Iodine stained light polarizer

• US 4,166,871 A
• Filed: 04/27/1978
• Issued: 09/04/1979
• Est. Priority Date: 06/29/1977
• Status: Expired due to Term

• Current Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Original Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Inventors: Schuler, Norman W.
• Primary Examiner(s): Hoffman, James R.
• Application Number:
  US05/900,728
• Time in Patent Office: 495 Days
• Field of Search: 427/160, 427/163, 350/154, 350/155
• US Class Current: 427/163.1
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid

Abstract

A visible range light polarizer is prepared by staining an oriented film of polyvinyl alcohol with a solution containing iodine and its red light dichroism is enhanced by treating the stained film with a boric acid solution containing a zinc salt.

Claims

1. A method of preparing a light polarizing element which comprises:

uniaxially stretching a film of polyvinyl alcohol; and

staining the stretched film with an iodine solution; and

treating the stained film with an aqueous solution containing zinc ion in a concentration effective to stabilize absorption of red light by the polarizer against degradation on heating.

2. The method of claim 1 wherein the stained film is treated with an aqueous solution of boric acid.

3. The method of claim 2 wherein said solution of boric acid additionally contains potassium iodide.

4. The method of claim 2 wherein said boric acid solution contains said zinc ion.

5. The method of claim 4 wherein said zinc ion results from dissolving zinc chloride in said solution.

6. A method of preparing a light polarizing element which comprises:

uniaxially stretching a film of polyvinyl alcohol; and

staining the stretched film with an iodine solution; and

treating the stained film with an aqueous borating solution containing zinc ion in a concentration effective to stabilize absorption of red light by the polarizer against degradation on heating.

7. The method of claim 6 wherein said aqueous borating solution containing zinc ion additionally contains potassium iodide.

8. The method of claim 7 wherein said aqueous borating solution comprises boric acid.

9. In a light polarizing sheet comprising a uniaxially stretched film of polyvinyl alcohol stained with iodine, the improvement wherein said film comprises zinc ion which is absorbed by said film after it is stained with iodine, in a concentration whereby absorption of red light by said polarizer is stabilized against degradation on heating.

10. The polarizer of claim 9 which additionally comprises a complex of said polyvinyl alcohol and boric acid.

11. The polarizer of claim 10 which additionally comprises potassium iodide.

12. The polarizer of claim 9 which additionally comprises potassium iodide.