JPH0872281A - Thermal head - Google Patents

Abstract

PURPOSE: To provide a thermal head which can print large dots with an area near the size of a heat generating area of a heat generating resistor on a thermal recording sheet without increasing applied power to the resistor. CONSTITUTION: A thermal head comprises an electrically insulating board 1 covered with a heat storage layer 2, which is covered with a heat generating resistor 3 and a plurality of pairs of electrodes 4, and a heat storage material 2a having higher thermal conductivity than that of the layer 2 in the layer 2 disposed at the center between the electrodes 4 of each pair.

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 as a printer mechanism for a word processor, a facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6, a thermal head incorporated as a printer mechanism for a word processor or the like has an electrical insulating substrate 11 made of alumina ceramics on which a heat storage layer 12 is deposited, and an electrical insulating material such as tantalum nitride. A heat-generating resistor 13 made of a resistance material and a pair of electrodes 14 connected to the heat-generating resistor 13 and arranged with a predetermined gap therebetween are sequentially applied, and the heat-generating resistor 1 is further provided.
3 and a pair of electrodes 14 are covered with a protective layer 15, a predetermined electric power is applied between the pair of electrodes 14 to cause the heating resistor 13 between the electrodes 14 to generate Joule heat, and The generated heat is conducted to the heat-sensitive recording paper, and the heat-sensitive recording paper is colored to form print dots on the heat-sensitive recording paper, thereby functioning as a thermal head.

The heat storage layer 12 is for accumulating a part of the heat generated by the heating resistor 13 to improve the thermal response characteristics of the thermal head, and has a low thermal conductivity such as glass or polyimide resin. It is made of material.

The protective layer 15 is for protecting the heating resistor 13 and the pair of electrodes 14 from oxidative corrosion due to contact of moisture contained in the atmosphere and abrasion due to sliding contact of thermal recording paper. Yes, it is formed of silicon nitride, sialon, or the like.

[0005]

However, in this conventional thermal head, for example, a pair of electrodes 1
A predetermined electric power (0.2 mJ) is applied between the four heating resistors 1
When Joule 3 is heated by Joule, the surface temperature of the heating resistor 13 is largely different between the central region and the peripheral region of the heating region R as shown in FIG. 7, and the central region (surface temperature: about 1
The surrounding area (surface temperature: approx. 90) where the temperature is the lowest at 50 ℃
And a large temperature difference of about 60 ° C. occurs. The heating resistor 13 of the thermal head is
When a predetermined thermosensitive recording paper (for example, TSP-F50US manufactured by Fuji Photo Film Co., Ltd.) that develops color when the surface temperature of the sheet reaches a temperature of about 120 ° C. or more is slidably contacted for printing, the thermosensitive recording paper Develops in the central area of the heating resistor 13, but does not develop in the peripheral area, and the size of the print dots formed on the thermal recording paper is extremely smaller than the size of the heating area R of the heating resistor 12. Had the drawback that

In order to solve the above-mentioned drawbacks, it is conceivable to increase the electric power applied to the heating resistor 13 so that the heat-sensitive recording paper also develops color in the peripheral area of the heating area R.

However, when printing is performed with a large electric power applied to the heating resistor 13, the central region of the heating region R of the heating resistor 13 becomes excessively hot, and the heating resistor 13 is heated in a short time. There is a risk of damage.

Further, as described above, when printing is performed with a large electric power applied to the heating resistor 13, the amount of electric power required for printing increases, and the thermal efficiency of the thermal head decreases.

[0009]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to adjust the size of the heating area of the heating resistor on the heat-sensitive recording paper without increasing the electric power applied to the heating resistor. An object of the present invention is to provide a thermal head capable of forming large print dots having a close area.

[0010]

The thermal head of the present invention has a heat storage layer deposited on an electrically insulating substrate, and
A thermal head comprising a heating resistor and a plurality of pairs of electrodes deposited on the heat storage layer, wherein the heating resistor between the pair of electrodes is selectively heated to perform printing. The heat storage layer located in the central region between the pair of electrodes is embedded with a heat storage material having a higher thermal conductivity than the heat storage layer.

Further, in the thermal head of the present invention, the heating resistor and the plurality of pairs of electrodes are covered with a protective layer, and the protective layer located in the central region between the pair of electrodes has a higher heat than the protective layer. It is characterized in that a protective material having conductivity is embedded.

[0012]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of a thermal head of the present invention, and FIG. 2 is a plan view of the thermal head shown in FIG. 1, where 1 is an electrically insulating substrate, 2 is a heat storage layer, and 2a is heat storage. Material, 3 is a heating resistor, 4 is a pair of electrodes, and 5 is a protective layer.

The electrically insulative substrate 1 is made of an electrically insulative material such as alumina ceramics, and is mixed with an appropriate organic solvent or solvent to the ceramic raw material powder such as alumina, silica, magnesia or the like to form a slurry. A ceramic green sheet is formed by adopting a conventionally known doctor blade method, calender roll method or the like, and thereafter, the ceramic green sheet is punched into a predetermined shape and at a high temperature (about 1600).
It is manufactured by firing at (° C).

On the upper surface of the electrically insulating substrate 1, for example, 4.0 × 10 ^{−4 to} 7.5 × 10 ⁻⁴ cal / mm ·
A semi-arcuate heat storage layer 2 made of a low heat conductive material having a thermal conductivity of ℃ is applied to a thickness of 25 to 60 μm,
The heat storage layer 2 accumulates a part of the heat generated by the heating resistor 3 deposited on the upper surface of the heat storage layer 2 to improve the thermal response characteristics of the thermal head, specifically, to reduce the surface temperature of the thermal head. It functions as the temperature required for forming print dots on the thermal recording paper in time.

The heat storage layer 2 also has a higher thermal conductivity than that of the heat storage layer 2 (for example, 8.0 × 10 ^{-4) in} the central region between each pair of electrodes 4, which will be described later, that is, in the central region of the heat generating region R. ~ 12.
The heat storage material 2a having a temperature of 0 × 10 ⁻⁴ cal / mm · ° C.) is embedded. Therefore, when a predetermined current is applied to the heat generating resistor 3 to cause the heat generating resistor 3 to generate Joule heat, The heat generated by 3 is efficiently accumulated in the peripheral region of the heat generating region R as compared with the central region of the heat generating region R in which the heat storage material 2a is embedded, and the peripheral region of the heat generating region R is effectively heated to a high temperature. You can do it.

FIG. 3 shows an infrared thermometer for measuring the surface temperature of the heating resistor 3 when Joule heat is applied to the heating resistor 3 by applying electric power of 0.2 mJ between the pair of electrodes 4 of the thermal head of FIG. It is a figure showing the result measured using, and as is apparent from the measurement result, the surface temperature in the central region of the heat generation region R is about 150 ° C. which is the same as that of the conventional thermal head.
It can be seen that the surface temperature in the peripheral portion of the heat generating region R has risen to about 110 ° C., which is about 20 ° C. higher than that of the conventional thermal head.

In the heating resistor 3 of the thermal head,
When printing is performed by sliding on a specified thermal recording paper (TSP-F50US manufactured by Fuji Photo Film Co., Ltd.) that develops color when the surface temperature of the heating resistor 3 reaches a temperature of about 120 ° C or higher, thermal recording is performed. Large print dots are formed on the paper, which are close to the area of the heat generating resistor 3 arranged between each pair of electrodes 4, that is, the area of each heat generating region R, whereby application to the heat generating resistor 3 is performed. It is possible to form a good and clear printed image on the thermosensitive recording paper without increasing the electric power. Moreover, since the surface temperature in the central region of the heat generating region R does not become excessively high, it is possible to effectively prevent the heat generating resistor 3 from being damaged by heat in a short time, and to make the thermal head function well for a long time. It will be possible.

Each heat storage material 2 buried in the heat storage layer 2
The area of a is preferably 40 to 80% of the area of the heating resistor 3 arranged between each pair of electrodes 4.

A heat storage layer 2 in which the heat storage material 2a is embedded
First, on the electrically insulating substrate 1, for example, 6.0 × 10
^A varnish, which is a polyimide resin having a thermal conductivity of ^-4 cal / mm · ° C, is applied using a dispenser or the like, and this is thermally cured at a temperature of about 400 ° C to form the heat storage layer 2, and then A recess is formed at a predetermined position of the heat storage layer 2 by etching, and the recess is, for example, 9.8.
Fill a varnish that becomes a polyimide resin having a thermal conductivity of × 10 ^-4 cal / mm · ° C, and finally fill it with about 400 ° C.
It is formed on the electrically insulative substrate 1 by being thermally cured at the temperature of 1 to form the heat storage material 2a.

A plurality of heating resistors 3 (width W: 115 μm, length L: 175 μ) are also formed on the upper surface of the heat storage layer 1a.
m) and a pair of electrodes 4 connected to each heating resistor 3 are sequentially deposited.

The heating resistor 3 is made of TaSiO ₂ , Ta.
Since it is made of N or the like and has a predetermined electric resistivity, Joule heat is generated between the pair of electrodes 4 when a predetermined electric power is applied through the pair of electrodes 4.

On the other hand, the pair of electrodes 4 connected to each of the heating resistors 3 is made of aluminum or the like.
Serves to apply a predetermined electric power required for causing the heating resistor 3 to generate Joule heat.

The heat generating resistor 3 and the pair of electrodes 4 are formed by the well-known sputtering method and photolithography technique. The center of the heat generating resistor 3 located between the pair of electrodes 4 is the heat storage material of the heat storage layer 2. A predetermined pattern and a predetermined thickness (thickness of 0.5 μm to 2.0 μm) are applied so as to be arranged on 2a.

The heating resistor 3 and the pair of electrodes 4 are covered with a protective layer 5. The protective layer 5 oxidizes the heating resistor 3 and the pair of electrodes 4 by contact with moisture contained in the atmosphere. Protects against corrosion and abrasion caused by sliding contact of thermal recording paper.

The protective layer 5 has a predetermined thermal conductivity and covers the heating resistor 3 between the pair of electrodes 4 and a first protective material 5a, and a thermal conductivity lower than that of the first protective material 5a. Have a rate,
If it is formed of the pair of electrodes 4 and the second protective material 5b that covers the heat storage layer 2 between the adjacent heating resistors 3, the heating resistor 3 is formed.
When Joule heat is generated in the heat generating region R of the heat generating resistor 3 by applying a current to the heat generating region 3, the heat generated by the heat generating resistor 3 is less likely to be diffused in the plane direction, and the heat generating region R can store heat more effectively. Therefore, the protective layer 5 has a predetermined thermal conductivity, the first protective material 5a covering the heating resistor 3 between the pair of electrodes 4, and the thermal conductivity lower than that of the first protective material 5a. ,
It is preferably formed by the pair of electrodes 4 and the second protective material 5b that covers the heat storage layer 2 between the adjacent heating resistors 3.

The protective layer 5 is made of, for example, silicon carbide (heat conductivity: 7.0 × 10 ^-2 cal / mm).
.Degree. C.), the second protective material 5b is made of silicon nitride (thermal conductivity: 1.7.times.10.sup.- ² cal / mm.degree. C.) or silicon oxide (thermal conductivity: 0.1.times.10.sup.- ² cal). /Mm.degree. C.) and is deposited on the upper surface of the heating resistor 3 and the pair of electrodes 4 to a thickness of 3 to 6 .mu.m by a conventionally known sputtering method or the like.

Thus, the thermal head of the present invention applies a predetermined electric power between the pair of electrodes 4 based on the print signal to selectively cause the heating resistor 3 between the electrodes 4 to generate Joule heat and to generate the heat. The generated heat is conducted to the heat-sensitive recording paper, and the heat-sensitive recording paper is colored to form print dots on the heat-sensitive recording paper, thereby functioning as a thermal head.

(Other Embodiments) Next, other embodiments of the thermal head of the present invention will be described.

FIG. 4 is a sectional view showing another embodiment of the thermal head of the present invention. 1 is an electrically insulating substrate, 2 is a heat storage layer, 2a is a heat storage material, 3 is a heating resistor, and 4 is a pair. , 5 is a protective layer, 5c is a first protective material, 5d is a second protective material, and 6 is an antioxidant layer.

The thermal head of this embodiment differs from the thermal head shown in FIG. 1 in that the protective layer 5 located in the central region between each pair of electrodes 4 has a higher thermal conductivity than the protective layer 5. The material 5c is embedded, specifically, the protective layer 5 located in the central region has a thermal conductivity of 0.2 cal / cm.
The first protective material 5c made of an inorganic substance (for example, silicon carbide or the like) having a temperature of sec.degree. C. or higher, and the protective layer 5 in the peripheral region surrounding the central region has a thermal conductivity of 0.1 cal / cm.se.
Inorganic substances below c · ° C (eg, silicon oxide, silicon nitride, etc.)
It is a point formed by the second protective material 5d composed of.

In the thermal head of this embodiment, the heat storage layer 2 corresponding to the heat generating area is projected by 2 to 7 μm, and the thickness between the heat storage layer 2 and the heating resistor 3 is 5 μm.
The anti-oxidation layer 6 of m or more is interposed.

By embedding the protective material 5c having a higher thermal conductivity than that of the protective layer 5 in the protective layer 5 located in the central region between the pair of electrodes 4 as described above, the protective layer 5 becomes (1) It contributes to the temperature increase in the peripheral area more efficiently than in the central area where the protective material 5c is embedded, and the peripheral area of the heat generating area can be effectively heated to a high temperature.

Further, since the heat storage layer 2 has a portion corresponding to the heat generating region protruding by 2 to 7 μm, it is possible to effectively prevent the thermal paper or the like from coming into contact with the electrodes 4 or the like at the time of printing to prevent the thermal head and the thermal paper or the like. It is possible to improve the adhesiveness with and to effectively prevent the concentration of stress due to the sliding contact of the thermal paper or the like, thereby eliminating the peeling of the protective layer 5.

On the other hand, if the thickness of the antioxidation layer 6 is set to 5 μm or more, the heating resistor 3 is effectively prevented from being broken due to the entrapment of foreign matter (paper scraps) during printing. Therefore, the thermal head can function properly and normally for a long period of time. Therefore, the thickness of the antioxidant layer 6 is preferably set to 5 μm or more. If the total thickness of the antioxidant layer 6 and the protective layer 5 is set to 13 μm or less, most of the heat generated by the heating resistor 3 contributes to printing, and the thermal efficiency of the thermal head is extremely high. be able to. Therefore, it is preferable that the total thickness of the antioxidant layer 6 and the protective layer 5 is set to 13 μm or less.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the gist of the present invention. For example, in the above-mentioned embodiments, the heat storage material is It was made of polyimide resin,
Instead of this, the heat storage material may be formed of glass, and in this case also, the same effect as that of the above-described embodiment is obtained.

Further, in the above embodiment, the heat storage layer is formed in a semi-circular shape, but instead of this, as shown in FIG. 5, a semi-circular glass frame member 2c (radius is formed on the electrically insulating substrate 1). 0.5 mm, width 0.34 mm, height 30 μm), and the frame member 2c is filled with a heat storage layer 2 made of a polyimide resin, and the heating resistor 3 is further deposited on the heat storage layer 2. A heat storage material 2a made of a material having a higher thermal conductivity than the heat storage layer 2 may be embedded in the central region of the heat generation region R. In this case, in addition to the same effect as the above embodiment, It is possible to effectively suppress deformation and the like at the time of depositing 2 by the frame member 2c.

[0038]

According to the thermal head of the present invention, a heat storage material having a higher thermal conductivity than that of the heat storage layer is embedded in the heat storage layer located in the central region between each pair of electrodes. When a predetermined current is passed through the body to cause Joule heat,
The heat storage material is more efficiently accumulated in the peripheral area of the heat generating area than in the central area of the heat generating area in which the heat storage material is embedded, and the peripheral area of the heat generating area can be effectively heated to a high temperature. Moreover, since the surface temperature in the central area of the heat generating area does not become excessively high, it is possible to effectively prevent the heat generating resistor from being damaged by heat in a short time, and to make the thermal head function well for a long time. .

[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 partially enlarged view of the thermal head shown in FIG.

FIG. 3 is a diagram showing a surface temperature of a heating resistor in the thermal head of the present invention.

FIG. 4 is a sectional view showing another embodiment of the thermal head of the present invention.

FIG. 5 is a sectional view showing a modified example of the thermal head of the present invention.

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

FIG. 7 is a diagram showing a surface temperature of a heating resistor in a conventional thermal head.

[Explanation of reference numerals] 1 ... Electric insulating substrate 2 ... Heat storage layer 2a ... Heat storage material 3 ... Heating resistor 4 ... Pair of electrodes 5 ... Protective layer R: heating area 5c: first protective material 5d: second protective material

Claims (2)

[Claims] 1. A heat storage layer is deposited on an electrically insulating substrate, and a heat-generating resistor and a plurality of electrodes are deposited on the heat storage layer. The heat-generating resistor between each pair of electrodes. A thermal head for selectively heating a body to perform printing, wherein a heat storage material located in the central region between the pair of electrodes is embedded with a heat storage material having a higher thermal conductivity than the heat storage layer. The thermal head. 2. The heating resistor and the pair of electrodes are covered with a protective layer, and a protective material having a higher thermal conductivity than that of the protective layer is embedded in a protective layer located in a central region between the pair of electrodes. The thermal head according to claim 1, wherein the thermal head is used.