JPH04353471A - Thermal head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head suitably used as thermal printing means in serial printers, line printers, and the like.

0002

2. Description of the Related Art FIG. 6 is a sectional view of a conventional thermal head 1. As shown in FIG. The thermal head 1 is made of alumina ceramic, for example, and has a thickness d1 (for example, 0.5 mm to 0.5 mm).
1.0mm), thermal conductivity k=50~70×1
It is equipped with an insulating substrate 2 with a thermal conductivity of 0-3 cal/cm・℃・sec, and on the insulating substrate 2 is made of silicate glass or the like that extends perpendicularly to the plane of the paper in FIG. .9×
A glaze layer 3 of 10 −3 cal/cm·°C·sec is formed. Over the entire surface of the insulating substrate 2 including the glaze layer 3,
For example, a resistor layer 4 made of tantalum nitride Ta3N4 formed by a thin film technique such as sputtering, and a common electrode 5 and individual electrodes 6 obtained by etching a metal thin film such as aluminum are formed. A plurality of heating resistors 7 are arranged vertically.

The vicinity of the heating resistor 7 is covered with a protective film 8 made of, for example, tantalum pentoxide Ta2O5, thereby forming a head substrate 11. For example, on the opposite side of the insulating substrate 2 from the glaze layer 3, an epoxy adhesive layer 9 is provided.
For example, a support plate 10 obtained by die-casting a metal material such as aluminum is fixed. When the support plate 10 is made of aluminum, the thermal conductivity k=5000
×10 −4 cal/cm·°C·sec.

0004

In the thermal head 1 having the above-described structure, electricity is applied between the common electrode 5 and the individual electrodes 6, the heating resistor 7 generates heat, and the platen roller 12 facing the head substrate 11 Thermal recording is performed between the At this time, the glaze layer 3 functions as a heat insulating layer that controls heat dissipation and heat accumulation from the heat generating resistor 7, but since the glaze layer 3 is made of glass, The degree of heat storage is low, and the heat from the heat generating resistor 7 is radiated through the insulating substrate 2 and the support plate 10, and the ratio of the electric power applied to the heat generating resistor 7 to the heat contributing to thermal application is low. In other words, it is difficult to sufficiently improve thermal efficiency.

As another conventional example for solving such problems, as described in Japanese Patent Application Laid-Open No. 52-100245, the glaze layer 3 is made of a resin material with low thermal conductivity such as polyimide resin. There are known techniques to do this. That is, by forming the glaze layer 3 with a resin material, the heat from the heat generating resistor 7 is stored in the glaze layer 3, thereby improving thermal efficiency.

However, in this conventional example, the glaze layer 3 is formed from a synthetic resin material such as polyimide resin, and this glaze layer 3 is in direct contact with the heating resistor 7 whose temperature reaches 300 to 400°C. Here, the heat resistant temperature of the polyimide resin is around the maximum temperature when the heat generating resistor 7 is used. Therefore, the heat resistant temperature of the polyimide resin is insufficient for the temperature condition of the heat generating resistor 7, and as a result of use. The material will deteriorate. In addition, polyimide resin is
There is a problem in that the adhesive force with the ceramic substrate is insufficient, and peeling may occur after long-term use, resulting in low reliability.

Furthermore, if foreign matter such as dust gets caught between the thermal recording paper 13 and the protective film 8 during the printing operation, if a resin layer is used instead of the glaze layer 3, the mechanical strength of the polyimide resin will be reduced. Because it is low, the protective film 8 is easily cracked,
Moisture enters from the outside through the crack, and the electrodes 5,
There is a problem in that it causes corrosion of the resistor layer 6 and deterioration of the characteristics of the resistor layer 4.

Furthermore, in order to reduce the weight of electronic devices such as facsimile communication devices to which the thermal head 1 is attached, the thermal head 1 is also required to be smaller and lighter. Support plate 1 consisting of
0 is relatively heavy, which hinders weight reduction.

An object of the present invention is to provide a thermal head that solves the above-mentioned technical problems and has excellent thermal efficiency, improved reliability, and can be reduced in weight.

0010

[Means for Solving the Problems] The present invention is characterized in that a support member for mounting and fixing a head substrate comprising a plurality of heating resistors formed in a row on an insulating substrate is made of a heat-resistant resin. It is a thermal head.

The present invention is also characterized in that the heat-resistant resin is polycarbonate.

The present invention is also characterized in that the heat-resistant resin is polyphenylene sulfide.

The present invention is also characterized in that the heat-resistant resin is polyetheretherketone.

[0014] Furthermore, the present invention is characterized in that the heat-resistant resin is an acrylic resin.

Further, the present invention is characterized in that the heat conductivity of the heat-resistant resin is selected to be 2×10 −3 cal/cm·°C·sec or less.

[0016]

[Operation] In the thermal head according to the present invention, the support member on which the insulating substrate is placed and fixed is made of heat-resistant resin. Resin materials have lower thermal conductivity than metals,
Therefore, of the heat generated from the heat generating resistor row formed in a row on the insulating substrate, the proportion of heat radiated through the support member can be significantly suppressed, and the electric power applied to the heat generating resistor can be significantly reduced. On the other hand, the proportion of the generated heat that contributes to heat-sensitive application, that is, the thermal efficiency, can be significantly improved. Furthermore, by employing a resin material as the support member, the thermal head can be made much lighter in weight than when a metal material is used.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a thermal head 21 according to an embodiment of the present invention. The thermal head 21 is made of alumina ceramic, for example, and has a plate thickness of d1 (for example, 0
．． 5mm to 1.0mm), thermal conductivity k=50
~70×10-3 cal/cm・℃・sec Insulating substrate 22
The insulating substrate 22 is made of a material such as silicate glass that extends perpendicularly to the plane of the paper in FIG. A glaze layer 23 is formed. A resistor layer 24 made of tantalum nitride Ta3N4 formed over the entire surface of the insulating substrate 22 including the glaze layer 23 by a thin film technique such as sputtering, and a common electrode obtained by etching a metal thin film such as aluminum. 25 and individual electrodes 26 are formed, and a plurality of heating resistors 27 arranged in a direction perpendicular to the plane of FIG. 1 are configured.

The vicinity of the heating resistor 27 is covered with a protective film 28 made of, for example, tantalum pentoxide Ta2O5.
A head substrate 31 is configured. For example, an epoxy adhesive layer 29 is provided on the opposite side of the insulating substrate 22 from the glaze layer 23.
A support plate 30 obtained by die-casting a metal material such as aluminum is fixed thereto. When the support plate 30 is made of aluminum, the thermal conductivity is k
=5000 x 10-4 cal/cm·°C·sec.

In this embodiment, the support plate 30 is made of a heat-resistant resin material with low thermal conductivity and low specific gravity, such as polyphenylene sulfide resin. Polyphenylene sulfide resin has a thermal conductivity k=7×10
For example, the thermal conductivity of aluminum, k=5000×
Since it is extremely small compared to 10-4 cal/cm·°C·sec, the proportion of heat radiated from the head substrate 31 via the support plate 30 can be significantly reduced, and the thermal efficiency can be significantly improved. .

The inventor of the present invention measured the print density on the thermal recording papers 13 and 33 by changing the applied pulse width for the conventional thermal head 1 and the thermal head 21 of this embodiment. The results are shown in lines L1 and L2 in FIG. In other words, the line L1 indicating the printing result based on the thermal head 21 of this embodiment has a higher printing density than the line L2 based on the conventional thermal head 1, and the thermal efficiency is improved regardless of the pulse width. be understood. Therefore, when trying to achieve the same printing density as that of the conventional example, the pulse width of the applied pulse can be shortened, and therefore the driving power can be suppressed.

A portion of the heat generated from the heating resistor 27 is radiated upward in FIG. 1 and contributes to thermal recording on the thermal recording paper 33. On the other hand, a portion of the heat radiated downward is stored in the glaze layer 23, and the remaining heat is transferred to the support plate 30 via the insulating substrate 22 and the adhesive layer 29. In this embodiment, the support plate 30 is made of the synthetic resin material, and the heat conduction within the support plate 30 is significantly suppressed compared to the case where the support plate 30 is made of a metal material as in the conventional example. The movement of heat from the heating resistor 27 downward in FIG. 1 is suppressed, and the proportion of heat contributing to thermal recording on the thermal recording paper 33 is significantly increased.

Furthermore, by continuing the thermal printing operation,
Heat is accumulated throughout the insulating substrate 22, that is, the head substrate 31, and the temperature of the insulating substrate 22 increases. Therefore, the higher the temperature of the insulating substrate 22 is maintained, the more the thermal efficiency will be improved. Using the thermal head 21 of this embodiment, the inventor performed a thermal recording operation by setting the usage environment temperature of the thermal head 21 to 25° C. and 36° C., and measured the resulting print density. . The results are shown in lines L3 and L4 in FIG.

In other words, the higher the surrounding temperature in use, the higher the temperature of the insulating substrate 22 is maintained, and thereby even if the driving pulses applied to the heating resistor 27 have the same width, high-density printing can be achieved. . Furthermore, in order to achieve printing with the same density, the higher the temperature of the insulating substrate 22 can be maintained, the more the applied power can be suppressed.

The present inventor has developed a conventional thermal head 1.
and the insulating substrates 2 and 22 and the support plates 10 and 3 when a driving pulse is applied using the thermal head 21 of this embodiment.
The change in temperature rise from 0 was measured. The results are shown in FIGS. 4 and 5.

That is, lines L5 and L6 in FIG. 4 indicate the state of temperature change between the insulating substrate 2 and the support plate 10 of the thermal head 1, and the driving pulse is applied between the energization start time t1 and the time t2. Then, the insulating substrate 2 reaches the temperature T3, and the support plate 10 reaches the temperature T4.

Lines L7 and L8 in FIG. 5 indicate temperature changes between the insulating substrate 22 and the support plate 30 of the thermal head 21 of this embodiment. Between energization start time t1 and time t3,
When a driving pulse is applied, the insulating substrate 22 reaches a temperature T7 and the support plate 30 reaches a temperature T8. In other words, T3=
At T7,

[0027]

[Math. 1] t2-t1>t3-t1 becomes.

That is, in the thermal head 21 of this embodiment, the insulating substrate 22 can realize a characteristic of rapid temperature rise, and the thermal efficiency is significantly improved compared to the conventional example.

Furthermore, in this embodiment, the thermal efficiency is significantly improved as described above, and since the glaze layer 23 is made of silicate glass, the glaze layer 3 is Compared to the case where the material is made of polyimide resin or the like, even if foreign matter such as dust gets caught between the protective film 28 and the thermal recording paper 33 pressed by the platen roller 32 during thermal printing operation, the glaze will not form. layer 23
The mechanical strength of the protective film 28 is high, and the occurrence of cracks in the protective film 28 can be prevented, thereby significantly improving reliability.

Further, the specific gravity of the polyphenylene sulfite constituting the support plate 30 is 1.34, which is about half of the specific gravity of aluminum in the conventional example, which is 2.7. For example, the weight can be reduced by approximately half, and the weight of the thermal head 21 can be reduced.

As another embodiment of the present invention, the material constituting the support plate 30 is not limited to the polyphenylene sulfide mentioned above, but has a thermal conductivity k=5 to 7×10 −4 cal/cm·° C.
・Polycarbonate resin with a specific gravity of 1.2 and a thermal conductivity of k=7 to 8×10-4 cal/cm・℃・second and a specific gravity of 1.3, or a thermal conductivity of k=4 The material is appropriately selected from synthetic resin materials having relatively low thermal conductivity and low specific gravity, such as acrylic resins with ~6×-4 cal/cm·°C·sec and specific gravity of 1.2.

[0032]

As described above, in the thermal head according to the present invention, the support member on which the insulating substrate is placed and fixed is made of heat-resistant resin. Resin materials have lower thermal conductivity than metals, and therefore, of the heat generated from the heat generating resistor array formed in a row on the insulating substrate, the proportion of heat radiated through the support member is significantly suppressed. Therefore, it is possible to significantly improve the proportion of the generated heat that contributes to heat-sensitive application with respect to the electric power applied to the heating resistor, that is, the thermal efficiency. Furthermore, by employing a resin material as the support member, the thermal head can be made much lighter in weight than when a metal material is used.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a thermal head 21 according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the driving pulse width of the thermal head 1 and the thermal head 21 and print density.

FIG. 3 is a graph showing the relationship between pulse width and print density when the environmental temperature is changed in the thermal head 21.

4 is a graph showing temperature changes between the insulating substrate 2 and the support plate 10 in the thermal head 1. FIG.

5 is a graph showing temperature changes between an insulating substrate 22 and a support plate 30 in a thermal head 21. FIG.

FIG. 6 is a sectional view of a conventional thermal head 1.

[Explanation of symbols]

21 Thermal head 22 Insulating substrate 27 Heating resistor 30 Support plate 31 Head board 33 Thermal recording paper

Claims (6)

[Claims] 1. A thermal head characterized in that a support member for mounting and fixing a head substrate comprising a plurality of heating resistors formed in a row on an insulating substrate is made of a heat-resistant resin. 2. The thermal head according to claim 1, wherein the heat-resistant resin is polycarbonate. 3. The thermal head according to claim 1, wherein the heat-resistant resin is polyphenylene sulfide. 4. The thermal head according to claim 1, wherein the heat-resistant resin is polyetheretherketone. 5. The thermal head according to claim 1, wherein the heat-resistant resin is an acrylic resin. 6. The heat conductivity of the heat-resistant resin is 2×1
The thermal head according to claim 1, wherein the thermal head is selected to be 0-3 cal/cm·°C·sec or less.