Float glass for chemical strengthening

Patent metadata

Field	Value
Publication number	US-9714193-B2
Application number	US-201514753416-A
Country	US
Kind code	B2
Filing date	Jun 29, 2015
Priority date	Dec 27, 2012
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

The present invention relates to a float glass for chemical strengthening, containing a bottom surface coming into contact with a molten metal at the time of forming and a top surface opposing the bottom surface, in which a difference Δ(N—Na 2 O 2 ) determined by subtracting a square of a normalized Na 2 O surface concentration of the bottom surface which is a value obtained by dividing an Na 2 O concentration in the bottom surface by an Na 2 O concentration at a depth position of 100 μm therefrom, from a square of a normalized Na 2 O surface concentration of the top surface which is a value obtained by dividing an Na 2 O concentration in the top surface by an Na 2 O concentration at a depth position of 100 μm therefrom, is 0.040 or less.

First claim

The invention claimed is:

1. A float glass for chemical strengthening, comprising a bottom surface coming into contact with a molten metal at the time of forming of the float glass and a top surface opposing the bottom surface, wherein a difference Δ(N—Na 2 O 2 ) determined by subtracting a square of a normalized Na 2 O surface concentration of the bottom surface from a square of a normalized Na 2 O surface concentration of the top surface is 0.040 or less, where the normalized Na 2 O surface concentration is obtained by dividing an Na 2 O concentration in a measured surface, which is the bottom surface or the top surface, by an Na 2 O concentration at a depth of 100 μm from the measured surface, where the Na 2 O concentration is a value measured by a fluorescent X-ray analysis using an Na—Kα ray.

2. The float glass as claimed in claim 1 , wherein W3 determined according to the following formula (5-1) is 58 or less:
W 3=744×[(ΔN—Na 2 O)+0.01×(Sn concentration difference)]  formula (5-1),

wherein, in formula (5-1):
the ΔN—Na 2 O is a value determined by subtracting the normalized Na 2 O surface concentration in the bottom surface from the normalized Na 2 O surface concentration in the top surface; and
the Sn concentration difference is a difference obtained by subtracting an Sn deposition amount per unit area (unit: μg/cm 2 ) in the top surface from an Sn deposition amount per unit area (unit: μg/cm 2 ) in the bottom surface, where the Sn deposition amount per unit area is a deposition mass in terms of SnO 2 per 1 cm 2 when Sn is assumed to exist in the form of SnO 2 .

3. The float glass as claimed in claim 1 , wherein Δion exchange amount 2 which is a value obtained by subtracting an ion exchange amount 2 in the bottom surface from an ion exchange amount 2 in the top surface is 0.33 or less,
where the ion exchange amount 2 is a value determined according to the following formula (6-1):
Ion exchange amount 2=−0.02×(H/Si)+5.54×(N—Na 2 O concentration)−0.037×(Sn concentration)  formula (6-1),

wherein, in formula (6-1):
the H/Si is a normalized hydrogen concentration, where the normalized hydrogen concentration is a value obtained by dividing an average hydrogen concentration at a depth of 0 to 10 μm by an average hydrogen concentration at a depth of 105 to 110 μm, and the average hydrogen concentration at a depth of 0 to 10 μm and the average hydrogen concentration at a depth of 105 to 110 μm are values measured under the following analysis conditions (a) to (i):
(a) Measurement apparatus: secondary ion mass spectrometry apparatus with a quadrupole mass spectrometer,
(b) Primary ion species: Cs + ,
(c) Primary accelerating voltage: 5.0 kV,
(d) Primary ion current: 1 μA,
(e) Primary ion incident angle (angle from direction perpendicular to sample surface): 60°,
(f) Luster size: 200×200 μm 2 ,
(g) Detection region: 40×40 μm 2 ,
(h) Secondary ion polarity: minus, and
(i) Electron gun for neutralization: used;
the N—Na 2 O concentration is the normalized Na 2 O surface concentration; and
the Sn concentration is an Sn deposition amount per unit area(unit: μg/cm 2 ), where the Sn deposition amount is a deposition mass in terms of SnO 2 when Sn is assumed to exist in the form of SnO 2 .

4. The float glass as claimed in claim 1 , wherein the float glass is used for chemical strengthening in which a chemical strengthening temperature is T (unit: K) and a chemical strengthening time is t (unit: hours) and contains SiO 2 , and a dol determined according to the following formula by using respective contents in mass % of SiO 2 , Al 2 O 3 , MgO, CaO, SrO, BaO, ZrO 2 , Na 2 O and K 2 O is 20 or less:
dol=−0.13×Al 2 O 3 −1.88×MgO−2.41×CaO−1.85×SrO−1.35×BaO−1.59×ZrO 2 +1.50×Na 2 O+2.42×K 2 O−129359/T+9.28×t 0.5 +182.88.

5. The float glass as claimed in claim 1 , comprising: in mass %, from 60 to 80% of SiO 2 , from 0 to 8% of Al 2 O 3 , from 8 to 22% of Na 2 O, from 0 to 7% of K 2 O, from 0 to 17% of MgO, from 0 to 22% of CaO, from 0 to 8% of SrO, from 0 to 8% of BaO, and from 0 to 5% of ZrO 2 .

6. The float glass as claimed in claim 5 , comprising at least one of CaO, SrO and BaO, wherein the total of the CaO, SrO and BaO contents is from 1 to 7%.

7. The float glass as claimed in claim 1 , comprising: in mass %, from 60 to 80% of SiO 2 , from 0.01 to 8% of Al 2 O 3 , from 8 to 22% of Na 2 O, from 0 to 7% of K 2 O and from 0 to 5% of ZrO 2 , wherein in the case where at least one of MgO, CaO, SrO and BaO is contained in the float glass, the total of the MgO, CaO, SrO and BaO contents is from 5 to 25%, and a ratio of the Na 2 O content to the Al 2 O 3 content (Na 2 O/Al 2 O 3 is 1.5 or more.

8. The float glass as claimed in claim 7 , wherein the ratio Na 2 O/Al 2 O 3 is 6 or less.

9. A method for producing a chemically strengthened glass having a depth of compressive stress layer of 20 μm or less, comprising chemically strengthening the float glass as claimed in claim 1 .

10. A float glass for chemical strengthening, comprising a bottom surface coming into contact with a molten metal at the time of forming of the float glass and a top surface opposing the bottom surface, wherein a Δion exchange amount 1 which is a value obtained by subtracting an ion exchange amount 1 in the bottom surface from an ion exchange amount 1 in the top surface is 0.32 or less,
where the ion exchange amount 1 is a value determined according to the following formula (2-1):
Ion exchange amount 1=5.51×(normalized Na 2 O surface concentration)−0.038×(Sn concentration)  formula (2-1),

wherein, in formula (2-1):
the normalized Na 2 O surface concentration is a value obtained by dividing an Na 2 O concentration at a measured surface, which is the bottom surface or the top surface, by an Na 2 O concentration at a depth position of 100 μm from the measured surface, where the Na 2 O concentration is a value measured by a fluorescent X-ray analysis using an Na—Kα ray; and
the Sn concentration is an Sn deposition amount per unit area (unit: μg/cm 2 ) in the measured surface, where the Sn deposition amount per unit area is a deposition mass in terms of SnO 2 per 1 cm 2 when Sn is assumed to exist in the form of SnO 2 .

11. The float glass as claimed in claim 10 , wherein W3 determined according to the following formula (5-1) is 58 or less:
W 3=744×[(ΔN—Na 2 O)+0.01×(Sn concentration difference)]  formula (5-1),

wherein, in formula (5-1):
the ΔN—Na 2 O is a value determined by subtracting the normalized Na 2 O surface concentration in the bottom surface from the normalized Na 2 O surface concentration in the top surface; and
the Sn concentration difference is a difference obtained by subtracting an Sn deposition amount per unit area (unit: μg/cm 2 ) in the top surface from an Sn deposition amount per unit area (unit: μg/cm 2 ) in the bottom surface.

12. The float glass as claimed in claim 10 , wherein Δion exchange amount 2 which is a value obtained by subtracting an ion exchange amount 2 in the bottom surface from an ion exchange amount 2 in the top surface is 0.33 or less,
where the ion exchange amount 2 is a value determined according to the following formula (6-1):
Ion exchange amount 2=−0.02×(H/Si)+5.54×(N—Na 2 O concentration)−0.037×(Sn concentration)  formula (6-1),

wherein, in formula (6-1):
the H/Si is a normalized hydrogen concentration, where the normalized hydrogen concentration is a value obtained by dividing an average hydrogen concentration at a depth of 0 to 10 μm by an average hydrogen concentration at a depth of 105 to 110 μm, and the average hydrogen concentration at a depth of 0 to 10 μm and the average hydrogen

Assignees

• Asahi Glass Co Ltd

Inventors

• Suzuki Yuichi
• Nakashima Tetsuya
• Sasai Jun

Classifications

• C03B18/20

  Composition of the atmosphere above the float bath; Treating or purifying the atmosphere above the float bath · CPC title

• G01N23/223

  by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence · CPC title

• G01N23/2258

  Measuring secondary ion emission, e.g. secondary ion mass spectrometry [SIMS] (mass-to-charge ratio analysis aspects of SIMS for material analysis G01N27/62) · CPC title

• C03B18/18

  Controlling or regulating the temperature of the float bath; Composition or purification of the float bath · CPC title

• C03B25/08

  of glass sheets · CPC title