JP6191113B2 - Optical laminate, polarizing plate, and image display device - Google Patents

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 laminate having an antireflection layer, for example, 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 is known.
Such a low refractive index layer is required to have a low refractive index in order to enhance the antireflection performance of the optical laminate. For example, Patent Document 1 contains hollow silica fine particles, a fluorine atom-containing polymer, and the like. An optical laminate (antireflection film) having a low refractive index layer is disclosed.

In general, an optical laminated body is wound up into a roll at the time of molding from the viewpoint of improving productivity. However, the conventional optical laminated body provided with the low refractive index layer has a problem that a phenomenon (so-called blocking) in which the overlapped films adhere to each other occurs when the take-up roll is used. When blocking occurs, the film cannot be smoothly fed out from the roll, and in the next step, the film is wrinkled or the film meanders. In the case of severe blocking, unevenness may occur in the blocked portion, resulting in a loss of transparency, haze, and optical uniformity of the produced optical laminate.

For example, a method of causing a part of the hollow silica fine particles contained in the low refractive index layer to protrude from the surface of the low refractive index layer is conceivable for such a blocking problem. However, since the hollow silica fine particles used in the conventional low refractive index layer are spherical, if there are hollow silica fine particles protruding from the surface of the low refractive index layer, the hollow silica fine particles fall off. There was a problem that it was easy and inferior in scratch resistance.

Furthermore, as an optical laminated body having a low refractive index layer, an optical laminated body having a structure in which a light-transmitting substrate, a hard coat layer, and a low refractive index layer are laminated in this order has been conventionally known. However, the optical laminate having such a structure is disadvantageous in terms of manufacturing cost because a process for forming a hard coat layer and a low refractive index layer is required at the time of manufacture, and the hard coat layer and the low refractive index are low. Adhesion with the rate layer sometimes became a problem.
Furthermore, for the purpose of preventing blocking, an optical laminate in which spherical silica (nano-size silica) is contained in a hard coat layer is also known, but the optical laminate having such a hard coat layer has a reflectivity. It could not be lowered, and was not effective in preventing reflection.

JP 2007-301970 A

In view of the above situation, the present invention provides an optical laminate having a hard coat layer having a single-layer structure and excellent antireflection performance and excellent blocking resistance, a polarizing plate and an image display device using the optical laminate. Is intended to provide.

The present invention is an optical laminate having a hard coat layer on one surface of a light-transmitting substrate, wherein the hard coat layer contains cubic hollow silica fine particles, and the cubic hollow silica fine particles are The cubic hollow silica fine particles are unevenly distributed in the upper layer of the hard coat layer, and the corners of the cubic hollow silica fine particles protrude from the surface of the hard coat layer . The cubic hollow silica fine particles have a primary particle side of 30 to 200 nm. The outer layer has a thickness of 3 to 15 nm, and the corner portion protrudes from the surface of the hard coat layer in the range of 10 to 200 nm .

The optical layered body of the present invention has the above cubic hollow silica fine particles 70 to 100 in a region from the interface opposite to the light-transmitting substrate of the hard coat layer to a third of the thickness of the hard coat layer. % Is preferably contained.
Further, the content of the cubic hollow silica fine particles in the hard coat layer is 0.5 to 20 parts by mass with respect to a total of 100 parts by mass of the resin component constituting the hard coat layer and the cubic hollow silica fine particles. it is preferable that.

This invention is also a polarizing plate provided with a polarizing element, Comprising: The said polarizing plate is provided with the above-mentioned optical laminated body on the said polarizing element surface, It is also a polarizing plate characterized by the above-mentioned.
The present invention is also an image display device including the above-described optical laminate or the above-described polarizing plate.
The present invention is described in detail below.

The optical layered body of the present invention has a hard coat layer on one surface of the light-transmitting substrate.
The said hard-coat layer means the thing which shows the hardness of 2H or more by the pencil hardness test prescribed | regulated by JISK5600-5-4 (1999). The hardness is more preferably 3H or more. Moreover, as a film thickness (at the time of hardening) of the said hard-coat layer, it is 0.1-100 micrometers, Preferably it is 0.8-20 micrometers.

The hard coat layer contains cubic hollow silica fine particles.
The cubic hollow silica fine particles are hollow silica fine particles having a cubic shape. Here, the “cubic shape” is a shape surrounded by six faces, includes a shape approximated to a cube, and is not limited to a complete cube. That is, the cubic hollow silica fine particles do not have to have the same area on the six surfaces, and may be constituted by curved surfaces between the six surfaces. The “hollow silica fine particles” mean a silica fine particle having a structure filled with a gas and having a refractive index that is in inverse proportion to the gas occupancy compared to the original refractive index of the silica fine particles.

In the optical layered body of the present invention, the cubic hollow silica fine particles are unevenly distributed in the upper layer of the hard coat layer. The upper layer of the hard coat layer means a region from the interface opposite to the light transmissive substrate of the hard coat layer to a third in the thickness direction.
Since the cubic hollow silica fine particles are unevenly distributed in the hard coat layer, the hard coat layer has a refractive index of the upper layer portion more than that of the non-uniform distribution of the cubic hollow silica fine particles. The upper layer portion plays the same role as the low refractive index layer. That is, the hard coat layer in the optical layered body of the present invention has the same effect as the conventional multilayered optical layered body in which the hard coat layer and the low refractive index layer are stacked in this order in a single layer structure. it can.

The hard coat layer preferably has a refractive index of 1.43 or less. If it exceeds 1.43, the antireflection performance of the optical layered body of the present invention becomes insufficient, and it may not be possible to cope with the high level display quality of recent image display devices. A more preferable upper limit of the refractive index of the hard coat layer is 1.41.
The refractive index of the hard coat layer is a calculated value calculated from the refractive index and the blending ratio of the material constituting the hard coat layer such as the cubic hollow silica fine particles and the resin component described later.

The cubic hollow silica fine particles in the hard coat layer may be monodispersed or may form aggregates. When the cubic hollow silica fine particles form an aggregate, the average secondary particle diameter is preferably 2 μm or less. When the average secondary particle diameter of the aggregate exceeds 2 μm, the haze of the hard coat layer may be deteriorated. The average secondary particle diameter of the cubic hollow silica fine particles can be measured by observing the cross section of the hard coat layer with an electron microscope such as TEM or STEM.

A part of the cubic hollow silica fine particles protrudes from the surface of the hard coat layer.
Since a part of the cubic hollow silica fine particles protrudes from the surface of the hard coat layer, the optical layered body of the present invention has excellent blocking properties.
Here, as described above, a technique for improving the blocking performance by causing the hard coat layer to contain spherical fine particles and causing a part of the spherical fine particles to protrude from the surface is well known. However, when spherical fine particles are projected on the surface of the hard coat layer, there is a problem that the spherical fine particles easily fall off. On the other hand, the cubic hollow silica fine particles in the optical layered body of the present invention are mainly in a state in which the corner portions protrude from the surface of the hard coat layer, so that the cubic shapes are compared with the spherical fine particles. The hollow silica fine particles are not easily dropped off.
Further, since the cubic hollow silica fine particles are hollow, the refractive index of the hard coat layer can be suitably reduced, and as a result, the reflectance on the surface of the hard coat layer can be sufficiently lowered. it can.
Here, the “state in which the corner portion protrudes from the surface of the hard coat layer” refers to the case where the corner portion of the cubic hollow silica fine particle directly protrudes from the surface of the hard coat layer, as well as the cubic shape. The case where the corner | angular part of hollow silica fine particles protrudes from the surface of the said hard-coat layer in the state covered with the thin film of the resin component which comprises the said hard-coat layer is included. Examples of the thin film include a nanometer-order layer having a thickness of less than 1000 nm.
Further, in the optical layered body of the present invention, since the corners of the cubic hollow silica fine particles protrude from the surface of the hard coat layer, the contact area when contacting the hard coat layer surface decreases. Excellent scratch resistance. Further, it is presumed that the pencil hardness is improved as compared with the case of containing spherical fine particles because the corner portions of the cubic hollow silica fine particles protrude from the surface of the hard coat layer.

The hard coat layer contains 70 to 100% of the cubic hollow silica fine particles in a region from the interface opposite to the light-transmitting substrate to a third of the thickness of the hard coat layer. The lower limit is more preferably 80%. If it is less than 70%, cubic hollow silica fine particles protruding from the surface of the hard coat layer are reduced, and sufficient anti-blocking performance may not be obtained.
The abundance of the cubic hollow silica fine particles in the hard coat layer can be measured by observing a cross section in the thickness direction of the hard coat layer with an electron microscope such as SEM.

The cubic hollow silica fine particles preferably protrude from the surface of the hard coat layer at a corner in the range of 10 to 200 nm.
In the present specification, the “surface of the hard coat layer” is a surface on the side from which the cubic hollow silica fine particles protrude and is a flat surface other than a portion from which the cubic hollow silica fine particles protrude. means.
When the protrusions of the corners of the cubic hollow silica fine particles from the surface of the hard coat layer are less than 10 nm, sufficient anti-blocking performance may not be obtained. Fine particles may fall off, or the amount of reflected light scattered on the surface of the hard coat layer by the protruding cubic hollow silica fine particles may increase, resulting in an increase in haze. The more preferable lower limit of the protrusion of the cubic hollow silica fine particles from the hard coat layer surface is 15 nm, and the more preferable upper limit is 150 nm.
The protruding distance of the cubic hollow silica fine particles from the surface of the hard coat layer is the cubic hollow silica protruding from the surface of the hard coat layer from the surface where the cubic hollow silica fine particles do not protrude from the surface of the hard coat layer. This is the vertical distance to the corner of the fine particle. Specifically, it is obtained as an average value obtained by measuring the above vertical distance at 10 points by electron microscope observation.

The cubic hollow silica fine particles preferably have a primary particle having a side of 30 to 200 nm and an outer shell thickness of 3 to 15 nm.
When one side of the primary particles is less than 30 nm, the cubic hollow silica fine particles cannot be sufficiently projected from the surface of the hard coat layer, and the blocking performance may be inferior. On the other hand, if it exceeds 200 nm, haze may increase or the cubic hollow silica fine particles may fall off. A more preferable lower limit of one side of the primary particles is 90 nm, and a more preferable upper limit is 110 nm.
In addition, if the outer diameter of the primary particles is less than 3 nm, the strength of the cubic hollow silica fine particles may be insufficient, and it is difficult to produce the cubic hollow silica fine particles themselves. If it exceeds 15 nm, the upper layer portion of the hard coat layer may not be sufficiently lowered in refractive index. A more preferable lower limit of the outline of the primary particles is 8 nm, and a more preferable upper limit is 10 nm.
The length of one side of the primary particles of the cubic hollow silica fine particles and the thickness of the outer shell can be measured by observing the cross section of the hard coat layer with an electron microscope such as TEM or STEM.

Such cubic hollow silica fine particles are produced, for example, by causing a basic compound to act on silicon alkoxide to promote hydrolysis and polycondensation reaction of the silicon alkoxide to produce silica as an outer shell, thereby forming a cubic core. Cover the surface of the particles. Then, it can manufacture by dissolving and removing the said core particle.

The silicon alkoxide is not particularly limited as long as it is a silicon alkoxide such as a silane coupling agent, for example, tetramethoxysilane, trimethoxysilane, tetraethoxysilane, triethoxysilane, tetrapropoxysilane, tetrabutoxysilane, etc. Is mentioned. Of these, tetraethoxysilane is preferably used.
Commercially available products may be used as the silicon alkoxide, for example, ethyl silicate (product name “high purity ethyl silicate”: tetraethoxysilane) manufactured by Tama Chemical Co., Ltd., alkoxy manufactured by Shin-Etsu Chemical Co., Ltd. Silane (product name “KBE-04”: tetraethoxysilane) and the like.
Further, the silicon alkoxide may be a silane coupling agent having an ultraviolet-reactive functional group in the molecule. Examples of such commercially available silicon alkoxide include KBM503 and KBM502 manufactured by Shin-Etsu Chemical Co., Ltd. And KBE503 (both containing methacrylate groups as UV-reactive functional groups), KBM5103 (containing acrylate groups as UV-reactive functional groups), and the like.

Examples of the basic compound include ammonia (NH ₃ ), amine, amide, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) ₂ ), and the like.
In the production of the cubic hollow silica fine particles, it is preferable to gradually generate the basic compound by applying a catalyst to the basic compound precursor substance.
Examples of the basic compound precursor substance include urea ((NH ₂ ) ₂ CO) that generates ammonia by the action of a catalyst. Moreover, as said catalyst, a urease (urea decomposing enzyme) is mentioned, for example.

The core particles in the cubic form are preferably calcium carbonate fine particles. The crystal of calcium carbonate is calcite and hexagonal, but it can be grown into a cubic shape, that is, a “cubic shape” by controlling the synthesis conditions.
The method for growing the calcium carbonate fine crystal is not particularly limited. For example, a method of introducing carbon dioxide into a calcium hydroxide slurry to precipitate calcium carbonate, sodium carbonate in an aqueous solution of a soluble calcium salt such as calcium chloride. And the like, for example, by adding a soluble carbonate such as calcium carbonate to precipitate calcium carbonate.

The core particles preferably have an outer diameter in the range of 8 to 160 nm. By using core particles having such an outer diameter, cubic hollow silica fine particles having the above-described size can be produced.
In addition, as a method for obtaining the above-mentioned outer diameter calcium carbonate fine particles, it is preferable to increase the speed of the precipitation reaction of calcium carbonate at a relatively low temperature. Specifically, for example, in the case of introducing carbon dioxide gas into the calcium hydroxide slurry as a method of growing the calcium carbonate fine particle crystals, the liquid temperature when introducing the carbon dioxide gas is 30 ° C. or less, and carbon dioxide gas is used. The introduction rate is preferably 1.0 L / min or more per 100 g of calcium hydroxide.
In addition, as a calcium carbonate fine particle which has the said outer diameter, you may use a commercial item, For example, the fine calcium carbonate by Hayashi Kasei Co., Ltd., the synthetic calcium carbonate by Shiraishi Kogyo Co., etc. can be used.

As a more specific method for producing the above-mentioned cubic hollow silica fine particles, first, a colloidal dispersion of core particles or a dispersion obtained by mixing a dry powder with a solvent such as water or alcohol and dispersing by ultrasonic irradiation or the like. A silicon alkoxide is mixed here at a predetermined concentration to prepare a reaction solution.
The obtained reaction liquid is put into a reaction vessel such as a stirrer, stirred or circulated, a basic compound is added, and silica particles are coated on the surface of core particles by hydrolysis of silicon alkoxide and condensation polymerization reaction. When a basic compound precursor is added to the reaction solution instead of the basic compound, a catalyst is then added to decompose the basic compound precursor to sequentially generate the basic compound, thereby hydrolyzing silicon alkoxide. The surface of the core particles is coated with silica by a condensation polymerization reaction.
The core particles coated with silica are recovered from the reaction vessel, dried, redispersed in a solvent, and the core particles are dissolved and removed by adding an acid such as hydrochloric acid to produce cubic hollow silica fine particles. Can do.

In the hard coat layer, the content of the cubic hollow silica fine particles is 0.5 to 20 parts by mass with respect to a total of 100 parts by mass of the resin component constituting the hard coat layer and the cubic hollow silica fine particles. Preferably there is. If it is less than 0.5 parts by mass, not only the lower refractive index of the upper layer part of the hard coat layer cannot be sufficiently lowered, but also the anti-blocking performance of the optical laminate of the present invention may be inferior, If it exceeds, the hardness of the hard coat layer may be insufficient. A more preferable lower limit of the content of the cubic hollow silica fine particles is 2 parts by mass, and a more preferable upper limit is 15 parts by mass.

The resin component constituting the hard coat layer is an ionizing radiation curable resin, an ionizing radiation curable resin and a solvent drying resin (added to adjust the solid content during coating), which is a resin curable by ultraviolet rays or electron beams. And the like, or a thermosetting resin or the like, preferably an ionizing radiation curable resin.
Examples of the ionizing radiation curable resin include compounds having one or more unsaturated bonds such as a compound having an acrylate functional group. 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 polymethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri ( Polyfunctional compounds such as (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, or the above polyfunctional compound and (meth) acrylate And the like (for example, poly (meth) acrylate ester of polyhydric alcohol) and the like. In the present specification, “(meth) acrylate” refers to methacrylate and acrylate.

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.

When the ionizing radiation curable resin is used as an ultraviolet curable resin, it is preferable to use a photopolymerization initiator.
Examples of the photopolymerization initiator include acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetramethylchuram monosulfide, and thioxanthones.
Further, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine and the like.

The solvent-drying resin used by mixing with the ionizing radiation curable resin mainly includes a thermoplastic resin, and the thermoplastic resin is not particularly limited, and conventionally known ones can be used. By adding the solvent-drying resin, coating film defects on the coated surface can be effectively prevented.
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. Resins, polyamide resins, cellulose derivatives, silicone resins and rubber or elastomers can be mentioned. 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 viewpoints of film forming properties, transparency, and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives, and the like are preferable.
According to a preferred embodiment of the present invention, when the material of the light transmissive substrate described later is a cellulose resin such as cellulose triacetate, preferred specific examples of the thermoplastic resin include cellulose derivatives such as nitrocellulose, acetylcellulose, Examples thereof include cellulose acetate propionate and ethyl hydroxyethyl cellulose.

Examples of the thermosetting resin include phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation resin, silicon resin. And polysiloxane resin.
When using the said thermosetting resin, as needed, hardening agents, such as a crosslinking agent and a polymerization initiator, a polymerization accelerator, a solvent, a viscosity modifier, etc. can be further added and used.

The hard coat layer is a coating film formed by applying a composition for a hard coat layer prepared by mixing each material such as the above-described cubic hollow silica fine particles and a resin component onto a light-transmitting substrate. It can be formed by drying as necessary and curing by irradiation with ionizing radiation or heating.

The method of mixing each material such as the cubic hollow silica fine particles and the resin component is not particularly limited, and examples thereof include known methods such as a paint shaker or a bead mill.
Here, the cubic hollow silica fine particles in the composition for a hard coat layer immediately after preparation are uniformly dispersed. However, since the cubic hollow silica fine particles have a specific gravity lighter than that of the resin component, when the coating film is formed, it moves to the opposite side of the light-transmitting substrate in the coating film and is unevenly distributed above the coating film. It becomes. Then, by curing such a coating film, a hard coat layer in which the cubic hollow silica fine particles as described above are unevenly distributed in the upper layer can be formed.
In order to make the cubic hollow silica fine particles unevenly distributed in the upper layer, it is preferable to use a monomer having a low viscosity as the resin component in the hard coat layer composition, considering the hardness of the hard coat layer to be formed. For example, it is preferable to use pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, ditrimethylolpropane tetraacrylate.

The method for applying the hard coat layer composition onto the light-transmitting substrate is not particularly limited. For example, spin coating, dipping, spraying, dye coating, bar coating, roll coater, meniscus, and the like. Various methods such as a coater method, a flexographic printing method, a screen printing method, and a pea coater method may be mentioned.
Moreover, it does not specifically limit as a drying method of the said coating film, an ionizing radiation irradiation method, and a heating method, A conventionally well-known method is mentioned.
In addition, after the coating film is dried and the solvent described later is removed, heat is applied before curing to lower the viscosity of the resin component contained in the coating film, thereby increasing the fluidity, so that the cubic hollow Silica fine particles can be more unevenly distributed in the upper layer of the coating film.

The hard coat layer composition preferably contains a solvent.
The solvent is not particularly limited, and examples thereof include alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, and PGME; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and heptanone. Ketones such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl formate, ethyl formate, propyl formate, butyl formate, and PGMEA; aliphatic hydrocarbons such as hexane and cyclohexane; Halogenated hydrocarbons such as chloride, chloroform and carbon tetrachloride; aromatic hydrocarbons such as benzene, toluene and xylene; dimethylformamide, dimethylacetamide and n-methylpyrrolidone Amide; diethyl ether, dioxane, ethers such as tetrahydrofuran; ether alcohols such as 1-methoxy-2-propanol. Of these, methyl isobutyl ketone, methyl ethyl ketone, isopropyl alcohol (IPA), n-butanol, s-butanol, t-butanol, PGME, and PGMEA are preferable.

The composition for hard coat layers may contain other components other than the above-described materials as necessary.
Examples of the other components include leveling agents, crosslinking agents, curing agents, polymerization accelerators, viscosity modifiers, antistatic agents, high refractive index agents, high hardness / low curl materials such as colloidal silica, other than those described above. Examples thereof include resins.

The optical layered body of the present invention has a light transmissive 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 transmissive substrate include, for example, polyester (polyethylene terephthalate, polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, Examples of the thermoplastic resin include polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, and polyurethane. Preferably, polyester (polyethylene terephthalate, polyethylene naphthalate) and cellulose triacetate are used.

The light-transmitting substrate preferably uses the thermoplastic resin as a flexible film-like body, but uses a plate of these thermoplastic resins depending on the use mode in which curability is required. It is also possible, or a glass plate plate may be used.

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-based resin), Sumitrite FS-1700 manufactured by Sumitomo Bakelite, Arton (modified norbornene-based 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.

The thickness of the light transmissive substrate is preferably 5 to 300 μm, more preferably the lower limit is 20 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 base material is provided with an anchor in addition to physical treatment such as corona discharge treatment, atmospheric pressure plasma treatment, oxidation treatment, etc., in order to improve adhesion when forming the hard coat layer or the like thereon. Application of a paint called an agent or a primer may be performed in advance. When the material forming the light transmissive substrate is triacetyl cellulose, chemical treatment such as alkali treatment (saponification treatment) may be performed in advance.

The optical layered body of the present invention has a configuration in which the above-described hard coat layer is laminated on one surface of the light transmissive substrate, and is publicly known between the light transmissive substrate and the hard coat layer. A structure in which an antistatic layer comprising an antistatic agent and a binder resin is formed may be used.

The total light transmittance of the optical layered body of the present invention is preferably 90% or more. If it is less than 90%, color reproducibility and visibility may be impaired when it is mounted on the display surface. The total light transmittance is more preferably 95% or more, and still more preferably 96% or more.

In the optical layered body of the present invention, the haze is preferably less than 1.0%, and more preferably less than 0.5%. If it exceeds 1.0%, the color reproducibility and visibility may be impaired when mounted on the display surface, and a desired contrast may not be obtained.
The 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 has a hardness of preferably 2H or more, more preferably 3H or more, in a pencil hardness test (load 4.9 N) according to JIS K5600-5-4 (1999).

In addition, the optical laminate of the present invention was subjected to 10 reciprocal frictions with a friction load of 500 g / cm ² using steel wool # 0000 (trade name: BON STAR, manufactured by Nippon Steel Wool Co., Ltd.). When observed, it is preferable that no peeling of the coating film on the surface is observed, and it is more preferable that peeling of the coating film on the surface is not observed after 10 reciprocating frictions at 700 g / cm ² . Most preferably, it is 1000 g / cm ² or more and similarly 10 reciprocating frictions cause no surface coating peeling.

Examples of the method for producing the optical layered body of the present invention include a method having a step of forming a hard coat layer by applying the above-described composition for a hard coat layer on a light-transmitting substrate.
The method for forming the hard coat layer is as described above.

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 examples thereof include a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, and an ethylene-vinyl acetate copolymer saponified film that are dyed and stretched with iodine or the like.
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 (preferably a 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 (electrodes are formed on the surface) and a rear glass substrate (disposed with electrodes and minute grooves on the surface) disposed opposite to the front glass substrate with a discharge gas sealed between them. And forming red, green, and blue phosphor layers in the groove). 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.

In the optical layered body of the present invention, the hard coat layer has a single layer structure and has excellent antireflection performance and excellent blocking resistance.
Therefore, 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), electronic paper, a touch panel, It can be suitably applied to a tablet PC or the like.

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 transparent base material (thickness 60 μm triacetyl cellulose resin film; manufactured by Fuji Photo Film Co., Ltd., TF60UL) is prepared, and the following hard coat layer composition is applied to one side of the light transparent base material to form a coating film. Formed. Next, it is dried for 30 seconds in a hot oven at a temperature of 70 ° C. (no air drying), and further heated for 30 seconds in a hot oven at a temperature of 100 ° C. to evaporate the solvent in the coating film so that the dry film thickness becomes 7 μm. Thereafter, ultraviolet rays were irradiated so that the integrated light amount was 200 mJ / cm ² to cure the coating film to form a hard coat layer, thereby producing an optical laminate.

(Composition for hard coat layer)
Pentaerythritol triacrylate (PETA) (Nippon Kayaku Co., Ltd .; PET30)
90 parts by mass cubic hollow silica fine particles (side 100 nm, outer thickness 7 nm) 10 parts by mass photopolymerization initiator (Irgacure 184, manufactured by BASF) 4 parts by mass solvent (MEK) 100 parts by mass leveling agent (F477, manufactured by DIC) , F leveling agent) 0.1 parts by weight

The cubic hollow silica fine particles were obtained by the following method.
Calcium carbonate fine particles as core particles are mixed and dispersed in ethanol distilled water. Tetraethoxysilane, urea and urease are added and stirred in this, and the tetraethoxysilane is hydrolyzed, dehydrated and subjected to condensation polymerization. Silica was coated on the surface of the core particles. Thereafter, the resultant is washed with ethanol to wash away excess tetraethoxysilane, urea and urease, and dried to obtain silica-coated calcium carbonate fine particles. The fine particles are redispersed in distilled water, and diluted hydrochloric acid ( 3 mol / L) was added to dissolve and remove the calcium carbonate fine particles as the core particles to obtain cubic hollow silica fine particles having silica as an outer shell.
In addition, the size of one side and the thickness of the outline of the cubic hollow silica fine particles can be arbitrarily adjusted by appropriately adjusting the size of the core particles to be used and the treatment conditions when the core particles are coated with silica. Came to control.

(Example 2)
A hard coat layer was formed on a light-transmitting substrate in the same manner as in Example 1 except that cubic hollow silica fine particles in the hard coat layer composition had a side of 80 nm and an outer thickness of 7 nm. A laminate was produced.

(Example 3)
A hard coat layer was formed on a light-transmitting substrate in the same manner as in Example 1 except that cubic hollow silica fine particles in the hard coat layer composition were those having a side of 120 nm and an outer thickness of 7 nm. A laminate was produced.

Example 4
A hard coat layer was formed on a light-transmitting substrate in the same manner as in Example 1 except that the cubic hollow silica fine particles in the hard coat layer composition were those having a side of 50 nm and an outer thickness of 7 nm. A laminate was produced.

(Example 5)
A hard coat layer was formed on a light-transmitting substrate in the same manner as in Example 1 except that cubic hollow silica fine particles in the composition for hard coat layer were those having a side of 180 nm and an outer thickness of 7 nm. A laminate was produced.

(Example 6)
A hard coat layer was formed on a light-transmitting substrate in the same manner as in Example 1 except that cubic hollow silica fine particles in the hard coat layer composition had a side of 100 nm and an outer thickness of 5 nm. A laminate was produced.

(Example 7)
A hard coat layer was formed on a light-transmitting substrate in the same manner as in Example 1 except that the cubic hollow silica fine particles in the hard coat layer composition were those having a side of 100 nm and an outer thickness of 13 nm. A laminate was produced.

(Example 8)
In the hard coat layer composition, the hard coat layer was made light-transmissive in the same manner as in Example 1 except that the amount of cubic hollow silica fine particles was 20 parts by mass and the amount of pentaerythritol triacrylate was 80 parts by mass. It formed on the base material and manufactured the optical laminated body.

Example 9
In the hard coat layer composition, the hard coat layer was made light-transmissive in the same manner as in Example 1 except that the amount of cubic hollow silica fine particles was 5 parts by mass and the amount of pentaerythritol triacrylate was 95 parts by mass. It formed on the base material and manufactured the optical laminated body.

(Example 10)
Instead of pentaerythritol triacrylate in the hard coat layer composition, dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd .; DPHA) was used, and the hard coat layer was formed into a light-transmitting substrate in the same manner as in Example 1. An optical layered body was produced by forming the above.

(Example 11)
In the hard coat layer composition, the hard coat layer was made light-transmissive in the same manner as in Example 1 except that the amount of cubic hollow silica fine particles was 30 parts by mass and the amount of pentaerythritol triacrylate was 70 parts by mass. It formed on the base material and manufactured the optical laminated body.

(Example 12)
A hard coat layer was formed on the light-transmitting substrate in the same manner as in Example 1 except that the drying temperature of the coating film was 100 ° C., and an optical laminate was produced.

(Example 13)
A hard coat layer was formed on the light transmissive substrate in the same manner as in Example 1 except that the drying temperature of the coating film was 50 ° C., and an optical laminate was produced.

(Comparative Example 1)
A hard coat layer was formed on the light-transmitting substrate in the same manner as in Example 1 except that the coating film was dried at 100 ° C. for 30 seconds while blowing air to produce an optical laminate.

(Comparative Example 2)
In the composition for hard coat layer, hard coat was performed in the same manner as in Example 1 except that spherical solid silica fine particles (manufactured by Nissan Chemical Co., Ltd., diameter: 12 nm, trade name: MIBKSD) were used instead of cubic hollow silica fine particles. A layer was formed on the light-transmitting substrate to produce an optical laminate.

(Comparative Example 3)
In the composition for hard coat layer, instead of the cubic hollow silica fine particles, spherical solid silica fine particles (CIK Nanotech Co., Ltd., diameter: 250 nm, trade name: E65) were used, and the blending amount of the spherical solid silica fine particles was 30 parts by mass. A hard coat layer was formed on the light-transmitting substrate in the same manner as in Example 1 except that the amount of pentaerythritol triacrylate was 70 parts by mass, and an optical laminate was manufactured.

(Reference Example 1)
In the composition for hard coat layer, the hard coat layer was formed into a light-transmitting group in the same manner as in Example 1 except that spherical hollow silica fine particles (diameter 55 nm, outer thickness 7 nm) were used instead of cubic hollow silica fine particles. It formed on the material and manufactured the optical laminated body.

(Reference Example 2)
In the hard coat layer composition, the hard coat layer was made light-transmitting in the same manner as in Example 1 except that the amount of cubic hollow silica fine particles was 50 parts by mass and the amount of pentaerythritol triacrylate was 50 parts by mass. It formed on the base material and manufactured the optical laminated body.

(Reference Example 3)
In the hard coat layer composition, the hard coat layer was made light-transmissive in the same manner as in Example 1 except that the amount of cubic hollow silica fine particles was 1 part by mass and the amount of pentaerythritol triacrylate was 99 parts by mass. It formed on the base material and manufactured the optical laminated body.

The following evaluation was performed about the optical laminated body which concerns on an Example, a comparative example, and a reference example. The results are shown in Table 1.

(Uniformity ratio)
Cut each optical laminate in the thickness direction of the hard coat layer, observe the cross-section electron microscope of the hard coat layer, and among the silica fine particles that appeared on the cross section of the hard coat layer, hard from the interface opposite to the light-transmitting substrate The ratio of silica fine particles contained in the region at 1/3 μm of the thickness of the coat layer was calculated.

(Projection distance from hard coat layer surface)
The distance of the silica fine particles protruding from the surface of the hard coat layer of each optical laminate was determined as an average value measured at 10 points by observation with an electron microscope.

(Abrasion resistance)
Using the # 0000 steel wool (trade name: BON STAR, manufactured by Nippon Steel Wool Co., Ltd.), the surface of the hard coat layer of each optical laminate was subjected to 10 reciprocal frictions by changing the friction load. The presence or absence of scratches or peeling was visually observed and evaluated according to the following criteria.
○: No scratch at 500 g / cm ² ×: Scratch or peeling of coating film at 500 g / cm ²

(Reflectance)
A black vinyl tape (Yamato Vinyl Tape No 200-38-21 38 mm width was applied to the side opposite to the measurement side, where the hard coat layer of each optical laminate was provided, and then a reflectance measuring device (V7100 type). VAR-7010 (manufactured by JASCO Corporation) was used to measure 5 ° regular reflectance (%) on the surface of the optical laminate.

(Blocking resistance)
The optical laminates according to the examples, comparative examples and reference examples were used in a clean room room (room temperature 25 ° C., humidity 50% environment at 3900 m / min using a 1330 mm wide light-transmitting substrate). The product was manufactured by coating) and wound up.
After winding, in the same clean room, after 24 hours, it was rolled back and the state of sticking inside the roll was evaluated.
○: No sticking occurred ×: Sticking occurred

(Total light transmittance)
About the total light transmittance of each optical laminated body, it measured by the method based on JISK-7361 (total light transmittance) using a haze meter (Murakami Color Research Laboratory make, product number; HM-150), and the following Evaluation based on the criteria.
○: Total light transmittance is 90% or more ×: Total light transmittance is less than 90%

(Haze)
The haze of each optical laminate was measured according to JIS K-7361 using a haze meter (Murakami Color Research Laboratory, product number: HM-150).

As shown in Table 1, the optical laminates according to the examples were excellent in all evaluations.
On the other hand, the optical laminate according to Comparative Example 1 in which the cubic hollow silica fine particles were not unevenly distributed in the hard coat layer, and the optical laminate according to Comparative Example 2 using the spherical hollow silica fine particles having a diameter of 12 nm, The spherical hollow silica fine particles hardly protrude from the surface of the hard coat layer, and were inferior in each evaluation of scratch resistance, reflectance and blocking resistance.
Moreover, the optical laminated body which concerns on the comparative example 3 using the spherical solid silica fine particle whose diameter is 250 nm was inferior to each evaluation of abrasion resistance, a reflectance, a total light transmittance, and a haze.
In addition, since the size of one side of the cubic hollow silica fine particles in the optical laminate according to Reference Example 1 was too small, the spherical hollow silica fine particles hardly protrude from the surface of the hard coat layer, and the scratch resistance and reflectivity were reduced. And it was inferior to each evaluation of blocking resistance.
In addition, since the optical laminate according to Reference Example 2 contained a large amount of cubic hollow silica fine particles in the hard coat layer, the spherical hollow silica fine particles greatly protruded from the surface of the hard coat layer. It was inferior to each evaluation of rate and haze.
In addition, the optical laminate according to Reference Example 3 had a small amount of cubic hollow silica fine particles in the hard coat layer, so that the spherical hollow silica fine particles hardly protrude from the hard coat layer surface, and scratch resistance, It was inferior to each evaluation of reflectance and blocking resistance.

Since the optical layered body of the present invention has the above-described configuration, the hard coat layer has a single-layer structure and has excellent antireflection performance and excellent blocking resistance. Therefore, 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), electronic paper, a touch panel, and a tablet. It can be suitably applied to a PC or the like.

Claims (5)

An optical laminate having a hard coat layer on one surface of the light transmissive substrate,
The hard coat layer contains cubic hollow silica fine particles,
The cubic hollow silica fine particles are unevenly distributed in the upper layer of the hard coat layer, and corner portions of the cubic hollow silica fine particles protrude from the surface of the hard coat layer ,
In the cubic hollow silica fine particles, one side of the primary particles is 30 to 200 nm, the outer thickness is 3 to 15 nm, and the corner portion protrudes from the surface of the hard coat layer in the range of 10 to 200 nm. An optical laminate characterized by the above. From the opposite side surface and light-transmitting substrate of the hard coat layer, in the region of up to one third of the thickness of the hard coat layer, according to claim 1 wherein 70% to 100% of the cubic hollow silica fine particles are contained Optical laminate. The content of the cubic hollow silica fine particles in the hard coat layer is 0.5 to 20 parts by mass with respect to a total of 100 parts by mass of the resin component constituting the hard coat layer and the cubic hollow silica fine particles. Item 3. The optical laminate according to Item 1 or 2 . A polarizing plate comprising a polarizing element,
The said polarizing plate is equipped with the optical laminated body of Claim 1, 2 or 3 on the said polarizing element surface, The polarizing plate characterized by the above-mentioned. An image display device comprising the optical laminate according to claim 1, 2 or 3 or the polarizing plate according to claim 4 .