KSF - INKS

Abstract

Described are liquid compositions containing luminescent particles in a high loading, particularly from the class of red luminescent phosphor particles, in a diluent, particularly from the class of curable monomers with low polarity. The invention further provides for the manufacture of such inks and to the use of such inks for preparing films and lighting devices.

Claims

1. A liquid composition containing luminescent particles in a diluent, wherein the concentration of said luminescent particles in said liquid composition is between 25-75 wt %; the diluent comprises a curable monomer selected from the class of acrylate monomers, the curable monomer having a molar ratio z of the sum of (oxygen+nitrogen+halogens+sulfur) to carbon, wherein z?0.25; and the diluent optionally comprises additives; and the diluent is essentially free of solvent or free of solvent; and the luminescent particles are selected from the class of red luminescent phosphor particles showing luminescence in the range of 610-650 nm, and have a volume-weighted average primary particle size s.sub.p, 100 nm?s.sub.p?50 ?m; and are Mn+4 doped phosphor particles of formula (II): [A].sub.x[MF.sub.y]:Mn.sup.4+ (II), wherein: A represents Li, Na, K, Rb, Cs or a combination thereof, M represents Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof, x represents the absolute value of the charge of the [MFy] ion, and y represents 5, 6 or 7, and wherein the viscosity of the liquid composition is more than 500 cP at room temperature and measured by rotational viscosimetry.

2. The composition of claim 1, wherein the luminescent particles are Mn+4 doped phosphor particles of formula (II): K.sub.2SiF.sub.6:Mn.sup.4+ (II).

3. The composition according to claim 1, wherein the concentration of said luminescent particles in said composition is between 40-70 wt %.

4. The composition according to claim 1, wherein the curable monomer is selected from the class of mono-functional acrylate monomers, di-functional acrylate monomers, multi-functional acrylate monomers and combinations thereof.

5. The composition according to claim 1, wherein the curable monomer is selected from compounds of formulae (III), (V), (VI) and combinations thereof: ##STR00007## wherein: R.sup.9 represents H or CH.sub.3, R.sup.10 represents a cyclic, linear or branched C.sub.1-25 alkyl, or a C.sub.6-26 aryl group, each optionally substituted with one or more cyclic, linear or branched C.sub.1-20 alkyl, phenyl or phenoxy, n represents 0 or 1, and X represents a spacer from the group of alkoxylates comprising 1-8 carbon atoms and 1-4 oxygen atoms; ##STR00008## wherein: R.sup.21 independently from each other represent H or CH.sub.3; R.sup.23 represents a linear or branched C.sub.1-25 alkyl group, each optionally substituted with one or more cyclic, linear or branched C.sub.1-20 alkyl, phenyl or phenoxy; X.sup.22 independently from each other represent a direct bond (i.e. no spacer) or a spacer selected from the group of alkoxylates, whereby both substituents X.sup.22 together comprise 8-40 carbon atoms and 2-20 oxygen atoms; ##STR00009## wherein: R.sup.31 independently from each other represent H or CH.sub.3; R.sup.33 represents a cyclic C.sub.5-25 alkyl, or a C.sub.6-26 aryl group, each optionally substituted with one or more cyclic, linear or branched C.sub.1-20 alkyl, phenyl or phenoxy; X.sup.32 independently from each other and are either not present (R.sup.33 directly bound to the oxygen by a single bond, no spacer) or represent a spacer selected from the group of alkoxylates, whereby both substituents X.sup.32 together comprise 1-8 carbon atoms and 1-8 oxygen atoms.

6. The composition according to claim 5 comprising acrylate monomers where R.sup.10 and/or R.sup.33 are independently selected from the group consisting of isobornyl, dicyclopentanyl (di-cp), dicyclopentenyl, 3,3,5-trimethyl cyclohexyl, and 4-tert-butylcyclohexyl.

7. The composition according to claim 4 comprising multifunctional acrylates, wherein 80%-100% (n/n) of said acrylate is a trifunctional acrylate.

8. The composition according to claim 1 additionally comprising one or more initiators, preferably one or more photoinitiators.

9. The composition according to claim 1 additionally comprising one or more viscosity modifiers, preferably selected from the group of polymers or thixotropy additives.

10. The composition according to claim 1, wherein the viscosity of said composition is more than 5000 cP, preferably more than 50,000 cP, each at room temperature and measured by rotational viscosimetry.

11. A method of manufacturing a composition according to claim 1, said method comprising the steps of: a) providing a first composition containing luminescent particles, preferably in the form of a dry powder and a second composition containing curable monomer and optionally initiator, both compositions being free of solvent, then b) combining said first and second composition, optionally followed by degassing, c) optionally adding and dissolving a viscosity modifier in the composition of step b); to thereby obtain the luminescent liquid composition.

12. A method for manufacturing a luminescent film or a luminescent component comprising the step of coating a liquid composition according to claim 1 on a substrate.

13. A method for manufacturing a display, particularly an LCD display, said method comprising the step of coating a liquid composition according to claim 1 on a substrate and assembling the thus obtained luminescent film or component to thereby obtain a display.

14. A method of manufacturing a composition according to claim 1, said method comprising the steps of: a) providing a first composition containing luminescent particles, preferably in the form of a dry powder, and a second composition containing curable monomer and solvent; b) combining said first and second composition optionally followed by degassing; c) removing said solvent from the obtained liquid composition, and d) optionally adding and dissolving a viscosity modifier in the composition of either step b) or c); to thereby obtain the luminescent liquid composition.

Description

EXAMPLE 1

[0145] 120 g commercially available KSF particles (volume-weighted average particle size of 8 micron) were mixed into 100 g commercially available acrylate FA-DCPA (Hitachi-Chemical; CAS: 33791-58-1; z ratio=0.15) and stirred for 1 h using a magnetic stirrer. The obtained liquid composition is degassed by applying vacuum. The obtained liquid composition has a final viscosity of of 15 cP and contains 55 wt % KSF.

[0146] The red emission quantum yield of the obtained liquid composition was measured using an integrating sphere (Quan-taurus, Hamamatsu) 2 weeks after preparation resulting in a quantum yield of 95%. This shows that the chemical compatibility between the diluent and the KSF particles is given because the KSF particles have retained their outstanding optical properties.

[0147] After 2 weeks of preparation, 3 wt % of photoinitiator (TPO) were then dissolved in the liquid composition and coated on a PET-film, laminated with a second PET film and cured with UV-light to obtain a free-standing red luminescent film with a cured layer of 20 micron thickness. After treating the obtained film 1000 for hours under 60? C./90% r. H. the film quantum yield did not degrade. This shows that the curable monomer used in the liquid composition resulted in cured red luminescent films able to retain the optical properties of the KSF particles under accelerated degradation conditions (high temperature and high humidity) for an extended time.

Example 2

[0148] 100 g commercially available KSF particles (volume-weighted average particle size of 8 micron) were mixed into 100 g commercially available acrylate FA-DCPA (Hitachi-Chemical; CAS: 33791-58-1; z ratio=0.15) and stirred for 1 h using a magnetic stirrer. Then 100 g of a commercially available multi-functional acrylate monomer (viscosity>100000 cP) was added and dissolved by stirring. The obtained liquid composition is degassed by applying vacuum. The obtained liquid composition has a final viscosity of 750 cP and contains 33 wt % KSF.

[0149] The quantum yield of the liquid composition after 2 weeks of room temperature storage was similar as in example 1. A red luminescent film was prepared analogous to examples 1 and the quantum yield after 1000 hours under 60? C./90% r. H. could also be retained.

Example 3

[0150] 100 g commercially available KSF particles (volume-weighted average particle size of 8 micron) were mixed into 100 g commercially available trimethyl cyclohexanol methacrylate (CAS: 7779-31-9; z ratio=0.15) and stirred for 1 h using a magnetic stirrer. Then 14 g of a commercially available viscosity modifier (polystyrene) was added and dissolved with a high-shear mixer. The obtained liquid composition is degassed by applying vacuum. The obtained liquid composition has a final viscosity of of 6000 cP and contains 47 wt % KSF.

[0151] The quantum yield of the liquid composition after 2 weeks of room temperature storage was similar as in example 1. A red luminescent film was prepared analogous to examples 1 and the quantum yield after 1000 hours under 60? C./90% r.H. could also be retained.

Example 4

[0152] 100 g commercially available KSF particles (volume-weighted average particle size of 8 micron) were mixed into 100 g toluene and stirred for 1 h using a magnetic stirrer. Then 100 g of a commercially available multi-functional acrylate monomer (viscosity>100000 cP) was added and dissolved by stirring. Then the toluene is distilled off from the liquid composition by using a rotary evaporator. The obtained liquid composition has a final viscosity of ca. 130000 cP and contains 50 wt % KSF.

[0153] The quantum yield of the liquid composition after 2 weeks of room temperature storage was similar as in example 1. A red luminescent film was prepared analogous to examples 1 and the quantum yield after 1000 hours under 60? C./90% r.H. could also be retained.