Iridescent film with thermoplastic elastomeric components

Abstract

Improvements in multilayer light reflecting film are effected by the use of a thermoplastic elastomer resin in a system in which two or more resinous materials form a plurality of the layers.

Description

BACKGROUND OF THE INVENTIONThe present invention relates to multilayer coextruded light-reflecting films which have a narrow reflection band due to light interference. When the reflection band occurs within the range of visible wavelength, the film is iridescent. Similarly, when the reflection band falls outside the range of visible wavelength, the film is either ultraviolet or infrared reflecting. Such multilayer films and methods by which they can be produced are known in the art.The multilayer films are composed of a plurality of generally parallel layers of transparent thermoplastic resinous material in which the contiguous adjacent layers are of diverse resinous material whose index of refraction differs by at least about 0.03. The film contains at least 10 layers and more usually at least 35 layers and, preferably, at least about 70 layers.The individual layers of the film are very thin, usually in the range of about 30 to 500 nm, preferably about 50-400 nm, which causes const...

AI Technical Summary

Benefits of technology

This invention relates to an improved multilayer light-reflecting film and more particularly to a transparent thermoplastic resinous film of at least 10 generally parallel layers in which the contiguous adjacent layers are of diverse transparent thermoplastic resinous material differing in refractive index by at least about 0.03 and at least one of the resinous materials being an engineering thermoplastic elastomer resin.

Problems solved by technology

Examination of iridescent films of desirable optical properties revealed deficiencies in certain mechanical properties.

For example, the adhesion between individual layers of the multilayer structure may be insufficient, and the film may suffer from internal delamination or separation of layers during use.

Delamination of the film is unsightly and may even lead to separation of the glued joints of carton.

In additional, the solvent resistance and heat stability of such films are not as great as desired for widespread utilization.

That fact, in turn, means that there are inherent significant differences between the two polymers and their relative adhesion to each other, chemical resistance, toughness, etc.

As a result, the film itself is generally no better than a particular characteristic than the weaker or poorer of the polymers employed.