JP5894931B2 - Method for producing retardation film - Google Patents

Description

  The present invention relates to a retardation film. More specifically, the present invention relates to a retardation film exhibiting wavelength dispersibility (reverse wavelength dispersibility) in which the phase difference decreases as the wavelength of light decreases, at least in the visible light range. Moreover, this invention relates to the manufacturing method of the said retardation film, and an image display apparatus provided with the said retardation film.

  Optical members using birefringence generated by polymer orientation are widely used in the field of image display. One such optical member is a retardation film incorporated in an image display device for the purpose of color tone compensation, viewing angle compensation, and the like. For example, in a reflective liquid crystal display device (LCD), a retardation film (λ /) having an optical path length difference (retardation) based on the phase difference caused by birefringence is approximately ¼ of the wavelength of light in the visible light range. 4 plates) are used. In an organic EL display (OLED), an antireflection plate in which a polarizing plate and a λ / 4 plate are combined may be used for the purpose of preventing reflection of external light (see JP 2007-273275 A).

  Conventionally, polycarbonate and cycloolefin polymers have been mainly used for retardation films. However, a retardation film composed of these general polymers exhibits wavelength dispersion in which the retardation increases as the wavelength of light decreases. In order to obtain an image display device having excellent display characteristics, on the contrary, a retardation film having a wavelength dispersion property in which the phase difference decreases as the wavelength of light becomes shorter is desired. In this specification, “a wavelength dispersion in which the phase difference decreases as the wavelength of light becomes shorter, at least in the visible light region” follows the commonly used name of those skilled in the art, and is a retardation film formed of a general polymer. This is called “reverse wavelength dispersion” based on the fact that it is opposite to the wavelength dispersion shown in FIG.

  So far, various studies have been made to produce a retardation film with controlled wavelength dispersion.

  Japanese Patent Application Laid-Open No. 5-27118 discloses a phase difference film in which two types of phase difference films having different phase differences and wavelength dispersion properties are bonded and laminated so that their optical axes cross each other, and particularly perpendicular to each other. Is disclosed. Japanese Patent Application Laid-Open No. 10-68816 discloses a retardation film in which a λ / 4 plate and a λ / 2 plate are bonded together with their optical axes intersecting at a preset angle. In these two documents, an attempt is made to realize a retardation film that can function as a specific wave plate over the entire visible light region. However, two types of retardation films having different optical properties are bonded so that their optical axes intersect with each other, and a retardation film bonded together is difficult to continuously produce and is inferior in productivity. To give a more specific example, the retardation film made of a laminate is co-stretched of the original film having a laminated structure from the viewpoint of productivity (stretching two or more layers in the same direction while being laminated) It is desirable to manufacture by. However, the retardation films disclosed in these two documents cannot be produced by co-stretching because the optical axes of the respective layers constituting the film intersect.

  JP-A-2001-337222 discloses a retardation film comprising a resin composition containing a polymer having positive intrinsic birefringence and a polymer having negative intrinsic birefringence. JP-A-2001-235622 discloses a retardation film comprising a copolymer having a molecular chain having positive intrinsic birefringence and a molecular chain having negative intrinsic birefringence. Although the retardation film disclosed in these two documents is a single layer, it exhibits reverse wavelength dispersion. However, in the retardation film, the resin composition (co-polymer) is considered in consideration of the compatibility between polymers (molecular chains) having different positive and negative intrinsic birefringence, and various properties of the retardation film such as moldability and heat resistance. It is necessary to determine the composition of the coalescence. For this reason, the composition range which the resin composition (copolymer) which comprises the said retardation film can take is practically limited. That is, the retardation films disclosed in these two documents do not necessarily have a high degree of freedom in optical design.

  JP-A-2009-237534 discloses that a resin having a positive intrinsic birefringence and a resin having a negative intrinsic birefringence are laminated by coextrusion to form a layer made of a resin having a positive intrinsic birefringence and an intrinsic birefringence. After obtaining a raw film laminated with a layer made of a negative resin, the obtained raw film is uniaxially stretched in a direction perpendicular to the longitudinal direction of the film to exhibit reverse wavelength dispersion. A method for obtaining a retardation film is disclosed. In this method, the retardation film is formed by coextrusion molding and co-stretching, so it is possible to continuously produce retardation films, for example, from the extrusion of raw film to the formation of retardation films. It is.

JP 2007-273275 A JP-A-5-27118 Japanese Patent Laid-Open No. 10-68816 JP 2001-337222 JP 2001-235622 A JP 2009-237534

  In recent years, mobile devices having an image display unit such as an LCD have been widely used. In order to incorporate a retardation film into the image display section of such a mobile device, a retardation film that exhibits a sufficient retardation corresponding to the optical design despite its thinness is desired. An object of the present invention is to provide a retardation film exhibiting reverse wavelength dispersion, which has a laminated structure, can be produced by co-stretching, and can exhibit a sufficient retardation while being thin, and a method for producing the same. And

  The retardation film of the present invention is made of a resin (A) having positive intrinsic birefringence, and has a wavelength dispersion (reverse wavelength dispersion) in which the retardation becomes smaller as the wavelength becomes shorter at least in the visible light region. And a second stretched layer made of a resin (B) having positive intrinsic birefringence. The composition of the resin (A) and the composition of the resin (B) are different from each other. The optical axes of the first and second stretched layers are parallel to each other. In the retardation film of the present invention, the in-plane retardation for light having a wavelength of 590 nm is 20 nm or more and 300 nm or less. The retardation film of the present invention exhibits reverse wavelength dispersion.

  The method for producing a retardation film of the present invention is the method for producing the retardation film of the present invention, wherein the resin (A) and the resin (B) are co-extruded and formed from the resin (A). Forming an original film having a laminated structure of the first resin layer and the second resin layer made of the resin (B); by stretching the formed original film, the original resin layer Forming a first stretched layer and forming the second stretched layer from the second resin layer to obtain the retardation film;

  The method for producing a retardation film of the present invention as seen from another aspect is a method for producing the retardation film of the present invention, and is composed of one resin selected from the resin (A) and the resin (B). A solution containing the other resin is applied to the surface of the resin layer, the coating film formed by applying the solution is dried, and the resin layer and the coating layer composed of the other resin Forming an original film having a laminated structure; stretching the formed original film to form the first and second stretched layers from the resin layer and the coating layer to obtain the retardation film; Is the method.

  The image display device of the present invention includes the retardation film of the present invention.

  The retardation film of the present invention has a laminated structure, can be produced by co-stretching, can exhibit a sufficient retardation even though it is thin, and exhibits reverse wavelength dispersion.

  In the production method of the present invention, such a retardation film can be produced with high productivity.

It is sectional drawing which shows an example of the phase difference film of this invention typically. It is sectional drawing which shows another example of the retardation film of this invention typically.

  In the present specification, “resin” is a broader concept than “polymer”. The resin may be composed of, for example, one or two or more polymers, and if necessary, materials other than the polymer, such as ultraviolet absorbers, antioxidants, fillers, compatibilizers and stabilizers. Such additives may be included.

  The retardation film of this invention consists of a laminated body containing a 1st extending | stretching layer and a 2nd extending | stretching layer. Each stretched layer exhibits a retardation and wavelength dispersion depending on the composition of the resin constituting the layer and the stretched state of the layer. The composition of the resin (A) and the composition of the resin (B) are different from each other. That is, the retardation film of the present invention has a laminated structure in which two or more stretched layers that express mutually different retardation and / or wavelength dispersion are laminated. Thereby, compared with a single layer retardation film, it becomes a retardation film with a high degree of freedom of optical design, such as wavelength dispersion and retardation value. This is because the optical properties of the retardation film can be controlled without considering the compatibility between the polymers or between the molecular chains in the copolymer.

  In the retardation film of the present invention, the optical axes of the first and second stretched layers are parallel to each other. For this reason, the retardation film of the present invention is produced by co-stretching an original film having a laminated structure including a resin layer that becomes a first stretched layer after stretching and a resin layer that becomes a second stretched layer after stretching. Is possible. Thereby, compared with the retardation film which laminated | stacked the two or more layers by making a mutual optical axis cross | intersect, it becomes a retardation film with high productivity. Also, in the case where the first and second stretched layers are formed separately, and the formed stretched layers are bonded together to produce a retardation film, the optical axis of the stretched layer is usually one of the layers. Therefore, productivity can be improved compared to the case where two or more layers are stacked with their optical axes crossing each other. In particular, when laminating individually formed strip-shaped stretch layers, both the first and second stretch layers are made of a resin having positive intrinsic birefringence, so that the optical axis of each stretch layer is the longitudinal direction of the layer. Therefore, a retardation film can be produced with high productivity by so-called “roll to roll” lamination.

  The retardation film obtained by the method of JP-A-2009-237534 has a laminated structure and can be produced by co-stretching. However, since the retardation film has opposite positive and negative intrinsic birefringence and has a laminated structure of two layers stretched in the same direction, the retardation generated in each layer cancels each other. For this reason, the retardation shown as the whole retardation film must be reduced, and in order to obtain a sufficient retardation corresponding to the optical design of the image display device, it is necessary to increase the thickness of the retardation film. The technical idea of controlling the wavelength dispersion while canceling out the phase difference is disclosed in Japanese Patent Laid-Open Nos. 5-27118, 10-68816, 2001-337222, and 2001-235622. This also applies to the retardation film. In the retardation films of JP-A-5-27118 and JP-A-10-68816, since the wavelength dispersion is controlled by crossing the optical axes of the respective layers constituting the film, they are generated in the respective layers. The phase differences cancel each other. Although the retardation films of JP-A-2001-337222 and JP-A-2001-235622 are monolayers, the film has two intrinsic birefringences whose positive and negative are opposite to each other and oriented in the same direction. Reverse wavelength dispersion is realized by canceling out the phase difference caused by the coalescence (molecular chain).

  On the other hand, in the retardation film of the present invention, both the first stretched layer and the second stretched layer are made of a resin having positive intrinsic birefringence. The optical axes of the first and second stretched layers are parallel to each other. Thereby, the phase difference which develops in both the stretched layers is integrated without conversely canceling each other. Moreover, when the 1st extending | stretching layer shows reverse wavelength dispersion, the whole retardation film shows reverse wavelength dispersion. That is, in the retardation film of the present invention, reverse wavelength dispersibility is realized while obtaining the sum of retardations generated in two kinds of stretched layers stretched in the same direction as the retardation of the entire retardation film. Such a retardation film can exhibit a large retardation even though it is thin as compared with a conventional retardation film that obtains reverse wavelength dispersion while canceling out the retardation generated in different layers.

  An example of the retardation film of the present invention is shown in FIG. The retardation film 1 shown in FIG. 1 consists of a laminated body of the 1st extending | stretching layer 2 and the 2nd extending | stretching layer 3 (it has the laminated structure of the extending | stretching layers 2 and 3). The first stretched layer 2 is made of a resin (A) having positive intrinsic birefringence, and at least in the visible light range, the phase difference becomes smaller (birefringence becomes smaller) as the wavelength of light becomes shorter. This is a layer exhibiting reverse wavelength dispersion. The 2nd extending | stretching layer 3 is a layer which consists of resin (B) which has a positive intrinsic birefringence. The composition of the resin (A) and the composition of the resin (B) are different from each other. The optical axis of the 1st extending | stretching layer 2 and the optical axis of the 2nd extending | stretching layer 3 are mutually parallel. The in-plane retardation Re of the retardation film 1 with respect to light having a wavelength of 590 nm is 20 nm or more and 300 nm or less. The retardation film 1 exhibits reverse wavelength dispersion.

  The positive or negative of the intrinsic birefringence of the resin is determined by the molecular chain in the layer out of light incident perpendicularly to the principal surface of the layer in a layer (for example, a film) in which the molecular chains of the polymer contained in the resin are uniaxially oriented. This can be determined based on the value “n1-n2” obtained by subtracting the refractive index n2 of light in the direction perpendicular to the alignment axis from the refractive index n1 of light in the direction parallel to the direction of alignment (alignment axis). The value of the intrinsic birefringence of the resin is determined by the balance of the intrinsic birefringence value exhibited by each polymer contained in the resin.

  The optical axis of the stretched layer (stretched resin layer) means a slow axis in the in-plane direction of the stretched layer. The slow axis is the direction in which the main refractive index nx in the in-plane direction of the layer is obtained. “Optical axis is parallel” means that a slight “deviation” of the optical axis unavoidably occurs in the manufacturing process of the retardation film, especially in the case of bonding the stretched layers to form the retardation film. Is included. This “deviation” is usually within 1 °, preferably 0.5 °, as an angle generated between the optical axes of the first and second stretched layers as seen from the direction perpendicular to the main surface of the retardation film. Is within.

  “The resin composition is different” means that the polymer contained in the resin is different, or the resin contains the same type of polymer, but the content is different.

  The in-plane retardation Re is nx as the main refractive index in the in-plane direction of the retardation film, ny as the refractive index in the in-plane direction orthogonal to the direction indicating the main refractive index, and d as the film thickness. This is a value represented by the formula Re = (nx−ny) × d. The refractive indexes nx, ny and nz in this specification are values for light having a wavelength of 590 nm.

[First stretched layer]
A 1st extending | stretching layer consists of resin (A) which has a positive intrinsic birefringence. A 1st extending | stretching layer is an extending | stretching body which extended | stretched the resin layer which consists of resin (A). The stretched state is as long as the first stretched layer exhibits reverse wavelength dispersibility and the in-plane retardation Re and reverse wavelength dispersibility described above are obtained as the entire retardation film including the first and second stretched layers. For example, it may be a uniaxially stretchable layer or a biaxially stretchable layer.

  The composition of the resin (A) is not limited as long as the intrinsic birefringence as the resin (A) is positive and the first stretched layer exhibits reverse wavelength dispersion. The resin (A) includes, for example, a polymer having positive intrinsic birefringence and a polymer exhibiting reverse wavelength dispersion. The former polymer and the latter polymer may be the same or different.

  The positive or negative of the intrinsic birefringence of the polymer is such that the molecular chain in the layer of the layer in which the molecular chain of the polymer is uniaxially oriented (for example, a film) is perpendicular to the main surface of the layer. This can be determined based on a value “n3−n4” obtained by subtracting the refractive index n4 of light in the direction perpendicular to the alignment axis from the refractive index n3 of light in the direction parallel to the direction (alignment axis). The intrinsic birefringence value of the polymer can be determined by calculation based on its molecular structure.

  “A polymer exhibits reverse wavelength dispersion” means that a layer (for example, a film) in which molecular chains of the polymer are oriented exhibits reverse wavelength dispersion. Similarly, when the layer in which the molecular chains of the polymer are oriented exhibits wavelength dispersion (forward wavelength dispersion) in which the phase difference increases as the wavelength of light decreases at least in the visible light region, the polymer is forward wavelength dispersive. It shows that.

  The wavelength dispersion of a polymer having a positive intrinsic birefringence is not limited, and the polymer does not necessarily have to exhibit reverse wavelength dispersion. On the other hand, the positive / negative of intrinsic birefringence of a polymer exhibiting reverse wavelength dispersion is not limited, and the polymer does not necessarily have positive intrinsic birefringence. A person skilled in the art adjusts the content of both polymers in the resin, and further adjusts the content of other polymers as necessary, that is, by adjusting the resin composition, (A) can be obtained.

  Resin (A) contains a cellulose derivative, for example. Cellulose derivatives generally have positive intrinsic birefringence and, depending on the type, exhibit reverse wavelength dispersion. When a cellulose derivative shows reverse wavelength dispersibility, resin (A) which does not contain a polymer other than the said cellulose derivative may be sufficient.

  The cellulose derivative has high transparency. For this reason, the retardation film of this invention which has a 1st extending | stretching layer containing a cellulose derivative is suitable for use for image display apparatuses, such as LCD.

  A cellulose derivative is not limited, For example, they are a cellulose aromatic carboxylic acid ester polymer and a cellulose fatty acid ester polymer. A cellulose lower fatty acid ester polymer is preferred because a retardation film having excellent optical properties can be obtained. A lower fatty acid is a fatty acid having 5 or less carbon atoms. The cellulose lower fatty acid ester polymer is, for example, cellulose acetate, cellulose propionate, cellulose butyrate, or cellulose pivalate. The cellulose derivative may be a cellulose mixed fatty acid ester polymer such as cellulose acetate propionate or cellulose acetate butyrate. From the viewpoint of flexibility and transparency of the retardation film, cellulose acetate such as cellulose triacetate, cellulose acetate propionate, and cellulose acetate butyrate is preferable. Cellulose acetate propionate and cellulose acetate butyrate are particularly preferable because they exhibit reverse wavelength dispersion.

  The number average molecular weight Mn of the cellulose derivative is preferably 50,000 to 150,000, more preferably 55,000 to 120,000, and further preferably 60,000 to 100,000. The molecular weight dispersity (= weight average molecular weight Mw / number average molecular weight Mn) in the cellulose derivative is preferably 1.3 to 5.5, more preferably 1.5 to 5.0, and 1.7 to 4.0. Further preferred is 2.0 to 3.5.

  The cellulose derivative can be produced by a known method. For example, it can be produced by substituting the hydroxyl group of the raw material cellulose with an acetyl group, a propionyl group and / or a butyl group by a conventional method using acetic anhydride, propionic anhydride and / or butyric anhydride. In that case, the methods described in JP-A-10-45804 and JP-A-6-501040 are helpful. The raw material cellulose is not particularly limited, and examples thereof include wood pulp and cotton linter. The wood pulp may be softwood pulp or hardwood pulp, but softwood pulp is preferred. From the viewpoint of releasability when forming into a film, cotton linter is preferred. Two or more types of raw material cellulose can be used.

  Resin (A) includes, for example, a polymer (D) having a positive intrinsic birefringence and an α, β-unsaturated monomer unit having a heteroaromatic group (hereinafter simply referred to as “unsaturated monomer unit”). And a polymer (C) having a negative intrinsic birefringence. When the orientation is added in the same direction to the polymers (C) and (D) at the time of stretching orientation (when forming the first stretched layer) of the resin (hereinafter referred to as resin (A1)), Since the slow axes of these polymers are orthogonal to each other, their birefringences cancel each other. Here, since the degree to which birefringence cancels differs depending on the wavelength, the first stretched layer made of the resin (A) containing the polymers (C) and (D) exhibits reverse wavelength dispersion.

  The polymer (D) is not limited as long as it has positive intrinsic birefringence, and is, for example, a cycloolefin polymer, a cellulose derivative, or a (meth) acrylic polymer. The (meth) acrylic polymer typically has a ring structure in the main chain.

  The polymer (D) is preferably a cycloolefin polymer or a (meth) acrylic polymer having a ring structure in the main chain. In this case, the freedom degree of control of reverse wavelength dispersion in the retardation film of the present invention having the first stretched layer and the layer is improved. The birefringence wavelength dispersibility exhibited by the polymer (C) having an unsaturated monomer unit as a constituent unit is a cycloolefin polymer or a polymer (D) that is a (meth) acrylic polymer having a ring structure in the main chain (D). This is considerably larger than the wavelength dispersion of birefringence indicated by Thus, the freedom degree of control of reverse wavelength dispersion improves by combining polymer (C) and (D) from which the wavelength dispersion of birefringence differs greatly.

  Cycloolefin polymers and (meth) acrylic polymers have high transparency and mechanical properties. For this reason, the retardation film of this invention which has the 1st extending | stretching layer containing these polymers is suitable for use for image display apparatuses, such as LCD.

  From the viewpoint of the surface strength of the retardation film of the present invention having the first stretched layer and the layer, the polymer (D) is preferably a (meth) acrylic polymer having a ring structure in the main chain.

  The cycloolefin polymer is a polymer having cycloolefin units in an amount of 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more of all the structural units.

  The cycloolefin unit is, for example, a structural unit formed by polymerization of the following monomers: dicyclopentadiene and derivatives thereof (those having a substituent in the ring, for example, 2,3-dihydrodicyclopentadiene); Norbornene and its alkyl-substituted products, polar group-substituted products such as halogen or alkylidene-substituted products such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2 -Norbornene, 5-ethylidene-2-norbornene; dimethanooctahydronaphthalene and alkyl substituents thereof, polar group substituents such as halogen or alkylidene substituents such as 6-methyl-1,4: 5,8-dimethano- 1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6 Ethyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4 4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1, 4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octa Hydronaphthalene; Adduct of cyclopentadiene and tetrahydroindene; Cyclopen Diene tri-tetramers, such as 4,9: 5,8-dimethano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10 : 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentanthracene.

  The cycloolefin polymer has a ring structure in the main chain. For this reason, it has a high glass transition temperature (Tg), and the heat resistance of the retardation film of the present invention having the first stretched layer and the layer is improved. A retardation film having high heat resistance is suitable for use in an image display device such as an LCD having a structure in which heating elements such as a light source, a power source, and a circuit board are integrated in a limited space.

  The cycloolefin polymer has particularly low birefringence wavelength dispersion. This characteristic contributes to the fact that the first stretched layer containing the polymer (D) exhibits strong reverse wavelength dispersion for the phase difference of the layer.

  The cycloolefin polymer can be produced by a known method.

  The (meth) acrylic polymer is a polymer having (meth) acrylic acid ester units in an amount of 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more based on all structural units. The (meth) acrylic polymer may contain a ring structure that is a derivative of a (meth) acrylic acid ester unit. In this case, the total of the (meth) acrylic acid ester unit and the ring structure is 50 mol of all the structural units. If it is% or more, it becomes a (meth) acrylic polymer.

  The (meth) acrylic polymer that is the polymer (D) preferably has a ring structure in the main chain. That the (meth) acrylic polymer has a ring structure in the main chain means that the first stretched layer containing the polymer (D) and the retardation film of the present invention having the layer exhibit a large in-plane retardation Re. Contribute to.

  In addition to this, the Tg of the (meth) acrylic polymer having a ring structure in the main chain is high, for example, 110 ° C. or higher, 120 ° C. or higher, and further 130 ° C. or higher depending on the configuration of the polymer. By including the (meth) acrylic polymer having a high Tg as described above, the heat resistance of the retardation film of the present invention having the first stretched layer and the layer is improved.

  The ring structure that the (meth) acrylic polymer may have in the main chain is, for example, a ring structure having an ester group, an imide group, or an acid anhydride group.

  A more specific example of the ring structure is at least one selected from a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure. These ring structures have a large contribution to the fact that the retardation film of the present invention having the first stretched layer and the layer exhibits a large in-plane retardation Re.

  The ring structure is preferably at least one selected from a lactone ring structure and a glutarimide structure, and more preferably a lactone ring structure. A (meth) acrylic polymer having a lactone ring structure or a glutarimide structure, particularly a lactone ring structure, in the main chain has particularly low birefringence wavelength dispersion. This characteristic contributes to the fact that the first stretched layer containing the polymer (D) and the retardation film of the present invention having the layer exhibit strong reverse wavelength dispersion.

  Although the specific lactone ring structure which (meth) acrylic polymer may have is not specifically limited, For example, it is a structure shown by the following formula | equation (1).

In the formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The organic residue is, for example, an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, or a propyl group; an unsaturated aliphatic carbonization having 1 to 20 carbon atoms such as an ethenyl group or a propenyl group. A hydrogen group; an aromatic hydrocarbon group having 1 to 20 carbon atoms such as a phenyl group or a naphthyl group; one of hydrogen atoms in the alkyl group, the unsaturated aliphatic hydrocarbon group and the aromatic hydrocarbon group; One or more groups are substituted with at least one group selected from a hydroxyl group, a carboxyl group, an ether group and an ester group.

The lactone ring structure represented by the formula (1) is obtained by copolymerizing a monomer group including, for example, methyl methacrylate (MMA) and 2- (hydroxymethyl) methyl acrylate (MHMA), Adjacent MMA units and MHMA units in the coalescence can be formed by dealcoholization cyclocondensation. At this time, R ¹ is H, R ² and R ³ are CH ₃ .

  The following formula (2) shows a glutarimide structure and a glutaric anhydride structure.

R ⁴ and R ⁵ in the formula (2) are each independently a hydrogen atom or a methyl group, and X ¹ is an oxygen atom or a nitrogen atom. When X ¹ is an oxygen atom, R ⁶ does not exist, and when X ¹ is a nitrogen atom, R ⁶ is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group, or a phenyl group. .

When X ¹ is a nitrogen atom, the ring structure represented by the formula (2) is a glutarimide structure. The glutarimide structure can be formed, for example, by imidizing a (meth) acrylic acid ester polymer with an imidizing agent such as methylamine.

When X ¹ is an oxygen atom, the ring structure represented by the formula (2) is a glutaric anhydride structure. The glutaric anhydride structure can be formed, for example, by subjecting a copolymer of (meth) acrylic acid ester and (meth) acrylic acid to dealcoholization cyclocondensation within the molecule.

  The following formula (3) shows an N-substituted maleimide structure and a maleic anhydride structure.

R ⁷ and R ⁸ in the formula (3) are independently a hydrogen atom or a methyl group, and X ² is an oxygen atom or a nitrogen atom. When X ² is an oxygen atom, R ⁹ does not exist, and when X ² is a nitrogen atom, R ⁹ is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group, or a phenyl group. .

When X ² is a nitrogen atom, the ring structure represented by the formula (3) is N- substituted maleimide structure. The acrylic resin having an N-substituted maleimide structure in the main chain can be formed, for example, by copolymerizing an N-substituted maleimide and a (meth) acrylic ester.

When X ² is an oxygen atom, the ring structure represented by the formula (3) is a maleic anhydride structure. The acrylic resin having a maleic anhydride structure in the main chain can be formed, for example, by copolymerizing maleic anhydride and (meth) acrylic acid ester.

  When the (meth) acrylic polymer has a ring structure in the main chain, the content of the ring structure in the (meth) acrylic polymer is not limited. The said content rate is 5 to 90 weight% normally, and 20 to 90 weight% is preferable. The content is more preferably 30 to 90% by weight, 35 to 90% by weight, 40 to 80% by weight, and 45 to 75% by weight. The content of the ring structure can be determined by the method described in JP-A-2001-151814.

  The (meth) acrylic polymer having a ring structure in the main chain can be produced by a known method.

  As long as the effect of the present invention is obtained, the (meth) acrylic polymer has a structural unit other than the structural unit formed by the polymerization of the above-described (meth) acrylic monomer and a ring structure that is a derivative of the structural unit. You may do it. The said structural unit is a structural unit formed by superposition | polymerization of styrene, vinyl toluene, (alpha) -methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate, for example.

  The polymer (C) is not limited as long as it has an unsaturated monomer unit and has negative intrinsic birefringence. The unsaturated monomer unit has the effect of greatly increasing the birefringence wavelength dispersibility in the polymer (C) having the unit as a constituent unit. For this reason, the combination of the polymers (D) and (C) improves the degree of freedom in controlling the reverse wavelength dispersion in the retardation film of the present invention having the first stretched layer and the layer. The polymer (D) is a cycloolefin polymer or a (meth) acrylic polymer having a ring structure in the main chain, particularly a (meth) acrylic polymer having a lactone ring structure or a glutarimide structure in the main chain (as described above) These polymers have a very low birefringence wavelength dispersion), and the degree of freedom in controlling the reverse wavelength dispersion in the retardation film of the present invention having the first stretched layer and the layer is further increased. Become.

  An unsaturated monomer unit is not limited, for example, the heteroaromatic group which the said unit has is not specifically limited. The hetero atom in the heteroaromatic group is typically an oxygen atom, a sulfur atom or a nitrogen atom. The hetero atom is preferably a nitrogen atom because it is excellent in the action of increasing the birefringence wavelength dispersibility in the polymer (C).

  The heteroaromatic group is at least one selected from, for example, a carbazole group, a pyridine group, an imidazole group, and a thiophene group.

  The unsaturated monomer unit is, for example, at least one selected from an N-vinylcarbazole unit, a vinylpyridine unit, a vinylimidazole unit, and a vinylthiophene unit.

  The N-vinylcarbazole unit is shown in the following formula (4). In addition, a part of hydrogen atom on the ring shown in Formula (4) may be substituted by the group exemplified as the organic residue in Formula (1).

  The unsaturated monomer unit is preferably an N-vinylcarbazole unit because it is particularly excellent in the action of increasing the birefringence wavelength dispersibility in the polymer (C).

  The polymer (C) may have a constituent unit other than the unsaturated monomer unit as long as the intrinsic birefringence is negative and the effect of the present invention is obtained. At this time, the content of unsaturated monomer units in the polymer (C) is preferably 20% by weight or more, and more preferably 30% by weight or more.

  For example, the polymer (C) may have an unsaturated monomer unit and a (meth) acrylic acid ester unit as constituent units. In this case, the compatibility with the polymer (D) which is a (meth) acrylic polymer is improved, and the first stretched layer and the retardation film have higher transparency.

  The polymer (C) may have the above-described ring structure in the main chain. In this case, it becomes the 1st extending | stretching layer and retardation film which are more excellent in heat resistance.

  As a specific example, the polymer (C) may have a structural unit formed by polymerization of the following monomers: acrylic acid, methacrylic acid, acrylic acid alkyl ester (for example, methyl acrylate, ethyl) Acrylate, carbazoylethyl acrylate), methacrylic acid alkyl esters (eg methyl methacrylate, ethyl methacrylate, carbazoyl ethyl methacrylate), acrylic acid aminoalkyl esters (eg diethylaminoethyl acrylate), methacrylic acid aminoalkyl esters, acrylic acid and glycols Monoesters, monoesters of methacrylic acid and glycol (for example, hydroxyethyl methacrylate), alkali metal salts of acrylic acid, alkali metal salts of methacrylic acid, ammonium salts of acrylic acid, Ammonium salt of crylic acid, quaternary ammonium derivative of aminoalkyl ester of acrylic acid, quaternary ammonium derivative of aminoalkyl ester of methacrylic acid, quaternary ammonium compound of diethylaminoethyl acrylate and methyl sulfate, vinyl methyl ether, vinyl ethyl Ether, alkali metal salt of vinyl sulfonic acid, ammonium salt of vinyl sulfonic acid, styrene sulfonic acid, styrene sulfonate, allyl sulfonic acid, allyl sulfonate, methallyl sulfonic acid, methallyl sulfonate, vinyl acetate, vinyl Stearate, N-vinylacetamide, N-vinylformamide, acrylamide, methacrylamide, N-alkylacrylamide, N-methylolacrylamide, N, N-methylenebisacryl Bromide, glycol diacrylate, glycol dimethacrylate, divinylbenzene, glycol diallyl ether.

  The polymer (C) can be produced by a known method.

  The mixing ratio of the polymer (C) and the polymer (D) in the resin (A1) is desired as the absolute value of the intrinsic birefringence of each polymer, or the first stretched layer and the retardation film having the layer. Since it differs depending on the degree of reverse wavelength dispersion, etc., it cannot be generally described. However, for example, (D) :( C) = 1: 99 to 99: 1 in terms of weight ratio, and (D) : (C) = 10: 90 to 90:10 is preferable, and (D) :( C) = 20: 80 to 80:20 is more preferable. Within this range, the degree of freedom in controlling the reverse wavelength dispersion in the first stretched layer can be improved, and a retardation film having good reverse wavelength dispersion according to the application can be obtained.

  Resin (A1) has two or more types of polymers (C) or two or more types as long as the intrinsic birefringence is positive and the first stretched layer made of resin (A1) exhibits reverse wavelength dispersion. A polymer (D) may be included.

The content of the polymer contained in the resin and the content of the structural unit in the polymer can be determined by a known method such as ¹ H nuclear magnetic resonance ( ¹ H-NMR) or infrared spectroscopic analysis (IR).

  The resin (A) has, for example, a polymer (E) having a structural unit that gives positive intrinsic birefringence to the polymer and a structural unit that gives negative intrinsic birefringence to the polymer, and exhibits reverse wavelength dispersion. including. When orientation is added to the polymer (E) at the time of stretching orientation of the resin (hereinafter referred to as resin (A2)) (during formation of the first stretched layer), birefringence caused by each structural unit is generated. Negate each other. Here, since the degree to which birefringence cancels differs depending on the wavelength, the polymer (E) exhibits reverse wavelength dispersion. The polymer (E) itself may have positive intrinsic birefringence or negative intrinsic birefringence. Since the resin (A) has positive intrinsic birefringence, the polymer (E) preferably has positive intrinsic birefringence.

  Constituent units that give positive intrinsic birefringence to the polymer include, for example, a part of the above-described cycloolefin units, a part of the (meth) acrylic acid ester units, and the (meth) acrylic polymer in the main chain. Part of the ring structure that may be present. The ring structure is at least one selected from, for example, a lactone ring structure, a glutarimide structure, and a glutaric anhydride structure. These ring structures have a large contribution to the fact that the retardation film of the present invention having the first stretched layer and the layer exhibits a large in-plane retardation Re. The ring structure is preferably at least one selected from a lactone ring structure and a glutarimide structure, and more preferably a lactone ring structure. The specific structure of the ring structure and the content of the ring structure in the polymer (E) are as described above in the description of the polymer (D).

  The structural unit that gives negative intrinsic birefringence to the polymer is, for example, the unsaturated monomer unit described above. The preferred kind of unsaturated monomer and the preferred content of unsaturated monomer in the polymer (E) are as described above in the description of the polymer (C).

  The polymer (E) is, for example, a (meth) acrylic polymer having an unsaturated monomer unit. The (meth) acrylic polymer may have the ring structure in the main chain.

  The polymer (E) can be produced by a known method.

  The resin (A2) may contain two or more polymers (E) as long as the intrinsic birefringence is positive and the first stretched layer made of the resin (A2) exhibits reverse wavelength dispersion.

  The resin (A) may contain two or more kinds of polymers as long as the intrinsic birefringence is positive and the first stretched layer made of the resin (A) exhibits reverse wavelength dispersion. The polymer as well as any material may be included.

  Resin (A) may contain an additive. Additives include, for example, stabilizers such as antioxidants, light stabilizers, weather stabilizers, heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; ultraviolet absorbers; near infrared absorbers; Tris (dibromopropyl) Flame retardants such as phosphate, triallyl phosphate and antimony oxide; antistatic agents composed of anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers Resin modifier, plasticizer, lubricant, organic, inorganic or organic-inorganic hybrid elastic fine particles (for example, rubber fine particles). The additive may be an optical property adjusting agent such as a retardation increasing agent or retardation reducing agent, or an optical property stabilizing agent such as a retardation stabilizing agent or a humidity stabilizing agent. The content of the additive in the resin (A) is preferably less than 10% by mass, more preferably 5% by mass or less, further preferably 2% by mass or less, and particularly preferably 0.5% by mass or less.

  Resin (A) can be formed by a known method. For example, materials such as a polymer and an additive corresponding to the composition of the resin (A) to be obtained may be mixed by a known method. For example, the resin (A) is formed by pre-blending each material with a mixer such as an omni mixer and then extruding and kneading the resulting mixture. A known kneader, for example, a single screw extruder, a twin screw extruder, or a pressure kneader can be used for the extrusion kneading.

  The first stretched layer can be formed by a known method. For example, an original film may be formed from the resin (A) and the formed original film may be stretched. A known film forming method can be applied to the formation of the original film. A known film stretching method can be applied to the stretching of the original film. It is also possible to simultaneously form the second stretched layer and the first stretched layer by coextrusion molding and costretching described later.

[Second Stretched Layer]
A 2nd extending | stretching layer consists of resin (B) which has a positive intrinsic birefringence. A 2nd extending | stretching layer is an extending | stretching body which extended | stretched the resin layer which consists of resin (B). The stretched state is not limited as long as the in-plane retardation Re and reverse wavelength dispersibility described above are obtained as the entire retardation film including the first and second stretched layers. For example, the stretched layer is a uniaxially stretchable layer. Or a biaxially stretchable layer.

  The composition of the resin (B) is not limited as long as the intrinsic birefringence as the resin (B) is positive, but the resin (B) needs to contain at least one polymer having a positive intrinsic birefringence.

  The wavelength dispersibility exhibited by the second stretched layer is not limited. As long as the entire retardation film including the first and second stretched layers exhibits reverse wavelength dispersibility, the second stretched layer has a wavelength dispersibility (in order of increasing retardation as the wavelength becomes shorter, at least in the visible light region). Wavelength dispersion). In general, resins that exhibit a large retardation due to orientation often exhibit forward wavelength dispersion when used as a stretched layer. In order to reduce the thickness of the retardation film while ensuring a large retardation, it is preferable to exhibit a large retardation even though the second stretched layer is thin. From this viewpoint, it is preferable that the resin (B) and the second stretched layer made of the resin exhibit forward wavelength dispersion.

  The resin (B) includes, for example, a cycloolefin polymer or a (meth) acrylic polymer having a positive intrinsic birefringence. The (meth) acrylic polymer typically has a ring structure in the main chain.

  Cycloolefin polymers and (meth) acrylic polymers have high transparency and mechanical properties. For this reason, the retardation film of the present invention having the second stretched layer containing these polymers is suitable for use in an image display device such as an LCD.

  From the viewpoint of the surface strength of the retardation film of the present invention having the second stretched layer and the layer, the resin (B) preferably contains a (meth) acrylic polymer having a ring structure in the main chain.

  The cycloolefin polymer has a positive intrinsic birefringence. A specific cycloolefin polymer is not limited, For example, it is a cycloolefin polymer mentioned above in description of resin (A).

  The (meth) acrylic polymer is not limited as long as it has a positive intrinsic birefringence. Specific (meth) acrylic polymers including (meth) acrylic polymers having a ring structure in the main chain are not limited. For example, among the (meth) acrylic polymers described above in the description of the resin (A), A polymer having positive intrinsic birefringence.

  The cycloolefin polymer has a ring structure in the main chain. For this reason, it has high Tg, and the heat resistance of the retardation film of this invention which has a 2nd extending | stretching layer and the said layer improves.

  The (meth) acrylic polymer having a ring structure in the main chain has a high Tg, for example, 110 ° C. or higher, 120 ° C. or higher, and further 130 ° C. or higher depending on the configuration of the polymer. By including the (meth) acrylic polymer having a high Tg as described above, the heat resistance of the retardation film of the present invention having the second stretched layer and the layer is improved.

  The resin (B) may contain two or more kinds of polymers as long as its intrinsic birefringence is positive.

  As long as the intrinsic birefringence is positive, the resin (B) may contain a polymer other than those described above and any material, for example, the additives described above in the description of the resin (A).

  Resin (B) can be formed by a known method. For example, materials such as a polymer and an additive corresponding to the composition of the resin (B) to be obtained may be mixed by a known method. For example, the resin (B) is formed by pre-blending each material with a mixer such as an omni mixer and then extruding and kneading the resulting mixture. A known kneader, for example, a single screw extruder, a twin screw extruder, or a pressure kneader can be used for the extrusion kneading.

  The second stretched layer can be formed by a known method. For example, an original film may be formed from the resin (B) and the formed original film may be stretched. A known film forming method can be applied to the formation of the original film. A known film stretching method can be applied to the stretching of the original film. It is also possible to simultaneously form the first stretched layer and the second stretched layer by coextrusion molding and costretching described later.

[Phase difference film]
The retardation film of the present invention has an in-plane retardation of 20 to 300 nm with respect to light having a wavelength of 590 nm. The retardation film of the present invention is suitable as a λ / 4 plate or a λ / 2 plate used for an image display device such as an LCD.

  The retardation film of the present invention exhibits a large retardation even though it is thin, depending on its configuration. In the retardation film of the present invention, the in-plane retardation Re per 100 μm thickness with respect to light having a wavelength of 590 nm is, for example, 150 nm or more, and is 180 nm or more, further 240 nm or more depending on the configuration of the retardation film.

  The in-plane retardation Re for light having a wavelength of 590 nm in the retardation film of the present invention is preferably 20 to 300 nm, more preferably 50 to 300 nm, and still more preferably 100 to 300 nm. When the retardation film of the present invention is used as a λ / 4 plate, the in-plane retardation Re for light with a wavelength of 590 nm in the retardation film is preferably 130 to 165 nm, more preferably 135 to 160 nm, and 140 to 155 nm. Is more preferable.

  The retardation film of the present invention exhibits reverse wavelength dispersion. The degree of reverse wavelength dispersion depends on the wavelength dispersion exhibited by each of the first and second stretched layers. The preferable degree of reverse wavelength dispersion is expressed by the ratio Re (447) / Re (590) and the ratio Re (750) / Re (590), which will be described later, and is 0.50 for the ratio Re (447) / Re (590). -0.99 is preferable, 0.60-0.98 is more preferable, and 0.70-0.95 is further more preferable. Moreover, about ratio Re (750) / Re (590), 1.00-1.40 are preferable, 1.00-1.35 are more preferable, and 1.00-1.30 are further more preferable.

  The first and second stretched layers are made of a resin having positive intrinsic birefringence, and the optical axis of the first stretched layer and the optical axis of the second stretched layer are parallel to each other. A phase difference film usually exhibits positive birefringence. Positive birefringence indicates that the stretching direction of each stretched layer constituting the retardation film matches the direction of the slow axis. However, this is not the case when the retardation film of the present invention includes layers other than the first and second stretched layers, and the layer greatly affects the birefringence of the retardation film of the present invention.

  Although the thickness of the retardation film of the present invention is not limited, it exhibits a large retardation even though it is thin depending on its configuration. For example, it can be 100 μm or less, further 90 μm or less, and 80 μm or less. In the retardation film of the present invention, the in-plane retardation Re per 100 μm thickness with respect to light having a wavelength of 590 nm is, for example, 150 nm or more. Therefore, the retardation film of the present invention has, for example, a thickness of 100 μm or less depending on the configuration. It can be used as a λ / 4 plate having a thickness.

  In the retardation film of the present invention, as long as the in-plane retardation Re for light with a wavelength of 590 nm in the film is 20 nm or more and 300 nm or less and the film exhibits reverse wavelength dispersion, the first stretched layer and the second stretched film are used. The ratio of the layer thicknesses (stacking ratio) can be set freely.

  For example, in the retardation film of the present invention, the first stretched layer exhibits reverse wavelength dispersion, whereby the retardation film as a whole exhibits reverse wavelength dispersion, but the first stretched layer exhibits strong reverse wavelength dispersion. In the case of being formed of the resin shown, the thickness of the first stretched layer can be reduced. On the other hand, when the second stretched layer is made of a resin having strong retardation, the thickness of the second stretched layer can be reduced. Depending on the resin constituting the first and second stretch layers, which stretch layer is a relatively thin layer differs, but the thickness of the “relatively thin layer” and the “relatively thick layer” The ratio is, for example, 2:98 to 50:50. The specific thickness of each layer varies depending on the thickness of the retardation film as a whole. For example, when a retardation film having a thickness of 100 μm is used, the thickness of the relatively thin layer is 2 to 50 μm. The thickness of the thicker layer is 50 to 98 μm. In the case where the retardation film has two or more first (or second) stretched layers, the total is defined as the thickness of the first (or second) stretched layer.

  In the examples described later, the thickness of the first stretched layer is larger than the thickness of the second stretched layer and is twice or more. Depending on the resin constituting the first and second stretched layers and the stretched state of the stretched layer, the thickness of the first stretched layer is not less than 2 times, not less than 5 times the thickness of the second stretched layer, and Is 8 times or more.

  When the second stretched layer is made of a resin having a strong retardation, the in-plane retardation Re per 100 μm thickness with respect to light having a wavelength of 590 nm in the second stretched layer is, for example, the first stretched layer. This is at least twice the in-plane retardation Re per 100 μm thickness for light with a wavelength of 590 nm in the layer. Depending on the type of resin constituting each of the first and second stretched layers and the stretched state of each stretched layer, the in-plane retardation Re in the second stretched layer may be the in-plane position in the first stretched layer. The phase difference Re is 5 times or more, further 8 times or more.

  The number of the 1st and 2nd extending | stretching layers in the retardation film of this invention is not limited as long as the effect of this invention is acquired. For example, first stretch layer / second stretch layer, first stretch layer / second stretch layer / first stretch layer, second stretch layer / first stretch layer / second stretch layer, It has the following layer structure. An example is shown in FIG. The retardation film 4 shown in FIG. 2 has a layer configuration of second stretched layer 3 / first stretched layer 2 / second stretched layer 3. Thus, the retardation film of the present invention may be a multilayer body of two kinds of stretched layers.

  When the resin constituting the stretched layer contains elastic fine particles, the elastic fine particles may be exposed on the surface depending on the film forming conditions of the layer, and the haze of the layer may increase. In this case, an increase in haze can be suppressed by sandwiching the stretched layer containing elastic fine particles with another layer. For example, in the retardation film 4 shown in FIG. 2, even when the resin (A) constituting the first stretched layer 2 includes elastic fine particles, the first stretched layer 2 is formed by the pair of second stretched layers 3. By sandwiching, an increase in haze based on the fine particles can be suppressed.

  The retardation film of the present invention may contain any layer other than the first and second stretched layers as long as the effects of the present invention are obtained.

  The retardation film of the present invention can be used for optical compensation of LCDs in various modes including VA mode LCDs and IPS mode LCDs. In addition to the LCD, it can be used for various image display devices and optical devices.

  The method for producing the retardation film of the present invention is not limited. The retardation film of this invention can be manufactured with the manufacturing method of the retardation film of this invention, for example.

[Method for producing retardation film]
In the production method of the present invention, the resin (A) and the resin (B) are coextruded to form a first resin layer made of the resin (A) and a second resin layer made of the resin (B). By forming an original film having a laminated structure and stretching the formed original film, that is, by co-stretching the first resin layer and the second resin layer, the first resin layer can be A stretched layer is formed, and a second stretched layer is formed from the second resin layer to obtain the retardation film of the present invention. This method is highly productive. For example, it is possible to perform production from the co-extrusion of the original film to the formation of the retardation film by co-stretching.

  In the production method of the present invention viewed from another aspect, a solution containing the other resin is applied to the surface of the resin layer composed of one resin selected from the resin (A) and the resin (B), The coating film formed by coating is dried to form an original film having a laminated structure of the resin layer and the coating layer composed of the other resin; by stretching the formed original film, that is, By co-stretching the resin layer and the coating layer, the first and second stretched layers are formed from the resin layer and the coating layer to obtain the retardation film of the present invention. This method is highly productive. For example, it is possible to perform production from the formation of an original film to the formation of a retardation film by co-stretching. In addition, a 1st extending | stretching layer is formed from the layer comprised by resin (A), and the 2nd extending | stretching layer is formed from the layer comprised by resin (B) among a resin layer and a coating layer.

  In the latter production method, the type of the resin (the other resin) used as the coating layer by applying and drying the solution is not limited, and may be either resin (A) or (B). Since the coating layer is thinner than the resin layer, a resin (B) exhibiting strong retardation and a resin (A) exhibiting strong reverse wavelength dispersion can be obtained even when a thin stretched layer is used. And it is sufficient. For example, in the latter manufacturing method, the one resin is the resin (A) and the other resin is the resin (B), and the first stretched layer is formed from the resin layer by stretching the original film. Then, the second stretched layer may be formed from the coating layer.

  In the production method of the present invention, the method for stretching the original film is not limited, and a known method for stretching the resin film may be applied.

  In the former production method, the method of forming the original film by coextrusion molding of the resins (A) and (B) is not limited, and a known coextrusion molding method may be applied.

  The solvent of the solution containing the other resin used in the latter production method is not limited as long as it can dissolve the other resin and form a coating layer made of the other resin on the resin layer. , Dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene and other halogenated hydrocarbons; phenols such as phenol and parachlorophenol; benzene, toluene, xylene, methoxybenzene, 1, 2 -Aromatic hydrocarbons such as dimethoxybenzene; Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Esters such as ethyl acetate and butyl acetate; Alcohol such as methanol, ethanol and butyl alcohol Glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, ethyl cellosolve, butyl cellosolve, 2-pyrrolidone, N -Methyl-2-pyrrolidone, pyridine, triethylamine, dimethylformamide, dimethylacetamide, acetonitrile, butyronitrile, carbon disulfide. Two or more of these solvents may be mixed and used.

  As long as the coating layer is formed, the solution may contain various additives such as a surfactant, an antifoaming agent, a plasticizer, an ultraviolet absorber, an antioxidant, a dye, a pigment, and an adhesion improver. Good.

  The application method of the solution is not limited, and a known method can be applied. Specifically, kiss coat, spin coat, roll coat, dip coat, curtain coat, bar coat, doctor blade coat, knife coat, air knife coat, die coat, gravure coat, micro gravure coat, offset gravure coat, lip coat, spray coat The solution may be applied on the resin layer by various methods such as comma coating.

  What is necessary is just to dry the coating film formed on the resin layer by application | coating of a solution with a dryer, oven, etc., for example. The drying time is about 30 seconds to 30 minutes. The drying temperature is preferably set to a temperature not higher than the boiling point of the solvent in the initial stage of drying, and then raised to a temperature lower than Tg of the resin layer. If the drying temperature is excessively high, bubbles may be generated in the finally obtained retardation film. If the drying temperature is excessively low, the solvent remains in the coating layer, and the remaining solvent volatilizes little by little, so that the optical characteristics of the retardation film may change over time.

  The retardation film of the present invention can be produced by a method other than the production method of the present invention. For example, the first and second stretch layers can be formed separately, and the first and second stretch layers can be laminated so that their optical axes are parallel to each other. However, it is preferable to manufacture the retardation film of the present invention by the manufacturing method of the present invention using co-stretching because the optical axis shift between the stretched layers can be minimized and the productivity is excellent.

[Difference in glass transition temperature between resins (A) and (B) ΔTg]
In the retardation film of the present invention and the production method of the present invention, the difference ΔTg in glass transition temperature between the resins (A) and (B) is preferably 10 ° C. or less. The retardation exhibited by the retardation film can be controlled by the stretching temperature during production. When ΔTg between the resins (A) and (B) is 10 ° C. or less, a change in wavelength dispersion is suppressed even when the stretching temperature is changed during the production of the retardation film. That is, while using the same original film, retardation films having substantially the same wavelength dispersion and different retardation values can be produced. Such a retardation film can easily change the value of the retardation while maintaining the wavelength dispersion substantially constant during the production thereof.

  When the resin layer is stretched, the degree of orientation of the polymer contained in the layer is greatly influenced by the magnitude relationship and temperature difference between the glass transition temperature (Tg) of the layer and the stretching temperature. Specifically, as the stretching temperature is lower than the Tg of the layer (if it is too low, the resin layer breaks, making stretching itself impossible), the degree of orientation of the polymer becomes stronger and the resulting complex Refraction increases. The magnitude of the effect also varies depending on how far the stretching temperature changes from the Tg. For example, even when the stretching temperature changes by the same amount, the change in the birefringence caused by the change in the stretching temperature is larger as the stretching temperature is farther from the Tg of the layer. That is, when ΔTg between the resins (A) and (B) is large, when the stretching temperature is changed, the degree of change in birefringence differs greatly for each of the resin layers A and B, and the retardation film. The wavelength dispersibility of is easily changed. On the other hand, by setting the ΔTg between the resins (A) and (B) to 10 ° C. or less, it is possible to suppress the difference between the birefringence changes in the resin layers A and B when the stretching temperature is changed. . Thereby, the value of the phase difference can be changed while keeping the wavelength dispersion substantially the same.

  The effect of setting ΔTg to 10 ° C. or less is remarkable when a retardation film is continuously produced by co-stretching, and it is consistent from the co-extrusion of the original film to the formation of the retardation film by co-stretching. This is particularly noticeable when performed. Usually, in order to obtain a retardation film having substantially the same wavelength dispersion but different retardation values, it is necessary to individually select and adjust the composition and thickness of each layer constituting the film. For this purpose, the original film is exchanged or the inside of the extrusion molding machine is “washed” with new resin one by one. However, by setting ΔTg to 10 ° C. or less, it is possible to obtain a retardation film having a substantially constant wavelength dispersion and a different retardation value while omitting these operations. This method is advantageous in terms of production cost of the retardation film.

  The Tg of the resin can be determined according to JIS K7121. Even when the resin is composed of two or more kinds of polymers, the measured Tg is basically one point because the polymers are compatible with each other. When Tg based on a polymer is measured at two or more points, a weighted average of each Tg may be obtained based on the content (% by weight) of each polymer in the resin, and this may be used as the Tg of the resin. When the additive is a low molecule, it does not affect the Tg of the resin. When the additive is a particle having a polymer component, for example, a rubber fine particle added to a retardation film for the purpose of improving mechanical properties, Tg derived from the particle may be measured. However, in this case, the Tg derived from these particles and the Tg derived from the polymer constituting the film can be easily distinguished, and the latter may be the resin Tg. These particles are not oriented by stretching of the original film, that is, do not affect the wavelength dispersion and retardation value of the retardation film.

  The phase dispersion having substantially the same wavelength dispersion means that for the two retardation films to be compared, the in-plane retardation Re (447) for light having a wavelength of 447 nm and the in-plane retardation Re for light having a wavelength of 590 nm (590). ) And the ratio of the in-plane phase difference Re (750) for light with a wavelength of 750 nm to the in-plane phase difference Re (590) for light with a wavelength of 590 nm [ The difference of Re (750) / Re (590)] is 0.02 or less. Re (447), Re (590), and Re (750) are values when the thicknesses of the retardation films are made uniform.

  The glass transition temperature difference ΔTg between the resins (A) and (B) is preferably 7 ° C. or less, more preferably 5 ° C. or less, and further preferably 3 ° C. or less. In this case, when the stretching temperature is changed, the occurrence of a difference in the degree to which birefringence changes in the first and second stretched layers is further suppressed.

[Image display device]
The image display device of the present invention includes the retardation film of the present invention. As a result, the image display device is excellent in image display characteristics, for example, an image display device with high contrast and a wide viewing angle.

  The image display device of the present invention is, for example, an LCD. More specifically, for example, a VA mode LCD and an IPS mode LCD.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.

  Initially, the evaluation method of the polymer produced in the present Example and retardation film is shown.

[Polymerization reaction rate, polymer composition analysis]
The polymerization reaction rate during the production of the polymer and the content of the constituent units in the produced polymer were calculated from the amount of unreacted monomer remaining in the obtained polymerization solution. The amount of unreacted monomer was measured by gas chromatography (manufactured by Shimadzu Corporation, GC2010).

[Weight average molecular weight]
The weight average molecular weight of the polymer was determined by polystyrene conversion using gel permeation chromatography (GPC) according to the following measurement conditions.

Measurement system: Tosoh GPC system HLC-8220
Developing solvent: Chloroform (Wako Pure Chemical Industries, special grade)
Solvent flow rate: 0.6 mL / min Standard sample: TSK standard polystyrene (manufactured by Tosoh, PS-oligomer kit)
Measurement side column configuration: Tosoh, TSK-GEL super HZM-M 6.0X150, 2 in series
Tosoh, TSK-GEL super HZ-L 4.6X35, 1 reference column configuration: Tosoh, TSK-GEL SuperH-RC 6.0X150, 2 in-line connection Column temperature: 40 ° C

[Glass transition temperature (Tg)]
The glass transition temperature (Tg) of the polymer and resin was determined in accordance with the provisions of JIS K7121. Specifically, using a differential scanning calorimeter (Rigaku, Thermo plus EVO DSC-8230), a sample of about 10 mg was heated from room temperature to 200 ° C. in a nitrogen gas atmosphere (temperature increase rate 20 ° C./min). From the DSC curve obtained in this way, the starting point method was used for evaluation. Α-alumina was used as a reference.

[Film thickness d]
The thickness of the retardation film was measured using a Digimatic micrometer (manufactured by Mitutoyo).

[Total light transmittance and haze ratio]
The total light transmittance and haze ratio of the retardation film were measured using NDH-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

[Average refractive index]
The average refractive index of the retardation film was measured using a refractometer (manufactured by Atago, Digital Abbe refractometer DR-M2) at 23 ° C. with respect to a measurement wavelength of 589 nm, in accordance with JIS K7142.

[Phase difference]
The in-plane retardation Re and the thickness direction retardation Rth of the retardation film with respect to light having a wavelength of 590 nm were measured using a retardation film / optical material inspection apparatus (RETS-100, manufactured by Otsuka Electronics Co., Ltd.). The thickness d and average refractive index of the retardation film input to the apparatus at the time of measurement were measured according to the method described above. At the time of measuring Rth, the retardation film to be measured was tilted. Of the slow axis and the fast axis of the film, the tilt axis is Re (S40 °) measured with the slow axis as the tilt axis, and Re (F40 °) measured with the fast axis as the tilt axis. In comparison, a larger value was obtained.

[Wavelength dispersion]
For the wavelength dispersion of the retardation film, the in-plane retardation Re (447), Re (590) and Re (750) for light having wavelengths of 447 nm, 590 nm and 750 nm were changed to 447 nm, 590 nm and 750 nm, respectively. The ratio Re (447) / Re (590) and the ratio Re (750) / Re (590) were calculated and evaluated. When the ratio Re (447) / Re (590) is less than 1 and the ratio Re (750) / Re (590) exceeds 1, the retardation film exhibits reverse wavelength dispersion. On the other hand, when the ratio Re (447) / Re (590) is 1 or more and the ratio Re (750) / Re (590) is 1 or less, the retardation film exhibits forward wavelength dispersion.

(Production Example 1)
As a cycloolefin polymer, pellets of polynorbornene (manufactured by JSR, ARTON RH5200J, Tg: 142 ° C.) were prepared. Next, the prepared pellets are put into a single-screw extruder (φ = 20 mm, L / D = 25, cylinder temperature 280 ° C.) equipped with a coat hanger type film-forming die (width 150 mm). Film formation at a preset temperature of 290 ° C. yielded an unstretched polynorbornene film (1F-1) having a thickness of 14 μm. Apart from the production of the polynorbornene film (1F-1), the take-up speed of the film discharged from the die was adjusted to obtain an unstretched polynorbornene film (1F-2) having a thickness of 40 μm.

  The intrinsic birefringence of the polynorbornene constituting the produced films (1F-1) and (1F-2) was positive. In addition, the positive / negative of the intrinsic birefringence of resin which comprises a film was evaluated as follows. First, the produced unstretched film was made into a 80 mm × 50 mm film piece, and uniaxially stretched at a stretching temperature of 125 ° C. and a stretching ratio of 2 times using an autograph (manufactured by Shimadzu Corporation) equipped with a heated room, and stretched It was. Since 20 mm at both ends in the longitudinal direction of the film piece was used as the allowance for attaching the chuck, the substantially stretched film piece portion was 40 mm × 50 mm. Next, the orientation angle of the stretched film was determined using a fully automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-WR). If the measured orientation angle is in the vicinity of 0 ° (that is, if it is parallel or substantially parallel to the stretch direction of the stretched film), the intrinsic birefringence of the resin constituting the film is positive, and the measured orientation If the angle is in the vicinity of 90 ° (that is, if the direction is perpendicular or nearly perpendicular to the stretching direction of the stretched film), the intrinsic birefringence of the resin constituting the film is negative. Also in the following manufacture examples, the positive / negative of the intrinsic birefringence of resin which comprises a film was evaluated similarly.

  The wavelength dispersibility of the stretched film obtained by stretching the produced films (1F-1) and (1F-2) alone is such that the ratio Re (447) / Re (590) is 1.01, and the ratio Re (750). The forward wavelength dispersibility was / Re (590) of 0.99. The stretched film was produced in the same manner as when positive / negative evaluation of intrinsic birefringence was performed. The evaluation method of wavelength dispersion was the same in the following production examples.

(Production Example 2)
As a cellulose derivative, cellulose acetate propionate (CAP) [acetyl group substitution degree 2.5% by weight, hydroxyl group substitution degree 1.8% by weight, propionyl group substitution degree 46% by weight, number average molecular weight Mn = 63,000 , Weight average molecular weight Mw = 175,000, Tg: 136 ° C.] is put into a twin screw extruder (φ = 15 mm, L / D = 45, barrel temperature 250 ° C.), melt-kneaded, pellets Got. Next, the pellets were put into a single-screw extruder (φ = 20 mm, L / D = 25, cylinder temperature 240 ° C.) equipped with a coat hanger type film forming die (width 150 mm), and the die set temperature was set. Film formation at 240 ° C. was performed to obtain an unstretched CAP film (2F-1) having a thickness of 99 μm. Separately from the production of the CAP film (2F-1), the take-up speed of the film discharged from the die was adjusted to obtain an unstretched CAP film (2F-2) having a thickness of 113 μm.

  The intrinsic birefringence of CAP constituting the produced films (2F-1) and (2F-2) was positive. The wavelength dispersibility of the stretched film obtained by stretching the produced films (2F-1) and (2F-2) alone is 0.79 for the ratio Re (447) / Re (590), and the ratio Re (750). / Re (590) was 1.11 with reverse wavelength dispersion.

(Production Example 3)
To a reactor having an internal volume of 30 L equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introduction pipe, 7000 g of methyl methacrylate (MMA), 3000 g of methyl 2- (hydroxymethyl) methyl acrylate (MHMA) and a polymerization solvent 12000 g of toluene was charged, and the temperature was raised to 105 ° C. while passing nitrogen through it. When refluxing with the temperature increase started, 6.0 g of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 570) was added as a polymerization initiator, and the above t-amyl was added to 100 g of toluene. While a solution in which 12.0 g of peroxyisononanoate was dissolved was added dropwise over 2 hours, solution polymerization was allowed to proceed under reflux at about 105 to 110 ° C., followed by further aging for 4 hours. At this time, the polymerization reaction rate was 92.9%, and the content of MHMA units in the formed polymer was 30.2% by weight.

  Next, 20 g of an octyl phosphate / dioctyl mixture is added to the resulting polymerization solution as a catalyst for the cyclization condensation reaction (cyclization catalyst), and the cyclization condensation reaction is performed at reflux of about 80 to 105 ° C. for 2 hours. Made progress. Next, 4000 g of methyl ethyl ketone was added to dilute the polymerization solution, and then the cyclization condensation reaction was allowed to proceed for an additional 1.5 hours in an autoclave at 240 ° C. (pressurized to a maximum of 2 MPa with a gauge pressure).

  Next, the obtained polymerization solution was introduced into a screwed twin screw extruder, and 26.5 g of zinc octylate (Nikka Octix zinc 18% manufactured by Nippon Chemical Industry Co., Ltd.), 4.4 g of antioxidant (2 2 g of Ciba Specialty Chemicals IRGANOX1010 + 2.2 g of ADEKA ADK STAB AO-412S) and 61.6 g of toluene were introduced into the extruder to further progress the cyclization condensation reaction and devolatilization of volatile components. went. The introduction speed of the above mixed liquid into the extruder was 20 g / hour.

  Next, the resin inside was discharged from the tip of the extruder, cooled by a water bath, and then pelletized by a pelletizer to obtain transparent pellets made of a (meth) acrylic polymer having a lactone ring structure in the main chain. When dynamic TG measurement was performed on the obtained pellets, the actual weight loss rate (X) was 0.21% by weight. The obtained (meth) acrylic polymer had a weight average molecular weight of 110,000 and Tg of 140 ° C.

  Next, the prepared pellets were put into a single screw extruder (φ = 20 mm, L / D = 25, cylinder temperature 280 ° C.) equipped with a coat hanger type film-forming die (width 150 mm), and the die was set. Film formation at a temperature of 290 ° C. yielded an unstretched acrylic film (3F-1) having a thickness of 14 μm. Separately from the production of the acrylic film (3F-1), the take-up speed of the film discharged from the die is adjusted so that the unstretched acrylic film (3F-2) having a thickness of 28 μm and the unstretched acrylic having a thickness of 21 μm. A film (3F-3) was obtained.

  The intrinsic birefringence of the (meth) acrylic polymer constituting the produced films (3F-1), (3F-2), and (3F-3) was positive. The wavelength dispersibility of the stretched film obtained by stretching the produced films (3F-1), (3F-2), and (3F-3) alone is 1.03 in the ratio Re (447) / Re (590). The forward wavelength dispersion was such that the ratio Re (750) / Re (590) was 0.98.

(Production Example 4)
The main chain has a lactone ring structure in the same manner as in Production Example 3 except that the monomer and polymerization solvent charged in the reactor were 5000 g of MMA, 3000 g of MHMA, 2000 g of benzyl methacrylate, and 10,000 g of toluene ( Transparent pellets made of a (meth) acrylic polymer were obtained. The Tg of the (meth) acrylic polymer was 132 ° C.

(Production Example 5)
A reactor equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introduction pipe was charged with 14400 g of MMA, 3600 g of MHMA, 2000 g of N-vinylcarbazole and 16000 g of toluene as a polymerization solvent, and nitrogen was introduced into the reactor. The temperature was raised to ° C. When reflux accompanying the temperature increase started, 20 g of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 570) was added as a polymerization initiator, and the above-mentioned t-amyl peroxy was added to 2000 g of toluene. While a solution in which 40 g of isononanoate was dissolved was dropped over 2 hours, solution polymerization was allowed to proceed under reflux at about 105 to 110 ° C., and aging was further performed for 4 hours.

  Next, the polymerization solution thus obtained is subjected to a cyclization condensation reaction and devolatilization of volatile components in the same manner as in Production Example 3, so that the main chain has a lactone ring structure and constitutes an N-vinylcarbazole unit. Transparent pellets made of a (meth) acrylic polymer as a unit were obtained. The Tg of the (meth) acrylic polymer was 137 ° C.

(Production Example 6)
After dry blending 10 parts by weight of the (meth) acrylic polymer pellets produced in Production Example 3 and 20 parts by weight of the (meth) acrylic polymer pellets produced in Production Example 5, a screw twin screw extruder (plastic) The mixture was kneaded at 260 ° C. using BT-30-S21C-30-1) manufactured by Engineering Laboratory. Next, the molten resin obtained by kneading is put into a single-screw extruder (φ = 20 mm, L / D = 25, cylinder temperature 280 ° C.) equipped with a coat hanger type film forming die (width 150 mm). The film was melted at a die setting temperature of 290 ° C. to obtain an unstretched acrylic film (4F-1) having a thickness of 71 μm.

  The intrinsic birefringence of the acrylic resin constituting the produced film (4F-1) was positive, and Tg was 138 ° C. The wavelength dispersibility of the stretched film obtained by stretching the produced film (4F-1) alone is 0.68 for the ratio Re (447) / Re (590), and the ratio Re (750) / Re (590). The reverse wavelength dispersibility was 1.14.

(Production Example 7)
In the same manner as in Production Example 6 except that the (meth) acrylic polymer pellets produced in Production Example 4 were used instead of the (meth) acrylic polymer pellets produced in Production Example 3, an uncoated 71 μm thick A stretched acrylic film (5F-1) was obtained.

  The intrinsic birefringence of the acrylic resin constituting the produced film (5F-1) was positive, and Tg was 135 ° C. The wavelength dispersibility of the stretched film obtained by stretching the produced film (5F-1) alone is 0.80 for the ratio Re (447) / Re (590), and the ratio Re (750) / Re (590). The reverse wavelength dispersibility was 1.08.

(Production Example 8)
Instead of 10 parts by weight of the (meth) acrylic polymer pellets produced in Production Example 3, 10 parts by weight of an acrylic imide polymer (Rohm and Haas, KAMAX T-240) and Production Example 5 (Metal) ) An unstretched acrylic film (6F-1) having a thickness of 57 μm was obtained in the same manner as in Production Example 6 except that 25 parts by weight of an acrylic polymer pellet was used.

  The intrinsic birefringence of the acrylic resin constituting the produced film (6F-1) was positive, and Tg was 143 ° C. Regarding the wavelength dispersibility of the stretched film obtained by stretching the produced film (6F-1) alone, the ratio Re (447) / Re (590) is 0.71, and the ratio Re (750) / Re (590) is The reverse wavelength dispersion was 1.05.

(Production Example 9)
Single-screw extruder (φ = 20 mm, L / D = 25) to which polystyrene (made by Toyostyrene, Toyostyrene H1 H650, Tg: 100 ° C.) was attached with a film hanger type film-forming die (width 150 mm). , Cylinder temperature 220 ° C.) and melt-cast at a die setting temperature of 220 ° C. to obtain an unstretched polystyrene film (7F-1) having a thickness of 200 μm.

  The intrinsic birefringence of polystyrene constituting the produced film (7F-1) was negative. As for the wavelength dispersibility of the stretched film obtained by stretching the produced film (7F-1) alone, the ratio Re (447) / Re (590) is 1.06, and the ratio Re (750) / Re (590) is The forward wavelength dispersibility was 0.96.

(Production Example 10)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe and a dropping funnel, MHMA 15 parts by weight, MMA 27 parts by weight, methacrylic acid (MA) 10 parts by weight, N-vinylcarbazole (NVCz) 6 parts by weight and As a polymerization solvent, 37 parts by weight of toluene and 2 parts by weight of methanol were charged, and the temperature was raised to 95 ° C. while passing nitrogen therein. At the start of the reflux with temperature rise, 0.029 parts by weight of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 575) was added as a polymerization initiator, and 15 parts by weight of MHMA Then, dropwise addition of a mixture of 27 parts by weight of MMA, 17 parts by weight of toluene and 0.082 parts by weight of the above t-amylperoxy-2-ethylhexanoate was started. While this mixture was added dropwise over 8 hours, solution polymerization was allowed to proceed under reflux at about 90 to 100 ° C. In addition to this, 23.3 parts by weight of toluene was added dropwise over 3 hours from the time when 5 hours had elapsed from the start of polymerization to dilute the polymerization solution.

  Next, 0.24 parts by weight of an octyl phosphate / dioctyl mixture as a cyclization catalyst was added to the obtained polymerization solution, and the cyclization condensation reaction was allowed to proceed for 2 hours under reflux at about 80 to 105 ° C. Next, after 21.4 parts by weight of methyl isobutyl ketone (MIBK) was added to dilute the polymerization solution, the cyclization condensation reaction was further advanced, volatile components were devolatilized and pelletized in the same manner as in Production Example 3. A transparent pellet made of a (meth) acrylic polymer having a lactone ring structure in the main chain and having an N-vinylcarbazole unit as a constituent unit was obtained. The obtained (meth) acrylic polymer had a weight average molecular weight of 110,000 and Tg of 132 ° C.

(Production Example 11)
A lactone is added to the main chain in the same manner as in Production Example 3, except that the monomer and polymerization solvent charged in the reactor are MMA 30 parts by weight, MHMA 15 parts by weight, n-butyl methacrylate 5 parts by weight and toluene 50 parts by weight. Transparent pellets made of a (meth) acrylic polymer having a ring structure were obtained. The obtained (meth) acrylic polymer had a weight average molecular weight of 110,000 and Tg of 132 ° C.

(Production Example 12)
In a polymerization vessel equipped with a cooler and a stirrer, 710 parts by weight of deionized water and 1.5 parts by weight of sodium lauryl sulfate were added to dissolve sodium lauryl sulfate in deionized water. Next, after raising the temperature in the polymerization vessel to 70 ° C., 0.93 parts by weight of sodium formaldehyde sulfoxylate (SFS), 0.001 part by weight of ferrous sulfate, disodium ethylenediaminetetraacetate (EDTA) 0 A mixed solution of 0.003 parts by weight and 20 parts by weight of deionized water was charged into the polymerization vessel at a time, and then the polymerization vessel was sufficiently replaced with nitrogen gas.

  Next, 7.1 parts by weight of butyl acrylate (BA), 2.9 parts by weight of styrene (St), 0.02 part by weight of 1,4-butanediol dimethacrylate (BDMA) and allyl methacrylate (AMA) 0 0.02 part by weight of monomer mixture (M-1) and t-butyl hydroperoxide (PBH) 0.13 part by weight and deionized water 10.0 part by weight in a polymerization vessel The monomers contained in the monomer mixture (M-1) were allowed to polymerize for 60 minutes. Next, a monomer mixture (M-2) consisting of 63.9 parts by weight of BA, 25.2 parts by weight of St and 0.9 parts by weight of AMA, and a polymerization start consisting of 0.246 parts by weight of PBH and 20.0 parts by weight of deionized water The agent solution was continuously dropped into the polymerization vessel from different routes over 90 minutes, and the polymerization of the monomer contained in the monomer mixture (M-2) was advanced. The polymerization was continued for another 60 minutes after the completion of the dropping. Thereby, the part used as the core in the rubber-like polymer which has a core / shell structure was obtained.

  Next, a monomer mixed solution (M-3) comprising 73.0 parts by weight of St and 27.0 parts by weight of acrylonitrile (AN), a polymerization initiator solution comprising 0.27 parts by weight of PBH and 20.0 parts by weight of deionized water Was continuously dropped into the polymerization vessel from separate routes over 100 minutes, and the polymerization of the monomer contained in the monomer mixture (M-3) was allowed to proceed. In addition, even after completion | finish of dripping, the temperature in a superposition | polymerization container was heated up to 80 degreeC, and the further superposition | polymerization was advanced for 120 minutes.

  Thereafter, the temperature in the polymerization vessel was cooled to 40 ° C., and then the solution in the vessel was passed through a 300-mesh wire mesh to obtain an emulsion polymerization solution of a rubbery polymer. Next, the obtained emulsion polymerization solution is salted out with calcium chloride to solidify the rubbery polymer contained in the polymerization solution, and the resulting solidified product is washed with water and dried to obtain a powdery rubber. Polymer particles (G1, average particle size 0.105 μm) were obtained.

(Production Example 13)
After dry blending 90 parts by weight of the (meth) acrylic polymer pellets produced in Production Example 11 and 10 parts by weight of the rubbery polymer particles (G1) produced in Production Example 12, a screw twin screw extruder (plastic) A transparent pellet was obtained by kneading at 260 ° C. using BT-30-S21C-30-1) manufactured by Engineering Research Laboratory. The obtained pellet had a Tg of 131 ° C.

(Production Example 14)
In a pressure-resistant reaction vessel equipped with a stirrer, 70 parts by weight of deionized water, 0.5 parts by weight of sodium pyrophosphate, 0.2 parts by weight of potassium oleate, 0.005 parts by weight of ferrous sulfate, 0.2 parts by weight of dextrose , A reaction mixture consisting of 0.1 parts by weight of p-menthane hydroperoxide and 28 parts by weight of 1,3-butadiene is charged, the temperature in the container is raised to 65 ° C., and the polymerization of the reaction mixture proceeds for 2 hours. I let you. Next, 0.2 parts by weight of p-menthane hydroperoxide was added, and then a mixture of 72 parts by weight of 1,3-butadiene, 1.33 parts by weight of potassium oleate and 75 parts by weight of deionized water was added over 2 hours. Continuous dripping. After completion of the dropping, the polymerization was continued for 21 hours from the start of polymerization to obtain a butadiene rubber polymer latex having an average particle size of 0.240 μm.

  Next, in a polymerization vessel equipped with a cooler and a stirrer, 120 parts by weight of deionized water, 50 parts by weight of the butadiene rubber polymer latex prepared above (in terms of solids), 1.5 parts by weight of potassium oleate, and SFS0. After charging 6 parts by weight, the inside of the polymerization vessel was sufficiently replaced with nitrogen gas.

  Next, after raising the temperature in the polymerization vessel to 70 ° C., a monomer mixed solution consisting of 36.5 parts by weight of St and 13.5 parts by weight of AN, 0.27 parts by weight of cumene hydroxy peroxide and 20 parts by weight of deionized water. The polymerization initiator solution consisting of parts was continuously dropped into the polymerization vessel from separate routes over 2 hours to proceed the polymerization. In addition, also after completion | finish of dripping, the temperature in a superposition | polymerization container was heated up to 80 degreeC, and superposition | polymerization was advanced for 2 hours. Thereafter, the temperature in the polymerization vessel was cooled to 40 ° C., and then the solution in the vessel was passed through a 300-mesh wire mesh to obtain an emulsion polymerization solution of elastic organic fine particles. Next, by salting out the obtained emulsion polymerization solution with calcium chloride, the elastic organic fine particles contained in the polymerization solution are coagulated, and the obtained coagulated product is washed with water and dried to obtain a powdery elastic organic material. Fine particles (G2, average particle size: 0.260 μm, refractive index of soft polymer layer: 1.516) were obtained.

(Production Example 15)
(Meth) acrylic polymer pellets produced in Production Example 10, elastic organic fine particles (G2) produced in Production Example 14, and styrene-acrylonitrile copolymer (AS resin: ratio of styrene unit / acrylonitrile unit is 73 wt%. / 27 wt%, weight average molecular weight 220,000) was kneaded at 240 ° C. using a twin screw extruder so as to obtain a weight ratio of 81: 14: 5 to obtain transparent pellets. The Tg of the obtained pellet was 129 ° C.

(Production Example 16)
A reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introduction pipe was charged with 10 parts by weight of MHMA, 40 parts by weight of MMA and 50 parts by weight of toluene as a polymerization solvent, and the temperature was raised to 105 ° C. while passing nitrogen through this. . At the beginning of the recirculation with increasing temperature, 0.05 parts by weight of t-amylperoxyisononanoate (Arkema Yoshitomi, trade name: Luperox 570) was added as a polymerization initiator, and the above-mentioned t-amylperoxyisononoate was added. While 0.10 parts by weight of nanoate was added dropwise over 2 hours, solution polymerization was allowed to proceed under reflux at about 105 to 110 ° C. After completion of the dropwise addition, the mixture was further heated for 4 hours to continue the polymerization.

  Next, 0.05 part by weight of stearyl phosphate (product name: Phoslex A-18, manufactured by Sakai Chemical Co., Ltd.) as a cyclization catalyst is added to the obtained polymerization solution, and the mixture is refluxed at about 80 to 105 ° C. for 2 hours. The cyclization condensation reaction was allowed to proceed. Next, in the same manner as in Production Example 3, volatile components were devolatilized and pelletized to obtain transparent pellets made of a (meth) acrylic polymer having a lactone ring structure in the main chain. The obtained (meth) acrylic polymer had a weight average molecular weight of 130,000 and Tg of 130 ° C.

(Production Example 17)
The (meth) acrylic polymer pellets produced in Production Example 16 and the AS resin used in Production Example 15 were kneaded at 240 ° C. using a twin-screw extruder so as to have a weight ratio of 90:10. Pellets were obtained. The obtained pellet had a Tg of 125 ° C.

(Production Example 18)
The (meth) acrylic polymer pellets produced in Production Example 16, the rubbery polymer particles (G1) produced in Production Example 12 and the AS resin used in Production Example 15 have a weight ratio of 86: 10: 4. Thus, it knead | mixed at 240 degreeC using the twin-screw extruder, and obtained the transparent pellet. The Tg of the obtained pellet was 126 ° C.

Example 1
The film (2F-1) produced in Production Example 2 and the film (1F-1) produced in Production Example 1 are laminated one by one so that the flow directions at the time of forming each film coincide. A raw film having a laminated structure was produced. Next, a film piece of 80 mm in the flow direction and 20 mm in the width direction was cut out from the produced original film. Next, the cut film piece was uniaxially stretched at a stretching temperature of 137 ° C. and a stretching ratio of 2 in the flow direction using an autograph (manufactured by Shimadzu Corporation) equipped with a heated room to obtain a retardation film. . In addition, since 20 mm of the both ends of the flow direction in the film piece was used as the allowance for attaching the chuck, the substantially stretched film piece portion was 40 mm × 20 mm.

  A film (2F-1) consists of resin which has a positive intrinsic birefringence, and shows reverse wavelength dispersion by extending | stretching. The film (1F-1) is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. As for the optical axis of the stretched body of the film (2F-1) and the stretched body of the film (1F-1) constituting the obtained retardation film, the retardation film is the film (2F-1), (1F-1). Since the film (2F-1) and the resin constituting the film (1F-1) both have positive intrinsic birefringence, they are parallel to each other. In addition, the ratio of the thickness of the film (2F-1) and the film (1F-1) was maintained even by stretching. The retention of the thickness ratio before and after stretching was the same in the following examples and comparative examples.

  The retardation film thus obtained exhibited positive birefringence and in-plane retardation Re and reverse wavelength dispersion shown in Table 1 below.

(Example 2)
A film (2F-1) produced in Production Example 2 is laid on a glass plate, and a solution of the polynorbornene pellets used in Production Example 1 dissolved in methylene chloride is cast on the surface using a wire bar. And left at room temperature for 3 minutes. Thereafter, drying was performed at 80 ° C. for 2 minutes and at 100 ° C. for 2 minutes to produce an original film having a laminated structure of a film (2F-1) and a polynorbornene layer (thickness: 14 μm). Next, the produced original film was stretched in the same manner as in Example 1 to obtain a retardation film.

  A film (2F-1) consists of resin which has a positive intrinsic birefringence, and shows reverse wavelength dispersion by extending | stretching. The polynorbornene layer is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. The optical axis of the stretched product of the film (2F-1) and the stretched polynorbornene layer constituting the obtained retardation film is prepared by co-stretching the film (2F-1) and the polynorbornene layer. Since both the film (2F-1) and the resin constituting the polynorbornene layer have positive intrinsic birefringence, they are parallel to each other.

  The retardation film thus obtained exhibited positive birefringence and in-plane retardation Re and reverse wavelength dispersion shown in Table 2 below.

(Example 3)
The film (2F-2) produced in Production Example 2 and the film (3F-1) produced in Production Example 3 are laminated one by one so that the flow directions at the time of forming each film coincide with each other. A raw film having a laminated structure was produced. Next, the produced original film was stretched in the same manner as in Example 1 to obtain a retardation film.

  The film (2F-2) is made of a resin having positive intrinsic birefringence and exhibits reverse wavelength dispersion by stretching. The film (3F-1) is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. The optical axes of the stretched film (2F-2) and the stretched film (3F-1) constituting the obtained retardation film are the retardation films of the films (2F-2) and (3F-1). Since the resin constituting the film (2F-2) and the film (3F-1) both have positive intrinsic birefringence, they are parallel to each other.

  The retardation film thus obtained exhibited positive birefringence and in-plane retardation Re and reverse wavelength dispersion shown in Table 3 below.

Example 4
The film (4F-1) produced in Production Example 6 and the film (1F-1) produced in Production Example 1 are laminated one by one so that the flow directions at the time of forming each film coincide. A raw film having a laminated structure was produced. Next, the produced original film was stretched in the same manner as in Example 1 to obtain a retardation film.

  A film (4F-1) consists of resin which has a positive intrinsic birefringence, and shows reverse wavelength dispersion by extending | stretching. The film (1F-1) is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. As for the optical axis of the stretched body of the film (4F-1) and the stretched body of the film (1F-1) constituting the obtained retardation film, the retardation film is the film (4F-1), (1F-1). Since the film (4F-1) and the resin constituting the film (1F-1) both have positive intrinsic birefringence, they are parallel to each other.

  The retardation film thus obtained exhibited positive birefringence and in-plane retardation Re and reverse wavelength dispersion shown in Table 4 below.

(Example 5)
The film (5F-1) produced in Production Example 7 and the film (1F-1) produced in Production Example 1 are laminated one by one so that the flow directions at the time of forming each film coincide with each other. A raw film having a laminated structure was produced. Next, the produced original film was stretched in the same manner as in Example 1 to obtain a retardation film.

  A film (5F-1) consists of resin which has a positive intrinsic birefringence, and shows reverse wavelength dispersion by extending | stretching. The film (1F-1) is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. As for the optical axis of the stretched body of the film (5F-1) and the stretched body of the film (1F-1) constituting the obtained retardation film, the retardation film is the film (5F-1), (1F-1). Since the film (5F-1) and the resin constituting the film (1F-1) both have positive intrinsic birefringence, they are parallel to each other.

  The retardation film thus obtained exhibited positive birefringence and in-plane retardation Re and reverse wavelength dispersion shown in Table 5 below.

(Example 6)
The film (6F-1) produced in Production Example 8 and the film (3F-2) produced in Production Example 3 are laminated one by one so that the flow directions at the time of forming each film coincide. A raw film having a laminated structure was produced. Next, the produced original film was stretched in the same manner as in Example 1 to obtain a retardation film.

  A film (6F-1) consists of resin which has a positive intrinsic birefringence, and shows reverse wavelength dispersion by extending | stretching. The film (3F-2) is made of a resin having positive intrinsic birefringence, and exhibits forward wavelength dispersion by stretching. As for the optical axis of the stretched film of the film (6F-1) and the stretched film of the film (3F-2) constituting the obtained retardation film, the retardation film is a film (6F-1) or (3F-2). Since the resin constituting the film (6F-1) and the film (3F-2) both have positive intrinsic birefringence, they are parallel to each other.

  The retardation film thus obtained exhibited positive birefringence and in-plane retardation Re and reverse wavelength dispersion shown in Table 6 below.

(Examples 7 to 14)
In Examples 7 to 14, combinations of resin (A) and resin (B) shown in Table 7 below were set. In addition, the intrinsic birefringence of all the resins (A) and (B) shown in Table 7 is positive, all the resins (A) exhibit reverse wavelength dispersion, and all the resins (B) have forward wavelength dispersion. showed that. The intrinsic birefringence and wavelength dispersion of each resin (A) and (B) were evaluated by the method described in Production Example 1.

  In each example, the resin (A) set as shown in Table 7 was transferred to a single screw extruder A (φ = 30 mm, L / D = 25, cylinder temperature 280 ° C.), and the resin (B) was transferred to another single screw extruder. Machine B (φ = 30 mm, L / D = 25, cylinder temperature 280 ° C.) and using a multi-manifold die, a laminated structure of resin (B) layer / resin (A) layer / resin (B) layer A raw film having At that time, the thickness of each layer in the original film was controlled by adjusting the discharge amount of each of the extruders A and B. The film thickness of the obtained original film is shown in Table 8 below.

  Next, a film piece of 80 mm in the flow direction and 20 mm in the width direction was cut out from the produced original film. Next, the cut film piece was uniaxially stretched at a stretching temperature of 133 ° C. and a stretching ratio of 2 in the flow direction using an autograph (manufactured by Shimadzu Corporation) equipped with a heating chamber to obtain a retardation film. . In addition, since 20 mm of the both ends of the flow direction in the film piece was used as the allowance for attaching the chuck, the substantially stretched film piece portion was 40 mm × 20 mm.

  The retardation film thus obtained exhibited positive birefringence and in-plane retardation Re and reverse wavelength dispersion shown in Table 9 below.

(Comparative Example 1)
The film (1F-1) produced in Production Example 1 and the film (3F-3) produced in Production Example 3 are laminated one by one so that the flow directions at the time of forming each film coincide. A raw film having a laminated structure was produced. Next, the produced original film was stretched in the same manner as in Example 1 to obtain a retardation film.

  The film (1F-1) is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. The film (3F-3) is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. The optical axes of the stretched film (1F-1) and the stretched film (3F-3) constituting the obtained retardation film are the films (1F-1) and (3F-3) of the retardation film. Since the resin constituting the film (1F-1) and the film (3F-3) both have positive intrinsic birefringence, they are parallel to each other.

  The retardation film thus obtained showed positive birefringence but did not show reverse wavelength dispersion (see Table 10).

(Comparative Example 2)
The film (1F-2) produced in Production Example 1 and the film (7F-1) produced in Production Example 9 are laminated one by one so that the flow directions at the time of forming each film coincide. A raw film having a laminated structure was produced. Next, the produced original film was stretched in the same manner as in Example 1 to obtain a retardation film.

  The film (1F-2) is made of a resin having positive intrinsic birefringence and exhibits forward wavelength dispersion by stretching. The film (7F-1) is made of a resin having negative intrinsic birefringence, and exhibits forward wavelength dispersion by stretching. As for the optical axis of the stretched body of the film (1F-2) and the stretched body of the film (7F-1) constituting the obtained retardation film, the retardation film is the film (1F-2), (7F-1). Since the film (1F-2) and the resin constituting the film (1F-1) have inherent birefringence with opposite signs, they are perpendicular to each other.

  The retardation film thus obtained exhibits positive birefringence and reverse wavelength dispersion, but if the film thickness is not increased to 140 μm, the same in-plane retardation Re as in the example can be obtained. It was not possible (see Table 11).

(Example 15)
In Example 15, the same combination of resin (A) and resin (B) as in Example 7 was set. Specifically, the resin (A) was a pellet (Tg: 132 ° C.) prepared in Production Example 10, and the resin (B) was polynorbornene (manufactured by JSR, ARTON RX4500, Tg: 132 ° C.). The intrinsic birefringence of the resins (A) and (B) was positive. Resin (A) showed reverse wavelength dispersion, and resin (B) showed forward wavelength dispersion. The intrinsic birefringence and wavelength dispersion of the resins (A) and (B) were evaluated by the method described in Production Example 1. The difference ΔTg between the Tg of the resin (A) and the Tg of the resin (B) was 0 ° C.

  Next, in the same manner as in Example 7, using a single screw extruder A, B and a multi-manifold die, an original film having a laminated structure of resin (B) layer / resin (A) layer / resin (B) layer (Thickness 100 μm) was prepared. At that time, the thickness of each layer in the original film was adjusted to B layer / A layer / B layer = 5/90/5 (μm) by adjusting the discharge amount of each of the extruders A and B.

  Next, a film piece of 80 mm in the flow direction and 20 mm in the width direction was cut out from the produced original film. Next, the cut film piece was uniaxially stretched in the same manner as in Example 7 to obtain a retardation film. At that time, the stretching temperature and the stretching ratio were changed as shown in Table 12 below. The obtained retardation film exhibited positive birefringence. Table 12 below shows the thickness of the obtained retardation film, the in-plane retardation Re and the wavelength dispersion exhibited by the retardation film.

  As shown in Table 12, the retardation film produced in Example 15 exhibited reverse wavelength dispersion. In addition, the wavelength dispersibility of the retardation film did not change due to a change in the stretching temperature during the production. On the other hand, the in-plane retardation Re becomes larger as the stretching temperature is lower, and the Re at the stretching temperature of 133 ° C. is 144 nm, which is approximately 1.4 times the Re at the stretching temperature of 138 ° C. In Example 15, the in-plane retardation Re could be controlled by changing the stretching temperature while maintaining the wavelength dispersion at a constant value. On the other hand, by changing the draw ratio, the in-plane retardation Re could be controlled while keeping the wavelength dispersion constant. This is considered to be an effect of co-stretching a laminated film having no difference in Tg between the resins (A) and (B) constituting each layer.

(Example 16)
In Example 16, the same combination of resin (A) and resin (B) as in Example 10 was set. Specifically, the resin (A) was a pellet (Tg: 129 ° C.) prepared in Production Example 15, and the resin (B) was polynorbornene (manufactured by JSR, ARTON RX4500, Tg: 132 ° C.). The intrinsic birefringence of the resins (A) and (B) was positive. Resin (A) showed reverse wavelength dispersion, and resin (B) showed forward wavelength dispersion. The intrinsic birefringence and wavelength dispersion of the resins (A) and (B) were evaluated by the method described in Production Example 1. The difference ΔTg between the Tg of the resin (A) and the Tg of the resin (B) was 3 ° C.

  Next, in the same manner as in Example 10, using the single screw extruders A and B and the multi-manifold die, an original film having a laminated structure of resin (B) layer / resin (A) layer / resin (B) layer (Thickness 100 μm) was prepared. At that time, the thickness of each layer in the original film was adjusted to B layer / A layer / B layer = 5/90/5 (μm) by adjusting the discharge amount of each of the extruders A and B.

  Next, a film piece of 80 mm in the flow direction and 20 mm in the width direction was cut out from the produced original film. Next, the cut film piece was uniaxially stretched in the same manner as in Example 10 to obtain a retardation film. At that time, the stretching temperature and the stretching ratio were changed as shown in Table 13 below. The obtained retardation film exhibited positive birefringence. Table 13 below shows the film thickness of the obtained retardation film, the in-plane retardation Re and the wavelength dispersion exhibited by the retardation film.

  As shown in Table 13, the retardation film produced in Example 16 exhibited reverse wavelength dispersion. In addition to this, the wavelength dispersibility of the retardation film was not substantially changed by a change in the stretching temperature during production. On the other hand, the in-plane retardation Re becomes larger as the stretching temperature is lower, and the Re at the stretching temperature of 133 ° C. is 149 nm, which is approximately 1.4 times the Re at the stretching temperature of 138 ° C. In Example 16, the in-plane retardation Re could be controlled by changing the stretching temperature while maintaining the wavelength dispersion at a constant value. On the other hand, by changing the draw ratio, the in-plane retardation Re could be controlled while keeping the wavelength dispersion constant. It was confirmed that even if the difference in Tg between the resins (A) and (B) constituting each layer is 3 ° C., the in-plane retardation Re can be controlled while maintaining the wavelength dispersion substantially constant. .

(Example 17)
In Example 17, the same combination of resin (A) and resin (B) as in Example 5 was set. Specifically, the resin (A) is a pellet (Tg: 135 ° C.) prepared in Production Example 7, and the resin (B) is a polynorbornene (manufactured by JSR, ARTON RH5200J, Tg: 142 ° C.) used in Production Example 1. there were. The intrinsic birefringence of the resins (A) and (B) was positive. Resin (A) showed reverse wavelength dispersion, and resin (B) showed forward wavelength dispersion. The intrinsic birefringence and wavelength dispersion of the resins (A) and (B) were evaluated by the method described in Production Example 1. The difference ΔTg between the Tg of the resin (A) and the Tg of the resin (B) was 7 ° C.

  Next, in the same manner as in Examples 7 to 14, a single-screw extruder A, B and a multi-manifold die were used to have a laminated structure of resin (B) layer / resin (A) layer / resin (B) layer. Original films (thickness 100 μm and 200 μm) were prepared. At that time, by adjusting the discharge amount of each of the extruders A and B, the ratio of the thickness of each layer in the original film (B layer / A layer / B layer lamination ratio) was set to the values shown in Table 14 below. .

  Next, a film piece of 80 mm in the flow direction and 20 mm in the width direction was cut out from the produced original film. Next, the cut-out film piece was uniaxially stretched similarly to Examples 7-14, and the phase difference film was obtained. At that time, the stretching temperature was set to 133 ° C or 138 ° C. The draw ratio was 2 times. All of the obtained retardation films exhibited positive birefringence. Table 14 (stretching temperature 133 ° C.) and Table 15 below show the thickness of the obtained retardation film and the in-plane retardation Re and wavelength dispersion (Re (447) / Re (590)) indicated by the retardation film. (Stretching temperature 138 ° C.)

  As shown in Tables 14 and 15, the retardation film produced in Example 17 exhibited reverse wavelength dispersion. In addition to this, the wavelength dispersibility of the retardation film was not substantially changed by a change in the stretching temperature during production. On the other hand, the in-plane retardation Re was larger when the stretching temperature was lower. In Example 17, the in-plane retardation Re could be controlled by changing the stretching temperature while maintaining the wavelength dispersion at a constant value. In addition to this, it was confirmed that the in-plane retardation Re indicated by the retardation film can be controlled by changing the lamination ratio.

( Reference Example 1)
As cellulose derivatives, cellulose acetate butyrate (CBP) [acetyl group substitution degree 15.5% by weight, hydroxyl group substitution degree 0.8% by weight, butyryl group substitution degree 35.5% by weight, number average molecular weight Mn = 70,000, An unstretched CBP film (8F-1) having a thickness of 113 μm was obtained in the same manner as in Production Example 2 except that Tg: 128 ° C. was used. The intrinsic birefringence of CBP constituting the produced film (8F-1) was positive. The wavelength dispersibility of the stretched film obtained by stretching the produced film (8F-1) alone is 0.87 for the ratio Re (447) / Re (590), and for the ratio Re (750) / Re (590). The reverse wavelength dispersion was 1.07.

  The produced film (8F-1) and the film (1F-1) produced in Production Example 1 are laminated one by one so that the flow directions at the time of forming each film coincide with each other, thereby forming a laminated structure. An original film was prepared. Next, a film piece of 80 mm in the flow direction and 20 mm in the width direction was cut out from the produced original film. Next, the cut-out film piece was uniaxially stretched similarly to Examples 7-14, and the phase difference film was obtained. At that time, the stretching temperature and the stretching ratio were changed as shown in Table 16 below. The obtained retardation film exhibited positive birefringence. Table 16 below shows the thickness of the obtained retardation film, the in-plane retardation Re and the wavelength dispersion exhibited by the retardation film.

As shown in Table 16, the retardation film produced in Reference Example 1 exhibited reverse wavelength dispersion. However, the retardation film changed its wavelength dispersibility due to a change in the stretching temperature at the time of production (showing the dependency of wavelength dispersion on the stretching temperature).

  The retardation film of the present invention can be used in various image display devices and optical devices including LCDs. The retardation film of the present invention is suitable for optical compensation of an image display device.

Claims (14)

A first stretched layer comprising a resin (A) having a positive intrinsic birefringence, and having a wavelength dispersion property in which a phase difference is reduced as a wavelength is shortened at least in a visible light region, and a resin having a positive intrinsic birefringence ( A second stretched layer comprising B), and a laminate comprising:
The composition of the resin (A) and the composition of the resin (B) are different from each other.
The optical axes of the first and second stretched layers are parallel to each other;
The in-plane retardation for light having a wavelength of 590 nm is 20 nm or more and 300 nm or less,
At least in the visible light region, a method for producing a retardation film exhibiting wavelength dispersion in which the retardation decreases as the wavelength decreases ,
The resin (A) and the resin (B) are coextruded to form a laminated structure of a first resin layer made of the resin (A) and a second resin layer made of the resin (B). Forming an original film having
The retardation film is formed by co-stretching the formed original film to form the first stretched layer from the first resin layer, and to form the second stretched layer from the second resin layer. And
The manufacturing method of retardation film whose difference (DELTA) Tg of the glass transition temperature between the said resin (A) and (B) is 7 degrees C or less. A first stretched layer comprising a resin (A) having a positive intrinsic birefringence, and having a wavelength dispersion property in which a phase difference is reduced as a wavelength is shortened at least in a visible light region, and a resin having a positive intrinsic birefringence ( A second stretched layer comprising B), and a laminate comprising:
The composition of the resin (A) and the composition of the resin (B) are different from each other.
The optical axes of the first and second stretched layers are parallel to each other;
The in-plane retardation for light having a wavelength of 590 nm is 20 nm or more and 300 nm or less,
At least in the visible light region, a method for producing a retardation film exhibiting wavelength dispersion in which the retardation decreases as the wavelength decreases ,
A solution containing the other resin is applied to the surface of the resin layer composed of one resin selected from the resin (A) and the resin (B), and the coating film formed by applying the solution is dried. And forming an original film having a laminated structure of the resin layer and the coating layer composed of the other resin,
By co-stretching the formed original film, the first and second stretched layers are formed from the resin layer and the coating layer to obtain the retardation film,
The manufacturing method of retardation film whose difference (DELTA) Tg of the glass transition temperature between the said resin (A) and (B) is 7 degrees C or less. 3. The method for producing a retardation film according to claim 1, wherein the second stretched layer exhibits wavelength dispersibility in which the retardation becomes larger as the wavelength becomes shorter at least in the visible light region. The method for producing a retardation film according to claim 1 or 2, wherein a thickness of the first stretched layer is larger than a thickness of the second stretched layer. The method for producing a retardation film according to claim 4, wherein the thickness of the first stretched layer is twice or more the thickness of the second stretched layer. The in-plane retardation per 100 μm thickness with respect to light having a wavelength of 590 nm in the second stretched layer is
3. The method for producing a retardation film according to claim 1, wherein the first stretched layer is at least twice the in-plane retardation per 100 μm thickness with respect to light having a wavelength of 590 nm in the first stretched layer. The method for producing a retardation film according to claim 1, wherein an in-plane retardation per 100 μm thickness with respect to light having a wavelength of 590 nm of the retardation film is 150 nm or more. The method for producing a retardation film according to claim 1, wherein the resin (A) contains a cellulose derivative. The resin (A) is
A polymer (C) having a negative intrinsic birefringence and having an α, β-unsaturated monomer unit having a heteroaromatic group as a constituent unit;
The method for producing a retardation film according to claim 1, comprising a polymer (D) having a positive intrinsic birefringence. The method for producing a retardation film according to claim 1, wherein the resin (B) contains a cycloolefin polymer or a (meth) acrylic polymer having a positive intrinsic birefringence. The method for producing a retardation film according to claim 10, wherein the (meth) acrylic polymer has a ring structure in the main chain. The one resin is the resin (A),
The other resin is the resin (B);
The method for producing a retardation film according to claim 2 , wherein the first stretched layer is formed from the resin layer and the second stretched layer is formed from the coating layer by co-stretching the original film. . The resin (A) contains a cellulose derivative,
The resin (B) has a positive intrinsic birefringence (meth) method for producing a retardation film according to claim 1 or 2 including the acrylic polymer. The resin (A) has a negative intrinsic birefringence having a (meth) acrylic polymer having a positive intrinsic birefringence and an α, β-unsaturated monomer unit having a heteroaromatic group as constituent units. Or a (meth) acrylic polymer having an α, β-unsaturated monomer unit having a heteroaromatic group as a constituent unit.
The resin (B) The method for producing a retardation film according to claim 1 or 2 including a cycloolefin polymer.

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