Glass plate for substrate, method for producing same, and method for producing TFT panel

1. A glass plate for a substrate, comprising, as a glass matrix composition, in mol % on a basis of oxide moles:

SiO 2 from 67 to 72,

Al 2 O 3 from 1 to 7,

B 2 O 3 from 0 to 4,

MgO from 11 to 15,

CaO from 0 to 3,

SrO from 0 to 3,

BaO from 0 to 4,

ZrO 2 from 0 to 4,

Na 2 O from 8 to 15, and

K 2 O from 0 to 7,

wherein

SiO 2 +Al 2 O 3 is from 71 to 75.2,

MgO+CaO+SrO+BaO is from 11 to 17,

Na 2 O+K 2 O is from 8 to 17, and

K 2 O/(Na 2 O+K 2 O)≦0.13×(SiO 2 +Al 2 O 3 +0.5B 2 O 3 +0.3BaO)−9.4 is satisfied, and

wherein

the glass plate has a β-OH value (mm −1 ) of from 0.05 to 0.5, and

a heat shrinkage ratio (C) of 16 ppm or less.

2. A glass plate for a substrate, comprising, as a glass matrix composition, in mol % on a basis of oxide moles:

SiO 2 from 67 to 72,

Al 2 O 3 from 1 to 7,

B 2 O 3 from 0 to 4,

MgO from 11 to 15,

CaO from 0 to 3,

SrO from 0 to 3,

BaO from 0 to 2,

ZrO 2 from 0 to 4,

Na 2 O from 8 to 15, and

K 2 O from 0 to 7,

wherein

SiO 2 +Al 2 O 3 is from 73 to 77,

MgO+CaO+SrO+BaO is from 11 to 17,

Na 2 O+K 2 O is from 8 to 17, and

K 2 O/(Na 2 O+K 2 O)≦0.13×(SiO 2 +Al 2 O 3 )−9.4 is satisfied, and

wherein

the glass plate has the β-OH value (mm −1 ) of from 0.05 to 0.5, and

the heat shrinkage ratio (C) of 16 ppm or less.

3. The glass plate for a substrate according to claim 1 , wherein

an average thermal expansion coefficient of the glass plate at 50 to 350° C. is 85×10 −7 /° C. or less,

a glass transition temperature (Tg) of the glass plate is 560° C. or more,

a temperature T 2 at which a viscosity of the glass of the glass plate becomes 10 2 dPa·s is 1,700° C. or less, and

a temperature T 4 at which the viscosity of the glass of the glass plate becomes 10 4 dPa·s is 1,250° C. or less.

4. The glass plate for a substrate according to claim 1 , wherein the β-OH value (mm −1 ) is from 0.2 to 0.5.

5. The glass plate for a substrate according to claim 1 , wherein,

the content of SiO 2 is from 67 to 70.5, and

the content of Na 2 O is from 8 to 12.8.

6. A method to produce the glass plate for a substrate of claim 1 , comprising:

melting the glass raw material composition to obtain a molten glass;

forming the molten glass into a ribbon-shaped glass plate in a float forming furnace; and

cooling the glass plate to obtain the glass plate for a substrate

in a room temperature state, wherein

a water amount in the molten glass is controlled such that the β-OH value (mm −1 ) of the glass plate for a substrate is from 0.05 to 0.5, and

when a surface temperature of the glass plate withdrawn from the float forming furnace is cooled from a temperature T H (° C.) to room temperature T L (° C.), and a time required for the surface temperature of the glass plate to reach T L from T H with said cooling is set to t (min) at an average cooling rate represented by (T H −T L )/t of 10 to 300° C./min.

7. The production method of claim 6 wherein

the water amount in the molten glass is controlled such that the β-OH value (mm −1 ) of the glass plate for a substrate is from 0.2 to 0.5.

8. A method for producing a TFT panel, comprising:

depositing an array substrate gate insulating film on a surface of a glass plate for a substrate;

laminating together the array substrate and a color filter substrate; wherein

the film deposition comprises heating the film deposition region on a surface of the glass plate for a substrate according to claim 1 to a film deposition temperature within the range of from 150 to 300° C., holding the film deposition region at the film deposition temperature for 5 to 60 minutes, and depositing the gate insulating film in the film deposition region.