Low refractive index surface layers and related methods

Patent metadata

Field	Value
Publication number	US-2019017166-A1
Application number	US-201715649448-A
Country	US
Kind code	A1
Filing date	Jul 13, 2017
Priority date	Jul 13, 2017
Publication date	Jan 17, 2019
Grant date	—

Abstract

The disclosure relates to a method for forming a low refractive index layer on a substrate. The method generally includes (a) applying a block copolymer layer on a substrate, the block copolymer including a polar polymeric block and a non-polar polymeric block; (b) swelling the block copolymer layer with a solvent to increase the block copolymer layer thickness; (c) depositing a metal oxide or metalloid oxide layer on polar polymeric blocks of the block copolymer layer; and (d) removing the block copolymer layer from the substrate, thereby forming a porous metal oxide or metalloid oxide layer on the substrate.

First claim

What is claimed is:

1 . A method for forming a low refractive index layer on a substrate, the method comprising:
(a) applying a block copolymer layer on a substrate, the block copolymer comprising a polar polymeric block and a non-polar polymeric block; (b) swelling the block copolymer layer with a solvent to increase the block copolymer layer thickness; (c) depositing a metal oxide or metalloid oxide layer on polar polymeric blocks of the block copolymer layer; and (d) removing the block copolymer layer from the substrate, thereby forming a porous metal oxide or metalloid oxide layer on the substrate.

2 . The method of claim 1 , wherein the non-polar polymeric block comprises a non-polar polymeric hydrocarbon.

3 . The method of claim 1 , wherein the polar polymeric block comprises a polar polymeric hydrocarbon comprising an oxygen-containing polar functional group, a nitrogen-containing polar functional group, or a combination thereof.

4 . The method of claim 1 , wherein the block copolymer is selected from the group consisting of polystyrene-b-polymethylmethacrylate (PS-b-PMMA), polystyrene-b-polyvinylpyridine (PS-b-PVP or PS-b-P4VP for a 4-vinyl pyridine block), polybutadiene-polybutylmethacrylate, polybutadiene-polydimethylsiloxane, polybutadiene-b-polymethylmethacrylate, polybutadiene-b-polyvinylpyridine, polybutadiene-b-polyvinylpyridine, polyethyleneoxide-b-polyisoprene, polyethyleneoxide-b-polybutadiene, polyethyleneoxide-b-polystyrene, polyethylene-b-polyvinylpyridine, polyisoprene-b-polymethylmethacrylate, polyisoprene-b-polyvinylpyridine, polyisobutylene-b-polybutylmethacrylate, polyisobutylene-b-polydimethoxysiloxane, polyisobutylene-b-polymethylmethacrylate, polyisobutylene-b-polyvinylpyridine, polyethylene-b-polymethylmethacrylate, polystyrene-b-polybutylacrylate, polystyrene-b-polybutylmethacrylate, polystyrene-b-polydimethoxysiloxane, polystyrene-b-lactic acid, and combinations thereof.

5 . The method of claim 1 , wherein:
the polar polymeric block is present in the block copolymer in an amount ranging from 10 to 90 wt. %; and the non-polar polymeric block is present in the block copolymer in an amount ranging from 10 to 90 wt. %.

6 . The method of claim 1 , wherein the block copolymer has a molecular weight ranging from 20 to 500 kDa.

7 . The method of claim 1 , wherein the block copolymer layer as applied has a thickness ranging from 10 to 1000 n m .

8 . The method of claim 1 , wherein the substrate comprises a transparent material.

9 . The method of claim 8 , wherein the transparent material has an index of refraction ranging from 1.3 to 2.5.

10 . The method of claim 8 , wherein the transparent material is selected from the group consisting of fused glass, crown glass, sapphire glass, alkali-aluminosilicate plate glass, polycarbonate, poly(methyl methacrylate), plate glass, flint glass, and diamond.

11 . The method of claim 1 , wherein the solvent comprises one or more of ethanol, methanol, propanol, acetic acid, tetrahydrofuran, acetone, thioacetone, acetonitrile, ethyl acetate, methyl ethyl ketone (i.e., butanone), dimethylformamide (DMF), diethyl carbonate (DEC), toluene, benzene, methoxybenzene, chloroform, chlorobenzene, and dichloromethane.

12 . The method of claim 1 , comprising:
swelling the block copolymer layer with the solvent for a time ranging from 10 to 600 minutes; and swelling the block copolymer layer with the solvent at a temperature ranging from 20 to 120° C.

13 . The method of claim 1 , wherein the block copolymer layer thickness after swelling relative to the block copolymer layer thickness prior to swelling ranges from 1.1 to 3.

14 . The method of claim 1 , wherein depositing the metal oxide or metalloid oxide layer comprises performing atomic layer deposition (ALD) (i) to selectively deposit a first precursor on polar polymeric blocks of the block copolymer layer in a first deposition half-cycle, and (ii) to react the deposited first precursor with a second precursor in a second subsequent deposition half-cycle, thereby forming the metal oxide or metalloid oxide layer.

15 . The method of claim 1 , wherein depositing the metal oxide or metalloid oxide layer comprises performing a plurality of deposition cycles.

16 . The method of claim 1 , wherein the metal oxide or metalloid oxide layer has a thickness corresponding to that of the block copolymer layer thickness after swelling.

17 . The method of claim 1 , wherein the metal oxide or metalloid oxide is selected from the group consisting of alumina (Al 2 O 3 ), silica (SiO 2 ), titanium dioxide (TiO 2 ), zinc oxide (ZnO), hafnium dioxide (HfO 2 ), yttrium oxide (Y 2 O 3 ), and combinations thereof.

18 . The method of claim 1 , wherein removing the block copolymer layer from the substrate comprises performing thermal annealing.

19 . The method of claim 1 , wherein the formed porous metal oxide or metalloid oxide layer has a thickness ranging from 10 to 1000 n m .

20 . The method of claim 1 , wherein the formed porous metal oxide or metalloid oxide layer has a porosity ranging from 10 to 90 wt. %.

21 . The method of claim 1 , wherein the formed porous metal oxide or metalloid oxide layer has an index of refraction value 0.05-0.5 less than a corresponding index of refraction for a bulk metal oxide or metalloid oxide material.

22 . The method of claim 1 , wherein the formed porous metal oxide or metalloid oxide layer has an index of refraction ranging from 1.0 to 2.5.

23 . The method of claim 8 , wherein the formed porous metal oxide or metalloid oxide layer has an index of refraction (n c ) and a thickness (d c ) selected according to the following relationship:
n c =( n s n m ) 0.5   (I)
d c =λ 0 /(4 n c )  (II)
wherein:
n s is the index of refraction of the optically transparent material of the substrate;
n m is the index of refraction of the medium through which incident light passes before passing through the formed porous metal oxide or metalloid oxide layer and the transparent material of the substrate (e.g., selected to be 1.0 for intended uses with air as the incident light medium; can be selected to be any value for a different fluid (liquid or gas) medium, such as a value ranging from 1.0 to 1.5, for instance 1.33 for water, etc.);
λ 0 is an incident wavelength to be fully transmitted through the porous metal oxide or metalloid oxide layer and the transparent material of the substrate, λ 0 being a selected single wavelength in range from 250 to 3000 n m ;
the index of refraction (n c ) of the porous metal oxide or metalloid oxide layer is within ±0.03 units of the value of n s specified by equation (I); and
the thickness (d c ) of the porous metal oxide or metalloid oxide layer is within ±10% of the value of d c specified by equation (II).

24 . The method of claim 8 , comprising performing steps (a)-(d) at least twice in succession for form at least two porous metal oxide or metalloid oxide layers.

25 . The method of claim 24 , wherein:
(i) a first porous metal oxide or metalloid oxide layer formed adjacent to the transparent material substrate has an index of refraction within ±0.03 units of the index of refraction of the transparent material substrate; and (ii) an outer porous metal oxide or metalloid oxide layer formed has an index of refraction within ±0.15 units of the index of refraction of a selected medium external to th

Assignees

• Uchicago Argonne Llc

Inventors

• Shevchenko Elena
• Berman Diana
• Guha Supratik

Classifications

• C23C16/04

  Coating on selected surface areas, e.g. using masks · CPC title

• G02B2207/107

  Porous materials, e.g. for reducing the refractive index · CPC title

• C23C16/403

  of aluminium, magnesium or beryllium · CPC title

• G02B1/118

  having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures · CPC title

• C23C16/56

  After-treatment · CPC title