Method for producing polarizing element

1. A method for producing a polarizing element, comprising the steps of:

forming a coating film of a metal on a glass substrate;

forming an island-shaped film composed of a metal halide on the glass substrate by partially removing the coating film and also halogenating the metal;

forming needle-shaped particles of the metal halide by stretching the glass substrate through heating to elongate the island-shaped film; and

forming needle-shaped metal particles composed of the metal by reducing the metal halide of the needle-shaped particles.

2. The method for producing a polarizing element according to claim 1 , wherein the step of forming the island-shaped film composed of the metal halide includes the steps of:

forming the island-shaped film by etching the coating film; and

halogenating the metal by exposing the glass substrate to a gas containing a halogen or a halogen compound.

3. The method for producing a polarizing element according to claim 1 , wherein the step of forming the island-shaped film composed of the metal halide is a step of exposing the coating film to plasma of a gas containing a halogen or a halogen compound, thereby halogenating the metal while partially removing the coating film.

4. The method for producing a polarizing element according to claim 1 , wherein the metal is one or more metals selected from Au, Ag, Cu, Cd, and Al.