Abstract: A lubricant oil composition according to the present invention comprises: a lubricant base oil whose kinematic viscosity at 100° C. is 1 to 20 mm2/s; and a viscosity index improver in which a ratio M1a/M2a of a total area M1a of peaks in a chemical shift between 29-31 ppm to a total area M2a of peaks in a chemical shift between 64-69 ppm based on a total area of all the peaks is not less than 10 in a spectrum obtained by 13C-NMR.

Abstract: The lubricating oil composition of the invention comprises a lubricating base oil with a kinematic viscosity at 100° C. of 1-20 mm2/s, and a viscosity index improver having a ratio M1/M2 of 0.20 or greater, between the total area of the peaks between chemical shifts of 36-38 ppm M1 and the total area of the peaks between chemical shifts of 64-66 ppm M2, with respect to the total area of all of the peaks, in the spectrum obtained by 13C-NMR. The lubricating oil composition of the invention has excellent effects, with a sufficiently high HTHS viscosity at 150° C., and a sufficiently low kinematic viscosity at 40° C., a sufficiently low kinematic viscosity at 100° C. and a sufficiently low HTHS viscosity at 100° C.

Abstract: The lubricating oil composition of the invention comprises a lubricating base oil with a kinematic viscosity at 100° C. of 1-20 mm2/s, and a viscosity index improver having a ratio M1/M2 of 0.20 or greater, between the total area of the peaks between chemical shifts of 36-38 ppm M1 and the total area of the peaks between chemical shifts of 64-66 ppm M2, with respect to the total area of all of the peaks, in the spectrum obtained by 13C-NMR. The lubricating oil composition of the invention has excellent effects, with a sufficiently high HTHS viscosity at 150° C., and a sufficiently low kinematic viscosity at 40° C., a sufficiently low kinematic viscosity at 100° C. and a sufficiently low HTHS viscosity at 100° C.

Abstract: A lubricant oil composition according to the present invention comprises: a lubricant base oil whose kinematic viscosity at 100° C. is 1 to 20 mm2/s; and a viscosity index improver in which a ratio M1a/M2a of a total area M1a of peaks in a chemical shift between 29-31 ppm to a total area M2a of peaks in a chemical shift between 64-69 ppm based on a total area of all the peaks is not less than 10 in a spectrum obtained by 13C-NMR.

Abstract: An optical glass for a prism, which has high transmittance, high homogeneity and excellent thermal stability, and an optical part for a prism, which is formed of the optical glass, the optical glass being an optical glass (1) wherein the absolute value of K&Dgr;t represented by the relational expression (I), 1 K ⁢   ⁢ Δ ⁢   ⁢ t = [ ( specific ⁢   ⁢ heat × specific ⁢   ⁢ gravity ) / thermal ⁢   ⁢ conductivity ] × Young ' ⁢ s ⁢   ⁢ modulus × thermal ⁢   ⁢ expansion ⁢   ⁢ coefficient × ( 1 - Poisson ' ⁢ s ⁢   ⁢ ratio ) × photoelastic ⁢   ⁢ constant ( I )