JP4715258B2 - Glass and glass manufacturing method - Google Patents

Description

  The present invention relates to glass and a glass manufacturing method.

  In general, glass substrates for flat panel displays are largely divided into alkali-containing glasses containing 10% or more of alkali metal oxides in terms of mass percentage and alkali-free glasses containing substantially no alkali metal oxides. Separated. Alkali-containing glass is used for glass substrates such as plasma display (PDP), plasma-assisted liquid crystal display (PALC), field emission display (FED), and alkali-free glass is a thin film transistor-driven color liquid crystal display (TFT- LCD), glass substrates such as electroluminescence display (EL).

  Such a glass substrate for a flat panel display is required to have substantially no visible defect. One of the typical drawbacks is bubbles in the glass, and it is particularly preferable that bubbles of 100 μm or more do not exist.

In order to satisfy the requirements regarding such foam, the glass raw material usually contains a refining agent for removing the foam from the molten glass obtained by melting the raw material. General fining agents applied to glass include oxide-based fining agents such as As ₂ O ₃ and Sb ₂ O ₃ , and sulfates such as Na ₂ SO ₄ , K ₂ SO ₄ , CaSO ₄ and BaSO _4. Refiners, NaCl, etc. are known. (For example, see Non-Patent Document 1.) Although sulfate is considered to be present as SO ₄ ²⁻ in molten glass, it is described as SO _{3 in} the present invention when it is displayed as an oxide. .

For example, a glass substrate for TFT-LCD or a glass substrate for organic EL uses non-alkali glass that does not substantially contain an alkali metal oxide, and As ₂ O ₃ or Sb ₂ O ₃ is often used as a fining agent. (For example, refer to Patent Document 1).

In addition, Fe ₂ O ₃ , SnO ₂ , Cl, F and the like are known as fining agents for alkali-free glass (see, for example, Patent Documents 2 and 3).

  In order to sufficiently remove the bubbles in the glass, it is necessary not only to remove bubbles by a clarification reaction at the time of melting the raw material, but also to suppress bubbles generated again after clarification.

  That is, the melted and clarified glass passes through a homogenization process by a stirrer and an introduction pipe that connects each process until a molding process such as a float process, but the interface between platinum and brick, which are these structures, and glass. It is necessary to suppress bubbles generated in the above (hereinafter referred to as reboil bubbles).

Japanese Patent No. 3465238 JP-A-10-324526 Japanese Patent Laid-Open No. 11-4330 Masayuki Yamane et al. “Glass Engineering Handbook” Asakura Shoten 1999

  As described above, the requirements for the suppression of bubbles in the glass substrate for flat panel display are very strict, and it is preferable that bubbles having a size of 100 μm or more do not exist, and even a small bubble of several tens of μm is required to be small. Is done.

As described above, non-alkali glass that does not substantially contain alkali is conventionally used for a TFT-LCD glass substrate or an organic EL glass substrate, and As ₂ O ₃ or Sb ₂ O ₃ is used as a fining agent. Many are used. As ₂ O ₃ and Sb ₂ O ₃ , especially As ₂ O ₃ are refining agents that are extremely excellent in terms of removing bubbles from the molten glass, but they have a large environmental load and are required to be suppressed.

On the other hand, sulfate is a refining agent that is extremely excellent in that the load on the environment is significantly less than that of As ₂ O ₃ . Even in alkali-free glass, sulfate is used in combination with Cl or the like. However, the alkali-free glass has a problem that the refining action is inferior and the suppression of bubbles is inferior, and reboiling bubbles are likely to be generated after clarification once.

  An object of the present invention is to solve such a problem, that is, to provide a glass and a glass production method that substantially contain no As and Sb and effectively suppress the generation of bubbles by sulfate.

In the present invention, SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO and BaO are used as a mother composition, and the content of CaO in the mother composition is 15% or less in terms of an oxide-based mass percentage. And the content of the BaO in the matrix composition is 1% or less in terms of oxide-based mass percentage, and sulfur is represented by mass percentage or mass percentage with respect to the total mass of the matrix composition. Containing ₃ ppm or more and less than 0.02%, and Na and / or K in terms of mass percentage is 0.03% or more and 0.1% in terms of R ₂ O (R means Na or K) A glass substrate containing Fe in an amount of 0.0015% or more in terms of mass percentage in terms of Fe ₂ O ₃ , wherein the reduction degree of the glass is expressed as a ratio of Fe ions, and Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) Less than 0.67 A glass substrate having a corresponding reduction degree is provided.

  Moreover, this invention provides the said glass substrate containing 0.05 to 1% of Cl by mass percentage display with respect to the total amount of the said mother composition.

Further, according to the present invention, the matrix composition may be expressed as SiO ₂ 51-68 % in terms of oxide based mass percentage.
Al ₂ O ₃ 10~22%
B ₂ O ₃ 6~16%
MgO 1-7 %
CaO 2-12 %
SrO 0.5-10 %
BaO 0 to 1 %
A glass substrate containing the above is provided.
In addition, the present invention provides the glass substrate, wherein the mother composition does not substantially contain the BaO.

  The present invention also provides the glass substrate, wherein the glass substrate is a glass substrate for TFT-LCD or a glass substrate for organic EL.

This invention also provides a method of manufacturing a glass by dissolving the raw _{material, SiO 2, Al 2 O 3} , B 2 O 3, MgO, CaO, SrO and BaO as a base composition of the raw material, the mother composition The content of CaO is not more than 15% in terms of oxide-based mass percentage, and the content of BaO in the matrix composition is not more than 1% in terms of oxide-based mass percentage. On the other hand, in terms of mass percentage, sulfate is converted to SO ₃ and is 0.05% or more and less than 1.0%, and Na and / or K is represented by R ₂ O (R is Na, K in terms of mass percentage). meaning) converted at least 0.03%, prepared as contained in the raw material at a rate of less than 0.1% of Fe in mass percentage to the raw material at the rate of 0.0015% or more in terms _{of Fe} 2 _{O 3} Prepare to be included and reduce the reduction degree of the glass to Fe Provided is a method for producing a glass, characterized by melting the glass so that the reduction ratio corresponding to Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) is 0.67 or less .

  Further, the present invention is characterized in that the glass is prepared such that chloride is contained in the raw material at a ratio of 0.1 to 3% in terms of Cl with respect to the total amount of the matrix composition. A manufacturing method is provided.

Further, according to the present invention, the matrix composition may be expressed as SiO ₂ 51-68 % in terms of oxide based mass percentage.
Al ₂ O ₃ 10~22%
B ₂ O ₃ 6~16%
MgO 1-7 %
CaO 2-12 %
SrO 0.5-10 %
BaO 0 to 1 %
It contains, The manufacturing method of the said glass characterized by the above-mentioned is provided.
The present invention also provides a method for producing the glass, wherein the matrix composition does not substantially contain the BaO.

In addition, the present invention provides a method for producing the glass, wherein the glass melting maximum temperature when the raw material is melted to produce the glass is 1610 ° C. or less.
Moreover, this invention is characterized by the maximum temperature of glass melting at the time of manufacturing a glass by melt | dissolving a raw material being 1500-1600 degreeC, and hold | maintaining molten glass at 1200-1500 degreeC after that, and defoaming. A method for producing the glass is provided.

The glass of the present invention contains a trace amount of alkali that does not affect the manufacturing process of TFT-LCD or the like, thereby increasing the basicity of the glass, and to the glass melt of SO ₃ during glass melting production. The solubility of is improved. As a result, the effect of suppressing bubbles as a clarifier of SO ₃ can be improved, and the generation of reboyl bubbles after the clarification reaction can be suppressed.

  In addition, the glass contains a trace amount of alkali, which accelerates the melting of the silica sand, which is the main raw material of the glass, improves the homogeneity of the glass, and generates unmelted silica sand in the initial stage of melting. It is also possible to suppress foaming. The glass of the present invention is particularly effective as a glass substrate for TFT-LCD or a glass substrate for organic EL.

Hereinafter, the composition of the glass is expressed in terms of mass percentage, and for example, the Si content in terms of SiO _{2 in} terms of oxide based mass percentage may be simply referred to as SiO ₂ content or SiO ₂ . In addition, trace components of 0.1% or less may be expressed in parts per million (ppm).

  Alkali-free glass has heretofore been essentially free of alkali oxide in glass, but the glass of the present invention has an alkali oxide content of 0.03% or more and less than 0.1%, When used as a TFT-LCD glass substrate or an organic EL glass substrate, it does not affect the TFT manufacturing process and the like, and can be used in place of conventional alkali-free glass. If the glass contains an alkali oxide of 0.1% or more, for example, in the TFT manufacturing process, transistor characteristics formed on the glass substrate deteriorate, which is not preferable.

The alkali component is mainly supplied as a glass raw material, and Na ₂ CO ₃ , Na ₂ SO ₄ , NaCl, NaNO ₃ , KCO ₃ , K ₂ SO ₄ , KCl, and KNO ₃ can be used. Ordinary soda-lime glass cullet used for window glass or the like can also be used.

  The glass transition temperature (Tg) of the glass of the present invention is 670 ° C. or higher and 770 ° C. or lower, and the strain point is typically 640 ° C. or higher, particularly 660 ° C. or higher and 730 ° C. or lower.

The coefficient of thermal expansion (value measured according to JIS R3102 (1995)) of the glass of the present invention is typically 25 to 50 × 10 ⁻⁷ ° C. ⁻¹ (measurement temperature range 50 to 350 ° C.). .

The glass of the present invention typically has SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO and BaO as a parent composition, and the parts per million by mass with respect to the total amount of the mother composition Contains 1 ppm or more and less than 0.02% of sulfur in terms of SO _{3 in} terms of display or mass percentage, and 0 in terms of R ₂ O (R means Na, K) in terms of Na and / or K in terms of mass percentage. 0.03% or more and less than 0.1%, and the matrix composition is SiO ₂ 45 to 70% in terms of mass percentage based on oxide.
Al ₂ O ₃ 5-25%
B ₂ O ₃ 1-20%
MgO 0-10%
CaO 0-15%
SrO 0-15%
BaO 0-20%
Containing. For example, “MgO 0 to 10%” indicates that MgO may be contained up to 10%.

SiO ₂ is an essential component, and if it exceeds 70%, the solubility of the glass is lowered and the glass tends to devitrify. Preferably it is 68% or less, More preferably, it is 65% or less. If it is less than 45%, the specific gravity increases, the strain point decreases, the thermal expansion coefficient increases, and the chemical resistance decreases. In order to obtain sufficient acid resistance, it is preferably 51% or more, more preferably 57% or more.

Al ₂ O ₃ is a component that suppresses the phase separation of the glass and increases the strain point, and is essential. If it exceeds 25%, devitrification tends to occur, and chemical resistance decreases. Preferably it is 22% or less, More preferably, it is 19% or less. If it is less than 5%, the glass tends to undergo phase separation, or the strain point decreases. Preferably it is 10% or more, More preferably, it is 14% or more.

B ₂ O ₃ is a component that decreases the specific gravity, increases the solubility of the glass, and makes it difficult to devitrify, and is essential. If it exceeds 20%, the strain point is lowered, the chemical resistance is lowered, or the volatilization at the time of melting the glass becomes remarkable and the inhomogeneity of the glass is increased. Preferably it is 16% or less, More preferably, it is 12% or less. If it is less than 1%, the specific gravity increases, the solubility of the glass decreases, and devitrification easily occurs. Preferably it is 3% or more, More preferably, it is 6% or more.

  MgO is a component that reduces the specific gravity and improves the solubility of the glass. If it exceeds 10%, the glass tends to undergo phase separation, devitrification tends to occur, or chemical resistance decreases. Preferably it is 7% or less, More preferably, it is 5% or less. When it contains MgO, it is preferable to contain 0.1% or more. In particular, it is preferable to contain 1% or more in order to reduce the specific gravity while maintaining the solubility.

  CaO can be contained up to 15% in order to increase the solubility of the glass and make it difficult to devitrify. If it exceeds 15%, the specific gravity will increase, the thermal expansion coefficient will increase, and devitrification will tend to occur. Preferably it is 12% or less, More preferably, it is 8% or less. When it contains CaO, it is preferable to contain 2% or more. More preferably, it is 4% or more.

  SrO can be contained up to 15% in order to suppress the phase separation of the glass and make it difficult to devitrify. If it exceeds 15%, the specific gravity increases, the thermal expansion coefficient increases, and devitrification tends to occur. Preferably it is 12% or less, More preferably, it is 10% or less. When it contains SrO, it is preferable to contain 0.5% or more. More preferably, it is 3% or more.

BaO can be contained up to 20% in order to suppress the phase separation of the glass and make it difficult to devitrify. If it exceeds 20%, the specific gravity increases and the thermal expansion coefficient becomes large. Preferably it is 10% or less, More preferably, it is 1% or less. It is preferable not to contain it especially when weight reduction is important.
In the glass of the present invention, ZnO can be contained up to 5%.

The glass of the present invention, also _As 2 _{O 3} or _Sb 2 _{O 3} is not substantially contained, SO ₃ or, _Cl to _{SO 3, F, SnO 2,} CeO 2, TiO 2 or the like is added fining agents By adding, defoaming can be efficiently performed and reboiling foam can be suppressed, so that generation of foam can be effectively suppressed.

As described above, the sulfate is considered to be present as SO ₄ ²⁻ in the molten glass, but in the present invention, the content is defined as SO ₃ .

The glass of the present invention contains 1 ppm or more and less than 0.02% SO ₃ with respect to the matrix composition. SO ₃ is mainly supplied as a glass raw material, and BaSO ₄ , SrSO ₄ , CaSO ₄ , Na ₂ SO ₄ , and an anhydrous salt or hydrated salt of K ₂ SO ₄ can be used. The total amount of SO ₃ supplied from the raw material is preferably 0.05% or more and less than 1%. Depending on the glass composition and the raw materials used, about several hundred ppm of SO ₃ is supplied as impurities from BaCO ₃ or SrCO ₃ which are raw materials of glass.

SO ₃ supplied from the glass raw material is easily volatilized when the glass is melted. The amount of SO ₃ remaining (contained) in the glass is generally 1/10 or less of the supply amount from the raw material. The amount of SO ₃ remaining in the glass is very small with respect to the supplied amount, and a large part depends on the thermal history such as the melting temperature and melting time of the glass, the redox state of the glass, and the glass composition. When the SO ₃ finally remaining in the glass is less than 1 ppm, the refining effect is small. In order to generate a good clarification effect, the SO ₃ residual amount is 1 ppm or more, preferably 5 ppm or more. Further, when 0.02% of SO ₃ remaining the reboil bubbles is likely to occur. In order to suppress reboiling, it is necessary to make the residual amount less than 0.02%, preferably less than 0.01%.

The glass of the present invention contains a trace amount of an alkali metal oxide. Alkali increases the solubility of SO _3, that is, SO ₄ ²⁻ , so that the clarification effect is enhanced and reboiling bubbles are less likely to be generated.

It is known that clarification with sulfate is the following reaction.
2SO ₄ ²⁻ → 2SO ₂ + O ₂ + 2O ²⁻ (1)
This reaction can be exemplified as the following reaction in a glass containing Ba and substantially not containing alkali.
2BaSO ₄ → 2SO ₂ + O ₂ + 2BaO (2)
Here, the same reaction can be considered even if Ba is replaced with Mg, Ca, Sr. By adding a small amount of Na, it can be expected that the next reaction proceeds simultaneously.
2Na ₂ SO ₄ → 2SO ₂ + O ₂ + 2Na ₂ O (3)
Here, the same reaction can be considered even if Na is replaced with K.
The tendency of the reaction as glass can be known by performing thermodynamic calculation of the chemical reactions of the glass components. The equilibrium constant Ke of the reaction is as follows:
Ke = (pSO ₂ ) ² × (pO ₂ ) × [RO] ² / [RSO ₄ ] ² (4)
(R is any of Mg, Ca, Sr, Ba, Na ₂ and K ₂ ).

Here, (pSO ₂ ) and (pO ₂ ) indicate the partial pressure of SO ₂ and O ₂ , and [RO] and [RSO ₄ ] indicate the activities of RO and RSO ₄ in the glass. Table 1 shows the equilibrium constants at 1400 ° C. Table 1 shows the calculation results of log (pSO ₂ ) when [RO] and [RSO ₄ ] are assumed to be 1 and log (pO ₂ ) = − 5. FIG. 1 shows the relationship between log (pO ₂ ) and log (pSO ₂ ) at 1400 ° C. based on the same assumption. In addition, the thermodynamic calculation software "HSC Chemistry Version 4.1" of Autokumpu was used for the thermodynamic calculation.

In FIG. 1, the oxygen partial pressure in the glass can be estimated from the redox state of FeO and Fe ₂ O ₃ , and in the case of the glass of the present invention, log (pO ₂ ) corresponds to around −4 to −6. Can be estimated. However, such an estimate is effective only when there is no compound such as SnO ₂ whose state changes with an oxygen partial pressure. From Table 1, when the alkaline earth component of the alkali-free glass is composed of only Mg and Ca is, log since (pSO ₂₎ is positive, the SO ₂ when _SO ^{4 2-is} present in the glass It can be seen that the partial pressure is 1 atm or more and SO ₂ bubbles are easily generated.

When Sr or Ba is contained in the glass, log (pSO ₂ ) is negative, but its value is small, and it is understood that the solubility of SO ₄ ^{2− in} the glass is low. On the other hand, when Na or K is contained in the glass, the log (pSO ₂ ) becomes sufficiently small and the solubility of SO ₄ ²⁻ increases, that is, the reaction of the formula (3) can be easily reversibly moved to the left side. You can see it going. It can also be seen that K has a greater effect of dissolving SO ₄ ²⁻ in glass than Na.

As described above, [RO] and [RSO ₄ ] are considered as 1, but it is known that these activities depend on the concentration in the glass. Since the difference between the equilibrium constants of Na and Ba is 10 ⁶ or more, even if the difference in activity due to the concentration is taken into consideration, the amount of alkali less than 0.1% with respect to dissolution of SO ₄ ^{2− in} the glass It turns out that the effect more than Ba is exhibited.

The content of R ₂ O (R is one or more of Na and K) is preferably excessive with respect to dissolved SO ₃ , and is 0.03% or more, more preferably 0 with respect to the mother composition. The effect becomes remarkable when it contains 0.05% or more. For the purpose of removing bubbles in the glass and suppressing reboil bubbles, it is preferable that the content of R ₂ O is large, but it does not affect the characteristics of the transistor formed on the glass in the manufacturing process of TFT-LCD or the like. For this purpose, R ₂ O is preferably less than 0.1%.

In addition to Na and K, Li is considered to have the same effect. However, since Li has a smaller effect of lowering log (pSO ₂ ) than Na and K, it is preferable to use Na and K. In the case of adding the R ₂ O component, it is usually used for Na ₂ CO ₃ , Na ₂ SO ₄ , NaCl, NaNO ₃ , KCO ₃ , K ₂ SO ₄ , KCl, KNO ₃ , or window glass. It is preferable to add a cullet of soda-lime glass in an amount of 0.03% or more and less than 0.1% in terms of R ₂ O.

The glass of the present invention is substantially free of both As and Sb.
The glass of the present invention can be defoamed more efficiently by adding a refining agent in which Cl, F, SnO ₂ , CeO ₂ , TiO _2, etc. are added to SO _3, and reboiling can be suppressed. Therefore, generation | occurrence | production of a bubble can be suppressed effectively.

It is effective to combine SO ₃ and Cl as a fining agent. When defoaming is performed in combination with vacuum defoaming, Cl generates HCl gas under reduced pressure, so inclusion of Cl exhibits a preferable defoaming effect. When vacuum degassing is performed with Cl, the glass is placed under reduced pressure in the range of 4 kPa or more and 50 kPa or less, more preferably 18 kPa or more and 35 kPa or less in absolute pressure, for 15 minutes or more and less than 120 minutes. Is preferred.

Cl can be contained by using BaCl ₂ .2H ₂ O, SrCl ₂ .6H ₂ O, NaCl, KCl, NH ₄ Cl or the like as a glass raw material. It is preferable to add chloride to the glass raw material in an amount corresponding to 0.1 to 3% in terms of Cl. Cl in the raw material is reduced from 1/2 to 1/5 in the course of glass melting. In order for Cl to act effectively as a fining agent, the content in the glass is 0.05% to 1%, preferably 0.1% to 1%, expressed as a percentage by mass. When the content exceeds 1%, when the glass of the present invention is used for a TFT-LCD glass substrate, the strain point or chemical resistance may be lowered, so that it is preferably 1% or less.

SnO _{2, CeO 2,} TiO ₂ or the like suppresses the reboil of SO ₂ mechanism is not necessarily clear, these oxides to release oxygen at high temperature, affecting the oxygen partial pressure, the SO ₂ It is thought that reboil is suppressed.

In order for SnO ₂ , CeO ₂ , and TiO ₂ to exhibit a reboyl suppressing effect, it is necessary to contain 0.01% or more, more preferably 0.05% or more. Sn, the case of adding at least one member selected from the group consisting of Ce and _Ti, in terms of SnO 2, CeO ₂ or TiO ₂ 0.01 to 2%, especially 0.01 to 1%, even 0 It is preferable to add to the glass raw material in an amount corresponding to 0.05 to 0.5%.

When the glass of the present invention is produced by a float process, excess SnO ₂ may be metalized because it passes through the reducing atmosphere of the float bath. The content of SnO ₂ needs to be suppressed to 1% or less, more preferably 0.5% or less.

When the glass of the present invention is produced by a fusion method or a slot down draw method, SnO ₂ has an effect of increasing the devitrification temperature, so the content is preferably 2% or less. More preferably, it is 1% or less.

CeO ₂ is known to react with Fe ₂ O ₃ in glass by ultraviolet irradiation to cause solarization. In order to prevent this, the content of CeO ₂ should be 1% or less, more preferably not contained.

TiO ₂ is known to be colored yellow in glass. In order to prevent this, the content of TiO ₂ should be 1% or less, more preferably not contained.

  In the glass of the present invention, F can be added as a fining agent. F has the effect of lowering the viscosity of the glass and promotes the rise of bubbles in the glass. Moreover, the same clarification effect as Cl can be expected at a higher temperature.

F can be contained by using BaF ₂ , SrF ₂ , CaF ₂ , MgF ₂ or the like as a glass raw material. The addition amount of the fluoride in the raw material is preferably 0.05% or more and 1% or less in terms of F in mass percentage. The residual amount of F in the glass is preferably 0.2% or less in terms of mass percentage. When the content exceeds 0.2%, when the glass of the present invention is used for a TFT-LCD glass substrate, the strain point may be remarkably lowered.

The glass of the present invention is particularly preferably composed of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO and BaO as a mother composition and expressed in parts by mass relative to the total amount of the mother composition. Alternatively, sulfur is contained at 1 ppm or more and less than 0.02% in terms of SO _{3 in} terms of mass percentage, and Na and / or K is expressed in terms of R ₂ O (R means Na and K) in terms of mass percentage of 0. 0.05% or more, and contains less than 0.1%, a Cl containing 0.05 to _1%, containing 0.01% to 1% of one or more of selected from the group consisting of SnO 2, CeO ₂ and TiO _2, The matrix composition is SiO ₂ 51 to 68% in terms of oxide based mass percentage,
Al ₂ O ₃ 10-22%,
B ₂ O ₃ 6-16%,
MgO 1-7%,
CaO 2-12%,
SrO 0.5-10%,
BaO 0-1%
Containing.

As shown in the formulas (1) to (3), the clarification reaction of the glass of the present invention greatly depends on the oxygen partial pressure at the time of melting the glass, and the oxygen partial pressure at the time of melting the glass is the redox of the obtained glass. It can be evaluated as a state. The redox degree of glass is generally expressed as r = Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) using the content of Fe ^{2+ and} the content of Fe ³⁺ , but in the glass of the present invention, r Is preferably 0.67 or less. When the reducibility is increased beyond 0.67, it means that the oxygen partial pressure at the time of melting the glass is low, and the reactions shown in the formulas (1) to (3) easily proceed to the right side. As a result, the solubility of SO ₄ ^{2− in} the glass is lowered, and SO ₂ reboil bubbles are likely to be generated. Further, once generated SO ₂ bubbles cannot easily return into the glass. Preferably, when r is 0.63 or less, and more preferably 0.59 or less, the suppression and absorption of SO ₂ reboyl bubbles act effectively.

In order to enable r measurement, the glass of the present invention contains Fe as an essential component when Fe ions are used as an index. The Fe ₂ O ₃ equivalent content of Fe (total amount of Fe ²⁺ and Fe ³⁺ ) needs to be 0.0015% or more. If the Fe ₂ O ₃ equivalent content of Fe is less than 0.0015%, r measurement becomes difficult. In order to make r measurement easier, the Fe ₂ O ₃ equivalent content of Fe is preferably 0.01% or more. Further, the Fe ₂ O ₃ equivalent content of Fe is typically 0.3% or less. In the case of display glass, it is preferably 0.2% or less. If it exceeds 0.2%, it is colored blue, which is not preferable as a display glass. Preferably it is 0.1% or less, More preferably, it is 0.07% or less.

The value of r varies with the addition of SnO ₂ , TiO ₂ , and CeO ₂ . Since these metal ions change the value of r by exchanging electrons with Fe ions in the glass, r should be used as an index of the oxygen partial pressure in glasses containing SnO ₂ , TiO ₂ , and CeO _2. Is not preferred.

When there is no ion whose valence changes other than Fe, the melting temperature is the most effective method for controlling r. That is, when the melting temperature rises, oxygen is released from the glass and Fe ²⁺ increases. In order to set the value of r to 0.67 or less, it is effective to keep the glass melting temperature at 1610 ° C. or less.

The glass of the present invention is produced, for example, by the following method.
The raw materials prepared so as to obtain a glass having the target composition are heated and melted to obtain molten glass. The molten glass is cooled after defoaming, homogenization and the like. The homogenization of the molten glass may be promoted by stirring, for example. Further, it is usually formed into a sheet glass suitable for a glass substrate during cooling.
The raw material is usually made of silica sand and other raw materials, but may contain waste glass (cullet).

  The melting may be performed, for example, by putting a raw material in a suitable crucible and putting the crucible in a furnace such as an electric furnace maintained at a high temperature, or by continuously feeding the raw material into a glass melting furnace. Good. In general industrial production, each component raw material of the glass of the present invention that is normally used is prepared to have a target composition, and the raw material is prepared. In a glass melting furnace having a maximum temperature of about 1500 to 1600 ° C., for example. Continuously charged and melted to obtain molten glass. An appropriate amount of an alkali component is added to the raw material.

  The molten glass is then defoamed, for example, held at 1200 to 1500 ° C., and at that time, it is also possible to defoam using vacuum defoaming.

  The defoamed molten glass is formed into, for example, plate glass. Examples of the molding method include a float method, a fusion method, and a slot down draw method. In the present invention, since the effect of suppressing bubbles is particularly great, the float method is preferred in consideration of producing large glass with stable quality. The plate glass is cut after slow cooling, and is formed into a glass substrate for TFT-LCD or a glass substrate for EL having a thickness of 0.4 to 1.5 mm and a dimension of 1700 × 1400 mm or more, for example.

Tables 2 and 3 show the components input as industrial glass raw materials, and Tables 4 and 5 show the obtained glass in terms of mass percentage with respect to the total amount of SiO _{2 to} BaO. .

The obtained glass has a Cl content of about 0.15% (0.14 to 0.16%) in terms of mass percentage, and an SO ₃ content of about 0.005% (0.003 to 0.003 in terms of mass percentage). 007%). In Tables 4 and 5, Fe ₂ O ₃ is the Fe ₂ O ₃ equivalent content of Fe (total amount of Fe ²⁺ and Fe ³⁺ ).

All the glasses shown in Tables 4 and 5 have a density of 2.51 g / cm ³ , a coefficient of thermal expansion of 38 × 10 ⁻⁷ ° C. ⁻¹ (50 to 350 ° C.), a Young's modulus of 77 GPa, and a strain point of 665. ° C and the glass transition temperature is 716 ° C. The change in physical properties due to the difference in the fining agent composition is slight and is substantially the same value. In addition, the composition in the glass raw material used in the present Example was increased by 5% from the values in Tables 4 and 5 for B ₂ O ₃ . SiO ₂ , Al ₂ O ₃ , and MgO to Fe ₂ O ₃ had almost the same composition ratio in the raw material and glass composition ratio. The addition amounts of Cl and SO _{3 to} the glass material were 0.5% and 0.3%, respectively.

Industrial raw materials were prepared so as to have the content ratios shown in Tables 2 and 3, and raw materials for forming 600 g of glass were prepared. Dihydrate gypsum was used as the SO ₃ raw material, and strontium hexahydrochloride was used as the Cl raw material in Examples A1 to 9 and A11. In Example A10, ammonium chloride was used as the Cl raw material. Each industrial raw material contains a trace amount of Na ₂ O. Example A11 is not particularly added Na ₂ O, but it is meant that it contains 0.009% of the Na ₂ O as raw materials an impurity, shown in parentheses.

  The raw material was put in a platinum crucible, and dissolved in an electric furnace in a nitrogen gas atmosphere having a dew point of 80 ° C. and held at 1580 ° C. for 6 hours. During melting, the glass was homogenized by performing stirrer as appropriate (the first 4 hours out of the 6 hours). The molten glass was poured into a carbon plate, solidified and then slowly cooled.

The r of the obtained glass was measured by the following method. Fe ²⁺ in the glass was quantified by bipyridyl spectrophotometry, and total Fe ions, that is, Fe ²⁺ + Fe ³⁺ were quantified by ICP emission spectroscopy. R described in the table is a value obtained by actually measuring A1 to A5 and A9 to A11 in Example 1.

When the composition of the glass after melting was analyzed by the fluorescent X-ray method, the Cl content was about 0.15% in any of the glasses of Examples A1 to 11. Similarly, SO ₃ was also analyzed, and it was about 0.005% in any of the glasses of Examples A1 to 11.

  The poured glass was processed into a cylindrical shape having a diameter of 40 mmφ and a height of 15 mm, placed in a platinum crucible having an inner diameter of 40 mmφ, and remelted in an air atmosphere using an electric furnace. The melting temperature was 1400 ° C., the temperature was raised from room temperature at 1 ° C./min, held for 1 hour, and then lowered at 1 ° C./min.

  When the glass after remelting was observed from the top of the crucible, bubbles were found to adhere to the bottom and side surfaces of the crucible and the interface between the glass and platinum. Since there is no such bubble in the glass before remelting, and no bubble is observed during melting at 1400 ° C., the bubble at the interface between the glass and platinum is a bubble corresponding to reboil. Conceivable. After cooling to room temperature, the number (bubbles) of 200 μm or more adhering to the bottom of the crucible was measured. The number of bubbles 1 in Tables 4 and 5 indicates the number of bubbles measured in this way, and is not yet measured.

Example A1~5 the embodiment changed the amount of Na ₂ O and _{K 2} O, Example A6 Example of adding SnO ₂ added to Na ₂ O, Example A9 was allowed to contain BaO added to Na ₂ O Example, A10 is an example in which NH ₄ Cl is used as a Cl source to make the glass reducible, and A11 is a comparative example.

From the results of Examples A1 to 5, it is understood that the number of bubbles at the interface between glass and platinum decreases when Na ₂ O or K ₂ O is added. It can be seen that when SnO ₂ is added in Example A6, the decrease in the number of bubbles becomes more remarkable. Even if BaO is contained in Example A9, the number of bubbles is reduced as compared with, for example, A1, so in alkaline earths (Mg, Ca, Sr, Ba) there is an element having a large molecular weight (for example, Ba), which is similar to alkali. You can see the effect. In Example A10, since ammonium chloride was used, r was 0.65, which was reduced compared to Example A2, and it was found that the number of bubbles increased.

  In Example 2, an experiment was performed separately from Example 1 under the same conditions as in Example 1. Example 1 evaluates reboil bubbles generated in a static field, while Example 2 evaluates reboil bubbles generated in a dynamic field during stirring.

A raw material was prepared in the same manner as in Example 1, and dissolved in a nitrogen gas atmosphere having a dew point of 80 ° C at 1580 ° C for 6 hours. During melting, the glass was homogenized by performing stirrer as appropriate (the first 4 hours out of the 6 hours).

The flow of nitrogen gas was stopped and the atmosphere was switched to the atmosphere, and the temperature was lowered to 1380 ° C., and stirring was performed for 30 minutes with a platinum stirrer. After the stirring was stopped, the mixture was poured into a carbon plate and solidified and then gradually cooled. The gradually cooled glass was sliced and polished to a thickness of 2 mm, and the number of bubbles (pieces / g) of 100 μm or more was measured. The number of bubbles 2 in Tables 4 and 5 indicates the number of bubbles measured in this way, and is not yet measured. R described in the table is the value actually measured in Example 2 for A6 to A8. However, since it contains SnO ₂ , CeO ₂ , and TiO ₂ as described above, it was used as a reference value with parentheses.

When Example A2 and A4 are compared with Example A11, the effect which suppresses the bubble by stirring is recognized slightly. Example A6 is a case where SnO ₂ , Example A7 is CeO ₂ , and Example A8 is a case where TiO ₂ is added. It can be seen that the number of bubbles generated by stirring is reduced. In Example A10, foam generated by stirring is increased, but since it is more reducing than Example A2, it is considered that SO ₂ is somewhat more likely to reboil.

Table 6 shows the components supplied as industrial glass raw materials, and Table 7 shows the content of each of the obtained glasses in terms of mass percentage with respect to the total amount of SiO _{2 to} BaO.

The obtained glass has a Cl content of about 0.15% (0.14 to 0.16%) in terms of mass percentage, and an SO ₃ content of about 0.005% (0.003 to 0.003 in terms of mass percentage). 007%). In addition, the composition in the glass raw material used in the present Example was increased by 5% from the values in Table 6 for B ₂ O ₃ (8.4%). SiO ₂ , Al ₂ O ₃ and MgO to Fe ₂ O _{3 in} Table 6 had almost the same composition ratio and glass composition ratio in the raw material. The addition amounts of Cl and SO _{3 to} the glass material are 0.5% and 0.3%, respectively.

Industrial raw materials were prepared so as to have the content ratios shown in Table 6, and raw materials for forming 125 g of glass were prepared. This raw material was mixed with 125 g of the same component glass cullet to obtain a raw material for melting. The alkaline component has the values shown in Table 6 including cullet. In Example B1, soda lime glass cullet used for building window glass was used as an alkali source. In Example B2, sodium chloride (NaCl) was used, and the amount of Cl added was made constant by adjusting the amount of strontium chloride 6 water. Example B3 used mirabilite (Na ₂ SO ₄ ), and the amount of SO ₃ added was made constant by adjusting dihydrate gypsum. Example B4 used soda ash (Na ₂ CO ₃ ). In Example B5, no Na ₂ O component was added, but 0.009% Na ₂ O was contained as a raw material impurity, and is shown in parentheses.

  A mixture of the industrial raw material and glass cullet was placed in a platinum crucible, and was melted without stirring with a stirrer by holding it at 1580 ° C. for 1 hour in a nitrogen gas atmosphere having a dew point of 50 ° C. using an electric furnace. The molten glass was poured into a carbon plate, solidified and then slowly cooled. The gradually cooled glass was sliced and polished to a thickness of 2 mm, and the number of bubbles (pieces / g) was measured. The number of bubbles 3 in Table 7 indicates the number of bubbles thus measured.

Under the conditions in which the alkalis of Examples B1 to 4 were added, the number of bubbles was lower than that in Example B5 where no alkali was added. This is thought to be because the SO ₃ concentration in the glass at the initial stage of dissolution increased due to alkali, and the clarification effect of sulfate became prominent. In addition, it is considered that the addition of alkali promotes the dissolution of the silica sand and the speed of disappearance of the silica sand, which is the generation nucleus of bubbles, is considered to be acting.

As described above, when SnO ₂ , CeO ₂ , TiO ₂ or the like is further added to the glass of the present invention, it is effective in suppressing reboil bubbles from Example 1, and from Example 2 in suppressing reboil bubbles in stirring. It turns out that there is an effect. Further, it can be seen from Example 3 that the glass of the present invention is effective in reducing bubbles in the initial stage of dissolution. The glass of these Examples is used as a glass substrate for TFT-LCD, a glass substrate for organic EL, and the like. For example, a glass substrate having a thickness of 0.7 mm and dimensions of 2400 × 2200 mm is produced.

Since the glass substrate of the present invention can effectively reduce bubbles in the glass without using harmful substances such as arsenic and antimony, the glass substrate for flat panel display, particularly the glass substrate for TFT-LCD, organic EL It can be used as a glass substrate for use.

Equilibrium relationship between oxygen partial pressure and sulfurous acid partial pressure of alkali metals and alkaline earth metals

Claims (11)

SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO and BaO are used as a mother composition, and the content of CaO in the mother composition is 15% or less in terms of oxide-based mass percentage, The content of the BaO in the mother composition is 1% or less in terms of oxide based mass percentage, and 1 ppm in terms of SO _{3 in} terms of SO _{3 in} terms of mass percentage or mass percentage with respect to the total amount of the mother composition. Or more, containing less than 0.02%, and containing Na and / or K in terms of mass percentage in terms of R ₂ O (R means Na, K), containing 0.03% or more and less than 0.1% , It is a glass substrate that contains Fe in an amount of 0.0015% or more in terms of mass percentage in terms of Fe ₂ O ₃ , wherein the degree of reduction of the glass is expressed as a ratio of Fe ions, and Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) is 0.00. Returns equivalent to 67 or less A glass substrate that is normal .   The glass substrate of Claim 1 which contains 0.05 to 1% of Cl by the mass percentage display with respect to the total amount of the said mother composition. The matrix composition is SiO ₂ 51 to 68 % in terms of mass percentage based on oxide.
Al ₂ O ₃ 10~22%
B ₂ O ₃ 6~16%
MgO 1-7 %
CaO 2-12 %
SrO 0.5-10 %
BaO 0 to 1 %
The glass substrate according to claim 1 or 2 , which contains The glass substrate according to claim 1, wherein the mother composition does not substantially contain the BaO. It said glass substrate is a glass substrate according to any one of claims 1 to 4, which is a glass substrate for a glass substrate or an organic EL for TFT-LCD. A method for producing glass by melting raw materials, wherein SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO, and BaO are used as a raw material mother composition, and the content of CaO in the mother composition Is 15% or less in terms of oxide-based mass percentage, the BaO content in the matrix composition is 1% or less in terms of oxide-based mass percentage, and is based on the total mass of the matrix composition. In terms of sulfate, SO ₃ is converted to SO ₃ and is 0.05% or more and less than 1.0%, and in terms of mass percentage, Na and / or K is converted to R ₂ O (R means Na, K). Prepared to be included in the raw material at a rate of 0.03% or more and less than 0.1%, and prepared so that Fe is included in the raw material at a rate of 0.0015% or more in terms of Fe ₂ O _{3 in} terms of mass percentage. And the reduction degree of the glass in terms of Fe ions It represents and melt | dissolves glass so that it may become a reduction | restoration degree equivalent to Fe2 ⁺ / (Fe2 ⁺⁺⁺ Fe3 ⁺ ) 0.67 or less, The manufacturing method of the glass characterized by the above-mentioned . Wherein the total amount of the matrix composition, with Cl terms chloride represented by mass percentage, of glass according to claim 6, wherein the preparation to be contained in the raw material at the rate of 0.1% to 3% Production method. The matrix composition is SiO ₂ 51 to 68 % in terms of mass percentage based on oxide.
Al ₂ O ₃ 10~22%
B ₂ O ₃ 6~16%
MgO 1-7 %
CaO 2-12 %
SrO 0.5-10 %
BaO 0 to 1 %
It contains, The manufacturing method of the glass of Claim 6 or 7 characterized by the above-mentioned. The manufacturing method of the glass in any one of Claims 6-8 in which the said mother composition does not contain the said BaO substantially. The glass manufacturing method according to any one of claims 6 to 9 , wherein the maximum temperature of glass melting when melting the raw material to produce glass is 1610 ° C or lower. The maximum temperature of glass melting when melting raw materials to produce glass is 1500 to 1600 ° C, and thereafter the molten glass is held at 1200 to 1500 ° C and defoamed. Glass manufacturing method.

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