JP6745625B2 - Anisotropic optical film - Google Patents

Description

The present invention relates to an anisotropic optical film.

Members having a light diffusing property (light diffusing members) are used in display devices as well as lighting fixtures and building materials. Examples of this display device include a liquid crystal display device (LCD). The light diffusion manifestation mechanism of the light diffusing member includes light diffusion due to unevenness formed on the surface (surface light diffusion), light diffusion due to the difference in refractive index between the matrix resin and the fine particles dispersed therein (internal light diffusion), And by both surface light diffusion and internal light diffusion. However, these light diffusing members are generally isotropic in light diffusing property, and even if the incident light angle is slightly changed, the light diffusing property of the transmitted light is not largely different.

On the other hand, an anisotropic optical film is known that is capable of strongly diffusing incident light in a certain angle region and transmitting incident light of other angles, that is, capable of changing the amount of transmitted light according to the incident light angle. Has been. As such an anisotropic optical film, a group of a plurality of rod-shaped cured regions that extend parallel to a predetermined direction P are all provided inside a resin layer made of a cured product of a composition containing a photocurable compound. An anisotropic diffusion medium having a body is disclosed (for example, see Patent Document 1). In addition, hereinafter, in the present specification, an assembly of a plurality of rod-shaped cured regions extending in parallel to a predetermined direction as described in Patent Document 1 is referred to as a “pillar structure region”, and a pillar structure region. One of the structures is referred to as a "pillar structure", and the structure of the anisotropic light diffusion layer or the anisotropic optical film in which the pillar structure region is formed is referred to as a "pillar structure".

In the anisotropic optical film having such a pillar structure, when light is incident on the film from above to below, the flow direction in the film manufacturing process (hereinafter, referred to as “MD direction”), The same light diffusibility is exhibited in the width direction of the film perpendicular to the MD direction (hereinafter, referred to as “TD direction”). That is, the light diffusivity of the anisotropic optical film having the pillar structure is isotropic. Therefore, the anisotropic optical film having the pillar structure is unlikely to cause a rapid change in brightness and glare.

However, although the pillar-shaped anisotropic optical film spreads the viewing angle almost equally in all directions, it cannot meet the demand for a wider viewing angle in a certain direction (for example, horizontal direction). If the diffusion angle is widened, there is a problem that the front luminance is reduced due to the diffusion of light.

On the other hand, as the anisotropic optical film, not the pillar structure but the regions having different refractive indexes, for example, a large number of rod-shaped light sources or point light sources used for the structure formation are continuously arranged linearly (hereinafter, these There is disclosed a film-shaped composition in which a layer having a periodic microstructure is formed in a state of being aligned in parallel with the major axis direction (such as a light source is referred to as a linear light source) (see, for example, Patent Document 2). In addition, hereinafter, in the present specification, an aggregate of a plurality of microstructures that periodically exist in a state of being aligned parallel to the long axis direction of the linear light source, as described in Patent Document 2, will be referred to as a “louver structure region”. Furthermore, one structure in the louver structure region is referred to as a “louver structure”, and the structure of the anisotropic light diffusion layer or the anisotropic optical film forming the louver structure region is referred to as a “louver structure”. I will call it.

In the anisotropic optical film having such a louver structure, when light is incident on the film from above to below, the film exhibits different light diffusivity in the MD direction and the TD direction. That is, the light diffusivity of the anisotropic optical film having the louver structure exhibits anisotropy. Specifically, for example, if the width (diffusion width) of the light diffusion region in the MD direction is wider than that in the pillar structure, the diffusion width in the TD direction is narrower than that in the pillar structure. Therefore, in the anisotropic optical film having the louver structure, for example, when the diffusion width is narrowed in the TD direction, a rapid change in luminance occurs in the TD direction, and as a result, light interference easily occurs and glare easily occurs. is there.

Furthermore, since the pillar structure has a pillar structure, the linear transmittance (the amount of transmitted light in the linear direction when incident on an anisotropic optical film at a certain incident light angle (hereinafter, “the amount of linear transmitted light”) Of the incident light) (hereinafter referred to as “incident light amount”) tends to be lower than that of the louver structure, and the louver structure has a louver structure. The linear transmittance tends to be higher than that of the pillar structure.

To solve these problems, Patent Document 3 discloses an anisotropic optical film having an intermediate structure between the pillar structure and the louver structure. Hereinafter, the structure of this anisotropic optical film will be referred to as a "louver rod structure". In the patent document, as a method for obtaining a louver rod structure, a thin plate-shaped photopolymerization cured product having a plurality of columnar structures is stretched uniaxially along the surface of the thin plate to obtain a cross-sectional shape of the columnar structures. The method of uniaxial extension is adopted.

JP, 2005-265915, A Japanese Patent No. 4802707 JP, 2012-11709, A

However, in the conventional manufacturing method of the louver rod structure, it is difficult to finely adjust the shape of the louver rod structure to achieve desired optical characteristics. Therefore, it is an object of the present invention to provide an anisotropic optical film in which glare and abrupt changes in brightness are suppressed and the balance of optical characteristics including light diffusivity is optimized.

The present inventors have conducted extensive research to solve the above problems. As a result, in the anisotropic light-diffusing layer of the anisotropic optical film, the shape of the cross section orthogonal to the column axis direction of the plurality of louver rod structures (the thickness direction of the anisotropic light-diffusing layer) is optimized to have substantially rounded corners. The present invention has been completed by finding that the above problems can be solved by forming a rectangle. That is,
The present invention (1) is an anisotropic optical film in which the amount of transmitted light changes depending on the incident light angle of light, wherein the anisotropic optical film has at least one anisotropic light diffusing layer. The diffusion layer has a plurality of louver rod structures and a matrix region, and has a cross-sectional shape orthogonal to the column axis direction of the louver rod structure such that each end of the two substantially parallel lines has a substantially arc shape. It is an anisotropic optical film characterized in that it is formed into a substantially rounded rectangular shape.
In the present invention (2), the parallel line width of the two substantially parallel lines is L, the long diameter line width of the substantially long diameter line which is the maximum width of the substantially rounded rectangle is Y, and (Y−L)/2 is set. When r is set, the anisotropic optical film described in (1) is characterized by satisfying Formula 2r<L<10r.
The present invention (3) is the anisotropic optical film as described in (1) or (2), wherein the thickness of the anisotropic light diffusion layer is in the range of 10 μm to 100 μm.
In the present invention (4), the anisotropy according to any one of (1) to (3), wherein the length of r is in the range of 0.01 μm or more and less than 0.4 μm. It is an optical film.

According to the present invention, it is possible to provide an anisotropic optical film in which glare and abrupt changes in luminance are suppressed and the balance of optical characteristics including light diffusivity is optimized.

It is a schematic diagram which shows an example of a structure of the anisotropic light diffusion layer which concerns on this invention, (a) is an anisotropic light diffusion layer plane shape schematic diagram, (b) is anisotropic light diffusion cut|disconnected by the AA line of (a). It is a cross-sectional schematic diagram of the thickness direction of a layer. It is a schematic diagram which shows an example of a structure of the anisotropic diffusion layer in the anisotropic optical film of this invention, and is a schematic diagram showing a substantially rounded rectangle shape. It is explanatory drawing which shows the evaluation method of the linear transmitted light amount and linear transmittance of an anisotropic optical film. It is a graph for demonstrating evaluation of the linear transmitted light amount of an anisotropic optical film. It is a schematic diagram which shows an example of the photomask pattern used by this invention. It is a schematic diagram which shows an example of the whole photomask used by this invention. It is an appearance photograph of the photomask used in the present invention. It is a partial surface photograph of the photomask pattern used in the present invention. It is explanatory drawing which shows the evaluation method of the rapid change of the brightness|luminance of an anisotropic light-diffusion layer (anisotropic optical film).

Here, the definition of each term in this claim and this specification is demonstrated.

The "low refractive index region" and the "high refractive index region" are regions formed by the local difference in the refractive index of the material forming the anisotropic optical film, and have a lower refractive index than the other. It is a relative one indicating whether it is high or high. These regions are formed when the material forming the anisotropic light diffusion layer of the anisotropic optical film is cured.

The “diffusion central axis” means the direction in which the light diffusivity coincides with the incident light angle of light having substantially symmetry with the incident light angle as a boundary when the incident light angle of light is changed. The reason for having “substantially symmetry” here is that the anisotropic light diffusion layer of the present invention does not have strict symmetry of light diffusion strictly. The diffusion center axis can be found by observing the inclination of the film cross section with an optical microscope and observing the projected shape of light through the anisotropic optical film by changing the incident light angle.

The linear transmittance is represented by the following formula.
Linear transmittance (%)=(amount of linearly transmitted light/amount of incident light)×100

The “light” in the present invention is an electromagnetic wave including visible light having a wavelength of 380 nm to 780 nm and ultraviolet light having a wavelength of 100 nm to 400 nm.

The contents of the present invention will be described below with reference to the drawings.

<<Structure of anisotropic optical film>>
<Overall structure>
The anisotropic optical film according to the present invention includes at least an anisotropic light diffusion layer. Therefore, it may be an optical laminated body in which a plurality of layers including an anisotropic light diffusion layer are laminated.
If the anisotropic light diffusing layer is a single layer and does not include other layers, the anisotropic light diffusing layer is an anisotropic optical film depending on the application.

<Anisotropic light diffusion layer>
1 and 2 are schematic views showing an example of the configuration of the anisotropic light diffusion layer 1 in the anisotropic optical film of the present invention. 1A is a schematic plan view of the anisotropic light diffusing layer 1, and FIG. 1B is a schematic sectional view in the thickness direction of the anisotropic light diffusing layer 1 taken along the line AA in FIG. 1A. FIG. 2 and FIG. 2 are schematic diagrams showing a substantially rounded rectangular shape.

As shown in FIG. 1, the anisotropic light diffusion layer 1 has a plurality of louver rod structures 2 and a matrix region 3. The plurality of louver rod structures 2 have a regular distribution in the anisotropic light diffusion layer 1 in FIG. 1A, but may have an irregular distribution. Whether it is regular or not depends on the pattern of the photomask described later.

Further, as shown in FIG. 1B, in the structure of the anisotropic light diffusion layer 1, a plurality of louver rod structures 2 and the matrix region 3 are alternately arranged in the plane direction of the anisotropic light diffusion layer 1. Is formed in.
Further, in FIG. 1B, a plurality of louver rod structures 2 extend parallel to the thickness direction of the anisotropic light diffusion layer 1. The cross-sectional shape with respect to the thickness direction may be one that satisfies the optical characteristics described later, and the linear shape of the axially outer peripheral portion of the louver rod structure 2 column may be another shape such as a corrugated shape, an inclined shape, or a bent shape. It may be a shape or a mixture of shapes.

In addition, the plurality of louver rod structures 2 are irregularly or regularly distributed over the entire area of the anisotropic light diffusing layer 1, so that the obtained optical characteristics can be obtained at any position of the anisotropic light diffusing layer 1. Even if it measures, it becomes almost the same.

Here, the refractive index of the matrix region 3 may be different from the refractive indices of the plurality of louver rod structures 2, and there is no particular limitation on how different the refractive indices are, and which is the high refractive region. , Relative.
That is, when the refractive index of the matrix region 3 is lower than the refractive index of the plurality of louver rod structures 2, the matrix region 3 is a low refractive index region, an aggregate of the plurality of louver rod structures 2 (hereinafter referred to as “louver rod structure region”). ") is a high refractive index region.
Conversely, when the refractive index of the matrix region 3 is higher than the refractive index of the plurality of louver rod structures 2, the matrix region 3 is a high refractive index region and the louver rod structure region is a low refractive index region.

[Louvre rod structure]
The plurality of louver rod structures 2 in the anisotropic light diffusing layer 1 of the present invention shown in FIG. 1 are characterized in that the cross-sectional shape orthogonal to the column axis direction has a substantially rounded rectangle.
Specifically, as shown in FIG. 2, the substantially rounded rectangle has a shape in which two ends of two substantially parallel lines having a parallel line width L are connected by a substantially arc. A long diameter line width Y of the substantially major axis line the maximum width of the substantially square RoundRectangle, parallel line width L can be confirmed by observing the anisotropic light-diffusing layer (anisotropic optical film) by an optical microscope.
In addition, as shown in FIG. 2, S, which is a substantially rectangular rounded rectangle width in the direction perpendicular to the substantially rounded rectangular long diameter line width Y, is hereinafter referred to as a short diameter line width.
The shape of the substantially rounded rectangle may be one that satisfies the rules and mathematical expressions described later, and the linear shape or curved shape of the outer circumference of the substantially rounded rectangle is another shape, for example, a wavy shape or an inclined shape, The shapes may be mixed.

By having the above-described shape, a lens effect in which the transmitted light of the anisotropic optical film is appropriately diffused is expressed, a glare and a rapid change in brightness due to light interference are suppressed, and a balance of optical characteristics including light diffusivity is achieved. Can be optimized.

(Relationship between Y and S)
In the present invention, since the cross-sectional shape of the plurality of louver rod structures orthogonal to the column axis direction is a substantially rounded rectangle, the relationship between the long diameter line width Y and the short diameter line width S is S<Y. Must be In addition, the major axis line width Y is preferably 0.5 μm to 50.0 μm , more preferably 1.0 μm to 10.0 μm , and even more preferably 1.0 μm. ~ 5.0 μm. If it is less than 0.5 μm, the pattern of the photomask cannot be faithfully irradiated onto the uncured resin composition layer of the anisotropic light diffusion layer, and it may be easily affected by the optical proximity effect. In this case, glare due to light interference may easily occur.

(Length of r)
In the present invention, the length of r in the substantially rounded rectangle is a value in which the relation of r=(Y−L)/2 holds in the relation between the long diameter line width Y and the parallel line width L. .. The length of r is preferably 0.01 or more and less than 0.4 μm, and more preferably 0.05 μm to 0.3 μm. If it is less than 0.01 μm, the light diffusibility may be reduced, and if it is 0.4 μm or more, the amount of transmitted light may be reduced. Hereinafter, this r is referred to as a rounded corner radius width.

(Value of L/r)
It is preferable that the value obtained by dividing the parallel line width L by the rounded corner radius width r is in the range of more than 2 and less than 10. More preferably, it is in the range of 2-8. If it is 2 or less, the amount of transmitted light may decrease, and if it is 10 or more, the light diffusibility may decrease.

(S/r value)
A value obtained by dividing the short diameter line width S by the rounded corner radius width r is preferably in the range of 0.4 to 10.0. The range is more preferably 0.8 to 5.0, and further preferably more than 1.3 and 2.5 or less. If it exceeds 10.0, the light diffusivity is lowered, and if it is less than 0.4, the transmitted light amount is lowered.

(Thickness T of anisotropic light diffusion layer)
The thickness T of the anisotropic light diffusion layer 1 (see FIG. 1B) is preferably 10 μm to 100 μm. By setting the thickness T of the anisotropic light diffusion layer within the above range, the problem of cost is reduced and the contrast of the image becomes sufficient. Further, the lower limit value of the thickness T of the anisotropic light diffusion layer 1 is more preferably 15 μm or more. As the thickness T becomes smaller, the balance of light diffusion and light collecting properties may become insufficient. On the other hand, the upper limit of the thickness T of the anisotropic diffusion layer 1 is more preferably 70 μm or less. As the thickness T increases, the material cost increases and the manufacturing time increases, and the image is easily blurred due to reflection and refraction of light in the thickness T direction. Therefore, the contrast may be easily lowered.

In the present invention, it is preferable to have a configuration in which the interfaces between the plurality of louver rod structures and the matrix region are present continuously without interruption over the thickness direction of one anisotropic light diffusion layer. Since the plurality of louver rod structures and the interface of the matrix region are connected to each other, diffusion and collection of light by light transmission, reflection, and refraction are continuous while passing through the anisotropic light diffusion layer. Is more likely to occur, and the efficiency of light diffusion and light collection is improved. On the other hand, in the cross section in the thickness direction of the anisotropic light diffusion layer, if the plurality of louver rod structures and the matrix region are mainly mottled like spots, it becomes difficult to collect light, which is not preferable. ..

If the maximum linear transmittance of the light incident on the anisotropic light diffusing layer at the incident light angle that maximizes the linear transmittance of the anisotropic light diffusing layer (anisotropic optical film) is defined, The layer preferably has a maximum linear transmission of 35% to 95%. The upper limit value of the maximum linear transmittance of the anisotropic light diffusion layer is more preferably 80% or less, further preferably 70% or less.
On the other hand, the lower limit of the maximum linear transmittance is more preferably 40% or more, further preferably 50% or more.

By setting the maximum linear transmittance within the above-specified range, it is possible to obtain appropriate optical anisotropy, so that the applicable range of the anisotropic optical film can be expanded. For example, when an anisotropic optical film is applied to a display device, if the optical anisotropy is too strong, the light diffusion and light collection properties in the horizontal direction of the display device are excellent, but the light diffusion and light collection in the vertical direction are excellent. However, since the anisotropic optical film of the present invention has the above-specified maximum linear transmittance, excellent anisotropic light diffusion and light converging property in the horizontal direction are maintained. Thus, it is possible to sufficiently provide light diffusion and light collecting properties in the vertical direction.

If the linear transmittance of the light incident on the anisotropic light diffusing layer at the incident light angle at which the anisotropic light diffusing layer has the minimum linear transmittance is defined as the “minimum linear transmittance”, the anisotropic light diffusing layer has the minimum linear transmittance. It is preferable that the rate is 25% or less. The upper limit of the minimum linear transmittance of the anisotropic light-diffusing layer is more preferably 20% or less, further preferably 15% or less. The lower limit value is not limited, but is 0%, for example.

Here, the linear transmittance can be measured by the method shown in FIG.
First, as shown in FIG. 3, the anisotropic light diffusion layer 10 (sample) is arranged between the light source 4 and the detector 5. In the present embodiment, the incident light angle when the irradiation light I from the light source 4 is incident from the plane normal direction of the anisotropic light diffusion layer 10 is set to 0°. The anisotropic light diffusing layer 10 has the direction of the rotation axis P of the anisotropic light diffusing layer 10 shown in FIG. 3 and the line AA of the anisotropic light diffusing layer (anisotropic optical film) shown in FIG. The light source 4 and the detector 5 are fixed in such a manner that the directions thereof coincide with each other and can be arbitrarily rotated about the rotation axis P.

That is, according to this method, the sample is arranged between the light source 4 and the detector 5, and the incident light angle from the light source 4 to the sample is rotated while the sample is rotated about the rotation axis P of the sample as a central axis. The linear transmission light amount and the linear transmission rate { linear transmission rate=(linear transmission light amount of detector with sample/linear transmission light amount of detector without sample) ×100} are measured by the detector 5 for each time. An optical profile is obtained from the obtained data, and the maximum linear transmittance and the minimum linear transmittance are obtained from this optical profile. When the linearly transmitted light amount and the linear transmittance are measured for each incident light angle by making the axis orthogonal to the line AA coincide with the rotation axis P shown in FIG. 3, the incident light is incident as shown in FIG. The linear transmitted light amount near zero is shown regardless of the light angle.

(Diffusion width)
The diffusion width is an index of light diffusivity.
From the above, the maximum linear transmittance and the minimum linear transmittance of the anisotropic light diffusing layer (anisotropic optical film) are obtained from the optical profile, and the linear transmittance is 2 which is an intermediate value between the maximum linear transmittance and the minimum linear transmittance. The width of the incident light angle range between the two incident light angle values (inside the two incident light angle in the optical profile) is determined. This width becomes the diffusion width which is the light diffusion area, and the width of the incident light angle range excluding it (outside the two incident light angles in the optical profile) becomes the non-diffusion area.
Here, in the optical profile, the incident light angle of 0°, which is the case where light is incident from the plane normal to the anisotropic light diffusion layer, is used as a reference, and the incident light angle is indicated by a negative value and a positive value. Therefore, the incident light angle may have a negative value. If the two incident light angles have a plus value and a minus value, the sum of the absolute value of the minus value and the plus value becomes the diffusion width.
When the two incident light angles are both positive values, the difference obtained by subtracting the smaller positive value from the larger positive value is the diffusion width. When the two incident light angles are both negative values, their absolute values are taken, and the difference obtained by subtracting the smaller value from the larger value is the diffusion width.

The diffusion width is preferably 30° to 80°. If the diffusion width is less than 30°, the light diffusivity of the anisotropic optical film is not at a practical level. A more preferable diffusion width is 40° to 70°.

Depending on the material forming the anisotropic light diffusion layer, the angle at which the plurality of louver rod structures diffuse light strongly depends on the direction of the column axis of the louver rod structure, that is, the inclination of the diffusion center axis and the louver rod structure. This is when the difference between the inclination of the traveling direction of the incident light and the inclination thereof is approximately ±10°.
Further, when the louver rod structure is bent and extended in the column axis direction, the region where light is strongly diffused can be further widened. This is because by bending, the louver rod structure has a plurality of angular ranges in which the light is strongly diffused in the column axis direction.
If multiple having the bending added, a region for diffusing light strongly, it is possible to form continuously in the column direction, while maintaining the intensity of light substantially constant, the more the light diffusion and The light collecting property can be enhanced.

The angle (bending angle) when the column axis direction of the louver rod structure bends is preferably 10° to 40° in order to obtain a sufficient area for strongly diffusing light.
Further, when the bending angle is 15 ° to 25°, it is more preferable because the region where light is strongly diffused can be further widened.

The louver rod structure may have an inclination. When the column axis direction of the louver rod structure has one inclination, the inclination is preferably within a range of ±70° when the normal direction to the plane of the anisotropic light diffusion layer is 0°. , ±35° is more preferable, and ±15° is still more preferable. Incident light smaller than -70° or larger than +70° is likely to be reflected on the surface of the anisotropic light diffusion layer and difficult to enter into the anisotropic light diffusion layer, depending on the material forming the anisotropic light diffusion layer. is there. With these ranges, the region where light is strongly diffused can be expanded.

Furthermore, when the column axis direction of the louver rod structure has a plurality of inclinations, each inclination is within a range of ±70° when the normal direction to the plane of the anisotropic light diffusion layer is 0°. It is suitable. The number of the plurality of slope is not limited, it is preferred to be between 2-5. This is because as the number of tilts increases, the thickness of the anisotropic light diffusion layer increases to form the tilts, and the productivity decreases.

At least one of the plurality of inclinations of the louver rod structure column axis direction is preferably in a range of ±5° when the normal direction to the plane of the anisotropic light diffusion layer is 0°. And, another inclination is preferably in the range of -15° to -5°, or +5° to +15°. As a result, it is possible to further widen the region that strongly diffuses light. Further, since the region that strongly diffuses the light can be continuously formed in the column axis direction, it is possible to further enhance the light diffusion and condensing property while keeping the light intensity substantially constant.

The shape of the louver rod structure that bends in the column axis direction may be one in which the bent portion bends in a substantially straight line shape, may gradually change (for example, curved), or may be steep. It may be changed to (for example, linear). This facilitates obtaining the effect of the present invention. Further, in the present invention, it is preferable that the bending of the louver rod structure gradually changes without interruption in the column axis direction. By gradually changing without interruption, light can be diffused and condensed efficiently. Such a structure in which the tilt in the axial direction of the column bends can be combined with shape adjustment of a substantially rounded rectangle of the louver rod structure to further optimize the balance of optical characteristics.

[Other layers]
An anisotropic optical film in which the other layer is provided on one surface of the anisotropic light diffusion layer may be used. Examples of the other layer include an adhesive layer, a polarizing layer, a light diffusion layer, a low reflection layer, an antifouling layer, an antistatic layer, an ultraviolet ray or near infrared (NIR) absorption layer, a neon cut layer, and an electromagnetic wave shield layer. be able to.
Further, other layers may be sequentially laminated. Further, other layers may be laminated on both surfaces of the anisotropic light diffusion layer. The other layer laminated on both surfaces may be a layer having the same function or a layer having another function.

<<Method for producing anisotropic optical film>>
The anisotropic optical film of the present invention is formed by forming an anisotropic light diffusion layer by irradiating an uncured resin composition layer of a specific photocurable resin composition with ultraviolet rays and/or visible rays under special conditions. It can be made. Hereinafter, the raw material of the anisotropic light diffusion layer will be described first, and then the manufacturing process will be described.

<Raw material for anisotropic light diffusion layer>
The material for forming the anisotropic light-diffusing layer of the present invention is composed of a photocurable compound selected from macromonomers, polymers, oligomers or monomers having a radically polymerizable or cationically polymerizable functional group, and a photoinitiator. It is a material that is polymerized and cured by irradiating a photocurable resin composition with ultraviolet rays and/or visible rays. Here, even if there is only one type of photo-curable compound forming the anisotropic light-diffusing layer, a difference in refractive index occurs due to the height difference in density. Since the curing speed becomes fast in the portion where the irradiation intensity of ultraviolet rays and/or visible light is strong, the curing material moves around the curing region, and as a result, a region having a high refractive index and a region having a low refractive index are formed. Because. The (meth)acrylate means that either acrylate or methacrylate may be used.

Here, the refractive index difference (absolute value) between the low refractive index region and the high refractive index region is preferably 0.02 or more. It is more preferably 0.03 or more, and further preferably 0.04 or more. As the refractive index difference increases, the degree of anisotropy increases, and it becomes easier to confirm whether or not the louver rod structure is formed with an optical microscope or the like.

[Photocurable compound]
The radically polymerizable compound mainly contains one or more unsaturated double bonds in the molecule, and specifically includes epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, polybutadiene acrylate, silicone acrylate and the like. Acrylic oligomer called by name, 2-ethylhexyl acrylate, isoamyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isonorbornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-acryloyloxyphthalic acid, dicyclopentenyl acrylate, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, EO adduct of bisphenol A diacrylate, trimethylolpropane triacrylate, EO Examples of the acrylate monomer include modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol hexaacrylate. Further, these compounds may be used alone or in a mixture of two or more. Similarly, methacrylate can be used, but acrylate is generally preferable to methacrylate because it has a higher photopolymerization rate.

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

Further, as the compound having an epoxy group, 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) Cyclohexane-meta-dioxane, di(3,4-epoxycyclohexylmethyl)adipate, di(3,4-epoxy-6-methylcyclohexylmethyl)adipate, 3,4-epoxy-6-methylcyclohexyl-3',4'. -Epoxy-6'-methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexane), dicyclopentadiene diepoxide, ethylene glycol di(3,4-epoxycyclohexylmethyl) ether, ethylenebis(3,4-epoxy) Cyclohexanecarboxylate), lactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, tetra(3,4-epoxycyclohexylmethyl)butanetetracarboxylate, di(3,4-epoxycyclohexylmethyl) )-4,5-Epoxy tetrahydrophthalate and other alicyclic epoxy compounds are also included, but are not limited thereto.

Examples of the compound having a vinyl ether group include diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, trimethylolpropane trivinyl ether. , Propenyl ether propylene carbonate and the like, but are not limited thereto. The vinyl ether compound is generally cationically polymerizable, but radical polymerization is also possible by combining it with an acrylate.

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

The above cationically polymerizable compounds may be used alone or in a mixture of two or more.
Furthermore, the photocurable compound is not limited to the above. In addition, in order to generate a sufficient refractive index difference, a fluorine atom (F) may be introduced into the photocurable compound in order to achieve a low refractive index, and a sulfur atom may be introduced in order to achieve a high refractive index. You may introduce (S), a bromine atom (Br), and various metal atoms. In addition, as disclosed in Japanese Patent No. 4423040, the surface of ultrafine particles made of a metal oxide having a high refractive index such as titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), tin oxide (SnOx), etc. It is also effective to add functional ultrafine particles into which a photopolymerizable functional group such as a group, a methacrylic group or an epoxy group is introduced to the above photocurable compound.

(Photocurable compound having a silicone skeleton)
In the present invention, it is preferable to use a photocurable compound having a silicone skeleton as the photocurable compound. The photocurable compound having a silicone skeleton is aligned and polymerized and cured according to its structure (mainly an ether bond) to form a low refractive index region, a high refractive index region, or a low refractive index region and a high refractive index region. Form. By using the photocurable compound having a silicone skeleton, it becomes easy to incline or bend the column axis direction of the louver rod structure, and the light diffusion and light collecting properties are improved. The low refractive index region corresponds to either the louver rod structure region or the matrix region, and the other corresponds to the high refractive index region.

Here, in the low refractive index region, it is preferable that the silicone resin, which is a cured product of a photocurable compound having a silicone skeleton, is relatively increased. This makes it easier to incline or bend the column axis direction of the louver rod structure, thereby further improving the light diffusion and light collecting properties. Since the silicone resin contains more silicon (Si) than a compound having no silicone skeleton, by using an EDS (energy dispersive X-ray spectroscope) with this silicon as an index, You can check the quantity.

The photocurable compound having a silicone skeleton is a monomer, an oligomer, a prepolymer or a macromonomer having a radically polymerizable or cationically polymerizable functional group. Examples of the radically polymerizable functional group include an acryloyl group, methacryloyl group and allyl group, and examples of the cationically polymerizable functional group include an epoxy group and an oxetane group. There is no particular limitation on the type and number of these functional groups, but as the number of functional groups increases, the crosslinking density increases, and it is preferable because the difference in the refractive index is likely to occur. It is suitable. Further, a compound having a silicone skeleton may be insufficient in compatibility with other compounds due to its structure, but in such a case, compatibility can be increased by urethane formation. In the present invention, silicone/urethane/(meth)acrylate having an acryloyl group or a methacryloyl group at the terminal is preferably used.

The weight average molecular weight (Mw) of the photocurable compound having a silicone skeleton is preferably in the range of 500 to 50,000. More preferably, it is in the range of 2,000 to 20,000. When the weight average molecular weight is within this range, a sufficient photocuring reaction occurs and the silicone resin is easily oriented in the anisotropic light diffusion layer. Further, with the orientation of the silicone resin, it becomes easy to incline or bend the column axis direction of the louver rod structure.

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

(Compound without silicone skeleton)
When an anisotropic light diffusing layer is formed by blending a compound having no silicone skeleton with a photocurable compound having a silicone skeleton, the low refractive index region and the high refractive index region are likely to be formed separately from each other. The degree of is strong, which is preferable. As the compound having no silicone skeleton, a thermoplastic resin or a thermosetting resin can be used in addition to the photocurable compound, or these can be used in combination.
As the photocurable compound, a polymer, oligomer, monomer or the like having a radically polymerizable or cationically polymerizable functional group can be used (provided that it does not have a silicone skeleton). Examples of the thermoplastic resin include polyester, polyether, polyurethane, polyamide, polystyrene, polycarbonate, polyacetal, polyvinyl acetate, acrylic resin and its copolymers and modified products. When a thermoplastic resin is used, it is dissolved using a solvent capable of dissolving the thermoplastic resin, and after coating and drying, the photocurable compound having a silicone skeleton is cured with ultraviolet rays and/or visible rays to form an anisotropic light diffusion layer. Mold. Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, urea resin, unsaturated polyester and copolymers and modified products thereof. When a thermosetting resin is used, the photocurable compound having a silicone skeleton is cured by irradiation with ultraviolet rays and/or visible rays, and then appropriately heated, thereby thermosetting the thermosetting resin to achieve anisotropic light diffusion. Mold the layers. The most preferable compound having no silicone skeleton is a photocurable compound, which is easily separated from the low refractive index region and the high refractive index region, and is a solvent as in the case of using a thermoplastic resin. This is because it is excellent in productivity, for example, since it does not require a drying process and does not require a thermosetting process such as a thermosetting resin.

The ratio of the photocurable compound having a silicone skeleton to the compound having no silicone skeleton is preferably in the range of 15:85 to 85:15 by mass ratio. More preferably, it is in the range of 30:70 to 70:30. Within the range, phase separation between the low refractive index region and the high refractive index region is facilitated, and the column axis direction of the louver rod structure is easily inclined or bent. When the ratio of the photocurable compound having a silicone skeleton is less than the lower limit value or more than the upper limit value, it becomes difficult for phase separation to proceed, and it becomes difficult for the louver rod structure to tilt or bend in the column axis direction. When silicone/urethane/(meth)acrylate is used as the photocurable compound having a silicone skeleton, the compatibility with the compound having no silicone skeleton is improved. This makes it possible to easily incline or bend the column axis direction of the louver rod structure even if the material mixing ratio is widened.

[Photoinitiator]
As a photoinitiator capable of polymerizing a radically polymerizable compound, benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2- Diethoxyacetophenone, benzyl dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2 -Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1,1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1 -One, bis(cyclopentadienyl)-bis [ 2,6-difluoro-3-(pyr-1-yl) phenyl] titanium, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl) -Butanone-1,2,4,6-trimethylbenzoyldiphenylphosphine oxide and the like can be mentioned. Further, these compounds may be used alone or in a mixture of two or more.

The photoinitiator capable of polymerizing the cationically polymerizable compound is a compound capable of generating an acid by irradiation with ultraviolet rays and/or visible light, and polymerizing the above cationically polymerizable compound by the generated acid, Generally, onium salts and metallocene complexes are preferably used. As the onium salt, a diazonium salt, a sulfonium salt, an iodonium salt, a phosphonium salt, a selenium salt, or the like is used, and these counterions include anions such as BF ₄ −, PF ₆ −, AsF ₆ −, and SbF ₆ −. Used. Specific examples include 4-chlorobenzenediazonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, (4-phenylthiophenyl)diphenylsulfonium hexafluoroantimonate, (4-phenylthiophenyl)diphenyl. Sulfonium hexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluorophosphate, (4-methoxyphenyl) Diphenylsulfonium hexafluoroantimonate, (4-methoxyphenyl)phenyliodonium hexafluoroantimonate, bis(4-t-butylphenyl)iodonium hexafluorophosphate, benzyltriphenylphosphonium hexafluoroantimonate, triphenylselenium hexafluorophosphate, Examples include (η5-isopropylbenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate, but are not limited thereto. Further, these compounds may be used alone or in a mixture of two or more.

In the present invention, the photoinitiator, relative to the photocurable compound 100 parts by weight, 0.01 parts by weight to 10 parts by weight, more preferably 0.1 part by weight to 7 parts by weight, more preferably 0 it is preferable to be .1 to 5 parts by weight approximately formulation. This is because, if less than 0.01 part by weight, the photocurability is lowered, and if more than 10 parts by weight is blended, only the surface is cured and the internal curability is lowered, and coloring, This is because the formation of the louver rod structure is hindered. These photoinitiators are usually used by directly dissolving the powder in the photocurable compound, but if the solubility is poor, the photoinitiator should be dissolved in a very small amount of solvent in advance to a high concentration. It can also be used. It is more preferable that such a solvent is photocurable, and specific examples thereof include propylene carbonate and γ-butyrolactone. In addition, various known dyes and sensitizers can be added to improve photocurability. Further, in the case of a photocurable compound which can be cured by heat, a thermosetting initiator capable of curing the photocurable compound by heating can be used together with the photoinitiator. In this case, it is possible to further accelerate the polymerization/curing of the photocurable compound by heating after the photocuring.

[Other raw materials]
(Polymer resin)
In the present invention, the above-mentioned photocurable compound can be used alone or a photocurable resin composition obtained by mixing a plurality of the photocurable compounds can be cured to form an anisotropic light diffusion layer. The anisotropic light diffusion layer of the present invention can also be formed by curing a mixture of non-curable polymer resins. As the polymer resin that can be used here, acrylic resin, styrene resin, styrene-acrylic copolymer, polyurethane resin, polyester resin, epoxy resin, cellulose resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer, Examples thereof include polyvinyl butyral resin. These polymer resins and photocurable compounds need to have sufficient compatibility before photocuring, but various organic solvents, plasticizers, etc. are used to ensure this compatibility. It is also possible. When acrylate is used as the photo-curable compound, it is preferable that the polymer resin is selected from acrylic resins in terms of compatibility.

≪Process≫
Next, a method (process) for manufacturing the anisotropic optical film of the present invention will be described with reference to FIGS. By sequentially performing the following steps, having a plurality of louver rod structures, and a matrix region, the cross-sectional shape orthogonal to the column axis direction of the louver rod structure, each end of the two substantially parallel lines, An anisotropic optical film having a substantially rounded rectangular shape connected by a substantially arc can be obtained.
(1) Coating the photocurable resin composition on a substrate to provide a coating film (uncured resin composition layer), (2) Coating a photomask on the uncured resin composition layer Photomask laminating step (3) Obtaining parallel rays from a light source, parallel rays obtaining step (4) Irradiating parallel rays onto the photomask surface on the uncured resin composition layer to polymerize and cure the uncured resin composition layer Cure process
(5) Other layer laminating step of laminating another layer on the anisotropic light-diffusing layer according to the application (optional)

<Coating process>
The coating step suitable for the present invention is a sheet-like coating of a photocurable resin composition on a suitable substrate such as a transparent polyethylene terephthalate (PET) film to form a coating film (uncured resin composition). Physical layer).
As the coating, a usual coating method or printing method is applied. Specifically, air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, calendar coating, dam coating, dip coating. Coating such as die coating, intaglio printing such as gravure printing, stencil printing such as screen printing, and the like can be used. When the photocurable resin composition has a low viscosity, it is also possible to provide a weir of a certain height around the base film and cast the photocurable resin composition in the area surrounded by the weir. The coating film is preferably dried to volatilize the solvent, if necessary.

<Photomask stacking process>
On the uncured resin composition layer, in order to form a cross-sectional shape orthogonal to the column axis direction of the plurality of louver rod structures of the anisotropic light diffusion layer in the anisotropic optical film of the present invention as a desired substantially rounded rectangle A step of laminating a photomask can be provided.
As the photomask, it is possible to use a substrate on which a desired substantially rounded rectangle is patterned according to the photomask manufacturing procedure.
As a specific photomask manufacturing procedure, first, a chrome film for forming a light-shielding film that blocks ultraviolet rays is formed over the entire surface of a glass substrate that serves as a photomask. After that, an electron beam resist (photosensitive material) is applied and baked, and then exposed, developed and rinsed by an electron beam drawing device to pattern the electron beam resist on the chromium film. After that, the unnecessary chrome film is melted by etching, a hole through which ultraviolet rays are transmitted is opened, and then the resist is removed by a chemical solution to complete the photomask.
Most substrates used for photomasks have a drawing pattern formed on glass or synthetic quartz using chromium as a light-shielding film as described above, but the pattern is drawn on a transparent polymer film called an emulsion mask. It may be In that case, it is preferable to form the light-shielding film with blackened metal silver instead of chromium.
Although the pattern size of the photomask varies depending on the conditions, in the present invention, the pattern was prepared with a size of 3 cm×3 cm. FIG. 5 is a schematic diagram showing an example of the pattern of the photomask used in the present invention, and FIG. 6 is a schematic diagram showing an example of the entire photomask used in the present invention.
In FIG. 6, the size of the photomask is 5 inches×5 inches, the pattern is divided into nine blocks, the pitch between each pattern is 0.85 cm, and the distance between the photomask outer periphery and each pattern outer periphery is 1 cm. is there.
In the present invention, by using a photomask, the cross-sectional shape of the plurality of louver rod structures of the anisotropic light diffusing layer, which is orthogonal to the column axis direction, can be formed into a desired substantially rounded rectangular shape. However, if the pattern size of the photomask becomes smaller than the wavelength when irradiating the uncured resin composition layer with parallel rays, it becomes impossible to faithfully irradiate the uncured resin composition layer with the pattern of the photomask. It may be affected by the effect. As a countermeasure against this, a method of previously providing optical proximity correction (OPC) on the mask pattern of the photomask can be applied.
By using the photomask, the cross-sectional shape of the plurality of louver rod structures of the anisotropic light diffusion layer orthogonal to the column axis direction can be formed into a desired substantially rounded rectangular shape.
Furthermore, the photomask also serves to prevent oxygen inhibition during curing of the uncured resin composition layer.

<Parallel ray acquisition process>
As a light source for irradiating the photomask surface on the uncured resin composition layer with parallel rays of ultraviolet rays and/or visible rays, a short arc ultraviolet ray generating light source is usually used. A mercury lamp, a metahalide lamp, a xenon lamp, etc. can be used. The light to be irradiated needs to include a wavelength capable of curing the photocurable resin composition, and light having a wavelength centered around 365 nm of a mercury lamp is usually used. Any lamp can be used as long as it is a light source including a wavelength close to the absorption wavelength.

In order to make parallel rays from the light from the ultraviolet ray generating light source of the short arc, for example, a reflecting mirror is arranged behind the light source so that the light is emitted as a point light source in a predetermined direction, and the light is further reflected by the Fresnel. A parallel light beam can be formed by a lens. The Fresnel lens is a lens in which a normal lens is divided into concentric areas to reduce the thickness, and has a saw-like cross section. When the light emitted as the point light source passes through the Fresnel lens, the directions of the light, which were scattered in different directions, are unified into one direction and become parallel light rays. However, a Fresnel lens is not necessarily required in order to obtain parallel rays necessary for producing the anisotropic optical film of the present invention, and various methods including laser can be used.

<Curing process>
It is a step of irradiating the surface of the photomask on the uncured resin composition layer with parallel rays to polymerize and cure the uncured resin composition layer.
By injecting parallel rays of ultraviolet rays and/or visible rays from the photomask surface laminated on the uncured resin composition layer, the uncured resin composition layer is polymerized and cured, and then the substrate is peeled off. The anisotropic optical film (anisotropic light diffusing layer) is used, or, if necessary, another layer is laminated on the anisotropic light diffusing layer, and the process is further advanced to another layer laminating process. The anisotropic optical film may be used as it is without peeling the base material.

The illuminance of parallel rays of ultraviolet rays and/or visible rays with which the uncured resin composition layer is irradiated is preferably in the range of 0.01 mW/cm ^{2 to} 100 mW/cm ² , and more preferably 0. The range is 0.1 mW/cm ^{2 to 20} mW/cm ² . Since illuminance takes a long time to cure it is less than 0.01 mW / cm ^2, the production efficiency is deteriorated, without causing cure too fast structure formation of the photo-curable resin composition exceeds 100 mW / cm ² In some cases, the desired optical properties including light diffusivity may not be exhibited.

The irradiation time of the parallel rays of ultraviolet rays and/or visible rays is not particularly limited, but is 10 seconds to 180 seconds, more preferably 30 seconds to 120 seconds.

As described above, the anisotropic light-diffusing layer of the present invention is irradiated with parallel rays of low illuminance of ultraviolet rays and/or visible rays for a relatively long time so that a specific internal structure in the uncured resin composition layer is It is obtained by being formed. Therefore, there is a case where unreacted monomer components remain only by such parallel light irradiation and stickiness occurs, which causes problems in handling property and durability. In such a case, the residual monomer can be polymerized and cured by additionally irradiating with 1000 mW/cm ² or more of high illuminance ultraviolet light. Irradiation at this time is preferably performed not from the photomask surface but from the substrate surface side.

The method for obtaining the bending structure in the column axis direction of the plurality of louver rod structures of the anisotropic light-diffusing layer of the present invention is not particularly limited, but the photocurable resin composition contains a light having a silicone skeleton. A method of using a curable compound, a method of obtaining a temperature distribution in the thickness direction of the uncured resin composition layer when the uncured resin composition layer is cured, and the like are effective. The methods can be appropriately combined.
For example, in the case of the method of obtaining the above temperature distribution, the photomask surface on which parallel rays of ultraviolet rays and/or visible rays are incident is cooled by applying cool air, and the surface of the base material which is the opposite side is various. It is possible to generate a temperature distribution in the thickness direction perpendicular to the plane of the uncured resin composition layer by heating with the temperature control plate or the like. Since the refractive index of the photocurable resin composition changes with temperature, the irradiated ultraviolet rays and/or parallel rays of visible rays bend when passing through the inside of the uncured resin composition layer. The bending angle, position, and direction of this bending can be adjusted by the refractive index of the photocurable resin composition, the reaction rate, the temperature gradient, the film thickness, the inclination of parallel rays, and the like.
Here, the reaction rate of the photocurable resin composition is appropriately adjusted by the reactivity of the composition itself, the viscosity, the irradiation intensity of parallel rays of ultraviolet rays and/or visible rays, the type and amount of the photoinitiator, and the like. It

Further, the method for obtaining the tilted structure in the column axis direction of the plurality of louver rod structures of the anisotropic light diffusion layer of the present invention is not particularly limited, and for example, the photocurable resin composition has a silicone skeleton. A method using a photocurable compound, a method obtained by inclining parallel rays of ultraviolet rays and/or visible rays, and the like are effective. These methods can be combined appropriately.

<Other layer stacking process>
It is an optional step of stacking other layers on the anisotropic light diffusion layer obtained by the curing step depending on the application.
The anisotropic optical film of the present invention can be obtained by laminating the above-mentioned other layer on the anisotropic light diffusing layer directly or via an adhesive layer or an adhesive layer depending on the application.
Although the method is not limited, as a pressure-sensitive adhesive or adhesive application method for forming an adhesive layer or an adhesive layer, when directly applying to the anisotropic light diffusion layer, the application means is not particularly limited, roll coating Known techniques including a method, a gravure coating method, and the like can be adopted.
As another method, other layers may be directly coated by the same method.
In addition, a method of laminating a sheet-shaped non-carrier type film in which an adhesive layer or an adhesive layer is sandwiched between separators having different peeling forces in advance by a laminator is also possible.

≪Use≫
The anisotropic optical film of the present invention can be used by adhering it to a desired place via an adhesive layer or a pressure-sensitive adhesive layer, and for example, a liquid crystal display device (LCD), a plasma display panel (PDP), electroluminescence. It can be applied to a display device such as a display (ELD), a cathode ray tube display device (CRT), a surface electric field display (SED), electronic paper, etc., and particularly preferably is a transmissive type, a reflective type, or a transflective type. Can be used for the liquid crystal display device (LCD).

An anisotropic optical film of the present invention and an anisotropic optical film of a comparative example were manufactured according to the following methods.

[Example 1]
A PET film having a thickness of 100 μm and a size of 150 mm ×150 mm (manufactured by Toyobo Co., Ltd., trade name: A4100) is used as a base material, and a photocurable resin composition having a height of 0.05 mm is used around the entire circumference of the edge part thereof using a dispenser. The partition was formed. The height of the partition wall roughly corresponds to the thickness of the anisotropic light diffusion layer obtained. A photocurable resin composition having the composition shown below is filled in the partition wall to form an uncured resin composition layer, and subsequently, on the surface of the uncured resin composition layer, a glass substrate photomask made of a chromium film. (Thickness 2 mm) was laminated.
The photomask used is of the standard shown in FIG. 6, the size is 5 inches×5 inches, the pattern is divided into 9 blocks, the pitch between each pattern is 0.85 cm, the photomask outer periphery and each pattern. The distance from the outer circumference was 1 cm. FIG. 7 is a photograph of the appearance.
In addition, the pattern uses the standard shown in FIG. 5, and the size is 3 cm×3 cm, and the substantially rounded rectangular shape has a major axis line width Y of 1.5 μm, a parallel line width L of 0.9 μm, and a rounded corner radius width. r is 0.3 μm, the short diameter line width S is 0.5 μm, the pitch between the substantially rounded rectangles in the long diameter line width Y direction is 1.1 μm, and the substantially rounded rectangles in the short diameter line width S direction are between The pitch was 0.4 μm. FIG. 8 is a partial surface photograph thereof.
Silicone urethane acrylate (refractive index: 1.460, weight average molecular weight: 5,890) 20 parts by weight (RAHN, trade name: 00-225/TM18)
・Neopentyl glycol diacrylate (refractive index: 1.450) 30 parts by weight (manufactured by Daicel Cytec Co., Ltd., trade name: Ebecryl145)
· EO adduct diacrylate of bisphenol A (refractive index: 1.536) 15 parts by weight (manufactured by Daicel-Cytec Co., Ltd., trade name: Ebec r yl150)
-Phenoxyethyl acrylate (refractive index: 1.518) 40 parts by weight (Kyoeisha Chemical Co., Ltd., trade name: light acrylate PO-A)
-2,2-dimethoxy-1,2-diphenylethan-1-one 4 parts by weight (BASF, trade name: Irgacure651)
Parallel light rays (wavelength: emitted from an irradiation unit for epi-illumination of a UV spot light source (manufactured by Hamamatsu Photonics KK, product name: L2859-01) from the surface of the photomask on the uncured resin composition layer on which this photomask is laminated. (UV ray of 365 nm) was irradiated for 1 minute at an irradiation intensity of 5 mW/cm ² , and further, an ultraviolet ray having an irradiation intensity of 20 mW/cm ² was irradiated from the substrate side to completely cure. From there, the substrate and the photomask were peeled off to obtain the anisotropic light diffusion layer (anisotropic optical film) of Example 1.

[Example 2]
After laminating a glass substrate photomask (thickness: 2 mm) with a chromium film on the surface of the uncured resin composition layer , the base material side of the uncured resin composition layer was placed on a hot plate heated to 80° C. Anisotropic light diffusion in Example 2 was performed in the same manner as in Example 1 except that the mask surface was cooled by blowing air from the air blower, and parallel rays were irradiated from the photomask side of the uncured resin composition layer. A layer (anisotropic optical film) was obtained.
In addition, when the thickness direction of the anisotropic light diffusion layer (direction perpendicular to the plane of the anisotropic light diffusion layer) was confirmed with an optical microscope, it had two diffusion center axes and the thickness direction of the anisotropic light diffusion layer was 0°. In this case, the inclinations of the central axes of diffusion were 0° and 15°, and the bending angle was 15°.

[Example 3]
A glass substrate photomask (thickness: 2 mm) made of a chromium film is laminated on the surface of the uncured resin composition layer, and then parallel rays are emitted from the photomask surface on the uncured resin composition layer to the normal line to the plane of the photomask. An anisotropic light diffusing layer (anisotropic optical film) of Example 3 was obtained in the same manner as in Example 1 except that irradiation was performed with an inclination of 10° from the direction.
Moreover, when the thickness direction of the anisotropic light diffusion layer (direction perpendicular to the plane of the anisotropic light diffusion layer) was confirmed with an optical microscope, a plurality of louver rod structures were tilted by about 10° with respect to the thickness direction. Had.

[Example 4]
The pattern of the photomask has a size of 3 cm×3 cm and a substantially rounded rectangular shape. The major axis line width (Y) is 1.5 μm, the parallel line width (L) is 1.1 μm, and the rounded corner radius width (r) is 0. 2 μm, the short diameter line width S is 0.5 μm, the pitch between the substantially rounded rectangles in the long diameter line width Y direction is 1.3 μm, and the pitch between the substantially rounded rectangles in the short diameter line width S direction is 0. An anisotropic light diffusing layer (anisotropic optical film) of Example 4 was obtained in the same manner as in Example 1 except that the thickness was 0.4 μm.

[Comparative Example 1]
On the surface of the uncured resin composition layer, a PET film having a thickness of 50 μm and a size of 150 mm ×150 mm (manufactured by Toyobo Co., Ltd., trade name: A4100) was laminated instead of the photomask made of a glass substrate made of a chromium film. In the same manner as in Example 1, an anisotropic light diffusing layer (anisotropic optical film) of Comparative Example 1 was obtained.
In the anisotropic light diffusing layer of Comparative Example 1, a plurality of pillar structures are formed in the anisotropic light diffusing layer instead of the plurality of louver rod structures, and the cross-sectional shape of the plurality of pillar structures orthogonal to the column axis direction is When confirmed by an optical microscope, it was found to be substantially circular.

[Comparative Example 2]
The pattern of the photomask has a size of 3 cm×3 cm and a substantially rounded rectangular shape. The major axis line width (Y) is 1.5 μm, the parallel line width (L) is 1.3 μm, and the rounded corner radius width (r) is 0. 1 μm, the short diameter line width S is 0.5 μm, the pitch between the substantially rounded rectangles in the long diameter line width Y direction is 1.5 μm, and the pitch between the substantially rounded rectangles in the short diameter line width S direction is 0. An anisotropic light diffusing layer (anisotropic optical film) of Comparative Example 2 was obtained in the same manner as in Example 1 except that the thickness was 0.4 μm.

[Comparative Example 3]
The pattern of the photomask has a size of 3 cm×3 cm and a substantially rectangular shape with rounded corners. The major axis line width (Y) is 1.5 μm, the parallel line width (L) is 0.5 μm, and the rounded corner radius width (r) is 0. 5 μm, the short diameter line width S is 0.5 μm, the pitch between the substantially rounded rectangles in the long diameter line width Y direction is 0.8 μm, and the pitch between the substantially rounded rectangles in the short diameter line width S direction is 0. An anisotropic light diffusing layer (anisotropic optical film) of Comparative Example 3 was obtained in the same manner as in Example 1 except that the thickness was 0.4 μm.

"Evaluation method"
The anisotropic light diffusing layers (anisotropic optical films) of the examples and comparative examples manufactured as described above were evaluated as follows.

<Surface observation of anisotropic light diffusion layer (anisotropic optical film)>
The surface (irradiation side at the time of parallel light irradiation) of the anisotropic light diffusion layers (anisotropic optical films) of Examples and Comparative Examples was observed with an optical microscope, and the long diameter line width (Y) of substantially rounded rectangles and parallel lines were observed. The width (L) and the rounded corner radius width (r) were measured. In addition, the width is an average value obtained by measuring 100 arbitrary substantially rounded rectangles.

<Thickness of anisotropic light diffusion layer (anisotropic optical film)>
The thickness of the anisotropic light diffusing layer (anisotropic optical film) in the examples and comparative examples was evaluated by a micrometer. At the time of measurement, the measurement was performed so that the surface shape was not crushed. The measured value is the average of the measured values at a total of 5 points, including the four corners of the plane of the anisotropic light diffusing layer (anisotropic optical film) and one point near the center of the plane. It was thick.

<Linear transmittance and diffusion width of anisotropic light diffusion layer (anisotropic optical film)>
Anisotropic light diffusing layers of Examples and Comparative Examples using a goniophotometer (manufactured by Genecia Co., Ltd.) capable of arbitrarily changing the projection angle of the light source and the reception angle of the detector as shown in FIG. The optical characteristics of the (anisotropic optical film) were evaluated. The detector 5 was fixed at a position for receiving straight light from the light source 4, and the anisotropic light diffusing layer (anisotropic optical film) 10 obtained in Examples and Comparative Examples was set in the sample holder between them. As shown in FIG. 3, the anisotropic light diffusing layer 10 is rotated about the rotation axis P of the anisotropic light diffusing layer 10 (the direction is coincident with the line AA of the anisotropic light diffusing layer shown in FIG. 1A). The linear transmitted light amount and the linear transmittance corresponding to each incident light angle at each rotation position of the anisotropic light diffusion layer 10 were measured by the detector 5. With this evaluation method, it is possible to evaluate at which incident light angle the incident light is diffused. The amount of linearly transmitted light was measured for a wavelength in the visible light region using a luminosity filter.
An optical profile was obtained from the obtained data, and the maximum linear transmittance and the minimum linear transmittance were obtained from this optical profile.
Further, the width of the incident light angle range between the two incident light angle values with respect to the linear transmittance that is an intermediate value between the maximum linear transmittance and the minimum linear transmittance obtained by the optical profile (the two values in the optical profile). The inside of the incident light angle) was determined and used as the diffusion width.

<Glitter of anisotropic light diffusion layer (anisotropic optical film)>
A light reflecting layer is provided as a lower layer of the anisotropic light diffusing layer (anisotropic optical film) of Examples and Comparative Examples, light is incident from above the anisotropic light diffusing layer, and glare of the reflected light is visually confirmed. When no glare was confirmed, it was evaluated as ○, and when glare was confirmed, it was evaluated as ×.

<Rapid change in brightness of anisotropic light diffusion layer (anisotropic optical film)>
In order to evaluate the rapid change in luminance, the incident light having the maximum linear transmittance F _A (%) in the graph (optical profile) shown in FIG. If the linear transmittance changes abruptly between the angle A (°) and the incident light angle B (°) that takes the minimum linear transmittance F _B (%), it means that the brightness also changes abruptly. , the change in the linear transmittance with respect to change of the incident light angle, i.e. seeking tilt the F _a and a, and with respect to the F _B and B, there is a sudden change in luminance if inclined outs steep, the If the slope was gentle, it was determined that there was no sudden change in brightness.
Specifically, when the above-mentioned inclination is α, α is (F _A −F _B )/|A−B|, and if α is α≧1.5, there is a rapid change in the luminance. , X, and if α<1.5, the change in luminance was gentle and there was no discomfort, so it was evaluated as ◯.
As shown in FIG. 9, in two types of maximum linear transmittances (F _A1 and F _A2 ) and minimum linear transmittances (F _B1 and F _B2 ), slopes α ₁ and α ₂ of the following expressions The above determination was performed for the numerical value having the larger slope.
α ₁ : (F _A1 −F _B1 )/|A ₁ −B ₁ |
α ₂ : (F _A2- F _B2 )/|A ₂ -B ₂ |

The above evaluation was performed, and the evaluation results are summarized in Table 1.

As shown in the above results, the anisotropic light diffusing layers (anisotropic optical films) of Examples 1 to 4 had good maximum linear transmittance, minimum linear transmittance, diffusion width, glare, and rapid changes in luminance. , Especially Examples 2 and 3 gave better results. In the anisotropic light-diffusing layer of the anisotropic optical film, the shape of the cross section orthogonal to the column axis direction of the plurality of louver rod structures (the thickness direction of the anisotropic light-diffusing layer) is optimized to have substantially rounded corners. By making it rectangular, the lens effect that the emitted light of the anisotropic light diffusing layer is appropriately diffused is expressed, glare and abrupt change of brightness due to light interference are suppressed, and the balance of optical characteristics including light diffusivity is optimized. This is probably because I was able to do it.
Furthermore, since the anisotropic light-diffusing layers of Examples 1 to 4 of the present invention are within the range of the rounded corner radius width defined above, the diffusion width can be widened.
Further, it is considered that the reason why the diffusion width in Example 3 is large is that the louver rod structure was appropriately inclined, and the reason why the diffusion width in Example 2 is the largest is that the louver rod structure is large. It is considered that since it has a bend in the column axis direction, it is possible to further widen the region that strongly diffuses light and increase the diffusion width.

On the other hand, in the anisotropic light-diffusing layer (anisotropic optical film) of Comparative Example 1, since the PET film was used instead of the photomask, a plurality of pillar structures were formed, and the pillar axes of the plurality of pillar structures were formed. The shape of the cross section orthogonal to the direction became a substantially circular shape instead of a substantially rounded rectangular shape, and the maximum linear transmittance and the diffusion width were inferior to those of the present invention.
Further, since Comparative Example 2 was not an optimized substantially rounded rectangle, the minimum linear transmittance, the diffusion width, the glare, and the abrupt changes in luminance were inferior to those of the present invention.
In Comparative Example 3 as well, the maximum linear transmittance was inferior to that of the present invention because it was not an optimized substantially rounded rectangle.

As described above, the anisotropic optical film of the present invention suppresses abrupt changes in glare and brightness, and the balance of optical characteristics including light diffusivity is optimized. Therefore, the anisotropic optical film can be used in various display devices. It can be used.

1 Anisotropic light diffusion layer (anisotropic optical film)
2 louver rod structure 3 matrix region 4 light source 5 detector 10 anisotropic light diffusing layer (anisotropic optical film or sample)
Y major axis line width L parallel line width r corner radius radius width S minor axis line width T anisotropic light-diffusing layer thickness

Claims (8)

An anisotropic optical film in which the amount of transmitted light changes depending on the incident light angle of light,
The anisotropic optical film has at least one anisotropic light diffusion layer,
The anisotropic light diffusion layer,
A plurality of louver rod structures and a matrix region,
The louver rod structure is a columnar structure extending in the thickness direction of the anisotropic light diffusion layer,
The cross-sectional shape of the louver rod structure in an anisotropic light diffusion layer cross section orthogonal to the column axis direction of the louver rod structure is a rounded rectangle connecting both ends of two parallel lines with an arc,
When the parallel line width of the two parallel lines is L, the long diameter line width of the long diameter line which is the maximum width of the rounded rectangle is Y, and (Y−L)/2 is the rounded radius radius r. , Expression 2r<L<10r is satisfied,
Wherein Y is Ri range der of 1.0Myuemu～10.0Myuemu,
Anisotropic optical film in which a plurality of louvers rod structure, characterized by Rukoto lined along a plurality of long diameter line width direction are identical to each other in the anisotropic light-diffusing layer section. The louver rod structure has one inclination in the column axis direction, and the inclination is within ±70° when the normal direction to the plane of the anisotropic light diffusion layer is 0°. The anisotropic optical film according to claim 1, wherein the anisotropic optical film is present. The said louver rod structure is bent and extended in the said column axial direction, and the bending angle exists in the range of 10 degrees-40 degrees, The difference of Claim 1 or 2 characterized by the above-mentioned. Directional optical film. The anisotropic optical film according to any one of claims 1 to 3, wherein the anisotropic light diffusion layer has a thickness within a range of 10 µm to 100 µm. The maximum linear transmittance, which is the linear transmittance of light incident on the anisotropic light diffusing layer at the incident light angle at which the linear light transmittance of the anisotropic light diffusing layer is maximized, is in the range of 40% to 95%. The minimum linear transmittance, which is the linear transmittance of light incident on the anisotropic light diffusing layer at an incident light angle that minimizes the linear transmittance of the isotropic light diffusing layer, is in the range of 25% or less. An anisotropic optical film given in any 1 paragraph of 1-4. The diffusion width, which is the width of the incident light angle range of the two incident light angle values with respect to the linear transmittance that is an intermediate value between the maximum linear transmittance and the minimum linear transmittance, falls within the range of 30° to 80°. The anisotropic optical film according to claim 5 , wherein the anisotropic optical film is present. The anisotropic optical film according to claim 1, wherein a refractive index of the plurality of louver rod structures is different from a refractive index of the matrix region. The anisotropic optical film according to any one of claims 1 to 7, wherein the plurality of louver rod structures and the matrix region are made of resin.