Anisotropic light-diffusing film and display device

Abstract

Provided is an anisotropic light-diffusing film having a superior effect of improving viewing-angle dependency to the prior art for changes in color and luminance due to the viewing angle. This anisotropic light-diffusing film, for which the linear transmittance ((the amount of incident light transmitted in a linear direction) / (the amount of incident light)) changes in accordance with the light incidence angle, has a matrix region and a plurality of columnar regions the refractive index of which differs from that of the matrix region, further has one scattering central axis, and is characterized in that, in a tilted orientation of the scattering central axis, the linear transmittance for an incidence angle of 60° is 10% or less, and the diffuse transmittance in a polar angle 60° direction for light with an incidence angle of 0° is 0.001% or greater.

Description

[Technical field]

[0001] The present invention relates to an anisotropic light-diffusing film and a display device including the anisotropic light-diffusing film. [Background technology]

[0002] Display devices, such as transmissive TN liquid crystal displays, have problems related to viewing angle dependency, such as a decrease in brightness and contrast and a change in color (tone inversion) from that seen from the front when viewed obliquely in a specific orientation.

[0003] In order to eliminate such viewing angle dependency, anisotropic optical bodies are used in which the linear transmittance [(amount of light transmitted in the linear direction of incident light) / (amount of incident light)] changes depending on the angle of incidence of light.

[0004] For example, in Patent Document 1, the problems of brightness and color change due to viewing angle are improved by using an anisotropic optical film in a display device, in which the direction in which the color change of the display device is minimized and the scattering central axis are in a specific angular range. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication 2015-127819 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in view of the diversification of display methods and display sizes of display devices, there is a demand for anisotropic optical bodies having a more excellent effect of improving viewing angle dependency.

[0007] Therefore, an object of the present invention is to provide an anisotropic light-diffusing film that has a more excellent effect of improving the viewing angle dependency with respect to the luminance and color change depending on the viewing angle than ever before. [Means for solving the problem]

[0008] The inventors have found that the above problems can be solved by providing an anisotropic light-diffusing film having specific properties, and have completed the present invention.

[0009] The present invention (1) is An anisotropic light-diffusing film having a linear transmittance, which is (amount of transmitted light in a linear direction of incident light) / (amount of incident light), that changes depending on the angle of incidence of light, the anisotropic light-diffusing film has a matrix region and a plurality of columnar regions having a refractive index different from that of the matrix region; Furthermore, the anisotropic light-diffusing film has one scattering central axis, In the tilt direction of the scattering central axis, The in-line transmittance at an incident angle of 60° is 10% or less, This is an anisotropic light-diffusing film characterized by having a diffuse transmittance of 0.001% or more in the direction of a polar angle of 60° for light with an incident angle of 0°. The present invention (2) is If the polar angle between the surface normal direction of the anisotropic light-diffusing film and the scattering central axis direction is defined as the scattering central axis angle, The anisotropic light-diffusing film according to the above aspect (1) is characterized in that the scattering central axis angle of the anisotropic light-diffusing film is 20° to 60°. The present invention (3) is The anisotropic light-diffusing film according to the above invention (1) or (2) is characterized in that the haze value of the anisotropic light-diffusing film is 75% or more. The present invention (4) is The anisotropic light-diffusing film according to any one of the above inventions (1) to (3) is characterized in that the thickness of the anisotropic light-diffusing film is 15 μm to 100 μm. The present invention (5) is The plurality of columnar regions of the anisotropic light-diffusing film are The anisotropic light diffusing film is oriented and extends from one surface to the other surface, The anisotropic light-diffusing film according to any one of the above inventions (1) to (4) is characterized in that the aspect ratio of the columnar regions, which is the average long axis / average short axis of the columnar regions in a cross section perpendicular to the column axis of the columnar regions of the anisotropic light-diffusing film, is less than 2. The present invention (6) is The liquid crystal display device is characterized in that the anisotropic light-diffusing film according to any one of the above aspects (1) to (5) is laminated on the viewing side of a liquid crystal layer. The present invention (7) is The organic EL display device is characterized in that the anisotropic light-diffusing film according to any one of the above inventions (1) to (5) is laminated on the viewing side of the light-emitting layer. Effect of the Invention

[0010] According to the present invention, it is possible to provide an anisotropic light-diffusing film having a more excellent effect of improving the viewing angle dependency with respect to the luminance and color change depending on the viewing angle than ever before. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory diagram showing the incident light angle dependency of an anisotropic light-diffusing film. [Diagram 2] FIG. 2 is a top view showing the surface structure of an anisotropic light-diffusing film. [Diagram 3] 1 is a schematic diagram illustrating an example of an anisotropic light-diffusing film. [Figure 4] 1 is a three-dimensional polar coordinate representation for explaining the central scattering axis in an anisotropic light-diffusing film. [Diagram 5] 1 is an optical profile of an anisotropic light-diffusing film. [Figure 6] FIG. 2 is a schematic diagram showing a method for measuring the incident light angle dependency of an anisotropic light-diffusing film. [Figure 7] FIG. 2 is a schematic diagram showing a method for producing an anisotropic light-diffusing film according to the present invention, including optional steps 1-3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The anisotropic light-diffusing film according to the present invention will be briefly described below, followed by explanations of its structure, physical properties, production method, and specific applications.

[0013] <<<<Anisotropic light diffusion film>>>> An anisotropic light-diffusing film is a film having optical anisotropy, in which the linear transmittance [(amount of incident light transmitted in a linear direction) / (amount of incident light)] changes depending on the angle of incidence of light. That is, with respect to light incident on an anisotropic light-diffusing film, incident light within a certain angle range is transmitted while maintaining linearity, and incident light within other angle ranges exhibits diffusivity.

[0014] For example, the anisotropic light-diffusing film shown in FIG. 1 exhibits diffusivity when the incident angle is 20° to 50°, but does not exhibit diffusivity at other incident angles and exhibits linear transmittance.

[0015] <<<Structure>>> The anisotropic light-diffusing film of the present invention has a matrix region and a plurality of columnar regions having a refractive index different from that of the matrix region. The plurality of columnar regions included in the anisotropic light-diffusing film are usually configured to be oriented and extend from one surface to the other surface of the anisotropic light-diffusing film (see FIG. 3, etc.).

[0016] Here, the difference in refractive index means that there is a difference to the extent that at least a portion of the light incident on the anisotropic light-diffusing film is reflected at the interface between the matrix region and the columnar region. Although there are no particular limitations, for example, the difference in refractive index between the matrix region and the columnar region may be 0.001 or more.

[0017] <<Columnar area>> The length of the columnar region is not particularly limited, and may extend from one surface of the anisotropic light-diffusing film to the other surface, or may be short enough not to reach from one surface to the other surface.

[0018] The cross-sectional shape of the multiple columnar regions included in the anisotropic light-diffusing film in a cross section perpendicular to the column axis of the anisotropic light-diffusing film can have a minor axis and a major axis.

[0019] The cross-sectional shape of the columnar region is not particularly limited, and can be, for example, a circle, an ellipse, or a polygon. In the case of a circle, the minor axis and the major axis are equal, in the case of an ellipse, the minor axis is the length of the minor axis, and the major axis is the length of the major axis, and in the case of a polygon, the shortest length within the polygon can be the minor axis, and the longest length can be the major axis. Figure 2 shows the columnar region as viewed from the surface direction of the anisotropic light-diffusing film. In Figure 2, LA represents the major axis, and SA represents the minor axis.

[0020] The short diameter and long diameter of the columnar regions can be determined by observing a cross section of the anisotropic light-diffusing film perpendicular to the column axis with an optical microscope, measuring the short diameter and long diameter of each of 20 arbitrarily selected columnar regions, and taking the average value of these.

[0021] <Short diameter> In the anisotropic light-diffusing film, the average value of the minor axes of the columnar regions (average minor axis) is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more. On the other hand, the average minor axis of the columnar regions is preferably 5.0 μm or less, more preferably 4.0 μm or less, and even more preferably 3.0 μm or less. The lower and upper limits of the minor axes of the columnar regions can be appropriately combined.

[0022] <Long diameter> In the anisotropic light-diffusing film, the average value of the major axis of the columnar region (average major axis) is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more. On the other hand, the average major axis of the columnar region is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. The average major axis of the columnar region is preferably shorter than the length of the columnar region. In this way, it is possible to increase the linear light transmittance of the anisotropic light-diffusing film. The lower limit and upper limit of the major axis of the columnar region can be appropriately combined.

[0023] The ratio of the average major axis to the average minor axis of the columnar regions (average major axis / average minor axis), ie, the aspect ratio, is not particularly limited, but can be 1-20, for example.

[0024] FIG. 2(a) shows an anisotropic light-diffusing film in which the aspect ratio of the columnar regions is 2 to 20, and FIG. 2(b) shows an anisotropic light-diffusing film in which the aspect ratio of the columnar regions is 1 or more and less than 2.

[0025] When the aspect ratio is 1 or more and less than 2, the transmitted light is diffused isotropically when light parallel to the axial direction of the columnar region is irradiated {see Figure 3(a)}. On the other hand, when the aspect ratio is 2 to 20, the transmitted light is diffused anisotropically according to the aspect ratio when light parallel to the axial direction is irradiated {see Figure 3(b)}.

[0026] The anisotropic light-diffusing film may include a plurality of columnar regions having one aspect ratio, or may include a plurality of columnar regions having different aspect ratios.

[0027] <<<Scattering center axis>>> The anisotropic light-diffusing film has a scattering central axis. The scattering central axis and the orientation direction (extension direction) of the columnar region are usually parallel to each other. Note that the scattering central axis and the orientation direction of the columnar region being parallel to each other only need to satisfy the law of refractive index (Snell's law), and do not need to be strictly parallel to each other.

[0028] Snell's law states that when light is incident on the interface between a medium with a refractive index n1 and a medium with a refractive index n2, the relationship between the incident light angle θ1 and the refraction angle θ2 is n1sinθ1=n2sinθ2. For example, if n1=1 (air) and n2=1.51 (anisotropic light-diffusing film), when the incident light angle is 30°, the orientation direction (refraction angle) of the columnar region is about 19°. Even if the incident light angle and the refraction angle are different in this way, as long as they satisfy Snell's law, they are included in the concept of parallelism in the present invention.

[0029] Next, the scattering central axis P in the anisotropic light-diffusing film will be described in more detail with reference to Fig. 4. Fig. 4 is a three-dimensional polar coordinate representation for explaining the scattering central axis P in the anisotropic light-diffusing film.

[0030] The central scattering axis means a direction that coincides with the angle of incidence of light whose light diffusibility is approximately symmetrical with respect to the angle of incidence when the angle of incidence of light to the anisotropic light-diffusing film is changed. The angle of incidence of light at this time is approximately the center (the center of the diffusion region) between the minimum values ​​in the optical profile (Fig. 5) which is obtained by measuring the linear transmittance of the anisotropic light-diffusing film and plotting the linear transmittance for each angle of incidence of light.

[0031] In a three-dimensional polar coordinate representation as shown in Figure 4, the scattering central axis can be expressed by a polar angle θ and an azimuthal angle φ, where the surface of the anisotropic light-diffusing film is the xy plane and the normal to the surface of the anisotropic light-diffusing film is the z axis.

[0032] Here, the polar angle θ (−90°<θ<90°) between the normal to the anisotropic light-diffusing film (z-axis shown in FIG. 4) and the columnar region can be defined as the scattering central axis angle. In the process of photocuring the uncured resin composition layer to form a columnar region, the axial angle of the columnar region can be adjusted to a desired range by changing the direction of the irradiated light beam.

[0033] The scattering central axis angle θ of the anisotropic light-diffusing film is not particularly limited, but is preferably 20° to 60°, and more preferably 20° to 50°.

[0034] By setting the scattering central axis angle θ in this way, it is possible to achieve a desired angle dependency.

[0035] <<<Optical profile>>> As shown in Fig. 5, the anisotropic light diffusion film has light diffusion property that depends on the angle of incident light, that is, the linear transmittance changes depending on the angle of incident light. Hereinafter, the curve showing the light diffusion property dependency on the angle of incident light, as shown in Fig. 5, is referred to as the "optical profile".

[0036] The optical profile can be created, for example, as follows.

[0037] As shown in FIG. 6, an anisotropic light-diffusing film is placed between a light source 1 and a detector 2. In this embodiment, the incident light angle is set to 0° when the irradiated light I from the light source 1 is incident from the normal direction of the anisotropic light-diffusing film. The anisotropic light-diffusing film is placed so that it can be rotated arbitrarily around a straight line V as the axis of rotation, and the light source 1 and the detector 2 are fixed. That is, according to this method, a sample (anisotropic light-diffusing film) is placed between the light source 1 and the detector 2, and the linear transmittance of light passing through the sample and entering the detector 2 is measured while changing the angle around the straight line V on the sample surface as the axis of rotation. Then, this linear transmittance is plotted for each angle to create an optical profile.

[0038] Although the optical profile does not directly express the light diffusion properties, if one interprets it as meaning that a decrease in linear transmittance results in an increase in diffuse transmittance, it can be said that the optical profile generally indicates the light diffusion properties.

[0039] A typical isotropic light diffusing film exhibits a mountain-shaped optical profile that peaks at an incident light angle of approximately 0°.

[0040] For example, when the scattering central axis angle of an anisotropic light-diffusing film is taken as 0° (Figure 5), the linear transmittance is small at incident light angles around 0° (-20° to +20°), and the linear transmittance increases as the incident light angle (absolute value) increases, showing a valley-shaped optical profile.

[0041] Thus, an anisotropic light-diffusing film has the property that the incident light is strongly diffused in the incident light angle range close to the scattering central axis, but the diffusion weakens and the linear transmittance increases in a larger incident light angle range.

[0042] When the scattering central axis angle is other than 0°, the optical profile shifts so that the linear transmittance decreases at incident light angles near the scattering central axis angle (the valley of the optical profile shifts toward the scattering central axis angle).

[0043] <<<Linear transmittance>>> As shown in FIG. 5, the linear transmittance of light incident on the anisotropic light-diffusing film at an incident angle at which the linear transmittance is maximized is referred to as the maximum linear transmittance.

[0044] As shown in FIG. 5, the linear transmittance of light incident on the anisotropic light-diffusing film at an incident angle at which the linear transmittance is minimum is called the minimum linear transmittance.

[0045] As shown in Figure 5, the angular range of the two incident light angles for a linear transmittance intermediate between the maximum linear transmittance and the minimum linear transmittance is called the diffusion region (the width of this diffusion region is the "diffusion width"), and the incident light angle range excluding this is called the non-diffusion region (transmitting region).

[0046] The linear transmittance of the anisotropic light-diffusing film at an incident angle of 60° in the tilt direction of the scattering central axis is preferably 10% or less, more preferably 5% or less, and particularly preferably less than 2.5%.

[0047] The linear transmittance can be adjusted by the refractive index of the material of the anisotropic light diffusion film (the refractive index difference when multiple resins are used), the thickness of the coating film, UV illuminance, the temperature during structure formation, the irradiation angle during UV irradiation, etc. The linear transmittance at an incident angle of 60° tends to decrease, for example, when UV irradiation is performed, the farther the irradiation angle is from the normal direction of the coating film, the thicker the coating film is, the higher the temperature of the coating film is, and the larger the refractive index difference is when multiple resins are used.

[0048] <<<<Diffuse transmittance in the direction of a polar angle of 60° at the inclination direction of the scattering central axis for light with an incident angle of 0°>>> A light source is placed in the normal direction (incident angle = 0°) of one surface of the anisotropic light-diffusing film, and a detector is placed on the other surface. The normal direction on the detector side is set to a polar angle θ = 0°, and the brightness is measured while varying the polar angle of the detector. The diffuse transmittance is a relative value with the brightness in the normal direction (polar angle θ = 0°) when no anisotropic light-diffusing film is used as 100%.

[0049] The anisotropic light-diffusing film preferably has a diffuse transmittance of 0.001% or more in the direction of a polar angle of 60° in the tilt direction of the scattering central axis for light with an incident angle of 0°. Although there are no particular limitations on the upper limit, the upper limit is preferably 0.01% or less, and more preferably 0.005% or less.

[0050] By setting the linear transmittance of the anisotropic light-diffusing film at an incident angle of 60° within the appropriate range described above, and setting the diffuse transmittance of light at an incident angle of 0° into the anisotropic light-diffusing film in the direction of a polar angle of 60° in the inclination direction of the scattering central axis within this range, light can be diffused sufficiently up to a viewing angle of approximately 80°.

[0051] The diffuse transmittance of light with an incident angle of 0° in the direction of a polar angle of 60° in the inclination direction of the scattering central axis of the anisotropic light-diffusing film tends to increase as the coating film becomes thicker and the temperature of the coating film becomes higher during UV irradiation. In addition, when the coating film is irradiated with UV light, the irradiation angle is easily within the above-mentioned range when it is 20° to 60° from the normal direction of the coating film.

[0052] <<<Haze value>>> The haze value (total haze) of an anisotropic light-diffusing film is an index showing the diffusibility of the anisotropic light-diffusing film. The larger the haze value, the higher the diffusibility of the anisotropic light-diffusing film.

[0053] The method for measuring the haze value is not particularly limited, and the haze value can be measured by a known method, for example, according to JIS K7136-1:2000 "Method for determining haze of plastics-transparent materials."

[0054] The haze value of the anisotropic light-diffusing film is not particularly limited, but is preferably 75% or more. By setting the haze value in this range, the effect of the present invention can be further improved.

[0055] The haze value can be adjusted by the refractive index of the material of the anisotropic light-diffusing film (the difference in refractive index when multiple resins are used), the thickness of the coating film, and curing conditions such as UV illuminance and temperature during structure formation. For example, the haze value tends to increase when the irradiation angle during UV irradiation is close to the normal direction of the uncoated film, the coating layer is thick, the coating temperature is high, and the difference in refractive index when multiple resins are used is large.

[0056] <<Thickness>> The thickness of the anisotropic light-diffusing film is not particularly limited, but is preferably 15 μm to 100 μm, and more preferably 30 μm to 60 μm. By setting the thickness in this range, it is possible to reduce the manufacturing costs, such as the cost of materials and the cost required for UV irradiation, while ensuring a sufficient visual dependency improving effect.

[0057] The method for producing the anisotropic light-diffusing film will now be described.

[0058] <<<Manufacturing of anisotropic light diffusion film>>> <<Raw materials>> The raw materials of the anisotropic light-diffusing film will be explained in the following order: (1) photopolymerizable compound, (2) photoinitiator, (3) blending amount, and other optional components.

[0059] <Photopolymerizable compound> The photopolymerizable compound is a material that is composed of a photopolymerizable compound selected from macromonomers, polymers, oligomers, and monomers having a radically polymerizable or cationic polymerizable functional group and a photoinitiator, and is polymerized and cured by exposure to ultraviolet light and / or visible light.

[0060] Here, even if the anisotropic light-diffusing film is made of only one material, differences in density will result in differences in refractive index. The curing speed will be faster in areas where the UV irradiation intensity is strong, and the polymerized and cured material will move around the cured area, resulting in the formation of areas with high and low refractive indexes. Note that (meth)acrylate means that it can be either acrylate or methacrylate.

[0061] Radical polymerizable compounds mainly contain one or more unsaturated double bonds in the molecule. Specifically, acrylic oligomers called epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, polybutadiene acrylate, silicone acrylate, etc., and 2-ethylhexyl acrylate, isoamyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isonorbornyl acrylate, 2-hydroxyethyl ... Examples of the acrylate monomer include acrylate monomers such as hydroxypropyl acrylate, 2-acryloyloxyphthalic acid, dicyclopentenyl acrylate, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, EO adduct diacrylate of bisphenol A, trimethylolpropane triacrylate, EO modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol hexaacrylate. These compounds may be used alone or in combination. Methacrylates can also be used, but generally acrylates are preferred over methacrylates because they have a faster photopolymerization rate.

[0062] As the cationic polymerizable compound, a compound having one or more epoxy groups, vinyl ether groups, or oxetane groups in the molecule can be used. Examples of the compound having an epoxy group include 2-ethylhexyl diglycol glycidyl ether, glycidyl ether of biphenyl, diglycidyl ethers of bisphenols such as bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetrachloro bisphenol A, and tetrabromo bisphenol A, polyglycidyl ethers of novolac resins such as phenol novolac, cresol novolac, brominated phenol novolac, and ortho-cresol novolac, diglycidyl ethers of alkylene glycols such as ethylene glycol, polyethylene glycol, polypropylene glycol, butanediol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane, 1,4-cyclohexanedimethanol, an EO adduct of bisphenol A, and a PO adduct of bisphenol A, and glycidyl esters such as a glycidyl ester of hexahydrophthalic acid and a diglycidyl ester of dimer acid.

[0063] Further examples of compounds having an epoxy group include 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'-methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexa and alicyclic epoxy compounds such as, but not limited to, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, tetra(3,4-epoxycyclohexylmethyl)butane tetracarboxylate, and di(3,4-epoxycyclohexylmethyl)-4,5-epoxytetrahydrophthalate.

[0064] Examples of compounds having a vinyl ether group include, but are not limited to, diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexane dimethanol divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, trimethylolpropane trivinyl ether, propenyl ether propylene carbonate, etc. Incidentally, vinyl ether compounds are generally cationic polymerizable, but can also be radically polymerized by combining with an acrylate.

[0065] Examples of compounds having an oxetane group that can be used include 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene and 3-ethyl-3-(hydroxymethyl)-oxetane.

[0066] The above cationic polymerizable compounds may be used alone or in combination. The photopolymerizable compounds are not limited to those mentioned above.

[0067] In order to generate a sufficient refractive index difference, a fluorine atom (F) may be introduced into the photopolymerizable compound to lower the refractive index, or a sulfur atom (S), a bromine atom (Br), or various metal atoms may be introduced into the photopolymerizable compound to increase the refractive index. Furthermore, as disclosed in JP-A-2005-514487, titanium oxide (TiO 2 ), zirconium oxide (ZrO 2 ), tin oxide (SnO x It is also effective to add functional ultrafine particles, which are made of ultrafine particles of a metal oxide having a high refractive index such as methyl acrylate, ethyl acrylate, ethyl methacrylate, or epoxy group, to the surface of the ultrafine particles to the above-mentioned photopolymerizable compound.

[0068] It is preferable to use a photopolymerizable compound having a silicone skeleton as the photopolymerizable compound. The photopolymerizable compound having a silicone skeleton is oriented according to its structure (mainly ether bond) and polymerized and hardened to form a low refractive index region, a high refractive index region, or a low refractive index region and a high refractive index region. By using a photopolymerizable compound having a silicone skeleton, it becomes easier to tilt the columnar region, improving the light collecting ability in the front direction. The low refractive index region corresponds to either the columnar region or the matrix region, and the other corresponds to the high refractive index region.

[0069] In the low refractive index region, it is preferable that the silicone resin, which is a cured product of a photopolymerizable compound having a silicone skeleton, is relatively more. This makes it easier to tilt the scattering central axis, improving the light collecting ability in the front direction. Since silicone resin contains more silicon (Si) than compounds that do not have a silicone skeleton, the relative amount of silicone resin can be confirmed by using EDS (energy dispersive X-ray spectroscope) using this silicon as an indicator.

[0070] The photopolymerizable compound having a silicone skeleton is a monomer, oligomer, prepolymer, or macromonomer having a radically polymerizable or cationic polymerizable functional group. Examples of the radically polymerizable functional group include an acryloyl group, a methacryloyl group, and an allyl group, and examples of the cationic polymerizable functional group include an epoxy group and an oxetane group. There is no particular limit to the type and number of these functional groups, but the more functional groups there are, the higher the crosslinking density becomes and the easier it is to cause a difference in refractive index, so it is preferable to have a polyfunctional acryloyl group or methacryloyl group. In addition, a compound having a silicone skeleton may have insufficient compatibility with other compounds due to its structure, but in such a case, the compatibility can be increased by urethane conversion. In this embodiment, a silicone-urethane-(meth)acrylate having an acryloyl group or methacryloyl group at the end is preferably used.

[0071] The weight-average molecular weight (Mw) of the photopolymerizable compound having a silicone skeleton is preferably in the range of 500 to 50,000, and more preferably in the range of 2,000 to 20,000. When the weight-average molecular weight is in the above range, a sufficient photocuring reaction occurs, and the silicone resin present in each anisotropic light-diffusing film of the anisotropic light-diffusing film 0 is easily oriented. The orientation of the silicone resin makes it easier to tilt the scattering central axis.

[0072] An example of the silicone skeleton is one represented by the following general formula (1). In general formula (1), R1, R2, R3, R4, R5, and R6 each independently have a functional group such as a methyl group, an alkyl group, a fluoroalkyl group, a phenyl group, an epoxy group, an amino group, a carboxyl group, a polyether group, an acryloyl group, or a methacryloyl group. In general formula (1), n ​​is preferably an integer of 1 to 500.

[0073] [ka]

[0074] When a photopolymerizable compound having a silicone skeleton is blended with a compound not having a silicone skeleton to form an anisotropic light-diffusing film, low refractive index regions and high refractive index regions are easily formed separately, which results in a stronger degree of anisotropy, which is preferable.

[0075] As the compound not having a silicone skeleton, in addition to a photopolymerizable compound, a thermoplastic resin or a thermosetting resin can be used, and these can also be used in combination.

[0076] As the photopolymerizable compound, a polymer, oligomer, or monomer having a radically polymerizable or cationic polymerizable functional group can be used (however, it does not have a silicone skeleton).

[0077] Examples of the thermoplastic resin include polyester, polyether, polyurethane, polyamide, polystyrene, polycarbonate, polyacetal, polyvinyl acetate, acrylic resin, and copolymers or modified products thereof. When using a thermoplastic resin, the thermoplastic resin is dissolved in a solvent that dissolves the thermoplastic resin, and after coating and drying, the photopolymerizable compound having a silicone skeleton is cured with ultraviolet light to form an anisotropic light-diffusing film.

[0078] Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, urea resin, unsaturated polyester, and its copolymer or modified product. When using a thermosetting resin, a photopolymerizable compound having a silicone skeleton is cured with ultraviolet light, and then heated appropriately to cure the thermosetting resin and form an anisotropic light-diffusing film.

[0079] The most preferred compounds that do not have a silicone skeleton are photopolymerizable compounds, which have excellent productivity because the low refractive index region and the high refractive index region are easily separated, there is no need for a solvent when using a thermoplastic resin, and there is no need for a drying process, and there is no need for a heat curing process like with thermosetting resins.

[0080] <Photoinitiator> Examples of photoinitiators capable of polymerizing radically polymerizable compounds include benzophenone, benzil, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone, benzil dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl ether, and 1-methyl-2-phenylpropan-1-one. phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(pyr-1-yl)phenyl]titanium, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc. Also, these compounds may be used alone or in combination.

[0081] The photoinitiator for the cationic polymerizable compound is a compound that generates an acid upon irradiation with light and can polymerize the above-mentioned cationic polymerizable compound by the acid generated. In general, an onium salt or a metallocene complex is preferably used.

[0082] As the onium salt, a diazonium salt, a sulfonium salt, an iodonium salt, a phosphonium salt, a selenium salt, etc. are used, and as the counter ion thereof, an anion such as BF4-, PF6-, AsF6-, SbF6-, etc. are used. Specific examples include 4-chlorobenzenediazonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, (4-phenylthiophenyl)diphenylsulfonium hexafluoroantimonate, (4-phenylthiophenyl)diphenylsulfonium hexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluoroantimonate, and bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluorophosphate. Examples of the hexafluorophosphate include, but are not limited to, fluorophosphate, (4-methoxyphenyl)diphenylsulfonium hexafluoroantimonate, (4-methoxyphenyl)phenyliodonium hexafluoroantimonate, bis(4-t-butylphenyl)iodonium hexafluorophosphate, benzyltriphenylphosphonium hexafluoroantimonate, triphenylselenium hexafluorophosphate, (η5-isopropylbenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate, etc. Furthermore, these compounds may be used alone or in combination.

[0083] The photoinitiator is blended in an amount of 0.01 to 10 parts by mass, preferably 0.1 to 7 parts by mass, and more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the photopolymerizable compound. This is because if it is blended in an amount of less than 0.01 parts by mass, the photocurability decreases, and if it is blended in an amount of more than 10 parts by mass, it causes problems such as only the surface curing and decreasing the curability inside, coloring, and inhibition of the formation of a columnar structure.

[0084] <Other ingredients> The photoinitiator is usually used by directly dissolving the powder in the photopolymerizable compound, but if the solubility is poor, the photoinitiator can be used by dissolving it in a very small amount of solvent at a high concentration in advance. It is more preferable that such a solvent is photopolymerizable, and specific examples include propylene carbonate and γ-butyrolactone. It is also possible to add various known dyes and sensitizers to improve photopolymerizability.

[0085] Furthermore, a heat curing initiator capable of curing the photopolymerizable compound by heating can be used together with the photoinitiator. In this case, it is expected that the polymerization curing of the photopolymerizable compound can be further promoted and completed by heating after photocuring. The photopolymerizable compound can be cured alone or a composition in which multiple photopolymerizable compounds are mixed can be cured to form an anisotropic light-diffusing film.

[0086] An anisotropic light-diffusing film can also be formed by curing a mixture of a photopolymerizable compound and a polymer resin that is not photocurable.

[0087] Examples of polymer resins that can be used here include acrylic resins, styrene resins, styrene-acrylic copolymers, polyurethane resins, polyester resins, epoxy resins, cellulose-based resins, vinyl acetate-based resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral resins, etc. These polymer resins and photopolymerizable compounds must have sufficient compatibility before photocuring, and various organic solvents, plasticizers, etc. can be used to ensure this compatibility.

[0088] When an acrylate is used as the photopolymerizable compound, it is preferable to select an acrylic resin as the polymer resin in terms of compatibility.

[0089] The ratio of the photopolymerizable compound having a silicone skeleton to the compound not having a silicone skeleton is preferably in the range of 15:85 to 85:15 by mass ratio. More preferably, it is in the range of 30:70 to 70:30. By setting it in this range, phase separation between the low refractive index region and the high refractive index region is facilitated, and the columnar region is easily tilted. If the ratio of the photopolymerizable compound having a silicone skeleton is less than the lower limit or more than the upper limit, phase separation is difficult to proceed, and the columnar region is difficult to tilt.

[0090] When silicone-urethane-(meth)acrylate is used as a photopolymerizable compound with a silicone skeleton, the compatibility with compounds without a silicone skeleton is improved, which allows the columnar region to be inclined even when the mixture ratio of the materials is wide.

[0091] Examples of the solvent that can be used when preparing a composition containing a photopolymerizable compound include ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, and xylene.

[0092] <<Manufacturing process>> Next, a manufacturing process for the anisotropic light-diffusing film will be described.

[0093] First, a composition containing the above-mentioned photopolymerizable compound (hereinafter, sometimes referred to as "photocurable resin composition") is applied to a suitable substrate such as a transparent PET film to form a sheet, and then a film is formed to provide a photocurable resin composition layer. This photocurable resin composition layer is dried as necessary to volatilize the solvent, and then the photocurable resin composition layer is irradiated with light to produce an anisotropic light-diffusing film.

[0094] More specifically, the process for forming the anisotropic light-diffusing film mainly includes the following steps. (1) Step 1-1: Providing an uncured resin composition layer on a substrate (2) Step 1-2: Obtaining parallel light from a light source (3) Optional Step 1-3: Step to obtain directional light beam (4) Step 1-4: Step of curing the uncured resin composition layer

[0095] <Step 1-1: Step of Providing Uncured Resin Composition Layer on Substrate> The photocurable resin composition is provided on the substrate in the form of a sheet as an uncured resin composition layer by a normal coating method or printing method.Specifically, coating such as 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, die coating, intaglio printing such as gravure printing, stencil printing such as screen printing, etc. can be used.When the composition has a low viscosity, a dam of a certain height can be provided around the substrate, and the composition can be cast into the area surrounded by the dam.

[0096] In step 1-1, in order to prevent oxygen inhibition of the uncured resin composition layer and efficiently form the columnar regions that are characteristic of the anisotropic light-diffusing film, it is also possible to laminate a mask that adheres closely to the light-irradiated side of the uncured resin composition layer and locally changes the irradiation intensity of the light.

[0097] The mask material is preferably one in which a light-absorbing filler such as carbon is dispersed in a matrix, so that part of the incident light is absorbed by the carbon, but the openings are configured to allow sufficient light transmission. Such a matrix may be transparent plastics such as PET, TAC, PVAc, PVA, acrylic, polyethylene, etc., inorganic materials such as glass and quartz, or sheets containing such matrices that are patterned to control the amount of ultraviolet light transmitted or that contain pigments that absorb ultraviolet light.

[0098] When such a mask is not used, it is also possible to prevent oxygen inhibition of the uncured resin composition layer by performing light irradiation under a nitrogen atmosphere. In addition, simply laminating a normal transparent film on the uncured resin composition layer is effective in preventing oxygen inhibition and promoting the formation of columnar regions. In the light irradiation through such a mask or transparent film, a photopolymerization reaction occurs in the composition containing the photopolymerizable compound according to the irradiation intensity, so that a refractive index distribution is easily generated, which is effective for producing the anisotropic light diffusion film according to this embodiment.

[0099] <Step 1-2: Step of obtaining parallel light from a light source> As the light source, a short-arc ultraviolet light source is usually used, and specifically, a high-pressure mercury lamp, a low-pressure mercury lamp, a metahalide lamp, a xenon lamp, etc., can be used. At this time, it is necessary to obtain a light beam parallel to the desired scattering central axis, and such a parallel light beam can be obtained, for example, by arranging a point light source and arranging an optical lens such as a Fresnel lens for irradiating a parallel light beam between the point light source and the uncured resin composition layer, or by arranging a reflecting mirror behind the light source so that light is emitted as a point light source in a predetermined direction.

[0100] <Optional step 1-3: Step to obtain directional light> Optional step 1-3 is a step of making parallel light enter a directional diffusion element to obtain a directional light beam. Fig. 7 is a schematic diagram showing a method for producing an anisotropic light-diffusing film according to the present invention, including optional step 1-3.

[0101] The directional diffusion elements 301 and 302 used in the optional step 1-3 may be any element capable of imparting directionality to the parallel light beam D incident from the light source 300.

[0102] 7 shows that directional light E is incident on uncured resin composition layer 303 in a state in which it is diffused mostly in the X direction and hardly diffused in the Y direction. In order to obtain such directional light, for example, a method can be adopted in which needle-shaped filler having a high aspect ratio is contained in directional diffusion elements 301 and 302 and the needle-shaped filler is oriented so that its major axis direction extends in the Y direction. Various methods can be used for directional diffusion elements 301 and 302 in addition to the method using needle-shaped filler.

[0103] Here, the aspect ratio of the directional light E is preferably 2 to 20. A columnar region having an aspect ratio approximately corresponding to the aspect ratio is formed. The upper limit of the aspect ratio is more preferably 10 or less, and more preferably 5 or less. If the aspect ratio exceeds 20, interference rainbows and glare may occur.

[0104] In optional step 1-3, the size (aspect ratio, minor axis SA, major axis LA, etc.) of the columnar region to be formed can be appropriately determined by adjusting the spread of the directional light E. For example, the anisotropic light-diffusing film of this embodiment can be obtained in either FIG. 7(a) or (b). The difference between FIG. 7(a) and (b) is that the spread of the directional light E is large in (a) but small in (b). The size of the columnar region differs depending on the size of the spread of the directional light E.

[0105] The spread of the directional light E mainly depends on the type of directional diffusion elements 301 and 302 and the distance from the uncured resin composition layer 303. As the distance is shortened, the size of the columnar region becomes smaller, and as the distance is lengthened, the size of the columnar region becomes larger. Therefore, the size of the columnar region can be adjusted by adjusting the distance.

[0106] <Step 1-4: Step of curing the uncured resin composition layer> The light beam that is irradiated onto the uncured resin composition layer to cure the uncured resin composition layer must contain a wavelength capable of curing the photopolymerizable compound, and light with a wavelength centered at 365 nm from a mercury lamp is usually used. When using this wavelength band to produce an anisotropic light-diffusing film, the illuminance is 0.01 mW / cm. 2 ~100mW / cm 2 The range of 0.1 mW / cm is preferred. 2 ~20mW / cm 2 More preferably, the illuminance is 0.01 mW / cm 2 If the power is less than 100 mW / cm, it will take a long time to cure, resulting in poor production efficiency. 2 If the curing time exceeds this limit, the photopolymerizable compound will cure too quickly, resulting in no structure formation and making it impossible to achieve the desired optical properties.

[0107] The light irradiation time is not particularly limited, but is preferably 10 to 180 seconds, and more preferably 30 to 120 seconds. By irradiating with the light beam, the anisotropic light-diffusing film of the present embodiment can be obtained.

[0108] As described above, the anisotropic light-diffusing film is obtained by forming a specific internal structure in the uncured resin composition layer by irradiating the film with low-intensity light for a relatively long period of time. Therefore, only such light irradiation may leave unreacted monomer components, causing stickiness and problems with handling and durability. In such cases, it is recommended to use a light irradiation of 1000 mW / cm 2 The remaining monomer can be polymerized by additionally irradiating the film with light of such a high intensity. The light irradiation may be performed from the side opposite to the side where the mask is laminated.

[0109] As described above, when curing the uncured resin composition layer, the scattering central axis of the resulting anisotropic light-diffusing film can be made as desired by adjusting the angle of light irradiated onto the uncured resin composition layer. In addition, the uncured resin composition layer is preferably adjusted in the range of 30°C to 100°C.

[0110] <<<<<Applications of anisotropic light diffusion film>>>> The anisotropic light-diffusing film has an excellent effect of improving the viewing angle dependency, and therefore can be applied to all kinds of display devices such as liquid crystal display devices, organic EL display devices, plasma displays, etc. The anisotropic light-diffusing film can be particularly preferably used in TN-type liquid crystal displays, which are prone to problems with viewing angle dependency.

[0111] Here, according to the present invention, it is possible to provide a liquid crystal display device including a liquid crystal layer and an anisotropic light-diffusing film. In this case, the anisotropic light-diffusing film is provided on the viewing side of the liquid crystal layer. The liquid crystal display device may be any of a TN type, a VA type, an IPS type, and the like. More specifically, a general liquid crystal device has a layer structure in which a light source, a polarizing plate, a glass substrate with a transparent electrode, a liquid crystal layer, a glass substrate with a transparent electrode, a color filter, and a polarizing plate are laminated in this order from the display device toward the viewing side, and further has an appropriate functional layer, but the anisotropic light-diffusing film may be provided at any position on the viewing side of the liquid crystal layer.

[0112] According to the present invention, it is also possible to provide an organic EL display device including a light-emitting layer and an anisotropic light-diffusing film. In this case, the anisotropic light-diffusing film is provided (laminated) on the viewing side of the light-emitting layer (including an electrode connected to the light-emitting layer). The organic EL display device may be of either a top emission type or a bottom emission type, and in the case of a color organic EL display device, it may be of either an RGB coloring type or a color filter type. The organic EL display may also be further multi-layered. EXAMPLES

[0113] <<<Example>>> EXAMPLES Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0114] <Anisotropic optical film> A partition wall having a height of 40 to 60 μm was formed with a curable resin using a dispenser around the entire edge of a 100 μm thick PET film (manufactured by Toyobo Co., Ltd., product name: A4300). The following ultraviolet curable resin composition was dropped into this, and it was covered with another PET film.

[0115] Silicone urethane acrylate (refractive index: 1.460, weight average molecular weight: 5890) 20 parts by weight (RAHN, product name: 00-225 / TM18) Neopentyl glycol diacrylate (refractive index: 1.450) 30 parts by weight (Manufactured by Daicel Cytec, product name Ebecryl145) Bisphenol A EO adduct diacrylate (refractive index: 1.536) 15 parts by weight (Manufactured by Daicel Cytec, product name Ebecryl150) Phenoxyethyl acrylate (refractive index 1.518) 40 parts by weight (Kyoeisha Chemical Company, product name: Light Acrylate PO-A) 2,2-dimethoxy-1,2-diphenylethan-1-one 4 parts by weight (BASF, product name: Irgacure 651)

[0116] The liquid film, 40 to 60 μm thick, was sandwiched between PET films on both sides and irradiated with a UV spot light source (Hamamatsu Photonics, product name: L2859-01) at an intensity of 10 to 100 mW / cm. 2 By changing parameters such as the irradiation angle, thickness of the liquid film, UV illuminance, and temperature of the liquid film during irradiation with the parallel light, anisotropic light-diffusing films 1 to 5 of the examples and anisotropic light-diffusing films 6 to 10 of the comparative examples having the optical properties shown in Table 1 were obtained.

[0117] <Measurement of thickness of anisotropic light-diffusing film> A cross section was formed using a microtome on the anisotropic light-diffusing film obtained in the examples, and the cross section was then observed under an optical microscope to measure the thickness at 10 points. The average of these measurements was taken as the thickness of the anisotropic light-diffusing film.

[0118] <Measurement of the central scattering axis angle and linear transmittance of anisotropic light-diffusing film> As shown in FIG. 6, a variable angle photometer (manufactured by Genesia) capable of arbitrarily varying the projection angle of the light source and the receiving angle of the detector was used to measure the linear transmittance of the anisotropic light diffusion film of the embodiment shown in Table 1 (including the linear transmittance at an incident angle of 60°). The detector was fixed at a position where it received the linear light from the light source, and the anisotropic light diffusion film obtained in the embodiment was set in the sample holder between them. As shown in FIG. 6, the sample was rotated around the rotation axis (V) to measure the linear transmittance corresponding to each incident light angle. This evaluation method makes it possible to evaluate the range of angles at which the incident light is diffused. This rotation axis (V) is a line on the anisotropic light diffusion film perpendicular to the tilt direction of the scattering central axis. The linear transmittance was measured at wavelengths in the visible light region using a luminosity filter. Based on the optical profile obtained as a result of the above measurements, the maximum value (maximum linear transmittance) and minimum value (minimum linear transmittance) of the linear transmittance, as well as the angle of the scattering central axis at the approximate center between the minimum values ​​in the optical profile (the center of the diffusion region) were determined and are summarized in Table 1.

[0119] <Measurement of diffuse transmittance in the direction of a polar angle of 60° at the inclination direction of the scattering central axis for light with an incident angle of 0°> Using a variable angle photometer goniophotometer (manufactured by Genesia), the diffuse transmittance of the light with an incident angle of 0° of the anisotropic light diffusion film of the example shown in Table 1 in the direction of a polar angle of 60° in the tilt direction of the scattering central axis was measured. Specifically, the anisotropic optical film obtained in the example was set in a sample holder, a light source was placed in the normal direction (incident angle = 0°) of one surface of the anisotropic light diffusion film, and a detector was placed on the other surface. The normal direction on the detector side was set to a polar angle θ = 0°, and the brightness was measured while varying the polar angle of the detector. The diffuse transmittance was a relative value with the brightness in the normal direction (polar angle θ = 0°) when the anisotropic light diffusion film was not used being 100%. The obtained diffuse transmittance is shown in Table 1.

[0120] <Measurement of the aspect ratio of columnar structures (surface observation of anisotropic light-diffusing film)> The cross section perpendicular to the column axis of the anisotropic light-diffusing film obtained in the examples (the side irradiated with ultraviolet light) was observed with an optical microscope, and the long diameter LA and short diameter SA of the columnar structures in the columnar region were measured. The average long diameter LA and the average short diameter SA were calculated as the average values ​​of 20 arbitrary structures. In addition, the average long diameter LA / average short diameter SA was calculated as the aspect ratio for the obtained average long diameter LA and average short diameter SA, and the ratio is summarized in Table 1.

[0121] <Measurement of haze of anisotropic light-diffusing film> The haze of the anisotropic light-diffusing films obtained in the examples was measured using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and the results are summarized in Table 1.

[0122] [Table 1]

[0123] <<Evaluation method>> The anisotropic light-diffusing films produced in the above Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated as follows.

[0124] <Evaluation of tone inversion> The anisotropic light-diffusing film was attached to the surface of a TN mode liquid crystal display so that the angle between the direction in which tone inversion occurs in the liquid crystal display and the tilt direction of the scattering central axis of the anisotropic light-diffusing film a was 0°. Next, using a viewing angle measuring device Conometer80 (Westboro), the luminance distribution was measured in the polar angle range of 0 to 80° relative to the normal direction of the display when a gray scale divided into 11 gradations from white to black was displayed on the display. The "white luminance / black luminance" was calculated at a polar angle of 80°, the direction in which grayscale inversion occurs on the LCD monitor alone, and this was taken as the contrast. Additionally, the minimum polar angle at which the measured 11 grayscales are reversed from the original grayscale in the direction in which grayscale inversion occurs on the LCD monitor alone was taken as the grayscale inversion angle. These are summarized in Table 2. Here, in an evaluation of the display alone, without the anisotropic light-diffusing film attached, the contrast was 8.0 and the tone inversion angle was 28°.

[0125] <Criteria for determining tone inversion> The tone inversion angle of 65° or more was rated as ⊚, that of 52° or more and less than 65° was rated as ◯, and that of less than 52° was rated as x.

[0126] <Contrast criteria for polar angle 80°> A contrast of 11 or more was rated as ◎, between 9 and 11 as ○, and less than 9 as ×.

[0127] [Table 2]

[0128] <<Evaluation Results>> As shown in Examples 1 to 5, the effect of improving tone inversion and the contrast at 80° of the present invention using a predetermined anisotropic light-diffusing film are superior to those of Comparative Examples 1 to 5. In Comparative Examples 1 and 3, the linear transmittance is high at an incident angle of 60°, and the diffuse transmittance in the polar angle 60° direction in the tilt azimuth of the scattering central axis for light at an incident angle of 0° is also low, so that the light in the 60° direction where the grayscale-inverted light is emitted cannot be diffused, and the light in the 0° direction with the correct grayscale cannot be diffused to angles with a large polar angle. In Comparative Example 2, the diffuse transmittance is sufficient, but the linear transmittance is insufficient, and conversely, in Comparative Examples 4 and 5, the linear transmittance is sufficient, but the diffuse transmittance is insufficient, so that both have small grayscale inversion angles.

[0129] It is believed that the present invention was able to obtain the above evaluation results by using a specific anisotropic light-diffusing film as a diffusion medium having specific diffusion characteristics.

[0130] Therefore, when the light diffusion film of the embodiment is used in, for example, a TN liquid crystal display device, it is possible to suppress gray scale inversion and improve contrast at deep angles, thereby ensuring visibility even in orientations where visibility is normally difficult.

Claims

1. An anisotropic light-diffusing film having a linear transmittance, which is (amount of transmitted light in a linear direction of incident light) / (amount of incident light), that changes depending on the angle of incidence of light, the anisotropic light-diffusing film has a matrix region and a plurality of columnar regions having a refractive index different from that of the matrix region; Furthermore, the anisotropic light-diffusing film has one scattering central axis, In the tilt direction of the scattering central axis, The linear transmittance at an incident angle of 60° is 10% or less, The diffuse transmittance of light at an incident angle of 0° in a polar angle direction of 60° is 0.001% or more, 1. An anisotropic light-diffusing film, characterized in that the haze value of the anisotropic light-diffusing film is 75% or more.

2. If the polar angle between the surface normal direction of the anisotropic light-diffusing film and the scattering central axis direction is defined as the scattering central axis angle, 2. The anisotropic light-diffusing film according to claim 1, wherein the scattering central axis angle of the anisotropic light-diffusing film is 20° to 60°.

3. 3. The anisotropic light-diffusing film according to claim 1, wherein the thickness of the anisotropic light-diffusing film is 15 μm to 100 μm.

4. The plurality of columnar regions of the anisotropic light-diffusing film are The anisotropic light diffusing film is oriented and extends from one surface to the other surface, An anisotropic light-diffusing film as described in any one of claims 1 to 3, characterized in that the aspect ratio of the columnar regions, which is the average long axis / average short axis of the columnar regions in a cross section perpendicular to the column axis of the anisotropic light-diffusing film, is less than 2.

5. A liquid crystal display device, comprising: an anisotropic light-diffusing film according to any one of claims 1 to 4 laminated on a viewing side of a liquid crystal layer.

6. 5. An organic electroluminescence display device, comprising: an anisotropic light-diffusing film according to claim 1 laminated on a viewing side of a light-emitting layer.

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