NOVELTY - Polymer substrate (50) has thickness of 1-20 mm, and comprises hard-coat layer on the surface of substrate. The hard-coat comprises substrate hardened layer (70) which is laminated on the surface of the polymer substrate, and containing hydrolysis-condensation product of organosilicon compound as main component, and having thickness of 0.1-20 mu m, and silicon-oxide layer (80) which is directly in contact with the substrate hardened layer on the other side of the polymer substrate, formed by chemical vapor deposition method using organosilicon compound as raw material.    USE - Polymer substrate is used for motor vehicle window material, building materials, and surface-protection board of solar cell.    ADVANTAGE - The polymer substrate has excellent heat resistance, high environmental resistance and high degree of abrasion resistance, and provides high efficient resin grading material.    DETAILED DESCRIPTION - Polymer substrate has thickness of 1-20 mm, and comprises hard-coat layer on the surface of substrate. The hard-coat comprises substrate hardened layer which is laminated on the surface of the polymer substrate, and containing hydrolysis-condensation product of organosilicon compound as main component, and having thickness of 0.1-20 mu m, and silicon-oxide layer which is directly in contact with the substrate hardened layer on the other side of the polymer substrate, formed by plasma-enhanced chemical vapor deposition method (PE-CVD) using organosilicon compound as raw material. The film thickness of the silicon-oxide layer is 3.5-9 mu m. The largest indentation depth of surface of silicon-oxide layer by nanoindentation measurement at maximum load of 1 mN is 150 nm or less. In 3-point bending test of polymer substrate with hard-coat layer which gives pushing displacement in which surface where silicon-oxide layer is laminated becomes concave, and the value of the critical upsetting ratio (K) of the silicon-oxide layer calculated by formula: K=(R-D/2)/R-(0.00215x d) and R=((G/2)2-(( Delta )L)2)/(2x ( Delta )L), is 0.975 or less, where D is the whole polymer substrate thickness with a hard-coat layer (mm), d is film thickness ( mu m) of silicon-oxide layer, G is the distance (mm) between the edge portion in 3 point bending test apparatus, ( Delta )L is pushing displacement amount (mm) in case the silicon-oxide layer starts peeling from the cut line previously drawn in the central-bearing position of the load application during 3-point bending test, and R is curvature radius (mm) of the polymer substrate with hard-coat layer in case the silicon-oxide layer starts peeling from the cut line previously drawn in the central-bearing position of the load application during 3-point bending test. An INDEPENDENT CLAIM is included for manufacture of polymer substrate.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of polymer substrate.    Polymer substrate (50)    Contact bonding layer (60)    Substrate hardened layer (70)    Silicon-oxide layer (80)