JPH1199682A - Thermal head - Google Patents

Abstract

(57) [Summary] [Problem] Heat is hardly accumulated in a glaze layer in both end regions of a heating resistor array, and when all heating resistors are heated simultaneously, both end regions of the heating resistor array are compared with a central region. As a result, the surface temperature of the thermal head was lowered, and the density unevenness of the print was formed. A glaze layer (2) is applied in a strip shape on an insulating substrate (1), and a plurality of heat generating resistor rows (3) are formed on the glaze layer (2). In the attached thermal head, protruding portions 2a having an arc-shaped cross section are formed at both ends in the longitudinal direction of the glaze layer 2, and heating resistors located at both ends of the heating resistor array at the top of the protruding portions 2a. The body 3 is placed.

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 of a word processor, a facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, a thermal head incorporated as a printer mechanism of a word processor or the like, for example, has a glaze layer made of glass or the like applied in a band shape on an insulating substrate made of alumina ceramics, and a plurality of glaze layers are formed on the glaze layer. It has a structure in which a heating resistor array formed by arranging heating resistors linearly is applied along the glaze layer,
Such a thermal head applies an external power to the heating resistor to cause the heating resistor to individually and selectively generate Joule heat based on a print signal, and to conduct the generated heat to a recording medium such as thermal paper. The recording head functions as a thermal head by forming a predetermined print on the recording medium.

The glaze layer accumulates and dissipates the heat generated by the heat-generating resistor attached to the upper surface of the glaze layer to an appropriate temperature to maintain good thermal response characteristics of the thermal head. When the glaze layer is formed of, for example, glass, a predetermined glass paste is printed and applied on the upper surface of the insulating substrate by a conventionally known screen printing or the like, and is baked at a high temperature to obtain a predetermined thickness (15 mm). ７０70 μm). At this time,
The glaze layer is formed such that its thickness is substantially constant (within ± 1 μm) over the area where the heating resistor array is provided.

[0004]

However, according to the conventional thermal head, due to the difference in the degree of influence due to the heat generated by the adjacent heating resistors, the center of the heating resistor array during printing is not suitable for printing. The generated heat tends to be easily stored in the glaze layer, whereas heat tends to hardly be stored in the glaze layer in both end regions of the heating resistor row. For this reason, if all the heating resistors are heated simultaneously, the surface temperature of the thermal head is lower in both end regions of the heating resistor array than in the central region, and as a result, density unevenness of printing is formed on the recording medium. Had drawbacks. In particular, when this thermal head is applied to a serial type thermal printer (a recording type thermal printer in which the thermal head is moved to the left and right with respect to the recording paper to perform printing on a line-by-line basis), the above-described disadvantages are caused. As a result, white streaks were conspicuous at the boundaries between the lines, and the printing quality was extremely deteriorated.

[0005]

Means for Solving the Problems The present invention has been devised in view of the above-mentioned drawbacks, and a thermal head of the present invention has a glaze layer applied in a strip shape on an insulating substrate, and a glaze layer is formed on the glaze layer. In a thermal head in which a plurality of heating resistors are linearly arranged at regular intervals and a heating resistor array is attached, the glaze layer has a protruding portion having an arc-shaped cross section at both ends in a length direction. Heating resistors located at both ends of the heating resistor row are arranged at the tops of the protruding portions.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing one embodiment of the thermal head of the present invention, FIG. 2 is a sectional view taken along line XX of FIG.
FIG. 2 is a sectional view showing a usage example when the thermal head of FIG. 1 is applied to a serial type thermal printer, wherein 1 is an insulating substrate, 2 is a glaze layer, and 3 is a heating resistor.

The insulating substrate 1 is formed in a quadrangular shape by an electrically insulating material such as alumina ceramics, and supports a glaze layer 2, a heating resistor 3, electrodes 4, 5 and the like described later on the upper surface thereof. Acts as a supporting base material for

When the insulating substrate 1 is made of, for example, alumina ceramics, a ceramic material powder such as alumina, silica, magnesia or the like is mixed with an appropriate organic solvent and a solvent to form a slurry. The ceramic green sheet is formed by adopting the method or the calendar roll method, and then
The ceramic green sheet is manufactured by stamping into a predetermined shape and firing at a high temperature.

On the upper surface of such an insulating substrate 1, a glaze layer 2 having arc-shaped protruding portions 2a at both ends in the longitudinal direction is attached and formed in a strip shape. The glaze layer 2
Is formed of a low thermal conductive material such as high melting point glass or polyimide resin, and accumulates and dissipates heat generated by the heat generating resistor 3 attached to the upper surface thereof to an appropriate temperature, thereby reducing the temperature of the thermal head. It works to maintain good thermal response characteristics.

When the glaze layer 2 is made of, for example, high melting point glass, a predetermined glass paste obtained by adding and mixing an appropriate organic solvent and an organic solvent to the powder of the high melting point glass is conventionally screen-printed. Print and apply to the thickness of 15 μm to 70 μm along one side of the upper surface of the insulating substrate by a method such as above.
By baking at about 1200 ° C., it is attached and formed along one side of the insulating substrate 1. At this time, bulges are formed at both ends of the partial glaze layer 2 due to the surface tension of the glass paste, whereby two protrusions 2 a are formed at both ends of the glaze layer 2. The glaze layer 2 is formed such that the height H of the protruding portion 2a is 2 μm to 4 μm, and the thickness of the central region is substantially constant (within ± 1 μm).

On the upper surface of the glaze layer 2, a heating resistor array in which a plurality of heating resistors 3 are linearly arranged at regular intervals (40 μm to 170 μm) is attached along the glaze layer 2. You.

Since the heating resistor 3 is made of tantalum nitride or the like and has a predetermined electric resistivity, power from outside is applied through a common electrode 4 and an individual electrode 5 which will be described later. Then, Joule heat is generated, and a predetermined temperature (for example, 2 ° C.) required to form a print on the recording medium M is generated.
(00 ° C to 350 ° C).

[0013] Such a heating resistor array is attached on the glaze layer 2 such that the heating resistors 3 located at both ends thereof are arranged near the top of the above-mentioned protruding portion 2a. Therefore, by appropriately setting the height H of the protruding portion 2a according to the power applied to the heating resistor 3, etc.,
Even when printing is performed by causing all the heating resistors 3 to generate heat at the same time, the state of heat storage in the glaze layer 2 can be made substantially equal over the area where the heating resistor rows are to be applied, thereby preventing density unevenness. Good prints can be formed. Therefore, when such a thermal head is used in a serial type thermal printer, the occurrence of white streaks at boundaries between rows can be eliminated, and the printing quality can be improved.

The heating resistor row is formed by applying an electric resistance material such as tantalum nitride to a predetermined thickness (0.01 μm to 0.5 μm) by a conventionally well-known sputtering method or the like, and applying this to a conventionally well-known photo. Processing into a predetermined pattern by employing lithography technology, specifically, so that a plurality of heating resistors 3 are linearly arranged over a region between two protruding portions 2 a provided at both ends of the glaze layer 2. The pattern is formed.

A common electrode 4 and an individual electrode 5 made of a metal material such as aluminum are connected to each of the heating resistors 3 in such a heating resistor row, and furthermore, a whole is covered by a protective film 6 made of silicon nitride or the like. Is coated. The common electrode 4 and the individual electrodes 5 are for applying a predetermined electric power necessary for causing the heating resistor 3 to generate Joule heat, and a metal such as aluminum is used for the heating resistor 3 described above. As in the case of No. 3, it is formed by applying a predetermined thickness by a conventionally known sputtering method or the like, and processing this into a predetermined pattern by employing photolithography technology or the like.

The protective film 6 protects the heating resistor 3, the common electrode 4, the individual electrodes 5 and the like from oxidative corrosion due to contact with moisture or the like contained in the air and abrasion due to sliding contact of the recording medium M. It is formed by applying silicon nitride or the like to a thickness of 2 to 15 μm on the upper surface of the heating resistor 3 or the like by a conventionally known sputtering method or the like.

Thus, in the above-described thermal head, predetermined power is applied between the common electrode 4 and the individual electrodes 5 to selectively cause the heating resistor 3 to generate Joule heat based on the printing signal, and record the generated heat. By transmitting the light to the medium M and forming a predetermined print image on the recording medium M, it functions as a thermal head.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the glaze layer 2 is formed with a constant width in the length direction, but the protrusion 2a is formed in order to increase the heat storage effect of the glaze layer 2 at both end regions of the heating resistor row. The width of both ends of the glaze layer 2 may be wider than the center.

[0019]

According to the thermal head of the present invention, since the heating resistors located at both ends of the heating resistor array are arranged on the tops of the projections provided at both ends of the glaze layer, the height of the projections is increased. Is appropriately set in accordance with the heat storage characteristics of the glaze layer, so that even when all the heating resistors are simultaneously heated and printing is performed, the heat storage state in the glaze layer is applied to the heating resistor array. It can be made substantially equal over the area, thereby making it possible to form a good print without density unevenness.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a thermal head according to the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a cross-sectional view showing a usage example when the thermal head of FIG. 1 is applied to a serial type thermal printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Glaze layer 2a ... Projection part 3 ... Heating resistor

Claims (1)

[Claims] A glazing layer is applied in a strip shape on an insulating substrate, and a heating resistor array in which a plurality of heating resistors are linearly arranged at regular intervals is attached on the glaze layer. In the thermal head, projecting portions having an arc-shaped cross section are formed at both ends in the length direction of the glaze layer, and heating resistors located at both ends of the heating resistor row are arranged at the tops of the projecting portions. A thermal head characterized by the following.