Durability-enhanced thermochromic film and method of manufacturing same

Abstract

A thermochromic film includes a substantially transparent substrate, and a polymer matrix layer coated on the substrate, the polymer matrix layer having cross-linked molecule chains generated before the coating, and the polymer matrix layer being embedded with randomly dispersed thermochromic nanoparticles before the coating.

What is claimed is: 
     
         1 . A thermochromic film comprising:
 a substantially transparent substrate; and   a polymer matrix layer coated on the substrate, the polymer matrix layer having cross-linked molecule chains generated before the coating, and the polymer matrix layer being embedded with randomly dispersed thermochromic nanoparticles before the coating.   
     
     
         2 . The thermochromic film of  claim 1 , wherein the substrate is a biaxially-oriented polyethylene terephthalate (BoPET) sheet. 
     
     
         3 . Thermochromic film of  claim 1 , wherein the thermochromic nanoparticles are crystalline vanadium dioxide (VO 2 ) nanoparticles. 
     
     
         4 . The thermochromic film of  claim 3 , wherein the crystalline vanadium dioxide (VO 2 ) nanoparticles are synthesized from vanadium pentoxide (V 2 O 5 ) powder. 
     
     
         5 . The thermochromic film of  claim 4 , wherein the synthesizing process comprises:
 adding a predetermined amount of vanadium pentoxide (V 2 O 5 ) powder to a predetermined amount of deionized water to form a first mixture;   stirring the first mixture for a first predetermined amount of time;   adding a predetermined amount of oxalic acid dihydrate to the first mixture to form a second mixture;   further stirring the second mixture until a clear light green or blue slurry is formed;   keeping the second mixture at a first predetermined elevated temperature for a second predetermined amount of time;   air-cooling the second mixture to room temperature to obtain black-precipitates;   washing the black-precipitates with deionized water and ethanol sequentially; and   drying the washed black-precipitates with a vacuum furnace at a second elevated temperature for a third predetermined amount of time.   
     
     
         6 . The thermochromic film of  claim 5 , wherein the first predetermined amount of time is approximately 20 minutes. 
     
     
         7 . The thermochromic film of  claim 5 , wherein the first elevated temperature is approximately 260° C. 
     
     
         8 . The thermochromic film of  claim 5 , wherein the second amount of time is approximately 24 hours. 
     
     
         9 . The thermochromic film of  claim 5 , wherein the second elevated temperature is approximately 120° C. 
     
     
         10 . The thermochromic film of  claim 5 , wherein the third predetermined amount of time is approximately 5 hours. 
     
     
         11 . The thermochromic film of  claim 3 , wherein the polymer matrix layer is produced by dispersing a predetermined amount of the thermochromic nanoparticles in a predetermined amount of a polymer matrix material to form a third mixture, and stirring the third mixture for a fourth predetermined amount of time. 
     
     
         12 . The thermochromic film of  claim 11 , wherein the fourth predetermined amount of time is approximately 12 hours. 
     
     
         13 . The thermochromic film of  claim 11 , wherein ultrasonic energy is applied to the polymer matrix material during the dispersing. 
     
     
         14 . The thermochromic film of  claim 11 , wherein the polymer matrix material is poly(methyl methacrylate) (PMMA) with a molecular weight of approximately 950,000 forming a matrix. 
     
     
         15 . The thermochromic film of  claim 14 , wherein a lifetime of the crystalline vanadium dioxide (VO 2 ) nanoparticles embedded in the cross-linked polymer matrix material is longer than approximately 900 hours under a temperature of approximately 60° C., and a relative humidity of approximately 95%. 
     
     
         16 . The thermochromic film of  claim 11 , wherein the cross-linked molecule chains are generated by irradiating the third mixture with a radiation for a fifth predetermined amount of time while stirring the third mixture at a predetermined rev per minute (rpm). 
     
     
         17 . The thermochromic film of  claim 16 , wherein the radiation is a UV radiation with a wavelength shorter than 300 nm. 
     
     
         18 . The thermochromic film of  claim 16 , wherein a dose of the radiation is adjusted to control a cross-link degree in the polymer matrix material. 
     
     
         19 . The thermochromic film of  claim 16 , wherein the fifth predetermined amount of time is approximately 10 hours. 
     
     
         20 . The thermochromic film of  claim 16 , wherein the predetermined rev per minute (rpm) is approximately 300. 
     
     
         21 . The thermochromic film of  claim 16 , wherein the irradiated third mixture is maintained at a substantially constant temperature of approximately 75° C. for approximately 40 minutes. 
     
     
         22 . The thermochromic film of  claim 1 , wherein the polymer matrix layer is coated on the substrate using a blade moving relative to the substrate at a predetermined speed while maintaining a predetermined gap to the substrate. 
     
     
         23 . The thermochromic film of  claim 1 , the polymer matrix layer coated substrate is dried in a fume hood for approximately 2 hours.