WO2014208521A1

WO2014208521A1 - Alkali-free glass

Info

Publication number: WO2014208521A1
Application number: PCT/JP2014/066622
Authority: WO
Inventors: 周平野村; 和孝小野; 順秋山
Original assignee: 旭硝子株式会社
Priority date: 2013-06-27
Filing date: 2014-06-24
Publication date: 2014-12-31
Also published as: TW201509857A; CN105339317A; JP2016155692A; KR20160023698A

Abstract

The present invention relates to an alkali-free glass which has a high specific modulus, a high Young's modulus, a high glass transition point, and a low average thermal expansion coefficient, and which is easily float formed. More specifically, the present invention relates to an alkali-free glass which has a Young's modulus of at least 87 GPa, and which includes, expressed in oxide mass%, 61-68.5 mass% of SiO₂, 17-23.5 mass% of Al₂O₃, 6.5-15 mass% of MgO, and 3-13 mass% of CaO, with the caveat that 0.42 < MgO/(MgO+CaO) ≤ 0.68.

Description

Alkali-free glass

The present invention is a non-alkali glass which is suitable for display substrate glass and photomask substrate glass used in the production of various flat panel displays (FPD) and which can be float-molded substantially free of alkali metal oxides. About.

Conventionally, various display substrate glasses, particularly those in which a metal or oxide thin film is formed on the surface, have been required to have the following characteristics as shown in Patent Document 1, for example.
(1) When an alkali metal oxide is contained, alkali metal ions diffuse into the thin film and deteriorate the film characteristics, so that the alkali metal ions are not substantially contained.
(2) The glass transition point is high so that, when exposed to a high temperature in the thin film formation step, the deformation (thermal shrinkage) associated with glass deformation and glass structural stabilization can be minimized.

(3) Sufficient chemical durability against various chemicals used for semiconductor formation. In particular, buffered hydrofluoric acid (BHF: mixture of hydrofluoric acid and ammonium fluoride) for etching SiO _x and SiN _x , and chemicals containing hydrochloric acid used for etching ITO, various acids used for etching metal electrodes (Nitric acid, sulfuric acid, etc.) Resistant to alkali of resist stripping solution.
(4) There are no defects (bubbles, striae, inclusions, pits, scratches, etc.) inside and on the surface.

In addition to the above requirements, in recent years, there are the following situations.
(5) The weight reduction of the display is required, and the glass itself is desired to have a low density glass.
(6) A reduction in the weight of the display is required, and a reduction in the thickness of the substrate glass is desired.

(7) In addition to the conventional amorphous silicon (a-Si) type liquid crystal display, a polycrystalline silicon (p-Si) type liquid crystal display having a slightly higher heat treatment temperature has been produced (a-Si). : About 350 ° C. → p-Si: 350 to 550 ° C.).
(8) A glass having a small average thermal expansion coefficient is required to increase productivity and thermal shock resistance by increasing the temperature raising / lowering rate of the heat treatment for producing a liquid crystal display.

Japanese Unexamined Patent Publication No. 2001-348247

As the FPD becomes higher in definition and size, there is a concern that deformation due to deflection due to its own weight occurs in the manufacturing process and yield decreases. Further, in order to sufficiently ensure the practical strength of a large FPD, it is useful to improve the fracture toughness of the substrate glass.
For this reason, various display substrate glasses are required to have a high specific modulus and a high Young's modulus.

An object of the present invention is to provide an alkali-free glass having a high specific elastic modulus and a high Young's modulus, a high glass transition point, a small average thermal expansion coefficient, and easy float forming.

The present invention has a Young's modulus of 87 GPa or more and is expressed in mass% based on oxide.
SiO ₂ 61-68.5,
Al ₂ O ₃ 17-23.5,
MgO 6.5-15,
An alkali-free glass containing CaO 3 to 13 and satisfying 0.42 <MgO / (MgO + CaO) ≦ 0.68 is provided.

The alkali-free glass of the present invention is suitable as a substrate glass for various displays and a substrate glass for a photomask, but can also be used as a glass substrate for a magnetic disk. However, considering the demand for larger and thinner glass plates for various display substrate glasses and photomask substrate glasses, it has a high Young's modulus, so various display substrate glasses and photomask substrate glasses It is effective as

Next, the composition range of each component will be described. If SiO ₂ exceeds 68.5% (mass%, the same unless otherwise specified), the Young's modulus becomes low. Further, it is less than 61%, devitrification viscosity is lowered, T ₄ -T _L becomes too small. Preferably it is 61.5 to 68%, more preferably 62 to 67.5%.

Al ₂ O ₃ suppresses the phase separation of glass, lowers the average thermal expansion coefficient, and raises the glass transition point. However, if it is less than 17%, this effect does not appear, and the devitrification temperature also increases. If it exceeds 23.5%, the solubility of the glass tends to deteriorate, and the devitrification temperature may increase. Preferably it is 17 to 23%, more preferably 19 to 22.5%.

MgO needs to be contained by 6.5% or more in order to improve solubility and improve Young's modulus. However, if it exceeds 15%, the devitrification temperature may increase. The amount of relatively SiO ₂ is reduced, devitrification viscosity becomes to T ₄ -T _L becomes too small low. Preferably it is 7 to 14.5%, more preferably 8% to 14%.

Since CaO improves solubility and contains together with MgO, generation of devitrification can be suppressed, so it is necessary to contain 3% or more. However, if it exceeds 13%, the average thermal expansion coefficient becomes large. The amount of relatively SiO ₂ is reduced, devitrification viscosity becomes to T ₄ -T _L becomes too small low. Preferably it is 3.5 to 12.5%, more preferably 4 to 12%.

When MgO / (CaO + MgO) is higher than 0.68, the devitrification temperature is increased. On the other hand, when it is 0.42 or less, the Young's modulus is lowered and the specific elastic modulus is also lowered. 0.44 to 0.66 is more preferable, and 0.46 to 0.64 is even more preferable.

Other components such as the following components may be contained as long as the effects of the present invention are not hindered. The other component in this case is preferably less than 5%, more preferably less than 3%, still more preferably less than 1%, and even more preferably less than 0.5% in order to suppress a decrease in Young's modulus. Yes, and particularly preferably, it is preferable not to contain substantially, i.e. excluding inevitable impurities. Therefore, in the present invention, the total content of SiO ₂ , Al ₂ O ₃ , CaO, and MgO is preferably 95% or more, more preferably 97% or more, and 99% or more. More preferably, it is still more preferably 99.5% or more. It is particularly preferred that it consists essentially of SiO ₂ , Al ₂ O ₃ , CaO and MgO, excluding unavoidable impurities.

B ₂ O ₃ can be contained in an amount of less than 5% in order to improve the melting reactivity of the glass and to lower the devitrification temperature. However, if the amount is too large, the Young's modulus decreases. Accordingly, it is preferably less than 3%, more preferably less than 1%, even more preferably less than 0.5%, and particularly preferably not substantially contained.

SrO can be contained in an amount of less than 1.5% in order to improve the solubility without increasing the devitrification temperature of the glass. However, if the amount is too large, the average thermal expansion coefficient will increase. Accordingly, it is preferably less than 1%, more preferably less than 0.5%, and particularly preferably substantially not contained.

BaO can be contained in less than 5% in order to improve the solubility of the glass. However, if the amount is too large, the average thermal expansion coefficient will increase. Accordingly, it is preferably less than 3%, more preferably less than 1%, even more preferably less than 0.5%, and particularly preferably not substantially contained.

ZrO ₂ can be contained in an amount of less than 3% in order to improve the Young's modulus of the glass. However, if the amount is too large, the devitrification temperature will increase. Accordingly, it is preferably less than 2%, more preferably less than 1%, even more preferably less than 0.5%, and particularly preferably not substantially contained.

Further, in the present invention, in order to improve the solubility, clarity and formability of the glass, the total amount of ZnO, SO ₃ , Fe ₂ O ₃ , F, Cl and SnO ₂ is less than 1%, preferably 0.8%. It can be contained less than 5%, more preferably less than 0.3%, and even more preferably less than 0.1%.

The glass of the present invention does not contain an alkali metal oxide in excess of the impurity level (ie substantially) in order not to cause deterioration of the characteristics of the metal or oxide thin film provided on the glass surface during panel production. In order to facilitate recycling of the glass, it is preferable that PbO, As ₂ O ₃ and Sb ₂ O ₃ are not substantially contained.

Since the alkali-free glass of the present invention has a Young's modulus of 87 GPa or more, the fracture toughness is improved, and it is suitable for various display substrate glasses and photomask substrate glasses that require a larger or thinner glass plate. is there. 88 GPa or more is more preferable, and 89 GPa or more is more preferable.

The alkali-free glass of the present invention has a glass transition point of 760 ° C. or higher in order to suppress thermal shrinkage during panel production and to make it possible to apply a method by laser annealing as a method for producing p-Si TFTs. Is preferred.
When the glass transition point is 760 ° C. or more, the fictive temperature of the glass tends to increase in the production process (for example, an organic EL having a thickness of 0.7 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less). Suitable for a display substrate or lighting substrate for use in the like, or a thin display substrate or lighting substrate having a thickness of 0.3 mm or less, preferably 0.1 mm or less.
When forming a sheet glass having a plate thickness of 0.7 mm or less, further 0.5 mm or less, further 0.3 mm or less, and further 0.1 mm or less, the drawing speed at the time of forming tends to increase. Rises and the compaction of the glass tends to increase. In this case, compaction can be suppressed when the glass has a high glass transition point.

The alkali-free glass of the present invention preferably has an average coefficient of thermal expansion at 50 to 350 ° C. of 48 × 10 ⁻⁷ / ° C. or less. When the average thermal expansion coefficient at 50 to 350 ° C. is 48 × 10 ⁻⁷ / ° C. or less, the thermal shock resistance is large, and the productivity during panel production can be increased. More preferably, it is 46 × 10 ⁻⁷ / ° C. or less, and further preferably 44 × 10 ⁻⁷ / ° C. or less.

In order to facilitate melting, the alkali-free glass of the present invention has a temperature T _{2 at} which the viscosity η is 10 ² poise (dPa · s), preferably 1720 ° C. or less, more preferably 1700 ° C. or less, More preferably, it is 1680 degrees C or less.

The alkali-free glass of the present invention has a temperature T _{4 at} which the viscosity η is 10 ⁴ poise (dPa · s), preferably 1320 ° C. or less, more preferably 1300, in order to facilitate molding by the float process. ° C or lower, more preferably 1280 ° C or lower.

Further, the alkali-free glass of the present invention, the temperature T ₄ of the glass viscosity η is 10 ⁴ poise, and devitrification temperature T _L, and the difference (T ₄ -T _L) of preferably -100 ° C. or higher, In the present invention, molding by the float method is possible. It is more preferably −70 ° C. or higher, and further preferably −50 ° C. or higher.
In this specification, the devitrification temperature is obtained by putting crushed glass particles in a platinum dish and performing heat treatment for 17 hours in an electric furnace controlled at a constant temperature. It is an average value of the maximum temperature at which crystals are deposited inside and the minimum temperature at which crystals are not deposited.

The alkali-free glass of the present invention preferably has a specific elastic modulus (Young's modulus / density) of 34.5 GPa · cm ³ / g or more in order to reduce its own weight deflection. For this reason, there is little deformation resulting from its own weight deflection in the manufacturing process, and it is suitable for various display substrate glasses and photomask substrate glasses that require a larger or thinner glass plate. 34.7 GPa · cm ³ / g or more is more preferable, and 34.9 GPa · cm ³ / g or more is more preferable.

The alkali-free glass of the present invention can be produced, for example, by the following method. The raw materials of each component that are normally used are blended so as to become target components, which are continuously charged into a melting furnace, heated to 1550 to 1650 ° C. and melted. The molten glass is formed into a predetermined plate thickness by the float method, and then the glass plate can be obtained by slow cooling and cutting.

In the following, Examples 1-22 and 26-27 are Examples, and Examples 23-25 are Comparative Examples. The raw materials of each component were prepared so as to have a target composition, and were melted at a temperature of 1550 to 1650 ° C. using a platinum crucible. In melting, the mixture was stirred using a platinum stirrer to homogenize the glass. Next, the molten glass was poured out, formed into a plate shape, and then slowly cooled.

Tables 1 to 3 show the glass composition (unit: mass%), density ρ (g / cm ³ ), Young's modulus E (GPa) (measured by an ultrasonic method), specific modulus E / ρ (GPa · cm ³ / g), glass transition point Tg (unit: ° C.), average thermal expansion coefficient α (unit: × 10 ⁻⁷ / ° C.) at 50 to 350 ° C., temperature T ₂ (glass viscosity η becomes 10 ² poise) unit: ° C.), the temperature T ₄ of the glass viscosity η is 10 ⁴ poise (unit: ° C.), the devitrification temperature T _L (unit: ° C.), and show the T ₄ -T _L.
In Tables 1 to 3, the values shown in parentheses are calculated values.

As is clear from the table, all the glasses of the examples have a high Young's modulus of 87 GPa or more and a specific modulus of 34.5 GPa · cm ³ / g or more. The average thermal expansion coefficient at 50 ~ 350 ° C. is not more than ^{48 × 10 -7 / ℃, T} 2 is at 1720 ° C. or less, T ₄ -T _L is -100 ° C. or higher.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2013-134751 filed on June 27, 2013, the contents of which are incorporated herein by reference.

Claims

Young's modulus is 87 GPa or more, expressed in mass% based on oxide,
SiO 2 61-68.5,
Al 2 O 3 17-23.5,
MgO 6.5-15,
CaO 3-13
Containing
Alkali-free glass where 0.42 <MgO / (MgO + CaO) ≦ 0.68.
The alkali-free glass according to claim 1, wherein the specific elastic modulus is 34.5 GPa · cm 3 / g or more.
3. The alkali-free glass according to claim 1, wherein the glass transition point is 760 ° C. or higher.
4. The alkali-free glass according to claim 1, wherein an average coefficient of thermal expansion at 50 to 350 ° C. is 48 × 10 −7 / ° C. or less.
Alkali-free glass according to any one of claims 1 to 4 difference T 4 -T L between the temperature T 4 and devitrification temperature T L at which the viscosity η is 10 4 poise is -100 ° C. or higher.