Optical film

An optical film for a cover plate of a flexible display, which is disposed on a display side of the flexible display sequentially including:

• an optical substrate layer having a thickness in a range of 38 μm to 57 μm adjacent to the flexible display;
• a first adhesive layer having a first thickness t1 in a range of 5 μm to 12 μm, and the first adhesive layer is an acrylic pressure sensitive adhesive having a storage modulus G′ of between 0.5×105 Pa and 1.5×105 Pa;
• a polarizing layer having a thickness in a range of 38 μm to 57 μm;
• a second adhesive layer having a second thickness t2 in a range of 5 μm to 12 μm, and the second adhesive layer is an acrylic pressure sensitive adhesive having a storage modulus G′ of between 3×105 Pa and 4×105 Pa;
• and
• a surface functional film having a thickness in a range of 43 μm to 67 μm which is disposed on a folding side of the flexible display;
• wherein the optical film satisfies the following formula (1):
• 17.49×10−3 (Gpa/μm)≤E′/T≤18.77×10−3 (Gpa/μm) (1)
• wherein T represents a total thickness of the optical film, and the total thickness T is between 152 μm and 191 μm, and E′ is an integrated bending modulus in a range of 2.65 Gpa to 3.58 Gpa obtained by three-point bending test and calculated by the following formula (2):
• E′=L3F/4wt3d (2)
• wherein F represents a stress applied to the optical film in the three-point bending test, L represents a measuring length of the optical film, w represents a measuring width of the optical film, d represents a strain of the optical film, and t represents a total thickness of the optical substrate layer, the polarizing layer and the surface functional film.