JP2009288440A - Retardation film, method for manufacturing retardation film, polarizing plate, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film and a method for manufacturing the film, by which a retardation film satisfying Nz<1 is inexpensively manufactured by stretching a liquid crystal layer having fixed homeotropic alignment, the three-dimensional refractive index distribution of the retardation film is accurately controlled, and problems such as cracks are prevented during stretching a film. <P>SOLUTION: The retardation film is obtained by subjecting a liquid crystal composition showing positive uniaxial property to homeotropic alignment in a liquid crystal state, and then stretching the liquid crystal layer with the homeotropic alignment, as the alignment fixed. The film has a principal refractive index nx1 in the plane of the stretched liquid crystal layer, a refractive index ny1 in a direction orthogonal to nx1 (where nx1≥ny1), a principal refractive index nz1 in the thickness direction, thickness d1, in-plane retardation Re1 and retardation Rth1 in the thickness direction, wherein Nz1 represented by Nz1=Rth1/Re1+0.5 satisfies Nz1<1.0. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a retardation film, a method for producing a retardation film, a polarizing plate provided with the retardation film, and a liquid crystal display device.

An optical film having a refractive index anisotropy plays an important industrial role such as being used for improving the image quality of a liquid crystal display device. Furthermore, with the recent increase in size of liquid crystal display screens and diversification of drive modes, it is very important to control the three-dimensional refractive index distribution for the characteristics required for the retardation film.
The main refractive index in the film plane of the retardation film is nx, the refractive index in the direction orthogonal to nx is ny (however, nx ≧ ny), the main refractive index in the film thickness direction is nz, and the thickness of the film is d, When the in-plane retardation (Re) and the retardation in the thickness direction (Rth) are represented by formulas (a2) and (a3), Nz is defined by formula (a1).
Nz = Rth / Re + 0.5 (a1)
Re = (nx−ny) × d [nm] (a2)
Rth = {(nx + ny) / 2−nz} × d [nm] (a3)
Nz can also be written as in equation (a4).
Nz = (nx-nz) / (nx-ny) (a4)

  In general, a retardation film is a roll of a thermoplastic material that can be obtained at low cost, such as a polycarbonate or cycloolefin polymer, formed by a casting method, a melt extrusion method, or the like, and these thermoplastic polymer films are known as general stretching methods. Although these materials can all be produced by a stretching method or a tenter stretching method, since all of these materials have a positive intrinsic refractive index, all of the retardation films obtained after stretching have a refractive index in the film normal direction that is higher than the refractive index in the film plane. Becomes smaller. That is, these films have Nz ≧ 1 (three-dimensional refractive index relationships are nx = ny> nz, nx> ny> nz, nx> ny = nz). Conversely, a retardation film having a refractive index in the film thickness direction larger than the refractive index in the film plane, that is, a retardation film satisfying Nz <1, is known to be difficult in both materials and production. .

As a retardation film satisfying Nz ≦ 0, a retardation film satisfying nz>nx> ny and nx = nz> ny stretches a thermoplastic film having a negative intrinsic refractive index or has a negative intrinsic refractive index. As a liquid crystal material, it has been proposed that a film in which a disc-shaped liquid crystal material is oriented perpendicularly to a substrate can be produced (Patent Documents 1 and 2).
However, thermoplastic films having a negative intrinsic refractive index are very limited, and polystyrene or the like is known as the material. However, there are many problems in manufacturing such as the film is fragile and easily cut during stretching. In addition, the disk-like liquid crystal material is complicated to synthesize and expensive, and even if it is vertically aligned on the substrate, only a uniaxial film satisfying nx = nz> ny can be produced, and a biaxial film is produced. I can't.

  In addition, a biaxial film satisfying 0 <Nz <1 (that is, nx> nz> ny) is a region that cannot be produced by stretching a material having a positive or negative intrinsic refractive index as a single material. In the biaxial film satisfying Nz = 0.5, the retardation value is almost constant regardless of the viewing angle, and the viewing angle characteristics of the liquid crystal display device are greatly improved by using such a retardation film. If it is known and can be manufactured industrially at low cost, it is very beneficial.

As a method for producing a biaxial film satisfying nx>nz> ny, a heat-shrinkable film is attached to a resin film such as polycarbonate to form a laminate, and the laminate is then stretched. A method of using a film obtained by peeling as a retardation film has been proposed (Patent Document 3).
However, the method described in Patent Document 3 requires a heat-shrinkable film and an adhesive in addition to the polycarbonate film, and there is a problem that it is difficult to produce a retardation film at low cost. In addition, there is a problem that a large amount of peeled heat-shrinkable film becomes industrial waste.

As another method, a film obtained by stretching a thermoplastic polymer film having a relationship of nz> nx≈ny with respect to the refractive indexes nx and ny in the in-plane direction of the film and the main refractive index nz in the thickness direction. A method for use as a retardation film has been proposed (Patent Document 4).
However, in the method described in Patent Document 4, the types of polymer materials that become thermoplastic polymer films having a relationship of nz> nx≈ny by the casting method or the melt extrusion method are limited, and the nx of the film obtained by stretching is limited. And nz and / or ny have a small difference in refractive index, and depending on the retardation value that is important as the performance of the retardation film, the film thickness becomes thick, and it is difficult to satisfy the demand for thin liquid crystal display devices.

As a material satisfying nz> nx = ny, a homeotropic alignment liquid crystal film in which rod-like liquid crystals are generally homeotropically aligned is known, and a liquid crystal material that does not cause defects such as cracks during stretching is selected and homeotropic alignment is performed. If a film on which liquid crystal is fixed can be stretched, a retardation film satisfying Nz <1 that has been difficult to produce can be produced at low cost.
Although a method for stretching a polymer liquid crystal is known (Patent Document 5), Patent Document 5 states that a material having a high degree of alignment can be obtained by simply stretching a nematic liquid crystal that has not been subjected to an alignment treatment. This is merely specified, and there is no description regarding a method for fixing the orientation of the homeotropic alignment liquid crystal layer and a method for stretching the homeotropic alignment liquid crystal layer without causing defects such as cracks during stretching.
JP-A-2005-275104 JP 2006-301614 A JP-A-5-157911 JP 2006-3715 A JP-A-1-70584

  In view of the problems of the prior art, the present invention can produce a retardation film satisfying Nz <1 at low cost by stretching a liquid crystal layer in which homeotropic alignment is fixed. Provided are a retardation film that can accurately control the three-dimensional refractive index distribution of the retardation film and that does not cause defects such as cracks during stretching, a method for producing the retardation film, a polarizing plate, and a liquid crystal display device using the retardation film. For the purpose.

The present inventors have found that the above problem can be solved by stretching a liquid crystal layer in which a specific alignment is fixed, and have completed the present invention.
That is, the present invention is as follows.

[1] A retardation film obtained by subjecting a liquid crystalline composition exhibiting positive uniaxiality to homeotropic alignment in a liquid crystal state and then stretching a homeotropic alignment liquid crystal layer in which the alignment is fixed. The main refractive index in the plane of the liquid crystal layer is nx1, the refractive index in the direction orthogonal to nx1 is ny1 (where nx1 ≧ ny1), the main refractive index in the thickness direction is nz1, and the thickness is d1. Nz1 defined by the formula (A) satisfies Nz1 <1.0 when (Re1) and the retardation in the thickness direction (Rth1) are the formula (A) and the formula (C), respectively. Phase difference film.
Nz1 = Rth1 / Re1 + 0.5 (A)
Re1 = (nx1-ny1) × d1 [nm] (A)
Rth1 = {(nx1 + ny1) / 2−nz1} × d1 [nm] (c)

[2] The retardation film according to [1], wherein the homeotropic alignment liquid crystal layer is composed of a liquid crystalline composition including at least a side chain type liquid crystalline polymer having an oxetanyl group.

[3] The retardation film as described in [1], wherein the homeotropic alignment liquid crystal layer is composed of a liquid crystalline composition comprising at least a low molecular liquid crystal substance having a reactive functional group.

[4] A homeotropic alignment liquid crystal layer in which a liquid crystal composition exhibiting positive uniaxial property is homeotropically aligned in a liquid crystal state and then the alignment is fixed is formed on an alignment film or an adhesive on a thermoplastic polymer film. Is a retardation film obtained by stretching a laminate integrated and laminated via
The in-plane main refractive index of the stretched liquid crystal layer is nx1, the refractive index in the direction orthogonal to nx1 is ny1 (where nx1 ≧ ny1), the main refractive index in the thickness direction is nz1, and the thickness is d1. The in-plane retardation (Re1) and the thickness direction retardation (Rth1) of the liquid crystal layer are defined by the formula (ki) and the formula (ku), respectively.
Re1 = (nx1-ny1) × d1 [nm] (G)
Rth1 = {(nx1 + ny1) / 2−nz1} × d1 [nm]
The in-plane main refractive index of the stretched thermoplastic polymer film is nx2, the refractive index in the direction orthogonal to nx2 is ny2 (where nx2 ≧ ny2), the main refractive index in the thickness direction is nz2, and the thickness is d2. The in-plane retardation (Re2) and the thickness direction retardation (Rth2) of the stretched thermoplastic polymer film are defined by the formula (ke) and the formula (co), respectively.
Re2 = (nx2-ny2) × d2 [nm]
Rth2 = {(nx2 + ny2) / 2-nz2} × d2 [nm] (G)
The total in-plane retardation (total Re) and total thickness direction retardation (total Rth) defined as the sum of Re1 and Rth1 of the stretched liquid crystal layer and Re2 and Rth2 of the thermoplastic polymer film are respectively expressed by the formula (D) When the formula (e) is satisfied, the total Nz value defined by the formula (f) satisfies the total Nz <1.0.
Total Re = Re1 + Re2 (D)
Total Rth = Rth1 + Rth2 (e)
Total Nz = Total Rth / Total Re + 0.5 (f)

[5] The retardation film as described in [4], wherein the thermoplastic polymer film is a cycloolefin resin.

[6] The retardation film as described in [4], wherein the thermoplastic polymer film is a cellulose resin.

[7] (1) First step of forming an alignment layer on the thermoplastic polymer film for forming a homeotropic alignment of a liquid crystalline composition exhibiting positive uniaxiality;
(2) On the alignment layer, a layer of a liquid crystalline composition exhibiting positive uniaxiality is applied, and after homeotropic alignment of the layer, a homeotropic alignment liquid crystal layer having a fixed alignment is formed, A second step of obtaining a laminated film comprising a plastic polymer film / alignment layer / homeotropic alignment liquid crystal layer;
(3) a third step of obtaining a retardation film by stretching a laminated film comprising the thermoplastic polymer film / alignment layer / homeotropic alignment liquid crystal layer;
A method for producing a retardation film, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0.

[8] (1) A layer of a liquid crystalline composition exhibiting positive uniaxiality is applied on an alignment substrate, the layer is homeotropically aligned, and then a homeotropic alignment liquid crystal layer in which the alignment is fixed is formed. A first step of obtaining a laminate (A) comprising an alignment substrate / homeotropic alignment liquid crystal layer,
(2) After adhering the homeotropic alignment liquid crystal layer side of the laminate (A) to the thermoplastic polymer film via the adhesive layer 1, the alignment substrate is peeled off to form the homeotropic alignment liquid crystal layer. A second step of transferring to a thermoplastic polymer film to obtain a laminate (B) comprising a thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer;
(3) A third step of obtaining a retardation film by stretching the laminate (B) comprising the thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer.
A method for producing a retardation film, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0.

[9] (1) A layer of a liquid crystalline composition exhibiting positive uniaxiality is applied on an alignment substrate, the layer is homeotropically aligned, and then a homeotropic alignment liquid crystal layer having a fixed alignment is formed. A first step of obtaining a laminate (A) comprising an alignment substrate / homeotropic alignment liquid crystal layer,
(2) a second step of obtaining a laminate (C) by stretching the laminate (A) comprising the alignment substrate / homeotropic alignment liquid crystal layer;
(3) After the homeotropic alignment liquid crystal layer side of the laminate (C) is bonded to the thermoplastic polymer film via the adhesive layer 1, the alignment substrate / homeotropic alignment liquid crystal layer is bonded to the thermoplastic high-molecular layer. A third step of obtaining a retardation film comprising a thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer after peeling the alignment substrate after transferring to the molecular film;
A method for producing a retardation film, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0.

[10] The method for producing a retardation film as described in any one of [7] to [9], wherein the thermoplastic polymer film is surface-treated.

[11] The method for producing a retardation film as described in [10], wherein the surface treatment is a corona discharge treatment.

[12] The liquid crystal composition according to any one of [7] to [11], wherein the homeotropic alignment liquid crystal layer is composed of a liquid crystalline composition including at least a side chain type liquid crystalline polymer having an oxetanyl group. The method for producing a retardation film.

[13] The position according to any one of [7] to [11], wherein the homeotropic alignment liquid crystal layer is composed of a liquid crystalline composition comprising at least a low-molecular liquid crystal substance having a reactive functional group. A method for producing a phase difference film.

[14] The method for producing a retardation film as described in any one of [7] to [13], wherein the thermoplastic polymer film is a cycloolefin resin.

[15] The method for producing a retardation film as described in any one of [7] to [13], wherein the thermoplastic polymer film is a cellulose resin.

[16] The retardation film according to any one of [1] to [6] is laminated with a polarizing element, and a slow axis of the retardation film and an absorption axis of the polarizing element are parallel to each other. Alternatively, the polarizing plate is arranged orthogonally.

[17] A liquid crystal display device, wherein the polarizing plate according to [16] is arranged on at least one side of a liquid crystal cell.

  In the above description of the layer configuration, “/” represents the interface of each layer, and the same applies hereinafter.

  According to the present invention, a retardation film satisfying Nz <1 can be produced at a low cost, and the three-dimensional refractive index distribution of such a retardation film can be controlled with high accuracy, and defects such as cracks can be produced during stretching. It is possible to obtain a retardation film in which no occurrence occurs.

Hereinafter, the present invention will be described in detail.
The retardation film of the present invention is a retardation film obtained by subjecting a liquid crystalline composition exhibiting positive uniaxiality to homeotropic alignment in a liquid crystal state and then stretching a homeotropic alignment liquid crystal layer in which the alignment is fixed. The main refractive index in the plane of the stretched liquid crystal layer is nx1, the refractive index in the direction orthogonal to nx1 is ny1 (where nx1 ≧ ny1), the main refractive index in the thickness direction is nz1, and the thickness is d1. When the in-plane retardation (Re1) and the retardation in the thickness direction (Rth1) are represented by formulas (A) and (C), Nz1 defined by formula (A) satisfies Nz1 <1.0. A retardation film characterized by the following.
Nz1 = Rth1 / Re1 + 0.5 (A)
Re1 = (nx1-ny1) × d1 [nm] (A)
Rth1 = {(nx1 + ny1) / 2−nz1} × d1 [nm] (c)

  In addition, when the retardation film of the present invention is stretched while the laminated body in which the homeotropic alignment liquid crystal layer and the thermoplastic polymer film are integrated through an adhesive layer or an alignment film is stretched, it is stretched. The total Nz value calculated from the sum of the liquid crystal layer and the thermoplastic polymer film satisfies the total Nz <1.0.

The total Nz value defined here is the in-plane retardation (Re1) and thickness direction retardation (Rth1) of the stretched liquid crystal layer and the in-plane retardation (Re2) and thickness of the stretched thermoplastic polymer film. When the total in-plane retardation (total Re) and total Rth defined as the total value of direction retardation (Rth2) are represented by formula (d) and formula (e), respectively, the value defined by formula (f) It is.
Total Re = Re1 + Re2 (D)
Total Rth = Rth1 + Rth2 (e)
Total Nz = Total Rth / Total Re + 0.5 (f)

Here, the Re1 value and the Rth1 value of the stretched liquid crystal layer are the main refractive index in the plane of the stretched liquid crystal layer nx1, the refractive index in the direction orthogonal to nx1 (where nx1 ≧ ny1), and the thickness. When the main refractive index in the direction is nz1 and the thickness is d1, they are defined by the formula (ki) and the formula (ku), respectively.
Re1 = (nx1-ny1) × d1 [nm] (G)
Rth1 = {(nx1 + ny1) / 2−nz1} × d1 [nm]

The Re2 value and the Rth2 value of the stretched thermoplastic polymer film are the main refractive index in the plane of the stretched thermoplastic polymer film nx2, and the refractive index in the direction perpendicular to nx2 is ny2 (however, nx2 ≧ ny2), where the main refractive index in the thickness direction is nz2 and the thickness is d2, respectively, they are defined by formula (ke) and formula (co), respectively.
Re2 = (nx2-ny2) × d2 [nm]
Rth2 = {(nx2 + ny2) / 2-nz2} × d2 [nm] (G)

The value of Nz1 or total Nz of the retardation film of the present invention is less than 1.0.
The Nz value can also be defined by the above formula (a4). However, since the homeotropic alignment liquid crystal layer that satisfies nz> nx = ny is stretched, the lower limit cannot be defined, but nz> nx = ny is not included. Any material satisfying the following range may be used.
0 <Nz <1 nx>nz> ny
Nz = 0 nz = nx> ny
Nz <0 nz>nx> ny

  The in-plane retardation (Re1) of the liquid crystal layer and the total in-plane retardation (total Re) when integrated with the thermoplastic polymer film are usually 10 nm to 300 nm, preferably 30 nm to 200 nm, more preferably 50 nm to 150 nm. Range. When the Re1 value and the total Re value are out of the above ranges, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

  The thickness direction retardation (Rth1) of the liquid crystal layer and the total thickness retardation (total Rth) when integrated with the thermoplastic polymer film are usually −400 nm to 200 nm, preferably −300 nm to 150 nm, more preferably −200 nm to The range is 100 nm. When the Rth1 value and the total Rth value are out of the above ranges, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

Various materials used in the present invention will be described below.
First, the liquid crystal composition will be described.
The liquid crystalline composition used in the present invention is a liquid crystalline composition exhibiting positive uniaxiality capable of fixing the alignment in a homeotropic alignment state.
As a means for fixing the liquid crystalline composition in the alignment state, in the case of a composition mainly composed of a polymer liquid crystal substance, a method of rapidly cooling from the alignment state to fix it in a vitrified state, a low molecule having a reactive functional group Examples include a method of aligning a liquid crystal substance or a polymer liquid crystal substance and then immobilizing the functional group by reacting (curing, crosslinking, etc.).
Examples of the reactive functional group include a vinyl group, a (meth) acryloyl group, a vinyloxy group, an oxiranyl group, an oxetanyl group, a carboxyl group, a hydroxyl group, an amino group, an isocyanate group, and an acid anhydride group. The reaction is carried out by a method suitable for the above.

  The liquid crystal material that can be used in the liquid crystal composition is selected from a wide range regardless of whether it is a low-molecular liquid crystal material or a high-molecular liquid crystal material, depending on the intended use of the retardation film of the present invention and the performance required for it. A polymeric liquid crystal material is preferred.

  Low molecular liquid crystal substances include saturated benzene carboxylic acids, unsaturated benzene carboxylic acids, biphenyl carboxylic acids, aromatic oxycarboxylic acids, Schiff base types, bisazomethine compounds, azo compounds, azoxy compounds, and cyclohexane ester compounds. A compound having a liquid crystallinity in which the reactive functional group is introduced at the terminal of a group capable of becoming a mesogenic group such as a sterol compound, or a composition in which a crosslinkable compound is added to a compound having liquid crystallinity among the compounds. Can be mentioned.

More specifically, the low-molecular liquid crystal substance is preferably a compound represented by the following formula (X) having a mesogenic group represented by MG.
P- (Sp-X) _n- MG-R (X)
In formula (X), P is the above-mentioned reactive functional group, and when a plurality of P are bonded, they may be the same or different. Sp is a spacer group having 1 to 20 carbon atoms, X is —O—, —S—, —CO—, —COO—, —OCO—, —OCOO— or a single bond, and n is , 0, 1, or 2, MG is a mesogenic group or a mesogenic supporting group, and this group is preferably selected from the group represented by the following formula (Y), and R is 25 An alkyl group having up to 1 carbon atom, which group is unsubstituted or substituted by one or more halogen or cyano groups, one CH ₂ group present in this group Alternatively, two or more non-adjacent CH ₂ groups are also independently of each other such that oxygen atoms are not directly bonded to each other, and —O—, —S—, —NH—, —N (CH ₃ ) -, -CO-, -COO-, -OCO-, -OCO-O- , -S-CO-, -CO-S- or -C≡C-, or R is also a halogen or a cyano group, or independently P- (Sp-X ) _Has one of the meanings indicated for _n −. In addition, when the compound represented by Formula (X) has several P, they may be the same or different.

_{^{- (A 1 -Z 1) m}} -A 2 -Z 2 -A 3 - (Y)
(In the formula (Y), A ¹ , A ² and A ³ are each independently a 1,4-phenylene group, and one or more CH groups present in this group are also represented by N Or a 1,4-cyclohexylene group, in which one CH ₂ group or _two non-adjacent CH ₂ groups are also O and / or Optionally substituted by S, or a 1,4-cyclohexenylene group or a naphthalene-2,6-diyl group, all of which are unsubstituted or one or more than one It may be substituted by halogen, cyano group or nitro group or by alkyl group, alkoxy group or alkanoyl group having 1 to 7 carbon atoms, in which one or more H atoms are F Others may be substituted by Cl, ^{Z l} and ^{Z 2} are each _{independently, -COO -, - OCO -,} - CH 2 CH 2 -, - OCH 2 -, - CH 2 O -, - CH ═CH—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond, and m is 0, 1 or 2.

As the polymer liquid crystal substance, various main chain type polymer liquid crystal substances, side chain type polymer liquid crystal substances, or a mixture (composition) thereof can be used.
Main chain polymer liquid crystal materials include polyester, polyamide, polycarbonate, polyimide, polyurethane, polybenzimidazole, polybenzoxazole, polybenzthiazole, polyazomethine, polyesteramide, polyester carbonate Polymer liquid crystal substances such as polyester and polyesterimide, or mixtures thereof. Of these, liquid crystalline polyesters having the above reactive functional groups bonded are preferred from the viewpoints of ease of synthesis, orientation, glass transition point, and the like.

Examples of the side chain type polymer liquid crystal material include materials having a linear or cyclic skeleton such as polyacrylate, polymethacrylate, polyvinyl, polysiloxane, polyether, polymalonate, and polyester. In addition, a polymer liquid crystal substance in which a mesogen group is bonded as a side chain, or a mixture thereof.
More specifically, it is obtained by homopolymerizing a (meth) acrylic moiety of a (meth) acrylic compound having an oxetanyl group represented by the following general formula (1) or copolymerizing with another (meth) acrylic compound. A side chain type liquid crystalline polymer substance is preferably used.

In the above formula (1), R ₁ represents hydrogen or a methyl group, R ₂ represents hydrogen, a methyl group or an ethyl group, and L ₁ and L ₂ each independently represent a single bond, —O—, —O—CO. -Represents either-or -CO-O-, M represents Formula (2), Formula (3) or Formula (4), and n and m each represent an integer of 0 to 10.
-P ₁ -L ₃ -P ₂ -L ₄ -P _3- (2)
-P ₁ -L ₃ -P _3- (3)
-P _3- (4)

In formulas (2) to (4), P ₁ and P ₂ each independently represent a group selected from formula (5), P ₃ represents a group selected from formula (6), and L ₃ and L ₄ are Each represents a single bond, —CH═CH—, —C≡C—, —O—, —O—CO— or —CO—O—.

  In the formula (5), Et represents an ethyl group, iPr represents an isopropyl group, nBu represents a normal butyl group, and tBu represents a tertiary butyl group.

  The method for synthesizing these (meth) acrylic compounds having an oxetanyl group is not particularly limited, and can be synthesized by applying a method used in an ordinary organic chemical synthesis method. For example, by combining a site having an oxetanyl group and a site having a (meth) acrylic group by means such as Williamson's ether synthesis or ester synthesis using a condensing agent, oxetanyl group and (meth) acrylic group 2 A (meth) acrylic compound having an oxetanyl group having two reactive functional groups can be synthesized. However, in the reaction, since the oxetanyl group has cationic polymerizability, it is necessary to select reaction conditions in consideration of causing side reactions such as polymerization and ring opening under strong acidic conditions.

  The (meth) acrylic group having the oxetanyl group represented by the formula (1) is represented by the following formula (7) by homopolymerizing or copolymerizing with another (meth) acrylic compound. A side-chain liquid crystalline polymer substance containing units can be obtained. The polymerization conditions are not particularly limited, and normal radical polymerization or anionic polymerization conditions can be employed.

  As an example of radical polymerization, a (meth) acrylic compound corresponding to each component is dissolved in a solvent such as dimethylformamide (DMF) or diethylene glycol dimethyl ether, and 2,2′-azobisisobutyronitrile (AIBN) or benzoyl peroxide is dissolved. The method of making it react for several hours at 60-120 degreeC by using (BPO) etc. as an initiator is mentioned. Moreover, in order to make the liquid crystal phase appear stably, copper bromide (I) / 2,2′-bipyridyl series, 2,2,6,6-tetramethylpiperidinooxy free radical (TEMPO) series, etc. are used. A method of controlling the molecular weight distribution by conducting living radical polymerization as an initiator is also effective. These radical polymerizations need to be performed under deoxygenated conditions.

  An example of anionic polymerization is a method in which a (meth) acrylic compound corresponding to each component is dissolved in a solvent such as tetrahydrofuran (THF) and reacted with a strong base such as an organic lithium compound, an organic sodium compound, or a Grignard reagent as an initiator. Can be mentioned. In addition, the molecular weight distribution can be controlled by optimizing the initiator and the reaction temperature for living anionic polymerization. These anionic polymerizations need to be performed under dehydration and deoxygenation conditions.

  In addition, the (meth) acryl compound to be copolymerized at this time is not particularly limited and may be anything as long as the synthesized polymer substance exhibits liquid crystallinity, but in order to increase the liquid crystallinity of the synthesized polymer substance, A (meth) acrylic compound having a mesogenic group is preferred. For example, a (meth) acrylic compound represented by the following formula can be exemplified as a preferred compound.

  Here, R represents H, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a cyano group.

  The side chain type liquid crystalline polymer substance preferably contains 5 to 100 mol% of the unit represented by the formula (7), and particularly preferably contains 10 to 100 mol%. The side chain type liquid crystalline polymer substance preferably has a weight average molecular weight of 2,000 to 100,000, particularly preferably 5,000 to 50,000. Outside this range, it is not preferable because cracks occur during stretching or the orientation deteriorates.

  In the liquid crystalline composition used in the present invention, various compounds that can be mixed without impairing liquid crystallinity can be contained in addition to the side chain liquid crystalline polymer substance. Examples of compounds that can be contained include compounds having a cationic polymerizable functional group such as an oxetanyl group, an epoxy group, and a vinyl ether group, various polymer substances having film-forming ability, and various low-molecular liquid crystal compounds exhibiting liquid crystallinity. And polymer liquid crystalline compounds. When the side chain liquid crystalline polymer substance is used as a composition, the proportion of the side chain liquid crystalline polymer substance in the entire composition is 10% by mass or more, preferably 30% by mass or more, and more preferably. Is 50 mass% or more. If the content of the side chain type liquid crystalline polymer substance is less than 10% by mass, the concentration of the polymerizable group in the composition is low, and the orientation is not sufficiently fixed, which is not preferable.

Furthermore, you may mix | blend the various compounds which have a functional group or site | part which can react by a heat | fever or a photocrosslinking reaction etc. in the liquid crystalline composition in the range which does not prevent liquid crystalline expression. Examples of the functional group capable of undergoing a crosslinking reaction include the various reactive functional groups described above.
For example, when the poly (meth) acrylate represented by the formula (7) is used, it is preferable to contain a dioxetane compound represented by the following general formula (8).

In Formula (8), each R ⁷ independently represents hydrogen, a methyl group or an ethyl group, and each L ³ independently represents a single bond or — (CH ₂ ) _n — (n is an integer of 1 to 12). X ¹ represents each independently a single bond, —O—, —O—CO— or —CO—O—, and M ¹ is represented by formula (9) or formula (10). P ¹ in formula (9) and formula (10) each independently represents a group selected from formula (11), P ² represents a group selected from formula (12), and L ⁴ Each independently represents a single bond, —CH═CH—, —C≡C—, —O—, —O—CO— or —CO—O—.
-P ¹ -L ⁴ -P ² -L ⁴ -P ^1- (9)
-P ¹ -L ⁴ -P ^1- (10)

  In the formulas (11) and (12), Et represents an ethyl group, iPr represents an isopropyl group, nBu represents a normal butyl group, and tBu represents a tertiary butyl group.

More specifically, the linking groups connecting the left and right oxetanyl groups as viewed from the M ¹ group may be different (asymmetric) or the same (symmetric), particularly when two L ³ are different or other Depending on the structure of the linking group, it may not exhibit liquid crystallinity, but it is not a restriction for use.
The compound represented by the general formula (8) can be exemplified by a number of compounds from the combination of M ¹ , L ³ and X ¹ , and preferably the following compounds can be mentioned.

These compounds can be synthesized according to a usual synthesis method in organic chemistry, and the synthesis method is not particularly limited.
In the synthesis, since the oxetanyl group has cationic polymerizability, it is necessary to select reaction conditions in consideration of causing side reactions such as polymerization and ring opening under strong acidic conditions. The oxetanyl group is less likely to cause a side reaction than an oxiranyl group that is a similar cationically polymerizable functional group. Furthermore, various compounds such as similar alcohols, phenols, carboxylic acids and the like may be reacted one after another, and utilization of protecting groups may be considered as appropriate.

  As a more specific synthesis method, for example, hydroxybenzoic acid is used as a starting compound, an oxetanyl group is bound by Williamson's ether synthesis method, etc., and then the resulting compound and a diol suitable for the present invention are combined with an acid chloride. Or by condensing using a carbodiimide condensation method or the like, or conversely protecting the hydroxyl group of hydroxybenzoic acid with an appropriate protecting group in advance, condensing with a diol suitable for the present invention, removing the protecting group, and Examples thereof include a method of reacting a hydroxyl group with a compound having an oxetanyl group (oxetane compound), for example, a haloalkyloxetane or the like.

  For the reaction between the oxetane compound and the hydroxyl group, a reaction condition suitable for the form and reactivity of the compound used may be selected. Usually, the reaction temperature is -20 ° C to 180 ° C, preferably 10 ° C to 150 ° C. The reaction time is 10 minutes to 48 hours, preferably 30 minutes to 24 hours. Outside these ranges, the reaction does not proceed sufficiently or side reactions occur, which is not preferable. Moreover, the mixing ratio of both is preferably 0.8 to 1.2 equivalents of the oxetane compound per equivalent of hydroxyl group.

  The reaction can be carried out without solvent, but is usually carried out in a suitable solvent. The solvent used is not particularly limited as long as it does not interfere with the intended reaction. For example, aromatic hydrocarbons such as benzene, toluene and xylene, amides such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone, methyl ethyl ketone, Examples include ketones such as methyl isobutyl ketone, ethers such as dibutyl ether, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate and ethyl benzoate, halogenated hydrocarbons such as chloroform and dichloromethane, and mixtures thereof. .

  Whether the liquid crystalline composition used in the present invention is the above liquid crystalline compound alone or a mixture of various liquid crystalline compounds and various activators and additives, the whole is liquid crystalline. Can be shown. These liquid crystalline compositions contain at least 10% by mass, preferably 30% by mass or more, and more preferably 50% by mass or more of the above low-molecular liquid crystal substance or polymer liquid crystal substance, and exhibit liquid crystallinity. . When the content of the low-molecular liquid crystal substance or the high-molecular liquid crystal substance is less than 10% by mass, the concentration of the compound exhibiting liquid crystallinity in the composition becomes low, and the composition may not exhibit liquid crystallinity, which is not preferable.

  As described above, the liquid crystalline composition in the present invention can contain various compounds that can be mixed without impairing liquid crystallinity in addition to the low-molecular liquid crystal substance or the high-molecular liquid crystal substance. Examples of the compound that can be contained include various polymerizable compounds having a radical polymerizable group such as a vinyl group and a (meth) acryloyl group and a cationic polymerizable group such as an oxetanyl group, an oxiranyl group, and a vinyloxy group, a carboxyl group, and an amino group. A compound having a reactive group such as a group or an isocyanate group, or various polymer compounds having film-forming ability can also be blended. In addition, when a surfactant, antifoaming agent, leveling agent, etc., or a compound having a reactive functional group or a low-molecular or high-molecular liquid crystal substance is used, a reaction initiator or activity suitable for each functional group is used. Agents, sensitizers and the like may be added within a range not departing from the object of the present invention.

The liquid crystalline composition having a reactive group is allowed to react under conditions suitable for reacting the reactive group after realizing a desired alignment.
Examples of the reaction initiator include organic peroxides, azo compounds and various photopolymerization initiators used for general radical polymerization.
Examples of the photopolymerization initiator include a photo radical initiator that cleaves with appropriate light to generate radicals, and a photo cation generator that cleaves with appropriate light to generate cations. If necessary, a thermal cation generator that can generate cations when heated to an appropriate temperature can also be used.

As the photo radical initiator, commercially available benzoin ethers, acyl phosphine oxides, triazine derivatives, biimidazole derivatives generally used for known ultraviolet (UV) curable paints, UV curable adhesives, negative resists, etc. And the like.
Examples of the photocation generator include organic sulfonium salt systems, iodonium salt systems, and phosphonium salt systems. Antimonates, phosphates, borates and the like are preferably used as counter ions of these compounds. Specific examples of the compound include Ar ₃ S ⁺ SbF ₆ ⁻ , Ar ₃ P ⁺ BF ₄ ⁻ and Ar ₂ I ⁺ PF ₆ ⁻ (wherein Ar represents a phenyl group or a substituted phenyl group). In addition, sulfonate esters, triazines, diazomethanes, β-ketosulfone, iminosulfonate, benzoinsulfonate, and the like can also be used.
Examples of the thermal cation generator include benzylsulfonium salts, benzylammonium salts, benzylpyridinium salts, benzylphosphonium salts, hydrazinium salts, carboxylic acid esters, sulfonic acid esters, amine imides, antimony pentachloride-acetyl chloride complex , Diaryl iodonium salt-dibenzyloxy copper, boron halide-tertiary amine adduct, and the like.

  The amount of these reaction initiators added to the liquid crystal composition varies depending on the structure of the mesogen part and spacer part, the molecular weight, the alignment condition of the liquid crystal, etc. constituting the liquid crystal compound to be used. On the other hand, it is usually in the range of 100 mass ppm to 20 mass%, preferably 1000 mass ppm to 10 mass%, more preferably 0.5 mass% to 7 mass%. If the amount is less than 100 mass ppm, the amount of active species generated from the reaction initiator may not be sufficient and the reaction may not proceed. If the amount is more than 20 mass%, it remains in the liquid crystal composition. This is not preferable because there is a risk that the decomposition residue of the reaction initiator and the like increase in color and the light resistance and the like deteriorate.

Next, the thermoplastic polymer film used in the present invention will be described.
As the thermoplastic polymer film used in the present invention, those having excellent transparency are preferable. For example, cellulose resins such as diacetyl cellulose and triacetyl cellulose (TAC), polyester resins, polycarbonate resins, polyamide resins, polyimide resins. , Polyethersulfone resin, polyetherketone resin, polyamideimide resin, polysulfone resin, polystyrene resin, cycloolefin resin, polyolefin resin, acrylic resin, acetate resin, polymethyl methacrylate resin and the like.

  Moreover, a conventionally well-known optical film can also be used. Specifically, the product name “Fujitac” manufactured by FUJIFILM Corporation, the product name “ZEONOR” manufactured by ZEON CORPORATION, the product name “ARTON” manufactured by JSR Corporation, and the product manufactured by Sekisui Chemical Co., Ltd. The brand name “Essina” can be mentioned. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 is mentioned. As this polymer material, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain can be used. For example, an alternating copolymer composed of isobutene and N-methylmaleimide, acrylonitrile, And a resin composition having a styrene copolymer.

Moreover, the thickness of these thermoplastic polymer films is 12-200 micrometers normally, Preferably it is 20-150 micrometers, More preferably, it is 25-100 micrometers. If the thickness is 12 μm or more, the coating accuracy in the coating process described later is further improved, and if the thickness is 200 μm or less, for example, the appearance when mounted on a liquid crystal cell is further improved. Can do.
The optical properties of the thermoplastic polymer film are not particularly limited. The thermoplastic polymer film may have already been stretched and / or shrunk to have optical anisotropy, and has such optical properties. It may not be. A commercially available product may be used as it is. There is no particular limitation on the retardation value of the thermoplastic film before stretching.

The in-plane retardation (Re2) of the thermoplastic film when the thermoplastic film develops a retardation after stretching is usually in the range of 10 nm to 300 nm, preferably 30 nm to 200 nm, more preferably 50 nm to 150 nm. When the Re2 value is out of the above range, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed from an oblique direction.
When the thermoplastic film exhibits retardation after stretching, the thickness direction retardation (Rth2) of the thermoplastic film is usually in the range of −300 nm to 300 nm, preferably −200 nm to 200 nm, and more preferably −150 nm to 150 nm. When the Rth2 value is out of the above range, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

  The alignment substrate used for forming the homeotropic alignment liquid crystal layer preferably has a smooth plane, and examples thereof include a film or sheet made of an organic polymer material, a glass plate, and a metal plate. From the viewpoint of cost and continuous productivity, it is preferable to use a material made of an organic polymer. Examples of organic polymer materials include polyvinyl alcohol, polyimide, polyphenylene sulfide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polyethylene naphthalate, polyethylene terephthalate, polyarylate, cycloolefin polymer, triacetyl cellulose. Etc. can be exemplified. In order to stably obtain homeotropic alignment using the above-mentioned liquid crystalline composition, the material constituting these substrates has a long chain (usually 4 or more carbon atoms, preferably 8 or more) alkyl group. More preferably. Of these, polyvinyl alcohol having a long-chain alkyl group is most preferred. These organic polymer materials may be used alone as a substrate, or may be formed as a thin film on another substrate.

The alignment layer used in the present invention will be described.
In the present invention, since the alignment of the liquid crystalline composition is homeotropic alignment, the liquid crystalline composition layer formed on the thermoplastic polymer film or the alignment substrate can form homeotropic alignment in a liquid crystal state. An alignment layer is required. The formation of the alignment layer is not particularly limited as long as the liquid crystalline composition can be homeotropically aligned. Some thermoplastic polymer films and alignment substrates exhibit a sufficient homeotropic alignment ability for the liquid crystalline composition used in the present invention without performing a treatment for expressing the alignment ability again. However, when the orientation ability is insufficient or does not show the orientation ability, various physical treatments, chemical treatments, or a combination of these treatments can be used.

  Examples of the physical treatment include stretching under moderate heating, performing a so-called rubbing treatment in which the film surface is rubbed in one direction with a rayon cloth or the like, or forming a Langmuir-Blodgett film. As the chemical treatment, a known alignment agent such as a polyimide having a long-chain alkyl group (usually having 4 or more carbon atoms, preferably 8 or more) bonded to the film, a surfactant such as polyvinyl alcohol or a silane coupling agent, and the like. For example, a vapor deposition treatment of silicon oxide or the like provided with an alignment film made of Alternatively, homeotropic alignment ability may be expressed by appropriately combining them.

  In the field of liquid crystal, rubbing treatment with a cloth or the like is generally performed on a substrate, but the homeotropic alignment liquid crystal layer of the present invention is an alignment in which in-plane anisotropy basically does not occur. Because of the structure, rubbing is not necessarily required. However, it is more preferable to perform a weak rubbing treatment from the viewpoint of suppressing repelling when the liquid crystalline composition is applied. An important setting value that defines the rubbing condition is a peripheral speed ratio. This represents the ratio between the movement speed of the cloth and the movement speed of the substrate when the rubbing cloth is wound around a roll and rubbed while the substrate is rubbed. In the present invention, the weak rubbing treatment usually has a peripheral speed ratio of 50 or less, more preferably 25 or less, and particularly preferably 10 or less. When the peripheral speed ratio is larger than 50, the effect of rubbing is too strong, and the liquid crystalline composition cannot be completely aligned vertically, and there is a fear that the alignment is tilted in the in-plane direction from the vertical direction.

As a method for forming a liquid crystalline composition layer by spreading the liquid crystalline composition on the thermoplastic polymer film or the alignment substrate, the liquid crystalline composition is applied on the thermoplastic polymer film or the alignment substrate in a molten state. And a method of applying a solution of a liquid crystalline composition on a thermoplastic polymer film or an alignment substrate and then drying the coating film to distill off the solvent.
The solvent used for preparing the solution is not particularly limited as long as it is a solvent that can dissolve the liquid crystal composition used in the present invention and can be distilled off under appropriate conditions, and generally includes acetone, methyl ethyl ketone, isophorone, cyclohexanone, and the like. Ketones, ether alcohols such as butoxyethyl alcohol, hexyloxyethyl alcohol, methoxy-2-propanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate, ethyl lactate and γ-butyrolactone, phenol , Phenols such as chlorophenol, amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, chloroform, tetrachloroethane, dichlorobenzene Halogenated hydrocarbons such or a mixture of these systems, such as Zen are preferably used. Moreover, in order to form a uniform coating film on a thermoplastic polymer film or an alignment substrate, a surfactant, an antifoaming agent, a leveling agent, or the like may be added to the solution.

There is no particular limitation on the application method, either a method of directly applying a liquid crystalline composition or a method of applying a solution, as long as the uniformity of the coating film is ensured, and a known method is adopted. be able to. Examples thereof include various die coating methods, bar coating methods, curtain coating methods, dip coating methods, roll coating methods, and spin coating methods.
In the method of applying the liquid crystal composition solution, it is preferable to include a drying step for removing the solvent after the application. As long as the uniformity of a coating film is maintained, this drying process can employ | adopt a well-known method, without being specifically limited. For example, a method such as a heater (furnace) or hot air blowing may be used.

  Subsequently, the liquid crystal composition layer formed on the thermoplastic polymer film is formed into a liquid crystal alignment by a method such as heat treatment, and a method suitable for the liquid crystal composition used, for example, light irradiation and / or heat treatment. React with to fix. In the first heat treatment, the liquid crystal is aligned by the self-alignment ability inherent in the liquid crystal composition by heating to the liquid crystal phase expression temperature range of the liquid crystal composition used. As the conditions for the heat treatment, the optimum conditions and limit values differ depending on the liquid crystal phase behavior temperature (transition temperature) of the liquid crystal composition to be used, but it cannot be generally stated, but is usually 10 to 250 ° C., preferably 30 to 160 ° C. It is preferable that the heat treatment be performed at a temperature not lower than the glass transition point (Tg) of the liquid crystalline composition, more preferably not lower than 10 ° C. higher than Tg. If the temperature is too low, the liquid crystal alignment may not proceed sufficiently, and if the temperature is high, the reactive functional group in the liquid crystalline composition, the thermoplastic polymer film or the alignment substrate may be adversely affected. Moreover, about heat processing time, it is 3 seconds-30 minutes normally, Preferably it is the range of 10 seconds-10 minutes. If the heat treatment time is shorter than 3 seconds, the liquid crystal alignment may not be completed sufficiently, and if the heat treatment time exceeds 30 minutes, the productivity is deteriorated.

  After forming the homeotropic alignment of the liquid crystalline composition layer by a method such as heat treatment, the liquid crystalline composition is cured by a reaction of a reactive functional group in the composition while maintaining the alignment state. The purpose of the curing step is to fix the liquid crystal alignment state by a curing (crosslinking) reaction of the completed liquid crystal alignment.

Since the liquid crystalline composition of the present invention has a reactive functional group, it is necessary to set the reaction conditions in accordance with the reactivity of the reactive functional group for reaction.
For example, in the case of a liquid crystalline composition using the side chain type liquid crystalline polymer substance represented by the above formula (7), since it has a polymerizable oxetanyl group, the polymerization (crosslinking) of the reactive group is not necessary. As described above, it is preferable to use a cationic polymerization initiator (photo cation generator and / or thermal cation generator). As the polymerization initiator, it is preferable to use a photo cation generator rather than a thermal cation generator.

  When a photo cation generator is used, if the steps from the addition of the photo cation generator to the heat treatment for liquid crystal alignment are performed under dark conditions (light blocking conditions that do not cause the photo cation generator to dissociate), liquid crystal properties The composition can be oriented with sufficient fluidity without curing until the orientation stage. Thereafter, the liquid crystal composition layer is cured by generating cations by irradiating light from a light source that emits light of an appropriate wavelength.

As a light irradiation method, a photocation is generated by irradiating light from a light source such as a metal halide lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, an arc lamp, or a laser having a spectrum in the absorption wavelength region of the photocation generator used. Cleave the generator. The dose per square centimeter is usually in the range of 1 to 2000 mJ, preferably 10 to 1000 mJ as the cumulative dose. However, this is not the case when the absorption region of the photocation generator and the spectrum of the light source are significantly different, or when the liquid crystalline polymer constituting the liquid crystalline composition has the ability to absorb the light source wavelength. In these cases, it is possible to adopt a method such as using a suitable photosensitizer or a mixture of two or more photocation generators having different absorption wavelengths.
The temperature at the time of light irradiation needs to be in a temperature range in which the liquid crystalline composition takes a liquid crystal phase. In order to sufficiently enhance the curing effect, it is preferable to perform light irradiation at a temperature equal to or higher than Tg of the liquid crystalline composition.

  The method for producing the retardation film of the present invention will be described later. In addition to the method of forming and stretching a homeotropic alignment liquid crystal layer on the thermoplastic polymer film, a homeotropic alignment liquid crystal layer is separately formed on the alignment substrate. From the formed form, it can also be produced from a form in which the liquid crystal layer is transferred to a thermoplastic polymer film.

As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, a homeotropic alignment liquid crystal layer formed on an alignment substrate is laminated with a thermoplastic polymer film via an adhesive. Then, if necessary, the adhesive may be cured, and the alignment substrate may be peeled from the laminate to transfer only the liquid crystal layer to the thermoplastic polymer film.
The adhesive used for the transfer is not particularly limited as long as it is of optical grade, and generally used ones such as acrylic, epoxy, and urethane can be used. In addition, it can replace with an adhesive agent and can also use an adhesive by the performance.

Next, the adhesive layer that can be used in the present invention will be described.
As an adhesive used for transferring the homeotropic alignment liquid crystal layer on the alignment substrate to the thermoplastic polymer film, the adhesive has a sufficient adhesive force to the liquid crystal layer and the thermoplastic polymer film, and the liquid crystal As long as the optical properties of the layer are not impaired, there is no particular limitation. For example, acrylic resin-based, methacrylic resin-based, epoxy resin-based, ethylene-vinyl acetate copolymer system, rubber system, urethane system, polyvinyl ether system and Various reactive types such as a mixture system, a thermosetting type and / or a photocurable type, and an electron beam curable type can be exemplified.

  Since the reaction (curing) conditions for the reactive substances vary depending on the components, viscosity, reaction temperature, and the like, the conditions suitable for each may be selected. For example, in the case of a photo-curing type, various known photoinitiators are preferably added, and light from a light source such as a metal halide lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, a xenon lamp, an arc lamp, a laser, or a synchrotron radiation source is used. Irradiation may be performed to cause the reaction. The amount of irradiation per unit area (one square centimeter) is usually in the range of 1 to 2000 mJ, preferably 10 to 1000 mJ as the integrated irradiation amount. However, this is not the case when the absorption region of the photoinitiator and the spectrum of the light source are significantly different, or when the reactive compound itself has the ability to absorb the light source wavelength. In these cases, an appropriate photosensitizer or a method of using a mixture of two or more photoinitiators having different absorption wavelengths can be used. The acceleration voltage in the case of the electron beam curable type is usually 10 kV to 200 kV, preferably 50 kV to 100 kV.

  The adhesive layer may be formed in the same manner as the liquid crystal layer, or a so-called non-carrier type adhesive in which the adhesive layer is formed on a suitable substrate provided with an easily peelable layer such as silicone. May be used. Pressurization using a laminator, roll, pressurizer, etc. to improve the strength of the homeotropic alignment liquid crystal layer and the thermoplastic polymer film, to prevent the generation of bubbles due to residual air at the bonding interface, etc. Heating or the like may be added.

  Although the thickness of an adhesive bond layer changes with structural components, intensity | strength, use temperature, etc., it is 1-50 micrometers normally, Preferably it is 2-30 micrometers, More preferably, it is 3-10 micrometers. Outside this range, the adhesive strength is insufficient, or bleeding from the end is not preferable.

  In order to improve the adhesion between the liquid crystal layer and the thermoplastic polymer film, the liquid crystal layer or the thermoplastic polymer film may be subjected to a surface treatment. Moreover, you may provide an easily bonding layer on a thermoplastic polymer liquid crystal film.

The thermoplastic polymer film used in the present invention is preferably surface-treated alone or in the form of a laminate (A) in the production method (II) described later.
For the surface treatment, a method suitable for a thermoplastic polymer film may be used, and examples of such a method include corona discharge treatment, flame treatment, low-pressure UV irradiation, plasma treatment, and the like. When a polymer is used, corona discharge treatment is preferable.

The corona discharge treatment may be performed under normal conditions, for example, on the surface in contact with the adhesive. The treatment conditions may vary depending tacky adhesive in contact Seijo or corona treatment apparatus such as a surface, for example 1~300W · min / m ² as the energy density is preferred. The surface tension is increased by performing the corona discharge treatment, but it is desirable to increase the surface tension to 40 dyn / cm or more.

Next, the manufacturing method of the retardation film of this invention is demonstrated in detail.
The method for producing the retardation film obtained in the present invention is selected from the following three production methods (I) to (III).
[A] Manufacturing method (I)
(1) a first step in which an alignment layer for forming a homeotropic alignment is formed on a thermoplastic polymer film by a liquid crystalline composition exhibiting positive uniaxiality;
(2) On the alignment layer, a layer of a liquid crystalline composition exhibiting positive uniaxiality is applied, and after homeotropic alignment of the layer, a homeotropic alignment liquid crystal layer having a fixed alignment is formed, A second step of obtaining a laminated film comprising a plastic polymer film / alignment layer / homeotropic alignment liquid crystal layer;
(3) a third step of obtaining a retardation film by stretching a laminated film comprising the thermoplastic polymer film / alignment layer / homeotropic alignment liquid crystal layer;
A method for producing a retardation film comprising at least each of the steps, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0.

[B] Production method (II)
(1) A layer of a liquid crystalline composition exhibiting positive uniaxiality is applied on an alignment substrate, the layer is homeotropically aligned, and then a homeotropic alignment liquid crystal layer with a fixed alignment is formed to align the layer. A first step of obtaining a laminate (A) comprising a substrate / homeotropic alignment liquid crystal layer;
(2) After adhering the homeotropic alignment liquid crystal layer side of the laminate (A) to the thermoplastic polymer film via the adhesive layer 1, the alignment substrate is peeled off to form the homeotropic alignment liquid crystal layer. A second step of transferring to a thermoplastic polymer film to obtain a laminate (B) comprising a thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer;
(3) A third step of obtaining a retardation film by stretching the laminate (B) comprising the thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer.
A method for producing a retardation film comprising at least each of the steps, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0.

[C] Production method (III)
(1) A layer of a liquid crystalline composition exhibiting positive uniaxiality is applied on an alignment substrate, the layer is homeotropically aligned, and then a homeotropic alignment liquid crystal layer with a fixed alignment is formed to align the layer. A first step of obtaining a laminate (A) comprising a substrate / homeotropic alignment liquid crystal layer;
(2) a second step of obtaining a laminate (C) by stretching the laminate (A) comprising the alignment substrate / homeotropic alignment liquid crystal layer;
(3) After the homeotropic alignment liquid crystal layer side of the laminate (C) is bonded to the thermoplastic polymer film via the adhesive layer 1, the alignment substrate / homeotropic alignment liquid crystal layer is bonded to the thermoplastic high-molecular layer. A third step of obtaining a retardation film comprising a thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer after peeling the alignment substrate after transferring to the molecular film;
A method for producing a retardation film comprising at least each of the steps, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0.

Manufacturing method (I) is demonstrated.
First, the first step will be described.
An alignment layer in which the liquid crystalline composition forms homeotropic alignment may be formed on the above-described thermoplastic polymer film, and as such a forming method, the thermoplastic polymer film used from the above-described physical treatment or chemical treatment is used. Processing suitable for the above may be performed.
Next, the manufacturing method in the second step will be described.
On the alignment layer produced in the first step, a coating film of a liquid crystalline composition exhibiting positive uniaxiality is formed by an appropriate method, the solvent is removed as necessary, and the liquid crystalline composition is heated by heating or the like. The alignment is completed, and the homeotropic alignment of the liquid crystalline composition is fixed by means suitable for the liquid crystalline composition used. Thus, a laminate composed of thermoplastic polymer film / alignment layer / homeotropic alignment liquid crystal layer is obtained.
Next, as the third step, the retardation film of the present invention can be obtained by stretching the laminate.

  The obtained retardation film may be provided with a translucent overcoat layer or a temporary surface protective film may be bonded to protect the surface. Here, the translucent overcoat can be appropriately selected from the aforementioned adhesives.

Stretching methods include, for example, free end longitudinal stretching in which the laminate is uniaxially stretched in the longitudinal direction, fixed end lateral stretching in which the film is stretched in the width direction, and stretching in both the longitudinal direction and the width direction. Examples of the method include biaxial stretching in which these are sequentially or simultaneously performed.
Stretching is usually performed while heating, and the heating temperature is generally 100 to 250 ° C, preferably 120 to 250 ° C, more preferably 130 to 200 ° C. When the heating temperature is 100 ° C. or lower, the film may crack during stretching, and when the heating temperature is 250 ° C. or higher, a desired phase difference may not be obtained.

  When the uniaxial or biaxial stretching is performed, the stretching ratio is usually 1.01 to 3.0 times, preferably 1.03 to 2.0 times, more preferably 1.05 to 1.6 times. It can be as follows. When the draw ratio is less than 1.01, the effect of stretching is not sufficient, and there is a possibility that the film has a structure close to the refractive index structure of the homeotropic alignment liquid crystal layer of the film. When the draw ratio is larger than 3.0 times, there is a possibility that a non-uniform refractive index structure is formed due to uneven drawing or cracks occur in the liquid crystal layer.

Next, production method (II) will be described.
First, the manufacturing method of the laminated body (A) which is a 1st process is demonstrated.
Form a coating film of a liquid crystalline composition exhibiting positive uniaxiality on an alignment substrate having homeotropic alignment ability by an appropriate process, etc., by removing the solvent, etc. The material layer is homeotropically aligned, and the alignment is fixed by means suitable for the liquid crystal composition used. Thus, a laminate (A) composed of an alignment substrate / homeotropic alignment liquid crystal layer can be obtained.
Next, the manufacturing method in the second step will be described.
After the homeotropic alignment liquid crystal layer side of the laminate (A) is in close contact with the thermoplastic polymer film via the adhesive layer 1, the adhesive layer 1 is reacted (cured) if necessary, and then the alignment substrate Then, the homeotropic alignment liquid crystal layer is transferred to the thermoplastic polymer film. Thus, a laminate (B) comprising a thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer can be obtained.
Next, as the third step, the retardation film of the present invention can be obtained by stretching the laminate (B). The stretching conditions may be the same as in production method (I).
Thus, the retardation film of the present invention can be obtained.

Moreover, the obtained retardation film may provide a translucent overcoat layer for surface protection, or may bond a temporary surface protection film. Here, the translucent overcoat can be selected from the aforementioned adhesives.
In the present invention, a plurality of homeotropic alignment liquid crystal layers can be stacked by repeatedly stacking homeotropic alignment liquid crystal layers with an adhesive layer interposed therebetween.

Next, production method (III) will be described.
First, about the manufacturing method of the laminated body (A) which is a 1st process, it is the same as that of manufacturing method (II).
Next, as a second step, the laminate (C) comprising the oriented substrate / homeotropic alignment liquid crystal layer can be obtained by stretching the laminate (A). The stretching conditions may be the same as in production method (I).
Next, as a third step, the homeotropic alignment liquid crystal layer side of the laminate (C) is adhered to the thermoplastic polymer film via the adhesive layer 1, and then the adhesive layer 1 is reacted (cured) as necessary. Then, the alignment substrate is peeled off, and the homeotropic alignment liquid crystal layer is transferred to the thermoplastic polymer film.
Thus, the retardation film of the present invention can be obtained.

  Moreover, the obtained retardation film may provide a translucent overcoat layer for surface protection, or may bond a temporary surface protection film. Here, the translucent overcoat can be selected from the aforementioned adhesives.

  The homeotropic alignment liquid crystal layer before stretching formed in the above production method has a thickness of the liquid crystal layer d3, a main refractive index in the liquid crystal layer plane of nx3, ny3, a main refractive index in the thickness direction of nz3, and , Nx3 ≧ ny3, the in-plane retardation value (Re3) is Re3 = (nx3-ny3) × d3 [nm], and the thickness direction retardation value (Rth3) is Rth3 = (nx3-nz3). ) × d3 [nm], Re3 and Rth3 are general because they depend on the type of liquid crystal display device and various optical parameters when used as a viewing angle improving film of a liquid crystal display device. However, for monochromatic light of 550 nm, Re3 is usually in the range of 0 nm to 50 nm, preferably 0 nm to 30 nm, more preferably 0 nm to 10 nm, and , Rth3 is usually controlled to be −600 to −30 nm, preferably −400 to −50 nm, and more preferably −400 to −100 nm.

  The aforementioned Re3 and Rth3 can be quantified by measuring the optical phase difference of the liquid crystal layer at an angle inclined from normal incidence. In the case of homeotropic alignment liquid crystal layers, this retardation value is symmetric with respect to normal incidence. Several methods can be used for measuring the optical phase difference. For example, an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments) and a polarizing microscope can be used. This homeotropic alignment liquid crystal layer appears black between the crossed Nicol polarizers. Thus, homeotropic orientation was evaluated.

  The configuration of the retardation film of the present invention is not particularly limited as long as the retardation film satisfying Nz <1 as described above is provided, and according to various optical uses, the retardation film alone is used alone. You may use it, and you may use the thing combined with other optical members.

  The polarizing plate of the present invention is obtained by laminating the retardation film and a polarizing element. As long as the retardation film and the polarizing element are provided, there is no particular limitation on the other configurations. The retardation film and the polarizing element may be bonded directly or may be laminated via another member.

  The polarizing element that can be used in the present invention is not particularly limited, and various types can be used. Examples of polarizing elements include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films, and two colors such as iodine and dichroic dyes. And polyene-based oriented films such as those obtained by adsorbing an active substance, polyvinyl chloride dehydrochlorinated products, and the like. Among these, those obtained by stretching a polyvinyl alcohol film and adsorbing and orienting a dichroic material (iodine, dye) are preferably used. The thickness of the polarizing element is not particularly limited, but is generally about 5 to 80 μm.

  A polarizing element in which a polyvinyl alcohol film is dyed with iodine and uniaxially stretched can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As the translucent protective film provided on one surface of the polarizing element, an optically isotropic substrate is preferable, for example, triacetylcellulose such as Fujitac (product of Fujifilm) or Konicatak (product of Konica Minolta Opto). Cycloolefin polymers such as (TAC) film, Arton film (product of JSR), ZEONOR film, ZEONEX film (product of Nippon Zeon), TPX film (product of Mitsui Chemicals), Acryprene film (product of Mitsubishi Rayon) However, triacetyl cellulose and cycloolefin polymers are preferable from the viewpoint of flatness, heat resistance, moisture resistance, and the like when a polarizing plate is used. Generally the thickness of a translucent protective film is 200 micrometers or less, and 1-100 micrometers is preferable. In particular, the thickness is preferably 5 to 50 μm.

As the light-transmitting protective film, a film having a hard coat layer, antireflection treatment, anti-sticking, light diffusion or antiglare treatment on the surface can be used.
The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, the protective film is applied with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a light diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, light diffusing layer, antiglare layer, etc. can be provided on the translucent protective film itself, and separately from the translucent protective film layer as an optical layer. It can also be provided.

Next, a liquid crystal display device to which the retardation film of the present invention is applied will be described.
The liquid crystal display device of the present invention has at least the retardation film. When disposing the retardation film of the present invention in a liquid crystal cell, it is necessary to dispose the retardation film between the polarizing element layer and the liquid crystal cell, or to replace at least one polarizing plate with the polarizing plate of the present invention. It is.

  A liquid crystal display device is generally composed of a polarizing plate, a liquid crystal cell, a retardation compensator, a reflective layer, a light diffusing layer, a backlight, a front light, a light control film, a light guide plate, a prism sheet, and the like. In the present invention, there is no particular limitation except that the retardation film is used. The use position of the retardation film is not particularly limited, and may be one or a plurality of places. Moreover, it can also be used in combination with other phase difference plates.

The liquid crystal cell is not particularly limited, and a general liquid crystal cell such as a liquid crystal layer sandwiched between a pair of transparent substrates provided with electrodes can be used.
The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate in which the substrate itself has a property of orienting liquid crystals, a transparent substrate in which an alignment film having the property of orienting liquid crystals is provided, but the substrate itself lacks the alignment ability. Either can be used. Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. Usually, it can be provided on the surface of the transparent substrate in contact with the liquid crystal layer, and when a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.

  The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystal substances, polymer liquid crystal substances, and mixtures thereof that can constitute various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired.

In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later.
As the liquid crystal cell system, TN (Twisted Nematic) system, STN (Super Twisted Nematic) system, ECB (Electrically Controlled Birefringence) system, IPS (In-Plane Switching) system, VA (Vertical Alignment) system, OCB (Optically Compensated Birefringence (HAN), Hybrid Aligned Nematic (HAN), ASM (Axially Symmetric Aligned Microcell), halftone gray scale, domain division, or display using ferroelectric or antiferroelectric liquid crystal There are various methods.
Also, the liquid crystal cell driving method is not particularly limited, and a passive matrix method used for STN-LCDs, etc., and an active matrix method using active electrodes such as TFT (Thin Film Transistor) electrodes and TFD (Thin Film Diode) electrodes, Any driving method such as a plasma addressing method may be used.

The retardation compensation plate used in the liquid crystal display device is not particularly limited as long as it has excellent transparency and uniformity, but a polymer stretched film or an optical compensation film made of liquid crystal can be preferably used. Examples of the stretched polymer film include uniaxial or biaxial retardation films made of cellulose, polycarbonate, polyarylate, polysulfone, polyacryl, polyether sulfone, cycloolefin polymer, and the like. it can. Of these, polycarbonate-based and cycloolefin-based polymers are preferable from the viewpoint of cost and film uniformity.
In addition, the optical compensation film made of liquid crystal is not particularly limited as long as it is a film that can utilize the optical anisotropy generated from the alignment state by aligning the liquid crystal. For example, known materials such as various optical functional films using nematic liquid crystal, discotic liquid crystal, smectic liquid crystal and the like can be used.
The phase difference compensator exemplified here may be used alone or in a plurality of sheets when constituting a liquid crystal display device. Further, both a polymer stretched film and an optical compensation film made of liquid crystal can be used.

  The reflective layer is not particularly limited, and is a metal such as aluminum, silver, gold, chromium, or platinum, an alloy containing them, an oxide such as magnesium oxide, a dielectric multilayer film, a liquid crystal exhibiting selective reflection, or these. The combination of these can be illustrated. These reflective layers may be flat or curved. In addition, the reflective layer is processed to have a surface shape such as a concavo-convex shape so as to have diffuse reflectivity, the liquid crystal cell is combined with an electrode on the electrode substrate opposite to the observer side, and the thickness of the reflective layer It may be a semi-transmissive reflective layer in which light is partially transmitted by thinning or forming a hole or the like, or a combination thereof.

The light diffusion layer is not particularly limited as long as it has a property of diffusing incident light isotropically or anisotropically. For example, it may be composed of two or more regions, with a difference in refractive index between the regions, or with surface irregularities. Examples of the two or more regions having a refractive index difference between the regions include those in which particles having a refractive index different from that of the matrix are dispersed in the matrix. The diffusion layer itself may have an adhesive property.
The film thickness of the light diffusing layer is not particularly limited, but is usually preferably 10 μm or more and 500 μm or less.
Further, the total light transmittance of the light diffusion layer is preferably 50% or more, and particularly preferably 70% or more. Further, the haze value of the light diffusion layer is usually 10 to 95%, preferably 40 to 90%, and more preferably 60 to 90%.

  The backlight, front light, light control film, light guide plate, and prism sheet are not particularly limited, and known ones can be used.

  The liquid crystal display device of the present invention can be provided with other constituent members in addition to the constituent members described above. For example, by attaching a color filter to the liquid crystal display device of the present invention, a color liquid crystal display device capable of performing multicolor or full color display with high color purity can be manufactured.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In addition, each analysis method used in the Example is as follows.
(1) Measurement of GPC The compound was dissolved in tetrahydrofuran, and TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 were connected in series with an 8020 GPC system manufactured by Tosoh Corporation and measured using tetrahydrofuran as an eluent. Polystyrene standards were used for molecular weight calibration.
(2) Microscope observation The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(3) Measurement of optical parameters An automatic birefringence meter KOBRA21ADH manufactured by Oji Scientific Instruments was used.
(4) Film thickness measurement method SURFACE TEXTURE ANALYSIS SYSTEM Dektak 3030ST made by SLOAN was used. Moreover, the method of calculating | requiring a film thickness from the data of interference wave measurement (The JASCO Corporation UV / visible / near infrared spectrophotometer V-570) and refractive index data was used together.

[Example 1]
A liquid crystal polymer of the following formula (13) was synthesized. The molecular weight was Mn = 8000 and Mw = 15000 in terms of polystyrene. Formula (13) is represented by the structure of the block polymer, but represents the composition ratio of the monomers.
After dissolving 1.0 g of the polymer of the formula (13) in 9 ml of cyclohexanone and adding 0.1 g of a triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (manufactured by Aldrich) in the dark, A liquid crystal composition solution was prepared by filtration through a 0.45 μm polytetrafluoroethylene filter.

  The alignment substrate was prepared as follows. A 38 μm-thick polyethylene terephthalate film (PET, manufactured by Toray Industries, Inc.) was cut into a 15 cm square, and a 5% by mass solution of alkyl-modified polyvinyl alcohol (PVA, manufactured by Kuraray Co., Ltd., MP-203) (the solvent was water and (A mixed solvent of isopropyl alcohol having a mass ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 120 ° C. for 10 minutes.

The liquid crystal composition solution described above was applied to the alignment substrate thus obtained by spin coating. Subsequently, it dried for 10 minutes with a 60 degreeC hotplate, and heat-processed for 2 minutes in 150 degreeC oven, and orientated the liquid crystalline composition. Next, the sample is placed in close contact with an aluminum plate heated to 60 ° C., and then irradiated with ultraviolet light (measured at 365 nm) of 600 mJ / cm ^{2 with} a high-pressure mercury lamp lamp, Cured to obtain a laminate A composed of PET film / PVA layer / liquid crystal composition layer.

Since the PET film used as the alignment substrate has a large birefringence, it is difficult to measure the optical parameters (Re3, Rth3, etc.) of the liquid crystalline composition layer (homeotropic alignment liquid crystal layer) in the form of the laminate A. A liquid crystalline composition layer (homeotropic alignment liquid crystal layer) was transferred onto an acetylcellulose (TAC) film as follows.
That is, on the liquid crystal composition layer (homeotropic alignment liquid crystal layer) on the PET film, an ultraviolet curable adhesive is applied as the adhesive layer 1 so as to have a thickness of 5 μm and laminated with a TAC film (40 μm thickness). After curing the adhesive by irradiating ultraviolet rays from the TAC film side, the PVA layer and the PET film are peeled off, and the laminate B (liquid crystalline composition layer (homeotropic alignment liquid crystal layer) / adhesive layer 1 / TAC film) was obtained.

  When the obtained laminate B was observed under a polarizing microscope, it was found that there was no disclination and the monodomain was uniformly oriented, and conoscopic observation showed homeotropic orientation having a positive uniaxial refractive index structure. The in-plane direction retardation value (Re) of the laminate B measured using KOBRA21ADH was 0.5 nm, and the thickness direction retardation value (Rth) was −160 nm. Since the TAC film used alone was negative uniaxial, Re was −0.5 nm, and Rth was +40 nm, Re3 of the homeotropic alignment liquid crystal layer alone was estimated to be 0 nm, and Rth3 was estimated to be −200 nm. . In addition, Re and Rth of a TAC film are the same definitions as Re3 and Rth3.

A commercially available UV curable adhesive (UV-3400, manufactured by Toagosei Co., Ltd.) was applied to the homeotropic alignment liquid crystal layer of the laminate A to a thickness of 5 μm as the adhesive layer 2, and 250 W · min was added thereto. A Zeonor film (film thickness: 100 μm, manufactured by Nippon Zeon Co., Ltd.) subjected to corona treatment under the conditions of / m ² is laminated on the corona-treated surface within 30 seconds after the corona treatment, and the adhesive layer is irradiated by UV irradiation of about 600 mJ. 2 was cured. The PET film / PVA layer / homeotropic alignment liquid crystal layer / adhesive layer 2 / Zeonor film is peeled off from the laminate in which the PET film and PVA layer are integrated to form a homeotropic alignment liquid crystal layer / adhesive layer 2 / Zeonor. A laminate C made of a film was obtained. The total thickness of the layered product C was 110 μm.

Thereafter, the laminate C was stretched 20% in the longitudinal direction while being heated to 140 ° C. to obtain a retardation film D.
Further, a ZEONOR film alone (film thickness: 100 μm, manufactured by Nippon Zeon Co., Ltd.) was heated to 140 ° C. in the same manner as the laminate C, and a retardation film E stretched by 20% in the longitudinal direction was obtained.

When the retardation value in the oblique direction of the retardation film E was measured using an automatic birefringence meter, Re2 = 161 nm and Rth2 = 85 nm.
Similarly, when the retardation value in the oblique direction of the laminate D was measured, the total Re = 222 nm and the total Rth = 34 nm.
From the above formulas (d), (e) and (f)
Total Re = Re1 + Re2 (D)
Total Rth = Rth1 + Rth2 (e)
Total Nz = Total Rth / Total Re + 0.5 (f)
Re1 and Rth1 of the liquid crystal layer only are
Re1 = 222-161 = 61 nm
Rth1 = 34−85 = −51 nm
The Nz1 value of the liquid crystal layer is
Nz1 = Rth1 / Re1 + 0.5
= −51 / 61 + 0.5 = −0.34 (<1.0)
Met. Moreover, the total Nz value was total Nz = 34/222 + 0.5 = 0.65 (<1.0) based on the formula (f).

[Example 2]
A 100 μm thick ZEONOR film (manufactured by Nippon Zeon Co., Ltd.) was cut into a 15 cm square, and a 5 mass% solution of alkyl-modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., MP-203) (the solvent was the mass of water and isopropyl alcohol). A mixed solvent having a ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 120 ° C. for 10 minutes.
On the substrate thus obtained, the liquid crystalline composition solution prepared in Example 1 was applied by spin coating. Subsequently, it dried for 10 minutes with a 60 degreeC hotplate, and heat-processed for 2 minutes in 150 degreeC oven, and orientated the liquid crystalline composition layer. Next, the sample is placed in close contact with an aluminum plate heated to 60 ° C., and then the ultraviolet light of 600 mJ / cm 2 is irradiated with a high-pressure mercury lamp lamp to cure the liquid crystalline composition layer, and the ZEONOR film / PVA layer / The laminated body F which consists of a homeotropic alignment liquid crystal layer was obtained.
Thereafter, the laminate F was stretched by 20% in the longitudinal direction while being heated to 140 ° C. to obtain a retardation film G.
Further, a ZEONOR film alone (film thickness: 100 μm, manufactured by Nippon Zeon Co., Ltd.) was heated to 140 ° C. in the same manner as the laminate F, and a retardation film H stretched by 20% in the longitudinal direction was obtained.
When the retardation value in the oblique direction of the retardation film H was measured using an automatic birefringence meter, Re2 = 161 nm and Rth2 = 85 nm.
Similarly, when the retardation value in the oblique direction of the retardation film G (laminate of ZEONOR film and liquid crystal layer) was measured, the total Re = 223 nm and the total Rth = 31 nm.
By calculating in the same manner as in Example 1, Re1 and Rth1 of the liquid crystal layer only are
Re1 = 223-161 = 60 nm
Rth1 = 31−85 = −54 nm
The Nz1 value of the liquid crystal layer is
Nz1 = Rth1 / Re1 + 0.5
= −54 / 60 + 0.5 = −0.39 (<1.0)
Met. Further, the total Nz value was total Nz = 31/223 + 0.5 = 0.64 (<1.0) based on the formula (f).

[Example 3]
In Example 2, a commercially available UV curable adhesive (UV-3400, Toagosei Co., Ltd.) was applied to the homeotropic alignment liquid crystal layer of the obtained retardation film G, which was stretched 20% in the longitudinal direction while heating the laminate F at 140 ° C. ZEONOR film 2 (film thickness: 100 μm, Nippon Zeon Co., Ltd.) applied as an adhesive layer 2 to a thickness of 5 μm and subjected to corona treatment on the condition of 250 W · min / m ² The product was laminated on the corona-treated surface within 30 seconds after the corona treatment, and the adhesive layer 2 was cured by UV irradiation of about 600 mJ. By separating the ZEONOR film and the PVA layer from the laminate in which the ZEONOR film / PVA layer / homeotropic alignment liquid crystal layer / adhesive layer 2 / ZEONOR film 2 are integrated, the homeotropic alignment liquid crystal layer / adhesive layer 2 / A retardation film I made of ZEONOR film 2 was obtained.
When the retardation value in the oblique direction of the retardation film I was measured using an automatic birefringence meter, Re2 = 60 nm and Rth2 = −54 nm.
Since the phase difference value of the ZEONOR film alone 2 is an unstretched film, the front and oblique directions were almost 0 nm. By calculating in the same manner as in Example 1, Re1 and Rth1 of the liquid crystal layer only are
Re1 = 60-0 = 60 nm
Rth1 = −54−0 = −54 nm
The Nz1 value of the liquid crystal layer is
Nz1 = Rth1 / Re1 + 0.5
= −54 / 60 + 0.5 = −0.38 (<1.0)
Met.

[Example 4]
Using the retardation film D (Re = 222 nm, Nz = 0.65) produced in Example 1, as shown in FIG. 1, the backlight, the lower polarizing plate, the IPS type liquid crystal cell, and the upper polarizing plate were used in this order. The retardation film was disposed between the upper polarizing plate and the liquid crystal cell of a commercially available IPS type liquid crystal television. As a result, it was found that when the retardation film produced in Example 1 was mounted, the viewing angle was enlarged compared to the case of using only the polarizing plate, and a good image was obtained even when viewed from an oblique direction.

[Comparative Example 1]
A ZEONOR film alone (thickness: 100 μm, manufactured by Nippon Zeon Co., Ltd.) without a homeotropic liquid crystal layer was stretched 25% in the longitudinal direction while being heated to 140 ° C. to obtain a retardation film J. When the retardation value in the oblique direction of the retardation film J was measured using an automatic birefringence meter, Re2 = 220 nm and Rth2 = 115 nm. Nz2 of the retardation film E is
Nz2 = Rth2 / Re2 + 0.5
= 115/220 + 0.5 = 1.02 (> 1.0)
It was almost positive uniaxial.

[Comparative Example 2]
Using the retardation film J (Re = 220 nm, Nz = 1.02) prepared in Comparative Example 1, the upper polarizing plate and the liquid crystal of the commercially available IPS liquid crystal television shown in FIG. The retardation film was disposed between the cells. As a result, it was found that the viewing angle characteristics of the retardation film D produced in Example 1 were almost the same as those of the polarizing plate alone. It can be understood that when the Nz value is approximately 1, the viewing angle improvement effect was not seen.

6 is a conceptual diagram of a liquid crystal display used in Example 3. FIG.

Explanation of symbols

1 Polarizing plate 2 Retardation film 3 IPS liquid crystal panel
4 Polarizing plate 5 Backlight

Claims (17)

A phase difference film obtained by subjecting a liquid crystalline composition exhibiting positive uniaxiality to homeotropic alignment in a liquid crystal state and then stretching a homeotropic alignment liquid crystal layer in which the orientation is fixed, the stretched liquid crystal layer In-plane retardation (Re1) where nx1 is the main refractive index in the plane, ny1 is the refractive index in the direction perpendicular to nx1 (where nx1 ≧ ny1), nz1 is the main refractive index in the thickness direction, and d1 is the thickness. A retardation film characterized in that Nz1 defined by the formula (A) satisfies Nz1 <1.0 when the retardation (Rth1) in the thickness direction is represented by the formula (A) and the formula (C), respectively.
Nz1 = Rth1 / Re1 + 0.5 (A)
Re1 = (nx1-ny1) × d1 [nm] (A)
Rth1 = {(nx1 + ny1) / 2−nz1} × d1 [nm] (c)   The retardation film according to claim 1, wherein the homeotropic alignment liquid crystal layer is composed of a liquid crystalline composition composed of at least a side chain type liquid crystalline polymer having an oxetanyl group.   The retardation film according to claim 1, wherein the homeotropic alignment liquid crystal layer is formed of a liquid crystalline composition including at least a low-molecular liquid crystal substance having a reactive functional group. After homeotropic alignment of a liquid crystalline composition exhibiting positive uniaxiality in a liquid crystal state, a homeotropic alignment liquid crystal layer in which the alignment is fixed is formed on a thermoplastic polymer film via an alignment film or an adhesive. It is a retardation film obtained by stretching a laminated body that is laminated,
The in-plane main refractive index of the stretched liquid crystal layer is nx1, the refractive index in the direction orthogonal to nx1 is ny1 (where nx1 ≧ ny1), the main refractive index in the thickness direction is nz1, and the thickness is d1. The in-plane retardation (Re1) and the thickness direction retardation (Rth1) of the liquid crystal layer are defined by the formula (ki) and the formula (ku), respectively.
Re1 = (nx1-ny1) × d1 [nm] (G)
Rth1 = {(nx1 + ny1) / 2−nz1} × d1 [nm]
The in-plane main refractive index of the stretched thermoplastic polymer film is nx2, the refractive index in the direction orthogonal to nx2 is ny2 (where nx2 ≧ ny2), the main refractive index in the thickness direction is nz2, and the thickness is d2. The in-plane retardation (Re2) and the thickness direction retardation (Rth2) of the stretched thermoplastic polymer film are defined by the formula (ke) and the formula (co), respectively.
Re2 = (nx2-ny2) × d2 [nm]
Rth2 = {(nx2 + ny2) / 2-nz2} × d2 [nm] (G)
The total in-plane retardation (total Re) and total thickness direction retardation (total Rth) defined as the sum of Re1 and Rth1 of the stretched liquid crystal layer and Re2 and Rth2 of the thermoplastic polymer film are respectively expressed by the formula (D) When the formula (e) is satisfied, the total Nz value defined by the formula (f) satisfies the total Nz <1.0.
Total Re = Re1 + Re2 (D)
Total Rth = Rth1 + Rth2 (e)
Total Nz = Total Rth / Total Re + 0.5 (f)   The retardation film according to claim 4, wherein the thermoplastic polymer film is a cycloolefin resin.   The retardation film according to claim 4, wherein the thermoplastic polymer film is a cellulose resin. (1) a first step in which an alignment layer for forming a homeotropic alignment is formed on a thermoplastic polymer film by a liquid crystalline composition exhibiting positive uniaxiality;
(2) On the alignment layer, a layer of a liquid crystalline composition exhibiting positive uniaxiality is applied, and after homeotropic alignment of the layer, a homeotropic alignment liquid crystal layer having a fixed alignment is formed, A second step of obtaining a laminated film comprising a plastic polymer film / alignment layer / homeotropic alignment liquid crystal layer;
(3) a third step of obtaining a retardation film by stretching a laminated film comprising the thermoplastic polymer film / alignment layer / homeotropic alignment liquid crystal layer;
A method for producing a retardation film, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0. (1) A layer of a liquid crystalline composition exhibiting positive uniaxiality is applied on an alignment substrate, the layer is homeotropically aligned, and then a homeotropic alignment liquid crystal layer with a fixed alignment is formed to align the layer. A first step of obtaining a laminate (A) comprising a substrate / homeotropic alignment liquid crystal layer;
(2) After adhering the homeotropic alignment liquid crystal layer side of the laminate (A) to the thermoplastic polymer film via the adhesive layer 1, the alignment substrate is peeled off to form the homeotropic alignment liquid crystal layer. A second step of transferring to a thermoplastic polymer film to obtain a laminate (B) comprising a thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer;
(3) A third step of obtaining a retardation film by stretching the laminate (B) comprising the thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer.
A method for producing a retardation film, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0. (1) A layer of a liquid crystalline composition exhibiting positive uniaxiality is applied on an alignment substrate, the layer is homeotropically aligned, and then a homeotropic alignment liquid crystal layer with a fixed alignment is formed to align the layer. A first step of obtaining a laminate (A) comprising a substrate / homeotropic alignment liquid crystal layer;
(2) a second step of obtaining a laminate (C) by stretching the laminate (A) comprising the alignment substrate / homeotropic alignment liquid crystal layer;
(3) After the homeotropic alignment liquid crystal layer side of the laminate (C) is bonded to the thermoplastic polymer film via the adhesive layer 1, the alignment substrate / homeotropic alignment liquid crystal layer is bonded to the thermoplastic high-molecular layer. A third step of obtaining a retardation film comprising a thermoplastic polymer film / adhesive layer 1 / homeotropic alignment liquid crystal layer after peeling the alignment substrate after transferring to the molecular film;
A method for producing a retardation film, wherein the total Nz value defined by the formula (f) satisfies the total Nz <1.0.   The method for producing a retardation film according to claim 7, wherein the thermoplastic polymer film is surface-treated.   The method for producing a retardation film according to claim 10, wherein the surface treatment is a corona discharge treatment.   The retardation film according to any one of claims 7 to 11, wherein the homeotropic alignment liquid crystal layer is composed of a liquid crystalline composition comprising at least a side chain type liquid crystalline polymer having an oxetanyl group. Method.   The method for producing a retardation film according to claim 7, wherein the homeotropic alignment liquid crystal layer is composed of a liquid crystalline composition comprising at least a low-molecular liquid crystal substance having a reactive functional group.   The method for producing a retardation film according to any one of claims 7 to 13, wherein the thermoplastic polymer film is a cycloolefin resin.   The method for producing a retardation film according to claim 7, wherein the thermoplastic polymer film is a cellulose resin.   The retardation film according to any one of claims 1 to 6 and a polarizing element are laminated, and a slow axis of the retardation film and an absorption axis of the polarizing element are arranged in parallel or orthogonal to each other. A polarizing plate characterized by having   A liquid crystal display device, wherein the polarizing plate according to claim 16 is disposed on at least one side of a liquid crystal cell.

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