To provide an optical glass having the optical characteristics of a high refractive index and low dispersion, and moreover, which makes it possible to further reduce devitrification and which can be stably obtained, and a preform and an optical element using the same. The optical glass comprises, expressed in cation % (mol %), 17.0% to 42.0% of P.sup.5+, 7.0% to 30.0% of Al.sup.3+, more than 0% to 22.0% of Mg.sup.2+, more than 0% to 25.0% Ca.sup.2+, more than 0% to 30.0% of Sr.sup.2+, more than 0% to 35.0% Ba.sup.2+, and expressed in anion % (mol %), a content ratio of F.sup. of 37.0 to 64.0%, a content ratio of O.sup.2 of 36.0 to 63.0%, a refractive index (nd) of 1.48 to 1.58, and having an Abbe number (vd) of 70 to 88, and a liquidus temperature of 800 C. or less.

To provide an optical glass having the optical characteristics of a high refractive index and low dispersion, and moreover, which makes it possible to further reduce devitrification and which can be stably obtained, and a preform and an optical element using the same. The optical glass comprises, expressed in cation % (mol %), 17.0% to 42.0% of P.sup.5+, 7.0% to 30.0% of Al.sup.3+, more than 0% to 22.0% of Mg.sup.2+, more than 0% to 25.0% Ca.sup.2+, more than 0% to 30.0% of Sr.sup.2+, more than 0% to 35.0% Ba.sup.2+, and expressed in anion % (mol %), a content ratio of F.sup. of 37.0 to 64.0%, a content ratio of O.sup.2 of 36.0 to 63.0%, a refractive index (nd) of 1.48 to 1.58, and having an Abbe number (vd) of 70 to 88, and a liquidus temperature of 800 C. or less.

An optical glass includes, in terms of mol % of cations, a total amount of La.sup.3+, Y.sup.3+, and Gd.sup.3+ components falling within a range of from 5% to 65% and a total amount of Zr.sup.4+, Hf.sup.4+, and Ta.sup.5+ components failing within a range of from 5% to 65%, and a relationship expressed in Expression (1) given below is satisfied. (La.sup.3++Y.sup.3++Gd.sup.3+)(Zr.sup.4+Hf.sup.4++Ta.sup.3+) 400(%).sup.2

A glass frit includes Bi.sub.2O.sub.3 and has a glass transition temperature (Tg) in a range of 280 C. to 320 C. A display device includes the glass frit including Bi.sub.2O.sub.3 and the glass transition temperature (Tg) in the range of 280 C. to 320 C. The display device shows excellent internal reliability and drop strength.

A glass frit includes Bi.sub.2O.sub.3 and has a glass transition temperature (Tg) in a range of 280 C. to 320 C. A display device includes the glass frit including Bi.sub.2O.sub.3 and the glass transition temperature (Tg) in the range of 280 C. to 320 C. The display device shows excellent internal reliability and drop strength.

The invention provides a high-refraction low-dispersion optical glass with refractive index of 1.76-1.80 and Abbe number of 47-51. The optical glass, comprising the following components by weight percentage: 0-3% of SiO.sub.2; 25-40% of B.sub.2O.sub.3; 20-40% of La.sub.2O.sub.3; 12-25% of Gd.sub.2O.sub.3; 6.5-15% of ZrO.sub.2; greater than 10% but less than or equal to 20% of ZnO; 0-5% of Ta.sub.2O.sub.5; 0-5% of Nb.sub.2O.sub.5; 0-10% of Li.sub.2O; less than 0.45 of (Ta.sub.2O.sub.5+Nb.sub.2O.sub.5)/(ZnO+Li.sub.2O); 0-10% of Y.sub.2O.sub.3; and below 625 C. of glass transition temperature Tg. With reasonable component ratio, the high-refraction low-dispersion optical glass favorable to precision molding with excellent transmittance can be easily enabled while realizing the required optical constant of the glass of the present invention.

The invention provides a high-refraction low-dispersion optical glass with refractive index of 1.76-1.80 and Abbe number of 47-51. The optical glass, comprising the following components by weight percentage: 0-3% of SiO.sub.2; 25-40% of B.sub.2O.sub.3; 20-40% of La.sub.2O.sub.3; 12-25% of Gd.sub.2O.sub.3; 6.5-15% of ZrO.sub.2; greater than 10% but less than or equal to 20% of ZnO; 0-5% of Ta.sub.2O.sub.5; 0-5% of Nb.sub.2O.sub.5; 0-10% of Li.sub.2O; less than 0.45 of (Ta.sub.2O.sub.5+Nb.sub.2O.sub.5)/(ZnO+Li.sub.2O); 0-10% of Y.sub.2O.sub.3; and below 625 C. of glass transition temperature Tg. With reasonable component ratio, the high-refraction low-dispersion optical glass favorable to precision molding with excellent transmittance can be easily enabled while realizing the required optical constant of the glass of the present invention.

The invention provides a high-refraction low-dispersion optical glass with refractive index of 1.76-1.80 and Abbe number of 47-51. The glass has an excellent transmittance when the content of Ta.sub.2O.sub.5 in glass component is reduced. The optical glass comprises the following components by molar percentage: 40-65% of B.sub.2O.sub.3; 6-21% of La.sub.2O.sub.3; 1-15% of Gd.sub.2O.sub.3; greater than 6.5% but less than or equal to 15% of ZrO.sub.2; ad 10-28% of ZnO. According to the present invention, the transmittance of glass becomes excellent without introducing SnO.sub.2; the product cost is optimized by reducing the content of Ta.sub.2O.sub.5; with reasonable component ratio, the high-refraction low-dispersion optical glass in favor of precision molding and with excellent transmittance, as well as the glass preform and optical element made of the optical glass can be easily enabled while the required optical constant of the glass is realized.

The invention provides a high-refraction low-dispersion optical glass with refractive index of 1.76-1.80 and Abbe number of 47-51. The glass has an excellent transmittance when the content of Ta.sub.2O.sub.5 in glass component is reduced. The optical glass comprises the following components by molar percentage: 40-65% of B.sub.2O.sub.3; 6-21% of La.sub.2O.sub.3; 1-15% of Gd.sub.2O.sub.3; greater than 6.5% but less than or equal to 15% of ZrO.sub.2; ad 10-28% of ZnO. According to the present invention, the transmittance of glass becomes excellent without introducing SnO.sub.2; the product cost is optimized by reducing the content of Ta.sub.2O.sub.5; with reasonable component ratio, the high-refraction low-dispersion optical glass in favor of precision molding and with excellent transmittance, as well as the glass preform and optical element made of the optical glass can be easily enabled while the required optical constant of the glass is realized.

An optical glass comprising: by cation %, more than 0% and up to 40% of a content rate of La.sup.3+; 15% to 65% of a content rate of Ti.sup.4+; and more than 0% and up to 20% of a content rate of Zr.sup.4+; wherein a refractive index (n.sub.d) with respect to a d-line is from 2.00 to 2.35.