JP2014002187A - Light diffusion film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light diffusion film whose incident light diffusion area has been effectively increased by allowing incident light to diffuse not only in a longitudinal direction of the film but also in a direction orthogonal to the longitudinal direction.SOLUTION: A longitudinally extending light diffusion film has a first louver structure and a second louver structure arranged in order from the bottom in the film thickness direction. The first louver structure and the second louver structure each comprise a plurality of tabular regions, each having a different refractive index, which are arranged alternately in parallel in an arbitrary direction along the film surface. Looking from above the film, an acute angle θ1 between an extending direction of the tabular regions in the first louver structure and an extending direction of the tabular regions in the second louver structure shall be within a range of 10 to 90 degrees.

Description

The present invention relates to a light diffusion film.
In particular, the present invention relates to a light diffusing film that effectively spreads the diffusion area of incident light by diffusing incident light not only in the direction along the longitudinal direction but also in the direction perpendicular to the longitudinal direction.

  2. Description of the Related Art Conventionally, for example, in the optical technical field to which a liquid crystal display device or the like belongs, light that can be diffused in a specific direction for incident light from a specific direction and transmitted straight as it is for incident light from other directions. The use of diffusion films has been proposed.

  Various forms are known as such a light diffusion film, and in particular, a louver formed by alternately arranging a plurality of plate-like regions having different refractive indexes along any one direction along the film surface. A light diffusion film having a structure is widely used (for example, Patent Documents 1 and 2).

That is, Patent Document 1 discloses a light control plate (light diffusion film) that is a plastic sheet and selectively scatters incident light in two or more angular ranges with respect to the sheet. ing.
In Patent Document 1, a resin composition composed of a plurality of compounds having one or more polymerizable carbon-carbon double bonds in a molecule having a difference in refractive index is maintained in a film shape and specified. A first step of curing the composition by irradiating ultraviolet rays from the direction of the step, and irradiating ultraviolet rays from a direction different from the first step while maintaining the resin composition on the obtained cured product as a film. The manufacturing method of the light control board (light diffusion film) characterized by consisting of the 2nd process hardened in this and repeating a 2nd process as needed is disclosed.

  Further, in Patent Document 2, the haze value has an angle dependency, and when light is incident on the surface at an angle of 0 to 180 °, a light scattering angle region (a haze value of 60% or more) A projection screen comprising a plurality of light control films (light diffusion films) having a light diffusion incident angle region) of 30 ° or more, as shown in FIGS. As described above, two of the plurality of light control films (light diffusion films) are laminated so that the directions of the light scattering angle region (light diffusion incident angle region) are substantially orthogonal to each other. A screen is disclosed.

JP 63-309902 A (Claims) Japanese Patent Laying-Open No. 2005-316354 (Claims)

However, in Patent Document 1, when mass-producing a light diffusion film continuously, a linear light source is applied to the application layer while moving the application layer made of the composition for light diffusion film on a conveyor or the like. By irradiating with active energy rays, a light diffusion film having a predetermined louver structure is produced.
Furthermore, in the case of Patent Document 1, although it is possible to obtain a light diffusion film that diffuses incident light in the moving direction of the coating layer, that is, the direction along the longitudinal direction of the film, There was a problem that it was not possible to obtain a light diffusion film that diffused light in a direction perpendicular to the direction.

More specifically, in order to obtain a light diffusion film that diffuses incident light in a direction perpendicular to the longitudinal direction of the film, a louver structure consisting of a plate-like region extending in the longitudinal direction of the film is formed. There is a need to.
For this reason, when it is going to form such a louver structure in patent document 1, a linear light source will be arrange | positioned so that the long-axis direction of a linear light source may become the direction along the moving direction of a coating layer.
However, even if the linear light source is arranged in such a manner, when viewed from the cross section in the moving direction of the coating layer, the active energy rays from the linear light source are irradiated at different angles depending on the position in the width direction on the surface of the coating layer. Therefore, the light diffusion characteristics of the obtained light diffusion film become non-uniform.
Therefore, in Patent Document 1, when obtaining an elongated light diffusion film that diffuses incident light in a direction perpendicular to the longitudinal direction, first, when the film is viewed from above, the width direction It is necessary to obtain a light diffusing film having a louver structure in which plate-like regions are arranged along. Next, it is necessary to cut them and change the 90 ° direction to connect the plurality of light diffusion films. For this reason, the problem that the light diffusibility became non-uniform | heterogenous in the joint part, or the intensity | strength of a film fell easily was seen.
Patent Document 1 substantially discloses the extending direction of the plate-like region in the louver structure obtained in the first step and the extending direction of the plate-like region in the louver structure obtained in the second step. Are basically parallel in the width direction of the film.
For this reason, although incident light diffuses in the direction along the longitudinal direction, it is fundamentally impossible to diffuse the light in the direction orthogonal to the longitudinal direction. It was observed.

On the other hand, in Patent Document 2, as shown in FIGS. 24A to 24B, two of the plurality of light diffusion films are laminated so that the directions of the light diffusion incident angle regions are almost orthogonal to each other. Therefore, it seems that incident light can be diffused not only in the direction along the longitudinal direction but also in the direction orthogonal to the longitudinal direction.
However, even in the case of Patent Document 2, when mass-producing a light diffusion film continuously, a linear light source is used while moving a coating layer made of the composition for light diffusion film on a conveyor or the like. Active energy rays will be irradiated.
Therefore, it is difficult to obtain a light diffusion film 221 that diffuses incident light in a direction orthogonal to the longitudinal direction of the film as shown in FIG. It becomes.
Therefore, after all, even the light diffusion film disclosed in Patent Document 2 is shown in FIG.
When trying to obtain a long light diffusion film 221 that diffuses incident light as shown in a) in a direction orthogonal to the long direction, it is necessary to connect a plurality of light diffusion films. As in the case of Patent Document 1, the light diffusibility becomes non-uniform at the joint, or the strength of the film tends to decrease.
For this reason, there is a problem that the diffusion area of incident light cannot be effectively expanded by diffusing the incident light not only in the direction along the longitudinal direction but also in the direction perpendicular to the longitudinal direction. It was.
Under such circumstances, there has been a demand for a long light diffusing film that can be easily provided on a large-screen screen or the like and does not cause problems such as seams.
That is, a long light diffusion film that effectively spreads the diffusion area of incident light by diffusing incident light not only in the direction along the long direction but also in the direction perpendicular to the long direction. Was demanded.

Accordingly, the inventors of the present invention made extensive efforts in view of the above circumstances, and as a result of carrying out a predetermined manufacturing method, the extending direction of the plate-like region in the first louver structure, and the second The present inventors have found that a long light diffusion film obtained by intersecting the extending direction of the plate-like region in the louver structure at a predetermined angle can be obtained, and the present invention has been completed.
That is, the object of the present invention is to have a predetermined louver structure so that incident light is diffused not only in the direction along the longitudinal direction but also in the direction perpendicular to the longitudinal direction. An object of the present invention is to provide a light diffusion film in which the light diffusion area is effectively expanded.

According to the present invention, a long light diffusion film having a first louver structure and a second louver structure sequentially from below along the film thickness direction, the first louver structure and the second louver structure. The louver structure is composed of a plurality of plate-like regions each having a different refractive index, and a plurality of plate-like regions having different refractive indexes are alternately arranged in parallel in any one direction along the film surface. And when viewed from above the film, the acute angle θ1 formed by the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure is 10 to 90 °. A light diffusion film characterized by having a value within the range is provided, and the above-described problems can be solved.
That is, in the light diffusing film of the present invention, the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure are crossed at a predetermined angle. Therefore, the diffusion area of the incident light can be effectively expanded by diffusing the incident light not only in the direction along the longitudinal direction but also in the direction orthogonal to the longitudinal direction.

In constructing the light diffusion film of the present invention, when viewed from above the film, the acute angle θ2 formed by the extending direction of the plate-like region in the first louver structure and the longitudinal direction of the film is 10-80. A value within the range of °, and when viewed from above the film, the acute angle θ3 formed by the extending direction of the plate-like region in the second louver structure and the longitudinal direction of the film is in the range of 10 to 80 °. It is preferable to set the value within the range.
By comprising in this way, the diffusion area of incident light can be expanded more effectively.

Further, in configuring the light diffusion film of the present invention, when viewed from above the film, the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure are: It is preferable that the line is symmetrical with respect to a virtual line orthogonal to the longitudinal direction of the film.
With this configuration, incident light can be diffused more uniformly.

Moreover, in comprising the light-diffusion film of this invention, while making the length of the short direction in a light-diffusion film into the value within the range of 0.1-3 m, let the length of a long direction be a value of 3 m or more. It is preferable.
By comprising in this way, the elongate and the large area light-diffusion film which expanded the diffusion area of incident light effectively can be obtained.

Moreover, when comprising the light-diffusion film of this invention, it is preferable to be wound by roll shape.
By comprising in this way, the elongate and the larger area light-diffusion film which effectively extended the diffusion area of incident light can be obtained.

Further, in configuring the light diffusion film of the present invention, it is preferable that the thicknesses of the first louver structure and the second louver structure are each in the range of 50 to 500 μm.
With such a configuration, the diffusion area of incident light can be further effectively increased.

Further, in configuring the light diffusion film of the present invention, it is preferable that the widths of the plate-like regions in the first louver structure and the second louver structure are set to values in the range of 0.1 to 15 μm, respectively.
With this configuration, the diffusion area of incident light can be more effectively expanded.

In constituting the light diffusing film of the present invention, the raw material of the diffusing film is preferably a composition for a light diffusing film containing two polymerizable compounds having different refractive indexes.
With this configuration, the diffusion area of incident light can be further effectively increased.

Fig.1 (a)-(b) is a figure provided in order to demonstrate the outline of the louver structure in a light-diffusion film. FIGS. 2A to 2B are diagrams for explaining incident angle dependency, anisotropy, and an opening angle in a light diffusion film. FIGS. 3A to 3C are diagrams provided to explain the basic configuration of the light diffusion film of the present invention. FIGS. 4A and 4B are diagrams for explaining the louver structure. FIG. 5A to FIG. 5C are diagrams for explaining the extending direction of the plate-like region. FIGS. 6A to 6B are diagrams provided for explaining the shape of the long light diffusion film. FIGS. 7A to 7E are diagrams for explaining the relationship between the extending direction of the plate-like region and the diffusion area of incident light. FIGS. 8A to 8E are photographs provided to explain the relationship between the extending direction of the plate-like region and the diffusion area of incident light. FIGS. 9A to 9D are diagrams provided to explain each step in the method for producing a light diffusion film of the present invention. FIGS. 10A and 10B are diagrams provided to explain active energy ray irradiation using a linear light source. FIGS. 11A to 11B are diagrams provided to explain the arrangement angle of the linear light source. FIG. 12 is another diagram provided for explaining active energy ray irradiation using a linear light source. FIG. 13 is a diagram provided for explaining the configuration of the long light diffusion film of Example 1. FIG. FIGS. 14A to 14B are photographs provided to explain the state of the cross section of the long light diffusion film of Example 1. FIG. FIGS. 15A to 15B are diagrams provided for explaining the light diffusion characteristics of the long light diffusion film of Example 1. FIG. FIGS. 16A to 16C are diagrams provided to explain the configuration of the first coating layer on which the first louver structure in Reference Example 1 is formed. FIG. 17 is a diagram provided for explaining the configuration of the long light diffusion film of Reference Example 1. FIGS. 18A to 18B are photographs provided to explain the state of the cross section of the long light diffusion film of Reference Example 1. FIG. FIGS. 19A to 19B are a spectrum diagram and a photograph provided for explaining the light diffusion characteristics in the non-seam portion of the long light diffusion film of Reference Example 1. FIG. 20A to 20B are a spectrum diagram and a photograph provided for explaining the light diffusion characteristics at the joint portion of the long light diffusion film of Reference Example 1. FIG. FIG. 21 is a diagram provided for explaining the configuration of the long light diffusion film of Comparative Example 1. FIGS. 22A to 22B are photographs provided to explain the state of the cross section of the long light diffusion film of Comparative Example 1. FIG. FIGS. 23A and 23B are a spectrum diagram and a photograph provided for explaining the light diffusion characteristics of the long light diffusion film of Comparative Example 1. FIG. 24 (a) to 24 (b) are diagrams provided to explain a conventional light diffusion film.

An embodiment of the present invention is a long light diffusing film having a first louver structure and a second louver structure sequentially from below along the film thickness direction. The louver structure is composed of a plurality of plate-like regions each having a different refractive index, and a plurality of plate-like regions having different refractive indexes are alternately arranged in parallel in any one direction along the film surface. When viewed from above the film, the acute angle θ1 formed by the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure is 10 to 90 °. It is a light-diffusion film characterized by setting it as the value within the range.
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings as appropriate. In order to facilitate understanding of the description, first, the basic principle of light diffusion in a light diffusion film and the light diffusion of the present invention will be described. The basic structure of the film will be described.

1. Basic Principle of Light Diffusion in Light Diffusion Film First, the basic principle of light diffusion in the light diffusion film will be described with reference to FIGS.
First, FIG. 1A shows a top view (plan view) of the light diffusion film 10, and FIG. 1B shows the light diffusion film 10 shown in FIG. A cross-sectional view of the light diffusion film 10 when cut in the vertical direction along A and viewing the cut surface from the arrow direction is shown.
2A shows an overall view of the light diffusing film 10 having a single-layer louver structure, and FIG. 2B shows the light diffusing film 10 of FIG. 2A viewed from the X direction. FIG.
As shown in the plan view of FIG. 1A, the light diffusion film 10 has a plate-like region 12 having a relatively high refractive index and a relatively refractive index in any one direction along the film surface. A low plate-like region 14 and a louver structure 13 arranged alternately in parallel are provided.
In addition, as shown in the cross-sectional view of FIG. 1B, the relatively high refractive index plate-like region 12 and the relatively low refractive index plate-like region 14 each have a predetermined thickness. Also in the normal direction (film thickness direction) to the light diffusion film 10, the state of being alternately arranged in parallel is maintained.

Thereby, as shown to Fig.2 (a), when an incident angle is in a light diffusion incident angle area | region, it is estimated that incident light is diffused by the light-diffusion film 10. FIG.
That is, as shown in FIG. 1B, the incident angle of the incident light with respect to the light diffusion film 10 is a value within a predetermined angle range from parallel to the boundary surface 13 ′ of the louver structure 13, that is, the light diffusion incident angle. When the value is within the region, incident light (52, 54) passes through the relatively high refractive index plate-like region 12 in the louver structure along the film thickness direction while changing the direction. Thus, it is estimated that the traveling direction of light on the light exit surface side is not uniform.
As a result, when the incident angle is within the light diffusion incident angle region, it is estimated that the incident light is diffused by the light diffusion film 10 (52 ′, 54 ′).
On the other hand, when the incident angle of the incident light with respect to the light diffusion film 10 deviates from the light diffusion incident angle region, the incident light 56 is not diffused by the light diffusion film as shown in FIG. It is estimated that the light diffusing film 10 is transmitted as it is (56 ').
In the present invention, the “light diffusion incident angle region” refers to the angle of incident light corresponding to emitting diffused light when the angle of incident light from a point light source is changed with respect to the light diffusing film. Means range.
Further, as shown in FIG. 2A, the “light diffusion incident angle region” is an angle region determined for each light diffusion film depending on a refractive index difference or an inclination angle of the louver structure in the light diffusion film. is there.

Based on the above basic principle, the light diffusing film 10 provided with the louver structure 13 can exhibit incident angle dependency in light transmission and diffusion, for example, as shown in FIG.
Moreover, as shown in FIGS. 1-2, the light-diffusion film which has the single louver structure 13 will have "anisotropy" normally.
Here, in the present invention, “anisotropy” means, as shown in FIG. 2 (a), when incident light is diffused by the film, in the plane parallel to the film in the diffused emitted light, It means that the diffusion state of the light (the shape of the spread of the diffused light) has different properties depending on the direction in the same plane.
More specifically, as shown in FIG. 2 (a), the component perpendicular to the direction of the louver structure extending along one arbitrary direction along the film surface is selected from the components included in the incident light. On the other hand, while light diffusion occurs, it is presumed that anisotropic light diffusion is realized because light diffusion hardly occurs with respect to a component parallel to the direction of the louver structure included in incident light.
Therefore, the shape of the spread of the diffused light in the light diffusion film having anisotropy is substantially elliptical as shown in FIG.

Further, as described above, the incident light component contributing to the light diffusion is a component perpendicular to the direction of the louver structure mainly extending along any one direction along the film surface. In the present invention, the “incident angle θ4” of incident light means an incident angle of a component perpendicular to the direction of the louver structure extending along any one direction along the film surface. Shall. At this time, the incident angle θ4 means an angle (°) when the angle with respect to the normal to the incident side surface of the light diffusion film is 0 °.
In the present invention, the “light diffusion angle region” means an angle range of diffused light obtained by fixing a point light source at an angle at which incident light is most diffused with respect to the light diffusion film. Shall.
Furthermore, in the present invention, the “diffuse light opening angle” is the width of the “light diffusion angle region” described above, and, as shown in FIG. 2B, along any one direction along the film surface. The opening angle θ5 of the diffused light when the section of the film is viewed from the direction X parallel to the direction of the extending louver structure.

In addition, as shown in FIG. 2 (a), the light diffusing film has an incident angle of incident light included in the light diffusing incident angle region. Almost the same light diffusion can be achieved.
Therefore, it can be said that the obtained light-diffusion film has the condensing effect | action which concentrates light on a predetermined location.
In addition, the direction change of the incident light inside the high refractive index region 12 in the louver structure is a step index type in which the direction changes linearly and zigzag by total reflection as shown in FIG. A gradient index type in which the direction changes in a curved shape is also conceivable.
Further, in FIGS. 1A and 1B, the interface between the plate-like region 12 having a relatively high refractive index and the region 14 having a relatively low refractive index is represented by a straight line for simplicity. Actually, the interface is slightly meandering, and each plate-like region forms a complex refractive index distribution structure with branching and disappearance.
As a result, it is presumed that the non-uniform distribution of optical characteristics increases the light diffusibility.

2. Basic Configuration Next, the basic configuration of the light diffusion film of the present invention will be described with reference to FIG.
That is, as shown in FIG. 3 (c), the light diffusing film 20 of the present invention has the first louver structure 13a shown in FIG. 3 (a) and the second louver structure 13b shown in FIG. It is characterized by having sequentially from the bottom along the film thickness direction.
Furthermore, the extending direction of the plate-like region in the first louver structure 13a shown in FIG. 3A is different from the extending direction of the plate-like region in the second louver structure 13b shown in FIG. When viewed from above the film, they intersect.
Therefore, if it is the light-diffusion film 20 of this invention, the light which injected with respect to the film will first be diffused anisotropically by the 2nd louver structure 13b, for example, as shown to Fig.3 (a).
Next, the anisotropic light diffused by the second louver structure 13b is further diffused by the first louver structure 13a in a direction different from that of the second louver structure 13b as shown in FIG. 3B. Will diffuse.
As a result, as shown in FIG. 3C, the light incident on the light diffusion film 20 of the present invention is diffused into a square shape, and the diffusion area of incident light can be effectively expanded. .
In addition, the "downward" mentioned above means the side close | similar to the process sheet | seat in the film thickness direction of a coating layer, when a coating layer is provided on the process sheet | seat. Therefore, it is a convenient term for describing the present invention, and does not restrict the vertical direction of the light diffusion film itself.
In addition, as shown in FIG. 3C, the “diffused area of incident light” means a plane parallel to the film at a predetermined distance from the film in the diffused emitted light when the incident light is diffused by the film. It means the area where diffused light is distributed.
Hereinafter, the light diffusion film according to this embodiment will be described in detail.

3. First louver structure (1) Refractive index In the first louver structure, a difference in refractive index between plate-like regions having different refractive indexes, that is, a refractive index of a plate-like region having a relatively high refractive index, and a relative In particular, the difference from the refractive index of the plate-like region having a low refractive index is preferably set to a value of 0.01 or more.
This is because, by setting the difference in refractive index to a value of 0.01 or more, incident light is stably reflected in the first louver structure, and the incident angle dependency derived from the first louver structure. It is because it can improve more.
More specifically, when the difference in refractive index is less than 0.01, the angle range at which incident light is totally reflected in the first louver structure is narrowed, and the incident angle dependency is excessively reduced. It is because there is a case to do.
Accordingly, the difference in refractive index between the plate-like regions having different refractive indexes in the first louver structure is more preferably 0.05 or more, and further preferably 0.1 or more.
The difference between the refractive index of the high refractive index plate-like region and the refractive index of the low refractive index plate-like region is preferably as large as possible. However, from the viewpoint of selecting a material capable of forming the first louver structure, 0.3 is preferable. The degree is considered the upper limit.

In the first louver structure, the refractive index of the plate-like region having a relatively high refractive index is preferably set to a value in the range of 1.5 to 1.7.
The reason for this is that when the refractive index of the high refractive index plate-like region is less than 1.5, the difference from the low refractive index plate-like region becomes too small, making it difficult to obtain a desired louver structure. Because there is. On the other hand, when the refractive index of the high refractive index plate-shaped region exceeds 1.7, the compatibility between the material substances in the composition for light diffusion film may be excessively lowered.
Therefore, it is more preferable to set the refractive index of the high refractive index plate-like region in the first louver structure to a value in the range of 1.52 to 1.65, and a value in the range of 1.55 to 1.6. More preferably.
In addition, the refractive index of a high refractive index plate-shaped area | region can be measured according to JISK0062, for example.

In the first louver structure, the refractive index of the plate-like region having a relatively low refractive index is preferably set to a value in the range of 1.4 to 1.5.
The reason for this is that when the refractive index of the low refractive index plate-like region is less than 1.4, the rigidity of the obtained light diffusion film may be lowered. On the other hand, when the refractive index of the low refractive index plate-like region exceeds 1.5, the difference from the refractive index of the high refractive index plate-like region becomes too small, and it is difficult to obtain a desired louver structure. This is because it may become.
Therefore, it is more preferable to set the refractive index of the low refractive index plate-like region in the first louver structure to a value in the range of 1.42 to 1.48, and to a value in the range of 1.44 to 1.46. More preferably.
In addition, the refractive index in a low refractive index plate-shaped area | region can be measured according to JISK0062, for example.

(2) Width As shown in FIG. 4A, in the first louver structure 13a, the widths (S1, S2) of the high refractive index plate-like region 12 and the low refractive index plate-like region 14 having different refractive indexes. Is preferably set to a value in the range of 0.1 to 15 μm.
The reason for this is that the width of these plate-like regions is set to a value in the range of 0.1 to 15 μm so that incident light is more stably reflected in the first louver structure, and the first louver structure. This is because the incident angle dependency derived from can be improved more effectively.
That is, if the width of the plate-like region is a value less than 0.1 μm, it may be difficult to show light diffusion regardless of the incident angle of incident light. On the other hand, when the width exceeds 15 μm, the light traveling straight in the first louver structure increases, and the uniformity of the diffused light may deteriorate.
Therefore, in the first louver structure, the width of the plate-like regions having different refractive indexes is more preferably set to a value in the range of 0.5 to 10 μm, and the value in the range of 1 to 5 μm. Further preferred.
In addition, the width | variety, length, etc. of the plate-shaped area | region which comprises a 1st louver structure can be measured by observing a film cross section with an optical digital microscope.

(3) Inclination angle As shown in FIG. 4A, in the first louver structure, a plurality of high-refractive index plate-like regions 12 and a plurality of low-refractive index plate-like regions 14 having different refractive indexes are formed as films. It is preferable that they are arranged in parallel at a constant inclination angle θa with respect to the thickness direction.
The reason for this is that by making each inclination angle θa of the plate-like region constant, the incident light is more stably reflected in the first louver structure, and the incident angle dependency derived from the first louver structure. This is because the can be further improved.
Note that θa is 0 ° as the angle of the normal to the film surface measured in a cross section when the film is cut in a plane perpendicular to the first louver structure extending in one arbitrary direction along the film surface. In this case, the inclination angle (°) of the plate-like region is meant.
More specifically, as shown in FIG. 4 (a), it means the angle on the narrow side of the angle formed between the normal line of the upper end surface of the first louver structure and the uppermost part of the plate-like region. As shown in FIG. 4A, the inclination angle when the plate-like region is inclined to the right is used as a reference, and the inclination angle when the plate-like region is inclined to the left is expressed as minus.

Moreover, as shown in FIG.4 (b), it is also preferable that the plate-shaped area | region (12,14) from which the refractive index in a 1st louver structure differs is curving from upper direction to the downward direction along the film thickness direction. .
This is because the plate-like region is curved, so that the balance between reflection and transmission in the first louver structure can be complicated, and the opening angle of the diffused light can be effectively expanded.
In addition, it is thought that such a curved louver structure is obtained by delaying the polymerization reaction rate by ultraviolet rays in the thickness direction of the coating film.
Specifically, it can be formed by suppressing the illuminance of ultraviolet rays emitted from a linear light source and moving the coating film in an irradiated state at a low speed.

(4) Thickness The thickness of the first louver structure, that is, the length L1 of the first louver structure existing portion in the normal direction of the film surface shown in FIGS. A value in the range of 500 μm is preferable.
This is because the length of the first louver structure is stably secured along the film thickness direction by setting the thickness of the first louver structure to a value within this range, and the first louver structure This is because the incident light can be more stably reflected in the inside, and the uniformity of the intensity of the diffused light within the light diffusion angle region derived from the first louver structure can be further improved.
That is, when the thickness L1 of the first louver structure becomes a value of less than 50 μm, the length of the first louver structure is insufficient, and incident light that goes straight through the first louver structure increases. This is because it may be difficult to obtain the uniformity of the intensity of the diffused light within the light diffusion angle region. On the other hand, when the thickness L1 of the first louver structure exceeds 500 μm, when the first louver structure is formed by irradiating the composition for light diffusion film with active energy rays, This is because the traveling direction of photopolymerization is diffused by the formed louver structure, and it may be difficult to form a desired first louver structure.
Therefore, the thickness L1 of the first louver structure is more preferably set to a value within the range of 70 to 300 μm, and further preferably set to a value within the range of 80 to 200 μm.

(5) Extension direction As shown in FIG. 5A, when viewed from above the film, the extension direction N1 of the plate-like regions (12, 14) in the first louver structure 13a and the length of the film The acute angle θ2 formed by the direction E ′ is preferably set to a value within the range of 10 to 80 °.
This is because, by setting the extending direction of the plate-like region in the first louver structure to a value within this range, the incident light is coupled in the longitudinal direction in combination with the extending direction of the plate-like region in the second louver structure. This is because the diffusion area of incident light can be effectively expanded by diffusing light not only in the direction along the direction but also in the direction perpendicular to the longitudinal direction.
That is, when the acute angle is less than 10 °, generally, the light diffusion characteristic in the direction along the longitudinal direction of the film is excessively lowered although it depends on the extending direction of the plate-like region in the second louver structure. This is because the diffusion area of incident light may become excessively small. On the other hand, when the acute angle exceeds 80 °, generally, the light diffusion characteristics in the direction perpendicular to the longitudinal direction of the film is excessive, although it depends on the extending direction of the plate-like region in the second louver structure. This is because the diffusion area of incident light may be excessively reduced.
Therefore, when viewed from above the film, the acute angle formed by the extending direction of the plate-like region in the first louver structure and the longitudinal direction of the film is more preferably set to a value within the range of 35 to 55 °. The value is more preferably in the range of 40 to 50 °, and more preferably in the range of 44 to 46 °.

4). Second Louver Structure Since the configuration of the second louver structure is basically the same as the configuration of the first louver structure, only the following points are described to avoid duplication.
That is, as shown in FIG. 5 (b), when viewed from above the film, the extending direction N2 of the plate-like regions (12, 14) in the second louver structure 13b, the longitudinal direction E ′ of the film, It is preferable that the acute angle θ3 formed by is set to a value within the range of 10 to 80 °.
The reason for this is that, by setting the extending direction of the plate-like region in the second louver structure to a value within this range, the incident light is combined with the extending direction of the plate-like region in the first louver structure in the longitudinal direction. This is because the diffusion area of incident light can be effectively expanded by diffusing light not only in the direction along the direction but also in the direction perpendicular to the longitudinal direction.
Therefore, when viewed from above the film, the acute angle formed by the extending direction of the plate-like region in the second louver structure and the longitudinal direction of the film is more preferably set to a value within the range of 35 to 55 °. The value is more preferably in the range of 40 to 50 °, and more preferably in the range of 44 to 46 °.

5. Film thickness It is also preferable to set the film thickness of the light diffusion film to a value within the range of 50 to 500 μm.
The reason for this is that when the film thickness is less than 50 μm, the length of the louver structure in the film thickness direction formed in the film becomes excessively short, and the incident light that goes straight through the louver structure increases. This is because it may be difficult to obtain sufficient incident angle dependency. On the other hand, when the film thickness exceeds 500 μm, the irradiation light is irradiated for a long time, so that the mass productivity is excessively reduced or the irradiation light is diffused by the louver structure formed in the initial stage. This is because it may be difficult to form a desired louver structure.
Therefore, the film thickness of the light diffusion film is more preferably set to a value within the range of 70 to 300 μm, and further preferably set to a value within the range of 80 to 200 μm.
In the film thickness direction of the light diffusion film, for example, there may be a portion where the louver structure does not exist in the surface layer portion or the like.
Therefore, the film thickness of the light diffusion film is equal to or greater than the sum of the thickness of the first louver structure and the thickness of the second louver structure.

6). The shape of the film Moreover, the shape of the light-diffusion film of this invention is elongate.
More specifically, as shown in FIG. 6A, the length L2 in the short direction (width direction) of the light diffusion film 10 is preferably set to a value within the range of 0.1 to 3 m. More preferably, the value is in the range of 5 to 2 m.
On the other hand, the length in the longitudinal direction is not particularly limited.
That is, the light diffusion film of the present invention can be continuously manufactured by carrying out a manufacturing method as described later.
Accordingly, the length L3 in the longitudinal direction is preferably 3 m or more, and more preferably 15 m or more.
This is because the film has such a shape, so that the incident light can be diffused not only in the direction along the longitudinal direction but also in the direction perpendicular to the longitudinal direction. This is because a light diffusion film having a large area can be obtained.

Moreover, as shown in FIG.6 (b), it is preferable that the light-diffusion film 20 is wound by roll shape.
The reason for this is that, by forming a roll shape, a long and large-area light diffusing film capable of diffusing incident light in a direction perpendicular to the longitudinal direction or in the vicinity thereof is obtained. Because it can.
Moreover, it is because the handleability in storage and carrying can be improved.
That is, if it is a roll shape, even if it is a case where the size etc. of the display etc. which are going to apply a film are various, it can chip-cut for every required size afterwards.
Moreover, if it is a roll shape, it can bond by another film by roll-to-roll in the next process, and productivity can be improved rather than the case where a sheet-to-sheet or a sheet-to-sheet is employ | adopted.

7). Combination of Extension Direction In the light diffusion film of the present invention, as shown in FIG. 5C, the extension of the plate-like regions (12, 14) in the first louver structure 13a when viewed from above the film. The acute angle θ1 formed by the direction N1 and the extending direction N2 of the plate-like regions (12, 14) in the second louver structure 13b is set to a value in the range of 10 to 90 °.
The reason for this is that by diffusing the incident light not only in the direction along the longitudinal direction but also in the direction orthogonal to the longitudinal direction, the diffusion area of the incident light is reduced. This is because an elongated film that is effectively spread can be obtained.
That is, when the acute angle is less than 10 °, the incident light diffusion area may be excessively reduced.
Therefore, when viewed from above the film, the acute angle formed by the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure is within the range of 80 to 90 °. More preferably, the value is more preferably in the range of 85 to 90 °, and even more preferably in the range of 89 to 90 °.

5C, when viewed from above the film, the extending direction N1 of the plate-like regions (12, 14) in the first louver structure 13a and the plate-like shape in the second louver structure 13b. The extending direction N2 of the regions (12, 14) is preferably line symmetric with respect to an imaginary line E ″ that is orthogonal to the longitudinal direction E ′ of the film.
The reason for this is that the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure intersect in this manner to diffuse the incident light more uniformly. It is because it can do.
That is, particularly in the case of θ2 = 45 °, θ3 = 45 °, or when each is a peripheral value thereof, the extending direction of the plate-like region in each louver structure is made line-symmetric so that FIG. As shown in (a), the spread in the left-right direction and the spread in the vertical direction in the diffused light can be maximized.
Therefore, when such a light diffusion film is applied to a screen, the horizontal viewing angle and the vertical viewing angle can be maximized.

Here, the relationship between the extending direction of the plate-like region and the diffusion area of incident light will be described with reference to FIGS.
That is, FIGS. 7A to 7E show the first louver structure 13a on the left side and the diffusion state 50 'of light incident thereon, and the second louver structure 13b on the right side and incident thereon. A diffusion state 51 ′ of diffused light by the first louver structure 13a is shown.
First, FIG. 7A shows the degree of diffusion of incident light in the case of θ1 = 90 °, θ2 = 45 °, and θ3 = 45 °, but the final incident light diffusion area is sufficiently widened. (51 ').
On the other hand, FIG. 7B shows the degree of diffusion of incident light when θ1 = 60 °, θ2 = 30 °, and θ3 = 30 °. Compared to the case of FIG. It turns out that the light diffusion characteristic to the direction along the elongate direction E 'of this falls, and the diffusion area of incident light becomes small (51').
FIG. 7C shows the incident light diffusion in the case of θ1 = 60 °, θ2 = 60 °, and θ3 = 60 °. Compared to the case of FIG. It turns out that the light diffusion characteristic to the direction orthogonal to the elongate direction E 'falls, and the diffusion area of incident light becomes small (51').
On the other hand, FIG. 7D shows the degree of diffusion of incident light when θ1 = 30 °, θ2 = 15 °, and θ3 = 15 °. Compared to the case of FIG. It can be seen that the light diffusion characteristics in the direction along the long direction E ′ of the light source are further reduced, and the diffusion area of the incident light is further reduced (51 ′).
FIG. 7E shows the degree of diffusion of incident light when θ1 = 30 °, θ2 = 75 °, and θ3 = 75 °. Compared to the case of FIG. It can be seen that the light diffusion characteristics in the direction orthogonal to the longitudinal direction E ′ of the light source are further reduced, and the diffusion area of incident light is further reduced (51 ′).
In addition, the photograph of the diffused light corresponding to Fig.7 (a)-(e) is shown to Fig.8 (a)-(e).

8). Adhesive layer Moreover, the light-diffusion film obtained by the manufacturing method of this invention may be equipped with the adhesive layer for laminating | stacking with respect to a to-be-adhered body in the single side | surface or both surfaces.
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited, and conventionally known pressure-sensitive adhesives such as acrylic, silicone, urethane, and rubber can be used.

9. Manufacturing method Moreover, the light-diffusion film of this invention can be manufactured with the manufacturing method containing the following process (a)-(e), for example.
(A) The process of preparing the composition for light diffusion films containing two polymeric compounds from which refractive index differs (b) The composition for light diffusion films is apply | coated with respect to a process sheet | seat, and a 1st application layer is formed. Step (c) A step of forming a first louver structure by performing first active energy ray irradiation using a linear light source while moving the first coating layer with respect to the first coating layer (d) (E) Applying the composition for light diffusion film to the first coating layer on which the first louver structure is formed, to form a laminate comprising the first coating layer and the second coating layer (e) A second active energy ray is irradiated using a linear light source while moving the laminate composed of the first coating layer and the second coating layer with respect to the second coating layer, and the second louver structure is formed. The first step when the film is viewed from above. A step of setting an acute angle θ1 ′ formed by the major axis direction of the linear light source in the irradiation of sexual energy rays and the major axis direction of the linear light source in the second active energy ray irradiation to a value in the range of 10 to 90 ° or less Such a manufacturing method will be specifically described with reference to the drawings.

(1) Process (a): Preparation process of the composition for light diffusion films Process (a) is a process of preparing the predetermined composition for light diffusion films.
More specifically, it is preferably a step of mixing at least two polymerizable compounds having different refractive indexes, a photopolymerization initiator, and other additives as required.
In mixing, the mixture may be stirred as it is at room temperature. However, from the viewpoint of improving uniformity, for example, stirring is performed under a heating condition of 40 to 80 ° C. to obtain a uniform mixed solution. Is preferred.
Moreover, it is also preferable to add a dilution solvent so that it may become the desired viscosity suitable for coating.
Hereinafter, the step (a) will be described more specifically.

(1) -1 High Refractive Index Polymerizable Compound (i) Type Among two polymerizable compounds having different refractive indices, a polymerizable compound having a relatively high refractive index (hereinafter sometimes referred to as component (A)). Type) is not particularly limited, but the main component is preferably a (meth) acrylic acid ester containing a plurality of aromatic rings.
The reason for this is that by including a specific (meth) acrylic acid ester as the component (A), the polymerization rate of the component (A) is changed to a polymerizable compound having a relatively low refractive index (hereinafter referred to as (B). It is presumed that the polymerization rate between these components can be effectively reduced by making the polymerization rate faster than the polymerization rate of the component)) It is to be done.
As a result, when photocured, a so-called louver structure in which the plate-like regions derived from the component (A) and the plate-like regions derived from the component (B) extend alternately can be formed efficiently. .
In addition, by including a specific (meth) acrylic acid ester as the component (A), the monomer stage has sufficient compatibility with the component (B), but a plurality of stages in the polymerization process. Then, it is presumed that the louver structure can be formed more efficiently by reducing the compatibility with the component (B) to a predetermined range.
Furthermore, by including a specific (meth) acrylic acid ester as the component (A), the refractive index of the plate-like region derived from the component (A) in the louver structure is increased, and the plate derived from the component (B) The difference from the refractive index of the region can be adjusted to a value greater than or equal to a predetermined value.
Therefore, by including a specific (meth) acrylic acid ester as the component (A), combined with the characteristics of the component (B) described later, the louver structure in which plate-like regions having different refractive indexes are alternately extended can be efficiently used. Can get to.
In addition, "(meth) acrylic acid ester containing a plurality of aromatic rings" means a compound having a plurality of aromatic rings in the ester residue portion of (meth) acrylic acid ester.
“(Meth) acrylic acid” means both acrylic acid and methacrylic acid.

  Examples of the (meth) acrylic acid ester containing a plurality of aromatic rings as the component (A) include, for example, biphenyl (meth) acrylate, naphthyl (meth) acrylate, anthracyl (meth) acrylate, Benzylphenyl (meth) acrylate, biphenyloxyalkyl (meth) acrylate, naphthyloxyalkyl (meth) acrylate, anthracyloxyalkyl (meth) acrylate, benzylphenyloxyalkyl (meth) acrylate, or aromatic Examples thereof include those in which a part of hydrogen atoms on the ring are substituted by halogen, alkyl, alkoxy, halogenated alkyl or the like.

  Moreover, it is preferable that the (meth) acrylic acid ester containing a plurality of aromatic rings as the component (A) includes a compound containing a biphenyl ring, and particularly includes a biphenyl compound represented by the following general formula (1). It is preferable.

(In General Formula (1), R ^{1 to} R ¹⁰ are each independent, and at least one of R ^{1 to} R ¹⁰ is a substituent represented by the following General Formula (2), and the rest is hydrogen. It is a substituent of any one of an atom, a hydroxyl group, a carboxyl group, an alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxyalkyl group, a carboxyalkyl group and a halogen atom.)

(In the general formula (2), R ¹¹ is a hydrogen atom or a methyl group, the carbon number n is an integer of 1 to 4, and the repeating number m is an integer of 1 to 10.)

The reason for this is that by including a biphenyl compound having a specific structure as the component (A), a predetermined difference is caused in the polymerization rate of the component (A) and the component (B), and the component (A) and the component (B) This is because it is estimated that the compatibility between the two components can be reduced by reducing the compatibility with the component to a predetermined range.
In addition, the refractive index of the plate-like region derived from the component (A) in the louver structure is increased, and the difference from the refractive index of the plate-like region derived from the component (B) can be more easily set to a predetermined value or more. Can be adjusted.

Moreover, when R < ¹ > -R < ¹⁰ > in General formula (1) contains either an alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxyalkyl group, and a carboxyalkyl group, carbon number of the alkyl part is set. A value in the range of 1 to 4 is preferable.
The reason for this is that when the number of carbon atoms exceeds 4, the polymerization rate of the component (A) decreases, or the refractive index of the plate-like region derived from the component (A) becomes too low. This is because it may be difficult to efficiently form the structure.
Therefore, when R ^{1 to} R ¹⁰ in the general formula (1) include any of an alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxyalkyl group, and a carboxyalkyl group, the number of carbon atoms in the alkyl portion is determined. A value in the range of 1 to 3 is more preferable, and a value in the range of 1 to 2 is more preferable.

Moreover, it is preferable that R < ¹ > -R < ¹⁰ > in General formula (1) is a substituent other than a halogenated alkyl group or a halogen atom, ie, a halogen-free substituent.
This is because dioxins are prevented from being generated when the light diffusing film is incinerated, and is preferable from the viewpoint of environmental protection.
Incidentally, in a light diffusion film having a conventional louver structure, in order to obtain a predetermined louver structure, it is general that halogen substitution is performed on the monomer component for the purpose of increasing the refractive index of the monomer component.
In this regard, the biphenyl compound represented by the general formula (1) can have a high refractive index even when halogen substitution is not performed.
Therefore, if it is a light-diffusion film formed by photocuring the composition for light-diffusion films in this invention, even if it does not contain a halogen, favorable incident angle dependence can be exhibited.
“Good incident angle dependency” means that the distinction between the light diffusion incident angle region and the non-diffuse incident angle region where the incident light is transmitted without being diffused is clearly controlled. .

Moreover, it is preferable that any one of R < ² > -R < ⁹ > in General formula (1) is a substituent represented by General formula (2).
This is because, by setting the position of the substituent represented by the general formula (2) to a position other than R ¹ and R ¹⁰ , the components (A) are oriented and crystallized in the stage before photocuring. This is because it can be effectively prevented.
Furthermore, it is liquid at the monomer stage before photocuring, and apparently can be uniformly mixed with the component (B) without using a diluting solvent or the like.
Thereby, in the stage of photocuring, the aggregation and phase separation of the component (A) and the component (B) can be performed at a fine level, and a light diffusion film having a louver structure can be obtained more efficiently. Because.
Further, from the same viewpoint, it is particularly preferable that any one of R ³ , R ⁵ , R ⁶ and R ^{8 in} the general formula (1) is a substituent represented by the general formula (2).

Moreover, it is preferable to make the repeating number m in the substituent represented by General formula (2) into the integer of 1-10 normally.
The reason for this is that when the number of repetitions m exceeds 10, the oxyalkylene chain connecting the polymerization site and the biphenyl ring becomes too long, which may inhibit the polymerization of the components (A) at the polymerization site. Because.
Therefore, the repeating number m in the substituent represented by the general formula (2) is more preferably an integer of 1 to 4, and particularly preferably an integer of 1 to 2.
From the same viewpoint, it is preferable that the carbon number n in the substituent represented by the general formula (2) is usually an integer of 1 to 4.
In addition, considering the position of the polymerizable carbon-carbon double bond that is the polymerization site is too close to the biphenyl ring, the biphenyl ring becomes sterically hindered, and the polymerization rate of the component (A) decreases, The carbon number n in the substituent represented by the general formula (2) is more preferably an integer of 2 to 4, and particularly preferably an integer of 2 to 3.

  In addition, specific examples of the biphenyl compound represented by the general formula (1) include compounds represented by the following formulas (3) to (4).

(Ii) Molecular weight Moreover, it is preferable to make the molecular weight of (A) component into the value within the range of 200-2,500.
The reason for this is that by setting the molecular weight of component (A) within a predetermined range, the polymerization rate of component (A) can be further increased, and the copolymerizability of component (A) and component (B) can be made more effective. This is because it is estimated that it can be lowered.
As a result, it is possible to more efficiently form a louver structure in which plate-like regions derived from the component (A) and plate-like regions derived from the component (B) extend alternately when photocured. .
That is, when the molecular weight of the component (A) is less than 200, the polymerization rate decreases due to steric hindrance, becomes close to the polymerization rate of the component (B), and copolymerization with the component (B) is likely to occur. Because there is. On the other hand, when the molecular weight of the component (A) exceeds 2,500, the polymerization rate of the component (A) decreases as the difference in molecular weight with the component (B) decreases. This is because the polymerization rate of the component is close and it is estimated that copolymerization with the component (B) is likely to occur, and as a result, it may be difficult to efficiently form the louver structure.
Therefore, the molecular weight of the component (A) is more preferably set to a value within the range of 240 to 1,500, and further preferably set to a value within the range of 260 to 1,000.
The molecular weight of component (A) can be determined from the calculated value obtained from the molecular composition and the atomic weight of the constituent atoms, and can also be measured as a weight average molecular weight using gel permeation chromatography (GPC). .

(Iii) Single use Moreover, although the composition for light-diffusion films in this invention contains (A) component as a monomer component which forms the plate-shaped area | region where the refractive index in a louver structure is relatively high, It is characterized by the above-mentioned. , (A) component is preferably contained as one component.
This is because the louver structure is effectively suppressed by suppressing the variation in the refractive index in the plate-like region derived from the component (A), that is, the plate-like region having a relatively high refractive index. This is because the provided light diffusing film can be obtained more efficiently.
That is, when the compatibility with the component (B) in the component (A) is low, for example, when the component (A) is a halogen compound, the third component for compatibilizing the component (A) with the component (B) In other cases, other components (A) (for example, non-halogen compounds) are used in combination.
However, in this case, due to the influence of the third component, the refractive index in the plate-like region having a relatively high refractive index derived from the component (A) may be varied or easily lowered.
As a result, the refractive index difference from the plate-like region having a relatively low refractive index derived from the component (B) may become non-uniform or may be excessively lowered.
Therefore, it is preferable to select a monomer component having a high refractive index that is compatible with the component (B) and use it as the sole component (A).
For example, since the biphenyl compound represented by the formula (3) as the component (A) has a low viscosity, it has compatibility with the component (B), so it is used as a single component (A). can do.

(Iv) Refractive index Moreover, it is preferable to make the refractive index of (A) component into the value within the range of 1.5-1.65.
This is because the refractive index of the plate-like region derived from the component (A) and the refractive index of the plate-like region derived from the component (B) are set by setting the refractive index of the component (A) within the range. This is because the light diffusing film having the louver structure can be more efficiently obtained by adjusting the difference from the above.
That is, when the refractive index of the component (A) is less than 1.5, the difference from the refractive index of the component (B) becomes too small, and it may be difficult to obtain an effective light diffusion angle region. Because there is. On the other hand, when the refractive index of the component (A) exceeds 1.65, the difference with the refractive index of the component (B) increases, but even an apparent compatibility state with the component (B) is formed. This is because it may be difficult.
Therefore, the refractive index of the component (A) is more preferably set to a value within the range of 1.52 to 1.65, and further preferably set to a value within the range of 1.56 to 1.6.
In addition, the refractive index of (A) component mentioned above means the refractive index of (A) component before hardening by light irradiation.
The refractive index can be measured according to, for example, JIS K0062.

(V) Content The content of the component (A) in the composition for light diffusion film is 25 with respect to 100 parts by weight of the component (B) which is a polymerizable compound having a relatively low refractive index, which will be described later. It is preferable to set it as the value within the range of -400 weight part.
The reason for this is that when the content of the component (A) is less than 25 parts by weight, the ratio of the component (A) to the component (B) decreases, and the width of the plate-like region derived from the component (A) However, this is because the width of the plate-like region derived from the component (B) is excessively small, and it may be difficult to obtain a louver structure having good incident angle dependency. Moreover, it is because the length of the louver in the thickness direction of the light diffusing film becomes insufficient, and the light diffusing property may not be exhibited. On the other hand, when the content of the component (A) exceeds 400 parts by weight, the ratio of the component (A) to the component (B) increases, and the width of the plate-like region derived from the component (A) increases. This is because the width of the plate-like region derived from the component (B) becomes excessively large, and on the contrary, it may be difficult to obtain a louver structure having good incident angle dependency. Moreover, it is because the length of the louver in the thickness direction of the light diffusing film becomes insufficient, and the light diffusing property may not be exhibited.
Therefore, the content of the component (A) is more preferably set to a value in the range of 40 to 300 parts by weight with respect to 100 parts by weight of the component (B), and a value in the range of 50 to 200 parts by weight. More preferably.

(1) -2 Low Refractive Index Polymerizable Compound (i) Type Among the two polymerizable compounds having different refractive indexes, the type of the polymerizable compound having the relatively low refractive index (component (B)) is particularly The main component is not limited, and examples thereof include urethane (meth) acrylate, (meth) acrylic polymer having (meth) acryloyl group in the side chain, (meth) acryloyl group-containing silicone resin, unsaturated polyester resin, and the like. In particular, urethane (meth) acrylate is preferable.
The reason for this is that if urethane (meth) acrylate is used, the difference between the refractive index of the plate-like region derived from the component (A) and the refractive index of the plate-like region derived from the component (B) can be adjusted more easily. This is because the light diffusion film having a louver structure can be obtained more efficiently by effectively suppressing the variation in the refractive index of the plate-like region derived from the component (B).
Therefore, in the following, urethane (meth) acrylate as the component (B) will be mainly described.
In addition, (meth) acrylate means both acrylate and methacrylate.

First, urethane (meth) acrylate is (B1) a compound containing at least two isocyanate groups, (B2) a polyol compound, preferably a diol compound, particularly preferably a polyalkylene glycol, and (B3) a hydroxyalkyl (meth). Formed from acrylate.
The component (B) includes an oligomer having a urethane bond repeating unit.
Among these, as the compound containing at least two isocyanate groups as the component (B1), for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate Arocyclic polyisocyanates such as aromatic polyisocyanates such as 1,4-xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, etc. Isocyanates and their biurets, isocyanurates, and adducts that are a reaction with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil (for example, Xylylene diisocyanate Inert based trifunctional adduct), and the like.

Moreover, among the above-mentioned, it is especially preferable that it is an alicyclic polyisocyanate.
This is because, in the case of alicyclic polyisocyanates, compared to aliphatic polyisocyanates, it is easy to provide a difference in the reaction rate of each isocyanate group due to the conformation and the like.
This suppresses that the (B1) component reacts only with the (B2) component, or the (B1) component reacts only with the (B3) component, and the (B1) component is converted into the (B2) component and (B3) It can react reliably with a component and generation | occurrence | production of an extra by-product can be prevented.
As a result, variation in the refractive index of the plate-like region derived from the component (B) in the louver structure, that is, the low-refractive index plate-like region can be effectively suppressed.

Moreover, if it is an alicyclic polyisocyanate, compared with an aromatic polyisocyanate, the compatibility with the obtained (B) component and (A) component is reduced to a predetermined range, and a louver structure is obtained. It can be formed more efficiently.
Furthermore, if it is an alicyclic polyisocyanate, compared with an aromatic polyisocyanate, the refractive index of the (B) component obtained can be made small, Therefore The difference with the refractive index of (A) component is shown. The louver structure can be formed more efficiently, and the light diffusibility can be expressed more reliably, and the louver structure with high uniformity of diffused light within the light diffusion angle region can be formed more efficiently.
Of these alicyclic polyisocyanates, alicyclic diisocyanates containing only two isocyanate groups are preferred.
This is because if it is an alicyclic diisocyanate, it can react quantitatively with the component (B2) and the component (B3) to obtain a single component (B).
As such an alicyclic diisocyanate, isophorone diisocyanate (IPDI) can be particularly preferably mentioned.
This is because an effective difference can be provided in the reactivity of the two isocyanate groups.

Among the components that form urethane (meth) acrylate, examples of the polyalkylene glycol that is the component (B2) include polyethylene glycol, polypropylene glycol, polybutylene glycol, polyhexylene glycol, and the like. Particularly preferred is glycol.
This is because polypropylene glycol can be handled without a solvent because of its low viscosity.
Moreover, if it is a polypropylene glycol, when it hardens | cures (B) component, it becomes a favorable soft segment in the said hardened | cured material, and it can improve the handling property and mounting property of a light-diffusion film effectively. is there.
The weight average molecular weight of the component (B) can be adjusted mainly by the weight average molecular weight of the component (B2). Here, the weight average molecular weight of (B2) component is 2,300-19,500 normally, Preferably it is 4,300-14,300, Most preferably, it is 6,300-12,300.

Moreover, as a hydroxyalkyl (meth) acrylate which is a (B3) component among the components which form urethane (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3 -Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. are mentioned.
In addition, from the viewpoint of reducing the polymerization rate of the obtained urethane (meth) acrylate and more efficiently forming a predetermined louver structure, hydroxyalkyl methacrylate is more preferable, and 2-hydroxyethyl methacrylate is particularly preferable. Is more preferable.

Moreover, the synthesis | combination of the urethane (meth) acrylate by (B1)-(B3) component can be implemented in accordance with a conventional method.
At this time, the blending ratio of the components (B1) to (B3) is preferably set to a ratio of (B1) component: (B2) component: (B3) component = 1-5: 1: 1-5 in molar ratio. .
The reason for this is that by setting such a blending ratio, one isocyanate group of the component (B1) reacts and binds to the two hydroxyl groups of the component (B2), and two more components (B1) This is because the urethane (meth) acrylate in which the hydroxyl group of the component (B3) reacts with and bonds to the other isocyanate group possessed by each can be synthesized efficiently.
Therefore, the blending ratio of the components (B1) to (B3) is preferably set to a ratio of (B1) component: (B2) component: (B3) component = 1-3: 1: 1-3 in molar ratio. Preferably, the ratio is 2: 1: 2.

(Ii) Weight average molecular weight Moreover, it is preferable to make the weight average molecular weight of (B) component into the value within the range of 3,000-20,000.
This is because, by setting the weight average molecular weight of the component (B) within a predetermined range, a predetermined difference is caused in the polymerization rate of the component (A) and the component (B), and the copolymerizability of both components is effectively improved. This is because it can be lowered.
As a result, when photocured, a louver structure in which plate-like regions derived from the component (A) and plate-like regions derived from the component (B) extend alternately can be efficiently formed.
That is, when the weight average molecular weight of the component (B) is less than 3,000, the polymerization rate of the component (B) is increased to be close to the polymerization rate of the component (A). This is because polymerization may easily occur, and it may be difficult to efficiently form a louver structure. On the other hand, when the weight average molecular weight of component (B) exceeds 20,000, it is difficult to form a louver structure in which plate-like regions derived from component (A) and component (B) extend alternately. This is because the compatibility with the component (A) may be excessively decreased, and the component (A) may be precipitated at the coating stage.
Therefore, the weight average molecular weight of the component (B) is more preferably set to a value within the range of 5,000 to 15,000, and further preferably set to a value within the range of 7,000 to 13,000.
In addition, the weight average molecular weight of (B) component can be measured using a gel permeation chromatography (GPC).

(Iii) Single use Moreover, although (B) component may use together 2 or more types from which molecular structure and a weight average molecular weight differ, the dispersion | variation in the refractive index of the plate-shaped area | region derived from (B) component in a louver structure From the viewpoint of suppressing the above, it is preferable to use only one type.
That is, when a plurality of (B) components are used, the refractive index in the plate-like region where the refractive index derived from the (B) component is relatively low varies or increases, and the refraction derived from the (A) component. This is because the difference in refractive index from the plate-like region having a relatively high rate may become non-uniform or excessively decrease.

(Iv) Refractive index Moreover, it is preferable to make the refractive index of (B) component into the value within the range of 1.4-1.55.
The reason for this is that the difference between the refractive index of the plate-like region derived from the component (A) and the plate-like region derived from the component (B) is obtained by setting the refractive index of the component (B) to a value within this range. This is because the light diffusing film having the louver structure can be more efficiently obtained by adjusting the above.
That is, when the refractive index of the component (B) is less than 1.4, the difference from the refractive index of the component (A) increases, but the compatibility with the component (A) is extremely deteriorated, and the louver structure It is because there exists a possibility that it cannot form. On the other hand, when the refractive index of the component (B) exceeds 1.55, the difference from the refractive index of the component (A) becomes too small, making it difficult to obtain the desired incident angle dependency. Because there is.
Therefore, the refractive index of the component (B) is more preferably set to a value within the range of 1.45 to 1.54, and further preferably set to a value within the range of 1.46 to 1.52.
In addition, the refractive index of (B) component mentioned above means the refractive index of (B) component before hardening by light irradiation.
The refractive index can be measured, for example, according to JIS K0062.

The difference between the refractive index of the component (A) and the refractive index of the component (B) is preferably set to a value of 0.01 or more.
The reason for this is that a light diffusion film having a better incident angle dependency in light transmission and diffusion and a wider light diffusion incident angle region is obtained by setting the difference in refractive index to a value within a predetermined range. Because it can.
That is, when the difference in refractive index is less than 0.01, the angle range in which incident light is totally reflected in the louver structure is narrowed, so that the opening angle in light diffusion may be excessively narrowed. is there. On the other hand, if the difference in refractive index becomes an excessively large value, the compatibility between the component (A) and the component (B) is too deteriorated, and the louver structure may not be formed.
Therefore, the difference between the refractive index of the component (A) and the refractive index of the component (B) is more preferably set to a value in the range of 0.05 to 0.5, More preferably, the value is within the range.
In addition, the refractive index of (A) component and (B) component here means the refractive index of (A) component and (B) component before hardening by light irradiation.

(V) Content Further, the content of the component (B) in the composition for light diffusion film is a value within the range of 10 to 80% by weight with respect to 100% by weight of the total amount of the composition for light diffusion film. It is preferable to do.
The reason for this is that when the content of the component (B) is less than 10% by weight, the ratio of the component (B) to the component (A) decreases, and the width of the plate-like region derived from the component (B) However, this is because the width of the plate-like region derived from the component (A) is excessively small, and it may be difficult to obtain a louver structure having good incident angle dependency. Moreover, it is because the length of the louver in the thickness direction of the light diffusion film may be insufficient. On the other hand, when the content of the component (B) exceeds 80% by weight, the ratio of the component (B) to the component (A) increases, and the width of the plate-like region derived from the component (B) increases. This is because the width of the plate-like region derived from the component (A) is excessively large and, on the contrary, it may be difficult to obtain a louver structure having good incident angle dependency. Moreover, it is because the length of the louver in the thickness direction of the light diffusion film may be insufficient.
Therefore, it is more preferable to make content of (B) component into the value within the range of 20 to 70 weight% with respect to 100 weight% of the total amount of the composition for light diffusion films, More preferably, the value is within the range.

(1) -3 Photopolymerization initiator Moreover, in the composition for light diffusion films in this invention, it is preferable to contain a photoinitiator as (C) component as needed.
This is because a louver structure can be formed efficiently when the composition for a light diffusing film is irradiated with active energy rays by containing a photopolymerization initiator.
Here, the photopolymerization initiator refers to a compound that generates radical species by irradiation with active energy rays such as ultraviolet rays.

Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, and 2,2-dimethoxy-2-phenylacetophenone. 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] 2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4-diethyl Minobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylamine benzoate, oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propane and the like Of these, one of them may be used alone, or two or more of them may be used in combination.
In addition, as content in the case of containing a photoinitiator, it is set as the value within the range of 0.2-20 weight part with respect to 100 weight part of total amounts of (A) component and (B) component. Preferably, the value is in the range of 0.5 to 15 parts by weight, and more preferably in the range of 1 to 10 parts by weight.

(1) -4 Other Additives Additives other than the above-described compounds can be appropriately added within a range not impairing the effects of the present invention.
Examples of such additives include antioxidants, ultraviolet absorbers, antistatic agents, polymerization accelerators, polymerization inhibitors, infrared absorbers, plasticizers, diluent solvents, and leveling agents.
In general, the content of such additives is preferably set to a value in the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of the total amount of the component (A) and the component (B). The value is more preferably in the range of 0.02 to 3 parts by weight, and still more preferably in the range of 0.05 to 2 parts by weight.

(2) Process (b): 1st application | coating process A process (b) apply | coats the prepared composition for light diffusion films with respect to the process sheet | seat 2, as shown to Fig.9 (a), and is 1st. This is a step of forming the coating layer 1a.
Either a plastic film or paper can be used as the process sheet.
Among these, examples of the plastic film include polyester films such as polyethylene terephthalate films, polyolefin films such as polyethylene films and polypropylene films, cellulose films such as triacetyl cellulose films, and polyimide films.
Examples of the paper include glassine paper, coated paper, and laminated paper.
Moreover, when the process mentioned later is considered, as the process sheet | seat 2, it is preferable that it is a plastic film excellent in the dimensional stability with respect to a heat | fever or an active energy ray.
As such a plastic film, among those described above, a polyester film, a polyolefin film and a polyimide film are preferably exemplified.

In addition, for the process sheet, a release layer is provided on the application surface side of the composition for light diffusion film in the process sheet in order to easily peel the obtained light diffusion film from the process sheet after photocuring. Is preferred.
Such a release layer can be formed using a conventionally known release agent such as a silicone release agent, a fluorine release agent, an alkyd release agent, or an olefin release agent.
In addition, it is preferable that the thickness of the process sheet is usually a value within a range of 25 to 200 μm.

  Examples of the method for applying the light diffusing film composition on the process sheet include conventionally known methods such as knife coating, roll coating, bar coating, blade coating, die coating, and gravure coating. Can be performed.

Moreover, it is preferable to make the film thickness of a 1st application layer into the value within the range of 80-700 micrometers.
This is because the first louver structure can be formed more efficiently by setting the film thickness of the first coating layer to a value within this range.
That is, when the thickness of the first coating layer is less than 80 μm, the length of the first louver structure to be formed is insufficient and incident light that goes straight through the first louver structure increases. This is because it may be difficult to obtain the uniformity of the intensity of the diffused light within the light diffusion angle region. On the other hand, when the thickness of the first coating layer exceeds 700 μm, the first coating layer was formed in the initial stage when the first coating layer was irradiated with active energy rays to form the first louver structure. This is because the direction of photopolymerization is diffused by the louver structure, and it may be difficult to form a desired louver structure.
Therefore, the thickness of the first coating layer is more preferably set to a value within the range of 100 to 500 μm, and further preferably set to a value within the range of 120 to 300 μm.

(3) Process (c): 1st active energy ray irradiation process A process (c) moves the said 1st application layer 1a with respect to the 1st application layer 1a, as shown in FIG.9 (b). In this step, the first active energy ray irradiation 150a is performed using the linear light source 125a while moving along the direction E, thereby forming the first louver structure 13a.
More specifically, for example, as shown in FIG. 10A, an ultraviolet irradiation device 120 in which a condensing cold mirror 122 is provided on a linear ultraviolet lamp 125a (for example, a commercially available product is an eyepiece). By placing the heat ray cut filter 121 and the light-shielding plate 123 (123a, 123b) on a graphics (ECS-4011GX, etc.), the active energy ray 150a consisting only of direct light whose irradiation angle is controlled is taken out. The first coating layer 1a formed on the process sheet 2 is irradiated.

Further, as shown in FIG. 11A, when viewed from above the film, along the long axis direction of the linear light source 125a in the first active energy ray irradiation and the moving direction E of the first coating layer 1a. The imaginary line E ′ (in the longitudinal direction of the film) and the acute angle θ2 ′ formed are preferably set to a value within the range of 10 to 80 °.
The reason for this is that by defining the arrangement angle of the linear light source in this way, coupled with the arrangement angle of the linear light source in the step (e) described later, not only the direction along the longitudinal direction of the incident light, This is because it is possible to more efficiently manufacture a long light diffusion film in which the diffusion area of incident light is effectively expanded by diffusing light in the direction perpendicular to the long direction.
That is, when the value θ2 ′ is less than 10 °, generally, the light diffusion characteristic in the direction along the longitudinal direction of the film is excessive although it depends on the arrangement angle of the linear light source in the step (e) described later. This is because the diffusion area of incident light may become excessively small. On the other hand, when the θ2 ′ exceeds 80 °, generally, the light diffusion characteristics in the direction perpendicular to the longitudinal direction of the film is generally obtained depending on the arrangement angle of the linear light source in the step (e) described later. This is because it may decrease excessively and the incident light diffusion area may be excessively small.
Therefore, when viewed from above the film, the acute angle θ2 ′ formed by the major axis direction of the linear light source in the first active energy ray irradiation and the virtual line along the moving direction of the first coating layer is 35 to 35. A value within the range of 55 ° is more preferable, a value within the range of 40 to 50 ° is more preferable, and a value within the range of 44 to 46 ° is even more preferable.
Note that the distance between the linear light source 125a and the coating layer 1a is preferably substantially the same at any position.

Further, as the irradiation angle of the active energy ray, as shown in FIG. 10B, the irradiation angle θ6 when the angle of the normal to the surface of the first coating layer 1a is 0 ° is usually −80 to A value within the range of 80 ° is preferable.
The reason for this is that when the irradiation angle is outside the range of −80 to 80 °, the influence of reflection on the surface of the first coating layer 1a becomes large, and it is difficult to form a sufficient louver structure. This is because it may become.
The irradiation angle θ6 preferably has a width (irradiation angle width) θ6 ′ of 1 to 80 °.
This is because, when the irradiation angle width θ6 ′ is a value less than 1 °, the moving speed of the coating layer must be excessively decreased, and the production efficiency may be decreased. On the other hand, when the irradiation angle width θ6 ′ exceeds 80 °, the irradiation light is excessively dispersed and it may be difficult to form the louver structure.
Therefore, the irradiation angle width θ6 ′ of the irradiation angle θ6 is more preferably set to a value within the range of 2 to 45 °, and further preferably set to a value within the range of 5 to 20 °.
In addition, when it has irradiation angle width | variety (theta) 6 ', let the angle of the intermediate position just be irradiation angle (theta) 6.

In addition, the first active energy ray irradiation is performed through a light shielding plate having a long groove-like active energy ray transmitting portion, and the longitudinal direction of the active energy ray transmitting portion is parallel to the longitudinal direction of the linear light source. Preferably there is.
The active energy ray transmitting portion may be in any form as long as it is in a state of transmitting the active energy ray.
For example, it may be made of quartz glass, or may be a simple space where no light shielding material is present.
Specifically, as shown in FIG. 12, it is performed through a long groove-like gap (active energy ray transmitting portion) formed by two light shielding plates 123 (123a, 123b) and the length of the long groove-like gap. The direction is preferably a direction parallel to the major axis direction of the linear light source 125a.
By arranging the light shielding plate in this way, the irradiation angle θ6 of the active energy ray 150a shown in FIG. 10A is adjusted to a value within a predetermined range, and depending on each position on the surface of the first coating layer 1a, This is because the active energy ray 150a from the linear light source 125a can be effectively suppressed from being irradiated at an excessively different angle.
As a result, the inclination angle of the plate-like region in the formed louver structure can be made uniform, and as a result, the light diffusion characteristics of the obtained long light diffusion film can be made uniform.

Moreover, it is preferable to make the peak illumination intensity in the surface of the 1st application layer in 1st active energy ray irradiation into the value within the range of 0.1-50 mW / cm < ² >.
This is because the first louver structure can be formed more efficiently by setting the peak illuminance in the first active energy ray irradiation to a value within such a range.
That is, if the peak illuminance is less than 0.1 mW / cm ² , it may be difficult to clearly form the first louver structure. On the other hand, when the peak illuminance is a value exceeding 50 mW / cm ² , it is estimated that the curing speed becomes too fast, and the first louver structure may not be clearly formed.
Therefore, the peak illuminance on the surface of the first coating layer in the first active energy ray irradiation is more preferably set to a value within the range of 0.3 to 10 mW / cm ² , and 0.5 to 5 mW / cm ² . More preferably, the value is within the range.
The peak illuminance here means a measured value at a portion where the active energy ray irradiated on the surface of the first coating layer shows the maximum value.

Moreover, it is preferable to make the integrated light quantity in the surface of the 1st coating layer in 1st active energy ray irradiation into the value within the range of 5-300 mJ / cm < ² >.
The reason for this is that the first louver structure can be formed more efficiently by setting the integrated light quantity in the first active energy ray irradiation to a value within this range.
That is, when the integrated light quantity is less than 5 mJ / cm ² , it may be difficult to sufficiently extend the first louver structure from the top to the bottom. On the other hand, when the integrated light quantity exceeds 300 mJ / cm ² , the resulting light diffusion film may be colored.
Therefore, it is more preferably set to a value within the range of accumulated light amount of 10~200mJ / cm ² in the first surface of the coating layer in the first active-energy ray irradiation, a value in the range of 20~150mJ / cm ² More preferably.

Moreover, it is preferable to make the moving speed of the 1st application layer into the value within the range of 0.1-10 m / min.
This is because the first louver structure can be formed more efficiently by setting the moving speed of the first coating layer to a value within this range.
That is, when the moving speed of the first coating layer becomes a value less than 0.1 m / min, productivity may be excessively lowered. On the other hand, when the moving speed of the first coating layer exceeds 10 m / min, the first coating layer is hardened, in other words, faster than the formation of the first louver structure, and the activity on the first coating layer is increased. This is because the incident angle of the energy beam changes and the formation of the first louver structure may be insufficient.
Therefore, the moving speed of the first coating layer is more preferably set to a value within the range of 0.2 to 5 m / min, and further preferably set to a value within the range of 0.5 to 3 m / min.

It is also preferable to irradiate the upper surface of the first coating layer with active energy rays in a state where the active energy ray transmitting sheet is laminated.
The reason is that by laminating the active energy ray transmitting sheet, the influence of oxygen inhibition can be effectively suppressed and the first louver structure can be formed more efficiently.
That is, by laminating the active energy ray-transmitting sheet on the upper surface of the first coating layer, the upper surface of the first coating layer is allowed to pass through the sheet while stably preventing contact with oxygen. This is because the active energy ray can be efficiently irradiated to the first coating layer.
In addition, as an active energy ray permeable sheet, if the active energy ray can permeate | transmit among the process sheets described in the process (b) (application | coating process), it can use without a restriction | limiting in particular.

In addition to the first active energy ray irradiation as the step (c), it is preferable to further irradiate the active energy ray so that the first application layer has an integrated light amount that is sufficiently cured.
Since the active energy ray at this time is intended to sufficiently cure the first coating layer, it is preferable to use random light in any traveling direction instead of parallel light.

(4) Process (d): 2nd application | coating process As shown in FIG.9 (c), process (d) is 1st application | coating in which the 1st louver structure 13a was formed, as shown in FIG.9 (c). This is a step of applying to the layer 1a ′ to form a laminated body 1c composed of the first coating layer 1a ′ and the second coating layer 1b.
When forming the first louver structure 13a, if an active energy ray transmitting sheet is used, the above operation is performed after the sheet is peeled to expose the surface of the coating layer 1a '.
Moreover, it is preferable that the composition for light diffusion films used for formation of the 2nd coating layer 1b uses the same thing as the composition for light diffusion films used for formation of the 1st coating layer 1a.
This is because by using the same composition for light diffusion film, reflection at the interface between the coating layer 1a ′ and the coating layer 1b ′ can be suppressed, and the adhesion can be improved.
Examples of the method for applying the light diffusing film composition on the first coating layer on which the first louver structure is formed include, for example, knife coating, roll coating, bar coating, blade coating, and die coating. It can carry out by the method similar to the process (b) mentioned above, such as a method and a gravure coat method.

Moreover, it is preferable to make the film thickness of a 2nd coating layer into the value within the range of 80-700 micrometers.
This is because the second louver structure can be formed more efficiently by setting the thickness of the second coating layer to a value within this range.
That is, when the thickness of the second coating layer is less than 80 μm, the length of the second louver structure to be formed is insufficient, and the incident light that goes straight through the second louver structure increases. This is because it may be difficult to obtain the uniformity of the intensity of the diffused light within the light diffusion angle region. On the other hand, when the thickness of the second coating layer exceeds 700 μm, the second coating layer was formed at the initial stage when the second coating layer was irradiated with active energy rays to form the second louver structure. This is because the direction of photopolymerization is diffused by the louver structure, and it may be difficult to form a desired louver structure.
Therefore, the thickness of the second coating layer is more preferably set to a value within the range of 100 to 500 μm, and further preferably set to a value within the range of 120 to 300 μm.

(5) Step (e): Second active energy ray irradiation step In the step (e), as shown in FIG. 9D, the first louver structure 13a is formed on the second coating layer 1b. The second active energy ray is irradiated using the linear light source 125b while moving the laminated body 1c composed of the first coating layer 1a 'and the second coating layer 1b to form the second louver structure 13b. 11B, when viewed from above the film, the major axis direction of the linear light source 125a in the first active energy ray irradiation and the second active energy ray irradiation This is a step of setting the acute angle θ1 ′ formed by the major axis direction of the linear light source 125b to a value within the range of 10 to 90 °.

That is, in the two active energy ray irradiation steps using the linear light source, the extending direction of the plate-like region in the first louver structure is defined by defining the relationship between the arrangement angles of the respective linear light sources within a predetermined range. And the elongate light-diffusion film which cross | intersects the extension direction of the plate-shaped area | region in a 2nd louver structure at a predetermined angle can be manufactured efficiently.
Therefore, long light that effectively spreads the diffusion area of incident light by diffusing the incident light not only in the direction along the longitudinal direction but also in the direction orthogonal to the longitudinal direction. A diffusion film can be manufactured efficiently.
More specifically, incident light can be diffused in a direction along the longitudinal direction and in a direction orthogonal to the longitudinal direction without connecting a plurality of light diffusion films as in the prior art. A long light diffusion film can be obtained.

That is, when the acute angle θ1 ′ shown in FIG. 11B is less than 10 °, the diffusion area of incident light may be excessively reduced.
Therefore, when viewed from above the film, the acute angle θ1 ′ formed by the long axis direction of the linear light source in the first active energy ray irradiation and the long axis direction of the linear light source in the second active energy ray irradiation is A value within the range of 80 to 90 ° is more preferable, a value within the range of 85 to 90 ° is more preferable, and a value within the range of 89 to 90 ° is even more preferable.

Further, as shown in FIG. 11B, when viewed from above the film, the long axis direction of the linear light source 125b in the second active energy ray irradiation and the first louver structure 13a are formed. It is preferable that an acute angle θ3 ′ formed by a virtual line E ′ along the moving direction E of the laminate 1c composed of the coating layer 1a ′ and the second coating layer 1b is set to a value within a range of 10 to 80 °. .
The reason for this is that, by defining the arrangement angle of the linear light source in this way, coupled with the arrangement angle of the linear light source in the step (c) described above, not only the direction along the longitudinal direction of the incident light, This is because it is possible to more efficiently manufacture a long light diffusion film in which the diffusion area of incident light is effectively expanded by diffusing light in the direction perpendicular to the long direction.
That is, when the value θ3 ′ is less than 10 °, generally, the light diffusion characteristics in the direction along the longitudinal direction of the film are excessive, depending on the arrangement angle of the linear light source in the step (c) described above. This is because the diffusion area of incident light may become excessively small. On the other hand, when the value θ3 ′ exceeds 80 °, generally, the light diffusion characteristics in the direction perpendicular to the longitudinal direction of the film are dependent on the arrangement angle of the linear light source in the step (c) described above. This is because it may decrease excessively and the incident light diffusion area may be excessively small.
Therefore, when viewed from above the film, a virtual line along the major axis direction of the linear light source in the second active energy ray irradiation and the moving direction of the laminate composed of the first coating layer and the second coating layer Is more preferably set to a value within the range of 35 to 55 °, more preferably a value within the range of 40 to 50 °, and a value within the range of 44 to 46 °. It is more preferable to do this.
Note that the distance between the linear light source 125b and the coating layer 1b is preferably substantially the same at any position.
In addition, the irradiation angle and irradiation angle width of the active energy ray are preferably set in the same numerical range as in the case of the first active energy ray irradiation described with reference to FIGS.

11B, when viewed from above the film, the long axis direction of the linear light source 125a in the first active energy ray irradiation and the linear light source 125b in the second active energy ray irradiation. The major axis direction is symmetrical with respect to an imaginary line E ″ perpendicular to the moving direction E of the laminate composed of the first coating layer 1a ′ and the second coating layer 1b. preferable.
This is because the incident light can be diffused more uniformly in the obtained light diffusion film by arranging the linear light source in the second active energy ray irradiation in this way.
In particular, when θ2 ′ = 45 ° and θ3 ′ = 45 °, or when each is a peripheral value thereof, the linear light sources are arranged so as to be symmetrical with respect to each other, thereby spreading the diffused light in the horizontal direction. And the spread in the vertical direction can be maximized.
Therefore, when such a light diffusion film is applied to a large-screen projection screen, the horizontal viewing angle and the vertical viewing angle can be maximized.

  Further, as shown in FIG. 12, the second active energy ray irradiation is also performed through a long groove-like gap formed by two light shielding plates for the same reason as in the case of the first active energy ray irradiation. In addition, it is preferable that the longitudinal direction of the long groove-like gap is parallel to the long axis direction of the linear light source.

Moreover, it is preferable to make the peak illumination intensity in the surface of the 2nd coating layer in 2nd active energy ray irradiation into the value within the range of 0.1-50 mW / cm < ² >.
This is because the second louver structure can be more efficiently formed by setting the peak illuminance in the second active energy ray irradiation to a value within such a range.
That is, if the peak illuminance is less than 0.1 mW / cm ² , it may be difficult to clearly form the second louver structure. On the other hand, when the peak illuminance is a value exceeding 50 mW / cm ² , it is estimated that the curing speed is too high, and the second louver structure may not be clearly formed.
Therefore, the peak illuminance on the surface of the second coating layer in the second active energy ray irradiation is more preferably set to a value within the range of 0.3 to 10 mW / cm ² , and 0.5 to 5 mW / cm ² . More preferably, the value is within the range.

Moreover, it is preferable to make the integrated light quantity in the surface of the 2nd application layer in 2nd active energy ray irradiation into the value within the range of 5-300 mJ / cm < ² >.
This is because the second louver structure can be formed more efficiently by setting the integrated light quantity in the second active energy ray irradiation to a value within this range.
That is, when the integrated light quantity becomes a value less than 5 mJ / cm ² , it may be difficult to sufficiently extend the second louver structure from above to below. On the other hand, when the integrated light quantity exceeds 300 mJ / cm ² , the resulting light diffusion film may be colored.
Therefore, it is more preferably set to a value within the range of accumulated light amount of 10~200mJ / cm ² in the second surface of the coating layer in the second active energy ray irradiation, a value in the range of 20~150mJ / cm ² More preferably.

  Also in the second active energy ray irradiation, for the same reason as in the case of the first active energy ray irradiation, a laminate composed of the first coating layer and the second coating layer on which the first louver structure is formed. The body moving speed is preferably set to a value within the range of 0.1 to 10 / min, more preferably set to a value within the range of 0.2 to 5 m / min, and 0.5 to 3 m / min. More preferably, the value is within the range.

From the same viewpoint as in the case of the step (c), it is also preferable to irradiate the upper surface of the second coating layer with the active energy ray in a state where the active energy ray transmitting sheet is laminated.
In addition to the second active energy ray irradiation as the step (e), it is also preferable to further irradiate the active energy ray so that the second application layer has an integrated light amount that is sufficiently cured.
Since the active energy ray at this time is intended to sufficiently cure the second coating layer, it is preferable to use random light in any traveling direction instead of parallel light.
In addition, the process (d)-(e) mentioned above may be performed continuously with process (b)-(c) using one conveyor, and obtained by process (b)-(c). The first coating layer on which the first louver structure is formed may be collected in the form of a roll, and this may be separately placed on a conveyor to perform steps (b) to (c).
Therefore, in the former case, the linear light source in step (c) and the linear light source in step (e) are arranged separately, and in the latter case, the same linear light source is arranged at an angle of arrangement. It may be used after being changed (turned).

  Hereinafter, with reference to an Example, the manufacturing method of the light-diffusion film of this invention is demonstrated in more detail.

[Example 1]
1. Synthesis of low refractive index polymerizable compound (B) component In a container, 1 mol of polypropylene glycol (PPG) having a weight average molecular weight of 9,200 as component (B2) is isophorone diisocyanate as component (B1). After 2 mol of (IPDI) and 2 mol of 2-hydroxyethyl methacrylate (HEMA) as component (B3) were accommodated, polymerization was performed according to a conventional method to obtain a polyether urethane methacrylate having a weight average molecular weight of 9,900.

In addition, the weight average molecular weight of polypropylene glycol and polyether urethane methacrylate is a polystyrene conversion value measured according to the following conditions by gel permeation chromatography (GPC).
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
-GPC column: manufactured by Tosoh Corporation (hereinafter, described in order of passage)
TSK guard column HXL-H
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

2. Preparation of composition for light diffusing film Next, 100 parts by weight of polyether urethane methacrylate having a weight average molecular weight of 9,900 as the obtained component (B) is represented by the following formula (3) as the component (A). 100 parts by weight of o-phenylphenoxyethoxyethyl acrylate having a weight average molecular weight of 268 (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester A-LEN-10), and 2-hydroxy-2-methylpropiophenone as component (C) After adding 5 parts by weight, the mixture was heated and mixed under conditions of 80 ° C. to obtain a composition for a light diffusing film for forming a first louver structure and a second louver structure.
The refractive indexes of the components (A) and (B) were measured according to JIS K0062 using an Abbe refractometer (Atago Co., Ltd., Abbe refractometer DR-M2, Na light source, wavelength 589 nm). , 1.58 and 1.46, respectively.

3. First Application Step Next, the obtained composition for light diffusion film was applied to a film-like transparent polyethylene terephthalate film (hereinafter referred to as PET) as a process sheet, and a first film having a thickness of 165 μm. A coating layer was formed.

4). First active energy ray irradiation step Next, an ultraviolet irradiation device (ECS-4011GX, manufactured by Eye Graphics Co., Ltd.) in which a condensing cold mirror is attached to a linear high-pressure mercury lamp as shown in FIG. ) Was prepared.
At this time, when viewed from above the film, the ultraviolet irradiation device is set so that the acute angle θ2 formed by the major axis direction of the linear light source and the virtual line along the moving direction of the first coating layer is 45 °. installed.
Next, a light shielding plate is installed on the heat ray cut filter frame, and the ultraviolet rays applied to the surface of the first coating layer are normal to the surface of the first coating layer when viewed from the long axis direction of the linear light source. In the case of 0 °, the irradiation angle of direct ultraviolet rays from the linear light source (θ6 in FIG. 10B) was set to 16 °.
Further, the height from the surface of the first coating layer to the linear light source was set to 2000 mm, the peak illuminance was set to 1.26 mW / cm ² , and the integrated light amount was set to 23.48 mW / cm ² .
In addition, in order to prevent the reflected light from the light shielding plate or the like from becoming stray light inside the irradiator and affecting the photocuring of the first coating layer, as shown in FIG. A plate was installed and set so that only the ultraviolet rays directly emitted from the linear light source were applied to the first coating layer.
More specifically, as shown in FIG. 12, it is arranged so that a long groove-like gap (gap width: 35 cm) formed by two light shielding plates is formed, and the longitudinal direction of the long groove-like gap is The linear light source was installed so as to be parallel to the long axis direction.
Next, the conveyor is irradiated with ultraviolet rays while moving the first coating layer in the right direction in FIG. 9B at a speed of 1.0 m / min, and the longitudinal direction (moving direction of the first coating layer). ) Having a length of 30 m, a length in the short direction of 1.4 m, and a film thickness of 165 μm, a long first louver structure was obtained.
Subsequently, in order to achieve reliable curing, on the exposed surface side of the first coating layer, as an active energy ray-transmitting sheet, a release film having a thickness of 38 μm and having UV transmittance (manufactured by Lintec Corporation, SP-PET382050; The center line average roughness 0.01 μm, haze value 1.80%, image sharpness 425, transmittance at wavelength 360 nm 84.3% on the surface on the ultraviolet irradiation side was laminated.
Next, the scattered light irradiation was performed so that the peak illuminance was 13.7 mW / cm ² and the integrated light amount was 213.6 mJ / cm ² .
The above-described peak illuminance and integrated light amount were measured by installing a UV METER (manufactured by Eye Graphics Co., Ltd., eye ultraviolet integrated illuminance meter UVPF-A1) equipped with a light receiver at the position of the first coating layer. .
Moreover, the film thickness of the 1st coating layer in which the obtained elongate 1st louver structure was formed was measured using the constant-pressure thickness measuring device (Takekku PG-02J by Takara Seisakusho Co., Ltd.). did.

5. Second Application Step Next, the active energy ray-transmitting sheet was peeled off from the first application layer on which the long first louver structure was formed.
Subsequently, the composition for light diffusion films obtained in the above-described step was applied to the exposed surface of the first coating layer on which the obtained long first louver structure was formed, and the film thickness was 165 μm. A second coating layer was formed.

6). Second active energy ray irradiation step Next, when viewed from above the film, the long axis direction of the linear light source in the first active energy ray irradiation and the long axis direction of the linear light source in the second active energy ray irradiation In the same manner as in the first active energy ray irradiating step, the ultraviolet ray is irradiated, and the first louver structure and the second irradiating structure are formed in the inside, except that the ultraviolet irradiation device is installed so that the acute angle θ1 formed is 90 °. Thus, a long light diffusion film having a film thickness of 330 μm having a louver structure was obtained.
When viewed from above the film, the virtual axis along the long axis direction of the linear light source and the moving direction of the laminate composed of the first coating layer and the second coating layer on which the first louver structure is formed. The acute angle θ3 formed by the line was 45 °.
In addition, after irradiating the second coating layer with ultraviolet rays, as in the case of the first coating layer, the active energy ray transmitting sheet (ultraviolet transparent release film) is laminated and irradiated with scattered light. And reliable curing was achieved.

Further, as shown in FIG. 13, the obtained light diffusion film has an extension direction of the plate-like region in the first louver structure and an extension of the plate-like region in the second louver structure when viewed from above the film. It was confirmed that the acute angle formed by the direction was 90 °.
Further, when viewed from above the film, it was confirmed that the acute angle formed by the extending direction of the plate-like region in the first louver structure and the longitudinal direction of the film was 45 °.
Furthermore, when viewed from above the film, it was confirmed that the acute angle formed by the extending direction of the plate-like region in the second louver structure and the longitudinal direction of the film was 45 °.
Moreover, the photograph of the cross section which cut | disconnected the obtained light-diffusion film in the surface orthogonal to the elongate direction of a film was cut | disconnected in Fig.14 (a) by the surface parallel to the elongate direction of a film and orthogonal to the film surface. Cross-sectional photographs are shown in FIG.
The light diffusing film was cut using a razor, and a cross-sectional photograph was taken using an optical microscope (reflection observation).

7). Measurement As shown in FIG. 13, light was incident on the film from the direction perpendicular to the film surface from the lower side (side on which the first louver structure was located) of the obtained light diffusion film.
Next, a spectrum chart of diffused light in a direction perpendicular to the longitudinal direction of the film and in a direction parallel to the longitudinal direction of the film, using a colorimeter (VC-2 manufactured by Suga Test Instruments Co., Ltd.) Got.
That is, as shown in FIG. 15A, the light diffusion angle (°) in the diffused light diffused by the light diffusion film is taken on the horizontal axis, and the relative intensity (−) of the diffused light is taken on the vertical axis. A spectrum chart was obtained.
Here, the spectrum chart A shown in FIG. 15A corresponds to the diffused light in the direction orthogonal to the longitudinal direction of the film, and the spectrum chart B represents the diffused light in the direction parallel to the longitudinal direction of the film. It corresponds to.
Moreover, the photograph of the diffused light at the time of seeing from the Z direction in FIG. 13 was obtained as shown in FIG.15 (b) using the conoscope (made by autotronic-MELCHERS GmbH).
The results shown in FIGS. 15 (a) to 15 (b) were consistent with the light diffusion characteristics expected from the film having the internal structure as shown in FIG.

[Reference Example 1]
In Reference Example 1, the acute angle formed by the long direction of the linear light source and the imaginary line along the moving direction of the first coating layer when viewed from above the film in the first active energy ray irradiation step. Except for setting θ2 to 90 °, the first active energy ray irradiation step is performed on the first coating layer in the same manner as in Example 1, and the first coating layer (the first louver structure is formed inside). Obtained).
The first coating layer on which the first louver structure obtained at this time is formed, as shown in FIG. 16 (a), when viewed from above the film, the extending direction of the plate-like region in the louver structure, It was confirmed that the longitudinal direction and the acute angle formed by the direction were 90 °.

Next, as shown in FIG. 16B, the long first coating layer on which the obtained first louver structure is formed is cut every 1.1 m in the long direction to obtain the first A plurality of non-long first coating layers having a louver structure were formed.
Next, as shown in FIG. 16C, the plurality of first non-elongated first coating layers formed with the first louver structure are rotated by 90 ° in the plane, respectively, They were joined together so that the distance was 0.5 mm or less.
Thus, as shown in FIG. 16C, the first louver having an acute angle of 0 ° formed by the extending direction of the plate-like region in the louver structure and the longitudinal direction when viewed from above the film. A long first coating layer having the structure formed thereon (with the first louver structure formed therein) was obtained.

  Next, the elongated coating layer shown in FIG. 16A is formed into a film on the elongated first coating layer on which the obtained first louver structure shown in FIG. A light diffusing film was obtained by laminating as a long second coating layer having a second louver structure formed through an acrylic transparent adhesive layer having a thickness of 25 μm.

Further, as shown in FIG. 17, the obtained light diffusing film has an extension direction of the plate-like region in the first louver structure and a plate-like region in the second louver structure region when viewed from above the film. It was confirmed that the acute angle formed by the extending direction was 90 °.
Further, when viewed from above the film, it was confirmed that the acute angle formed by the extending direction of the plate-like region in the first louver structure and the longitudinal direction of the film was 0 °.
Furthermore, when viewed from above the film, it was confirmed that the acute angle formed by the extending direction of the plate-like region in the second louver structure and the longitudinal direction of the film was 90 °.
Moreover, the photograph of the cross section which cut | disconnected the obtained light-diffusion film in the surface orthogonal to the elongate direction of a film was cut | disconnected in FIG. 18 (a) by the surface parallel to the elongate direction of a film and orthogonal to the film surface. Cross-sectional photographs are shown in FIG.

Moreover, the light diffusion condition in the case where light was incident on the film from the direction perpendicular to the film surface was measured from the lower side of the obtained light diffusion film in the same manner as in Example 1.
FIG. 19A shows a spectrum chart of diffused light obtained by injecting light into a seamless portion, and FIG. 19B shows a photograph of diffused light when viewed from the Z direction in FIG. Show.
The results shown in FIGS. 19 (a) to 19 (b) were consistent with the light diffusion characteristics expected from a film having an internal structure as shown in FIG.
However, when light is incident on the seam portion, as shown in FIGS. 20A to 20B, it is confirmed that the light diffusibility tends to be uneven due to the seam portion of the film. It was done.

[Comparative Example 1]
In Comparative Example 1, a light diffusion film was produced in the same manner as in Example 1 except that the second coating step and the second active energy ray irradiation step were not performed.

Further, as shown in FIG. 21, the obtained light diffusing film has an acute angle of 45 ° between the extending direction of the plate-like region in the louver structure and the longitudinal direction of the film when viewed from above the film. I confirmed that there was.
Moreover, the photograph of the cross section which cut | disconnected the obtained light-diffusion film in the surface orthogonal to the elongate direction of a film was cut | disconnected in Fig.22 (a) by the surface parallel to the elongate direction of a film and orthogonal to the film surface. The photograph of a cross section is shown in FIG.22 (b), respectively.

Moreover, the light diffusion condition in the case where light was incident on the film from the direction perpendicular to the film surface was measured from the lower side of the obtained light diffusion film in the same manner as in Example 1.
FIG. 23A shows a spectrum chart of the obtained diffused light, and FIG. 23B shows a photograph of the diffused light when viewed from the Z direction in FIG.
However, FIG. 23A shows a spectrum chart in the direction along the diffusion direction (major axis direction) of the diffused light shown in FIG.
The results shown in FIGS. 23A to 23B were consistent with the light diffusion characteristics expected from the film having the internal structure as shown in FIG.

As described above in detail, according to the present invention, by performing a predetermined manufacturing method, the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure are performed. And a long light diffusing film obtained by crossing them at a predetermined angle.
As a result, in the long light diffusion film, the incident light is diffused not only in the direction along the longitudinal direction but also in the direction perpendicular to the longitudinal direction, thereby reducing the diffusion area of the incident light. It became possible to spread effectively.
Therefore, the light diffusing film of the present invention is expected to contribute significantly to the productivity and quality improvement of a large area light diffusing film used for projection screens, reflective liquid crystal devices and the like.

DESCRIPTION OF SYMBOLS 1a: 1st coating layer, 1a ': 1st coating layer in which the 1st louver structure was formed, 1b: 2nd coating layer, 1c: Lamination | stacking which consists of a 1st coating layer and a 2nd coating layer Body, 2: process sheet, 10: light diffusion film, 12: plate-like region having a relatively high refractive index, 13: louver structure, 13a: first louver structure, 13b: second louver structure, 13 ′: Interface surface of louver structure, 14: plate-like region having a relatively low refractive index, 20: light diffusion film obtained by the production method of the present invention, 50 ′: light diffusion condition, 51 ′: diffusion light diffusion condition, 120: UV irradiation device, 121: heat ray cut filter, 123: light shielding plate, 125: linear light source, 150: active energy ray

Claims (8)

A long light diffusing film having a first louver structure and a second louver structure sequentially from below along the film thickness direction,
The first louver structure and the second louver structure are each composed of a plurality of plate-like regions having different refractive indexes, and the plurality of plate-like regions having different refractive indexes are in any one direction along the film surface. It is a louver structure that is alternately arranged in parallel, and
When viewed from above the film, the acute angle θ1 formed by the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure is 10 to 90 °. A light diffusion film having a value within the range.   When viewed from above the film, the acute angle θ2 formed by the extending direction of the plate-like region in the first louver structure and the longitudinal direction of the film is set to a value within the range of 10 to 80 °, and the film When viewed from above, the acute angle θ3 formed by the extending direction of the plate-like region in the second louver structure and the longitudinal direction of the film is set to a value in the range of 10 to 80 °. The light diffusion film according to claim 1.   When viewed from above the film, a virtual direction in which the extending direction of the plate-like region in the first louver structure and the extending direction of the plate-like region in the second louver structure are orthogonal to the longitudinal direction of the film. The light diffusion film according to claim 1, wherein the light diffusion film is line symmetric with respect to the line.   The length in the short direction of the light diffusion film is set to a value within a range of 0.1 to 3 m, and the length in the long direction is set to a value of 3 m or more. The light diffusion film according to claim 1.   The light-diffusion film as described in any one of Claims 1-4 formed by roll shape.   6. The light diffusion film according to claim 1, wherein thicknesses of the first louver structure and the second louver structure are set to values within a range of 50 to 500 μm, respectively.   7. The width of the plate-like region in each of the first louver structure and the second louver structure is set to a value within a range of 0.1 to 15 μm, respectively. The light diffusion film as described.   The light diffusion film according to any one of claims 1 to 7, wherein a raw material of the light diffusion film is a composition for a light diffusion film containing two polymerizable compounds having different refractive indexes.