JP6167480B2 - Optical film, polarizing plate, liquid crystal panel, and image display device - Google Patents

Description

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

  An image display surface of an image display device such as a liquid crystal display device, a cathode ray tube display device (CRT), a plasma display, an electroluminescence display (ELD), a field emission display (FED) or the like is usually directly or other member (for example, An optical film having a functional layer expected to exhibit a desired function is provided via a touch panel sensor. As a typical functional layer, a hard coat layer intended to improve scratch resistance is exemplified.

  Further, as the light-transmitting substrate of the optical film that supports the functional layer, an optically isotropic film having no birefringence, typically a film made of cellulose ester represented by triacetylcellulose. It is used. When a film having birefringence is applied to a display surface of a display device using polarized light such as a liquid crystal display device, there is a problem that unevenness of different colors (hereinafter also referred to as “Nizimura”) is visually recognized. Because it will end up. However, the cellulose ester film has disadvantages that it is inferior in heat-and-moisture resistance and deteriorates polarizing functions such as polarizing function and hue when used in a hot and humid environment.

  From the problem of such a cellulose ester film, it is desired to use a versatile film that is easily available in the market or that can be produced by a simple method as a light-transmitting substrate of an optical film, Various studies have been conducted. For example, in Patent Document 1, a white light-emitting diode is used as a light source, and a polymer film having a retardation of 3000 nm to 30000 nm is arranged so that an angle between an absorption axis of a polarizing plate and a slow axis of the polymer film is 45 degrees. Thus, it has been reported that when the screen is observed through a polarizing plate such as sunglasses, good visibility can be secured regardless of the observation angle.

JP2011-107198A

  However, when a hard coat layer is formed on a polyester film or a polycarbonate film, which is a preferred polymer film in Patent Document 1, it is possible to suppress the occurrence of nitrile, but interference fringes are observed as another problem. There is a problem that it is easy. Here, the interference fringes are partially caused by interference between light reflected on the surface of the functional layer and light reflected once at the interface between the functional layer and the light-transmitting substrate after entering the functional layer. This is a phenomenon in which a rainbow-like color is observed, and is a phenomenon that occurs because the wavelength that strengthens changes according to the viewing direction. This phenomenon is not only difficult to see for the user but may give an unpleasant impression, and improvement is strongly demanded.

  Currently, as a method of eliminating interference fringes, a method of aligning the refractive indexes of the polymer film (refractive index: Np) and the hard coat layer (refractive index: Nh) as much as possible (hereinafter, this method is referred to as interference fringe elimination method 1). Or an intermediate layer having a predetermined refractive index between the refractive index Np of the polymer film and the refractive index Nh of the hard coat layer and having a predetermined thickness (for example, adhesion) between the polymer film and the hard coat layer A method of providing an improvement layer) is known (hereinafter, this method is referred to as interference fringe elimination method 2).

  However, in Patent Document 1, in order to give a high retardation value to the polymer film, the refractive index in the longitudinal direction and the lateral direction of the polymer film (hereinafter also referred to as Nx and Ny, respectively, where Np- Nx = Ny−Np). Therefore, the refractive index Nh of the hard coat layer cannot be determined based on the interference fringe elimination method 1, and even if Nh is an average value of Nx and Ny, the longitudinal and lateral directions of the polymer film Then, since there are refractive index differences of | Nh−Nx | and | Nh−Ny |, respectively, interference fringes cannot be eliminated. Similarly, since the refractive index of the polymer film in the vertical and horizontal directions is different, the refractive index of the intermediate layer cannot be determined based on the interference fringe elimination method 2, and the intermediate layer is set to the optimum refractive index. Even if it does, an interference fringe will always arise. That is, unless the thickness of the polymer film is increased, the larger the retardation, the greater the problem of interference fringes. In Patent Document 1, it is possible to avoid the problem of image quality degradation due to the occurrence of interference fringes. It was impossible.

  In addition, in order to make interference fringes difficult to observe, it is conceivable to form an antiglare layer having a concavo-convex shape on the surface of the polymer film. However, when such an antiglare layer is formed, antiglare properties can be obtained. Since an uneven shape to the extent possible is formed on the surface of the antiglare layer, there is a problem that a cloudiness is likely to occur in the optical film.

  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, a polarizing plate, a liquid crystal panel, and an image display device that can suppress the occurrence of azimuthal in the display image of the image display device, in which interference fringes are not easily observed, and white turbidity is suppressed. And

  According to one aspect of the present invention, there is provided an optical film comprising a light-transmitting substrate having birefringence in a plane, and a functional layer provided on the light-transmitting substrate, wherein the light transmitting The functional substrate has a retardation of 3000 nm or more, the functional layer has an uneven surface forming the surface of the optical film, and the film surface in the cross section along the normal direction of the film surface of the optical film When the inclination angle of the concavo-convex surface is a surface angle, the ratio of the region where the surface angle is 0.05 ° or more in the concavo-convex surface is 50% or more, and the mean square of the roughness curve in the concavo-convex surface An optical film is provided in which the square root slope RΔq is 0.003 or less.

  According to another aspect of the present invention, the optical film described above and a polarizing element formed on the surface of the light transmissive substrate opposite to the surface on which the functional layer is formed are provided. A polarizing plate 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 another aspect of the present invention, there is provided an image display device comprising the above optical film or the above polarizing plate.

  According to one aspect and another aspect of the present invention, a light-transmitting substrate having a retardation of 3000 nm or more is used as a light-transmitting substrate having birefringence in the plane. It is possible to suppress the occurrence of nitrile in the display image. In addition, since the ratio of the area where the surface angle is 0.05 ° or more on the uneven surface of the functional layer is 50% or more, even if interference fringes occur, the interference fringes can be resolved by the human eye. It occurs at the following pitch. Furthermore, since the root mean square slope RΔq of the roughness curve on the uneven surface of the functional layer is 0.003 or less, the cloudiness can be suppressed. Accordingly, it is possible to suppress the occurrence of nysilla in the display image of the image display device, to provide an optical film, a polarizing plate, a liquid crystal panel, and an image display device in which interference fringes are hardly observed and white turbidity is suppressed. it can.

It is a schematic block diagram of the optical film which concerns on 1st Embodiment. It is a figure for demonstrating what pitch a red light bright line generate | occur | produces when the surface angle of an uneven surface is 0.05 degree. 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, and FIG. 2 explains how many red light lines are generated when the surface angle of the concavo-convex surface is 0.05 °. FIG. 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.

≪Optical film≫
As shown in FIG. 1, the optical film 10 includes at least a light-transmitting substrate 11 having birefringence in a plane, and a functional layer 12 provided on the light-transmitting substrate 11. . The optical film 10 shown in FIG. 1 includes an adhesion improving layer 13 for improving the adhesion between the light transmissive substrate 11 and the functional layer 12 between the light transmissive substrate 11 and the functional layer 12. However, the adhesion improving layer 13 may not be provided.

<Light transmissive substrate>
The light transmissive substrate 11 has a retardation of 3000 nm or more. When the optical film 10 is incorporated into an image display device by using a light transmissive substrate having a retardation of 3000 nm or more as a light transmissive substrate having birefringence in the plane, a display image of the image display device It is possible to suppress the occurrence of Nijimura.

  Retardation is an index representing the degree of in-plane 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.

Retardation Re (unit: nm) is the refractive index (n _x ) in the direction having the highest refractive index (slow axis direction) in the plane of the light-transmitting substrate, and the direction orthogonal to the slow axis direction (fast phase) Using the refractive index (n _y ) in the axial direction and the thickness d (unit: nm) of the light-transmitting substrate, it is expressed by the following formula (1).
_{Re = (n x -n y)} × d ... (1)

Retardation can be set to a measured value by setting the measurement angle to 0 ° and the measurement wavelength to 548.2 nm using, for example, KOBRA-WR manufactured by Oji Scientific Instruments. 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,} the n x -n _y referred to as [Delta] n) was calculated, the refractive index difference [Delta] n and the light-transmitting substrate The retardation can be obtained by the product of the thickness d (nm).

  From the viewpoint of setting the retardation of the light transmissive substrate 11 to 3000 nm or more, 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 11, durability of the light transmissive base material 11 in a moisture-heat 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 11 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 11 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 11 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.

  The thickness of the light-transmitting substrate 11 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-transmitting substrate 11 is preferably 15 μm or more from the viewpoint of handling properties. 25 μm or more is more preferable. The upper limit of the thickness of the light transmissive substrate 11 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 11, 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.

  The light-transmitting substrate 11 is not particularly limited as long as it has a retardation of 3000 nm or more, and examples thereof include an acrylic substrate, a polyester substrate, a polycarbonate substrate, and a cycloolefin polymer substrate. Among these, a polyester base material is preferable from the viewpoint of cost and mechanical strength.

  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) of other polyesters. 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.

  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 of the glass transition temperature or higher. 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.

  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.

  The refractive index of the light transmissive substrate 11 can be 1.40 or more and 1.80 or less. In this case, the “refractive index of the light transmissive substrate” means an average refractive index.

  Further, the light transmissive substrate 11 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.

<Adhesion improvement layer>
As described above, the adhesion improving layer 13 is a layer for improving the adhesion between the light-transmitting substrate 11 and the functional layer 12, and can be composed of the same material as a known primer layer. is there. Specifically, the resin contained in the adhesion improving layer 13 is, for example, polyurethane resin, polyester resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate copolymer, acrylic resin, 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, light It can be composed of at least one of a polymer of a polymerizable 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.

  When the adhesion improving layer 13 is formed using a photopolymerizable compound, a polymerization initiator capable of initiating polymerization of the photopolymerizable compound is added to the adhesion improving layer 13. Is preferred. Thereby, when hardening the adhesive improvement layer 13, the adhesive improvement layer 13 and the functional layer 12 can be bridge | crosslinked firmly.

  The thickness of the adhesion improving layer 13 can be 30 nm or more and 10 μm or less. When the thickness of the adhesion improving layer 13 is less than 30 nm, the uniformity of the adhesion improving layer 13 is lowered. The upper limit of the thickness of the adhesion improving layer 13 is not particularly set in terms of the function of the adhesion improving layer 13, but is preferably set to 1 μm or less for industrial reasons.

  In addition, the thickness (at the time of hardening) of the adhesive improvement layer 13 is measured values of arbitrary 10 points obtained by observing the cross section of the adhesive improvement layer 13 with an electron microscope (SEM, TEM, STEM), for example. As an average value (nm). When the adhesion improving layer 13 is very thin, it can be measured by recording what was observed at a high magnification as a photograph and further enlarging it. When enlarged, a layer interface line that is very thin enough to be clearly recognized as a boundary line becomes a thick line. In that case, what is necessary is just to measure the center part which divided the thick line width into 2 equally as a boundary line.

  The refractive index of the adhesion improving layer 13 can be 1.40 or more and 1.80 or less. The refractive index of the adhesion improving layer 13 can be measured by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd.) or an ellipsometer after forming a single layer of the adhesion improving layer 13. In addition, as a method for 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 JISK7142 (2008) B method (for powder or granular transparent material) Becke method (using a Cargill reagent with a known refractive index, placing the powdered sample on a glass slide, dropping the reagent on the sample, and immersing the sample in the reagent. And a method in which the refractive index of the reagent is such that the bright line (Becke line) generated in the sample outline cannot be visually observed due to the difference in refractive index between the sample and the reagent.

<Functional layer>
“Functional layer” means a layer intended to exhibit some function in an optical film, and specifically includes, for example, a hard coat layer, an antistatic layer, a high refractive index layer, and a low refractive index layer. And antifouling layer. The functional layer is not limited to a single layer but may be a laminate of two or more layers. The functional layer 12 of this embodiment functions as a 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”. Moreover, the functional layer may be comprised from the hard-coat layer and the other functional layer provided between the hard-coat layer and the light transmissive base material. In this case, the surface of the optical film (uneven surface of the functional layer) is the surface of the hard coat layer. In addition, the functional layer is provided on the first hard coat layer having irregularities on the surface, and a second hard coat for adjusting the irregularities on the surface of the first hard coat layer. And a hard coat layer having irregularities on the surface as shown in the second embodiment, and a low refractive index lower than that of the hard coat layer. You may be comprised from the low-refractive-index layer which has a refractive index. In this case, the surface of the optical film (uneven surface of the functional layer) is the surface of the second hard coat layer or the low refractive index layer.

  The functional layer 12 has an uneven surface 12 </ b> A that forms the surface of the optical film 10. Specifically, when the inclination angle of the concavo-convex surface 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, the surface angle is 0.05 ° or more in the concavo-convex surface 12A. There are 50% or more of the regions. Here, the “film surface” refers to a surface that coincides with the planar direction when the target optical film is viewed as a whole and globally. The “surface angle” is an absolute value.

  The lower limit of the ratio of the region where the surface angle on the irregular surface 12A 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 uneven surface is defined by the ratio of the surface angle of 0.05 ° or more if the surface angle is 0.05 ° or more, even if interference fringes occur for the following reasons, This is because interference fringes are hardly observed in the eyes. 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. 2, for example, in the region 101 </ b> A where the surface angle on the surface of the hard coat layer 101 formed on the light transmissive substrate 100 is 0.05 °, the surface of the hard coat layer 101 The red light 102 and 103 that is reflected interferes with the red light 104 and 105 that is reflected at the interface (uneven interface) between the hard coat layer 100 and the light-transmitting substrate so as to strengthen each other, and the red light at the pitch A Assuming that light bright lines R1 and R2 (hereinafter, red light bright lines are referred to as "red bright lines") are generated, adjacent red bright lines R1 in a region where the surface angle is 0.05 °. , R2 occurs at a pitch A. Hereinafter, the pitch A is obtained from a triangle having a pitch A as a base and a distance B and a height as shown in FIG. Note that the hard coat layer 101 shown in FIG. 2 is an extremely enlarged portion of the hard coat layer 101.

First, in the region where the surface angle is 0.05 °, the following formula (2) is established.
tan0.05 = B / A (2)
The distance B in the formula (1) is not an optical distance but an actual distance.

Further, if the optical path difference between the red light 104 and the red light 105 is b and the refractive index of the hard coat layer 101 is n, the distance B can be expressed by the following formula (3).
B = b / 2n (3)

  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.

Then, while substituting 0.78 μm for the optical path difference b in equation (3) and substituting equation (3) into B in equation (2), the following equation (4) is obtained.
tan 0.05 = 0.78 / (2 × A × n) (4)

  Further, since the refractive index of the hard coat layer is usually about 1.5, when the refractive index n of the formula (4) is 1.5 and the formula (4) is solved for the pitch A, the pitch A is 299 μm.

  Accordingly, if a red bright line is generated in a region where the surface angle is 0.05 °, a red bright line is generated at a pitch of 299 μm. On the other hand, if the pitch is less than 300 μm from the above theory, the interference pattern of the red bright line is not recognized by the human eye. Therefore, in the region where the surface angle is 0.05 °, the red bright line Interference fringes will not be recognized by the human eye. In addition, the bright line of blue light and green light is generated at a pitch narrower than the pitch of 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 will not be recognized by human eyes. Therefore, it can be said that a surface angle of 0.05 ° or more is an angle at which interference fringes are not recognized by human eyes.

  The surface angle can be obtained by measuring the surface shape of the uneven surface. 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 the 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 (5). 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 (7), it can be calculated | required from following formula (7).
θ _i = tan ⁻¹ Δi (5)

  In the measurement of the surface shape of the uneven surface, it is necessary to form the unevenness within the resolution of the human eye, so the surface angle from the uneven shape excluding the waviness component with a high-pass filter with a cutoff value of 300 μm Is preferably calculated.

  It is known that the surface angle is greatly affected by the sampling interval. In the present invention, the sampling interval is preferably 1 μm or more and 4 μm or less. This is because if the sampling interval is too small, high-frequency components of unevenness on the noise will be picked up, and the surface angle may be excessively estimated. If the sampling interval is too large, the surface angle can be accurately estimated. It is because there is a risk of disappearing. The wider measurement area is preferable, and the measurement is preferably performed in an area of at least 500 μm × 500 μm or more, more preferably 2 mm × 2 mm or more.

  Further, in the uneven surface 12A, the root mean square slope RΔq of the roughness curve is 0.003 or less. The reason why RΔq is 0.003 or less is that when RΔq is 0.003 or less, it is not recognized from the human eye detection ability that the cloudiness is generated. That is, since RΔq is an average value of the inclination in a minute region, if RΔq is increased, surface scattering is increased, so that the cloudiness may be increased. However, if RΔq is an uneven surface of 0.003 or less, it is not recognized from the human eye detection ability that the cloudiness is generated. The average inclination angle θa is a parameter representing the surface shape of the concavo-convex surface similar to RΔq. However, since RΔq averages the inclination of the micro area, a larger angle component is emphasized. Therefore, it can be said that RΔq is more sensitive than θa to the cloudiness.

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（７）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 dZi / dXi in JIS-B0601: 2001, and is represented by the following formula (6).

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 (7), 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 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.

  The root mean square slope RΔq is obtained by measuring the surface shape of the concavo-convex surface 12A 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.

  The kurtosis Rku of the roughness curve on the uneven surface 12A is preferably less than 3.0. Rku is an index representing the sharpness of the unevenness constituting the uneven surface 12A. If there are steep irregularities in the irregular surface, the image light is deflected by the irregular surface, which may cause problems of image quality degradation such as a decrease in the brightness and sharpness of the image, and a decrease in bright room and dark room contrast. On the other hand, since Rku on the concavo-convex surface 12A 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（８）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 (8).

In Formula (8), Rq represents root mean square roughness, lr represents a reference length, and Z (x) represents a roughness curve.

  The skewness RSk of the roughness curve on the uneven surface 12A 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 12A. Since Rsk on the concavo-convex surface 12A is 0.3 or less, the inclination of the inclination angle distribution is small, and it is difficult for the human eye to recognize the image quality deterioration.

式（９）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 (9).

In Formula (9), Rq represents the root mean square roughness, lr represents the reference length, and Z (x) represents the roughness curve.

  In the irregular surface 12A of the functional layer 12, the average interval Sm between the irregularities constituting the irregular surface 12A is preferably 0.20 mm or more and 0.60 mm or less, and is 0.22 mm or more and 0.50 mm or less. It is more preferable. In the uneven surface 12A of the functional layer 12, the average inclination angle θa of the unevenness constituting the uneven surface 12A is preferably 0.01 ° or more and 0.1 ° or less, and is 0.04 ° or more and 0.08 °. More preferably, it is as follows.

  In the uneven surface 12A of the functional layer 12, the arithmetic average roughness Ra of the unevenness constituting the uneven surface 12A is preferably 0.02 μm or more and 0.10 μm or less, and is 0.04 μm or more and 0.08 μm or less. More preferably. In the uneven surface 12A of the functional layer 12, the maximum height roughness Ry of the unevenness constituting the uneven surface 12A is preferably 0.20 μm or more and 0.60 μm or less, and is 0.25 μm or more and 0.40 μm or less. More preferably. In the uneven surface 12A of the functional layer 12, the 10-point average roughness Rz of the unevenness constituting the uneven surface 12A is preferably 0.15 μm or more and 0.50 μm or less, and 0.18 μm or more and 0.30 μm or less. More preferably.

The definitions of the above “Sm”, “Ra”, “Ry” and “Rz” shall conform to JIS B0601-1994. 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, θa is represented by the following formula (10).
θa = tan ⁻¹ Δa (10)
In the formula, Δa represents the slope as an aspect ratio, and is a value obtained by dividing the total sum of the differences between the minimum and maximum portions of each unevenness (corresponding to the height of each convex portion) by the reference length.

Sm, θa, Ra, Ry, and Rz can be measured under the following measurement conditions using, for example, a surface roughness measuring instrument (model number: SE-3400 / manufactured by Kosaka Laboratory).
1) Stylus of surface roughness detector (trade name SE2555N (2μ 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
・ Preliminary length: (cutoff value λc) × 2
・ Vertical magnification: 2000 times ・ Horizontal magnification: 10 times

  When the functional layer 12 is a hard coat layer as in this embodiment, the thickness of the functional layer 12 is preferably 0.1 μm or more and 100 μm or less. If the thickness of the functional layer 12 is within this range, a desired hardness can be obtained. In addition, the functional layer can be made thinner, while the functional layer can be prevented from cracking and curling. The thickness of the functional layer can be measured by observing the cross section with an electron microscope (SEM, TEM, STEM). The lower limit of the thickness of the functional layer 12 is more preferably 0.5 μm or more, and the upper limit is more preferably 20 μm or less.

  When the functional layer 12 is a hard coat layer as in this embodiment, the refractive index of the functional layer 12 can be 1.40 or more and 1.80 or less. The refractive index of the functional layer 12 can be measured by the same method as the measurement of the refractive index of the adhesion improving layer 13 described above.

  The functional layer 12 having the concavo-convex surface 12A is, for example, (1) a method of applying a resin composition for a functional layer containing fine particles and a photopolymerizable compound to be a binder resin after polymerization to a light-transmitting substrate; A method of applying the layer composition to the light-transmitting substrate 11 and then embossing the functional layer composition with a mold having a groove having a reverse shape of the uneven surface on the surface, or (3) unevenness corresponding to the uneven surface It can be formed by applying a resin composition for a functional layer in which disk-shaped particles having a shape on the surface are dispersed to a light-transmitting substrate and arranging the disk-shaped particles on the surface of the functional layer. It is. Among these, the method (1) is preferable because of easy production.

  In the above method (1), when the photopolymerizable compound is polymerized (crosslinked) to become a binder resin, the photopolymerizable compound undergoes curing shrinkage in the portion where fine particles are not present, and thus shrinks as a whole. To do. On the other hand, in the portion where the fine particles are present, since the fine particles do not cause curing shrinkage, only the photopolymerizable compounds existing above and below the fine particles cause curing shrinkage. Thereby, since the film thickness of the functional layer is thicker in the part where the fine particles are present than in the part where the fine particles are not present, the surface of the functional layer becomes uneven. Therefore, the functional layer 12 having the concavo-convex surface 12A can be formed by appropriately selecting the type and particle size of the fine particles and the type of the photopolymerizable compound and adjusting the coating film forming conditions.

  Hereinafter, an example in which the functional layer 12 includes fine particles and a binder resin will be described. For example, the functional layer 12 containing such fine particles and a binder resin can be formed by the method (1).

(Fine particles)
The fine particles may be either inorganic fine particles or organic fine particles. Among these, for example, silica (SiO ₂ ) fine particles, alumina fine particles, titania fine particles, tin oxide fine particles, antimony-doped tin oxide (abbreviation: ATO) fine particles. Inorganic oxide fine particles such as zinc oxide fine particles are preferred. The inorganic oxide fine particles can form aggregates in the functional layer, and a specific uneven surface 12A can be formed by the degree of aggregation of the aggregates.

  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 curing shrinkage of the fine particles in the curing 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 the irregular surface 12A.

  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 functional layer 12 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, and the inorganic oxide fine particles can be prevented from excessively agglomerating, so that a functional layer 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 functional layer 12. The aggregate of the inorganic oxide fine particles preferably has a structure in which the inorganic oxide fine particles are three-dimensionally connected in the functional layer 12. Examples of the structure in which the inorganic oxide fine particles are three-dimensionally connected include a hook shape and a string shape. Aggregates having a structure in which inorganic oxide fine particles are three-dimensionally linked are easily and uniformly crushed when the photopolymerizable compound that becomes the binder resin after curing is cured and contracted. As a result, the uneven surface can be made to be a very smooth surface. As a result, the uneven surface having a steep slope is not formed, and a functional layer having a unique uneven surface can be formed. Even when organic fine particles are used as described above, the functional layer 12 having the uneven surface 12A can be formed by appropriately adjusting the degree of crosslinking.

  The content of fine particles with respect to the functional layer 12 is not particularly limited, but is preferably 0.1% by mass or more and 5.0% by mass or less. Since the content of fine particles is 0.1% by mass or more, a peculiar uneven surface can be formed more reliably, and the content of fine particles is 5.0% by mass or less, so Aggregation does not occur excessively, and it is possible to suppress internal diffusion and / or generation of large irregularities on the surface of the functional layer, thereby suppressing 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 functional layer having a peculiar uneven surface can be formed more easily, and the average primary particle size is 100 nm or less. Diffusion 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 using organic fine particles as the fine particles, the organic fine particles can easily reduce the difference in refractive index from the binder resin by changing the copolymerization ratio of resins having different refractive indexes, for example, less than 0.01. Light diffusion due to fine particles can be suppressed. Therefore, the average primary particle size may be less than 8.0 μm, preferably 5.0 μm or less.

  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 preferable from the viewpoint of easily forming a functional layer having a specific uneven 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 (SiCl ₄ ) 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 functional layer composition, and are sufficiently sparse such as cocoon-like or string-like shapes. Aggregates are formed. For this reason, the agglomerates of fumed silica fine particles are easily and uniformly crushed when the photopolymerizable compound which becomes the binder resin after curing undergoes curing shrinkage. Thereby, a functional layer having a specific uneven surface can be formed.

(Binder resin)
The binder resin is obtained by polymerizing (crosslinking) a photopolymerizable compound by light irradiation. The photopolymerizable compound has at least one photopolymerizable functional group. The definition of “photopolymerizable functional group” is the same as described in the column of the adhesion improving layer 13.

  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 functional 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 80,000, the viscosity is high, so that the coating suitability is lowered, and the appearance of the obtained optical laminate may be deteriorated. Examples of the polyfunctional polymer include urethane (meth) acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, and epoxy (meth) acrylate.

  The functional layer 12, after the functional layer composition containing the fine particles and the photopolymerizable compound is applied on the adhesion improving layer 13 and dried, the coating-like functional layer composition is irradiated with light such as ultraviolet rays. Can be formed by polymerizing (crosslinking) the photopolymerizable compound.

  In addition to the fine particles and the photopolymerizable compound, if necessary, a thermoplastic resin, a thermosetting resin, a solvent, and a polymerization initiator may be added to the functional layer composition. Furthermore, according to the purpose of increasing the hardness of the functional layer, suppressing curing shrinkage, or controlling the refractive index, the functional layer composition includes conventionally known dispersants, surfactants, antistatic agents, Silane coupling agent, thickener, anti-coloring agent, coloring agent (pigment, dye), antifoaming agent, leveling agent, flame retardant, UV absorber, adhesion-imparting agent, polymerization inhibitor, antioxidant, surface modification An agent, a lubricant, etc. may be added.

  The thermoplastic resin added to the functional layer composition is preferably non-crystalline and soluble in an organic solvent (especially a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoint of transparency and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

  The thermosetting resin added to the functional layer composition is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, Examples thereof include amino alkyd resins, melamine-urea cocondensation resins, silicon resins, polysiloxane resins, and the like.

  When a functional layer as an antistatic layer is used instead of the hard coat layer, this functional layer can be formed by incorporating an antistatic agent into the functional 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.

  According to this embodiment, since the retardation of the light transmissive substrate 11 is 3000 nm or more, when the optical film 10 is incorporated in the image display device, it is possible to suppress the occurrence of nitrite spots in the display image of the image display device. it can. Further, since the ratio of the region having a surface angle of 0.05 ° or more is 50% or more on the uneven surface 12A of the functional layer 12, even if the interference fringes are generated, the interference fringes are not easily observed by human eyes. . Moreover, since the root mean square slope RΔq of the roughness curve is 0.003 or less on the uneven surface 12A of the functional layer 12, the cloudiness can be suppressed.

  In addition, since the conventional anti-glare layer is the action of the anti-glare layer to prevent the reflection of the external image, the unevenness existing on the surface of the anti-glare layer is sure to be the external image transferred to the observer. It is an essential requirement that it is spread. For this reason, the unevenness | corrugation which exists in the surface of a glare-proof layer needs a very large thing compared with the unevenness | corrugation which exists in the uneven surface of the functional layer of this invention. Therefore, in the uneven surface 12A of the functional layer 12, the ratio of the region having a surface angle of 0.05 ° or more is 50% or more, and the root mean square slope RΔq of the roughness curve is 0.003 or less. It can be said that the above-described effect is a remarkable effect that exceeds the range that can be predicted in light of the technical level of the conventional antiglare layer.

  When the optical film 10 is incorporated in a liquid crystal display, what is the angle between the slow axis of the light-transmitting substrate 11 and the absorption axis of the polarizing plate (polarizing plate installed on the viewing side of the liquid crystal cell)? Even if it can suppress generation | occurrence | production of Nijimura, it is preferable to arrange | position the optical film 10 so that it may become 0 degree +/- 30 degree or 90 degree +/- 30 degree. The angle between the slow axis of the light-transmitting substrate 11 and the absorption axis of the polarizing plate (polarizing plate installed on the viewing side of the liquid crystal cell) is within the above range, so that the display image of the liquid crystal display has a It can be suppressed to a very high degree.

  When the optical film 10 is incorporated in a liquid crystal display, the angle formed by the slow axis of the light-transmitting substrate 11 and the absorption axis of the polarizing plate (polarizing plate installed on the viewing side of the liquid crystal cell) is 45 ° ± By installing the optical film 10 so as to be 15 °, good visibility can be obtained even when a liquid crystal display is observed through a polarizing plate such as sunglasses.

≪Polarizing plate≫
The optical film 10 can be used by being incorporated into a polarizing plate, for example. FIG. 3 is a schematic configuration diagram of a polarizing plate incorporating the optical film according to the present embodiment. As shown in FIG. 3, the polarizing plate 20 includes an optical film 10, a polarizing element 21, and a protective film 22. The polarizing element 21 is formed on the surface of the light transmissive substrate 11 opposite to the surface on which the functional layer 12 is formed. The protective film 22 is provided on the surface opposite to the surface on which the optical film 10 of the polarizing element 21 is provided. The protective film 22 may be a retardation film.

  Examples of the polarizing element 21 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 laminating the optical film 10 and the polarizing element 21, it is preferable to saponify the light-transmitting substrate 11 in advance. 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. 4 is a schematic configuration diagram of a liquid crystal panel incorporating the optical film according to the present embodiment.

  The liquid crystal panel 30 shown in FIG. 4 has a protective film 31, such as a triacetyl cellulose film (TAC film), a polarizing element 32, a retardation film 33, an adhesive, from the light source side (backlight unit side) to the viewer side. The agent layer 34, the liquid crystal cell 35, the adhesive layer 36, the retardation film 37, the polarizing element 21, and the optical film 10 are stacked in this order. In the liquid crystal cell 35, 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 33 and 37 include a triacetyl cellulose film and a cycloolefin polymer film. The retardation film 37 may be the same as the protective film 22. Examples of the adhesive constituting the adhesive layers 34 and 36 include a pressure sensitive adhesive (PSA).

≪Image display device≫
The optical film 10, the polarizing plate 20, and the liquid crystal panel 30 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. 5 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 40 shown in FIG. 5 is a liquid crystal display. An image display device 40 shown in FIG. 5 includes a backlight unit 41 and a liquid crystal panel 30 including the optical film 10 disposed on the viewer side with respect to the backlight unit 41. The “image display device” of the present invention may not include a backlight unit. A known backlight unit can be used as the backlight unit 41. Although it does not specifically limit as a light source used for the backlight unit 41, 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. 6 is a schematic configuration diagram of an optical film according to the present embodiment.

≪Optical film≫
As shown in FIG. 6, the optical film 50 includes at least a light transmissive substrate 51 having a retardation having birefringence in the plane of 3000 nm or more, and a functional layer 52 provided on the light transmissive substrate 51. And. Further, the optical film 50 shown in FIG. 6 includes an adhesion improving layer 53 that improves the adhesion between the light transmissive substrate 51 and the functional layer 52 between the light transmissive substrate 51 and the functional layer 52. Have. The light transmissive substrate 51 is the same as the light transmissive substrate 11 described in the first embodiment, and the adhesion improving layer 53 is the same as the adhesion improving layer 13 described in the first embodiment. Therefore, the description is omitted in this embodiment.

<Functional layer>
In this embodiment, the functional layer 52 includes a hard coat layer 54 and a low refractive index layer 55 provided on the hard coat layer 54. The functional layer 52 has an uneven surface 52A that forms the surface of the optical film 50, and the uneven surface 52 A of the functional layer 52 is the surface of the low refractive index layer 55.

  Similar to the concavo-convex surface 12A of the functional layer 12, the concavo-convex surface 52A (surface of the low refractive index layer 55) of the functional layer 52 is concavo-convex with respect to the film surface in the cross section along the normal direction N of the film surface of the optical film 50. When the inclination angle of the surface 52A is the surface angle, the region where the surface angle is 0.05 ° or more is 50% or more.

  The lower limit of the ratio of the region in which the surface angle of the irregular surface 52A of the functional layer 52 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.

  Similar to the concavo-convex surface 12A of the functional layer 12, in the concavo-convex surface 52A of the functional layer 52, the root mean square slope RΔq of the roughness curve is 0.003 or less. 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.

  Further, the uneven surface 52A of the functional layer 52 preferably has the same Sm, θa, Ra, Ry, Rz as the uneven surface 12A of the functional layer 12.

(Hard coat layer)
Since the hard coat layer 54 is the same as the functional layer 12 described in the first embodiment, description thereof is omitted in this embodiment. However, unlike the functional layer 12, the surface of the hard coat layer 54 does not have to be 50% or more in the region where the surface angle is 0.05 ° or more, and the root mean square slope RΔq of the roughness curve. May not be 0.003 or less.

(Low refractive index layer)
The low refractive index layer 55 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 50. The low refractive index layer 55 has a lower refractive index than the hard coat layer 54. Specifically, for example, the low refractive index 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 55 is not limited, but 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 55 preferably satisfies the following formula (11).
d _A = mλ / (4n _A ) (11)
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 55 preferably satisfies the following formula (12) from the viewpoint of reducing the reflectance.
120 <n _A d _A <145 (12)

  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 55 preferably includes 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) silica or magnesium fluoride. Fluorine resin, 4) A thin film of a low refractive index material such as silica or magnesium fluoride, etc. can be used. As for the resin other than the fluorine-based resin, a resin similar to the binder resin constituting the functional layer described above can be used.

  Further, 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.

  As the fluorine-based resin, a polymerizable compound containing at least a fluorine atom in the molecule or a polymer thereof can be used. Although it does not specifically limit as a polymeric compound, For example, what has hardening reactive groups, such as a photopolymerizable functional group and a thermosetting polar group, is preferable. Moreover, the compound which has these reactive groups simultaneously may be sufficient. In contrast to this polymerizable compound, a polymer has no reactive groups as described above.

  As the photopolymerizable compound, fluorine-containing monomers having an ethylenically unsaturated bond can be widely used. More specifically, to illustrate fluoroolefins (eg, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluorobutadiene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.) Can do. As those having a (meth) acryloyloxy group, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2- (perfluorobutyl) ) Ethyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 2- (perfluorooctyl) ethyl (meth) acrylate, 2- (perfluorodecyl) ethyl (meth) acrylate, α-trifluoro (Meth) acrylate compounds having a fluorine atom in the molecule, such as methyl methacrylate and α-trifluoroethyl methacrylate; a C 1-14 fluoroalkyl group having at least 3 fluorine atoms in the molecule, fluoro A cycloalkyl group or a fluoroalkylene group and at least two (medium There are also fluorine-containing polyfunctional (meth) acrylic acid ester compounds having an acryloyloxy group.

  Preferable examples of the thermosetting polar group include hydrogen bond forming groups such as a hydroxyl group, a carboxyl group, an amino group, and an epoxy group. These are excellent not only in adhesion to the coating film but also in affinity with inorganic ultrafine particles such as silica. Examples of the polymerizable compound having a thermosetting polar group include 4-fluoroethylene-perfluoroalkyl vinyl ether copolymer; fluoroethylene-hydrocarbon vinyl ether copolymer; epoxy, polyurethane, cellulose, phenol, polyimide, and the like. Examples include fluorine-modified products of each resin.

  The polymerizable compound having both the photopolymerizable functional group and the thermosetting polar group includes acrylic or methacrylic acid moieties and fully fluorinated alkyl, alkenyl, aryl esters, fully or partially fluorinated vinyl ethers, fully or partially. Examples thereof include fluorinated vinyl esters, fully or partially fluorinated vinyl ketones, and the like.

  Examples of the fluorine-based resin include the following. Polymer of monomer or monomer mixture containing at least one fluorine-containing (meth) acrylate compound of a polymerizable compound having an ionizing radiation curable group; at least one fluorine-containing (meth) acrylate compound; and methyl (meth) Copolymers with (meth) acrylate compounds that do not contain fluorine atoms in the molecule such as acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; fluoroethylene , Fluorine-containing compounds such as vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 3,3,3-trifluoropropylene, 1,1,2-trichloro-3,3,3-trifluoropropylene, hexafluoropropylene Monomer homopolymer or Copolymer such as. Silicone-containing vinylidene fluoride copolymers obtained by adding a silicone component to these copolymers can also be used. The silicone components in this case include (poly) dimethylsiloxane, (poly) diethylsiloxane, (poly) diphenylsiloxane, (poly) methylphenylsiloxane, alkyl-modified (poly) dimethylsiloxane, azo group-containing (poly) dimethylsiloxane, Dimethyl silicone, phenylmethyl silicone, alkyl aralkyl modified silicone, fluorosilicone, polyether modified silicone, fatty acid ester modified silicone, methyl hydrogen silicone, silanol group containing silicone, alkoxy group containing silicone, phenol group containing silicone, methacryl modified silicone, acrylic Modified silicone, amino modified silicone, carboxylic acid modified silicone, carbinol modified silicone, epoxy modified silicone, mercapto modified silicone Over emissions, fluorine-modified silicones, polyether-modified silicone and the like. Among these, those having a dimethylsiloxane structure are preferable.

  Furthermore, non-polymers or polymers composed of the following compounds can also be used as the fluororesin. That is, a fluorine-containing compound having at least one isocyanate group in the molecule is reacted with a compound having at least one functional group in the molecule that reacts with an isocyanate group such as an amino group, a hydroxyl group, or a carboxyl group. Compound obtained: a compound obtained by reacting a fluorine-containing polyol such as fluorine-containing polyether polyol, fluorine-containing alkyl polyol, fluorine-containing polyester polyol, fluorine-containing ε-caprolactone-modified polyol with a compound having an isocyanate group Can be used.

  Moreover, each binder resin as described in the said functional layer 12 can also be mixed and used with the polymeric compound and polymer which have the above-mentioned fluorine atom. Furthermore, various additives and solvents can be used as appropriate in order to improve the curing agent for curing reactive groups and the like, to improve the coating property, and to impart antifouling properties.

  In the formation of the low refractive index layer 55, the viscosity of the composition for a low refractive index layer obtained by adding the above-described material is 0.5 to 5 mPa · s (25 ° C.), preferably 0. It is preferable to set it as the thing of the range of 7-3 mPa * s (25 degreeC). An antireflection layer excellent in visible light can be realized, a uniform thin film with no coating unevenness can be formed, and a low refractive index layer particularly excellent in adhesion can be formed.

  The curing means for the low refractive index layer composition may be the same as that described for the functional layer 12 described above. When a heating means is used for the curing treatment, it is preferable to add a thermal polymerization initiator that generates, for example, a radical by heating to start polymerization of the polymerizable compound, to the fluororesin composition.

  According to this embodiment, since the retardation of the light transmissive substrate 51 is 3000 nm or more, when the optical film 50 is incorporated in the image display device, it is possible to suppress the occurrence of nitrite spots in the display image of the image display device. it can. Further, in the uneven surface 52A of the functional layer 52 (the surface of the low refractive index layer 55), the ratio of the region having a surface angle of 0.05 ° or more is 50% or more. Interference fringes are difficult to observe in the eyes. Further, since the root mean square slope RΔq of the roughness curve is 0.003 or less on the uneven surface 52A of the functional layer 52, the cloudiness can be suppressed.

  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 composition for hard coat layer>
First, each component was mix | blended so that it might become the composition shown below, and the composition for hard-coat layers was obtained.
(Composition 1 for hard coat layer)
Fumed silica (octylsilane treatment, average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd.): 1 part by mass Pentaerythritol tetraacrylate (PETTA) (Product name: PETA, manufactured by Daicel Cytec Co., Ltd.): 60 parts by mass Urethane acrylate (Product name: UV1700B, manufactured by Nippon Synthetic Chemical Co., Ltd., weight average molecular weight 2000, functional group number 10): 40 parts by mass / polymerization initiator (Irgacure 184, manufactured by BASF Japan): 5 parts by mass / polyether-modified silicone (product name) : TSF4460, manufactured by Momentive Performance Materials Co., Ltd.): 0.025 parts by mass, toluene: 105 parts by mass, isopropyl alcohol: 30 parts by mass, cyclohexanone: 15 parts by mass Note that the fumed silica is treated with octylsilane (octyl). With silane The silanol group on the surface of the fumed silica was substituted with an octylsilyl group to make it hydrophobic.

(Composition 2 for hard coat layer)
-Fumed silica (octylsilane treatment, average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd.) 1.5 parts by mass-Pentaerythritol tetraacrylate (PETTA) (Product name: PETA, manufactured by Daicel Cytec Co., Ltd.): 60 parts by mass-Urethane Acrylate (Product name: UV1700B, manufactured by Nippon Synthetic Chemical Co., Ltd., weight average molecular weight 2000, functional group number 10): 40 parts by mass / polymerization initiator (Irgacure 184, manufactured by BASF Japan): 5 parts by mass / polyether modified silicone (TSF4460) Momentive Performance Materials): 0.025 parts by mass Toluene: 105 parts by mass Isopropyl alcohol: 30 parts by mass Cyclohexanone: 15 parts by mass

(Composition 3 for hard coat layer)
Fumed silica (octylsilane treatment, average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd.): 0.5 part by mass Pentaerythritol tetraacrylate (PETTA) (Product name: PETA, manufactured by Daicel Cytec Co., Ltd.): 60 parts by mass Urethane acrylate (product name: UV1700B, manufactured by Nippon Synthetic Chemical Co., Ltd., weight average molecular weight 2000, functional group number 10): 40 parts by mass / polymerization initiator (Irgacure 184, manufactured by BASF Japan): 5 parts by mass / polyether-modified silicone ( Product name: TSF4460, manufactured by Momentive Performance Materials, Inc.): 0.025 parts by mass, toluene: 105 parts by mass, isopropyl alcohol: 30 parts by mass, cyclohexanone: 15 parts by mass

(Composition 4 for hard coat layer)
Pentaerythritol tetraacrylate (PETTA) (Product name: PETA, manufactured by Daicel Cytec): 60 parts by mass Urethane acrylate (Product name: UV1700B, manufactured by Nippon Synthetic Chemical Co., Ltd., weight average molecular weight 2000, functional group number 10): 40 Mass parts / polymerization initiator (Irgacure 184, manufactured by BASF Japan): 5 mass parts / polyether-modified silicone (TSF4460, manufactured by Momentive Performance Materials): 0.025 mass parts / Toluene: 105 mass parts / isopropyl Alcohol: 30 parts by massCyclohexanone: 15 parts by mass

(Composition 5 for hard coat layer)
Organic fine particles (hydrophilic treatment acrylic-styrene copolymer particles, average particle size 2.0 μm, refractive index 1.515, manufactured by Sekisui Plastics Co., Ltd.): 3 parts by mass Fumed silica (methylsilane treatment, average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd .: 1 part by mass, pentaerythritol tetraacrylate (PETTA) (product name: PETA, manufactured by Daicel Cytec): 60 parts by mass, urethane acrylate (product name: UV1700B, manufactured by Nippon Synthetic Chemical Co., Ltd.) Weight average molecular weight 2000, functional group number 10): 40 parts by mass Polymerization initiator (Irgacure 184, manufactured by BASF Japan): 5 parts by mass Polyether-modified silicone (TSF4460, manufactured by Momentive Performance Materials): 0. 025 parts by mass-Toluene: 105 parts by mass-Isopropyl alcohol : 30 parts by weight Cyclohexanone: 15 parts by weight

(Composition 6 for hard coat)
Organic fine particles (hydrophilic treatment acrylic-styrene copolymer particles, average particle size 2.0 μm, refractive index 1.55, manufactured by Sekisui Plastics Co., Ltd.): 3 parts by mass Fumed silica (methylsilane treatment, average particle size 12 nm, manufactured by Nippon Aerosil Co., Ltd .: 1 part by mass, pentaerythritol tetraacrylate (PETTA) (product name: PETA, manufactured by Daicel Cytec): 60 parts by mass, urethane acrylate (product name: UV1700B, manufactured by Nippon Synthetic Chemical Co., Ltd.) Weight average molecular weight 2000, functional group number 10): 40 parts by mass Polymerization initiator (Irgacure 184, manufactured by BASF Japan): 5 parts by mass Polyether-modified silicone (TSF4460, manufactured by Momentive Performance Materials): 0. 025 parts by mass, toluene: 105 parts by mass, isopropyl alcohol 30 parts by weight Cyclohexanone: 15 parts by weight

(Composition 7 for hard coat)
Organic fine particles (non-hydrophilic treatment acrylic-styrene copolymer particles, average particle size 3.5 μm, refractive index 1.55, manufactured by Sekisui Plastics Co., Ltd.): 8 parts by mass Pentaerythritol triacrylate (PETA) (Product Name: PETIA, manufactured by Daicel-Cytec): 80 parts by mass, isocyanuric acid EO-modified triacrylate (product name: M-315, manufactured by Toagosei Co., Ltd.): 20 parts by mass, polymerization initiator (Irgacure 184, manufactured by BASF Japan) ): 5 parts by mass-polyether-modified silicone (TSF4460, manufactured by Momentive Performance Materials): 0.025 parts by mass-Toluene: 120 parts by mass-cyclohexanone: 30 parts by mass

<Preparation of composition for adhesion improving layer>
Each component was mix | blended so that it might become a composition shown below, and the composition for adhesive improvement layers was obtained.
(Adhesion improving layer composition)
-Aqueous dispersion of polyester resin (solid content 60%): 28.0 parts by mass-Water: 72.0 parts by mass

<Preparation of composition for low refractive index layer>
Each component was mix | blended so that it might become the composition shown below, and the composition for low refractive index layers was obtained.
(Composition for low refractive index layer)
Hollow silica fine particles (solid content of hollow silica fine particles: 20% by mass, solution: methyl isobutyl ketone, average particle size: 50 nm): 40 parts by mass Pentaerythritol triacrylate (PETA) (Product name: PETIA, Daicel Cytec) 10 parts by mass / polymerization initiator (Irgacure 127; manufactured by BASF Japan): 0.35 parts by mass / modified silicone oil (X22164E; manufactured by Shin-Etsu Chemical Co., Ltd.): 0.5 parts by mass / methyl isobutyl ketone (MIBK) ): 320 parts by mass-Propylene glycol monomethyl ether acetate (PGMEA): 161 parts by mass

<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.), then stretched at 120 ° C. at a stretch ratio of 4.5 times, and then improved in adhesiveness on one side. The layer composition was uniformly applied with a roll coater. Then, the coating film was dried at 95 ° C., the performed stretching at stretching ratio 1.5 times in the direction of 90 degrees to the stretch direction, _{n x} is 1.70, _{n y} is 1.60, the thickness A polyethylene terephthalate base material having a thickness of 80 μm, retardation of 8000 nm, and an adhesion improving layer thickness of 100 nm was obtained. Subsequently, the composition 1 for hard-coat layers was apply | coated on the formed adhesive improvement layer, and the coating film was formed.

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 coating film was cured by irradiation to form a hard coat layer having a thickness (at the time of curing) of 4 μm. Thus, an optical film according to Example 1 was produced.

<Example 2>
In Example 2, an optical film was produced in the same manner as in Example 1 except that the hard coat layer composition 2 was used instead of the hard coat layer composition 1.

<Example 3>
In Example 3, a hard coat layer was formed in the same manner as in Example 1 except that the cumulative amount of ultraviolet light was 50 mJ / cm ² . Next, the composition for a low refractive index layer is applied to the surface of the hard coat layer so that the film thickness after drying (40 ° C. × 1 minute) is 0.1 μm, and under a nitrogen atmosphere (oxygen concentration of 200 ppm or less) Then, the low refractive index layer was formed by irradiating with an ultraviolet ray with an integrated light quantity of 100 mJ / cm ² to form an optical film according to Example 3.

<Example 4>
In Example 4, an optical film was produced in the same manner as in Example 3 except that the hard coat layer composition 2 was used instead of the hard coat layer composition 1.

<Example 5>
In Example 5, an optical film was produced in the same manner as in Example 1 except that the composition 3 for hard coat layer was used instead of the composition 1 for hard coat layer.

<Example 6>
In Example 6, by adjusting the extrusion amount and the draw ratio at the time of the polyethylene terephthalate substrate formed, _{n x} is 1.69, _{n y} is 1.61, a thickness of 44 .mu.m, retardation polyethylene terephthalate substrate of 3500nm An optical film was produced in the same manner as in Example 1 except that the polyethylene terephthalate substrate was used.

<Example 7>
In Example 7, by adjusting the extrusion amount and the draw ratio at the time of the polyethylene terephthalate substrate formed, _{n x} is 1.70, _{n y} is 1.60, a thickness of 190 .mu.m, retardation polyethylene terephthalate substrate of 19000nm An optical film was produced in the same manner as in Example 1 except that the polyethylene terephthalate substrate 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 hard coat layer composition 4 was used instead of the hard coat layer composition 1.

<Comparative example 2>
In Comparative Example 2, an optical film body was produced in the same manner as in Example 3, except that the hard coat layer composition 5 was used instead of the hard coat layer composition 1.

<Comparative Example 3>
In Comparative Example 3, an optical film was produced in the same manner as in Example 1 except that the hard coat layer composition 6 was used instead of the hard coat layer composition 1.

<Comparative Example 4>
In Comparative Example 4, the hard coat layer composition 7 was used instead of the hard coat layer composition 1, and the film thickness of the hard coat layer at the time of curing was changed to 5 μm, in the same manner as in Example 1, An optical film was produced.

<Comparative Example 5>
In Comparative Example 5, by adjusting the extrusion amount and the draw ratio at the time of the polyethylene terephthalate substrate formed, _{n x} is 1.67, _{n y} is 1.63, a thickness of 63 .mu.m, retardation polyethylene terephthalate substrate of 2500nm An optical film was produced in the same manner as in Example 1 except that the polyethylene terephthalate substrate was used.

<Measurement of retardation of light transmissive substrate>
The retardation of the light-transmitting substrate used in Examples and Comparative Examples was measured as follows. First, a light transmitting substrate after stretching, using two polarizing plates, determined the orientation direction of the film, the refractive index for the wavelength 590nm of the two axes orthogonal to the orientation axis (n _x, n _y ) was determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd.). Here, an axis showing a larger refractive index is defined as a slow axis. The film thickness d (nm) was measured using an electric micrometer (manufactured by Anritsu), and the unit was converted to nm. Then, the refractive index difference between _(n x -n _y), than the product of the thickness of the film d (nm), was determined retardation.

<Measurement of surface angle and root mean square slope RΔq>
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 above-mentioned analysis software (MetroPro 8.3.2-Microscope Application) displayed a SlopeX MAP screen (display of the inclination in the x direction) to display rms. This rms corresponds to the root mean square slope RΔq.

Further, the slope Δi of each point over the entire surface is obtained, the slope Δi is converted into the surface angle θ _i by the above formula (7), and from there, the absolute value of the surface angle θ _i is 0.05 ° or more. The percentage of was calculated.

<Nizimura evaluation>
Each optical film obtained in the examples and comparative examples was placed on the observer-side polarizing element of an LED backlight liquid crystal monitor (FLATRON IPS226V (manufactured by LG Electronics Japan)) to prepare a liquid crystal display device. The angle between the slow axis of the polyethylene terephthalate substrate and the absorption axis of the polarizing element on the viewer side of the liquid crystal monitor was set to 45 °. In the dark and bright places (illuminance around the LCD monitor 400 lux), the display image is observed visually and through polarized sunglasses from the front and oblique directions (about 50 degrees), and the presence or absence of nidimra is evaluated according to the following criteria. did. Observation through polarized sunglasses is a much stricter evaluation method than visual observation. The observation is performed by 10 people, and the largest number of evaluations are the observation results.
A: Nijimura was not observed through polarized sunglasses.
◯: Nizimura was observed through polarized sunglasses, but it was thin, no azimuth was observed visually, and it was at a level of no problem in practical use.
Δ: Nizimura was observed through polarized sunglasses, and Nizimura was observed very thin by visual observation.
X: Nizimura was strongly observed through polarized sunglasses, and Nizimura was also observed visually.

<Interference fringe observation evaluation>
Black for preventing back surface reflection through a transparent adhesive on the surface opposite to the surface on which the hard coat layer is formed in the polyethylene terephthalate substrate of each optical film obtained in Examples and Comparative Examples. An acrylic plate was attached, each optical film was irradiated with light from the hard coat layer side, and visually observed. 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.

<Observation evaluation of cloudiness>
A black acrylic plate is attached to the surface opposite to the surface on which the hard coat layer is formed in the polyethylene terephthalate substrate of each optical film obtained in the examples and comparative examples, with a transparent adhesive, in a dark room. The cloudiness was observed under a table lamp (three-wavelength fluorescent lamp tube) and evaluated according to the following criteria.
○: Whiteness was not observed.
X: Whiteness was observed.

The results are shown in Table 1.

  As shown in Table 1, in Comparative Examples 1 to 5, (1) the retardation of the polyethylene terephthalate substrate is 3000 nm or more, and (2) the surface angle on the surface of the optical film is 0.05 ° or more. The ratio of the area is 50% or more, and (3) the root mean square slope RΔq of the roughness curve on the surface of the optical film does not satisfy any requirement of 0.003 or less. , And / or a cloudiness sensation was observed. On the other hand, in Examples 1-7, (1) The ratio of the area | region where the retardation of a polyethylene terephthalate base material is 3000 nm or more, and (2) The surface angle in the surface of an optical film is 0.05 degree or more. 50% or more, and (3) the root mean square slope RΔq of the roughness curve on the surface of the optical film satisfies all the requirements of 0.003 or less. Although not observed or slight interference fringes were observed, there were no problems and no cloudiness was observed.

DESCRIPTION OF SYMBOLS 10, 50 ... Optical film 11, 51 ... Light-transmitting base material 12, 52 ... Functional layer 12A, 52A ... Uneven surface 13, 53 ... Adhesion improvement layer 54 ... Hard coat layer 55 ... Low refractive index layer 20 ... Polarizing plate 21 ... Polarizing element 30 ... Liquid crystal panel 40 ... Image display device

Claims (16)

An optical film comprising a light-transmitting base material having birefringence in a plane, and a functional layer provided on the light-transmitting base material,
The light-transmitting substrate has a retardation of 3000 nm or more,
The functional layer has an uneven surface forming the surface of the optical film,
The inclination angle of the concavo-convex surface with respect to the film surface in the cross section along the normal direction of the film surface of the optical film is defined as a surface angle, the inclination Δi of each point over the entire surface of the concavo-convex surface is obtained, : When converting the surface angle θ _i by θ _i = tan ⁻¹ Δi and calculating the ratio of the area where the absolute value of the surface angle θ _i is 0.05 ° or more, the surface angle θ The ratio of the region where the absolute value of _i is 0.05 ° or more is 50% or more and 90% or less , and the root mean square slope RΔq of the roughness curve on the uneven surface is 0.0027 or less. An optical film characterized. The optical film of Claim 1 whose root mean square inclination R (DELTA) q of the roughness curve in the said uneven surface is 0.0025 or less. The optical film according to claim 1, wherein the root mean square slope RΔq of the roughness curve on the uneven surface is 0.002 or less. The optical film as described in any one of Claims 1-3 whose ratio of the area | region where the said surface angle is 0.05 degrees or more in the said uneven surface is 50% or more and 65.7% or less. The light transmissive substrate has a refractive index (n _x ) in the slow axis direction which is the direction in which the refractive index in the plane of the light transmissive substrate is the largest, and a direction orthogonal to the slow axis direction. fast axis direction of the refractive index difference between the _{(n y) (n x -n} y) is 0.05 to 0.20, optical film according to any one of claims 1-4. The optical film according to any one of claims 1 to 5, wherein the functional layer includes a hard coat layer, and a surface of the hard coat layer is the uneven surface. The functional layer includes a hard coat layer and a low refractive index layer provided on the hard coat layer and having a refractive index lower than that of the hard coat layer, and the surface of the low refractive index layer is the uneven surface. The optical film according to any one of claims 1 to 6, wherein The optical film according to claim 6 or 7 , wherein the hard coat layer contains fine particles and a binder resin. The optical film according to claim 8 , wherein the fine particles are inorganic oxide fine particles. The optical film according to claim 9 , wherein the inorganic oxide fine particles are inorganic oxide fine particles whose surface has been subjected to a hydrophobic treatment. The optical film according to claim 10 , wherein the inorganic oxide fine particles form an aggregate in the hard coat layer, and an average particle diameter of the aggregate is 100 nm or more and 2.0 μm or less. The optical film according to any one of claims 1 to 11 , wherein the light-transmitting substrate is a polyester substrate. The optical film according to any one of claims 1 to 12 ,
A polarizing plate comprising: a polarizing element formed on a surface opposite to a surface on which the functional layer is formed in the light transmissive substrate of the optical film. A liquid crystal display panel provided with the optical film as described in any one of Claims 1-12 , or the polarizing plate of Claim 13 . An image display apparatus provided with the optical film as described in any one of Claims 1-12 , or the polarizing plate of Claim 13 . The image display device according to claim 15 , further comprising a backlight unit having a white light emitting diode as a light source.

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