TW201509855A - 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 relates to an alkali-free glass which is preferably a substrate glass for a display for producing various flat panel displays (FPD) or a substrate glass for a photomask, and which is substantially free of an alkali metal oxide and which can be float-formed.

Conventionally, for example, a substrate glass for a display, particularly a metal or oxide film formed on the surface, has been required to have the following characteristics as shown in, for example, Patent Document 1.

(1) When an alkali metal oxide is contained, an alkali metal ion diffuses in a film and deteriorates film characteristics, and therefore substantially does not contain an alkali metal ion.

(2) It has sufficient chemical durability for various chemicals used for semiconductor formation. In particular, it is used for etching SiO _x or SiN _x buffered hydrofluoric acid (BHF: a mixture of hydrofluoric acid and ammonium fluoride), and a chemical solution containing hydrochloric acid for etching ITO, for etching metal electrodes. The base of the acid (nitric acid, sulfuric acid, etc.) and the resist stripper has durability.

(3) No defects on the inside and the surface (bubbles, veins, inclusions, pits, damage, etc.).

In addition to the above requirements, in recent years, the situation is as follows.

(4) The weight of the display is required, and the glass itself is also expected to have a lower density of glass.

(5) It is required to reduce the weight of the display, and it is desirable to thin the substrate glass.

(6) In addition to the production of amorphous-type (a-Si) type liquid crystal displays to date, a number of polycrystalline germanium (p-Si) type liquid crystal displays (a-Si: about 350 ° C) have been gradually produced. →p-Si: 350~550°C).

(7) Improve productivity in order to speed up the temperature rise and fall of the heat treatment of the liquid crystal display Or to improve the thermal shock resistance, it is required to have a glass having a small average coefficient of thermal expansion.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2001-348247

With the high definition and large-scale trend of FPD, there is a fear that deformation due to self-weight bending and a decrease in yield occur in the manufacturing steps. Further, in order to sufficiently ensure the practical strength of the large-sized FPD, it is useful to increase the fracture toughness of the substrate glass.

Therefore, a high specific modulus of elasticity and a high Young's modulus are required for various substrate glass for displays.

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

SUMMARY OF THE INVENTION An object of the present invention is to provide an alkali-free glass which has a high specific modulus of elasticity and a high Young's modulus, a high glass transition point, a low degree of compaction, and is easy to float.

The present invention provides an alkali-free glass having a Young's modulus of 90 GPa or more, a compactness C1 of 5 ppm or less, a compactness C2 of 50 ppm or less, and an SiO ₂ 40 to 65 in terms of an oxide-based mass %. Al ₂ O _{3 is} more than 23.5 and less than or equal to 30, MgO is 2.5 to 20, CaO 2 to 30, and SiO ₂ + Al ₂ O ₃ is 70 or more and 90 or less.

The alkali-free glass of the present invention is preferably used as a substrate glass for various displays or a substrate glass for a photomask, and can also be used as a glass substrate for a magnetic disk. In addition, in consideration of the increase in size or thickness of the glass sheet for various display substrate glass or photomask substrate glass, it is effective for use as a substrate glass or a mask for various displays because of its high Young's modulus. Substrate glass.

Next, the composition range of each component will be described. When SiO ₂ exceeds 65% (% by mass, the same applies hereinafter unless otherwise specified), the Young's modulus is lowered. Further, there is a tendency that the viscosity is also high, the melting temperature is raised, or the bubbles are not completely defoamed and the bubbles are mixed. Moreover, it is easy to cause devitrification of the mullite and the devitrification temperature T _L rises. If it is less than 40%, the average coefficient of thermal expansion increases. Moreover, it is easy to cause devitrification of the spinel, and the devitrification temperature T _L rises. It is preferably 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 increases the glass transition point Tg. However, if it is 23.5% or less, the effect is not exhibited. Also, the Young's modulus is lowered and the degree of compaction is increased. Al ₂ O ₃ functions as a network forming agent in the same manner as SiO ₂ . Therefore, when it exceeds 30%, the viscosity increases, the melting temperature increases, and bubbles are mixed. Moreover, there is a tendency to cause devitrification of mullite, anorthite, spinel, etc., and the devitrification temperature T _L rises. It is preferably 24 to 29%, more preferably 24.5 to 28%.

MgO increases the meltability and increases the Young's modulus, so it needs to contain 2.5% or more. However, if it exceeds 20%, the degree of compaction increases. Moreover, it is easy to cause devitrification of the spinel, and the devitrification temperature T _L rises. It is preferably from 3 to 19%, more preferably from 3.5% to 18%.

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

When SiO ₂ +Al ₂ O ₃ exceeds 90%, the Young's modulus decreases, and in addition, devitrification of the mullite is liable to occur, and the devitrification temperature T _L increases. Further, there is a case where the ratio of the network forming agent is excessive, the viscosity is increased, the melting temperature is increased, and the bubbles are mixed. Moreover, if it is less than 70%, the degree of compaction increases. Also, the average coefficient of thermal expansion also increases. It is preferably 72% to 88%, more preferably 74% to 86%.

Other components such as the following components may be contained within the scope of the effects of the present invention. The other component in this case is 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 the Young's modulus. %, especially preferably, is not contained except for the 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, still more preferably 99% or more, and still more preferably 99.5% or more. . It is particularly preferable to contain SiO ₂ , Al ₂ O ₃ , CaO and MgO in addition to the inevitable impurities.

B ₂ O ₃ makes the melting reactivity of the glass good, and further reduces the devitrification temperature T _L , so it may contain less than 5%. However, if it is too much, the Young's modulus decreases. Therefore, it is preferably less than 3%, more preferably less than 1%, still more preferably 0.5%, and particularly preferably substantially not contained.

SrO does not increase the devitrification temperature T _{L of} the glass to improve the meltability, and therefore may contain less than 5%. However, if too much, the average coefficient of thermal expansion increases. Therefore, it is preferably less than 3%, more preferably less than 1%, still more preferably less than 0.5%, and particularly preferably substantially not contained.

BaO increases the meltability of the glass and therefore may contain less than 5%. However, if too much, the average coefficient of thermal expansion increases. Therefore, it is preferably less than 3%, more preferably less than 1%, still more preferably less than 0.5%, and particularly preferably substantially not contained.

ZrO ₂ increases the Young's modulus of the glass and therefore may contain less than 3%. However, if it is too much, the devitrification temperature T _L rises. Therefore, it is preferably less than 2%, more preferably less than 1%, still more preferably less than 0.5%, and particularly preferably substantially not contained.

Further, in the present invention, in order to improve the meltability, clarity, and formability of the glass, the glass raw material may be contained in an amount of less than 1%, preferably less than 0.5%, more preferably less than 0.3%, based on the total amount. More preferably, it is less than 0.1% of ZnO, SO ₃ , Fe ₂ O ₃ , F, Cl, and SnO ₂ .

Further, in order to prevent degradation of the characteristics of the metal or oxide film provided on the glass surface during the production of the panel, the glass of the present invention contains (i.e., does not substantially contain) the alkali metal oxide without exceeding the impurity level. Further, in order to facilitate the reuse of the glass, it is preferable that substantially no PbO, As ₂ O ₃ or Sb ₂ O ₃ is contained.

Since the Young's modulus of the alkali-free glass of the present invention is 90 GPa or more, the fracture toughness is improved, and it is suitable for various display substrate glass or photomask substrate glass which are required to increase the size or thickness of the glass plate. More preferably, it is 92 GPa or more, and further preferably 94 GPa or more.

Further, in order to reduce the self-weight bending, the alkali-free glass of the present invention preferably has a specific modulus (Young's modulus/density) of 35 GPa‧cm ³ /g or more. Therefore, in the manufacturing process, since the deformation due to the self-weight bending is small, it is suitable for various substrate glass for display or substrate glass for a mask which requires an increase in size or thickness of the glass sheet. More preferably, it is 36 GPa‧cm ³ /g or more, and further preferably 37 GPa‧cm ³ /g or more.

The alkali-free glass of the present invention has extremely low compactness.

The degree of compaction is the heat shrinkage rate of the glass due to the relaxation of the glass structure during the heat treatment. The degree of compaction in the present invention means a value measured by the method described in the next step.

First, the glass to be melted is melted at 1550 ° C to 1650 ° C, and then the molten glass is allowed to flow out, formed into a plate shape, and then cooled. The obtained sheet glass was subjected to a grinding process to obtain a glass plate of 100 mm × 20 mm × 1 mm.

Then, the obtained glass plate was heated to a 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, the surface of the glass plate was marked with two indentations at intervals A (A = 90 mm) along the longitudinal direction, and the sample was treated as a sample.

Then, the sample before treatment is heated to 450 ° C at a heating rate of 100 ° C / h, at 450 ° C After holding for 2 hours, it was cooled to room temperature at a cooling rate of 100 ° C / h, and was set as sample 1 after the treatment.

Then, the distance W1 between the indentations of the sample 1 after the treatment was measured.

From the A and B1 thus obtained, the degree of compaction C1 was calculated using the following formula.

C1[ppm]=(A-B1)/A×10 ⁶

Further, the sample before the treatment was heated to 600 ° C at a temperature increase rate of 100 ° C / h, and maintained at 600 ° C for 1 hour, and then cooled to room temperature at a temperature drop rate of 100 ° C / h to prepare a sample 2 after the treatment.

Then, the distance B2 between the indentations of the treated sample 2 was measured.

From the A and B2 thus obtained, the degree of compaction C2 was calculated using the following formula.

C2[ppm]=(A-B2)/A×10 ⁶

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

The alkali-free glass of the present invention preferably has a glass transition point of 740 ° C or higher in order to suppress the heat shrinkage during the manufacture of the panel, and to apply the method of laser annealing as a method of producing a p-Si TFT.

When the glass transition point is 740 ° C or higher, it is suitable for applications in which the pseudo temperature of the glass is easily increased in the manufacturing process (for example, an organic EL (Electroluminescence) having a thickness of 0.7 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less. A substrate for a display or an illumination substrate for use in electroluminescence, or a substrate for display or a substrate for illumination having a thickness of 0.3 mm or less, preferably 0.1 mm or less.

In the case of a plate glass having a 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 molding tends to increase, so that the pseudo temperature of the glass rises and the pressure of the glass increases. Reality tends to increase. In this case, if the glass is a high glass transition point Tg, the degree of compaction can be suppressed.

Further, in order to make the alkali-free glass of the present invention easy to melt, the temperature T _{2 at} which the viscosity η is 10 ² poise (dPa ‧ s) is preferably 1730 ° C or lower, more preferably 1710 ° C or lower, and still more preferably 1690 ° C or lower. .

Further, in order to facilitate the molding of the alkali-free glass of the present invention by the floating method, the temperature T _{4 at} which the viscosity η is 10 ⁴ poises (dPa ‧ s) is preferably 1370 ° C or lower, more preferably 1350 ° C or lower, and further preferably It is below 1330 °C.

The alkali-free glass of the present invention can be produced, for example, by the following method. The raw materials of the components which are usually used are blended in such a manner as to be a target component, and they are continuously introduced into a melting furnace and heated to 1550 to 1650 ° C to be melted. The molten glass is formed into a specific thickness by a floating method, and is slowly cooled and then cut, whereby a plate glass can be obtained.

Example

Hereinafter, Examples 1 to 16 and 20 to 22 are examples, and examples 17 to 19 are comparative examples. The raw materials of the respective components are blended in such a manner as to be a target composition, and the platinum crucible is used and melted at a temperature of 1550 to 1650 °C. At the time of melting, the glass was homogenized by stirring using a platinum stirrer. Then, the molten glass is allowed to flow out, formed into a plate shape, and then slowly cooled.

Tables 1-3 show: glass composition (unit: mass%), density ρ (g/cm ³ ), Young's modulus E (GPa) (measured by ultrasonic method), specific elastic modulus E/ ρ(GPa‧cm ³ /g), glass transition point Tg (unit: °C), glass viscosity η becomes 10 ² poise temperature T ₂ (unit: ° C), glass viscosity η becomes 10 ⁴ poise temperature T ₄ (unit : ° C) and compaction degrees C1, C2 (measured by the above method, unit: ppm).

Furthermore, the values indicated by the brackets in Tables 1 to 3 are calculated values.

It is understood from the table that the glass of the examples has a high Young's modulus and is 90 GPa or more, and the glass transition point Tg is 740 ° C or higher. Further, T ₂ is 1730 ° C or lower, and T ₄ is 1370 ° C or lower. Further, the degree of compaction C1 is 5 ppm or less, and the degree of compaction C2 is 50 ppm or less.

The present invention has been described in detail with reference to the specific embodiments thereof, and it is understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

The present application is based on Japanese Patent Application No. 2013-134921, filed on Jun.

[Industrial availability]

The alkali-free glass of the present invention is preferably used as a substrate glass for various displays or a substrate glass for a photomask, and can also be used as a glass substrate for a magnetic disk. In addition, in consideration of the increase in size or thickness of the glass sheet for various display substrate glass or photomask substrate glass, it is effective for use as a substrate glass or a mask for various displays because of its high Young's modulus. The substrate glass can be effectively used because it is required to minimize the dimensional change of the deformation of the glass and the stabilization of the structure of the glass when exposed to a high temperature in the film formation step, since the degree of compaction is low. It is used as a substrate glass for various displays or a substrate glass for a photomask.

Claims (5)

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