| 摘要 |
<p>Four different optical interference films are formed on the outer surface (13) of an incandescent lamp (11) to achieve good color rendering properties at a high color temperature. A first film formed on the lamp (11) includes high (31) and low (33) refractive index layers alternately stacked so that the total number of layers is n (where n is odd number greater than 5) and the optical thickness of each thereof is 0.12 SIMILAR 0.7 mu m. A second film formed on the first film has the low refractive layer (33) and the optical thickness of 0.132 0.2125 mu m, which is calculated by the equation (K + 1) x d/2, wherein K is 1.2 SIMILAR 1.5 and d is the optical thickness of each refractive index layer of the first film. A third film formed on the second film has at least a high refractive layer (31). The total number of refractive index layers of the third film is an odd number of 1 SIMILAR (n -4) and the optical thickness of each refractive index layer thereof is 0.144 SIMILAR 0.255 mu m, which is calculated by the expression (K x d). A fourth film includes the low refractive index layer (33) having the optical thickness of 0.0720 SIMILAR 0.1275 mu m, which is calculated by the expression (K x d/2).</p> |
