JPH04289685A - Transparent sheet-like heater - Google Patents

Abstract

PURPOSE:To uniformly and efficiently heat by laminating in order an adhesive layer, a transparent substrate, a transparent conductive thin film, a transparent insulating layer, anadhesive layer and a transparent film layer while having an electrode consisting of conductive resin on both ends of the transparent conductive thin film. CONSTITUTION:A conductive thin film layer 2 is formed by performing sputtering on a polaester film substrate 1, the back is provided with an adhesive layer 3 by applying an adhesive in order to obtain a transparent film. This film is cut to provide an acrylate group transparent insulating layer 4 while leaving both ends, later, an Ag paste is printed on both ends in order to obtain a conductive resin layer 5 of a first layer. Continuously, a copper foil 6 is pasted on the layer 5, further, thereon a second layer and a third layer of Ag paste is printed exactly similarly to the layer 5. Further, a transparent film 9 is laminated through an adhesive layer 8 having an acrylate group adhesive so as to allover cover in order to obtain a transparent sheet-like heater. Thereby, a result of visible ray transmittivity of 73% and 5.5OMEGA of a heater can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent heater, and more particularly to a heater for liquid crystal elements.

The operating characteristics of a liquid crystal element are greatly influenced by the environmental temperature in which it is installed. When the temperature drops,
For example, when the temperature is below 0°C, the response speed decreases, and when the temperature is below -30°C, it becomes a practical problem.

[0003] For example, devices used as various displays in automobiles and the like are desired to operate normally even at low temperatures.

[0004] Conventionally, liquid crystal elements used in such an environment have been heated by a heating resistor arranged in a lattice shape or around the periphery (for example, as disclosed in Japanese Unexamined Patent Publication No. 126517/1983,
Japanese Utility Model Application Publication No. 59-106124) has been proposed. With this method, it is difficult to uniformly heat the entire liquid crystal element, and the placement of an opaque heating resistor may interfere with the display of the liquid crystal element, and may also reduce the display area. There is.

[0005] In recent years, a heating element in which a metal thin film is formed on a transparent sheet has been proposed. For example, Jikko Sho 61-196
There is a publication No. 222. However, it has been difficult to uniformly and efficiently heat the entire liquid crystal element.

[0006] The inventors of the present invention have made extensive studies to solve these problems, and as a result, have arrived at the present invention.

That is, a transparent surface in which electrodes are provided at both ends of a transparent conductive thin film laminated on a transparent substrate, and heat is generated in the transparent conductive thin film between the electrodes by applying a voltage to the electrodes. The heater has a structure in which an adhesive layer, a transparent substrate, a transparent conductive thin film, a transparent insulating layer, an adhesive layer, and a transparent film are laminated in this order, and both ends of the transparent conductive thin film are conductive. This is a transparent planar heater having an electrode made of a resin, a conductive metal foil having an insulating adhesive layer, and a conductive resin covering the conductive metal foil.

According to the present invention, it is possible to uniformly and efficiently heat the entire liquid crystal element.

FIG. 1 shows a cross-sectional view of the transparent sheet heater of the present invention.

The transparent substrate 1 used in the present invention can be made of polyester resin, polynaphthalate resin, polyamide resin, polyimide resin, acrylate resin, polycarbonate resin, or conventionally known polymer resins, and may be in the form of a plate or a film. Any condition is acceptable. A polymer resin in the form of a film with a thickness of 50 to 500 μm is used from the viewpoints of subsequent processing such as electrode processing, protective layer processing, and further processing such as attachment to a polarizing plate, light weight, and impact resistance. Particularly suitable is a thickness of 75 to 180 μm.

The adhesive layer 3 of the present invention is made of a conventionally known adhesive,
Although any pressure-sensitive adhesive can be used, an acrylate-based pressure-sensitive adhesive is preferably used from the viewpoint of workability to the transparent substrate, attachment to the polarizing plate 11 described below, and durability.

The thickness of the adhesive layer 3 is not particularly limited, but it is usually 5 to 100 μm, particularly 10 to 70 μm. The adhesive layer 3 may be formed by processing the transparent conductive thin film 2 on the transparent substrate 1 in advance, or may be processed on the other side after the transparent conductive thin film 2 is processed on the transparent substrate 1. I can do it. Particularly in the latter case, a high quality transparent conductive thin film 2 can be obtained.

[0013] After processing the transparent film 9 having the transparent substrate 1, transparent conductive thin film 2, transparent insulating layer 4, electrodes and adhesive layer 8, the adhesive layer 3 may be processed. In particular, in this case, compared to the case where the adhesive layer 3 is processed in advance as described above, there is a possibility that there will be damage between each layer due to cutting powder of the adhesive during subsequent processing and handling and adhesive extrusion during the processing process. Since contamination can be removed, transparent planar heaters can be obtained with higher yield. When this processing method is used, it is preferable to process an appropriate prevention layer on the back surface of the transparent substrate 1 in advance in order to prevent the generation of scratches or oligomers on the transparent substrate 1 during the processing step.

The transparent conductive thin film 4 used in the method of the present invention is usually a metal thin film, a semiconductor thin film, or the like. The metal thin film is made of Ag,
Cu, Au, Ni, Al, Cr, etc. are known, but from the viewpoint of transparency and conductivity, it is preferable to use one selected from the group of Ag, Cu, and Au or an alloy.

The thickness of the metal thin film is 10 angstroms or more from the viewpoint of transparency and the amount of heat generated with respect to the applied voltage.
00 angstroms or less is selected, and in particular, 50 angstroms or more and 300 angstroms are preferably used. Of course, in order to further improve transparency, a structure may be adopted in which a high refractive index dielectric layer is combined.

[0016] The semiconductor thin film is made of In2O3, SnO2
, ITO, etc. are known, but in terms of the amount of heat generated, 2
A film thickness of 00 angstroms or more and 7000 angstroms is used, and a film thickness of 700 angstroms or more and 5000 angstroms is particularly preferred. As semiconductor thin films become thicker, their bending resistance decreases, so care must be taken.

The above metal thin film is particularly excellent in terms of electrical resistance, electrode processing, and processing of the transparent insulating layer 4.

These thin films are placed on the transparent substrate 1 described above.
It is formed by a conventionally known method.

For the transparent insulating layer 4 in the method of the present invention, conventionally known thermosetting or ultraviolet curing resins are used. Any resin may be used as long as it is transparent, but from the viewpoint of durability, one with a low content of halogen elements is preferred, and is usually 500%
ppm or less, particularly preferably 100 ppm or less. The transparent insulating layer 4 is provided by a conventionally known printing method, coating method, etc., and has a film thickness of 2 to 50 μm, particularly 5 to 30 μm.

The electrodes 10 in the method of the present invention are formed on both ends (both ends in the sense of an electric circuit) of the transparent conductive thin film 2.

A conductive resin 5 is formed on the transparent conductive thin film 2 by a conventionally known method such as a printing method or a coating method. The conductive resin layer 5 is usually made of silver powder, gold powder, carbon powder, or other metal powder, and vinyl, phenol, epoxy, or other metal powder.
Any mixture with a polyamide resin or the like can be used. In particular, from the viewpoint of conductivity as an electrode, a mixture of silver powder and the above resin system is preferably used. The film thickness after firing is 2 to 20 μm, usually 5 to 20 μm.

[0022] In the method of the present invention, on the conductive resin layer 5,
A conductive metal foil 6 having an insulating adhesive layer is provided. The conductive metal foil 6 can be copper, silver, gold, or any other metal foil, but copper foil is sufficient and a film thickness of 5 to 50 μm is usually used. Resin layer 5
The film thickness of the conductive metal foil 6 is 15 to 50μ in order to improve the processability of the conductive resin layer 7, the subsequent processability of the conductive resin layer 7, the processability of the transparent film 9, and to avoid appearance defects such as air bubbles.
m is preferably used.

Note that the insulating adhesive layer provided on the conductive metal foil 6 usually has a thickness of 5 to 100 μm from the viewpoint of processability.
A film thickness of pressure sensitive adhesive is provided. In particular, the conductive resin layer 5
Adhesive force to the electrode part 10, overall thickness of the transparent film 9
A thickness of 10 to 60 μm is preferably used to prevent air bubbles from being trapped after processing. The insulating adhesive layer can reduce costs compared to conventional conductive adhesives, and
As mentioned above, since the film thickness of the entire electrode portion can be kept small, it is excellent in terms of workability.

In the method of the present invention, a conductive resin layer 7 is formed on the conductive metal foil 6 so that the conductive metal foil 6 is entirely covered.
Processed in one or two layers. The conductive resin layer 7 may be made of the same material as the conductive resin layer 5, or may be made of a different material as described above. The film thickness per layer is 2 to 20 μm, preferably 5 to 20 μm after firing. In one-layer processing, the conductive resin layer may not adhere well to the ends of the conductive metal foil, so two-layer processing is preferable.

In the method of the present invention, a transparent film 9 having an adhesive layer 8 is further provided on the above-mentioned structure by a conventionally known method such as lamination. The adhesive layer 8 is not particularly limited, and may be the same type as the adhesive layer 3 with a thickness of 5 to 100 μm.
m, especially 10 to 70 μm is commonly used. transparent film 9
is made of the same kind of material as the transparent substrate 1, and preferably has a thickness of usually 1 to 100 μm, particularly 5 to 50 μm.

The thus obtained structural body 15 is used by laminating the polarizing plate 11, the liquid crystal element 12, and the polarizing plate 13 in advance, and then press-bonding the layers.

Examples will be shown next, but the method of the present invention is not limited thereto.

[0028]

[Example 1] On a 125 μm polyester film,
Ag-Cu (Cu10
Sputtering is performed using a target (% by weight),
A conductive thin film layer having a thickness of 160 angstroms is formed to obtain a transparent conductive film. Visible light transmittance 75% (at
550 nm), and the surface resistance was 7Ω/□.

Next, a 40 μm thick acrylate pressure-sensitive adhesive is applied to the back surface of the transparent conductive film to obtain a transparent conductive film coated with an adhesive.

The above-mentioned transparent conductive film was cut into 100 mm square pieces, and an acrylate-based transparent insulating layer (manufactured by Teikoku Ink, TEC-4440) was cut to a width of 80 mm and a film thickness of 20 μm, leaving 10 mm on each end. After screen printing, it is irradiated with ultraviolet light to harden it.

[0031] After that, Ag paste was printed on both ends with a width of 10 mm to a film thickness of 10 μm (converted to film thickness after drying).
Dry at 0° C. for 30 minutes to obtain a first conductive resin layer. Next, a copper foil with a thickness of 30 μm having a width of 5 mm and a length of 120 mm and an acrylate adhesive layer of 20 μm is pasted on top of the first layer of conductive resin, and on top of that, a first layer with a width of 10 mm is applied. In exactly the same way as above, apply Ag paste to the second and third layers.
Print layers and dry.

Furthermore, on the above structure, a 100 mm square protective film made of a 25 μm thick polyester film having an acrylate adhesive (20 μm thick) was laminated so as to cover the entire surface, thereby forming a transparent planar heater. get it. The visible light transmittance of the thus obtained heater was 7.
At 3%, it was 5.5Ω.

The heaters obtained as described above were visually inspected, and the appearance acceptance rate was calculated using foreign matter of 0.15 mm or less as an acceptance criterion, and as a result, 60% passed the inspection. Then,
The heater obtained above was pressure-bonded to the polarizing plate, liquid crystal element, and polarizing plate as shown in Figure 3, and kept in a constant temperature oven at -20°C. When a voltage of 13V was applied to the electrode part for 1 minute, the heater The surface temperature was measured at five points within the surface and was within the range of 5°C±3°C, and when the liquid crystal element was driven, it was driven uniformly over the entire surface.

[0034]

[Example 2] In the same manner as in Example 1, a conductive thin film layer was formed on a polyester film (125 μm) whose back surface had been previously processed with a silicon-based hard coat layer. Visible light transmittance 76%, surface resistance 7.1Ω/□
A conductive film was obtained.

A transparent insulating layer was printed on the above conductive film under the same conditions as in Example 1, and then a first conductive resin layer, a copper foil with an acrylate adhesive layer, a second layer, and a third layer were printed on the conductive film.
Conductive resin layers are laminated, and a protective film is further laminated in the same manner as in Example 1. Next, in advance,
Acrylate adhesive layer sandwiched between release films (thickness: 40 mm)
A transparent sheet heater is obtained by transferring the adhesive layer onto the hard coated surface while peeling off one of the release films. Visible light transmittance 73.5%,
It was 5.6Ω.

[0036] As in Example 1, the appearance pass rate was examined by visual inspection, and 80% passed. Example 1
The defects caused by foreign particles caused by adhesive powder, which were seen in the rejected products, have been greatly reduced, and most of the defects were caused by dust that seemed to have gotten mixed in during processing.

[0037] Similarly to Example 1, when the surface temperature is kept in a -20°C constant temperature bath and a voltage of 13V is applied for 1 minute, the surface temperature is measured at 5 points on the surface and is within the range of 5°C ± 3°C. It is in
The liquid crystal element driven in the same manner as in Example 1 operated uniformly over the entire surface.

[0038]

[Comparative Example 1] A heater was produced in the same manner as in Example 2 except that the hard coat layer was not processed on the back surface and the step of transferring the adhesive layer to the back surface was omitted.

The appearance pass rate by visual inspection was 20%. When the defective product was inspected, it was found that there were many scratches on the back surface, and that the entire heater was cloudy due to oligomer precipitation due to heat treatment during processing.

The obtained transparent planar heater was placed on the polarizing plate side of the liquid crystal element, and the surface end electrode portion of the heater was held down with a jig, and the in-plane temperature was measured at -20° C. in the same manner as in Example 1.
There is a large variation of 5°C ± 15°C, and when the liquid crystal element is driven, there are parts in the plane of the liquid crystal element that are operating and parts that are extremely slow to operate, and even a part of the center part is not activated. I didn't.

[Brief explanation of the drawing]

FIG. 1 shows a conceptual cross-sectional view of a transparent sheet heater of the present invention.

FIG. 2 shows a conceptual cross-sectional view when used in combination with a liquid crystal element.

[Explanation of symbols]

1 Transparent substrate 2 Transparent conductive thin film 3, 8
Adhesive layer 4 Transparent insulating layers 5, 7 Conductive resin layer 6 Conductive metal foil with insulating adhesive layer 9 Transparent film 10 Electrodes 11, 13 Polarizing plate 12 Liquid crystal element 14 Backlight

Claims (1)

[Claims] [Claim 1] A transparent surface having electrodes provided at both ends of a transparent conductive thin film laminated on a transparent substrate, and applying a voltage to the electrodes to generate heat in the transparent conductive thin film between the electrodes. The heater has a structure in which an adhesive layer, a transparent substrate, a transparent conductive thin film, a transparent insulating layer, an adhesive layer, and a transparent film are laminated in this order, and both ends of the transparent conductive thin film are conductive. A transparent planar heater comprising a resin, a conductive metal foil having an insulating adhesive layer, and an electrode made of a conductive resin covering the conductive metal foil.