Hard coating film

Abstract

Disclosed herein is a hard coating film, which exhibits high hardness and excellent properties without a supporting substrate. The hard coating film can find useful applications in various fields thanks to its excellent hardness, scratch resistance, transparency, durability, light resistance, light transmittance, and the like.

Claims

1. A single-layered substrate-less hard coating film, comprising: a photocurable crosslinking copolymer; and inorganic particles dispersed in the photocurable crosslinking copolymer, wherein the photocurable crosslinking copolymer is a copolymer in which a tri- to hexa-functional acrylate monomer is crosslinked with a photocurable elastic polymer, and the photocurable crosslinking copolymer includes 5 to 20 weight parts of the photocurable elastic polymer and 80 to 95 weight parts of the tri- to hexa-functional acrylate monomer based on 100 weight parts thereof, wherein the photocurable elastic polymer comprises a polyrotaxane, wherein the polyrotaxane comprises a cyclic moiety (macrocycle) in which lactone compounds with a (meth)acrylate moiety conjugated to the end thereof are bonded to each other; a thread moiety held within the macrocycle; and stoppers provided at both ends of the thread moiety so as to prevent dissociation of the macrocycle, and wherein the hard coating film exhibits a pencil hardness of 7H or more at a load of 1 kg.

2. The hard coating film of claim 1, wherein the photocurable elastic polymer has an elongation of 15 to 200%, as measured according to ASTM D638.

3. The hard coating film of claim 1, wherein the hard coating film includes 40 to 90 weight parts of the photocurable crosslinking copolymer and 10 to 60 weight parts of the inorganic particles, based on 100 weight parts thereof.

4. The hard coating film of claim 1, wherein the inorganic particles have a particle diameter of 100 nm or less.

5. The hard coating film of claim 1, wherein the inorganic particles include at least one selected from the group consisting of silica nanoparticles, aluminum oxide nanoparticles, titanium oxide nanoparticles and zinc oxide nanopaticles.

6. The hard coating film of claim 1, wherein the tri- to hexa-functional acrylate monomer includes at least one selected from the group consisting of trimethylolpropane triacrylate (TMPTA), trimethylolpropane ethoxytriacrylate (TMPEOTA), glycerin propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA).

7. The hard coating film of claim 1, wherein the hard coating film does not crack when a 22 g steel ball is freely dropped 10 times thereon from a height of 50 cm.

8. The hard coating film of claim 1, wherein the hard coating film allows two or less scratches to appear thereon after it is doubly rubbed 400 times with a steel wool #0000 under a load of 500 g.

9. The hard coating film of claim 1, having a light transmittance of 91% or more, a haze of 0.4 or less and a color b* value of 1.0 or less.

10. The hard coating film of claim 1, the difference between an initial color b* value and a color b* value after exposure to UV B for 72 hrs is 0.5 or less.

11. The hard coating film of claim 1, wherein the hard coating film has a thickness of 50 to 500 m.

12. The hard coating film of claim 1, wherein when the hard coating film is disposed on a plane after exposure to a temperature of 50 C. or more at a humidity of 80% or more for 70 hrs or more, each edge or side of the hard coating film is spaced apart from the plane by 1.0 mm or less, maximally.

13. The hard coating film of claim 1, further comprising at least one selected from the group consisting of a plastic resin film, an adhesive film, a releasable film, an electrically conductive film, an electrically conductive layer, a curable resin layer, a non-conductive film, a metal mesh layer, and a patterned metal layer, each of which is attached to one side thereof.

Description

EXAMPLES

Preparation Example 1: Preparation of Photocurable Elastic Polymer

(1) In a reactor, 50 g of a caprolactone-grafted polyrotaxane polymer [A1000, Advanced Soft Material INC] was mixed with 4.53 g of Karenz-AOI [2-acryloylethyl isocyanate, Showadenko Inc.], 20 mg of dibutyltin dilaurate [DBTDL, Merck Corp.], 110 mg of hydroquinone monomethylene ether, and 315 g of methyl ethyl ketone. Then, the mixture was reacted at 70 C. for 5 hrs to obtain polyrotaxane in which polylactone with an acrylate moiety conjugated to the end thereof acted as the macrocycle while cyclodextrin was positioned as the stopper.

(2) The polyrotaxane had a weight average molecular weight of 600,000 g/mol, and was found to have an elongation of 20%, as measured according to ASTM D638.

Example 1

(3) A hard coating composition was prepared by mixing 9 g of a silica-dipentaerythritolhexacrylate (DPHA) composite in which silica nanoparticles with a particle size of 2030 nm were dispersed by 40 wt % (silica 3.6 g, DPHA 5.4 g), 1 g of the polyrotaxane of Preparation Example 1, 0.2 g of a photoinitiator (brand name: Darocur TPO), 0.1 g of a benzotriazole-based yellowing inhibitor (brand name: Tinuvin 400), 0.05 g of a fluorine surfactant (brand name: FC4430) and 1 g of methylethylketone.

(4) The hard coating composition was applied onto a silicon-treated PET film 100 m thick with a size of 15 cm20 cm, and then subjected to photocuring by exposure to 280350 nm UV light from a black light fluorescence lamp to prepare a hard coating film.

(5) After completion of the photocuring of the hard coating composition, the PET film was detached from the hard coating film. The thickness of the hard coating film, from which the PET Film had been detached, was 188 m.

Example 2

(6) A hard coating film was prepared in the same manner as in Example 1, with the exception that 1 g of a urethane acrylate polymer (brand name: UA200PA, Shinnakamura Chemicals Corp., weight average molecular weight: 2,600 g/mol, elongation measured according to ASTM D638: 170%) was used, instead of 1 g of the polyrotaxane of Preparation Example 1 in the hard coating composition.

Example 3

(7) A hard coating film was prepared in the same manner as in Example 1, with the exception that 1 g of a urethane acrylate polymer (brand name: UA340P, Shinnakamura Chemicals Corp., weight average molecular weight: 13,000 g/mol, elongation measured according to ASTM D638: 150%) was used, instead of 1 g of the polyrotaxane of Preparation Example 1 in the hard coating composition.

Example 4

(8) A hard coating film was prepared in the same manner as in Example 1, with the exception that the thickness of the hard coating film was 250 m.

Example 5

(9) A hard coating film was prepared in the same manner as in Example 1, with the exception that the thickness of the hard coating film was 300 m after completion of photocuring of the hard coating composition in Example 1.

Example 6

(10) A hard coating film was prepared in the same manner as in Example 1, with the exception that the thickness of the hard coating film was 450 m after completion of photocuring of the hard coating composition in Example 1.

Comparative Example 1

(11) A hard coating composition was prepared by mixing 10 g of a silica-dipentaerythritolhexacrylate (DPHA) composite in which silica nanoparticles with a particle size of 2030 nm were dispersed by 40 wt % (silica 4 g, DPHA 6 g), 0.2 g of a photoinitiator (brand name: Darocur TPO), 0.1 g of a benzotriazole-based yellowing inhibitor (brand name: Tinuvin 400), 0.05 g of a fluorine surfactant (brand name: FC4430) and 1 g of methylethylketone.

(12) The hard coating composition was applied onto a silicon-treated PET film 100 m thick with a size of 15 cm20 cm, and then subjected to photocuring by exposure to 280350 nm UV light from a black light fluorescence lamp to prepare a hard coating film.

(13) After completion of the photocuring of the hard coating composition, the PET film was detached from the hard coating film. The thickness of the hard coating film, from which the PET Film had been detached, was 188 m.

(14) The major components and thicknesses of the hard coating films of Examples 1 to 6 and Comparative Example 1 are summarized in Table 1 below.

(15) TABLE-US-00001 TABLE 1 Acrylate Photocurable Inorganic monomer elastic polymer particles Thickness Ex. 1 DPHA 5.4 g polyrotaxane 1 g 3.6 g 188 m Ex. 2 DPHA 5.4 g UA200PA 1 g 3.6 g 188 m Ex. 3 DPHA 5.4 g UA340P 1 g 3.6 g 188 m Ex. 4 DPHA 5.4 g polyrotaxane 1 g 3.6 g 250 m Ex. 5 DPHA 5.4 g polyrotaxane 1 g 3.6 g 300 m Ex. 6 DPHA 5.4 g polyrotaxane 1 g 3.6 g 450 m C. Ex. 1 DPHA 6 g 4 g 188 m

Test Examples

(16) Measuring Method

(17) 1) Pencil Hardness

(18) Pencil hardness was evaluated according to the Japanese Standard JIS K5400. In this regard, the hard coating film was doubly rubbed three times with a pencil hardness meter under a load of 1.0 kg to determine the hardness at which no scratches appeared.

(19) 2) Scratch Resistance

(20) The hard coating film was doubly rubbed 400 times with a steel wool (#0000) under a load of 0.5 kg in a friction tester, and scratches thus formed were counted. Evaluation was made of the scratch resistance of the films by marking for two or less scratches, for two to less than five scratches, and x for five or more scratches.

(21) 3) Light Resistance

(22) Differences in color b* value of the hard coating films were measured before and after exposure to UVB from UV lamp for 72 hrs.

(23) 4) Transmittance and Haze

(24) The hard coating films were measured for transmittance and haze using a spectrophotometer (brand name: CHO-400).

(25) 5) Curl Property at High Humidity and Temperature

(26) After a hard coating film piece with dimensions of 10 cm10 cm was stored for 72 hrs in a chamber maintained at a temperature of 85 C. and a humidity of 85%, it was placed on a flat plane. A maximal distance at which each edge of the piece was spaced apart from the plane was measured.

(27) 6) Cylindrical Bending Test

(28) Each of the hard coating films was wound on a cylindrical mandrel having a diameter of 3 cm. When the hard coating film was not cracked, it was evaluated as OK. If the hard coating film was cracked, it was evaluated as X.

(29) 7) Impact Resistance

(30) The impact resistance of each of the hard coating films was evaluated by determining whether or not each of the hard coating films was cracked when a 22 g steel ball was freely dropped 10 times thereon from a height of 50 cm. Each of the hard coating films was evaluated as OK when it was not cracked, and as X when cracked.

(31) The results of the physical properties measured in each of the hard coating films are summarized in Table 2 below.

(32) TABLE-US-00002 TABLE 2 C. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 1 Pencil hardness 8H 9H 8H 9H 9H 9H 9H Scratch resistance Light resistance 0.10 0.12 0.11 0.18 0.23 0.36 0.20 Transmittance 93.1 92.8 92.7 92.8 92.4 92.1 93.0 Haze 0.2 0.3 0.3 0.4 0.4 0.4 0.2 Bending test OK OK OK OK OK OK X Curl property at 0.0 0.0 0.0 0.0 0.0 0.0 0.0 high humidity & mm mm mm mm mm mm mm temperature Impact resistance OK OK OK OK OK OK X

(33) As shown in Table 2 above, it can be ascertained that all of the hard coating films of Examples exhibited good physical properties. In contrast, the hard coating film of Comparative Example 1, which does not include a photocurable elastic polymer, was found to be insufficient in impact resistance.