JP6872330B2 - An optical member, a set of polarizing plates using the optical member, and a liquid crystal display device. - Google Patents

Description

The present invention relates to an optical member, a set of polarizing plates, and a liquid crystal display device. More specifically, the present invention relates to an optical member including a wavelength conversion layer, a low refractive index layer, and a prism sheet, a polarizing plate set using the optical member, and a liquid crystal display device.

As an image display device with low power consumption and space saving, the spread of liquid crystal display devices is remarkable. One of the demands for improving the performance of liquid crystal display devices is to improve color reproducibility. In relation to such demands, quantum dots have been attracting attention as a light emitting material in recent years, and quantum dot films using quantum dots have been commercialized. When light is incident on the quantum dot film from the backlight, the quantum dots are excited and emit fluorescence. For example, when a blue LED backlight is used, a part of blue light is converted into red light and green light by the quantum dot film, and a part of blue light is emitted as blue light as it is. As a result, white light can be realized. Further, it is said that by using such a quantum dot film, color reproducibility of 100% or more of NTSC can be realized.

On the other hand, since the color conversion efficiency of the quantum dot film is insufficient, techniques for improving the brightness and hue by using a prism sheet have been proposed (for example, Patent Documents 1 and 2). However, there is a strong demand for further improvements in brightness and hue.

Japanese Unexamined Patent Publication No. 2015-11518 International Publication No. 2014/1238336 Pamphlet

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to have excellent mechanical strength, high brightness, suppression of display unevenness, and excellent hue. An object of the present invention is to provide an optical member capable of realizing a liquid crystal display device.

The optical member of the present invention has a wavelength conversion layer, a low refractive index layer having a refractive index of 1.30 or less, a first prism sheet, and a second prism sheet in this order, and the wavelength conversion is performed. From the layer to the second prism sheet is integrated. In each of the first prism sheet and the second prism sheet, a plurality of columnar unit prisms having a flat first main surface on the low refractive index layer side and convex on the opposite side to the low refractive index layer are arranged. The convex portion of the second main surface of the first prism sheet by the unit prism is bonded to the first main surface of the second prism sheet.
In one embodiment, the wavelength conversion layer comprises a matrix and quantum dots dispersed in the matrix.
In one embodiment, the wavelength conversion layer has a barrier function against oxygen and / or water vapor.
In one embodiment, the refractive index of the low refractive index layer is 1.20 or less.
In one embodiment, the wavelength conversion layer comprises a light diffusing material.
In one embodiment, the optical member further has a polarizing plate containing an absorption type polarizer on the opposite side of the second prism sheet from the first prism sheet.
In one embodiment, the optical member further has a reflective polarizer between the second prism sheet and the polarizing plate.
In one embodiment, the optical member further has a light diffusing layer between the polarizing plate and the reflective polarizer.
In one embodiment, the optical member further has a reflective polarizer on the opposite side of the second prism sheet from the first prism sheet.
In one embodiment, the optical member further has a light diffusing layer on the opposite side of the reflective polarizer to the second prism sheet.
In one embodiment, the optical member further has a second low refractive index layer having a refractive index of 1.30 or less between the second prism sheet and the reflective polarizer. In one embodiment, the refractive index of the second low refractive index layer is 1.20 or less.
In one embodiment, the optical member further comprises a light guide plate on the opposite side of the wavelength conversion layer to the low refractive index layer.
In one embodiment, the optical member further has a third low refractive index layer having a refractive index of 1.30 or less between the wavelength conversion layer and the light guide plate.
According to another aspect of the invention, a set of polarizing plates is provided. This set of polarizing plates includes the above-mentioned optical member used as a back-side polarizing plate and a viewing-side polarizing plate.
According to yet another aspect of the present invention, a liquid crystal display device is provided. This liquid crystal display device includes a liquid crystal cell, a viewing side polarizing plate arranged on the viewing side of the liquid crystal cell, a back side polarizing plate arranged on the side opposite to the viewing side of the liquid crystal cell, and the back side polarizing plate. It has the above-mentioned optical member arranged on the outside of the. A liquid crystal display device according to another embodiment includes a liquid crystal cell, a polarizing plate arranged on the viewing side of the liquid crystal cell, and the above-mentioned optical member arranged on the side opposite to the viewing side of the liquid crystal cell.

According to the present invention, in an optical member in which a prism sheet is integrated, two prism sheets are used, and a flat surface of one prism sheet and a convex portion of the other prism sheet by a unit prism are bonded together. Further, by using a predetermined low refractive index layer and a wavelength conversion layer containing quantum dots in combination, the mechanical strength is excellent, the brightness is high, the display unevenness is suppressed, and the hue is excellent. It is possible to provide an optical member that can realize a liquid crystal display device.

It is schematic cross-sectional view explaining the optical member by one Embodiment of this invention. It is schematic cross-sectional view explaining the optical member by another embodiment of this invention. It is schematic cross-sectional view explaining the optical member by still another Embodiment of this invention. It is schematic cross-sectional view explaining the optical member by still another Embodiment of this invention. It is a schematic perspective view of an example of a reflective polarizer that can be used in the optical member of the present invention. It is a chromaticity diagram which shows the color shift of the liquid crystal display apparatus obtained in an Example and a comparative example.

A. Overall configuration of optical member First, a typical embodiment of the overall configuration of the optical member will be described with reference to the drawings. In each drawing, the same components are designated by the same reference numerals, and duplicate description will be omitted. Also, for the sake of clarity, the thickness ratio of each layer in the drawing is different from the actual one. The components of the optical member will be described in detail in Sections B to K.

FIG. 1 is a schematic cross-sectional view illustrating an optical member according to one embodiment of the present invention. The optical member 100 has a wavelength conversion layer 10, a low refractive index layer 20, a first prism sheet 30, and a second prism sheet 40 in this order. The refractive index of the low refractive index layer 20 is 1.30 or less. In the optical member 100 according to the present embodiment, the wavelength conversion layer 10 to the second prism sheet 40 are integrated. By incorporating the prism sheet into the optical member and integrating it in this way, the air layer between the prism sheet and the adjacent layer can be eliminated, which can contribute to the thinning of the liquid crystal display device. .. The thinning of the liquid crystal display device has a great commercial value because it expands the range of design choices. Furthermore, by integrating the prism sheet, it is possible to avoid scratches on the prism sheet due to rubbing when the prism sheet is attached to a surface light source device (backlight unit, substantially a light guide plate), which is caused by such scratches. It is possible to obtain a liquid crystal display device which can prevent the display from becoming turbid and has excellent mechanical strength. Further, by incorporating the wavelength conversion layer into such an integrated member, display unevenness can be satisfactorily suppressed when the optical member is applied to the liquid crystal display device.

The first prism sheet 30 typically has a base material portion 31 and a prism portion 32. The second prism sheet 40 typically has a base material portion 41 and a prism portion 42. The first prism sheet 30 and the second prism sheet 40 have a flat first main surface (flat surfaces of the base materials 31 and 41) on the low refractive index layer 20 side and a side opposite to the low refractive index layer 20, respectively. It has a second main surface having a concavo-convex shape (a surface having convex portions due to columnar unit prisms 33, 43 arranged on the opposite side of the low refractive index layer). In the embodiment of the present invention, the convex portion of the second main surface of the first prism sheet 30 by the unit prism 33 is attached to the first main surface of the second prism sheet 40 (the flat surface of the base material portion 41). It is matched. As a result, a gap is defined between the recess on the second main surface of the first prism sheet 30 and the first main surface of the second prism sheet 40. With such a configuration, when the optical member is applied to a liquid crystal display device, high brightness, excellent hue, and suppression of display unevenness can be realized at the same time. In the present specification, such adhesion of only the convex portion of the prism sheet (substantially, the unit prism) may be referred to as "point adhesion" for convenience. The technical significance of adopting such point bonding is as follows. The wavelength conversion layer applied to the liquid crystal display device converts a part of the incident blue to bluish purple light into green light and red light, and emits a part as blue light as it is, so that red light and green light are emitted. And blue light to achieve white light. Further, the wavelength conversion layer applied to the liquid crystal display device is often yellow to orange due to the relationship between the constituent materials and light absorption. The prism sheet is typically used to supplement the color conversion efficiency, which is insufficient by the wavelength conversion layer alone, by utilizing its retroreflection, and to improve the brightness and hue. Here, since the prism sheet has a function of condensing the spread light in the front direction, high conversion efficiency is not sufficiently realized in the oblique direction, and as a result, the hue in the oblique direction is the color of the wavelength conversion layer. It stands out and looks yellow to orange, which often causes deterioration of the display quality of the image display device. According to the embodiment of the present invention, by adopting the point bonding, the air layer is eliminated at the point bonding portion, the light collecting property is reduced, and the light spreads to the surroundings. That is, as compared with the configuration in which the prism sheet is simply placed (separately placed), the light is diffused to the surroundings, and as a result, the hue in the front and oblique directions (particularly in the oblique direction) can be improved. By adjusting the degree of point adhesion (eg, the number and position of point adhesion portions, the thickness of the adhesive used for point adhesion), the desired balance of brightness and hue can be achieved in both the front and diagonal directions. it can. In addition, further excellent brightness and hue can be realized by adjusting the degree of point adhesion to form a void portion having a predetermined void degree.

FIG. 2 is a schematic cross-sectional view illustrating an optical member according to another embodiment of the present invention. The optical member 101 further has a polarizing plate 50 on the side opposite to the low refractive index layer 20 of the second prism sheet 40. The polarizing plate 50 is typically a protective layer 52 arranged on one side of an absorbing polarizing element 51, an absorbing polarizing element 51, and a protective layer 53 arranged on the other side of the absorbing polarizing element 51. And have. In the present embodiment, preferably, a reflective polarizer 60 may be further provided between the second prism sheet 40 and the polarizing plate 50. Further, in the present embodiment, a second low refractive index layer 70 may be further provided between the second prism sheet 40 and the reflective polarizer 60. The refractive index of the second low refractive index layer 70 is typically 1.30 or less. In the present embodiment, the convex portion of the second prism sheet 40 by the unit prism 43 on the second main surface is the polarizing plate 50 (if present, the reflective polarizing element 60 or the second low refractive index layer 70). ) Is pasted. That is, the second prism sheet and the polarizing plate (if present, a reflective polarizer or a second low refractive index layer) are point-bonded. According to the present embodiment, the first prism sheet 30 and the second prism sheet 40 are point-bonded, and the second prism sheet 40 and the polarizing plate (if present, a reflective polarizer or a second). Due to the synergistic effect of the two point-adhesion, which is the point-adhesion with the low-refractive-index layer), the desired light distribution is realized in the optical member, and as a result, the hue is obtained from either the front or the oblique direction. It is possible to realize a liquid crystal display device that is constant and has excellent display quality.

In one embodiment, the optical member may further include a light diffusing layer (not shown). In the embodiment shown in FIG. 2, the light diffusing layer may be provided between the reflective polarizer 60 and the polarizing plate 50. In the embodiment in which the polarizing plate 50 is omitted, the light diffusing layer may be provided on the opposite side of the reflective polarizer 60 from the second prism sheet 40. In the embodiment in which the reflective polarizer 60 is omitted, the light diffusing layer may be provided on the second prism sheet 40 side of the polarizing plate 50. Further, the optical member may further have a barrier layer (not shown) adjacent to the wavelength conversion layer 10 on at least one side of the wavelength conversion layer 10, if necessary. Specifically, the barrier layer may be provided between the low refractive index layer 20 and the wavelength conversion layer 10 and / or on the opposite side of the wavelength conversion layer 10 from the low refractive index layer 20.

FIG. 3 is a schematic cross-sectional view illustrating an optical member according to still another embodiment of the present invention. The optical member 102 further has a light guide plate 80 on the side opposite to the low refractive index layer 20 of the wavelength conversion layer 10. In the present embodiment, preferably, a third low refractive index layer 90 may be further provided between the wavelength conversion layer 10 and the light guide plate 80. The refractive index of the third low refractive index layer 90 is typically 1.30 or less.

In one embodiment, the optical member of the present invention may be elongated. That is, the wavelength conversion layer, the low refractive index layer, the first and second prism sheets, the polarizing plate, the reflective polarizer and the like can be elongated. Since the long optical member can be manufactured by roll-to-roll, it is excellent in manufacturing efficiency.

Each component of the optics can be laminated via any suitable adhesive layer (eg, adhesive layer, adhesive layer: not shown).

The above embodiments may be combined as appropriate, and the components of the above embodiments may be modified in the art. For example, as shown in FIG. 4, the embodiment of FIG. 2 and the embodiment of FIG. 3 may be combined. Further, for example, in the illustrated example, the case where two prism sheets (that is, the first prism sheet 30 and the second prism sheet 40) are provided has been described, but the prism sheet and the layer adjacent to the convex portion of one prism sheet have been described. Any suitable configuration may be adopted as long as it is point-bonded to a flat surface such as an optical film or a member. For example, three or more prism sheets may be provided depending on the purpose. Further, depending on the purpose, one of the first protective layer 52 and the second protective layer 53 of the polarizing plate 50 may be omitted. For example, if the reflective polarizer 60 can also function as a protective layer for the absorbing polarizer 51, the second protective layer 53 may be omitted. Further, in the embodiment of FIG. 2, the polarizing plate 50 may be omitted (that is, only the reflective polarizer (and, if necessary,) on the opposite side of the second prism sheet 40 from the first prism sheet 30. A second refractive index layer 70) may be provided). Further, each component may be replaced with an optically equivalent structure.

B. Wavelength conversion layer The wavelength conversion layer 10 typically includes a matrix and wavelength conversion materials dispersed in the matrix.

B-1. Matrix As a material constituting the matrix (hereinafter, also referred to as a matrix material), any suitable material can be used. Examples of such a material include resins, organic oxides, and inorganic oxides. The matrix material preferably has low oxygen permeability and moisture permeability, high photostability and chemical stability, has a predetermined index of refraction, has excellent transparency, and / or , Has excellent dispersibility with respect to wavelength conversion materials. Practically, the matrix can be composed of a resin film or an adhesive.

B-1-1. When the resin film matrix is a resin film, any suitable resin can be used as the resin constituting the resin film. Specifically, the resin may be a thermoplastic resin, a thermosetting resin, or an active energy ray-curable resin. Examples of the active energy ray-curable resin include an electron beam-curable resin, an ultraviolet-curable resin, and a visible light-curable resin. Specific examples of the resin include epoxy, (meth) acrylate (eg, methyl methacrylate, butyl acrylate), norbornene, polyethylene, poly (vinyl butyral), poly (vinyl acetate), polyurea, polyurethane, aminosilicone (AMS), etc. Polyphenylmethylsiloxane, polyphenylalkylsiloxane, polydiphenylsiloxane, polydialkylsiloxane, silsesquioxane, fluorinated silicones, vinyl and hydride substituted silicones, styrene-based polymers (eg, polystyrene, aminopolystyrene (APS), poly (eg, polystyrene, aminopolystyrene (APS), poly) Acrylic nitrile ethylene styrene) (AES)), polymers crosslinked with bifunctional monomers (eg divinylbenzene), polyester polymers (eg polyethylene terephthalates), cellulose polymers (eg triacetyl cellulose), vinyl chloride polymers , Amid-based polymer, imide-based polymer, vinyl alcohol-based polymer, epoxy-based polymer, silicone-based polymer, acrylic urethane-based polymer. These may be used alone or in combination (eg, blend, copolymer). These resins may be subjected to treatments such as stretching, heating, and pressurization after forming the film. A thermosetting resin or an ultraviolet curable resin is preferable, and a thermosetting resin is more preferable. This is because it can be suitably applied when the optical member of the present invention is manufactured by roll-to-roll.

B-1-2. When the pressure-sensitive adhesive matrix is a pressure-sensitive adhesive, any suitable pressure-sensitive adhesive can be used as the pressure-sensitive adhesive. The pressure-sensitive adhesive preferably has transparency and optical isotropic properties. Specific examples of the pressure-sensitive adhesive include rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, and cellulose-based pressure-sensitive adhesives. A rubber-based pressure-sensitive adhesive or an acrylic-based pressure-sensitive adhesive is preferable.

B-2. Wavelength conversion material The wavelength conversion material can control the wavelength conversion characteristics of the wavelength conversion layer. The wavelength conversion material may be, for example, a quantum dot or a phosphor.

The content of the wavelength conversion material in the wavelength conversion layer (the total content when two or more kinds are used) is preferably based on 100 parts by weight of the matrix material (typically, resin or pressure-sensitive adhesive solid content). It is 0.01 parts by weight to 50 parts by weight, more preferably 0.01 parts by weight to 30 parts by weight. When the content of the wavelength conversion material is in such a range, it is possible to realize a liquid crystal display device having an excellent hue balance of all RGB.

B-2-1. Quantum dots The emission center wavelength of quantum dots can be adjusted according to the material and / or composition, particle size, shape, etc. of the quantum dots.

Quantum dots can be made of any suitable material. The quantum dots may be preferably composed of an inorganic material, more preferably an inorganic conductor material or an inorganic semiconductor material. Examples of the semiconductor material include group II-VI, group III-V, group IV-VI, and group IV semiconductors. Specific examples include Si, Ge, Sn, Se, Te, B, C (including diamonds), P, BN, BP, BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdSeZn, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeSe, Se, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, CuI, Si ₃ N ₄ , Ge ₃ N ₄ , Al ₂ O ₃ , (Al, Ga, In) ₂ (S, Se, Te) ₃ , Al ₂ CO can be mentioned. These may be used alone or in combination of two or more. The quantum dots may contain a p-type dopant or an n-type dopant. Further, the quantum dots may have a core-shell structure. In the core-shell structure, any suitable functional layer (single layer or multiple layers) may be formed around the shell depending on the purpose, and the shell surface may be surface-treated and / or chemically modified. Good.

As the shape of the quantum dot, any appropriate shape can be adopted depending on the purpose. Specific examples include a true spherical shape, a flaky shape, a plate shape, an elliptical spherical shape, and an amorphous shape.

As the size of the quantum dots, any appropriate size may be adopted depending on the desired emission wavelength. The size of the quantum dots is preferably 1 nm to 10 nm, more preferably 2 nm to 8 nm. When the size of the quantum dots is in such a range, each of green and red emits sharp light, and high color rendering properties can be realized. For example, green light can emit light when the size of the quantum dots is about 7 nm, and red light can emit light when the size of the quantum dots is about 3 nm. The size of the quantum dots is, for example, an average particle size when the quantum dots are spherical, and is a dimension along the minimum axis in the shape when the quantum dots have other shapes.

Details of the quantum dots are described in, for example, Japanese Patent Application Laid-Open No. 2012-169271, Japanese Patent Application Laid-Open No. 2015-102857, Japanese Patent Application Laid-Open No. 2015-65158, Japanese Patent Application Laid-Open No. 2013-544018, and Japanese Patent Application Laid-Open No. 2010-533996. The descriptions in these publications are incorporated herein by reference. Commercially available products may be used as the quantum dots.

B-2-2. Phosphor As the phosphor, any suitable phosphor capable of emitting light of a desired color depending on the intended purpose can be used. Specific examples include a red phosphor and a green phosphor.

Examples of the red phosphor include a composite fluoride phosphor activated with ^{Mn 4+.} The composite fluoride phosphor contains at least one coordination center (for example, M described later), is surrounded by a fluoride ion acting as a ligand, and is surrounded by a counter ion (for example, A described later) as necessary. ) Refers to a coordination compound whose charge is compensated by. Specific examples thereof include A ₂ [MF ₅ ]: Mn ⁴⁺ , A ₃ [MF ₆ ]: Mn ⁴⁺ , Zn ₂ [MF ₇ ]: Mn ⁴⁺ , A [In ₂ F ₇ ]: Mn ⁴⁺ , A ₂ [ M'F ₆ ]: Mn ⁴⁺ , E [M'F ₆ ]: Mn ⁴⁺ , A ₃ [ZrF ₇ ]: Mn ⁴⁺ , Ba _0.65 Zr _0.35 F _2.70 : Mn ⁴⁺ . Here, A is Li, Na, K, Rb, Cs, NH ₄ or a combination thereof. M is Al, Ga, In or a combination thereof. M'is Ge, Si, Sn, Ti, Zr or a combination thereof. E is Mg, Ca, Sr, Ba, Zn or a combination thereof. A composite fluoride phosphor having a coordination number of 6 at the coordination center is preferable. Details of such a red phosphor are described in, for example, Japanese Patent Application Laid-Open No. 2015-84327. The entire description of this publication is incorporated herein by reference in its entirety.

Examples of the green phosphor include a compound containing a solid solution of sialon having _{a β-type Si 3} N _{4 crystal structure as a main component.} Preferably, a treatment is performed so that the amount of oxygen contained in such a sialon crystal is a specific amount (for example, 0.8% by mass) or less. By performing such a process, a green phosphor having a narrow peak width and emitting sharp light can be obtained. Details of such a green phosphor are described in, for example, Japanese Patent Application Laid-Open No. 2013-28814. The entire description of this publication is incorporated herein by reference in its entirety.

The wavelength conversion layer may be a single layer or may have a laminated structure. When the wavelength conversion layers have a laminated structure, each layer may typically contain wavelength conversion materials having different emission characteristics.

The thickness of the wavelength conversion layer (in the case of having a laminated structure, the total thickness thereof) is preferably 1 μm to 500 μm, and more preferably 100 μm to 400 μm. When the thickness of the wavelength conversion layer is in such a range, conversion efficiency and durability can be excellent. When the wavelength conversion layer has a laminated structure, the thickness of each layer is preferably 1 μm to 300 μm, and more preferably 10 μm to 250 μm.

Water vapor transmission rate of thickness 50μm in terms of the wavelength conversion layer (moisture permeability) is preferably not more than 100g ^/ m 2 · day, more preferably not more than 80g ^/ m 2 · day. The water vapor permeability can be measured by a measurement method based on JIS K7129 in an atmosphere of 40 ° C. and 90% RH.

B-3. Barrier Function Whether the matrix is a resin film or an adhesive, the wavelength conversion layer preferably has a barrier function against oxygen and / or water vapor. As used herein, the term "having a barrier function" means controlling the amount of oxygen and / or water vapor that penetrates the wavelength conversion layer to substantially block the wavelength conversion material from them. The wavelength conversion layer can exhibit a barrier function by imparting a three-dimensional structure such as a core shell type or a tetrapod type to the wavelength conversion material itself. In addition, the wavelength conversion layer can exhibit a barrier function by appropriately selecting a matrix material.

B-4. The other wavelength conversion layer may further contain any suitable additive depending on the purpose. Examples of the additive include a light diffusing material, a material that imparts anisotropy to light, and a material that polarizes light. Specific examples of the light diffusing material include acrylic resin, silicone resin, styrene resin, and fine particles composed of a copolymer resin thereof. Specific examples of the material that imparts anisotropy to light and / or the material that polarizes light include elliptical spherical fine particles, core-shell fine particles, and laminated fine particles having different birefringences on the major axis and the minor axis. The type, number, blending amount, etc. of the additive can be appropriately set according to the purpose.

The wavelength conversion layer can be formed, for example, by applying a liquid composition containing a matrix material, a wavelength conversion material, and if necessary, an additive. For example, when the matrix material is a resin, the wavelength conversion layer applies a liquid composition containing the matrix material, the wavelength conversion material and optionally an additive, a solvent and a polymerization initiator to any suitable support. And then can be formed by drying and / or curing. The solvent and polymerization initiator can be appropriately set depending on the type of matrix material (resin) used. As the coating method, any appropriate coating method can be used. Specific examples include a curtain coating method, a dip coating method, a spin coating method, a print coating method, a spray coating method, a slot coating method, a roll coating method, a slide coating method, a blade coating method, a gravure coating method, and a wire bar method. Be done. Curing conditions can be appropriately set according to the type of matrix material (resin) used, the composition of the composition, and the like. When the wavelength conversion material is added to the matrix material, it may be added in the form of particles or in the state of a dispersion liquid dispersed in a solvent. The wavelength conversion layer may be formed on the barrier layer.

The wavelength conversion layer formed on the support can be transferred to other components of the optical member (eg, barrier layer, low index of refraction layer).

C. Low refractive index layer The refractive index of the low refractive index layer 20 is 1.30 or less as described above. The refractive index of the low refractive index layer 20 is preferably as close to the refractive index of air (1.00) as possible. Specifically, the refractive index of the low refractive index layer is preferably 1.20 or less, more preferably 1.15 or less. The lower limit of the refractive index of the low refractive index layer is, for example, 1.01. When the refractive index of the low refractive index layer is within such a range, it is possible to realize a liquid crystal display device having high brightness while eliminating the air layer and realizing remarkable thinning.

The low refractive index layer typically has voids inside. The porosity of the low index of refraction layer can take any suitable value. The porosity is, for example, 5% to 99%, preferably 25% to 95%. 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.

The low refractive index layer having voids inside may have, for example, a structure having at least one particle-like, fibrous-like, or flat plate-like shape. The structure (constituent unit) forming the particles may be real particles or hollow particles, and specific examples thereof include silicone particles, silicone particles having micropores, silica hollow nanoparticles, and silica hollow nanoballoons. The fibrous structural unit is, for example, nanofibers having a diameter of nanofibers, and specific examples thereof include cellulose nanofibers and alumina nanofibers. Examples of the flat plate-shaped structural unit include nanoclay, and specific examples thereof include nano-sized bentonite (for example, Kunipia F [trade name]). Further, in the void structure of the present invention, the single, one or more structural units forming the fine void structure are chemically, for example, directly or indirectly through catalytic action. Includes connecting parts. In the present invention, "indirectly bonded" to each other means that the constituent units are bonded to each other via a small amount of binder component equal to or less than the amount of the constituent units. The term "directly bonded" to each other means that the constituent units are directly bonded to each other without the intervention of a binder component or the like.

Any suitable material may be adopted as the material constituting the low refractive index layer. As the material, for example, the materials described in International Publication No. 2004/1193966, Japanese Patent Application Laid-Open No. 2013-254183, and Japanese Patent Application Laid-Open No. 2012-189802 can be adopted. Specifically, for example, silica-based compounds; hydrolyzable silanes and their partial hydrolysates and dehydration condensates; organic polymers; silicon compounds containing silanol groups; silicates in contact with acids and ion exchange resins. Active silica obtained by allowing the mixture; polymerizable monomers (eg, (meth) acrylic monomers, and styrene monomers); curable resins (eg, (meth) acrylic resins, fluorine-containing resins, and urethane resins); These combinations can be mentioned.

Examples of the organic polymer include polyolefins (for example, polyethylene and polypropylene), polyurethanes, and fluorine-containing polymers (for example, a fluorine-containing monomer unit and a fluorine-containing copolymer having a constituent unit for imparting cross-linking reactivity as constituents). Polymers), polyesters (eg, poly (meth) acrylic acid derivatives (in this specification, (meth) acrylic acid means acrylic acid and methacrylic acid, and "(meth)" all have such meanings. )), Polyethers, polyamides, polyimides, polyureas, and polycarbonates.

The material preferably contains a silica-based compound; hydrolyzable silanes, and partial hydrolysates and dehydration condensates thereof.

Examples of the silica-based compound include SiO ₂ (silicic anhydride); SiO ₂ , Na ₂ O-B ₂ O ₃ (borosilicate), Al ₂ O ₃ (alumina), B ₂ O ₃ , TiO ₂ , and so on. _{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 _{a compound containing at least one compound selected from the group consisting of Sb 2} O _3- SnO ₂ (the above-mentioned "-" indicates that it is a composite oxide);

Examples of the hydrolyzable silanes include hydrolyzable silanes containing an alkyl group which may have a substituent (for example, fluorine). The hydrolyzable silanes, as well as their partial hydrolysates and dehydration condensates, are preferably alkoxysilanes and silsesquioxane.

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

Silsesquioxane is a general _{term for network-like polysiloxane 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 a straight chain or a branched chain and has 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 cage type. By using silsesquioxane as the above material, a low refractive index layer having excellent uniformity, weather resistance, transparency, and hardness can be obtained.

Any suitable particles may be adopted as the particles. The particles are typically made of a silica-based compound.

The shape of the silica particles can be confirmed, for example, by observing with a transmission electron microscope. The average particle size of the particles is, for example, 5 nm to 200 nm, preferably 10 nm to 200 nm. By having the above structure, 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 this specification, the average particle size is given by the formula of average particle size = (2720 / specific surface area) from ^{the specific surface area (m 2} / g) measured by the nitrogen adsorption method (BET method). It shall mean a value (see Japanese Patent Application Laid-Open No. 1-317115).

Examples of the method for obtaining the low refractive index layer include JP-A-2010-189212, JP-A-2008-040171, JP-A-2006-01175, Pamphlet 2004/119366, and their references. The method described in is mentioned. Specifically, a silica-based compound; a method for hydrolyzing and polycondensing at least one of hydrolyzable silanes and a partial hydrolyzate and dehydration condensate thereof, porous particles and / or hollow fine particles are used. A method for forming an airgel layer using a springback phenomenon, a pulverized gel obtained by pulverizing a gel obtained by a sol-gel, and chemically bonding fine pore particles in the pulverized solution with a catalyst or the like. The method to be used, etc. can be mentioned. However, the low refractive index layer is not limited to this production method, and may be produced by any production method.

The low index of refraction layer is attached to the wavelength conversion layer and the first prism sheet via any suitable adhesive layer (eg, adhesive layer, adhesive layer: not shown). When the low refractive index layer is composed of an adhesive, the adhesive layer can be omitted.

The haze of the low refractive index layer is, for example, 0.1% to 30%, preferably 0.2% to 10%.

As for the mechanical strength of the low refractive index layer, for example, it is desirable that the scratch resistance by Bencot (registered trademark) is 60% to 100%.

The anchoring force between the low refractive index layer and the wavelength conversion layer is not particularly limited, but is, for example, 0.01 N / 25 mm or more, preferably 0.1 N / 25 mm or more, and more preferably 1 N / 25 mm or more. .. In order to increase the mechanical strength and anchoring force, undercoating treatment, heat treatment, humidification treatment, UV treatment, etc. Corona treatment, plasma treatment and the like may be performed.

The thickness of the low refractive index layer 20 is preferably 100 nm to 5000 nm, more preferably 200 nm to 4000 nm, further preferably 300 nm to 3000 nm, and particularly preferably 500 nm to 2000 nm. When the thickness of the low refractive index layer is within such a range, it is possible to realize a low refractive index layer that optically exhibits sufficient functions with respect to light in the visible light region and has excellent durability.

D. Prism sheet D-1. First Prism Sheet As described above, the first prism sheet 30 typically has a base material portion 31 and a prism portion 32. The first prism sheet 30 is a prism unit 32 that keeps the polarized light emitted from the backlight unit in a polarized state when the optical member of the present invention is arranged on the backlight side of the liquid crystal display device. It is guided to the polarizing plate as polarized light having the maximum intensity in the substantially normal line direction of the liquid crystal display device by total internal reflection or the like. The base material portion 31 may be omitted depending on the purpose and the configuration of the prism sheet. For example, when the low refractive index layer 20 can function as a support member for the prism sheet, the base material portion 31 may be omitted. The "abbreviated normal direction" includes a direction within a predetermined angle from the normal direction, for example, a direction within a range of ± 10 ° from the normal direction.

D-1-1. Prism section In one embodiment, the first prism sheet 30 (substantially, the prism section 32) has a plurality of columnar unit prisms 33 that are convex on the opposite side to the low refractive index layer 20 as described above. It is arranged and configured. Preferably, the unit prism 33 has a columnar shape, and its longitudinal direction (ridge line direction) is oriented in a direction substantially orthogonal to or substantially parallel to the transmission axis of the polarizing plate. In the present specification, the expressions "substantially orthogonal" and "substantially orthogonal" include the case where the angle formed by the two directions is 90 ° ± 10 °, preferably 90 ° ± 7 °, and further. It is preferably 90 ° ± 5 °. The expressions "substantially parallel" and "substantially parallel" include the case where the angle between the two directions is 0 ° ± 10 °, preferably 0 ° ± 7 °, and even more preferably 0 ° ±. It is 5 °. Further, the term "orthogonal" or "parallel" in the present specification may include substantially orthogonal or substantially parallel states. The first prism sheet 30 may be arranged so that the ridge line direction of the unit prism 33 and the transmission axis of the polarizing plate form a predetermined angle (so-called oblique arrangement). By adopting such a configuration, the occurrence of moire may be prevented more satisfactorily. The range of the oblique arrangement is preferably 20 ° or less, and more preferably 15 ° or less.

As the shape of the unit prism 33, any suitable configuration can be adopted as long as the effects of the present invention can be obtained. The unit prism 33 may have a triangular cross-sectional shape in a cross section parallel to the arrangement direction and parallel to the thickness direction, and other shapes (for example, one or both slopes of the triangle have different inclination angles). It may have a shape having a plurality of flat surfaces). The triangular shape may be a shape that is asymmetric with respect to a straight line passing through the apex of the unit prism and orthogonal to the sheet surface (for example, an isosceles triangle), or a shape that is symmetric with respect to the straight line (for example, two). It may be an isosceles triangle). Further, the apex of the unit prism may be a chamfered curved surface, or may be cut so that the tip is a flat surface to have a trapezoidal cross section. The detailed shape of the unit prism 33 can be appropriately set according to the purpose. For example, as the unit prism 33, the configuration described in JP-A-11-84111 can be adopted.

The height of the unit prism 33 may be the same for all the unit prisms or may have different heights. If the unit prisms have different heights, in one embodiment the unit prisms have two heights. With such a configuration, only the unit prism having the higher height can be point-bonded. Therefore, by adjusting the position and number of the unit prisms having the higher height, point bonding can be realized to a desired degree. Can be done. For example, the unit prisms having a high height and the unit prisms having a low height may be arranged alternately, or the unit prisms having a high height (or a low height) may be arranged every three, four, five, or the like. Often, they may be arranged irregularly according to the purpose, or they may be arranged completely randomly. In another embodiment, the unit prism has a height of three or more. With such a configuration, the degree of embedding of the unit prism to be point-bonded in the adhesive can be adjusted, and as a result, point bonding can be realized with a more precise degree.

D-1-2. Base material portion When the base material portion 31 is provided on the first prism sheet 30, the base material portion 31 and the prism portion 32 may be integrally formed by extrusion molding or the like of a single material. The prism portion may be formed on the film for the base material portion. The thickness of the base material portion is preferably 25 μm to 150 μm. With such a thickness, handleability and strength can be excellent.

As the material constituting the base material portion 31, any suitable material can be adopted depending on the purpose and the configuration of the prism sheet. When the prism portion is formed on the base film, specific examples of the base film are (meth) acrylic resins such as cellulose triacetate (TAC) and polymethyl methacrylate (PMMA). , A film formed of a polycarbonate (PC) resin. The film is preferably an unstretched film.

When the base material portion 31 and the prism portion 32 are integrally formed with a single material, the same material as the material for forming the prism portion when the prism portion is formed on the film for the base material portion should be used as the material. Can be done. Examples of the material for forming the prism portion include epoxy acrylate-based and urethane acrylate-based reactive resins (for example, ionizing radiation curable resins). When forming the integrally configured prism sheet, a polyester resin such as PC or PET, an acrylic resin such as PMMA or MS, or a light-transmitting thermoplastic resin such as cyclic polyolefin can be used.

The base material portion 31 is preferably substantially optically isotropic. As used herein, the term "substantially optically isotropic" means that the phase difference value is so small that it does not substantially affect the optical characteristics of the liquid crystal display device. For example, the in-plane retardation Re of the base material portion is preferably 20 nm or less, more preferably 10 nm or less. The in-plane retardation Re is an in-plane retardation value measured with light having a wavelength of 590 nm at 23 ° C. The in-plane phase difference Re is represented by Re = (nx−ny) × d. Here, nx is the refractive index in the direction in which the refractive index is maximized in the plane of the optical member (that is, the slow-phase axis direction), and ny is the direction perpendicular to the slow-phase axis in the plane (that is, the phase-advancing axis direction). It is the refractive index (in the axial direction), and d is the thickness (nm) of the optical member.

Furthermore, the photoelastic coefficient of the base portion 31 is preferably ^{-10 × 10 -12 m 2 / N~10} × 10 -12 m 2 / N, more preferably -5 × ¹⁰ -12 ^m 2 / N a ^{~5 × 10 -12 m 2 / N} , more preferably from ^{-3 × 10 -12 m 2 / N~3} × 10 -12 m 2 / N.

D-2. Second Prism Sheet In the embodiment of the present invention, as described above, the first prism sheet 30 and the second prism sheet 40 are bonded together by point bonding. With such a configuration, when the optical member is applied to the liquid crystal display device, the liquid crystal display device having excellent mechanical strength, high brightness, suppression of display unevenness, and excellent hue can be obtained. It can be realized. The configuration, function, and the like of the second prism sheet are as described in Section D-1 with respect to the first prism sheet.

E. Polarizer As described above, the polarizing plate 50 is typically placed on the absorption type polarizer 51, the protective layer 52 arranged on one side of the absorption type polarizer 51, and the other side of the absorption type polarizer 51. It has an arranged protective layer 53.

E-1. Polarizer As the absorption type polarizer 51, any suitable polarizer can be adopted. For example, the resin film forming the polarizer may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer system partially saponified film. Examples thereof include those which have been dyed and stretched with a bicolor substance such as iodine or a bicolor dye, and polyene-based oriented films such as a dehydrated product of PVA and a dehydrogenated product of polyvinyl chloride. Preferably, since the PVA-based film is excellent in optical characteristics, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is used.

The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment or while dyeing. Alternatively, it may be stretched and then dyed. If necessary, the PVA-based film is subjected to a swelling treatment, a cross-linking treatment, a washing treatment, a drying treatment and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible not only to clean the dirt and blocking inhibitor on the surface of the PVA-based film, but also to swell the PVA-based film to prevent uneven dyeing. Can be prevented.

Specific examples of the polarizer obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and the resin. Examples thereof include a polarizer obtained by using a laminate with a PVA-based resin layer coated and formed on a base material. The polarizer obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the resin base material. It is produced by forming a PVA-based resin layer on the resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; and stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer. obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further include, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous 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 for the polarizer), and the resin base material is peeled off from the resin base material / polarizer laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of the method for producing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.

The thickness of the polarizer is preferably 15 μm or less, more preferably 1 μm to 12 μm, further preferably 3 μm to 12 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 of 380 nm to 780 nm. The simple substance transmittance of the polarizer is 43.0% to 46.0%, preferably 44.5% to 46.0%, as described above. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

The simple substance 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 the 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 polarizing element produced by superimposing two identical polarizers so that their absorption axes are parallel to each other. Further, the orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizing element produced by superimposing two identical polarizers so that their absorption axes are orthogonal to each other. These transmittances are Y values obtained by correcting the luminosity factor with the 2 degree field of view (C light source) of JlS Z 8701-1982.

E-2. Protective layer The protective layer is formed of any suitable film that can be used as a protective film for the polarizing plate. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of 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 a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition. The protective layers 52 and 53, respectively, may be the same or different.

The thickness of the protective layer is preferably 20 μm to 100 μm. The protective layer may be laminated on the polarizer via an adhesive layer (specifically, an adhesive layer or an adhesive layer), or may be laminated in close contact with the polarizer (without an adhesive layer). Good. The adhesive layer is formed with any suitable adhesive. Examples of the adhesive include a water-soluble adhesive containing a polyvinyl alcohol-based resin as a main component. The water-soluble adhesive containing a polyvinyl alcohol-based resin as a main component may preferably further contain a metal compound colloid. The metal compound colloid can be one in which the metal compound fine particles are dispersed in a dispersion medium, and can be electrostatically stabilized due to mutual repulsion of the same kind of charges 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 characteristics such as the polarization characteristics. It 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 adhesiveness can be ensured, and the knick can be suppressed. The "knick" refers to a local uneven defect that occurs at the interface between the polarizer and the protective layer.

F. Reflective Polarizer The reflective polarizing element 60 has a function of transmitting polarized light in a specific polarized state (polarization direction) and reflecting light in other polarized states. The reflective polarizer 60 may be a linearly polarized light separated type or a circularly polarized light separated 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 on which a cholesteric liquid crystal is immobilized and a λ / 4 plate.

FIG. 5 is a schematic perspective view of an example of a reflective polarizer. The reflective polarizer is a multilayer laminate in which a layer A having birefringence and a layer B having substantially no birefringence are alternately laminated. For example, the total number of layers of such a multi-layer laminate 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 of the B layer and the refractive index ny in the y-axis direction are substantially the same. is there. Therefore, the difference in refractive index between the A layer and the B layer is large in the x-axis direction and 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 difference in refractive index between the A layer and the B layer in the x-axis direction is preferably 0.2 to 0.3. The x-axis direction corresponds to the stretching direction of the reflective polarizer in the method for manufacturing the reflective polarizer.

The layer A is preferably composed of a material that exhibits birefringence by stretching. Representative examples of such materials include polyester naphthalenedicarboxylic acid (eg, polyethylene naphthalate), polycarbonate and acrylic resins (eg, polymethylmethacrylate). Polyethylene naphthalate is preferred. The B layer is preferably composed 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 polarizing element transmits light having a first polarization direction (for example, a 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 waves). At the interface between the A layer and the B layer, the reflected light is partially transmitted as light having a first polarization direction and partially reflected as light having a second polarization direction. By repeating such reflection and transmission many times inside the reflective polarizer, the efficiency of light utilization can be improved.

In one embodiment, the reflective polarizer may include a reflective layer R as the outermost layer on the opposite side of the polarizing plate 50, as shown in FIG. By providing the reflective layer R, it is possible to further utilize the light that has returned to the outermost side of the reflective polarizer without being finally utilized, so that the efficiency of light utilization can be further improved. 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 contained in the reflective polarizer, and the like. The overall thickness of the reflective polarizer is preferably 10 μm to 150 μm.

In one embodiment, in the optical member 100, the reflective polarizer 60 is arranged so as to transmit light in the polarization direction parallel to the transmission axis of the polarizing plate 50. That is, the reflective polarizer 60 is arranged so that its transmission axis is substantially parallel to the transmission axis direction of the polarizing plate 50. With such a configuration, the light absorbed by the polarizing plate 50 can be reused, the utilization efficiency can be further improved, and the brightness can be improved.

Reflective polarizers can typically be made by combining coextrusion and transverse stretching. Coextrusion can be done in any suitable manner. For example, it may be a feed block system or a multi-manifold system. For example, the material forming the A layer and the material forming the B layer are extruded in the feed block, and then multi-layered using a multiplier. Such a multi-layer device is known to those skilled in the art. Next, the obtained elongated multilayer laminate is typically stretched in a direction (TD) orthogonal to the transport direction. The material (for example, polyethylene naphthalate) constituting the layer A has an increased refractive index only in the stretching direction due to the lateral stretching, and as a result, exhibits birefringence. The refractive index of the material constituting the B layer (for example, copolyester of naphthalenedicarboxylic acid and terephthalic acid) does not increase in any direction 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 of FIG. 5 and MD corresponds to the y-axis. Corresponds to the direction). The stretching operation can be performed using any suitable device.

As the reflective polarizer, for example, those described in JP-A-9-507308 can be used.

As the reflective polarizer, a commercially available product may be used as it is, or the commercially available product may be used after secondary processing (for example, stretching). Examples of commercially available products include the product name DBEF manufactured by 3M and the product name APF manufactured by 3M.

The reflective polarizer 60 is attached to the polarizing plate 50 via an arbitrary appropriate adhesive layer (for example, an adhesive layer, an adhesive layer: not shown).

G. Second Low Refractive Index Layer The refractive index of the second low refractive index layer 70 is typically 1.35 or less, preferably 1.30 or less. The refractive index of the second low refractive index layer 70 is preferably as close to the refractive index of air (1.00) as possible. The lower limit of the refractive index of the low refractive index layer is, for example, 1.01. The specific configuration, function, and the like of the second low refractive index layer 70 are as described in Section C with respect to the low refractive index layer 20.

H. Light guide plate As the light guide plate 80, any suitable light guide plate can be used. For example, a light guide plate having a lens pattern formed on the back side and a light guide plate having a prism shape or the like formed on the back side and / or the viewing side are used so that light from the lateral direction can be deflected in the thickness direction. .. Preferably, a light guide plate having a prism shape formed on the back surface side and the viewing side is used. In the light guide plate, it is preferable that the prism shape formed on the back surface side and the prism shape formed on the viewing side are orthogonal to each other in the ridge line direction. By using such a light guide plate, light that is more easily focused can be incident on the prism sheet.

I. Third Low Refractive Index Layer The refractive index of the third low refractive index layer 90 is typically 1.30 or less, preferably 1.25 or less. The refractive index of the third low refractive index layer 90 is preferably as close to the refractive index of air (1.00) as possible. The lower limit of the refractive index of the low refractive index layer is, for example, 1.01. The specific configuration, function, and the like of the third low refractive index layer 90 are as described in Section C with respect to the low refractive index layer 20.

J. Light diffusing layer The light diffusing layer may be made of a light diffusing element or a light diffusing adhesive. The light diffusing element includes a matrix and light diffusing fine particles dispersed in the matrix. In the light diffusing pressure-sensitive adhesive, the matrix is composed of the pressure-sensitive adhesive.

The light diffusion performance of the light diffusion layer can be expressed by, for example, a haze value and / or a light diffusion half-value angle. The haze value of the light diffusion layer is preferably 50% to 95%, more preferably 60% to 95%, and even more preferably 70% to 95%. By setting the haze value in the above range, desired diffusion performance can be obtained, and the occurrence of moire can be satisfactorily suppressed. The light diffusion half-value angle of the light diffusion layer is preferably 5 ° to 50 °, more preferably 10 ° to 30 °. The light diffusing performance of the light diffusing layer is controlled by adjusting the constituent materials of the matrix (adhesive in the case of the light diffusing adhesive), the constituent materials of the light diffusing fine particles, the volume average particle size, the blending amount, and the like. be able to.

The total light transmittance of the light diffusion layer is preferably 75% or more, more preferably 80% or more, and further preferably 85% or more.

The thickness of the light diffusion layer can be appropriately adjusted according to the configuration, diffusion performance, and the like. For example, when the light diffusing layer is composed of a light diffusing element, the thickness is preferably 5 μm to 200 μm. Further, for example, when the light diffusion layer is composed of a light diffusion adhesive, the thickness is preferably 5 μm to 100 μm.

As described above, the light diffusing layer may be made of a light diffusing element or a light diffusing adhesive. When the light diffusing layer is composed of a light diffusing element, the light diffusing layer includes a matrix and light diffusing fine particles dispersed in the matrix. The matrix is composed of, for example, an ionizing wire curable resin. Examples of the ionized wire include ultraviolet rays, visible light, infrared rays, and electron beams. It is preferably UV light, and therefore the matrix is preferably composed of UV curable resin. Examples of the ultraviolet curable resin include acrylic resins, aliphatic (for example, polyolefin) resins, and urethane resins. The form of the light diffusing fine particles in which the light diffusing layer is composed of the light diffusing adhesive will be described later.

Preferably, the light diffusing layer is composed of a light diffusing adhesive. By adopting such a configuration, the adhesive layer (adhesive layer or adhesive layer) required when the light diffusion layer is composed of the light diffusion element becomes unnecessary, so that the optical member (as a result, the optical member (as a result) The liquid crystal display device) can be made thinner, and the adverse effect of the adhesive layer on the display characteristics of the liquid crystal display device can be eliminated. In this case, the light diffusing layer contains a pressure-sensitive adhesive and light-diffusing fine particles dispersed in the pressure-sensitive adhesive. Any suitable adhesive can be used as the pressure-sensitive adhesive. Specific examples thereof include rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, cellulose-based pressure-sensitive adhesives, and the like, and acrylic-based pressure-sensitive adhesives are preferable. By using an acrylic pressure-sensitive adhesive, a light diffusion layer having excellent heat resistance and transparency can be obtained. The pressure-sensitive adhesive may be used alone or in combination of two or more.

As the acrylic pressure-sensitive adhesive, any suitable one can be used. The glass transition temperature of the acrylic pressure-sensitive adhesive is preferably −60 ° C. to −10 ° C., more preferably −55 ° C. to −15 ° C. The weight average molecular weight of the acrylic pressure-sensitive adhesive is preferably 200,000 to 2 million, more preferably 250,000 to 1.8 million. By using an acrylic pressure-sensitive adhesive having such characteristics, appropriate pressure-sensitive adhesiveness can be obtained. The refractive index of the acrylic pressure-sensitive adhesive is preferably 1.40 to 1.65, and more preferably 1.45 to 1.60.

The acrylic pressure-sensitive adhesive is usually obtained by polymerizing a main monomer that imparts adhesiveness, a comonomer that imparts cohesiveness, and a functional group-containing monomer that serves as a cross-linking point while imparting adhesiveness. Acrylic pressure-sensitive adhesives having the above properties can be synthesized by any appropriate method. For example, they can be synthesized with reference to "Adhesive / Adhesive Chemistry and Applications" by Katsuhiko Nakamae published by Dainippon Tosho Co., Ltd.

The content of the pressure-sensitive adhesive in the light diffusion layer is preferably 50% by weight to 99.7% by weight, more preferably 52% by weight to 97% by weight.

Any suitable light diffusing fine particles can be used. Specific examples include inorganic fine particles and polymer fine particles. The light diffusing fine particles are preferably polymer fine particles. Examples of the material of the polymer fine particles include silicone resin, methacrylic resin (for example, polymethyl methacrylate), polystyrene resin, polyurethane resin, and melamine resin. Since these resins have excellent dispersibility with respect to the pressure-sensitive adhesive and an appropriate refractive index difference with the pressure-sensitive adhesive, a light diffusion layer having excellent diffusion performance can be obtained. Preferably, it is a silicone resin or polymethyl methacrylate. The shape of the light diffusing fine particles can be, for example, a true spherical shape, a flat shape, or an indefinite shape. The light diffusing fine particles may be used alone or in combination of two or more.

The volume average particle size of the light diffusing fine particles is preferably 1 μm to 10 μm, and more preferably 1.5 μm to 6 μm. By setting the volume average particle size in the above range, a light diffusing layer having excellent light diffusing performance can be obtained. The volume average particle size can be measured using, for example, an ultracentrifugal automatic particle size distribution measuring device.

The refractive index of the light diffusing fine particles is preferably 1.30 to 1.70, more preferably 1.40 to 1.65.

The absolute value of the difference in refractive index between the light diffusing fine particles and the matrix (typically, an ionizing wire curable resin or an adhesive) is preferably more than 0 and 0.2 or less, and more preferably more than 0. It is 0.15 or less, more preferably 0.01 to 0.13.

The content of the light diffusing fine particles in the light diffusing layer is preferably 0.3% by weight to 50% by weight, more preferably 3% by weight to 48% by weight. By setting the blending amount of the light diffusing fine particles within the above range, a light diffusing layer having excellent light diffusing performance can be obtained.

K. Barrier layer The barrier layer preferably has a barrier function against oxygen and / or water vapor. By providing the barrier layer, deterioration of the wavelength conversion material due to oxygen and / or water vapor can be prevented, and as a result, a long life of the function of the wavelength conversion layer can be achieved. The oxygen permeability of the barrier layer is preferably 500 cc / m ² · day · atm or less, more preferably 100 cc / m ² · day · atm or less, and even more preferably 50 cc / m ² · day · atm or less. is there. Oxygen permeability can be measured by a measurement method based on JIS K7126 in an atmosphere of 25 ° C. and 100% RH. The water vapor permeability (permeability) of the barrier layer is preferably 500 g / m ² · day or less, more preferably 100 g / m ² · day or less, and further preferably 50 g / m ² · day or less. ..

The barrier layer is typically a laminated film in which, for example, a metal vapor deposition film, a metal or silicon oxide film, an oxide nitride film or a nitride film, or a metal foil is laminated on a resin film. Depending on the configuration of the optical member, the resin film may be omitted. Preferably, the resin film may have barrier function, transparency and / or optical isotropic properties. Specific examples of such resins include cyclic olefin resins, polycarbonate resins, cellulosic resins, polyester resins, and acrylic resins. Preferably, it has a cyclic structure such as a cyclic olefin resin (for example, norbornene resin), a polyester resin (for example, polyethylene terephthalate (PET)), and an acrylic resin (for example, a lactone ring or a glutarimide ring in the main chain). Acrylic resin). These resins can have an excellent balance of barrier function, transparency and optical isotropic properties.

Examples of the metal of the metal vapor deposition film include In, Sn, Pb, Cu, Ag, and Ti. Examples of the metal oxide include ITO, IZO, AZO, SiO ₂ , MgO, SiO, SixOy, Al ₂ O ₃ , GeO, and TiO ₂ . Examples of the metal foil include aluminum foil, copper foil, and stainless steel foil.

Moreover, you may use an active barrier film as a barrier layer. The active barrier film is a film that reacts with oxygen and actively absorbs oxygen. Active barrier films are commercially available. Specific examples of commercially available products include Toyobo's "Oxyguard", Mitsubishi Gas Chemical's "Ageless Omac", Kyodo Printing's "Oxycatch", and Kuraray's "Evar AP".

The thickness of the barrier layer is, for example, 50 nm to 50 μm.

L. Set of polarizing plate In the embodiment in which the optical member includes a polarizing plate (for example, the embodiment of FIGS. 2 and 4), the optical member is typically arranged on the side opposite to the visual side of the liquid crystal display device. It can be used as a polarizing plate (hereinafter, may be referred to as a backside polarizing plate). In this case, a set of polarizing plates including the back side polarizing plate and the viewing side polarizing plate can be provided. Any suitable polarizing plate can be adopted as the viewing side polarizing plate. The viewing-side polarizing plate typically has a polarizing element (for example, an absorption-type polarizing element) and a protective layer arranged on at least one side of the polarizing element. As the polarizer and the protective layer, those described in the above item E can be used. The viewing-side polarizing plate may further have an arbitrary appropriate optical functional layer (for example, a retardation layer, a hard coat layer, an antiglare layer, an antireflection layer) depending on the purpose. The set of polarizing plates is set on each side of the liquid crystal cell so that the absorption axis of the viewing side polarizing plate (polarizer) and the absorption axis of the back side polarizing plate (polarizer) are substantially orthogonal or parallel to each other. Is placed in.

M. Liquid Crystal Display Device According to yet another aspect of the present invention, a liquid crystal display device is provided. In the embodiment in which the optical member does not include a polarizing plate (for example, the embodiments of FIGS. 1 and 3), the liquid crystal display device includes a liquid crystal cell, a viewing side polarizing plate arranged on the viewing side of the liquid crystal cell, and the viewing side polarizing plate. The back side polarizing plate arranged on the side opposite to the viewing side of the liquid crystal cell, the optical member according to the above items A to K arranged outside the back side polarizing plate, and arranged outside the optical member. It has a backlit unit. In an embodiment in which the optical member includes a polarizing plate (for example, an embodiment of FIGS. 2 and 4), the liquid crystal display device includes a liquid crystal cell, a polarizing plate arranged on the visual side of the liquid crystal cell, and the liquid crystal cell. It has the optical member according to the above items A to K arranged on the side opposite to the viewing side of the above, and a backlight unit arranged on the outside of the optical member. Since the configuration of the liquid crystal cell, the drive mode, and the configuration of the backlight unit are well known in the art, specific description thereof will be omitted.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present 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) Method for measuring refractive index and film thickness The refractive index and film thickness were determined by performing reflection measurement using an ellipsometer (product name "Woollam M2000", manufactured by JA Woollam Co., Ltd.).
(2) Front Brightness of Liquid Crystal Display Device The liquid crystal display device was set to display white on the entire screen, and was measured with a conoscope (manufactured by AUTRONIC MELCHERS Co., Ltd.) (unit: cd / m ² ).
(3) Diffuse illuminance of the liquid crystal display device Light by installing a conoscope (manufactured by AUTRONIC MELCHERS Co., Ltd.) at a predetermined interval above the liquid crystal display device and measuring the brightness L at 1 ° intervals in all directions. The diffused illuminance (unit: Lx) was calculated.
(4) Evaluation method of color shift A white image is displayed on a liquid crystal display device, and a conoscope (manufactured by AUTRONIC MELCHERS Co., Ltd.) is used to perform hues having an azimuth angle of 0 ° to 360 ° in a polar angle of 0 ° to 60 °. The x and y values were measured.

<Example 1>
(Wavelength conversion material, prism sheet)
A commercially available tablet PC (manufactured by AMAZON, trade name "Kindle Fire HDX 8.9") was disassembled, and a wavelength conversion material (wavelength conversion layer) and a prism sheet contained on the backlight side were used.
(Reflective polarizer)
A 40-inch TV manufactured by SHARP (product name: AQUOS, product number: LC40-Z5) was disassembled, and a reflective polarizer was taken out from the backlight member. The diffusion layers provided on both sides of the reflective polarizer were removed to obtain the reflective polarizer of the present embodiment.
(Preparation of polarizing plate)
While immersing a polymer film containing polyvinyl alcohol as the main component [Kuraray product name "9P75R (thickness: 75 μm, average degree of polymerization: 2,400, saponification degree 99.9 mol%)"] in a water bath for 1 minute. After stretching 1.2 times in the transport direction, the film (original length) that is not stretched at all in the transport direction is used as a reference while being dyed by immersing it in an aqueous solution having an iodine concentration of 0.3% by weight for 1 minute. As a result, it was stretched three times. Next, while immersing this stretched film in an aqueous solution having a boric acid concentration of 4% by weight and a potassium iodide concentration of 5% by weight, the stretched film was further stretched up to 6 times in the transport direction based on the original length, and dried at 70 ° C. for 2 minutes. By doing so, a polarizer was obtained.
On the other hand, an alumina colloid-containing adhesive was applied to one side of a triacetyl cellulose (TAC) film (manufactured by Konica Minolta, product name "KC4UW", thickness: 40 μm), and this was applied to one side of the polarizer obtained above. They were laminated by roll-to-roll so that the transport directions of both were parallel. The alumina colloid-containing adhesive is methylol melamine based on 100 parts by weight of a polyvinyl alcohol-based resin having an acetoacetyl group (average polymerization degree 1200, saponification degree 98.5 mol%, acetoacetylation degree 5 mol%). 50 parts by weight is dissolved in pure water to prepare an aqueous solution having a solid content concentration of 3.7% by weight, and a positively charged alumina colloid (average particle size 15 nm) is added to 100 parts by weight of this aqueous solution at a solid content concentration of 10. It was prepared by adding 18 parts by weight of an aqueous solution contained in% by weight. Subsequently, similarly, the TAC film coated with the alumina colloid-containing adhesive was laminated on the opposite surface of the polarizer by roll-to-roll so that the transport directions thereof were parallel to each other, and then at 55 ° C. 6 Allowed to dry for minutes. In this way, a polarizing plate having a TAC film / polarizer / TAC film configuration was obtained.
(Preparation of low refractive index layer)
A low refractive index layer was formed on the surface of a triacetyl cellulose (TAC) film (manufactured by Konica Minolta, product name "KC4UYW", thickness: 40 μm) as described below. To a mixture of 2.2 g of dimethyl sulfoxide (DMSO) and 0.95 g of methyltrimethoxysilane (MTMS), which is a precursor of a silicon compound, 0.5 g of a 0.01 mol / L aqueous oxalic acid solution was added. MTMS was hydrolyzed by stirring at room temperature for 30 minutes to produce tris (hydroxy) methylsilane. Then, 0.38 g of 28% aqueous ammonia and 0.2 g of pure water were added to 5.5 g of DMSO, and then the hydrolyzed mixture was further added and stirred at room temperature for 15 minutes to Tris. Gelation of (hydroxy) methylsilane was carried out to obtain a gelled silicon compound. The gelled mixed solution was incubated as it was at 40 ° C. for 20 hours for aging treatment. Next, the aged gel-like silicon compound was crushed into granules having a size of several mm to several cm using a spatula. 40 g of isopropyl alcohol (IPA) was added thereto, and the mixture was lightly stirred and then allowed to stand at room temperature for 6 hours to decant the solvent and catalyst in the gel. The same decantation treatment was repeated 3 times to complete the solvent substitution. Then, the gelled silicon compound in the mixed solution was pulverized. For the pulverization treatment, a homogenizer (trade name "UH-50", manufactured by SMT) was used, and ^{1.18 g of gel and 1.14 g of IPA were weighed in a 5 cm 3} screw bottle, and then 50 W and 20 kHz were used for 2 minutes. Was crushed. By the pulverization treatment, the gelled silicon compound in the mixed solution was pulverized, and as a result, the mixed solution became a sol solution of the pulverized product. When the volume average particle size showing the variation in the particle size of the pulverized product contained in the mixed solution was confirmed, it was 0.5 μm to 0.7 μm. Further, a 0.3% by weight KOH aqueous solution was prepared, and 0.02 g of KOH was added to 0.5 g of the sol solution to prepare a coating liquid. The layer obtained by coating the TAC film surface with the above coating liquid and drying at 80 ° C. for 1 minute was used as a low refractive index layer. When the film thickness and the refractive index of this layer were evaluated, the film thickness was 1000 nm and the refractive index was 1.07.

(Dot adhesion of prism sheet)
Using two prism sheets obtained above, an acrylic photocurable adhesive is applied to the smooth surface of the second prism sheet, and the convex portion of the first prism sheet is adhered to the second prism sheet. A laminated body of a prism sheet / a first prism sheet was produced. At this time, the thickness of the adhesive layer to which the convex portions were point-bonded was 3 μm.
(Creation of optical members)
The TAC coated with the low refractive index layer obtained above and the wavelength conversion material (wavelength conversion layer) are bonded together via an acrylic pressure-sensitive adhesive, and the TAC surface is further laminated with the prism sheet obtained above. The body was bonded to the body via an acrylic pressure-sensitive adhesive to obtain an optical member having a composition of a second prism sheet / first prism sheet / low refractive index layer / wavelength conversion material (wavelength conversion layer).

(Manufacturing of liquid crystal display device using optical member)
Evaluation was performed using an IPS mode liquid crystal display device (manufactured by AMAZON, trade name "Kindle fire HDX 9.8"). An evaluation was carried out by incorporating the laminate of the polarizing plate and the reflective polarizer obtained above and the optical member obtained above on the lower side (back side) of the liquid crystal cell. At this time, the configuration of the lower optical member is composed of a polarizing plate / reflective polarizer / air / second prism sheet / first prism sheet / low refractive index layer / wavelength conversion layer / air / light guide plate / air / It became a reflector. The brightness and hue of the obtained liquid crystal display device were measured. The results are shown in Table 1.

<Example 2>
Low refractive index of 1.2 using a mixed solution prepared by dissolving n-hexadecyltrimethylammonium chloride and urea in a cellulose nanofiber sol solution (concentration 2%, manufactured by Sugino Machine Limited) and then adding MTMS. A rate layer was prepared. An optical member and a liquid crystal display device were produced in the same manner as in Example 1 except that this low refractive index layer was used. The obtained liquid crystal display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative example 1>
An optical member having a structure of a prism sheet / low refractive index layer / wavelength conversion layer was produced in the same manner as in Example 1 except that only one prism sheet was used. A liquid crystal display device was produced in the same manner as in Example 1 except that this optical member was used. The obtained liquid crystal display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative example 2>
Second prism sheet / air / first prism in the same manner as in Example 1 except that the second prism sheet and the first prism sheet were not point-bonded (that is, simply placed). An optical member having a structure of a sheet / low refractive index layer / wavelength conversion layer was produced. A liquid crystal display device was produced in the same manner as in Example 1 except that this optical member was used. The obtained liquid crystal display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative example 3>
A second prism sheet / first prism sheet / acrylic pressure-sensitive adhesive / wavelength in the same manner as in Example 1 except that an acrylic pressure-sensitive adhesive having a refractive index of 1.47 was used instead of the low-refractive index layer. An optical member having a conversion layer structure was obtained. A liquid crystal display device was produced in the same manner as in Example 1 except that this optical member was used. The obtained liquid crystal display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Evaluation>
The chromaticity diagram corresponding to Table 1 is shown in comparison with FIG. 6 with respect to Examples 1 and 2 and Comparative Examples 1 and 2. As is clear from FIG. 6, it can be seen that the liquid crystal display device according to the embodiment of the present invention realizes a neutral hue. On the other hand, it can be seen that the liquid crystal display device of Comparative Example 1 is whitish and yellowish, and the liquid crystal display device of Comparative Example 2 is bluish.

The optical member of the present invention can be suitably used for a liquid crystal display device. According to the embodiment in which the optical member includes a polarizing plate, the optical member can be suitably used as a back-side polarizing plate of a liquid crystal display device. Liquid crystal display devices using such optical members include mobile devices such as mobile information terminals (PDAs), mobile phones, clocks, digital cameras, and portable game machines, personal computer monitors, laptop computers, OA devices such as copiers, and video. Household electrical equipment such as cameras, LCD TVs and microwave ovens, back monitors, car navigation system monitors, in-vehicle equipment such as car audio, exhibition equipment such as information monitors for commercial stores, security equipment such as surveillance monitors, It can be used for various purposes such as nursing care / medical equipment such as nursing care monitors and medical monitors.

10 Wave conversion layer 20 Low refractive index layer 30 First prism sheet 40 Second prism sheet 50 Plate plate 51 Polarizer 60 Reflective polarizer 70 Second low refractive index layer 80 Light guide plate 90 Third low refractive index Layer 100 Optical member 101 Optical member 102 Optical member 103 Optical member

Claims (17)

It has a wavelength conversion layer, a low refractive index layer having a refractive index of 1.30 or less, a first prism sheet, and a second prism sheet in this order, and the wavelength conversion layer to the second prism. Even the seat is integrated,
A plurality of columnar unit prisms in which the first prism sheet and the second prism sheet are convex on the side opposite to the low refractive index layer and the flat first main surface on the low refractive index layer side are arranged, respectively. Has a second main surface and
The convex portion of the second main surface of the first prism sheet by the unit prism is bonded to the first main surface of the second prism sheet.
Optical member. The optical member according to claim 1, wherein the wavelength conversion layer includes a matrix and quantum dots dispersed in the matrix. The optical member according to claim 1 or 2, wherein the wavelength conversion layer has a barrier function against oxygen and / or water vapor. The optical member according to any one of claims 1 to 3, wherein the wavelength conversion layer contains a light diffusing material. The optical member according to any one of claims 1 to 4, wherein the low refractive index layer has a refractive index of 1.20 or less. The optical member according to any one of claims 1 to 5, further comprising a polarizing plate containing an absorption-type polarizing element on the side of the second prism sheet opposite to the first prism sheet. The optical member according to claim 6, further comprising a reflective polarizing element between the second prism sheet and the polarizing plate. The optical member according to claim 7, further comprising a light diffusing layer between the polarizing plate and the reflective polarizing element. The optical member according to any one of claims 1 to 5, further comprising a reflective polarizer on the side of the second prism sheet opposite to the first prism sheet. The optical member according to claim 9, further comprising a light diffusion layer on the opposite side of the reflective polarizer to the second prism sheet. The optical member according to any one of claims 7 to 10, further comprising a second low refractive index layer having a refractive index of 1.30 or less between the second prism sheet and the reflective polarizer. .. The optical member according to claim 11, wherein the second low refractive index layer has a refractive index of 1.20 or less. The optical member according to any one of claims 1 to 12, further comprising a light guide plate on the opposite side of the wavelength conversion layer to the low refractive index layer. The optical member according to claim 13, further comprising a third low refractive index layer having a refractive index of 1.30 or less between the wavelength conversion layer and the light guide plate. A set of polarizing plates including the optical member according to any one of claims 6 to 14, which is used as a back-side polarizing plate, and a viewing-side polarizing plate. The liquid crystal cell, the viewing side polarizing plate arranged on the viewing side of the liquid crystal cell, the back side polarizing plate arranged on the side opposite to the viewing side of the liquid crystal cell, and the back side polarizing plate arranged outside the liquid crystal cell. A liquid crystal display device having the optical member according to any one of claims 1 to 5. The optical member according to any one of claims 6 to 14, which has a liquid crystal cell, a viewing-side polarizing plate arranged on the viewing side of the liquid crystal cell, and a viewing-side polarizing plate arranged on the side opposite to the viewing side of the liquid crystal cell. Liquid crystal display device.

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