An object is to solve the problems which can be peculiarly generated in a coating-type optical film, and provide an optical film which hardly causes deterioration in optical performance over time. A display device equipped with the optical film, and a process for producing the optical film are also provided. There is provided a polarizing plate having a diffusion preventing layer A having a thickness of 0.05 μm to 3 μm, a polarizing film containing a polymer of a polymerizable liquid crystal and a dichroic coloring matter, and a diffusion preventing layer B having a thickness of 0.05 μm to 3 μm, in this order.