JP2016194573A - Anisotropic optical film and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic optical film containing a columnar region comprising a plurality of inclined structures excellent in diffusing property and a diffusion width.SOLUTION: The anisotropic optical film includes at least an anisotropic diffusion layer; the anisotropic diffusion layer has a structural region including a matrix region and a columnar region comprising a plurality of inclined structures having such a shape that a diameter of the structure increases from one surface side of the anisotropic diffusion layer to the other surface side. The inclined structure is oriented in a parallel direction penetrating the anisotropic diffusion layer; and a ratio of a diameter at a 5 μm location from the one surface side of the structural region to a diameter at a 5 μm location from the other surface side of the structural region ranges from 1:1.5 to 1:4.0.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an anisotropic optical film in which the diffusibility of transmitted light changes according to an incident angle, and a method for manufacturing the same.

  Members having light diffusibility are used in display devices as well as lighting fixtures and building materials. Examples of the display device include a liquid crystal display device (LCD) and an organic electroluminescence element (organic EL). The light diffusion expression mechanism of the light diffusing member includes diffusion due to irregularities formed on the surface (surface diffusion), diffusion due to a difference in refractive index between the matrix resin and fine particles dispersed therein (internal diffusion), and surface diffusion. This is due to both internal diffusion. However, these light diffusing members generally have isotropic diffusion performance, and even if the incident angle is slightly changed, the diffusion characteristics of the transmitted light are not greatly different.

  On the other hand, there is an anisotropic optical film in which incident light in a certain angle region is strongly diffused and incident light at other angles is transmitted, that is, the amount of linear transmitted light can be changed according to the incident light angle. Are known. As such an anisotropic optical film, an assembly of a plurality of rod-like cured regions extending in parallel with a predetermined direction P inside a resin layer made of a cured product of a composition containing a photopolymerizable compound. An anisotropic diffusion medium in which a body is formed is disclosed (for example, see Patent Document 1). In the following, in this specification, the structure of an anisotropic optical film in which an assembly of a plurality of rod-shaped cured regions extending in parallel with a predetermined direction P as described in Patent Document 1 is formed. It will be referred to as a “pillar structure”.

  In such an anisotropic optical film having a pillar structure, when light is incident on the film from above to below, the flow direction in the film manufacturing process (hereinafter referred to as “MD direction”). The film shows the same diffusion in the width direction of the film perpendicular to the MD direction (hereinafter referred to as “TD direction”). That is, the diffusion in the anisotropic optical film having a pillar structure is isotropic. Therefore, in an anisotropic optical film having a pillar structure, a rapid change in brightness and glare are unlikely to occur. Moreover, since it has a pillar structure, the linear transmittance tends to be lower than that of the louver structure.

  On the other hand, as an anisotropic optical film, an anisotropic film in which an aggregate of one or a plurality of plate-like cured regions is formed inside a resin layer made of a cured product of a composition containing a photopolymerizable compound, instead of the pillar structure. By using a diffractive optical film (see, for example, Patent Document 2), the linear transmittance in the non-diffusion region can be improved and the diffusion width can be widened. Hereinafter, in this specification, the structure of an anisotropic optical film in which an aggregate of one or a plurality of plate-like cured regions as described in Patent Document 2 is referred to as a “louver structure”. .

  In such an anisotropic optical film having a louver structure, when light is incident on the film from the upper side to the lower side, diffusion is different in the MD direction and the TD direction. That is, the diffusion in the anisotropic optical film having a louver structure exhibits anisotropy. Specifically, for example, if the width of the diffusion region (diffusion width) is wider than the pillar structure in the MD direction, the diffusion width is narrower than the pillar structure in the TD direction. Therefore, in the anisotropic optical film having a louver structure, for example, when the diffusion width is narrowed in the TD direction, a sharp change in luminance occurs in the TD direction, and thus light interference is likely to occur and glare is likely to occur. Moreover, since it is a louver structure, the linear transmittance tends to be higher than that of the pillar structure.

  With these problems as problems, Patent Document 3 discloses an anisotropic optical film having an intermediate structure between the pillar structure and the louver structure. The structure of this anisotropic optical film is referred to as a “louver rod structure”. In this patent document, as a technique for obtaining a louver rod structure, a thin plate-like photopolymerized cured product having a plurality of columnar structures is stretched in a uniaxial direction along the surface of the thin plate, and the cross-sectional shape of the columnar structures is obtained. A method of extending in a uniaxial direction is adopted.

JP 2005-265915 A Japanese Patent No. 4802707 JP 2012-11709 A

  As described above, the anisotropic optical film (light control film) has been developed in various forms according to its function and application. However, in such an anisotropic optical film, it may be structurally difficult to obtain a balanced optical characteristic that is excellent in diffusibility and has a wide diffusion width.

  Then, an object of this invention is to provide the anisotropic optical film excellent in the diffusibility and the diffusion width | variety including the columnar area | region which is a some inclination structure, and its manufacturing method.

The inventors of the present invention have intensively studied to solve the above problems. As a result, it was found that an anisotropic optical film having excellent diffusibility and diffusion width can be formed by providing a region having a specific structure in the cured resin layer, and the present invention has been completed. That is, the present invention is as follows.
The present invention (1)
An anisotropic optical film comprising at least an anisotropic diffusion layer,
The anisotropic diffusion layer is a matrix region, and a columnar region that is a plurality of inclined structures having a shape that expands from one surface side to the other surface side of the anisotropic diffusion layer, Having a structural region including
The inclined structure is
Oriented along a parallel direction through the anisotropic diffusion layer,
The ratio of the diameter at the 5 μm point from the one surface side of the structural region to the diameter at the 5 μm point from the other surface side of the structural region is 1: 1.5 to 1: 4.0, It is an anisotropic optical film whose diffusivity changes depending on the incident angle of light.
The present invention (2)
The inclined structure has a diameter at a point of 5 μm from the one surface side of the structural region of 0.5 μm or more to less than 2.0 μm, and a diameter at a point of 5 μm from the other surface side of the structural region, The anisotropic optical film of the invention (1), wherein the anisotropic optical film has a thickness of 2.0 μm to 5.0 μm.
The present invention (3)
The inclined structure is an anisotropic optical film according to the invention (1) or (2), characterized in that it has a frustum shape.
The present invention (4)
The inclined structure is an anisotropic optical film according to any one of the inventions (1) to (3), wherein the inclined structure has a truncated cone shape.
The present invention (5)
The anisotropic optical film according to any one of the inventions (1) to (4), wherein the anisotropic optical film has a thickness of 20 μm to 100 μm.
The present invention (6)
Including a curing step of curing the uncured resin layer to form an anisotropic diffusion layer by irradiating light on one surface of the photocurable uncured resin layer through a light diffusion medium,
The light diffusion medium has an absolute value of an angular range measured by the following method of more than 2 ° and not more than 8 °. It is a manufacturing method.
(How to find the angle range)
Set the measurement sample to the variable angle photometer goniophotometer (Genesia Co., Ltd.), set the light source to the measurement sample at an angle where the incident light of the light source is 0 ° with respect to the normal direction, The intensity of diffused light is measured in a range of −90 ° to + 90 ° with respect to the normal direction of the measurement sample, and an angle range corresponding to 1/10 of the diffuse transmittance is obtained from the maximum value of the diffuse transmittance.

  Here, the definition of each term in this invention is demonstrated.

  The “light” in the present invention is an electromagnetic wave including visible light having a wavelength of 380 nm to 780 nm and ultraviolet light having a wavelength of 100 nm to 400 nm.

  The “low refractive index region” and the “high refractive index region” are regions formed by a difference in local refractive index of the material constituting the anisotropic optical film and have a lower refractive index than the other. It is a relative one indicating whether it is expensive. These regions are formed when the material forming the anisotropic optical film is cured.

Linear transmittance is the ratio of the amount of transmitted light in the linear direction and the amount of incident light when incident from an incident angle, with respect to the linear transmittance of the incident light on the anisotropic optical film. It is expressed by a formula.
Linear transmittance (%) = (Linear transmitted light amount / incident light amount) × 100

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the anisotropic optical film including the columnar area | region which is a several inclined structure excellent in the diffusibility and the diffusion width, and its manufacturing method.

FIG. 1A is a conceptual diagram of an anisotropic optical film according to this embodiment, and FIG. 1B is a conceptual diagram of an anisotropic optical film according to the prior art. FIG. 2 is a conceptual diagram of the anisotropic optical film according to the present embodiment. FIG. 3 is a conceptual diagram relating to a method for measuring the light diffusion characteristics of the light diffusion medium according to the present embodiment. FIG. 4 is a conceptual diagram relating to a method for measuring the diffusion width of the anisotropic optical film according to the present embodiment. FIG. 5 is a conceptual diagram showing an example of a sample structure used for measuring the diffusion width of the anisotropic optical film according to the present embodiment. FIG. 6 is a cross-sectional photograph of the anisotropic optical film according to the example. FIG. 7 is a cross-sectional photograph of an anisotropic optical film according to the prior art.

  Hereinafter, although the anisotropic optical film which concerns on this invention, and its manufacturing method are demonstrated, this invention is not limited to this form.

<< Structure of anisotropic optical film >>
<Overall structure>
The anisotropic optical film according to this embodiment has at least an anisotropic diffusion layer.

[Anisotropic diffusion layer]
The outline of the anisotropic diffusion layer according to this embodiment will be described in comparison with the anisotropic diffusion layer according to the prior art.

  The anisotropic optical film which concerns on this form has a layer (photocurable resin composition layer) which consists of a photocurable resin composition as an anisotropic diffused layer (continuous one layer). A photocurable resin composition layer is a layer which consists of a photocurable resin composition hardened | cured with light (for example, ultraviolet-ray). In the photocurable resin composition layer, a plurality (numerous) columnar regions (columnar bodies) oriented in the direction penetrating the layer are formed in the plane direction. Further, in the anisotropic diffusion layer, a layer in which such a columnar region exists (a region in which a columnar region exists on the cross section when the anisotropic diffusion layer is viewed in a cross section parallel to the layer) A layer in which the columnar region does not exist (a region in which the columnar region does not exist on the cross section when the anisotropic diffusion layer is viewed in a cross section parallel to the layer) is defined as a non-structured region. The “columnar region” refers to a minute rod-like photocurable resin composition region having a refractive index slightly different from that of the peripheral region. Moreover, let the photocurable resin composition area | region in anisotropic diffusion layers other than such a "columnar area | region" be a matrix area | region. As described above, the refractive index of the columnar region only needs to be different from the refractive index of the matrix region, but how much the refractive index differs is not particularly limited and is a relative one. When the refractive index of the matrix region is lower than the refractive index of the columnar region, the matrix region becomes a low refractive index region. Conversely, when the refractive index of the matrix region is higher than the refractive index of the columnar region, the matrix region becomes a high refractive index region.

  Here, in particular, the structural region in the present invention refers to a parallel line that is substantially parallel to a reference line (an average line of the roughness curve) on the outermost part of the anisotropic diffusion layer (for example, a light irradiation side described later). In this case, the ratio of the number of columnar body regions in contact with the parallel lines to the total number of columnar regions is more than 50%.

  Next, the characteristics of the structure of the anisotropic diffusion layer according to this embodiment will be described with reference to FIG.

  FIG. 1 is a conceptual diagram relating to an anisotropic diffusion layer according to this embodiment and an anisotropic diffusion layer according to the prior art. Focusing on the layer cross section of the photocurable resin composition layer as shown in the figure, the layer cross section is formed with a plurality of (innumerable) columnar regions that are oriented in the direction penetrating the layer. In addition, a structural region is formed.

  Here, according to the anisotropic diffusion layer according to the present embodiment shown in FIG. 1A, the columnar region extends from the vicinity of one surface side (the upper side in the drawing) of the anisotropic diffusion layer to the other surface side ( The inclined structure has a shape whose diameter increases toward the vicinity in the vicinity of the lower side in the drawing. On the other hand, the anisotropic diffusion layer according to the prior art shown in FIG. 1B includes a matrix region and a columnar region as in the anisotropic diffusion layer according to the present embodiment. Are not inclined structures {the diameter in the vicinity of one surface side (upper side in the drawing) of the anisotropic diffusion layer, the diameter in the vicinity of the other surface side (lower side in the drawing), The diameters are almost equal}.

  As described above, according to the anisotropic optical film according to the present embodiment, the columnar region can be refracted with light having a larger incident angle by using an inclined structure, and thus has excellent diffusibility. It can be.

(Columnar area)
The specific structure of the columnar region included in the anisotropic diffusion layer according to this embodiment is a tilted structure as described above. Here, the inclined structure is different from a simple column or bar (a structure having two congruent plane figures as the bottom and top surfaces), as represented by a cone, from one side to the other. It is the structure which has the shape extended while the diameter expands toward the side.

-Shape Although it does not specifically limit as a shape of an inclined structure, even if the shape in the surface side vicinity is not trapezoid as shown to Fig.2 (a), there exists an effect which concerns on this invention, but it is frustum shape It is preferable that the shape is a truncated cone. In particular, in the case of a truncated cone shape, there is an effect that light is diffused by a circle and glare is reduced.

  Further, as shown in FIG. 2B, the inclined structure may be a structure (axially inclined structure) whose central axis is inclined.

  Here, as shown in FIG. 2 (c), a part of the inclined structure is reduced in diameter from the vicinity of one surface side of the anisotropic diffusion layer toward the vicinity of the other surface side, and further expanded. You may have the structure to do. Moreover, as shown in FIG.2 (d), in the inclination structure which has a diameter-reduction structure shown in FIG.2 (c), it is good also as an axis | shaft inclination structure where the central axis inclined. Further, as shown in FIG. 2 (e), in the inclined structure having a reduced diameter structure shown in FIG. 2 (d), the reduced diameter structure that reduces the diameter from the vicinity of one surface side of the anisotropic diffusion layer. You may comprise so that the center axis | shaft of a part may not correspond with the center axis | shaft of the diameter-expanded structure part diameter-expanded toward the other surface side vicinity of an anisotropic diffused layer.

  Furthermore, the anisotropic optical film according to the present invention may have an unstructured region as shown in FIG.

-Diameter As described above, the inclined structure has a diameter in the vicinity of one surface side of the structural region that is larger than the diameter in the vicinity of the other surface side of the structural region, and expands from the surface side toward the substrate side. It is configured to have a shape that goes on. Note that “near one surface side” and “near the other surface side” indicate a position at a depth of 5 μm from the reference surface in the cross section of the anisotropic diffusion layer. Here, the reference surface is a surface that is the outermost part of the structural region (for example, when there is a non-structural region, it is a boundary surface between the structural region and the non-structural region, and the structural region is a substrate or If it is joined to other members, it is the boundary surface).

  Here, the diameter in the vicinity of one surface side of the structural region is preferably 0.5 μm or more and less than 2.0 μm, and more preferably 0.5 μm or more and less than 1.5 μm. If it is less than 0.5 μm, the permeability tends to decrease, and if it is 2.0 μm or more, the diffusibility tends to decrease.

  In addition, the diameter in the vicinity of the other surface side of the structural region is preferably 2.0 μm or more and 5.0 μm or less, and more preferably 3.0 μm or more and 5.0 μm or more. If the thickness is less than 0.2 μm, the permeability tends to decrease, and if it exceeds 5.0 μm, the light diffusibility tends to decrease.

  The diameter in the vicinity of one surface side: The diameter in the vicinity of the other surface side is preferably 1: 1.5 to 1: 4.0, and is 1: 1.5 to 1: 3.0. It is more preferable that the ratio is 1: 1.5 to 1: 2.0. Below this ratio, it becomes difficult to obtain the effect of improving the diffusibility, and when above this ratio, the diffusivity decreases.

  The inclination of the inclined structure is appropriately adjusted depending on the amount, shape and size of the filler added to the light diffusion medium in the manufacturing process described later.

(Thickness)
The thickness of the anisotropic diffusion layer according to this embodiment is not particularly limited, but is preferably 20 to 100 μm, and more preferably 25 to 55 μm. If it is less than 20 μm, the light diffusibility decreases, and if it exceeds 100 μm, it becomes excessive.

[Other layers]
An anisotropic optical film in which another layer is provided on one surface of the anisotropic diffusion layer may be used. Examples of other layers include an adhesive layer, a polarizing layer, a light diffusion layer, a low reflection layer, an antifouling layer, an antistatic layer, an ultraviolet / near infrared (NIR) absorption layer, a neon cut layer, and an electromagnetic wave shielding layer. be able to. Other layers may be sequentially stacked. Other layers may be laminated on both surfaces of the anisotropic diffusion layer. The other layer laminated on both surfaces may be a layer having the same function or a layer having another function.

≪Method for producing anisotropic optical film≫
The anisotropic optical film according to the present embodiment can be provided directly on the reflective base material or the isotropic diffusion medium by coating or the like, but with an ordinary processing technique via an adhesive or an adhesive. Can be pasted together. For example, it is preferable to use a pressure-sensitive adhesive or an adhesive even when the anisotropic optical film according to this embodiment is bonded to a flexible support or a board. Needless to say, when the flexible support or the board itself is reflective, an anisotropic optical film can be directly laminated on the reflective surface. Hereinafter, the raw material of the anisotropic diffusion layer will be described first, and then the manufacturing process will be described.

<Raw material for anisotropic diffusion layer>
[Photocurable resin composition]
The photocurable resin composition, which is an essential material for forming the anisotropic diffusion layer of this embodiment, is a photopolymerizable material selected from polymers, oligomers, and monomers having a radical polymerizable or cationic polymerizable functional group. It is a material composed of a compound and a photoinitiator and polymerized and solidified by irradiation with ultraviolet rays and / or visible rays.

(Photopolymerizable compound)
The radically polymerizable compound mainly contains one or more unsaturated double bonds in the molecule, and specifically includes epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, polybutadiene acrylate, silicone acrylate, and the like. Acrylic oligomer called by name, 2-ethylhexyl acrylate, isoamyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isonorbornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-acryloyloxyphthalic acid, dicyclopentenyl acrylate, triethylene glycol diacrylate, Opentyl glycol diacrylate, 1,6-hexanediol diacrylate, EO adduct diacrylate of bisphenol A, trimethylolpropane triacrylate, EO modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylol Examples thereof include acrylate monomers such as propanetetraacrylate and dipentaerythritol hexaacrylate. These compounds may be used alone or in combination. Similarly, although methacrylate can be used, acrylate is generally preferable to methacrylate because it has a higher photopolymerization rate.

  As the cationic polymerizable compound, a compound having at least one epoxy group, vinyl ether group or oxetane group in the molecule can be used. Examples of the compound having an epoxy group are 2-ethylhexyl diglycol glycidyl ether, glycidyl ether of biphenyl, bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetrachloro Diglycidyl ethers of bisphenols such as bisphenol A and tetrabromobisphenol A, polyglycidyl ethers of novolac resins such as phenol novolak, cresol novolak, brominated phenol novolak, orthocresol novolak, ethylene glycol, polyethylene glycol, polypropylene glycol, Butanediol, 1,6-hexanediol, neopentyl glycol, trimethyl Diglycidyl ethers of alkylene glycols such as diol propane, 1,4-cyclohexanedimethanol, bisphenol A EO adduct, bisphenol A PO adduct, glycidyl ester of hexahydrophthalic acid, diglycidyl ester of dimer acid, etc. Examples thereof include glycidyl esters.

  Furthermore, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, di- (3,4-epoxycyclohexylmethyl) adipate, di (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ', 4'-epoxy-6'-methyl Cyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di (3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylenebis (3,4-epoxycyclohexanecarboxylate), lactone modification 3, -Epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexanecarboxylate, tetra (3,4-epoxycyclohexylmethyl) butanetetracarboxylate, di (3,4-epoxycyclohexylmethyl) -4,5-epoxytetrahydrophthalate, etc. Although the alicyclic epoxy compound of these is also mentioned, it is not limited to these.

  Examples of the compound having a vinyl ether group include diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, and trimethylolpropane trivinyl ether. , Propenyl ether propylene carbonate and the like, but are not limited thereto. Vinyl ether compounds are generally cationically polymerizable, but radical polymerization is also possible by combining with acrylates.

  As the compound having an oxetane group, 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene, 3-ethyl-3- (hydroxymethyl) -oxetane and the like can be used.

The above cationic polymerizable compounds may be used alone or in combination. The photopolymerizable compound is not limited to the above. Further, in order to cause a sufficient difference in refractive index, fluorine atoms (F) may be introduced into the photopolymerizable compound in order to reduce the refractive index, and in order to increase the refractive index, Sulfur atoms (S), bromine atoms (Br), and various metal atoms may be introduced. Further, as disclosed in JP 2005-514487, on the surface of ultrafine particles made of a metal oxide having a high refractive index such as titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), tin oxide (SnOx), It is also effective to add functional ultrafine particles into which a photopolymerizable functional group such as an acryl group, a methacryl group, or an epoxy group is introduced to the above-described photopolymerizable compound.

(Photoinitiator)
Photoinitiators that can polymerize radically polymerizable compounds include benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2- Diethoxyacetophenone, benzyldimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2 -Methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1 ―On, bis (cyclo Ntadienyl) -bis (2,6-difluoro-3- (pyrl-1-yl) titanium, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2,4,6 -Trimethylbenzoyldiphenylphosphine oxide, etc. These compounds may be used alone or in combination.

The photoinitiator of a cationically polymerizable compound is a compound that generates an acid upon irradiation with light and can polymerize the above cationically polymerizable compound with the generated acid. Generally, an onium salt or a metallocene complex is used. Are preferably used. As the onium salt, a diazonium salt, a sulfonium salt, an iodonium salt, a phosphonium salt, a selenium salt, or the like is used, and these counter ions include anions such as BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ^{− and the} like. Used. Specific examples include 4-chlorobenzenediazonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, (4-phenylthiophenyl) diphenylsulfonium hexafluoroantimonate, (4-phenylthiophenyl) diphenyl. Sulfonium hexafluorophosphate, bis [4- (diphenylsulfonio) phenyl] sulfide-bis-hexafluoroantimonate, bis [4- (diphenylsulfonio) phenyl] sulfide-bis-hexafluorophosphate, (4-methoxyphenyl) Diphenylsulfonium hexafluoroantimonate, (4-methoxyphenyl) phenyliodonium hexafluoroantimonate Bis (4-t-butylphenyl) iodonium hexafluorophosphate, benzyltriphenylphosphonium hexafluoroantimonate, triphenyl selenium hexafluorophosphate, (η5-isopropylbenzene) (η5-cyclopentadienyl) iron (II) hexa Although fluorophosphate etc. are mentioned, it is not limited to these. These compounds may be used alone or in combination.

(Blend amount, other optional ingredients)
In this embodiment, the photoinitiator is 0.01 to 10 parts by weight, preferably 0.1 to 7 parts by weight, more preferably about 0.1 to 5 parts by weight with respect to 100 parts by weight of the photopolymerizable compound. Blended. This is because when less than 0.01 parts by weight, the photocurability decreases, and when it exceeds 10 parts by weight, only the surface is cured and the internal curability decreases, coloring, columnar regions This is because it inhibits the formation of. These photoinitiators are usually used by directly dissolving powder in a photopolymerizable compound, but if the solubility is poor, a photoinitiator dissolved beforehand in a very small amount of solvent at a high concentration is used. Can also be used. Such a solvent is more preferably photopolymerizable, and specific examples thereof include propylene carbonate and γ-butyrolactone. It is also possible to add various known dyes and sensitizers in order to improve the photopolymerizability. Furthermore, a thermosetting initiator capable of curing the photopolymerizable compound by heating can be used together with the photoinitiator. In this case, by heating after photocuring, it can be expected to further accelerate the polymerization and curing of the photopolymerizable compound to complete it.

  In this embodiment, the anisotropic diffusion layer can be formed by curing the above-described photo-curable resin composition alone or by mixing a plurality of the mixed compositions. Moreover, you may use the mixture of the polymeric resin which does not have a photocurable resin composition and photocurable property. Polymer resins that can be used here include acrylic resin, styrene resin, styrene-acrylic copolymer, polyurethane resin, polyester resin, epoxy resin, cellulose resin, vinyl acetate resin, PVC-vinyl acetate copolymer, polyvinyl Examples include butyral resin. These polymer resins and photocurable resin compositions need to have sufficient compatibility before photocuring, but various organic solvents, plasticizers, etc. are used to ensure this compatibility. It is also possible to use it. In addition, when using an acrylate as a photocurable resin composition, it is preferable from a compatible point to select as a polymer resin from an acrylic resin.

<Process>
As a method for producing an anisotropic diffusion layer, a photocurable resin composition is applied on a suitable substrate film or provided in a sheet form (application process), and dried as necessary to volatilize the solvent. Then, a light irradiation mask is provided on the photocurable resin composition (light irradiation mask bonding step), and a light diffusion medium is disposed on the light irradiation mask (light diffusion medium arrangement step), and further on the light diffusion medium. An anisotropic optical film can be produced by arranging a light source and irradiating light (curing step) to the photocurable resin composition through a light irradiation mask. Hereinafter, each step will be described in detail.

[Coating process]
An uncured photocurable resin composition is applied or provided in a sheet form on the base film to form an uncured resin composition layer.

  Here, as a method of providing the photocurable resin composition on the base film, a normal coating method or printing method is applied. Specifically, air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, calendar coating, dam coating, dip coating Coating such as die coating, intaglio printing such as gravure printing, printing such as stencil printing such as screen printing, and the like can be used. In addition, when the photocurable resin composition has a low viscosity, for example, a partition wall made of a curable resin is formed using a dispenser along an edge where an anisotropic diffusion layer is to be formed, and is surrounded by the partition wall. What is necessary is just to cast the photocurable resin composition of a non-hardened state inside.

  Here, the base film is not limited at all as long as it does not inhibit the curing of the photocurable resin composition in the curing step described later. For example, an appropriate film such as a transparent PET film may be used. I can do it.

[Light irradiation mask bonding process]
Next, a light irradiation mask is joined (contacted) on the uncured resin composition layer formed in the coating process. Hereinafter, the properties and the like of the light irradiation mask used in this step will be described in detail.

  The light irradiation mask is used for the purpose of promoting the effect and formation of the photocurable resin composition, preventing oxygen inhibition during curing, and controlling the strength of anisotropic diffusion. The material of the light irradiation mask is not particularly limited as long as it is a transparent flexible sheet that transmits light, but in order to form the columnar region more efficiently, a light-absorbing filler (for example, carbon) is used. It is dispersed in the polymer matrix, and a part of the incident light is absorbed by the light-absorbing filler, but a light-opening portion where no light-absorbing filler is present is preferably a mask that can sufficiently transmit light.

  Here, as the light irradiation mask bonding step, as described above, the light irradiation mask may be bonded (contacted) on the uncured resin composition layer. A step of simultaneously performing the coating step and the light irradiation mask joining step by filling an uncured photocurable resin composition in a space formed by the partition wall and the light irradiation mask, etc. Also good. As described above, the light irradiation mask has various functions. However, since the anisotropic diffusion layer can be manufactured without using the light irradiation mask, the light irradiation mask bonding step is an indispensable step. is not.

[Light diffusion medium arrangement process]
Next, in order to impart appropriate characteristics to the light irradiated to the uncured resin composition layer, a light diffusion medium is disposed (the light diffusion medium includes a light source for curing the uncured resin composition layer, It is a member arranged between the cured resin composition layer).

(Light diffusion medium)
As shown in FIG. 3, the light diffusing property of the light diffusing medium is such that the incident light of the light source is normal to the measurement sample that is a light diffusing medium using a goniophotometer (Genecia Co., Ltd.). The light source is set at an angle of 0 ° with respect to the direction, and the light receiving unit (detector) measures the intensity of the diffused light by varying it in the range of -90 ° to + 90 ° with respect to the normal direction of the measurement sample. In this case, the absolute value of the angle range corresponding to the diffuse transmittance of 1/10 from the maximum value of the diffuse transmittance (light reception intensity) is more than 2 ° and not more than 8 °. When the absolute value of the angle of the diffusion range of incident light in the light diffusion medium deviates from such a numerical range, a desired columnar region is not formed. In addition, this numerical value is a numerical value measured with respect to the wavelength of the light irradiated in the below-mentioned hardening process.

  Although it does not specifically limit as a light-diffusion medium which has such a property, For example, diffusion plates, such as a resin plate (for example, acrylic board) containing a filler (for example, polystyrene particle), can be mentioned. In this case, the properties of the light diffusion medium can be adjusted by the amount, shape, and size of the filler added. Alternatively, a lens diffuser plate (LSD, Luminit, LLC) etc. that transfers fine irregularities due to the interference wavefront of the hologram to the surface of the film and diffuses incident light at a certain angle by the refraction or diffraction action of the structure Is also applicable. Here, as described above, the light diffusion medium is a member for imparting appropriate characteristics to incident light and irradiating the uncured resin composition layer. Therefore, as long as it is possible to irradiate the uncured resin composition layer with light having the appropriate characteristics, a combination of a plurality of diffusion plates or the like may be used as the light diffusion medium (in this case, the entire light diffusion medium And measuring the light diffusion characteristics). The same effect can be obtained by using two lenticular lenses in combination.

  Thus, by irradiating light through the light diffusion medium according to the present embodiment, the light irradiated to the uncured resin composition layer is diffused in all directions immediately before entering the resin layer. Curing proceeds along the diffused direction, and the upper side (light incident side) and the lower side (base film side) have different shapes (for example, frustum shapes).

  Here, as described above, the inclined structure according to the present invention may be a structure (axially inclined structure) whose central axis is inclined as shown in FIG.

-Haze value As a haze value of a light-diffusion medium, 5 to 30% is suitable, and 15 to 30% is more suitable. If the haze value is too small, it becomes difficult to obtain a frustum-shaped (conical frustum-like) structure, and if the haze value is too large, it is difficult to form a columnar region itself that is a plurality of inclined structures.

  In addition, as an arrangement | positioning location of a light-diffusion medium, you may arrange | position directly on a light irradiation mask, and may arrange | position so that it may separate from a light irradiation mask. Further, when the light irradiation mask bonding step is not provided (the light irradiation mask is not used), the light diffusion medium is directly on the uncured resin composition layer (so as to be in contact with the uncured resin composition layer). ), Or may be arranged so as to be separated from the uncured resin composition layer.

  Here, as described above, the light irradiation mask bonding step is not an essential step. When the light irradiation mask bonding step is not performed, the light diffusing medium arranging step is performed prior to the coating step when (1) the light diffusing medium is arranged so as to be separated from the uncured resin composition layer. (2) When the light diffusion medium is disposed directly on the uncured resin composition layer (so as to be in contact with the uncured resin composition layer), the above-mentioned partition is provided, A step of simultaneously performing the coating step and the light diffusion medium arrangement step by filling an uncured photocurable resin composition in a space formed by a film, a partition wall, and a light diffusion medium, etc. It may be.

[Curing process]
Next, by irradiating the uncured resin composition layer with light through a light irradiation mask and a light diffusion medium, the uncured resin composition layer is irradiated with light that is a diffused light beam that diffuses in all directions. The cured resin composition layer is cured to form an anisotropic diffusion layer (photocurable resin composition layer) in which columnar regions having a plurality of inclined structures are formed.

  The light source for irradiating the uncured resin composition layer with light varies depending on the photocurable resin composition to be used. However, when an ultraviolet curable resin composition is used, an ultraviolet light source for short arc is usually used. Specifically, a high-pressure mercury lamp, a low-pressure mercury lamp, a metahalide lamp, a xenon lamp, or the like can be used.

The light beam applied to the uncured resin composition layer needs to include a wavelength capable of curing the uncured resin composition layer. When an ultraviolet curable resin composition is used, a mercury lamp is usually used. Light having a wavelength centered at 365 nm is used. When fabricating the anisotropic diffusion layer of the present embodiment uses the wavelength band, it is preferred that as the illumination intensity is in the range of 0.01 to 100 mW / cm ^2, more preferably of 0.1~20mW / cm ² It is a range. If the illuminance is 0.01 mW / cm ² or less, curing takes a long time, resulting in poor production efficiency. If the illuminance is 100 mW / cm ² or more, the photocurable resin composition is cured too quickly, resulting in structure formation. This is because the desired anisotropic diffusion characteristics may not be exhibited.

  Although the irradiation time of UV is not particularly limited, it is 10 to 180 seconds, more preferably 30 to 120 seconds. Then, the anisotropic diffusion layer which concerns on this form can be obtained by peeling a light irradiation mask and a base film.

The anisotropic diffusion layer of the present invention is obtained by forming columnar regions in an uncured resin composition layer by irradiating light (low illumination UV light) for a relatively long time as described above. . For this reason, unreacted monomer components may remain by such light irradiation (UV irradiation) alone, resulting in stickiness and problems in handling and durability. In such a case, the residual monomer can be polymerized by additionally irradiating light with high illuminance (UV light) of 1000 mW / cm ² or more. The light irradiation (UV irradiation) at this time is preferably performed from the opposite side of the light irradiation mask side.

≪Physical properties of anisotropic optical film≫
Next, the physical properties of the anisotropic optical film according to the present invention will be described.

<Diffusion of an anisotropic optical film (haze value)>
The diffusibility (haze value) of the anisotropic optical film according to the present invention is preferably 75 to 95%, more preferably 85 to 95%. In addition, the measuring method of the diffusibility (haze value) of an anisotropic optical film follows a below-mentioned method.

<Diffusion width of anisotropic optical film>
The diffusion width of the anisotropic optical film according to the present invention is preferably 40 to 70 °, more preferably 45 to 60 °. The method for measuring the diffusion width of the anisotropic optical film follows the method described later.

≪Use of anisotropic optical film≫
An anisotropic optical film according to the present invention includes a projector screen, a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), a cathode ray tube display (CRT), a surface electric field display (SED), The present invention can be applied to a display device such as electronic paper. It is particularly preferably used for a liquid crystal display (LCD). Moreover, the anisotropic optical film which concerns on this form can also be bonded together and used for a desired place through an adhesive layer or an adhesion layer. Furthermore, the anisotropic optical film according to this embodiment can be used for a transmissive, reflective, or transflective liquid crystal display device. Further, since the anisotropic optical film according to the present invention is integrally formed as a resin layer, it can be manufactured at a low cost, and moisture, dust, dust and the like are difficult to enter therein. Since it has a structure and further has few structural defects, it is considered that it has excellent durability against bending and the like. Therefore, it is applicable to a wide range of environments and various uses.

  According to the following method, the anisotropic optical film of the present invention and the anisotropic optical film of the comparative example were produced.

[Example 1]
A PET film having a thickness of 100 μm and a size of 76 × 26 mm (made by Toyobo Co., Ltd., trade name: A4100, haze = 0.5%) is used as a base film, and the entire circumference of the edge is highly curable with a dispenser. A partition wall having a thickness of 100 μm was formed. The partition wall was filled with the following photocurable resin composition, and covered with a PVA film having a haze of 1.3% as a UV irradiation mask (light irradiation mask).
Silicone urethane acrylate (refractive index: 1.460, weight average molecular weight: 5,890) 20 parts by weight (trade name: 00-225 / TM18, manufactured by RAHN)
-Neopentyl glycol diacrylate (refractive index: 1.450) 30 parts by weight (manufactured by Daicel-Cytec Co., Ltd., trade name: Ebecryl 145)
Bisphenol A EO adduct diacrylate (refractive index: 1.536) 15 parts by weight (manufactured by Daicel-Cytec Co., Ltd., trade name: Ebecyl 150)
・ Phenoxyethyl acrylate (refractive index: 1.518) 40 parts by weight (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate PO-A)
・ 2,2-dimethoxy-1,2-diphenylethane-1-one 4 parts by weight (manufactured by BASF, trade name: Irgacure 651)
A 100 μm-thick liquid film sandwiched between the two surfaces is placed on a hot plate heated to 80 ° C., and a UV spot light source (trade name: L2859-01, manufactured by Hamamatsu Photonics Co., Ltd.) is reflected from the UV irradiation mask side. Haze obtained by dispersing polystyrene particles having an average particle diameter of 1 μm in an acrylic resin as a light diffusion medium for UV light to be irradiated with parallel light (ultraviolet light having a wavelength of 365 nm) emitted from an irradiation unit for irradiation with an irradiation intensity of 5 mW / cm ² Was irradiated for 1 minute through a diffusion plate of 15%, and further, UV light having an irradiation intensity of 20 mW / cm ^{2 was} irradiated from the base film side to be completely cured. From there, the anisotropic optical film of Example 1 having a columnar region which is a plurality of inclined structures as shown in FIG. Obtained.
The light diffusion property of the light diffusion medium used in this example was 4 °.

[Example 2]
An anisotropic optical film having a thickness of 52 μm was obtained in the same manner as in Example 1 except that the thickness of the partition walls was 50 μm.
The light diffusion property of the light diffusion medium used in this example was 4 ° as in Example 1.

[Example 3]
An anisotropic optical film with a thickness of 49 μm was used in the same manner as in Example 1 except that the partition wall thickness was 50 μm, and a 19.8% haze PVA film in which carbon was dispersed and formed was used as the UV irradiation mask. A film was obtained.
The light diffusion property of the light diffusion medium used in this example was 4 ° as in Example 1.

[Example 4]
Using a PVA film having a haze of 19.8% with a partition wall thickness of 50 μm and dispersed carbon as a UV irradiation mask, polystyrene particles having an average particle diameter of 1 μm are acrylic resin as a light diffusion medium for UV light to be irradiated. An anisotropic optical film having a thickness of 52 μm was obtained in the same manner as in Example 1 except that a diffusion plate having a haze dispersed in 25% was used.
The light diffusion characteristic of the light diffusion medium used in this example was 7 °.

[Example 5]
The partition wall thickness is 50 μm, a 19.8% haze PVA film formed by dispersing carbon as a UV irradiation mask is used, and the diffusion direction of the two lenticular lenses is perpendicular to the light diffusion medium for the UV light to be irradiated. An anisotropic optical film having a thickness of 48 μm was obtained in the same manner as in Example 1 except that a diffuser plate having a haze of 30% was used.
The light diffusion property of the light diffusion medium used in this example was 8 °.
[Example 6]
The partition wall thickness is 30 μm, and a 19.8% haze PVA film formed by dispersing carbon is used as the UV irradiation mask, and the diffusion direction of the two lenticular lenses is perpendicular to the light diffusion medium for the UV light to be irradiated. An anisotropic optical film having a thickness of 29 μm was obtained in the same manner as in Example 1 except that a diffusion plate having a haze of 30% was used.
The light diffusion property of the light diffusion medium used in this example was 8 °.
[Example 7]
An anisotropic optical film having a thickness of 22 μm was obtained in the same manner as in Example 1 except that the thickness of the partition walls was 20 μm.

[Comparative Example 1]
An anisotropic optical film having a thickness of 101 μm was obtained in the same manner as in Example 1 except that no light diffusion medium was used.
The light diffusion property of the irradiated UV light was 2 °.

[Comparative Example 2]
The partition wall thickness is 50 μm, a 19.8% haze PVA film in which carbon is dispersed is used as a UV irradiation mask, and a silica filler having an average particle size of 5 μm is used as a light diffusion medium for UV light to be irradiated. An anisotropic optical film having a thickness of 52 μm was obtained in the same manner as in Example 1 except that a diffusion plate having a haze of 40% dispersed in the resin was used.
The light diffusion property of the light diffusion medium used in this comparative example was 11 °.

<Measurement of haze of UV irradiation mask and diffusion medium>
Haze was measured according to JIS K7136 using Nippon Denshoku Industries Co., Ltd. haze meter NDH-2000.

<Measurement of light diffusion characteristics of light diffusion medium>
The light diffusion media of Examples and Comparative Examples were evaluated using a variable angle photometer goniophotometer (manufactured by Genesia Co., Ltd.) capable of arbitrarily changing the light projection angle of the light source and the light reception angle of the light receiver. The light source is set at an angle at which the incident light of the light source is 0 ° with respect to the normal direction with respect to the measurement sample which is a light diffusion medium, and the light receiving unit is −90 to + 90 ° with respect to the normal direction of the measurement sample. The intensity of diffused light was measured in a variable range. The light diffusing characteristic of the light diffusing medium was set to an angle range corresponding to the received light intensity of 1/10 from the maximum value of received light intensity (diffuse transmittance).

<Measurement of diffusibility (haze value) of anisotropic optical film>
The haze value was measured based on JIS K7136 using Nippon Denshoku Industries Co., Ltd. haze meter NDH-2000. The higher the haze value, the more anisotropic the optical film.

<Measurement of diffusion width of anisotropic optical film>
The anisotropic optical films of Examples and Comparative Examples were evaluated using a variable angle photometer goniophotometer (manufactured by Genesia Co., Ltd.) capable of arbitrarily changing the light projecting angle of the light source and the light receiving angle of the light receiver. The light receiving part was fixed at a position where the light traveling straight from the light source was received, and the anisotropic optical films obtained in Examples and Comparative Examples were set in the sample holder therebetween. As shown in FIG. 4, the sample was rotated as the rotation axis (L), and the amount of linear transmitted light corresponding to each incident angle was measured. By this evaluation method, it is possible to evaluate in which angle range the incident light is diffused. This rotation axis (L) is the same axis as the C-C axis in the sample structure shown in FIG. 5 (in FIG. 5, a normal pillar structure is used for simplicity). The linear transmitted light amount was measured by measuring the wavelength in the visible light region (380 nm to 780 nm) using a visibility filter. Thus, the “diffusion width” is a diffusion angle range of incident light with respect to a linear transmittance that is an intermediate value between the maximum linear transmittance and the minimum linear transmittance.

<Evaluation of glare of anisotropic optical film>
Regarding the interference (rainbow) of the anisotropic optical film, the transmitted light was visually observed from various angles, and the glare (interference rainbow) was evaluated.

<Section observation of anisotropic optical film>
As for the cross section of the anisotropic optical film, an observation sample that was thinly sectioned with a microtome was observed with a 200 × optical microscope. From the observed cross-sectional photograph, 100 inclined structures were observed at the 5 μm point from the surface side (light irradiation side) and the 5 μm point from the substrate side (substrate film application side) with respect to the structural region of the anisotropic optical film. The width was measured and the average value was regarded as the outer diameter of the inclined structure. As described above, the structural region is drawn when a parallel line that is substantially parallel to the reference line (average line of the roughness curve) of the outermost part of the anisotropic diffusion layer (light irradiation side described later) is drawn. The ratio of the number of columnar body regions in contact with the parallel lines to the total number of columnar regions was set to be a region exceeding 50%.

  Here, FIG. 6 is a cross-sectional photograph of an anisotropic optical film having a plurality of inclined structures according to the present example, and FIG. 7 is a cross-sectional photograph of an anisotropic optical film having no inclined structures according to the prior art. Each is shown.

  The processing conditions in Examples and Comparative Examples and the evaluation results of the obtained anisotropic optical films are summarized in Tables 1 and 2.

  As shown in Tables 1 and 2, the optical films of the examples have excellent diffusibility and a wide diffusion width, while the anisotropic optical films of the comparative examples have anisotropic optical properties having a narrow diffusion width. It became a film and was inferior. In particular, the anisotropic optical film of Example 3 had no glare (interference rainbow), and had excellent diffusibility and a wide diffusion width. Further, the anisotropic optical film of Example 5 had excellent diffusibility and a wide diffusion width although the glare was slightly inferior. Furthermore, in the anisotropic optical film of Example 6, although the glare was slightly inferior, it had excellent diffusibility and a wide diffusion width although it was a thin film.

Claims (6)

An anisotropic optical film comprising at least an anisotropic diffusion layer,
The anisotropic diffusion layer is a matrix region, and a columnar region that is a plurality of inclined structures having a shape that expands from one surface side to the other surface side of the anisotropic diffusion layer, Having a structural region including
The inclined structure is
Oriented along a parallel direction through the anisotropic diffusion layer,
The ratio of the diameter at the 5 μm point from the one surface side of the structural region to the diameter at the 5 μm point from the other surface side of the structural region is 1: 1.5 to 1: 4.0, An anisotropic optical film whose diffusivity changes depending on the incident angle of light.   The inclined structure has a diameter at a point of 5 μm from the one surface side of the structural region of 0.5 μm or more to less than 2.0 μm, and a diameter at a point of 5 μm from the other surface side of the structural region, The anisotropic optical film according to claim 1, wherein the anisotropic optical film has a thickness of 2.0 μm to 5.0 μm.   The anisotropic optical film according to claim 1, wherein the inclined structure has a frustum shape.   The anisotropic optical film according to claim 1, wherein the inclined structure has a truncated cone shape.   The anisotropic optical film according to claim 1, wherein the anisotropic optical film has a thickness of 20 μm to 100 μm. Including a curing step of curing the uncured resin layer to form an anisotropic diffusion layer by irradiating light on one surface of the photocurable uncured resin layer through a light diffusion medium,
The light diffusion medium has an absolute value of an angular range measured by the following method of more than 2 ° and not more than 8 °. Production method.
(How to find the angle range)
Set the measurement sample to the variable angle photometer goniophotometer (Genesia Co., Ltd.), set the light source to the measurement sample at an angle where the incident light of the light source is 0 ° with respect to the normal direction, The intensity of diffused light is measured in a range of −90 ° to + 90 ° with respect to the normal direction of the measurement sample, and an angle range corresponding to 1/10 of the diffuse transmittance is obtained from the maximum value of the diffuse transmittance.