Polymeric minus filter

• US 5,238,738 A
• Filed: 10/29/1991
• Issued: 08/24/1993
• Est. Priority Date: 10/29/1991
• Status: Expired due to Fees

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Miller, Robert H.
• Primary Examiner(s): SLUBY, PATRICIA
• Application Number:
  US07/784,367
• Time in Patent Office: 665 Days
• Field of Search: 428/516, 428/461, 428/412, 428/419, 428/447, 428/521, 428/522, 428/333, 428/913, 427/10, 427/162, 427/164, 350/1.6, 350/166
• US Class Current: 428/333
• CPC Class Codes: G02B 5/287 comprising at least one layer of organic material
• CPC Class Codes: Y10S 428/913 Material designed to be responsive to temperature, light, moisture
• CPC Class Codes: Y10T 428/261 In terms of molecular thickness or light wave length
• CPC Class Codes: Y10T 428/31507 Of polycarbonate
• CPC Class Codes: Y10T 428/31533 Of polythioether
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane
• CPC Class Codes: Y10T 428/31692 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31913 Monoolefin polymer
• CPC Class Codes: Y10T 428/31931 Polyene monomer-containing
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

Abstract

A polymeric minus filter for an incident electromagnetic spectral band comprises at least one polymeric interference stack tuned to a predetermined design wavelength centered around λ₀, wherein λ₀ is in the range of 300 nm to 2000 nm, said filter comprises an optically transparent substrate and having deposited thereon at ambient temperatures (20° to 23° C.) a multiplicity of pairs of polymeric thin interference layers plus one final polymeric layer having index of refraction n₂, each pair of interference layers having a total optical thickness equal to 1/2 wavelength of λ₀, the members of each pair having refractive indices n₁ and n₂, respectively, wherein the layer having refractive index n₂ is directly superimposed upon said substrate having refractive index n_s and wherein n_s is approximately equal to n₁, and wherein n₂ <n₁.

Claims

1. A polymeric minus filter for an incident electromagnetic spectral band comprising at least one polymeric interference stack tuned to a predetermined design wavelength centered around λ

₀, wherein λ

₀ is in the range of 300 nm to 2000 nm, said filter comprising an optically transparent substrate and having deposited thereon a multiplicity of pairs of polymeric thin interference layers plus one final polymeric thin interference layer having index of refraction n₂, each pair of interference layers having a total optical thickness equal to 1/2 wavelength of λ

₀, the members of each pair having refractive indices n₁ and n₂, respectively, wherein the layer having refractive index n₂ is directly superimposed upon said substrate having refractive index n_s and wherein n_s is approximately equal to n₁, and wherein n₂ is less than n₁.

2. The minus filter according to claim 1 wherein said substrate is transparent.

3. The minus filter according to claim 1 wherein said substrate is partially absorbing.

4. The filter according to claim 1 wherein said substrate is selected from the group consisting of polycarbonate, polystyrene, polyacrylate, polyaryl sulfone, polyester, and polysulfone.

5. The filter according to claim 4 wherein said substrate is polycarbonate or polystyrene.

6. The filter according to claim 1 wherein said polymeric thin interference layer having refractive index n₁, is selected from the group consisting of plasma polymerized polystyrene, hexamethyl disiloxane, and polymethyl methacrylate.

7. The filter according to claim 1 wherein said polymeric thin interference layer having refractive index n₂ is selected from the group consisting of plasma polymerized polymethyl methacrylate, polystyrene, and hexamethyl disiloxane.

8. The filter according to claim 1 having a number of interleaved polymeric stacks equal to the number of rejection bands of wavelengths.

9. The filter according to claim 8 wherein each of said stacks has in the range of 25 to 2500 pairs of interference layers.

10. The filter according to claim 1 wherein said substrate is polycarbonate, said interference layer having index of refraction n₁ is plasma polymerized hexamethyl disiloxane, and said interference layer having index of refraction n₂ is polymethyl methacrylate or plasma polymerized hexamethyl disiloxane.

11. The filter according to claim 1 wherein λ

₀ is a wavelength in the visible range.

12. The filter according to claim 1 wherein λ

₀ is a wavelength in the near infrared range.

13. The filter according to claim 1 wherein said substrate is polycarbonate.

14. The filter according to claim 1 wherein said interference layer having index of refraction n₂ is plasma polymerized hexamethyl disiloxane.

15. The filter according to claim 1 wherein said interference layer having index of refraction n₁ is polymerized hexamethyl disiloxane.

16. The film according to claim 10 wherein said interference layers are deposited on said substrate at ambient temperatures.

19. A method of protecting a radiation sensitive object from at least one selected wavelength of unwanted electromagnetic radiation comprising the step of:

providing the minus filter according to claim 1 which is positioned so as to prevent said selected wavelength of electromagnetic radiation from reaching said object to be protected.

20. The polymeric minus filter according to claim 1 wherein said polymeric thin interference layers are vacuum deposited by plasma polymerization.

17. A method for preparing a minus filter comprising a stack of organic layers for rejecting an incident electromagnetic spectral band comprising the step of

depositing on an optically transparent substrate having refractive index n_s a multiplicity of pairs of plasma polymerized organic interference layers having refractive indices n₁ and n₂, n₂ being lower than n₁, wherein a layer having refractive index n₂ is directly superimposed upon the substrate, and n_s is approximately equal to n₁, and depositing a final plasma polymerized organic layer having refractive index n₂, said layers and substrate providing a polymeric interference stack which is tuned to a predetermined design wavelength centered around λ

₀, wherein λ

₀ is in the range of 300 nm to 2000 nm.

18. A method for rejecting multiple bands of incident electromagnetic radiation comprising a composite of multistacks, each of said stacks being prepared by the method according to claim 17.