JPH06329439A - Li2o-al2o3-sio2 crystallized glass - Google Patents

Abstract

PURPOSE:To produce a crystallized glass of Li2O-Al2O3-SiO2 ternary system free from denitrification on production of the glass material. CONSTITUTION:This crystallized glass is composed of 55.0 to 70.0wt.% of SiO2, 15.0 to 30.0wt.% of Al2O3, 2.5 to 6.0wt.% of Li2O, 0.1 to 0.9wt.% of ZnO, 0.1 to 0.9wt.% of BaO, 1.3 to 2.9wt.% of TiO2, 0.5 to 4.0wt.% of ZrO2, 0.1 to 5.0wt.% of P2O5, 0 to 0.9wt.% of MgO, 0 to 4.0wt.% of Na2O, and 0 to 4.0wt.% of K2O and beta-quartz solid solution or beta-spodumene solid solution is precipitated as a major crystal.

Description

Detailed Description of the Invention

[0001]

The present invention relates to Li ₂ O--Al ₂ O _3-
The present invention relates to SiO ₂ type crystallized glass.

[0002]

2. Description of the Related Art Conventionally, front windows for petroleum, firewood, and other stoves, substrates for high-tech products such as substrates for color filters and image sensors, setters for firing electronic parts, shelf boards for microwave ovens, top plates for electromagnetic cookers. As a material such as Li ₂ O—Al ₂ O ₃ —SiO ₂ type low expansion crystallized glass is used. For example, Japanese Patent Publication No. 39-21
049, JP-B-40-20182 and JP-A Hei 1-308845 discloses such, main crystal as β- quartz solid solution _{(Li 2 O · Al 2 O} 3 · nSiO 2 [ provided that n
≧ 2]) and β-spodumene solid solution (Li ₂ O.Al ₂
L formed by depositing O ₃ · nSiO ₂ [where n ≧ 4])
_{i 2 O-Al 2 O 3} -SiO 2 based crystallized glass is disclosed.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Li ₂ O-A
The 1 ₂ O ₃ —SiO ₂ type crystallized glass has a low thermal expansion coefficient and a high mechanical strength, and thus has excellent thermal characteristics. In addition, since the precipitated crystals can be changed by changing the heat treatment conditions in the crystallization step,
Both a transparent crystallized glass and a white opaque crystallized glass can be produced from a raw glass having the same composition, and they can be selectively used according to their respective applications.

However, the conventional Li ₂ O--Al ₂ O ₃
The —SiO ₂ -based crystallized glass is liable to cause devitrification during the production of so-called raw glass before crystallization, resulting in poor productivity of the raw glass. Further, in applications such as a stove full-scale window and a substrate for high-tech products which are required to be transparent, deterioration of appearance quality due to the devitrified matter is considered a problem.

An object of the present invention is to provide a Li ₂ O--Al ₂ O ₃ --SiO ₂ type crystallized glass which does not cause devitrification during the production of raw glass.

[0006]

As a result of various studies, the present inventors have found that the above object can be achieved by containing a small amount of ZnO and BaO as essential components, and propose the present invention. .

Li ₂ O--Al ₂ O ₃ --SiO _{2 of the} present invention
The system crystallized glass has a weight percentage of SiO ₂ 55.0 to
70.0%, Al ₂ O ₃ 15.0 to 30.0%, Li ₂
O2.5-6.0%, ZnO 0.1-0.9%, Ba
_{O 0.1~0.9%, TiO 2 1.3~2.9%} , Z
rO ₂ 0.5 to 4.0%, P ₂ O ₅ 0.1 to 5.0%,
MgO 0-0.9%, Na ₂ O 0-4.0%, K ₂
It is characterized in that it has a composition of O 0 to 4.0% and comprises a β-quartz solid solution or a β-spodumene solid solution as a main crystal.

[0008]

In the present invention, the reason why the composition range is limited as described above will be described below.

SiO ₂ is a glass network former and a constituent of crystals, but if its content is less than 55.0%, the glass tends to devitrify and the chemical durability deteriorates. On the other hand, if it is more than 70.0%, the melting property of glass is deteriorated.

Al ₂ O ₃ is a component constituting the crystal, but if it is less than 15.0%, the meltability of the glass deteriorates. On the other hand, if it is more than 30.0%, the glass tends to devitrify and the chemical durability deteriorates.

Li ₂ O is a component that constitutes crystals,
If it is less than 2.5%, it becomes difficult to deposit desired crystals. On the other hand, if it is more than 6.0%, the chemical durability of the glass deteriorates.

ZnO is a component for facilitating crystal precipitation and a component for preventing devitrification.
If the amount is less than the above range, the chemical durability is deteriorated and devitrified substances are easily generated. On the other hand, when it is more than 0.9%, the glass tends to devitrify, and the color tone becomes brown and the transparency is impaired.

BaO is a component that improves the solubility and prevents the formation of devitrification substances, but if it is less than 0.1%, the solubility of the glass will be poor, and if it is more than 0.9%. A devitrified material is likely to be generated, or the coefficient of thermal expansion is increased to deteriorate the thermal characteristics.

TiO ₂ acts as a nucleating agent,
If it is less than 1.3%, crystallization does not occur stably and the crystals become coarse, resulting in poor chemical durability. On the other hand, 2.
If it exceeds 9%, the color tone becomes brown and the transparency is impaired.

ZrO ₂ acts as a nucleating agent,
If it is less than 0.5%, crystallization does not occur stably and the crystals become coarse. On the other hand, if it is more than 4.0%, devitrified substances are likely to be generated in the glass.

The total amount of TiO ₂ and ZrO ₂ is 2.0.
It is desirable to be in the range of ˜6.9%. If the total amount of these is less than 2.0%, sufficient nucleation does not occur, the crystals become coarse and the chemical durability deteriorates, and if it exceeds 6.9%, the solubility of the glass deteriorates and the color tone is deteriorated. Becomes brown and the transparency is impaired.

P ₂ O ₅ is Z contained as a nucleating agent.
Although it has an effect of remarkably improving the poor solubility of rO ₂ ,
If it is less than 0.1%, it has no effect. On the other hand, 5.0%
If the amount is larger than the above, the glass is likely to undergo phase separation, and uniform glass cannot be obtained.

MgO is a component for facilitating the precipitation of crystals, but if it exceeds 0.9%, the thermal expansion coefficient becomes too large.

Na ₂ O and K ₂ O have the effect of improving the solubility of the glass, but if they are more than 4.0% each, the chemical durability becomes extremely poor. The total amount of these components is 7.0.
If it exceeds%, the dielectric loss of the crystalline material will increase.

Further, the Li ₂ O--Al ₂ O ₃ --S of the present invention is used.
In addition to the above components, the io ₂ crystallized glass is As ₂ O.
_By containing 2% or less of each of the components such as ₃ , CaO and PbO, the solubility, workability and uniformity of the glass can be improved. In addition to these characteristics, in order to improve the stabilization of the glass, F ₂ , Cl ₂ , SO ₃ , Fe ₂
It is possible to contain any one kind or two or more kinds of O _{3 in} a total amount of 0.5% or less.

[0021]

EXAMPLES Hereinafter, Li ₂ O—Al ₂ O ₃ —Si of the present invention will be described.
The O ₂ type crystallized glass will be described based on Examples.

Tables 1 and 2 show examples of the present invention (Sample N).
o. 1 to 5) and comparative examples (sample Nos. 6 to 7) are shown.

[0023]

[Table 1]

[0024]

[Table 2]

Each sample in the table was prepared as follows.

Glass raw materials were prepared so as to have the composition shown in the table, melted in a platinum crucible at 1580 ° C. for 16 hours, then poured onto a carbon stand and roller-molded to obtain a plate-shaped raw glass. Next, each raw glass was crystallized under the following two types of heat treatment conditions and then cooled in a furnace to obtain a sample. (Heat treatment condition 1) The temperature was raised to 740 ° C. at a rate of 300 ° C./hour, the temperature was maintained for 2 hours to perform nucleation, then the temperature was raised to 850 ° C. at a rate of 80 ° C./hour, and at that temperature It was kept for 2 hours for crystal growth. (Heat treatment condition 2) The temperature was raised to 740 ° C. at a rate of 300 ° C./hour, the temperature was maintained for 2 hours to perform nucleation, and then the temperature was raised to 1180 ° C. at a rate of 80 ° C./hour, and at that temperature It was kept for 1 hour for crystal growth.

Next, the appearance, main crystals and coefficient of thermal expansion of the obtained sample were evaluated. In addition, the number of devitrified substances generated was measured using raw glass. The results are shown in the table.

As is clear from the table, all the samples had a transparent appearance under the heat treatment condition 1 and the main crystal was β-.
Quartz solid solution, and -4.0 to -2.0 × 10 ^-7 /
The coefficient of thermal expansion in ° C was shown. Further, under heat treatment condition 2, it had a white opaque appearance, the main crystal was a β-spodumene solid solution, and showed a thermal expansion coefficient of 9.0 to 12.5 × 10 ^-7 / ° C.

However, regarding the number of devitrified substances generated,
Sample No. which is an example of the present invention. No devitrified substances were observed in Nos. 1 to 5, whereas sample No. 1 as a comparative example.
6 and 7 were each also 500/10 cm ² and 450/10 cm ^2.

These facts are due to the fact that the Li ₂ O--Al of the present invention is
₂ O ₃ —SiO ₂ type crystallized glass contains a small amount of BaO and Z.
Since nO is contained as an essential component, generation of devitrified substances is prevented.

The main crystal was obtained by a powder X-ray diffraction method,
The thermal expansion coefficient was calculated by a differential detection type relative dilatometer. The number of devitrified substances generated was evaluated as follows. First, 100 g of raw glass of each sample was melted by holding it in a melting furnace at 1450 ° C. for 1 hour using a platinum crucible, then cooled to 1350 ° C. and held for 24 hours. Subsequently, the glass was taken out from the platinum crucible, annealed, and then evaluated by observing devitrified substances in the glass with a stereoscopic microscope.

[0032]

As described above, the Li ₂ O of the present invention is used.
In the -Al ₂ O ₃ -SiO ₂ -based crystallized glass, devitrification substances do not occur in the process of manufacturing the raw glass, so that the productivity of the raw glass can be significantly improved.

Moreover, since there is no deterioration in appearance quality due to devitrified substances, it is suitable as a stove full-scale window or a substrate for high-tech products. Furthermore, conventional Li ₂ O-Al ₂ O ₃ -SiO ₂
Since the coefficient of thermal expansion is very low, similar to that of the system crystallized glass,
It can be used as many industrial materials such as a setter for baking electronic parts, a shelf for microwave ovens, and a top plate for electromagnetic cookers.

Claims (1)

[Claims] 1. A weight percentage of SiO ₂ 55.0-7.
0.0%, Al ₂ O ₃ 15.0 to 30.0%, Li ₂ O
2.5-6.0%, ZnO 0.1-0.9%, Ba
_{O 0.1~0.9%, TiO 2 1.3~2.9%} , Z
rO ₂ 0.5 to 4.0%, P ₂ O ₅ 0.1 to 5.0%,
MgO 0-0.9%, Na ₂ O 0-4.0%, K ₂
Li ₂ O-Al ₂ O ₃ -SiO ₂ -based crystallized glass having a composition of O 0 to 4.0% and depositing β-quartz solid solution or β-spodumene solid solution as a main crystal. .