JP2009104065A - Luminance enhancing film and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luminance enhancing film which can be formed by a simple operation and hardly causes a shift of a transmission spectrum even after long-term exposure in a hot environment, and a liquid crystal display device. <P>SOLUTION: The luminance enhancing film includes a resin layer having cholesteric regularity and a barrier layer, wherein the barrier layer includes a circularly polarized light separating sheet obtained by curing a composition containing a polymer A such as PVA and a silane coupling agent. The liquid crystal display device includes the luminance enhancing film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a brightness enhancement film, a manufacturing method thereof, and a liquid crystal display device including the brightness enhancement film.

Conventionally, natural light emitted from a backlight used in a liquid crystal display device has been incident on the liquid crystal cell as natural light. Recently, it is necessary to improve the luminance of the backlight due to the increase in size and the miniaturization of the liquid crystal display device, and techniques relating to this have been studied. In addition, a technique for polarizing light from a backlight has been studied.
For example, studies are being made to provide a brightness enhancement film on the back side of the liquid crystal cell of the liquid crystal display device, that is, on the backlight side. The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis or circularly polarized light having a predetermined spiral axis direction and reflecting other light when light is incident from a light source such as a backlight of a liquid crystal display device or the like. Is.
When light incident from a light source such as a backlight enters the brightness enhancement film, light in a predetermined polarization state among the light is transmitted. On the other hand, light other than the predetermined polarization state is reflected without being transmitted and returns to the backlight. The polarization state of the light that has returned to the backlight is inverted by a reflector or the like provided there. When the light whose polarization state is inverted is incident again on the brightness enhancement film, the light in the predetermined polarization state among the light passes through the brightness enhancement film. By repeating this cycle, it is possible to increase the amount of light that can be used in a liquid crystal display device by supplying light that passes through the brightness enhancement film or polarized light that is not easily absorbed by the polarizing plate, thereby increasing the brightness of the liquid crystal display device. Can be improved.

The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropy. Transmits either left-handed or right-handed circularly polarized light and reflects other light, such as a linearly polarized light separating element, a cholesteric liquid crystal polymer alignment film, or a film substrate that supports the alignment liquid crystal layer. A circularly polarized light separating element that exhibits characteristics has been proposed.
Among them, in a brightness enhancement film including a circularly polarized light separating element that transmits circularly polarized light such as a cholesteric liquid crystal layer, circularly polarized light that has been transmitted can be incident on the polarizing plate as it is, but it suppresses absorption loss in the polarizing plate. More preferably, the circularly polarized light is linearly polarized through an optically anisotropic element such as a retardation plate and is incident on a polarizing plate. By using a quarter wave plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

  As such a circularly polarized light separating element (circularly polarized light separating sheet), one having a resin layer having cholesteric regularity is known. Specifically, a substrate obtained by applying a polymer exhibiting cholesteric liquid crystallinity on a substrate, orienting, drying, and the like, and a liquid crystal composition containing a polymerizable monomer exhibiting cholesteric liquid crystallinity. Those obtained by coating, orienting, and polymerizing are known. As such a liquid crystal composition, many specific examples are conventionally known (for example, Patent Documents 1 to 3). A circularly polarized light separating sheet having a resin layer having cholesteric regularity has many advantages such that it can be produced by a simple operation such as application and curing of a liquid.

  In an environment where the display device is used, the circularly polarized light separating sheet incorporated in the display device is exposed to a high temperature environment due to heat generated from the backlight and other devices. When placed in such an environment for a long time, the optical properties of the resin layer having cholesteric regularity change. Specifically, an undesirable phenomenon occurs in which the transmission spectrum shifts and the hue changes significantly.

US Patent Application Publication No. 2005/0045854 Japanese Patent No. 3767632 JP-A-8-3111

  An object of the present invention is to provide a brightness enhancement film and a liquid crystal display device which can be prepared by a simple operation and hardly cause a transmission spectrum shift even when exposed to a high temperature environment for a long period of time.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have solved the above problems by coating a resin layer having cholesteric regularity with a barrier layer containing a specific substance in a circularly polarized light separating sheet. As a result, the present invention has been completed. That is, according to the present invention, the following is provided.

[1] A resin layer having a cholesteric regularity, a barrier layer, and a retardation film, wherein the barrier layer is formed by curing a composition containing the polymer A and a silane coupling agent. A brightness enhancement film.
[2] The brightness enhancement film, wherein the silane coupling agent has a primary or secondary amino group.
[3] The brightness enhancement film, wherein the resin layer having cholesteric regularity is a non-liquid crystalline resin layer.
[4] The brightness enhancement film, wherein the polymer A is a water-soluble or alcohol-soluble polymer.
[5] The brightness enhancement film, wherein the polymer A is polyvinyl alcohol.
[6] The brightness enhancement film further including a base material layer and an alignment film, and further including the base material layer, the alignment film, the resin layer having the cholesteric regularity, the barrier layer, and a retardation film in this order.
[7] The brightness enhancement film having two or more combinations of the base material layer, the alignment film, a resin layer having cholesteric regularity, and a barrier layer.
[8] A method for producing the brightness enhancement film, comprising a step of laminating a composition containing the polymer A and a silane coupling agent on the resin layer having the cholesteric regularity.
[9] A liquid crystal display device comprising the brightness enhancement film and a liquid crystal panel.

  The brightness enhancement film of the present invention has many advantages based on having a resin layer having a cholesteric regularity, such as being able to be produced by a simple operation, and a transmission spectrum shift even when exposed to a high temperature environment for a long period of time. Therefore, it is excellent in heat resistance and therefore suitable for a brightness enhancement film. In the method for producing a brightness enhancement film of the present invention, the brightness enhancement film can be easily produced.

  The liquid crystal display device of the present invention provided with the brightness enhancement film of the present invention can be produced by a simple method and has excellent heat resistance and a long life.

1. The brightness enhancement film of the present invention comprises a resin layer having cholesteric regularity (hereinafter sometimes simply referred to as “cholesteric resin layer”), a barrier layer, and a retardation film. Is obtained by curing a composition containing polymer A and a silane coupling agent.

1-1. Cholesteric resin layer The cholesteric regularity of the cholesteric resin layer in the brightness enhancement film of the present invention is that the molecular axes are aligned in a certain direction on one plane, but the direction of the molecular axes forms a slight angle on the next plane. This is a structure in which the angle of the molecular axis is shifted (twisted) as it advances through the plane where the molecules are arranged in a certain direction, such that the angle is further shifted in the next plane. Thus, the structure in which the direction of the molecular axis is twisted becomes an optically chiral structure.

  A resin having cholesteric regularity has a circularly polarized light separation function. That is, it has a function of transmitting left-rotated or right-rotated circularly polarized light in a specific wavelength region and reflecting other circularly polarized light.

  In this invention, it is preferable to provide the cholesteric resin layer which exhibits this circularly polarized light separation function over the entire wavelength region of visible light. For example, a cholesteric resin layer having a circularly polarized light separation function is preferable for light in any wavelength region of blue (wavelength 410 to 470 nm), green (wavelength 520 to 580 nm), and red (wavelength 600 to 660 nm).

  The wavelength that exhibits the circularly polarized light separation function depends on the pitch of the chiral structure in the cholesteric resin. The pitch of the chiral structure is a distance in the plane normal direction until the angle of the molecular axis in the chiral structure gradually shifts as it advances along the plane and then returns to the original molecular axis direction again. By changing the pitch of this chiral structure, the wavelength at which the circularly polarized light separating function is exhibited can be changed.

  The cholesteric resin layer used in the present invention is preferably a non-liquid crystalline resin layer. This is because the cholesteric regularity does not change depending on the ambient temperature, electric field, or the like when it is non-liquid crystalline. The non-liquid crystalline cholesteric resin layer can be obtained by aligning the liquid crystalline compound in a cholesteric liquid crystal phase and then polymerizing the liquid crystalline compound in a composition layer containing a liquid crystalline and polymerizable compound.

  As the cholesteric resin layer used in the present invention, for example, (i) a cholesteric resin layer in which the pitch of the chiral structure is changed stepwise, and (ii) the pitch of the chiral structure is continuously changed. A cholesteric resin layer etc. are mentioned.

  (I) The cholesteric resin layer in which the pitch of the chiral structure is changed stepwise includes, for example, a cholesteric resin layer having a chiral structure pitch that exhibits a circularly polarized light separation function with light in a blue wavelength range, It can be obtained by laminating a cholesteric resin layer having a chiral structure pitch that exhibits a circularly polarized light separating function with light and a cholesteric resin layer having a chiral structure pitch that exhibits a circularly polarized light separating function with light in the red wavelength region. it can. Further, cholesteric resin layers having a central wavelength of reflected circularly polarized light of 470 nm, 550 nm, 640 nm, and 770 nm are respectively produced, and these cholesteric resin layers are arbitrarily selected, and the order of the central wavelengths of reflected light is 3 to 3 It can be obtained by laminating seven layers. When the cholesteric resin layers having different chiral structure pitches are laminated, it is preferable that the rotation directions of the circularly polarized light reflected by the cholesteric resin layers are the same. In addition, in order to obtain a liquid crystal display device having a wide viewing angle, the stacking order of the cholesteric resin layers having different chiral structure pitches may be ascending or descending in order of the chiral structure pitch. preferable. The lamination of these cholesteric resin layers may be merely overlaid, or may be fixed via an adhesive or an adhesive.

  (Ii) The cholesteric resin layer in which the pitch of the chiral structure is continuously changed is not particularly limited by its manufacturing method, but as a preferable example of the manufacturing method of such a cholesteric resin layer, a cholesteric resin layer is formed. A cholesteric liquid crystal composition containing a polymerizable liquid crystal compound for coating is preferably applied on another layer such as an alignment film to obtain a liquid crystal layer, and then subjected to light irradiation and / or heating treatment at least once. A method of curing the liquid crystal layer can be mentioned. Preferable embodiments of the cholesteric liquid crystal composition include cholesteric liquid crystal composition (X) described in detail below.

The cholesteric liquid crystal composition (X) contains a compound represented by the following general formula (1) and a specific rod-like liquid crystal compound. Each of these components will be described in turn.
R ¹ -A ¹ -BA ² -R ² (1)

In General Formula (1), R ¹ and R ² are each independently a linear or branched alkyl group having 1 to 20 carbon atoms, or a linear or branched chain having 1 to 20 carbon atoms. And a group selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group. Here, (meth) acryl means acryl and methacryl.

  The alkyl group and alkylene oxide group may be unsubstituted or substituted with one or more halogen atoms. The halogen atom, hydroxyl group, carboxyl group, (meth) acryl group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group are bonded to an alkyl group having 1 to 2 carbon atoms or an alkylene oxide group. May be.

Preferable examples of R ¹ and R ² include a halogen atom, hydroxyl group, carboxyl group, (meth) acryl group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group.

Moreover, it is preferable that at least one of R ¹ and R ² is a reactive group. By having a reactive group as R ¹ and / or R ² , the compound represented by the general formula (1) is fixed in the liquid crystal layer at the time of curing, and a stronger film can be formed. Here, examples of the reactive group include a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, and an amino group.

In the general formula (1), A ¹ and A ² are each independently 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′-biphenylene group, 4, It represents a group selected from the group consisting of a 4′-bicyclohexylene group and a 2,6-naphthylene group. The 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′-biphenylene group, 4,4′-bicyclohexylene group, and 2,6-naphthylene group are , It may be unsubstituted or substituted with one or more halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, amino groups, alkyl groups having 1 to 10 carbon atoms, or halogenated alkyl groups. In each of A ¹ and A ² , when two or more substituents are present, they may be the same or different.

Particularly preferred examples of A ¹ and A ² include groups selected from the group consisting of 1,4-phenylene group, 4,4′-biphenylene group, and 2,6-naphthylene group. These aromatic ring skeletons are relatively rigid as compared with the alicyclic skeletons, have high affinity with the mesogens of rod-like liquid crystalline compounds described later, and have higher alignment uniformity.

In the general formula (1), B represents a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —C. = N-N = C -, - NHCO -, - OCOO -, - CH 2 COO-, and is selected from the group consisting of -CH ₂ OCO-.

  Particularly preferable examples of B include a single bond, —OCO—, and —C═N—N═C—.

  As for the compound of General formula (1), it is preferable that at least 1 type has liquid crystallinity, and it is preferable to have chirality. The cholesteric liquid crystal composition (X) preferably contains a mixture of a plurality of optical isomers as the compound of the general formula (1). For example, a mixture of plural kinds of enantiomers and / or diastereomers can be contained. At least one of the compounds of the general formula (1) preferably has a melting point in the range of 50 ° C to 150 ° C.

  When the compound of the general formula (1) has liquid crystallinity, a high Δn is preferable. By containing the high Δn liquid crystal, Δn as the cholesteric liquid crystal composition (X) can be improved, and a broadband circularly polarized light separating sheet can be produced. At least one Δn of the compound of the general formula (1) is preferably 0.18 or more, more preferably 0.22 or more.

  Specific examples of particularly preferred compounds of the general formula (1) include the following compounds (A1) to (A3) and (A5) to (A10):

  In the compound (A3), “*” represents a chiral center.

The cholesteric liquid crystal composition (X) contains a rod-like liquid crystal compound having Δn of 0.18 or more and having at least two or more reactive groups in one molecule.
Examples of the rod-like liquid crystalline compound include compounds represented by the formula (2).
^{R 3 -C 3 -D 3 -C 5} -M-C 6 -D 4 -C 4 -R 4 Formula (2)
(Wherein R ³ and R ⁴ are reactive groups, each independently (meth) acryl group, (thio) epoxy group, oxetane group, thietanyl group, aziridinyl group, pyrrole group, vinyl group, allyl group, D ³ and D ⁴ each represent a group selected from the group consisting of a fumarate group, a cinnamoyl group, an oxazoline group, a mercapto group, an iso (thio) cyanate group, an amino group, a hydroxyl group, a carboxyl group, and an alkoxysilyl group. A group selected from the group consisting of a bond, a linear or branched alkyl group having 1 to 20 carbon atoms, and a linear or branched alkylene oxide group having 1 to 20 carbon atoms; C ^{3 to} C ⁶ are a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —C═. N—N═C—, —NHCO— _{, -OCOO -, - CH 2 COO-} , and .M represents a group selected from the group consisting of -CH ₂ OCO- represents a mesogenic group, specifically, have a unsubstituted or substituted group Azomethines, azoxys, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted Two to four skeletons selected from the group of phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles are converted to —O—, —S—, —S—S—, —CO—, —CS. -, - OCO -, - CH 2 -, - OCH 2 -, - C = N-N = C -, - NHCO -, - OCOO -, - C ₂ COO-, and is formed are joined by a linking group of -CH ₂ OCO-, and the like.)
Examples of the substituent that the mesogenic group M may have include a halogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, a cyano group, a nitro group, —O—R ⁵ , —O—C. (═O) —R ⁵ , —C (═O) —O—R ⁵ , —O—C (═O) —O—R ⁵ , —NR ⁵ —C (═O) —R ⁵ , —C ( ═O) —NR ⁵ or —O—C (═O) —NR ⁵ . Here, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and when it is an alkyl group, the alkyl group includes —O—, —S—, —O—C (═O) —. , —C (═O) —O—, —O—C (═O) —O—, —NR ⁶ —C (═O) —, —C (═O) —NR ⁶ —, —NR ⁶ —, Alternatively, -C (= O)-may be present (except when two or more of -O- and -S- are present adjacent to each other). Wherein, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the substituent in the “optionally substituted alkyl group having 1 to 10 carbon atoms” include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, and an alkoxy group having 1 to 6 carbon atoms. Group, alkoxyalkoxy group having 2 to 8 carbon atoms, alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms, alkoxycarbonyl group having 2 to 7 carbon atoms, alkylcarbonyloxy having 2 to 7 carbon atoms Group, an alkoxycarbonyloxy group having 2 to 7 carbon atoms, and the like.
In the present invention, the rod-like liquid crystalline compound preferably has an asymmetric structure. Here, the asymmetric structure is a structure in which R ³ -C ³ -D ³ -C ⁵ -and -C ⁶ -D ⁴ -C ⁴ -R ⁴ are different in the general formula (2) with the mesogenic group M as the center. Say. By using a rod-like liquid crystal compound having an asymmetric structure, alignment uniformity can be further improved.

  In the present invention, the rod-like liquid crystal compound has a Δn value of 0.18 or more, preferably 0.22 or more. When a compound having an Δn value of 0.30 or more is used, the absorption edge on the long wavelength side of the ultraviolet absorption spectrum may extend to the visible range, but desired optical performance even when the absorption edge of the spectrum extends to the visible range. It can be used as long as it does not adversely affect By having such a high Δn value, a circularly polarized light separating sheet having high optical performance (for example, circularly polarized light separating characteristics) can be provided.

  In the present invention, the rod-like liquid crystalline compound has at least two or more reactive groups in one molecule. Specific examples of the reactive group include an epoxy group, a thioepoxy group, an oxetane group, a thietanyl group, an aziridinyl group, a pyrrole group, a fumarate group, a cinnamoyl group, an isocyanate group, an isothiocyanate group, an amino group, a hydroxyl group, and a carboxyl group. , Alkoxysilyl groups, oxazoline groups, mercapto groups, vinyl groups, allyl groups, methacryl groups, and acrylic groups. By having these reactive groups, a stable cured product can be obtained when the cholesteric liquid crystal composition is cured. When a compound having one or less reactive group in one molecule is used, when the cholesteric liquid crystal composition is cured, a crosslinked cured product cannot be obtained, so that a film strength that can withstand practical use cannot be obtained. Even when a cross-linking agent described later is used, the film strength is insufficient and practical use is difficult. The film strength that can be practically used is HB or more, preferably H or more, in pencil hardness (JIS K5400). If the film strength is lower than HB, the film is easily scratched and lacks handling properties. The upper limit of preferable pencil hardness is not particularly limited as long as it does not adversely affect the optical performance and durability test.

  In the cholesteric liquid crystal composition (X), the weight ratio of (total weight of the compound of the general formula (1)) / (total weight of the rod-like liquid crystal compound) is 0.05 to 1, preferably 0.1 to 0. .65, more preferably 0.15 to 0.45. When the weight ratio is less than 0.05, the alignment uniformity may be insufficient. On the other hand, when the weight ratio is more than 1, the alignment uniformity decreases, the stability of the liquid crystal phase decreases, and the liquid crystal composition As a result, the desired optical performance (for example, circularly polarized light separation characteristics) may not be obtained. The total weight indicates the weight when one kind is used and the total weight when one or more kinds are used.

  In the cholesteric liquid crystal composition (X), the compound of the general formula (1) preferably has a molecular weight of less than 600, and the rod-like liquid crystal compound has a molecular weight of 600 or more. When the molecular weight of the compound of the general formula (1) is less than 600, it can enter the gap between the rod-like liquid crystalline compounds having a larger molecular weight than that, and the alignment uniformity can be improved.

In the present invention, the cholesteric liquid crystal composition such as the cholesteric liquid crystal composition (X) can optionally contain a cross-linking agent in order to improve the film strength and durability after curing. As the cross-linking agent, it reacts simultaneously when the liquid crystal layer coated with the liquid crystal composition is cured, or heat treatment is performed after curing to accelerate the reaction, or the reaction proceeds spontaneously by moisture to increase the crosslinking density of the liquid crystal layer. Those that can be enhanced and that do not deteriorate the alignment uniformity can be appropriately selected and used, and those that are cured by ultraviolet rays, heat, moisture, etc. can be suitably used. Specific examples of the crosslinking agent include, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 2- (2-vinyl Polyfunctional acrylate compounds such as loxyethoxy) ethyl acrylate; epoxy compounds such as glycidyl (meth) acrylate, ethylene glycol diglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether; 2,2-bishydroxymethylbutanol-tris [ 3- (1-aziridinyl) propionate], 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane, trimethylolpropane-tri-β-aziridinini Aziridine compounds such as lupropionate; Isocyanurate type isocyanates derived from hexamethylene diisocyanate, hexamethylene diisocyanate, isocyanurate type isocyanates, biuret type isocyanates, adduct type isocyanates; polyoxazoline compounds having an oxazoline group in the side chain; vinyltrimethoxysilane; N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, N- (1 , 3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine and the like alkoxysilane compounds. Moreover, a well-known catalyst can be used according to the reactivity of this crosslinking agent, and productivity can be improved in addition to an improvement in film strength and durability.
The blending ratio of the crosslinking agent is preferably 0.1 to 15% by weight in a cured film obtained by curing the cholesteric liquid crystal composition. When the blending ratio of the crosslinking agent is less than 0.1% by weight, the effect of improving the crosslinking density cannot be obtained. Conversely, when the blending ratio is more than 15% by weight, the stability of the liquid crystal layer is lowered, which is not preferable.

In the present invention, the cholesteric liquid crystal composition can optionally contain a photoinitiator. As the photoinitiator, known compounds that generate radicals or acids by ultraviolet rays or visible rays can be used. Specifically, benzoin, benzylmethyl ketal, benzophenone, biacetyl, acetophenone, Michler's ketone, benzyl, benzylisobutyl ether, tetramethylthiuram mono (di) sulfide, 2,2-azobisisobutyronitrile, 2,2-azobis -2,4-dimethylvaleronitrile, benzoyl peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4 -Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, methylbenzoyl formate, 2,2-dieto Cyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α-amylcinnac aldehyde, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, pp′-dichlorobenzophenone, pp ′ -Bisdiethylaminobenzophenone, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin n-butyl ether, diphenyl sulfide, bis (2,6-methoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1 [ 4- (Methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, anthracenebenzophenone, α-chloroanthraquinone , Diphenyl disulfide, hexachlorobutadiene, pentachlorobutadiene, octachlorobutene, 1-chloromethylnaphthalene, 1,2-octanedione, 1- [4- (phenylthio) -2- (o-benzoyloxime)] and 1- Carbazole oxime compounds such as [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl] ethanone 1- (o-acetyloxime), (4-methylphenyl) [4- (2-methyl Propyl) phenyl] iodonium hexafluorophosphate, 3-methyl- - butynyl tetramethyl hexafluoroantimonate, diphenyl - (p-phenylthiophenyl) sulfonium hexafluoroantimonate, and the like. In addition, two or more compounds can be mixed depending on the desired physical properties, and if necessary, a known photosensitizer or a tertiary amine compound as a polymerization accelerator is added to control curability. You can also.
The blending ratio of the photoinitiator is preferably 0.03 to 7% by weight in the cholesteric liquid crystal composition. When the blending amount of the photoinitiator is less than 0.03% by weight, the degree of polymerization is lowered and the film strength may be lowered. On the other hand, if it is more than 7% by weight, the alignment of the liquid crystal is inhibited and the liquid crystal phase may become unstable.

  In the present invention, the cholesteric liquid crystal composition can optionally contain a surfactant. As the surfactant, those not inhibiting the orientation can be appropriately selected and used. As the surfactant, specifically, a nonionic surfactant containing siloxane or fluorinated alkyl group in the hydrophobic group portion can be preferably used, and an oligomer having two or more hydrophobic group portions in one molecule. Is particularly preferred. These surfactants are OMNOVA PolyFox PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, PF-652, Neos's Fantgent FTX- 209F, FTX-208G, FTX-204D, Seimi Chemical's Surflon KH-40, and the like can be used. The blending ratio of the surfactant is preferably 0.05% by weight to 3% by weight in the cured film obtained by curing the cholesteric liquid crystal composition. When the blending ratio of the surfactant is less than 0.05% by weight, the orientation regulating force at the air interface is lowered and an orientation defect may occur, which is not preferable. On the other hand, when the amount is more than 3% by weight, it is not preferable because an excessive surfactant may enter between liquid crystal molecules and lower the alignment uniformity.

  In the present invention, the cholesteric liquid crystal composition can optionally contain a chiral agent. Specific examples of the chiral agent include JP-A-2005-289881, JP-A-2004-115414, JP-A-2003-66214, JP-A-2003-313187, JP-A-2003-342219, JP-A-2000-290315, JP-A-6-072962, U.S. Pat. No. 6,468,444, WO98 / 00428, JP-A-2007-176870, etc. can be used as appropriate. For example, it can be obtained as LC756 of BASF Corporation Paliocolor.

  The chiral agent can be added within a range that does not deteriorate the desired optical performance. The content ratio of the chiral agent is usually 1 to 60% by weight in the cholesteric liquid crystal composition.

  In the present invention, the cholesteric liquid crystal composition can further contain other optional components as necessary. Examples of the other optional components include a solvent, a polymerization inhibitor for improving pot life, an antioxidant for improving durability, an ultraviolet absorber, and a light stabilizer. These optional components can be added as long as the desired optical performance is not deteriorated.

  The method for producing the cholesteric liquid crystal composition in the present invention is not particularly limited, and can be produced by mixing the above-described components.

  A cholesteric liquid crystal composition such as the cholesteric liquid crystal composition (X) is applied onto another layer such as an alignment film to obtain a liquid crystal layer, and then the liquid crystal is subjected to light irradiation and / or heating treatment at least once. A cholesteric resin layer can be obtained by curing the layer. The application can be carried out by a known method such as an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method, or a bar coating method.

  Before the liquid crystal layer obtained by the application is cured, an alignment treatment can be performed as necessary. The alignment treatment can be performed, for example, by heating the liquid crystal layer at 50 to 150 ° C. for 0.5 to 10 minutes. By performing the alignment treatment, the cholesteric liquid crystal layer can be aligned well.

The curing step can be performed by a combination of one or more light irradiations and a heating treatment. Specifically, the heating condition is, for example, a temperature of 40 to 200 ° C., preferably 50 to 200 ° C., more preferably 50 to 140 ° C., and a time of 1 second to 3 minutes, preferably 5 to 120 seconds. it can. The light used for light irradiation in the present invention includes not only visible light but also ultraviolet rays and other electromagnetic waves. Specifically, the light irradiation can be performed by, for example, irradiating light having a wavelength of 200 to 500 nm for 0.01 second to 3 minutes. Further, for example, a weakly irradiated ultraviolet ray of 0.01 to 50 mJ / cm ² and heating may be alternately repeated several times to obtain a circularly polarized light separating sheet having a wide reflection band. After extending the reflection band by the above-mentioned weak ultraviolet irradiation, etc., a relatively strong ultraviolet ray of 50 to 10,000 mJ / cm ² is irradiated to completely polymerize the liquid crystalline compound to form a cholesteric resin layer. it can. The expansion of the reflection band and the irradiation with strong ultraviolet rays may be performed in the air, or a part or all of the process may be performed in an atmosphere in which the oxygen concentration is controlled (for example, in a nitrogen atmosphere). .

  In the present invention, the step of applying and curing the cholesteric liquid crystal composition on another layer such as an alignment film is not limited to one time, and the coating and curing are repeated a plurality of times to form two or more cholesteric resin layers. You can also. However, in the present invention, even when the cholesteric liquid crystal composition is applied and cured only once, a cholesteric resin layer having a well-oriented rod-like liquid crystalline compound having a Δn of 0.18 or more and a thickness of 5 μm or more can be easily formed. Can be formed.

  In the brightness enhancement film of the present invention, the dry film thickness of the cholesteric resin layer is preferably 3.0 μm to 10.0 μm, more preferably 3.5 to 8 μm. When the dry film thickness of the cholesteric resin layer is less than 3.0 μm, the reflectance decreases, and conversely, when thicker than 10.0 μm, the cholesteric resin layer is colored when observed from an oblique direction, Each is not preferred. The dry film thickness refers to the total film thickness of each layer when the cholesteric resin layer is two or more layers, and the film thickness when the cholesteric resin layer is one layer.

1-2. Barrier layer The brightness enhancement film of the present invention has a barrier layer. The said barrier layer hardens | cures the composition containing the polymer A and a silane coupling agent.

  Here, as the polymer A contained in the barrier layer, a water-soluble or alcohol-soluble polymer can be used. Specifically, polyvinyl alcohol (PVA), polyamide, gelatin, and cellulose can be used. The water-soluble polymer is a polymer that dissolves in an amount of 0.5 g or more in 100 g of water at 25 ° C. The alcohol-soluble polymer is a polymer that can be dissolved in 0.5 g or more in 100 g of ethanol at 25 ° C. And the thing which does not have an amino group as a substituent from a viewpoint that the external appearance of the resin layer with a cholesteric regularity improves, or the solubility to the solvent containing the silane coupling agent mentioned later improves. Of these exemplified polymers A, polyvinyl alcohol is most suitable. The polyvinyl alcohol used in the present invention is not limited by its saponification degree, but preferably has a saponification degree of 85 to 95%.

  Although the polymer A used for this invention is not restrict | limited by the polymerization degree, Preferably it is 50-5000, More preferably, it is 80-4,000, More preferably, it is 100-3,000. If the degree of polymerization is too low, the film becomes soft and easily blocked, resulting in poor appearance. On the other hand, if the degree of polymerization is too high, the solubility in water or alcohol tends to be low.

In the present invention, examples of the silane coupling agent contained in the barrier layer include compounds represented by the following formula (3).
^{_{R 10 - (CH 2) n}} SiY 3 Equation (3)
In said Formula (3), n is an integer greater than or equal to 1, and the range of 1 or more and 3 or less is preferable. In the formula (3), Y is a hydrolyzable substituent such as an alkoxy group or halogen, and R ¹⁰ is a vinyl group, epoxy group, amino group, acryloxy group, methacryloxy group, chloropropyl group, mercapto group, isocyanate. It is a substituent that easily reacts with an organic substance, such as a group. Silane coupling agents which can be used in the present invention is not limited thereto, aminosilane having a substituent R ¹⁰ as primary amino groups (H 2 _N-) or secondary amino group (-NH-) It is particularly preferable from the viewpoint of compatibility with the cholesteric resin layer and polyvinyl alcohol. The aminosilane may have other functional groups such as a phenyl group, an ether group, a sulfide group, and a disulfide group in addition to the amino group.

  Specific examples of aminosilane include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl)- 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3- Aminopropyltriethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylethyldiethoxysilane, 3-aminopropyltrihydroxysilane, 3-aminopropyldimethylhydroxysilane, 3-aminopropyldiethylhydroxysilane, 3-amino Propylethyldihydroxysilane and 3-aminopropy Such as methyl dihydroxy silane. In particular, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxysilane are preferable.

  The molecular weight of aminosilane is usually 100 to 1,500, preferably 170 to 1,000. If the molecular weight is too low, it tends to volatilize at room temperature, and handling tends to be inconvenient. If the molecular weight is too high, the compatibility with the polymer A and the solubility in various solvents tend to be low.

  The polymer A and the silane coupling agent are preferably contained in the barrier layer in a weight ratio of preferably 1:99 to 99: 1, more preferably 75:25 to 96: 4. When there is too little polymer A, a membrane | film | coat will become soft and it will block easily and an external appearance will be bad. On the other hand, when there is too much polymer A, the spectrum shift inhibitory effect will fall.

  In addition to containing the polymer A and the silane coupling agent, the barrier layer may further contain other components. Specifically, for example, a cross-linking agent such as a titanium compound such as boric acid, titanium lactate, titanium triethanolamate, or a bifunctional aldehyde can be included. These content ratios can be 0.1 to 10% by weight with respect to the polymer A.

  The barrier layer can be formed by laminating a composition containing the polymer A and a silane coupling agent on the cholesteric resin layer. In this case, the surface of the cholesteric resin layer is preferably subjected to corona discharge treatment for the purpose of improving the coating property of the barrier layer. Specifically, it is formed by applying a composition containing the polymer A, the silane coupling agent, and, if necessary, the other components to obtain a coating film of the composition, and then curing the coating film. be able to. As a method of laminating a barrier layer to a resin layer having cholesteric regularity, 1) a method of coating, drying and curing on a resin layer having cholesteric regularity; 2) on a resin substrate (for example, PET film) By coating, drying, and curing the barrier layer-forming composition on a release substrate in which a silicone resin or an alkyd resin is laminated, and attaching the resulting composition to a cholesteric resin layer, the release substrate is then released. And a method of transferring the barrier layer to a resin layer having cholesteric regularity.

  The composition for forming the barrier layer can contain a solvent in addition to the above components. Examples of the solvent include water, alcohol, ketone, ether and the like. Among these, water or alcohol is preferable. The alcohol is particularly preferably methanol, ethanol, i-propyl alcohol, or n-propanol. The mixing ratio of the solvent can be water: alcohol = 95: 5 to 50:50 (weight ratio). The composition for forming the barrier layer is applied by spin coating, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, die coating, gravure printing, and the like. be able to. The method for curing the coating film of the composition is not particularly limited, and can be performed by, for example, drying the coating film.

1-3. Other Layers The brightness enhancement film of the present invention can further contain other layers in addition to the cholesteric resin layer and the barrier layer. Specifically, for example, layers such as a base material layer and an alignment film can be included.
The brightness enhancement film of the present invention preferably has the base layer, the alignment film, the cholesteric resin layer, the barrier layer, and a retardation film in this order. The brightness enhancement film of the present invention may further include two or more combinations of the base material layer, the alignment film, the cholesteric resin layer, and the barrier layer.
For example, there are two combinations of the base material layer, the alignment film, the cholesteric resin layer, and the barrier layer, and the first base material layer, the first alignment film, the first cholesteric resin layer, the first barrier layer, It can be set as the structure which has a 2nd base material layer, a 2nd alignment film, a 2nd cholesteric resin layer, and a 2nd barrier layer in this order.
In the brightness enhancement film of the present invention, another layer may optionally be further provided between each layer. That is, each of the above layers may be directly laminated, or may be laminated via other layers. For example, the first barrier layer and the second base material layer may be bonded via an adhesive layer or an adhesive layer. However, from the viewpoint of protecting the surface of the cholesteric resin layer, the barrier layer is preferably provided directly on the surface of the cholesteric resin layer. Further, since the alignment film controls the alignment in the preparation of the cholesteric resin layer, the cholesteric resin layer is usually provided directly on the surface of the alignment film.
The adhesive layer or the pressure-sensitive adhesive layer can contain a diffusing agent as necessary. The material as the diffusing agent is not particularly limited, and inorganic and organic diffusing agents can be appropriately selected and used.
Inorganic diffusing agents include glass, silicon oxide, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, etc .; organic diffusing agents include fluorine resin, polystyrene resin, acrylic resin, polycarbonate Resins, silicone resins, polyethylene resins, ethylene-vinyl acetate copolymers, acrylonitrile, polyurethane, polyvinyl chloride, polyacrylonitrile, polyamides, polysiloxane resins, melamine resins, benzoguanamine resins, or cross-linked products thereof It is done.
The shape of the diffusing agent is not particularly limited, and examples thereof include a spherical shape, an ellipsoidal shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fiber shape. A spherical shape or an ellipsoidal shape close to a spherical shape is preferable in that it can be made squarely.
The size of the diffusing agent is preferably 0.2 μm to 50 μm in diameter, more preferably 0.5 μm to 10 μm. In addition, when the diameter here is not a perfect sphere, the diameter of the sphere of the same volume is substituted. In the case of a filler having a significantly different size in one direction such as a needle shape, a diameter of a circle having the same area as the cross-sectional area of the cross section perpendicular to the direction is substituted.
The refractive index of the diffusing agent is preferably different from the refractive index of the main polymer used as the base material of the adhesive layer or the pressure-sensitive adhesive layer, and the refractive index difference is more preferably 0.05 or more.
The diffusing agent may be a single material, size, refractive index or other properties, or a mixture of two or more diffusing agents. Moreover, you may use what consists of 2 or more types of raw materials as a spreading | diffusion agent.
The content of the filler in the adhesive layer is preferably 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the polymer constituting the adhesive layer or the pressure-sensitive adhesive layer.
The ratio of the average particle diameter d of the diffusing agent contained in the adhesive layer or the adhesive layer and the thickness l of the adhesive layer or the adhesive layer is preferably 0.05 ≦ d / l ≦ 0.6, particularly preferably 0.07. ≦ d / l ≦ 0.3. If it is less than 0.05, the particle size of the diffusing agent is too small, or the film thickness of the adhesive layer or the pressure-sensitive adhesive layer is too thick. Or there exists a possibility that an adhesive layer may generate | occur | produce an unnecessary phase difference, and when it exceeds 0.6, a required adhesion area cannot be obtained, there exists a possibility that adhesive force may run short and an adhesive layer may peel.

  The said base material layer can be comprised with a transparent resin base material. The transparent resin substrate is not particularly limited, and a substrate having a thickness of 1 mm and a total light transmittance of 80% or more can be used. Specifically, alicyclic olefin polymers, chain olefin polymers such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, modified acrylic polymer, epoxy resin, Examples thereof include a single layer or laminated film made of a synthetic resin such as polystyrene or acrylic resin. Among these, an alicyclic olefin polymer or a chain olefin polymer is preferable, and an alicyclic olefin polymer is particularly preferable from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like.

The alignment film can be provided on the base material layer. By providing the alignment film, the cholesteric liquid crystal composition applied thereon can be aligned in a desired direction. The alignment film is subjected to a corona discharge treatment, if necessary, on the surface of the substrate, and then a solution obtained by dissolving the alignment film material in water or a solvent, reverse gravure coating, direct gravure coating, die coating, It can be formed by applying and drying using a known method such as bar coating and then subjecting the dried coating film to a rubbing treatment. As materials for the alignment film, cellulose, silane coupling agent, polyimide, polyamide, polyvinyl alcohol, epoxy acrylate, silanol oligomer, polyacrylonitrile, phenol resin, polyoxazole, cyclized polyisoprene, etc. can be used. Polyamide is particularly preferred.
Examples of the modified polyamide include those obtained by modifying an aromatic polyamide or an aliphatic polyamide, and those obtained by modifying an aliphatic polyamide are preferred. Specifically, for example, modified to nylon-6, nylon-66, nylon-12, ternary to quaternary copolymer nylon, fatty acid polyamide, or fatty acid block copolymer (for example, polyether ester amide, polyester amide). Can be mentioned. Examples of the modification include terminal amino modification, carboxyl modification, hydroxyl modification and the like, and modification in which a part of the amide group is alkylaminated or N-alkoxyalkylated. Examples of the N-alkoxyalkylated modified polyamide include N-methoxymethylated part of the amide group of a copolymer nylon such as nylon-6, nylon-66, or nylon-12. The weight average molecular weight of the modified polyamide is preferably 5,000 to 500,000, more preferably 10,000 to 200,000.
The thickness of the alignment film may be any film thickness that provides the desired alignment uniformity of the liquid crystal layer, and is preferably 0.001 to 5 μm, and more preferably 0.01 to 2 μm.

  By providing the cholesteric resin layer and the barrier layer on the alignment film by the method described above, a circularly polarized light separating sheet having the base material layer, the alignment film, the cholesteric resin layer, and the barrier layer in this order can be obtained. . By sticking such a circularly polarized light separating sheet composed of four layers through an adhesive layer or an adhesive layer, the first base material layer, the first alignment film, the first cholesteric resin layer, the first A circularly polarized light separating sheet having a barrier layer, a second base material layer, a second alignment film, a second cholesteric resin layer, and a second barrier layer in this order can be obtained.

2. Luminance-enhancing film The luminance-enhancing film of the present invention includes the circularly polarized light separating sheet and the retardation film. Specifically, a circularly polarized light separating sheet and a retardation film can be laminated to obtain the brightness enhancement film of the present invention. The lamination can be achieved by integrating the circularly polarized light separating sheet and the retardation film via an adhesive or a pressure-sensitive adhesive. Furthermore, for the purpose of improving the durability and rigidity of the brightness enhancement sheet, an additional transparent resin substrate is integrated on the transparent resin substrate and / or the retardation film via an adhesive or pressure sensitive adhesive. It can also be made.

  As the retardation film used in the present invention, (i) a film-like polymer stretched or (ii) a liquid crystal material applied on a transparent resin substrate, oriented and cured is used. Can do. When the retardation film of (ii) is used, the liquid crystal material is applied on an appropriate substrate, oriented, and cured, and the retardation film obtained by integrating the retardation film with the circularly polarized light separating sheet is improved in luminance. Alternatively, a film may be formed, or an alignment film may be provided on the circularly polarized light separating sheet as necessary to perform various alignment treatments, and a liquid crystalline material is applied thereon, aligned, and cured. Thus, a layer of a retardation film integrated with the circularly polarized light separating sheet can be provided to obtain a brightness enhancement film.

  Preferred examples of the retardation film used in the present invention include the optically anisotropic elements described below.

  In the present invention, the optically anisotropic element can have a retardation Re in the front direction (hereinafter sometimes abbreviated as “Re”) of approximately ¼ wavelength of transmitted light. Here, the wavelength range of the transmitted light can be a desired range required for the brightness enhancement film of the present invention, and specifically, for example, 400 nm to 700 nm. Further, the retardation Re in the front direction is approximately ¼ wavelength of transmitted light, and the Re value is ± 65 nm from the ¼ value of the center value in the center value of the wavelength range of transmitted light, preferably It means ± 30 nm, more preferably ± 10 nm.

The optically anisotropic element desirably has a thickness direction retardation Rth (hereinafter sometimes abbreviated as “Rth”) of less than 0 nm. The value of retardation Rth in the thickness direction is preferably −30 nm to −1000 nm, more preferably −50 nm to −300 nm, in the central value of the wavelength range of transmitted light. By adopting such an optically anisotropic element having an Re value and Rth, it is possible to reduce color unevenness of emitted light while improving brightness and reducing brightness unevenness.
Here, the retardation Re in the front direction is represented by the formula I: Re = (nx−ny) × d (where nx is a direction perpendicular to the thickness direction (front direction) and gives the maximum refractive index). Ny represents a refractive index in a direction perpendicular to the thickness direction (in-plane direction) and perpendicular to nx, and d represents a film thickness). The direction retardation Rth is expressed by the formula II: Rth = {(nx + ny) / 2−nz} × d (where nx is a direction perpendicular to the thickness direction (in-plane direction) and gives the maximum refractive index) Ny is the refractive index in the direction perpendicular to the thickness direction (in-plane direction) and orthogonal to nx, nz is the refractive index in the thickness direction, and d is the film thickness. ).
In addition, the retardation Re in the front direction and the retardation Rth in the thickness direction are measured using a commercially available phase difference measuring apparatus, and the optically anisotropic elements are spaced 100 mm apart in the longitudinal direction and the width direction (longitudinal or lateral length). If the distance is less than 200 mm, three points are specified at equal intervals in that direction), and measurement is performed in a lattice point shape over the entire surface, and the average value is obtained.

  Although the material which comprises the said optically anisotropic element is not specifically limited, What has the layer which consists of a styrene resin can be used preferably. Here, the styrene-based resin is a polymer resin having a styrene structure as a part or all of the repeating unit, and polystyrene, styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene. , Styrene monomers such as p-nitrostyrene, p-aminostyrene, p-carboxystyrene, p-phenylstyrene, ethylene, propylene, butadiene, isoprene, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, acrylic acid Examples thereof include copolymers with other monomers such as methyl, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic anhydride, and vinyl acetate. Among these, polystyrene or a copolymer of styrene and maleic anhydride can be suitably used.

  The molecular weight of the styrenic resin used for the optically anisotropic element is appropriately selected according to the purpose of use, but is the weight average molecular weight (Mw) of polyisoprene measured by gel permeation chromatography using cyclohexane as a solvent. Usually, 10,000 to 300,000, preferably 15,000 to 250,000, and more preferably 20,000 to 200,000.

  The optically anisotropic element preferably has a laminated structure of a layer made of the styrenic resin and a layer containing another thermoplastic resin. By having the laminated structure, it is possible to provide an element that has both the optical characteristics of the styrene resin and the mechanical strength of other thermoplastic resins. Other thermoplastic resins include alicyclic olefin polymers, methacrylic resins, polycarbonates, acrylic ester-vinyl aromatic compound copolymer resins, methacrylic ester-vinyl aromatic compound copolymer resins, polyethersulfone, etc. Can be mentioned. Among these, a resin having an alicyclic structure or a methacrylic resin can be preferably used.

  The alicyclic olefin polymer is an amorphous olefin polymer having a cycloalkane structure or a cycloalkene structure in the main chain and / or side chain. Specifically, (1) norbornene polymer, (2) monocyclic olefin polymer, (3) cyclic conjugated diene polymer, (4) vinyl alicyclic hydrocarbon polymer, and these A hydride etc. are mentioned. Among these, norbornene-based polymers are more preferable from the viewpoints of transparency and moldability. Examples of the resin having these alicyclic structures include those described in JP-A No. 05-310845, JP-A No. 05-097978, and US Pat. No. 6,511,756.

  Specific examples of the norbornene-based polymer include ring-opening polymers of norbornene-based monomers, ring-opening copolymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization, hydrides thereof, and norbornene-based monomers. And addition copolymers with other monomers copolymerizable with norbornene monomers.

  The methacrylic resin is a polymer having a methacrylic acid ester as a main component, and includes a methacrylic acid ester homopolymer and a copolymer of a methacrylic acid ester and other monomers. Usually, alkyl methacrylate is used. In the case of a copolymer, acrylic acid esters, aromatic vinyl compounds, vinylcyan compounds, etc. are used as other monomers copolymerized with methacrylic acid esters.

  As a preferred specific embodiment of the optically anisotropic element used in the present invention, a multilayer film formed by laminating a film (b layer) made of another thermoplastic resin on both surfaces of a film (a layer) made of polystyrene resin. A stretched multilayer film formed by stretching can be mentioned. Hereinafter, this specific embodiment will be described.

  As the polystyrene resin constituting the a layer, the same “styrene resin” as described above can be used.

  The polystyrene resin constituting the a layer preferably has a glass transition temperature of 120 ° C. or higher, more preferably 120 to 200 ° C., and still more preferably 120 to 140 ° C.

  In the present invention, the polystyrene resin and the other thermoplastic resin have Tg (a)> Tg (b) when their glass transition temperatures are Tg (a) (° C.) and Tg (b) (° C.), respectively. ) It is preferable to satisfy the relationship of + 20 ° C. By satisfying such a relationship, optical anisotropy can be effectively given to the a layer made of polystyrene resin when stretched, and a good optical anisotropic element can be obtained.

  The method of laminating the polystyrene resin that is the material of the a layer and the other thermoplastic resin that is the material of the b layer to form a multilayer film is not particularly limited, but is a coextrusion T-die method, coextrusion inflation Known methods such as a method of forming by coextrusion such as a method, a coextrusion lamination method, a film lamination forming method such as dry lamination, and a coating forming method may be appropriately used. Among these, a molding method by coextrusion is preferable from the viewpoints of production efficiency and that volatile components such as a solvent do not remain in the film. The extrusion temperature can be appropriately selected according to the type of the polystyrene resin used and the other thermoplastic resin.

  The multilayer film is formed by laminating the b layer on both surfaces of the a layer. An adhesive layer or a pressure-sensitive adhesive layer can be provided between the a layer and the b layer, but the a layer and the b layer are directly laminated (that is, lamination of a three-layer configuration of b layer / a layer / b layer). Body). In the multilayer film, the thickness of the a layer and the b layer laminated on both sides thereof is not particularly limited, but preferably 10 to 300 μm and 10 to 400 μm, respectively.

The stretched multilayer film is formed by stretching the multilayer film. The stretched multilayer film may include an A layer provided by stretching the a layer and a B layer provided by stretching the b layer. The stretched multilayer film is a stretched film having a three-layer structure of B layer / A layer / B layer formed by stretching a laminate of b layer / a layer / b layer of the multilayer film. It is preferable.
The stretching can be preferably performed by uniaxial stretching or oblique stretching, and more preferably by uniaxial stretching or oblique stretching by a tenter.

  The front direction retardation Re and the thickness direction retardation Rth of the optically anisotropic element can be produced by appropriately adjusting stretching conditions such as a stretching temperature and a stretching ratio. The stretching temperature is preferably Tg (a) -10 ° C to Tg (a) + 20 ° C, and more preferably in the range of Tg (a) -5 ° C to Tg (a) + 15 ° C. The draw ratio is preferably 1.05 to 30 times, and more preferably 1.1 to 10 times. If the stretching temperature and the stretching ratio are out of the above ranges, the orientation may be insufficient and the refractive index anisotropy and thus the retardation may be insufficiently developed, or the laminate may be broken.

  The thickness of the optically anisotropic element is preferably 50 to 1000 μm, more preferably 50 to 600 μm.

3. Liquid crystal display device The liquid crystal display device of the present invention includes the brightness enhancement film of the present invention and a liquid crystal panel.

  The liquid crystal panel is not particularly limited, and those used in liquid crystal display devices can be used as appropriate. For example, TN (Twisted Nematic) type liquid crystal panel, STN (Super Twisted Nematic) type liquid crystal panel, HAN (Hybrid Alignment Nematic) type liquid crystal panel, IPS (In Plane Switching) type liquid crystal panel, VA (vertical type liquid crystal panel). Examples thereof include a MVA (Multiple Vertical Alignment type liquid crystal panel) and an OCB (Optical Compensated Bend) type liquid crystal panel.

  The liquid crystal display device of the present invention can further include a backlight, and can have a configuration in which a brightness enhancement film is disposed between the backlight and the liquid crystal panel. More specifically, the brightness enhancement film of the present invention is disposed between the backlight of the liquid crystal display device and the liquid crystal cell so that the layer of the circularly polarized light separating sheet is on the backlight side of the layer of the retardation film. , Brightness improvement can be achieved.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

(Example 1: Creation of a brightness enhancement film having one cholesteric resin layer)
(1-1: Preparation of transparent resin substrate having alignment film)
Both surfaces of a film made of an alicyclic olefin polymer (manufactured by Optes Co., Ltd .; trade name “Zeonor film ZF14-100”) were subjected to corona discharge treatment. An aqueous solution of 5% modified polyamide (FR105 / CM4000 70/30 mixture, FR105: methoxymethylated nylon manufactured by Lead City Co., Ltd. CM4000: copolymerized polyamide manufactured by Toray Industries, Inc.) is coated with # 2 wire bar on one side of the film. It was used and applied, and the coating film was dried to form an alignment film having a thickness of 0.1 μm. Next, the alignment film was rubbed to prepare a transparent resin substrate having the alignment film.

(1-2: Formation of first cholesteric resin layer)
A cholesteric liquid crystal composition prepared by mixing each component at the blending ratio shown in Table 1 is applied to the surface having the alignment film of the transparent resin substrate having the alignment film prepared above using a # 10 wire bar. did. The coating film is subjected to an orientation treatment at 100 ° C. for 5 minutes, and the coating film is subjected to a process of irradiation with weak ultraviolet rays of 0.1 to 45 mJ / cm ² followed by a heating treatment at 100 ° C. for 1 minute. After repeating twice, the first cholesteric resin layer having a dry film thickness of 5 μm was obtained by irradiating with an ultraviolet ray of 800 mJ / cm ² under a nitrogen atmosphere.

(1-3: Formation of barrier layer, preparation of circularly polarized light separating sheet)
In a solvent comprising pure water / isopropyl alcohol = 90/10 (weight ratio), PVA (manufactured by Kuraray Co., Ltd .; Kuraray Poval PVA226, polymerization degree 2600, saponification degree 88%), and silane coupling agent (manufactured by Shin-Etsu Chemical; KBM603 (N-2 (aminoethyl) -3-aminopropyltrimethoxysilane, molecular weight 222) and KBE903 (1-aminopropyl triethoxysilane, molecular weight 221) 1; 1 mixture) 80/20 (weight) Ratio) to a solid content of 3% by weight to obtain a barrier layer material composition having a viscosity of 27 to 30 cp (23 ° C.).
On the cholesteric resin layer prepared in (1-2) above, the barrier layer material composition is applied using a # 4 wire bar, dried and cured at 110 ° C. for 2 to 3 minutes, and dried film thickness A barrier layer of 0.1 μm ± 0.05 μm was obtained, and a laminate (1-a) having a base material layer, an alignment film, a first cholesteric resin layer, and a barrier layer in this order was obtained. As used below.

(1-4: Preparation of retardation film)
A monomer composition composed of 97.8% by weight of methyl methacrylate and 2.2% by weight of methyl acrylate was polymerized by a bulk polymerization method to obtain resin pellets.

  Rubber particles were produced according to Example 3 of JP-B-55-27576. This rubber particle has a spherical three-layer structure, the core inner layer is a crosslinked polymer of methyl methacrylate and a small amount of allyl methacrylate, and the inner layer is composed of butyl acrylate and styrene as main components and a small amount of acrylic acid. It is a soft elastic copolymer obtained by crosslinking and copolymerizing allyl, and the outer layer is a hard polymer of methyl methacrylate and a small amount of ethyl acrylate. The average particle size of the inner layer was 0.19 μm, and the particle size including the outer layer was 0.22 μm.

  70 parts by weight of the resin pellets and 30 parts by weight of the rubber particles were mixed and melt kneaded with a twin screw extruder to obtain a methacrylic acid ester polymer composition A (glass transition temperature 105 ° C.).

  By coextruding the methacrylic ester polymer composition A (b layer) and the styrene maleic anhydride copolymer (glass transition temperature 130 ° C.) (a layer) at a temperature of 280 ° C., a b layer / a layer A multilayer film having an average thickness of 45/70/45 (μm) with a three-layer structure of / b layers was obtained. The laminated film is stretched obliquely at a stretching temperature of 134 ° C. and a stretching ratio of 1.8 times so that the slow axis is in a direction inclined by 45 degrees with respect to the MD direction by a tenter stretching machine. Got.

  The retardation in the front direction of the optically anisotropic layer was 140 nm, and the retardation in the thickness direction was −85 nm (each numerical value is a measured value after stretching). Further, one side of the optically anisotropic layer was subjected to corona discharge treatment so that the wetting index was 56 dyne / cm. This optically anisotropic layer was used as a retardation film in the following.

(1-5: Creation of brightness enhancement film)
The circularly polarized light separating sheet (laminate 1-a) obtained in (1-3) and the retardation film obtained in (1-4) are so adhesive that the barrier layer and the retardation film face each other. The laminate (1-b) was obtained by laminating with (Daido Chemicals; acrylic adhesive, E-5301). The same alicyclic ring as that used in (1-1) is further bonded to the retardation film surface of this laminate (1-b) via an adhesive (manufactured by Daido Kasei; acrylic adhesive, E-5301). A film made of the formula olefin polymer was attached. Thereby, the first base material layer, the first alignment film, the first cholesteric resin layer, the first barrier layer, the adhesive layer, the retardation film, the adhesive layer, and the second base material layer are laminated in this order. An eight-layer brightness enhancement film was obtained.

(1-6: Evaluation)
The brightness enhancement film obtained in the above (1-5) was heated in an oven at 110 ° C., and the relationship between the heating time and the transmission spectrum shift was measured.
The transmission spectrum was measured with an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation; trade name JASCO-V550, using an integrating sphere option). The transmittance at each frequency was measured before heating (0 h) and at 5 minutes, 10 minutes, 30 minutes, 1 hour and 2 hours after the start of heating. Since the light source of the spectrophotometer's spectroscope has polarization, the film is rotated by 0 °, 45 °, 90 °, and 135 ° around the light irradiation direction from the light source to the film when measuring the transmittance. The four types of values were measured and the average value was determined. Even after heating for 2 hours, almost no shift in the transmission spectrum was observed.
The color difference ΔE * of the brightness enhancement film before heating and after heating for 2 hours was measured using a spectroscopic color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd .; trade name SE-200) and found to be 1.80. It was. The results are shown in Table 1.

(Example 2: Creation of a brightness enhancement film having two cholesteric resin layers)
(2-1: Preparation of first laminate (2-a))
As the cholesteric liquid crystal composition, in place of the composition used in the above (1-2), except that the composition shown as the “first layer” composition in Table 1 was used, the above (1-1) to ( The same operation as in 1-3) was performed to obtain a laminate (2-a) having a base material layer, an alignment film, a first cholesteric resin layer, and a barrier layer in this order.

(2-2: Preparation of second laminate (2-b))
On the other hand, except that the composition shown as the “second layer” composition in Table 1 was used as the cholesteric liquid crystal composition, the same operation as in the above (1-1) to (1-3) was carried out. A laminate (2-b) having an alignment film, a second cholesteric resin layer, and a barrier layer in this order was obtained.

(2-3: Creation of circularly polarized light separating sheet having two cholesteric resin layers)
The barrier layer of the laminate (2-a) and the base material layer of the laminate (2-b) are bonded together via an adhesive (manufactured by Daido Kasei; acrylic adhesive, E-5301). A circularly polarized light separating sheet (2-c) containing a cholesteric resin layer was obtained.

(2-4: Creation of brightness enhancement film)
The circularly polarized light separating sheet (laminate 2-c) obtained in (2-3) and the retardation film obtained in (1-4) are so adhesive that the barrier layer and the retardation film face each other. The laminate (2-d) was obtained by laminating with (Daido Chemicals; acrylic adhesive, E-5301). The same alicyclic ring as that used in (1-1) is further bonded to the retardation film surface of the laminate (2-d) via an adhesive (Daido Chemicals; acrylic adhesive, E-5301). A film made of the formula olefin polymer was attached. Accordingly, the first base material layer, the first alignment film, the first cholesteric resin layer, the first barrier layer, the adhesive layer, the second base material layer, the second alignment film, and the second cholesteric resin. A 13-layer brightness enhancement film was obtained in which a layer, a second barrier layer, an adhesive layer, a retardation film, an adhesive layer, and a third base material layer were laminated in this order. This brightness enhancement film was evaluated in the same manner as in Example 1. The results are shown in Table 1. In Table 1, the composition of the liquid crystal composition and the composition of the barrier layer all represent parts by weight.

(Examples 3 and 4)
As a silane coupling agent used for the formation of the barrier layer, instead of the one described in (1-3), the substituent is not an amino group but an epoxy group (Example 3, manufactured by Shin-Etsu Chemical; KBM-303) , A molecular weight 246) or a mercapto group (Example 4, manufactured by Shin-Etsu Chemical; KBM-803, molecular weight 196) was used to obtain a brightness enhancement film comprising 13 layers in the same manner as in Example 2. ,evaluated. The results are shown in Table 1.

(Comparative Examples 1 and 2)
Except that the barrier layer was not prepared, the same operation as in Examples 1 and 2 was performed, and the first substrate layer, the first alignment film, the first cholesteric resin layer, the adhesive layer, the retardation film, the adhesive layer, And a brightness enhancement film (Comparative Example 1) consisting of seven layers, a first base material layer, a first alignment film, a first cholesteric resin layer, and an adhesive layer. The second base material layer, the second alignment film, the second cholesteric resin layer, the adhesive layer, the retardation film, the adhesive layer, and the third base material layer are laminated in this order, and consists of 11 layers. A brightness enhancement film (Comparative Example 2) was obtained and evaluated in the same manner as in Examples 1 and 2. The results are shown in Table 2. It was observed that the transmission spectrum shifted to the lower wavelength side by about 95 nm and 78 nm by heating for 2 hours, respectively. The color difference ΔE * was 18.10 and 10.00, respectively. In Table 2, the composition of the liquid crystal composition and the composition of the barrier layer all represent parts by weight.

(Comparative Examples 3 and 4)
As the barrier layer material composition, the same composition as in Example 2 (Comparative Example 3) except that it does not contain polymer A, or the same composition as in Example 2 except that it does not contain a silane coupling agent (Comparative Example 4) The first base material layer, the first alignment film, the first cholesteric resin layer, the first barrier layer, the adhesive layer, and the second base material layer are operated in the same manner as in Example 2. A luminance composed of 13 layers in which a second alignment film, a second cholesteric resin layer, a second barrier layer, an adhesive layer, a retardation film, an adhesive layer, and a third base material layer are laminated in this order. An improved film was obtained and evaluated. Table 2 shows the results of the transmission spectrum shift amount and the color difference ΔE.

The abbreviations in Table 1 and Table 2 indicate the following:
Compound (1); Compound A2
Compound (2) A; Δn = 0.18 Number of polymerizable groups in one molecule, average refractive index of 1.645
Compound (2) B; Δn = 0.20 Two polymerizable groups in one molecule, average refractive index 1.638
Photopolymerization initiator X: Irgacure 907 (Ciba Specialty Chemicals)
Polymer A: Kuraray Poval PVA226 (manufactured by Kuraray Co., Ltd.)

(Example 5: Liquid crystal display device)
A commercially available liquid crystal display device (manufactured by Sharp, AQUAS, LC-37BE1W) was disassembled, and the brightness enhancement film obtained in Example 2 was attached and reassembled to obtain a liquid crystal display device. The liquid crystal display device includes a backlight, a diffusion plate, a diffusion sheet, a prism sheet, an optical composite element, and a liquid crystal panel in this order.

When this liquid crystal display device was continuously driven with white display, no color unevenness was observed even after 500 hours.
(Comparative Example 5)
A liquid crystal display device was prepared and evaluated in the same manner as in Example 5 except that the brightness enhancement film used was obtained in Comparative Example 2 instead of that obtained in Example 2. When 100 hours had elapsed, color unevenness was observed.

Claims (9)

A resin layer having cholesteric regularity, a barrier layer, and a retardation film are provided.
The brightness enhancement film, wherein the barrier layer is formed by curing a composition containing a polymer A and a silane coupling agent.   The brightness enhancement film according to claim 1, wherein the silane coupling agent has a primary or secondary amino group.   The brightness enhancement film according to claim 1, wherein the resin layer having cholesteric regularity is a non-liquid crystalline resin layer.   The brightness enhancement film according to claim 1, wherein the polymer A is a water-soluble or alcohol-soluble polymer.   The brightness enhancement film according to any one of claims 1 to 4, wherein the polymer A is polyvinyl alcohol.   The base material layer and the alignment film are further included, and the base material layer, the alignment film, the resin layer having the cholesteric regularity, the barrier layer, and the retardation film are provided in this order. The brightness enhancement film described in 1.   The brightness enhancement film according to claim 6, comprising two or more combinations of the base material layer, the alignment film, a resin layer having cholesteric regularity, and a barrier layer.   It is a manufacturing method of the brightness improvement film of any one of Claims 1-7, Comprising: The composition containing the said polymer A and a silane coupling agent is laminated | stacked on the resin layer which has the said cholesteric regularity. A manufacturing method including a process.   A liquid crystal display device comprising the brightness enhancement film according to any one of claims 1 to 7 and a liquid crystal panel.