JP2011112720A - Reflection type circular polarized light separation element and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type circular polarized light separation element capable of suppressing occurrence of color unevenness and a liquid crystal display device capable of suppressing the occurrence of color unevenness. <P>SOLUTION: The reflection type circular polarized light separation element is provided with a resin layer having cholesteric regularity and an optical isotropic medium layer provided in contact with at least one surface of the resin layer having the cholesteric regularity. The average refractive index (na) of the ordinary refractive index (no) and the extraordinary refractive index (ne) of a nematic layer constituting the interface of the resin layer having the cholesteric regularity in a wave length (λ) of light reflected, polarized and separated on the interface of the side of the resin layer having the cholesteric regularity, which is brought into contact with the optical isotropic medium layer, and the refractive index (nb) of the optical isotropic medium layer in the wave length (λ) satisfies a relation of nb-0.05<na<nb+0.03. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflective polarization separation element and a liquid crystal display device.

  In a display device such as a liquid crystal display device, it is known to provide various optical members in order to improve the performance. For example, in a liquid crystal display device, it is known to provide a brightness enhancement film as an optical member for effectively using light from a backlight device to improve brightness and increase luminous efficiency. As a brightness enhancement film, for example, a resin layer having a cholesteric regularity (hereinafter referred to as “cholesteric resin layer” as appropriate) and a quarter-wave plate are laminated with an adhesive layer or the like as required. Is known (Patent Documents 1 and 2).

JP 2005-215437 A Japanese Patent No. 3401743

  Conventionally, in a liquid crystal display device provided with a brightness enhancement film, color unevenness sometimes occurs when the display surface is viewed from the front. Similar color unevenness is also observed when the light exit surface of the brightness enhancement film is viewed through the linear polarizing plate. One of the causes of such color unevenness is non-uniformity in the film thickness of the cholesteric resin layer of the brightness enhancement film and non-uniformity in the direction of the director of the surface molecules of the cholesteric resin layer caused by such non-uniformity.

  For example, it is assumed that the color unevenness can be improved by aligning the directions of the directors of the liquid crystal molecules on the surface of the cholesteric resin layer. However, in order to align the direction of the director so that the color unevenness is not visible, in a liquid crystal having a high refractive index anisotropy Δn (for example, Δn = 0.23), the thickness of the cholesteric resin layer is about 20 nm or less. It is required to control with the control, and the control is very difficult.

  It is an object of the present invention to provide a reflective polarization separation element that can suppress the occurrence of color unevenness and a liquid crystal display device that can suppress the occurrence of color unevenness.

As a result of diligent studies to solve the above-described problems and achieve the object, the inventor has a layer of an optically isotropic medium having a refractive index close to the refractive index of a predetermined portion of the cholesteric resin layer in contact with the cholesteric resin layer. The present inventors have found that a reflection-type circularly polarized light separating element can suppress the above-described color unevenness and completed the present invention.
That is, according to the present invention, the following [1] to [9] are provided.

[1] a resin layer having cholesteric regularity;
A reflective circularly polarized light separating element comprising an optically isotropic medium layer provided in contact with at least one surface of the resin layer having the cholesteric regularity,
The nematic-like layer constituting the interface of the resin layer having the cholesteric regularity at the wavelength λ of the resin layer having the cholesteric regularity at the wavelength λ that is reflected and polarized at the interface on the side in contact with the optically isotropic medium layer. The average refractive index na of the normal refractive index no and the extraordinary refractive index ne, and the refractive index nb at the wavelength λ of the optical isotropic medium layer are expressed by the following formula (1):
nb−0.05 <na <nb + 0.03 (1)
A reflective circularly polarized light separating element that satisfies the above.
[2] The reflective circularly polarized light separating element according to [1], wherein the resin layer having cholesteric regularity has a pitch gradient.
[3] The reflective circularly polarized light separating element according to [1] or [2], wherein the reflective polarization separation band of the resin layer having cholesteric regularity is a band including a range of 430 to 750 nm.
[4] The pitch gradient is a gradient in which the pitch gradually increases as the distance from the first surface of the resin layer having the cholesteric regularity approaches the second surface, and the first surface includes the cholesteric regularity. The reflective circularly polarized light separating element according to [2] or [3], which is an interface of a resin layer having a surface on a side in contact with the optical isotropic medium layer.
[5] The pitch gradient is a gradient in which the pitch gradually increases as the distance from the first surface of the resin layer having the cholesteric regularity approaches the second surface, and the second surface includes the cholesteric regularity. The reflective circularly polarized light separating element according to [2] or [3], which is an interface of a resin layer having a surface on a side in contact with the optical isotropic medium layer.
[6] The reflective circularly polarized light according to any one of [1] to [5], further comprising a retardation layer bonded to the resin layer having the cholesteric regularity through the optical isotropic medium layer. Separating element.
[7] The reflective circularly polarized light separating element according to [6], wherein the retardation layer is a quarter wavelength plate.
[8] The optically isotropic medium layer includes an acrylic adhesive, or a mixture of the acrylic adhesive and titanium oxide, aluminum oxide, antimony pentoxide, zirconium oxide, or a combination thereof. The reflective circularly polarized light separating element according to any one of [1] to [7].
[9] A liquid crystal display device comprising the reflective circularly polarized light separating element according to any one of [1] to [8] and a liquid crystal cell.

When the reflective polarization separation element of the present invention is provided in a liquid crystal display device, it can suppress the occurrence of color unevenness in the liquid crystal display device, and is useful as an optical member such as a brightness enhancement film.
According to the liquid crystal display device of the present invention, the occurrence of color unevenness can be suppressed.

FIG. 1 is an exploded perspective view showing an apparatus for evaluating a reflection type circularly polarized light separating element of the present invention used in Examples and Comparative Examples of the present application.

[1. Overview〕
The reflective circularly polarized light separating element of the present invention is an optical element provided in contact with a resin layer having cholesteric regularity (hereinafter sometimes referred to as “cholesteric resin layer”) and at least one surface of the cholesteric resin layer. And an isotropic medium layer. The reflective circularly polarized light separating element of the present invention may further include an arbitrary layer such as a retardation layer. When the retardation layer is a quarter wavelength plate, the reflective circularly polarized light separating element of the present invention is an element that can function as a brightness enhancement film.

[2. (Cholesteric resin layer)
The cholesteric regularity of the cholesteric resin layer is that the molecular axes are aligned in a certain direction on one plane, but the molecular axis direction is slightly shifted on the next plane, and further on the next plane The structure is such that the angle of the molecular axis is shifted (twisted) as it moves on a plane in which molecules are arranged in a certain direction. Thus, the structure in which the direction of the molecular axis is twisted becomes an optically chiral structure.

  The cholesteric resin layer has a circularly polarized light separation function. That is, it has a function of reflecting left-handed or right-handed circularly polarized light in a specific wavelength band and transmitting other circularly-polarized light. With this function, the cholesteric resin layer functions as a reflective polarization separation layer.

  The wavelength band in which the cholesteric resin layer exhibits the circularly polarized light separation function (hereinafter referred to as “reflection polarized light separation band” as appropriate) can be set according to the application. The reflected polarized light separation band is preferably within the wavelength band of visible light, and more preferably over the entire wavelength band of visible light. For example, it is preferable to have a circularly polarized light separating function over the entire region of 430 to 750 nm.

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

  Suitable cholesteric resin layers include, for example, (i) a cholesteric resin layer in which the size of the helical pitch of the chiral structure is changed stepwise, and (ii) a cholesteric resin layer having a pitch gradient, that is, a spiral pitch of the chiral structure. Examples thereof include a cholesteric resin layer whose size is continuously changed.

  (I) A cholesteric resin layer in which the spiral pitch of the chiral structure is changed stepwise includes, for example, a cholesteric resin layer having a spiral pitch of a chiral structure that exhibits a circularly polarized light separation function with light in a blue wavelength region, and a green wavelength A cholesteric resin layer having a chiral helical spiral pitch that exhibits a circularly polarized light separating function with light in the wavelength range and a cholesteric resin layer having a chiral helical spiral pitch that exhibits a circularly polarized light separating function with light in the red wavelength range Can be obtained. In addition, for example, cholesteric resin layers whose center wavelengths of reflected circularly polarized light are 470 nm, 550 nm, 640 nm, and 770 nm are respectively produced, and these cholesteric resin layers are arbitrarily selected, and in the order of the center wavelengths of reflected light It can be obtained by laminating 3 to 7 layers. When the cholesteric resin layers having different spiral pitch sizes in the chiral structure are laminated, it is preferable that the rotation directions of the circularly polarized light reflected by the respective cholesteric resin layers are the same. Moreover, the stacking order of the cholesteric resin layers having different spiral pitch sizes in the chiral structure is set in the ascending or descending order according to the spiral pitch size of the chiral structure, thereby obtaining a liquid crystal display device having a wide viewing angle. Therefore, it is 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 having a pitch gradient is not particularly limited by the production method. As a preferred example of a method for producing a cholesteric resin layer having a pitch gradient, a cholesteric liquid crystal composition containing a polymerizable liquid crystal compound for forming a cholesteric resin layer is preferably applied on another layer such as an alignment film. The liquid crystal layer is obtained, and then the liquid crystal layer is cured by light irradiation and / or heating treatment at least once. By having such a pitch gradient, a cholesteric resin layer having a wide reflected polarization separation band can be obtained.
Preferable embodiments of the cholesteric liquid crystal composition include a cholesteric liquid crystal composition (X) described in detail below. Note that the material referred to as a liquid crystal composition here for convenience includes not only a mixture of two or more substances but also a material made of a single substance.

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 -ZA ² -R ² (1)

In the 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 group having 1 to 20 carbon atoms. Represents a group selected from the group consisting of a chain alkylene oxide group, 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 not be substituted and may be substituted with one or more halogen atoms. Furthermore, when two or more substituents are present in each of the alkyl group and the alkylene oxide group, they may be the same or different.
In addition, the halogen atom, hydroxyl group, carboxyl group, (meth) acryl group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group are alkyl groups and / or alkylene oxides having 1 to 2 carbon atoms. It may be bonded to a group.

Preferred examples of R ¹ and R ² include 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.

At least one of R ¹ and R ² is preferably 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 , 4′-bicyclohexylene group and a group selected from the group consisting of 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 May be unsubstituted, substituted with one or more substituents such as halogen atom, hydroxyl group, carboxyl group, cyano group, amino group, alkyl group having 1 to 10 carbon atoms, halogenated alkyl group, etc. May be. Furthermore, when two or more substituents are present in each of A ¹ and A ² , they may be the same or different.

Particularly preferable examples of A ¹ and A ² include a 1,4-phenylene group, a 4,4′-biphenylene group, and a 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), Z represents a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —CH. = N-N = CH -, - NHCO -, - OCOO -, - CH 2 COO-, and is selected from the group consisting of _-CH 2 OCO-. Particularly preferable examples of Z include a single bond, —OCO—, and —CH═N—N═CH—.

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

  When the compound represented by the general formula (1) has liquid crystallinity, the refractive index anisotropy is preferably high. By containing a liquid crystalline compound having a high refractive index anisotropy, the refractive index anisotropy as the cholesteric liquid crystal composition (X) can be improved, and a broadband circularly polarized light separating element can be produced. . The refractive index anisotropy of at least one compound represented by the general formula (1) is preferably 0.18 or more, more preferably 0.22 or more.

  Specific examples of particularly preferable compounds represented by the general formula (1) include the following compounds (A1) to (A9). In the compound (A3), “*” represents a chiral center.

On the other hand, examples of the rod-like liquid crystalline compound that the cholesteric liquid crystal composition (X) has include a compound represented by the general formula (2).
^{R 3 -C 3 -D 3 -C 5} -M-C 6 -D 4 -C 4 -R 4 (2)

In the general formula (2), R ³ and R ⁴ are reactive groups, each independently (meth) acrylic group, (thio) epoxy group, oxetane group, thietanyl group, aziridinyl group, pyrrole group, vinyl group. , An allyl group, 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.

In the general formula (2), D ³ and D ⁴ are each independently a single bond, divalent saturated carbonization such as a linear or branched methylene group having 1 to 20 carbon atoms and an alkylene group. It represents a group selected from the group consisting of a hydrogen group and a linear or branched alkylene oxide group having 1 to 20 carbon atoms.

In the general formula (2), C ^{3 to} C ⁶ are each independently a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH. _{2 -, - OCH 2 -,} - CH = N-N = CH -, - NHCO -, - OCOO -, - CH 2 COO-, and represents a group selected from the group consisting of _-CH 2 OCO-.

In the general formula (2), M represents a mesogenic group. Specific examples of M include azomethines, azoxys, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoic acid esters, cyclohexanecarboxylic acid, which may be unsubstituted or have a substituent. 2-4 skeletons selected from the group of acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, alkenylcyclohexylbenzonitriles, —, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —CH═N—N═CH—, —NHCO—, —OCOO And groups formed by bonding with bonding groups such as —, —CH ₂ COO—, and —CH ₂ OCO—.

Examples of the substituent that the mesogenic group M may have include, for example, 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 R ⁶ or —O—C (═O) —NR ⁵ R ⁶ is represented.
Here, R ⁵ and R ⁶ represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When R ⁵ and R ⁶ are an alkyl group, the alkyl group includes —O—, —S—, —O—C (═O) —, —C (═O) —O—, —O—C. (═O) —O—, —NR ⁷ —C (═O) —, —C (═O) —NR ⁷ —, —NR ⁷ —, or —C (═O) — may be present. (However, the case where two or more of -O- and -S- are adjacent to each other is excluded). Here, R ⁷ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the substituent in the above-mentioned “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 1 to 6 carbon atoms. Alkoxy 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, alkylcarbonyl having 2 to 7 carbon atoms Examples thereof include an oxy group and an alkoxycarbonyloxy group having 2 to 7 carbon atoms.

The rod-like liquid crystal 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. That means. By using a rod-like liquid crystal compound having an asymmetric structure, alignment uniformity can be further improved.

  The rod-like liquid crystalline compound has a refractive index anisotropy of usually 0.18 or more, preferably 0.22 or more. When a rod-like liquid crystalline compound having a refractive index anisotropy 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 the absorption edge of the spectrum extends to the visible range. However, it can be used as long as the desired optical performance is not adversely affected. By having such a high refractive index anisotropy, a circularly polarized light separating element having high optical performance (for example, circularly polarized light separating characteristics) can be realized.

  The rod-like liquid crystalline compound preferably has at least two reactive groups in one molecule. Examples of reactive groups include epoxy groups, thioepoxy groups, oxetane groups, thietanyl groups, aziridinyl groups, pyrrole groups, fumarate groups, cinnamoyl groups, isocyanate groups, isothiocyanate groups, amino groups, hydroxyl groups, carboxyl groups, alkoxysilyls. Group, oxazoline group, mercapto group, vinyl group, allyl group, methacryl group, acrylic group and the like. The rod-like liquid crystalline compound may have one type of reactive group or two or more types of reactive groups in combination at any ratio. By having these reactive groups, a stable cured product can be obtained when the cholesteric liquid crystal composition (X) is cured. Conversely, 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. Sometimes. Even when a cross-linking agent described later is used, the film strength tends to be insufficient and practical use tends to be difficult. The film strength that can withstand practical use is HB or higher, preferably H or higher, 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 represented by the general formula (1)) / (total weight of the rod-like liquid crystal compound) is preferably 0.05 or more. 1 or more is more preferable, 0.15 or more is particularly preferable, 1 or less is preferable, 0.65 or less is more preferable, and 0.45 or less is particularly preferable. If the weight ratio is too small, the alignment uniformity may be insufficient. On the other hand, if the weight ratio is too large, the alignment uniformity decreases, the stability of the liquid crystal phase decreases, and the refractive index as a liquid crystal composition. In some cases, anisotropy is lowered, and desired optical performance (for example, circularly polarized light separation characteristics) cannot be obtained. The total weight indicates the weight when one kind is used, and indicates the total weight when two or more kinds are used.

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

  The cholesteric liquid crystal composition such as the cholesteric liquid crystal composition (X) can optionally contain a crosslinking agent in order to improve the film strength and durability after curing. As the cross-linking agent, the liquid crystal layer coated with the liquid crystal composition reacts simultaneously when cured, or heat treatment is performed after curing to accelerate the reaction, or the reaction proceeds spontaneously due to moisture. Those that can increase the density and do not deteriorate the alignment uniformity can be appropriately selected and used. Moreover, what can harden | cure with an ultraviolet-ray, a heat | fever, moisture etc. can be used conveniently as a crosslinking agent, for example.

Specific examples of the crosslinking agent include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and 2- (2-vinyloxyethoxy). ) Polyfunctional acrylate compounds such as 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-aziridinyl Aziridine compounds such as pionate; isocyanate compounds such as isocyanurate type isocyanate, biuret type isocyanate and adduct type isocyanate derived from hexamethylene diisocyanate, hexamethylene diisocyanate; polyoxazoline compound 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; In addition, 1 type may be used for a crosslinking agent and it may use it combining 2 or more types by arbitrary ratios.
Moreover, a well-known catalyst can be used according to the reactivity of a crosslinking agent, and productivity can be improved in addition to membrane strength and durability improvement.

  The blending ratio of the crosslinking agent is preferably such that the concentration of the crosslinking agent in the cured film obtained by curing the cholesteric liquid crystal composition is 0.1 to 15% by weight. If the blending ratio of the crosslinking agent is less than 0.1% by weight, the effect of improving the crosslinking density may not be obtained. Conversely, if it exceeds 15% by weight, the stability of the liquid crystal layer may be lowered.

  The cholesteric liquid crystal composition can optionally contain a photopolymerization initiator. As the photopolymerization initiator, for example, a known compound that generates radicals or acids by ultraviolet rays or visible rays can be used. Specific examples include 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, methylbenzoylformate, 2,2- Ethoxyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α-amylcinnackaldehyde, 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, Ru-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) ] Or 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl] ethanone 1- (o-acetyloxime), (4-methylphenyl) [4- (2-Methylpropyl) phenyl] iodonium hexafluorophosphate , 3-methyl-2-butynyl tetramethyl hexafluoroantimonate, diphenyl - (p-phenylthiophenyl) sulfonium hexafluoroantimonate, and the like. In addition, according to the desired physical property, one type of photopolymerization initiator may be used, or two or more types may be used in combination at any ratio. Further, if necessary, the curability can be controlled by using a known photosensitizer or a tertiary amine compound as a polymerization accelerator in combination.

  The blending ratio of the photopolymerization initiator is preferably 0.03 to 7% by weight in the cholesteric liquid crystal composition. When the blending amount of the photopolymerization initiator 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 liquid crystal phase may become unstable due to the inhibition of the alignment of the liquid crystal.

  The cholesteric liquid crystal composition can optionally contain a surfactant. As the surfactant, those not inhibiting the orientation can be appropriately selected and used. When the example of the said surfactant is given, the nonionic surfactant etc. which contain a siloxane and a fluorinated alkyl group in a hydrophobic group part can be used conveniently. Of these, oligomers having two or more hydrophobic group moieties in one molecule are particularly suitable. These surfactants include, for example, OM-NOVA PolyFox PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, PF-652; FTX-209F, FTX-208G, FTX-204D; KH-40 of Surflon, Seimi Chemical Co., Ltd. can be used. In addition, 1 type of surfactant may be used and it may use it combining 2 or more types by arbitrary ratios.

  The blending ratio of the surfactant is preferably such that the concentration of the surfactant in the cured film obtained by curing the cholesteric liquid crystal composition is 0.05% by weight to 3% by weight. When the blending ratio of the surfactant is less than 0.05% by weight, the alignment regulating force at the air interface is lowered and alignment defects may occur. On the other hand, when the amount is more than 3% by weight, an excessive surfactant may enter between the liquid crystal molecules, thereby reducing the alignment uniformity.

  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, It is possible to appropriately use those disclosed in Kai 2000-290315, JP-A-6-072962, U.S. Pat. No. 6,468,444, WO 98/00428, JP-A 2007-176870, and the like. it can. Specific examples thereof include, for example, LC756, a PASF color produced by BASF. Note that one type of chiral agent may be used, or two or more types may be used in combination at any ratio.

  The concentration of the chiral agent is set in a range that does not deteriorate the desired optical performance. A specific content ratio of the chiral agent is usually 1% by weight to 60% by weight in the cholesteric liquid crystal composition.

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. In addition, these arbitrary components may use one type and may use it combining two or more types by arbitrary ratios.
These optional components can be contained in a range that does not deteriorate the desired optical performance.

  The manufacturing method of a cholesteric liquid crystal composition is not specifically limited, It can manufacture by mixing said each component.

  A cholesteric liquid crystal composition such as the cholesteric liquid crystal composition (X) is applied on another layer such as a base material and an alignment film to obtain a liquid crystal layer as a coating film, and then subjected to light irradiation and / or application one or more times. A cholesteric resin layer can be obtained by curing the liquid crystal layer by heat treatment. 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 is 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 liquid crystal layer can be aligned well.

The curing step can be performed by one or more times of light irradiation, heating treatment, or a combination thereof. The heating condition is, for example, a temperature of usually 40 ° C. or higher, preferably 50 ° C. or higher, usually 200 ° C. or lower, preferably 140 ° C. or lower, usually 1 second or longer, preferably 5 seconds or longer, usually 3 minutes or shorter, preferably Is performed in 120 seconds or less.
Moreover, the light used for the light irradiation includes not only visible light but also ultraviolet rays and other electromagnetic waves. The light irradiation can be performed, for example, by irradiating light having a wavelength of 200 to 500 nm for 0.01 second to 3 minutes. Further, for example, it is also possible to obtain a circularly polarized light separating element having a wide reflection polarization separation band by alternately repeating weak ultraviolet irradiation of 0.01 to 50 mJ / cm ² and heating a plurality of times alternately. After expanding the reflection polarization separation band by the above-mentioned weak ultraviolet irradiation, for example, a relatively strong ultraviolet ray of, for example, 50 to 10,000 mJ / cm ² is irradiated to completely polymerize the liquid crystalline compound, and the cholesteric resin layer and can do. The expansion of the reflection polarization separation band and the irradiation with strong ultraviolet rays may be performed in the air, or 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). You can also.

  The step of applying and curing the cholesteric liquid crystal composition on the other layers such as the alignment film is not limited to one time, and two or more cholesteric resin layers can be formed by repeating the application and curing a plurality of times. . However, even by applying and curing the cholesteric liquid crystal composition only once, it is possible to easily form a cholesteric resin layer containing the well-aligned rod-like liquid crystalline compound and having a thickness of 5 μm or more.

  The dry film thickness of the cholesteric resin layer is preferably 3.0 μm or more, more preferably 3.5 μm or more, preferably 10.0 μm or less, more preferably 8 μm or less. A sufficient reflectance can be obtained by setting the thickness of the cholesteric resin layer to 3.0 μm or more, and the change in hue when observed from an oblique direction can be reduced by setting the thickness to 10 μm or less. it can.

  In general, the thickness of the cholesteric resin layer is non-uniform when measured with high accuracy, and has some variation. The degree of variation in the film thickness of the cholesteric resin layer (that is, the difference between the maximum value and the minimum value of the film thickness) is usually 40 nm or more and usually 100 nm or less, for example, as an in-plane variation of 1000 mm × 1000 mm.

  As the base material to which the cholesteric liquid crystal composition is applied, a transparent resin base material is usually used. As the transparent resin substrate, for example, a substrate having a thickness of 1 mm and a total light transmittance of 80% or more is used. Specific examples include 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. Examples thereof include a single layer or laminated film made of a synthetic resin such as resin, polystyrene, and acrylic resin. Among these, those made of an alicyclic olefin polymer or a chain olefin polymer are preferable, and those made of an alicyclic olefin polymer are particularly preferable from the viewpoints of transparency, low hygroscopicity, dimensional stability, lightness, and the like. In addition, the material of a transparent resin base material may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  Alternatively, an alignment film may be provided on the substrate, and a cholesteric resin layer may be produced by applying a cholesteric liquid crystal composition on the alignment film. By providing the alignment film, the cholesteric liquid crystal composition applied thereon can be aligned in a desired direction. For example, the alignment film is subjected to a corona discharge treatment or the like on the surface of the substrate, if necessary, and then a solution obtained by dissolving the alignment film material in water or a solvent is used for reverse gravure coating, direct gravure coating, die It can be formed by applying and drying using a known method such as coating or bar coating, and then subjecting the dried coating film to rubbing treatment. Examples of the material of the alignment film include cellulose, silane coupling agent, polyimide, polyamide, polyvinyl alcohol, epoxy acrylate, silanol oligomer, polyacrylonitrile, phenol resin, polyoxazole, and cyclized polyisoprene. Polyamide is particularly preferred. In addition, the material of the alignment film may be used alone or in combination of two or more in any combination and ratio.

  Examples of the modified polyamide include those obtained by modifying an aromatic polyamide or an aliphatic polyamide. Of these, a modified aliphatic polyamide is preferred. Specific examples include nylon-6, nylon-66, nylon-12, ternary to quaternary copolymer nylon, fatty acid polyamide, or fatty acid block copolymer (eg, polyether ester amide, polyester amide). And the like added. 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 copolymer nylon such as nylon-6, nylon-66, or nylon-12. The weight average molecular weight of the modified polyamide is preferably 5000 or more, more preferably 10,000 or more, preferably 500,000 or less, more preferably 200,000 or less.

  The thickness of the alignment film can be set to a film thickness that provides desired alignment uniformity of the cholesteric resin layer. Specifically, 0.001 μm or more is preferable, 0.01 μm or more is more preferable, 5 μm or less is preferable, and 2 μm or less is more preferable.

  The base material and the alignment film may be peeled off from the cholesteric resin layer after the production of the cholesteric resin layer, but remain attached to the cholesteric resin layer without being peeled off. It is good also as a part of component. For example, the base material can be a part of the constituent elements of the reflective circularly polarized light separating element of the present invention as a support.

[3. Optical isotropic medium layer)
The optical isotropic medium layer is provided in contact with at least one surface of the cholesteric resin layer.
The optical isotropic medium layer is an optically isotropic layer. Here, the optically isotropic layer is a very small layer having no refractive index anisotropy with respect to light incident from the main surface of the layer at at least one wavelength (for example, Re is 10 μm in a layer having a thickness of 10 μm). 1 nm or less, more preferably 0.5 nm or less). Here, it is preferable that the requirement is satisfied at least at a wavelength λ described later as the one wavelength.

In the reflective type circularly polarized light separating element of the present invention, the resin having the cholesteric regularity at the wavelength λ of the resin layer having the cholesteric regularity which is separated by the reflected polarized light at the interface contacting the optically isotropic medium layer. The average refractive index na of the normal refractive index no and the extraordinary refractive index ne of the nematic layer constituting the interface, and the refractive index nb at the wavelength λ of the optically isotropic medium layer are expressed by the following formula (1). Is satisfied.
nb−0.05 <na <nb + 0.03 (1)

  The normal refractive index and extraordinary refractive index of the nematic layer constituting the interface are the cholesteric phase formed by stacking many layers of nematic-oriented structures. The normal refractive index and the extraordinary refractive index exhibited by the layer in the near layer.

  The refractive index of the optically isotropic medium layer and the normal refractive index and the extraordinary refractive index of the nematic-like layer at the interface of the cholesteric resin layer can be measured by an ellipsometer (manufactured by Woollam). Further, the wavelength λ which is separated by polarized light at the interface of the cholesteric resin layer can be known from the expression P = λ / na from the pitch length P on the output interface side of the cholesteric resin layer and the average refractive index na. it can. Here, P can be measured by observing a cross section with a TEM (transmission electron microscope).

In the reflective circularly polarized light separating element of the present invention, the color of light incident from the cholesteric resin layer and emitted through the optical isotropic medium layer when the cholesteric resin layer and the optically isotropic medium layer satisfy the above formula (1). Unevenness can be reduced. Although not bound by any particular theory, the following matters are presumed as the reason why the occurrence of color unevenness can be suppressed in this way.
That is, there is a difference in refractive index between light emitted parallel to the direction of the director on the surface of the cholesteric resin layer and light emitted perpendicularly to the direction of the director. It is thought that this was one of the causes of polarized light. However, in the reflective circularly polarized light separating element of the present invention, the polarized light emitted from the cholesteric resin layer and incident on the optically isotropic medium layer has the refractive index of the cholesteric resin layer regardless of which direction the light is emitted. The light enters the optical isotropic medium having a close refractive index. Therefore, in the reflective circularly polarized light separating element of the present invention, even if the director direction is not uniform at the interface between the cholesteric resin layer and the optically isotropic medium layer, the influence of the difference in refractive index depending on the emission direction is not affected. The color unevenness caused by elliptically polarized light can be eliminated.

  The thickness of the optical isotropic medium layer is preferably 1 to 10 μm. By setting the thickness to 1 μm or more, optical defects such as coating unevenness and color loss due to foreign matters can be removed. Moreover, favorable adhesive force can be hold | maintained by setting it as 10 micrometers or less.

  As the optical isotropic medium constituting the optical isotropic medium layer, an organic material or an inorganic material may be used. Further, as the optical isotropic medium, one type of compound may be used alone, or a composition containing two or more types of compounds may be used.

  When the reflective circularly polarized light separating element of the present invention has a layer configuration of (cholesteric resin layer)-(optical isotropic medium layer)-(other layer), as an optical isotropic medium constituting the optical isotropic medium layer It is preferable to use a material having a function of an adhesive or a pressure-sensitive adhesive. Thereby, it becomes possible to laminate | stack another layer on a cholesteric resin layer via an adhesive agent or an adhesive, and the reflection type circularly polarized light separation element of a laminated structure provided with a cholesteric resin layer and another layer can be manufactured easily. Here, the adhesive means an adhesive substance that does not exhibit tackiness at room temperature (20 ± 15 ° C .: JIS standard), and the adhesive means an adhesive substance that exhibits tackiness at room temperature. Moreover, not showing the said adhesiveness means showing the adhesiveness of less than 2 by a ball number by the measurement by the inclination-type ball tack measurement of JISZ0237.

  The optical isotropic medium layer preferably contains an acrylic adhesive. Alternatively, the optical isotropic medium layer preferably includes a refractive index adjusting agent in addition to the acrylic adhesive in order to adjust the refractive index within the predetermined range. As such a refractive index adjuster, titanium oxide, aluminum oxide, antimony pentoxide, zirconium oxide, or a combination thereof can be used. Specific examples of the acrylic adhesive include a mixture of (meth) acrylate (A) and (B) described below.

As a more preferable example of the optical isotropic medium layer,
(A) Oligomer type polyfunctional (meth) acrylate (hereinafter sometimes referred to as “(meth) acrylate (A)”) having 3 or less functional groups per molecule, and (B) temperature 20 ± 1.0 ° C. The mono (meth) acrylate having a viscosity of 10 mPa · s or more and less than 500 mPa · s and having at least one hydroxyl group in one molecule (hereinafter sometimes referred to as “(meth) acrylate (B)”).
And a cured adhesive layer obtained by curing an active energy ray-curable adhesive composition containing Here, (meth) acrylate means acrylate and / or methacrylate.

((Meth) acrylate (A))
The (meth) acrylate (A) preferably has 2 or 3 functional groups per molecule. Specific examples of (meth) acrylate (A) include radical polymerizability such as polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) acrylate, and silicone (meth) acrylate. Examples thereof include acrylic oligomers having various functional group numbers of 3 or less. These oligomers can be used alone or in a mixture of two or more.

  The molecular weight of the acrylic oligomer as the (meth) acrylate (A) is preferably from 500 to 10,000 in terms of weight average molecular weight (Mw) in terms of polyisoprene measured by gel permeation chromatography. From the standpoint of expressing

The polyester (meth) acrylate is obtained by reacting a terminal hydroxyl group of a polyester obtained from a polybasic acid and a polyhydric alcohol with (meth) acrylic acid.
Examples of the polybasic acid include phthalic acid, adipic acid, maleic acid, itaconic acid, succinic acid, and terephthalic acid.
Examples of the polyhydric alcohol include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol.
Specific examples of the polyester (meth) acrylate include, for example, EBECRYL 851,852,853,884,885 (manufactured by Daicel Cytec), Olester (manufactured by Mitsui Chemicals), and Aronix M-6100,6200,6250,6500 ( Manufactured by Toagosei Co., Ltd.).

Epoxy (meth) acrylate is a reaction product obtained by ring-opening addition reaction of (meth) acrylic acid to an epoxy resin.
Examples of the epoxy resin include bisphenol A type composed of bisphenol A and epichlorohydrin, novolac type composed of phenol novolac and epichlorohydrin, aliphatic type, and alicyclic type. Aliphatic epoxy resins include ethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylol Propane diglycidyl ether, polyethylene glycol diglycidyl ether, and the like can be used, and unsaturated fatty acid epoxy resins such as butadiene-based epoxy resins and isoprene-based epoxy resins can also be used. The alicyclic epoxy resin is vinylcyclohexene monooxide, 1,2-epoxy-4-vinylcyclohexane, 1,2: 8,9-diepoxysilimonene, 3,4-epoxycyclohexenylmethyl-3 ′, 4 ′. -Epoxy cyclohexene carboxylate and the like can be used.

  Specific examples of the epoxy (meth) acrylate include, for example, EBECRYL600, 860, 3105, 3420, 3700, 3701, 3702, 3703, 3708, 6040 (manufactured by Daicel Cytec), Neopole 8101, 8250, 8260, 8270, 8355, 8351, 8335, 8414, 8190, 8195, 8316, 8317, 8318, 8319, 8371 (manufactured by Iupika Japan), Denacol acrylate DA212, 250, 314, 721, 722, DM201 (manufactured by Nagase ChemteX), Van Beam ( Harima Chemicals) and Miramer PE210, PE230, EA2280 (Toyo Chemicals).

  Urethane (meth) acrylate is a reaction product having a urethane skeleton at the center, obtained by the reaction of a (meth) acrylic monomer having a hydroxyl group, a polyfunctional isocyanate and a polyhydric alcohol. Examples of the (meth) acrylic monomer having a hydroxyl group include 4-hydroxybutyl acrylate. Examples of the polyfunctional isocyanate include tolylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, trimethylolpropane tolylene diisocyanate, and diphenylmethane triisocyanate. Among them, hexamethylene diisocyanate having good weather resistance is preferably used. As a polyhydric alcohol, what can be used for polyester (meth) acrylate can be used.

  Specific examples of urethane (meth) acrylate include, for example, EBECRYL 204, 210, 220, 230, 270, 4858, 8200, 8201, 8402, 8804, 8807, 9260, 9270, KRM 8098, 7735, 8296 (manufactured by Daicel Cytec) , UX2201, 2301, 3204, 3301, 4101, 6101, 7101, 8101, 0937 (manufactured by Nippon Kayaku Co., Ltd.), UV6640B, 6100B, 3700B, 3500BA, 3520TL, 3200B, 3000B, 3310B, 3210EA, 7000B, 6630B, 7461TE ( (Manufactured by Nippon Synthetic Chemical Co., Ltd.), Iupica 8921, 8932, 8940, 8936, 8937, 8980, 8975, 8976 (manufactured by Nippon Iupika), and Miramer PU2 0, can be mentioned PU340 (manufactured by Toyo Chemicals, Inc.).

  Polyether (meth) acrylate is a reaction product of polyether polyol and (meth) acrylic acid. Examples thereof include ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, and EBECRYL81 (manufactured by Daicel Cytec).

  Of these acrylic oligomers, polyester (meth) acrylate, epoxy (meth) acrylate, and urethane (meth) acrylate are preferable. When the number of functional groups per molecule is 3 or less, curing shrinkage when the adhesive composition is cured with active energy rays can be reduced, and the glass transition temperature of the cured product can be lowered, and cholesteric Good adhesion to the resin layer can be maintained.

  The content ratio of (meth) acrylate (A) in the active energy ray-curable adhesive composition is preferably 30 to 80 in order to facilitate the laminating process and maintain adhesive strength.

((Meth) acrylate (B))
Specific examples of (meth) acrylate (B) include 2-hydroxypropyl acrylate (10.9 mPa · s), 4-hydroxybutyl acrylate (17 mPa · s), 2-hydroxy-3-phenoxypropyl acrylate (373 mPa · s). ), Glycerin monomethacrylate: Blemmer GLM (150 mPa · s, manufactured by NOF Corporation), polyethylene glycol monomethacrylate: BREMMER PE-90 (15 mPa · s, manufactured by NOF Corporation), PE-200 (30 mPa · s, NOF Corporation) Manufactured), PE-350 (45 mPa · s, manufactured by NOF Corporation), polypropylene glycol monomethacrylate: BLEMMER PP-1000 (50 mPa · s, manufactured by NOF Corporation), PP-500 (75 mPa · s, manufactured by NOF Corporation) , Poly (ethylene propylene glycol) monometa Relate: Blemmer 50PEP-300 (55 mPa · s, manufactured by NOF Corporation), polyethylene glycol / polypropylene glycol monomethacrylate: BREMMER 70PEP-350B (79 mPa · s, manufactured by NOF Corporation), propylene glycol / polybutylene glycol monomethacrylate: Blemmer 10 PPB-500B (48 mPa · s, manufactured by NOF Corporation), polyethylene glycol monoacrylate: BREMMER AE-200 (15 mPa · s, manufactured by NOF Corporation), polypropylene glycol monoacrylate: Blemmer AP-400 (48 mPa · s, NOF Corporation) Aliphatic epoxy acrylate: EBECRYL112 (55 mPa · s, Daicel Cytec), PA500 (71.8 mPa · s, manufactured by Toho Chemical Co., Ltd.) and the like. In the example of the (meth) acrylate (B), the description of the viscosity in parentheses is the viscosity at a temperature of 20 ± 1.0 ° C.

  The use of (meth) acrylate (B) is preferable because the viscosity of the active energy ray-curable adhesive composition can be adjusted to a range suitable for coating, and the cured product exhibits a stronger adhesive force. The viscosity range of (meth) acrylate (B) is more preferably 50 mPa · s to 400 mPa · s, and still more preferably 70 to 350 mPa · s.

  The content ratio of (meth) acrylate (B) in the active energy ray-curable adhesive composition is 35 to 85 parts by weight in 100 parts by weight of the total solid content in the active energy ray-curable adhesive composition. Is preferred. By being within this range, a stronger adhesive force can be obtained.

(Refractive index modifier)
The active energy ray-curable adhesive composition can contain a refractive index adjusting agent as required. By containing such a refractive index adjusting agent, the refractive index of the cured adhesive layer (that is, the optically isotropic medium layer) obtained by curing the adhesive composition can be within the predetermined range of the present application. As such a refractive index adjuster, titanium oxide, aluminum oxide, antimony pentoxide, zirconium oxide, or a combination thereof can be used. When the adhesive composition contains a refractive index adjuster, the content is preferably 20 to 250 parts by weight with respect to 100 parts by weight of the total of (meth) acrylates (A) and (B).

(Other ingredients)
The active energy ray-curable adhesive composition is a polymerization initiator, a crosslinking agent, an inorganic filler, a polymerization inhibitor, a color pigment, a dye, an antifoaming agent, and a leveling agent as long as the effects of the present invention are not impaired as necessary. , Dispersants, light diffusing agents, plasticizers, antistatic agents, surfactants, non-reactive polymers (inactive polymers), viscosity modifiers, near-infrared absorbers, and other optional components may also be included.

The polymerization initiator can be appropriately selected according to the type of active energy ray.
When the active energy ray-curable adhesive composition is cured by a photocuring reaction, one or more photopolymerization initiators can be used. Moreover, a photosensitizer can be used arbitrarily.

  Examples of photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane- 1-one, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, methylbenzoyl formate, 2,2-diethoxyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α -Amilcinnaldehyde, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, p, p'-dichlorobenzophenone, p, p'-bisdiethylaminobenzophenone, benzoin ethyl ether, benzo 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-trimethylbenzoyl diphenyl -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-chloro Methylnaphthalene, 1,2-octanedione, 1- [4- (phenylthio)-, 2- (o-benzoyl)] oxime, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole- 3-yl] ethanone 1- (o-acetyloxime), (4-methylphenyl) [4- (2-methylpropyl) phenyl] iodonium hexafluorophosphate, 3-methyl-2-butynyltetramethylsulfonium hexafluoro Examples include antimonate and diphenyl- (p-phenylthiophenyl) sulfonium hexafluoroantimonate.

The addition amount of the photopolymerization initiator is preferably 0.5 to 10 parts by weight and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the total solid content contained in the active energy ray-curable adhesive composition.
Further, for example, n-butylamine, triethylamine, poly-n-butylphosphine or the like can be added as a photosensitizer to control curability.

As the defoaming agent, BYK051,052,055,057,1790,065,070,088,354,392 manufactured by Big Chemie Japan, LR-20R, OP-80R, OP-83RAT, OP-85R manufactured by Nippon Oil & Fats Co., Ltd. , PP-40R, SO-80R, SP-60R, BP-70R, CP-08R, DS-60HN, and the like.
The antifoaming agent can be added to such an extent that the adhesive strength of the adhesive layer does not decrease. The addition amount of the antifoaming agent is preferably 0.1 to 1.0 part by weight, more preferably 0.1 to 0.5 part by weight, based on 100 parts by weight of the total solid content of the active energy ray-curable adhesive composition.

  As the crosslinking agent, a (meth) acrylate monomer having a molecular weight of less than 500 and having 2 or more functional groups per molecule can be used.

  Specifically, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, glycerin dimethacrylate, 2-hydroxy-3-acryloxypropyl methacrylate, tetraethylene diacrylate, polyethylene glycol # 400 Diacrylate, tricyclodecane dimethanol di (meth) acrylate, dipentaerythritol hexaacrylate, 1,6-hexanediol di (meth) acrylate, hydroxypibane phosphate neopentyl glycol diacrylate, 1,9-nonanediol di (Meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol triacrylate, penta Lithritol tetraacrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetraacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, Mention may be made of ethoxylated bisphenol A dimethacrylate.

  The addition amount of the crosslinking agent is preferably 0.5 to 10 parts by weight, and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the total solid content contained in the active energy ray-curable adhesive composition. When 10 parts by weight or more is mixed, it is not preferable because curing of the cured adhesive layer proceeds so much that adhesive force for bonding the cholesteric resin layer and other layers may be reduced. The amount of 0.5 parts by weight or less is not preferable because the effect of the crosslinking agent may not be exhibited.

As a viscosity modifier, a slurry in which metal oxide nanoparticles of several nm to several hundred nm are dispersed in a solvent can be used.
Metal oxides include silica, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, and mixtures thereof. For example, organosilica sol methanol silica sol, IPA-ST, IPA-ST-UP, IPA-ST-ZL, EG-ST, NPC-ST-30, DMAC-ST, MEK-ST, MIBK-ST, XBA -ST, PMA-ST, PGM-ST, Fuso Chemical Co., Ltd. PL-1-IPA, PL-1-TOL, PL-2L-PGME, PL-2L-MEK, etc. can be mentioned.

  The range of the preferred amount of addition of the viscosity modifier is 50 at a temperature of 20 ± 1.0 ° C. when the viscosity of the uncured layer of the adhesive composition (the layer that has undergone the drying process but is not subjected to active energy ray irradiation). It can be set within a range of ˜6000 mPa · s and a decrease in adhesive force is not observed. For example, it is preferable that it is 1-15 weight part with respect to a total of 100 weight part of (meth) acrylate (A) and (B) contained in an active energy ray hardening-type adhesive composition, and 5-10 weight part. It is more preferable that When the viscosity modifier is a slurry in which a metal oxide is dispersed in a solvent, the amount of the metal oxide solid content is preferably within the above range. If the amount is less than 1 part by weight, the effect may not be observed, which is not preferable.

The light diffusing agent is a particle having a property of diffusing light, and can be roughly classified into an inorganic filler and an organic filler. Examples of the inorganic filler include glass, silica, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, and a mixture thereof. Examples of the organic filler include acrylic resin, polyurethane resin, polyvinyl chloride resin, polystyrene resin, polyacrylonitrile resin, polyamide resin, polysiloxane resin, melamine resin, benzoguanamine resin, fluorine resin, polycarbonate resin, silicone resin, polyethylene resin, Examples thereof include ethylene-vinyl acetate copolymer, acrylonitrile, and a cross-linked product thereof. Among these, as the organic filler, an acrylic resin, a polystyrene resin, a polysiloxane resin, and fine particles made of a crosslinked product thereof are preferable in terms of high dispersibility, high heat resistance, and no coloration (yellowing) during molding. . Among these, fine particles made of a crosslinked product of an acrylic resin are more preferable in terms of more excellent transparency. Moreover, what consists of 2 or more types of materials as a light-diffusion agent may be used, and 2 or more types of light-diffusion agents may be mixed and used.
The addition amount of the light diffusing agent is preferably 0.5 to 20 parts by weight in 100 parts by weight of the total solid content of the active energy ray-curable adhesive composition. The addition amount of the light diffusing agent can be determined according to the desired haze value and the film thickness of the adhesive layer.

The inactive polymer is a polymer that is inactive with respect to polymerization and curing, that is, a polymer that is not cured by active energy rays irradiated to the layer of the composition upon curing of the active energy ray-curable adhesive composition. is there.
When the thickness of the cured adhesive layer is designed to be 5 μm or more in order to achieve a desired haze value by adding a light diffusing agent, and when the total thickness of the reflective circularly polarized light separating element is set to a desired thickness When the film thickness of the adhesive layer is designed to be 5 μm or more, such an inert polymer can be added in order to stably maintain the film thickness of the coating film of the adhesive composition before being cured.
The glass transition temperature of the inert polymer is preferably from −10 ° C. to 80 ° C., and more preferably from −5 ° C. to 50 ° C. By setting this glass transition temperature, the adhesive strength of the cured adhesive layer after curing can be maintained.

Specific examples of the inert polymer include urethane resin, methyl methacrylate polymer, styrene polymer, polyacrylonitrile, polyvinyl chloride, polyvinyl acetate, polyester, polycarbonate resin, triacetyl cellulose resin, and butyral resin. Examples thereof include a random copolymer obtained by copolymerizing at least species, a block copolymer, a graft copolymer obtained by grafting a molecule having a carboxylic acid, a sulfonic acid, an ester thereof, a hydroxyl group or a mercapto group in the side chain.
The addition amount of the inert polymer is preferably 10 to 60 parts by weight and more preferably 20 to 50 parts by weight in 100 parts by weight of the total solid content of the active energy ray-curable adhesive composition. When less than 10 parts by weight, when the thickness of the cured adhesive layer is designed to be 5 μm or more, the film thickness is not stable because the viscosity of the coating film of the adhesive composition before curing is low, and the film thickness is not stable. When the diffusing agent is mixed, the haze value may not be stabilized, which is not preferable. When the amount is more than 60 parts by weight, the hardness of the coating film of the adhesive composition in an uncured state is increased, and there is a possibility that air bubbles are frequently mixed during bonding, which is not preferable.

[4. Other layers]
In addition to the cholesteric resin layer and the optically isotropic medium layer described above, the reflective circularly polarized light separating element of the present invention can include an arbitrary layer as necessary. For example, the reflective circularly polarized light separating element of the present invention can further include a retardation layer. Specifically, by providing a retardation layer bonded to a resin layer having cholesteric regularity through an optical isotropic medium layer, the reflective circularly polarized light separating element of the present invention functions as a brightness enhancement film. It can be set as the optical member which has.

(Retardation layer)
The retardation layer can be a layer having functions such as a quarter-wave plate and a half-wave plate. In particular, by providing a layer having a function as a quarter-wave plate, the reflective circularly polarized light separating element of the present invention can be an optical member having a function as a brightness enhancement film.

(¼ wavelength plate)
As the quarter wavelength plate, for example, a stretched film formed by stretching a film-like polymer can be used. As the polymer, a transparent resin can be preferably used. As the transparent resin, for example, a 1 mm thick plate having a total light transmittance of 80% or more can be used. Examples thereof include polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, amorphous polyethylene, triacetyl cellulose, and a resin having an alicyclic structure. Preferable examples include a quarter wavelength plate formed by stretching a resin film including a styrene resin layer and a quarter wavelength plate formed by stretching a resin film having an alicyclic structure. More preferable examples include the optically anisotropic elements described below.

  The quarter-wave plate can have a retardation Re (hereinafter sometimes abbreviated as “Re”) in the front direction to be substantially a quarter wavelength of transmitted light. Here, the wavelength range of the transmitted light can be a desired range required for the composite optical member, 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. By having such a retardation value, a polarization conversion function, that is, a function of converting circularly polarized light into linearly polarized light can be exhibited.

  The quarter-wave plate desirably has a retardation Rth in the thickness direction (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 (in-plane 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 retardation Rth in the thickness direction 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 direction perpendicular to the thickness direction (in-plane direction) and perpendicular to nx, nz is the thickness direction refractive index, 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 with a quarter-wave plate in the longitudinal direction and the width direction at intervals of 100 mm (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 of the optically anisotropic element which comprises a quarter wavelength plate is not specifically limited, What has the layer which consists of a styrene resin can be used preferably. Here, the styrene resin is a polymer resin having a styrene structure as a part or all of the repeating units, and a polystyrene or a copolymer of styrene and maleic anhydride can be preferably 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. As the other thermoplastic resin, a resin having an alicyclic structure or a methacrylic resin can be suitably used.

  Examples of the resin having an alicyclic structure include alicyclic olefin polymers. 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.

  The methacrylic resin is a polymer containing methacrylic acid ester as a main component, and examples thereof include a homopolymer of methacrylic acid ester and a copolymer of methacrylic acid ester and other monomers. As the methacrylic acid ester, alkyl methacrylate is usually 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 quarter-wave plate, 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 is stretched. A stretched multilayer film 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 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 can be provided between the a layer and the b layer, but the a layer and the b layer are directly laminated (that is, a laminate having a three-layer structure of b layer / a layer / b layer). Is preferred. 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 stretching can be preferably performed by uniaxial stretching or oblique stretching, and more preferably by uniaxial stretching or oblique stretching by a tenter.

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

  The quarter wavelength plate itself may also have a function as an optical compensation layer, but may additionally have an optical compensation layer in addition to the quarter wavelength plate. As such an optical compensation layer, the same optical anisotropic element as described above can be used, and a homeotropic liquid crystal alignment film obtained by homeotropic alignment of liquid crystal molecules on a substrate and curing (Japanese Patent No. 399969). ), A nematic hybrid liquid crystal alignment film (Japanese Patent Laid-Open No. 2000-66192) obtained by curing a state in which liquid crystal molecules are nematic hybrid aligned on a substrate can be used.

[5. Layer structure)
In the reflective circularly polarized light separating element of the present invention, it is preferable that the surface of the cholesteric resin layer having the lower uniformity in the direction of the director is the interface in contact with the optical isotropic medium layer. For example, when a cholesteric liquid crystal composition is applied on a substrate or an alignment film and cured to obtain a cholesteric resin layer, the direction of the director is on the surface that is in contact with the substrate or the alignment film. The direction of the director is relatively non-uniform on the opposite surface. Therefore, when the reflective circularly polarized light separating element of the present invention has such a cholesteric resin layer, the surface on the side opposite to the side in contact with the substrate or the alignment film is the interface on the side in contact with the optical isotropic medium layer. Preferably there is.
However, the present invention is not limited to the above embodiment, and for example, optical isotropic medium layers may be provided in contact with both surfaces of the cholesteric resin layer, respectively.

When the cholesteric resin layer has a pitch gradient in the reflective circularly polarized light separating element of the present invention, the pitch gradient can take the following two modes in the circularly polarized light separating element.
(Aspect 1) The pitch gradient is a gradient in which the pitch gradually increases as the distance from the first surface of the cholesteric resin layer becomes closer to the second surface, and the first surface is an optically isotropic medium of the cholesteric resin layer. The aspect which is an interface of the side which contact | connects a layer.
(Aspect 2) The pitch gradient is a gradient in which the pitch gradually increases as the distance from the first surface of the cholesteric resin layer becomes closer to the second surface, and the second surface is an optically isotropic medium of the cholesteric resin layer. The aspect which is an interface of the side which contact | connects a layer.

  When the cholesteric liquid crystal composition was applied onto the substrate or the alignment film and cured to obtain a cholesteric resin layer, when the above-described aspect 1 was taken, the cholesteric resin layer was in contact with the substrate or the alignment film. It is preferable that the surface on the side becomes the second surface. On the other hand, when taking the said aspect 2, it is preferable that the surface of the side which was contacting the base material or alignment film of a cholesteric resin layer becomes a said 1st surface.

[6. Production method〕
The reflective circularly polarized light separating element of the present invention can be preferably manufactured by a manufacturing method including the following steps (I) and (II).
(I) An active energy ray-curable adhesive composition is applied on one surface of the cholesteric resin layer to obtain a coating film of the adhesive composition.
(II) The coating film is cured.

Furthermore, one or more of the following steps (Ia) and (Ib) can be optionally performed between steps (I) and (II).
(Ia) The coating film of the adhesive composition is dried to obtain an uncured layer of the adhesive composition (a layer that has been subjected to a drying process but not subjected to irradiation with active energy rays).
(Ib) Another layer is attached to the cholesteric resin layer via the coating film (the coating film that has not been dried or the uncured layer that has been dried).

  Further, in the step (I), a laminate having a layer configuration of (base material)-(cholesteric resin layer) or a layer configuration of (base material)-(alignment film)-(cholesteric resin layer) is formed of the cholesteric resin layer. When used as a supply source, in any stage after step (I), a step of peeling the substrate or the substrate and the alignment film can be performed as step (III). Step (III) is optional, and the final product can also be formed with the substrate and / or alignment film left.

  More specifically, a production method including performing the steps (I), (Ia), (Ib), (II) and (III) in this order is preferable.

Prior to step (I), the surface of the cholesteric resin layer to which the adhesive composition is applied can be subjected to a pretreatment such as corona treatment as necessary to enhance the adhesiveness of the adhesive composition.
As a coating method in the step (I), a roll coating method, a curtain coating method, a die coating method such as a slot coating method, and a spray coating method, which are generally applied to a continuous film, can be used. There is no particular limitation.
Although the thickness of a coating film can be suitably adjusted according to the thickness of a desired hardening adhesive bond layer, it is preferable that it is 0.5-100 micrometers, and it is more preferable that it is 1-50 micrometers. By setting the thickness of the coating film to 100 μm or less, it is possible to prevent the curing rate of the uncured layer from becoming too slow and to achieve sufficient curing, which is preferable.

  In the step (Ia), the drying can be performed, for example, by treating at 60 to 120 ° C. for 1 to 5 minutes.

  In the step (Ib), the sticking can be performed by a laminating means that is generally performed. For example, a long laminate having a cholesteric resin layer and a coating film (an undried coating film or a dried uncured layer) and a long retardation film as another layer are continuously formed by a nip roll. It is possible to take a means of applying pressure and applying by roll-to-roll.

  Irradiation of the active energy ray to the coating film in the step (II) is performed from one surface side through a cholesteric resin layer or the other layer from a radiation source (light source or the like), or from both surface sides as necessary. be able to. Since the light transmittance of the other layer is often higher than that of the cholesteric resin layer, when the coating film is sandwiched between these two layers, efficient curing is achieved by irradiation through the other layer. can do. Moreover, when the coating film is not coat | covered with another layer, an active energy ray can also be irradiated to a coating film directly from a radiation source (light source etc.).

  The active energy ray to be irradiated can be various energy rays suitable for the adhesive composition to be used, for example, ultraviolet rays, visible rays and other electron rays. It is preferable to irradiate ultraviolet rays using an ultraviolet curable adhesive composition. Irradiation can be performed, for example, by applying uniform irradiation in the width direction of the film to the bonded long film after completion of the step (Ib) and continuously supplying the film to the irradiation region.

Examples of the light source used for irradiating ultraviolet rays include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, and a metal halide lamp.
Although the irradiation intensity at the time of irradiating an ultraviolet-ray is not specifically limited, It is preferable that the irradiation intensity | strength of the wavelength range effective for activation of a polymerization initiator is 50-5000 mW / cm < ² >. Irradiation intensity of such regions, more preferably 100~3000mW / cm ^2, It is even more preferred that 300~2000mW / cm ^2. When the irradiation intensity is less than 50 mW / cm ² , the reaction time becomes too long and the curing may be insufficient. If the irradiation intensity exceeds 5000 mW / cm ² , the adhesive may turn yellow due to radiant heat from the lamp, heat of polymerization reaction, etc., or the curing shrinkage of the cured adhesive layer may increase, resulting in a decrease in adhesive strength. .
The light irradiation time is appropriately selected according to the curing state and is not particularly limited. However, the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 5,000 mJ / cm ^2. It is preferable to set to. The accumulated light amount is more preferably 100 to 3000 mJ / cm ² , and even more preferably 500 to 2000 mJ / cm ² .

  The series of steps (I), (Ia), (Ib), (II) and (III) can be carried out continuously in part or all inline, if necessary, thereby improving efficiency. Manufacturing becomes possible.

[7. (Use)
The application of the reflective circularly polarized light separating element of the present invention is not particularly limited, but can be particularly preferably used as a brightness enhancement film. For example, it can be preferably used as a brightness enhancement film by forming an element in which a cholesteric resin layer and a quarter-wave plate are bonded via an optical isotropic medium layer. In the liquid crystal display device, the brightness enhancement film is provided between the backlight and the liquid crystal cell, and supplies only predetermined circularly polarized light from the light supplied from the backlight to the liquid crystal cell, while light other than the predetermined circularly polarized light. Is returned to the backlight, and the function of supplying the liquid crystal cell with the light that is reflected by the backlight and changes its polarization state to become the predetermined circularly polarized light can be exhibited. With this function, the brightness enhancement film can efficiently supply desired polarized light to the liquid crystal cell.

[8. Liquid crystal display device)
The liquid crystal display device of the present invention comprises the reflective circularly polarized light separating element of the present invention and a liquid crystal cell. For example, a liquid crystal display device comprising the reflective circularly polarized light separating element of the present invention in a form in which a cholesteric resin layer and a quarter-wave plate are bonded via an optical isotropic medium layer can be provided. .

  Specifically, the reflective circularly polarized light separating element of the present invention having such an aspect can be provided between a liquid crystal cell and a backlight to constitute a liquid crystal display device. More specifically, the reflective circularly polarized light separating element of the present invention having such an embodiment is bonded to a polarizing plate, and (cholesteric resin layer)-(cured adhesive layer)-(¼ wavelength plate)- A polarizing plate composite having a layer configuration of (polarizing plate) or an optional layer (for example, an adhesive layer for bonding a quarter-wave plate and a polarizing plate) between these layers as necessary. By providing on the light incident surface side of the liquid crystal cell, a liquid crystal display device having a cholesteric resin layer, a quarter-wave plate and a polarizing plate between the backlight and the liquid crystal cell can be easily configured.

  In the following, the present application will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the following, “parts” and “%” relating to the quantity ratio of the components represent parts by weight unless otherwise specified. In Examples and Comparative Examples, various physical properties were measured as follows.

<Comparative Example 1>
(1-1. Laminate having a cholesteric resin layer)
One side of a film made of an alicyclic olefin polymer having a thickness of 100 μm (trade name “Zeonor film ZF14-100” manufactured by Nippon Zeon Co., Ltd.) was subjected to corona discharge treatment so that the wetting index was 56 mN / m. An aqueous solution of 5% polyvinyl alcohol (trade name “Poval PVA203”, manufactured by Kuraray Co., Ltd.) was applied to the corona discharge treated surface using a # 2 wire bar, the coating film was dried, and the film thickness was 0.1 μm. An alignment film was formed. Next, the alignment film was rubbed to prepare a transparent resin substrate having the alignment film.

  Each component was mixed at the following blending ratio to prepare a cholesteric liquid crystal composition having a solid content of 40% by weight (ratio of components other than 2-butanone as a solvent). This cholesteric liquid crystal composition was applied to the surface having the alignment film of the transparent resin substrate having the alignment film using a # 10 wire bar to obtain a coating film of the cholesteric liquid crystal composition.

Cholesteric liquid crystal composition ratio:
Rod-like liquid crystalline compound 1 35.12 parts by weight Chiral agent 2 1.12 parts by weight Chiral agent 4 2.52 parts by weight Surfactant 0.04 parts by weight Polymerization initiator 1.2 parts by weight 2-butanone 60 parts by weight Rod-like liquid crystal Compound 1; compound represented by the following formula, Δn 0.23, 2 reactive groups in one molecule, average refractive index 1.638

Chiral agent 2; LC756 (BASF), induced spiral twist direction; right twist, HTP (helical twisting power); 49
Chiral agent 4; compound represented by the following formula, induced spiral twist direction; right twist, HTP; 18

Surfactant: Fluorosurfactant KH40 (Seimi Chemical Co.)
Polymerization initiator: Polymerization initiator Irgacure OXE02 (Ciba Specialty Chemicals)

The coating film is subjected to an orientation treatment at 120 ° C. for 3 minutes, and the coating film is irradiated with a weak ultraviolet ray of 0.1 to 45 mJ / cm ² followed by a heating treatment at 100 ° C. for 1 minute. After repeating twice, an ultraviolet ray of 800 mJ / cm ² was irradiated in a nitrogen atmosphere to form a resin layer having a cholesteric regularity with a dry film thickness of 5.3 μm. The irradiation treatment with the weak ultraviolet rays is performed so that the weak ultraviolet rays emitted from the light source are incident on the surface on the coating film side of the laminate having the layer structure of (base material)-(alignment film)-(coating film). went. As a result, a laminate having a layer structure of (base material)-(alignment film)-(cholesteric resin layer) was obtained.

  In the obtained laminate, the average value na of the normal refractive index no and the extraordinary refractive index ne at the wavelength λ of the nematic layer on the surface opposite to the substrate was measured by an ellipsometer. there were. Further, by observing the cross section with TEM, the pitch length P on the surface opposite to the base material was read, and the reflected polarized light separation wavelength λ of the surface was calculated from the formula λ = P · na, and was 430 nm.

(1-2.1 / 4 wavelength plate)
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 of the resin pellets and 30 parts 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 acid 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., the b layer-a layer A multilayer film having a three-layer structure of -b layers, each layer having an average thickness of 45-70-45 (μm) was obtained. This multilayer film was tenter uniaxially stretched at a stretching temperature of 128 ° C., a stretching ratio of 1.4 times, and a stretching speed of 10 m / min to obtain a quarter-wave plate as a stretched multilayer film. Further, one side of this quarter-wave plate was subjected to corona discharge treatment so that the wetting index was 56 dyne / cm.
With respect to the retardation value of the obtained quarter-wave plate at a wavelength of 550 nm, the retardation Rth in the thickness direction was −118 nm, and the retardation Re in the in-plane direction was 140 nm.

(1-3. Adhesive composition)
Urethane acrylate (trade name “UV-7000B”, manufactured by Nippon Synthetic Chemical Co., Ltd., functional group number 2-3) 54.5 parts, (meth) acrylate (A) as 2-hydroxy-3-phenoxypropyl acrylate (product) Name “DA141”, manufactured by Nagase Chemitech Co., Ltd., viscosity 373 mPa · s) 36.4 parts, (meth) acrylate (B) as 4-hydroxybutyl acrylate 9.1 parts, methyl ethyl ketone 17.8 parts, and photopolymerization initiator ( 0.9 parts of a trade name “IRGACURE651” (manufactured by Ciba Specialty Chemicals) was mixed to obtain an adhesive composition.

(1-4. Laminate having adhesive layer)
The cholesteric resin layer surface of the laminate produced in (1-1) was subjected to corona discharge treatment (treatment condition: 150 W · min / m ² ). On this corona discharge-treated surface, the adhesive composition obtained in (1-3) above was applied using a # 6 bar, dried at 65 ° C. for 1 minute, and an adhesive composition having a film thickness of 3.4 μm. An uncured layer of the product was formed, and a laminate having a layer structure of (base material)-(alignment film)-(cholesteric resin layer)-(uncured layer) was produced.

(1-5. Brightness enhancement film)
The corona discharge treatment surface of the quarter-wave plate obtained in (1-2) above and the surface on the adhesive composition uncured layer side of the laminate obtained in (1-4) above were overlapped, and the speed was 0 They were bonded together with a laminator at 0.5 m / min and a narrow pressure of 0.3 to 0.4 MPa. UV irradiation (a large UV irradiation device manufactured by Nihon Battery Co., Ltd., a metal halide lamp, an irradiation time of 12 seconds, a light amount of lamination of 1200 J / cm ² ) is performed from the 1/4 wavelength plate side of this laminate, and an uncured layer of the adhesive composition is formed. Cured to form a cured adhesive layer.
Subsequently, the base material and the alignment film are peeled from the laminate, and the brightness enhancement film having a layer configuration of (cholesteric resin layer)-(cured adhesive layer)-(quarter wave plate) (dimensions 1000 mm × 1000 mm) Got.
Separately from this, an adhesive composition obtained in (1-3) on a film made of an alicyclic olefin polymer having a thickness of 100 μm (manufactured by Zeon Corporation, trade name “Zeonor film ZF14-100”). Is coated, dried and cured under the same conditions as above to prepare a sample of a cured adhesive layer, and the refractive index nb of the cured adhesive layer at a wavelength of 430 nm (wavelength λ) is set to “Prism Coupler” manufactured by METRICON. It was 1.54 when measured by "Model 2010" (brand name).

(1-6. Evaluation)
The obtained brightness enhancement film 1 was evaluated in the apparatus shown in FIG.
A white reflective sheet (trade name “E6SV”, manufactured by Toray Industries, Inc.) is pasted on the bottom surface 102 and the four side surfaces 103 of the backlight housing 101 having an inner size of 5 cm × 5 cm × 1 cm. The backlight device 100 was configured by attaching the center line at a position 0.5 cm away from the bottom surface 102. In the upper opening of the backlight device 100, a diffusion plate 111 (flat plate diffusion plate, manufactured by ZEON CORPORATION, total light transmittance 65%, haze 95%), a diffusion sheet 112 (trade name “BS-912”, manufactured by Eiwa Co., Ltd.) ), The brightness enhancement film 113 obtained in (1-5) above (the brightness enhancement film of 1000 mm × 1000 mm cut into small pieces of 50 mm × 50 mm) and the polarizing plate 114 (trade name “Vallite HLC2-5618RE”, The product for evaluation 10 was produced by placing (manufactured by Sanritz) in this order. The brightness enhancement film 113 was placed so that the cholesteric resin layer was on the lower side (side closer to the backlight device 100) and the quarter-wave plate was on the upper side. For the sake of illustration, FIG. 1 shows an exploded perspective view in which the backlight device 100, the diffusion plate 111, the diffusion sheet 112, the brightness enhancement film 113 and the polarizing plate 114 are separated from each other. They were stacked and placed in contact with each other.

The cold cathode tube of the obtained evaluation apparatus was energized, and the front hue observed on the polarizing plate 114 was measured with “CONOSSCOPE CONCONTROL” (trade name, LCD viewing angle characteristic evaluation apparatus) manufactured by AUTORONIC-MELCHERS. The measurement position was set at the center of the backlight output surface, and each of the small pieces of the brightness enhancement film 113 was measured, and chromaticity coordinates (x, y) in each measurement were obtained.
On the other hand, as a control device, a device having the same configuration as that of the evaluation device except that the brightness enhancement film 113 was removed was produced, and the front hue was measured in the same manner to obtain chromaticity coordinates (x ₀ , y ₀ ). .
Relative values (Δx, Δy) (that is, (x−x ₀ , y−y ₀ )) of the chromaticity coordinates obtained at each measurement point of the evaluation device with respect to the chromaticity coordinates measured by the control device are obtained, and Δx And Δy are plotted on a coordinate plane with the horizontal axis and the vertical axis, respectively, and the distance between the two points that are farthest among the plotted points (the two points are (Δx ₁ , Δy ₁ ) (Δx ₂ , Δy ₂ ), ((Δx ₁ −Δx ₂ ) ² − (Δy ₁ −Δy ₂ ) ² ) ^1/2 = ((x ₁ −x ₂ ) ² − (y ₁ −y ₂ ) ² ) ^1/2 Table 1 shows the results.

<Comparative example 2>
As an adhesive liquid, instead of the one obtained in the above (1-3), acrylic resin pressure-sensitive adhesive (acrylic pressure-sensitive adhesive (manufactured by Soken Chemical Co., Ltd., trade name: SK Dyne 2094), 100 parts by weight, curing agent (Soken Chemical Co., Ltd.) Manufactured under the trade name E-AX), 2.6 parts by weight, and a mixture of 27.5 parts by weight of ethyl acetate, and a refractive index nb = 1.50 at 430 nm. Improved films were manufactured and evaluated. Further, the refractive index of the adhesive layer was measured in the same manner as in (1-5) above. The results are shown in Table 1.

<Comparative Example 3>
In the above (1-5), in place of the brightness enhancement film 113, the laminate obtained in the above (1-1) and the quarter wavelength plate obtained in the above (1-2) were used in an overlapping manner. In the same manner as in Comparative Example 1, a brightness enhancement film was produced and evaluated. In the evaluation apparatus, the laminate obtained in the above (1-1) is on the lower side, and the quarter wave plate obtained in the above (1-2) is on the upper side. A gap was provided so that the layer (refractive index 1.0) was interposed. The results are shown in Table 1.

<Examples 1-4 and Comparative Examples 4-5>
In (1-3) above, urethane acrylate 54.5 parts, 2-hydroxy-3-phenoxypropyl acrylate 36.4 parts, 4-hydroxybutyl acrylate 9.1 parts, methyl ethyl ketone 17.8 parts, and photopolymerization initiator In addition to 0.9 part, various amounts of zirconium oxide powder (refractive index = 1.8) were mixed to adjust the refractive index of the optically isotropic medium layer as shown in Table 1, and Similarly, a brightness enhancement film was produced and evaluated. Moreover, the refractive index of the contact bonding layer in wavelength 430nm was measured similarly to what was performed by said (1-5). The results are shown in Table 1.

<Comparative Example 6>
(6-1. Laminate having cholesteric resin layer)
An adhesive (comparative example) is formed on the surface of the laminate having the layer structure of (base material)-(alignment film)-(cholesteric resin layer) obtained in (1-1) of Comparative Example 1 on the cholesteric resin layer side. Through the same acrylic resin adhesive used in No. 2 (Transfer base material (film made of Nippon Zeon Co., Ltd., trade name “Zeonor film ZF14-100”) made of 100 μm thick alicyclic olefin polymer) Then, the base material and the alignment film were peeled off to obtain a laminate having a layer structure of (transfer base material)-(adhesive layer)-(cholesteric resin layer).
In the obtained laminate, the reflected polarized light separation wavelength λ on the surface opposite to the transfer substrate side was 700 nm. When the average value of the normal refractive index no and the extraordinary refractive index ne of the nematic layer on the surface at the wavelength λ was measured, it was 1.61.

(6-2. Production and evaluation of brightness enhancement film)
A brightness enhancement film was produced in the same manner as Comparative Example 1 except that the following points were changed.
-It replaced with the laminated body which has the layer structure of (base material)-(alignment film)-(cholesteric resin layer) obtained by said (1-1) (base material for transcription | transfer) obtained by said (6-1) A laminate having a layer configuration of-(adhesive layer)-(cholesteric resin layer) was used.
When pasting the quarter wavelength plate of (1-5), a sample in which the slow axis of the quarter wavelength plate is pasted in the direction of + 45 ° from the major axis direction of the molecule of the cholesteric resin layer, and −45 ° Two types of samples attached in the direction of were prepared. This is because in the laminate prepared in (6-1) above, the orientation of the directors of the cholesteric resin layer on the surface opposite to the transfer base material side is aligned. It is for producing the test example which simulated the aspect which the orientation of the director shifted | deviated to the maximum using.
In the step of peeling in (1-6), an operation corresponding to peeling of the base material and the alignment film was not performed.
The measurement of the refractive index in the above (1-5) was 1.52 when performed at 700 nm instead of 430 nm.

  The obtained brightness enhancement film was evaluated in the same manner as in Comparative Example 1. However, the distance between the coordinates (Δx, Δy) of each of the two types of samples was defined as the deviation of the surface hue, instead of selecting the one having the longest distance of the coordinates (Δx, Δy) in a wide range. The results are shown in Table 2.

<Comparative Examples 7-8>
A brightness enhancement film was produced in the same manner as in Comparative Examples 2 to 3 except that the laminate obtained in (6-1) was used instead of the laminate obtained in (1-1). For each of these, as in Comparative Example 6, the refractive index of the adhesive layer was measured at a wavelength of 700 nm, and the brightness enhancement film was evaluated. The results are shown in Table 2.

<Examples 5-7 and Comparative Examples 9-11>
In (1-3) above, urethane acrylate 54.5 parts, 2-hydroxy-3-phenoxypropyl acrylate 36.4 parts, 4-hydroxybutyl acrylate 9.1 parts, methyl ethyl ketone 17.8 parts, and photopolymerization initiator In addition to 0.9 part, various amounts of zirconium oxide powder (refractive index = 1.8) were mixed to adjust the refractive index of the optical isotropic medium layer as shown in Table 2, and Similarly, a brightness enhancement film was produced, the refractive index of the cured adhesive layer was measured at a wavelength of 700 nm, and the brightness enhancement film was evaluated. The results are shown in Table 2.

  As is apparent from the results of the examples and comparative examples, in the examples in which the refractive index of the cured adhesive layer (that is, the optically isotropic medium layer) is within the range specified in the present application, the surface hue shift is compared with the comparative examples. Can be suppressed to a small range.

DESCRIPTION OF SYMBOLS 10 Evaluation apparatus 100 Backlight apparatus 101 Backlight housing | casing 102 Backlight bottom face 103 Backlight side face 104 Cold cathode tube 111 Diffusion plate 112 Diffusion sheet 113 Brightness enhancement film 114 Polarizing plate

Claims (9)

A resin layer having cholesteric regularity;
A reflective circularly polarized light separating element comprising an optically isotropic medium layer provided in contact with at least one surface of the resin layer having the cholesteric regularity,
The nematic-like layer constituting the interface of the resin layer having the cholesteric regularity at the wavelength λ of the resin layer having the cholesteric regularity at the wavelength λ that is reflected and polarized at the interface on the side in contact with the optically isotropic medium layer. The average refractive index na of the normal refractive index no and the extraordinary refractive index ne, and the refractive index nb at the wavelength λ of the optical isotropic medium layer are expressed by the following formula (1):
nb−0.05 <na <nb + 0.03 (1)
A reflective circularly polarized light separating element that satisfies the above.   The reflective circularly polarized light separating element according to claim 1, wherein the resin layer having cholesteric regularity has a pitch gradient.   The reflective circularly polarized light separating element according to claim 1 or 2, wherein the reflective polarization separation band of the resin layer having cholesteric regularity is a band including a range of 430 to 750 nm.   The pitch gradient is a gradient in which the pitch gradually increases as the distance from the first surface of the resin layer having the cholesteric regularity becomes closer to the second surface, and the first surface has the resin having the cholesteric regularity. The reflective circularly polarized light separating element according to claim 2 or 3, wherein the reflective circularly polarized light separating element is an interface on a side of the layer in contact with the optically isotropic medium layer.   The pitch gradient is a gradient in which the pitch gradually increases as the distance from the first surface of the resin layer having the cholesteric regularity approaches the second surface, and the second surface is the resin having the cholesteric regularity. The reflective circularly polarized light separating element according to claim 2 or 3, wherein the reflective circularly polarized light separating element is an interface on a side of the layer in contact with the optically isotropic medium layer.   The reflective circularly polarized light separating element according to claim 1, further comprising a retardation layer bonded to the resin layer having the cholesteric regularity through the optical isotropic medium layer.   The reflective circularly polarized light separating element according to claim 6, wherein the retardation layer is a ¼ wavelength plate.   The optically isotropic medium layer comprises an acrylic adhesive or a mixture of the acrylic adhesive and titanium oxide, aluminum oxide, antimony pentoxide, zirconium oxide, or a combination thereof. The reflection type circularly polarized light separation element of any one of -7.   A liquid crystal display device comprising the reflective circularly polarized light separating element according to claim 1 and a liquid crystal cell.

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