An optical glass has a refractive index (n.sub.d) of 1.64 or more. A P value represented by the following formula (1) is in a range of 7.0<P value<10.0: P value=log(A.sub.450×P.sub.450+A.sub.550×P.sub.550+A.sub.650×P.sub.650+A.sub.750×P.sub.750) (1). A.sub.450, A.sub.550, A.sub.650 and A.sub.750 are absorbances of the optical glass with a plate thickness of 10 mm at a wavelength of 450 nm, 550 nm, 650 nm and 750 nm, respectively. P.sub.450, P.sub.550, P.sub.650 and P.sub.750 are radiances of light having a wavelength of 450 nm, 550 nm, 650 nm and 750 nm, respectively, at 1,300° C. according to Planck's radiation law. All of internal transmittances in terms of a 10-mm thickness at wavelengths of 450 nm, 550 nm, 650 nm and 750 nm are 91% or more.

Provided is a light guide plate for an image display device which uses lead-free glass, has excellent color reproducibility and a light weight, and may obtain a wide viewing angle. A light guide plate for an image display device, which guides image light inputted from an image display element and outputs the image light toward a user's pupil, is configured to be made of lead-free glass having a refractive index of 1.8 or more with respect to a wavelength of the image light, and to have internal transmittance of 0.6 or more with respect to a wavelength of 400 nm when a plate thickness is 10 mm.

Provided is a light guide plate for an image display device which uses lead-free glass, has excellent color reproducibility and a light weight, and may obtain a wide viewing angle. A light guide plate for an image display device, which guides image light inputted from an image display element and outputs the image light toward a user's pupil, is configured to be made of lead-free glass having a refractive index of 1.8 or more with respect to a wavelength of the image light, and to have internal transmittance of 0.6 or more with respect to a wavelength of 400 nm when a plate thickness is 10 mm.

Disclosed is a composition for sealing inorganic substrates. The composition includes a glass frit and optionally a filler material, wherein the glass frit contains: 30 to 65 wt % V.sub.2O.sub.5; 5 to 35 wt % P.sub.2O.sub.5; 0 to 30 wt % TeO.sub.2; 0 to 30 wt % Bi.sub.2O.sub.3; 0 to 15 wt % ZnO; 0 to 10 wt % MnO; 0 to 5 wt % B.sub.2O.sub.3; 0 to 5 wt % total alkali metal oxides; 0 to 2 wt % Nb.sub.2O.sub.5; 0 to 2 wt % WO.sub.3; 0 to 2 wt % MoO.sub.3; 0 to 2 wt % SiO.sub.2; and 0 to 2 wt % Al.sub.2O.sub.3.

A glass composition is provided. The glass composition includes: 25-40 wt % SiO.sub.2; 2.5-10 wt % B.sub.2O.sub.3; 0-10 wt % Al.sub.2O.sub.3; 0-15 wt % Li.sub.2O; 0-16 wt % of Li.sub.2O, Na.sub.2O, and K.sub.2O in total; 10-25 wt % CaO; 0-15 wt % BaO; 0-5 wt % MgO; 0-5 wt % SrO; 10-30 wt % CaO, BaO, MgO, and SrO in total; 0-7 wt % ZnO; 2-10 wt % ZrO; 2-15 wt % TiO.sub.2; 5-25 wt % Nb.sub.2O.sub.5; 0-5 wt % Ta.sub.2O.sub.5; 5-25 La.sub.2O.sub.3; and 0-5 wt % Y.sub.2O.sub.3. The glass composition has a refractive index from about 1.74 to about 1.80, a density from about 3.5 g/cm.sup.3 to about 4.0 g/cm.sup.3, a critical cooling rate from about 1° C./min to about 50° C./min, and a liquidus viscosity greater than 25 Poises.

Provided is a wavelength conversion member that is less decreased in luminescence intensity with time by irradiation with light of an LED or LD and a light emitting device using the wavelength conversion member. A wavelength conversion member is formed of an inorganic phosphor dispersed in a glass matrix, wherein the glass matrix contains, in % by mole, 30 to 85% SiO.sub.2, 0 to 20% B.sub.2O.sub.3, 0 to 25% Al.sub.2O.sub.3, 0 to 3% Li.sub.2O, 0 to 3% Na.sub.2O, 0 to 3% K.sub.2O, 0 to 3% Li.sub.2O+Na.sub.2O+K.sub.2O, 0 to 35% MgO, 0 to 35% CaO, 0 to 35% SrO, 0 to 35% BaO, 0.1 to 45% MgO+CaO+SrO+BaO, and 0 to 4% ZnO, and the inorganic phosphor is at least one selected from the group consisting of an oxide phosphor, a nitride phosphor, an oxynitride phosphor, a chloride phosphor, an oxychloride phosphor, a halide phosphor, an aluminate phosphor, and a halophosphate phosphor.

Provided is a wavelength conversion member that is less decreased in luminescence intensity with time by irradiation with light of an LED or LD and a light emitting device using the wavelength conversion member. A wavelength conversion member is formed of an inorganic phosphor dispersed in a glass matrix, wherein the glass matrix contains, in % by mole, 30 to 85% SiO.sub.2, 0 to 20% B.sub.2O.sub.3, 0 to 25% Al.sub.2O.sub.3, 0 to 3% Li.sub.2O, 0 to 3% Na.sub.2O, 0 to 3% K.sub.2O, 0 to 3% Li.sub.2O+Na.sub.2O+K.sub.2O, 0 to 35% MgO, 0 to 35% CaO, 0 to 35% SrO, 0 to 35% BaO, 0.1 to 45% MgO+CaO+SrO+BaO, and 0 to 4% ZnO, and the inorganic phosphor is at least one selected from the group consisting of an oxide phosphor, a nitride phosphor, an oxynitride phosphor, a chloride phosphor, an oxychloride phosphor, a halide phosphor, an aluminate phosphor, and a halophosphate phosphor.

A cover glass of the present invention is characterized by including in a glass composition at least three or more components selected from SiO.sub.2, Al.sub.2O.sub.3, B.sub.2O.sub.3, Li.sub.2O, Na.sub.2O, K.sub.2O, MgO, CaO, BaO, TiC.sub.2, Y.sub.2O.sub.3, ZrO.sub.2, and P.sub.2O.sub.5, and having an X value of 7, 400 or more calculated by the following equation. The X value is a value calculated by the equation

X=61.1×[SiO.sub.2]+174.3×[Al.sub.2O.sub.3]+11.3×[B.sub.2O.sub.3]+124.7×[Li.sub.2O]−5.2×[Na.sub.2O]+226.7×[K.sub.2O]+139.4×[MgO]+117.5×[CaO]+89.6×[BaO]+191.8×[TiO.sub.2]+226.7×[Y.sub.2O.sub.3]+157.9×[ZrO.sub.2]−42.2×[P.sub.2O.sub.5].

It is demanded that a LTCC substrate composition capable of maintaining low relative permittivity k and high Q value without having a reactivity with a silver which is an electrode material and causing migration of the silver during a co-firing operation at a low temperature. Provided with a low temperature co-fired substrate composition containing 83 to 91 wt. % of CaO-B.sub.2O.sub.3-SiO.sub.2 based glass powder, 7.5 to 14 wt. % of two or more kinds of nanometer-sized SiO.sub.2 powders having different ranges of particle diameter and 1.5 to 3 wt. % of β-wollastonite powder as a crystallization agent wherein the glass powder contains 40.0 to 45.0 wt. % of CaO, 9.0 to 20.0 wt. % of B.sub.2O.sub.3 and 40.0 to 46.0 wt. % of SiO.sub.2.

Coated glass or glass ceramic substrates having high temperature resistance, high strength, and a low coefficient of thermal expansion. The coating includes pores, is fluid-tight and suitable for coating a temperature-resistant, high-strength glass or glass ceramic substrate with a low coefficient of thermal expansion, and to a method for producing such a coated substrate.