Anti-reflective film, polarizing plate, and display apparatus

Abstract

The present invention relates to an anti-reflective film having mechanical properties such as high abrasion resistance and scratch resistance and excellent optical properties, and a polarizing plate and a display apparatus including the same.

Claims

1. An anti-reflective film comprising a hard coating layer, and a low-refractive index layer satisfying Equation 1,
0.2% p≥ΔR=|R.sub.1−R.sub.0|  [Equation 1] wherein in the Equation 1, R.sub.0 is an average reflectance % of the low-refractive index layer before performing a rubbing test as measured in a wavelength range of 380 to 780 nm, and R.sub.1 is an average reflectance % of the low-refractive index layer after performing the rubbing test as measured in a wavelength range of 380 to 780 nm, wherein the rubbing test is performed by rubbing a surface of the-low refractive index layer by applying a load of 500 g to a steel wool and reciprocating ten times at a speed of 33 rpm, and % p=ΔR, wherein AR is the degree of change of the average reflectance before and after the rubbing test, wherein the low refractive index layer comprises a binder resin, and two or more groups of hollow inorganic particles dispersed in the binder resin and having different particle diameters, wherein the two or more groups of hollow inorganic particles having different particle diameters include a first group of hollow inorganic particles having a particle diameter of 40 nm to 60 nm as measured by Dynamic Light Scattering (DLS), and a second group of hollow inorganic particles having a particle diameter of 65 nm to 100 nm as measured by Dynamic Light Scattering (DLS), and wherein a weight ratio between the first group of hollow inorganic particles and the second group of hollow inorganic particles is 7:3 to 3:7.

2. The anti-reflective film of claim 1, wherein the R.sub.0 value in the Equation 1 is 0.1 to 2.0%.

3. The anti-reflective film of claim 1, wherein the R.sub.1 value in the Equation 1 is 0.3 to 2.2%.

4. The anti-reflective film of claim 1, wherein the low-refractive index layer also satisfies Equation 2:
1≥Δb*=|b*.sub.1−b*.sub.0|  [Equation 2] wherein in the Equation 2, b*.sub.0 is a b* value in a CIE (L*a*b*) color coordinate system of the low-refractive index layer before the rubbing test as defined by the International Commission on Illumination, and b*.sub.1 is a b* value in a CIE (L*a*b*) color coordinate system of the low-refractive index layer after the rubbing test as defined by the International Commission on Illumination.

5. The anti-reflective film of claim 4, wherein the b*.sub.0 value in the Equation 2 is 2 to −10.

6. The anti-reflective film of claim 4, wherein the b*.sub.1 value in the Equation 2 is 3 to −9.

7. The anti-reflective film of claim 1, wherein the binder resin of the low-refractive index layer comprises a copolymer of a polyfunctional (meth)acrylate-based monomer containing a 2- to 4-functional (meth)acrylate-based monomer and a 5- or a 6-functional (meth)acrylate-based monomer.

8. The anti-reflective film of claim 7, wherein a weight ratio between the 2- to 4-functional (meth)acrylate-based monomer and the 5- or 6-functional (meth)acrylate-based monomer is 9:1 to 6:4.

9. The anti-reflective film of claim 7, wherein 2 to 4-functional (meth)acrylate-based monomer has a pentaerythritol structure at its center, represented by the following Chemical Formula 1 ##STR00003## in Chemical Formula 1, R.sub.1 to R.sub.4 are a hydroxy group, a (meth)acrylate group, or a substituted or unsubstituted C.sub.1-40 alkoxy group, with the proviso that at least one of them is a (meth)acrylate group, and the 5- or 6-functional (meth)acrylate-based monomer has a dipentaerythritol structure at its center, represented by the following Chemical Formula 2 ##STR00004## in Chemical Formula 2, R.sub.11 to R.sub.16 are a hydroxyl group, a (meth)acrylate group, or a substituted or unsubstituted C.sub.1-40 alkoxy group, with the proviso that at least one of them is a (meth)acrylate group.

10. The anti-reflective film of claim 7, wherein the 2- to 4-functional (meth)acrylate-based monomer and the 5- or 6-functional (meth)acrylate-based monomer are included in a weight ratio of 9:1 to 6:4.

11. The anti-reflective film of claim 1, wherein the anti-reflective film further comprises a light-transmitting substrate of which retardation (Rth) in the thickness direction of 3000 nm or more as measured at a wavelength of 400 nm to 800 nm.

12. A polarizing plate comprising the anti-reflective film of claim 1.

13. A display apparatus comprising the anti-reflective film of claim 1.

14. A display apparatus comprising the polarizing plate of claim 12.

15. The anti-reflective film of claim 9, wherein the 2- to 4-functional (meth)acrylate-based monomer is selected from pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, or a mixture thereof, and wherein the 5- to a 6-functional (meth)acrylate-based monomer is selected from dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, or a mixture thereof.

16. The anti-reflective film of claim 10, wherein the weight ratio between the 2- to 4-functional (meth)acrylate-based monomer and the 5- to 6-functional (meth)acrylate-based monomer is 8.5:1.5 to 6.5:3.5.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

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

PREPARATION EXAMPLES 1 to 3

Hard Coating Layer 1

Preparation Example 1

(2) 30 g of pentaerythritol triacrylate, 2.5 g of a high molecular weight copolymer (BEAMSET 371, Arakawa Corporation, Epoxy Acrylate, molecular weight: 40,000), 20 g of methyl ethyl ketone, and 0.5 g of a leveling agent (Tego Wet 270) were uniformly mixed. Then, 2 g of acrylic-styrene copolymer resin fine particles (volume average particle size: 2 μm, manufactured by Sekisui Plastic) with a refractive index of 1.525 were added to the mixture to prepare a hard coating composition.

(3) The hard coating composition thus obtained was coated onto a triacetylcellulose film with a #10 Mayer bar and dried at 90° C. for one minute. The dried product was irradiated with ultraviolet light at 150 mJ/cm.sup.2 to prepare a hard coating layer having a thickness of 4 μm.

Preparation Example 2

(4) The hard coating composition of Preparation Example 1 was coated on a PET film having a thickness of 80 μm and retardation of 10,000 nm with a #10 Mayer bar, and dried at 60° C. for one minute.

(5) The dried product was irradiated with ultraviolet rays at 150 mJ/cm.sup.2 to prepare a hard coating layer having a thickness of 4 μm.

Preparation Example 3

(6) KYOEISHA salt type of antistatic hard coat solution (solid content: 50 wt %, product name: LJD-1000) was coated on a triacetyl cellulose film with a #10 Mayer bar, and dried at 90° C. for one minute.

(7) The dried product was then irradiated with ultraviolet rays at 150 mJ/cm.sup.2 to prepare a hard coating layer having a thickness of about 5 μm.

EXAMPLES 1 to 6

Preparation of Anti-Reflective Film

Example 1

(8) Based on 100 parts by weight of a mixed binder of pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) (weight ratio of PETA:DPHA of 7:3), 100 parts by weight of hollow silica nanoparticles (diameter: about 50 to 60 nm, manufactured by JGC Catalyst and Chemicals), 12 parts by weight of a fluorine-based compound (RS-907, DIC), and 13.4 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in a MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3 wt % to prepare a photocurable coating composition.

(9) The photocurable coating composition was coated onto the hard coating film of Preparation Example 1 at a thickness of about 110 to 120 nm with a #4 Mayer bar, and dried and cured at 60° C. for one minute to prepare an anti-reflective film.

(10) At the time of curing, ultraviolet light at 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

Example 2

(11) Based on 100 parts by weight of a mixed binder of pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) (weight ratio of PETA:DPHA was 6:4), 150 parts by weight of hollow silica nanoparticles (diameter range: about 50 to 60 nm, manufactured by JGC Catalyst and Chemicals), 100 parts by weight of solid silica nanoparticles (diameter: about 15 nm), 16 parts by weight of a fluorine-based compound (RS-90, DIC), and 8 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3.5 wt % to prepare a photocurable coating composition.

(12) The photocurable coating composition was coated onto the hard coating film of Preparation Example 1 at a thickness of about 110 to 120 nm with a #4 Mayer bar, dried and cured at 60° C. for one minute to prepare an anti-reflective film.

(13) At the time of curing, ultraviolet light at 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

Example 3

(14) Based on 100 parts by weight of a mixed binder of pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) (weight ratio of PETA:DPHA was 7:3), 350 parts by weight of hollow silica nanoparticles (diameter range: about 50 to 60 nm, manufactured by JGC Catalyst and Chemicals), 100 parts by weight of solid silica nanoparticles (diameter: about 13 nm), 30 parts by weight of a fluorine-based compound (F477, DIC), and 37 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3.0 wt % to prepare a photocurable coating composition.

(15) The photocurable coating composition was coated onto the hard coating film of Preparation Example 2 at a thickness of about 110 to 120 nm with a #4 Mayer bar, dried and cured at 60° C. for one minute to prepare an anti-reflective film.

(16) At the time of curing, ultraviolet light at 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

Example 4

(17) Based on 100 parts by weight of a mixed binder of pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) (weight ratio of PETA:DPHA was 6:4), 400 parts by weight of hollow silica nanoparticles (diameter: about 50 to 60 nm, manufactured by JGC Catalyst and Chemicals), 120.1 parts by weight of solid silica nanoparticles (diameter: about 14 nm), 41 parts by weight of a fluorine-based compound (RS-537, DIC), and 22.2 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3.3 wt % to prepare a photocurable coating composition.

(18) The photocurable coating composition was coated onto the hard coating film of Preparation Example 3 at a thickness of about 110 to 120 nm with a #4 Mayer bar, dried and cured at 60° C. for one minute to prepare an anti-reflective film.

(19) At the time of curing, ultraviolet light at 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

Example 5

(20) Based on 100 parts by weight of a mixed binder of pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) (weight ratio of PETA:DPHA was 7:3), 323.5 parts by weight of hollow silica nanoparticles (diameter: about 60 to 70 nm, manufactured by JGC Catalyst and Chemicals), 125 parts by weight of solid zirconia nanoparticles (diameter: about 15 nm), 29.4 parts by weight of a fluorine-based compound (RS-90, DIC), and 17.6 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3.2 wt % to prepare a photocurable coating composition.

(21) The photocurable coating composition was coated onto the hard coating film of Preparation Example 3 at a thickness of about 110 to 120 nm with a #4 Mayer bar, dried and cured at 60° C. for one minute to prepare an anti-reflective film.

(22) At the time of curing, ultraviolet light at 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

Example 6

(23) Based on 100 parts by weight of trimethylol triacrylate (TMPTA), 45 parts by weight of first hollow silica nanoparticles (DLS measured diameter: 58.2 nm), 78 parts by weight of second hollow silica nanoparticles (DLS measured diameter: 66.7 nm), 71 parts by weight of solid silica nanoparticles (diameter: about 15 nm), 23 parts by weight of a fluorine-based compound (RS-90, DIC), and 25 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3.1 wt % to prepare a photocurable coating composition.

(24) The photocurable coating composition was coated onto the hard coating film of Preparation Example 1 at a thickness of about 110 to 120 nm with a #4 Mayer bar, dried and cured at 60° C. for one minute to prepare an anti-reflective film. At the time of curing, ultraviolet light at 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

Example 7

(25) Based on 100 parts by weight of a mixed binder of pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) (weight ratio of PETA:DPHA was 8:2), 55 parts by weight of first hollow silica nanoparticles (DLS measured diameter: 58.2 nm), 90 parts by weight of second hollow silica nanoparticles (DLS measured diameter: 66.7 nm), 71 parts by weight of solid silica nanoparticles (diameter: about 15 nm), 25 parts by weight of a fluorine-based compound (RS-90, DIC), and 15 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3.1 wt % to prepare a photocurable coating composition.

(26) The photocurable coating composition was coated onto the hard coating film of Preparation Example 3 at a thickness of about 110 to 120 nm with a #4 Mayer bar, dried and cured at 60° C. for one minute to prepare an anti-reflective film.

(27) At the time of curing, ultraviolet light at 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

COMPARATIVE EXAMPLES 1 to 6

Preparation of Anti-Reflective Film

Comparative Example 1

(28) An anti-reflective film was prepared in the same manner as in Example 1, except that only pentaerythritol triacrylate (PETA) was used without using a mixed binder.

Comparative Example 2

(29) An anti-reflective film was prepared in the same manner as in Example 2, except that pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) were mixed in a mixing ratio of 5:5.

Comparative Example 3

(30) An anti-reflective film was prepared in the same manner as in Example 3, except that pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) were mixed in a mixing ratio of 4:6.

Comparative Example 4

(31) An anti-reflective film was prepared in the same manner as in Example 4, except that pentaerythritol triacrylate (PETA) and dipentaerythritol hexaacrylate (DPHA) were mixed in a mixing ratio of 2:8.

Comparative Example 5

(32) An anti-reflective film was prepared in the same manner as in Example 5, except that only dipentaerythritol hexaacrylate (DPHA) was used without using a mixed binder.

Comparative Example 6

(33) An anti-reflective film was prepared in the same manner as in Example 6, except that only 123 parts by weight of hollow silica nanoparticles (DLS measured diameter: 58.2 nm) were used instead of 45 parts by weight of first hollow silica nanoparticles (DLS measured diameter: 58.2 nm) and 78 parts by weight of second hollow silica nanoparticles (DLS measured diameter: 66.7 nm).

Evaluation

1. Measurement of Reflectance Rise Before and After Rubbing Test

(34) By applying a load of 500 g to a grade #0000 steel wool and reciprocating ten times at a speed of 33 rpm, the surface in which a hard coating layer and a low refractive index layer of the anti-reflective films obtained in the examples and comparative examples were not formed was subjected to a darkening process so as to prevent transmission of light, and a rubbing test for rubbing the surface of the low refractive index layer was conducted. Thereafter, the average reflectance of the low refractive index layer of the anti-reflective film before and after the rubbing test was measured.

(35) Specifically, before performing the rubbing test, the surface not formed of the hard coating layer and the low refractive index layer was subjected to a darkening process so as to prevent transmission of light, and then the reflectance mode of SolidSpec 3700 (UV-VIS spectrophotometer, SHIMADZU) was used to measure the average reflectance in a wavelength range of 380 nm to 780 nm. The results are shown as “R.sub.0” in Table 1 below.

(36) Then, after performing the rubbing test, the average reflectance was measured in the same manner as in the measurement method of R.sub.0 with respect to the low refractive index layer, and the results are shown as “R.sub.1” in Table 1 below.

(37) In addition, the difference between R.sub.0 and R.sub.1 was calculated and the degree of change of the reflectance before and after the rubbing test is shown as “ΔR” in Table 1 below.

2. Measurement of Color Coordinate Value (b*)

(38) By applying a load of 500 g to a grade #0000 steel wool and reciprocating ten times at a speed of 33 rpm, the surface in which a hard coating layer and a low refractive index layer of the anti-reflective films obtained in the examples and comparative examples were not formed was subjected to a darkening process so as to prevent transmission of light, and a rubbing test for rubbing the surface of the low refractive index layer was conducted. Before and after the rubbing test, the reflectance mode of SolidSpec 3700 (UV-VIS spectrophotometer, SHIMADZU) was used to measure the average reflectance. Then, the color coordinate value (b*) of the low refractive index layer was measured by using a UV-2401 PC color analysis program.

(39) Specifically, before the rubbing test, the color coordinate values of the low refractive index layer were measured, and the results are shown as “b*.sub.0” in Table 1 below. Thereafter, after performing the rubbing test, the color coordinate values were measured in the same manner as in the measurement of b*.sub.0 for the low refractive index layer, and the results are shown as “b*.sub.1” in Table 1 below. In addition, the difference between b*.sub.0 and b*.sub.1 was calculated, and the degree of change of the color coordinate values before and after the rubbing test is shown as “Δb*” in Table 1 below.

3. Measurement of Scratch Resistance

(40) The surfaces of the low refractive index layers obtained in the examples and comparative examples were rubbed while applying a load to a grade #0000 steel wool and reciprocating ten times at a speed of 27 rpm.

(41) Then, a maximum load at which one or less scratches (1 cm or less) was generated as observed by the naked eye was measured, and the results are shown in Table 1 below.

4. Measurement of Anti-Fouling Property

(42) An anti-fouling property was measured by drawing a straight line having a length of 5 cm on surfaces of the anti-reflective films obtained in the examples and comparative examples using a black pen and confirming the number of scrubbing actions required for erasing the straight line at the time of scrubbing the anti-reflective film with a wiper. The results are shown in Table 1 below.

(43) <Measurement Standard>

(44) ◯: The number of rubbing actions required for erasing the straight line was 10 or less.

(45) Δ: The number of rubbing actions required for erasing the straight line was 11 to 20.

(46) X: The number of rubbing actions required for erasing the straight line was more than 20.

(47) TABLE-US-00001 TABLE 1 Scratch Anti- ΔR resistance fouling R.sub.0(%) R.sub.1(%) (% p) b*.sub.0 b*.sub.1 Δb* (g) Property Example 1 1.54 1.6 0.06 −1.3 −1.1 0.2 300 ∘ Example 2 1.6 1.61 0.01 −2.1 −1.9 0.2 800 ∘ Example 3 0.9 0.92 0.02 −3.2 −3.1 0.1 600 ∘ Example 4 0.31 0.33 0.02 −3.7 −3.9 0.2 300 ∘ Example 5 0.15 0.17 0.02 −4.5 −4.8 0.3 200 ∘ Example 6 1.45 1.47 0.02 −3.1 −3.3 0.2 500 ∘ Example 7 1.5 1.55 0.05 −3.2 −3.4 0.2 500 ∘ Comparative 1.53 1.76 0.23 −1.4 −0.1 1.3 300 ∘ Example 1 Comparative 1.59 1.8 0.21 −2.0 −0.5 1.5 800 ∘ Example 2 Comparative 0.88 1.13 0.25 −3.3 −1.5 1.8 600 ∘ Example3 Comparative 0.3 0.6 0.3 −4.1 −1.1 3.0 300 ∘ Example 4 Comparative 0.17 0.5 0.33 −5.2 −2.1 3.1 200 ∘ Example5 Comparative 1.44 1.66 0.22 −2.9 −1.1 1.8 500 ∘ Example 6

(48) As shown in Table 1, it was confirmed that in Examples 1 to 7, the degree of change of the average reflectance (ΔR) before and after the rubbing test was 0.02% p or less, and the degree of change in color (Δb*) before and after the rubbing test was 0.3 or less, and therefore, the increase in reflectance and the change in color were effectively suppressed at the portion that was damaged/deformed due to the rubbing test compared to Comparative Examples 1 to 6, thereby being excellent in visibility.