JP7667679B2 - Anisotropic light-diffusing film laminate and display device - Google Patents

Description

The present invention relates to an anisotropic light-diffusing film laminate and a display device equipped with the anisotropic light-diffusing film laminate.

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

To eliminate this viewing angle dependency, anisotropic optical bodies are used, whose linear transmittance [(amount of light transmitted in the linear direction of incident light)/(amount of incident light)] changes depending on the angle of incidence of light.

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

JP 2015-127819 A

However, in light of the diversification of display methods and display sizes of display devices, there is a demand for anisotropic optical bodies that have even better effects in improving viewing angle dependency.

Therefore, the objective of the present invention is to provide an anisotropic light-diffusing film laminate that has a more excellent effect of improving the viewing angle dependency in terms of luminance and color change due to the viewing angle than conventional films.

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

The present invention relates to
An anisotropic light-diffusing film laminate having a haze value of 70% to 85%, comprising at least two or more anisotropic light-diffusing films each having a linear transmittance, the linear transmittance being determined by dividing the linear transmittance by the incident angle of light, and the linear transmittance being equal to (amount of transmitted light in a linear direction of incident light)/(amount of incident light), and the anisotropic light-diffusing film laminate having a haze value of 70% to 85%,
the anisotropic light-diffusing film has one scattering central axis, a matrix region, and a plurality of columnar regions having a refractive index different from that of the matrix region;
the plurality of columnar regions are oriented and extend from one surface of the anisotropic light-diffusing film to the other surface,
In the anisotropic light-diffusing film, if the first anisotropic light-diffusing film is designated as an anisotropic light-diffusing film a and the second anisotropic light-diffusing film is designated as an anisotropic light-diffusing film b,
The anisotropic light-diffusing film a and the anisotropic light-diffusing film b are laminated together directly or via a pressure-sensitive adhesive layer,
In the aspect ratio of the columnar region, the average major axis/average minor axis of the columnar region in a cross section perpendicular to the column 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 has an aspect ratio of 1 to 10;
If the polar angle between the normal direction of the surface of the anisotropic light-diffusing film and the scattering central axis direction is defined as the scattering central axis angle,
the scattering central axis angle of the anisotropic light-diffusing film a is 20° to 35°;
the scattering central axis angle of the anisotropic light-diffusing film b is 40° to 55°;
The anisotropic light-diffusing film laminate is characterized in that the 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°.

It is preferable that the anisotropic light-diffusing film a and the anisotropic light-diffusing film b 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 haze value of the anisotropic light-diffusing film a is 30% to 70%,
The haze value of the anisotropic light-diffusing film b is preferably 20% to 70%.
The anisotropic light-diffusing film a has a maximum linear transmittance of 50% to 70% and a minimum linear transmittance of 4% or less;
It is preferable that the maximum linear transmittance of the anisotropic light-diffusing film b is 30% to 70% and the minimum linear transmittance is 6% or less.
The maximum linear transmittance of the anisotropic light-diffusing film laminate is 15% to 30%,
The in-line transmittance at an incident light angle of 0° is preferably between 6% and 16%.

The present invention relates to
A liquid crystal display device comprising a liquid crystal layer and the anisotropic light-diffusing film laminate,
The liquid crystal display device may be characterized in that the anisotropic light-diffusing 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 on the viewing side relative to the anisotropic light-diffusing film a.

The present invention relates to
An organic EL display device comprising a light-emitting layer and the anisotropic light-diffusing film laminate,
The organic EL display device may be characterized in that the anisotropic light-diffusing 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 on the viewing side relative to the anisotropic light-diffusing film a.

The present invention makes it possible to provide an anisotropic light-diffusing film laminate that has a more excellent effect of improving viewing angle dependence in terms of luminance and color change due to viewing angle than conventional films.

FIG. 1 is an explanatory diagram showing an example of the incidence angle dependency of an anisotropic light-diffusing film. FIG. 2 is a top view showing the surface structure of an anisotropic light-diffusing film. 1 is a schematic diagram illustrating an example of an anisotropic light-diffusing film. 1 is a three-dimensional polar coordinate representation for explaining the scattering central axis in an anisotropic light-diffusing film. 1 is a graph showing an example of an optical profile in an anisotropic light-diffusing film. FIG. 2 is a schematic diagram showing a method for measuring the incident light angle dependency of an anisotropic light-diffusing film. FIG. 2 is a schematic diagram showing an example of an anisotropic light-diffusing film laminate. 1 is a three-dimensional polar coordinate representation for explaining the scattering central axis in each anisotropic light-diffusing film constituting an anisotropic light-diffusing film laminate. 1A to 1C are schematic diagrams illustrating a method for producing an anisotropic light-diffusing film according to the present invention.

Below, we will briefly explain the anisotropic light-diffusing film of the present invention, and then explain the structure, physical properties, manufacturing method, and specific uses of the anisotropic light-diffusing film laminate.

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

For example, the anisotropic light diffusion film shown in Figure 1 shows diffusivity when the incident angle is between 20° and 50°, but does not show diffusivity at other incident angles and shows linear transmittance.

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

Here, the difference in refractive index means that there is no particular limitation as long as there is a difference in the degree to which at least a portion of the light incident on the anisotropic light-diffusing film is reflected at the interface between the matrix region and the columnar region.

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

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

The shape of the columnar region in a cross section perpendicular to its column axis is not particularly limited, and can be, for example, circular, elliptical, or polygonal. In the case of a circle, the minor axis and the major axis are equal, in the case of an ellipse, the minor axis is the length of the minor axis and the major axis is the length of the major axis, and in the case of a polygon, the shortest length within the polygon can be the minor axis and the longest length can be the major axis. Figure 2 shows the cross-sectional shape of the columnar region in a cross section perpendicular to its column axis. In Figure 2, LA represents the major axis and SA represents the minor axis.

<Minor diameter>
In the anisotropic light-diffusing film, the average value of the minor axis of the columnar region (average minor axis) is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more. On the other hand, the average minor axis of the columnar region is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, and particularly preferably 1.6 μm or less. The lower limit and upper limit of the minor axis of the columnar region can be appropriately combined.

<Long diameter>
In the anisotropic light-diffusing film, the average value of the major axis of the columnar region (average major axis) is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 1.5 μm or more, and particularly preferably 4.5 μm or more. On the other hand, the average major axis of the columnar region is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 10.0 μm or less. The average major axis of the columnar region is preferably shorter than the length of the columnar region. In this way, it is possible to increase the linear light transmittance of the anisotropic light-diffusing film. The lower limit and upper limit of the major axis of the columnar region can be appropriately combined.

The short and long diameters of the columnar regions can be determined by observing a cross section of the anisotropic light-diffusing film perpendicular to the columnar axis of the columnar regions (a cross section near the center of the thickness of the anisotropic light-diffusing film) with an optical microscope, measuring the short and long diameters of 20 arbitrarily selected columnar regions, and averaging these values.

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

Figure 2(a) shows an anisotropic light-diffusing film in which the aspect ratio of the columnar region is 2 to 10, and Figure 2(b) shows an anisotropic light-diffusing film in which the aspect ratio of the columnar region is 1 or more and less than 2.

When the aspect ratio is between 1 and 2, and light is irradiated parallel to the axial direction of the columnar region, the transmitted light is diffused isotropically (see Figure 3(a)). On the other hand, when the aspect ratio is between 2 and 10, and light is irradiated parallel to the axial direction, the light is diffused anisotropically according to the aspect ratio (see Figure 3(b)).

An anisotropic light-diffusing film may contain multiple columnar regions with one aspect ratio, or may contain multiple columnar regions with different aspect ratios.

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

According to Snell's law, when light is incident on the interface between a medium with a refractive index _n1 and a medium with a refractive index _n2 , the relationship _n1 sin _θ1 = n2 sin _θ2 holds between the incident light angle _{θ1 and} the refraction angle _θ2 . For example, if _n1 = 1 (air) and _n2 = 1.51 (anisotropic light-diffusing film), when the incident light angle is 30°, the orientation direction (refraction angle) of the columnar region is approximately 19°. Even if the incident light angle and the refraction angle differ in this way, as long as they satisfy Snell's law, they are included in the concept of parallel in the present invention.

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

As described above, the central scattering axis refers to the direction that coincides with the angle of incidence of light whose light diffusibility is approximately symmetrical across the angle of incidence when the angle of incidence of light on the anisotropic light-diffusing film is changed. The angle of incidence of light in this case is approximately the center (the center of the diffusion region) between the minimum values in the optical profile (Figure 5), which is obtained by measuring the linear transmittance of the anisotropic light-diffusing film and plotting the linear transmittance for each angle of incidence of light.

In a three-dimensional polar coordinate representation as shown in Figure 4, the scattering central axis can be expressed by the polar angle θ and the azimuthal angle φ, where the surface of the anisotropic light-diffusing film is the xy plane and the normal to the surface of the anisotropic light-diffusing film is the z axis. In other words, Pxy in Figure 4 can be said to be the length direction of the scattering central axis projected onto the surface of the anisotropic light-diffusing film.

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

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

<<<<Optical profile>>>>
FIG. 5 is a graph showing an example of an optical profile in an anisotropic light-diffusing film having a scattering central axis angle of 0°. In the present invention, the optical profile refers to a curve showing the dependency of light diffusivity on the angle of incident light.
As shown in FIG. 5, the anisotropic light-diffusing film has light-diffusing property that depends on the angle of incident light, that is, the linear transmittance changes depending on the angle of incident light.

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

As shown in FIG. 6, the anisotropic light diffusion film is disposed between the light source 1 and the detector 2. In this embodiment, the incident light angle is set to 0° when the irradiated light I from the light source 1 is incident from the normal direction of the anisotropic light diffusion film. The anisotropic light diffusion film is disposed so that it can be rotated arbitrarily around the line V as the rotation axis, and the light source 1 and the detector 2 are fixed. That is, according to this method, a sample (anisotropic light diffusion film) is disposed between the light source 1 and the detector 2, and the amount of linear transmitted light that passes through the sample in a straight line and enters the detector 2 is measured while changing the angle around the line V on the sample surface as the rotation axis. Then, the linear transmittance is calculated from the linear transmitted light amount, and the linear transmittance is plotted for each angle to create an optical profile.
This evaluation method makes it possible to evaluate the range of angles at which incident light is diffused.

The optical profile does not directly express light diffusion, but if we interpret it as meaning that a decrease in linear transmittance means an increase in diffuse transmittance, it can be said to generally indicate light diffusion.

A typical isotropic light diffusion film exhibits a mountain-shaped optical profile that peaks at an incident light angle of around 0°.

In contrast, the optical profile graph of an anisotropic light-diffusing film with a scattering central axis angle of 0° in Figure 5, for example, shows a valley-shaped optical profile in which the linear transmittance is small at incident light angles around 0° (-20° to +20°), and the linear transmittance increases as the absolute value of the incident light angle increases.

In this way, anisotropic light diffusion films have the property that the incident light is strongly diffused in the incident light angle range close to the scattering central axis, but the diffusion weakens and the linear transmittance increases in the incident light angle range beyond that.

In addition, in the case of an anisotropic light-diffusing film with a scattering central axis angle other than 0°, the optical profile shifts so that the linear transmittance decreases at incident light angles near the scattering central axis angle (the valley of the optical profile shifts toward the scattering central axis angle).

＜＜＜Linear transmittance＞＞＞
5, the linear transmittance of light incident on the anisotropic light-diffusing film at an incident angle at which the linear transmittance is maximum is referred to as the maximum linear transmittance. The anisotropic light-diffusing film preferably has a maximum linear transmittance of 30% to 70%.

As shown in FIG. 5, the linear transmittance of light incident on the anisotropic light-diffusing film at an angle of incidence at which the linear transmittance is minimum is referred to as the minimum linear transmittance. It is preferable that the anisotropic light-diffusing film has a minimum linear transmittance of 6% or less.

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

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

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

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

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

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

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

<<<<<<Anisotropic light-diffusing film laminate>>>>>
<<<<<Structure>>>>
The anisotropic light-diffusing film laminate of the present invention is a laminate in which at least two layers of anisotropic light-diffusing films having specific properties are laminated together. FIG. 7 is a schematic diagram showing an example of an anisotropic light-diffusing film laminate.

With regard to the two layers of anisotropic light-diffusing film contained in the anisotropic light-diffusing film laminate of the present invention, the first anisotropic light-diffusing film is designated as anisotropic light-diffusing film a, and the second anisotropic light-diffusing film is designated as anisotropic light-diffusing film b.

The anisotropic light-diffusing film laminate of the present invention may have an anisotropic light-diffusing film 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 including three or more layers of anisotropic light-diffusing films including the anisotropic light-diffusing film a and the anisotropic light-diffusing film b.
The other anisotropic light-diffusing film may be a single layer or multiple layers. When multiple layers of the other anisotropic light-diffusing film are present, the layers of the anisotropic light-diffusing film laminate may have the same or different structures and properties.

However, in the present invention, the anisotropic light-diffusing film a and the anisotropic light-diffusing film b are laminated directly without other anisotropic light-diffusing films or via an adhesive layer. That is, as shown in FIG. 7, examples of lamination of anisotropic light-diffusing films in an anisotropic light-diffusing film laminate include "anisotropic light-diffusing film a/anisotropic light-diffusing film b" (FIG. 7(a)), "other anisotropic light-diffusing film/anisotropic light-diffusing film a/anisotropic light-diffusing film b" (FIG. 7(b)), "anisotropic light-diffusing film a/anisotropic light-diffusing film b/other anisotropic light-diffusing film" (FIG. 7(c)), and "other anisotropic light-diffusing film/anisotropic light-diffusing film a/anisotropic light-diffusing film b/other anisotropic light-diffusing film" (FIG. 7(d), where the two layers of other anisotropic light-diffusing films may have the same structure and characteristics or different structures and characteristics.

Other anisotropic light-diffusing films may be laminated directly or via an adhesive layer, etc.

The adhesive of the adhesive layer used for laminating the anisotropic light-diffusing films together is not particularly limited as long as it is transparent, but it is preferable to use an adhesive that has pressure-sensitive adhesion at room temperature. Examples of such adhesives include polyester resins, epoxy resins, polyurethane resins, silicone resins, and acrylic resins. In particular, acrylic resins are preferred because of their high optical transparency.

In addition, a layer having a different function other than the anisotropic light-diffusing film can be laminated on the surface of the anisotropic light-diffusing film laminate, as long as the effect of the present invention is not impaired. Examples of layers having a different function include a retardation film, a UV-cut layer, and a low moisture permeable layer.

The anisotropic light-diffusing film laminate may also be laminated on a transparent substrate such as a glass substrate.

<<<<Physical properties/properties>>>>
<<<Haze value>>>
The haze value of the entire anisotropic light-diffusing film laminate is preferably 70% to 85%. When laminating anisotropic light-diffusing films having specific scattering central axes, an excellent effect of improving viewing angle dependency can be achieved by setting the haze value of the entire anisotropic light-diffusing film laminate in this range.

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

＜＜＜Linear transmittance＞＞＞
The linear transmittance of the anisotropic light-diffusing film laminate can be measured for the anisotropic light-diffusing film on the viewing side of the anisotropic light-diffusing film laminate by the same method as that for measuring the linear transmittance of the anisotropic light-diffusing film described above.

It is preferable that the anisotropic light-diffusing film laminate has a maximum linear transmittance of 15% to 30%.

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

It is preferable that the anisotropic light-diffusing film laminate 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-diffusing film laminate and the linear transmittance at an incident light angle of 0° within such ranges, light can be diffused sufficiently and problems such as a decrease in visual clarity are less likely to occur.

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

<<<Anisotropic Light-Diffusion Film A and Anisotropic Light-Diffusion Film B>>>
Next, the characteristics 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 characteristics 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, etc. Unless otherwise specified, the preferred ranges shown below may be either the case where at least one of the two layers satisfies the range, or the case where both layers satisfies the range.

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

<Aspect ratio>
It is preferable that one of the anisotropic light-diffusing films a and b has an aspect ratio of 2 to 10 and the other has an aspect ratio of 1 to 10 (1 or more and less than 2 or 2 to 10), and it is preferable that one of the anisotropic light-diffusing films a and b has an aspect ratio of 2 to 8 and the other has an aspect ratio of 1 to 10 (1 or more and less than 2 or 2 to 10). 10), or it is more preferable that the aspect ratio of one of the anisotropic light-diffusing films a and b is 2 to 10 and the aspect ratio of the other film is 1 to 8 (1 or more and less than 2 or 2 to 8), and it is even more preferable that the aspect ratio of one of the anisotropic light-diffusing films a and b 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. 8. Fig. 8 is a three-dimensional polar coordinate representation for explaining the scattering central axes in each anisotropic light-diffusing film constituting the anisotropic light-diffusing film laminate.

In the anisotropic light-diffusing film laminate of the present invention, the anisotropic light-diffusing film a and the anisotropic light-diffusing film b each have a scattering central axis Pa and a scattering central axis Pb, respectively. By setting the scattering central axis Pa and the scattering central axis Pb within an appropriate range, it is possible to adjust the diffusivity of the entire anisotropic light-diffusing film laminate, and to achieve a better effect of improving the viewing angle dependency than a single-layer anisotropic light-diffusing film.

More specifically, in a typical display, light with the correct color and high illuminance is obtained near the normal direction (polar angle θ = 0°). The viewing angle can be improved by diffusing the light near the normal direction in a direction with a larger polar angle θ in the direction in which the viewing angle is to be improved. According to the present invention, the light in the front direction is gradually changed to a direction with a larger polar angle θ, that is, the scattering central axis angle θ is appropriately diffused in two stages by the anisotropic light-diffusing film a and the anisotropic light-diffusing film b. An anisotropic light-diffusing film with a small scattering central axis angle θ alone cannot sufficiently diffuse light in a direction with a larger polar angle θ, and an anisotropic light-diffusing film with a large scattering central axis angle θ alone cannot sufficiently diffuse light in a direction with a larger polar angle θ due to insufficient diffusivity in the normal direction.

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

The scattering central axis angle θ _b of the scattering central axis Pb of the anisotropic light-diffusing film b is preferably 40° to 55°, more preferably 46° to 52°, and even more preferably 49° to 51°. By setting the scattering central axis angle θ _a and the scattering central axis angle θ _b in this manner, it is possible to achieve an 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°, and more preferably 10° to 30°. By setting the difference (θ _ab ) between the scattering central axis angle θ _a and the scattering central axis angle θ _b in this manner, the diffusibility of light is increased, and it is possible to achieve an effect of improving the viewing angle dependency.

Furthermore, the angle φ _ab between the azimuths of the scattering central axes of the anisotropic light-diffusing films a and b (in other words, the difference between the azimuth angle φ _a of the scattering central axis Pa of the anisotropic light-diffusing film a and the azimuth angle φ _b of the scattering central axis Pb of the anisotropic light-diffusing film b) is preferably 0° to 40°, more preferably 5° to 40°, and even more preferably 10° to 30°. If the angle φ _ab exceeds 40°, the deviation in the azimuths of the scattering central axes Pa and Pb becomes large, making it difficult to achieve the desired effect of improving the viewing angle dependency.

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

<<In-line transmittance>>
The anisotropic light-diffusing film a preferably has a maximum linear transmittance of 40% to 70%, and more preferably 45% to 66%.

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

The maximum linear transmittance of the anisotropic light-diffusing film b is preferably 30% to 70%, and more preferably 50% to 60%.

The anisotropic light-diffusing film b preferably has a minimum linear transmittance of 4% or less, more preferably 3% or less, and even more preferably 1.5% or less.

By setting the scattering center axis Pa of anisotropic light-diffusing film a and the scattering center axis Pb of anisotropic light-diffusing film b within the appropriate range described above, and setting the maximum linear transmittance and minimum linear transmittance of anisotropic light-diffusing film a and anisotropic light-diffusing film b within such ranges, light can be diffused sufficiently 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-diffusing film b is preferably 20% to 70%.

<<Thickness>>
The thickness of the anisotropic light-diffusing film a and the anisotropic light-diffusing film b is not particularly limited, but is preferably 15 μm to 100 μm, more preferably 30 μm to 60 μm. By setting the thickness within such a range, it is possible to reduce the manufacturing costs such as the cost of materials and the cost required for UV irradiation, while suppressing the occurrence of a decrease in image visibility clarity and a decrease in contrast due to an increase in the diffusivity in the thickness direction of the anisotropic light-diffusing film a and the second anisotropic light-diffusing film b, and further to ensure sufficient light diffusivity and light collection.

<<<<<Method of manufacturing anisotropic light-diffusing film laminate>>>>
The anisotropic light-diffusing film laminate is a laminate having a plurality of anisotropic light-diffusing films. For example, the anisotropic light-diffusing film laminate can be produced by separately producing a first anisotropic light-diffusing film and a second anisotropic light-diffusing film, and laminating the first anisotropic light-diffusing film and the second anisotropic light-diffusing film with a pressure-sensitive adhesive layer interposed therebetween.

As mentioned above, examples of adhesives include polyester resins, epoxy resins, polyurethane resins, silicone resins, acrylic resins, and other resins.

The adhesive application method and curing conditions can be conventional and well known, depending on the adhesive used.

The anisotropic light-diffusing film laminate can also be produced by producing a first anisotropic light-diffusing film, and then directly forming a second anisotropic light-diffusing film on the first anisotropic light-diffusing film using the first anisotropic light-diffusing film as a substrate. More specifically, a composition layer containing a photopolymerizable compound is cured to produce a first anisotropic light-diffusing film, and then a composition containing a photopolymerizable compound is directly applied onto the first anisotropic light-diffusing film, provided in a sheet form, and cured to form a second anisotropic light-diffusing film.

The manufacturing method for anisotropic light diffusion film is explained below.

<<<<Production of anisotropic light-diffusing film>>>
<<Ingredients>>
The raw materials of the anisotropic light-diffusing film will be described in the following order: (1) photopolymerizable compound, (2) photoinitiator, (3) blending amount, and other optional components.

<Photopolymerizable Compound>
The photopolymerizable compound is a material that is composed of a photopolymerizable compound selected from a macromonomer, polymer, oligomer, or monomer having a radically polymerizable or cationic polymerizable functional group and a photoinitiator, and that polymerizes and hardens when irradiated with ultraviolet light and/or visible light.

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

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

As a cationic polymerizable compound, a compound having one or more epoxy groups, vinyl ether groups, or oxetane groups in the molecule can be used. Examples of compounds having an epoxy group include 2-ethylhexyl diglycol glycidyl ether, glycidyl ether of biphenyl, diglycidyl ethers of bisphenols such as bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetrachloro bisphenol A, and tetrabromo bisphenol A, polyglycidyl ethers of novolac resins such as phenol novolac, cresol novolac, brominated phenol novolac, and orthocresol novolac, diglycidyl ethers of alkylene glycols such as ethylene glycol, polyethylene glycol, polypropylene glycol, butanediol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane, 1,4-cyclohexanedimethanol, EO adduct of bisphenol A, and PO adduct of bisphenol A, and 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, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane, di(3,4-epoxycyclohexylmethyl)adipate, di(3,4-epoxy-6-methylcyclohexylmethyl)adipate, 3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexa Examples of epoxy compounds include, but are not limited to, alicyclic epoxy compounds such as dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylene bis(3,4-epoxycyclohexanecarboxylate), lactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, tetra(3,4-epoxycyclohexylmethyl)butane tetracarboxylate, and di(3,4-epoxycyclohexylmethyl)-4,5-epoxytetrahydrophthalate.

Examples of compounds having a vinyl ether group include, but are not limited to, diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, trimethylolpropane trivinyl ether, propenyl ether propylene carbonate, etc. Note that vinyl ether compounds are generally cationic polymerizable, but can also undergo radical polymerization when combined with an acrylate.

Compounds having an oxetane group include 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene and 3-ethyl-3-(hydroxymethyl)-oxetane.

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

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

As the photopolymerizable compound, it is preferable to use a photopolymerizable compound having a silicone skeleton. The photopolymerizable compound having a silicone skeleton is oriented according to its structure (mainly ether bonds) and polymerizes and hardens to form a low refractive index region, a high refractive index region, or a low refractive index region and a high refractive index region. By using a photopolymerizable compound having a silicone skeleton, it becomes easier to tilt the columnar region, improving the light collection in the front direction. The low refractive index region corresponds to either the columnar region or the matrix region, and the other corresponds to the high refractive index region.

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. This makes it easier to tilt the scattering axis, improving the light collection in the forward direction. Silicone resin contains more silicon (Si) than compounds that do not have a silicone skeleton, so the relative amount of silicone resin can be confirmed by using an EDS (energy dispersive X-ray spectrometer) using silicon as an indicator.

The photopolymerizable compound having a silicone skeleton is a monomer, oligomer, prepolymer, or macromonomer having a radically polymerizable or cationic polymerizable functional group. Examples of 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 limitations on the type and number of these functional groups, but it is preferable to have a polyfunctional acryloyl group or methacryloyl group because the more functional groups there are, the higher the crosslinking density and the more likely the refractive index difference is to occur. In addition, compounds having a silicone skeleton may have insufficient compatibility with other compounds due to their structure, but in such cases, the compatibility can be increased by urethane conversion. In this embodiment, a silicone urethane (meth)acrylate having an acryloyl group or methacryloyl group at the end is preferably used.

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

An example of the silicone skeleton is one represented by the following general formula (1): In general formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ each independently have a functional group such as a methyl group, an alkyl group, a fluoroalkyl group, a phenyl group, an epoxy group, an amino group, a carboxyl group, a polyether group, an acryloyl group, or a methacryloyl group. In general formula (1), n is preferably an integer of 1 to 500.

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

Compounds that do not have a silicone skeleton can be photopolymerizable compounds, as well as thermoplastic resins and thermosetting resins, and these can also be used in combination.

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

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

Examples of thermosetting resins include epoxy resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, and their copolymers and modified products. When using a thermosetting resin, a photopolymerizable compound having a silicone skeleton is cured with ultraviolet light, and then appropriately heated to harden the thermosetting resin and form an anisotropic light-diffusing film.

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

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

The photoinitiator for the cationic polymerizable compound is a compound that generates an acid when irradiated with light and can polymerize the above-mentioned cationic polymerizable compound using the generated acid. In general, onium salts and metallocene complexes are preferably used.

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

The photoinitiator is preferably blended in an amount of about 0.01 to 10 parts by mass, more preferably about 0.1 to 7 parts by mass, and even more preferably about 0.1 to 5 parts by mass, per 100 parts by mass of the photopolymerizable compound. This is because if it is less than 0.01 parts by mass, the photocurability decreases, and if it is blended in more than 10 parts by mass, only the surface will harden and the internal curability will decrease, which will lead to coloring and inhibition of the formation of columnar structures.

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

Furthermore, a heat-curing initiator capable of curing the photopolymerizable compound by heating can be used together with the photoinitiator. In this case, it is expected that the polymerization and curing of the photopolymerizable compound can be further promoted and completed by heating after photocuring. An anisotropic light-diffusing film can be formed by curing a single photopolymerizable compound or a composition in which multiple photopolymerizable compounds are mixed.

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

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

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

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

When silicone urethane (meth)acrylate is used as a photopolymerizable compound with a silicone skeleton, compatibility with compounds that do not have a silicone skeleton is improved. This makes it possible to tilt the columnar regions even when the material mixing ratio is wide.

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

<<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-mentioned composition for anisotropic light-diffusing films (hereinafter sometimes referred to as "photocurable resin composition") is applied to a suitable substrate such as a transparent PET film to form a sheet, which is then dried as necessary to volatilize the solvent to provide an uncured resin composition layer. An anisotropic light-diffusing film can be produced by irradiating light onto this uncured resin composition layer.

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

<Step 1-1: Step of Providing Uncured Resin Composition Layer on Substrate>
The photocurable resin composition is provided on the substrate in the form of a sheet as an uncured resin composition layer by a normal coating method or printing method.Specifically, coating such as air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, calendar coating, dam coating, dip coating, die coating, intaglio printing such as gravure printing, stencil printing such as screen printing, etc. can be used.When the composition has a low viscosity, a dam of a certain height can be provided around the substrate, and the composition can be cast into the area surrounded by the dam.

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 anisotropic light-diffusing films, it is also possible to laminate a mask that adheres closely to the light-irradiated side of the uncured resin composition layer and locally changes the light irradiation intensity.

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

When such a mask is not used, it is also possible to prevent oxygen inhibition of the uncured resin composition layer by performing light irradiation under a nitrogen atmosphere. In addition, simply laminating a normal transparent film on the uncured resin composition layer is also effective in preventing oxygen inhibition and promoting the formation of columnar regions. When light is irradiated through such a mask or transparent film, a photopolymerization reaction occurs in the photocurable resin composition according to the irradiation intensity, which makes it easy to generate a refractive index distribution, and is effective in producing the anisotropic light-diffusing film of this embodiment.

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

<Optional step 1-3: Step of obtaining a directional light beam>
Optional step 1-3 is a step of making parallel light incident on a directional diffusion element to obtain a directional light beam. Fig. 9 is a schematic diagram showing a method for producing an anisotropic light-diffusing film in optional step 1-3 according to the present invention.

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

Figure 9 shows that directional light E is incident on the uncured resin composition layer 303 in a state where it is diffused mostly in the X direction and hardly at all in the Y direction. In order to obtain such directional light, for example, a method can be adopted in which needle-shaped fillers with a high aspect ratio are contained in the directional diffusion elements 301 and 302 and the needle-shaped fillers are oriented so that their major axis direction extends in the Y direction. Various methods can be used for the directional diffusion elements 301 and 302 in addition to the method using needle-shaped fillers.

Here, the aspect ratio of the directional light E is preferably 2 to 20. A columnar region having an aspect ratio roughly 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, there is a risk of interference rainbows and glare.

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

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

<Step 1-4: Step of curing the uncured resin composition layer>
The light irradiated to the uncured resin composition layer to cure the uncured resin composition layer must contain a wavelength capable of curing the photopolymerizable compound, and light with a wavelength centered at 365 nm from a mercury lamp is usually used. When using this wavelength band to produce an anisotropic light-diffusing film, the illuminance is preferably in the range of 0.01 mW/cm ² to 100 mW/cm ² , and more preferably 0.1 mW/cm ² to 20 mW/cm ^2. If the illuminance is less than 0.01 mW/cm ² , it takes a long time to cure, resulting in poor production efficiency, and if it exceeds 100 mW/cm ² , the curing of the photopolymerizable compound is too fast to form a structure, making it impossible to express the desired optical properties.

The light irradiation time is not particularly limited, but is preferably 10 to 180 seconds, and more preferably 30 to 120 seconds. By irradiating the light beam, the anisotropic light diffusion film of this embodiment can be obtained.

As described above, the anisotropic light diffusion film is obtained by forming a specific internal structure in the uncured resin composition layer by irradiating low-intensity light for a relatively long time. Therefore, such light irradiation alone may leave unreacted monomer components, causing stickiness and problems in handling and durability. In such cases, the remaining monomers can be polymerized by additionally irradiating high-intensity light of 1000 mW/cm2 or ^more . The light irradiation at this time may be performed from the opposite side to the side where the mask is laminated.

As described above, when curing the uncured resin composition layer, the angle of light irradiated onto the uncured resin composition layer can be adjusted to obtain the desired scattering central axis of the resulting anisotropic light-diffusing film.

<<<<<Applications of anisotropic light-diffusing film laminates>>>>
The anisotropic light-diffusing film laminate has an excellent effect of improving the viewing angle dependency, and therefore can be applied to all kinds of displays such as liquid crystal displays, organic EL displays, and plasma displays. The anisotropic light-diffusing film laminate can be particularly preferably used in TN-type liquid crystal displays that are prone to problems with viewing angle dependency. In this case, in order to achieve an excellent effect of improving the viewing angle dependency, it is preferable that the anisotropic light-diffusing film b is laminated 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-diffusing film laminate. In this case, the anisotropic light-diffusing film laminate is provided (laminated) on the viewing side of the liquid crystal layer. The liquid crystal display device may be any of the TN type, VA type, IPS type, etc. More specifically, a typical liquid crystal device has a layer structure in which 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 are laminated in this order from the display device toward the viewing side, and further has an appropriate functional layer, but the anisotropic light-diffusing film laminate may be provided at any location on the viewing side of the liquid phase layer.

According to the present invention, it is also possible to provide an organic EL display device including a light-emitting layer and an anisotropic light-diffusing film 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 of the top emission type and bottom emission type, and in the case of a color organic EL display device, it may be of any of the RGB coloring type and color filter type. The organic EL display may also be further multi-layered.

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

<<Anisotropic Optical Film>>
A partition wall having a height of 30 to 60 μm was formed with a curable resin using a dispenser around the entire edge of a 100 μm thick PET film (manufactured by Toyobo Co., Ltd., product name: A4300). The following ultraviolet curable resin composition was dropped into this to form a liquid film having a thickness of 30 μm to 60 μm, and this 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, product name: 00-225/TM18)
Neopentyl glycol diacrylate (refractive index: 1.450) 30 parts by weight
(Manufactured by Daicel Cytec, product name Ebecryl 145)
Bisphenol A EO adduct diacrylate (manufactured by Daicel Cytec, product name Ebecryl 150, refractive index: 1.536) 15 parts by weight Phenoxyethyl acrylate (manufactured by Kyoeisha Chemical, product name: Light Acrylate PO-A, refractive index 1.518) 40 parts by weight 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF, product name: Irgacure 651) 4 parts by weight

The liquid film sandwiched between PET films on both sides was irradiated with parallel ultraviolet light having an intensity of 10 mW/cm ² to 100 mW/cm ² from an epi-illumination unit of a UV spot light source (manufactured by Hamamatsu Photonics, product name: L2859-01) either directly or through a PMMA lens.
In the case of irradiation through a PMMA lens, the aspect ratio of the columnar region was adjusted by spreading the parallel light beam in the horizontal direction during ultraviolet irradiation using the PMMA lens.
Furthermore, by adjusting the liquid film temperature, irradiation angle, etc. when irradiating parallel light or parallel light spread in the horizontal direction, the maximum linear transmittance in the inclination direction, scattering central axis angle, and haze value of the anisotropic light-diffusing film were adjusted.
By adjusting the parameters as described above, anisotropic light-diffusing films 1 to 15 having the optical properties shown in Table 1 were obtained.

<Measurement of thickness of anisotropic light-diffusing film>
The anisotropic light-diffusing film obtained in the examples was measured using a micrometer (manufactured by Mitutoyo Corporation). The average value of the measurements taken at five points including the four corners and one point near the center of the plane of the anisotropic light-diffusing film was taken as the thickness of the anisotropic light-diffusing film.

<Measurement of the Angle of the Scattering Axis and the Linear Transmittance of the Anisotropic Light Diffusion Film>
The linear transmittance of the anisotropic light-diffusing film obtained in the examples was measured using a variable angle goniophotometer (manufactured by Genesia) that can arbitrarily change the projection angle of the light source 1 and the reception angle of the detector 2 as shown in Figure 6.
A detector 2 was fixed at a position where it received a linear light I from a fixed light source 1, and the anisotropic light-diffusing film obtained in the example was set in the sample holder between them. At that time, it was set so that the TD direction shown in Fig. 3 was the linear direction of the line V shown in Fig. 6 (this line V is a line on the anisotropic light-diffusing film perpendicular to the tilt direction of the scattering central axis).
Next, the anisotropic light-diffusing film was rotated about the axis of line V to measure the amount of linear transmitted light that passed straight through the anisotropic light-diffusing film and entered the detector 2. Thereafter, the linear transmittance was calculated from the amount of linear transmitted light, and the linear transmittance was plotted for each angle to create an optical profile.
The linear transmittance was measured at wavelengths 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 scattering central axis angle were determined from the approximate center part (center part of the diffusion region) sandwiched between the minimum values in the optical profile.

<Measurement of the aspect ratio of columnar structures (surface observation of anisotropic light-diffusing film)>
The cross section perpendicular to the column axis of the columnar region on the surface of the anisotropic light-diffusing film obtained in the examples (the side of the light irradiated during ultraviolet irradiation) was observed with an optical microscope, and the major axis LA and minor axis SA of the columnar region were measured. The average major axis LA and the average minor axis SA were calculated as the average values of 20 arbitrary columnar regions. In addition, the average major axis LA/average minor axis SA was calculated as the aspect ratio for the average major axis LA and the average minor axis SA.

<Measurement of Haze of Anisotropic Light Diffusion Film>
The haze value of the anisotropic light-diffusing film obtained in the examples was measured using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

<<Anisotropic Light Diffusion Film Laminate>>
An anisotropic light-diffusing film laminate was produced by the method described below.

Example 1
The anisotropic light-diffusing film 1 and the anisotropic light-diffusing film 2 obtained in the examples were cut into rectangular shapes so that the long side direction coincided with the scattering central axis direction of the anisotropic light-diffusing film, and then laminated via an adhesive layer of a transparent adhesive made of an acrylic resin such that the angle (φ _ab ) between the scattering central axis directions of the anisotropic light-diffusing film 1 and the anisotropic light-diffusing film 2 was the target value of 0° shown in Table 2, thereby obtaining an anisotropic light-diffusing film laminate 1 of Example 1. Furthermore, as shown in Table 2, the actual value of φ _ab measured with a measuring microscope after lamination was 1°.
As shown in Table 2, the anisotropic light-diffusing film 2 was designated as anisotropic light-diffusing film a, and the anisotropic light-diffusing film 1 was designated as anisotropic light-diffusing film b.

<Examples 2 to 7, Comparative Examples 1 to 8>
The two types of anisotropic light _- diffusing films used were laminated in the same manner as in Example 1, except that they were laminated via an adhesive layer of a transparent adhesive made of an acrylic resin in accordance with the combinations shown in Table 2 so that φ ab was the target value shown in Table 2, to obtain anisotropic light-diffusing film laminates 2 to 15 of Examples 2 to 7 and Comparative Examples 1 to 8. The φ _ab values measured with a measuring microscope after lamination of each anisotropic light-diffusing film are shown in Table 2.

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

<Measurement of Haze Value of Anisotropic Light-Diffusing Film Laminate>
The haze value of the anisotropic light-diffusing film laminate obtained in each example was measured using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

<Measurement of In-Line Transmittance of Anisotropic Light-Diffusing Film Laminate>
The linear transmittance of the anisotropic light-diffusing film laminates obtained in the examples and comparative examples was measured using a variable angle goniophotometer (manufactured by Genesia) that can arbitrarily change the projection angle of the light source 1 and the reception angle of the detector 2 as shown in Figure 6.
A detector 2 was fixed at a position where it received linear light I from a fixed light source 1, and the anisotropic light-diffusing film laminates obtained in the Examples and Comparative Examples were set in a sample holder between them. At that time, the anisotropic light-diffusing film on the viewing side of the anisotropic light-diffusing film laminate was set so that the MD direction shown in Fig. 3 was aligned with the straight line V shown in Fig. 6 (this straight line V is a line on the anisotropic light-diffusing film laminate perpendicular to the tilt direction of the scattering central axis).
Next, the anisotropic light-diffusing film laminate was rotated about the axis of line V to measure the amount of linear transmitted light that passed straight through the anisotropic light-diffusing film laminate and entered the detector 2. Thereafter, the linear transmittance was calculated from the amount of linear transmitted light, and the linear transmittance was plotted for each angle to create an optical profile.
The linear transmittance was measured at wavelengths 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° were determined.

<Evaluation of contrast and tone inversion>
The anisotropic light-diffusing film laminates of the examples and comparative examples were attached to the surface of a TN mode liquid crystal display so that the angle between the orientation relative to the direction in which tone inversion occurs in the liquid crystal display and the orientation relative to the tilt direction of the scattering center axis of the anisotropic light-diffusing film a was 0°.
Next, a viewing angle measuring device Conometer 80 (manufactured by Westboro) was used to measure the luminance distribution in the polar angle range of 0 to 80° relative to the normal direction of the display when a gray scale divided into 11 gradations from white to black was displayed on the liquid crystal display screen.
Here, the "white luminance/black luminance" was calculated at a polar angle of 75° in the direction in which the grayscale inversion occurs in the liquid crystal display alone, and this was taken as the contrast. In addition, the minimum polar angle at which the 11 grayscales measured above are reversed from the original grayscales in the direction in which the grayscale inversion occurs in the liquid crystal display alone was taken as the grayscale inversion angle. This is summarized in Table 3.
Here, when the display alone was evaluated without the anisotropic light-diffusing film laminate attached, the contrast was 8.0 and the tone inversion angle was 28°.

<Evaluation of visibility clarity>
The anisotropic light-diffusing film laminates of the examples and comparative examples were attached to the surface of a TN mode liquid crystal display so that the angle between the orientation in the direction in which tone inversion occurs on the liquid crystal display and the orientation relative to the inclination direction of the scattering central axis of the anisotropic light-diffusing film a was 0°.
Next, when a white screen was displayed on the display using a scale magnifying glass, the visibility and clarity of the color filter was visually evaluated.
Regarding visual clarity, when the vertical and horizontal boundaries of the color filter matrix were distinguishable, it was rated 4, when only the boundary in one direction was distinguishable, it was rated 3, when the boundary was indistinguishable, it was rated 2, and when the color filter was indistinguishable, it was rated 1. These are summarized in Table 3.
Here, the visual clarity was evaluated as 4 when the display alone was evaluated without the anisotropic light-diffusing film laminate attached.

<Contrast evaluation criteria at 75° polar angle>
A contrast of 18 or more was rated as ⊚, 14 or more but less than 18 as ◯, and less than 14 as x.

<Criteria for determining tone inversion>
The tone inversion angle was rated as ⊚ when it was more than 80° and not more than 90°, ◯ when it was 75° to 80°, and x when it was less than 75°.

<Criteria for determining visibility clarity>
In the above evaluation method, 4 was rated as ⊚, 3 was rated as ○, and less than 2 was rated as ×.

<<Evaluation Results>>
As can be seen from Table 3, the liquid crystal displays using the anisotropic light-diffusing film laminates of Examples 1 to 7 were superior in overall evaluation, including contrast, tone inversion, and visual clarity, to the liquid crystal displays using the anisotropic light-diffusing film laminates of Comparative Examples 1 to 8. In particular, Example 1 was the most excellent, with all evaluations being "◎".
It is believed that Comparative Examples 1 and 2 had low haze values, which resulted in low diffusion and low contrast at 75°.
It is believed that Comparative Examples 3 to 6 had a high haze value, which adversely affected the visual clarity.
In Comparative Example 7, it is believed that the aspect ratio of one anisotropic light-diffusing film was large, which resulted in reduced diffusivity in the inclined direction and low contrast at 75°.
In Comparative Example 8, the angle (φ _ab ) between the directions of the scattering central axes of the anisotropic light-diffusing films a and b was large, which is thought to be the reason for the low diffusivity and low contrast at 75°.

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 grayscale inversion, improve contrast at deep angles, and suppress a decrease in image visibility clarity in the front direction. This makes it possible to achieve both visibility in directions where visibility is normally difficult and visibility in the front direction when viewed in a static state, and is expected to have a viewing angle dependency effect that is superior to conventional methods in terms of brightness and color change due to viewing angle.

Claims (9)

An anisotropic light-diffusing film laminate having a haze value of 70% to 85%, comprising only two layers laminated as an anisotropic light-diffusing film whose linear transmittance, which is (amount of transmitted light in a linear direction of incident light)/(amount of incident light), changes depending on the angle of incidence of light,
the anisotropic light-diffusing film has one scattering central axis, a matrix region, and a plurality of columnar regions having a refractive index different from that of the matrix region;
the plurality of columnar regions are oriented and extend from one surface of the anisotropic light-diffusing film to the other surface,
In the anisotropic light-diffusing film, if the first anisotropic light-diffusing film is designated as an anisotropic light-diffusing film a and the second anisotropic light-diffusing film is designated as an anisotropic light-diffusing film b,
The anisotropic light-diffusing film a and the anisotropic light-diffusing film b are laminated together directly or via a pressure-sensitive adhesive layer,
In the aspect ratio of the columnar region, the average major axis/average minor axis of the columnar region in a cross section perpendicular to the column axis of the columnar region,
the anisotropic light-diffusing film a and the anisotropic light-diffusing film b have an aspect ratio of 2 to 10 ;
If the polar angle between the normal direction of the surface of the anisotropic light-diffusing film and the scattering central axis direction is defined as the scattering central axis angle,
the scattering central axis angle of the anisotropic light-diffusing film a is 20° to 35°;
the scattering central axis angle of the anisotropic light-diffusing film b is 40° to 55°;
An anisotropic light-diffusing film laminate, characterized in that the 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-diffusing film laminate according to claim 1, characterized in that the anisotropic light-diffusing film a and the anisotropic light-diffusing film b 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 haze value of the anisotropic light-diffusing film a is 30% to 70%,
3. The anisotropic light-diffusing film laminate according to claim 1, wherein the haze value of the anisotropic light-diffusing film b is 20% to 70%. The anisotropic light-diffusing 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 laminate according to any one of claims 1 to 3, characterized in that the maximum linear transmittance of the anisotropic light-diffusing film b is 30% to 70% and the minimum linear transmittance is 6% or less. The maximum linear transmittance of the anisotropic light-diffusing film laminate is 15% to 30%,
5. The anisotropic light-diffusing 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-diffusing film laminate according to any one of claims 1 to 5,
A liquid crystal display device, comprising: the anisotropic light-diffusing film laminate laminated on a viewing side of the liquid crystal layer. The liquid crystal display device according to claim 6, characterized in that the anisotropic light-diffusing film b is laminated so as to be on the viewing side of the anisotropic light-diffusing film a. An organic EL display device comprising a light-emitting layer and the anisotropic light-diffusing film laminate according to any one of claims 1 to 5,
An organic electroluminescence display device, comprising: the anisotropic light-diffusing film laminate laminated on a viewing side of the light-emitting layer. The organic EL display device according to claim 8, characterized in that the anisotropic light-diffusing film b is laminated so as to be on the viewing side of the anisotropic light-diffusing film a.

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