WO2014208524A1 - Alkali-free glass - Google Patents

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 compaction, 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 90 GPa, a compaction (C1) of not more than 5 ppm, and a compaction (C2) of not more than 50 ppm, and which includes, expressed in oxide mass%, 40-65 mass% of SiO₂, more than 23.5 mass% but not more than 30 mass% of Al₂O₃, 2.5-20 mass% of MgO, and 2-30 mass% of CaO, with the caveat that SiO₂ + Al₂O₃ is in the range of 70-90 mass% inclusive.

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) 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.
(3) 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.
(4) The weight reduction of a display is requested | required and the glass itself has a low density glass.
(5) The weight reduction of a display is requested | required and thickness reduction of a substrate glass is desired.

(6) 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.).
(7) A glass having a small average thermal expansion coefficient is required in order to increase the temperature raising / lowering rate of the heat treatment for producing a liquid crystal display to increase the productivity and the thermal shock resistance.

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.

Further, in recent years, it is required that the glass compaction is low in order to minimize the deformation of the glass and the dimensional change accompanying the stabilization of the glass structure when exposed to a high temperature in the thin film forming process.

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, low compaction, and easy float forming.

In the present invention, the Young's modulus is 90 GPa or more, the compaction C1 is 5 ppm or less, the compaction C2 is 50 ppm or less, and expressed in mass% based on the oxide.
SiO ₂ 40-65,
Al ₂ O _{3 over} 23.5-30
MgO 2.5-20,
CaO 2-30
Containing
Provided is an alkali-free glass having SiO ₂ + Al ₂ O ₃ of 70 or more and 90 or less.

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 65% (mass%, the same unless otherwise specified), the Young's modulus becomes low. In addition, the viscosity is increased, and there is a risk that bubbles may be mixed in due to an increase in melting temperature or bubbles that cannot be completely removed during clarification. Further, devitrification of mullite easily occurs, and the devitrification temperature T _L increases. If it is less than 40%, the average thermal expansion coefficient will increase. Moreover, devitrification of the spinel is likely to occur, and the devitrification temperature T _L is increased. Preferably it is 42 to 63%, more preferably 44 to 61%.

Al ₂ O ₃ suppresses the phase separation property of the glass, lowers the average thermal expansion coefficient, and raises the glass transition point Tg, but this effect does not appear at 23.5% or less. In addition, the Young's modulus decreases and compaction increases. Since Al ₂ O ₃ works as a network former like SiO _2, if it exceeds 30%, the viscosity increases, and there is a risk of increasing the melting temperature and mixing bubbles. Further, devitrification such as mullite, anorthite, and spinel is likely to occur, and the devitrification temperature _TL may be increased. Preferably it is 24 to 29%, more preferably 24.5 to 28%.

MgO needs to be contained at 2.5% or more in order to improve solubility and improve Young's modulus. However, if it exceeds 20%, compaction will increase. Moreover, devitrification of the spinel is likely to occur, and the devitrification temperature T _L is increased. Preferably it is 3 to 19%, more preferably 3.5 to 18%.

CaO improves solubility and can be prevented from being devitrified by containing it together with MgO, so it is necessary to contain 2% or more. However, if it exceeds 30%, the average thermal expansion coefficient becomes large. It also causes an increase in compaction. Preferably it is 3 to 29%, more preferably 4 to 28%.

If SiO ₂ + Al ₂ O ₃ exceeds 90%, the Young's modulus decreases, and devitrification of mullite easily occurs and the devitrification temperature T _L increases. In addition, the ratio of the network former is excessively increased, the viscosity is increased, the melting temperature is increased, and bubbles may be mixed. If it is less than 70%, compaction will increase. The average coefficient of thermal expansion also increases. Preferably it is 72% to 88%, more preferably 74% to 86%.

Other components such as the following components may be contained as long as the effects of the present invention are not hindered. The other components in this case are preferably less than 5%, more preferably less than 3%, even more preferably less than 1%, and even more preferably less than 0.5% in order to suppress a decrease in Young's modulus, etc. Particularly preferably, it is preferable not to contain substantially except unavoidable 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 _TL . 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 5% in order to improve the solubility without increasing the devitrification temperature _TL 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.

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 T _L 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 90 GPa or more, 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. 92 GPa or more is more preferable, and 94 GPa or more is more preferable.

The alkali-free glass of the present invention preferably has a specific elastic modulus (Young's modulus / density) of 35 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. 36 GPa · cm ³ / g or more is more preferable, and 37 GPa · cm ³ / g or more is more preferable.

The alkali-free glass of the present invention has a very low compaction.
Compaction is the glass heat shrinkage generated by relaxation of the glass structure during the heat treatment. In the present invention, compaction means a value measured by the method described below.
First, the target glass is melted at 1550 ° C. to 1650 ° C., then the molten glass is poured out, formed into a plate shape, and then cooled. The obtained plate glass is polished to obtain a glass plate of 100 mm × 20 mm × 1 mm.
Next, the obtained glass plate is heated to the glass transition point Tg + 70 ° C., held at this temperature for 1 minute, and then cooled to room temperature at a temperature drop rate of 40 ° C./min. Thereafter, two indentations are made on the surface of the glass plate in the long side direction at intervals A (A = 90 mm) to obtain a sample before processing.
Next, the pre-treatment sample is heated to 450 ° C. at a temperature increase rate of 100 ° C./hour, held at 450 ° C. for 2 hours, and then cooled to room temperature at a temperature decrease rate of 100 ° C./hour to obtain a sample 1 after treatment.
And the distance B1 between impressions of the sample 1 after a process is measured.
The compaction C1 is calculated from A and B1 thus obtained using the following formula.
C1 [ppm] = (A−B1) / A × 10 ⁶
The sample before treatment is heated to 600 ° C. at a temperature rising rate of 100 ° C./hour, held at 600 ° C. for 1 hour, and then cooled to room temperature at a temperature lowering rate of 100 ° C./hour to obtain sample 2 after treatment.
And the distance B2 between impressions of the sample 2 after a process is measured.
The compaction C2 is calculated from A and B2 thus obtained using the following formula.
C2 [ppm] = (A−B2) / A × 10 ⁶

The alkali-free glass of the present invention has a compaction C1 of 5 ppm or less. On the other hand, the compaction C2 is 50 ppm or less. Preferably it is 47 ppm or less, More preferably, it is 44 ppm or less.

The alkali-free glass of the present invention has a glass transition point of 740 ° C. or higher in order to suppress thermal shrinkage during panel manufacture and to make it possible to apply a method by laser annealing as a method for manufacturing a p-Si TFT. Is preferred.
When the glass transition point is 740 ° C. or higher, the glass fictive temperature tends to increase in the production process (for example, organic EL having a thickness of 0.7 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less). Display substrate or illumination substrate, or a thin display substrate or illumination 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 Tg.

In addition, the alkali-free glass of the present invention has a temperature T _{2 at} which the viscosity η becomes 10 ² poise (dPa · s) in order to facilitate melting, preferably 1730 ° C. or less, more preferably 1710 ° C. or less, More preferably, it is 1690 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 1370 ° C. or less, more preferably 1350, in order to facilitate molding by the float process. ° C or lower, more preferably 1330 ° C or lower.

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 to 16 and 20 to 22 are examples, and Examples 17 to 19 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 the ultrasonic method), specific elastic modulus E / ρ (GPa · cm ³ / g), glass transition point Tg (unit: ° C.), the glass viscosity η is 10 ² poise temperature T ₂ (unit: ° C.), the temperature T ₄ of the glass viscosity η is 10 ⁴ poise (unit: ° C.) , And compaction C1 and C2 (measured by the method described above, unit: ppm).
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 90 GPa or higher and a glass transition point Tg of 740 ° C. or higher. Further, T ₂ is 1730 ° C. or lower and T ₄ is 1370 ° C. or lower. Moreover, the compaction C1 is 5 ppm or less, and the compaction C2 is 50 ppm or less.

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. 2013-134922 filed on June 27, 2013, the contents of which are incorporated herein by reference.

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, as the substrate glass for various displays and the substrate glass for the photomask, considering that the glass plate needs to be enlarged or thinned, it has a high Young's modulus, and when exposed to high temperatures in the thin film formation process, Considering that it is required to minimize the dimensional change associated with glass deformation and glass structure stabilization, the compaction is low, and therefore it is effective as substrate glass for various displays and photomask substrate glass.

Claims (5)

Young's modulus is 90 GPa or more, compaction C1 is 5 ppm or less, compaction C2 is 50 ppm or less,
In mass% display based on oxide,
SiO ₂ 40-65,
Al ₂ O _{3 over} 23.5-30
MgO 2.5-20,
CaO 2-30
Containing
Non-alkali glass having SiO ₂ + Al ₂ O ₃ of 70 or more and 90 or less. The alkali-free glass according to claim 1, which has a specific elastic modulus of 35 GPa · cm ³ / g or more. 3. The alkali-free glass according to claim 1, wherein the glass transition point is 740 ° C. or higher. The alkali-free glass according to any one of claims 1 to 3, wherein the temperature T _{2 at} which the viscosity η becomes 10 ² poise is 1730 ° C or lower. The alkali-free glass according to any one of claims 1 to 4, wherein a temperature T _{4 at} which the viscosity η becomes 10 ⁴ poise is 1370 ° C or lower.