K-sheet type polarizers prepared from polyvinyl alcohol graft copolymers

• US 3,914,017 A
• Filed: 11/05/1973
• Issued: 10/21/1975
• Est. Priority Date: 11/05/1973
• Status: Expired due to Term

• Current Assignee: Lloyd D. Taylor, Stanley F. Bedell
• Original Assignee: Lloyd D. Taylor, Stanley F. Bedell
• Inventors: Bedell, Stanley F., Taylor, Lloyd D.
• Primary Examiner(s): Chatmon, Jr., Saxfield
• Application Number:
  US05/412,541
• Time in Patent Office: 715 Days
• Field of Search: 350/281,282,147,154,155 260/29.6B,29.6BM,29.7WA
• US Class Current: 359/487.06
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid

Abstract

K-sheet type polarizers are prepared from polyvinyl alcohol graft copolymers, said graft copolymers being obtained by a redox type grafting procedure utilizing certain transition metal cation catalysts.

Claims

1. A DICHROIC LIGHT POLARIZER COMPRISING A TRANSPARENT SHEET OF A GRAFT COPOLYMER, SAID GRAFT COPOLYMER COMPRISING A POLYVINYL ALCOHOL BACKBONE ONTO WHICH ARE GRAFTED POLYMERIC SUBSTITUENTS SELECTED FROM POLYMERIZED MONOMERS HAVING A POLYMERIZABLE VINYL GROUP ON EACH MONOMER DERIVATIVE POLYMERIZED MONOMER HAVING A POLYMERIZABLE VINYLIDENE GROUP ON EACH MONOMER DEIVATIVE AND MIXTURE THEREOF, SAID POLYVINYL ALCOHOL BACKBONE BEING SUBSTANTIALLY MOLECULARY ORIENTERED AND AT LEAST PARTIALLY DEHYDRATED.

2. The polarizer of claim 1 wherein said polymeric substituents comprise polymerized styrene.

3. The polarizer of claim 1 wherein said polymeric substituents comprise polymerized alkyl acrylate.

4. The polarizer of claim 3 wherein said alkyl acrylate comprises ethyl acrylate and methyl methacrylate.

5. The polarizer of claim 1 wherein said polymeric substituents comprise polymerized acrylonitrile.

6. The process of preparing a dichroic light polarizer comprising a transparent sheet of a graft copolymer, said graft copolymer comprising a polyvinyl alcohol backbone onto which are grafted polymeric substituents selected from polymerized monomers having a polymerizable vinyl group on each monomer derivative, polymerized monomers having a polymerizable vinylidene group on each monomer derivative, and mixtures thereof, said polyvinyl alcohol backbone being substantially molecularly oriented and at least partially dehydrated, comprising:

preparing an emulsion of said graft copolymer by mixing a solution containing said polyvinyl alcohol with said polymerizable monomers and a transition metal cation catalyst at a pH of less than 7, said cation catalyst possessing an oxidation potential in acidic media of at least one volt when said cation is reduced to the next lower oxidation state, said cation being stable in acidic media in both of said oxidation states, casting a sheet of said graft copolymer from said emulsion, heating said sheet in the presence of an acid catalyst to at least partially dehydrate said polyvinyl alcohol, and stretching said heated sheet to substantially orient the molecules of said polyvinyl alcohol.

7. The process of claim 6 wherein said transition metal cation catalyst is Ce 5 and said acid catalyst is a concentrated solution of hydrochloric acid which is fumed upon said sheet.

8. The process of preparing a dichroic light polarizer comprising a trAnsparent sheet of a graft copolymer, said graft copolymer comprising a polyvinyl alcohol backbone onto which are grafted polymeric substituents selected from polymerized monomers having a polymerizable vinyl group on each monomer derivative, polymerized monomers having a polymerizable vinylidene group on each monomer derivative, and mixtures thereof, said polyvinyl alcohol backbone being substantially molecularly oriented and at least partially dehydrated, comprising:

preparing an emulsion of said graft copolymer by mixing a solution containing said polyvinyl alcohol with said polymerizable monomers and a transition metal cation catalyst at a pH of less than 7, said cation catalyst possessing an oxidation potential in acidic media of at least one volt when said cation is reduced to the next lower oxidation state, said cation being stable in acidic media in both of said oxidation states, mixing said emulsion of said graft copolymer with an acid catalyst to incorporate said acid catalyst into said emulsion, casting a sheet of said graft copolymer and acid catalyst from said emulsion, heating said sheet containing said acid catalyst to at least partially dehydrate said polyvinyl alcohol, and stretching said heated sheet to substantially orient the molecules of said polyvinyl alcohol.

9. The process of claim 8 wherein said acid catalyst is phosphoric acid.

10. The process of claim 8 wherein said acid catalyst is p-toluenesulfonic acid.

11. The process of preparing a dichroic light polarizer comprising a transparent sheet of a graft copolymer, said graft copolymer comprising a polyvinyl alcohol backbone onto which are grafted polymeric substituents selected from polymerized monomers having a polymerizable vinyl group on each monomer derivative, polymerized monomers having a polymerizable vinylidene group on each monomer derivative, and mixtures thereof, said polyvinyl alcohol backbone being substantially molecularly oriented and at least partially dehydrated, comprising:

preparing an emulsion of said graft copolymer by mixing a solution containing said polyvinyl alcohol with said polymerizable monomers and a transition metal cation catalyst at a pH of less than 7, said cation catalyst possessing an oxidation potantial in acidic media of at least one volt when said cation is reduced to the next lower oxidation state, said cation being stable in acidic media in both of said oxidation states, casting a sheet of said graft copolymer from said emulsion, contacting said sheet with an acid catalyst and then heating said sheet to at least partially dehydrate said polyvinyl alcohol, and stretching said heated sheet to substantially orient the molecules of said polyvinyl alcohol.

12. The process of claim 11 wherein said acid catalyst is anhydrous hydrochloric acid which is fumed upon said sheet.