JP7206780B2 - 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 such as poor image definition, low contrast, and in a strong external light environment, the screen becomes white and the image is difficult to see.

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, an object of the present invention is to provide a laminated film that can suppress iridescence and ensure high transparency and image clarity when used in an environment of a light source having a steep emission peak, and a polarizing plate using the same. etc. is to be provided.

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, which has 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.

The laminated film of the present invention can suppress iridescence and ensure high transparency and image clarity when used in an environment of a light source having a sharp emission peak.

The laminated film preferably has an optically isotropic layer on the uneven surface of the substrate film having the uneven surface (roughened surface). In addition, when it is simply called a laminated film below, this shall be meant.
(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 preferable. 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 preferable. 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, but if the ΔRe of the base film is relatively low, or if the roughness of the uneven surface is relatively small, iridescence can be effectively suppressed. Therefore, it is preferable to make both surfaces of the base film uneven and to provide the optically isotropic layers 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

The laminated film of the present invention may further have various functional layers according to each application. Examples of various functional layers include a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, a conductive layer, an antistatic layer, a colored layer, an ultraviolet absorption layer, an antifouling layer, and an adhesive layer.

(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. When the optically isotropic layer is a layer having the function of a polarizing plate surface such as a hard coat layer or an antiglare layer, it is preferable to provide a polarizer on the substrate film surface.

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.

(Image display device)

The image display device preferably includes the polarizing plate described above.
The image display device preferably has a light source side polarizing plate, an image display cell, and a viewing side polarizing plate in this order. The above-described polarizing plate is preferably used as either the light source side polarizing plate or the viewing side polarizing plate of the display device, and it is also preferable to use it for both. The laminated film of the present invention is preferably used as a polarizer protective film on the opposite side of the image display cell.

The light sources (backlights) for liquid crystal display devices 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, and wavelength conversion using quantum dots. A light source, a semiconductor 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.

Also, the image display device may be an organic EL display device. The organic EL display device preferably has a circularly polarizing plate on the viewing side of the image display cell. The laminated film of the present invention can also be suitably used as a polarizer protective film for a 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. bottom.

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 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.

Example 1
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 is applied and dried to obtain an easy adhesion of about 30 nm. layer was established. Further, the coating agent a for the optically isotropic layer was applied thereon with an applicator, and then cured from the coated surface with a high-pressure mercury lamp to obtain a laminated film F1.

Examples 2-7, 9-14, and Comparative Examples 1-3
Laminated films F2 to F8 and F10 to F17 were obtained in the same manner as in Example 1, except that the type of surface-roughened film and/or coating agent was changed. Note that the laminated film F15 was provided with an optical isotropic layer on both sides.

Example 8
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 is applied and dried to obtain an easy adhesion of about 30 nm. layer was established. Furthermore, after applying the coating agent a for the optically isotropic layer on it with an applicator, a surface nickel-plated metal plate mold having a concave-convex structure provided on the coated surface to provide anti-glare properties is superimposed, and the substrate film is coated. A laminated film F9 having an antiglare property in the optically isotropic layer was obtained by curing from the surface with a high-pressure mercury lamp.

Example 15
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 layers of the obtained two laminate films were superimposed and passed between rolls heated to 100° C., and the two laminate films were bonded together so that the slow axes were parallel to each other. Byron 200 has a refractive index of 1.55.

(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

(character sharpness)
The laminated film was placed at a position 1 cm above the newspaper, and whether characters on the newspaper (about 3.8 mm long and about 3.9 mm wide) could be recognized was evaluated according to the following criteria. In addition, since anti-glare processing has an influence on the anti-glare processing, evaluation was not performed.
A: Characters were clearly recognized.
◯: Slightly blurred, but recognized without problems.
△: Kanji other than kanji with a large number of strokes could be recognized.
x: Recognition was difficult.

Table 4 shows the physical properties and evaluation results of the laminated films of Examples 1 to 15 and Comparative Examples 1 to 3.

(Manufacture of polarizing plate)
(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).

(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.

Example 16
After coating the uneven surface of the surface-roughened film A1 of 20 cm×30 cm with an applicator, the adhesive coating agent i as an optically isotropic layer was cured from the coated surface 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 into a size of 20 cm×30 cm were pasted together to form a polarizing plate P1. The transmission axis of the polarizer and the slow axis of the surface-roughened film (base film) were made parallel.

Comparative example 4
A polarizing plate P3 was obtained in the same manner as in Example 16, except that the optical adhesive sheet j was used as an optically isotropic layer on the uneven surface of the surface-roughened film A1.

Example 17
After coating the uneven surface of the 20 cm×30 cm surface-roughened film A1 with a coating agent k for adhesive as an optically isotropic layer using an applicator, it was dried at 100° C. to obtain a laminated film. Thereafter, a polarizing plate P2 was obtained in the same manner as in Example 16.

Examples 18, 19, and 20
The coating agent b for the optical isotropic layer was applied with an applicator to the uneven surface of the surface-roughened film A1 of 20 cm×30 cm. 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 P4.
A polarizing plate P5 or P6 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.

Table 6 shows the physical properties of the polarizing plates P1 to P6, the presence or absence of iridescence, and the sharpness of characters in the same manner as described above.

(Production of polarizing plate using laminated films F1 to F18)
An ultraviolet curable acrylic adhesive was applied to the surfaces of the optically isotropic layers of the laminated films F1 to F8 and F10 to F17 with an applicator. The polarizer surface of the TAC film laminated polarizer cut to 20 cm × 30 cm was superimposed on the coated surface, and the laminated film surface was irradiated with a high-pressure mercury lamp to be cured to obtain polarizing plates PF1c to PF8c and PF10c to PF17c.
In addition, polarizing plates PF1b to PF1b were prepared in the same manner as described above, except that the surfaces of the laminated films F1 to F14 and F16 to F18 on which the optically isotropic layer was not provided were coated with an ultraviolet-curing acrylic adhesive. PF114b, and PF16b-PF18b were obtained. The transmission axis of the polarizer and the slow axis of the base film were made parallel.

PF4b2 and PF5b2 were obtained in the same manner as above, except that the transmission axis of the polarizer and the slow axis of the base film were perpendicular to each other in the preparation of PF4b and PF5b.

(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.

(Manufacture of polarizing plate)
After bonding the adhesive layer surface of the laminated film used in the production of the polarizing plate of Example 17 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. P7 was obtained. A commercially available optical adhesive sheet was laminated on the polarizer surface of the polarizing plate P7. The transmission axis of the polarizer and the slow axis of the base film were made parallel.

An ultraviolet curable acrylic adhesive was applied to the optically isotropic layer surface of the laminated film F5 with an applicator. After the polarizer surface of the substrate-laminated polarizer is attached to this coated surface, light is irradiated from the surface of the laminate film F5 with a high-pressure mercury lamp, and the substrate of the substrate-laminated polarizer is peeled off to obtain a single-sided protective film polarizer P8. got A commercially available optical adhesive sheet was laminated on the polarizer surface of the polarizing plate P8. The transmission axis of the polarizer and the slow axis of the base film were made parallel.
A single-sided protective film polarizing plate P9 was obtained in the same manner as described above, except that the surface-roughened film A1 of the laminated film F9 was provided with an ultraviolet curable acrylic adhesive. A commercially available optical adhesive sheet was laminated on the polarizer surface of the polarizing plate P9. The transmission axis of the polarizer and the slow axis of the base film were made parallel.

Tables 7 and 8 summarize the physical properties and evaluation of these polarizing plates obtained from each laminated film. Evaluation criteria are as described later.

(Evaluation of liquid crystal display device)
The polarizing plates on the viewing side and the light source side mounted on a liquid crystal display device (REGZA Z20X manufactured by Toshiba Corp.) having a KSF light source were peeled off, and the resulting polarizing plates were bonded instead. In the case of a polarizing plate using a TAC film laminated polarizer, a commercially available optical adhesive sheet is laminated on the TAC surface, and in the case of a polarizing plate having a protective film on only one side, an optical adhesive sheet laminated on the polarizer surface is used. The adhesive sheet surface for the tape was pasted together. 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 △: Slight iridescence was observed ×: Iridescence was 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 adhered to the adhesive layer surface of the single-sided protective film polarizing plates P7 to P9 laminated with the above adhesive 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 can suppress iridescence and ensure high transparency and image clarity when used in an environment with a light source having a steep peak.

Claims (5)

A laminated film for use in an image display device having a light source using a KSF phosphor, the laminated film having a substrate film and an 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.)
(d) The plane orientation degree of the substrate film is 0.09 to 0.15.
(e) Bfnx of the base film is from 1.67 to 1.73.
(f) The base film is a polyester film. 2. The laminated film according to claim 1, wherein the in-plane retardation of the base film is 3000 to 30000 nm. 3. The laminated film according to claim 1, which is a polarizer protective film, a depolarizing film, a transparent conductive substrate film for a touch panel, or a scattering prevention film. A polarizing plate for use in an image display device having a light source using a KSF phosphor, the polarizing plate using the laminated film according to claim 1 or 2 as a polarizer protective film. An image display device comprising the polarizing plate according to claim 4 and having a light source using a KSF phosphor .