JP6631942B2 - Alkali-free glass plate - Google Patents

Description

  The present invention relates to an alkali-free glass, particularly to an alkali-free glass suitable for an organic EL display.

  2. Description of the Related Art Electronic devices such as organic EL displays are thin and excellent in displaying moving images and have low power consumption, and thus are used for applications such as displays of mobile phones.

A glass plate is widely used as a substrate for an organic EL display. The glass plate for this purpose is mainly required to have the following characteristics. In particular, the following required characteristics (2) are regarded as important.
(1) In order to prevent a situation in which alkali ions are diffused into a semiconductor substance formed in a heat treatment step, the semiconductor substance does not substantially contain an alkali metal oxide.
(2) The strain point is high in the manufacturing process of the p-Si TFT in order to reduce the thermal shrinkage of the glass plate.
(3) In order to reduce the cost of the glass plate, it must be excellent in productivity, especially excellent in devitrification resistance and melting property.
(4) High chemical resistance so as not to be deteriorated by various chemicals such as acids and alkalis used in the photo-etching step, especially hydrofluoric acid-based chemicals.
(5) When the glass plate becomes large and thin, the Young's modulus and Young's modulus / density (specific Young's modulus) are reduced in order to reduce the amount of deflection (oscillation width) of the glass plate during the manufacturing process of the display. Be high.

Japanese Patent No. 3804112

A panel maker of an organic EL display manufactures a plurality of devices on a large glass plate formed by a glass maker, and cuts and divides each device to reduce costs (so-called multi-paneling). ). In this multi-chamfering process, after the glass plate is cut, two glass plates are attached to each other or cut after the attachment to complete the organic EL display. In many cases, it is not applied, and the post-process flows in a state where the cut surface remains as it is, or it becomes a final product. Under such circumstances, it is important to improve the crack resistance when performing multi-panning.

Further, according to the detailed experiments by the present inventors, it is effective to reduce the content of B ₂ O ₃ in the glass composition in order to satisfy the above-mentioned requirement (2). However, when the content of B ₂ O ₃ in the glass composition is reduced, the crack resistance tends to decrease. Further, the chemical resistance and the melting property are also liable to be lowered, and it is difficult to satisfy the above-mentioned properties (3) and (4).

Therefore, the present invention has been made in view of the above circumstances, and the technical problem is that even when the content of B ₂ O ₃ in the glass composition is small, the glass composition can have both crack resistance and chemical resistance. The idea is to create alkali-free glass.

As a result of repeating various experiments, the present inventors have found that the above technical problem can be solved by strictly regulating the glass composition range of the alkali-free glass and regulating the glass properties to a predetermined range. It is proposed as an invention. That is, the alkali-free glass of the present invention has, as a glass composition, 66 to 78% of SiO ₂ , 8 to 15% of Al ₂ O ₃ , 0 to 1.8% of B ₂ O ₃ , and 0 to 8% of MgO in mol%. , CaO 1 to 15%, SrO 0 to 8%, and BaO 1 to 8%, containing substantially no alkali metal oxide and having a strain point higher than 725 ° C. Here, “substantially contains no alkali metal oxide” means that the content of the alkali metal oxide (Li ₂ O, Na ₂ O, K ₂ O) in the glass composition is 0.5 mol% or less. Refers to the case. "Strain point" refers to a value measured based on the method of ASTM C336.

Second, the alkali-free glass of the present invention preferably has a B ₂ O ₃ content of less than 0.1 mol%.

Thirdly, the alkali-free glass of the present _invention, it is preferable that the content of B 2 _{O 3} is less than 0.1 mol%.

Fourth, the alkali-free glass of the present invention preferably further contains 0.001 to 1 mol% of SnO ₂ as a glass composition.

  Fifth, the alkali-free glass of the present invention preferably has a Young's modulus of more than 78 GPa. Here, the “Young's modulus” can be measured by the bending resonance method.

Sixth, the alkali-free glass of the present invention preferably has a specific Young's modulus greater than 29.5 GPa / g · cm ⁻³ . Here, the “density” can be measured by the Archimedes method.

  Seventh, the alkali-free glass of the present invention preferably has a liquidus temperature lower than 1260 ° C. Here, the “liquidus temperature” was determined by passing through a standard sieve 30 mesh (500 μm), placing the glass powder remaining on the 50 mesh (300 μm) in a platinum boat, and holding the glass powder in a temperature gradient furnace for 24 hours. Can be calculated by measuring the temperature at which

Eighth, the alkali-free glass of the present ^invention, it is preferable that the temperature at ^{10 2.5} poise is 1720 ° C. or less. Here, the "temperature at 10 ^2.5 poise" can be measured by a platinum ball pulling method.

Ninth, the alkali-free glass of the present invention preferably has a viscosity at the liquidus temperature (liquidus viscosity) of ^104.8 poise or more. Here, the “viscosity at the liquidus temperature” can be measured by a platinum ball pulling-up method.

  Tenth, it is preferable that the alkali-free glass of the present invention is formed by an overflow downdraw method.

  Eleventh, the alkali-free glass of the present invention is preferably used for an organic EL device, particularly for an organic EL display.

  The reasons for limiting the content of each component as described above in the alkali-free glass of the present invention are described below. In the description of the content of each component,% represents mol%.

SiO ₂ is a component that forms a glass skeleton. The content of SiO ₂ is 66-78%, preferably 69-76%, 70-75%, 71-74%, especially 72-73%. If the content of SiO ₂ is too small, it becomes difficult to increase the strain point, and the density becomes too high. On the other hand, if the content of SiO ₂ is too large, the high-temperature viscosity increases, the meltability tends to decrease, and devitrified crystals such as cristobalite precipitate, and the liquidus temperature tends to increase.

Al ₂ O ₃ is a component that forms a glass skeleton, is a component that increases the strain point, and is a component that further suppresses phase separation. The content of Al ₂ O ₃ is 8-15%, preferably 9-14%, the 9.5 to 13% 10 to 12%, in particular 10.5 to 11.5%. If the content of Al ₂ O ₃ is too small, the strain point tends to decrease, and the glass tends to undergo phase separation. On the other hand, if the content of Al ₂ O ₃ is too large, devitrified crystals such as mullite and anorthite are precipitated, and the liquidus temperature tends to increase.

If the content of B ₂ O ₃ is too large, the crack point and the chemical resistance are liable to be reduced, in addition to the significant decrease in the strain point. Therefore, the content of B ₂ O ₃ is 1.8% or less, preferably 1.5% or less, 1% or less, less than 1%, 0.7% or less, particularly 0.6% or less. On the other hand, if a small amount of B ₂ O ₃ is introduced, crack resistance is improved, and meltability and devitrification resistance are improved. Therefore, the content of B ₂ O ₃ is preferably 0.01% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, particularly 0.5% or more. is there.

  MgO is a component that lowers high-temperature viscosity and enhances meltability. The content of MgO is 0-8%, preferably 0-5%, 0-4%, 0.01-3.5%, 0.1-3.2%, 0.5-3%, especially 1 to 2.7%. If the content of MgO is too large, the strain point tends to decrease.

The content of B ₂ O ₃ + MgO (the total amount of B ₂ O ₃ and MgO) is preferably 6% or less, 0.1 to 5%, 1 to 4.5%, and especially 2% from the viewpoint of increasing the strain point. ~ 4%. If the content of B ₂ O ₃ + MgO is too small, the meltability, crack resistance, and chemical resistance are likely to decrease.

The molar ratio B ₂ O ₃ / MgO is preferably 0.3 or less, 0.25 or less, 0.22 or less, 0.01 to 0.2, 0.05 to 0.18, particularly 0.1 to 0. Seventeen. This makes it easier to control the devitrification resistance to an appropriate range.

  CaO is a component that lowers the high-temperature viscosity and significantly enhances the meltability without lowering the strain point. In addition, CaO is a component that reduces the raw material cost because the introduced raw material is relatively inexpensive among alkaline earth metal oxides. The content of CaO is 1 to 15%, preferably 3 to 12%, 4 to 10%, 4.7 to 8.9%, particularly 5.8 to 8.5%. If the content of CaO is too small, it becomes difficult to enjoy the above-mentioned effects. On the other hand, if the content of CaO is too large, the coefficient of thermal expansion becomes too high, and the component balance of the glass composition is impaired, so that the glass is easily devitrified.

  SrO is a component that suppresses phase separation and enhances devitrification resistance. Further, it is a component that lowers the high-temperature viscosity and increases the meltability without lowering the strain point, and also suppresses the rise in the liquidus temperature. The content of SrO is 0 to 8%, preferably 0.1 to 6%, 0.5 to 5%, 0.8 to 4%, particularly 1 to 3%. If the content of SrO is too small, it is difficult to enjoy the effect of suppressing the phase separation and the effect of increasing the devitrification resistance. On the other hand, if the content of SrO is too large, the component balance of the glass composition is impaired, and strontium silicate-based devitrified crystals are likely to precipitate.

  BaO is a component that significantly enhances the devitrification resistance among alkaline earth metal oxides. The content of BaO is 1 to 8%, preferably 2 to 7%, 3 to 6%, 3.5 to 5.5%, especially 4 to 5%. When the content of BaO is too small, the liquidus temperature increases, and the devitrification resistance tends to decrease. On the other hand, if the content of BaO is too large, the component balance of the glass composition is impaired, and devitrified crystals containing BaO tend to precipitate.

  The RO (total amount of MgO, CaO, SrO and BaO) is preferably 12 to 18%, 13 to 17.5%, 13.5 to 17%, particularly 14 to 16.8%. If the RO content is too small, the meltability tends to decrease. On the other hand, if the content of RO is too large, the component balance of the glass composition is impaired, and the devitrification resistance is liable to decrease.

  The molar ratio MgO / RO is preferably 0.3 or less, 0.25 or less, 0.22 or less, 0.01 to 0.2, 0.05 to 0.18, particularly 0.1 to 0.17. . In this case, it is easy to suppress a decrease in strain point, crack resistance, and chemical resistance.

  The molar ratio CaO / RO is preferably 0.8 or less, 0.7 or less, 0.1 to 0.7, 0.2 to 0.65, 0.3 to 0.6, particularly 0.45 to 0.5. 55. This makes it easier to optimize the devitrification resistance and the meltability.

  The molar ratio SrO / RO is preferably 0.4 or less, 0.35 or less, 0.3 or less, 0.01 to 0.2, 0.03 to 0.18, particularly 0.05 to 0.15. . This makes it easier to suppress the precipitation of strontium silicate-based devitrified crystals.

  The molar ratio BaO / RO is preferably 0.5 or less, 0.4 or less, 0.1 to 0.37 or less, 0.2 to 0.35, 0.24 to 0.32, particularly 0.27 to 0. .3. By doing so, it becomes easy to increase the devitrification resistance while improving the melting property.

  In addition to the above components, for example, the following components may be added to the glass composition. The content of other components other than the above components is preferably 10% or less, particularly 5% or less in terms of the total amount, from the viewpoint of properly enjoying the effects of the present invention.

  ZnO is a component that enhances the melting property. However, when ZnO is contained in a large amount, the glass is easily devitrified and the strain point is easily lowered. The content of ZnO is preferably 0 to 5%, 0 to 3%, 0 to 0.5%, particularly preferably 0 to 0.3%, and it is desirable that ZnO is not substantially contained. Here, "substantially contains no ZnO" refers to a case where the content of ZnO in the glass composition is 0.2% or less.

P ₂ O ₅ is a component that increases the strain point. However, when P ₂ O ₅ is contained in a large amount, the glass is likely to be phase-separated. The content of P ₂ O ₅ is preferably 0 to 1.5%, 0 to 1.2%, and particularly preferably 0 to 1%.

TiO ₂ is a component that lowers high-temperature viscosity and enhances meltability, and is a component that suppresses solarization. However, when a large amount of TiO ₂ is contained, glass is colored and transmittance is easily reduced. . Thus, the content of TiO ₂ is 0-3%, 0 to 1% 0 to 0.1%, especially 0 to 0.02% is preferable.

Y ₂ O ₃ , Nb ₂ O ₅ , and La ₂ O ₃ have a function of increasing a strain point, a Young's modulus, and the like. However, when the content of these components is too large, the density and the raw material cost tend to increase. _Thus, the content of _{Y 2 O 3, Nb 2 O} 5, La 2 O 3 , respectively 0-3%, 0 to 1%, in particular from 0 to 0.1% are preferred.

SnO ₂ is a component that has a good fining action in a high temperature range, is a component that increases the strain point, and is a component that lowers the viscosity at high temperature. The content of SnO ₂ is preferably 0 to 1%, 0.001 to 1%, 0.05 to 0.5%, and particularly preferably 0.1 to 0.3%. If the content of SnO ₂ is too large, a devitrified crystal of SnO ₂ tends to precipitate. If the content of SnO ₂ is less than 0.001%, it is difficult to obtain the above effects.

SnO ₂ is suitable as a fining agent, but fining agents other than SnO ₂ may be used as long as glass properties are not significantly impaired. Specifically, As ₂ O ₃ , Sb ₂ O ₃ , CeO ₂ , F ₂ , Cl ₂ , SO ₃ , and C may be added in a total amount of, for example, 1%, and a metal powder such as Al or Si may be added. It may be added in a total amount of, for example, 1%.

As ₂ O ₃ and Sb ₂ O ₃ are excellent in clarity, but are preferably not introduced as much as possible from an environmental point of view. Furthermore, when As ₂ O ₃ is contained in a large amount in glass, the solarization resistance tends to decrease, so the content is preferably 0.5% or less, particularly preferably 0.1% or less, and substantially, It is desirable not to contain. Here, “substantially contains no As ₂ O ₃ ” refers to a case where the content of As ₂ O ₃ in the glass composition is less than 0.05%. Further, the content of Sb ₂ O ₃ is preferably 1% or less, particularly preferably 0.5% or less, and it is desirable that the content is not substantially contained. Herein, the phrase "substantially free of _Sb 2 _{O 3",} the content of _Sb 2 _{O 3} in the glass composition refers to a case of less than 0.05%.

Cl ₂ has the effect of accelerating the melting of alkali-free glass. If Cl ₂ is added, the melting temperature can be lowered, and the action of the fining agent is promoted. As a result, the melting cost can be reduced while the melting cost can be reduced. The service life of the manufacturing kiln can be extended. However, if the content of Cl ₂ is too large, the strain point decreases. Therefore, the content of Cl ₂ is preferably 0.5% or less, particularly preferably 0.1% or less. In addition, as a raw material for introducing Cl ₂ , a chloride of an alkaline earth metal oxide such as strontium chloride, aluminum chloride, or the like can be used.

  In the alkali-free glass of the present invention, the strain point is higher than 725 ° C, preferably 730 ° C or higher, more preferably 735 ° C or higher, and further preferably 740 ° C or higher. In this way, the heat shrinkage of the glass plate can be suppressed in the manufacturing process of the p-Si TFT.

  The Young's modulus is more than 78 GPa, 78.5 GPa or more, 79 GPa or more, 79.5 GPa or more, and particularly preferably 79.7 Pa or more. In this case, since the bending of the glass plate can be suppressed, the glass plate can be easily handled in a display manufacturing process or the like.

Young's modulus / density 29.5GPa / g · ^{cm -3} greater, 29.8GPa / g · ^{cm -3} or higher, 30.1
GPa / g · ^{cm -3} or more, 30.3GPa / g · ^{cm -3} or more, particularly 30.5GPa / g · ^{cm -3} or more. When the value of the Young's modulus / density is increased, the amount of bending of the glass plate can be significantly suppressed.

  The liquidus temperature is less than 1260 ° C, 1250 ° C or less, particularly preferably 1240 ° C or less. This makes it easier to prevent a situation in which devitrified crystals are generated during the production of glass and the productivity is reduced. Further, since the glass sheet can be easily formed by the overflow down draw method, the surface quality of the glass sheet can be improved, and the manufacturing cost of the glass sheet can be reduced. The liquidus temperature is an index of devitrification resistance, and the lower the liquidus temperature, the better the devitrification resistance.

10 ^2.5 Temperature in poise 1720 ° C. or less, 1700 ° C. or less, 1690 ° C. or less, particularly preferably 1680 ° C.. When the temperature is increased at 10 ^2.5 poise, solubility, it becomes difficult to ensure clarity, the manufacturing cost of the glass plate is high.

Viscosity ^{10 4.8} poise or more at the liquidus ^{temperature, 10 5.0} poise or ^{more, 10 5.2} poise or higher, particularly preferably at least ^{10 5.3} poise. This makes it difficult to cause devitrification at the time of molding, so that the glass sheet can be easily formed by the overflow down draw method, and as a result, the surface quality of the glass sheet can be improved, and the production of the glass sheet can be improved. The cost can be reduced. The liquidus viscosity is an index of moldability, and the higher the liquidus viscosity, the better the moldability.

  In the alkali-free glass of the present invention, when the β-OH value is reduced, the strain point can be increased. β-OH value is preferably 0.5 / mm or less, 0.45 / mm or less, 0.4 / mm or less, 0.35 / mm or less, 0.3 / mm or less, particularly 0.25 / mm or less. It is. If the β-OH value is too large, the strain point tends to decrease. If the β-OH value is too small, the meltability tends to decrease. Therefore, the β-OH value is preferably 0.01 / mm or more, particularly 0.05 / mm or more.

The following method is mentioned as a method of lowering the β-OH value. (1) Select a raw material having a low water content. (2) A component (such as Cl or SO ₃ ) for lowering the β-OH value is added to glass. (3) Reduce the amount of water in the furnace atmosphere. (4) performing the _{N 2} bubbling in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of the molten glass. (7) The electric melting method is adopted.

Here, the “β-OH value” indicates a value obtained by measuring the transmittance of glass using FT-IR and using the following equation.
β-OH value = (1 / X) log (T ₁ / T ₂ )
X: Glass wall thickness (mm)
T ₁ : transmittance (%) at reference wavelength 3846 cm ⁻¹
T ₂ : minimum transmittance (%) around a hydroxyl group absorption wavelength of 3600 cm ⁻¹

  The alkali-free glass of the present invention is preferably formed by an overflow down draw method. In the overflow down draw method, the molten glass overflows from both sides of the heat-resistant gutter-like structure, and the overflowed molten glass is joined at the lower end of the gutter-like structure and stretched downward to produce a glass sheet. Is the way. In the overflow down draw method, the surface to be the surface of the glass sheet is formed in a free surface state without contacting the gutter-like refractory. For this reason, a glass plate which is not polished and has good surface quality can be manufactured at low cost. The structure and material of the gutter-like structure used in the overflow downdraw method are not particularly limited as long as desired dimensions and surface accuracy can be achieved. Further, the method of applying a force when performing downward stretch molding is not particularly limited. For example, a method in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with glass, or a method in which a plurality of pairs of heat-resistant rolls are brought into contact only near the end face of the glass. You may employ the method of extending | stretching.

  In addition to the overflow downdraw method, a glass plate can be formed by, for example, a downdraw method (such as a slot down method) or a float method.

  The alkali-free glass of the present invention is preferably used for an organic EL device, particularly for an organic EL display. A panel maker of an organic EL display manufactures a plurality of devices on a large glass plate formed by a glass maker, and cuts and divides each device to reduce costs (so-called multi-paneling). ). Particularly in TV applications, the devices themselves are becoming larger, and large-sized glass sheets are required to obtain multiple devices. Since the alkali-free glass of the present invention has a low liquidus temperature and a high liquidus viscosity, it is easy to form a large glass plate, and can satisfy such requirements.

  In the alkali-free glass of the present invention, the thickness (plate thickness) is preferably 0.7 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, and particularly preferably 0.05 to 0.1 mm. The smaller the thickness, the easier it is to make the display lighter and thinner and more flexible.

  Hereinafter, the present invention will be described based on examples. However, the following embodiments are merely examples. The present invention is not limited to the following examples.

  Tables 1 to 3 show Examples (Sample Nos. 1 to 14) of the present invention and Comparative Examples (Sample Nos. 15 to 17).

First, a glass batch prepared by mixing glass raw materials so as to have the glass composition shown in the table was put in a platinum crucible and then melted at 1600 to 1650 ° C. for 24 hours. Upon melting the glass batch, the mixture was stirred using a platinum stirrer to homogenize. Next, the molten glass was poured out onto a carbon plate, formed into a plate shape, and then gradually cooled at a temperature near the annealing point for 30 minutes. For each sample obtained, the density, the average coefficient of thermal expansion CTE in the temperature range of 30 to 380 ° C., Young's modulus, the Young's modulus / density, strain point Ps, the annealing point Ta, the softening point Ts, the hot viscosity of 10 ⁴ poises temperature was evaluated temperature, the temperature in the high temperature viscosity of ^{10 2.5} poises, liquidus temperature TL, and viscosity at the liquidus temperature (liquidus viscosity _{log 10 ηTL)} in high temperature viscosity 10 ³ poise.

  The density is a value measured by the well-known Archimedes method.

  The average coefficient of thermal expansion CTE in the temperature range of 30 to 380 ° C is a value measured by a dilatometer.

  The Young's modulus is a value measured by a bending resonance method.

  The Young's modulus / density is a value obtained by dividing the Young's modulus measured by the bending resonance method by the density measured by the Archimedes method.

  The strain point Ps, annealing point Ta, and softening point Ts are values measured based on the method of ASTM C336.

High temperature viscosity 10 ⁴ poises, 10 ^{3 poise,} temperature at ^{10 2.5} poise is a value measured by a platinum ball pulling method.

  The liquidus temperature TL is determined by passing through a standard sieve 30 mesh (500 μm), placing the glass powder remaining on the 50 mesh (300 μm) in a platinum boat, and holding the glass powder in a temperature gradient furnace for 24 hours to obtain a temperature at which crystals precipitate. Is the value measured. The viscosity at the liquidus temperature is a value measured by a platinum ball pulling-up method.

The crack resistance was evaluated as follows. First, each sample is placed on a stage of a Vickers hardness meter in a thermo-hygrostat kept at a humidity of 30% and a temperature of 25 ° C., and a Vickers indenter (diamond-shaped diamond indenter) is placed on a glass surface (optically polished surface). Press for 15 seconds with various loads. Next, the number of cracks generated from the four corners of the indentation up to 15 seconds after the unloading is counted, and the ratio to the maximum number of cracks (four) is determined to be the crack occurrence rate. The crack occurrence rate was measured 20 times under the same load, and the average value was obtained. Finally, the load at which the crack occurrence rate becomes 50% is defined as a crack resistance value,
Those having a crack resistance of 140 gf or more were evaluated as "O", and those having a crack resistance of less than 140 gf were evaluated as "X".

The chemical resistance was evaluated as follows. First, both surfaces of each sample were optically polished, a part was masked, and then immersed in a 63BHF solution (HF: 6% by mass, NH ₄ F: 30% by mass) at 20 ° C. for 30 minutes. After immersion, the mask is removed, and the level difference between the mask portion and the eroded portion is measured with a surface roughness meter, and the value is defined as the erosion amount. If the erosion amount is 8.0 μm or less, “○” indicates that the erosion amount exceeds 8.0 μm. Was evaluated as "x".

  The alkali-free glass of the present invention is not limited to a glass plate for a flat panel display such as a liquid crystal display and an organic EL display, but also a cover glass for an image sensor such as a charge-coupled device (CCD) and a 1 × proximity solid-state imaging device (CIS). It can be suitably used for glass plates and cover glasses for solar cells, glass plates for organic EL lighting, and the like.

Claims (11)

As a glass composition, 66 to 78% of SiO _2, 11.82 to 15% of Al ₂ O _3, 0.1 to 1.8% of B ₂ O ₃ , 0 to 5% of MgO, and B ₂ O ₃ + MgO in mol%. 0.1~6%, CaO 5.48 ~15%, SrO 0~8%, BaO 1~8%, Y 2 O 3 0~1%, containing 2 O 3 0~1% _La, the molar ratio B ₂ O ₃ / MgO is 0.39 or less, molar ratio CaO / (MgO + CaO + SrO + BaO) is 0.36 to 0.52, molar ratio SrO / (MgO + CaO + SrO + BaO) is 0.15 or less, and substantially alkali metal not containing an oxide, a strain point higher than 725 ° C., non-alkali glass plate, wherein the viscosity at the liquidus temperature is 10 ^4.8 poise or higher. Alkali-free glass plate according to claim 1, the content of B ₂ O _3, characterized in that 0.5 mol% or more.   The alkali-free glass plate according to claim 1 or 2, wherein the content of BaO is 3 mol% or more. As a glass composition, further, the alkali-free glass plate according to claim 1, characterized in that it comprises an SnO ₂ 0.001 to 1 mol%.   The non-alkali glass plate according to any one of claims 1 to 4, wherein the Young's modulus is greater than 78 GPa. The alkali-free glass plate according to any one of claims 1 to 5, wherein Young's modulus / density is larger than 29.5 GPa / g · cm ^-3 .   The alkali-free glass plate according to any one of claims 1 to 6, wherein the liquidus temperature is lower than 1260 ° C. The alkali-free glass plate according to any one of claims 1 to 7, wherein the temperature at 10 ^2.5 poise is 1720 ° C or lower. Alkali-free glass plate according to claim 1 having a viscosity at the liquidus temperature is equal to or is 10 ^5.3 poise or higher.   The alkali-free glass plate according to any one of claims 1 to 9, which is formed by an overflow down draw method.   The alkali-free glass plate according to any one of claims 1 to 10, which is used for an organic EL device.