TW201609591A - Alkali-free glass - Google Patents

Abstract

The subject of the present invention is to provide an alkali-free glass that has low viscosity although its coefficient of thermal expansion is smaller and strain point is higher, especially the temperature T2 for obtaining the glass viscosity of 10<SP>2</SP> dPa,s is lower. The strain point of the alkali-free glass of this invention is above 695DEG C; the average coefficient of thermal expansion at 50~350DEG C is less than 43x10<SP>-7</SP>/ DEG C; the temperature T2 for obtaining the glass viscosity of 102 dPa,s is below 1690DEG C. When expressed in mol% on an oxide basis, the alkali-free glass contains 63~70 of SiO2, 8~16 of Al2O3, 1.5~ less than 4 of B2O3, 0~8 of MgO, 0~20 of CaO, 1.5~10 of SrO, 0~0.5 of BaO, and the content of MgO+CaO is 0~28, MgO+CaO+SrO+BaO is 12~30, SrO/CaO is 0.33~0.85, and (23.5x[SiO2]+3.5x[Al2O3]-5x[B2O3])/(2.1x[MgO]+4.2x[CaO]+10x[SrO]+12x[BaO]) is more than 17.

Description

Alkali-free glass

The present invention relates to an alkali-free glass which can be suitably used as a substrate glass for a display or a substrate glass for a photomask, which is substantially free of an alkali metal oxide and which can be float-formed. The alkali-free glass of the present invention does not substantially contain an alkaline component (i.e., except for unavoidable impurities).

Conventionally, the following characteristics have been demanded for various display substrate glass, particularly for forming a metal or oxide film on the surface.

(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) The strain point is high, and the deformation of the glass and the shrinkage (heat shrinkage) accompanying the stabilization of the structure of the glass can be suppressed to a minimum when exposed to a high temperature in the film forming step.

(3) It has sufficient chemical durability for various chemicals used for semiconductor formation. In particular, a buffered hydrofluoric acid (BHF: a mixture of hydrofluoric acid and ammonium fluoride) for etching SiO _x or SiN _x , and a hydrochloric acid-containing medicine for etching ITO (Indium Tin Oxide) The liquid, the various acids (nitric acid, sulfuric acid, etc.) used to etch the metal electrode, and the base of the resist stripper have durability.

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

In addition to the above requirements, the following conditions have occurred in recent years.

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

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

(7) In addition to the amorphous-type (a-Si) type liquid crystal display so far, it has gradually begun A polycrystalline silicon (p-Si) type liquid crystal display having a slightly higher heat treatment temperature (a-Si: about 350 ° C → p-Si: 350 to 550 ° C) was produced.

(8) In order to speed up the temperature rise and decrease of the heat treatment of the liquid crystal display to improve productivity or to improve thermal shock resistance, glass having a small average thermal expansion coefficient of glass is required.

On the other hand, as the drying of etching progresses, the requirement for BHF resistance is gradually weakened. In order to achieve good BHF resistance, glass having hitherto has a glass containing 6 to 10 mol% of B ₂ O ₃ . However, B ₂ O ₃ has a tendency to lower the strain point. As the alkali-free glass of Example ₂ O ₃ content of free or less B, there is a person.

Patent Document 1 discloses a glass containing 0 to 3% by weight of B ₂ O ₃ , but the strain point of the example is 690 ° C or lower.

Patent Document 2 discloses a glass containing 0 to 5 mol% of B ₂ O ₃ , but an average thermal expansion coefficient at 50 to 350 ° C exceeds 50 × 10 ^-7 / ° C.

In order to solve the problem of the glass described in Patent Documents 1 and 2, the alkali-free glass described in Patent Document 3 is proposed. The alkali-free glass described in Patent Document 3 has a high strain point and can be molded by a floating method, and is considered to be suitably used for applications such as a substrate for a display and a substrate for a photomask.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 4-325435

[Patent Document 2] Japanese Patent Laid-Open No. Hei 5-232458

[Patent Document 3] Japanese Patent Laid-Open No. Hei 9-263421

In recent years, a high-definition small display such as a mobile phone such as a smart phone has been subjected to a laser annealing method as a manufacturing method of a high-quality p-Si TFT (p-Si Thin-Film Transistor). Further reducing the heat shrinkage rate and requiring strain points Higher glass. Further, as the glass substrate is largely plated and thinned, a glass having a high Young's modulus and a higher specific modulus (Young's modulus/density) is required.

On the other hand, in view of the need in the glass manufacturing process, it is required not to excessively increase the strain point.

Object of the present invention is to solve the above disadvantages, although there is provided a low coefficient of thermal expansion, a high strain point, low viscosity, but, in particular, the glass viscosity becomes 10 ² dPa‧s temperature T ₂ of the low-alkali glass.

The invention provides an alkali-free glass having a strain point of 695 ° C or higher, an average thermal expansion coefficient of 43×10 ^-7 /° C. at 50-350° C., and a glass viscosity of 10 ² dPa·s at a temperature T ₂ of 1690° C. Hereinafter, the molar percentage based on the oxide is expressed as

SiO ₂ 63~70, Al ₂ O ₂ 8~16, B ₂ O ₃ 1.5~under 4, MgO 0~8, CaO 0~20, SrO 1.5~10, BaO 0~0.5, and MgO+CaO is 0 ~28, MgO+CaO+SrO+BaO is 12~30, SrO/CaO is 0.33~0.85, (23.5×[SiO ₂ ]+3.5×[Al ₂ O ₃ ]-5×[B ₂ O ₃ ])/ (2.1×[MgO]+4.2×[CaO]+10×[SrO]+12×[BaO]) is 17 or more.

The alkali-free glass of the present invention is particularly suitable for use in a substrate for a display for high strain point applications, a substrate for a photomask, and the like, which is easy to float. The alkali-free glass of the present invention can also be used as a glass substrate for a magnetic disk.

Next, the composition range of each component will be described. When SiO _{2 is} less than 63% (% by mole, the following is the same unless otherwise specified), the strain point is not sufficiently increased, the coefficient of thermal expansion is increased, and the density is increased. Therefore, SiO ₂ is 63% or more. It is preferably 64% or more, more preferably 65% or more, and still more preferably 66% or more. When it exceeds 70%, the meltability is lowered, and the glass viscosity becomes a temperature T ₂ of 10 ² dPa ‧ or a temperature T ₄ of 10 ⁴ dPa ‧ increases, and the devitrification temperature rises. Therefore, SiO ₂ is 70% or less. It is preferably 69.5% or less, more preferably 69% or less, still more preferably 68.5% or less.

Al ₂ O ₃ suppresses the phase separation property of the glass, lowers the coefficient of thermal expansion, and increases the strain point. However, if it is less than 8%, the effect is not exhibited, and other components which increase the expansion are increased, and as a result, thermal expansion becomes large. Therefore, Al ₂ O ₃ is 8% or more. It is preferably 9% or more, 10% or more, and further preferably 11.1% or more. When it exceeds 16%, the meltability of glass may deteriorate or the devitrification temperature may rise. Accordingly, Al ₂ O ₃ is 16% or less. It is preferably 15% or less, more preferably 14.5% or less, still more preferably 14% or less.

B ₂ O ₃ is contained in an amount of 1.5% or more and less than 4% in order to improve the melt reactivity of the glass and to lower the devitrification temperature. In order to obtain the above effects, it is preferably contained in an amount of 1.6% or more, more preferably 1.7% or more, still more preferably 1.8% or more. However, if too much, the strain point becomes low, and the Young's modulus becomes small, so it is set to less than 4%. It is preferably 3.5% or less, more preferably 3% or less, further preferably 2.8% or less, further preferably 2.6% or less, and particularly preferably 2.5% or less.

MgO has a characteristic of not increasing the expansion in the alkaline earth family and increasing the Young's modulus while maintaining the low density, and also improves the meltability, so that it can be contained. In order to obtain the above effects, the content is preferably 0.1% or more, more preferably 1% or more, further preferably 2% or more, and particularly preferably 3% or more. However, if the devitrification temperature rises too much, it is set to 8% or less. It is preferably less than 8%, preferably 7.5% or less, more preferably 7% or less, still more preferably 6.5% or less and 6% or less.

CaO has a characteristic of not increasing the swelling in the alkaline earth family and increasing the Young's modulus while maintaining the low density, and also improves the meltability, so that it can be contained. In order to obtain the above effects, the content is preferably 0.1% or more, more preferably 1% or more, further preferably 3% or more, and particularly preferably 5% or more. However, if it is too large, the devitrification temperature rises or the amount of phosphorus which is an impurity in limestone (CaCO ₃ ) which is a CaO raw material is mixed in a large amount, and therefore it is 20% or less. It is preferably 15% or less, more preferably 12% or less, still more preferably 10% or less.

SrO does not increase the devitrification temperature of the glass, and improves the meltability. However, if it is less than 1.5%, the effect cannot be sufficiently exhibited. Therefore, SrO is 1.5% or more. It is preferably 2% or more, more preferably 2.5% or more, still more preferably 3% or more. However, if it exceeds 10%, there is a problem that the expansion coefficient increases. Therefore, SrO is 10% or less. It is preferably 8% or less, more preferably 6% or less, still more preferably 5% or less.

BaO improves the meltability and therefore can be contained. However, if the amount is too large, the expansion and density of the glass are excessively increased, so that it is made 0.5% or less. When considering the environmental load, BaO is preferably substantially (ie, excluding impurities which are unavoidable).

MgO and CaO have the effect of lowering the devitrification temperature. The total amount of MgO and CaO is preferably 2% or more, more preferably 5% or more, further preferably 8% or more, and particularly preferably 10% or more. If it is more than 28%, the coefficient of thermal expansion and the specific gravity become large. Therefore, it is set to 28% or less. It is preferably 24% or less, more preferably 20% or less, still more preferably 16% or less.

In the case where MgO, CaO, SrO, and BaO are not excessively high in the temperature T _{2 at} which the glass viscosity is 10 ² dPa·s, the total amount is 12% or more. It is preferably 14% or more, more preferably 16% or more, and still more preferably 17% or more. If it is more than 30%, the strain point tends to become low. Therefore, it is set to 30% or less of the total amount. It is preferably 25% or less, more preferably 22% or less, still more preferably 20% or less.

When the SrO/CaO is less than 0.33, the devitrification temperature rises. Therefore, SrO/CaO is set to 0.33 or more. It is preferably 0.36 or more, more preferably 0.4 or more, still more preferably 0.45 or more. If it is more than 0.85, the coefficient of thermal expansion and the specific gravity become large. Therefore, SrO/CaO is set to 0.85 or less. It is preferably 0.8 or less, more preferably 0.75 or less, still more preferably 0.7 or less.

If SrO/(MgO+CaO) is less than 0.05, the devitrification temperature is liable to rise. It is preferably 0.05 or more, more preferably 0.1 or more, still more preferably 0.14 or more, still more preferably 0.18 or more. If it is more than 4.0, the coefficient of thermal expansion and specific gravity tend to become large. It is preferably 4.0 or less, more preferably 3.0 or less, still more preferably 2.0 or less, still more preferably 1.0 or less, and still more preferably 0.7 or less.

By (23.5 × [SiO ₂ ] + 3.5 × [Al ₂ O ₃ ] - 5 × [B ₂ O ₃ ] / / 2.1 × [MgO] + 4.2 × [CaO] + 10 × [SrO] + 12 × [BaO]) is 17 or more, and is not only a high strain point, but does not cause the glass viscosity to become too high at a temperature T ₂ of 10 ² dPa ‧ s, and does not excessively increase thermal expansion. It is preferably 17.5 or more, more preferably 18 or more, still more preferably 18.5 or more.

Further, in order to prevent the deterioration of the characteristics of the metal or oxide film provided on the glass surface during the manufacture of the panel, the glass of the present invention contains (i.e., substantially does not contain) the alkali metal oxide without exceeding the impurity level. Further, in order to make the glass easy to reuse, it is preferable to substantially contain no PbO, As ₂ O ₃ or Sb ₂ O _{3 .}

Further, for the same reason, it is preferred that substantially no P ₂ O ₅ is contained. The amount of the impurities to be mixed is preferably 23 mol ppm or less, more preferably 18 mol ppm or less, further preferably 11 mol ppm or less, and particularly preferably 5 mol ppm or less.

In addition to the above components, the alkali-free glass of the present invention may contain ZnO or Fe ₂ O ₃ in an amount of 1% or less in total, in order to improve the meltability, clarity, and moldability (floating formability) of the glass. SO ₃ , F, Cl, and SnO _{2 are} preferably 0.9% or less, more preferably 0.8% or less, still more preferably 0.7% or less. It is preferably substantially free of ZnO.

In the alkali-free glass of the present invention, in addition to the above components, in order to lower the glass melting temperature or to increase the Young's modulus, at most 1% of ZrO ₂ may be contained. If it exceeds 1%, the devitrification temperature rises. It is preferably 0.7% or less, more preferably 0.5% or less, still more preferably 0.3% or less, and particularly preferably substantially not contained.

The alkali-free glass of the present invention has a strain point of 695 ° C or higher.

Since the alkali-free glass of the present invention has a strain point of 695 ° C or higher, heat shrinkage at the time of panel production can be suppressed. Further, a laser annealing method can be applied as a method of manufacturing a p-Si TFT. It is preferably 700 ° C or higher, more preferably 705 ° C or higher, and still more preferably 710 ° C or higher.

Since the alkali-free glass of the present invention has a strain point of 695 ° C or higher, it is suitable for high strain point applications (for example, a sheet thickness of 0.7 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less, still more preferably 0.1 mm or less). A substrate for a display of a thin plate, a substrate for illumination, or the like).

When the sheet 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 is formed, the pulling speed at the time of molding tends to increase, so that the pseudo temperature of the glass tends to rise. The heat shrinkage rate of glass tends to increase. In this case, if it is a high strain point glass, the heat shrinkage rate can be suppressed.

Further, in the alkali-free glass of the present invention, the glass transition point is preferably 730 ° C or higher, more preferably 740 ° C or higher, and still more preferably 750 ° C or higher, for the same reason as the strain point.

Further, the alkali-free glass of the present invention has an average thermal expansion coefficient of 43 × 10 ^-7 /° C or less at 50 to 350 ° C, and has high thermal shock resistance, which can improve productivity in the manufacture of a panel. With respect to the alkali-free glass of the present invention, 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 .} It is more preferably 39.5 × 10 ^-7 / ° C or less, and more preferably 39 × 10 ^-7 / ° C or less.

Further, in the alkali-free glass of the present invention, the specific gravity is preferably 2.62 or less, more preferably 2.60 or less, further preferably 2.58 or less, and still more preferably 2.55 or less.

Further, in the alkali-free glass of the present invention, the temperature T ₂ at which the viscosity η is 10 ² poise (dPa ‧ s) is 1690 ° C or lower, preferably 1680 ° C or lower, more preferably 1675 ° C or lower, and further preferably 1670 ° C. Hereinafter, it is more preferably 1665 ° C or less, and therefore it is relatively easy to melt.

Further, in the alkali-free glass of the present invention, the temperature T ₄ at which the viscosity η is 10 ⁴ poise is 1310 ° C or lower, preferably 1305 ° C or lower, more preferably 1300 ° C or lower, and further preferably less than 1300 ° C and 1295 ° C. Below, below 1290 ° C, suitable for floating molding.

Further, in the alkali-free glass of the present invention, the devitrification temperature is preferably 1315 ° C or less from the viewpoint of easy float formation. It is preferably 1300 ° C or less, less than 1300 ° C, 1290 ° C or less, more preferably 1280 ° C or less. Moreover, it is preferable that the temperature T ₄ (the temperature at which the glass viscosity η becomes 10 ⁴ poise, the unit: ° C) and the devitrification temperature (T ₄ - devitrification temperature) which are the standards of the float formability or the melt formability are preferably -20 ° C or more, -10 ° C or more, further 0 ° C or more, more preferably 10 ° C or more, further preferably 20 ° C or more, and particularly preferably 30 ° C or more.

The devitrification temperature in the present specification is that the pulverized glass particles are placed in a platinum dish, heat-treated in an electric furnace controlled to a certain temperature for 17 hours, and observed by an optical microscope after heat treatment on the surface and inside of the glass. The average value of the highest temperature of the precipitated crystal and the lowest temperature of the precipitated crystal.

Further, in the alkali-free glass of the present invention, the Young's modulus is preferably 78 GPa or more, more preferably 79 GPa or more, 80 GPa or more, further 81 GPa or more, and still more preferably 82 GPa or more.

Further, in the alkali-free glass of the present invention, the photoelastic constant is preferably 31 nm/MPa/cm or less.

The stress generated by the liquid crystal display panel manufacturing step or the liquid crystal display device causes the glass substrate to have birefringence. Therefore, it has been confirmed that the black display is grayed out and the contrast of the liquid crystal display is lowered. By setting the photoelastic constant to 31 nm/MPa/cm or less, the phenomenon can be suppressed to a relatively small extent. It is preferably 30 nm/MPa/cm or less, more preferably 29 nm/MPa/cm or less, further preferably 28.5 nm/MPa/cm or less, and particularly preferably 28 nm/MPa/cm or less.

Further, in the alkali-free glass of the present invention, the photoelastic constant is preferably 23 nm/MPa/cm or more, and more preferably 25 nm/MPa/cm or more, in consideration of easiness of securing other physical properties.

Further, the photoelastic constant can be measured by a disk compression method at a measurement wavelength of 546 nm.

Further, the alkali-free glass of the present invention preferably has a small amount of shrinkage upon heat treatment. When the liquid crystal panel is manufactured, the heat treatment step is different from the color filter side on the array side. Therefore, particularly with respect to the high-definition panel, if the heat shrinkage rate of the glass is large, there is a problem that a dot shift occurs at the time of fitting. Further, the evaluation of the heat shrinkage rate can be carried out in the following order. Place the sample on the glass transfer point + After maintaining at a temperature of 100 ° C for 10 minutes, it was cooled to room temperature at a rate of 40 ° C per minute. At this time, the full length of the test sample is measured. Thereafter, the mixture was heated to 600 ° C at a temperature increase rate of 100 ° C per hour, and maintained at 600 ° C for 80 minutes, and then cooled to room temperature at a cooling rate of 100 ° C per hour, and the total length of the test sample was again counted. The ratio of the shrinkage amount of the sample before and after the heat treatment at 600 ° C to the total length of the sample before the heat treatment at 600 ° C was taken as the heat shrinkage ratio. According to the above evaluation method, the heat shrinkage ratio is preferably 200 ppm or less, more preferably 150 ppm or less, further preferably 100 ppm or less, further preferably 80 ppm or less, and particularly preferably 60 ppm or less.

[Examples]

Hereinafter, Examples 1 to 11 and 15 to 28 are examples, and examples 12 to 14 are comparative examples. The raw materials of the respective components are blended in such a manner as to have a target composition, and the platinum crucible is melted at a temperature of 1550 to 1650 °C. Regarding the particle size of the cerium in the raw material, the median diameter D ₅₀ is 26 μm, the ratio of particles having a particle diameter of 2 μm or less is less than 0.1% by volume, and the ratio of particles having a particle diameter of 100 μm or more is less than 0.1% by volume. 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 to 4 show the glass composition (unit: mole %), the coefficient of thermal expansion at 50 to 350 ° C (unit: × 10 ^-7 / ° C), strain point (unit: ° C), glass transfer point (unit: °C), specific gravity, Young's modulus (GPa) (measured by ultrasonic method), temperature T ₂ as a standard of meltability as a high-temperature viscosity value (glass viscosity η becomes a temperature of 10 ² poise, unit: °C) Temperature T ₄ (temperature at which glass viscosity η becomes 10 ⁴ poise, unit: ° C), devitrification temperature (unit: ° C), and photoelastic constant (unit: Nm/MPa/cm) (measured by a circular plate compression method at a measurement wavelength of 546 nm) and a heat shrinkage ratio (unit: ppm). The evaluation of the heat shrinkage rate was carried out in the following order. A glass plate sample (a sample having a length of 100 mm × a width of 10 mm × a thickness of 1 mm which was mirror-polished with yttrium oxide) was held at a glass transition point of +100 ° C for 10 minutes, and then cooled at a rate of 40 ° C per minute to Room temperature. At this time, the full length (length direction) L1 of the test sample is counted. Thereafter, the mixture was heated to 600 ° C at a rate of 100 ° C per hour and held at 600 ° C for 80 minutes, and cooled to room temperature at a rate of 100 ° C per hour, and the full length L 2 of the test sample was again counted. The ratio (L1-L2) of the total length before and after the heat treatment at 600 °C (L1-L2) to the total length L1 of the sample before the heat treatment at 600 °C (L1-L2) / L1 × 10 ^{6 was taken} as the heat shrinkage ratio.

Furthermore, in Tables 1 to 4, the values shown in parentheses are calculated values.

It can be seen from the table that the glass strain point of the examples is as high as 695 ° C or higher, the thermal expansion coefficient is as low as 43 × 10 ^-7 / ° C or less, and the glass viscosity is 10 ² dPa ‧ the temperature T ₂ is below 1690 ° C, so Excellent in meltability when manufacturing glass.

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. 2014-148112, filed on Jan.

[Industrial availability]

The alkali-free glass of the present invention has a high strain point and can be float-formed, and is suitable for applications such as a substrate for a display and a substrate for a photomask. Moreover, it is also suitable for applications such as substrates for information recording media and substrates for solar cells.

Claims (5)

An alkali-free glass having a strain point of 695 ° C or higher, an average thermal expansion coefficient of 50 × 350 ° C of 43 × 10 ^-7 / ° C or less, a glass viscosity of 10 ² dPa ‧ and a temperature T ₂ of 1690 ° C or less The mole % of the oxide standard means SiO ₂ 63-70, Al ₂ O ₃ 8~16, B ₂ O ₃ 1.5~Unless 4, MgO 0~8, CaO 0~20, SrO 1.5~10, BaO 0 ~0.5, and MgO+CaO is 0~28, MgO+CaO+SrO+BaO is 12~30, SrO/CaO is 0.33~0.85, (23.5×[SiO ₂ ]+3.5×[Al ₂ O ₃ ]-5 ×[B ₂ O ₃ ])/(2.1×[MgO]+4.2×[CaO]+10×[SrO]+12×[BaO]) is 17 or more. The alkali-free glass of claim 1, wherein the SrO/(MgO+CaO) is 0.05 to 4.0. The alkali-free glass of claim 1 or 2 has a Young's modulus of 78 GPa or more. The alkali-free glass according to any one of claims 1 to 3, which has a photoelastic constant of 31 nm/MPa/cm or less. The alkali-free glass according to any one of claims 1 to 4, which has a heat shrinkage ratio of 200 ppm or less.