Light diffuser for horticultural lighting
The invention relates to a light-diffusing material, having a high transmission of UVA light, useful for horticultural lighting. The light-diffusing material has a hiding power of greater than 50% at 350 nm and a transmission of light at 350 nm of at least 30 percent, and preferably at least 50%. Additionally the light-diffusing material also transmits and diffuses at least 50% of light at 300 nm, 465 nm, and at 800 nm. The light-diffusing material is especially useful as a glazing for horticultural use.
1. A unit for horticultural production, comprising at least one sheet of a diffusing composition and at least one LED light engine,
wherein the diffusing sheet or film is positioned between the LED light engine and at least one plant and has a hiding power of ±30 across the spectrum 300 nm-1000 nm,
wherein the diffusing composition comprises a transparent or translucent polymer matrix, transmits at least 30 percent of UVB light at 300 nm, and transmits at least 50% of the UVA light at each of 350 nm 465 nm, 665 nm and 800 nm, and
wherein the diffusing composition has a level of diffusion, as measured by hiding power, of at least 25 percent.
2. The unit of claim 1 , wherein the diffusing composition is in the form of a glazing sheet or a glazing film.
3. The unit of claim 1 , wherein the polymer matrix is a thermoplastic selected from the group consisting of polycarbonate (PC), polyethylene terephthalate, glycol modified (PETG), polyvinyl chloride (PVC), impact modified PVC, polyesters, styrene acrylonitrile (SAN), acrylonitrile-acrylate copolymer, acrylonitrile-methyl methacrylate copolymer, methyl methacrylate-styrene copolymer, methacrylate-butadiene-styrene terpolymer, acrylonitrile-styrene-acrylate (ASA) terpolymer, acrylonitrile butadiene styrene (ABS) terpolymer, polystyrene (PS), high impact polystyrene (HIPS), polyolefins, impact modified polyolefins, polycyclo-hexylethylene, cyclic olefin copolymer (COC), polyvinylidene fluoride (PVdF), PVdF-acrylic copolymers, imidized acrylic polymer, acrylic polymers, impact modified acrylic polymers, and mixtures thereof.
4. The unit of claim 3 , wherein the polymer matrix is a polymethylmethacrylate (PMMA) homopolymer, or a PMMA copolymer comprising at least 50 weight percent of methyl methacrylate monomer units.
5. The unit of claim 1 , wherein the polymer matrix is a thermosetting polymer selected from the group consisting of silicones and epoxides.
6. The unit of claim 1 , wherein the diffusing composition further comprises impact modifiers and UVB and/or UVC absorbers.
7. The unit of claim 1 , wherein the diffusing composition further comprises from 0.1 to 40 weight percent of diffusing particles dispersed in the polymer matrix.
8. The unit of claim 7 , wherein the diffusing particles are organic, inorganic, or a mixture thereof.
9. The unit of claim 7 , wherein the dispersing particles are inorganic, organic or a mixture thereof; have a spherical, near spherical or irregular shape; and have a refractive index mis-match with the polymer matrix of +/−0.01 to 0.25.
10. The unit of claim 7 , wherein the diffusing particles have an average particle size of from 500 nm to 120 micrometers.
11. The unit of claim 7 , wherein the dispersing particles comprise at least two different populations of number average particle sizes.
12. The unit of claim 6 , wherein the impact modifiers have a core/shell morphology, where the core comprises a polysiloxane.
13. The unit of claim 1 , where the diffusion is caused by a multi-modal distribution of diffusion particle sizes, a textured surface, or both.
14. The unit of claim 1 , wherein a coated diffusing glazing comprises a sheet or film comprising the diffusing composition, and wherein the sheet or film further comprises a coating layer on at least one side.
15. The unit of claim 14 , wherein the coating layer is a film layer.
16. The unit of claim 14 , wherein the coating layer is a diffusing layer.
17. The unit of claim 14 , wherein the coating layer is a dirt-shedding or weather resistant layer.