JP2008268357A - Reflection preventing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection preventing film having excellent antidazzle properties, nearly free from reduction of display contrast and free from the glare. <P>SOLUTION: In the reflection preventing film having at least one hard coat layer containing light transmissible particles having 5 to 12 μm average particle diameter and resin on a film base material, at least one over coat layer containing inorganic fine particles having ≤0.1 μm average particle diameter in a flocculation state on the hard coat layer and at least one low refractive index layer on the over coat layer, a surface rugged shape of the low refractive index layer has 1 to 4° average inclined angle θ. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antireflection film.

In a liquid crystal display device (LCD), Patent Document 1 is known as an anti-glare hard coat film which is disposed on the surface of a display to prevent a decrease in contrast due to reflection of external light or reflection of an image. However, the technique disclosed in Patent Document 1 has a problem that the antiglare property is insufficient. Furthermore, it has been found that there is a problem that glare (image distortion or unevenness due to surface unevenness of the antiglare film) tends to deteriorate for a liquid crystal panel having a small pixel size such as a full-spec high-definition liquid crystal television.
JP 2007-41533 A

  An object of the present invention is to provide an antireflection film having excellent antiglare properties, little display contrast reduction, and no glare.

  As a result of intensive studies by the inventor, as a scatterer of light transmitted from the LCD panel, light-transmitting particles having an average particle size of 5 to 12 μm are used as the hard coat layer. An overcoat layer is newly provided on the substrate, and a low refractive index layer is further provided thereon, and the overcoat layer contains inorganic fine particles having an average particle size of 0.1 μm or less in an aggregated state. Utilizing this, the inventors found that the above-mentioned problems can be achieved by adjusting the average inclination angle θ of the surface irregularity shape of the low refractive index layer to 1 to 4 °, and the present invention has been achieved.

  In the present invention, the inorganic fine particles in the overcoat layer in an aggregated state have a primary particle size as small as 0.1 μm or less, and thus do not function as a scatterer of transmitted light from the LCD panel, and form an uneven surface shape. Only available for that.

In addition, when the surface irregularities are formed by the conventional spherical translucent fine particles of several μm size as shown in FIG. 1, the coating forms a dome-shaped convex portion by the spherical upper part of the spherical translucent fine particles as shown in FIG. To do.
On the other hand, the inorganic fine particles in the agglomerated state of the present invention are filament-like agglomerates composed of particles having a primary particle size of 0.1 μm or less, so that the overcoat layer has a small conical projection as shown in FIG. Is different. And the surface irregularity shape consisting of this small conical convex part is superior in antiglare property, less glare than the surface irregularity shape consisting of dome-shaped convex part, and black display property in bright place As a result, it was found that there is an excellent feature that the display contrast in a bright place is high.

  Furthermore, by providing a low refractive index layer to obtain an antireflection ability, the black display property in a bright place is improved, so that the display contrast in a bright place is high.

  That is, the above object of the present invention has been achieved by the following means.

(1) On the film substrate, at least one hard coat layer containing translucent particles having an average particle diameter of 5 to 12 μm and a resin, and an average particle diameter of 0.1 μm on the hard coat layer It has at least one overcoat layer containing the following inorganic fine particles in an aggregated state, and further has at least one low refractive index layer thereon, and the average inclination angle of the surface irregularity shape of the low refractive index layer An antireflection film having θ of 1 to 4 °.
(2) The antireflection film according to (1), wherein the display contrast characteristic of the antireflection film is 80 or more.
(3) The antireflection film according to (1) or (2), wherein the inorganic fine particles having an average particle size of 0.1 μm or less are silica fine particles.
(4) The antireflection film according to any one of (1) to (3), wherein a difference in refractive index between the translucent particles having an average particle diameter of 5 to 12 μm and the resin is 0.05 or less.
(5) The antireflection film as described in any one of (1) to (4), wherein the low refractive index layer contains hollow silica fine particles.
(6) The antireflection film according to any one of (1) to (5), wherein the low refractive index layer has a refractive index of 1.20 to 1.40.

  An antireflection film having excellent antiglare properties, little display contrast reduction, and no glare can be obtained.

  Hereinafter, the antireflection film of the present invention will be described.

<Antireflection film>
[Layer structure of antireflection film]
The antireflection film of the present invention comprises at least one hard coat layer on a transparent film substrate (also referred to as a support), at least one overcoat layer thereon, and at least one layer thereon. The other refractive layers can be provided alone or in a plurality of layers depending on the purpose.

  As a preferred embodiment, there can be mentioned an antireflection film laminated on the substrate in consideration of the refractive index, the film thickness, the number of layers, the layer order, etc. so that the reflectance is reduced by optical interference. The antireflection film is preferably constituted by combining a hard coat layer and an overcoat layer having substantially the same refractive index as that of the substrate, and a low refractive index layer having a refractive index lower than that of the substrate.

The example of the preferable layer structure of the film of the said aspect is shown below. In the following configuration, the film substrate refers to a support composed of a film.
-Film substrate / hard coat layer / overcoat layer / low refractive index layer- Film substrate / moisture-proof layer / hard coat layer / overcoat layer / low refractive index layer-Moisture-proof layer / film substrate / hard coat layer / over Coat layer / Low refractive index layer ・ Film substrate / Hard coat layer / Conductive layer / Overcoat layer / Low refractive index layer ・ Film substrate / Conductive layer / Hard coat layer / Overcoat layer / Low refractive index layer

These layers can be formed by methods such as vapor deposition, atmospheric pressure plasma, and coating. From the viewpoint of productivity, it is preferably formed by coating.
Each constituent layer will be described below.

[Low refractive index layer]
In the present invention, the low refractive index layer is located on the outermost surface side of the antireflection film, and is the layer having the lowest refractive index among the layers of the antireflection film. By coating the low refractive index layer to obtain an antireflection ability, the black display property in a bright place is improved, so that an effect of high display contrast in a bright place can be obtained.

The refractive index of the low refractive index layer is preferably 1.20 to 1.50, more preferably 1.25 to 1.45, and most preferably 1.20 to 1.40. .
Here, the refractive index of the low refractive index layer can be quantitatively evaluated by directly measuring with an Abbe refractometer or by measuring a spectral reflection spectrum or a spectral ellipsometry.

  The integrated reflectance is preferably 0.5 to 2.50%, more preferably 0.5 to 2.00%, and most preferably 0.5 to 1.80%.

  The thickness of the low refractive index layer is preferably 10 nm to 500 nm, more preferably 20 nm to 200 nm, and most preferably 50 nm to 150 nm.

(Fluorine-containing compound having an ethylenically unsaturated group)
The low refractive index layer preferably contains a fluorine-containing compound having an ethylenically unsaturated group. Specifically, the ethylenically unsaturated group means that the terminal is a vinyl group, an allyl group, an acrylolyl group, a methacryloyl group, or an isopropenyl group, and an acrylolyl group or a methacryloyl group is particularly preferable. Although one ethylenically unsaturated group may be present in one molecule, it is more preferable that the fluorine-containing compound having an ethylenically unsaturated group has two or more ethylenically unsaturated groups in one molecule.

  As specific examples of the fluorine-containing compound having two or more ethylenically unsaturated groups, those described in known techniques can be used. For example, fluorine-containing compounds described in JP-A-9-301925 can be used. Functional (meth) acrylic acid ester, fluorine-containing polyfunctional (meth) acrylic acid ester described in JP-A-10-182745, fluorine-containing polyfunctional (meth) acrylic acid ester described in JP-A-10-182746, Mention may be made of fluorine-containing polyfunctional (meth) acrylic esters described in JP-A No. 2001-72646.

  Further, the fluorine-containing compound having an ethylenically unsaturated group is preferably a polymer, and has a polystyrene-equivalent number average molecular weight measured by gel permeation chromatography (hereinafter referred to as GPC) using tetrahydrofuran (hereinafter referred to as THF) as a solvent. It is preferably 1000 to 500,000. A number average molecular weight of 500,000 or less is preferred because the viscosity of the composition does not become too high and disadvantages such as difficulty in thinning do not occur.

  Specific examples of the fluorine-containing polymer having an ethylenically unsaturated group that are preferred in the present invention can be those known in the art, such as JP-A-2005-89536 and JP-A-2005-290133. And an ethylenically unsaturated group-containing fluoropolymer described in JP-A-2006-36835.

  The addition amount of the fluorine-containing compound having an ethylenically unsaturated group is preferably 10 to 100% by mass, more preferably 20 to 90% by mass, and more preferably 30 to 90% by mass with respect to 100% by mass of the solid content of the low refractive index layer. % Is most preferred.

  The fluorine-containing compound having an ethylenically unsaturated group forming the low refractive index layer can be cured by the method described in (Curing method) in [Method for forming each layer] described later.

(Hollow silica fine particles)
In order to lower the refractive index of the low refractive index layer, it is preferable to use hollow silica fine particles in the low refractive index layer. The hollow silica fine particles have a refractive index of 1.17 to 1.40, more preferably 1.17 to 1.35, and still more preferably 1.17 to 1.30. The refractive index here represents the refractive index of the whole particle, and does not represent the refractive index of only the outer shell silica forming the hollow silica fine particles.

At this time, the radius r _i of the cavity inside the particle, the radius of the outer shell of the particle is r _o, the porosity x is calculated by the following equation (4).
Equation (4): x = (4πr i 3/3) / (4πr o 3/3) × 100

The porosity x of the hollow silica fine particles is preferably 10 to 60%, more preferably 20 to 60%, and most preferably 30 to 60%. If the hollow silica fine particles are made to have a lower refractive index and a higher porosity, the thickness of the outer shell becomes thinner and the strength of the particles becomes weaker. From the viewpoint of scratch resistance, the low refractive index is less than 1.17. Rate particles are difficult.
The refractive index of these hollow silica fine particles was measured with an Abbe refractometer {manufactured by Atago Co., Ltd.}.

  The amount of the hollow silica fine particles added is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and most preferably 30 to 60% by mass with respect to 100% by mass of the solid content of the low refractive index layer.

[Overcoat layer]
In the present invention, the overcoat layer is in a lower layer than the low refractive index layer of the antireflection film, is in an upper layer than the hard coat layer, and contains inorganic fine particles having an average particle size of 0.1 μm or less in an aggregated state.

  In the antireflection film of the present invention, by containing inorganic fine particles having an average particle size of 0.1 μm or less in an aggregated state as described above, the low refraction located on the outermost surface of the antireflection film is described later. An uneven shape having a specific average inclination angle θ can be formed on the surface of the rate layer, and thus the antireflection film of the present invention exhibits sufficient antiglare properties and has less glare. The display contrast is excellent.

(Inorganic fine particles)
The inorganic fine particles having an average particle size of 0.1 μm or less refer to fine particles made of an inorganic substance such as silica and alumina, and silica fine particles are particularly preferable.

  The silica fine particles can be obtained by a so-called wet method synthesized by a neutralization reaction between sodium silicate and sulfuric acid, but is not limited thereto. The wet method is further roughly classified into a precipitation method and a gelation method, and either method may be used. Specifically, “NIPEGEL” series manufactured by Tosoh Silica Co., Ltd., “OSCAL” series manufactured by Catalytic Chemical Industry Co., Ltd., high-purity organosol manufactured by Fuso Chemical Industry Co., Ltd., manufactured by Denki Kagaku Kogyo Co., Ltd. Commercial products such as Ultra Fine Powder and Snowtex UP manufactured by Nissan Chemical Industries, Ltd. can be used.

  The inorganic fine particles are required to have an average primary particle size of 0.1 μm or less, particularly preferably 1 to 100 nm, most preferably 5 to 80 nm, and spherical particles as the primary particles. Are preferably connected or agglomerated, or elongated particles.

Moreover, when the aggregation state of the inorganic fine particles is expressed as a secondary particle diameter, the size is preferably equal to or smaller than the film thickness of the overcoat layer, and more preferably 0.3 to 1.0 μm.
Here, the agglomerated state means a state in which inorganic fine particles having an average particle size of 0.1 μm or less are randomly gathered in units of several tens to several hundreds in the overcoat layer. FIG. 3 schematically shows the aggregated state of the inorganic fine particles and the small conical surface protrusions formed thereby.
The aggregated state of the inorganic fine particles is preferably in the form of a filament with little visible light scattering property.

“Containing inorganic fine particles in an aggregated state” means that the inorganic fine particles having an average particle size of 0.1 μm or less are in an aggregated state in the cured film after coating and drying the overcoat layer coating solution. They may be aggregated at any stage before being added to the coating solution, in the coating solution for the overcoat layer, or after coating the overcoat layer.
As a preferred method for agglomerating inorganic fine particles having an average particle size of 0.1 μm or less, a solvent having a slightly poor dispersion stability of the inorganic fine particles is selected as a coating solution solvent, so that the coating solution or coating film is dried. Aggregates can be formed. In that case, the aggregate of the inorganic fine particles can be made as large as the thickness of the overcoat layer. In the present invention, the specific coating solvent is preferably a ketone solvent. However, in the case of inorganic fine particles that have been surface-modified beforehand with a ketone solvent such as Snowtex MEK-ST and MIBK-ST manufactured by Nissan Chemical Industries, It does not aggregate and is not preferable.
Moreover, you may add the additive which has the effect | action which aggregates inorganic fine particles to a coating liquid.

  The inorganic fine particles having an average particle size of 0.1 μm or less are blended in the formed overcoat layer so as to be contained in an amount of 1 to 30% by mass in the total solid content of the overcoat layer. More preferably, it is 2-25 mass%.

  The refractive index of the overcoat layer is preferably substantially the same as the refractive index of the hard coat layer, and the value is preferably 1.40 to 1.80, particularly 1.45 to 1.70. More preferably, it is most preferably 1.45 to 1.60.

  The thickness of the overcoat layer is preferably 0.3 to 10 μm, more preferably 0.5 to 5 μm, and most preferably 0.5 to 3 μm.

(resin)
In the present invention, the overcoat layer contains a resin. The curable resin used to form the overcoat layer can be cured by a method described in (Curing method) in [Method for forming each layer] described later to obtain a resin. The curable resin preferably contains a polyfunctional monomer having two or more (meth) acryloyl groups in one molecule.

  As polyfunctional monomers, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol Di (meth) acrylate, tripropylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, 3-methylpentanediol di (meth) acrylate, diethylene glycol bis-β- (meth) acryloyloxypropionate, trimethylol Ethanetri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (2- (Droxyethyl) isocyanate di (meth) acrylate, pentaerythritol tetra (meth) acrylate, 2,3-bis (meth) acryloyloxyethyloxymethyl [2.2.1] heptane, poly-1,2-butadiene di (meth) Acrylate, 1,2-bis (meth) acryloyloxymethylhexane, nonaethylene glycol di (meth) acrylate, tetradecane ethylene glycol di (meth) acrylate, 10-decanediol (meth) acrylate, 3,8-bis (meth) Acryloyloxymethyltricyclo [5.2.10] decane, hydrogenated bisphenol A di (meth) acrylate, 2,2-bis (4- (meth) acryloyloxydiethoxyphenyl) propane, 1,4-bis (( (Meth) acryloyloxy Examples include methyl) cyclohexane, hydroxypivalin sun ester neopentyl glycol di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, and epoxy-modified bisphenol A di (meth) acrylate. Only one type of polyfunctional monomer may be used, or two or more types may be used in combination.

  In the present invention, the addition amount of these curable resins is preferably 10 to 90% by mass, more preferably 30 to 90% by mass, and most preferably 40 to 80% by mass with respect to 100% by mass of the solid content of the overcoat layer. .

[Hard coat layer]
In the present invention, the hard coat layer is in a lower layer than the overcoat layer, and contains translucent particles having an average particle diameter of 5 to 12 μm and a resin.

(Translucent particles)
The average particle size of the translucent particles needs to be in the range of 5 to 12 μm. If the average particle size is less than 5 μm, the display contrast in a bright place is undesirably large. On the other hand, if it exceeds 12 μm, the film thickness of the hard coat layer becomes too thick and it tends to curl.

Specific examples of the translucent particles include resin particles such as acrylic particles, styrene particles, or acrylic-styrene particles; inorganic particles mainly containing silica, such as poly {(meth) acrylate} particles. Preferred examples include resin particles such as crosslinked poly {(meth) acrylate} particles, polystyrene particles, crosslinked polystyrene particles, crosslinked poly (acryl-styrene) particles, melamine resin particles, and benzoguanamine resin particles. Among these, crosslinked resin particles are preferable, and crosslinked polystyrene particles, crosslinked poly {(meth) acrylate} particles, and crosslinked poly (acryl-styrene) particles are preferably used.
Moreover, you may use together and use 2 or more types of translucent particle | grains from which a particle diameter differs.

  The said translucent particle | grain is mix | blended so that it may contain 5-60 mass% in the hard-coat layer total solid content in the formed hard-coat layer. More preferably, it is 10-50 mass%.

(resin)
In the present invention, the hard coat layer contains a resin. The curable resin used to form the hard coat layer can be cured by the method described in (Curing method) in [Method of forming each layer] described later to obtain a resin. The curable resin preferably contains a polyfunctional monomer having two or more (meth) acryloyl groups in one molecule. Examples of the polyfunctional monomer include those similar to those used in the overcoat layer.

  In the present invention, the addition amount of these curable resins is preferably 10 to 90% by mass, more preferably 30 to 90% by mass, and most preferably 40 to 80% by mass with respect to 100% by mass of the solid content of the hard coat layer. .

(Refractive index difference)
In the hard coat layer constituting the antireflection film of the present invention, the difference in refractive index between the translucent particles and the resin (the refractive index of the translucent fine particles−the refractive index of the resin) is 0.05 or less as an absolute value. Is more preferable, and 0.001 to 0.050 is more preferable.

  Here, the refractive index of the resin can be quantitatively evaluated by directly measuring the refractive index with an Abbe refractometer or by measuring a spectral reflection spectrum or a spectral ellipsometry. The refractive index of the translucent particles is measured by measuring the turbidity by dispersing an equal amount of the translucent particles in the solvent in which the refractive index is changed by changing the mixing ratio of two types of solvents having different refractive indexes. It is measured by measuring the refractive index of the solvent when the turbidity is minimized with an Abbe refractometer.

  In the present invention, the uneven shape on the surface is preferably formed only by an aggregate of inorganic fine particles having an average particle size of the overcoat layer of 0.1 μm or less. Therefore, the average particle size of the translucent particles in the hard coat layer On the other hand, the thickness of the hard coat layer is preferably the same or larger, and the thickness of the hard coat layer is preferably 5.0 to 20 μm, and most preferably 5.0 to 15 μm.

[Characteristics of antireflection film]
(Average tilt angle)
In the antireflection film of the present invention, the average inclination angle θ of the surface irregularity shape of the low refractive index layer located on the outermost surface needs to be in the range of 1 to 4 °. The irregularities on the surface of the low refractive index layer are formed when inorganic fine particles having an average particle size of 0.1 μm or less contained in the overcoat layer are in an aggregated state, and a large number of small conical convex portions are formed on the surface. Can do. When the average inclination angle θ is less than 1 °, there is a disadvantage that sufficient anti-glare property cannot be exhibited and reflection of external light or the like occurs. On the other hand, when θ exceeds 4 °, the glare deteriorates and there is a disadvantage that the display contrast in a bright place is greatly reduced.

In the present invention, the average inclination angle θ of the surface irregularity shape of the low refractive index layer is a value defined by the following mathematical formula (1).
Formula (1): θ = tan ⁻¹ Δa

In the above formula (1), Δa is JIS B− as shown in the following formula (2).
For the reference length L of the roughness curve defined in 0601 (1994 version), the sum (h ₁ + h ₂ + h ₃ + ...) of the difference (height h) between the apex of the adjacent mountain and the lowest point of the valley + H _n ) divided by the reference length L. The roughness curve is a curve obtained by removing a surface waviness component longer than a predetermined wavelength from a cross-sectional curve with a phase difference compensation type wide-area filter. The cross-sectional curve is a contour that appears at the cut end when the target surface is cut along a plane perpendicular to the target surface. FIG. 4 shows an example of the roughness curve, the height h, and the reference line L.
Formula (2): Δa = (h ₁ + h ₂ + h ₃ +... + H _n ) / L

(Display contrast)
In the present invention, the display contrast refers to the display contrast in a bright place, and the contrast ratio (brightness in white display / brightness in black display) measured in the bright place environment shown in the embodiment is expressed by the following formula (3). It is a calculated relative value.
Formula (3): Display contrast = (contrast ratio of antireflection film) / (contrast ratio of simple transparent hard coat film) × 100
It is preferable to set the display contrast characteristic to 80 or more because the display quality of the LCD panel in a bright place can be improved.

[Film substrate]
The film substrate used in the present invention is not particularly limited as long as it has an excellent visible light transmittance (preferably a light transmittance of 90% or more) and excellent transparency (preferably a haze value of 1% or less). . Specifically, for example, a polyester polymer such as polyethylene terephthalate and polyethylene naphthalate; a cellulose polymer such as diacetyl cellulose and triacetyl cellulose; a polycarbonate polymer; and a transparent polymer such as an acrylic polymer such as polymethyl methacrylate Is mentioned. Also, styrene polymers such as polystyrene and acrylonitrile / styrene copolymer; polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin polymers such as ethylene / propylene copolymer; vinyl chloride polymers, nylon and aromatic polyamides Examples thereof include a film made of a transparent polymer such as an amide polymer. Furthermore, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene Examples thereof include a film made of a transparent polymer such as a polymer, an epoxy polymer, and a blend of these polymers. In particular, those having a small optical birefringence are preferably used.

  When the antireflection film of the present invention is used as a protective film for a polarizing plate, the film substrate is preferably triacetyl cellulose (TAC), polycarbonate, acrylic polymer, polyolefin having a cyclic or norbornene structure, or the like. . The film base material may be a polarizer itself described later. With such a configuration, the obtained polarizing plate does not require a protective film made of TAC or the like, and the structure of the polarizing plate can be simplified, so that the number of manufacturing steps can be reduced and the production efficiency can be improved. Further, the polarizing plate can be further thinned. Furthermore, the antireflection film of the present invention also serves as a cover plate attached to the surface of the liquid crystal cell.

  The thickness of the film substrate can be appropriately determined, but is generally about 10 to 500 μm in consideration of workability such as strength and handleability, and thin layer properties. 20-300 micrometers is especially preferable, and 30-200 micrometers is more preferable. Furthermore, it does not restrict | limit especially as a refractive index of a film base material, It is usually about 1.30-1.80, It is especially preferable that it is 1.40-1.70.

[Method for forming each layer]
(Application method)
Each layer of the antireflection film of the present invention can be formed by the following known coating method, but is not limited to this method.
Dip coating method, air knife coating method, curtain coating method, roller coating method, wire bar coating method, gravure coating method, extrusion coating method (die coating method) (see US Pat. No. 2,681,294), micro gravure coating method and the like. Among these, the micro gravure coating method and the die coating method are preferable.

  Here, the micro gravure coating method is a method in which a gravure roll having a diameter of about 10 to 100 mm, preferably about 20 to 50 mm and engraved with a gravure pattern is installed below the support (film substrate), and A position where the gravure roll is rotated in the reverse direction with respect to the transport direction of the support and the surplus coating liquid is scraped off from the surface of the gravure roll by a doctor blade so that the upper surface of the support is in a free state. The coating method is characterized in that the coating solution is transferred onto the lower surface of the support in the coating method. A roll-shaped transparent support can be continuously unwound, and at least one layer can be coated on one side of the unwound support by a microgravure coating method.

  As coating conditions by the micro gravure coating method, the number of lines of the gravure pattern imprinted on the gravure roll is preferably 50 to 800 lines / inch, and more preferably 100 to 300 lines / inch. The depth of the gravure pattern is preferably 1 to 600 μm, more preferably 5 to 200 μm. The rotation speed of the gravure roll is preferably 3 to 800 rpm, more preferably 5 to 200 rpm. It is preferable that the conveyance speed of a support body is 0.5-100 m / min, and 1-50 m / min is more preferable.

In order to supply the antireflection film of the present invention with high productivity, an extrusion method (die coating method) is preferably used in a region where the wet coating amount is small (20 cc / m ² or less).

  Moreover, in this invention, it is preferable to apply | coat the coating liquid of 2 layers or more containing a hard-coat layer and an overcoat layer simultaneously. The coating method can be selected from a curtain coating method, an extrusion coating method (die coating method) (see US Pat. No. 2,681,294), a slide coating method, and combinations thereof. In particular, a die coating method including one or more die coating slots and a die / slide composite coating method are preferable, but the method is not particularly limited to this method.

(Curing method)
In the present invention, the coated and dried antireflection film can be cured by heat and / or ultraviolet irradiation. Here, curing by ultraviolet irradiation means low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, carbon arc lamp, metal halide lamp, xenon lamp, etc., ArF excimer laser, KrF excimer laser, excimer lamp or synchrotron radiation. This refers to curing the film by irradiating the dried film with ultraviolet light using a light source such as light.

The irradiation conditions vary depending on individual lamps, but the amount of light irradiated is preferably 20~10000mJ / cm ^2, more preferably from 100 to 2000 mJ / cm ^2, particularly preferably 400~2000mJ / cm ^2.

  In the case of curing with ultraviolet rays, each layer may be irradiated one by one or after lamination. From the viewpoint of productivity, it is preferable to irradiate ultraviolet rays after forming the low refractive index layer.

(Image display device)
The antireflection film of the present invention is preferably used as a surface film of a liquid crystal panel screen.
The liquid crystal panel used includes a VA mode in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied, and is horizontally aligned when a voltage is applied, and an MVA mode in which the multi-domain is formed, and a nematic The IPS mode in which switching is performed by applying a lateral electric field to the liquid crystal, and the OCB mode in which rod-like liquid crystalline molecules are aligned substantially symmetrically at the upper and lower portions of the liquid crystal cell are modes having a wide viewing angle. The antireflection film can be preferably used.
Furthermore, the higher the resolution of the liquid crystal panel, the more preferably the antireflection film of the present invention can be used. In particular, the liquid crystal panel is preferably used for a high-resolution liquid crystal panel called full-spec high-definition having 1920 × 1080 or 1440 × 1080. Can be used.

The compounds used in this example are shown below.
-Fluorine-containing polymer The methacryl-modified fluorine-containing polymer (A-1) obtained according to the method described in Production Example 2 of JP-A-2006-36835 was used.

Hollow silica fine particle dispersion Hollow silica fine particle sol (isopropyl alcohol silica sol, average particle diameter 60 nm, shell thickness 10 nm, silica concentration 20% by mass, silica particle refractive index 1.31, preparation example of JP 2002-79616 A 4), 500 g, 30 g of acryloyloxypropyltrimethoxysilane {manufactured by Shin-Etsu Chemical Co., Ltd.} and 1.5 g of diisopropoxyaluminum ethyl acetate are mixed, and then 9 g of ion-exchanged water. Was added. After reacting at 60 ° C. for 8 hours, the mixture was cooled to room temperature, and 1.8 g of acetylacetone was added. While adding cyclohexanone to 500 g of this dispersion so that the content of silica was almost constant, solvent substitution by vacuum distillation was performed. There was no generation of foreign matter in the dispersion, and the viscosity when the solid content concentration was adjusted to 20% by mass with cyclohexanone was 5 mPa · s at 25 ° C. When the residual amount of isopropyl alcohol in the obtained dispersion was analyzed by gas chromatography, it was 1.5%.

Curable resin: Dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate mixture “DPHA” [manufactured by Nippon Kayaku Co., Ltd.], cured film refractive index 1.52
・ Photopolymerization initiator: "Irgacure 184" [Ciba Specialty Chemicals Co., Ltd.]

-Silica fine particles: "OSCAL12" (manufactured by Catalytic Chemical Industry Co., Ltd.), silica fine particles with a primary particle size of 12 nm-Cross-linked acrylic particles: "MX" series [manufactured by Soken Chemical Co., Ltd.], refractive index 1.49

  In addition, the addition amount in a table | surface was represented by the mass% as solid content.

<Preparation of antireflection film>
Example 1
Antireflection film samples (101) to (106) were prepared with the structure shown in Table 1.

[Coating solution adjustment]
[Hard coat layer]
According to Table 1, a methyl isobutyl ketone solution in which the curable resin “DPHA” and the photopolymerization initiator “Irgacure 184” were dissolved was prepared.
Further, in accordance with Table 1, crosslinked acrylic particles (average particle diameter is described in Table 1) were added. The amount added at that time was expressed as a solid content.
The solid content concentration of the hard coat layer coating solution was adjusted to 40% by mass.
Table 1 shows the total solid content of the hard coat layer as 100% by mass.

[Overcoat layer]
According to Table 1, a methyl isobutyl ketone solution in which the curable resin “DPHA” and the photopolymerization initiator “Irgacure 184” were dissolved was prepared.
Furthermore, according to Table 1, 12 nm size of “OSCAL” series manufactured by Catalytic Chemical Industry Co., Ltd. was added. The amount added at that time was expressed as a solid content. These particles become aggregated in the film after coating and drying. The solid content concentration of the overcoat layer coating solution was adjusted to 40% by mass.
Table 1 shows the total solid content of the overcoat layer as 100% by mass.

[Low refractive index layer]
As a fluorine-containing polymer having an ethylenically unsaturated group, 59.0% by mass in terms of solid content of the methacryl-modified fluorine-containing polymer (A-1), and 40. in terms of solid content of the hollow silica fine particle dispersion. 0% by mass and 1.0% by mass of the photopolymerization initiator “Irgacure 184” were mixed to prepare a coating solution for the low refractive index layer using methyl ethyl ketone as a solvent. The solid content concentration of the coating solution for the low refractive index layer was 5%. The refractive index of the low refractive index layer after curing was 1.38.

[Coating method of antireflection film]
As a film base material, a triacetyl cellulose film “TAC-TD80U” (manufactured by FUJIFILM Corporation) is unwound in a roll form, and a coater having a throttle die is used to first extrude the hard coat layer coating solution directly. And applied. After coating at a transfer speed of 30 m / min, drying at 30 ° C. for 15 seconds and at 80 ° C. for 20 seconds, and then applying an “air-cooled metal halide lamp” {manufactured by Eye Graphics Co., Ltd.) of 160 W / cm under a nitrogen purge. It was used to irradiate ultraviolet rays with an irradiation amount of 90 mJ / cm ² to cure and wind up the coating layer. The dry film thickness of the hard coat layer is shown in Table 1.

Further, the overcoat layer coating solution was applied onto the hard coat layer using a coater having a throttle die. After coating at a transfer speed of 30 m / min, drying at 30 ° C. for 15 seconds and at 80 ° C. for 20 seconds, and then applying an “air-cooled metal halide lamp” {manufactured by Eye Graphics Co., Ltd.) of 160 W / cm under a nitrogen purge. Then, the coating layer was cured by irradiating with an ultraviolet ray having an irradiation amount of 90 mJ / cm ² . Table 1 shows the dry film thickness of the overcoat layer.

On the overcoat layer of the laminated film obtained as described above, using the coater having a throttle die, the above-described coating solution for a low refractive index layer was applied and dried: dried at 80 ° C. for 60 seconds, Using an “air-cooled metal halide lamp” (manufactured by Eye Graphics Co., Ltd.) of 240 W / cm in an atmosphere with an oxygen concentration of 0.1% by nitrogen purge, ultraviolet rays with an irradiation amount of 400 mJ / cm ² were irradiated. An antireflection film having the structure shown was produced.
In Table 1, the component ratio is described with the total solid content of each layer as 100% by mass.

Each antireflection film was evaluated by the following evaluation method.
The evaluation of steel wool scratch resistance and adhesion was evaluated using a film processed with a polarizing plate described later.

〔Evaluation methods〕
[Integral reflectance]
Using the spectrophotometer {manufactured by JASCO Corp.}, the back side of the produced antireflection film was roughened with sandpaper and then treated with black ink, and the backside reflection was eliminated. In the wavelength region of 380 to 780 nm, the integrated spectral reflectance at an incident angle of 5 ° was measured. The arithmetic average value of the integrated reflectance of 450 to 650 nm was used for the result.

[Measurement of average inclination angle θ]
A glass plate having a thickness of 1.3 mm was bonded to the non-coated surface of the produced antireflection film with an adhesive. Measured with a high-precision fine shape measuring instrument “Surf Corder ET4000” (trade name) {Kosaka Laboratory Ltd.}, an arithmetic average roughness Ra value described in JIS B0601-1994, and an average interval Sm value of irregularities are obtained. The average inclination angle θ value was obtained by automatic calculation.

[Evaluation of anti-glare properties]
On the sample piece for measuring the average tilt angle, a bare fluorescent lamp (8000 cd / m ² ) without a louver is projected from an angle of 45 °, and the degree of blurring of the reflected image when observed from the direction of −45 ° is as follows. It was evaluated with.
◎: Fluorescent lamp outline is completely unknown Level: Fluorescent lamp outline is slightly understood △: Fluorescent lamp is blurred, but the outline can be identified ×: Fluorescent lamp is hardly blurred

[Measurement of display contrast]
(1) The prepared antireflection film was prepared by attaching an acrylic adhesive having a film thickness of about 20 μm to the non-coated surface, and attaching it to a polarizing plate having a smooth surface (50 mm × 50 mm).
(2) Remove the polarizing plate with the antireflection film from the viewing side polarizing plate of the 32-inch full high-definition LCD TV “LC-32GS10” {manufactured by Sharp Corporation} (number of pixels; 1920 × 1080), Pasted.
(3) For the mounted liquid crystal television, set the light receiver “SPECTRORADIOMETER CS1000A” {manufactured by Konica Minolta Co., Ltd.} so as to be parallel 50 cm upward, and ring illumination “MHF-G150LR” {diameter 37 mm, ) Moritex} was set at a height of 27 mm. The irradiation angle of the light irradiated on the liquid crystal television screen from the ring illumination light at this set position was set to 30 °.
(4) An illuminometer “ILLUMINANCE METER” {manufactured by Topcon Co., Ltd.} was used to adjust the illuminance to 1000 Lx.
(5) The image on the liquid crystal television screen was switched between black display and white display, and the luminance at the black display and the white display at the central portion of the polarizing plate were measured as black luminance and white luminance, respectively. The contrast ratio (white luminance / black luminance) was calculated based on the value.
(6) As a reference value, using the antireflection film (101) in which fine particles are not blended in the hard coat layer, the contrast ratio is measured by the methods (1) to (5), and the value is set to 100. As standardized.

[Evaluation of glare]
With the produced antireflection film attached to the above-mentioned liquid crystal television, the state of glare on the screen when the liquid crystal television was fully G-displayed was sensory evaluated.
○: Level at which glare does not matter at all.
Δ: A level at which slight glare occurs but does not matter.
X: Level at which glare occurs strongly and becomes a problem.

  The evaluation results are shown in Table 1.

In Table 1, the antireflection films (101) to (106) are all compared when the average inclination angle θ is 1.1 °. In the antireflection film (101) of the comparative example having no light-transmitting particles in the hard coat layer, there is nothing that scatters the transmitted light from the LCD panel, so that glare is a problem. When the light-transmitting particle size of the hard coat layer is small, the transmitted light from the LCD panel is scattered, but a preferable scattered light distribution is not obtained, and only a low display contrast value can be obtained. The antireflection film (106) of the comparative example which does not contain the aggregated inorganic fine particles in the overcoat layer forms surface irregularities due to the light-transmitting particles of the hard coat layer, but this is insufficient in antiglare property, and is not glare. However, the display contrast characteristics in a bright place were inferior. From these comparisons, the antireflection films (103), (104) and (105) of the present invention were superior to the prior art, and the display contrast characteristics in a bright place were 80 or more.
When the cross section of each of the antireflection films 101 to 105 is observed with an electron microscope, the silica fine particles of the overcoat layer are aggregated to have a secondary particle diameter of about 1 μm, and small conical convex portions are formed on the surface. The formation was confirmed.

Example 2
In the antireflection film (104) of Example 1, the composition of the overcoat layer was changed, the film thickness was changed to adjust the average inclination angle, and other than that, the antireflection films (201) to (201) to ( 206).
The composition of each layer is shown in Table 2.
In Table 2, the component ratio is described with the total solid content of each layer being 100% by mass.

  The obtained antireflection films (201) to (206) were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

In Table 2, the antireflection film (204) of the comparative example having an average inclination angle outside the range has a large surface irregularity shape, a glare deterioration is observed, and the display contrast is greatly decreased.
Further, the antireflection films (205) and (206) of the comparative examples that do not contain aggregated inorganic fine particles in the overcoat layer form surface irregularities due to the light-transmitting particles of the hard coat layer. Insufficient glare was also a problem level, and the display contrast characteristics in a bright place were inferior. From these comparisons, the antireflection films (201), (202) and (203) of the present invention were superior to the prior art, and the display contrast characteristics in a bright place were 80 or more.
When the cross section of each of the antireflection films 201 to 203 is observed with an electron microscope, the silica fine particles of the overcoat layer are aggregated to have a secondary particle diameter of about 1 μm, and small conical convex portions are formed on the surface. The formation was confirmed.

Example 3
An antireflection film was produced in the same manner as in Example 2 except that the following materials were used.
-Silica fine particle 2: "Snowtex UP" manufactured by Nissan Chemical Industries, Ltd., slender silica particles having a primary particle size of 40 to 100 nm-Silica fine particle 3: "Snowtex MIBK-ST" manufactured by Nissan Chemical Industries, Ltd., Silica fine particles having a primary particle size of 20 nm are surface-treated to form a MIBK dispersion. Silica fine particles 4: “SFP-20M” manufactured by Denki Kagaku Kogyo KK, silica fine particles having a primary particle size of 0.3 μm

  Table 3 shows the composition of each layer of the antireflection film, and the evaluation results of evaluating the obtained antireflection films (301) to (304) in the same manner as in Example 1.

In Comparative Examples 302 and 303, even silica fine particles having an average particle size of 0.1 μm or less do not aggregate. It can be seen that the average tilt angle cannot be increased because no agglomeration is formed.
Comparative Example 304 is a case of silica fine particles having an average particle size of 0.3 μm, and aggregates are formed in the overcoat layer. Therefore, the average inclination angle can be designed as intended, but the particles are too large and are in an aggregated state. As a result, the scattering property of visible light cannot be ignored, resulting in a decrease in display contrast.
The present invention 301 is excellent in all of antiglare properties, glare and display contrast. When the cross section is observed with an electron microscope, the silica fine particles of the overcoat layer are aggregated to a size of about 1 μm in secondary particle diameter. It was confirmed that small conical convex portions were formed on the surface.

Schematic diagram of cross section of hard coat layer that forms surface irregularities with conventional translucent fine particles The schematic diagram showing the relationship between the translucent fine particle and this layer surface unevenness | corrugation in the hard-coat layer of FIG. Schematic diagram showing the relationship between the aggregation of inorganic fine particles and the surface irregularities of the layer in the overcoat layer of the present invention The figure which shows an example of a roughness curve, height h, and the reference line L

Claims (6)

  On the film substrate, at least one hard coat layer containing translucent particles having an average particle diameter of 5 to 12 μm and a resin, and an inorganic having an average particle diameter of 0.1 μm or less on the hard coat layer It has at least one overcoat layer containing fine particles in an agglomerated state, and further has at least one low refractive index layer thereon, and the average inclination angle θ of the surface irregularity shape of the low refractive index layer is 1 Antireflective film that is ~ 4 °.   The antireflection film according to claim 1, wherein the display contrast characteristic of the antireflection film is 80 or more.   The antireflection film according to claim 1, wherein the inorganic fine particles having an average particle size of 0.1 μm or less are silica fine particles.   The antireflection film according to any one of claims 1 to 3, wherein a difference in refractive index between the translucent particles having an average particle diameter of 5 to 12 µm and the resin is 0.05 or less.   The antireflection film according to claim 1, wherein the low refractive index layer contains hollow silica fine particles.   The antireflective film according to claim 1, wherein the low refractive index layer has a refractive index of 1.20 to 1.40.

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