Patent attributes
The present invention is intended to provide wave plates which have excellent initial properties, are hardly influenced by the usage environment or the production environment and have excellent long-term reliability. The first wave plate of the invention is a wave plate comprising two or more retardation films, wherein the retardation films are not bonded to each other in the laser beam transmission area and further they are bonded to each other in at least a part of other area than the laser beam transmission area. The second wave plate is a wave plate comprising at least two retardation films which are laminated on each other, on at least one surface of said laminated retardation films a glass substrate being laminated, wherein the retardation films, and the retardation film and the glass substrate are lamination-fixed respectively with different adhesives which are selected from an adhesive (A) having a glass transition temperature of not higher than 0° C. and a Young's modulus at 23° C. of not more than 10 MPa and an adhesive (B) having a glass transition temperature of not lower than 40° C. and a Young's modulus at 23° C. of not less than 30 MPa (with the proviso that a difference in glass transition temperature between the adhesive (A) and the adhesive (B) is 60° C. or more and a difference in Young's modulus at 23° C. between the adhesive (A) and the adhesive (B) is 40 Mpa or more).
