JP2000143280A - Soda-lime silica glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change brittleness for the better and to improve chemical resistance of conventional soda-lime silica glass, and to obtain a glass compsn. capable of plate-forming without making largely change a molding and an annealing temp. with a melting property compatible of ones of conventional soda-lime silica glass. SOLUTION: This glass compsn. is by wt.%, 71-83 SiO2, 0-11 Al2O3, 0-5 B2O3, 0-5 Li2O, 6-20 Na2O, 0-12 K2O, 6-20 an alkaline metal oxide R'2O consisting of the above Li2O+Na2O+K2O, 0-8 MgO, 0-10 CaO, 3-10 MgO+CaO, 0-5 SrO, 0-5 BaO, 3-10 divalent metal oxide RO consisting of the above MgO+CaO+ SrO+BaO, 0.5-3 ZrO2, and the glass has a thermal expansion coefficient α(30-300 deg.C) of 70-90×107/ deg.C and Vickers hardness Hv of <=5.2 GPa. Or in replacing for the Vickers hardness, free space V of the glass is >=70%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a soda-lime-silica-based glass which has improved brittleness and excellent chemical resistance and is easy to melt and mold.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication Nos. 9-52729 and 9-52730 disclose a composition range of components and a density lower than that of a so-called ordinary soda lime silica glass. A scratch-resistant glass having the above-mentioned specification is disclosed. Incidentally, both fragility index value B is 6700m ^over
It is as low as ^1/2 or less, and it is said that it is excellent in scratch resistance by that amount [brittleness index value B=Vickers hardness Hv/fracture toughness value Kc was proposed by Lawn et al. the pushing load when pushed Vickers indenter, the diagonal length of the indenter mark, from the generated crack length relationship can be expressed by the fragility index value ^{B = 2386P -1/4 (C / a} ) 3/2 Is found].

However, the above composition is out of the range of the component composition of the ordinary soda lime silica type glass, has a large amount of alkali, is inferior in chemical resistance to the ordinary soda lime silica type glass, and is apt to cause so-called burns. In addition, in long-term use, raindrops and trace amounts of harmful gases (COx, SO
x, etc.) may cause stains that cannot be easily removed. Further, the thermal expansion coefficient also deviates from the soda-lime-silica-based glass, and it is difficult to thermally strengthen it, and the matching property with the members of various article devices that have been matched with the expansion coefficient of the conventional soda-lime-silica-based glass. There is a harmful effect of damaging.

An object of the present invention is to provide a soda-lime-silica glass which solves these problems, is easy to melt and mold, has improved brittleness, and has excellent chemical resistance.

[0005]

According to the present invention, the glass composition is SiO ₂ 71-83, Al ₂ O ₃ 0-11, B ₂ O ₃ 0-5, L in wt %.
i ₂ O 0-5, Na ₂ O 6-20, K ₂ O 0-12, Li ₂ O+Na ₂ O+K
Alkali metal oxides consisting of _{2 O R '2 O 6~20,} MgO 0~8,
CaO 0-10, MgO+CaO 3-10, SrO 0-5, BaO 0-5, the above
Divalent metal oxide RO 3 to 10 consisting of MgO + CaO + SrO + BaO,
ZrO ₂ 0.5 to 3 and coefficient of thermal expansion α (30 to 300°C) 70 to 90
It is a soda-lime-silica glass with a Vickers hardness of Hv≦5.2 GPa at ×10 ⁻⁷ /°C.

In the above, the Vickers hardness is changed to a glass free space V≧70%.

Further, in the above-mentioned chemical resistance test by the surface method, the amount of weight loss after dipping a glass plate in distilled water at 95° C. for 40 hours is less than 0.020 mg/cm ² .

[0008]

[However, when the Vickers indenter is pushed in, the pushing load is P, the diagonal length of the indenter mark is 2a, and the crack length (total diagonal length including the mark) is 2C. ]

In the above publications, the brittleness index value B
Has a close relation with density.

Based on the above, the present inventors have made various investigations and studies on various soda-lime-silica glass components, and have found the following matters. That is, the fracture toughness value Kc of soda lime silica glass is in a very narrow range,
It can be said that it is almost constant (that is, Kc in the brittleness index value B=Hv/Kc proposed by Loan et al. is almost constant), and the brittleness index value B=f(Hv) <Hv: Vickers hardness> The Vickers hardness is an effective measurement in that easy and accurate measurement values can be obtained, an evaluation means, and the brittleness of the soda-lime-silica glass is represented by Vickers hardness. To do.

Further, the correlation between the brittleness index value and the density is established only in a limited component composition range, and is essentially a free space (Free s) determined by the refractive index.
pace) was found to be most closely related to the brittleness of glass.

"Free space"
For example, Mathematical Approach to Glass (MB
Volf: 1988) is known.

[0013] Free space V, the molar volume V _M, in relation to the molar refraction index _{R M, V = 100 (V} M -R M) / V M R M = V M (n 2 -1) / (n 2 From the known formula of +2), the free space V can be obtained from the refractive index n. As a preferable range for suppressing brittleness, the Vickers hardness of glass is Hv≦5.2 GPa, and the corresponding glass free space V≧70%.

From another point of view, it has been found that the brittleness index value has a correlation with the bulk modulus. The bulk modulus is
By the sing-around method using a vibrator with a specific frequency, the longitudinal and transverse wave velocities propagating in the glass are measured,
Separately from the density of the glass measured by the Archimedes method,
The Young's modulus and Poisson's ratio can be obtained, and further can be obtained from the relational expression between the Young's modulus and Poisson's ratio and the bulk modulus. When the bulk modulus κ is κ≦46 GPa, the degree of brittleness tends to be suppressed.

The general composition of soda-lime-silica glass (hereinafter referred to as ordinary glass) is approximately wt%.
_{In, SiO 2 66~75, Al 2 O} 3 0~6, Na 2 O 12~20, K 2 O
0-3, MgO 0-6, CaO 7-12, and coefficient of thermal expansion α
(30-300°C) 80-95×10-7/°C, alkaline elution test by surface method shows that the amount of dissolved alkali after dipping in distilled water at 95°C for 40 hours is 0.020-0.025mg/cm ² , density 2.
50 to 2.53 g/cm ³ , and the brittleness index value is B≧7000 m
^-1/2 , Vickers hardness is Hv≧5.5GPa, and free space is V<70%.

By the way, regarding the coefficient of thermal expansion α,
It is well known that the α value is a major factor in the development of strength in the case of thermally strengthening glass, and that the moderately higher the α value, the higher the degree of strengthening. In ordinary glass, the α value is higher than many other glass types. Of course, if the content of alkali metal oxides and divalent metal oxides in the glass is increased, the α value can be further increased, but it is possible to clarify the melting of glass, ease of molding, mass productivity, chemical resistance of the product, etc. Considering physical properties and the like, it is not possible to increase only the α value.

Also in the present invention, the coefficient of thermal expansion α (30 to 300° C.) is set to 70 to 90×10 ⁻⁷ /° C. so as to approximate the coefficient of thermal expansion of the ordinary glass and perform effective thermal strengthening. In this case, the component composition range is adjusted accordingly.
In addition, there are many cases where a thermal expansion coefficient similar to that of ordinary glass is required so as not to impair the matching property with members of various article devices such as a display device substrate such as a PDP substrate. The glass of the present invention can be effectively adopted also in those.

Regarding the chemical resistance, measurement of the weight loss by the surface method (mainly the amount of alkali elution) is typical. Needless to say, it is preferable to suppress the amount of alkali in the glass in order to reduce the amount of alkali elution, but in the same manner as above, in consideration of melting and fining of glass, ease of molding, mass productivity, physical properties of products, etc. The range of the glass of can not be largely removed. The compositions disclosed in JP-A-9-52729 and the like generally contain an excessive amount of alkali metal oxides, so that it is difficult to obtain a low alkali elution amount that is lower than that of ordinary glass. In the present invention, an alkali elution amount lower than that of ordinary glass is obtained, and the component composition range and the added and introduced components are adjusted accordingly.

That is, if the degree of brittleness, that is, the Vickers hardness of the glass is lowered (or the free space of the glass is increased), the content of the divalent metal oxide tends to be smaller than that of ordinary glass, and the meltability is deteriorated. In order to maintain the glass, there is a tendency to increase the content of alkali metal oxides, which deteriorates the chemical durability of the glass and also drastically changes the melting and forming behavior. On the other hand, in the present invention, by containing ZrO ₂ in a specific range,
The chemical durability of glass can be improved more than that of ordinary glass, and the melting and molding behavior can be made closer to that of ordinary glass.

The introduction range of each component will be described below.
SiO ₂ is an essential component for forming the network structure of glass, and contributes to a reasonably low density, scratch resistance and chemical durability, and is in the range of 71 to 83 wt% in glass. Introduce. If it is less than 71 wt%, the density of glass increases.
Vickers hardness, that is, the degree of brittleness increases. The other
If it exceeds 83 wt%, glass melting becomes difficult and the coefficient of thermal expansion becomes too small.

Al ₂ O ₃ is appropriately introduced in order to improve the chemical durability of glass, and the introduced amount is 11 wt% or less in the glass. If it exceeds 11 wt %, the melt homogeneity of the glass is deteriorated, the coefficient of thermal expansion is made too small, and the degree of brittleness is increased.

B ₂ O ₃ is appropriately introduced in order to facilitate the melting property of glass, and the introduction amount is within 5 wt% in the glass. If it exceeds 5% by weight, the coefficient of thermal expansion of glass becomes too small,
The degree of brittleness also increases.

Na ₂ O is an essential component for melting promotion, homogenization, defoaming, and glass forming in melting the glass batch, and is incorporated in the glass in the range of 6 to 20 wt %. If it is less than 6% by weight, it is difficult to melt and mold the glass, and the thermal expansion coefficient of the glass is too small. If it exceeds 20% by weight, the chemical resistance of the glass is deteriorated.

[0024] Li₂OK₂O is Na₂Appropriate by replacing with O
Introduce. Li₂O is a more effective flux, and also other
The degree of brittleness can be reduced as compared with alkali metal oxides. However
Li ₂The amount of O introduced into the glass is 5 wt% or less.
If it exceeds 5 wt%, the glass tends to devitrify and the molding temperature range
To make molding difficult and make the thermal expansion coefficient too small. K₂
O moderately increases the thermal expansion coefficient and helps improve devitrification
But especially Na₂Na coexists with O₂O plain or K₂O unit
Can improve chemical resistance to taste glass. K₂O moth
The amount introduced into the lath should be 12 wt% or less,
Glass increases the brittleness of the glass and deteriorates the chemical resistance.
To do.

[0025] Overall Li ₂ O, Na ₂ O, alkali metal oxides consisting of _{K 2 O (R '2 O} ) , the melt promoting glass, homogenization, deaeration, and the range of the glass forming 6～20Wt% However, if it is less than 6 wt%, it becomes difficult to melt and mold the glass, and if it exceeds 20 wt%, the chemical resistance of the glass deteriorates.

Originally, MgO and/or CaO replaces the alkali in the soda (alkali)-silica glass and is introduced to maintain the high temperature meltability of the glass,
It was introduced to improve the chemical resistance of glass without impairing the melting and forming properties, and was established as soda lime silica glass.

In this component system, MgO and/or C
aO is introduced in the range of 3 to 10 wt %, and if it is less than 3 wt %, the content of alkali metal oxides increases relatively,
The chemical resistance of glass deteriorates, and the glass viscosity also deviates from ordinary glass, degrading moldability. On the other hand, if it exceeds 10 wt%, the degree of brittleness of glass increases and worsens (especially CaO).
However, devitrification is also likely to occur.

Of these, CaO is introduced into the glass in the range of 0 to 10 wt %, and if it exceeds 10 wt %, the glass becomes brittle,
The devitrification tendency also increases. MgO improves the degree of brittleness with respect to other divalent metal oxides, and is introduced in the range of 0 to 8 wt %. If it exceeds 8% by weight, the coefficient of thermal expansion of the glass becomes too small and the meltability deteriorates.

SrO and BaO can be introduced into the glass in the range of 0 to 5 wt% by substituting for MgO+CaO. Their heating behavior, chemical resistance, degree of brittleness, etc. are similar to CaO (the effect on brittleness is smaller than that of CaO), but MgO and/or CaO have SrO and/or
Alternatively, coexistence of BaO suppresses the devitrification tendency of the glass and improves the formability. However, both are 5 wt%
Above 5%, these properties are not further improved, but rather the raw material cost rises, so it should be kept to 5 wt% or less.

In general, the amount of the divalent metal oxide composed of MgO, CaO, SrO and BaO is set in the range of 3 to 10 wt% in the glass. If it is less than 3 wt %, the melting and forming properties of the glass are deteriorated. If it exceeds 10 wt%, the degree of brittleness increases and worsens, and the devitrification tendency also increases.

ZrO ₂ improves the chemical resistance of the glass as described above, and since the amount of the divalent metal oxide introduced is too small in this component system, it remains as it is in the molding and annealing temperature as compared with ordinary glass. It is introduced in order to prevent a large change in the content, etc., and the introduction amount is 0.5 to 3 wt% in the glass. If it is less than 0.5 wt%, the above-mentioned action is insufficient, and 3 wt%
If it exceeds, the glass density increases, and the degree of brittleness increases and worsens.

In order to adjust the viscosity and coefficient of thermal expansion of glass, TiO ₂ can be introduced into the glass in the range of 0.5 wt% or less.

According to the present invention, the brittleness of ordinary glass can be improved, the chemical resistance can be improved, the melting property of ordinary glass can be exhibited, and the molding and annealing temperatures can be largely changed. Without it, it is possible to make a plate, and thus float molding is also possible.

[0034]

The present invention will be described below with reference to examples.

[Preparation of Glass Sample] As a glass raw material,
Silica sand, aluminum hydroxide, anhydrous boric acid, lithium carbonate,
Sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate and zirconium oxide were prepared.

Batch preparation was carried out so that the oxide composition (glass composition) shown in Tables 1 to 3 was obtained, and a batch corresponding to 600 g of glass was filled in a platinum rhodium crucible and heated at 1400 to 1550° C. in an electric furnace. After melting for about 6 hours to make a clear glass melt, take out the crucible, flow the glass melt onto a heat-resistant, inert carbon plate and cast it into a plate glass shape, and then in the electric furnace a glass transition point. After maintaining at a temperature above 100°C, gradually cooling, after cooling, optical polishing is performed to a thickness of about 5 mm to form a glass plate, then again at a temperature sufficiently exceeding the glass transition point, then slowly cooling at an extremely low cooling rate, and various characteristics after cooling. And the like.

Tables 1 to 3 show the glass compositions of Examples and Comparative Examples, as well as various observation and measurement results described later. In the table, Comparative Example 1 is an example of a normal glass composition, and Comparative Examples 2 and 3 are examples of known glass compositions.

[Observation of Meltability] In the glass raw material, part of sodium carbonate and 0.5 wt% of Na ₂ O were replaced with sodium sulfate as a fining agent (in Comparative Example 3, part of magnesium carbonate and MgO). 0.5 wt% equivalent of magnesium sulfate was replaced with magnesium sulfate) to prepare a batch, and the crucible was filled in the same manner as above.
After melting for 2 hours at 1550°C, which is the same level as ordinary glass, in an electric furnace, remove the crucible, cast the glass melt on a carbon plate, and observe the presence or absence of fine bubbles that are thought to affect unmelting and bubble breakage. did. The results were evaluated in the following three stages and shown in Tables 1 to 3. ○: No undissolved and no fine bubbles observed, as in ordinary glass △: No undissolved, but some fine bubbles remain (there is room for eliminating fine bubbles by adjusting the fining agent) × Mark: undissolved, fine bubbles remain

[Measurement of Thermal Physical Properties] A glass sample was partially cut out into a rectangular rod shape, heated by a thermal expansion meter at a heating rate of 5° C./min, and a thermal expansion curve was recorded. 300
The transition point Tg was determined from the average thermal expansion coefficient α at ℃ and the inflection point of the thermal expansion curve.

When the coefficient of thermal expansion is 70 to 90×10 ⁻⁷ /° C., it can be evaluated as being similar to or close to that of ordinary glass. Further, the transition point is a standard for representing the thermal behavior in the medium to low temperature range involved in molding and slow cooling, and is a normal glass (Comparative Example 1).
Although it is about 560°C, it can be evaluated that it is similar to ordinary glass at 500 to 580°C. (In the display, the numerical unit of the coefficient of thermal expansion is a value of ×10 ^-7 /°C, and the transition point is °C.)

[Measurement of Density] A sample is placed in distilled water at room temperature.
And measure the glass density ρ by the Archimedes method.
It was Glass density is not specified in the present invention.
2.48g/cm³Inclination to reduce the degree of brittleness
In the direction. (In the display, the numerical unit is g/cm ³Indicates)

[Measurement of Vickers Hardness and Brittleness Index Value] A Vickers indenter is pushed into the sample surface, and the pushing load P at that time, the diagonal length 2a of the indenter mark, the crack length (diagonal length including the mark) The brittleness index value was calculated by the following formula from the total length) 2C. Fragility index value ^{B = 2386P -1/4 (C / a} ) 3/2

Further, the Vickers hardness Hv was obtained from the load of the Vickers indenter and the length of the indenter mark. The results are shown in the table, and it can be seen that the brittleness index value and the Vickers hardness have a high correlation. In the brittleness index value, B≦6600 m ^−1/2 ,
Further, it can be evaluated that when Vvs hardness is Hv≦5.2 GPa, the degree of brittleness is low, that is, the brittleness is improved. (In the display, the numerical unit of the brittleness index value is m ^-1/2 , and the Vickers hardness is GPa.)

[Measurement of Free Space] The refractive index of the glass sample was measured by the Karl New refractometer (prism spectroscopy), and the free space V was obtained from the following formula. Molar refractive index ^{_{R M = V M (n 2}} -1) / (n 2 +2) (n is the refractive index,
V _M is the molar volume) free space _{V = 100 (V M -R M} ) / V M = 100 [1- (n 2
−1)/(n ² +2)] In the free space V≧70% of glass, the degree of brittleness is low, that is, it can be evaluated that the brittleness is improved. (In the display, the numerical unit of free space is%)

[Measurement of Bulk Elastic Modulus] As described above, the brittleness index value B has a correlation with the bulk elastic modulus κ. The bulk modulus is shown for reference. The longitudinal wave velocity V _i and transverse wave velocity V s propagating in the glass were measured by the sing-around method (transmission method) using a 5 MHz oscillator, and separately from the density ρ of the glass measured by the Archimedes method, the following known formula was used. The Young's modulus E and the Poisson's ratio υ can be obtained, and further can be obtained from the relational expression between the Young's modulus E and the Poisson's ratio υ and the bulk modulus κ.

Alcohol was used for bonding the longitudinal wave oscillator, and transverse wave introducing grease was used for bonding the transverse wave oscillator. Fused silica glass (V _i =5968 m·s) was used for calibrating the device.
⁻¹ , Vs=3765 m·s ⁻¹ ) was used. Young's modulus ^{_{E = ρVs 2 (V i 2}} -4 / 3Vs 2) (V i 2 -Vs 2) ^-1 Poisson's ratio upsilon = 1/2 _{[1 - [(V i / Vs} ) 2 -1] ^-1] Bulk Elastic Modulus κ=E[2(1+υ)] ⁻¹ As shown in the table, the bulk elastic modulus has a correlation with the brittleness index value. When the bulk modulus κ is κ≦46 GPa, the degree of brittleness tends to be suppressed. (In the display, the numerical unit indicates GPa)

[Measurement of Chemical Resistance (Weight Reduction)] A glass sample of 40 mm×40 mm×5 mm (thickness) previously weighed was put at 95° C.
It was immersed in distilled water for 40 hours, and the weight was measured after the immersion to determine the weight reduction amount per unit area (the weight reduction is due to the elution of the alkali content). Measurements were made for each of the three samples, and the following three-stage evaluations were made and shown in the table. ○: The weight loss was <0.020 mg/cm ² for all three samples. △: The average weight loss is 0.020 to 0.025 mg/cm ² (usually normal glass) ×: The average weight loss is >0.025 mg/ cm ²

As shown in Tables 1 to 3, the sample of this example shows good results in all the observation and measurement items, while the sample of the comparative example is inferior in one to a plurality of items.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Component SiO ₂ 79.0 78.0 79.0 78.0 78.0 (wt%) Al ₂ O ₃ 2.0 2.0 2.0 2.0 2.0 B ₂ O ₃ − − − − − Subtotal 81.0 80.0 81.0 80.0 80.0 Li ₂ O − − − − − _{Na 2 O 11.0 12.0 12.0 13.0 14.0} K 2 O 2.0 2.0 2.0 2.0 2.0 R '2 O Subtotal 13.0 14.0 14.0 15.0 16.0 MgO 2.0 2.0 1.0 2.0 2.0 CaO 3.0 3.0 3.0 2.0 1.0 SrO - - - - - BaO - - - - - RO Subtotal 5.0 5.0 4.0 4.0 3.0 ZrO ₂ 1.0 1.0 1.0 1.0 1.0 TiO ₂ − − − − − Total 100.0 100.0 100.0 100.0 100.0 Characteristic Meltability ○ ○ ○ ○ ○ Thermal expansion coefficient 72 74 75 78 83 Transition point 544 541 520 517 515 Density 2.398 2.411 2.391 2.401 2.398 Fleece hose 70.6 70.3 70.7 70.7 70.7 Brittleness index value 6100 6600 5900 6000 5800 Heckers hardness 5.10 5.20 5.00 5.15 5.00 Bulk modulus 44 45 43 43 42 Alkali elution amount ○ ○ ○ ○ ○

[Table 2] Example 6 Example 7 Example 8 Example 9 Example 10 Component SiO ₂ 77.0 78.0 82.0 72.0 72.0 (wt%) Al ₂ O ₃ 2.0 2.0 − 4.0 2.0 B ₂ O ₃ − − − − − Subtotal 79.0 80.0 82.0 76.0 74.0 Li ₂ O − − − − 4.0 Na ₂ O 14.0 16.0 13.0 17.0 15.0 K ₂ O 2.0 − − − − R′ ₂ O Subtotal 16.0 16.0 13.0 17.0 19.0 MgO 2.0 2.0 − 6.0 6.0 CaO 2.0 1.0 4.0 − − SrO − − − − − BaO − − − − − RO Subtotal 4.0 3.0 4.0 6.0 6.0 ZrO ₂ 1.0 1.0 1.0 1.0 1.0 TiO ₂ − − − − − Total 100.0 100.0 100.0 100.0 100.0 Characteristic Meltability ○ ○ ○ ○ ○ Thermal expansion coefficient 82 86 78 86 95 Transition point 516 526 552 Density 2.411 2.405 2.425 2.436 2.430 Fleece hose 70.6 70.7 70.7 70.3 70.0 Index of brittleness 6000 5900 5500 6300 6500 Hickers hardness 5.13 5.05 4.90 5.17 5.20 Bulk modulus 43 42 41 44 46 Alkali elution amount ○ ○ ○ ○ ○

[Table 3] Example 11 Example 12 Comparative Example 1 Comparative Example 2 Comparative Example 3 Component SiO ₂ 79.0 79.0 73.0 68.5 75.1 (wt%) Al ₂ O ₃ 2.0 2.0 1.7 3.4 − B ₂ O ₃ − − − − − Subtotal 81.0 81.0 74.7 71.9 75.1 Li ₂ O − − − 3.0 15.5 Na ₂ O 12.0 12.0 13.0 21.1 − K ₂ O 1 1 0.7 3.0 − R′ ₂ O Subtotal 13.0 13.0 13.7 27.1 15.5 MgO 2.0 2.0 3.7 − 9.4 CaO − − 7.8 1.0 − SrO 3.0 − − − − BaO − 3.0 − − − RO Subtotal 5.0 5.0 11.5 1.0 9.4 ZrO ₂ 1.0 0.9 − − − TiO ₂ − 0.1 − − − Total 100.0 100.0 99.9 100.0 100.0 Characteristic Meltability ○ ○ ○ ○ ○ Thermal expansion coefficient 80 83 85 125 89 Transition point 560 Density 2.462 2.478 2.52 2.45 2.36 Fleece hose 69.8 70.0 68.5 Index of brittleness 6400 6500 7100 6600 6800 Hickers hardness 5.00 5.00 5.50 5.15 5.21 Bulk modulus 47 43 53 Alkali elution amount ○ ○ △ × △

[0052]

EFFECTS OF THE INVENTION According to the present invention, the brittleness of ordinary glass is improved, the chemical resistance is improved, and the melting property of ordinary glass is exhibited. On the other hand, it is possible to make a plate without making a great change, and thus it is possible to perform float forming.

─────────────────────────────────────────────────── ─── front page of continued F-term (reference) 4G062 AA01 BB03 DA07 DB01 DB02 DB03 DB04 DC01 DC02 DC03 DD01 DE01 DF01 EA01 EA02 EA03 EB03 EB04 EC01 EC02 EC03 EC04 ED01 ED02 ED03 EE01 EE02 EE03 EF01 EF02 EF03 EG01 EG02 EG03 FA01 FB01 FC02 FC03 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 KK10 NN33 KK10 NN33 KK05 MM07 KK05 NN03 KK05 MM07 KK05 MM07 KK05 NN

Claims (3)

[Claims] 1. A glass composition comprising SiO ₂ 71 to 83 and Al _{2 in} wt %.
_{O 3 0~11, B 2 O 3} 0~5, Li 2 O 0~5, Na 2 O 6~20, K 2 O 0
12, wherein the _{Li 2 O + Na 2 O +} K 2 alkali metal oxides R _'2 O6~20 consisting O, MgO 0~8, CaO 0~10, MgO + CaO 3~10, S
rO 0 to 5, BaO 0 to 5, the divalent metal oxide RO 3 to 10 composed of MgO+CaO+SrO+BaO, ZrO ₂ 0.5 to 3, and the thermal expansion coefficient α (30 to 300° C.) 70 to 90×10 ⁻⁷ / C, Vickers hardness Hv≦5.2 GPa, soda lime silica glass. 2. The soda lime-based glass according to claim 1, wherein the free space V of the glass is changed to Vickers hardness.
Soda-lime-silica based glass characterized by ≧70%. 3. A chemical resistance test by a surface method, wherein the weight loss after dipping a glass plate in distilled water at 95° C. for 40 hours is
The soda lime silica-based glass according to claim 1 or 2, which is less than 0.020 mg/cm ² .