JP2002169015A - Optical film, polarizing element, method for manufacturing polarizing element, polarizing plate, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film which can improve the front luminance and the dependence of luminance on the viewing angle of a liquid crystal dis play. SOLUTION: In the optical film having an optically anisotropic discontinuous phase dispersed in an optically isotropic continuous phase, an amphipathic photochemical reactive compound is added to the optically anisotropic discontinuous phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film in which an optically anisotropic discontinuous phase is dispersed inside an optically isotropic continuous phase, a polarizing element using the same, a method for manufacturing a polarizing element, The present invention relates to a polarizing plate and a liquid crystal display.

[0002]

2. Description of the Related Art Polarizing elements are mainly used in liquid crystal display devices (eg,
In the electric field control birefringence mode or the twisted nematic mode), it is an almost indispensable member (Susumu Sato, liquid crystal and its application, published by Sangyo Tosho Co., Ltd., 96-115)
Page (1984)). A polarizing element used in a liquid crystal display device is generally an iodine-based or dye-based dichroic polarizing element. A dichroic polarizing element is a light-absorbing polarizing element that substantially transmits one of two linearly polarized lights whose polarization planes are orthogonal to each other and substantially absorbs the other. Since the polarization is generated by light absorption, when the degree of polarization is close to 100%, the upper limit of the light transmittance is 50% in principle. Therefore, an actual liquid crystal display device can use only less than half of the light. The brightness of the displayed image decreases in accordance with the light use efficiency.

Hitherto, means for improving the light use efficiency of a polarization selecting element have been proposed (for example, Japanese Patent Application Laid-Open Nos. 63-121821, 5-224175, and 5-232433). Described). In general, by using a light-absorbing polarizing element and a light-scattering polarizing element that substantially scatters one of two linearly polarized light beams whose polarization planes are orthogonal to each other and that substantially transmits the other, Improve light use efficiency. As a light-scattering type polarizing element, a film (anisotropic scatterer) obtained by stretching a composite of a polymer and a liquid crystal has been proposed (Liquid Crystals, 199).
3 years, 15 volumes, NO. 3, 395-407).

[0004] WO95 / 17691, WO95
No./17692 and WO95 / 17699, the uniaxially stretched film and the unstretched film are laminated in multiple layers to increase the difference in the refractive index in the stretching direction, thereby increasing the anisotropy of the reflectance and transmittance. And a method of increasing the light use efficiency of the backlight by laminating this element and a normal dichroic polarizing element and using the laminated element as a backlight-side polarizing element. According to this method, the front luminance is increased by about 1.6 times, but the viewing angle dependence of the luminance is large, and the luminance decreases when viewed obliquely. In addition, since it is necessary to increase the number of layers to be stacked to several tens or more in order to obtain a large polarization degree, it is difficult to increase productivity.

Further, WO97 / 32223, WO9
7/32224, WO97 / 32225, WO97
/ 32226, and JP-A-9-2741
Nos. 08 and 11-174231 propose a method of producing an anisotropic scatterer by blending a positive intrinsic birefringent polymer and a negative intrinsic birefringent polymer and uniaxially stretching them. I have. By arranging the anisotropic scatterer method between the backlight and the polarizing element, a bright liquid crystal display device can be obtained. However, the front luminance is improved by about 1.45 times and the above-described reflectance anisotropy is used. Smaller than the previous method. The feature of this method is that the luminance has a small viewing angle dependence and a simple structure with excellent productivity. However, in an arrangement in which one film is further inserted between a polarizing element having a protective film on both sides and having a three-layer structure (protective film / polarizing element / protective film) and a backlight, the liquid crystal display device itself is thick. Become. For this reason, optical absorption is increased, and there is also interface reflection with air, so that the light transmittance is low, and the luminance originally supposed to be obtained is not sufficiently obtained. In addition, since the refractive index is controlled by uniaxially stretching the polymer medium, the refractive index of the polymer medium changes due to the elastic strain due to the heat of the backlight, and the problem of in-plane luminance unevenness has been found. .

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical film in which an optically anisotropic discontinuous phase is uniformly dispersed with an appropriate particle size inside an optically isotropic continuous phase. It is to be. Another object of the present invention is to provide a light-scattering type polarizing element in which appropriate optical properties are realized at an interface between an optically isotropic continuous phase and an optically anisotropic discontinuous phase. . Still another object of the present invention is to provide a polarizing plate capable of improving the front luminance of a liquid crystal display and the viewing angle dependence of the luminance. Still another object of the present invention is to propose a liquid crystal display device in which in-plane luminance unevenness hardly occurs.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide the following optical films (1) to (10) and the following (11) to (1)
3) A polarizing element, a method for producing a polarizing element described in (14) and (15) below, a polarizing plate described in (16) below, and a following (17)
Liquid crystal display device. (1) An optical film in which an optically anisotropic discontinuous phase is dispersed inside an optically isotropic continuous phase, wherein the optically anisotropic discontinuous phase comprises an amphiphilic photochemically reactive compound. An optical film characterized by including:

(2) The optical film according to (1), wherein the photochemically reactive compound is a photocrosslinkable compound. (3) The optical film according to (1), wherein the photochemically reactive compound is a photoisomerizable compound.

(4) The photochemically reactive compound has the following formula (P
The optical film according to (1), which has a photochemically reactive group represented by c): (Pc) -Y ¹ = Y ² -Ar wherein Y ¹ and Y ² are each independently N or CR R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; and Ar is an aromatic group].

(5) The optical film according to (1), wherein the photochemically reactive compound has an anionic group as a hydrophilic group. (6) The optical film according to (1), wherein the photochemically reactive compound has a hydrocarbon group having 6 or more carbon atoms as a hydrophobic group.

(7) The optical film according to (4), wherein the photochemically reactive compound is a compound represented by the following formula (I): (I) Hy-L ¹ (-Hb-L ² -Pc) _n [Wherein Hy is a hydrophilic group; L ¹ is a single bond or an n + 1 valent linking group; Hb is a divalent hydrophobic group; L ² is a divalent linking group Yes; Pc is a photoreactive group represented by the formula (Pc);
Is 1 or 2.

(8) The photochemically reactive compound has the following formula (I)
A copolymer having a repeating unit and a repeating unit represented by the following formula (III) represented by I) (optical film according to _{4): (II) -CH 2} -CR 1 (-Hy) - ( ^{_{III) -CH 2 -CR 2 (-L}} 2 -Pc) - [ wherein, Hy is an hydrophilic group; R ¹ and R ^2,
L is each independently a hydrogen atom or methyl;
² is a divalent linking group; and Pc is a photochemically reactive group represented by the formula (Pc)].

(9) The optical film according to (1), wherein the optically anisotropic discontinuous phase further contains a liquid crystalline compound. (10) The optical film according to (1), wherein the optically anisotropic discontinuous phase is formed by a polymerization reaction of a liquid crystalline compound having a polymerizable group.

(11) A polarizing element having, on a transparent support, an anisotropic scattering layer which substantially scatters one of two linearly polarized lights whose polarization planes are orthogonal to each other and substantially transmits the other. The anisotropic scattering layer comprises an optically isotropic continuous phase and an optically anisotropic discontinuous phase, and the optically anisotropic discontinuous phase contains an amphiphilic photochemically reactive compound. Polarizing element. (12) The difference in the refractive index at the interface between the optically isotropic continuous phase and the optically anisotropic discontinuous phase is 0.05 or more on the axis that scatters the linearly polarized light most strongly. Polarizing element. (13) The difference between the refractive indices at the interface between the optically isotropic continuous phase and the optically anisotropic discontinuous phase is less than 0.05 on the axis at which the transmittance of linearly polarized light is maximized (11). The polarizing element as described in the above.

(14) emulsifying or dispersing an optically anisotropic phase containing an amphiphilic photochemically reactive compound and a liquid crystalline compound having a polymerizable group in an optically isotropic continuous phase;
A step of applying the obtained emulsion or dispersion on a transparent support; a step of irradiating linearly polarized light to orient the liquid crystal compound; and a step of irradiating ultraviolet light to polymerize the liquid crystal compound. The manufacturing method of the polarizing element implemented by. (15) The production method according to (14), wherein the linearly polarized light used in the step of aligning the liquid crystal compound is ultraviolet light, and has a different wavelength from the ultraviolet light used in the step of polymerizing the liquid crystal compound.

(16) A light-scattering type polarizing element which substantially scatters one of two linearly polarized lights whose polarization planes are orthogonal to each other and substantially transmits the other, and a linearly polarized light whose two polarization planes are orthogonal to each other. A polarizing plate comprising a light-absorbing polarizing element and a light-absorbing polarizing element that substantially transmits one side and substantially absorbs the other, wherein the light-scattering type polarizing element is optically different from the optically isotropic continuous phase. A polarizing plate comprising an isotropic discontinuous phase, wherein the optically anisotropic discontinuous phase contains an amphiphilic photochemically reactive compound.

(17) A liquid crystal display device in which a backlight, a polarizing plate, a liquid crystal cell, and a polarizing plate are laminated in this order, wherein the polarizing plate between the backlight and the liquid crystal cell has polarizing planes orthogonal to each other. A light-scattering type polarizing element that substantially scatters one of the two linearly polarized lights and substantially transmits the other, and substantially transmits one of the two linearly polarized lights whose polarization planes are orthogonal to each other, and substantially transmits the other. A polarizing plate on which a light-absorbing polarizing element that absorbs light is laminated, and the light-scattering polarizing element is composed of an optically isotropic continuous phase and an optically anisotropic discontinuous phase, A liquid crystal display device wherein the isotropic discontinuous phase contains an amphiphilic photochemically reactive compound.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION [Transparent Support] An optical film or a polarizing element generally has a transparent support. The transparent support is preferably formed from a material having a light transmittance of 80% or more. As the transparent support, a polymer film can be used. Examples of the polymer include polyolefin (eg, polyethylene), norbornene resin, polyethylene terephthalate, polyethylene naphthalate, polypropylene, polycarbonate, polystyrene, polyarylate, polysulfone, polyether sulfone,
Examples include polyvinyl chloride, polyvinyl alcohol, and cellulose esters (eg, cellulose acetate). A film in which two or more kinds of polymers are mixed may be used.
A commercially available polymer (eg, ZEONEX, ZEONOR, manufactured by Nippon Zeon Co., Ltd .; ARTON, manufactured by Nippon Synthetic Rubber Co., Ltd.) or a polymer film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) can also be used.
Cellulose acetate, polyethylene terephthalate,
Polyethylene naphthalate and polycarbonate are particularly preferred.

In the polarizing element, the transparent support preferably has the performance as a protective film. From the viewpoint of moisture permeability, which is important in manufacturing a polarizing element, a cellulose acetate film is preferred. From the viewpoint of durability as a polarizing element, the acetylation degree of cellulose acetate is 55 to 61.
5% is preferable, and 59-61% is more preferable. An undercoat layer can be provided to increase the adhesive strength between the transparent support and the anisotropic scattering layer. As the polymer forming the undercoat layer, gelatin, styrene-butadiene rubber and polyvinyl alcohol are preferred. Instead of providing the undercoat layer, the transparent support may be subjected to a surface treatment. Examples of surface treatments include flame treatment, corona treatment, glow treatment and saponification treatment.

[Anisotropic scattering layer] The anisotropic scattering layer has an orthogonal property that substantially scatters one of two linearly polarized lights whose polarization planes are orthogonal to each other and substantially transmits the other. I have. In the present invention, the anisotropic scattering layer is composed of an optically isotropic continuous phase and an optically anisotropic discontinuous phase (dispersed phase). The thickness of the anisotropic scattering layer is preferably 0.5 to 500 μm, more preferably 1 to 100 μm.

The optically isotropic continuous phase is composed of an optically isotropic substance. Preferably, the optically isotropic continuous phase comprises a relatively hydrophilic polymer. Examples of relatively hydrophilic polymers include cellulose esters (eg, cellulose acetate), cellulose ethers (eg, methyl cellulose, hydroxyethyl cellulose), polyvinyl alcohol, polyvinyl alcohol derivatives, polyacrylates, polymethacrylates (eg, Polymethyl methacrylate), proteins (eg, gelatin) and polysaccharides other than cellulose (eg, pullulan, carrageenan) The hydrophilic polymer is more preferably water-soluble, and polyvinyl alcohol, a polyvinyl alcohol derivative and gelatin are preferred. The birefringence of the optically isotropic continuous phase is preferably less than 0.05, more preferably less than 0.03.

The optically anisotropic dispersed phase contains an amphiphilic photoreactive compound. The optically anisotropic dispersed phase preferably contains a substance exhibiting a refractive index anisotropy in addition to the photochemically reactive compound. It is preferable that the substance exhibiting the refractive index anisotropy is uniaxially oriented by irradiating the anisotropic scattering layer with linearly polarized light, whereby the refractive index anisotropy is expressed. Refractive index anisotropy means that the refractive index for one of two linearly polarized lights whose polarization planes are orthogonal to each other is different from that for the other. The substance exhibiting a refractive index anisotropy is preferably a liquid crystal compound. As the liquid crystal compound, a difference between the ordinary light refractive index (no) and the extraordinary light refractive index (ne), that is, a liquid crystal compound having a large intrinsic birefringence is preferable. The intrinsic birefringence is preferably 0.1 or more,
More preferably, it is 0.15 or more. The difference between the ordinary refractive index (no) of the liquid crystalline compound and the refractive index of the optically isotropic continuous phase is preferably less than 0.05, and 0.03.
More preferably, it is less than. The difference between the extraordinary light refractive index (ne) of the liquid crystal compound and the refractive index of the optically isotropic continuous phase is preferably 0.05 or more, more preferably 0.1 or more.

The liquid crystal compound is preferably a low-molecular liquid crystal exhibiting a nematic phase or a smectic phase at room temperature or when heated. As the low-molecular liquid crystal, a cyanobiphenyl liquid crystal, a cyanophenylcyclohexane liquid crystal, a cyanophenyl ester liquid crystal, a benzoic acid phenyl ester liquid crystal, a phenylpyrimidine liquid crystal, or a mixture thereof can be used. Alternatively, a polymer liquid crystal exhibiting a nematic phase or a smectic phase at room temperature or in a heated state can be used.

As the liquid crystal compound, a rod-shaped liquid crystal compound can be preferably used. For the rod-like liquid crystal compound and its composition, see Chapter 4 of the Quarterly Chemistry Review, Chemistry of Liquid Crystals (1994), Chapters 4, 7, and 10 of the Chemical Society of Japan, and Liquid Crystal Device Handbook. It is described in Chapter 3 of the 142 Committee.
In many cases, it is difficult to maintain the alignment state of the liquid crystal compound stably for a long period of time or for temperature, humidity, or mechanical deformation. In order to improve the stability of the alignment state of the liquid crystal, it is preferable to introduce a polymerizable group into the liquid crystal compound. A liquid crystal polymer (having a functional group corresponding to the liquid crystal in a side chain) previously synthesized by polymerization may be added to the discontinuous phase. In order to improve the heat resistance and the uniformity of the alignment, it is preferable to introduce photopolymerizable groups at both ends of the rod-like liquid crystal molecules. The polymerizable group is preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group. Hereinafter, examples of the rod-shaped liquid crystalline compound will be described.

[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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[0033]

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[0034]

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[0035]

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[0036]

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[0037]

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The liquid crystalline compound is composed of 1 g of an optically isotropic continuous phase.
The amount is preferably 0.001 to 1.5 g, more preferably 0.01 to 1.0 g.

The amphiphilic photochemically reactive compound is a compound having three types of functional groups, a hydrophilic group, a hydrophobic group and a photochemically reactive group. The hydrophilic group includes a cationic group, an anionic group (eg, a quaternary ammonium group and a salt thereof), and a nonionic group (eg, a hydroxyl group). Cationic groups are particularly preferred. Examples of the cationic group include a carboxylic acid group and a salt thereof, a sulfonic acid group and a salt thereof, and a phosphoric acid group and a salt thereof. The hydrophobic group is preferably a hydrocarbon group having 6 or more carbon atoms. Preferably, the hydrocarbon group is saturated. A hydrocarbon group (eg, a benzene ring of a cinnamoyl group) contained in a photochemically reactive group (described later) may function as a hydrophobic group. When the photochemically reactive compound is a polymer, the hydrocarbon backbone of the polymer can also function as a hydrophobic group.

A photochemically reactive group undergoes a photochemical reaction (eg, photolysis,
(Photocrosslinking, photopolymerization, photooxidation and reduction, phototransition, photoisomerization). A functional group that performs a photocrosslinking reaction or a functional group that performs a photoisomerization reaction is particularly preferable. The functional group that performs the photocrosslinking reaction breaks bonds in the molecule by light irradiation, or bonds active molecules such as radicals generated by partial cleavage of the bond (photodimerization) or other Molecules are radicalized and undergo a binding reaction. Examples of the photocrosslinkable functional group include a cinnamoyl group, a cinnamylidene group, a diazo group, an azide group, an acryloyl group, a chalcone group, and a coumarin group. Photodimerizable functional groups (eg, cinnamoyl group, cinnamylidene group, chalcone group, coumarin group) are particularly preferred.

Examples of the functional group that performs the photoisomerization reaction include azobenzene groups that undergo cis-trans isomerization by light irradiation (K. Ichimura et al, Langmuir. Vol. 4, 2); I
chimura et al, Appl. Phys. Lett. Vol. 63, No. 4, P
age449 (1993); Ishizuki, Langmuir. Vol. 9, Pa
ge3298 (1993); Ishizuki, Langmuir. Vol. 9, P
age857 (1993)), a hydrazono-β-ketoester group (S. Yamamura et al, Liquid Crystal, Vol. 13, No.
2, page189 (1993)), stilbene group (Kunihiro Ichimura et al., Journal of Polymers, Vol. 47, No. 10, p. 771 (1990)), and spiropyran group (K. Ichimura et al, Chemistry Lett)
ers, Page 1063 (1992); Ichimura et al, Thin
Solid Films, Vol. 235, Page 101 (1993)). Azobenzene groups and stilbene groups are particularly preferred.

The photochemically reactive group is preferably represented by the following formula (Pc). In ^{(Pc) -Y 1 = Y 2} -Ar formula (Pc), Y ¹ and Y ² are each independently N or CR. Preferably, Y ¹ and Y ² are each N or CR. R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R
Is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom or methyl, and even more preferably a hydrogen atom. Most preferably, Y ¹ and Y ² are each CH. In the formula (Pc), the double bond between Y ¹ and Y ² is preferably a trans type. The formula (P
In c), Ar is an aromatic group.

In the present specification, the aromatic group means an aryl group and a substituted aryl group. Examples of the aryl group include phenyl and naphthyl. A heterocyclic ring or an aliphatic ring may be fused to the benzene ring of the aryl group.

Examples of the substituent of the substituted aryl group include halogen
Atoms (eg, chlorine, bromine, iodine), fats
Group, aromatic group, heterocyclic group, cyano, amino, hydroxy
Sil, nitro, carboxyl, silyloxy, carbamo
Iloxy, ureido, sulfamoylamino, merca
Put, sulfamoyl, sulfo, carbamoyl, phosph
Ino, phosphinyl, phosphinyloxy, phosphinyl
Ruamino, silyl, -OR, -O-Si (-R)_Three,
-O-CO-R, -O-CO-NH-R, -O-CO-
N (-R)_Two, -O-CO-OR, -NH-R, -N
(-R)_Two, -NH-CO-R, -NH-SO_Two-R,
-N (-R) -CO-NH-R, -NH-CO-N (-
R)_Two, -NH-CO-OR, -NH-CO-O-
R, -NH-SO_Two-NH-R, -NH-SO_Two-N
(-R)_Two, -NH-SO_Two-R, -SR, -SO_Two
-NH-R, -SO_Two-N (-R)_Two, -SO_Two-NH
-CO-R, -SO_Two-NH-CO-NH-R, -SO
-R, -SO_Two-R, -CO-R, -CO-OR,-
CO-NH-R, -CO-N (-R)_Two, -CO-NH
-SO_Two-R, -N = NR, -P (-R)_Two, -P
(-R) -OR, -P (-OR)_Two, -P (= O)
(-R)_Two, -P (= O) (-R) -OR, -P (=
O) (-OR)_Two, -OP (= O) (-R)_Two, −
OP (= O) (-R) -OR, -OP (= O)
(-OR)_Two, -NH-P (= O) (-R) _Two, -N
HP (= O) (-R) -OR, -NH-P (= O)
(-OR)_Two, -NH-P (= O) (-R) -NH-
R, -NH-P (= O) (-NH-R) _TwoAnd -Si
(-R)_ThreeIs included. R is an aliphatic group or an aromatic group
Or a heterocyclic group.

In the present specification, the aliphatic group means an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group and a substituted alkynyl group.
The aliphatic group may have a cyclic or branched structure.
The aliphatic group preferably has 1 to 30 carbon atoms. An aromatic ring or a heterocyclic ring may be fused to the aliphatic ring of the cyclic aliphatic group. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl, cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl, bicyclo [1,2,2] heptane-2-. Yl and bicyclo [2,2,2] octan-3-yl. Examples of alkenyl groups include vinyl, allyl, prenyl, geranyl, oleyl, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl, bicyclo [2,2,1] hept-2-en-1-yl And bicyclo [2,2,2]
Oct-2-en-4-yl). Examples of the alkynyl group include ethynyl and propargyl.

A substituted alkyl group, a substituted alkenyl group and
Examples of the substituent of the substituted alkynyl group include a halogen atom
(E.g., chlorine, bromine, iodine), aromatic groups,
Heterocyclic group, cyano, amino, hydroxyl, nitro,
Ruboxyl, silyloxy, carbamoyloxy, urea
Id, sulfamoylamino, mercapto, sulfamo
Il, sulfo, carbamoyl, phosphino, phosphini
, Phosphinyloxy, phosphinylamino, silyl
, -OR, -O-Si (-R)_Three, -O-CO-
R, -O-CO-NH-R, -O-CO-N (-
R)_Two, -O-CO-OR, -NH-R, -N (-
R)_Two, -NH-CO-R, -NH-SO_Two-R, -N
(-R) -CO-NH-R, -NH-CO-N (-R)
_Two, -NH-CO-OR, -NH-CO-OR,-
NH-SO_Two-NH-R, -NH-SO_Two-N (-R)
_Two, -NH-SO_Two-R, -SR, -SO_Two-NH-
R, -SO_Two-N (-R)_Two, -SO_Two-NH-CO-
R, -SO_Two-NH-CO-NH-R, -SO-R,-
SO_Two-R, -CO-R, -CO-OR, -CO-N
HR, -CO-N (-R)_Two, -CO-NH-SO_Two
-R, -N = NR, -P (-R)_Two, -P (-R)-
OR, -P (-OR)_Two, -P (= O) (-
R)_Two, -P (= O) (-R) -OR, -P (= O)
(-OR)_Two, -OP (= O) (-R)_Two, -O-
P (= O) (-R) -OR, -OP (= O) (-O
-R) _Two, -NH-P (= O) (-R)_Two, -NH-P
(= O) (-R) -OR, -NH-P (= O) (-O
-R)_Two, -NH-P (= O) (-R) -NH-R,-
NH-P (= O) (-NH-R)_TwoAnd -Si (-
R)_ThreeIs included. R is an aliphatic group, an aromatic group or
Is a heterocyclic group.

In the present specification, the heterocyclic group means an unsubstituted heterocyclic group and a substituted heterocyclic group. The heterocyclic ring of the heterocyclic group is preferably a 5- or 6-membered ring. The heterocyclic ring of the heterocyclic group may be condensed with another heterocyclic ring, aromatic ring or heterocyclic ring. Examples of the heterocyclic group include 2-furyl, 2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl, N-succinimide and N-phthalimide.

Examples of the substituent of the substituted heterocyclic group include a halogen atom (eg, a chlorine atom, a bromine atom, an iodine atom), an aliphatic group, an aromatic group, a heterocyclic group, cyano, amino, hydroxyl, nitro, Carboxyl, silyloxy, carbamoyloxy, ureido, sulfamoylamino, mercapto, sulfamoyl, sulfo, carbamoyl, phosphino, phosphinyl, phosphinyloxy, phosphinylamino, silyl, -OR, -O-Si (-R ) ₃ ,-
O-CO-R, -O-CO-NH-R, -O-CO-N
(-R) ₂ , -O-CO-OR, -NH-R, -N
_{(-R) 2, -NH-CO} -R, -NH-SO 2 -R,
-N (-R) -CO-NH-R, -NH-CO-N (-
R) ₂ , -NH-CO-OR, -NH-CO-O-
_{R, -NH-SO 2 -NH-} R, -NH-SO 2 -N
_{(-R) 2, -NH-SO} 2 -R, -S-R, -SO 2
_{-NH-R, -SO 2 -N (} -R) 2, -SO 2 -NH
_{-CO-R, -SO 2 -NH-} CO-NH-R, -SO
_{-R, -SO 2 -R, -CO-} R, -CO-O-R, -
CO-NH-R, -CO-N (-R) ₂ , -CO-NH
_{-SO 2 -R, -N = N-} R, -P (-R) 2, -P
(-R) -OR, -P (-OR) ₂ , -P (= O)
(-R) ₂ , -P (= O) (-R) -OR, -P (=
O) (-OR) ₂ , -OP (= O) (-R) ₂ ,-
OP (= O) (-R) -OR, -OP (= O)
(-OR) ₂ , -NH-P (= O) (-R) ₂ , -N
HP (= O) (-R) -OR, -NH-P (= O)
(-OR) ₂ , -NH-P (= O) (-R) -NH-
R, -NH-P (= O) (-NH-R) ₂ and -Si
(-R) ₃ . R is an aliphatic group, an aromatic group or a heterocyclic group.

The amphiphilic photochemically reactive compound is a compound in which the above-mentioned three types of functional groups, ie, a hydrophilic group, a hydrophobic group, and a photochemically reactive group, are bonded directly or via an arbitrary linking group. is there. The photochemically reactive compound has the following formula (I)
It is preferable that the compound is represented by ^{(I) Hy-L 1 (} -Hb-L 2 -Pc) n

In the formula (I), Hy is a hydrophilic group. The hydrophilic group is as described above. In the formula (I), L ¹ is a single bond or an n + 1-valent linking group. The linking group includes an n + 1-valent saturated aliphatic group (an alkylene group in the case of divalent), -O-, -CO-, -NH-,
It is preferred that -N <or a combination thereof. The saturated aliphatic group preferably has 1 to 5 carbon atoms. Give an example of L ¹ below. The left side binds to the hydrophilic group (Hy), and the right side binds to the hydrophobic group (Hb). L ^10: a single bond L ^11: - alkylene -O- L ^12: -O- alkylene -O- L ^13: -3 divalent saturated aliphatic group ^{_{(-CO-O-) 2 L 14}} :-( alkylene -O ) _m -; m is 1 to 20 integer L ^15: (- alkylene ^{_{-) 2 N-CO- L 16}} : -O- L 17: - alkylene -O-CO-

In the formula (I), Hb is a divalent hydrophobic group. The hydrophobic group is preferably an unsubstituted hydrocarbon group, more preferably an unsubstituted hydrocarbon group having 6 or more carbon atoms, and an unsubstituted aliphatic group having 6 or more carbon atoms. More preferably, the number of carbon atoms is 6
Most preferably, it is the above unsubstituted alkylene group.
In the formula (I), L ² is a divalent linking group. L ²
Is an alkylene group, an arylene group, -O-, -CO-,
-NH-, -CH = CH- or a combination thereof is preferred. Give an example of L ² below. The left side is bonded to a hydrophobic group (Hb), and the right side is a photoreactive group (Pb).
c). ^{L 21: -O-CO- L 22} : -O- arylene ^{- L 23: -O-CO-} CH = CH- L 23: -O-CO- alkylene -O- arylene - L ^24: -O-CO- alkylene ^{-O-CO- L 25: -CO-} O- alkylene -O-CO- the L ²¹ is particularly preferred.

In the formula (I), Pc is the same as the formula (P
It is a photochemically reactive group represented by c). In the formula (I), n is 1 or 2. The photochemically reactive compound is
More preferably, it is a compound represented by the following formula (Ia) or (Ib).

[0053]

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In the formulas (Ia) and (Ib), Hy
Is a hydrophilic group. The hydrophilic group is as described above. In the formula (Ia), L ¹ is a single bond or a divalent linking group. The linking group is an alkylene group, -O
-, -CO-, -NH- or a combination thereof is preferred. The alkylene group preferably has 1 to 5 carbon atoms. Formulas (Ia) and (Ib)
In the formula, Hb is a divalent hydrophobic group. The hydrophobic group is preferably an unsubstituted hydrocarbon group, more preferably an unsubstituted hydrocarbon group having 6 or more carbon atoms, and an unsubstituted aliphatic group having 6 or more carbon atoms. And more preferably an unsubstituted alkylene group having 6 or more carbon atoms. In the formulas (Ia) and (Ib), Ar is an aromatic group. The aromatic group is as described above.

The photochemically reactive compound is also preferably a copolymer having a repeating unit represented by the following formula (II) and a repeating unit represented by the following formula (III). ^{_{(II) -CH 2 -CR 1 (}} -Hy) - (III) -CH 2 -CR 2 (-L 2 -Pc) -

In the formulas (II) and (III), R ¹ and R ² are each independently a hydrogen atom or methyl. In the formula (II), Hy is a hydrophilic group. The hydrophilic group is as described above. In the formula (III), L ² is a divalent linking group. L ² is an alkylene group, an arylene group, -O -, - CO -, - NH -, -
Preferably, CH = CH- or a combination thereof. Examples of L ² are the same as L ²¹ ~L ²⁵ of the formula (I). However, L ²³ ~L ²⁵ is preferred. In the formula (III), Pc is a photochemically reactive group represented by the formula (Pc).

The repeating unit represented by the formula (II) is preferably contained in the copolymer in an amount of 45 to 99% by weight, more preferably 55 to 95% by weight, and more preferably 65 to 90% by weight. More preferably, it is contained, most preferably 75 to 85% by weight. The repeating unit represented by the formula (III) is preferably contained in the copolymer in an amount of 1 to 55% by weight,
More preferably, it is contained in an amount of 5 to 45% by weight.
More preferably, 0 to 35% by weight is contained,
Most preferably, the content is 15 to 25% by weight.
The copolymer may have a repeating unit other than those represented by the formulas (II) and (III) (for example, a repeating unit obtained by polymerizing another ethylenically unsaturated monomer). Other ethylenically unsaturated monomers are described in Research Disclosure No. 1955 (1980, 7
Month).

The photochemically reactive compound is more preferably a copolymer having a repeating unit represented by the following formula (IIa) and a repeating unit represented by the following formula (IIIa).

[0059]

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In the formulas (IIa) and (IIIa), R
² is a hydrogen atom or methyl. In the formula (IIa), Hy is a hydrophilic group. The hydrophilic group is as described above. In the formula (IIIa), L ²¹ is a single bond or a divalent linking group. L ²¹ is an alkylene group,
It is preferably -O-, -CO- or a combination thereof. In the formula (IIIa), Ar is an aromatic group. The aromatic group is as described above. Hereinafter, examples of the amphiphilic photochemically reactive compound will be described. In addition,
The proportion of the repeating unit in (15), (16), (17) and (21) is% by weight.

[0061]

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[0062]

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[0063]

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[0064]

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[0065]

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[0066]

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[0067]

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[0068]

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[0069]

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[0070]

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When a liquid crystalline compound and an amphiphilic photochemically reactive compound are used in combination, the photochemically reactive compound is preferably used in an amount of 0.001 to 1 g per 1 g of the liquid crystalline compound, and is preferably used in an amount of 0.01 to 0.1 g. It is more preferred to use 1 g.

The anisotropic scattering layer is formed by adding a solution (preferably an aqueous solution) of a material (eg, a hydrophilic polymer) constituting an optically isotropic continuous phase to a material (preferably an aqueous anisotropic discontinuous phase). For example, a liquid obtained by emulsifying or dispersing a liquid crystalline compound, an amphiphilic photochemically reactive compound) on a transparent support,
It is preferable to dry and then irradiate with linearly polarized light. It is preferable that the photochemically reactive compound exists unevenly at the interface between the optically anisotropic discontinuous phase and the optically isotropic continuous phase.

When the liquid crystal compound is emulsified or dispersed,
An amphiphilic photochemically reactive compound exhibits a surfactant function. A surfactant other than the photochemically reactive compound may be added to control the dispersion particle size or to impart dispersion stability. Nonionic, anionic, cationic or amphoteric surfactants can be used. As the nonionic surfactant, a surfactant having a nonionic hydrophilic group of polyoxyethylene, polyoxypropylene, polyoxybutylene, polyglycidyl or sorbitan is preferable. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene-polyoxypropylene glycol, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, and polyoxyethylene polyhydric alcohol fatty acid partial ester. Oxyethylene fatty acid esters, polyglycerin fatty acid esters, fatty acid diethanolamide, and triethanolamine fatty acid partial esters are included.

As the anionic surfactant, a surfactant having a carboxylate, sulfate, sulfonate or phosphate salt as an anionic hydrophilic group is preferable. Examples of anionic surfactants include fatty acid salts, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfonates, α-olefin sulfonates, dialkyl sulfosuccinates, α-sulfonated fatty acid salts, N-methyl-N-oleyl taurine, petroleum sulfonate, alkyl sulfate, sulfated oil, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene styrenated phenyl ether sulfate, alkyl phosphoric acid Salts, polyoxyethylene alkyl ether phosphate and naphthalene sulfonate formaldehyde condensates are included. As the cationic surfactant, a surfactant having an amine salt, a quaternary ammonium salt or a pyridium salt as a cationic hydrophilic group is preferable. Examples of the cationic surfactant include primary to tertiary fatty amine salts and quaternary ammonium salts (eg, tetraalkylammonium salts, trialkylbenzylammonium salts, alkylpyridium salts, alkylimidazolium salts). It is.
Carboxybetaine and sulfobetaine are preferred as amphoteric surfactants. Examples of amphoteric surfactants include:
N-trialkyl-N-carboxymethyl ammonium betaine and N-trialkyl-N-sulfoalkylene ammonium betaine are included. And the like.

The surfactant is also described in Application of Surfactant (written by Koshobo and Takao Karimei, published on September 1, 1980). When the surfactant is added, the amount used is preferably from 0.001 to 1 g, more preferably from 0.01 to 0.1 g, per 1 g of the liquid crystal compound in the dispersed phase. For dispersion or emulsification, it is preferable to use a stirrer (eg, ultrasonic dispersion method, homogenizer) or a kneader (eg, sand mill, colloid mill). The particle size of the dispersed discontinuous phase is an average diameter of an approximate circle in which each region is approximated by a circle having substantially the same area, and is preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm. .

The coating is performed by dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, or extrusion coating (described in US Pat. No. 2,681,294).
Can be implemented. Two or more layers may be applied simultaneously.
The simultaneous coating method is described in U.S. Pat.
No. 41898, No. 3508947, No. 3526528
Issue specifications and Yuji Harasaki, Coating Engineering, 2
53, Asakura Shoten (1973). The thickness of the anisotropic scattering layer is preferably 0.5 to 100 μm, more preferably 1 to 70 μm.

The wavelength of the linearly polarized light to be irradiated is determined according to the wavelength region in which the photochemically reactive compound used has optical absorption. Generally, the thickness is preferably 190 nm or more and less than 500 nm, and more preferably 250 nm or more and less than 450 nm. The light source is preferably an ultra high pressure mercury lamp, a flash mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a low pressure mercury lamp, a deep UV lamp, a xenon lamp, a xenon flash lamp or a metal halide lamp. It is preferable that the ultraviolet light emitted from the light source is passed through a polarizing element to be linearly polarized. The polarizing element is
It is preferable to use a prism-based element (eg, a Glan-Taylor-type prism or a Glan-Thompson-type prism) or a reflective polarizing element using a Brewster angle. The irradiation light amount is preferably 1 to 2000 mJ / cm ² , and more preferably 5 to 1000 mJ / cm ² . In order to develop optical anisotropy in a short time, linearly polarized light may be irradiated while heating. The temperature at which the linearly polarized light is applied is preferably from 0 ° C. to less than 200 ° C., more preferably from 10 ° C. to less than 150 ° C. The liquid crystal compound can also be oriented by irradiating obliquely unpolarized light (Polym. Mater. Sci. Eng., 66,
p263 (1992)).

After irradiating the photochemically reactive compound with linearly polarized light, the liquid crystal compound can be oriented. In order to maintain the alignment state over a long period of time, it is desirable to use a polymerizable liquid crystal compound, polymerize in the alignment state, and form a network structure by crosslinking. As a means for polymerizing the polymerizable liquid crystal compound, either thermal polymerization or photopolymerization can be used. Photopolymerization is preferred, and photopolymerization using ultraviolet light is more preferred. Examples of the photopolymerization initiator include thioxanthone-based photopolymerization initiators (eg, 2,4-diethylthioxanthone, 2-chlorothioxanthone) and benzophenone-based photopolymerization initiators (eg, benzophenone, (4- (methylphenylthio) phenyl) Phenylmethanone) or an anthraquinone-based photopolymerization initiator (eg, ethylanthraquinone) can be used. Commercially available photopolymerization initiator (Ciba Spec
ialty Chemicals. Inc. Made of Irgacure 184, Irgacure
369, Irgacure500, Irgacure651, Irgacure7
84, Irgacure 819, Irgacure 907, Irgacure 10
00, Irgacure 1300, Irgacure 1700, Irgacure
1800, Irgacure 1850, Irgacure 2959, Daro
cur 1173, Darocur 4265) may be used. The photopolymerization initiator is 0.0% based on the total amount of the polymerizable liquid crystal compound.
It is preferably used at 1% to 20% by weight, more preferably 0.5% to 10% by weight.

In addition to the photopolymerizable initiator, a spectral sensitizer and a photopolymerization accelerator (eg, isoamyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate) may be used. The spectral sensitizer and the photopolymerization accelerator are preferably used in an amount of 10% by weight or more and less than 300% by weight of the photopolymerization initiator, and more preferably in an amount of 20% by weight or more and less than 200% by weight. . The irradiation light wavelength, irradiation light amount, light source, and substrate temperature during irradiation in the light irradiation polymerization are the same as those in the case of the linearly polarized light irradiation described above. The irradiation light wavelength for irradiating linearly polarized light and the irradiation light wavelength for photopolymerizing a polymerizable liquid crystalline compound are different (50 n in wavelength).
m or more). A dispersion or an emulsion is prepared, coated on a transparent support, the liquid crystal molecules are aligned by irradiation with linearly polarized light, and, if necessary, the anisotropic scattering layer is formed by photopolymerizing the aligned liquid crystal molecules. Can be made.

FIG. 1 is a schematic sectional view showing the basic structure of an optical film. In the optical film shown in FIG. 1, on the transparent support (11), the polarization selection layer 12 is composed of an optically isotropic continuous phase (13) and an optically anisotropic discontinuous phase (14).
Phase separation. The continuous phase (13) consists of an optically isotropic hydrophilic polymer. The discontinuous phase (14) comprises an optically anisotropic compound having birefringence and an amphiphilic photochemically reactive compound. In other words, the two refractive indexes n1 and n2 of the discontinuous phase differ depending on the properties of the optically anisotropic compound used or the degree of orientation in the discontinuous phase. In order for the optical film to function as a polarizing element, one of n1 and n2 has a value substantially equal to the refractive index of the continuous phase, that is, 0.05.
It is necessary to be less than. The direction of n1 or n2 at which the refractive indices become substantially equal corresponds to the transmission axis of the polarization selection layer.

[Liquid Crystal Display Device] The polarizing element having the anisotropic scattering layer described above is preferably used for a liquid crystal display device, particularly for a transmission type liquid crystal display device. The transmission type liquid crystal display device basically comprises a liquid crystal cell and two polarizing elements arranged on both sides thereof. A liquid crystal cell carries a liquid crystal between two electrode substrates. The liquid crystal cell is preferably in an OCB mode, a VA mode, or a TN mode. In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied. In the VA mode liquid crystal cell,
(1) In addition to a narrowly defined VA mode liquid crystal cell (described in JP-A-2-176625) in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied, and are aligned substantially horizontally when voltage is applied. (2) A liquid crystal cell (SID97, Digest of tech. Papers (preparations) 2) in which the VA mode is multi-domain (in the MVA mode) in order to enlarge the viewing angle.
8 (1997) 845), and (3) a liquid crystal cell of a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when voltage is applied. Proceedings 58-59
(1998)) and (4) SURVAIVAL mode liquid crystal cell (presented at LCD International 98).

The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are substantially (symmetrically) aligned in upper and lower directions of the liquid crystal cell. And disclosed in U.S. Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is OCB
(Optically Compensatory Bend) Also called liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage that the response speed is high. In a TN mode liquid crystal cell, rod-like liquid crystalline molecules are substantially horizontally aligned when no voltage is applied, and further twisted at 60 to 120 °. TN mode liquid crystal cells are most frequently used as color TFT liquid crystal display devices, and are described in many documents.

The light scattering type polarizing element is used as a back light for a liquid crystal cell.
Used in combination with the light-absorbing polarizing element
It is preferred to use Light-absorbing polarizing elements are orthogonal
Polarized light that absorbs one of the linearly polarized light and substantially transmits the other
Element. Light-absorbing polarizers are generally five times or more
I in the stretched polyvinyl alcohol film_Three-I _Five-
Alternatively, the organic dichroic dye is highly uniaxially oriented and
Cross-linked protection like cellulose triacetate
It has a structure sandwiched by films. Light absorption type
The degree of polarization of the optical element is preferably at least 99%.
The degree of polarization is defined by the following equation. Degree of polarization (%) = 100 × {(PC) / (P + C)}
^1/2 In the formula, P transmits through two polarizing elements whose transmission axes are parallel to each other.
And C is orthogonal to the transmission axis
This is the transmittance of light passing through two polarizing elements. 400n
Average light of light-absorbing polarizing element measured from m to 700 nm
The transmittance is desirably 40% or more.

FIG. 2 is a schematic diagram showing various configurations of a liquid crystal display device using a light scattering type polarizing element. FIG. 2 (a)
Is a simple configuration example showing the effect of the light scattering type polarizing element. The light-scattering polarizing element (31) selectively transmits polarized light in the same direction as the transmission axis of the light-absorbing polarizing element (24), and partially depolarizes polarized light orthogonal to the polarizing plate transmission axis by forward scattering. The use efficiency is improved by aligning the polarization plane in the transmission axis direction, and part of the light returns to the light source side due to backscattering, is depolarized by a light guide plate or the like, is reflected by the reflection plate, and is again formed on the optical film (31). By being returned and reused, utilization efficiency is improved.

FIG. 2B shows a configuration example in which a polarizing plate (32) using a light scattering type polarizing element as a protective film of a polarizing plate is combined with a film having another function. The light emitted from the light source has a uniform brightness in the plane by the scattering sheet (33), and the film (34) having a function of condensing the light in a predetermined direction provides an extremely oblique direction without being seen by the user. the light. Light is collected near the front to improve the usage efficiency. On the other hand, this film reduces light in a slightly oblique direction from the front, which is likely to be seen by the user.
According to the same principle as (a), the luminance is improved and a natural viewing angle distribution of luminance is obtained. FIG.
In the configuration of (a), since the light is reflected on the surface of the light scattering type polarizing element (31) on the side opposite to the polarization selection layer and on the light absorbing type polarizing element surface, the light use efficiency is reduced by about 10%. The use of the protective film eliminates this reflective surface, so that the use efficiency of light alone increases by about 10%.

FIG. 2C shows an example of the configuration of a liquid crystal display device in which the function of improving the brightness of a light scattering type polarizing element or a polarizing plate is further improved. By providing the antireflection layer (35) directly or via another layer on the surface of the polarization selection layer, reflection on the surface can be reduced, and the amount of light incident on the polarization selection layer can be increased. Further, by using a λ / 4 plate (36) below the polarizing plate (32) as in the above-mentioned back-scattering polarized light rotating type, polarized light orthogonal to the transmission axis of the back-scattered light-scattering polarizing plate is reduced by two. When the light passes through the λ / 4 plate, the light is rotated so as to have a polarization plane at the transmission axis of the polarizing plate, and the light use efficiency can be improved.

The light-scattering polarizing element may be used as a separate polarizing element from the light-absorbing polarizing element as shown in FIG. 2A, or may be used as a light-absorbing polarizing element as shown in FIG. One of the protective films of the element may be replaced and used integrally with the light absorbing polarizing element. At this time, it is desirable to use the polarizing element having the anisotropic scattering layer so that the transmission axis of the polarizing element is substantially parallel to the transmission axis of the light absorbing polarizing element. In addition, the polarizing element having the transmission axis anisotropic scattering layer of the anisotropic scattering layer is used as a backlight side polarizing element of the two polarizing elements of the liquid crystal cell, and the anisotropic scattering layer is larger than the light absorbing polarizing element. It is desirable to arrange it so as to be on the backlight side.

When the light emitted from the backlight passes through a polarizing element having an anisotropic scattering layer, it scatters one of orthogonal linearly polarized light and substantially transmits the other. The transmitted linearly polarized light then passes through the light-absorbing polarizing element and enters the liquid crystal cell. Of the other linearly polarized light, most of the backscattered light scattered toward the backlight is reflected by the backlight (for example, a light guide plate, a light diffusion plate, and a condensing sheet) and then returned to the anisotropic scattering layer again. Incident on. The re-incident light undergoes depolarization upon reflection and becomes elliptically polarized light, so that a polarization component parallel to the light transmission axis of the polarizing element is generated. Further, the forward scattered light is also slightly scattered and becomes elliptically polarized light, so that a polarized light component parallel to the light transmission axis is generated. As a result, the polarization component parallel to the light transmission axis of the polarizing element increases, and the transmittance of the polarizing element of the backlight increases in total.

When the polarizing element is combined with an optical compensation film of a liquid crystal display, a wide viewing angle and high luminance can be obtained. Patent No. 258 discloses an optical compensation film.
It is preferable to use the discotic compound described in No. 7398. Further, the optical compensation film can be integrated with the polarizing element (Japanese Patent Application Laid-Open No. 7-191217).
No.). An anti-reflection layer can also be provided on the surface of the light scattering type polarizing element on the backlight side. The anti-reflection layer reduces surface reflections and, as a result, can increase the brightness of the display. This anti-reflection layer is described in, for example, Journal of the Photographic Society of Japan, 29, p. 137 (1966), a laminate of a low refractive index layer and a high refractive index layer, or a structure having only one low refractive index layer may be used.

It is also preferable to further arrange a λ / 4 plate between the backlight and the laminate of the light scattering type polarizing element and the light absorbing type polarizing element. Here, by arranging the transmission axis of the light scattering type polarizing element and the light absorbing type polarizing element and the slow axis of the λ / 4 plate to be substantially 45 °, the backscattered polarized light is circularly polarized, By inverting the polarization direction at the time of reflection, the light use efficiency can be improved. By using a light-scattering type polarizing element in a liquid crystal display device, the light use efficiency is increased, and as a result, the brightness of the display is increased. In order to increase the luminance, the transmittance (Tma) on the polarization plane where the total light transmittance of the anisotropic scatterer is maximized.
x) is 75% or more and the transmittance (Tm) at the polarization plane where the transmittance is minimum.
in) is preferably 60% or less, Tmax is preferably 80% or more, and Tmin is more preferably 50% or less, and particularly preferably Tmax is 85% or more and Tmin is 40% or less.

[0091]

[Example 1] (Preparation of coating liquid for anisotropic scattering layer) 4'-pentyl-4-
4 g of biphenylcarbonitrile, 0.4 g of amphiphilic photochemically reactive compound (2), 0.2 g of sodium n-dodecylbenzenesulfonate and 2 g of ethyl acetate were added to 10% by weight of polyvinyl alcohol (PVA205, manufactured by Kuraray Co., Ltd.). The solution was mixed with 120 g of an aqueous solution, and this solution was dispersed using a homogenizer to prepare a coating solution for an anisotropic scattering layer. The average diameter of the dispersed phase was 0.35 μm.

(Formation of Coating Film and Photo Alignment) Thickness 80 μm
m of cellulose triacetate film (manufactured by Fuji Photo Film Co., Ltd.) using a bar coater, and dried at 100 ° C. for 5 minutes.
The film thickness was 10 μm. Thereafter, using an ultraviolet polarization exposure apparatus (manufactured by Nikon Technical Studio, 1 kW ultrahigh pressure mercury lamp), linearly polarized light of 313 nm was irradiated at an irradiation light intensity of 10 mW / c.
Irradiation was performed at room temperature for 10 minutes at m ² to produce an optical film.

Example 2 (Preparation of Coating Solution for Anisotropic Scattering Layer) 4 g of a polymerizable liquid crystalline compound (N26), a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, Nippon Kayaku 0.1 g, photopolymerization initiator (Irgacure 907, Ciba-Geigy)
0.1 g was dissolved in 2 g of ethyl acetate and filtered with a polypropylene filter having a pore size of 30 μm to prepare a polymerizable liquid crystal solution for a discontinuous phase. Separately, an amphiphilic photochemically reactive compound (3) 0.4 was added to 120 g of a 10% by weight aqueous solution of polyvinyl alcohol (PVA205, manufactured by Kuraray Co., Ltd.).
g and sodium dodecylbenzenesulfonate (surfactant) (0.2 g) were added, dissolved, and filtered through a polypropylene filter having a pore size of 30 μm to prepare an aqueous solution for continuous phase. 200 g of the polymerizable liquid crystal solution for the discontinuous phase and 200 g of the aqueous solution for the continuous phase were mixed, and the mixture was dispersed by ultrasonic dispersion to prepare a coating liquid for an anisotropic scattering layer. The average dispersion diameter was 0.3 μm.

(Formation of Coating Film and Photo Alignment) Thickness 80 μm
m of cellulose triacetate film (manufactured by Fuji Photo Film Co., Ltd.) using a bar coater, and dried at 100 ° C. for 5 minutes.
The thickness was 8 μm. Thereafter, using an ultraviolet polarization exposure apparatus (manufactured by Nikon Technical Studio, 1 kW ultrahigh pressure mercury lamp), linearly polarized light of 313 nm was irradiated at an irradiation light intensity of 10 mW / c.
Irradiation was performed for 10 minutes at a substrate temperature of 70 ° C. at m ² . This film together with the support was left in a thermostat at 100 ° C. for 2 minutes, aged, and then used with a 160 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd., wavelength range 200 to 500 nm, maximum wavelength 365 nm). Illuminance 200mW / cm ² , irradiation amount 400mJ / cm
^The dispersed film was cured while maintaining the anisotropic state by irradiating the ultraviolet ray of No. ² to obtain an optical film of Example 2.

[Example 3] (Preparation of coating liquid for anisotropic scattering layer) 4'-pentyl-4-
4 g of biphenylcarbonitrile, 0.4 g of the amphiphilic photochemically reactive compound (17) and 2 g of ethyl acetate were mixed with 120 g of a 10% by weight aqueous solution of polyvinyl alcohol (PVA205, manufactured by Kuraray Co., Ltd.), and the solution was mixed using a homogenizer. Was dispersed to prepare a coating liquid for an anisotropic scattering layer. The average diameter of the dispersed phase was 0.4 μm.

(Formation of Coating Film and Photo Alignment) Thickness 80 μm
m is coated on a cellulose triacetate film (manufactured by Fuji Photo Film Co., Ltd.) using a bar coater, dried at 100 ° C. for 5 minutes, and saponified as it is. (Fuji Photo Film Co., Ltd.) was laminated using a 5% by weight aqueous solution of polyvinyl alcohol (PVA117, Kuraray Co., Ltd.) as a glue. Thereafter, using an ultraviolet polarization exposure apparatus (manufactured by Nikon Corporation), a linearly polarized light having a wavelength of 365 nm and an irradiation light intensity of 10 mW / c were used.
Irradiation was performed at room temperature for 10 minutes at m ² to produce an optical film of Example 3.

[Example 4] (Preparation of coating liquid for anisotropic scattering layer) 4'-pentyl-4-
4 g of biphenylcarbonitrile, 0.4 g of the amphipathic photochemically reactive compound (20) and 2 g of ethyl acetate were mixed with 120 g of a 10% by weight aqueous solution of polyvinyl alcohol (PVA205, manufactured by Kuraray Co., Ltd.), and the solution was mixed using a homogenizer. Was dispersed to prepare a coating liquid D for an anisotropic scattering layer.
The average diameter of the dispersed phase was 0.3 μm.

(Formation of Coating Film and Optical Alignment) Thickness 80 μm
The above-mentioned coating liquid C for an anisotropic scattering layer was applied to a cellulose triacetate film m (manufactured by Fuji Photo Film Co., Ltd.) using a bar coater, and dried at 100 ° C. for 5 minutes. After this, an ultraviolet polarized light exposure device (manufactured by Nikon Technology Studio,
Using an ultra-high pressure mercury lamp of 1 kW), linearly polarized light of 365 nm was irradiated at an irradiation light intensity of 10 mW / cm ² for 10 minutes at room temperature to produce an optical film.

(Preparation of Light Absorption Polarizing Element and Integration with Light Scattering Polarizing Element) 5.0 g of iodine was added to the PVA film.
/ L, aqueous solution of 10.0 g / l of potassium iodide at 25 ° C
And then dipped in an aqueous solution of boric acid 10 g / l at 25 ° C. for 60 seconds, and then 7.0 using a roll stretching machine.
It was stretched twice. Thereafter, the stretched film was combined with the prepared optical film and saponified cellulose triacetate film (manufactured by Fuji Photo Film Co., Ltd.) and polyvinyl alcohol (PVA117, Kuraray Co., Ltd.) at 5% by weight.
Lamination was performed using the aqueous solution as a paste. During lamination, the transmission axis of the anisotropic scattering layer and the transmission axis of the light-absorbing polarizing element were substantially parallel to each other, and the anisotropic scattering layer was arranged so as to be in contact with the light-absorbing polarizing element. Thereafter, drying was performed at 70 ° C. for 5 minutes to obtain a polarizing plate.

[Comparative Example 1] (Preparation of coating liquid for anisotropic scattering layer) 4'-pentyl-4-
4 g of biphenylcarbonitrile, 0.4 g of the following comparative compound (1), 0.2 g of sodium n-dodecylbenzenesulfonate, and 2 g of ethyl acetate were added to 120 g of a 10% by weight aqueous solution of polyvinyl alcohol (PVA205, manufactured by Kuraray Co., Ltd.). The mixture was mixed and dispersed using a homogenizer to prepare a coating liquid for an anisotropic scattering layer. The average diameter of the dispersed phase was 0.4 μm.

[0101]

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(Formation of Coating Film and Photo Alignment) Thickness 80 μm
m of cellulose triacetate film (manufactured by Fuji Photo Film Co., Ltd.) using a bar coater, and dried at 100 ° C. for 5 minutes.
The film thickness was 9 μm. Thereafter, using an ultraviolet polarization exposure apparatus (manufactured by Nikon Technical Studio, 1 kW ultrahigh pressure mercury lamp), linearly polarized light of 313 nm was irradiated at an irradiation light intensity of 10 mW / c.
Irradiation was performed at room temperature for 10 minutes at m ² to produce an optical film of Comparative Example 1.

[Comparative Example 2] (Preparation of coating liquid for anisotropic scattering layer) 4'-pentyl-4-
4 g of biphenylcarbonitrile, 0.4 g of the following comparative compound (2), 0.2 g of sodium n-dodecylbenzenesulfonate and 2 g of ethyl acetate were added to 120 g of a 10% by weight aqueous solution of polyvinyl alcohol (PVA205, manufactured by Kuraray Co., Ltd.). The mixture was mixed and dispersed using a homogenizer to prepare a coating liquid for an anisotropic scattering layer. The average diameter of the dispersed phase was 0.4 μm.

[0104]

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(Formation of Coating Film and Photo Alignment) Thickness 80 μm
m of cellulose triacetate film (manufactured by Fuji Photo Film Co., Ltd.) using a bar coater, and dried at 100 ° C. for 5 minutes.
The film thickness was 9 μm. Thereafter, using an ultraviolet polarization exposure apparatus (manufactured by Nikon Corporation), a linearly polarized light having a wavelength of 365 nm and an irradiation light intensity of 10 mW / c were used.
Irradiation was performed at room temperature for 10 minutes at m ² to produce an optical film of Comparative Example 2.

(Evaluation of anisotropy of diffuse transmittance) The diffuse transmittance of the obtained film was measured using a spectrophotometer UV-31 manufactured by Shimadzu Corporation.
The measurement was performed using an apparatus in which a large polarizer assembly was set to 00PC (with a 60φ integrating sphere). The measurement is performed by inserting a large polarizer between the light source and the film, and the one where the transmission axis of the polarizer and the transmission axis of the anisotropic scattering type polarizing element are matched is set to the parallel transmittance (T0), and the orthogonal one is set. The ratio between the two (T0 / T1) was evaluated as the orthogonal transmittance (T1). When the polarization characteristics of the anisotropic scattering type polarizing element are high, T0 is larger than T1, and T0 / T1 becomes larger.

Table 1 shows the results. In each of Examples 1 to 4, the transmittance was 75% or more at T0 and 60% or less at T0. On the other hand, Comparative Examples 1 and 2 show almost no polarization.

[0108]

[Table 1] Table 1 Optical film T0 (%) T1 (%) T0 / T1──────────────────────────────────── Example 1 83 47 1.8 Example 2 81 48 1.7 Example 3 76 46 1.7 Example 4 78 0.1 780.0 Comparative Example 1 76 62 1.2 Comparative Example 2 74 58 1.3 ────────────────────────────

Example 5 (Production of Liquid Crystal Display) A polyimide alignment film was provided on a glass substrate provided with an ITO transparent electrode, and rubbing treatment was performed. Two substrates were stacked via a 5 μm spacer so that the alignment films faced each other. The orientation of the substrate was adjusted so that the rubbing directions of the alignment films were orthogonal. In the gap between the substrates, rod-like liquid crystalline molecules (ZL4792, manufactured by Merck)
Was injected to form a liquid crystal layer. Δn of the liquid crystalline molecule is 0.
0969.

A transparent support, a polarizing element, a transparent support with an optical compensation layer, a TN liquid crystal cell, a transparent support with an optical compensation layer, and a polarizing element were provided on both sides of the TN liquid crystal cell produced as described above. The prepared transparent support with anisotropic scattering layer,
Then, the liquid crystal display device was manufactured by sticking them in the order of the backlight. The slow axis of the laminate of the optically anisotropic layer and the transparent support was arranged to be orthogonal to the rubbing direction of the liquid crystal cell.

A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the ratio of the transmittance between white display and black display at 2 V for white display and 5 V for black display is defined as a contrast ratio. The area without tonal reversal was measured as the viewing angle. As a result, the vertical viewing angle was 70 ° and the horizontal viewing angle was 126 °. The front contrast was 122. The liquid crystal display device of the present invention has a front luminance of about 53% higher than that of a conventional liquid crystal display device using a polarizing element, and has a luminance even after being stored at 40 ° C. and 80% RH for 3 days. Did not decrease at all.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an optical film.

FIG. 2 is a schematic view illustrating various configurations of a liquid crystal display device using a light scattering type polarizing element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Transparent support 12 Polarization selection layer 13 Optically isotropic continuous phase 14 Optically anisotropic discontinuous phase 21 Backlight light source 22 Reflector 23 Light guide plate 24 Lower light absorption type polarization element 25 Upper light absorption type polarization element 26 Liquid Crystal Cell 31 Light Scattering Polarizer 32 Polarizer 33 Scattering Sheet 34 Light Concentrating Film 35 Antireflection Layer 36 λ / 4 Plate

Claims (17)

[Claims] 1. An optical film in which an optically anisotropic discontinuous phase is dispersed inside an optically isotropic continuous phase, wherein the optically anisotropic discontinuous phase has amphiphilic photochemical reactivity. An optical film comprising a compound. 2. The optical film according to claim 1, wherein the photochemically reactive compound is a photocrosslinkable compound. 3. The optical film according to claim 1, wherein the photochemically reactive compound is a photoisomerizable compound. 4. A photochemically reactive compound represented by the following formula (Pc):
The optical film of claim 1 having in represented by photochemically reactive ^{groups: (Pc) -Y 1 = Y} 2 -Ar [ wherein, Y ¹ and Y ² each independently met N or CR And R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; and Ar is an aromatic group]. 5. The optical film according to claim 1, wherein the photochemically reactive compound has an anionic group as a hydrophilic group. 6. The photochemically reactive compound has 6 carbon atoms.
2. The optical film according to claim 1, which has the above hydrocarbon group as a hydrophobic group. 7. The optical film according to claim 4, wherein the photochemically reactive compound is a compound represented by the following formula (I): (I) Hy-L ¹ (-Hb-L ² -Pc) _n [ Wherein Hy is a hydrophilic group; L ¹ is a single bond or an (n + 1) -valent linking group; Hb is a divalent hydrophobic group; L ² is a divalent linking group Pc is a photoreactive group represented by the formula (Pc);
Is 1 or 2. 8. The optical film according to claim 4, wherein the photochemically reactive compound is a copolymer having a repeating unit represented by the following formula (II) and a repeating unit represented by the following formula (III): ^{_{II) -CH 2 -CR 1 (-Hy}} ) - (III) -CH 2 -CR 2 (-L 2 -Pc) - [ wherein, Hy is an hydrophilic group; R ¹ and R ^2,
L is each independently a hydrogen atom or methyl;
² is a divalent linking group; and Pc is a photochemically reactive group represented by the formula (Pc)]. 9. The optical film according to claim 1, wherein the optically anisotropic discontinuous phase further contains a liquid crystalline compound. 10. The optical film according to claim 1, wherein the optically anisotropic discontinuous phase is formed by a polymerization reaction of a liquid crystalline compound having a polymerizable group. 11. A polarizing element having, on a transparent support, an anisotropic scattering layer that substantially scatters one of two linearly polarized lights whose polarizing planes are orthogonal to each other and substantially transmits the other.
The anisotropic scattering layer comprises an optically isotropic continuous phase and an optically anisotropic discontinuous phase, and the optically anisotropic discontinuous phase contains an amphiphilic photochemically reactive compound. Polarizing element. 12. The difference between the refractive indices at the interface between the optically isotropic continuous phase and the optically anisotropic discontinuous phase is 0.05 or more on the axis that scatters the linearly polarized light most strongly.
4. The polarizing element according to item 1. 13. The method according to claim 1, wherein the difference in refractive index at the interface between the optically isotropic continuous phase and the optically anisotropic discontinuous phase is less than 0.05 on the axis at which the transmittance of linearly polarized light is maximized. 1
2. The polarizing element according to 1. 14. A step of emulsifying or dispersing an optically anisotropic phase containing an amphiphilic photochemically reactive compound and a liquid crystalline compound having a polymerizable group in an optically isotropic continuous phase; Applying the resulting emulsion or dispersion onto a transparent support; irradiating linearly polarized light to orient the liquid crystal compound; and irradiating ultraviolet light to polymerize the liquid crystal compound in this order. Method for manufacturing a polarizing element. 15. The production method according to claim 14, wherein the linearly polarized light used in the step of aligning the liquid crystal compound is ultraviolet light, and has a different wavelength from the ultraviolet light used in the step of polymerizing the liquid crystal compound. 16. A light-scattering type polarizing element that substantially scatters one of two linearly polarized lights whose polarization planes are orthogonal to each other and substantially transmits the other, and one of two linearly polarized lights whose polarization planes are orthogonal to each other. Is substantially transmitted, and a light absorbing polarizing element that substantially absorbs the other is a laminated polarizing plate,
The light scattering type polarizing element comprises an optically isotropic continuous phase and an optically anisotropic discontinuous phase, and the optically anisotropic discontinuous phase contains an amphiphilic photochemically reactive compound. Polarizing plate. 17. A liquid crystal display device comprising a backlight, a polarizing plate, a liquid crystal cell, and a polarizing plate laminated in this order, wherein the polarizing plate between the backlight and the liquid crystal cell has polarizing planes orthogonal to each other. A light-scattering type polarization element that substantially scatters one of the two linearly polarized lights and substantially transmits the other, and substantially transmits one of two linearly polarized lights whose polarization planes are orthogonal to each other and substantially transmits the other. A polarizing plate in which a light-absorbing polarizing element that absorbs light is laminated, and a light-scattering polarizing element is composed of an optically isotropic continuous phase and an optically anisotropic discontinuous phase,
A liquid crystal display device, wherein the optically anisotropic discontinuous phase contains an amphiphilic photochemically reactive compound.