LIGHT DIFFUSING INK FOR PRINTING ON TRANSPARENT SUBSTRATES

Abstract

A light diffusing ink for printing on transparent substrates suitable for being integrated with devices for lighting said substrate from the edge, in order to print drawings, graphics, letters on said substrate and also to realize a full-field background whose thickness varies as a function of users' requirements on the surface of said substrate. The coating printed on said substrate is consequently only visible whenever said substrate is lit laterally, whereas it is not visible in the absence of a lateral light.

Claims

1.-8. (canceled)

9. A screen printing light diffusing ink for printing on an optically transparent substrate, such as a panel preferably made with glass, polymethylethacrylate, polycarbonate and being integrable with devices used to light said substrate from an edge with a light incident angle less than 42° and being said ink visible in the presence of light coming from the edge of said panel and optically transparent in the absence of light coming from the edge of said panel once printed, comprising an organic matrix and having a light diffusion inorganic oxide agent dispersed in the matrix, wherein the light diffusing inorganic oxide agent has a refractive index minimum of 1.8 measured at 589 nm and an average hydrodynamic diameter, measured by Dynamic Light Scattering (DLS), comprises between 100 nm and 500 nm, preferably between 150 nm and 250 nm.

10. The screen printing light diffusing ink according to claim 9, wherein the inorganic oxide agent is present in an amount less than 5.0% by weight of said light diffusing ink.

11. The screen printing light diffusing ink according to claim 9, wherein the inorganic oxide agent is preferably selected from zinc oxide, zirconium oxide, titanium dioxide.

12. The screen printing light diffusion ink according to claim 9, wherein the organic matrix is a solvent-based matrix comprising at least one resin dissolved in solvents in an amount from 20% to 50% by weight of the screen printing light diffusing ink and said matrix being at least 95% by weight of the screen printing light diffusing ink.

13. The screen printing light diffusing ink according to claim 9, wherein the organic matrix comprising at least one resin in an amount from 10% to 30% by weight of the screen printing light diffusing ink dissolved in monomers, oligomers or monomers and oligomers and said matrix is at least 95% by weight of the ink, named UV-based matrix.

14. The light diffusing ink according to claim 12, wherein the resin belongs to at least one of the chemical families including polyacrylic, functionalized polyacrylic, polymethacrytic, functionalized polymethacrylic, polyvinylic, functionalized polyvinylic, polyester, polyether, hydrocarbonic, chetonic, aldehydic, maleic, polyphenolic, polyethylenic, alkedic, ureic, melaminic, polyamydic, polyamine, epoxy, epoxy-ester, epoxy-urethane, and cellulose derivative families.

15. The light diffusing ink according to claim 12, wherein the monomers are acrylates or methacrylates, both monofunctional or bifunctional or trifunctional or polyfunctional, the oligomers belonging to at least one of the chemical families including urethane acrylate, urethane methacrylate, epoxy acrylate, epoxy methacrylate, polyester acrylate, polyester methacrylate, polyether acrylate, polyether methacrylate, amino acrylate, amino methacrylate, oligoamino acrylate, and oligoatmino methacrylate oligomers.

16. The light diffusing ink according to claim 12, wherein the matrix comprises at least one fluorescent material in an amount less than 5% by weight of the ink and suitable for optically absorbing the light coming from an illuminating device.

Description

DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1 shows a print of the ink according to example 1, paired with a traditional blue color ink, deposited on a transparent cast PMMA plate via a silk-screen printing process using a 120 threads/cm frame.

[0056] The drawing printed on the plate is a full-field rectangle, apart from a writing “EPTAINKS” in the middle, The left-hand half of the rectangle is obtained by printing a traditional blue ink, whereas the right-band half of the rectangle is obtained by printing the ink according to example 1.

[0057] The light source of the optical device is a white LED strip, used to light the transparent substrate from the lower edge.

[0058] As shown in FIG. 1, the ink according to example 1 is not visible in the absence of light, and also no drawings or letters are visible. On the contrary, note that the part treated with a traditional ink is visible and half-reveals a part of a blue colored rectangle internally to which a writing “EPTA” is apparent-in negative-(see the photograph identified by the letter “a”).

[0059] Once the source is on (see the photograph identified by the letter “b”), the ink according to example 1 diffuses a light of the same “color” as that coming from the source, in this case white light, and shows the second half of the rectangle in a white color and the writing “INKS” in negative.

[0060] FIG. 2 shows the average hydrodynamic diameter of the inorganic material (I) dispersed within the ink described in example 2, as measured according to the Dynamic Light Scattering (DLS) analysis. The ink has been diluted 1:50 with one of the solvents present in the formula, so as to get a low-viscosity optically diluted solution. In the prepared solutions, viscosity has been measured by using a viscometer Brookfield LV and has been used as a parameter in performing the analysis.

[0061] FIG. 3 shows a print of the ink according to example 4, deposited on an extra-clear glass plate by ray of a silk-screen printing process using a 120 threads/cm frame.

[0062] The light source of the optical device is a blue LED strip, used to light the transparent substrate from the lower edge.

[0063] As shown in the image, no ink is visible in the absence of light (see the photograph identified by the letter “a”). Once the blue source is switched on (see the photograph identified by the letter)“b”), the plate guides the blue light all throughout the surface. When light finds the writing “EPTAINKS” printed with the ink according to example 4, it emits a light spectrum different from that coming from the source, owing to the diffusion and fluorescence optical phenomena; in this case, the writing “EPTAINKS” diffuses green light instead of blue light.