Solvent-free formulations and nanocomposites
The present disclosure provides a high-refractive index acrylic formulation embedded with sub-30 nm metal oxide nanocrystals. The formulation is solvent-free, low-viscosity, injectable (among other film deposition techniques) and produces high-refractive index, high transparency nanocomposites for a variety of optical applications including OLED lighting and display applications.
1. A formulation comprising at least partially capped metal oxide nanocrystals dispersed in a matrix, wherein the metal oxide is at least one oxide selected from zirconium oxide, titanium oxide, hafnium oxide, zinc oxide, tantalum oxide, and niobium oxide, wherein:
a) the formulation comprises less than 5 wt % solvent;
b) the matrix comprises acrylate and/or methacrylate monomers;
c) the formulation does not comprise benzyl methacrylate or trimethylolpropane triacrylate;
d) the viscosity of the formulation is within the range of 5-100 cP, when measured at 25° C. with a Brookfield RVDV II+ cone and plate viscometer;
e) the formulation has a weight loading of the metal oxide nanocrystals ranging from 20 wt % to 80 wt % of the formulation; and
e) the formulation comprises a monofunctional acrylate and/or methacrylate monomer with high refractive index, wherein the monofunctional acrylate and/or methacrylate monomer comprises benzyl acrylate, ethylene glycol phenyl ether acrylate, ethylene glycol phenyl ether methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 2-phenoxy benzyl acrylate, biphenyl methacrylate, 2-phenylphenol methacrylate, isobutyl acrylate, 2-phenylethyl acrylate, 2-(phenylthio) ethyl acrylate, or a combination thereof.
2. The formulation of claim 1 , further comprising one or more agents independently selected from a curing agent, a surfactant, a wetting agent, an antioxidant, an adhesion promoter, a leveling agent, a dispersing agent, a plasticizer, a toughener, a thickener, a thinner, a dispersant, a flexibilizer, an organic dopant, and other functional additives.
3. The formulation of claim 1 , wherein the matrix comprises one or more agents independently selected from reactive diluents and curing agents.
4. The formulation of claim 1 , wherein the average particle diameter of the at least partially capped nanocrystals is in the range from 1-40 nm, as measured by DLS or TEM.
5. The formulation of claim 1 , wherein said nanocrystals are at least partially capped with at least one capping agent selected from the group consisting of methyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n octyltrimethoxysilane, n-octyltriethoxysilane, phenytrimethoxysilane, dodecyltrimethoxysilane, m,p-ethylphenethyl trimethoxysilane, 2-[methoxy (polyethyleneoxy) propyl] trimethoxysilane, methoxy (triethyleneoxy) propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-(methacryloyloxy) propyl trimethoxysilane, 3-(acryloyloxy) propyl trimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, 1-hexenyltrimethoxysilane, 1-octenyltrimethoxysilane, heptanol, hexanol, octanol, benzyl alcohol, phenol, ethanol, propanol, butanol, oleylalcohol, dodecylalcohol, octadecanol, triethylene glycol monomethyl ether, octanoic acid, acetic acid, propionic acid, 2-[2-(2-methoxyethoxy) ethoxy] acetic acid, oleic acid, benzoic acid, stearic acid, trifluoroacetic acid, biphenyl-4-carboxylic acid, 2-(2-methoxyethoxy) acetic acid, methacrylic acid, mono-2-(Methacryloyloxy) ethyl succinate, and combinations thereof.
6. The formulation of claim 1 , wherein the formulation comprises a di-, tri-, tetra-, or penta-functional acrylate or di-, tri-, tetra-, or penta-functional methacrylate monomer comprising 1,6-hexanediol diacrylate, 1,6-hexanediol di-methacrylate, di(ethyleneglycol) diacrylate, di(ethyleneglycol) di-methacrylate, ethylene glycol diacrylate, glycerol 1,3-diglycerolate diacrylate, tri (propylene glycol) diacrylate, trimethylolpropane tri methacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane ethoxylate tri-methacrylate, 1,6-hexanediol ethoxylate diacrylate, pentaerythritol tetraacrylate, dipentaerythritol penta-/hexa-acrylate, or a combination thereof.
7. The formulation of claim 1 , wherein the formulation further comprises a reactive diluent selected from 1-vinyl-2-pyrrolidone, N-vinyl caprolactam, 2-(2-vinyloxyethoxy) ethyl acrylate, 2-(2-vinyloxyethoxy) ethyl methacrylate, isobutyl acrylate, styrene, 4-methylstyrene, 4-vinylanisole, and divinylbenzene, wherein the weight percent of the reactive diluent is 25-70 wt % with respect to the total monomer content.
8. The formulation of claim 1 , wherein the formulation further comprises a di-, tri-, or tetra-functional thiol crosslinker, or a combination thereof.
9. The formulation of claim 1 , wherein the formulation further comprises a sulfur-containing resin and/or adhesive.
10. The formulation of claim 1 , wherein the formulation further comprises a reactive organic dopant, in the concentration range from 1 to 50 wt %.
11. The formulation of claim 1 , wherein the formulation further comprises a surfactant comprising a polyether-modified siloxane, a fluoro-surfactant, or a combination thereof, wherein the surfactant is either non-reactive or reactive in the acrylate monomer system, wherein the concentration of said surfactant within the total formulation is in the range from 0.1-2.0 wt %.
12. The formulation of claim 1 , wherein the formulation further comprises scattering particles comprising titanium dioxide, aluminum oxide, silicon dioxide, low- or high-index polymer particles, or a combination thereof, wherein the scattering particle sizes range from 100-400 nm, wherein the concentration of said scattering particles within the total formulation ranges from 0.1-30.0 wt %.
13. The formulation of claim 1 , further comprising a curing agent or photoinitiator, wherein the concentration of said curing agent or photoinitiator within the total formulation is in the range from 0.1-20 wt % with respect to the monomer content.
14. The formulation of claim 1 , wherein the formulation has a nanocrystal loading of 35-60% by weight.
15. The formulation of claim 1 , wherein the refractive index of the formulation is 1.52-1.94 at 589 nm as measured by an Abbe refractometer.
16. The formulation of claim 1 , wherein the surface tension of the formulation is within the range of 20-40 dyne/cm, when measured at 25° C. with a Rame-Hart surface tensiometer.
17. The formulation of claim 1 , wherein the % Transmittance of the formulation is 99%-10% in the visible wavelengths of 400-700 nm.
18. The formulation of claim 1 , which is inkjet-printable, wherein droplets of the formulation can be ejected from printhead types, with droplet volumes between 6-40 pL at drop velocities from 3-9 m/s.
19. A nanocomposite film prepared from a process comprising applying the formulation of claim 1 via spin coating, slot-die coating, screen-printing, ink-jet printing, nanoimprinting, photopatterning, 3D printing, dip coating, draw-bar coating, roll-to-roll printing, spray coating, dispensing, volume casting, screen printing, or any combination thereof, to a surface, and curing the applied formulation.
20. The nanocomposite film of claim 19 , wherein the curing is conducted via UV irradiation under a UV LED source with a wavelength at 365 nm, 385 nm, 395 nm, or 405 nm or via a mercury “D”, “H” and/or “V” lamp(s) at a UV dose ranging from 0.1-10 J/cm2.
21. The nanocomposite film of claim 20 , having a thickness ranging from 50 nanometers to 100 micrometers, or from 0.5 micrometer to 20 micrometers.
22. The nanocomposite film of claim 19 , wherein the % Transmittance of the nanocomposite film at thicknesses less than 10 microns is 99%-10% in a visible wavelength from 400 nm-700 nm.
23. The nanocomposite film of claim 19 , which has a refractive index of 1.54-2.00 at 550 nm.