JPH04288244A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head which can perform excellent quality printing by enabling a strike property of a heating element on a platen to be extremely raised even when a thermal response property is raised by thinning a thickness of a glazed layer, and can make life for printing long. CONSTITUTION:A glazed layer 2 is formed on a surface of a substrate 1, and a plurality of heating elements 3 according to a number of dots are arranged on an upper surface of the glazed layer 2. In a thermal head composed by continuously connecting electrodes 4, 5 to be connected to those respective heating elements, said substrate 1 is formed with silicone. Beside, a protruding part 9 is formed to the substrate 1, and said glazed layer 2 is formed on a crest surface of the protruding part 9.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a thermal head.
In particular, the present invention relates to a thermal head that makes it possible to improve the contact between the heating resistor and the platen even when using a glaze layer that is formed thinly and has improved thermal responsiveness.

0002

2. Description of the Related Art A thermal head mounted on a thermal printer has, for example, a plurality of heating resistors arranged linearly on the same substrate, and the heating resistors are heated by energization according to desired printing information. It is used for color recording on thermal recording paper or for transfer recording on plain paper via an ink ribbon.

FIG. 2 shows a conventional thermal head, in which a glaze layer 2 made of glass or the like that functions as a heat storage layer is formed on an insulating substrate 1 made of ceramic such as alumina. The cross-sectional shape of the upper surface of the layer 2 in the area where the heating resistor is to be formed is formed into an arc shape. On the upper surface of this glaze layer 2, Ta2
A heating resistor 3 made of N or the like is deposited by vapor deposition, sputtering, etc., and then etched to form a plurality of dots arranged in a straight line according to the number of dots. A common electrode 4 connected to each heating resistor 3 is formed on one side. In addition, each heating resistor 3
On the other side, individual electrodes 5 are connected to each heating resistor 3 to supply current independently, and the common electrode 4 and the individual electrodes 5 are made of, for example, aluminum, copper, or gold, and are made of vapor-deposited material. After being deposited by sputtering or the like, it is formed into a desired pattern by etching.

Furthermore, these heating resistors 3 and common electrodes 4
A protective layer 6 having a thickness of approximately 7 to 10 μm is formed on the surface of the individual electrode 5 to protect the heating resistor 3 and each electrode 4, 5.
, 5 except for the terminal portions thereof. The protective layer 6 is made of approximately 2μ of SiO2 or the like and protects the heating resistor 3 from deterioration due to oxidation.
An oxidation-resistant layer 7 with a film thickness of
and a wear-resistant layer 8 of about 5 to 8 μm thick made of Ta2O5 or the like that protects each electrode 4, 5.The oxidation-resistant layer 7 and the wear-resistant layer 8 of this protective layer 6 are
are sequentially formed by means such as sputtering, and then
In the final step, the insulating substrate 1 is divided to obtain desired thermal head chips.

In the conventional thermal head, the heating resistor 3 is selected based on a predetermined print signal while the thermal head is in pressure contact with a predetermined sheet of paper that is conveyed to the platen portion via an ink ribbon. individual electrode 5
By applying electricity to generate heat in the desired heating resistor 3, the ink of the ink ribbon sent to the heating resistor 3 is melted and transferred onto the paper, and desired printing is performed on the paper. There is. Furthermore, desired printing can be performed on thermal recording paper with the thermal head directly pressed against it without using an ink ribbon.

[0006]

[Problems to be Solved by the Invention] However, in the conventional thermal head, the glaze layer 2 is formed in an arc shape, and the heat generating resistor 3 is disposed on the top of the glaze layer 2, so that the heat generating resistor 3 is not easily attached to the platen. However, in recent years, there has been a demand for higher printing speeds using thermal heads, and with this increase in speed, the thickness of the glaze layer 2 has been increased in order to increase the thermal response speed. The thickness of the glaze layer 2 has been reduced year by year to reduce the amount of heat stored, and the thickness of the glaze layer 2 has been reduced year by year from 40 μm to 30 μm and further to 20 μm. In this way, as the thickness of the glaze layer 2 becomes thinner, the contact between the heat generating resistor 3 and the platen decreases, and as a result, the heat generating resistor 3 is forced into intensive pressure contact with the platen. There was a problem in that good printing quality could not be obtained because the heat transfer through the heating resistor 3 was not sufficient.

[0007] Conventionally, therefore, when performing high-speed printing, it has been necessary to increase the applied power to the thermal head and the pressure force against the platen, which has caused the problem of significantly shortening the printing life of the thermal head. are doing.

The present invention has been made in view of these points, and even when the thickness of the glaze layer is made thin to improve thermal response, the contact between the heating resistor and the platen can be significantly improved. It is an object of the present invention to provide a thermal head which is capable of printing with good print quality and which can extend the printing life.

[0009]

[Means for Solving the Problems] In order to achieve the above object, a thermal head according to the present invention includes a glaze layer formed on the surface of a substrate, and a plurality of heating resistors corresponding to the number of dots on the upper surface of the glaze layer. In the thermal head, which has a series of electrodes connected to each of these heating resistors,
The invention is characterized in that the substrate is made of silicon, a protrusion is formed on the substrate, and the glaze layer is formed on the top surface of the protrusion.

0010

[Function] According to the present invention, even when the thickness of the glaze layer is formed to be thin, the contact between the heating resistor and the platen can be significantly improved by the protrusions formed on the substrate. The heating resistor is pressed against the platen with a high contact force, and the amount of heat generated by the heating resistor can be transferred well to the paper, making it possible to perform high-quality printing in response to high-speed printing. Moreover, the life of the thermal head can be extended. In addition, since the substrate is made of silicon, it is possible to use a glaze material with high heat resistance, which significantly improves the heat resistance limit of the thermal head. It is something that can be obtained.

[0011]

[Embodiment] An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows an embodiment of the thermal head according to the present invention, in which the upper surface of a substrate 1 made of single crystal silicon has a substantially trapezoidal cross-sectional shape and a height of approximately 30 μm.
A protrusion 9 is formed, and the protrusion 9 is formed, for example, by forming a photoresist mask on the silicon substrate 1 and then etching the silicon by photolithography. In this case, since silicon, which is the substrate material, has extremely good workability, the protrusion 9 can be easily formed.

Furthermore, a glaze layer 2 with a thickness of about 20 μm is formed on the top surface of the protrusion 9 of the substrate 1 by applying a glaze paste made of glass and baking it. The top portion is formed into a substantially trapezoidal cross-sectional shape by photolithography. Further, the substrate 1
The surface of the glaze layer 2 is SiO
2 oxide film is formed and has insulating properties,
Further, on the upper surface side of the substrate 1 and the glaze layer 2,
An etching-resistant insulating layer 10 is formed by sputtering, CVD, or the like.

Further, on the upper surface of the insulating layer 10, Ta2
Heat generating resistor 3 made of N or Ta-SiO2, etc.
A common electrode 4 and an individual electrode 5 made of aluminum or the like are formed on the upper surface of the heating resistor 3 by means such as sputtering, and after this sputtering, the heating resistor 3 and the common electrode 5 are formed by photolithography. By etching the electrodes 4 and the individual electrodes 5, a plurality of heat generating resistors 3 corresponding to the number of dots are formed on the top surface of the glaze layer 2, and predetermined heat generating resistors 3 are respectively connected to the heat generating resistors 3. The common electrode 4 and the individual electrodes 5 are formed in such a pattern as shown in FIG.

Furthermore, the surfaces of the heating resistor 3 and each of the electrodes 4 and 5 are coated with a protective layer 6 having a thickness of about 5 μm and made of sialon or the like which has high hardness and can be easily formed into a thin film.

Next, the operation of this embodiment will be explained.

In this embodiment, with the thermal head in pressure contact with a predetermined sheet of paper conveyed to the platen portion via an ink ribbon, individual heating resistors 3 selected based on a predetermined print signal are printed. energize the electrode 5,
By generating heat in a desired heating resistor 3, the ink of the ink ribbon sent to the heating resistor 3 is melted and transferred onto the paper, thereby performing desired printing on the paper. Furthermore, desired printing can be performed on thermal recording paper with the thermal head directly pressed against it without using an ink ribbon.

At this time, in this embodiment, since the protrusions 9 are formed on the substrate 1, even when the thickness of the glaze layer 2 is formed to be thin in order to increase the thermal response speed, the thickness of the glaze layer 2 is reduced. Sufficient contact between the heating resistor 3 formed on the top surface and the platen can be ensured.

Therefore, in this embodiment, the protrusions 9 formed on the substrate 1 significantly improve the contact between the heating resistor 3 and the platen even when the thickness of the glaze layer 2 is made thin. As a result, the heating resistor 3 is pressed against the platen with a high pressure contact force, and the amount of heat generated by the heating resistor 3 can be transferred to the paper properly. It can handle high-speed printing and can perform high-quality printing. Furthermore, since there is no need to increase the pressure contact force of the thermal head, and furthermore, there is no need to increase the power applied to the heating resistor 3, the life of the thermal head can be extended.

[0020] Conventionally, alumina has been used as a substrate material, so as a glaze material, it has a glass transition point of 7.
Although it was not possible to use a material that has heat resistance of 50°C or higher, in this example, the material for forming the substrate 1 is silicon, so its thermal expansion coefficient is 1/2 that of alumina, and it is similar to that of SiO2. It is possible to use a highly heat-resistant glaze material with a large number of components, and it is possible to significantly improve the heat resistance limit of the thermal head.

Furthermore, in conventional substrates made of alumina materials, since there are many impurities in the alumina, they tend to react with the glaze material and cause bubbles and devitrification, making it impossible to stably form a thin glaze layer. However, since the silicon substrate 1 has a high precision in thickness, is smooth, has extremely few impurities, and has good compatibility with SiO2, the main component of the glaze layer 2, when the glaze layer 2 is formed thinly. However, devitrification of the glaze does not occur, and an extremely good glazed surface with stable quality can be obtained. For example, even if the width of the glaze layer 2 is 0.2 mm, by using a direct drawing device, it is possible to form a layer with excellent linearity, and a glaze layer 2 with a smaller heat capacity can be obtained. Furthermore, since silicon has a thermal conductivity about five times higher than that of alumina, it has excellent heat dissipation properties and is extremely effective for high-speed printing.

Note that the protrusion 9 of the substrate 1 may be formed by, for example, grinding using a diamond blade. In this case, the grinding when forming the protrusion 9 having a large step may be performed. can be done efficiently,
In particular, for a line head in which long heating resistors are arranged in parallel in a straight line, this is effective when the relative height of the drive element to the heating resistor is set low.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be modified in various ways as necessary.

[0024]

As described above, in the thermal head according to the present invention, even when the thickness of the glaze layer is made thin, the contact between the heating resistor and the platen can be improved by the protrusion formed on the substrate. In addition, it is possible to perform high-quality printing corresponding to high-speed printing, and furthermore, it is possible to extend the life of the thermal head. In addition, since the substrate is made of silicon, it is possible to use a glaze material with high heat resistance, which significantly improves the heat resistance limit of the thermal head. It has the advantage that it can be formed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a portion showing an embodiment of the present invention.

[Figure 2
] Partial vertical cross-sectional view showing a conventional thermal head

[Explanation of symbols]

1 Board 2 Glaze layer 3 Heating resistor 4 Common electrode 5 Individual electrodes 6 Protective layer 9 Protrusion 10 Insulating layer

Claims (1)

[Claims] Claim 1: A glaze layer is formed on the surface of a substrate, a plurality of heat generating resistors are arranged on the upper surface of this glaze layer according to the number of dots, and electrodes are connected to each of these heat generating resistors in series. 1. A thermal head characterized in that the substrate is made of silicon, a protrusion is formed on the substrate, and the glaze layer is formed on the top surface of the protrusion.