or less.

A plurality of heating resistors 3 are linearly arranged on the upper surface of the heat storage layer 2, and the heating resistors 3 are made of tantalum nitride or the like and have a predetermined electric resistivity. Therefore, when a predetermined power is applied, Joule heat is generated and is converted into conductive heat and radiant heat, and the temperature required to form a printed image on thermal paper or the like,
For example, heat is generated at a temperature of 200 to 300 ° C.

A heating resistor 3 made of tantalum nitride or the like.
Is about 0.1% on the upper surface of the heat storage layer 2 by using the well-known sputtering method and photolithography technique.
It is deposited to a thickness of 1 μm.

A pair of conductive layers 4 made of a metal material such as aluminum is formed on the upper surface of the heating resistor 3 in an amount of about 1.0 μm.
The pair of conductive layers 4 are applied to the heating resistor 3 to apply a predetermined electric power to cause Joule heat generation in the heating resistor 3 and convert the Joule heat into conduction heat and radiant heat. It acts to convert.

The pair of conductive layers 4 are formed by depositing a metal material such as aluminum on the upper surface of the heating resistor 3 by employing the conventionally known sputtering method and photolithography technique.

The surfaces of the heating resistor 3 and the pair of conductive layers 4 are also covered with a protective layer 5. The protective layer 5 is oxidatively corroded by the contact of moisture in the atmosphere and the thermal paper 6 or the like. It serves to protect the heating resistor 3 and the conductive layer 4 from abrasion due to sliding.

The protective layer 6 is made of silicon nitride or sialon (S
IALON) or the like, and is applied to the upper surfaces of the heating resistor 3 and the conductive layer 4 with a thickness of, for example, 3 to 6 μm by employing a conventionally known sputtering method or the like.

Thus, in the thermal head of the present invention, a predetermined electric power is applied between the pair of conductive layers 4, the heating resistor 3 is heated to a predetermined temperature necessary for printing, and the heat is conducted to a thermal paper or the like. It functions as a thermal head by forming a printed image on thermal paper.

(Embodiment 2) FIG. 2 is a sectional view showing another embodiment of the thermal head of the present invention. The basic structure of this thermal head is the same as that of the thermal head of Embodiment 1 shown in FIG. However, the only difference is that the heat ray reflective layer 6 made of a metal such as Cr is deposited on the surface of the protective layer 5.

In the thermal head having the above structure, when a predetermined electric power energy is supplied to the heating resistor 3, Joule heat is generated in the heating resistor 3 and is converted into conduction heat and radiant heat. In the radiant heat transfer mechanism, in addition to the mechanism shown in the first embodiment, of the radiant heat radiated from the heating resistor 3, one that is radiated upward is reflected by the heat ray reflective layer 6 toward the heat storage layer 2 side. Heat storage layer 2
It is adapted to be absorbed by an inorganic substance such as SiC contained therein.

In this case, the S contained in the heat storage layer 2
Since the inorganic substance such as iC absorbs both of the radiant heat generated in the heating resistor 3 that is radiated toward the heat storage layer 2 side and the radiant heat that is radiated toward the protective layer 5 side, thermal It is possible to raise the temperature of the head in a short time depending on the temperature required for printing.

(Embodiment 3) The thermal head shown in FIG. 3 is a sectional view showing another embodiment of the thermal head of the present invention, and the basic structure of this thermal head is the embodiment 1 shown in FIG. It is the same as the thermal head of, and the protective layer 5
With a lower layer 5a made of silicon nitride, sialon, or the like, and Si
_{C, WC, TaSiO 2, AlN} X, SiC-N, Si
The only difference is that it has a two-layer structure of an upper layer 5b made of an inorganic substance such as C—O, TaO _x , TiO _x , SiN _x , and CrO _x .

In the thermal head having the above-mentioned structure, when a predetermined electric power energy is supplied to the heating resistor 3, Joule heat is generated in the heating resistor 3 and is converted into conduction heat and radiant heat. The transmission mechanism of
In addition to the mechanism shown in the first embodiment, of the radiant heat generated by the heating resistor 3, the one radiated upward is the protective layer 5.
The upper layer 5b is absorbed without leakage by an inorganic substance such as SiC.

In this case, the inorganic material such as SiC forming the upper layer 5b of the protective layer 5 absorbs radiant heat generated by the heating resistor 3 and is radiated toward the protective layer 5 side. Since it is itself formed of a material having a high thermal conductivity, the temperature of the thermal head can be raised in a short time depending on the temperature required for printing.

(Experimental Example) Next, an experimental example of the present invention will be described.

First, a heat storage layer made of glass was deposited on the upper surface of an insulating substrate made of alumina ceramics, and a heating resistor, a pair of conductive layers and a protective layer made of silicon nitride were sequentially deposited on the heat storage layer. On the upper surface of the conventional thermal head and an insulating substrate made of alumina ceramics, SiC
A heat storage layer containing SiC (here, SiC is contained in the heat storage layer in a volume ratio of 5% with respect to the total volume of the heat storage layer), and a heating resistor and a pair of conductive layers are deposited on the heat storage layer. And a thermal head A of the present invention in which a protective layer made of silicon nitride is sequentially deposited, and a thermal ray reflective layer of Cr having a thickness of 1 μm is deposited on the surface of the protective layer of the thermal head A. Four thermal head samples of the thermal head C of the present invention in which the protective layer of the thermal head A and the protective layer of the thermal head A have a two-layer structure and whose lower layer is silicon nitride and whose upper layer is SiC are prepared.

Next, for each of the four thermal head samples, a predetermined power (pulse width: 2 msec,
The amount of electric power: 0.2 W) was applied to generate Joule heat and radiant heat from the heating resistor, and the surface temperature of the thermal head was measured using an infrared radiation thermometer to examine the temperature rise of the thermal head. The result is shown in FIG.

According to FIG. 4, the surface temperature of the conventional thermal head increased only up to 220 ° C., whereas the thermal head A of the present invention (solid line a in the figure) up to approximately 280 ° C. The thermal heads B and C (solid lines b and c in the figure, respectively) each have about 300
It can be seen that the temperature rises to 0 ° C., and the radiant heat radiated from the heating resistor largely contributes to increasing the surface temperature of the thermal head.

Further, the thermal efficiency of each of the thermal heads A to C of the present invention was converted based on the temperature characteristic of the conventional thermal head. The results are shown in Table 1.

[0036]

[Table 1]

According to Table 1, the thermal efficiency of each of the thermal heads A to C is improved by 30% or more, and the power energy supplied to the heating resistor is used more efficiently than the conventional thermal head. You can see that

The present invention is not limited to the above embodiments, and various changes and improvements can be made without departing from the gist of the present invention. For example, heat storage containing an inorganic substance such as SiC. If the layer is thinly formed to a thickness of about 20 to 30 μm, it is possible to minimize variations in the amount of heat stored in the heat storage layer and effectively prevent unevenness in the density of the printed image on the thermal paper or the like. . Therefore, the thickness of the heat storage layer containing an inorganic substance such as SiC is 20 to 30 μm.
It is preferable to form it to a small thickness.

[0039]

According to the thermal head of the present invention, since the heat storage layer contains an inorganic substance that absorbs the radiant heat radiated from the heating resistor, the temperature of the thermal head is the conduction generated by the heating resistor. The heat and the radiant heat can be raised to a predetermined temperature required for printing in an extremely short time.

Further, according to the thermal head of the present invention, as the temperature of the heat storage layer itself rises, secondary radiation occurs, but since the heat storage layer has an extremely large thickness of 20 to 40 μm, The heat emitted by the radiation is absorbed in the heat storage layer, whereby the temperature rise of the thermal head during printing can be made faster.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a thermal head of the present invention.

FIG. 2 is a sectional view showing another embodiment of the thermal head of the present invention.

FIG. 3 is a sectional view showing another embodiment of the thermal head of the present invention.

FIG. 4 is a diagram showing a change in surface temperature of each thermal head sample.

FIG. 5 is a sectional view of a conventional thermal head.

FIG. 6 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Heat storage layer 3 ... Heating resistor 4 ... A pair of conductive layers 5 ... Protective layer 5a ... Lower layer 5b ... Upper layer 6 ... Heat ray reflective layer

Claims (1)

[Claims] 1. A thermal head comprising a heat storage layer deposited on an upper surface of an insulating substrate, and a heating resistor and a pair of conductive layers deposited on the heat storage layer, wherein the heat storage layer internally generates heat. A thermal head comprising an inorganic substance that absorbs radiant heat emitted from a resistor.