JPH0446909B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a glass composition with low alkali elution for use in display substrates using liquid crystals or EL, physical and chemical instruments, and the like. [Prior Art] For example, liquid crystal display devices such as calculators and digital watches use thin glass as a substrate. In addition to being transparent and having the ability to hold liquid crystal, this substrate glass is required to have a small amount of alkali elution from the glass. This is because when alkali elution occurs on the inner surface of the glass substrate that holds the liquid crystal in a sandwich-like pattern, a leakage current occurs, resulting in an increase in power consumption and a disordered display pattern. Conventional glasses for liquid crystal substrates include silica-soda-lime-based ordinary plate glass coated with a SiO ₂ film, and alkali-free or low-alkali borosilicate or aluminoborosilicate glass. However, in the case of the former, although the plate glass itself can be obtained at a low price and of high quality, the SiO ₂ coating liquid, such as ethyl silicate, is extremely expensive, and the coated film is prone to pinholes, so the final product is expensive. It has the disadvantage of becoming On the other hand, the latter does not have the disadvantage of alkali elution from the glass, but has a disadvantage of low glass meltability and moldability due to the small amount of alkali metal components in the glass, and low manufacturing yield. [Problems to be Solved by the Present Invention] An object of the present invention is to provide a glass composition that has little alkali elution and excellent solubility and moldability. [Means for Solving the Problems of the Present Invention] In order to solve the above problems, the present invention provides a method in which the basic components expressed in weight percent are SiO ₂ 60-75, B ₂ O ₃ 8-14,
_{Al2O32 ~} 6, TiO20 _~ 5, BaO0~2.5, ZnO3~
8. Li ₂ O with Li 2 O 0 ~ 2, Na ₂ O 0 ~ 10, K ₂ O ₀ ~ 10
+ _Na2O + _K2O6 ~15, and _Na2O /
A glass composition with low alkali elution in which (Na ₂ O + K ₂ O) is in the range of 0.35 to 0.65. [Function] SiO ₂ 60-75wt%: A component that forms the skeleton of glass. If it is less than 60%, the water resistance of the glass will decrease and the amount of alkali elution will increase, and if it exceeds 75%, it will be difficult to melt the glass. . B ₂ O ₃ 8 to 14 wt%: Similar to SiO ₂ , it forms a glass skeleton and also has a flux action that helps glass melting. If it is less than 8%, it has a poor flux action, and if it exceeds 14%, it becomes an alkali metal oxide. As they bond together and volatilize from the molten glass,
This causes the glass to become airless, making it difficult to mold. Al ₂ O ₃ 2-6wt%: Also serves as a skeleton forming component,
In addition, it prevents phase separation of glass containing silicic acid and boric acid to improve the acid resistance and water resistance of the glass, and also improves the water resistance of the glass by entering the skeleton itself. If it is less than 2%, the above-mentioned water resistance and acid resistance will be insufficient, and if it exceeds 6%, the viscosity of the molten glass will increase and the moldability will deteriorate. TiO ₂ -5wt%: It is preferable to add 1% or more since it improves the acid resistance of the glass. The chemical durability of glass is mainly brought about by Al ₂ O ₃ and ZnO, so it is not essential, but the addition of TiO ₂ further improves the acid resistance, for example, during acid cleaning in the pretreatment process of liquid crystal substrate manufacturing. be effective. Even if it exceeds 5%, there is no improvement in acid resistance, and on the contrary, the solubility of the glass decreases. BaO 0 to 2.5 wt%: Since it has a flux effect that improves the solubility without reducing the chemical durability of the glass, it is preferable to add about 1%, but if it exceeds 2.5%, the chemical durability will decrease. ZnO3 to 8wt%: Essential for improving the chemical durability of glass. Less than 3% is less effective, and more than 8% does not improve the effect. It also has the effect of increasing low-temperature viscosity and making the temperature-viscosity curve of the glass steeper, so its content is preferably about 5%. but
TiO ₂ also has similar properties, so if they coexist, ZnO +
Preferably, TiO ₂ is 8% or less. Li ₂ O 0 to 2 wt%: Has a flux effect to improve glass meltability, but coexists with Na ₂ O and K ₂ O and reduces to 2%
Even if it exceeds, the effect will not improve. Na ₂ O 0 to 10 wt%, K ₂ O 0 to 10 wt%: Acts as a flux for glass melting, is cheaper than Li ₂ O, and has a wide range of components that have a flux effect, but if it exceeds 10%, the glass chemistry durability is reduced. Even if Na ₂ O and K _{2 O} are within the above range, if either exists alone, _the chemical durability of the glass will be _poor . It is necessary that (Na ₂ O + K ₂ O) be within the range of 0.35 to 0.65. Also, Li ₂ O + Na ₂ O is used as a flux for glass melting.
If the total amount of +K ₂ O is less than 6%, a high temperature is required to melt the glass, and if it exceeds 15%, the chemical durability of the glass decreases. In addition to the above basic components, CaO and MgO may be added for the purpose of adjusting the viscosity characteristics of the glass.
It is undesirable for each to exceed 10%. In addition, impurities such as Fe ₂ O ₃ in raw materials, AS ₂ O ₃ , Sb ₂ O ₃ , SO ₃ , Cl, F, etc., which are glass refining agents, can be contained in the glass composition of the present invention even if they are contained up to 1% each. It doesn't spoil the purpose of the thing. [Example] Raw materials were adjusted so as to obtain glasses having the respective compositions shown in Table 1, melted in a platinum crucible, and then poured into a mold and slowly cooled to obtain samples. Measurement of water resistance and acid resistance
Performed according to JIS R-3502, 1 ml of each glass was measured for particle size.
Grind to 250-420 μm and immerse in 50 ml of water at 100°C for 60 minutes or in 0.01N, 5 ml of nitric acid at 100°C for 60 minutes.
The eluted alkali metals were determined by atomic absorption spectrometry. Samples Nos. 1 to 9 are glasses within the composition range of the present invention, Samples Nos. 10 and 11 are glasses outside the composition range of the present invention, and No. 10 has a similar composition to commercially available float plate glass; No. 11 has a similar composition to Pyrex (trademark of Corning Inc.), a typical borosilicate glass. [Effects of the Invention] As is clear from the results in Table 1, the glass composition of the present invention has less elution of alkali metals in water or acid than the silica-soda-lime plate glass composition. In addition, compared to borosilicate glass, the melting temperature (temperature at which the logarithmic viscosity log η = 2) and working temperature (log
η=4), softening point (log η=7.6), and other temperatures during melting and molding.

【table】

[Table] It is a glass with a much lower value and excellent meltability and moldability.

Claims (1)

[Claims] 1 Basic components expressed in weight% are SiO ₂ 60-75, B ₂ O ₃ 8-14, Al ₂ O ₃ 2-6, TiO ₂ 0
~5, BaO0~2.5, ZnO3~8, Li ₂ O0~2,
_Na2O0 ~10, _K2O0 ~10, _Li2O + _Na2O + _K2O6
~15 and Na ₂ O/(Na ₂ O + K ₂ O) is 0.35
Glass composition with low alkali elution in the range of ~0.65.