OPTICAL LAMINATE AND FLEXIBLE DISPLAY DEVICE INCLUDING THE SAME

Abstract

The present disclosure relates to an optical laminate for a flexible display device comprising: a support substrate layer; and a hard coating layer positioned on at least one surface of the support substrate layer and having a thickness of 10 μm to 250 μm, wherein the hard coating layer is a polysiloxane containing 70 mol % or more of a repeating unit including an epoxy group-containing functional group; and an elastomeric polymer including polycaprolactone polyol, and wherein the polysiloxane has a number average molecular weight of more than 3,000 and less than 10,000, and a polydispersity Index (PDI) of 1.0 or more and less than 5.0, and a flexible display device including the same.

Claims

1. An optical laminate for a flexible display device comprising: a support substrate layer; and a hard coating layer positioned on at least one surface of the support substrate layer and having a thickness of 10 μm to 250 μm, wherein the hard coating layer comprises a polysiloxane containing 70 mol % or more of a repeating unit including an epoxy group-containing functional group; and an elastomeric polymer including polycaprolactone polyol, and wherein the polysiloxane has a number average molecular weight of more than 3,000 Da and less than 10,000 Da, and a polydispersity Index (PDI) of 1.0 or more and less than 5.0.

2. The optical laminate for a flexible display device of claim 1, wherein the optical laminate has an impact absorption rate of −4% or less as calculated according the following Equation 1:
Impact absorption rate=(A.sub.1−A.sub.0/A.sub.0)×100  [Equation 1] in the Equation 1, A.sub.0 is an impact force (N) measured by an impact force measurement sensor when a ball weighing 22 g is dropped from a height of 100 mm onto the impact force measurement sensor, and A.sub.1 is an impact force (N) measured by an impact force measurement sensor when the optical laminate is positioned on the impact force measurement sensor and a ball weighing 22 g is dropped from a height of 100 mm with respect to the hard coat layer of the optical laminate.

3. The optical laminate for a flexible display device of claim 1, wherein the hard coating layer contains 5 to 80 parts by weight of the elastomeric polymer based on 100 parts by weight of the polysiloxane containing 70 mol % or more of a repeating unit including the epoxy group-containing functional group.

4. The optical laminate for a flexible display device of claim 1, wherein the epoxy group-containing functional group is at least one selected from the group consisting of an alicyclic epoxy group and a functional group represented by the following Chemical Formula 1: ##STR00002## in the Chemical Formula 1, R.sub.a is a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynylene group having 2 to 20 carbon atoms, —R.sub.b—CH═CH—COO—R.sub.c—, —R.sub.d—OCO—CH═CH—R.sub.e—, —R.sub.fOR.sub.g—, —R.sub.hCOOR.sub.i—, or —R.sub.jOCOR.sub.k—, and R.sub.b to R.sub.k are each independently a single bond; or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms.

5. The optical laminate for a flexible display device of claim 1, wherein the polysiloxane is represented by the following Chemical Formula 2:
(R.sup.1SiO.sub.3/2).sub.a(R.sup.2SiO.sub.3/2).sub.b(R.sup.3R.sup.4SiO.sub.2/2).sub.c(R.sup.5R.sup.6R.sup.7SiO.sub.1/2).sub.d(SiO.sub.4/2).sub.e(O.sub.1/2R.sup.8).sub.f  [Chemical Formula 2] in the Chemical Formula 2, R.sup.1 to R.sup.7 are each independently hydrogen, an epoxy group-containing functional group, an amino group, a mercapto group, an ether group, an ester group, a carbonyl group, a carboxyl group, a (meth)acrylate, a sulfone group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 2 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 20 carbon atoms, or a substituted or unsubstituted alkylaryl group having 7 to 20 carbon atoms, with the proviso that at least one of R.sup.1 to R.sup.7 is the epoxy group-containing functional group, R.sup.8 is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and 0<a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 0≤e≤1, and 0≤f≤1.

6. The optical laminate for a flexible display device of claim 1, wherein the polysiloxane has a weight average molecular weight of 3,000 to 250,000 g/mol.

7. The optical laminate for a flexible display device of claim 1, wherein the epoxy group-containing functional group equivalent weight contained in the polysiloxane is 2.5 to 6.3 mmol/g.

8. The optical laminate for a flexible display device of claim 1, wherein the polycaprolactone polyol has a number average molecular weight (Mn) of 300 to 10,000 Da.

9. The optical laminate for a flexible display device of claim 1, wherein the hard coating layer further comprises a reactive monomer including at least one functional group capable of crosslinking with the polysiloxane.

10. The optical laminate for a flexible display device of claim 9, wherein a weight ratio of the polysiloxane; and the reactive monomer including at least one functional group capable of crosslinking with the polysiloxane is 99:1 to 80:20.

11. The optical laminate for a flexible display device of claim 1, wherein the optical laminate has a pencil hardness of at least 5H under load of 750 g on a surface of the hard coating layer.

12. The optical laminate for a flexible display device of claim 1, wherein cracks do not occur when placing the optical laminate at an interval of 5 mm in the middle of the optical laminate and repeating 100,000 times the process of folding and spreading inward of the hard coating layer at a 90° angle so that the hard coating layer faces to each other at 25° C. at a rate of once per second,

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

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

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0101] FIG. 1 is a view schematically showing a method for evaluating dynamic bending properties.

[0102] Hereinafter, the present disclosure will be described in more detail by way of the following examples. However, these examples are provided for illustrative purposes only and are not intended to limit the scope of the present disclosure.

Preparation Example

Preparation Example 1: Preparation of Polysiloxane A

[0103] Silane monomer 3-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403™, Shin-Etsu), water and toluene were placed in a 1000 mL 3-neck flask, mixed and stirred. (GPTMS:water:toluene=1 mol:3 mol:0.5 mol).

[0104] Next, a basic catalyst (trimethylammonium hydroxide; TMAH) was added to the resulting mixed solution in an amount of 1 part by weight based on 100 parts by weight of the silane monomer, and reacted at 100° C. for 2 hours to prepare polysiloxane A of the following composition containing 100 mol % of glycidoxypropyl modified silicone (hereinafter referred to as GP) (number average molecular weight: 3,100 g/mol, polydispersity index (PDI): 1.8, glycidoxypropyl group equivalent weight: 6.0 mmol/g).

(R.sup.1SiO.sub.3/2).sub.a(R.sup.2SiO.sub.3/2).sub.b(R.sup.3R.sup.4SiO.sub.2/2).sub.c(R.sup.5R.sup.6R.sup.7SiO.sub.1/2).sub.d(SiO.sub.4/2).sub.e(O.sub.1/2R.sup.8).sub.f  (2)

[0105] (in Chemical Formula 2, R.sub.1 is a glycidoxypropyl group (in Chemical Formula 1, R.sub.a is —R.sub.bOR.sub.c—, R.sub.b is a propylene group, and R.sub.c is a methylene group), R.sup.8 is a hydrogen atom or a methyl group, a=0.93, b, c, d, e=0, f=0.07.)

Preparation Example 2: Preparation of Polysiloxane B

[0106] Silane monomer 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECTMS, KBM-303™, Shin-Etsu), water and toluene were placed in a 1000 mL 3-neck flask, mixed and stirred (ECTMS:water:toluene=1 mol:3 mol:0.5 mol).

[0107] Next, a basic catalyst (trimethylammonium hydroxide; TMAH) was added to the resulting mixed solution in an amount of 1 part by weight based on 100 parts by weight of the silane monomer, and reacted at 100° C. for 2 hours to prepare polysiloxane B having the following composition containing 2-(3,4-epoxycyclohexyl) Polysiloxane B having the following composition was prepared containing 100 mol % of 2-(3,4-epoxycyclohexyl) ethyl modified silicone (hereinafter referred to as EC) (number average molecular weight: 3,300 g/mol, polydispersity index (PDI): 1.8, epoxycyclohexyl group equivalent weight: 5.6 mmol/g).

(R.sup.1SiO.sub.3/2).sub.a(R.sup.2SiO.sub.3/2).sub.b(R.sup.3R.sup.4SiO.sub.2/2).sub.c(R.sup.8R.sup.6R.sup.7SiO.sub.1/2).sub.d(SiO.sub.4/2).sub.e(O.sub.1/2R.sup.8).sub.f  (2)

[0108] (in the Chemical Formula 2, R.sup.1 is a 2-(3,4-epoxycyclohexyl)ethyl group, R.sup.8 is a hydrogen atom or a methyl group, a=0.95, b, c, d, e=0, f=0.05.)

Preparation Example 3: Preparation of Polysiloxane C

[0109] Silane monomer 3-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403™, Shin-Etsu), phenyltrimethoxysilane (PTMS, Shin-Etsu), water and toluene were placed in a 1000 mL 3-neck flask, mixed and stirred (GPTMS:PTMS:water:toluene=0.7 mol:0.3 mol:3 mol:0.5 mol).

[0110] Next, a basic catalyst (ammonia) was added to the resulting mixed solution in an amount of 1 part by weight with respect to 100 parts by weight of the silane monomer, and reacted at 100° C. for 2 hours to prepare polysiloxane C having the following composition (number average molecular weight: 3,400 g/mol, polydispersity index (PDI): 1.9, glycidoxypropyl group equivalent: 4.5 mmol/g).

(R.sup.1SiO.sub.3/2).sub.a(R.sup.2SiO.sub.3/2).sub.b(R.sup.3R.sup.4SiO.sub.2/2).sub.c(R.sup.5R.sup.8R.sup.7SiO.sub.1/2).sub.d(SiO.sub.4/2).sub.e(O.sub.1/2R.sup.8).sub.f  (2)

[0111] (in Chemical Formula 2, R.sup.1 is a glycidoxypropyl group (in Chemical Formula 1, R.sub.a is —R.sub.bOR.sub.c—, R.sub.b is a propylene group, and R.sub.c is a methylene group), R.sup.2 is a phenyl group, R.sup.8 is a hydrogen atom or a methyl group, a=0.7, b=0.3, c, d, e=0, f<0.01.)

Preparation Example 4: Preparation of Polysiloxane D

[0112] Polysiloxane D having the following composition containing 100 mol % of 2-(3,4-epoxycyclohexyl)ethyl modified silicone (number average molecular weight: 1,400 g/mol, polydispersity index (PDI): 1.4, 2-(3,4-epoxycyclohexyl) ethyl group equivalent weight: 5.6 mmol/g) was prepared in the same manner as in Preparation Example 2, except that the toluene ratio was used at 5 mol.

Preparation Example 5: Preparation of Polysiloxane E

[0113] Polysiloxane E having the following composition (number average molecular weight: 3,300 g/mol, polydispersity index (PDI): 1.7, glycidoxypropyl group equivalent weight: 3.4 mmol/g) was prepared in the same manner as in Preparation Example 3, except that the silane monomer 3-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403™, Shin-Etsu), phenyltrimethoxysilane (PTMS, Shin-Etsu), water and toluene were added, mixed and stirred (GPTMS:PTMS:water:toluene=0.5 mol:0.5 mol:3 mol:0.5 mol).

(R.sup.1SiO.sub.3/2).sub.a(R.sup.2SiO.sub.3/2).sub.b(R.sup.3R.sup.4SiO.sub.2/2).sub.c(R.sup.5R.sup.6R.sup.7SiO.sub.1/2).sub.d(SiO.sub.4/2).sub.e(O.sub.1/2R.sup.8).sub.f  (2)

[0114] (In Chemical Formula 2, R.sup.1 is a glycidoxypropyl group (in Chemical Formula 1, R.sub.a is —R.sub.bOR.sub.c—, R.sub.b is a propylene group, and R.sub.c is a methylene group), R.sub.2 is a phenyl group, R.sub.8 is a hydrogen atom or a methyl group, a=0.5, b=0.45, c, d, e=0, f<0.01.)

Examples and Comparative Examples

Example 1

[0115] 75 g of polysiloxane A prepared in Preparation Example 1, 22 g of polycaprolactone triol (number average molecular weight: 300 Da, manufacturer: Merck) as an elastomeric polymer, 3 g of Irgacrue 250 as a photoinitiator, and 10 g of methyl ethyl ketone as a solvent were mixed to prepare a resin composition for forming a hard coating layer.

[0116] The resin composition for forming the hard coating layer was coated onto one surface of a polyethylene terephthalate (PET) film having a size of 15 cm×20 cm and a thickness of 50 μm, and irradiated with ultraviolet rays using a lamp (irradiation amount: 1,000 mJ/cm.sup.2) and photocured to form the hard coating layer with a thickness of 80 μm, thereby producing an optical laminate.

Example 2

[0117] The optical laminate was manufactured in the same manner as in Example 1, except that polysiloxane B prepared in Preparation Example 2 was used instead of polysiloxane A prepared in Preparation Example 1.

Example 3

[0118] The optical laminate was manufactured in the same manner as in Example 1, except that polysiloxane C prepared in Preparation Example 3 was used instead of polysiloxane A prepared in Preparation Example 1.

Comparative Example 1

[0119] The optical laminate was manufactured in the same manner as in Example 1, except that polysiloxane D prepared in Preparation Example 4 was used instead of polysiloxane A prepared in Preparation Example 1.

Comparative Example 2

[0120] The optical laminate was manufactured in the same manner as in Example 1, except that Gp-D4 was used instead of polysiloxane A prepared in Preparation Example 1, and polycaprolactone triol was not used.

[0121] At this time, Gp-D4 is “2,4,6,8-tetramethyl-2,4,6,8-tetrakis (propyl glycidyl ether) cyclotetrasiloxane”, and the number average molecular weight is 664 g/mol.

Comparative Example 3

[0122] The optical laminate was manufactured in the same manner as in Example 1, except that polysiloxane E prepared in Preparation Example 5 was used instead of polysiloxane A prepared in Preparation Example 1.

Comparative Example 4

[0123] The optical laminate was manufactured in the same manner as in Example 1, except that polysiloxane B prepared in Preparation Example 2 was used instead of polysiloxane A prepared in Preparation Example 1, and polycaprolactone triol which is an elastomeric polymer was not used.

Experimental Example

[0124] The physical properties of the optical laminates prepared in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 1 below.

[0125] 1. Measurement of Surface Pencil Hardness

[0126] A pencil was set on the surface of the hard coating layer of the optical laminate at an angle of 45° under a load of 750 g and the surface was scratched a total of 5 times for each pencil hardness of 20 mm. Whether the test specimen was scratched or not was determined with the naked eye, and the maximum pencil hardness that did not cause surface damage more than 3 times was measured.

[0127] 2. Measurement of Impact Absorption Rate

[0128] When a ball weighing 22 g was dropped from a height of 100 mm onto the optical laminate, the impact absorption rate of the optical laminate was measured.

[0129] Specifically, in the control group, the impact force (N) was measured with an impact force measurement sensor, when the optical laminate was not positioned on the impact force measurement sensor and a ball weighing 22 g was dropped from a height of 100 mm onto the impact force measurement sensor itself, which was defined as “A.sub.0”. Next, the impact force (N) was measured by the impact force measuring sensor, when the optical laminate was positioned on the impact force measurement sensor, more specifically, the impact force measurement sensor and the support substrate layer of the optical laminate were position so as to be in contact with each other, and a ball weighing 22 g was dropped from a height of 100 mm with respect to the hard coating layer of the optical laminate, which was defined as “A.sub.1”.

[0130] Thereafter, “A.sub.0” and “A.sub.1” were substituted into Equation 1 below to calculate the shock absorption rate.

Impact absorption rate=(A.sub.1−A.sub.0/A.sub.0)×100  [Equation 1]

[0131] 3. Dynamic Bending Properties

[0132] FIG. 1 is a view schematically showing a method for evaluating dynamic bending properties of the optical laminate according to an embodiment of the present disclosure.

[0133] The optical laminate was cut, but laser cutting was performed into a size of 80×140 mm so as to minimize fine cracks at the edge portions. The laser cut film was placed on the measuring equipment the hard coating layer was set inward, 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 at room temperature were repeated 100,000 times by continuous operations (the speed at which the film was folded was once every 1 second at 25° C.), and the dynamic bending properties were evaluated according to the following criteria.

[0134] Excellent: No cracks occurred

[0135] Defective: Cracks occurred

[0136] 4. Elongation at Break

[0137] The optical laminate was cut into a width of 10 mm and a length of 150 mm, and the elongation at break in the longitudinal direction was measured with UTM (Universal Testing Machine, Instron's sample) and the following conditions. [0138] Sample measurement length 100 mm, [0139] Measurement speed 10 mm/min

TABLE-US-00001 TABLE 1 Example Example Example Comparative Comparative Comparative Comparative 1 2 3 Example 1 Example 2 Example 3 Example 4 Surface 7H 7H 6H 7H Not 2H 7H pencil measurable hardness Impact −7.5% −6.3% −8.1% −3.7% −0.9% −1.4% −6.5% absorption rate Dynamic Excellent Excellent Excellent Defective Defective Excellent Defective bending properties Elongation at  .sup.  6%  .sup.  5%  .sup.  5%  .sup.  3%  .sup.  2%  .sup.  3%  .sup.  3% break (%)

[0140] According to Table 1, it was confirmed that the optical laminates of Examples have a high surface hardness of 6H or more, and do not cause cracks in repeated continuous operation of folding and spreading 100,000 times, and also have a shock absorption rate of −6.3% or less, which thus have high toughness and excellent impact resistance.

[0141] On the other hand, it was confirmed that the optical laminates of Comparative Examples 1 to 3 have an impact absorption rate of −3.7% or more and have low toughness and low impact resistance, and that Comparative Examples 1, 2, and 4 cause cracks in a continuous operation of repeatedly folding and spreading 100,000 times. In addition, it was confirmed that in Comparative Examples 2 and 3, the pencil hardness is as low as 2H or less.