Water-and-oil repellent layer-attached substrate, and method for manufacturing same
A water/oil repellent layer-provided substrate including a substrate, an undercoat layer formed on a surface of the substrate, and a water/oil repellent layer formed on a surface of the undercoat layer in this order. The water/oil repellent layer contains a condensate of a fluorinated compound having a reactive silyl group, the undercoat layer contains an oxide containing silicon and contains no alkali metal nor aluminum, and the substrate includes silica glass containing an alkali metal and aluminum.
1. A water/oil repellent layer-provided substrate, comprising:
a substrate;
an undercoat layer formed on A surface of the substrate; and
a water/oil repellent layer formed on a surface of the undercoat layer in this order,
wherein the water/oil repellent layer comprises a condensate of a fluorinated compound having a reactive silyl group, the undercoat layer contains an oxide containing silicon and contains no alkali metal nor aluminum, the substrate comprises silica glass containing an alkali metal and aluminum, and
when the following (a), (b) and (c) are specified from a depth profile (measurement interval: 2.0 nm or shorter) obtained by X-ray photoelectron spectroscopy (XPS) by C 60 ion sputtering from a surface of the water/oil repellent layer, taking a total concentration of fluorine, silicon, aluminum, the alkali metal element and oxygen as 100 at %, an alkali deficiency index determined by the following (c) is higher than 0.0; provided that a depth indicated by a horizontal axis of the depth profile is a depth calculated from a sputtering rate of a thermally oxidized film having a known thickness on a silicon wafer:
(a): in the depth profile taking the total concentration of fluorine, silicon, aluminum, the alkali metal element and oxygen as 100 at %, obtained by XPS, a point at which a fluorine concentration becomes 10 at % or lower for a first time is taken as a boundary between the water/oil repellent layer and the undercoat layer;
(b): from the depth profile taking the total concentration of fluorine, silicon, aluminum, the alkali metal element and oxygen as 100 at %, obtained by XPS, a proportion of aluminum to silicon (Al/Si) and a total proportion of the alkali metal element to silicon (alkali metal element/Si) are obtained, and based on average values of values of (Al/Si) and values of (alkali metal element/Si) in a region at a depth of at least 70.0 nm and at most 80.0 nm respectively being 1, the (Al/Si) and (alkali metal element/Si) at respective positions in a depth direction are respectively normalized, and a point at which the normalized (Al/Si) value becomes 0.50 or higher for a first time is taken as a boundary between the undercoat layer and the substrate;
(c): a region from the boundary between the undercoat layer and the substrate determined by (b) as an origin up to 20 nm in the depth direction from the origin is taken as a region X, and the alkali deficiency index in the region X defined by the following formula is obtained:
alkali deficiency index=[(average value of normalized Al/Si in the region X)−(average value of normalized alkali metal element/Si in the region X)]×20.
2. The water/oil repellent layer-provided substrate according to claim 1 , wherein the alkali deficiency index is higher than 0.5.
3. The water/oil repellent layer-provided substrate according to claim 1 , wherein the substrate is made of chemically tempered glass having chemical tempering treatment applied to at least one surface, and the undercoat layer is formed on the surface having chemical tempering treatment applied thereto.
4. The water/oil repellent layer-provided substrate according to claim 1 , wherein the average fluorine concentration which is the average value of the fluorine concentrations in the water/oil repellent layer specified by (a) is at least 15 at %.
5. The water/oil repellent layer-provided substrate according to claim 1 , wherein the thickness of the undercoat layer specified by (a) and (b) is from 1.0 to 45.0 nm.
6. The water/oil repellent layer-provided substrate according to claim 1 , wherein the thickness of the undercoat layer specified by (a) and (b) is from 7.0 to 25.0 nm.
7. The water/oil repellent layer-provided substrate according to claim 1 , wherein the thickness of the substrate is from 0.1 to 1.5 mm.
8. The water/oil repellent layer-provided substrate according to claim 1 , wherein the fluorinated compound is a fluorinated compound having two or more reactive silyl groups.
9. The water/oil repellent layer-provided substrate according to claim 1 , wherein the fluorinated compound is a fluorinated ether compound having a poly(oxyfluoroalkylene) chain and a reactive silyl group.
10. The water/oil repellent layer-provided substrate according to claim 9 , wherein in the poly(oxyfluoroalkylene) chain a proportion of a number of units of a oxyperfluoroalkylene group to a total number of units is from 50 to 100%.
11. A method for producing the water/oil repellent layer-provided substrate as defined in claim 1 , which comprises forming, on the surface of the substrate, the undercoat layer containing an oxide containing silicon and an alkali metal,
forming, on the surface of the undercoat layer, the water/oil repellent layer comprising a condensate of a fluorinated compound having a reactive silyl group, and
subjecting the water/oil repellent layer-formed side to an aqueous medium treatment.
12. The method for producing the water/oil repellent layer-provided substrate according to claim 11 , wherein the aqueous medium treatment is washing treatment with an aqueous acid solution or dipping treatment in an aqueous acid solution.
13. The water/oil repellent layer-provided substrate according to claim 2 , wherein the substrate is made of chemically tempered glass having chemical tempering treatment applied to at least one surface, and the undercoat layer is formed on the surface having chemical tempering treatment applied thereto.
14. The water/oil repellent layer-provided substrate according to claim 2 , wherein the average fluorine concentration which is the average value of the fluorine concentrations in the water/oil repellent layer specified by (a) is at least 15 at %.
15. The water/oil repellent layer-provided substrate according to claim 2 , wherein the thickness of the undercoat layer specified by (a) and (b) is from 1.0 to 45.0 nm.
16. The water/oil repellent layer-provided substrate according to claim 2 , wherein the thickness of the undercoat layer specified by (a) and (b) is from 7.0 to 25.0 nm.
17. The water/oil repellent layer-provided substrate according to claim 2 , wherein the thickness of the substrate is from 0.1 to 1.5 mm.
18. The water/oil repellent layer-provided substrate according to claim 2 , wherein the fluorinated compound is a fluorinated compound having two or more reactive silyl groups.
19. The water/oil repellent layer-provided substrate according to claim 2 , wherein the fluorinated compound is a fluorinated ether compound having a poly(oxyfluoroalkylene) chain and a reactive silyl group.
20. The water/oil repellent layer-provided substrate according to claim 19 , wherein in the poly(oxyfluoroalkylene) chain a proportion of a number of units of a oxyperfluoroalkylene group to a total number of units is from 50 to 100%.