JP4636600B2 - Birefringent film, laminated retardation plate, optical film, and image display device - Google Patents

Description

The present invention relates to a birefringent film , a laminated retardation plate , an optical film, and an image display device on which the birefringent film is laminated.

The retardation plate is an optical member used for obtaining polarized light such as linearly polarized light, circularly polarized light, and elliptically polarized light. As the retardation plate, a λ / 4 plate whose phase difference corresponds to ¼ of the wavelength λ and a λ / 2 plate whose phase difference corresponds to ½ of the wavelength λ are mainly known. The λ / 4 plate has an optical function of converting linearly polarized light into circularly polarized light, and the λ / 2 plate has an optical function of converting the polarization vibration plane of the linearly polarized light by 90 degrees. These retardation plates are required to exhibit a predetermined phase difference such as λ / 4 for all incident light in the visible light region.
However, for example, chromatic dispersion in a polymer film is generally larger on the short wavelength side and smaller on the long wavelength side. Such a retardation film composed of a single polymer film does not exhibit a predetermined retardation in all the light in the visible light region as described above.

  Therefore, an optically anisotropic layer made of a material having a positive in-plane intrinsic birefringence value and a material having a negative intrinsic birefringence value as a retardation plate showing a predetermined phase difference in all light in the visible light region There is known a laminated phase difference plate obtained by laminating an optically anisotropic layer made of the above so that their optical axes are parallel to each other (for example, JP-A-2002-156525).

Among the two types of optically anisotropic layers, a relatively large number of optical materials having a positive intrinsic birefringence value are known. However, there are relatively few known optical materials having a negative intrinsic birefringence value. Therefore, there is a problem that there is little room for material selection when the laminated retardation plate is manufactured.
The laminated retardation plate is required to have a so-called reverse wavelength dispersion characteristic in which the retardation on the short wavelength side is small and the retardation on the long wavelength side is large, so that the intrinsic birefringence value is positive optical anisotropy. The layer is required to have a small wavelength dispersion of the in-plane retardation in the visible light region, while an optically anisotropic layer having a negative intrinsic birefringence value has a large wavelength dispersion.
However, at present, few optical materials are known which have a large wavelength dispersion in the visible light region and a negative intrinsic birefringence value.

JP 2002-156525 A

  Accordingly, an object of the present invention is to provide a birefringent film that exhibits optical characteristics having a negative intrinsic birefringence value and that has a relatively large in-plane retardation wavelength dispersion in the visible light region. . Furthermore, this invention makes it a subject to provide the laminated phase difference plate using this birefringent film, an optical film, an image display apparatus, etc.

（一般式（I）中、Ｒ^１は、水素原子又は炭素数１〜８のアルキル基を示す。Ｒ^２及びＲ^６はそれぞれ独立に、水素原子、炭素数１〜４の直鎖状若しくは分枝状のアルキル基、炭素数１〜４の直鎖状若しくは分枝状のアルコキシ基、炭素数１〜４の直鎖状若しくは分枝状のチオアルコキシ基、ハロゲン、ニトロ基、アミノ基、水酸基又はチオール基を示す（但し、Ｒ^２及びＲ^６は同時に水素原子ではない）。Ｒ^３〜Ｒ^５はそれぞれ独立に、水素原子又は置換基を示す）。

（一般式（II）中、Ｒ^７は、水素原子又は炭素数１〜８のアルキル基を示す。Ａは、置換基を有していてもよいナフチル基、置換基を有していてもよいアントラセニル基、又は置換基を有していてもよいフェナントレニル基を示す。ナフチル基、アントラセニル基、又はフェナントレニル基を構成する炭素原子のうち１以上の炭素原子は窒素原子で置換されていてもよい）。

（一般式（IV）中、Ｒ ^８ は、水素原子、又は、炭素数１〜１２の直鎖状、分鎖状若しくは環状のアルキル基を示し、アルキル基の炭素原子は隣接しない酸素原子によって置換されていてもよい。繰り返し単位（Ａ）〜（Ｃ）の配列は、ブロック状、ランダム状のいずれであってもよい）。 As a result of diligent research on various materials under the above problems, the present inventors have found that the above problems can be solved by the following means.
That is, the first means of the present invention is a stretched polymer film, in which the polymer is at least one of the structures represented by the following general formula (I) or general formula (II) as the repeating unit (A). On the other hand, it has a repeating unit (B) represented by the following formula (III) and a repeating unit (C) represented by the following general formula (IV), and the repeating unit (A) is 27 mol%. A birefringent film comprising -95 mol%, 1 to 5 mol% of repeating units (B), and 1 to 5 mol% of repeating units (C) is provided.

(In general formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ² and R ⁶ are each independently a hydrogen atom, a linear or branched group having 1 to 4 carbon atoms. Branched alkyl group, linear or branched alkoxy group having 1 to 4 carbon atoms, linear or branched thioalkoxy group having 1 to 4 carbon atoms, halogen, nitro group, amino group, hydroxyl group Or R ² and R ⁶ are not hydrogen atoms at the same time, and R ^{3 to} R ⁵ each independently represents a hydrogen atom or a substituent.

(In General Formula (II), R ⁷ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. A may have a naphthyl group or a substituent which may have a substituent. anthra cell group, or may have a substituent represents an phenanthrenyl group. naphthyl group, one or more of the carbon atoms of the carbon atoms constituting the anthra cell group, or phenanthrenyl groups substituted with a nitrogen atom May be).

(In the general formula (IV), R ⁸ represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, and the carbon atom of the alkyl group is substituted by an oxygen atom which is not adjacent to the alkyl group. The arrangement of the repeating units (A) to (C) may be either a block shape or a random shape.

  In a preferred embodiment of the present invention, the refractive index nx in the in-plane stretching direction and the refractive index ny in the direction perpendicular to the in-plane stretching direction satisfy the relationship nx <ny. A birefringent film is provided.

  Further, in a preferred embodiment of the present invention, the in-plane retardation Re (450) in the light having a wavelength of 450 nm and the in-plane retardation Re (550) in the light having a wavelength of 550 nm are represented by Re (450) / Re The above birefringent film satisfies the relationship (550)> 1.08.

（一般式（V）中、ｌは、２７モル％〜９５モル％、ｍは、１モル％〜５モル％、ｎは、１モル％〜５モル％を示す）。 Furthermore, in a preferred embodiment of the present invention, there is provided the birefringent film, wherein the polymer is a polymer having a structure represented by the following general formula (V).

(In general formula (V), l represents 27 mol% to 95 mol%, m represents 1 mol% to 5 mol%, and n represents 1 mol% to 5 mol%).

  The second means of the present invention is a laminated phase difference plate in which each of the birefringent films and at least one optically anisotropic layer are laminated, and the slow axis of the birefringent film and the optical axis. Provided is a laminated retardation plate in which a birefringent film and an optically anisotropic layer are laminated so that the slow axis of the anisotropic layer is substantially orthogonal.

  Furthermore, in a preferred embodiment of the present invention, there is provided a laminated phase difference plate in which each of the birefringent films and at least one optically anisotropic layer are laminated, and an in-plane retardation at a wavelength of at least 450 nm to 650 nm. Provides a retardation plate that is smaller on the shorter wavelength side and larger on the longer wavelength side.

  Moreover, in a preferred aspect of the present invention, there is provided the laminated retardation plate, wherein the optically anisotropic layer includes a film formed by fixing the orientation of a liquid crystal compound.

  Furthermore, in a preferred aspect of the present invention, there is provided the laminated retardation plate, wherein the optically anisotropic layer includes a stretched film of norbornene resin.

Furthermore, the third means of the present invention provides an optical film having any one of the above birefringent films or any one of the above laminated retardation plates.

Furthermore, a fourth means of the present invention provides an image display device comprising any one of the above birefringent films, any of the above laminated retardation plates, or the above optical film.

The birefringent film of the present invention exhibits optical characteristics having a negative intrinsic birefringence value by orienting the polymer. Further, the birefringent film has a relatively large in-plane retardation wavelength dispersion in the visible light region. Therefore, the birefringent film of the present invention is an optically anisotropic layer having a positive intrinsic birefringence value. By laminating, it is possible to provide a laminated phase difference plate that exhibits a predetermined phase difference such as λ / 4 or λ / 2 with respect to light of almost all wavelengths λ in the visible light region of 400 to 650 nm.
The polymer for a film of the present invention can be oriented to obtain a birefringent film having a negative intrinsic birefringence value. By providing such a polymer, there are many choices of optical materials when designing a laminated phase difference plate, and the demand for diversifying optical members can be met.
Furthermore, the birefringent film of the present invention is excellent in transparency and has effects such as heat resistance and solvent solubility during production due to its preferred embodiment.

Hereinafter, the present invention will be specifically described.
In the present specification, “inherent birefringence value is positive” means that the refractive index of light in a direction substantially parallel to the alignment direction of molecules is higher than the refractive index of light in a direction substantially orthogonal to the alignment direction. For example, in the case of a uniaxially stretched film, a film having a positive intrinsic birefringence value is a light whose refractive index of light in a direction substantially parallel to the stretching direction is substantially perpendicular to the stretching direction. A film whose refractive index is greater than that.
“Negative birefringence value is negative” means that the refractive index of light in a direction substantially parallel to the alignment direction of molecules is smaller than the refractive index of light in a direction substantially perpendicular to the alignment direction. For example, in the case of a uniaxially stretched film, a film having a negative intrinsic birefringence value means that the refractive index of light in a direction substantially parallel to the stretching direction is greater than the refractive index of light in a direction substantially perpendicular to the stretching direction. Also says a small film.
Furthermore, “nx” represents the refractive index in the in-plane stretching direction (or the molecular orientation direction for those not stretched). “Ny” represents a refractive index in a direction perpendicular to the stretching direction in the plane (a direction perpendicular to the x-axis in the plane). “Nz” represents the refractive index in the thickness direction (direction perpendicular to the n-axis and the y-axis).
Re (450), Re (550), and Re (650) represent in-plane phase differences measured at wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and are obtained by Re (λ) = (nx−ny) · thickness. be able to.

（一般式（I）中、Ｒ^１は、水素原子又は炭素数１〜８のアルキル基を示す。Ｒ^２及びＲ^６はそれぞれ独立に、水素原子、炭素数１〜４の直鎖状若しくは分枝状のアルキル基、炭素数１〜４の直鎖状若しくは分枝状のアルコキシ基、炭素数１〜４の直鎖状若しくは分枝状のチオアルコキシ基、ハロゲン、ニトロ基、アミノ基、水酸基又はチオール基を示す（但し、Ｒ^２及びＲ^６は同時に水素原子ではない）。Ｒ^３〜Ｒ^５はそれぞれ独立に、水素原子又は置換基を示す）。

（一般式（II）中、Ｒ^７は、水素原子又は炭素数１〜８のアルキル基を示す。Ａは、置換基を有していてもよいナフチル基、置換基を有していてもよいアントラセニル基、又は置換基を有していてもよいフェナントレニル基を示す。ナフチル基、アントラセニル基、又はフェナントレニル基を構成する炭素原子のうち１以上の炭素原子は窒素原子で置換されていてもよい）。 (About polymer for film)
The polymer for a film according to the present invention used for production of a birefringent film has at least one of the structures represented by the following general formula (I) or general formula (II) as the repeating unit (A). It is.

(In general formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ² and R ⁶ are each independently a hydrogen atom, a linear or branched group having 1 to 4 carbon atoms. Branched alkyl group, linear or branched alkoxy group having 1 to 4 carbon atoms, linear or branched thioalkoxy group having 1 to 4 carbon atoms, halogen, nitro group, amino group, hydroxyl group Or R ² and R ⁶ are not hydrogen atoms at the same time, and R ^{3 to} R ⁵ each independently represents a hydrogen atom or a substituent.

(In General Formula (II), R ⁷ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. A may have a naphthyl group or a substituent which may have a substituent. anthra cell group, or may have a substituent represents an phenanthrenyl group. naphthyl group, one or more of the carbon atoms of the carbon atoms constituting the anthra cell group, or phenanthrenyl groups substituted with a nitrogen atom May be).

The alkyl group having 1 to 8 carbon atoms of R ^{1 in} the general formula (I) is not particularly limited. For example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl Group, t-butyl group, n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group and the like are exemplified. Specific examples of the alkyl group having 1 to 4 carbon atoms of R ² and R ⁶ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, and an isobutoxy group. Moreover, as a substituent of said R < ³ > -R < ⁵ >, the following substituent etc. which were illustrated by general formula (II) are mentioned.

Among the repeating units (A) represented by the general formula (I), the planar structure of the aromatic group is easily arranged in a substantially orthogonal direction due to steric hindrance with the oxygen atom, so that R ^{1 in the} general formula (I) is , Those which are hydrogen atoms (sterically small) are preferred. In particular, since the planar structure of the aromatic group is easy to be arranged in a substantially orthogonal direction, R ^{1 in the} general formula (I) is a hydrogen atom, and R ² and R ⁶ are both linear having 1 to 4 carbon atoms. Or a branched alkyl group, an alkoxy group, a thioalkoxy group, a halogen, a nitro group, an amino group, a hydroxyl group, or a thiol group (wherein R ² and R ⁶ are not hydrogen atoms) are preferable. Furthermore, it is preferable that R ¹ in the general formula (I) is a hydrogen atom, and R ² and R ⁶ are each a linear or branched alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a halogen. . In addition to the above reasons, from the viewpoint of ease of introduction of the acetal structure and stability of the acetal structure, each of R ¹ , R ³ and R ^{5 represented by} the general formula (I) is a hydrogen atom, R ² , Particularly preferred are those wherein each of R ⁴ and R ⁶ is a methyl group.

In the above formula (II), a naphthyl group, if anthra cell group, or a phenanthrenyl group has a substituent, the substituent is not particularly limited, for example, straight-1 to 8 carbon atoms as described above Chain or branched alkyl group or alkoxy group, cycloalkyl group or cycloalkoxy group having 3 to 6 carbon atoms, hydroxyl group, carboxyl group, amino group, halogen, nitro group, thiol group, aldehyde group, cyano group, sulfone Examples include acid groups. One of these may be substituted, or two or more of the same or different substituents may be substituted.
Among the repeating units (A) represented by the general formula (II), the planar structure of the benzene ring is easily arranged in a substantially orthogonal direction due to steric hindrance with an oxygen atom, and therefore, represented by the general formula (II). a is (with i.e. unsubstituted or substituted) may have a substituent and which are preferred 9-anthra cell group.

  The film polymer of the present invention has a repeating unit represented by the general formula (I), a repeating unit represented by the general formula (II), or represented by the general formula (I). And those having both the repeating unit represented by formula (II).

  In order to use the film polymer as a material having a negative intrinsic birefringence value, the repeating unit (A) needs to be contained in an amount of 27 mol% or more, preferably 30 mol% or more, more preferably 33 mol%. It is good to be included. On the other hand, the upper limit is not particularly limited, but it is desirable that the polymer for film of the present invention has other repeating units as described later. Therefore, the repeating unit (A) is preferably 95 mol% or less, and more preferably 90 mol. % Or less is more preferable.

  The polymer having the repeating unit (A) includes a polymer having a main chain that is a straight chain and a part of which has a short branched chain. In the stretched film containing such a polymer, the main chain is oriented in the stretching direction. Therefore, the orientation direction of the polymer can be said to be the same as the stretching direction when uniaxially stretched, and the same direction as the main stretching direction in the case of biaxial stretching.

The polymer having the repeating unit (A) represented by the general formula (I) has two oxygen atoms in the general formula (I) (directly connected to the main chain) oriented in the orientation direction of the main chain by stretching. It will be lined up along. On the other hand, in the aromatic group in the general formula (I), the ortho positions R ² and R ⁶ of the benzene ring are not simultaneously hydrogen atoms, and either one of them is substituted with a substituent such as an alkyl group. The steric hindrance between the substituent and the oxygen atom is increased. As a result, the substituent is coordinated between two oxygen atoms. Therefore, the repeating unit (A) represented by the general formula (I) has two planar structures of the aromatic group (benzene ring). It is considered that they are arranged in a direction substantially perpendicular to a virtual line connecting oxygen atoms.
On the other hand, in the polymer having the repeating unit (A) represented by the general formula (II), two oxygen atoms are arranged along the alignment direction of the main chain depending on the orientation. On the other hand, A in the general formula (II) is an aromatic group in which two or more benzene rings are condensed, and is steric due to the presence of a benzene ring bonded in a condensed form to a benzene ring bonded to —OCO—. And the steric hindrance between the condensed benzene ring and the oxygen atom increases. As a result, the benzene ring present in the condensed form is conformed between two oxygen atoms, and therefore the repeating unit (A) represented by the general formula (II) has two planar structures of aromatic groups. It is considered that they are arranged in a direction substantially perpendicular to a virtual line connecting oxygen atoms.
In addition, it is considered that any aromatic group has a planar structure not strictly arranged at 90 degrees with respect to the orientation direction of the main chain, but is actually about 75 to 105 degrees.

  Thus, the polymer for a film of the present invention contains 27 mol% or more of the repeating unit (A) in which the planar structure of the aromatic group can be arranged in a direction substantially orthogonal to the orientation direction of the main chain as described above. Therefore, since the retardation value (Δnd) in the direction perpendicular to the stretching direction is larger than the retardation value (Δnd) in the stretching direction, the birefringent film formed by stretching the polymer is nx It shows optical characteristics satisfying the relationship <ny. Where Δnd represents an in-plane retardation value.

（一般式（IV）中、Ｒ^８は、水素原子、又は直鎖状、分枝状若しくは環状のアルキル基を示し、アルキル基の炭素原子は隣接しない酸素原子によって置換されていてもよい）。

（一般式（VI）中、Ｂは、アミノ基、チオール基、アルコキシ基、ハロゲン、シアノ基、ニトロ基、エステル基、ケトン基、アルデヒド基、アミド基、ウレタン基、ウレア基、カーボネート基などの置換基を示す）。 Moreover, although the polymer for a film of the present invention has a repeating unit (A), it may further have a repeating unit other than the repeating unit (A). The repeating unit other than the repeating unit (A) is not particularly limited, and examples thereof include a repeating unit represented by the following formula (III), (IV) or (VI).

(In the general formula (IV), R ⁸ represents a hydrogen atom or a linear, branched or cyclic alkyl group, and the carbon atom of the alkyl group may be substituted by an oxygen atom which is not adjacent).

(In general formula (VI), B is an amino group, thiol group, alkoxy group, halogen, cyano group, nitro group, ester group, ketone group, aldehyde group, amide group, urethane group, urea group, carbonate group, etc. Indicates a substituent).

In these, since the solubility with respect to the solvent at the time of film forming becomes favorable, the polymer has a hydroxyl group in the side chain as a repeating unit (B) other than the repeating unit (A), for example, the above What has a unit represented by general formula (III) is preferable.
In addition, the polymer has a group represented by the general formula (IV) as a repeating unit (C) other than the repeating unit (A) because the transparency is improved and the glass transition temperature can be lowered. Is preferred. Among the groups represented by the general formula (IV), R ⁸ is a hydrogen atom, or a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms (the carbon atom of the alkyl group is not an adjacent oxygen atom) In which R ⁸ is a methyl group or an ethyl group is more preferable.

What is necessary is just to adjust suitably the introduction amount of a repeating unit (B) and / or a repeating unit (C) in the range of the residual amount of a repeating unit (A). However, in order to improve the solubility, the repeating unit (B) having a hydroxyl group is preferably contained in an amount of 1 mol% or more, more preferably 2 mol% or more. On the other hand, the upper limit of the repeating unit (B) is appropriately adjusted according to the amount of the repeating unit (A) and the like, preferably 5 mol% or less, and more preferably 4 mol% or less.
Similarly, the introduction amount of the repeating unit (C) is preferably 1 mol% or more and more preferably 2 mol% or more in order to achieve an effect such as improvement of transparency. . On the other hand, the upper limit of the repeating unit (C) is preferably 5 mol% or less, and more preferably 4 mol% or less.
The arrangement of the repeating unit (A) and the repeating unit (B) and / or (C) may be either a block shape or a random shape.
Moreover, as long as the objective of this invention is not inhibited, the said polymer may have a repeating unit of another structure other than a repeating unit (A) and a repeating unit (B) and (C) as needed.

  The polymer for a film of the present invention has a repeating unit (A), and has a repeating unit (B) and a repeating unit (C) as necessary. As described above, the polymer of the present invention includes those of various embodiments selected from the above, and the most preferable one is any one of the following formulas (V), (VII), or (VIII). It has the following structure.

（一般式（V）中、ｌは、２７〜９５モル％、ｍは、１〜５モル％、ｎは、１〜５モル％を示す）。

(In general formula (V), l represents 27 to 95 mol%, m represents 1 to 5 mol%, and n represents 1 to 5 mol%).

（一般式（VII）中、ｌは、２７〜９５モル％、ｍは、１〜５モル％、ｎは、１〜５モル％を示す）。

(In general formula (VII), l represents 27 to 95 mol%, m represents 1 to 5 mol%, and n represents 1 to 5 mol%).

（一般式（VIII）中、ｌは、２７〜９５モル％、ｍは、１〜５モル％、ｎは、１〜５モル％、ｏは、１〜５モル％を示す）。

(In the general formula (VIII), l represents 27 to 95 mol%, m represents 1 to 5 mol%, n represents 1 to 5 mol%, and o represents 1 to 5 mol%).

Next, the manufacturing method of the said polymer is demonstrated.
The production method of the polymer for a film of the present invention is not particularly limited, and can be produced by various production methods.
Among various production methods, the above polymer can be obtained relatively easily. Therefore, polyvinyl alcohol is reacted with a specific aromatic aldehyde or aromatic ketone to introduce acetalization (introduction of RCH (OR) (OR) structure) or It is preferable to produce by carrying out ketalization (introduction of RRC (OR) (OR) structure). As the polyvinyl alcohol, for example, ordinary polyvinyl alcohol used for a film for a retardation plate can be used as appropriate. However, considering its heat resistance, a high saponification degree and a high polymerization degree are preferable. Examples of polyvinyl alcohol that can be suitably used include those having a saponification degree of 95% or more, more preferably 98% or more, and a polymerization degree of 1000 or more, more preferably about 1500 to 3000.

When a specific aromatic aldehyde is reacted with this polyvinyl alcohol, a polymer in which R ^{1 of the} above general formula (I) and R ⁷ of the general formula (II) are hydrogen atoms is obtained, and when a specific aromatic ketone is reacted Since it is introduced, a polymer in which R ¹ and R ⁷ are alkyl groups can be obtained.
For example, when obtaining a chain polymer having the repeating unit (A) represented by the general formula (I), benzaldehyde or acetophenone having a substituent in at least one of the ortho positions is added to polyvinyl alcohol under acidic conditions. What is necessary is just to make it react. Specific examples of benzaldehyde or acetophenone having at least a substituent at one of the ortho positions include 2,4,6-trimethylbenzaldehyde (mesitaldehyde), 2,4,6-triethylbenzaldehyde, 2,6-dimethylbenzaldehyde, Examples include 2-methylbenzaldehyde, 2-methylacetophenone, and 2,4-dimethylacetophenone.
Similarly, when a polymer having the repeating unit (A) represented by the general formula (II) is obtained, a condensed aromatic aldehyde or a condensed aromatic ketone may be reacted with polyvinyl alcohol. Specific examples of the condensed aromatic aldehyde or ketone include 1-naphthaldehyde having a substituent, 2-naphthaldehyde having a substituent, 9-anthraldehyde, 9-anthraldehyde having a substituent, and acetonaphthone. Is done.

  Further, by adjusting the amount of aromatic aldehyde or aromatic ketone to be reacted with polyvinyl alcohol, the hydroxyl group of polyvinyl alcohol is substituted with the aromatic group, and the unsubstituted hydroxyl group remains, so that the repeating unit (A) And a polymer having the repeating unit (B) can be obtained.

  Further, by repeating acetalization of saturated aliphatic aldehyde having 1 to 12 carbon atoms (for example, propionaldehyde, acetaldehyde, etc.) or formaldehyde together with aromatic aldehyde, etc., the repeating unit (A) and the repeating unit are obtained. A polymer having (C) can be obtained. Further, by adjusting the amount of aromatic aldehyde or aromatic ketone to be reacted with polyvinyl alcohol, and the above saturated aliphatic aldehyde or formaldehyde, an unsubstituted hydroxyl group remains, and the repeating units (A) to (C) are changed. The polymer which has can be obtained.

The degree of polymerization of the polymer thus obtained is not particularly limited as long as it can be suitably used as an optical film. From the viewpoint of sufficient film strength to withstand stretching, for example, about 100 to 20000, preferably 500 to Those having a degree of polymerization of about 10,000 are preferable, and can be adjusted by appropriately changing the type and amount of the repeating unit (A).
Moreover, although the glass transition temperature of a polymer changes with kinds and quantity of repeating unit (A)-(C), it is about 80-180 degreeC in the said preferable range, and has sufficient heat resistance as an optical film. Is. Furthermore, for example, unlike a conventional polymer that exhibits a high glass transition temperature exceeding about 200 ° C., it exhibits an appropriate glass transition temperature, so that not only uniaxial stretching but also Z stretching by a conventionally known method is possible. is there.

(About birefringent film)
The birefringent film of the present invention comprises a stretched polymer film obtained by forming and stretching the above polymer for film.
In addition, the term “film” in the present specification is meant to include what is generally called “sheet”.
The birefringent film of the present invention is composed of a single layer film obtained by blending the above polymer for a film with an appropriate additive as required, and forming and stretching the obtained resin composition. The film forming method is not particularly limited, and can be formed into a film by, for example, a casting method, a melt extrusion method, a calendar method, or the like. Especially, since it is excellent in thickness accuracy and an optically homogeneous film can be obtained, it is preferable to shape | mold by the casting method. In the casting method, a solvent is usually used to dissolve the polymer. However, the polymer for a film of the present invention having a hydroxyl group as the repeating unit (B) can be used for a solvent that cannot be used in conventional casting. May also exhibit good solubility. Suitable solvents for the film polymer of the present invention include, for example, tetrahydrofuran, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, cyclopentanone, cyclohexanone, methyl ethyl ketone, ethyl acetate, Examples include dichloromethane and toluene. In addition, when dissolving a polymer, you may heat as needed.

The birefringent film of the present invention can be obtained by stretching the obtained film. There is no particular limitation on such stretching method, for example, a normal uniaxial stretching method such as a denter stretching method, an inter-roll stretching method, an inter-roll compression stretching method, a simultaneous biaxial stretching treatment method using an all tenter method, or a roll tenter method. A normal biaxial stretching method such as a sequential secondary stretching method may be employed. In order to reliably obtain a film having optical characteristics satisfying the relationship of nx <ny, it is preferable to produce the film by uniaxial stretching.
In the present invention, the film can be Z-stretched in biaxial stretching depending on the type (characteristic) of the polymer. In such Z stretching, for example, when the film is stretched by heating, a stretching stress is generated in the thickness direction (Z-axis direction) by shrinking the film in the direction perpendicular to the stretching direction (X-axis direction) (Y-axis direction). It can carry out by the usual Z extending | stretching method.

  Further, when a birefringent film is produced, for example, phthalic acid esters such as dimethyl phthalate, diethyl phthalate, and dibutyl phthalate, trimethyl phosphate, triethyl phosphate, triphenyl in order to improve the stretchability. One or more plasticizers such as fatty acid esters such as phosphate esters such as acid esters, diethyl adipate, and dibutyl fumarate may be added. The amount of the plasticizer added is preferably about 1 to 20 parts by weight with respect to 100 parts by weight of the polymer in consideration of the effect of improving stretchability and the influence on the wavelength dispersion of the obtained retardation plate. In addition to the plasticizer, additives such as an antioxidant and an ultraviolet absorber may be appropriately added depending on the purpose.

Stretching conditions such as temperature and magnification when stretching the film vary depending on the type and amount of the repeating unit (A) of the polymer and the repeating units (B) and (C) introduced as necessary, and therefore are set appropriately. For example, the stretching temperature is preferably about 50 to 200 ° C., and the stretching ratio is preferably about 1.1 to 4.0 times.
The birefringent film thus obtained has excellent transparency, and has a visible light transmittance of about 88 to 93% and a haze of about 0.1 to 3% as measured in accordance with JIS K 7105. Further, the thickness can be made sufficiently small, usually about 20 to 200 μm, and further about 40 to 100 μm.

The birefringent film of the present invention comprises a film obtained by forming and stretching the above polymer, and exhibits optical characteristics satisfying the relationship of nx <ny.
Further, the birefringent film satisfies the relationship of Re (450) / Re (550)> 1.08, preferably Re (450) / Re (550)> 1.10.
As described above, the birefringent film of the present invention has a large wavelength dispersion in the visible light region, and is suitable as a film having a negative intrinsic birefringence value used for a laminated retardation plate described later.

  The birefringent film of the present invention is suitable for use as a laminated retardation plate by laminating an optically anisotropic layer having a positive intrinsic birefringence value, as will be described later. The birefringent film is not limited to the use of the laminated retardation plate, and can be used alone as an optical member.

(About optically anisotropic layer)
The laminated retardation plate of the present invention has the birefringent film and at least one optically anisotropic layer, and the slow axis of the optically anisotropic layer is substantially orthogonal to the slow axis of the refractive film. It consists of a laminated body laminated | stacked so.
The optically anisotropic layer is not particularly limited as long as the intrinsic birefringence value is a positive material, and various polymer materials can be used. Examples include olefin polymers such as polyethylene, polypropylene, norbornene and cycloolefin, polyester polymers such as polyethylene terephthalate and polybutylene terephthalate, polyarylene sulfide polymers such as polyphenylene sulfide, polyvinyl alcohol polymers, polycarbonate polymers, poly Arylate polymers, cellulose ester polymers (though some have negative intrinsic birefringence values), polyether sulfone polymers, polysulfone polymers, polyallyl sulfone polymers, polyvinyl chloride polymers, or their multiples (Binary, ternary, etc.) copolymers and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, olefin polymers are preferable, and among olefin polymers, norbornene is particularly preferable from the viewpoints of light transmittance characteristics, heat resistance, dimensional stability, photoelastic characteristics, and the like.

  Examples of the norbornene-based resin include (1) a ring-opening (co) polymer of a norbornene-based monomer, which is subjected to polymer modification such as maleic acid addition or cyclopentadiene addition as necessary, and then hydrogenated ( 2) Those obtained by addition-type polymerization of norbornene-based monomers, and (3) those obtained by addition-type copolymerization with norbornene-based monomers and olefin monomers such as ethylene and α-olefin. The polymerization method and the hydrogenation method can be performed by conventional methods.

  Examples of the norbornene-based monomer include norbornene and alkyl and / or alkylidene substituted products thereof such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl. 2-Norbornene, 5-ethylidene-2 mononorbornene, etc., polar group-substituted products such as halogens; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, its alkyl and / or alkylidene Substituents and polar group substituents such as halogen, for example, 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, Ethyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydrona Talen, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano- 1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a- Octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8 -Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene and the like; 3-pentamer of cyclopentadiene, for example, 4,9: 5,8-dimethanol 3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4, 1: 5,10: 6,9 Torimetano -3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a- dodecahydro -1H- cyclopentadiene anthracene, and the like.

  The norbornene-based resin has a number average molecular weight (Mn) of 25,000 to 200,000, preferably 30,000 to 100,000, more preferably measured by a gel permeation chromatograph (GPC) method using a toluene solvent. Is in the range of 40,000 to 80,000. When the number average molecular weight is within the above range, a material having excellent mechanical strength, good solubility, moldability, and casting operability can be obtained.

  When the norbornene-based resin is obtained by hydrogenating a ring-opening polymer of a norbornene-based monomer, a hydrogenation rate of 90% or more is usually used from the viewpoint of heat deterioration resistance, light deterioration resistance, and the like. It is done. Preferably it is 95% or more. More preferably, it is 99% or more.

An optically anisotropic layer made of various polymer films such as norbornene-based resin can be obtained by forming a film by a known film forming method and uniaxially stretching it. The stretching method can be performed by a known stretching method exemplified for the birefringent film. The draw ratio is preferably about 1.1 to 4.0 times.
The optically anisotropic layer made of the obtained stretched film has a large refractive index in the stretching direction and satisfies the relationship of nx> ny≈nz.

Moreover, a liquid crystalline compound can also be used as a material which comprises the optically anisotropic layer of this invention.
Such a liquid crystalline compound is not particularly limited as long as it has a positive intrinsic birefringence value, and a conventionally known material can be used. Examples of the liquid crystal compound include a liquid crystal polymer, a liquid crystal monomer, a liquid crystal prepolymer, and the like, and examples thereof include a rod-like liquid crystal compound and a flat liquid crystal compound. These may be used alone or in combination of two or more. Specifically, for example, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines , Phenyldioxanes, tolans, alkenylcyclohexylbenzonitriles, and the like, and polymers thereof. Furthermore, when the liquid crystalline compound is a liquid crystalline monomer, for example, a polymerizable monomer or a crosslinkable monomer is preferable. This is because the alignment state of the liquid crystalline monomer and the like can be fixed by aligning the liquid crystalline compounds as described later and then polymerizing or crosslinking them. The liquid crystalline compound is preferably a liquid crystal material (nematic liquid crystal) in which the liquid crystal phase is a nematic phase. For example, a polymerizable nematic liquid crystal monomer represented by the following general formula (X) is preferably used.

（一般式（X）中、Ａ^１及びＡ^２は、それぞれ重合性基を表し、同一でも異なっていてもよい。また、Ａ^１及びＡ^２のいずれか一方は水素であってもよい。Ｗは、それぞれ単結合、−Ｏ−、−Ｓ−、−Ｃ＝Ｎ−、−Ｏ−ＣＯ−、−ＣＯ−Ｏ−、−Ｏ−ＣＯ−Ｏ−、−ＣＯ−ＮＲ−、−ＮＲ−ＣＯ−、−ＮＲ−、−Ｏ−ＣＯ−ＮＲ−、−ＮＲ−ＣＯ−Ｏ−、−ＣＨ_２−Ｏ−又は−ＮＲ−ＣＯ−ＮＲを示し、前記Ｗに於けるＲは、ＨまたはＣ_１〜Ｃ_４アルキルを示し、Ｍはメソゲン基を示す）。

(In General Formula (X), A ¹ and A ² each represent a polymerizable group, and may be the same or different. ^One of A ¹ and A ² may be hydrogen. W Are each a single bond, —O—, —S—, —C═N—, —O—CO—, —CO—O—, —O—CO—O—, —CO—NR—, —NR—CO, respectively. —, —NR—, —O—CO—NR—, —NR—CO—O—, —CH ₂ —O— or —NR—CO—NR, wherein R in W is H or C _1. -C ₄ represents an alkyl, M represents a mesogenic group).

In the general formula (X), W may be the same or different, but the same one is preferable, and A ² is preferably located in the ortho position with respect to A ¹ .
Furthermore, it is preferable that A ¹ and A ² in the general formula (X) are each independently represented by the following general formula (XI).
General formula (XI): Z-W- (Sp) _n
(In general formula (XI), Z represents a crosslinkable group, W is the same as in the above general formula (X), and Sp is a linear or branched alkyl having 1 to 30 C atoms. And n represents 0 or 1. The carbon chain in the Sp is, for example, oxygen in an ether functional group, sulfur in a thioether functional group, a non-adjacent imino group, or C ₁ -C ₄ . It may be interrupted by an alkylimino group or the like).

A ¹ and A ^{2 in} the general formula (X) are preferably the same group. In addition, Z in the general formula (XI) is preferably any one of atomic groups represented by the following formula (XII). In the formula (XII), examples of R include groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, and t-butyl.

  In the general formula (XI), Sp is preferably any one of atomic groups represented by the following general formula (XIII). In the following general formula (XIII), q is 1 to 3, p Is preferably 1-12.

In the general formula (X), M is preferably represented by the following general formula (XIV). In the general formula (XIV), W is the same as W in the general formula (X). Q represents, for example, a substituted or unsubstituted alkylene or aromatic hydrocarbon group, and may be, for example, a substituted or unsubstituted linear or branched C _{1 to} C ₁₂ alkylene.

  When Q is an aromatic hydrocarbon atomic group, for example, an atomic group represented by the following general formula (XV) or a substituted analog thereof is preferable.

The substituted analog of the aromatic hydrocarbon group represented by the general formula (XV) may have, for example, 1 to 4 substituents per aromatic ring, and the aromatic ring Or you may have 1 or 2 substituents per group. These substituents may be the same or different. Examples of the substituent include C ₁ -C ₄ alkyl, halogen such as nitro, F, Cl, Br, and I, phenyl, C ₁ -C ₄ alkoxy, and the like.

  Specific examples of the liquid crystal monomer described in detail above include, for example, monomers represented by the following structural formula.

  When the liquid crystalline compound contains a liquid crystalline monomer or a liquid crystalline prepolymer, a polymerization agent or a crosslinking agent is added. Although it does not restrict | limit especially as a polymerization agent and a crosslinking agent, For example, the following can be used. As the polymerization agent, for example, benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN) and the like can be used, and as the crosslinking agent, for example, an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, etc. Can be used. These may be either one of them, or two or more of them may be used in combination. Further, as photopolymerization initiators, for example, Irgacure907, Irgacure369, Irgacure184 (all trade names) manufactured by Ciba Specialty Chemicals, and mixtures thereof can be preferably used. The addition amount of the polymerization agent and the crosslinking agent is not particularly limited, and is, for example, in the range of 0.01 to 15% by weight, preferably in the range of 0.03 to 10% by weight, more preferably 1 with respect to the liquid crystal compound. It is in the range of ˜7% by weight.

  The coating liquid can be prepared, for example, by dissolving and dispersing the liquid crystal monomer and the like in an appropriate solvent. The solvent is not particularly limited, but for example, halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene, phenol, p-chloro. Phenols such as phenol, o-chlorophenol, m-cresol, o-cresol, p-cresol, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, acetone, methyl ethyl ketone ( MEK), ketone solvents such as methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone, and ester solvents such as ethyl acetate and butyl acetate. , Alcohol solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, dimethylformamide, Amide solvents such as dimethylacetamide, nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane, carbon disulfide, ethyl cellosolve, butyl cellosolve, etc. it can. Among these, toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl acetate cellosolve are preferable. These solvents may be, for example, one kind or a mixture of two or more kinds.

  Moreover, you may mix | blend various additives with a coating liquid suitably as needed, for example. Examples of the additive include an antioxidant, a modifier, a surfactant, a dye, a pigment, a discoloration inhibitor, and an ultraviolet absorber. Any one of these additives may be added, or two or more of them may be used in combination. Specifically, as the anti-aging agent, for example, phenol compounds, amine compounds, organic sulfur compounds, phosphine compounds, etc., and as the modifier, for example, glycols, silicones, alcohols, etc. Known ones can be used. The surfactant is added, for example, to smooth the surface of the optical film. For example, a surfactant such as silicone, acrylic or fluorine can be used, and silicone is particularly preferable.

  When the liquid crystal monomer is used, the prepared coating liquid exhibits a viscosity excellent in workability such as coating and spreading. The viscosity of the coating liquid usually varies depending on the concentration and temperature of the liquid crystal monomer, but when the monomer concentration in the coating liquid is, for example, 5 to 70% by weight, the viscosity is, for example, 0.2 to 20 mPa · s. The range is preferably 0.5 to 15 mPa · s, and particularly preferably 1 to 10 mPa · s. Specifically, when the monomer concentration in the coating solution is 30% by weight, for example, the range is 2 to 5 mPa · s, and preferably 3 to 4 mPa · s. If the viscosity of the coating liquid is 0.2 mPa · s or more, for example, generation of a liquid flow by running the coating liquid can be further prevented, and if the viscosity is 20 mPa · s or less, for example, the surface Smoothness is further improved, thickness unevenness can be further prevented, and coating properties are also excellent. In addition, as said viscosity, although the range in the temperature of 20-30 degreeC was shown, it is not limited to this temperature.

  The coating solution is applied onto the alignment substrate to form a spread layer. The coating method of the coating liquid is not particularly limited. For example, the coating liquid is fluidized by a conventionally known method such as a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, or a spray coating method. Of these, spin coating and extrusion coating are preferred from the viewpoint of coating efficiency.

The alignment substrate is not particularly limited as long as the liquid crystal monomer can be aligned. For example, substrates obtained by rubbing the surface of various polymer films with rayon cloth or the like can be used. Although it does not restrict | limit especially as said polymer film, For example, polyolefin, such as a triacetyl cellulose (TAC), polyethylene, a polypropylene, poly (4-methyl pentene-1), a polyimide, a polyimide amide, a polyether imide, a polyamide, a polyether Ether ketone, polyether ketone, polyketone sulfide, polyethersulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulose Examples include films made of plastics, epoxy resin, phenol resin, etc. In addition, a polymer film as described above is arranged on the surface of a metal substrate such as aluminum, copper, iron, etc., a ceramic substrate, a glass substrate, etc., or a SiO ₂ oblique deposition film is formed on the surface, etc. Can also be used. Moreover, the laminated body which laminated | stacked the stretched film etc. which gave the extending | stretching process of uniaxial stretching etc. on the polymer film as mentioned above as an oriented film can also be used as an oriented substrate. In addition, when the substrate itself has birefringence, the rubbing treatment as described above or the lamination of a birefringent film on the surface can be omitted. As a method for imparting birefringence to the substrate itself as described above, for example, in the formation of the substrate, there is a method of performing casting, extrusion molding, or the like in addition to the stretching treatment.

Subsequently, the liquid crystal monomer is aligned in a liquid crystal state by subjecting the spread layer to a heat treatment.
The temperature condition of the heat treatment can be appropriately determined according to, for example, the type of liquid crystal monomer, specifically the temperature at which the liquid crystal monomer exhibits liquid crystallinity, but is usually in the range of 40 to 120 ° C., preferably 50 to It is in the range of 100 ° C, more preferably in the range of 60 to 90 ° C. If the temperature is 40 ° C. or higher, the liquid crystal monomer can usually be sufficiently aligned. If the temperature is 120 ° C. or lower, for example, selection of various alignment substrates as described above in terms of heat resistance is possible. The nature is also wide.

Next, the development layer in which the liquid crystal monomer is aligned is subjected to a crosslinking treatment or a polymerization treatment, whereby the liquid crystal monomer is fixed while being aligned along the alignment substrate. The liquid crystal compound becomes a non-liquid crystal polymer by fixing the alignment state.
The polymerization treatment and the crosslinking treatment can be appropriately determined depending on, for example, the type of the polymerization agent and the crosslinking agent used. For example, when a photopolymerization agent or a photocrosslinking agent is used, light irradiation is performed, and when an ultraviolet polymerization agent or an ultraviolet crosslinking agent is used, ultraviolet irradiation is performed.

  For example, when the liquid crystal monomer represented by the general formula (X) is used, the optically anisotropic layer composed of such a non-liquid crystal polymer film has a large refractive index in the alignment direction of the liquid crystalline compound, and the optical axis is in-plane. It shows uniaxial optical anisotropy existing in the direction, and satisfies the relational expression nx> ny≈nz.

(About laminated phase difference plate)
In the laminated retardation plate of the present invention, the birefringent film and the optically anisotropic layer are laminated so that the slow axis of the birefringent film and the slow axis of the optically anisotropic layer are substantially orthogonal to each other. It consists of a laminated body.
That is, the laminated retardation plate is constructed by laminating the birefringent film and the optically anisotropic layer so that the stretching direction (or the molecular orientation direction) is substantially parallel. .
Such a laminated phase difference plate is formed by laminating the optically anisotropic layer having a positive intrinsic birefringence value and the birefringent film having a negative intrinsic birefringence value, and therefore has a visible light region of at least 400 to 650 nm. It shows a predetermined phase difference (for example, λ / 4, λ / 2, etc.) with respect to light of all wavelengths λ.

The method for laminating both is not particularly limited, and can be performed by a known method.
For example, as described above, when an optically anisotropic layer formed into a film is used, it is laminated by adhering this to a birefringent film with a known adhesive or pressure-sensitive adhesive. A phase difference plate can be manufactured.

  The adhesive or pressure-sensitive adhesive is not particularly limited, and conventionally known ones such as transparent pressure-sensitive adhesives and pressure-sensitive adhesives such as acrylic, silicone, polyester, polyurethane, polyether, and rubber are known. Can be used. Among these, those that do not require a high-temperature process during curing and drying are preferable from the viewpoint of preventing changes in the optical properties of the laminated retardation plate, and specifically, a long curing process and drying time are required. Acrylic adhesives that do not work are preferred.

In addition, the lamination method is not limited to adhesion. For example, by applying a coating liquid containing the above liquid crystalline compound on a birefringent film and fixing the orientation of the liquid crystalline compound, the intrinsic birefringent film is coated. An optically anisotropic layer having a positive refractive value can also be laminated. With such a laminating method, an adhesive or pressure-sensitive adhesive application step is not necessary, and further, since an adhesive layer or a pressure-sensitive adhesive layer is not necessary, the number of layers can be reduced to realize further thinning.
The preparation, coating method, immobilization method and the like of the liquid crystalline compound constituting the optically anisotropic layer may be appropriately performed according to the method described in the section of the optically anisotropic layer.

Further, when using the above thermoplastic resin such as norbornene-based resin as an optically anisotropic layer having a positive intrinsic birefringence value, a laminated film is obtained by co-extrusion of the thermoplastic resin and the film polymer of the present invention, By subjecting this to a uniaxial stretching treatment, a laminated retardation plate can also be produced. With such a lamination method, the adhesive layer or the pressure-sensitive adhesive layer is unnecessary, and further, the layer containing the thermoplastic resin has a positive intrinsic birefringence value by stretching in the laminated state, and the film polymer. The intrinsic birefringence value of the layer containing is negative, and the laminated retardation plate can be produced by a single stretching process.
The co-extrusion and stretching methods can be appropriately performed according to the method described in JP-A No. 2002-156525 exemplified as a known document.

In the laminated retardation plate of the present invention, the birefringent film having a negative intrinsic birefringence value is laminated with one layer, and the optically anisotropic layer having a positive intrinsic birefringence value is laminated with two layers. Although the thing of the layer structure was illustrated, the lamination | stacking phase difference plate of this invention is not limited to this.
For example, by laminating one layer of the birefringent film having a negative intrinsic birefringence value and two or more optically anisotropic layers having the same or different intrinsic birefringence values, the laminated retardation of the present invention A plate may be configured. Further, by laminating two or more layers of the birefringent film having a negative intrinsic birefringence value and one or more layers of the optically anisotropic layer having a positive intrinsic birefringence value, the laminated retardation plate of the present invention can be obtained. It may be configured. Further, the birefringent film having a negative intrinsic birefringence value is one or more layers, the birefringent layer made of another optical material having a negative intrinsic birefringence value is one or more layers, and the intrinsic birefringence value is positive. The laminated phase difference plate of the present invention may be constituted by laminating one or more optically anisotropic layers.

(About optical film and image display device)
The birefringent film and laminated retardation plate of the present invention can be used in the form of an optical film by laminating with other optical materials. For example, it can utilize as optical films, such as an elliptically polarizing plate and a circularly-polarizing plate, by laminating | stacking the laminated phase difference plate or birefringent film of this invention on a polarizing plate. Further, the laminated retardation plate or birefringent film of the present invention in which the retardation is adjusted to λ / 4 and the retardation plate in which the retardation is adjusted to λ / 2 are laminated on a polarizing plate to form an optical film. It can also be configured. The laminated phase difference plate or birefringent film of the present invention may be laminated directly on the polarizer of the polarizing plate, or may be laminated via a protective film. An adhesive layer for adhering to other members such as a liquid crystal cell can also be provided. In addition, when an adhesion layer is exposed on the surface, it is preferable to cover with a release paper. In addition, the laminated retardation plate or birefringent film of the present invention, such as an optical film laminated in the order of polarizing plate / laminated retardation plate / bandpass filter of the present invention, and an optical film with a protective film attached to the surface. Can be used in the form of various optical films by laminating with optical materials having different functions.

  Moreover, the birefringent film, the laminated phase difference plate, and the optical film of the present invention can be preferably used as components for various image display devices such as a liquid crystal display device. For example, the liquid crystal display device can have an appropriate structure according to the prior art, such as a transmissive type, a reflective type, or a transmissive / reflective type in which the optical film or the like is disposed on one or both sides of a liquid crystal cell. Therefore, the liquid crystal cell forming the liquid crystal display device is arbitrary, and for example, a liquid crystal cell of an appropriate type such as a simple matrix driving type typified by a thin film transistor type may be used. Moreover, when providing the optical film of this invention in the both sides of a liquid crystal cell, they may be the same and may differ. Furthermore, when forming the liquid crystal display device, for example, appropriate components such as a prism array sheet, a lens array sheet, a diffusion plate, and a backlight can be arranged in one or more layers at appropriate positions.

Next, the retardation plate of the present invention will be described in more detail based on the following examples, but the present invention is not limited to only these examples.
The measurement conditions for each characteristic are as follows.

(Measurement of composition ratio)
¹ H-NMR (heavy DMSO solvent) 0.83 ppm, 0.95-2.0 ppm, 3.5-
It calculated | required from the peak of 5.0 ppm and 6.76 ppm.
(Measurement of in-plane retardation)
Measurement was performed using “KOBRA21-ADH” manufactured by Oji Scientific Instruments.
(Measurement of thickness)
It measured using the micrometer (product made from MITUTOYO).

Production Example 1
4.4 g of PVA having a degree of polymerization of 1800 (Nippon Synthetic Chemical, NH-18) dried at 105 ° C. for 2 hours was dissolved in 257 ml of DMSO. Mesitaldehyde 4.45g, propionaldehyde 1.16g, and p-toluenesulfonic acid monohydrate 1.56g were added here, and it stirred at 40 degreeC for 4 hours. Next, reprecipitation was performed in water in which 2.30 g of sodium bicarbonate was dissolved. The polymer obtained by filtration was dissolved in DMF and reprecipitated in methanol. After filtering and drying, 4.94 g of a white polymer was obtained. The molar ratio of the vinyl mecital, vinyl propional, and vinyl alcohol portions of this polymer was 30:21:49.

Production Example 2
The reaction was carried out in the same manner as in Production Example 1 except that propionaldehyde was not used in Production Example 1 but 3.71 g of mesitaldehyde and 84 g of DMSO were used. After purification 5.95 g of white polymer was obtained. The molar ratio of vinyl mesital and vinyl alcohol in this polymer was 28:72.

Example 1
The polymer obtained in Production Example 1 was dissolved in DMF and formed into a film using an applicator. The film obtained by drying was stretched 1.5 times at 146 ° C. using a stretching machine to obtain a uniaxially stretched film having a thickness of 58 μm. When the in-plane retardation of the obtained stretched film was measured, they were Re (450) = − 191.2 nm, Re (550) = − 162.1 nm, and Re (650) = − 125.0 nm.
Therefore, Re (450) / Re (550) ≈1.18, and this film had a negative intrinsic birefringence value and a large wavelength dispersion.

Example 2
The polymer obtained in Production Example 1 was dissolved in DMF and formed into a film using an applicator. The film obtained by drying was stretched 2.0 times at 150 ° C. using a stretching machine to obtain a uniaxially stretched film having a thickness of 88 μm. When the in-plane retardation of the obtained stretched film was measured, Re (450) = − 329.9 nm, Re (550) = − 273.6 nm, and Re (650) = − 256.0 nm.
Therefore, Re (450) / Re (550) ≈1.21, and this film had a negative intrinsic birefringence value and a large wavelength dispersion.

Example 3
The polymer obtained in Production Example 2 was dissolved in DMF and formed into a film using an applicator. The film obtained by drying was stretched 2.0 times at 118 ° C. using a stretching machine to obtain a uniaxially stretched film having a thickness of 102 μm. When the in-plane retardation of the obtained stretched film was measured, they were Re (450) = − 437.6 nm, Re (550) = − 389.1 nm, and Re (650) = − 363.9 nm.
Therefore, Re (450) / Re (550) ≈1.12, and this film had a negative intrinsic birefringence value and a large wavelength dispersion.

Comparative production example 1
The reaction was carried out in the same manner as in Production Example 1 except that 2.97 g of mecitaldehyde and 1.74 g of propionaldehyde were used in Production Example 1. After purification, 5.31 g of white polymer was obtained. The molar ratio of vinyl mesital, vinyl propional, and vinyl alcohol in this polymer was 19:30:51.

Comparative production example 2
The reaction was performed in the same manner as in Production Example 1 except that 15.9 g of benzaldehyde and 66 g of DMSO were used without using mecitaldehyde and propionaldehyde in Production Example 1. Next, reprecipitation was performed in water / methanol = 1/2 in which 2.30 g of sodium bicarbonate was dissolved, and after filtration and drying, 5.42 g of a white polymer was obtained. The molar ratio of each site of vinyl benzal and vinyl alcohol in this polymer was 61:39.

Comparative Example 1
The polymer obtained in Comparative Production Example 1 was dissolved in DMF and formed into a film using an applicator. The film obtained by drying was stretched 1.5 times at 120 ° C. using a stretching machine to obtain a uniaxially stretched film having a thickness of 37 μm. When the in-plane retardation of the obtained stretched film was measured, Re (450) = 11 nm, Re (550) = 260 nm, Re (650) = 34 nm, and the intrinsic birefringence value was not a negative film. It was.

Comparative Example 2
The polymer obtained in Comparative Production Example 2 was dissolved in THF and formed into a film using an applicator. The film obtained by drying was stretched 1.5 times at 130 ° C. using a stretching machine to obtain a uniaxially stretched film having a thickness of 34 μm. When the in-plane retardation of the obtained stretched film was measured, Re (450) = 93 nm, Re (650) = 95 nm, Re (650) = 95 nm, and the intrinsic birefringence value was not a negative film. It was.

Example 4
A coating liquid was prepared by dissolving 10 g of a polymerizable liquid crystal monomer shown below and 3 g of a photopolymerization initiator (Irgacure907, manufactured by Ciba Specialty Chemicals) in 40 g of toluene. On the uniaxially stretched PET film, this coating solution was applied by a bar coating method to form a thin film. The thin film was heated to 90 ° C. and allowed to cool to room temperature to form a horizontally oriented nematic monodomain phase. Furthermore, 600 mJ / cm < ² > of ultraviolet rays were irradiated and photopolymerization was performed, the orientation state was fixed, and an optically anisotropic layer (thickness 3 [mu] m) was formed. When the in-plane retardation of this optically anisotropic layer was measured, Re (450) = 446.0 nm, Re (550) = 411.1 nm, Re (650) = 402.8 nm, and the intrinsic birefringence value was It was positive.

The optically anisotropic layer and the stretched film were combined with an acrylic pressure-sensitive adhesive (Nitto Denko) so that the alignment axis of the liquid crystal of the optically anisotropic layer and the stretched axis of the stretched film obtained in Example 2 were parallel. Layered).
When the in-plane retardation of the obtained laminated retardation plate was measured, Re (450) = 16.5 nm, Re (550) = 137.8 nm, Re (650) = 147.0 nm, and a wavelength range of 450 to 650 nm. And showed good λ / 4 plate characteristics.

Example 5
A norbornene-based film (manufactured by JSR, trade name: arton) was stretched 1.5 times at 180 ° C. to obtain a uniaxially oriented film having a thickness of 96 μm. When the in-plane retardation of this film was measured, Re (450) = 309.6 nm, Re (550) = 300.8 nm, Re (650) = 296.3 nm, and the intrinsic birefringence value was positive. .
Both films were laminated via an acrylic pressure-sensitive adhesive (same as above) so that the stretching axis of the uniaxially stretched film was parallel to the stretching axis of the stretched film obtained in Example 1.
When the in-plane retardation of the obtained laminated retardation plate was measured, Re (450) = 18.7 nm, Re (550) = 138.9 nm, Re (650) = 151.1 nm, and a wavelength range of 450 to 650 nm. And showed good λ / 4 plate characteristics.

Comparative Example 3
A polystyrene film (Okura Industrial Co., Ltd., Cellomer M) was stretched twice at 130 ° C. to obtain a stretched polystyrene film.
The polystyrene film and the optically anisotropic layer of Example 4 were laminated so that the stretching axis of this stretched polystyrene film and the alignment axis of the liquid crystal of the optically anisotropic layer of Example 4 were parallel. When the in-plane retardation of the obtained laminated retardation plate was measured, Re (450) = 149.4 nm, Re (550) = 140.1 nm, Re (650) = 133.8 nm, and the retardation was a wavelength. Depending on the above, a satisfactory λ / 4 plate could not be obtained.

Claims (10)

A stretched polymer film, wherein the polymer is represented by at least one of the structures represented by the following general formula (I) or general formula (II) as the repeating unit (A) and the following formula (III): The repeating unit (B) and the repeating unit (C) represented by the following general formula (IV) are included, the repeating unit (A) is 27 mol% to 95 mol%, and the repeating unit (B) is A birefringent film comprising 1 mol% to 5 mol% and 1 mol% to 5 mol% of a repeating unit (C) .

(In general formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ² and R ⁶ are each independently a hydrogen atom, a linear or branched group having 1 to 4 carbon atoms. Branched alkyl group, linear or branched alkoxy group having 1 to 4 carbon atoms, linear or branched thioalkoxy group having 1 to 4 carbon atoms, halogen, nitro group, amino group, hydroxyl group Or R ² and R ⁶ are not hydrogen atoms at the same time, and R ^{3 to} R ⁵ each independently represents a hydrogen atom or a substituent.

(In General Formula (II), R ⁷ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. A may have a naphthyl group or a substituent which may have a substituent. anthra cell group, or may have a substituent represents an phenanthrenyl group. naphthyl group, one or more of the carbon atoms of the carbon atoms constituting the anthra cell group, or phenanthrenyl groups substituted with a nitrogen atom May be)

(In the general formula (IV), R ⁸ represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, and the carbon atom of the alkyl group is substituted by an oxygen atom which is not adjacent to the alkyl group. The arrangement of the repeating units (A) to (C) may be either a block shape or a random shape.   2. The birefringent film according to claim 1, wherein the refractive index nx in the in-plane stretching direction and the refractive index ny in the direction perpendicular to the in-plane stretching direction satisfy a relationship of nx <ny.   The relationship between the in-plane retardation Re (450) in light having a wavelength of 450 nm and the in-plane retardation Re (550) in light having a wavelength of 550 nm is Re (450) / Re (550)> 1.08. The birefringent film according to claim 1 or 2, wherein: The birefringent film according to any one of claims 1 to 3, wherein the polymer is a polymer having a structure represented by the following general formula (V).

(In general formula (V), l represents 27 mol% to 95 mol%, m represents 1 mol% to 5 mol%, and n represents 1 mol% to 5 mol%).   A laminated phase difference plate in which the birefringent film according to any one of claims 1 to 4 and at least one optically anisotropic layer are laminated, wherein the slow axis of the birefringent film and the optical The laminated phase difference plate, wherein the birefringent film and the optically anisotropic layer are laminated so that the slow axis of the anisotropic layer is substantially orthogonal.   A laminated phase difference plate in which the birefringent film according to any one of claims 1 to 4 and at least one optically anisotropic layer are laminated, and an in-plane retardation at a wavelength of at least 450 nm to 650 nm. A laminated phase difference plate characterized in that is smaller on the short wavelength side and larger on the long wavelength side.   The laminated phase difference plate according to claim 5 or 6, wherein the optically anisotropic layer includes a film formed by fixing the orientation of a liquid crystal compound.   The laminated phase difference plate according to claim 5 or 6, wherein the optically anisotropic layer comprises a stretched film of norbornene resin.   An optical film having the birefringent film according to any one of claims 1 to 4 or the laminated retardation plate according to any one of claims 5 to 8.   The image display apparatus which has a birefringent film in any one of Claims 1-4, the laminated phase difference plate in any one of Claims 5-8, or the optical film of Claim 9.