Optical film, anti-reflection film, polarizing plate and image display device

A process for producing an anti-reflection film,

• the anti-reflection film comprising a transparent support;
• a hard coat layer as an optical layer on or above the transparent support;
• and a low refractive index layer on or above the hard coat layer, wherein the hard coat layer contains a thickening agent and has a thickness of 5 μm or more,
• the process comprising:
• coating a coating composition for the hard coat layer on or above the transparent support, wherein the coating composition contains the thickening agent which shows a viscosity of 10 mPa·sec or more at 25° C. when dissolved in 2-butanone in a content of 3% by mass, and the coating composition has a viscosity of 10 mPa·sec or more at 25° C.;
• coating a coating composition of the low refractive index layer on or above the transparent support,
• wherein
• the process does not include hardening of the hard coat layer and winding up of the transparent support between the coating of the coating composition for the hard coat layer and the coating of the coating composition for the low refractive index layer, and the coating of the coating composition for the hard coat layer and the coating of the coating composition for the low refractive index layer are performed in one conveying of the transparent support.