Light diffusing and reflective coatings

Abstract

A multi-layer coating that transmits and reflects light can include a first coating layer and a second coating layer applied over the first coating layer. The first coating layer is prepared from a coating composition that includes a film forming resin, crosslinked organic particles, and inorganic pigment particles. The crosslinked organic particles and the inorganic pigment particles each have a refractive index that is different from the refractive index of the film forming resin. The second coating layer is prepared from a coating composition that includes a film forming resin and reflective and/or translucent particles.

Claims

1. A multi-layer coating that transmits and reflects light comprising: a) a first coating layer prepared from a coating composition comprising a film forming resin, crosslinked organic particles, and inorganic pigment particles, wherein the crosslinked organic particles and the inorganic pigment particles each have a refractive index that is different from the refractive index of the film forming resin, and wherein the inorganic pigment particles comprise a pigment blend comprising (i) titanium dioxide and (ii) at least one other inorganic pigment particle that is different from titanium dioxide, wherein the titanium dioxide comprises less than 30 weight % 15 weight % of the total solids weight of the inorganic pigment particles and the crosslinked organic particles; and b) a second coating layer applied over the first coating layer, the second coating layer prepared from a coating composition comprising a film forming resin and reflective and/or translucent particles, wherein the first and second coating layers together have a light transmittance of at least 8%.

2. The multi-layer coating of claim 1, wherein a difference between the refractive index of the crosslinked organic particles and the film forming resin is from 0.01 to 0.2.

3. The multi-layer coating of claim 1, wherein the film forming resin of the coating composition of the first coating layer and/or the second coating layer comprises a (meth)acrylic resin.

4. The multi-layer coating of claim 1, wherein the film forming resin of the coating composition of the first coating layer and/or the second coating layer is completely free of reactive functional groups.

5. The multi-layer coating of claim 1, wherein the crosslinked organic particles comprise methyl (meth)acrylate particles, styrene particles, acrylonitrile particles, polymethyl urea particles, silicone polymers particles, vinyl acetate particles, sulfur-containing particles, fluoro-containing particles, or a combination thereof.

6. The multi-layer coating of claim 1, wherein the crosslinked organic particles have an average particle size of 0.1 micron to 10 microns.

7. The multi-layer coating of claim 1, wherein the crosslinked organic particles have a particle size distribution of 1 micron to 8 microns.

8. The multi-layer coating of claim 1, wherein the at least one other inorganic pigment particle that is different from titanium dioxide comprises zinc oxide, barium sulfate, calcium carbonate, talc, or combinations thereof.

9. The multi-layer coating of claim 1, wherein the first coating layer coating composition has a weight ratio of inorganic pigment particles to film forming resin of 1:1 to 1:10.

10. The multi-layer coating of claim 1, wherein the reflective and/or translucent particles comprise aluminum, micas, or a mixture thereof.

11. The multi-layer coating of claim 10, wherein the aluminum particles have a particle size of less than 6 microns.

12. The multi-layer coating of claim 10, wherein the micas have a particle size of 30 to 60 microns.

13. The multi-layer coating of claim 1, wherein the first and second coating layer together have an L value measured at a 15° angle of greater than 110.

14. The multi-layer coating of claim 1, further comprising a third coating layer applied over the second coating layer, wherein the third coating layer is prepared from a coating composition comprising inorganic pigment particles and a film forming resin.

15. The multi-layer coating of claim 14, further comprising a clear layer positioned between the second coating layer and the third coating layer.

16. The multi-layer coating of claim 14, further comprising an abrasion resistant topcoat applied over the third coating layer.

17. The multi-layer coating of claim 1, wherein the titanium dioxide comprises less than 10 weight % of the total solids weight of the inorganic pigment particles and the crosslinked organic particles.

18. A substrate at least partially coated with the multi-layer coating of claim 1.

19. The at least partially coated substrate of claim 18, wherein the substrate is a plastic substrate.

20. The at least partially coated substrate of claim 18, wherein the substrate is a keyboard comprising a light source.

Description

EXAMPLE 1

Preparation of a Light Diffusing Coating Composition

(1) Three (3) light diffusing basecoatcoating compositions were prepared from thecomponents listed in Table 1.

(2) TABLE-US-00001 TABLE 1 Basecoat 1 Basecoat 2 Basecoat 3 Components (grams) (grams) (grams) Dianal MB-2952 resin 34.73 34.78 34.82 solution.sup.1 Dianal LR-7671.sup.2 10.50 10.52 10.53 CAB381-2 solution.sup.3 7.73 7.74 7.74 Methyl ethyl ketone 9.89 10.00 10.00 AFCONA-3777.sup.4 0.41 0.42 0.42 Ceraflour 996.sup.5 2.76 2.77 2.77 TiO.sub.2 Intermediate.sup.6 0.57 0.57 0.57 Cross-linked organic 8.41 5.61 3.38 particle Intermediate.sup.7 BaSO.sub.4 Intermediate.sup.8 5.44 7.26 8.73 Acetone 7.59 7.90 8.41 2-Butoxyethanol 2.17 2.26 2.33 Ethyl Acetate 9.77 10.17 10.30 .sup.1Acrylic resin, commercially available from Shanghai Nagase Trading Co., LTD, mixed with methyl ethyl ketone and N-butyl acetate. .sup.2Acrylic resin, commercially available from Mitsubishi Rayon Company, LTD. .sup.3Cellulose acetate butyrate, commercially available from Eastman Chemical Company, mixed with methyl ethyl ketone and N-butyl acetate. .sup.4Flurocarbon modified polymer, commercially available from Afcona Additives. .sup.5Micronized PTFE-modified polyethylene wax, commercially available from BYK-CeraB.V. .sup.6A titanium dioxide intermediate solution prepared from acrylic resin, Aromatic 100 (aromatic hydrocarbon mixture, commercially available from Ashland Inc.), DISPERBYK ® 110 (saturated polyester with acidic groups, commercially available from BYKChemie GMBH), N-butyl acetate, methyl ether propylene glycol, BENTONE ® 34 (montmorillonit clay, commercially available from Elementis Specialties), TRONOX ® CR 826 (titanium dioxide, commercially available from Tronox Inc.), and Microtalc CM2 (hydrated magnesium silicate, commercially available from Soc. Industries Lombarda). .sup.7An intermediate solution containing crosslinked organic particles was prepared from SX-350H (crosslinked styrene particles, commercially available from Soken Chemical & Engineering Co., LTD.), Dianal MB-2952 (acrylic resin, commercially available from Shanghai Nagase Trading Co., LTD), DISPERBYK ® 110 (saturated polyester with acidic groups,commercially available from BYKChemie GMBH), isopropanol, xylene, ethyl acetate, N-butyl acetate, and methyl ether propylene glycol. .sup.8A barium sulfate intermediate solution was prepared from blanc fixe (barium sulfate, commercially available from Sachtleben Corporation), Dianal MB-2952 (acrylic resin, commercially available from Shanghai Nagase Trading Co., LTD), DISPERBYK ® 110 (saturated polyester with acidic groups,commercially available from BYKChemie GMBH), isopropanol, xylene, ethyl acetate, N-butyl acetate, and methyl ether propylene glycol.

(3) The components of samples 1, 2, and 3 were weighed in a half pint container and mixed with a paddle blade air motor stirrer for 20 minutes. After the components of each sample were mixed, each mixed sample was diluted with a solvent blend (blend of 2-butoxyethanol,methyl ethyl ketone, acetone, and ethyl acetate) at a ratio of solvent to sample of 2:1.

EXAMPLE 2

Preparation of a Reflective and Light Diffusing Coating Composition

(4) A reflective and light diffusing coating composition was prepared from thecomponents listed in Table 2.

(5) TABLE-US-00002 TABLE 2 Weight Components (grams) Dianal MB-2952 resin solution.sup.1 44.97 Dianal LR-7671.sup.2 14.99 CAB 381-2 solution.sup.3 9.99 Methyl ethyl ketone 9.99 Disparlon NS-5501.sup.9 5.00 Disparlon 4200-10.sup.10 1.00 Afcona-3777.sup.4 0.50 Amorso-475.sup.11 2.00 METALURE ® 55700.sup.12 3.28 .sup.9Hybrid thixotropic agent, commercially available from Kusumoto Chemicals, LTD. .sup.10Polyolefin xylol dispersion, commercially available from Kusumoto Chemicals, LTD. .sup.11Polyester resin, commercially available from Amorson Inc. .sup.12Aluminum pigment dispersion, commercially available from Eckart GMBH & Co.

(6) All the components listed in Table 2, except for METALURE® 55700, were weighed in a half pint container and mixed with a paddle blade air motor stirrer for 5 minutes. METALURE® 55700 was then added under agitation. The mixture was allowed to mix for 20 minutes. The final mixture was then diluted with a solvent blend (blend of 2-butoxyethanol,methyl ethyl ketone, acetone, and ethyl acetate) at a ratio of solvent to mixture of 2:1.

EXAMPLE 3

Preparation and Evaluation of a Multi-Layer Coating that Transmits and Reflects Light

(7) The light diffusing coating compositions of basecoat coating compositions 1-3 of Example 1 were hand shaken and sprayed onto clear polycarbonate plastic panels or keyboard key substrates. Application onto the substrates was performed with a Spraymation unit with a Binks model 95A spray gun with a 66S nozzle and pin set-up. The compositions were sprayed at a 25 psi air pressure 6 inches from the substrate with a 1 inch index drop for each pass. After application, each composition was allowed to flash for ten minutes. The compositions were then dried to form a coating.

(8) The reflective and light diffusing coating compositions of Example 2 were then sprayed over the basecoats formed from the compositions of Example 1. The composition of Example 2 was sprayed with a Spraymation unit with a Binks model 95A spray gun with a 66S nozzle and pin set-up. The compositions were sprayed at a 25 psi air pressure 6 inches from the coated substrate with a 1 inch index drop for each pass. After application, each composition was allowed to flash for ten minutes. The reflective and light diffusing coating compositions were then baked for 30 minutes at 120° F. Various properties of the multi-layer coating were evaluated including the light transmittance and L values. These properties are shown in Table 3.

(9) TABLE-US-00003 TABLE 3 Silver Basecoat second average coat dry- average L- Multi- film dry-film Value Light layer Visual thickness thickness at Transmission Coat Observation (μm).sup.13 (μm).sup.13 15°.sup.14 (%).sup.15 Basecoat Cannot see 6.3 5.7 131 15 1 light source through panel Basecoat Cannot see 6.3 5.9 135 16 2 light source through panel Basecoat Cannot see 6.4 5.8 134 14 3 light source through panel .sup.13Dry film thickness determined with a Deltascope film build instrument. .sup.14L-value was determined with a GRETAGMACBETH COLOR-EYE ® 2145 Spectrophotometer using the CIE94 color system using L*a*b* coordinates. .sup.15Light transmission determined was with a NIPPON DENSHOKU, NDH 2000N Turbidity (Haze) Meter.

(10) As shown in Table 3, multi-layer coatings 1-3 each exhibited good hiding, good light transmission, and good light reflectance.

(11) The present invention is also directed to the following clauses.

(12) Clause 1: A multi-layer coating that transmits and reflects light comprising: (a) a first coating layer prepared from a coating composition comprising a film forming resin, crosslinked organic particles, and inorganic pigment particles, wherein the crosslinked organic particles and the inorganic pigment particles each have a refractive index that is different from the refractive index of the film forming resin; and (b) a second coating layer applied over the first coating layer, the second coating layer prepared from a coating composition comprising a film forming resin and reflective and/or translucent particles.

(13) Clause 2: The multi-layer coating of clause 1, wherein a difference between the refractive index of the crosslinked organic particles and the film forming resin is from 0.01 to 0.2.

(14) Clause 3: The multi-layer coating of any of clauses 1 or 2, wherein the film forming resin of the coating composition of the first coating layer and/or the second coating layer comprises a (meth)acrylic resin.

(15) Clause 4: The multi-layer coating of any of clauses 1-3, wherein the film forming resin of the coating composition of the first coating layer and/or the second coating layer is completely free of reactive functional groups.

(16) Clause 5: The multi-layer coating of any of clauses 1-4, wherein the crosslinked organic particles comprise methyl (meth)acrylate particles, styrene particles, acrylonitrile particles, polymethyl ureaparticles, silicone polymers particles, vinyl acetate particles, sulfur-containing particles, fluoro-containing particles, or a combination thereof.

(17) Clause 6: The multi-layer coating of any of clauses 1-5, wherein the crosslinked organic particles have an average particle size of 0.1 micron to 10 microns.

(18) Clause 7: The multi-layer coating of any of clauses 1-6, wherein the crosslinked organic particles have a particle size distribution of 1 micron to 8 microns.

(19) Clause 8: The multi-layer coating of any of clauses 1-7, wherein the inorganic pigment particles comprise titanium dioxide, zinc oxide, barium sulfate, calcium carbonate, talc, or combinations thereof.

(20) Clause 9: The multi-layer coating of any of clauses 1-7, wherein the inorganic pigment particles comprise a pigment blend comprising (i) titanium dioxide and (ii) at least one other inorganic pigment particle that is different from titanium dioxide, wherein the titanium dioxide comprises less than 30 weight % of the total solids weight of the inorganic pigment particles and the crosslinked organic particles.

(21) Clause 10: The multi-layer coating of any of clauses 1-9, wherein the first coating layer coating composition has a weight ratio of pigment particles to film forming resin of 1:1 to 1:10.

(22) Clause 11: The multi-layer coating of any of clauses 1-10, wherein the reflective and/or translucent particles comprise aluminum, micas, or a mixture thereof.

(23) Clause 12: The multi-layer coating of clause 11, wherein the aluminum particles have a particle size of less than 6 microns.

(24) Clause 13: The multi-layer coating of clause 11, wherein the micas have a particle size of 30 to 60 microns.

(25) Clause 14: The multi-layer coating of any of clauses 1-13, wherein the first and second coating layer together have a light transmittance of at least 8% and an L value measured at a 15° angle of greater than 110.

(26) Clause 15: The multi-layer coating of any of clauses 1-14, further comprising a third coating layer applied over the second coating layer, wherein the third coating layer is prepared from a coating composition comprising inorganic pigment particles and a film forming resin.

(27) Clause 16: The multi-layer coating of any of clauses 1-15, further comprising a clear layer positioned between the second coating layer and the third coating layer.

(28) Clause 17: The multi-layer coating of any of clauses 1-16, further comprising an abrasion resistant topcoat applied over the third coating layer.

(29) Clause 18: A substrate at least partially coated with the multi-layer coating of any of clauses 1-17.

(30) Clause 19: The at least partially coated substrate of clause 18, wherein the substrate is a plastic substrate.

(31) Clause 20: The at least partially coated substrate of any of clauses 18 or 19, wherein the substrate is a keyboard comprising a light source.

(32) Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.