Anti-reflective film

Abstract

Disclosed herein is an anti-reflective film including: a hard coating layer; and a low-refractive layer containing a binder resin, and hollow inorganic nanoparticles and solid inorganic nanoparticles which are dispersed in the binder resin, wherein the low-refractive layer includes a first layer containing at least 70 vol % of the entire solid inorganic nanoparticles and a second layer containing at least 70 vol % of the entire hollow inorganic nanoparticles, and at the time of fitting polarization ellipticity measured by ellipsometry for the first layer or/and the second layer included in the low-refractive layer using a Cauchy model represented by the following General Equation 1, the second layer satisfies a predetermined condition.

Claims

1. An anti-reflective film comprising: a hard coating layer; and a low-refractive index layer, wherein the low-refractive index layer contains hollow inorganic nanoparticles and solid inorganic nanoparticles that are dispersed in a binder resin, wherein the low-refractive index layer includes a first layer having a refractive index of 1.420 or more and a second layer having a refractive index of 1.400 or less when measured at a wavelength of 550 nm, and wherein the first layer contains at least 70 vol% of the total volume of the solid inorganic nanoparticles located within 50% of the total thickness of the low-refractive index layer from the interface between the hard coating layer and the low-refractive index layer.

2. The anti-reflective film according to claim 1, wherein the second layer contains at least 70 vol% of the total volume of hollow inorganic nanoparticles.

3. The anti-reflective film according to claim 1, wherein the first layer is positioned closer to an interface between the hard coating layer and the low-refractive layer than the second layer.

4. The anti-reflective film according to claim 1, wherein the second layer has polarization ellipticity measured by ellipsometry using a Cauchy model represented by the following General Equation 1 in which A is 1.0 to 1.50, B is 0 to 0.007, and C is 0 to 1*10.sup.-3: $\begin{array}{cc}n\left(\lambda \right)=A+\frac{B}{{\lambda }^2}+\frac{C}{{\lambda }^4}& \left[\mathrm{General}\mathrm{Equation}1\right]\end{array}$ in General Equation 1, n(λ) is a refractive index at a wavelength of λ, λ is in a range of 300 nm to 1800 nm, and A, B, and C are Cauchy parameters.

5. The anti-reflective film according to claim 1, wherein the first layer has polarization ellipticity measured by ellipsometry using a Cauchy model represented by the following General Equation 1, in which A is 1.0 to 1.65: $\begin{array}{cc}n\left(\lambda \right)=A+\frac{B}{{\lambda }^2}+\frac{C}{{\lambda }^4}& \left[\mathrm{General}\mathrm{Equation}1\right]\end{array}$ wherein, in General Equation 1, n(λ) is a refractive index at a wavelength of λ, λ is in a range of 300 nm to 1800 nm, and A, B, and C are Cauchy parameters.

6. The anti-reflective film according to claim 1, wherein the solid inorganic nanoparticles have a density that is at least 0.50 g/cm.sup.3 higher than that of the hollow inorganic nanoparticles.

7. The anti-reflective film according to claim 1, wherein the binder resin contained in the low-refractive layer contains a cross-linked (co)polymer formed from cross-linking a (co)polymer of a photopolymerizable compound and a fluorine-containing compound including a photoreactive functional group.

8. The anti-reflective film according to claim 7, wherein the low-refractive layer contains 10 to 400 parts by weight of the hollow inorganic nanoparticles and 10 to 400 parts by weight of the solid inorganic nanoparticles, based on 100 parts by weight of the (co)polymer of the photopolymerizable compound.

9. The anti-reflective film according to claim 7, wherein the fluorine-containing compound including the photoreactive functional group has a weight average molecular weight of 2000 to 200,000.

10. The anti-reflective film according to claim 7, wherein the binder resin contains 20 to 300 parts by weight of the fluorine-containing compound including the photoreactive functional group based on 100 parts by weight of the (co)polymer of the photopolymerizable compound.

11. The anti-reflective film according to claim 1, wherein the hard coating layer contains a binder resin containing a photocurable resin, and organic or inorganic fine particles dispersed in the binder resin.

12. The anti-reflective film according to claim 11, wherein the organic fine particles have a particle diameter of 1 to 10 μm, and the inorganic fine particles have a particle diameter of 1 nm to 500 nm.

13. The anti-reflective film according to claim 1, wherein the first layer included in the low refraction layer has a refractive index in a range of 1.420 to 1.600 when measured at a wavelength of 550 nm, and the second layer included in the low refractive layer has a refractive index in a range of 1.200 to 1.410 when measured at a wavelength of 550 nm.

14. The anti-reflective film according to claim 1, wherein the hollow inorganic particles are in a higher amount by weight than the solid inorganic particles.

15. The anti-reflective film according to claim 1, wherein each of the solid inorganic nanoparticles and the hollow inorganic nanoparticles contains one or more reactive functional groups selected from the group consisting of a (meth)acrylate group, an epoxide group, a vinyl group, and a thiol group on a surface thereof.

16. The anti-reflective film according to claim 1, wherein the hard coating layer contains a binder resin made of a photocurable resin, and an antistatic agent dispersed in the binder resin.

17. The anti-reflective film of claim 1, having a reflectance of 1.5% or less at a wavelength of 380 nm to 780 nm.

18. The anti-reflective film of claim 1, having a reflectance of 0.70% or less at a wavelength of 380 nm to 780 nm.

19. The anti-reflective film of claim 1, wherein the solid inorganic nanoparticles has a diameter of 5 to 100 nm, and the hollow inorganic nanoparticles has a diameter of 1 to 200 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a transmission electron microscope (TEM) photograph of a cross-section of an anti-reflective film in Example 1.

(2) FIG. 2 is a TEM photograph of a cross-section of an anti-reflective film in Example 2.

(3) FIG. 3 is a TEM photograph of a cross-section of an anti-reflective film in Example 3.

(4) FIG. 4 is a TEM photograph of a cross-section of an anti-reflective film in Example 4.

(5) FIG. 5 is a TEM photograph of a cross-section of an anti-reflective film in Example 5.

(6) FIG. 6 is a TEM photograph of a cross-section of an anti-reflective film in Example 6.

(7) FIG. 7 is a TEM photograph of a cross-section of an anti-reflective film in Comparative Example 1.

(8) FIG. 8 is a TEM photograph of a cross-section of an anti-reflective film in Comparative Example 2.

DETAILED DESCRIPTION

(9) The present invention will be described in more detail through the following examples. However, the following examples are only to exemplify the present invention, and contents of the present invention are not limited by the following examples.

PREPARATION EXAMPLE

Preparation Example: Manufacturing of Hard Coating Film

(10) A salt-type antistatic hard coating solution (KYOEISHA Chemical Co., Ltd., solid content: 50 wt %, product name: LJD-1000) was coated on a triacetyl cellulose film using a #10 Mayer bar, dried at 90° C. for 1 minute, and irradiated with UV light (150 mJ/cm.sup.2), thereby manufacturing a hard coating film having a thickness of about 5 μm.

Examples 1 to 5: Manufacturing of Anti-Reflective Film

Examples 1 to 4

(11) (1) Preparation of Photocurable Coating Composition for Forming Low-Refractive Layer

(12) Based on 100 parts by weight of pentaerythritol triacrylate (PETA), 281 parts by weight of hollow silica nanoparticles (diameter: about 50 to 60 nm, density: 1.96 g/cm.sup.3, JGC Catalyst and Chemicals), 63 parts by weight of solid silica nanoparticles (diameter: about 12 nm, density: 2.65 g/cm.sup.3), 131 parts by weight of a first fluorine-containing compound (X-71-1203M, Shin-Etsu), 19 parts by weight of a second fluorine-containing compound (RS-537, DIC), and 31 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in a solvent in which methyl isobutyl ketone (MIBK), diacetone alcohol (DAA), and isopropyl alcohol were mixed at a weight ratio of 3:3:4 so that a solid content was 3 wt %.

(13) (2) Manufacturing of Low-Refractive Layer and Anti-Reflective Film

(14) The photocurable coating composition obtained above was coated on the hard coating film in the preparation example using a #4 Mayer bar so as to have a thickness of about 120 nm, and dried and cured at a temperature illustrated in the following Table 1 for a time illustrated in the following Table 1. At the time of curing, the dried coating resultant was irradiated with UV light (252 mJ/cm.sup.2) under nitrogen purging.

Example 5

(15) (1) Preparation of Photocurable Coating Composition for Forming Low-Refractive Layer

(16) Based on 100 parts by weight of trimethylolpropane triacrylate (TMPTA), 268 parts by weight of hollow silica nanoparticles (diameter: about 50 to 60 nm, density: 1.96 g/cm.sup.3, JGC Catalyst and Chemicals), 55 parts by weight of solid silica nanoparticles (diameter: about 12 nm, density: 2.65 g/cm.sup.3), 144 parts by weight of a first fluorine-containing compound (X-71-1203M, Shin-Etsu), 21 parts by weight of a second fluorine-containing compound (RS-537, DIC), and 31 parts by weight of an initiator (Irgacure 127, Ciba) were diluted in a methyl isobutyl ketone (MIBK) solvent so that a solid content was 3 wt %.

(17) (2) Manufacturing of Low-Refractive Layer and Anti-Reflective Film

(18) The photocurable coating composition obtained above was coated on the hard coating film in the preparation example using a #4 Mayer bar so as to have a thickness of about 110 to 120 nm, and dried and cured at a temperature illustrated in the following Table 1 for a time illustrated in the following Table 1. At the time of curing, the dried coating resultant was irradiated with UV light (252 mJ/cm.sup.2) under nitrogen purging.

(19) TABLE-US-00001 TABLE 1 Drying Drying Temperature Time Example 1 40° C. 1 min Example 2 60° C. 1 min Example 3 80° C. 1 min Example 4 60° C. 2 min Example 5 60° C. 3 min

Example 6

(20) (1) Preparation of Hard Coating Later (HD2)

(21) 30 g of pentaerythritol triacrylate, 2.5 g of a high molecular weight copolymer (BEAMSET 371, Arakawa Co. Ltd., Epoxy Acrylate, molecular weight 40,000), 20 g of methylethylketone, and 0.5 g of a leveling agent (Tego wet 270) were uniformly mixed, and then 2 g of an acryl-styrene copolymer (volume average particle diameter: 2 μm, Manufacturing Company: Sekisui Plastic) with a refractive index of 1.525 was added as fine particles to prepare a hard coating composition.

(22) The above-obtained hard coating composition was coated on a triacetyl cellulose film with a #10 Mayer bar and dried at 90° C. for 1 minute. The dried coating was irradiated by UV at 150 mJ/cm.sup.2 to prepare a hard coating layer with a thickness of 5 μm.

(23) (2) Preparation of a Low Refractive Layer and an Anti-Reflective Film

(24) Based on 100 parts by weight of pentaerythritol triacrylate (PETA), 135 parts by weight of hollow silica nanoparticles (diameter: about 50 to 60 nm, density: 1.96 g/cm.sup.3, manufactured by JSC Catalysts and Chemicals Ltd.), 88 parts by weight of solid silica nanoparticles (diameter: about 12 nm, density: 2.65 g/cm.sup.3), 38 parts by weight of a first fluorine-containing compound (X-71-1203M, ShinEtsu Chemical Co., Ltd.), 11 parts by weight of a second fluorine-containing compound (RS-537,DIC Corporation), and 7 parts by weight of an initiator (Irgacure 127, Ciba Corporation) were diluted in a mixed solvent of MIBK (methyl isobutyl ketone):diacetone alcohol (DAA):isopropyl alcohol at a weight ratio of 3:3:4 such that the solid concentration became 3 wt %, thus preparing a photocurable coating composition for forming a low refractive layer.

(25) On the above-prepared hard coating film (HD2), the above obtained photocurable coating composition for forming a low refractive layer was coated to a thickness of about 110 to 120 nm with a #4 Mayer bar, and dried and cured at a temperature of 60° C. for 1 minute. During the curing, UV at 252 mJ/cm.sup.2 was irradiated to the dried coating under nitrogen purging.

Comparative Example: Manufacturing of Anti-Reflective Film

Comparative Example 1

(26) An anti-reflective film was manufactured by the same method as in Example 1, except for applying the photocurable coating composition for forming a low-refractive layer and drying the applied photocurable coating composition at room temperature (25° C.).

Comparative Example 2

(27) A photocurable coating composition for forming a low-refractive layer was prepared by the same method as in Example 1, except for replacing 63 parts by weight of the solid silica nanoparticles used in Example 1 with 63 parts by weight of pentaerythritol triacrylate (PETA), and an anti-reflective film was manufactured by the same method as in Example 1.

Experimental Example: Measurement of Physical Properties of Anti-Reflective Film

(28) Experiments composed of the following categories were performed on the anti-reflective films obtained in the examples and comparative examples.

(29) 1. Measurement of Average Reflectance of Anti-Reflective Film

(30) Average reflectances of the anti-reflective films obtained in the examples and comparative examples in a visible light region (380 to 780 nm) were measured using Solidspec 3700 (SHIMADZU).

(31) 2. Measurement of Anti-Pollution Property

(32) An anti-pollution 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 name pen and confirming the number of scrubbing actions required for erasing the straight line at the time of scrubbing the antireflective film with a wiper.

(33) <Measurement Standard>

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

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

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

(37) 3. Measurement of Scratch Resistance

(38) Steel wool was rubbed on surfaces of the anti-reflective films obtained in the examples and comparative examples under load while reciprocating the anti-reflective film at a rate of 27 rpm 10 times. A maximum load at which the number of scratches (1 cm or less) observed by the naked eye was 1 or less was measured.

(39) 4. Confirmation of Phase-Separation

(40) When 70 vol % of the entire used solid inorganic nanoparticles (solid silica nanoparticles) was present within a distance of 30 nm from the hard coating layer in cross-sections of the anti-reflective films in FIGS. 1 to 6, it was determined that phase separation occurred.

(41) 5. Ellipsometry Measurement

(42) Polarization ellipticities of the low-refractive layers obtained in the examples and comparative examples, respectively, were measured using ellipsometry.

(43) In detail, linear polarization of each of the low-refractive layers obtained in the examples and comparative examples was measured in a wavelength range of 380 nm to 1000 nm at an incident angle of 70° using an ellipsometer (J. A. Woollam Co. M-2000). The measured linear polarization data (ellipsometry data (ψ, Δ)) were fitted for the first and second layers (Layer 1 and Layer 2) of the low-refractive layer using Complete EASE software and a Cauchy model represented by the following General Equation 1 so that MSE was 3 or less.

(44) $\begin{array}{cc}n\left(\lambda \right)=A+\frac{B}{{\lambda }^2}+\frac{C}{{\lambda }^4}& \left[\mathrm{General}\mathrm{Equation}1\right]\end{array}$

(45) In General Equation 1, n(λ) is a refractive index at a wavelength of λ, λ is in a range of 300 nm to 1800 nm, and A, B, and C are Cauchy parameters.

(46) 6. Measurement of Refractive Index

(47) The refractive index at 550 nm was calculated using elliptically polarized light and a Cauchy model measured at a wavelength of 380 nm to 1000 nm for each of the first layer and the second layer included in the low refractive index layer obtained in the above examples.

(48) TABLE-US-00002 TABLE 2 Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 1 Example 2 Average 0.63 0.62 0.67 0.64 0.65 0.67 0.78 0.66 Reflectance (%) Scratch 500 500 500 500 500 500 150 50 Resistance(g) Anti-pollution 0 0 0 0 0 0 X X property Phase Separation 0 0 0 0 0 0 X X Ellipsometry measurment Layer 1 A 1.502 1.505 1.498 1.491 1.511 1.505 1.25 1.206 B 0.00351 0.00464 0.00311 0.00573 0.001924 0.00316 0.00192 0.07931 C 4.1280*10.sup.−4 3.4882*10.sup.−4 4.1352*10.sup.−4 3.9821*10.sup.−4 2.6729*10.sup.−4 0 0.003 −0.004 Layer 2 A 1.35 1.349 1.321 1.346 1.211 1.375 1.33 1.32 B 0.00513 0.00304 0.00312 0 0.00253 0.00178 0.00786 0.00040374 C 2.5364*10.sup.−4 0 4.1280*10.sup.−4 4.8685*10.sup.−4 1.6421*10.sup.−4 1.2131*10.sup.−5 0.000953 0.000782

(49) TABLE-US-00003 TABLE 3 Refractive Exam- Exam- Exam- Exam- Exam- Exam- index ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 Layer 1 1.502 1.505 1.498 1.491 1.511 1.505 Layer 2 1.35 1.349 1.321 1.346 1.211 1.375

(50) As illustrated in FIGS. 1 to 6, it was confirmed that in the low-refractive layers of the anti-reflective films in Examples 1 to 6, phase separation between the hollow inorganic nanoparticles and the solid inorganic nanoparticles occurred.

(51) More specifically, as can be seen from the analysis results of FIGS. 1 to 6, it was confirmed that the low-refractive layer included a first layer containing at least 70 vol % of the total volume of solid inorganic nanoparticles and a second layer containing at least 70 vol % of the total volume of hollow inorganic nanoparticles, most of the solid inorganic nanoparticles were present and concentrated toward an interface between the hard coating layer and the low-refractive layer of the anti-reflective film, and most of the hollow inorganic nanoparticles were present and concentrated in a region far from the hard coating layer. Accordingly, the first layer containing at least 70% by volume of the total solid inorganic nanoparticles is located within 50% of the total thickness of the low refractive layer from the interface between the hard coating layer and low-refractive layer.

(52) In addition, at the time of fitting polarization ellipticity measured by ellipsometry for the second layer included in the low-refractive layer using the Cauchy model represented by General Equation 1, the second layer satisfied the following conditions: A was 1.0 to 1.50, B was 0 to 0.007, and C was 0 to 1*10.sup.−3. In addition, at the time of fitting polarization ellipticity measured by ellipsometry for the first layer included in the low-refractive layer using the Cauchy model represented by General Equation 1, the first layer satisfied the following conditions: A was 1.0 to 1.65, B was 0.0010 to 0.0350, and C was 0 to 1*10.sup.−3.

(53) In addition, as illustrated in Table 2, it was confirmed that the anti-reflective films in Examples may have a low reflectance of 0.70% or less in the visible light region and simultaneously implement high scratch resistance and anti-pollution property as illustrated in Table 2.

(54) In addition, as shown in Table 3, the first layer and the second layer included in the low refraction layer of the examples exhibit different refractive indexes. Specifically, it was confirmed that the first layer of the low refraction layer has a refractive index of 1.420 or more and the second layer of the low refraction layer exhibited a refractive index of 1.400 or less.

(55) On the contrary, as illustrated in FIGS. 6 and 7, it was confirmed that in the low-refractive layers of the anti-reflective films in Comparative Examples 1 and 2, the hollow inorganic nanoparticles and the solid inorganic nanoparticles were not phase-separated, but mixedly existed.

(56) Further, it was confirmed that in the anti-reflective films in Comparative Examples 1 and 2, at the time of fitting the polarization ellipticity measured by ellipsometry using the Cauchy model represented by General Equation 1, measurement results and fitting results by the Cauchy model were in a different range from those in the anti-reflective films in Examples, and the anti-reflective films had low scratch resistance and anti-pollution property while having a relatively high reflectance.