JP2017114685A - Alkali-free glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali-free glass high in a strain point, low in viscosity, large in etching rate by hydrofluoric acid and easy to be float molded.SOLUTION: There is provided an alkali-free glass having a strain point of 680°C or more, average thermal expansion coefficient of 30×10to 43×10/°C, temperature with viscosity of 10dPa s of 1670°C or less, temperature with viscosity of 10dPa s of 1320°C or less, hydrofluoric acid mass reduction during 20 minutes impregnation of 3.1 mg/cmor more and containing, by mol%, SiO:60 to 70, AlO:11 to 16, BO:0 to 1.5, MgO:7 to 12, CaO:0 to 7, SrO:4.5 to 10, BaO:0 to 0.5 with MgO+CaO+SrO+BaO of 16 to 22, (SiO+AlO)/(MgO+CaO+SrO+BaO) of 4.7 or more, MgO/CaO of 1.05 or more, SrO/CaO of 1.05 or more and (MgO+SrO)/(MgO+CaO+SrO+BaO) of 0.7 or more.SELECTED DRAWING: None

Description

  The present invention relates to an alkali-free glass that is suitable for various display substrate glasses and photomask substrate glasses and that is substantially free of alkali metal oxides and can be float-molded.

Conventionally, the following characteristics have been required for various display substrate glasses, particularly those in which a metal or oxide thin film is formed on the surface.
(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) When exposed to a high temperature in the thin film forming process, the strain point is high so that 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: liquid mixture of hydrofluoric acid and ammonium fluoride) for etching SiO _x and SiN _x , and chemicals containing hydrochloric acid for etching ITO and 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.

On the other hand, dry etching has progressed, and the demand for BHF resistance has become weaker. As the conventional glass, a glass containing 6 to 10 mol% of B ₂ O ₃ has been often used in order to improve the BHF resistance. However, B ₂ O ₃ tends to lower the strain point. Examples of non-alkali glass not containing B ₂ O ₃ or having a low content are as follows.

Patent Document 1 discloses SiO ₂ —Al ₂ O ₃ —SrO glass that does not contain B ₂ O ₃ , but the temperature required for melting is high, resulting in difficulty in production.

Patent Document 2 discloses a glass containing 0 to 5 mol% of B ₂ O ₃ , but the average thermal expansion coefficient at 50 to 300 ° C. exceeds 50 × 10 ⁻⁷ / ° C.

  In order to solve the problems in the glasses described in Patent Documents 1 and 2, an alkali-free glass described in Patent Document 3 has been proposed. The alkali-free glass described in Patent Document 3 has a high strain point, can be molded by a float process, and is suitable for uses such as a display substrate and a photomask substrate.

JP 62-1113735 A Japanese Patent Laid-Open No. 5-232458 JP-A-10-45422 Republished Patent No. 2009-066664

There is a solid-phase crystallization method as a method for producing a high-quality p-Si TFT, and in order to implement this, it is required to increase the strain point.
On the other hand, due to demands in the glass production process, particularly melting and molding, the viscosity of the glass, specifically, the temperature T _{2 at which} the glass viscosity becomes 10 ² dPa · s and the temperature at which the glass viscosity becomes 10 ⁴ dPa · s. to lower of T ₄ is required.
On the other hand, in the field of small and medium-sized liquid crystal displays (LCDs) and organic EL displays (OELDs), especially portable displays such as mobiles, digital cameras and mobile phones, weight reduction and thinning of the displays are important issues. . In order to realize further thinning of the glass substrate, a process of thinning (thinning) the plate thickness by applying an etching process to the glass substrate surface after the array / color filter bonding step is widely employed. For example, the surface of a glass substrate is etched with an etchant containing hydrofluoric acid (HF) (hereinafter referred to as “hydrofluoric acid etching process”) to thin the glass substrate (patent). Reference 4).
When the glass substrate is thinned by the hydrofluoric acid etching process, it is required that the etching rate during the hydrofluoric acid etching process be high.

The object of the present invention is to solve the above drawbacks, have a high strain point, low viscosity, specifically, a temperature T _{2 at which} the glass viscosity becomes 10 ² dPa · s, and a glass viscosity of 10 ⁴ dPa · s. low temperature T ₄ comprising a large etching rate at the time of hydrofluoric acid etching treatment is that the float forming can provide easy alkali-free glass.

The present invention has a strain point of 680 ° C. or higher, an average coefficient of thermal expansion at 50 to 350 ° C. of 30 × 10 ⁻⁷ to 43 × 10 ⁻⁷ / ° C., and a glass viscosity of 10 ² dPa · s. An etching solution (25 ° C., 5%) containing a hydrofluoric acid (HF) having a temperature T ₂ of 1670 ° C. or less and a glass viscosity of 10 ⁴ dPa · s and a temperature T ₄ of 1320 ° C. or less. The mass reduction per unit area when immersed in an aqueous HF solution for 20 minutes is 3.1 mg / cm ² or more,
SiO ₂ 60 to 70 in terms of mol% based on oxide,
Al ₂ O ₃ 11-16,
B ₂ O ₃ greater than 0 and 1.5 or less,
MgO over 7 and below 12,
CaO over 0 and below 7,
SrO 4.5 over 10 and below,
BaO 0-0.5, MgO + CaO + SrO + BaO is 16-22,
(SiO ₂ + Al ₂ O ₃ ) / (MgO + CaO + SrO + BaO) is 4.7 or less, MgO / CaO is 1.05 or more, SrO / CaO is 1.05 or more, and (MgO + SrO) / (MgO + CaO + SrO + BaO) is An alkali-free glass that is 0.7 or more is provided.

  The alkali-free glass of the present invention is particularly suitable for a display substrate, a photomask substrate and the like for high strain point use, and is a glass that is easy to float.

Next, the composition range of each component will be described. When SiO ₂ is less than 60% (mol%, the same unless otherwise specified), the strain point is not sufficiently increased, the thermal expansion coefficient is increased, and the density is increased. It is preferably 63% or more, more preferably 65% or more, and further preferably 65.5% or more. If it exceeds 70%, the solubility is lowered. 69% or less is preferable, 68% or less is more preferable, and 67.5% or less is more preferable.

Al ₂ O ₃ suppresses the phase separation of the glass, lowers the thermal expansion coefficient and raises the strain point. However, if it is less than 11%, this effect does not appear, and other components that increase the expansion increase. As a result, thermal expansion increases. 11.5% or more is preferable, 12% or more is more preferable, and 12.5% or more is more preferable. If it exceeds 16%, the solubility of the glass becomes poor. It is preferably 15% or less, more preferably 14% or less, and further preferably 13.5% or less.

B ₂ O ₃ can be added more than 0% and 1.5% or less in order to improve the melting reactivity of the glass. In order to acquire said effect, 0.2% or more is preferable, 0.5% or more is more preferable, and 0.7% or more is further more preferable. However, if it is too much, the strain point is lowered. Therefore, it is preferably 1.4% or less, more preferably 1.3% or less, and further preferably 1.2% or less.

MgO has the characteristics that it does not increase the expansion in alkaline earth and does not excessively lower the strain point, and also improves the solubility.
If it is 7% or less, the above-described effect due to the addition of MgO is not sufficiently exhibited. 7.5% or more is preferable, 8% or more is more preferable, and 8.5% or more is more preferable. However, if it exceeds 12%, the devitrification temperature may increase. It is preferably 11% or less, more preferably 10% or less, and even more preferably 9.5% or less.

CaO has the characteristics that it does not increase the expansion in alkaline earth next to MgO and does not excessively lower the strain point, and improves the solubility. Therefore, CaO can be added more than 0% and 7% or less.
1% or more is preferable, 1.5% or more is more preferable, and 2% or less is more preferable. However, if it exceeds 7%, a large amount of phosphorus, which is an impurity in limestone (CaCO ₃ ), which is a CaO raw material, may be mixed. 6% or less is preferable, 5% or less is more preferable, and 4.5% or less is more preferable.

  SrO improves the solubility, but this effect is not sufficiently exhibited at 4.5% or less. 4.7% or more is preferable, 4.9% or more is more preferable, and 5.3% or more is more preferable. However, if it exceeds 10%, the expansion coefficient may increase. It is preferably 9% or less, more preferably 8.5% or less, and even more preferably 8% or less.

  BaO is not essential, but can be contained to improve solubility. However, too much increases the expansion and density of the glass excessively, so the content is made 0.5% or less. 0.3% or less is preferable, 0.1% or less is more preferable, and it is still more preferable not to contain substantially. “Substantially not contained” means not containing any inevitable impurities.

ZrO ₂ may be contained up to 0.5% in order to lower the glass melting temperature or to promote crystal precipitation during firing. If it exceeds 0.5%, the glass becomes unstable or the relative dielectric constant ε of the glass increases. 0.3% or less is preferable, 0.1% or less is more preferable, and it is especially preferable not to contain substantially.

  If the total amount of MgO, CaO, SrO and BaO is less than 16%, the solubility is poor. It is preferably 17% or more, more preferably 17.5% or more, and further preferably 18% or more. If it exceeds 22%, there is a risk that the thermal expansion coefficient cannot be reduced. It is preferably 21% or less, more preferably 20% or less, and further preferably 19.5% or less.

In the alkali-free glass of the present invention, the total amount of MgO, CaO, SrO and BaO satisfies the above and satisfies the following conditions, thereby increasing the viscosity of the glass without increasing the thermal expansion coefficient. temperature T ₂ which the glass viscosity of 10 ² dPa · s, and may reduce the temperature T ₄ which glass viscosity of 10 ⁴ dPa · s.
(SiO ₂ + Al ₂ O ₃ ) / (MgO + CaO + SrO + BaO) is 4.7 or less, preferably 4.6 or less, more preferably 4.5 or less, and even more preferably 4.4 or less.

By satisfying the following three conditions, the alkali-free glass of the present invention can reduce the glass viscosity, particularly the temperature T _{4 at} which the glass viscosity becomes 10 ⁴ dPa · s, and the etching rate during the hydrofluoric acid etching treatment. Becomes larger.
MgO / CaO is 1.05 or more, preferably 1.3 or more, more preferably 1.5 or more, and still more preferably 2 or more.
SrO / CaO is 1.05 or more, preferably 1.08 or more, more preferably 1.1 or more, and even more preferably 1.15 or more.
(MgO + CaO) / (MgO + CaO + SrO + BaO) is 0.7 or more, preferably 0.75 or more, and more preferably 0.8 or more. 0.82 or more is more preferable.

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. For the same reason, it is preferred not to contain P ₂ O ₅ substantially. Furthermore, 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.

In addition to the above components, the alkali-free glass of the present invention contains ZnO, Fe ₂ O ₃ , SO ₃ , F, Cl, SnO _2, etc. in order to improve the solubility, clarity, and moldability (float moldability) of the glass. 1% or less, preferably 0.9% or less, more preferably 0.8% or less, and still more preferably 0.7% or less. It is preferable that ZnO is not substantially contained.

Since the alkali-free glass of the present invention has a strain point of 680 ° C. or higher, thermal shrinkage during panel production can be suppressed. Further, a solid phase crystallization method can be applied as a method for manufacturing the p-Si TFT.
Since the alkali-free glass of the present invention has a strain point of 680 ° C. or higher, it is used for a high strain point (for example, a display substrate or lighting substrate for organic EL, or a thin display substrate or lighting plate having a thickness of 100 μm or less). Suitable for use on a substrate).
Preferably it is 690 degreeC or more, More preferably, it is 700 degreeC or more, More preferably, it is 710 degreeC or more.

  The alkali-free glass of the present invention has a glass transition point of preferably 745 ° C. or higher, more preferably 750 ° C. or higher, and further preferably 755 ° C. or higher for the same reason as the strain point.

The alkali-free glass of the present invention has an average coefficient of thermal expansion at 50 to 350 ° C. of 30 × 10 ⁻⁷ to 43 × 10 ⁻⁷ / ° C., has high thermal shock resistance, and has high productivity during panel production. it can. In the alkali-free glass of the present invention, the average thermal expansion coefficient at 50 to 350 ° C. is preferably 35 × 10 ⁻⁷ or more. The average thermal expansion coefficient at 50 to 350 ° C. is preferably 42 × 10 ⁻⁷ / ° C. or less, more preferably 41 × 10 ⁻⁷ / ° C. or less, and further preferably 40 × 10 ⁻⁷ / ° C. or less.

  Furthermore, the alkali-free glass of the present invention has a specific gravity of preferably 2.7 or less, more preferably 2.67 or less, and further preferably 2.65 or less.

The alkali-free glass of the present invention has a temperature T _{2 at} which the viscosity η becomes 10 ² poise (dPa · s), 1670 ° C. or less, preferably less than 1670 ° C., preferably 1665 ° C. or less, more preferably 1660 ° C. or less, Furthermore, since it is 1655 degrees C or less preferably, melt | dissolution is easy.

Further, the alkali-free glass of the present invention has a temperature T _{4 at} which the viscosity η becomes 10 ⁴ poise is 1320 ° C. or less, preferably less than 1320 ° C., preferably 1315 ° C. or less, more preferably 1310 ° C. or less, and further preferably 1305 ° C. or less. It is suitable for float forming.

In addition, the alkali-free glass of the present invention preferably has a devitrification temperature of 1350 ° C. or less because molding by the float method is easy. Preferably it is 1340 degrees C or less, More preferably, it is 1330 degrees C or less.
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.

  Further, the alkali-free glass of the present invention preferably has a Young's modulus of 80 GPa or more, further 82 GPa or more, and more preferably 84 GPa or more.

The alkali-free glass of the present invention preferably has a compaction of 120 ppm or less measured by the procedure described in the examples described later. Compaction is the glass heat shrinkage generated by relaxation of the glass structure during the heat treatment.
In the alkali-free glass of the present invention, the compaction measured by the procedure described in the examples described later is more preferably 100 ppm or less, further preferably 80 ppm or less, further 60 ppm or less, and particularly preferably 50 ppm or less.

The alkali-free glass of the present invention preferably has a photoelastic constant of 31 nm / MPa / cm or less.
Due to the birefringence of the glass substrate due to stress generated during the manufacturing process of the liquid crystal display panel and the liquid crystal display device, a phenomenon in which the black display becomes gray and the contrast of the liquid crystal display decreases may be observed. By setting the photoelastic constant to 31 nm / MPa / cm or less, this phenomenon can be suppressed small. Preferably it is 30 nm / MPa / cm or less, More preferably, it is 29 nm / MPa / cm or less, More preferably, it is 28.5 nm / MPa / cm or less, Most preferably, it is 28 nm / MPa / cm or less.
The alkali-free glass of the present invention has a photoelastic constant of preferably 23 nm / MPa / cm or more, more preferably 25 nm / MPa / cm or more, considering the ease of securing other physical properties.
The photoelastic constant can be measured at a measurement wavelength of 546 nm by a disk compression method.

The alkali-free glass of the present invention has a mass loss per unit area of 3.1 mg / cm when immersed in 5% by mass hydrofluoric acid (HF) at 25 ° C., which is an index of etching rate during hydrofluoric acid etching treatment. ² or more.

  The alkali-free glass of the present invention can be produced, for example, by the following method. The raw materials of each component normally used are mixed so as to become target components, which are continuously charged into a melting furnace, and heated to 1500 to 1800 ° C. to be melted. A plate glass can be obtained by forming this molten glass into a predetermined plate thickness by a float method or a fusion method, preferably by a float method, and cutting after slow cooling. The molded plate thickness is preferably 0.7 mm or less, more preferably 0.5 mm or less, 0.3 mm or less, or 0.1 mm or less.

  In the following, Examples 1 to 12 are Examples, and Examples 13 to 14 are Comparative Examples. The raw material of each component was prepared so that it might become a target composition, and it melt | dissolved at the temperature of 1500-1650 degreeC using the 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 and 2 show the glass composition (unit: mol%), the coefficient of thermal expansion at 50 to 350 ° C. (unit: × 10 ⁻⁷ / ° C.), the strain point (unit: ° C.), and the glass transition point (unit: unit). ° C), specific gravity, Young's modulus (GPa) (measured by ultrasonic method), high temperature viscosity value, T ₂ (temperature at which glass viscosity η becomes 10 ² poise, unit: ° C) Temperature T ₄ (temperature at which the glass viscosity η becomes 10 ⁴ poise, unit: ° C), devitrification temperature (unit: ° C), photoelastic constant (unit: nm / MPa /) cm) (measured by a disk compression method at a measurement wavelength of 546 nm), mass reduction per unit area when immersed in 5% hydrofluoric acid (HF) at 25 ° C. for 20 minutes (in the table, “mass after 5% HF immersion” "Decreased") (measured by the following procedure) and compact ® emissions (Unit: ppm) show the. In addition, the measuring method of mass reduction after immersion in 5% HF and the measuring method of compaction are as described below.
[Measurement method of mass reduction per unit area]
The raw materials of each component are prepared so as to have the target compositions shown in Tables 1 and 2, dissolved in a continuous melting kiln, and plate-formed by a float method to obtain an alkali-free glass substrate. The alkali-free glass substrate cut into a 40 mm square that has been mirror-polished is washed, and then the mass is measured. Immerse in 5% by mass hydrofluoric acid at 25 ° C. for 20 minutes and measure the mass after immersion. The surface area is calculated from the sample dimensions, the mass reduction amount is divided by the surface area, and then the immersion time is further divided to obtain the unit area and the mass reduction per unit time.
[Measurement method of compaction]
A glass plate sample (length 100 mm × width 10 mm × thickness 1 mm sample mirror-polished with cerium oxide) is held at a temperature of glass transition point + 100 ° C. for 10 minutes, and then cooled to room temperature at 40 ° C. per minute. Here, the total length (length direction) L1 of the sample is measured. Thereafter, the sample is heated at 100 ° C. to 600 ° C., held at 600 ° C. for 80 minutes, cooled to room temperature at 100 ° C. per hour, and the total length L2 of the sample is measured again. The ratio (L1−L2) / L1 between the difference in total length before and after the heat treatment at 600 ° C. (L1−L2) and the total length L1 of the sample before the heat treatment at 600 ° C. is defined as compaction.
In Tables 1 and 2, the values shown in parentheses are calculated values.

As is clear from the table, all the glasses of the examples have a low thermal expansion coefficient of 30 × 10 ⁻⁷ to 43 × 10 ⁻⁷ / ° C. and a strain point of 680 ° C. or higher.

Temperature T ₂ which is a measure of the solubility is also easy to dissolve low as 1670 ° C. or less, a temperature T ₄ which is a measure of formability is at 1320 ° C. or less, it is easily molded by a float process.

  A photoelastic constant is 31 nm / MPa / cm or less, and when used as a glass substrate of a liquid crystal display, a decrease in contrast can be suppressed.

The mass decrease per unit area when immersed in 5% by mass hydrofluoric acid (HF) at 25 ° C., which is an index of the etching rate during the hydrofluoric acid etching treatment, is 3.1 mg / cm ² or more.

  The alkali-free glass of the present invention has a high strain point and can be formed by a float process, and is suitable for uses such as a display substrate and a photomask substrate. It is also suitable for applications such as magnetic disk substrates and solar cell substrates.

Claims (3)

The temperature T at which the strain point is 680 ° C. or higher, the average coefficient of thermal expansion at 50 to 350 ° C. is 30 × 10 ⁻⁷ to 43 × 10 ⁻⁷ / ° C., and the glass viscosity is 10 ² dPa · s. ₂ is 1670 ° C. or lower, the temperature T ₄ at which the glass viscosity is 10 ⁴ dPa · s is 1320 ° C. or lower, and an etching solution (25 ° C., 5% HF aqueous solution) containing hydrofluoric acid (HF) is used. The mass reduction per unit area when immersed for 20 minutes is 3.1 mg / cm ² or more,
SiO ₂ 60 to 70 in terms of mol% based on oxide,
Al ₂ O ₃ 11-16,
B ₂ O ₃ greater than 0 and 1.5 or less,
MgO over 7 and below 12,
CaO over 0 and below 7,
SrO 4.5 over 10 and below,
BaO 0-0.5, MgO + CaO + SrO + BaO is 16-22,
(SiO ₂ + Al ₂ O ₃ ) / (MgO + CaO + SrO + BaO) is 4.7 or less, MgO / CaO is 1.05 or more, SrO / CaO is 1.05 or more, and (MgO + SrO) / (MgO + CaO + SrO + BaO) is Alkali-free glass that is 0.7 or more. SiO ₂ 63 to 68 in terms of mol% based on oxide,
Al ₂ O ₃ 12-14,
B ₂ O ₃ 0.5-1.3,
MgO 8-11,
CaO 1.5-5,
SrO 5-9,
BaO 0-0.3, MgO + CaO + SrO + BaO is 17.5-20,
(SiO ₂ + Al ₂ O ₃ ) / (MgO + CaO + SrO + BaO) is 4.6 or less, MgO / CaO is 1.3 or more, SrO / CaO is 1.1 or more, and (MgO + SrO) / (MgO + CaO + SrO + BaO) is The alkali-free glass according to claim 1, which is 0.75 or more. SiO ₂ 65.5 to 67.5 in terms of mol% based on oxide,
Al ₂ O ₃ 12.5 to 13.5,
B ₂ O ₃ 0.7-1.2,
MgO 8.5-10,
CaO 2-4.5,
Containing SrO 5.3-8,
Substantially free of BaO,
MgO + CaO + SrO is 18 to 19.5,
(SiO ₂ + Al ₂ O ₃ ) / (MgO + CaO + SrO) is 4.5 or less, MgO / CaO is 2 or more, SrO / CaO is 1.15 or more, and (MgO + SrO) / (MgO + CaO + SrO) is 0. The alkali-free glass according to claim 1 or 2, which is 8 or more.