Optical film having organic and inorganic particles of different sizes, and polarizing plate comprising same

Abstract

The present invention relates to a resin composition for forming an optical film, an optical film, and a polarizing plate, in which the resin composition for forming an optical film improves adhesion between an antiglare layer and a light-transmitting substrate film and enables the antiglare layer and the optical film to exhibit excellent optical properties such as appropriate haze, low gloss value, and excellent antiglare properties. The composition for forming an optical film is a resin composition for forming an optical film for forming an infiltration layer and an antiglare layer having surface irregularities on a light-transmitting substrate film, and comprises: a binder-forming compound including a polyfunctional (meth)acrylate-based compound having three or more functionalities, and a permeable compound having a hydrophilic functional group and a photo-curable functional group; two or more light-transmitting fine particles having a sub-micron (sub-μm) scale; and a permeable solvent capable of dissolving at least a part of the light-transmitting substrate film, wherein the binder-forming compound and the permeable solvent have a weight ratio of 1:0.04 or more.

Claims

1. An optical film comprising: a light-transmitting substrate film; an infiltration layer having at least a part that is infiltrated into the light-transmitting substrate film so as to overlap with at least a part of the light-transmitting substrate film, and including a first binder containing a first (meth)acrylate-based cross-linked polymer; and an antiglare layer which includes a second binder containing a second (meth)acrylate-based cross-linked polymer, and at least two light-transmitting fine particles dispersed on the second binder, and is formed so as to have surface irregularities on the infiltration layer, wherein the at least two light-transmitting fine particles comprise organic fine particles having a particle diameter of 1 to 5 μm and inorganic fine particles having a particle diameter of 10 nm to 300 nm, wherein the infiltration layer has a thickness of 600 nm or more and 1.0 μm or less, wherein the antiglare layer has a thickness of 4.4 to 10 μm, and wherein the optical film has a total haze value of 1 to 5% and a 60-degree gloss value of 80% to 88%.

2. The optical film of claim 1, wherein the optical film has a 20-degree gloss value of 45% to 68%.

3. The optical film of claim 1, wherein the second binder has a refractive index of 1.50 to 1.60.

4. The optical film of claim 1, further comprising a low refractive index layer which is formed on the antiglare layer and includes a binder resin containing a (co)polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin.

5. The optical film of claim 4, wherein the low refractive index layer has a refractive index of 1.3 to 1.5 and a thickness of 1 to 300 nm.

6. A polarizing plate comprising the optical film of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an electron micrograph showing the cross-sectional shape of the optical film formed in Example 2 (particularly, the formation of substrate film/infiltration layer/antiglare layer).

(2) FIG. 2 is an electron micrograph showing the cross-sectional shape of the optical film formed in Example 3 (in particular, the formation of the substrate film/infiltration layer/antiglare layer).

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) 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.

(4) <Preparation Example: Preparation of Composition for Forming an Antiglare Layer/an Infiltration Layer>

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

(6) The components shown in Tables 1 and 2 below were uniformly mixed to prepare a composition for forming an optical film (antiglare layer). The contents of all components used in Tables 1 and 2 are shown in parts by weight.

(7) TABLE-US-00001 TABLE 1 Preparation Preparation Preparation Preparation Preparation Preparation Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Permeable THFA 1.79 1.79 3.6 compound HEA 1.8 1.79 3.45 Other binder UA-306T 3.60 8.80 3.6 3.45 Beamset371 12.4 8.80 3.60 8BR-500 7.2 12.41 7.30 TMPTA 4.14 3.6 12.41 6.20 PETA 12.4 8.27 12.41 8.9 6.20 Organic fine 103BQ 1.1 0.44 0.67 0.4 particles (about 1.52) (refractive 113BQ 0.44 0.33 0.4 0.99 0.91 index) (about 1.56) Inorganic fine MA-ST 0.1 0.29 0.17 0.3 0.17 0.26 particles (12 nm) (refractive (1.430) index) Initiator I184 1.8 0.80 0.80 1.8 0.80 0.80 Leveling agent T100 0.5 0.13 0.13 0.4 0.13 0.13 Permeable Methyl ethyl 1.1 1.48 1.48 1.1 1.34 1.34 solvent ketone Other solvent IPA 34.4 34.91 34.91 22.9 34.98 34.98 EtOH 34.4 34.91 34.91 45.8 34.98 34.98 Total 100 100 100 100 100 100 Permeable solvent/Binder- 0.041 0.06 0.06 0.04 0.05 0.05 forming compound (weight ratio)

(8) TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Preparation Preparation Preparation Preparation Preparation Preparation Preparation Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Permeable THFA compound HEA 12.4 3.45 Other binder UA-306T 3.45 3.60 3.45 3.60 Beamset371 13.3 13.5 12.4 8.80 8.80 8BR-500 10.75 7.30 TMPTA 6.20 8.27 6.20 8.27 PETA 13.3 13.5 1.8 6.20 5.93 6.20 5.93 Organic fine 103BQ 1.2 1.1 0.5 0.44 0.44 particles (about 1.52) (refractive 113BQ 0.5 0.91 0.44 0.91 0.44 index) (about 1.56) Inorganic fine MA-ST 0.2 0.1 0.2 0.26 0.29 0.26 0.29 particles (12 nm) (refractive (1.430) index) Initiator I184 1.8 1.8 1.8 0.80 0.80 0.80 0.80 Leveling agent T100 0.4 0.4 0.13 0.13 0.13 0.13 Permeable Methyl ethyl 5.8 1.34 1.48 5.86 solvent ketone Other solvent IPA 34.9 32.1 35.0 34.98 34.91 32.72 47.50 EtOH 34.9 32.1 35.0 34.98 34.91 32.72 23.80 Total 100 100 100 100 100 100 100 Permeable solvent/Binder- 0 0.21 0 0.05 0.06 0.22 0 forming compound (weight ratio) 1) THFA: tetrahydrofurfuryl alcohol 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) T-100 (Tego glide 100): Leveling agent, manufactured by Evonik 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-113BQ, manufactured by Sekisui Plastic): PMMA-PS cross-linked copolymer fine particles having a refractive index of 1.555 (about 1.56) and an average particle diameter of 2 μm 12) 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)

Examples 1 to 6 and Comparative Examples 1 to 7: Preparation of Optical Film

(9) As shown in Tables 3 and 4 below, the compositions prepared in Preparation Examples 1 to 6 or Comparative Preparation Examples 1 to 7 were respectively coated onto a PET substrate film having a thickness of 80 μm and a refractive index of 1.6 to 1.7 (or an acrylic substrate film having a thickness of 60 μm and a refractive index of 1.4 to 1.6), dried at 90° C. for 1 minute, and then irradiated with ultraviolet rays of 150 mJ/cm.sup.2 to prepare an antiglare layer.

(10) An antiglare layer was formed and an optical film was prepared. The cress sections of the optical films of Examples 2 and 3 were observed with an electron microscope, and the formation of infiltration layer was confirmed. The electron micrographs of Examples 2 and 3 are shown in FIGS. 1 and 2, respectively (In FIG. 1, the light-transmitting fine particles are not observed due to the observation direction). In the same manner, it was confirmed whether or not an infiltration layer was formed in the remaining Examples and Comparative Examples.

Experimental Example: Measurement of Physical Properties of Optical Film

(11) The physical properties of the optical films prepared above were measured according to the following methods, and the results are shown in Tables 3 and 4 below.

(12) 1. Measurement of Refractive Index

(13) 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 low refractive index layer 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.

(14) 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.

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

(16) wherein 1, n(λ) is a refractive index at a wavelength λ (300 nm to 1800 nm), and A, B and C are Cauchy parameters.

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

(18) 2. Evaluation of Infiltration Layer/Antiglare Layer

(19) The average thickness of the infiltration layer/the antiglare layer was measured through the electron micrographs as shown in FIGS. 1 and 2.

(20) 3. Evaluation of Total/Internal/External Haze Value

(21) 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.

(22) 4. Evaluation of 20°/60° Gloss Value

(23) 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.

(24) 5. Evaluation of Pencil Hardness (500 gf)

(25) The pencil hardness was measured according to ASTM D3363, and the measuring instrument used was a pencil hardness tester (JS Tech). During the measurement, the film specimen was cut into 7 cm×7 cm and fixed on a glass plate. The pencil, product of Mitsubishi Pencil Co., Ltd., Japan, was used to measure the hardness under a load of 500 g. When measured five times per pencil and four or more times were better, it was evaluated that there was no scratch at the corresponding hardness. The measurement length was 5 cm, and the hardness was determined by excluding scratches at 0.5 cm in the early stage.

(26) 6. Adhesion Evaluation

(27) The adhesion between the antiglare layer and the substrate film was measured on the surface of the scattering side.

(28) TABLE-US-00003 TABLE 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Substrate film PET Acryl Acryl PET Acryl Acryl Refractive index 1.6~1.7 1.4~1.6 1.4~1.6 1.6~1.7 1.4~1.6 1.4~1.6 of substrate film (birefringence) (birefringence) Preparation Preparation Preparation Preparation Preparation Preparation Composition Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Thickness of 4.5 4.4 5 5 5.1 5.5 antiglare layer (μm) Antiglare layer 1.524 1.522 1.526 1.524 1.516 1.519 (refractive index of second binder) Formation of ◯ ◯ ◯ ◯ ◯ ◯ infiltration layer Thickness of ~500 nm ~900 nm ~600 nm ~500 nm ~600 nm ~1000 nm infiltration layer Total haze value 1.1 2.9 3.1 2.1 2.5 2.6 Internal haze value 0.6 2.1 2.3 1.8 1.3 1.6 Gloss value (20- 67 64 65 65.2 63 63 degree) Gloss value (60- 86.0 84 86 86.3 85 87 degree) Pencil hardness 3H 3H 3H 3H 3H 3H Adhesion >4B 5B 5B >4B 5B 5B

(29) TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Substrate film PET PET PET Acryl Acryl Acryl Acryl Refractive index 1.6~1.7 1.6~1.7 1.6~1.7 1.4~1.6 1.4~1.6 1.4~1.6 1.4~1.6 of substrate film (birefringence) (birefringence) (birefringence) Comparative Comparative Comparative Comparative Comparative Comparative Comparative Preparation Preparation Preparation Preparation Preparation Preparation Preparation Composition Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Thickness of 4.5 4.5 4.5 5 4.6 5.4 5.1 antiglare layer Antiglare layer 1.524 1.524 1.523 1.522 1.521 1.519 1.521 (refractive index of second binder) Formation of X ◯ ◯ X X ◯ X infiltration layer Thickness of 0 ~500 nm ~1.5 μm 0 0 ~1100 nm 0 infiltration layer Total haze value 1.2 0.7 2.2 3.2 3.1 1.9 2.9 Internal haze value 0.7 0.6 2.0 2.3 2.1 1.7 1.8 Gloss value (20- 66.6 70.7 70.0 65 64 70 64 degree) Gloss value (60- 87.1 92.6 91.7 86 85 91.5 86 degree) Pencil hardness 3H 3H H 3H 3H 3H 3H Adhesion 2B >4B 3B <3B <3B 5B <3B

(30) Referring to Table 3, it was confirmed that the optical films of Examples exhibit not only excellent optical properties such as low gloss value and appropriate level of haze property, but also excellent mechanical properties such as high surface hardness and adhesion.

(31) On the contrary, it was confirmed that in the case of Comparative Examples 1 to 7, which are formed from a composition not containing the permeable compound and/or the permeable solvent or deviating from proper ratio/content, an infiltration layer is not formed and thus the adhesion is deteriorated (Comparative Examples 1, 4, 5 and 7), and the agglomeration of the organic fine particles is not properly controlled during the formation of the infiltration layer so that the surface hardness is poor (Comparative Example 3) and the optical properties (the haze value is too low or the gloss value was high) are poor(Comparative Examples 2, 3, and 6).

(32) For reference, if the gloss value is too high, the reflection of external light cannot be suppressed properly, and if the haze value is too low, the external reflection image is visible without being scattered, so that the visibility and image sharpness of the screen are poor.