JPH07153313A - Transparent conductive adhesive - Google Patents

Abstract

PURPOSE:To provide an adhesive having transparent property and conductivity and high adhesion strength by containing needle-like indium tin oxide(ITO) with specified size and shape and providing specified transmittance for the whole light ray and specified specific resnstance. CONSTITUTION:A transparent and conductive adhesive is an adhesive containing needle-like ITO with 3mum longer diameter and the ratio of the longer diameter to the shorter diameter at least 5 and having 50% or more transmittance for the whole light ray and 10OMEGA.cm or less specific resistance and the adhesive has as high adhesion strength as 10kgf/cm<2> or more tensile shear strength. The needle-like ITO is prepared by calcinating tin-containing needle-like indium basic nitrate and one having 0.03OMEGA.cm green resistance is preferable. The adhesive is prepared by mixing the needle-like ITO with resin at ratio of needle-like ITO to resin (50:50)-(70:30) and, if necessary, adding and dispersing a solvent uniformly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a translucent and electrically conductive adhesive.

[0002]

2. Description of the Related Art Conventionally, as conductive adhesives, silver, copper,
A paste in which a conductive metal filler such as nickel is dispersed in a resin is used. For example, a silver paste obtained by dispersing silver powder in an epoxy resin or a polyimide resin has a specific resistance of 10 ⁻³ to 10 ⁻⁴ Ω · cm and a tensile shear stress of 10 to 70 kgf / cm ² . However, there is no adhesive that has a total light transmittance of 50% or more and is translucent and electrically conductive.

Generally, in a conductive adhesive, it is necessary that a resin component for adhesion be sufficiently present on the adhesive surface. However, when a particle-shaped conductive filler is used, it is necessary to use a large amount of the filler in order to exhibit conductivity, so that the resin content is reduced and the tensile shear stress is 10%.
It becomes difficult to obtain an adhesive strength of kgf / cm ² or more. The size of the conductive filler is several μm to several tens μ
A size of about m is preferable. Since the contact resistance between the conductive fillers is the highest, the size of the conductive filler is sub-μ.
If it is less than m, the conductivity will deteriorate. Further, when the size of the conductive filler is small, the capillary phenomenon is large, and thus the resin component is easily absorbed, so that the resin component on the adhesive surface is reduced and the adhesive strength may be reduced.

On the other hand, when the size of the conductive filler is large, the unevenness of the adhesive surface becomes large and the adhesive strength becomes small, which is not preferable. In order to obtain translucency with a total light transmittance of 50% or more, the coating film thickness is preferably about several μm to several tens of μm.
However, if the thickness of the coating film is reduced to several μm to several tens of μm,
There is a problem that the surface resistance of the adhesive increases.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a translucent and electrically conductive adhesive.

[0006]

In order to solve the problems of the prior art, the present invention is a needle-shaped indium oxide having a major axis of 3 μm or more and a major axis-minor axis ratio (hereinafter referred to as an aspect ratio) of 5 or more.
A transparent conductive adhesive containing tin oxide (hereinafter referred to as acicular ITO), having a total light transmittance of 50% or more and a specific resistance of 10 Ω · cm or less.

[0007]

In the present invention, in order to obtain high conductivity with a specific resistance of 10 Ω · cm or less and high adhesive strength with a tensile shear stress of 10 kgf / cm ² or more, a needle having a major axis of 3 μm or more and an aspect ratio of 5 or more is used as a conductive filler. ITO: powder is used. This acicular ITO powder is obtained, for example, by calcining acicular indium basic nitrate containing tin, and has a powder resistance:
It is preferably about 0.03 Ω · cm (powder resistance: specific resistance of powder measured under a pressure of 100 kgf / cm ² ).

This acicular ITO powder is added to a thermoplastic resin, a thermosetting resin, or an ultraviolet curable resin, if necessary, with a solvent or the like, and then dispersed to obtain a translucent conductive adhesive. As the above-mentioned resin, one having translucency and high adhesive strength is selected. The ratio of the acicular ITO powder to the resin is preferably in the range of acicular ITO: resin = 50: 50 to 70:30 by weight. If the amount of ITO is larger than this, the adhesive strength is low and it is difficult to use it as an adhesive. If the amount of needle-like ITO powder is less than that, the specific resistance becomes too high and the conductivity is insufficient. When granular ITO ultrafine powder is used as a conductive filler, in order to develop conductivity, IT
Since the granular ITO in the ratio of O: resin = 70: 30 or more is required, the adhesive strength cannot be obtained and it cannot be used as a translucent conductive adhesive.

In the adhesion with an adhesive, first, an adhesive is printed or applied on one adhesive surface, and if a solvent is contained, it is dried well to remove the solvent, and then the adhesive surface is attached to the other adhesive surface.
When a thermosetting resin or an ultraviolet curable resin is used, after bonding, each is heated and cured by irradiation with ultraviolet rays,
To glue.

[0010]

【Example】

(Example 1) After needle-like indium basic nitrate containing tin was calcined, 6.0 g of needle-like ITO powder having a low resistance of 1.7 wt% tin content and a powder resistance of 0.03 Ω · cm was prepared. , Table 1
4.0 g of the thermosetting resin and 4.6 of cyclohexanone
g was thoroughly mixed and the acicular ITO powder was dispersed to obtain a translucent conductive adhesive. This was applied to a primer-treated polyester film (HP-7 100 μm thick manufactured by Teijin Ltd.) with a wire bar having a wire diameter of 0.4 mm, dried by far infrared heating at 70 ° C. for 2 minutes to remove the solvent, and then the primer. The treated polyester film and the laminated polyester film were laminated as shown in FIG. 1 and further cured at 120 ° C. for 1 hour. After curing, the tensile shear stress and optical properties of the laminated samples were measured. Further, in order to examine the resistance and the film thickness of the adhesive layer, the surface resistance and the film thickness were measured by directly curing the adhesive coated and dried film without laminating them. Tensile shear stress,
Table 2 shows the total light transmittance, haze value, surface resistance, specific resistance, and film thickness.

Example 2 Bonding was performed in the same manner as in Example 1 except that the adhesive was applied using a wire bar having a wire diameter of 0.15 mm, and the same measurement was performed. The results are shown in Table 2.
Shown in.

(Example 3) A needle-like ITO similar to that of Example 1
6.0 g of the powder, 4.0 g of the ultraviolet curable resin shown in Table 1 and 1.5 g of cyclohexanone were mixed well, and the needle-like ITO powder was dispersed to obtain a transparent conductive adhesive. Wire diameter 0.3
After applying it to the polyester film that has been primed with a wire bar of mm
After drying for one minute and removing the solvent, the primer-treated polyester film was laminated in the same manner as in Example 1, and further cured by a metal halide lamp at an illuminance of 150 mW / cm ² for 10 seconds. After curing, the tensile shear stress and optical properties of the laminated samples were measured. In order to check the resistance and film thickness of the adhesive layer, the film coated with the adhesive and dried is not laminated but is cured in nitrogen gas with a metal halide lamp at an illuminance of 150 mW / cm ² for 10 seconds to obtain the surface resistance and film thickness. Was measured. The results are shown in Table 2.

(Embodiment 4) A transparent conductive adhesive produced by the same method as in Embodiment 1 is used, and the same wire diameter as in Embodiment 2 is 0.1.
Glass plate with ITO film formed by sputtering with 5 mm wire bar (surface resistance: 90Ω / □, total light transmittance: 88.4%, haze value: 0.2%, plate thickness 1 mm)
The same glass plate as the above-mentioned glass plate was laminated as shown in FIG.
It was cured in the same manner as in Example 1 and the tensile shear stress and optical properties were measured. The results are shown in Table 2.

The electrical resistance between the electrodes shown in FIG. 2 was measured. As a result, it was 41Ω. From this result, it is understood that the inter-electrode resistance is the resistance of the ITO film formed by sputtering, and the resistance of the adhesive layer of the translucent conductive adhesive is sufficiently low.

The film thickness is measured by a surface roughness measuring device manufactured by Tokyo Seimitsu Co., Ltd.
The surface resistance was measured with a trade name Surfcom 900A, and the surface resistance was measured with a trade name Loresta MCP-T400 manufactured by Mitsubishi Petrochemical Co., Ltd. The total light transmittance and the haze value were measured together with the glass plate of the substrate and the polyester film by a direct reading haze computer HGM-ZDP manufactured by Gas Test Machine Co., Ltd. Tensile shear stress is Shimadzu Autograph AGS-5
It was measured at 0A.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, a translucent and electrically conductive adhesive can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a bonding method in Examples 1 to 3 of the present invention.

FIG. 2 is a diagram showing a bonding method according to a fourth embodiment of the present invention.

[Explanation of reference numerals] 1 adhesive part 2 electrode (conductive tape)

Claims (1)

[Claims] 1. A needle-shaped indium-tin oxide having a major axis of 3 μm or more and a major axis / minor axis ratio of 5 or more, having a total light transmittance of 50% or more and a specific resistance of 10 Ω · cm or less. Characteristic translucent conductive adhesive.