Ricoh Optical Industries Co., Ltd.

Masaaki Sato

Kazuhiro Umeki

Shosen Sato

To provide a gradation mask which can easily assure distribution of desired exposure intensity. �Means to accomplish the object!A metal and/or metallic compound film 2 (FIG. 1) is uniformly formed on a transparent substrate 1 such that they have a transmittance of 10% or less. An etching mask having a desired pattern is formed on the metal and/or metallic compound film 2. The metal and/or metallic compound film 2 is dry- or wet-etched. The metal and/or metallic compound film 2 is repeatedly subject to patterning and etching steps by using etching masks with different patterns, so that the obtained layers have a thickness Z(X, Y) varying in three or more steps in accordance with desired transmittance.

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Hanamaki, Japan

Masaaki Sato