OPTICAL LAMINATE AND DISPLAY DEVICE

Abstract

The present invention relates to an optical laminate including: a substrate; and a hard coating layer formed on at least one surface of the substrate and containing a binder resin and two or more types of inorganic particles having different average radii, wherein a domain formed by surrounding two or more first inorganic particles by two or more second inorganic particles is formed in the hard coating layer, and wherein the first inorganic particles and the second inorganic particles are different components from each other, and a display device including the optical laminate.

Claims

1. An optical laminate comprising: a substrate; and a hard coating layer formed on at least one surface of the substrate and containing a binder resin and at least two groups of inorganic particles having different average radii, wherein the hard coating layer includes a domain formed by surrounding two or more of a first group inorganic particles with two or more of a second group inorganic particles, and wherein the first group inorganic particles and the second group inorganic particles are different components from each other.

2. The optical laminate of claim 1, wherein the second group inorganic particles have a larger average radius compared to the first inorganic particles.

3. The optical laminate of claim 1, wherein the domain is formed by surrounding the two or more of the first group inorganic particles having an average radius of 10 to 15 nm with the two or more of the second group inorganic particles having an average radius of 20 to 35 nm.

4. The optical laminate of claim 1, wherein a distance (Rd) between centers of two of the second group inorganic particles is 60 nm to 100 nm when the two of the second group inorganic particles are located opposite to each other with respect to the first group inorganic particles located at the center in the domain.

5. The optical laminate of claim 1, wherein the first group inorganic particles and the second group inorganic particles are metal particles different from each other and are each independently silica fine particles, aluminum oxide particles, titanium oxide particles, or zinc oxide particles.

6. The optical laminate of claim 1, wherein the hard coating layer exhibits a pencil hardness of at least 5 H under a load of 750 g.

7. The optical laminate of claim 1, wherein the hard coating layer has a thickness of at least 25 μm.

8. The optical laminate of claim 1, wherein the hard coating layer includes 20 to 80 parts by weight of the total amount of the first group inorganic particles and the second group inorganic particles based on 100 weight of the binder resin.

9. The optical laminate of claim 1, wherein the binder resin includes a polymer or copolymer of a 3- to 6-functional (meth)acrylate-based monomer.

10. The optical laminate of claim 1, wherein the hard coating layer is formed on one surface of the substrate, and a second hard coating layer containing a second binder resin is formed on another surface of the substrate, and wherein the second binder resin includes a polymer or copolymer of (meth)acrylate-based monomer.

11. The optical laminate of claim 10, wherein the second hard coating layer has a thickness of 30 μm to 100 μm.

12. The optical laminate of claim 1, wherein the substrate has a thickness of 20 μm to 300 μm.

13. The optical laminate of claim 1, wherein the optical laminate is a cover window or an element substrate of a flexible display device.

14. A display device comprising the optical laminate of claim 1.

15. The optical laminate of claim 2, wherein a distance (Rd) between centers of two of the second group inorganic particles is 60 nm to 100 nm when the two of the second group inorganic particles are located opposite to each other with respect to the first group inorganic particles located at the center in the domain.

16. The optical laminate of claim 1, wherein the first group inorganic particles and the second group inorganic particles are oxides, carbides, hydroxides, perhydroxides or nitrides that contain metals different from each other.

17. The optical laminate of claim 9, wherein the 3- to 6-functional acrylate-based monomer includes trimethylolpropane triacrylate (TMPTA), trimethylolpropaneethoxy triacrylate (TMPEOTA), glycerin propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), dipentaerythritol hexaacrylate (DPHA) or a mixture thereof.

18. A cover window of a flexible display device comprising the optical laminate of claim 1.

19. An element substrate of a flexible display device comprising the optical laminate of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] FIG. 1 schematically shows a cross section of a domain formed in a hard coating layer included in an optical laminate of one exemplary embodiment.

[0082] FIG. 2 shows the results of small-angle X-ray scattering measurement of the hard coating layer of Example 1 using two groups of inorganic particles, and the fitting results thereon (black line).

[0083] FIG. 3 shows the results of small-angle X-ray scattering measurement of the hard coating layer using one group of inorganic particles (diameter of 13 nm), and the fitting results thereon (black line).

[0084] FIG. 4 shows the results of small-angle X-ray scattering measurement of the hard coating layer using one group of inorganic particles (diameter of 25 nm), and the fitting results thereon (black line).

[0085] FIG. 5 is a diagram schematically illustrating a method for performing a bending durability test for a film according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0086] Hereinafter, the operation and effect of the invention will be described in more detail by way of concrete examples. However, these examples are merely presented for illustrative purposes only, and the scope of the invention is not determined thereby.

PREPARATION EXAMPLE

Preparation of Coating Liquid for Forming Hard Coating Layer

[0087] The components shown in Tables 1 and 2 below were mixed to prepare a coating solution for forming a hard coating layer. (In Tables 1 to 2 below, R means the average radius of the inorganic particles calculated through the X-ray scattering experiment.)

TABLE-US-00001 TABLE 1 Preparation Preparation Preparation Preparation Preparation Preparation (Unit: g) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Monomer TMPTA 10 10 10 10 10 10 for PETA 20 20 20 20 20 20 forming DPEPA 20 20 20 20 20 20 binder TPGDA 5 5 5 5 5 5 TA-604AU 5 5 5 5 5 5 Inorganic SiO.sub.2 20 20 — — — — particles (R = 25 nm) SiO.sub.2 — — 20 — — 20 (R = 13 nm) TiO.sub.2 — — 20 20 — — (R = 24 nm) TiO.sub.2 20 — — — 20 — (R = 12 nm) ZrO.sub.2 — — — — 20 20 (R = 27 nm) ZrO.sub.2 — 20 — 20 — — (R = 11 nm) Leveling agent 0.06 0.06 0.06 0.06 0.06 0.06 Photo-initiator 0.72 0.72 0.72 0.72 0.72 0.72 Organic solvent 50 50 50 50 50 50 (Methyl Ethyl Ketone)

TABLE-US-00002 TABLE 2 Preparation Preparation Preparation Preparation Preparation Preparation Preparation (Unit: g) Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Monomer TMPTA 10 10 10 10 10 10 10 for PETA 20 20 20 20 20 20 10 forming DPEPA 20 20 20 20 20 20 10 binder TPGDA 5 5 5 5 5 5 20 TA-604AU 5 5 5 5 5 5 50 Inorganic SiO.sub.2 40 — — — — — — particles (R = 25 nm) SiO.sub.2 — 40 — — — — — (R = 13 nm) TiO.sub.2 — — 40 — — — — (R = 24 nm) TiO.sub.2 — — — 40 — — — (R = 12 nm) ZrO.sub.2 — — — — 40 — — (R = 27 nm) ZrO.sub.2 — — — — — 40 — (R = 11 nm) Leveling agent 0.06 0.06 0.06 0.06 0.06 0.06 0.1 Photo-initiator 0.72 0.72 0.72 0.72 0.72 0.72 1.21 Organic solvent 50 50 50 50 50 50 30 (Methyl Ethyl Ketone)

TABLE-US-00003 TABLE 3 Molecular Number Acrylate Chemical name/product weight of equivalent Component name Manufacturer (g/mol) Acrylate weight TMPTA Trimethylolpropane — 338 3 113 Triacrylate PETA Pentaerythritol Tetraacryl — 352 4 88 DPEPA Dipentaerythritol — 525 5 105 Pentaacrylate TPGDA Tripropyleneglycol — 300 2 150 Diacrylate TA-604AU — NOF 2300 3 767 Corporation Leveling F477 DIC — — — agent Corporation Photoinitiator Irgacure 127 Ciba — — — Specialty Chemicals

EXAMPLE AND COMPARATIVE EXAMPLE

Preparation of Optical Laminate

[0088] The coating composition shown in Tables below was coated onto a polyimide substrate (size: 20 cm×30 cm, thickness: 35 μm) having an elastic modulus value of 6.0 GPa as measured according to ASTM D882 by a bar or slot coating method, and dried at 80° C. for 3 minutes under an air atmosphere. It was photo-cured with a metal halide lamp (light quantity: 200 mJ/cm.sup.2) having a wavelength of 290 to 320 nm to form an optical laminate. The photocuring was performed under a nitrogen or argon atmosphere, and the light irradiation time was 30 seconds.

EXPERIMENTAL EXAMPLE

Measurement of Physical Properties of Optical Laminate

Experimental Example 1: Domain Confirmation of Inorganic Particles and Measurement of Distance (Rd) Between Centers of Two Second Inorganic Particles in the Domain

[0089] (1) Intensity vs. wavevector (q) curve secured by small-angle X-ray scattering method was fitted using a model function included in NIST SANS package. Through this method, it was confirmed whether the domain of inorganic particles was formed in Hard 1 (front side) of each of the optical laminates of Examples and Comparative Examples, and the distance (Rd) between the centers of two second inorganic particles in the domains of the inorganic particles was determined.

[0090] FIG. 2 shows the results of small-angle X-ray scattering measurement of the hard coating layer of Example 1 using two groups of inorganic particles, and the fitting results thereon (black line). FIGS. 3 and 4 show the results of small-angle X-ray scattering measurement of the hard coating layer using one group of inorganic particles (diameter of 13 nm and diameter of 25 nm), and the fitting results thereon (black line).

[0091] 1) Apparatus

[0092] u-SAXS beam-line 9A from Pohang Accelerator Laboratory (Pohang Light Source)

[0093] <Measurement conditions>

[0094] E=11.1 KeV, 19.9 keV,

[0095] ΔE/E=2*10.sup.−4

[0096] q range used: 0.0024=q(Å.sup.−1)=0.5

[0097] Sample to detector distance (SDD; 6.5 m (11.1 keV), 2.5 m (19.9 keV))

[0098] Pin holes collimated

[0099] 2D CCD Detector (Rayonix SX165, USA)

[0100] 2) Measurement Method

[0101] Film-type samples were attached to a sample holder using a transparent tape.

[0102] The 2D image obtained in the experiment was averaged in a circle on the basis of the beam stop and converted to a 1D image (the unit is arbitrary unit, a.u. since the intensity value of the experimental data was not changed to an absolute value).

[0103] Data measured with an SDD of 6.5 m at an energy of −11.1 KeV and two data sets per sample measured at 2.5 m SDD at an energy of 19.9 keV, were merged by NIST SANS data reduction package, and the analysis of the data was performed using the model function included in the NIST SANS package.

Experimental Example 2: Pencil Hardness

[0104] For the hard coating layer formed in the front face of the optical laminate of each of Examples and Comparative Examples, the maximum hardness without scratches was confirmed after moving the pencil back and forth three times at an angle of 45 degrees under a load of 750 g using a pencil hardness tester in accordance with standard JIS K5400-5-4.

Experimental Example 3: Measurement of Dent Resistance

[0105] In the optical laminate of each of Examples and Comparative Examples, a cohesive layer (material: OCA, thickness: 25 μm) and a polyimide film (thickness: 50 μm) were laminated on Hard 2 (back face), respectively. This laminated film was placed on the bottom so that Hard 1 (front side) faces upward.

[0106] Using a 3H hardness pencil, while starting under a load of 100 g and adding a load by 100 g, the first coating layer surface was moved once at an angle of 45 degrees, and then the maximum weight without damage such as pressing marks on all layers was confirmed. If no damage occurred by checking up to 1500 g, the test did not proceed anymore.

Experimental Example 4: Bending Durability Test

[0107] FIG. 5 is a diagram schematically illustrating a method for performing a bending durability test for a film according to an exemplary embodiment of the present invention.

[0108] Each optical laminate of Examples and Comparative Examples was cut, but laser-cut to a size of 80×140 mm so as to minimize fine cracks at an edge portion. The laser-cut film was placed on the measuring device and set so that the interval between the folded portions was 5 mm. Then, processes of folding and spreading both sides of the films at 90 degrees toward the bottom surface were repeated 10,000 times at room temperature (the speed at which the film was folded was once every 1.5 seconds).

[0109] After repeating 10,000 times, the film was peeled off, and then it was observed whether cracking of 3 mm or more in length was occurred (OK, NG). When cracks did not occur, bending was repeated 10,000 times and the occurrence of cracks were observed to determine the maximum number of repetitions that cracks did not occur. If no cracks occurred until 100,000 times of repetition, it was determined that bending durability was good.

[0110] The measurement results of the physical properties are shown in Tables 4 to 5 below.

TABLE-US-00004 TABLE 4 Pencil Formation Hard 1(front side) Hard 2(back side) hardness Dent 100,000 of domain Thickness Thickness (front occurrence times of inorganic Rd Composition (um) Composition (um) side) load folding particles (nm) Example 1 Preparation 40 Preparation 70 7H 1500 g OK ◯ About70~90 Example 1 Example 13 Example 2 Preparation 40 Preparation 70 7H 1500 g OK ◯ About79~90 Example 2 Example 13 Example 3 Preparation 40 Preparation 70 7H 1500 g OK ◯ About60~85 Example 3 Example 13 Example 4 Preparation 40 Preparation 70 7H 1500 g OK ◯ About60~85 Example 4 Example 13 Example 5 Preparation 40 Preparation 70 7H 1500 g OK ◯ About70~100 Example 5 Example 13 Example 6 Preparation 40 Preparation 70 7H 1500 g OK ◯ About70~100 Example 6 Example 13 Example 7 Preparation 30 Preparation 70 5H 1300 g OK ◯ About70~90 Example 1 Example 13 Example 8 Preparation 30 Preparation 70 5H 1300 g OK ◯ About79~90 Example 2 Example 13 Example 9 Preparation 30 Preparation 70 5H 1300 g OK ◯ About60~85 Example 3 Example 13 Example 10 Preparation 30 Preparation 70 5H 1300 g OK ◯ About60~85 Example 4 Example 13 Example 11 Preparation 30 Preparation 70 5H 1300 g OK ◯ About70~100 Example 5 Example 13 Example 12 Preparation 30 Preparation 70 5H 1300 g OK ◯ About70~100 Example 6 Example 13

TABLE-US-00005 TABLE 5 Pencil Formation Hard 1 (front side) Hard 2(back side) hardness Dent 100,000 of domain Thickness Thickness (front occurrence times of inorganic Rd Composition (um) Composition (um) side) load folding particles (nm) Comparative Preparation 40 Preparation 70 4H 1200 g OK X — Example 1 Example 7 Example 13 Comparative Preparation 40 Preparation 70 4H 1200 g OK X — Example 2 Example 8 Example 13 Comparative Preparation 40 Preparation 70 4H 1200 g OK X — Example 3 Example 9 Example 13 Comparative Preparation 40 Preparation 70 4H 1200 g OK X — Example 4 Example 10 Example 13 Comparative Preparation 40 Preparation 70 4H 1200 g OK X — Example 5 Example 11 Example 13 Comparative Preparation 40 Preparation 70 4H 1200 g OK X — Example 6 Example 12 Example 13 Comparative Preparation 30 Preparation 70 3H 1000 g OK X — Example 7 Example 7 Example 13 Comparative Preparation 30 Preparation 70 3H 1000 g OK X — Example 8 Example 8 Example 13 Comparative Preparation 30 Preparation 70 3H 1000 g OK X — Example 9 Example 9 Example 13 Comparative Preparation 30 Preparation 70 3H 1000 g OK X — Example 10 Example 10 Example 13 Comparative Preparation 30 Preparation 70 3H 1000 g OK X — Example 11 Example 11 Example 13 Comparative Preparation 30 Preparation 70 3H 1000 g OK X — Example 12 Example 12 Example 13

[0111] As shown in Tables 4 to 5 above, it was confirmed that “the domain formed by surrounding two or more first inorganic particles having an average radius of 10 to 15 nm by two or more second inorganic particles having an average radius of 20 to 35 nm” is formed in the hard coating layer formed on the front side of the optical laminate of Examples (at this time, the first inorganic particles and the second inorganic particles are different components from each other). As such, it was confirmed that the optical laminates of Examples had a high surface hardness of 5H or more, and had a high dent resistance together with excellent durability in a bending test.

[0112] On the contrary, it was confirmed that in the optical laminates of Comparative Examples including the hard coating layer prepared using one group of inorganic particle, the domain of the inorganic particles was not formed, and relatively low surface hardness and dent resistance appeared.

[0113] In addition, it was confirmed that the optical laminate of Comparative Examples including the hard coating layer in which two groups of inorganic particles were used but the domain of the inorganic particles was not formed also exhibited relatively low surface hardness and dent resistance.