referring to fig1 , an optical film 100 , according to a first embodiment , is shown . the optical film 100 includes a substrate 50 made of a transparent polymer material . the substrate 50 includes a number of cone - shaped micro - protrusions 51 . a layer 52 containing hydrophobic - functional - groups is formed on the surfaces of the cone - shaped micro - protrusions 51 . referring to fig2 - 9 , a method for manufacturing the optical film 100 , according to a second embodiment , is shown . the method includes steps as follows . in step 1 , referring to fig2 , a template 10 is provided . the template 10 can be made from monocrystal or metal . in the embodiment , the template 10 is made from monocrystalline silicon . the template 10 includes a polished surface 101 . an aluminum film 11 is coated on the polished surface 101 of the template 10 . the aluminum film 11 may be coated by a vacuum deposition method , or a magnetron sputtering method , etc . in step 2 , referring to fig3 and 4 , a number of regular cone - shaped microstructures 21 are formed on a surface of the aluminum film 11 , the microstructures 21 are nano - scale protrusions . in one embodiment , the cone - shaped microstructure 21 is formed in the following manner . the template 10 with the aluminum film 11 is dipped in the electrolytic oxidation tank which contains an electrolyte solution and a voltage is applied on the electrolyte solution . the aluminum film 11 is anodized to form an alumina layer 12 with a number of micro pores 13 . the micro pores 13 are anodic aluminum oxide ( aao ) holes . the electrolyte solution can be selected from the group consisting of a sulfuric acid solution , a phosphoric acid solution and an oxalic acid solution . in the embodiment , the electrolyte solution is an oxalic acid solution with a concentration of about 0 . 3 moles / liters , and the temperature of the electrolyte solution is about 17 ° c . the anodizing time is about 15 minutes and the voltage is about 40 volts . then the template 10 with the micro pores 13 is dipped in a phosphoric acid solution with a concentration of about 5 % by weight and the temperature of about 30 ° c . a voltage is then applied to the phosphoric acid solution to ream the micro pores 13 , and the reaming time is about 8 minutes . the template 10 is cleaned after reaming . the action of reaming and cleaning are repeated for 5 times . a number of regular cone - shaped microstructures 21 with the depth of about 150 nm is formed on the surface of aluminum film 11 . in step 3 , referring to fig5 and 6 , a self - assembled monolayer 22 is formed on the surfaces of the regular cone - shaped microstructures 21 . in one embodiment , the template 10 with the regular cone - shaped microstructures 21 is placed in a hot vacuum chamber . an inert gas is introduced into the vacuum chamber . the temperature of the vacuum chamber is adjusted to about 200 ° c . then long carbon chain perfluorinated fatty acids 30 is introduced into the vacuum chamber . the volume ratio between the long carbon chain perfluorinated fatty acid 30 and the vacuum chamber is about 0 . 2 %. the formula of the long carbon chain fluorinated fatty acid 30 is cf 3 ( cf 2 ) n cooh wherein n = 3 , 6 , 8 , 10 , or 16 . the long carbon chain perfluorinated fatty acid 30 is gasified at a high temperature . the long carbon chain perfluorinated fatty acid 30 and the anodic aluminum oxide take place chemical grafting reaction under the condition of annealing in the vacuum chamber and a high hydrophobic self - assembled monolayer 22 is generated on the surfaces of the regular cone - shaped microstructures 21 . in the embodiment , the annealing time is about 3 hours . the purpose of generating the self - assembled monolayer 22 on the surfaces of the regular tapered microstructures 21 is to increase the mold release ability in a later hot embossing step . in step 4 , the template 10 is washed after the chemical grafting reaction . in this step , the template 10 is cooled to room temperature , and then scoured successively by chloroform , acetone , ethanol and deionized water . the chloroform is used for removing the excess of long carbon chain perfluorinated fatty acid 30 . the acetone , ethanol and deionized water are used for reducing polarity and removing the organic solvent on a surface of the self - assembled monolayer 22 . in step 5 , referring to fig7 and 8 , a substrate 50 is provided . the cone - shaped microstructures 21 of the template 10 are transferred to the substrate 50 . the material of the substrate 50 is poly methyl methacrylate ( pmma ). in one embodiment , the substrate 50 is placed facing with the cone - shaped microstructures 21 , and then the substrate 50 and the template 10 as a entirety are placed in a hot embossing machine 60 . the hot embossing machine 60 is heated to a glass transition temperature of the substrate 50 . the glass transition temperature of the substrate 50 is about 120 ° c . the shape of the cone - shaped microstructures 21 is printed on the substrate 50 . accordingly , the substrate 50 with the cone - shaped micro - protrusions 51 is obtained . in step 6 , referring to fig9 , a hydrophobic - functional - group layer 52 is formed on the surfaces of the cone - shaped micro - protrusions 51 and the optical film 100 is obtained . in one embodiment , the substrate 50 with the micro - protrusions 51 is placed in a plasma machine and a carbon tetrafluoride ( cf 4 ) gas is gradually introduced into the plasma machine . under the plasma condition , hydrogen atoms in the carbon chain of pmma are replaced by the fluorine atoms of cf 4 . in this way , the layer 52 containing the hydrophobic - functional - groups is obtained . the surface energy of the pmma is reduced by the chemical reaction . the contact angle between the surface of the optical film 100 and water is greater than 150 degrees according to cassie - baxter model . the optical film 100 manufactured by the above mentioned method has anti - reflective and self - cleaning properties . it is to be understood , however , that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description , together with details of the structures and functions of the embodiments , the disclosure is illustrative only , and changes may be made in detail , especially in the matters of shape , size , and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed .