JP2005084320A - Antireflection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antireflection film which has a low-refractive index layer having excellent scratching resistance and a low refractive index, is consequently excellent in antireflection performance, and is highly resistant to flawing and is highly durable when applied to the surface of a display etc. <P>SOLUTION: The antireflection film is formed by laminating a hard coat layer 2, a high-refractive index layer 3 and the low-refractive index layer 4 in this order on a transparent base material film 1. The low-refractive index layer 4 is formed by curing a coating film containing a fluorine-containing (meth)acrylic compound expressed by general formula: A<SP>1</SP>-O(CH<SB>2</SB>)na-Rf-(CH<SB>2</SB>)nbO-A<SP>2</SP>, polyfunctional (meth)acrylic compound and silica particulate subjected to (meth)acryl denaturation at the terminal and the refractive index of light of a wavelength 500 to 600 nm is 1.39 to 1.47. In the general formula, A<SP>1</SP>and A<SP>2</SP>respectively independently represent an acrylol group, methacryloyl group, α-fluoroacryloyl group or trifluoromethacryloyl group; Rf represents a perfluoroakylene group; na and nb respectively independently represent an integer of 0 to 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is excellent in scratch resistance and antireflection performance suitable for various displays such as word processors, computers, CRTs, plasma televisions, liquid crystal displays, organic EL, and window glass for automobiles, buildings, trains, etc. It relates to a high antireflection film.

  Reflections on word processors, computers, CRTs, plasma televisions, liquid crystal displays, organic EL displays, and window glass for automobiles, buildings, trains, etc. to prevent light reflection and ensure high light transmission A protective film is applied.

  Conventionally, as an antireflection film used for this type of application, a film obtained by providing a high refractive index layer and a low refractive index layer on the surface of a transparent substrate film has been provided. In this antireflection film, an antireflection function is obtained by utilizing the refractive index difference between the high refractive index layer and the low refractive index layer. As the high refractive index layer and the low refractive index layer, there is an inorganic thin film by sputtering or vapor deposition, but the inorganic thin film has a high film formation cost. In contrast, a resin-based thin film can be formed at low cost.

  Conventionally, as a coating-type antireflection film, as shown in FIG. 1, a hard coat layer 2, a high refractive index layer 3, and a low refractive index are formed on the surface of a transparent base film 1 made of a synthetic resin from the lower layer side. What laminated | stacked the layer 4 one by one is mainly used.

In order to improve the antireflection performance of such an antireflection film, it is essential to lower the refractive index of the low refractive index layer, and the low refractive index layer has excellent scratch resistance from its application. Is also required. Therefore, conventionally, the following method has been proposed in order to lower the refractive index of the low refractive index layer and to obtain scratch resistance.
(i) Silica fine particles are mixed with the base resin polyfunctional acrylic resin.
(ii) The magnesium fluoride fine particles are mixed with the polyfunctional acrylic resin of the base resin.
(iii) A fluorine-based acrylic resin is used as the base resin (Japanese Patent Laid-Open No. 9-203801).
JP-A-9-203801

  Among the above conventional methods, the method using the silica fine particles (i) cannot achieve a low refractive index because the refractive index of silica is as high as 1.47. In addition, in the case of using the magnesium fluoride fine particles of (ii), it is difficult to modify the terminal acrylic of the magnesium fluoride, so that the film strength is inferior.

  Japanese Patent Laid-Open No. 9-203801 using a fluorine-based acrylic resin of (iii) describes that a low refractive index layer having a low refractive index and excellent scratch resistance can be formed. Actually, this low refractive index layer is inferior in scratch resistance, as is apparent from the results of Comparative Examples 1 and 5 described later. JP-A-9-203801 also describes that a small amount of a polyfunctional acrylic resin is used in combination with a fluorine-based acrylic resin. In this case, although the scratch resistance is improved, the refractive index is increased. Will increase.

  The present invention solves the above-mentioned conventional problems, has excellent scratch resistance, has a low refractive index layer having a low refractive index, and therefore has excellent antireflection performance and is applied to the surface of a display or the like. An object of the present invention is to provide an antireflection film that is extremely resistant to scratching and excellent in durability.

The antireflective film of the present invention is an antireflective film obtained by laminating a hard coat layer, a high refractive index layer and a low refractive index layer in this order on a transparent substrate film. A coating film containing a fluorine-containing (meth) acrylic compound represented by the formula (1), a polyfunctional (meth) acrylic compound, and silica fine particles having a terminal (meth) acryl-modified, is cured, and has a wavelength of 500 The refractive index of light of ˜600 nm is 1.39 to 1.47.
^{_{A 1 -O (CH 2) na}} -Rf- (CH 2) nb O-A 2 ...... (1)
(In the formula (1), A ¹ and A ² each independently represents an acryloyl group, a methacryloyl group, an α-fluoroacryloyl group, or a trifluoromethacryloyl group, Rf represents a perfluoroalkylene group, and na, nb Each independently represents an integer of 0 to 3.)

  In the present invention, “(meth) acryl” means “acryl and / or methacryl”. In the following description, “refractive index” indicates “refractive index for light having a wavelength of 500 to 600 nm”.

  As described above, the fluorinated acrylic resin is excellent in low refractive index property but inferior in scratch resistance.

  In the present invention, the resin component derived from the fluorine-containing (meth) acrylic compound represented by the general formula (1) (hereinafter referred to as “fluorinated bifunctional (meth) acrylic resin”) is modified with (meth) acrylic modification. In the case of only a fluorine-based bifunctional (meth) acrylic resin by blending silica fine particles and a resin component derived from a polyfunctional (meth) acrylic compound (hereinafter referred to as “polyfunctional (meth) acrylic resin”). Compared with the case where only polyfunctional (meth) acrylic resin is blended with fluorine-based bifunctional (meth) acrylic resin, the film strength is refracted by blending with (meth) acrylic modified silica fine particles. Minimize the rate increase. For this reason, it can be set as the low-refractive-index layer excellent in scratch resistance with a low refractive index.

In the present invention, Rf in the general formula (1) is preferably (CF ₂ ) _m (m is an integer of 2 or more).

  The content of the resin component derived from the fluorine-containing (meth) acrylic compound in the low refractive index layer is 60 to 95% by weight, and is derived from (meth) acryl-modified silica fine particles and polyfunctional (meth) acrylic compound. The total content of the resin components is 5 to 40% by weight, and the content ratio of the resin component derived from the (meth) acryl-modified silica fine particles and the polyfunctional (meth) acrylic compound is 40:60 to 80:20 (weight). Ratio). The average particle diameter of the (meth) acryl-modified silica fine particles is preferably 5 to 200 nm.

  The low refractive index layer according to the present invention is preferably cured by ultraviolet rays (UV) or electron beams (EV).

  The antireflection film of the present invention has a low refractive index layer having excellent scratch resistance and a low refractive index, and therefore excellent in antireflection performance, and when applied to the surface of a display or the like, it is extremely difficult to be damaged. Excellent durability.

  Embodiments of the antireflection film of the present invention will be described below.

  As shown in FIG. 1, the antireflection film of the present invention is obtained by laminating a hard coat layer 2, a high refractive index layer 3 and a low refractive index layer 4 in this order on a transparent substrate film 1.

  In the present invention, the base film 1 includes polyester, polyethylene terephthalate (PET), polybutylene terephthalate, polymethyl methacrylate (PMMA), acrylic, polycarbonate (PC), polystyrene, cellulose triacetate (TAC), polyvinyl alcohol, poly Vinyl chloride, polyvinylidene chloride, polyethylene, ethylene-vinyl acetate copolymer, polyurethane, cellophane, etc., preferably PET, PC, PMMA transparent films.

  The thickness of the base film 1 is appropriately determined depending on the required properties (for example, strength and thin film properties) depending on the use of the obtained antireflection film, and is usually in the range of 1 μm to 10 mm.

  The hard coat layer 2 is preferably a synthetic resin type, and particularly, an ultraviolet curable or electron beam curable synthetic resin, particularly a polyfunctional acrylic resin is suitable. The thickness of the hard coat layer 2 is preferably 2 to 20 μm.

The high refractive index layer 3 is preferably a synthetic resin-based material containing metal oxide fine particles, and the synthetic resin is particularly an ultraviolet curable or electron beam curable synthetic resin, especially an acrylic resin, an epoxy resin, or a styrene resin. Resins, most preferably acrylic resins. Further, the metal oxide fine particles are selected from the group consisting of ITO, TiO ₂ , ZrO ₂ , CeO ₂ , Al ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , LaO ₂ and Ho ₂ O _3. Alternatively, one or more of two or more kinds of high refractive index metal oxide fine particles, particularly preferably TiO ₂ fine particles and ITO fine particles are preferable.

  The ratio of the metal oxide fine particles and the synthetic resin in the high refractive index layer 3 is such that when the metal oxide fine particles are excessively large and the synthetic resin is insufficient, the chemical resistance is deteriorated. Therefore, the ratio of the metal oxide fine particles to the total of the metal oxide fine particles and the synthetic resin is preferably 10 to 60% by volume, particularly preferably 20 to 40% by volume.

  The thickness of the high refractive index layer 3 is preferably about 80 to 100 nm. The high refractive index layer 3 preferably has a refractive index of 1.65 or more, particularly 1.66 to 1.85. In this case, the refractive index of the low refractive index layer 4 is 1.39 to 1.47. By setting it as this, it can be set as the antireflection film excellent in the antireflection performance of the minimum reflectance 1% or less of a surface reflectance. In particular, when the refractive index of the low refractive index layer 4 is 1.45 or less, it is possible to further improve the antireflection performance and to form an antireflection film having a minimum surface reflectance of 0.5% or less. is there.

  In the present invention, the low refractive index layer 4 is made of the following resin, but the low refractive index layer 4 is also preferably an ultraviolet curable type or an electron beam curable type.

The low refractive index layer 4 according to the present invention includes a fluorine-containing (meth) acrylic compound represented by the following general formula (1), a polyfunctional (meth) acrylic compound, and (meth) acryl-modified silica fine particles. Formed by the resin composition.
^{_{A 1 -O (CH 2) na}} -Rf- (CH 2) nb O-A 2 ...... (1)
(In the formula (1), A ¹ and A ² each independently represents an acryloyl group, a methacryloyl group, an α-fluoroacryloyl group, or a trifluoromethacryloyl group, Rf represents a perfluoroalkylene group, and na, nb Each independently represents an integer of 0 to 3.)

In the general formula (1), Rf is preferably (CF ₂ ) _m (m is 2 or more, preferably an integer of 2 to 8).

  (Meth) acrylic modified silica fine particles are silica fine particles treated with a silane coupling agent having a terminal (meth) acrylic group to bind the silane coupling agent to the Si-OH group on the surface of the silica fine particles. A terminal (meth) acrylic group is introduced on the surface of the silica fine particle, and if it is such a (meth) acryl-modified silica fine particle, the binder is introduced via the (meth) acrylic group introduced on the surface of the silica fine particle. It becomes possible to covalently bond to the resin, and the bondability to the resin component is high, and excellent functionality can be obtained. The average particle diameter of the silica fine particles is preferably 5 to 200 nm, particularly preferably 5 to 25 nm. When the average particle diameter of the silica fine particles is less than 5 nm, the scratch resistance is lowered, and when it exceeds 200 nm, the Hz is increased and the smoothness is impaired.

  Examples of the polyfunctional (meth) acrylic compound include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, tri Methylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol tetra (meth) acrylate , Ditrimethylolpropane tri (meth) acrylate, 1,1,1-tris [(meth) acryloyloxyethoxyethoxy] propane, tris (hydroxyethyl) ) Isocyanurate tri (meth) acrylate, tris (one or more, such as hydroxyethyl) isocyanurate di (meth) acrylate. The polyfunctional (meth) acrylic compound may be an oligomer obtained by polymerizing or copolymerizing one or more of these.

  In the present invention, the content of the fluorine-based bifunctional (meth) acrylic resin (the resin component derived from the fluorine-containing (meth) acrylic compound represented by the general formula (1)) in the low refractive index layer is 60 to 95 weight. %, Particularly 60 to 80% by weight, and the total content of (meth) acryl-modified silica fine particles and polyfunctional (meth) acrylic resin (resin component derived from polyfunctional (meth) acrylic compound) is 5 to 40 wt. %, Particularly 5 to 35% by weight is preferred. If the amount of the fluorine-based bifunctional (meth) acrylic resin is less than this range, the low refractive index property due to the fluorine-based bifunctional (meth) acrylic resin is impaired, and if it is large, the effect of improving the scratch resistance can be sufficiently obtained. Can not.

  The ratio of the (meth) acryl-modified silica fine particles and the polyfunctional (meth) acrylic resin in the low refractive index layer is (meth) acryl-modified silica fine particles: polyfunctional (meth) acrylic resin = 40: 60 to 80:20. (Weight ratio) is preferable. If there are more polyfunctional (meth) acrylic resins than this range and less (meth) acryl-modified silica fine particles, the effect of reducing the refractive index due to the incorporation of (meth) acryl-modified silica fine particles cannot be obtained sufficiently. If the polyfunctional (meth) acrylic resin is small and the (meth) acryl-modified silica fine particles are large, the effect of improving the scratch resistance due to the blending of the polyfunctional (meth) acrylic resin cannot be sufficiently obtained.

  The low refractive index layer according to the present invention is a mixture of the above-mentioned fluorine-containing (meth) acrylic compound, polyfunctional (meth) acrylic compound and (meth) acryl-modified silica fine particles in a predetermined ratio, and light as required. A resin composition containing a polymerization initiator is applied on the high refractive index layer and cured to form a film, and the refractive index is 1.39 to 1.47, preferably 1.39 to 1.46. . Even if the refractive index of the low refractive index layer 4 is less than 1.39, it is difficult to further reduce the minimum reflectance of the surface reflectance of the antireflection film, and the refractive index of the low refractive index layer 4 exceeds 1.47. And sufficient function as an antireflection film cannot be obtained.

  The thickness of such a low refractive index layer is preferably 85 to 110 nm.

  In the present invention, in order to form the hard coat layer 2, the high refractive index layer 3 and the low refractive index layer 4 on the base film 1, an uncured resin composition (containing the above fine particles as necessary). It is preferable to apply UV light or an electron beam. In this case, each layer 2 to 4 may be applied and cured one by one, or after three layers are applied, they may be cured together.

  As a specific method of coating, a method of coating a coating solution in which a monomer component such as an acrylic monomer is dissolved in a solvent such as toluene with a gravure coater, then drying, and then curing by irradiation with ultraviolet rays or electron beams Is exemplified. This wet coating method has the advantage that the film can be uniformly formed at high speed at low cost. After this coating, for example, by curing by irradiating with ultraviolet rays or electron beams, the effect of improving the adhesion and increasing the hardness of the film can be obtained.

  Such an antireflection film of the present invention ensures good light transmission and scratch resistance when applied to a PDP for OA equipment, a front filter for a liquid crystal plate, or a window material for a vehicle or a special building. can do.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

In the following, the refractive index of the low refractive index layer and the scratch resistance of the antireflection film were measured as follows.
<Measurement of refractive index>
In the same manner as in the examples and comparative examples, a low refractive index layer-forming composition was applied to a PET film without an easy-adhesion layer (“East Lerre mirror”, film thickness 50 μm) at a wavelength of about 1 / 4λ with respect to a light wavelength of 550 nm. It was applied to a thickness and cured. The curing conditions were an ultraviolet integrated dose of 300 mJ / cm ² and an oxygen concentration at curing of 150 ppm. Thereafter, a black vinyl tape was applied to the uncoated surface, the reflectance was measured, and the refractive index was determined by calculation from the minimum reflectance of this reflection spectrum.
<Measurement of Scratch Resistance (Eraser Resistance)>
About the antireflection film created in each example and comparative example, the surface (low refractive index layer surface) was reciprocated with a pressure of about 2.5 × 10 ³ N / m ² with a TOMBO eraser “NONDUST” The number of times until sticking was measured. Scratch resistance is good (○) when scratches are not more than 100 reciprocations, excellent scratch resistance (◎) is those that are not scratches more than 500 reciprocations, and those that are scratched less than 100 reciprocations are scratch resistance. Defective (x).

  The antireflective performance of the antireflective film is such that the refractive index of the low refractive index layer is 1.440 or less (◎) and 1.440 from the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. Exceeding 1.451, good (◯), exceeding 1.451 and not more than 1.481 were acceptable (Δ), and exceeding 1.451 were unacceptable (x).

Examples 1-6, Comparative Examples 1-8
After a hard coat (“Z7503” manufactured by JSR) is applied onto a TAC film (“TAC film” manufactured by Fuji Film Co., Ltd.) having a thickness of 50 μm, it is dried and cured, and then a hard having a thickness of 5 μm and a pencil hardness of 3H. A coat layer was formed. The curing conditions were an ultraviolet integrated dose of 300 mJ / cm ² and an oxygen concentration at curing of 150 ppm. Next, an ITO fine particle-containing acrylic resin composition (“Ei-3” manufactured by Dainippon Paint Co., Ltd.) was applied, dried and cured, and a high refractive index layer having a thickness of about 90 nm and a refractive index of 1.67. Formed. Curing conditions were an integrated UV irradiation dose of 300 mJ / cm ² and an oxygen concentration during curing of 150 ppm.

Next, a composition for forming a low refractive index layer containing the following components at a predetermined ratio was applied onto the high refractive index layer, dried and cured to form a low refractive index layer having a thickness of 100 nm. Curing conditions were an integrated UV irradiation dose of 300 mJ / cm ² and an oxygen concentration during curing of 150 ppm.

  The content of each component in the low refractive index layer is as shown in Table 1.

<Low refractive index layer component>
Monomer A for fluorine-based bifunctional (meth) acrylic resin (fluorine-containing (meth) acrylic compound) A: In the general formula (1), A ¹ is an acryloyl group, A ² is an acryloyl group, and Rf is (CF ₂ ). ₈ , a fluorine-containing (meth) acrylic compound having na of 2 and nb of 2 and containing 5% by weight of a photopolymerization initiator based on the fluorine-containing (meth) acrylic compound)
Monomer B for fluorine-based bifunctional (meth) acrylic resin (fluorine-containing (meth) acrylic compound) B: In the general formula (1), A ¹ is an acryloyl group, A ² is an acryloyl group, and Rf is (CF ₂ ) ₂ , a fluorine-containing (meth) acrylic compound having na of 2 and nb of 2 and a photopolymerization initiator containing 5% by weight based on the fluorine-containing (meth) acrylic compound)
(Meth) acryl-modified silica fine particles: Silica fine particles (average particle size 10 nm) treated with a terminal acryloyl group silane coupling agent to introduce terminal acrylic groups Multifunctional (meth) acrylic compound: pentaerythritol tetraacrylate, Dipentaerythritol hexaacrylate etc.

  Table 1 shows the measurement results of the refractive index of each low refractive index layer, the scratch resistance of the antireflection film, and the evaluation results of the antireflection performance.

  From Table 1, the following is clear.

  In Comparative Examples 1 and 5 using only the fluorine-based bifunctional (meth) acrylic resin, the refractive index of the low refractive index layer is as low as 1.425 or 1.445, but the scratch resistance is poor, and it is 1 or 40 reciprocations. Scratched.

  In Comparative Examples 2 to 4 and Comparative Examples 6 to 8 in which only the polyfunctional (meth) acrylic resin is added to the fluorine-based bifunctional (meth) acrylic resin, the scratch resistance is improved by adding the polyfunctional (meth) acrylic resin. However, the refractive index of the low refractive index layer becomes very high as the polyfunctional (meth) acrylic resin is added, and the refractive index becomes very high when the scratch resistance exceeds 100 reciprocations. The antireflection performance fell.

  In contrast, in Examples 1 to 3 and Examples 4 to 6 in which (meth) acryl-modified silica fine particles and polyfunctional (meth) acrylic resin were added to the fluorine-based bifunctional (meth) acrylic resin, according to these additions Although the refractive index is high, the increase in the refractive index is small compared to the case where only the polyfunctional (meth) acrylic resin is added, and even if the scratch resistance exceeds 100 reciprocations, the refractive index is low and good antireflection Performance was obtained.

  The antireflection film of the present invention having both antireflection performance and scratch resistance, that is, durability, includes various displays such as word processors, computers, CRTs, plasma televisions, liquid crystal displays, and organic EL, and automobiles, buildings, and trains. It is useful for window glass etc.

It is typical sectional drawing which shows the structure of a general coating-type antireflection film.

Explanation of symbols

1 Base film 2 Hard coat layer 3 High refractive index layer 4 Low refractive index layer

Claims (6)

In the antireflection film formed by laminating a hard coat layer, a high refractive index layer and a low refractive index layer in this order on the transparent substrate film,
The low refractive index layer comprises a fluorine-containing (meth) acrylic compound represented by the following general formula (1), a polyfunctional (meth) acrylic compound, and a silica fine particle having a terminal (meth) acryl-modified. The film is cured,
An antireflection film, wherein the refractive index of light having a wavelength of 500 to 600 nm is 1.39 to 1.47.
^{_{A 1 -O (CH 2) na}} -Rf- (CH 2) nb O-A 2 ...... (1)
(In the formula (1), A ¹ and A ² each independently represents an acryloyl group, a methacryloyl group, an α-fluoroacryloyl group, or a trifluoromethacryloyl group, Rf represents a perfluoroalkylene group, and na, nb Each independently represents an integer of 0 to 3.) According to claim 1, antireflection film, wherein the Rf in the general formula (1) is _{(CF 2)} m (m is an integer of 2 or more).   The content of the resin component derived from the fluorine-containing (meth) acrylic compound in the low refractive index layer according to claim 1 or 2 is 60 to 95% by weight, and the (meth) acryl-modified silica fine particles and polyfunctional The total content of the resin component derived from a (meth) acrylic compound is 5 to 40% by weight.   4. The antireflection film according to claim 1, wherein the (meth) acryl-modified silica fine particles have an average particle diameter of 5 to 200 nm.   5. The content ratio of the resin component derived from the (meth) acryl-modified silica fine particles and the polyfunctional (meth) acrylic compound in the low refractive index layer according to claim 1 is 40:60 to 80: 5. An antireflective film characterized by being 20 (weight ratio).   The antireflection film according to any one of claims 1 to 5, wherein the coating film is cured by ultraviolet rays or electron beams.

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