JP2003276226A - Thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal head which generates few printing density irregularities, is power-saving and has a superior heat responsivity at a high speed. <P>SOLUTION: The thermal head has a plurality of heating resistors 16 and power supply elements 17 and 18 formed on an upper face of a substrate 11 formed of glass, a plurality of heating elements 16a aligned and formed by the plurality of heating resistors 16 and power supply elements 17, 18, and a protecting layer 19 for coating at least upper faces of the heating elements 16a. A heat sink layer 12 of pure aluminum or an aluminum alloy with a transition metal added is formed on the substrate 11, and an inorganic heat insulating layer 13 formed of an inorganic material is stacked on the heat sink layer 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a thermal printer, and more particularly to a thermal head having high printing quality, high speed printing and power saving.

[0002]

2. Description of the Related Art In recent years, thermal heads have been widely used in recording devices for various information equipment. The recording devices used for these information devices have high printing speed, low cost, power saving, downsizing, etc., and especially thermal heads have little printing density unevenness, have low power consumption, and have high-speed thermal response. Things are desired. As a major factor of the print density unevenness caused by the thermal head, for example, since a conventionally used glazed alumina substrate is formed by firing an alumina green sheet, the shrinkage is large and the surface is essentially swelled.

When a thick film of glass glaze is formed on the alumina substrate having poor flatness and baked, the swell of the alumina substrate is transferred to the surface of the glaze heat retaining layer, and uniform pressure contact with the platen cannot be obtained. . Therefore, even if the heating temperature of the heating element is made uniform, variations in heat transfer to the recording medium occur, and uneven printing density cannot be eliminated. For this reason, the conventional thermal head replaces the expensive and inferior flatness of the glazed alumina with the material of the substrate.
The glass used was inexpensive and excellent in flatness.

Such a conventional thermal head C is shown in FIG.
In the following description, a substrate 1 made of glass and having a heat retaining property is disposed in the lower portion, and a trapezoidal ridge portion 2 is formed on the surface of the substrate 1 by photolithography. Ta-Si is formed on the upper surface of the substrate 1 made of glass.
A heating resistor 3 made of O2, Ti-SiO2, or the like is laminated by sputtering deposition or the like, and is formed by a photolithography technique.
The pattern of the heating resistor 3 is formed. On the upper surface of the heating resistor 3, a common power feeding member 4 made of Al, Cu or the like is provided.
And the individual power feeding body 5 is formed, and the heating element 3 a is formed between the common power feeding body 4 and the individual power feeding body 5. A protective layer 6 made of ceramic such as sialon is formed on the heating resistor 3 and the like so as to prevent oxidation and wear of the heating resistor 3 and the like.

In such a conventional thermal head C, since the heating element 3a is formed directly on the substrate 1 made of glass, the substrate 1 has a small thermal conductivity and a heat retaining property. It can also serve as a layer. Moreover, the substrate 1 made of glass is inexpensive and has excellent flatness.

[0006]

However, in the conventional thermal head C, the thermal conductivity of glass is about 1 w / m. As shown in FIG. 3, the temperature rise curve of the substrate becomes steep with the application of the drive pulse because it has a small k and has a heat retaining property. Therefore, when the printing speed is increased, a large amount of heat is generated from the heating element. The heat flowing into the substrate 1 is accumulated in the substrate 1, and the temperature of the substrate 1 instantly reaches the printing stop temperature D shown by the broken line. Such a rapid rise in the substrate temperature makes it impossible to control the heat generation temperature of the heat generating element even if the energy applied to the heat generating element is reduced.

Therefore, the temperature of the substrate 1 is the printing stop temperature D.
In that case, the printing is temporarily stopped and the thermal head C is cooled for a predetermined time in the cooling process. Therefore, the conventional thermal head C has a problem that high-speed printing cannot be performed. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a thermal head capable of high-speed printing with less uneven printing density.

[0008]

As a first solving means for solving the above-mentioned problems, a thermal head of the present invention comprises a plurality of heating resistors and a power feeding body formed on an upper surface of a substrate made of glass, and a plurality of the heating resistors. A plurality of heat generating elements aligned by the heat generating resistor and the power feeding body, and a protective layer covering at least the upper surface of the heat generating element, and a heat radiating layer made of a metal layer is formed on the substrate. An inorganic heat insulating layer made of an inorganic material is laminated on the above.

As a second means for solving the above problems, the heat dissipation layer is made of pure aluminum or an aluminum alloy to which a transition metal is added.

As a third means for solving the above problems, an organic heat insulating layer made of an organic material is formed between the heat dissipation layer and the inorganic heat insulating layer to form a multi-layer heat insulating layer. It was configured.

As a fourth means for solving the above problems, the inorganic heat insulating layer is composed of a multi-element oxide ceramic layer of Si, a transition metal and oxygen.

As a fifth means for solving the above-mentioned problems, the organic heat retaining layer is composed of a polyimide resin layer.

As a sixth means for solving the above-mentioned problems, the substrate has a structure in which a ridge having a height of 1 to 50 μm is formed in a trapezoidal shape.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermal head of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of a main part according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of a main part according to a second embodiment of the present invention.
6 is a graph comparing the heat storage characteristics of the present invention and a conventional thermal head.

The thermal head A according to the first embodiment of the present invention will be described with reference to FIG. 1. A substrate 11 made of glass and having a heat retaining property is disposed in the lower portion. The surface of the substrate 11 may be 1 to 50 by photolithography technique.
The ridge 11a having a height of μm is formed in a trapezoidal shape with a smooth cross section. Further, the substrate 1 including the ridge portion 11a
The upper surface of 1 is pure Al, or Al-Cu, Al-C
The heat dissipation layer 12 having a high thermal conductivity and made of an alloy of aluminum and a transition metal such as r, Al-Ni, Al-Y is 1 to 50.
It is laminated to a thickness of μm by sputtering deposition or the like.

Since the heat dissipation layer 12 is mainly composed of aluminum, it is inexpensive and highly productive. And the thermal conductivity of aluminum is about 100 w / m. k, and 1 w / m.g. of glass. It is almost 100 times higher than k. Therefore, the problem of film stress due to thickening can be minimized, and by appropriately selecting and setting the film thickness of the heat dissipation layer 12, it is possible to prevent rapid heat accumulation of the substrate 11 even when high-speed printing is performed. A heating element 16a that can be formed and will be described later
It is possible to maintain a state in which the energization heat control can be performed.

An inorganic heat insulating layer 13 made of Si, a transition metal, and oxygen is laminated on the heat dissipation layer 12 to a thickness of 10 to 30 μm by sputtering deposition or the like. The inorganic heat insulating layer 13 composed of Si, transition metal and oxygen has a thermal conductivity of 0.9 w / m. It is the smallest among the inorganic materials and has excellent heat insulation. Further, on the inorganic heat insulating layer 13, SiO 2
Layer, or a heating resistor 16 made of cermet such as Ta-SiO2 is laminated by sputtering deposition to a thickness of about 0.1 μm through an insulating layer 15 having an etching resistance and an insulating property made of an Al2O3 layer, A pattern of a plurality of heating resistors 16 is formed by the photolithography technique.

Further, Al or C is formed on the heating resistor 16.
The material of the power supply such as u is approximately 1μ by sputter deposition.
The common power supply body 17 and the individual power supply body 18 are formed with a predetermined gap by photolithography technology. A heating element 16a is formed on the heating resistor 16 in the portion sandwiched between the common power feeding body 17 and the individual power feeding body 18. Further, a protective layer 19 made of ceramics such as sialon is sputter-deposited with a thickness of about 5 μm on at least the heating element 16a, the common power supply body 17, the individual power supply and others 18 in order to prevent them from being oxidized or worn. The thermal head A according to the first embodiment of the present invention is configured by being laminated and coated with.

In the thermal head A according to the first embodiment of the present invention as described above, the inorganic heat insulating layer 13 has a small thermal conductivity and is excellent in heat insulation. Even if the layers are laminated in a single layer, as shown in FIG. 3, the temperature rise curve of the substrate can be made slower with the application of the drive pulse. Therefore, even if high-speed printing is performed, the time until the printing stop temperature D is reached can be set to a level at which there is no practical problem. Since it is not necessary to cool the thermal head A in the conventional cooling process, the cooling time can be eliminated and high-speed printing can be performed with high throughput.

A thermal head B according to a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. First, the ridges 12 are formed on the surface of the substrate 11.
Are formed, and the heat dissipation layer 12 is laminated on these. An organic heat insulating layer 14 made of an organic material is formed between the heat dissipation layer 12 and the inorganic heat insulating layer 13, and the inorganic heat insulating layer 13 and the organic heat insulating layer 14 form a multi-layer heat insulating layer. The organic heat insulating layer 14 is formed by laminating a polyimide resin to a thickness of 10 to 30 μm by a vacuum deposition polymerization method, and then laminating an inorganic heat insulating layer 13 to form a plurality of heat insulating layers 14, 13.
I am trying. In addition, the same as in the first embodiment, the insulating layer 15, each of the power supply members 17 and 18, and the protective layer 19 are laminated on the inorganic heat retaining layer 13, and the thermal head B according to the second embodiment.
Is configured.

The heat insulation layer 14 has a thermal conductivity of 0.3.
w / m. k, which is as small as about 1/3 of the inorganic heat insulating layer 13, the heat flow resistance to the substrate 11 side is increased so that the heat of the substrate 11 is accumulated as shown in FIG. It can be slower than A. Therefore, the thermal head B according to the second embodiment of the present invention is
Higher-speed printing and power saving can be realized than the thermal head A of the first embodiment. Further, the thermal head B of the second embodiment of the present invention is inferior in heat resistance and mechanical strength because the organic heat insulating layer 14 is made of a polyimide resin, but the inorganic heat insulating layer 13 is formed on the organic heat insulating layer 14. By forming the thermal head B, it is possible to obtain a thermal head B having high heat insulation properties, excellent heat resistance, and excellent mechanical strength.

In the thermal head B according to the second embodiment of the present invention, the film thicknesses of the heat dissipation layer 12, the organic heat retaining layer 14 and the inorganic heat retaining layer 13 are changed so that the substrate 11 shown in FIG. The temperature rise curve can be changed appropriately. In particular, by forming the heat dissipation layer 12 as thick as 1 to 50 μm, it can be made similar to a thermal head (not shown) using a metal substrate having good heat dissipation.

[0023]

As described above, in the thermal head of the present invention, a heat dissipation layer made of a metal layer is formed on a substrate made of glass, and an inorganic heat insulating layer made of an inorganic material is laminated on the heat dissipation layer. Therefore, the heat flow from the heat generating element can be diffused and radiated quickly by utilizing the large thermal conductivity of the heat dissipation layer made of a metal layer, and the heat storage of the substrate immediately below the heat generating element can be moderated. Therefore, it is possible to eliminate the cooling process for cooling the thermal head as described in the related art, it is not necessary to stop the printing for cooling, and it is possible to achieve high throughput and high-speed printing. be able to. Further, by using glass that is inexpensive and has excellent flatness as the material of the substrate, the pressure contact of the thermal head with respect to the platen can be made uniform, and uneven printing density can be eliminated.

Since the heat dissipation layer is made of pure aluminum or an aluminum alloy to which a transition metal is added,
A heat dissipation layer having excellent heat dissipation and low cost can be obtained. Further, by appropriately selecting the film thickness of the heat dissipation layer, rapid heat storage of the substrate can be prevented, and high-speed printing can be continuously performed.

Further, since an organic heat insulating layer made of an organic material is formed between the heat dissipation layer and the inorganic heat insulating layer to form a multi-layer heat insulating layer, an organic heat insulating layer having a thermal conductivity smaller than that of the inorganic heat insulating layer can be obtained.
Further, it is possible to provide a thermal head capable of slowing the heat storage of the substrate and further capable of high-speed printing and power saving.

Further, since the inorganic heat retaining layer is composed of a multi-element oxide ceramic layer of Si, transition metal and oxygen, it can be an inorganic heat retaining layer having the smallest thermal conductivity among the inorganic substances and excellent heat insulating properties. Therefore, a thermal head capable of high-speed printing and power saving can be provided even if the heat insulating layer is a single layer having only an inorganic heat insulating layer.

Further, since the organic heat insulating layer is composed of a polyimide resin layer, the heat conductivity of the organic heat insulating layer is 1 / th that of the inorganic heat insulating layer.
3, the heat flow resistance to the substrate side can be further increased, and the heat storage of the substrate can be slowed down.

Further, since the ridges having a height of 1 to 50 μm are formed in a trapezoidal shape on the substrate, the heating elements are formed on the ridges so that the heating elements can be used as thermal paper or ink ribbon. It is possible to provide a thermal head that can be pressed strongly against a part and that can achieve high print quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts according to a second embodiment of the present invention.

FIG. 3 is a graph comparing heat storage characteristics of the present invention and a conventional thermal head.

FIG. 4 is a sectional view of a main part of a conventional thermal head.

[Sharp sign]

11 board 12 Heat dissipation layer 13 Inorganic insulation layer 14 Organic heat insulation layer 15 Insulation layer 16 Heating resistor 16a heating element 17 Common power supply 18 Individual power supply 19 Protective layer

Claims (6)

[Claims] 1. A plurality of heat generating resistors and a power supply body formed on the upper surface of a substrate made of glass, a plurality of heat generating elements aligned with the plurality of heat generating resistor bodies and the power supply body, and at least an upper surface of the heat generating element. And a protective layer covering
A thermal head characterized in that a heat dissipation layer made of a metal layer is formed on the substrate, and an inorganic heat insulation layer made of an inorganic material is laminated on the heat dissipation layer. 2. The thermal head according to claim 1, wherein the heat dissipation layer is made of pure aluminum or an aluminum alloy to which a transition metal is added. 3. The thermal insulation layer according to claim 1, wherein an organic thermal insulation layer made of an organic material is formed between the heat dissipation layer and the inorganic thermal insulation layer to form a multilayer thermal insulation layer. head. 4. The thermal head according to claim 1, wherein the inorganic heat insulating layer comprises a multi-element oxide ceramic layer of Si, a transition metal and oxygen. 5. The thermal head according to claim 3, wherein the organic heat insulation layer is made of a polyimide resin layer. 6. The thermal head according to claim 1, wherein the substrate is formed with a protrusion having a height of 1 to 50 μm in a trapezoidal shape.