JP6756392B2 - Alkaline-free glass - Google Patents

Description

The present invention relates to a non-alkali glass which is suitable as a substrate glass for various displays and a substrate glass for a photomask, which does not substantially contain an alkali metal oxide and can be float-formed. The non-alkali glass in the present invention is substantially free of alkaline components (ie, except for unavoidable impurities).

Conventionally, various display substrate glasses, particularly those forming a metal or oxide thin film on the surface, have been required to have the following characteristics. (1) When alkali metal oxides are contained, alkali metal ions diffuse into the thin film and deteriorate the film characteristics. Therefore, the alkali metal ions should not be substantially contained. (2) The strain point is high so that the shrinkage (heat shrinkage) due to the deformation of the glass and the structural stabilization of the glass can be minimized when exposed to a high temperature in the thin film forming step.

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

In addition to the above requirements, the following situations have been encountered in recent years.
(5) The weight of the display is required to be reduced, and the glass itself is desired to have a low density. (6) Weight reduction of the display is required, and thinning of the substrate glass is desired.

(7) In addition to the conventional amorphous silicon (a-Si) type liquid crystal displays, polycrystalline silicon (p-Si) type liquid crystal displays having a slightly higher heat treatment temperature have been manufactured (a-Si). : Approximately 350 ° C → p-Si: 350 to 550 ° C). (8) Liquid Crystal Display Fabrication Glass with a small average coefficient of thermal expansion is required in order to increase the elevating temperature rate of the heat treatment to increase productivity and thermal shock resistance.

On the other hand, as etching becomes dry, the demand for BHF resistance is becoming weaker. As the glass so far, in order to improve the BHF resistance, a glass containing 6 to 10 mol% of B ₂ O ₃ has been often used. However, B ₂ O ₃ tends to lower the distortion point. Examples of non-alkali glass that does not contain or has a low content of B ₂ O ₃ are as follows.

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 the average coefficient of thermal expansion at 50 to 350 ° C. exceeds 50 × 10 ^-7 / ° C.

In order to solve the problems in the glass described in Patent Documents 1 and 2, the non-alkali glass described in Patent Document 3 has been proposed. The non-alkali glass described in Patent Document 3 has a high distortion point, can be molded by the float method, and is said to be suitable for applications such as a display substrate and a photomask substrate.

Japanese Unexamined Patent Publication No. 4-325435 Japanese Unexamined Patent Publication No. 5-232458 Japanese Unexamined Patent Publication No. 9-263421

In recent years, high-definition small displays such as portable terminals such as smartphones have adopted a laser annealing method as a method for manufacturing high-quality p-Si TFTs, but distortion points are used to further reduce the heat shrinkage rate. High glass is required. Further, as the glass substrate becomes larger and thinner, glass having a high Young's modulus and a high specific elastic modulus (Young's modulus / density) is required.
On the other hand, from the demand in the glass manufacturing process, it is required not to raise the strain point excessively.

An object of the present invention is to solve the above-mentioned drawbacks and to provide non-alkali glass having a small coefficient of thermal expansion, a high strain point, a low photoelastic constant, a high Young's modulus, and a small thermal shrinkage.

In the present invention, the strain point is 695 ° C. or higher, the average coefficient of thermal expansion at 50 to 350 ° C. is 43 × 10 ^-7 / ° C. or lower, the photoelastic constant is 31 nm / MPa / cm or lower, and Young's modulus. Is 78 GPa or more, and the thermal shrinkage is 200 ppm or less.
SiO ₂ 64.9 to 70, Al ₂ O ₃ 8 to 16, B ₂ O ₃ 2.7 or more, MgO 0 to 7.5, CaO 3 to 20, SrO 1.5 in molar% representation based on oxides. Contains 10 and
MgO + CaO is 0 to 28, MgO + CaO + SrO + BaO is 12 to 30, SrO / CaO is 0.58 to 0.74, and so on.
(23.5 x [SiO ₂ ] + 3.5 x [Al ₂ O ₃ ] -5 x [B ₂ O ₃ ]) / (2.1 x [MgO] + 4.2 x [CaO] + 10 x [SrO] Provided is a non-alkali glass for a display having +12 × [BaO]) of 17 or more.

The non-alkali glass of the present invention is particularly suitable for a display substrate, a photomask substrate, etc. for high strain point applications, and is a glass that can be easily float-molded. The non-alkali 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. If SiO ₂ is less than 63% (mol%, the same unless otherwise specified), the strain point does not rise sufficiently, the coefficient of thermal expansion increases, and the density increases. Therefore, SiO ₂ is 63% or more. 64% or more is preferable, 65% or more is more preferable, and 66% or more is further preferable. In 70%, solubility decreases, the temperature T ₄ which is a temperature T ₂ and 10 ⁴ dPa · s glass viscosity becomes 10 ² dPa · s is increased, the liquidus temperature rises. Therefore, SiO ₂ is 70% or less. 69.5% or less is preferable, 69% or less is more preferable, and 68.5% or less is further preferable.

Al ₂ O ₃ suppresses the phase separation of glass, lowers the coefficient of thermal expansion and raises the strain point, but if it is less than 8%, this effect does not appear and other components that raise expansion will increase. As a result, the thermal expansion becomes large. Therefore, Al ₂ O ₃ is 8% or more. 9% or more, 10% or more, and further 11.1% or more is preferable. If it exceeds 16%, the solubility of the glass may be deteriorated or the devitrification temperature may be increased. Therefore, 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 dissolution reactivity of the glass and lower the devitrification temperature. In order to obtain the above effects, the content is preferably 1.6% or more, more preferably 1.7% or more, still more preferably 1.8% or more. However, if it is too large, the distortion point becomes low and the Young's modulus becomes small, so it is set to less than 4%. 3.5% or less is preferable, 3% or less is more preferable, 2.8% or less is further preferable, 2.6% or less is further preferable, and 2.5% or less is particularly preferable.

MgO has a characteristic of increasing Young's modulus while maintaining a low density without increasing expansion in alkaline earth, and can be contained because it also improves solubility. In order to obtain the above effects, the content is preferably 0.1% or more, more preferably 1% or more, still more preferably 2% or more, and particularly preferably 3% or more. However, if it is too large, the devitrification temperature rises, so the temperature should be 8% or less. Less than 8% is preferable, 7.5% or less is preferable, 7% or less is more preferable, and 6.5% or less and 6% or less are further preferable.

CaO has a characteristic of increasing Young's modulus while maintaining a low density without increasing expansion in alkaline earth, and can be contained because it also improves solubility. In order to obtain the above effects, the content is preferably 0.1% or more, more preferably 1% or more, still more preferably 3% or more, and particularly preferably 5% or more. However, if it is too much, the devitrification temperature may rise and phosphorus, which is an impurity in limestone (CaCO ₃ ), which is a CaO raw material, may be mixed in a large amount, so the content should be 20% or less. It is preferably 15% or less, more preferably 12% or less, still more preferably 10% or less.

SrO does not raise the devitrification temperature of the glass and improves the solubility, but if it is less than 1.5%, this effect is not sufficiently exhibited. Therefore, SrO is 1.5% or more. 2% or more is preferable, 2.5% or more is more preferable, and 3% or more is further preferable. However, if it exceeds 10%, the expansion coefficient may increase. Therefore, SrO is 10% or less. 8% or less is preferable, 6% or less is more preferable, and 5% or less is further preferable.

BaO can be contained to improve solubility. However, if it is too large, the expansion and density of the glass will be excessively increased, so the content should be 0.5% or less. Considering the environmental load, it is preferable that BaO is substantially not contained (that is, except for unavoidable impurities).

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 specific gravity will be large. Therefore, it should be 28% or less. It is preferably 24% or less, more preferably 20% or less, and even more preferably 16% or less.

The total amount of MgO, CaO, SrO, and BaO is 12% or more because the temperature T _{2 at} which the glass viscosity becomes 10 ² dPa · s is not too high. 14% or more is preferable, 16% or more is more preferable, and 17% or more is further preferable. If it is more than 30%, the distortion point tends to be low. Therefore, the total amount should be 30% or less. 25% or less is preferable, 22% or less is more preferable, and 20% or less is further preferable.

When SrO / CaO is smaller than 0.33, the devitrification temperature rises. Therefore, SrO / CaO is set to 0.33 or more. 0.36 or more is preferable, 0.4 or more is more preferable, and 0.45 or more is further preferable. If it is larger than 0.85, the coefficient of thermal expansion and specific gravity will be large. Therefore, SrO / CaO is set to 0.85 or less. It is preferably 0.8 or less, more preferably 0.75 or less, and even more preferably 0.7 or less.
When SrO / (MgO + CaO) is smaller than 0.05, the devitrification temperature tends to rise. 0.05 or more is preferable, 0.1 or more is more preferable, 0.14 or more is further preferable, and 0.18 or more is further preferable. If it is larger than 4.0, the coefficient of thermal expansion and specific gravity tend to be large. 4.0 or less is preferable, 3.0 or less is more preferable, 2.0 or less is further preferable, 1.0 or less is further preferable, and 0.7 or less is particularly preferable.

(23.5 x [SiO ₂ ] + 3.5 x [Al ₂ O ₃ ] -5 x [B ₂ O ₃ ]) / (2.1 x [MgO] + 4.2 x [CaO] + 10 x [SrO] Since +12 × [BaO]) is 17 or more, the temperature T ₂ at which the glass viscosity becomes 10 ² dPa · s is not made too high and the thermal expansion is not made too large, even though the strain point is high. 17.5 or more is preferable, 18 or more is more preferable, and 18.5 or more is further preferable.

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

Further, for the same reason, it is preferable that P ₂ O ₅ is substantially not contained. The amount mixed as an impurity 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 non-alkali glass of the present invention contains ZnO, Fe ₂ O ₃ , SO ₃ , F, Cl, and SnO ₂ in total in order to improve the solubility, clarity, and moldability (float moldability) of the glass. It can contain 1% or less, preferably 0.9% or less, more preferably 0.8% or less, still more preferably 0.7% or less. It is preferable that ZnO is substantially not contained.

In addition to the above components, the non-alkali glass of the present invention may contain ZrO _{2 up} to 1% in order to lower the glass melting temperature or improve Young's modulus. If it exceeds 1%, the devitrification temperature rises. It is preferably 0.7% or less, more preferably 0.5% or less, further preferably 0.3% or less, and particularly preferably not substantially contained.

The non-alkali glass of the present invention has a strain point of 695 ° C. or higher.
Since the non-alkali glass of the present invention has a strain point of 695 ° C. or higher, heat shrinkage during panel manufacturing can be suppressed. Further, as a method for manufacturing a p-Si TFT, a method by laser annealing can be applied. 700 ° C. or higher is preferable, 705 ° C. or higher is more preferable, and 710 ° C. or higher is even more preferable.
Since the non-alkali glass of the present invention has a strain point of 695 ° C. or higher, it is used for high strain point applications (for example, a plate thickness of 0.7 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less, still more preferably. It is suitable for a thin display substrate or an illumination substrate of 0.1 mm or less.
In the molding of plate glass with 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 molding tends to be faster, so that the virtual temperature of the glass Is likely to increase and the heat shrinkage rate of the glass is likely to increase. In this case, if the glass has a high strain point, the heat shrinkage rate can be suppressed.

Further, the non-alkali glass of the present invention has a glass transition point of preferably 730 ° C. or higher, more preferably 740 ° C. or higher, and further preferably 750 ° C. or higher for the same reason as the strain point.

Further, the non-alkali glass of the present invention has an average coefficient of thermal expansion of 43 × 10 ^-7 / ° C. or less at 50 to 350 ° C., has high thermal shock resistance, and can increase productivity during panel manufacturing. In the non-alkali glass of the present invention, the average coefficient of thermal expansion 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. It is / ° C. or lower, more preferably 39.5 × 10 ^-7 / ° C. or lower, and particularly preferably 39 × 10 ^-7 / ° C. or lower.

Further, the non-alkali glass of the present invention has a specific gravity of preferably 2.62 or less, more preferably 2.60 or less, still more preferably 2.58 or less, still more preferably 2.55 or less.

Further, the non-alkali glass of the present invention has a 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. Since the temperature is below ° C., more preferably below 1665 ° C., dissolution is relatively easy.

Further, the alkali-free glass of the present invention the temperature T ₄ at which the viscosity η is 10 ⁴ poise 1310 ° C. or less, preferably 1305 ° C. or less, more preferably 1300 ° C. or less, more preferably less than 1300 ° C., 1295 ° C. or less, 1290 It is below ° C and suitable for float molding.
Further, the non-alkali glass of the present invention preferably has a devitrification temperature of 1315 ° C. or lower because molding by the float method is easy. It is preferably 1300 ° C. or lower, less than 1300 ° C., 1290 ° C. or lower, and more preferably 1280 ° C. or lower. Moreover, (the temperature at which glass viscosity η is 10 ⁴ poise, unit: ° C.) temperature T ₄ which is a float moldability and fusion moldability measure the difference between the devitrification temperature (T ₄ - devitrification temperature), preferably Is −20 ° C. or higher, −10 ° C. or higher, further 0 ° C. or higher, more preferably 10 ° C. or higher, still more preferably 20 ° C. or higher, and particularly preferably 30 ° C. or higher.
The devitrification temperature in the present specification is obtained by placing crushed glass particles in a platinum dish, heat-treating the glass particles in an electric furnace controlled to a constant temperature for 17 hours, and observing the glass surface and an optical microscope after the heat treatment. It is the average value of the maximum temperature at which crystals precipitate inside and the minimum temperature at which crystals do not precipitate.

Further, the non-alkali glass of the present invention preferably has a Young's modulus of 78 GPa or more, more preferably 79 GPa or more, 80 GPa or more, further 81 GPa or more, and further preferably 82 GPa or more.

Further, the non-alkali glass of the present invention preferably has a photoelastic constant of 31 nm / MPa / cm or less.
Due to the stress generated during the process of manufacturing the liquid crystal display panel or the use of the liquid crystal display device, the glass substrate has birefringence, so that the black display becomes gray and the contrast of the liquid crystal display is lowered. By setting the photoelastic constant to 31 nm / MPa / cm or less, this phenomenon can be suppressed to a small value. It is preferably 30 nm / MPa / cm or less, more preferably 29 nm / MPa / cm or less, still more preferably 28.5 nm / MPa / cm or less, and particularly preferably 28 nm / MPa / cm or less.
Further, the non-alkali 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, in consideration of the ease of securing other physical properties.
The photoelastic constant can be measured at a measurement wavelength of 546 nm by the disk compression method.

Further, the non-alkali glass of the present invention preferably has a small amount of shrinkage during heat treatment. In liquid crystal panel manufacturing, the heat treatment process differs between the array side and the color filter side. Therefore, especially in a high-definition panel, when the heat shrinkage rate of the glass is large, there is a problem that the dots are displaced at the time of fitting. The evaluation of the heat shrinkage rate can be measured by the following procedure. The sample is held at a glass transition point + 100 ° C. for 10 minutes and then cooled to room temperature at 40 ° C. per minute. Here, the total length of the sample is measured. Then, the sample is heated to 600 ° C. at a heating rate of 100 ° C. per hour, held at 600 ° C. for 80 minutes, cooled to room temperature at a temperature decreasing rate of 100 ° C. per hour, and the total length of the sample is measured again. The ratio of the amount of shrinkage 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. is defined as the heat shrinkage rate. In the above evaluation method, the heat shrinkage rate is preferably 200 ppm or less, more preferably 150 ppm or less, further preferably 100 ppm or less, further 80 ppm or less, and particularly preferably 60 ppm or less.

In the following, Examples 7, 19, 21-23, 25-28 are Examples, and Examples 1-6, 8-18, 20, 24 are Comparative Examples. The raw materials of each component were prepared so as to have a target composition, and melted at a temperature of 1550 to 1650 ° C. using a platinum crucible. Regarding the particle size of silica sand in the raw material, the median particle size D ₅₀ was 26 μm, the proportion of particles having a particle size of 2 μm or less was less than 0.1% by volume, and the proportion of particles having a particle size of 100 μm or more was less than 0.1% by volume. .. For melting, the glass was homogenized by stirring with platinum starla. Next, the molten glass was poured out, molded into a plate shape, and then slowly cooled.

Tables 1 to 4 show the glass composition (unit: mol%), the thermal expansion coefficient at 50 to 350 ° C (unit: × 10 ^-7 / ° C), the strain point (unit: ° C), and the glass transition point (unit: ° C). ), Specific gravity, Young ratio (GPa) (measured by ultrasonic method), High temperature viscosity value, temperature T ₂ (temperature at which glass viscosity η is 10 ² poisons, unit: ° C), and float moldability and the temperature T ₄ which is a measure of the fusion formability (glass viscosity η is 10 ⁴ poise temperature, unit: ° C.), devitrification temperature (unit: ° C.), photoelastic constant (unit: nm / MPa / cm ) (Measured at a measurement wavelength of 546 nm by the disk compression method) and the heat shrinkage rate (unit: ppm) are shown. The heat shrinkage rate was evaluated by the following procedure. A glass plate sample (a sample of 100 mm in length × 10 mm in width × 1 mm in thickness) 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. Then, the sample was 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 was measured again. The ratio (L1-L2) / L1 × 10 ⁶ of the difference in total length before and after the heat treatment at 600 ° C. and the total length L1 of the sample before the heat treatment at 600 ° C. was defined as the heat shrinkage ratio.
In Tables 1 to 4, the values shown in parentheses are calculated values.

As is clear from the table, all of the glasses of the examples have a high strain point of 695 ° C. or higher, a low coefficient of thermal expansion of 43 × 10 ^-7 / ° C. or lower, and a temperature T at which the glass viscosity is 10 ² dPa · s. _{Since 2} is 1690 ° C. or lower, the solubility is excellent at the time of glass production.

The non-alkali glass of the present invention has a high distortion point and can be molded by the float method, and is suitable for applications such as a display substrate and a photomask substrate. It is also suitable for applications such as information recording medium substrates and solar cell substrates.

Claims (2)

The strain point is 695 ° C or higher, the average coefficient of thermal expansion at 50 to 350 ° C is 43 × 10 ^-7 / ° C or lower, the photoelastic constant is 31 nm / MPa / cm or lower, and the Young's modulus is 82 GPa or higher. , The coefficient of thermal shrinkage is 200 ppm or less,
In molar% representation based on oxides, SiO ₂ 64.9 to 70, Al ₂ O ₃ 8 to 16, B ₂ O ₃ 2.7 or more and less than 4 , MgO 0 to 7.5, CaO 3 to 20, SrO 1 .5-10 , containing BaO 0-0.5,
MgO + CaO is 0 to 28, MgO + CaO + SrO + BaO is 12 to 30, SrO / CaO is 0.58 to 0.74, and so on.
(23.5 x [SiO ₂ ] + 3.5 x [Al ₂ O ₃ ] -5 x [B ₂ O ₃ ]) / (2.1 x [MgO] + 4.2 x [CaO] + 10 x [SrO] +12 x [BaO]) is 17 or more, non-alkali glass for display. The non-alkali glass for a display according to claim 1, wherein SrO / (MgO + CaO) is 0.05 to 4.0.