JP2013025266A - Polarizing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing material containing dispersed flat metal particles whose minor axes are oriented in a constant direction and including glass as a base material, and glass containing dispersed and oriented flat metal halide particles for manufacturing the material.SOLUTION: The polarizing material contains flat metal particles which are dispersed in at least a surface layer of a glass base material and have minor axes oriented in a constant direction. The polarizing material has a glass transition point not more than Tg 500°C and a viscosity η not less than 1.0×10dPa*s at Tg+10°C. Glass for manufacturing the polarizing material has these characteristics and contains flat metal halide particles.

Description

  The present invention relates to a polarizing material, particularly a polarizer, and more particularly to a polarizing material particularly suitable for use in the visible light region.

  Organic absorption polarizers are mainly used in liquid crystal projectors, liquid crystal rear projection displays, and the like. Organic absorption polarizers have the disadvantage that they degrade over time due to heat and light (especially high-energy blue light). Therefore, an inorganic polarizer excellent in heat resistance and light resistance is required.

  As an inorganic absorption type polarizer, Patent Documents 1 to 3 show basic methods for producing a polarizer containing dispersed metallic silver particles having shape anisotropy. In these methods, a glass containing Ag and halogen (Cl, Br or I) as components is heat-treated to precipitate silver halide grains, and then the glass is extruded or stretched to form a spindle-shaped anisotropic shape. Glass containing silver halide grains dispersed in a form in which the major axis is oriented in a specific direction, and then reducing the glass to form spindle-shaped metallic silver grains in a particular direction. The polarizer is dispersed and contained in an oriented form. In order to function as a polarizer, the direction in which the long axes of spindle-shaped metallic silver particles are aligned and the light incident surface (surface on which light is incident) of the polarizer must be parallel.

  Patent Documents 4 and 5 show methods for reducing the size of silver halide grains as a method for producing a polarizer exhibiting a high transmittance and a high extinction ratio in the green region of the visible light region.

  However, the polarizers obtained so far using metallic silver particles have a drawback that it is difficult to achieve both high transmittance and high extinction ratio in the visible light region, particularly in the blue to green region. .

  Further, in Patent Document 6, glass containing metallic silver particles and / or silver halide particles is extruded by a method in which the particles are stretched and aligned in the flow direction of the glass, thereby photochromic or non-chromic. A method for producing photochromic, polarizing glass is disclosed. The document states that when the particles obtained by extrusion are spindle-shaped, the dichroic ratio is 1.8 to 3.0 on average, and when the particles are oblate rather than spindle-shaped. It is stated that the color ratio is larger (up to 5.0). However, the degree of polarization exhibited by such dichroic ratio values is much lower than the level of polarization (extinction ratio) required for polarizers. Also, in the same document, regarding a specific method of extrusion molding, a glass disk having a diameter of 1 inch was extruded into a rod having a diameter of 0.25 inch, that is, the cross-sectional area was reduced to 1/16. It is only described (thus, the dimension in the direction of the central axis is estimated to have been extended 16 times). However, in this method, the original glass disk extends in the thickness (length) direction while being compressed from the periphery to the center direction, so that the contained particles should be deformed into a spindle shape. Cannot be. That is, this document does not describe a method for forming oblate spherical particles.

  Non-Patent Document 1 discloses that cylindrical glass containing silver chloride microcrystals is compressed in the height direction under heating to form a disk, a sample is cut out, and the shape of silver chloride contained is oblate. It is said that there was. Then, after irradiating the sample cut with a surface parallel to the compression direction with ultraviolet light and coloring it, the light polarized in the direction parallel to the compression direction and the light polarized in the direction perpendicular to the sample were incident on the sample, and the measured absorbance was measured. The graph is displayed (FIG. 5 (a) and (b) on page 98). However, in these graphs, when the three wavelengths 450 nm, 550 nm, and 500 nm in the blue to green region are viewed, the difference in absorbance between the two incident lights having different polarization directions is about 1.6 times, It is only about 2.4 times and about 2.0 times, and the polarization property is extremely insufficient.

  Patent Documents 7 and 8 describe a polarizer in which metal particles having three-dimensionally different lengths are dispersed and oriented on at least a surface layer of a dielectric. To improve performance in the visible light, particularly in the blue region. The required particle shape, metal type, and refractive index of the dielectric are not described, and the thermophysical properties for deforming the dielectric are not described. The glass materials used as dielectrics in this document are described as Pyrex (registered trademark) and BK-7, respectively, and both have a glass transition point of 550 ° C. or higher.

US Patent No. 4,304,584 US Pat. No. 4,479,819 JP-A-4-208844 JP 2008-162810 A JP 2008-225483 A US Pat. No. 4,282,222 Japanese Patent Laid-Open No. 07-056018 JP 10-1333015 A

Y. Kimura et al., Physics and Chemistry of Glasses, 18 (5), p.96-100 (1977). A.N.Gent, J.Appl.Phys., 17, p458, (1946).

  In the above background, prior to this application, the applicant of the present application contains flattened metal particles dispersed in a transparent inorganic solid substrate such as glass instead of spindle-shaped metal particles, and the minor axis of the flattened metal particles is A method for producing a polarizing material, which is oriented in a certain direction, was invented, and a patent application was filed for this method (Japanese Patent Application No. 2010-198286 unpublished at the time of filing this application). According to the manufacturing method, a polarizer exhibiting high performance in the visible light region, particularly in the blue region, can be manufactured.

  If a polarizing glass in which flattened metal particles are dispersed is produced by uniaxial stretching, it is necessary to take a method such as stretching in different directions several times, but such a method is difficult to implement. It is preferable to take a molding method such as compression or extrusion. However, in the drawing, the high temperature part of the glass does not come into contact with the components of the equipment, whereas in the compression or extrusion, the high temperature glass and the mold are in direct contact with each other at a high pressure, so that the mold is rapidly deteriorated. There is a problem of going forward. In order to suppress the deterioration of the mold, it is effective to lower the temperature during molding. The glass transition point Tg or the yield point At can be used as an index of the temperature at which the molding is performed. However, a component that lowers the glass transition point contributes to a higher refractive index, and if it is contained in a large amount, it causes a problem of increasing absorption loss in the blue region.

  The object of the present invention is to solve these problems, to contain flattened metal particles in a dispersed manner, and to have a short axis of these particles oriented in a certain direction. Disclosed are materials, and glass for the production of such polarizing materials, containing flattened metal halide particles dispersedly, the minor axes of these particles being oriented in a certain direction. It is.

As a result of examining the molding conditions in order to solve the above problems, the present inventor has found that the viscosity at the molding temperature (which is higher than the glass transition point) is preferably not too low. As a result of examining various glass compositions based on this result, it has been found that a glass substrate whose η (Tg + 10 ° C.) is not less than 1.0 × 10 ¹² dPa · s is preferable using the viscosity η at Tg + 10 ° C. as an index. . Based on this finding, the present invention has been further studied and found a glass substrate that has been conventionally suitable as a transparent inorganic solid substrate, and the present invention has been completed based on this. That is, the present invention provides the following.

(1) A polarizing material comprising flattened metal particles dispersed and contained in at least a surface layer in a glass substrate, wherein the short axis of the flattened metal particles is oriented in a certain direction. A polarizing material characterized in that the transition point Tg does not exceed 500 ° C., and the viscosity η at Tg + 10 ° C. does not fall below 1.0 × 10 ¹² dPa · s.
(2) The polarizing material according to 1 above, wherein the yield point At does not exceed 550 ° C.
(3) The polarizing material according to 1 or 2 above, wherein the refractive index nd with respect to the d-line does not exceed 1.50.
(4) The polarizing material according to any one of 1 to 3 above, wherein the average value of the ratio of the width (b) of the particles to the length (a) of the short axis of the flattened metal particles is at least 1.2.
(5) The polarizing material according to any one of 1 to 4 above, wherein the metal is silver or a silver alloy.
(6) The polarizing material as described in 5 above, which contains 0.05% by weight or more of silver.
(7) The flattened metal particle has a minor axis and two major axes orthogonal to each other and different from each other, and the minor axis and the two major axes are respectively in a fixed direction. 7. The polarizing material according to any one of 1 to 6 above, which is oriented.
(8) The average value of the ratio of the shorter length (b) of the two major axes to the minor axis length (a) of the flattened metal particles is at least 1.2, The polarizing material according to any one of 1 to 7.
(9) The polarizing material has a composition
SiO ₂ + Al ₂ O ₃ : 10 to 60% by weight
B ₂ O _3: 25~60 wt%
Na ₂ O + K ₂ O: 5 to 20% by weight
Ag: 0.05% by weight or more Cl: 0.05% by weight or more The light-polarizing material according to any one of 1 to 8 above, which comprises 0.05% by weight or more.
(10) The polarizing material according to any one of 1 to 9 above, which is formed into a plate shape, and the orientation direction of the short axis of the flattened metal particles is parallel to the surface of the plate A polarizer.
(11) The polarizing material according to any one of 1 to 9, which is formed in a plate shape, and the orientation of the short axis and one long axis of the flattened metal particles with respect to the surface of the plate A polarizer whose directions are parallel to each other.
(12) The polarizer according to 11 above, wherein the average value of the ratio of the length of the major axis oriented in the direction perpendicular to the surface of the plate to the length of the minor axis of the flattened metal particles is at least 1.4. .
(13) Of the two major axes of the flattened metal particles, the length of the major axis oriented perpendicular to the surface of the plate from the length of the major axis oriented parallel to the surface of the plate The polarizer according to 11 or 12 above, which is longer.
(14) For linearly polarized light having a wavelength of 430 nm to 700 nm, the transmittance is 30% or more and the extinction ratio is 10 dB or more when the orientation direction of the minor axis of the particle is parallel to the electric field vector of the linearly polarized light. The polarizer according to any one of 11 to 13 above.
(15) The polarizer according to any one of the above 11 to 14, wherein an extinction ratio to linearly polarized light is 15 dB or more over at least any wavelength range of 430 nm to 450 nm, 450 nm to 500 nm, and 500 nm to 550 nm.
(16) The flattened metal halide particles are dispersed and contained in the glass substrate, the short axes of the flattened metal halide particles are oriented in a certain direction, and the glass transition point Tg does not exceed 500 ° C. A glass for producing a polarizing material, wherein the viscosity η at Tg + 10 ° C. does not fall below 1.0 × 10 ¹² dPa · s.
(17) The glass for producing a polarizing material as described in 16 above, wherein the yield point At does not exceed 550 ° C.
(18) The glass for producing a polarizing material according to the above 16 or 17, wherein the refractive index nd with respect to the d-line does not exceed 1.50.
(19) The polarization property according to any one of 16 to 18 above, wherein the average value of the ratio of the width (b) of the flat metal halide particles to the short axis length (a) is at least 1.2. Glass for material production.
(20) The glass for producing a polarizing material according to any one of 16 to 19, wherein the metal is silver or a silver alloy.
(21) The glass for producing a polarizing material as described in 20 above, which contains 0.05% by weight or more of silver.
(22) The flattened metal halide particle has a minor axis and two major axes perpendicular to each other and different from each other, and the minor axis and the two major axes are constant. The glass for producing a polarizing material according to any one of 16 to 21, which is oriented in a direction.
(23) The average value of the ratio of the shorter length (b) of the two major axes to the minor axis length (a) of the flattened metal halide particles is at least 1.2. The glass for producing a polarizing material according to any one of 16 to 22 above.
(24) The polarizing material manufacturing glass has a composition,
SiO ₂ + Al ₂ O ₃ : 10 to 60% by weight
B ₂ O _3: 25~60 wt%
Na ₂ O + K ₂ O: 5 to 20% by weight
The glass for producing a polarizing material according to any one of 1 to 8 above, comprising Ag: 0.05% by weight or more and Cl: 0.05% by weight or more.
(25) The glass for producing a polarizing material according to any one of 16 to 24, wherein the glass is formed in a plate shape, and the short axis orientation of the flattened metal halide particles is relative to the surface of the plate. Polarizing material manufacturing glass with parallel directions.
(26) The glass for producing a polarizing material according to any one of 16 to 25, wherein the glass is formed in a plate shape, and the short axis and one of the flattened metal halide particles are formed on the surface of the plate. A glass for producing a polarizing material, in which the orientation directions of the major axes are parallel to each other.
(27) The average value of the ratio of the length of the major axis oriented in the direction perpendicular to the surface of the plate to the length of the minor axis of the flattened metal halide particles is at least 1.4. Polarizing material manufacturing glass.
(28) Of the two major axes of the flattened metal halide particles, the major axis oriented perpendicular to the surface of the plate is longer than the length of the major axis oriented parallel to the surface of the plate. 26. The glass for producing a polarizing material as described in 26 or 27 above, which has a longer length.

  According to the present invention, it is possible to obtain a polarizing material, particularly a polarizer, which exhibits characteristics superior to those of conventional ones in the visible light region, particularly in the blue to green region.

The transmittance | permeability curve in 1 mm thickness of heat-processed base material glass of Example 1. FIG. FIG. 3 is a conceptual diagram illustrating the deformation of glass in Example 1. 4 is a transmittance curve of the polarizer manufactured in Example 1. FIG. E // a is the transmittance of polarized light when the electric field vector is parallel to the orientation direction (a) of the short axis of the flat metal particle, and E // b is the transmittance curve when the electric field vector is perpendicular thereto. Indicates.

  As described in the Examples section, as a result of experiments, the polarizer of the present invention exhibits superior characteristics in the visible light region, particularly in the blue to green region, as compared with a polarizer using conventional spindle-shaped metal particles. Was found.

  In the present invention, the term “polarizing material” refers to a material having a polarizing property and includes a polarizer.

  In the present invention, the glass for producing a polarizing material is reduced (after processing such as cutting if necessary), and at least a part of the flattened metal halide particles oriented in a certain direction is flattened metal particles. By converting to, a polarizing material is given.

  In the present invention, regarding the flattened metal particles, “at least included in the surface layer” means that it is not necessary to convert all of the flattened silver halide grains contained in the center of the glass into metal particles. For the sake of illustration only, a “surface layer” does not mean that the layer must have any particular thickness.

  The polarizing material of the present invention, particularly the polarizer, is prepared, for example, by preparing a transparent inorganic solid material (glass) containing dispersed metal halide particles (spherical) such as silver halide, which is uniaxially heated. Compress and flatten, thereby flattening the particles at the same time. Cut the resulting material directly into a plate shape with a plane parallel to the direction of the short axis (that is, in the compression direction) to convert the metal halide particles into metal particles. It can be carried out by reducing.

  In the present invention, the “flattened” shape for a sphere is a shape obtained by placing the center of the sphere at the origin of Cartesian coordinates (Cartesian coordinates) and (i) reducing the size of the sphere in the x-axis direction, for example. In addition to (oblate shape: oblate), (ii) shapes obtained by enlarging the dimensions in the z-axis direction, for example, simultaneously with such reduction in the x-axis direction are also included. Since the volume of an actual spherical particle is substantially constant, compression in the x-axis direction results in an expansion of the diameter in the radial direction orthogonal to this, but the shape obtained can be any of those obtained in (i) above. Is substantially similar to In addition, by compressing an actual spherical particle in the x-axis direction and simultaneously preventing or suppressing it from expanding in the y-axis direction, extra expansion in the z-axis direction occurs, which is obtained in (ii) above. It is roughly similar to the resulting shape.

  The shape of the above type (ii) is also closer to the shape of the above type (i) as the degree of suppression of expansion in the y-axis direction is smaller, and if the degree of suppression is zero, the shape of the above type (i) Therefore, the shape of (i) above is included in the latter as a special case of the shape of (ii) above. Further, the flattened metal particles (and the flattened metal halide particles before reduction) in the polarizing material of the present invention agree with the shape of (i) or (ii) with mathematical strictness. Is not required, and it is sufficient if it can be considered as a shape of the type (i) or (ii). That is, the particle of type (i) has only one short axis and may be substantially circular in the cross section perpendicular to the short axis, and the particle of type (ii) has one short axis. It only has to be substantially oval in a cross section having an axis and perpendicular to the minor axis.

  In the present invention, the “short axis” of the flattened metal particles means the shortest length (a) among the three axes of the particles. In the case of the oblate spherical flattened metal particles of type (i) above, the directions of the two major axes are indefinite, but their lengths (b, c) are determined and they are equal to each other (ie, a <B = c). In the case of flattened metal particles of the above type (ii) having three different lengths, two axes other than the short axis (length a) are the major axes, and the shorter one of them Is represented by b, and the longer one is represented by c (that is, a <b <c).

  In a polarizer based on a conventional spindle-shaped metal particle, the polarization characteristics are obtained by orienting the long axis of the particle in parallel with the surface of the polarizer (light incident surface). The short axis is made parallel to the surface of the polarizer. In particular, in the case of the flattened metal particles of the above type (i), the major axis direction is indefinite in the first place. In the polarizer using the flattened metal particles of type (ii) having three axes with different lengths, the minor axis of the particles is parallel to the surface of the polarizer, while the particles are perpendicular to the surface. In the depth direction, it has an axis longer than the minor axis, which is one of the important features not found in a polarizer using spindle-shaped particles. The depth axis perpendicular to the surface can be any of the two long axes. Further, when the longer major axis is oriented perpendicularly to the surface of the polarizer, that is, in the depth direction, it is particularly advantageous for producing a polarizer excellent in the blue to green region.

  The polarizing material of the present invention is suitable for use as a polarizer by cutting or polishing as necessary.

  In the present invention, “oriented” with respect to a certain axis of particles contained suspended in a glass substrate means that the distribution of those particles contained in the direction of the axis in a specific direction as a whole. This means there is a bias (ie, it is not isotropic). This bias in the specific direction does not necessarily require that all of the axes are oriented in the specific direction substantially accurately. This is because the polarization property is a property that is observed as a result of the innumerable particles contained in the substrate dispersed and interacting with the incident light as a group, so that the group of particles as a whole (ie, This is because the polarization characteristic can be obtained if the axis is oriented in a specific direction (as an average value of the distribution in the axial direction of the particles).

  In the present invention, the glass base material has an internal transmittance of 80% or more in the wavelength band to be used as a polarizer in the wavelength band to be used (excluding the reflection loss on the front and back surfaces, the inside of the object). It is preferably an inorganic material exhibiting a transmittance when light crosses.

  In the present invention, the refractive index of the glass substrate (equal to the refractive index of the polarizing material) (nd: the refractive index of helium with respect to the d-line) is 1.50 or less, so that superior performance can be achieved compared to the prior art. More preferably, it should be 1.49 or less, and more preferably 1.48 or less.

  In the present invention, the glass transition point (equal to the glass transition point of the polarizing material) Tg of the glass substrate preferably does not exceed 500 ° C, more preferably does not exceed 480 ° C, and does not exceed 450 ° C or less. Is more preferable.

The yield point (At) preferably does not exceed 550 ° C, more preferably does not exceed 520 ° C, and further preferably does not exceed 490 ° C.
The yield point (At) is the maximum point at which the expansion curve changes from rising to falling due to softening of the glass when the thermal expansion is measured with a thermomechanical analyzer (TMA).

  In the present invention, the term “average value of the ratio of the width of the particle to the length of the minor axis” for the flattened metal particles refers to the case of the flattened metal particles of the type (i) above. It means the number average of ratios determined by “width (ie, length of major axis) / length of minor axis” for individual particles observed in the material. In addition, when referring to the above-mentioned type (ii) of flattened metal particles, it means the number average of ratios determined by “long axis length / short axis length” for each particle. Each is calculated for the long axis of the book.

  In the present invention, the average value of the ratio of the width (or long axis length (b = c)) of the flat metal particles in the polarizing material to the short axis length (a) is 1.2. It is preferable that it is above, and it is more preferable that it is 1.4 or more. Although there is no particular upper limit to this ratio, it is usually 100 or less, more preferably 70 or less, still more preferably 40 or less, still more preferably 15 or less, and particularly preferably 10 or less.

    Similarly, in the case of particles of the above type (ii) having three different axes (a, b, c) (each length, a <b <c), the ratio of b to a is also the same. The average value of is preferably at least 1.2, more preferably 1.4 or more. The average value of the ratio of c to b can be set to an arbitrary value exceeding 1, but is preferably at least 1.2 in order to take advantage of the further advantage of this type of particle. It is more preferably 4 or more, further preferably 3 or more, and particularly preferably 5 or more. There is no particular upper limit to the ratio of c to b, but usually 10 or less is sufficient and may be 8 or less. The average value of the ratio of c to a is determined according to the average value of the ratio of a and b and the average value of the ratio of b and c, and there is no particular limitation other than that.

  The flattened metal particles are likely to have a high transmittance even in a short wavelength region as the average value of the particle size (length of the short axis) is small, and the particle size is preferably 200 nm or less, and preferably 150 nm or less. More preferably, it is 100 nm or less.

  In the present invention, silver or a silver alloy is particularly preferable as the metal constituting the flattened metal particles. Examples of the “silver alloy” include alloys of silver, cadmium, and indium, but may be alloys of other metals and silver. In the case of an alloy of silver and a metal other than cadmium and indium, the silver content in the alloy is preferably 50% by weight or more.

  Whether any of copper, cadmium, indium and / or alloys thereof, or an alloy of copper, cadmium, indium and silver is used as the metal constituting the flattened metal particles, or only silver is used, the halogen is similarly used. In the form of metal halide, for example, compounded in a glass substrate, heated to disperse and precipitate as spherical metal halide particles, the glass is compressed and flattened, and after the glass is solidified, hydrogen gas under atmospheric pressure The polarizing material of the present invention can be provided by reducing by an appropriate method such as heating in the same, and a polarizer can be produced therefrom.

  A glass containing metal halide spherical particles dispersed therein can be obtained by producing a glass having an appropriate composition containing halogen and the metal as a composition and heat-treating it.

In the present invention, in the step of flattening the spherical particles of the metal halide in the glass substrate and orienting its short axis (and other axes if applicable), the glass is heated to a temperature that softens the glass. Applying pressure from one direction to deform the glass and the particles dispersed in it, and when unloaded, the particles will not return to their original spherical shape (usually if cooled to a temperature 50 degrees below the glass transition temperature) Uncool after cooling to (good). The degree of softening varies depending on the type and magnitude of pressure applied and the pressurization time, but is generally in the range of η = 10 ¹¹ to 10 ¹³ dPa · s.

Uniaxial compression of glass containing dispersed metal halide spherical particles can be performed, for example, by pressing the heated glass and applying pressure in a single direction. The magnitude of the pressure applied to the glass is appropriate, but in order to sufficiently deform the metal halide particles, it is usually preferably at least 100 kgf / cm ² , more preferably 200 kgf / cm ² or more, More preferably, it is 300 kgf / cm ² or more. However, the pressure may be appropriately set according to the viscosity of the glass under heating as long as it is gently compressed. Although the time for compression may be appropriate, it can usually be several minutes to several hours, for example. Of course, as long as the glass follows the speed of compression deformation, the compression may be completed in a shorter time.

  The production of a polarizing material containing flattened metal particles having three axes of different lengths (respectively a, b, c and a <b <c) of the type (ii) described above is various. Can be done by the method. For example, as described in the examples, a glass containing dispersed metal halide spherical particles is fitted into a groove of a predetermined size and compressed from above (uniaxial constrained uniaxial compression). Can be performed. In this case, the glass is not deformed in the direction perpendicular to the groove wall and extends only in the longitudinal direction of the groove. When the glass is compressed so that the dimension in the compression direction is 1 / n (n> 1), the dimension in the compression direction: the dimension in the width direction: the dimension in the longitudinal direction = 1 / n: 1: n = 1: n: n2. Become. Accordingly, the metal halide particles that were originally spherical are deformed to have three axes with different lengths.

  As another method, both sides of the groove are configured with movable walls, and during uniaxial compression, these walls are pressed with a predetermined force from both sides (buffering material, spring, hydraulic pressure, etc.) By doing so, the wall retracts to a position where the pressure from both sides and the lateral stress (product of the contact area of both) generated in the viscous glass due to uniaxial pressurization are balanced. On the other hand, since the glass extends freely in the longitudinal direction of the groove, it is shortened in the pressing direction, expanded freely in the longitudinal direction of the groove, and in addition to this, it is expanded to some extent in the direction perpendicular to the groove. The glass can be deformed, and accordingly, the shape of the metal halide particles contained is also deformed so that a short axis and two long axes with different lengths are generated.

  As yet another method, a glass containing spherical metal halide particles dispersed therein may be compressed from two orthogonal biaxial directions (biaxial compression). This can be performed, for example, by compressing the glass from above the groove in the above manner by pressing the movable walls forming both sides of the groove inward to narrow the width of the groove. When biaxial compression is performed, the compression ratio in the direction (Db) perpendicular to the compression ratio in the main compression direction (Da) (the dimension before compression of the glass: the dimension after compression) may be made smaller. Preferably, the compression ratio in the Da direction is 50% or less, more preferably 40% or less, and particularly preferably 35% or less.

  By subjecting the glass containing the flattened metal halide particles obtained above to reduction treatment, at least a part of the flattened metal halide particles can be reduced and converted into metal particles. The reduction treatment can be performed, for example, by heating the glass in a hydrogen atmosphere. The heating is preferably performed at a temperature at which the flattened metal halide particles are not likely to be re-sphericalized. This fear can be avoided by heating at a temperature lower than the glass transition point.

  In the polarizer of the present invention, for linearly polarized light having a wavelength of 430 nm to 700 nm, the transmittance when the orientation direction of the minor axis of the particle is parallel to the electric field vector of the linearly polarized light is preferably 50% or more. It is preferably 60% or more, more preferably 70% or more, and the extinction ratio for the light is preferably 10 dB or more, more preferably 15 dB or more, and further preferably 20 dB or more.

In the present invention, as a glass as a transparent inorganic solid substrate, Ag and halogen are added to glass mainly composed of SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , alkali metal oxide (R ₂ O) or the like. Can be used.

More specifically,
SiO ₂ + Al ₂ O ₃ : 10 to 60% by weight
B ₂ O _3: 25~60 wt%
Na ₂ O + K ₂ O: 5 to 20% by weight
A glass mainly composed of Ag: 0.05% by weight or more and Cl: 0.05% by weight or more can be suitably used in the present invention.

The composition of the polarizing glass in the present invention will be described in more detail.
SiO ₂ has the effect of increasing the Tg of the glass and increasing the viscosity near the Tg of the glass. In view of these, the content of SiO ₂ is preferably 10 to 50% by weight, more preferably 20 to 47% by weight, and still more preferably 30 to 45% by weight.

B ₂ O ₃ can lower the Tg of glass, but lowers the viscosity in the vicinity of Tg. From these considerations, the content of B ₂ O ₃ is preferably 25 to 60% by weight, more preferably 30 to 50% by weight.

Al ₂ O ₃ has the effect of increasing the Tg of the glass, increasing the viscosity in the vicinity of Tg, and significantly improving the weather resistance. In view of these balances, the content of SiO ₂ + Al ₂ O ₃ is preferably 10 to 60% by weight, more preferably 20 to 55% by weight, and still more preferably 30 to 50% by weight.

Alkali metal oxide is an essential component for lowering Tg. It is preferable to select Na ₂ O and K ₂ O that have a small effect of increasing the refractive index. The content of Na ₂ O + K ₂ O is preferably 5 to 20% by weight, more preferably 8 to 17% by weight, and still more preferably 10 to 15% by weight.

  When silver is employed as the flattened metal particles, the amount of silver contained in the original glass substrate is preferably 0.05% by weight or more, more preferably 0.10% by weight or more, More preferably, it is 0.15% by weight or more. Although there is no clear upper limit to the silver content, it is preferably 1.5% by weight or less, more preferably 1.2% by weight or less in order to reduce the concern about devitrification. For example, it can be 0.2 to 0.8% by weight.

  As the halogen, Cl is preferably selected so that the precipitated silver halide does not absorb light in the blue region. The amount of Cl is not less than the chemical equivalent of Ag, preferably not less than 0.05% by weight, and more preferably not less than 0.10% by weight. Although there is no clear upper limit to the Cl content, it is preferably 1.0% by weight or less, and more preferably 0.8% by weight or less in order to reduce the concern about devitrification. For example, it may be 0.15 to 0.6% by weight.

  Further, although F is a halogen element, it does not precipitate as AgF, but remains in the glass and produces an effect of lowering the Tg of the glass.

In addition, Li ₂ O, MgO, CaO, SrO, BaO, ZnO, PbO, TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , La ₂ O ₃ , CeO ₂ , Sb ₂ O _3, etc. are optional properties. Although it can be used to adjust (thermal expansion coefficient, hardness, chemical durability, etc.), since it is a component having a high refractive index, it is preferable to suppress the content. The total of the components listed here is preferably 5% by weight or less, for example.

  Moreover, it is preferable not to contain CuO because glass is a coloring component.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, it is not intended that the present invention be limited to the examples.

[Example 1]
<Manufacture of base glass>
SiO ₂ : 44.6, B ₂ O ₃ : 33.8, Al ₂ O ₃ : 2.9, AlF ₃ : 4.8, K ₂ O: 13.5, Ag: 0.32, Cl by weight% : A base glass having a composition of 0.15 was produced. That is, the raw materials mixed so as to give each composition were melted at 1450 ° C. in a 500 cc platinum crucible, poured into a mold, and once cooled to below the glass transition point, a base glass block was obtained. The produced glass had a glass transition point Tg of 410 ° C., a yield point At of 485 ° C. (measured by TMA), and a refractive index nd of 1.477.

Viscosity η (Tg + 10 ° C.) was measured and calculated based on the parallel plate method described in Non-Patent Document 2 with a 10 mmφ × 10 mmH cylindrical preform loaded at 10 kN. In Equation 1, F is the load, t is the time, V is the volume of the glass cylinder, h ₀ is the height of the cylinder at time 0, and h is the height of the cylinder at time t. η (Tg + 10 ° C.) = 3.0 × 10 ¹² dPa · s.

  This base glass block was heat-treated in an electric furnace maintained at 560 ° C. for 4 hours to produce a heat-treated base glass block. This heat-treated base glass was cloudy white due to the precipitation of silver halide crystals. The heat-treated base glass was polished to a thickness of 1 mm, and the transmittance was measured using a spectrophotometer. The transmittance curve is shown in FIG.

  In addition, the grain size of precipitated silver halide crystals was measured for the heat-treated base glass. The measurement procedure is as follows. That is, the heat-treated base glass was broken to obtain a smooth surface. The resulting smooth surface was etched with a 5 wt% HF aqueous solution for 15 seconds. A spherical hole formed by selectively dissolving the precipitated particle portion was observed with a scanning electron microscope (SEM). Although the particle size was small and could not be measured accurately, it was 50 nm or less.

<Uniaxial quasi-constrained uniaxial compression>
The heat-treated base glass was processed into a prismatic shape of 10 mm × 10 mm × 25 mm to obtain a preform. An h-BN lubricant release agent was applied to the preform surface. A mold having a groove of 10 mm × 40 mm × 40 mm holes shown in FIG. 2 was used. In this mold, a gap is provided between the outer surface of the inner partial mold 1, 1 ′ and the cylindrical outer frame 2 surrounding the periphery thereof, and this is filled with Al ₂ O ₃ powder. Has been. When the base glass G inserted between the partial molds 1 and 1 ′ is compressed by the partial mold 4 from above, the partial molds 1 and 1 ′ are mutually connected by the base glass G that is going to spread in the horizontal direction. The pressure is applied in the direction of leaving, and this pressure is transmitted to the filling 3 (Al ₂ O ₃ powder) between the partial molds 1, 1 ′ and the outer frame 3. The filling 3 almost prevents the space between the partial molds 1 and 1 'from being freely expanded, but the space between the partial molds 1 and 1' is slightly widened because it is slightly compressed and thinned by itself. Accordingly, the base glass G can be slightly expanded without being completely constrained in that direction (quasi-constraint). The base glass G to be inserted is not restricted in the c direction in FIG.

  The base glass G was inserted into this mold so that the surface receiving the compressive load was a 10 mm × 10 mm surface, and the compressive load was applied while heating to 440 ° C. Two minutes after the start of loading of the compressive load, the compressive load reached 4000 kgf, and after that, after continuing to load 4000 kgf for 1 minute, the load was started to be lowered without changing the load. After an additional 1 minute, the glass was unloaded when the glass temperature reached 420 ° C., and then the glass was slowly cooled to room temperature. The shape after compression was about 24 mm × 13.0 mm × 8.1 mm. The pressure in the compression direction at the final stage calculated from the shape after compression is about 1300 kgf / cm 2.

<Reduction treatment>
The glass compressed above is cut in a plane parallel to both the compression direction and the quasi-constraining direction (and thus perpendicular to the c direction in FIG. 2), then precision polished to a thickness of 0.4 mm in a hydrogen atmosphere. The reduction treatment was applied. The reduction treatment was performed at 380 ° C. for 4 hours while flowing 100% hydrogen gas at a flow rate of 10 ml / min under atmospheric pressure.

  One side of the reduced glass was polished to a thickness of 0.2 mm, and the transmittance of linearly polarized light was measured with a spectrophotometer. The obtained transmittance curve is shown in FIG. From the figure, the polarizer obtained in the present example has a transmittance of 30% or more and a wavelength of 460 nm to 640 nm at a wavelength of 430 nm to 700 nm, and the linearly polarized light whose parallel direction of the short axis of the particle is parallel to the electric field vector. It is 50% or more, and within these ranges, the extinction ratio is 10 dB or more. At the same time, the extinction ratio for linearly polarized light is 15 dB or more over the wavelength ranges of 430 nm to 450 nm, 450 nm to 500 nm, and 500 nm to 550 nm. These facts indicate that the polarizer obtained in this example has high polarization performance in the blue to green region.

[Reference Examples 1-14]
A glass block was prepared in the same manner as in Example 1, and Tg, At, η (Tg + 10 ° C.), and nd were measured. However, for those having a high Tg, the mold was deteriorated, so viscosity measurement and formability evaluation were not performed.

  The compositions and measurement results of Examples and Reference Examples are summarized in the following table.

The present invention provides a polarizing material using flattened metal particles and a polarizer comprising the polarizing material. The polarizer is highly useful as a polarizer having a high transmittance and a high extinction ratio in the visible light region, particularly in the blue to green region, as compared with a conventional one using spindle-shaped particles.

Claims (28)

A polarizing material comprising flattened metal particles dispersed and contained in at least a surface layer of a glass substrate, the short axis of the flattened metal particles being oriented in a certain direction, and having a glass transition point Tg A polarizing material, characterized by not exceeding 500 ° C. and having a viscosity η at Tg + 10 ° C. of not less than 1.0 × 10 ¹² dPa · s.   The polarizing material according to claim 1, wherein the yield point At does not exceed 550 ° C.   The polarizing material according to claim 1 or 2, wherein the refractive index nd with respect to d-line does not exceed 1.50.   4. The polarizing material according to claim 1, wherein an average value of a ratio of the width (b) of the particles to the length (a) of the short axis of the flattened metal particles is at least 1.2.   The polarizing material according to claim 1, wherein the metal is silver or a silver alloy.   The polarizing material according to claim 5, which contains 0.05% by weight or more of silver.   The flattened metal particles have a minor axis and two major axes perpendicular to each other and different from each other, and the minor axis and the two major axes are each oriented in a certain direction. The polarizing material according to any one of claims 1 to 6, wherein:   The average value of the ratio of the shorter length (b) of the two major axes to the minor axis length (a) of the flattened metal particles is at least 1.2. 7. The polarizing material according to any one of 7 above. As the composition of the polarizing material,
SiO ₂ + Al ₂ O ₃ : 10 to 60% by weight
B ₂ O _3: 25~60 wt%
Na ₂ O + K ₂ O: 5 to 20% by weight
The polarizing material according to any one of claims 1 to 8, which comprises Ag: 0.05% by weight or more and Cl: 0.05% by weight or more.   The polarizing material according to any one of claims 1 to 9, wherein the polarizing material is formed in a plate shape, and the orientation direction of the minor axis of the flattened metal particles is parallel to the surface of the plate. , Polarizer.   The polarizing material according to any one of claims 1 to 9, wherein the polarizing material is formed in a plate shape, and the orientation direction of the minor axis and one major axis of the flattened metal particles is relative to the surface of the plate. Polarizers that are both parallel.   The polarizer according to claim 11, wherein an average value of a ratio of a length of a major axis oriented in a direction perpendicular to a surface of the plate to a length of a minor axis of the flattened metal particle is at least 1.4.   Of the two major axes of the flattened metal particles, the length of the major axis oriented perpendicular to the surface of the plate is greater than the length of the major axis oriented parallel to the surface of the plate. The polarizer according to claim 11 or 12, which is long.   For linearly polarized light of any wavelength between 430 nm and 700 nm, the transmittance when the orientation direction of the minor axis of the particle is parallel to the electric field vector of the linearly polarized light is 30% or more, and the extinction ratio is 10 dB or more. The polarizer according to claim 11.   The polarizer according to any one of claims 11 to 14, wherein an extinction ratio with respect to linearly polarized light is 15 dB or more over at least one of a wavelength range of 430 nm to 450 nm, 450 nm to 500 nm, and 500 nm to 550 nm. Flattened metal halide particles are dispersed and contained in a glass substrate, the short axis of the flattened metal halide particles is oriented in a certain direction, the glass transition point Tg does not exceed 500 ° C., and Tg + 10 A glass for producing a polarizing material, wherein the viscosity η at ° C is not less than 1.0 × 10 ¹² dPa · s.   The glass for producing a polarizing material according to claim 16, wherein the yield point At does not exceed 550 ° C.   The glass for producing a polarizing material according to claim 16 or 17, wherein the refractive index nd with respect to d-line does not exceed 1.50.   19. The production of a polarizing material according to claim 16, wherein the average value of the ratio of the width (b) of the particles to the length (a) of the minor axis of the flattened metal halide particles is at least 1.2. Glass.   The glass for producing a polarizing material according to claim 16, wherein the metal is silver or a silver alloy.   21. The glass for producing a polarizing material according to claim 20, wherein 0.05% by weight or more of silver is contained.   The flattened metal halide particles have a minor axis and two major axes perpendicular to each other and different from each other, and the minor axis and the two major axes are each oriented in a certain direction. The glass for producing a polarizing material according to any one of claims 16 to 21, wherein   The average value of the ratio of the shorter length (b) of the two major axes to the minor axis length (a) of the flattened metal halide particles is at least 1.2. A glass for producing a polarizing material according to any one of 16 to 22. The glass for producing a polarizing material is a composition,
SiO ₂ + Al ₂ O ₃ : 10 to 60% by weight
B ₂ O _3: 25~60 wt%
Na ₂ O + K ₂ O: 5 to 20% by weight
The glass for producing a polarizing material according to any one of claims 1 to 8, which comprises Ag: 0.05% by weight or more and Cl: 0.05% by weight or more.   25. The glass for producing a polarizing material according to claim 16, wherein the glass is formed in a plate shape, and the orientation direction of the minor axis of the flattened metal halide particles is relative to the surface of the plate. Glass for manufacturing polarizing materials that are parallel.   The glass for producing a polarizing material according to any one of claims 16 to 25, wherein the glass is formed into a plate shape, and the short axis and one length of the flattened metal halide particles are formed on the surface of the plate. A glass for manufacturing a polarizing material, in which both axes have parallel orientation directions.   27. Polarizing property according to claim 26, wherein the average value of the ratio of the length of the major axis oriented in the direction perpendicular to the surface of the plate to the length of the minor axis of the flattened metal halide particles is at least 1.4. Glass for material production. Of the two major axes of the flattened metal halide particles, the length of the major axis oriented perpendicular to the surface of the plate is greater than the length of the major axis oriented parallel to the surface of the plate. The glass for producing a polarizing material according to claim 26 or 27, wherein the glass is longer.

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