JP2013114141A - Obliquely oriented polarizing film and elliptical polarizing plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an obliquely oriented polarizing film, which can maintain high durability even under high temperature and high humidity conditions, has an absorption axis obliquely oriented with respect to the flowing direction of the film, thereby, enables production of an elliptical polarizing plate by laminating with a retardation compensation film by a roll-to-roll method.SOLUTION: The polarizing film contains a polarizing material composed of metal-plated nanowires obtained by forming a metal plating layer having a thickness of 1 to 15 nm on the surfaces of nanowires composed of a dielectric material having an average thickness of 10 to 300 nm and an average length of 0.4 μm or more. The polarizing material is oriented in substantially the same direction within a range of 5 to 80° with respect to the flowing direction of the polarizing film, and thereby, the direction of the absorption axis of the polarizing film is obliquely oriented in substantially the same direction within a range of 5 to 80° with respect to the flowing direction.

Description

  The present invention relates to an obliquely oriented polarizing film using metal-plated nanowires as a polarizing material and an elliptically polarizing plate using the same.

  Currently, a polarizing plate for liquid crystal display or the like is used for a flat panel display such as a liquid crystal display. As the polarizing plate, what is generally called an absorption-type polarizing plate is widely used. This is obtained by orienting an anisotropic dye on the film. Specifically, a water-absorbing polyvinyl alcohol (PVA) film is impregnated with a water-soluble iodine compound and then stretched, and further boron is added. After crosslinking with an acid or the like, it is produced by laminating a protective film such as triacetyl cellulose (TAC). And at the time of extending | stretching, in order to provide a high degree of polarization to a polarizing plate, it is necessary to perform extending | stretching accompanying necking of about 5-6 times normally. Therefore, the polarizing plate currently marketed has an extending | stretching axis | shaft (= absorption axis) in the flow direction (The flow direction at the time of film forming = The film advancing direction in FIG.4 and FIG.6).

  In a flat panel display such as a liquid crystal display, a polarizing plate is rarely used alone, and may be used in combination with a retardation compensation film for the purpose of compensating birefringence of light that has passed through a liquid crystal cell or the like. Many. And the member which combined the polarizing plate and the phase difference compensation film is generally called the "elliptical polarizing plate" or the "circular polarizing plate".

  Here, the polarizing plate and the retardation compensation film are often laminated at a specific angle. For example, a “circular polarizing plate” can be obtained by laminating so that the slow axis of the retardation compensation film is arranged at an angle of 45 ° with respect to the absorption axis of the polarizing plate. It can be widely used for the application of electrode antireflection for organic EL displays.

  Patent documents 1 and 2 etc. are publicly known as prior art about a general elliptically polarizing plate.

JP 2007-155970 A Japanese Patent Laid-Open No. 10-186131

The conventional elliptically polarizing plate (circularly polarizing plate) has the following problems.
(1) Dyes such as iodine compounds used in conventional elliptically polarizing plates have low heat resistance, fading under high temperature conditions and lowering the polarization performance.
(2) Since the PVA film is stretched at a high magnification, the polarizing performance may be reduced by shrinking under high temperature conditions, or birefringence may occur in the protective film and light leakage may occur in the flat panel display. is there.
(3) Since the hygroscopicity of the PVA film and the TAC film is large, when these films absorb moisture, the elliptically polarizing plate is easily curled.
(4) Since the absorption axis of the polarizing plate exists in the flow direction, when laminating so that the slow axis of the retardation compensation film is oblique to the absorption axis of the polarizing plate, the slow axis of the retardation compensation film Since generally exists only in the longitudinal direction or the width direction, it is necessary to laminate the retardation compensation film obliquely with respect to the polarizing plate. That is, it cannot be efficiently laminated by roll-to-roll. Although some retardation compensation films having a slow axis oriented obliquely have been commercialized, they are not practical in terms of poor production efficiency and high cost.

  Based on the above, the present invention can maintain high durability even under high temperature and high humidity conditions, and the absorption axis is obliquely oriented with respect to the flow direction, so that the retardation compensation film and the roll to roll are laminated. An object of the present invention is to provide a diagonally oriented polarizing film film that can produce an elliptically polarizing plate. Another object of the present invention is to provide an elliptically polarizing plate obtained by laminating the obliquely oriented polarizing film and the retardation compensation film in a roll-to-roll manner.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have obtained a diagonally-oriented polarizing film obtained by obliquely orienting a polarizing material, which is a specific metal-plated nanowire, with respect to the flow direction. The inventors have found that the object can be achieved and have completed the present invention.

That is, the present invention relates to the following obliquely oriented polarizing film and an elliptically polarizing plate using the same.
1. Polarizing material, which is a metal-plated nanowire obtained by forming a metal plating layer having a thickness of 1 to 15 nm on the surface of a nanowire made of a dielectric material having an average thickness of 10 to 300 nm and an average length of 0.4 μm or more A polarizing film containing
When the polarizing material is oriented in substantially the same direction within a range of 5 to 80 ° with respect to the flow direction of the polarizing film, the direction of the absorption axis of the polarizing film is relative to the flow direction. An obliquely oriented polarizing film that is obliquely oriented in substantially the same direction within a range of 5 to 80 °.
2. An elliptically polarizing plate formed by laminating a retardation compensation film on one side or both sides of the obliquely oriented polarizing film according to Item 1,
(1) The flow directions of the two types of films are the same,
(2) The retardation compensation film has a slow axis in its longitudinal direction or width direction.
Elliptical polarizing plate.
3. Item 3. The phase difference compensation film according to Item 2, wherein the retardation compensation film is made of at least one material selected from the group consisting of triacetylcellulose, norbornene, (meth) acryl, polyimide, polycarbonate, polysulfone, polystyrene, and polyethersulfone. Elliptical polarizing plate.
4). Item 4. The elliptically polarizing plate according to Item 2 or 3, wherein a protective film mainly composed of polyethylene terephthalate or polyethylene is laminated on one side or both sides.
5. 5. An elliptically polarizing plate roll obtained by winding the elliptically polarizing plate according to item 4 into a roll shape.
6). 6. A liquid crystal display device, an organic EL display device or an elliptically polarized sunglasses for 3D display using the elliptically polarizing plate according to any one of items 2 to 5.

  Hereinafter, the relationship between the metal nanowire and the polarizing property will be described first, and then the polarizing material (metal-plated nanowire) used in the present invention, the obliquely oriented polarizing film film and the elliptically polarizing plate of the present invention will be described.

The relational light between the metal nanowire and the polarizing property can be divided into two polarized lights (referred to as p-polarized light and s-polarized light in this specification) that vibrate in directions perpendicular to each other in a plane perpendicular to the traveling direction. The polarizing film has a function of transmitting one of the two polarized lights and blocking (absorbing or reflecting) the other polarized light.

  Recently, it has been reported that a rod-like metal having a nanometer size in width and length exhibits anisotropy with respect to electromagnetic waves such as light. A rod-shaped metal having a length of 1 μm or more is sometimes referred to as a metal nanowire, and a rod-shaped metal having a length of less than 1 μm is sometimes referred to as a metal nanorod. In the present specification, both are collectively referred to as a rod-shaped metal having a length of 0.4 μm or more. Is called a metal nanowire.

  Hereinafter, light will be described as an example of electromagnetic waves.

  Consider a case where the length of the metal nanowire is longer than the wavelength of light and the width is sufficiently narrower than the wavelength of light. When light enters the metal nanowire, polarized light having an electric field vibration plane in the length direction of the metal nanowire is absorbed or reflected by vibrating the free electrons of the metal nanowire. On the other hand, polarized light having an electric field vibration plane in the width direction of the metal nanowire is transmitted because the free electrons of the metal nanowire are less likely to oscillate in resonance with light (exactly speaking, the expression “scatter forward”) is correct. It is simply called “transmitting”.)

  The reason why metal absorbs or reflects light is that light is an electromagnetic wave, and free electrons in the metal vibrate in resonance with the electric field of light, so that the energy of light changes to kinetic energy. Therefore, in order for the metal to absorb or reflect light, a width of the metal that allows free electrons in the metal to vibrate in a direction perpendicular to the light traveling direction is necessary.

  According to Mie's theory and Rayleigh's scattering theory, it is considered that when the width of the metal is about 10 nm or less, free electrons cannot vibrate, and light is not absorbed or reflected and transmitted. Conversely, if the width of the metal is equal to or greater than the wavelength of light, it is considered that the metal is efficiently absorbed or reflected. Therefore, in the case of metal nanowires, it is considered that a good polarizing material is obtained if the length is longer than the wavelength of light and the width is about 10 nm or less.

  Next, the difference in light absorption and reflection when the length of the metal nanowire is longer than the wavelength of light and the width is about 10 nm will be described with reference to FIG. Note that light whose electric field vibration plane matches the length direction of the metal nanowire is s-polarized light, and light whose electric field vibration plane matches the width direction of the metal nanowire is p-polarization. FIG. 1 shows the relationship between the vibration direction of the electric field of s-polarized light and p-polarized light, and the length direction, width direction, and thickness direction of the metal nanowire when square columnar metal nanowires are arranged perpendicular to the light traveling direction. It is shown.

  The p-polarized light does not vibrate free electrons of the metal nanowire if the width of the metal nanowire is about 10 nm or less. Therefore, regardless of the length and thickness of the metal nanowire, p-polarized light is transmitted without being absorbed or reflected.

  The s-polarized light vibrates the free electrons of the metal nanowire if the length of the metal nanowire is longer than the wavelength of light. At this time, light is absorbed or reflected even if the width is 10 nm or less. Whether light is absorbed or reflected depends on the thickness of the metal nanowire.

  The thickness at which the intensity of incident light is 1 / square of the natural logarithm (= about 1 / 7.5) is called “skin depth”, and the skin depth is 1/2 of (2 / ωμσ). It is. Is the angular frequency of light, μ is the permeability of the metal, and σ is the conductivity of the metal.

Therefore, in the case of visible light having a wavelength of 500 nm, ωμ is 4.7 × 10 ⁹ and is substantially constant, and the metal conductivity σ (S / m) is silver: 61 × 10 ⁶ , aluminum: 40 × 10 ^6. Since nickel: 15 × 10 ⁶ and tantalum: 8 × 10 ⁶ , the skin depths are silver: 2.7 nm, aluminum: 3.5 nm, nickel: 4.1 nm, and tantalum: 5.3 nm, respectively.

That is, when light is incident on a highly conductive metal having a conductivity of about 8 × 10 ⁶ S / m or more, the light is absorbed if the thickness is about 4 to 5 nm. On the other hand, if the thickness is twice or more (10 nm or more), after absorbing light on the surface, the electromagnetic field causes an opposite current in the lower layer of the metal to generate reflected light, and light reflection occurs. That is, if the thickness of the metal nanowire is about 5 nm, it is absorbed, and if the thickness is about 10 nm, it is reflected. This is the same even when the shape of the metal nanowire is changed from a quadrangular column to a polygonal column.

  Considering the depth of the metal skin, it can be seen that if the length of the metal nanowire is 400 nm (0.4 μm) or more and the thickness is 5 nm or less, p-polarized light is transmitted and s-polarized light is absorbed. It can also be seen that when the length is 400 nm (0.4 μm) or more and the thickness is about 10 nm, p-polarized light is transmitted and s-polarized light is reflected. Therefore, a polarizing film can be obtained by orienting metal nanowires of this size in substantially the same direction.

  However, in order to increase the polarization and orientation, the metal nanowires are required to be straight. However, almost all methods for producing metal nanowires with a width of several nanometers and good linearity and good productivity are known. Absent. In addition, the thinner the metal nanowires, the more bent and agglomerated during handling, and there is a problem in production.

  Therefore, in the present invention, instead of the metal nanowire, a metal plating layer having a thickness of 1 to 15 nm is formed on the surface of the nanowire made of a dielectric material having an average thickness of 10 to 300 nm and an average length of 0.4 μm or more. The metal plating nanowire obtained by this is used as a polarizing material. With this metal-plated nanowire, a dielectric having an average thickness of 10 to 300 nm and an average length of 0.4 μm or more can be manufactured with good linearity with good productivity. Good metal-plated nanowires can be produced with high productivity. Moreover, by forming a metal plating layer having a thickness of 1 to 15 nm, a polarizing film that transmits light in the thickness direction and absorbs light in the length direction can be obtained, and can be used as a polarizing material. . Furthermore, the metal plating layer is a substitute for a conventional dye (means for expressing the polarization), and a polarizing film having excellent heat resistance can be provided.

Polarizing material used in the present invention The polarizing material used in the present invention is a metal plating having a thickness of 1 to 15 nm on the surface of a nanowire made of a dielectric having an average thickness of 10 to 300 nm and an average length of 0.4 μm or more. It is a metal-plated nanowire obtained by forming a layer.

  In the present invention, a nanowire made of a dielectric material having an average thickness of 10 to 300 nm and an average length of 0.4 μm or more is used. The “average” is an average value of thickness and length when 10 nanowires are arbitrarily selected from an electron microscope image.

  The average thickness of the dielectric is 10 to 300 nm, preferably 50 to 200 nm. When the dielectric is cylindrical or pseudo-cylindrical, the thickness = thickness. Otherwise, for example, the thickness = thickness even when the polygonal column or the polygonal column is twisted. . The length of one side of the polygonal column is preferably sufficiently shorter than the wavelength of light.

  The aspect ratio of the dielectric is not limited, but is preferably 10 or more. When the length of the dielectric exceeds 20 μm, the linearity of the dielectric may be easily lost. On the other hand, when the aspect ratio is less than 10, the polarization and orientation may be lowered.

  As nanowires made of a dielectric, nanowires of (meth) acrylic resin, nanowires of silica, etc. are synthesized as nanowires obtained by electrospinning. Moreover, nanowires, such as an alumina, are synthesize | combined as a nanowire obtained by a gaseous-phase method. In addition, in Langmuir, 2004, 20 (11), 4784-4786 and Crystal Growth and Design, 2006, 6 (6), 1504-1508, nanowires obtained by the hydrothermal method have a thickness of 30-120 nm. A nanowire of hydroxyapatite or fluoroapatite having a length of several μm to 50 μm (both have a refractive index of about 1.64) has been reported. Furthermore, in Langmuir, 2007, 23 (19), pages 9850 to 9859, a method for synthesizing boehmite nanowires (refractive index of about 1.7) is reported.

  In addition, as nanowires made of dielectrics, nanowires made of oxides or hydroxides of silicon, aluminum, etc., magnesium, aluminum, calcium, zinc and potassium metal phosphates, sulfates, borates, Nanowires made of silicate or phenyl phosphate are also known.

  In this invention, it is not limited to these dielectrics, If it is a nanowire whose refractive index (nd) of a dielectric material is 1.47-2.2, it can be used conveniently. Among these, the refractive index (nd) is more preferably 1.47 to 1.8. In the present invention, among these dielectrics, (meth) acrylic resins such as poly (meth) methyl acrylate, calcium carbonate, fluoroapatite, potassium titanate, magnesium sulfate, and the like can be particularly preferably used.

  When the dielectric is made of crystal, it usually has a polygonal column shape or a shape in which the polygonal column is twisted. Therefore, if necessary, the surface of the dielectric may be coated with the same or different dielectric having the same refractive index, and may be used after forming a cylindrical or quasi-cylindrical nanowire with a curved surface. . In this case, the nanowires after coating have an average thickness of 10 to 300 nm, an average length of 0.4 μm or more, and preferably an aspect ratio of 10 or more.

  Specifically, the dielectric has a core layer and a coat layer formed on the surface thereof, the core layer has a refractive index of 1.47 to 2.2, and the coat layer has a refractive index of the core layer. The refractive index is nc, and is preferably within nc ± 0.4. Among these, the refractive index (nc) of the core layer is more preferably 1.47 to 1.8, and the refractive index of the coat layer is more preferably within nc ± 0.2.

  Examples of the coating layer include, but are not limited to, those obtained by depositing the same compound as the core layer by shortening the time so that the crystallization time is not spent in the same precipitation reaction.

  As the core layer, for example, (meth) acrylic resin, silicon resin and the like are preferable. If necessary, a core layer may be formed by adding a crosslinking agent (for example, a titanium-based crosslinking agent or a zirconium-based crosslinking agent) to (meth) acrylic resin, silicon resin, or the like. By adding a crosslinking agent, the refractive index of the core layer can be adjusted, and the orientation of the finally obtained polarizing material can be increased.

  J.Am.Chem.Soc., 2005 is the production of nanowires with a curved surface by forming a coating layer with amorphous resin such as (meth) acrylic resin or silicon resin on the surface of the core layer. , 127 (46), 16040-16041, Crystal Growth and Design, 2006, 6 (11), 2422-2426, J. Phys. Chem. B, 2006, 110 (2), 807-811, etc. It is described in. Further, it is possible to form a coating layer using silica in J. Phys. Chem. B, 2005, 109 (1), pages 151 to 154 and J. Phys. Chem. B, 2006, 110 (2). Pp. 807-811.

  The metal plating layer formed on the surface of the nanowire made of a dielectric is preferably formed by electroless plating. Metals to be electrolessly plated are: 1) those that are likely to precipitate due to reactions in the liquid layer, 2) those that are difficult to corrode, and 3) those that are difficult to corrode by forming a passive layer or a protective layer equivalent thereto on the surface. Preferably there is.

  The metal used for the metal plating layer is preferably at least one of nickel, chromium, zinc, tantalum, niobium, silver, iron and aluminum. Among these, at least one of nickel, chromium, zinc, tantalum, niobium, and aluminum is more preferable from the viewpoint of ensuring the non-coloring property of the metal plating layer. Particularly regarding aluminum plating, it is reported in Chem. Mater. 2006, 18, 1634 that cyclopentadienylaluminum is deposited in mesitylene by thermal decomposition, and aluminum plating may be performed in this reaction solution.

  The thickness of the metal plating layer may be 1 to 15 nm, and preferably 1 to 10 nm. When the surface of the metal plating layer is covered with a passive film, the thickness of the passive film is preferably thinner than the thickness of the metal plating layer. The total thickness of the metal plating layer and the passive film is preferably not more than twice the thickness of the metal plating layer. In addition, when forming a passive film intentionally, it can form by heating metal plating nanowire in a solvent, or surface-treating with an oxidizing agent.

  When forming a metal plating layer with a thickness of several nanometers, it is difficult to obtain a uniform metal plating layer by using a plating solution that has a high affinity with the metal and agglomerating the metal in the solvent. It has been known. In this regard, J.Phys.Chem.B, 2004, 108 (28), 9745-9975, J.Phys.Chem.C, 2008, 112 (11), 4042-4048, about several nm. In the case of forming a metal plating layer, it has been reported that it is preferable to use a solvent having a low coordination property or to make the reaction near the boiling point of the solvent. Therefore, it is preferable to select such a solvent or to perform metal plating after increasing the affinity with the metal by treating the surface of the nanowire with a coupling agent.

  In the present invention, if necessary, the surface of the metal-plated nanowire may be further coated with a dielectric film having a thickness of 50 nm or less. The dielectric used for the coating preferably has a refractive index within ± 0.4 with respect to nd, more preferably within nd ± 0.2. As the coating material, for example, a copolymer obtained by hydrolyzing alkoxysilane and alkoxyzirconium with acid or alkali, and a copolymer obtained by hydrolyzing alkoxysilane and alkoxyzirconium with acid or alkali. Examples thereof include a copolymer of alkoxysilane and alkoxyzirconium obtained. As described above, when the surface of the metal-plated nanowire is further coated with a dielectric coating, the refractive index of the polarizing material can be adjusted and the orientation of the polarizing material can be further improved.

  The polarizing material of the present invention can be used as a polarizing film by dispersing and orienting it in a resin having a refractive index (nr) within nd ± 0.4. The refractive index (nr) is more preferably within nd ± 0.2.

  The content of the polarizing material when dispersed in the resin is preferably about 10 to 70% by weight, more preferably about 30% to 50% by weight, with the total amount of the resin and the polarizing material being 100% by weight. Moreover, in order to orient efficiently after making it disperse | distribute in resin, it is preferable to uniaxially stretch after dispersion | distribution. Thereby, a polarizing film is obtained.

  The optical behavior of the polarizing material of the present invention is as follows.

  If the length of the polarizing material is equal to or longer than the wavelength of light, the s-polarized light is absorbed or reflected by free electron vibration in the metal plating layer and does not pass through. In p-polarized light, if the thickness of the metal plating layer is sufficiently shorter than the wavelength of light, the movement of free electrons in the metal plating layer does not occur, and the metal exhibits an optical behavior similar to that of a dielectric. Scattered by dipole vibrations of electrons bound to molecules. In this case, it is necessary to confirm whether or not the scattering becomes forward scattering (= transmission). Further, since this light is similarly scattered in the internal dielectric layer, it is necessary to confirm the scattering direction. Hereinafter, the scattering direction will be verified.

  In the dipole vibration caused by the electrons in the molecule, the same light as the incident light is elastically scattered. Light travels straight in the uniform layer, but at the interface of materials having different dielectric constants, reflected light or evanescent waves are generated when the interface is a plane sufficiently larger than the wavelength of light. This is based on the fact that molecular groups resonate and dipole vibrate at an interface having a length corresponding to the wavelength across the interface.

  However, in the case of p-polarized light, since there is no interface length corresponding to the wavelength in the thickness direction of the metal-plated nanowire, reflected light and evanescent waves do not occur. Therefore, for the p-polarized light, the direction of light passing through the metal-plated nanowire can be examined.

  Hereinafter, it is considered that the polarizing material (metal plated nanowire) of the present invention is dispersed and oriented in the resin, and the polarizing material is composed of a dielectric layer (one dielectric layer) and a metal plated layer. Direction = wave direction normal direction (unit vector is represented by s) is confirmed with reference to FIG.

In FIG. 2, light proceeds in the order of resin layer (1) → boundary a → metal plating layer (2) → boundary b → dielectric layer (3), and the magnetic field in the resin layer (1) is changed to H ₁ . The velocity is v ₁ , the refractive index is n ₁ , the wavefront normal unit vector is s ₁ , the magnetic field in the metal plating layer (2) is H ₂ , the speed of light is v ₂ , the refractive index is n ₂ , and the wavefront normal is S ₂ , the magnetic field in the dielectric layer (3) is H ₃ , the speed of light is v ₃ , the refractive index is n ₃ , the wavefront normal unit vector is s ₃ , the time is t, and the boundary a Assume that the position vector is r _a and the position vector of the boundary b is r _b . At this time, the magnetic field _{H 1} of the resin layer (1) of the boundary a, respectively magnetic field of _{H 2} in the metal plating layer (2) is _{H 1 = H 01 expiω (t} -r a · s 1 / v 1) and H ₂ = H ₀₂ expω (t−r _a · s ₂ / v ₂ ).
Since the tangential component and normal component of the magnetic field component at the boundary a are continuous,
s ₁ / v ₁ = s ₂ / v ₂ and for this, s _1x / v ₁ = s _2x / v ₂
From v ₁ n ₁ = v ₂ n ₂ , s _1x / s _2x = sin θ ₁ / sin θ _{2 is changed} to n ₁ sin θ ₁ = n ₂ sin θ ₂ , the amplitude remains unchanged, and the traveling direction is refracted in the same manner as Snell's law.
Similarly, at the boundary b, the amplitude does not change,
n ₃ sin θ ₃ = n ₂ sin θ ₂ = n ₁ sin θ ₁
If n ₃ = n ₁ , θ ₃ = θ ₁ , and the light incident on the metal-plated nanowire does not change the light intensity or the light traveling direction before and after the metal plating layer (2). Similarly, the light that exits in the order of the dielectric layer (3) → the metal plating layer (2) → the resin layer (1) does not change in intensity or traveling direction. Accordingly, the p-polarized light is transmitted through the metal-plated nanowire while maintaining the traveling direction. This is based on the fact that forward scattering occurs because no reflection occurs.

  Furthermore, when a passive film having a thickness of several nanometers with low light absorption is present on the surface of the metal plating layer, the thickness of the film can be regarded as constant. If the refractive index of the resin layer and that of the dielectric layer are the same, the amplitude and traveling direction of the light will not change, and p-polarized light will be transmitted. That is, s-polarized light is absorbed or reflected, and p-polarized light is transmitted.

  In order to increase the degree of polarization, it is better that the width w in the vibration direction of the p-polarized light in FIG. 2 is as short as possible. Therefore, w is preferably 100 nm or less. Among these, if the metal plating layer is thin and the side surface of the nanowire faces in all directions, the thickness of the nanowire is 200 nm or less, the average value of w is sufficiently shorter than 100 nm, and the degree of polarization required as a polarizing film is achieved. I think that.

The paint for producing a polarizing film and the paint for producing an obliquely oriented polarizing film film of the present invention contain the above polarizing material and contain at least one of a resin binder, a solvent and the like for use as a paint.

  As a method for orienting metal nanowires with high productivity, Japanese Patent Application Laid-Open No. 2008-279434 discloses an alignment coating method for metal nanowires. In the present invention, a coating material is applied using this coating method, and a polarizing material is applied. It is preferable to orient on the substrate. In addition, it is preferable to use the board | substrate which can peel the polarizing film obtained by coating as a board | substrate. Such a substrate is required to have surface smoothness and heat resistance against drying heat, and examples thereof include polyethylene terephthalate and polyethylene naphthalate.

  In the above coating method, a coating material containing a polarizing material is applied with a coating bar, and in order to orient the polarizing material, the Brownian motion of the polarizing material during coating needs to be gentle. It is. Here, the Brownian motion is gentler as the polarizing material is heavier and longer.

  The polarizing material used in the present invention is small in both size and specific gravity. Therefore, for efficient orientation, it is preferable to use a paint having a viscosity of at least several hundreds mPa · s in which a thickening resin is dissolved for the purpose of suppressing Brownian motion. In this case, the resin for thickening becomes a resin layer surrounding the polarizing material in the coating film after the coating film is dried. In order to improve the transmittance of p-polarized light, the refractive index of this resin layer is preferably within ± 0.4, and within ± 0.2, as described above, with respect to the refractive index nd of the nanowire. Is more preferable. The refractive index of the resin layer is, for example, 1.47 by using a (meth) acrylic resin or an acrylamide resin as a main component and using a crosslinking agent (for example, a titanium-based crosslinking agent, a zirconium-based crosslinking agent, etc.) as necessary. It can be adjusted to ~ 2.2.

  Preferably, a viscosity of 300 mPa · s or more is obtained by adding a (meth) acrylic resin or an acrylamide resin to a solvent having a boiling point of 150 ° C. or less and, if necessary, a crosslinking agent (for example, a titanium-based crosslinking agent, a zirconium-based crosslinking agent). A polarizing material is dispersed in the obtained resin solution to obtain a paint.

And when applying the above-mentioned paint to a substrate by a bar coating method using a coating bar,
(1) The coating is performed under the condition that the contact length P between the circumferential portion of the coating bar and the substrate film is P ≧ 1000 × L (L: average length of metal-plated nanowires). Coating,
(2) The coating bar is provided with a groove evenly at least in a region where the coating bar and the base film are in contact, and the width W of the groove is 50 × φ ≦ W ≦ 10000 × φ. (Φ: average thickness of metal-plated nanowires) is preferable.

  The groove width W needs to be sufficiently wider than the average thickness of the metal-plated nanowires. However, if the groove width is too wide or the contact length P is short, the orientation becomes insufficient.

  In the present invention, as the coating bar provided with the groove, a wire having a certain diameter is tightly wound around the surface of the coating bar (so-called “wire bar”), or on the surface of the coating bar itself. A groove (so-called “Meyer bar”) in which grooves having a certain width and depth are provided at a certain pitch is used. In addition, about a wire bar, the clearance gap between adjacent wires turns into a groove | channel.

  The groove is set such that the width W of the groove is 50 × φ ≦ W ≦ 10000 × φ (φ: average thickness of metal-plated nanowires). If 50 × φ> W, the average thickness φ × 50 of the metal-plated nanowires becomes larger than the width W of the groove, and the short axis of the metal-plated nanowires does not enter the groove, so that it cannot be oriented. Further, when W> 10000 × φ, the short axis of the metal-plated nanowire is difficult to be oriented. When the width W of the groove satisfies the above condition, a shear flow occurs in the metal plated nanowire in each groove, and the metal plated nanowire is oriented in the coating direction (substantially the same direction). The depth of the groove is not particularly limited as long as it is larger than the average thickness φ of the metal-plated nanowire.

  In the present invention, the contact length P between the circumferential portion of the coating bar and the base film is set so as to satisfy the condition of P ≧ 1000 × L (L: average length of metal-plated nanowires). If the contact length P does not satisfy the above conditions, a sufficient shear flow does not occur, and it is difficult to orient the metal-plated nanowires with an orientation ratio of 80% or more.

  The contact length P is set so as to satisfy the above condition by adjusting the holding angle θ according to the diameter R of the coating bar to be used. That is, each adjustment may be made so as to satisfy πR × θ / 360 ≧ 150 × L.

  The diameter R of the coating bar is preferably 15 to 200 mm. If the diameter of the coating bar is made thinner than 15 mm, the adhesion between the coating bar and the substrate film tends to be poor due to the influence of the bending elasticity of the substrate. On the other hand, if it is 200 mm or more, the coating bar becomes heavy, and a load is applied to the motor of the coating machine.

  The holding angle θ is not particularly limited as long as πR × θ / 360 ≧ 150 × L can be satisfied, and may be appropriately determined according to the coating apparatus or the like.

  The thickness of the dried coating film is not limited, but is preferably about 0.1 μm to 10 μm in order to exhibit desirable polarization characteristics.

  In the polarizing material (metal-plated nanowire) after orientation, it is preferable that the gap between adjacent polarizing materials is less than the wavelength of light.

  In addition, the solvent used for the paint preferably has a boiling point lower than 150 ° C., aliphatic alcohol, aliphatic ether, aliphatic ketone, fatty acid ester, aliphatic halide, aromatic alcohol, aromatic ether, aromatic ketone, Of the aromatic esters and aromatic halides, those having a boiling point of 150 ° C. or lower are preferred.

  In the obliquely oriented polarizing film of the present invention, the polarizing material is oriented in substantially the same direction within a range of 5 to 80 ° with respect to the flow direction of the polarizing film, so that the direction of the absorption axis of the polarizing film is Are obliquely oriented in substantially the same direction within a range of 5 to 80 ° with respect to the flow direction. As shown in FIG. 4, the obliquely oriented polarizing film has a wire roll (coating bar) arranged at an arbitrary angle with respect to the film traveling direction (substrate traveling direction), and the film traveling direction and the wire bar shearing direction. Is obtained by orienting the polarizing material in the direction of the combined vector. Here, the orientation direction of the polarizing material is the absorption axis direction of the polarizing film. In addition to the method using the coating bar, a method of drawing a kneaded product of a polarizing material and a resin binder into a film and then stretching the polarizing material so that it is obliquely oriented in a specific direction is adopted. You can also.

  In the obliquely oriented polarizing film of the present invention, the direction of the absorption axis of the polarizing film is obliquely oriented in substantially the same direction within the range of 5 to 80 ° with respect to the flow direction, so the longitudinal direction (flow direction) or An elliptically polarizing plate can be efficiently produced by laminating a retardation compensation film having a slow axis in the width direction in a roll-to-roll manner. In addition, a roll to roll means laminating | stacking so that the flow direction of a diagonally-oriented polarizing film film and a phase difference compensation film may correspond.

Elliptically polarizing plate The elliptically polarizing plate present invention of the present invention is an elliptically polarizing plate formed by laminating a retardation film on one or both surfaces of obliquely aligned polarizing membrane film of the present invention,
(1) The flow directions of the two types of films are the same,
(2) The retardation compensation film has a slow axis in the longitudinal direction or the width direction.

  The elliptically polarizing plate of the present invention having the above characteristics can be efficiently produced by laminating an obliquely oriented polarizing film and a retardation compensation film in a roll-to-roll manner. In addition, the metal plating layer of the metal plating nanowire is a substitute for a conventional dye (a dye exhibiting polarization such as an iodine compound) and has high heat resistance. Further, it is not necessary to use a PVA film that is likely to shrink or curl under high temperature and high humidity conditions, and high durability can be maintained even under high temperature and high humidity conditions.

  The phase difference compensation film is provided for the purpose of compensating for the birefringence of light that has passed through a liquid crystal cell, etc., and has a slow axis in the longitudinal direction or the width direction, which is used in known elliptically polarizing plates. Can be applied as is.

  The material of the retardation compensation film is not limited, but for example, at least one material selected from the group consisting of triacetylcellulose, norbornene, (meth) acryl, polyimide, polycarbonate, polysulfone, polystyrene, and polyethersulfone. Is preferred. The retardation compensation film is a method of stretching the above listed resin uniaxially or biaxially after extrusion film formation, a method of forming a film by the solvent cast method after adding a retardation improver to the above listed resin, and the above solvent casting method After film formation, the film is obtained by a method of further stretching, etc., and any method has a slow axis in the longitudinal direction or the width direction. Among these, in order to set the slow axis in the longitudinal direction, it is desirable to use a longitudinal uniaxial stretching device between nip rolls or a longitudinal uniaxial stretching device between adjacent rolls. It is desirable to use a stretching device.

  The retardation compensation film used in the present invention preferably has a glass transition temperature (Tg) of 120 ° C. or higher, more preferably 130 to 150 ° C. from the viewpoint of durability. Moreover, since it is mainly used for a flat panel display, the total light transmittance is preferably 85% or more.

  An adhesive can be used when laminating the obliquely oriented polarizing film and the retardation compensation film. Urethane-based, acrylic-based, and polyvinyl alcohol-based adhesives are preferable, and when these adhesives are used, it is easy to ensure transparency. Further, the adhesive preferably has a refractive index difference within ± 0.3 with respect to the retardation compensation film.

  In the elliptically polarizing plate of the present invention, it is preferable that a protective film mainly composed of polyethylene terephthalate or polyethylene is laminated on one side or both sides. The protective film is preferably substantially made of polyethylene terephthalate or polyethylene, and usually a polyethylene terephthalate film or a polyethylene film is used. Such a protective film is provided on the outermost surface in order to protect the elliptically polarizing plate itself. The thickness of the protective film is preferably about 20 to 80 μm, more preferably about 40 to 60 μm. By laminating these protective films, the slipperiness of the surface is improved, and it is also effective for preventing the occurrence of scratches during transportation, so that the elliptically polarizing plate is easy to roll. This invention also includes the invention of the elliptically polarizing plate roll obtained by laminating | stacking the protective film which has a polyethylene terephthalate or polyethylene as a main component on one side or both surfaces, and winding up in roll shape.

  In addition to the protective film provided on the outermost surface, the elliptically polarizing plate of the present invention can be provided with a protective film for protecting the obliquely oriented polarizing film at a position adjacent to the obliquely oriented polarizing film. As a protective film for protecting the obliquely oriented polarizing film, a known TAC film or the like can be used. About 20-80 micrometers is preferable and, as for the thickness of the protective film which protects a diagonally-oriented polarizing film film, about 30-60 micrometers is more preferable.

  The elliptically polarizing plate of the present invention can maintain high durability even under high-temperature and high-humidity conditions, and can be suitably used as a member of flat panel displays, particularly liquid crystal display devices and organic EL display devices. Besides, elliptically polarized sunglasses for 3D displays It can use suitably also for uses, such as.

  In the obliquely oriented polarizing film of the present invention, the direction of the absorption axis of the polarizing film is obliquely oriented in substantially the same direction within the range of 5 to 80 ° with respect to the flow direction, so the longitudinal direction (flow direction) or An elliptically polarizing plate can be efficiently produced by laminating a retardation compensation film having a slow axis in the width direction in a roll-to-roll manner. In the elliptically polarizing plate of the present invention, the metal plating layer of the metal-plated nanowire is a substitute for a conventional dye (a dye exhibiting polarization properties such as an iodine compound) and has high heat resistance. Further, it is not necessary to use a PVA film that is likely to shrink or curl under high temperature and high humidity conditions, and high durability can be maintained even under high temperature and high humidity conditions.

It is a figure which shows the relationship between the vibration direction of the electric field of s polarization | polarized-light and p polarization | polarized-light, and the length direction of a metal nanowire, the width direction, and the thickness direction at the time of arranging a square columnar metal nanowire at right angles to the advancing direction of light. Specifically, the s-polarized light is absorbed or reflected, and the p-polarized light is transmitted to form a polarizing material. It is a figure which shows the advancing direction and electric field of p polarized light which pass through resin layer (1)-> metal plating layer (2)-> dielectric material layer (3). The p-polarized electric field is parallel to the paper surface and vibrates in the direction perpendicular to the traveling direction. With this electric field, the free electrons in the plating layer move in the direction of w. It is a figure explaining. It is a figure which shows the model for simulating the polarization property of the polarizing film (an example) used by this invention by a finite difference time domain method. It is a figure which shows the relationship of a wire bar shear direction, a film advancing direction, and a synthetic | combination vector direction (absorption axis direction). It is a conceptual diagram of the continuous coating apparatus used in Examples 1 and 2. In Example 1, 2, it is a figure which shows the wire bar installation direction for making the absorption-axis angle of a polarizing film into 45 degrees.

The present invention will be specifically described below with reference to production examples, comparative production examples, examples and comparative examples. However, the present invention is not limited to the production examples and examples.
(Production of polarizing film and evaluation of its characteristics)
Production Example 1
A metal-plated nanowire in which a metal plating layer is formed on the surface of a cylindrical polymethyl methacrylate (PMMA) nanowire having an average thickness of 100 nm and an average length of 2 μm is placed in an acrylic resin (refractive index 1.49) coating film. It was dispersed and oriented (see FIG. 3). The refractive index of the PMMA nanowire is 1.49. The coating film was dried to obtain a polarizing film. Hereinafter, it is abbreviated as “coating film”.

Table 1 shows the results of calculating the polarization performance of the coating film using commercially available finite difference time domain method software.
(However, for nickel-plated nanowires, the calculation when a large amount of nickel-plated nanowires overlap in the coating film is enormous, so as shown in FIG. 3, nanowires with an average thickness of 100 nm are 200 nm. One layer is a film having a thickness and oriented in parallel at an average pitch of 200 nm, the transmittance of one layer is obtained by the finite difference time domain method, and 2.6 μm = 13 layers using the Lambert-Beer method. The transmittance of the minute was obtained.

Polarization in Table 1, the transmittance of the p-polarized light and T _x, the transmittance of s-polarized light is T _y, single transmittance is calculated from these T, para transmittance T _p and the cross transmittance T _c Used to calculate. Specifically, this is as follows, and the same applies to other production examples and comparative production examples.
・ Single transmittance T (%) = (T _x + T _y ) / 2
Para transmittance T _p (%) = (T _x ² + T _y ² ) / 2
Cross transmittance T _c (%) = T _x · T _y

  From the results of Table 1, the performance of the coating film as a polarizing plate when the metal plating layer is nickel (3.5 nm thickness) is good.

Production Examples 2 to 4 and Comparative Production Examples 1 to 2
A metal-plated nanowire in which a chromium plating layer is formed as a metal plating layer on the surface of a columnar fluoroapatite (refractive index: 1.635) nanowire having an average thickness of 100 nm and an average length of 20 μm is coated with an acrylic resin (refractive index). 1.49, thickness 0.2 μm). The thickness of the chromium plating layer was changed for each example and comparative example. Table 2 shows the results of evaluating the polarization performance of the coating film using a polarization analyzer (custom product) manufactured by Sigma Koki Co., Ltd.

  When the chromium plating layer is thin (Comparative Production Example 1), the reflectance of s-polarized light is low, and sufficient polarization separation cannot be obtained. Further, when the chrome plating layer is thick (Comparative Production Example 2), the reflectance of s-polarized light is high and the transmittance is low and polarization separation is sufficiently obtained, but the transmittance of p-polarized light is lowered and the polarizing element is obtained. This is not preferable because the loss of is increased. Therefore, the thickness of the metal plating layer is preferably set to 2 to 15 nm.

Production Examples 5-7
A metal-plated nanowire in which an aluminum plating layer having a thickness of 7.5 μm is formed on a cylindrical PMMA (refractive index 1.49) nanowire having an average length of 20 μm with a changed average thickness is coated with an acrylic resin coating film (refractive index 1). 49) was dispersed and oriented. Table 3 shows the results of evaluating the polarization performance of the coating film using the above ellipsometer. The thickness of the coating film was 0.2 μm when the average nanowire thickness was 100 nm, 0.3 μm when the nanowire average thickness was 200 nm, and 0.35 μm when 300 nm.

  When the average thickness is large (Production Example 7), the reflectance of s-polarized light is large and polarization separation is obtained, and the polarization function is exhibited even at a thickness of 300 nm. However, since the transmittance of s-polarized light is also recognized to some extent in Comparative Production Example 4, a more preferable nanowire thickness is 100 to 200 nm.

Production Examples 8 to 9 and Comparative Production Example 3
A metal-plated nanowire having a 10 nm-thick chromium plating layer formed on the surface of a columnar fluoroapatite (refractive index: 1.635) nanowire having an average thickness of 100 nm and varying the average length is coated with an acrylic resin coating (refractive In a ratio of 1.49 and a thickness of 0.2 μm). Table 4 shows the results of evaluating the polarization performance of the coating film using the above ellipsometer.

  When the average length of the nanowire is short (Comparative Production Example 3), the transmittance is higher than the reflectance of s-polarized light, and polarization separation cannot be sufficiently obtained. If the average length of the nanowire is 2 μm or more, the polarization separation function is exhibited. However, from the viewpoint of easy handling of nanowires, 20 μm or less is preferable.

Production Examples 10 to 12 and Reference Production Example 1
Metal plated nanowires in which an aluminum plating layer having a thickness of 7.5 μm was formed on cylindrical nanowires having an average thickness of 100 nm and an average length of 20 μm were dispersed and oriented in a resin coating film. Table 5 shows the results of evaluating the polarization performance of the coating film using the above-described ellipsometer. Each production example and comparative production example have different refractive index differences, and the combinations (nanowire / resin) are as follows.
Production Example 10: Magnesium sulfate (refractive index 1.53) / acrylic (refractive index 1.49)
Production Example 11: Potassium titanate (refractive index 2.2) / episulfide system (refractive index 1.8)
Production Example 12: Potassium titanate (refractive index 2.2) coated with 10 nm thick episulfide system (refractive index 1.8) / thiourethane system (refractive index 1.65)
Reference production example 1: potassium titanate (refractive index 2.2) / acrylic (refractive index 1.49)
Although the polarization separation function is sufficiently exerted even if the refractive index difference between the nanowire and the coating film is somewhat large as in the production example, if the refractive index difference is too large as in the reference production example, the transmittance of s-polarized light increases. The polarization separation performance is degraded.

(Slant orientation method and its characteristic evaluation)
As the polarizing film used in Examples 1 and 2, the resin solution prepared in Production Example 1 was prepared (Ni plating = 3.5 nm). Further, in order to control the orientation direction of the polarizing material, a continuous coating apparatus shown in FIG. 5 was prepared.

  The continuous coating apparatus has a film unwinding section and a winding section, a wire bar coater capable of changing the direction between them, and then a drying furnace.

  By setting the wire bar coater at an arbitrary angle and adjusting the rotation speed, the shear direction was adjusted, and a polarizing plate having an absorption axis oblique to the roll traveling direction was obtained. FIG. 6 exemplarily shows the orientation direction when the wire bar installation angle is 135 degrees.

  The absorption axis direction is measured with a polarizing microscope when the light leakage when the crossed Nicol is set to the reference polarizing plate is minimum, and all are within the range of ± 1.0 degrees of the target angle. Confirmed that.

(Manufacture of elliptical polarizing plate and evaluation of its characteristics)
Examples 1-2 and Comparative Examples 1-2
As the polarizing film used in Examples 1 and 2, a polarizing film having a wire bar installation angle of 135 degrees and an orientation angle of the polarizing material of 45 degrees was prepared. Moreover, as a polarizing film used in Comparative Examples 1 and 2, a commercially available plain polarizing plate (Nitto Denko type F: absorption axis angle 0 degree) was purchased, and the TAC film (protective film) was carefully peeled and removed in water. I prepared something.

The following two types of retardation compensation films were prepared.
(1) Retardation compensation film 1
ZEONOR # 1420R manufactured by Nippon Zeon Co., Ltd., which is a cyclic polyolefin resin (norbornene), was prepared. The resin was dried at 100 ° C. for 4 hours, then charged into a single screw extruder and melted, and the film that passed through the mold was uniformly solidified with a cooling roll, and a roll having a thickness of 80 μm was collected.

The roll was continuously put into a free-width neck-in type longitudinal uniaxial stretching apparatus and stretched 1.5 times in the length direction to obtain a uniaxially stretched product (nx> ny = nz), Ro = 140 nm. . Note that nx, ny, and nz indicate the refractive indexes in the respective directions.
(2) Retardation compensation film 2
Teijin Chemicals Co., Ltd .: Pure Ace-80, which is polycarbonate, was prepared, and a roll with Ro = 138 nm was collected by stretching 1.5 times in the length direction in the same manner as (1) above.

  The roll was continuously put into a free-width neck-in type longitudinal uniaxial stretching apparatus and stretched 1.5 times in the length direction to obtain a uniaxially stretched product (nx> ny = nz), Ro = 140 nm. . Note that nx, ny, and nz indicate the refractive indexes in the respective directions.

  Each retardation compensation film was laminated on one side of the polarizing film by roll-to-roll so as to have an absorption axis angle and a slow axis angle shown in Table 7 below, and used for Test Example 1 below.

Test example 1
Durability tests of the elliptically polarizing plates produced in the examples and comparative examples were performed. The procedure of the durability test was as follows.

  The elliptically polarizing plates produced in the examples and comparative examples were punched into a 100 mm square so that the absorption axis direction of the polarizing plate was 45 degrees. This is a condition in which the influence of the shrinkage stress of the polarizing plate is most easily manifested. Then, it arrange | positions so that a phase difference compensation film surface may become a bonding surface, and it bonds to a glass plate with a laminator through a 25-micrometer highly durable acrylic adhesive, and is made into an autoclave (50 degreeC, 5 atmospheres, 10 minutes). Accommodates and removes excess air during bonding.

The durability test conditions were as follows.
(Condition 1) 100 ° C. DRY oven (Condition 2) 80 ° C., 90% wet heat oven 100, 500, 1000, 1500 and 2000 hours after taking out and measuring the following measurement items 1 to 3.
≪Measurement item 1: Polarization degree≫
The measurement was performed using a polarization analyzer APAS manufactured by Sigma Koki Co., Ltd. This is an index of a decrease in polarization due to heat and moisture (in the case of a conventional polarizing plate, sublimation of iodine).
<< Measurement item 2: Observation of light loss >>
Uniform polarized light was irradiated from the rear, and peripheral edge light leakage in a crossed Nicol state was visually observed. Moreover, it confirmed not only from the front but also from the diagonal direction. This is an indicator of a change in the retardation value due to the contraction of the polarizer.

When light omission was not recognized, it was evaluated as ◯, when light omission was confirmed within 5 mm from the edge part, and when the light omission of 5 mm or more was confirmed from the edge part, it was evaluated as x.
≪Measurement item 3: Observation of peeling state≫
The peeled state of the edge portion from the glass was visually observed. This is an index of change in contraction of the polarizer due to heat.

  When peeling was not recognized, it evaluated as (circle), when peeling was recognized to less than 2 mm from an edge part, (triangle | delta), and when peeling of 2 mm or more from edge part was recognized, it evaluated as x.

  The results of each measurement item are shown in Table 8 below.

  As is clear from the results in Table 8, the elliptically polarizing plates produced in the examples are more durable (the degree of polarization reduction from the initial stage, the frame-like light leakage, the pressure-sensitive adhesive) than the elliptically polarizing plates produced in the comparative examples. It can be seen that there is a significant improvement in peeling.

Claims (6)

Polarizing material, which is a metal-plated nanowire obtained by forming a metal plating layer having a thickness of 1 to 15 nm on the surface of a nanowire made of a dielectric material having an average thickness of 10 to 300 nm and an average length of 0.4 μm or more A polarizing film containing
When the polarizing material is oriented in substantially the same direction within a range of 5 to 80 ° with respect to the flow direction of the polarizing film, the direction of the absorption axis of the polarizing film is relative to the flow direction. An obliquely oriented polarizing film that is obliquely oriented in substantially the same direction within a range of 5 to 80 °. An elliptically polarizing plate formed by laminating a retardation compensation film on one or both sides of the obliquely oriented polarizing film according to claim 1,
(1) The flow directions of the two types of films are the same,
(2) The retardation compensation film has a slow axis in its longitudinal direction or width direction.
Elliptical polarizing plate.   The phase difference compensation film is made of at least one material selected from the group consisting of triacetylcellulose, norbornene, (meth) acryl, polyimide, polycarbonate, polysulfone, polystyrene, and polyethersulfone. Elliptical polarizing plate.   The elliptically polarizing plate according to claim 2 or 3, wherein a protective film mainly composed of polyethylene terephthalate or polyethylene is laminated on one side or both sides.   An elliptically polarizing plate roll obtained by winding the elliptically polarizing plate according to claim 4 into a roll shape.   A liquid crystal display device, an organic EL display device or an elliptically polarized sunglasses for 3D display using the elliptically polarizing plate according to any one of claims 2 to 5.

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