This invention relates to a polymer film for smart window and more particularly, to the polymer film for smart window which can optionally control the intensity of light passing through a window via the rotation of dichroic particles on the part of users.
In general, the methods of dispersing dichroic particles so as to manufacture a smart window containing dichroic particles are divided into the following two methods: one method is to disperse the particles into liquid, while the other is to disperse the particles into a polymer film.
The first method to prepare the smart window is that particles are dispersed in the selected liquid having similar specific gravity to the particles and placed between the glass plates. However, this method has recognized some disadvantage in that with the lapse of time, particles are precipitated.
The second method is that particles are dispersed in a polymer film and then, this film is placed on the electrode of glass plate. In spite of the fact that unlike the first method, particles are not precipitated, there is a possibility that a dispersion polymer surrounding the particles is dispersed with the heterogeneous size in the film and since the size of dispersed particles has larger than that of visible light wavelength, the film itself becomes opaque.
To overcome the aforementioned shortcomings such as opaque film and inconstant color due to larger size of dispersed particles than visible light wavelength and heterogeneous dispersion, when dichroic particles are dispersed in a polymer film, an object of this invention is to provide a polymer film for smart window which has excellent properties such as (1) during the polymerization of siloxane polymer used as a film medium polymer, some of methyl groups can be substituted into methylphenyl groups and the molecular weight distribution is reduced less than 1.8 by using chloroform, ethanol and methanol, so that the compatibility between the dispersion polymer and the medium polymer is increased and the particles are homogeneously distributed with the size of less than 1 xcexcm, (2) when the medium polymer is cross-linked to prepare a film, the film is transparent with constant color, and (3) the colors on the whole part of the film can be homogeneously changed depending on the changes of electric field.