JP2001328819A - Method for producing glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a glass in which a high-quality non-alkali glass having a small content of arsenic oxide and containing little amounts of bubbles causing display defects is produced even when cullets containing the arsenic oxide are effectively used. SOLUTION: This method for producing the glass is characterized in that a batch comprising the cullet and a clarifier except the arsenic oxide is melted and formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing glass, and more particularly to a method for producing alkali-free glass.

[0002]

2. Description of the Related Art Conventionally, non-alkali glass has been used as a transparent glass substrate for a liquid crystal display or the like. Alkali-free glass used for display applications is required to be free from bubbles that cause display defects in addition to heat resistance and chemical resistance.

[0003] In order to obtain a bubble-free glass, a fining gas is generated in both a relatively low temperature region where the vitrification reaction starts and a relatively high temperature region where defoaming and homogenization of the glass melt occurs. The method of adding an agent to a glass raw material mixture is general. In this method, a gas generated when a raw material undergoes a vitrification reaction is expelled, and fine bubbles remaining in the glass melt during the defoaming and homogenization processes are enlarged to remove the bubbles.

[0004]

By the way, alkali-free glass containing no alkali component has a high viscosity of the glass melt and is melted at a higher temperature than glass containing an alkali component. In this kind of alkali-free glass,
Usually, a vitrification reaction occurs at 1200 to 1300 ° C.
Defoaming and homogenization are performed at a high temperature of 400 ° C. or higher. Therefore, a fining agent that can generate a fining gas in a wide temperature range (about 1200 to 1600 ° C.) is required, and arsenic oxide has been widely used in the past.

However, alkali-free glass used for a glass substrate for a liquid crystal display has a very strict specification of bubble defects. Therefore, even if it is refined using arsenic oxide, its yield is relatively low, and a large amount of cullet is produced. Occurs. In addition, arsenic oxide is highly toxic, and may pollute the environment during the glass manufacturing process, waste glass treatment, and the like, and its use is being restricted.

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a high-quality alkali-free glass having a low arsenic oxide content and having no bubbles serving as display defects while effectively utilizing a cullet containing arsenic oxide. It is to provide a method for producing glass.

[0007]

The method for producing glass of the present invention is characterized in that a batch comprising cullet and a fining agent other than arsenic oxide is melted and formed.

[0008]

According to the method of the present invention, a cullet prepared by melting and shaping a glass material once is used for fining other than arsenic oxide such as antimony oxide and tin oxide to such an extent that the properties of the glass are hardly changed. A batch is prepared by adding an agent and then re-melted to obtain a glass having a high foam quality.

In other words, apart from the fining agent, by forming the batch only with cullet, even if it is an alkali-free glass, it becomes a glass melt at a relatively low temperature, and defoaming and homogenization are performed in a relatively low temperature region. Can be. Moreover, this makes it possible for the antimony oxide to generate a fining gas during the defoaming and homogenization process, and it is easy to float the bubbles remaining in the glass melt by enlarging them. The effect can be obtained.

The mixing ratio of the cullet and the fining agent is, as a percentage by weight, 95 to 99.99% of the cullet and 5 to 0.0% of the fining agent.
It is preferably 1%. The reason for such limitation is that if the amount of the fining agent is too small, there is almost no effect, while if it is too large, the properties of the glass are changed, which is not preferable.

The fining agent used in the present invention is preferably one having a property of changing the valence with the temperature rise of the glass to release oxygen, such as antimony oxide or tin oxide. The reasons for using this type of fining agent are as follows. That is, a fining agent whose valence does not change, for example, BaC
When a chloride such as l ₂ or a sulfate such as Na ₂ SO ₄ is used,
Cations such as Ba ²⁺ and Na ⁺ are added to the glass, and the basic composition of the glass changes. However, in the method of the present invention in which a batch is prepared using only cullet, since a component for adjusting the composition is not added, only a small amount of a fining agent can be added to maintain a predetermined composition. On the other hand, it is preferable to use a fining agent that generates a fining gas due to a change in valence, since a sufficient amount of the fining agent can be added since the basic composition of the glass is not affected.

As antimony oxide, Sb_TwoO_FiveAnd S
b_TwoO_ThreeExists. In addition, tin oxide is SnO_TwoAnd SnO
There is. In the present invention, Sb_TwoO_FiveAnd SnO_TwoAs
It is preferable to use a fining agent that is in a very expensive state.
The fining agent in the expensive state generates fining gas by a chemical reaction.
appear. Also Sb_TwoO_ThreeAnd low-valent states like SnO
If a fining agent is used, the oxygen content
It is desirable to adjust the pressure to 15% or more, especially 20% or more.
New That is, Sb_TwoO_ThreeAnd low-valent states like SnO
Even if a fining agent is used, if the oxygen partial pressure is high,
Sb_TwoO_FiveAnd SnO _TwoChange to expensive number state like, expensive
The same effect as when several clarifying agents are added
That's why.

The cullet used in the present invention is:
As described above, it is produced by once melting and shaping a glass raw material. As the cullet, a cullet containing no fining agent component may be used, but if a cullet containing an arsenic oxide is used, a higher fining effect can be obtained. That is, in the cullet containing arsenic oxide, most of the arsenic oxide is present in the state of As ₂ O ₃ , and the ability to generate a fining gas is almost lost. When added, the oxidation effect of As ₂
O ₃ changes valence to As ₂ O ₅ . The fining action of the antimony oxide itself is reduced by this chemical reaction. However, arsenic oxides that release fining gas in a wide range from low to high temperatures are activated. be able to. By utilizing this effect, a cullet containing an arsenic oxide that has already been manufactured can be reused without adding a new arsenic oxide.

In the present invention, when alkali-free glass used for a liquid crystal display substrate or the like is produced, 40% to 70% by weight of SiO _{2
l 2 O 3 6~25%, B} 2 O 3 5~20%, MgO 0~
10%, CaO 0-15%, SrO 0-10%, B
It is preferable to use glass having a composition of aO 0-30% and ZnO 0-10%.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Table 1 shows cullets used in Examples of the present invention and Comparative Examples.

[0017]

[Table 1]

The cullet was prepared as follows. First, a glass raw material was prepared so as to obtain a glass having the composition shown in the table, and was melted at 1600 ° C. for 1 hour in an electric furnace. Then
The molten glass was poured out onto a carbon table, and after slow cooling, the number of bubbles remaining in the glass was counted.If the number of bubbles in 100 g of glass exceeded 100 ×, 21 to 100 △,
The clarity of the obtained glass was evaluated, with 11 to 20 being ○ and 10 or less being ◎. The glass was further crushed into cullet.

Table 2 shows a glass sample (sample Nos. 1 to 4) prepared by the method of the present invention using the above cullet and a glass sample prepared by using the method of the present invention (sample No. 1).
5) are shown.

[0020]

[Table 2]

Each glass sample was prepared as follows.
First, antimony oxide and tin oxide shown in the table were added as fining agents to the prepared cullet, and 1400
After melting at 30 ° C. for 30 minutes, the temperature was raised to 1600 ° C. and melting was continued for another 30 minutes. Next, the molten glass was poured on a carbon table to obtain a glass sample. Clarity was evaluated in the same manner as in the cullet method.

As is clear from the table, the No. 1 prepared according to the method of the present invention. Glass samples 1-4 showed good clarity.

[0023]

As described above, according to the method of the present invention, cullet containing arsenic oxide can be reused without adding new arsenic oxide, so that bubbles which become display defects do not exist. Therefore, it is possible to easily produce alkali-free glass having a low arsenic oxide content.

Claims (9)

[Claims] 1. A method for producing glass, comprising melting and forming a batch comprising cullet and a fining agent other than arsenic oxide. 2. The method for producing glass according to claim 1, wherein a cullet made of non-alkali glass is used. 3. The method for producing glass according to claim 1, wherein the batch comprises 95 to 99.99% by weight of cullet and 5 to 0.01% by weight of a fining agent. 4. The method for producing glass according to claim 1, wherein a fining agent having a property of changing its valence and releasing oxygen as the temperature of the glass rises is used. 5. A fining agent comprising antimony oxide and / or
5. The method for producing glass according to claim 4, wherein tin oxide is used. 6. The method for producing glass according to claim 4, wherein a fining agent in an expensive state is used. 7. Sb ₂ O ₅ and / or Sn as a fining agent
Process for producing a glass according to claim 6, wherein the use of O _2. 8. The method for producing glass according to claim 4, wherein a fining agent in a low valence state is used, and the oxygen partial pressure in the melting atmosphere gas is adjusted to 15% or more. 9. Sb ₂ O ₃ and / or Sn as a fining agent
9. The method for producing glass according to claim 8, wherein O is used.