JPH0362492A - Transparent face heating element - Google Patents

Abstract

PURPOSE:To uniformly generate a heat from the whole heat generating surface by giving a surface resistance value according to the change of distance between electrodes of a transparent face heating element in which a pair of facing electrodes are not parallel to each other to a transparent conductive film. CONSTITUTION:The thickness of a transparent conductive film is changed according to the distance between electrodes to change the surface resistance value. Namely, the transparent conductive film is thinned where the distance between electrodes is long, and thickened where the distance between electrodes is short. When the distance between electrodes is L cm and the surface resistance value of the transparent conductor is R (OMEGA/opening), the surface resistance value R of the part of the distance L is regulated according to the distance L between electrodes to satisfy the value of R=A/L<2> (wherein A is a constant determined by applied voltage). The surface resistance is changed in the longitudinal direction of the band electrode from side edge to side edge on the both sides having no pair of electrodes, but not changed in the direction along the distance between electrodes.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a transparent sheet heating element, and more specifically, it is capable of uniformly generating heat despite the difference in distance between opposing edges, and is suitable for use as a defroster, The present invention relates to a transparent sheet heating element that can be suitably used as a transparent heater or the like.

(Prior art) Conventionally, in order to apply a voltage to a transparent conductive film that becomes the heating element and generate heat by energization, a pair of band-shaped electrodes are attached to the transparent conductive film. Planar heating elements provided on opposing parallel edges are known.

(Problem to be Solved by the Invention) However, since the opposing edges of windows to which the above-mentioned transparent sheet heating element is applied are not necessarily parallel, the degree of freedom in the planar shape to which it is applied is severely limited. That will happen.

In addition, in a planar transparent sheet heating element whose opposing edges are not parallel, when a pair of non-parallel band-shaped electrodes are provided along the edges and a voltage is applied, the relative distance between the electrodes is When the distance between the electrodes is short, the electrical resistance between them is low, so the surface temperature becomes high; conversely, where the distance between the electrodes is long, the resistance value becomes high, so the surface temperature becomes low, and uniform heat generation cannot be obtained. Moreover, the heat generation effect is also poor. For example, when used as a defroster, the glass surface may partially fog up in areas where the surface temperature is low, blocking visibility, and may pose a risk of burns or the like in areas where the temperature is high. On the other hand, in order to obtain uniform heat generation, if a pair of band-shaped electrodes are installed straight in parallel by removing the curved portion of the curved edge of the transparent heating element, the electrodes Since the electrodes are located inside the edge frame, the electrodes become noticeable and unsightly, and the areas not sandwiched between the electrodes cannot generate heat.

The present invention is intended to solve the above-mentioned problems, and its purpose is to provide a transparent sheet heating element that can uniformly generate heat despite the difference in distance between opposing edges. .

(Means for Solving the Problems) The present inventors have conducted repeated research to solve the above problems, and as a result, they have arrived at the present invention.

That is, one aspect of the present invention is that in a transparent sheet heating element that generates heat through electric current by applying a voltage to a resistive heating element made of a transparent conductive film, a resistive heating element is formed on the surface of the transparent conductive film in which distances between opposing edges are different from each other along the edges. A pair of strip-shaped electrodes are provided, and the relationship between the distance L (cm) between the electrodes and the surface resistance value R (Ω/□) of the transparent conductive film is determined according to the change in the distance between the electrodes using formula 9 R=A/L2
The object of the present invention is to provide a transparent sheet heating element which is adjusted to satisfy (A: a constant determined by applied voltage).

Hereinafter, one aspect of the present invention will be explained in detail.

In the present invention, the electrical resistance of the transparent conductive film is changed depending on the distance between the electrodes. In other words, where the distance between the electrodes is long, the surface resistance value of the transparent conductive film is decreased to reduce the resistance value between the electrodes, whereas where the distance between the electrodes is short, the surface resistance value of the transparent conductive film is increased. to increase the resistance between the electrodes. By changing the surface resistance value of the transparent conductive film in accordance with the distance between the electrodes in this way.

Even if the distance between the electrodes changes, the resistance value between the electrodes can be made equal.

Specifically, the surface resistance value is changed by changing the thickness of the transparent conductive film depending on the distance between the electrodes.

That is, where the distance between the electrodes is long, the thickness of the transparent conductive film is set to less than 1, whereas where the distance between the electrodes is short, the thickness of the transparent conductive film is made thinner.

The distance between electrodes as used in the present invention is measured between two electrodes at right angles to a straight line connecting the ends of the opposite strip-shaped electrodes on the same side. However, in this case, the straight line connecting one end of the two electrodes and the straight line connecting the other end of the electrode are parallel.

FIG. 1 shows an example of a plan view of a transparent sheet heating element of the present invention. In FIG. 1, the distance between electrodes E is L.
The central part has the maximum inter-electrode distance Lm&K, and the opposite ends have the minimum inter-electrode distance Lai.

The distance between the electrodes is L (cm), and the surface resistance value of the transparent conductor is R.
(Ω/□), adjust the surface resistance value R at that distance according to the distance between the electrodes so that it satisfies the value of R=A/L2 (A: a constant determined by the applied voltage). do. The surface resistance value changes in the length direction of the strip-shaped electrode from edge to edge on both sides where a pair of electrodes are not provided, but the surface resistance value does not change in the direction along the distance between the electrodes.

The constant A determined by the applied voltage will be explained in more detail. Heat generation temperature (1) of heating element and power density (W/
cnf ), there is a correlation, so once the power density is determined, the temperature of one heat generation is determined.

Here, if the applied voltage is V (V), the power density is
Since D=V'/RxL" is given.

R=V 2/D

For example, the present invention provides a transparent material having two opposing edges, one of which is a straight line and the other curved, and the other two opposing edges having a parallel planar shape, as shown in FIG. It can be preferably applied to a planar heating element or a transparent planar heating element in which two opposing edges are both curved and the other two opposing edges are parallel. These transparent planar heating elements may not only be planar, but may also be three-dimensional and whose developed view has a planar shape as described above.

Next, nine application examples of the transparent planar heating element of the present invention will be given. 1st
The figure is a plan view of a transparent sheet heating element that is used by attaching it to a transparent shield that covers the front of a full-face helmet.The planar shape of this transparent sheet heating element is close to both edges in the vertical direction. However, it is narrow and wide in the center. by the way.

Full-face helmets use body heat to warm the inside of the helmet when the outside temperature is low, such as in the winter.

The inner surface of the helmet shield will become cloudy.

Visibility may be blocked, creating a dangerous situation. In order to prevent this fogging, the transparent sheet heating element of the present invention is coupled to the shield of the helmet and the shield is heated, thereby uniformly heating the shield and uniformly removing fog over the entire surface of the shield.

The transparent planar heating element of the present invention uses a transparent film or the like as a substrate, and indium oxide and tin oxide are placed on the substrate.

It is manufactured by forming a transparent conductive film of a metal oxide such as an indium oxide/tin oxide mixture (ITO) by a vacuum evaporation method, an ion blasting method, a sputtering method, or the like.

(Example) The present invention will be specifically explained below using two examples.

Example 1 A transparent polyethylene terephthalate film with a thickness of 75 μm was used as a substrate, and by vacuum evaporation method,
A transparent conductive film made of ITO was formed.

At that time, the horizontal length W = 30cm, Lmax = 13c
m.

When L, ゎ = 9 cm and the shape shown in Fig. 1 is used, the surface resistance value calculated by formula 9 R = A / L2 (however, A = 2500) is distributed as shown by curve a in Fig. 2. As shown, a transparent conductive film with a thickness of 0.2 to 0.3 μm is formed,
A transparent conductive film was created.

The obtained transparent conductive film was shaped as shown in FIG.

Strip-shaped electrodes E with a width of 1 cm are formed using conductive paste (silver paste) along the curved edges and straight edges that face each other, and then a lead wire is connected to each electrode E to form a full-face helmet. A transparent planar heating element for shielding was obtained.

This transparent sheet heating element was attached to the outer surface of the shield with a silicone adhesive so that the ITO side was on the shield side of the helmet.

A voltage of 12 V is applied to the transparent heating element on the outer surface of the shield using a DC power supply to generate heat in an atmosphere with a temperature of 10°C and a relative humidity of 60%.9 After 10 minutes of electricity application, the inside of the shield is measured using a contact surface thermometer. When the temperature (° C.) was measured, as shown by the numbers in FIG. 3, even when the pair of electrodes were not parallel, it was possible to generate heat uniformly over the entire surface of the shield.

Transmittance of the obtained transparent sheet heating element (parallel light 550 nm
The transmittance was 69% in the center where the surface resistance was low and the film was thick, and 73% in the high surface resistance near both the left and right sides.

There was no problem in using it as a helmet shield.

Comparative Example 1 A transparent conductive film having a surface resistance value of 15 Ω/□ was obtained in the same manner as in Example 1, except that a transparent conductive layer made of ITO with a uniform thickness of 0.3 μm was formed on the entire surface. A transparent planar heating element was made from the obtained transparent conductive film in the same manner as in Example 1, and then attached to the outer surface of the shield of a helmet to generate heat in the same manner as in Example 1. The temperature distribution was as shown. As is clear from FIG. 4, there is an extremely large temperature distribution, and it can be seen that heat is generated non-uniformly.

(Effects of the Invention) As described above, the present invention provides a transparent conductive film with a surface resistance value that corresponds to a change in the distance between the electrodes in a transparent planar heating element in which a pair of opposing electrodes are not parallel. 1
Uniform heat generation can be obtained over the entire heating surface.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of the transparent heating element of the present invention;
Figure 2 is a graph showing changes in surface resistance of the transparent sheet heating element, Figure 3 is a plan view of the transparent sheet heating element of the example with measured surface temperature values, and Figure 4 is the measured surface temperature values. FIG. 3 is a plan view of a transparent sheet heating element of a comparative example with .

Claims (1)

[Claims] (1) In a transparent sheet heating element that generates heat by applying a voltage to a resistive heating element made of a transparent conductive film and passing an electric current, a pair of resistive heating elements are placed on the surface of the transparent conductive film with different distances between opposing edges along the edges. Strip-shaped electrodes are provided, and the relationship between the distance L (cm) between the electrodes and the surface resistance value R (Ω/□) of the transparent conductive film is calculated using the formula R=A/L^2 according to the change in the distance between the electrodes. A transparent planar heating element, characterized in that it is adjusted to satisfy (A: a constant determined by applied voltage).