ANTIREFLECTIVE COATINGS WITH CONTROLLABLE POROSITY AND REFRACTIVE INDEX PROPERTIES USING A COMBINATION OF THERMAL OR CHEMICAL TREATMENTS
In some embodiments, the current invention discloses methods and apparatuses for making coated articles including a two step treatment process of a coated layer. The first step of the heat treatment involves a thermally assisted curing of the coated layer at a low temperature, which can strengthen the bond formation in the coated layer, leading to better layer stability during the subsequent heat treatment. The second step of the heat treatment involves annealing of the cured layer at a high temperature, which can control a porosity of the coated layer.
1 . A method of forming a porous coating on a substrate, the method comprising:
forming a coated layer on the substrate, wherein the coated layer comprises an alkylalkoxysilane-based binder and silica based particles;
performing a pretreatment of the coated substrate at a first temperature;
performing a heat treatment of the coated substrate at a second temperature, wherein the heat treatment forms a porous coating.
2 . A method as in claim 1 wherein a time of the pretreatment is between 1 second and less than or equal to 5 minutes.
3 . A method as in claim 1 wherein a time of the heat treatment is between 1 second and less than or equal to 30 minutes.
4 . A method as in claim 1 wherein the first temperature is between 100 C and less than or equal to 400 C.
5 . A method as in claim 1 wherein the second temperature is between 300 C and 750 C.
6 . A method as in claim 1 , wherein the alkylalkoxysilane-based binder comprises a bis(alkoxylsilylalkane) binder.
7 . A method as in claim 1 wherein the alkylalkoxysilane-based binder comprises one of n-hexyltriethoxysilane or cyclohexyltrimethoxysilane.
8 . A method of forming a porous coating on a substrate, the method comprising:
forming a coated layer on the substrate, wherein the coated layer comprises an alkylalkoxysilane-based binder and silica based particles;
exposing the coated layer to an alkaline ambient;
heat treating the coated substrate, wherein the heat treatment forms a porous coating.
9 . A method as in claim 8 wherein the alkaline ambient comprises ammonia.
10 . A method as in claim 8 wherein a time of the exposure is between 1 second and less than equal to 5 minutes.
11 . A method as in claim 8 wherein a temperature of the exposure is at room temperature.
12 . A method as in claim 8 wherein a temperature of the exposure is between 100 C and less than equal to 200 C.
13 . A method as in claim 8 wherein a temperature of the exposure is between 100 C and less than equal to 400 C.
14 . A method as in claim 8 wherein the time of the heat treatment is between 1 second and less than equal to 30 minutes.
15 . A method as in claim 8 wherein the temperature of the heat treatment is between 300 C and 750 C.
16 . A coated article comprising:
a substrate;
a coated layer over the substrate, wherein the coated layer is formed by a method comprising:
forming a coated layer on the substrate, wherein the coated layer comprises an alkylalkoxysilane-based binder and silica based particles;
performing a pretreatment of the coated layer;
performing a heat treatment of the coated layer at a second temperature, wherein the heat treatment forms a porous coating.
17 . An article as in claim 16 wherein the alkylalkoxysilane-based binder comprises a bis(alkylalkoxysilane)-based binder.
18 . An article as in claim 16 wherein the alkylalkoxysilane-based binder is selected from the group consisting of n-propyltriethoxysilane, n-pentyltriethoxysilane, n-hexyltriethoxysilane, cyclohexyltrimethoxysilane, and combinations thereof.
19 . An article as in claim 16 wherein the coated layer further comprises an alcohol containing solvent and an acid or base containing catalyst.
20 . An article as in claim 16 wherein the pretreatment comprises a thermal treatment at a first temperature or an exposure to an alkaline ambient