JP2015031749A - Optical laminate, polarizing plate and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical laminate that has excellent antireflection performance and anti-coloring performance and can give an image display device with high display qualities.SOLUTION: The optical laminate includes an optical functional layer and a low refractive index layer, disposed in this order on one surface of a light-transmitting substrate. The low refractive index layer has irregular thickness and a rugged pattern on a surface thereof; and in the rugged pattern on the surface of the low refractive index layer, an arithmetic average roughness Ra is 0.01 to 0.05 μm at a cutoff wavelength of 0.25 mm in a rugged portion in accordance with JIS B0601-1994. A thin film portion of the low refractive index layer is present in a protruding portion of the surface of the low refractive index layer, while a thick film portion of the low refractive index layer is present in a recessed portion of the low refractive index layer, with a difference in the film thickness between the thin film portion and the thick film portion of the low refractive index layer satisfying an expression of d≥0.18×d. In the expression, drepresents a difference (nm) in the thickness between the thin film portion and the thick film portion of the low refractive index layer; and drepresents an average film thickness (nm) of the low refractive index layer.

Description

The present invention relates to an optical laminate, a polarizing plate, and an image display device.

Image display surface in image display devices such as cathode ray tube display (CRT), liquid crystal display (LCD), plasma display (PDP), electroluminescence display (ELD), field emission display (FED), touch panel, electronic paper, tablet PC However, it is required to reduce the reflection due to the light rays emitted from the external light source and to improve the visibility. On the other hand, it is common to reduce the reflection of the image display surface of the image display device and improve the visibility by using an optical layered body in which an antireflection layer is formed on the light transmissive substrate. Has been done.

As an optical laminated body having an antireflection layer, a structure in which a low refractive index layer having a refractive index lower than that of a light-transmitting substrate is provided on the outermost surface has been known.
As an optical laminated body in which such a low refractive index layer is formed on the outermost surface, for example, Patent Document 1 has a low refractive index layer containing hollow silica fine particles, a fluorine atom-containing polymer, and an antifouling agent. An optical laminate is disclosed.

However, in recent years, the display quality required for the image display apparatus has become very high, and the optical characteristics required for the optical laminate provided on the image display surface are also extremely high. It is coming.
However, in the conventional optical laminated body provided with the low refractive index layer, coloring may occur in the low refractive index layer, and it is not possible to sufficiently meet the recent demand for high display quality of image display devices. It was.

JP 2007-301970 A

In view of the above situation, the present invention provides an optical laminate that is excellent in antireflection performance and anti-coloring performance, and that can provide an image display device with high display quality, a polarizing plate and an image display using the optical laminate. The object is to provide an apparatus.

The present invention is an optical laminate in which an optical functional layer and a low refractive index layer are provided in this order on one surface of a light-transmitting substrate, and the low refractive index layer has a non-uniform thickness. The surface of the low refractive index layer has a concavo-convex shape, and the concavo-convex shape of the concavo-convex portion has an arithmetic average roughness Ra of 0.01 to 0.25 mm according to JIS B0601-1994. 0.05 μm, a thin film portion of the low refractive index layer is present on the convex portion of the surface of the low refractive index layer, and a thick film portion of the low refractive index layer is formed on the concave portion of the surface of the low refractive index layer. And the difference in thickness between the thin film portion and the thick film portion of the low refractive index layer satisfies the following formula.
d _D ≧ 0.18 × d _A
In the above formula, d _D represents the thickness difference (nm) between the thin film portion and the thick film portion of the low refractive index layer, and d _A represents the average film thickness (nm) of the low refractive index layer.

In the optical layered body of the present invention, the uneven shape on the surface of the low refractive index layer is such that when the average inclination angle of the uneven portion is θa and the skewness of the uneven portion is Sk, the absolute value of Sk and θa are the following formulas: It is preferable to satisfy.
0.05 ° ≦ θa ≦ 0.15 °
| Sk | ≦ 0.5

This invention is also a polarizing plate provided with a polarizing element, The said polarizing plate is also a polarizing plate characterized by providing the above-mentioned optical laminated body on the polarizing element surface.
The present invention is also an image display device including the above-described optical layered body or the above-described polarizing plate.
The present invention is described in detail below.
In the present invention, unless otherwise specified, curable resin precursors such as monomers, oligomers, and prepolymers are also referred to as “resins”.

As a result of intensive studies on the optical laminate in which the optical functional layer and the low refractive index layer are provided in this order on one surface of the light-transmitting substrate, the present inventors configured the outermost surface of the optical laminate. When the low refractive index layer has a predetermined thickness difference and has a thin film portion and a thick film portion, that is, the low refractive index layer has a predetermined size variation in the thickness, As a result, it was found that the coloring can be suitably prevented, and the present invention has been completed.

The present invention is an optical laminate in which an optical functional layer and a low refractive index layer are provided in this order on one surface of a light-transmitting substrate.
The light transmissive substrate preferably has smoothness and heat resistance and is excellent in mechanical strength. Specific examples of the material forming the light-transmitting substrate include, for example, polyester (polyethylene terephthalate, polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyester, polyamide, polyimide, polyethersulfone, poly Examples thereof include thermoplastic resins such as sulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, and polyurethane, and glass. Preferably, polyester (polyethylene terephthalate, polyethylene naphthalate) and cellulose triacetate are used.

The light-transmitting substrate is preferably used as a flexible film-like material, but a plate-like material may be used depending on the use mode in which curability is required. .

In addition, examples of the light transmissive substrate include an amorphous olefin polymer (Cyclo-Olefin-Polymer: COP) film having an alicyclic structure. This is a base material in which a norbornene polymer, a monocyclic olefin polymer, a cyclic conjugated diene polymer, a vinyl alicyclic hydrocarbon polymer, and the like are used. Zeonoa (norbornene resin), Sumitrite FS-1700 manufactured by Sumitomo Bakelite, Arton (modified norbornene resin) manufactured by JSR, Appel (cyclic olefin copolymer) manufactured by Mitsui Chemicals, Topas (cyclic) manufactured by Ticona Olefin copolymer), Optretz OZ-1000 series (alicyclic acrylic resin) manufactured by Hitachi Chemical Co., Ltd., and the like.
Further, the FV series (low birefringence, low photoelastic modulus film) manufactured by Asahi Kasei Chemicals is also preferable as an alternative base material for triacetylcellulose.

In the case of a film-like body, the thickness of the light transmissive substrate is preferably 20 to 300 μm, more preferably the lower limit is 30 μm and the upper limit is 200 μm. When the light-transmitting substrate is a plate-like body, the thickness may exceed these thicknesses.
The light-transmitting substrate has an anchor agent or primer in addition to a physical or chemical treatment such as corona discharge treatment or oxidation treatment in order to improve adhesion when the hard coat layer is formed thereon. Application | coating of a coating called may be performed previously.
In addition, when triacetylcellulose, which is often used mainly as a light-transmitting substrate for LCD, is used as a material and a display thin film is desired, the thickness of the light-transmitting substrate is preferably 20 to 65 μm. .

The optical layered body of the present invention has a low refractive index layer.
The low refractive index layer is a layer that plays a role of reducing the reflectance when light from the outside (for example, a fluorescent lamp, natural light, etc.) is reflected on the surface of the optical laminate.
The low refractive index layer is preferably provided on the outermost surface of the optical laminate of the present invention, and the optical laminate of the present invention having such a low refractive index layer reduces reflection from the surroundings. , The transmittance can be improved.

In the optical layered body of the present invention, the low refractive index layer is non-uniform in thickness and has an uneven shape on the surface.
Such an uneven shape on the surface of the low refractive index layer is formed by providing an uneven shape on the surface of the optical functional layer described later, and providing a low refractive index layer so as to follow the uneven shape on the surface of the optical functional layer. can do. The uneven shape of the surface of the low refractive index layer formed in this way is such that the thin film portion of the low refractive index layer exists on the convex portion of the surface of the low refractive index layer, and the thick film portion of the low refractive index layer. Is present in the recesses on the surface of the low refractive index layer, and the thickness of the low refractive index layer can be made non-uniform.

Moreover, the uneven | corrugated shape of the surface of the said low-refractive-index layer is 0.01-0.05 micrometer in arithmetic mean roughness Ra in 0.25-mm cut-off wavelength by JISB0601-1994 of an uneven | corrugated | grooved part. If the cut-off wavelength is 0.25 mm, the reference length is also 0.25 mm, and if Ra has a significant size, then the uneven spacing, that is, the thickness of the low refractive index layer is not uniform. Is generated within 0.25 mm. Due to the non-uniformity of the thickness of the low refractive index layer in such a range, the difference in color due to the difference in thickness of the low refractive index layer appears to be mixed with the naked eye, and the optical laminate is colored. It is no longer observed with the naked eye. If the Ra is less than 0.01 μm, the effect of the coloring of the optical laminate not being observed with the naked eye is insufficient. If the Ra exceeds 0.05 μm, the optical laminate of the present invention has a cloudiness or the like. End up.

In the optical layered body of the present invention, the low refractive index layer has a non-uniform thickness.
When the average thickness of the low refractive index layer is d _A (nm) and the refractive index is n _A , the thickness of the low refractive index layer is uniform (that is, the thickness is uniform at d _A ). Since the spectral spectrum of the reflectance of the refractive index layer draws a curve with the wavelength λ satisfying d _A = λ / (4n _A ) as the bottom, a wavelength with a low reflectance and a high wavelength appear. The low refractive index layer will be colored. On the other hand, if the thickness of the low refractive index layer is not uniform, the wavelength λ satisfying the above formula: d _A = λ / (4n _A ) varies depending on the thickness of the low refractive index layer, and as a result, reflection for each wavelength. Since the rate is averaged, the difference in reflectance due to wavelength can be reduced. Thereby, coloring of the low refractive index layer can be suppressed. Specifically, when the low refractive index layer is distributed so that λ is about ± 50 nm or more as the thin film portion and the thick film portion, the low refractive index layer can be effectively imparted with anti-coloring properties. .
That is, the low film of the thin portion of the refractive index layer thickness _{d L = (λ-50)} / (4n A) thickness of the thick portion and the _{d H = (λ + 50)} / (4n A) Thickness difference between _{d D} Satisfies the following formula:
d _D ≧ d _A × 100 / λ
Furthermore, since λ is usually about 550 nm, which is the center of the visible light region (400 to 700 nm), the optical laminate of the present invention satisfies the following formula.
d _D ≧ 0.18 × d _A

Further, when the film thickness of the low refractive index layer to greater than the visible light region is distributed, there is a possibility that the anti-reflection property is poor, the d _D preferably satisfies the following equation.
d _D ≦ d _A × 400 / λ
The optical layered body of the present invention preferably satisfies the following formula, where λ is 550 nm, which is the center of the visible light region.
d _D ≦ 0.72 × d _A
That is, the low refractive index layer has a variation in thickness, but the thin film portion and the thick film portion have a specific relationship to be described later, so that the image display provided with the optical laminate of the present invention is installed. The apparatus has excellent anti-coloring performance in addition to anti-reflection performance.
In the present specification, the “thin film portion” means a portion where the thickness of the low refractive index layer is thin, and specifically means a portion where the thickness is in the range of 5 nm or more thinner than the average film thickness. Further, the “thick film portion” means a portion where the thickness of the low refractive index layer is thick, and specifically means a portion where the thickness is in the range of 5 nm or more thicker than the average film thickness. Actually, when the low-refractive-index layer is observed with an optical microscope reflection so that there is no reflection from the back surface by attaching a black acrylic plate to the back surface, the thin film portion and the thick film portion are different in color. As observed. Therefore, about each color part, the thickness of a thin film part and a thick film part can be measured by measuring and averaging the thickness of ten low refractive index layers from a cross-sectional electron micrograph. The average film thickness will be described later.

In the optical layered body of the present invention, as described above, the difference in thickness (d _D ) between the thin film portion and the thick film portion of the low refractive index layer is 0.18 × d _A nm or more. If it is less than 0.18 × d _A nm, the anti-coloring performance of the low refractive index layer will be insufficient. The preferable lower limit of the thickness of the thin film portion and the thick film portion is 0.27 × d _A nm, and the more preferable lower limit is 0.36 × d _A nm. Further, since the antireflection performance may be inferior, the low refractive index. The difference in thickness (d _D ) between the thin film portion and the thick film portion of the layer is preferably 0.72 × d _A nm or less, and a more preferable upper limit is 0.63 × d _A nm.

The low refractive index layer is preferably 1) a resin containing low refractive index particles such as silica and magnesium fluoride, 2) a fluorine-based resin which is a low refractive index resin, and 3) silica or magnesium fluoride. Fluorine-based resin, 4) A thin film of a low refractive index material such as silica or magnesium fluoride. As for the resin other than the fluorine-based resin, a resin similar to the binder resin constituting the hard coat layer described later can be used.
Moreover, it is preferable that the silica mentioned above is a hollow silica fine particle, and such a hollow silica fine particle can be produced by, for example, a production method described in Examples of JP-A-2005-099778.
These low refractive index layers preferably have a refractive index of 1.45 or less, particularly 1.42 or less.

In the optical layered body of the present invention, the thickness of the low refractive index layer is not particularly limited as long as it has the above-described thin film portion and thick film portion, and the average film thickness is usually 30 nm to 1 μm. What is necessary is just to set suitably so that it may become a grade. Among them, the optical laminate of the present invention, the the average film thickness of the low refractive index layer d _{A (nm),} the following equation (1):
d _A = λ / (4n _A ) (1)
(In the above formula,
n _A represents the refractive index of the low refractive index layer;
λ is a wavelength, preferably a value in the range of 480 to 580 nm)
Those satisfying these conditions are preferred.
The average film thickness of the low refractive index layer can be measured, for example, by calculating an average value at 50 locations by observing the cross section of the low refractive index layer with an electron microscope.

In addition, although the low refractive index layer is effective as a single layer, it is possible to provide two or more low refractive index layers as appropriate for the purpose of adjusting a lower minimum reflectance or a higher minimum reflectance. . When the two or more low refractive index layers are provided, it is preferable to provide a difference in the refractive index and thickness of each low refractive index layer. However, even when two or more low refractive index layers are provided, it is necessary to have the above-described thin film portion and thick film portion as a whole.

As the fluororesin, a polymerizable compound containing a fluorine atom in at least a molecule or a polymer thereof can be used. Although it does not specifically limit as a polymeric compound, For example, what has hardening reactive groups, such as a functional group hardened | cured by ionizing radiation, and a polar group thermally cured, is preferable. Moreover, the compound which has these reactive groups simultaneously may be sufficient. In contrast to this polymerizable compound, a polymer has no reactive groups as described above.

As the polymerizable compound having a functional group that is cured by ionizing radiation, fluorine-containing monomers having an ethylenically unsaturated bond can be widely used. More specifically, to illustrate fluoroolefins (eg, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluorobutadiene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.) Can do. As those having a (meth) acryloyloxy group, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2- (perfluorobutyl) ) Ethyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 2- (perfluorooctyl) ethyl (meth) acrylate, 2- (perfluorodecyl) ethyl (meth) acrylate, α-trifluoro (Meth) acrylate compounds having a fluorine atom in the molecule, such as methyl methacrylate and α-trifluoroethyl methacrylate; a C 1-14 fluoroalkyl group having at least 3 fluorine atoms in the molecule, fluoro A cycloalkyl group or a fluoroalkylene group and at least two (medium There are also fluorine-containing polyfunctional (meth) acrylic acid ester compounds having an acryloyloxy group.

Preferable examples of the thermosetting polar group include hydrogen bond forming groups such as a hydroxyl group, a carboxyl group, an amino group, and an epoxy group. These are excellent not only in adhesion to the coating film but also in affinity with inorganic ultrafine particles such as silica. Examples of the polymerizable compound having a thermosetting polar group include 4-fluoroethylene-perfluoroalkyl vinyl ether copolymer; fluoroethylene-hydrocarbon vinyl ether copolymer; epoxy, polyurethane, cellulose, phenol, polyimide, and the like. Examples include fluorine-modified products of each resin.
Examples of the polymerizable compound having both a functional group curable by ionizing radiation and a polar group curable by heat include acrylic or methacrylic acid moieties and fully fluorinated alkyl, alkenyl, aryl esters, fully or partially fluorinated vinyl ethers, fully Alternatively, partially fluorinated vinyl esters, fully or partially fluorinated vinyl ketones and the like can be exemplified.

Moreover, as a fluorine resin, the following can be mentioned, for example.
Polymer of monomer or monomer mixture containing at least one fluorine-containing (meth) acrylate compound of a polymerizable compound having an ionizing radiation curable group; at least one fluorine-containing (meth) acrylate compound; and methyl (meth) Copolymers with (meth) acrylate compounds that do not contain fluorine atoms in the molecule such as acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; fluoroethylene , Fluorine-containing compounds such as vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 3,3,3-trifluoropropylene, 1,1,2-trichloro-3,3,3-trifluoropropylene, hexafluoropropylene Monomer homopolymer or Copolymer such as. Silicone-containing vinylidene fluoride copolymers obtained by adding a silicone component to these copolymers can also be used. The silicone components in this case include (poly) dimethylsiloxane, (poly) diethylsiloxane, (poly) diphenylsiloxane, (poly) methylphenylsiloxane, alkyl-modified (poly) dimethylsiloxane, azo group-containing (poly) dimethylsiloxane, Dimethyl silicone, phenylmethyl silicone, alkyl aralkyl modified silicone, fluorosilicone, polyether modified silicone, fatty acid ester modified silicone, methyl hydrogen silicone, silanol group containing silicone, alkoxy group containing silicone, phenol group containing silicone, methacryl modified silicone, acrylic Modified silicone, amino modified silicone, carboxylic acid modified silicone, carbinol modified silicone, epoxy modified silicone, mercapto modified silicone Over emissions, fluorine-modified silicones, polyether-modified silicone and the like. Of these, those having a dimethylsiloxane structure are preferred.

Furthermore, non-polymers or polymers composed of the following compounds can also be used as the fluororesin. That is, a fluorine-containing compound having at least one isocyanato group in the molecule is reacted with a compound having at least one functional group in the molecule that reacts with an isocyanato group such as an amino group, a hydroxyl group, or a carboxyl group. Compound obtained: a compound obtained by reacting a fluorine-containing polyol such as fluorine-containing polyether polyol, fluorine-containing alkyl polyol, fluorine-containing polyester polyol, fluorine-containing ε-caprolactone modified polyol with a compound having an isocyanato group Can be used.

Moreover, each binder resin as described in the hard-coat layer mentioned later can also be mixed and used with the polymeric compound and polymer which have the above-mentioned fluorine atom. Furthermore, various additives and solvents can be used as appropriate in order to improve the curing agent for curing reactive groups and the like, to improve the coating property, and to impart antifouling properties.

In the formation of the low refractive index layer, the viscosity of the composition for low refractive index layer obtained by adding the above-mentioned material is 0.5 to 5 mPa · s (25 ° C.), preferably 0. It is preferable to set it as the range of 7-3 mPa * s (25 degreeC). An antireflection layer excellent in visible light can be realized, a uniform thin film with no coating unevenness can be formed, and a low refractive index layer particularly excellent in adhesion can be formed.

The resin curing means may be the same as that described in the hard coat layer described later. When a heating means is used for the curing treatment, it is preferable to add a thermal polymerization initiator that generates, for example, a radical by heating to start polymerization of the polymerizable compound, to the fluororesin composition.

In the optical layered body of the present invention, it is preferable that the low refractive index layer has an uneven shape on the surface, so that the optical layered body of the present invention can prevent occurrence of interference fringes.
Conventionally, for the purpose of imparting antiglare properties, an optical laminate (antiglare film) having a concavo-convex shape on the surface is known, but the present invention in the case where the surface of the low refractive index layer has a concavo-convex shape This optical laminate is different from such an antiglare film. That is, the concavo-convex shape formed on the surface of the low refractive index layer of the optical laminate of the present invention has a lower concavo-convex height than the concavo-convex shape formed on the surface of the conventional antiglare film, In addition, it is preferable that the inclination angle of the concavo-convex portion is gentler. Therefore, in the optical laminate of the present invention in which such a concavo-convex shape is formed in the low refractive index layer, the antiglare property as in the conventional antiglare film cannot be obtained. On the other hand, according to the present invention, it is possible to obtain an optical laminate that provides an image with excellent contrast without causing the occurrence of white turbidity due to external light, which is a problem with anti-glare films.
The uneven shape on the surface of the low refractive index layer is preferably such that the slope of the uneven portion is gentle compared to the slope of the uneven portion of the uneven shape of the conventionally known anti-glare layer, and the average slope of the uneven portion. When the angle is θa and the unevenness skewness is Sk, it is preferable that θa and Sk satisfy the following expressions.
0.05 ° ≦ θa ≦ 0.15 °
| Sk | ≦ 0.5

The reason that the interference fringes can be prevented by the uneven shape formed on the surface of the low refractive index layer is that light reflected from the surface of the low refractive index layer diffuses and becomes non-interfering light. In order to diffuse light, the uneven surface needs to be inclined, and the index is the average inclination angle θa.
In the optical layered body of the present invention, the lower limit of the average inclination angle θa of the concavo-convex portion is preferably 0.05 °. If it is less than 0.05 °, the inclination may not be sufficient and interference fringes may not be prevented. A more preferred lower limit is 0.07 °, and a still more preferred lower limit is 0.08 °. Moreover, it is preferable that the upper limit of the average inclination | tilt angle (theta) a of the said uneven | corrugated | grooved part is 0.15 degree. If the angle exceeds 0.15 °, the inclination angle of the concavo-convex portion is excessively large, which may cause a problem of cloudiness due to diffuse reflection of external light. A more preferred upper limit is 0.13 °, and a still more preferred upper limit is 0.12 °.

In the present invention, the absolute value of the unevenness skewness Sk is preferably 0.5 or less. The skewness Sk indicates that the larger the absolute value, the greater the asymmetry of the surface unevenness with respect to the average line. When the asymmetry of the surface irregularity shape is large, there are steep peak portions and gentle valley portions (when Sk> 0), and even if the average inclination angle θa satisfies the above range, the inclination angle distribution thereof Indicates that there is a bias. That is, the inclination angle of the peak portion is increased, and the inclination angle of the valley portion is decreased (when Sk <0, the relationship between the peak and the valley is reversed). In such a case, in a portion where the inclination angle is large, light diffusion is excessively increased, and there is a possibility that a cloudiness problem may occur. On the other hand, in a portion where the inclination angle is small, interference fringes may not be suitably prevented. If the absolute value of Sk is 0.5 or less, the asymmetry of the surface irregularity shape is small, so that the deviation of the inclination angle distribution can be moderately suppressed, and interference fringes can be suitably prevented. Can be suppressed. The absolute value of the Sk is more preferably 0.4 or less, and still more preferably 0.2 or less.

Moreover, it is preferable that the ten-point average roughness (Rz) of the concavo-convex shape formed on the surface of the low refractive index layer is less than 0.5 μm, and a more preferable upper limit is 0.3 μm. If the Rz is 0.5 μm or more, the unevenness is too large and a cloudiness may be observed. The lower limit of Rz is not particularly limited, and is appropriately adjusted within a range where a diffusion effect can be obtained.

ここで、ｌは基準長さを表し、ｆ（ｘ）は粗さ曲線を表し、Ｒｑは二乗平均平方根粗さであり下記の式により定義される。

このようなθａ、Ｓｋ、Ｒａ及びＲｚは、例えば、表面粗さ測定器：ＳＥ−３４００／株式会社小坂研究所製等により測定して求めることができる。 In the present specification, the above θa, Sk, Ra, and Rz are values obtained by setting a cutoff wavelength and a reference length to 0.25 mm from a roughness curve obtained by a method according to JIS B 0601-1994. It is. Ra and Rz are values defined in JIS B 0601-1994, and θa is described in a surface roughness measuring instrument: SE-3400 instruction manual (revised 1995.07.20) (Kosaka Laboratory Ltd.) As shown in FIG. 1, the arc tangent θa = tan ⁻¹ {(the sum (h ₁ + h ₂ + h ₃ +... + H _n ) of the heights of the convex portions existing in the reference length L. h ₁ + h ₂ + h ₃ +... + h _n ) / L}.
The Sk is a value defined by the following equation.

Here, l represents a reference length, f (x) represents a roughness curve, Rq is a root mean square roughness, and is defined by the following equation.

Such θa, Sk, Ra, and Rz can be determined by measuring with, for example, a surface roughness measuring instrument: SE-3400 / manufactured by Kosaka Laboratory Ltd.

The optical layered body of the present invention has an optical functional layer between the light transmissive substrate and the low refractive index layer.
The optical functional layer has an uneven shape on the surface.
As described above, the low refractive index layer is provided on the optical functional layer. However, the surface of the optical functional layer is suitable for the surface of the low refractive index layer formed on the surface by having an uneven shape. An uneven shape can be formed.
The uneven shape on the surface of the optical functional layer is preferably in a range in which the uneven shape on the surface of the low refractive index layer satisfies the above-described θa, Sk, Ra, and Rz.

The optical functional layer preferably contains inorganic oxide fine particles.
The inorganic oxide fine particle is a material that forms an uneven shape on the surface of the optical functional layer. In the optical laminate of the present invention, the inorganic oxide fine particle forms an aggregate in the optical functional layer. It is preferable that the irregular shape of the surface of the optical functional layer is formed by the aggregate of the inorganic oxide fine particles.
Examples of the inorganic oxide particles include silica fine particles, alumina fine particles, zirconia fine particles, titania fine particles, tin oxide fine particles, ATO particles, and zinc oxide fine particles.

The inorganic oxide fine particles are preferably surface-treated. Since the inorganic oxide fine particles are surface-treated, the distribution of the aggregates of the inorganic oxide fine particles in the optical functional layer can be suitably controlled, and the chemical resistance of the inorganic oxide fine particles themselves And improvement of saponification resistance.

The surface treatment is preferably a hydrophobizing treatment, and examples thereof include a method of treating the inorganic oxide fine particles with a silane compound having a methyl group or an octyl group.
Here, a hydroxyl group is usually present on the surface of the inorganic oxide fine particle, but the surface treatment reduces the hydroxyl group on the surface of the inorganic oxide fine particle, and the BET method of the inorganic oxide fine particle. As a result, the inorganic oxide fine particles can be prevented from agglomerating excessively, and the above-described specific uneven shape can be formed on the surface of the optical functional layer.

The inorganic oxide fine particles are preferably amorphous. If the inorganic oxide fine particles are crystalline, the Lewis acidity of the inorganic oxide fine particles becomes strong due to lattice defects contained in the crystal structure, and excessive aggregation of the inorganic oxide fine particles cannot be controlled. is there.

As such inorganic oxide fine particles, for example, fumed silica is preferably used because it tends to aggregate itself and easily form an aggregate described later. Here, the fumed silica refers to amorphous silica having a particle size of 200 nm or less prepared by a dry method, and is obtained by reacting a volatile compound containing silicon in a gas phase. Specifically, for example, a silicon compound, for example, one produced by hydrolyzing SiCl ₄ in a flame of oxygen and hydrogen can be used. Specifically, AEROSIL R805 (made by Nippon Aerosil Co., Ltd.) etc. are mentioned, for example.

Although it does not specifically limit as content of the said inorganic oxide fine particle, It is preferable that it is 0.1-5.0 mass% in the said optical function layer. When the amount is less than 0.1% by mass, the above-described specific uneven shape cannot be formed on the surface of the optical function layer, and interference fringes may not be prevented. This causes internal diffusion and / or large surface irregularities in the optical functional layer, which may cause a problem of cloudiness. A more preferable lower limit is 0.5% by mass, and a more preferable upper limit is 3.0% by mass.

The inorganic oxide fine particles preferably have an average primary particle diameter of 1 to 100 nm. When the thickness is less than 1 nm, the above-described specific uneven shape may not be formed on the surface of the optical functional layer. When the thickness exceeds 100 nm, light is diffused by the inorganic oxide fine particles, and an image using the optical laminate of the present invention is used. The dark room contrast of the display device may be inferior. A more preferred lower limit is 5 nm, and a more preferred upper limit is 50 nm.
In addition, the average primary particle diameter of the inorganic oxide fine particles is measured using an image processing software from an image of a cross-sectional electron microscope (a transmission type such as TEM or STEM and preferably a magnification of 50,000 times or more). Value.

The inorganic oxide fine particles preferably have a spherical shape in a single particle state. Since the single particle of the inorganic oxide fine particles is spherical, a high-contrast display image can be obtained when the optical layered body of the present invention is applied to an image display device.
In addition, the above “spherical” includes, for example, a true spherical shape, an elliptical spherical shape and the like, and has a meaning excluding so-called indefinite shape.

In the present invention, the aggregate of inorganic oxide fine particles preferably has a structure in which the inorganic oxide fine particles described above are connected in a bead shape (pearl necklace shape) in the optical functional layer.
By forming an aggregate in which the inorganic oxide fine particles are arranged in a bead shape in the optical functional layer, the convex portion based on the aggregate has a gentle shape with little inclination. It becomes easy to make the surface uneven shape into the specific uneven shape described above.
The structure in which the inorganic oxide fine particles are connected in a bead shape is, for example, a structure in which the inorganic oxide fine particles are continuously connected in a straight line (linear structure), a structure in which a plurality of the linear structures are entangled, Any structure such as a branched structure having one or two or more side chains in which a plurality of inorganic oxide fine particles are continuously formed in the linear structure is mentioned.

In addition, the aggregate of the inorganic oxide fine particles preferably has an average particle diameter of 100 nm to 2.0 μm. When the thickness is less than 100 nm, the above-described specific uneven shape may not be formed on the surface of the optical functional layer. When the thickness exceeds 2.0 μm, light is diffused by the aggregate of the inorganic oxide fine particles, and the optical characteristics of the present invention. The dark room contrast of an image display device using a laminate may be inferior. The more preferable lower limit of the average particle diameter of the aggregate is 200 nm, and the more preferable upper limit is 1.5 μm.
The average particle diameter of the aggregates of the inorganic oxide fine particles is selected from a 5 μm square region containing a large amount of aggregates of inorganic oxide fine particles from observation with a cross-sectional electron microscope (about 10,000 to 20,000 times). The particle diameters of the aggregates of the inorganic oxide fine particles in the region are measured, and the particle diameters of the aggregates of the top 10 inorganic oxide fine particles are averaged. The “particle diameter of the aggregate of the inorganic oxide fine particles” is the maximum distance between the two straight lines when the cross section of the aggregate of the inorganic oxide fine particles is sandwiched between any two parallel straight lines. It is measured as the distance between straight lines in a combination of two straight lines. The particle diameter of the aggregate of the inorganic oxide fine particles may be calculated using image analysis software.

The optical functional layer preferably has a hard coat performance. For example, the hardness is preferably H or more in a pencil hardness test (load 4.9 N) according to JIS K5600-5-4 (1999). More preferably.

In the optical layered body of the present invention, the optical functional layer is preferably a hard coat layer.
The thickness of the hard coat layer is preferably 2.0 to 7.0 μm. If it is less than 2.0 μm, the surface of the hard coat layer may be easily damaged, and if it exceeds 7.0 μm, not only the hard coat layer cannot be thinned, but also the hard coat layer tends to break, Curling can be a problem. A more preferable range of the thickness of the hard coat layer is 2.0 to 5.0 μm. In addition, the thickness of the said hard-coat layer can be measured by cross-sectional microscope observation.

In the hard coat layer, the silica fine particles are preferably dispersed in a binder resin.
As the binder resin, for example, the polarity is preferably adjusted according to the hydrophobicity of the hydrophobized silica fine particles. Examples of the method for adjusting the polarity of the binder resin include adjusting the hydroxyl value of the binder resin. By optimizing the polarity of the binder resin, the aggregation / dispersibility of the silica fine particles is suitably controlled, and the above-described capillary blood vessels are easily distributed in the optical functional layer.

As said binder resin, a transparent thing is preferable, for example, it is preferable that the ionizing radiation hardening type resin which is resin hardened | cured by an ultraviolet-ray or an electron beam hardens | cures by irradiation of an ultraviolet-ray or an electron beam.

Examples of the ionizing radiation curable resin include compounds having one or more unsaturated bonds such as compounds having functional groups such as acrylates. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and pentaerythritol. Tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) ) Acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate Rate, tetrapentaerythritol deca (meth) acrylate, isocyanuric acid tri (meth) acrylate, isocyanuric acid di (meth) acrylate, polyester tri (meth) acrylate, polyester di (meth) acrylate, bisphenol di (meth) acrylate, diglycerin Polyfunctional compounds such as tetra (meth) acrylate, adamantyl di (meth) acrylate, isoboronyl di (meth) acrylate, dicyclopentane di (meth) acrylate, tricyclodecane di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate Etc. Of these, pentaerythritol tetraacrylate (PETTA) is preferably used. In the present specification, “(meth) acrylate” refers to methacrylate and acrylate. In the present invention, as the ionizing radiation curable resin, a compound obtained by modifying the above-described compound with PO, EO or the like can also be used.

In addition to the above compounds, relatively low molecular weight polyester resins having unsaturated double bonds, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, etc. It can be used as an ionizing radiation curable resin.

The ionizing radiation curable resin is used in combination with a solvent-drying resin (a thermoplastic resin or the like, which is a resin that forms a film only by drying the solvent added to adjust the solid content during coating). You can also By using the solvent-drying resin in combination, film defects on the coating surface of the coating liquid can be effectively prevented when forming the hard coat layer.
The solvent-drying resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and a thermoplastic resin can be generally used.
The thermoplastic resin is not particularly limited. For example, a styrene resin, a (meth) acrylic resin, a vinyl acetate resin, a vinyl ether resin, a halogen-containing resin, an alicyclic olefin resin, a polycarbonate resin, or a polyester resin. Examples thereof include resins, polyamide-based resins, cellulose derivatives, silicone-based resins, rubbers, and elastomers. The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoint of transparency and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

The hard coat layer may contain a thermosetting resin.
The thermosetting resin is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation Examples thereof include resins, silicon resins, polysiloxane resins, and the like.

The hard coat layer containing the silica fine particles and the binder resin is prepared by, for example, applying the above-described silica fine particles, the hard coat layer composition containing the monomer component of the binder resin and the solvent onto the light-transmitting substrate and drying. It can be formed by curing the coating film formed by ionizing radiation irradiation or the like.

Examples of the solvent contained in the hard coat layer composition include alcohols (eg, methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol), ketones, and the like. (Acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons ( Toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates, sulfo Sid compound (dimethylsulfoxide), amides (dimethylformamide, dimethylacetamide, etc.) and the like can be exemplified, or a mixture thereof.

The hard coat layer composition preferably further contains a photopolymerization initiator.
The photopolymerization initiator is not particularly limited, and known ones can be used. Specific examples include, for example, acetophenones, benzophenones, Michler benzoylbenzoate, α-amyloxime ester, thioxanthones, propio Examples include phenones, benzyls, benzoins, and acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

As the photopolymerization initiator, when the binder resin is a resin system having a radical polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. may be used alone or in combination. preferable. When the binder resin is a resin system having a cationic polymerizable functional group, examples of the photopolymerization initiator include aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, metallocene compounds, benzoin sulfonate esters, and the like. Are preferably used alone or as a mixture.

The content of the photopolymerization initiator in the hard coat layer composition is preferably 0.5 to 10.0 parts by mass with respect to 100 parts by mass of the binder resin. If the amount is less than 0.5 parts by mass, the hard coat performance of the hard coat layer to be formed may be insufficient. If the amount exceeds 10.0 parts by mass, there is a possibility of inhibiting curing. It is not preferable.

Although it does not specifically limit as a content rate (solid content) of the raw material in the said composition for hard-coat layers, Usually, it is preferable to set it as 5-70 mass%, especially 25-60 mass%.

In the hard coat layer composition, according to the purpose of increasing the hardness of the hard coat layer, suppressing curing shrinkage, controlling the refractive index, etc., conventionally known dispersants, surfactants, antistatic agents, Silane coupling agent, thickener, anti-coloring agent, coloring agent (pigment, dye), antifoaming agent, leveling agent, flame retardant, UV absorber, adhesion-imparting agent, polymerization inhibitor, antioxidant, surface modification An agent, a lubricant, etc. may be added.
As the leveling agent, for example, silicone oil, fluorine-based surfactant and the like are preferable because the hard coat layer is prevented from having a Benard cell structure. When a resin composition containing a solvent is applied and dried, a surface tension difference or the like is generated between the coating film surface and the inner surface in the coating film, thereby causing many convections in the coating film. The structure generated by this convection is called a Benard cell structure, and causes a problem such as the skin and coating defects in the hard coat layer to be formed.
Further, the Benard cell structure has a possibility that the irregularities on the surface of the hard coat layer become too large and the appearance of the optical laminate is impaired. When the leveling agent as described above is used, this convection can be prevented, so that not only a hard coat layer film free from defects and unevenness can be obtained, but also the uneven shape of the hard coat layer surface can be easily adjusted.

The method for preparing the hard coat layer composition is not particularly limited as long as each component can be uniformly mixed. For example, the composition can be performed using a known apparatus such as a paint shaker, a bead mill, a kneader, or a mixer.

The method for applying the hard coat layer composition onto the light-transmitting substrate is not particularly limited. For example, spin coating, dipping, spraying, die coating, bar coating, roll coater, meniscus coater And publicly known methods such as a method, a flexographic printing method, a screen printing method, and a pea coater method.
After applying the hard coat layer composition by any of the methods described above, the film is transported to a heated zone to dry the formed coating film, and the coating film is dried by various known methods to evaporate the solvent. By selecting the solvent relative evaporation rate, solid content concentration, coating solution temperature, drying temperature, drying air velocity, drying time, solvent atmosphere concentration in the drying zone, etc., the distribution state of the aggregates of inorganic oxide fine particles can be determined. Can be adjusted.
In particular, a method of adjusting the distribution state of the aggregates of inorganic oxide fine particles by selecting drying conditions is simple and preferable. The specific drying temperature is preferably 30 to 120 ° C., and the drying wind speed is preferably 0.2 to 50 m / s, and the inorganic oxidation is performed by performing the drying treatment appropriately adjusted within this range once or a plurality of times. It is possible to adjust the distribution state of the aggregates of the product fine particles to a desired state.

In addition, as a method of irradiating ionizing radiation when curing the coating film after drying, for example, a light source such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc lamp, a black light fluorescent lamp, or a metal halide lamp is used. A method is mentioned.
Moreover, as a wavelength of an ultraviolet-ray, the wavelength range of 190-380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as a cockcroft-wald type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type.

The optical layered body of the present invention preferably has a total light transmittance of 90% or more. If it is less than 90%, color reproducibility and visibility may be impaired when the optical laminate of the present invention is mounted on the surface of an image display device. The total light transmittance is more preferably 91% or more.
In addition, the said total light transmittance can be measured by the method based on JISK-7361 using a haze meter (the product number; HM-150 by Murakami Color Research Laboratory).

The optical layered body of the present invention preferably has a total haze of less than 2.0%. If it is 2.0% or more, desired optical characteristics cannot be obtained, and the visibility when the optical laminate of the present invention is placed on the image display surface may be lowered. Preferably it is 1.5% or less, More preferably, it is 1.0% or less.
The total haze can be measured by a method based on JIS K-7136 using a haze meter (manufactured by Murakami Color Research Laboratory, product number: HM-150).

The optical layered body of the present invention preferably has a transmitted image definition of 75 to 95% for a 0.125 mm comb and 95% or more for a 2.0 mm comb. If the transmitted image definition of a 0.125 mm comb is less than 75%, the clarity of the image when the image is displayed may be impaired, and the image quality may be inferior. If it exceeds 95%, the interference fringes may not be suitably prevented. It is more preferable that the transmitted image definition in a 0.125 mm comb is 80 to 90%. Further, if the transmitted image definition in a 2.0 mm comb is less than 95%, the clarity of the image is impaired, and there is a risk that white turbidity due to diffuse reflection of external light may occur.
The transmission image definition can be measured by a method based on the image definition transmission method of JIS K-7105 using a image clarity measuring device (manufactured by Suga Test Instruments, product number: ICM-1T).

The optical layered body of the present invention preferably has a contrast ratio of 80% or more, more preferably 90% or more. If it is less than 80%, when the optical laminate of the present invention is mounted on the display surface, the dark room contrast is inferior and the visibility may be impaired. In the present specification, the contrast ratio is a value measured by the following method.
That is, using a cold cathode tube light source with a diffusion plate as a backlight unit, using two polarizing plates (AMN-3244TP manufactured by Samsung Co.), the light passing through when the polarizing plate is installed in parallel Nicol the _{L max} luminance values divided by the brightness of _{L min} of light passing through when installed in a cross nicol state with _(L max _{/ L min)} and contrast, optical laminate (light-transmitting substrate + hard coat layer, etc. the contrast _{(L 1)} of the) divided by the contrast _{(L 2)} of the light-transmitting substrate _{(L 1 / L 2) ×} 100 (%) is the contrast ratio.
Note that the luminance is measured in a dark room. The luminance is measured with a color luminance meter (BM-5A manufactured by Topcon Corporation), the measurement angle of the color luminance meter is set to 1 °, and the measurement is performed with a visual field of 5 mm on the sample. The light quantity of the backlight is set so that the luminance is 3600 cd / m ² when the two polarizing plates are set in parallel Nicol without the sample.

In the optical laminate of the present invention, in the case where the optical functional layer is the hard coat layer and a low refractive index layer is laminated on the optical functional layer, for example, silica fine particles are formed on the light-transmitting substrate. After forming the hard coat layer using the hard coat layer composition containing the monomer component of the binder resin and the solvent, the low refractive index on the hard coat layer using the above-described low refractive index layer composition It can be manufactured by forming a layer.
About the formation method of the said composition for hard-coat layers and a hard-coat layer, the composition for low-refractive-index layers, and the formation method of a low-refractive-index layer, the material and method similar to having mentioned above are mentioned.

The optical layered body of the present invention can be made into a polarizing plate by providing the optical layered body according to the present invention on the surface of the polarizing element opposite to the surface where the hard coat layer is present in the optical layered body. Such a polarizing plate is also one aspect of the present invention.

The polarizing element is not particularly limited, and for example, a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film, etc. dyed and stretched with iodine or the like can be used. In the laminating process of the polarizing element and the optical laminate of the present invention, it is preferable to saponify the light-transmitting substrate (triacetyl cellulose film). By the saponification treatment, the adhesiveness is improved and an antistatic effect can be obtained.

This invention is also an image display apparatus provided with the said optical laminated body or the said polarizing plate.
The image display device may be an image display device such as LCD, PDP, FED, ELD (organic EL, inorganic EL), CRT, tablet PC, touch panel, and electronic paper.

The LCD, which is a typical example of the above, includes a transmissive display body and a light source device that irradiates the transmissive display body from the back. When the image display device of the present invention is an LCD, the optical laminate of the present invention or the polarizing plate of the present invention is formed on the surface of this transmissive display.

In the case where the present invention is a liquid crystal display device having the optical laminate, the light source of the light source device is irradiated from the lower side of the optical laminate. Note that a retardation plate may be inserted between the liquid crystal display element and the polarizing plate. An adhesive layer may be provided between the layers of the liquid crystal display device as necessary.

The PDP, which is the image display device, has a front glass substrate (electrode is formed on the surface) and a rear glass substrate (disposed with electrodes and minute grooves) disposed with a discharge gas sealed between the front glass substrate and the front glass substrate. Formed on the surface and forming red, green and blue phosphor layers in the grooves). When the image display device of the present invention is a PDP, the above-mentioned optical laminate is provided on the surface of the surface glass substrate or the front plate (glass substrate or film substrate).

The above image display device is a zinc sulfide or diamine substance that emits light when a voltage is applied: a light emitting material is deposited on a glass substrate, and an ELD device that performs display by controlling the voltage applied to the substrate, or converts an electrical signal into light Alternatively, it may be an image display device such as a CRT that generates an image visible to human eyes. In this case, the optical laminated body described above is provided on the outermost surface of each display device as described above or the surface of the front plate.

In any case, the image display device of the present invention can be used for display display of a television, a computer, electronic paper, a touch panel, a tablet PC, or the like. In particular, it can be suitably used for the surface of high-definition image displays such as CRT, liquid crystal panel, PDP, ELD, FED, and touch panel.

Since the optical layered body of the present invention has the above-described configuration, it is possible to provide an optical layered body that is excellent in antireflection performance and anticoloring performance and can provide an image display device with high display quality.
Therefore, the optical laminate of the present invention is suitable for cathode ray tube display (CRT), liquid crystal display (LCD), plasma display (PDP), electroluminescence display (ELD), field emission display (FED), electronic paper, etc. Can be applied to.

It is explanatory drawing of the measuring method of (theta) a.

The contents of the present invention will be described with reference to the following examples, but the contents of the present invention should not be construed as being limited to these embodiments. Unless otherwise specified, “part” and “%” are based on mass.

Example 1
A light-transmitting base material (thickness 60 μm triacetyl cellulose resin film, manufactured by Fuji Film Co., Ltd., TD60UL) was prepared, and a hard coat layer composition having the following composition was applied to one side of the light-transmitting base material. A coating film was formed. Next, 70 ° C. dry air was passed through the formed coating film at a flow rate of 0.2 m / s for 15 seconds, and then 70 ° C. dry air was passed through for 30 seconds at a flow rate of 10 m / s. By evaporating the solvent in the coating film, the accumulated light amount is 50 mJ / cm in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb). ^By irradiating the coating film so as to be ² , a hard coat layer having a thickness of 4 μm (during curing) was formed.

(Composition for hard coat layer)
Fumed silica (octylsilane treatment; average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd.)
1 part by mass pentaerythritol tetraacrylate (PETTA) (product name: PETA, manufactured by Daicel Cytec) 60 parts by mass urethane acrylate (product name: UV1700B, manufactured by Nippon Gosei Kagaku) 40 parts by mass Irgacure 184 (manufactured by BASF Japan) 5 parts by mass polyether-modified silicone (TSF4460, manufactured by Momentive Performance Materials) 0.025 parts by mass Toluene 105 parts by mass Isopropyl alcohol 30 parts by mass Cyclohexanone 15 parts by mass Fumed silica is a silane compound having an octyl group The silanol group is substituted with an octylsilyl group and is hydrophobized with (octylsilane).

Next, a composition for a low refractive index layer having the following composition is applied to the surface of the formed hard coat layer, dried at 40 ° C. for 1 minute, and an ultraviolet irradiation device (manufactured by Fusion UV System Japan Co., Ltd., light source H bulb) is used. And using a nitrogen atmosphere (oxygen concentration of 200 ppm or less) under ultraviolet light irradiation with an integrated light quantity of 100 mJ / cm ² to cure to form a low refractive index layer having an average film thickness of 100 nm. A laminate was produced.

(Composition for low refractive index layer)
Hollow silica fine particles (solid content of the silica fine particles: 20% by mass, solution; methyl isobutyl ketone, average particle size: 50 nm) 40 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec)
10 parts by mass polymerization initiator (Irgacure 127; manufactured by BASF Japan) 0.35 parts by mass modified silicone oil (X22164E; manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass MIBK 320 parts by mass PGMEA 161 parts by mass

(Example 2)
A composition for a hard coat layer was prepared in the same manner as in Example 1 except that the amount of fumed silica was changed to 0.5 parts by mass. Example 1 except that the composition for hard coat layer was used. In the same manner, an optical laminate according to Example 2 was manufactured.

Example 3
A composition for hard coat layer was prepared in the same manner as in Example 1 except that the amount of fumed silica was changed to 2.5 parts by mass, and Example 1 was prepared except that the composition for hard coat layer was used. In the same manner, an optical laminate according to Example 3 was manufactured.

(Comparative Example 1)
An optical laminate according to Comparative Example 1 was produced in the same manner as in Example 1 except that the hard coat layer composition having the following composition was used and the hard coat layer to be formed was 10 μm thick (at the time of curing). .

(Composition for hard coat layer)
Pentaerythritol triacrylate (PETA) (product name: PET30, manufactured by Nippon Kayaku Co., Ltd.) 100 parts by mass Irgacure 184 (manufactured by BASF Japan) 5 parts by mass polyether-modified silicone (TSF4460, manufactured by Momentive Performance Materials) 0 0.025 parts by mass Methyl ethyl ketone (MEK) 80 parts by mass Methyl isobutyl ketone (MIBK) 35 parts by mass

(Comparative Example 2)
An optical laminate according to Comparative Example 2 was produced in the same manner as in Example 1 except that the hard coat layer composition having the following composition was used.
(Composition for hard coat layer)
Organic fine particles (acryl-styrene copolymer particles, average particle size 2.0 μm, refractive index 1.52, manufactured by Sekisui Plastics Co., Ltd.) 3 parts by mass pentaerythritol tetraacrylate (PETTA) (product name: PETA, Daicel Cytec) 60 parts by mass urethane acrylate (product name: UV1700B, manufactured by Nippon Synthetic Chemical Co., Ltd.) 40 parts by mass Irgacure 184 (manufactured by BASF Japan) 5 parts by mass polyether-modified silicone (TSF4460, manufactured by Momentive Performance Materials) 0.025 parts by mass Toluene 105 parts by mass Isopropyl alcohol 30 parts by mass Cyclohexanone 15 parts by mass

The optical laminates according to the obtained examples and comparative examples were evaluated for the following items.
All the results are shown in Table 1.

(Measurement of the difference in thickness between the thin film portion and the thick film portion of the low refractive index layer)
The cross section of the low refractive index layer of the optical layered body according to each example and comparative example was observed with an electron microscope, the thin film part (the part whose thickness is 5 nm or more thinner than the average film thickness) and the thick film part (the thickness is the average film thickness). The average value was calculated at 10 points of a portion thicker than 5 nm), and the difference was calculated.

(With or without coloring)
The surface (light transmissive substrate surface) opposite to the hard coat layer of each optical laminate obtained in Examples and Comparative Examples was attached to a black acrylic plate via a transparent adhesive, and a table stand ( Under the three-wavelength fluorescent lamp tube), the presence or absence of coloring was observed and evaluated according to the following criteria.
○: I was not worried about coloring.
X: It was observed to such an extent that coloring was a concern.

(Average inclination angle (θa) of uneven portion, skewness of uneven portion (Sk), arithmetic average roughness of uneven portion (Ra)
Using a surface roughness measuring instrument: SE-3400 / manufactured by Kosaka Laboratory Co., Ltd., in accordance with JIS B 0601-1994, and measuring the roughness curve under the following conditions, θa, Sk and Ra are It was measured. In Table 1, skewness (Sk) indicates an actual measurement value.
(1) The stylus of the surface roughness detector:
Model No./SE2555N (2μ stylus), manufactured by Kosaka Laboratory Ltd. (tip radius of curvature 2μm / vertical angle: 90 degrees / material: diamond)
(2) Measurement conditions of surface roughness measuring instrument:
Reference length (cutoff value λc of roughness curve): 0.25 mm
Evaluation length (reference length (cutoff value λc) × 5): 1.25 mm
Contact speed of stylus: 0.1 mm / s
Preliminary length: (cutoff value λc) × 2
Vertical magnification: 2000 times Horizontal magnification: 10 times

(Haze)
Based on JIS K7136, the haze of the obtained optical laminated body was measured using haze meter HM-150 (made by Murakami Color Research Laboratory).

(Transparent image definition)
In accordance with JIS K7105, transmission image definition was measured at 0.125 mm comb and 2.0 mm comb of the obtained optical laminate by transmission measurement using a image clarity measuring device ICM-1T (manufactured by Suga Test Instruments). .

(Interference fringes)
The surface (light transmissive substrate surface) opposite to the hard coat layer of each optical laminate obtained in Examples and Comparative Examples is pasted on a black acrylic plate for preventing back reflection through a transparent adhesive. Each optical layered product was irradiated with a sodium lamp from the surface of the hard coat layer or the low refractive index layer and visually observed, and the presence or absence of interference fringes was evaluated according to the following criteria.
A: No interference fringes were generated.
○: Some interference fringes were generated, but there was no problem.
X: Interference fringes were generated.
(Cloudiness)
The surface (light transmissive substrate surface) opposite to the hard coat layer of each optical laminate obtained in Examples and Comparative Examples was attached to a black acrylic plate via a transparent adhesive, and a table stand ( The cloudiness was observed under a three-wavelength fluorescent lamp tube) and evaluated according to the following criteria.
A: Whiteness was not observed.
○: Slight whiteness was observed but not so much.
X: Whiteness was observed.

As shown in Table 1, the optical laminates according to the examples were not colored and were good in all evaluations of transmitted image definition, haze, interference fringes, and cloudiness.
On the other hand, the optical laminated body according to Comparative Example 1 was observed to be colored with a small film thickness difference in the low refractive index layer. Moreover, the optical laminated body which concerns on the comparative example 2 was inferior in cloudiness because Ra was too large.

The optical laminate of the present invention includes a cathode ray tube display (CRT), a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (ELD), a field emission display (FED), a touch panel, electronic paper, a tablet PC, and the like. It can be suitably applied to.

Claims (4)

An optical laminate in which an optical functional layer and a low refractive index layer are provided in this order on one surface of a light-transmitting substrate,
The low refractive index layer is non-uniform in thickness and has an uneven shape on the surface,
The concavo-convex shape on the surface of the low refractive index layer has an arithmetic average roughness Ra of 0.01 to 0.05 μm at a cutoff wavelength of 0.25 mm according to JIS B0601-1994 of the concavo-convex part.
The thin film portion of the low refractive index layer exists in the convex portion on the surface of the low refractive index layer, and the thick film portion of the low refractive index layer exists in the concave portion on the surface of the low refractive index layer,
An optical laminate, wherein a difference in thickness between the thin film portion and the thick film portion of the low refractive index layer satisfies the following formula.
d _D ≧ 0.18 × d _A
In the above formula, d _D represents the thickness difference (nm) between the thin film portion and the thick film portion of the low refractive index layer, and d _A represents the average film thickness (nm) of the low refractive index layer. 2. The optical laminate according to claim 1, wherein the uneven shape on the surface of the low refractive index layer has an average inclination angle of the uneven portion of θa and an unevenness skewness of Sk, and the absolute value of Sk and θa satisfy the following expression: body.
0.05 ° ≦ θa ≦ 0.15 °
| Sk | ≦ 0.5 A polarizing plate comprising a polarizing element,
The polarizing plate comprises the optical layered body according to claim 1 or 2 on a polarizing element surface. An image display device comprising the optical laminate according to claim 1 or 2, or the polarizing plate according to claim 3.

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