JPH11228181A - Li2-al2o3-sio2 based glass ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide Li2 -Al2 O3 -SiO2 based glass ceramics having properties equal to or more than a conventional products, even though As2 O3 is not used as a fining agent. SOLUTION: This glass ceramics have a composition of (by wt.%) 60-75% SiO2 , 17-27% Al2 O3 , 3-6% Li2 , 0-2.9% MgO, 0-4% ZnO, 0.3-10% BaO, 0-3% Na2 O, 0-3% K2 O, 0-2% TiO2 , 1-4% ZrO2 , 0-3% P2 O5 , 0.1-2% SnO2 , and 0-1% Cl, and BaO/SnO2 is in the range of 0.2-10 in a weight ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to Li ₂ O—Al ₂ O ₃ −
It relates to an SiO ₂ -based crystallized glass.

[0002]

2. Description of the Related Art Conventionally, front windows of oil stoves, wood stoves, etc., substrates for high-tech products such as color filters and image sensor substrates, setters for firing electronic components, shelf plates for microwave ovens, top plates for electromagnetic cooking, Li ₂ O—Al ₂ O ₃ —Si as a material for window glass for fire doors, etc.
O ₂ -based crystallized glass is used. For example, Shoko 3
No. 9-21049, Japanese Patent Publication No. 40-20182, Japanese Patent Application Laid-Open No. 1-308845, etc. disclose β as a main crystal.
-Quartz solid solution (Li ₂ O.Al ₂ O ₃ .nSiO ₂ [n ≧ 2]) or β-spodumene solid solution (Li ₂ O.
A Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass obtained by depositing Al ₂ O ₃ .nSiO ₂ [where n ≧ 4]) is disclosed.

A Li ₂ O—Al ₂ O ₃ —SiO ₂ crystallized glass has a low coefficient of thermal expansion and a high mechanical strength.
Has excellent thermal properties. Further, since the precipitated crystals can be changed by changing the heat treatment conditions in the crystallization step, a transparent crystallized glass (β-quartz solid solution is precipitated) and a white opaque crystallized glass (β -Spodumene solid solution) can be produced, and can be used properly depending on the application.

[0004]

However, when producing this type of crystallized glass, a high temperature exceeding 1400 ° C.
In particular, it is necessary to melt at about 1550-1750 ° C.
Therefore, the fining agent added to the glass batch is capable of generating a large amount of fining gas during melting at a high temperature.
s ₂ O ₃ is used.

In batch melting, As ₂ O ₃
Is oxidized to As ₂ O ₅ at 400-500 ° C.
At 00 to 1800 ° C., it is reduced again to As ₂ O ₃ and releases oxygen gas. The diffusion of the oxygen gas into the bubbles in the glass melt promotes the expansion and flotation of the bubbles, and removes the bubbles from the melt. As ₂ O ₃ is, by this action,
Are widely used as a fining agent for glass, it is very effective as a fining agent for _{Li 2 O-Al 2 O 3} -SiO 2 based glass ceramics requiring particularly hot melt.

[0006] However, As ₂ O ₃ is highly toxic and may pollute the environment during the glass manufacturing process or the treatment of waste glass.

An object of the present invention is to provide As ₂ O ₃ as a fining agent.
An object of the present invention is to provide a Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass having clarity equal to or higher than that of a conventional product even without using.

[0008]

The Li ₂ O—Al of the present invention
₂ O ₃ —SiO ₂ -based crystallized glass has a weight percentage of Si
O ₂ 60-75%, Al ₂ O ₃ 17-27%, Li
₂ O 3-6%, MgO 0-2.9%, ZnO 0
4%, BaO 0.3-10%, Na ₂ O 0-3%,
_{K 2 O 0~3%, TiO 2} 0~2%, ZrO 2 1
_{~4%, P 2 O 5 0~3} %, SnO 2 0.1~2
%, Cl 0-1%, and BaO / SnO ₂ in a weight ratio of 0.2-10.

[0009]

The Li ₂ O—Al ₂ O ₃ —SiO ₂ crystallized glass of the present invention precipitates a β-quartz solid solution or a β-spodumene solid solution as a main crystal. By precipitation of these crystals, about −10 to 30 × 10 ⁻⁷ / ° C. (30 to ⁷
A glass having a low coefficient of thermal expansion (50 ° C.) and high mechanical strength. When a β-quartz solid solution is precipitated as a main crystal, a transparent crystallized glass is obtained, and when a β-spodumene solid solution is precipitated, a white opaque crystallized glass is obtained.

The Li ₂ O—Al ₂ O ₃ —Si of the present invention
O ₂ -based crystallized glass uses SnO ₂ as a fining agent. Further, Cl is added as required.

SnO ₂ is used in a high temperature range of 1400 ° C. or more,
Chemical reaction (SnO ₂ [4
(Valency) → SnO (divalent)) to release a large amount of oxygen gas as a fining gas. The released oxygen gas diffuses into the residual bubbles in the glass and increases the bubble diameter to float, so that the bubbles can be removed from the melt. Cl is added as a chloride to the glass raw material and exists in the form of Cl ions in the glass melt. Cl ions, like oxygen gas, diffuse into bubbles as the temperature of the melt increases, and serve to expand and float the bubbles. In the present invention, C
It is not necessary to add l, but it is preferable to add Cl in order to obtain higher clarity.

By the way, when SnO ₂ and As ₂ O ₃ are compared at the same addition amount, the amount of released oxygen of SnO ₂ from the batch vitrification temperature (around 1300 ° C.) to the glass melting temperature (1550-1750 ° C.) is As ₂ O _Since it is less than ₃ , even if As ₂ O ₃ is simply replaced with the same amount of SnO ₂ , the same fining effect cannot be obtained. According to experiments of the present inventors, when increasing the amount of SnO ₂ to a 3 times the As ₂ O _3, but the same fining effect and As ₂ O ₃ is obtained is known, In this case, it is not preferable because SnO ₂ undissolved matter is generated and impurities (Fe ions) are colored.

[0013] Therefore the method for improving the refining effect of SnO ₂ a result of various studies, there is work to improve the refining effect of SnO ₂ to BaO, the oxygen gas from the SnO ₂ is effective by combination of SnO ₂ and BaO It has been found that it acts on clarification and that a clarification effect equivalent to that of As ₂ O ₃ can be obtained. This is considered to be because BaO has the following functions.

By promoting the dissolution of the SnO ₂ raw material, which is difficult to melt, the scattering of the SnO ₂ raw material is reduced, and the release of oxygen gas before the melting of the raw material is suppressed. Promotes dissolution of undissolved raw materials and shortens fining time. Reduce the melt viscosity, increase the fining gas diffusion rate,
Speeds up the expansion of bubbles.

As described above, the refining effect of SnO ₂ is BaO
In particular, it is important that the value of BaO / SnO ₂ is in the range of 0.2 to 10, especially 0.3 to 7 by weight. If the value of BaO / SnO ₂ is smaller than 0.2, it is difficult to obtain a sufficient refining effect, and if it is larger than 10, the crystallinity is reduced and the amount of crystallization is insufficient, and it is difficult to obtain desired characteristics.

It should be noted that the effect of BaO described above is based on N
It is also found in a ₂ O, K ₂ O, MgO and ZnO. However, Na ₂ O and K ₂ O have a large increase in the coefficient of thermal expansion with respect to the added amount, and MgO and ZnO form a solid solution in the precipitated crystal and affect the crystallization characteristics, so that the refining effect of SnO ₂ is improved. Cannot be added in a sufficient amount. Therefore, in the present invention, BaO is selected as a component for improving the refining effect of SnO ₂ .

Next, the reasons for limiting the composition range in the present invention will be described.

The content of SiO ₂ is 60-75%, preferably 60-71%. If SiO ₂ is less than 60%, the coefficient of thermal expansion becomes too large, and if it is more than 75%, glass melting becomes difficult.

The content of Al ₂ O ₃ is 17 to 27%, preferably 17 to 24%. If the content of Al ₂ O ₃ is less than 17%, the chemical durability is lowered and the glass is apt to be devitrified. On the other hand, if it is more than 27%, the viscosity of the glass becomes too large, and it becomes difficult to melt the glass.

The content of Li ₂ O is 3 to 6%, preferably 3.2 to 5%. When the content of Li ₂ O is less than 3%, the thermal expansion coefficient becomes too large, and when a transparent crystallized glass is obtained, the crystal is easily clouded. On the other hand, if it is more than 6%, the glass tends to be devitrified, and when obtaining a transparent crystallized glass, the crystal tends to be cloudy.

The content of MgO is 0-2.9%, preferably 0-2.5%, and the content of ZnO is 0-4%, preferably 0-3%. 2.9% MgO and Zn
When O is more than 4%, the crystallinity is reduced, and when a transparent crystallized glass is obtained, the crystal is easily clouded.

As described above, BaO has the effect of increasing the refining effect of SnO _{2 and} , when obtaining white opaque crystallized glass, has the effect of increasing the whiteness of the crystal.
It is 3 to 10%, preferably 0.3 to 7%. If the content of BaO is less than 0.3%, a sufficient refining effect cannot be obtained. If the content is more than 10%, the crystallinity is lowered, and a sufficient amount of crystals cannot be obtained, and the thermal expansion coefficient becomes too large.

The content of Na ₂ O is 0-3%, preferably 0-2%, and the content of K ₂ O is 0-3%, preferably 0-2%. Na ₂ O and K ₂ O are each 3%
If it is larger than this, the crystallinity becomes low and a sufficient amount of crystals cannot be obtained, and the coefficient of thermal expansion becomes too large. Further, when a transparent crystallized glass is obtained, the crystal is easily clouded.

TiO ₂ is a nucleating agent, and its content is 0 to 2%, preferably 0 to 1.5%. In the present invention, SnO ₂ is used as a fining agent in place of As ₂ O ₃ , but SnO ₂ has a strong reducing action and enhances coloring (yellow) of Fe ions mixed as impurities from many raw materials. However, since this coloring occurs in the presence of TiO ₂ ,
If the content of TiO ₂ is reduced, even if SnO ₂ is used, F
It is possible to reduce e-ion coloring. TiO ₂ is 2
%, The coloring becomes remarkable, so that a colorless and transparent crystallized glass cannot be obtained.

ZrO ₂ is a nucleating agent, and its content is 1 to 4%, preferably 1 to 3.5%. If ZrO ₂ is less than 1%, the crystallinity becomes low and a sufficient amount of crystals cannot be obtained.

The content of P ₂ O ₅ is 0 to 3%, preferably 0 to 2%. If the content of P ₂ O ₅ is more than 3%, the coefficient of thermal expansion becomes too large, and when a transparent crystallized glass is obtained, the crystal is easily clouded.

The content of SnO ₂ is 0.1 to ₂ %, preferably 0.3 to 1.8%. As described above, SnO ₂ acts as a fining agent and also has a function as a nucleating agent, and forms a ZrO ₂ —TiO ₂ —SnO ₂ system crystal nucleus. In the present invention, the TiO ₂ content is limited to 2% or less in order to prevent Fe ion coloring.
Since nO ₂ functions as a nucleating agent, there is no problem of reduced crystallinity due to TiO ₂ reduction. However, if SnO ₂ is less than 0.1%, the refining effect is not sufficient, and the crystallinity is reduced. On the other hand, SnO ₂ has a strong reducing property,
There is a tendency that the coloring of the ions tends to be enhanced. In particular, if it is more than 2%, the coloring of Fe ions becomes remarkable, which is not preferable. In addition, glass melting becomes difficult or devitrification tends to occur.

Cl is a fining agent, and its content is from 0 to 1
%, Preferably 0.005 to 0.3%. Cl is 1
%, The chemical durability decreases.

In the above composition, BaO / Li ₂
It is preferable that the value of O is in the range of 0.07 to 2.5, particularly 0.1 to 2 by weight. This is because if the value of BaO / Li ₂ O is smaller than 0.07, the crystallinity becomes too strong to cause cracks in the crystallized glass, and when white transparent crystallized glass is obtained, the smoothness of the surface is easily lost. Also, if this value is larger than 2.5, the crystallinity tends to decrease.

In the crystallized glass of the present invention, components other than those described above can be added as long as desired properties are not impaired. For example, a small amount of a coloring agent such as V ₂ O ₅ can be added.

The Li ₂ O—Al of the present invention having the above composition
₂ O ₃ -SiO ₂ based crystallized glass can be produced as follows.

First, SiO ₂ 60-75 by weight percentage.
_{%, Al 2 O 3 17~27%} , Li 2 O 3~6%,
MgO 0-2.9%, ZnO 0-4%, BaO
_{0.3~10%, Na 2 O 0~3%} , K 2 O 0~3
_{%, TiO 2 0~2%, ZrO} 2 1~4%, P 2 O
_The raw materials are prepared so as to have a composition of 50 to 3%. At this time, SnO ₂ is added as a fining agent raw material in an amount of 0.1 to ₂ % and, if necessary, chloride is added up to 5% in terms of Cl.
BaO and SnO ₂ are adjusted so that the weight ratio of BaO / SnO ₂ is in the range of 0.2 to 10.

Next, the prepared glass raw materials were mixed with 1550-17
After melting at 50 ° C. for 4 to 8 hours, molding is performed.

Subsequently, the glass molded body is held at 700 to 800 ° C. for 1 to 4 hours to form nuclei. In the case of forming a transparent crystallized glass, heat treatment is performed at 800 to 950 ° C. for 0.5 to 2 hours. Precipitation of the quartz solid solution; In the case of a white opaque crystallized glass, 1050 to 1250 after nucleation is formed.
Heat treatment at 0.5 ° C. for 0.5 to 2 hours may precipitate a β-spodumene solid solution.

The crystallized glass thus obtained is subjected to post-processing such as cutting and polishing, or painted on the surface, and used for various purposes.

[0036]

EXAMPLES The following of the present invention based on examples Li ₂ O-
The Al ₂ O ₃ -SiO ₂ -based crystallized glass will be described.

Tables 1 to 3 show examples of the present invention (sample No. 1).
10 to 10) and Comparative Example (Sample No. 11).
The sample No. 12 is a conventional example.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

Each sample was prepared as follows.

First, the respective raw materials were prepared in the form of oxides, hydroxides, halides, carbonates, nitrates and the like so as to obtain a glass having the composition shown in the table, and then uniformly mixed. Melted in a furnace at 1550-1650 ° C. for 8-20 hours. Next, the molten glass was poured on a carbon platen, formed into a thickness of 5 mm using a stainless steel roller, and further cooled to room temperature using a slow cooling furnace. This glass compact was placed in an electric furnace, heat-treated on each of the following two schedules, and cooled in the furnace.

(1) Nucleation: 780 ° C. for 2 hours → Crystal growth: 850 ° C. for 3 hours (2) Nucleation: 780 ° C. for 2 hours → Crystal growth: 1130 ° C. for 1 hour

The heating rate was 300 ° C./h from room temperature to the nucleation temperature and 8 ° C. from the nucleation temperature to the crystal growth temperature.
0 ° C./h.

For each sample obtained, the main crystal, appearance,
And the coefficient of thermal expansion. As a result, each sample obtained by the heat treatment of schedule (1) has β-
Quartz solid solution is precipitated, and it has a colorless and transparent appearance.
The coefficient of thermal expansion at 0 to 750 ° C is -3 to ⁷ × 10 ^-7 /
° C. Each sample obtained by the heat treatment of schedule (2) had a β-spodumene solid solution precipitated as a main crystal, had a white opaque appearance, and had a thickness of 30 to 750.
The coefficient of thermal expansion at 8 ° C. was 8 to 15 × 10 ⁻⁷ / ° C. Further, when the clarity of each sample was evaluated, the number of bubbles was 6
~ 17 particles / kg, which proved to have the same clarity as the conventional product (sample No. 12).

On the other hand, in Comparative Example No. Eleven samples were
Although the main crystal, appearance, and coefficient of thermal expansion were the same as those of the example, the number of bubbles was 1 because BaO was not contained.
It was 20 particles / kg, and the clarity was extremely poor.

The main crystal was evaluated using an X-ray diffractometer. As for the thermal expansion coefficient, a sample was processed into a solid rod of 50 mm × 5 mmφ, and the average linear thermal expansion coefficient in a temperature range of 30 to 750 ° C. was measured. Evaluation of clarity was carried out using 1550 glass materials.
Melting was performed at １６1650 ° C. for 4 to 8 hours, and a roll was formed to prepare a sample, and then the number of bubbles per unit weight in the sample was counted.

[0048]

As described above, the Li ₂ O of the present invention is used.
Since there is no need to use As ₂ O ₃ as a fining agent, the —Al ₂ O ₃ —SiO ₂ -based crystallized glass has no risk of polluting the environment.

Also, since it has a low coefficient of thermal expansion and a high mechanical strength, it has excellent thermal characteristics, and is used for high-tech products such as front windows of oil stoves, wood stoves, etc., color filters and substrates for image sensors. It is suitable as a material for substrates, setters for firing electronic components, shelf plates for microwave ovens, top plates for electromagnetic cooking, window glasses for fire doors, and the like.

Claims (2)

[Claims] 1. 60 to 75% of SiO _{2 by} weight,
_{Al 2 O 3 17~27%, Li} 2 O 3~6%, Mg
O 0-2.9%, ZnO 0-4%, BaO 0.3
_{~10%, Na 2 O 0~3%} , K 2 O 0~3%, T
_{iO 2 0~2%, ZrO 2 1~4} %, P 2 O 5 0
~3%, SnO ₂ 0.1~2%, having a composition of Cl 0~1%, Li ₂ to BaO / SnO _2, characterized in that the in the range of 0.2 to 10 by weight ratio O- Al ₂ O ₃ -S
iO ₂ -based crystallized glass. 2. The composition according to claim 1, wherein the weight ratio of BaO / Li ₂ O is 0.07 to
_2. The Li _{2 according} to claim 1, which is in the range of 2.5.
O-Al ₂ O ₃ -SiO ₂ based crystallized glass.