JP2005265896A - Optical laminated body and luminance improvement film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical laminated body having a liquid crystal layer having a prescribed orientation which is uniformly manufactured at a low cost, a method of manufacturing thereof, a luminance improvement film using the optical laminated body, a polarization light source apparatus and a liquid crystal display. <P>SOLUTION: The luminance improvement film includes: an optical lamination (broad band circular polarization separation film) having a liquid crystal layer having a structure in which a spiral pitch of the liquid crystal layer is gradually varied in the thickness direction by applying a liquid crystal composition including a chemical compound having a fluoro-alkyl group on a transparent base material and applying a chemical reaction irradiation; a phase difference element having Rth defined by the equation Rth=ä(nx+ny)/2-nz}×d (where nx and ny represent refractive indecis in two directions which are perpendicular to the thickness direction and orthogonal to each other, respectively, nx>ny, nz represents the refractive index in the thickness direction, and d represents the film thickness); and a 1/4λ wavelength plate. The polarization light source apparatus and the liquid crystal display are provided with the luminance improvement film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical laminate having a liquid crystal layer whose orientation is controlled on a transparent substrate, a method for producing the same, a brightness enhancement film using the optical laminate, a polarized light source device, and a liquid crystal display device.

  In recent years, various devices including a small and compact liquid crystal display device have become more popular than CRT display devices. For example, there is a great market need for downsizing various devices including consumer devices such as personal computers and video cameras. Specifically, there are a wide range of downsized portable devices called laptop computers or cameras with LCD monitors. It has become popular. In these devices, it is indispensable to have a liquid crystal display device, and there is a strong demand for high performance and high performance such as color display and high brightness. Accordingly, there are increasing demands on the performance, productivity, and manufacturing cost of optical films such as polarizing plates, viewing angle compensation films, broadband quarter-wave plates, and brightness enhancement films used in liquid crystal display devices.

In addition to a retardation film that controls the polarization state of light used for display, a brightness enhancement film for increasing brightness during display is known as an optical film. As the brightness enhancement film, a film having a polarization separation film for separating incident light into transmitted light and reflected light according to the polarization state is currently used.
As the polarization separation film, a linear polarization separation film in which many anisotropic polymer layers are laminated, a circular polarization separation film using a cholesteric liquid crystal layer, and the like are known. Among these, the former linearly polarized light separating layer has a problem that it is necessary to stack several hundred anisotropic layers and is very expensive. The latter circularly polarized light separating film has a liquid crystal layer having a structure in which rod-like liquid crystal molecules or liquid crystalline groups of side chain type liquid crystalline polymers are twisted in the thickness direction about a helical axis parallel to the layer normal. Then, by utilizing the selective reflection characteristic, the circularly polarized light rotated left and right is separated into transmitted light and reflected light. However, when this selective reflection layer is formed using liquid crystal, the selective reflection wavelength range of this selective reflection layer is about several tens of nanometers and cannot be used as a brightness enhancement film as it is. Therefore, in order to perform circularly polarized light separation over the entire visible light region, it is necessary to widen the reflection band in the visible region.
As a broadening method, a method of providing a plurality of liquid crystal layers having different reflection bands as disclosed in Patent Document 1, and a chiral monomer and a nematic monomer mixture having different reactivities as disclosed in Patent Document 2, respectively. Applying a broadband selective reflection layer by applying a chemical action such as ultraviolet ray or X-ray with a profile that changes the intensity and then gradually changing the helical pitch of the cholesteric liquid crystal layer in the thickness direction. Attempts have been made to form. However, the present situation is that both methods still have problems regarding productivity and cost.

JP-A-8-271731 JP-A-6-281814

The present invention has been made in view of such problems of the prior art, and is an optical laminate having a liquid crystal layer in a specific alignment state, which can be produced uniformly and at low cost, a method for producing the same, and an optical laminate comprising the optical laminate. It is an object to provide a brightness enhancement film to be used, a polarized light source device, and a liquid crystal display device.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors applied a liquid crystal composition containing a compound having a fluorinated alkyl group on a transparent substrate, and then irradiated with a chemical action to produce a liquid crystal. It has been found that a liquid crystal layer having a structure in which the spiral pitch of the layer is gradually changed in the thickness direction can be formed easily and reliably, and the present invention has been completed.

Thus, according to the present invention,
(1) An optical laminate having a liquid crystal layer in which the helical pitch of liquid crystal molecules continuously changes on a transparent substrate, wherein the liquid crystal layer contains a compound having a fluorinated alkyl group. Optical laminates,
(2) The optical laminate according to (1), wherein the compound having a fluorinated alkyl group is a terminal fluorinated alkyl group-containing polymer,
(3) The optical laminate according to (1) or (2), wherein the compound having a fluorinated alkyl group has an optically active site at least in part.
(4) The optical layered body according to any one of (1) to (3), wherein the liquid crystal layer is a cholesteric layer,
(5) The optical lamination according to any one of (1) to (4), comprising a step of applying a liquid crystal coating liquid containing at least a compound having a fluorinated alkyl group, a liquid crystal compound, and a solvent on a transparent substrate. Body manufacturing method,
(6) The optical laminate according to any one of (1) to (5), the formula Rth = {(nx + ny) / 2−nz} × d (where nx and ny are perpendicular to the thickness direction) The refractive index in two directions orthogonal to each other, nx> ny, nz represents the refractive index in the thickness direction, and d represents the film thickness.) Rth defined by −20 nm to −1000 nm A brightness enhancement film comprising a phase difference element and a quarter-wave plate;
(7) A polarized light source device comprising the brightness enhancement film according to (6),
as well as,
(8) A liquid crystal display device comprising the polarized light source device according to (7) and further including a liquid crystal cell thereabove is provided.

  By applying a liquid crystal composition containing a compound having an alkyl fluoride group on a transparent substrate, a liquid crystal layer having a structure in which the helical pitch of the liquid crystal layer is gradually changed in the thickness direction is easily and reliably formed. As a result, it has become possible to produce a broadband circularly polarized light separating film uniformly and efficiently. By integrating this broadband circularly polarized light separation film, a retardation element having a specific Rth, and a quarter-wave plate, it becomes possible to produce a brightness enhancement film with good viewing angle characteristics that balances performance and cost. .

  Hereinafter, the present invention will be described in detail by dividing it into 1) an optical laminate, 2) a brightness enhancement film, 3) a polarized light source device, and 4) a liquid crystal display device.

1) Optical laminate The optical laminate of the present invention has a liquid crystal layer in which the helical pitch of liquid crystal molecules continuously changes on a transparent substrate, and the liquid crystal layer contains a compound having a fluorinated alkyl group. It is characterized by being.

1-1) Liquid Crystal Layer Since the liquid crystal layer constituting the optical laminate of the present invention can realize a wide reflection band, it is formed of a cholesteric layer, and the helical pitch of the compound continuously changes in the thickness direction. Has the structure.
A cholesteric layer is a state in which liquid crystal molecules aligned in one direction form a layer, and the liquid crystal molecular layers are sequentially stacked with the alignment direction slightly shifted for each adjacent liquid crystal molecular layer, forming a spiral structure The helical pitch refers to the thickness of the molecular layer when the orientation direction of the molecular layer is rotated 360 degrees. In this case, the continuously changed structure is as follows: I) a liquid crystal layer in which the spiral pitch changes with a certain regularity in the thickness direction of the liquid crystal layer, and II) the thickness of the liquid crystal layer in the spiral pitch. It is a liquid crystal layer that irregularly changes in direction.

The liquid crystalline compound used in the liquid crystal layer of the optical layered body of the present invention is not particularly limited and is appropriately selected according to the target alignment state. For example, a rod-like liquid crystal compound, a disk-like liquid crystal compound, a polymer liquid crystal and the like can be mentioned.
Examples of the rod-like liquid crystal compound include compounds represented by the formula (I).
Formula (I): R1-B1-A1-B3-M-B4-A2-B2-R2
In formula (I), R1 and R2 represent a reactive group. Specific examples of the reactive groups R1 and R2 include (r-1) to (r-15) shown in the following chemical formula 1, but are not limited thereto. B1, B2, B3 and B4 each independently represent a single bond or a divalent linking group. In addition, at least one of B3 and B4 is preferably —CO—O—.
A1 and A2 represent a spacer group having 2 to 20 carbon atoms. Examples of the spacer group include a polymethylene group and a polyoxymethylene group. The number of carbon atoms contained in the structural unit forming the spacer group is appropriately determined depending on the chemical structure of the mesogenic group, and is generally 0 to 20, preferably 2 to 12, in the case of a polymethylene group. In the case of a group, it has 0 to 10 carbon atoms, preferably 1 to 3 carbon atoms.
M represents a mesogenic group. The material for forming the mesogenic group M is not particularly limited, but azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.

  Examples of the discotic liquid crystalline compound include various documents (for example, C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); Liquid Crystal Handbook Editorial Committee, Liquid Crystal Handbook, Chapter 2, Section 2.1.1 (2000) The thing which introduce | transduced the connection group similar to what was mentioned by the above-mentioned rod-shaped liquid crystalline compound, a spacer group, and a polymeric group can be used for a thing.

The polymer liquid crystal is not particularly limited, and various types can be used. For example, those described in Liquid Crystal Handbook, Liquid Crystal Handbook Editorial Committee, Chapter 3, Section 3.8 (2000) can be used, and a conjugated linear atomic group imparting liquid crystal orientation ( Various types such as a liquid crystal polymer in which a mesogen) is introduced into the main chain of the polymer and a liquid crystal polymer of a type in which the mesogen is introduced into a side chain of the polymer can be used. Among these, a side chain type polymer liquid crystal is preferable from the viewpoint of alignment uniformity.
As the liquid crystal polymer in which mesogen is introduced into the main chain of the polymer, a polyester system or polyamide having a structure in which a mesogenic group composed of a para-substituted cyclic compound or the like is bonded directly or via a spacer portion imparting flexibility as necessary. And polymers such as polycarbonate, polyester imide and the like.
In addition, as a liquid crystal polymer in which mesogen is introduced into the side chain of the polymer, the main chain skeleton is polyacrylate, polymethacrylate, polysiloxane, polymalonate, etc., and a spacer part composed of a conjugated atomic group as a side chain as necessary Having a low molecular crystal compound (mesogen part) composed of a para-substituted cyclic compound, etc., a nematic liquid crystal polymer containing a low molecular chiral agent, a liquid crystal polymer incorporating a chiral component, a mixed liquid crystal polymer of nematic and cholesteric, etc. Is mentioned.
In addition, para-substituted cyclic compounds that impart nematic orientation such as para-substituted aromatic units and para-substituted cyclohexyl units such as azomethine, azo, azoxy, ester, biphenyl, phenylcyclohexane, and bicyclohexane. Cholesteric orientation can also be obtained by introducing an appropriate chiral component composed of a compound having an asymmetric carbon, a low molecular chiral agent or the like into a compound having an asymmetric carbon (JP-A-55-21479). U.S. Pat. No. 5,332,522). Here, examples of the terminal substituent at the para position in the para-substituted cyclic compound include a cyano group, an alkyl group, and an alkoxyl group.
Examples of the spacer portion include a polymethylene chain and a polyoxymethylene chain. The number of carbon atoms contained in the structural unit forming the spacer portion is appropriately determined depending on the chemical structure of the mesogen portion, and is generally 0 to 20, preferably 2 to 12 in the case of a polymethylene chain. In the case of a chain, the carbon number is 0 to 10, preferably 1 to 3.

  Examples of a method for producing a polymer of a type in which mesogen is introduced into the polymer main chain include a method in which component monomers are polymerized by radical polymerization, cationic polymerization, anionic polymerization, or the like. In addition, as a method of producing a polymer of a type in which mesogen is introduced into the side chain of the polymer, a mesogenic group is introduced into a vinyl monomer such as an ester of acrylic acid or methacrylic acid, directly or through a spacer portion as required. A method of polymerizing a monomer obtained by radical polymerization or the like, a method of adding a vinyl-substituted mesogenic monomer in the presence of a platinum-based catalyst via a Si-H bond of polyoxymethylsilylene, and a functional group imparted to the main chain polymer. A method of introducing a mesogenic group through an esterification reaction using a phase transfer catalyst, a method of subjecting a mesogenic group to a part of malonic acid via a spacer group, if necessary, and a polycondensation reaction, etc. Can be mentioned.

In order to continuously change the spiral pitch of the cholesteric layer of the liquid crystal layer in the thickness direction of the liquid crystal layer, the compound concentration that does not form a spiral in the thickness direction of the liquid crystal layer is continuously increased in the thickness direction of the liquid crystal layer. Or by changing the concentration of the chiral agent continuously in the thickness direction of the liquid crystal layer.
In the present invention, when a liquid crystal coating liquid containing a compound having a fluorinated alkyl group is applied on a substrate, the surface free energy at the air interface is minimized because the critical surface tension of the fluorinated alkyl group is low. A driving force works, the compound moves to the air interface, and a structure in which the concentration distribution of the compound having a fluorinated alkyl group continuously changes in the thickness direction of the coating film can be formed. At that time, when the compound having a fluorinated alkyl group is a compound that does not form a helix, the compound shows an effect of inhibiting the helix pitch, and as a result, the helix pitch continuously changes in the thickness direction of the coating film. Can be formed.
The compound having a fluorinated alkyl group is not particularly limited as long as it is a compound having a carbon-fluorine bond. Specific examples thereof include a fluorine-containing surfactant, a polymer of a fluorine-containing olefin compound, and a terminal fluorinated alkyl group-containing polymer which is a polymer using a fluoroalkaloyl peroxide as a polymerization initiator.

As the fluorine-containing surfactant, any of cationic, anionic and nonionic surfactants can be used and is not particularly limited. However, anionic surfactants are preferred from the viewpoint of availability. As the fluorine-containing anionic surfactant, compounds represented by the following formulas (1) to (4) are preferable.
Formula (1): Rf-Q-COOM
Equation (2): Rf-Q- SO 3 M
Equation (3): Rf-Q- OSO 3 M
Formula (4): (Rf-QO) _d PO (OM) _3-d
In the formulas (1) to (4), Rf is a group in which one or more hydrogen atoms of the alkyl group are substituted with fluorine atoms, and M is an atom or compound having a cation structure such as a hydrogen atom, sodium atom or ammonium. Indicates. The Rf group preferably has 2 to 20 carbon atoms, particularly preferably 4 to 16 carbon atoms. When the carbon number is in the above range, good compatibility with the liquid crystal compound is maintained. The Rf group has a linear structure or a branched structure, and a linear structure is preferable. In the case of a branched structure, it is preferable that the branched portion is present at the terminal portion of the Rf group and the branched portion is a short chain having about 1 to 4 carbon atoms. The Rf group may contain a halogen atom other than the fluorine atom. As another halogen atom, a chlorine atom is preferable. Furthermore, an etheric oxygen atom or a thioetheric sulfur atom may be inserted between the carbon-carbon bonds in the Rf group. Examples of the structure of the terminal portion of the Rf group include —CF ₂ CF ₃ , —CF (CF ₃ ) ₂ , —CF ₂ H, —CFH ₂ , —CF ₂ Cl, and the like, —CF ₂ CF ₃ is preferred. The number of fluorine atoms in the Rf group is expressed by [(number of fluorine atoms in the Rf group) / (number of hydrogen atoms contained in the corresponding alkyl group having the same carbon number as the Rf group)] × 100 (%) 60% or more is preferable, and 80% or more is particularly preferable. The Rf group is preferably a perfluoroalkyl group (hereinafter referred to as “RF group”) which is a group in which all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms. Further, the RF group is preferably a straight-chain RF group, that is, a group represented by F (CF ₂ ) _i — (i is an integer of 2 to 20), and particularly a group in which i is an integer of 4 to 16. preferable.

In the above formulas (1) to (4), Q is a single bond or a divalent organic group, and — (CH ₂ ) _{p + q} −, — (CH ₂ ) _p O (CH ₂ ) _q —, —CF═ _{CH (CH 2) p -,} - (CH 2) p CONH (CH 2) q -, - (CH 2) p OCONH (CH 2) q -, - (CH 2) p SO 2 NR (CH 2) q _{-, - (CH 2) p} NHCONH (CH 2) q -, - (CH 2) p CH (OH) (CH 2) q - and the like are preferable. However, R shows a hydrogen atom or an alkyl group. Moreover, p and q show an integer greater than or equal to 0, respectively, and p + q is an integer of 1-22. Of _{these, - (CH 2) p +} q -, - (CH 2) p CONH (CH 2) q -, - (CH 2) p SO 2 NR (CH 2) q - and it is, and, q is 2 or more It is preferable that p + q is 2 to 6. In particular, — (CH ₂ ) _{p + q} − when p + q is 2 to 6, that is, a dimethylene group, a trimethylene group, a pentamethylene group, or a hexamethylene group is preferable.
Specific examples of the Rf group are given below. In the following examples, structural isomer groups that are different groups having the same molecular formula are included, and C ₄ F ₉ , C ₅ F ₁₁ , C ₆ F ₁₃ , C ₇ F ₁₅ , C ₈ F ₁₇ , C ₉ F ₁₉ , C ₁₀ F ₂₁ , C ₁₂ F ₂₅ , C ₁₄ F ₂₉ , C ₁₆ F ₃₃ , H (CF ₂ ) t, Cl (CF ₂ ) _t (t is an integer of 2 to 20), (CF ₃ ) ₂ CF (CF ₂ ) _j (j is an integer of 1 to 17).
Specific examples of the case where the Rf group is a group in which an etheric oxygen atom or a thioetheric sulfur atom is inserted between carbon-carbon bonds include F (CF ₂ ) ₅ OCF (CF ₃ ), F [CF (CF _{3) CF 2 O] rCF (} CF 3) CF 2 CF 2, F [CF (CF 3) CF 2 O] z CF (CF 3), F [CF (CF 3) CF 2 O] z CF 2 CF 2 , F (CF ₂ CF ₂ CF ₂ O) _z CF ₂ CF ₂ , F (CF ₂ CF ₂ O) _w CF ₂ CF ₂ , C ₈ F ₁₇ SO ₂ N (CH ₃ ), C ₈ F ₁₇ SO ₂ N (C ₂ H ₅ ) and the like. However, r is an integer of 1-5, z is an integer of 1-6, w is an integer of 1-9.

Specific examples of the fluorine-containing surfactant of the above formula (1) include C ₇ F ₁₅ COOH, C ₇ F ₁₅ COONH ₄ , C ₉ F ₁₉ COOH, C ₉ F ₁₉ COONH ₄ , C ₈ F ₁₇ CH _{2. COOH, C 10 F 21 CH 2} COOH, C 8 F 17 CH 2 CH 2 OCH 2 CH 2 COOH, C 10 F 21 CH 2 CH 2 OCH 2 CH 2 COOH, C 8 F 17 SO 2 N (CH 3) ( CH ₂ ) ₂ OCH ₂ CH ₂ COOH and the like.
Specific examples of compound 2 include C ₈ F ₁₇ SO ₃ Na, C ₈ F ₁₇ SO ₃ H, C ₈ F ₁₇ SO ₃ NH _{4 and the} like. Specific examples of compound 3 include C ₈ F ₁₇ CH _{2 CH 2 OSO 3 H, C 10} F 21 CH 2 CH 2 OSO 3 H, C 8 F 17 CH 2 CH 2 OSO 3 Na, C 10 F 21 CH 2 CH 2 OSO 3 Na, C 8 F 17 SO 2 N ( CH ₃ ) (CH ₂ ) ₂ OSO ₃ H and the like.
Specific examples of the compound _{4, C 8 F 17 CH 2 CH} 2 OPO (OH) 2, C 10 F 21 CH 2 CH 2 OPO (OH) 2, (C 8 F 17 CH 2 CH 2 O) 2 PO ( _{OH), (C 10 F 21} CH 2 CH 2 O) 2 PO (OH), C 8 F 17 CH 2 CH 2 OPO [ON (CH 2 CH 2 OH) 2] 2, C 10 F 21 CH 2 CH 2 _{OPO [ON (CH 2 CH 2} OH) 2] 2, (C 8 F 17 CH 2 CH 2 O) 2 PO [ON (CH 2 CH 2 OH) 2], (C 10 F 21 CH 2 CH 2 O) ₂ PO [ON (CH ₂ CH ₂ OH) ₂ ] and the like.
In addition, the fluorine-containing surfactant may be composed of a mixture of two or more.

The polymer of a fluorine-containing olefin compound is a polymer which contains a fluorine-containing olefin compound in a repeating unit, and can be obtained by performing a polymerization reaction in the presence of a polymerization initiator such as an azo or organic peroxide.
Examples of the fluorine-containing olefin compound include a fluorine-containing vinyl ether compound, a fluorine-containing allyl ether compound, a fluorine-containing vinyl ester compound, and a fluorine-containing (meth) acrylate compound.
As a fluorine-containing olefin compound, the compound part represented by Formula (5) and Formula (6) is mentioned.
Formula (5): CX ¹ X ² = CX ³ X ⁴
Formula (6): CX ¹ X ² = CX ³ Rf
In the formula, X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom, a fluorine atom or a chlorine atom. Rf is Rf described above, preferably an Rf group containing no etheric oxygen atom or thioetheric sulfur atom, and more preferably an RF group.
Specific examples of the olefin compound represented by the formula (5) include tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, 1-chloro-1,2-difluoroethylene, 1, Examples include 1-dichloro-2,2-difluoroethylene.
Specific examples of the compound represented by the formula (6) include hexafluoropropene, 1,1,3,3,3-pentafluoropropene, 2,3,3,3-tetrafluoropropene, 1,1,2, -Trifluoropropene, 3,3,3-trifluoropropene, hexafluoroisobutene and the like.

As a fluorine-containing vinyl ether compound part, the compound represented by Formula (7) is mentioned.
Formula (7): CX ¹ ₂ = CX ² -O-Rf
In formula (7), X ¹ and X ² each independently represent a hydrogen atom or a fluorine atom. Rf is Rf described above, preferably an Rf group containing no etheric oxygen atom or thioetheric sulfur atom, and more preferably an RF group.
Specific examples of the compound represented by the formula (7) include 1,1,1-trifluoroethyl vinyl ether, perfluoroethyl vinyl ether, 2,2-difluoroethyl vinyl ether, tetrafluoroethyl vinyl ether, perfluoroethyl vinyl ether, 2 , 2,3,3-tetrafluoropropyl vinyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl vinyl ether, 2,2,3,3,4,4,5,5,6 6,7,7,8,8,9,9-hexadecafluorononyl vinyl ether and the like.

As a fluorine-containing allyl ether compound, the compound represented by Formula (8) is mentioned.
Formula (8): CX ¹ ₂ = CX ^2- (CX ³ ₂ -O-Rf)
In the formula, X ¹ , X ² and X ³ each independently represent a hydrogen atom or a fluorine atom. Rf is Rf described above, preferably an Rf group containing no etheric oxygen atom or thioetheric sulfur atom, and more preferably an RF group.
Specific examples of the compound represented by the formula (8) include 1,1,1-trifluoroethyl allyl ether, perfluoroethyl allyl ether, 2,2-difluoroethyl allyl ether, tetrafluoroethyl allyl ether, perfluoro Ethyl allyl ether, 2,2,3,3-tetrafluoropropyl allyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl allyl ether, 2,2,3,3,4, 4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononylallyl ether and the like.

Examples of the fluorine-containing vinyl ester compound include a compound represented by the formula (9).
Equation ^{(9): CX 1 CX 2} = CX 3 - (- O-CO-Rf)
In formula (9), X ¹ , X ² and X ³ each independently represent a hydrogen atom or a fluorine atom. Rf is Rf described above, preferably an Rf group containing no etheric oxygen atom or thioetheric sulfur atom, and more preferably an RF group.
Specific examples of the compound represented by the formula (9) include vinyl trifluoroacetate and vinyl perfluoroacetate.

Examples of the fluorine-containing (meth) acrylate compound include a compound represented by the formula (10).
Equation _{(10): CH 2 = CRCOO} -Rf
In formula (10), R represents a hydrogen atom or a methyl group. Rf is Rf described above, preferably an Rf group containing no etheric oxygen atom or thioetheric sulfur atom, and more preferably an RF group.
Specific examples of the compound represented by the formula (10) include (meth) acrylic acid-2,2,2-trifluoroethyl, (meth) acrylic acid-2,2,3,3,3-pentafluoropropyl. , (Meth) acrylic acid-2,2,3,3,4,4,4-heptafluorobutyl, (meth) acrylic acid-2,2,3,3,4,4,5,5,5-nona Fluoropentyl, (meth) acrylic acid-2,2,3,3,4,4,5,5,6,6,6-undecafluorohexyl, (meth) acrylic acid-2,2,3,3 4,4,5,5,6,6,7,7,7-tridecafluoroheptyl, (meth) acrylic acid-2,2,3,3,4,4,5,5,6,6,7 , 7,8,8,8-pentadecafluorooctyl, (meth) acrylic acid-3,3,4,4,5,5,6,6,7,7,8 8,8-tridecafluorooctyl, (meth) acrylic acid-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10 , 10-nonadecafluorodecyl, (meth) acrylic acid-3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadeca Fluorodecyl, (meth) acrylic acid-2-trifluoromethyl-3,3,3-trifluoropropyl, (meth) acrylic acid-3-trifluoromethyl-4,4,4-trifluorobutyl, (meth) 1-methyl-2,2,3,3,3-pentafluoropropyl acrylate, 1-methyl-2,2,3,3,4,4,4-heptafluorobutyl (meth) acrylate, etc. Can be mentioned.

The fluorine-containing olefin compound polymer may be a copolymer of the above-described compound and a radically polymerizable compound not having fluorine.
The fluorine-containing olefin compound polymer is preferably a terminal fluorinated alkyl group-containing polymer from the viewpoint of the orientation of the fluorinated alkyl group and the compatibility with the liquid crystal molecules. As a terminal fluorinated alkyl group-containing polymer, a desired polymerizable component can be obtained by performing a polymerization reaction using, for example, a fluoroalkaloyl peroxide represented by the following formula (11).
Equation ^{(11): Rf 1 -CO-} O-O-CO-Rf 2
Rf ¹ and Rf ² in formula (11) are a C 1-25 fluoroalkyl group which may be interrupted by an oxygen atom. In this case, the fluoroalkyl group may be linear or branched, and is preferably a perfluoroalkyl group represented by — (CF ₂ ) _m F (m = 1 to 15), or CF (CF ₃ ) O ( A perfluoroalkyl group represented by CF ₂ CF (CF ₃ ) O) _n C ₃ F ₇ (n = 0 to 6) can be given. Specific examples of Rf ¹ include -CF ₃ , -C ₂ F ₅ , -C ₃ F ₇ , -C ₆ F _13, and -C ₇ F _15, etc. -C _q F _{2q + 1} (q = 1 to 10) is the fluoroalkyl _{group; -CF (CF 3) OC 3} F 7, -CF (CF 3) [OCF 2 CF (CF 3)] OC 3 F 7, and _{-CF (CF 3) [OCF 2} CF (CF _3)], etc. ₂ OC ₃ groups represented by F ₇ or the like (group containing oxy fluoroalkylene group and fluoroalkyl groups).
Specific examples of the fluoroalkanoyl peroxide represented by the formula (11) include diperfluorobutyryl peroxide, diperfluoro-2-methyl-3-oxahexanoyl peroxide, and diperfluoro-2,5-dimethyl peroxide. -3,6-dioxanonanoyl etc. are mentioned.

The polymerizable component used in the terminal fluorinated alkyl group-containing polymer is not particularly limited as long as it has radical polymerizability, and various olefin compounds can be used.
Specific examples of the radical polymerizable component include the aforementioned fluorine-containing olefin compound, olefin compound, vinyl ether compound, allyl ether compound, vinyl ester compound, (meth) acrylic acid compound, and (meth) acrylamide compound.

In the method for producing a terminal fluorinated alkyl group-containing polymer, the charged molar ratio in reacting the fluoroalkanoyl peroxide 11 with the polymerizable component is 1 / perfluoroalkanoyl peroxide 11 / polymerizable component from the viewpoint of productivity. A range of (0.1 to 5000) is preferable, and a range of 1 / (0.5 to 1000) is particularly preferable. Moreover, the molecular weight of the terminal fluorinated alkyl group-containing polymer obtained by adjusting the charged molar ratio of the fluoroalkanoyl peroxide 11 can be adjusted. That is, if the charged molar ratio of fluoroalkanoyl peroxide 11 is increased, a polymer having a low molecular weight can be obtained. If the charged molar ratio of fluoroalkanoyl peroxide 11 is decreased, a polymer having a high molecular weight can be obtained.
In the method for producing a terminal fluorinated alkyl group-containing polymer, the fluoroalkanoyl peroxide 11 and the specific polymerizable component can be reacted at normal pressure, and the reaction temperature is − from the viewpoint of productivity. The range of 20 to + 150 ° C. is preferred, the range of 0 to 100 ° C. is particularly preferred, and the reaction time is preferably in the range of 30 minutes to 20 hours, particularly preferably in the range of 1 to 10 hours.
In the method for producing a terminal fluorinated alkyl group-containing polymer, by reacting the fluoroalkanoyl peroxide 11 with the polymerizable component, the desired terminal fluorinated alkyl group-containing polymer can be obtained directly by a one-step reaction. However, it is preferable to use a solvent in order to handle and react the fluoroalkanoyl peroxide 11 more smoothly. As the solvent, a halogenated aliphatic solvent is particularly preferable, and specifically, for example, methylene chloride, chloroform, 2-chloro-1,2-dibromo-1,1,2-trifluoroethane, 1,2-dibromo. Hexafluoropropane, 1,2-dibromotetrafluoroethane, 1,1-difluorotetrachloroethane, 1,2-difluorotetrachloroethane, fluorotrichloromethane, heptafluoro-2,3,3-trichlorobutane, 1,1,1 , 3-tetrachlorotetrafluoropropane, 1,1,1-trichloropentafluoropropane, 1,1,2-trichlorotrifluoroethane, 1,1,1,2,2-pentafluoro-3,3-dichloropropane 1,1,2,2,3-pentafluoro-1,3-dichloropropane, etc. In particular, industrially, 1,1,1,2,2-pentafluoro-3,3-dichloropropane, 1,1,2,2,3-pentafluoro-1,3-dichloropropane, 1, Examples include 1,2-trichlorotrifluoroethane. When the solvent is used, the concentration of fluoroalkanoyl peroxide 11 in the solvent is preferably 0.5 to 30% by weight based on the entire solution.

From the viewpoint of effectively and continuously changing the helical pitch of the liquid crystal layer, it is preferable that at least a part of the compound having a fluorinated alkyl group has an optically active site. When the compound having a fluorinated alkyl group has an optically active site, the compound exhibits the characteristics of a chiral agent, and the helical pitch of the cholesteric layer can be effectively formed. By applying a liquid crystal coating liquid containing the compound on a substrate, the compound moves to the air interface, and the concentration distribution of the compound having a fluoroalkyl group continuously changes in the thickness direction of the coating film. Can be formed. At that time, since the compound having a fluorinated alkyl group has the characteristics of a chiral agent, the obtained liquid crystal layer forms a structure in which the concentration distribution of the chiral agent continuously changes in the thickness direction of the coating film. As a result, a structure in which the helical pitch continuously changes in the thickness direction of the coating film can be effectively formed.
The compound having a fluorinated alkyl group having an optically active site is not particularly limited as long as the structure contains a part of the optically active site. A surfactant having an optically active site, an optically active site A copolymer of an olefin compound having fluorine and a fluorine-containing olefin compound, a polymer obtained by polymerizing an olefin compound having an optically active site using fluoroalkaloyl peroxide, or an optically active site using fluoroalkaloyl peroxide And a copolymer of an olefin compound having a hydrogen atom and another monomer having radical polymerization activity. Specific examples of the olefin compound having an optically active site include compounds having an asymmetric carbon described in JP-A-8-36164 and JP-A-2002-69107, JP-A-2003-207642, JP-A-2003-207644, and the like. And compounds having axial asymmetry described in 1.
The amount of the optically active site in the case where the compound having a fluorinated alkyl group having an optically active site is a polymer is not particularly limited, but from the viewpoint of effectively forming the helical pitch of the cholesteric layer, the optically active site is selected. The repeating unit is preferably 80 to 100 mol%, more preferably 90 to 100 mol%.

As a compound having a fluorinated alkyl group having an optically active site, a compound having a fluorinated alkyl group exhibits liquid crystallinity, or the compound is a compound in order to avoid a change in phase transition temperature due to the addition of the compound. When it is a polymer, a polymer of a compound in which the repeating unit exhibits liquid crystallinity, or a polymer of a compound having a substituent having liquid crystallinity in the side chain of the repeating unit is preferable. The fluorine content is preferably from 0.5 to 40% by weight, more preferably from 2 to 30% by weight, more preferably from 5 to 20%, from the viewpoint of surface alignment of the compound and compatibility with the liquid crystal compound. More preferably, it is% by weight. The fluorine content can be measured by a known method. For example, it can be determined by a potassium carbonate capsule decomposition method, a pyrohydration combustion method, or the like.
The molecular weight of the compound having a fluorinated alkyl group used for the liquid crystal layer is not particularly limited, but from the viewpoint of compatibility with the liquid crystal compound, the number average molecular weight is preferably 500 to 9,000, and 2,000 to 8,000. More preferably, 3,000 to 7,000 can be measured by gel permeation chromatography (GPC) as a method for measuring the molecular weight of a compound having a fluorinated alkyl group.
The amount of the compound having a fluorinated alkyl group used in the liquid crystal layer can be appropriately adjusted depending on the effect of forming the helical pitch of the cholesteric layer. From the viewpoint of cost, it is usually 0.001 to 50% by weight, preferably 0.01 to 20% by weight, more preferably 0.5 to 5% by weight, based on the solid content of the coating solution.

The liquid crystal layer used in the optical laminate of the present invention may contain a chiral agent as necessary. The chiral agent is not particularly limited, and conventionally known agents can be used. Examples thereof include a chiral monomer described in JP-A-6-281814, a chiral agent described in JP-A-8-209127, and a photoreactive chiral compound described in JP-A-2003-131187.
Further, as the chiral agent, in order to avoid an unintended change of the phase transition temperature due to the addition of the chiral agent, a chiral agent that exhibits liquid crystallinity is preferable. Furthermore, from the viewpoint of economy, a material having a large HTP defined by HTP = 1 / P · c, which is an index representing the efficiency of twisting the liquid crystal compound, is preferable. Here, P represents the helical pitch length of the cholesteric phase, and c represents the concentration of the chiral agent.

The liquid crystal layer used in the present invention may contain a surfactant other than the above if necessary. The surfactant is used to adjust the surface tension of the coating liquid and the liquid crystal layer before polymerization. The surfactant is not particularly limited, and a commercially available one can be used, but the use of a nonionic surfactant is preferable. Among these, the use of a nonionic surfactant which is an oligomer having a molecular weight of about several thousand is particularly preferable.
The liquid crystal layer used in the present invention may contain an alignment regulator as necessary. The alignment regulator is for controlling the alignment state of the air side surface of the liquid crystal layer formed on the substrate. The alignment regulator may also serve as the surfactant. The alignment regulator is not particularly limited, and various types can be used depending on the target alignment state. Examples thereof include resins such as polyvinyl alcohol, polyvinyl butyral, and modified products thereof.

The liquid crystal layer used in the present invention can be used by laminating a plurality of liquid crystal layers having different selective reflection center wavelengths.
The thickness of the liquid crystal layer (the total thickness in the case where the liquid crystal layer is composed of a plurality of layers) is based on the viewpoints such as prevention of disorder of alignment and reduction of transmittance, and the wide range of selective reflection wavelength range (reflection wavelength range). Therefore, it is usually 1 to 50 μm, preferably 2 to 30 μm, more preferably 2 to 10 μm. Moreover, when it has a support base material, the total thickness including the base material is 20-200 micrometers normally, Preferably it is 25-150 micrometers, More preferably, it is 30-100 micrometers.

1-2) Transparent base material The transparent base material used for this invention will not be specifically limited if it is an optically transparent base material, For example, a transparent resin film, a quarter wavelength plate, a negative letterer, a positive letterer, etc. And a phase difference element, a glass substrate, and the like. From the viewpoint of productivity, a long transparent resin film is more preferable. The transparent resin film may be a single-layer film or a multi-layer film in which a plurality of films are laminated, but preferably has a thickness of 1 mm and a total light transmittance of 80% or more.

The resin material of the transparent resin film includes a polymer resin having an alicyclic structure, a chain olefin polymer such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, poly Examples include ether sulfone, amorphous polyolefin, modified acrylic polymer, and epoxy resin. These can be used alone or in combination of two or more. Among these, a polymer resin or a chain olefin polymer having an alicyclic structure is preferable, and a polymer resin having an alicyclic structure from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like. Is more preferable.
The polymer resin having an alicyclic structure has an alicyclic structure in the repeating unit of the polymer resin, and a polymer resin having an alicyclic structure in the main chain and an alicyclic structure in the side chain. Any of the polymer resins having 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 proportion of the repeating unit having an alicyclic structure in the polymer resin having an alicyclic structure is appropriately selected depending on the purpose of use, but is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90%. % By weight or more. When there are too few repeating units having an alicyclic structure, the heat resistance of the film may be reduced.
Specifically, the polymer resin having an alicyclic structure includes (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, and (4) vinyl. Examples thereof include alicyclic hydrocarbon polymers and hydrogenated products thereof. Among these, norbornene-based polymers are more preferable from the viewpoints of transparency and moldability.
Specific examples of the norbornene-based polymer include ring-opening polymers of norbornene-based monomers, ring-opening copolymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization, and hydrogenated products thereof, norbornene-based polymers Examples include addition polymers of monomers and addition copolymers with other monomers copolymerizable with norbornene-based monomers. Among these, from the viewpoint of transparency, a ring-opening polymer hydrogenated product of a norbornene-based monomer is most preferable.
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 resin material of the transparent resin film suitably used in the present invention is preferably 80 ° C. or higher, more preferably 100 to 250 ° C. A substrate made of a transparent resin having a glass transition temperature in such a range is excellent in durability without causing deformation or stress in use at high temperatures.
The molecular weight of the resin material of the transparent resin film suitably used in the present invention is a weight average molecular weight (Mw) measured by GPC using cyclohexane (toluene when the polymer resin is not dissolved) as a solvent, and is usually 10,000. To 100,000, preferably 25,000 to 80,000, more preferably 25,000 to 50,000. When the weight average molecular weight is in such a range, the mechanical strength and moldability of the film are highly balanced and suitable.
The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the resin material of the transparent resin film suitably used in the present invention is not particularly limited, but is usually 1.0 to 10.0, preferably 1.0. It is -4.0, More preferably, it is the range of 1.2-3.5.

The polymer resin having an alicyclic structure suitably used in 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. Hereinafter, it is more preferably 2% by weight or less. When the amount of the oligomer component is large, when the resin laminate is stretched, fine convex portions are generated on the surface or thickness unevenness is caused, resulting in poor surface accuracy. 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, 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 GPC using cyclohexane (toluene if the polymer resin does not dissolve). The thickness of the transparent substrate used in the present invention is not particularly limited, but the material cost, thickness and weight are reduced. In view of the above, the thickness is usually 1-1000 μm, preferably 5-300 μm, more preferably 30-150 μm.
In addition, the transparent substrate used in the present invention is preferably subjected to surface treatment in advance. By performing the surface treatment, the adhesion between the transparent substrate and the alignment film described later can be enhanced. Examples of the surface treatment include glow discharge treatment, plasma discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, and flame treatment. In addition, it is also preferable to provide an adhesive layer (undercoat layer) on the transparent support in order to enhance the adhesion between the transparent substrate and the alignment film described later.

It is preferable to provide an alignment film for aligning the liquid crystal compound on the surface of the transparent substrate. The alignment film can be formed by means such as rubbing treatment of an organic compound, oblique vapor deposition of an inorganic compound, formation of a micro group, or accumulation of an organic compound by a Langmuir-Blodgett method. In addition, an alignment film in which an alignment function is generated by application of an electric field or a magnetic field or light irradiation can be provided. Among these, the alignment film formed on the transparent substrate is preferably formed by applying a polymer and rubbing it from the viewpoint of enabling continuous treatment. The rubbing treatment can be performed by rubbing the surface of the polymer layer with a cloth in a certain direction.
The polymer used for forming the alignment film is not particularly limited, and a polymer corresponding to the type of liquid crystal compound to be used and the desired alignment can be appropriately selected. The alignment film preferably has a polymerizable group for the purpose of imparting adhesion between the liquid crystal compound and the substrate. The thickness of the alignment film is usually 0.001 to 50 μm, preferably 0.01 to 5 μm, more preferably 0.05 to 1 μm.

1-3) Method for Producing Optical Laminate The method for producing an optical laminate of the present invention comprises a step of applying a liquid crystal coating liquid containing at least a compound having a fluorinated alkyl group, a liquid crystal compound, and a solvent on a transparent substrate. Have.

In the production method of the present invention, the transparent substrate and the liquid crystal coating liquid are a compound having a fluorinated alkyl group, a liquid crystal compound and a solvent as essential components, and as the compound having a fluorinated alkyl group and the liquid crystal compound, the aforementioned compounds are used. be able to.
As the solvent for the liquid crystal coating solution used in the production method of the present invention, an organic solvent is preferable. The organic solvent is not particularly limited, and ketones, halogenated hydrocarbons, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, ethers, and the like can be used. These may be used alone or in combination of two or more. Among these, in consideration of environmental load, it is preferable to use ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

The liquid crystal coating liquid used in the production method of the present invention may contain a chiral agent, a surfactant, an alignment regulator or a polymerization initiator as necessary. The compound mentioned above can be used as a chiral agent, surfactant, and orientation adjusting agent.
The polymerization initiator can be suitably used when a liquid crystal compound having a polymerizable reactive group is used. As the polymerization initiator, either a thermal polymerization initiator or a photopolymerization initiator can be used. Use of a photoinitiator is preferred because the polymerization reaction is rapid. Examples of the photopolymerization initiator include polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), oxadiazole compounds (described in US Pat. No. 4,212,970), α-carbonyl compounds ( U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in U.S. Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin compound (as described in U.S. Pat. No. 2,722,512) ), Combinations of triarylimidazole dimers and p-aminophenyl ketone (described in US Pat. No. 3,549,367), acridine and phenazine compounds (described in Japanese Patent Application Laid-Open No. 60-105667, US Pat. No. 4,239,850) ) And the like. The usage-amount of a polymerization initiator is 0.001 to 50 weight% normally with respect to solid content of a liquid-crystal coating liquid, Preferably it is 0.01 to 20 weight%, More preferably, it is 0.5 to 5 weight%.
The method for applying the liquid crystal layer coating liquid on the transparent substrate is not particularly limited, and spin coating method, roll coating method, flow coating method, printing method, dip coating method, casting film forming method, bar coating method, gravure printing. A known coating method such as a method can be employed.

In the production method of the present invention, since the basic structure of the liquid crystal phase (the spiral structure of the cholesteric phase itself) is maintained as much as possible, the liquid crystal coating solution is applied on a transparent substrate and then fixed. Is preferred.
As a method for immobilization, the type of polymerizable group, a method in which the number of polymerizable groups per molecule is adjusted is used as a liquid crystalline compound, and it is fixed by heating or light irradiation. Examples include a method of fixing by heating or light irradiation using a mixture with a crystalline liquid crystal, and a method of fixing by rapidly cooling when a predetermined alignment state is obtained using a polymer liquid crystal. Among these, from the viewpoint of productivity, a method using light irradiation is preferable, and a method using ultraviolet rays is more preferable. The light irradiation energy is usually 1 mJ / cm ^{2 to} 50 J / cm ² , preferably 1 mJ / cm ^{2 to} 800 mJ / cm ² .

  The shape of the optical laminate of the present invention is not particularly limited, but is preferably a film. As described below, the film-shaped optical laminate of the present invention is useful as a raw material for producing a brightness enhancement film and a liquid crystal display device.

2) Brightness-enhancing film The brightness-enhancing film of the present invention comprises an optical laminate in which a liquid crystal layer having a desired alignment state is formed on a transparent substrate, and a formula: Rth = {(nx + ny) / 2-nz} × d ( In the formula, nx and ny represent refractive indexes in two directions perpendicular to each other perpendicular to the thickness direction, and nx> ny, nz represents the refractive index in the thickness direction, and d represents the film thickness. It includes a retardation element whose Rth is defined to be −20 nm to −1000 nm and a quarter-wave plate.
Moreover, the optical laminated body mentioned above can be utilized as a brightness enhancement film by combining with a quarter wavelength plate.

2-1) Phase difference element The phase difference element used for the brightness enhancement film of the present invention has substantially no in-plane retardation, and the formula: Rth = {(nx + ny) / 2−nz} × d ( In the formula, nx and ny represent refractive indexes in two directions perpendicular to each other perpendicular to the thickness direction, and nx> ny, nz represents the refractive index in the thickness direction, and d represents the film thickness. Rth defined is in the range of −20 nm to −1000 nm, preferably −50 nm to −500 nm. The retardation element having Rth in such a range has a function of compensating for a phase difference of light incident obliquely on the quarter wavelength plate from the light source side.
In the retardation element used in the brightness enhancement film of the present invention, the relationship between the main refractive indexes nx, ny and nz (nx, ny and nz are the same as described above) is nz> nx, nz> ny, nx≈ It is necessary to satisfy ny. The retardation element may be composed of a plurality of layers. When this retardation element is composed of a plurality of layers, the main refractive index of each layer may be different, and the refractive index of the entire element only needs to satisfy the above relationship. This main refractive index can be measured by an automatic birefringence meter (for example, “KOBRA series” manufactured by Oji Scientific Instruments). Note that nx≈ny means that the refractive index difference is usually within 0.0002, preferably within 0.0001, and more preferably within 0.00005.
The in-plane retardation Re defined by the formula: Re = (nx−ny) × d (nx, ny and d are as defined above) of the retardation element used in the brightness enhancement film of the present invention is Usually, it is 20 nm or less, preferably 10 nm or less, more preferably 5 nm or less.
Examples of the retardation element having such optical characteristics include a layer including a layer obtained by stretching and orientation of a material having at least a negative intrinsic birefringence value (hereinafter, sometimes referred to simply as a negative material). be able to.

Here, a material having a negative intrinsic birefringence value refers to a material having a characteristic that exhibits optically negative uniaxiality when molecules are oriented in a uniaxial order. Materials with negative intrinsic birefringence values include discotic liquid crystals, discotic liquid crystal polymers, aromatic vinyl polymers, polyacrylonitrile polymers, polymethacrylate polymers, cellulose ester polymers, and multiple elements of these structural units. (Binary, ternary, etc.) copolymers and the like. These can be used alone or in combination of two or more. Among these, at least one selected from an aromatic vinyl polymer, a polyacrylonitrile polymer, and a polymethyl methacrylate polymer is preferable. Of these, aromatic vinyl polymers are more preferable from the viewpoint of high birefringence.
An aromatic vinyl polymer is a homopolymer of an aromatic vinyl monomer, a copolymer of two or more of these, or a copolymer of an aromatic vinyl monomer and a monomer copolymerizable therewith. Refers to a polymer. Examples of the aromatic vinyl monomer include styrene; styrene derivatives such as 4-methylstyrene, 4-chlorostyrene, 3-methylstyrene, 4-methoxystyrene, 4-tert-butoxystyrene, and α-methylstyrene; It is done. Two or more of these may be used in combination.
Examples of monomers copolymerizable with the aromatic vinyl monomer include olefin compounds such as propylene, butene, and vinyl chloride; acrylonitrile; (meth) acrylate compounds such as (meth) acrylic acid or methyl (meth) acrylate; Maleic anhydride; maleimide; vinyl acetate; and the like. Among these, from the viewpoint of high heat resistance, a copolymer of styrene and / or a styrene derivative and maleic anhydride is preferable.
The glass transition temperature TgA of the material having negative intrinsic birefringence is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint of durability.

  As a retardation element, a film or sheet made of a material having a negative intrinsic birefringence value is uniaxially stretched or unbalanced biaxially stretched, and the stretching directions (directions in which the refractive index is maximum or minimum) are orthogonal to each other. Two layers laminated, or a balanced biaxially stretched (stretched so that the refractive index is substantially equal in any direction in the plane) can be used as a single layer. In particular, from the viewpoint of mechanical strength and the like, a layer (B layer) made of a transparent resin material is used on at least one side of a layer (A layer) obtained by stretching and orientation of the negative material. From the viewpoint of preventing warpage due to moisture absorption, temperature change, or change over time, a layer (B layer) made of a transparent resin material on both sides of a layer (A layer) made of a material having a negative intrinsic birefringence value. ) Are more preferably laminated.

The transparent resin material used here is not particularly limited as long as it has a thickness of 1 mm and a total light transmittance of 80% or more. For example, the same materials as those described above can be used as the transparent base material of the optical layered body in the present invention.
Although the thickness of the layer (B layer) which consists of transparent resin materials is not specifically limited, Usually, 15-250 micrometers, Preferably it is 25-150 micrometers.
The material having the negative intrinsic birefringence value and / or the transparent resin material may include an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and a dispersant as necessary. , Chlorine scavengers, flame retardants, crystallization nucleating agents, antiblocking agents, antifogging agents, mold release agents, pigments, dyes, organic or inorganic extenders, neutralizing agents, lubricants, decomposition agents, metal deactivators Well-known additive components such as antifouling agents, antibacterial agents, other resins, and thermoplastic elastomers can be added as long as the effects of the present invention are not impaired. The addition amount of these additives is usually 0 to 20% by weight, preferably 0 to 10% by weight, and more preferably 0 to 5% by weight with respect to the resin material.

The retardation element used in the present invention has an adhesive layer (C layer) between a layer (A layer) made of a material having a negative intrinsic birefringence value and a layer (B layer) made of a transparent resin material. It may be provided. The adhesive layer (C layer) can be formed from a material having an affinity for both the material having a negative intrinsic birefringence value used for the A layer and the transparent resin material used for the B layer. Examples thereof include vinyl acetate-based, polyvinyl alcohol-based, polyvinyl acetal-based, vinyl chloride-based, acrylic-based, polyamide-based, polyethylene-based, and cellulose-based pressure-sensitive adhesives or adhesives. Among these, a vinyl acetate-based pressure-sensitive adhesive or adhesive and an acrylic pressure-sensitive adhesive or adhesive are preferable. A copolymer of ethylene and vinyl acetate is preferred as the main component in the vinyl acetate pressure-sensitive adhesive or adhesive. As the main component in the acrylic pressure-sensitive adhesive or adhesive, a copolymer of ethyl acrylate, butyl acrylate, -2-ethylhexyl acrylate, and the like with methacrylic acid ester, styrene, acrylonitrile, vinyl acetate, or the like is preferable. .
Among the adhesive and pressure-sensitive adhesive, a pressure-sensitive adhesive or adhesive having a glass transition temperature lower than the stretching temperature is preferable from the viewpoint of birefringence, and in particular, the transparent resin material, and the negative intrinsic birefringence value. A pressure-sensitive adhesive or adhesive having a glass transition temperature lower by 5 ° C. or more is more preferable, and a pressure-sensitive adhesive or adhesive having a temperature lower by 20 ° C. or higher is particularly preferable.
Although the thickness of an adhesive bond layer (C layer) is not specifically limited, Preferably it is 1-50 micrometers, More preferably, it is 5-30 micrometers.

A method for producing the retardation element is not particularly limited, but a layer (B layer) made of a transparent resin material is not laminated on at least one side of a layer (A layer) made of a material having a negative intrinsic birefringence value. A method of obtaining a stretched laminate and stretching it uniaxially or biaxially is preferable.
As a method for obtaining an unstretched laminate, a coextrusion T die method, a coextrusion inflation method, a coextrusion molding method such as a coextrusion lamination method, a film lamination molding method such as dry lamination, and a base resin film A known method such as a coating molding method for coating a resin solution can be appropriately used. Among these, from the viewpoint of production efficiency and the like, a molding method by coextrusion is preferable. The extrusion temperature may be appropriately selected according to the material having a negative intrinsic birefringence value, a transparent resin material, and the type of adhesive used as necessary.
There is no restriction | limiting in particular in the method of extending | stretching the said unstretched laminated body, A conventionally well-known method may be applied. Specifically, a uniaxial stretching method such as a method of uniaxial stretching in the longitudinal direction using the difference in peripheral speed on the roll side, a method of uniaxial stretching in the lateral direction using a tenter, etc .; At the same time as stretching in the longitudinal direction, use the simultaneous biaxial stretching method that stretches in the transverse direction according to the spread angle of the guide rail or the longitudinal direction using the difference in peripheral speed between the rolls, and then grip the both ends of the clip And a biaxial stretching method such as a sequential biaxial stretching method of stretching in the transverse direction using a tenter. A biaxial stretching method is preferred in order to balance the refractive index in the plane direction and to make the in-plane retardation substantially zero.

Although the stretching temperature is not particularly limited, when the retardation element has the laminated structure, the glass transition temperature Tg _A of a material having a negative intrinsic birefringence is (Tg _A −30) ° C. to (Tg _A +60) ° C. More preferably, the range is (Tg _A −10) ° C. to (Tg _A +50) ° C., and more preferably (Tg _A −5) ° C. to (Tg _A +15) ° C. By setting the stretching temperature in the above range, refractive index anisotropy can be made difficult to develop in the B layer during stretching, and the relationship between the target in-plane orthogonal axis direction and the refractive index in the thickness direction can be easily achieved. Can be obtained.
The draw ratio is usually 1.01 to 30 times, preferably 1.01 to 10 times, and more preferably 1.01 to 5 times. If the draw ratio is out of the above range, the orientation may be insufficient, the refractive index anisotropy and thus the retardation may be insufficiently developed, or the laminate may be broken.

2-2) 1/4 wavelength plate The 1/4 wavelength plate used in the present invention is not particularly limited as long as it gives a phase difference of 1/4 wavelength to incident light. Is preferred. Here, the broadband quarter-wave plate is a quarter-wave plate whose retardation is almost ¼ wavelength in the entire visible light region including wavelengths of 410 to 660 nm.
The quarter-wave plate used in the present invention includes at least one layer (D layer) made of a material having a positive intrinsic birefringence value and a layer (E layer) made of a material having a negative intrinsic birefringence value. And having the same orientation direction of molecular chains in the D layer and the E layer are preferable.

The material having a positive intrinsic birefringence value constituting the D layer refers to a material having optically positive uniaxial characteristics when molecules are oriented in a uniaxial order. Examples of the material having a positive intrinsic birefringence value include a rod-like liquid crystal, a rod-like liquid crystal polymer, a polymer resin having an alicyclic structure, an olefin polymer, a polyester polymer, a polyarylene sulfide polymer, and polyvinyl alcohol. Polymer, polycarbonate polymer, polyarylate polymer, cellulose ester polymer, polyethersulfone polymer, polysulfone polymer, polyallylsulfone polymer, polyvinyl chloride polymer, or these Examples thereof include multi-component (binary, ternary, etc.) copolymers of structural units. These can be used alone or in combination of two or more.
In the present invention, among these, it is preferable to use a polymer resin or an olefin polymer having an alicyclic structure. From the viewpoint of light transmittance characteristics, heat resistance, dimensional stability, photoelastic characteristics, and the like, The use of a polymer resin having a cyclic structure is more preferable. As the polymer resin having an alicyclic structure used here, the same resin as described above can be used as the material for the transparent substrate of the optical laminate in the present invention. The glass transition temperature of the polymer resin having an alicyclic structure may be appropriately selected according to the purpose of use, but is preferably 80 ° C. or higher, more preferably 100 to 250, from the viewpoint of obtaining excellent optical properties. ° C, more preferably in the range of 120-200 ° C.

  Moreover, as a material which has a negative intrinsic birefringence value which comprises a (E) layer, use of an aromatic vinyl type polymer is preferable. Examples of the aromatic vinyl polymer include the same ones listed in the retardation element.

  The method for producing a quarter-wave plate used in the present invention is not particularly limited. For example, (i) a D layer and an E layer are separately formed, and dry lamination is performed through an adhesive layer (F layer). Examples include a method of laminating to form a laminate, and (ii) a method of forming a laminate by coextrusion to obtain a laminate. Among these, the film forming method by the co-extrusion method (ii) is preferable because a laminate having a high delamination strength can be obtained and the production efficiency is excellent. Specifically, a method of obtaining a laminate by a coextrusion method is to extrude a material having a positive intrinsic birefringence value and a material having a negative intrinsic birefringence value from a multilayer die using a plurality of extruders. Thus, a film is formed.

As necessary, the quarter wave plate used in the present invention includes an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, a dispersant, a chlorine scavenger, a flame retardant, Crystallization nucleating agent, antiblocking agent, antifogging agent, release agent, pigment, dye, organic or inorganic extender, neutralizing agent, lubricant, decomposition agent, metal deactivator, antifouling agent, antibacterial agent and Other additives such as other resins and thermoplastic elastomers can be added as long as the effects of the present invention are not impaired. The addition amount of these additives is usually 0 to 20% by weight, preferably 0 to 10% by weight, and more preferably 0 to 5% by weight with respect to the resin material.
In order to laminate a layer made of a material having a positive intrinsic birefringence value (D layer) and a layer made of a material having a negative intrinsic birefringence value (E layer) with the slow axes orthogonal to each other, the molecular chain of each layer It is sufficient to make the orientation directions of the same. That is, since the quarter wave plate is a laminate of layers (D layer and E layer) made of materials having different intrinsic birefringence values, the stretching direction of the D layer and the E layer should be matched. The slow phases of the two phases can inevitably be orthogonal.

Such a quarter-wave plate can be manufactured by stretching a laminate composed of a material having a positive intrinsic birefringence value and a material having a negative intrinsic birefringence value. There is no restriction | limiting in particular in the method of extending | stretching a laminated body, A conventionally well-known method is employable. Examples of the stretching method include a method of uniaxial stretching in the longitudinal direction using a difference in peripheral speed on the roll side, and a method of uniaxial stretching in the lateral direction using a tenter. Among these, uniaxial stretching in the longitudinal direction is preferable. Although there is no restriction | limiting in particular in the draw ratio of uniaxial stretching, it is preferable that it is 1.1 to 3.0 times, and it is more preferable that it is 1.2 to 2.2 times. If the draw ratio is out of the above range, the orientation may be insufficient, the refractive index anisotropy and thus the retardation may be insufficiently developed, or the laminate may be broken.
The temperature at which the laminate is stretched is preferably (Tg-30) ° C to (Tg + 60) ° C, more preferably (Tg + 60) ° C, where Tg is the glass transition temperature of the resin constituting the D layer and E layer. The temperature range is from Tg-10) ° C to (Tg + 50) ° C. By setting the stretching temperature within the above range, a target retardation can be easily obtained.
In addition, when the laminate is manufactured by the above-described coextrusion method, operations such as cutting out a stretched film chip and pasting the cut chip, which are necessary when manufacturing a conventional quarter-wave plate, are performed. Is not necessary, and a long quarter-wave plate can be continuously produced by a so-called roll-to-roll method.

The quarter-wave plate is particularly limited to the layer structure as long as it has at least one D layer and at least one E layer, and the optical layered body has the same molecular chain orientation in the D layer and the E layer. However, it is preferable to have a layer structure of D layer / E layer / D layer or E layer / D layer / E layer. Further, an F layer (adhesive layer) is further provided between the D layer and the E layer. For example, a three-layer structure of D layer-F layer-E layer, or D layer-F layer-E layer-F layer A five-layer structure of -D layer or E layer-F layer-D layer-F layer-E layer can be employed. About the adhesive which comprises the said F layer, the thing similar to what was listed in the said phase difference element can be used.
The thickness of the quarter-wave plate can be appropriately determined according to the purpose of use. From the viewpoint of obtaining a homogeneous stretched film by a stable stretching treatment, the thickness is preferably 10 to 300 μm, more preferably 30 to 200 μm.

  In the present invention, in addition to the above-described broadband quarter-wave plate, a half-wave plate and a quarter wavelength described in JP-A-5-100114, JP-A-11-231132, etc. A laminate of plates or a broadband retardation film WRF (manufactured by Teijin Ltd.) can also be suitably used.

The brightness enhancement film of the present invention includes the optical laminate having the liquid crystal layer described above, the retardation element described above, and a quarter wavelength plate.
An example of the layer structure of the brightness enhancement film of the present invention is shown in FIG. In FIG. 1, 1 is an optical laminate, 2 is a phase difference element, and 3 is a quarter-wave plate. For example, as shown in FIG. 2, the brightness enhancement film 10 shown in FIG. 1 can be used by sequentially arranging the light source A, the diffusion plate 4, the brightness enhancement film 10, the prism sheet 5, and the polarizing plate 6. The light beam L emitted from the light source A is converted into diffused light having a uniform distribution by passing through the diffusion plate 4. Next, the light beam incident on the brightness enhancement film 10 is separated into circularly polarized light having different rotational directions, circularly polarized light in one rotational direction is transmitted, and circularly polarized light in the other rotational direction is reflected. The transmitted circularly polarized light is converted into linearly polarized light parallel to the transmission axis of the polarizing plate 6 by the quarter wavelength plate 3. On the other hand, the reflected circularly polarized light is depolarized by the depolarizing action of the diffusing plate 4 and then emitted again to the diffusing plate side for reuse by the reflecting plate B disposed on the back side of the light source A. As a result, the light emitted from the light source can be effectively used, and the display luminance can be improved.
The brightness enhancement film shown in FIG. 1 can be manufactured, for example, as follows. First, an alignment film is formed on a transparent substrate, a liquid crystal composition containing a compound having a fluorinated alkyl group is applied on the alignment film, and then a chemical action irradiation is performed, whereby the helical pitch of the liquid crystal layer is reduced. An optical laminate having a structure that gradually changes in the thickness direction is formed. Next, the formula: Rth = {(nx + ny) / 2−nz} × d (where nx and ny are perpendicular to each other in the thickness direction) on the optical layered body or through the adhesive layer or the pressure-sensitive adhesive layer. Represents the refractive index in two orthogonal directions, nx> ny, nz represents the refractive index in the thickness direction, and d represents the film thickness.) Rth defined by −20 nm to −1000 nm A retardation element is formed by laminating a retardation film. Next, a desired wavelength enhancement film can be obtained by laminating a quarter wavelength plate directly or via an adhesive layer or a pressure-sensitive adhesive layer on the retardation element.

  By using the brightness enhancement film of the present invention in combination with an appropriate surface light source such as a side light type light guide plate, the reflection circular loss by depolarizing the reflected circularly polarized light by the cholesteric liquid crystal layer and reusing it as the output light is reflected. Can be eliminated. Moreover, absorption loss due to the polarizing plate is prevented by phase-controlling the emitted light through an optical layered body laminated on the cholesteric liquid crystal layer and converting it into a state containing a large amount of linearly polarized light components that are transparent to the polarizing plate. Therefore, the luminance can be improved.

3) Polarized light source device The polarized light source device of the present invention includes the brightness enhancement film of the present invention. The polarized light source device of the present invention includes a light reflection layer, a light source, and the brightness enhancement film of the present invention, and the light emitted from the light source is incident from the cholesteric liquid crystal layer side of the brightness enhancement film and reflected by the brightness enhancement film. The light reflection layer, the light source, and the brightness enhancement film are preferably disposed so that the light reflection layer is reflected by the light reflection layer and reenters the brightness enhancement film.
An example of the layer structure of the polarized light source device in the present invention is shown in FIG. In FIG. 3, C is a light source holder, and D is a light guide plate. The brightness enhancement film 10 includes a cholesteric liquid crystal layer 1, a retardation element 2, and a quarter wavelength plate 3.
The light from the light source A arranged on the side surface enters the light guide plate D and exits upward (the cholesteric liquid crystal layer 1 side). The light incident on the cholesteric liquid crystal layer 1 is transmitted through one of the left and right circularly polarized light, and the other circularly polarized light is reflected and reenters the light guide plate D. The light that re-enters the light guide plate is reflected by the reflective layer B on the lower surface, is incident on the cholesteric liquid crystal layer 1 again, and is separated again into transmitted light and reflected light. Thereby, the effective utilization of the light emitted from the light source A is achieved, and an excellent luminance improvement effect can be obtained. The light source A is not particularly limited, and a conventionally known light source can be used.
As the light guide plate D, a light guide plate having a shape in which the thickness of the side end portion facing the incident surface is thinner than that of the incident surface (wedge type) is preferable. Moreover, the thing of the structure which has the fine prism-shaped convex part from viewpoints, such as being excellent in the output efficiency from an output surface and excellent in the perpendicularity with respect to the output surface and aiming at the effective use of an emitted light, is preferable. The light guide plate D can be formed of a transparent material such as a norbornene polymer, polymethyl methacrylate, polycarbonate, or polystyrene. Further, the reflective layer B can be appropriately formed by, for example, a plating layer, a metal vapor deposition layer, a metal foil, a metal vapor deposition sheet, a plating sheet, or the like. The reflection layer may be integrated with the opposite surface of the light guide plate, or may be formed as a reflection sheet or the like so as to overlap the light guide plate.
Since the polarized light source device of the present invention is provided with the brightness enhancement film of the present invention, it has an excellent brightness enhancement effect and has a wide viewing angle characteristic.

4) Liquid crystal display device The liquid crystal display device of the present invention has the polarized light source device of the present invention, and further includes a liquid crystal cell above it. In general, a liquid crystal display device can be manufactured by combining a liquid crystal cell that functions as a liquid crystal shutter, and accompanying components such as a driving device, a polarizing plate, a backlight, and a retardation plate for compensation as necessary. . The liquid crystal display device of the present invention is not particularly limited except that the optical laminate of the present invention is used, and can be produced by a method according to a conventional method.
An example of the layer structure of the liquid crystal display device according to the present invention is shown in FIG. The liquid crystal display device shown in FIG. 4 uses the polarized light source device of the present invention in a backlight system. In FIG. 4, 7 is a liquid crystal cell, 6a is a lower polarizing plate, 6b is an upper polarizing plate, and 4a and 4b are diffusion plates. The lower polarizing plate 6a and the diffusion plates (4a and 4b) can be omitted.
The liquid crystal mode to be used is not particularly limited. Liquid crystal modes include TN (Twisted Nematic) type, STN (Super Twisted Nematic) type, HAN (Hybrid Alignment Nematic) type, VA (Vertical Alignment Pile), MVA (Multiple Vertical Type). OCB (Optical Compensated Bend) type etc. are mentioned. Moreover, it does not restrict | limit especially as a polarizing plate (6a and 6b), A conventionally well-known thing can be used.
Since the liquid crystal display device of the present invention has the optical layered body of the present invention, it is possible to obtain an excellent brightness improvement effect and to obtain a wide viewing angle characteristic.

  EXAMPLES Next, although an Example demonstrates this invention, this invention is not limited at all.

(Example 1)
[Synthesis of polymer containing terminal fluorinated alkyl group having optically active name moiety]
To a four-necked flask equipped with a condenser, a thermometer, a stirrer, and a dropping funnel, a fluorinated solvent AK-225 (Asahi Glass Co., Ltd., 1,1,1,2,2-pentafluoro-3,3-dichloropropane: 1 , 1,2,2,3-pentafluoro-1,3-dichloropropane = 1: 1.35 (molar ratio) mixed solvent)) 50 parts by weight, reactivity having optical activity of the structure shown below A chiral agent (compound 1, in which * indicates an optically active site) is charged with 5.22 parts by weight, the reaction vessel is adjusted to 45 ° C., and then diperfluoro-2-methyl-3-oxahexanoyl peroxide / 6.58 parts by weight of a 10% by weight solution of AK225 was added dropwise over 5 minutes. After completion of the dropwise addition, the reaction is carried out in a nitrogen stream at 45 ° C. for 5 hours, after which the product is concentrated to 5 ml, reprecipitated with hexane, and dried to contain a terminal fluorinated alkyl group. 3.5 parts by weight of polymer (Compound A) (yield 60%) was obtained. When the molecular weight of the obtained polymer was measured using GPC and THF (tetrahydrofuran) as a developing solvent, Mn = 4,000 (Mw / Mn = 1.77) and the fluorine content was measured to determine the fluorine content. Was 5.89% by weight.

[Production of optical laminate]
A polymer resin having an optically isotropic alicyclic structure having a thickness of 100 μm, a width of 680 mm, and a length of 500 m was used as a transparent support. After performing plasma discharge treatment on both surfaces of this transparent support, an alignment film coating solution consisting of 10 parts by weight of polyvinyl alcohol and 371 parts by weight of water was applied to one side of the transparent support and dried to form an alignment film having a thickness of 1 μm. . Next, a rubbing treatment was performed on the alignment film continuously in a direction parallel to the longitudinal direction of the transparent support.
On the alignment film, 8.2 parts by weight of the liquid crystal compound (compound 2) shown in the following chemical formula 3, 0.3 parts by weight of the photopolymerization initiator (compound 3) shown in the chemical formula 4 below, and the optically active name site previously prepared A liquid crystal coating solution consisting of 1.9 parts by weight of a terminal fluorinated alkyl group-containing polymer (compound A) having 2 mol parts and 24.0 parts by weight of methyl ethyl ketone was applied using a bar coater, dried at room temperature for 10 seconds, and then 100 Heated in an oven at 0 ° C. for 2 minutes (alignment aging), and further irradiated with ultraviolet rays for 30 seconds to produce a circularly polarized light separating layer (B) having a cholesteric liquid crystal layer (A) having a thickness of 5.0 μm. When the cross section of the cholesteric liquid crystal layer (A) was observed with a scanning electron microscope, the cholesteric liquid crystal layer (A) had a structure in which the spiral axis was in the normal direction of the layer and the cholesteric pitch was continuously changed in the thickness direction.

[Production of retardation element]
Styrene-maleic anhydride copolymer (“Dylark D332”, manufactured by Nopa Chemical Co., Tg = 131 ° C.) as a material having a negative intrinsic birefringence value, and norbornene-based resin (trade name: ZEONOR1020, Nippon Zeon Co., Ltd.) as a transparent resin material Manufactured, Tg = 105 ° C.). First, the norbornene-based resin and the styrene-maleic anhydride copolymer in a molten state were respectively stored in the extruders of the extrusion dies in which two extruders were integrally combined with the extrusion die. The extrusion flow path of the extruder storing the norbornene-based resin is branched into two, and the norbornene-based resin extruded from the branched flow path is styrene-maleic anhydride co-polymer extruded from another extruder. The union was sandwiched and a three-layer laminate was formed inside the extrusion die. In addition, a filter is disposed at a communication port to the extrusion die of the two extruders, and the norbornene resin and the styrene-maleic anhydride copolymer are passed through the filter and then extruded into the extrusion die. Thus, a laminate having three structures was obtained. The thickness unevenness of the laminate was measured using a scanning thickness meter. The measurement was performed by continuously scanning in the longitudinal direction of the laminate. The obtained laminate had an average thickness of 300 μm, and the thickness unevenness was 2.5% with respect to the average thickness.
Next, the laminate was sequentially fed into a zone-heated longitudinal uniaxial stretching apparatus and a tenter stretching (transverse uniaxial stretching) apparatus and subjected to sequential biaxial stretching to produce a retardation element (E). The stretching temperature was 140 ° C. for both longitudinal stretching and lateral stretching, and the stretching ratio was 1.8 times for longitudinal stretching and 1.5 times for lateral stretching.
When the average thickness of the obtained retardation element (E) was 120 μm and the refractive index and retardation were measured using an automatic birefringence measuring apparatus KOBRA-21SDH (manufactured by Oji Scientific Instruments), the refractive index in the plane direction was nx. = 1.5732, ny = 1.5731, and the refractive index in the thickness direction was nz = 1.5757. As for retardation, in-plane Re was 10 nm and thickness direction Rth was -300 nm.

[Preparation of quarter wave plate]
Norbornene-based resin (trade name: ZEONOR1420, manufactured by Nippon Zeon Co., Ltd., Tg = 136 ° C.) as a material having a positive intrinsic birefringence value, and styrene-maleic anhydride copolymer (product) as a material having a negative intrinsic birefringence value Name: Dilark D332, manufactured by Nova Chemical Co., Ltd., Tg = 131 ° C.) was used to obtain a laminate having a three-layer structure in the same manner as the retardation element. The thickness unevenness of the laminate was measured using a scanning thickness meter. The measurement was performed by continuously scanning in the longitudinal direction of the laminate. The obtained laminate had an average thickness of 120 μm, and the thickness unevenness was 2.2% with respect to the average thickness.
Next, the laminate was stretched 1.7 times with a longitudinal uniaxial stretching apparatus at 125 ° C., and the retardation was measured using an automatic birefringence measuring apparatus KOBRA-21SDH (manufactured by Oji Scientific Instruments). Broadband quarter-wave plates (F) were obtained in which the ratio of retardation to wavelength at 450 nm, 550 nm, and 650 nm was 0.235, 0.250, and 0.232, respectively.

[Production of brightness enhancement film]
The circularly polarized light separating layer (B) obtained in the example was laminated with the retardation element (E) and the broadband quarter-wave plate (F) prepared in the above order to obtain a brightness enhancement film (G). .

[Production of polarized light source device]
A light-diffusion sheet and a brightness enhancement film (G) are sequentially placed on the light-emitting plate side where a cold cathode tube is arranged on the incident end face side and a light-reflecting sheet is provided on the back side, and the circularly polarized light separating layer is on the diffusion sheet side. The polarizing light source device was manufactured by stacking so as to face the surface.

[Production of liquid crystal display devices]
A polarizing plate, a viewing angle widening film (trade name: WV film, manufactured by Fuji Photo Film Co., Ltd.), a transmissive TN liquid crystal display element, and a polarizing plate are sequentially arranged on the quarter wavelength plate side of the polarized light source device. A liquid crystal display device was produced.

(Comparative Example 1)
A circularly polarized light separating layer (C) was produced in the same manner as in the example, except that the terminal fluorinated alkyl group-containing polymer having an optically active name site in the example was changed to the compound 4 shown in the following chemical formula 5. Furthermore, the retardation element (E) and the broadband quarter-wave plate (F), in which the circularly polarized light separating layer (C) was produced in the example, were laminated in this order to obtain a brightness enhancement film (H). Furthermore, a polarized light source device and a liquid crystal display device were produced by the same operation as in the example using the obtained brightness enhancement film (H).

(Comparative Example 2)
In a four-necked flask equipped with a condenser, a thermometer, a stirrer, and a dropping funnel, 30 parts by weight of toluene, 30 parts by weight of methyl ethyl ketone, and the reactive chiral agent shown in Chemical Formula 2 having optical activity (compound 1, in which * is optical) 10 parts by weight (indicating the active site) were charged, the reaction vessel was adjusted to 45 ° C., and then 6.67 parts by weight of diisobutyl peroxide (Perroyl IB, manufactured by NOF Corporation) / methyl ethyl ketone 10% by weight solution over 5 minutes. It was dripped. After completion of the dropwise addition, the mixture was reacted in a nitrogen stream at 45 ° C. for 5 hours, and then the product was concentrated to 5 ml, reprecipitated with hexane, and dried to obtain 8.6 parts by weight of a chiral agent polymer (Compound B). (Yield 80.6%) was obtained. When the molecular weight of the obtained polymer was measured using GPC and THF (tetrahydrofuran) as a developing solvent, it was Mn = 4,600 (Mw / Mn = 2.01).
Next, a circular fluorination was carried out in the same manner as in the example except that the terminal fluorinated alkyl group-containing polymer (A) having an optically active site in the production of the optical laminate in the example was changed to the chiral agent polymer (B). A polarization separation layer (D) was produced. Furthermore, the phase difference element (E) and the broadband quarter-wave plate (F) in which the circularly polarized light separating layer (D) was produced in the examples were laminated in this order to obtain a brightness enhancement film (I). Furthermore, a polarized light source device and a liquid crystal display device were produced by the same operation as in the Examples using the obtained brightness enhancement film (I).

[Performance comparison]
In the liquid crystal display device obtained by using the brightness enhancement film (G) composed of a liquid crystal layer containing a compound having a fluorinated alkyl group in the liquid crystal layer, good white display was achieved over the entire screen. On the other hand, in the liquid crystal display device obtained by using the brightness enhancement film (H) composed of a liquid crystal layer not containing a compound having a fluorinated alkyl group (H), (I), the entire display surface is colored, Good display was not possible.

It is the schematic which shows the principle and structure of a brightness enhancement film. It is a figure which shows the layer structure of the brightness enhancement film of this invention. It is a figure which shows the structure of the polarized light source device of this invention. It is a figure which shows the structure of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical laminated body, 2 ... Phase difference element, 3 ... 1/4 wavelength plate, 4, 4a, 4b ... Diffusing plate, 5 ... Prism sheet, 6, 6a, 6b ... Polarizing plate, 7 ... Liquid crystal cell, 10 ... Brightness enhancement film, A ... light source, B ... reflector (reflective layer), C ... light source holder, D ... light guide plate

Claims (8)

An optical laminate having a liquid crystal layer in which the helical pitch of liquid crystal molecules continuously changes on a transparent substrate, wherein the liquid crystal layer contains a compound having a fluorinated alkyl group body. 2. The optical laminate according to claim 1, wherein the compound having a fluorinated alkyl group is a terminal fluorinated alkyl group-containing polymer. The optical laminate according to claim 1 or 2, wherein the compound having a fluorinated alkyl group has an optically active site at least in part. The optical layered body according to claim 1, wherein the liquid crystal layer is a cholesteric layer. The manufacturing method of the optical laminated body of any one of Claims 1-4 which has the process of apply | coating the liquid crystal coating liquid containing the compound which has an fluorinated alkyl group at least, a liquid crystal compound, and a solvent on a transparent base material. The optical layered body according to claim 1, the formula Rth = {(nx + ny) / 2−nz} × d (where nx and ny are refractive indexes in two directions perpendicular to the thickness direction and perpendicular to each other) Nx> ny, nz represents the refractive index in the thickness direction, and d represents the film thickness.) Rth defined by -20 nm to -1000 nm, and ¼ wavelength A brightness enhancement film comprising a plate. A polarized light source device comprising the brightness enhancement film according to claim 6. A liquid crystal display device comprising the polarized light source device according to claim 7 and further comprising a liquid crystal cell above the polarized light source device.