WO2018225741A1

WO2018225741A1 - Optical member, image display device, and method for manufacturing optical member

Info

Publication number: WO2018225741A1
Application number: PCT/JP2018/021577
Authority: WO
Inventors: 大輔服部; 諒太森島; 恒三中村; 池田　哲朗
Original assignee: 日東電工株式会社
Priority date: 2017-06-07
Filing date: 2018-06-05
Publication date: 2018-12-13
Also published as: TW201910824A; JPWO2018225741A1

Abstract

Provided is an optical member capable of contributing to improvement of contrast of an image display device when used in the image display device. The optical member according to the present invention has a polarizer, a reflective polarizer, and a low-refractive-index layer with a refractive index of 1.25 or less. The low-refractive-index layer is stacked on at least one side of the polarizer. In the optical member, the reflective polarizer, the polarizer, and the low-refractive-index layer are typically integrated together in this order.

Description

OPTICAL MEMBER, IMAGE DISPLAY DEVICE, AND OPTICAL MEMBER MANUFACTURING METHOD

The present invention relates to an optical member, an image display device, and a method for manufacturing the optical member.

A liquid crystal display device, which is a typical image display device, has polarizing plates disposed on both sides of a liquid crystal cell due to its image forming method. The polarizing plate typically includes a polarizer that is uniaxially stretched by adsorbing a dichroic substance on a polyvinyl alcohol (PVA) film, and protective films that are disposed on both sides of the polarizer. In addition, it has been proposed to use an optical member in which a reflective polarizer and a polarizer are integrated in an image display device (for example, Patent Document 1).

JP-T 9-507308

However, the image display device using the optical member as described above has a problem that the contrast is insufficient. The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide an optical member that can contribute to improvement of contrast of the image display device when used in the image display device, and the optical member. Another object of the present invention is to provide a high-contrast image display device and a method for producing the optical member.

The optical member of the present invention has a polarizer, a reflective polarizer, and a low refractive index layer having a refractive index of 1.25 or less, and the low refractive index layer is laminated on at least one side of the polarizer. Has been.
In one embodiment, the reflective polarizer, the polarizer, and the low refractive index layer are integrated in this order.
In one embodiment, it has further an adhesion layer arranged on the opposite side to the above-mentioned polarizer of the above-mentioned low refractive index layer.
In one embodiment, the reflective polarizer, the low refractive index layer, and the polarizer are integrated in this order.
In one embodiment, it further has a protective film disposed on the opposite side of the polarizer from the low refractive index layer.
In one embodiment, the porosity of the low refractive index layer is 35% or more, and the thickness of the low refractive index layer is thinner than the thickness of the polarizer.
According to another aspect of the present invention, an image display device is provided. This image display apparatus has the optical member.
According to still another aspect of the present invention, a method for manufacturing an optical member is provided. The method for producing the optical member is a method for producing the optical member, in which the low refractive index coating liquid is applied to the surface of the polarizer or the reflective polarizer and then dried, whereby the low refractive index is obtained. Forming the layer, or applying the low refractive index coating liquid on the surface of the substrate and drying the low refractive index layer formed on the substrate, the polarizer or the reflective type Transferring to the surface of the polarizer.

According to the present invention, an optical member that can contribute to an improvement in contrast of an image display device when used in an image display device, a high-contrast image display device including the optical member, and a method for manufacturing the optical member. Can be provided.

It is sectional drawing of the polarizing plate which concerns on one Embodiment of this invention. It is sectional drawing of the optical member by another embodiment of this invention. It is a schematic perspective view which shows an example of the reflection type polarizer which can be used in embodiment of this invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Overall Configuration of Optical Member FIG. 1 is a cross-sectional view of an optical member according to one embodiment of the present invention. As shown in FIG. 1, the optical member 100 includes a polarizer 10, a reflective polarizer 20, and a low refractive index layer 30 laminated on at least one side of the polarizer. The refractive index of the low refractive index layer is 1.25 or less. As shown in FIG. 1, in the optical member 100 of one embodiment, the reflective polarizer 20, the polarizer 10, and the low refractive index layer 30 are integrated in this order. A protective film (not shown) may be provided between the polarizer 10 and the low refractive index layer 30. That is, the polarizer 10 and the low refractive index layer 30 may be integrated with a protective film interposed therebetween. The optical member 100 may typically further include an adhesive layer (not shown) disposed on the opposite side of the low refractive index layer 30 from the polarizer 10. The reflective polarizer 20 can function as a protective layer for the polarizer 10. Therefore, the protective layer of the polarizer 10 can be omitted, and the optical member 100 can be made thinner. The optical member 100 can be typically used in an image display device, and can contribute to an improvement in contrast of the image display device.

FIG. 2 is a cross-sectional view of an optical member according to another embodiment of the present invention. In the optical member 101 of the present embodiment, the reflective polarizer 20, the low refractive index layer 30, and the polarizer 10 are integrated in this order. The optical member 101 can typically further include a protective film (not shown) disposed on the opposite side of the polarizer 10 from the low refractive index layer 30. In a conventional optical member in which a reflective polarizer and a polarizer are integrated, light incident obliquely from the reflective polarizer side (when the angle at which the light enters the surface perpendicularly is 0 °, Even light polarized in a direction parallel to the reflection axis of the reflective polarizer may pass through the reflective polarizer without being reflected by the reflective polarizer. The light transmitted through the reflective polarizer is absorbed by the polarizer, and the light utilization efficiency when the optical member is used in an image display device can be reduced. As a result, the contrast of the image display device can be reduced. On the other hand, the

optical members

100 and 101 of the present embodiment are light that is incident obliquely from the reflective polarizer side, and polarized light that vibrates in a direction parallel to the reflection axis of the reflective polarizer is reflected. It is totally reflected at the interface between the type polarizer and the low refractive index layer and can be reused. Therefore, the light utilization efficiency when the optical member is used in the image display device can be improved. As a result, the contrast of the image display device can be improved.

Preferably, the porosity of the low refractive index layer 30 is 35% or more, and the thickness of the low refractive index layer 30 is thinner than the thickness of the polarizer 10. The angle formed by the reflection axis of the reflective polarizer 20 and the absorption axis of the polarizer 10 is preferably −5 ° to 5 °.

B. Polarizer Any appropriate polarizer may be adopted as the polarizer. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and ethylene / vinyl acetate copolymer partially saponified films. In addition, there may be mentioned polyene-based oriented films such as those subjected to dyeing treatment and stretching treatment with dichroic substances such as iodine and dichroic dyes, PVA dehydrated products and polyvinyl chloride dehydrochlorinated products. Preferably, a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching is used because of excellent optical properties.

The dyeing with iodine is performed, for example, by immersing a PVA film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or may be performed while dyeing. Moreover, you may dye | stain after extending | stretching. If necessary, the PVA film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment and the like. For example, by immersing the PVA film in water and washing it before dyeing, not only can the surface of the PVA film be cleaned of dirt and anti-blocking agents, but the PVA film can be swollen to cause uneven staining. Can be prevented.

As a specific example of a polarizer obtained by using a laminate, a laminate of a resin substrate and a PVA resin layer (PVA resin film) laminated on the resin substrate, or a resin substrate and the resin Examples thereof include a polarizer obtained by using a laminate with a PVA resin layer applied and formed on a substrate. For example, a polarizer obtained by using a laminate of a resin base material and a PVA resin layer applied and formed on the resin base material may be obtained by, for example, applying a PVA resin solution to a resin base material and drying it. A PVA-based resin layer is formed thereon to obtain a laminate of a resin base material and a PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer a polarizer; obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, the stretching may further include, if necessary, stretching the laminate in the air at a high temperature (for example, 95 ° C. or higher) before stretching in the aqueous boric acid solution. The obtained resin base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer of the polarizer), and the resin base material is peeled from the resin base material / polarizer laminate. Any appropriate protective layer according to the purpose may be laminated on the release surface. Details of a method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. This publication is incorporated herein by reference in its entirety.

The thickness of the polarizer is, for example, 1 μm to 80 μm. In one embodiment, the thickness of the polarizer is preferably 1 μm to 15 μm, more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm. When the thickness of the polarizer is in such a range, curling during heating can be satisfactorily suppressed, and good appearance durability during heating can be obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is 35.0% to 46.0%, preferably 37.0% to 46.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

The single transmittance and the degree of polarization can be measured using a spectrophotometer. As a specific method for measuring the degree of polarization, the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizer are measured, and the formula: degree of polarization (%) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100. The parallel transmittance (H ₀ ) is a value of the transmittance of a parallel laminated polarizer prepared by superposing two identical polarizers so that their absorption axes are parallel to each other. The orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizer produced by superposing two identical polarizers so that their absorption axes are orthogonal to each other. Note that these transmittances are Y values obtained by correcting the visibility with the 2-degree field of view (C light source) of JlS Z 8701-1982.

C. Reflective Polarizer The reflective polarizer has a function of transmitting polarized light in a specific polarization state (polarization direction) and reflecting light in other polarization states. The reflective polarizer may be a linearly polarized light separation type or a circularly polarized light separation type. Hereinafter, as an example, a linearly polarized light separation type reflective polarizer will be described. Examples of the circularly polarized light separation type reflective polarizer include a laminate of a film in which cholesteric liquid crystal is fixed and a λ / 4 plate.

FIG. 3 is a schematic perspective view of an example of a reflective polarizer. The reflective polarizer is a multilayer laminate in which layers A having birefringence and layers B having substantially no birefringence are alternately laminated. For example, the total number of layers in such a multilayer stack can be 50-1000. In the illustrated example, the refractive index nx in the x-axis direction of the A layer is larger than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction of the B layer are substantially the same. is there. Accordingly, the difference in refractive index between the A layer and the B layer is large in the x-axis direction and is substantially zero in the y-axis direction. As a result, the x-axis direction becomes the reflection axis, and the y-axis direction becomes the transmission axis. The refractive index difference in the x-axis direction between the A layer and the B layer is preferably 0.2 to 0.3. The x-axis direction corresponds to the extending direction of the reflective polarizer in the manufacturing method described later.

The A layer is preferably made of a material that develops birefringence by stretching. Representative examples of such materials include naphthalene dicarboxylic acid polyesters (for example, polyethylene naphthalate), polycarbonates, and acrylic resins (for example, polymethyl methacrylate). Polyethylene naphthalate is preferred. The B layer is preferably made of a material that does not substantially exhibit birefringence even when stretched. A typical example of such a material is a copolyester of naphthalenedicarboxylic acid and terephthalic acid.

The reflective polarizer transmits light having a first polarization direction (for example, p-wave) at the interface between the A layer and the B layer, and has a second polarization direction orthogonal to the first polarization direction. Reflects light (eg, s-wave). The reflected light is partially transmitted as light having the first polarization direction and partially reflected as light having the second polarization direction at the interface between the A layer and the B layer. The light utilization efficiency can be increased by repeating such reflection and transmission many times inside the reflective polarizer.

In one embodiment, the reflective polarizer may include a reflective layer R as the outermost layer opposite to the polarizer, as shown in FIG. By providing the reflective layer R, it is possible to further use the light that has not been finally used and has returned to the outermost part of the reflective polarizer, so that the light use efficiency can be further increased. The reflective layer R typically exhibits a reflective function due to the multilayer structure of the polyester resin layer.

The overall thickness of the reflective polarizer can be appropriately set according to the purpose, the total number of layers included in the reflective polarizer, and the like. The total thickness of the reflective polarizer is preferably 10 μm to 150 μm.

In one embodiment, in the optical member, the reflective polarizer is arranged so as to transmit light having a polarization direction parallel to the transmission axis of the polarizer. In other words, the reflective polarizer preferably has a reflection axis in a direction substantially parallel to the absorption axis of the polarizer (the angle between the reflection axis and the absorption axis is, for example, −5 ° to 5 °). Arranged. With such a configuration, when the optical member is used in an image display device, the light absorbed by the polarizing plate can be reused, the utilization efficiency can be further increased, and the luminance is also increased. It can be improved.

The reflective polarizer can typically be produced by a combination of coextrusion and transverse stretching. Coextrusion can be performed in any suitable manner. For example, a feed block method or a multi-manifold method may be used. For example, the material constituting the A layer and the material constituting the B layer are extruded in a feed block, and then multilayered using a multiplier. Such a multi-layer apparatus is known to those skilled in the art. Next, the obtained long multilayer laminate is typically stretched in a direction (TD) orthogonal to the transport direction. The material constituting the A layer (for example, polyethylene naphthalate) increases the refractive index only in the stretching direction due to the transverse stretching, and as a result, develops birefringence. The refractive index of the material constituting the B layer (for example, a copolyester of naphthalenedicarboxylic acid and terephthalic acid) does not increase in any direction even by the transverse stretching. As a result, a reflective polarizer having a reflection axis in the stretching direction (TD) and a transmission axis in the transport direction (MD) can be obtained (TD corresponds to the x-axis direction in FIG. 3 and MD is the y-axis). Corresponding to the direction). In addition, extending | stretching operation can be performed using arbitrary appropriate apparatuses.

As the reflective polarizer, for example, the one described in JP-T-9-507308 can be used. As the reflective polarizer, a commercially available product may be used as it is, or a commercially available product may be used after secondary processing (for example, stretching). As a commercial item, 3M company brand name DBEF and 3M company brand name APF are mentioned, for example.

D. Low refractive index layer and production method thereof The refractive index of the low refractive index layer is 1.25 or less as described above. The refractive index is preferably 1.25 to 1.10, more preferably 1.20 to 1.05. As described above, the thickness of the low refractive index layer is preferably smaller than the thickness of the polarizer. The thickness of the low refractive index layer is preferably 10 nm to 10000 nm, more preferably 200 nm to 2000 nm.

The low refractive index layer typically has voids inside. The porosity of the low refractive index layer can take any appropriate value. The porosity is, for example, 5% to 90%, preferably 35% to 80%. When the porosity is within the above range, the refractive index of the low refractive index layer can be sufficiently lowered, and high mechanical strength can be obtained.

Examples of the low refractive index layer having voids therein include a porous layer and / or a low refractive index layer having at least a part of an air layer. The porous layer typically includes aerogels and / or particles (eg, hollow microparticles and / or porous particles). The low refractive index layer is preferably a nanoporous layer (specifically, a porous layer having a diameter of 90% or more of fine pores in the range of 10 ⁻² to 10 ³ nm).

The low refractive index layer of the present invention may be formed of, for example, a silicon compound. Further, the low refractive index layer of the present invention may be, for example, a low refractive index layer formed by chemical bonding between microporous particles. For example, the fine pore particles may be a crushed gel.

In the present invention, the gel pulverized product may have, for example, a structure having at least one of a particle shape, a fiber shape, and a flat plate shape. The particulate and flat structural units may be made of an inorganic substance, for example. In addition, the constituent element of the particulate structural unit may include at least one element selected from the group consisting of Si, Mg, Al, Ti, Zn, and Zr, for example. The structure (structural unit) that forms the particles may be a real particle or a hollow particle, and specifically includes silicone particles, silicone particles having fine pores, silica hollow nanoparticles, silica hollow nanoballoons, and the like. The fibrous structural unit is, for example, a nanofiber having a diameter of nanometer, and specifically includes cellulose nanofiber, alumina nanofiber, and the like. Examples of the plate-like structural unit include nanoclay, and specifically, nano-sized bentonite (for example, Kunipia F [trade name]). The fibrous structural unit is not particularly limited, but for example, from the group consisting of carbon nanofiber, cellulose nanofiber, alumina nanofiber, chitin nanofiber, chitosan nanofiber, polymer nanofiber, glass nanofiber, and silica nanofiber. It may be at least one fibrous material selected.

In the method for producing a low refractive index layer of the present invention, the gel pulverized product-containing liquid containing the gel pulverized product is, for example, a sol solution containing particles (pulverized product particles) obtained by pulverizing the gel. is there.

In the method for producing a low refractive index layer of the present invention, the gel is, for example, a silicon compound gel containing at least a trifunctional or lower saturated bond functional group.

According to the gel pulverized product-containing liquid of the present invention, for example, the present invention as a functional porous body is formed by forming the coating film and chemically bonding the pulverized products in the coating film. The low refractive index layer can be formed. According to the gel pulverized product-containing liquid of the present invention, for example, the low refractive index layer of the present invention can be applied to various objects. Therefore, the gel pulverized product-containing liquid and the production method thereof of the present invention are useful, for example, in the production of the low refractive index layer of the present invention.

In order to obtain the layer (low refractive index layer) having a high porosity, the gel pulverized product-containing liquid of the present invention is, for example, coated (coated) on the substrate and further dried. It may be a gel pulverized product-containing liquid. Moreover, the gel pulverized product-containing liquid of the present invention may be, for example, a gel pulverized product-containing liquid for obtaining a high porosity porous material (large thickness or massive bulk material). The bulk body can be obtained, for example, by performing bulk film formation using the gel pulverized product-containing liquid.

As described above, the low refractive index layer of the present invention may be a void layer. Hereinafter, the low refractive index layer of the present invention which is a void layer may be referred to as “the void layer of the present invention”. For example, a step of producing the gel pulverized product-containing liquid of the present invention, a step of coating the gel pulverized product-containing liquid on a substrate to form a coating film, and a step of drying the coating film The void layer of the present invention having a high porosity can be produced by the production method including the above.

Also, for example, the step of producing the gel crushed product-containing liquid of the present invention, the step of feeding out the roll-shaped resin film, and the coating of the gel crushed product-containing solution on the fed out resin film A process comprising a step of forming a film, a step of drying the coating film, and a step of winding the laminated film in which the low refractive index layer of the present invention is formed on the resin film after the drying step A laminated film roll can be produced by the method. Hereinafter, such a production method may be referred to as a “production method of the laminated film roll of the present invention”. Moreover, below, the laminated film roll manufactured by the manufacturing method of the laminated film roll of this invention may be called "the laminated film roll of this invention."

In the gel pulverized product-containing liquid of the present invention, the range of the volume average particle diameter of the pulverized product (porous gel particles) is, for example, 1 nm to 1000 nm, 10 nm to 700 nm, and 100 nm to 500 nm. The said volume average particle diameter shows the particle size variation of the said ground material in the gel ground material containing liquid of this invention. As described above, the volume average particle diameter is, for example, a particle size distribution evaluation apparatus such as a dynamic light scattering method or a laser diffraction method, and an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Can be measured.

In the gel pulverized product-containing liquid of the present invention, the gel (for example, porous gel) is not particularly limited, and examples thereof include a silicon compound.

The silicon compound is not particularly limited, and examples thereof include a silicon compound containing at least a trifunctional or lower saturated bond functional group. The above-mentioned “including a saturated bond functional group having 3 or less functional groups” means that the silicon compound has 3 or less functional groups, and these functional groups are saturatedly bonded to silicon (Si). Means.

The silicon compound is, for example, a compound represented by the following formula (1) or the following formula (2).

In the formula (1), for example, X is 2, 3 or 4, and R ¹ is a linear or branched alkyl group. The carbon number of R ¹ is, for example, 1-6, 1-4, 1-2. Examples of the linear alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Examples of the branched alkyl group include an isopropyl group and an isobutyl group. X is, for example, 3 or 4.

Specific examples of the silicon compound represented by the formula (1) include a compound represented by the following formula (1 ′) in which X is 3. In the following formula (1 ′), R ¹ is the same as in the above formula (1), and is, for example, a methyl group. When R ¹ is a methyl group, the silicon compound is tris (hydroxy) methylsilane. When X is 3, the silicon compound is, for example, a trifunctional silane having three functional groups.

Further, specific examples of the silicon compound represented by the formula (1) include a compound in which X is 4. In this case, the silicon compound is, for example, a tetrafunctional silane having four functional groups.

In the formula (2), for example, X is 2, 3 or 4,
R ¹ and R ² are each a linear or branched alkyl group,
R ¹ and R ² may be the same or different,
R ^{1 s} may be the same as or different from each other when X is 2.
R ² may be the same as or different from each other.

Wherein X and ^{R 1} are, for example, the same as X and ^{R 1} in the formula (1). Moreover, the said R < ² > can use the illustration of R < ¹ > in the said Formula (1), for example.

Specific examples of the silicon compound represented by the formula (2) include a compound represented by the following formula (2 ′) in which X is 3. In the following formula (2 ′), R ¹ and R ² are the same as those in the formula (2), respectively. When R ¹ and R ² are methyl groups, the silicon compound is trimethoxy (methyl) silane (hereinafter also referred to as “MTMS”).

In the gel pulverized product-containing liquid of the present invention, examples of the solvent include a dispersion medium. The dispersion medium (hereinafter also referred to as “coating solvent”) is not particularly limited, and examples thereof include a gelling solvent and a grinding solvent described later, and the grinding solvent is preferable. The coating solvent includes an organic solvent having a boiling point of 70 ° C. or higher and lower than 180 ° C. and a saturated vapor pressure at 20 ° C. of 15 kPa or lower.

Examples of the organic solvent include carbon tetrachloride, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene, isobutyl alcohol, isopropyl alcohol, isopentyl alcohol, 1-pentyl alcohol (pentanol), Ethyl alcohol (ethanol), ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-normal-butyl ether, ethylene glycol monomethyl ether, xylene, cresol, chlorobenzene, isobutyl acetate, isopropyl acetate, isopentyl acetate, ethyl acetate, Normal-butyl acetate, normal-propyl acetate, normal-pentyl acetate, cyclohexanol, cyclohexanone, 1,4-dioxa , N, N-dimethylformamide, styrene, tetrachloroethylene, 1,1,1-trichloroethane, toluene, 1-butanol, 2-butanol, methyl isobutyl ketone, methyl ethyl ketone, methyl cyclohexanol, methyl cyclohexanone, methyl normal butyl ketone, iso And pentanol. The dispersion medium may contain an appropriate amount of a perfluoro-based surfactant, a silicon-based surfactant or the like that lowers the surface tension.

The gel pulverized material-containing liquid of the present invention includes, for example, a sol particle liquid that is the sol-like pulverized material dispersed in the dispersion medium. The gel pulverized product-containing liquid of the present invention, for example, continuously forms a void layer having a film strength of a certain level or more by performing chemical crosslinking by a bonding step described later after coating and drying on a substrate. Is possible. In the present invention, “sol” means that a three-dimensional structure of a gel is pulverized so that a pulverized product (that is, a nano-three-dimensional porous sol particle retaining a part of a void structure) is dissolved in a solvent. The state which disperse | distributes to and shows fluidity.

The gel pulverized product-containing liquid of the present invention may contain, for example, a catalyst for chemically bonding the gel pulverized products. The content of the catalyst is not particularly limited, and is 0.01% to 20% by weight, 0.05% to 10% by weight, or 0.1% by weight with respect to the weight of the pulverized product of the gel. ~ 5% by weight.

The gel pulverized product-containing liquid of the present invention may further contain, for example, a crosslinking aid for indirectly bonding the gel pulverized products. The content of the cross-linking auxiliary agent is not particularly limited. For example, the content is 0.01% to 20% by weight, 0.05% to 15% by weight, or 0.1% with respect to the weight of the gel pulverized product. % By weight to 10% by weight.

In the present invention, examples of the silicon compound include a hydrolyzate of trimethoxy (methyl) silane.

The silicon compound of the monomer is not particularly limited, and can be appropriately selected according to the use of the functional porous body to be produced, for example. In the production of the functional porous body, for example, when the low refractive index property is important, the silicon compound is preferably the trifunctional silane from the viewpoint of excellent low refractive index property, and also has strength (for example, scratch resistance). ) Is preferred, the tetrafunctional silane is preferable from the viewpoint of excellent scratch resistance. Moreover, the said silicon compound used as the raw material of the said silicon compound gel may use only 1 type, for example, and may use 2 or more types together. As a specific example, the silicon compound may include, for example, only the trifunctional silane, may include only the tetrafunctional silane, may include both the trifunctional silane and the tetrafunctional silane, Furthermore, other silicon compounds may be included. When two or more types of silicon compounds are used as the silicon compound, the ratio is not particularly limited and can be set as appropriate.

The gelation of the porous body such as the silicon compound can be performed, for example, by a dehydration condensation reaction between the porous bodies. The dehydration condensation reaction is preferably performed, for example, in the presence of a catalyst. Examples of the catalyst include acid catalysts such as hydrochloric acid, oxalic acid, and sulfuric acid, and ammonia, potassium hydroxide, sodium hydroxide, ammonium hydroxide, and the like. And a dehydration condensation catalyst such as a base catalyst. The dehydration condensation catalyst may be an acid catalyst or a base catalyst, but a base catalyst is preferred. In the dehydration condensation reaction, the amount of the catalyst added to the porous body is not particularly limited, and the catalyst is, for example, 0.01 mol to 10 mol, 0.05 mol to 7 mol per mol of the porous body. Mol, 0.1 mol to 5 mol.

The gelation of the porous body such as the silicon compound is preferably performed in a solvent, for example. The ratio of the porous body in the solvent is not particularly limited. Examples of the solvent include dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), N, N-dimethylacetamide (DMAc), dimethylformamide (DMF), γ-butyllactone (GBL), acetonitrile (MeCN), ethylene Examples thereof include glycol ethyl ether (EGEE). For example, one type of solvent may be used, or two or more types may be used in combination. Hereinafter, the solvent used for the gelation is also referred to as “gelling solvent”.

The gelation conditions are not particularly limited. The treatment temperature for the solvent containing the porous body is, for example, 20 ° C. to 30 ° C., 22 ° C. to 28 ° C., 24 ° C. to 26 ° C., and the treatment time is, for example, 1 minute to 60 minutes, 5 minutes to 40 minutes. Minutes, 10 minutes to 30 minutes. When performing the said dehydration condensation reaction, the process conditions in particular are not restrict | limited, These illustrations can be used. By performing the gelation, when the porous body is a silicon compound, for example, a siloxane bond grows, primary particles of the silicon compound are formed, and further the reaction proceeds, so that the primary particles are A gel with a three-dimensional structure is formed in a bead shape.

The porous gel obtained by the gelation may be used, for example, as it is in the solvent replacement step and the first pulverization step, but may be subjected to an aging treatment in the aging step prior to the first pulverization step. Good. In the aging step, the gelled porous body (porous gel) is aged in a solvent. In the aging step, conditions for the aging treatment are not particularly limited, and for example, the porous gel may be incubated in a solvent at a predetermined temperature. According to the aging treatment, for example, the porous particles having a three-dimensional structure obtained by gelation can further grow the primary particles, thereby increasing the size of the particles themselves. is there. As a result, the contact state of the neck portion where the particles are in contact can be increased from, for example, point contact to surface contact, and the contact area can be increased. The porous gel subjected to the aging treatment as described above, for example, increases the strength of the gel itself, and as a result, the strength of the three-dimensional basic structure of the pulverized product after pulverization can be further improved. Thereby, when forming a coating film using the gel pulverized product-containing liquid of the present invention, for example, in the drying step after coating, the pore size of the void structure in which the three-dimensional basic structure is deposited, It can suppress shrinking | contraction with the volatilization of the solvent in the said coating film which arises in the said drying process.

The lower limit of the temperature of the aging treatment is, for example, 30 ° C. or more, 35 ° C. or more, 40 ° C. or more, and the upper limit thereof is, for example, 80 ° C. or less, 75 ° C. or less, 70 ° C. or less. For example, 30 ° C. to 80 ° C., 35 ° C. to 75 ° C., 40 ° C. to 70 ° C. The predetermined time is not particularly limited, and the lower limit thereof is, for example, 5 hours or more, 10 hours or more, 15 hours or more, and the upper limit thereof is, for example, 50 hours or less, 40 hours or less, 30 hours or less. The range is, for example, 5 hours to 50 hours, 10 hours to 40 hours, 15 hours to 30 hours. The optimum conditions for aging are preferably set, for example, as described above, so that an increase in the size of the primary particles and an increase in the contact area of the neck portion can be obtained in the porous gel. . In the aging step, the temperature of the aging treatment preferably takes into account, for example, the boiling point of the solvent used. In the aging treatment, for example, if the aging temperature is too high, the solvent is excessively volatilized, and there is a possibility that problems such as closing of the pores of the three-dimensional void structure occur due to the concentration of the coating solution. is there. On the other hand, in the aging treatment, for example, if the aging temperature is too low, the effect due to the aging is not sufficiently obtained, temperature variation with time of the mass production process increases, and a product with poor quality may be produced. There is.

Furthermore, after producing the liquid containing the fine pore particles or during the production process, a catalyst containing the fine pore particles and the catalyst is produced by adding a catalyst that chemically bonds the fine pore particles to each other. can do. The amount of the catalyst to be added is not particularly limited, but is, for example, 0.01 wt% to 20 wt%, 0.05 wt% to 10 wt%, or 0. 0% by weight with respect to the weight of the pulverized product of the gel silicon compound. 1% to 5% by weight. The catalyst may be, for example, a catalyst that promotes cross-linking between the microporous particles. As a chemical reaction for chemically bonding the fine pore particles, it is preferable to use a dehydration condensation reaction of residual silanol groups contained in silica sol molecules. By promoting the reaction between the hydroxyl groups of the silanol group with the catalyst, it is possible to form a continuous film that cures the void structure in a short time. Examples of the catalyst include a photoactive catalyst and a thermally active catalyst. According to the photoactive catalyst, for example, in the void layer forming step, the microporous particles can be chemically bonded (for example, crosslinked) without being heated. According to this, for example, in the gap layer forming step, since the shrinkage of the entire gap layer hardly occurs, a higher porosity can be maintained. In addition to or instead of the catalyst, a substance that generates a catalyst (catalyst generator) may be used. For example, in addition to or instead of the photoactive catalyst, a substance that generates a catalyst by light (photocatalyst generator) may be used, or in addition to or instead of the thermally active catalyst A substance that generates water (thermal catalyst generator) may be used. The photocatalyst generator is not particularly limited, and examples thereof include a photobase generator (a substance that generates a basic catalyst by light irradiation), a photoacid generator (a substance that generates an acidic catalyst by light irradiation), and the like. A photobase generator is preferred. Examples of the photobase generator include 9-anthrylmethyl N, N-diethylcarbamate (trade name WPBG-018), (E) -1- [3- (2- Hydroxyphenyl) -2-propenoyl] piperidine ((E) -1- [3- (2-hydroxyphenyl) -2-propenoyl] piperidine, trade name WPBG-027), 1- (anthraquinone-2-yl) ethyl imidazolecarboxy Rate (1- (anthraquinon-2-yl) ethyl imidazolecarboxylate, trade name WPBG-140), 2-nitrophenylmethyl 4-methacryloyloxypiperidine-1-carboxylate (trade name WPBG-165), 1,2-diisopropyl- 3- [bis (dimethylamino) methylene] guanidium 2- (3-benzoylphenyl) propionate (trade name WPBG-266), 1 , 2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium n-butyltriphenylborate (trade name WPBG-300) and 2- (9-oxoxanthen-2-yl) propionic acid 1, 5,7-triazabicyclo [4.4.0] dec-5-ene (Tokyo Chemical Industry Co., Ltd.), a compound containing 4-piperidinemethanol (trade name HDPD-PB100: manufactured by Heraeus), and the like. The trade names including “WPBG” are trade names of Wako Pure Chemical Industries, Ltd. Examples of the photoacid generator include aromatic sulfonium salts (trade name SP-170: ADEKA), triarylsulfonium salts (trade name CPI101A: San Apro), and aromatic iodonium salts (trade name Irgacure 250: Ciba Japan). Company). Further, the catalyst for chemically bonding the fine pore particles is not limited to the photoactive catalyst and the photocatalyst generator, and may be a thermal active catalyst or a thermal catalyst generator, for example. Examples of the catalyst that chemically bonds the fine pore particles include a base catalyst such as potassium hydroxide, sodium hydroxide, and ammonium hydroxide, and an acid catalyst such as hydrochloric acid, acetic acid, and oxalic acid. Of these, base catalysts are preferred. The catalyst or catalyst generator that chemically bonds the fine pore particles is added to, for example, a sol particle liquid (eg, suspension) containing the pulverized product (fine pore particles) immediately before coating. Alternatively, it can be used as a mixed solution in which the catalyst or the catalyst generator is mixed with a solvent. The mixed liquid is, for example, a coating liquid dissolved by directly adding to the sol particle liquid, a solution in which the catalyst or catalyst generator is dissolved in a solvent, or a dispersion in which the catalyst or catalyst generator is dispersed in a solvent. But you can. The solvent is not particularly limited, and examples thereof include water and a buffer solution.

Further, for example, a crosslinking aid for indirectly bonding the crushed gels may be added to the gel-containing liquid of the present invention. This crosslinking aid enters between the particles (the pulverized product), and the particles and the crosslinking aid interact or bond with each other, so that it is possible to bind particles that are slightly apart in distance. The strength can be increased efficiently. As the crosslinking aid, a polycrosslinked silane monomer is preferable. Specifically, the multi-crosslinked silane monomer has, for example, an alkoxysilyl group having 2 or more and 3 or less, the chain length between alkoxysilyl groups may be 1 to 10 carbon atoms, and an element other than carbon May also be included. Examples of the crosslinking aid include bis (trimethoxysilyl) ethane, bis (triethoxysilyl) ethane, bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, bis (triethoxysilyl) propane, bis (Trimethoxysilyl) propane, bis (triethoxysilyl) butane, bis (trimethoxysilyl) butane, bis (triethoxysilyl) pentane, bis (trimethoxysilyl) pentane, bis (triethoxysilyl) hexane, bis (tri Methoxysilyl) hexane, bis (trimethoxysilyl) -N-butyl-N-propyl-ethane-1,2-diamine, tris- (3-trimethoxysilylpropyl) isocyanurate, tris- (3-triethoxysilylpropyl) ) Isocyanurate and the like. The addition amount of the crosslinking auxiliary agent is not particularly limited. For example, it is 0.01% to 20% by weight, 0.05% to 15% by weight, or 0% with respect to the weight of the pulverized product of the silicon compound. .1% to 10% by weight.

The chemical reaction in the presence of the catalyst is, for example, light irradiation or heating on the coating film containing the catalyst or the catalyst generator previously added to the gel pulverized product-containing liquid, or on the coating film. It can be carried out by light irradiation or heating after spraying the catalyst, or by light irradiation or heating while spraying the catalyst or catalyst generator. For example, when the catalyst is a photoactive catalyst, the porous silicon body can be formed by chemically bonding the microporous particles by light irradiation. Moreover, when the said catalyst is a heat active catalyst, the said microporous particle can be chemically combined by heating and the said silicone porous body can be formed. Light irradiation amount in the irradiation (energy) is not particularly limited, @ in 360nm terms, for ^{^{example, 200mJ / cm 2 ~ 800mJ /}} cm 2, 250mJ / cm 2 ~ 600mJ / cm 2 or 300 mJ / ^cm 2 ~, 400 mJ / cm ² . From the viewpoint of preventing the irradiation amount from being insufficient and the decomposition due to light absorption of the catalyst generator from proceeding and preventing the effect from becoming insufficient, an integrated light amount of 200 mJ / cm ² or more is good. Further, from the viewpoint of preventing the base material under the low refractive index layer from being damaged and generating thermal wrinkles, an integrated light amount of 800 mJ / cm ² or less is good. The wavelength of light in the light irradiation is not particularly limited, but is, for example, 200 nm to 500 nm, 300 nm to 450 nm. The light irradiation time in the light irradiation is not particularly limited, and is, for example, 0.1 minutes to 30 minutes, 0.2 minutes to 10 minutes, or 0.3 minutes to 3 minutes. The conditions for the heat treatment are not particularly limited, and the heating temperature is, for example, 50 ° C. to 250 ° C., 60 ° C. to 150 ° C., 70 ° C. to 130 ° C., and the heating time is, for example, 0.1 minutes. 30 minutes, 0.2 minutes to 10 minutes, and 0.3 minutes to 3 minutes. As the solvent used, for example, a solvent having a low surface tension is preferable for the purpose of suppressing the generation of shrinkage stress accompanying the solvent volatilization during drying and the resulting cracking phenomenon of the low refractive index layer. Examples thereof include, but are not limited to, lower alcohols typified by isopropyl alcohol (IPA), hexane, perfluorohexane, and the like.

Examples of the silicon compound (silica-based compound) include SiO ₂ (anhydrous silicic acid); SiO ₂ , Na ₂ O—B ₂ O ₃ (borosilicate), Al ₂ O ₃ (alumina), B ₂ O _3. , TiO ₂ , ZrO ₂ , SnO ₂ , Ce ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , MoO ₃ , ZnO ₂ , WO ₃ , TiO ₂ —Al ₂ O ₃ , TiO ₂ —ZrO ₂ , In ₂ O ₃ -SnO _2, and _Sb 2 _O 3 at least one compound with a compound containing a selected from the group consisting of -SnO ₂ (the "-" indicates that the compound oxide.); a was in Also good.

The low refractive index layer may be formed of hydrolyzable silanes. Examples of the hydrolyzable silanes include hydrolysis containing an alkyl group which may have a substituent (for example, fluorine). Silanes. The hydrolyzable silanes, and the partial hydrolysates and dehydration condensates thereof are preferably alkoxysilanes and silsesquioxanes.

The alkoxysilane may be a monomer or an oligomer. The alkoxysilane monomer preferably has 3 or more alkoxyl groups. Examples of alkoxysilane monomers include methyltrimethoxysilane, methyltriethoxysilane, phenyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetrapropoxysilane, diethoxydimethoxysilane, dimethyldimethoxysilane, and dimethyldimethoxysilane. An ethoxysilane is mentioned. As the alkoxysilane oligomer, a polycondensate obtained by hydrolysis and polycondensation of the above monomers is preferable. By using alkoxysilane as the material, a low refractive index layer having excellent uniformity can be obtained.

Silsesquioxane is a general term for network-like polysiloxanes represented by the general formula RSiO _1.5 (where R represents an organic functional group). Examples of R include an alkyl group (which may be linear or branched and having 1 to 6 carbon atoms), a phenyl group, and an alkoxy group (for example, a methoxy group and an ethoxy group). Examples of the structure of silsesquioxane include a ladder type and a saddle type. By using silsesquioxane as the material, a low refractive index layer having excellent uniformity, weather resistance, transparency and hardness can be obtained.

Any appropriate particles can be adopted as the particles contained in the porous layer. The particles are typically made of a silica-based compound.

The average particle diameter of the particles is, for example, 5 nm to 200 nm, preferably 10 nm to 200 nm. By having the above configuration, a low refractive index layer having a sufficiently low refractive index can be obtained, and the transparency of the low refractive index layer can be maintained. In the present specification, the average particle diameter is given by the formula of average particle diameter = (2720 / specific surface area) from the specific surface area (m ² / g) measured by the nitrogen adsorption method (BET method). It means a value (see JP-A-1-317115).

In one embodiment, the low refractive index layer is formed by applying a coating liquid containing the above material to the surface of a reflective polarizer (or a polarizer formed on the reflective polarizer) and drying it. Can be done. In another embodiment, the low-refractive index layer is formed by applying a coating liquid containing the above-described material onto any appropriate substrate, drying, and then reflecting through any appropriate adhesive layer. It can be formed by transferring to a polarizer (or polarizer). In the case where the low refractive index layer is composed of an adhesive, the adhesive layer can be omitted.

E. Protective film The protective film is formed of any suitable film that can be used as a film for protecting the polarizer. Specific examples of the material as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based materials. And transparent resins such as polystyrene, polynorbornene, polyolefin, (meth) acryl, and acetate. Further, thermosetting resins such as (meth) acrylic, urethane-based, (meth) acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Further, a polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

The thickness of the protective film is preferably 10 μm to 100 μm. The protective film may be laminated to the polarizer via an adhesive layer (specifically, an adhesive layer or an adhesive layer), or may be adhered to the polarizer (without an adhesive layer). Good. The adhesive layer is formed of any appropriate adhesive. As an adhesive agent, the water-soluble adhesive agent which has a polyvinyl alcohol-type resin as a main component is mentioned, for example. The water-soluble adhesive mainly composed of a polyvinyl alcohol-based resin can preferably further contain a metal compound colloid. The metal compound colloid can be one in which metal compound fine particles are dispersed in a dispersion medium, and can be electrostatically stabilized due to mutual repulsion of the same kind of charge of the fine particles, and can have permanent stability. . The average particle size of the fine particles forming the metal compound colloid can be any appropriate value as long as it does not adversely affect the optical properties such as polarization properties. The thickness is preferably 1 nm to 100 nm, more preferably 1 nm to 50 nm. This is because the fine particles can be uniformly dispersed in the adhesive layer, the adhesion can be ensured, and the nick can be suppressed. The “knic” refers to a local uneven defect generated at the interface between the polarizer and the protective film. The pressure-sensitive adhesive layer is composed of any appropriate pressure-sensitive adhesive.

F. Image Display Device The optical members described in the items A to F can be used for an image display device such as a liquid crystal display device. Specifically, the optical member can be used as a polarizing plate disposed on the back side of the liquid crystal cell of the liquid crystal display device by being attached to the liquid crystal cell with the reflective polarizer on the back side. Therefore, the present invention includes an image display device using the optical member. The image display apparatus by embodiment of this invention is equipped with the optical member as described in said A term to F term.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The tests and evaluation methods in the examples are as follows. Unless otherwise specified, “parts” and “%” in the examples are based on weight.
(1) Measuring method of refractive index and film thickness The refractive index and the film thickness were determined by performing reflection measurement using an ellipsometer (product name “Woolam M2000”, manufactured by JA Woollam Co., Ltd.).
(2) Display characteristics of liquid crystal display device The liquid crystal display device was made to display a full screen white, and the front luminance (white luminance) was measured with a conoscope (manufactured by AUTRONIC MELCHERS Co., Ltd.) (unit: cd / m ² ). . Next, the liquid crystal display device was made to display full screen black, and the front luminance (black luminance) was measured with a conoscope (manufactured by AUTRONIC MELCHERS Co., Ltd.) (unit: cd / m ² ). The value of (white luminance / black luminance) was calculated and used as the front contrast.

<Production Example 1>
(Production of polarizer)
A long amorphous polyethylene terephthalate (A-PET) film (manufactured by Mitsubishi Plastics, trade name “Novaclear”, thickness: 100 μm) is prepared as a base material, and polyvinyl alcohol (PVA) is provided on one side of the base material. An aqueous solution of resin (product name “GOHSENOL (registered trademark) NH-26” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) is applied and dried at 60 ° C. to form a PVA resin layer on the substrate, and then the laminate Was immersed in an insolubilizing bath having a liquid temperature of 30 ° C. for 30 seconds (insolubilizing step). Subsequently, it was immersed in a dyeing bath having a liquid temperature of 30 ° C. for 60 seconds (dyeing process). Next, it was immersed in a crosslinking bath at a liquid temperature of 30 ° C. for 30 seconds (crosslinking step). Thereafter, the laminate was uniaxially stretched in the machine direction (longitudinal direction) between rolls having different peripheral speeds while being immersed in a boric acid aqueous solution having a liquid temperature of 60 ° C. The immersion time in the boric acid aqueous solution was 120 seconds, and the laminate was stretched until just before breaking. Thereafter, the laminate was immersed in a cleaning bath and then dried with warm air of 60 ° C. (cleaning / drying step). In this way, a laminate in which a polarizer having a thickness of 5 μm (single transmittance: 38.1%, polarization degree: 99.99%) was formed on the base material was obtained.

<Production Example 2>
(Adjustment of low refractive index coating solution)
0.5 g of 0.01 mol / L oxalic acid aqueous solution was added to a mixed solution in which 0.95 g of methyltrimethoxysilane (MTMS), which is a silicon compound precursor, was dissolved in 2.2 g of dimethyl sulfoxide (DMSO). MTMS was hydrolyzed by stirring at room temperature for 30 minutes to produce tris (hydroxy) methylsilane. Thereafter, after adding 0.38 g of 28% ammonia water and 0.2 g of pure water to 5.5 g of DMSO, the above hydrolyzed mixture was further added, and the mixture was stirred at room temperature for 15 minutes. Gelation of (hydroxy) methylsilane was performed to obtain a gel-like silicon compound. The mixed solution subjected to the gelation treatment was incubated at 40 ° C. for 20 hours as it was to be aged. Next, the aging-treated gel silicon compound was crushed into granules of several mm to several cm using a spatula. Then, as a substitution solvent, water, isopropyl alcohol (IPA), isobutyl alcohol (IBA) were added in an order of 4 times the volume of the gel, and allowed to stand at room temperature for 4 hours, and the solvent in the gel was finally added. The replacement with IBA was completed. At this time, the substitution step with each solvent was performed three times each. And the gelatinous silicon compound in the said liquid mixture was grind | pulverized. For the pulverization process, a homogenizer (trade name “UH-50”, manufactured by SMT Co., Ltd.) was used, and 1.85 g of gel and 1.14 g of IBA were weighed into a 5 cm ³ screw bottle, then 2 under the conditions of 50 W and 20 kHz. Minute grinding was performed. By the pulverization treatment, the gel-like silicon compound in the mixed solution was pulverized. As a result, the mixed solution became a sol solution of a pulverized product. To 3 g of this pulverized liquid, 0.36 g of a 1.5% concentration MIBK solution of a photobase generator (WPNG-266: Wako) and 0.5% concentration MIBK solution of bis (trimethoxysilyl) ethane (TCI) as a crosslinking aid were added. 11 g was added and mixed to prepare a low refractive index layer coating solution.

<Example 1>
1. Production of Optical Member The polarizer-side surface of the laminate obtained in Production Example 1 was bonded to a reflective polarizer (manufactured by 3M, product name “DBEF”) via an adhesive.
Next, the base material is peeled from the polarizer of the laminate, the low refractive index coating liquid obtained in Production Example 2 is applied to the peeled surface, dried at 80 ° C. for 20 seconds, and then 300 mJ / cm ² UV. Irradiation was performed to form a low refractive index layer on the surface of the polarizer, thereby obtaining an optical member having a configuration of reflective polarizer / polarizer / low refractive index layer. The low refractive index layer had a thickness of 800 nm, a porosity of 59%, and a refractive index of 1.16.
2. Production of Liquid Crystal Display Device A liquid crystal panel was taken out from an IPS mode liquid crystal display device (trade name “iPad (registered trademark) 2” manufactured by Apple Inc.), and the lower (rear side) polarizing plate was removed from the liquid crystal panel. .
Next, instead of the lower polarizing plate, the surface of the optical member obtained above on the low refractive index layer side was attached to the lower side of the liquid crystal cell via an acrylic optical adhesive (12 μm). At this time, the polarizer was bonded so that the absorption axis of the polarizer of the optical member was orthogonal to the absorption axis of the polarizer of the polarizing plate on the viewing side.
By attaching a liquid crystal panel having the optical member as a lower polarizing plate to the liquid crystal display device, a liquid crystal display device of this example was obtained. The liquid crystal display device was subjected to evaluation of luminance and contrast. The results are shown in Table 1.

<Example 2>
The surface of a reflective polarizer (manufactured by 3M, product name “DBEF”) is coated with the low refractive index coating liquid obtained in Production Example 2, dried at 80 ° C. for 20 seconds, and then 300 mJ / cm ² . UV irradiation was performed to form a low refractive index layer on the surface of the reflective polarizer. The low refractive index layer had a thickness of 800 nm, a porosity of 59%, and a refractive index of 1.16.
Next, the surface of the laminate obtained in Production Example 1 on the side opposite to the reflective polarizer of the low refractive index layer was bonded via an adhesive. Subsequently, the base material was peeled from the polarizer of the laminate, thereby obtaining an optical member having a configuration of reflective polarizer / low refractive index layer / polarizer.
A liquid crystal display device was obtained in the same manner as in Example 1 except that the surface on the polarizer side of the optical member obtained above was attached to the lower side of the liquid crystal cell. The liquid crystal display device was subjected to evaluation of luminance and contrast. The results are shown in Table 1.

<Example 3>
An acrylic protective film (thickness 40 μm) was bonded to the surface of the laminate obtained in Production Example 1 via a UV curable adhesive, and the substrate was peeled from the polarizer side of the laminate. .
Next, the acrylic protective film surface was coated with the low refractive index coating solution obtained in Production Example 2, dried at 80 ° C. for 20 seconds, and then irradiated with UV at 300 mJ / cm ² to obtain the acrylic protective film. A low refractive index layer was formed on the surface. Next, a reflective polarizer (product name “DBEF”, manufactured by 3M Co.) is bonded to the surface of the polarizer via an acrylic optical adhesive (12 μm), thereby reflecting the polarizer / polarizer / acrylic. An optical member having a configuration of protective film / low refractive index layer was obtained.
A liquid crystal display device was obtained in the same manner as in Example 1 except that the surface of the optical member obtained above was bonded to the lower side of the liquid crystal cell. The liquid crystal display device was subjected to evaluation of luminance and contrast. The results are shown in Table 1.

<Comparative Example 1>
An optical member having a reflective polarizer / polarizer configuration was obtained in the same manner as in Example 1 except that the low refractive index layer was not formed.
A liquid crystal display device was obtained in the same manner as in Example 1 except that the surface on the polarizer side of the optical member obtained above was attached to the lower side of the liquid crystal cell. The liquid crystal display device was subjected to evaluation of luminance and contrast. The results are shown in Table 1.

As is clear from Table 1, the liquid crystal display devices of Examples 1 to 3 have higher contrast than the liquid crystal display device of the comparative example.

The optical member of the present invention is suitably used for image display devices such as liquid crystal display devices and organic EL display devices.

DESCRIPTION OF SYMBOLS 10 Polarizer 20 Reflective polarizer 30 Low refractive index layer 100 Optical member 101 Optical member

Claims

A polarizer, a reflective polarizer, and a low refractive index layer having a refractive index of 1.25 or less,
An optical member in which the low refractive index layer is laminated on at least one side of the polarizer.
The optical member according to claim 1, wherein the reflective polarizer, the polarizer, and the low refractive index layer are integrated in this order.
The optical member according to claim 2, further comprising an adhesive layer disposed on the side of the low refractive index layer opposite to the polarizer.
The optical member according to claim 1, wherein the reflective polarizer, the low refractive index layer, and the polarizer are integrated in this order.
The optical member according to claim 4, further comprising a protective film disposed on the opposite side of the polarizer from the low refractive index layer.
The porosity of the low refractive index layer is 35% or more,
The optical member according to claim 1, wherein a thickness of the low refractive index layer is thinner than a thickness of the polarizer.
The optical member according to any one of claims 1 to 6, wherein an angle formed between a reflection axis of the reflective polarizer and an absorption axis of the polarizer is -5 ° to 5 °.
An image display device comprising the optical member according to any one of claims 1 to 7.
It is a manufacturing method of the optical member according to any one of claims 1 to 7,
Forming the low refractive index layer by applying and drying a low refractive index coating liquid on the surface of the polarizer or the reflective polarizer, or
Transfer the low refractive index layer formed on the base material by applying a low refractive index coating solution on the surface of the base material and drying the liquid onto the surface of the polarizer or the reflective polarizer. The manufacturing method of the optical member containing these.