JPH04175242A - Non-alkali glass - Google Patents

Abstract

PURPOSE:To obtain a non-alkali glass suitable as a substrate for a p-Si-TFT liquid crystal display by compounding SiO2, Al2O3, B2O3, MgO, CaO, SrO, BaO, ZnO, etc., at specific ratios and melting the mixture. CONSTITUTION:Raw material components are compounded to get a composition containing 55-65mol% of SiO2, 5-15mol% of Al2O3, 0.1-5mol% of B2O3, 5-15mol% of MgO, 5-15mol% of CaO, 1-9mol% of SrO, 1-9mol% of BaO and 0-3mol% of ZnO (total amount of the above components is >=95mol%). The mixture is continuously charged into a melting furnace, melted by heating at 1500-1600 deg.C formed in the form of a plate having a prescribed thickness by a float process, slowly cooled and cut to obtain a non-alkali glass having a strain point of >=650 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alkali-free glass that substantially does not contain alkali metal oxides and can be float-formed, and is suitable as a substrate glass for various displays and photomasks. It is something.

C. Prior Art Conventionally, various types of display glass, especially those on which a metal or oxide thin film is formed, have been required to have the following characteristics.

・It has a high strain point because it is exposed to high temperatures during the thin film formation process.

- If the film contains an alkali metal oxide, the alkali metal ions will diffuse into the thin film and deteriorate the film properties, so it must be substantially free of alkali metal ions.

- Defects inside and on the surface (bubbles, striae, inclusions,
No bits, scratches, etc.)

・Have chemical durability that can withstand cleaning processes.

In particular, in recent years, so-called a-Si-TFT (Thin Film), which forms semiconductor transistors etc. on glass substrates, has been developed.
(mTransistor) type liquid crystal displays are increasing in number. Corning #7059 is used as a glass that satisfies these requirements, but its strain point is around 600°C, so it is not suitable for use as a p-3i-TFT type liquid crystal substrate, which requires heat treatment at an even higher temperature. There was a problem that it was difficult to use.

On the other hand, as a glass having a strain point of 650°C or more required for p-5i-TPT, JP-A-58-32O
There is a glass disclosed in No. 3038, but since the glass composition contains lead oxide, an exclusion device must be installed in compounding equipment, melting equipment, polishing equipment, etc.

Furthermore, it is clear that this is not a desirable working environment.

As for the forming method, the float method is the most preferable because it has the advantage of being able to mold wide objects and can supply glass substrates at low cost because it can be mass-produced. It has been manufactured using the fusion method. However, the roll-out method has the drawback that the glass must be polished, and the fusion method has the drawback that the maximum molding size is about 1 m, making it difficult to handle future large-sized liquid crystal displays.

C Problems to be Solved by the Present Invention] The purpose of the present invention is to solve the above-mentioned drawbacks, to have a material that does not substantially contain alkali metal oxides, has excellent heat resistance, has a low coefficient of thermal expansion, and has chemical durability. The purpose of the present invention is to provide a substrate glass that has excellent properties, is easy to remove bubbles and striae, has good melting properties, and can be formed by the float method.

[Means for Solving the Problems] The glass of the present invention has been made to solve the above-mentioned problems, and has a mole percentage of 5iOa 55-65% A1.Os 5-15% B, 0.0.1- 5% MgO 5-15% CaO 5-15% SrO 1-9% BaO 1-9% ZnO 0-3% The total of these components is 95% or more.

Detailed explanation of the structure The rationale for limiting the glass composition range in the present invention will be explained below.

5ins is a glass network homer and 6ins
If it exceeds 5%, the viscosity becomes high and the meltability decreases, which is undesirable. On the other hand, if SiO□ is less than 55%, the durability of the glass deteriorates and the coefficient of expansion increases, which is undesirable.

The content of SiOx is more preferably in the range of 57% to 63% within the above range.

A1□0. is added to stabilize the glass. 5%
If it is less than 15%, the chemical durability deteriorates, and if it is more than 15%, the meltability deteriorates, and crystals of MgO・Aft(h) tend to precipitate, which is not preferable. A1.O, is 7% in the above range. A range of −13% is more preferable.

B2O30. has the effect of reducing viscosity at high temperatures without increasing the coefficient of thermal expansion. B2O3 is 0.1%
If it is less than 5%, such effects will not be obtained substantially, and if it exceeds 5%, chemical durability will deteriorate, which is not preferable. B25
Among the above ranges, s is more preferably in the range of 0.1% to 3%.

MgO has the effect of improving meltability without increasing the coefficient of thermal expansion. If MgO is less than 5%, this effect will be small, and if it exceeds 15%, MgO・A1.0. Alternatively, MgO3iO□ crystals are likely to precipitate, so neither is preferable.
% is preferred.

CaO has the effect of improving meltability and suppressing the devitrification temperature, but if it is less than 5%, this effect is insufficient;
%, the expansion rate becomes too large and CaO・A
Crystals of 1□03.SiO□ precipitate, which is not preferable. For CaO, the range of 7-13% is more preferable.

By adding SrO, almost the same effect as CaO can be obtained. If the SrO content is less than 1%, this effect will be small, and if it exceeds 9%, the expansion coefficient will be too large (too much), which are both undesirable.The SrO content is more preferably in the range of 2-7%.

By adding BaO, almost the same effect as CaO can be obtained. If the BaO content is less than 1%, this effect will be small, and if it exceeds 9%, the expansion rate will become too large, and both are unfavorable. The BaO content is more preferably in the range of 2-7%.

ZnO is reduced and evaporated in the float bath, forming a heterogeneous layer on the surface layer and making float molding difficult, so it is desirable that the content is 3% or less. The ZnO content is more preferably in the range of O-1.5%.

In order to improve moldability etc., PbO1TiO of 5% or less
a, ZrOx, P2O5, F, CI, etc. can be added.

The glass of the present invention can be manufactured, for example, by the following method. The raw materials for each component that are normally used are blended to achieve the target component, and this is continuously fed into a melting furnace.
Heat to 600°C to melt. This molten glass is formed into a predetermined thickness by the float method, slowly cooled, and then cut.

[Example] Table 1 shows examples of the present invention (No. 1 to No. 6).

Raw materials for each component were mixed to have a target composition, and heated and melted at a temperature of 1500 to 1600°C for 5 to 4 hours using a platinum crucible.

During melting, a platinum stirrer was inserted and stirred for 1 to 2 hours to homogenize the glass.

Next, the molten glass was poured out, formed into a plate shape, and then slowly cooled.

It also showed float formability as checked in a small float furnace.

Table 1 shows glass composition, coefficient of thermal expansion, high temperature viscosity, devitrification temperature,
degree, strain point, water resistance, and acid resistance. Water resistance is 95℃
After being immersed in ion-exchanged water for 40 hours, the weight loss was measured and expressed in terms of weight loss per unit area of glass.

Acid resistance is 2 oz in 1/100 normal HN at 95°C.
After being immersed in O2 for 30 hours, the weight loss was measured and expressed in terms of weight loss per unit area of glass.

As is clear from the table, the glass according to the present invention (No. 1
~6) shows a low swelling coefficient of 40 to 50X 10-'/'C, and the temperature at which log η = 2.5 (where η is the glass viscosity expressed in voice, the same applies hereinafter), which is a guideline for dissolution. It can be seen that it is easy to dissolve.

Further, the difference between the temperature at which 1ogl=4.0, which is a measure of float moldability, and the devitrification temperature was sufficiently large, and there were no problems such as generation of devitrification during molding.

It also has a strain point of 650° C. or higher, which seems to be enough to withstand the high temperature heat treatment that is expected to occur in the p-3iTPT process.

In Comparative Example No. 7, warpage and distortion occur on the surface due to the aggressiveness of ZnO during float molding.

Table 1 [Effects of the Invention] The glass according to the present invention can be molded by a float method. Furthermore, it has excellent melting and moldability, excellent heat resistance, and a low coefficient of thermal expansion, making it ideal for substrates for p-5i TFT type night crystal displays. In addition, it is also suitable for EL (electroluminescence) substrates and photomask substrates.

'Go 4? Procedural amendment March lk, 1991

Claims (2)

[Claims] (1) Consisting of SiO_255-65%, Al_2O_35-15%, B_2O_30.1-5%, MgO5-15%, CaO5-15%, SrO1-9%, BaO5-9%, ZnO0-3% in mole percent, and substantially eliminates alkali oxides. Alkali-free glass with a total of 95% or more of these components (2) Substantially in mole percent SiO_257-63% Al_2O_37-13% B_2O_30.1~3% MgO7-13% CaO7-13% SrO2~7% BaO2~7% ZnO0~1.5% The alkali-free glass according to claim 1 consisting of