UV CURABLE COATING COMPOSITION, METHOD OF APPLYING THE SAME AND SUBSTRATE COATED THEREWITH

Abstract

A high-hardness anti-steel wool UV curable coating composition comprises a high-functionality UV curable polyurethane acrylate. A method of coating a substrate with the high-hardness anti-steel UV curable coating composition and the substrate coated with the same are also provided.

Claims

1. An UV curable coating composition, comprising an UV curable polyurethane acrylate having functionality greater than or equal to 6.

2. The UV curable coating composition according to claim 1, wherein the UV curable polyurethane acrylate has a number average molecular weight from 800 to 4000.

3. The UV curable coating composition according to claim 1 or 2, wherein the UV curable polyurethane acrylate is selected from the group consisting of six-functionality aliphatic polyurethane acrylate, ten-functionality aliphatic polyurethane acrylate, and a mixture thereof.

4. The UV curable coating composition according to any one of preceding claims, wherein the UV curable polyurethane acrylate comprises 5-50 wt % of six-functionality aliphatic polyurethane acrylate and 5-50 wt % of ten-functionality aliphatic polyurethane acrylate, based on the weight of the coating composition.

5. The UV curable coating composition according to any one of preceding claims, wherein the six-functionality aliphatic polyurethane acrylate is a reaction product of isophorone diisocyanate and pentaerythritol triacrylate.

6. The UV curable coating composition according to any one of preceding claims, wherein the ten-functionality aliphatic polyurethane acrylate is polymerized by isophorone diisocyanate monomers.

7. The UV curable coating composition according to any one of preceding claims, further comprising 0.1-3 wt % of a fluorine-containing acrylic soil-repellent, based on the weight of the coating composition.

8. A method of forming a coating on a substrate, comprising applying an UV curable coating composition to at least a portion of the substrate, wherein the UV curable coating composition comprises an UV curable polyurethane acrylate having functionality greater than or equal to 6.

9. A coated substrate, comprising a substrate and an UV curable coating composition deposited on at least a portion of the substrate, wherein the UV curable coating composition comprises an UV curable polyurethane acrylate having functionality greater than or equal to 6.

10. The coated substrate according to claim 9, wherein the substrate comprises a substrate formed from the group consisting of polymethyl methacrylate, polycarbonate, and polyethylene terephthalate.

11. The coated substrate according to claim 9 or 10, wherein the substrate is a substrate useful for a display on board, a PET protective film and a display for computers and mobile phones.

Description

EXAMPLES

[0025] The following examples are provided to illustrate the invention, which, however, are not to be considered as limiting the invention to their details. Unless otherwise indicated, all parts and percentages in the following examples, as well as throughout the specification, are by weight.

Preparation Examples

[0026] The UV curable coating composition according to the present invention was prepared by mixing the components and amounts thereof listed in Table 1.

TABLE-US-00001 TABLE 1 Formulation of UV curable coating composition Example 1 Example 2 Example 3 (wt %) (wt %) (wt %) polyurethane 10 30 50 acrylate oligomer .sup.1 polyurethane 50 30 10 acrylate oligomer .sup.2 Solvent.sup.3 37 37 37 Photoinitiator.sup.4 2.5 2.5 2.5 Stain 0.5 0.5 0.5 repellent.sup.5 Total 100 100 100 .sup.1 Six-functionality aliphatic polyurethane acrylate, W4560 from Wuxing .sup.2 Ten-functionality aliphatic polyurethane acrylate, U-0672-100 from Lida .sup.3Solvent: a mixture of butyl acetate and isobutyl acetate .sup.4Irgacure 184, Taiwan DBC .sup.5KY1203, Xinyue

[0027] Preparation Process of Coats

[0028] The coating compositions were diluted with a diluent formulated by mixing ethyl acetate, isopropanol, and ethylene glycol monobutyl ether in an appropriate ratio, such that the coating compositions after dilution have a viscosity of 7.5-8.5 s where the viscosity was measure through an IWATA 2# CUP. Then, the diluted coating compositions were coated onto the PMMA/PC/PET substrate via any of spraying, curtain coating, rolling, dipping/immersion coating followed by baking at 60-80 C. for 5-10 min to remove the solvent. The photoinitiator decomposed to generate active free radicals via exposure to UV light radiation (UV energy: 400-1600 mJ/cm.sup.2, light intensity: 80-300 mw/cm.sup.2) and initiated a polymerization between the monomer and the resin, forming a film of three-dimensional crosslinked network to obtain the basecoat.

[0029] Then, the substrates coated with the UV curable coating composition of the present invention were tested for the following properties. Results were shown in Table 2.

[0030] Testing Items

[0031] 1. Pencil Hardness

[0032] Requirement on pencil: Mitsubishi 4H pencil and 1000# sandpaper were chosen. Pencil point is at an angle of 90 with the plane of the sandpaper, and then it was worn into a cylindrical shape.

[0033] Testing method. The pencil was mounted on a pencil hardness tester, calibrated, adjusted into balance, and loaded with a weight of 1 kg. Three lines having a 5-10 mm length were cut at an angle of 451 in different positions of the fingerprint sensing surface of the sensor. Then, pencil scratches were erased with an eraser.

[0034] Note: rotating the pencil 90 degrees after scratching once to avoid the abrasion area of the pencil point, otherwise, testing results were invalid.

[0035] 2. Scratch Resistance

[0036] BONSTAR 0000# steel wool was used with a load of 1000 g and a steel wool area of 20 mm*20 mm. Testing is conducted at a rate of 60 cycles/min with a friction distance of 35-40 mm. 2000 continuous frictions were done on the film-coated surface of the covering plate of the sample. It is required the contact angle after steel wool testing is greater than 90.

[0037] 3. Adhesion of Cured Film

[0038] The sample surface was cut by 66 lines with a NT knife (1 mm.sup.2 gird (lattice), total number of 25; the marking penetrating all the way to the substrate) and the testing surface remained as even as possible (keeping the blade sharp). If the sample was too small to have enough cross-cutting space, a 45 cross-cut grid would be taken. Nichiban tape (No. 405), Scotch tape (No. 610), or other tapes of the same type (18 mm broad, tape viscosity should be greater than or equal to 5.3 N/18 mm broadth) was applied over the sample surface and compacted with a rubber to allow the tape sufficiently in contact with the sample surface. The sample standed for 3 min. Tape was removed by pulling it off rapidly back over itself in an angle of 90. The testing surface was visually examined and assessed with reference to ISO standard.

[0039] ISO Standard Rating

[0040] 0 scale: 5B

[0041] Edges of incisions are completely smooth, and no peeling occurs at the edges of lattices.

[0042] 1 scale: 4B

[0043] There is a small piece of peeling at the intersections of incisions, and actual failure is less than or equal to 5%.

[0044] 2 scale: 3B

[0045] There is peeling at the edges or intersections of incisions, with a peeling area from 5% to 15%.

[0046] 3 scale: 2B

[0047] There is partial peeling or a large piece of peeling along the edges of incisions, or part of lattices are wholly peeled off, with a peeling area in a range of 15%-35%.

[0048] 4 scale: 1B

[0049] There is much peeling at the edges of incisions, or part or all of some lattices are peeled off, with a peeling area in a range of 35%-65%.

[0050] 5 scale: 0B

[0051] The painting peels off significantly at the edges or intersections of incisions, with a peeling area greater than 65%.

[0052] The testing result is required at or above 4B.

[0053] 4. Water Contact Angle

[0054] A commercial contact angle tester was used. An initial contact angle greater than 105 is required.

[0055] 5. Transmittance Testing

[0056] Testing procedure was carried out in accordance with WI-SOP-164 <optical transmittance measuring instrument>. Transmittance greater than 90 is required for a transparent material.

TABLE-US-00002 TABLE 2 Performance Testing Results Example 1 Example 2 Example 3 Pencil hardness 4H 4H 4H Scratch resistance 93.1 95.1 95.8 Adhesion of cured 4B 4B 4B film Water contact angle 108.9 109.8 109.9 Transmittance 91.3 91.3 91.4 testing

[0057] Although particular aspects of this invention have been explained and described above, it will be evident to those skilled in the art that numerous variations and modifications to the present invention may be made without departing from the scope and spirit of the present invention. Therefore, the appended claims are intended to encompass these variations and modifications falling within the present invention.