A manufacturing method of a glass panel for a glass panel unit includes a melting step, a spreading step, an annealing step, a cutting step, and a spacer disposition step. The spacer disposition step is a step of disposing spacers onto a glass sheet and is performed by a spacer disposition device prior to the cutting step.

Apparatus and method for producing a reliable breaking line for the industrial cutting to length of glass sheets by means of a cutting wheel running on a float glass line under pressure imposed from above, with the following features: a) the location of the beginning of a breaking line is determined and a cutting wheel holder (20) with a cutting wheel (2) is brought into position, b) the cutting wheel holder (20) is lowered and the cutting wheel (2) is lowered onto the glass sheet (1) concerned with the desired pressing pressure, wherein the pressing pressure is set by means of a swing arm (3) and is monitored by means of a strain gauge (4) secured thereto, c) a change in the height of the glass sheet (1) prompts a control signal for an actuating motor (12) to be derived from the change in the resistance of the strain gauge (4), and the actuating motor brings about a corresponding change in the pressing pressure of the cutting wheel (2).

Apparatus and method for producing a reliable breaking line for the industrial cutting to length of glass sheets by means of a cutting wheel running on a float glass line under pressure imposed from above, with the following features: a) the location of the beginning of a breaking line is determined and a cutting wheel holder (20) with a cutting wheel (2) is brought into position, b) the cutting wheel holder (20) is lowered and the cutting wheel (2) is lowered onto the glass sheet (1) concerned with the desired pressing pressure, wherein the pressing pressure is set by means of a swing arm (3) and is monitored by means of a strain gauge (4) secured thereto, c) a change in the height of the glass sheet (1) prompts a control signal for an actuating motor (12) to be derived from the change in the resistance of the strain gauge (4), and the actuating motor brings about a corresponding change in the pressing pressure of the cutting wheel (2).

A tempered glass of the present invention includes, as a glass composition, in terms of mass %, 45 to 75% of SiO.sub.2, 0 to 30% of Al.sub.2O.sub.3, and 0 to 30% of Li.sub.2O+Na.sub.2O+K.sub.2O and has a β-OH value of 0.3 to 1/mm.

The present invention relates to an alkali-free glass substrate, in which when two arbitrary sites in one main surface thereof are selected, an absolute value of a difference between a thermal shrinkage ratio in an arbitrary direction at one site and a thermal shrinkage ratio in a direction orthogonal to the arbitrary direction at another site is 2 ppm or less, provided that the thermal shrinkage ratio is calculated by measuring a deformation amount in a measuring direction of the glass substrate between before and after a heat treatment of raising a temperature from normal temperature to 600° C. at 100° C./hour, holding the glass substrate at 600° C. for 80 minutes, and lowering the temperature from 600° C. to normal temperature at 100° C./hour.

A glass for chemical strengthening that is a float-formed glass for chemical strengthening includes, as represented by mass percentage based on oxides, from 65 to 72% of SiO.sub.2, from 3.6 to 8.6% of Al.sub.2O.sub.3, from 3.3 to 6% of MgO, from 6.5 to 9% of CaO, from 13 to 16% of Na.sub.2O and from 0 to 0.9% of K.sub.2O. In the glass for chemical strengthening, (Na.sub.2O+K.sub.2O)/Al.sub.2O.sub.3 is from 2.2 to 5. The glass for chemical strengthening has a sheet thickness (t) of 0.1 mm or more and 2 mm or less. A SnO.sub.2 amount of a bottom surface in an unpolished state of the glass for chemical strengthening is 6.2 μg/cm.sup.2 or less (0.1≦t≦1 mm) or (2t+4.2) μg/cm.sup.2 or less (1<t≦2 mm).

A glass for chemical strengthening that is a float-formed glass for chemical strengthening includes, as represented by mass percentage based on oxides, from 65 to 72% of SiO.sub.2, from 3.6 to 8.6% of Al.sub.2O.sub.3, from 3.3 to 6% of MgO, from 6.5 to 9% of CaO, from 13 to 16% of Na.sub.2O and from 0 to 0.9% of K.sub.2O. In the glass for chemical strengthening, (Na.sub.2O+K.sub.2O)/Al.sub.2O.sub.3 is from 2.2 to 5. The glass for chemical strengthening has a sheet thickness (t) of 0.1 mm or more and 2 mm or less. A SnO.sub.2 amount of a bottom surface in an unpolished state of the glass for chemical strengthening is 6.2 μg/cm.sup.2 or less (0.1≦t≦1 mm) or (2t+4.2) μg/cm.sup.2 or less (1<t≦2 mm).

The present invention relates to a float glass substrate including an alkali-free glass, the float glass substrate having a Cl content of from 0.10 to 0.50 mass %, containing substantially no SnO.sub.2, and having a Pt content of, by mass, from 0.001 to 0.30 ppm. The float glass substrate may have a Rh content of, by mass, from 0.001 to 0.50 ppm.

An alkali-free glass includes, in mol % in terms of oxides: SiO.sub.2: 63-75%; Al.sub.2O.sub.3:10-16%; B.sub.2O.sub.3: larger than 0.5% and 5% or smaller; MgO: 0.1-15%; CaO: 0.1-12%; SrO: 0-8%; and BaO: 0-6%. [MgO]/[CaO] is larger than 1.5. A value of Formula (A) is 82.5 or larger. A value of Formula (B) is 690 or larger and 800 or smaller. A value of Formula (C) is 100 or smaller. A value of Formula (D) is 20 or smaller. The alkali-free glass has a Young's modulus of 83 GPa or larger and a surface devitrification viscosity η.sub.c of 10.sup.4.2 dPa.Math.s or higher.

An alkali-free glass includes, in mol % in terms of oxides: SiO.sub.2: 63-75%; Al.sub.2O.sub.3: 10-16%; B.sub.2O.sub.3: 0-5%; MgO: 0.1-15%; CaO: 0.1-12%; SrO: 0-8%; and BaO: 0-6%. [MgO]/[CaO] is 1.5 or smaller. A value of Formula (A) is 82.5 or larger. A value of Formula (B) is 690 or larger and 800 or smaller. A value of Formula (C) is 100 or smaller. A value of Formula (D) is 20 or smaller. The alkali-free glass has a Young's modulus of 83 GPa or larger and a surface devitrification viscosity η.sub.c of 10.sup.4.2 dPa.Math.s or higher.