| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a wavelength plate for optical information recording/reproducing device which has an excellent initial characteristic, is hardly affected by usage environments and manufacture environments and has excellent long period reliability. <P>SOLUTION: In the wavelength plate using an optical retardation film made of cyclic olefin resin, when wavelength is defined as λ, wave front aberration is ≤50 mλ. It is preferable to use the optical retardation film hat the value γ defined by the following equation (a) is ≤7 as the optical retardation film made of the cyclic olefin resin. The equation (a) is expressed by γ=(¾α-β¾/Re)×10<SP>4</SP>(a). In the equation (a), α is the coefficient of heat contraction (%) in the main stretching direction after heating at 120°C for 24 hr, β is the coefficient of heat contraction (%) in the sub-stretching direction after heating at 120°C for 24 hr, and Re is the retardation (nm) at wavelength 590 nm of the retardation film. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
