Method for preparing porous polymer film having controlled pore depth, and porous polymer film prepared thereby

A method for preparing a porous polymer film, the method comprising the steps of:

• applying a thermosetting polymer resin on a substrate;
• and
• curing the thermosetting polymer resin while spraying vapor thereto to form a porous structure on a surface or on a surface and inside of the porous polymer film,
• wherein a pore formation depth is controlled within a range from about 15 μm to about 120 μm by adjusting a rate of the curing of the thermosetting polymer resin, such that (i) when the curing rate of the thermosetting polymer resin is faster than a permeation rate of the vapor, a porous structure is formed only on a surface of the polymer film;
• and (ii) when the curing rate of the thermosetting polymer resin is slower than the permeation rate of the vapor, a porous structure is formed on the surface and interior of the polymer film,
• wherein the step of curing the thermosetting polymer resin while spraying vapor is performed by placing a supporting block on a bottom of a pressure vessel capable of forming high temperature and high pressure;
• placing water on the bottom of the vessel;
• placing the substrate on which the thermosetting polymer resin is applied on the supporting block;
• and then applying the high temperature and high pressure to form the vapor so that the vapor is permeated to the surface of the polymer being cured,
• wherein the high temperature is from 100° C. to 140° C. and the high pressure is from 70 kPa to 200 kPa, and
• wherein the porous polymer film is a light reflective film, and a light reflectance of the light reflective film is adjusted by the controlling of the pore formation depth.