JP2008009345A - Phase difference film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase difference film in which adhesion between respective layers is excellent, variation of phase difference is small even under high temperature high humidity atmosphere and further which is excellent in productivity. <P>SOLUTION: The phase difference film comprises a transparent substrate made of a resin material and an optical anisotropic layer which is formed on the transparent substrate and which contains the resin material and an optical anisotropic material having refractive index anisotropy. The phase difference film has a property as an optically negative C plate and amount of solvents remaining in the phase difference film is ≤20 mg/m<SP>2</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retardation film used for a viewing angle compensation film of a liquid crystal display device.

Since the liquid crystal display device has features such as power saving, light weight, thinness, etc., the conventional C
Instead of RT display, it has been rapidly spreading in recent years. As shown in FIG. 3, the general liquid crystal display device includes an incident-side polarizing plate 102 </ b> A, an output-side polarizing plate 102 </ b> B, and a liquid crystal cell 104. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light (schematically illustrated by arrows in the figure) having a vibration surface in a predetermined vibration direction. They are arranged to face each other in a crossed Nicol state so as to have a right angle relationship with each other. The liquid crystal cell 104 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

  Such a liquid crystal display device is known to use various driving methods depending on the arrangement form of the liquid crystal material used in the liquid crystal cell. The main liquid crystal display devices that are widely used today are TN, It is classified into STN, MVA, IPS and OCB. In particular, today, those having the MVA and IPS drive systems have come into widespread use.

  On the other hand, the liquid crystal display device has the advantages as described above, but there is a problem of viewing angle dependency as a unique problem. This problem of viewing angle dependency is a problem in which the color and contrast of a visually recognized image change between when the liquid crystal display device is viewed from the front and when viewed from an oblique direction. Such a problem of viewing angle characteristics is becoming more serious as the liquid crystal display device has recently been enlarged.

  In order to improve such a problem of viewing angle dependency, various techniques have been developed so far, and a representative method is a method using a retardation film. The method using this retardation film improves the viewing angle problem by disposing a retardation film 30 having predetermined optical characteristics between the liquid crystal cell 104 and the polarizing plate 102B as shown in FIG. It is a method to do. Since this method can improve the problem of the viewing angle dependency only by incorporating the retardation film 30 in the liquid crystal display device, it has been widely used as a method for easily obtaining a liquid crystal display device having excellent viewing angle characteristics. .

  As the retardation film, an alignment film 42 is provided on an arbitrary transparent substrate 41 as shown in FIG. 4, and an optical anisotropic layer 43 having an optical anisotropic material is further formed on the alignment film 42. In general, the alignment film 42 has a configuration in which the optically anisotropic material is aligned by the alignment regulating force of the alignment film 42 to develop a desired refractive index anisotropy. As such a retardation film, for example, in Patent Document 1 or Patent Document 2, an optically anisotropic layer having a cholesteric regular molecular structure (an optically anisotropic layer exhibiting birefringence) is used. A film is disclosed. Patent Document 3 discloses a retardation film using an optically anisotropic layer (an optically anisotropic layer exhibiting birefringence) made of a discotic compound.

The retardation film using such an optically anisotropic layer is advantageous in that the refractive index anisotropy can be arbitrarily adjusted by changing the arrangement form of the optically anisotropic material, Since the optically anisotropic material has a large intrinsic birefringence, it has an advantage that the refractive index anisotropy is easily developed.
However, on the other hand, the retardation film having such an optically anisotropic layer has a problem that adhesion between the transparent substrate and the optically anisotropic layer is low.

  In this regard, Patent Document 4 discloses a retardation film in which a material containing a resin material and an optically anisotropic material constituting the transparent substrate is used as the optically anisotropic layer. Such a retardation film can improve the adhesion between the optically anisotropic layer and the transparent substrate by containing the resin material constituting the transparent substrate in the optically anisotropic layer. Therefore, it has attracted attention as a highly practical retardation film that overcomes the drawbacks of conventional retardation films.

By the way, as a method for producing a retardation film using an optically anisotropic layer containing an optically anisotropic material as described above, the optically anisotropic material is usually dissolved in a solvent on the transparent substrate. A method of forming the optically anisotropic layer by coating the applied optically anisotropic layer forming coating liquid and arranging the optically anisotropic materials is used. Although such a method is generally widely used as a method for producing a retardation film, in the retardation film in which the solvent used in the optically anisotropic layer forming coating solution is produced. If the residual solvent remains, the phase difference of the optically anisotropic layer changes due to volatilization of the residual solvent over time. In particular, in a high-temperature and high-humidity atmosphere, the above-mentioned residual solvent is likely to volatilize over time, and such problems are becoming apparent.
For this reason, when manufacturing a retardation film by the above methods, it is calculated | required that the amount of residual solvents should be made as small as possible.

  Here, the retardation film disclosed in Patent Document 4 has an advantage that the optically anisotropic layer is excellent in adhesiveness by containing the resin constituting the substrate. On the other hand, the optically anisotropic material contained in the optically anisotropic layer needs to be arranged in the coexistence with the resin material. It has been found that the time required for the alignment of the functional material is increased. Therefore, when producing a retardation film as disclosed in Patent Document 4, a solvent having a high boiling point is used as the solvent used in the optically anisotropic layer forming coating solution, and the solvent is dried. In many cases, the time required for the optical anisotropy material is increased by increasing the time required for the process. For this reason, in the process of producing a retardation film as disclosed in Patent Document 4, in order to prevent the solvent having a high boiling point from remaining in the optically anisotropic layer, the above optical anisotropy is used. After arranging the functional materials, it is necessary to sufficiently reduce the solvent by performing a drying process for a long time or a drying process at a high temperature.

However, if a long drying process is performed in order to sufficiently reduce the amount of residual solvent, the productivity of the retardation film is remarkably lowered and the energy cost is increased, so that industrial productivity is impaired. There is a problem that. In addition, if the drying process is performed at a high temperature, the amount of shrinkage of the film accompanying drying increases, wrinkles occur in the retardation film during production, and the curl of the retardation film produced increases. There is a problem such as.
On the other hand, if the drying is insufficient, the amount of residual solvent in the produced retardation film increases, and the amount of change in retardation over time in a high-temperature and high-humidity atmosphere is more than the allowable range of the liquid crystal display device. There is a problem that it becomes large.

  For this reason, the retardation film as disclosed in Patent Document 4 has an advantage of excellent adhesion, but it is difficult to achieve both the durability of retardation and productivity. There was a problem of lack of practicality.

JP-A-3-67219 JP-A-4-322223 Japanese Patent Laid-Open No. 10-312166 International Publication No. 2006/028217 Pamphlet

  The present invention has been made in view of the above problems, and has good adhesion between layers, little retardation variation over time even in a high-temperature and high-humidity atmosphere, and a retardation film with excellent productivity. The main purpose is to provide

In the retardation film having the configuration of the present invention, the present inventors have intensively studied the relationship between the amount of residual solvent in the retardation film and the amount of change in retardation in a high-temperature and high-humidity atmosphere. The present inventors have found that the amount of change in retardation under a high-temperature and high-humidity atmosphere is remarkably reduced around the above-mentioned residual solvent amount of about 20 mg / m ² , thereby completing the present invention.

That is, in order to solve the above-described problems, the present invention provides an optical material containing a transparent substrate made of a resin material, and the resin material and an optically anisotropic material having refractive index anisotropy formed on the transparent substrate. A retardation film having properties as an optically negative C plate, wherein the amount of the solvent remaining in the retardation film is 20 mg / m ² or less. A retardation film is provided.

According to the present invention, when the amount of the solvent remaining in the retardation film is 20 mg / m ² or less, the change in retardation due to the evaporation of the solvent from the retardation film in a high temperature and high humidity atmosphere. The amount can be reduced. For this reason, according to the present invention, it is possible to obtain a retardation film with little variation in retardation even under a high temperature and high humidity atmosphere.
Further, according to the present invention, since the amount of the solvent remaining in the retardation film is 20 mg / m ² , an excessive drying step is not necessary in the process for producing the retardation film of the present invention. An excellent retardation film can be obtained.
Furthermore, according to this invention, the said optically anisotropic layer contains the resin material which comprises the said transparent substrate, The adhesiveness of the said optically anisotropic layer and the said transparent substrate can be improved. it can.
For this reason, according to the present invention, the adhesiveness between the optically anisotropic layer and the transparent substrate is good, there is little variation in retardation even in a high temperature and high humidity atmosphere, and the retardation is excellent in productivity. A film can be obtained.

  In the present invention, the boiling point of the solvent remaining in the retardation film is preferably 110 ° C. or higher. Even if the solvent having such a boiling point remains in the retardation film, it is difficult to volatilize in a high-temperature and high-humidity atmosphere, so that a retardation film with less variation in retardation can be obtained in a high-temperature and high-humidity atmosphere. Because.

  The present invention provides an effect that a retardation film having good adhesion between layers, little change in retardation over time even in a high temperature and high humidity atmosphere, and excellent productivity can be obtained.

  Hereinafter, the retardation film of the present invention will be described in detail.

The retardation film of the present invention includes a transparent substrate made of a resin material, an optically anisotropic layer formed on the transparent substrate and containing the resin material and an optically anisotropic material having refractive index anisotropy, And having an optically negative C plate property, the amount of the solvent remaining in the retardation film is 20 mg / m ² or less.

Such a retardation film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of the retardation film of the present invention. As illustrated in FIG. 1, a retardation film 10 of the present invention includes a transparent substrate 1 made of a resin material, a resin material that is formed on the transparent substrate 1 and forms the transparent substrate 1, and an anisotropic refractive index. And an optically anisotropic layer 2 containing an optically anisotropic material having properties.
The retardation film 10 of the present invention has properties as an optically negative C plate as a whole of the retardation film 10.
In such an example, the retardation film 10 of the present invention is characterized in that the amount of the solvent remaining in the retardation film 10 is 20 mg / m ² or less.

Conventionally, a retardation film having a structure containing a resin constituting a transparent substrate in an optically anisotropic layer as in the present invention has an advantage of excellent adhesion between the optically anisotropic layer and the transparent substrate. However, on the other hand, the time required for arranging the optically anisotropic material in the manufacturing process is increased. For this reason, when producing a retardation film having such a configuration, a coating liquid for forming an optically anisotropic layer containing a high-boiling solvent that takes time to dry is used, and the arrangement of the optically anisotropic materials described above is used. In many cases, measures were taken to lengthen the time.
On the other hand, if the amount of residual solvent in the retardation film is large, the amount of change in retardation due to volatilization of the remaining solvent over time in a high-temperature and high-humidity atmosphere becomes large. In the process of producing a film, it has been necessary to carry out a long drying process or a drying process at a high temperature in order to prevent the high boiling point solvent from remaining in the optically anisotropic layer.
However, if a drying process is performed for a long time in order to sufficiently reduce the amount of residual solvent, the productivity of the retardation film is remarkably lowered and the energy cost is increased, so that industrial productivity is impaired. There was a problem. In addition, if the drying process is performed at a high temperature, the amount of shrinkage of the film accompanying drying increases, wrinkles occur in the retardation film during production, and the curl of the retardation film produced increases. There was a problem such as.
For this reason, the retardation film having the configuration of the present invention has the advantage of excellent adhesion, but both the durability of retardation in a high-temperature and high-humidity atmosphere and the productivity are conventionally known. It was difficult to obtain an excellent retardation film.

In this respect, the present invention realizes both the above-mentioned retardation property and productivity by making the residual solvent amount in the retardation film 20 mg / m ² or less, and the adhesion of each layer is good. In addition, it is possible to provide a retardation film that exhibits little change in retardation over time even in a high-temperature and high-humidity atmosphere and that is excellent in productivity.
According to the present invention, when the amount of the solvent remaining in the retardation film is 20 mg / m ² or less, the retardation caused by volatilization of the solvent from the retardation film over time in a high temperature and high humidity atmosphere. The amount of change in sex can be reduced. For this reason, according to the present invention, it is possible to obtain a retardation film with little variation in retardation over time even in a high temperature and high humidity atmosphere.
Further, according to the present invention, since the amount of the solvent remaining in the retardation film is 20 mg / m ² , an excessive drying process is not required in the process for producing the retardation film of the present invention, so that productivity is improved. An excellent retardation film can be obtained.
Furthermore, according to this invention, the adhesiveness of the said optically anisotropic layer and the said transparent substrate can be improved because the said optically anisotropic layer contains the resin material which comprises the said transparent substrate.

  For this reason, according to the present invention, even a retardation film having the configuration of the present invention has little variation in retardation over time even in a high-temperature and high-humidity atmosphere, and is excellent in productivity. A retardation film can be obtained.

Moreover, the phase difference film of the present invention has a residual solvent amount of 20 mg / m ² or less. For example, the phase difference film of the present invention is formed into a long shape and wound into a roll. In such a case, there is an advantage that the “blocking phenomenon” in which the retardation films which are overlapped with each other do not adhere closely can be reduced.

Furthermore, the retardation film of the present invention has a residual solvent amount of 20 mg / m ² or less. For example, when the optically anisotropic layer contains a polymerization initiator or a polymerization inhibitor, the polymerization is performed. The advantage that the yellowness of the optically anisotropic layer can be prevented from changing by volatilization of the initiator over time, and the degree of cure of the optically anisotropic layer by the volatilization of the polymerization inhibitor over time. It also has the advantage that it can be prevented from changing.

The retardation film of the present invention has at least the transparent substrate and an optically anisotropic layer.
Hereafter, each structure used for the retardation film of this invention is demonstrated in order.

1. Optically anisotropic layer First, the optically anisotropic layer used in the present invention will be described. The optically anisotropic layer used in the present invention contains a resin material constituting a transparent substrate described later and an optically anisotropic material having refractive index anisotropy. The optically anisotropic layer used in the present invention has a function of imparting desired retardation to the retardation film of the present invention.
In the present invention, by containing the resin material in the optically anisotropic layer, a retardation film having excellent adhesion between the optically anisotropic layer and the transparent substrate can be obtained.

In addition, in a retardation film using an optically anisotropic layer having an optically anisotropic material as in the present invention, an alignment layer for arranging the optically anisotropic material is generally used. It was the target. However, in the present invention, by containing the resin material in the optically anisotropic layer, the optically anisotropic material is optically negative in the retardation film of the present invention without using such an alignment layer. It becomes possible to arrange so that the property as a C plate can be provided. Therefore, the inclusion of the resin material in the optically anisotropic layer in the present invention results in the need for the alignment layer, and the retardation film of the present invention can be made excellent in productivity. It will also have the advantage.
Hereinafter, such an optically anisotropic layer will be described in detail.

(1) Optically anisotropic material The optically anisotropic material used in the present invention has refractive index anisotropy.
Here, “refractive index anisotropy” means that the refractive index with respect to incident light differs depending on the incident direction of light.

The optically anisotropic material used in the present invention is not particularly limited as long as it can impart a desired retardation to the optically anisotropic layer. In particular, in the present invention, it is preferable to use a rod-like compound as the optically anisotropic material. This is because the rod-shaped compound can exhibit excellent retardation by being regularly arranged, and therefore it is easy to impart desired retardation to the retardation film of the present invention.
Here, the “rod-shaped compound” in the present invention refers to a compound in which the main skeleton of the molecular structure is rod-shaped.

As the rod-like compound, a compound having a relatively small molecular weight is preferable. More specifically, a compound having a molecular weight in the range of 200 to 1200 is preferable, and a compound having a molecular weight in the range of 400 to 800 is particularly preferably used. The reason is as follows.
That is, the optically anisotropic layer used in the present invention contains the optically anisotropic material and a resin material constituting the transparent substrate described later, but the compound having a relatively small molecular weight as the rod-shaped compound. This is because the rod-like compound can be easily mixed with the resin material in the optically anisotropic layer.
In addition, when using the material which has a polymerizable functional group as said rod-shaped compound, the molecular weight of the said rod-shaped compound shall show the molecular weight of the monomer before superposition | polymerization.

  Moreover, it is preferable that the rod-shaped compound used for this invention is a liquid crystalline material which shows liquid crystallinity. This is because the liquid crystalline material has a property of being regularly arranged, and thus by using such a liquid crystalline material, it is easy to impart desired retardation to the retardation film of the present invention.

  The liquid crystalline material is not particularly limited as long as a desired retardation can be imparted to the retardation film of the present invention. Examples of such a liquid crystalline material include materials exhibiting a liquid crystal phase such as a nematic phase, a cholesteric phase, and a smectic phase. In the present invention, any material exhibiting any of these liquid crystal phases can be suitably used, but among these, a liquid crystalline material exhibiting a nematic phase is preferably used. This is because a liquid crystalline material exhibiting a nematic phase is easily arranged regularly as compared with liquid crystalline materials exhibiting other liquid crystal phases.

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

As the rod-shaped compound used in the present invention, those having a polymerizable functional group in the molecule are preferably used, and among them, those having a polymerizable functional group capable of three-dimensional crosslinking are more preferably used. Since the rod-shaped compound has a polymerizable functional group, the rod-shaped compound can be polymerized and fixed. Therefore, an optically anisotropic layer that has excellent alignment stability and is less likely to change over time in retardation. Because it can be obtained.
In the present invention, the rod-shaped compound having the polymerizable functional group may be mixed with the rod-shaped compound having no polymerizable functional group.
The “three-dimensional cross-linking” means that liquid crystal molecules are polymerized three-dimensionally to form a network (network) structure.

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

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

  Specific examples of the rod-like compound used in the present invention include compounds represented by the following formulas (1) to (6).

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

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

  In addition, the said rod-shaped compound used for this invention may be only 1 type, or 2 or more types. For example, when the rod-shaped compound is used by mixing a liquid crystalline material having one or more polymerizable functional groups at both ends and a liquid crystalline material having one or more polymerizable functional groups at one end, The polymerization density (crosslink density) and the optical characteristics can be arbitrarily adjusted by adjusting the ratio, which is preferable.

  The content of the optically anisotropic material contained in the optically anisotropic layer in the present invention is not particularly limited as long as it is within a range in which a desired retardation can be imparted to the retardation film of the present invention. Absent. Especially in this invention, it is preferable to exist in the range of 40 mass%-90 mass%. It is because it may become difficult to provide desired retardation to the retardation film of this invention when content is less than the said range. Moreover, when there is more content than the said range, it is because there exists a possibility that the adhesiveness of an optically anisotropic layer and the transparent substrate mentioned later may fall.

  When a compound having a polymerizable functional group is used as the optically anisotropic material, the optically anisotropic material contained in the optically anisotropic layer is usually polymerized via the polymerizable functional group. It becomes a polymer.

(2) Resin Material Next, the resin material used in the present invention will be described. The resin material used for this invention is the same as the resin material which comprises the transparent substrate mentioned later.
In this invention, the retardation film excellent in the adhesiveness of an optically anisotropic layer and a transparent substrate can be obtained by containing such a resin material in the said optically anisotropic layer.

  Here, since the resin material used in the present invention will be described in detail in the section of “2. Transparent substrate” described later, description thereof is omitted here.

  The amount of the resin material contained in the optically anisotropic layer in the present invention is within a range in which the adhesiveness between the optically anisotropic layer and the transparent substrate described later can be within a desired range in the retardation film of the present invention. There is no particular limitation as long as it is present. Especially in this invention, it is preferable to exist in the range of 10 mass%-60 mass%. This is because if the content is more than the above range, it may be difficult to impart desired retardation to the retardation film of the present invention. Further, if the amount is less than the above range, the adhesion between the optically anisotropic layer and the transparent substrate described later may be insufficient.

(3) Optically anisotropic layer The optically anisotropic layer used in the present invention may contain other compounds in addition to the optically anisotropic material and the resin material. Examples of the other compounds used in the present invention include silicon leveling agents such as polydimethylsiloxane, methylphenylsiloxane, and organically modified siloxane; linear polymers such as polyalkyl acrylate and polyalkyl vinyl ether; fluorine-based interfaces Surfactants such as activators and hydrocarbon surfactants; fluorine leveling agents such as tetrafluoroethylene; photopolymerization initiators and the like.
Especially in this invention, when using the rod-shaped compound which has a polymerizable functional group which superposes | polymerizes by light irradiation as said optically anisotropic material, it is preferable that a photoinitiator is included as said other compound.

  Examples of the photopolymerization initiator used in the present invention include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-amino acetophenone, 4,4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpro Piophenone, p-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethyl ketal, benzylmethoxyethyla Tar, benzoin methyl ether, benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzsuberon, methyleneanthrone, 4-azidobenzylacetophenone, 2,6-bis ( p-azidobenzylidene) cyclohexane, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-phenyl-propanedione 2- (o-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o- Nzoyl) oxime, Michler's ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone , Naphthalene sulfonyl chloride, quinoline sulfonyl chloride, n-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, Adeca N1717, carbon tetrabromide And a combination of a photoreductive dye such as tribromophenylsulfone, benzoin peroxide, eosin, and methylene blue with a reducing agent such as ascorbic acid and triethanolamine. In this invention, these photoinitiators can be used 1 type or in combination of 2 or more types.

  The content of the photopolymerization initiator is not particularly limited as long as the rod-shaped compound can be polymerized in a desired time, but usually 1 to 10 parts by weight with respect to 100 parts by weight of the rod-shaped compound. Is preferably within the range of 3 parts by weight to 6 parts by weight.

  When the photopolymerization initiator is used, a photopolymerization initiation assistant can be used in combination. Examples of such photopolymerization initiation assistants include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as ethyl 2-dimethylaminoethylbenzoate and ethyl 4-dimethylamidebenzoate. Yes, but not limited to these.

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

  In addition, as thickness of the optically anisotropic layer used in the present invention, a desired retardation is imparted to the retardation film of the present invention according to the type of the optically anisotropic material or the transparent substrate described later. If it is in the range which can do, it will not specifically limit. In particular, the thickness of the optically anisotropic layer in the present invention is usually preferably in the range of 0.5 μm to 20 μm.

2. Transparent substrate Next, the transparent substrate used in the present invention will be described. The transparent substrate used in the present invention is made of a resin material.

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

The transparent substrate used in the present invention may have a phase difference. At this time, the retardation value of the transparent substrate is not particularly limited as long as it is within a range in which a desired retardation can be imparted to the retardation film of the present invention. Among them, the transparent substrate used in the present invention preferably has a retardation value at 550 nm in the range of 0 nm to 50 nm.
Here, the retardation value (hereinafter may be simply referred to as “Re”) is the refractive index in the slow axis direction in the in-plane direction of the transparent substrate nx, and the phase advance in the in-plane direction. When the refractive index in the axial direction is ny and the thickness of the transparent substrate is d, this is an amount represented by Re = (nx−ny) × d. And such Re can be measured by a parallel Nicol rotation method, for example using KOBRA-WR by Oji Scientific Instruments.

The wavelength dependency of Re of the transparent substrate used in the present invention may be positive dispersion having a larger value on the short wavelength side than on the long wavelength side, or on the short wavelength side than on the long wavelength side. The inverse dispersion having a small value may be used, and further, flat dispersion in which the value does not change between the long wavelength side and the short wavelength side may be used.
The “positive dispersion” in the present invention is the ratio of the retardation value (Re ₄₅₀ ) at a wavelength of ₄₅₀ nm to the retardation value (Re ₅₅₀ ) at a wavelength of 550 nm (Re ₄₅₀ / Re ₅₅₀ ) (hereinafter simply “Re Is sometimes greater than 1), and the “reverse dispersion” in the present invention means that the Re ratio is smaller than 1. Further, in the present invention, “Flat dispersion” means that the Re ratio is 1.

The transparent substrate used in the present invention preferably has a retardation in the thickness direction (Rth) at a wavelength of 550 nm in the range of 0 nm to 100 nm.
Here, the retardation in the thickness direction (hereinafter sometimes simply referred to as “Rth”) includes the refractive index nx in the slow axis direction in the plane of the transparent substrate and the refraction in the fast axis direction in the plane. It is a value represented by the formula of Rth = {(nx + ny) / 2−nz} × d by the refractive index ny, the refractive index nz in the thickness direction, and the thickness d (nm) of the transparent substrate. The value of retardation (Rth) in the thickness direction in the present invention can be measured by, for example, KOBRA-WR manufactured by Oji Scientific Instruments.

Furthermore, the thickness of the transparent substrate used in the present invention is not particularly limited as long as necessary self-supporting properties are obtained depending on the use of the retardation film of the present invention. Usually, it is appropriately selected from various thickness forms called a plate, a sheet, or a film. In particular, the thickness of the transparent substrate used in the present invention is preferably in the range of 10 μm to 1000 μm, particularly preferably in the range of 20 μm to 125 μm, and more preferably in the range of 30 μm to 80 μm. preferable.
This is because if the thickness of the transparent substrate is thinner than the above range, the necessary self-supporting property may not be imparted to the retardation film of the present invention. Further, when the thickness is larger than the above range, for example, when cutting the retardation film of the present invention, there is a case where processing waste increases or wear of the cutting blade is accelerated.

Examples of the resin material constituting such a transparent substrate include cellulose derivatives, cycloolefin resins, polymethyl methacrylate, polyvinyl alcohol, polyimide, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, amorphous polyolefin, and modified acrylic. Examples include polymers, polystyrene, epoxy resins, polycarbonates, polyesters, and the like.
In particular, in the present invention, it is preferable to use a cellulose derivative or a cycloolefin resin as the resin material. This is because the cellulose derivative and the cycloolefin-based resin are excellent in optical isotropy, and the use of such a resin material facilitates the design of the optical characteristics of the retardation film of the present invention.

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

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

In the present invention, among the above lower fatty acid esters, cellulose acetate can be particularly preferably used. As the cellulose acetate, it is most preferable to use triacetyl cellulose having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0). Since triacetyl cellulose has a molecular structure having a relatively bulky side chain, by using a transparent substrate made of such triacetyl cellulose, adhesion between the transparent substrate and the above optically anisotropic layer can be improved. It is because it can improve more.
Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation can be determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like). In addition, after removing impurities, such as a plasticizer contained in a film, the acetylation degree of the triacetyl cellulose which comprises a triacetyl cellulose film can be calculated | required by said method.

On the other hand, the cycloolefin resin is not particularly limited as long as it is a resin having a monomer unit composed of a cyclic olefin (cycloolefin). Examples of such a monomer comprising a cyclic olefin include norbornene and polycyclic norbornene monomers.
Further, as the cycloolefin resin used in the present invention, either a cycloolefin polymer (COP) or a cycloolefin copolymer (COC) can be suitably used.

  The cycloolefin resin used in the present invention may be a homopolymer of a monomer composed of the above cyclic olefin or a copolymer.

Further, the cycloolefin resin used in the present invention preferably has a saturated water absorption at 23 ° C. of 1% by mass or less, and particularly preferably within a range of 0.1% by mass to 0.7% by mass. . This is because by using such a cycloolefin-based resin, it is possible to make the retardation film of the present invention less susceptible to changes in optical properties and dimensions due to water absorption.
Here, the saturated water absorption is obtained by immersing in 23 ° C. water for 1 week according to ASTM D570 and measuring the increased weight.

  Furthermore, the cycloolefin resin used in the present invention preferably has a glass transition point in the range of 100 ° C to 200 ° C, particularly preferably in the range of 100 ° C to 180 ° C, and in particular, 100 ° C. What is in the range of -150 degreeC is preferable. This is because, when the glass transition point is within the above range, the retardation film of the present invention can be made more excellent in heat resistance and processability.

  Specific examples of the transparent substrate made of cycloolefin resin used in the present invention include, for example, Ticona Topas, JSR Arton, ZEON Corporation ZEONOR, ZEON Corporation ZEONEX, Mitsui Chemicals, Inc. Can be mentioned.

The configuration of the transparent substrate in the present invention is not limited to a configuration composed of a single layer, and may have a configuration in which a plurality of layers are laminated.
Moreover, when it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.

3. Other Configurations The retardation film of the present invention may have other configurations in addition to the optically anisotropic layer and the transparent substrate. Such other configurations are not particularly limited as long as a desired function can be imparted to the retardation film of the present invention in accordance with the use of the retardation film of the present invention.
Examples of such other configurations include a hard coat layer, an overcoat layer, an AG layer, and an AR layer.

4). Retardation Film The retardation film of the present invention is characterized in that the amount of residual solvent is 20 mg / m ² or less. The residual solvent amount of the retardation film of the present invention is not particularly limited as long as it is 20 mg / m ² or less. In particular, in the present invention, the amount of the residual solvent is preferably 18 mg / m ² or less, particularly preferably 15 mg / m ² or less. This is because, when the amount of residual solvent is in the above range, the retardation film of the present invention can have a small amount of change in the retardation layer in a higher temperature and high humidity atmosphere.

Here, the residual solvent amount in the present invention means the total amount of the solvent remaining in the entire retardation film of the present invention.
The residual solvent is usually the solvent used when the retardation layer is formed or the solvent used when the transparent substrate is formed.

As the amount of the residual solvent in the present invention, a value measured by the gas chromatography method under the following conditions is used.
<Measurement instrument>
Shimadzu GC-9A (Data processor: Shimadzu CR-4A)
<Measurement conditions>
A phase difference film having a size of 100 mm × 100 mm is sealed in a vial, and the sealed vial is heated under the following conditions and then measured by gas chromatography.
・ Insulation temperature: 150 ℃
・ Insulation time: 10 minutes ・ Repetition count: 1
-Column temperature: 100 ° C
・ Vaporization chamber temperature: 150 ℃
・ Syringe temperature: 150 ° C
・ Detector polarity: 2
・ Detection range: 2
・ Period: 5

  The solvent remaining in the retardation film of the present invention is not particularly limited, but a solvent having a boiling point of 110 ° C. or higher is preferable. Even if the solvent having such boiling point remains in the retardation film, it is difficult to volatilize in a high temperature and high humidity atmosphere, so that a retardation film with less variation in retardation can be obtained in a high temperature and high humidity atmosphere. Because it can.

  The solvent remaining in the retardation film of the present invention preferably has a refractive index in the range of 1.3 to 1.6. This is because, if such a solvent is used, even if it is volatilized from the retardation film over time, the fluctuation in retardation can be reduced.

  Examples of such residual solvent include hydrocarbon solvents such as benzene and hexane; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and methylcyclohexanone; ether solvents such as tetrahydrofuran and 1,2-dimethoxyethane: Alkyl halide solvents such as chloroform and dichloromethane; ester solvents such as methyl acetate, butyl acetate and propylene glycol monomethyl ether acetate; amide solvents such as N, N-dimethylformamide, and sulfoxide solvents such as dimethyl sulfoxide, etc. Can be mentioned.

  The solvent remaining in the retardation film of the present invention may be only one type of solvent or two or more types of solvents.

The retardation of the retardation film of the present invention is not particularly limited as long as it exhibits a property as an optically negative C plate.
Here, “the property as an optically negative C plate” means the refractive index nx in the slow axis direction in the plane of the retardation film of the present invention and the refractive index ny in the fast axis direction in the plane. And the relationship of nx = ny> nz, nx>ny> nz, or ny>nx> nz is established in the refractive index nz in the thickness direction.
Among them, the retardation film of the present invention preferably has properties as a λ / 4 plate or properties as a λ / 2 plate.
Here, “having the properties as a λ / 4 plate” usually means that the absolute value of retardation shows a value of ¼ of the wavelength of incident light. The retardation film of the present invention preferably has an absolute value of retardation at a wavelength of 550 nm in the range of 120 nm to 150 nm.
Moreover, the above-mentioned “having properties as a λ / 2 plate” usually means that the absolute value of retardation shows a half value of the wavelength of incident light. The retardation film of the invention preferably has an absolute value of retardation at a wavelength of 550 nm in a range of 250 nm to 300 nm.
Here, since the definition of Re and the measurement method are the same as those described in the section “2. Transparent substrate”, the description thereof is omitted here.

  The wavelength dependency of Re of the retardation film of the present invention may be positive dispersion having a larger value on the short wavelength side than on the long wavelength side (Re becomes a function of decreasing the wavelength), or may be long. The reverse dispersion may be a smaller value on the short wavelength side than on the wavelength side (Re becomes an increase function of the wavelength), and further, flat dispersion in which the value does not change between the long wavelength side and the short wavelength side. May be. Here, the “normal dispersion”, “reverse dispersion”, and “flat dispersion” are the same as those described in the section “2. Transparent substrate”, and thus the description thereof is omitted here.

The retardation (Rth) in the thickness direction of the retardation film of the present invention is preferably in the range of 0 nm <Rth ≦ 400 nm.
Here, the retardation in the thickness direction (Rth) is the in-plane slow axis direction refractive index nx, the in-plane fast axis direction refractive index ny, the thickness direction refractive index nz, and the transparent substrate. The thickness d (nm) is a value represented by the formula Rth = {(nx + ny) / 2−nz} × d.
Here, the value of retardation (Rth) in the thickness direction can be measured by, for example, KOBRA-WR manufactured by Oji Scientific Instruments.

  The retardation film of the present invention has a configuration in which the optically anisotropic layer is formed on the transparent substrate. In the present invention, the transparent substrate and the optically anisotropic layer are laminated. As an aspect, the transparent substrate and the optically anisotropic layer may be laminated as independent layers, or there is no clear interface between the transparent substrate and the optically anisotropic layer. In addition, a mode in which the content of the optically anisotropic material is continuously changed between the two may be employed.

An embodiment in which the transparent substrate and the optically anisotropic layer are laminated will be described with reference to the drawings. FIG. 2 is a schematic view showing an example of an aspect in which the transparent substrate and the optically anisotropic layer are laminated in the retardation film of the present invention. As illustrated in FIG. 2, the retardation film 10, 10 ′ of the present invention may be an embodiment in which the transparent substrate 1 and the optically anisotropic layer 2 are laminated as independent layers (FIG. 2). (A)) or there is no clear interface between the transparent substrate 1 and the optically anisotropic layer 2 ′, and the content (concentration) of the optically anisotropic material continuously changes between the two. It is also possible to use a layered structure (FIG. 2B).
In particular, in the case of a laminated structure in which two layers are clearly separated as shown in FIG. 2A, the content of the optically anisotropic material in the optically anisotropic layer 2 is usually in the thickness direction. Although it is a constant value, of course, if desired, the content can be a function of the position in the thickness direction (having a concentration gradient).

Further, the retardation film of the present invention has a residual solvent amount of 20 mg / m ² , so that the amount of change in retardation is small even in a high-temperature and high-humidity atmosphere, and the retardation property is excellent in durability. The degree of durability of the retardation film of the present invention is not particularly limited, and may be appropriately adjusted according to the use of the retardation film of the present invention.
In particular, the retardation film of the present invention preferably has a change amount of Re and Rth of less than 4.5% when left for 24 hours or more in an environment at a temperature of 40 ° C. It is preferably in the range of 01% to 4%, and more preferably in the range of 0.01% to 3%.

  The retardation film of the present invention preferably has a change amount of Re and Rth of less than 4.5% when left for 24 hours or more in an environment where the humidity is 50% RH or more. The content is preferably within a range of 0.01% to 4%, and more preferably within a range of 0.01% to 3%.

  Furthermore, the retardation film of the present invention preferably has a change amount of Re and Rth of less than 4.5% when left for 24 hours or more in an environment of a temperature of −40 ° C. or more, particularly 0 The content is preferably within a range of 0.01% to 4%, and more preferably within a range of 0.01% to 3%.

  As a form of the retardation film of this invention, it can be set as a desired form according to the use etc. of the retardation film of this invention. Therefore, for example, it may be formed in a long shape and wound into a roll shape, or may be in a sheet shape cut into a predetermined size.

5. Use of Retardation Film The retardation film of the present invention can be used as an optical compensator, an elliptically polarizing plate, a brightness enhancement plate and the like used in a liquid crystal display device.

  When the retardation film of the present invention is used as an optical compensator for a liquid crystal display device, the retardation film of the present invention can be used alone, and the retardation film of the present invention has other optical functions. It is also possible to use it laminated with a film.

  As an example of laminating and using the retardation film of the present invention and another optical functional film, for example, it can be used as an optical compensation film for VA system by laminating the retardation film of the present invention with an A plate. . Further, when the retardation film of the present invention has properties as an A plate, it can be used as a VA optical compensation film by laminating with a negative C plate. Furthermore, when the retardation film of the present invention has an optical property as an A plate, it can be used as an optical compensation film for an IPS system by laminating with a positive C plate.

  In addition, the retardation film of the present invention is obtained by laminating a positive C plate and a liquid crystal layer containing cholesteric aligned liquid crystal molecules in this order on the retardation film of the present invention. It can also be used as an enhancement film.

  Furthermore, the retardation film of the present invention can be used for a polarizing plate by being bonded to a polarizer. That is, the polarizing plate is usually composed of a polarizer and a polarizing plate protective film formed on both surfaces thereof. In the present invention, for example, as one polarizing plate protective film, the retardation of the present invention is used. By using a film, a polarizing plate having a viewing angle compensation function of a liquid crystal display device can be obtained.

  Although it does not specifically limit as said polarizer, For example, a dye type polarizer using a dichroic dye, a dichroic dye, a polyene type polarizer, etc. can be used. In general, iodine-based polarizers and dye-based polarizers are manufactured using polyvinyl alcohol.

6). Production method of retardation film The production method of the retardation film of the present invention is not particularly limited as long as it can produce the retardation film having the above-described configuration. As such a production method, for example, a coating for forming an optically anisotropic layer using the above-mentioned transparent substrate and containing a solvent capable of dissolving the above-mentioned optically anisotropic material and a resin material constituting the transparent substrate. The method of forming an optically anisotropic layer on the said transparent substrate can be mentioned by applying a liquid on the said transparent substrate.
Hereinafter, such a method will be described as an example of the method for producing the retardation film of the present invention.

  As a solvent used in the coating liquid for forming the optically anisotropic layer, a solvent capable of dissolving a resin material constituting a transparent substrate, which will be described later, and a solvent capable of dissolving the optically anisotropic material at a desired concentration If it is, it will not specifically limit. Thus, when applying the optically anisotropic layer-forming coating liquid on the transparent substrate by using the solvent that can dissolve the resin material constituting the transparent substrate and the optically anisotropic material as the solvent, Since a part of the surface of the transparent substrate can be dissolved, an optically anisotropic layer containing the resin material constituting the transparent substrate and the optically anisotropic material can be formed.

  Moreover, the solvent used for the said coating liquid for optically anisotropic layer formation becomes the main solvent which remains in the retardation film of this invention. Therefore, as the solvent, when remaining in the retardation film of the present invention as a residual solvent, a solvent that does not easily volatilize from the film, or a solvent that causes little change in retardation due to volatilization from the film. It is preferable to use it. From such a viewpoint, the solvent preferably has a boiling point of 110 ° C. or higher. Even if the solvent having such boiling point remains in the retardation film, it is difficult to volatilize in a high temperature and high humidity atmosphere, so that a retardation film with less variation in retardation can be obtained in a high temperature and high humidity atmosphere. Because it can.

  From the viewpoint described above, the solvent is preferably a solvent having a refractive index in the range of 1.3 to 1.6.

Examples of such solvents include hydrocarbon solvents such as benzene and hexane; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and methylcyclohexanone; ether solvents such as tetrahydrofuran and 1,2-dimethoxyethane: chloroform And alkyl halide solvents such as dichloromethane; ester solvents such as methyl acetate, butyl acetate and propylene glycol monomethyl ether acetate; amide solvents such as N, N-dimethylformamide, and sulfoxide solvents such as dimethyl sulfoxide. Can do.
Of these, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and methyl cyclohexanone are preferably used in the present invention.
Furthermore, when a transparent substrate made of a cellulose derivative is used as the transparent substrate, it is preferable to use cyclohexanone or methylcyclohexanone as the solvent.

  In addition, the said solvent is not restricted to what consists of a single solvent, The mixed solvent of a some solvent may be sufficient. Examples of such a mixed solvent include a mixed solvent of cyclohexanone and methyl ethyl ketone, a mixed solvent of cyclohexanone and an alcohol solvent, and the like.

The optically anisotropic material used in the coating liquid for forming the optically anisotropic layer is the same as that described in the above section “1. Optically anisotropic layer”. Omitted.
Further, the transparent substrate is the same as that described in the section “2. Transparent substrate”, and the description thereof is omitted here.

  As a method of coating the optically anisotropic layer forming coating solution on the transparent substrate, any method can be used as long as a predetermined amount of the optically anisotropic layer forming coating solution can be applied on the transparent substrate. It is not particularly limited. As such a coating method, for example, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, immersion pulling method , Curtain coating method, die coating method, casting method, bar coating method, extrusion coating method, E-type coating method, and the like.

The method for drying the coating film of the optically anisotropic layer-forming coating solution is not particularly limited as long as the residual solvent amount in the produced retardation film can be 20 mg / m ² or less. As such a drying method, a commonly used drying method such as a heat drying method, a reduced pressure drying method, a gap drying method, or the like can be used. In addition, the drying method in this step is not limited to a single method, and a plurality of drying methods may be employed, for example, by sequentially changing the drying method according to the amount of solvent remaining in the coating film. .

  When a compound having a polymerizable functional group is used as the optically anisotropic material, the optically anisotropic material is polymerized after the coating film of the optically anisotropic layer forming coating liquid is dried. However, at this time, the method for polymerizing the optically anisotropic material may be arbitrarily determined according to the type of the polymerizable functional group of the optically anisotropic material. As such a method, generally, a method of polymerizing by irradiation with actinic radiation is preferably used.

  The actinic radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable material. Usually, ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus. Among them, it is preferable to use irradiation light having a wavelength of 150 to 500 nm, preferably 250 to 450 nm, more preferably 300 to 400 nm.

  As a light source of this irradiation light, a low pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high pressure discharge lamp (high pressure mercury lamp, metal halide lamp), a short arc discharge lamp (super high pressure mercury lamp, xenon lamp, mercury xenon). Lamp). Among these, use of a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, etc. is recommended. The irradiation intensity can be appropriately adjusted according to the content of the photopolymerization initiator.

In the production of the retardation film of the present invention, if necessary, after forming the optically anisotropic layer on the transparent substrate, a step of stretching the transparent substrate and the optically anisotropic layer is performed. Also good. At this time, as an extending | stretching aspect implemented, uniaxial stretching may be sufficient and biaxial stretching may be sufficient.
In the stretching, it is usually desirable to heat the optically anisotropic layer and the transparent substrate to a glass transition temperature or higher and a melting point temperature or lower.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(1) Example 1
A coating liquid for forming an optically anisotropic layer was prepared by dissolving a photopolymerizable liquid crystal compound represented by the following formula as a refractive index anisotropic material in cyclohexanone at 15% by mass.
Next, a TAC film (trade name: KC4UYW: manufactured by Konica Minolta Co., Ltd.) was used as the transparent substrate, and the optically anisotropic layer forming coating solution was applied onto the TAC film by bar coating. At this time, the coating amount of the optically anisotropic layer forming coating solution was such that the film thickness after drying was 4 μm.

  Next, the coating film was heated at 40 ° C. for 2 minutes and at 115 ° C. for 30 seconds to remove the solvent, and the photopolymerizable liquid crystal compound was mixed with triacetyl cellulose constituting the TAC film.

  Next, the photopolymerizable liquid crystal material was fixed by irradiating the dried coating film with ultraviolet rays to obtain a retardation film.

The produced retardation film was cut into 10 cm × 10 cm, and further cut in half to produce two 5 cm × 10 cm strip-shaped samples. The two strip-shaped samples were rounded and packed in a vial, and when the residual solvent in the retardation film was measured by gas chromatography, it was 9 mg / m ² .
Further, when the produced retardation film was left in an oven at a temperature of 90 ° C. for 24 hours or more, the amount of change in Re before and after was 1.31%.

(2) Example 2
A retardation film was produced in the same manner as in Example 1 except that the drying condition of the coating film was 2 minutes at 40 ° C. and 1 minute at 100 ° C.

It was 16 mg / m < ² > when the amount of residual solvents in the produced retardation film was measured by the method similar to Example 1. FIG.
Moreover, when the produced retardation film was left in an oven at a temperature of 90 ° C. for 24 hours or more, the amount of change in Re before and after was 1.52%.

(3) Example 3
A retardation film was produced in the same manner as in Example 1 except that the drying conditions of the coating film were changed to 40 ° C. for 2 minutes and 100 ° C. for 30 seconds.

When the amount of residual solvent in the produced retardation film was measured by the same method as in Example 1, it was 18 mg / m ² .
Further, when the produced retardation film was left in an oven at a temperature of 90 ° C. for 24 hours or more, the change amount of Re before and after was 1.55%.

(4) Example 4
A retardation film was produced in the same manner as in Example 1 except that the drying conditions of the coating film were 2 minutes at 40 ° C. and 1 minute at 95 ° C.

When the amount of residual solvent in the produced retardation film was measured by the same method as in Example 1, it was 19 mg / m ² .
Further, when the prepared retardation film was left in an oven at a temperature of 90 ° C. for 24 hours or more, the change amount of Re before and after was 1.60%.

(5) Comparative Example 1
A retardation film was produced in the same manner as in Example 1 except that the drying condition of the coating film was 2 minutes at 40 ° C. and 1 minute at 90 ° C.

It was 22 mg / m < ² > when the amount of residual solvents in the produced retardation film was measured by the method similar to Example 1. FIG.
Further, when the produced retardation film was left in an oven at a temperature of 90 ° C. for 24 hours or more, the amount of change in Re before and after was 4.50%.

(6) Comparative Example 2
A retardation film was produced in the same manner as in Example 1 except that the drying condition of the coating film was 2 minutes at 40 ° C.

When the amount of residual solvent in the produced retardation film was measured by the same method as in Example 1, it was 65 mg / m ² .
Further, when the produced retardation film was left in an oven at a temperature of 90 ° C. for 24 hours or more, the amount of change in Re before and after was 6.61%.

It is the schematic which shows an example of the retardation film of this invention. It is the schematic which shows the other example of the retardation film of this invention. It is the schematic which shows an example of the conventional liquid crystal display device. It is the schematic which shows an example of the conventional phase difference film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2, 2 '... Optically anisotropic layer 10, 10' ... Retardation film 30 ... Retardation film 100 ... Liquid crystal display device 102A, 102B ... Polarizing plate 104 ... Liquid crystal cell

Claims (2)

A transparent substrate made of a resin material, and an optically anisotropic layer formed on the transparent substrate and containing the resin material and an optically anisotropic material having refractive index anisotropy, and optically negative A retardation film having properties as a C plate,
A retardation film, wherein the amount of the solvent remaining in the retardation film is 20 mg / m ² or less. The retardation film according to claim 1, wherein a boiling point of the solvent is 110 ° C. or more.

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