Antireflection film

Abstract

The present invention relates to an antireflection film being capable of realizing high scratch resistance and antifouling property while simultaneously having low reflectivity and high light transmittance, and further being capable of enhancing screen sharpness of a display device.

Claims

1. An antireflection film comprising: a hard coating layer or an antiglare layer; and a low refractive index layer formed on one side of the hard coating layer or the antiglare layer, wherein the low refractive index layer includes a binder resin, and hollow silica nanoparticles, metal oxide nanoparticles, and inorganic nanoparticles dispersed in the binder resin, wherein a first region containing the hollow silica nanoparticles, a second region containing the metal oxide nanoparticles, and a third region containing the inorganic nanoparticles are present in the low reflective index layer, and wherein the second region contained in the low refractive index layer has polarization ellipticity measured by an ellipsometry method using a Cauchy model represented by the following General Formula 1, in which A is 1.53 to 3.0, B is 0 to 0.1 nm.sup.2, and C is 0 to 1*10.sup.2 nm.sup.4: $\begin{array}{cc}n\left(\right)=A+\frac{B}{{}^2}+\frac{C}{{}^4}& \left[\mathrm{General}\mathrm{Formula}1\right]\end{array}$ wherein, in the above General Formula 1, n() is a refractive index at a wavelength , is in a range of 300 nm to 1800 nm, and A, B, and C are Cauchy parameters.

2. The antireflection film of claim 1, wherein, the first region contained in the low refractive index layer has the polarization ellipticity measured by the ellipsometry method using a Cauchy model represented by the following General Formula 1, in which A is 1.0 to 1.45, B is 0 to 0.1 nm.sup.2, and C is 0 to 1*10.sup.2nm.sup.4: $\begin{array}{cc}n\left(\right)=A+\frac{B}{{}^2}+\frac{C}{{}^4}& \left[\mathrm{General}\mathrm{Formula}1\right]\end{array}$ wherein, in the above General Formula 1, n() is a refractive index at a wavelength , is in a range of 300 nm to 1800 nm, and A, B, and C are Cauchy parameters.

3. The antireflection film of claim 1, wherein, the third region contained in the low refractive index layer has the polarization ellipticity measured by the ellipsometry method using a Cauchy model represented by the following General Formula 1, in which A is 1.0 to 1.8, B is 0 to 0.01 nm.sup.2, and C is 0 to 1*10.sup.2nm.sup.4: $\begin{array}{cc}n\left(\right)=A+\frac{B}{{}^2}+\frac{C}{{}^4}& \left[\mathrm{General}\mathrm{Formula}1\right]\end{array}$ wherein, in the above General Formula 1, n() is a refractive index at a wavelength , is in a range of 300 nm to 1800 nm, and A, B, and C are Cauchy parameters.

4. The antireflection film of claim 1, wherein the polarization ellipticity measured by the ellipsometry method is determined by carrying out the ellipticity measurement at an incident angle of 70 over a wavelength range of 380 nm to 1000 nm.

5. The antireflection film of claim 1, wherein the first region, the second region, and the third region satisfy the following General Formula 2: [General Formula 2]
Refractive Index (n1) of First Region<Refractive Index (n3) of Third Region<Refractive Index (n2) of Second Region wherein n1, n2, and n3 are refractive indexes obtained by carrying out the ellipsometry measurement at an incident angle of 70 over a wavelength range of 380 nm to 1000 nm.

6. The antireflection film of claim 1, wherein the first region includes 70% by volume or more of the entire hollow silica nanoparticles, the second region includes 70% by volume or more of the entire metal oxide nanoparticles, and the third region includes 70% by volume or more of the entire inorganic nanoparticles.

7. The antireflection film of claim 1, wherein in the low refractive index layer, the third region is located closer to an interface between the hard coating layer or the antiglare layer and the low refractive index layer, compared to the second region, and the second region is located closer to an interface between the hard coating layer or the antiglare layer and the low refractive layer, compared to the first region.

8. The antireflection film of claim 1, wherein the first region, the second region, and the third region in the low refractive index layer are present in a continuous phase by one binder resin.

9. The antireflection film of claim 1, wherein the low refractive index layer is obtained by coating with a resin composition comprising a binder resin, a hollow silica nanoparticle, a metal oxide nanoparticle, and an inorganic nanoparticle.

10. The antireflection film of claim 1, wherein the average diameter of the hollow silica nanoparticle, the metal oxide nanoparticle, and the inorganic nanoparticle satisfies the following General Formula 3: [General Formula 3]
Average Diameter of Inorganic Nanoparticles<Average Diameter of Metal Oxide Nanoparticles<Average Diameter of Hollow Silica Nanoparticles.

11. The antireflection film of claim 1, wherein the ratio of the average diameter of the inorganic nanoparticles to the average diameter of the metal oxide nanoparticles is 0.5 to 0.9.

12. The antireflection film of claim 1, wherein the ratio of the average diameter of the inorganic nanoparticles to the average diameter of the hollow silica nanoparticles is 0.01 to 0.5.

13. The antireflection film of claim 1, wherein the refractive index of the first region is less than 1.4, the refractive index of the second region is more than 1.55, and the refractive index of the third region is more than 1.4 and less than 1.55.

14. The antireflection film of claim 1, wherein the thicknesses of the first region, the second region, and the third region are respectively 10 nm to 200 nm.

15. The antireflection film of claim 1, wherein the antireflection film exhibits average reflectivity of 0.3% or less in the visible light wavelength band of 380 nm to 780 nm.

16. The antireflection film of claim 1, wherein the binder resin contained in the low refractive index layer includes a (co)polymer of a photopolymerizable compound and a fluorine-containing compounds containing a photoreactive functional group, and the fluorine-containing compound containing the photoreactive functional group has a weight average molecular weight of 2000 to 200,000.

17. The antireflection film of claim 16, wherein the binder resin includes 20 parts by weight to 300 parts by weight of the fluorine-containing compound containing the photoreactive functional group based on 100 parts by weight of the (co)polymer of a photopolymerizable compound.

18. The antireflection film of claim 16, wherein the fluorine-containing compound containing the photoreactive functional group includes at least one reactive functional group selected from the group consisting of: i) an aliphatic compound or an aliphatic cyclic compound in which at least one photoreactive functional group is substituted and at least one fluorine is substituted for at least one carbon; ii) a heteroaliphatic compound or heteroaliphatic cyclic compound in which at least one photoreactive functional group is substituted, at least one hydrogen is substituted with fluorine, and at least one carbon is substituted with silicon; iii) a polydialkylsiloxane-based polymer in which at least one photoreactive functional group is substituted and at least one fluorine is substituted for at least one silicon; and iv) a polyether compound in which at least one photoreactive functional group is substituted and at least one hydrogen is substituted with fluorine.

19. The antireflection film of claim 1, wherein the hard coating layer or the antiglare layer includes: a binder resin including a photocurable resin; and an antistatic agent dispersed in the binder resin.

20. The antireflection film of claim 19, wherein the hard coating layer or the antiglare layer further includes at least one compound selected from the group consisting of an alkoxysilane-based oligomer and a metal alkoxide-based oligomer.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The present invention will be described by way of examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention thereto.

PREPARATION EXAMPLE

Preparation Example 1

Preparation of Hard Coating Layer

(2) A salt type of antistatic hard coating solution (manufactured by KYOEISHA Chemical, solid content: 50 wt %, product name: LJD-1000) was coated onto a triacetyl cellulose (TAC) film with a #10 Meyer bar, dried at 90 C. for 1 minute, and then irradiated with ultraviolet light of 150 mJ/cm.sup.2 to prepare a hard coating film having a thickness of about 5 to 6 m.

EXAMPLES 1 to 5

Preparation of Antireflection Film

Examples 1 to 3

(3) (1) Preparation of a Photocurable Coating Composition for Preparing a Low Refractive Index Layer

(4) 40 wt % of hollow silica nanoparticles (average particle diameter: about 50 to 60 nm), 18 wt % of TiO.sub.2 nanoparticles (average particle diameter: about 17 nm, average length: about 30 nm), 12 wt % of solid-type silica nanoparticles (average particle diameter: about 12 nm), 3 wt % of a first fluorine-containing compound (X-71-1203M, Shin-Etsu Chemical), 7 wt % of a second fluorine-containing compound (RS-537, DIC Corporation), 15 wt % of pentaerythritol triacrylate (PETA), and 5 wt % of an initiator (Irgacure 127, Ciba) were diluted in an MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 4 wt %.

(5) (2) Preparation of Low Refractive Index Layer and Antireflection Film

(6) The photocurable coating composition obtained as described above was coated on the hard coating film of the above preparation example to a thickness of about 180 nm to 200 nm with a #4 Meyer bar, and dried and cured at the pressure, temperature, and time shown in Table 1 below, respectively. At the time of curing, ultraviolet light of 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

Examples 4 and 5

(7) (1) Preparation of a Photocurable Coating Composition for Preparing a Low Refractive Index Layer

(8) 40 wt % of hollow silica nanoparticles (average particle diameter: about 60 to 70 nm), 15 wt % of TiO.sub.2 nanoparticles (average particle diameter: about 17 nm, average length: about 30 nm), 10 wt % of solid-type silica nanoparticles (average particle diameter: about 12 nm), 3 wt % of a first fluorine-containing compound (X-71-1203M, Shin-Etsu Chemical), 7 wt % of a second fluorine-containing compound (RS-537, DIC Corporation), 20 wt % of pentaerythritol triacrylate (PETA), and 5 wt % of an initiator (Irgacure 127, Ciba) were diluted in an MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 4 wt %.

(9) (2) Preparation of Low Refractive Index Layer and Antireflection Film

(10) The photocurable coating composition obtained as described above was coated onto the hard coating film of the above preparation example to a thickness of about 180 nm to 200 nm with a #4 Meyer bar, and dried and cured at the pressure, temperature, and time shown in Table 1, respectively. At the time of curing, ultraviolet light of 252 mJ/cm.sup.2 was irradiated to the dried coating under a nitrogen purge.

(11) TABLE-US-00001 TABLE 1 Preparation conditions of antireflection film of Examples Category Drying temperature ( C.) Drying time Example 1 60 1 min Example 2 90 1 min Example 3 60 2 min Example 4 60 1 min Example 5 90 1 min

COMPARATIVE EXAMPLES 1 TO 3

Preparation of Antireflection Film

Comparative Example 1

(12) The antireflection film was prepared in the same manner as in Example 1, except that a composition in which 65 wt % of hollow silica nanoparticles (average diameter: about 60 to 70 nm), 5 wt % of a first fluorine-containing compound (X-71-1203M, Shin-Etsu Chemical), 5 wt % of a second fluorine-containing compound (RS-537, DIC Corporation), 20 wt % of pentaerythritol triacrylate (PETA), and 5 wt % of an initiator (Irgacure 127, Ciba) were diluted in an MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3 wt %, was used as a photocurable coating composition for preparing a low refractive index layer.

Comparative Example 2

(13) The antireflection film was prepared in the same manner as in Example 1, except that a composition in which 55 wt % of hollow silica nanoparticles (average diameter: about 50 to 60 nm), 10 wt % of solid-type silica nanoparticles (average particle diameter: about 12 nm), 3 wt % of a first fluorine-containing compound (X-71-1203M, Shin-Etsu Chemical), 10 wt % of a second fluorine-containing compound (RS-537, DIC Corporation), 17 wt % of pentaerythritol triacrylate (PETA), and 5 wt % of an initiator (Irgacure 127, Ciba) were diluted in an MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3 wt %, was used as a photocurable coating composition for preparing a low refractive index layer.

Comparative Example 3

(14) The antireflection film was prepared in the same manner as in Example 2, except that a composition in which 50 wt % of hollow silica nanoparticles (average diameter: about 50 to 60 nm), 10 wt % of solid-type silica nanoparticles (average particle diameter: about 12 nm), 5 wt % of a first fluorine-containing compound (X-71-1203M, Shin-Etsu Chemical), 6 wt % of a second fluorine-containing compound (RS-537, DIC Corporation), 24 wt % of pentaerythritol triacrylate (PETA), and 5 wt % of an initiator (Irgacure 127, Ciba) were diluted in an MIBK (methyl isobutyl ketone) solvent so that the solid content concentration became 3 wt %, was used as a photocurable coating composition for preparing a low refractive index layer.

EXPERIMENTAL EXAMPLES

Measurement of Physical Properties of Antireflection Films

(15) The following experiments were conducted for the antireflection films obtained in the examples and comparative examples.

(16) 1. Measurement of Average Reflectivity

(17) The average reflectivity of the antireflection films obtained in the examples and comparative examples shown in a visible light region (380 to 780 nm) was measured using a Solidspec 3700 (SHIMADZU) apparatus, and the results are shown in Table 2 below.

(18) 2. Measurement of Scratch Resistance

(19) The surfaces of the antireflection films obtained in the examples and comparative examples were rubbed while applying a load to steel wool (area of 2 cm.sup.2) and reciprocating ten times at a speed of 27 rpm. The maximum load at which one or less scratches with a size of 1 cm or less were generated, as observed with the naked eye, was measured, and the results are shown in Table 2 below.

(20) 3. Measurement of Antifouling Property

(21) Straight lines with a length of 5 cm were drawn with a red permanent marker on the surface of the antireflection films obtained in the examples and comparative examples. Then, the antifouling property was measured by confirming the number of times of erasing when rubbed with a nonwoven cloth. The results are shown in Table 2 below.

(22) <Measurement Standard>

(23) O: Erase when rubbing 10 times or less

(24) : Erase when rubbing 11 to 20 times

(25) X: Erase when rubbing 20 times or more

(26) TABLE-US-00002 TABLE 2 Results of Experiments for Examples and Comparative Examples Average Scratch Antifouling Category Reflectivity (%) Resistance (g) Property Example 1 0.28 300 Example 2 0.27 300 Example 3 0.25 300 Example 4 0.23 300 Example 5 0.25 300 Comparative 0.29 100 X Example 1 Comparative 0.66 350 Example 2 Comparative 0.61 400 Example 3

(27) As shown in Table 2, the antireflection films of Examples 1 to 5, in which three kinds of particles (hollow silica nanoparticles, TiO.sub.2 nanoparticles, and solid-type silica nanoparticles) were contained in the low refractive index layer could realize high scratch resistance and antifouling property while simultaneously exhibiting low reflectivity of 0.30% or less in the visible light range.

(28) In contrast, it was confirmed that the low refractive index layer of the antireflection film of Comparative Example 1 contained only hollow silica nanoparticles and thus exhibited lower scratch resistance as compared with the examples, and the antifouling property was also decreased.

(29) Further, it was confirmed that, in the low refractive index layers of the antireflection films of Comparative Examples 2 and 3, the hollow silica nanoparticles and the solid silica nanoparticles were included so that the scratch resistance and antifouling properties were high. However, the average reflectivity was measured to be higher than 0.6% and it was difficult to realize ultra-low reflectivity.

(30) That is, in the case of the examples, as three kinds of particles were dispersed in the low refractive index layer, it was confirmed that the ultra-low reflectivity of 0.30% or less could be achieved and at the same time and the scratch resistance and antifouling property could be maintained at an appropriate level.

(31) 4. Ellipsometry Measurement

(32) The polarization ellipticity was measured for the low refractive index layer obtained in each of the examples and comparative examples by an ellipsometry method.

(33) Specifically, the ellipticity measurement was carried out for the low refractive index layer obtained in each of the above examples and comparative examples at an incidence angle of 70 over a wavelength range of 380 nm to 1000 nm by using a J. A. Woollam Co. M-2000 apparatus. The measured ellipsometry data (, ) was fitted to a Cauchy model of the following General Formula 1 using CompleteEASE software so that MSE became 5 or less.

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

(35) In the above General Formula 1, n() is a refractive index at a wavelength , is in a range of 300 nm to 1800 nm, and A, B, and C are Cauchy parameters. The value of Cauchy parameters A, B, and C are shown in Table 3 below.

(36) TABLE-US-00003 TABLE 3 Results of Experiments for Examples and Comparative Examples Comparative Comparative Comparative Example Example Example Example Example Example Example Example Catergory 1 2 3 4 5 1 2 3 First A 1.361 1.315 1.313 1.291 1.301 1.363 1.322 1.310 region B 0.00032156 0.00677 0.00843 0.00683 0.00577 0.00267 0.00058 0.000284 C 0.00384 0.00031315 0.0001366 0.00033169 0.0001364 0.000101 0.00001511 0.004 Second A 1.601 1.671 1.541 1.587 1.615 1.366 1.352 1.361 region B 0.01323 0.04213 0.02354 0.06341 0.04541 0.00278 0.00521 0.00521 C 0.00233 0.00232 0.00135 0.005311 0.006531 0.000132 0.000643 0.008765 Third A 1.525 1.521 1.522 1.532 1.523 1.365 1.522 1.521 region B 0.03215 0.00315 0.00316 0.00734 0.00753 0.00732 0.00188 0.000621 C 0.0006543 0.00025631 0.0064521 0.00015341 0.000332 0.0000074 0.0000469 0.0000422

(37) As shown in Table 3, in the antireflection films obtained in Examples 1 to 5, it was confirmed that, when the polarization ellipticity measured by ellipsometry method for the second region contained in the low refractive index layer was fitted to a Cauchy model of the General Formula 1, it satisfied the condition that A is 1.53 to 3.0, B is 0 to 0.1 nm.sup.2, and C is 0 to 1*10.sup.2 nm.sup.4. Also, when the polarization ellipticity measured by an ellipsometry method for the first region contained in the low refractive index layer was fitted to a Cauchy model of the General Formula 1, it satisfied the condition that A is 1.0 to 1.45, B is 0 to 0.1 nm.sup.2, and C is 0 to 1*10.sup.2 nm.sup.4. Further, when the polarization ellipticity measured by ellipsometry method for the third region contained in the low refractive index layer was fitted to a Cauchy model of the General Formula 1, it satisfied the condition that A is 1.0 to 1.8, B is 0 to 0.01 nm.sup.2, and C is 0 to 1*10.sup.2 nm.sup.4.

(38) That is, in the low refraction index layers of the antireflection films of Examples 1 to 5, the values of Cauchy parameters A, B, and C were respectively analyzed by the ellipsometry method so as to be distinguished into the three regions (the first region, the second region, and the third region) not belonging to the same range. Thus, it was confirmed that three regions were formed in the low refraction index layers.

(39) On the other hand, in the antireflection films of Comparative Examples 1 to 3, when the polarization ellipticity measured by the ellipsometry method was fitted to a Cauchy model of the General Formula 1, it exhibited different regions from the antireflection films of the examples in the measurement result and the fitting result by the Cauchy model. In particular, in the case of Comparative Example 1, the values of Cauchy parameters A, B, and C were respectively analyzed by the ellipsometry method as belonging to the same range in the first region, the second region, and the third region. Thus, it appears that the regions were not distinguished by the Cauchy parameters. In the case of Comparative Examples 2 and 3, the respective values of Cauchy parameters A, B, and C were analyzed by the ellipsometry method as being the same range in the first region and the second region, and as being different ranges in the third region. Thus, it was confirmed that they were distinguished into the two regions by the Cauchy parameters.