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US-12619008-B2 - Optical halogenated polymer thin film with ultra-high refractive index

US12619008B2US 12619008 B2US12619008 B2US 12619008B2US-12619008-B2

Abstract

A high refractive index coating made by forming a solid thin layer of a polymer such as P4VP by a process such as iCVD and halogenating the solid layer to thereby form a film that has a greatly increased refractive index and other desirable optical and physical properties.

Inventors

  • Wyatt TENHAEFF
  • Ni Huo

Assignees

  • UNIVERSITY OF ROCHESTER

Dates

Publication Date
20260505
Application Date
20220701

Claims (20)

  1. 1 . A coating comprising: a polymer or copolymer layer in which one or more of Chlorine (Cl), Bromine (Br) and Iodine (I) halogens have been introduced after the layer has been formed to thereby form a film as a charge transfer complex of the previously formed layer and said one or more of Cl, Br and I; wherein: the film exhibits a refractive index of 1.7 or more for wavelengths in the 400-800 nm range; and the film thickness is in the 10-2000 nm range.
  2. 2 . The coating of claim 1 , in which an extinction coefficient of the film is no more than 7×10 −4 at wavelengths in the 650-800 nm range.
  3. 3 . The coating of claim 1 , in which an extinction coefficient of the film is no more than 2.4×10 −3 at wavelengths in the 650-800 nm range.
  4. 4 . The coating of claim 1 , in which the refractive index of the film is more than 1.8 for wavelengths in the 400-800 nm range.
  5. 5 . The coating of claim 1 , in which the refractive index of the film is more than 2.0 for wavelengths in the 400-800 nm range.
  6. 6 . The coating of claim 1 , in which the copolymer comprises p(4VP-co-EGDMA).
  7. 7 . The coating of claim 1 , in which the copolymer comprises 4VP and EGDMA in proportions configured for a selected tuning of the refractive index of the film prior to halogen incorporation.
  8. 8 . The coating of claim 1 , in which the polymer or copolymer is in a charge transfer complex with I—Cl.
  9. 9 . The coating of claim 1 , in which the polymer or copolymer is in a charge transfer complex with I—Br.
  10. 10 . The coating of claim 1 , in which the polymer or copolymer is in a charge transfer complex with I 2 .
  11. 11 . The coating of claim 1 , in which the film thickness is in the range of 10-500 nm.
  12. 12 . A coating comprising: a film comprising a polymer or copolymer layer in which one or more of Cl, Br and I have been introduced after the layer has been formed to thereby form a charge transfer complex of the layer and one or more of Cl, Br and I; wherein: the film exhibits a refractive index of 1.7 or more for wavelengths in the 400-800 nm range; and the film thickness is in the 10-2000 nm range.
  13. 13 . The coating of claim 12 , in which the polymer layer comprises P4VP.
  14. 14 . The coating of claim 13 , in which the copolymer comprises P4VP and PEGDMA, p(4VP-co-EGDMA).
  15. 15 . The coating of claim 12 , in which the film exhibits a refractive index of 1.8 or more.
  16. 16 . The coating of claim 12 , in which the polymer comprises one or more of poly(2-vinyl pyridine), poly(4-vinyl pyridine), poly(2-vinyl pyrazine), poly(vinyl pyrrolidinone), poly(vinyl imidazole), poly(4-methyl-5-vinylthiazole), poly(vinyl 1,2,4-triazole), poly(2-methyl-1-vinyl imidazole), poly(1-vinyl-1H-benzimidazole), poly(4-vinylaniline), poly(3-vinylaniline), poly(2-isopropenylaniline), poly(ethylene imine), poly(N-vinylcaprolactam), and poly(2-vinyl-1H-pyrrole).
  17. 17 . The coating of claim 12 , in which the polymer or copolymer comprises at least one the following monomers: 2-vinyl pyridine, 4-vinyl pyridine, 2-vinyl pyrazine, 1-vinyl-2-pyrrolidinone, 1-vinyl imidazole, 4-methyl-5-vinylthiazole, 1-vinyl-1,2,4-triazole, 2-methyl-1-vinyl imidazole, 1-vinyl-1H-benzimidazole, 4-vinylaniline, 3-vinylaniline, 2-isopropenylaniline, N-vinylcaprolactam and 2-vinyl-1H-pyrrole.
  18. 18 . The coating of claim 12 , in which the polymer contains moieties that act as Lewis bases that can form molecular complexes with halogen species.
  19. 19 . The coating of claim 1 , in which the polymer comprises one or more of poly(2-vinyl pyridine), poly(4-vinyl pyridine), poly(2-vinyl pyrazine), poly(vinyl pyrrolidinone), poly(vinyl imidazole), poly(4-methyl-5-vinylthiazole), poly(vinyl 1,2,4-triazole), poly(2-methyl-1-vinyl imidazole), poly(1-vinyl-1H-benzimidazole), poly(4-vinylaniline), poly(3-vinylaniline), poly(2-isopropenylaniline), poly(ethylene imine), poly(N-vinylcaprolactam), and poly(2-vinyl-1H-pyrrole).
  20. 20 . The coating of claim 1 , in which the polymer or copolymer comprises at least one the following monomers: 2-vinyl pyridine, 4-vinyl pyridine, 2-vinyl pyrazine, 1-vinyl-2-pyrrolidinone, 1-vinyl imidazole, 4-methyl-5-vinylthiazole, 1-vinyl-1,2,4-triazole, 2-methyl-1-vinyl imidazole, 1-vinyl-1H-benzimidazole, 4-vinylaniline, 3-vinylaniline, 2-isopropenylaniline, N-vinylcaprolactam and 2-vinyl-1H-pyrrole.

Description

REFERENCE TO RELATED APPLICATION This application claims the benefit of and incorporates by reference U.S. Provisional Patent Application No. 63/219,200 filed on Jul. 7, 2021. FIELD This patent specification relates to high refractive index films and more specifically to films of this type that have desirable combinations of optical and physical properties. BACKGROUND High refractive index polymers (HRIP) are an important class of materials with actual or potential applications in optoelectronic devices, such as anti-reflective components for displays, encapsulants for light emitting diodes, and optical sensors. Some of the desirable properties of such films are high refractive index, good manufacturability and low cost, high transmission at least at selected wavelengths, and resistance to physical damage. As discussed in Higashihara T. and Ueda M., Recent Progress in High Refractive Index Polymers, Macromolecules 2015, 48, 1915-1929 (DOI:10.1021/ma502569r), which is hereby incorporated by reference in this patent specification, “a very high-n exceeding 1.7 and even 1.8 is frequently desired.” The article discusses the use of multi-layer films, for example as seen in FIG. 6 thereof, and on page 1922 refers to a three-layer polymer coating in which a layer has a titania content of 50 wt % and refractive index n=1.86. Another publication discusses halogenated polymers with a refractive index that can be adjusted within a range from 1.51 to 1.57. See Qi Y, Ding J, Day M, Jiang J, and Callender C, Cross-linkable highly halogenated poly(arylene ether ketone/sulfone)s with tunable refractive index: Synthesis, characterization and optical properties, Polymer 47(2006) 8263-8271 (doi:10.1016/j.polymer.2006.09.065), hereby incorporated by reference in this patent specification. It would be desirable to develop polymer coatings with better optical and physical properties that are more easily manufacturable and are less expensive. The subject matter described or claimed in this patent specification is not limited to embodiments that solve any specific disadvantages or that operate only in environments such as those described above. Rather, the above background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced. SUMMARY The summary below reflects the initially claimed subject matter, which can evolve in prosecution of this patent application. According to some embodiments, a coating comprises: a film formed of a layer comprising poly(4-vinylpyridine) (P4VP) in which one or more of Chlorine (CI), Bromine (Br) and Iodine (I) halogens have been introduced after the layer has been formed to thereby form the film as a charge transfer complex of the previously formed layer and said one or more of Cl, Br and I; wherein: (a) the film exhibits a refractive index of 1.707 or more at 632.8 nm; and (b) the film thickness is in the 10-2000 nm range. According to some embodiments, the coating can include one or more of the following features: (a) the extinction coefficient of the film is no more than 7×10−4, or 2.4×10−3, at wavelengths in the 650-800 nm range; (b) the refractive index of the film is more than 1.8, or 2.0, for wavelengths in the 400-800 nm range; (c) the polymer comprises p(4VP-co-EGDMA), a copolymer of 4-vinylpyridine (4VP) and ethylene glycol dimethacrylate (EGDMA); (d) the polymer comprises a copolymer of 4VP and EGDMA in proportions configured for a selected tuning of the refractive index of the film; (e) the coating comprises poly(4-vinylpyridine) (P4VP) in a charge transfer complex with I—Cl, or I—Br, or I2; (f) the film thickness is in the range of 10-500 nm; and (g) the film thickness is approximately 200 nm. According to some embodiments, a process of making a film having a selected refractive index comprises: forming a layer comprising a first polymer; introducing one or more of Cl, Br, and I into the layer after the layer has been formed to thereby form a film of a charge transfer complex of one or more of Cl, Br, and 12 with the layer and has: (a) refractive index of 1.7 or more for wavelengths in the 400-800 nm range; and (b) film thickness in the 10-1000 nm range. According to some embodiments, the process can further include one or more of the following features; (a) the step of forming the layer further includes forming the layer of a copolymer of 4VP and EGDMA, p(4VP-co-EGDMA), to thereby tune the refractive index of the film; (b) the step of forming the film comprises forming a film that has a refractive index of more than 1.8 for wavelengths in the 400-800 nm range; and (c) the step of forming the film comprises forming a film that has a refractive index of more than 2.0 for wavelengths in the 400-800 nm range. According to some embodiments, a coating comprises: a film comprising a polymer layer in which one or more of the halogens Cl, Br and I have been introduced after the layer has been formed to thereby form a charge transfer com