Protective film temporarily lamination to electromagnetic wave shielding sheet, method for producing the same, and electromagnetic wave shielding sheet

Abstract

The present invention is to provide an electromagnetic wave shielding sheet with a protective film that is temporarily laminated on a copper mesh layer for shielding electromagnetic waves, the electromagnetic wave shielding sheet is not discolored even after long-term use, especially at high temperature and high humidity, while the protective film exhibits appropriate adhesion properties. To achieve the object, there is provided an electromagnetic wave shielding sheet comprising a transparent substrate, at least a copper mesh layer provided on one surface of the transparent substrate and a protective film temporarily laminated to the copper-mesh-layer-side surface, the protective film comprises a support and an adhesive layer containing a polymer having repeating units derived from an acrylic ester and / or a methacrylic ester on the support, and the amount of free organic acids in the adhesive layer is an amount which makes 10 or less the color difference ΔEL*a*b* of the copper-mesh-layer-side surface of the electromagnetic wave shielding sheet before and after the adhesive layer surface is laminated on the copper-mesh-layer-side surface and they are left for 200 hours in an atmosphere of a temperature of 60° C. and a relative humidity of 95%.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an electromagnetic wave shielding sheet to shield electromagnetic waves produced from displays such as cathode-ray tubes (CRT) or plasma display panels (PDP.) In particular, the present invention relates to a protective film that causes no discoloration of an electromagnetic wave shielding sheet even after long-term storage at high temperature and high humidity, a method for producing the protective film, and an electromagnetic wave shielding sheet with the protective film.[0003]2. Description of the Related Art[0004]With the sophistication of function and the increasing use of electrical and electronic devices in recent years, electromagnetic interference (ERI) has increased and displays such as cathode-ray tubes and plasma display panels produce electromagnetic waves. To shield the electromagnetic waves, electromagnetic wave shielding sheets to be disposed on the front face of a displa...

AI Technical Summary

Benefits of technology

[0008]The present invention has been achieved in light of the above-stated problems. The object of the present invention is firstly to provide a protective film for temporary lamination to an electromagnetic wave shielding sheet, which film leaves no adhesive residue behind when peeled off and causes no partial peeling of a blackened layer and the like if the blackened layer and the like are further laminated on the copper mesh layer, while the film having appropriate adhesion properties that involves easy adhesion and easy peelability in a balanced manner with respect to a copper mesh layer of the electromagnetic wave shielding sheet. Especially, the present invention is to provide a protective film for temporary lamination to an electromagnetic wave shielding sheet that causes no discoloration of the electromagnetic wave shielding sheet even after long-term use, especially at high temperature and high humidity.

[0021]In the electromagnetic wave shielding sheet of the present invention, surface roughness of the copper-mesh-layer-side surface to which the protective film is temporarily laminated is preferably a ten-point average roughness “Rz JIS” (JIS B0601 (1994)) of the profile from 0.5 to 5.0 μm when a roughness profile is used as a profile of the surface, and a center line average roughness “Ra” (JIS B0601 (1994)) of fine irregularities on the surface from 0.1 to 3.0 μm from the viewpoint of appropriate adhesion and removability when combined with an adhesive specified in the present invention, that is, the protective film leaves no adhesive residue behind when peeled off and causes no partial peeling of a blackened layer and the like if the blackened layer and the like are further laminated on the copper mesh layer, while having easy adhesion and easy peelability.

Problems solved by technology

However, at the time of peeling off a protective film, some adhesives cause problems such that a blackened layer that is further laminated on a copper mesh layer is partially peeled off together with the protective film and adhesive residue is left behind.

In the case where a film having an adhesive layer is temporarily laminated to a conductive mesh layer such as a copper mesh layer, some adhesives cause a problem of blue-green discoloration of the copper mesh layer when the electromagnetic wave shielding sheet is stored for a longtime, especially at high temperature and high humidity.

Such discoloration of a copper mesh layer causes blue discoloration of the electromagnetic wave shielding sheet and the color reproducibility of a display is adversely affected.

This problem also occurs when a blackened layer comprising a thin film of cooper-cobalt alloy particles, nickel sulfide particles or the like is formed on a copper mesh and an adhesive layer is laminated thereon.

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