TW202202916A - Anisotropic light diffusing film and display device - Google Patents

Abstract

The present invention provides an anisotropic light diffusing film which has a viewing angle dependence improving effect superior to the conventional ones with respect to brightness and color change depending on viewing angle. The anisotropic light diffusing film of the present invention has a linear transmittance changing in accordance to the incident angle of light, wherein the linear transmittance is (the amount of transmitted light of the incident light in the linear direction) / (the amount of light of the incident light). The anisotropic light diffusing film has a matrix region and a plurality of columnar regions having different refractive indexes from the matrix region. Further, the anisotropic light diffusing film has one scattering center axis, wherein in the inclination direction of the scattering center axis, the linear transmittance at an incident angle of 60° is 10% or less, and the diffusion transmittance of light at an incident angle of 0° in the polar angle of 60° is 0.001% or more.

Description

Anisotropic light diffusing film and display device

The present invention relates to an anisotropic (also called anisotropic) light diffusing film and a display device having the anisotropic light diffusing film.

For display devices, such as transmissive TN-mode liquid crystals, when the display device is recognized from an oblique direction in a specific orientation, the brightness or contrast will decrease, or the color level will change with the color level different from the front direction (the color level is reversed). problems related to the perspective dependence of

In order to solve such a viewing angle dependency, the linear transmittance [(the amount of transmitted light in the linear direction of the incident light)/(the amount of light of the incident light)] is applied, which varies according to the incident angle of the light. Sexual optics.

For example, in Patent Document 1, an anisotropic optical film in which the direction in which the color change of the display device is minimized and the scattering center axis are within a specific angle range is used in the display device to improve the brightness and color change caused by the viewing angle. question.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-127819

However, considering the diversification of display methods and display sizes of display devices, etc., we are looking for anisotropic optical bodies having a more excellent viewing angle dependence improvement effect.

Therefore, the subject of this invention is to provide the anisotropic light-diffusion film which has the viewing angle dependence improvement effect which is more excellent than the conventional thing with respect to the brightness and color change by a viewing angle.

The inventors of the present invention found that the above-mentioned problems can be solved by using an anisotropic light-diffusion film having specific properties, and completed the present invention. That is, the present invention is as follows.

The present invention (1) is an anisotropic light diffusing film, the linear transmittance of which varies according to the incident angle of light, wherein the linear transmittance is (the amount of transmitted light in the linear direction of the incident light)/(the incident light light amount of light),

The aforementioned anisotropic light-diffusing film has a matrix region and a plurality of columnar regions whose refractive index is different from the matrix region,

Furthermore, the aforementioned anisotropic light-diffusion film system has one scattering center axis,

In the inclined azimuth of the aforementioned scattering center axis,

When the incident angle is 60°, the linear transmittance is less than 10%,

The diffuse transmittance of light with an incident angle of 0° toward a polar angle of 60° is more than 0.001%.

The present invention (2) is the anisotropic light-diffusing film according to the aforementioned invention (1), wherein the polar angle formed by the surface normal direction of the anisotropic light-diffusing film and the scattering center axis direction is taken as the scattering center axis angle ,

The scattering center axis angle of the anisotropic light diffusing film is 20° to 60°.

The present invention (3) is the anisotropic light-diffusion film according to the aforementioned invention (1) or (2), wherein the haze value of the anisotropic light-diffusion film is 75% or more.

The present invention (4) is the anisotropic light-diffusion film according to any one of the aforementioned inventions (1) to (3), wherein the thickness of the anisotropic light-diffusion film is 15 μm to 100 μm.

The present invention (5) is the anisotropic light-diffusion film according to any one of the aforementioned inventions (1) to (4), wherein,

The plurality of columnar regions of the anisotropic light diffusing film are configured to be aligned from one surface of the anisotropic light diffusing film to the other surface and extending from one surface to the other surface of the anisotropic light diffusing film,

In the cross section perpendicular to the column axis of the columnar region of the anisotropic light diffusing film, the average long axis/average short axis of the columnar region, that is, the aspect ratio of the columnar region is less than 2.

The liquid crystal display device of the present invention (6) has the anisotropic light-diffusion film according to any one of the aforementioned inventions (1) to (5) laminated on the viewing side of the liquid crystal layer.

The organic EL display device of the present invention (7) is formed by laminating the anisotropic light-diffusion film according to any one of the aforementioned inventions (1) to (5) on the viewing side of the light-emitting layer.

According to the present invention, it is possible to provide an anisotropic light-diffusion film having a viewing angle dependence improvement effect that is more excellent than before in terms of brightness and color changes due to viewing angles.

300: light source

301: Directional diffusion element

302: Directional diffusion element

303: Uncured resin composition layer

V: Rotation axis

E: light

LA: long diameter

SA: Short diameter

FIG. 1 is an explanatory diagram showing the incident light angle dependence of an anisotropic light-diffusion film.

FIG. 2 is a plan view showing the surface structure of the anisotropic light-diffusion film.

FIG. 3 is a schematic view showing an example of an anisotropic light-diffusion film.

FIG. 4 is used to illustrate the three-dimensional polar coordinate display of the scattering center axis of the anisotropic light-diffusing film.

Figure 5 is an optical profile in an anisotropic light diffusing film.

FIG. 6 is a schematic diagram showing a method for measuring the incident light angle dependence of an anisotropic light-diffusion film.

FIG. 7 is a schematic diagram showing a method for producing the anisotropic light-diffusion film of the present invention including any of steps 1-3.

Hereinafter, after briefly explaining the anisotropic light-diffusion film of the present invention, the structure, physical properties, manufacturing methods, and specific applications will be explained.

<<<<Anisotropic Light Diffusion Film>>>>

The anisotropic light diffusing film is a film with optical anisotropy whose linear transmittance [(the amount of transmitted light in the linear direction of the incident light)/(the amount of incident light)] changes according to the incident angle of the light. That is, regarding the incident light to the anisotropic light-diffusion film, the incident light in a predetermined angular range maintains linearity and penetrates, and the incident light in the other angular range shows diffusivity.

For example, the anisotropic light diffusing film shown in FIG. 1 shows diffusivity when the incident angle is 20° to 50°, but does not show diffusivity at other incident angles, but shows straight line penetration.

<<<Construction>>>

The anisotropic light-diffusion film of the present invention has a matrix region and a plurality of columnar regions whose refractive index is different from that of the matrix region. The plurality of columnar regions included in the anisotropic light diffusing film are usually configured to be aligned from one surface of the anisotropic light diffusing film to the other surface and extending from one surface to the other surface of the anisotropic light diffusing film (refer to FIG. 3 etc. ).

Here, the difference in refractive index means that at least a part of the light incident on the anisotropic light-diffusion film causes a difference in the degree of reflection at the interface between the matrix region and the columnar region, and is not particularly limited. For example, the matrix The difference in the refractive index between the region and the columnar region should just be 0.001 or more.

<<Columnar area>>

The length of the columnar region is not particularly limited, and may be a length that penetrates from one surface of the anisotropic light-diffusing film to the other surface, or a length that does not reach the other surface from one surface.

The cross-sectional shape of the plurality of columnar regions in the cross-section perpendicular to the column axis of the anisotropic light-diffusing film of the plurality of columnar regions included in the anisotropic light-diffusing film can be set to have a shape with a short axis and a long axis.

The cross-sectional shape of the columnar region is not particularly limited, and may be, for example, a circle, an ellipse, or a polygon. In the case of a circle, the short diameter and the long diameter are equal. In the case of an elliptical circle, the short diameter is the length of the short axis, and the long diameter is the length of the long axis. In the case of a polygon, the polygon can be made The shortest length inside is set as the short diameter, and the longest length is set as the long diameter. In FIG. 2, the columnar area|region seen from the surface direction of an anisotropic light-diffusion film is shown. In FIG. 2 , the LA system represents the long axis, and the SA system represents the short axis.

The short and long diameters of the columnar regions are the cross sections perpendicular to the column axis of the anisotropic light-diffusing film observed with an optical microscope, and the short and long diameters of each of the 20 randomly selected columnar regions are measured, and can be set as these the average.

<Short diameter>

As for the anisotropic light-diffusion film, it is preferable that the average value (average short diameter) of the short diameters of the columnar regions is 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 short diameter 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 limit value and the upper limit value of the short diameter of these columnar regions can be appropriately combined.

<long diameter>

As for the anisotropic light-diffusion film, it is preferable that the average value (average long diameter) of the long diameters of the columnar regions is 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 diameter of the columnar regions is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. The average length of the columnar region is preferably shorter than the length of the columnar region. In this way, the linear transmittance of the light of the anisotropic light-diffusion film can be improved. The lower limit value and the upper limit value of the long diameter of these columnar regions can be appropriately combined.

The ratio of the average long diameter to the average short diameter of the columnar region (average long diameter/average short diameter), that is, the aspect ratio is not particularly limited, but can be set to 1 to 20, for example.

FIG. 2( a ) shows an anisotropic light-diffusion film with a columnar region having an aspect ratio of 2 to 20, and FIG. 2( b ) shows an anisotropic light-diffusing film with a columnar region having an aspect ratio of 1 or more and less than 2 .

When the aspect ratio is 1 or more and less than 2, when the light parallel to the axis of the columnar region is irradiated, the transmitted light is diffused in an isotropic (also known as isotropic) manner {refer to Figure 3(a) }. Other On the other hand, when the aspect ratio is 2 to 20, when the light parallel to the axis is irradiated in the same way, diffusion is performed with anisotropy depending on the aspect ratio {see FIG. 3( b )}.

The anisotropic light-diffusion film system may include a plurality of columnar regions with one aspect ratio, or a plurality of columnar regions with different aspect ratios.

<<<Central axis of scattering>>>

The anisotropic light-diffusion film system has a scattering center axis. The central axis of scattering and the alignment direction (extending direction) of the columnar regions are generally in a parallel relationship. In addition, it is only necessary to satisfy the law of refractive index (Snell's law) that the scattering center axis and the alignment direction of the columnar regions are parallel, and do not need to be strictly parallel.

Snell's law is that when light is incident from the interface of a medium with a refractive index n1 to a medium with a refractive index n2, between the incident light angle θ1 and the refraction angle θ2, the relationship of n1sinθ1=n2sinθ2 is established, for example, if n1=1 (air), n2=1.51 (anisotropic light diffusing film), when the incident light angle is 30°, the alignment direction (refraction angle) of the columnar region is about 19°, but if so, even if the incident light angle and the refraction angle are different However, if Snell's law is satisfied, the concept of parallelism is also included in the present invention.

Next, referring to FIG. 4 , the center axis P of scattering of the anisotropic light-diffusion film will be described in more detail. FIG. 4 is a 3-dimensional polar coordinate display for explaining the scattering center axis P of the anisotropic light-diffusion film.

The central axis of scattering refers to the direction that is consistent with the incident light angle of light in a specific direction, wherein, when changing the incident light angle to the anisotropic light diffusing film, the light diffusivity is based on the incident light angle of the light. symmetry. In addition, regarding the incident light angle at this time, the linear transmittance of the anisotropic light-diffusion film was measured, and the linear transmittance for each incident light angle was estimated. The slightly central portion (the central portion of the diffusion region) surrounded by the minimum value in the optical curve (FIG. 5) drawn.

According to the three-dimensional polar coordinate display as shown in Fig. 4, when the surface of the anisotropic light diffusing film is taken as the xy plane, and the normal line relative to the surface of the anisotropic light diffusing film is taken as the z axis, the central scattering axis can be determined by the polar angle θ. It is expressed with the azimuth angle φ.

Here, the polar angle θ (-90°<θ<90°) formed by the normal line (z-axis shown in FIG. 4 ) of the anisotropic light diffusing film and the columnar region can be defined as the scattering center axis angle. In the step of photocuring the uncured resin composition layer and forming the columnar region, the angle of the axial direction of the columnar region can be adjusted to a desired range by changing the direction of the irradiated light.

The scattering center axis angle θ of the anisotropic light-diffusion film is not particularly limited, but is preferably 20° to 60°, more preferably 20° to 50°.

By setting the scattering center axis angle θ in this way, a desired angle dependence can be exhibited.

<<<Optical Curve>>>

As shown in FIG. 5 , the anisotropic light-diffusion film is an incident-light-angle-dependent light diffusing property in which the linear transmittance varies depending on the incident light angle. Here, as shown in FIG. 5 , a curve showing the dependence of the light diffusivity on the incident light angle is hereinafter referred to as an “optical curve”.

The optical curve system can be produced, for example, as follows.

As shown in FIG. 6 , the anisotropic light-diffusion film is arranged between the light source 1 and the detector 2 . In this embodiment, the incident light angle is 0° when the irradiation light I from the light source 1 is incident from the normal line direction of the anisotropic light-diffusion film. Moreover, the anisotropic light-diffusion film is arrange|positioned so that it may rotate arbitrarily with the straight line V as a rotation axis, and the light source 1 and the detector 2 are fixed. That is, according to the party In the method, the sample (anisotropic light diffusing film) is arranged between the light source 1 and the detector 2, and the angle is changed with the straight line V on the surface of the sample as the rotation axis, and the measurement is carried out when the sample penetrates straight and enters Linear transmittance of detector 2. Afterwards, the linear transmittance is plotted according to each angle, and an optical curve is produced.

The optical curve does not directly express the light diffusivity, but if it is interpreted that the diffusion transmittance increases due to the decrease in the linear transmittance, it can be said that it can roughly show the light diffusivity.

Generally, an isotropic light-diffusion film system exhibits a mountain-shaped optical curve with an incident light angle near 0° as a peak.

For example, in the anisotropic light diffusing film system, it is shown that if the angle of the central axis of scattering is taken as 0° (Fig. 5), the incident light angle of the linear transmittance near 0° (-20° to +20°) is small, and as the incident light The angle (absolute value) increases, and the linear transmittance increases the valley-shaped optical curve.

In this way, the anisotropic light diffusing film system has the following properties: the incident light will be strongly diffused when the incident light angle range is close to the scattering central axis, but the diffusion will be weakened and the linear transmittance will increase when the incident light angle range above it is. .

When the scattering central axis angle is other than 0°, the optical curve moves in such a way that the linear transmittance becomes smaller at the incident light angle near the scattering central axis angle (the trough of the optical curve moves toward the scattering central axis angle side).

<<<Linear penetration rate>>>

As shown in FIG. 5 , the linear transmittance of light incident on the anisotropic light-diffusion film at the incident angle at which the linear transmittance becomes the maximum is referred to as the maximum linear transmittance.

As shown in FIG. 5 , the linear transmittance of light incident on the anisotropic light-diffusing film at the incident angle at which the linear transmittance becomes the smallest is referred to as the minimum linear transmittance.

As shown in FIG. 5 , the angular range of the two incident light angles relative to the linear transmittance between the maximum linear transmittance and the minimum linear transmittance is referred to as the diffusion area (the width of the diffusion area is referred to as the diffusion area). "Diffusion width"), and the angular range of incident light excluding this angular range is called the non-diffusion area (transmission area).

The linear transmittance of the anisotropic light diffusing film at an incident angle of 60° in the inclined azimuth of the scattering center axis is preferably less than 10%, more preferably less than 5%, and particularly preferably less than 2.5%.

The linear transmittance can be based on the refractive index of the material of the anisotropic light diffusing film (the difference in refractive index when multiple resins are used) or the film thickness of the coating film, the UV illuminance or the temperature when the structure is formed, and the irradiation angle during UV irradiation Adjust according to hardening conditions. The linear transmittance at an incident angle of 60° is, 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, and the refractive index when using multiple resins. The bigger the difference, the more it tends to decrease.

<<<Diffuse transmittance in the direction of polar angle of 60° in the inclined azimuth of the scattering center axis for light with an incident angle of 0°>>>

The light source was arranged in the normal direction (incidence angle=0°) of one surface of the anisotropic light-diffusion film, and the detector was arranged on the other surface. Using the normal direction of the detector side as the polar angle θ=0°, the luminance was measured while changing the polar angle of the detector. The diffuse transmittance is a relative value of 100% with the luminance in the normal direction (polar angle θ=0°) when the anisotropic light diffusing film is not used.

It is preferable that the diffusion transmittance of light with an incident angle of 0° of the anisotropic light diffusing film in the direction of the polar angle of 60° in the inclined azimuth of the scattering center axis is 0.001% or more. In addition, although this upper limit is not specifically limited, Preferably it is 0.01% or less, More preferably, it is 0.005% or less.

The linear transmittance when the incident angle of the anisotropic light diffusing film is 60° is set to the above appropriate range, and the light with the incident angle of the anisotropic light diffusing film 0° is inclined toward the central axis of scattering The diffusion transmittance in the direction of the polar angle of 60° is set in such a range that the light can be sufficiently diffused to a viewing angle of about 80°.

The diffusion transmittance of light with an incident angle of 0° toward the polar angle of 60° in the inclination of the scattering center axis of anisotropic light diffusing film is the thicker the film thickness of the coating film during UV irradiation, the higher the temperature of the coating film. , tends to increase. In addition, when UV irradiation is performed on the coating film, when the irradiation angle is 20° to 60° from the normal direction of the coating film, it is easy to satisfy the above numerical range.

<<<Haze value>>>

The haze value (total haze) of the anisotropic light-diffusion film is an index showing the diffusivity of the anisotropic light-diffusion film. When the haze value becomes large, the diffusivity of the anisotropic light-diffusion film becomes high.

The measurement method of the haze value is not particularly limited, and it can be measured by a known method. For example, it can be measured according to JIS K7136-1:2000 "Plastics-Method for obtaining haze of transparent materials".

The haze value of the anisotropic light-diffusion film is not particularly limited, but is preferably 75% or more. By setting it as such a range, the effect of this invention can be improved more.

The haze value can be adjusted according to the refractive index of the material of the anisotropic light-diffusion film (the difference in refractive index when plural resins are used), the thickness of the coating film, UV illuminance, or curing conditions such as the temperature at which the structure is formed. The haze value is, for example, the closer the irradiation angle is to the normal direction of the uncoated film during UV irradiation, the thicker the layer thickness of the coating film, the higher the temperature of the coating film, and the greater the refractive index difference when using multiple resins, the more increasing tendency.

<<Thickness>>

The thickness of the anisotropic light-diffusion film is not particularly limited, but is preferably 15 μm to 100 μm, more preferably 30 μm to 60 μm. By setting it as such a range, the manufacturing cost, such as material cost and the cost required for UV irradiation, can be reduced, and the visual dependence improvement effect can be made sufficient.

Hereinafter, the manufacturing method of the related anisotropic light-diffusion film is demonstrated.

<<<Manufacture of anisotropic light diffusing film>>>

<<Raw materials>>

About the raw material of an anisotropic light-diffusion film, (1) photopolymerizable compound, (2) photoinitiator, (3) compounding amount, and other optional components are demonstrated in this order.

<Photopolymerizable compound>

The photopolymerizable compound is composed of a photopolymerizable compound and a photoinitiator selected from macromonomers, polymers, oligomers, and monomers with functional groups having radical polymerizability or cationic polymerizability, and is produced by Materials that are irradiated with ultraviolet and/or visible light to polymerize/harden.

Here, even if the material which forms an anisotropic light-diffusion film is 1 type, a difference in refractive index can be produced by the height difference of formation density. The part with strong UV irradiation intensity is due to the fact that the curing speed becomes faster, and the polymerized/cured material moves around the hardened area. As a result, a region with a high refractive index and a region with a low refractive index are formed. In addition, the term "(meth)acrylate" means that either acrylate or methacrylate may be used.

Radical polymerizable compounds are mainly those containing one or more unsaturated double bonds in the molecule, and specific examples thereof include epoxy acrylate, urethane acrylate, polyester acrylate, and polyether. Acrylic oligomers called acrylates, polybutadiene acrylates, polysiloxane acrylates, etc., and 2-ethylhexyl acrylate, isoamyl acrylate, butoxyethyl acrylate, ethoxy Diethylene glycol acrylate, phenoxyethyl acrylate, propylene Tetrahydrofuran methyl acrylate, isonorbornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-acryloyloxyphthalic acid, dicyclopentenyl acrylate, triethylene glycol diacrylate, new Pentylene glycol diacrylate, 1,6-hexanediol diacrylate, EO adduct diacrylate of bisphenol A, trimethylolpropane triacrylate, EO modified trimethylolpropane triacrylate , Neopentaerythritol triacrylate, Neotaerythritol tetraacrylate, Di-trimethylolpropane tetraacrylate, Dipivalerythritol hexaacrylate and other acrylate monomers. In addition, these compounds may be used individually by each monomer, and may be used in mixture of a plurality of types. In addition, methacrylate can also be used similarly, but the photopolymerization rate of acrylate is generally faster than that of methacrylate, so it is preferable.

As the cationically polymerizable compound, a compound having one or more epoxy groups, vinyl ether groups, or oxycyclobutyl groups in the molecule can be used. Compounds having an epoxy group include 2-ethylhexyl diethylene glycol glycidyl ether, glycidyl ether of biphenyl, bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, bisphenol A Diglycidyl ethers of bisphenols such as phenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetrachlorobisphenol A, tetrabromobisphenol A, novolak, cresol novolac, Polyglycidyl ethers, ethylene glycol, polyethylene glycol, polypropylene glycol, butanediol, 1,6-hexanediol, neopentyl Diglycidyl ethers of alkanediols such as diols, trimethylolpropane, 1,4-cyclohexanedimethanol, EO adducts of bisphenol A, PO adducts of bisphenol A, etc., Glycidyl esters such as glycidyl ester of hexahydrophthalic acid or diglycidyl ester of dimer acid.

Further examples of the compound having an epoxy group include 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl -5,5-spiro-3,4-epoxy)cyclohexane-methyl-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, bis(3,4 -Epoxy-6-methylcyclohexylmethyl)adipate, 3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy- 6'-Methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexane), dicyclopentadiene diepoxide, ethylene glycol bis(3,4-cyclohexane) Oxycyclohexylmethyl) ether, ethylidene bis(3,4-epoxycyclohexanecarboxylate), lactone-modified 3,4-epoxycyclohexylmethyl-3',4' - Epoxycyclohexanecarboxylate, tetrakis(3,4-epoxycyclohexylmethyl)butane tetracarboxylate, bis(3,4-epoxycyclohexylmethyl)-4,5 - Alicyclic epoxy compounds, such as epoxy tetrahydrophthalate, are not limited to these.

Examples of compounds having a vinyl ether group include diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, and cyclohexanedimethanol. Divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, trimethylolpropane trivinyl ether, propenyl ether propylene carbonate, etc., but not limited thereto . In addition, vinyl ether compounds are generally cationically polymerizable, but can also be radically polymerized by combining with acrylates.

In addition, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 3-ethyl-3-(hydroxyl methyl)-oxetane, etc.

In addition, the above-mentioned cationically polymerizable compound system may be used individually by each monomer, and may be used in mixture of two or more. The said photopolymerizable compound is not limited to the above.

In addition, in order to generate a sufficient refractive index difference, in the above-mentioned photopolymerizable compound, a fluorine atom (F) may be introduced for the purpose of lowering the refractive index, and a sulfur atom (S) may be introduced for the purpose of increasing the refractive index. , bromine atom (Br), various metal atoms. Furthermore, as disclosed in Japanese Patent Publication No. 2005-514487, a metal having a high refractive index such as titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), and tin oxide (SnO _x ) is added to the above-mentioned photopolymerizable compound. Functional ultrafine particles in which photopolymerizable functional groups such as acrylic groups, methacrylic groups, and epoxy groups are introduced into the surfaces of ultrafine particles composed of oxides are also effective.

Preferably, a photopolymerizable compound having a polysiloxane skeleton is used as the photopolymerizable compound. The photopolymerizable compound with a polysiloxane skeleton is aligned and polymerized/hardened according to its structure (mainly ether bonds) 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 polysiloxane skeleton, the columnar region can be easily inclined, and the light condensing property in the frontal direction can be improved. In addition, 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.

In the low-refractive-index region, the polysiloxane resin, which is preferably a cured product of a photopolymerizable compound having a polysiloxane skeleton, relatively increases. Thereby, since the center axis of scattering can be more easily inclined, the light condensing performance in the frontal direction can be improved. Compared with compounds without polysiloxane skeleton, polysiloxane contains a lot of silicon (Si), so using this silicon as an indicator, polysiloxane can be confirmed by using EDS (Energy Dispersive X-ray Spectrometer) the relative amount.

Photopolymerizable compounds with polysiloxane skeleton are monomers, oligomers, prepolymers or macromonomers with functional groups of radical polymerizability or cationic polymerizability. Examples of the radically polymerizable functional group include acryl group, methacryloyl group, and allyl group, and examples of the cationically polymerizable functional group include epoxy groups, oxycyclobutyl groups, and the like. The types and numbers of these functional groups are not particularly limited, but the more functional groups, the higher the crosslinking density and the easier the difference in refractive index. Therefore, it is preferable to use polyfunctional acryl or methacryloyl groups. base is better. In addition, the compound having a polysiloxane skeleton may be insufficient in compatibility with other compounds due to its structure, but in such a case, urethane can be performed to improve compatibility. In this form, polysiloxane/urethane/(meth)acrylate having an acryl group or a methacryl group at the terminal is suitably used.

The weight average molecular weight (Mw) of the photopolymerizable compound having a polysiloxane skeleton is preferably in the range of 500 to 50,000. More preferably, it is in the range of 2,000 to 20,000. by The weight-average molecular weight is in the above-mentioned range, so that sufficient photohardening reaction occurs, and the polysiloxane present in the anisotropic light-diffusing film of the anisotropic light-diffusion film can be easily aligned. With the alignment of the polysiloxane, it is easy to tilt the scattering center axis.

The polysiloxane skeleton is, for example, equivalent to that represented by the following general formula (1). In the general formula (1), R1, R2, R3, R4, R5, and R6 each independently have a methyl group, an alkyl group, a fluoroalkyl group, a phenyl group, an epoxy group, an amino group, a carboxyl group, a polyether group, Functional groups such as acryl and methacryloyl. In addition, in the general formula (1), n is preferably an integer of 1 to 500.

If a compound without a polysiloxane skeleton is mixed into a photopolymerizable compound with a polysiloxane skeleton, if an anisotropic light-diffusion film is formed, the low-refractive-index region and the high-refractive-index region are easily separated and formed, and the degree of anisotropy becomes stronger , is better.

In addition to photopolymerizable compounds, thermoplastic resins, thermosetting resins, or a combination of these can also be used for compounds that do not have a polysiloxane skeleton.

As the photopolymerizable compound, polymers, oligomers, and monomers having functional groups of radical polymerizability or cation polymerizability (however, those having no polysiloxane skeleton) can be used.

The thermoplastic resin includes polyester, polyether, polyurethane, polyamide, polystyrene, polycarbonate, polyacetal, polyvinyl acetate, acrylic resin, and copolymers or modified products thereof. When using a thermoplastic resin, use a solvent that dissolves the thermoplastic resin, and after dissolving, apply After cloth and drying, the photopolymerizable compound having a polysiloxane skeleton is cured with ultraviolet rays to form an anisotropic light-diffusion film.

The thermosetting resins include epoxy resins, phenol resins, melamine resins, urea resins, unsaturated polyesters, and copolymers or modified products thereof. When a thermosetting resin is used, the photopolymerizable compound having a polysiloxane skeleton is hardened with ultraviolet rays, and then appropriately heated to harden the thermosetting resin to form an anisotropic light-diffusion film.

The best compound without a polysiloxane skeleton is a photopolymerizable compound, and the low-refractive-index region and the high-refractive-index region are easily separated, do not require a solvent in the use of thermoplastic resins, do not require a drying process, and do not A thermosetting process such as a thermosetting resin is required, and the productivity is excellent.

<Photoinitiator>

Examples of photoinitiators capable of polymerizing radically polymerizable compounds include benzophenone, benzophenone (benzil), Michler's ketone, 2-chlorothioxanthone, and 2,4-diethylsulfide Xanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone, benzyl dimethyl 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-N-

Morpholinylacetone-1, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, bis(cyclopentadienyl) -Bis[2,6-difluoro-3-(pyrrol-1-yl)phenyl]titanium, 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)- Butanone-1,2,4,6-trimethylbenzyldiphenylphosphine oxide, etc. In addition, these compounds may be used individually by each monomer, and may be used in mixture of two or more.

As the photoinitiator of the cationically polymerizable compound, an acid can be generated by light irradiation, and the cationically polymerizable compound can be polymerized by the generated acid. Generally, onium salts and metallocene complexes are suitably used.

As the onium salts, diazonium salts, peronium salts, iodonium salts, phosphonium salts, selenonium salts, etc. are used, and anions such as BF4-, PF6-, AsF6-, and SbF6- are used as counter ions. Specific examples include 4-chlorobenzenediazonium hexafluorophosphate, triphenylperylene hexafluoroantimonate, triphenylperylene hexafluorophosphate, (4-phenylthiophenyl)diphenylperylenehexa Fluoroantimonate, (4-phenylthiophenyl)diphenylperylium hexafluorophosphate, bis[4-(diphenyldihydrothio)phenyl]sulfide-bishexafluoroantimonate, bis[4-(diphenylthiophenyl)phenyl]sulfide-bishexafluoroantimonate [4-(Diphenylsulfonyl)phenyl]thioether-bis-hexafluorophosphate, (4-methoxyphenyl)diphenylperylium hexafluoroantimonate, (4-methoxybenzene base) phenyl iodonium hexafluoroantimonate, bis(4-tert-butylphenyl) iodonium hexafluorophosphate, benzyltriphenylphosphonium hexafluoroantimonate, triphenylselenonium hexafluorophosphate , (η5-isopropylbenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate, etc., but not limited thereto. In addition, these compounds can be used individually by each monomer, and can also be used in mixture of several types.

The photoinitiator is blended in 0.01 to 10 parts by mass, preferably 0.1 to 7 parts by mass, and more preferably about 0.1 to 5 parts by mass relative to 100 parts by mass of the photopolymerizable compound. If this is less than 0.01 parts by mass, the photocurability will decrease, and if it is more than 10 parts by mass, only the surface will be hardened and the internal curability will be reduced, resulting in damage, coloring, and formation of a columnar structure.

<Other ingredients>

The photoinitiator is usually used by directly dissolving the powder in the photopolymerizable compound. However, when the solubility is poor, the photoinitiator may be pre-dissolved in a very small amount of solvent to obtain a high concentration. Such as The solvent is more preferably photopolymerizable, and specific examples thereof include propylene carbonate, γ-butyrolactone, and the like. Moreover, in order to improve photopolymerizability, various well-known dyes or sensitizers may be added.

Furthermore, a photoinitiator may be used together with a thermosetting initiator for curing the photopolymerizable compound by heating. In this case, it can be expected to further accelerate the polymerization and curing of the photopolymerizable compound by heating after photocuring, and to form a completely cured one. The anisotropic light-diffusion film can be formed by curing the photopolymerizable compound alone or by curing a plurality of compositions mixed together.

An anisotropic light-diffusion film can be formed even if it is cured by a mixture of a photopolymerizable compound and a polymer resin having no photocurable properties.

The polymer resins that can be used here include acrylic resins, styrene resins, styrene-acrylic copolymers, polyurethane resins, polyester resins, epoxy resins, cellulose-based resins, and vinyl acetate-based resins. , vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, etc. These polymer resins and the photopolymerizable compound must have sufficient compatibility before photocuring, but in order to secure the compatibility, various organic solvents, plasticizers, and the like may be used.

When an acrylate is used as the photopolymerizable compound, the polymer resin is preferably selected from acrylic resins from the viewpoint of compatibility.

The ratio of the photopolymerizable compound having a polysiloxane skeleton to the compound not having a polysiloxane skeleton is preferably in the range of 15:85 to 85:15 in terms of mass ratio. More preferably, it is in the range of 30:70 to 70:30. By being in this range, the phase separation of the low-refractive-index region and the high-refractive-index region becomes easy, and the columnar region becomes easy to incline. If the ratio of the photopolymerizable compound having a polysiloxane skeleton is less than the lower limit value or the upper limit value or more, phase separation becomes difficult, and the columnar region becomes difficult to incline.

When polysiloxane/urethane/(meth)acrylate is used as the photopolymerizable compound having a polysiloxane skeleton, the compatibility with a compound not having a polysiloxane skeleton is improved. Thereby, even if the mixing ratio of the material is increased, the columnar region can be inclined.

For example, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, xylene, etc. can be used as a solvent system when a composition containing a photopolymerizable compound is prepared.

<<Manufacturing process>>

Next, the manufacturing process of the anisotropic light-diffusion film will be described.

First, the above-mentioned composition containing a photopolymerizable compound (hereinafter, sometimes referred to as a "photocurable resin composition") is coated on a suitable substrate such as a transparent PET film to form a sheet, and film formation is performed. Instead, a photocurable resin composition layer is provided. After drying the photocurable resin composition layer as necessary and volatilizing the solvent, light can be irradiated on the photocurable resin composition layer to produce an anisotropic light-diffusion film.

More specifically, the formation step of an anisotropic light-diffusion film mainly has the following steps.

(1) Step 1-1: Step of laying the unhardened resin composition layer on the base

(2) Step 1-2: The step of obtaining parallel rays from the light source

(3) Arbitrary steps 1-3: the step of obtaining a directional light

(4) Step 1-4: Step of hardening the unhardened resin composition layer

<Step 1-1: The step of laying the unhardened resin composition layer on the base>

The method of disposing the photocurable resin composition in the form of a sheet on the substrate as an uncured resin composition layer is to apply the usual coating method or printing method. Specifically, air knife coating, rod Bar coating, knife coating, knife coating, reverse roll coating, transfer roll coating, gravure roll coating, dosing roll coating, cast coating, spray coating, slot coating, roll coating , Weir coating, dip coating, coating such as die-slot coating, or printing such as gravure printing such as gravure printing, stencil printing such as screen printing, etc. When the composition is of low viscosity, a weir body with a certain height can also be arranged around the base body, and the composition is cast in the surrounding of the weir body.

In step 1-1, in order to prevent the oxygen barrier of the uncured resin composition layer and efficiently form the columnar regions that are the characteristics of the anisotropic light-diffusion film, it is also possible to closely adhere to the light irradiation side of the uncured resin composition layer. In addition, a mask that locally changes the irradiation intensity of light is laminated.

The material of the mask is made by dispersing a light-absorbing filler such as carbon in the matrix, and part of the incident light is absorbed by the carbon, but the opening portion is preferably constituted so that the light can penetrate sufficiently. Such substrates can also be transparent plastics such as PET, TAC, PVAc, PVA, acrylic, polyethylene, etc., or inorganic materials such as glass, quartz, or the like. Or pigments that absorb ultraviolet light.

When such a mask is not used, light irradiation in a nitrogen environment can also prevent oxygen inhibition of the uncured resin composition layer. In addition, it is also effective to prevent oxygen barrier and promote the formation of columnar regions by simply laminating a normal transparent film on the uncured resin composition layer. Light irradiation through such a mask or transparent film is in the composition containing the photopolymerizable compound, because the photopolymerization reaction occurs according to the irradiation intensity, so the refractive index distribution is easily generated, which is not suitable for the anisotropic light diffusion film of this type. is made to be valid.

<Step 1-2: Steps for obtaining parallel rays from the light source>

The light source is usually a short-arc ultraviolet light source, specifically, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, a xenon lamp, and the like can be used. At this point, it is necessary to obtain the Light rays with parallel central axes are scattered, but for such parallel rays, for example, a point light source can be arranged, and an optical lens such as a Fresnel lens for irradiating parallel rays can be arranged between the point light source and the uncured resin composition layer. A reflector is arranged behind the light source, and it is obtained by emitting light in a predetermined direction as a point light source or the like.

<Arbitrary steps 1-3: Steps for obtaining directional light>

Arbitrary steps 1-3 are the steps of making parallel light rays incident on the directional diffusing element to obtain directional light rays. FIG. 7 is a schematic diagram showing a method for producing the anisotropic light-diffusion film of the present invention including any of steps 1-3.

The directional diffusing elements 301 and 302 used in any of the steps 1-3 only need to be those that impart directivity to the parallel light D incident from the light source 300 .

In FIG. 7 , the light E having directivity is shown to be incident on the uncured resin composition layer 303 in a state where the light E having directivity is mostly diffused in the X direction and hardly diffused in the Y direction. In order to obtain directional light in this way, for example, the directional diffusion elements 301 and 302 may contain needle-shaped fillers with a high aspect ratio, and the needle-shaped fillers may extend in the Y direction along the long axis direction. method of alignment. The directional diffusion elements 301 and 302 can use various methods other than the method of using needle-shaped fillers.

Here, the aspect ratio of the light E with directivity is preferably set to 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 even more preferably 5 or less. When the aspect ratio exceeds 20, there is a risk of interference rainbow or glare.

In any of steps 1-3, by adjusting the expansion of the light E having directivity, the size (aspect ratio, short axis SA, long axis LA, etc.) of the columnar region to be formed can be appropriately determined. example For example, in any of Fig.7 (a), (b), the anisotropic light-diffusion film of this type can also be obtained. Although the difference between (a) and (b) in FIG. 7 has the spread of the directional light E, it is large in (a) and relatively small in (b). The size of the columnar area varies depending on the size of the expansion of the directional light E.

The spread of the directional light E mainly depends on the types of the 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 it grows, the size of the columnar region becomes larger. Therefore, by adjusting the distance, the size of the columnar region can be adjusted.

<Step 1-4: Step of Hardening the Uncured Resin Composition Layer>

The light irradiated to the uncured resin composition layer to harden the uncured resin composition layer must contain a wavelength that can harden the photopolymerizable compound, and usually a light with a wavelength centered at 365 nm of a mercury lamp is used. When producing an anisotropic light-diffusion film using this wavelength band, the illuminance is preferably in the range of 0.01mW/cm ² to 100mW/cm ² , more preferably 0.1mW/cm ² to 20mW/cm ² . If the illuminance is less than 0.01 mW/cm ² , it will take a long time to harden, so the production efficiency will be deteriorated. If the illuminance exceeds 100 mW/cm ² , the hardening of the photopolymerizable compound will be too fast to cause structure formation, and the purpose of the purpose will not be realized. optical properties.

In addition, the irradiation time of light is not particularly limited, but is preferably 10 seconds to 180 seconds, and more preferably 30 seconds to 120 seconds. By irradiating the above-mentioned light rays, the anisotropic light-diffusion film of this type can be obtained.

The anisotropic light-diffusion film is obtained by irradiating low-intensity light for a relatively long time to form a specific internal structure in the uncured resin composition layer as described above. Therefore, only such light irradiation leaves unreacted monomer components, which may cause sticking and cause problems in workability and durability. In such a case, it is possible to additionally irradiate light with a high illuminance of 1000 mW/cm ² or more to polymerize the remaining monomers. The light irradiation at this time may be performed from the side opposite to the side of the laminated mask.

As described above, when the uncured resin composition layer is cured, by adjusting the angle of the light irradiated to the uncured resin composition layer, the scattering center axis of the obtained anisotropic light-diffusion film can be set to a desired one. Moreover, it is preferable to adjust an unhardened resin composition layer in the range of 30 degreeC - 100 degreeC.

<<<<Application of anisotropic light diffusing film>>>>

Since the anisotropic light-diffusion film is excellent in the viewing angle dependence improvement effect, it can be applied to all display devices, such as a liquid crystal display device, an organic EL display device, and a plasma display device. In particular, it is preferable to use an anisotropic light-diffusion film in a liquid crystal of a TN mode, which tends to have a problem of viewing angle dependence.

Here, according to the present invention, a liquid crystal display device including a liquid crystal layer and an anisotropic light diffusing film can be provided. At this time, the anisotropic light-diffusion film is provided on the viewing side rather than the liquid crystal layer. The liquid crystal display device may be any of a TN method, a VA method, an IPS method, and the like. More specifically, a general liquid crystal device has a light source, a polarizer, a glass substrate with a transparent electrode, a liquid crystal layer, a glass substrate with a transparent electrode, a color filter, and a polarized light from the display device toward the viewing side. The layer structure of the laminated layers in the order of the plates has more appropriate functional layers, but the anisotropic light-diffusion film can be provided at any place on the viewing side than the liquid crystal layer.

Furthermore, according to the present invention, an organic EL display device including a light-emitting layer and an anisotropic light-diffusion film can be provided. In this case, the anisotropic light-diffusion film is provided on the viewing side (laminated layer) rather than the light-emitting layer (including an electrode connected to the light-emitting layer). The organic EL display device can be either of the top emission method and the bottom emission method, and when it is a color organic EL display device, it can be Either of the RGB separate coating method and the color filter method. In addition, the organic EL display system may be multilayered.

[Example]

<<<Example>>>

Next, although an Example and a comparative example demonstrate this invention more concretely, this invention is not limited at all by these examples.

<Anisotropic Optical Film>

Using a dispenser, partition walls with a height of 40 to 60 μm were formed with curable resin on the four peripheries of a 100 μm-thick PET film (manufactured by Toyobo Co., Ltd., trade name: A4300). In this, the following ultraviolet curable resin composition was dripped, and it covered with another PET film.

‧Polysiloxane/urethane/acrylate (refractive index: 1.460, weight average molecular weight: 5890) 20 parts by weight

(manufactured by RAHN Corporation, trade name: 00-225/TM18)

‧Neopentyl glycol diacrylate (refractive index: 1.450) 30 parts by weight

(made by DAICEL CYTEC, brand name Ebecryl145)

‧Diacrylate of EO adduct of bisphenol A (refractive index: 1.536) 15 parts by weight

(made by DAICEL CYTEC, trade name Ebecryl150)

‧Phenoxyethyl acrylate (refractive index 1.518) 40 parts by weight

(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, brand name: Irgacure651)

The liquid film with a thickness of 40 to 60 μm sandwiched by the PET film on both sides is irradiated from a UV point light source (manufactured by Hamamatsu Photonics, trade name: L2859-01) with an irradiation unit for epi-radiation at an irradiation intensity of 10 to 100 mW/cm ² of the ultraviolet rays of parallel rays. At this time, parameters such as irradiation angle or thickness of liquid film, UV illuminance, liquid film temperature when irradiated with parallel light, etc. were changed to obtain the anisotropic light diffusing films 1 to 5 of Examples and Comparative Examples having the optical properties in Table 1. Anisotropic light diffusing films 6 to 10 .

<Measurement of the thickness of anisotropic light-diffusion film>

About the anisotropic light-diffusion film obtained in the Example, after forming a cross-section using a microtome, the cross-section was observed with an optical microscope, the thickness of 10 places was measured, and the average value of the measured value was set as the thickness of the anisotropic light-diffusion film.

<Measurement of scattering center axis angle and linear transmittance of anisotropic light diffusing film>

Using a Goniophotometer (manufactured by GENESIA) that can arbitrarily change the projection angle of the light source and the light reception angle of the detector as shown in FIG. Measurement of transmittance (including linear transmittance at an incident angle of 60°). The detector was fixed at a position receiving straight light from the light source, and the anisotropic light-diffusing film obtained in the Example was mounted therebetween with a sample support. As shown in FIG. 6 , the linear transmittance corresponding to each incident light angle was measured by rotating the sample as the rotation axis (V). By this evaluation method, it is possible to evaluate whether the incident light is diffused in a range of any angle. The rotation axis (V) is a line on the anisotropic light-diffusing film in an oblique orientation perpendicular to the scattering center axis. The straight-line transmittance was measured at wavelengths in the visible light region using a sensitivity filter. According to the optical curve obtained from the above measurement results, the maximum value (maximum linear transmittance) and the minimum value (minimum linear transmittance) of the linear transmittance are obtained. Line transmittance), and the angle from the center of the scattering center (the center of the diffusion region) that is sandwiched by the minimum value in the optical curve are summarized in Table 1.

<Measurement of diffusion transmittance in the direction of polar angle of 60° with respect to the inclination of the scattering center axis for light with an incident angle of 0°>

Using a Goniophotometer (manufactured by GENESIA), the anisotropic light-diffusion films of the examples shown in Table 1 were measured for the light with an incident angle of 0° in the direction of the polar angle of 60° in the inclined azimuth of the scattering center axis. Diffusion penetration. Specifically, the anisotropic optical film obtained in the Example was mounted on the sample support, the light source was arranged in the normal direction (incidence angle=0°) of one surface of the anisotropic light-diffusion film, and the detector was arranged on the other surface. . The luminance was measured while changing the polar angle of the detector with the normal direction on the detector side as the polar angle θ=0°. The diffusion transmittance is a relative value with the luminance in the normal direction (polar angle θ=0°) when the anisotropic light-diffusion film is not used as 100%. The obtained diffusion penetration is shown in Table 1.

<Measurement of the aspect ratio of the columnar structure (observation of the surface of the anisotropic light-diffusion film)>

The cross section perpendicular to the column axis of the anisotropic light-diffusion film obtained in the Example (the irradiated light side during ultraviolet irradiation) was observed with an optical microscope, and the long axis LA and the short axis SA of the columnar structures in the columnar region were measured. The average major axis LA and the mean minor axis SA were calculated as the average value among 20 arbitrary structures. Moreover, with respect to the calculated|required average long diameter LA and the average short diameter SA, the average long diameter LA/average short diameter SA was calculated as an aspect ratio, and is compiled in Table 1.

<Measurement of Haze of Anisotropic Light Diffusing Film>

The haze of the anisotropic light-diffusion films obtained in Examples was measured using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries), and the results are summarized in Table 1.

[Table 1]

<<Evaluation method>>

The anisotropic light-diffusion films produced in the above-mentioned Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated as follows.

<Evaluation of gradation inversion>

The anisotropic light-diffusion film was attached to the surface of the TN-mode liquid-crystal display so that the angle formed by the orientation generated by the color-level inversion of the liquid crystal display and the inclined orientation of the scattering center axis of the anisotropic light-diffusion film a was 0°.

Next, using a viewing angle measuring device Conometer 80 (manufactured by Westboro Corporation), when the display displays gray scales divided into 11 levels from white to black, the polar angle in the range of 0 to 80° relative to the normal direction of the display is measured. Brightness distribution.

The "white luminance/black luminance" of the polar angle of 80° in the direction in which the gradation inversion occurs in the liquid crystal display unit was calculated as the contrast ratio. In addition, in the direction in which the color gradation inversion of a single liquid crystal display occurs, the minimum polar angle at which the measured 11 color gradations are reversed from the original color gradation is used as the color gradation inversion angle. This is compiled in Table 2.

Here, in the evaluation of only the display to which the anisotropic light-diffusion film is not attached, the contrast ratio was 8.0, and the gradation inversion angle was 28°.

<Judgment criteria for gradation inversion>

The gradation reversal angle was 65° or more as ⊚, 52° or more and less than 65° as ○, and less than 52° as ×.

<Judgment Criteria for Contrast at a Polar Angle of 80°>

A contrast ratio of 11 or more was set as ⊚, 9 or more and less than 11 was set as ○, and less than 9 was set as ×.

[Table 2]

<<Evaluation results>>

As shown in Examples 1 to 5, compared with Comparative Examples 1 to 5, the present invention using a predetermined anisotropic light-diffusion film is superior in the effect of improving tone inversion or the contrast at 80°.

Comparative Examples 1 and 3 have high linear transmittance when the incident angle is 60°, and the diffusion transmittance in the direction of polar angle 60° in the inclined azimuth of the incident angle 0° toward the scattering center axis is also low, so it is impossible to The light in the direction of 60°, which emits the light whose color gradation has been inverted, is diffused, and the light in the direction of 0° of the correct color gradation cannot be diffused to an angle with a large polar angle. In Comparative Example 2, although the diffusion penetration rate was sufficient, the linear penetration rate was insufficient. Conversely, in Comparative Examples 4 and 5, the linear penetration rate was sufficient, but the diffusion penetration rate was not sufficient. The inversion angle of the color scale is also small.

It is considered that the present invention uses a specific anisotropic light-diffusing film as a diffusing medium having specific diffusing properties, and this evaluation result can be obtained.

Therefore, when the light diffusing film of the embodiment is used in, for example, a TN liquid crystal display device, the inversion of the gradation can be suppressed and the contrast ratio at a deep angle can be improved, so that it is usually possible to ensure the visibility even in an orientation that is difficult to see. sex.

Claims (7)

An anisotropic light diffusing film whose linear transmittance varies according to the incident angle of light, wherein the linear transmittance is (the amount of transmitted light in the linear direction of the incident light)/(the amount of the incident light), The aforementioned anisotropic light-diffusing film has a matrix region and a plurality of columnar regions whose refractive index is different from the matrix region, Furthermore, the aforementioned anisotropic light-diffusion film system has one scattering center axis, In the inclined azimuth of the aforementioned scattering center axis, When the incident angle is 60°, the linear transmittance is less than 10%, The diffuse transmittance of light with an incident angle of 0° toward a polar angle of 60° is more than 0.001%. The anisotropic light-diffusion film according to claim 1, wherein, if the polar angle formed by the surface normal direction of the anisotropic light-diffusion film and the direction of the scattering center axis is taken as the scattering center axis angle, The scattering center axis angle of the anisotropic light diffusing film is 20° to 60°. The anisotropic light-diffusion film according to claim 1 or 2, wherein the haze value of the anisotropic light-diffusion film is 75% or more. The anisotropic light-diffusion film according to any one of claims 1 to 3, wherein the thickness of the anisotropic light-diffusion film is 15 μm to 100 μm. The anisotropic light-diffusing film according to any one of claims 1 to 4, wherein, The plurality of columnar regions of the anisotropic light diffusing film are configured to be aligned from one surface of the anisotropic light diffusing film to the other surface and extending from one surface to the other surface of the anisotropic light diffusing film, In the cross section perpendicular to the column axis of the columnar region of the anisotropic light diffusing film, the average long axis/average short axis of the columnar region, that is, the aspect ratio of the columnar region is less than 2. A liquid crystal display device in which the anisotropic light-diffusion film according to any one of claims 1 to 5 is laminated at a position closer to the viewing side than a liquid crystal layer. An organic EL display device in which the anisotropic light-diffusion film according to any one of claims 1 to 5 is laminated on the viewing side of the light-emitting layer.

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