JP2009086257A - Retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film which is desirable for use, as a viewing angle compensation film in an IPS system liquid crystal display and which is superior in stabilization of the optical characteristics. <P>SOLUTION: This retardation film has a transparent substrate, consisting of a cellulose derivative, an optically anisotropic film formed on this transparent substrate and having an optically anisotropy layer, containing a bar shaped compound, having a refractive index anisotropy and satisfying the relation nx<SB>1</SB>>ny<SB>1</SB>≥nz<SB>1</SB>among a refractive index nx<SB>1</SB>in the slow axis direction in the plane; a refractive index ny<SB>1</SB>in the advance axis direction in the plane; a refractive index nz<SB>1</SB>in the thickness direction; and the retardation layer formed on the optically anisotropic film and containing a liquid crystal material that forms a homeotropic orientation and satisfying the relation nx<SB>2</SB>≤ny<SB>2</SB><nz<SB>2</SB>among the refractive indexes nx<SB>2</SB>, ny<SB>2</SB>in arbitrary x, y directions that perpendicularly cross each other in the plane and the refractive index nz<SB>2</SB>in the thickness direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a retardation film suitably used for an IPS liquid crystal display device.

  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. 4, 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 liquid crystal display devices that are popular today are classified into TN, STN, MVA, IPS (including FFS mode and FLC mode), OCB, and the like. In particular, today, those having the MVA 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 specific 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 this retardation film, the 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 the problem. Since such a method can improve the viewing angle dependency problem only by incorporating the retardation film 103 in the liquid crystal display device, it can be easily obtained as a liquid crystal display device having excellent viewing angle characteristics. It has been widely used.
Here, as the retardation film, for example, a film having a structure in which a retardation layer containing a regularly arranged liquid crystal material is formed on a transparent substrate or a film made of a stretched film is generally known. It has been.

  In recent years, the method of using the retardation film as the polarizing plate protective film constituting the polarizing plate has become the mainstream, not the method of separately arranging the retardation film and the polarizing plate as illustrated in FIG. It is coming. That is, as illustrated in FIG. 6, 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. 6A) (here, for convenience of explanation, a 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. 6B, the inner polarizing plate of the two polarizing plate protective films 112a and 112b. The use of polarizing plates 102A ′ and 102B ′ using the retardation film 103 as the protective film 112a has become the mainstream in recent years.

  The retardation of the retardation film depends on the driving method of the liquid crystal display device that is the object of improving the viewing angle characteristics, and in particular, the IPS (In-Plane Switching) type liquid crystal display device. It is desirable to use a retardation film having properties as an optically positive C plate and a retardation film having properties as an optically positive A plate. In the conventional IPS liquid crystal display device, the above-described retardation film having properties as an optically positive C plate and the retardation film having properties as an optically positive A plate are individually provided. However, in recent years, a retardation film in which these retardation films are integrally formed is known and has been used. Such a retardation film is disclosed in Patent Document 1, for example.

By the way, the retardation film having the property as the optically positive C plate usually achieves predetermined optical characteristics by including a retardation layer in which liquid crystal materials are arranged in a predetermined form. . Therefore, in the retardation film in which the retardation film having the property as the optically positive A plate and the retardation film having the property as the optically positive C plate are integrally formed, the liquid crystal In general, a retardation layer in which materials are arranged in a predetermined form has a configuration in which a retardation film having properties as an optically positive A plate is laminated (for example, the above-mentioned Patent Document 1). However, in the retardation film having such a configuration, the alignment of the liquid crystal material in the retardation layer over time is impaired by the action of the retardation film having the properties as the optically positive A plate, There was a problem that optical characteristics fluctuated.
In the retardation film described in Patent Document 1, the alignment property of the liquid crystal material in the retardation layer between the retardation film having the property as an optically positive A plate and the retardation layer. Although a layer made of a urethane emulsion for stabilizing the film is formed, even if such a layer is formed, the problem of fluctuations in the optical characteristics cannot be solved.

JP 2007-155757 A

  The present invention has been made in view of such problems, and is a retardation film that is suitably used as a viewing angle compensation film of an IPS liquid crystal display device, and has excellent optical property stability. The object is to provide a film.

In order to solve the above problems, the present invention includes a transparent substrate made of a cellulose derivative, and a rod-shaped compound having a refractive index anisotropy formed on the transparent substrate, and further, a slow axis direction in the in-plane direction An optical anisotropy in which a relationship of nx ₁ > ny ₁ ≧ nz ₁ is established among the refractive index nx ₁ of the first layer, the refractive index ny ₁ of the fast axis direction in the in-plane direction, and the refractive index nz ₁ of the thickness direction An optically anisotropic film having a conductive layer and a liquid crystal material formed on the optically anisotropic film and having homeotropic alignment, and further refracted in any x and y directions orthogonal to each other in the in-plane direction A retardation film having a retardation layer in which a relationship of nx ₂ ≦ ny ₂ <nz ₂ is established between the refractive indices nx ₂ and ny ₂ and the refractive index nz ₂ in the thickness direction, Film and the above phase Wherein the intermediate layer containing a polymer of 4 or more functional urethane (meth) acrylates between the layers are formed, to provide a phase difference film.

According to the present invention, an intermediate layer is formed between the optically anisotropic film and the retardation layer, and the intermediate layer contains a tetrafunctional or higher functional urethane (meth) acrylate polymer. By being a thing, it can prevent that the homeotropic orientation property of the liquid-crystal material in the said phase difference layer is impaired by the effect | action of the said optically anisotropic film.
In the retardation film of the present invention, the optically anisotropic layer has optical characteristics in which a relationship of nx ₁ > ny ₁ ≧ nz ₁ is established in nx ₁ , ny ₁ , and nz ₁ , and When the retardation layer has optical characteristics that satisfy the relationship of nx ₂ , ny ₂ , and nz ₂ , it can be suitably used as a viewing angle compensation film for an IPS liquid crystal display device.
Therefore, according to the present invention, a retardation film that is suitably used as a viewing angle compensation film of an IPS liquid crystal display device, and can obtain a retardation film having excellent optical property stability. .

  In the present invention, the ratio (molecular weight / number of functional groups) between the number of functional groups and the molecular weight of the urethane (meth) acrylate is preferably 1000 or less. Thereby, since the intermediate layer used in the present invention has a higher crosslink density and can be made dense, it becomes possible to highly block the action of the retardation layer and the optically anisotropic film. This is because the retardation film of the present invention can be further improved in stability of optical characteristics.

In order to solve the above problems, the present invention includes a transparent substrate comprising a cellulose derivative, and a rod-shaped compound having a refractive index anisotropy formed on the transparent substrate, and further, a slow phase in the in-plane direction. An optical difference in which a relationship of nx ₁ > ny ₁ ≧ nz ₁ is established among the refractive index nx ₁ in the axial direction, the refractive index ny _{1 in the} fast axis direction in the in-plane direction, and the refractive index nz _{1 in} the thickness direction. An optically anisotropic film having an isotropic layer; and a liquid crystal material formed on the optically anisotropic film and having homeotropic alignment, and further having any x and y directions orthogonal to each other in the in-plane direction. A retardation film having a relationship of nx ₂ ≦ ny ₂ <nz ₂ between the refractive indexes nx ₂ and ny ₂ and the refractive index nz _{2 in} the thickness direction. Isotropic film and above To provide a phase difference film, wherein an intermediate layer containing a polymer of a polyalkylene oxide chain-containing polymer having a reactive functional group at the terminal between the retardation layer is formed.

According to the present invention, a polymer of a polyalkylene oxide chain-containing polymer in which an intermediate layer is formed between the optically anisotropic film and the retardation layer, and the intermediate layer has a reactive functional group at the terminal. It is possible to prevent the homeotropic orientation of the liquid crystal material in the retardation layer from being damaged by the action of the optically anisotropic film.
In the retardation film of the present invention, the optically anisotropic layer has optical characteristics in which a relationship of nx ₁ > ny ₁ ≧ nz ₁ is established in nx ₁ , ny ₁ , and nz ₁ , and When the retardation layer has optical characteristics that satisfy the relationship of nx ₂ , ny ₂ , and nz ₂ , it can be suitably used as a viewing angle compensation film for an IPS liquid crystal display device.
Therefore, according to the present invention, a retardation film that is suitably used as a viewing angle compensation film of an IPS liquid crystal display device, and can obtain a retardation film having excellent optical property stability. .

  In the present invention, the polyalkylene oxide chain-containing polymer preferably has 3 or more reactive functional groups. In the present invention, the polyalkylene oxide chain-containing polymer preferably has a molecular weight of 1000 or more. Thereby, since the intermediate layer used in the present invention has a higher crosslink density and can be made dense, it becomes possible to highly block the action of the retardation layer and the optically anisotropic film. This is because the retardation film of the present invention can be further improved in stability of optical characteristics.

  In the retardation film of the present invention, the Nz factor (Nz) is preferably in the range of −0.5 <Nz <0.5. This is because the retardation film of the present invention can be made more excellent in the viewing angle compensation function of the IPS liquid crystal display device.

  Furthermore, in the present invention, the cellulose derivative is preferably triacetyl cellulose. This is because triacetyl cellulose is excellent in optical isotropy, and therefore has advantages such as easy design of optical characteristics of the retardation film of the present invention. Further, when the retardation film of the present invention is also used as a polarizing plate protective film, there is an advantage that the adhesiveness with the polarizer is excellent.

  The retardation film of the present invention is suitably used as a viewing angle compensation film for an IPS liquid crystal display device, and exhibits an effect of excellent stability of optical characteristics.

  The retardation film of the present invention can be divided into two embodiments depending on the composition of the intermediate layer. Therefore, hereinafter, the retardation film of the present invention will be described in detail for each embodiment.

A. First, the retardation film of the first aspect of the present invention will be described. The retardation film of this embodiment contains a transparent substrate made of a cellulose derivative, and a rod-shaped compound formed on the transparent substrate and having refractive index anisotropy, and further has a refractive index in the slow axis direction in the in-plane direction. and nx _1, the refractive index ny ₁ in fast axis direction in the plane direction, between the refractive index nz ₁ in the thickness _direction, an optically anisotropic layer relationship nx _1> ny 1 ≧ nz 1 is satisfied An optically anisotropic film having a liquid crystal material formed on the optically anisotropic film and having homeotropic alignment, and having a refractive index nx ₂ in any x and y directions orthogonal to each other in the in-plane direction. , Ny ₂ and a retardation layer in which a relationship of nx ₂ ≦ ny ₂ <nz ₂ is established between the refractive index nz ₂ in the thickness direction, the optically anisotropic film, and 4 officers between the retardation layer It is characterized in that the intermediate layer containing a polymer of more urethane (meth) acrylates are formed.

Such a retardation film of this embodiment will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the retardation film of this embodiment. As illustrated in FIG. 1, the retardation film 10 of this embodiment includes a transparent substrate 1 a made of a cellulose derivative, a rod-shaped compound that is formed on the transparent substrate 1 and has refractive index anisotropy, and further has a surface. Between the refractive index nx ₁ in the slow axis direction in the inward direction, the refractive index ny _{1 in the} fast axis direction in the in-plane direction, and the refractive index nz _{1 in the} thickness direction, nx ₁ > ny ₁ ≧ nz ₁ An optically anisotropic film 1 having an optically anisotropic layer 1b in which the relationship is established; and a liquid crystal material formed on the optically anisotropic film 1 and having homeotropic alignment, and further in the in-plane direction. A retardation layer 2 in which a relationship of nx ₂ ≦ ny ₂ <nz ₂ is established between refractive indexes nx ₂ and ny ₂ in arbitrary x and y directions orthogonal to each other and a refractive index nz _{2 in} the thickness direction Is.
In such an example, the retardation film 10 of this embodiment includes an intermediate layer containing a polymer of tetrafunctional or higher urethane (meth) acrylate between the optically anisotropic film 1 and the retardation layer 2. 3 is formed.

According to this aspect, the intermediate layer is formed between the optically anisotropic film and the retardation layer, and the intermediate layer contains a tetrafunctional or higher functional urethane (meth) acrylate polymer. By being a thing, it can prevent that the homeotropic orientation property of the liquid-crystal material in the said phase difference layer is impaired by the effect | action of the said optically anisotropic film.
Further, in the retardation film of this aspect, the optically anisotropic layer has optical characteristics in which the relationship of nx ₁ > ny ₁ ≧ nz ₁ is established in nx ₁ , ny ₁ , and nz ₁ , and When the retardation layer has optical characteristics that satisfy the relationship of nx ₂ , ny ₂ , and nz ₂ , it can be suitably used as a viewing angle compensation film for an IPS liquid crystal display device.
For this reason, according to this aspect, a retardation film that is suitably used as a viewing angle compensation film of an IPS liquid crystal display device, and can provide a retardation film having excellent optical property stability. .

The retardation film of this aspect has at least the above-mentioned optically anisotropic film, a retardation layer, and an intermediate layer, and may have other configurations as necessary.
Hereinafter, each structure used for the retardation film of this aspect is demonstrated in order.

1. Intermediate Layer First, the intermediate layer used in this embodiment will be described. The intermediate layer used in this embodiment is formed between an optically anisotropic film described later and a retardation layer, and contains a polymer of tetrafunctional or higher urethane (meth) acrylate. Since the retardation film of this embodiment has such an intermediate layer formed, the action between the retardation layer and the optically anisotropic layer is blocked, and the liquid crystal material in the retardation layer described later is used. As a result of being able to stabilize the alignment, the optical properties can be made excellent.
Hereinafter, the intermediate layer used in this embodiment will be described in detail.

(1) Polymer of urethane acrylate First, the polymer of urethane acrylate will be described. The urethane acrylate polymer used in this embodiment is obtained by polymerizing urethane acrylate.

The urethane acrylate used in this embodiment has 4 or more (meth) acrylate groups. In this embodiment, such urethane acrylate is used because if the number of (meth) acrylate groups present in the molecule is less than 4, the shielding effect between the retardation layer and the optically anisotropic film by the intermediate layer is not good. This is because, as a result, the stability of the optical characteristics of the retardation film becomes insufficient.
The urethane acrylate used in this embodiment is not particularly limited as long as the number of (meth) acrylate groups in the molecule is 4 or more, but in this embodiment, the urethane acrylate is within the range of 4 to 30. It is preferable that it is within the range of 6-15.
In the present specification, the “(meth) acrylate group” means a methacrylate group or an acrylate group.

  The urethane acrylate used in this embodiment preferably has a ratio of the number of (meth) acrylate groups in the molecule to the molecular weight (molecular weight / (meth) acrylate number) of 1000 or less, within the range of 80 to 1000. It is more preferable that it is in the range of 100 to 500. When the ratio is within such a range, the intermediate layer used in this embodiment can have a higher crosslink density and a higher density, so that the action of the retardation layer and the optically anisotropic film can be enhanced. This is because the retardation film of this embodiment can be further improved in stability of optical characteristics.

  The molecular weight of the urethane acrylate used in this embodiment is appropriately determined so that, for example, the ratio between the number of (meth) acrylate groups in the molecule and the molecular weight (molecular weight / (meth) acrylate number) can be within the above-described range. It is good. Among these, the molecular weight of the urethane acrylate used in this embodiment is preferably in the range of 300 to 12000, more preferably in the range of 500 to 9000, and still more preferably in the range of 600 to 6000. .

  As a specific example of the urethane acrylate used in this embodiment, for example, it may be composed of a polyol compound and a polyisocyanate compound. Specific examples of the polyol compound include ethylene glycol, propylene glycol, neopentyl glycol, tricyclodecane dimethylol, cyclohexane dimethylol, trimethylolpropane, glycerin, 1,3-propanediol, 1,4-butanediol, 1, 3-butanediol, 2,3-butanediol, 1,5-pentanediol, 2,4-pentanediol, 1,2-hexanediol, 1,6-hexanediol, diethylene glycol, tripropylene glycol, 1,9- Nonanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A polyethoxyglycol, polycarbonate polyol, pentaerythritol, sorbitol, Loose, quadroleol polybutadiene polyol, hydrogenated polybutadiene polyol, hydrogenated dimer diol pentaerythritol, etc .; a compound containing tetravalent or higher hydroxyl groups such as trimethylolpropane, glycerin, pentaerythritol, sorbitol, sucrose, quadrol Polyether polyol obtained by modifying with cyclic ether compounds such as (EO), propylene oxide (PO), butylene oxide, tetrahydrofuran; polycaprolactone polyol obtained by modifying with caprolactone; polyester comprising dibasic acid and diol And polyester polyols obtained by modification with the above; and mixtures of two or more thereof.

  More specifically, EO-modified trimethylolpropane, PO-modified trimethylolpropane, tetrahydrofuran-modified trimethylolpropane, caprolactone-modified trimethylolpropane, EO-modified glycerol, PO-modified glycerol, tetrahydrofuran-modified glycerin, caprolactone-modified glycerol, EO-modified pentaerythritol. , PO-modified pentaerythritol, tetrahydrofuran-modified pentaerythritol, caprolactone-modified pentaerythritol, EO-modified sorbitol, PO-modified sorbitol, caprolactone-modified sorbitol, EO-modified sucrose, PO-modified sucrose, EO-modified sucrose, EO-modified quadrole, etc. Can be mentioned.

  Specific examples of the polyisocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, tetramethylxylylene diisocyanate, Biphenylene diisocyanate, 1,5-naphthylene diisocyanate, o-tolidine diisocyanate, hexamethylene diisocyanate, 4,4'-methylenebiscyclohexyl isocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, 1,3- (isocyanatomethyl) cyclohexane, and Examples thereof include polycondensates such as burettes and nurates, and mixtures of two or more thereof. Particularly preferred are isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate and nurateated hexamethylene diisocyanate, isophorone diisocyanate nurateated, and more preferably isophorone diisocyanate, hexamethylene diisocyanate nurateated, isophorone diisocyanate. Examples thereof include uretrates.

  In addition, the urethane acrylate used for this aspect may be only one type, or may be two or more types.

  The urethane acrylate polymer used in this embodiment is obtained by polymerizing the urethane acrylate. The polymer of urethane acrylate used in this embodiment may be one obtained by polymerizing a single urethane acrylate, or may be one obtained by polymerizing a plurality of urethane acrylates.

(2) Other compound Although the intermediate | middle layer used for this aspect contains the polymer of the said urethane acrylate at least, it may contain another compound as needed. Other compounds used in this embodiment can be appropriately selected according to the use of the retardation film of this embodiment, the performance required for the retardation film of this embodiment, and the like. Examples of such other compounds include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing a polyhydric alcohol with a monobasic acid or polybasic acid. Bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amino group epoxy resin, triphenolmethane type epoxy resin , Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting an epoxy resin such as a dihydroxybenzene type epoxy resin and (meth) acrylic acid; a photopolymerizable liquid crystalline compound having an acrylic group or a methacrylic group Etc., other than the above The compounds, e.g., surfactants, polymerization initiators, polymerization inhibitors, plasticizers, stabilizers, leveling agents, and can include a silane coupling agent or the like.

(3) Intermediate layer The thickness of the intermediate layer used in this embodiment imparts stability of desired optical properties to the retardation film of this embodiment depending on the type of urethane acrylate constituting the polymer of urethane acrylate. There is no particular limitation as long as it is possible. In particular, the thickness of the intermediate layer used in this embodiment is preferably in the range of 1 μm to 10 μm, more preferably in the range of 1 μm to 8 μm, and still more preferably in the range of 1 μm to 5 μm. .

  The polymer of urethane acrylate is a process including a coating, a solvent removal step, and a polymerization step after preparing a coating liquid for forming an intermediate layer by diluting a precursor monomer, oligomer or prepolymer with various solvents. After passing, it is preferable to form an intermediate layer. Examples of the solvent include alcohols such as isopropyl alcohol, methanol, and ethanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, and butyl acetate; chloroform, methylene chloride, tetrachloroethane, and the like Or a mixture thereof, preferably esters and ketones. More specific examples include acetone, methyl acetate, ethyl acetate, butyl acetate, chloroform, methylene chloride, trichloroethane, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, nitromethane, 1,4-dioxane, dioxolane, N-methylpyrrolidone. N, N-dimethylformamide, methanol, ethanol, isopropyl alcohol, butanol, isobutyl alcohol, diisopropyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, preferably methyl acetate, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone And cyclohexanone. The amount of the solvent added can be determined as appropriate, but is 0.1 to 95 parts by weight, more preferably 1 to 90 parts by weight, more preferably, based on the total amount of the intermediate layer forming coating solution. 5 to 85 parts by weight.

2. Optically anisotropic film Next, the optically anisotropic film used in this embodiment will be described. The optically anisotropic film used in this embodiment contains a transparent substrate made of a cellulose derivative, and a rod-shaped compound formed on the transparent substrate and having refractive index anisotropy, and further has a slow axis in the in-plane direction. An optical difference in which a relationship of nx ₁ > ny ₁ ≧ nz ₁ is established among the refractive index nx _{1 in the} direction, the refractive index ny _{1 in the} fast axis direction in the in-plane direction, and the refractive index nz _{1 in} the thickness direction. It has an anisotropic layer.

Such an optically anisotropic film used in this embodiment will be described with reference to the drawings. FIG. 2 is a schematic cross-sectional view showing an example of the optically anisotropic film used in this embodiment. As illustrated in FIG. 2, the optically anisotropic film 1 used in this embodiment includes a transparent substrate 1a made of a cellulose derivative, and a rod-shaped compound A formed on the transparent substrate 1a and having refractive index anisotropy. Furthermore, the refractive index nx ₁ in the slow axis direction in the in-plane direction, the refractive index ny _{1 in the} fast axis direction in the in-plane direction, and the refractive index nz _{1 in the} thickness direction nx ₁ > It has the optically anisotropic layer 1b in which the relationship of ny ₁ ≧ nz ₁ is established.

  Hereinafter, such an optically anisotropic film will be described in detail.

(1) Transparent substrate First, the transparent substrate used for this aspect is demonstrated. The transparent substrate used in this embodiment is made of a cellulose derivative. The retardation film of this embodiment has an advantage that it has excellent adhesion to a polarizer when used as a polarizing plate protective film, for example, when a film made of such a cellulose derivative is used as a transparent substrate. Become a thing.
Hereinafter, such a transparent substrate will be described in detail.

  The cellulose derivative constituting the transparent substrate used in this embodiment has a desired water permeability, and is contained in the polarizer in the polarizing plate production process when the retardation film of this embodiment is used as a polarizing plate protective film. It is not particularly limited as long as it can permeate moisture and can suppress a decrease in polarization characteristics over time to a desired level. Especially in this aspect, it is preferable to use cellulose esters as the cellulose derivative, and among the cellulose esters, it is preferable to use cellulose acylates. This is because cellulose acylates are advantageous in terms of availability because they are widely used industrially.

  As said cellulose acylates, C2-C4 lower fatty acid ester is preferable. The lower fatty acid ester may include only a single lower fatty acid ester such as cellulose acetate, and may include a plurality of fatty acid esters such as cellulose acetate butyrate and cellulose acetate propionate. There may be.

  In this embodiment, cellulose acetate can be particularly preferably used among the above lower fatty acid esters. As the cellulose acetate, 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). Since triacetyl cellulose has a molecular structure having a relatively bulky side chain, by using a transparent substrate made of such triacetyl cellulose, the adhesion between the transparent substrate and the optically anisotropic layer is further improved. It is because it can improve.

  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 (testing method for cellulose acetate, etc.). In addition, the acetylation degree of the triacetyl cellulose which comprises a triacetyl cellulose film can be calculated | required by said method, after removing impurities, such as a plasticizer contained in a film.

The transparency of the transparent substrate used in this embodiment may be arbitrarily determined according to the transparency required for the retardation film of this embodiment, but it is usually preferable that the transmittance in the visible light region is 80% or more. 90% or more is more preferable.
Here, the transmittance of the transparent substrate can be measured by JIS K7361-1 (Testing method for total light transmittance of plastic-transparent material).

  Moreover, the thickness of the transparent substrate used for this aspect will not be specifically limited if it is in the range in which required self-supporting property is obtained according to the use of the phase difference film of this aspect, etc. In particular, in this embodiment, it is preferably in the range of 10 μm to 188 μm, particularly preferably in the range of 20 μm to 125 μm, and more preferably in the range of 30 μm to 80 μm. 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 of this embodiment. Moreover, when thickness is thicker than said range, when cutting the retardation film of this aspect, for example, a process waste may increase or abrasion of a cutting blade may become quick.

  Further, the in-plane retardation of the transparent substrate used in the present embodiment is not particularly limited as long as it is within a range in which a desired retardation can be imparted to the retardation film of the present embodiment, and the retardation film of the present embodiment. It can be arbitrarily adjusted according to the specific use of the optically anisotropic film used in this embodiment and this embodiment. In particular, the transparent substrate used in this embodiment preferably has an in-plane retardation at a wavelength of 550 nm in the range of 0 nm to 50 nm.

  Here, the wavelength dependence of the in-plane retardation of the transparent substrate used in this embodiment may be any of a reverse dispersion type, a normal dispersion type, and a flat dispersion type.

  The transparent substrate used in this embodiment preferably has a thickness direction retardation at a wavelength of 550 nm in the range of 0 nm to 100 nm.

In addition, the structure of the transparent substrate used for this aspect is not restricted to the structure which consists of a single layer, You may have the structure by which the several layer was laminated | stacked.
Moreover, 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) Optically anisotropic layer Next, the optically anisotropic layer used for this aspect is demonstrated. The optically anisotropic layer used in this embodiment is formed on the transparent substrate, contains a rod-like compound having refractive index anisotropy, and further has a refractive index nx ₁ in the in-plane slow axis direction x, A relationship of nx ₁ > ny ₁ ≧ nz ₁ is established between the refractive index ny _{1 in the} axial direction y and the refractive index nz _{1 in} the thickness direction z.

(Bar compound)
The rod-shaped compound used in this embodiment will be described. The rod-like compound used in this embodiment has a refractive index anisotropy in the molecule, and is contained in the optical anisotropic layer in a predetermined manner, whereby the above-mentioned nx ₁ > ny is contained in the optical anisotropic layer. _The optical characteristic is not particularly limited as long as the optical characteristic that satisfies the relationship ₁ ≧ nz ₁ can be imparted. Among them, the rod-shaped compound used in the present invention preferably has a retardation wavelength dependency of a positive dispersion type, and particularly preferably has a Re ratio in the range of 1 to 2.
Here, the Re ratio of the rod-shaped compound is such that an alignment film such as polyimide is formed, a layer composed of the rod-shaped compound is formed on an isotropic substrate such as a glass substrate subjected to alignment treatment, and the Re ratio at a wavelength of 450 nm is obtained. It can be calculated by measuring (Re ₄₅₀ ) and Re (Re ₅₅₀ ) at a wavelength of 550 nm.

  In addition, the rod-shaped compound used in the present invention preferably has a structure in which a polymerizable functional group and a mesogenic group are bonded via an alkyl chain. A typical example of a compound having such a structure is a polymerizable liquid crystal compound.

  Examples of the polymerizable liquid crystal compound used in the present invention include a polyfunctional polymerizable liquid crystal compound having a plurality of polymerizable functional groups and a monofunctional polymerizable liquid crystal compound having a single polymerizable functional group. In the present invention, any of the polyfunctional polymerizable liquid crystal compound and the monofunctional polymerizable liquid crystal compound can be suitably used. In particular, in the present invention, it is preferable to use the monofunctional polymerizable liquid crystal compound. The monofunctional polymerizable liquid crystal compound has a higher degree of freedom of the mesogenic group than the polyfunctional polymerizable liquid crystal compound, and in the case of performing a stretching treatment after polymerization, a crosslinking point that restricts and inhibits the reorientation of molecules. Since the density of the polymer is low and the orientation of the molecule (the electric dipole efficiency vector) becomes easy, by using such a monofunctional polymerizable liquid crystal compound, the optically anisotropic layer can be made to exhibit more optical anisotropy. It is because it can be made excellent.

The polymerizable liquid crystal compound is one in which the mesogenic group and the polymerizable functional group are bonded by an alkyl chain, and the number of carbon atoms constituting the alkyl chain is preferably 4 or more. It is preferably within the range of 12, and particularly preferably within the range of 6 to 10. When the number of carbon atoms is within the above range, the mesogenic group provided in the polymerizable liquid crystal compound can have a higher degree of freedom in molecular orientation. It is because it can improve further.
In the present invention, the “number of carbon atoms constituting the alkyl chain” means the number of carbon atoms constituting the main chain portion of the alkyl group that binds the polymerizable functional group and the mesogenic group. . Therefore, for example, when the alkyl group is a branched chain having a side chain, the number of carbon atoms constituting the side chain is not included in the “number of carbon atoms constituting the alkyl chain”.

  The alkyl chain used in the present invention is not particularly limited as long as the carbon number is within the above range. Therefore, the alkyl chain used in the present invention may be a straight chain having no side chain or a branched chain having a side chain. Moreover, the saturated alkyl chain which consists only of a saturated bond may be sufficient, or the unsaturated alkyl chain which has an unsaturated bond may be sufficient. Furthermore, it may have a structure in which an arbitrary functional group is bonded to a hydrocarbon chain.

  Moreover, when using the said polyfunctional polymerizable liquid crystal compound in this invention, all the carbon number which comprises the alkyl chain couple | bonded with each polymeric functional group may be the same, or may differ.

The mesogenic group used in the polymerizable liquid crystal compound is not particularly limited as long as it can give a predetermined optical anisotropy to the optically anisotropic layer by arranging regularly. In particular, in the present invention, those having a rod-like structure as the mesogenic group are usually used. This is because mesogenic groups having a rod-like structure can easily exhibit optical anisotropy by being regularly arranged.
Here, the “rod-like structure” means a compound in which the main skeleton of the structure of the mesogen group is a rod-like structure.

  Further, the mesogenic group used in the present invention is preferably a liquid crystalline compound among the mesogenic groups having the rod-like structure. This is because by using a mesogenic group exhibiting liquid crystallinity, it becomes easy to impart desired optical anisotropy to the optically anisotropic film used in the present invention.

  When using what has liquid crystallinity as said mesogenic group, the kind of liquid crystal phase which the said mesogenic group shows is not specifically limited. Examples of such a liquid crystal phase include a nematic phase, a cholesteric phase, and a smectic phase. In the present invention, any mesogenic group exhibiting any of these liquid crystal phases can be preferably used, but among them, a mesogenic group exhibiting a nematic phase is preferably used. This is because mesogenic groups exhibiting a nematic phase can be easily arranged regularly as compared with mesogenic groups exhibiting other liquid crystal phases.

  Specific examples of such a mesogenic group include those in which two or more ring structures represented by the following formulas (1) to (11) are connected directly or via a bonding group.

Here, any hydrogen in the ring structures of the above formulas (1) to (11) has halogen, —CN, —CF ₃ , —CF ₂ H, —NO ₂ , or 1 to 7 carbon atoms. It may be replaced with alkyl. In the alkyl having 1 to 7 carbon atoms, arbitrary —CH ₂ — may be replaced by —O—, —CH═CH— or —C≡C—, and arbitrary hydrogen may be replaced by halogen. May be.

  The linking group is not particularly limited as long as it can bond the ring structure at a predetermined distance. Examples of such a linking group include those represented by the following formulas (12) to (23).

  The polymerizable functional group used in the polymerizable liquid crystal compound is not particularly limited as long as it can be polymerized by performing a desired polymerization treatment, depending on the method for producing the retardation film of the present invention. Can be appropriately selected and used. Examples of such polymerizable functional groups 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) can be given. Moreover, an epoxy group etc. can be mentioned as a specific example of the said cation polymerizable functional group. In addition, examples of the polymerizable functional group used in the present invention include an isocyanate group and an unsaturated triple bond. In the present invention, among these polymerizable functional groups, a functional group having an ethylenically unsaturated double bond is preferably used from the viewpoint of the process.

  When the polyfunctional polymerizable liquid crystal compound is used as the polymerizable liquid crystal compound used in the present invention, all the polymerizable functional groups used in the polyfunctional polymerizable liquid crystal compound may be the same or different. It may be.

The polymerizable liquid crystal compound used in the present invention is preferably a compound having a relatively small molecular weight. 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 preferable. The reason is as follows. That is, the optically anisotropic layer used in the present invention contains the rod-shaped compound and a cellulose derivative constituting the transparent substrate described later, but a compound having a relatively small molecular weight as the polymerizable liquid crystal compound. When used, the polymerizable liquid crystal compound is easily mixed with the cellulose derivative in the optically anisotropic layer. For this reason, it is because the haze of the said optically anisotropic layer can be made smaller by using the polymeric liquid crystal compound whose molecular weight is in the said range.
The molecular weight of the polymerizable liquid crystal compound means a molecular weight in a monomer state before polymerization.

  Specific examples of the polymerizable liquid crystal compound used in the present invention include compounds represented by the following formula.

  Here, the polymerizable liquid crystal compounds represented by the above formulas (I), (IV) and (V) are, for example, DJBroer et al., Makromol Chem. 190, 3201-3215 (1989) or DJBroer et al., Makromol Chem. It can be prepared according to the method disclosed in .190,2250 (1989) or by a method similar thereto. In addition, the polymerizable liquid crystal compounds represented by the chemical formulas (II) and (III) can be prepared by the method disclosed in DE195, 04, 224, for example.

  Moreover, as an example of the polymeric liquid crystal compound used for this invention, the compound represented by a following formula can be illustrated, for example.

  The polymerizable liquid crystal compound used in the present invention may be only one type or two or more types. When two or more kinds of polymerizable liquid crystal compounds are used, the polymerizable liquid crystal compound may be selected only from the monofunctional polymerizable liquid crystal compound, or may be selected only from the polyfunctional polymerizable liquid crystal compound. Or you may select from both the said monofunctional polymerizable liquid crystal compound and the said polyfunctional polymerizable liquid crystal compound. In particular, in the present invention, it is preferable to select at least the monofunctional polymerizable liquid crystal compound. This is because the monofunctional polymerizable liquid crystal compound is excellent in optical anisotropy as described above.

(Sequence form of rod-shaped compound)
As an aspect in which the rod-shaped compound is contained in the optically anisotropic layer, the refractive index nx ₁ in the in-plane slow axis direction x and the refractive index ny in the fast axis direction y with respect to the optically anisotropic layer. ₁ and the refractive index nz _{1 in} the thickness direction z are not particularly limited as long as optical characteristics satisfying the relationship of nx ₁ > ny ₁ ≧ nz ₁ can be provided. In particular, in this embodiment, it is preferable that the rod-like compound forms an irregular random homogeneous orientation in the optically anisotropic layer. This is because it becomes easy to impart the above-described optical characteristics to the optically anisotropic layer.
Here, the irregular random homogeneous orientation represents one aspect of the arrangement state of the rod-like compounds, and is a novel arrangement aspect that can achieve the optical characteristics described above using the rod-like compounds.
Hereinafter, such irregular random homogeneous orientation will be described in detail.

The irregular random homogeneous orientation has at least the following three characteristics. That is, the irregular random homogeneous orientation in this embodiment is
First, when the optically anisotropic layer is viewed from the direction perpendicular to the surface of the optically anisotropic layer, the arrangement direction of the rod-shaped compounds has anisotropy (hereinafter simply referred to as “anisotropic”). ),
Second, the size of the domain formed by the rod-shaped compound in the optically anisotropic layer is smaller than the wavelength in the visible light region (hereinafter sometimes simply referred to as “dispersibility”);
Thirdly, the rod-like compound molecules in the optically anisotropic layer are present on a plane parallel to the surface of the optically anisotropic layer (in the example of FIG. 1, a plane parallel to the xy plane) (hereinafter simply “ Sometimes referred to as “in-plane orientation”),
At least.

  Next, the irregular random homogeneous orientation in this embodiment will be described with reference to the drawings. FIG. 3A is a front view of the retardation film of this embodiment from the direction perpendicular to the surface (xy plane) of the optically anisotropic layer represented by Z in FIG. 2 described above (xy plane). It is the schematic in the case. FIGS. 3B and 3C are cross-sectional views taken along line X-X ′ in FIG.

First, “anisotropy” possessed by the irregular random homogeneous orientation in this embodiment will be described with reference to FIG. As shown in FIG. 3A, the “anisotropy” refers to an optically anisotropic layer when the retardation film 10 of this embodiment is viewed from the direction perpendicular to the surface of the optically anisotropic layer 1b. 1b shows that the rod-like compounds A are arranged in one direction on average.
That is, when the probability distribution function (probability density function) of each rod-like compound molecule oriented in each direction in the xy plane (surface of the optically anisotropic layer) is obtained, the probability distribution function is expressed in a specific direction in the xy plane (FIG. 3). In this example, the distribution is such that it has a peak (average orientation direction) in the x direction and has a predetermined dispersion (variation width in the orientation direction) in the orientation direction. Furthermore, in other words, the orientation direction of the major axis of the rod-like compound molecule is not that all the molecules are aligned in parallel, but that is not completely messy. An example thereof is shown in FIG.
Here, in this embodiment, in order to explain the arrangement direction of the rod-shaped compound A, the molecular major axis direction (hereinafter referred to as a molecular axis) represented by a in FIG. . Therefore, the fact that the rod-shaped compounds are arranged in one direction means that the molecular axis a of the rod-shaped compound A contained in the optically anisotropic layer is oriented in one direction on average.
As described above, the “anisotropy” in this embodiment does not require that the rod-shaped compounds are completely arranged in one direction, and the arrangement direction of the rod-shaped compounds is arranged in one direction on average. It is sufficient that the optical anisotropic layer is provided with desired optical biaxiality. The degree of such anisotropy will be described later.

  Next, the “dispersibility” possessed by the irregular random homogeneous orientation in this embodiment will be described with reference to FIG. As shown in FIG. 3A, the above “dispersibility” means that when the rod-shaped compound A forms the domain b in the optically anisotropic layer 1b, the size of the domain b is larger than the wavelength in the visible light region. Is also small. In this embodiment, the smaller the size of the domain b is, the more preferable, and the state where the rod-like compound is dispersed in a single molecule is most preferable.

Next, “in-plane orientation” possessed by the irregular random homogeneous orientation in this embodiment will be described with reference to FIG. As shown in FIG. 3B, the above-mentioned “in-plane orientation” indicates that the rod-like compound A in the optically anisotropic layer 1b has a molecular axis “a” in the normal direction Z (see FIG. 2) of the optically anisotropic layer 1b. It is oriented so as to be substantially perpendicular to the z direction in FIG. 2 (substantially parallel to the xy plane in FIG. 2). As the “in-plane orientation” in this embodiment, as shown in FIG. 3B, the molecular axes a of all the rod-like compounds A in the optically anisotropic layer 1b are substantially in the normal direction Z. For example, as shown in FIG. 3C, the rod-like compound A whose molecular axis a ′ is not perpendicular to the normal direction Z is formed on the optically anisotropic layer 1b. Even if it exists, the case where the average direction of the molecular axis a of the rod-shaped compound A existing in the optically anisotropic layer 1b is substantially perpendicular to the normal direction Z is included.
That is, in FIG. 3, even if the molecular axis direction of each rod-like compound molecule has a distribution, the molecular axis direction averaged over all the molecules of the rod-like compound exists substantially in the xy plane.

  As described above, the irregular random homogeneous orientation in this embodiment is characterized by exhibiting the above-mentioned “anisotropic”, “dispersibility” and “in-plane orientation”, but the rod-shaped compound forms an irregular random homogeneous orientation. This can be confirmed by the following method.

First, a method for confirming “anisotropy” included in the irregular random homogeneous orientation in this embodiment will be described. The “anisotropy” can be confirmed by evaluating the in-plane retardation of the optically anisotropic layer (hereinafter sometimes simply referred to as “Re ¹ ”).

The fact that the rod-shaped compound has the above “anisotropy” means that the in-plane retardation (Re ¹ ) value of the optically anisotropic layer indicates that the optically anisotropic layer exhibits optical biaxiality. Can be confirmed by being within a possible range. In particular, in this embodiment, the in-plane retardation (Re ¹ ) of the optically anisotropic layer is preferably in the range of 5 nm to 300 nm, and in particular in the range of 10 nm to 200 nm. It is particularly preferable that the thickness is in the range of 40 nm to 150 nm.
Here, Re ¹ is a value represented by the equation Re = (nx ¹ −ny ¹ ) × d ^{1 based on} nx ¹ , ny ¹ and the thickness d ¹ (nm) of the optically anisotropic layer. is there.

The in-plane retardation (Re ¹ ) of the optically anisotropic layer is obtained, for example, by subtracting the in-plane retardation of the layer other than the optically anisotropic layer from the in-plane retardation (Re) of the retardation film. be able to. That is, in-plane retardation measurement was performed on the entire retardation film and the optically anisotropic layer excised from the retardation film, and the surface of the optically anisotropic layer was obtained by subtracting the latter measured value from the former measured value. Internal retardation can be obtained. In-plane retardation can be measured by, for example, the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

When the rod-shaped compound having a rod-shaped main skeleton to which two or more benzene rings are bonded is used, the “anisotropy” refers to the in-plane direction of the optically anisotropic layer. This can also be confirmed by measuring the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ). Namely, the Raman peak intensity ratio in the in-plane slow axis direction of the optically anisotropic layer in the present embodiment ^{(1605cm -1} / ^2942cm -1) is, fast axis direction Raman peak intensity ratio of the plane (1605 cm ^-1 / 2942 cm ⁻¹ ), it can be confirmed that the above “anisotropy” is provided. In particular, in this embodiment, the Raman peak intensity ratio in the slow axis direction (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the plane of the optically anisotropic layer is equal to the Raman peak intensity ratio (1605 cm in the fast axis direction in the plane). preferably ^-1 / ^{2942cm -1)} is 1.1 times or more, preferably in particular 1.15 times or more, preferably further in the range of 1.20 ～3.00 times.

Here, the "Raman peak intensity ratio ^{(1605cm -1} / 2942cm -1)" means the ratio of the in the Raman spectrum (spectral light intensity of the spectral light intensity / wave number 2942cm ^-1 in wavenumber 1605 cm ^-1) To do.

Here, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in this embodiment is obtained by using, for example, a laser Raman spectrophotometer (JASCO: NRS-3000) and the linearly polarized electric field vibration surface is optically different. Injecting measurement light so that it coincides with the slow axis direction and the fast axis direction in the plane of the isotropic layer, the Raman spectrum for each of the fast axis direction in the plane and the fast axis direction in the plane Can be obtained by evaluating the peak intensity of 1605 cm ⁻¹ (C—H bond-derived peak) and the peak intensity of 2942 cm ⁻¹ (benzene ring-derived peak). The conditions for measuring a Raman spectrum using the laser Raman spectrophotometer are an exposure time of 15 seconds, an integration count of 8 times, and an excitation wavelength of 532.11 nm.

  Next, a method for confirming “dispersibility” possessed by the irregular random homogeneous orientation in this embodiment will be described. The “dispersibility” can be confirmed by the fact that the haze value of the optically anisotropic layer is within the range indicating that the domain size of the rod-shaped compound is not more than the wavelength in the visible light region. Among these, in this embodiment, the haze value of the optically anisotropic layer is preferably in the range of 0% to 5%, particularly preferably in the range of 0% to 1%, and more preferably 0% to It is preferable to be within the range of 0.5%.

  Here, the haze value of the optically anisotropic layer can be obtained, for example, by subtracting the haze value of a layer other than the optically anisotropic layer from the haze value of the retardation film. That is, the haze value of the optically anisotropic layer is determined by measuring the haze value of the whole retardation film and the optically anisotropic layer cut from the retardation film, and subtracting the latter haze value from the former haze value. Can be requested. As the haze value, a value measured according to JIS K7105 is used.

  The size of the domain in the present embodiment is less than or equal to the wavelength of visible light, but the specific size is preferably 380 nm or less, more preferably 350 nm or less, particularly 200 nm or less. Preferably there is. In this embodiment, since the rod-shaped compound is preferably monomolecularly dispersed, the lower limit value of the domain size is the size of a single molecule of the rod-shaped compound. The size of such a domain can be evaluated by observing the optically anisotropic layer with a polarizing microscope, AFM, SEM, or TEM.

Next, a method for confirming “in-plane orientation” possessed by the irregular random homogeneous orientation in this embodiment will be described. The above “in-plane orientation” means that the in-plane retardation (Re ¹ ) of the optically anisotropic layer constituting the retardation film of this embodiment is in the above-described range, and the optically anisotropic layer in this embodiment Can be confirmed by having a retardation in the thickness direction (hereinafter sometimes simply referred to as “Rth ¹ ”) that can exhibit optical biaxiality. In particular, Rth ¹ of the optically anisotropic layer in this embodiment is preferably in the range of 50 nm to 400 nm, more preferably in the range of 75 nm to 300 nm, and particularly in the range of 100 nm to 250 nm. It is preferable.
Here, the Rth ¹ is a value represented by the formula Rth ¹ = {(nx ¹ + ny ¹ ) / 2−nz ¹ } × d ^{1 by} the nx ¹ , ny ¹ , nz ¹ , and d ^1. is there.
In addition, Rth ¹ value in this aspect shall point out the absolute value of the value represented by the said formula.

For the retardation in the thickness direction (Rth ¹ ) of the optically anisotropic layer, for example, the retardation in the thickness direction indicated by the layers other than the optically anisotropic layer is subtracted from the retardation (Rth) in the thickness direction of the retardation film. Can be obtained. That is, the retardation film in the thickness direction was measured for the whole retardation film and the optically anisotropic layer cut out from the retardation film, and the optically anisotropic layer was obtained by subtracting the latter measured value from the former measured value. The retardation in the thickness direction can be obtained. The retardation in the thickness direction can be measured, for example, by the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

When the rod-shaped compound having a rod-shaped main skeleton to which two or more benzene rings are bonded is used, the “in-plane orientation” is the thickness direction of the optically anisotropic layer. This can also be confirmed by measuring the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ). That is, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the direction perpendicular to the thickness direction in the cut surface in the thickness direction of the optically anisotropic layer is the Raman peak intensity ratio in the direction parallel to the thickness direction. By being larger than (1605 cm ⁻¹ / 2942 cm ⁻¹ ), it can be confirmed that the above “in-plane orientation” is provided. In particular, in this embodiment, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the direction perpendicular to the thickness direction in the cut surface in the thickness direction of the optically anisotropic layer is parallel to the thickness direction. Is preferably 1.1 times or more of the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ), particularly preferably 1.50 times or more, and more preferably in the range of 1.20 times to 3.00 times. It is preferable to be within.

Here, the "Raman peak intensity ratio ^{(1605cm -1} / 2942cm -1)" means the ratio of the in the Raman spectrum (spectral light intensity of the spectral light intensity / wave number 2942cm ^-1 in wavenumber 1605 cm ^-1) To do.

Here, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in this embodiment is obtained by using, for example, a laser Raman spectrophotometer (JASCO: NRS-3000) and the linearly polarized electric field vibration surface is optically different. The measurement light is incident on the cut surface in the thickness direction of the anisotropic layer so as to coincide with the parallel direction and the vertical direction with respect to the thickness direction, whereby the parallel direction and the vertical direction with respect to the thickness direction in the cut surface in the thickness direction After measuring the Raman spectrum for each of the above, the peak intensity of 1605 cm ⁻¹ (C—H bond-derived peak) and the peak intensity of 2942 cm ⁻¹ (benzene ring-derived peak) can be determined. The conditions for measuring a Raman spectrum using the laser Raman spectrophotometer are an exposure time of 15 seconds, an integration count of 8 times, and an excitation wavelength of 532.11 nm.
The Raman peak intensity ratio of the optically anisotropic layer can be determined by, for example, preparing a slice by cutting a retardation film in the thickness direction and then measuring a Raman spectrum of only a portion corresponding to the optically anisotropic layer. It can be determined by measuring.

(Other compounds)
The optically anisotropic layer in this embodiment may contain other compounds in addition to the rod-shaped compound. Such other compounds are not particularly limited as long as they do not impair the optical properties of the optically anisotropic layer. As said other compound in this aspect, the polymeric material generally used for a hard-coat agent can be mentioned, for example.

  Examples of the polymerizable material include polyester (meth) acrylates obtained by reacting (meth) acrylic acid with polyester prepolymers obtained by condensing polyhydric alcohols with monobasic acids or polybasic acids; Polyurethane (meth) acrylate obtained by reacting a compound having a polyol group and 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, novolac type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amino group epoxy resin, triphenolmethane type epoxy resin, dihydroxybenzene type epoxy resin and the like , (Meta) It may be mentioned a photopolymerizable liquid crystal compound having an acryl group or a methacryl group or the like; photopolymerizable compounds such as epoxy (meth) acrylates obtained by reacting an acrylic acid.

  In this embodiment, when the optically anisotropic layer is directly formed on the transparent substrate, the optically anisotropic layer preferably contains a cellulose derivative constituting the transparent substrate. Thereby, in the retardation film of this aspect, the adhesiveness between the transparent substrate and the optically anisotropic layer can be improved.

(Optically anisotropic layer)
The optically anisotropic layer in this embodiment is preferably formed directly on the transparent substrate described above. This is because the optically anisotropic layer is directly formed on the transparent substrate, whereby the retardation film of this embodiment can be made excellent in adhesion between the optically anisotropic layer and the transparent substrate.
Thus, it is understood that the adhesion mechanism between the two is improved by the direct formation of the optically anisotropic layer on the transparent substrate due to the following mechanism. That is, when the optically anisotropic layer is directly formed on the transparent substrate, rod-like molecules contained in the optically anisotropic layer penetrate into the transparent substrate from the surface of the transparent substrate, or the optically anisotropic layer Depending on the solvent used in forming the transparent substrate, the surface of the transparent substrate can be dissolved and the rod-shaped compound and the transparent substrate can be mixed, so that there is a clear interface at the bonded portion between the transparent substrate and the optically anisotropic layer. It does not exist, and both are “mixed”. For this reason, it is considered that the adhesion is remarkably improved as compared with the adhesion by the conventional interface interaction.

  The thickness of the optically anisotropic layer in this embodiment is not particularly limited as long as it is within a range in which desired optical characteristics can be imparted to the optically anisotropic layer, depending on the type of the rod-shaped compound. In particular, in this embodiment, the thickness of the optically anisotropic layer is preferably in the range of 0.5 μm to 10 μm, more preferably in the range of 0.5 μm to 5 μm, particularly in the range of 1 μm to 3 μm. It is preferable to be within. If the thickness of the optically anisotropic layer is larger than the above range, “in-plane orientation”, which is one of the characteristics of irregular random homogeneous orientation, is impaired, and the desired optical characteristics may not be obtained. Because. On the other hand, if the thickness is smaller than the above range, the target optical characteristics may not be obtained depending on the kind of the rod-shaped compound.

(Optically anisotropic film)
Moreover, in the optically anisotropic film used in this embodiment, the transparent substrate and the optically anisotropic layer are laminated as an independent layer of the transparent substrate and the optically anisotropic layer. It may be a laminated mode, or there is no clear interface between the transparent substrate and the optically anisotropic layer, and the content of the optically anisotropic material continuously changes between the two. In this way, the layers may be laminated.

3. Retardation layer Next, the retardation layer used in this embodiment will be described. The retardation layer used in this embodiment includes a liquid crystal material formed on the optically anisotropic film and having homeotropic alignment, and further has a refractive index in any x and y directions orthogonal to each other in the in-plane direction. A relationship of nx ₂ ≦ ny ₂ <nz ₂ is established between nx ₂ and ny ₂ and the refractive index nz ₂ in the thickness direction. The retardation film of this embodiment can improve the viewing angle characteristics of the IPS liquid crystal display device by forming such a retardation layer.

Here, the aspect in which the retardation layer is formed on the optically anisotropic film may be an aspect in which the optically anisotropic film is formed on a transparent substrate, or the optically anisotropic film. The phase difference layer may be formed on the optically anisotropic layer of the conductive film.
Hereinafter, the retardation layer used in this embodiment will be described in detail.

(1) Liquid crystal material First, the liquid crystal material will be described. The liquid crystal material is not particularly limited as long as it is a homeotropic liquid crystal material that can form homeotropic alignment and can impart a phase difference that satisfies the above relationship to nx ₂ , ny ₂ , and nz _2. It is not something. Especially, it is preferable that the homeotropic liquid crystal material used in this embodiment has a polymerizable functional group. This is because by using such a homeotropic liquid crystal material, they can be polymerized with each other via a polymerizable functional group, so that the mechanical strength of the retardation layer used in this embodiment can be improved. In addition, the alignment stability of the homeotropic liquid crystal material in the retardation layer can 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.
Examples of other polymerizable functional groups that can be used in this embodiment include an isocyanate group and an unsaturated triple bond.
In particular, in this embodiment, among these polymerizable functional groups, a functional group having an ethylenically unsaturated double bond is preferably used from the viewpoint of the process.

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

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

In the case where the second homeotropic liquid crystal material is used in this embodiment, in order to cause the homeotropic liquid crystal material to be homeotropically aligned in the retardation layer, the alignment usually has an alignment regulating force for causing the liquid crystal material to be homeotropically aligned. A method using an alignment control compound having a function of using a layer or a homeotropic alignment of the liquid crystal material in the retardation layer is used. The orientation control compound is described in, for example, JP-A-10-319408.
In addition, a retardation layer in which the second homeotropic 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 transparent substrate or the optically anisotropic layer. A transfer method can also be used. In such a transfer method, a method for forming a retardation layer on the other substrate is disclosed in, for example, JP-A No. 2003-177242.

  As the first homeotropic liquid crystal material, any homeotropic alignment can be formed without using a vertical alignment film, and a desired retardation can be imparted to the retardation layer used in this embodiment. It is not particularly limited. Examples of the first homeotropic 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. Liquid crystal such as a side chain type liquid crystal polymer containing, 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 Mention may be made of polymers. 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, as the second homeotropic liquid crystal material, a homeotropic alignment can be formed by using a vertical alignment film or the like, and a desired retardation can be imparted to the retardation layer used in this embodiment. If it is, it will not specifically limit. Especially, in this aspect, the nematic liquid crystal material which shows a nematic phase is used suitably.

  Specific examples of the second homeotropic liquid crystal material used in this embodiment include compounds described in JP-A-10-508882 and JP-A-2003-287623. .

  Examples of the first homeotropic liquid crystal material used in this embodiment include compounds described in JP-A-10-319408. Especially in this aspect, the compound represented by the following chemical formula can be used suitably.

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.

  In addition, when a compound having a polymerizable functional group is used as the homeotropic liquid crystal material, the homeotropic liquid crystal material contained in the retardation layer used in the present embodiment is polymerized via the polymerizable functional group. It becomes a thing.

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

(2) Other compounds The retardation layer used in this embodiment may contain other compounds 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 retardation layer or the optical properties of the retardation layer, and the retardation film of this embodiment It can be appropriately selected and used depending on the purpose of use. Among these, examples of the other compound suitably used in this embodiment include an alignment control compound that assists in forming homeotropic alignment of the liquid crystal material. By using such an alignment control compound, there is an advantage that the homeotropic liquid crystal material of the second aspect can be used. Further, even when the homeotropic 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 retardation layer used in this embodiment. Among these, as the orientation control compound used in this embodiment, a surfactant can be suitably used. In the retardation layer, the surfactant is unevenly distributed at the air interface and can be arranged with the specific direction of the molecule directed toward the retardation layer, so that the homeotropic alignment regulating force is easily imparted to the retardation layer. Because it can.

  As said surfactant used for this aspect, a sulfonate surfactant can be mentioned, for example, A fluorinated sulfonate surfactant is used suitably especially.

  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 used for this aspect, a polymerization initiator, a polymerization inhibitor, a plasticizer, surfactant, a silane coupling agent etc. can be mentioned, for example.

  Moreover, the compound as shown below can be added to the phase difference layer used for this aspect within the range which does not impair the objective of this aspect. 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.

(3) Retardation layer The retardation layer used in this embodiment is provided between the refractive indices nx ₂ and ny ₂ in arbitrary x and y directions orthogonal to each other in the in-plane direction and the refractive index nz _{2 in the} thickness direction. The relationship of nx ₂ ≦ ny ₂ <nz ₂ is established. For this reason, the retardation layer used in this embodiment has a property as a so-called positive C plate.

The retardation in the thickness direction (Rth ² ) of the retardation layer used in this embodiment is not particularly limited as long as the Nz factor of the retardation film of this embodiment is within the range specified in this embodiment. Absent. In particular, in this embodiment, the Rth ² is preferably in the range of −270 nm to −50 nm. This is because, when Rth ² is within the above range, the retardation film of this embodiment can be made more excellent in the viewing angle compensation function of the IPS liquid crystal display device.
Here, Rth ² can be measured by a parallel Nicol rotation method using, for example, KOBRA-WR manufactured by Oji Scientific Instruments.

  The thickness of the retardation layer in this embodiment is not particularly limited as long as it is within a range in which desired optical characteristics can be imparted to the retardation layer, depending on the type of the liquid crystal material, and the like, but within a range of 0.5 μm to 10 μm. It is preferable that it is within a range of 0.5 μm to 5 μm, particularly preferably within a range of 1 μm to 3 μm.

4). Retardation film The optical properties of the retardation film of this embodiment include adjusting the optical properties of the optically anisotropic layer or using the retardation layer according to the application of the retardation film of this embodiment. It can be adjusted as appropriate. In particular, the retardation film of this embodiment preferably has an Nz factor in the range of −0.5 to 0.5, and more preferably in the range of 0 to 0.5. This is because, when the Nz factor is within the above range, the retardation film of this embodiment can be suitably used as a viewing angle compensation film for an IPS liquid crystal display device.

Here, the Nz factor (Nz) is a parameter indicating the shape of the refractive index ellipsoid included in the retardation film of the present embodiment, and is represented by the following equation.
Nz = (Rth / Re) +0.5
Here, Rth and Re respectively represent retardation in the thickness direction and in-plane retardation of the retardation layer of the retardation film of this embodiment.

Further, the in-plane retardation (Re) and the retardation in the thickness direction (Rth) of the retardation film of this embodiment are not particularly limited, and are appropriately adjusted according to the use of the retardation film of this embodiment. It is something that can be done. In particular, the in-plane retardation (Re) of the retardation film of this embodiment is preferably in the range of 50 nm to 170 nm, more preferably in the range of 70 nm to 150 nm, and in the range of 80 nm to 130 nm. More preferably it is.
Here, unless otherwise specified, Re and Rth mean values measured by entering measurement light having a wavelength of 550 nm in a direction parallel to the thickness direction. Such Re and Rth can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

The haze value of the retardation film of the present invention is preferably in the range of 0% to 5.0%, more preferably in the range of 0.1% to 3.0%. More preferably, it is within the range of 3% to 1.0%.
Here, as the haze value, a value measured according to JIS K7105 is used.
A large haze value causes a decrease in contrast, so a smaller haze value is desirable.

  The form of the retardation film of this embodiment is not particularly limited. For example, the retardation film of the present embodiment may be in the form of a sheet that matches the screen size of a liquid crystal display device using the retardation film of the present embodiment, or may be long. There may be.

5). Use of Retardation Film The retardation film of this embodiment can be used as a viewing angle compensation film, an elliptically polarizing plate, a brightness enhancement film and the like used in a liquid crystal display device. In particular, it can be suitably used as a viewing angle compensation film for an IPS liquid crystal display device.

  Moreover, the retardation film of this aspect can be used also for the use as a polarizing plate by bonding together with a polarizer. That is, the polarizing plate is usually composed of a polarizer and a polarizing plate protective film formed on both surfaces thereof. In this embodiment, for example, as one polarizing plate protective film, the retardation of this embodiment is provided. By using a film, it can be used as a polarizing plate having a viewing angle compensation function of a liquid crystal display device.

6). Manufacturing method of retardation film Next, the manufacturing method of the retardation film of this aspect is demonstrated. The method for producing the retardation film of the present embodiment is not particularly limited as long as the method can produce the retardation film having the above configuration. As such a method, for example, a transparent substrate made of a cellulose derivative is used, and an optically anisotropic layer is formed by coating an optically anisotropic layer-forming coating solution containing the rod-shaped compound on the transparent substrate. Forming an optically anisotropic film, a step of stretching the retardation film, and an optically anisotropic layer or a transparent substrate of the optically anisotropic film stretched by the stretching step. Applying a coating liquid for forming an intermediate layer containing the urethane acrylate, and curing the coating solution; and forming a retardation layer containing the liquid crystal material on the intermediate layer By applying the liquid, a method including a step of forming a retardation layer on the optically anisotropic layer can be exemplified.

In addition, as an apparatus and a processing method used for the stretching process, basically the same apparatus as that used for the stretching process of a normal synthetic resin film is used. In view of the retardation value, the film may be stretched under appropriate conditions.
For stretching, either uniaxial stretching treatment or biaxial stretching treatment may be performed. The biaxial stretching process may be an unbalanced biaxial stretching process. In unbalanced biaxial stretching, a polymer film is stretched at a certain ratio in a certain direction, and stretched at a larger ratio in a direction perpendicular thereto. The bi-directional stretching process may be performed simultaneously.
Further, the stretching treatment is not particularly limited. For example, it can be appropriately performed by an arbitrary stretching method such as a roll stretching method, a long gap stretching method, a tenter stretching method, and a tubular stretching method. In the stretching treatment, the polymer film is preferably heated to, for example, a glass transition temperature or higher and a melting temperature (or melting temperature) or lower. In particular, in this embodiment, tenter stretching is preferably used because it can be rolled to roll with a polarizing member made of a hydrophilic resin such as PVA.
Furthermore, the draw ratio of the drawing treatment is appropriately determined depending on the retardation value to be obtained, and is not particularly limited. From the point of making the retardation value uniform at each point in the in-plane direction of the film, it is preferably in the range of 1.03 to 2 times.
In addition, since a method generally used for producing a retardation film for a liquid crystal display device can be used as a specific method for performing each step in each of the above methods, detailed description thereof is omitted here. To do.

B. Next, the retardation film of the second aspect of the present invention will be described. The retardation film of this embodiment contains a transparent substrate made of a cellulose derivative, and a rod-shaped compound formed on the transparent substrate and having refractive index anisotropy, and further has a refractive index in the slow axis direction in the in-plane direction. and nx _1, the refractive index ny ₁ in fast axis direction in the plane direction, between the refractive index nz ₁ in the thickness _direction, an optically anisotropic layer relationship nx _1> ny 1 ≧ nz 1 is satisfied An optically anisotropic film having a liquid crystal material formed on the optically anisotropic film and having homeotropic alignment, and having a refractive index nx ₂ in any x and y directions orthogonal to each other in the in-plane direction. , Ny ₂ and a retardation layer in which a relationship of nx ₂ ≦ ny ₂ <nz ₂ is established between the refractive index nz ₂ in the thickness direction, and the optically anisotropic film, And the above retardation layer Wherein the intermediate layer containing a polymer of a polyalkylene oxide chain-containing polymer having a reactive functional group at the terminal is formed between, to provide a phase difference film.

According to this aspect, an intermediate layer is formed between the optically anisotropic film and the retardation layer, and the intermediate layer contains a polymer of a polyalkylene oxide chain-containing polymer. This can prevent the homeotropic alignment of the liquid crystal material in the retardation layer from being damaged by the action of the optically anisotropic film.
Further, in the retardation film of this aspect, the optically anisotropic layer has optical characteristics in which the relationship of nx ₁ > ny ₁ ≧ nz ₁ is established in nx ₁ , ny ₁ , and nz ₁ , and When the retardation layer has optical characteristics that satisfy the relationship of nx ₂ , ny ₂ , and nz ₂ , it can be suitably used as a viewing angle compensation film for an IPS liquid crystal display device.
For this reason, according to this aspect, a retardation film that is suitably used as a viewing angle compensation film of an IPS liquid crystal display device, and can provide a retardation film having excellent optical property stability. .

The retardation film of this aspect has at least the above-mentioned optically anisotropic film, a retardation layer, and an intermediate layer, and may have other configurations as necessary.
Hereinafter, each structure used for the retardation film of this aspect is demonstrated in order.

1. Intermediate Layer First, the intermediate layer used in this embodiment will be described. The intermediate layer used in this embodiment is formed between an optically anisotropic film described later and a retardation layer, and contains a polymer of a polyalkylene oxide chain-containing polymer. In the retardation film of this embodiment, since such an intermediate layer is formed, the action between the retardation layer and the optically anisotropic layer can be blocked. It can be made excellent.
Hereinafter, the intermediate layer used in this embodiment will be described in detail.

(1) Polymer of polyalkylene oxide chain-containing polymer First, the polymer of the polyalkylene oxide chain-containing polymer will be described. The polymer of the polyalkylene oxide chain-containing polymer used in this embodiment is obtained by polymerizing a polyalkylene oxide chain-containing polymer.
Here, the polyalkylene oxide chain-containing polymer means one represented by the following formula.

In the formula (I), X is a linear, branched, or cyclic hydrocarbon chain, which may be a single group or a combination thereof, and the hydrocarbon chain may have a substituent, and between the hydrocarbon chains. Is a trivalent or higher valent organic group having 3 to 10 carbon atoms, excluding the substituent, which may contain different atoms. k represents an integer of 3 to 10. L _{1 to} L _k are each independently a divalent group including one or more selected from the group consisting of an ether bond, an ester bond, and a urethane bond, or a direct bond. R _{1 to} R _k are each independently a linear or branched hydrocarbon group having 1 to 4 carbon atoms. n1, n2,... nk are independent numbers. Y _{1 to} Y _k each independently represent a compound residue having one or more reactive functional groups.

In the formula (I), X is a linear, branched, or cyclic hydrocarbon chain, which may be a single group or a combination thereof, and the hydrocarbon chain may have a substituent, and between the hydrocarbon chains. Is a trivalent or higher valent organic group having 3 to 10 carbon atoms, excluding the substituent, which may contain different atoms. In the polyalkylene oxide chain-containing polymer represented by the formula (I), X is a short main chain having k branch points from which the polyalkylene oxide chain (O—R _K ) nk portion which is a linear side chain is exposed. It corresponds to.

The hydrocarbon chain includes a saturated hydrocarbon such as —CH ₂ — or an unsaturated hydrocarbon such as —CH═CH—. The cyclic hydrocarbon chain may be composed of an alicyclic compound or may be composed of an aromatic compound. Further, different atoms such as O and S may be contained between the hydrocarbon chains, and ether bonds, thioether bonds, ester bonds, urethane bonds, etc. may be contained between the hydrocarbon chains. In addition, the hydrocarbon chain branched via a different atom with respect to a linear or cyclic hydrocarbon chain is counted as the carbon number of the substituent mentioned later.

  Specific examples of the substituent that the hydrocarbon chain may have include a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an epoxy group, an isocyanate group, a mercapto group, a cyano group, a silyl group, a silanol group, and a nitro group. Group, acetyl group, acetoxy group, sulfone group and the like are mentioned, but not particularly limited. Substituents that may be present in the hydrocarbon chain include hydrocarbon chains that are branched via a hetero atom with respect to a linear or cyclic hydrocarbon chain as described above. A group (RO-, where R is a saturated or unsaturated linear, branched, or cyclic hydrocarbon chain), an alkylthioether group (RS-, where R is a saturated or unsaturated linear chain, Branched or cyclic hydrocarbon chains), alkyl ester groups (RCOO-, where R is a saturated or unsaturated linear, branched, or cyclic hydrocarbon chain). .

X is a trivalent or higher valent organic group having 3 to 10 carbon atoms excluding the substituent. When the number of carbon atoms excluding the substituent of X is less than 3, it is difficult to have three or more polyalkylene oxide chain (O—R _K ) nk portions which are linear side chains. On the other hand, when the number of carbon atoms excluding the substituent of X exceeds 10, the flexible portion increases and adversely affects the alignment of the vertically aligned liquid crystal. The number of carbon atoms excluding the above substituent is preferably 3-7, more preferably 3-5.

  X is not particularly limited as long as the above conditions are satisfied. For example, what has the following structure is mentioned.

  Among them, preferable structures include the above structures (x-1), (x-2), (x-3), (x-7) and the like.

  Among the raw materials for X, among others, 1,2,3-propanetriol (glycerol), trimethylolpropane, pentaerythritol, dipentaerythritol and the like are polyvalent having 3 to 10 carbon atoms having 3 or more hydroxyl groups in the molecule. Alcohols, polyvalent carboxylic acids having 3 to 10 carbon atoms having 3 or more carboxyl groups in the molecule, polyvalent amine acids having 3 to 10 carbon atoms having 3 or more amino groups in the molecule, etc. Preferably used.

In the formula (I), k represents the number of polyalkylene oxide chains (O—R _K ) nk in the molecule and represents an integer of 3 to 10. The k is preferably 3-7, more preferably 3-5.

In the formula (I), L _{1 to} L _k are each independently a divalent group including one or more selected from the group consisting of an ether bond, an ester bond, and a urethane bond, or a direct bond. The divalent group including one or more selected from the group consisting of an ether bond, an ester bond, and a urethane bond is an ether bond (—O—), an ester bond (—COO—), a urethane bond (—NHCOO—). ) Itself. Since these bonds are easy to spread molecular chains and have a high degree of freedom, it is easy to achieve compatibility with other resin components.

  Examples of the divalent group containing one or more selected from the group consisting of an ether bond, an ester bond, and a urethane bond include —O—R—O— and —O (C═O) —R—O—. -O (C = O) -R- (C = O) O-,-(C = O) O-R-O-,-(C = O) O-R- (C = O) O-, — (C═O) O—R—O (C═O) —, —NHCOO—R—O—, —NHCOO—R—O (C═O) NH—, —O (C═O) NH—R —O—, —O (C═O) NH—R—O (C═O) NH—, —NHCOO—R—O (C═O) NH—, —NHCOO—R— (C═O) O— , —O (C═O) NH—R— (C═O) O—, —NHCOO—R—O (C═O) —, —O (C═O) NH—R—O (C═O) -Etc. are mentioned. Here, R represents a saturated or unsaturated, linear, branched or cyclic hydrocarbon chain.

  Specific examples of the divalent group include, for example, diols such as (poly) ethylene glycol and (poly) propylene glycol, dicarboxylic acids such as fumaric acid, maleic acid, and succinic acid, tolylene diisocyanate, hexamethylene diisocyanate, Although the residue remove | excluding active hydrogen, such as diisocyanates, such as isophorone diisocyanate, is mentioned, It is not limited to these.

In the formula (1), (O—R _K ) nk is a polyalkylene oxide chain in which the alkylene oxide is a linear side chain of repeating units. Here, R1 to Rk are each independently a linear or branched hydrocarbon group having 1 to 4 carbon atoms. Examples of the alkylene oxide include methylene oxide, ethylene oxide, propylene oxide, isobutylene oxide, and the like, and ethylene oxide and propylene oxide which are linear or branched hydrocarbon groups having 2 to 3 carbon atoms are preferably used.

N1, n2... Nk, which are the number of repeating units of alkylene oxide R _K —O, are independent numbers. n1, n2... nk are not particularly limited as long as the weight average molecular weight as a whole molecule is 1000 or more. n1, n2... nk may be different from each other, but preferably have substantially the same chain length. Therefore, the difference between n1, n2,... Nk is preferably about 0 to 100, more preferably about 0 to 50, particularly about 0 to 10. n1, n2... nk are each preferably a number of 2 to 500, and more preferably a number of 2 to 300.

Y1 to Yk each independently represent a reactive functional group or a compound residue having one or more reactive functional groups. This results in three or more reactive functional groups at the end of the polyalkylene oxide chain-containing polymer.
When Y1 to Yk are reactive functional groups themselves, examples of Y1 to Yk include polymerizable unsaturated groups such as (meth) acryloyl groups, hydroxyl groups, carboxyl groups, amino groups, epoxy groups, and isocyanates.

  Examples of the reactive functional group in the case where Y1 to Yk are compound residues having one or more reactive functional groups include, for example, (meth) acryloyl group, (meth) acryloyloxy group, vinyl group (CH2 = CH -), A polymerizable unsaturated group such as CH2 = CR- (where R is a hydrocarbon group), a hydroxyl group, a carboxyl group, an amino group, an epoxy group, an isocyanate group, and the like. When Y1 to Yk is a compound residue, the number of reactive functional groups that Y1 to Yk has may be one, but if it is two or more, the crosslinking density can be further increased. It is also preferable because fluctuation can be suppressed.

When Y1-Yk is a compound residue having one or more reactive functional groups, the compound residue is further a reactive substituent separately from at least one reactive functional group and the reactive functional group. This is a residue obtained by removing the reactive substituent or a part of the reactive substituent (such as hydrogen) from the compound having the above.
For example, as a compound residue having an ethylenically unsaturated group, specifically, for example, a reactive substituent other than the ethylenically unsaturated group of the following compound or a part of the reactive substituent (such as hydrogen) is removed. Residue. Examples include (meth) acrylic acid, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and pentaerythritol tri (meth) acrylate, but are not limited thereto.
In addition, specific examples of the compound residue having an epoxy group include glycidol.

  Further, the molecular weight of the polyalkylene oxide chain-containing polymer used in the present invention is 1000 or more, more preferably 5000 or more, particularly preferably 10,000 or more from the viewpoint of giving flexibility to the cured film.

Commercially available products containing the polyalkylene oxide chain-containing polymer (A) represented by the above formula (I) include, for example, trade name Beam Set 371 (manufactured by Arakawa Chemical Industries), trade name Dia Beam UK-4153 (Mitsubishi Rayon) Manufactured; in formula (I), X is (x-7), k is 3, L _{1 to} L ₃ are each a direct bond, R _{1 to} R ₃ are each ethylene, and the total of n1, n2, and n3 is 20 , Y1 to Y3 are each an acryloyloxy group.) And the like.

  In addition, the polyalkylene oxide chain containing polymer used for this aspect may be only one type, or may be two or more types.

  The polymer of the polyalkylene oxide chain-containing polymer used in this embodiment is obtained by polymerizing the above polyalkylene oxide chain-containing polymer. The polymer of the polyalkylene oxide chain-containing polymer used in this embodiment may be obtained by polymerizing a single polyalkylene oxide chain-containing polymer, or a plurality of polyalkylene oxide chain-containing polymers may be polymerized. It may be.

(2) Other compounds The intermediate layer used in this embodiment contains at least a polymer of the above-mentioned polyalkylene oxide chain-containing polymer, but may contain other compounds as necessary. Other compounds used in this embodiment can be appropriately selected according to the use of the retardation film of this embodiment, the performance required for the retardation film of this embodiment, and the like. Such other compounds are the same as those described in the above section “A. Retardation film of first aspect”, and thus the description thereof is omitted here.

(3) Intermediate layer The thickness of the intermediate layer used in this embodiment depends on the type of the polyalkylene oxide chain-containing polymer constituting the polymer of the above-mentioned polyalkylene oxide chain-containing polymer. There is no particular limitation as long as the stability of the optical properties of the net can be imparted. Here, the suitable thickness of the intermediate layer used in this embodiment is the same as that described in the section “A. Retardation film of first embodiment” above.

2. Retardation film The use of the optically anisotropic film, retardation layer and retardation film used in the present embodiment is the same as that described in the above section “A. Retardation film of first embodiment”. The description here is omitted.

  The optical characteristics of the retardation film of this aspect are appropriately adjusted by adjusting the optical characteristics of the optical anisotropic layer or using the retardation layer according to the use of the retardation film of this aspect. It can be adjusted. Here, suitable optical characteristics of the retardation film of the present invention are the same as those described in the section “A. Retardation film of first aspect” above.

  The form of the retardation film of this embodiment is not particularly limited. For example, the retardation film of the present embodiment may be in the form of a sheet that matches the screen size of a liquid crystal display device using the retardation film of the present embodiment, or may be long. There may be.

  The method for producing the retardation film of the present embodiment has been described in the section “A. Retardation film of the first embodiment” except that a polyalkylene oxide chain-containing polymer is used as the material for forming the intermediate layer. Since it is the same as that of a thing, description here is abbreviate | omitted.

  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. Production of Optical Anisotropic Film Optical anisotropic films (A) to (C) were produced by the following method.
(1) Production of optically anisotropic film (A) A polymerizable liquid crystal compound represented by the following formula (A) is dissolved in cyclohexanone so as to be 12% by mass, and further a photopolymerization initiator Lucillin TPO (manufactured by BASF). Was added in an amount of 4% by mass based on the solid content to adjust the optical anisotropy forming coating solution.

Next, a triacetyl cellulose film (hereinafter referred to as TAC film) (trade name: TF80UL, manufactured by Fuji Film Co., Ltd.) is used as the transparent substrate, and the optically anisotropic layer forming coating solution is bar coated on the surface of the transparent substrate. Was applied such that the coating amount after drying was 2.2 g / m ² . Subsequently, it heated at 40 degreeC for 4 minute (s), the solvent was dried and removed, the ultraviolet rays were irradiated to the coating surface, the said photopolymerizable liquid crystal compound was fixed, and the optical laminated body was formed.
Subsequently, the optically laminated body was uniaxially stretched in the in-plane direction while being heated at 165 ° C. so that the stretch ratio was 1.2 times by a stretching experiment machine, thereby producing an optically anisotropic film. The obtained optically anisotropic film had Re = 118 nm and Nz = 1.48.

(1) Production of optically anisotropic film (B) 12% by mass of 25% by mass of polymerizable liquid crystal compound represented by the following formula (B) and 75% by mass of polymerizable liquid crystal compound represented by the above formula (A) in cyclohexanone. Then, a photopolymerization initiator Lucillin TPO (manufactured by BASF) was added at 4% by mass with respect to the solid content to prepare a coating solution for forming optical anisotropy.

Next, a triacetyl cellulose film (hereinafter referred to as TAC film) (trade name: TF80UL, manufactured by Fuji Film Co., Ltd.) is used as the transparent substrate, and the optically anisotropic layer forming coating solution is bar coated on the surface of the transparent substrate. Was applied such that the coating amount after drying was 2.8 g / m ² . Subsequently, it heated at 40 degreeC for 4 minute (s), the solvent was dried and removed, the ultraviolet rays were irradiated to the coating surface, the said photopolymerizable liquid crystal compound was fixed, and the optical laminated body was formed.
Next, the optically laminated body was uniaxially stretched in the in-plane direction while being heated at 165 ° C. so as to have a draw ratio of 1.225 times by a stretching experiment machine, thereby producing an optically anisotropic film. The obtained optically anisotropic film had Re = 115 nm and Nz = 1.50.

(3) Production of optically anisotropic film (C) The optically anisotropic film (C) was produced in the same manner as the production of the optically anisotropic film (B) except that the coating amount was 2.5 g / m ^2. Produced. The obtained optically anisotropic film had Re = 90 nm and Nz = 1.73.

2. Adjustment of intermediate layer forming coating solution The intermediate layer forming coating solutions 1 to 10 were adjusted as follows.

(1) Intermediate layer forming coating solution 1
・ Aromatic urethane acrylate (molecular weight 3000, 9 functional) 30% by mass
(Manufactured by Daicel Cytec, KRM7804)
-Polymerization initiator (Irgacure 184) 0.9 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.15% by mass
・ Methyl isobutyl ketone (hereinafter referred to as MIBK) 70% by mass

(2) Intermediate layer forming coating solution 2
-Urethane acrylate (molecular weight 2000, 10 functional) 30% by mass
(Nippon GOHSEI, purple light UV1700B)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ MIBK 70% by mass

(3) Intermediate layer forming coating solution 3
・ Urethane acrylate (molecular weight 1500, hexafunctional) 30% by mass
(Manufactured by Nippon Synthetic Chemical Co., Ltd., purple light UV7640B)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 35% by mass
・ Methyl ethyl ketone (hereinafter referred to as MEK) 35% by mass

(4) Intermediate layer forming coating solution 4
-Urethane acrylate (molecular weight 1500, 15 functional) 30% by mass
(Negami Kogyo Co., Ltd., Art Resin UN-3320HD)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 35% by mass
・ Methyl ethyl ketone 35% by mass

(5) Intermediate layer forming coating solution 5
-Polymer acrylate (molecular weight 36,000, 100-150 functional) 15% by mass
(Arakawa Chemical Industries, beam set 371)
-Urethane acrylate (molecular weight 2000, 10 functional) 15% by mass
(Nippon GOHSEI, purple light UV1700B)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 35% by mass
・ Methyl ethyl ketone 35% by mass

(6) Intermediate layer forming coating solution 6
・ Neopentyl glycol-modified trimethylolpropane diacrylate 30% by mass
(Nippon Kayaku Co., Ltd., R-604)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 70% by mass

(7) Intermediate layer forming coating solution 7
・ Caprolactone-modified dipentaerythritol hexaacrylate 30% by mass
(Nippon Kayaku Co., Ltd., DPCA-20)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 70% by mass

(8) Intermediate layer forming coating solution 8
Aliphatic urethane acrylate: 1,6-hexanediol diacrylate = 65: 35
30% by mass
(Daicel Cytec, EBECRYL4820)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 70% by mass

(9) Intermediate layer forming coating solution 9
・ Aromatic urethane acrylate 30% by mass
(Daicel Cytec, EBECRYL210)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 70% by mass

(10) Intermediate layer forming coating solution 10
-Aliphatic urethane acrylate 30% by mass
(Daicel Cytec, EBECRYL8402)
-Polymerization initiator (Irgacure 184) 1.5 mass%
・ Leveling agent (Big Chemie, BYK361N) 0.075% by mass
・ MIBK 70% by mass

  The compositions of the intermediate layer forming coating liquids 1 to 10 are shown in Table 1.

Example 1
The intermediate layer-forming coating solution 1 prepared above is placed on the back side of the optically anisotropic layer forming surface of the optically anisotropic film (B), that is, on the TAC film surface side (hereinafter referred to as TAC surface side). Coating was performed so that the coating amount after drying was 3.5 g / m ² by coating. Subsequently, the solvent was dried and removed by heating at 80 ° C. for 3 minutes, and an ultraviolet ray of 196 mJ / cm ² was irradiated on the coated surface, thereby forming an intermediate layer on the optically anisotropic film (B).

Next, a liquid crystal mixture of 50% by mass of a side chain polymer represented by the following formula (C) and 50% by mass of a photopolymerizable liquid crystal represented by the following formula (D), a photopolymerization initiator (manufactured by Ciba Specialty Chemicals) , Irgacure 907, 5% by mass with respect to the photopolymerizable compound) was dissolved in toluene so as to have a solid content of 20%, and a leveling agent was added to obtain a coating solution for forming a retardation layer. After coating the retardation layer forming coating solution on the intermediate layer, the liquid crystal mixture was homeotropically aligned by drying at 100 ° C. for 1 minute and then cooling to room temperature to obtain a retardation layer. . Furthermore, it was cured by UV of 190 mJ / cm ² to prepare a retardation film.

(Example 2)
The intermediate layer-forming coating solution 2 prepared above was applied to the TAC surface side of the optically anisotropic film (A) by bar coating so that the coating amount after drying was 3.5 g / m ^2. did. Subsequently, the solvent was dried and removed by heating at 80 ° C. for 3 minutes, and an ultraviolet ray of 196 mJ / cm ² was irradiated on the coated surface, thereby forming an intermediate layer on the optically anisotropic film (B).
Next, a liquid crystal mixture containing a liquid crystal material represented by the following formulas (E), (F), and (G), a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 907, 5 masses with respect to the liquid crystal mixture) %) Was dissolved in toluene to a solid content of 20% by mass, and a leveling agent was further added to obtain a coating solution for forming a retardation layer. Next, the retardation layer forming coating solution was applied onto a glass substrate on which a vertical alignment film was formed, and then dried at 60 ° C. for 2 minutes to achieve homeotropic alignment. Furthermore, it was cured by irradiating UV of 196 mJ / cm ² to form a retardation layer.
Next, the retardation layer was peeled from the glass substrate, and bonded to the intermediate layer of the optically anisotropic film via an adhesive to produce a retardation film.

(Example 3)
A retardation film was obtained in the same manner as in Example 1, except that an intermediate layer was formed on the optically anisotropic film (A) using the intermediate layer forming coating solution 3 in Example 1.

Example 4
A retardation film was obtained in the same manner as in Example 1 except that the intermediate layer was formed using the intermediate layer forming coating solution 4 in Example 1.

(Example 5)
A retardation film was obtained in the same manner as in Example 2, except that an intermediate layer was formed on the optically anisotropic film (B) using the intermediate layer forming coating solution 5 in Example 2.

(Example 6)
In Example 1, except that the intermediate layer was formed using 1 in the intermediate layer forming coating solution on the optical anisotropic layer forming surface side (hereinafter referred to as LC surface side) of the optical anisotropic film (C). A retardation film was obtained in the same manner as in Example 1.

(Example 7)
A retardation film was obtained in the same manner as in Example 2, except that an intermediate layer was formed on the LC surface side of the optically anisotropic film (C) using the intermediate layer forming coating solution 4 in Example 2.

(Example 8)
A retardation film was obtained in the same manner as in Example 1, except that an intermediate layer was formed using the intermediate layer forming coating solution 5 on the LC surface side of the optically anisotropic film (C) in Example 1.

(Comparative Example 1)
A retardation film was obtained in the same manner as in Example 3, except that an intermediate layer was formed using the intermediate layer forming coating solution 6 in Example 3.

(Comparative Example 2)
A retardation film was obtained in the same manner as in Example 5 except that the intermediate layer was formed using the intermediate layer forming coating solution 7 in Example 5.

(Comparative Example 3)
A retardation film was obtained in the same manner as in Example 3 except that the intermediate layer was formed using the intermediate layer forming coating solution 8 in Example 3.

(Comparative Example 4)
A retardation film was obtained in the same manner as in Example 5 except that an intermediate layer was formed using the intermediate layer forming coating solution 9 in Example 5.

(Comparative Example 5)
A retardation film was obtained in the same manner as in Example 5 except that the intermediate layer was formed using the intermediate layer forming coating solution 10 in Example 5.

(Comparative Example 6)
A retardation film was obtained in the same manner as in Example 7 except that the intermediate layer was formed using the intermediate layer forming coating solution 10 in Example 7.

(Optical property evaluation of retardation film)
In-plane retardation Re and Nz were evaluated for the optically anisotropic films prepared in the above Examples and Comparative Examples, and Rth and Nz factors were evaluated for the retardation film. Each in-plane retardation, thickness direction retardation and Nz factor were evaluated using an automatic birefringence measuring apparatus KOBRA.

(Evaluation by long-term reliability test)
The obtained retardation film was put into a constant temperature and humidity oven under conditions of a temperature of 80 ° C. and a temperature of 65 ° C. and a humidity of 95%, and after 500 hours, the amount of change in Rth of the retardation film was confirmed by the same method as described above.

  The above evaluation results are shown in Table 2.

It is a schematic sectional drawing which shows an example of the phase difference film of this invention. It is a schematic perspective view which shows the other example of the optically anisotropic film used for this invention. It is a schematic sectional drawing which shows the other example of the optically anisotropic film used for this invention. It is a schematic sectional drawing which illustrates typically a part of common liquid crystal display device. It is a schematic sectional drawing which illustrates typically a part of liquid crystal display device in which phase contrast film was used. It is a schematic sectional drawing which shows an example of the usage condition of retardation film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optically anisotropic film 1a ... Transparent substrate 1b ... Optically anisotropic layer 2 ... Phase difference layer 3 ... Intermediate | middle layer 10 ... Phase difference film 101 ... Liquid crystal cell 102A, 102B, 102A ', 102B' ... Polarizing plate 103 ... Retardation film 111 ... Polarizer 112a, 112b ... Polarizing plate protective film

Claims (7)

A transparent substrate made of a cellulose derivative, and a rod-shaped compound formed on the transparent substrate and having refractive index anisotropy, and further, a refractive index nx ₁ in the slow axis direction in the in-plane direction, and in the in-plane direction An optically anisotropic film having an optically anisotropic layer satisfying a relationship of nx ₁ > ny ₁ ≧ nz ₁ between the refractive index ny _{1 in the} fast axis direction and the refractive index nz _{1 in} the thickness direction;
A liquid crystal material formed on the optically anisotropic film and containing homeotropic alignment is contained, and the refractive indexes nx ₂ and ny ₂ in arbitrary x and y directions orthogonal to each other in the in-plane direction, and the thickness direction A retardation film having a relationship of nx ₂ ≦ ny ₂ <nz ₂ between the refractive index nz ₂ and a retardation film,
A retardation film comprising an intermediate layer containing a tetrafunctional or higher functional urethane (meth) acrylate polymer between the optically anisotropic film and the retardation layer.   2. The retardation film according to claim 1, wherein a ratio between the number of functional groups of the urethane (meth) acrylate and the molecular weight (molecular weight / number of functional groups (meth) acrylates) is 1000 or less. A transparent substrate made of a cellulose derivative, and a rod-shaped compound formed on the transparent substrate and having refractive index anisotropy, and further, a refractive index nx ₁ in the slow axis direction in the in-plane direction, and in the in-plane direction An optically anisotropic film having an optically anisotropic layer satisfying a relationship of nx ₁ > ny ₁ ≧ nz ₁ between the refractive index ny _{1 in the} fast axis direction and the refractive index nz _{1 in} the thickness direction;
A liquid crystal material formed on the optically anisotropic film and containing homeotropic alignment is contained, and the refractive indexes nx ₂ and ny ₂ in arbitrary x and y directions orthogonal to each other in the in-plane direction, and the thickness direction A retardation film having a relationship of nx ₂ ≦ ny ₂ <nz ₂ between the refractive index nz ₂ and a retardation film,
An intermediate layer containing a polymer of a polyalkylene oxide chain-containing polymer having a reactive functional group at a terminal is formed between the optically anisotropic film and the retardation layer. Phase difference film.   The retardation film according to claim 3, wherein the polyalkylene oxide chain-containing polymer has 3 or more reactive functional groups.   The retardation film according to claim 3 or 4, wherein the polyalkylene oxide chain-containing polymer has a molecular weight of 1000 or more.   The retardation film according to claim 1, wherein the Nz factor (Nz) is in a range of −0.5 <Nz <0.5.   The retardation film according to any one of claims 1 to 6, wherein the cellulose derivative is triacetylcellulose.

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