TECHNICAL FIELD

The present invention relates to a functional sheet for sunglasses in which a protective layer formed by a transparent plastic sheet or film is laminated on at least one surface of a functional layer, which is a polyvinyl alcohol-based polarizing film layer, a photochromic layer, or a combination of these layers, with an adhesive layer being interposed there between, and a functional lens for sunglasses.

BACKGROUND ART

A functional sheet is obtained by laminating a transparent plastic sheet or film, particularly, an aromatic polycarbonate resin sheet or the like on a polarizing film, which is obtained by dyeing a polyvinyl alcohol-based film (hereinafter, PVA) with a dichroic dye, a photochromic layer in which a photochromic dye is dispersed in a matrix resin, or a functional layer obtained by combining the polarizing film and the photochromic layer, by using a two-component thermosetting resin or the like as an adhesive. The functional sheet is subjected to heat bending, and then, from the viewpoint of improving durability, the heat-bent product is inserted into a mold to obtain an injection molding lens. Functional polycarbonate lenses for sunglasses using this injection molding lens have been generally widespread (Patent Document 1).

It has been pointed out that these functional polycarbonate lenses have a problem in that, in a case where the lens is used in a frame for glasses formed by plastic containing a plasticizer such as cellulose acetate, the plasticizer in the frame for glasses is bled out to cause cracks in lenses configured by a polycarbonate resin. From these circumstances, disclosed is a polarizable laminate for sunglasses, or the like, in which a sheet formed by a polyamide resin is stretched to impart a retardation, thereby obtaining a protective layer (Patent Document 2).

CITATION LIST

Patent Document

Patent Document 1: JP H08-313701 A

Patent Document 2: JP 4739950 B2

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

An object of the present invention is to provide a polyamide functional sheet in which air bubbles are not generated or are considerably reduced in a polarizing and/or photochromic functional sheet when the polarizing and/or photochromic functional sheet is manufactured using a sheet or film formed by the above-described polyamide resin as a protective layer, and a polyamide functional lens using the polyamide functional sheet. Incidentally, in the present specification, a sheet and a film are not discriminated. That is, the sheet or the film is simply referred to as the sheet or simply referred to as the film in some cases, but these have the same meaning.

As described above, there is a demand for a functional sheet using a polyamide resin sheet as a protective layer because of chemical resistance of the polyamide resin. When a functional sheet is manufactured by changing a protective layer of a polycarbonate functional sheet having hitherto been manufactured to a polyamide resin sheet, the present inventors have observed generation of air bubbles at such a degree that the appearance of the sheet is impaired.

Manufacturing conditions except that an aromatic polycarbonate sheet is changed to a polyamide resin sheet are the same. Since air bubbles are observed after the protective layer is attached to the functional layer with an adhesive layer being interposed therebetween, the air bubbles are considered to be generated by reaction between the adhesive layer and the functional layer. The present inventors have studied a difference in physical properties between the aromatic polycarbonate sheet and the polyamide resin sheet, and as a result, have focused on the difference in gas barrier properties between the both sheets and conducted comparison examination. As a result, it becomes clear that the polyamide resin sheet has higher gas barrier properties than the aromatic polycarbonate sheet as shown in a low oxygen transmission rate.

That is, it is considered that gas generated by reaction between components of the adhesive layer and the functional layer is confined by the protective layer formed by the polyamide resin having high gas barrier properties, and as a result, air bubbles are generated.

If generation of air bubbles can be recognized during the manufacturing process, it is considered that the generation thereof is prevented by appropriately adjusting the cementing speed or stress of each layer in order to release the gas; however, it is difficult to specify a time point of generation of air bubbles and a manufacturing method in which this point has to be considered is not suitable for industrial manufacturing in terms of production efficiency.

In addition, regarding the adhesive, an adhesive used in manufacturing of the polycarbonate functional sheet by the present inventors is a thermosetting resin. In the invention of the present application, an adhesive layer formed by such a thermosetting resin can be stably used in heat bending and injection molding processes without being peeled off, and thus the adhesive layer is preferably used as long as air bubbles are not generated.

Solutions to the Problems

The inventors of the present application have found that generation of air bubbles that is problematic can be reduced or eliminated in the case of using a polyamide resin sheet exhibiting a predetermined oxygen transmission rate as a protective layer, thereby completing the invention of the present application. That is, the present invention is as follows.

(1) A polyamide functional sheet being obtained by disposing a protective layer formed by a transparent plastic sheet or film on at least one surface of a functional layer, which is a polyvinyl alcohol-based polarizing film layer, a photochromic layer, or a combination of these layers, with an adhesive layer being interposed therebetween, characterized in that the protective layer is a sheet or film formed by a polyamide resin, and an oxygen transmission rate at 23° C. and 85% RH is 50 cm3/m2·24 hr·bar or more.

In the invention of the above item (1), the polyamide functional sheet is characterized in that:

(2) the polyamide resin of the protective layer is a non-crystalline or microcrystalline polyamide;

(3) the adhesive layer is a urethane resin solvent-based adhesive; and

(4) a retardation of the protective layer is 200 nm or less or 2,000 nm or more.

In addition, the present invention also relates to

(5) a polyamide functional lens using the functional sheet described in the above items (1) to (4).

In addition, the present invention relates to

(6) a method for manufacturing a polyamide functional lens, the method including a step of punching the functional sheet described in any one of the above items (1) to (4) into an individual lens piece, and a step of heat bending the lens piece.

In addition, the present invention relates to

(7) a method for manufacturing a polyamide functional lens, the method including a step of punching the functional sheet described in any one of the above items (1) to (4) into an individual lens piece, a step of heat bending the lens piece, and a step of heat fusing a thermoplastic resin to a concave surface side of the sheet subjected to heat bending.

