JP6277576B2 - Optical film substrate, optical film, polarizing plate, liquid crystal panel, and image display device - Google Patents

Description

  The present invention relates to an optical film substrate, an optical film, a polarizing plate, a liquid crystal panel, and an image display device.

  On the image display surface of an image display device such as a liquid crystal display (LCD), a cathode ray tube display device (CRT), a plasma display (PDP), an electroluminescence display (ELD), a field emission display (FED), or the front surface of the image display device The provided touch panel or the like is provided with, for example, an antireflection film provided with an antireflection layer on the outermost surface for suppressing reflection of external light.

  The antireflection film mainly includes a light-transmitting substrate, a hard coat layer provided on the light-transmitting substrate, and a low refractive index layer provided on the hard coat layer. The antireflection film reduces reflected light itself by canceling out light reflected on the surface of the low refractive index layer and light reflected on the interface between the low refractive index layer and the hard coat layer.

  However, in such an antireflection film, light reflected at the interface between the light transmissive substrate and the hard coat layer and low refraction due to the difference in refractive index between the light transmissive substrate and the hard coat layer. There is a problem in that the light reflected at the interface between the rate layer and the hard coat layer interferes to generate an iridescent uneven pattern called interference fringes.

  For such problems, when forming the hard coat layer on the light transmissive substrate, the components of the composition for the hard coat layer are infiltrated into the upper portion of the light transmissive substrate, so Near the interface with the coating layer, a mixed region is formed in which the components of the light-transmitting substrate and the components of the hard coating layer are mixed, and the mixed region reduces the refractive index difference between the light-transmitting substrate and the hard coating layer. Thus, a technique for preventing the generation of interference fringes has been developed (see, for example, Patent Document 1).

  However, this technique can be applied when a cellulose ester substrate such as triacetyl cellulose is used as the light transmissive substrate, but a polyester substrate such as polyethylene terephthalate as the light transmissive substrate, a cycloolefin substrate, Or when using an acrylic base material etc., since the component of the composition for hard-coat layers does not osmose | permeate these base materials, it cannot apply.

  Polyester substrates are available at low cost and are excellent in moisture resistance and heat resistance, and are currently being studied for use as light transmissive substrates for antireflection films. For this reason, there is a demand for solving the problem of interference fringes not only in the cellulose ester base material but also in the polyester base material.

  As another method for preventing the occurrence of interference fringes, a hard coat layer is provided on the surface of a light-transmitting substrate having irregularities on the surface by pressing or blasting, or a light-transmitting substrate having a primer layer having an irregular surface. In addition, there is a method in which the interface between the light-transmitting substrate and the hard coat layer is an uneven surface (for example, see Patent Document 2).

  However, in this method, since the interface between the light-transmitting substrate and the hard coat layer is an uneven surface, the image light is deflected by the uneven surface, reducing the brightness and sharpness of the image, the bright room and There is a risk of image quality degradation such as a decrease in dark room contrast.

JP 2003-131007 A JP-A-8-197670

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide an optical film substrate, an optical film, a polarizing plate, a liquid crystal panel, and an image display device in which interference fringes and image quality deterioration are not easily recognized by human eyes.

According to one aspect of the present invention, there is provided a substrate for an optical film which is used for an optical film and is provided adjacent to a first functional layer constituting a part of the optical film on one surface, An uneven surface forming a surface on the first functional layer side, an average inclination angle of the uneven surface being θa, a maximum inclination angle of the uneven surface being θmax, and the uneven surface in the optical film substrate the refractive index of the portion constituting the _{n c,} the refractive index of the first functional layer _{n f} (although, _{n c} ≠ _{n f)} when _{^{a, θa> tan -1 (0.0013 /}} n f), and .theta.max ^<satisfy a relationship of _{tan -1 (0.0087 / │n c -n} f │), an optical film base material is provided.

  According to another aspect of the present invention, there is provided an optical film comprising the above-described optical film substrate and a first functional layer provided adjacent to the uneven surface of the optical film substrate. The

  According to another aspect of the present invention, the polarized light formed on the surface of the optical film opposite to the surface on which the first functional layer is formed in the optical film substrate of the optical film. A polarizing plate comprising the element is provided.

  According to another aspect of the present invention, there is provided a liquid crystal display panel comprising the above optical film or the above polarizing plate.

  According to the other aspect of this invention, an image display apparatus provided with a backlight unit and said optical film or said polarizing plate is provided.

  According to the optical film substrate of one embodiment of the present invention and the optical film, polarizing plate, liquid crystal panel, and image display device of another embodiment, the average inclination angle θa of the uneven surface satisfies the above relational expression. Therefore, even if interference fringes occur, they occur at a pitch less than the resolution of the human eye. This makes it difficult for human eyes to recognize the interference fringes. In addition, since the maximum inclination angle θmax of the concavo-convex surface satisfies the above relational expression, it is difficult for human eyes to recognize image quality deterioration.

It is a schematic block diagram of the optical film which concerns on 1st Embodiment. It is a figure for demonstrating average inclination | tilt angle (theta) a. It is a figure for calculating | requiring inclination | tilt angle (theta) ₁ in which an interference fringe is hard to be recognized by human eyes. It is a figure for calculating | requiring inclination | tilt angle (theta) _{2 with} which it is hard to recognize image quality degradation for a human eye in the case of _nc1 > _nf1 . It is a figure for calculating | requiring inclination | tilt angle (theta) _{2 with} which it is hard to be recognized for image quality degradation by human eyes in the case of _nf1 > _nc1 . It is a schematic block diagram of the polarizing plate which concerns on 1st Embodiment. It is a schematic block diagram of the liquid crystal panel which concerns on 1st Embodiment. It is a schematic block diagram of the liquid crystal display which is an example of the image display apparatus which concerns on 1st Embodiment. It is a schematic block diagram of the optical film which concerns on 2nd Embodiment.

(First embodiment)
Hereinafter, an optical film according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an optical film according to the present embodiment, FIG. 2 is a diagram for explaining an average inclination angle θa, and FIG. 3 is an inclination angle θ ₁ in which interference fringes are difficult to be recognized by human eyes. FIG. 4 is a diagram for _obtaining an inclination angle θ ₂ where it is difficult for human eyes to recognize image quality degradation when n _c1 > n _f1 , and FIG. 5 is a diagram for _obtaining n _f1 > n _c1. FIG. 6 is a diagram for obtaining the tilt angle θ ₂ in which the image quality deterioration is hardly recognized by human eyes. In the present specification, terms such as “film”, “sheet”, and “plate” are not distinguished from each other only based on the difference in names. Therefore, for example, “film” is a concept including a member that can also be called a sheet or a plate. As a specific example, the “optical film” includes members called “optical sheet”, “optical plate”, and the like.

<< Substrate for optical film and optical film >>
As shown in FIG. 1, the optical film 10 includes at least an optical film substrate 20 and a first functional layer 30 provided adjacent to the optical film substrate 20. The optical film 10 shown in FIG. 1 further includes a second functional layer 40 formed on the first functional layer 30. The optical film 10 may not include the second functional layer 40.

<Base material for optical film>
The optical film substrate 20 has an uneven surface 20A that forms the surface on the first functional layer 30 side. The optical film substrate 20 shown in FIG. 1 has a laminated structure including a light transmissive substrate 21 and a concavo-convex layer 22 provided on the light transmissive substrate 21 and having a concavo-convex surface 20A. Yes.

The optical film substrate 20 has an average inclination angle of the concavo-convex surface 20A of θa, a maximum inclination angle of the concavo-convex surface 20A of θmax, and the refractive index of the portion 20B constituting the concavo-convex surface 20A of the optical film substrate 20 is n. _{When c} and the refractive index of the first functional layer 30 are n _f (where n _c ≠ n _f ), the relationship of the following formula (1) and the following formula (2) is satisfied.
θa> tan ⁻¹ (0.0013 / n _f ) (1)
θmax <tan ⁻¹ (0.0087 / | n _c −n _f |) (2)

In the present embodiment, as shown in FIG. 1, the uneven layer 22 includes a portion 20B constituting the uneven surface 20A. In the present embodiment, since the refractive index of the uneven layer 22 has a value equal across uneven layer 22, the refractive index of the uneven layer 22 has a refractive index n _c of the portion 20B constituting the irregular surface 20A It is the same value.

The definition of “θa” is in accordance with the surface roughness measuring instrument: SE-3400 / Kosaka Laboratory Co., Ltd. instruction manual (revised 1995.07.20). Specifically, as shown in FIG. 2, the sum of the heights of the convex portions existing in the reference length L (h ₁ + h ₂ + h ₃ +... + H _n ) is divided by the reference length, It can be expressed by the arctangent of that value. That is, θa can be expressed by the following formula (3).
θa = tan ⁻¹ {(h ₁ + h ₂ + h ₃ +... + h _n ) / L} (3)

θa can be measured, for example, using a surface roughness measuring device (model number: SE-3400 / manufactured by Kosaka Laboratory Ltd.) under the following measurement conditions.
1) Stylus of surface roughness detector (trade name SE2555N (2 μ standard) manufactured by Kosaka Laboratory Ltd.)
・ Tip radius of curvature 2μm, apex angle 90 degrees, material diamond 2) Measurement conditions of surface roughness measuring instrument ・ Reference length (cutoff value λc of roughness curve): 2.5 mm
Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・ Feeding speed of stylus: 0.5mm / s

  As described above, θmax is the maximum inclination angle of the uneven surface, and θmax is obtained, for example, by measuring the surface shape of the uneven surface and analyzing the data obtained there. Examples of the apparatus for measuring the surface shape include a contact-type surface roughness meter and a non-contact-type surface roughness meter (for example, an interference microscope, a confocal microscope, an atomic force microscope, etc.). Among these, an interference microscope is preferable from the viewpoint of simplicity of measurement. Examples of such an interference microscope include “New View” series manufactured by Zygo.

When using an interference microscope, the inclination Δi of each point over the entire surface of the concavo-convex surface is obtained, the inclination Δi is converted into the surface angle θ _i, and from there, the one with the smaller relative cumulative frequency of the absolute value of the surface angle θ _i The surface angle at 90% is calculated, and this surface angle is defined as “maximum tilt angle θmax”. Here, the surface angle when the relative cumulative frequency of the absolute value of the surface angle θ _i is 90% from the smaller one is used because the relative cumulative frequency of the absolute value of the surface angle θ _i is decreased from the smaller one to 100%. This is because the influence of the abnormal value in the measurement is large at the surface angle. Note that the inclination Δi can be obtained by the same equation as Equation (32) described later, and the surface angle θ _i can be obtained by the same equation as Equation (30) described later.

Refractive index _{n c} and a first refractive index _{n f} of the functional layer 30 of the portion 20B constituting the irregular surface 20A is formed by forming a single layer, respectively, an Abbe refractometer (manufactured by Atago NAR-4T) and Ellipsometry It can be measured with a meter. Further, as a method of measuring the refractive index after becoming an optical film, the cured film of each layer is scraped off with a cutter or the like to prepare a powder sample, and JIS K7142 (2008) B method (powder or granular transparent material) Becke method (using a Cargill reagent having a known refractive index, placing the powdered sample on a slide glass, etc., dropping the reagent onto the sample, and immersing the sample in the reagent. A bright line generated in the sample outline when the refractive index of the sample and that of the reagent are different from each other by observation, and a method in which the refractive index of the reagent in which the Becke line cannot be visually observed are used as the refractive index of the sample can be used.

  The reason that the average inclination angle θa of the uneven surface 20A needs to satisfy the relationship of the above formula (1) is that if the average inclination angle θa of the uneven surface 20A satisfies the above expression (1), For this reason, even if an interference fringe is generated, it is difficult for the human eye to recognize the interference fringe. However, the present invention is not limited to the following theory.

  When the pitch of the interference fringes is narrower than the resolution of the human eye, the pitch is too narrow and is not recognized as an interference fringe. Therefore, in order not to be recognized as interference fringes by human eyes, it is necessary to make the pitch of the interference fringes narrower than the resolution of human eyes. Here, when the brightness changes to a rectangular shape, the resolution of a human eye with a visual acuity 1 is 1 minute. Therefore, when the clear viewing distance is 25 cm, the human detects a light-dark stripe with a pitch of about 70 μm. be able to. However, it is known that the sensitivity that can be detected by humans is reduced to several to several tens of times when the brightness is not rectangular but changes with gradation. Since the interference fringes change with gradation, even if the pitch of the interference fringes (bright lines) is 300 μm, it is considered that the interference fringes cannot be recognized by human eyes. Therefore, if the pitch of the interference fringes is less than 300 μm, it is considered that the interference fringes are not recognized by human eyes.

On the other hand, as shown in FIG. 3, for example, on the first layer 100 having the uneven surface 100 </ b> A, the surface (back surface) on the first layer 100 side corresponds to the shape of the uneven surface 100 </ b> A of the first layer 100. In the case where the second layer 101 having a flat surface (surface) opposite to the surface on the first layer 100 side is formed, the uneven surface 100A of the first layer 100 is formed. Is the angle of inclination θ _1, and red light 102 and 103 reflected on the surface of the second layer 101 and red reflected on the interface (uneven interface) between the first layer 100 and the second layer 101. Assuming that light 104 and 105 interfere with each other so that red light bright lines R1 and R2 (hereinafter, the red light bright lines are referred to as “red light lines”) are generated at pitch A. From the above theory, if the pitch A is less than 300 μm, the bright red interference fringes are human. Eye and thus not recognized in. Therefore, hereinafter, in FIG. 3, the inclination angle θ ₁ when the pitch A is 300 μm is obtained. The bright line of blue light and green light is generated at a pitch narrower than the bright line of red light. If the bright line of red light cannot be recognized, the bright line of blue light or green light is generated. However, it is not recognized by human eyes. Further, the first layer 100 shown in FIG. 3 is an extremely enlarged part of the first layer 100.

First, in a triangle having a pitch A (300 μm) shown in FIG. 3 as a base and a distance B and a height, the following formula (4) is established.
tan θ ₁ = B / A = B / 300 (4)
The distance B in the formula (4) is not an optical distance but an actual distance.

Further, when the optical path difference between the red light 104 and the red light 105 is b and the refractive index of the second layer 101 is n, the distance B can be expressed by the following formula (5).
B = b / 2n (5)

  Here, the bright red line R1 and the bright red line R2 are adjacent to each other, and the red light 104 interferes with the red light 102 and the red light 105 intensifies with the red light 103. Assuming 0.78 μm (780 nm), the optical path difference b is one wavelength of red light, that is, 0.78 μm.

By substituting 0.78 μm for the optical path difference b in equation (5) and substituting equation (5) for B in equation (4), the following equation (6) is obtained.
tan θ ₁ = 0.78 / (2 × 300 × n) (6)

Then, when equation (6) is solved for θ ₁ , the following equation (7) is obtained.
θ ₁ = tan ⁻¹ (0.78 / 600n)
= Tan ⁻¹ (0.0013 / n) (7)

Therefore, if the tilt angle θ ₁ is larger than tan ⁻¹ (0.0013 / n), that is, if the tilt angle θ satisfies the relationship of the following formula (8), the light reflected on the surface of the second layer 101 and Even if the light reflected at the interface between the first layer 100 and the second layer 101 interferes to generate interference fringes, it can be said that the interference fringes are not recognized by human eyes.
θ ₁ > tan ⁻¹ (0.0013 / n) (8)

Accordingly, the first layer 100 is an uneven layer 22, the following equation if the second layer 101 is a first functional layer 30 is obtained by replacing the n in the above formula (8) _{n f} (9 ) Satisfying the relationship ( ₁ ), the light reflected by the surface of the first functional layer 30 and the light reflected by the interface between the first functional layer 30 and the concavo-convex layer 22 (concave / convex interface). Even if interference fringes are generated due to interference, the interference fringes are not recognized by human eyes.
θ ₁ > tan ⁻¹ (0.0013 / n _f ) (9)

Then, by replacing the inclination angle theta ₁ in the formula (9) to the average inclination angle .theta.a, the equation (1) is obtained. Therefore, if the average inclination angle of the concavo-convex surface 20A satisfies the relationship of the above formula (1), the light reflected on the surface of the first functional layer 30 and the interface between the first functional layer 30 and the concavo-convex layer 22 will be described. Even if the interference with the light reflected by the light causes interference fringes, the interference fringes are hardly recognized by human eyes.

  The reason that the maximum inclination angle θmax of the uneven surface 20A needs to satisfy the relationship of the above formula (2) is that if the maximum inclination angle θmax of the uneven surface 20A satisfies the above expression (2), For this reason, image degradation is not perceived by the human eye. However, the present invention is not limited to the following theory.

As shown in FIG. 4, the light-transmitting base material 201, the concave-convex layer 202 having an inclined angle of θ ₂ and a refractive index of n _c1 , and the functional layer 203 having a refractive index of n _f1. In the optical film 200 formed in this order, when n _c1 > n _f1 , the image light was incident on the concave and convex layer 202 along the normal direction N of the optical film 200 from the light transmissive substrate 201 side. In this case, the image light is deflected by the concavo-convex surface 202 </ b> A, and the angle with respect to the normal direction N of the optical film 200 becomes Ψ and proceeds in the functional layer 203. The image light traveling in the functional layer 203 is emitted from the surface of the functional layer 203. When the image light is emitted from the surface of the functional layer, the image light is deflected again, and an angle (emission angle) with respect to the normal direction N of the optical film 200 Becomes α and emerges from the functional layer 203. Here, when the emission angle α is large, the human eye recognizes the image quality degradation of the image light. On the other hand, when the emission angle α is small, even if the image light is not in the normal direction N of the optical film 200, the human eye does not recognize the image quality degradation of the image light, and the normal of the optical film 200 It is recognized that the image quality is equivalent to that when the image light is emitted in the direction N. Therefore, considering the emission angle α where it is difficult for the human eye to recognize the image quality degradation of the image light, first, in JIS K7136, the haze is 2 from the incident light due to the forward scattering of the transmitted light passing through the test piece. It is specified that the percentage of transmitted light deviates by more than 5 °. That is, in the definition of haze, transmitted light of 2.5 ° or more is measured as haze, but if it is transmitted light of less than 2.5 °, it is not measured as haze. For this reason, it is also conceivable that the emission angle α is less than 2.5 °, which makes it difficult for the human eye to recognize the image quality degradation of the image light. However, as a result of intensive studies, the present inventor has found that there is a possibility that degradation of image quality may be perceived by the human eye if the emission angle α is actually an angle of 0.5 ° or more. Therefore, in the present invention, the outgoing angle α is less than 0.5 °, which makes it difficult for the human eye to recognize image quality degradation of the image light. On the other hand, since the emission angle α varies with the angle of inclination theta ₂ of the uneven surface 202A, hereinafter, the output angle α is to be calculated inclination angle theta ₂ of the uneven surface 202A of less than 0.5 °.

First, the following formula (10) is established from Snell's law.
n _c1 × sin θ ₂ = n _f1 × sinξ (10)
In Expression (10), ξ represents an angle between the normal direction of the uneven surface 202A having the inclination angle θ ₂ and the image light traveling in the functional layer 203 as shown in FIG. Here, since there is a relationship of ξ = θ ₂ + ψ in FIG. 4, when this is substituted into the above equation (10), the following equation (11) is obtained.
n _c1 × sin θ ₂ = n _f1 × sin (θ ₂ + ψ) (11)

Applying the trigonometric addition theorem to the above equation (11), the following equation (12) is obtained.
_{n c1 × sinθ 2 = n f1} × (sinθ 2 × cosψ + cosθ 2 × sinψ) ... (12)
And if the said Formula (12) is deform | transformed, it will become the following Formula (13).
sin θ ₂ / cos θ ₂ = n _f1 × sinφ / (n _c1 −n _f1 cosφ) (13)

On the other hand, at the interface between the functional layer 203 and air, the following formula (14) is established according to Snell's law. And if a formula (14) is changed, a following formula (15) will be obtained.
n _f1 × sinψ = sin α (14)
sinψ = sin α / n _f1 (15)

Further, the following formula (16) is established from the interrelationship of trigonometric functions. Then, when the above formula (15) is substituted into the following formula (16), the following formula (17) is obtained.
cos ψ = (1-sin ² ψ) ^1/2 (16)
= (1-sin ² α / n _f1 ² ) ^1/2 (17)

The sinθ ₂ / cosθ ₂ of the above formula (13) as a tan .theta _2, the above expression (14) and the equation (17) is substituted into the equation (13), the following equation (18) is obtained.
tan θ ₂ = sin α / (n _c1 −n _f1 × (1-sin ² α / n _f1 ² ) ^1/2 ) (18)
Here, when α is small, (1-sin ² α / n _f1 ² ) ^1/2 = 1 may be set. Therefore, in the above formula (18), (1-sin ² α / n _f1 ² ) ^1/2 = Assuming 1, the above equation (18) becomes the following equation (19).
tan θ ₂ = sin α / (n _c1 −n _f1 ) (19)

When this is solved for θ ₂ , the following equation (20), which is a relational expression between the inclination angle θ ₂ of the uneven surface 202A and the emission angle α, is obtained.
θ ₂ = tan ⁻¹ (sin α / (n _c1 −n _f1 )) (20)

Then, by substituting 0.5 for α in the above equation (20), the following equation (21) is obtained.
θ ₂ = tan ⁻¹ (0.0087 / (n _c1 −n _f1 )) (21)
Therefore, if θ ₂ is a value smaller than tan ⁻¹ (0.0087 / (n _c1 −n _f1 ), that is, if the inclination angle θ ₂ satisfies the relationship of the following equation (22), the image quality deterioration is caused. It will be difficult for human eyes to recognize.
θ ₂ <tan ⁻¹ (0.0087 / (n _c1 −n _f1 )) (22)

In the above description, the case of n _c1 > n _f1 has been described, but the same can be said for n _f1 > n _c1 .

In the case of n _f1 > n _c1 , unlike in the case of n _c1 > n _f1 , as shown in FIG. 5, ξ = θ ₂ −ψ, so the following equation (23) is satisfied instead of the above equation (11). .
n _c1 × sin θ ₂ = n _f1 × sin (θ ₂ −ψ) (23)

When calculation similar to the above is performed based on the above formula (23), the following formula (24) is obtained.
θ ₂ <tan ⁻¹ (0.0087 / (n _f1 −n _c1 )) (24)

And when the said Formula (22) and the said Formula (24) are represented by one type | formula, it will become the following formula | equation (25).
θ ₂ <tan ⁻¹ (0.0087 / | n _c1 −n _f1 |) (25)

Then, by replacing the inclination angle theta ₂ in the formula (25) to the maximum inclination angle .theta.max, the formula (2) is obtained. Here, in the above formula (2), when the average inclination angle θa is used instead of the maximum inclination angle θmax, an inclination angle larger than the average inclination angle θa also exists in the uneven surface. Therefore, even if the average inclination angle θa satisfies the above formula (2), since there is an inclination angle larger than the average inclination angle θa in the concavo-convex surface, the emission angle α is 0.5 ° or more. There is a possibility that the image light exists and the human eye recognizes the image quality deterioration. On the other hand, since θmax is the maximum inclination angle of the unevenness existing on the uneven surface, there is no inclination angle larger than θmax in the uneven surface. For this reason, there is no image light having an emission angle α of 0.5 ° or more. For this reason, in the above equation (2), the maximum inclination angle θmax is used instead of the average inclination angle θa. Therefore, in the case of n _c > n _f , regardless of the case of n _f > n _c , if the maximum inclination angle θmax of the concavo-convex surface 20A satisfies the relationship of the above equation (2), even if image quality degradation occurs, human It is difficult for the eyes to perceive image quality degradation.

In the above description, when the emission angle α is less than 0.5 °, it is assumed that the image quality deterioration is not easily recognized by the human eye, but in order to prevent the human eye from recognizing the image quality deterioration more, the emission angle α Is preferably less than 0.3 °. Therefore, it is preferable that θmax of the uneven surface 20A satisfy the following formula (26). The following formula (26) is derived by substituting 0.3 for α in the above formula (20).
θmax <tan ⁻¹ (0.0052 / | n _c −n _f |) (26)

Furthermore, since the resolution of the human eye is 1 minute (1/60 °) as described above, the emission angle α may be set to 1 minute or less in order to prevent the human eye from more reliably recognizing image quality degradation. Particularly preferred. Therefore, it is particularly preferable that θmax of the uneven surface 20A satisfies the following formula (27). The following equation (27) is derived by substituting 1/60 for α in the above equation (20).
θmax <tan ⁻¹ (0.0003 / | n _c −n _f |) (27)

The difference between the refractive index _{n f} of the refractive index _{n c} of the first functional layer 30 of the portion 20B constituting the irregular surface 20A (│n _c -n _f │) is also 0.03 to 1.0 Is possible. When | n _c −n _f | is set to 1.0 or less, interference fringes and image quality deterioration are hardly recognized by human eyes. The lower limit of | n _c −n _f | may be 0.05 or more or 0.1 or more.

  The kurtosis Rku of the roughness curve on the uneven surface 20A is preferably less than 3.0. Rku is an index representing the sharpness of the unevenness constituting the uneven surface 20A. Since Rku on the concavo-convex surface 20A is less than 3.0, there is no steep concavo-convex surface in the concavo-convex surface, making it difficult for human eyes to perceive image quality degradation.

式（２８）中、Ｒｑは二乗平均平方根粗さを表し、ｌｒは基準長さを表し、Ｚ（ｘ）は粗さ曲線を表す。 Rku is defined in JIS B0601: 2001 and is represented by the following formula (28).

In formula (28), Rq represents the root mean square roughness, lr represents the reference length, and Z (x) represents the roughness curve.

  The skewness RSk of the roughness curve on the uneven surface 20A is preferably 0.3 or less. Rsk is an index representing the degree of bias of the inclination angle distribution of the unevenness constituting the uneven surface 20A. Since Rsk on the concavo-convex surface 20A is 0.3 or less, the inclination of the inclination angle distribution is small, and it is more difficult for the human eye to perceive image quality degradation.

式（２９）中、Ｒｑは二乗平均平方根粗さを表し、ｌｒは基準長さを表し、Ｚ（ｘ）は粗さ曲線を表す。 Rsk is defined in JIS B0601: 2001 and is represented by the following formula (29).

In Formula (29), Rq represents the root mean square roughness, lr represents the reference length, and Z (x) represents the roughness curve.

  In the concavo-convex surface 20A, a region where the surface angle is 0.05 ° or more when the inclination angle of the concavo-convex surface 20A with respect to the film surface in the cross section along the normal direction N of the film surface of the optical film 10 is a surface angle Is preferably 50% or more. When the ratio of the area where the surface angle is 0.05 ° or more is 50% or more, interference fringes are not easily recognized by human eyes. The lower limit of the ratio of the region where the surface angle is 0.05 ° or more is preferably 55% or more, and more preferably 60% or more. Further, the upper limit of the ratio of the region where the surface angle is 0.05 ° or more is preferably 95% or less, and more preferably 90% or less.

  The surface angle is obtained by measuring the surface shape of the uneven surface 20A. Examples of the apparatus for measuring the surface shape include a contact-type surface roughness meter and a non-contact-type surface roughness meter (for example, an interference microscope, a confocal microscope, an atomic force microscope, etc.). Among these, an interference microscope is preferable from the viewpoint of simplicity of measurement. Examples of such an interference microscope include “New View” series manufactured by Zygo.

In order to calculate the ratio of the region where the surface angle is 0.05 ° or more using an interference microscope, for example, the inclination Δi of each point over the entire surface of the concavo-convex surface is obtained, and the inclination Δi is calculated by the following equation (30). in terms of surface angle theta _i, from which the absolute value of the surface angle theta _i calculates the ratio of the area to be 0.05 ° or more. In addition, since inclination (DELTA) i is the same as the local inclination dZi / dXi calculated by following formula (32), it can be calculated | required from following formula (32).
θ _i = tan ⁻¹ Δi (30)

  In the uneven surface 20A, the root mean square slope RΔq of the roughness curve is preferably 0.003 or less. By setting the root mean square slope RΔq of the roughness curve to 0.003 or less, it is possible to further reduce image quality degradation for human eyes. The lower limit of RΔq is preferably 0.0005 or more, and more preferably 0.001 or more. Further, the upper limit of RΔq is preferably 0.0025 or less, and more preferably 0.002 or less.

式中、ｎは全測定点であり、ｄＺ_ｉ／ｄＸ_ｉはｉ番目の局部傾斜である。測定面の各点における局部傾斜は例えば下記式（３２）により求められる。 The root mean square slope RΔq of the roughness curve is defined as the root mean square of the local slope dZ _i / dX _i in JIS B0601: 2001, and is represented by the following formula (31).

Where n is the total measurement point and dZ _i / dX _i is the i th local slope. The local inclination at each point on the measurement surface is obtained by the following equation (32), for example.

式中、測定面の一つ方向をＸ方向としたとき、Ｘ_ｉはｉ番目のＸ方向の位置であり、Ｚ_ｉはｉ番目の高さであり、ΔＸはサンプリング間隔である。

In the equation, when one direction of the measurement surface is an X direction, X _i is a position in the i-th X direction, Z _i is an i-th height, and ΔX is a sampling interval.

  The root mean square slope RΔq is obtained by measuring the surface shape of the concavo-convex surface 20A in the same manner as the surface angle. Examples of the apparatus for measuring the surface shape include a contact-type surface roughness meter and a non-contact-type surface roughness meter (for example, an interference microscope, a confocal microscope, an atomic force microscope, etc.). Among these, an interference microscope is preferable from the viewpoint of simplicity of measurement. Examples of such an interference microscope include “New View” series manufactured by Zygo.

  In the uneven surface 20A, when it is desired that the optical film substrate 20 itself does not have antiglare properties, the arithmetic average roughness Ra of the unevenness constituting the uneven surface 20A is 0.10 μm or less. It is preferable that it is 0.08 μm or less, and the maximum height roughness Ry of the unevenness constituting the uneven surface 20A is preferably 0.60 μm or less, and is 0.40 μm or less. More preferably, the 10-point average roughness Rz of the unevenness constituting the uneven surface 20A is preferably 0.50 μm or less, and more preferably 0.30 μm or less. In addition, when a functional layer is laminated | stacked on the base material 20 for optical films, since the reflectance and permeation | transmission diffusion angle in an interface reduce, the expression of anti-glare property is suppressed. For this reason, Ra, Ry, and Rz in the uneven surface 20A are not limited to the above ranges.

  The above definitions of “Ra”, “Ry” and “Rz” shall conform to JIS B0601-1994.

Ra, Ry, and Rz can be measured under the following measurement conditions using, for example, a surface roughness measuring device (model number: SE-3400 / manufactured by Kosaka Laboratory Ltd.).
1) Stylus of surface roughness detector (trade name SE2555N (2 μ standard) manufactured by Kosaka Laboratory Ltd.)
・ Tip radius of curvature 2μm, apex angle 90 degrees, material diamond 2) Measurement conditions of surface roughness measuring instrument ・ Reference length (cutoff value λc of roughness curve): 2.5 mm
Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・ Feeding speed of stylus: 0.5mm / s

In the optical film substrate 20, the haze value of the optical film substrate 20 was set to H _b (%), and the slide glass was overlapped on the irregular surface 20 </ _b > A of the optical film substrate 20 through liquid paraffin. When the haze value is H _bin (%), it is preferable to satisfy the following formula (33). By satisfy | filling following formula (33), the grade of the diffusion resulting from an uneven surface is suppressed low, and even if it is the base material 20 for optical films itself, anti-glare property will become difficult to be recognized.
│H _b -H _bin │ <1.0 (33)
In the case where a functional layer having a refractive index of n _f is laminated on the optical film substrate 20, when the value measured using a fluid having a refractive index of n _f instead of liquid paraffin is H _bin , If the said Formula (33) is satisfy | filled, the glare-proof nature resulting from the base material 20 for optical films will be hard to be recognized.

The haze value _Hb and the haze value _Hbin of the optical film substrate 20 are measured according to JIS K7136 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory).

  In the present invention, the concave / convex surface 20A having the average inclination angle θa satisfying the above formula (1) is formed to make it difficult for human eyes to recognize interference fringes. The base material 20 does not need to be formed with a mixed region in which the optical film base material 10 and a binder resin component described later of the first functional layer 30 are mixed. Further, by not forming the mixed region, the thickness of the first functional layer 30 can be reduced, and the manufacturing cost can be reduced.

(Light transmissive substrate)
The light transmissive substrate 21 is not particularly limited as long as it has light transmissive properties. The light-transmitting substrate 21 may be a cellulose ester substrate, but in the present invention, interference fringes can be made difficult to be recognized by human eyes without forming a mixed region. This is particularly effective for a substrate in which formation of a region is difficult. Examples of the light transmissive substrate in which the mixed region is difficult to form include an acrylic substrate, a polyester substrate, a polycarbonate substrate, a cycloolefin polymer substrate, and a glass substrate.

  As a cellulose ester base material, a cellulose triacetate base material and a cellulose diacetate base material are mentioned, for example. The cellulose ester base material is excellent in light transmittance, and among the cellulose acylate base materials, a triacetyl cellulose base material (TAC base material) is preferable. A triacetyl cellulose base material is a light-transmitting base material capable of setting an average light transmittance to 50% or more in a visible light region of 380 to 780 nm. The average light transmittance of the triacetyl cellulose base material is preferably 70% or more, and more preferably 85% or more.

  In addition, as a triacetyl cellulose base material, in addition to pure triacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like may be used in combination with components other than acetic acid as a fatty acid forming an ester with cellulose. Good. Further, these triacetylcelluloses may be added with other additives such as other cellulose lower fatty acid esters such as diacetylcellulose, or plasticizers, ultraviolet absorbers, and lubricants as necessary.

  Examples of the acrylic base material include a poly (meth) methyl acrylate base material, a poly (meth) ethyl acrylate base material, and a (meth) methyl acrylate- (meth) butyl acrylate copolymer base material. .

  Examples of the polyester base material include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene-2,6-naphthalate.

  The polyester used for the polyester substrate may be a copolymer of the above-mentioned polyester, and the polyester is the main component (for example, a component of 80 mol% or more), and a small proportion (for example, 20 mol% or less) It may be blended with a kind of resin. Polyethylene terephthalate or polyethylene-2,6-naphthalate is particularly preferable as the polyester because of good balance between mechanical properties and optical properties. In particular, it is preferably made of polyethylene terephthalate (PET). This is because polyethylene terephthalate is highly versatile and easily available. In the present invention, an optical film capable of producing a liquid crystal display device with high display quality can be obtained even if the film is extremely versatile, such as polyethylene terephthalate. Furthermore, polyethylene terephthalate is excellent in transparency, heat or mechanical properties, can be controlled by stretching, has a large intrinsic birefringence, and can obtain a large retardation relatively easily even when the film thickness is small.

  Examples of the polycarbonate substrate include aromatic polycarbonate substrates based on bisphenols (bisphenol A and the like), aliphatic polycarbonate substrates such as diethylene glycol bisallyl carbonate, and the like.

  As a cycloolefin polymer base material, the base material which consists of polymers, such as a norbornene-type monomer and a monocyclic cycloolefin monomer, is mentioned, for example.

  Examples of the glass substrate include glass substrates such as soda lime silica glass, borosilicate glass, and alkali-free glass.

  The refractive index of the light transmissive substrate 21 can be 1.40 or more and 1.80 or less. In addition, when using the base material which has birefringence as the light transmissive base material 21, the said "refractive index of a light transmissive base material" shall mean an average refractive index.

  In the case where a base material having birefringence is used as the light-transmitting base material 21, light transmission is performed from the viewpoint of suppressing the occurrence of unevenness of different colors (Nijimura) as disclosed in JP-A-2011-107198. The conductive substrate 21 preferably has a retardation Re of 3000 nm or more. Retardation Re is an index representing the degree of birefringence. From the viewpoint of preventing azimuth and thinning, it is more preferably 6000 nm or more and 25000 nm or less, and further preferably 8000 nm or more and 20000 nm or less.

The retardation Re (unit: nm) of the light transmissive substrate 21 is the refractive index (n _x ) in the direction having the highest refractive index (slow axis direction) in the plane of the light transmissive substrate 21, and the slow axis. The refractive index (n _y ) in the direction orthogonal to the direction (fast axis direction) and the thickness d (unit: nm) of the light-transmitting substrate are represented by the following formula (34).
_{Re = (n x -n y)} × d ... (34)

For example, the retardation can be set to a measured value using a KOBRA-WR manufactured by Oji Scientific Instruments with a measurement angle of 0 ° and a measurement wavelength of 548.2 nm. The retardation can also be obtained by the following method. First, using two polarizing plates, determined the orientation direction of the light-transmitting substrate, the refractive index of the two axes orthogonal to the orientation axis (n _{x, n y)} of an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd.) Here, an axis showing a larger refractive index is defined as a slow axis. Further, the thickness of the light-transmitting substrate is measured using, for example, an electric micrometer (manufactured by Anritsu). Then, by using the refractive index obtained, refractive index difference _(n x _-n y) _{(hereinafter,} n x -n _y is referred to as [Delta] n) is calculated, and the refractive index difference [Delta] n and the light transmissive substrate 21 Retardation can be obtained by the product of the thickness d (nm).

  The refractive index difference Δn is preferably 0.05 to 0.20. When the refractive index difference Δn is less than 0.05, the thickness necessary for obtaining the retardation value described above may be increased. On the other hand, if the refractive index difference Δn exceeds 0.20, it is necessary to make the draw ratio excessively high, so that tearing, tearing, etc. are likely to occur, and the practicality as an industrial material may be significantly reduced. More preferably, the lower limit of the refractive index difference Δn is 0.07, and the upper limit of the refractive index difference Δn is 0.15. In addition, when refractive index difference (DELTA) n exceeds 0.15, depending on the kind of the light transmissive base material 21, durability of the light transmissive base material 21 in a heat-and-moisture resistance test may be inferior. From the viewpoint of ensuring excellent durability in the heat and humidity resistance test, a more preferable upper limit of the refractive index difference Δn is 0.12.

As the refractive indices _{n x} in the slow axis direction of the light-transmitting substrate 21 is preferably 1.60 to 1.80, more preferable lower limit is 1.65, more preferable upper limit is 1.75 is there. As the refractive index _{n y} in the fast axis direction of the light transmitting substrate 21 is preferably 1.50 to 1.70, more preferable lower limit is 1.55, more preferable upper limit is 1.65 is there. By the refractive index n _y in the refractive indices n _x and the fast axis direction in the slow axis direction of the light transmitting substrate 21 is in the above range, and is satisfied the relationship of the above-mentioned refractive index difference [Delta] n, more preferably The inhibitory effect of Nijimura can be obtained.

  For example, as a method of obtaining a polyester base material having a retardation of 3000 nm or more, a polyester such as polyethylene terephthalate is melted, and the unstretched polyester extruded and formed into a sheet shape is transversal using a tenter or the like at a temperature equal to or higher than the glass transition temperature. A method of performing a heat treatment after stretching is mentioned. The transverse stretching temperature is preferably 80 to 130 ° C, more preferably 90 to 120 ° C. Further, the transverse draw ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.5 times. When the transverse draw ratio exceeds 6.0 times, the transparency of the resulting polyester base material tends to be lowered, and when the draw ratio is less than 2.5 times, the draw tension becomes small. The birefringence of the material is reduced, and the film thickness for obtaining the desired retardation is increased. Further, when the polyester base material is extruded into a sheet shape, stretching in the flow direction (machine direction), that is, longitudinal stretching may be performed. In this case, from the viewpoint of stably ensuring the value of the refractive index difference Δn within the above-described preferred range, the longitudinal stretching preferably has a stretching ratio of 2 times or less. Instead of longitudinal stretching during extrusion molding, longitudinal stretching may be performed after lateral stretching of the unstretched polyester is performed under the above conditions. Moreover, as processing temperature at the time of the said heat processing, 100-250 degreeC is preferable, More preferably, it is 180-245 degreeC.

  Examples of the method for controlling the retardation of the polyester substrate produced by the above-described method to 3000 nm or more include a method of appropriately setting the draw ratio, the drawing temperature, and the film thickness of the produced polyester substrate. Specifically, for example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the easier it is to obtain high retardation. The lower the stretching ratio, the higher the stretching temperature, and the film thickness. The thinner, the easier it is to obtain low retardation.

  The thickness of the light transmissive substrate 21 is not particularly limited, but can usually be 5 μm or more and 1000 μm or less, and the lower limit of the thickness of the light transmissive substrate 21 is preferably 15 μm or more from the viewpoint of handling properties and the like. 25 μm or more is more preferable. The upper limit of the thickness of the light transmissive substrate 21 is preferably 80 μm or less from the viewpoint of thinning.

  When a polyester substrate having a retardation of 3000 nm or more is used as the light transmissive substrate 21, the thickness of the polyester substrate is preferably 15 μm or more and 500 μm or less. When the thickness is less than 15 μm, the retardation of the polyester base material cannot be increased to 3000 nm or more, the anisotropy of mechanical properties becomes remarkable, and tearing, tearing, etc. are likely to occur, and the practicality as an industrial material is significantly reduced. There is. On the other hand, when it exceeds 500 μm, the flexibility specific to the polymer film is lowered, and the practicality as an industrial material may be lowered. The minimum with more preferable thickness of the said polyester base material is 50 micrometers, a more preferable upper limit is 400 micrometers, and a still more preferable upper limit is 300 micrometers.

  Further, the light transmissive substrate 21 may be subjected to a surface treatment such as a saponification treatment, a glow discharge treatment, a corona discharge treatment, an ultraviolet (UV) treatment, and a flame treatment without departing from the spirit of the present invention.

(Uneven layer)
The uneven layer 22 is a layer that is provided on the light-transmitting substrate 21 and has an uneven surface 20A. Since the uneven surface 20A has been described above, the description thereof will be omitted here.

The uneven layer 22 includes a portion 20B constituting the uneven surface 20A. The refractive index of the uneven layer 22 may be a value larger or smaller than the refractive index n _{f as} long as it is not the same as the refractive index n _{f of} the first functional layer 30. Specifically, the refractive index of the concavo-convex layer 22 can be 1.40 or more and 1.80 or less. Moreover, the one where the refractive index difference of the uneven | corrugated layer 22 and the light transmissive base material 21 is smaller is preferable.

  The concavo-convex layer 22 only needs to have the concavo-convex surface 20 </ b> A, but the adhesion improving layer improves the adhesion between the light-transmitting base material 21, particularly the base material in which the mixed region is difficult to form and the first functional layer 30. It preferably functions as

  The concavo-convex layer 22 can be composed of, for example, a resin and fine particles, but the concavo-convex surface has an average inclination angle θa that satisfies the above formula (1) and a maximum inclination angle θmax that satisfies the above expression (2). The material constituting the uneven layer 22 is not particularly limited as long as it is a material capable of forming the uneven layer 22 having a slag. Hereinafter, the uneven surface satisfying the above formulas (1) and (2) is referred to as a “specific uneven surface”.

When the resin uneven | corrugated layer 22 functions as an adhesive improvement layer, the resin contained in the uneven | corrugated layer 22 can be comprised from the material similar to the conventional primer layer. Specifically, the resin contained in the uneven layer 22 is, for example, a polyurethane resin, a polyester resin, a polyvinyl chloride resin, a polyvinyl acetate resin, a vinyl chloride-vinyl acetate copolymer, an acrylic resin, or a polyvinyl alcohol resin. , Polyvinyl acetal resin, copolymer of ethylene and vinyl acetate or acrylic acid, copolymer of ethylene and styrene and / or butadiene, thermoplastic resin such as olefin resin and / or modified resin thereof, photopolymerization It can be composed of at least one of a polymer of a compound and a thermosetting resin such as an epoxy resin.

  The photopolymerizable compound has at least one photopolymerizable functional group. In the present specification, the “photopolymerizable functional group” is a functional group capable of undergoing a polymerization reaction by light irradiation. Examples of the photopolymerizable functional group include ethylenic double bonds such as a (meth) acryloyl group, a vinyl group, and an allyl group. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”. The light irradiated when polymerizing the photopolymerizable compound includes visible light and ionizing radiation such as ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

  Examples of the photopolymerizable compound include a photopolymerizable monomer, a photopolymerizable oligomer, and a photopolymerizable polymer, and these can be appropriately adjusted and used. As the photopolymerizable compound, a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable polymer is preferable.

  In the case where the first functional layer 30 is formed using a photopolymerizable compound, a polymerization initiator capable of initiating polymerization of the photopolymerizable compound may be added to the concavo-convex layer 22. preferable. Thereby, when the 1st functional layer 30 is hardened, the uneven | corrugated layer 22 and the 1st functional layer 30 can be bridge | crosslinked firmly.

Fine particles The fine particles may be either inorganic fine particles or organic fine particles, as long as they have resistance to volume shrinkage of the coating film that occurs when the coating film of the composition for the uneven layer is dried or polymerized. . In the case where the particle diameter of the fine particles is equal to or greater than the visible light wavelength, it is preferable that the difference between the refractive index of the fine particles and the refractive index of the resin is not substantially reduced because transparency is not impaired. Specifically, the difference between the refractive index of the fine particles and the refractive index of the resin is preferably 0.02 or less, and more preferably 0.01 or less.

As the inorganic fine particles, for example, inorganic oxide fine particles such as silica (SiO ₂ ) fine particles, alumina fine particles, titania fine particles, tin oxide fine particles, antimony-doped tin oxide (abbreviated as ATO) fine particles, and zinc oxide fine particles are preferable. The inorganic oxide fine particles can form an aggregate in the functional layer, and a specific uneven surface can be formed by the degree of aggregation of the aggregate.

  Examples of the organic fine particles include plastic beads. Specific examples of the plastic beads include polystyrene beads, melamine resin beads, acrylic beads, acrylic-styrene beads, silicone beads, benzoguanamine beads, benzoguanamine / formaldehyde condensation beads, polycarbonate beads, polyethylene beads, and the like.

  It is preferable that the organic fine particles have moderately adjusted resistance to volume shrinkage of the fine particles in the volume shrinkage described above. In order to adjust the resistance to shrinkage, by making multiple optical films containing organic fine particles with different hardness created in advance by changing the degree of three-dimensional crosslinking, and evaluating the uneven surface of the optical film It is preferable to select a degree of cross-linking suitable for providing a specific uneven surface.

  When inorganic oxide particles are used as the fine particles, the inorganic oxide particles are preferably subjected to surface treatment. By subjecting the inorganic oxide fine particles to surface treatment, the distribution of the fine particles in the uneven layer 22 can be suitably controlled, and the chemical resistance and saponification resistance of the fine particles themselves can be improved.

  As the surface treatment, a hydrophobizing treatment for making the surface of the fine particles hydrophobic is preferable. Such a hydrophobization treatment can be obtained by chemically reacting the surface of the fine particles with a surface treatment agent such as silanes or silazanes. Specific examples of the surface treatment agent include dimethyldichlorosilane, silicone oil, hexamethyldisilazane, octylsilane, hexadecylsilane, aminosilane, methacrylsilane, octamethylcyclotetrasiloxane, and polydimethylsiloxane. When the fine particles are inorganic oxide fine particles, hydroxyl groups are present on the surface of the inorganic oxide fine particles. However, by performing the hydrophobic treatment as described above, the hydroxyl groups present on the surface of the inorganic oxide fine particles are reduced. In addition, the specific surface area of the inorganic oxide fine particles measured by the BET method can be reduced, the inorganic oxide fine particles can be prevented from excessively agglomerating, and the uneven layer 22 having a specific uneven surface can be formed.

  When inorganic oxide particles are used as the fine particles, the inorganic oxide fine particles are preferably amorphous. This is because when the inorganic oxide particles are crystalline, the Lewis acid salt of the inorganic oxide fine particles becomes strong due to lattice defects contained in the crystal structure, and excessive aggregation of the inorganic oxide fine particles can be controlled. It is because there is a risk of disappearing.

  When inorganic oxide particles are used as the fine particles, the inorganic oxide fine particles preferably form aggregates in the uneven layer 22. The aggregate of the inorganic oxide fine particles preferably has a structure in which the inorganic oxide fine particles are three-dimensionally connected instead of a lump in the uneven layer 22. Examples of the structure in which the inorganic oxide fine particles are three-dimensionally connected instead of a lump shape include a hook shape and a string shape. That is, in the case of an aggregate having a structure in which inorganic oxide fine particles are three-dimensionally connected instead of a lump, they are easily and uniformly crushed during the volume shrinkage. As a result, the uneven surface can be made to be a very smooth surface, and as a result, an uneven layer having a unique uneven surface can be formed instead of an uneven surface having a steep slope. Even when organic fine particles are used as described above, the uneven layer 22 having a specific uneven surface can be formed by appropriately adjusting the degree of crosslinking.

  The content of fine particles with respect to the uneven layer 22 is not particularly limited, but is preferably 0.1% by mass or more and 5.0% by mass or less. Since the content of the fine particles is 0.1% by mass or more, a unique uneven surface can be formed more reliably, and the content of the fine particles is 0.5% by mass or less. Aggregation does not occur excessively, and it is possible to suppress internal diffusion and / or generation of large unevenness on the surface of the uneven layer, thereby suppressing the cloudiness. The lower limit of the content of fine particles is more preferably 0.5% by mass or more, and the upper limit of the content of fine particles is more preferably 3.0% by mass or less.

  The fine particles are preferably spherical in shape in a single particle state. Since the single particles of the fine particles are spherical, an image having excellent contrast can be obtained when the optical film is disposed on the image display surface of the image display device. Here, “spherical” means, for example, a true spherical shape, an elliptical spherical shape, etc., but a so-called indeterminate shape is not included.

  When inorganic oxide fine particles are used as the fine particles, the average primary particle size of the inorganic oxide fine particles is preferably 1 nm or more and 100 nm or less. Since the average primary particle size of the fine particles is 1 nm or more, a unique uneven surface can be more easily formed, and transparency can be obtained because the average primary particle size is 100 nm or less. . Moreover, the diffusion of light by the fine particles can be suppressed, and an excellent darkroom contrast can be obtained. The lower limit of the average primary particle size of the fine particles is more preferably 5 nm or more, and the upper limit of the average primary particle size of the fine particles is more preferably 50 nm or less. The average primary particle size of the fine particles is a value measured using an image processing software from an image of a cross-sectional electron microscope (a transmission type such as TEM or STEM and preferably having a magnification of 50,000 times or more).

  When inorganic oxide fine particles are used as the fine particles, the average particle size of the aggregates of the inorganic oxide fine particles is preferably 100 nm or more and 2.0 μm or less. If the thickness is 100 nm or more, a specific uneven surface can be easily formed. If the thickness is 2.0 μm or less, the diffusion of light due to the aggregate of fine particles can be suppressed, and an image image of an optical film excellent in dark room contrast. A display device can be obtained. The average particle diameter of the fine particle aggregate is preferably 200 nm or less at the lower limit, and preferably 1.5 μm or less at the upper limit.

  The average particle diameter of the aggregates of the inorganic oxide fine particles was selected from a 5 μm square region containing a large amount of aggregates of the inorganic oxide fine particles based on observation with a cross-sectional electron microscope (about 10,000 to 20,000 times). The particle diameter of the aggregate of inorganic oxide fine particles was measured, and the average particle diameter of the aggregate of the top 10 inorganic oxide fine particles was measured. The “particle diameter of the aggregate of the inorganic oxide fine particles” is the maximum distance between the two straight lines when the cross section of the aggregate of the inorganic oxide fine particles is sandwiched between any two parallel straight lines. It is measured as the distance between straight lines in a combination of two straight lines. The particle diameter of the aggregate of inorganic oxide fine particles may be calculated using image analysis software.

  When silica particles are used as the fine particles, fumed silica fine particles are preferred from the viewpoint of easily forming a concavo-convex layer having a specific concavo-convex surface among the silica particles. Fumed silica is amorphous silica having a particle size of 200 nm or less prepared by a dry method, and can be obtained by reacting a volatile compound containing silicon in a gas phase. Specific examples include those produced by hydrolyzing a silicon compound such as silicon tetrachloride (SiCl4) in a flame of oxygen and hydrogen. Examples of commercially available fumed silica fine particles include AEROSIL R805 manufactured by Nippon Aerosil Co., Ltd.

  Among the fumed silica fine particles, there are those showing hydrophilicity and those showing hydrophobicity. Among these, from the viewpoint of facilitating dispersion in the functional layer composition, the hydrophobicity is reduced. Is preferable. Hydrophobic fumed silica can be obtained by chemically reacting the above-mentioned surface treatment agent with silanol groups present on the surface of the fumed silica fine particles. From the viewpoint of easily obtaining the aggregate as described above, the fumed silica is most preferably treated with octylsilane.

  Although the fumed silica fine particles form aggregates, the aggregates of the fumed silica fine particles are not dense aggregates in the composition for the uneven layer, and are sufficiently sparse such as cocoon-like or string-like shapes. Aggregates are formed. For this reason, the aggregate of fumed silica fine particles is easily and uniformly crushed during the volume shrinkage described above. Thereby, the uneven | corrugated layer which has a specific uneven surface can be formed.

  In order to form the concavo-convex layer 22, first, the resin and / or photopolymerizable compound and fine particles were dissolved or dispersed in a solvent together with known additives used for a hard coat layer, which will be described later, as necessary. A composition for an uneven layer is prepared.

  And after applying this composition for uneven | corrugated layers on the surface of the transparent base material 21 to make a coating film, it is dried. Alternatively, it is polymerized by heat or ultraviolet light after drying, if necessary. Thereby, the uneven | corrugated layer 22 which has the unusual uneven surface 20A by the effect | action of microparticles | fine-particles can be formed.

  In the above description, an example in which a specific uneven surface is formed using fine particles has been described. However, it is also possible to form a specific uneven surface without using fine particles. Specifically, for example, a concavo-convex layer composition containing a photopolymerizable compound or a thermosetting resin is applied onto a light-transmitting substrate, and a mold having a concavo-convex surface opposite to a specific concavo-convex surface is provided. It is also possible to transfer and form the shape of the concavo-convex layer having a specific concavo-convex surface by polymerizing a photopolymerizable compound or a thermosetting resin while pressing. It is also possible to form a concavo-convex layer having a specific concavo-convex surface by phase separation by using two or more resins having poor compatibility with each other.

  The method for preparing the concavo-convex layer composition is not particularly limited as long as each component can be mixed uniformly. For example, the composition can be performed using a known apparatus such as a paint shaker, a bead mill, a kneader, or a mixer.

  Examples of the method for applying the uneven layer composition include known coating methods such as spin coating, dipping, spraying, slide coating, bar coating, roll coating, gravure coating, and die coating.

  When the composition for the concavo-convex layer contains a photopolymerizable compound and ultraviolet rays are used as light for curing the photopolymerizable compound, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc Ultraviolet rays emitted from metal halide lamps can be used. Moreover, as a wavelength of an ultraviolet-ray, the wavelength range of 190-380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as a cockcroft-wald type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type.

<First functional layer>
The 1st functional layer 30 is a layer adjacent to the uneven | corrugated surface 20A of the base material 20 for optical films, Comprising: It is a single layer. Further, the first functional layer 30 is a layer intended to exhibit some function in the optical film 10, and specifically includes, for example, a hard coat layer, an antistatic layer, a high refractive index layer, a low refractive index, and the like. Rate layer, antifouling layer and the like.

  In the first functional layer 30, the surface (back surface) on the optical film substrate 20 side is a concavo-convex surface corresponding to the concavo-convex surface 20 </ b> A of the optical film substrate 20. The surface (surface) opposite to the surface is flat. By making the surface of the first functional layer 30 flat, there is no white turbidity and surface gloss equivalent to that of the antireflection film can be obtained. For example, if the arithmetic average roughness Ra on the surface of the first functional layer 30 is 0.10 μm or less, the surface of the first functional layer 30 can be said to be flat. Note that the definition of “Ra” conforms to JIS B0601-1994.

  The first functional layer 30 of the present embodiment functions as a hard coat layer. The hard coat layer will be described below.

(Hard coat layer)
The “hard coat layer” is a layer for improving the scratch resistance of the optical film, and specifically, a pencil hardness test (4.9 N load) defined in JIS K5600-5-4 (1999). And having a hardness equal to or higher than “H”.

If the refractive index of the hard coat layer have the same value as the refractive index of the relief layer, even larger than the refractive index n _c, it may be a small value. Specifically, the refractive index of the hard coat layer can be 1.40 or more and 1.80 or less.

  The thickness of the hard coat layer is preferably 1.0 μm or more and 10.0 μm or less. If the thickness of the hard coat layer is within this range, a desired hardness can be obtained. In addition, it is possible to reduce the thickness of the hard coat layer, while suppressing the occurrence of cracking and curling of the hard coat layer. The thickness of the hard coat layer can be measured by cross-sectional microscope observation. The lower limit of the thickness of the hard coat layer is more preferably 1.5 μm or more, the upper limit is more preferably 7.0 μm or less, and the thickness of the hard coat layer is 2.0 μm or more and 5.0 μm or less. Further preferred.

  The hard coat layer includes, for example, at least a binder resin. The binder resin is obtained by polymerizing (crosslinking) a photopolymerizable compound by light irradiation. This photopolymerizable compound has at least one photopolymerizable functional group as described in the section of the uneven layer.

  Examples of the photopolymerizable compound include a photopolymerizable monomer, a photopolymerizable oligomer, and a photopolymerizable polymer, and these can be appropriately adjusted and used. As the photopolymerizable compound, a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable polymer is preferable.

Photopolymerizable monomer The photopolymerizable monomer has a weight average molecular weight of less than 1000. The photopolymerizable monomer is preferably a polyfunctional monomer having two or more photopolymerizable functional groups (that is, bifunctional). In the present specification, the “weight average molecular weight” is a value obtained by dissolving in a solvent such as THF and converting to polystyrene by a conventionally known gel permeation chromatography (GPC) method.

  Examples of the bifunctional or higher monomer include trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and pentaerythritol tri (meth). Acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditri Methylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate, Lapentaerythritol deca (meth) acrylate, isocyanuric acid tri (meth) acrylate, isocyanuric acid di (meth) acrylate, polyester tri (meth) acrylate, polyester di (meth) acrylate, bisphenol di (meth) acrylate, diglycerin tetra ( (Meth) acrylate, adamantyl di (meth) acrylate, isoboronyl di (meth) acrylate, dicyclopentane di (meth) acrylate, tricyclodecane di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and these are PO, EO And the like modified.

  Among these, from the viewpoint of obtaining a hard coat layer having high hardness, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA) and the like are preferable. .

The photopolymerizable oligomer The photopolymerizable oligomer has a weight average molecular weight of 1,000 or more and less than 10,000. The photopolymerizable oligomer is preferably a bifunctional or higher polyfunctional oligomer. Polyfunctional oligomers include polyester (meth) acrylate, urethane (meth) acrylate, polyester-urethane (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate, and isocyanurate (meth). Examples include acrylate and epoxy (meth) acrylate.

Photopolymerizable polymer The photopolymerizable polymer has a weight average molecular weight of 10,000 or more, and the weight average molecular weight is preferably 10,000 or more and 80,000 or less, and more preferably 10,000 or more and 40,000 or less. When the weight average molecular weight exceeds 80000, the viscosity is high, so that the coating suitability is lowered, and the appearance of the obtained optical film may be deteriorated. Examples of the polyfunctional polymer include urethane (meth) acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, and epoxy (meth) acrylate.

  The hard coat layer is obtained by applying the composition for hard coat layer containing the photopolymerizable compound to the uneven surface of the uneven layer and drying it, and then applying ultraviolet light or the like to the coated hard coat layer composition. It can be formed by irradiating and polymerizing (crosslinking) the photopolymerizable compound.

  In addition to the photopolymerizable compound, if necessary, the thermoplastic resin, thermosetting resin, solvent, and polymerization initiator may be added to the hard coat layer composition. Furthermore, the hard coat layer composition includes conventionally known dispersants, surfactants and antistatic agents depending on purposes such as increasing the hardness of the hard coat layer, suppressing cure shrinkage, and controlling the refractive index. , Silane coupling agents, thickeners, anti-coloring agents, colorants (pigments, dyes), antifoaming agents, leveling agents, flame retardants, UV absorbers, adhesion promoters, polymerization inhibitors, antioxidants, surface modification A quality agent, a lubricant, etc. may be added.

  Since the method for preparing the composition for hard coat layer, the coating method, and the ultraviolet ray for curing are the same as in the case of the above composition for concave and convex layers, the description thereof will be omitted here.

  When an antistatic layer is used instead of the hard coat layer, the antistatic layer can be formed by incorporating an antistatic agent in the hard coat layer composition. As the antistatic agent, conventionally known ones can be used. For example, a cationic antistatic agent such as a quaternary ammonium salt, fine particles such as tin-doped indium oxide (ITO), a conductive polymer, or the like can be used. Can do. When using the said antistatic agent, it is preferable that the content is 1-30 mass% with respect to the total mass of all the solid content.

<Second functional layer>
The second functional layer 40 is a layer formed on the first functional layer 30 and intended to exhibit some function in the optical film 10. The second functional layer 40 may be composed of not only a single layer but also two or more layers. Specific examples include a low refractive index layer or an antifouling layer. Since the second functional layer 40 of the present embodiment functions as a low refractive index layer having a lower refractive index than the hard coat layer, the low refractive index layer will be described below.

(Low refractive index layer)
The low refractive index layer is for reducing the reflectance when external light (for example, a fluorescent lamp, natural light, etc.) is reflected on the surface of the optical film. The low refractive index layer has a lower refractive index than the hard coat layer. Specifically, for example, the low refractive index layer preferably has a refractive index of 1.45 or less, and more preferably has a refractive index of 1.42 or less.

The thickness of the low-refractive index layer is not limited, but it may be set appropriately from the range of about 30 nm to 1 μm. The thickness d _A (nm) of the low refractive index layer preferably satisfies the following formula (35).
d _A = mλ / (4n _A ) (35)
In the above formula, n _A represents the refractive index of the low refractive index layer, m represents a positive odd number, preferably 1, and λ is a wavelength, preferably a value in the range of 480 nm to 580 nm.

The low refractive index layer preferably satisfies the following formula (36) from the viewpoint of reducing the reflectance.
120 <n _A d _A <145 (36)

  The effect can be obtained with a single layer of the low refractive index layer, but it is also possible to appropriately provide two or more low refractive index layers for the purpose of adjusting a lower minimum reflectance or a higher minimum reflectance. When two or more low refractive index layers are provided, it is preferable to provide a difference in the refractive index and thickness of each low refractive index layer.

  The low refractive index layer is preferably 1) a resin containing low refractive index particles such as silica and magnesium fluoride, 2) a fluorine-based resin which is a low refractive index resin, and 3) fluorine containing silica or magnesium fluoride. 4) It can be composed of any one of a thin film of a low refractive index material such as silica and magnesium fluoride. As for the resin other than the fluorine-based resin, the same resin as the binder resin constituting the hard coat layer described above can be used.

  The silica is preferably hollow silica fine particles, and such hollow silica fine particles can be produced by, for example, a production method described in Examples of JP-A-2005-099778.

  The case where an antifouling layer is used as the second functional layer 40 instead of the low refractive index layer will be described below.

(Anti-fouling layer)
The antifouling layer is a layer that plays a role of preventing dirt (fingerprints, water-based or oil-based inks, pencils, etc.) from adhering to the outermost surface of the liquid crystal display device or easily wiping off even when adhering. . Further, by forming the antifouling layer, it is possible to improve the antifouling property and scratch resistance of the liquid crystal display device. The antifouling layer can be formed of, for example, a composition containing an antifouling agent and a resin.

  The antifouling agent is mainly intended to prevent the outermost surface of the image display device from being stained, and can also impart scratch resistance to the liquid crystal display device. Examples of the antifouling agent include fluorine compounds, silicon compounds, and mixed compounds thereof. More specifically, silane coupling agents having a fluoroalkyl group, such as 2-perfluorooctylethyltriaminosilane, and the like can be mentioned, and those having an amino group can be preferably used. It does not specifically limit as said resin, The resin material illustrated with the above-mentioned composition for hard-coat layer formation is mentioned.

  The antifouling layer is preferably formed so as to be particularly the outermost surface. The antifouling layer can be replaced, for example, by imparting antifouling performance to the hard coat layer itself.

<Physical properties of optical film>
In the optical film 10, the haze value of the optical film 10 is set to H 2 _O (%), and the haze value measured by overlaying a slide glass on the concavo-convex surface 20 A of the optical film substrate 20 through liquid paraffin is H _bin ( %), It is preferable to satisfy the following formula (37). By satisfying the following expression (37), the degree of diffusion caused by the first functional layer 30 is suppressed to a low level, thereby making it difficult for human eyes to perceive image quality degradation.
│H _O -H _bin │ <0.3 (37)

The haze value H 2 _O and the haze value H _bin of the optical film 10 are measured according to JIS K7136 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory).

≪Polarizing plate≫
The optical film 10 can be used by being incorporated into a polarizing plate, for example. FIG. 6 is a schematic configuration diagram of a polarizing plate incorporating the optical film according to the present embodiment. As shown in FIG. 6, the polarizing plate 50 includes an optical film 10, a polarizing element 51, and a protective film 52. The polarizing element 51 is formed on the surface opposite to the surface on which the first functional layer 30 is formed in the optical film substrate 20. The protective film 52 is provided on the surface of the polarizing element 51 opposite to the surface on which the optical film 10 is provided. The protective film 52 may be a retardation film.

  Examples of the polarizing element 51 include a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film, which are dyed and stretched with iodine or the like. When a cellulose ester substrate is used as the light transmissive substrate 21, it is preferable to saponify the light transmissive substrate 21 in advance when the optical film 10 and the polarizing element 51 are laminated. By performing the saponification treatment, the adhesiveness is improved and an antistatic effect can be obtained.

≪LCD panel≫
The optical film 10 and the polarizing plate 20 can be used by being incorporated in a liquid crystal panel. FIG. 7 is a schematic configuration diagram of a liquid crystal panel incorporating the optical film according to the present embodiment.

  A liquid crystal panel 60 shown in FIG. 7 has a protective film 61 such as a triacetyl cellulose film (TAC film), a polarizing element 62, a retardation film 63, an adhesive, and the like from the light source side (backlight unit side) to the viewer side. The agent layer 64, the liquid crystal cell 65, the adhesive layer 66, the retardation film 67, the polarizing element 51, and the optical film 10 are stacked in this order. In the liquid crystal cell 65, a liquid crystal layer, an alignment film, an electrode layer, a color filter, and the like are disposed between two glass substrates.

  Examples of the retardation films 63 and 67 include a triacetyl cellulose film and a cycloolefin polymer film. The retardation film 67 may be the same as the protective film 52. Examples of the adhesive constituting the adhesive layers 64 and 66 include a pressure sensitive adhesive (PSA).

≪Image display device≫
The optical film 10, the polarizing plate 50, and the liquid crystal panel 60 can be used by being incorporated in an image display device. Examples of the image display device include a liquid crystal display (LCD), a cathode ray tube display device (CRT), a plasma display (PDP), an electroluminescence display (ELD), a field emission display (FED), a touch panel, a tablet PC, and electronic paper. Can be mentioned. FIG. 8 is a schematic configuration diagram of a liquid crystal display which is an example of an image display device incorporating the optical film according to the present embodiment.

  The image display device 70 shown in FIG. 8 is a liquid crystal display. The image display device 70 includes a backlight unit 71 and a liquid crystal panel 60 including the optical film 10 that is disposed closer to the viewer than the backlight unit 71. A known backlight unit can be used as the backlight unit 71. Although it does not specifically limit as a light source used for the backlight unit 71, A white light emitting diode (white LED) is preferable. The white LED is an element that emits white by combining a phosphor with a phosphor type, that is, a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor. Above all, white light-emitting diodes, which consist of light-emitting elements that combine blue light-emitting diodes using compound semiconductors with yttrium, aluminum, and garnet yellow phosphors, have a continuous and broad emission spectrum. Therefore, it is suitable for the backlight light source in the present invention. Further, since white LEDs with low power consumption can be widely used, it is possible to achieve an energy saving effect.

(Second Embodiment)
Hereinafter, an optical film according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a schematic configuration diagram of an optical film according to the present embodiment.

<< Substrate for optical film and optical film >>
As shown in FIG. 9, the optical film 80 includes at least an optical film substrate 90 and a first functional layer 30 provided on the optical film substrate 90. The optical film 90 shown in FIG. 9 further includes a second functional layer 40 formed on the first functional layer 30.

<Base material for optical film>
The optical film substrate 90 has an uneven surface 90 </ b> A that forms the surface on the first functional layer 30 side. Unlike the first embodiment, the optical film substrate 90 shown in FIG. 9 has a single-layer structure of the light transmissive substrate 91. Therefore, the light-transmitting substrate 91 has the uneven surface 90A and includes a portion 90B that forms the uneven surface 90A. In the present embodiment, since the refractive index of the light transmissive substrate 91 is the same value for the entire light transmissive substrate 91, the refractive index of the light transmissive substrate 91 is a portion constituting the uneven surface 90A. It has the same value as the refractive index _{n c} of 90B. The light transmissive substrate 91 can be made of the same material as the light transmissive substrate 21.

An optical film base material 90, the average inclination angle of the uneven surface 90A and .theta.a, the maximum inclination angle of the uneven surface 90A and .theta.max, the refractive index of the portion 90B constituting the irregular surface 90A and _{n c,} the first function When the refractive index of the layer 30 is n _f (where n _c ≠ n _f ), the relationship of the following formula (38) and the following formula (39) is satisfied.
θa> tan ⁻¹ (0.0013 / n _f ) (38)
θmax <tan ⁻¹ (0.0087 / | n _c −n _f |) (39)

  The above formula (38) is the same formula as the above formula (1), and the above formula (39) is the same formula as the above formula (2). Therefore, also in the present embodiment, the average inclination angle θa of the uneven surface 90A satisfies the relationship of the above formula (38), and the maximum inclination angle θmax of the uneven surface 90A satisfies the relationship of the above formula (39). For the same reason as described in the first embodiment, it is difficult for human eyes to recognize interference fringes and image quality degradation of image light.

  The light transmissive substrate 91 having such an uneven surface 90A can be formed by, for example, pressing or blasting.

  Since other configurations are the same as the configurations described in the first embodiment, description thereof will be omitted in the present embodiment.

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited to these descriptions.

<Preparation of uneven layer composition>
First, each component was mix | blended so that it might become the composition shown below, and the composition for uneven | corrugated layers was obtained.
(Composition 1 for uneven layer)
Fumed silica (octylsilane treatment, average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd.): 1.5 parts by massPentaerythritol tetraacrylate (PETTA) (product name “PETA”, manufactured by Daicel Cytec Co., Ltd.): 10 parts by mass -Zirconia fine particle-containing hard coat composition (product name "Desolite Z7404", manufactured by JSR): 80 parts by mass-Polyester resin (product name "Byron 103", manufactured by Toyobo Co., Ltd.): 30 parts by mass-Crosslinking agent (product name) "Duranate MF", blocked isocyanate, manufactured by Asahi Kasei Chemicals Co., Ltd .: 10 parts by mass, polymerization initiator (product name "Irgacure 184", manufactured by BASF Japan): 5 parts by mass, polyether-modified silicone (product name: TSF4460, Momentive)・ Performance Materials): 0.005 quality Part Methyl ethyl ketone: 130 parts by weight was measured for refractive index of a single cured coating film formed by uneven layer composition 1 having the above composition was 1.65.

(Composition 2 for uneven layer)
Fumed silica (octylsilane treatment, average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd.): 1.5 parts by massPentaerythritol tetraacrylate (PETTA) (product name “PETA”, manufactured by Daicel Cytec Co., Ltd.): 30 parts by mass・ Modified polyolefin resin (product name “Unistor P-901”, manufactured by Mitsui Chemicals, Inc.): 180 parts by mass. 2- (2-acryloxyethoxy) biphenyl (product name “TO1463”, manufactured by Toagosei Co., Ltd.): 30 Mass parts / polymerization initiator (product name “Irgacure 184”, manufactured by BASF Japan): 2 parts by mass / polyether-modified silicone (product name “TSF4460”, manufactured by Momentive Performance Materials): 0.005 parts by mass -Cyclohexanone: 300 parts by weight Formed with the composition 2 for an uneven layer having the above composition. Measurement of the refractive index of a single cured film was 1.53.

(Composition 3 for uneven layer)
Pentaerythritol tetraacrylate (PETTA) (product name “PETA”, manufactured by Daicel Cytec): 10 parts by mass • Hard coat composition containing zirconia fine particles (product name “Desolite Z7404”, manufactured by JSR): 80 parts by mass Polyester resin (product name “Byron 103”, manufactured by Toyobo Co., Ltd.): 30 parts by mass / crosslinking agent (product name “Duranate MF”, blocked isocyanate, manufactured by Asahi Kasei Chemicals): 10 parts by mass / polymerization initiator (product name “ "Irgacure 184", manufactured by BASF Japan): 5 parts by mass, polyether-modified silicone (Product name: TSF4460, manufactured by Momentive Performance Materials): 0.005 parts by mass, methyl ethyl ketone: 130 parts by mass Of the cured coating film formed by the composition 3 for The refractive index was measured and found to be 1.65.

(Composition 4 for uneven layer)
- amorphous silica (average particle size 2.5 [mu] m, product name "SS-50F", manufactured by Tosoh Silica Corporation): 1 2 parts by mass Pentaerythritol tetraacrylate (PETTA) (product name "PETA", Daicel-Cytec ): 10 parts by mass-Zirconia fine particle-containing hard coat composition (product name "Desolite Z7404", manufactured by JSR): 80 parts by mass-Polyester resin (Product name "Byron 103", manufactured by Toyobo Co., Ltd.): 30 parts by mass Cross-linking agent (product name “Duranate MF”, block isocyanate, manufactured by Asahi Kasei Chemicals): 10 parts by mass / polymerization initiator (product name “Irgacure 184”, manufactured by BASF Japan): 5 parts by mass / polyether-modified silicone (product) Name “TSF4460”, manufactured by Momentive Performance Materials): 0.005 mass Methyl ethyl ketone: 130 parts by weight was measured for refractive index of a single cured coating film formed by uneven layer composition 4 having the above composition was 1.65.

(Composition 5 for uneven layer)
Pentaerythritol tetraacrylate (PETTA) (product name “PETA”, manufactured by Daicel Cytec): 30 parts by mass Modified polyolefin resin (product name “Unistol P-901”, manufactured by Mitsui Chemicals): 180 parts by mass 2- (2-acryloxyethoxy) biphenyl (product name “TO1463”, manufactured by Toagosei Co., Ltd.): 30 parts by mass / polymerization initiator (product name “Irgacure 184”, manufactured by BASF Japan): 2 parts by mass / poly Ether-modified silicone (product name “TSF4460”, manufactured by Momentive Performance Materials): 0.005 parts by mass / cyclohexanone: 300 parts by mass Independent refraction of a cured coating film formed by the uneven layer composition 5 having the above composition. When the rate was measured, it was 1.53.

<Preparation of composition for hard coat layer>
Each component was mix | blended so that it might become the composition shown below, and the composition for hard-coat layers was obtained.
(Composition for hard coat layer)
-Dipentaerythritol hexaacrylate (DPHA) (manufactured by Nippon Kayaku Co., Ltd.): 100 parts by mass-Polymerization initiator (product name "Irgacure 184", manufactured by BASF Japan): 5 parts by mass-Polyether-modified silicone (product name " TSF4460 ", manufactured by Momentive Performance Materials): 0.025 parts by mass-Toluene: 100 parts by mass-Methyl isobutyl ketone (MIBK): 40 parts by mass A cured coating film formed from the hard coat layer composition having the above composition. It was 1.51 when the independent refractive index of was measured.

<Example 1>
The polyethylene terephthalate material was melted at 290 ° C., extruded through a film-forming die, into a sheet form, closely adhered onto a water-cooled and cooled rotating quenching drum, and cooled to produce an unstretched film. This unstretched film was preheated at 120 ° C. for 1 minute with a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.), and then stretched at 120 ° C. at a stretch ratio of 4.5 times. Stretching was performed at a stretching ratio of 1.5 times in the direction of the degree to obtain a light-transmitting substrate having n _1x = 1.70, n _1y = 1.60, a film thickness of 80 μm, and a retardation = 8000 nm. On one side of the polyethylene terephthalate substrate obtained above, the uneven layer composition 1 was applied to form a coating film. Next, the formed coating film is dried at 50 ° C. for 1 minute to evaporate the solvent in the coating film, and the integrated light quantity is 50 mJ / cm ² under a nitrogen atmosphere (oxygen concentration of 200 ppm or less). Irradiation was performed to cure the coating film, whereby a concavo-convex layer having a concavo-convex surface thickness (at the time of curing) of 4 μm was formed. After forming the uneven layer, the hard coat layer composition was applied to form a coating film.

Next, the formed coating film is dried at 70 ° C. for 2 minutes to evaporate the solvent in the coating film, and the accumulated light amount is 100 mJ / cm ² under a nitrogen atmosphere (oxygen concentration of 200 ppm or less). The hard coat layer having a thickness (at the time of curing) of 7 μm was formed by curing the coating film by irradiation. Thus, an optical film according to Example 1 was produced.

<Example 2>
In Example 2, a cycloolefin polymer base material (Zeonor (registered trademark) ZF16 (refractive index: 1.53), manufactured by Nippon Zeon Co., Ltd.) is used as the light-transmitting base material, and the uneven layer composition 1 is used. An optical film was prepared in the same manner as in Example 1 except that the uneven layer composition 2 was used.

<Comparative Example 1>
In Comparative Example 1, an optical film was produced in the same manner as in Example 1 except that the uneven layer composition 3 was used instead of the uneven layer composition 1.

<Comparative example 2>
In Comparative Example 2, an optical film was produced in the same manner as in Example 1 except that the uneven layer composition 4 was used in place of the uneven layer composition 1 and the uneven layer thickness was 2 μm.

<Comparative Example 3>
In Comparative Example 3, an optical film was produced in the same manner as in Example 2 except that the uneven layer composition 5 was used instead of the uneven layer composition 2.

<Measurement of average inclination angle θa>
In Examples and Comparative Examples, the average inclination angle θa on the concavo-convex surface of the concavo-convex layer at the stage before forming the hard coat layer, that is, the stage where the concavo-convex layer was formed on the polyethylene terephthalate base or the cycloolefin polymer base, Using a surface roughness measuring instrument (model number: SE-3400 / manufactured by Kosaka Laboratory Ltd.), the measurement was performed under the following measurement conditions.

1) Stylus of surface roughness detector (trade name SE2555N (2 μ standard) manufactured by Kosaka Laboratory Ltd.)
・ Tip radius of curvature 2μm, apex angle 90 degrees, material diamond 2) Measurement conditions of surface roughness measuring instrument ・ Reference length (cutoff value λc of roughness curve): 2.5 mm
Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・ Feeding speed of stylus: 0.5mm / s

<Measurement of maximum inclination angle θmax>
The optical film obtained in Examples and Comparative Examples is attached to a glass plate through a transparent adhesive on the surface opposite to the surface on which the hard coat layer is formed, and a white interference microscope ( The surface shape of the optical film was measured and analyzed under the following conditions using New View 6300 (manufactured by Zygo). The analysis software used was MicroScope Application 8.3.2 Microscope Application.

[Measurement condition]
Objective lens: 2.5 times Zoom: 2 times Data points: 992 × 992 points Resolution (interval per point): 2.2 μm

[Analysis conditions]
Removed: None
Filter: HighPass
FilterType: GaussSpline
Low wavelength: 300 μm
Under the above conditions, a concavo-convex shape from which a swell component is removed can be obtained with a high-pass filter having a cutoff value of 300 μm.
Remove spikes: on
Spike Height (xRMS): 2.5
Spike-like noise can be removed under the above conditions.

Next, the inclination Δi of each point over the entire surface is obtained, the inclination Δi is converted into the surface angle θ _i by the above equation (30), and from there, the one with the smaller relative cumulative frequency of the absolute value of the surface angle θ _i The surface angle at 90% was calculated, and this surface angle was defined as the maximum inclination angle θmax.

<Interference fringe observation evaluation>
Reflection of the back surface of each optical film obtained in Examples and Comparative Examples on the opposite side of the surface of the polyethylene terephthalate substrate or cycloolefin polymer substrate from which the hard coat layer is formed via a transparent adhesive. A black acrylic plate was attached to prevent this, and each optical film was irradiated with light from the hard coat layer side and observed visually. As a light source, an interference fringe inspection lamp (sodium lamp) manufactured by Funatech was used. The occurrence of interference fringes was evaluated according to the following criteria.
(Double-circle): The interference fringe was not confirmed.
A: Interference fringes were slightly confirmed, but at a level that was not problematic for practical use.
X: Interference fringes were clearly confirmed.

<Image quality evaluation>
The polarizing plate on the outermost surface of the liquid crystal television “KDL-40X2500” manufactured by Sony Corporation was peeled off, and a polarizing plate without surface coating was attached. Next, the optical films according to Examples and Comparative Examples obtained thereon were transparent adhesive films for optical films (total light transmittance 91% or more, haze 0.3% so that the hard coat layer side would be the outermost surface. Hereafter, it stuck by the product of film thickness 20-50micrometer, for example, MHM series: the product made by a Niei processing company etc.). This LCD TV is installed in a room with an illuminance of approximately 200Lx, and the DVD “Media Phantom” by Media Factory is displayed. The sensory evaluation was carried out on the following items by viewing 15 videos from various angles. The evaluation criteria are as follows. Judgment was made based on whether the contrast was high and the image was shone or sharp.
◎: 13 or more people who answered good ○: 8-12 people who answered good ×: 7 or less people who answered good

The results are shown in Table 1. In each example and comparative example, the right side of the above formula (1) is 0.05, and the right side of the above formula (2) in Example 1, Comparative Example 1 and Comparative Example 2 is 3.56. The right side of the above formula (2) in 2 and Comparative Example 3 is 23.5.

  As shown in Table 1, in Comparative Examples 1 to 3, the average inclination angle θa of the uneven surface in the uneven layer does not satisfy the above formula (1), or the maximum inclination angle θmax satisfies the above formula (2). Since it was not satisfied, interference fringes were observed or image quality degradation was observed. On the other hand, in Example 1 and Example 2, the average inclination angle θa of the uneven surface in the uneven layer satisfies the above formula (1), and the maximum inclination angle θmax satisfies the above formula (2). Therefore, no interference fringes were observed and no image quality degradation was confirmed.

DESCRIPTION OF SYMBOLS 10, 80 ... Optical film 20, 90 ... Optical film base material 20A, 90A ... Irregular surface 20B, 90B ... Part 21 which comprises an uneven surface, 91 ... Light-transmitting base material 22 ... Irregular layer 30 ... 1st function Layer 40 ... second functional layer 50 ... polarizing plate 51 ... polarizing element 60 ... liquid crystal panel 70 ... image display device 71 ... backlight

Claims (18)

A substrate for an optical film having an uneven surface;
An optical film comprising a first functional layer provided adjacent to the concave-convex surface of the optical film substrate,
The 10-point average roughness Rz of the unevenness constituting the uneven surface is 0.30 μm or less,
The root mean square slope RΔq of the roughness curve on the uneven surface is 0.0025 or less,
The average tilt angle of the uneven surface and .theta.a, and θmax the maximum inclination angle of the uneven surface, the refractive index of the portion constituting the irregular surface of the optical film base material and n _c, the first functional layer When the refractive index of n is n _f (where n _c ≠ n _f ),
_{^{θa> tan -1 (0.0013 / n}} f), and satisfies the relationship ^{θmax <tan -1 (0.0087 / │n} c -n f │), the optical film. When the haze value of the optical film base material as a H _b, the haze values measured repeatedly slides through the liquid paraffin on the irregular surface of the optical film base material was H _bin,
│H _b -H _bin │ <1.0 %
The optical film according to claim 1, satisfying the relationship:   The optical film according to claim 1, wherein a kurtosis Rku of the roughness curve on the uneven surface is less than 3.0. A light transmissive substrate;
The optical film as described in any one of Claims 1 thru | or 3 provided with the uneven | corrugated layer provided on the said transparent base material and including the part which comprises the said uneven | corrugated surface.   The said light transmissive base material is a base material selected from the group which consists of an acrylic base material, a polyester base material, a polycarbonate base material, a cycloolefin polymer base material, and a glass base material. The optical film according to one item.   The optical film according to claim 1, wherein the light transmissive substrate is a substrate having birefringence.   The optical film according to claim 6, wherein the light transmissive substrate has a retardation of 3000 nm or more.   The optical according to any one of claims 1 to 7, wherein an arithmetic average roughness Ra of a surface on the side opposite to the surface on the optical film substrate side in the first functional layer is 0.10 µm or less. the film. When the haze value of the optical film is H 2 _O and the haze value measured by overlaying a slide glass on the uneven surface of the optical film substrate through liquid paraffin is H _bin ,
│H _O -H _bin │ <0.3 %
The optical film as described in any one of Claims 1 thru | or 8 satisfy | filling these relationships.   10. The optical film according to claim 1, further comprising a second functional layer provided on a surface of the first functional layer opposite to the surface on the substrate side for the optical film. 10. .   The optical film according to claim 10, wherein the first functional layer is a hard coat layer, and the second functional layer is a low refractive index layer having a lower refractive index than the first functional layer. The optical film according to any one of claims 1 to 11,
A polarizing plate comprising: a polarizing element formed on a surface of the optical film substrate opposite to the surface on which the first functional layer is formed in the optical film substrate.   A liquid crystal display panel provided with the optical film as described in any one of Claims 1 thru | or 11, or the polarizing plate of Claim 12. A backlight unit;
An image display device comprising: the optical film according to claim 1; or the polarizing plate according to claim 12.   The image display device according to claim 14, wherein the backlight unit includes a white light emitting diode.   12. A method for suppressing occurrence of interference fringes recognized by human eyes and image light image quality degradation in an image display device including an optical film, wherein the optical film is according to any one of claims 1 to 11. The method, wherein an optical film is used.   The method according to claim 16, wherein the image display device comprises the polarizing plate according to claim 12 or the liquid crystal display panel according to claim 13.   The method according to claim 16, wherein the image display device is the image display device according to claim 14.

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