JP2014041249A - Optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film having excellent hardness and low reflectivity.SOLUTION: An optical film includes at least a hard coat layer and a low refractive index layer, disposed in this order on one surface of a light-transmitting substrate. The low refractive index layer comprises one or more kinds of compounds selected from the group consisting of an alkoxysilane and a hydrolysate thereof, hollow fine particles and inorganic solid fine particles. The low refractive index layer is formed of a cured product of a composition for a low refractive index layer which includes the inorganic solid fine particles of 10 to 200 pts. mass based on 100 pts. mass of the hollow fine particles.

Description

  The present invention relates to an optical film.

With the spread of tablet terminals and the like, cases of using display devices such as liquid crystal displays not only indoors but also outdoors are increasing.
Therefore, there is a demand for a display device having a surface material that is hard to be damaged even outdoors with a lot of dust and that has a surface material that is hard enough to withstand a “sandfall test” for building materials.

  Patent Document 1 discloses an antireflection film using a coating composition in which a specific hydrolyzable silane and a specific fluorine-containing polymer are combined. According to the method of Patent Document 1, it is described that the film has excellent antireflection effect, contamination resistance, and the like, and also has scratch resistance. However, in the method of Patent Document 1, the antireflection film has insufficient scratch resistance, and a higher hardness optical film is required.

JP 2002-22905 A

  A cured film formed by a sol-gel method using hydrolyzable silane is likely to have an uneven shape on the surface due to shrinkage during condensation. The inventors of the present invention have found that depending on the concavo-convex shape produced when the low refractive index layer is formed by the sol-gel method, the hardness becomes insufficient and scratches may be caused by dust or the like.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical film having excellent hardness and low reflectivity.

  The optical film according to the present invention is an optical film in which at least a hard coat layer and a low refractive index layer are provided in this order on one side of a light-transmitting substrate, and the low refractive index layer is an alkoxy film. It contains at least one selected from the group consisting of silane and its hydrolyzate, hollow fine particles, and inorganic solid fine particles, and 10 to 200 mass of inorganic solid fine particles with respect to 100 parts by mass of the hollow fine particles. It consists of the hardened | cured material of the composition for low refractive index layers which is a part.

  In the optical film of the present invention, the hard coat layer is a high refractive index hard coat layer containing fine particles of high refractive index, and is preferably adjacent to the low refractive index layer from the viewpoint of excellent low reflectivity. .

  In the optical film of the present invention, the inorganic solid fine particles in the low refractive index layer are deformed silica fine particles in which 2 to 20 substantially spherical silica fine particles having an average particle diameter of 1 to 100 nm are bonded by an inorganic chemical bond. It is preferable that a certain level of hardness can be achieved.

  In the optical film of the present invention, the indentation hardness of the low refractive index layer is preferably 0.6 GPa or more.

  According to the present invention, an optical film having excellent hardness and low reflectivity can be provided.

FIG. 1 is a schematic view showing an example of an optical film according to the present invention. FIG. 2 is a schematic view showing another example of the optical film according to the present invention. FIG. 3 is a schematic view showing another example of the optical film according to the present invention.

Hereinafter, the optical film according to the present invention will be described.
In the present invention, the curability refers to a property that becomes hard through a chemical reaction.
In the present invention, (meth) acrylate represents acrylate and / or methacrylate.
In the present invention, the average particle size of each fine particle, such as a hollow fine particle, an inorganic solid particle, and a high refractive index fine particle in a solution, such as a composition for a low refractive index layer, refers to dynamic light scattering of the particle in a solution. It means a 50% particle diameter (d50 median diameter) when measured by the method and the particle diameter distribution is represented by a volume cumulative distribution. The average particle size can be measured using a Microtrac particle size analyzer manufactured by Nikkiso Co., Ltd. or a Nanotrac particle size analyzer.
The average particle size in the solution represents the average of the primary particle size if the particles are not aggregated, and represents the average of the dispersed particle size if the particles are aggregated particles.
Moreover, in this invention, the average particle diameter of each fine particle in each layer which comprises an optical film can be calculated | required by the method of directly measuring the magnitude | size of a primary particle from the electron micrograph of the cross section of an optical film. Specifically, the minor axis diameter and major axis diameter of each primary particle are measured, and the average is used as the particle diameter of the particle. Next, the particle diameter of each of 100 or more particles is obtained, and the average is calculated. The average particle size is set. Note that the same result can be obtained regardless of whether the electron microscope is a transmission type (TEM) or a scanning type (SEM).

  The optical film according to the present invention is an optical film in which at least a hard coat layer and a low refractive index layer are provided in this order on one side of a light-transmitting substrate, and the low refractive index layer is an alkoxy film. It consists of hardened | cured material of the composition for low-refractive-index layers containing 1 or more types selected from the group which consists of a silane and its hydrolyzate, a hollow microparticle, and an inorganic solid microparticle.

As illustrated in FIG. 1, the optical film 10 of the present invention is provided with at least a hard coat layer 2 and a low refractive index layer 3 in this order on one surface side of a light-transmitting substrate 1. is there. The hard coat layer 2 in FIG. 1 may be adjacent to the low refractive index layer 3 as a high refractive index hard coat layer 2 ′ containing high refractive index fine particles as shown in FIG. In this case, the hard coat layer 2 ′ is a layer having the high refractive index layer 4. Further, as illustrated in FIG. 3, the optical film 10 of the present invention has a hard coat layer 2, a high refractive index layer 4, and a low refractive index layer 3 on one surface side of the light transmissive substrate 1. It may be provided in this order.
In the present invention, since the low refractive index layer 3 is made of a cured product of the specific composition for low refractive index layer, the surface uneven shape is compared with a layer made of normal alkoxysilane and its hydrolyzate. The friction is reduced and the hardness is excellent.

The optical film of the present invention has at least a light-transmitting substrate, a hard coat layer, and a low refractive index layer, and other layers are added as necessary unless the effects of the present invention are impaired. You may have.
Hereinafter, although the structure of the optical film of this invention is demonstrated in detail in order, it demonstrates from the low refractive index layer characteristic in this invention.

[Low refractive index layer]
In the present invention, the low refractive index layer is a cured low refractive index layer composition containing at least one selected from the group consisting of alkoxysilanes and hydrolysates thereof, hollow fine particles, and inorganic solid fine particles. It consists of things. The composition for a low refractive index layer may contain other components as necessary as long as the effects of the present invention are not impaired. In the present invention, the low refractive index layer is a layer having a lower refractive index than at least an adjacent layer.

  The low refractive index layer of the present invention is a combination of one or more selected from the group consisting of alkoxysilanes and hydrolysates thereof (hereinafter sometimes referred to as alkoxysilanes), hollow fine particles, and inorganic solid fine particles. By using it, it can be set as the low refractive index layer excellent in hardness.

The action that exerts the above effects by the specific combination is estimated as follows.
The cured film obtained by curing alkoxysilane or the like by the sol-gel method has a higher hardness than the case of using a conventional UV curable resin, but the surface is likely to have an uneven shape due to shrinkage during condensation, and the hardness Was still inadequate.
The low refractive index layer of the present invention uses alkoxysilane or the like and hollow fine particles in combination with inorganic solid fine particles. By mixing inorganic solid fine particles, hardness can be imparted, and materials such as alkoxysilane that can easily shrink can be reduced, and shrinkage can be suppressed. In addition, since the inorganic solid fine particles enter the uneven shape that can occur on the surface, it is presumed that the difference in height of the uneven shape is relaxed and a smooth surface shape with reduced friction is obtained. Due to these synergistic effects, it is possible to obtain a low-refractive index layer having excellent hardness that is hardly damaged by dust and the like.

<Composition for low refractive index layer>
The composition for a low refractive index layer contains at least alkoxysilane and the like, hollow fine particles, and inorganic solid fine particles, and other components are added as necessary unless the effects of the present invention are impaired. It may be contained.
Hereinafter, each component which comprises the composition for low refractive index layers is demonstrated.

(Alkoxysilane, etc.)
As the composition for a low refractive index layer used in the present invention, one or more selected from the group consisting of alkoxysilanes and hydrolysates thereof are used.
The alkoxysilane can be appropriately selected from those having hydrolyzability. As an alkoxysilane used for this invention, what is represented by following General formula (1) is mentioned, for example.
General formula (1): (R ¹ ) _n Si (OR ² ) _(4-n)
(In General Formula (1), R ¹ represents an organic group having 1 to 8 carbon atoms, R ² represents an alkyl group having 1 to 12 carbon atoms, and n is an integer of 0 to ^3. R ¹ and When there are a plurality of R ^{2 s} , a plurality of R ^{1 s} and a plurality of R ^{2 s} may be the same as or different from each other.)

In the present invention, the organic group means a group having one or more carbon atoms. Among them, the organic group in R ¹ is preferably an alkyl group or a phenyl group, and the alkyl group and the phenyl group may further have a substituent. Examples of the substituent include halogen atoms such as fluorine, chlorine and bromine, amino groups, and epoxy groups. The alkyl group may have a double bond.
R ² represents an alkyl group having 1 to 12 carbon atoms, and a hydrogen atom in the alkyl group may be substituted with a halogen atom such as fluorine, chlorine, or bromine.
In General formula (1), it is preferable that n is 0-1.

Among them, the alkoxysilane is preferably represented by the following general formula (2) from the viewpoint that the low refractive index layer has high hardness.
General formula (2): Si (OR ² ) ₄
(R ² in the general formula (2) is the same as R ² in the general formula (1).)

  Specific examples of the alkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, and the like. It is not limited.

From the viewpoint of reducing the refractive index of the low refractive index layer, it is preferable that the hydrogen atom in the alkyl group is substituted with a fluorine atom. On the other hand, from the viewpoint of improving the strength of the low refractive index layer, it is preferable that the hydrogen atom in the alkyl group is not substituted with a halogen atom.
From the viewpoint of improving the film strength, R ² is preferably 1 to 8 carbon atoms, more preferably 1-5.

(Hollow particles)
In the present invention, the hollow fine particles refer to particles that are porous or hollow inside the outer shell layer and contain air inside the particles, and are used for imparting low refractive index. The refractive index of the hollow fine particles is preferably 1.44 or less and more preferably 1.40 or less from the viewpoint of imparting low refractive index properties.

The outer shell layer of the hollow fine particles may be inorganic or organic, and examples thereof include those made of metal, metal oxide, and resin, and silica is preferable. When the outer shell layer is silica, the silica may be in a crystalline state, a sol state, or a gel state.
The shape of the hollow fine particles may be any of a substantially spherical shape, a chain shape, a needle shape, a plate shape, a piece shape, a rod shape, a fiber shape and the like. Especially, it is preferable that it is substantially spherical shape, and it is more preferable that it is elliptical spherical shape or a true spherical shape.
In the present invention, the term “substantially spherical” means an elliptical sphere or a shape that can approximate a sphere including a polyhedron, and is a concept that includes a true sphere.

  The average particle diameter of the hollow fine particles is preferably 1 nm to 100 nm, and more preferably 10 nm to 60 nm. When the average particle size is not more than the above upper limit, transparency is excellent. Moreover, if an average particle diameter is more than the said lower limit, the said hollow fine particle will be easy to disperse | distribute uniformly and it will be easy to provide low refractive index property.

  In the present invention, it is preferable to use a combination of two or more kinds of hollow silica fine particles having different average particle diameters from the viewpoint of achieving superior hardness. When two or more kinds of hollow silica fine particles having different average particle diameters are used, it is preferable that the hollow silica fine particles have the same particle diameter. Specifically, the standard deviation of the particle diameters is 20 times the average particle diameter. % Or less, and more preferably 10% or less. A particularly excellent hardness can be achieved by using a combination of two or more types of hollow silica fine particles having a small variation in particle size and different average particle sizes.

  Specific examples of the hollow fine particles include composite oxide sols or hollow silica fine particles disclosed in JP-A Nos. 7-133105 and 2001-233611. Among these, hollow silica fine particles prepared using the technique disclosed in JP-A-2001-233611 are preferable. Since the inorganic fine particles have high hardness, the layer strength of the low refractive index layer is improved, and the refractive index can be adjusted within a range of about 1.20 to 1.44.

(Inorganic solid fine particles)
In the present invention, the inorganic solid fine particles mean inorganic fine particles having no voids. Since the inorganic solid fine particles are neither porous nor hollow, the inorganic solid fine particles are less likely to be crushed by the pressure (external pressure) applied to the particles from the outside and have excellent pressure resistance compared to the hollow fine particles. In the present invention, by including the inorganic solid fine particles in the low refractive index layer, the condensation component is reduced by replacing it with a matrix such as alkoxysilane, and at the same time, the condensed uneven shape is entered, and the height difference of the uneven shape is alleviated. . By such an action, the surface friction of the low refractive index layer can be reduced and the hardness can be increased.
Since the inorganic solid fine particles do not have voids, the refractive index is 1.42 to 1.46, which is higher than that of the hollow fine particles. The particles may be in an amorphous state or a crystalline state.

  As the inorganic solid fine particles, inorganic solid fine particles used in conventionally known antireflection films and hard coat films can be used. For example, a metal oxide, a metal nitride, a metal sulfide, a metal fluoride, etc. are mentioned. As inorganic solid fine particles, silica fine particles are particularly preferable.

The shape of the solid silica fine particles may be any of a substantially spherical shape, a chain shape, a needle shape, a plate shape, a piece shape, a rod shape, and a fiber shape. From the viewpoint of improving the hardness of the low refractive index layer, it is preferable that the layer is substantially spherical or chain, and more preferably elliptical spherical silica particles or chain silica particles.
Further, from the viewpoint of improving the hardness of the low refractive index layer, the solid silica fine particles are deformed silica fine particles in which 2 to 20 substantially spherical silica fine particles having an average particle diameter of 1 to 100 nm are bonded by an inorganic chemical bond. It is more preferable.

Examples of the inorganic chemical bond in the deformed silica fine particle include an ionic bond, a metal bond, a coordination bond, and a covalent bond. Among them, even when the irregular silica fine particles are added to a polar solvent, a bond that does not disperse the bonded fine particles, specifically, a metal bond, a coordinate bond, and a covalent bond are preferable, and a covalent bond is more preferable. In the aggregate of silica fine particles, the aggregate may be separated by a physical external force. In the aggregate of silica fine particles, there is a possibility that the aggregate may be separated by a component such as a solvent, a binder component, or a surfactant that breaks the aggregation in addition to physical external force. In addition, even after the protective layer is formed, the aggregates may be separated by physical external force (contact with a pointed object or the like), which may cause damage to the protective layer. On the other hand, if the silica fine particles constituting the irregular-shaped silica fine particles are bonded by a covalent bond, decomposition due to physical and chemical forces hardly occurs and is stable.

  As the particle state of the irregular shaped silica fine particles, 2 to 20 silica fine particles are bonded by an inorganic chemical bond and aggregated particles (aggregated particles), and 2 to 20 silica fine particles are bonded by an inorganic chemical bond. Examples thereof include chain-like particles that are bound and chain-bound. In particular, from the viewpoint of increasing the hardness of the low refractive index layer, it is preferable that the irregular silica fine particles have a chain shape.

  As such deformed silica fine particles, for example, commercially available products such as V-8803 manufactured by Catalytic Chemical Co., Ltd. can be used.

  The average particle diameter of the inorganic solid fine particles is preferably 1 nm to 100 nm, and more preferably 10 nm to 60 nm. When the average particle size is not more than the above upper limit, transparency is excellent. Moreover, if an average particle diameter is more than the said lower limit, it will become a low-refractive-index layer of high hardness.

(Relationship between hollow particles and inorganic solid particles)
The mass ratio of the hollow fine particles and the inorganic solid fine particles contained in the low refractive index layer of the present invention is 10 to 200 parts by mass of the inorganic solid fine particles with respect to 100 parts by mass of the hollow fine particles. More preferably, it is 120 parts by mass. If it is more than the said lower limit, the hardness of a low-refractive-index layer is especially excellent. On the other hand, if it is below the upper limit, the refractive index of the low refractive index layer is likely to be lowered.
The ratio of the average particle size of the hollow fine particles to the inorganic solid fine particles is such that when the average primary particle size of the hollow fine particles is 1, the average particle size of the inorganic solid fine particles is 0.1 to 1. Preferably, it is 0.2-1.

(Other ingredients)
In order to improve the coating property, a solvent is usually used for the composition for a low refractive index layer. The solvent used in the composition for the low refractive index layer may be appropriately selected from those that do not react with each component in the composition for the low refractive index layer and that can uniformly dissolve or disperse each component. . Examples of such a solvent include various alcohol solvents such as ethanol and isopropanol.

  Further, a catalyst may be used to accelerate the curing of the alkoxysilane or the like. The catalyst may be appropriately selected from known acid catalysts or alkali catalysts used in the sol-gel method.

(Mixing ratio of each component in the composition for low refractive index layer)
The total content of alkoxysilane and the like is preferably 5 to 50% by mass and more preferably 10 to 25% by mass with respect to the total solid content of the composition for a low refractive index layer. Within the above range, the low refractive index layer has a high hardness.
The content of the hollow fine particles is preferably 10 to 60% by mass and more preferably 15 to 50% by mass with respect to the total solid content of the composition for a low refractive index layer. If it is not less than the above lower limit value, it is easy to impart low refractive index properties, and if it is not more than the above upper limit value, the film strength is excellent.
The content of the inorganic solid fine particles is preferably 10 to 70% by mass and more preferably 20 to 50% by mass with respect to the total solid content of the composition for a low refractive index layer. By setting the inorganic solid fine particles within the above range, the surface has a smooth shape and excellent scratch resistance against dust and the like.
In the case of using a catalyst, the content of the catalyst is preferably 1 to 8% by mass, more preferably 2 to 5% by weight, based on the total solid content of the composition for a low refractive index layer. .
Moreover, it is preferable that it is 60-98 mass% with respect to the whole quantity of a low refractive index composition, and, as for content of a solvent, it is more preferable that it is 70-97 mass%.
In the present invention, the solid content means all components other than the solvent.

(Other ingredients)
In addition to the above components, various surfactants can be used for the low refractive index layer composition in order to further improve the properties such as anti-aggregation effect and anti-settling effect, and leveling properties. Examples of the surfactant include silicone oil, a fluorine-based surfactant, and preferably a fluorine-based surfactant containing a perfluoroalkyl group.
Further, the composition for a low refractive index layer of the present invention includes an antistatic agent, an antiglare agent, a sensitizer, an antifouling agent, a colorant (pigment, dye), a flame retardant, a silane coupling agent, and an ultraviolet absorber. , Infrared absorbers, adhesion promoters, polymerization inhibitors, antioxidants, surface modifiers, and the like can be added.
As described above, the composition for a low refractive index layer according to the present invention can further have functions such as hard coat properties, antiglare properties, antireflection properties, antistatic properties, and antifouling properties. is there.

(Method for forming low refractive index layer)
The low refractive index layer can be obtained by applying the low refractive index layer composition on the high refractive index layer and heating and curing as necessary.

  The method for applying the composition for a low refractive index layer may be any method as long as it can accurately apply an alignment layer having a desired thickness, and may be appropriately selected from conventionally known methods. For example, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, dip pulling method, curtain coating method, die coating method, casting Method, bar coating method, extrusion coating method, E-type coating method and the like.

(Indentation hardness of low refractive index layer)
The indentation hardness is a hardness measured by nanoindentation, and can be calculated by pressing an indenter into a sample and measuring a load-displacement curve. The indentation hardness of the low refractive index layer may be determined by measuring the indentation hardness of the low refractive index layer at the cut surface of the optical film.
The indentation hardness of the low refractive index layer thus obtained is preferably 0.6 GPa or more, and more preferably 0.8 GPa or more.
The indentation hardness can be measured with a micro indentation tester (for example, TI950 Triboindenter (manufactured by HYSITRON)) using a Barcovic indenter.

[Light transmissive substrate]
The light-transmitting substrate used in the present invention is a highly light-transmitting substrate, and a light-transmitting substrate such as a resin substrate or a glass substrate used in conventionally known optical films is appropriately selected. Can be used. Examples of the resin base material include acetyl cellulose resins such as triacetyl cellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, olefin resins such as polyethylene and polymethylpentene, acrylic resins, polyurethane resins, poly Examples include ether sulfone, polycarbonate, polysulfone, polyether, polyetherketone, acrylonitrile, methacrylonitrile, cycloolefin polymer, cycloolefin copolymer, and other resins mainly. Of these, triacetyl cellulose (TAC) is preferably used from the viewpoint of excellent light transmittance. In addition, “mainly” means a component having the highest content ratio among the constituent components of the base material, and may contain additives and the like as long as the curing of the present invention is not impaired. This means that the content of the main component is 90% by mass or more.

  The average light transmittance of the light transmissive substrate is preferably 70% or more, and more preferably 85% or more. Here, the transmittance of the light-transmitting substrate can be measured according to JIS K7361-1 (a test method for the total light transmittance of plastic-transparent material).

  In the present invention, the thickness of the light transmissive substrate can be appropriately selected and used. Usually, the thickness of the light-transmitting substrate is 10 to 300 μm, but it is preferably 40 to 200 μm from the viewpoint of hardly cracking the surface of the optical film and imparting hardness.

  In the present invention, a surface treatment (for example, saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment) may be applied to the light transmissive substrate, and a primer layer (adhesive layer) May be formed. The light-transmitting substrate in the present invention includes those including these surface treatments and primer layers.

[Hard coat layer]
The hard coat layer constituting the optical film of the present invention can be appropriately selected from conventionally known hard coat layers used for optical films.
The hard coat layer is usually composed of a cured product of a resin composition for a hard coat layer containing at least a binder component.
In addition, in this invention, a hard-coat layer means the thing which shows the hardness more than "H" in the pencil hardness test prescribed | regulated by JIS5600-5-4 (1999). The hard coat layer of the present invention is preferably 3H or higher, more preferably 4H or higher, in the pencil hardness test.

  The film thickness (at the time of curing) of the hard coat layer can be appropriately selected according to the strength and required performance of the substrate, and is 0.1 to 100 μm, preferably 0.8 to 20 μm. From the viewpoint of obtaining sufficient hardness and suppressing the occurrence of curling and cracking, the thickness is more preferably in the range of 3 to 20 μm.

<Resin composition for hard coat layer>
The composition for a hard coat layer used in the present invention contains at least a binder component, and further, if necessary, a solvent, a polymerization initiator, fine particles for adjusting hard coat properties and refractive index, and further a function. It may contain other components such as an antiglare agent, an antifouling agent, an antistatic agent and the like for the purpose of imparting properties, a leveling agent for controlling coating suitability, and a lubricant for the purpose of preventing blocking.

(Binder component)
The binder component used in the hard coat layer composition can be appropriately selected from conventionally known ones. Especially, what has the translucency which light permeate | transmits when it is set as a coating film is preferable. The binder component preferably contains a curable compound, and more preferably contains a photocurable compound. As a binder component, 1 type (s) or 2 or more types of binder components can be used, and the non-hardening compound may be included.
As a photocurable compound, the compound which has a photocurable functional group is mentioned. Examples of the photocurable functional group include an ethylenically unsaturated bond group such as a (meth) acryloyl group, a vinyl group, and an allyl group, an epoxy group, and an oxetanyl group. As the compound having a photocurable functional group, a compound having an ethylenically unsaturated bond group is preferable, and a compound having two or more ethylenically unsaturated bond groups is more preferable. Among them, two ethylenically unsaturated bond groups are preferable. The polyfunctional (meth) acrylate compound having the above is even more preferable.

As a polyfunctional (meth) acrylate compound, as a bifunctional (meth) acrylate, ethylene glycol di (meth) acrylate, bisphenol A tetraethoxydiacrylate, bisphenol A tetrapropoxy diacrylate, 1,6-hexanediol diacrylate Etc.
Examples of the tri- or more functional (meth) acrylate compound include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, di Examples include pentaerythritol tetra (meth) acrylate and isocyanuric acid-modified tri (meth) acrylate.
In addition, these (meth) acrylates may be partly modified in molecular skeleton, modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc. Can also be used.

In addition, as a polyfunctional (meth) acrylate compound having two or more ethylenically unsaturated bond groups, urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, polyether (meth) acrylate, Examples thereof include acrylate polymers represented by the following general formula (I).
Urethane (meth) acrylate is obtained by reaction of polyhydric alcohol and organic diisocyanate with hydroxy (meth) acrylate, for example.
Moreover, what is preferable in an epoxy (meth) acrylate is (meth) acrylate obtained by making (meth) acrylic acid react with an aromatic epoxy resin more than trifunctional, an alicyclic epoxy resin, an aliphatic epoxy resin, etc., Bifunctional or higher aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin and the like, (meth) acrylate obtained by reacting polybasic acid and (meth) acrylic acid, and bifunctional or higher aromatic epoxy It is a (meth) acrylate obtained by reacting a resin, an alicyclic epoxy resin, an aliphatic epoxy resin or the like with a phenol and (meth) acrylic acid.

The content of the binder component in the resin composition for a hard coat layer is usually 30 to 90% by mass when the fine particles described later are contained with respect to the total solid content of the resin composition for a hard coat layer. Is preferable, and it is more preferable that it is 60-85 mass%. Moreover, when it does not contain the microparticles | fine-particles mentioned later, it is preferable that it is 70-100 mass%.
In addition, when using the polymerization initiator mentioned later, content of the said polymerization initiator is 1-10 mass% normally with respect to the total solid of the resin composition for hard-coat layers, and in this case, of a binder component The content is preferably 20 to 89% by mass, and more preferably 50 to 84% by mass when the fine particles described below are contained. Moreover, when it does not contain the microparticles | fine-particles mentioned later, it is preferable that it is 60-99 mass%.

(solvent)
The resin composition for hard coat layers of the present invention may further contain a solvent. The solvent may be appropriately selected from solvents that do not react with each component in the resin composition for hard coat layers and can dissolve or disperse each component. For example, alcohol solvents such as isopropyl alcohol and ethanol; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate; halogenated hydrocarbons; aromatic hydrocarbons such as toluene and xylene; The mixed solvent is mentioned. Among the above solvents, a ketone solvent is preferably used.
The solid content concentration in the resin composition for hard coat layer (ratio of the total mass of the total solid content to the total mass of the composition) is preferably 0.1 to 30% by mass from the viewpoint of coating properties. More preferably, it is 1-10 mass%.

  When the resin composition for hard-coat layers has a photocurable compound, you may use it, selecting a photoinitiator suitably as needed. These polymerization initiators are decomposed by light irradiation to generate radicals or cations to promote radical polymerization and cationic polymerization.

(Fine particles)
The hard coat layer may contain fine particles for imparting hardness to the hard coat layer, adjusting the refractive index, and further imparting functions such as antistatic properties. Further, the hard coat layer may contain high refractive index fine particles described later and have a high refractive index property. In this case, the hard coat layer and the high refractive index layer may be the same layer.
The average particle size of the fine particles may be appropriately adjusted according to the thickness of the hard coat layer, the type of fine particles used, and the properties imparted to the hard coat layer, but is usually 5 to 100 nm, and 10 to 50 nm. It is preferable that The fine particles may be agglomerated particles. In the case of agglomerated particles, the secondary particle size is preferably within the above range. If the average particle size of the fine particles is not less than the above lower limit, sufficient hardness can be imparted to the hard coat layer. If the average particle size of the fine particles is not more than the above upper limit value, the hard coat layer is excellent in transparency.

  When fine particles are contained, it is preferably contained in an amount of 10 to 70% by mass, more preferably 10 to 40% by mass, based on the total solid content of the resin composition for hard coat layer. If it is less than 10% by mass, it is difficult to impart sufficient hardness to the hard coat layer. When it exceeds 70% by mass, the filling rate is excessively increased, and the hardness of the hard coat layer may be lowered. Here, solid content means components other than a solvent.

The fine particles may be inorganic fine particles or organic fine particles, but are preferably inorganic fine particles from the viewpoint of imparting hardness.
Examples of the inorganic fine particles include metal oxides such as silica (SiO ₂ ), aluminum oxide, zirconia, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide. Examples thereof include fine particles, fine metal fluoride particles such as magnesium fluoride and sodium fluoride. Metal fine particles, metal sulfide fine particles, metal nitride fine particles and the like may be used.
From the point of high hardness, silica or aluminum oxide is preferable.

Moreover, the said hard-coat layer can be made into a high refractive index hard coat layer by containing high refractive index microparticles | fine-particles.
High refractive index fine particles refer to fine particles having a refractive index of 1.50 or more, preferably 1.50 to 2.80.
As the high refractive index fine particles, conventionally known fine particles can be appropriately selected and used, and examples thereof include metal oxide fine particles. Specific examples of the metal oxide fine particles include, for example, titanium oxide (TiO ₂ , refractive index: 2.71), zirconium oxide (ZrO ₂ , refractive index: 2.10), cerium oxide (CeO ₂ , refractive index: 2). .20), tin oxide (SnO ₂ , refractive index: 2.00), antimony tin oxide (ATO, refractive index: 1.75 to 1.95), indium tin oxide (ITO, refractive index: 1.95). To 2.00), phosphorus tin compound (PTO, refractive index: 1.75 to 1.85), antimony pentoxide (Sb ₂ O ₅ , refractive index: 2.04), aluminum zinc oxide (AZO, refractive index) : 1.90 to 2.00), gallium zinc oxide (GZO, refractive index: 1.90 to 2.00), zinc antimonate (ZnSb ₂ O ₆ , refractive index: 1.90 to 2.00), etc. Is mentioned.

  The average particle diameter of the high refractive index fine particles is preferably 5 to 50 nm, more preferably 10 to 20 nm, from the viewpoints of transparency and curability.

The inorganic fine particles have a photoreactive property capable of forming a covalent bond by cross-linking reaction between the inorganic fine particles or the multifunctional photocurable compound of the binder component and the surface treatment compound on the surface of the inorganic fine particles. Reactive inorganic fine particles having a functional group on at least part of the particle surface are preferred. The hardness of the hard coat film can be further improved by a cross-linking reaction between the reactive inorganic fine particles or between the reactive inorganic fine particles and the polyfunctional photocurable compound and the surface treatment compound.
The reactive inorganic fine particles include those having two or more inorganic fine particles as a core per particle. Moreover, the reactive inorganic fine particle can raise the crosslinking point in the matrix of a hard-coat layer with respect to content by making a particle size small.

(Method for forming hard coat layer)
A hard-coat layer can be obtained by apply | coating the said composition for hard-coat layers on the said translucent base material, and making it harden | cure.
When forming a high refractive index hard coat layer containing high refractive index fine particles, the concentration of the high refractive index fine particles in the vicinity of the interface between the high refractive index hard coat layer and the photocurable substrate is intentionally non-uniform. By applying and drying the hard coat layer composition as described above, interference fringes can be reduced.
The method for applying the hard coat layer composition can be the same as the method for applying the low refractive index layer.

[High refractive index layer]
In the present invention, the high refractive index layer may be provided adjacent to the low refractive index layer as a layer different from the hard coat layer. The high refractive index layer is a layer containing at least high refractive index fine particles, and may contain other components as necessary as long as the effects of the present invention are not impaired. The high refractive index layer is usually formed using a high refractive index layer composition containing fine particles of high refractive index. In the present invention, the high refractive index layer is a layer having a higher refractive index than at least the low refractive index layer.

The film thickness of the high refractive index layer can be appropriately selected according to the strength and required performance of the base material, and is 0.1 to 100 μm, preferably 0.8 to 20 μm. From the viewpoint of obtaining sufficient hardness and suppressing the occurrence of curling and cracking, the thickness is more preferably in the range of 3 to 20 μm.
Moreover, although the refractive index of a high refractive index layer should just be set suitably, it is 1.50-2.80 normally.

<Composition for high refractive index layer>
In the present invention, the composition for a high refractive index layer contains at least high refractive index fine particles, and may contain other components such as a binder component and a solvent as necessary.
Since each component used for the composition for high refractive index layers can be the same as that described in the composition for hard coat layer, description thereof is omitted here.
The high refractive index layer can be formed by the same method as the hard coat layer.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

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

(Production Example 1: Preparation of composition for high refractive index hard coat layer)
The following components were mixed to prepare a composition for a high refractive index hard coat layer.
<Composition for high refractive index hard coat layer>
-Binder component: Mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYARAD-PET-30, molecular weights 298 and 352, photocurable groups 3 and 4): 25 parts by mass・ High refractive index fine particles: antimony pentoxide fine particles (average particle size: 20 nm, product name: V-4562, solid content: 40% by mass, solvent: MIBK): 30 parts by mass : 25 parts by mass. Solvent 2: methyl ethyl ketone (MEK): 18 parts by mass. Photopolymerization initiator (manufactured by Ciba Specialty Chemicals Co., Ltd., trade name: Irgacure 184): 2 parts by mass.

(Production Example 2: Preparation of composition 1 for low refractive index layer)
The following components were mixed to prepare a composition 1 for a low refractive index layer.
<Composition of composition 1 for low refractive index layer>
Hollow silica fine particles (average particle size 50 nm, solid content concentration 20% as SiO ₂ ): 5 parts by mass Solid colloidal silica (V-8803: manufactured by Catalyst Kasei Co., Ltd., substantially spherical silica fine particles having an average particle size of 20 nm 2 to 3 deformed silica fine particles bonded by inorganic chemical bonds, (average particle size 50 nm) solid content concentration of 40% as SiO ₂ ): 5 parts by mass. Hydrolyzate-containing ethanol solution of tetraethoxysilane (SiO ₂ Solid content concentration of 6%): 10 parts by mass. Isopropyl alcohol (IPA): 80 parts by mass.

(Production Example 3: Preparation of composition 2 for low refractive index layer)
In Production Example 2, instead of solid colloidal silica V-8803, another solid colloidal silica (Snowtex (methanol silica sol): manufactured by Nissan Chemical Industries, spherical silica fine particles, average particle size: 15 nm) was used. In the same manner as in Production Example 2, a composition 2 for a low refractive index layer in Production Example 3 was prepared.

(Production Example 4: Preparation of composition 3 for low refractive index layer)
In Production Example 2, a composition 3 for a low refractive index layer of Production Example 4 was prepared in the same manner as Production Example 2 except that the following two types of hollow silica fine particles having different particle diameters were used in combination. did.
<Hollow silica fine particles>
Hollow silica fine particles (average particle size 50 nm, standard deviation of particle size 5 nm, solid content concentration 20% as SiO ₂ ): 3 parts by mass Hollow silica fine particles (average particle size 60 nm, standard deviation of particle size 5 nm, SiO ₂ As a solid content concentration of 20%): 2 parts by mass

(Comparative Production Example 1: Preparation of Composition 1 for Comparative Low Refractive Index Layer)
In Production Example 2, a comparative low refractive index composition 1 of Comparative Production Example 1 was prepared in the same manner as Production Example 2 except that solid colloidal silica was not used.

(Example 1: Production of optical film)
(1) Formation of High Refractive Index Hard Coat Layer Obtained in Production Example 1 using a slot die coater on a triacetyl cellulose (TAC) substrate (manufactured by Konica Minolta, Inc., trade name: KC4UY, thickness 40 μm) The obtained composition for high refractive index hard coat layer was applied at a coating speed of 20 m / min to form a coating film. The coating film was dried at 80 ° C. for 30 seconds to remove the solvent. Subsequently, the coating film is cured by irradiating the coating film with ultraviolet rays at an irradiation amount of 80 mj / cm ² using an ultraviolet irradiation device, and the hard coating film 1 having a hard coating (HC) layer having a thickness of 7 μm after curing. Got.

(2) Formation of Low Refractive Index Layer On the HC layer of the hard coat film 1 obtained in (1) above, the composition 1 for low refractive index layer obtained in Production Example 2 is the same as in (1) above. Coating was performed using a slot die coater. The coating film was dried at 120 ° C. for 5 minutes, and then a low refractive index layer having a thickness of 100 nm after curing was formed. Thus, an optical film of Example 1 was obtained.
When the obtained optical film was cut and the cut surface was observed with a scanning electron microscope, the hollow silica fine particles in the low refractive index layer had an average particle diameter of 50 nm, and the solid colloidal silica had an average particle diameter of 50 nm. there were.

(Example 2: Production of optical film)
In Example 1, in place of the composition 1 for low refractive index layer, the composition for low refractive index layer 2 obtained in Production Example 3 was used, except that the composition of Example 2 was used. An optical film was obtained.
The average particle size of the hollow silica fine particles in the low refractive index layer was 50 nm, and the average particle size of the solid colloidal silica was 15 nm.

(Example 3: Production of optical film)
In Example 1, in place of the composition 1 for low refractive index layer, the composition for Example 3 was used in the same manner as in Example 1 except that the composition 3 for low refractive index layer obtained in Production Example 4 was used. An optical film was obtained.
The average particle size of the solid colloidal silica in the low refractive index layer was 50 nm. Moreover, when a histogram was created for the particle diameter of the hollow silica fine particles, it was confirmed that peaks were formed at 50 nm and 60 nm.

(Comparative Example 1: Production of comparative optical film)
In Example 1, it replaced with the composition 1 for low refractive index layers, and except having used the composition 1 for comparative low refractive index layers obtained by the comparative manufacture example 1, it carried out similarly to Example 1, and was a comparative example. 1 optical film was obtained.

[Evaluation]
<Indentation hardness evaluation>
The optical film obtained by the said Example and the said comparative example was cut | disconnected, and the indentation hardness of the low-refractive-index layer in a cut surface was evaluated using the micro indentation tester (TI950 Tribodenter (made by HYSITRON)).
A Berkovich indenter was used as the working indenter, and an indentation load was applied while oscillating 100 Hz in steps of every 0.1 μm. After reaching the maximum indentation depth, the indentation load was gradually reduced in the same manner. The measurement is performed under a constant temperature condition of 25 ° C., and after sufficiently stabilizing the measuring device and the temperature of the sample, the load / displacement curve is measured under the conditions of a maximum indentation depth of 1.0 μm and a maximum load holding time of 30 seconds. The indentation hardness was defined as the average value of 10 consecutive measurements. The higher the value, the higher the hardness. The results are shown in Table 1.

<Evaluation of falling sand test>
First, the transmittance of the optical films obtained by the above examples and the above comparative examples was measured using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-3100PC) (transmittance before a sandfall test).
Next, the optical film is disposed at an inclination angle of 45 degrees with respect to the horizontal plane so that the low refractive index layer side of the optical film is the upper surface, and sand is dropped from the optical film toward the optical film at a height of 1 m. It was. Thereafter, the optical film was washed, and the transmittance after the sandfall test was measured in the same manner as described above.
The hardness of the optical film was evaluated by determining the difference between the transmittance after the sandfall test and the transmittance before the sandfall test. The smaller the difference in transmittance before and after the sandfall test, the higher the hardness of the optical film. The results are shown in Table 1.
The sand used in the sand fall test is a carborundum produced by pulverizing and classifying black silicon carbide ingot and green silicon carbide ingot. In this test, carborundum # 24 having a center particle size of 600 to 850 μm. 800 cm ^{3 was} used.

[Summary of results]
Implementation having a low refractive index layer made of a cured product of a composition for a low refractive index layer containing at least one selected from the group consisting of alkoxysilanes and hydrolysates thereof, hollow fine particles, and inorganic solid fine particles The optical films of Examples 1 to 3 were found to have reduced surface friction and excellent hardness as compared with the optical film of Comparative Example 1 that did not contain inorganic solid fine particles.
The optical films of Examples 1 and 3 using deformed silica fine particles as solid fine particles were superior to the optical film of Example 2 using spherical silica fine particles as solid fine particles, particularly in terms of indentation hardness. .
Furthermore, the optical film of Example 3 using a combination of hollow fine particles having an average particle diameter of 50 nm and hollow fine particles having an average particle diameter of 60 nm has high indentation hardness, reduced surface friction, and falling sand. Also in the test, it was revealed that the transmittance is not easily lowered and has particularly excellent hardness.

DESCRIPTION OF SYMBOLS 1 Light transmissive base material 2 Hard coat layer 2 'High refractive index hard coat layer 3 Low refractive index layer 4 High refractive index layer 10 Optical film

Claims (4)

  An optical film in which at least a hard coat layer and a low refractive index layer are provided in this order on one surface side of a light transmissive substrate, and the low refractive index layer is made of alkoxysilane and a hydrolyzate thereof. 1 or more types selected from the group, hollow fine particles, and inorganic solid fine particles, and for the low refractive index layer, the inorganic solid fine particles are 10 to 200 parts by mass with respect to 100 parts by mass of the hollow fine particles. An optical film comprising a cured product of the composition.   The optical film according to claim 1, wherein the hard coat layer is a high refractive index hard coat layer containing high refractive index fine particles and is adjacent to the low refractive index layer.   The inorganic solid fine particles in the low refractive index layer are deformed silica fine particles in which 2 to 20 substantially spherical silica fine particles having an average particle diameter of 1 to 100 nm are bonded by an inorganic chemical bond. Item 3. The optical film according to Item 1 or 2.   The optical film according to claim 1, wherein an indentation hardness of the low refractive index layer is 0.6 GPa or more.