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Polarizing Inserts for Lens Blanks

IP.com Disclosure Number: IPCOM000020270D
Publication Date: 2003-Nov-08
Document File: 5 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Abstract

This article discloses several proposed structures for polarizing inserts for use with sunglasses. These structures may be used with either prescription or plano lenses. Any suitable absorbing, or dichroic polarizer may be used in these inserts.

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Polarizing Inserts for Lens Blanks

Introduction.

The advantages of using a polarizer in a sunglass lens, whether it is a prescription lens or a plano lens, have been known for over half a century. In the last few years the use of polarizing sunglass lenses has become much more widespread. Accordingly, the technology of inclusion of a polarizing element into the structure of a sunglass lens is the object of considerable research and development. Since there are many different techniques for manufacturing lenses, there are corresponding polarizing structures that are especially suited for a particular lens manufacturing technique.

In the following we disclose a number of these structures suitable for inclusion in the most commonly used technologies for manufacturing prescription or plano lenses for use in the sunglass application. Nearly all polarizing films of the absorbing type, commonly referred to as dichroic polarizers, are based on the complex of polyvinyl alcohol, iodine and boric acid. Frequently, a number of dichroic dyes, usually from the class known as direct cotton dyes are substituted for iodine. A third type of polarizing film, especially suited to high temperature applications, is also made from the partial dehydration of the polyvinyl alcohol. In the following disclosure, our reference to a polarizing film is intended to mean any of the above-described types.

Glass Laminated Lenses

Because of its properties of hardness and high optical quality, glass is still used in the manufacture of lenses in spite of its excessive weight. An “unsupported” polyvinyl alcohol polarizing film, with a typical thickness of 0.02 to 0.05 mm, is a suitable polarizing insert for glass lenses. The polyvinyl alcohol develops an excellent bond with a number of adhesives currently used in the glass industry. Examples of such adhesives are listed below:

  1. UV-cure: Loctite 3491 and Loctite 3492. Noland Adhesives NOA60 and NOA71
  2. Thermal cure: Epo-Tek 301 and 305

In the making of a polarizing glass lens, the polarizing film is first vacuum formed to the desired curvature, then it is mated between two glass shells with the coupling adhesive and subsequently cured. The glass shell may contain additional colorant and other funtionality such as photochromism, antireflection coatings, etc.

An alternative structure to a thin polarizing film is the structure represented below in Fig.1, where the polarizing film 2 is laminated to each side of a central support film 1.

The support film may be any suitable thermoplastic film such as cellulose acetate butyrate or cellulose triacetate. The support film is preferably optically isotropic or very low in optical retardance so as not to interfere with the polarizing function of film 2. The polarizing films 2 are laminated to the support film 1 after the surfaces of film1 are rendered hydrophilic by a conventional hydrolysis treatment. A suitable bonding agent for laminating film1 to films 2 is an aqueous solution of polyvin...