JP2012128401A - Polarizing material and coating for producing polarizing film containing the same, as well as polarizing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing material replacing a pigment and having excellent heat resistance, and a coating for producing a polarizing film containing the polarizing material, as well as the polarizing film.SOLUTION: A polarizing material comprises a metal-plated nanowire that is obtained by forming a metal plating layer of 1-15nm in thickness on a surface of a nanowire composed of a dielectric having an average thickness of 20-300nm and an average length of 0.4 μm or more. A coating for producing a polarizing film contains the polarizing material, and a polarizing film is obtained using the coating.

Description

  The present invention relates to a polarizing material particularly useful for the use of a polarizing plate and a polarizing plate for increasing brightness, a coating material for manufacturing a polarizing film containing the polarizing material, and a polarizing film.

  Currently, as a polarizer used near room temperature, a polarizing plate for liquid crystal display and a polarizing plate for increasing luminance (also referred to as a luminance increasing film) have been put into practical use. Moreover, as a polarizer requiring heat resistance, a polarizer for an optical isolator used for the purpose of noise removal at a connection interface of an optical fiber used for optical communication has been put into practical use.

  The polarizing plate is obtained by orienting an anisotropic pigment on the film. Specifically, the water-absorbing polyvinyl alcohol (PVA) film is impregnated with water-soluble iodine or a water-soluble dye and then stretched. It is made by doing.

  When the polarizing plate for raising the brightness is stretched, 100 to 200 layers of two kinds of polyester films having the same refractive index in the non-stretching direction and different in the stretching direction are alternately laminated and then stretched. Have been made. This brightness increasing polarizing plate reflects and reuses only polarized light having an electric field (electric field vibration surface) in the stretching direction, and has the effect of increasing the light utilization efficiency.

  The polarizer for the optical isolator is required to have heat resistance that temporarily withstands about 260 ° C. for soldering or the like. A so-called Lamipol is used as a polarizer for an optical isolator. Lamipol is manufactured by preparing a film in which aluminum having a thickness of about 10 nm is deposited on a silica film having a thickness of about 1 μm, laminating the film to form an alternating multilayer film of silica and aluminum, and then cutting it thin.

JP 2008-279434 A JP 2006-151540 A JP 2008-83656 A Japanese Patent No. 2005-097581

Nikkei Business Publications, Nikkei Microdevice, December 2005, 156-157 Applied Optics, vol.22, No.16, pages 2426-2428 IEEE Publishing, IEEE Journal of Quantum Electronics, 29, 175-181, 1993 IEEE / OSA Publishing, Journal of Lightwave Technology, 15, 1042-1050 American Chemical Society Publishing, Langmuir, 2004, 20, 11, 4784-4786 American Chemical Society, Crystal Growth and Design, 2006, 6, 6, 1504-1508 American Chemical Society Publishing, Crystal Growth and Design, 2006, 6, 11, 2422-2426 American Chemical Society, Journal of Physical Chemistry B, 2006, 110, 2, 807-811 American Chemical Society Publishing, Journal of the American Chemical Society, 2005, 127, 46, 16040-16041 American Chemical Society, Journal of Physical Chemistry B, 2005, 109, 1, 151-154 American Chemical Society, Journal of Physical Chemistry B, 2006, 110, 2, 807-811 American Chemical Society Publishing, ACS Nano, 2009, 3, 5, 1077-1084 American, Chemical Society, Journal of Physical Chemistry C, 2008, 112, 5, 1645-1649 American Chemical Society, Journal of Physical Chemistry B, 2004, 108, 28, 9745-9951 American Chemical Society, Chemistry of Materials, 2006, 18, p. 1634 American Chemical Society, Journal of Physical Chemistry B, 2004, 108, 28, 9745-9951 American Chemical Society, Journal of Physical Chemistry C, 2008, 112 (11), 4042-4048 IEEE Publishing, IEEE Journal of Quantum Electronics, 29, 175-181, 1993

The conventional polarizer has the following problems.
(1) Pigments such as iodine and dye used in conventional polarizing plates have low heat resistance. In addition, the stretched PVA film as a base material also has a problem that the dimensions change due to wet heat, thereby causing a phase difference and lowering the degree of polarization.
(2) Since the conventional brightness increasing polarizing plate is stretched by alternately laminating 100 to 200 layers of the two kinds of polyester films, uniform stretching is difficult and productivity is poor. There is also a problem that the light transmittance in the non-stretching direction is low.
(3) The Lamipol used in a polarizer for an optical isolator has a problem in that workability and productivity for production are poor, and it is easily broken during handling. However, a polarizer made of another material has a problem that there is no substitute material because of low heat resistance.

  These problems can be solved if there is a polarizing material having good heat resistance instead of a dye and a technique for orienting it on a substrate with high productivity.

  Therefore, the main object of the present invention is to provide a polarizing material having good heat resistance instead of a pigment, a coating material for manufacturing a polarizing film, and a polarizing film including the same.

  As a result of intensive studies to achieve the above object, the present inventor can use a specific metal-plated nanowire as a polarizing material, has good heat resistance, and can be oriented on a substrate with high productivity. As a result, the present invention has been completed.

That is, this invention relates to the following polarizing material, the coating material for polarizing film manufacture, and a polarizing film.
1. Polarizing material comprising metal-plated nanowires obtained by forming a metal plating layer having a thickness of 1 to 15 nm on the surface of nanowires comprising a dielectric having an average thickness of 20 to 300 nm and an average length of 0.4 μm or more .
2. The polarizing material according to Item 1, wherein the dielectric has a refractive index of 1.47 to 2.2.
3. The dielectric has a core layer and a coating layer formed on the surface thereof, the refractive index of the core layer is 1.47 to 2.2, and the refractive index of the coating layer is the same as that of the core layer. Item 2. The polarizing material according to Item 1, wherein the refractive index is nc, and the refractive index is within nc ± 0.4.
4). The polarizing material according to Item 1, wherein the metal plating layer is a plating layer of at least one metal selected from the group consisting of nickel, chromium, zinc, tantalum, niobium, silver, iron, and aluminum.
5. A paint for producing a polarizing film, comprising the polarizing material according to Item 1.
6). The paint according to Item 5, wherein the paint contains a resin, and the refractive index of the resin is within nd ± 0.4, where nd is the refractive index of the dielectric.
7). 4. A coating material for producing a polarizing film, comprising the polarizing material according to item 3 and a resin, wherein a refractive index of the resin is nc ± 0.4, where nc is a refractive index of the core layer.
8). The said coating material is a coating material of said claim | item 5 containing a (meth) acrylic resin and a crosslinking agent.
9. A polarizing film obtained by applying the coating material according to the above item 5 on the surface of the base film and then drying it.
10. The coating is coating 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),
Item 10. The polarizing film according to Item 9.
11. Item 10. The polarizing film according to Item 9, which is used as a polarizing plate or a luminance increasing polarizing plate.

  Hereinafter, the relationship between the metal nanowire and the polarizing property will be described first, and then the polarizing material (metal-plated nanowire), the coating material for manufacturing the polarizing film, and the polarizing film 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 approximately 4.8 × 10 ⁻⁹ and the electrical conductivity σ (S / m) of the metal is silver: 61 × 10 ⁶ , aluminum: 40 × 10. ⁶ , 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, if the metal nanowires of this size are oriented, a polarizing plate and a luminance increasing polarizing plate can be obtained.

  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 having an average thickness of 20 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. In the case of this metal plated nanowire, a dielectric having an average thickness of 20 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. In addition, by forming a metal plating layer having a thickness of 1 to 15 nm, a polarizing plate that transmits light in the thickness direction and absorbs light in the length direction, or transmits light in the thickness direction, It can be used as a polarizing plate for increasing brightness that reflects light in the length direction (including partial reflection), and can be used as a polarizing material. Furthermore, the metal plating layer is a substitute for a conventional pigment (means for expressing polarization), and a polarizing plate or a brightness increasing polarizing plate excellent in heat resistance can be provided.

Polarizing material of the present invention The polarizing material of the present invention has 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 20 to 300 nm and an average length of 0.4 μm or more. It is a metal-plated nanowire obtained by forming.

  In the present invention, a nanowire made of a dielectric material having an average thickness of 20 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 20 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 20 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 polarizer for a polarizing plate, a luminance increasing polarizing plate, or an optical isolator by dispersing and orienting it in a resin having a refractive index (nr) within nd ± 0.4. it can. 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 p-polarized light is shorter in FIG. 2, and Japanese Patent Application Laid-Open No. 2006-151540 and NIKKEI MICRODEVICE, December 2005, 156 From ~ 157 pages etc., 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 coating material for manufacturing a polarizing film and the polarizing film The present invention includes a coating material for manufacturing a polarizing film containing the polarizing material. The coating material for producing a polarizing film contains the above polarizing material and contains at least one of a resin binder, a solvent and the like for use as a coating material.

  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 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 of the present invention is small in 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 coating the base material film by the bar coating method using the 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. 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.

  The substrate film to which the paint is applied is not particularly limited as long as it can exhibit the polarization characteristics of the polarizing material of the present invention, and examples thereof include glass and resin films. Moreover, in order to improve orientation, you may extend | stretch a film by 2 times or less after coating.

  The film used as the base material has high visible light permeability and is preferably a water and heat resistant film. Polyester film such as polyethylene terephthalate, cellulose ester film such as unsaponified cellulose acetate, cyclic polyolefin resin film, polycarbonate resin film Polysulfone resin films, polyethersulfone resin films, and the like are preferable.

  Furthermore, in order to eliminate the influence of moisture and oxygen on the polarizing material, and to prevent curling of the film, after coating the paint and orienting the polarizing material, a polyester film using a resin adhesive Further, a film such as a cellulose ester film, a cyclic polyolefin resin film, a polycarbonate resin film, a polysulfone resin film, or a polyether sulfone resin film may be bonded and protected. Moreover, in order to stick on a liquid crystal cell, it is good also as a gas barrier film by laminating | stacking inorganic layers, such as an inorganic oxide, and an organic polymer layer on this film.

  In the case of the metal-plated nanowire of the present invention, a dielectric having an average thickness of 20 to 300 nm and an average length of 0.4 μm or more can be produced with good linearity with good productivity. A metal-plated nanowire with good properties can be produced with good productivity. In addition, by forming a metal plating layer having a thickness of 1 to 15 nm, a polarizing plate that transmits light in the thickness direction and absorbs light in the length direction, or transmits light in the thickness direction, It can be used as a polarizing plate for increasing brightness that reflects light in the length direction (including partial reflection), and can be used as a polarizing material. Furthermore, the metal plating layer is a substitute for a conventional pigment (means for expressing polarization), and a polarizing plate or a brightness increasing polarizing plate excellent in heat resistance can be provided.

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) of this invention by a finite difference time domain method.

  The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

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 examples and comparative 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 as a polarizing plate of a coating film when the metal plating layer is nickel (3.5 nm thickness), and the brightness enhancement polarizing plate of the coating film when the metal plating layer is aluminum (13 nm thickness) The performance of each is good.

Examples 2-4 and Comparative Examples 1-2
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 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 Example 2), the reflectance of s-polarized light is high and the transmittance is low and polarization separation is sufficiently obtained. This is not preferable because loss increases. Therefore, the thickness of the metal plating layer is preferably set to 2 to 15 nm.

Examples 5-6 and Comparative Examples 3-4
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 an average thickness changed, and 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 basically 0.2 μm, 0.3 μm when the average nanowire thickness was 200 nm, and 0.35 μm when 300 nm.

  When the average thickness of the nanowire is thin (Comparative Example 3), sufficient polarization separation cannot be obtained. When the average thickness is large (Comparative Example 4), 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, in Comparative Example 4, since the transmittance of s-polarized light is also recognized to some extent, the more preferable thickness of the nanowire is 100 to 200 nm.

Examples 7 to 8 and Comparative Example 5
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 Example 5), the transmittance becomes 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.

Examples 9 to 11 and Comparative Example 6
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 Example and Comparative Example have different refractive index differences, and combinations (nanowire / resin) are as follows.
Example 9: Magnesium sulfate (refractive index 1.53) / acrylic (refractive index 1.49)
Example 10: Potassium titanate (refractive index 2.2) / episulfide system (refractive index 1.8)
Example 11: Potassium titanate (refractive index 2.2) coated with 10 nm thick episulfide system (refractive index 1.8) / thiourethane system (refractive index 1.65)
Comparative Example 6: Potassium titanate (refractive index 2.2) / acrylic (refractive index 1.49)
As in the examples, the polarization separation function is sufficiently exerted even if the refractive index difference between the nanowire and the coating film is somewhat large. However, if the refractive index difference is too large as in the comparative example, the transmittance of s-polarized light increases and the luminance is increased. The performance when the rising polarizing plate is used is lowered.

Claims (11)

  Polarizing material comprising metal-plated nanowires obtained by forming a metal plating layer having a thickness of 1 to 15 nm on the surface of nanowires comprising a dielectric having an average thickness of 20 to 300 nm and an average length of 0.4 μm or more .   The polarizing material according to claim 1, wherein the dielectric has a refractive index of 1.47 to 2.2.   The dielectric has a core layer and a coating layer formed on the surface thereof, the refractive index of the core layer is 1.47 to 2.2, and the refractive index of the coating layer is the same as that of the core layer. The polarizing material according to claim 1, wherein the refractive index is nc, and is within nc ± 0.4.   The polarizing material according to claim 1, wherein the metal plating layer is a plating layer of at least one metal selected from the group consisting of nickel, chromium, zinc, tantalum, niobium, silver, iron, and aluminum.   A paint for producing a polarizing film, comprising the polarizing material according to claim 1.   The paint according to claim 5, wherein the paint contains a resin, and the refractive index of the resin is within nd ± 0.4, where nd is the refractive index of the dielectric.   A polarizing film-producing coating material comprising the polarizing material according to claim 3 and a resin, wherein the refractive index of the resin is nc ± 0.4, where nc is a refractive index of the core layer.   The said coating material is a coating material of Claim 5 containing a (meth) acrylic resin and a crosslinking agent.   The polarizing film obtained by applying the coating material of Claim 5 to the surface of a base film, and making it dry. The coating is coating 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),
The polarizing film according to claim 9.   The polarizing film according to claim 9, which is used as a polarizing plate or a luminance increasing polarizing plate.

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