JP2009075481A - Method for manufacturing retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a retardation film capable of manufacturing the retardation film of Nz<1.0 appropriate as a viewing angle compensation film of a liquid crystal display device of an IPS system with industrially high manufacturing efficiency. <P>SOLUTION: The method for manufacturing the retardation film comprises an optical laminate production step of producing an optical laminate which is laminated with a first retardation layer, and has a retardation value (Rth<SP>1</SP>) in a thickness direction within a range from 60 to 200 nm, and a second retardation layer which is formed on the first retardation layer and has a retardation value (Rth<SP>2</SP>) in the thickness direction within a range from 300 to -50 nm, and a drawing process of drawing the above optical laminate in an in-plane direction, in which the Nz coefficient is Nz<1.0. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a retardation film used for improving the viewing angle characteristics of a liquid crystal display device, and more particularly, to a method for producing a retardation film suitably used for improving the viewing angle characteristics of an IPS liquid crystal display device. Is.

  The liquid crystal display device has features such as power saving, light weight, thinness, and the like, and has rapidly spread in recent years in place of the conventional CRT display. As a general liquid crystal display device, as shown in FIG. 3, a liquid crystal display device having an incident side polarizing plate 102 </ b> A, an outgoing side polarizing plate 102 </ b> B, and a liquid crystal cell 101 can be exemplified. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light having a vibration surface in a predetermined vibration direction, and crossed Nicols so that the vibration directions are perpendicular to each other. It is arranged to face each other. The liquid crystal cell 101 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

  As such a liquid crystal display device, those using various driving methods are known depending on the arrangement form of the liquid crystal material used in the liquid crystal cell. The main ones of liquid crystal display devices that are popular today are classified into TN, STN, VA, IPS, OCB, and the like. In particular, today, those having the VA and IPS driving methods have come into widespread use.

  On the other hand, the liquid crystal display device has a problem of viewing angle dependency due to the refractive index anisotropy of the liquid crystal cell and the polarizing plate as a particular problem. This problem of viewing angle dependency is a problem that the color and contrast of an image that is visually recognized change when the liquid crystal display device is viewed from the front and when viewed from an oblique direction. Such a problem of viewing angle characteristics has become more serious as the liquid crystal display device has recently been enlarged.

  Various techniques have been developed so far to improve the viewing angle dependency problem. As a typical method, there is a method using a retardation film. In the method using such a retardation film, a retardation film 103 having predetermined optical characteristics is disposed between the liquid crystal cell 101 and the polarizing plates 102A and 102B as shown in FIG. It is a way to improve sex problems. Since this method can improve the above-described viewing angle dependency only by incorporating the retardation film 103 into the liquid crystal display device, it is widely used as a method for easily obtaining a liquid crystal display device having excellent viewing angle characteristics. Has come to be.

  Further, in recent years, as illustrated in FIG. 4, not the method of disposing the retardation film and the polarizing plate separately, but the method of using the retardation film as the polarizing plate protective film constituting the polarizing plate has become mainstream. It is coming. That is, as illustrated in FIG. 5, a general liquid crystal display device has a configuration in which polarizing plates 102 </ b> A and 102 </ b> B are disposed on both sides of the liquid crystal cell 101. The polarizer 111 is sandwiched between two polarizing plate protective films 112a and 112b (FIG. 5A) (here, for the convenience of explanation, the polarizing plate disposed on the liquid crystal cell 101 side) The protective film 112a is referred to as “inner polarizing plate protective film”, and the other polarizing plate protective film 112b is referred to as “outer polarizing plate protective film”. When the viewing angle characteristic of the liquid crystal display device is improved using the retardation film 103, as illustrated in FIG. 5B, the inner polarizing plate of the two polarizing plate protective films 112a and 112b. The use of polarizing plates 102A ′ and 102B ′ in which the retardation film 103 is used as the protective film 112a has become the mainstream in recent years.

Here, the retardation of the retardation film is appropriately determined depending on the driving method of the liquid crystal display device that is the object of improving the viewing angle characteristics, and in particular, IPS (In-Plane Switching). For the liquid crystal display device of the type, a retardation film having a retardation with an Nz coefficient of Nz <1.0 is preferably used. Here, the Nz coefficient is a parameter that defines the shape of the refractive index ellipsoid of the retardation film, and Nz = (Rth / Re) depending on the thickness direction retardation (Rth) and in-plane retardation (Re). It is represented by +0.5.
Conventionally, most of the retardation films that are generally used have an Nz coefficient of Nz ≦ 1.0, and a method for industrially producing a retardation film of Nz <1.0 is as follows. Little is known.
Under such circumstances, as one of methods for industrially producing a retardation film with Nz <1.0, a method for producing a retardation film by stretching the film in the thickness direction is known (patent). Reference 1). Such a method is in principle faithful as a method of setting the Nz coefficient to Nz <1.0 or less. However, there is a problem that it is difficult to stretch uniformly because a special technique of stretching in the thickness direction is used, and the retardation film produced by such a method has a slow phase in the in-plane direction. There is a problem that the accuracy of the shaft is low.

  In view of such problems, it is desirable to employ a method of stretching at least the film in the in-plane direction as a method of producing a retardation film having a characteristic film Nz <1.0 by stretching a film having the characteristics. I can say that. In this regard, Patent Document 2 discloses that a film with Nz <1.0 can be produced by stretching a styrene resin film in the in-plane direction. However, since styrene resin films have the disadvantages of low heat resistance and low mechanical strength, they are not put into practical use as retardation films.

  For this reason, conventionally, there has not been known a production method capable of industrially producing a retardation film of Nz <1.0, which is suitable as a viewing angle compensation film for an IPS liquid crystal display device, with high production efficiency. .

JP-A-5-297223 Japanese translation of PCT publication No. 2002-517583

  The present invention has been made in view of such problems, and industrially produces a retardation film of Nz <1.0, which is suitable as a viewing angle compensation film for an IPS liquid crystal display device, with high production efficiency. The main object of the present invention is to provide a method for producing a retardation film.

In order to solve the above problems, the present invention is formed on the first retardation layer having a retardation value (Rth ¹ ) in the thickness direction of 60 nm to 300 nm, and on the first retardation layer. An optical laminate production step of producing an optical laminate in which a second retardation layer having a retardation value (Rth ² ) in the range of −300 nm to −50 nm is laminated, and the optical laminate in the in-plane direction A retardation film having an Nz coefficient of Nz <1.0, and a method of producing a retardation film.

According to the present invention, in the optical laminate produced in the optical laminate production step, the first retardation layer and the second retardation layer whose retardation values in the thickness direction are within the above-described ranges are laminated. By having the structure, a retardation film having an Nz coefficient of Nz <1.0 can be easily produced by stretching the optical laminate in the in-plane direction in the stretching step.
For this reason, according to this invention, the manufacturing method of the retardation film which can manufacture the retardation film of Nz <1.0 industrially with high manufacturing efficiency can be provided.

  In the present invention, the in-plane retardation (Re) is preferably in the range of 50 nm <Re <160 nm, and the Nz coefficient is preferably in the range of 0 <Nz <0.6. This is because the retardation film produced according to the present invention can be made suitable as a viewing angle compensation film used in an IPS liquid crystal display device.

  In the present invention, the first retardation layer has a transparent substrate and an optically anisotropic layer formed on the transparent substrate and containing an optically anisotropic material. The two phase difference layer preferably contains a liquid crystal material having homeotropic alignment. This is because the retardation film produced according to the present invention can be made excellent in the development of retardation by configuring the first retardation layer and the second retardation layer as described above.

  The method for producing a retardation film of the present invention produces an effect that an Nz <1.0 retardation film, which is suitable as a viewing angle compensation film for an IPS liquid crystal display device, can be produced industrially with high production efficiency. It is.

  Hereinafter, the manufacturing method of the retardation film of this invention is demonstrated in detail.

As described above, the retardation film production method of the present invention is formed on the first retardation layer having a thickness direction retardation value (Rth ¹ ) in the range of 60 nm to 200 nm, and the first retardation layer. An optical laminate manufacturing step for manufacturing an optical laminate in which a second retardation layer having a thickness direction retardation value (Rth ² ) in the range of −300 nm to −50 nm is laminated; A retardation film having a stretching step of stretching the body in an in-plane direction and having a Nz coefficient of Nz <1.0.

Such a method for producing a retardation film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of a method for producing a retardation film of the present invention. As illustrated in FIG. 1, the method for producing a retardation film of the present invention includes an optical laminate production process for producing an optical laminate 10 (FIG. 1 (a)), and the optical laminate 10 in the in-plane direction. This is a method for producing a retardation film 20 having a stretching step (FIG. 1B) to be stretched and having an Nz coefficient of Nz <1.0 (FIG. 1C).
In such an example, the method for producing a retardation film of the present invention is such that the optical laminate produced in the optical laminate producing step (FIG. 1A) has a retardation value (Rth ¹ ) in the thickness direction. A first retardation layer 1 in the range of 60 nm to 200 nm and a retardation value (Rth ² ) in the thickness direction formed on the first retardation layer 1 in the range of −300 nm to −50 nm. The two-phase-difference layer 2 has a laminated structure.

According to the present invention, in the optical laminate produced in the optical laminate production step, the first retardation layer and the second retardation layer whose retardation values in the thickness direction are within the above-described ranges are laminated. By being a thing, the retardation film whose Nz coefficient is Nz <1.0 can be easily produced by extending | stretching the said optical laminated body in an in-plane direction in the said extending process.
For this reason, according to this invention, the manufacturing method of the retardation film which can manufacture the retardation film of Nz <1.0 industrially with high manufacturing efficiency can be provided.

The method for producing a retardation film of the present invention includes at least the optical layered body preparation step and the stretching step, and may include other steps as necessary.
Hereafter, each process used for this invention is demonstrated in order.

First Optical Laminate Fabrication Process First, the optical laminate fabrication process used in the present invention will be described. In this step, the retardation value (Rth ¹ ) in the thickness direction is formed on the first retardation layer 1 having a thickness in the range of 60 nm to 200 nm and the retardation layer 1 in the thickness direction. Rth ² ) is a step of producing an optical laminated body having a configuration in which the second retardation layer 2 having a range of −300 nm to −50 nm is laminated. In the method for producing a retardation film of the present invention, the optical laminate produced in this step has such a configuration, so that a retardation film of Nz <1.0 can be industrially produced with high production efficiency. It can be manufactured.
Hereinafter, after describing the optical layered body manufactured in this step, a method for manufacturing the optical layered body in this step will be described.

1. Optical laminated body The optical laminated body manufactured by this process is demonstrated. As described above, the optical laminate manufactured by this step has a configuration in which a first retardation layer and a second retardation layer having a retardation value in a predetermined thickness direction are laminated.

(1) First retardation layer The first retardation layer has a retardation value (Rth ¹ ) in the thickness direction in the range of 60 nm to 200 nm. Here, the Rth ¹ is not particularly limited as long as it is within the above range, and the Nz coefficient of the retardation film produced according to the present invention is within a range where Nz <1.0, and will be described later. It can be appropriately adjusted according to the Rth ² value of the two phase difference layer. In particular, Rth ¹ of the first retardation layer formed in this step is more preferably in the range of 80 nm to 160 nm.
Here, Rth ¹ is a refractive index in the slow axis direction in the in-plane direction of the first retardation layer nx ¹ , a refractive index in the fast axis direction ny ¹ , a refractive index in the thickness direction nz ¹ , and Rth ¹ = {(nx ¹ + ny ¹ ) / 2−nz ¹ } × d ¹ , where d ¹ is the thickness of the first retardation layer. Such Rth ¹ can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments. The Rth ¹ may vary depending on the wavelength to be measured, but Rth ¹ in the present invention means a value measured at a wavelength of 550 nm unless otherwise specified.

Further, the in-plane retardation (Re ¹ ) of the ^first retardation layer formed in this step is such that the Nz coefficient is Nz <1 when the optical layered body is stretched in the in-plane direction in the stretching step described later. Is not particularly limited as long as it is within a range in which a retardation film of 0.0 can be produced. In particular, Re ¹ is preferably in the range of 0 nm ≦ Re ¹ <50 nm, and more preferably in the range of 0 nm ≦ Re ¹ <10 nm. This is because when Re ¹ is in such a range, Nz <1.0 can be easily realized by stretching the optical layered body in the in-plane direction in the stretching step described later.
Here, Re ¹ is a value represented by Re ¹ = (nx ¹ −ny ¹ ) × d ¹ by nx ¹ , ny ¹ , and d ¹ . Such Re ¹ can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments. The value of Reh ¹ may vary depending on the wavelength to be measured, but Re ¹ in the present invention means a value measured at a wavelength of 550 nm unless otherwise specified.

The configuration of the first retardation layer is not particularly limited as long as it can be stretched in the in-plane direction in the stretching process described later and can achieve Rth ¹ in the above-described range. It is not something. Especially, it is preferable that the 1st phase difference layer formed in this process has a transparent substrate and the optically anisotropic layer formed on the said transparent substrate and containing an optically anisotropic material. This is because, when the first retardation layer has such a configuration, it is easy to make Rth ¹ within the above-described range. Moreover, it is because the optical characteristic expression property of the retardation film manufactured by this invention can be improved.
Hereinafter, the first retardation layer having such a configuration will be described in detail.

(1) Optically anisotropic layer The optically anisotropic layer is formed on a transparent substrate to be described later. By containing an optically anisotropic material, Rth ¹ of the first retardation layer is described above. It has a function within the range.

As an optically anisotropic material used in this step, any optically anisotropic layer can be imparted with retardation enough to make Rth ¹ of the first retardation layer within the above-mentioned range. It is not particularly limited, and can be appropriately selected and used according to the type of transparent substrate described later. Among these, the optically anisotropic material used in this step is preferably a rod-like compound. Since rod-shaped compounds can exhibit excellent retardation by arranging them regularly, it is easy to impart desired retardation to the optically anisotropic layer by using such rod-shaped compounds. It is.
Here, the “rod-like compound” in the present invention means a compound in which the main skeleton of the molecular structure is rod-like.

As the rod-shaped compound used in this step, a compound having a relatively small molecular weight is preferable. More specifically, a compound having a molecular weight in the range of 200 to 1200 is preferable, and a compound having a molecular weight in the range of 400 to 1000 is particularly preferably used.
In addition, when using the material which has a polymerizable functional group as said rod-shaped compound, the molecular weight of the said rod-shaped compound shall show the molecular weight of the monomer before superposition | polymerization.

  Moreover, it is preferable that the rod-shaped compound used for this process is a liquid crystalline material which shows liquid crystallinity. This is because the liquid crystalline material has a property of regularly arranging, and therefore has a large birefringence Δn (nx−ny) and easily imparts a desired retardation to the optically anisotropic layer.

  As the liquid crystalline material, any material exhibiting any liquid crystal phase such as a nematic phase, a cholesteric phase, and a smectic phase can be suitably used. In particular, in this step, it is preferable to use a liquid crystalline material exhibiting a nematic phase. This is because a liquid crystalline material exhibiting a nematic phase is easily arranged regularly as compared with liquid crystalline materials exhibiting other liquid crystal phases.

  Further, as the liquid crystalline material exhibiting the nematic phase, it is preferable to use a material having spacers at both ends of the mesogen. This is because the liquid crystalline material having spacers at both ends of the mesogen is excellent in flexibility, and by using such a liquid crystalline material, the optically anisotropic film used in the present invention can be made excellent in transparency.

Furthermore, as the rod-shaped compound used in this step, those having a polymerizable functional group in the molecule are preferably used, and among them, those having a polymerizable functional group capable of three-dimensional crosslinking are more preferably used. Since the rod-shaped compound has a polymerizable functional group, the rod-shaped compound can be polymerized and fixed. Therefore, an optically anisotropic layer that has excellent alignment stability and is less likely to change over time in retardation. Because it can be obtained.
Moreover, in this process, you may mix and use the rod-shaped compound which has the said polymeric functional group, and the rod-shaped compound which does not have the said polymeric functional group.
The “three-dimensional cross-linking” means that liquid crystal molecules are polymerized three-dimensionally to form a network (network) structure.

  Examples of the polymerizable functional group include polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat. Representative examples of these polymerizable functional groups include radically polymerizable functional groups or cationic polymerizable functional groups. Further, representative examples of radically polymerizable functional groups include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups having or not having substituents, An acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like can be given. Moreover, an epoxy group etc. are mentioned as a specific example of the said cation polymerizable functional group. In addition, examples of the polymerizable functional group include an isocyanate group and an unsaturated triple bond. Among these, from the viewpoint of the process, a functional group having an ethylenically unsaturated double bond is preferably used.

Furthermore, the rod-like compound is a liquid crystalline material exhibiting liquid crystallinity, and the one having the polymerizable functional group at the terminal is particularly preferable. By using such a liquid crystal material, for example, they can be polymerized three-dimensionally to form a network structure, so that they have alignment stability and excellent optical properties. This is because an optically anisotropic layer can be formed.
In this step, even when a liquid crystalline material having a polymerizable functional group at one end is used, the alignment can be stabilized by crosslinking with other molecules.

  Specific examples of the rod-shaped compound used in this step include compounds represented by the following formulas (1) to (6).

ここで、化学式（１）、（２）、（５）および（６）で示される液晶性材料は、Ｄ.Ｊ.Ｂｒｏｅｒら、Ｍａｋｒｏｍｏｌ．Ｃｈｅｍ．１９０,３２０１−３２１５（１９８９）、またはＤ.Ｊ.Ｂｒｏｅｒら、Ｍａｋｒｏｍｏｌ.Ｃｈｅｍ.１９０,２２５０（１９８９）に開示された方法に従い、あるいはそれに類似して調製することができる。また、化学式（３）および（４）で示される液晶性材料の調製は、ＤＥ１９５,０４,２２４に開示されている。

Here, the liquid crystalline materials represented by the chemical formulas (1), (2), (5) and (6) are disclosed in DJ Broer et al., Makromol. Chem. 190, 3201-3215 (1989), or DJ Broer et al., Makromol. Chem. 190, 2250 (1989), or can be prepared similarly. The preparation of liquid crystalline materials represented by the chemical formulas (3) and (4) is disclosed in DE 195,04,224.

Specific examples of the nematic liquid crystalline material having an acrylate group at the terminal include those represented by the following chemical formulas (7) to (17).

なお、本工程に用いられる液晶性材料は、１種類のみであってもよく、または、２種以上であってもよい。例えば、上記液晶性材料として、両末端に重合性官能基を１つ以上有する液晶性材料と、片末端に重合性官能基を１つ以上有する液晶性材料とを混合して用いると、両者の配合比の調整により重合密度（架橋密度）及び光学特性を任意に調整できる点から好ましい。

In addition, the liquid crystalline material used for this process may be only 1 type, or 2 or more types. For example, when the liquid crystalline material is a mixture of a liquid crystalline material having one or more polymerizable functional groups at both ends and a liquid crystalline material having one or more polymerizable functional groups at one end, This is preferable because the polymerization density (crosslinking density) and optical characteristics can be arbitrarily adjusted by adjusting the blending ratio.

  The optically anisotropic layer used in this step may contain other compounds in addition to the optically anisotropic material. Examples of such other compounds include silicon leveling agents such as polydimethylsiloxane, methylphenylsiloxane, and organically modified siloxane; linear polymers such as polyalkyl acrylate and polyalkyl vinyl ether; fluorine surfactants; Surfactants such as hydrocarbon surfactants; fluorine leveling agents such as tetrafluoroethylene; photopolymerization initiators and the like can be mentioned. Among these, when a rod-like compound having a polymerizable functional group that is polymerized by light irradiation is used as the optically anisotropic material, it is preferable that a photopolymerization initiator is included as the other compound.

  Examples of the photopolymerization initiator include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-amino · acetophenone, 4,4- Dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, p -Tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyl dimethyl ketal, benzyl methoxyethyl acetal, ben Inmethyl ether, benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzsuberone, methyleneanthrone, 4-azidobenzylacetophenone, 2,6-bis (p- Azidobenzylidene) cyclohexane, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-phenyl-propanedione-2 -(O-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o-benzoyl) o Shim, Michler's ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, naphthalene Sulfonyl chloride, quinoline sulfonyl chloride, n-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, Adeka N1717, carbon tetrabromide, tri Examples include combinations of photoreducing dyes such as bromophenyl sulfone, benzoin peroxide, eosin, and methylene blue with reducing agents such as ascorbic acid and triethanolamine.

  In this step, these photopolymerization initiators may be used alone or in combination of two or more.

  Moreover, when using the said photoinitiator, it is preferable to use a photoinitiator adjuvant together. Photopolymerization initiation aids that can be used in this step include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as 2-dimethylaminoethylbenzoic acid and ethyl 4-dimethylamidebenzoate. Although it can illustrate, it is not restricted to these.

  When the optically anisotropic layer contains the photopolymerization initiator, the content is not particularly limited as long as the optically anisotropic material can be polymerized in a desired time. The range of 1 to 10 parts by weight, preferably 3 to 6 parts by weight, is preferable with respect to 100 parts by weight of the compound.

  Furthermore, the following compounds can be added to the optically anisotropic layer as long as the object of the present invention is not impaired. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resins, polycarboxylic acid polyglycidyl esters, polyol polyglycidyl ethers, aliphatic or cycloaliphatic epoxy resins, amino group epoxy resins, triphenolmethane type epoxy resins, dihydroxybenzene type epoxy resins and the like (meta Acu Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting Le acid; photopolymerizable liquid crystal compound having an acryl group or methacryl group and the like. By containing such a compound, the mechanical strength of the optically anisotropic layer formed by this step is improved, and the stability may be improved.

  The thickness of the optically anisotropic layer is a range in which the optical characteristics of the first retardation layer formed by this step can be set to a desired value depending on the optically anisotropic material and the type of transparent substrate described later. If it is in, it will not specifically limit. Especially in this process, it is preferable to exist in the range of 0.5 micrometer-20 micrometers.

(2) Transparent substrate Next, the transparent substrate used for this process is demonstrated. The transparent substrate used in this step supports the optically anisotropic layer described above.

The transparent substrate used in this step can be stretched in a stretching step to be described later, and has a retardation that allows Rth ¹ of the first retardation layer produced in this step to be within the above-described range. It will not specifically limit if it is provided.

  Examples of such transparent substrates include cellulose derivatives, cycloolefin polymers, acrylic resins such as polymethyl methacrylate, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polyarylate, polyvinyl alcohol, polyimide, polysulfone, A transparent substrate made of polyethersulfone, amorphous polyolefin, modified acrylic polymer, polystyrene, epoxy resin, and polycarbonate can be exemplified. Among these, in this step, it is preferable to use a transparent substrate made of cellulose or a cycloolefin polymer.

  As the cellulose derivative used in this step, a cellulose ester is preferably used, and among the cellulose esters, cellulose acylates are preferably used. This is because cellulose acylates are advantageous in terms of availability because they are widely used industrially.

  As the cellulose acylates, C 2-4 lower fatty acid esters are preferably used. Such a lower fatty acid ester may contain only a single lower fatty acid ester, for example, cellulose acetate, and a plurality of fatty acid esters such as cellulose acetate butyrate and cellulose acetate propionate may be used. It may be included.

  In this step, cellulose acetate can be particularly preferably used among the lower fatty acid esters. Among cellulose acetates, it is most preferable to use triacetyl cellulose having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0). Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation can be determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).

  On the other hand, the cycloolefin polymer used in this step is not particularly limited as long as it is a resin having a monomer unit composed of a cyclic olefin (cycloolefin). Examples of such a monomer comprising a cyclic olefin include norbornene and polycyclic norbornene monomers.

  In addition, as said cycloolefin type polymer, any of a cycloolefin polymer (COP) or a cycloolefin copolymer (COC) can be used conveniently. In addition, the cycloolefin polymer used in this step may be a homopolymer of a monomer composed of the above cyclic olefin, or may be a copolymer.

The cycloolefin polymer used in this step preferably has a saturated water absorption at 23 ° C. of 1% by mass or less, and particularly preferably within a range of 0.1% by mass to 0.7% by mass. By using such a cycloolefin polymer, the retardation film produced according to the present invention can be made less susceptible to changes in optical properties and dimensions due to water absorption.
Here, the said saturated water absorption is calculated | required by immersing in 23 degreeC water for 1 week based on ASTMD570, and measuring an increase weight.

  In addition, the cycloolefin polymer used in this step preferably has a glass transition point in the range of 100 ° C to 200 ° C, particularly preferably in the range of 100 ° C to 180 ° C, and in particular, 100 ° C. What is in the range of -150 degreeC is preferable. This is because when the glass transition point is within the above range, the heat resistance and processability of the retardation film produced according to the present invention can be improved.

  Specific examples of the transparent substrate made of cycloolefin polymer used in this step include, for example, Ticona Topas, JSR Arton, ZEON Corporation ZEONOR, ZEON Corporation ZEONEX, Mitsui Chemicals Corporation And those obtained by subjecting these transparent substrates to stretching treatment.

  The thickness of the transparent substrate used in this step is not particularly limited as long as it can provide the necessary self-supporting property for the first retardation layer produced in this step, but is usually in the range of 25 μm to 1000 μm. It is preferable that it is in the range of 20 micrometers-100 micrometers especially. This is because if the thickness of the transparent substrate is thinner than the above range, the necessary self-supporting property may not be imparted to the retardation film produced according to the present invention. Further, if the thickness is thicker than the above range, for example, when cutting the retardation film produced according to the present invention, the processing waste may increase or the cutting blade may be worn quickly. It is.

  The configuration of the transparent substrate used in this step is not limited to a configuration consisting of a single layer, and may be a configuration in which a plurality of layers are laminated. When it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.

(2) Second Retardation Layer Next, the second retardation layer formed by this step will be described. The second retardation layer formed by this step has a thickness direction retardation value (Rth ² ) in the range of −300 nm to −50 nm. Here, the Rth ² is not particularly limited as long as it is within the above range, and the Nz coefficient of the retardation film produced according to the present invention is within the range where Nz <1.0, and the above-described Rth ² is the above. It is appropriately adjusted according to the value of Rth ¹ of one retardation layer. In particular, Rth ² of the second retardation layer formed in this step is more preferably in the range of −250 nm to −80 nm. Here, Rth ² is a refractive index in the slow axis direction in the in-plane direction of the first retardation layer nx ² , a refractive index in the fast axis direction ny ² , a refractive index in the thickness direction nz ² , and This is a value represented by Rth ² = {(nx ² + ny ² ) / 2−nz ² } × d ² when the thickness of the first retardation layer is d ² . Note that the measurement method and measurement wavelength of Rth ² are the same as those of Rth ¹ , and the description thereof is omitted here.

Further, the in-plane retardation (Re ² ) of the ^second retardation layer formed in this step is such that the Nz coefficient is Nz <1 when the optical layered body is stretched in the in-plane direction in the stretching step described later. Is not particularly limited as long as it is within a range in which a retardation film of 0.0 can be produced. In particular, Re ² is preferably in the range of 0 nm ≦ Re ² <10 nm.
This is because when Re ² is in such a range, Nz <1.0 can be easily realized by stretching the optical layered body in the in-plane direction in the stretching step described later.
Here, Re ² is a value represented by Re ² = (nx ² −ny ² ) × d ² by nx ² , ny ² , and d ² . The measurement method and measurement wavelength of Re ² are the same as those of Rth ² and will not be described here.

The configuration of the second retardation layer is not particularly limited as long as it can be stretched in the in-plane direction in a stretching process described later and can achieve Rth ² in the above-described range. It is not something. Especially, it is preferable that the 2nd phase difference layer formed in this process contains the liquid crystal material by which homeotropic alignment was carried out. This is because the retardation film produced according to the present invention can be made to have excellent retardation characteristics by configuring the second retardation layer as described above.

The liquid crystal material used in this step is not particularly limited as long as it can realize Rth ² in the above-described range by forming homeotropic alignment in the second retardation layer. Of these, the liquid crystal material used in the present invention preferably has a polymerizable functional group. By using such a liquid crystal material, it is possible to polymerize each other via a polymerizable functional group, so that the mechanical strength of the second retardation layer formed by this step can be improved. Further, the homeotropic alignment stability of the liquid crystal material in the second retardation layer can also be improved.

As the polymerizable functional group, various polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat can be used. Typical examples of these polymerizable functional groups include radical polymerizable functional groups or cationic polymerizable functional groups.
Representative examples of the radical polymerizable functional group include a functional group having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include a vinyl group having or not having a substituent, An acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like can be given.
Moreover, an epoxy group etc. are mentioned as a specific example of the said cation polymerizable functional group.
Furthermore, examples of polymerizable functional groups other than the above include isocyanate groups and unsaturated triple bonds.
In particular, in this step, among these polymerizable functional groups, a functional group having an ethylenically unsaturated double bond is preferably used from the viewpoint of the process.

  The liquid crystal material used in this step may have a plurality of the above polymerizable functional groups, or may have only one.

  The liquid crystal material that can be used in this step includes a homeotropic alignment (first liquid crystal material) that can form a homeotropic alignment without using a vertical alignment film, and a homeotropic alignment by itself. Although it cannot be used, a material (second liquid crystal material) that can form homeotropic alignment by using a vertical alignment film can be given. In this step, not only the first liquid crystal material but also the second liquid crystal material can be suitably used.

In the case where the second liquid crystal material is used in this step, in order to homeotropically align the liquid crystal material in the second retardation layer, the first retardation layer and the second retardation layer described above are usually used. A method using an alignment layer having an alignment regulating force for homeotropic alignment of the liquid crystal material between them, or using an alignment control compound having a function of homeotropic alignment of the liquid crystal material in the third retardation layer is used. The orientation control compound is described in, for example, JP-A-10-319408.
Also, a transfer method in which a second retardation layer in which the second liquid crystal material is homeotropically oriented is separately formed on another substrate such as a glass substrate, and then peeled off and laminated on the first retardation layer. Can also be used. In such a transfer method, a method of forming the second retardation layer on the other substrate is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-177242.

  The first liquid crystal material is not particularly limited as long as it can form homeotropic alignment without using a vertical alignment film and can impart desired retardation to the second retardation layer. is not. Examples of the first liquid crystal material include a monomer unit containing a liquid crystalline fragment side chain having positive refractive index anisotropy and a monomer unit containing a non-liquid crystalline fragment side chain. A liquid crystal polymer such as a side chain type liquid crystal polymer or a side chain type liquid crystal polymer containing a monomer unit containing the liquid crystalline fragment side chain and a monomer unit containing a liquid crystalline fragment side chain having an alicyclic ring structure; Can be mentioned. Examples of such a liquid crystal polymer include compounds described in JP-A No. 2003-121853, JP-A No. 2002-174725, and JP-A No. 2005-70098.

  On the other hand, the second liquid crystal material is not particularly limited as long as it can form a homeotropic alignment by using a vertical alignment film or the like and can impart a desired retardation to the second retardation layer. Is not to be done. In particular, in this step, a nematic liquid crystal material exhibiting a nematic phase is preferably used.

  Specific examples of the second liquid crystal material used in this step include compounds described in JP-T-10-508882 and JP-A-2003-287623. Especially in this process, the compound represented by said Formula (1)-(17) can be used suitably as said 2nd liquid crystal material.

  Moreover, as said 2nd liquid crystal material used for this invention, the compound as described in Unexamined-Japanese-Patent No. 10-319408 can be mentioned, for example. Especially in this process, the compound represented by the following chemical formula can be used suitably.

上記式において、ｘは１〜１２であり、Ｚは１，４−フェニレン基または１，４−シクロヘキシレン基であり、Ｒ^１はハロゲンまたはシアノであるか、あるいは炭素原子１〜１２個を有するアルキル基またはアルコキシ基であり、そしてＬは、Ｈ、ハロゲンまたはＣＮであるか、あるいは炭素原子１〜７個を有するアルキル基、アルコキシ基またはアシル基である。

In the above formula, x is 1 to 12, Z is a 1,4-phenylene group or 1,4-cyclohexylene group, R ¹ is halogen or cyano, or has 1 to 12 carbon atoms. An alkyl group or an alkoxy group, and L is H, halogen or CN, or an alkyl group, an alkoxy group or an acyl group having 1 to 7 carbon atoms.

  When a compound having a polymerizable functional group is used as the liquid crystal material, the liquid crystal material contained in the retardation layer used in the present invention is a polymer polymerized through the polymerizable functional group.

  The liquid crystal material used in this step may be one type or two or more types. When two or more kinds of liquid crystal materials are used, the first liquid crystal material and the second liquid crystal material may be mixed and used.

  In the case where the second retardation layer formed in this step contains the above-described liquid crystal material, the second retardation layer may contain a compound other than the liquid crystal material. . Such other compounds are not particularly limited as long as they do not impair the alignment state of the liquid crystal material in the second retardation layer and the optical properties of the second retardation layer. Can be appropriately selected and used according to the use of the retardation film produced by the above method. As said other compound used for this process, the alignment control compound which assists the homeotropic alignment formation of the said liquid-crystal material can be mentioned, for example. By using such an alignment control compound, there is an advantage that the liquid crystal material of the second aspect can be used. Further, even when the liquid crystal material of the first aspect is used, there is an advantage that the regularity of homeotropic alignment can be improved by using such an alignment control compound.

  The alignment control compound is not particularly limited as long as it can impart a desired homeotropic alignment regulating force to the second retardation layer. As such an alignment control compound, a surfactant can be suitably used. In the second retardation layer, the surfactant is unevenly distributed at the air interface, and a specific direction of molecules can be arranged toward the second retardation layer, so that the homeotropic alignment regulation is provided in the second retardation layer. This is because the force can be easily applied.

  Examples of the surfactant include a sulfonate surfactant, and a fluorinated sulfonate surfactant is particularly preferably used. Specific examples of the fluorinated sulfonate surfactant include trade names FC-4430 and FC-4432 (both manufactured by 3M Company).

  Moreover, as said other compound, a polymerization initiator, a polymerization inhibitor, a plasticizer, surfactant, a silane coupling agent etc. can be mentioned, for example.

(3) Optical Laminate As described above, the optical laminate formed in this step has a configuration in which the first retardation layer and the second retardation layer are laminated. A specific configuration of such an optical laminate is particularly limited as long as it can produce a retardation film with Nz <1.0 by being stretched in the in-plane direction in a stretching process described later. It is not a thing. In particular, in the optical layered body used in this step, the first retardation layer has the above-described transparent substrate and an optically anisotropic layer formed on the transparent substrate and containing an optically anisotropic material. It is preferable that the second retardation layer contains a liquid crystal material having the homeotropic alignment described above. By configuring the first retardation layer and the second retardation layer as described above, the retardation film produced according to the present invention is suitably used as a viewing angle compensation film for an IPS liquid crystal display device. Because it can be made.

The optical laminate having such a configuration will be described with reference to the drawings. FIG. 2 is a schematic view showing an example of an optical laminate produced by this process. As illustrated in FIG. 2, the optical laminate 10 formed by this step includes a transparent substrate 1a and an optically anisotropic layer 1b formed on the transparent substrate 1a and containing an optically anisotropic material. The first retardation layer 1 having the first retardation layer 1 and the second retardation layer 2 formed on the first retardation layer 1 and containing a homeotropically aligned liquid crystal material are preferable.
Here, when the optical laminated body 10 produced by this process has such a configuration, as an aspect in which the second retardation layer 2 is formed on the first retardation layer 1, As illustrated in FIG. 2A, the second retardation layer 2 may be formed on the transparent substrate 1a. Alternatively, as illustrated in FIG. Alternatively, the second retardation layer 2 may be formed on the conductive layer 1b.

2. Next, a method for manufacturing an optical layered body in this step will be described. The method for producing the optical laminate in this step is not particularly limited as long as it is a method capable of producing the optical laminate including the first retardation layer and the second retardation layer described above. It can be appropriately determined according to the configuration of the first retardation layer and the second retardation layer. Examples of such a method include the following method.
The first method uses a transparent substrate, and the first retardation layer is produced by coating an optically anisotropic layer-forming coating solution containing an optically anisotropic material on the transparent substrate. By applying a second retardation layer forming coating liquid containing the liquid crystal material on the retardation layer forming step and the first retardation layer produced by the first retardation layer forming step, A retardation layer forming step of forming a second retardation layer on the first retardation layer.
In the second method, a first retardation layer is produced by applying a coating liquid for forming an optically anisotropic layer containing the optically anisotropic material onto the transparent substrate using a transparent substrate. After forming a second retardation layer containing a liquid crystal material on a substrate provided with a one retardation layer forming step and a vertical alignment film, only the second retardation layer is placed on the first retardation layer. And a second retardation layer forming step of adhering via the method.

Second Stretching Step Next, the stretching step in the present invention will be described. This step is a step of obtaining a retardation film having an Nz coefficient of Nz <1.0 by stretching the optical laminate produced in the optical laminate production step in the in-plane direction.

In this step, the magnification at which the optical layered body is stretched in the in-plane direction is not particularly limited as long as the Nz coefficient can be set to Nz <1.0. In particular, in this step, it is preferable to stretch the optical laminate so that the Nz coefficient is 0 <Nz <0.6. Furthermore, the draw ratio at which the optical layered body is stretched in this step is such that the in-plane retardation (Re) of the optical layered body after stretching is in the range of 50 nm to 160 nm, more preferably in the range of 70 nm to 140 nm. It is preferable to be within a range that can be performed. This is because the retardation film produced according to the present invention can be made suitable as a viewing angle compensation film used in an IPS liquid crystal display device.
The specific draw ratio can be appropriately determined according to the configuration of the first retardation layer and the second retardation layer constituting the optical layered body.

  The aspect of stretching the optical laminate in this step is not particularly limited as long as the stretching direction of the optical laminate is an in-plane direction. Therefore, the mode of stretching may be uniaxial stretching or biaxial stretching.

In addition, the method for stretching the optical layered body in this step is not particularly limited as long as the Nz coefficient after stretching is within a range where Nz <1.0. As a method used in this step, for example, any stretching method such as a roll stretching method, a long gap stretching method, a tenter stretching method, and a tubular stretching method can be appropriately performed.
In addition, the optical laminate that is stretched in this step is preferably heated to, for example, a glass transition temperature or higher and a melting temperature (or melting temperature) or lower when stretching.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  Next, the present invention will be described more specifically by showing examples.

1. Example 1
A nematic liquid crystal material represented by the following formula (I) is dissolved in cyclohexanone by 15% by weight, applied to the surface of a transparent substrate made of a TAC film (manufactured by FUJIFILM Corporation, product name: TF80UL) by bar coating, 50 After removing the solvent by heating at 4 ° C. for 4 minutes, the first retardation layer was formed by irradiating the coated surface with ultraviolet rays. Here, the retardation (Rth ¹ ) in the thickness direction of the first retardation layer was 140 nm.

次に、下記式（Ａ）、（Ｂ）で表される液晶材料を、式（Ａ）で表される側鎖型ポリマー８０質量％と、下記式（Ｂ）で表される重合性液晶２０質量％との液晶混合物、光重合開始剤（チバスペシャリティケミカルズ社製、イルガキュア９０７、液晶混合物に対して５質量％）を、トルエン溶液に固形分２０質量％になるように溶解させ、更にレベリング剤を添加した。第１位相差層の透明基材側に、バーコーターにて塗工した後、１００℃で１分間乾燥し、そのまま室温まで冷却することにより、上記液晶混合物をホメオトロピック配向させた。さらに１００ｍＪ／ｃｍ^２のＵＶにて硬化させ、第２位相差層を形成し、光学積層体を得た。ここで、上記第２位相差層の厚み方向レターデーション（Ｒｔｈ^２）は、―１３０ｎｍであった。

Next, the liquid crystal material represented by the following formulas (A) and (B) is obtained by using 80% by mass of the side chain polymer represented by the formula (A) and the polymerizable liquid crystal 20 represented by the following formula (B). A liquid crystal mixture and a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 907, 5% by mass with respect to the liquid crystal mixture) are dissolved in a toluene solution so as to have a solid content of 20% by mass, and further a leveling agent Was added. After coating with a bar coater on the transparent substrate side of the first retardation layer, the liquid crystal mixture was homeotropically aligned by drying at 100 ° C. for 1 minute and then cooling to room temperature. Furthermore, it hardened | cured with 100 mJ / cm < ² > UV, the 2nd phase difference layer was formed, and the optical laminated body was obtained. Here, the thickness direction retardation (Rth ² ) of the ^second retardation layer was −130 nm.

次に、上記光学積層体を延伸実験装置により延伸倍率が１．２倍となるように１６０℃で加熱しながら面内方向にテンター延伸して位相差フィルムを作製した。この時、作製した位相差フィルムの面内レターデーション（Ｒｅ）は１２０ｎｍであり、Ｎｚ係数は、Ｎｚ＝０．４であった。

Next, the optical layered product was tenter-stretched in the in-plane direction while being heated at 160 ° C. so that the stretch ratio was 1.2 times using a stretching experiment apparatus, thereby producing a retardation film. At this time, the in-plane retardation (Re) of the produced retardation film was 120 nm, and the Nz coefficient was Nz = 0.4.

2. Example 2
Using the liquid crystal materials represented by the following formulas (II) and (III), the polymerizable liquid crystal material represented by the formulas (II) and (III) was dissolved 2: 1 by mass in cyclohexanone, and a TAC film ( By coating the surface of a transparent substrate made of FUJIFILM Corporation, trade name: TF80UL) by bar coating, heating at 50 ° C. for 4 minutes to remove the solvent, and then irradiating the coated surface with ultraviolet rays. One retardation layer was formed. Here, the retardation (Rth ¹ ) in the thickness direction of the first retardation layer was 80 nm.

下記式（Ｃ）、（Ｄ）、および、（Ｅ）に示される液晶材料を含有する光学異方性材料、光重合開始剤（チバスペシャリティケミカルズ社製、イルガキュア９０７、光学異方性材料に対して５質量％）を、トルエン溶液に固形分２０質量％になるように溶解させ、更にレベリング剤を添加した。次いで、垂直配向膜が形成されたガラス基板上に塗布し、６０℃で２分間乾燥し、ホメオトロピック配向させ、１００ｍＪ／ｃｍ^２のＵＶにて硬化させた。この時、第２位相差層のＲｔｈ^２＝―２５０ｎｍとなるように膜厚を調整した。
次いで、上記第２位相差層をガラス基板から剥離し、粘着剤を介して実施例２に記載の第１位相差層の透明基材側に貼り合せることにより光学積層体を作製した。

An optically anisotropic material containing a liquid crystal material represented by the following formulas (C), (D), and (E), a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 907, optically anisotropic material) 5% by mass) was dissolved in a toluene solution to a solid content of 20% by mass, and a leveling agent was further added. Then, it was applied on a glass substrate on which a vertical alignment film was formed, dried at 60 ° C. for 2 minutes, homeotropically aligned, and cured with 100 mJ / cm ² of UV. At this time, the film thickness was adjusted so that Rth ² of the second retardation layer was −250 nm.
Subsequently, the said 2nd phase difference layer was peeled from the glass substrate, and the optical laminated body was produced by bonding to the transparent base material side of the 1st phase difference layer as described in Example 2 through the adhesive.

次に、上記光学積層体を延伸実験装置により延伸倍率が１．１５倍となるように１５０℃で加熱しながら面内方向にテンター延伸して位相差フィルムを作製した。この時、作製した位相差フィルムの面内レターデーション（Ｒｅ）は７０ｎｍであり、Ｎｚ係数は、Ｎｚ＝０．３であった。

Next, the optical layered product was tenter-stretched in the in-plane direction while being heated at 150 ° C. so as to have a draw ratio of 1.15 times using a stretching experiment apparatus to produce a retardation film. At this time, the in-plane retardation (Re) of the produced retardation film was 70 nm, and the Nz coefficient was Nz = 0.3.

3. Example 3
An optical laminated body was produced by the same method as in Example 2. At this time, the optical properties of the first retardation layer and the second retardation layer of the produced optical laminate were Rth ¹ = 160 nm and Rth ² = −180 nm, respectively.

  Next, the produced optical layered body was stretched by the same method as in Example 2 except that the stretch ratio was 1.3 times, thereby producing a retardation film. At this time, the retardation retardation (Re) of the produced retardation film was 110 nm, and the Nz coefficient was Nz = 0.35.

4). Comparative Example 1
An optical laminated body was produced by the same method as in Example 1. At this time, the optical characteristics of the first retardation layer and the second retardation layer of the produced optical laminate were Rth ¹ = 80 nm and Rth ² = -40 nm, respectively.

  Next, except that the draw ratio was set to 1.15 times, the produced optical laminate was stretched by the same method as in Example 1 to produce a retardation film. At this time, the in-plane retardation (Re) of the produced retardation film was 70 nm, and the Nz coefficient was Nz = 2.8.

5). Comparative Example 2
An optical laminated body was produced by the same method as in Example 2. At this time, the optical characteristics of the first retardation layer and the second retardation layer of the produced optical laminate were Rth ¹ = 200 nm and Rth ² = -40 nm, respectively.

  Next, except that the draw ratio was 1.15 times, the produced optical laminate was stretched by the same method as in Example 2 to produce a retardation film. At this time, the in-plane retardation (Re) of the produced retardation film was 160 nm, and the Nz coefficient was Nz = 1.2.

It is the schematic which shows an example of the manufacturing method of the retardation film of this invention. It is the schematic which shows an example of the optical laminated body produced by the optical laminated body production process in this invention. It is the schematic which illustrates typically a part of common liquid crystal display device. It is the schematic which illustrates typically a part of liquid crystal display device with which the phase difference film was used. It is the schematic which shows an example of the usage condition of a phase difference film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st phase difference layer 1a ... Transparent substrate 1b ... Optically anisotropic layer 2 ... 2nd phase difference layer 10 ... Optical laminated body 101 ... Liquid crystal cell 102A, 102B, 102A ', 102B' ... Polarizing plate 103 ... Phase difference Film 111 ... Polarizer 112a, 112b ... Polarizing plate protective film

Claims (3)

A first retardation layer having a thickness direction retardation value (Rth ¹ ) in the range of 60 nm to 200 nm and the retardation layer in the thickness direction (Rth ² ) of −300 nm are formed on the first retardation layer. An optical laminate producing step of producing an optical laminate in which a second retardation layer in a range of -50 nm is laminated;
Stretching the optical laminate in an in-plane direction, and a stretching step,
A method for producing a retardation film, comprising producing a retardation film having an Nz coefficient of Nz <1.0.   2. The retardation film according to claim 1, wherein the in-plane retardation (Re) is in the range of 50 nm <Re <160 nm, and the Nz coefficient is in the range of 0 <NZ <0.6. Manufacturing method.   The first retardation layer has a transparent substrate, an optically anisotropic layer formed on the transparent substrate and containing an optically anisotropic material, and the second retardation layer is a homeosphere. The method for producing a retardation film according to claim 1, comprising a liquid crystal material having a tropic alignment.

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