Antireflection film, optical device, and production method for antireflection film

An antireflection film, comprising:

• a light shielding layer which is placed on a substrate and contains an electrical conductor;
• a first transmission layer which is placed on the light shielding layer and contains a dielectric;
• a semi-transmission layer which is placed on the first transmission layer and contains an electrical conductor;
• and
• a second transmission layer which is placed on the semi-transmission layer and contains a dielectric,
• wherein the light shielding layer and the semi-transmission layer have a larger extinction coefficient than the first transmission layer and the second transmission layer,
• the first transmission layer is an aluminum oxide layer having a thickness of 70 nm or more and 90 nm or less,
• the semi-transmission layer is a titanium layer having a thickness of 9 nm or more and 12 nm or less, and
• the second transmission layer is an aluminum oxide layer having a thickness of 60 nm or more and 80 nm or less.