JP7187964B2 - LAMINATED FILM AND POLARIZING PLATE USING THE SAME - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated film and a polarizing plate using the same.

It has been known that when a birefringent film such as a polyester film is used under the environment of a fluorescent lamp or a cold cathode tube light source, iridescence caused by retardation occurs. Therefore, optically isotropic cellulose-based films have been used as protective films for polarizers used in liquid crystal displays and the like.

Recently, a technique has been proposed to eliminate iridescence by combining a film having a high retardation with a white light source having a continuous emission spectrum (e.g., Patent Document 1, Patent Document 2, etc.), which is compatible with polarized sunglasses. It has been put to practical use as a depolarizing film or a polarizer protective film in liquid crystal displays and the like. However, this technology is improved when using a light source with a sharp emission peak in the red region of the emission spectrum, such as a cold cathode tube light source or a KSF phosphor (a phosphor in which Mn is added to K ₂ SiF ₆ crystal). There was room for In addition, the film needs to be thick in order to ensure a high retardation, and there is a fear that it will not be able to sufficiently cope with the thinning of image display devices in recent years.

As a depolarizing film for a liquid crystal display using a light source with a steep emission peak, by providing unevenness on the surface of the film having birefringence, it is possible to locally reduce the wavelength to λ/4 or more within a region smaller than the level visible to the naked eye. A film in which retardation is generated has been proposed (for example, Patent Document 3). However, such prior art has problems that the contrast of the image is low, and that the screen becomes white and the image is difficult to see in an environment of strong external light.

JP 2011-215646 A WO2011/162198 JP 2017-161599 A

The present invention has been made against the background of such problems of the prior art. That is, the object of the present invention is to suppress iridescence, ensure high transparency and vivid image displayability, and suppress reflection due to external light when used in an environment with a light source having a steep emission peak. The object is to provide a laminated film capable of

The present inventor has completed the present invention as a result of intensive studies to achieve this object.
That is, the present invention includes the following aspects.
Section 1.
A laminated film having a substrate film and an optically isotropic layer, the laminated film having a low refractive index layer on the substrate film and/or the optically isotropic layer, and having all of the following characteristics.
(a) At least one surface of the substrate film is uneven, and the arithmetic mean roughness (Ra) of the uneven surface is 0.2 to 10 μm.
(b) The refractive index anisotropy (Bfnx-Bfny) of the base film is from 0.04 to 0.2.
(c) An optically isotropic layer is provided on the uneven surface of the base film, and the refractive index of the optically isotropic layer is from Bfny−0.15 to Bfnx+0.15.
(However, the refractive index in the slow axis direction of the base film is Bfnx, and the refractive index in the fast axis direction is Bfny.)
Section 2.
A polarizing plate using the laminated film according to item 1 as a polarizer protective film.
Item 3.
Item 3. An image display device comprising the polarizing plate according to item 2.
In addition, "having a low refractive index layer on the base film and/or the optically isotropic layer" means that the low refractive index layer is laminated directly (in contact with) the base film and/or the optically isotropic layer. In addition to the case where the low refractive index layer is laminated on the base film and/or the optically isotropic layer via an arbitrary film or layer.

The laminated film of the present invention suppresses rainbow spots, ensures high transparency and vivid image displayability, and suppresses reflection due to external light when used in an environment with a light source having a steep emission peak. be able to.

The laminated film of the present invention has an optically isotropic layer on the uneven surface of a substrate film having an uneven surface (roughened surface), and a low refractive index layer on the substrate film and/or the optical isotropic layer. It is preferable to have In addition, the term "laminate film" or "low-reflection film" simply means this.
(Base film)
First, the base film will be explained.

At least the base film is not particularly limited as long as it can have refractive index anisotropy, and examples thereof include polyester, polyamide, polystyrene, syndiotactic polystyrene, polyamide, and polycarbonate. Among them, polyester is preferable because a film having high refractive index anisotropy can be easily obtained. Examples of polyester include polyethylene terephthalate, polyethylene naphthalate, polytetramethylene terephthalate, polytrimethylene terephthalate, etc. Among them, polyethylene terephthalate and polyethylene naphthalate are preferred. These polyesters include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and ethylene glycol, as long as they do not impair the mechanical properties, heat resistance, and dimensional stability of the film (for example, 10 mol % or less). . For example, in the case of a polyethylene terephthalate polymer, 1 to 2 mol of diethylene glycol, which is a by-product, is usually copolymerized during polymerization, and such a by-product may be contained.

The base film has birefringence. The lower limit of the slow axis refractive index (Bfnx) of the base film is preferably 1.65, more preferably 1.66, still more preferably 1.67, and particularly preferably 1.68. The upper limit of the slow axis direction refractive index (Bfnx) of the base film is preferably 1.73, more preferably 1.72, still more preferably 1.71, and particularly preferably 1.7.

The lower limit of the fast axis refractive index (Bfny) of the base film is preferably 1.53, more preferably 1.55, still more preferably 1.56, and particularly preferably 1.57. The upper limit of the fast axis direction refractive index (Bfny) of the base film is preferably 1.62, more preferably 1.61, still more preferably 1.6.

The lower limit of the refractive index anisotropy (ΔBfNxy=Bfnx−Bfny) of the substrate film is preferably 0.04, more preferably 0.05, still more preferably 0.06, and particularly preferably 0.07. When the lower limit is 0.04 or more, iridescence can be eliminated more effectively. The upper limit of the refractive index anisotropy of the substrate film is preferably 0.2, more preferably 0.18, still more preferably 0.17, and particularly preferably 0.16. When the upper limit is 0.2 or less, the mechanical strength in the fast axis direction can be adjusted within a practical range, and production is facilitated. The refractive index of the base film is a value measured under the condition of a wavelength of 589 nm.

The lower limit of the thickness of the base film before providing the uneven surface (before roughening) is preferably 15 μm, more preferably 20 μm, and still more preferably 25 μm. If the lower limit is 15 μm or more, excellent mechanical strength is obtained even if the thickness is reduced when the unevenness is imparted. The upper limit of the thickness of the base film before the uneven surface is provided is preferably 200 μm, more preferably 150 μm, still more preferably 100 μm, particularly preferably 90 μm, and most preferably 80 μm. If the upper limit is 200 μm or less, it is excellent in handleability and suitable for thinning (eg, for use in thin image display devices).

The lower limit of the in-plane retardation (Re) of the substrate film before imparting the uneven surface is preferably 2000 nm, more preferably 2500 nm, even more preferably 3000 nm, particularly preferably 3500 nm, most preferably 4000 nm. is. When the lower limit is 2000 nm or more, iridescence can be eliminated more effectively. The upper limit of the in-plane retardation (Re) of the substrate film before imparting the uneven surface is preferably 30000 nm, more preferably 20000 nm, even more preferably 15000 nm, still more preferably 12000 nm, and particularly preferably 10000 nm, more preferably 9000 nm, most preferably 8000 nm, most preferably 7500 nm. When the upper limit is 30000 nm or less, it is suitable for thinning.

The lower limit of the ratio (Re/Rth) between the in-plane retardation (Re) and the thickness direction retardation (Rth) of the base film before the uneven surface is imparted is preferably 0.2, more preferably 0.5, and even more preferably. is 0.6. When the lower limit is 0.2 or more, iridescence can be eliminated more effectively. The upper limit of Re/Rth of the base film before the rough surface is provided is preferably 2, more preferably 1.5, still more preferably 1.2, and particularly preferably 1 from the viewpoint of mechanical strength.

The lower limit of the Nz coefficient of the base film is preferably 1.3, more preferably 1.4, still more preferably 1.45. When the lower limit is 1.3 or more, the mechanical strength in the fast axis direction is also excellent. The upper limit of the Nz coefficient of the base film is preferably 2.5, more preferably 2.2, even more preferably 2, particularly preferably 1.8, most preferably 1.7. When the upper limit is 2.5 or less, iridescence can be more effectively eliminated.

The lower limit of the plane orientation degree ΔP of the substrate film is preferably 0.08, more preferably 0.09, and still more preferably 0.1. When the lower limit is 0.08 or more, not only can iridescence be effectively eliminated, but also thickness unevenness of the film can be reduced. The upper limit of the plane orientation degree ΔP of the substrate film is preferably 0.15, more preferably 0.14, and still more preferably 0.13. When the upper limit is 0.15 or less, the refractive index anisotropy can be kept higher.

The substrate film is preferably uniaxially oriented in order to have refractive index anisotropy. Orientation can be carried out by a normal method suitable for each resin. For example, if the melted resin is extruded on a cooling roll to form a sheet, the cooling roll is set to a speed higher than the speed of the extruded resin, and the unstretched film that has been melted and extruded is heated. Examples include a method of stretching and orienting the film in the longitudinal direction with a group of rolled rolls, and a method of stretching and orienting the unstretched film melted and extruded in the transverse direction or oblique direction by heating in a tenter.

Among these, the method of orienting the base film includes a method of stretching and orienting a melted and extruded unstretched film in the longitudinal direction with a group of heated rolls, and a method of stretching the melted and extruded unstretched film. A method of orientation by heating in a tenter and stretching in a horizontal direction or an oblique direction is preferred. The draw ratio in the longitudinal direction is preferably 2.5 to 10 times, more preferably 3 to 8 times, and particularly preferably 3.3 to 7 times. The draw ratio in the transverse direction or oblique direction is preferably 2.5 to 10 times, more preferably 3 to 8 times, and particularly preferably 3.3 to 7 times.

In addition, even in the case of orientation in the machine direction, it is weak (about 2.2 times or less) before stretching in the machine direction in order to increase the mechanical strength in the direction perpendicular to the orientation direction and to adjust the shrinkage characteristics. 2) transverse stretching may be added, or weak transverse stretching (about 1.5 times or less) may be added after longitudinal stretching. Similarly, even in the case of orientation in the transverse direction, a weak (about 2.2 times (less than 1.5 times) or weaker (less than about 1.5 times) stretching in the machine direction may be added after the stretching in the transverse direction. Further, in order to further increase the orientation in the orientation direction, the film may be slightly shrunk in the machine direction during or after stretching in the transverse direction. The width after shrinkage is preferably from 0.7 to 0.995 times, more preferably from 0.8 to 0.99 times, particularly preferably from 0.9 to 0.98 times the width during stretching. The stretching in the longitudinal direction and the stretching in the transverse direction may be performed by a tenter-type simultaneous biaxial stretching machine.

The stretching temperature (and preheating temperature) is preferably 80 to 150° C. both in the machine direction and in the transverse direction. Moreover, after stretching, in order to ensure the heat resistance of the base film, it is preferable to heat set at a temperature higher than the heating temperature during stretching. The heat setting temperature is preferably 150 to 250°C, more preferably 170 to 245°C.

The base film preferably has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at a wavelength of 380 nm is more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. The light transmittance at a wavelength of 380 nm is measured in the direction perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500).

In order to keep the light transmittance of the base film at a wavelength of 380 nm to 20% or less, it is desirable to appropriately adjust the type and concentration of the ultraviolet absorber to be blended in the base film, and the thickness of the base film. The ultraviolet absorbent used in the present invention includes organic ultraviolet absorbents and inorganic ultraviolet absorbents. From the viewpoint of transparency, organic UV absorbers are preferred. Examples of organic UV absorbers include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and combinations thereof, but are not particularly limited as long as the light transmittance is within the range described above. From the viewpoint of durability, benzotriazole-based and cyclic iminoester-based are particularly preferred. When two or more ultraviolet absorbers are used in combination, ultraviolet rays of different wavelengths can be absorbed at the same time, so that the ultraviolet absorption effect can be further improved.

In addition to the ultraviolet absorber, it is also preferable to incorporate various additives into the substrate film within a range that does not impair the effects of the present invention. Examples of additives include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light stabilizers, flame retardants, heat stabilizers, antioxidants, and anti-gelling agents. , surfactants, and the like. These additives can be used alone or in combination of two or more.
Moreover, in order to achieve high transparency, it is also preferred that the base film does not substantially contain particles. The term "substantially contains no particles" means, for example, in the case of inorganic particles, when the inorganic elements in the base film are quantified by fluorescent X-ray analysis, 50 ppm or less, preferably 10 ppm or less, particularly preferably less than the detection limit. means a content of

(Improvement of surface unevenness)
In the present invention, at least one surface of the substrate film has an uneven surface. The uneven surface may be provided only on one side of the base film, or may be provided on both sides. A substrate film having an uneven surface may be referred to as a roughened substrate film.

The lower limit of the arithmetic mean roughness (Ra) of the uneven surface of the roughened substrate film is preferably 0.2 μm, more preferably 0.4 μm, even more preferably 0.6 μm, and particularly preferably 0.7 μm. and most preferably 0.8 μm. The upper limit of Ra is preferably 10 μm, more preferably 7 μm, even more preferably 5 μm, particularly preferably 4 μm, most preferably 3 μm.

The lower limit of the root-mean-square roughness (Rq) of the uneven surface of the roughened substrate film is preferably 0.3 μm, more preferably 0.5 μm, still more preferably 0.7 μm, and particularly preferably 0.9. μm, most preferably 1 μm. The upper limit of Rq is preferably 13 μm, more preferably 10 μm, even more preferably 7 μm, particularly preferably 5 μm, most preferably 4 μm.

The lower limit of the ten-point average roughness (Rz) of the uneven surface of the roughened substrate film is preferably 1.0 μm, more preferably 2.0 μm, still more preferably 3.0 μm, and particularly preferably 3.5. μm, most preferably 4.0 μm. The upper limit of Rz is preferably 15 μm, more preferably 12 μm, even more preferably 10 μm, and particularly preferably 8 μm.

The lower limit of the maximum height (Ry) of the uneven surface of the roughened substrate film is preferably 2.0 μm, more preferably 3.0 μm, still more preferably 4.0 μm, and particularly preferably 4.5 μm. Yes, most preferably 5.0 μm. The upper limit of Ry is preferably 20 μm, more preferably 17 μm, even more preferably 15 μm, and particularly preferably 13 μm.

The lower limit of the maximum peak height (Rp) of the uneven surface of the roughened base film is preferably 1.0 μm, more preferably 1.5 μm, still more preferably 2.0 μm, and particularly preferably 2.5 μm. be. The upper limit of Rp is preferably 15 μm, more preferably 12 μm, even more preferably 10 μm, particularly preferably 8 μm.

The lower limit of the maximum valley depth (Rv) of the uneven surface of the roughened substrate film is preferably 1.0 μm, more preferably 1.5 μm, even more preferably 2.0 μm, and particularly preferably 2.5 μm. is. The upper limit of Rv is preferably 15 μm, more preferably 12 μm, even more preferably 10 μm, and particularly preferably 8 μm.

When the values of Ra, Rq, Rz, Ry, Rp, and Rv are at least the lower limits, iris spots can be eliminated more effectively.
Productivity is excellent when the values of Ra, Rq, Rz, Ry, Rp, and Rv are at least the upper limits.
Ra, Rq, Rz, Ry, Rp, and Rv are calculated from roughness curves measured using a contact roughness meter in accordance with JIS B0601-1994 or JIS B0601-2001.

By providing unevenness (roughening) on the surface of the base film, a retardation difference is provided in a minute area, and although there is coloring (rainbow spots) due to retardation in each area, the coloring is visually invisible. be able to. This retardation difference ΔRe can be represented by ΔRe=Ra×ΔBfNxy. The lower limit of ΔRe is preferably 30 nm, more preferably 50 nm, still more preferably 70 nm, particularly preferably 90 nm, most preferably 100 nm. When the lower limit is 30 nm or more, iridescence can be eliminated more effectively. The upper limit of ΔRe is preferably 1500 nm, more preferably 1000 nm, still more preferably 800 nm, particularly preferably 500 nm, most preferably 300 nm. When the upper limit is 1500 nm or less, productivity is also excellent.

The lower limit of the average spacing (Sm) of the unevenness of the roughened substrate film is preferably 5 µm, more preferably 10 µm, still more preferably 15 µm, particularly preferably 20 µm, and most preferably 25 µm. is. When the lower limit is 5 μm or more, the slope of the unevenness becomes gentle, and the image becomes clearer. The upper limit of the average spacing (Sm) of the unevenness of the roughened substrate film is preferably 500 μm, more preferably 450 μm, still more preferably 400 μm, particularly preferably 350 μm, most preferably 300 μm. is. When the upper limit is 500 μm or less, it is possible to prevent a feeling of coloring or a feeling of flickering due to the retardation of each minute region.
Sm is calculated from a roughness curve measured using a contact roughness meter in accordance with JIS B0601-1994.

The base film may become thinner than the original thickness by providing unevenness and roughening the surface. The lower limit of the thickness of the roughened substrate film is preferably 10 μm, more preferably 15 μm, even more preferably 20 μm, particularly preferably 25 μm, and most preferably 30 μm. When the lower limit is 10 μm or more, sufficient strength as a protective film can be ensured. The upper limit of the thickness of the roughened substrate film is preferably 150 μm, more preferably 120 μm, even more preferably 100 μm, particularly preferably 90 μm, and most preferably 80 μm. When the upper limit is 150 μm or less, it is suitable for thinning.
The thickness of the roughened base film is determined by embedding the roughened base film in epoxy resin, cutting out a section of the cross section, and observing it under a microscope. , the thickness is measured at 10 points at equal intervals, and the average value is calculated.

The lower limit of the in-plane retardation (Re) of the roughened substrate film is preferably 2000 nm, more preferably 2500 nm, still more preferably 3000 nm, particularly preferably 3500 nm, most preferably 4000 nm. be. When the lower limit is 2000 nm or more, iridescence can be eliminated more effectively. The upper limit of the in-plane retardation (Re) of the roughened substrate film is preferably 30000 nm, more preferably 20000 nm, still more preferably 15000 nm, even more preferably 12000 nm, and particularly preferably 10000 nm. is more preferably 9000 nm, most preferably 8000 nm, most preferably 7500 nm. When the upper limit is 30000 nm or less, it is suitable for thinning.

The method for providing unevenness is not particularly limited, and conventionally known methods for surface roughening treatment can be used. For example, sandblasting, sandpaper or file, treatment with a whetstone, etc., treatment with a sander (orbital sander, random sander, delta sander, belt sander, disc sander, roll sander, etc.), treatment with a metal brush, etc., chemical etching, mold Examples include shaping by pressing with. Of these, sandblasting, sanding, and chemical etching are preferred.
Sandblasting may be, for example, a method in which a roll-shaped base film is supplied to a centrifugal blast machine and an abrasive is projected onto the base film surface. In this case, the roughness can be adjusted by the type of abrasive, the size of the abrasive, the processing time, the speed of the rotor blades, and the like. Further, the sandblasting treatment may be a method in which a substrate film is attached to a glass plate, set in air blasting, and an abrasive is blown onto the surface of the substrate film. In this case, the roughness can be adjusted by the type of abrasive, the size of the abrasive, the spraying pressure, the treatment time, and the like.
The treatment with a sander is, for example, a method in which a roll-shaped base film is guided to a conveying device having a roll sander attached to a part of the roll surface of the film conveying roll (roll sander). good. In this case, the roughness can be adjusted by the type of sanding paper, the rotation speed of the roll sander, the transport speed of the film, and the like. Also, the processing direction can be adjusted by the angle between the roll sander and the film, the rotation speed of the roll sander, the transport speed of the film, and the like.
In addition, sanding is performed by attaching urethane foam to a glass plate, then attaching a base film on top of it, and sanding the surface of the base film in four directions: vertical, horizontal, and diagonal (45 degrees, 135 degrees). It may be a method of processing from. Roughness can be adjusted by the type of sanding disk of the sander, processing time, and the like.
In addition, after sanding and sandblasting, the treated surface may be further polished with sandpaper or the like in order to remove local projections.
Chemical etching may be a method of immersing in an acid or alkaline solution, washing with water, peeling off the masking film, and drying. Roughness can be adjusted by immersion time or the like. Chemical etching is basically a double-sided treatment, but in the case of single-sided treatment, for example, a masking film is adhered to one side of the substrate film.

(optical isotropic layer)
An optically isotropic layer is preferably provided on the uneven surface of the base film. The optically isotropic layer is preferably provided in contact with the uneven surface. "Provided in contact with" means that it is provided in direct contact with the uneven surface without interposing another layer. However, an easy-adhesion layer may be provided to improve the adhesion between the uneven surface and the optically isotropic layer. The thickness of the easy-adhesion layer is preferably a thickness that is not optically detectable, preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 20 nm or less. If the easy-adhesion layer satisfies the refractive index range of the optical isotropic layer described below, the easy-adhesion layer and the optically isotropic layer provided thereon together are regarded as one optically isotropic layer. be able to. Moreover, if the easy-adhesion layer has a sufficient thickness as an optically isotropic layer, the easy-adhesion layer may be regarded as an optically isotropic layer. By providing the optically isotropic layer, it is possible to reduce diffused reflection due to unevenness on the surface of the base film and ensure transparency. The preferable refractive index of the easy-adhesion layer is the same as the preferable refractive index range of the optically isotropic layer described below, and the method of adjusting the refractive index is also the same.

The lower limit of the refractive index of the optically isotropic layer is preferably Bfny-0.15, more preferably Bfny-0.12, even more preferably Bfny-0.1, even more preferably Bfny-0.08, and particularly preferably Bfny, most preferably Bfny+0.02.
The upper limit of the refractive index of the optically isotropic layer is preferably Bfnx+0.15, more preferably Bfnx+0.12, even more preferably Bfnx+0.1, even more preferably Bfnx+0.08, and particularly preferably Bfnx, most preferably Bfnx-0.02.
Within the above range, the contrast or sharpness of the image can be maintained, and the phenomenon that the screen becomes whitish when exposed to strong external light can be suppressed.

The lower limit of the refractive index of the optically isotropic layer is preferably 1.44, more preferably 1.47, even more preferably 1.49, even more preferably 1.51, and particularly preferably 1.53, more particularly preferably 1.55, most preferably 1.57, most particularly preferably 1.59. The upper limit of the refractive index of the optically isotropic layer is preferably 1.85, more preferably 1.83, even more preferably 1.80, still more preferably 1.78, and particularly preferably 1.76, more particularly preferably 1.74, most preferably 1.72, still most preferably 1.70, most particularly preferably 1.68. By setting the ratio within the above range, the contrast or the sharpness of the image can be maintained, and the phenomenon that the screen becomes whitish when exposed to strong external light can be suppressed. The refractive index of the optically isotropic layer is also a value measured under the condition of a wavelength of 589 nm.

Although the composition of the optically isotropic layer is not particularly limited, acrylic, polystyrene, polyester, polycarbonate, polyurethane, epoxy resin, thioepoxy resin and the like are preferable. By appropriately adjusting the composition, it is possible to set the refractive index within the above range. For example, PMMA (polymethyl methacrylate) generally has a refractive index of about 1.49. In acrylic pressure-sensitive adhesives, a long-chain or branched alkyl group is often introduced, further lowering the refractive index. In order to increase the refractive index, it is effective to copolymerize an acrylic monomer having an aromatic group or copolymerize styrene.
Introducing a sulfur, bromine, fluorene group or the like into a polymer or resin is also a preferred method for increasing the refractive index. A thioepoxy resin or the like is preferable as the high refractive index resin.

Adding highly refractive fine particles to a polymer or resin is also a suitable method for adjusting the refractive index.
The refractive index of the high refractive fine particles is preferably 1.60 to 2.74. Fine particles of TiO ₂ , ZrO ₂ , CeO ₂ , Al ₂ O ₃ , BaTiO ₃ , Nb ₂ O ₅ , SnO ₂ and the like can be used as high refractive particles. The high-refractive fine particles preferably have an average primary particle size of 3 nm to 100 nm as observed by TEM (transmission electron microscope). These high refractive fine particles may be used singly or in combination of two or more.
In the specification, "average primary particle size" or "average particle size of primary particles" refers to a 50% volume cumulative particle size. More specifically, 200 primary particles of the particles are observed under a microscope at an appropriate magnification, the diameter of each is measured, the volume is calculated, and the 50% particle size of the cumulative volume is taken as the average primary particle size. do.

The optically isotropic layer is preferably crosslinked and cured. The curing method is not particularly limited, and radiation curing such as heat curing, ultraviolet rays, and electron beams is preferred. Cross-linking agents for curing include isocyanate compounds, epoxy compounds, carbodiimides, oxazoline compounds, amino resins such as melamine, polyfunctional acrylates, and the like.

The optical isotropic layer is produced by applying a coating agent comprising the above components to the uneven surface of the base film, applying the release film to the uneven surface of the base film, and transferring the optical isotropic layer to the uneven surface of the base film. The optically isotropic layer provided on the film can be laminated by a method such as bonding to the uneven surface of the substrate film. In this case, the coating agent is preferably dissolved or diluted with a solvent so as to have a viscosity that facilitates coating. Moreover, the coating agent may be solventless as long as it is a radiation curing type coating agent such as acrylic.

For example, a radiation-curing type coating agent such as acrylic usually contains a photopolymerizable compound.

Photopolymerizable compounds include photopolymerizable monomers, photopolymerizable oligomers, and photopolymerizable polymers, and these can be appropriately adjusted and used. The photopolymerizable compound is preferably a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable polymer.

Photopolymerizable Monomer Photopolymerizable monomers are those having a weight average molecular weight of less than 1000. As the photopolymerizable monomer, a polyfunctional monomer having two (that is, bifunctional) or more photopolymerizable functional groups is preferable. As used herein, "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 polyfunctional monomers include tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, di Pentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol Penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanurate tri(meth)acrylate, isocyanurate di(meth)acrylate, polyester tri(meth)acrylate, polyester di( meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, Those modified with PO, EO or the like can be mentioned.

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

Photopolymerizable Oligomer The photopolymerizable oligomer has a weight average molecular weight of 1,000 or more and less than 10,000. As the photopolymerizable oligomer, a bifunctional or higher polyfunctional oligomer is preferable. 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)acrylate. Acrylate, epoxy (meth)acrylate, and the like.

Photopolymerizable Polymer The photopolymerizable polymer has a weight average molecular weight of 10,000 or more, preferably 10,000 or more and 80,000 or less, more preferably 10,000 or more and 40,000 or less. If the weight-average molecular weight exceeds 80,000, the resulting laminated film may have poor appearance due to poor coating suitability due to its high viscosity. As the photopolymerizable polymer, a polyfunctional polymer having two or more functionalities is preferable. Polyfunctional polymers include urethane (meth)acrylate, isocyanurate (meth)acrylate, polyester-urethane (meth)acrylate, epoxy (meth)acrylate and the like.

The coating agent may contain a polymerization initiator, a cross-linking agent catalyst, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a leveling agent, a surfactant, and the like, in addition to the above components.

Alternatively, the melted optically isotropic layer composition is extruded and laminated on the uneven surface of the base film, or the melted optically isotropic layer composition is extruded between the uneven surface of the base film and another film. A method such as lamination is also preferred.

The optically isotropic layer has a function of reducing irregular reflection on the uneven surface by being provided on the uneven surface, but may also have other functions. The optically isotropic layer may have functions such as a hard coat layer, an antireflection layer, an antiglare layer, and an antistatic layer. Also, the optically isotropic layer may be another film or sheet, a pressure-sensitive adhesive layer or an adhesive layer for bonding to a constituent member of a device.

The lower limit of the thickness of the optically isotropic layer is preferably 0.5 μm, more preferably 1.0 μm, still more preferably 2 μm, particularly preferably 3 μm, most preferably 4 μm. When the thickness is 0.5 μm or more, the unevenness of the substrate film can be flattened, the haze can be reduced, and the sharpness can be improved.
The upper limit of the thickness of the optically isotropic layer is preferably 30 μm, more preferably 25 μm, still more preferably 20 μm, particularly preferably 15 μm, most preferably 10 μm. When the thickness is 30 μm or less, it is suitable for thinning.
The thickness of the optically isotropic layer is the value obtained by subtracting the thickness of the roughened base film from the thickness of the laminated film described later.

The upper limit of the in-plane retardation of the optically isotropic layer is preferably 50 nm, more preferably 30 nm, even more preferably 10 nm, and particularly preferably 5 nm, from the viewpoint of suppressing the occurrence of iridescence.

The upper limit of the refractive index difference between the refractive index in the direction of the highest refractive index and the refractive index in the direction of the lowest refractive index of the optically isotropic layer is preferably 0.01, and more It is preferably 0.007, more preferably 0.005, particularly preferably 0.003, most preferably 0.002.

(Laminated film)
The lower limit of the thickness of the laminated film is preferably 12 µm, more preferably 15 µm, even more preferably 18 µm, and particularly preferably 20 µm. When the lower limit is 12 μm or more, the strength of the laminated film is excellent, and handling in production or subsequent processing is facilitated.
The upper limit of the thickness of the laminated film is preferably 180 µm, more preferably 150 µm, still more preferably 120 µm, particularly preferably 100 µm, and most preferably 90 µm. When the upper limit is 180 µm or less, it is suitable for thinning in various applications.
The thickness of the laminated film is calculated by embedding the laminated film in an epoxy resin, cutting out a section of the cross section, observing the section with a microscope, measuring the thickness at 10 points at equal intervals, and calculating the average value.

In the laminated film, only one side of the base film may be an uneven surface. In order to suppress spots, it is preferable that both surfaces of the base film are made uneven and optically isotropic layers are provided on both surfaces.

The upper limit of the haze of the laminated film is preferably 10%, more preferably 7%, still more preferably 5%, particularly preferably 4%, most preferably 3%, and most preferably is 2.5%, most preferably 2%. When the upper limit is 10% or less, it is possible to more effectively suppress a decrease in contrast and a screen from becoming whitish when exposed to strong external light.

The laminated film of the present invention may have two or more substrate films having an uneven surface (roughened surface), may have two or more optically isotropic layers, and may have an uneven surface (roughened surface). It may have a film or layer other than the substrate film having a flattened surface and the optically isotropic layer.
Examples of lamination include types 1 to 4 below.
(Type 1) Base film (uneven surface)/optical isotropic layer (adhesive or adhesive)/Other film (Type 2) Base film (uneven surface)/optical isotropic layer (adhesive or adhesive) / (Uneven surface) Base film (type 3) Base film (uneven surface) / Optical isotropic layer (adhesive or adhesive) / Other film / Optical isotropic layer (adhesive or adhesive) / (Uneven Surface) Base film (Type 4) Other film/Optical isotropic layer (adhesive or adhesive)/(Uneven surface) Base film (uneven surface)/Optical isotropic layer (adhesive or adhesive)/Other Film When the ΔBfNxy of the base film with refractive index anisotropy is relatively small or the roughness of the unevenness is relatively small, it is preferable to adopt the configuration of type 2 to type 4. In the following description of the application of the laminated film of the present invention, etc., the term "laminated film" includes the configurations of types 1 to 4 described above. In the case of Types 2 and 3, the slow axes of the two substrate films are preferably parallel or perpendicular to each other, preferably parallel from the viewpoint of ease of production. Here, "parallel or perpendicular" is allowed from 0 degree or 90 degrees, preferably ±10 degrees, further ±7 degrees, particularly ±5 degrees.

In addition, when referring to an adhesive or an adhesive layer in the specification, a coating agent for an adhesive is applied to an object and crosslinked or dried, or a substrate-less optical adhesive is transferred. means

(Low refractive index layer)
The low refractive index layer is preferably provided directly on the substrate film and/or the optically isotropic layer, or provided via another film or layer (eg, easy-adhesion layer, hard coat layer). When a laminated film without a low refractive index layer is used on the surface of display devices, show windows, etc., external light such as lighting and scenery may be reflected, making it difficult to see display contents and exhibits inside. In a laminated film having a low refractive index layer, the reflectance of the film surface can be reduced, the reflection of these can be suppressed, the glare can be reduced, and the display contents, exhibits inside, etc. can be easily seen. .

Methods for providing a low refractive index layer on the base film and/or the optically isotropic layer include, for example, a method of coating a composition for a low refractive index layer, and a method of separately providing a low refractive index layer on a release film or the like. , a method of transferring.

The refractive index of the low refractive index layer is preferably 1.45 or less, more preferably 1.42 or less. Moreover, the refractive index of the low refractive index layer is preferably 1.20 or more, more preferably 1.25 or more.
The refractive index of the low refractive index layer is a value measured under the condition of a wavelength of 589 nm.

The thickness of the low-refractive-index layer is not limited, but it may be appropriately set within the range of about 30 nm to 1 μm. In addition, the reflection on the surface of the low refractive index layer and the interface reflection between the low refractive index layer and its inner layer (base film, hard coat layer, optical isotropic layer, etc.) are offset to further lower the reflectance. For that purpose, the thickness of the low refractive index layer is preferably 70 to 120 nm, more preferably 75 to 110 nm.

The low refractive index layer may be a single layer, or two or more layers may be provided. When two or more low refractive index layers are provided, the refractive index and thickness of each low refractive index layer may be the same or different, but preferably different.

The low refractive index layer preferably includes (1) a layer made of a resin composition containing a binder resin and low refractive index particles, (2) a layer made of a fluororesin that is a low refractive index resin, (3) silica or (4) a thin film of a low refractive index substance such as silica and magnesium fluoride;

As the binder resin contained in the resin composition (1), polyester, polyurethane, polyamide, polycarbonate, acryl, etc. can be used without particular limitation. Among them, acrylic is preferred, and one obtained by polymerizing (crosslinking) a photopolymerizable compound by light irradiation is preferred.

Photopolymerizable compounds include photopolymerizable monomers, photopolymerizable oligomers, and photopolymerizable polymers, and these can be appropriately adjusted and used. The photopolymerizable compound is preferably a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable polymer. The photopolymerizable compound is exemplified by those exemplified for the optically isotropic layer.

Examples of the low refractive index particles contained in the resin composition (1) include silica particles (for example, hollow silica particles), magnesium fluoride particles, etc. Among them, hollow silica particles are preferred. Such hollow silica particles can be produced, for example, by the production method described in Examples of JP-A-2005-099778.

The average particle size of the primary particles of the low refractive index particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, even more preferably 10 to 80 nm.

The low refractive index particles are more preferably surface-treated with a silane coupling agent, and more preferably surface-treated with a silane coupling agent having a (meth)acryloyl group.

The content of the low refractive index particles in the low refractive index layer is preferably 10 to 250 parts by mass, more preferably 50 to 200 parts by mass, and even more preferably 100 to 180 parts by mass with respect to 100 parts by mass of the binder resin.

As the fluororesin (2), a polymerizable compound containing at least a fluorine atom in the molecule or a polymer thereof can be used. The polymerizable compound is not particularly limited, but preferably has a curing reactive group such as a photopolymerizable functional group or a thermosetting polar group. A compound having these multiple curing reactive groups at the same time may also be used. In contrast to this polymerizable compound, the polymer does not have the above curing reactive groups.

As a compound having a photopolymerizable functional group, for example, a fluorine-containing monomer having an ethylenically unsaturated bond can be widely used. More specifically, fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluorobutadiene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.) are exemplified. can be done. Those having a (meth)acryloyloxy group include 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 fluorine atoms in the molecule such as methyl methacrylate and ethyl α-trifluoromethacrylate; fluoroalkyl groups having at least 3 fluorine atoms in the molecule and having 1 to 14 carbon atoms, fluorocycloalkyl fluorinated polyfunctional (meth)acrylic acid ester compounds having a group or a fluoroalkylene group and at least two (meth)acryloyloxy groups.

Preferred as the thermosetting polar group are, for example, hydrogen bond forming groups such as hydroxyl, carboxyl, amino and epoxy groups. These are excellent not only in adhesion to coating films but also in affinity with inorganic ultrafine particles such as silica.
Polymerizable compounds having a thermosetting polar group include, for example, 4-fluoroethylene-perfluoroalkyl vinyl ether copolymer; fluoroethylene-hydrocarbon vinyl ether copolymer; epoxy, polyurethane, cellulose, phenol, polyimide, and the like. Fluorine-modified resins and the like can be mentioned.

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

Examples of fluorine-based resins include the following.
- A polymer of a monomer or a monomer mixture containing at least one fluorine-containing (meth)acrylate compound of the polymerizable compound having a curing reactive group;
- At least one of the above fluorine-containing (meth)acrylate compounds and in the molecule of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. A copolymer with a (meth) acrylate compound that does not contain fluorine atoms in;
・Fluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 3,3,3-trifluoropropylene, 1,1,2-trichloro-3,3,3-trifluoropropylene, hexafluoropropylene, etc. A homopolymer or copolymer of a fluorine-containing monomer.
A silicone-containing vinylidene fluoride copolymer obtained by adding a silicone component to these polymers can also be used. In this case, the silicone component includes (poly)dimethylsiloxane, (poly)diethylsiloxane, (poly)diphenylsiloxane, (poly)methylphenylsiloxane, alkyl-modified (poly)dimethylsiloxane, azo group-containing (poly)dimethylsiloxane, Dimethylsilicone, phenylmethylsilicone, 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, methacrylic-modified silicone, acrylic Modified silicone, amino-modified silicone, carboxylic acid-modified silicone, carbinol-modified silicone, epoxy-modified silicone, mercapto-modified silicone, fluorine-modified silicone, polyether-modified silicone and the like are exemplified. Among these, those having a dimethylsiloxane structure are preferred.

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 that reacts with the isocyanate group such as an amino group, hydroxyl group, or carboxyl group in the molecule. Compounds obtained; Compounds obtained by reacting fluorine-containing polyols such as fluorine-containing polyether polyols, fluorine-containing alkyl polyols, fluorine-containing polyester polyols, and fluorine-containing ε-caprolactone-modified polyols with compounds having isocyanate groups, etc. can be used.

In addition, the binder resin can be mixed with the polymerizable compound or polymer having a fluorine atom and used. Furthermore, a curing agent for curing reactive groups and the like, and various additives and solvents for improving coatability and imparting antifouling properties can be used as appropriate.

The low refractive index layer is, for example, a composition for a low refractive index layer containing a photopolymerizable compound, applied to a base film and / or an optically isotropic layer, dried, and then applied to a resin composition in the form of a coating film. It can be formed by irradiating light such as ultraviolet rays to polymerize (crosslink) a photopolymerizable compound.

A thermoplastic resin, a thermosetting resin, a solvent, and a polymerization initiator may be added to the low refractive index layer, if necessary. Further, the functional layer composition may contain conventionally known dispersants, surfactants, antistatic agents, etc., depending on the purpose of increasing the hardness of the functional layer, suppressing curing shrinkage, or controlling the refractive index. , silane coupling agents, thickeners, anti-coloring agents, coloring agents (pigments, dyes), antifoaming agents, leveling agents, flame retardants, UV absorbers, adhesion promoters, polymerization inhibitors, antioxidants, surface modifiers A stabilizing agent, lubricating agent, or the like may be added.

For the purpose of improving anti-fingerprint properties, it is also preferable to appropriately add a known polysiloxane-based or fluorine-based antifouling agent to the low refractive index layer. Preferable examples of polysiloxane-based antifouling agents include acrylic group-containing polyether-modified polydimethylsiloxane, polyether-modified dimethylsiloxane, acrylic group-containing polyester-modified dimethylsiloxane, polyether-modified polydimethylsiloxane, and polyester-modified polydimethylsiloxane. Examples include siloxane and aralkyl-modified polymethylalkylsiloxane. The fluorine-based antifouling agent preferably has a substituent that contributes to formation of the low refractive index layer or compatibility with the low refractive index layer. There may be one or more substituents, and the plurality of substituents may be the same or different. Examples of preferred substituents include acryloyl groups, methacryloyl groups, vinyl groups, aryl groups, cinnamoyl groups, epoxy groups, oxetanyl groups, hydroxyl groups, polyoxyalkylene groups, carboxyl groups, amino groups and the like.

The surface of the low refractive index layer may be an uneven surface (for example, an anti-glare surface), but a smooth surface is also preferable.
When the surface of the low refractive index layer is a smooth surface, the arithmetic mean roughness Ra (JIS B0601:1994) of the surface of the low refractive index layer is preferably 20 nm or less, more preferably 15 nm or less, and still more preferably. is 10 nm or less, particularly preferably 1 to 8 nm. The ten-point average roughness Rz (JIS B0601:1994) of the surface of the low refractive index layer is preferably 160 nm or less, more preferably 50 to 155 nm.
In order to make the Ra of the low refractive index layer within the above range, for example, the following method can be employed.
- Do not use particles with a particle size exceeding 1/2 of the thickness of the low refractive index layer, or reduce the amount of particles added.
- Reducing the surface roughness of layers (base film layer, optically isotropic layer, hard coat layer, etc.) inside the low refractive index layer.
・If the substrate film and the optically isotropic layer are very rough, they are smoothed with a hard coat layer or the like.

(Hard coat layer)
The hard coat layer may be provided directly on the substrate film and/or the optical isotropic layer, or via another film or layer (for example, an easy-adhesion layer).
The hard coat layer may have other functions and may be an optically isotropic layer.
The hard coat layer preferably has a pencil hardness of H or more, more preferably 2H or more. The hard coat layer can be provided, for example, by applying and curing a composition solution of thermosetting resin or radiation-curable resin.

Thermosetting resins include acrylic resins, urethane resins, phenolic resins, urea melamine resins, epoxy resins, unsaturated polyester resins, silicone resins, combinations thereof, and the like. If necessary, a curing agent is added to these curable resins in the thermosetting resin composition.

The radiation-curable resin is preferably a compound having a radiation-curable functional group. Examples of the radiation-curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, and epoxy groups. , oxetanyl group, and the like. Among these, as the ionizing radiation-curable compound, a compound having an ethylenically unsaturated bond group is preferable, and a compound having two or more ethylenically unsaturated bond groups is more preferable. Polyfunctional (meth)acrylate compounds having the above are more preferable. A polyfunctional (meth)acrylate compound may be a monomer, an oligomer, or a polymer.

As specific examples thereof, those mentioned as the binder resin for the low refractive index layer are used.
In order to achieve hardness as a hard coat, the difunctional or higher monomer content in the compound having a radiation-curable functional group is preferably 50% by mass or more, more preferably 70% by mass or more. Furthermore, in the compound having a radiation-curable functional group, the trifunctional or higher monomer preferably accounts for 50% by mass or more, more preferably 70% by mass or more.
The compounds having radiation-curable functional groups can be used singly or in combination of two or more.

The thickness of the hard coat layer is preferably in the range of 0.1-100 μm, more preferably in the range of 0.8-20 μm.

The hard coat layer preferably has a refractive index of 1.45 to 1.70, more preferably 1.50 to 1.60.
The refractive index of the hard coat layer is a value measured at a wavelength of 589 nm.

Examples of adjusting the refractive index of the hard coat layer include a method of adjusting the refractive index of the resin, and a method of adjusting the refractive index of the particles when particles are added.
Examples of the particles include those exemplified as particles for the optically isotropic layer or the low refractive index layer.

(Antistatic layer)
It is also a preferable form to separately provide an antistatic layer. The antistatic layer is between the base film and the low refractive index layer, between the optically isotropic layer and the low refractive index layer, between the base film and the hard coat layer, and between the optically isotropic layer and the hard coat layer. It is preferably provided on the surface of the substrate film or optically isotropic layer on which the low refractive index layer is not laminated. The antistatic layer preferably comprises an antistatic agent and a binder resin.
Antistatic agents include quaternary ammonium salts, conductive polymers such as polyaniline and polythiophene, acicular metal fillers, conductive high refractive index fine particles such as tin-doped indium oxide fine particles and antimony-doped tin oxide fine particles, and combinations thereof. be done.
As the binder resin, polyester, polyurethane, polyamide, acryl, or the like is used.
An antistatic agent may be added to the hard coat layer so that the hard coat layer functions as an antistatic layer. Conventionally known antistatic agents can be used as the antistatic agent added to the hard coat layer. Examples include cationic antistatic agents such as quaternary ammonium salts, fine particles such as tin-doped indium oxide (ITO), conductive polymers etc. can be used. The content of the antistatic agent is preferably 1 to 30% by mass with respect to the total mass of the total solid content of the hard coat layer.

The laminated film of the present invention may further have various functional layers according to each application. Various functional layers include an antiglare layer, an antireflection layer, a conductive layer, a colored layer, an ultraviolet absorbing layer, an antifouling layer, an adhesive layer, and the like.

(Application of laminated film)
The laminated film of the present invention is not only an optical film such as a polarizer protective film or a depolarizing film, a transparent conductive substrate film such as a touch panel, a scattering prevention film, a surface design imparting film, but also a scattering prevention such as a window glass. It can be used in various fields such as films and decorative films.

First, a polarizing plate using the laminated film as a polarizer protective film, which is a typical application example, will be described.
(Lamination of polarizer and laminated film)
As a polarizer used in the polarizing plate, for example, uniaxially stretched polyvinyl alcohol (PVA) to which iodine or an organic dichroic dye is adsorbed, or a liquid crystal compound and an organic dichroic dye to be oriented. Alternatively, a liquid crystalline polarizer containing a liquid crystalline dichroic dye, a wire grid type polarizer, or the like can be used without particular limitation.

In the case of a film-shaped polarizer in which iodine or an organic dichroic dye is adsorbed on uniaxially stretched polyvinyl alcohol (PVA), the laminated film of the present invention is laminated on at least one side of the polarizer to form a polarizing plate. be able to. At the time of lamination, a PVA-based adhesive, an ultraviolet curable adhesive, or a pressure-sensitive adhesive can be used. Alternatively, the uneven surface of the base film and the polarizer may be bonded together with an adhesive or pressure-sensitive adhesive having properties corresponding to the optically isotropic layer of the present invention. In this case, the base film and the adhesive or pressure-sensitive adhesive form the laminate film having the base film and the optically isotropic layer referred to in the present invention. The thickness of this type of polarizer is preferably 5 to 50 μm, more preferably 10 to 30 μm, particularly preferably 12 to 25 μm. The thickness of the adhesive or adhesive is preferably 1-10 μm, more preferably 2-5 μm.

A polarizer obtained by coating an unstretched base material such as PET or polypropylene with PVA and uniaxially stretching it together with the base material to adsorb iodine or an organic dichroic dye is also preferably used. In the case of this polarizer, the polarizer surface of the polarizer laminated on the substrate (the surface on which the substrate is not laminated) and the laminated film of the present invention are attached with an adhesive or pressure-sensitive adhesive, and then the polarizer is attached. A polarizing plate can be obtained by peeling off the base material used for the production. Also in this case, the uneven surface of the base film and the polarizer may be bonded together with an adhesive or pressure-sensitive adhesive having properties corresponding to the optical isotropic layer of the present invention. The thickness of this type of polarizer is preferably 1 to 10 μm, more preferably 2 to 8 μm, particularly preferably 3 to 6 μm. The thickness of the adhesive or adhesive is preferably 1-10 μm, more preferably 2-5 μm.

In the case of a liquid crystalline polarizer, the laminated film of the present invention is laminated with an oriented polarizer composed of a liquid crystal compound and an organic dichroic dye, or the laminated film of the present invention is laminated with liquid crystalline. A polarizing plate can be obtained by applying a coating liquid containing a dichroic dye, drying it, photocuring or thermal curing, and laminating a polarizer. Examples of the method for orienting the liquid crystalline polarizer include a method of rubbing the surface of the object to be coated and a method of irradiating polarized ultraviolet rays to cure the liquid crystalline polarizer while aligning it. The surface of the laminated film of the present invention may be directly rubbed and coated with the coating solution, or the laminated film may be directly coated with the coating solution and irradiated with polarized ultraviolet rays. In addition, it is also a preferable method to provide an orientation layer on the laminated film of the present invention before providing the liquid crystalline polarizer (that is, to laminate the liquid crystalline polarizer on the laminated film of the present invention via the orientation layer). be. As a method for providing the orientation layer,
- A method of coating polyvinyl alcohol and its derivatives, polyimide and its derivatives, acrylic resin, polysiloxane derivative, etc., and rubbing the surface thereof to form an alignment layer (rubbing alignment layer);
- A method of applying a coating solution containing a polymer or monomer having a photoreactive group such as a cinnamoyl group or a chalcone group and a solvent, and irradiating polarized ultraviolet rays to harden the alignment layer (photoalignment layer), etc. is mentioned.
A rubbing orientation layer having characteristics corresponding to the optical isotropic layer of the present invention may be provided on the uneven surface of the base film, and the base film and the rubbing orientation layer may be used as the laminated film of the present invention.

A film having releasability is provided with a liquid crystalline polarizer according to the above method, the liquid crystalline polarizer surface and the laminated film of the present invention are bonded together with an adhesive or a pressure-sensitive adhesive, and then the film has releasability. A polarizing plate can be obtained by peeling the film. Also in this case, the uneven surface of the base film and the polarizer may be bonded together with an adhesive or pressure-sensitive adhesive having properties corresponding to the optical isotropic layer of the present invention.
The thickness of the liquid crystalline polarizer is preferably 0.1 to 7 μm, more preferably 0.3 to 5 μm, particularly preferably 0.5 to 3 μm. The thickness of the adhesive or adhesive is preferably 1-10 μm, more preferably 2-5 μm.

In the case of a wire grid system, fine conductive wires may be provided on the laminated film of the present invention. When fine grooves are required to provide fine conductive wires, a separate layer for providing the grooves may be provided, or the layer for providing the grooves may be the optically isotropic layer of the present invention.

The angle formed by the transmission axis of the polarizer and the slow axis of the laminated film is not particularly limited, but when the laminated film is used as a polarizer protective film for a polarizing plate for linearly polarizing normal transmitted light. are preferably parallel or perpendicular. "Parallel or perpendicular" is allowed from 0 or 90 degrees, preferably ±10 degrees, further ±7 degrees, especially ±5 degrees.

Further, when the laminated film is used as a polarizer protective film for a polarizing plate that emits depolarized light, such as when used on the viewing side of an image display device, the transmission axis of the polarizer and the slow axis of the laminated film The angle formed by the two is preferably 20 to 70 degrees, more preferably 25 to 65 degrees, still more preferably 30 to 60 degrees, and particularly preferably 35 to 55 degrees.

The surface of the laminated film of the present invention on which the polarizer is laminated may be either the substrate film surface or the optically isotropic layer surface. A polarizer is preferably provided on the surface of the base film or the optically isotropic layer on which the low refractive index layer is not laminated.

The other surface of the polarizer of the polarizing plate thus obtained can take various forms depending on its purpose. Examples of the layer laminated on the other side of the polarizer include glass, a polarizer protective film having no birefringence, an optical compensation film, a λ/4 retardation film, a λ/2 retardation film, retardation (optical Compensation) Examples include a coating layer, a protective coat layer, those without these protective layers, and an adhesive layer. The layer laminated on the other surface of the polarizer may be the laminated film of the present invention.

Examples of non-birefringent polarizer protective films include TAC films, acrylic films, cyclic olefin films, and polypropylene films.
Examples of the optical compensation film include those having positive or negative A plate and C plate characteristics, and the surface of the above film or polycarbonate film stretched, TAC film, etc. coated with a rod-like liquid crystal compound or discotic liquid crystal compound. and so on. These are appropriately selected as the polarizing plate of the liquid crystal display according to the characteristics of the liquid crystal cell.
A λ/4 retardation film and a λ/2 retardation film can be obtained by the same method as the optical compensation film. These are used for circularly polarizing plates, for example, and are suitable for antireflection films such as organic EL display devices. The thickness of these layers is preferably 10-80 μm, more preferably 20-60 μm.

Uses for thinning image display devices include retardation (optical compensation) coating layers, protective coating layers, those without these protective layers, pressure-sensitive adhesive layers, and the like.
The retardation (optical compensation) coating layer can be formed by a method of coating a liquid crystal compound on a polarizer, or a method of separately providing a retardation layer on a release film and transferring it. In particular, when thinning the polarizing plate, it is preferably combined with a liquid crystalline polarizer as a base material or a polarizer that transfers a polarizer laminated on a base material.

(Display device)

The polarizing plate described above is preferably used on either the light source side polarizing plate or the viewing side polarizing plate of the display device, and it is also a preferred form to use it on both sides. The laminated film of the present invention is preferably used as a polarizer protective film on the opposite side of the display cell.

Backlights for liquid crystal displays include blue light emitting diodes and yellow phosphor light sources, blue, green and red light emitting diode light sources, blue light emitting diodes, green phosphors, and red phosphor light sources, wavelength conversion light sources using quantum dots, and semiconductors. A laser light source, a cold cathode tube, or the like can be used without particular limitation.

In a polarizing plate using the laminated film of the present invention as a polarizer protective film, even in a liquid crystal display device having a light source with a steep emission peak, rainbow spots are reduced to a level that cannot be recognized, and the emission peak of each color is reduced to a level that is not visible. A more preferable form is a combination with a light source having a narrow half width. As for the half-value width of the light source, the half-value width of the emission peak with the narrowest half-value width is preferably 25 nm or less, more preferably 20 nm or less, still more preferably 15 nm or less, and particularly preferably 10 nm or less. The lower limit of the half-value width is 0.5 nm in terms of a realistic value or the resolution of the measuring instrument. Specific preferred light sources include a QD (quantum dot) light source and a light source using a KSF phosphor for the red region, and the most preferred light source uses a KSF phosphor.

In addition, when the laminated film of the present invention is used as a polarizer protective film in line with recent thinning, the thickness of the laminated film of the present invention is preferably 12 to 60 μm, more preferably 15 to 50 μm. In the case of such a thin image display device, the light source is preferably a blue light emitting diode and a yellow phosphor light source, a light source using a KSF phosphor, a QD light source, or the like.

The laminated film of the present invention can also be suitably used as a polarizer protective film for an antireflection circularly polarizing plate of an organic EL display device.

Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples, and it is possible to carry out the present invention with appropriate modifications within the scope of the gist of the present invention. All of them are included in the technical scope of the present invention.
Methods for evaluating physical properties in Examples are as follows.

(1) Slow axis refractive index (Bfnx), fast axis refractive index (Bfny), and refractive index anisotropy (ΔBfNxy) of the base film
Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), the orientation axis direction of the base film before roughening is determined, and the orientation axis direction is 4 cm so that the long side becomes. A 2 cm x 2 cm rectangle was cut out and used as a measurement sample. The biaxial refractive index (Bfnx, Bfny) and the refractive index (Bfnz) in the thickness direction of this sample were measured using an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm). , and the absolute value of the biaxial refractive index difference (|Bfny−Bfnx|) was defined as the refractive index anisotropy (ΔBfNxy). The refractive index of the roughened substrate film can be measured by polishing the roughened surface with water-resistant emery paper or the like to flatten the roughened surface.

(2) Thickness d of raw film
Using an electric micrometer (Millitron 1245D manufactured by Fineruff Co.), the thickness was measured at five points, and the average value was obtained.

(3) In-plane retardation (Re)
The in-plane retardation (Re) was obtained from the product (ΔBfNxy×d) of the refractive index anisotropy (ΔBfNxy) and the film thickness d (nm).

(4) Nz Coefficient A value obtained by |Bfnx−Bfnz|/|Bfnx−Bfny| was used as the Nz coefficient.

(5) Degree of plane orientation (ΔP)
A value obtained by (Bfnx+Bfny)/2-Bfnz was defined as the degree of planar orientation (ΔP).

(6) Retardation in thickness direction (Rth)
The retardation in the thickness direction is obtained by multiplying the two birefringences ΔBfNxz (=|Bfnx−Bfnz|) and ΔBfNyz (=|Bfny−Bfnz|) when viewed from the cross section in the thickness direction of the film by the film thickness d. is a parameter that indicates the average retardation obtained by Bfnx, Bfny, Bfnz and the film thickness d (nm) are obtained in the same manner as described above, and the average value of (ΔBfNxz×d) and (ΔBfNyz×d) is calculated to calculate the thickness direction retardation (Rth). Calculated: Rth=(ΔBfNxz×d+ΔBfNyz×d)/2.

(7) Surface roughness (Ra, Rq, Rz, Ry, Rp, Rv, Sm)
Each parameter of the surface roughness is obtained from a roughness curve measured using a contact roughness meter (Mitutoyo, SJ-410, detector: 178-396-2, stylus: standard stylus 122AC731 (2 μm)). asked. The settings are as follows.
Curve: R
Filter: GAUSS
λc: 0.8mm
λs: 2.5 μm
Measuring length: 5mm
Measurement speed: 0.5mm/s
Rq was determined according to JIS B0601-2001, and others were determined according to JIS B0601-1994.

(8) Thickness of optically isotropic layer The thickness of the roughened base film and laminated film was determined by embedding each film in epoxy resin, cutting out a section of the cross section, and observing it under a microscope. The thickness was measured and taken as the average value. A polarizing microscope was used when the interface was difficult to see. In addition, the uneven surface of the roughened base film was based on the center of the convex portion and the concave portion in the field of view. The thickness of the optically isotropic layer was determined by subtracting the thickness of the roughened base film from the thickness of the laminated film.

(9) Refractive index of optically isotropic layer Under the same conditions as in the case of providing an optically anisotropic layer on a release film on an uneven surface, the refractive index of a sample peeled off from the release film was measured so as to have a thickness of about 20 μm. It was measured in the same manner as the base film. It was confirmed that nx, ny, and nz are the same value.

(Production of easy-adhesion layer component)
(Polymerization of polyester resin)
194.2 parts by weight of dimethyl terephthalate, 184.5 parts by weight of dimethyl isophthalate, and 14.8 parts by weight of dimethyl-5-sodium sulfoisophthalate were added to a stainless steel autoclave equipped with an agitator, thermometer, and partial reflux condenser. , 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and transesterification was carried out at a temperature of 160° C. to 220° C. over 4 hours. Then, the temperature was raised to 255° C., and the pressure in the reaction system was gradually reduced, followed by reaction under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin. The resulting copolymerized polyester resin was pale yellow and transparent. When the reduced viscosity of the copolymerized polyester resin was measured, it was 0.70 dl/g. The glass transition temperature by DSC was 40°C.

(Preparation of polyester aqueous dispersion)
A reactor equipped with a stirrer, a thermometer and a reflux device was charged with 30 parts by mass of a copolymer polyester resin and 15 parts by mass of ethylene glycol n-butyl ether, heated at 110° C. and stirred to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution with stirring. After the addition, the liquid was cooled to room temperature while stirring to prepare a milky white polyester water dispersion having a solid content of 30% by mass.

(Polymerization of block polyisocyanate-based cross-linking agent used in easy-adhesion layer)
A flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 100 parts by mass of a polyisocyanate compound having an isocyanurate structure made from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals) and 55 parts by mass of propylene glycol monomethyl ether acetate. , and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight: 750) were charged and held at 70° C. for 4 hours in a nitrogen atmosphere. After that, the temperature of the reaction solution was lowered to 50° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. By measuring the infrared spectrum of the reaction solution, it was confirmed that the absorption of isocyanate groups had disappeared, and an aqueous blocked polyisocyanate dispersion having a solid content of 75% by mass was obtained.

(Adjustment of coating liquid for easy adhesion layer)
A P1 coating solution was prepared by mixing the following coating agents.
Water 50.00% by mass
Isopropanol 33.00% by mass
Polyester water dispersion 12.00% by mass
Block isocyanate-based cross-linking agent 0.80% by mass
Particles 1.40% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (organotin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.50% by mass
(Silicone type, solid content concentration 10% by mass)

(Manufacture of polyester resin for film)
(Production Example 1-Polyester X)
When the temperature of the esterification reactor reaches 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol are charged, and 0.017 parts by mass of antimony trioxide as a catalyst is added while stirring. , 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were charged. Then, the pressure was increased and the temperature was increased, and the pressure esterification reaction was performed under the conditions of gauge pressure 0.34 MPa and 240° C., then the pressure in the esterification reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. . Furthermore, the temperature was raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, dispersion treatment was performed with a high-pressure disperser. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and polycondensation reaction was performed at 280°C under reduced pressure.

After the polycondensation reaction is completed, filtration is performed with a NASLON (registered trademark) filter having a 95% cut diameter of 5 μm, extruded from the nozzle in strand form, and cooling water that has been pre-filtered (pore size: 1 μm or less) is filtered. It was cooled, solidified and cut into pellets. The resulting polyethylene terephthalate resin (X) had an intrinsic viscosity of 0.62 dl/g and contained substantially no inert particles or internal precipitated particles. (Hereinafter abbreviated as PET (X).)

(Production of raw films A and B)
PET (X) resin pellets containing no particles as a raw material for film are supplied to an extruder, extruded in a sheet form from a nozzle, and then wound around a casting drum with a surface temperature of 30 ° C. using an electrostatic casting method. It was cooled and solidified to produce an unstretched film. Next, the P1 coating liquid was applied to both sides of this unstretched PET film by a reverse roll method so that the coating amount after drying was 0.12 g / m ² , and then led to a dryer and dried at 80 ° C. for 20 seconds. did.

The unstretched film with the coating layer formed thereon was guided to a tenter stretching machine, and while holding the ends of the film with clips, was guided to a hot air zone at a temperature of 135° C. and stretched 3.8 times in the width direction. Next, while maintaining the width stretched in the width direction, it was treated at a temperature of 225 ° C. for 30 seconds, and then cut at both ends of the film cooled to 130 ° C. with a shear blade, and a tension of 0.5 kg / mm ² After cutting off the selvages, the film was wound up to obtain a raw film A having a film thickness of 80 μm.

A raw film B having a different film thickness was obtained in the same manner as the raw film A except that the thickness of the unstretched film was changed by increasing the line speed after casting.

(Manufacturing raw film C)
An unstretched film (coated with an easy-adhesion layer) produced by the same method as the raw film A is heated to 105 ° C. using a heated roll group and an infrared heater, and then a roll group with a peripheral speed difference. After being stretched 2.0 times in the running direction in the same manner as the raw film A, it was led to a hot air zone at a temperature of 135° C. and stretched 4.0 times in the width direction to obtain a raw film C.

(Original film D)
An unstretched film (coated with an easy-adhesion layer) produced by the same method as the raw film A is heated to 105 ° C. using a heated roll group and an infrared heater, and then a roll group with a peripheral speed difference. After the film was stretched 3.5 times in the running direction, it was led to a hot air zone at a temperature of 135° C. and stretched 3.5 times in the width direction by the same method as for raw film A, to obtain raw film D.

(Production of surface-roughened film)
Attach urethane foam to a glass plate, and then attach the periphery of the original film A with double-sided tape. 45 degrees and 135 degrees) to obtain a surface-roughened film A1.
The periphery of raw film A was attached to a glass plate with double-sided tape, set in a dry sandblaster, and treated by spraying an abrasive (sandblasting) to obtain surface-roughened film A2.
A masking film made of polypropylene film is attached to one side of the original film A, which is immersed in a 38% potassium hydroxide aqueous solution (95 ° C.) (chemical etching), washed with water, and then the masking film is peeled off and dried. A surface-roughened film A4 was obtained.
Various surface-roughened films shown in Table 2 were obtained from raw films A, B, C, and D by changing the belt sander conditions (sanding belt type, etc.) and sandblasting conditions (abrasive particle size, etc.). rice field.
A #320 sanding belt was used to manufacture B1 and C1, and a #180 sanding belt was used to manufacture A3 and D1. Abrasives of the sand blaster were used in the order of A5, A6, B2 and A2.
In addition, in order to eliminate the influence of local projections, the belt-sanded and sandblasted surfaces were lightly polished with #400 sandpaper.

(Manufacture of optical isotropic layer laminated film)
(Preparation of coating agent for optically isotropic layer)
As a coating agent for the optically isotropic layer, those shown in Table 3 were prepared.

On the uneven surface of the surface roughened film A1 of 20 cm × 30 cm, the above-mentioned easy adhesion layer diluted 4 times with a solution of water / isopropanol = 2/1 was applied and dried to obtain an easy adhesion of about 30 nm. layer was established. Further, the optically isotropic layer coating agent a was applied thereon with an applicator, and then cured from the coated surface with a high-pressure mercury lamp to obtain an optically isotropic layer laminated film F1.

Optically isotropic layer laminate films F2 to F16 were obtained in the same manner as described above, except that the type of surface-roughened film and/or coating agent was changed. Note that the laminated film F14 was provided with an optical isotropic layer on both sides.

A solution of Vylon (registered trademark) 200 (RV200) (manufactured by Toyobo Co., Ltd.) in a 20% toluene/methyl ethyl ketone mixed solvent is applied to the uneven surface of the 20 cm × 30 cm roughened film B2, and then dried to form an optically isotropic layer. was established. The optically isotropic layer surfaces of the obtained two optically isotropic layered laminated films are superimposed and passed between rolls heated to 100° C. to bond the two optically isotropic layered laminated films to obtain an optically isotropic layered laminated film. F17 was obtained. In addition, the slow axes of the surface-roughened film B2 were bonded together so that they were parallel to each other. Byron 200 has a refractive index of 1.55.
Table 4 shows the structure of each optically isotropic layer laminated film.

(Manufacturing of laminated film (low reflection film))
As the composition for the low refractive index layer and the composition for the hard coat layer, the following were prepared.
(Composition A for low refractive index layer)
Peltron (trademark) A-2508LR (manufactured by Pernox Co., Ltd., hollow silica-containing type, refractive index 1.33 (Abbe))
(Composition B for low refractive index layer)
CYTOP A type (Fluorine resin, refractive index 1.34, manufactured by AGC Asahi Glass Co., Ltd.)
(Composition for hard coat layer)
Peltron (TM) A-2005 (manufactured by Pelnox Co., Ltd.)
(Diluted with toluene/methyl ethyl ketone (1/1 mass ratio) so that the solid content is 50%)
3% by mass (based on the solid content) of Irgacure 184 was added as a photopolymerization initiator to the low refractive index composition A and the hard coat layer composition.

(Preparation of laminated film having low refractive index layer on optically isotropic layer surface)
Examples 1-13 and Comparative Examples 1-3
The composition A for low refractive index layer was applied to the optically isotropic layer surface. After that, it was dried in an oven at 80° C. to evaporate the solvent, and irradiated with ultraviolet rays to form a low refractive index layer A (thickness: 0.5 μm) to obtain laminated films LRF1c-A to LRF16c-A.

(Preparation of laminated film having low refractive index layer on base film)
Examples 14-26 and Comparative Examples 4-6
The hard coat layer composition was applied to the surface of the substrate film, dried in an oven at 100° C. to evaporate the solvent, and irradiated with ultraviolet rays to form a hard coat layer. The thickness of the hard coat layer was 5 μm.
Further, a low refractive index layer A was formed on the hard coat layer in the same manner as in Example 1 to obtain laminated films LRF1b-A to LRF17b-A.

Example 27
A hard coat layer having a thickness of 5 μm was formed in the same manner as in Example 14 on the optically isotropic layer surface of the laminated film F5.
Furthermore, the composition B for low refractive index layer was applied on the hard coat layer. Then, the film was dried in an oven at 80°C to evaporate the solvent, and further heated at 120°C for 10 minutes to form a low refractive index layer B (thickness: 86 nm) to obtain a laminated film LRF5c-B.

Example 28
A hard coat layer having a thickness of 5 μm was formed in the same manner as in Example 14 on the base film surface of the laminated film F5.
Further, a low refractive index layer B composed of the low refractive index layer composition B was formed on the hard coat layer in the same manner as in Example 27 to obtain a laminated film LRF5b-B.

Example 29
A low refractive index layer B (thickness: 230 nm) composed of composition B for low refractive index layer was formed on the substrate film surface of optical laminated film F5 in the same manner as in Example 27 to obtain laminated film LRF5b-B2.

(Evaluation of laminated film)
(Observation of rainbow spots)
The laminated film is placed between two polarizing plates arranged in crossed Nicols so that the slow axis is at 45 degrees with the transmission axis of the polarizing plate on the light source side, and the transmitted light is viewed from the front about 60 cm away from the polarizing plate on the viewing side. was observed, and the presence or absence of iridescence was evaluated according to the following criteria. A cold cathode tube was used as the light source.
○: No iridescence was observed △: Slight iridescence was observed ×: Iridescence was observed

(whitening)
The laminated film was irradiated with a halogen lamp from below, and the degree of whitening of the laminated film was observed from an obliquely upward direction of 45 degrees. The surface of the low refractive index layer was turned up, and salad oil was applied to the surface of the low refractive index layer in order to avoid the influence of irregular reflection on the surface of the low refractive index layer.
A: Almost no whitening was observed.
◯: Slight whitening was observed, but the transparency was high.
Δ: Whitening was observed, and the transparency was slightly inferior.
x: Whitening was observed, and the transparency was also low.
Incidentally, Examples 30 to 35 were evaluated using a polarizing plate.

(Reflectivity evaluation)
The laminated film was placed on a landscape print, irradiated with a fluorescent lamp from 45 degrees diagonally above, and observed from 45 degrees above on the opposite side of the fluorescent lamp. The evaluation is based on a laminated film without a low refractive index layer (when a low refractive index layer is provided on the optically isotropic layer side, the optical isotropic layer surface, and when a low refractive index layer is provided on the base film side, the substrate It was evaluated by whether the reflection is reduced with respect to the film surface).
⊚: Reflection was effectively suppressed, and the printed matter was clearly visible.
◯: Reflection was suppressed, and printed matter was visible.
x: There was almost no effect of suppressing reflection.
Incidentally, Examples 30 to 35 were evaluated using a polarizing plate.

(Manufacture of polarizing plate)
(Manufacture of polarizer)
A polyvinyl alcohol resin film having a degree of saponification of 99.9% was led to rolls with a difference in peripheral speed, and uniaxially stretched at 100° C. to 3 times. The resulting stretched polyvinyl alcohol stretched film was dyed in a mixed aqueous solution of potassium iodide (0.3%) and iodine (0.05%), and then dyed in a 10% aqueous solution of boric acid at 72°C to 1.8%. It was uniaxially stretched twice. Thereafter, the film was washed with ion-exchanged water, immersed in a 6% potassium iodide aqueous solution, and dried at 45° C. to obtain a polarizer after removing the aqueous solution with an air knife. The thickness of the polarizer was 18 μm.

(Preparation of TAC film laminated polarizer)
First, a polarizer and a 60 μm-thick triacetyl cellulose (TAC) film coated with an ultraviolet curable acrylic adhesive were prepared, and the polarizer was laminated on this and a high-pressure mercury lamp was irradiated from the TAC surface. It was cured to obtain a TAC film laminated polarizer.

(Production of polarizing plates using laminated films of Examples 1 to 26 and Comparative Examples 1 to 6)
An ultraviolet curable acrylic adhesive was applied to the surface of the laminate film opposite to the low refractive index layer surface using an applicator. A polarizer surface of a TAC film laminated polarizer cut into a size of 20 cm×30 cm was superposed on the coated surface, and the laminated film surface was irradiated with a high-pressure mercury lamp for curing to obtain a polarizing plate. The transmission axis of the polarizer and the slow axis of the base film were made parallel.

Regarding the polarizing plates using the laminated films of Examples 4, 5, 17, and 18, the same polarizing plates were also prepared, except that the transmission axis of the polarizer and the slow axis of the base film were perpendicular to each other. made.

(Example of using an optically isotropic layer as an adhesive for a polarizer)
(Preparation of coating agent for adhesive used as optical isotropic layer and optical adhesive sheet)
The adhesives and optical adhesive sheets shown in Table 5 were used.

Preparation of high refractive index adhesive k 30 parts by mass of 2-ethylhexyl acrylate, 70 parts by mass of ethoxylated o-phenylphenol acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: A-LEN-10), and azo as a polymerization initiator 0.25 parts by mass of bisisobutyronitrile was reacted in ethyl acetate to obtain an ethyl acetate solution (solid concentration: 30% by mass) of a copolymer (Mw=400,000).
Example 30
A hard coat layer and a low refractive index layer A composed of the composition A for a low refractive index layer were formed in the same manner as in Example 14 on the smooth surface of the surface-roughened film A1 of 20 cm×30 cm. After coating the uneven surface of this film with the adhesive coating agent i as an optically isotropic layer using an applicator, the coated surface was cured with a high-pressure mercury lamp to obtain a laminated film. The adhesive layer surface of the obtained laminated film and the polarizer surface of the TAC film laminated polarizer cut to 20 cm×30 cm were pasted together to prepare a polarizing plate. The transmission axis of the polarizer and the slow axis of the surface-roughened film (base film) were made parallel.

Example 31
A pressure-sensitive adhesive coating agent k was applied as an optically isotropic layer to the uneven surface of the surface-roughened film A1 in which the low refractive index layer and the hard coat layer were laminated, using an applicator. After processing, a polarizing plate was obtained in the same manner as in Example 30, except that the film was dried at 100° C. to obtain a laminated film.

Examples 32-34
The coating agent b for the optically isotropic layer was applied with an applicator to the uneven surface of the surface-roughened film A1 in which the low refractive index layer and the hard coat layer were laminated, which was used in the production of the polarizing plate of Example 30. . A polarizer surface of a TAC film laminated polarizer cut into a size of 20 cm×30 cm was placed on the coated surface, and the surface-roughened film A1 was irradiated with a high-pressure mercury lamp for curing to obtain a polarizing plate.
A polarizing plate was obtained in the same manner as described above, except that e or f was used as the coating agent for the optically isotropic layer.

(Production of polarizing plate having protective film on only one side)
(Manufacturing of substrate-laminated polarizer)
An unstretched film having a thickness of 100 μm was prepared using PET (X) as a thermoplastic resin substrate, and an aqueous solution of polyvinyl alcohol having a degree of polymerization of 2400 and a degree of saponification of 99.9 mol% was applied to one side of the unstretched film. And dried to form a PVA layer to obtain a laminate.
The resulting laminate was stretched twice in the longitudinal direction between rolls having different peripheral speeds at 120° C. and wound up.
Next, the obtained laminate was treated with a 4% boric acid aqueous solution for 30 seconds, and then immersed in a mixed aqueous solution of iodine (0.2%) and potassium iodide (1%) for 60 seconds for dyeing. and then treated with a mixed aqueous solution of potassium iodide (3%) and boric acid (3%) for 30 seconds.
Furthermore, the obtained laminate was uniaxially stretched in the longitudinal direction in a mixed aqueous solution of boric acid (4%) and potassium iodide (5%) at 72 ° C., followed by washing with a 4% potassium iodide aqueous solution, After removing the aqueous solution with an air knife, the film was dried in an oven at 80° C., slit at both ends, and wound up to obtain a substrate laminated polarizer 1 having a width of 30 cm and a length of 1000 m.
The total draw ratio was 6.5 times, and the thickness of the polarizer was 5 μm. The thickness was read by embedding the base-material-laminated polarizer in an epoxy resin, cutting out a slice, and observing it with an optical microscope.

Example 35
After bonding the adhesive layer surface of the laminated film used in the production of the polarizing plate of Example 31 and the polarizer surface of the substrate-laminated polarizer, the substrate of the substrate-laminated polarizer was peeled off to obtain a single-sided protective film polarizer. got A commercially available optical adhesive sheet was laminated on the polarizer surface of this polarizing plate. The transmission axis of the polarizer and the slow axis of the base film were made parallel.

Example 36
A commercially available optical pressure-sensitive adhesive sheet is attached to the surface of the optically isotropic layer of the laminated film LR5c-A (Example 5), and the polarizer surface of the substrate-laminated polarizer is attached thereon. A single-sided protective film polarizing plate was obtained by peeling off the base material. A commercially available optical adhesive sheet was laminated on the polarizer surface of this polarizing plate. The transmission axis of the polarizer and the slow axis of the base film were made parallel.
Example 37
A single-sided protective film polarizing plate was obtained in the same manner as in Example 36, except that the laminated film LR5b-A (Example 18) was used.

Table 6 summarizes the physical properties and evaluation of these polarizing plates obtained from each laminated film. Evaluation criteria for iridescence and contrast in liquid crystal display devices are as described later.

(Evaluation of liquid crystal display device)
A TAC film laminated polarizer is obtained by peeling off the polarizing plates on the viewing side and the light source side mounted on a liquid crystal display device with a KSF light source (Toshiba REGZA Z20X) and bonding the obtained polarizing plates instead. In the case of a polarizing plate using TAC, a commercially available optical adhesive sheet was laminated on the TAC surface, and in the case of a polarizing plate having a protective film on only one side, the optical adhesive sheet surface laminated to the polarizer surface was laminated. . The transmission axis of the polarizer was made to be the same as the direction of the original liquid crystal display device. The portion of the liquid crystal cell that could not be covered by the polarizing plate was covered with black construction paper.
For the evaluation, confirmation of the iridescence and contrast of the image were observed.

(Observation of rainbow spots on liquid crystal display device)
The display of the liquid crystal display device was set to a single white color, and the presence or absence of rainbow spots was confirmed when viewed from the front and oblique directions.
◯: No iridescence was observed.
Δ: Slight iridescence was observed.
x: Iridescent spots were observed.

(observation of contrast)
A landscape image was displayed on the liquid crystal display device, and the contrast from the front was observed by irradiating light from a tabletop fluorescent lamp from above.
⊚: Vivid contrast remained.
Good: A slight reduction in contrast was observed due to scattered light.
Δ: A decrease in contrast was observed, but the image could be observed.
x: The image became difficult to see due to scattered light.

(Manufacture of circularly polarizing plate)
A λ/4 wavelength plate was attached to the adhesive layer surface of the single-sided protective film polarizing plate laminated with the adhesive of Examples 35 to 37 to prepare a circularly polarizing plate. The circularly polarizing plate of a smartphone using a commercially available organic EL was peeled off, and a circularly polarizing plate prepared instead was attached to the organic EL cell, and an image was observed. These circularly polarizing plates could be used without problems.

The laminated film of the present invention suppresses rainbow spots, ensures high transparency and vivid image displayability, and suppresses reflection due to external light when used in an environment with a light source having a steep peak. can be done.

Claims (7)

A laminated film having a substrate film and an optically isotropic layer, the laminated film having a low refractive index layer on the substrate film and/or the optically isotropic layer, and having all of the following characteristics.
(a) At least one surface of the substrate film is uneven, and the arithmetic mean roughness (Ra) of the uneven surface is 0.4 to 4 μm.
(b) The refractive index anisotropy ( ΔBfNxy ) of the base film is 0.07 to 0.2.
(c) An optically isotropic layer is provided on the uneven surface of the base film, and the refractive index of the optically isotropic layer is from Bfny−0.15 to Bfnx+0.15 and is 1.57 or more . .
(However, the refractive index in the slow axis direction of the base film is Bfnx, the refractive index in the fast axis direction is Bfny, and ΔBfNxy=Bfnx−Bfny )
(d) The substrate film has a retardation difference (ΔRe) of 90 to 800 nm.
(However, ΔRe=Ra×ΔBfNxy)
(e) The in-plane retardation of the base film is 3000 to 30000 nm
(f) Bfnx of the base film is 1.67 to 1.73.
(g) The base film is a polyester film.
(h) The optically isotropic layer is provided in direct contact with the irregular surface without any other layer interposed therebetween, or is provided only via the easy-adhesion layer. 2. The laminated film according to claim 1, wherein the base film has a plane orientation degree (ΔP) of 0.09 to 0.15. 3. The laminated film according to claim 1, wherein the optically isotropic layer has a refractive index of Bfny to Bfnx. 4. The laminated film according to claim 1, wherein the optically isotropic layer has a refractive index of Bfny+0.02 to Bfnx. A polarizing plate using the laminated film according to any one of claims 1 to 4 as a polarizer protective film. An image display device comprising the polarizing plate according to claim 5 . 7. The image display device according to claim 6, comprising a QD (quantum dot) light source and/or a light source using a KSF phosphor for the red region.