ND FILTER AND PROCESS FOR PRODUCING THE SAME

摘要

PROBLEM TO BE SOLVED: To solve the problems of low reproducibility of multilayer film deposition in vacuum deposition of an ND filter, complicatedness of steps and lowering of yield due to the same, and difficult response to a design change; to obtain an ND filter with good wavelength flatness, and to provide a simple process for producing such an ND (Neutral Density) filter with good reproducibility. SOLUTION: The ND filter contains a thermoplastic resin (A) having a specific light transmittance and carbon black (B) having a specific particle size. The ND filter satisfies the expression (1): 0.92×T(ave)≤T(min) and the expression (2): 1.08×T(ave)≥T(Max), wherein T(ave), T(min) and T(max) represent an average value, a minimum value and a maximum value of light transmittance in a range of 380-780 nm, respectively. COPYRIGHT: (C)2010,JPO&INPIT