JP5883629B2 - Manufacturing method of light diffusion film - Google Patents

Description

The present invention relates to a method for producing a light diffusion film.
In particular, with as possible out to be isotropic diffuse incident light, a method for producing a light diffusion film having excellent uniformity of the intensity of the diffused light.

Conventionally, light diffusing films have been used for lighting fixtures and building materials, but recently, they are also used for light diffusion in displays such as liquid crystal displays.
In addition, there are various modes for such a light diffusion film, and in particular, by irradiating a specific photocurable composition with active energy rays as parallel light over the entire surface, the film thickness of the film. A light diffusion film formed by forming a column structure region in which a plurality of columnar objects having a refractive index different from that of the medium is formed in the medium along the direction is disclosed (for example, Patent Documents 1 and 2). reference).

  That is, in Patent Document 1, a composition containing a photocurable compound is provided on a sheet, the composition is cured by irradiating the sheet with a parallel light beam from a predetermined direction P, and parallel to the predetermined direction P inside the sheet. A method of manufacturing a diffusion medium (light diffusion film) that forms an assembly of a plurality of rod-shaped hardened regions extending in a cylinder, and is a cylinder disposed in parallel to a predetermined direction P between a linear light source and a sheet There is disclosed a method for manufacturing a diffusion medium, characterized by interposing a collection of objects and irradiating light through the cylinder.

  Further, in Patent Document 2, a linear light source is disposed so as to be opposed to the photocurable resin composition film, and at least one of the photocurable resin composition film and the linear light source is moved while being linear. A manufacturing apparatus for irradiating light from a light source to cure a photocurable resin composition film to form a light control film (light diffusion film), in which the axial direction and the moving direction of the linear light source intersect each other A plurality of thin plate-shaped light-shielding members opposed to the light-curing member are arranged at a predetermined interval in a direction substantially perpendicular to the moving direction between the photocurable resin composition film and the linear light source, and the light-curing property of the light-shielding member. An apparatus for manufacturing a light control film is disclosed in which one side facing the resin composition film is provided in the same direction as the moving direction.

Japanese Patent No. 4095573 (claims, drawings, etc.) JP 2009-173018 A (Claims, drawings, etc.)

  However, although the light diffusion film having the column structure region disclosed in Patent Documents 1 and 2 can diffuse the incident light isotropically in a circular shape, the parallelism of the active energy rays irradiated at the time of photocuring Is insufficient, the intensity distribution in the diffused light is uneven, and it is difficult to ensure sufficient uniformity.

Therefore, the present inventors made extensive efforts in view of the circumstances as described above, and as a result, active energy was obtained using an array light source in which a plurality of LED light sources were arrayed with respect to a coating layer composed of the composition for a light diffusion film. The present invention has been completed by finding that a light diffusing film can be diffused isotropically by irradiating a line and an excellent uniformity of intensity of diffused light can be obtained. .
That is, an object of the present invention is a light diffusing film having a concentric inner structure composed of a plurality of concentric regions having different refractive indexes, and is capable of isotropically diffusing incident light as well as the intensity of diffused light. It is providing the manufacturing method of the light-diffusion film excellent in the uniformity of.

According to the present invention, there is provided a light diffusing film manufacturing method for diffusing incident light isotropically, which includes the following steps (a) to (c). The above-mentioned problem can be solved.
(A) A step of preparing a composition for light diffusion film (b) A step of applying the composition for light diffusion film to a process sheet and forming a coating layer (c) A half angle of a directivity angle with respect to the coating layer Using an array light source in which a plurality of LED light sources having a value in the range of 0 to 30 ° are arranged so that the distance between the centers of adjacent LED light sources is constant within a range of 14 to 50 mm. Light diffusion having an internal structure composed of a plurality of concentric circular regions having different refractive indexes, which is irradiated with active energy rays and arranged so that the distance from the lower end of the array light source is within a range of 10 to 50 cm. In other words, in the method for producing a light diffusing film of the present invention, the composition for a light diffusing film is irradiated with active energy rays using an array light source in which a plurality of LED light sources are arrayed. From, flat Degrees high active energy ray can be uniformly illuminated, so that it is possible to produce a light diffusion film having a concentric inner structure efficiently.
Therefore, according to the manufacturing method of the light diffusion film of the present invention, the incident light can be diffused isotropically due to the concentric inner structure, and the uniformity of the intensity of the diffused light is also effective. Can be improved.

In the following description, major terms used to describe the present invention are defined as follows.
That is, in the present invention, “isotropic light diffusion” means a light diffusion film that can diffuse incident light into a circular shape or a substantially circular shape.
In the present invention, the “concentric internal structure” means an internal structure composed of a plurality of concentric regions having different refractive indexes existing in the light diffusion film.
In the present invention, the “film surface direction” means an xy plane direction perpendicular to the film thickness direction when the film thickness direction is the z-axis.
In the present invention, the “light diffusion incident angle region” means an 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. It shall mean an angular range.
On the other hand, 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. .
Here, in the light diffusing film according to the present invention, the width of the light diffusing angle region (hereinafter sometimes referred to as “diffuse light opening angle”) and the width of the light diffusing incident angle region are approximately It will be the same.
Furthermore, “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, when implementing the manufacturing method of the light-diffusion film of this invention, when the some LED light source in an arrangement | sequence light source connects adjacent LED light sources with a line segment, it is the several square and line | wire which make a line segment one side. It is preferable that a plurality of equilateral triangles having one side as one side, or one line segment is arranged so as to be drawn.
By carrying out in this way, the illuminance distribution of the active energy rays on the surface of the coating layer becomes more uniform, and a light diffusion film having a concentric inner structure can be produced more efficiently.

Moreover, when implementing the manufacturing method of the light-diffusion film of this invention, it is preferable to make the peak wavelength of the active energy ray irradiated from a LED light source into the value within the range of 200-410 nm in a process (c).
By implementing in this way, the light-diffusion film which has a concentric internal structure can be manufactured more efficiently.

FIG. 1A to FIG. 1B are diagrams provided to explain the outline of the internal structure of the light diffusion film in the present invention. FIG. 2 is a diagram for explaining incident angle dependency and isotropic light diffusion of the light diffusion film in the present invention. FIGS. 3A to 3B are views provided to explain the outline of the internal structure of a conventional light diffusion film. FIG. 4 is a diagram for explaining incident angle dependency and isotropic light diffusion of a conventional light diffusion film. FIGS. 5A to 5C are diagrams provided for explaining the coating process and the active energy ray irradiation process. FIGS. 6A to 6C are diagrams for explaining the irradiation state of active energy rays when the array of LED light sources in the array light source is array 1. FIG. FIGS. 7A to 7C are diagrams for explaining the irradiation state of the active energy rays when the array of LED light sources in the array light source is array 2. FIG. FIGS. 8A to 8C are diagrams for explaining the irradiation state of active energy rays when the array of LED light sources in the array light source is array 3. FIG. FIGS. 9A to 9D are diagrams for explaining other variations of the array of LED light sources in the array light source. FIG. 10 is a diagram for explaining a half angle of a directivity angle of an active energy ray irradiated from an LED light source. FIG. 11 is a diagram for explaining an application example of the light diffusion film obtained by the present invention in the reflection type liquid crystal display device. FIGS. 12A to 12B are diagrams for explaining the array light source used in the first embodiment. FIGS. 13A to 13B are laser micrographs obtained by photographing the light diffusion film obtained in Example 1. FIG. FIGS. 14A to 14B are a photograph and a diagram provided to illustrate light diffusion by the light diffusion film obtained in Example 1. FIG.

Embodiment of this invention is a manufacturing method of the light-diffusion film for diffusing incident light isotropically, Comprising: The manufacturing method of the light-diffusion film characterized by including the following process (a)-(c). .
(A) Step of preparing a composition for light diffusion film (b) Step of applying the composition for light diffusion film to a step sheet and forming a coating layer (c) A plurality of LED light sources for the coating layer A step of irradiating active energy rays using an array light source that is arrayed, and forming a coating layer as a light diffusion film having an internal structure composed of a plurality of concentric regions having different refractive indexes. A specific explanation will be given with reference to the drawings as appropriate. In order to facilitate understanding of the explanation, first, the light diffusion film obtained by the production method of the present invention will be explained together with the basic principle of light diffusion by the light diffusion film. Then, the difference between the light diffusion film obtained by the production method of the present invention and the conventional light diffusion film will be described.

1. 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 a light diffusion film 10 obtained by the manufacturing method of the present invention, and FIG. 1B shows the light shown in FIG. A cross-sectional view of the light diffusion film 10 when the diffusion film 10 is cut in the vertical direction along the dotted line AA and the cut surface is viewed from the arrow direction is shown.
FIG. 2 shows an overall view of the light diffusion film 10 and how the incident light is diffused by the light diffusion film 10 when viewed from directly above (the shape of the spread of the diffused light).
As shown in the plan view of FIG. 1A, the light diffusion film 10 includes a concentric region 12 having a relatively high refractive index and a concentric region 14 having a relatively low refractive index. And the concentric internal structure 13 arranged alternately.
Further, as shown in the cross-sectional view of FIG. 1B, the cross section of the high refractive index concentric region 12 and the cross section of the low refractive index concentric region 14 are alternately arranged in the vertical direction of the light diffusion film 10. Are arranged in parallel with each other.
More specifically, as shown in FIG. 2, in the light diffusion film, a concentric internal structure composed of a plurality of concentric cylindrical regions having different refractive indexes, or a plurality of concentric conical shapes having different refractive indexes. The concentric internal structure consisting of regions is in a forested state.
Further, in the light diffusing film, the portion where such a structure is not confirmed includes a high refractive index material constituting the high refractive index concentric region 12 and a low refractive index constituting the low refractive index concentric region 14. Although the refractive index material is finely phase-separated, it is presumed that the structure is a portion that is clearly difficult to distinguish.
In addition, it is preferable that a plurality of concentric internal structures are formed in the light diffusion film, but there may be only one.

Thereby, as shown in FIG. 2, 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.
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 concentric inner structure 13, that is, In the case where the value is within the light diffusion incident angle region, the incident light (52, 54) changes in the film thickness direction while changing the direction inside the high refractive index concentric region 12 in the concentric inner structure 13. It is presumed that the traveling direction of light on the light exit surface side becomes non-uniform by passing along the line.
As a result, when the incident light 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 10 as shown in FIG. It is estimated that the light diffusing film 10a is transmitted as it is (56 ').

Based on the above basic principle, the light diffusing film 10 having the concentric inner structure 13 can exhibit incident angle dependency in light transmission and diffusion, for example, as shown in FIG.
Further, as shown in FIG. 2, when the incident angle of incident light is included in the light diffusion incident angle region, the light diffusing film 10 is substantially the same on the light exit surface side even when the incident angles are different. Light diffusion.
Therefore, it can be said that the obtained light diffusion film 10 also has a light condensing function that concentrates light at a predetermined location.

As shown in FIG. 2, the light diffusion incident angle region is an angle region determined for each light diffusion film 10 by the distribution of concentric internal structure in the light diffusion film 10, the refractive index difference, the inclination angle, and the like. It is.
Further, the direction change of incident light inside the high refractive index concentric region 12 in the concentric inner structure is a step index type in which the direction is linearly changed in a zigzag manner by total reflection as shown in FIG. In addition to the above, there may be a gradient index type in which the direction changes in a curved line.

Further, as shown in FIG. 2, in the light diffusion film 10, concentric regions having a relatively high refractive index and concentric regions having a relatively low refractive index are alternately arranged in the light diffusion film. Since the concentric inner structure 13 is provided, the incident light is diffused isotropically.
Here, “isotropic light diffusion” means that when incident light is diffused by the light diffusing film 10 as shown in FIG. It means that the diffusion state (the shape of the spread of diffused light) has a property that does not change depending on the direction in the same plane.
More specifically, in the case of the light diffusing film 10, as shown in FIG. 2, the diffusion degree of the diffused emitted light is circular or substantially circular in a plane parallel to the film.

2. Difference from Conventional Light Diffusion Film Next, with reference to FIGS. 3 to 4, for example, as shown in Patent Documents 1 and 2, the conventional light diffusion film and the light diffusion obtained by the manufacturing method of the present invention described above. Differences from the film will be described.

First, FIG. 3A shows a top view (plan view) of a conventional light diffusion film 10 ′, and FIG. 3B shows a conventional light diffusion film 10 shown in FIG. 'Is cut in the vertical direction along the dotted line AA, and a cross-sectional view of the conventional light diffusion film 10' when the cut surface is viewed from the direction of the arrow is shown.
FIG. 4 shows an overall view of a conventional light diffusion film 10 ′, and how incident light is diffused by the conventional light diffusion film 10 ′ when viewed from directly above (the shape of the spread of diffused light). is there.
As shown in the plan view of FIG. 3 (a), the conventional light diffusion film 10 ′ has a column structure 13 composed of a columnar body 12 ′ having a relatively high refractive index and a region 14 ′ having a relatively low refractive index. 'Is provided.
Further, as shown in the cross-sectional view of FIG. 3 (b), in the vertical direction of the conventional light diffusion film 10 ′, a high refractive index columnar body 12 ′ and a low refractive index region 14 ′ are respectively predetermined. They are in a state of being alternately arranged with a width.

Thus, as shown in FIG. 4, when the incident angle is within the light diffusion incident angle region, the incident light is converted into the conventional light diffusion film 10 according to the basic principle of light diffusion described with reference to FIGS. It is estimated that isotropic diffusion is caused by ′.
Therefore, even with such a conventional light diffusion film 10 ', the incident light can be diffused isotropically in the same manner as the light diffusion film 10 obtained by the production method of the present invention.
However, the conventional light diffusing film 10 'has a problem that the uniformity of the intensity of the diffused light tends to be insufficient as compared with the light diffusing film 10 obtained by the production method of the present invention.
That is, in the light diffusing film 10 obtained by the production method of the present invention, the concentric inner structure part contributes to isotropic light diffusion, and other parts of the light diffusing film are also made of a high refractive index material. Since the low refractive index material is finely phase-separated, it can contribute to isotropic light diffusion.
On the other hand, in the conventional light diffusion film 10 ', the columnar part contributes to isotropic light diffusion, but the other part of the light diffusion film cannot contribute to isotropic light diffusion at all.
Therefore, in the light diffusion film 10 obtained by the production method of the present invention, compared to the conventional light diffusion film 10 ', elements contributing to isotropic light diffusion are uniformly present inside the film, As a result, the uniformity of the intensity of the diffused light can be improved as compared with the conventional light diffusion film 10 '.
Hereinafter, the manufacturing method of the light-diffusion film which concerns on this embodiment is explained in full detail.

3. Step (a): Preparation Step for Composition for Light Diffusion Film Step (a) is a step for preparing a composition for light diffusion film.
More specifically, it is preferable to stir two polymerizable compounds having different refractive indexes under a high temperature condition of 40 to 80 ° C. to obtain a uniform mixed solution.
At the same time, an additive such as a photopolymerization initiator is added to the mixed solution as desired, and then a dilution solvent is further added as necessary so as to obtain a desired viscosity while stirring until uniform. It is preferable to obtain a solution of the composition for light diffusion film by adding.
Hereinafter, the step (a) will be described more specifically.

(1) High Refractive Index Polymerizable Compound (1) -1 Type Among two polymerizable compounds having different refractive indices, the polymerizable compound having the higher refractive index (hereinafter sometimes referred to as component (A)). Although the kind of is not specifically limited, It is preferable to make the main component into the (meth) acrylic acid ester containing a some aromatic ring.
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 referred to as a polymerizable compound having a lower refractive index (hereinafter referred to as component (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 above component) and causing a predetermined difference in the polymerization rate between these components. It is.
As a result, when photocured, a concentric internal structure consisting of a high refractive index concentric region derived from the component (A) and a low refractive index concentric region derived from the component (B) is efficiently formed. can do.
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 concentric inner structure can be formed more efficiently by reducing the compatibility with the component (B) to a predetermined range.
Further, by including a specific (meth) acrylic acid ester as the component (A), the refractive index of the high refractive index concentric region derived from the component (A) in the concentric internal structure is increased, The difference from the refractive index of the low refractive index concentric region derived from the component B) can be adjusted to a predetermined value or more.
Therefore, by including a specific (meth) acrylic acid ester as the component (A), light having a concentric inner structure composed of concentric regions having different refractive indexes in combination with the characteristics of the component (B) described later. A diffusion film can be obtained efficiently.
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 the like And those in which a part of is 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 General Formula (2), R ¹¹ is a hydrogen atom or a methyl group, carbon number n is an integer of 1 to 4, and repetition 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.
Further, the refractive index of the high refractive index concentric region derived from the component (A) in the concentric internal structure is increased, and the difference from the refractive index of the low refractive index concentric region derived from the component (B). Can be more easily adjusted to a value greater than or equal to a predetermined value.

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.
This is because when the number of carbon atoms exceeds 4, the polymerization rate of the component (A) decreases, or the refractive index of the high refractive index concentric region derived from the component (A) becomes too low. This is because it may be difficult to efficiently form a concentric internal 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 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, it is possible to aggregate and phase separate the component (A) and the component (B) at a fine level, and more efficiently obtain a light diffusion film having a concentric inner structure. Because it can.
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).

(1) -2 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, when photocured, a concentric internal structure composed of a high refractive index concentric region derived from the component (A) and a low refractive index concentric region derived from the component (B) is more efficient. Can be formed.
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 a concentric internal 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). .

(1) -3 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.
The reason for this is that by setting the refractive index of the component (A) to a value within this range, the refractive index of the concentric region having a high refractive index derived from the component (A) and the low refractive index derived from the component (B). This is because the difference between the refractive index and the refractive index of the concentric region can be adjusted more easily, and a light diffusion film having a concentric inner structure can be obtained more efficiently.
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 1.55 to 1.6, and further preferably set to a value within the range of 1.56 to 1.59.
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.

(1) -4 Content Further, the content of the component (A) in the composition for light diffusion film is set to a value within the range of 25 to 400 parts by weight with respect to 100 parts by weight of the component (B) described later. It is preferable.
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 a high refractive index concentric circle derived from the component (A). The width of the concentric region is excessively small compared with the width of the low refractive index concentric region derived from the component (B), making it difficult to obtain a concentric internal structure having good incident angle dependency This is because there may be cases. Moreover, it is because the length of the concentric internal structure 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 a high refractive index concentric circle derived from the component (A). The width of the region is excessively large compared to the width of the low refractive index concentric region derived from the component (B), and conversely, a concentric internal structure having good incident angle dependency can be obtained. This is because it may be difficult. Moreover, it is because the length of the concentric internal structure in the thickness direction of the light diffusing film becomes insufficient, and the light diffusing property may not be exhibited.
Therefore, it is more preferable to set the content of the component (A) to a value within the range of 40 to 300 parts by weight with respect to 100 parts by weight of the component (B), and a value within the range of 50 to 200 parts by weight. More preferably.

(2) Low Refractive Index Polymerizable Compound (2) -1 Type Among the two polymerizable compounds having different refractive indexes, the type of the polymerizable compound having the lower refractive index (component (B)) is not particularly limited. The main component includes, for example, 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 refractive index of the high refractive index concentric region derived from the component (A) and the refractive index of the low refractive index concentric region derived from the component (B) The light diffusion film having a concentric inner structure that effectively suppresses the variation in the refractive index of the low refractive index concentric region derived from the component (B) can be easily adjusted. This is because it can be obtained more efficiently.
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 formed from (a) a compound containing at least two isocyanate groups, (b) polyalkylene glycol, and (c) hydroxyalkyl (meth) acrylate.
Among these, as the compound containing at least two isocyanate groups as component (a), 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 Over preparative 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 (a) component reacts only with the (b) component, or the (a) component reacts only with the (c) component, and the (a) component is replaced with the (b) component and (C) It can react reliably with a component and generation | occurrence | production of an extra by-product can be prevented.
As a result, it is possible to effectively suppress variation in the refractive index of the low refractive index concentric region derived from the component (B) in the concentric internal structure.

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, The internal structure 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 concentric internal structure with high uniformity of diffused light in the light diffusion angle region can be formed more efficiently while increasing the light diffusion property more reliably.
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 (b) and the component (c) 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 (b) 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 is because the handling property and mounting property of a light-diffusion film can be improved effectively. is there.
In addition, the weight average molecular weight of (B) component can be mainly adjusted with the weight average molecular weight of (b) component. Here, the weight average molecular weight of (b) component is 2,300-19,500 normally, Preferably it is 4,300-14,300, Especially preferably, it is 6,300-12,300.

Moreover, as a hydroxyalkyl (meth) acrylate which is (c) 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 concentric internal structure, hydroxyalkyl methacrylate is more preferable, and 2-hydroxyethyl methacrylate is particularly preferable. More preferably.

Moreover, the synthesis | combination of the urethane (meth) acrylate by (a)-(c) component can be implemented in accordance with a conventional method.
At this time, the blending ratio of the components (a) to (c) is preferably set to a ratio of (a) component: (b) component: (c) 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 (a) reacts with and binds to two hydroxyl groups of the component (b), and two components (a) This is because it is possible to efficiently synthesize urethane (meth) acrylate in which the hydroxyl group of component (c) reacts with and binds to the other isocyanate group possessed by each.
Therefore, the mixing ratio of the components (a) to (c) is more preferably set to a ratio of (a) component: (b) component: (c) component = 1-3: 1: 1-3 in molar ratio. Preferably, the ratio is 2: 1: 2.

(2) -2 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 concentric internal structure consisting of a high refractive index concentric region derived from the component (A) and a low refractive index concentric region derived from the component (B) is efficiently formed. can do.
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 concentric internal structure. On the other hand, when the weight average molecular weight of the component (B) exceeds 20,000, it becomes difficult to form a concentric internal structure composed of the component (A) and the component (B). This is because the compatibility with the component is excessively lowered and the component (A) may be precipitated in 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).

(2) -3 Refractive index Moreover, it is preferable to make the refractive index of (B) component into the value within the range of 1.4-1.5.
The reason for this is that by setting the refractive index of the component (B) to a value within this range, a high refractive index concentric region derived from the component (A) and a low refractive index concentric circle derived from the component (B). This is because a light diffusion film having a concentric inner structure can be more efficiently obtained by more easily adjusting the difference from the refractive index of the region.
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) is increased, but the compatibility with the component (A) is extremely deteriorated, resulting in a concentric shape. This is because there is a possibility that the internal structure of the film cannot be formed. On the other hand, if the refractive index of the component (B) exceeds 1.5, 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 1.49, and further preferably set to a value within the range of 1.46 to 1.48.
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 within the concentric internal structure is narrowed, so that the opening angle in light diffusion may be excessively narrowed. Because there is. On the other hand, when the difference in refractive index is an excessively large value, the compatibility between the component (A) and the component (B) is too deteriorated, and a concentric internal 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.

(2) -4 Content The content of the component (B) in the composition for light diffusion film is 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 use a value.
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 a low refractive index concentric circle derived from the component (B). The width of the region is excessively small compared to the width of the high refractive index concentric region derived from the component (A), making it difficult to obtain a concentric internal structure having good incident angle dependency This is because there may be cases. Moreover, it is because the length of the concentric internal structure 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 a low refractive index concentric circle derived from the component (B). The width of the region is excessively larger than the width of the high refractive index concentric region derived from the component (A), and conversely, a concentric internal structure having good incident angle dependency can be obtained. This is because it may be difficult. Moreover, it is because the length of the concentric internal structure 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.

(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.
The reason for this is that by containing a photopolymerization initiator, a concentric internal structure can be efficiently formed when the composition for a light diffusing film is irradiated with active energy rays.
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.

(4) Other additives In addition, other additives can be appropriately added within a range not impairing the effects of the present invention.
Examples of other additives include an antioxidant, an ultraviolet absorber, an antistatic agent, a polymerization accelerator, a polymerization inhibitor, an infrared absorber, a plasticizer, a diluting solvent, and a leveling agent.
In general, the content of the other additives is preferably set to a value within 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). A value within the range of 0.02 to 3 parts by weight is more preferable, and a value within the range of 0.05 to 2 parts by weight is even more preferable.

4). Step (b): Application Step Step (b) is a step of forming the coating layer 1 by applying the prepared light diffusion film composition to the step sheet 2 as shown in FIG. is there.
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 film excellent in the dimensional stability with respect to a heat | fever or an active energy ray.
Preferred examples of such a film include polyester films, polyolefin films, and polyimide films among those described above.

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 a process sheet | seat is normally set to the value within the range of 25-200 micrometers.

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.
At this time, the thickness of the coating layer is preferably set to a value within the range of 100 to 700 μm.

5. Step (c): Active energy ray irradiation step In step (c), as shown in FIGS. 5B to 5C, an array light source 20 in which a plurality of LED light sources 25 are arrayed with respect to the coating layer 1 is formed. This is a step of irradiating the active energy ray 50 to make the coating layer 1 a light diffusing film 10 having a concentric inner structure 13 composed of a plurality of concentric regions having different refractive indexes in the light diffusing film.

(1) Array Light Source (1) -1 LED Light Source The array light source 20 of the present invention is characterized in that a plurality of LED light sources 25 are arrayed as shown in FIGS.
The reason for this is that an array of light sources in which a plurality of LED light sources are arranged can uniformly irradiate the coating layer with active energy rays having a high degree of parallelism, resulting in a concentric internal structure. This is because the light diffusion film can be efficiently produced.
That is, in the case of an array light source in which a plurality of LED light sources are arrayed, the LED light source is originally a light source with high directivity. This is because energy rays can be stably irradiated.
This is because it has been confirmed that the stable application of such active energy rays with high parallelism to the coating layer greatly contributes to the formation of the concentric internal structure.
Therefore, among the LED light sources, it is particularly preferable to use a bullet-type LED light source in which the bullet-shaped resin has a function of a lens and can obtain higher parallelism.

(1) -2 Array It is preferable that the plurality of LED light sources in the array light source are arrayed so that the distance between the centers of the adjacent LED light sources is constant.
The reason for this is that the illuminance distribution of the active energy rays on the surface of the coating layer becomes uniform and the light has a concentric internal structure because the distance between the centers of adjacent LED light sources is constant. This is because the diffusion film can be manufactured more efficiently.
Hereinafter, the arrangements 1 to 3 will be described as more specific arrangement modes.

(I) Sequence 1
First, as shown in FIG. 6A, when a plurality of LED light sources 25 in the array light source 20 connect adjacent LED light sources with a line segment 26, a plurality of squares with the line segment 26 as one side are drawn. It is preferable to take the sequence 1 arranged as described above.
The reason for this is that by arranging the LED light sources in this way, the illuminance distribution of the active energy rays on the surface of the coating layer becomes more uniform, and a light diffusion film having a concentric inner structure is more efficiently manufactured. It is because it can do.
That is, in the case of the arrangement 1, as shown in FIG. 6B, the active energy ray spreads 50 ′ irradiated from the respective LED light sources 25 are activated so that they do not overlap each other on the surface of the coating layer 1. This is because energy rays can be irradiated and the illuminance distribution of the active energy rays on the surface of the coating layer 1 can be made more uniform.

More specifically, when the spread of active energy rays irradiated from the respective LED light sources partially overlap each other on the surface of the coating layer, the overlapping portions are more active than the other portions. The illuminance of energy rays increases.
As a result, the (A) component having a higher polymerization rate than the (B) component starts preferentially photocuring starting from that portion, so that it becomes difficult to form a concentric internal structure.
In this case, in the light diffusion film, for example, a louver structure in which plate-like regions having a high refractive index and plate-like regions having a low refractive index are alternately arranged in parallel, or a mesh formed by combining such louver structures. A structure or the like is formed, and it becomes difficult to obtain a desired isotropic light diffusion.
On the other hand, when the spread of active energy rays irradiated from the respective LED light sources does not overlap with each other on the surface of the coating layer, parallel light having a high degree of parallelism derived from the LED light source is uniform with respect to the surface of the coating layer. It will be irradiated with illuminance distribution.
As a result, radicals are randomly generated from the photoinitiator contained in the coating layer, and as shown in FIG. 6C, a plurality of concentric internal structures are formed starting from the radicals. Presumed.

(Ii) Sequence 2
Further, as shown in FIG. 7A, when a plurality of LED light sources 25 in the array light source 20 connect adjacent LED light sources with a line segment 26, a plurality of equilateral triangles with the line segment 26 as one side is formed. It is also preferred to take the arrangement 2 arranged as depicted.
The reason for this is that by arranging the LED light sources in this way, the illuminance distribution of the active energy rays on the surface of the coating layer becomes more uniform, and a light diffusion film having a concentric inner structure is more efficiently manufactured. It is because it can do.
That is, in the case of the arrangement 2, as shown in FIG. 7B, the active energy ray spreads 50 ′ irradiated from the respective LED light sources 25 are activated so that they do not overlap each other on the surface of the coating layer 1. This is because energy rays can be irradiated and the illuminance distribution of the active energy rays on the surface of the coating layer 1 can be made more uniform.
As a result, as shown in FIG. 7C, a plurality of concentric internal structures can be formed.

(Iii) Sequence 3
Further, as shown in FIG. 8A, when a plurality of LED light sources 25 in the array light source 20 connect adjacent LED light sources with a line segment 26, they are arranged so that one line segment is drawn. It is also preferred to take the sequence 3.
The reason for this is that by arranging the LED light sources in this way, the illuminance distribution of the active energy rays on the surface of the coating layer becomes more uniform, and a light diffusion film having a concentric inner structure is more efficiently manufactured. It is because it can do.
That is, in the case of the arrangement 3, as shown in FIG. 8B, the spread 50 ′ of active energy rays irradiated from the respective LED light sources 25 is more illuminance distribution of the active energy rays on the surface of the coating layer 1. This is because it can be made uniform.
That is, in the case of the arrangement 3, as shown in FIG. 8B, the active energy ray spreads 50 ′ irradiated from the respective LED light sources 25 are activated so that they do not overlap each other on the surface of the coating layer 1. This is because energy rays can be irradiated and the illuminance distribution of the active energy rays on the surface of the coating layer 1 can be made more uniform.
As a result, as shown in FIG. 8C, a plurality of concentric internal structures can be formed.
In particular, in the case of the array 3, the application layer 1 is irradiated with active energy rays while moving the coating layer 1 in a direction orthogonal to the line segment 26 using a conveyor line or the like, for example, so that a concentric internal structure is efficiently formed. The light diffusing film 10 having 13 can be mass-produced.

(Iv) Other arrangements The arrangement of the LED light sources in the present invention may be other than the arrangements 1 to 3 described above.
More specifically, when adjacent minute light sources are connected by a line segment, the arrangement is such that a plurality of quadrangles, triangles, or one line segment with the line segment as one side are drawn, and adjacent The arrangement may be such that the distance between the centers of the LED light sources to be performed is not constant.
However, in this case, in the obtained light diffusion film, uneven curing, non-uniform light diffusion, and non-uniformity may easily occur.
Moreover, as shown to Fig.9 (a), when adjacent LED light source 25 is connected with the line segment 26, the arrangement | sequence in which several regular hexagons which make the line segment 26 one side may be drawn may be sufficient. As shown in FIGS. 9B to 9C, when adjacent LED light sources 15 are connected by a line segment 26, an array such that a plurality of octagons and rectangles having the line segment 26 as one side are drawn is shown. There may be.
Furthermore, as shown in FIG. 9D, an array in which the LED light sources 25 are arranged concentrically may be used.

(1) -3 Center-to-center distance In the array light source, it is preferable to set the center-to-center distance between adjacent LED light sources to a value in the range of 10 to 100 mm. The reason for this is that by setting the distance between the centers of adjacent LED light sources within this range, the illuminance distribution of the active energy rays on the surface of the coating layer becomes more uniform, and the light diffusion has a concentric internal structure. This is because the film can be produced more efficiently.
That is, when the center-to-center distance is less than 10 mm, the active energy rays derived from the LED light sources are excessively overlapped, the illuminance distribution on the surface of the coating layer becomes non-uniform, and a concentric internal structure is formed. This is because it may be difficult to achieve the desired isotropic light diffusion. On the other hand, when the distance between the centers exceeds 100 mm, the area of the coating layer surface where the active energy rays are not irradiated becomes excessively large, the irradiation of the active energy rays becomes extremely uneven, and the light diffusing property is reduced. This is because non-uniformity and heterogeneity are likely to occur.
Therefore, in the array light source, the center-to-center distance between adjacent LED light sources is more preferably set to a value within the range of 12 to 75 mm, and further preferably set to a value within the range of 14 to 50 mm.

(1) -4 Half angle of directivity angle Moreover, it is preferable to make half angle (theta) 3 of the directivity angle of the active energy ray irradiated from a LED light source into the value within the range of 0-30 degrees.
Here, with respect to the LED light source, the directivity angle is a half luminous intensity (relative luminous intensity 50%) from the brightest point (relative luminous intensity 100%) when a relative luminous intensity distribution diagram as shown in FIG. 10 is drawn. Means the angle value (the angle formed by two points having a relative luminous intensity of 50% on the relative luminous intensity distribution curve and a zero point at the center of the lower end of the distribution diagram).
Therefore, the half angle of the directivity angle means half of the directivity angle, and means θ3 in FIG.
The reason why the half angle of the directivity angle is preferably set to a value within the above-described range is that the half angle θ3 of the directivity angle of the active energy ray irradiated from the LED light source is set to a value within the above range, thereby This is because the illuminance distribution of the active energy rays becomes more uniform, and a light diffusion film having a concentric inner structure can be manufactured more efficiently.
That is, when the half angle θ3 of the directivity angle exceeds 20 °, the active energy lines derived from the LED light sources are excessively overlapped, the illuminance distribution on the coating layer surface becomes non-uniform, and the concentric internal This is because it becomes difficult to form the structure, and it may be difficult to achieve the desired isotropic light diffusion. On the other hand, if the half angle θ3 of the directivity angle is too small, the selection range of the LED light source is excessively limited.
Therefore, it is more preferable to set the half angle θ3 of the directivity angle of the active energy ray irradiated from the LED light source to a value in the range of 0.01 to 20 °, and to a value in the range of 0.1 to 15 °. Is more preferable.
The half angle θ3 of the directivity angle of the active energy ray emitted from the LED light source is the active energy ray when the irradiation direction of the active energy ray from the center of the LED light source 25 is 0 ° as shown in FIG. It is an angle indicating the spread of.

(2) Irradiation distance Moreover, it is preferable to make the space | interval of the surface of an application layer and the lower end of an arrangement | sequence light source into the value within the range of 5-100 cm.
The reason for this is that by setting the distance between the surface of the coating layer and the lower end of the array light source to a value within this range, the illuminance distribution of the active energy rays on the surface of the coating layer becomes more uniform, and the concentric internal This is because a light diffusing film having a structure can be more efficiently produced.
That is, when the distance is less than 5 cm, the area of the coating layer surface where the active energy ray is not irradiated becomes excessively large, the irradiation of the active energy ray becomes extremely uneven, and the light diffusibility is uneven. This is because heterogeneity tends to occur. On the other hand, when the interval exceeds 100 cm, the active energy rays derived from the LED light sources are excessively overlapped, the illuminance distribution on the surface of the coating layer becomes non-uniform, and a concentric internal structure is formed. This is because it may be difficult to achieve the desired isotropic light diffusion.
Accordingly, the distance between the surface of the coating layer and the lower end of the array light source is more preferably set to a value within the range of 8 to 80 cm, and further preferably set to a value within the range of 10 to 50 cm.

(3) Peak wavelength Moreover, it is preferable to make the peak wavelength of the active energy ray irradiated from a LED light source into the value within the range of 200-410 nm.
This is because the light diffusion film having a concentric internal structure can be more efficiently produced by setting the peak wavelength of the active energy ray to a value within this range.
That is, when the peak wavelength is less than 200 nm, polymerization initiation by the photopolymerization initiator may be difficult to occur appropriately. On the other hand, even when the peak wavelength exceeds 410 nm, polymerization initiation by the photopolymerization initiator may be difficult to occur appropriately.
Therefore, the peak wavelength of the active energy ray irradiated from the LED light source is more preferably set to a value within the range of 250 to 405 nm, and further preferably set to a value within the range of 300 to 400 nm.

(4) Illuminance Moreover, it is preferable to make the illuminance on the coating layer surface in active energy ray irradiation into the value within the range of 0.1-10 mW / cm < ² >.
This is because a concentric internal structure can be efficiently formed by setting the illuminance in active energy ray irradiation to a value within this range.
That is, when the illuminance is less than 0.1 mW / cm ² , it may be difficult to clearly form a concentric internal structure. On the other hand, when the illuminance value exceeds 10 mW / cm ² , the coating layer is cured before phase separation occurs between the high refractive index polymerizable compound and the low refractive index polymerizable compound, This is because it may be difficult to form a concentric internal structure necessary for isotropic light diffusion.
Therefore, it is more preferably set to a value within the range of the illuminance of 0.3~7mW / cm ² of the coating layer surface of the active energy ray irradiation, a value within a range of 0.5~5mW / cm ² Is more preferable.

(5) Light quantity Moreover, it is preferable to make the light quantity in the surface of the coating layer in active energy ray irradiation into the value within the range of 10-500 mJ / cm < ² >.
This is because a concentric internal structure can be efficiently formed by setting the amount of light in active energy ray irradiation to a value within this range.
That is, when the amount of light is less than 10 mJ / cm ² , it may be difficult to sufficiently extend the concentric internal structure from above to below.
On the other hand, when the amount of light exceeds 500 mJ / cm ² , abnormalities such as yellowing may occur in the obtained light diffusion film.
Therefore, it is more preferably set to a value within the range of the amount of light the 20~200mJ / cm ² of the coating layer surface of the active energy ray irradiation, still more preferably a value within the range of 30~150mJ / cm ^2.

(6) Suppression of oxygen inhibition Moreover, it is preferable to irradiate the coating layer with active energy rays in a non-oxygen atmosphere.
The reason for this is that, by performing active energy ray irradiation in a non-oxygen atmosphere, the influence of oxygen inhibition can be suppressed and a concentric internal structure can be efficiently formed.
In other words, if active energy ray irradiation is performed in an oxygen atmosphere instead of a non-oxygen atmosphere, a concentric internal structure is formed at a very shallow position near the surface of the coating layer when irradiated with high illuminance. This is because it may be difficult to obtain a difference in refractive index necessary for light diffusion.
On the other hand, when irradiated at a low illuminance, it may be difficult to form a concentric internal structure due to the influence of oxygen inhibition.
Note that “under a non-oxygen atmosphere” means a condition where the upper surface of the coating layer is not in direct contact with an oxygen atmosphere or an atmosphere containing oxygen.
Therefore, for example, it is possible to irradiate active energy rays in a “non-oxygen atmosphere” in a state where a film is laminated on the upper surface of the coating layer, or nitrogen is purged by replacing air with nitrogen gas. This corresponds to the irradiation of active energy rays.

Further, as the active energy ray irradiation in the “non-oxygen atmosphere” described above, it is particularly preferable to perform the active energy ray irradiation in a state where the active energy ray transmitting sheet is laminated on the upper surface of the coating layer.
The reason for this is that by performing active energy ray irradiation in this manner, the influence of oxygen inhibition can be effectively suppressed, and a concentric internal structure can be formed more efficiently.
That is, by laminating an active energy ray transmissive sheet on the upper surface of the coating layer, the coating layer efficiently penetrates the sheet while stably preventing the upper surface of the coating layer from coming into contact with oxygen. This is because active energy rays can be irradiated on the surface.
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.

Moreover, as an active energy ray permeable sheet, it is preferable that the surface centerline average roughness of the side which does not contact a coating layer is a value of 2 micrometers or less, and it is especially preferable that it is a value of less than 1 micrometer.
The reason for this is that with such center line average roughness, active energy rays can be effectively prevented from diffusing by the active energy ray transmitting sheet, and a concentric internal structure can be efficiently formed. .
The centerline average roughness can be determined according to JIS B 0633.
From the same viewpoint, the haze value of the active energy ray-transmitting sheet is preferably a value within a range of 0 to 8%, and particularly preferably a value within a range of 0.1 to 5%.
The haze value can be obtained according to JIS K 7136.

Moreover, it is preferable that the image definition (slit width: 0.125 mm, 0.25 mm, 0.5 mm, 1 mm, and 2 mm) of the active energy ray transmitting sheet is a value within a range of 200 to 500, A value in the range of 300 to 490 is particularly preferable.
The reason for this is that, if the image sharpness is in such a range, the active energy rays can be transmitted through the coating layer without being lost by the sheet, and a concentric internal structure can be efficiently formed. This is because it can.
The image definition can be obtained according to JIS K 7374.
From the same viewpoint, the transmittance of the active energy ray-transmitting sheet with respect to light having a wavelength of 360 nm is preferably a value in the range of 30 to 100%, and a value in the range of 45 to 95%. Particularly preferred.

(7) Apparatus Moreover, although it does not specifically limit as an apparatus for irradiating an active energy ray with respect to a coating layer, For example, it is set as an aspect as shown to FIG.5 (b)-(c). It is preferable.
That is, it is preferable that the mounting unit 60 for mounting the coating layer 1 is provided and the array light source 20 is provided above the mounting unit 60 so as to face the mounting unit 60.
Further, the mounting portion 60 and / or the array light source 20 can be moved up and down so that the distance between the surface of the coating layer 1 and the lower end of the array light source 60 can be adjusted as appropriate. Preferably there is.
The apparatus for irradiating the active energy ray to the coating layer may be a mode other than the stationary type as shown in FIGS. 5B to 5C, for example, a belt conveyor capable of moving the coating layer in parallel. The array light source may also be movable in parallel so as to follow the movement of the coating layer.
Further, following the movement of the coating layer, the LED light sources constituting the array light source may be appropriately turned on and off.
Furthermore, the coating layer and the array light source may be opposed to each other with a predetermined inclination angle. In this case, a concentric internal structure having a certain inclination angle is formed in the obtained light diffusion film.

6). Complete curing step In addition to the step (c), it is also preferable to irradiate an active energy ray so that the coating layer has a light amount that can be sufficiently cured.
Since the active energy ray at this time is intended to sufficiently cure the coating layer, it is preferable to use irradiation light whose traveling direction is random.
Moreover, the light-diffusion film after a complete hardening process will be in the state which can be finally used now by peeling a process sheet | seat.

7). Specific configuration of light diffusion film (1) Internal structure (1) -1 Refractive index In a concentric internal structure, a difference in refractive index between concentric regions having different refractive indexes, that is, a concentric region having a high refractive index It is preferable that the difference between the refractive index and the refractive index of the low refractive index concentric region be 0.01 or more.
This is because the difference in refractive index is set to a value of 0.01 or more, whereby incident light is stably reflected in the concentric internal structure, and the incident angle dependency in the light diffusion film is further improved. Because it can.
Therefore, the difference in refractive index between concentric regions having different refractive indexes in the concentric inner structure is preferably 0.05 or more, and more preferably 0.1 or more.
In addition, although the difference of the refractive index mentioned above is so preferable that it is large, from a viewpoint of selecting the material which can form a concentric internal structure, about 0.3 is considered to be an upper limit.

In the concentric internal structure, the refractive index of the high refractive index concentric region is preferably set to a value in the range of 1.5 to 1.7.
This is because when the refractive index of the high refractive index concentric region is less than 1.5, the difference from the low refractive index concentric region becomes too small, making it difficult to obtain a concentric internal structure. This is because it may become. On the other hand, if the refractive index of the high refractive index concentric region exceeds 1.7, the compatibility between the material substances in the composition for a light diffusion film may be excessively lowered.
Therefore, it is more preferable to set the refractive index of the high refractive index concentric region in the concentric inner 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.
The refractive index of the high refractive index concentric region can be measured according to, for example, JIS K 0062.

Further, in the concentric internal structure, the refractive index of the low refractive index concentric region is preferably set to a value in the range of 1.4 to 1.5.
This is because the rigidity of the resulting light diffusion film may be reduced when the refractive index of the low refractive index concentric region is less than 1.4. On the other hand, when the refractive index of the low refractive index concentric region exceeds 1.5, the difference from the refractive index of the high refractive index concentric region becomes too small to obtain a concentric internal structure. This may be difficult.
Therefore, the refractive index of the low refractive index concentric region in the concentric inner structure is more preferably set to a value in the range of 1.42 to 1.48, and a value in the range of 1.44 to 1.46. More preferably.
In addition, the refractive index in the low-refractive-index concentric area | region can be measured according to JISK0062, for example.

(1) -2 Width In the concentric internal structure as shown in FIG. 1B, the widths of the high-refractive index concentric region 12 and the low-refractive index concentric region 14 are set to 0.1 to 2, respectively. A value within the range of 15 μm is preferable.
This is because, by setting the width of these regions to a value in the range of 0.1 to 15 μm, the incident light is stably reflected in the concentric inner structure, and the incident angle dependency in the light diffusion film It is because it can improve more effectively.
That is, when the widths of the high-refractive index concentric region and the low-refractive index concentric region are less than 0.1 μm, it may be difficult to show light diffusion regardless of the incident angle of incident light. Because there is. On the other hand, when the width of the high-refractive index concentric region and the low-refractive index concentric region exceeds 15 μm, the light traveling straight in the concentric internal structure increases and the uniformity of the diffused light deteriorates. It is because there is a case to do.
Therefore, in the concentric inner structure, it is more preferable that the widths of the high refractive index concentric region and the low refractive index concentric region are each in the range of 0.5 to 10 μm, More preferably, the value is within the range.
The width and length of the high refractive index concentric region and the low refractive index concentric region constituting the concentric internal structure can be measured by observing the film cross section with an optical digital microscope.

(2) Film thickness Moreover, it is preferable to make the film thickness of the light-diffusion film of this invention into the value within the range of 30-250 micrometers.
This is because, when the total film thickness of the light diffusing film is less than 30 μm, the incident light traveling straight in the concentric internal structure increases, and it may be difficult to show light diffusion. On the other hand, when the thickness of the light diffusing film exceeds 250 μm, when the concentric inner structure is formed by irradiating the composition for light diffusing film with active energy rays, This is because the traveling direction of photopolymerization is diffused depending on the structure, and it may be difficult to form a concentric internal structure.
Therefore, the film thickness of the light diffusion film is more preferably set to a value within the range of 40 to 200 μm, and further preferably set to a value within the range of 50 to 150 μm.

8). Applications Further, as shown in FIG. 11, the light diffusion film obtained by the present invention is preferably used for the reflective liquid crystal display device 100.
The reason for this is that the light diffusing film obtained according to the present invention is efficient so that external light can be collected and efficiently transmitted to be taken into the liquid crystal display device and used as a light source. This is because it can be diffused.
Therefore, the light diffusing film obtained by the present invention is disposed on the upper surface or the lower surface of the liquid crystal cell 110 composed of the glass plates (104, 108) and the liquid crystal 106, the specular reflection plate 107, etc. 100 is preferably used as the light diffusion plate 103.
The light diffusion film obtained by the present invention can be applied to the polarizing plate 101 and the retardation plate 102 to obtain a wide viewing angle polarizing plate and a wide viewing phase retardation plate, a projection screen, It can also be applied to lighting fixtures.

  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. (B) Synthesis of component In a container, 2 mol of isophorone diisocyanate (IPDI) as component (a) with respect to 1 mol of polypropylene glycol (PPG) having a weight average molecular weight of 9,200 as component (b), And after accommodating 2 mol of 2-hydroxyethyl methacrylate (HEMA) as (c) component, it superposed | polymerized in accordance with the conventional method, and obtained the polyether urethane methacrylate of the weight average molecular weight 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 Light Diffusion Composition Next, the weight represented by the following formula (3) as the component (A) with respect to 100 parts by weight of the polyether urethane methacrylate having a weight average molecular weight of 9,900 as the component (B) obtained. 100 parts by weight of o-phenylphenoxyethoxyethyl acrylate having an average molecular weight of 268 (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester A-LEN-10) and 2-hydroxy-2-methylpropiophenone 5 as component (C) After adding a weight part, it heat-mixed on 80 degreeC conditions, and obtained the composition for light-diffusion films.
The refractive indices of the components (A) and (B) were measured according to JIS K0062 using an Abbe refractometer [manufactured by Atago Co., Ltd., product name “Abbe refractometer DR-M2”, Na light source, wavelength: 589 nm]. , 1.58 and 1.46, respectively.

3. Application of composition for light diffusion film 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 using an applicator. A coating layer having a thickness of 200 μm was obtained.

4). Next, an array light source as shown in FIG. 12A was prepared. FIG. 12 (b) shows an enlarged view of a group of nine micro light sources included in the array light source of FIG. 14 (a).
The specific configuration of such an array light source is as follows.
-Micro light source arrangement mode: square array (when adjacent micro light sources are connected by a line segment, an array in which a plurality of squares with a line segment as one side are drawn)
・ Center-to-center distance between adjacent micro light sources: 14 mm
-Number of micro light sources arranged: 5 vertical x 10 horizontal-Types of micro light sources: LED light source (Nitride Semiconductor Co., Ltd., NS375-5RLM)
-Diameter of micro light source: 5 mm
・ Peak wavelength of active energy rays irradiated from a micro light source: 375 nm
・ Half angle of active energy ray irradiated from micro light source: 15 °

Next, on the exposed surface side of the coating layer, as an active energy ray transmitting sheet, a release film having a thickness of 38 μm having UV transmittance (manufactured by Lintec Corporation, SP-PET 382050; centerline average roughness on the surface on the UV irradiation side) 0.01 μm, haze value 1.80%, image definition 425, transmittance of wavelength 360 nm) was laminated.
Next, in the apparatus as shown in FIGS. 5B to 5C, the active energy rays are arranged in a state in which the array light source described above is arranged in parallel so that the distance between the surface of the coating layer and the array light source is 15 cm. Was irradiated for 2 minutes to obtain a light diffusion film having a thickness of 200 μm.
At this time, the surface of the coating layer is irradiated with active energy rays so as to have a substantially uniform peak illuminance distribution, the peak illuminance at an arbitrary predetermined point is 0.95 mW / cm ² , and the integrated light amount is 33. 0.000 mJ / cm ² .
In addition, the film thickness of the light-diffusion film was measured using the constant-pressure thickness measuring device (Takara Seisakusho Co., Ltd. product, Teclock PG-02J).

Moreover, the obtained light-diffusion film has a concentric internal structure which consists of a concentric area | region with a high refractive index and a concentric area | region with a low refractive index as shown to Fig.1 (a)-(b). I confirmed that I have it.
The electron micrograph of the light-diffusion film obtained in Example 1 is shown to Fig.13 (a)-(b). That is, FIG. 13A is a laser micrograph of a cut surface obtained by cutting the light diffusion film along a plane substantially parallel to the film surface, and FIG. 13B is a surface perpendicular to the film surface. It is a laser microscope photograph of the cut surface.

5. Measurement Using a conoscope (manufactured by autonic-MELCHERS Gmbh), a direction perpendicular to the film surface with respect to the film from the lower side of the obtained light diffusion film, that is, the side in contact with the process sheet The incident light from was incident with a laser pointer having a wavelength of 500 nm.
A photograph of the diffused light obtained at this time is shown in FIG. 14 (a), and an outline of the diffused light in FIG. 14 (a) is shown in FIG. 14 (b).

As described above in detail, according to the present invention, the application layer made of the composition for light diffusion film is irradiated with active energy rays using an array light source in which a plurality of LED light sources are arrayed. A light diffusing film that can diffuse light isotropically and has excellent uniformity in intensity of diffused light can be obtained.
More specifically, it is a light diffusion film having a concentric internal structure composed of a plurality of concentric regions having different refractive indexes in the light diffusion film, and can diffuse incident light isotropically and diffuse. A light diffusing film excellent in uniformity of light intensity can be obtained.
Therefore, the method for producing a light diffusing film of the present invention can be applied to a viewing angle control film, a viewing angle control film, a viewing angle widening film, a projection screen, and a lighting fixture in addition to a light control film in a reflective liquid crystal device. It is expected to contribute significantly to the improvement of quality and the yield.

1: coating layer, 2: process sheet, 10: light diffusion film, 10 ′: conventional light diffusion film, 12: concentric region having a relatively high refractive index, 12 ′: columnar object having a relatively high refractive index , 13: concentric internal structure, 13 ′: column structure, 14: concentric region having a relatively low refractive index, 14 ′: region having a relatively low refractive index, 20: array light source, 25: LED light source, 26: line segment, 50: active energy ray, 50 ': spread of active energy ray, 60: mounting portion, 100: reflection type liquid crystal display device, 101: polarizing plate, 102: retardation plate, 103: light diffusion plate 104: glass plate, 105: color filter, 106: liquid crystal, 107: specular reflector, 108: glass plate, 110: liquid crystal cell

Claims (3)

A method for producing a light diffusing film for diffusing incident light isotropically,
The manufacturing method of the light-diffusion film characterized by including the following process (a)-(c).
(A) Step of preparing a composition for light diffusing film (b) Step of applying the composition for light diffusing film to a step sheet and forming a coating layer (c) Directional angle with respect to the coating layer An array light source in which a plurality of LED light sources each having a half angle in a range of 0 to 30 ° are arranged so that a distance between centers of adjacent LED light sources is constant within a range of 14 to 50 mm. An internal structure comprising a plurality of concentric regions having different refractive indexes, the active layer being used to irradiate active energy rays, and the coating layer disposed so that the distance from the lower end of the array light source is within a range of 10 to 50 cm For making a light diffusion film having When the LED light sources in the array light source connect adjacent LED light sources with line segments, a plurality of squares with the line segment as one side, a plurality of equilateral triangles with the line segment as one side, or one 2. The method for producing a light diffusing film according to claim 1 , wherein the light diffusing film is arranged so that line segments of the book are drawn. The method for producing a light diffusing film according to claim 1 or 2 , wherein in the step (c), the peak wavelength of the active energy ray irradiated from the LED light source is set to a value within a range of 200 to 410 nm. .