JP5045182B2 - Circularly polarized light separating sheet, manufacturing method, and liquid crystal display device - Google Patents

Description

  The present invention relates to a circularly polarized light separating sheet, a method for producing the same, and a liquid crystal display device having the circularly polarized light separating sheet.

  In a display device such as a liquid crystal display device, it is known to provide a circularly polarized light separating sheet that transmits specific circularly polarized light and reflects other light for the purpose of improving the luminance. As such a main part of the circularly polarized light separating sheet, an alignment film is provided on a base material, and a composition containing a liquid crystal compound (hereinafter sometimes simply referred to as “liquid crystal composition”) is developed on the alignment film. The coating film is applied, uniformly oriented, and further subjected to a broadening treatment such as providing a gradient of the degree of polymerization as required, and finally the coating film is cured to have a polymer structure with cholesteric regularity. What is obtained by forming the resin layer which shows circularly polarized light separation ability is known.

  In the preparation of such a circularly polarized light separating sheet, high precision is required for each step in order to obtain a high optical accuracy. In particular, it is important to uniformly develop and align the liquid crystal composition liquid on the alignment film. If the development and alignment of the liquid crystal composition are not uniform, alignment defects may occur on the circularly polarized light separating sheet or clouding may occur, and the desired precise circularly polarized light separating ability cannot be obtained.

  Patent Document 1 provides a liquid crystal layer to which an additive made of a solvent having a specific contact angle is added for the purpose of preventing defects such as pinholes in the production of an optical retardation plate including a liquid crystal layer. Is described. However, Patent Document 1 does not particularly describe improving the overall appearance of the liquid crystal layer by preventing the occurrence of repelling, bursing, or the like in the liquid crystal layer, and a solution to such a problem. Is not presented at all.

JP 2004-287407 A

An object of the present invention is to provide a circularly polarized light separating sheet and a method for producing the same, in which a layer of a cured product of a liquid crystal composition is uniformly provided, and there are few defects such as surface repellency and barge, and can be easily produced. There is.
It is a further object of the present invention to provide a liquid crystal display device having high and uniform brightness.

  As a result of intensive investigations in view of the above object, the present inventor unexpectedly produced a circularly polarized light separating sheet having a base material, an alignment film, and a cholesteric resin layer in this order as described above. It has been found that the surface tension greatly affects the orientation of the cholesteric resin layer provided through the alignment film. The inventor of the present application has also found that the above problem can be solved by setting the surface tension of the base material within a predetermined range, and has come to invent the present application.

  That is, according to the present invention, the following is provided.

[1] In a circularly polarized light separation sheet in which an alignment film containing a modified polyamide is provided on the surface of a substrate, and a resin layer having cholesteric regularity is provided on the alignment film, the side of the substrate on which the alignment film is provided A circularly polarized light separating sheet characterized by having a surface tension of 35 to 60 mN / m at 23 ° C.
[2] The alignment film is an alignment film obtained by applying an alignment film composition liquid to the substrate to obtain a coating film, and drying the coating film, and the surface tension of the alignment film composition liquid is 23. The circularly polarized light separating sheet, which is 22 to 31 mN / m at ° C.
[3] The circularly polarized light separating sheet, wherein the substrate is a single layer or multilayer film having a resin having an alicyclic structure as a surface layer.
[4] A method for producing the circularly polarized light separating sheet, wherein the alignment film is provided on the surface of the sheet-like substrate, the surface of the alignment film is rubbed, and the cholesteric regularity is applied to the surface of the alignment film. The manufacturing method including the process of providing the resin layer which expand | deploys the polymeric composition liquid which can form the resin layer which has, provides a coating film, hardens the said coating film, and has the said cholesteric regularity.
[5] A liquid crystal display device having the circularly polarized light separating sheet.

In the circularly polarized light separating sheet of the present invention, the cured product layer of the liquid crystal composition is uniformly provided on the alignment film, and there are few defects such as surface repelling and bursing, and it can be easily produced.
In the method for producing a circularly polarized light separating sheet of the present invention, a circularly polarized light separating sheet in which a cured product layer of a liquid crystal composition is uniformly provided on an alignment film and has few defects such as surface repellency and barge is easily produced. Can do.
Since the liquid crystal display device of the present invention has the circularly polarized light separating sheet of the present invention, the liquid crystal display device has high and uniform luminance and is inexpensive to manufacture.

(Base material)
The circularly polarized light separating sheet of the present invention has a substrate. The substrate is preferably a sheet-like transparent resin film made of a transparent resin material.

  In the base material used for this invention, the surface tension of the surface by which side alignment film is provided is 35-60 mN / m in 23 degreeC. The method of setting the surface of the substrate to such a specific surface tension is not particularly limited, but can be performed by performing plasma discharge treatment, corona discharge treatment, flame treatment, and ultraviolet irradiation treatment on the surface of the substrate. . Alternatively, by appropriately selecting a resin such as polyethylene terephthalate or an acrylic resin as the base material, the surface tension in the above range may be obtained without particular surface treatment.

  The conditions for the plasma discharge treatment and the corona discharge treatment are not particularly limited, but atmospheric pressure plasma discharge treatment and corona discharge treatment are preferably used as a method for easily increasing the surface tension of the substrate surface. As a treatment method, a commercially available conveyor type treatment device is used, and the treatment is performed in the air at an output of 0.1 kW to 0.5 kW at an output of 0.1 kW to 0.5 kW at a line speed of 5 m / min or more. The surface tension of can be made.

  The base material used in the present invention may have an adhesive layer (undercoat layer) on the surface on which the alignment film is provided. By providing such an adhesive layer, the adhesion between the base film and the alignment film can be enhanced.

  When the transparent resin is used as the base material used in the present invention, the transparent resin is a resin having a total light transmittance of 70% or more measured with a 2 mm-thick plate based on JIS K7361-1. Can be preferably used. For example, polyethylene, propylene-ethylene copolymer, polypropylene, polystyrene, a copolymer of an aromatic vinyl monomer and an acrylic acid alkyl ester having a lower alkyl group, a methacryl having an aromatic vinyl monomer and a lower alkyl group. Examples include copolymers with acid alkyl esters, polyethylene terephthalate, terephthalic acid-ethylene glycol-cyclohexane dimethanol copolymer, polycarbonate, acrylic resins, and resins having an alicyclic structure. It is particularly preferable that it is a resin. In addition, (meth) acrylic acid is acrylic acid and methacrylic acid.

  The resin having an alicyclic structure is an amorphous resin having an alicyclic structure in a repeating unit, and is a resin having an alicyclic structure in the main chain and a resin having an alicyclic structure in the side chain. Either can be used. Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, and a cycloalkane structure is preferable from the viewpoint of thermal stability. Although there is no restriction | limiting in particular in carbon number which comprises an alicyclic structure, Usually, 4-30 pieces, Preferably it is 5-20 pieces, More preferably, it is 6-15 pieces.

  The ratio of the repeating unit having an alicyclic structure in the resin having an alicyclic structure is appropriately selected according to the purpose of use, but is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight. That's it. When there are too few repeating units having an alicyclic structure, the heat resistance of the film may be reduced.

  Specifically, the resin having an alicyclic structure includes (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, and (4) a vinyl alicyclic hydrocarbon. Examples thereof include polymers and hydrogenated products thereof. Among these, norbornene polymers and hydrogenated products thereof are more preferable from the viewpoints of transparency and moldability.

  Examples of norbornene polymers include, for example, ring-opening polymers of norbornene monomers, ring-opening copolymers of norbornene monomers with other monomers capable of ring-opening copolymerization, and hydrogenated products thereof; addition polymers of norbornene monomers; Examples include addition copolymers with other monomers copolymerizable with norbornene monomers. Among these, a ring-opening polymer hydrogenated product of norbornene monomer is most preferable from the viewpoint of transparency. The polymer having the alicyclic structure is selected from known polymers disclosed in, for example, JP-A No. 2002-321302.

  The glass transition temperature of the transparent resin suitable for the present invention is preferably 80 ° C. or higher, more preferably 100 to 250 ° C. A transparent resin film made of a resin material having a glass transition temperature in such a range is excellent in durability without causing deformation or stress during use at high temperatures.

  The molecular weight of the transparent resin suitable for the present invention is polyisoprene measured by gel permeation chromatography (hereinafter abbreviated as “GPC”) using cyclohexane (toluene when the resin material is not dissolved) as a solvent. The weight average molecular weight (Mw) in terms of conversion (when the solvent is toluene, in terms of polystyrene) is usually 10,000 to 100,000, preferably 25,000 to 80,000, more preferably 25,000 to 50,000. It is. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the substrate are highly balanced, which is preferable.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the transparent resin suitable for the present invention is not particularly limited, but is usually 1 to 10, preferably 1 to 4, more preferably 1.2 to 3. .5 range.

  The transparent resin suitable for the present invention has a resin component (that is, oligomer component) having a molecular weight of 2,000 or less, preferably 5% by weight or less, more preferably 3% by weight or less, and further preferably 2% by weight. It is as follows. When the amount of the oligomer component is within the above range, fine convex portions are hardly generated on the surface, the thickness unevenness is reduced, and the surface accuracy is improved. In order to reduce the amount of the oligomer component, the selection of the polymerization catalyst and the hydrogenation catalyst, the reaction conditions such as polymerization and hydrogenation, and the temperature conditions in the step of pelletizing the resin as a molding material may be optimized. . The amount of the oligomer component can be measured by the GPC described above.

The substrate used in the present invention is preferably a single layer or multilayer film having a resin having an alicyclic structure as a surface layer. By using a single-layer or multilayer film having a resin having an alicyclic structure as a surface layer, adhesion with an alignment film containing a modified polyamide can be easily ensured by surface treatment such as corona treatment. When the base material is a multilayer film having a resin having an alicyclic structure in the surface layer, the surface layer may be a structure having a resin having an alicyclic structure, and the resin used for other layers is not particularly limited, What is necessary is just to select suitably from the said transparent resin. In the present invention, when a single-layer or multilayer film having a resin having an alicyclic structure as a substrate is used as a substrate, the surface on which the alignment film is provided is a resin layer having an alicyclic structure. .
The average thickness of the base material used for this invention is 1-1000 micrometers normally, 5-300 micrometers is preferable, and 30-100 micrometers is more preferable.

(Alignment film)
The circularly polarized light separating sheet of the present invention is provided with an alignment film on the surface of the substrate. The alignment film includes a modified polyamide.

The modified polyamide is obtained by modifying at least a part of the structure of the polyamide.
Examples of the modified polyamide include those obtained by modifying an aromatic polyamide or an aliphatic polyamide, and those obtained by modifying an aliphatic polyamide are preferred. Specifically, for example, modified to nylon-6, nylon-66, nylon-12, ternary to quaternary copolymer nylon, fatty acid polyamide, or fatty acid block copolymer (for example, polyether ester amide, polyester amide). Can be mentioned. Examples of the modification include terminal amino modification, carboxyl modification, hydroxyl modification and the like, and modification in which a part of the amide group is alkylaminated or N-alkoxyalkylated. Examples of the N-alkoxyalkylated modified polyamide include N-methoxymethylated part of the amide group of a copolymer nylon such as nylon-6, nylon-66, or nylon-12. The weight average molecular weight of the modified polyamide is preferably 5,000 to 500,000, more preferably 10,000 to 200,000.

  In the present invention, the alignment film may contain only the modified polyamide as a polymer, but may optionally contain another polymer. Examples of the other polymer include cellulose, silane coupling agent, polyimide, polyvinyl alcohol, epoxy acrylate, silanol oligomer, polyacrylonitrile, phenol resin, polyoxazole, cyclized polyisoprene, modified products thereof, and polyamides other than the modified polyamide. , And mixtures thereof.

  The alignment film is formed by applying an alignment film composition liquid on the sheet-like substrate subjected to corona discharge treatment or the like as necessary to obtain a coating film, and further drying the coating film. Can do.

  The alignment film composition liquid contains the modified polyamide. Optionally, the other polymer may be included. Further, the alignment film composition liquid may contain a solvent in addition to the solid content of the polymer or the like. Examples of such a solvent include water; alcohols such as methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, cyclohexanol, 1-hexanol; formamide, glycerol, pyridine, acetic acid; and mixtures thereof. .

  The alignment film composition liquid preferably has a surface tension of 22 to 31 mN / m for obtaining a more uniform cholesteric resin layer. The method of setting the surface tension of the alignment film composition liquid within such a specific range is not particularly limited, but a solvent composition containing 70% by weight or more of methanol, ethanol, 1-propanol, and isopropyl alcohol in the alcohol, The solid content can be adjusted to 1 to 15% by weight, preferably 2 to 10% by weight.

  In addition, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivatives, polyoxyethylene sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, polyethylene as nonionic surfactants Glycol, polyvinyl alcohol or the like is added in an amount of 0.1 to 5% by weight based on the solid content of the alignment film composition liquid, or alkyl sulfate salt, polyoxyethylene alkyl ether sulfate salt, alkyl benzene as an anionic surfactant. By adding 0.05 to 3% by weight of sulfonate, alkylnaphthalenesulfonate, alkylsulfosuccinate, etc. to the solid content of the alignment film composition liquid, the surface tension is adjusted to the above range. It can be.

The measurement of the surface tension of the alignment film composition liquid can be calculated by, for example, using a surface tension meter to produce a quantitative droplet and analyzing it by the formula I using the hanging drop method. Here, the droplet diameters de and ds can be obtained by measuring the droplet 12 suspended from the thin tube 11 as shown in FIG.
γ _L = g · ρ · (de) ² H ^-1 Formula I
γ _L : surface tension of liquid crystal composition g: gravitational acceleration ρ: liquid density
de: Maximum droplet diameter
H ⁻¹ : Correction term obtained from ds / de
ds: Diameter at the bottom of the liquid de

  The step of applying the alignment film composition liquid can be performed using a known method such as reverse gravure coating, direct gravure coating, die coating, or bar coating, and is performed by appropriately drying and volatilizing the solvent. it can. Drying conditions can be performed, for example, at a temperature in the range of 80 to 150 ° C, preferably 90 to 130 ° C, more preferably 100 to 120 ° C.

  The formed alignment film can be subjected to a rubbing treatment as necessary and then used for forming a cholesteric resin layer described later. The average thickness of the alignment film is not particularly limited as long as the desired alignment uniformity of the resin layer can be obtained, but is preferably 0.001 to 5 μm, and more preferably 0.01 to 2 μm.

The surface tension of the alignment film itself used in the present invention is not particularly limited, but the surface tension at 23 ° C. is preferably 34 to 45 mN / m, more preferably 35 to 40 mN / m. In order to make the surface tension of the alignment film in such a specific range, select a material whose surface tension of the main polymer used in the alignment film is in the above range, and multiple types of polymers with different surface tension in the alignment film. The polymer may be selected, mixed at an appropriate mixing ratio, and designed within the above range. In addition, the surface tension of the alignment film is measured using, for example, a surface tension meter or a contact angle meter, and using pure water A3 (JIS K0557) as a measurement sample solution, droplets are prepared on the alignment film sample surface. It can be measured by letting it adhere.
When the contact angle between the droplet and the alignment film surface is measured using a contact angle meter, the surface tension can be calculated using the empirical formula of Formula II.
cos θ = 0.0467 · γ _S −1.508 Formula II
θ: contact angle (degree) of pure water, γ _S is the surface tension (mN / m) of the alignment film.

(Cholesteric resin layer)
The circularly polarizing sheet of the present invention is sometimes referred to as a resin layer having a cholesteric regularity obtained by curing a composition containing a liquid crystal compound on the alignment film (in this specification, it is simply referred to as “cholesteric resin layer”). ). The liquid crystal composition can usually be a liquid, and the cholesteric resin layer can be obtained by spreading the liquid crystal composition on the surface of the alignment film, providing a coating film, and curing it by a method described in detail later.

  The liquid crystal compound contained in the liquid crystal composition includes a rod-like liquid crystal compound capable of exhibiting a cholesteric liquid crystal phase and a compound capable of exhibiting a nematic liquid crystal phase, which are blended together with other components such as a chiral agent to form a cholesteric liquid crystal phase. A rod-like liquid crystal compound capable of exhibiting the above can be used.

  In the present invention, the rod-like liquid crystalline compound preferably has one or more, more preferably two or more reactive groups per molecule. Specific examples of the reactive group include an epoxy group, a thioepoxy group, an oxetane group, a thietanyl group, an aziridinyl group, a pyrrole group, a fumarate group, a cinnamoyl group, an isocyanate group, an isothiocyanate group, an amino group, a hydroxyl group, and a carboxyl group. , Alkoxysilyl groups, mercapto groups, vinyl groups, allyl groups, methacryl groups, and acrylic groups. By having these reactive groups, a stable cured product can be obtained when the liquid crystal composition is cured. When the number of reactive groups per molecule of the liquid crystal compound is less than one, it is not preferable because when the liquid crystal composition is cured, a crosslinked cured product cannot be obtained, so that a film strength that can withstand practical use may not be obtained. . Even when a crosslinking agent described later is used, the film strength may be insufficient. The film strength that can be practically used is a pencil hardness (JIS K5400) of B or higher, preferably HB or higher. If the film strength is lower than B, 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.

Examples of the rod-like liquid crystalline compound include a compound represented by (Formula 1).
^{R 3 -C 3 -D 3 -C 5} -M-C 6 -D 4 -C 4 -R 4 ( Equation 1)
(Wherein R ³ and R ⁴ are reactive groups, each independently (meth) acryl group, (thio) epoxy group, oxetane group, thietanyl group, aziridinyl group, pyrrole group, vinyl group, allyl group, D ³ and D ⁴ are groups selected from the group consisting of fumarate group, cinnamoyl group, oxazoline group, mercapto group, iso (thio) cyanate group, amino group, hydroxyl group, carboxyl group, and alkoxysilyl group. A group selected from the group consisting of a bond, a linear or branched alkyl group having 1 to 20 carbon atoms, and a linear or branched alkylene oxide group having 1 to 20 carbon atoms; C ^{3 to} C ⁶ are a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —C═. N—N═C—, —NHCO— _{, -OCOO -, - CH 2 COO-} , and .M represents a group selected from the group consisting of -CH ₂ OCO- represents a mesogenic group, specifically, unsubstituted or halogen atom, a hydroxyl group, a carboxyl Group, cyano group, amino group, linear or branched alkyl group having 1 to 10 carbon atoms, one or more substituted with a halogenated alkyl group, azomethines, azoxys, biphenyls, Terphenyls, naphthalenes, anthracene, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxane , Tolanes, alkenyl cyclohexyl benzonitrile 2-4 backbone selected from the group of classes, -O -, - S -, - S-S -, - CO -, - CS -, - OCO -, - CH 2 -, - OCH 2 - , -C = N-N = C -, - NHCO -, - OCOO -, - CH 2 COO-, and is formed are joined by a linking group of -CH ₂ OCO-, etc.).

In the present invention, the rod-like liquid crystalline compound preferably has an asymmetric structure. Here, the asymmetric structure is a structure in which R ³ -C ³ -D ³ -C ⁵ -and -C ⁶ -D ⁴ -C ⁴ -R ⁴ are different in the general formula (1) with the mesogenic group M as the center. Say. By using a rod-like liquid crystal compound having an asymmetric structure, alignment uniformity can be further improved.

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

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

  The blending ratio of the crosslinking agent is preferably 0.1 to 15% by weight in the cholesteric resin layer obtained by curing the liquid crystal composition. When the blending ratio of the crosslinking agent is less than 0.1% by weight, the effect of improving the crosslinking density cannot be obtained. Conversely, when the blending ratio is more than 15% by weight, the stability of the liquid crystal layer is lowered, which is not preferable.

  The liquid crystal composition used in the present invention can optionally contain a photoinitiator. As the photopolymerization initiator, known compounds that generate radicals or acids by ultraviolet rays or visible rays can be used. Specifically, benzoin, benzylmethyl ketal, benzophenone, biacetyl, acetophenone, Michler's ketone, benzyl, benzylisobutyl ether, tetramethylthiuram mono (di) sulfide, 2,2-azobisisobutyronitrile, 2,2-azobis -2,4-dimethylvaleronitrile, benzoyl peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4 -Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, methylbenzoyl formate, 2,2-dieto Cyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α-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, 2-methyl- [4- (Methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, anthracene benzophenone, α-chloro Anthraquinone, diphenyl disulfide, hexachlorobutadiene, pentachlorobutadiene, octachlorobutene, 1-chloromethylnaphthalene, 1,2-octanedione, 1- [4- (phenylthio)-, 2- (o-benzoyl)] oxime, 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-butynyltetramethylsulfate Hexafluoroantimonate, diphenyl - (p-phenylthiophenyl) sulfonium hexafluoroantimonate, and the like. In addition, two or more compounds can be mixed depending on the desired physical properties, and if necessary, a known photosensitizer or a tertiary amine compound as a polymerization accelerator is added to control curability. You can also.

  The blending ratio of the photopolymerization initiator is preferably 0.03 to 7% by weight in the liquid crystal composition. When the blending amount of the photoinitiator is less than 0.03% by weight, the degree of polymerization is lowered and the film strength may be lowered. On the other hand, if it is more than 7% by weight, the alignment of the liquid crystal is inhibited and the liquid crystal phase may become unstable.

  The liquid crystal composition used in the present invention can optionally contain a surfactant. As the surfactant, those not inhibiting the orientation can be appropriately selected and used. As the surfactant, specifically, a nonionic surfactant containing siloxane or fluorinated alkyl group in the hydrophobic group portion can be preferably used, and an oligomer having two or more hydrophobic group portions in one molecule. Is particularly preferred. These surfactants are PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, PF-652 from PolyFox, OMNOVA, FTX- from Neos 209F, FTX-208G, FTX-204D, Gemco EF-121, EF-122A, EF-122B, EF-122C, Dainippon Ink and Chemicals MegaFuck F-472SF, F-480SF, F-178RM, ESM -1, Surflon KH-40 manufactured by Seimi Chemical Co., Ltd. can be used. The blending ratio of the surfactant is preferably 0.05% by weight to 3% by weight in the cholesteric liquid crystal layer obtained by curing the liquid crystal composition. When the blending ratio of the surfactant is less than 0.05% by weight, the orientation regulating force at the air interface is lowered to cause orientation defects, the surface tension of the composition liquid is increased, and a coating layer for the composition liquid is provided. In some cases, repelling may be observed on the coated surface. On the other hand, when it is more than 3% by weight, the alignment uniformity of the liquid crystal molecules may be lowered, which is not preferable.

  The liquid crystal composition used in the present invention can be usually liquid and can contain a solvent. Specifically, for example, a liquid having a surface tension of 23 to 35 mN / m, preferably 24 to 33 mN / m at 23 ° C. can be used as the solvent. Specific examples of the solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, toluene, and tetrahydrofuran. The mixing ratio of the solvent in the liquid crystal composition can be 30% to 95% by weight, preferably 50% to 80% by weight.

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

  The method for preparing the liquid crystal composition used in the present invention is not particularly limited, and the liquid crystal composition can be manufactured by mixing the above essential components and optional components.

In the present invention, the interfacial tension γ _SL (mN / m) at 23 ° C. between the alignment film and the liquid crystal composition is preferably 8 to 22, and preferably 9 to 15. The value of the interfacial tension γ _SL can be calculated based on the surface tension of the alignment film and the surface tension of the liquid crystal composition. The method of setting the value of the interfacial tension γ _{SL in} the above range is not particularly limited, but for example, by appropriately selecting the type and content ratio of the solvent and the surfactant in the liquid crystal composition and adjusting the surface tension of the liquid crystal composition. It can be carried out.

  The surface tension of the liquid crystal composition can be measured, for example, by using a surface tension meter to produce a quantitative droplet, and using the hanging drop method according to the formula II, similarly to the measurement of the surface tension of the alignment film composition liquid described above. It can be calculated by analysis.

  The cholesteric resin layer can be obtained by spreading the liquid crystal composition on the surface of the alignment film, providing a coating layer, and curing the coating layer. The liquid crystal composition can be developed by a known coating method such as reverse gravure coating, direct gravure coating, die coating, or bar coating. The thickness of the coating layer of the liquid crystal composition can be appropriately adjusted so that a desired dry film thickness of the cholesteric resin layer described later can be obtained.

  Before curing the coating layer obtained by the development, an orientation treatment can be performed as necessary. The alignment treatment can be performed, for example, by heating the coating layer at 50 to 150 ° C. for 0.5 to 10 minutes. By performing the alignment treatment, the liquid crystalline compound can be aligned well.

A circularly polarized light separating sheet having a cholesteric resin layer can be obtained by curing the coating layer after performing an orientation treatment as necessary. The curing step can be performed by one or more heating and / or light irradiation. Specifically, for example, the heating condition may be a temperature of 40 to 140 ° C. and a time of 1 second to 3 minutes. The light used for light irradiation in the present invention includes not only visible light but also ultraviolet rays and other electromagnetic waves. Specifically, the light irradiation can be performed by, for example, irradiating light having a wavelength of 200 to 500 nm for 0.01 second to 3 minutes. Further, for example, a weakly irradiated ultraviolet ray of 0.01 to 50 mJ / cm ² and heating may be alternately repeated several times to obtain a circularly polarized light separating sheet having a wide reflection band.

  In the present invention, the step of developing and curing the liquid crystal composition on the surface of the alignment film is not limited to once, and the development and curing can be repeated a plurality of times to form two or more cholesteric resin layers. However, in the present invention, a cholesteric resin layer containing a liquid crystalline compound that is well oriented and has a wide reflection bandwidth can be easily formed even by developing and curing the liquid crystal composition only once.

  In the circularly polarized light separating sheet of the present invention, the dry film thickness of the cholesteric resin layer is preferably 3.0 μm to 9.0 μm, more preferably 3.0 to 7.0, and particularly preferably 3.5 to 6.5 μm. be able to. When the dry film thickness of the cholesteric resin layer is less than 3.0 μm, the reflectance decreases, and conversely, when it is thicker than 7.0 μm, the cholesteric resin layer is colored when observed from an oblique direction. It is not preferable.

  The liquid crystal display device of the present invention has the circularly polarized light separating sheet of the present invention. The liquid crystal display device of the present invention specifically includes, for example, a liquid crystal display device including a brightness enhancement sheet formed by combining a quarter λ plate and the circularly polarized light separation sheet of the present invention between a backlight and a liquid crystal cell. It can be. More specifically, the circularly polarized light separating sheet of the present invention is disposed between the backlight of the liquid crystal display device and the liquid crystal cell so as to be closer to the backlight side than the quarter λ plate, thereby achieving improvement in luminance. it can. In the liquid crystal display device of the present invention, only one circularly polarized light separating sheet may be used, but selective reflection in a wider wavelength band is achieved by using a plurality of circularly polarized light separating sheets with different reflection bands. You can also.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to the following Example.

In the following examples and comparative examples, various physical properties were measured as follows:
(A) Surface tension of substrate Using Drop Master DM500 manufactured by Kyowa Interface Science Co., Ltd., setting the substrate on a table, using pure water A3 as a liquid for surface tension measurement, and measuring the contact angle by the droplet method Went. By substituting the measured contact angle into the above formula II, the surface tension of the substrate was determined.
(B) Surface tension of alignment film composition liquid Using Drop Master DM500 manufactured by Kyowa Interface Science Co., Ltd., using the alignment film composition liquid prepared by the procedure described later as a liquid for surface tension measurement, the hanging drop method From the above formula I, the surface tension of the alignment film composition liquid was determined.
(C) Minimum transmittance of circularly polarized light separating sheet The circularly polarized light separating sheet produced by the method described later was irradiated with parallel light using MCPD-3000 manufactured by Otsuka Electronics Co., Ltd., and the transmittance in the wavelength range of 400 nm to 800 nm was measured. .

<Example 1>
(1-1: Preparation of substrate having alignment film)
Using a conveyor corona discharge surface treatment manufactured by Kasuga Electric Co., Ltd. on one side of a norbornene resin film (Zeonor film ZF14-100, manufactured by Optes Co., Ltd.) having a thickness of 100 μm, a width of 50 mm, and a length of 200 mm, an output of 0.16 kW, Corona discharge treatment was performed at a line speed of 5 m / min and a film / treatment electrode distance of 10 mm.
An alignment film material obtained by mixing a polymer and a solvent having the composition shown in Table 1 at a weight ratio of polymer / solvent = 3/97 was applied to this corona discharge-treated surface with a # 4 bar, and 120 ° C. For 5 minutes to produce a dry film having a thickness of 0.2 μm. By rubbing the dry film in one direction, a substrate having an alignment film was obtained. The surface tension of the obtained alignment film was measured. The measurement results are shown in Table 1.

(1-2: Preparation of liquid crystal composition liquid)
A liquid crystal composition liquid having the following composition was prepared as a liquid for forming the cholesteric resin layer:
Liquid crystalline compound (rod-shaped liquid crystalline compound having Δn (= ne-no) = 0.18), 93.0 parts by weight Photopolymerization initiator (IRG907, manufactured by Ciba Specialty Chemicals) 3.1 parts by weight Surfactant (Seimi Chemical Co., Ltd. KH-40) 0.11 part by weight Chiral agent (LC756 made by BASF) 6.7 part by weight Solvent: methyl ethyl ketone / cyclopentanone = 75/25 (solid content (in liquid crystal composition Liquid crystal compounds, photopolymerization initiators, surfactants, chiral agents (weight fraction) added to be 40% by weight)

(1-3: Production and evaluation of circularly polarized light separating sheet)
On the alignment film of the substrate having the alignment film obtained in (1-1), the liquid crystal composition liquid obtained in (1-2) is applied using a wire bar # 6, and the temperature is 100 ° C. for 5 minutes. After drying and orientation aging of the coating film, 70 mJ / cm ² (UV-A) ultraviolet rays were irradiated from the substrate side, held at 100 ° C. for 1 to 5 minutes, and then irradiated with ultraviolet rays. Was completely cured to obtain a cholesteric resin layer having a thickness of 3 μm.
When the light transmittance of 400 nm to 800 nm of the obtained circularly polarized light separating sheet was measured, the minimum light transmittance within the reflection bandwidth of the circularly polarized light separating sheet was 54.0%. The selective reflection center wavelength was 490 nm.

Furthermore, the appearance of the cholesteric resin layer was visually observed and evaluated according to the following evaluation criteria. The results are shown in Table 1.
○: No glare or bursiness is seen in the resin layer visually. ×: Glitter or burse is seen in the resin layer visually.

<Example 2>
Using a polyethylene terephthalate film (Lumirror 100T60, manufactured by Toray Industries, Inc.) having a thickness of 100 μm as a base material, a circularly polarized light separation sheet was produced in the same manner as in Example 1 except that no corona treatment was performed. evaluated. The results are shown in Table 1. The selective reflection center wavelength was 490 nm.

<Example 3>
A laminate 1 prepared by the following production method was used as a base material, and the same procedure as in Example 1 was performed except that the corona treatment was not performed. A circularly polarized light-separating sheet was produced, and various physical properties were evaluated. The results are shown in Table 1. The selective reflection center wavelength was 490 nm.

(Manufacturing method of the laminated body 1)
A monomer composition composed of 97.8% by weight of methyl methacrylate and 2.2% by weight of methyl acrylate was polymerized by a bulk polymerization method to obtain resin pellets.
Rubber particles were produced according to Example 3 of JP-B-55-27576. This rubber particle has a spherical three-layer structure, the core inner layer is a crosslinked polymer of methyl methacrylate and a small amount of allyl methacrylate, and the inner layer is composed of butyl acrylate and styrene as main components and a small amount of acrylic acid. It is a soft elastic copolymer obtained by crosslinking and copolymerizing allyl, and the outer layer is a hard polymer of methyl methacrylate and a small amount of ethyl acrylate. The average particle size of the inner layer was 0.19 μm, and the particle size including the outer layer was 0.22 μm.
70 parts by weight of the resin pellets and 30 parts by weight of the rubber particles were mixed and melt kneaded with a twin screw extruder to obtain a methacrylic acid ester polymer composition A (glass transition temperature 105 ° C.).
By coextruding the methacrylic ester polymer composition A (b layer) and the styrene maleic anhydride copolymer (glass transition temperature 130 ° C.) (a layer) at a temperature of 280 ° C., a b layer / a layer A multilayer film having an average thickness of 45/70/45 (μm) with a three-layer structure of / b layers was obtained and used as the laminate 1.

<Example 4>
A circularly polarized light separating sheet was produced in the same manner as in Example 1 except that the laminate 1 was used as a substrate and corona treatment was performed at an output of 0.1 kW, and various physical properties were evaluated. The results are shown in Table 1. The selective reflection center wavelength was 490 nm.

<Example 5>
A circularly polarized light separating sheet was produced in the same manner as in Example 1 except that the composition of the alignment film composition liquid was changed as shown in Table 1, and various physical properties were evaluated. The results are shown in Table 1. The selective reflection center wavelength was 490 nm.

<Example 6>
A circularly polarized light separation sheet was produced in the same manner as in Example 1 except that the laminate 2 prepared by the following production method was used as a substrate and corona treatment was performed at an output of 0.1 kW, and various physical properties were evaluated. The results are shown in Table 1. The selective reflection center wavelength was 490 nm.

(Manufacturing method of the laminated body 2)
A norbornene-based resin (Zeonor 1020, manufactured by Nippon Zeon Co., Ltd., Tg = 105 ° C.) (b layer) and a styrene maleic anhydride copolymer (glass transition temperature 130 ° C.) (a layer) are used as the transparent resin material. By coextrusion molding at 280 degrees, a multilayer film having a three-layer structure of b layer / a layer / b layer, each layer having an average thickness of 50/200/50 (μm) was obtained.

<Comparative Example 1>
A circularly polarized light separating sheet was produced in the same manner as in Example 1 except that the corona treatment was not performed, and various physical properties were evaluated. The results are shown in Table 1. The selective reflection center wavelength was 490 nm.

<Comparative example 2>
A circularly polarized light separation sheet was produced in the same manner as in Example 1 except that the output was changed to 1.0 kW under the corona treatment conditions, and various physical properties were evaluated. The results are shown in Table 1. The selective reflection center wavelength was 490 nm.
<Comparative Example 3>
A circularly polarized light separating sheet was produced in the same manner as in Example 6 except that the corona treatment was not performed, and various physical properties were evaluated. The results are shown in Table 1. The selected center wavelength was 490 nm.

Abbreviations and product names in Table 1 are as follows.
FR105: Methoxymethylated nylon manufactured by Lead City Co., Ltd. CM4000: Copolymerized polyamide manufactured by Toray Industries, Ltd. In all examples and comparative examples, the weight ratio of the polymer to the solvent in the alignment film composition liquid was polymer / solvent = 3/97. It was.

  From the results shown in Table 1, in the production of the circularly polarized light separating sheet of the present invention, a liquid crystal composition liquid was successfully developed without generation of glare, bursage, etc., and a circularly polarized light separating sheet having a good appearance and light transmittance was obtained. You can see that

<Example 6>
(Circularly polarized light separating element)
A circularly polarized light separating sheet (hereinafter referred to as “ A circularly polarized light separating sheet 6 ”) was obtained. When the optical characteristics of the circularly polarized light separating sheet 6 were measured, the minimum light transmittance was 53.8% and the selective reflection center wavelength was 630 nm.

  The cholesteric resin layer side of the circularly polarized light separating sheet 6 and the base material side of the circularly polarized light separating sheet produced in Example 1 (hereinafter referred to as “circularly polarized light separating sheet 1”) are bonded together to form two cholesteric resin layers A composite circularly polarized light separating sheet having

<Phase difference compensation element laminate (also λ / 4 plate)>
The laminate obtained in Example 3 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 stretched multilayer film (phase difference compensation element). Furthermore, on one side of this phase difference compensation element, using a conveyor-type corona discharge surface treatment manufactured by Kasuga Electric Co., Ltd. so that the wetting index is 56 dyne / cm, the output is 0.12 kW, the line speed is 5 m / min, the film / processing Corona treatment was performed at a distance between electrodes of 10 mm.
With respect to the retardation value of the obtained retardation compensation element 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.
The retardation compensation element is bonded to the cholesteric resin layer side of the composite circularly polarized light separating sheet via an adhesive layer formed of an ethylene-vinyl acetate copolymer emulsion, and a retardation compensation element laminate (also serving as λ / 4) Plate).
The retardation compensator laminate (also known as λ / 4 plate) is bonded to the cholesteric resin layer side of the composite circularly polarized light separating sheet via an adhesive layer formed of an ethylene-vinyl acetate copolymer emulsion, A laminated sheet was obtained.

  Dismantle a commercially available liquid crystal television (AQUAOS 37 inch, manufactured by Sharp Corporation), take out the brightness enhancement film between the liquid crystal cell and the backlight, and replace the laminated sheet obtained above with the circularly polarized light separating sheet side as the backlight. As a side, a liquid crystal display device was obtained. When this liquid crystal display device was observed in the white display mode from the light exit surface side, no bright color was observed over the entire display surface, and a bright and good white display could be confirmed.

<Comparative Example 3>
A liquid crystal display device was prepared and observed in the same manner as in Example 6, except that the circularly polarized light separating sheet prepared in Comparative Example 1 was used instead of the circularly polarized light separating sheet prepared in Example 1. As a result, it was confirmed that the white display was darker than that in Example 6 due to the occurrence of glare over the entire surface.

FIG. 1 is a schematic diagram for explaining the measurement of the surface tension of a liquid crystal composition by the hanging drop method.

Explanation of symbols

11: capillary 12: droplet

Claims (5)

An alignment film comprising a modified polyamide obtained by methoxymethylating nylon amide groups on the surface of the substrate and a copolymerized polyamide different from the modified polyamide is provided.
In the circularly polarized light separating sheet provided with a resin layer having cholesteric regularity on the alignment film,
A circularly polarized light separating sheet, wherein the surface tension of the surface of the substrate on the side where the alignment film is provided is 35 to 60 mN / m at 23 ° C. The alignment film is an alignment film obtained by applying an alignment film composition liquid to the substrate to obtain a coating film, and drying the coating film.
2. The circularly polarized light separating sheet according to claim 1, wherein a surface tension of the alignment film composition liquid is 22 to 31 mN / m at 23 ° C. 3.   The circularly polarized light separating sheet according to claim 1 or 2, wherein the substrate is a single-layer or multilayer film having a resin having an alicyclic structure as a surface layer. It is a manufacturing method of the circularly polarized light separation sheet according to any one of claims 1 to 3,
The alignment film is provided on the surface of the sheet-like base material,
Rubbing the surface of the alignment layer;
On the surface of the alignment film, a polymerizable composition liquid capable of forming a resin layer having cholesteric regularity is developed to provide a coating film,
The manufacturing method including the process of hardening the said coating film and providing the resin layer which has the said cholesteric regularity.   A liquid crystal display device comprising the circularly polarized light separating sheet according to claim 1.

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