JP6443836B2 - Retardation film - Google Patents

Description

  The present invention relates to a retardation film useful for an image display device such as a liquid crystal display device, a liquid crystal display cell using the same, and a liquid crystal display device.

  Until now, CRT (Cathode Ray Tube) has been mainly used as a display device, but in recent years, liquid crystal display devices are widely used in various environments such as personal computer monitors, televisions, mobile phones, and in-vehicle monitors. . In addition, the display device is required to have high contrast, wide viewing angle characteristics, and higher durability.

  In a normal liquid crystal display device, a retardation film is used in addition to a liquid crystal cell and a polarizing plate. In a liquid crystal display device, there is a problem of viewing angle dependency that even if a liquid crystal material having anisotropy and a polarizing plate alone can provide a good display when viewed from the front, the display performance is degraded when viewed from an oblique direction. Therefore, a retardation film is used for the improvement.

  The retardation film has functions that can convert linearly polarized light into elliptically polarized light and circularly polarized light, or convert linearly polarized light in one direction into another direction (rotation). By using it, for example, the viewing angle and contrast of the liquid crystal display device can be improved. This retardation film is usually obtained by uniaxially or biaxially stretching a plastic film such as polycarbonate, polyarylate, or polyethersulfone. At this time, birefringence is generated by the anisotropy of the refractive index generated by stretching, and functions as a retardation film. The optical performance of the retardation film is, for example, the refractive index in the slow axis direction in the front direction of the retardation film at a certain wavelength (the direction in which the refractive index is maximum in the plane) and the fast axis direction (slow in the plane) It can be determined by the retardation value obtained by the product of the refractive index difference in the direction perpendicular to the phase axis direction) and the thickness of the retardation film. However, this retardation value has a so-called wavelength dependency (wavelength dispersion characteristic) and viewing angle dependency (viewing angle characteristic), and the retardation film has various properties in consideration of comprehensive performance including these various characteristics. Used for display.

  Among these, the viewing angle characteristic is the angle dependency of the retardation value, and is generally controlled by the stretching method of the retardation film. Stretching generates a refractive index nx in the stretching direction, a refractive index ny in a direction perpendicular to the film in the film plane, and a refractive index nz in the thickness direction, and the values determine the viewing angle characteristics of the retardation film. In uniaxial stretching, the relationship is usually nx> ny = nz, so that the retardation film has a so-called uniaxial property. On the other hand, biaxiality includes, for example, a case where nx> ny> nz or nz ≧ ny> nx or ny> nz> nx, and the phase difference having such a refractive index in normal uniaxial stretching. It was not easy to obtain a film.

  For example, in the case of a general retardation film obtained by uniaxially stretching a polymer film such as polycarbonate, the retardation value decreases as the inclination angle from the front direction increases when the film is inclined in the slow axis direction. On the contrary, when tilted in the fast axis direction, the phase difference value increases as the tilt angle from the front direction increases. This tendency is common to other uniaxially stretched general retardation films such as polyarylate, polyethersulfone, cycloolefin polymers such as ZEONOR (manufactured by Nippon Zeon) and ARTON (manufactured by JSR). . There are two types of use of the retardation film: the case where the characteristic that the retardation value changes with the inclination as described above is used, and the case where the characteristic that the retardation value changes with the inclination as much as possible is used. Whether to use a retardation film is appropriately selected depending on the purpose.

  As a retardation film that suppresses a change in retardation value associated with an inclination as much as possible, Patent Document 3 substantially performs biaxial stretching by bonding a shrinkable film to a stretched film and stretching it uniaxially. A method for producing a retardation film in which a change in retardation value associated with inclination is suppressed is disclosed. However, in the method in which the shrinkable film is pasted and substantially biaxially stretched, there are an increase in the steps of pasting the shrinkable film and peeling after stretching, which causes a problem of cost increase.

On the other hand, in order to achieve high image quality of the liquid crystal display device, there is a demand for controlling not only the in-plane delay (Re) of the retardation film but also the thickness direction delay (Rth).
For example, in a horizontal electric field (IPS) type liquid crystal display device that has been attracting attention in recent years, gradation inversion, coloring, and a decrease in contrast occur when viewed from a specific oblique direction, and the viewing angle decreases in that direction. Therefore, as with other liquid crystal display systems, a retardation film for an IPS liquid crystal display device that requires optical compensation by using a retardation film and needs to expand the viewing angle has a thickness. The direction delay is preferably a negative value. However, a film made of cellulose triacetate or polycarbonate has a positive value in the thickness direction retardation. Therefore, in addition to a small absolute value of the photoelastic coefficient, a retardation film having a negative thickness direction delay is required.

    Further, in the IPS liquid crystal display device, since the liquid crystal molecules have a homogeneous alignment substantially parallel to the substrate surface, a film having a high refractive index in a direction perpendicular to the substrate surface is used for optical compensation. Is valid. Therefore, in the retardation film used in the IPS liquid crystal display device, attention is also paid to controlling the nz value and the retardation (Re, Rth), and a material having a negative intrinsic birefringence value is used. In order to increase the refractive index in the direction perpendicular to the substrate surface, a special treatment is applied to a material having a positive intrinsic birefringence value.

  Specifically, in the case of a retardation film for an IPS liquid crystal display device, a film satisfying nx = nz> ny called a negative A plate or a film satisfying nx = ny <nz called a positive C plate is used. Is known to be effective in improving image quality.

For example, Patent Document 4 describes that a liquid crystal display device is optically compensated by a negative A plate using a material having negative intrinsic birefringence. However, polystyrene and polymethyl methacrylate, which are conventionally known as materials having negative intrinsic birefringence, have a problem that heat resistance is not sufficient and a photoelastic coefficient is large.
Patent Document 5 discloses the concept of optical compensation of an IPS liquid crystal display device using a positive C plate. However, Patent Document 3 only describes a configuration example by simulation, and does not describe a material for manufacturing such a film.
In Patent Document 6, as a retardation film suitable for an IPS liquid crystal display device, a heat-shrink film is bonded, and the film is stretched and / or shrunk under the action of the shrinkage force by heating to be tilted. A film having positive intrinsic birefringence such as a polycarbonate film or a cycloolefin film such as norbornene is disclosed. However, the production of this film includes a heat shrink film bonding step and a peeling step, and there is a problem in productivity.

  Usually, the refractive index ellipsoid of the polymer immediately after film formation is spherical, but when the film is stretched, the polymer chain is oriented in the stretching direction, so it usually becomes a refractive index ellipsoid horizontal to the film surface. Therefore, it is considered very difficult to obtain a coin-shaped refractive index ellipsoid standing in a direction perpendicular to the film plane.

  Thus, a retardation film suitable for an IPS liquid crystal display device or a retardation film suitable for producing a negative A plate is not yet known.

Japanese Patent No. 3174367 Japanese Patent No. 345779 Japanese Patent No. 2818983 US Pat. No. 5,612,801 JP 11-133408 A JP 2006-106180 A

An object of the present invention is to provide a retardation film having excellent viewing angle characteristics when used in a liquid crystal cell or a liquid crystal display device.
Another object of the present invention is to provide a retardation film capable of expressing optical characteristics as a negative A plate only by uniaxial stretching rather than biaxial stretching.

  As a result of diligent research to solve the above problems, the present inventors have obtained a specific three-dimensional retardation film that is uniaxially stretched from a lactic acid-derived polymer film having a specific structure without being biaxially stretched. Since it shows a refractive index, it discovered that the problem of the viewing angle characteristic of a liquid crystal cell or a liquid crystal display device could be solved. Furthermore, the present inventors have found that such a retardation film can exhibit optical characteristics as a negative A plate particularly useful for compensation of an IPS liquid crystal cell.

（式中、Ｒ^１及びＲ^２は異なっており、各々独立に、水素原子、置換基を有してもよいアルキル基、置換基を有してもよいアリール基、又は置換基を有してもよいヘテロアリール基を示し、或いはＲ^１及びＲ^２は互いに結合して隣接する不斉炭素（Ｃ＊）とともに非対称な環を形成してもよい。＊は不斉炭素を示す。）
で表される繰り返し単位を分子内に有するポリマーであり、該ポリマー中のメソ二連子（ｍ）とラセモ二連子（ｒ）の比（ｍ：ｒ）が６０：４０〜１００：０であるポリマーからなるフィルムを延伸して成る位相差フィルム。
［２］
前記ポリマーが下記式（４）：

（式中、Ｒ^１、Ｒ^２及び＊は、式（３）で定義される通りである。）
で表される化合物を含むモノマーをラジカル重合して得られる、［１］に記載の位相差フィルム。
［３］式（４）で表される化合物を含むモノマーまたは、当該モノマーの溶液をキャストし、ラジカル重合処理を施して得られたフィルムを、さらに延伸処理して得られる［２］に記載の位相差フィルム。
［４］式（４）で表される化合物を含むモノマーにラジカル重合処理を施したポリマーを用いて、押し出し法にて得られたフィルムを、さらに延伸処理して得られる［２］請求項１に記載の位相差フィルム。
［５］［１］〜［４］のいずれか１項に記載の位相差フィルムを備える液晶セル。
［６］［１］〜［４］のいずれか１項に記載の位相差フィルムを備える液晶表示装置。 That is, the present invention relates to the inventions described in [1] to [6] below.
[1] The three-dimensional refractive index at a measurement wavelength of 590 nm is the following formula (1) or (2):
nx ≧ nz> ny (1)
nz ≧ nx> ny (2)
(In the formulas (1) and (2), nx is the refractive index in the stretching direction in the retardation film plane, ny is the refractive index in the stretching direction and the orthogonal direction in the retardation film plane, and nz is the thickness. Is the refractive index in the direction)
General formula (3):

(In the formula, R ¹ and R ² are different and each independently has a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. Or R ¹ and R ² may be bonded to each other to form an asymmetric ring with the adjacent asymmetric carbon (C *). * Represents an asymmetric carbon.)
In the polymer, the ratio (m: r) of the meso duplex (m) to the racemo duplex (r) in the polymer is 60:40 to 100: 0. A retardation film formed by stretching a film made of a polymer.
[2]
The polymer is represented by the following formula (4):

(Wherein R ¹ , R ² and * are as defined in formula (3).)
The retardation film according to [1], obtained by radical polymerization of a monomer containing a compound represented by the formula:
[3] The monomer according to [2], obtained by casting a monomer containing the compound represented by formula (4) or a solution of the monomer and subjecting it to radical polymerization treatment, and further stretching treatment Retardation film.
[4] A film obtained by an extrusion method using a polymer obtained by subjecting a monomer containing a compound represented by formula (4) to radical polymerization treatment, and obtained by further stretching treatment. [2] Claim 1 The retardation film described in 1.
[5] A liquid crystal cell comprising the retardation film according to any one of [1] to [4].
[6] A liquid crystal display device comprising the retardation film according to any one of [1] to [4].

According to the present invention, a retardation film that can solve the problem of viewing angle characteristics of a liquid crystal cell or a liquid crystal display device can be provided.
In addition, the retardation film of the present invention has a characteristic that the three-dimensional refractive index can be arbitrarily controlled.
Furthermore, according to the present invention, there can be obtained a retardation film in which biaxiality is manifested only by uniaxial stretching and the viewing angle characteristics are controlled without performing substantial biaxial stretching. Optical characteristics as a plate can be expressed.

（式（３）において、Ｒ^１及びＲ^２は異なっており、各々独立に、水素原子、置換基を有してもよいアルキル基、置換基を有してもよいアリール基、又は置換基を有してもよいヘテロアリール基を示し、或いはＲ^１及びＲ^２は互いに結合して隣接する不斉炭素（Ｃ＊）とともに非対称な環を形成してもよい。＊は不斉炭素を示す。またＲ^１及びＲ^２は同じ置換基を有していても良く、Ｒ^１およびＲ^２には水素原子、置換基を有してもよいアルキル基、置換基を有してもよいアリール基、又は置換基を有してもよいヘテロアリール基を示し、或いはＲ^１及びＲ^２は互いに結合して隣接する炭素とともに対称な環を形成してもよい。）
で表される繰り返し単位を分子内に有するポリマーであり、該ポリマー中のメソ二連子（ｍ）とラセモ二連子（ｒ）の比（ｍ：ｒ）が６０：４０〜１００：０であるポリマーからなるフィルムを延伸して成る位相差フィルムである。 In one embodiment of the present invention, the three-dimensional refractive index at a measurement wavelength of 590 nm is represented by the following formula (1) or (2):
nx ≧ nz> ny (1)
nz ≧ nx> ny (2)
The filling,
General formula (3):

(In Formula (3), R ¹ and R ² are different, and each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. R ¹ and R ² may be bonded to each other to form an asymmetric ring with the adjacent asymmetric carbon (C *), and * represents an asymmetric carbon. R ¹ and R ² may have the same substituent, and R ¹ and R ² may be a hydrogen atom, an alkyl group that may have a substituent, an aryl group that may have a substituent, Or a heteroaryl group which may have a substituent, or R ¹ and R ² may be bonded to each other to form a symmetric ring with adjacent carbons.)
In the polymer, the ratio (m: r) of the meso duplex (m) to the racemo duplex (r) in the polymer is 60:40 to 100: 0. It is a retardation film formed by stretching a film made of a certain polymer.

  In the formulas (1) and (2), nx is the refractive index in the stretching direction in the retardation film plane, ny is the refractive index in the stretching direction and the orthogonal direction in the retardation film plane, and nz is the thickness direction. Is the refractive index.

  That is, the retardation film of the present invention is a film formed by stretching a film made of a polymer having a repeating unit represented by the general formula (3) in the molecule, and the three-dimensional refractive index at a measurement wavelength of 590 nm is nx. The relationship of ≧ nz> ny or nz ≧ nx> ny is satisfied. Here, when determining the sizes of nx, ny, and nz, if there is a difference in the fourth digit of the decimal point, it is determined that there is a significant difference in refractive index.

Examples of the alkyl group of the alkyl group which may have a substituent represented by R ¹ and R ² include a linear, branched, or cyclic C 1-10 alkyl group. Specific examples include C1-6 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, and isohexyl. Among these, an ethyl group, an isopropyl group, and a tert-butyl group are preferable, and an isopropyl group is more preferable. The alkyl group may have 1 to 3 substituents such as a halogen atom (for example, fluorine, chlorine, bromine, etc.), a carboxyl group, an ester group, an amide group, an optionally protected hydroxyl group, and the like. Good. Further, the alkyl group which may have a substituent represented by R ¹ and R ² may be a different substituent or the same substituent.

Examples of the aryl group of the aryl group which may have a substituent represented by R ¹ and R ² include monocyclic or bicyclic or more aryl groups, and specifically include phenyl, toluyl, xylyl, naphthyl. , Anthryl, phenanthryl and the like. Examples of the aryl group include an alkyl group (for example, C1-6 alkyl group), a halogen atom (for example, fluorine, chlorine, bromine, etc.), a carboxyl group, an ester group, an amide group, an optionally protected hydroxyl group, and the like. 1 to 3 substituents may be included.

The heteroaryl group of the heteroaryl group which may have a substituent represented by R ¹ and R ² is, for example, a heteroaryl group containing an oxygen, nitrogen and / or sulfur atom in the ring, such as furyl , Thienyl, imidazolyl, pyrazolyl, isoxazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolyl, quinolyl, isoquinolyl, thiazolyl and the like. The heteroaryl group includes, for example, an alkyl group (for example, C1-6 alkyl group), a halogen atom (for example, fluorine, chlorine, bromine, etc.), a carboxyl group, an ester group, an amide group, and an optionally protected hydroxyl group. 1 to 3 substituents may be included.

R ¹ and R ² may combine with each other to form an asymmetric ring with the adjacent asymmetric carbon (C *). For example, a 3- to 8-membered cyclic hydrocarbon is formed, and the cyclic hydrocarbon is, for example, an alkyl group (for example, a C1-6 alkyl group) or a halogen atom (for example, fluorine, Chlorine, bromine, etc.), carboxyl groups, ester groups, amide groups, 1 to 4 substituents such as optionally protected hydroxyl groups.

As R ¹ and ^{R 2,} preferably, ethyl ^{R 1} hydrogen, the ^{R 2,} isopropyl group or a tert- butyl group, ^{R 1} and ^{R 2} may be interchanged, particularly preferably hydrogen ^{R 1,} R ² is an isopropyl group, and R ¹ and R ² may be interchanged. R ¹ and R ² may be different from each other or the same substituent.

で表される化合物を含むモノマーをラジカル重合して得られるポリマーである。
ここで、式（４）中、Ｒ^１、Ｒ^２及び＊は、式（３）で定義される通りである。 In the present invention, the polymer having the repeating unit represented by the general formula (3) in the molecule is preferably the following formula (4):

Is a polymer obtained by radical polymerization of a monomer containing a compound represented by the formula:
Here, in formula (4), R ¹ , R ² and * are as defined in formula (3).

Here, since R ¹ and R ² are different, the carbon atom to which R ¹ and R ² are bonded is an asymmetric carbon (C *). The steric structure of the asymmetric carbon can be represented by R-form and S-form, but the compound represented by the formula (4) used in the present invention has a molar ratio of R-form and S-form with R-form ( S-form): S-form (R-form) = 70: 30 to 100: 0, preferably 75:25 to 100: 0, and more preferably 80:20 to 100: 0.

  The monomer represented by the formula (4) is produced by various methods. For example, MaGee, D .; I. et al. It can be produced according to the description of Tetrahedron, 62, 4153-61 (2006). A specific production scheme will be described.

（式中、Ｘはハロゲン原子を示す。Ｒ^１、Ｒ^２及び＊は前記に同じ。）

(In the formula, X represents a halogen atom. R ¹ , R ² and * are the same as above.)

Examples of the lactic acid represented by the general formula (6) include L-lactic acid, D-lactic acid, and fermented lactic acid. In the above scheme, L-lactic acid is used for the sake of convenience, but it can also be produced in the same manner when D-lactic acid, which is the enantiomer, is used. In this case, the compounds in the above scheme are those in which the configuration of the asymmetric carbon is reversed. Moreover, fermented lactic acid can be used as a raw material (green chemistry). In particular, since fermented lactic acid contains L-lactic acid in a rich manner, the separation process of enantiomers can be omitted. That is, a polymer obtained by radical polymerization from a monomer derived from fermented lactic acid has sufficiently high stereoregularity (isotactic). This is very important for practical industrialization.
A carbonyl compound represented by the general formula (5) (for example, isobutyraldehyde) and L-lactic acid represented by the general formula (6) in a solvent (for example, a hydrocarbon solvent such as n-pentane) In the presence of an acid catalyst (for example, p-toluenesulfonic acid, methanesulfonic acid, sulfuric acid, etc.), reflux is performed while removing water azeotropically using a reflux condenser equipped with a Dean-Stark fractionator.

  Known aldehydes and ketones can be widely used as the carbonyl compound represented by the general formula (5). Such aldehydes include acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, pivalaldehyde, valeraldehyde, trifluoroethanal, chloral, succinaldehyde, chlorofluoroacetaldehyde, menthone, cyclohexanecarbaldehyde, 2- Examples include pyrrole carbaldehyde, 3-pyridinecarbaldehyde, 2-furaldehyde, benzaldehyde, benzeneacetaldehyde, vanillin, piperonal, citronellal and the like. Examples of the ketone include methyl ethyl ketone, 2-pentanone, 2-hexanone, methyl sec-butyl ketone, methyl tert-butyl ketone, acetophenone, 2-furylmethyl ketone, 2-acetonaphthone, 2 (3H) -pyrazinone, pyrrolidone and the like. . Of these, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, pivalaldehyde and the like are preferable, and isobutyraldehyde is more preferable.

  The product in the condensation reaction is usually a mixture of two diastereomers represented by the general formula (7a) and / or (7b). These can be isolated and purified, for example, by distillation under normal pressure or reduced pressure, or by column chromatography. When it becomes a mixture of the compounds represented by the general formulas (7a) and (7b), they can be separated by using the isolation and purification methods described above.

  The temperature and time of the condensation reaction may be appropriately adjusted depending on, for example, the type of reagent, but the reaction temperature is usually about 0 to 180 ° C, preferably 0 to 80 ° C, more preferably 0 to 60 ° C. Moreover, reaction time is 0.5 to 100 hours normally, Preferably it is 0.5 to 30 hours, More preferably, it is 0.5 to 10 hours. The conditions of the temperature and time of the condensation reaction have a great influence on the production ratio of (7a) and (7b). Usually, the temperature is low, and the reaction ratio is high when the reaction time is short. In particular, a high diastereo ratio is achieved by stirring under conditions of 0 to 60 ° C. and 0.5 to 10 hours.

  In the case where the compound represented by the general formula (7a) and the compound represented by (7b) are a mixture, one compound has a high purity (high dia Preferably in stereo ratio). For example, the molar ratio of the compound represented by the general formula (7a): the compound represented by the general formula (7b) is 70:30 to 100: 0, preferably 80:20 to 100: 0, and more preferably 90: It is 10-100: 0, Most preferably, it is 95: 5-100: 0. The molar ratio of the compound represented by the general formula (11b): the compound represented by the general formula (7a) is 70:30 to 100: 0, preferably 80:20 to 100: 0, and more preferably 90: It is 10-100: 0, Most preferably, it is 95: 5-100: 0.

  Next, the compound represented by the general formula (7) obtained above (referred to as a generic name of the compound represented by the general formula (7a) and / or (7b)) is used, for example, as a solvent (for example, carbon tetrachloride, etc. ) In the presence of halogenating agents (for example, N-bromosuccinimide (NBS), N-chlorosuccinimide (NCS), N-iodosuccinimide (NIS), N, N-dibromohydantoin (NDDBH), N-bromosaccharin ( NBSA), bromine, chlorine, iodine etc.) and a radical initiator (eg 2,2′-azobis (isobutyronitrile) (AIBN) etc.) are reacted. Usually refluxed for a period of time in a flask equipped with a reflux condenser. After the reaction, the compound is treated by a conventional method to obtain a compound represented by the general formula (8) (collectively a compound represented by the general formula (8a) and / or (8b)).

Thereafter, the compound represented by the general formula (8) is added to a base (eg, triethylamine, diisopropylethylamine, pyridine, 4-dimethylaminopyridine, piperidine, DBU, Na ₂ ) in a solvent (eg, benzene, toluene, xylene, etc.). CO ₃ , NaOH, etc.) are allowed to act. Usually, a base is added to the solution of the compound represented by the general formula (8) and refluxed for a certain time. After the reaction, after distilling off the solvent, the product is isolated and purified by distillation, and is a compound represented by the general formula (4) (generic name of the compound represented by the general formula (4a) and / or (4b)). )
In addition, in order to improve stability during storage or use of the obtained compound, hydroquinone, p-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 3-hydroxythiophenol, during synthesis or after synthesis, A polymerization inhibitor such as p-benzoquinone, 2,5-dihydroxy-p-benzoquinone, or phenothiazine may be added as necessary. The amount of its use is 0.01-1 mass% with respect to a compound.

The compound (monomer) represented by the general formula (4) thus obtained has an enantio-ratio of the asymmetric carbon (C *) to which R ¹ and R ² are bonded (that is, the molar ratio of R-form to S-form). R-form (S-form): S-form (R-form) = 70: 30 to 100: 0, preferably 80:20 to 100: 0, more preferably 90:10 to 100: 0, and particularly preferably 95: 5 100: 0.
In particular, the monomer represented by the general formula (4) is preferably a compound represented by the following general formula (4c) from the viewpoint of the stereoregularity of the polymer after radical polymerization. R ¹¹ is preferably an isopropyl group.

  In one embodiment of the present invention, the retardation film of the present invention is obtained by casting a monomer containing a compound represented by formula (4) or a solution of the monomer, performing radical polymerization treatment, and forming into a film shape. be able to. (Hereinafter also referred to as “Production Method 1 of the Present Invention”)

  In one embodiment of the present invention, the retardation film of the present invention is a film obtained by casting a monomer containing a compound represented by formula (4) or a solution of the monomer, and subjecting it to radical polymerization treatment. Further, it can be obtained by stretching.

When casting a monomer solution containing the compound represented by formula (4), the monomer is first dissolved in a solvent. Solvents that can be used include halogenated hydrocarbon solvents such as methylene chloride and chloroform, acetates such as ethyl acetate, butyl acetate and methyl acetate, alcohols such as methanol, ethanol, propanol, isopropanol and benzyl alcohol, Non-polar solvents such as ketones such as 2-butanone, acetone, cyclopentanone and cyclohexanone, basic solvents such as benzylamine, triethylamine and pyridine, cyclohexane, benzene, toluene, xylene, anisole, hexane and heptane. Can be mentioned.
The weight concentration of the monomer containing the compound represented by the formula (4) is usually 1% to 99%, preferably 2.5% to 80%, more preferably 5% to 50%. Only one kind of these monomers may be blended or a plurality of kinds may be blended. Furthermore, you may add each solvent and plasticizer which were mentioned above as needed. Plasticizers include phthalates such as dimethyl phthalate, diethyl phthalate, and ethyl phthalyl ethyl glycolate, trimellitic esters such as tris (2-ethylhexyl) trimellitate, and aliphatic dibasic acids such as dimethyl adipate and dibutyl adipate Examples include esters, orthophosphates such as tributyl phosphate and triphenyl phosphate, sebacic acid esters such as sebacic acid-di-n-butyl, and acetic acid esters such as glyceryl triacetate or 2-ethylhexyl acetate. Only one kind of these compounds may be blended or a plurality of kinds may be blended.

Next, the obtained monomer solution is cast (applied) onto a substrate having a flat surface and a release property, and then subjected to radical polymerization treatment to be processed into a film.
Moreover, the monomer containing the compound represented by Formula (4) can also be used as it is, without melt | dissolving in a solvent. In this case, in the same manner as described above, the monomer is applied onto a substrate having a flat surface having a releasability and then subjected to radical polymerization to be processed into a film.

  The radical polymerization treatment can be carried out in the presence or absence of a radical polymerization initiator. Specifically, natural thermal polymerization can be performed in the absence of a radical polymerization initiator, or radical polymerization can be performed by light irradiation in the presence or absence of a radical polymerization initiator. In the case of radical polymerization by light irradiation, polymerization is usually performed using a light source such as a mercury lamp or a xenon lamp. The light source can be appropriately selected depending on the type of vinyl monomer, the type of polymerization initiator, and the like.

As light irradiation, for example, the irradiation amount of ultraviolet rays varies depending on the type and thickness of the monomer containing the compound represented by the formula (4), but the irradiation amount per time is preferably about 100 to 1000 mJ / cm ² . In addition, the atmosphere during ultraviolet irradiation may be air or an inert gas such as nitrogen. However, when the film thickness is reduced, it does not cure sufficiently due to oxygen damage. In such a case, ultraviolet light is irradiated in an inert gas. It is preferable to cure.

The radical polymerization initiator is not particularly limited as long as it can be generally used for radical polymerization. For example, azo polymerization initiators, peroxides such as benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, redox polymerization In addition to initiators, photopolymerization initiators such as benzoins, acetophenones, anthraquinones, thioxanthones, ketals, benzophenones, and phosphine oxides can be used. In addition to the above initiator, a living radical polymerization initiator system using an organic halogen substance (for example, ethyl 2-bromoisobutyrate), a nitroxide derivative, a thiocarbonyl substance, an organic tellurium substance or the like as an initiator or additive. Can be mentioned.
Of the radical polymerization initiators, an azo polymerization initiator is preferred, and specifically, 2,2′-azobis (isobutyronitrile) (AIBN), 2,2′-azobis (2-methylbutyro). Nitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis (cyclohexane-1- Carbonitrile), 2,2′-azobis (2-methylpropane), 2,2′-azobis (2,4,4-trimethylpentane), 2,2′-azobis [2- (3,4,5, 6-tetrahydropyrimidin-2-yl) propane] dihydrochloride and the like. Also, acetophenone, 2,2-diethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 2-hydroxy-2-methyl-phenylpropan-1-one, diethoxy Acetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, oligo [2-hydroxy-2-methyl-1- [4- (1- Acetophenones such as methylvinyl) phenyl] propanone], 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, diphenyl- (2,4,6- Trimethylbenzoyl) phosphineoxy Photopolymerization initiators such as phosphine oxides such as phosphine oxides are also preferable, and these can be added alone or in admixture and irradiated with ultraviolet rays to form a polymer.

  After performing radical polymerization treatment, the solvent is removed if necessary, and the film is peeled off from the substrate to obtain a transparent film.

  By further uniaxially stretching the film obtained by the production method 1 of the present invention, the retardation film of the present invention can be obtained. The stretching process can use general uniaxial stretching. For example, the film is stretched in one direction while fixing both ends of the film and heating. Or when a film is a long roll shape, the both ends of a film are fixed, for example with a nip roll, and it extends | stretches continuously by the difference in the rotation speed of both rolls. The optimum stretching temperature varies depending on the polymer having the repeating unit represented by the general formula (3) in the molecule.

  The stretching temperature for producing the retardation film of the present invention is 50 ° C to 300 ° C, more preferably about 150 ° C to 250 ° C.

The draw ratio varies depending on the type, thickness, and desired retardation value of the polymer having the repeating unit represented by formula (3) in the molecule, but is 1.1 to 10 times, more preferably 1.5. About 5 to 5 times is good. For example, when using a monomer in which R ¹ is hydrogen and R ² is an i-propyl group in Formula (3), the ratio is about 1.5 to 2.5 times.
The stretching speed is the same as the stretching temperature, and the optimum stretching speed varies depending on the type of polymer having the repeating unit represented by the general formula (3) in the molecule, but it is usually 10 times stretching / min or less, preferably 5 times stretching / min. Hereinafter, it is more preferably 2.5 times stretching / min or less.

    The thickness of the retardation film obtained by the production method 1 of the present invention is 10 to 500 μm, preferably 20 to 300 μm, more preferably about 30 to 150 μm.

  In one embodiment of the present invention, the retardation film of the present invention is a film obtained by subjecting a polymer obtained by subjecting a monomer containing a compound represented by formula (4) to radical polymerization treatment to a film form by an extrusion method. It can be obtained by molding. (Hereinafter also referred to as “Production Method 2 of the Present Invention”)

  In one embodiment of the present invention, the retardation film of the present invention is a film obtained by an extrusion method using a polymer obtained by subjecting a monomer containing a compound represented by formula (4) to radical polymerization treatment. Can be obtained by further stretching treatment.

  The radical polymerization is usually carried out by mixing the monomer represented by the formula (4) and, if necessary, a radical polymerization initiator in a container replaced with an inert gas or a vacuum deaerated container and stirring.

In the radical polymerization reaction, no solvent or a solvent (organic solvent or aqueous solvent) generally used in radical polymerization can be used. Examples of the organic solvent include benzene, toluene, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, chlorobenzene, dichlorobenzene, and trifluoro. Examples include methylbenzene and anisole. In addition, examples of the aqueous solvent include water and solvents containing methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyrocellosolve, 1-methoxy-2-propanol and the like as necessary.
In the case of using a solvent, the amount of the solvent used may be adjusted as appropriate. The amount is generally 0.1 to 20 liters, preferably 0.2 to 5 liters per 1 mol of all monomers including the monomer.

  The radical polymerization reaction can be carried out in the presence or absence of a radical polymerization initiator. Usually, it is preferable to carry out in the presence of a radical polymerization initiator. Of course, it is also possible to perform spontaneous thermal polymerization in the absence of a radical polymerization initiator, or radical polymerization by light irradiation in the presence or absence of a radical polymerization initiator. In the case of radical polymerization by light irradiation, polymerization is usually performed using a light source such as a mercury lamp or a xenon lamp. The light source can be appropriately selected depending on the type of vinyl monomer, the type of polymerization initiator, and the like.

  The radical polymerization reaction includes radical copolymerization in addition to radical homopolymerization of the monomer represented by the formula (4). In the case of radical copolymerization, particularly living radical copolymerization, diblock and triblock copolymerization is possible. As monomers capable of radical copolymerization, monomers having different structures among the monomers represented by formula (4) and monomers capable of radical polymerization other than the monomers represented by formula (4) can be used without limitation. it can.

  Examples of the monomer capable of radical polymerization other than the monomer represented by the formula (4) (hereinafter also referred to as “combined monomer”) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic acid. , (Meth) acrylic esters such as 2-hydroxyethyl (meth) acrylate, menthyl (meth) acrylate; α-acetoxyacrylic acid, α-acetoxymethyl acrylate, α-acetoxymethacrylate menthyl, α-acetamide Captitive substitution monomers such as acrylic acid, methyl α-acetamidoacrylate, menthyl α-acetamidoacrylate, methyl α-methoxyacrylate, menthyl α-methoxyacrylate (α-position is an electron donating group and an electron accepting group) Monomer substituted simultaneously with; cyclohexyl (meth) acrylate, (meth Cycloalkyl group-containing unsaturated monomers such as isobornyl acrylate and adamantyl (meth) acrylate (cycloalkyl group-containing (meth) acrylic acid ester)); maleic acid, fumaric acid, dimethyl fumarate, dibutyl fumarate, itaconic acid, 2 or more carboxyl group-containing unsaturated monomers such as ethyl itaconate, maleic anhydride, maleimide, N-cyclohexylmaleimide, N-phenylmaleimide; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-hydroxyethyl Amine-containing unsaturated monomers such as (meth) acrylamide ((meth) acrylic acid amide); styrene, α-methylstyrene, α-methoxystyrene, α-methoxy-2-methoxystyrene, 2-methylstyrene, 4-methylstyrene , 4-tert Aromatic unsaturated monomers such as butoxystyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 1-vinylnaphthalene, divinylbenzene, 4-styrenesulfonic acid or alkali metal salts thereof (sodium salt, potassium salt, etc.); 2 -Heterocyclic-containing unsaturated monomers such as vinylpyridine, 4-vinylpyridine, 2-vinylthiophene, 1-vinyl-2-pyrrolidone and vinylcarbazole; Vinylamides such as N-vinylacetamide and N-vinylbenzoylamide; Ethylene and propylene Α-olefin such as 1-hexene; diene monomer such as butadiene and isoprene; bifunctional having two acryloyl groups such as divinylbenzene, 4,4′-divinylbiphenyl, 1,6-hexanediol di (meth) acrylate ( (Meth) acrylate monomers, Polyfunctional monomers such as polyfunctional (meth) acrylate monomers having three or more acryloyl groups such as pentaerythritol penta (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate; urethane (Meth) acrylate, epoxy (meth) acrylate, (meth) acrylate oligomers such as polyester (meth) acrylate, (meth) acrylonitrile, methyl vinyl ketone, methyl isopropenyl ketone, ethyl vinyl sulfide, vinyl benzoate, vinyl acetate, chloride Examples include vinyl, vinylidene chloride, ethyl α-cyanoacrylate, coumarin, indene, indone and the like.

  When using a combination monomer in addition to the monomer represented by formula (4), the charge ratio of the combination monomer in all monomers is generally 40 mol% or less, preferably 30 mol% or less, more preferably 20 mol% or less. is there. The polymer having a repeating unit represented by the formula (3) obtained by radical polymerization reaction has a molar fraction of units derived from the combined monomer of usually 20 mol% or less, preferably 15 mol% or less, more preferably Is 12 mol% or less.

  Any radical polymerization initiator may be used as long as it can generally be used in radical polymerization, and the same kind of radical polymerization initiator as that described for production method 1 of the present invention can be used.

The amount of the radical polymerization initiator used may be appropriately adjusted depending on the polymer to be obtained, but is represented by the formula (4) with respect to 1 mol of the monomer represented by the formula (4) or in the case of copolymerization. It is usually 1 × 10 ^{−6 to} 1 mol, preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ , more preferably 1 × 10 ⁻³ to 1 × 10 ⁻² with respect to 1 mol of all monomers including the monomer. .
Among the above radical polymerization methods, the living radical polymerization method is particularly preferable because a polymer in which molecular weight, molecular weight distribution, steric structure and the like are more highly controlled can be produced.

Preferred living radical polymerization initiators include organic tellurium mediated living radical polymerization initiator systems, specifically AIBN / di-n-butyl ditelluride (DBT), AIBN / diphenyl ditelluride, AIBN / ethyl. Examples include 2-methyl-2-methylterranyl-propionate, AIBN / ethyl 2-methyl-2-butylterranyl-propionate (EMBTP), AIBN / ethyl 2-methyl-2-phenylterranyl-propionate, AIBN / DBT / EMBTP, and the like. .
In this case, the amount of AIBN used may be appropriately adjusted depending on the polymer to be obtained. However, the monomer represented by the formula (4) in the case of copolymerization with respect to 1 mol of the monomer represented by the formula (4). The amount is usually 1 × 10 ^{−6 to} 1 mol, preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ , more preferably 1 × 10 ⁻³ to 1 × 10 ⁻² with respect to 1 mol of all monomers including The amount of organic tellurium used is usually 1 × based on 1 mol of the monomer represented by the formula (4) or 1 mol of all monomers including the monomer represented by the formula (4) in the case of copolymerization. 10 ^{−6 to} 1 mol, preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ , more preferably 1 × 10 ⁻³ to 1 × 10 ⁻² .

  In the living radical polymerization, the production method of the block copolymer is as follows. This copolymerization contains at least one monomer represented by the formula (4), and the above combination monomers can be used in addition. In the case of AB-type diblock copolymerization, for example, in a nitrogen-substituted glove box or a degassed container, the monomer represented by formula (4) is added to the radical initiator in the presence or absence of a solvent. By adding and reacting, a polymer having a repeating unit represented by the formula (3) is obtained. Thereafter, a second monomer (a monomer represented by different formula (4) or a combined monomer) is mixed to obtain a copolymer. Further, the order of addition of the monomers may be reversed, and the monomer represented by the formula (4) may be reacted after the second monomer is reacted first. Furthermore, triblock copolymers such as ABA type and ABC type can also be produced by sequentially mixing the monomers after producing the above diblock copolymer.

The reaction temperature and reaction time may be appropriately adjusted depending on the type of the vinyl monomer and the type of the polymerization initiator. Preferably, each is stirred at 30 to 100 ° C. for 1 to 30 hours. At this time, the pressure is usually a normal pressure, but may be increased or decreased. At this time, examples of the inert gas include nitrogen, argon, helium, and the like. Argon and nitrogen are preferable. Nitrogen is particularly preferable.
By the polymerization reaction, a polymer having stereoregularity having a repeating unit represented by the formula (3) in the molecule is obtained. The ratio (m: r) of the meso duplex (m) to the racemo duplex (r) in the polymer is 60:40 to 100: 0, and (m: r) is 65:35 to 100: 0. Is preferable, 70:30 to 100: 0 is more preferable, 75:25 to 100: 0 is more preferable, and 80:20 to 100: 0 is particularly preferable. This ratio can be confirmed by ¹³ C-NMR analysis of a polymer having a repeating unit obtained by a ring-opening reaction.
In general, a polymer having a repeating unit represented by the general formula (3) tends to decrease in solubility in an organic solvent (for example, benzene, toluene, etc.) as the ratio of m (meso) increases.
The degree of polymerization of the polymer obtained by the radical polymerization reaction can be appropriately adjusted depending on the reaction time, initiator concentration, reaction temperature, solvent, etc., but the number average degree of polymerization is 10 to 20,000, particularly 50 to 5,000. It is. Further, the number average molecular weight (Mn) is about 1,000 to 4,000,000, and further about 5,000 to 1,000,000. As a method for measuring Mn and the weight average molecular weight (Mw), the GPC method described in Examples is adopted. In the present invention, a radical polymer having a molecular weight distribution (PDI = Mw / Mn) of 1.01 to 4.0, particularly 1.05 to 2.5 is usually obtained. Among these, the molecular weight distribution (PDI = Mw / Mn) of the living radical polymer is narrow and is controlled between 1.01 and 1.5, and further 1.05 to 1.30, particularly 1.1 to 1.25. Can be controlled within the range.

  Using a polymer obtained by subjecting a monomer containing the compound represented by formula (4) to radical polymerization treatment, it is formed into a film by an extrusion method. As the extrusion method, a known extrusion molding method can be used, and examples thereof include uniaxial extrusion molding and biaxial extrusion molding.

  The film obtained by the production method 2 of the present invention can be further stretched to obtain the retardation film of the present invention. The stretching process can use general uniaxial stretching. For example, the film is stretched in one direction while fixing both ends of the film and heating. Or when a film is a long roll shape, the both ends of a film are fixed, for example with a nip roll, and it extends | stretches continuously by the difference in the rotation speed of both rolls. The optimum stretching temperature varies depending on the polymer having the repeating unit represented by the general formula (3) in the molecule.

  The stretching temperature is 50 ° C to 300 ° C, more preferably about 150 ° C to 250 ° C.

The draw ratio varies depending on the type, thickness, and desired retardation value of the polymer having the repeating unit represented by formula (3) in the molecule, but is 1.1 to 10 times, more preferably 1.2. About 5 to 5 times is good. For example, when using a monomer in which R ¹ is hydrogen and R ² is an i-propyl group in Formula (3), the ratio is about 1.5 to 2.5 times.
The stretching speed is the same as the stretching temperature, and the optimum stretching speed varies depending on the type of polymer having the repeating unit represented by the general formula (3) in the molecule, but it is usually 10 times stretching / min or less, preferably 5 times stretching / min. Hereinafter, it is more preferably 2.5 times stretching / min or less.

  The thickness of the retardation film obtained by the production method 2 of the present invention is 10 to 500 μm, preferably 20 to 300 μm, more preferably about 30 to 150 μm.

  The retardation film of the present invention can be provided with various functions by being used in combination with other retardation films or polarizing films. For example, when the maximum refractive index in the film plane is na, the refractive index in the direction orthogonal to the film plane is nb, and the refractive index in the thickness direction is nc, na> nb> nc, na> nb = nc, Laminate another retardation film such that na = nb> nc, na = nb <nc, na> nc> nb and the retardation film of the present invention so that each slow axis has a desired angle. Thus, the composite retardation film of the present invention is obtained. Since this composite retardation film is different in wavelength dispersion and viewing angle characteristics from each retardation film alone, it is possible to further enhance the functions. Specifically, for example, the retardation film of the present invention and the retardation film satisfying na> nb> nc or na> nb = nc or na = nb> nc are set so that the slow axes thereof are parallel or orthogonal to each other. The composite retardation film obtained by laminating is improved than the viewing angle dependency of each. In addition, as a method of laminating | stacking, the method of bonding with an acrylic adhesive or an adhesive agent is mentioned, for example. An acrylic pressure-sensitive adhesive is suitably used as the pressure-sensitive adhesive when laminating, and various adhesives such as polyvinyl alcohol, urethane, isocyanate, acrylic, and epoxy can be appropriately used as the adhesive. Other retardation films include polycarbonate, polyarylate, polyethersulfone, norbornene derivatives, cycloolefin polymers, or cellulose derivatives described in Patent Document 2 and JP-A No. 2002-131539, which are uniaxially or biaxially stretched. The retardation film etc. which are obtained by these are mentioned.

Another aspect of the present invention is a liquid crystal cell comprising the retardation film of the present invention.
Another aspect of the present invention is a liquid crystal display device including the retardation film of the present invention.
The retardation film of the present invention is a retardation film capable of expressing optical characteristics as a negative A plate only by uniaxial stretching without being biaxially stretched, and a liquid crystal display cell comprising the retardation film of the present invention, and A liquid crystal display device provided with the retardation film of the present invention has excellent characteristics such as improved viewing angle characteristics as compared with conventional liquid crystal display devices.

  EXAMPLES Hereinafter, although this invention is explained in full detail using an Example, the scope of the present invention is not limited to this.

[measuring equipment]
In Examples and Comparative Examples, various physical properties were measured with the following equipment.
1H-NMR and 13C-NMR: JEOL EX-400 (400 MHz)
IR: JASCO FT / IR-230
Optical rotation: JASCO P-1030
Separation, purification: Tosoh HLC-8020
Molecular weight (number average molecular weight Mn, weight average molecular weight Mw) and molecular weight distribution (Mw / Mn): GPC (gel permeation chromatography): Tosoh HLC-8220 (column-TSKgel G7000HHR + G5000HHR + G3000) polystyrene standard

[Manufacture of monomers]
Synthesis example 1 (racemic monomer)
(Synthesis of 5-methylene-2-isopropyl-1,3-dioxolan-4-one)
600.0 g (5.99 mol) of isobutyraldehyde, 432.0 g (5.99 mol) of a racemic mixture of D-lactic acid and L-lactic acid, and 1.0 g (0.05 mmol) of p-toluenesulfonic acid were dissolved in 300 ml of toluene. A reflux condenser equipped with a Dean-Stark fractionator is attached to a 500 ml flask and refluxed for 5 hours. After the reaction, the reaction mixture was neutralized and washed with an aqueous sodium hydrogen carbonate solution, extracted with ether, and then the extract was dried over anhydrous magnesium sulfate. Thereafter, ether was distilled off to obtain 710.0 g (yield: 82.2%) of 5-methyl-2-isopropyl-1,3-dioxolan-4-one.
Formation of the target product was confirmed by IR, 1H-NMR. The optical rotation of 5-methylene-2-isopropyl-1,3-dioxolan-4-one obtained by this method was [α] D = 0 (CHCl 3).
5-methyl-2-isopropyl-1,3-dioxolan-4-one obtained above (60.0 g, 0.41 mol), N-bromosuccinimide, 73.8 g (0.41 mol), 2,2′-azobis ( 180 mg (1.1 mmol) of tolyl in isobutyro (AIBN) was dissolved in 180 ml of carbon tetrachloride and refluxed in a flask equipped with a reflux condenser for 4 hours. After the reaction, the salt precipitated by filtration was removed, and carbon tetrachloride in the filtrate was distilled off to obtain 83.0 g (0.36 mol) of 5-bromo-5-methyl-2-isopropyl-1,3-dioxolan-4-one. )
350 ml of the bromo compound and 350 ml of dehydrated benzene were placed in a dropping funnel and a flask equipped with a reflux condenser. The solution was slowly added dropwise and then refluxed for an additional hour. After the reaction, the salt precipitated by filtration is removed, and the dry benzene in the filtrate is distilled off. -20.0 g (yield: 38.9%) of dioxolan-4-one was produced.
5-Methylene-2-isopropyl-1,3-dioxolan-4-one:
IR (neat, cm-1) 1668 (C = C), 1798 (C = O), 2883-2974 (isopropyl)
1H-NMR (CDCl3, ppm) 1.00 (d, J = 0.8 Hz, 3H), 1.02 (d, J = 0.8 Hz, 3H), 2.04 (m, 1H), 4.86 (D, J = 2.8 Hz, 1H), 5.15 (d, J = 2.8 Hz, 1H), 5.60 (d, J = 4.4 Hz, 1H)
[Α] D = 0 (CHCl 3)
The obtained compound was a colorless and transparent liquid, and its viscosity was 5.4 mPa · s when measured at 25 ° C. using an E-type viscometer (TV-20: manufactured by Toki Sangyo Co., Ltd.). It was.

Synthesis example 2 (chiral monomer)
(Synthesis of 5-methylene-2-isopropyl-1,3-dioxolan-4-one)
435.2 g (6.04 mol) of isobutyraldehyde, 548.2 g (6.09 mol) of L-lactic acid, and 2.0 g (0.1 mmol) of p-toluenesulfonic acid were dissolved in 300 ml of n-pentane and subjected to Dean-Stark fractional distillation. A reflux condenser equipped with a vessel was attached to a 500 ml flask and refluxed for 5 hours. After the reaction, the reaction mixture was neutralized and washed with an aqueous sodium hydrogen carbonate solution, extracted with ether, and then the extract was dried over anhydrous magnesium sulfate. Thereafter, ether was distilled off to obtain a diastereomeric mixture of 5-methyl-2-isopropyl-1,3-dioxolan-4-one. This target product consisted of a diastereomeric mixture of cis / trans = 85/15 and was subjected to the next reaction without optical resolution.
The following steps were performed according to Production Example 1 for monomer synthesis.
Formation of the target product was confirmed by IR, 1H-NMR. The optical rotation of 5-methylene-2-isopropyl-1,3-dioxolan-4-one obtained by this method was [α] D = −5.6 (CHCl 3).
The obtained compound was a colorless and transparent liquid, and its viscosity was 2.4 mPa · s when measured at 25 ° C. using an E-type viscometer (TV-20: manufactured by Toki Sangyo Co., Ltd.). It was.

[Example 1]
A 20 mm × 50 mm × 0.2 mm deep mold is made on a glass substrate with a heat-resistant release tape, and the compound obtained in Synthesis Example 1 is dropped into it, and irradiated with 3000 mJ / cm ² with a high-pressure mercury lamp. After curing by irradiating an amount of ultraviolet rays, the sheet was removed from the mold to obtain a sheet-like cured product. The obtained cured product was a colorless and transparent film having a film thickness of about 200 μm. When pencil hardness was measured according to JIS K5600-5-4, the 2H pencil did not cause scratches.

[Example 2]
Create a 20 mm x 50 mm x 0.2 mm deep mold with heat-resistant release tape on a glass substrate, drop the compound obtained in Synthesis Example 1 into it, heat cure at 100 ° C for 3 hours, It peeled from the type | mold and the sheet-like hardened | cured material was obtained. The obtained cured product was a colorless and transparent film having a film thickness of about 200 μm. When pencil hardness was measured according to JIS K5600-5-4, the 2H pencil did not cause scratches.

[Example 3]
A sheet-like cured product was obtained in the same manner as in Example 2. The obtained cured product was a colorless and transparent film having a film thickness of about 200 to 300 μm. This is cut into a size of about 1.5 cm × 5 cm and used as a bulk film for stretching. The film is stretched 1.5 times while rolling on a hot plate heated to 160 ° C., and a retardation film 1 having a film thickness of 198 μm is obtained. Obtained.

[Example 4]
A sheet-like cured product was obtained in the same manner as in Example 2. The obtained cured product was a colorless and transparent film having a film thickness of about 200 to 300 μm. This was cut into a size of about 1.5 cm × 5 cm, used as a bulk film for stretching, and stretched twice while rolling on a hot plate heated to 200 ° C. to obtain a retardation film 2 having a thickness of 150 μm. .

[Example 5]
A sheet-like cured product was obtained in the same manner as in Example 4 except that the compound obtained in Synthesis Example 2 was used instead of the compound obtained in Synthesis Example 1. The obtained cured product was a colorless and transparent film having a film thickness of about 200 to 300 μm. This was stretched in the same manner as in Example 4 to obtain a retardation film 3 having a film thickness of 236 μm.

  Retardation film of the present invention obtained in Examples 3 to 5, biaxially stretched ZEONOR (Essina manufactured by Sekisui Chemical Co., Ltd.) C-Plate (Comparative Example 1), uniaxially stretched retardation film (PCR140) A-Plate (Comparative Example) For 2), the three-dimensional refractive index was measured using an automatic birefringence meter (KOBRA-WPR manufactured by Oji Scientific Instruments). The results are shown in Table 1.

As shown in Table 1, the retardation films of the present invention obtained in Examples 3 to 5 have a three-dimensional birefringence relationship of nx ≧ nz> ny, and are optical as a negative A plate. It was confirmed that the characteristics can be expressed.
Thus, according to the present invention, a retardation film capable of expressing optical characteristics as a negative A plate only by uniaxial stretching rather than biaxial stretching can be provided.

Claims (7)

The three-dimensional refractive index at a measurement wavelength of 590 nm is the following formula (1) or (2):
nx ≧ nz> ny (1)
nz ≧ nx> ny (2)
(In the formulas (1) and (2), nx is the refractive index in the stretching direction in the retardation film plane, ny is the refractive index in the stretching direction and the orthogonal direction in the retardation film plane, and nz is the thickness. Is the refractive index in the direction)
General formula (3):

(In the formula, R ¹ and R ² are different and each independently has a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. Or R ¹ and R ² may be bonded to each other to form an asymmetric ring with the adjacent asymmetric carbon (C *). * Represents an asymmetric carbon.)
A retardation film formed by stretching a film made of a polymer having a repeating unit represented by The polymer is represented by the following formula (4):

(Wherein R ¹ , R ² and * are as defined in formula (3).)
The retardation film of Claim 1 obtained by radical-polymerizing the monomer containing the compound represented by these. Following formula (4) :

(In the formula, R ¹ and R ² are different and each independently has a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. Or R ¹ and R ² may be bonded to each other to form an asymmetric ring with the adjacent asymmetric carbon (C *). * Represents an asymmetric carbon.)
A three-dimensional refractive index at a measurement wavelength of 590 nm, which includes further stretching treatment of a monomer containing a compound represented by formula (1) or a film obtained by casting a solution of the monomer and subjecting it to radical polymerization treatment, A method for producing a retardation film satisfying 1) or (2).
nx ≧ nz> ny (1)
nz ≧ nx> ny (2)
(In the formulas (1) and (2), nx is the refractive index in the stretching direction in the retardation film plane, ny is the refractive index in the stretching direction and the orthogonal direction in the retardation film plane, and nz is the thickness. The refractive index in the direction.) Following formula (4) :

(In the formula, R ¹ and R ² are different and each independently has a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a substituent. Or R ¹ and R ² may be bonded to each other to form an asymmetric ring with the adjacent asymmetric carbon (C *). * Represents an asymmetric carbon.)
A three-dimensional refractive index at a measurement wavelength of 590 nm including further stretching the film obtained by the extrusion method using a polymer obtained by subjecting a monomer containing a compound represented by radical polymerization treatment to the following formula ( A method for producing a retardation film satisfying 1) or (2).
nx ≧ nz> ny (1)
nz ≧ nx> ny (2)
(In the formulas (1) and (2), nx is the refractive index in the stretching direction in the retardation film plane, ny is the refractive index in the stretching direction and the orthogonal direction in the retardation film plane, and nz is the thickness. The refractive index in the direction.)   The manufacturing method according to claim 3 or 4, wherein the stretching is uniaxial stretching.   A liquid crystal cell comprising the retardation film according to claim 1.   A liquid crystal display device comprising the retardation film according to claim 1.