| 摘要 |
PROBLEM TO BE SOLVED: To selectively cut the light of wavelength which decreases color purity and to correct the color balance by using an optical filter having a layer containing at least neodymium and controlling the transmittance at a specified wavelength to a specified value or less. SOLUTION: A layer containing neodymium is formed on a transparent substrate. The preferable range of the transmittance of the optical filter containing a neodymium compound is 0.001 to 60% at 585 nm wavelength of the optical filter, and more preferably 0.005 to 20%, and most preferably 0.01 to 3%. The source material to introduce neodymium is selected from, for example, neodymium, neodymium oxide, neodymium chloride, neodymium fluoride, neodymium carbonate, neodymium nitrate, hydrates of these, neodymium salts of saturated or unsaturated carboxylic acids, and neodymium salts of aromatic carboxylic acids. As the saturated aliphatic carboxylic acids which constitute neodymium salts, for example, not only formic acid but monocarboxylic acids having 1 to 20 carbon atoms in alkyl groups and oxalic acid are used.
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