JPH05116360A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head suitable for high speed printing capable of/forming a sharp printing image on thermal paper. CONSTITUTION:In a thermal head wherein a heat accumulating layer 2 composed of glass is applied to a substrate 1 and a heating resistor layer 4 and a pair of conductive layers 5a,5b are applied on the heat accumulating layer 2, the heat accumulating layer 2 contains air bubbles and a smoothing layer 3 composed of a heat-resistant resin is applied to at least the surface of the heat accumulating layer 2 at the region where the heating resistor layer 4 and a pair of the conductive layers 5a,5b are applied. in this case, since the upper surface of the heat accumulating layer 2 becomes almost smooth and good by the smoothing layer 3, the thickness of the heating resistor layer 4 on the heat accumulating layer 2 becomes uniform and the thermal head suitable for high speed printing capable of fuming a sharp printing image on the thermal paper is constituted.

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, in a thermal head incorporated in a printer mechanism such as a word processor or a facsimile, as shown in FIG. 3, a heat storage layer 12 made of glass is adhered to an upper surface of a substrate 11 made of alumina ceramics and the like. A heating resistor layer 14 made of tantalum nitride or the like and a pair of conductive layers 15a, 15b made of aluminum or the like are deposited on the upper surface of 12, and the upper surfaces of the heating resistor layer 14 and the pair of conductive layers 15a, 15b are covered with silicon nitride. Has a structure covered with a protective layer 16 made of, for example, a predetermined electric power is applied between the pair of conductive layers 15a and 15b, and the heating resistor layer 14 is heated to a temperature necessary for forming a printed image. Functions as a thermal head by generating Joule heat and conducting the generated heat to thermal paper etc. to form a printed image on the thermal paper etc. That.

[0003]

However, in this conventional thermal head, the heating resistor layer 14 is used.
The heat storage layer 12 made of glass is disposed in the lower part of the glass. Since the heat storage layer 12 made of the glass usually has a relatively high thermal conductivity of 2.2 × 10 ⁻³ cal / cm · sec · deg, At the start of printing, part of the heat generated by the heating resistor layer 13 is absorbed by the heat storage layer 12 and the heating resistor layer 14
It takes a long time to reach the temperature required to form a printed image on thermal paper, etc., and as a result, the start-up of printing is poor, the printed image becomes unclear, and it is not used for high-speed printing. I had.

[0004]

In the thermal head of the present invention, a heat storage layer made of glass is deposited on an electrically insulating substrate, and a heating resistor layer and a pair of conductive layers are formed on the heat storage layer. A thermal head deposited, wherein the heat storage layer made of glass has air bubbles inside, and a heat-resistant resin is applied to at least a portion of the surface where the heating resistor layer and the pair of conductive layers are deposited. A smoothing layer consisting of is applied.

[0005]

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

FIG. 1 is a fragmentary sectional view of a thermal head of the present invention, FIG. 2 is a sectional view taken along line XX 'of FIG. 1, and 1 is a substrate,
2 is a heat storage layer, 3 is a smoothing layer, 4 is a heating resistor layer, 5a,
5b is a pair of conductive layers, and 6 is a protective layer.

The substrate 1 is made of, for example, an electrically insulating material having excellent heat resistance such as alumina ceramics, and a ceramic material powder such as alumina, silica, magnesia, etc. is mixed with an appropriate organic solvent or solvent to form a slurry. A ceramic green sheet is formed by adopting a conventionally known doctor blade method, and then the ceramic green sheet is punched into a predetermined shape and fired at a high temperature (about 1600 ° C.). ..

A heat storage layer 2 is formed on the upper surface of the substrate 1 in an amount of about 5
The heat accumulating layer 2 has a thickness of 0 μm, and a plurality of heat generating resistor layers 4 and a pair of conductive layers 5a and 5b are formed on the upper surface of the heat accumulating layer 2.
Is being worn.

The heat storage layer 2 is made of glass with bubbles.
The thermal conductivity of the bubble-containing glass is 1.0 to 2.0 × 10 ⁻³ cal / cm · sec · de depending on the gas in the bubbles.
Since it is as small as about g, the heat generated by the heating resistor layer 4 is less likely to be absorbed by the heat storage layer 2, and as a result, the heating resistor layer 4 is quickly transferred to thermal paper or the like at the start of printing. The temperature reaches the temperature required to form a printed image, the printing rises extremely quickly, and high-speed printing can be supported.

The heat storage layer 2 made of the bubble-containing glass.
Is, for example, a glass paste obtained by adding and mixing a foaming agent made of aluminum nitride or the like to a powder of borosilicate glass, an organic solvent or the like is applied by printing on the upper surface of the substrate 1 by a conventionally known screen printing method or the like, and thereafter, It is applied to the upper surface of the substrate 1 by heating it to a predetermined temperature to thermally decompose and foam the foaming agent and firing the glass paste.

Further, the heat storage layer 2 made of the bubble-containing glass.
When the total volume of bubbles is less than 10% with respect to the total volume of the heat storage layer 2, the thermal conductivity of the heat storage layer 2 becomes large and tends to be unsuitable for high-speed printing.
When the external force is applied at the time of printing, the heat storage layer 2 is cracked and the printing quality tends to be deteriorated. Therefore, the heat storage layer 2 made of bubbled glass
Is 10 to 6 with respect to the total volume of the heat storage layer 2 with respect to the total volume of the bubbles.
It is preferable to set it in the range of 0%.

Further, the heat storage layer 2 made of the bubble-containing glass.
When the average diameter of the bubbles is set in the range of 3 to 6 μm, the heat storage layer 2 appropriately stores the heat generated by the heating resistor layer 4, and the temperature of the thermal head can be raised to a temperature required for printing in a short time. .. Therefore, it is preferable that the heat storage layer 2 has an average diameter of bubbles entering the inside thereof in the range of 3 to 6 μm.

On the surface of the heat storage layer 2 made of the bubble-containing glass, at least the heating resistor layer 4 and the pair of conductive layers 5 are formed.
The smoothing layer 3 is applied to the portions where a and 5b are applied.

When the heat storage layer 2 is formed of bubble-containing glass as the smoothing layer 3, holes 2a are formed on the surface of the heat storage layer 2,
The heating resistor layer 4 and the pair of conductive layers 5a, 5 are formed in the hole 2a.
b has an effect of effectively preventing the occurrence of wire breakage, variation in conductive resistance, and the like, and the hole 2a formed in the surface of the heat storage layer 2 is completely filled in the surface of the heat storage layer 2 Be worn.

The smoothing layer 3 is made of a heat-resistant resin such as a polyimide resin, and a varnish which is a polyimide resin is applied to the upper surface of the heat storage layer 2 with a predetermined thickness by employing a conventionally known spin coating method or the like. Then, it is then heat-cured at a high temperature to be applied to the upper surface of the heat storage layer 2.

If the thickness of the smoothing layer 3 is less than 3 μm, the hole 2a formed on the surface of the heat storage layer 2 cannot be completely filled, and the heating resistor adhered to the upper surface of the hole 2a. There is a risk that the layer 4 and the pair of conductive layers 5a and 5b will be broken, and if the thickness exceeds 10 μm, an external force applied to the smoothing layer 3 due to contact sliding of thermal paper or the like will cause the external force. As a result, the smoothing layer 3 is largely deformed, and there is a risk that the heating resistor layer 4 and the pair of conductive layers 5a and 5b deposited on the surface of the smoothing layer 3 may be broken or have variations in conductive resistance. is there.

Therefore, the smoothing layer 3 preferably has a thickness in the range of 3 to 6 μm.

The heat storage layer 2 having the smoothing layer 3 deposited on the surface thereof also has a plurality of heating resistor layers 4 linearly deposited and arranged on the upper surface thereof, and further the individual heating resistor layers 4 are arranged. A pair of conductive layers 5a and 5b are deposited on the upper side with a constant gap therebetween.

The heating resistor layer 4 is made of, for example, tantalum nitride or the like, and has a predetermined electric resistivity, so that Joule heat is generated when power is applied through the pair of conductive layers 5a and 5b. Occurs, and heat is generated at a temperature necessary to form a printed image, for example, a temperature of 200 to 300 ° C.

The pair of conductive layers 5a and 5b deposited on the heating resistor layer 4 are made of metal such as aluminum and silver, and the conductive layers 5a and 5b generate Joule heat on the heating resistor layer 4. The action of applying a predetermined electric power necessary for causing

The heating resistor layer 4 and the pair of conductive layers 5a and 5b are sequentially formed on the heat storage layer 2 to which the smoothing layer 3 is deposited by adopting a conventionally known sputtering method, photolithography technique or the like. Be applied.

In this case, a smoothing layer 3 made of a heat-resistant resin is deposited on the upper surface of the heat storage layer 2 on which the heating resistor layer 4 and the pair of conductive layers 5a and 5b are deposited, whereby heat is stored. Since the upper surface of the layer 2 is almost smooth and good, the heating resistor layer 4 and the pair of conductive layers 5a and 5b are not uniform in thickness due to the hole 2a on the surface of the heat storage layer 2. Alternatively, the heating resistor layer 4 and the pair of conductive layers 5a and 5b are not disconnected at all, and the heating resistor layer 3 and the pair of conductive layers 5a and 5b having a substantially uniform thickness are formed on the heat storage layer 2. It can be applied well.

The heating resistor layer 4 having the pair of conductive layers 5a and 5b on its upper surface is also covered with a protective layer 6 made of silicon nitride or the like, and the protective layer 6 is covered with the heating resistor layer 4. It also protects the pair of conductive layers 5a and 5b from abrasion due to sliding with thermal paper or the like, and corrosion from moisture in the atmosphere or contaminants such as chlorine ions and sodium ions contained in the thermal paper.

The protective film 6 is deposited with a predetermined thickness on the upper surfaces of the heating resistor layer 4 and the pair of conductive layers 5a and 5b by adopting a conventionally known sputtering method or the like.

In this case, since the surface of the heat storage layer 2 is made substantially smooth and good by the smoothing layer 3, the upper surface of the protective layer 6 deposited on the heat storage layer 2 is also smooth and good. As a result, at the time of printing, the contact state between the protective layer 6 and the thermal paper or the like is always kept good, and a clear printed image is formed on the thermal paper or the like.

Thus, in the above-mentioned thermal head, electric power is applied between the pair of conductive layers 5a and 5b in response to an external electric signal to cause the heating resistor layer 4 to generate Joule heat to a predetermined temperature and to generate the generated heat. To the thermal paper,
It functions as a thermal head by forming a predetermined print image on thermal paper or the like.

The present invention is not limited to the above-mentioned embodiment, and various modifications and improvements can be made without departing from the scope of the present invention. For example, the smoothing layer 3 and the heat-generating resistor can be used. If a softening prevention layer 7 made of silicon oxide, silicon nitride, or the like is deposited between the layer 4 and the layer 4 with a thickness of 2 to 10 μm by a thin film forming technique such as sputtering,
The softening prevention layer 7 diffuses and relaxes the heat generated by the heating resistor layer 4, and it is possible to completely prevent the smoothing layer 3 made of resin from being softened and deformed by the heat of the heating resistor layer 4. Therefore, a thickness of 2 to 1 is provided between the smoothing layer 3 and the heating resistor layer 4.
It is preferable to interpose a softening prevention layer 7 of 0 μm made of silicon oxide or silicon nitride.

[0028]

In the thermal head of the present invention, since the heat storage layer is made of glass having a small thermal conductivity, the heat generated by the heating resistor layer is less likely to be absorbed by the heat storage layer. As a result, at the start of printing, the heating resistor layer reaches a temperature required to form a printed image on a thermal paper or the like in a short time, the start-up of printing is extremely fast, and high-speed printing can be supported.

Further, in the thermal head of the present invention,
By depositing a smoothing layer made of heat-resistant resin on the top surface of the heat storage layer, the surface of the heat storage layer becomes almost smooth, and as a result, the heating resistor layer and a pair of conductive layers are well formed on the top surface of the heat storage layer. In addition, it becomes possible to apply it to a uniform thickness.

Further, in the thermal head of the present invention,
By applying a smoothing layer on the upper surface of the heat storage layer, the surface condition was made almost smooth and good, so the upper surface of the protective layer applied on the heat storage layer was also smooth and good. As a result, at the time of printing, the contact state between the protective layer and the thermal paper or the like is always kept good, and a clear printed image is formed on the thermal paper or the like.

[Brief description of drawings]

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

2 is a cross-sectional view taken along line X-X 'of FIG.

FIG. 3 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Heat storage layer 2 ... Hole part 3 ... Smoothing layer 4 ... Heating resistor layer 5a, 5b ... A pair of conductive layers 6 ... Protective layer 7 ... ..Softening prevention layers

Claims (1)

[Claims] 1. A thermal head comprising a heat storage layer made of glass deposited on an electrically insulating substrate, and a heating resistor layer and a pair of conductive layers deposited on the heat storage layer.
The heat storage layer made of glass has bubbles inside, and a smoothing layer made of a heat-resistant resin is applied to at least a portion of the surface where the heating resistor layer and the pair of conductive layers are applied. The thermal head is characterized by