JP7238321B2 - 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 the problem that the screen is white and the image is difficult to see in an environment of low contrast and 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, an object of the present invention is to provide a transparent conductive film that can suppress iridescence and ensure high transparency and vivid image displayability when used in an environment of a light source having a steep emission peak. It is in.

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 transparent conductive film having a transparent conductive layer on at least one surface of a laminated film having a substrate film and an optically isotropic layer, which has the characteristics of the following (a) to (c).
(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 touch panel comprising the transparent conductive film according to Item 1.
Item 3.
Item 3. An image display device comprising the touch panel according to item 2. .

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

The present invention is a transparent conductive film having a transparent conductive layer on at least one surface of a laminated film having a refractive index anisotropic base film having an uneven surface (roughened surface) and an optically isotropic layer. . Hereinafter, the laminated film having the transparent conductive layer will be referred to as a transparent conductive film, and when simply referred to as the laminated film, it will be understood that the optically isotropic layer and the refractive index anisotropic base film having an uneven surface (roughened surface) are combined. means laminated film.
(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, even more preferably 3000 nm, particularly preferably 3500 nm, and 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 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 preferred. 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.

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.

In the case of the laminate film, only one side of the base film may be uneven, but if the ΔRe of the base film is relatively low or the roughness of the unevenness is relatively small, iridescence cannot be sufficiently eliminated. is preferably provided with an uneven surface and an optically isotropic layer on both sides.

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 to 4, the slow axes of the two base films are preferably parallel or perpendicular to each other, and 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

(Transparent conductive layer)
The transparent conductive layer is provided on at least one side of the laminated film, which may be the base film side or the optically isotropic layer side. It may be provided on both sides. Examples of transparent conductive layers include, but are not limited to, conductive paste mesh prints, carbon nanotube-containing coats, self-assembled nano-silver coats, acicular conductive filler-containing coats, and metal oxide thin films. Among them, metal oxide thin films are preferable, and thin films of indium oxide, zinc oxide, tin oxide, indium tin oxide (ITO), tin antimony oxide, zinc aluminum oxide, indium zinc oxide and the like are preferable.

It is preferable that the transparent conductive layer is formed into a pattern shape such as a line shape or a lattice shape by etching.

In the following, the most preferred ITO thin film will be described in detail as an example.
The thickness of the transparent conductive layer is preferably 5 to 500 nm, more preferably 15 to 250 nm, even more preferably 20 to 100 nm. Due to the above thickness, it is possible to suppress the tint caused by the conductive layer while ensuring conductivity.

The transparent conductive layer can be formed by known methods such as vacuum deposition, sputtering, CVD, ion plating, spraying and sol-gel.

After forming the transparent conductive layer, a resist mask having a predetermined pattern is formed by a photolithographic method, and then an etching treatment is performed to form a pattern or the like.

The transparent conductive layer may be amorphous, but the obtained transparent conductive layer is heat-treated at 130 to 180° C. for 0.5 to 2 hours to grow crystals to make the conductive layer crystalline and conductive. It is preferable to improve

It is also a preferred form to provide a hard coat layer and a refractive index adjusting layer as a lower layer of the conductive layer. The refractive index adjustment layer has the effect of making the pattern after etching difficult to see. The refractive index adjusting layer may be a layer (high refractive index layer) having a refractive index close to that of the conductive layer. position). In particular, it is preferable to provide the high refractive index layer and the low refractive index layer in this order.

(High refractive index layer)
The high refractive index layer may be provided directly on the base film and/or the optically isotropic layer, or via another film or layer (for example, easy adhesion layer, hard coat layer). The high refractive index layer is preferably a layer inside the low refractive index layer. The high refractive index layer may further have other functions and may be an optically isotropic layer.

The refractive index of the high refractive index layer is preferably 1.55 to 1.85, more preferably 1.56 to 1.80, even more preferably 1.56 to 1.75. The refractive index of the high refractive index layer is a value measured under the condition of a wavelength of 589 nm.

The thickness of the high refractive index layer is generally in the range of 20 to 2 μm. The thickness can be adjusted appropriately. When based on the concept of canceling the reflection at the interface with the thickness and refractive index of each refractive index layer, the thickness of the high refractive index layer is preferably 20 to 200 nm, more preferably 30 to 190 nm, more preferably 50 to 180 nm. preferable. Although the high refractive index layer may be a plurality of layers, it is preferably two layers or less, more preferably a single layer. In the case of a plurality of layers, it is preferable that the total thickness of the plurality of layers is the above thickness.

When two high refractive index layers are used, the refractive index of the high refractive index layer on the low refractive index layer side is preferably higher. Specifically, the refractive index of the high refractive index layer on the low refractive index layer side is The index is preferably 1.60 to 1.85, and the refractive index of the other high refractive index layer is preferably 1.55 to 1.70.

The high refractive index layer is preferably made of a resin composition containing the particles and resin mentioned in the optically isotropic layer. Among them, high refractive index particles include antimony pentoxide particles (1.79), zinc oxide particles (1.90), titanium oxide particles (2.3 to 2.7), cerium oxide particles (1.95), Tin-doped indium oxide particles (1.95 to 2.00), antimony-doped tin oxide particles (1.75 to 1.85), yttrium oxide particles (1.87), and zirconium oxide particles (2.10) are preferred. . The values in parentheses indicate the refractive index of the material of each particle. Among these, titanium oxide particles and zirconium oxide particles are preferred.

In one embodiment, two or more kinds of high refractive particles may be used in combination. In particular, it is also preferable to add the first high refractive index particles and the second high refractive index particles having a smaller surface charge amount to prevent aggregation. It is also preferable from the standpoint of dispersibility that the high refractive index particles are surface-treated.

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

The content of the high refractive particles is preferably 30 to 400 parts by mass, more preferably 50 to 200 parts by mass, and 80 to 150 parts by mass with respect to 100 parts by mass of the resin composition. More preferred.

In one embodiment, the high refractive index layer is preferably provided by a dry process such as vapor deposition or ITO film formation. For the dry process, a composite oxide containing Si and at least one selected from the group consisting of Ta, Nb, Zr and Ti is preferred. Examples thereof include a composite oxide of Nb and Si, a composite oxide of Ti and Si, a composite oxide of Zr and Si, a composite oxide of Ta and Si, and the like. When the high refractive index layer is provided by a dry process, the refractive index of the high refractive index layer is preferably 1.60 to 1.95, more preferably 1.65 to 1.90. In the dry process, the thickness of the high refractive index layer is preferably 5-50 nm, more preferably 10-40 nm.

The thickness of the high refractive index layer can be appropriately adjusted in both the wet process and the dry process, considering the refractive index and thickness of the low refractive index layer, the refractive index of the high refractive index layer, the thickness and refractive index of the transparent conductive layer, and the like. can.
(Low refractive index layer)
In one embodiment, it is preferable to further provide a low refractive index layer on top of the high refractive index layer. As a method of providing a low refractive index layer on a high refractive index layer, a method of coating a composition for a low refractive index layer on the high refractive index layer, or the like is preferable.

The refractive index of the low refractive index layer is preferably 1.50 or less, preferably 1.46 or less, preferably 1.45 or less, and 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.

Although the thickness of the low refractive index layer is not limited, it is preferably 5 to 120 nm, more preferably 10 to 100 nm, particularly preferably 15 to 70 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 low refractive index particles, (2) a layer made of a fluororesin that is a low refractive index resin, and (3) silica or magnesium fluoride. and (4) a thin film of a low refractive index substance such as silica and magnesium fluoride.

Examples of low refractive index particles include silica, magnesium fluoride, etc. Among them, hollow silica fine particles are preferable. Such hollow silica fine particles can be produced, for example, by the production method described in the 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.

Polyester, polyurethane, polyamide, polycarbonate and acryl can be used as the binder resin used when providing the high refractive index layer and/or the low refractive index layer by coating. 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 prepared and used. The photopolymerizable compound is preferably a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable polymer. Specifically, those mentioned as the optically isotropic layer can be used.

In one embodiment, the high refractive index layer and/or the low refractive index layer is formed by, for example, applying a resin composition containing the above fine particles and a photopolymerizable compound to a base film and/or an optically isotropic layer, followed by drying. After that, the resin composition in the form of a coating film is irradiated with light such as ultraviolet rays to polymerize (crosslink) the photopolymerizable compound.

A thermoplastic resin, a thermosetting resin, a solvent, and a polymerization initiator may be added to the high refractive index layer and/or 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.
- The low refractive index layer, the high refractive index layer, the hard coat layer, and the like do not use particles having a particle diameter exceeding 1/2 of the thickness of the low refractive index layer, or the amount thereof added is reduced.
- Reducing the surface roughness of layers (high refractive index layer, 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 base film and/or the optical isotropic layer, or via another film or 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 high refractive index layer, between the optically isotropic layer and the high 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 high 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.

Various functional layers may be provided on the surface of the laminated film of the present invention in accordance with each application. 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, 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.

In one embodiment, it is preferred to use the transparent conductive laminate film for a touch panel. Among them, it is preferably used for a capacitive touch panel.

When used as a touch panel, a touch sensor may be configured by combining two films provided with a transparent conductive layer only on one side, or the transparent conductive film of the present invention and a film such as TAC, COP, or general PET may be combined. It is good also as a structure of a touch sensor in combination with the transparent conductive film used as the base material. Furthermore, the transparent conductive film of the present invention may be combined with a transparent conductive layer provided on another component such as a surface cover glass to form a touch sensor. Also, a touch sensor may be configured by providing transparent conductive layers on both sides of the laminated film.

When the transparent conductive film of the present invention is laminated as a structure of a touch sensor, conventionally used pressure-sensitive adhesives and adhesives such as optical substrate-less pressure-sensitive adhesives, ultraviolet and thermosetting adhesives, and the like can be used without limitation. be able to.

The transparent conductive film can be used to prevent iridescence and coloration that occur when a liquid crystal display device or an organic EL display device provided with a circularly polarizing plate is viewed with polarized sunglasses. In this case, the angle formed by the transmission axis direction of the polarizer of the polarizing plate on the most visible side of the display device and the slow axis or fast axis of the base film of the laminated film is preferably 20 to 45 degrees. This angle is more preferably 25 to 45 degrees, more preferably 30 to 45 degrees, particularly preferably 35 to 45 degrees. If the above range is exceeded, there may be a large change in brightness (depending on viewing angle) when looking at the display device with the head tilted.

When using a combination of a general biaxially stretched PET film (retardation of 500 nm or more and less than 3000) and the transparent conductive film of the present invention as a base material for an anti-scattering film or a transparent conductive film, the transparent conductive film of the present invention and The arrangement order of a general biaxially stretched PET film is arbitrary.
When the transmission axis of the polarizer on the viewing side of the image display device is approximately 45 degrees with respect to the short side of the image display device, and the transparent conductive film is placed on the viewing side of the transparent resin molded product, the base of the laminated film The angle formed by the slow axis or fast axis of the material film and the transmission axis of the polarizer is preferably 20 degrees or less, more preferably 15 degrees or less, still more preferably 10 degrees or less.

When a plurality of general biaxially stretched PET films are used, it is preferable that the transparent conductive film of the present invention is provided on the most visible side or the most light source side. Such an arrangement can effectively prevent iridescence and coloration.

In the case of a VA type or IPS type liquid crystal display device or an organic EL display device, the transmission axis of the viewing side polarizer is generally parallel or perpendicular to the vertical direction (short side direction) of the screen. When the transparent conductive film is arranged in such a display device, the slow axis of the base film is preferably arranged at approximately 45 degrees (45 degrees ±10 degrees or less) with respect to the transmission axis of the polarizer.

In the case of a TN liquid crystal display device, the transmission axis of the viewer-side polarizer is generally set at approximately 45 degrees in the vertical direction (short side direction) of the screen. When the transparent conductive film is arranged on the side closest to the light source, the slow axis of the base film is preferably arranged at approximately 45 degrees (45 degrees ±10 degrees or less) with respect to the transmission axis of the polarizer. On the other hand, when the transparent conductive film is arranged on the most visible side, the slow axis of the base film is substantially parallel (0 degrees ± 10 degrees or less) or substantially perpendicular (90 degrees ± 10 degrees or less) to the transmission axis of the polarizer. is preferably
In the above, the most light source side and the most visible side refer to a general biaxially stretched PET film ( Retardation is 500 nm or more and less than 3000) means the side closest to the light source and the viewing side in the transparent conductive film of the present invention.

A touch panel using the transparent conductive film of the present invention is provided on the front surface of the display device. The display device is not particularly limited, and may be a liquid crystal display device, an organic electroluminescence display device, or the like. In the case of a liquid crystal display device, various light sources can be used without iridescence. Among them, a blue light emitting diode and a yellow phosphor light source, a light source using a KSF phosphor, a QD light source, and the like are preferable.

(Display device)

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.

Even when the display device including the transparent conductive film of the present invention has a light source having a steep emission peak, the rainbow spots are reduced to an unrecognizable level, and the light source has a narrow half width of the emission peak of each color. A combination with is a more preferable form. 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, even 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.

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.

(Production of laminated films F1 to F17)
(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 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.

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.

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.

Table 4 shows the structures and physical properties of the laminated films F1 to F17.

Examples 1 to 13 and Comparative Examples 1 to 3: Preparation of transparent conductive film having a transparent conductive layer on the optically isotropic layer surface A film roll was prepared by sticking one of them at intervals of about 20 m so that the optically isotropic layer surface faced up and winding it up. This film roll is placed in a take-up type sputtering device, and a 20 nm-thick indium tin oxide layer (0.4 Pa consisting of 98% argon gas and 2% oxygen) is used as a transparent conductive layer on the surface (optically isotropic layer surface). Sputtering using a sintered body composed of 97% by weight of indium oxide and 3% by weight of tin oxide) was laminated in an atmosphere, and then annealing was performed to crystallize the ITO layer to produce a transparent conductive film.

Examples 14-26, Comparative Examples 4-6
Peltron (TM) A-2005 (manufactured by Pelnox Co., Ltd.) was applied to the base film surfaces of the laminated films F1 to F17 and irradiated with ultraviolet rays to form a hard coat layer having a thickness of 5 μm. The resulting laminated film was attached to a biaxially stretched polyester film (A4300) manufactured by Toyobo Co., Ltd. so that the base film surface (hard coat surface) was facing up, and the surface (hard coat surface) was applied in the same manner as in Example 1. ) was provided with a transparent conductive layer to prepare a transparent conductive film.

Example 25
A high refractive index layer A (OPSTAR KZ6728 (manufactured by Arakawa Chemical Co., Ltd.) with a refractive index of 1.74) was provided on the optically isotropic layer surface of the laminated film F4 so as to have a thickness of 1.5 μm. Then, in the same manner as in Example 1, a transparent conductive layer was provided on the surface (high refractive index layer A) to produce a transparent conductive film.

Example 26
A hard coat layer was provided on the base film surface of the laminated film F5 in the same manner as in Example 14, and a high refractive index layer A was provided on the hard coat layer surface so as to have a thickness of 1.5 μm. Then, in the same manner as in Example 1, a transparent conductive layer was provided on the surface (high refractive index layer A) to produce a transparent conductive film.

Example 27
A low refractive index layer C (OPSTAR TU-2362 (manufactured by Arakawa Chemical Co., Ltd.) with a refractive index of 1.40) was provided on the optically isotropic layer surface of the laminated film F7 so as to have a thickness of 10 nm. Then, in the same manner as in Example 1, a transparent conductive layer was provided on the surface (low refractive index layer C) to produce a transparent conductive film.

Example 28
A transparent conductive film was produced in the same manner as in Example 25, except that the low refractive index layer C was provided on the high refractive index layer A so as to have a thickness of 10 nm.

Example 29
A transparent conductive film was produced in the same manner as in Example 26, except that the low refractive index layer C was provided on the high refractive index layer A so as to have a thickness of 10 nm.

Example 30
A high refractive index layer B (Opstar Z7415 (manufactured by Arakawa Chemical Co., Ltd.) refractive index 1.65) is provided on the base film surface of the laminated film F5 so as to have a thickness of 150 nm, and a low refractive index layer C is further provided thereon to have a thickness of 30 nm. was set to be Then, in the same manner as in Example 1, a transparent conductive layer was provided on the surface (low refractive index layer C) to produce a transparent conductive film.

Example 31
A hard coat layer was provided on the base film surface of the laminate film F5 in the same manner as in Example 14, and a high refractive index layer B was provided on the hard coat layer surface so as to have a thickness of 150 nm. A film is formed on the high refractive index layer B by a sputtering method using a silicon target doped with boron in a mixed atmosphere of 80% by volume of argon gas and 20% by volume of nitrogen gas. A refractive index layer (refractive index: 1.90, thickness: 10 nm) was provided, and then sputtering was performed using a silicon target doped with boron in a mixed atmosphere of 95% by volume of argon gas and 5% by volume of oxygen gas. and a low refractive index layer (refractive index (n3): 1.46, thickness: 30 nm) made of silicon oxide. Furthermore, a transparent conductive layer was provided on this low refractive index layer in the same manner as in Example 1 to prepare a transparent conductive film.

(Evaluation of transparent conductive film)
(Observation of rainbow spots)
A transparent conductive film is placed between two polarizing plates arranged in crossed Nicols so that the slow axis of the base film is at 45 degrees with the transmission axis of the polarizing plate on the light source side, and the transparent conductive layer is on the viewing side. , the state of transmitted light was observed from the front about 60 cm away from the polarizing plate on the viewing side, and the presence or absence of rainbow spots 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 transparent conductive film was irradiated with a halogen lamp from below, and the degree of whitening of the transparent conductive film was evaluated from an obliquely upward direction of 45 degrees according to the following criteria. The transparent conductive film was arranged so that the transparent conductive layer faced upward.
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.

(bone visible)
The transparent conductive layer of the transparent conductive film was patterned by etching into stripes with a conductive layer of 1 mm and an interval of 1 mm. The resulting patterned transparent conductive film was placed on black paper and irradiated with a halogen lamp from above to evaluate whether the pattern could be confirmed.
A: No pattern was observed.
○: The pattern was slightly visible △: The pattern was clearly visible

Table 5 shows the structure, physical properties, and evaluation results of the transparent conductive film.

１＊：積層フィルム番号
２＊：粗面化フィルム番号
３＊：凹凸面
４＊：光学等方性層コート剤
５＊：光学等方層屈折率
６＊：透明導電層を設けた表面
７＊：ハードコート層の有無
８＊：虹斑評価
９＊：白化評価
１０＊：高屈折率層の有無
１１＊：低屈折率層の有無
１２＊：骨見え

1*: laminated film number 2*: roughened film number 3*: uneven surface 4*: optically isotropic layer coating agent 5*: optically isotropic layer refractive index 6*: surface provided with transparent conductive layer 7* : Presence or absence of hard coat layer 8 *: Iridescent evaluation 9 *: Whitening evaluation 10 *: Presence or absence of high refractive index layer 11 *: Presence or absence of low refractive index layer 12 *: Bone visible

The transparent conductive film of the present invention can suppress iridescence and ensure high transparency and vivid image displayability when used in an environment of a light source having a sharp peak.

Claims (7)

A transparent conductive film having a transparent conductive layer on at least one surface of a laminated film having a substrate film and an optically isotropic layer, which has the following characteristics (a) to ( h ).
(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 substrate 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 transparent conductive film according to claim 1, wherein the substrate film has a plane orientation degree (ΔP) of 0.09 to 0.15. 3. The transparent conductive film according to claim 1, wherein the optically isotropic layer has a refractive index of Bfny to Bfnx. 4. The transparent conductive film according to claim 1, wherein the optically isotropic layer has a refractive index of Bfny+0.02 to Bfnx. A touch panel comprising the transparent conductive film according to any one of claims 1 to 4. An image display device comprising the touch panel 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.