Glass composition and laminated glass

Abstract

A laminated glass having a low haze ratio and an excellent infrared rays shield performance and a glass composition suitable for use in a laminated glass and easy with respect to melting and molding works, which is a glass composition comprising 65 to 74% of SiO2, 0 to 5% of B2O3, 1.9 to 2.5% of Al2O3, 1.0 to 3.0% of MgO, 5 to 10% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, 0 to 5% of Li2O, 13 to 17% of Na2O, 0.5 to 5% of K2O, 0 to 0.40% of TiO2 and 0.3 to 2.0% of total iron oxide in terms of Fe2O3, on a weight basis, in which the sum of MgO, CaO, SrO and BaO is from 10 to 15% and the sum of Li2O, Na2O and K2O is from 14 to 20%, wherein the glass composition has a visible light transmittance of 80% or more as measured with the CIE Standard illuminant A and a total solar energy transmittance of not more than 62% at a thickness of 2.1 mm, and a laminated glass using a glass sheet made of that glass composition.

Description

[0001] The present invention relates to a laminated glass having an excellent infrared rays (IR rays) shield performance and to a glass composition that is suitable for use in the laminated glass. More specifically, the invention relates to a laminated glass that does not use a specific interlayer or heat ray reflecting film but exhibits an infrared rays shield performance substantially equal to those having an interlayer or heat ray reflecting film and to a glass composition that is suitable for use in the laminated glass.DESCRIPTION OF THE RELATED ART[0002] In recent years, for reducing loads of air conditioning of automobiles, glazings having an infrared rays shield performance are used as automobile window shields. For example, there are thin film-provided glass sheets in which a thin film made of a metal or a metal oxide is laminated on the surface of a glass sheet. However, since such metal or metal oxide-made thin films have a conductive capacity and shield radio waves, there...

AI Technical Summary

Benefits of technology

[0026] Al.sub.2O.sub.3 is a component of enhancing durability of the glass. For imparting chemical durability at sufficient levels as automobile window shields and others, the content of Al.sub.2O.sub.3 is necessary to be 1.9% or more. When the content of Al.sub.2O.sub.3 is less than 1.9%, the durability of glass is poor. On the other hand, when it exceeds 2.5%, melting of the glass is difficult. More preferably, the content of Al.sub.2O.sub.3 is from 2.0 to 2.4%.

[0027] MgO and CaO are used for not only enhancing durability of the glass but also controlling liquidus temperature and viscosity during the forming. SrO and BaO are each not an essential component but are used for not only enhancing durability of the glass but also controlling liquidus temperature and viscosity during the forming. In the invention, by setting up the content of MgO at from 1.0 to 3.0% and the content of the sum of alkaline earth metal oxides (MgO+CaO+SrO+BaO) at 10% or more, it is possible to enhance a basicity of the glass, thereby shifting a peak of FeO to the long wavelength side and enhancing the infrared rays shield performance. Thus, it is possible to make the solubility consistent with the durability.

[0029] Na.sub.2O and K.sub.2O are used as a melting accelerator of the glass. Li.sub.2O is not an essential component but is used as a melting accelerator, too. When the content of Na.sub.2O is less than 13%, or the content of the sum of Li.sub.2O, Na.sub.2O and K.sub.2O is less than 14%, the melting acceleration effect is poor. On the other hand, when the content of Na.sub.2O exceeds 17%, or the content of the sum of Li.sub.2O, Na.sub.2O and K.sub.2O exceeds 20%, the durability of the glass is lowered. Since Li.sub.2O is expensive as compared with Na.sub.2O, it is not preferable that the content Li.sub.2O exceeds 5%. Also, when K.sub.2O is introduced into the glass in place of Li.sub.2O or Na.sub.2O, it has an effect for increasing the basicity of the glass. Accordingly, it is preferable to add K.sub.2O in an amount of 0.5% or more, and preferably 1% or more. The content of the sum of Li.sub.2O, Na.sub.2O and K.sub.2O is preferably from 14.5 to 19%.

Problems solved by technology

However, since such metal or metal oxide-made thin films have a conductive capacity and shield radio waves, there were caused inconveniences such that actions of a function system by transmitting and receiving of radio waves with the outside of automobiles are hindered and that communications by portable phones are hindered.

However, there was involved an inconvenience such that for making the transmission consistent with durability, both the melting point (log .eta.=2) and working point (log .eta.=4) temperatures are high.

Further, since MgO is not substantially contained, if the amount of FeO is increased for enhancing the infrared rays shield performance, there was involved an inconvenience such that amber coloration is liable to take place.

When the content of SiO.sub.2 is less than 65%, durability of the glass is lowered, whereas when it exceeds 74%, melting of the glass becomes difficult.

When the content of B.sub.2O.sub.3 exceeds 5%, a reduction in the transmittance in ultraviolet regions extends to visible regions, the tint tends to become yellowish, and inconveniences during the forming are caused due to volatilization of B.sub.2O.sub.3, etc.

When the content of Al.sub.2O.sub.3 is less than 1.9%, the durability of glass is poor.

On the other hand, when it exceeds 2.5%, melting of the glass is difficult.

On the other hand, when it is less than 10%, the glass tends to cause amber coloration so that sufficient FeO amount and visible light transmittance are not stably obtained.

Since raw materials of SrO and BaO are expensive, their contents are each from 0 to 10%.

Also, when the content of the sum of the alkaline earth metal oxides is less than 10%, not only a sufficient infrared rays shield performance is not obtained, but also the liquidus temperature during the forming increases, and it is difficult to make solubility consistent with durability.

When the content of Na.sub.2O is less than 13%, or the content of the sum of Li.sub.2O, Na.sub.2O and K.sub.2O is less than 14%, the melting acceleration effect is poor.