JP4433468B2 - Retardation plate, optical film, and image display device - Google Patents

Description

  The present invention relates to a retardation plate, an optical film using the retardation plate, and an image display device.

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 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 function as λ / 4 plates or λ / 2 plates for light of a specific wavelength, but do not function as λ / 4 plates or λ / 2 plates for light of different wavelengths. For example, a retardation plate designed to function as a λ / 4 plate for light having a wavelength of 550 nm does not function as a λ / 4 plate for light having a wavelength of 450 nm or 650 nm. Thus, the retardation plate exhibits wavelength dispersion whose retardation depends on the wavelength. For example, it is generally known that the wavelength dispersion in a polymer film is larger on the short wavelength side and smaller on the long wavelength side. ing.
When white light, which is a composite wave in which light in the visible light region is mixed, is incident on a retardation plate that exhibits such wavelength dispersion, the shape of polarization at each wavelength is caused by wavelength dispersion. The distribution of polarization states is greatly different. As a result, there is a big problem that incident white light is converted into colored light.
In order to cope with such a problem, Japanese Patent Application Laid-Open No. 10-239518 discloses two or more types of birefringent media having different wavelength dispersion values α (α = Δn (450 nm) / Δn (650 nm)) with their slow axes orthogonal to each other. In this state, a retardation plate having a chromatic dispersion value α smaller than 1 has been proposed. According to the retardation plate described in the publication, it is stated that the optical retardation at all wavelengths in the visible light range is uniform regardless of the light wavelength, and that white light can be easily obtained. .
However, since the retardation plate described in the above publication is composed of a laminate in which two or more types of birefringent media are laminated, a lamination adhesion process is necessary, and selection of an adhesive or selection of two or more types of materials can be performed. It must be made. Furthermore, a retardation plate made of a laminate is relatively thick and cannot be said to be suitable for applications such as a liquid crystal display device that is desired to be thinner.

Japanese Patent Laid-Open No. 10-239518

  Therefore, the present invention can be made relatively thin and has a phase difference of, for example, approximately λ / 2 or approximately λ / 4 with respect to light rays having a wavelength λ in the entire visible light region having a wavelength of 400 to 700 nm. It is an object of the present invention to provide a retardation plate, an optical film, and an image display device that exhibit dispersibility.

（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、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）。 As a result of diligent research on various materials under the above problems, it was found that the above problems can be solved by using a chain polymer in which a specific side chain is introduced into the main chain and another polymer. This means is provided.
That is, the first means of the present invention is a birefringent chain polymer (1) having at least one of the structures represented by the general formula (I) or the general formula (II) as the repeating unit (A). And a single layer film in which a polymer material containing the polymer (2) different from the chain polymer (1) is oriented, and the in- plane position of the single layer film at a wavelength of at least 450 to 650 nm. A retardation plate having a smaller retardation value on the shorter wavelength side and larger on the longer wavelength side 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. A branched alkyl group, a linear or branched alkoxy group having 1 to 4 carbon atoms, a linear or branched thioalkoxy group having 1 to 4 carbon atoms, a halogen, a nitro group, an amino group , or Represents a thiol group (provided that R ² and R ⁶ are not simultaneously a hydrogen atom) R ^{3 to} R ⁵ each independently represent 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. An anthracenyl group, or an optionally substituted phenanthrenyl group, wherein one or more carbon atoms constituting a naphthyl group, anthracenyl group, or phenanthrenyl group may be substituted with a nitrogen atom) .

Furthermore, in a preferred embodiment of the present invention, there is provided a retardation plate comprising a single layer film that can be obtained by forming and stretching a polymer material obtained by mixing the chain polymer (1) and the polymer (2). To do .
Also, in a preferred embodiment of the present invention, the polymer (2) is polyvinyl acetal, or, providing the retardation plate is a polynorbornene.

（繰り返し単位（Ａ）及び（Ｂ）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）。 Further, in a preferred embodiment of the present invention, the above retardation plate is a polymer in which the chain polymer (1) further has a repeating unit (B) represented by the general formula (III) in addition to the repeating unit (A). provide.

(The arrangement of the repeating units (A) and (B) may be either block or random).

（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）。 Furthermore, in a preferred embodiment of the present invention, the chain polymer (1) is a polymer having a repeating unit (C) represented by the general formula (IV) in addition to the repeating units (A) and (B). A phase difference plate is provided.

(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.

（一般式（V）中、ｌは、５〜３０モル％、ｍは、２０〜８０モル％、ｎは、１〜７０モル％を示す）。 In a preferred embodiment of the present invention, there is provided the above retardation plate, wherein the chain polymer (1) is a polymer having a structure represented by the general formula (V).

(In general formula (V), l represents 5 to 30 mol%, m represents 20 to 80 mol%, and n represents 1 to 70 mol%).

Moreover, the 2nd means of this invention provides the optical film which laminated | stacked the said phase difference plate.
Furthermore, a third means of the present invention provides an image display device comprising the retardation plate or the optical film.

Since the retardation plate of the present invention can be composed of a single layer film, the thickness can be reduced as compared with the conventional one. Furthermore, the phase difference plate of the present invention has a phase difference of, for example, about λ / 2 or about λ / 4 with respect to light of almost all wavelengths λ in the visible light region of 400 to 700 nm, and polarization of each wavelength is changed. The shape is almost the same. Therefore, the phase difference plate of the present invention can obtain colorless polarized light without being converted into colored polarized light when white light is incident.
Moreover, the phase difference plate of this invention is excellent in transparency by the preferable aspect, and has effects, such as heat resistance and the solvent solubility at the time of manufacture.

The inventors of the present invention provide a single-layer film obtained by orienting a polymer material containing a birefringent chain polymer (1) having a specific repeating unit (A) and a polymer (2) different therefrom. By finding that the in-plane retardation in the visible light region of at least a wavelength of 450 to 650 nm becomes smaller as the wavelength is shorter, the present invention makes it possible to reduce the thickness and reduce the wavelength from 400 to 400 by exclusively utilizing the properties of this film. The present invention provides a retardation plate that exhibits a predetermined retardation over substantially the entire visible light region of 700 nm.
The present invention will be specifically described below. In the present specification, the property of the retardation plate of the present invention in which the in-plane retardation in the visible light region becomes smaller as the wavelength is shorter is sometimes referred to as “reverse wavelength dispersion characteristic”.

（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）。 The chain polymer (1) used in the present invention has at least one of the structures represented by the following general formula (I) or general formula (II) as the repeating unit (A).

(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. An anthracenyl group, or an optionally substituted phenanthrenyl group, wherein one or more carbon atoms constituting a naphthyl group, anthracenyl group, or phenanthrenyl group may be substituted with a nitrogen atom) .

  The chain polymer (1) in the present invention includes a polymer in which the main chain is a straight chain and has a short branched chain in part. Also, the orientation of the polymer is generally brought about by stretching the film. Therefore, it can be said that the orientation direction of the chain polymer (1) is the same as the stretching direction in the case of uniaxial stretching, and the same direction as the main stretching direction in the case of biaxial stretching.

The chain polymer (1) having the repeating unit (A) represented by the general formula (I) is oriented in the general formula (I) (directly connected to the main chain) when oriented. Two oxygen atoms are arranged along the alignment direction of the main chain. 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 a virtual structure in which the planar structure of the benzene ring connects two oxygen atoms. It is considered that they are arranged in a direction substantially perpendicular to the line.
On the other hand, in the chain polymer (1) having the repeating unit (A) represented by the general formula (II), two oxygen atoms are aligned along the alignment direction of the main chain due to 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.
Then, when the planar structure of the aromatic group is directed in the direction substantially orthogonal to the orientation direction of the main chain, the repeating unit (A) acts as a negative large dispersion component, and thus this chain polymer (1 ) Is oriented such that the in-plane retardation is smaller on the shorter wavelength side and larger on the longer wavelength side in the visible light region.

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 substituent etc. which were illustrated by the following 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. Moreover, in R ¹ is a hydrogen atom of the general formula (I), a linear or branched alkyl group R ² and R ⁶ are both 1 to 4 carbon atoms, an alkoxy group, or those which are halogen are preferred . 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 general formula (II), when the naphthyl group, anthracenyl group, or phenanthrenyl group has a substituent, the substituent is not particularly limited. For example, the straight chain having 1 to 8 carbon atoms as described above 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, sulfonic acid group These may be exemplified, and these may be substituted by one, or may be substituted by two or more of the same or different substituents.
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). It is preferable that A is a 9- anthracenyl group which may have a substituent (that is, is unsubstituted or has a substituent).

  The chain polymer (1) of the present invention has a repeating unit represented by the general formula (I), a repeating unit represented by the general formula (II), or a general formula (I). And those having both the repeating unit represented by formula (II) and the repeating unit represented by formula (II) are included.

  The repeating unit (A) is preferably contained in an amount of 1 mol% or more, more preferably 5 mol% or more from the viewpoint of ensuring that the retardation plate exhibits reverse wavelength dispersion characteristics. Moreover, from the point of utilizing as a phase difference plate which has positive birefringence anisotropy, 50 mol% or less is preferable and it is more preferable that it is 30 mol% or less.

（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）。 The chain polymer (1) of the present invention has a repeating unit (A), but 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).

Among these, the chain polymer (1) used as the retardation plate of the present invention has improved reverse wavelength dispersion characteristics and improved solubility in a solvent during film formation. As the repeating unit (B) other than A), those having a hydroxyl group in the side chain, for example, those having a unit represented by the general formula (III) are 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 as represented by the following formula (VII) is more preferable.

The introduction amount of the repeating unit (B) and / or the repeating unit (C) may be appropriately adjusted within the range of the remaining amount of the repeating unit (A) in view of the properties of the target retardation plate. However, in order to obtain a more preferable reverse wavelength dispersion characteristic and to improve the solubility, the repeating unit (B) having a hydroxyl group is preferably 1 mol% or more, more preferably 5 mol% or more, and further preferably 20 mol% or more. More preferably it is included. On the other hand, the upper limit is appropriately adjusted according to the amount of the repeating unit (A) and the like, and is preferably 95 mol% or less, more preferably 80 mol% or less, and further preferably about 70 mol% or less.
Similarly, the introduction amount of the repeating unit (C) is preferably 1 mol% or more, more preferably 5 mol% or more, and more preferably 20 mol% or more in order to improve the transparency. On the other hand, the upper limit is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably about 50 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 chain polymer used as the retardation plate 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 chain polymer (1) used in the retardation plate of the present invention includes various embodiments selected from the above, and the most preferable one is the following formula (V) or formula It has any structure of (VIII).

（一般式（V）中、ｌは、５〜３０モル％、ｍは、２０〜８０モル％、ｎは、１〜７０モル％を示す）。

(In general formula (V), l represents 5 to 30 mol%, m represents 20 to 80 mol%, and n represents 1 to 70 mol%).

（一般式（VIII）中、ｌは、５〜３０モル％、ｍは、２０〜８０モル％、ｎは、１〜７０モル％を示す）。

(In general formula (VIII), l represents 5 to 30 mol%, m represents 20 to 80 mol%, and n represents 1 to 70 mol%).

  Next, the polymer (2) is not particularly limited as long as it is compatible with the polymer (1) and exhibits positive birefringence anisotropy (a property in which the refractive index in the stretching direction is maximized). , For example, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl acetal, poly (meth) acrylate, polyolefin, polyether ketone, polyether, polyester polycarbonate, polyamide, polyimide, polysulfone, polyarylate, Examples thereof include at least one selected from polysulfide, polynorbornene, polyacetal, cellulose ester and the like. In these, it is preferable to use polyvinyl acetals, such as polyvinyl butyral.

  As described above, since the retardation plate of the present invention is composed of a single layer film, the thickness can be reduced as compared with a conventional laminated retardation plate. Furthermore, the retardation plate of the present invention can be used with an in-plane retardation of approximately λ / 2 or λ / 4 for light of almost all wavelengths λ in the visible light region of 400 to 700 nm. Therefore, the phase difference plate of the present invention has substantially the same shape of polarized light at each wavelength. For example, when white light is incident, it is not converted into colored polarized light, and colorless polarized light can be obtained. In addition, the retardation plate of the present invention is excellent in transparency, has good solubility during film formation, has a glass transition temperature in a suitable range, has improved heat resistance, and can be stretched in Z. The effect of.

Next, the manufacturing method of the said chain polymer (1) is demonstrated.
The production method of the chain polymer (1) used for the retardation plate of the present invention is not particularly limited, and can be produced by various production methods.
Among various production methods, since the chain polymer (1) can be obtained relatively easily, a specific aromatic aldehyde or aromatic ketone is reacted with polyvinyl alcohol to form an acetal (RCH (OR) (OR) It is preferable to manufacture by carrying out (introduction of structure) or 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 chain polymer (1) in which R ¹ and R ⁷ are alkyl groups is obtained.
For example, in the case of obtaining the chain polymer (1) having the repeating unit (A) represented by the general formula (I), benzaldehyde having the substituent in at least one of the ortho positions or the same is added to polyvinyl alcohol under acidic conditions. What is necessary is just to make acetophenone etc. 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 chain polymer (1) having the repeating unit (B) can be obtained.

  Further, by repeating acetalization of a saturated aliphatic aldehyde having 1 to 12 carbon atoms (for example, propionaldehyde or acetaldehyde) or formaldehyde together with an aromatic aldehyde and the like, the repeating unit (A) and the repeating unit ( A chain polymer (1) having C) can be obtained. Furthermore, 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 has repeating units (A) to (C). A chain polymer (1) can be obtained.

The degree of polymerization of the chain polymer (1) thus obtained is not particularly limited as long as it can be suitably used as a retardation plate. From the viewpoint of sufficient film strength to withstand stretching, for example, about 100 to 20000, Preferably, those having a degree of polymerization of about 500 to 10,000 are preferable and can be adjusted by appropriately changing the type and amount of the repeating unit (A).
Further, the glass transition temperature of the chain polymer (1) varies depending on the types and amounts of the repeating units (A) to (C), but is, for example, about 80 to 180 ° C. within the above preferable range, and is sufficient as a retardation plate It has heat resistance. 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.

Next, a method for producing a retardation plate by forming a chain polymer (1) and a polymer (2) on a film will be described. In addition, the term “film” in the present specification is meant to include what is generally called “sheet”.
The retardation plate of the present invention is composed of a single-layer film obtained by forming a polymer material containing the chain polymer (1) and the polymer (2), and the film forming method is not particularly limited. The film can be formed by 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 chain polymer (1) of the present invention having a hydroxyl group as the repeating unit (B) can be used for casting a conventional retardation plate. There may be cases where good solubility is exhibited even in solvents that could not be formed. Suitable solvents for the polymer material 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 the said polymeric material, you may heat as needed.

The retardation 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.
Moreover, in this invention, according to the kind (characteristic) of both polymers (1) and (2) to mix, the film can also be Z-stretched in biaxial stretching. Such Z stretching also involves stretching stress in the thickness direction (Z-axis direction) by shrinking the film in a direction (Y-axis direction) perpendicular to or intersecting the stretching direction (X-axis direction) when the film is stretched by heating, for example. It can be performed by a normal Z stretching method such as a method of generating.

  In the film, for the purpose of improving stretchability, phosphoric acid such as phthalic acid ester such as dimethyl phthalate, diethyl phthalate and dibutyl phthalate, trimethyl phosphoric acid ester, triethyl phosphoric acid ester and triphenyl phosphoric acid ester is used. One or more plasticizers such as fatty acids such as 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 for stretching the film are the types and amounts of the repeating unit (A) of the chain polymer (1) and the repeating units (B) and (C) introduced as necessary, and Since it differs depending on the kind of the polymer (2) to be mixed, it is appropriately set. 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 retardation plate of the present invention 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 is usually sufficiently small, such as about 20 to 200 μm, and further about 40 to 100 μm.

  The retardation plate of the present invention is composed of a single layer film of a polymer material obtained by mixing the chain polymer (1) and the polymer (2), and exhibits reverse wavelength dispersion characteristics. Such a retardation plate itself has a wavelength dispersion of approximately λ / 2 or approximately λ / 4 with respect to almost all wavelengths λ of light in the entire visible light region. Conversion to is possible. The phase difference plate of the present invention has reverse wavelength dispersion characteristics, but the wavelength dispersion of the phase difference plate of the present invention measured under the conditions described later indicates the chain polymer (1) or polymer (2) constituting the polymer material. ), The relationship of Re (450) / Re (550) ≦ 0.97 and Re (650) / Re (550) ≧ 1.01 is generally satisfied. Here, Re (450), Re (550), and Re (650) represent in-plane phase differences measured at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.

When the retardation plate of the present invention is made of a film obtained by, for example, a uniaxial stretching method, the refractive index in the stretching direction (X-axis direction (the in-plane refractive index is the maximum direction)) is nx, and the stretching is performed. When the refractive index in the orthogonal direction (Y-axis direction) is ny and the refractive index in the thickness direction (Z-axis direction) is nz, the relationship represented by the formula: nx> ny = nz is satisfied. On the other hand, when the retardation plate of the present invention is obtained by the above Z stretching method among the biaxial stretching methods, these refractive indexes nx, ny and nz are represented by the formula: nx>nz> ny. Is satisfied. By the way, an Nz value represented by the formula: Nz = (nx−nz) / (nx−ny) is frequently used as a parameter indicating visual characteristics. If the Nz value is 0.5, a slow phase is obtained. Even when the retardation plate is inclined in the axial direction (X-axis direction), the phase difference with respect to the inclination angle does not change. That is, it is clear that the visual dependency of the phase difference is eliminated. Therefore, considering the effect of improving visual characteristics, it is desirable to perform stretching while paying particular attention to the control of the three-dimensional refractive index.
Further, the phase difference plate of the present invention, when light of a certain wavelength is incident, the refractive index (hereinafter, "n _e" hereinafter) for the extraordinary refractive index with respect to the ordinary light (hereinafter, referred to as "n _o") between refractive index _difference: n e -n _o (hereinafter referred to as △ n) is 0.005 or less at a wavelength of 550 nm. However, for example, when a film obtained by mixing a liquid crystal compound with the above polymer material is used, the Δn of the film itself usually obtained from the liquid crystal compound is relatively high. It is also possible to make Δn of 0.01 or more.
By increasing the Δn, it becomes possible to reduce the film thickness for expressing a desired phase difference. In particular, visible light having a film thickness of 100 μm or less, which is extremely difficult with a conventional phase difference plate, is obtained. It is also possible to give a phase difference of λ / 2 to light of almost all wavelengths in the entire region.

  Such a liquid crystalline compound is not particularly limited as long as it does not inhibit the object of the present invention. For example, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenyl Liquid crystal low-molecular compounds such as cyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, alkenylcyclohexylbenzonitriles, and (meth) acryloyloxy groups at the molecular ends of the liquid crystal low-molecular compounds And liquid crystal monomers having a polymerizable group such as an epoxy group, a vinyloxy group, a propargyl group, and an isocyanate group. From these, one or more kinds may be appropriately selected and used so that Δn of the obtained retardation plate has a desired value and depending on the kind of polymer to be used. The amount of the liquid crystalline compound is 1 part by weight or more, preferably 3 parts by weight or more with respect to 100 parts by weight of the polymer material of the present invention, so that the effect of improving Δn by using the liquid crystalline compound is sufficiently exhibited. Is desirable. Further, in order to maintain the characteristic that the phase difference becomes larger toward the longer wavelength side, it is desirably 20 parts by weight or less, preferably 10 parts by weight or less based on 100 parts by weight of the polymer material.

  The retardation plate of the present invention can be used in the form of an optical film by laminating with another optical material. For example, by laminating the retardation plate of the present invention on a polarizing plate, it can be used as an optical film such as an elliptically polarizing plate or a circularly polarizing plate. In addition, the retardation film of the present invention in which the retardation is adjusted to λ / 4 and the retardation film of the present invention in which the retardation is adjusted to λ / 2 are laminated on a polarizing plate to constitute an optical film. You can also. 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 retardation film of the present invention is an optical material having different functions, such as an optical film laminated in the order of polarizing plate / retardation plate / bandpass filter of the present invention, and an optical film having a protective film attached to the surface. Can be used in various optical film embodiments.

  The retardation film of the present invention or the optical film on which the retardation film is laminated can be preferably used as a component 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)
^It calculated | required from the peak of 0.83 ppm, 0.95-2.0 ppm, 3.5-5.0 ppm, 6.76 ppm of < ¹ > H-NMR (heavy DMSO solvent).
(Measurement of in-plane retardation)
It measured using "KOBRA21-ADH" by Oji Scientific Instruments.
(Measurement of thickness)
It measured using the micrometer (product made from MITUTOYO).

Production Example 8.8 g of PVA having a degree of polymerization of 1800 (NH-18, manufactured by Nippon Synthetic Chemical Co., Ltd.) dried at 105 ° C. for 2 hours was dissolved in 500 ml of DMSO. Mesitaldehyde 9.0g, propionaldehyde 2.3g and p-toluenesulfonic acid monohydrate 3.1g were added here, and it stirred at 40 degreeC for 4 hours. 1N aqueous sodium hydrogen carbonate solution was added to stop the reaction, and reprecipitation was performed in water. The polymer obtained by filtration was dissolved in DMF and reprecipitated in diethyl ether. After filtration and drying, 15.2 g of a white polymer was obtained. When the obtained polymer was measured by ¹ H-NMR, the molar ratio of vinyl mecital, vinyl propional, and vinyl alcohol was 30:21:49, and a polymer having a structure represented by the formula (V) was obtained. It was.

Example 100 parts by weight of the polymer obtained in Production Example and 200 parts by weight of polyvinyl butyral (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in DMF, and a film was formed using an applicator. The film obtained by drying was stretched 1.5 times at 95 ° C. using a stretching machine to obtain a uniaxially stretched film having a thickness of 77 μm. When the retardation of the obtained stretched film was measured, Re (450) = 127.6 nm, Re (550) = 154.1 nm, Re (650) = 165.9 nm, and Re (450) / Re (550 ) = 0.828, Re (650) / Re (550) = 1.077, and reverse wavelength dispersion was obtained.

Comparative Example The same polyvinyl butyral used in the example was dissolved in cyclopentanone and formed into a film using an applicator. The film obtained by drying was stretched twice at 70 ° C. using a stretching machine to obtain a uniaxially stretched film having a thickness of 96 μm. When the retardation of the obtained stretched film was measured, Re (450) = 399.5 nm, Re (550) = 398.7 nm, Re (650) = 397.0 nm, and Re (450) / Re (550 ) = 1.020, Re (650) / Re (550) = 0.996, not reverse wavelength dispersion.

Claims (8)

A birefringent chain polymer (1) having at least one of the structures represented by the following general formula (I) or general formula (II) as the repeating unit (A), and a polymer (2) different therefrom The in- plane retardation value of the single layer film at least at a wavelength of 450 to 650 nm is smaller at the short wavelength side and larger at the long wavelength side. Board.

(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. A branched alkyl group, a linear or branched alkoxy group having 1 to 4 carbon atoms, a linear or branched thioalkoxy group having 1 to 4 carbon atoms, a halogen, a nitro group, an amino group , or Represents a thiol group (provided that R ² and R ⁶ are not simultaneously a hydrogen atom) R ^{3 to} R ⁵ each independently represent 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. An anthracenyl group, or an optionally substituted phenanthrenyl group, wherein one or more carbon atoms constituting a naphthyl group, anthracenyl group, or phenanthrenyl group may be substituted with a nitrogen atom) . The phase difference plate according to claim 1, wherein the polymer (2) different from the chain polymer (1) is polyvinyl acetal. The phase difference plate according to claim 1, wherein the polymer (2) different from the chain polymer (1) is polynorbornene. The phase difference plate according to any one of claims 1 to 3, wherein the chain polymer (1) further has a repeating unit (B) represented by the following formula (III) in addition to the repeating unit (A).

(The arrangement of the repeating units (A) and (B) may be either block or random). The chain polymer (1) further has a repeating unit (C) represented by the following general formula (IV) in addition to the repeating units (A) and (B). Phase difference plate.

(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 may be substituted by an oxygen atom which is not adjacent. The arrangement of the repeating units (A) to (C) may be either block or random. The retardation plate according to any one of claims 1 to 5, wherein the chain polymer (1) is a polymer having a structure represented by the following general formula (V).

(In general formula (V), l represents 5 to 30 mol%, m represents 20 to 80 mol%, and n represents 1 to 70 mol%). The optical film which laminated | stacked the phase difference plate in any one of Claims 1-6. An image display apparatus provided with the phase difference plate in any one of Claims 1-6, or the optical film of Claim 7.