JP2022157897A - Anisotropic light diffusion film laminate and display device - Google Patents

Abstract

To provide an anisotropic light diffusion film laminate having view angle dependency improvement effect better than the prior art for brightness and color changes due to angle of field.SOLUTION: An anisotropic light diffusion film laminate is formed by laminating at least two or more anisotropic light diffusion films with linear transmittance variable by an incidence angle of light, and comprises: one scattering center axis; a matrix region; and a plurality of columnar regions differing in refractive index from the matrix region. The plurality of columnar regions are oriented and extended from one front face to the other front face of the anisotropic light diffusion film. The plurality of anisotropic light diffusion films are laminated in a prescribed condition.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an anisotropic light-diffusing film laminate and a display device including the anisotropic light-diffusing film laminate.

A display device, for example, a transmissive TN system liquid crystal, when the display device is viewed obliquely in a specific direction, the brightness and contrast decrease, the color changes (gradation reversal) different from that in the front direction, There is a problem related to viewing angle dependency.

In order to eliminate such viewing angle dependence, an anisotropic optical body whose linear transmittance [(transmitted light amount in the linear direction of incident light)/(light amount of incident light)] changes depending on the incident angle of light is being applied.

For example, in Patent Document 1, by using 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 in a specific angle range for the display device, luminance and color depending on the viewing angle Improving the problem of change.

JP 2015-127819 A

However, in view of the diversification of display methods and display sizes of display devices, there is a demand for an anisotropic optical body having a more excellent effect of improving viewing angle dependence.

Accordingly, an object of the present invention is to provide an anisotropic light-diffusing film laminate having an effect of improving the viewing angle dependence, which is superior to conventional ones, with respect to luminance and color change depending on the viewing angle.

The inventors have found that the above problems can be solved by providing an anisotropic light-diffusing film laminate having specific properties, and have completed the present invention. That is, the present invention is as follows.

The present invention
At least two layers of anisotropic light diffusing films with linear transmittance that changes by (the amount of transmitted light in the linear direction of incident light)/(the amount of incident light) depending on the angle of incidence of light, and the haze value is , an anisotropic light diffusion film laminate of 70% to 85%,
The anisotropic light diffusion film has one scattering central axis, a matrix region, and a plurality of columnar regions having different refractive indices from the matrix region,
The plurality of columnar regions are oriented and extend from one surface to the other surface of the anisotropic light diffusion film,
In the anisotropic light-diffusing film, when the first anisotropic light-diffusing film is an anisotropic light-diffusing film a and the second anisotropic light-diffusing film is an anisotropic light-diffusing film b,
The anisotropic light diffusion film a and the anisotropic light diffusion film b are laminated directly or via an adhesive layer,
The aspect ratio of the columnar region, which is the average major axis/average minor axis of the columnar region in a cross section perpendicular to the columnar axis of the columnar region,
one of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b has an aspect ratio of 2 to 10, and the other film has an aspect ratio of 1 to 10;
Assuming that the polar angle formed by the normal direction of the anisotropic light diffusion film surface and the scattering center axis direction is the scattering center axis angle,
The anisotropic light diffusion film a has a scattering center axis angle of 20° to 35°,
The anisotropic light diffusion film b has a scattering central axis angle of 40° to 55°,
The anisotropic light-diffusing film laminate is characterized in that the anisotropic light-diffusing film a and the anisotropic light-diffusing film b form an angle of 0° to 40° between the directions of the respective scattering central axes.

The anisotropic light-diffusing film a and the anisotropic light-diffusing film b preferably have an average minor axis of 0.5 μm to 1.6 μm and an average major axis of 4.5 μm to 10.0 μm.
The anisotropic light diffusion film a has a haze value of 30% to 70%,
The anisotropic light-diffusing film b preferably has a haze value of 20% to 70%.
The anisotropic light diffusion film a has a maximum linear transmittance of 50% to 70% and a minimum linear transmittance of 4% or less,
The anisotropic light-diffusing film b preferably has a maximum linear transmittance of 30% to 70% and a minimum linear transmittance of 6% or less.
The anisotropic anisotropic light diffusion film laminate has a maximum linear transmittance of 15% to 30%,
Preferably, the linear transmittance at an incident light angle of 0° is between 6% and 16%.

The present invention
A liquid crystal display device comprising a liquid crystal layer and the anisotropic light diffusion film laminate,
The liquid crystal display device may be characterized in that the anisotropic light diffusion film laminate is laminated on the viewing side of the liquid crystal layer.
It is preferable that the anisotropic light-diffusing film b is laminated so as to be closer to the viewer than the anisotropic light-diffusing film a.

The present invention
An organic EL display device comprising a light emitting layer and the anisotropic light diffusion film laminate,
The organic EL display device may be characterized in that the anisotropic light diffusion film laminate is laminated on the viewing side of the light emitting layer.
It is preferable that the anisotropic light-diffusing film b is laminated so as to be closer to the viewer than the anisotropic light-diffusing film a.

According to the present invention, it is possible to provide an anisotropic light-diffusing film laminate having an effect of improving the viewing angle dependence, which is superior to conventional ones, with respect to luminance and color change depending on the viewing angle.

FIG. 4 is an explanatory diagram showing an example of incident angle dependency of an anisotropic light diffusion film; FIG. 3 is a top view showing the surface structure of an anisotropic light-diffusing film; It is a schematic diagram which shows the example of an anisotropic light-diffusion film. It is a three-dimensional polar coordinate representation for explaining the scattering central axis in an anisotropic light diffusion film. 4 is a graph showing an example of an optical profile in an anisotropic light diffusion film; It is a schematic diagram which shows the incident light angle dependence measuring method of an anisotropic light-diffusion film. It is a schematic diagram which shows the example of an anisotropic light-diffusion film laminated body. It is a three-dimensional polar coordinate representation for explaining the scattering central axis in each anisotropic light-diffusing film constituting the anisotropic light-diffusing film laminate. It is a schematic diagram which shows the manufacturing method of the anisotropic light-diffusion film which concerns on this invention.

Hereinafter, after briefly describing the anisotropic light-diffusing film according to the present invention, the structure, physical properties, manufacturing method, and specific uses of the anisotropic light-diffusing film laminate will be described.

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

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

<<<<Structure>>>>
The anisotropic light-diffusing film of the present invention has a matrix region and a plurality of columnar regions having different refractive indices from those of the matrix region. A plurality of columnar regions included in the anisotropic light-diffusing film are usually oriented and extended from one surface to the other surface of the anisotropic light-diffusing film (see FIG. 3, etc.).

Here, the difference in refractive index is not particularly limited as long as at least part of the light incident on the anisotropic light diffusion film is reflected at the interface between the matrix region and the columnar region.

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

<<Shape of columnar region>>
In the columnar region included in the anisotropic light-diffusing film, the cross-sectional shape of the columnar region in the cross section perpendicular to the column axis can be a shape having a minor axis and a major axis.

The shape of the cross section of the columnar region perpendicular to the column axis is not particularly limited, and may be circular, elliptical, or polygonal, for example. 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; The shortest length can be used as the short axis, and the longest length can be used as the long axis. FIG. 2 shows the cross-sectional shape of the columnar region in the cross section perpendicular to the columnar axis of the columnar region. In FIG. 2, LA represents the major axis and SA represents the minor axis.

<minor diameter>
In the anisotropic light-diffusing film, the average short diameter (average short diameter) of the columnar regions is preferably 0.5 μm or more, more preferably 1.0 μm or more, and more preferably 1.5 μm or more. More preferred. 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, even more preferably 3.0 μm or less, and 1.6 μm or less. Especially preferred. The lower limit value and upper limit value of the minor axis of these columnar regions can be combined as appropriate.

<long diameter>
In the anisotropic light-diffusing film, the average major axis (average major axis) of the columnar regions is preferably 0.5 μm or more, more preferably 1.0 μm or more, further preferably 1.5 μm or more. , 4.5 μm or more. On the other hand, the average length of the columnar regions is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 10.0 μm or less. The average major axis of the columnar regions is preferably shorter than the length of the columnar regions. By doing so, 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 these columnar regions can be combined as appropriate.

The minor axis and major axis of the columnar region were obtained by observing a cross section of the anisotropic light diffusion film perpendicular to the columnar axis of the columnar region (the cross section near the center of the thickness of the anisotropic light diffusion film) with an optical microscope, and selecting 20 arbitrarily selected values. The short diameter and long diameter of each of the columnar regions can be measured and used as an average value.

<Aspect ratio>
The ratio of the average major axis to the average minor axis of the columnar regions (average major axis/average minor axis), that is, the aspect ratio can be in the range of 1-10, or in the range of 2-10.

FIG. 2(a) shows an anisotropic light-diffusing film in which the aspect ratio of the columnar regions is 2 to 10, 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. ing.

When the aspect ratio is 1 or more and less than 2, when light parallel to the axial direction of the columnar region is irradiated, the transmitted light is isotropically diffused (see FIG. 3A). On the other hand, when the aspect ratio is 2 to 10, when light parallel to the axial direction is similarly irradiated, diffusion occurs with an anisotropy corresponding to the aspect ratio {see FIG. 3(b)}.

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

<<<<scattering central axis>>>>
An anisotropic light-diffusing film has a central scattering axis. The scattering center axis and the orientation direction (extending direction) of the columnar regions are generally parallel to each other. It should be noted that the scattering center axis and the orientation direction of the columnar regions being parallel only need to satisfy the refractive index law (Snell's law), and need not be strictly parallel.

According to Snell's law, when light is incident from a medium with a refractive index of n1 to an interface of a medium with _a refractive index of _n2 , _{n 1} sin θ _{1 =} A relationship of n ₂ sin θ ₂ is established. For example, when n ₁ =1 (air) and n ₂ =1.51 (anisotropic light diffusion film), when the incident light angle is 30°, the orientation direction (refractive angle) of the columnar regions is about 19°. In the present invention, even if the incident light angle and the refraction angle are different from each other, if Snell's law is satisfied, the concept of parallelism is included in the present invention.

Next, the scattering central axis P in the anisotropic light diffusion 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 center axis P in the anisotropic light diffusion film.

As described above, the scattering central axis is the direction that coincides with the incident light angle of light whose light diffusion properties are substantially symmetrical with respect to the incident light angle when the incident light angle to the anisotropic light diffusion film is changed. means The incident light angle at this time is approximately between the minimum values in the optical profile (FIG. 5) obtained by measuring the linear transmittance of the anisotropic light diffusion film and plotting the linear transmittance for each incident light angle. It becomes the central part (the central part of the diffusion region).

According to the three-dimensional polar coordinate representation as shown in FIG. 4, the scattering center axis is the polar angle θ and the azimuth when the surface of the anisotropic light diffusion film is the xy plane and the normal line to the surface of the anisotropic light diffusion film is the z axis. can be expressed by the angle φ In other words, Pxy in FIG. 4 can be said to be the length direction of the scattering center axis projected on the surface of the anisotropic light diffusion film.

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

The scattering central axis angle θ of the anisotropic light diffusion film is preferably 20° to 55°. By setting the scattering center axis angle θ in this way, it is possible to achieve desired angle dependency.

<<<<Optical Profile>>>>
FIG. 5 is a graph showing an example of an optical profile in an anisotropic light diffusion film having a scattering central axis angle of 0°. point to
As shown in FIG. 5, the anisotropic light diffusing film has light diffusing properties dependent on the incident light angle, in which the linear transmittance changes depending on the incident light angle.

An optical profile can be created, for example, as follows.

An anisotropic light diffusing film is placed between the light source 1 and the detector 2 as shown in FIG. In this embodiment, the incident light angle is 0° when the irradiation light I from the light source 1 is incident from the normal direction of the anisotropic light diffusion film. Further, the anisotropic light diffusion film is arranged so as to be arbitrarily rotatable with the 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 diffusion film) is placed between the light source 1 and the detector 2, and the sample is transmitted straight through while changing the angle with the straight line V on the sample surface as the axis of rotation for detection. The amount of linearly transmitted light entering the device 2 is measured. After that, the linear transmittance is calculated from the amount of linearly transmitted light, and the linear transmittance is plotted for each angle to create an optical profile.
With this evaluation method, it is possible to evaluate in which range of angles the incident light is diffused.

The optical profile does not directly express the light diffusibility, but if it is interpreted that the diffuse transmittance increases due to the decrease in the in-line transmittance, it generally indicates the light diffusivity. It can be said that

A normal isotropic light diffusion film exhibits a mountain-shaped optical profile peaking at an incident light angle near 0°.

On the other hand, for example, in the optical profile graph of an anisotropic light diffusion film having a scattering center axis angle of 0° in FIG. 5, which is an example, the linear transmittance is It exhibits a small, valley-shaped optical profile in which the linear transmittance increases as the absolute value of the incident light angle increases.

As described above, the anisotropic light diffusion film has the property that incident light is strongly diffused in the incident light angle range close to the scattering center axis, but the diffusion is weakened and the linear transmittance is increased in the incident light angle range beyond that.

In addition, in the case of an anisotropic light diffusion film with a scattering central axis angle other than 0°, the optical profile moves so that the linear transmittance decreases at incident light angles near the scattering central axis angle (the troughs of the optical profile (Move to the scattering central axis angle side).

<<<Linear Transmittance>>>
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 is maximized is referred to as the maximum linear transmittance. The anisotropic light diffusion film preferably has a maximum linear transmittance of 30% to 70%.

Further, 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 is minimum is referred to as the minimum linear transmittance. The anisotropic light diffusion film preferably has a minimum in-line transmittance of 6% or less.

The in-line transmittance should be adjusted by adjusting the refractive index of the material of the anisotropic light diffusion film (difference in refractive index when multiple resins are used), coating film thickness, UV illumination, and curing conditions such as temperature during structure formation. can be done.

Furthermore, as shown in FIG. 5, the angle range of the two incident light angles with respect to the intermediate value of the linear transmittance between the maximum linear transmittance and the minimum linear transmittance is defined as a diffusion area (the width of this diffusion area is the "diffusion width"). and the incident light angle range other than that is called a non-diffusion region (transmission region).

<<<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. As the haze value increases, the diffusibility of the anisotropic light-diffusing film increases.

A method for measuring the haze value is not particularly limited, and the haze value can be measured by a known method. For example, it can be measured according to JIS K7136-1:2000 "Plastics - Determination of haze of transparent materials".
The haze value can also be measured by the same method for an anisotropic light-diffusing film laminate in which two or more layers of anisotropic light-diffusing films are laminated.

The haze value of the anisotropic light diffusion film is preferably 20% to 70%.

The haze value can be adjusted by adjusting the refractive index of the material of the anisotropic light diffusion film (difference in refractive index when multiple resins are used), coating film thickness, UV illuminance, and curing conditions such as temperature during structure formation. can.

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

<<<<<anisotropic light diffusion film laminate>>>>>>
<<<<Structure>>>>
The anisotropic light-diffusing film laminate of the present invention is obtained by laminating at least two layers of anisotropic light-diffusing films having specific properties. FIG. 7 is a schematic diagram showing an example of the anisotropic light-diffusing film laminate. .

Regarding the two layers of anisotropic light-diffusing films included in the anisotropic light-diffusing film laminate in the present invention, the first anisotropic light-diffusing film is anisotropic light-diffusing film a, and the second anisotropic light-diffusing film is anisotropic light-diffusing film b. do.

The anisotropic light-diffusing film laminate of the present invention may have anisotropic light-diffusing films other than the anisotropic light-diffusing film a and the anisotropic light-diffusing film b (FIG. 7). That is, the anisotropic light-diffusing film laminate may be a laminate containing three or more layers of anisotropic light-diffusing films, including the anisotropic light-diffusing film a and the anisotropic light-diffusing film b.
Other anisotropic light diffusion films may have only one layer or may have multiple layers. In addition, when there are multiple layers of other anisotropic light-diffusing films, each layer of the anisotropic light-diffusing film laminate may have the same or different structure and properties.

However, in the present invention, the anisotropic light-diffusing film a and the anisotropic light-diffusing film b are laminated directly without any other anisotropic light-diffusing film or via an adhesive layer. That is, for example, as shown in FIG. 7, lamination examples of the anisotropic light-diffusing film included in the anisotropic light-diffusing film laminate include "anisotropic light-diffusing film a/anisotropic light-diffusing film b" (FIG. 7(a)), " Other anisotropic light diffusion film/anisotropic light diffusion film a/anisotropic light diffusion film b” (FIG. 7(b)), “anisotropic light diffusion film a/anisotropic light diffusion film b/other anisotropic light diffusion film” (FIG. 7 (c)), "other anisotropic light diffusion film/anisotropic light diffusion film a/anisotropic light diffusion film b/other anisotropic light diffusion film" (Fig. 7(d), however, other two-layer anisotropic light diffusion film may be the same or different in structure and properties).

Other anisotropic light diffusion films may be directly laminated or may be laminated via an adhesive layer or the like.

The adhesive of the adhesive layer used for laminating the anisotropic light diffusion films is not particularly limited as long as it has transparency, but an adhesive having pressure-sensitive adhesiveness at room temperature can be used. preferable. Examples of such adhesives include resins such as polyester-based resins, epoxy-based resins, polyurethane-based resins, silicone-based resins, and acrylic-based resins. In particular, acrylic resins are preferred because of their high optical transparency.

Further, a layer having another function other than the anisotropic light-diffusing film can be laminated on the surface of the anisotropic light-diffusing film laminate within a range that does not interfere with the effects of the present invention. Layers having other functions include, for example, a retardation film, a UV cut layer, and a low moisture-permeable layer.

Moreover, the anisotropic light diffusion film laminate may be laminated on a transparent substrate such as a glass substrate.

<<<<physical properties/characteristics>>>>
<<<Haze value>>>
The haze value of the entire anisotropic light diffusion film laminate is preferably 70% to 85%. When laminating an anisotropic light-diffusing film having a specific scattering central axis, by setting the haze value of the entire anisotropic light-diffusing film laminate within such a range, an excellent effect of improving viewing angle dependence is exhibited.

The haze value of the entire anisotropic light-diffusing film laminate can be adjusted by the haze value of the anisotropic light-diffusing film a and the haze value of the anisotropic light-diffusing film b. Specifically, as the total haze value of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b increases, the haze value of the entire anisotropic light-diffusing film laminate tends to increase.

<<<Linear Transmittance>>>
The linear transmittance of the anisotropic light-diffusing film laminate can be measured with respect to the anisotropic light-diffusing film on the viewing side of the anisotropic light-diffusing film laminate by the same method as the linear transmittance measurement of the anisotropic light-diffusing film described above. can.

The anisotropic light diffusion film laminate preferably has a maximum linear transmittance of 15% to 30%.

The anisotropic light-diffusing film laminate preferably has a minimum in-line transmittance of 6% or less, more preferably 4% or less.

The anisotropic light diffusion film laminate preferably has a linear transmittance of 6% to 16% at an incident light angle of 0°.

By setting the maximum linear transmittance and minimum linear transmittance of the anisotropic light diffusion film laminate and the linear transmittance at an incident light angle of 0° to such ranges, light can be sufficiently diffused and visible. Problems such as reduction in sharpness are less likely to occur.

<<<Thickness>>>
The thickness of the anisotropic light-diffusing film laminate is preferably 30 μm to 500 μm, more preferably 30 μm to 300 μm, although it depends on the number of layers laminated. By setting the thickness of the anisotropic light-diffusing film laminate in such a range, the visual dependence improving effect can be made sufficient.

<<<anisotropic light diffusion film a and anisotropic light diffusion film b>>>
Next, the properties of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b of the present invention will be described. The basic structure and properties of the anisotropic light-diffusing film other than those described here are as described above. The anisotropic light-diffusing film a and the anisotropic light-diffusing film b may be the same or different in material, minor axis and major axis of the columnar region, aspect ratio, and the like. Unless otherwise specified, the preferred ranges shown below may be either the case where at least one of the two layers satisfies the ranges, or the case where both layers satisfy the ranges.

<<Column area>>
Next, the columnar regions of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b will be described.

<Aspect ratio>
In the anisotropic light-diffusing film a and the anisotropic light-diffusing film b, one of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b has an aspect ratio of 2 to 10, and the other film has an aspect ratio of It is preferably 1 to 10 (1 or more and less than 2 or 2 to 10), the aspect ratio of one of the anisotropic light diffusion film a and the anisotropic light diffusion film b is 2 to 8, and the other The aspect ratio of the film is 1 to 10 (1 or more and less than 2 or 2 to 10), or the aspect ratio of one of the anisotropic light diffusion film a and the anisotropic light diffusion film b is 2 to 10 and more preferably the aspect ratio of the other film is 1 to 8 (1 or more and less than 2 or 2 to 8), and the anisotropic light diffusion film a and the anisotropic light diffusion film b More preferably, the aspect ratio is 2 to 8, and the aspect ratio of the other film is 1 to 8 (1 or more and less than 2, or 2 to 8).

<<Scattering central axis>>
Next, the relationship between the scattering central axis Pa of the anisotropic light-diffusing film a and the scattering central axis Pb of the anisotropic light-diffusing film b will be described with reference to FIG. FIG. 8 is a three-dimensional polar coordinate representation for explaining the scattering central axis in each anisotropic light-diffusing film constituting the anisotropic light-diffusing film laminate.

In the anisotropic light-diffusing film laminate according to the present invention, the anisotropic light-diffusing film a and the anisotropic light-diffusing film b each independently have a scattering central axis Pa and a scattering central axis Pb. By setting the scattering center axis Pa and the scattering center axis Pb within appropriate ranges, the diffusibility of the entire anisotropic light-diffusing film laminate is adjusted, and the viewing angle dependency is improved to be superior to that of a single-layer anisotropic light-diffusing film. It is possible to have an effect.

More specifically, in a typical display, correct color and high illuminance can be obtained near the normal direction (polar angle θ=0°). The viewing angle can be improved by diffusing the light in the vicinity of the normal direction in the direction in which the polar angle θ of the azimuth for which the viewing angle is to be improved is large. According to the present invention, the light in the front direction is changed stepwise to the direction with a larger polar angle θ, that is, the anisotropic light diffusion film a and the anisotropic light diffusion film b change the scattering center axis angle θ in two stages. It will spread properly. An anisotropic light-diffusing film with a small scattering central axis angle θ alone cannot sufficiently diffuse light in a direction with a large polar angle θ. Due to the lack of diffusivity in the linear direction, the light cannot be diffused sufficiently in the direction where the polar angle θ is large.

The scattering central axis angle θa of the anisotropic light-diffusing film _a is preferably 20° to 35°, more preferably 27° to 32°, even more preferably 29° to 31°.

The scattering center axis angle θ _b of the scattering center axis Pb of the anisotropic light diffusion film b is preferably 40° to 55°, more preferably 46° to 52°, and more preferably 49° to 51°. It is even more preferable to have By setting the scattering central axis angle _θa and the scattering central axis angle _θb in this way, it is possible to obtain the effect of improving the viewing angle dependency.

Furthermore, the difference (θ _ab ) between the scattering central axis angle θ _a and the scattering central axis angle θ _b is preferably 5° to 40°, more preferably 10° to 30°. By setting the difference (θ _ab ) between the scattering center axis angle θ _a and the scattering center axis angle θ _b in this manner, the light diffusion is enhanced, and the viewing angle dependency can be improved.

Also, the angle φ _ab formed by the orientations of the scattering central axes of the anisotropic light diffusion film a and the anisotropic light diffusion film b (in other words, the azimuth angle φ _a of the scattering central axis Pa of the anisotropic light diffusion film a and the anisotropic light The difference between the azimuth angle φ _b of the scattering central axis Pb of the diffusion film b) is preferably 0° to 40°, more preferably 5° to 40°, and 10° to 30°. is more preferred. If the angle _φab exceeds 40°, the misalignment between the scattering central axis Pa and the scattering central axis Pb becomes large, making it difficult to achieve the desired effect of improving the viewing angle dependence.

As described above, the scattering central axis angle can be adjusted by changing the direction of the irradiating light beam in the step of photocuring the uncured resin composition layer to form the columnar regions. Also, the angle φ _ab can be adjusted by the direction in which the anisotropic light-diffusing film a and the anisotropic light-diffusing film b are laminated.

<<Linear Transmittance>>
The anisotropic light diffusion film a preferably has a maximum linear transmittance of 40% to 70%, more preferably 45% to 66%.

The anisotropic light diffusion film a preferably has a minimum in-line transmittance of 6% or less, more preferably 4% or less.

The anisotropic light diffusion film b preferably has a maximum linear transmittance of 30% to 70%, more preferably 50% to 60%.

The anisotropic light diffusion film b preferably has a minimum in-line transmittance of 4% or less, more preferably 3% or less, even more preferably 1.5% or less.

While keeping the central scattering axis Pa of the anisotropic light-diffusing film a and the central scattering axis Pb of the anisotropic light-diffusing film b within the appropriate ranges described above, the maximum linear transmittance and the minimum linear transmittance of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b By setting the transmittance to such a range, the light can be sufficiently diffused, and problems such as a decrease in visual clarity are less likely to occur.

<<Haze value>>
The haze value of the anisotropic light-diffusing film a is preferably 30% to 70%.

The haze value of the anisotropic light diffusion film b is preferably 20% to 70%.

<<Thickness>>
The thicknesses of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b are not particularly limited, but both are preferably 15 μm to 100 μm, more preferably 30 μm to 60 μm. By setting such a range, while reducing the manufacturing cost such as the material cost and the cost required for UV irradiation, the image due to the increase in the diffusivity in the thickness direction of the anisotropic light diffusion film a and the second anisotropic light diffusion film b It is possible to suppress the occurrence of a decrease in visual clarity and a decrease in contrast, and to make the light diffusibility and light gathering property sufficient.

<<<<Manufacturing Method of Anisotropic Light Diffusion Film Laminate>>>>
An anisotropic light-diffusing film laminate is a laminate having a plurality of anisotropic light-diffusing films. The anisotropic light-diffusing film laminate is obtained, for example, by separately producing a first anisotropic light-diffusing film and a second anisotropic light-diffusing film and laminating them via an adhesive layer. Laminates can be produced.

Examples of adhesives include resins such as polyester-based resins, epoxy-based resins, polyurethane-based resins, silicone-based resins, and acrylic-based resins, as described above.

The application method and curing conditions for the adhesive may be conventionally known methods depending on the adhesive to be used.

In the anisotropic light-diffusing film laminate, after manufacturing the first anisotropic light-diffusing film, the first anisotropic light-diffusing film is used as a base material, and the second anisotropic light-diffusing film is formed on the first anisotropic light-diffusing film. It can also be produced by directly forming the More specifically, after curing the composition layer containing the photopolymerizable compound to produce the first anisotropic light diffusion film, the photopolymerizable compound is directly applied onto the first anisotropic light diffusion film. The second anisotropic light-diffusing film may be formed by coating the composition containing the composition, forming a sheet, and curing the composition.

A method for producing an anisotropic light-diffusing film will be described below.

<<<Manufacture of anisotropic light diffusion film>>>
<<raw materials>>
Raw materials for the anisotropic light-diffusing film will be described in the order of (1) photopolymerizable compound, (2) photoinitiator, (3) blending amount, and other optional components.

<Photopolymerizable compound>
The photopolymerizable compound comprises a photopolymerizable compound selected from macromonomers, polymers, oligomers, and monomers having radically polymerizable or cationic polymerizable functional groups, and a photoinitiator, and emits ultraviolet rays and/or visible rays. It is a material that polymerizes and hardens when irradiated.

Here, even if the material forming the anisotropic light-diffusing film is of one kind, a difference in refractive index occurs due to a difference in density. This is because the hardening speed increases in areas where the UV irradiation intensity is high, and the polymerized/cured material moves around the hardened area, resulting in the formation of areas with a high refractive index and areas with a low refractive index. . (Meth)acrylate means that it may be either acrylate or methacrylate.

Radically polymerizable compounds mainly contain one or more unsaturated double bonds in the molecule, and specific examples include epoxy acrylates, urethane acrylates, polyester acrylates, polyether acrylates, polybutadiene acrylates, silicone acrylates, and the like. and 2-ethylhexyl acrylate, isoamyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isonorbornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate. , 2-acryloyloxyphthalic acid, dicyclopentenyl acrylate, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, EO adduct diacrylate of bisphenol A, trimethylolpropane triacrylate, Acrylate monomers such as EO-modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol hexaacrylate. In addition, these compounds may be used alone or in combination. Methacrylates can also be used, but acrylates are generally preferable to methacrylates because they have a faster photopolymerization rate.

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

Further examples of compounds having an epoxy group include 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate and 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-epoxycyclohexane), dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylenebis(3,4-epoxy) cyclohexanecarboxylate), lactone-modified 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate, tetra(3,4-epoxycyclohexylmethyl)butane tetracarboxylate, di(3,4-epoxycyclohexylmethyl) )-4,5-epoxytetrahydrophthalate and other cycloaliphatic epoxy compounds, but 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, cyclohexanedimethanol divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, trimethylolpropane tri vinyl ether, propenyl ether propylene carbonate, etc., but not limited thereto. Vinyl ether compounds are generally cationic polymerizable, but can be radically polymerized by combining them with acrylates.

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

The cationic polymerizable compounds described above may be used alone or in combination. The photopolymerizable compound is not limited to those mentioned above.

Further, in order to produce a sufficient refractive index difference, fluorine atoms (F) may be introduced into the photopolymerizable compound in order to lower the refractive index. A sulfur atom (S), a bromine atom (Br), and various metal atoms may be introduced. Furthermore, as disclosed in Japanese Patent Application Publication No. 2005-514487, ultrafine particles made of metal oxides with a high refractive index such as titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), tin oxide (SnO _x ), etc. It is also effective to add functional ultrafine particles having a photopolymerizable functional group such as an acrylic group, a methacrylic group or an epoxy group introduced to the surface of the above photopolymerizable compound.

A photopolymerizable compound having a silicone skeleton is preferably used as the photopolymerizable compound. A photopolymerizable compound having a silicone skeleton is oriented and polymerized and cured along with 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. Form. By using a photopolymerizable compound having a silicone skeleton, it becomes easier to incline the columnar region, and the light collecting property in the front direction is improved. 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, it is preferable that the amount of silicone resin, which is a cured product of a photopolymerizable compound having a silicone skeleton, is relatively large. As a result, the center axis of scattering can be more easily tilted, and the light condensing property in the front direction is improved. Silicone resins contain more silicon (Si) than compounds that do not have a silicone skeleton. amount can be checked.

Photopolymerizable compounds having a silicone skeleton are monomers, oligomers, prepolymers or macromonomers having radically polymerizable or cationically polymerizable functional groups. Examples of radically polymerizable functional groups include acryloyl groups, methacryloyl groups, and allyl groups, and examples of cationic polymerizable functional groups include epoxy groups and oxetane groups. There are no particular restrictions on the type and number of these functional groups, but the greater the number of functional groups, the higher the crosslink density and the greater the likelihood of a difference in refractive index. . Compounds having a silicone skeleton may have insufficient compatibility with other compounds due to their structure. In such cases, the compatibility can be enhanced by urethanization. In this embodiment, a silicone/urethane/(meth)acrylate having an acryloyl group or a methacryloyl group at its end is preferably used.

The weight average molecular weight (Mw) of the photopolymerizable compound having a silicone skeleton is preferably in the range of 500-50,000. It is more preferably in the range of 2,000 to 20,000. When the weight average molecular weight is within 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. With the orientation of the silicone resin, it becomes easier to tilt the scattering central axis.

Examples of the silicone skeleton include those represented by the following general formula (1). In general formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a methyl group, an alkyl group, a fluoroalkyl group, a phenyl group, an epoxy group, an amino group and a carboxyl group. , a polyether group, an acryloyl group, a methacryloyl group, and the like. Further, in general formula (1), n is preferably an integer of 1-500.

When a photopolymerizable compound having a silicone skeleton is blended with a compound having no silicone skeleton to form an anisotropic light-diffusing film, the low refractive index region and the high refractive index region are easily formed separately, resulting in an anisotropic The degree of is strong and is preferable.

The compound having no silicone skeleton can be a photopolymerizable compound, a thermoplastic resin, or a thermosetting resin, and these can also be used in combination.

As the photopolymerizable compound, polymers, oligomers, and monomers having radically polymerizable or cationic polymerizable functional groups can be used (provided that they do not have a silicone skeleton).

Examples of thermoplastic resins include polyesters, polyethers, polyurethanes, polyamides, polystyrenes, polycarbonates, polyacetals, polyvinyl acetates, acrylic resins and their copolymers and modified products. When a thermoplastic resin is used, the anisotropic light diffusion film is formed by dissolving the resin in a solvent that dissolves the thermoplastic resin, applying and drying the resin, and then curing the photopolymerizable compound having a silicone skeleton with ultraviolet rays.

Thermosetting resins include epoxy resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters and their copolymers and modified products. When a thermosetting resin is used, the 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 diffusion film.

A photopolymerizable compound is most preferable as a compound that does not have a silicone skeleton. It is easy to separate the low refractive index region and the high refractive index region, and when using a thermoplastic resin, no solvent is required and no drying process is required. and the need for a thermosetting process, unlike thermosetting resins, is excellent in productivity.

<Photoinitiator>
Photoinitiators capable of polymerizing radically polymerizable compounds include benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2- diethoxyacetophenone, benzyl dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2 -methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-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 and the like. In addition, these compounds may be used alone or in combination.

The photoinitiator of the cationically polymerizable compound is a compound that generates an acid upon irradiation with light and can polymerize the above-described cationically polymerizable compound with the generated acid. It is preferably used.

As onium salts, diazonium salts, sulfonium salts, iodonium salts, phosphonium salts, selenium salts and the like are used, and anions such as BF4-, PF6-, AsF6- and SbF6- are used as their counterions. Specific examples include 4-chlorobenzenediazonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, (4-phenylthiophenyl)diphenylsulfonium hexafluoroantimonate, (4-phenylthiophenyl)diphenyl Sulfonium hexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluorophosphate, (4-methoxyphenyl) diphenylsulfonium hexafluoroantimonate, (4-methoxyphenyl)phenyliodonium hexafluoroantimonate, bis(4-t-butylphenyl)iodonium hexafluorophosphate, benzyltriphenylphosphonium hexafluoroantimonate, triphenylselenium hexafluorophosphate, (η5-isopropylbenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate and the like, but are not limited thereto. In addition, these compounds may be used alone or in combination.

The photoinitiator is preferably blended about 0.01 to 10 parts by mass, more preferably about 0.1 to 7 parts by mass, per 100 parts by mass of the photopolymerizable compound. , 0.1 to 5 parts by mass. This is because if the amount is less than 0.01 part by mass, the photocurability is reduced, and if the amount is more than 10 parts by mass, only the surface is cured and the internal curability is reduced. This is because it leads to inhibition of the formation of

<Other ingredients>
The photoinitiator is usually used by directly dissolving the powder in the photopolymerizable compound, but if the solubility is poor, the photoinitiator should be pre-dissolved in a very small amount of solvent at a high concentration. can also Such a solvent is more preferably photopolymerizable, and specific examples thereof include propylene carbonate and γ-butyrolactone. Also, various known dyes and sensitizers can be added to improve the photopolymerizability.

Furthermore, a thermosetting initiator capable of curing the photopolymerizable compound by heating can be used together with the photoinitiator. In this case, it can be expected that the polymerization and curing of the photopolymerizable compound can be further accelerated and completed by heating after photocuring. An anisotropic light-diffusing film can be formed by curing a composition containing a single photopolymerizable compound or a mixture of multiple photopolymerizable compounds.

An anisotropic light diffusion film can also be formed by curing a mixture of a photopolymerizable compound and a non-photocurable polymer resin.

Polymer resins that can be used here include acrylic resins, styrene resins, styrene-acrylic copolymers, polyurethane resins, polyester resins, epoxy resins, cellulose resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, Polyvinyl butyral resin etc. are mentioned. These polymer resins and photopolymerizable compounds must have sufficient compatibility before photocuring, and various organic solvents and plasticizers are used to ensure this compatibility. is also possible.

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

The weight ratio of the photopolymerizable compound having a silicone skeleton to the compound having no silicone skeleton is preferably in the range of 15:85 to 85:15. More preferably, it is in the range of 30:70 to 70:30. Within this range, the phase separation between the low refractive index region and the high refractive index region is facilitated, and the columnar regions are facilitated to be inclined. 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 will be difficult to progress, and the columnar regions will be difficult to tilt.

When silicone/urethane/(meth)acrylate is used as the photopolymerizable compound having a silicone skeleton, compatibility with compounds having no silicone skeleton is improved. As a result, the columnar regions can be inclined even if the mixing ratio of the materials is widened.

Examples of solvents that can be used for preparing a composition containing a photopolymerizable compound include ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, and xylene.

<<manufacturing process>>
Next, a process for producing an anisotropic light-diffusing film using the composition for an anisotropic light-diffusing film will be described.

First, the above composition for an anisotropic light diffusion film (hereinafter sometimes referred to as "photocurable resin composition") is coated on an appropriate substrate such as a transparent PET film to form a sheet, and a film is formed. Then, if necessary, it is dried to volatilize the solvent to form an uncured resin composition layer. By irradiating the uncured resin composition layer with light, an anisotropic light diffusion film can be produced.

More specifically, the process of forming the anisotropic light-diffusing film mainly includes the following steps.
(1) Step 1-1: Step of providing an uncured resin composition layer on a substrate (2) Step 1-2: Step of obtaining parallel light from a light source (3) Optional step 1-3: Directive light Step (4) Step 1-4: Step of curing the uncured resin composition layer

<Step 1-1: Step of providing uncured resin composition layer on substrate>
The method of providing the photocurable resin composition in the form of a sheet on the substrate as an uncured resin composition layer is applied by a normal coating method or a printing method. Specifically, air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, calender coating, dam coating, dip coating , coating such as die coating, intaglio printing such as gravure printing, and printing such as stencil printing such as screen printing can be used. If 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.

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 diffusion film, the uncured resin composition layer is adhered to the light irradiation side. It is also possible to laminate a mask that locally changes the irradiation intensity of light.

As for the material of the mask, a light-absorbing filler such as carbon is dispersed in the matrix, and a part of the incident light is absorbed by the carbon, but the aperture is structured so that the light can be sufficiently transmitted. is preferred. Examples of such a matrix include transparent plastics such as PET, TAC, PVAc, PVA, acryl, and polyethylene; inorganic materials such as glass and quartz; It may contain a pigment that absorbs the

When such a mask is not used, it is possible to prevent oxygen inhibition of the uncured resin composition layer by performing light irradiation in a nitrogen atmosphere. Also, 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. Light irradiation through such a mask or transparent film causes a photopolymerization reaction in the photocurable resin composition according to the irradiation intensity, so that a refractive index distribution is likely to occur, and the anisotropic light diffusion film according to the present embodiment is effective for the production of

<Step 1-2: Step of obtaining parallel rays from the 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 methhalide lamp, a xenon lamp, or the like can be used. At this time, it is necessary to obtain a light beam parallel to the desired scattering center axis. In addition to arranging an optical lens such as a Fresnel lens for irradiation, it can be obtained by arranging a reflecting mirror behind the light source so that light is emitted as a point light source in a predetermined direction.

<Optional Step 1-3: Step of Obtaining Directive Light Rays>
Optional step 1-3 is a step of making parallel light beams incident on a directional diffusion element to obtain light beams with directivity. FIG. 9 is a schematic diagram showing a method for manufacturing an anisotropic light-diffusing film in optional step 1-3 according to the present invention.

The directional diffusing elements 301 and 302 used in optional step 1-3 may be any element that imparts directivity to the parallel light beams D incident from the light source 300 .

FIG. 9 describes that the directional light E is incident on the uncured resin composition layer 303 in such a manner that it diffuses much in the X direction and scarcely diffuses in the Y direction. In order to obtain light with such directivity, for example, needle-like fillers having a high aspect ratio are contained in the directional diffusion elements 301 and 302, and the needle-like fillers are arranged in the Y direction in the long axis direction. It is possible to adopt a method of orienting such that the Directional diffusion elements 301 and 302 can use various methods other than the method of using needle-like fillers.

Here, the aspect ratio of the light E having directivity is preferably 2-20. A columnar region having an aspect ratio substantially 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. If the aspect ratio exceeds 20, interference rainbows and glare may occur.

In the optional step 1-3, by adjusting the spread of the light E with directivity, the size of the columnar regions to be formed (aspect ratio, minor axis SA, major axis LA, etc.) can be appropriately determined. For example, the anisotropic light-diffusing film of this embodiment can be obtained in both FIGS. The difference between (a) and (b) of FIG. 9 is that the spread of the light E with directivity is large in (a) but small in (b). The size of the columnar region differs depending on the size of the spread of the light E having directivity.

The spread of the light E with directivity mainly depends on the type of the directional diffusion elements 301 and 302 and the distance from the uncured resin composition layer 303 . The shorter the distance, the smaller the size of the columnar region, and the longer the distance, the larger the size of the columnar region. Therefore, by adjusting the distance, the size of the columnar region can be adjusted.

<Step 1-4: Step of curing the uncured resin composition layer>
The light beam that is applied to the uncured resin composition layer to cure the uncured resin composition layer must contain a wavelength capable of curing the photopolymerizable compound, and is usually centered at 365 nm of a mercury lamp. wavelengths of light are used. When producing an anisotropic light diffusion film using this wavelength band, the illuminance is preferably in the range of 0.01 mW/cm ² to 100 mW/cm ² , more preferably 0.1 mW/cm ² to 20 mW/cm ² . When the illuminance is less ^{than 0.01 mW/cm 2 ,} it takes a long time for curing, resulting in poor production efficiency. , the desired optical characteristics cannot be exhibited.

Although the light irradiation time is not particularly limited, it is preferably 10 seconds to 180 seconds, more preferably 30 seconds to 120 seconds. The anisotropic light-diffusing film of this embodiment can be obtained by irradiating the light beam.

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 time. Therefore, such light irradiation alone may leave unreacted monomer components, causing stickiness and problems in handleability and durability. In such a case, the residual monomer can be polymerized by additionally irradiating light with a high illuminance of 1000 mW/cm ² or more. At this time, light irradiation may be performed from the side opposite to the side on which the mask is laminated.

As described above, when the uncured resin composition layer is cured, the scattering center axis of the resulting anisotropic light-diffusing film can be set to a desired value by adjusting the angle of light with which the uncured resin composition layer is irradiated. can be

<<<<Application of anisotropic light diffusion film laminate>>>>
Since the anisotropic light diffusion film laminate is excellent in the effect of improving the viewing angle dependence, it can be applied to all kinds of display devices such as liquid crystal display devices, organic EL display devices and plasma displays. The anisotropic light-diffusing film laminate can be particularly preferably used in TN mode liquid crystals, which tend to have viewing angle dependency problems. At that time, in order to exhibit an excellent effect of improving the viewing angle dependence, it is preferable to laminate the anisotropic light-diffusing film b so as to be closer to the viewing side than the anisotropic light-diffusing film a.

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 diffusion film laminate. In this case, the anisotropic light diffusion film laminate is provided (laminated) on the viewing side of the liquid crystal layer. The liquid crystal display device may be of any of the TN system, VA system, IPS system, and the like. More specifically, a general liquid crystal device includes a light source, a polarizing plate, a glass substrate, a transparent electrode film, a liquid crystal layer, a transparent electrode film, a color filter, a glass substrate, and a polarizing plate from the display device toward the viewing side. The anisotropic light-diffusing film laminate may be provided anywhere on the viewer side of the liquid phase layer, although it has a layer structure laminated in order and further has an appropriate functional layer.

Further, according to the present invention, it is possible to provide an organic EL display device including a light emitting layer and an anisotropic light diffusion film laminate. In this case, the anisotropic light-diffusing film laminate is provided (laminated) on the viewing side of the light-emitting layer (including the electrode connected to the light-emitting layer). The organic EL display device may be of any type such as a top emission method or a bottom emission method, and in the case of a color organic EL display device, may be of any type such as an RGB coloring method or a color filter method. good. Further, the organic EL display may be multi-layered.

<<<Example>>>
EXAMPLES Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited by these examples.

<<Anisotropic Optical Film>>
Partition walls with a height of 30 to 60 μm were formed from a curable resin using a dispenser around the entire edge of a 100 μm-thick PET film (manufactured by Toyobo Co., Ltd., trade name: A4300). The following UV curable resin composition was added dropwise to this to form a liquid film having a thickness of 30 μm to 60 μm, which was covered with another PET film.

・Silicone urethane acrylate (refractive index: 1.460, weight average molecular weight: 5890) 20 parts by weight (manufactured by RAHN, trade name: 00-225/TM18)
・Neopentyl glycol diacrylate (refractive index: 1.450) 30 parts by weight
(manufactured by Daicel Cytec, trade name Ebecryl145)
・ EO adduct diacrylate of bisphenol A (manufactured by Daicel Cytec, trade name Ebecryl 150, refractive index: 1.536) 15 parts by weight ・ Phenoxyethyl acrylate (manufactured by Kyoeisha Chemical, trade name: Light Acrylate PO-A, refractive index 1 .518) 40 parts by weight 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF, trade name: Irgacure 651) 4 parts by weight

The liquid film sandwiched between PET films on both sides was irradiated with an irradiation unit of UV spot light source (trade name: L2859-01, manufactured by Hamamatsu Photonics Co., Ltd.) with an irradiation intensity of 10 mW/cm ² to 100 mW/cm ² . Parallel UV light was applied either directly or through a PMMA lens.
Here, in the irradiation through the PMMA lens, the aspect ratio of the columnar region was adjusted by expanding parallel rays in the horizontal direction using the PMMA lens when irradiating the ultraviolet rays.
Furthermore, by adjusting the liquid film temperature, the irradiation angle, etc. when irradiating parallel rays or parallel rays spread in the horizontal direction, the maximum linear transmittance in the tilt direction of the anisotropic light diffusion film, the scattering central axis angle, the haze adjusted the value.
Anisotropic light diffusion films 1 to 15 having the optical properties shown in Table 1 were obtained by adjusting the parameters as described above.

<Measurement of thickness of anisotropic light diffusion film>
The anisotropic light diffusion films obtained in Examples were measured using a micrometer (manufactured by Mitutoyo Corporation). The thickness of the anisotropic light-diffusing film was taken as the average value of the values measured at a total of 5 points including the vicinity of four corners on the plane of the anisotropic light-diffusing film and one point near the center of the plane.

<Measurement of Angle of Scattering Central Axis and Linear Transmittance of Anisotropic Light Diffusion Film>
Anisotropic light diffusion obtained in the example using a variable angle photometer goniophotometer (manufactured by Genesia) that can arbitrarily change the light projection angle of the light source 1 and the light reception angle of the detector 2 as shown in FIG. The linear transmittance of the film was measured.
A detector 2 was fixed at a position where it received rectilinear light I from a fixed light source 1, and the anisotropic light diffusion film obtained in the example was set on a sample holder therebetween. At that time, the TD direction shown in FIG. 3 was installed so as to be the straight line direction of the straight line V shown in FIG. ).
Subsequently, the anisotropic light-diffusing film was rotated around the straight line V, and the amount of linearly transmitted light entering the detector 2 after passing straight through the anisotropic light-diffusing film was measured. After that, the linear transmittance was calculated from the amount of linearly transmitted light, and the linear transmittance was plotted for each angle to create an optical profile.
The linear transmittance was measured at a wavelength in the visible light region using a visibility filter.
Based on the optical profile obtained as a result of the above measurements, approximately the center between the maximum value (maximum linear transmittance) and minimum value (minimum linear transmittance) of the linear transmittance and the minimum value in the optical profile The scattering central axis angle was obtained from the part (central part of the diffusion region).

<Measurement of aspect ratio of columnar structure (surface observation of anisotropic light diffusion film)>
A cross section perpendicular to the columnar axis of the columnar region on the surface of the anisotropic light-diffusing film obtained in the example (on the irradiation light side during ultraviolet irradiation) was observed with an optical microscope to measure the major axis LA and the minor axis SA of the columnar region. An average value of arbitrary 20 columnar regions was used to calculate the average major axis LA and average minor axis SA. Also, the average major axis LA/average minor axis SA was calculated as an aspect ratio with respect to the obtained average major axis LA and average minor axis SA.

<Measurement of haze of anisotropic light diffusion film>
Using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the haze values of the anisotropic light diffusion films obtained in Examples were measured.

<<Anisotropic light diffusion film laminate>>
An anisotropic light-diffusing film laminate was produced by the method shown below.

<Example 1>
The anisotropic light-diffusing film 1 and the anisotropic light-diffusing film 2 obtained in Example were cut into a rectangular shape so that the long side direction coincides with the scattering central axis direction of the anisotropic light-diffusing film, and then the anisotropic light-diffusing film 1 and the anisotropic light-diffusing film 2 were cut. The anisotropic light diffusion film 2 is laminated with a transparent adhesive layer made of an acrylic resin interposed therebetween so that the angle (φ _ab ) formed by the directions of the respective scattering central axes of the anisotropic light diffusion film 2 becomes the target value of 0° shown in Table 2. Thus, an anisotropic light-diffusing film laminate 1 of Example 1 was obtained. Further, as shown in Table 2, the actual measurement value of φ _ab with a measuring microscope after lamination was 1°.
As shown in Table 2, the anisotropic light-diffusing film 2 is an anisotropic light-diffusing film a, and the anisotropic light-diffusing film 1 is an anisotropic light-diffusing film b.

<Examples 2 to 7, Comparative Examples 1 to 8>
Two types of anisotropic light diffusion films to be used are laminated via an adhesive layer of a transparent adhesive made of an acrylic resin according to the combination shown in Table 2 and so that φ _ab becomes the target value shown in Table 2. Anisotropic light-diffusing film laminates 2 to 15 of Examples 2 to 7 and Comparative Examples 1 to 8 were obtained in the same manner as in Example 1 except for the above. Table 2 shows the φ _ab values measured by a measuring microscope after lamination of each anisotropic light diffusion film.

<<Evaluation method>>
The anisotropic light-diffusing film laminates of Examples and Comparative Examples were evaluated as follows.

<Measurement of haze value of anisotropic light-diffusing film laminate>
Using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the haze values of the anisotropic light-diffusing film laminates obtained in Examples were measured.

<Measurement of linear transmittance of anisotropic light diffusion film laminate>
As shown in FIG. 6, using a variable angle photometer goniophotometer (manufactured by Genesia) that can arbitrarily change the light projection angle of the light source 1 and the light reception angle of the detector 2, were obtained in the examples and comparative examples. The in-line transmittance of the anisotropic light-diffusing film laminate was measured.
A detector 2 was fixed at a position receiving straight light I from a fixed light source 1, and the anisotropic light diffusion film laminates obtained in Examples and Comparative Examples were set on a sample holder therebetween. At that time, the anisotropic light-diffusing film on the viewing side of the anisotropic light-diffusing film laminate was placed so that the MD direction shown in FIG. line on the anisotropic light-diffusing film stack perpendicular to the tilt orientation of the axis).
Subsequently, the anisotropic light-diffusing film laminate was rotated around the straight line V, and the amount of linearly transmitted light entering the detector 2 through the anisotropic light-diffusing film laminate was measured. After that, the linear transmittance was calculated from the amount of linearly transmitted light, and the linear transmittance was plotted for each angle to create an optical profile.
The linear transmittance was measured at a wavelength in the visible light region using a visibility 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, and the linear transmittance at an incident light angle of 0° are obtained. rice field.

<Evaluation of Contrast/Gradation Reversal>
The anisotropic light-diffusing film laminates of Examples and Comparative Examples were placed on the surface of a TN mode liquid crystal display in the orientation with respect to the direction in which the gradation reversal of the liquid crystal display occurs and the orientation with respect to the tilting direction of the scattering center axis of the anisotropic light-diffusing film a. They were laminated together so that the angle formed with them was 0°.
Subsequently, using a viewing angle measuring device Conometer 80 (manufactured by Westboro), when gray scales divided into 11 gradations from white to black are displayed on the liquid crystal display screen, the polarity with respect to the normal direction of the display The luminance distribution in the angle range of 0 to 80° was measured.
Here, "white luminance/black luminance" at a polar angle of 75° in the azimuth with respect to the direction in which gradation reversal occurs in the liquid crystal display alone was calculated and used as the contrast. In addition, the minimum polar angle at which the 11 gradations measured above are reversed from the original gradation in the direction in which gradation reversal occurs in the liquid crystal display alone was defined as the gradation reversal angle. This is summarized in Table 3.
Here, in the evaluation of the display alone, to which the anisotropic light-diffusing film laminate was not adhered, the contrast was 8.0 and the gradation reversal angle was 28°.

<Evaluation of visual clarity>
The anisotropic light-diffusing film laminates of Examples and Comparative Examples were placed on the surface of a TN-mode liquid crystal display in the direction in which the gradation reversal of the liquid crystal display occurs, and in the direction of inclination of the scattering central axis of the anisotropic light-diffusing film a. They were laminated together so that the angle between them was 0°.
Subsequently, visual clarity of the color filter was visually evaluated when a white screen was displayed on the display with a scale magnifier.
The visual clarity was rated as 4 when the vertical and horizontal boundaries of the matrix of the color filter could be distinguished, 3 when the boundary in only one direction was distinguishable, 2 when the boundary was not distinguishable, and 1 when the color filter was not distinguishable. This is summarized in Table 3.
Here, the visual clearness was 4 in the evaluation of only the display to which the anisotropic light-diffusing film laminate was not adhered.

<Determination Criteria for Polar Angle 75° Contrast>
A contrast of 18 or more was evaluated as ⊚, a contrast of 14 or more and less than 18 was evaluated as ∘, and a contrast of less than 14 was evaluated as x.

<Determination Criteria for Gradation Inversion>
When the gradation reversal angle was more than 80° and within 90°, it was evaluated as ⊚;

<Judgment Criteria for Visual Clarity>
In the above evaluation method, 4 was rated as ⊚, 3 as ◯, and less than 2 as x.

<<Evaluation result>>
From Table 3, in the liquid crystal displays using the anisotropic light-diffusing film laminates of Examples 1 to 7, the comprehensive evaluation including contrast, gradation reversal and visual clarity is the same as the anisotropic light-diffusing film laminates of Comparative Examples 1 to 8. In particular, Example 1 was the most excellent with all evaluations of "⊚".
Since Comparative Examples 1 and 2 had low haze values, the diffusivity was low, and the contrast at 75° was considered to be low.
Comparative Examples 3 to 6 had a high haze value, which is thought to have adversely affected visual clarity.
In Comparative Example 7, the aspect ratio of one anisotropic light-diffusing film was large, so the diffusibility in the tilt direction was lowered, and the contrast at 75° was considered to be low.
In Comparative Example 8, the angle (φ _ab ) formed by the directions of the scattering central axes of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b was large, so the diffusibility was low, and the contrast at 75° was low. It is considered to be a thing.

As described above, when the anisotropic light-diffusing film of the present invention is used in a display device such as a TN liquid crystal display, it is possible to suppress gradation reversal, improve contrast at deep angles, and suppress reduction in image visibility sharpness in the front direction. As a result, it is possible to achieve both visibility in a direction that is normally difficult to see, and visibility in the front direction, which is visible in a static state. You can expect to have

Claims (9)

At least two layers of anisotropic light diffusing films with linear transmittance that changes by (the amount of transmitted light in the linear direction of incident light)/(the amount of incident light) depending on the angle of incidence of light, and the haze value is , an anisotropic light diffusion film laminate of 70% to 85%,
The anisotropic light diffusion film has one scattering central axis, a matrix region, and a plurality of columnar regions having different refractive indices from the matrix region,
The plurality of columnar regions are oriented and extend from one surface to the other surface of the anisotropic light diffusion film,
In the anisotropic light-diffusing film, when the first anisotropic light-diffusing film is an anisotropic light-diffusing film a and the second anisotropic light-diffusing film is an anisotropic light-diffusing film b,
The anisotropic light diffusion film a and the anisotropic light diffusion film b are laminated directly or via an adhesive layer,
The aspect ratio of the columnar region, which is the average major axis/average minor axis of the columnar region in a cross section perpendicular to the columnar axis of the columnar region,
one of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b has an aspect ratio of 2 to 10, and the other film has an aspect ratio of 1 to 10;
Assuming that the polar angle formed by the normal direction of the anisotropic light diffusion film surface and the scattering center axis direction is the scattering center axis angle,
The anisotropic light diffusion film a has a scattering central axis angle of 20° to 35°,
The anisotropic light diffusion film b has a scattering center axis angle of 40° to 55°,
An anisotropic light-diffusing film laminate, wherein an angle between the directions of the scattering central axes of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b is 0° to 40°. The anisotropic light diffusion film a and the anisotropic light diffusion film b are characterized in that the average minor axis is 0.5 μm to 1.6 μm and the average major axis is 4.5 μm to 10.0 μm. The anisotropic light-diffusing film laminate according to claim 1. The anisotropic light diffusion film a has a haze value of 30% to 70%,
3. The anisotropic light-diffusing film laminate according to claim 1, wherein the anisotropic light-diffusing film b has a haze value of 20% to 70%. The anisotropic light diffusion film a has a maximum linear transmittance of 50% to 70% and a minimum linear transmittance of 4% or less,
The anisotropic light diffusion film b according to any one of claims 1 to 3, wherein the maximum linear transmittance of the anisotropic light diffusion film b is 30% to 70% and the minimum linear transmittance is 6% or less. An anisotropic light-diffusing film laminate as described. The anisotropic anisotropic light diffusion film laminate has a maximum linear transmittance of 15% to 30%,
5. The anisotropic light diffusion film laminate according to claim 1, wherein the linear transmittance at an incident light angle of 0° is 6% to 16%. A liquid crystal display device comprising a liquid crystal layer and the anisotropic light diffusion film laminate according to any one of claims 1 to 5,
A liquid crystal display device, wherein the anisotropic light diffusion film laminate is laminated on the viewing side of the liquid crystal layer. 7. The liquid crystal display device according to claim 6, wherein the anisotropic light-diffusing film b is laminated so as to be closer to the viewer than the anisotropic light-diffusing film a. An organic EL display device comprising a light emitting layer and the anisotropic light diffusion film laminate according to any one of claims 1 to 5,
An organic EL display device, wherein the anisotropic light diffusion film laminate is laminated on the viewing side of the light emitting layer. 9. The organic EL display device according to claim 8, wherein the anisotropic light-diffusing film b is laminated so as to be closer to the viewer than the anisotropic light-diffusing film a.

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