Glass substrate, black matrix substrate, and display panel
The present invention relates to a glass substrate including a pair of main surfaces and an end surface, and having a surface layer diffusion Sn atom concentration of 2.0×10 18 atomic/cm 3 or more and 1.4×10 19 atomic/cm 3 or less in at least one of the main surfaces, the surface layer diffusion Sn atom concentration being obtained by subtracting an Sn atom concentration of an inside of the glass substrate from an Sn atom concentration of a surface layer of the glass substrate, in which the Sn atom concentration of a surface layer of the glass substrate is defined as an Sn atom concentration at a depth of 0.1 to 0.3 μm from the main surface and the Sn atom concentration of an inside of the glass substrate is defined as an Sn atom concentration at a depth of 9.0 to 9.2 μm from the main surface.
1. A glass substrate comprising a pair of main surfaces and an end surface, and
having a surface layer diffusion Sn atom concentration of 2.0×10 18 atomic/cm 3 or more and 1.4×10 19 atomic/cm 3 or less in at least one of the main surfaces, the surface layer diffusion Sn atom concentration being obtained by subtracting an Sn atom concentration of an inside of the glass substrate from an Sn atom concentration of a surface layer of the glass substrate,
wherein the Sn atom concentration of a surface layer of the glass substrate is defined as an Sn atom concentration at a depth of 0.1 to 0.3 μm from the main surface and the Sn atom concentration of an inside of the glass substrate is defined as an Sn atom concentration at a depth of 9.0 to 9.2 μm from the main surface,
having an Sn atom concentration gradient of a surface layer of the glass substrate of −1.0×10 23 atomic/cm 4 or more and −1.0×10 22 atomic/cm 4 or less in the at least one of the main surfaces,
wherein the Sn atom concentration gradient of a surface layer of the glass substrate is defined as an inclination of a linear function obtained by linearly approximating a depth profile of an Sn atom concentration (atomic/cm 3 ) at a depth of 0.1 to 0.5 μm from the main surface.
2. The glass substrate according to claim 1 , comprising an alkali-free glass comprising, in mol % on an oxide basis:
50 to 75% of SiO 2 ;
7 to 25% of Al 2 O 3 ;
0.1 to 12% of B 2 O 3 ; and
7 to 25% in total of at least one compound selected from the group consisting of MgO, CaO, SrO and BaO.
3. The glass substrate according to claim 2 , wherein the alkali-free glass has a strain point of 650° C. or higher, and an average thermal expansion coefficient at 50 to 350° C. of 30×10 −7 to 45×10 −7 /° C.
4. The glass substrate according to claim 2 , wherein the alkali-free glass has a content of alkali metal oxides of 0.5% or lower, in mol % on an oxide basis.
5. The glass substrate according to claim 1 , being produced by a float process.
6. The glass substrate according to claim 1 , wherein the at least one of the main surfaces is a polished surface formed by polishing.
7. The glass substrate according to claim 6 , wherein the polished surface has an Stdi value of 0.75 or less, the Stdi value is a texture-direction index obtained with an observation visual field of 1 μm×1 μm and the number of pixels of 256×256 by an AFM (Atomic Force Microscopy).
8. A black matrix substrate comprising the glass substrate according to claim 1 , and a black matrix film formed on at least one of the main surfaces of the glass substrate.
9. A display panel comprising the black matrix substrate according to claim 8 .