Antireflection film and display device

Abstract

The present invention relates to an antireflection film which includes a hard coating layer and a low refractive index layer formed on the hard coating layer, wherein the sum of the volume of the convex portion of the peak equal to or higher than the average line is less than 0.03 mm.sup.3 in the surface area of 1.47 mm.sup.2, and the sum of the volume of the concave portion of the valley equal to or lower than the average line is less than 0.03 mm.sup.3 in the surface area of 1.47 mm.sup.2, and a display device comprising the antireflection film.

Claims

1. An antireflection film comprising: a hard coating layer; and a low refractive index layer formed on the hard coating layer, wherein the antireflection film has a surface concavo-convex structure having a peak with a convex portion and a valley with a concave portion, and wherein the sum of the volume of the convex portion of the peak equal to or higher than an average line is greater than 0 and less than 0.03 mm.sup.3 in a surface area of 1.47 mm.sup.2, and the sum of the volume of the concave portion of the valley equal to or higher than an average line is greater than 0 and less than 0.03 mm.sup.3 in a surface area of 1.47 mm.sup.2.

2. The antireflection film of claim 1, wherein the sum of the volume of the convex portion of the peak equal to or higher than the average line and the sum of the volume of the concave portion of the valley equal to or lower than the average line are the results measured by a non-contact surface shape measuring instrument (3D optical profiler), respectively.

3. The antireflection film of claim 1, wherein an average reflectivity of the antireflection film is less than 5% in a wavelength range of 380 nm to 780 nm.

4. The antireflection film of claim 1, wherein the internal haze of the antireflection film is greater than 0 and less than 10%.

5. The antireflection film of claim 1, wherein the external haze of the antireflection film is greater than 0 and less than 0.5%.

6. The antireflection film of claim 1, wherein the hard coating layer comprises a binder resin containing a (co)polymer of a photopolymerizable compound and an organic or inorganic fine particle dispersed in the binder resin.

7. The antireflection film of claim 6, wherein the hard coating layer comprises 0.1 to 20 parts by weight of the organic or inorganic fine particles based on 100 parts by weight of the (co)polymer of the photopolymerizable compound.

8. The antireflection film of claim 6, wherein the hard coating layer further comprises 3 to 10% by weight of inorganic nanoparticles having a diameter of 1 nm to 50 nm based on the total weight of the organic or inorganic fine particles and inorganic nanoparticles.

9. The antireflection film of claim 8, wherein the hard coating layer further comprises an inorganic nanoparticle having a diameter greater than 50 nm, and a diameter less than or equal to 120 nm.

10. The antireflection film of claim 1, wherein the low refractive index layer comprises a binder resin including a cross-linked polymer between a photopolymerizable compound; a fluorine-based compound containing a photoreactive functional group; and a polysilsesquioxane in which at least one reactive functional group is substituted, and an inorganic fine particle dispersed in the binder resin.

11. The antireflection film of claim 10, wherein the reactive functional group substituted on the polysilsesquioxane comprises at least one functional group selected from the group consisting of alcohols, amines, carboxylic acids, epoxides, imides, (meth)acrylates, nitriles, norbornenes, olefins, polyethylene glycols, thiols, and vinyl groups.

12. The antireflection film of claim 11, wherein the polysilsesquioxane in which at least one reactive functional group is substituted is further substituted with at least one unreactive functional group selected from the group consisting of a linear or branched alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 6 to 30 carbon atoms, and an aryl groups having 6 to 30 carbon atoms.

13. The antireflection film of claim 10, wherein the polysilsesquioxane in which at least one reactive functional group is substituted comprises a polyhedral oligomeric silsesquioxane having a cage structure, in which at least one reactive functional group is substituted, and wherein at least one of the silicon atoms of the polyhedral oligomeric silsesquioxane having a cage structure is substituted with a reactive functional group, and the remaining silicon atoms, in which a reactive functional group is not substituted, are substituted with an unreactive functional group.

14. The antireflection film of claim 13, wherein the molar ratio of the reactive functional group to the unreactive functional group substituted on the polysilsesquioxane is 0.20 or more.

15. The antireflection film of claim 10, wherein the photoreactive functional group included in the fluorine-based compound is at least one selected from the group consisting of (meth)acrylate group, epoxide group, vinyl group, and thiol group.

16. The antireflection film of claim 10, wherein the fluorine-based compound containing a photoreactive functional group has a fluorine content of 1% by weight to 25% by weight and includes at least one 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 on at least one carbon; ii) a heteroaliphatic compound or a 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 on 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.

17. The antireflection film of claim 10, wherein the inorganic fine particles are hollow silica particles having a number average particle diameter of 10 nm to 100 nm.

18. The antireflection film of claim 10, wherein the low refractive index layer comprises 1 to 75 parts by weight of the fluorine-based compound containing a photoreactive functional group, 0.5 to 25 parts by weight of the polysilsesquioxane in which at least one reactive functional group is substituted, and 10 to 320 parts by weight of the inorganic fine particles based on 100 parts by weight of the photopolymerizable compound.

19. The antireflection film of claim 1, wherein the hard coating layer has a thickness of greater than 5 m and less than 10 m, and the low refractive index layer has a thickness of 1 nm to 300 nm.

20. A display device comprising the antireflection film according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1a schematically shows a cross section of a general TFT display device equipped with the antireflection film of Example 1.

(2) FIG. 1b schematically shows a cross section of a COT panel display device equipped with the antireflection film of Example 1.

(3) FIG. 2 is an optical microscopic image of the surface of the antireflection film prepared in Example 1 (reflection mode, magnification: 20).

(4) FIG. 3 is an optical microscopic image of the surface of the antireflection film prepared in Comparative Example 3 (reflection mode, magnification: 10).

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) Specific embodiments of the present invention will be described in more detail by way of Examples. However, the Examples are for illustrative purposes only, and the disclosure of the specific embodiments of the invention is not intended to be limited by these Examples.

Preparation Examples: Preparation of Hard Coating Composition and Photocurable Coating Composition for Forming Low Refractive Index Layer

(6) (1) Preparation of Hard Coating Composition

(7) A hard coating composition was prepared by uniformly mixing the components of Table 1 below. The contents of all components used in Table 1 are expressed in the unit of g. Further, in Table 1, the sum of particles refers to the sum of organic fine particles and inorganic nanoparticles.

(8) TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Preparation Preparation Preparation Preparation Preparation Preparation Preparation Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3 Binder UA-306T 4.247 4.804 4.434 4.260 4.883 4.790 4.426 8BR-500 7.964 8.948 6.771 7.999 9.155 8.993 8.223 TMPTA 19.720 22.161 12.313 22.671 PETA 11.084 19.806 22.269 20.234 Initiator I184 2.036 2.537 2.337 2.045 2.302 2.299 2.278 Leveling BYK-300 0.214 0.270 0.250 0.215 0.289 0.242 0.253 agent Solvent IPA 32.547 40.058 61.564 32.689 60.438 30.250 63.233 EtOH 32.146 20.024 32.286 30.250 Organic Fine 0.375 0.999 0.739 0.538 0.175 0.605 1.266 fine particle 1 particles Inorganic Silica 1 0.536 0.310 nano Silica 2 0.214 0.200 0.200 0.161 0.087 0.302 0.087 particles Dispersion liquid Sum 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Solid content (wt %) 35.306 39.919 38.437 35.024 39.562 39.500 36.767 Sum of binders (wt %) 31.931 35.913 34.601 32.065 36.709 36.052 32.883 Content of silica 0.064 0.060 0.060 0.048 0.026 0.091 0.026 2 in dispersion liquid 0536 (g) Sum of particles 0.975 1.059 1.109 0.586 0.201 0.696 1.292 (wt %) Weight of silica 6.583 5.666 5.410 8.238 12.979 13.025 2.020 2 relative to total particle weight (wt %)

(9) 1) PETA: Pentaerythritol triacrylate (molecular weight of 298 g/mol)

(10) 2) TMPTA: Trimethylolpropane triacrylate (molecular weight of 296 g/mol)

(11) 3) 8BR-500: Urethane-based acryl oligomer, molecular weight of 250,000 g/mol, manufactured by Taisei Fine Chemical.

(12) 4) UA-306T: Urethane-based acryl oligomer, molecular weight 1,000 g/mol, manufactured by Kyoeisha.

(13) 5) I184 (Irgacure 184): Photoinitiator, manufactured by Ciba.

(14) 6) BYK-300: Leveling agent, manufactured by Tego.

(15) 7) IPA (Isopropyl alcohol)

(16) 8) EtOH (Ethyl alcohol)

(17) 9) Fine particle 1: Acryl-styrene copolymer resin, which is a spherical organic fine particle having a volume average particle diameter of 2 m and a refractive index of 1.555, Techpolymer, manufactured by Sekisui Plastic.

(18) 10) Silica 1: Silica particles having a volume average particle size of 100 nm, X24-9600A, manufactured by Shinetsu.

(19) 11) Silica 2 Dispersion liquid: Dispersion liquid of nanosilica having a volume average particle diameter of 12 nm which is dispersed in methanol at a ratio of 30 wt %, MA-ST, manufactured by Nissan Chemical.

(20) (2) Preparation of Photocurable Coating Composition for Forming Low Refractive Index Layer.

(21) The components in Table 2 were mixed and diluted to a solid content of 5 wt % in a 1:1 mixed solution (weight ratio) of methyl isobutyl ketone (MIBK) and diacetone alcohol (DAA) to prepare a photocurable coating composition for forming a low refractive index layer. The contents of all components used in Table 2 are expressed in the unit of g.

(22) TABLE-US-00002 TABLE 2 Preparation Reference Preparation Example 5 Example 1 Dipentaerythritol 39 42 pentaacrylate THRULYA 4320 220 220 RS907 26.7 0 EP0408 3 3 Irgacure-184 6 6

(23) 1) Dipentaerythritol pentaacrylate, molecular weight of 524.51 g/mol, manufactured by Kyoeisha.

(24) 2) THRULYA 4320: Hollow silica dispersion liquid, solid content of 20 wt % in MIBK solvent, manufactured by Catalysts and Chemicals Ltd.

(25) 3) RS907: Fluorine-based compound containing a photoreactive functional group, diluted to a solid content of 30% by weight in MIBK solvent, manufactured by DIC.

(26) 4) EP0408: Polysilsesquioxane, manufactured by Hybrid Plastics.

Examples and Comparative Examples: Preparation of Antireflection Film

(27) As shown in Table 3 below, the hard coating composition prepared in each of Preparation Examples above was coated onto a triacetylcellulose (TAC) film with Meyer Bar, dried at 90 C. for 1 minute, and irradiated with ultraviolet rays of 150 mJ/cm.sup.3 to prepare a hard coating layer.

(28) Thereafter, the resin composition for preparing a low refractive index layer prepared in Preparation Example above was coated onto the hard coating layer with Meyer Bar #3 and dried at 90 C. for 1 minute. The thus-dried product was irradiated with ultraviolet rays of 180 mJ/cm.sup.2 under nitrogen purging to prepare a low refractive index layer having a thickness of 110 nm and subsequently, an anti-glare/anti-reflection film was prepared.

(29) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Comparative Comparative Reference Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Thickness 60 60 60 60 60 60 60 60 60 60 of TAC film (m) Composition Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Comparative Comparative Comparative Prepa- for hard coating ration ration ration ration ration ration Prepa- Prepa- Prepa- ration layer Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 ration ration ration Example 1 Example 1 Example 2 Example 3 Thickness 7 7 7 6 4 4 7 6 6 7 of hard coating layer (m) Composition Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Reference for low ration ration ration ration ration ration ration ration ration Prepa- refractive Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 ration index layer Example 1

Experimental Example: Measurement of Physical Properties of Hard Coating Layer and Antireflection Film

(30) The physical properties of the hard coating layers prepared above and the physical properties of the antireflection films including the same were measured according to the following methods and are shown in Table 4.

(31) 1. Measurement of Internal Haze and External Haze of Antireflection Film

(32) The total haze of the antireflection film is the sum of the internal haze and the external haze. After measuring the total haze and the internal haze by the following method, the external haze may be obtained by the difference between the total haze and the internal haze. Specifically, the transmittance was measured three times according to JIS K 7361 standard, and the haze was measured three times according to JIS K 7105 standard using a haze meter (HM-150, A light source, manufactured by Murakami), and then the average value of each measurement was calculated to obtain the total haze. Further, in order to make the surface of the coating layer flat, an adhesive having a haze of 0 was applied to the surface so that external irregularities were embedded in the adhesive, and then the haze was measured three times with the haze meter, and the average value was calculated to obtain the internal haze. Thereafter, the external haze value was obtained by subtracting the internal haze value from the total haze value.

(33) 2. Measurement of the Sum of the Volume of the Convex Portion of the Peak Equal to or Higher than the Average Line and the Sum of the Volume of the Concave Portion of the Valley Equal to or Less than the Average Line of Antireflection Film

(34) The sum of the volume of the convex portion of the peak equal to or higher than the average line and the sum of the volume of the concave portion of the valley equal to or less than the average line of the surface of the hard coating layer were measure using a white light three-dimensional optical interference profile (3D optical profiler, Model: NewView 7300, manufactured by Zygo). Herein, the area of 1.401.05 mm.sup.2 was measured under the conditions of 10 magnification of a lens and 0.5 magnification of software zoom.

(35) The thus-prepared antireflection film was placed in a flat state on a sample stage, and after obtaining an optical profiler image, an analysis was conducted. Herein, the sum of the volume of the convex portion of the peak equal to or higher than the average line and the sum of the volume of the concave portion of the valley equal to or less than the average line in the surface area of 1.47 mm.sup.2 were each measured.

(36) 3. Measurement of Average Reflectivity of Antireflection Film

(37) The average reflectivity was measured using SolidSpec 3700 manufactured by SHIMADZU.

(38) Specifically, a black tape (3M) was attached to the surface of the substrate film on which no hard coating layer was formed to prevent light from being transmitted, and the measurement conditions were fixed to a sampling interval of 1 nm, time constant of 0.1 second, slit width of 20 nm with a medium scanning speed. Thereafter, a light in the wavelength region of 380 nm to 780 nm was irradiated to the antireflection film at room temperature by applying 100T mode to measure the reflectivity.

(39) 4. Measurement of Gloss of Antireflection Film

(40) The gloss at 20 and 60 angles was measured using micro-TRI-gloss manufactured by BYK Gardner.

(41) Specifically, a black tape (vinyl tape 472 black, manufactured by 3M) was attached to the surface of the substrate film on which no hard coating layer was formed to prevent light from being transmitted, and the incidence angle of light was defined as the average value of data measured at least 5 times at 20 and 60 angles.

(42) 5. Measurement of Scratch Resistance

(43) The surface of the antireflection films obtained in Examples and Comparative Examples were rubbed back and forth 10 times with a steel wool (#0000) under a load at a speed of 27 rpm. The scratch resistance was evaluated by confirming the maximum load at which a scratch of 1 cm or less observed with the naked eye was 1 or less.

(44) 6. Evaluation of Defective Irregularities of Antireflection Film

(45) In order to confirm the presence or absence of defective irregularities of the antireflection films prepared in Examples and Comparative Examples, a black tape (vinyl tape 472 black, manufactured by 3M) was attached to the surface of the antireflection film on which no hard coating layer was formed to prevent light from being transmitted, and then a reflection image was photographed using an optical microscope (BX-51, manufactured by Olympus). The photographed image was in the size of 640480 pixels, and the magnification may be selected from 10 or 20. The amount of light was adjusted within the range of 50% to 100% of the maximum amount of light emerging from the optical microscope.

(46) The presence or absence of rainbow stains which exist on the surface of the antireflection film was observed in the used images and evaluated according to the following criteria. If such a rainbow stain is present in the antireflection film, it may lead to the occurrence of a defective pixel in the subsequent process, and thus it is preferred that the rainbow stains do not exist. The optical microscopic images of the antireflection films of Example 1 and Comparative Example 3 in the evaluation results are shown in FIGS. 2 and 3, respectively.

(47) <Measurement Criteria>

(48) x: No rainbow stain exists.

(49) : 1 to 3 rainbow stains exist (at magnification of 20).

(50) : More than 3 rainbow stains exist (at magnification of 20).

(51) TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Comparative Comparative Reference Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Composition Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Comparative Comparative Comparative Prepa- for hard coating ration ration ration ration ration ration Prepa- Prepa- Prepa- ration layer Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 ration ration ration Example 1 Example 1 Example 2 Example 3 Thickness 7 7 7 6 4 4 7 6 6 7 of hard coating layer (m) Composition Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Prepa- Reference for low ration ration ration ration ration ration ration ration ration Prepa- refractive Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 Example 5 ration index layer Example 1 Total haze (%) 2.4 2.3 2.5 2.3 2.6 2.0 0.8 3.1 2.9 2.7 Internal haze (%) 2.2 2.2 2.4 2.2 2.0 1.6 0.3 2.4 2.3 2.6 External haze (%) 0.2 0.1 0.1 0.1 0.6 0.4 0.5 0.7 0.6 0.1 Gloss (20/60) 29.2/51.2 26.5/52.0 26.9/52.2 27.1/52.2 30.2/51.8 26.5/52.4 26.5/50.9 28.2/53.1 27.6/52.9 30/51.1 Average 1.28 1.27 1.28 1.28 1.27 1.28 1.28 1.26 1.27 1.52 reflectivity (%) Sum of the volume 0.022 0.021 0.021 0.023 0.039 0.047 0.039 0.042 0.041 0.019 of the convex portion (mm.sup.3) Sum of the volume 0.023 0.019 0.021 0.022 0.037 0.047 0.039 0.041 0.040 0.022 of the concave portion (mm.sup.3) Existence x x x x of rainbow stains Scratch resistance 350 350 350 350 350 350 350 350 350 150 (g)

(52) As can be seen in Table 4, it was confirmed that, even when the same composition for a hard coating layer was used, the antireflection films (Comparative Examples 1 and 2) having a thickness of the hard coating layer of 5 m or less, and the antireflection films (Comparative Examples 3 to 5), in which the content of nanosilica (inorganic nanoparticles) having a diameter of 12 nm in the composition for a hard coating layer is too large or small, did not satisfy the range of the volume parameter of the present invention.

(53) On the other hand, it can be confirmed that the antireflection film of the Examples could exhibit a low external haze, and at the same time secure improved scratch resistance, while simultaneously satisfying both the sum of the volume of the convex portion of the peak equal to or higher than the average line of less than 0.03 mm.sup.3; and the sum of the volume of the concave portion of the valley equal to or less than the average line of less than 0.03 mm.sup.3.

(54) Further, in the case of Reference Example 1 having the composition for a low refractive index layer which does not simultaneously include a fluorine-based compound containing a photoreactive functional group and polysilsesquioxane having at least one reactive functional group substituted therein, it was confirmed that it satisfied the range of the volume parameter of the present invention, but the scratch resistance was reduced compared to that in the Examples.

(55) Furthermore, with reference to FIGS. 2 and 3, the antireflection films of the Examples having such physical properties as above showed a uniform surface concavo-convex shape, and unlike the antireflection films of the Comparative Examples, there existed no rainbow stains, and thus a liquid crystal display device without defective pixels can be implemented.