JP2004315354A - Alkali-free glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the compaction generated in a heat-treatment without allowing a strain point to rise remarkably. <P>SOLUTION: An alkali-free glass satisfies formula: 0 ≤ the ratio (▵an-st/α50-350) < 3.64, where ▵an-st (ppm/°C) is the inclination of an equilibrium density curve in the temperature range from about an annealing point (Tan) to about a strain point (Tst), and α50-350 (×10<SP>-6</SP>/°C) is an average coefficient of linear thermal expansion in the temperature range of 50-350°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an alkali-free glass suitable for a display substrate such as a liquid crystal display and a photomask substrate.

  Conventionally, glass used for a display substrate, particularly a display substrate on which a thin film of metal or oxide is formed in order to form an electrode, a thin film transistor (TFT) or the like on the surface thereof, is substantially made of an alkali metal oxide. The alkali-free glass is not required. Non-alkali glass suitable for such a display substrate is disclosed in Patent Documents 1-6.

In addition to non-alkali glass, the glass used for the display substrate is (1) less deformation of the glass substrate due to heating in the thin film formation process, especially heat shrinkage (compaction), and (2) on the glass substrate. it durability (BHF resistance) is higher for the formed SiO _x and SiN _x buffered hydrofluoric acid used for etching the (mixture of hydrofluoric acid and ammonium fluoride) to be formed in (3) a glass substrate High durability (acid resistance) against etching of nitric acid, sulfuric acid, hydrochloric acid, etc. used for etching metal electrodes or ITO (indium oxide doped with tin), (4) Sufficient for alkaline resist stripping solution (5) Low specific gravity (density) to reduce display weight, (6) Display production In order to increase the temperature raising / lowering speed in the process and to improve the thermal shock resistance, it is required that the expansion coefficient is small, and (7) it is difficult to devitrify.

  Among the characteristics required for the alkali-free glass used for these display substrates, (1), that is, the properties described in Patent Documents 1 to 6 regarding the deformation of the glass substrate and / or the reduction of compaction due to heating in the thin film formation process. Conventional non-alkali glass including alkali glass responds by increasing the strain point of glass. However, when the strain point is increased, it is necessary to carry out glass production processes such as melting and molding at higher temperatures. That is, it is necessary to make the equipment used in the glass manufacturing process such as a melting furnace capable of withstanding the use at a higher temperature, and the life of the equipment is shortened, which is not preferable.

  A thin film transistor (TFT) formed on a glass substrate as a driving circuit of a liquid crystal display is a TFT (p-p) manufactured from a polycrystalline silicon film using a low temperature process from a TFT manufactured from an amorphous silicon film (a-Si TFT). -Si TFT). However, in the p-Si TFT, it is necessary to perform the thin film formation process at a higher temperature than in the a-Si TFT. This means that the strain point of the glass substrate needs to be further increased, and the manufacturing process needs to be performed at a higher temperature. Moreover, one of the main reasons for the shift to p-TFT is high definition and high performance of the display, and higher surface accuracy is required for the display substrate. This is also the reason why reduction of compaction is required.

JP-A-8-109037 JP-A-9-169539 JP 10-72237 A Special table 2001-506223 gazette JP 2002-29775 A Special table 2003-503301 gazette

  In order to solve the above-described problems of the prior art, the present invention eliminates compaction generated during heat treatment, such as a thin film formation process when used as a display substrate, without significantly increasing the strain point. It is a first object to provide an alkali-free glass that can be reduced.

A second object of the present invention is to provide an alkali-free glass having the following characteristics.
・ High BHF resistance.
・ High acid resistance.
-Sufficient durability against alkaline resist stripping solution.
・ Low specific gravity (density).
-Small expansion coefficient.
-Hard to devitrify.

In order to achieve the above object, the present invention provides a gradient Δ _an-st (ppm / ° C.) of _an equilibrium density curve in the temperature region from the vicinity of the annealing point (T _an ) to the vicinity of the strain point (T _st ), The ratio (Δ _an-st / α _50-350 ) to the average linear expansion coefficient α _50-350 (× 10 ⁻⁶ / ° C.) at 350 ° C. is 0 or more and less than 3.64. Provide alkali glass.

The present invention also provides an alkali-free glass mainly composed of the following components.
68% ≦ SiO ₂ ≦ 80%
0% ≦ Al ₂ O ₃ <12%
0% <B ₂ O ₃ <7%
0% ≦ MgO ≦ 12%
0% ≦ CaO ≦ 15%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5% ≦ RO ≦ 18%
Here,% is mol% when the total of the above components is 100%, and RO represents MgO + CaO + SrO + BaO.

Furthermore, the present invention mainly comprises the following components, and the gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve in the temperature region from the vicinity of the annealing point (T _an ) to the vicinity of the strain point (T _st ). And the ratio (Δ _an-st / α _50-350 ) of the average linear expansion coefficient α _50-350 (× 10 ⁻⁶ / ° C.) at 50 to 350 ° C. is 0 or more and less than 3.64. A feature of the alkali-free glass is provided.
68% ≦ SiO ₂ ≦ 80%
0% ≦ Al ₂ O ₃ <12%
0% <B ₂ O ₃ <7%
0% ≦ MgO ≦ 12%
0% ≦ CaO ≦ 15%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5% ≦ RO ≦ 18%
Here,% is mol% when the total of the above components is 100%, and RO represents MgO + CaO + SrO + BaO.

In the alkali-free glass of the present invention, the (Δ _an-st / α _50-350 ) is preferably 0 or more and 3.5 or less.

In the alkali-free glass of the present invention, the SiO ₂ content is preferably 68% ≦ SiO ₂ ≦ 75%.

In the alkali-free glass of the present invention, the Al ₂ O ₃ content is preferably 5% ≦ Al ₂ O ₃ ≦ 11.5%.

In the alkali free glass of the present invention, it is preferable that the content of the B ₂ O ₃ is _{2% ≦ B 2 O 3 <} 7%.

  In the alkali-free glass of the present invention, the MgO content is preferably 3% ≦ MgO ≦ 10%.

  In the alkali-free glass of the present invention, the CaO content is preferably 0.5% ≦ CaO ≦ 12%.

  In the alkali-free glass of the present invention, the RO ratio is preferably 5.5% ≦ RO ≦ 18%.

In the alkali-free glass of the present invention, the viscosity η _{L at} the liquidus temperature is preferably 10 ^3.8 dPa · s or more.

Furthermore, the present invention mainly comprises the following components, and the gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve in the temperature region from the vicinity of the annealing point (T _an ) to the vicinity of the strain point (T _st ). And the ratio (Δ _an-st / α _50-350 ) of the average linear expansion coefficient α _50-350 (× 10 ⁻⁶ / ° C.) at 50 to 350 ° C. is 0 or more and 3.5 or less,
A non-alkali glass having a viscosity η _{L at a} liquidus temperature of 10 ^3.8 dPa · s or more is provided.
68% ≦ SiO ₂ ≦ 72.5%
8% ≦ Al ₂ O ₃ ≦ 10.5%
4.5% ≦ B ₂ O ₃ <7%
3% ≦ MgO ≦ 10%
2.5% ≦ CaO ≦ 7%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5.5% ≦ RO ≦ 18%
Here,% is mol% when the total of the above components is 100%, and RO represents MgO + CaO + SrO + BaO.

  The glass of the present invention can reduce the compaction that occurs during the heat treatment without significantly increasing the strain point. Accordingly, the compaction generated during the heat treatment such as the thin film forming process on the display substrate is reduced to a level required for the display substrate or less without significantly increasing the temperature of the glass manufacturing process such as melting and molding. can do.

Therefore, the glass of the present invention is high despite being heated at a relatively high temperature, such as a display substrate, particularly an active matrix LCD display substrate having p-Si TFT formed on the surface thereof. It is preferable as a display substrate that requires surface accuracy.
In addition, even if the compaction is the same, the larger the size of the glass substrate, the greater the amount of thermal shrinkage of the entire substrate, so the effect of reducing compaction with the glass of the present invention is a large display substrate. In particular.

The glass of the present invention has various characteristics suitable as a glass substrate for a display. In other words, a display such as a liquid crystal display can be reduced in weight because of its low specific gravity (low density), and its manufacturing efficiency can be increased because of its low expansion coefficient. Furthermore, it is possible to provide a display substrate that is excellent in durability against hydrochloric acid or the like used for etching of ITO or the like, and excellent in durability against buffered hydrofluoric acid used in etching of SiO _x or SiN _x . In addition, a glass that is not easily devitrified can be obtained, and the production efficiency can be increased.

  The alkali-free glass of the present invention (hereinafter referred to as the glass of the present invention) contains substantially no alkali metal oxide. Specifically, the total content of alkali metal oxides is preferably 0.5 mol% or less.

In the glass of the present invention, the gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve in the temperature range from the annealing point (T _an ) to the strain point (T _st ) and the average line at 50 to 350 ° C. The ratio (Δ _an-st / α _50-350 ) of the expansion coefficient α _50-350 (× 10 ⁻⁶ / ° C.) is 0 or more and less than 3.64.
Compaction is the thermal shrinkage of glass that occurs due to relaxation of the glass structure during heat treatment. The compaction can be derived from the density change by the following equation.
C = (1− (d ₀ / d) ^1/3 ) × 10 ⁶
C: Compaction (ppm)
d ₀ : Glass density before heat treatment (g / cm ³ )
d: Glass density after heat treatment (g / cm ³ )
From this, compaction can be reduced by reducing the density change due to the temperature change of the glass.

As a result of intensive studies, the present inventors have found that the gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve of the glass in the temperature region from the vicinity of the annealing point (T _an ) to the vicinity of the strain point (T _st ), If the ratio (Δ _an-st / α _50-350 ) of the average linear expansion coefficient α _50-350 (× 10 ⁻⁶ / ° C.) at 50 to 350 ° C. is made smaller than a specific value, the strain point is reduced. It has been found that the compaction generated during the heat treatment can be reduced without significantly increasing the temperature.
In the temperature region from the vicinity of the annealing point (T _an ) to the vicinity of the strain point (T _st ), the equilibrium density curve can be approximated to a straight line. Therefore, in the present invention, Δ _an-st means the slope of this straight line.

In the glass of the present invention, the gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve in the temperature range from the annealing point (T _an ) to the strain point (T _st ) and the average line at 50 to 350 ° C. When the ratio (Δ _an-st / α _50-350 ) of the expansion coefficient α _50-350 (× 10 ⁻⁶ / ° C.) is 0 or more and less than 3.64, the compaction generated during the heat treatment is reduced. Reduced. Specifically, the compaction calculated | required by the following procedure used in the Example mentioned later is less than 190 ppm, for example.

After compacting the specific molten glass into a plate shape, the compacted glass is held at a temperature near the annealing point for 1 hour and then slowly cooled to room temperature at a temperature lowering rate of 1 ° C./min. The obtained glass is processed into a predetermined shape, heated to 900 ° C., held at the temperature for 1 minute, and then cooled to room temperature at a temperature decrease rate of 100 ° C./min to obtain sample A. Next, the sample A was heated to a temperature (theoretical value) at which the viscosity of the glass was 17.8 dPa · s at a heating rate of 100 ° C./hour, held at that temperature for 8 hours, and then cooled down at a cooling rate of 100 ° C./hour. Slowly cool to obtain Sample B. The obtained samples A and B densities (dA, dB) are determined by the heavy liquid method. The compaction C (ppm) can be calculated using the density (dA, dB) thus obtained and the following formula.
C = (1- (dA / dB) ^1/3 ) × 10 ⁶

The heavy liquid method uses a liquid in which bromoform and pentachloroethane are mixed so that it is almost equal to the density of the glass, puts the glass bottle containing this into a water tank with a temperature gradient, and measures the position where the glass sample stays. This is a method for measuring the density of glass. The density value of the target glass is determined by measuring in advance by the Archimedes method and comparing it with a standard sample with a known density value.
The temperature (theoretical value) at which the viscosity of the glass becomes 17.8 dPa · s is 1000 ° on the horizontal axis using an annealing point (viscosity: 13.0 dPa · s) and a strain point (viscosity: 14.5 dPa · s). / T (K), and the vertical axis can be obtained by Arrhenius plot with viscosity (dPa · s).

Δ _an-st / α _50-350 is preferably 3.50 or less. When Δ _an-st / α _50-350 is 3.50 or less, the compaction obtained by the above procedure can be 180 ppm or less. If the compaction calculated | required by the said procedure is 180 ppm or less, the compaction which generate | occur | produces in the case of heat processing will fully be reduced, without making a strain point notably high. When the strain point rises, the glass melt viscosity rises, and it is necessary to change the equipment used for the glass manufacturing process, such as a melting furnace, to one that can withstand use at a higher temperature. This problem has been eliminated.
Δ _an-st / α _50-350 is more preferably 3.40 or less, further preferably 3.20 or less, further preferably 3.00 or less, and particularly preferably 2.80 or less. preferable.

The glass of the present invention is preferably produced by selecting the constituent components of the glass, specifically the composition ratio of the following seven components, so that Δ _an-st / α _50-350 is 0 or more and less than 3.64. can do.
The alkali-free glass is mainly composed of the following seven components.
_{SiO 2, Al 2 O 3,} B 2 O 3
MgO, CaO, SrO, BaO
The three components described in the upper part are components that mainly form glass, and the four components described in the lower part are flux components for melting the glass.
The present inventors conducted experiments by changing the content ratio of the seven components in the glass, and found that there is the following relationship between the seven components and Δ _an-st / α _50-350. It was.
Δ _an-st / α _50-350 Small SiO ₂ <Al ₂ O ₃ <B ₂ O ₃ Large
Small MgO <CaO <SrO Large Furthermore, it is presumed that the following relationship holds when the physical properties are taken into consideration.
Small MgO <CaO <SrO <BaO Large

In addition to Δ _an-st / α _50-350 being 0 or more and less than 3.64, the present inventors have other characteristics required for non-alkali glass used for display substrates, such as BHF resistance. From the viewpoints of durability against acid-resisting and alkaline resist stripping solutions, impact resistance, resistance to devitrification, and the like, the following preferred composition of the alkali-free glass of the present invention was found.
68% ≦ SiO ₂ ≦ 80%
0% ≦ Al ₂ O ₃ <12%
0% <B ₂ O ₃ <7%
0% ≦ MgO ≦ 12%
0% ≦ CaO ≦ 15%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5% ≦ RO ≦ 18%
Here,% is mol% when the total of the above components is 100%, and RO represents MgO + CaO + SrO + BaO.

Next, the composition of the glass of the present invention will be described with mol% simply expressed as%.
SiO ₂ is a network former and is essential. As described above, SiO _{2 minimizes} Δ _an-st / α _50-350 among the three components (SiO ₂ , Ai ₂ O ₃ , B ₂ O ₃ ) that form glass. Therefore, the glass of the present invention preferably has a high SiO ₂ content ratio. Specifically, the glass of the present invention has a SiO ₂ content of 68% or more and 80% or less. When the content ratio of SiO ₂ exceeds 80%, the solubility of the glass is lowered and devitrification tends to occur. Preferably it is 75% or less, More preferably, it is 74% or less, More preferably, it is 73% or less, More preferably, it is 72.5% or less, Most preferably, it is 72% or less. When the content ratio of SiO ₂ is 72.5% or less, it is particularly excellent in reducing the moldability of glass and the devitrification temperature. However, if it is less than 68%, the specific gravity increases (density increases), the strain point decreases, the expansion coefficient increases, the acid resistance decreases, the alkali resistance decreases, or the BHF resistance decreases. Preferably it is 69% or more, More preferably, it is 70% or more.

Al ₂ O ₃ is not essential, but is preferably contained in order to suppress the phase separation of the glass and increase the strain point. However, as described above, Al ₂ O ₃ increases Δ _an-st / α _50-350 in comparison with SiO ₂ among the three components forming glass. Therefore, the glass of the present invention preferably has a low content of Al ₂ O ₃ . Specifically, the glass of the present invention has an Al ₂ O ₃ content of 0% or more and less than 12%. The content ratio of Al ₂ O ₃ is preferably 11.5% or less, more preferably 11.0% or less, further preferably 10.5% or less, and further preferably 10.0% or less. Yes, and particularly preferably 9.5% or less. The lower limit is not particularly limited, but it is preferably added in an appropriate amount for suppressing phase separation, and is preferably 5% or more. When Al ₂ O ₃ is 5% or more, the effect of suppressing the phase separation of glass and the effect of increasing the strain point are excellent. Preferably it is 6% or more, More preferably, it is 7% or more, More preferably, it is 7.5% or more, Most preferably, it is 8% or more. When Al ₂ O ₃ is 8% or more, the effect of suppressing the phase separation of glass and the effect of increasing the strain point are particularly excellent.

The total content of SiO ₂ and Al ₂ O ₃ is preferably 76% or more. It is excellent in the effect which raises a strain point as it is 76% or more. More preferably, it is 77% or more, and particularly preferably 79% or more.

B ₂ O ₃ is a component that reduces the specific gravity (density), increases the BHF resistance, increases the solubility of the glass, makes it difficult to devitrify, and decreases the expansion coefficient, and is essential. However, as described above, Δ _an-st / α _50-350 is _maximized among the three components forming the glass. Therefore, the glass of the present invention preferably has a low content of B ₂ O ₃ . Since B ₂ O ₃ is a designated chemical substance in the Chemical Substance Management Promotion Law, it is preferable that the content ratio of B ₂ O ₃ is low considering the influence on the environment. Specifically, the glass of the present invention has a B ₂ O ₃ content of more than 0% and less than 7%. Although a lower limit is not specifically limited, It is preferable that it is 2% or more. When it is 2% or more, the specific gravity (density) is smaller, the BHF resistance and the glass solubility are excellent, the effect of reducing the expansion coefficient is excellent, and the glass becomes less devitrified. Preferably it is 3% or more, More preferably, it is 4% or more, More preferably, it is 4.5% or more, Most preferably, it is 5% or more. When the content ratio of B ₂ O ₃ is 4.5% or more, the moldability, the loss of devitrification temperature, and the BHF resistance are particularly excellent. It also contributes to weight reduction of the substrate.

The total SiO ₂ + B ₂ O ₃ content of SiO ₂ and B ₂ O ₃ is preferably 75% or more. When it is 75% or more, the specific gravity (density) and the expansion coefficient are appropriate values. More preferably, it is 77% or more, more preferably 78% or more, and most preferably 79% or more.

It is preferable _{Al 2 O 3 / B 2 O} 3 to the content divided by the content of B ₂ O ₃ of Al ₂ O ₃ is 2.0 or less. It is excellent in BHF resistance as it is 2.0 or less. More preferably, it is 1.7 or less, More preferably, it is 1.6 or less, Most preferably, it is 1.5 or less. _{Further, Al 2 O 3 / B 2} O 3 is preferably 0.8 or more. It is excellent in the effect which raises a strain point as it is 0.8 or more. More preferably, it is 0.9 or more, and particularly preferably 1.0 or more.

It is preferable Al ₂ O ₃ and B ₂ O ₃ in the total content divided by the content of _{SiO 2 (Al 2 O 3 +} B 2 O 3) / SiO 2 is 0.32 or less. If it exceeds 0.32, the acid resistance may decrease. More preferably, it is 0.31 or less, Especially preferably, it is 0.30 or less, Most preferably, it is 0.29 or less.

MgO is not essential, but it is preferably contained in order to reduce the specific gravity (density) and increase the solubility of the glass. If it exceeds 12%, the glass tends to undergo phase separation, it tends to devitrify, the BHF resistance decreases, or the acid resistance decreases. In addition, it is preferable that the content rate of MgO is 10% or less from a viewpoint of phase-separation suppression of glass, prevention of devitrification, improvement of BHF resistance, and acid resistance. Moreover, it is excellent in the solubility of glass as the content rate of MgO is 10% or less. Although the lower limit is not particularly limited, as described above, Δ _an-st / α _50-350 is _minimized in the flux components (MgO, CaO, SrO, BaO) for melting glass. The glass preferably has a high MgO content. Specifically, the glass of the present invention preferably has a MgO content of 2% or more. More preferably, it is 3% or more, further preferably 4% or more, further preferably 5% or more, and particularly preferably 6% or more.

  CaO is not essential, but may be contained up to 15% in order to reduce the specific gravity (density), to increase the solubility of the glass, or to prevent devitrification. If it exceeds 15%, the specific gravity may increase (density increase) or the expansion coefficient may increase. CaO is preferably 12% or less, more preferably 10% or less, still more preferably 8% or less, particularly preferably 7% or less, and most preferably 6% or less. When CaO is contained, the content is preferably 0.5% or more. More preferably, it is 1% or more, further preferably 2% or more, and particularly preferably 2.5% or more. When the content ratio of CaO is 2.5% or more and 7% or less, it is particularly excellent in improving the devitrification characteristics while enhancing the solubility of the glass.

MgO / (MgO + CaO) obtained by dividing the content of MgO by the total content of MgO and CaO is preferably 0.2 or more. When it is 0.2 or more, the specific gravity (density) and the expansion coefficient are moderate values, which is preferable for minimizing Δ _an-st / α _50-350 and also for increasing the Young's modulus. More preferably, it is 0.25 or more, and particularly preferably 0.4 or more.

Although SrO is not essential, it is a component that suppresses phase separation of the glass and makes it difficult to devitrify, and is preferably contained for the reasons described below.
As described above, in the flux component (MgO, CaO, SrO, BaO) for melting the glass, MgO reduces Δ _an-st / α _50-350 , so that the glass of the present invention contains the MgO content ratio. Is preferably increased. However, when a large amount of MgO is contained, the glass becomes relatively devitrified. The present inventors have found that when an appropriate amount of SrO is contained in the glass, the content of MgO can be increased without devitrifying the glass. However, if SrO exceeds 4%, the specific gravity (density) of the glass becomes too large. Preferably it is 3% or less, More preferably, it is 2.5% or less. However, in order to increase the content of MgO without devitrifying the glass, the content is preferably 0.1% or more. More preferably, it is 0.5% or more, More preferably, it is 1% or more, More preferably, it is 1.5% or more, It is especially preferable that it is 2% or more.

  BaO is not essential, but may be contained up to 1% in order to suppress phase separation of the glass and make it difficult to devitrify. If it exceeds 1%, the specific gravity (density) becomes too large. Preferably it is 0.5% or less. In order to reduce the specific gravity (density), it is preferable not to contain BaO. Since BaO is designated as a deleterious substance by the Chemical Substance Management Promotion Law, it is preferable not to contain BaO even in consideration of the influence on the environment.

The total SrO + BaO content of SrO and BaO is preferably 6% or less. If it exceeds 6%, the specific gravity (density) may be too large. More preferably, it is 4% or less. When it is desired to make the specific gravity smaller, or when SiO ₂ + B ₂ O ₃ is 79% or less, SrO + BaO is preferably 4% or less, more preferably 3% or less. In addition, when it is desired to make it more difficult to devitrify, SrO + BaO is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more.

In the glass of the present invention, the total content of MgO, CaO, SrO and BaO, that is, MgO + CaO + SrO + BaO (RO) is 5% or more and 18% or less. If RO is more than 18%, the specific gravity (density) may be too large, and the expansion coefficient may be too large. RO is preferably 16.5% or less. If it is 16.5% or less, the specific gravity and the expansion coefficient are appropriate values.
Further, if MgO + CaO + SrO + BaO is less than 5%, the solubility of the glass may be lowered. More preferably, it is 5.5% or more, more preferably 6% or more, and particularly preferably 7% or more.

  The glass of the present invention consists essentially of the above components, but may contain other components as long as the object of the present invention is not impaired. The total content of the other components is preferably 10 mol% or less. More preferably, it is 5% or less.

Examples of the other components include the following. That is, SO ₃ , F, Cl, SnO _{2 and the} like may be appropriately contained in the following ranges in order to improve solubility, clarity, and moldability.
SO ₃ 0 to 2 mol%, preferably 0 to 1 mol%
F 0-6 mol%, preferably 0-3 mol%
Cl 0-6 mol%, preferably 0-4 mol%
SnO ₂ 0-4 mol%, preferably 0-1 mol%
In addition, when these are contained, the total content is up to 10 mol%, preferably up to 5 mol%, more preferably up to 3 mol%, particularly preferably up to 2 mol%, still more preferably 1 ppm to 2 mol%. It is a range.

For the same reason, Fe ₂ O ₃ , ZrO ₂ , TiO ₂ , Y ₂ O _{3 and the} like may be appropriately contained within the following range.
Fe ₂ O ₃ 0 to 1 mol%, preferably 0 to 0.1 mol%
ZrO ₂ 0-2 mol%, preferably 0-1 mol%
TiO ₂ 0-4 mol%, preferably 0-2 mol%
Y ₂ O ₃ 0 to 4 mol%, preferably 0 to 2 mol%
CeO ₂ 0-2 mol%, preferably 0-1 mol%
When the other components are contained, the total content (SO ₃ + F + Cl + SnO ₂ + Fe ₂ O ₃ + ZrO ₂ + TiO ₂ + Y ₂ O ₃ + CeO ₂ ) is up to 15 mol%, preferably up to 10 mol%, more preferably Is up to 5 mol%, particularly preferably up to 3 mol%, more preferably in the range of 1 ppm to 3 mol%.

In consideration of the environment and recycling, it is preferable that As ₂ O ₃ , Sb ₂ O ₃ , PbO, ZnO and P ₂ O ₅ are not substantially contained. That is, the content of these five components is preferably 0.1% or less. The total content of these five components is more preferably 0.1% or less.

  However, it is preferable that ZnO is not substantially contained particularly when molding is performed by the float method, but when it is performed by other molding methods, for example, molding by the down draw method, it is appropriately contained exceeding 0.1%. May be. In particular, when it is desired to make it difficult to devitrify, it is preferably contained up to 2%. If it exceeds 2%, the specific gravity (density) may be too large.

Further, As ₂ O ₃ , Sb ₂ O ₃ , especially Sb ₂ O ₃ may be appropriately contained in an amount exceeding 0.1% in order to improve the clarity.

TiO ₂ is preferably substantially not contained when forming by the float method, but may be appropriately contained exceeding 0.1% when forming by other forming methods, for example, the down draw method. . In particular, when it is desired to make it difficult to devitrify, it is preferably contained up to 2%. If it exceeds 2%, the specific gravity (density) may be too large.

The specific gravity (density) of the glass of the present invention is preferably 2.46 g / cm ³ or less. When the specific gravity of the glass is 2.46 g / cm ³ or less, it is convenient for reducing the weight of the display. More preferably 2.43 g / cm ³ or less, more preferably 2.40 g / cm ³ or less, particularly preferably 2.39 g / cm ³ or less, most preferably 2.38 g / cm ³ or less.

The average linear expansion coefficient α _50-350 at 50 to 350 ° C. of the glass of the present invention is preferably 3.4 × 10 ⁻⁶ / ° C. or less. When it is 3.4 × 10 ⁻⁶ / ° C. or less, the thermal shock resistance is excellent. More preferably, it is 3.2 × 10 ⁻⁶ / ° C. or less, particularly preferably 3.0 × 10 ⁻⁶ / ° C. or less, and most preferably 2.9 × 10 ⁻⁶ / ° C. or less. Also, α _50-350 is preferably 2.4 × 10 ⁻⁶ / ° C. or more. When the film temperature is 2.4 × 10 ⁻⁶ / ° C. or more, when SiO _x or SiN _x is formed on the glass substrate, the expansion matching between the glass substrate and these films is good. From this viewpoint, it is more preferably 2.6 × 10 ⁻⁶ / ° C. or more, and further preferably 2.7 × 10 ⁻⁶ / ° C. or more.

In order to reduce the compaction, specifically less than 190 ppm, Δ _an-st (ppm / ° C.) is preferably 0 or more and less than 12.0.

  The strain point of the glass of the present invention is preferably 650 ° C. or higher. More preferably, it is 660 degreeC or more, More preferably, it is 670 degreeC or more, More preferably, it is 680 degreeC or more, It is especially preferable that it is 690 degreeC or more.

The temperature T _{2 at} which the viscosity of the glass of the present invention is 10 ² dPa · s is preferably 1840 ° C. or lower. When it is 1840 degrees C or less, it is preferable when melt | dissolving glass. More preferably, it is 1820 degrees C or less, More preferably, it is 1800 degrees C or less, Especially preferably, it is 1780 degrees C or less, Most preferably, it is 1760 degrees C or less.
The temperature T _{4 at} which the viscosity of the glass of the present invention is 10 ⁴ dPa · s is preferably 1380 ° C. or lower. When it is 1380 ° C. or lower, it is preferable for molding glass. More preferably, it is 1360 degrees C or less, Especially preferably, it is 1350 degrees C or less, Most preferably, it is 1340 degrees C or less.

The viscosity η _{L at} the liquidus temperature of the glass of the present invention is preferably 10 ^3.5 dPa · s or more. When it is 10 ^3.5 dPa · s or more, it is preferable for molding glass. It is particularly preferable that η _L is 10 ^3.8 dPa · s or higher because glass can be formed by the float process and the devitrification temperature of the glass can be reduced. η _L is more preferably 10 ⁴ dPa · s or more, and most preferably 10 ^4.1 dPa · s or more.
In particular, when molding is performed by the float process, even if Δ _an-st / α _50-350 is less than 3.64, η _L is preferably 10 ^3.8 dPa · s or more in consideration of moldability. Therefore, in Examples 1 to 5 shown later, the glass of Example 4 is good in terms of formability.

Therefore, a preferred embodiment of the glass of the present invention has the following composition, Δ _an-st / α _50-350 is 0 or more and 3.5 or less, and the viscosity η _{L at the} liquidus temperature is 10 It is an alkali-free glass characterized by being ^3.8 dPa · s or more.
68% ≦ SiO ₂ ≦ 72.5%
8% ≦ Al ₂ O ₃ ≦ 10.5%
4.5% ≦ B ₂ O ₃ <7%
3% ≦ MgO ≦ 10%
2.5% ≦ CaO ≦ 7%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5.5% ≦ RO ≦ 18%

When the glass of the present invention is immersed in an aqueous hydrochloric acid solution having a concentration of 0.1 mol / liter at 90 ° C. for 20 hours, it is preferable that white turbidity, discoloration, cracks, and the like do not occur on the surface. Further, the weight loss per unit surface area of the glass obtained from the mass change of the glass due to the immersion and the surface area of the glass ([Delta] W _HCl) is 0.6 mg / cm ² or less. More preferably, it is 0.4 mg / cm ² or less, particularly preferably 0.2 mg / cm ² or less, and most preferably 0.15 mg / cm ² or less.

In addition, the glass of the present invention was mixed in a volume ratio of 9: 1 with an ammonium fluoride aqueous solution having a mass percentage display concentration of 40% and a hydrofluoric acid aqueous solution having a display concentration of 50% (hereinafter referred to as buffered). When dipped in hydrofluoric acid (BHF) solution at 25 ° C. for 20 minutes, the surface is preferably not clouded. Hereinafter, the evaluation using this buffered hydrofluoric acid solution is referred to as BHF resistance evaluation, and the case where the surface does not become cloudy is referred to as good BHF resistance. Moreover, it is preferable that the mass reduction _| decrease amount (( _DELTA ) _WBHF ) per unit area of a glass calculated _| required from the surface area of glass and the mass change of the glass by the said immersion is 0.6 mg / cm < ² > or less. More preferably, it is 0.5 mg / cm ² or less, and still more preferably 0.4 mg / cm ² or less.

  The method for producing the glass of the present invention is not particularly limited, and various production methods can be adopted. For example, the raw material normally used is prepared so that it may become a target composition, and this is heated and melted at 1600 degreeC-1650 degreeC in a melting furnace. Homogenize the glass by adding bubbling, clarifying agent, or stirring. When used as a display substrate such as a liquid crystal display or a photomask substrate, it is formed into a predetermined thickness by a known press method, downdraw method, float method, etc., and after slow cooling, processing such as grinding and polishing To obtain a substrate of a predetermined size and shape.

Therefore, the size of the glass of the present invention is arbitrarily selected during production. However, the glass of the present invention is particularly useful for a large glass substrate. That is, even if the compaction, that is, the rate of thermal shrinkage of the glass is the same, as the size of the substrate increases, the amount of thermal shrinkage (absolute value of thermal shrinkage) of the entire substrate increases. For example, if the size of the display substrate is changed from 20 inches (50.8 centimeters) diagonal to 25 inches (63.5 centimeters) diagonal, the length of the diagonal line of the substrate increases accordingly, The amount of heat shrinkage also increases. As described above, since the compaction generated during the heat treatment is reduced in the glass of the present invention, the amount of heat shrinkage as a whole substrate is also reduced, and this effect becomes more remarkable as the substrate becomes larger.
The size of the glass of the present invention is preferably 30 centimeter squares or more, more preferably 40 centimeter squares or more, still more preferably 80 centimeter squares or more, and further preferably 1 centimeter squares or more. Yes, preferably 1.5 square meters or more, and particularly preferably 2 square meters or more. About the thickness of glass, about 0.3-1.0 mm is suitable.

Examples 1-5, to prepare a raw material so as to have the composition shown by mol% in the column of SiO ₂ ~BaO of Comparative Example Table 1, using a platinum crucible and melted at 1600 ° C. to 1650 ° C.. At this time, the mixture was stirred with a platinum stirrer to homogenize the glass. Next, molten glass was cast out and formed into a plate shape, held at a temperature near the annealing point expected from the glass composition for 1 hour, and then gradually cooled at a temperature lowering rate of 1 ° C./min. A comparative glass was obtained.

[Measurement of average linear expansion coefficient]
After processing the obtained glasses of Examples 1 to 5 and Comparative Example into a prescribed cylinder, they were heated to the vicinity of the annealing point (T _an ), held at the temperature for 1 hour, and then at a temperature drop rate of 1 ° C./min. The average linear expansion coefficient (alpha) _50-350 in 50-350 degreeC was measured for the slow-cooled sample by the method prescribed | regulated to JISR3102 using the differential thermal dilatometer (TMA).

[Creation of equilibrium density curve of glass]
The glasses of Examples 1 to 5 and Comparative Example obtained as described above were polished to about 4 cm square and 2 mm thick. The processed glass sample was held at a plurality of temperatures from the annealing point (T _an ) to the strain point (T _st ) for 16 hours or more, and then dropped on a carbon plate and rapidly cooled. The density of the cooled sample was measured by the so-called Archimedes method (JIS Z8807 section 4). Repeated measurement was performed by this procedure, and reproducibility up to the order of 0.0001 g / cm ³ was confirmed. The equilibrium density curve is created by regressing the slope of the density change with respect to the heat treatment temperature from the density measurement results at a plurality of temperatures, and in the temperature region from the annealing point (T _an ) to the strain point (T _st ). The gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve was determined.
From α _50-350 and Δ _{an-st thus} obtained, Δ _an-st / α _50-350 was calculated.

[Measurement of compaction]
The glasses of Examples 1 to 5 and Comparative Example obtained as described above were polished to about 5 mm square and 0.7 mm thick. The processed glass was heated to 900 ° C. and held at the temperature for 1 minute, and then cooled to room temperature at a temperature decrease rate of 100 ° C./min to obtain Sample A. Next, the sample A was heated to a temperature (theoretical value) at which the viscosity of the glass became 17.8 dPa · s at a heating rate of 100 ° C./hour, held at that temperature for 8 hours, and then cooled down at a rate of 100 ° C./hour. The sample B was obtained by slow cooling. The density (dA, dB) of the obtained samples A and B was determined by a heavy liquid method. The compaction C (ppm) was calculated using the density (dA, dB) thus obtained and the following formula.
C = (1- (dA / dB) ^1/3 ) × 10 ⁶
The temperature at which the viscosity of the glass becomes 17.8 dPa · s is determined using the annealing point (T _an ) (viscosity: 13.0 dPa · s) and the strain point (T _st ) (viscosity: 14.5 dPa · s), It was obtained by Arrhenius plot with the horizontal axis as 1000 / T (K) and the vertical axis as the viscosity (dPa · s). Here, the annealing point (T _an ) and the strain point (T _st ) were measured by the methods defined in JIS R3103.

[T ₂ , T ₄ , η _L ]
Temperature T ₄ which and a viscosity of 10 ⁴ dPa · s: temperature T ₂ which the glass viscosity of Examples 1-5 and Comparative Examples obtained by the above becomes 10 ^2.0 dPa · s (℃ Unit) (Unit: ° C.) Was measured using a rotational viscometer.
Further, the viscosity η _L (unit: dPa · s) at the liquid phase temperature was determined from the temperature-viscosity curve obtained by the rotational viscometer and the liquid phase temperature. As for the liquidus temperature, a plurality of glass pieces are heated and melted at different temperatures for 17 hours, and the glass temperature of the glass having the highest temperature among the glasses on which crystals are precipitated and the glass on which no crystals are precipitated. The average value with the glass temperature of the glass with the lowest temperature was defined as the liquidus temperature.

[HCl resistance (ΔW _HCl )]
The glasses of Examples 1 to 5 and Comparative Example obtained above were immersed in an aqueous hydrochloric acid solution having a concentration of 0.1 mol / liter at 90 ° C. for 20 hours, and the change in the mass of the glass before and after immersion was determined. The amount of mass reduction per unit surface area of glass (ΔW _HCl (mg / cm ² )) was determined from the surface area of glass and the surface area of glass.

[BHF resistance (ΔW _BHF , cloudiness)]
The glasses of Examples 1 to 5 and Comparative Example obtained above were buffered hydrofluoric acid (BHF) (ammonium fluoride aqueous solution having a mass percentage display concentration of 40%, and a hydrofluoric acid aqueous solution having a display concentration of 50%. In a mixture of 9: 1 by volume) at 25 ° C. for 20 minutes, and the change in the mass of the glass before and after the immersion is determined. From this and the surface area of the glass, the mass reduction per unit surface area of the glass The amount (ΔW _BHF (mg / cm ² )) was determined. Moreover, the presence or absence of cloudiness on the glass surface after immersion was confirmed visually. Here, when white turbidity was not observed on the glass surface, the BHF resistance was considered good (evaluation: ◯).

These results are shown in Table 1. Here, the specific gravity (density) (g / cm ³ ) is a numerical value converted from the density of the sample rapidly cooled from the annealing point (T _an ) obtained in the procedure for creating the equilibrium density curve.

Examples 6-14
In the same manner as in Example 1, raw materials are prepared so as to have the composition shown in Table 1, molten glass melted in a melting furnace is formed into a plate shape, and then gradually cooled to obtain glasses of Examples 6-14. For the glass obtained, α _30-350 , specific gravity (density), strain point (T _st ), annealing point (T _an ), T ₂ and T ₄ are determined. Regarding Δ _an-st , contribution a _i (i = 1 to 6 (the above six components) of each glass component (six components of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, and SrO)) )) Is obtained by regression calculation, and is obtained by calculation from Σa _i X _i + b (X _i is the molar fraction of each glass component, and b is a constant). α _50-350 , specific gravity (density), strain point (T _st ), T _2, and T ₄ are also calculated by the contribution of each glass component in the same manner as Δ _an-st . For compaction, Δ and C (compaction) are linearly regressed and calculated by calculation based on the regression equation. The results obtained are shown in Table 1.

Claims (12)

The gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve in the temperature range from the annealing point (T _an ) to the strain point (T _st ), and the average linear expansion coefficient α _{50-350 at} 50 to 350 ° C. (× 10 ⁻⁶ / ° C.) and a ratio (Δ _an-st / α _50-350 ) of 0 to less than 3.64. Alkali-free glass mainly composed of the following components.
68% ≦ SiO ₂ ≦ 80%
0% ≦ Al ₂ O ₃ <12%
0% <B ₂ O ₃ <7%
0% ≦ MgO ≦ 12%
0% ≦ CaO ≦ 15%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5% ≦ RO ≦ 18%
Here,% is mol% when the total of the above components is 100%, and RO represents MgO + CaO + SrO + BaO. The alkali-free glass according to claim 1, comprising mainly the following components.
68% ≦ SiO ₂ ≦ 80%
0% ≦ Al ₂ O ₃ <12%
0% <B ₂ O ₃ <7%
0% ≦ MgO ≦ 12%
0% ≦ CaO ≦ 15%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5% ≦ RO ≦ 18%
Here,% is mol% when the total of the above components is 100%, and RO represents MgO + CaO + SrO + BaO. The gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve in the temperature region from the vicinity of the annealing point (T _an ) to the vicinity of the strain point (T _st ), and the average linear expansion coefficient α _{50− at 50 to} 350 ° C. _The alkali-free glass according to claim 1 or 3, wherein a ratio (Δ _an-st / α _50-350 ) to ₃₅₀ (× 10 ^-6 / ° C) is 0 or more and 3.5 or less. . 5. The alkali-free glass according to claim ₂ , wherein a content ratio of the SiO ₂ is 68% ≦ SiO ₂ ≦ 75%. 6. The alkali-free glass according to claim _2, wherein a content ratio of the Al ₂ O ₃ is 5% ≦ Al ₂ O ₃ ≦ 11.5%. 7. The alkali-free glass according to claim _2, wherein a content ratio of the B ₂ O ₃ is 2% ≦ B ₂ O ₃ <7%.   The alkali-free glass according to any one of claims 2 to 7, wherein a content ratio of the MgO is 3%? MgO? 10%.   The alkali-free glass according to any one of claims 2 to 8, wherein a content ratio of the CaO is 0.5%? CaO? 12%.   10. The alkali-free glass according to claim 2, wherein a ratio of the RO is 5.5% ≦ RO ≦ 18%. The alkali-free glass according to any one of claims 1 to 10, wherein the viscosity η _{L at the} liquidus temperature is 10 ^3.8 dPa · s or more. It is mainly composed of the following components, and the gradient Δ _an-st (ppm / ° C.) of the equilibrium density curve in the temperature region from the vicinity of the annealing point (T _an ) to the strain point (T _st ) and at 50 to 350 ° C. The ratio (Δ _an-st / α _50-350 ) of the average linear expansion coefficient α _50-350 (× 10 ⁻⁶ / ° C.) is 0 or more and 3.5 or less, and the viscosity η _{L at the} liquidus temperature is 10. An alkali-free glass characterized by being 10 ^3.8 dPa · s or more.
68% ≦ SiO ₂ ≦ 72.5%
8% ≦ Al ₂ O ₃ ≦ 10.5%
4.5% ≦ B ₂ O ₃ <7%
3% ≦ MgO ≦ 10%
2.5% ≦ CaO ≦ 7%
0% ≦ SrO ≦ 4%
0% ≦ BaO ≦ 1%
5.5% ≦ RO ≦ 18%
Here,% is mol% when the total of the above components is 100%, and RO represents MgO + CaO + SrO + BaO.