“Refractive index modifier refers to any material useful to modify the refractive index of a material.   The terms "precursor solution" and "polymer precursor solution" are intended to broadly refer to a solution capable of being polymerized.  A precursor solution, for example, may be a solution containing a monomer, carrier or solvent, some polymer, un-saturated polymer, polymer dissolved in monomer solution, and/or additional materials. A precursor solution may also be substantially pure liquid monomer.”

“Refractive index modification is possible by adding a polymer that has a higher or lower refractive index than the candidate host polymer to respectively raise or lower its refractive index. The refractive index modifier should also be compatible with the host polymer to prevent phase segregation or other effects that could lead scattering of light in the resultant polymer. Another example refractive index modifier is any chemical(s) that alters the crystallinity or density or the polarizable electrons per unit volume of the host polymer. Chemicals that increase these properties can be used to increase the refractive index of the host polymer, and chemicals that decrease these properties can be used to decrease refractive index of host polymer.”

“Fluorinated polymers are examples of chemicals that increase refractive index, while chlorinated polymers are examples of chemicals that decrease the refractive index. Another refractive index modifier believed to be useful to raise the refractive index of polyester is polycarbonate.”

“In addition to chemicals, it has been discovered that nanoparticles are a suitable refractive index modifier.  Nanoparticles with a diameter that is less than that of visible light do not have a noticeable effect on the transmission of the visible light through the transparent polymer.  Visible light has a wavelength of between about 400-700 nm.  Accordingly, it is preferred that nanoparticles used in methods of the invention as a refractive index modifier have a diameter of less than about 400 nm, and more preferably of less than about 200 nm.  Nanoparticles may also be desirable since they can be used to introduce other functionalities in addition to increasing mechanical strength, such as reflecting short wavelength ultra-violet light.  Substantially platelet shaped, cylindrical shaped, and other shaped nanoparticles may be used.  Nanoparticles may be made of metal oxides such as titanium oxide and/or titanium dioxide, ceramics, in addition to other suitable materials.”

“Nanoparticles that have a refractive index greater than the host polymer will increase the refractive index of the polymer, and vice versa. By way of example, titanium dioxide nanoparticles have a refractive index greater than polyester. They may therefore be used in a method of the invention as a refractive index modifier to increase the refractive index of a polyester that results from the curing of a polyester precursor solution. Nanoparticles used as refractive index modifiers should also be selected to insure that other properties of the polymer are not adversely affected, with an example adverse effect being a reaction with the polymer over time.:

(Khanna, US Patent 7,819,997; 10/26/2010)

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