JPS5995173A - Thermal head - Google Patents

Abstract

PURPOSE:To prevent generation of heat from being concentrated at the center of a heating resistor and enhance durability, by forming a substantially circular hole at the center of the resistor element by irradiating with laser light or the like. CONSTITUTION:A resistor pattern 4 consisting of a plurality of resistor elements 4a-4f is provided on a ceramic substrate 1 by using Ni-Cr, Ta-SiO2 or the like, and each of the resistor elements 4a-4f is provided with a substantially circular hole 5, the area of which is so set that the difference in resistance between adjacent ones of the resistor elements 4a-4f becomes small. Since generation of heat is prevented from being concentrated at the center of each of the elements 4a-4f, durability can be enhanced. In addition, as a result of preventing the concentration of generation of heat, printed density can be made to be uniform, dot area can be enlarged, and image quality can be largely enhanced. Further, since the resistances of the resistor elements are made to be constant, development of color of each printed dot can be prevented from being scattered, and image quality can be further enhanced.

Description

[Detailed description of the invention] This invention relates to a thermal head.

Conventionally, as this type of thermal head, there have been those shown in FIGS. 1 to 3. In the above, (1) is a ceramic substrate, (2) is a resistor pattern formed on a ceramic substrate +11 and consists of a plurality of resistor elements (23) to (2f), and (3) is a resistor pattern formed on a ceramic substrate (1). The conductor pattern (3) is a plurality of approximately inverted-shaped voltage application terminals connected to the resistor elements C2a) to (2f).

Next, the manufacturing method will be explained. Conventionally, when manufacturing a thermal head, a resistor film and a conductor film are formed on a ceramic substrate (1) by a thin film forming method such as a sputtering method or a vacuum evaporation method, and then the resistor film and conductor film are deposited. The resistor pattern (2) and the base pattern (3) are formed by patterning using a chemical etching method, a plasma etching method, or the like. In this case, the resistor pattern (2) is formed in a thin film state of approximately 1000λ to 5000λ.

Next, the effect ζ will be explained. When a voltage is applied between the terminals s1 to So and the common terminal Vo, the resistor element Csu-(2
f) Ic is conductor (3a) - (3f) and common conductor (3
A current flows through the resistor elements (2a) to (2)
Joule heat is generated. At this time, when thermal paper is pressed against the resistor pattern (3), the thermal paper develops color due to the Joule heat generated in the resistor patterns 2;) to (2f).

Applying this principle, a desired image can be recorded on the thermal paper by moving the thermal head or the thermal paper and applying a voltage between appropriately selected terminals 81 to S6 and the common terminal vo.

However, with conventional thermal heads, when current is traced through a conductor, the current concentrates in the center of the resistor element, and the generated heat remains in the center, causing the middle heating part to become abnormally high temperature. In some cases, the resistor element may be damaged. Furthermore, since the resistance values between adjacent resistor elements vary, there is a problem in that even if a constant voltage is applied between the conductor terminals, a difference in heat generation energy occurs, which in turn causes variations in color development.

This invention was made to solve these problems by forming a substantially circular hole in the center of the resistor element by laser irradiation or the like.

The purpose is to provide a thermal rad that prevents heat generation from concentrating at the center of the element and improves surface durability.

An embodiment of the present invention will be described below.

Figures 4 and 5 show a thermal head according to an embodiment of the present invention. In the figure, (1) is an insulating substrate made of a ceramic substrate such as alumina, (.) is a ceramic substrate (1) formed using Ni-Cr, Ta-5i02, etc., and a plurality of resistor elements (4a). ) to (4f], and (5) is each resistor element (42) to (4f).
4f], and the hole (5) is formed in an area such that the difference in resistance value between adjacent resistor elements (4a) to (4f) is small. (6) is a conductor pattern formed using Au on the ceramic substrate (1), and the conductor pattern (6) is the resistor element (4a).
~(4f) It consists of a conductor (6a) for flowing current (6a) and a common conductor (6g).

Next, a method of manufacturing the thermal head of this embodiment will be explained.

When manufacturing this thermal head, first, a resistor film is formed on a ceramic substrate (1) using Ni-Cr, Ta-5i02 at a rate of approximately 1000A to 50001H/'fI by sputter link method or ferrodeposition method. This film is formed.

A conductor film is formed on the entire surface of the tertiary (resistor here, Qll, lj) using the sputtering method, !r, or air evaporation method.This conductor film has good adhesion, W][vertical Two or three layers are formed taking into consideration the properties and current capacity, etc. 2, and this dedicated film and antibody film are patterned into almost the desired shape by chemical etching method or plasma etching method. In this case, the resistor film is exposed by etching only the resistor film 4) and the conductor pattern (6).

Next, the central part of the resistor element (4a) of the resistor pattern (4) thus formed is irradiated with a laser beam to form a hole (5). When the resistor element (4a) reaches a predetermined resistance value, the laser beam irradiation is stopped.The area of the hole (5) is It is desirable that the area is 1/4 or less of the area of the element (43).
) to (4f) are also made with a hole (5) in the center using the same method.In this way, the thermal head of this embodiment can be obtained.

FIGS. 6 and 7 show on the A-A line in the resistor elements (2a) and (4a) of the conventional and present thermal heads,
Temperature distribution a, b on the B-B line and the resistor element (
2a) This is an experimental result showing the state of printed dots according to (4a). First, if we look at the temperature distribution, in the temperature distribution of the conventional thermal head, as shown by the solid lines a and b in KG 613+ (b), the ( The temperature increases from the Itll end to the center, reaching the maximum temperature of 300 or more at the center.On the other hand, in the temperature distribution of the thermal head of this embodiment, the 7th section + (b) Act. 19. As shown by λ, b, the temperature rises rapidly from the il+11 end of the element (4a) toward the center, whether on the A-A line or the B-13 line, and the temperature rises rapidly in the center part. The temperature is approximately constant at about 300'C, and it can be seen that no concentration of heat occurs in the medium heat of element (4a).

Next, if we look at the state of the printed dots, with conventional thermal heads, the 14 degree printing is very narrow in the center, and becomes thinner toward the periphery, and the shape of the dots becomes elliptical. On the other hand, the wood grain (in one example of a thermal head, there is a part with σ゛τ in the center of the printed 8 degrees, or the mark is uniform as a whole, or It can be seen that the shape of the dot is approximately square, and its area is larger than that of conventional printed dots.

In the thermal head of this embodiment as described above, since the concentration of heat generation in the resistor element at medium heat is prevented, the durability can be increased (improved). , the printing density can be made uniform, the dot area can be increased, and the image quality can be made thicker.Furthermore, since the resistance value of the resistor element is made constant, variations in the color development of each printing dot can be reduced. This can also improve image quality.

In addition, in the case of Honjitsu 71i11, a round hole was drilled by shining a laser beam on it, so the machining accuracy was very difficult (also, the hole was formed while measuring the resistance value of the resistor element. It is possible to do this, and the work is very easy +1.

In the above embodiments, the holes in the resistor element were formed so that the resistance value was constant, but the effect of preventing the concentration of heat generation can be obtained even if the holes are simply made.

As described above, in the thermal head according to the present invention, since the resistor element has a hole in the center, it is possible to prevent concentration of heat generation and improve durability and image quality. There is d

[Brief explanation of drawings]

The first figure is a perspective view of a conventional thermal head, the second figure is an equivalent circuit diagram of the above thermal head, the third figure is an enlarged view of the main part of the first figure, and the fourth figure is a thermal head according to an embodiment of the present invention. In addition to the above, Figure 5 is a diagram to explain the characteristics of the conventional thermal head.
The 6th plane (a) is the resistor element (2a), the 6th
Section 1 (b) is shown in Figure 6 (a) No A-A line and ll
A diagram showing the experimental results of the temperature j codistribution on the -B line, the 6th (C
) is a plan view showing the state of the printed data due to the resistor element (2a); 7th
Figure (a) is a plan view of the resistor element (4a), seventh figure] (
1)) shows the experimental results of the temperature distribution on the A-A line and the B-B line in Figure 7 (3), and No. 7 Kl (C) shows the state of the printed dots due to the resistor element (4a). FIG. (])...-(Niramic substrate (insulating substrate), (4
a) to (4f)...JJ (antibody element, (5)...hole, (6a) to (6f)...conductor. In the diagrams, the same reference numerals indicate the same or Japanese part. Agent 47 Nobu Nobu - Figure 1 Figure 3 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] (1) An insulating substrate, a resistor element formed on the insulating substrate and having a substantially circular hole in the middle thereof, and a resistor element formed on the insulating substrate and connected to the resistor element. A thermal head comprising: a conductor for passing current through the resistor element. +21 The thermal head according to claim 1, wherein the hole in the resistor element is formed in an area such that a difference in resistance value between adjacent resistor elements becomes small. (3) The thermal head according to claim 1 or N(2), wherein the hole in the resistor element is formed by irradiating a laser beam.