JP2009025384A - Antireflection film, polarizing plate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antireflection film which prevents glittering, has excellent anti-glare property and hardly causes deterioration of display contrast. <P>SOLUTION: The antireflection film includes: a film base material having roughness on the surface thereof; an anti-glare layer of refractive index n<SB>A</SB>; a hard coat layer of refractive index n<SB>B</SB>having substantially no roughness on the surface of the anti-glare layer; and a low-refractive index layer of refractive index n<SB>C</SB>on the hard coat layer, wherein n<SB>A</SB>, n<SB>B</SB>, n<SB>C</SB>satisfy the following conditions (1), (2): (1) n<SB>C</SB><n<SB>A</SB><n<SB>B</SB>, (2) n<SB>A</SB><SP>1/2</SP>×n<SB>C</SB>≤n<SB>B</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antireflection film that prevents glare, has an excellent antiglare property, and has little reduction in display contrast, and a polarizing plate and an image display device using the same.

In a liquid crystal display (LCD), it is required to prevent a decrease in contrast due to reflection of external light or reflection of an image. For this reason, various antireflection films having antiglare properties and hard coat properties that prevent contrast deterioration due to reflection of external light and reflection of images by arranging them on the surface of the display have been proposed.
However, the technique disclosed in Patent Document 1 has a problem that the antiglare property is insufficient. Furthermore, when applied to liquid crystal panels with a small pixel size, such as full-spec high-definition LCD TVs, it has been found that glare (image distortion and unevenness due to surface irregularities of the antiglare film) tends to deteriorate. It was.
In addition, Patent Document 2 has a coating layer called a surface adjustment layer on an antiglare layer, and is intended to form smooth irregularities by smoothing the irregularities of the antiglare layer. An antireflection film is described in which sea-island uneven shapes are formed on the surface of the surface adjustment layer.
However, the invention described in Patent Document 2 still has a problem that glare is likely to deteriorate.
JP 2007-41533 A JP-A-2005-316450

  An object of the present invention is to provide an antireflection film that prevents glare, has an excellent antiglare property, and has little reduction in display contrast.

  As a result of intensive studies by the inventor, the surface unevenness of the antiglare layer, which is the cause of glare, is covered with a hard coat layer having a flat surface with a higher refractive index, and light at the interface between the antiglare layer and the hard coat layer is covered. The refractive index of the hard coat layer prevents glare by reducing refraction, and the reflection of external light at the antiglare layer-hard coat layer interface is larger than the reflection of external light on the surface of the low refractive index layer. It was found that the antiglare property can be imparted by controlling the above, and the above problems have been solved.

  As a result, since the antireflection film of the present invention can prevent glare and impart antiglare properties, it is possible to design a light scattering of the film that causes a decrease in display contrast, that is, a low haze value. The display contrast of the LCD panel can be maximized by designing the antireflection film.

That is, the above object of the present invention has been achieved by the following means.
[1]
The film substrate has a surface irregularity, has an antiglare layer having a refractive index n _A , and has a refractive index n _B substantially free of surface irregularities on the antiglare layer. A hard coat layer, a low refractive index layer having a refractive index n _C on the hard coat layer, and n _A , n _B , and n _{C satisfy the} following conditions (1) and (2): Antireflection film to fill.
Condition (1); n _C <n _A <n _B
Condition (2); n _A ^1/2 · n _C ≦ n _B
[2]
The antireflection film according to [1], wherein the antiglare layer contains aggregated silica particles.
[3]
Has a surface unevenness, perforated to the side having the surface irregularities on the antiglare film substrate the refractive index n _F, substantially no surface irregularities, the hard coat layer is a refractive index n _B An antireflection film having a low refractive index layer having a refractive index n _C on the hard coat layer and satisfying the following conditions (3) and (4): n _F , n _B , n _C.
Condition (3); n _C <n _F <n _B
Condition (4); n _F ^1/2 · n _C ≦ n _B
[4]
The antireflection film according to any one of [1] to [3], wherein the hard coat layer has a thickness of 1.0 μm or more.
[5]
The antireflection film according to any one of [1] to [4], wherein the value of n _C is 1.31 to 1.40.
[6]
The antireflection film according to any one of [1] to [5], wherein the low refractive index layer contains hollow silica fine particles.
[7]
It is a polarizing plate which has a polarizing film and the protective film provided in the both sides of this polarizing film, Comprising: At least one of this protective film is an antireflection film in any one of [1]-[6] Polarizer.
[8]
The image display apparatus which has the antireflection film in any one of [1]-[6], or the polarizing plate of Claim 7.

Here, the difference between the present invention and the invention described in Patent Document 2 (Japanese Patent Laid-Open No. 2005-316450) will be described.
The present invention and the invention described in Patent Document 2 are that the invention described in Patent Document 2 has a coating layer called a surface adjustment layer on the antiglare layer, and the present invention is hard on the antiglare layer. This is the same in that it has a coating layer called a coat layer.
However, the surface adjustment layer described in Patent Document 2 is intended to form smooth unevenness by applying smoothing to the unevenness of the antiglare layer, as described in paragraph [0041] of Patent Document 2. Furthermore, it is described from the result of evaluation 1 of the example of Patent Document 2 that the surface of the surface adjustment layer has a sea-island uneven shape.
The present invention is different from the prior art in this point because the hard coat layer, which is a coating layer, is a layer having substantially no surface unevenness. In the present invention, if the surface of the hard coat layer has an uneven shape, it causes glare deterioration, so the hard coat layer has a structure that does not have an uneven shape, and the surface uneven shape with an air interface is eliminated as much as possible. This technology prevents glare.
In Example 9 of Patent Document 2, the refractive index of the antiglare layer is 1.51, and the refractive index of the surface adjustment layer containing the high refractive index agent is 1.60. The condition (1) of the invention can be satisfied. Although the refractive index of the low-refractive index layer in the example of Patent Document 2 is not described, the refractive index of the low-refractive index layer is assumed if the aspect of Example 9 of Patent Document 2 also satisfies the condition (2) of the present invention. Is calculated back to 1.30 or less. This refractive index is a refractive index that cannot be reached from the current practical technical level, and it is appropriate that Example 9 of Patent Document 2 does not satisfy the condition (2) of the present invention. . Condition (2) of the present invention means that the reflectance at the interface between the antiglare layer and the hard coat layer is equal to or higher than the reflectance at the low refractive index layer (and the air interface), as will be described later. It is a condition that positively reflects the external light with the uneven shape at the interface between the antiglare layer and the hard coat layer, thereby expressing the antiglare property.

  According to the present invention, it is possible to obtain an antireflection film that prevents glare, is excellent in antiglare properties, and has little reduction in display contrast.

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

[Layer structure of antireflection film]
As shown in FIG. 1, the antireflection film of the present invention has at least one antiglare layer on a transparent film substrate (hereinafter also referred to as “support”), and at least one layer thereon. A hard coat layer and at least one low refractive index layer thereon, or at least one hard coat layer on the anti-glare film substrate, as shown in FIG. And at least one low refractive index layer. Moreover, according to the objective, another functional layer can be provided individually or in multiple layers.

As one preferred embodiment, an antireflection film laminated on the film 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 can be mentioned. . The antireflection film is composed of an antiglare layer having the same refractive index as that of the base material, a hard coat layer having a higher refractive index than the antiglare layer, and a low refractive index layer having a lower refractive index than the base material. To do.
The antiglare layer and the hard coat layer, or the antiglare film substrate and the hard coat layer are preferably adjacent to each other.

The example of the preferable layer structure of the antireflection film of this invention is shown below. In the following configuration, the film substrate refers to a support composed of a film.
-Film substrate / Anti-glare layer / Hard coat layer / Low refractive index layer- Anti-glare film substrate / Hard coat layer / Low refractive index layer- Film substrate / Antistatic layer / Anti-glare layer / Hard coat Layer / low refractive index layer Antiglare film substrate / hard coat layer / antistatic 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.

A specific condition that the refractive index of each layer in the present invention satisfies will be described.
The specific conditions described above satisfying the refractive index of the antiglare layer: n _A , the refractive index of the hard coat layer: n _B, and the refractive index of the low refractive index layer: n _C are the following conditions (1) and (2): is there.
Condition (1); n _C <n _A <n _B
Condition (2); n _A ^1/2 · n _C ≦ n _B
Moreover, the specific conditions that the refractive index of the antiglare film substrate: n _F , the refractive index of the hard coat layer: n _B , and the refractive index of the low refractive index layer: n _C satisfy the following conditions (3) and (4) It is.
Condition (3); n _C <n _F <n _B
Condition (4); n _F ^1/2 · n _C ≦ n _B
Conditions (1) and (3) indicate the relative relationship of the refractive indexes of the antiglare layer (or antiglare film substrate), the hard coat layer, and the low refractive index layer.
Condition (2) is that the reflectance R ₁ of perpendicular incident light at the interface between the antiglare layer (or antiglare film substrate) and the hard coat layer is as follows:
R ₁ = (n _B −n _A / n _B + n _A ) ²
And the reflectivity R ₂ of the normal incidence light of the low refractive index layer (and the air interface) is R ₂ = (n _B −n _C ² / n _B + n _C ² ) ²
Given by
Inequality R ₂ ≦ R ₁
Is solved for n _B to obtain condition (2).
Similarly, if n _A is replaced with n _F , the condition (4) can also be obtained.
That is, the conditions (2) and (4) indicate that the reflectance of normal incident light at the interface between the antiglare layer (or antiglare film substrate) and the hard coat layer is that of the low refractive index layer (and air interface). This means that the reflectance of the normal incident light is equal to or greater than that. By satisfying this condition, external light reflection at the interface between the antiglare layer (or antiglare film substrate) and the hard coat layer is antiglare. Gives sex.
The refractive index n _B preferably has a value of n _B / n _A or n _B / n _F close to 1 in order to prevent glare, and further satisfies n _B ≦ n _C ² in order to exhibit antiglare properties. It is preferable.

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 n _C of the low refractive index layer is preferably 1.30 to 1.50, particularly preferably 1.30 to 1.45, and more preferably 1.31 to 1.40. Most preferred.
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 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)
As the ethylenically unsaturated group in the fluorine-containing compound having an ethylenically unsaturated group used as a constituent material of the low refractive index layer, specifically, the terminal is vinyl group, allyl group, acrylolyl group, methacryloyl group, isopropenyl group. In other words, an acrylolyl group and a methacryloyl group are 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 is a number average molecular weight in terms of polystyrene measured by gel permeation chromatography (hereinafter referred to as GPC) using tetrahydrofuran (hereinafter referred to as THF) as a solvent. 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.

  As the polymer as the fluorine-containing compound having an ethylenically unsaturated group, which is preferable in the present invention, specifically, a polymer by a known technique can be used. For example, JP-A-2005-89536 and JP-A-2005 Examples thereof include an ethylenically unsaturated group-containing fluoropolymer described in Japanese Patent No. 290133 and Japanese Patent Application Laid-Open No. 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 preferably 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.

In the hollow silica fine particles, the radius r _i of the cavity inside the _particle, and the radius of the outer shell of the particle is r _o, the porosity x is calculated by the following equation.
^{_{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. Therefore, the low refractive index is less than 1.17 from the viewpoint of scratch resistance. 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.

[Hard coat layer]
In the present invention, the hard coat layer is in a lower layer than the low refractive index layer of the antireflection film, and is in an upper layer than the antiglare layer (or the antiglare film substrate).
The refractive index n _B of the hard coat layer needs to satisfy both of the conditions (1) and (2) or both of the conditions (3) and (4), but the value is 1.65 to 1.90. It is preferable that it is 1.70-1.90.

  The thickness of the hard coat layer is preferably such that no optical interference occurs, preferably 1.0 μm or more, more preferably 2.0 μm or more, and 2.0 to 5.0 μm. Most preferred.

Next, the constituent material of the hard coat layer will be described. The hard coat layer is preferably composed of metal oxide fine particles and a resin.
(Metal oxide fine particles)
The metal oxide fine particles as a constituent material of the hard coat layer are high refractive index materials for adjusting the refractive index so as to satisfy the conditions (1) and (2), and in particular, titanium oxide fine particles or zirconium oxide fine particles. Is preferably used.
The average particle diameter of the high refractive index metal oxide fine particles is preferably in the range of 3 to 100 nm, and particularly preferably 5 to 50 nm. The average particle diameter of the metal oxide fine particles having a high refractive index can be obtained by measurement using an electron micrograph.
The metal oxide fine particles having a high refractive index are preferably contained in an amount of 50 to 95% by mass, more preferably 60 to 90% by mass, based on the total solid content of the hard coat layer.

(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.

  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, tetradecanethylene 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 addition to the above-mentioned components, other components such as a polymerization initiator can be added to the hard coat layer as long as the desired effects of the present invention are not impaired.
In the present invention, the hard coat layer is a layer that is substantially free of irregularities on the surface, but this “substantially no irregularities on the surface” means that the average roughness (Ra) is 0.02 μm or less. It means that there is.
If a material for forming surface irregularities such as translucent fine particles is not added to the hard coat layer, it can be easily controlled within such a range.

[Anti-glare layer]
In the present invention, the antiglare layer is in a lower layer than the hard coat layer and has irregularities on the surface.
Here, “having irregularities on the surface” means that the arithmetic average roughness (Ra) is 0.03 μm or more, preferably 0.05 to 0.20 μm, and average irregularities The period (RSm) is preferably 5.0 to 100 μm, more preferably 10 to 80 μm.
The arithmetic average roughness (Ra) can be measured by a commercially available stylus type surface roughness measuring instrument based on JIS standard B0601: 2001, and the average irregularity period (RSm) is based on JIS standard B0601: 2001, It can be measured with a commercially available stylus type surface roughness measuring instrument.
Examples of the method of controlling within such a range include a method using phase separation (spinodal decomposition), which will be described later, and a method of adding agglomerated metal oxide fine particles as translucent fine particles.

In the present invention, the antiglare layer can be formed using a conventionally known technique in order to form surface irregularities necessary for the antiglare property. Preferably, a method of forming (inducing) the concavo-convex structure by phase-separating a plurality of resins can be used. As a manufacturing method for phase-separating a plurality of resins, for example, a method in which a plurality of incompatible polymers are dissolved in a solvent and a liquid-liquid phase separated solution is applied to a sea-island structure and dried, or a common solvent is used. And a method of forming a concavo-convex structure by applying a solution in which a plurality of incompatible polymers are compatible with each other and performing phase separation (spinodal decomposition) upon drying.
Examples of the resin that can be used in this case include a combination of a curable acrylic acid polymer and a cellulose polymer such as cellulose acetate propionate.
The blending ratio of each resin is preferably 9: 1 to 6: 4.

Further, the antiglare layer may be configured to contain translucent fine particles and a curable resin as main components.
(Translucent fine particles)
The translucent fine particles are components used for forming surface irregularities necessary for antiglare properties, and examples thereof include aggregated metal oxide particles. Moreover, in the case of use, it can be used 1 type or in mixture of 2 or more types. Aggregated metal oxide particles are particularly preferably agglomerated silica particles and agglomerated alumina particles. Among them, agglomerated silica in which particles having a primary particle diameter of several tens of nanometers form an aggregate, This is preferable in that moderate surface irregularities can be stably formed. Agglomerated silica can be obtained, for example, 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 sedimentation method and a gelation method, and the present invention may be any method. The secondary particle size of the agglomerated silica is preferably in the range of 0.1 to 10.0 μm, but is selected in combination with the layer thickness of the antiglare layer containing the particles. The adjustment of the secondary particle size is performed by the degree of particle dispersion (control by mechanical dispersion using a sand mill or the like, or chemical dispersion using a dispersant or the like). In particular, the value obtained by dividing the secondary particle diameter of the agglomerated silica particles by the thickness of the hard coat layer containing the same is preferably 0.1 to 2.0, and preferably 0.3 to 1.0. Is more preferable.
The secondary particle diameter of the aggregated silica particles is measured by a Coulter counter method.
In order to form desired irregularities on the surface, it is preferable that the aggregated silica particles are contained in an amount of 0.1% by mass to 50% by mass with respect to the total solid content of the antiglare layer, and 1% by mass to 50% by mass. % Is more preferable, and 1% by mass to 30% by mass is even more preferable.

The refractive index n _A of the antiglare layer needs to satisfy both the conditions (1) and (2), but the value is preferably 1.45 to 1.55.

  The thickness of the antiglare layer is preferably such that no optical interference occurs, preferably 1.0 μm or more, more preferably 2.0 μm or more, and 2.0 to 10.0 μm. Most preferably it is.

(resin)
In the present invention, the antiglare layer contains a resin. The curable resin used to form the antiglare layer can be cured by the 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 a polyfunctional monomer, the thing similar to what is used with the said hard-coat layer can be mention | raise | lifted.

In the present invention, the addition amount of these curable resins is preferably 10 to 90 mass%, more preferably 30 to 90 mass%, most preferably 40 to 80 mass% with respect to 100 mass% of the solid content of the antiglare layer. preferable.
In addition to the above-described components, other components such as a polymerization initiator can be added to the antiglare layer in a range that does not impair the desired effect of the present invention.

[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; a film made of 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 substrate may be the polarizer itself. 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.

The refractive index n _F of the film substrate is usually preferably 1.45 to 1.55. Moreover, when there exists an anti-glare layer, it is preferable that the refractive index difference of an anti-glare layer and a film base material is 0.02 or less.

Moreover, in the antireflection film of the present invention, the antiglare film substrate having surface irregularities used in place of the above-mentioned film substrate and antiglare layer forms irregularities on the surface of the above film substrate. A film or the like can be used.
Conventional means can be arbitrarily used as the means for forming the surface irregularities of the antiglare film base material, but it is particularly preferable to perform surface processing means for the film base material using an embossed plate. -333936 and JP-A 2004-341070 can be referred to.

[Method for forming each layer]
(Application method)
Each layer of the antireflection film of the present invention can be formed by applying the composition for forming each layer 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. The transport speed of the support is preferably 0.5 to 100 m / min, and more preferably 1 to 50 m / min.

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 amount of wet coating is small (20 cc / m ² or less).

(Curing method)
In the present invention, the antireflection film on which each layer has been applied and dried 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.

[Characteristics of antireflection film]
(Haze)
The haze value of the antireflection film of the present invention is preferably 0% to 20% or less, more preferably 0% to 15%, and most preferably 0% to 10%. When the haze value exceeds 20%, the display contrast is remarkably deteriorated and is not suitable for the use of the image display apparatus.
About the haze value of this invention, the total haze value of the obtained optical film is measured according to JIS-K7136.

(Display contrast)
In the present invention, the display contrast refers to the display contrast in a bright place. The contrast ratio (brightness in white display / brightness in black display) measured in the bright place environment shown in the examples is calculated by the following formula. Value.
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.

(Polarizer)
The polarizing plate of the present invention is a polarizing plate having a polarizing film and protective films provided on both sides of the polarizing film, and at least one of the protective films is the antireflection film of the present invention. For example, an adhesive layer can be provided on one side of the optical film of the present invention and disposed on the outermost surface of the display.

(Image display device)
The antireflection film of the present invention is preferably used as a surface film of a screen of an image display device such as a liquid crystal panel.
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 the liquid crystal is switched by applying a horizontal electric field, 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.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not restrict | limited to these.

The compounds used in this example are shown below.
-Fluoropolymer The methacryl-modified fluoropolymer (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%.

Curing 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.]

-Agglomerated silica particles: secondary agglomerated diameter 2.0 μm [manufactured by Tosoh Silica Co., Ltd.]
・ Zirconium oxide fine particles “Nano Zirconia” [manufactured by Sumitomo Osaka Cement Co., Ltd.] Size 7 nm

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

<Preparation of antireflection film>
[Example 1]
With the configuration shown in Table 1, antireflection film samples (101) to (106) shown in Table 1 were prepared by the following manufacturing method.

[Coating solution adjustment]
[Anti-glare layer]
・ Anti-glare layer coating solution AG1
A methyl isobutyl ketone solution was prepared by adding 85% by mass of UV curable resin “DPHA”, 5% by mass of photopolymerization initiator “Irgacure 184” and 10% by mass of aggregated silica particles having a secondary aggregation diameter of 2.0 μm.
The solid content concentration of the coating solution for the antiglare layer was adjusted to 40% by mass, and the amount added was described assuming that the total solid content was 100% by mass.

・ Anti-glare layer coating solution AG2
Methyl to which 75% by mass of UV curable resin “DPHA”, 5% by mass of photopolymerization initiator “Irgacure 184”, 20% by mass of crosslinked acrylic particles (MX-500 manufactured by Soken Chemical Co., Ltd.) having an average particle size of 5 μm are added. An isobutyl ketone solution was prepared.
The solid content concentration of the coating solution for the antiglare layer was adjusted to 40% by mass, and the amount added was described assuming that the total solid content was 100% by mass.

[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, according to Table 1, zirconium oxide fine particles (manufactured by Sumitomo Osaka Cement Co., Ltd.) 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.

[Low refractive index layer]
・ Low refractive index coating liquid LN1
As a fluorine-containing polymer having an ethylenically unsaturated group, 50.0% by mass in terms of solid content of the methacryl-modified fluorine-containing polymer (A-1) and 49. 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 1.36.

[Coating method of antireflection film]
As a film base material, a triacetyl cellulose film “TAC-TD80U” (manufactured by Fuji Film Co., Ltd.) (thickness 80 μm) is unwound in a roll form, and a coater having a throttle die is used. The coating liquid for application was directly extruded 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 a dose of 90 mJ / cm ² to cure and wind up the coating layer. The dry film thickness of the antiglare layer is shown in Table 1.

Further, the hard coat layer coating solution was applied onto the antiglare 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. The applied 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 hard coat layer.

On the hard coat layer of the laminated film obtained as described above, using the coater having a throttle die, the above-described coating solution for the low refractive index layer was applied, and drying: 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 having 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.
Moreover, about the anti-glare layer and the hard-coat layer, arithmetic mean roughness (Ra) and average uneven | corrugated period (RSm) were measured, respectively. The results are shown in Table 1.

  Each antireflection film was evaluated by the following evaluation methods.

〔Evaluation methods〕
[Surface haze]
The total haze value of the obtained antireflection film was measured according to JIS-K7136.
[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.

[Evaluation of anti-glare properties]
On the sample piece for measuring the average inclination 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.
◎: Level at which the outline of the fluorescent lamp is not known at all ○: Level at which the outline of the fluorescent lamp is slightly understood △: Level at which the fluorescent lamp is blurred but the outline can be identified ×: Level at which the 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 an antireflection film from the viewing side polarizing plate of 32-inch full high-definition liquid crystal television “LC-32GS10” {manufactured by Sharp Corporation} (number of pixels; 1920 × 1080), Pasted.
(3) For the mounted liquid crystal television, set the receiver “SPECTRORADIOMETER CS1000A” {manufactured by Konica Minolta Co., Ltd.} 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) Using the antireflection film (101) as a reference value, the contrast ratio was measured by the methods (1) to (5), and the value was normalized to 100.

[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, each of the antireflection films (101) to (104) is an example in which a hard coat layer is provided on the antiglare layer.
As is clear from the results shown in Table 1, the antireflection films (101) and (102) of the comparative examples that do not satisfy either one of the conditions (1) and (2) are substantially free of surface irregularities. The antiglare property is at an unacceptable level due to the reflected light at the refractive index layer / air interface. On the other hand, the antireflection films (103) and (104) of the present invention satisfying both the conditions (1) and (2) are more antiglare layer / hard coat than reflected light at the low refractive index layer / air interface. Since the reflected light at the layer interface is large, the antiglare property is evaluated well due to the effect of the antiglare layer.
On the other hand, the antireflection films (105) and (106) of the comparative examples are a combination of only the antiglare layer and the low refractive index layer of the prior art, but (105) has a low haze value and scattering of transmitted light. Is low, the display contrast is high, but glare is not allowed due to the surface irregularities of the antiglare layer. Further, since (106) has a high haze value and high scattering of transmitted light, glare due to surface irregularities of the antiglare layer is reduced, but the display contrast is low and unacceptable.
The antireflection film of the present invention has a low haze value and low scattering of transmitted light, so that the display contrast is high, and the surface unevenness of the antiglare layer is covered with a hard coat layer, so that transmitted light due to the unevenness is transmitted. It can be seen that the refraction of the film becomes smaller and glare is less likely to occur.

[Example 2]
(Production of embossed roller E)
The surface of an S45C cored metal roll having a diameter of 20 cm and a width of 12 cm was subjected to plating treatment to obtain a hard chromium layer having a thickness of 50 μm. The electrode material was brass, and electric discharge machining was performed at a voltage of 70 V to obtain an embossed roller E having an arithmetic average roughness (Ra) of 0.13 μm, an average unevenness period (RSm) of 12 μm, and a surface hardness of 900 Hv.

(Production of anti-glare film substrate F)
Using an embossing calendar machine (manufactured by Yuri Roll Co., Ltd.) on one side of a cellulose triacetate film (trade name; TAC-TD80U, manufactured by Fuji Film Co., Ltd.) having a thickness of 80 μm, a linear pressure of 5.00 × 10 ³ The embossing roller E and the backup roller having the same structure that is not processed by the plate under the conditions of N / cm, the preheating temperature is normal temperature, the embossing roller temperature is 120 ° C., the backup roller 23 is normal temperature, and the conveyance speed is 1 m / min. The press operation was performed and the anti-glare film base material F was produced.
The obtained antiglare film substrate F had an arithmetic average roughness (Ra) of 0.12 μm and an average unevenness period (RSm) of 13 μm.

The hard coat layer having the structure shown in Table 2 and then the low refractive index layer having the structure shown in Table 2 were applied on the surface uneven surface of the obtained antiglare film substrate F in the same manner as in Example 1, and dried. Cured to prepare antireflection films (201) to (204).
The arithmetic average roughness (Ra) of the hard coat layer was 0.02 μm or less, and the average unevenness period (RSm) could not be measured accurately.
The composition ratio of each layer is shown in Table 2 with the component ratios described with the total solid content of each layer being 100% by mass.
The obtained antireflection films (201) to (204) were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

The results in Table 2 are examples in which surface irregularities are formed on the transparent substrate itself, and a hard coat layer and a low refractive index layer are applied thereon.
The antireflection films (201) and (202) of the comparative examples that do not satisfy one of the conditions (1) and (2) are prevented by the reflected light of the low refractive index layer / air interface that is substantially free of surface irregularities. Dazzle is at an unacceptable level. On the other hand, the antireflection films (203) and (204) of the present invention satisfying both the conditions (1) and (2) are antiglare layers / hard coats rather than the reflected light at the low refractive index layer / air interface. Since the reflected light at the layer interface is large, the antiglare property is evaluated well due to the effect of the antiglare layer.

[Example 3]
[Anti-glare layer]
According to Table 3, a predetermined amount of UV curable resin “DPHA”, photopolymerization initiator “Irgacure 184”, PMMA particles having an average particle diameter of 4.6 μm and PMMA particles having an average particle diameter of 3.5 μm were added, and methyl isobutyl ketone was added. Add the solution and stir, and finally add a hydrophobic styrene acrylic polymer (average molecular weight: 65,000) and stir to adjust the solid content concentration of the antiglare layer to 40% by mass to complete the coating solution did.
The addition amount of the coating solution for the antiglare layer is shown in Table 3 assuming that the total solid content of the antiglare layer is 100% by mass.

For the hard coat layer and the low refractive index layer, a coating solution was prepared as described in Table 3, and antireflection films 301 to 303 were produced in the same manner as in Example 1.
Moreover, it evaluated similarly to Example 1 with respect to the antireflection films 301-303. The results are shown in Table 3.

Comparative examples 301 and 302 reproduce the antiglare layer of Example 9 described in JP-A-2005-316450, on which a hard coat layer and a low refractive index layer are coated, It was produced so as to satisfy the conditions (1) and (2). In Samples 301 and 302, the PMMA particles of the antiglare layer form a three-dimensional three-dimensional aggregate due to the action of the styrene acrylic polymer added to the antiglare layer, and the surface of the hard coat layer has an uneven shape. Have. On the other hand, the sample 303 of the present invention did not add a styrene acrylic polymer, so it did not form an agglomerated portion of a three-dimensional structure, and the surface of the hard coat layer did not have an uneven shape.
From the evaluation results of Table 3, the samples 301 and 302 of the comparative example were deteriorated in glare due to the surface unevenness of the hard coat layer, and the sample 303 of the present invention was excellent in glare. From this, it can be seen that the prior art and the present invention differ in configuration and effect.

It is sectional drawing which shows typically one preferable embodiment of the antireflection film of this invention. It is sectional drawing which shows typically one preferable embodiment of the antireflection film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Low refractive index layer 2 Hard-coat layer 3 Anti-glare layer 4 Film base material 5 Anti-glare film base material

Claims (8)

The film substrate has a surface irregularity, has an antiglare layer having a refractive index n _A , and has a refractive index n _B substantially free of surface irregularities on the antiglare layer. A hard coat layer, a low refractive index layer having a refractive index n _C on the hard coat layer, and n _A , n _B , and n _C satisfy the following conditions (1) and (2): Antireflection film.
Condition (1); n _C <n _A <n _B
Condition (2); n _A ^1/2 · n _C ≦ n _B   The antireflection film according to claim 1, wherein the antiglare layer contains aggregated silica particles. Has a surface unevenness, perforated to the side having the surface irregularities on the anti-glare film substrate the refractive index n _F, substantially no surface irregularities, the hard coat layer is a refractive index n _B An antireflection film having a low refractive index layer having a refractive index n _C on the hard coat layer, and n _F , n _B , and n _C satisfy the following conditions (3) and (4).
Condition (3); n _C <n _F <n _B
Condition (4); n _F ^1/2 · n _C ≦ n _B   The antireflection film according to claim 1, wherein the hard coat layer has a thickness of 1.0 μm or more. The antireflection film according to claim 1 value of the _{n C} is 1.31 to 1.40.   The antireflection film according to any one of claims 1 to 5, wherein the low refractive index layer contains hollow silica fine particles.   A polarizing plate having a polarizing film and protective films provided on both sides of the polarizing film, wherein at least one of the protective films is the antireflection film according to claim 1. .   The image display apparatus which has the antireflection film in any one of Claims 1-6, or the polarizing plate of Claim 7.

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