Red enhancement in white LED displays using UV-cured color conversion films
Color conversion films for a LCD (liquid crystal display) having RGB (red, green, blue) color filters, as well as such displays, formulations, precursors and methods are provided, which improve display performances with respect to color gamut, energy efficiency, materials and costs. The color conversion films absorb backlight illumination and convert the energy to green and/or red emission at high efficiency, specified wavelength ranges and narrow emission peaks. For example, rhodamine-based fluorescent compounds are used in matrices produced by sol gel processes and/or UV (ultraviolet) curing processes which are configured to stabilize the compounds and extend their lifetime—to provide the required emission specifications of the color conversion films. Film integration and display configurations further enhance the display performance with color conversion films utilizing various color conversion elements.
1. A color conversion film for a LCD (liquid crystal display) having RGB (red, green, blue) color filters, the color conversion film comprising at least one rhodamine-based fluorescent (RBF) compound selected to absorb illumination from a backlight source of the LCD and have a R emission peak, wherein the backlight source of the LCD provides white illumination and the at least one RBF compound is red-fluorescent and defined by Formula 1:
wherein
R 1 is COOR, NO 2 , COR, COSR, CO(N-heterocycle), CON(R) 2 , or CN;
R 2 each is independently selected from H, halide, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle), NCO, NCS, OR, SR, SO 3 H, SO 3 M and COOR;
R 3 each is independently selected from H, halide, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle), NCO, NCS, OR, SR, SO 3 H, SO 3 M and COOR;
R 4 -R 16 and R 4′ -R 16′ are each independently selected from H, CF 3 , alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl, benzyl, halide, NO 2 , OR, N(R) 2 , COR, CN, CON(R) 2 , CO(N-Heterocycle) and COOR;
R is H, alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl, benzyl, —(CH 2 CH 2 O) r CH 2 CH 2 OH, —(CH 2 ) p OC(O)NH(CH 2 ) r Si(Oalkyl) 3 , —(CH 2 ) p OC(O)CH═CH 2 or —(CH 2 ) p Si(Oalkyl) 3 ;
n and m are each independently an integer between 1-4;
p and q are each independently an integer between 1-6;
r is an integer between 0-10;
M is a monovalent cation; and
X is an anion.
2. The color conversion film of claim 1 , produced at least partially by a UV (ultraviolet) curing process carried out using, to provide a matrix for the at least one RBF compound, a formulation comprising 65-70% monomers, 25-30% oligomers, and 5% photointiator.
3. The color conversion film of claim 2 , wherein:
the monomers consist of at least one of: dipropylene glycol diacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated (3) glyceryl acrylate and trimethylolpropane triacrylate,
the oligomers consist of at least one of: polyester acrylate, modified polyester resin diluted with dipropyleneglycol diacrylate and aliphatic urethane hexaacrylate, and
the photointiator consists of at least one of: alpha-hydroxy-cyclohexyl-phenyl-ketone and alpha-hydroxy ketone.
4. The color conversion film of claim 2 , wherein 0.005-0.05% of the at least one RBF compound is added to the formulation.
5. The color conversion film of claim 1 , further configured to shift some of a yellow region in the white illumination into a R transmission region of the R color filter.
6. An LCD comprising the color conversion film of claim 1 .
7. The LCD of claim 6 , wherein the color conversion film is in an LCD panel.