Alkali-free glass

Details Alkali-free glass Alkali-free glass

2000-08-02

2003-03-25

Sample, David (Department: 1755)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C501S070000

Reexamination Certificate

active

06537937

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alkali-free glass which is suitable as glass substrates for liquid crystal display devices or photomasks.
2. Discussion of Background
Heretofore, the following properties have been required for glass substrates to be used for display devices, particularly for glass substrates designed to have metal or oxide thin films formed on their surface.
(1) It contains substantially no alkali metal oxide i.e. it is alkali-free glass.
If alkali metal ions are contained in a glass substrate, they are likely to diffuse into the above thin film thereby to deteriorate the properties of the thin film.
(2) It has a high strain point, so that deformation of a glass substrate and/or shrinkage (shrinkage accompanied by stabilization of the glass structure) due to heating during the process for forming a thin film, can be suppressed to the minimum level.
(3) It has high chemical durability (BHF resistance) against buffered hydrofluoric acid (a mixed solution of hydrofluoric acid and ammonium fluoride) to be used for etching of SiO
x
or SiN
x
formed on a glass substrate.
(4) It has high chemical durability (acid resistance) against etching by nitric acid, sulfuric acid, hydrochloric acid or the like used for etching of ITO (tin-doped indium oxide) or a metal electrode formed on a glass substrate.
(5) It has adequate chemical durability against an alkaline resist remover.
In recent years, a glass satisfying the following properties as well has been desired.
(a) It has a small specific gravity, so that the weight of a display device can be reduced.
(b) It has a small expansion coefficient, so that the temperature raising or lowering rate in a process for producing a display device can be increased, and the thermal shock resistance can be improved.
(c) It has higher acid resistance.
(d) It has a high Young's modulus, so as to reduce deflection of a glass substrate or a glass sheet before cutting out the glass substrate, by its own weight, and to make the glass substrate or the glass sheet scarcely breakable at the time of e.g. transportation.
(e) It is hardly devitrified.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide an alkali-free glass which satisfies the properties (1) to (5) and (a) to (c).
A second object of the present invention is to provide an alkali-free glass which satisfies the properties (d) and (e) in addition to such properties.
The present invention provides an alkali-free glass consisting essentially of:
SiO
2
64 to 76 mol %, 
Al
2
O
3
5 to 14 mol %,
B
2
O
3
5 to 16 mol %,
MgO
1 to 16.5 mol %,
CaO
0 to 14 mol %,
SrO
0 to 6 mol %, and
BaO
0 to 2 mol %.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The alkali-free glass of the present invention (hereinafter referred to simply as the glass of the present invention) contains substantially no alkali metal oxide. The total content of alkali metal oxides is preferably not more than 0.5 mol %.
The specific gravity of the glass of the present invention is preferably at most 2.46. If it exceeds 2.46, it tends to be difficult to reduce the weight of a display device. It is more preferably at most 2.43, further preferably at most 2.40, particularly preferably at most 2.39, most preferably at most 2.38.
The average linear expansion coefficient &agr; within a range of from 50 to 350° C. of the glass of the present invention is preferably at most 34×10
−7
/° C. If it exceeds 34×10
−7
/° C., the thermal shock resistance tends to deteriorate. It is more preferably at most 32×10
−7
/° C., particularly preferably at most 30×10
−7
/° C., most preferably at most 29×10
−7
/° C. Further, a is preferably at least 24×10
−7
/° C. If it is less than 24×10
−7
/° C., expansion matching with SiO
x
or SiN
x
formed on the glass substrate, is likely to be difficult. From this viewpoint, it is more preferably at least 26×10
−7
/° C., further preferably at least 27×10
−7
/° C., particularly preferably at least 28×10
−7
/° C., most preferably at least 30×10
−7
/° C. In the following, an average linear expansion coefficient within a range of from 50 to 350° C. will be referred to simply as an expansion coefficient.
The strain point of the glass of the present invention is preferably at least 650° C., more preferably at least 660° C., further preferably at least 670° C., particularly preferably at least 675° C., most preferably at least 680° C.
The Young's modulus of the glass of the present invention is preferably at least 64 GPa, more preferably at least 68 GPa, further preferably at least 72 GPa, particularly preferably at least 73 GPa, most preferably at least 75 GPa.
The specific modulus of the glass of the present invention i.e. the value obtained by dividing the Young's modulus by the density, is preferably at least 27 MNm/kg. If it is less than 27 MNm/kg, the deflection of the glass substrate or the glass sheet prior to cutting out the glass substrate, by its own weight, tends to be too large. It is more preferably at least 28 MNm/kg, more preferably at least 29 MNm/kg, particularly preferably at least 30 MNm/kg, most preferably at least 31 MNm/kg.
The temperature T
2
at which the viscosity of the glass of the present invention becomes 10
2
poise, is preferably at most 1,820° C. If it exceeds 1,820° C., melting of the glass tends to be difficult. It is more preferably at most 1,800° C., further preferably at most 1,780° C., particularly preferably at most 1,760° C., most preferably at most 1,750° C.
The temperature T
4
at which the viscosity of the glass of the present invention becomes 10
4
poise, is preferably at most 1,380° C. If it exceeds 1,380° C., glass forming tends to be difficult. It is more preferably at most 1,360° C., particularly preferably at most 1,350° C., most preferably at most 1,340° C.
The viscosity &eegr;
L
at a liquidus temperature of the glass of the present invention is preferably at least 10
3.5
poise. If it is less than 10
3.5
poise, glass forming tends to be difficult. It is more preferably at least 10
3.8
poise, particularly preferably at least 10
4
poise, most preferably at least 10
4.1
poise.
When the glass of the present invention is immersed in an aqueous hydrochloric acid solution having a concentration of 0.1 mol/l at 90° C. for 20 hours, it is desired that no turbidity, color change or cracking takes place on its surface. Further, the mass reduction &Dgr;W per unit surface area of the glass obtained from the surface area of the glass and the mass change of the glass due to the above mentioned immersion, is preferably at most 0.6 mg/cm
2
, more preferably at most 0.4 mg/cm
2
, particularly preferably at most 0.2 mg/cm
2
, most preferably at most 0.15 mg/cm
2
Further, it is desired that when the glass of the present invention is immersed at 25° C. for 20 minutes in a solution (hereinafter referred to as a buffered hydrofluoric acid solution) obtained by mixing an aqueous ammonium fluoride solution having a mass percentage concentration of 40% and an aqueous hydrofluoric acid solution having a mass percentage concentration of 50% in a volume ratio of 9:1, the surface will not be turbidified. Hereinafter, this evaluation using the buffered hydrofluoric acid solution, will be referred to as BHF resistance evaluation. A case where the above surface will not be turbidified, will be regarded that the BHF resistance is good. Further, the weight loss per unit area of the glass obtained from the surface area of the glass and the mass change of the glass due to the above mentioned immersion, is desired to be at most 0.6 mg/cm
2
.
A preferred embodiment of the present invention may, for example, be an alkali-free glass which consists essentially of:
SiO
2
64 to 74 mol %,
Al
2
O
3
 5 to 14 mol %,
B
2
O
3
 6 to 10 mol %,
MgO
 3 to 16.5 mol %,
CaO
 0 to 5.4 mol %,
SrO
 0 to 2 mol %, and
BaO
 0 to 2 mol %.
wherein MgO+CaO&p

Affiliated with

Also associated with

Rating

Alkali-free glass does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Alkali-free glass, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Alkali-free glass will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3018170