KR20100085900A - Method for production of non-alkali glass - Google Patents

Abstract

Disclosed is a method for producing a highly uniform and highly flat non-alkali glass which has few bubbles formed therein. Specifically disclosed is a method for producing a non-alkali glass, which comprises melting a glass raw material comprising a glass base composition raw material containing a silica sand and a boron source and also comprising a clarifying agent and molding the molten material, wherein particles of the silica sand having a Dvalue of 15 to 60 μm and a particle diameter of 100 μm or more make up 2.5 vol% or less of the total volume of the particles of the silica sand, the boron source contains anhydrous boric acid in an amount of 10 to 100 mass% relative to 100 mass% of the total amount of the boron source, SnOis used as the clarifying agent, and the melting of the glass raw material is carried out by the following steps (a) and (b): (a) heating the glass raw material at a temperature at which the viscosity of the molten glass becomes more than 10dPa·s, thereby producing a molten glass; and (b) heating the molten glass at a temperature at which the viscosity of the molten glass becomes 10dPa·s or less and which is higher by 30°C or more than the temperature employed in the step (a), thereby removing air bubbles from the molten glass.

Description

Method for producing alkali-free glass {METHOD FOR PRODUCTION OF NON-ALKALI GLASS}

This invention relates to the manufacturing method of an alkali free glass.

Since it is requested | required that the alkali metal does not contain substantially in the glass for liquid crystal display substrates, the alkali free glass is used as the glass. In addition, the alkali free glass for liquid crystal display substrates is required to have high chemical resistance, high durability, low bubbles in the glass, high homogeneity, and high flatness. Therefore, in order to provide chemical resistance and durability to an alkali free glass, in order to contain a boron source in a glass raw material, and to reduce the bubble in an alkali free glass, the bubble contained in a molten glass is produced at the time of manufacturing an alkali free glass. Defoaming (hereinafter, referred to as clarification) is performed. As the boron source, orthoboric acid which is inexpensive and easy to obtain is used.

Refining method, a method of using SnO ₂ and generating a fining gas by the singer by the change in the Sn elevated temperature of the molten glass as a refining agent has been known (Patent Document 1).

However, compared with alkali containing glass, such as glass for plasma display substrates, building glass, and automotive glass, a non-alkali glass for liquid crystal display board | substrates is a glass with a high melting temperature of 100 degreeC or more, and hard to melt. Accordingly, the SnO ₂ is consumed when melting the glass raw material at a high temperature, a sufficient amount of SnO ₂ has a problem that when left to generate a refining gas by the temperature rise of the molten glass.

As an effective clarification method using SnO ₂ , a method is known in which a glass raw material is melted at a high temperature, held at a low temperature to regenerate SnO ₂ , and thereafter heated up above the melting temperature to generate a clarification gas. 2).

In the case of the method, an effective clarification can be expected, but since the process is complicated and the energy loss is large, it is difficult to stably produce an alkali-free glass having low bubbles at low cost. On the other hand, when the glass raw material is to be melted at a low temperature, since the silica sand which is the main component of the glass raw material is not melted well, unmelted silica is generated in the molten glass, resulting in defects or homogeneous glass is not obtained.

In addition, when silica sand with a small particle diameter is used to make the silica sand easy to melt, the silica sand tends to aggregate. When agglomeration of silica sand occurs, the homogeneity and flatness of an alkali free glass will fall.

Japanese Laid-Open Patent Publication 2004-075498 International Publication No. 2007/018910 Pamphlet

This invention provides the manufacturing method which can obtain the alkali free glass with few bubbles in glass, and high homogeneity and flatness.

The manufacturing method of the alkali free glass of this invention is a manufacturing method of the alkali free glass which melts and shape | molds the glass raw material which added the clarifier to the glass dummy material containing a silica sand and a boron source, As said silica sand, The boron anhydride was used in an amount of 10 to 100 mass% in 100 mass% (in terms of B ₂ O ₃ ) of boron anhydride as the boron source, using a particle having a diameter of 15 to 60 µm and a particle ratio of 100 µm or more to 2.5 vol% or less. B ₂ O ₃ in terms of use in that it contains), and is characterized in that as the refining agent, and at least using SnO _2, subjected to melting of the glass raw materials in the second step below at least.

(a) The process of heating the said glass raw material at the temperature which the viscosity of a molten glass becomes more than 10 ^2.4 dPa * s, and makes it a molten glass.

(b) After the said process (a), the said molten glass is heated at the temperature which the viscosity of a molten glass becomes 10 ^2.4 dPa * s or less, and also at the temperature 30 degreeC or more higher than the temperature in the said process (a), And degassing bubbles in the molten glass.

In the manufacturing method of the alkali free glass of this invention, it is preferable to contain the hydroxide of aluminum or alkaline-earth metal in the said glass dummy material.

In the manufacturing method of the alkali free glass of this invention, a glass dummy raw material is prepared so that it may become an alkali free glass of the following glass dummy properties (1) by the mass percentage display on an oxide basis, and tin is added with respect to the glass dummy raw material. by addition of 0.01 to 2% by mass in terms of SnO ₂ is preferably a glass material.

SiO ₂ : 50 to 66 mass%, Al ₂ O ₃ : 10.5 to 22 mass%, B ₂ O ₃ : 5 to 12 mass%, MgO: 0 to 8 mass%, CaO: 0 to 14.5 mass%, SrO: 0 -24 mass%, BaO: 0-13.5 mass%, MgO + CaO + SrO + BaO: 9-29.5 mass%. (One).

In the manufacturing method of the alkali free glass of this invention, with respect to the said glass dummy material, 3 mass% or less of chloride of 3 mass% or less in terms of Cl, 3 mass% or less of sulfate and SO of 3 mass% or less in terms of SO ₃ It is preferable to add 0.01-5 mass% in 1 or more types chosen from the group which consists of fluoride of a total amount, and to make it a glass raw material.

In the manufacturing method of the alkali-free glass of the present invention, the glass with respect to the base composition material, additional cullet (cullet) comprising a nitrate in 0.01 to 10% by mass and an alkali-free glass as NO ₃ in terms of 15 ~ 300% by weight of added It is preferable to set it as a glass raw material.

According to the manufacturing method of the alkali free glass of this invention, there are few bubbles in glass, and the alkali free glass with high homogeneity and flatness can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the point which cuts out the glass plate for a sample from columnar glass.

Best Mode for Carrying Out the Invention

<Method for producing alkali free glass>

An alkali free glass is manufactured by melting and shape | molding the glass raw material which added the clarifier to the glass dummy raw material containing a silica sand and a boron source. An alkali free glass is manufactured through the following process in order, for example.

(Iii) glass-like properties of alkali-free glass targeted to silica sand and boron sources, Al ₂ O ₃ , alkaline earth metal oxides (MgO, CaO, SrO, BaO) and / or hydroxides of aluminum or alkaline earth metals, if necessary A process of mixing at a ratio to prepare a glass imitation raw material, adding a clarifier etc. to this glass imitation raw material, and using it as a glass raw material.

(Ii) The glass raw material and the process which, as needed, continuously inject | pours a cullet into a molten kiln from the glass raw material inlet of a molten kiln, and melts it, and makes it molten glass.

(Iii) A step of molding the molten glass so as to be a glass ribbon of a predetermined thickness by a known molding method such as a float method.

(Iii) After cooling the molded glass ribbon by slow cooling, it is cut | disconnected to a predetermined | prescribed magnitude | size and obtained plate-shaped alkali free glass.

In the present invention, as the silica sand, one having a median diameter of 15 to 60 µm and a particle ratio of 100 µm or more having a particle size of 2.5% by volume or less is used. As the boron source, boric anhydride is 100 mass% (B ₂ O). ₃ to 10% by mass (in terms of B ₂ O ₃ ) of the composition, and at least SnO ₂ is used as the clarifier, and the step (ii) is divided into at least two steps. There is a characteristic.

(a) The process of heating the said glass raw material at the temperature which the viscosity of a molten glass becomes more than 10 ^2.4 dPa * s, and makes it a molten glass.

(b) After the said process (a), the said molten glass is heated at the temperature which the viscosity of a molten glass becomes 10 ^2.4 dPa * s or less, and also at the temperature 30 degreeC or more higher than the temperature in the said process (a), And degassing bubbles in the molten glass.

Process (ⅰ):

(Gross sand)

In the median diameter of the silica sand, that is, the particle size distribution of the powder, the particle diameter (hereinafter referred to as D ₅₀ ) in which the volume frequency of the particles larger than any particle size occupies 50% of the total powder is 15 to 60 μm, 20 -50 micrometers is preferable, 20-40 micrometers is more preferable, 20-30 micrometers is still more preferable. D ₅₀ of the silica sand is particularly preferably less than 30 μm, more preferably 27 μm or less. Because the silica sand is D ₅₀ of the agglomeration of silica suppressed by more than 15 ㎛, air bubbles are more low, the alkali-free glass homogeneity, high flatness is obtained.

Because the silica sand is uniformly melted easily by a silica D ₅₀ of less than 60 ㎛, small air bubbles, the alkali-free glass homogeneity, high flatness is obtained.

The particle ratio of 100 micrometers or more in particle size distribution of a silica sand is 2.5 volume% or less, and 0 volume% is more preferable. Since the silica sand becomes easy to melt uniformly by setting the particle ratio of particle size 100 micrometers or more to 2.5 volume% or less, there are few bubbles and an alkali free glass with high homogeneity and flatness is obtained.

The particle size distribution of silica sand is measured by the laser diffraction scattering method.

(Boron source)

Examples of the boron compound as the boron source include orthoboric acid (H ₃ BO ₃ ), metaboric acid (HBO ₂ ), tetraboric acid (H ₂ B ₄ O ₇ ), boric anhydride (B ₂ O ₃ ), and the like. In manufacture of a normal alkali free glass, orthoboric acid is used at the point of being cheap and easy to obtain.

However, when the glass raw material containing orthoboric acid is used, the following problems may arise.

(1) In the presence of orthoboric acid, silica sand having a small particle size tends to aggregate, and the amount of the glass raw material to the molten kiln tends to be unstable. Therefore, the molten glass temperature in a molten kiln becomes unstable and the circulation and residence time of a molten glass become unstable. As a result, melting of a glass raw material becomes nonuniform, and the composition of a molten glass becomes nonuniform.

(2) When a glass raw material contains an alkaline earth metal compound, the orthoboric acid melt | dissolved in the glass raw material inlet of a melting kiln and an alkaline earth metal compound aggregate, and aggregates generate | occur | produce easily. Since orthoboric acid and alkaline earth metal compounds are also components that promote the melting of silica sand, when aggregates are generated, the melting of the glass raw material in the melting kiln becomes uneven, and the composition of the molten glass becomes uneven.

When the problem of (1) or (2) arises, since the homogeneity of molten glass will worsen, the homogeneity and flatness of the molded alkali free glass will become low. Moreover, since circulation and residence time become unstable, a part of molten glass flows out from a molten kiln before a bubble comes out from the molten glass in a molten kiln by a clarifier. Moreover, since melting of a glass raw material is nonuniform, the effect of the clarifier to the silica sand melted late becomes inadequate, and foam | bubble does not fully fall out from a molten glass.

Regarding the problem of (1), the inventors of the present invention suggest that the flocculation of silica sand is caused by the moisture contained in the glass raw material, and in order to suppress the flocculation of the silica sand, the moisture contained in the glass raw material should be reduced, that is, the moisture in the molecule. It was found that the amount of orthoboric acid containing a large amount of porcelain may be reduced and the amount of boric anhydride increased.

In addition, about the problem of (2), the present inventors have lost one water | moisture content from orthoboric acid heated by the glass raw material input port, and it becomes metaboric acid, and the metabolic acid and alkaline-earth metal compound liquefied at 150 degreeC or more are aggregated. In addition, in order to suppress aggregation of metaboric acid and an alkaline earth metal compound, it has been found that a boron source containing boric anhydride in which water molecules are further lost from metaboric acid may be used.

Moreover, the following effects can also be anticipated by using the boron source containing boric anhydride.

(Iii) Since the amount of water in the glass raw material is suppressed, the heat of vaporization of water when melting the glass raw material is reduced. Therefore, the amount of energy consumed in the melting kiln by the amount of heat of vaporization reduced is reduced, energy saving can be achieved, and productivity is improved.

 (Ii) Since water (β-OH) in the molten glass is reduced, when Cl is contained in the clarifier, it becomes HCl and volatilization is suppressed by the following reaction. Therefore, the quantity of the clarifier can be reduced, and the processing burden of the exhaust gas containing HCl is reduced.

^{OH - + Cl - → HCl ↑} + O 2-.

(Iii) Metaboric acid produced by the loss of one water molecule from orthoboric acid is easily volatilized, but boric anhydride is hardly volatilized, so that the amount of boron source can be reduced, and the treatment of exhaust gas containing metaboric acid is carried out. The burden is reduced.

Therefore, in the present invention, there is provided a boron source, it is used in that it contains 100% by weight of anhydrous boric acid boron source 10 to 100 mass% of (B ₂ O ₃ basis) (B ₂ O ₃ basis). By making boric anhydride 10 mass% or more, aggregation of a glass raw material is suppressed and the effect of reducing foam | bubble, the homogeneity, and the improvement of flatness is acquired. As for boric anhydride, 20-100 mass% is more preferable, 50-100 mass% is more preferable, 100 mass% is especially preferable.

As boron compounds other than boric anhydride, orthoboric acid is preferable at the point of being cheap and easy to obtain.

(Other raw materials)

Other raw materials include Al ₂ O ₃ , alkaline earth metal oxides (MgO, CaO, SrO, BaO), Al (OH) ₃ , alkaline earth metal hydroxides (Mg (OH) ₂ , Ca (OH) ₂ , Ba (OH) ₂ , Sr (OH) ₂ ).

In this invention, it is preferable to contain the hydroxide of aluminum or alkaline-earth metal in a glass dummy material in the point which initial melting is promoted in the process (process (a)) of melting a glass raw material, and a molten glass is obtained at a low temperature. Do. Moreover, in this invention, you may contain the hydroxide which consists of aluminum and alkaline-earth metal in a glass dummy material.

In addition, as mentioned above, when one part or all part of the boron source in glass raw material is made into boric anhydride, in order to reduce the amount of water in a molten glass, the amount of water in a molten glass will fall excessively and it will bubble in a pressure reduction defoaming process. There is a possibility that the number of bubbles decreases, and the floating speed of bubbles decreases, resulting in deterioration of homogeneity and flatness of the alkali free glass. In this case, in order to replenish the amount of water in the molten glass, it is preferable to add a hydroxide of aluminum or alkaline earth metal.

As the hydroxide, it is preferable to use Al (OH) ₃ in that initial melting is accelerated. Moreover, as hydroxide of an alkaline earth metal, it is preferable to use at least one of Mg (OH) ₂ or Ca (OH) ₂ , and it is especially preferable to use Mg (OH) ₂ .

The content in the case of containing the alkaline earth metal hydroxide in the glass imitation raw material is preferably in the range of 15 to 100 mol% (MO equivalent) in 100 mol% of the alkaline earth metal source (wherein M is an alkaline earth metal element). . When the addition amount of the hydroxide is 15 mol% or more, the unmelted amount of the SiO ₂ component contained in the silica sand in the step (a) can be reduced. Therefore, when the unmelted SiO ₂ foams in the glass melt, it can be prevented from flowing into the bubble and collecting near the surface layer of the glass melt. And as a result, by the difference in the composition ratio of SiO ₂ eseo between the portion other than the surface layer and the surface layer of the glass melt occurs, it is possible to prevent the homogeneity and flatness of the glass to be lowered.

Further, as the molar ratio of the hydroxide in the alkaline earth metal source increases, the unmelted amount of the SiO ₂ component at the time of melting the glass raw material decreases, so the higher the molar ratio of the hydroxide, the better.

For the same reason as in the case of the alkaline earth metal hydroxide, the content in the case of containing Al (OH) ₃ in the glass imitation raw material is 15 to 100 mol% (Al in terms of Al ₂ O ₃ ) of aluminum source (Al). ₂ O ₃ conversion) is preferable.

Further, as the molar ratio of the hydroxide in the aluminum source increases, the unmelted amount of the SiO ₂ component at the time of melting the glass raw material decreases, so the higher the molar ratio of the hydroxide, the better.

(Glass imitation raw material)

A glass imitation raw material is a powder-like mixture which mixed each said raw material.

A glass imitation raw material is prepared so that it may become the alkali free glass which has the target glass imitation property.

As a composition of a glass imitation raw material, the composition used as the alkali free glass of the glass imitation property (1) mentioned later is preferable, and the composition used as the alkali free glass of the glass imitation property (2) or glass imitation property (3) mentioned later This is particularly preferred.

(Clarifier)

A clarifier is a component which improves clarity and is added to a glass dummy material.

In the present invention, at least SnO ₂ is used as a clarifier.

Sn oxide is hydrolyzed from SnO ₂ (Sn ⁴⁺ ) to SnO (Sn ²⁺ ) at a high temperature of 1400 ° C. or higher. With the change of the valence, a clarification gas (oxygen gas) is released. And if more than a certain percentage change in SnO ₂ SnO singer, since sufficient fining gases are released, it is possible to effectively fining.

The added amount of tin, the glass is 0.01 to 2 mass% in terms of SnO ₂ with respect to the preferred base material composition, more preferably 0.1 to 0.7% by weight. Clarification is fully performed by making the addition amount of tin into 0.01 mass% or more. By making the addition amount of tin 2 mass% or less, defect generation, such as unmelted tin, can be suppressed.

As other clarifiers, it is further selected from the group consisting of 3 mass% or less chlorides in terms of Cl, 3 mass% or less sulfates in terms of SO ₃ , and 3 mass% or less fluorides in terms of F, with respect to the glass imitation raw materials. You may add 0.01-5 mass% in 1 or more types used as a total amount. In addition, since a large number of steps are required for the treatment of the cullet, it is preferable not to contain PbO, As ₂ O ₃ , Sb ₂ O ₃ except for inevitably mixing them as impurities or the like.

(Colllet)

A cullet is the glass waste discharged | emitted in the manufacturing process of an alkali free glass, etc.

As a cullet, it is preferable to have the composition similar to the glass replica of the target alkali free glass.

As for the addition amount of a cullet, 15-300 mass% is preferable with respect to a glass imitation raw material. Initial meltability can be ensured by making the addition amount of a cullet 15 mass% or more. By the amount of the cullet to 300 mass%, the refining effect can be exhibited by the SnO _2.

(Other additives)

When using a cullet, it is preferred to add nitrates at the same time.

In the collet, the ratio of Sn oxide used as a clarifier in the state of SnO (Sn ²⁺ ) is large, and the ability to generate a clarification gas is reduced. Therefore, by adding nitrate during remelting of the cullet, since SnO (Sn ²⁺ ) is oxidized to SnO ₂ (Sn ⁴⁺ ) by the nitrate, the cullet can be effectively clarified without adding SnO ₂ again.

The amount of nitrate is, for the glass base material composition, 0.01 to 10% by mass is preferable in terms of NO _3. By the amount of the nitrate to 0.01% by mass, it is possible to effectively oxidize the SnO cullet of a SnO _2. Even when the amount of nitrate added exceeds 10 mass%, oxidation to SnO ₂ is saturated and the effect is small.

Process (ii):

(Step (a))

Step (a) is an initial melting step and is a step of melting and uniformly vitrifying a glass raw material.

The temperature in the process (a) is a temperature at which the viscosity of the molten glass becomes more than 10 ^2.4 dPa · s, and a temperature at which the viscosity of the molten glass is 10 ^2.5 dPa · s or more is preferable, and the viscosity of the molten glass is a 10 ^2.6 ~ 10 ^2.9 d㎩ · s, the temperature is more preferable. When the viscosity of a molten glass exceeds 10 ^2.9 dPa * s, initial stage melting will not become homogeneous well. Therefore, the temperature which becomes 10 ^2.9 dPa * s or less is preferable. Moreover, as for the temperature in a process (a), 1400 degreeC or more is preferable.

By the temperature of the step (a), the temperature, the viscosity of the molten glass 10 that is greater than ^2.4 d㎩ · s, while suppressing the consumption of SnO ₂ may be subjected to vitrification. Therefore, clarification in a later process (b) can be performed efficiently, and the bubble in glass can be reduced.

In this way the present invention, because it uses at least SnO ₂ as a fining agent, heating the glass raw material at a relatively low temperature, i.e., temperature, the viscosity of the molten glass 10 that d㎩ ^2.4 · s than is necessary to melt a glass have.

However, when only orthoboric acid is used as the boron source, silica sand tends to aggregate at the temperature, and thus unmelted silica tends to occur in the molten glass.

On the other hand, in the present invention, since the glass imitation raw material contains boric anhydride as the boron source, the glass raw material is uniformly melted even at that temperature, and generation of unmelted silica is suppressed.

100-900 minutes are preferable and, as for the time of a process (a), 150-500 minutes are more preferable.

(Step (b))

Process (b) is a clarification process, Comprising: A molten glass is made into a comparatively high temperature, ie, the temperature which the viscosity of a molten glass becomes 10 ^2.4 dPa * s or less, and also at the temperature 30 degreeC or more higher than the temperature in the said process (a). It is a process of heating, generating a clarification gas by the change of the valence of Sn, and defoaming the bubble in a molten glass.

The temperature in the process (b) is a temperature at which the viscosity of the molten glass becomes 10 ^2.4 dPa · s or less, and a temperature at which the viscosity of the molten glass is 10 ^2.3 dPa · s or less is preferable, and the viscosity of the molten glass 10 is a temperature which is ^1.8 ~ 10 ^2.2 · d㎩ s is more preferable. If the viscosity of a molten glass is less than 10 ^1.8 dPa * s, furnace material will become easy to corrode, and defects will arise easily. Therefore, the temperature which becomes 10 ^1.8 dPa * s or more is preferable.

Moreover, the temperature in a process (b) is 30 degreeC or more higher than the temperature in the said process (a), The temperature of 50 degreeC or more higher than the temperature in the said process (a) is preferable, The said process ( The temperature higher 70 ° C or more than the temperature in a) is more preferable. Moreover, 1700 degreeC or less is preferable for the temperature in a process (b).

The clarification gas is efficiently carried out by setting the temperature in the step (b) to a temperature at which the viscosity of the molten glass becomes 10 ^2.4 dPa · s or less and a temperature higher by 30 ° C. or more than the temperature in the step (a). It can generate | occur | produce and clarify efficiently, and the bubble in glass can be reduced.

60-800 minutes are preferable and, as for the time of a process (b), 120-300 minutes are more preferable.

The viscosity of the molten glass is measured using a high temperature rotational viscometer.

Process (ⅲ), process (ⅳ):

In step (iii) and step (iii), molding, slow cooling, and cutting are performed in the same manner as a known method for producing alkali-free glass.

<Alkali-free glass>

The alkali-free glass is obtained by the production process of the present invention contains B ₂ O ₃ derived from the glass SiO _2, and a boron source derived from a silica sand base in the composition. The alkali-free glass is, would that is substantially free of alkali metal oxides such as Na ₂ O, K ₂ O. Here, substantially free of an alkali metal oxide means that it does not contain an alkali metal oxide other than unavoidable impurities mixed from raw materials or the like. That is, it means not containing an alkali metal oxide intentionally.

Hereinafter, the preferable glass modeling property of an alkali free glass is demonstrated.

Glass imitation (1):

As an alkali free glass, it has the characteristics as a glass for liquid crystal display substrates (coefficient of thermal expansion ^25x10 <^-7> -60 * 10 <^-7> / degreeC), chemical-resistance, durability, etc.), and is suitable for shaping | molding to plate glass, As an indication of the mass percentage on the basis of an oxide, an alkali free glass having the following glass replica (1) is preferable.

SiO ₂ : 50 to 66 mass%, Al ₂ O ₃ : 10.5 to 22 mass%, B ₂ O ₃ : 5 to 12 mass%, MgO: 0 to 8 mass%, CaO: 0 to 14.5 mass%, SrO: 0 -24 mass%, BaO: 0-13.5 mass%, MgO + CaO + SrO + BaO: 9-29.5 mass%. (One).

Glass imitation (2):

As alkali-free glass, a strain point is 640 degreeC or more, a thermal expansion coefficient and a density are small, the clouding by buffered hydrofluoric acid (BHF) used for etching is suppressed, and it is excellent also in durability with respect to chemicals, such as hydrochloric acid, Since it is easy to shape | mold and it is suitable for float shaping | molding, the alkali free glass of the following glass imitation property (2) is more preferable in the mass percentage display on an oxide basis.

SiO ₂ : 58 to 66 mass%, Al ₂ O ₃ : 15 to 22 mass%, B ₂ O ₃ : 5 to 12 mass%, MgO: 0 to 8 mass%, CaO: 0 to 9 mass%, SrO: 3 -12.5 mass%, BaO: 0-2 mass%, MgO + CaO + SrO + BaO: 9-18 mass%. (2).

Each composition of this composition meter is demonstrated.

By the SiO ₂ more than 58% by mass, the strain point of alkali-free glass is raised, it becomes a good chemical resistance, the thermal expansion coefficient is lowered. By the SiO ₂ to less than 66 mass%, the melting property of the glass becomes satisfactory, it is excellent in devitrification property.

Al ₂ O ₃ suppresses the phase separation of the alkali free glass, lowers the coefficient of thermal expansion, and increases the strain point.

, The above effects are expressed by the Al ₂ O ₃ with at least 15% by weight. By the Al ₂ O ₃ less than 22% by mass, it is excellent in the melting property of the glass.

B ₂ O ₃ is thereby lowering the coefficient of thermal expansion and density of the alkali-free glass, and inhibit the cloudiness of the alkali-free glass by BHF, without increasing the viscosity at high temperature.

By the B ₂ O ₃ less than 5% by mass, it is excellent in BHF resistance of alkali-free glass. By the B ₂ O ₃ less than 12% by mass, the strain point becomes with good acid resistance of alkali-free glass is raised.

MgO suppresses the rise of the thermal expansion coefficient and density of an alkali free glass, and improves the meltability of a glass raw material.

By making MgO 8 mass% or less, the clouding by BHF is suppressed and the powdery phase of an alkali free glass is suppressed.

CaO improves the meltability of the glass raw material.

By making CaO 9 mass% or less, the thermal expansion coefficient of an alkali free glass falls and a devitrification characteristic becomes favorable.

SrO suppresses powder phase of an alkali free glass and suppresses the cloudiness of the alkali free glass by BHF.

The said effect is expressed by making SrO 3 mass% or more. By making SrO 12.5 mass% or less, the thermal expansion coefficient of an alkali free glass falls.

BaO suppresses powder phase of an alkali free glass, improves meltability, and improves devitrification characteristics.

By making BaO 2 mass% or less, the density of an alkali free glass falls and a thermal expansion coefficient falls. In addition, in consideration of environmental load, it is preferable not to contain substantially.

By making MgO + CaO + SrO + BaO 9 mass% or more, the meltability of the glass becomes good. By making MgO + CaO + SrO + BaO into 18 mass% or less, the density of an alkali free glass falls.

Glass imitation (3):

As the alkali free glass, it is excellent in characteristics as glass for liquid crystal display substrates, excellent in reduction resistance, homogeneity, bubble suppression, and suitable for molding by the float method. Alkali glass of composition (3) is especially preferable.

SiO ₂ : 50 to 61.5 mass%, Al ₂ O ₃ : 10.5 to 18 mass%, B ₂ O ₃ : 7 to 10 mass%, MgO: 2 to 5 mass%, CaO: 0 to 14.5 mass%, SrO: 0 -24 mass%, BaO: 0-13.5 mass%, MgO + CaO + SrO + BaO: 16-29.5 mass%. (3).

Each composition of this composition meter is demonstrated.

By the SiO ₂ at least 50% by mass, the acid resistance of alkali-free glass becomes good, the density is lowered, strain point is raised, lowered the coefficient of thermal expansion, Young's modulus is raised. By the SiO ₂ to less than 61.5 mass%, it is excellent in devitrification property of the alkali-free glass.

Al ₂ O ₃ suppresses powder phase of the alkali free glass, increases the strain point, and increases the Young's modulus.

, The above effects are expressed by the Al ₂ O ₃ more than 10.5% by weight. By the Al ₂ O ₃ less than 18% by mass, the devitrification property, the acid resistance and the BHF resistance of alkali-free glass becomes fine.

B ₂ O ₃ reduces the density of the alkali free glass, improves the BHF resistance, improves the meltability, improves the devitrification property, and lowers the coefficient of thermal expansion.

, The above effects are expressed by the B ₂ O ₃ less than 7% by mass. By the B ₂ O ₃ less than 10% by mass, strain point of alkali-free glass is raised, and the Young's modulus is increased, it is excellent in acid resistance.

MgO reduces the density of an alkali free glass, does not raise a thermal expansion coefficient, does not excessively reduce a strain point, and improves meltability.

The said effect is expressed by making MgO into 2 mass% or more. By making MgO 5 mass% or less, powder phase of an alkali free glass is suppressed and devitrification characteristic, acid resistance, and BHF resistance become favorable.

CaO does not raise the density of an alkali free glass, does not raise a thermal expansion coefficient, does not reduce a strain point excessively, and improves meltability.

By making CaO 14.5 mass% or less, the devitrification characteristic of an alkali free glass becomes favorable, a thermal expansion coefficient falls, a density falls, and acid resistance and alkali resistance become favorable.

SrO does not raise the density of an alkali free glass, does not raise a thermal expansion coefficient, does not reduce a strain point excessively, and improves meltability.

By making SrO 24 mass% or less, the devitrification characteristic of an alkali free glass becomes favorable, a thermal expansion coefficient falls, a density falls, and acid resistance and alkali resistance become favorable.

BaO suppresses powder phase of alkali free glass, improves devitrification characteristics, and improves chemical resistance.

By making BaO 13.5 mass% or less, the density of an alkali free glass falls, a thermal expansion coefficient falls, a Young's modulus rises, meltability becomes favorable, and BHF resistance becomes favorable. In addition, in consideration of environmental load, it is preferable not to contain substantially.

By making MgO + CaO + SrO + BaO 16 mass% or more, the meltability of the glass becomes good. By making MgO + CaO + SrO + BaO 29.5 mass% or less, the density of an alkali free glass and a thermal expansion coefficient fall.

Or more, according to the described method of producing the alkali-free glass of the present invention, as the silica sand, D ₅₀ is 15 ~ 60 ㎛ and also as a boron source, and more than 100 ㎛ particle ratio diameter used is not more than 2.5% by volume, boron anhydride acid used in that it contains source 100 mass% (B ₂ O ₃ basis) 10 to 100 mass% (B ₂ O ₃ basis) of, and as a refining agent, use at least SnO ₂ and having at least above-mentioned melting of the glass raw material Since it performs in two steps of a process (a) and a process (b), the alkali free glass with few bubbles in a glass, and high homogeneity and flatness can be obtained.

Example

Although an Example is given to the following and this invention is concretely demonstrated to it, it cannot be overemphasized that this invention is limited to these Examples.

Examples 1 and 2 are experimental examples showing low temperature meltability, Examples 3 to 5, 7, and 8 are examples, and Example 6 is a comparative example.

[Example 1]

In terms of mass percentage based on oxide, SiO ₂ : 60 mass%, Al ₂ O ₃ : 17 mass%, B ₂ O ₃ : 8 mass%, MgO: 3 mass%, CaO: 4 mass%, SrO: 8 mass% of glass, so that the alkali-free glass having base composition of silica sand 1 (D _50: 27 ㎛, particle diameter of 100 ㎛ particle ratio: 1 volume%, D ₉₉ (particle size distribution particle size of the volume frequency, which accounts for 99% of the): 69 µm), boric anhydride (100 mass%) as the boron source, Al ₂ O ₃ , and other raw materials as a source of aluminum were prepared to obtain a glass dummy material, and as a clarifier, the glass dummy raw material. 0.5 mass% of SnO ₂ , 0.5 mass% of SrCl ₄ , and 0.3 mass% of CaSO ₄ · 2H ₂ O were added to form a glass raw material.

The glass raw material of the quantity which becomes 250 g of mass after vitrification was put into the cylindrical persimmon made from platinum rhodium with a height of 90 mm and an outer diameter of 70 mm. The persimmon was put into a heating furnace, heated at 1525 ° C (temperature at which the molten glass had a viscosity of 10 ^2.6 dPa · s) for 30 minutes while blowing air at a dew point of 60 ° C from the side of the heating furnace, and then with a stirrer. Persimmon was forcibly stirred for 30 minutes, and the glass raw material was melted. Then, stirring was stopped and left still for 60 minutes, the molten glass in persimmon flowed out on the carbon plate, and it cooled in the slow cooling furnace. After cooling, the sample was taken out of the slow cooling furnace and the number of unmelted silica was counted by a stereo microscope while irradiating light from the edge of the sample. The results are shown in Table 1.

Furthermore, the same evaluation was carried out by the melting temperature of the glass raw material to 1550 ℃ (temperature, the viscosity of the molten glass which is 10 ^2.5 d㎩ · s). The results are shown in Table 1.

[Example 2]

Instead of silica sand 1, silica sand 2 (D ₅₀ : 39 μm, particle diameter: 100 μm or more particle ratio: 4.2 vol%, D ₉₉ : 153 μm) was used, except that orthoboric acid (100 mass%) was used as the boron source. Evaluation similar to Example 1 was performed. The results are shown in Table 1.

Melting temperature
(℃)

Viscosity of molten glass
(d㎩s)

Unmelted silica amount (pcs / kg) Example 1 Example 2 Silica 1 + Boric anhydride Silica 2 + orthoboric acid 1525 10 ^2.6 757 1230 1550 10 ^2.5 188 1021

The configuration of the present invention _{(D 50: 15 ~ 60 ㎛} , particle diameter of 100 ㎛ particle fraction: 2.5% by volume or less) of silica combination of the first and anhydrous boric acid, the composition and is a combination of different silica sand 2 and ortho-boric acid of the present invention and In comparison, it can be seen that the amount of unmelted silica is small, and initial dissolution is possible at a lower temperature. Moreover, since the amount of unmelted silica is small, it is glass with high homogeneity. Moreover, the glass with high flatness is obtained when shape | molding by plate glass.

[Example 3]

In Example 1 and the same base glass composition of the raw material and, as a further refining agent to, and the glass was added 0.5% by weight of SnO ₂ with respect to the base composition material to prepare a glass raw material.

Process (a):

Half of the glass raw material (equivalent to 125 g in terms of glass) was placed in a 300 kPa platinum persimmon and allowed to stand for 30 minutes in an electric furnace at 1500 ° C (temperature at which the molten glass had a viscosity of 10 ^2.7 dPa · s). Take out the platinum fruit from the electric furnace once, add the remaining half amount (equivalent to 125 g in glass conversion), and again, stand still for 30 minutes in an electric furnace of 1500 ℃ (temperature of the molten glass is 10 ^2.7 dPa · s) glass raw material Was melted.

Process (b):

Then, it transferred to the electric furnace of 1590 degreeC (temperature in which the viscosity of a molten glass becomes 10 ^2.3 dPa * s) rapidly, and left still for 30 minutes. Then, it moved to the electric furnace of 730 degreeC, and slow cooled the glass to 610 degreeC over 2 hours, and further cooled the glass to room temperature over about 10 hours. And the core and the glass of the upper center were dug out by the core drill with the columnar glass of diameter 38mm and height 35mm, and as shown in FIG. 1, the thickness containing the central axis 12 of the columnar glass 10 is shown. It cut out with the glass plate 14 of 2-5 mm. Both surfaces of the cut surface were subjected to optical polishing (mirror polishing finish) to prepare an evaluation sample. About the site | part corresponded between 1-10 mm from the glass upper surface of persimmon, the optically polished surface is observed with a stereomicroscope, the number of bubbles 50 micrometers or more in diameter in a glass plate is measured, and the value is divided into the volume of a glass plate, It was set as the number of remaining bubbles. The results are shown in Table 2.

[Example 4]

Except for changing the temperature of step (a) in 1550 ℃ (temperature, the viscosity of the molten glass which is 10 ^2.5 d㎩ · s), was carried out the same evaluation as in Example 3. The results are shown in Table 2.

[Example 5]

In terms of mass percentage based on oxide, SiO ₂ : 60 mass%, Al ₂ O ₃ : 17 mass%, B ₂ O ₃ : 8 mass%, MgO: 5 mass%, CaO: 6 mass%, SrO: 4 mass% Silica sand 1, boric anhydride (100 mass%) as a boron source, Al ₂ O ₃ , and other raw materials as an aluminum source are prepared so as to be an alkali-free glass having a glass imitation of. a second, that it is advantageous adding 0.5 mass% SnO ₂ with respect to the base composition material to prepare a glass raw material.

Process (a):

Half of the glass raw material (equivalent to 125 g in terms of glass) was placed in a 300 kPa platinum persimmon and allowed to stand for 30 minutes in an electric furnace at 1500 ° C (temperature at which the molten glass had a viscosity of 10 ^2.5 dPa · s). Take out the platinum fruit from the electric furnace once, add the remaining half amount (equivalent to 125 g in glass conversion), and again, stand still for 30 minutes in an electric furnace of 1500 ℃ (temperature at which the viscosity of the molten glass becomes 10 ^2.5 dPa · s) Was melted.

Process (b):

Then transferred quickly into an electric furnace of 1590 ℃ (temperature, the viscosity of the molten glass which is 10 ^2.1 d㎩ · s) was allowed to stand for 30 minutes. Then, it moved to the electric furnace of 730 degreeC, and slow cooled the glass to 610 degreeC over 2 hours, and further cooled the glass to room temperature over about 10 hours. And the evaluation sample was produced like Example 3, and the number of residual bubbles was calculated | required. The results are shown in Table 2.

[Example 6]

The same glass raw material as in Example 2 was prepared.

Process (a):

Half of the glass raw material (equivalent to 125 g in terms of glass) was placed in a 300 kPa platinum persimmon and allowed to stand for 30 minutes in an electric furnace at 1590 ° C (temperature at which the molten glass had a viscosity of 10 ^2.3 dPa · s). The platinum fruit from the electric furnace was once taken out from the furnace, and the remaining half (equivalent to 125 g in terms of glass) was added, and the mixture was left to stand for 30 minutes in an electric furnace at 1590 ° C (temperature at which the molten glass had a viscosity of 10 ^2.3 dPa · s) and dissolved. .

Process (b):

Then, it transferred to the electric furnace of 1590 degreeC (temperature in which the viscosity of a molten glass becomes 10 ^2.3 dPa * s) rapidly, and left still for 30 minutes. Then, it moved to the electric furnace of 730 degreeC, and slow cooled the glass to 610 degreeC over 2 hours, and further cooled the glass to room temperature over about 10 hours. And the evaluation sample was produced like Example 3, and the number of residual bubbles was calculated | required. The results are shown in Table 2.

Process (a) Process (b)
Temperature difference
(b)-(a)
(℃)
Remaining bubbles
(Pcs / cm 3) Temperature
(℃) Viscosity
(d㎩s) Temperature
(℃) Viscosity
(d㎩s) time
(minute) Example 3 1500 10 ^2.7 1590 10 ^2.3 30 90 60 Example 4 1550 10 ^2.5 1590 10 ^2.3 30 40 215 Example 5 1500 10 ^2.5 1590 10 ^2.1 15 90 160 Example 6 1590 10 ^2.3 1590 10 ^2.3 30 0 1235

[Example 7]

As aluminum source Al (OH) in the same way as in Example 1 except that there was used ₃ as a refining agent in addition glass to the parent composition of the raw material, and, the glass of 0.5% by mass of SnO ₂ with respect to the base composition material, the SrCl ₄ 0.5 added% by weight, CaSO ₄ · 2H ₂ O 0.1% by mass to 0.3% by mass, and CaF _2, was made of glass material.

Except having used the glass raw material obtained above, the evaluation sample was produced like Example 3, and the number of residual bubbles was calculated | required. The results are shown in Table 3.

[Example 8]

Evaluation similar to Example 7 was performed except having changed the temperature of a process (a) into 1450 degreeC (temperature which becomes a viscosity of 10 ^2.8 dPa * s). The results are shown in Table 3.

Process (a) Process (b)
Temperature difference
(b)-(a)
(℃)
Remaining bubbles
(Pcs / cm 3) Temperature
(℃) Viscosity
(d㎩s) Temperature
(℃) Viscosity
(d㎩s) time
(minute) Example 7 1500 10 ^2.7 1590 10 ^2.3 30 90 50 Example 8 1475 10 ^2.8 1590 10 ^2.3 30 115 45

The temperature at which the glass raw material is heated at a temperature at which the viscosity of the molten glass becomes more than 10 ^2.4 dPa · s in the step (a), and the viscosity of the molten glass is 10 ^2.4 dPa · s or less in the process (b). In Examples 3 to 5 heated at a temperature 30 ° C. or more higher than the temperature in the step (a) is a temperature at which the viscosity of the molten glass becomes 10 ^2.4 dPa · s or less in the raw material in the step (a). It heats at and compares with Example 6 which has no difference in the viscosity of the molten glass of a process (a) and a process (b), and it turns out that the number of remaining bubbles is small and a clarification effect is large.

In addition, in Examples 7 and 8 containing Al (OH) ₃ in the glass imitation raw material, in particular, Example 8 dissolves the glass raw material at a low temperature in the step (a), even though the viscosity of the molten glass is increased. It is understood that good melting characteristics are obtained, and in Example 7, 8, the number of remaining bubbles is small and the clarification effect is large.

The alkali free glass obtained by the manufacturing method of this invention has few bubbles in glass, and is high in homogeneity and flatness. In addition, the chemical resistance, since it contains B ₂ O _3, and the durability is also excellent. The alkali free glass is useful as a glass for liquid crystal display substrates.

In addition, all the content of the JP Patent application 2007-277802, a claim, drawing, and the abstract for which it applied on October 25, 2007 is referred here, and it introduces as an indication of the specification of this invention.

Claims (7)

In the manufacturing method of the alkali free glass which melts and shape | molds the glass raw material which added the clarifier to the glass imitation raw material containing a silica sand and a boron source,
As the silica sand, a median diameter of 15 to 60 µm and a particle ratio of 100 µm or more in particle size of 2.5 vol% or less were used.
As the boron source, and the use in that it contains 100% by weight of anhydrous boric acid boron source 10 to 100 mass% of (B ₂ O ₃ basis) (B ₂ O ₃ basis),
As the clarifier, at least SnO ₂ is used,
Melting of the said glass raw material is performed by the following 2 processes at least, The manufacturing method of the alkali free glass characterized by the above-mentioned.
(a) The process of heating the said glass raw material at the temperature which the viscosity of a molten glass becomes more than 10 ^2.4 dPa * s, and makes it molten glass.
(b) After the said process (a), the said molten glass is heated at the temperature which the viscosity of a molten glass becomes 10 ^2.4 dPa * s or less, and also at the temperature 30 degreeC or more higher than the temperature in the said process (a), And degassing bubbles in the molten glass. The method of claim 1,
The manufacturing method of the alkali free glass containing the hydroxide of aluminum or alkaline-earth metal in the said glass imitation raw material. The method according to claim 1 or 2,
In the mass percentage display on the basis of oxide, a glass imitation raw material is prepared so as to be an alkali free glass having the following glass imitation property (1), and 0.01 to 2% by mass of tin is added to the glass imitation raw material in terms of SnO ₂ and The manufacturing method of the alkali free glass used as a raw material.
SiO ₂ : 50 to 66 mass%, Al ₂ O ₃ : 10.5 to 22 mass%, B ₂ O ₃ : 5 to 12 mass%, MgO: 0 to 8 mass%, CaO: 0 to 14.5 mass%, SrO: 0 -24 mass%, BaO: 0-13.5 mass%, MgO + CaO + SrO + BaO: 9-29.5 mass%. (One). The method according to any one of claims 1 to 3,
In the mass percentage display on the basis of oxide, a glass imitation raw material is prepared so as to be an alkali free glass having the following glass imitation property (2), and 0.01-2 mass% of tin is added to the glass imitation raw material in terms of SnO ₂ , and the glass The manufacturing method of the alkali free glass used as a raw material.
SiO ₂ : 58 to 66 mass%, Al ₂ O ₃ : 15 to 22 mass%, B ₂ O ₃ : 5 to 12 mass%, MgO: 0 to 8 mass%, CaO: 0 to 9 mass%, SrO: 3 -12.5 mass%, BaO: 0-2 mass%, MgO + CaO + SrO + BaO: 9-18 mass%. (2). The method according to any one of claims 1 to 4,
In the mass percentage display on the basis of oxide, a glass imitation raw material is prepared so as to be an alkali free glass having the following glass imitation property (3), and 0.01-2 mass% of tin is added to the glass imitation raw material in terms of SnO ₂ , and the glass The manufacturing method of the alkali free glass used as a raw material.
SiO ₂ : 50 to 61.5 mass%, Al ₂ O ₃ : 10.5 to 18 mass%, B ₂ O ₃ : 7 to 10 mass%, MgO: 2 to 5 mass%, CaO: 0 to 14.5 mass%, SrO: 0 -24 mass%, BaO: 0-13.5 mass%, MgO + CaO + SrO + BaO: 16-29.5 mass%. (3). 6. The method according to any one of claims 1 to 5,
1 or more types selected from the group consisting of 3 mass% or less chloride in terms of Cl, 3 mass% or less in terms of SO ₃ , and 3 mass% or less in fluoride in terms of F with respect to the glass dummy material. The manufacturing method of the alkali free glass which adds 0.01-5 mass% in total amount and uses it as a glass raw material. The method according to any one of claims 1 to 6,
The method of alkali-free glass of the glass with respect to the base composition of the starting materials, the cullet comprising a nitrate in addition to 0.01 to 10% by mass and an alkali-free glass in terms of NO ₃ was added 15 ~ 300% by mass of a glass material.

Images