JPS58162356A - Thermal printer head - Google Patents

Abstract

PURPOSE:To make the temperature distribution on the surface of a heating part uniform, by making the length of the central part of a resistor part in the current flowing direction longer than that of the side edges of the resistor part, thereby constituting the thermal printer head. CONSTITUTION:End parts 3A and 4A of electrodes 3 and 4 which are provided on the surface of the resistor 2 are made to be an arc shape. The length of the central part of the resistor part 2A in the longitudinal direction is made long. The length of the resistor part 2A becomes shorter toward the side edges 2B and 2C. Therefore, a current density in the vicinity of the central part is smaller than that in the vicinity of the side edges. Thus the surface temperature in the vicinity of the central part is not increased very much, and the temperature distribution in the vicinity of the central part along the width direction becomes flat. When heat sensitive paper is colored under this state, the coloring density at the coloring part becomes approximately uniform to the vicinity of its peripheral part.

Description

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

As is well known, this type of F/fi is constructed by a pair of opposing current-carrying W poles and four resistors placed between the two electrodes (1).
'J' is arranged so that both electrodes IJ'
By applying l[1rEE, the resistor KWf
M is used to generate heat.

Normally, when using a thin film as a resistor, f:
The configuration is such that it accepts Figure X1 Vc. In the same figure, 1
Reference numerals denote an insulating substrate made of ceramic or the like, a resistor with a thickness of 2 orders of magnitude (for example, α05 to α15 μm), a pair of current-carrying W poles (about 2 μm thick) at 3° and 4, and a protective film of 5. Resistor 2Fi is elf on the surface of substrate 1, and 11 is on the surface.
rWA3.4 is Jlif! It is set up like this. W pole 3
, 4, each end 3A of the W pole 3.4,
Resistor part 2A that forms one dot existing between 4A
Figure 5 shows a part of a conventional head of this type without the protective film. This is a top view, and when a voltage is applied between both electrodes 3 and 4, the resistor portion 2A has a voltage from one electrode, for example, the end 3A of the electrode 3 to the other end 4A of the electrode 1'f@4. The W style is flowing towards us. Here, if W residue flows evenly in any part along the width direction of the resistor part 2A, it will flow in the part of the resistor part 2A shifted by b, and the amount of heat will be almost uniform. Book, both side edges 2B of resistor part 2A
.

2C is open to the outside, 〒, 911N2B, 2C
75x and others will dissipate heat to the outside. Therefore, the surface temperature distribution in the resistor portion 2A is as shown in the surface temperature curve B shown in FIG. The surface temperature gradually decreases from the top.

Resistor portion 2A'ft4 with such surface temperature distribution
．． If you make thermal paper color, the coloring part F!
If the color development area for one dot of 1% is small, it will be dark (colored) in the center of 1000, and lighter (lighter than this at the edge of 111). In order to avoid this, it is possible to increase the supplied power, increase the current flowing through the resistor portion 2AKfN, raise the surface temperature near the side walls 2B and 20, and increase the color density produced by this portion. Good. However, suddenly the central part becomes even higher, which promotes oxidation in this high temperature part. As oxidation progresses, that part becomes degraded, and in some cases, the altered part may be cut off. .

The purpose of this invention is not to increase the power supply, but also to equalize the temperature distribution on the surface of the heat generating portion of the resistor.

In this invention, the length direction along the dipping direction of fWr in the resistor portion 2A (the length of each end 3A, 4A of the electrodes 3, 4) is placed in the center with a b, and the area is As clearly shown in FIG. The resistor portion 2A has a circular arc shape, so that the length of the resistor portion 2A is longer in the center and shorter toward the side edges 2B and 20.

With this configuration, if the thickness of the two resistor parts is uniform, the part near the center will be long, so the resistance value in this part will be low.

The resistance value becomes lower as it approaches 2C. Therefore, in the conventional example shown in Figure 5, the current density of the two resistor parts was uniform in all parts, whereas in the case of the example shown in the figure, the wi density near the center was (Illll edge Therefore, the surface temperature near the center does not increase that much (as shown in the temperature distribution curve 1sA shown in Fig. flat and fk
debt. If the thermal paper is colored with such a temperature distribution pattern i1, the color density of the liquid in the coloring area will be almost uniform to the vicinity of the periphery. As a result, the color development area for one dot during printing becomes almost equal to the area of the resistor portion 2A, and the print quality is improved. Local breakage of the two resistor parts will no longer occur, and its lifespan will be extended by 4 years.

As shown in Figure 2 and *3, if the edges of the two resistor parts are made into a continuous circular arc, the resistance value will be the smallest between the edges 2B and 20, so the current will be applied here. becomes more concentrated. As a result, there is a risk that the edge W pole in the edge PK will be melted, but in order to solve this problem, as shown in Fig. 4, a slightly flat part Mf is formed near the edge #)P. If the current is not concentrated, the melting of the electrode will be reliably prevented.
Nahu.

In the above embodiments, the resistor 29w pole 3.4 is made thin, but the present invention can be applied to a case where one or both of them are formed as a thick film. Also, in the embodiment shown in the figure, the electric wit resistor is overlapped on the surface, but instead of this, it is possible to overlap the resistor (in this case, the resistor is often a thick film) across the surfaces of both electrodes. You may also do so.

According to the experimental results of the present inventor, the length at the center of the resistor portion 2A is preferably about 10 to 30 q/) longer than the length at the sides 1jk2B%2C, and when the length exceeds 30%, the length is < Suddenly, the heat generation temperature in the center decreases and the temperature distribution is not uniform.
If it is less than 0%, the temperature distribution will be significantly different from that of conventional books.

As detailed above, according to the present invention, it is possible to make the temperature distribution uniform over almost the entire surface of the heat-generating resistor portion, and as a result, the print quality can be made higher than that of conventional methods. Since it is not necessary to increase the power supplied to the power supply, it is effective to avoid the decrease in service life caused by localized high temperatures.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an embodiment of the invention, Figure 2 is Fi
FIG. 3 is a perspective view of the main part, FIG. 3 is a plan view of the main part showing a temperature distribution curve, FIG. 4 is a plan view of the main part showing another embodiment of the present invention, and FIG. 5 is a conventional example of IjA. A plan view with a power distribution curve.

Claims (1)

[Claims] A pair of energizing Wlf[[A resistor is provided which straddles and overlaps both the electrodes, and by applying a voltage between the two electrodes, the tia body s molecules that exist between the two electrodes''@
In a thermal printer head that is heated, the main length of the resistor part along the direction of the flow of wfii is set at the center of the resistor part from the edge.