Photocurable coating composition for forming low refractive layer

Abstract

The present invention relates to a photocurable coating composition for forming a low refractive layer, a method for preparing an antireflection film using the photocurable coating composition, and an anti-reflective film prepared by using the photocurable coating composition. According to the present invention, a low refractive layer is formed of a photocurable coating composition containing two or more types of photo-polymerizable compounds, a photoinitiator, surface-treated hollow inorganic nanoparticles, and surface-treated solid inorganic nanoparticles.

Claims

1. A photocurable coating composition for forming a low refractive layer, comprising two types of photopolymerizable compounds, a fluorine-containing compound including a photoreactive functional group, a photoinitiator, surface-treated hollow inorganic nanoparticles, and surface-treated solid inorganic nanoparticles, wherein at least one photopolymerizable compound of the two types of photopolymerizable compounds is 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, or 3-acryloxypropyldiethoxysilane, wherein the surface-treated hollow inorganic nanoparticles are present in an amount of 197 parts by weight based on 100 parts by weight of the two types of photopolymerizable compounds, wherein the fluorine-containing compound including a photoreactive functional group includes a silicon content of 0.1% to 20% by weight based on the fluorine-containing compound including photoreactive functional group, wherein the fluorine-containing compound including a photoreactive functional group is present in an amount of 79 parts by weight based on 100 parts by weight of the two types of photopolymerizable compounds, and wherein a weight ratio of the at least one photopolymerizable compound of the two types of photopolymerizable compounds and the other type photopolymerizable compound of the two types of photopolymerizable compound other than the at least one photopolymerizable compound of the two types of photopolymerizable compound is 1.1 to 1.0.

2. The photocurable coating composition of claim 1, wherein a density of the surface-treated hollow inorganic nanoparticles is 1.96 g/cm.sup.3, and wherein a density of the surface-treated solid inorganic nanoparticles is 2.65 g/cm.sup.3.

3. A method for preparing an antireflection film comprising the steps of: coating the photocurable coating composition of claim 1 on a hard coating layer; drying the photocurable coating composition coated on the hard coating layer to produce a dried product; and photocuring the dried product.

4. The method for preparing the antireflection film of claim 3, wherein the coating and drying of the photocurable coating composition is carried out at 35° C. to 100° C.

5. An antireflection film comprising: a hard coating layer; and a low refractive layer formed on one surface of the hard coating layer and including a photo-cured product of the photocurable coating composition of claim 1, wherein 70% by volume or more of the surface-treated solid inorganic nanoparticles relative to the total volume of the surface-treated solid nanoparticles in the low refractive layer are present within 50% of a total thickness of the low refractive layer from an interface between the hard coating layer and the low refractive layer.

6. The antireflection film of claim 5, wherein 30% by volume or more of the surface-treated hollow inorganic nanoparticles relative to the total volume of the surface-treated hollow inorganic nanoparticles in the low refractive layer are present at a greater distance relative to the interface between the hard coating layer and the low refractive layer in a thickness direction of the low refractive layer than any surface-treated solid inorganic nanoparticles in the low refractive laver.

7. The antireflection film of claim 5, wherein the low refractive layer includes a first layer and a second layer, wherein the first layer containing 70% by volume or more of the total amount of the surface-treated solid inorganic nanoparticles relative to the total volume of the surface-treated solid inorganic nanoparticles in the low refractive laver, wherein the second layer containing 70% by volume or more of the surface-treated hollow inorganic nanoparticles relative to the total volume of the surface-treated hollow inorganic nanoparticles in the low refractive layer, and wherein the first layer of the low refractive layer is located closer to the interface between the hard coating layer and the low refractive layer than the second layer of the low refractive laver.

8. The antireflection film of claim 5, wherein an average reflectance of the antireflection film is 0.7% or less in the visible light wavelength band region of 380 nm to 780 nm.

9. The antireflection film of claim 5, wherein 70% by volume or more of the surface-treated solid inorganic nanoparticles relative to the total volume of the surface-treated solid inorganic nanoparticles in the low refractive layer are present within 30% of the total thickness of the low refractive layer from the interface between the hard coating layer and the low refractive layer.

10. The antireflection film of claim 9, wherein 70% by volume or more of the surface-treated hollow inorganic nanoparticles relative to the total volume of the surface-treated hollow inorganic nanoparticles in the low refractive layer are present in a region exceeding 30% of the total thickness of the low refractive layer from the interface between the hard coating layer and the low refractive layer.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The actions and effects of the invention will be described in more detail through concrete examples of the invention below. However, these examples are given for illustrative purposes only, and these examples are not intended to limit the scope of the invention in any way.

Preparation Example 1: Preparation of Hard Coating Film

(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 film with a #10 Meyer bar, and dried at 90° C. for 1 minute. Then, an ultraviolet light of 150 mJ/cm.sup.2 was irradiated to the obtained coating film to prepare a hard coating film having a thickness of about 5 to 6 μm.

Example 1: Preparation of Antireflection Films

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

(4) 4.14 parts by weight of surface-treated hollow silica nanoparticles (diameter: about 50 to 60 nm, density: 1.96 g/cm3, organosilicon compound: 3-methacryloyloxypropylmethyldimethoxysilane, product name: THRULYA-4320, manufactured by JSC Catalysts and Chemicals), 0.38 parts by weight of surface-treated solid silica nanoparticles (diameter: about 12 nm, density: 2.65 g/cm3, organosilicon compound: 3-methacryloyloxypropylmethyldimethoxysilane), 1.67 parts by weight of a fluorine-containing compound including a photoreactive functional group (RS-537, manufactured by DIC), 0.33 parts by weight of an initiator (Irgacure 127, manufactured by Ciba), and 1.1 parts by weight of 3-methacryloxypropyl methyldimethoxysilane were added with respect to 1 part by weight of pentaerythritol triacrylate (PETA).

(5) Then, MIBK (methyl isobutyl ketone) was added to the obtained composition so that the composition had a solid content concentration of 3.2% by weight.

(6) (2) Preparation of Low Refractive Layer and Antireflection Film

(7) The photocurable coating composition obtained above was coated onto the coating layer of the hard coating film prepared in Preparation Example 1 with a #4 Meyer bar, and dried at 60° C. for 1 minute.

(8) Then, an ultraviolet light of 180 mJ/cm.sup.2 was irradiated to the dried coating film under nitrogen purging to form a low refractive layer having a thickness of 110 to 120 nm, thereby producing an antireflection film.

Example 2: Preparation of Antireflection Film

(9) An antireflection film was prepared in the same manner as in Example 1, except that 3-methacryloxypropyltrimethoxysilane was used instead of 3-methacryloxypropylmethyldimethoxysilane in Example 1.

Example 3: Preparation of Antireflection Film

(10) An antireflection film was prepared in the same manner as in Example 1, except that 3-methacryloxypropyltriethoxysilane was used instead of 3-methacryloxypropylmethyldimethoxysilane in Example 1.

Example 4: Preparation of Antireflection Film

(11) An antireflection film was prepared in the same manner as in Example 1, except that 3-acryloxypropyltrimethoxysilane was used instead of 3-methacryloxypropylmethyldimethoxysilane in Example 1.

Example 5: Preparation of Antireflection Film

(12) An antireflection film was prepared in the same manner as in Example 1, except that 3-acryloxypropylmethyldiethoxysilane was used instead of 3-methacryloxypropylmethyldimethoxysilane in Example 1.

Comparative Example 1: Preparation of Antireflection Film

(13) An antireflection film was prepared in the same manner as in Example 1, except that 3-glycidoxypropylmethyldiethoxysilane was used instead of 3-methacryloxypropylmethyldimethoxysilane in Example 1.

Comparative Example 2: Preparation of Antireflection Film

(14) An antireflection film was prepared in the same manner as in Example 1, except that N-phenyl-3-aminopropyltrimethoxysilane was used instead of 3-methacryloxypropylmethyldimethoxysilane in Example 1.

Comparative Example 3: Preparation of Antireflection Film

(15) An antireflection film was prepared in the same manner as in Example 1, except that p-styryltrimethoxysilane was used instead of 3-methacryloxypropylmethyldimethoxysilane in Example 1.

Comparative Example 4: Preparation of Antireflection Film

(16) An antireflection film was prepared in the same manner as in Example 1, except that 3-methacryloxypropylmethyldimethoxysilane used in Example 1 was not used.

Test Examples: Measurement of Physical Properties of Antireflection Films

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

(18) 1. Measurement of Average Reflectance of Antireflection Film

(19) The average reflectance of the antireflection films obtained in the examples and comparative examples showing in the visible light range (380 to 780 nm) was measured using Solidspec 3700 (SHIMADZU) equipment.

(20) 2. Measurement of Scratch Resistance

(21) The surfaces of the antireflection films obtained in the examples and comparative examples were rubbed while applying a specific load to steel wool (#0000) and reciprocating ten times at a speed of 27 reciprocations per minute.

(22) When observed with the naked eye under ceiling illumination of a 50 W LED, the maximum load at which scratches were not generated was measured.

(23) The above load is defined as weight (g) per area of 2 cm in width and 2 cm in height (2*2 cm.sup.2).

(24) 3. Measurement of Antifouling Property

(25) A straight line with a length of 5 cm was drawn with a black permanent marker on the surface of the antireflection films obtained in the examples and comparative examples.

(26) Then, the antifouling property was evaluated by counting the number of rubbing times with a nonwoven cloth until straight lines were erased.

(27) <Measurement Criteria>

(28) ◯: Erased when rubbed 10 times or less

(29) Δ: Erased when rubbed 11 to 20 times

(30) X: Erased or not erased when rubbed more than 20 times

(31) 4. Confirm Phase Separation

(32) When 70% by volume or more of the surface-treated solid inorganic nanoparticles in the entire surface-treated solid inorganic nanoparticles (surface-treated solid silica nanoparticles) were present within 30 nm from the hard coating layer, it was determined that phase separation occurred.

(33) TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Example 2 Example 3 Example 4 Average 0.53 0.52 0.51 0.53 0.51 0.55 0.68 0.71 0.80 reflectance [%] Scratch 700 700 700 650 700 100 100 150 100 resistance [g] Antifouling ∘ ∘ ∘ ∘ ∘ Δ Δ Δ Δ property Phase ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ separation

(34) Referring to Table 1, it was confirmed that when the surface-treated hollow inorganic nanoparticles and the surface-treated solid inorganic nanoparticles were distributed in the binder resin prepared from the compound represented by Chemical Formula 1 (first photo-polymerizable compound) so as to be distinguished from each other, as described in the examples, it exhibited lower reflectance and more improved scratch resistance as compared with the phase separated structure of the comparative examples. Consequently, by providing the binder resin capable of bonding to the hard coating layer, it was confirmed that the first photopolymerizable compound further reduces the reflectance of the antireflection film and further improves the scratch resistance, and that these effects cannot be realized with a compound having another reactive functional group such as an epoxy group, an amino group, or styryl group.