JPS61281041A - Alkali-free glass - Google Patents

Abstract

PURPOSE:To provide the titled glass composed of SiO2, Al2O3, B2O3, MgO, etc., at a specific composition, having excellent chemical durability, meltability, moldability and heat-resistance, suitable as a substrate of a display, etc., free of PbO and causing no environmental pollution. CONSTITUTION:The objective composition can be produced by compounding 50-60(wt)% SiO2, 10-20% Al2O3, 0.1-4% B2O3, 3-10% MgO, 6-14% ZnO, 3-10% CaO, 3-10% BaO, 0-4% ZrO2 and 0-5% SrO (CaO+SrO is 3-10%, BaO+SrO is 3-10%) (the sum of the above components is 98%), and adding the remaining part of a clarifying agent (e.g. Cl2) to the mixture. The composition is heated and melted in a smelting furnace at 1,500-1,600 deg.C, formed to a plate having a definite thickness, cooled slowly, cut to desired size and polished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an alkali-free glass that does not substantially contain alkali metal oxides.

[Conventional technology]

As alkali-free glasses for use in electronic components such as photomasks and various display substrates, glasses containing PI)O and glasses not containing PI)O have been proposed. Specific examples of the latter type of glass include, for example, those having the following composition (numbers are weight %).

■5iOz 50. Al20s 10. B20
s15. BaO25@5i0246.9. Bg
Os 14. BaO33, Alzos 6 However, glass containing PbO does not contain PbO during melting.
There are disadvantages in that air pollution is caused by the volatilization of carbon dioxide, and environmental pollution is caused by raw materials and waste. Also, pbo
Since the transmittance of ultraviolet rays decreases due to the transition metal contained as an impurity in the raw material, it is unsatisfactory for applications such as photomasks that require high transmittance.

On the other hand, glasses that do not contain pbo have insufficient heat resistance and chemical durability, and have limitations in terms of use.

[Problem to be solved by the invention]

An object of the present invention is to solve the above-mentioned difficulties of conventional glasses and to provide an alkali-free glass that has excellent glass melting and moldability and has a small coefficient of thermal expansion.

[Means for solving problems]

The present invention is expressed as 1% by weight, and is substantially 5i02 50~60Al2O
3 10~20Bz03
0.1~4MgO
3-10 ZnO 6-14Ca
O3~10 BaO3~10 ZrOz (1~4S
rO0~5C! a O+S ro 3-10
Provided is an alkali-free glass consisting of 3 to 10 BaO+SrO.

The reasons for limiting the composition in the present invention are as follows. Hereinafter, unless otherwise specified, ``chi'' means % by weight.

5102 is a glass network homer, 60
If it exceeds %, the viscosity increases and the meltability decreases, which is not preferable. On the other hand, if 5102 is less than 50 inches, the chemical durability of the glass will deteriorate and the coefficient of thermal expansion will increase, which is not preferable.

5102 is more preferably in the range of 53 to 57% of the above range.

Al2O3 is added to stabilize the glass.

If A'1203 is less than 10%, the viscosity of the glass becomes too large, which is undesirable, and if it exceeds 20%, MgO-Al
This is not preferable because crystals such as 20a-8i○z and ZnO-A12as tend to precipitate. More preferably, Al20a is in the range of 13 to 17% in the above range.

B2O3 has the effect of reducing viscosity at high temperatures without increasing the coefficient of thermal expansion. If the B2O3 content is less than 0.1%, such effects cannot be substantially obtained, and if it exceeds 5%, the chemical durability decreases, which is not preferable. B
It is more desirable that 2O3 be in the range of 0.1 to 3 cm within the above range.

MgO has the effect of improving meltability without increasing the coefficient of thermal expansion.If MgO is less than 3%, this effect is small, and if it exceeds 10%, MgO・Al2O3・5102
Both of these are unfavorable because crystals tend to precipitate.

Among the above ranges, MgO is more preferably in the range of 4 to 8.

By adding ZnO, almost the same effect as MgO can be obtained. If the amount of ZnO is less than 4, the effect of addition is small, and if it exceeds 14, ZnO--Al20a crystals tend to precipitate, and both are unfavorable. The ZnO content is more preferably in the range of 8 to 12% within the above range.

CaO has the effect of improving meltability and suppressing the devitrification temperature, but if it is less than 3%, this effect is insufficient;
If the value exceeds 1, the coefficient of thermal expansion becomes too large (too much), which is not preferable.It is more desirable for CaO to be in the range of 4 to 8.

By adding BaO, almost the same effect as OaO can be obtained. If the BaO content is less than 3%, this effect will be small, and if it exceeds 10%, the coefficient of thermal expansion will become too large, both of which are not preferred. Bo.

is more preferably in the range of 4 to 8 out of the above ranges.

Although Zr0z is not an essential component, its addition can reduce the coefficient of thermal expansion and improve chemical durability. When ZrO2 exceeds 4 inches, the viscosity becomes too large,
Moreover, it is not preferable because the stability of the glass deteriorates. Zr
(It is more desirable that h be less than 1.5 inches.

SrO is C! It can be used as a component to partially replace ao and BaO. If the total amount of SrO exceeds 5 inches, the coefficient of thermal expansion increases, which is not preferable.

Furthermore, glass in the range of 5i(h + Al2O368 to 72% is particularly desirable because it has excellent meltability.
+ZnO glass in the range of 13 to 18 degrees is particularly desirable because it has a low coefficient of thermal expansion and a low devitrification temperature. In the glass of the present invention, the total amount of the above components accounts for at least 98 degrees, with the remainder being C1z, F2°. SbgOg
, AB20s, E303, etc. can be contained.

The glass of the present invention can be manufactured, for example, as follows.

The raw materials for each component that are normally used are mixed to have the target composition, and this is continuously fed into a melting furnace.
Heat to 00°C to melt.

This molten glass is formed into a ribbon of a predetermined thickness by a roll-out method, and after being slowly cooled, it is cut. Next, the surface of this glass is polished to form a plate glass.

Example Raw materials for each component were mixed to have a target composition, and melted by heating at a temperature of 1500 to 1550° C. for 3 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, slowly cooled, and then the surface was polished to produce six types of glasses (samples &1 to 6) listed in Table 1.

For these glasses, thermal expansion coefficient, softening point, viscosity coefficient, devitrification temperature, water resistance, volume resistivity, melting property, acid resistance,
The alkali resistance was measured and the results are shown in Table 2. In addition,
Meltability is determined by using 0aC1z + Ba as a clarifier in the raw materials.
Add about 0.3% SO4 and heat at 1600℃4 in a platinum crucible.
It is expressed as the number of bubbles contained in I kg of molten glass after heating for an hour.

Water resistance was determined by measuring the weight loss after 40 hours of immersion in ion-exchanged water at 95° C., and converting the weight loss per unit surface area of the glass.

Acid resistance was determined by measuring the weight loss after immersing the sample in specified HNOa at 95° C. for 20 hours, and converting it into a value per unit surface area of the glass.

Alkali resistance was determined by measuring the weight loss after immersion in 54 NaOH at 80° C., and converting the weight loss per unit surface of the glass.

Separately, the above glass raw materials are put into a small melting furnace,
Molten glass was rolled out.

One hour after the start of roll-out molding, it is investigated whether devitrification exists in the formed glass, and if devitrification exists, it is marked with an
Items that do not exist are marked O in the formability column of Table 2.

On the other hand, as comparative examples, three types of glasses (boiled 7 to 9) were manufactured, and the same measurements were conducted, and the results are also listed in Tables 1 and 2.

As is clear from these tables, the glass according to the present invention has excellent chemical durability such as water resistance, acid resistance, and alkali resistance, excellent meltability, and excellent heat resistance due to its high softening point.

〔Effect of the invention〕

The glass according to the present invention has excellent chemical durability, meltability,
Since it has excellent moldability, excellent heat resistance, and a relatively low coefficient of thermal expansion, it is suitable for applications that require such properties, such as display substrates and photomasks.

Furthermore, since it does not contain PbO, there is no risk of environmental pollution.

Claims (3)

[Claims] (1) In weight%, substantially SiO_2 50~60 Al_2O_3 10-20 B_2O_3 0.1~4 MgO 3-10 ZnO 6-14 CaO　3～10 BaO 3-10 ZrO_2 0-4 SrO　0～5 CaO+SrO 3-10 BaO+SrO 3-10 Alkali-free glass made of (2) Substantially expressed in weight% SiO_2 53-57 Al_2O_3 13-17 B_2O_3 0.1~3 MgO 4-8 ZnO 8-12 CaO 4-8 BaO 4-8 ZrO_2 0-1.5 SrO　0～5 CaO+SrO 4-8 BaO+SrO 4-8 The alkali-free glass according to claim 1 consisting of (3) The alkali-free glass according to claim 1 or 2, which is substantially SiO_2+Al_2O_3 68-72 Mg+ZnO 13-18 in weight %.