Optical film and image display device including same

Abstract

The present invention relates to an optical film including a light-transmitting substrate film such as a polyester-based substrate film and an antiglare layer, and more specifically, to an optical film capable of effectively suppressing the occurrence of interference fringes derived from the substrate film, realizing excellent antiglare properties, and having excellent scratch resistance, and excellent adhesion between the substrate film and the antiglare layer, and the like, and to an image display device including the same.

Claims

1. An optical film comprising: a polyester-based substrate film, a primer layer formed on the polyester-based substrate film, having a thickness of 20 nm to 500 nm, an antiglare layer formed on the primer layer, including a binder containing a (meth)acrylate-based crosslinked polymer, and organic fine particles of a micron (μm) scale dispersed in the binder and inorganic fine particles of a nanometer (nm) scale dispersed in the binder, and a low refractive index layer formed on the antiglare layer, comprising a binder resin containing a crosslinked (co)polymer of a photopolymerizable compound and a fluorine-based compound containing a photoreactive functional group, and hollow silica particles dispersed in the binder resin, wherein the fluorine-based compound containing the photoreactive functional group has a fluorine content of 1 to 25% by weight, wherein the polyester-based substrate film is a polyethylene terephthalate (PET)-based film having a thickness of 100 to 200 μm, wherein the (meth)acrylate-based crosslinked polymer is a crosslinked polymer of 0 to 20 parts by weight of a monofunctional (meth)acrylate-based compound based on 100 parts by weight of the binder, and a polyfunctional (meth)acrylate-based compound with three or more functionalities, wherein an absolute value of the refractive index difference between the organic fine particles and the binder is 0.08 to 0.15, and an absolute value of the refractive index difference between the inorganic fine particles and the binder is less than 0.15, wherein the surface of the antiglare layer has a 20-degree gloss value of 50% to 70% and a 60-degree gloss value of 75% to 90%, and wherein the polyfunctional (meth)acrylate-based compound comprises: a monomolecular (meth)acrylate-based compound with three to six functionalities, and a polyurethane-based polymer, a poly(meth)acryl-based polymer, or a polyester-based polymer, each having a (meth)acrylate-based functional group with 40 to 80 functionalities.

2. The optical film of claim 1, wherein the binder has a refractive index of 1.5 to 1.60.

3. The optical film of claim 1, wherein the organic fine particles include a polystyrene-based resin, a poly(meth)acrylate-based resin or poly(meth)acrylate-co-styrene copolymer resin.

4. The optical film of claim 1, wherein the organic fine particles are spherical particles having a particle diameter of 1 to 5 μm and have a refractive index of 1.5 to 1.57.

5. The optical film of claim 1, wherein the inorganic fine particles are metal oxide fine particles including silica, alumina, zirconia or titania.

6. The optical film of claim 1, wherein the inorganic fine particles are spherical particles having a particle diameter of 10 nm to 300 nm, and have a refractive index of 1.4 to 1.75.

7. The optical film of claim 1, wherein the organic and inorganic fine particles are each contained in an amount of 0.1 to 10 parts by weight based on total 100 parts by weight of the antiglare layer.

8. The optical film of claim 1, wherein the antiglare layer has a thickness of 1 to 10 μm.

9. The optical film of claim 1, wherein the primer layer has a refractive index smaller than a refractive index of the substrate film and larger than a refractive index of the binder of the antiglare layer.

10. The optical film of claim 1, wherein the low refractive index layer has a refractive index of 1.3 to 1.5 and a thickness of 1 to 300 nm.

11. An optical film comprising: a light-transmitting substrate film, a primer layer formed on the light transmitting substrate film, having a thickness of 20 nm to 500 nm, an antiglare layer which is formed on the primer layer and includes a binder containing a (meth)acrylate-based crosslinked polymer, and organic fine particles of a micron (μm) scale and inorganic fine particles of a nano (nm) scale dispersed in the binder, and a low refractive index layer formed on the antiglare layer, comprising a binder resin containing a crosslinked (co)polymer of a photopolymerizable compound and a fluorine-based compound containing a photoreactive functional group, and hollow silica particles dispersed in the binder resin, wherein the fluorine-based compound containing the photoreactive functional group has a fluorine content of 1 to 25% by weight, wherein the light-transmitting substrate film is a polyester film having a thickness of 100 to 200 μm, wherein the (meth)acrylate-based crosslinked polymer is a crosslinked polymer of 0 to 20 parts by weight of a monofunctional (meth)acrylate-based compound based on 100 parts by weight of the binder, and a polyfunctional (meth)acrylate-based compound with three or more functionalities, wherein an absolute value of the refractive index difference between the organic fine particles and the binder of the antiglare layer is 0.08 to 0.15 and an absolute value of the refractive index difference between the inorganic fine particles and the binder is less than 0.15, wherein the polyfunctional (meth)acrylate-based compound includes a monomolecular (meth)acrylate-based compound with three to six functionalities and a polyurethane-based polymer, a poly(meth)acryl-based polymer, or a polyester-based polymer, each having a (meth)acrylate-based functional group with 40 to 80 functionalities, and wherein the surface of the antiglare layer has a 20-degree gloss value of 50% to 70% and a 60-degree gloss value of 75% to 90%.

12. An image display device comprising the optical film of claim 1.

13. The optical film of claim 1, wherein the film has a total haze value of 2.4 to 3.2%.

14. The optical film of claim 1, wherein the film has a scratch resistance of 1200-1500 g.

15. The optical film of claim 1, wherein the surface of the antiglare layer has a 20-degree gloss value of 58 to 68% and a 60-degree gloss value of 80 to 88%.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Specific embodiments of the present invention are now described in more detail by way of the following examples. However, these examples are given for illustrative purposes only, and the scope of the present invention is not intended to be limited to or by the examples.

Preparation Example: Preparation of Composition for Forming an Antiglare Layer, and Photo-Curable Coating Composition for Forming Low Refractive Index Layer

(2) (1) Preparation of Composition for Forming an Antiglare Layer

(3) The components shown in Table 1 below were uniformly mixed to prepare a composition for forming an antiglare layer. The contents of all components used in Table 1 are shown in parts by weight.

(4) TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Comparative Preparation Preparation Preparation Preparation Preparation Preparation Preparation Preparation Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3 Example 4 Binder OPPEA 5.0 23.0 HEA 8.5 UA- 15.0 10.6 4.0 306T Beamset 7.0 8.0 7.0 371 8BR-500 10.0 9.0 7.0 6.0 TMPTA 23.1 10.6 23.1 23.1 PETA 18.1 16.1 7.0 Organic 103BQ 0.5 fine (about particles 1.52) (refractive 113BQ 0.6 0.5 0.8 1.0 1.0 0.6 index) (about 1.56) 3.5 μm/ 1.0 1.555 (about 1.56) Inorganic 9600A 0.2 0.2 fine (1.43) particles MA-ST 0.2 0.5 0.2 0.1 1.0 0.5 0.1 0.2 (refractive (1.43) index) Initiator I184 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Dispersant BYK300 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Solvent IPA 33.2 22.1 33.1 22.2 33.0 32.8 33.2 EtOH 33.2 66.0 44.2 33.2 44.2 33.0 33.0 33.2 Refractive Binder* 1.51 1.55 1.52 1.53 1.51 1.58 1.52 1.51 index Organic 1.56 1.54 1.56 1.56 0 1.56 1.56 1.56 fine particles (average) Inorganic 1.43 1.43 1.43 1.43 1.43 1.43 1.43 1.43 fine particles (average) Absolute 0.05 0.01 0.04 0.03 1.51 0.02 0.04 0.05 value of refractive index difference (binder & Organic fine particles) Absolute 0.08 0.12 0.09 0.10 0.08 0.15 0.09 0.08 value of refractive index difference (binder & Inorganic fine particles) Total 100 100 100 100 100 100 100 100 *The refractive index of the binder is measured after crosslinking (co)polymerization according to the above constitution and preparation examples described hereinafter. 1) OPPEA: o-phenylphenoxyethyl acrylate 2) HEA: 2-hydroxyethyl acrylate 3) UA-306T: (Kyoeisha): hexafunctional acrylate-based compound formed by reacting toluene diisocyanate with two pentaerythritol triacrylates 4) Beamset 371 (ARAKAWA CHEMICAL): polymer to which an epoxy acrylate functional group having about 50 or more functionalities is bonded to a polyurethane/ester backbone 5) 8BR-500 (TAISEI FINE CHEMICAL): polymer to which a urethane acrylate functional group with about 40 functionalities is bonded to a polyacryl backbone 6) TMPTA: trimethylolpropane triacrylate 7) PETA: Pentaerythritol triacrylate 8) I184 (Irgacure 184): photoinitiator, manufactured by Ciba 9) BYK 300: PDMS dispersant 10) 103BQ (XX-103BQ, manufactured by Sekisui Plastic): PMMA-PS cross-linked copolymer fine particles having a refractive index of 1.515 (about 1.52) and an average particle diameter of 2 μm 11) 113BQ (XX-1136Q, manufactured by Sekisui Plastic): PMMA-PS crosslinked copolymer fine particles having a refractive index of 1.555 (about 1.56) and an average particle diameter of 2 μm 12) 3.5 μm/1.555: spherical acrylic/styrene copolymer resin fine particles (XX-68BQ, manufactured by Sekisui Plastic Co.) having a volume average particle diameter of 3 μm and a refractive index of 1.555 (about 1.56) 13) 9600A: spherical silica fine particles (X24-9600A; Shin-Etsu) having a volume average particle diameter of 100 nm and a refractive index of 1.43, 14) MA-ST: spherical silica fine particles having a volume average particle diameter of 12 nm and a refractive index of 1.43 (manufactured by Nissan Chemical)

Example and Comparative Example: Preparation of Optical Film

(5) As shown in Table 2 below, the antiglare layer compositions respectively prepared in Preparation Examples 1 to 4 or Comparative Preparation Examples 1 to 3 were coated onto a PET substrate film having a thickness of 100 μm and a refractive index of 1.6 to 1.7, dried at 90° C. for 1 minute, and then irradiated with ultraviolet rays of 150 mJ/cm.sup.2 to prepare an antiglare layer.

Experimental Example: Measurement of Physical Properties of Optical Film

(6) The physical properties of the optical films prepared above were measured according to the following methods, and the results are shown in Table 2 below.

(7) 1. Measurement of Refractive Index

(8) The refractive indexes of the binder and the antiglare layer contained in the optical film were measured in a state of being coated on the wafer using an ellipsometer. More specifically, the refractive indexes of the binder, the antiglare layer and the like were measured by a method in which each composition was applied to a 3 cm×3 cm wafer, coated using a spin coater (coating condition: 1500 rpm, 30 seconds), dried at 90° C. for 2 minutes and irradiated with ultraviolet rays under the condition of 180 mJ/cm.sup.2 under nitrogen purge. Thereby, each coating layer having a thickness of 100 nm was formed.

(9) The ellipsometry was measured for the coating layer at an incidence angle of 70° over a wavelength range of 380 nm to 1000 nm by using J. A. Woollam Co. M-2000 apparatus. The measured ellipsometry data (LP, A) was fitted to a Cauchy model of the following general formula 1 using Complete EASE software so that MSE became 3 or less.

(10) $n\left(\lambda \right)=A+\frac{B}{{\lambda }^2}+\frac{C}{{\lambda }^4}$

(11) Wherein, n(λ) is a refractive index at a wavelength λ (300 nm to 1800 nm), and A, B and C are Cauchy parameters.

(12) Meanwhile, the refractive indexes of the substrate film and the respective fine particles used information provided on the commercially available product.

(13) 2. Evaluation of the Occurrence of Interference Fringes—Evaluation of Occurrence of Rainbow Stains/Measurement of Rainbow Variation Rate

(14) In the optical films prepared in Examples and Comparative Examples, a black tape (Vinyl tape 472 Black, manufactured by 3M) was attached to the surface on which the antiglare layer was not formed so as not to transmit light, and then reflection images were taken using a three-wavelength light source. The size of the captured image was 640×480 pixels (15 cm×10 cm), and the light quantity was adjusted to the range of 70% of the maximum quantity of light emitted from the three-wavelength lamp.

(15) The presence or absence of rainbow stains present on the surface of the optical film was observed in the images used and evaluated according to the following criteria. The evaluation results are shown in Table 2 below.

(16) <Measurement Criteria>

(17) O: There was no rainbow stains, or the rainbow interval is 0.2 mm or less, and rainbow was not observed compared to the complementary colors such as red and green.

(18) X: Rainbow interval was 0.2 mm or more, rainbow was observed compared to the complementary colors such as red and green, and rainbow was recognized even with the light source of general fluorescent light.

(19) 3. Evaluation of Total/Internal Haze Value

(20) A 4 cm×4 cm optical film specimen was prepared. The average value was calculated by measuring three times with a haze meter (HM-150, A light source, Murakami Color Research Laboratory), which was calculated as a total haze value. In the measurement, the transmittance was measured according to JIS K 7361, and the haze value was measured according to JIS K 7105. In measuring the internal haze value, an adhesive film having a total haze value of 0 was bonded to the coated surface of the optical film to be measured to make the irregularities of the surface smooth, and an internal haze value was measured in the same manner as that of the total haze value.

(21) 4. Evaluation of Gloss Value

(22) The 20°/60° gloss value was measured using the micro-TRI-gloss manufactured by BYK Gardner Co., Ltd. At the time of measurement, a black tape (3M) was attached to the surface of the substrate film on which the coating layer was not formed so as not to transmit light. The 20°/60° gloss value was measured by varying the incidence angle of light to 20°/60°, and the average value measured five or more times was calculated as the gloss value.

(23) 5. Evaluation of Scratch Resistance

(24) The optical film to be measured was cut into a width of 4 cm and a length of 15 cm and fixed on a scratch measuring instrument. The coated surface was then rubbed back and forth 10 times under a constant load, and it was observed whether the scratch occurred on the surface. While increasing the load in increments of 100 g, the maximum load not causing scratches was calculated as the scratch resistance evaluation result.

(25) TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3 Example 4 Substrate film PET PET PET PET PET PET PET PET Refractive 1.6~1.7 1.6~1.7 1.6~1.7 1.6~1.7 1.6~1.7 1.6~1.7 1.6~1.7 1.6~1.7 index of (birefringence) (birefringence) (birefringence) (birefringence) (birefringence) (birefringence) (birefringence) (birefringence) substrate film Constitution of Preparation Preparation Preparation Preparation Comparative Comparative Comparative Comparative antiglare layer Example 1 Example 2 Example 3 Example 4 Preparation Preparation Preparation Preparation Example 1 Example 2 Example 3 Example 4 Primer layer formed formed formed formed formed formed formed formed Thickness of 100 100 100 100 100 100 100 100 primer layer (nm) Rainbow ◯ ◯ ◯ ◯ X X X X Total haze 3.2 2.7 2.5 2.8 1.2 2.8 2.2 5.2 value (%) Internal haze 2.8 2.4 2.3 2.7 1 2.6 2 4.7 value (%) Gloss value 60.5 65 61.8 59.8 72.5 56.5 72 39.2 (20-degree) Gloss 86 86.9 85.5 83.2 92.3 83.5 91.7 73.5 value (60- degree Scratch 1200 1200 1500 1300 1300 200 900 1200 resistance (g)

(26) Referring to Table 2, it was confirmed that the optical films of Examples 1-4 suppress the interference fringes (rainbow) derived from the substrate film, and exhibit excellent optical properties such as low gloss value and haze value and high scratch resistance.

(27) However, it was confirmed that in Comparative Examples 1 to 4, as the monofunctional (meth)acrylate-based compound is used in an excessively high content, or the refractive index difference between the respective fine particles and the binder is 0.15 or more, or the binder is formed without using a compound having ten or more functionalities, the scratch resistance or optical properties are deteriorated, and the occurrence of interference fringes is increased.