TW202229430A - Multilayer film, optical film, and manufacturing method - Google Patents

Abstract

This multilayer film comprises: a pA layer composed of a crystalline resin (a) having a positive intrinsic birefringence; and a pB layer composed of a material (b) having a negative intrinsic birefringence, wherein the pA layer and the pB layer satisfy specific optical requirements. An optical film is a uniaxial co-stretched product of the multilayer film and comprises: an A layer composed of a crystalline resin (a) having a positive intrinsic birefringence; and a B layer composed of a material (b) having a negative intrinsic birefringence. A manufacturing method comprises a step for applying a specific liquid composition onto a film oA composed of a crystalline resin (a).

Description

Multilayer films, optical films, and methods of making the same

The present invention relates to optical films, multilayer films that can be advantageously used as components for producing the optical films, and methods for producing the same.

Conventionally, resin films having specific optical properties have been used for optical applications. For example, a film whose NZ coefficient satisfies 0<Nz<1 is called a three-dimensional retardation film. It is known that when a three-dimensional retardation film is provided in a display device such as a liquid crystal display device, it can exhibit effects such as reducing discoloration of the display surface when viewed from an oblique direction. In particular, a film that is a three-dimensional retardation film and has a so-called reverse wavelength dispersion in the relationship between the retardation and the wavelength can obtain desired optical effects in a wide wavelength range. In addition, the three-dimensional retardation film is also required to be thin due to the requirement of thinning of the display device.

The three-dimensional retardation film has a larger retardation in the z-axis direction (that is, the thickness direction) than the retardation in the y-axis direction (that is, the in-plane direction orthogonal to the in-plane slow axis direction). Therefore, it cannot be produced by a common retardation film production method, such as simple stretching of a common optical film with a positive intrinsic birefringence with a resin. Therefore, it has been proposed to manufacture a three-dimensional retardation film or a similar film by combining a resin with a positive intrinsic birefringence and a resin with a negative intrinsic birefringence (for example, Patent Documents 1 to 2).

"Patent Documents" "Patent Document 1": International Patent Publication No. 2019/188205 "Patent Document 2": International Patent Publication No. 2020/137409

The method for producing a three-dimensional retardation film that has been proposed so far by combining a resin with a positive intrinsic birefringence and a resin with a negative intrinsic birefringence requires a complicated stretching process and a post-stretching lamination process, and the positioning is very troublesome. . In particular, it is difficult to easily produce reverse wavelength dispersion. In addition, in such a combination, it is required to increase the proportion of resins with negative intrinsic birefringence to a certain extent. However, since most of the resins with negative intrinsic birefringence generally have low mechanical strength, it is possible to increase the proportion of such resins. A problem of low mechanical strength arises. Low mechanical strength can be particularly problematic in the case of thin films. In addition, there is also a problem of fogging along with the extension of the resin, which may impair the display quality of the display device.

Therefore, an object of the present invention is to provide a film that can exhibit good effects as a three-dimensional retardation film in a wide wavelength range, has high mechanical strength, has a thin thickness, can improve the display quality of a display device, and can be easily manufactured. A method of manufacturing such a film.

The present inventors have studied to solve the aforementioned problems. As a result, the present inventors have found that when a specific material is used as one of the multilayer films in which the layer of the material having positive intrinsic birefringence and the layer of material having negative intrinsic birefringence are combined, the composition can be A multilayer film that exhibits good effects as a three-dimensional retardation film in a wide wavelength range and can be easily produced. Based on this knowledge, the present inventors have completed the present invention.

That is, the present invention includes the following.

[1] A multilayer film comprising a pA layer composed of a crystalline resin having positive intrinsic birefringence (a) and a pB layer composed of a material (b) having negative intrinsic birefringence, The pA layer satisfies the following formulae (1) to (2), and the pB layer satisfies the following formulae (3) to (4): nz(pA)＞nx(pA)≧ny(pA) ・・・(1) nx(pA)－ny(pA)≦0.0003 ・・・（2） nz(pB)＞nx(pB)≧ny(pB) ・・・(3) nx(pB)－ny(pB)≦0.0003 ・・・（4） in nx(pA), ny(pA) and nz(pA) are the principal refractive indices of the aforementioned pA layer, nx(pB), ny(pB) and nz(pB) are the principal refractive indices of the aforementioned pB layer.

[2] The multilayer film according to [1], which is an elongated film.

[3] The multilayer film according to [1] or [2], wherein the pA layer and the pB layer are in direct contact.

[4] The multilayer film according to any one of [1] to [3], wherein the thickness of the pB layer is 20 μm or less.

[5] An optical film, which is a uniaxially coextensive product of the multilayer film according to any one of [1] to [4], and which comprises a crystalline resin (a) having a positive intrinsic birefringence The optical film of the A layer and the B layer of the material (b) with negative intrinsic birefringence, It satisfies the following formulas (5) and (6): Re(450)＜Re(550)＜Re(650) ・・・(5) Nz＜1 ・・・（6） in Re(450), Re(550) and Re(650) are the in-plane retardation of the aforementioned optical film at a wavelength of 450 nm, the in-plane retardation of the aforementioned optical film at a wavelength of 550 nm, and the aforementioned optical film at a wavelength of 650 nm, respectively The in-plane delay of , Nz is the NZ coefficient of the aforementioned optical film.

[6] The optical film according to [5], which is an elongated film.

[7] The optical film according to [5] or [6], wherein the uniaxial co-extension is longitudinal uniaxial co-extension, transverse uniaxial co-extension, or oblique uniaxial co-extension.

[8] The optical film according to any one of [5] to [7], wherein the thickness of the B layer is 20 μm or less.

[9] The optical film according to any one of [5] to [8], comprising one layer of the A layer and two layers of the B layer formed on both surfaces thereof.

[10] A method for producing a multilayer film, which is the method for producing a multilayer film according to any one of [1] to [4], comprising: Step (I), preparing a thin film oA made of the crystalline resin (a), and In step (II), a liquid composition comprising a solvent and a material (b) having a negative intrinsic birefringence dissolved in the solvent is applied to one or both sides of the thin film oA, thereby forming a pB layer and making the thin film oA The birefringence in the thickness direction is changed to form a pA layer, and a multilayer film having the aforementioned pA layer and the aforementioned pB layer is obtained.

[11] A method for producing an optical film, which is the method for producing an optical film according to any one of [5] to [9], comprising: In the step (I), a thin film oA made of the crystalline resin (a) is prepared, In step (II), a liquid composition comprising a solvent and a material (b) having a negative intrinsic birefringence dissolved in the solvent is applied to one or both sides of the thin film oA, thereby forming a pB layer and making the thin film oA The birefringence in the thickness direction is changed to form a pA layer, and a multilayer film having the aforementioned pA layer and the aforementioned pB layer is obtained, and In the step (III), the above-mentioned multilayer film is uniaxially co-stretched.

According to the present invention, there is provided an optical film which can exhibit good effects as a three-dimensional retardation film in a wide wavelength range, has high mechanical strength, has a thin thickness, can improve the display quality of a display device, and can be easily manufactured, which can be advantageously used as an optical film for Multilayer films for making components of such optical films, and methods for easily producing such multilayer films and optical films.

In the following description, the in-plane retardation Re of a structure having a film-like shape (a film and a layer constituting a part of a film formed of a multilayered layer, etc.) is represented by Re=(nx unless otherwise noted. -ny)×d the value shown. The retardation Rth in the thickness direction of the film-like structure is a value represented by Rth={[(nx+ny)/2]-nz}×d unless otherwise noted. The NZ coefficient of the film-like structure is the value shown by (nx-nz)/(nx-ny) unless otherwise noted.

nx, ny and nz, unless otherwise noted, are the principal refractive indices of thin film structures. The principal refractive indices nx, ny, and nz are the refractive indices in three directions perpendicular to the thickness direction, with the nx direction being the slow axis direction and the nz direction being the direction perpendicular to the thickness direction. That is, nx represents the refractive index in the direction (in-plane direction) perpendicular to the thickness direction of the thin-film structure and in the direction in which the maximum refractive index is given. ny represents the refractive index in the direction orthogonal to the direction of nx in the in-plane direction of the thin-film structure. nz represents the refractive index in the thickness direction of the thin-film structure. d represents the thickness of the film-like structure. Measurement wavelength, unless otherwise noted, is 590 nm.

In this application, the optical properties of a structure marked with a mark are indicated by a combination of a mark representing the optical property (eg, nx, ny, nz, Re, Rth, Nz, etc.) and the mark of the structure. According to this designation, for example, the principal refractive indices nx, ny and nz of the A layer can be denoted as nx(A), ny(A) and nz(A), respectively. In addition, the principal refractive indices nx, ny, and nz of the pA layer are expressed as nx(pA), ny(pA), and nz(pA), respectively.

In the following description, a material whose intrinsic birefringence is positive means a material whose refractive index in the extending direction becomes larger than the refractive index in the direction perpendicular thereto, unless otherwise noted. In addition, the material whose intrinsic birefringence is negative means the material whose refractive index in the extending direction becomes smaller than the refractive index in the direction perpendicular to it, unless otherwise noted. The value of intrinsic birefringence can be calculated from the dielectric constant distribution.

In the following description, the so-called "long-shaped" film refers to a film having a length of 5 times or more relative to the width, preferably 10 times or more in length, and specifically refers to a film having a rewindable length. A length of film that can be stored or handled in a roll. The upper limit of the length is not particularly limited, but is usually 100,000 times or less the width.

In the following description, the slow axis of the film-like structure is the in-plane slow axis unless otherwise noted.

[Multilayer Films: Optical Properties]

The multilayer film of the present invention includes a pA layer made of a crystalline resin (a) having positive intrinsic birefringence and a pB layer made of a material (b) having negative intrinsic birefringence.

The pA layer satisfies the following formulae (1) to (2), and the pB layer satisfies the following formulae (3) to (4). nz(pA)＞nx(pA)≧ny(pA) ・・・(1) nx(pA)－ny(pA)≦0.0003 ・・・（2） nz(pB)＞nx(pB)≧ny(pB) ・・・(3) nx(pB)－ny(pB)≦0.0003 ・・・（4）

nx(pA), ny(pA) and nz(pA) are the principal refractive indices of the pA layer, and nx(pB), ny(pB) and nz(pB) are the principal refractive indices of the pB layer.

The pA layer satisfying formulae (1) to (2) and the pB layer satisfying formulae (3) to (4) are called positive C plates. Regarding the formula (1), the ratio of nz(pA) to nx(pA), that is, nz(pA)/nx(pA), is greater than 1, preferably 1.0002 or more. The upper limit of the ratio is set to, for example, 2 or less. Regarding the formula (2), the ratio of nz(pB) to nx(pB), that is, nz(pB)/nx(pB), is greater than 1, preferably 1.0002 or more. The upper limit of the ratio is set to, for example, 2 or less.

The multilayer film of the present invention has both a layer with positive intrinsic birefringence and a layer with negative intrinsic birefringence, and both are positive C plates with a high nz value, and can be uniaxially stretched, etc. It is a simple method and can be easily produced as a three-dimensional retardation film with reverse wavelength dispersion.

The respective slow axis directions of the pA layer and the pB layer are appropriately adjusted so that the optical properties of the multilayer film and the optical film prepared using the same can be adjusted to desired values. are almost the same, so the direction of the slow axis must be set arbitrarily.

[Multilayer Film: Other Features]

The multi-layered film of the present invention can be made into an elongated film. The so-called "strip-shaped" film refers to a film having a length of 5 times or more relative to the width, preferably 10 times or more in length, and specifically refers to a film that can be wound into a roll for storage or The length of the film is as long as it is transported. The upper limit of the length is not particularly limited, but is usually 100,000 times or less the width. Efficient production of optical films can be achieved by the multilayer films being elongated films.

The multi-layer film of the present invention may have one pA layer and one pB layer. In addition, the multilayer film of the present invention may include two or more pA layers, or may include two or more pB layers.

In one aspect, it is preferable that the multilayer film of the present invention includes one pA layer and one pB layer from the viewpoint of efficiently performing the method for producing the multilayer film of the present invention described later.

In another aspect, the multilayer film of the present invention preferably has one pA layer and two pB layers formed on both sides thereof. That is, the multilayer film of the present invention can be formed as a film having a layer structure of (pB layer)/(pA layer)/(pB layer). In the manufacturing method of the multilayer thin film of the present invention to be described later, since the pB layers can be formed on both sides of the thin film for forming the pA layer, it is possible to easily manufacture the thin film having (pB layer)/(pA layer)/(pB layer) layer-structured films. In the case of having such a layer structure, even if the thickness of the pB layer of each layer is thin, a multilayer film having desired optical properties can be easily obtained, which is preferable.

In the case of having a plurality of pA layers, the optical properties of the state "after overlapping these" may be determined as the optical properties of the pA layers described above, and the overlapping is the same as that in the multilayer film. The same relationship is the same as the plane position relationship. Similarly, in the case of having a plurality of pB layers, the optical properties of the state "after overlapping these" can be determined as the optical properties of the pB layers described above, and the overlapping is related to the multi-layer film. Among these, the plane positional relationship is the same.

In addition to the pA layer and the pB layer, the multilayer film of the present invention may have any layer body. For example, an adhesive layer must be provided between the pA layer and the pB layer. However, in the multilayer film of the present invention, it is preferable that the pA layer and the pB layer are in direct contact. By being a multilayer film in which the pA layer and the pB layer are in direct contact, the thickness of the obtained optical film can be made thin and at the same time, the optical film can be given good optical properties. Such a multilayer film can be easily produced by the method for producing a multilayer film of the present invention, which will be described later.

Generally, optical films used in devices such as display devices require a certain thickness or more in order to exhibit optical properties. The thickness of the multilayer film of the present invention is not particularly limited, but by satisfying the requirements of the present invention, it is possible to form an optical film that satisfies desired optical properties even if the thickness is thin. Specifically, the thickness of the multilayer film of the present invention is preferably set to be 150 μm or less, more preferably 100 μm or less. The lower limit of the thickness of the multilayer film is not particularly limited, but may be set to, for example, 10 μm or more.

The respective thicknesses of the pA layer and the pB layer are appropriately adjusted so that desired optical properties can be obtained. The thickness of the pA layer is preferably 10 μm or more, more preferably 30 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The thickness of the pB layer is preferably 1 μm or more, more preferably 5 μm or more, and preferably 20 μm or less, more preferably 15 μm or less. In the case where the multilayer film includes a plurality of pA layers, the total thickness of these may be adjusted to the above-mentioned favorable range. Similarly, when the multilayer thin film includes a plurality of pB layers, the total thickness of these should be adjusted to the above-mentioned preferable range.

[Material constituting the pA layer]

The crystalline resin (a) constituting the pA layer should be a resin containing a polymer having crystallinity. The "polymer having crystallinity" means a polymer having a melting point Tm. That is, the "polymer having crystallinity" means a polymer whose melting point can be observed by a differential scanning calorimeter (DSC). In the following description, a polymer having crystallinity may be referred to as a "crystalline polymer". The crystalline resin is preferably a thermoplastic resin.

Crystalline polymers have positive intrinsic birefringence. By using a crystalline polymer with positive intrinsic birefringence, an optical film having desired optical properties can be easily produced in combination with the material (b).

Crystalline polymers can also be polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc.; polyolefins such as polyethylene (PE) and polypropylene (PP); etc., Although it does not specifically limit, It is preferable to contain an alicyclic structure. By using a crystalline polymer containing an alicyclic structure, the mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability and light weight of the optical film can be optimized. The alicyclic structure-containing polymer refers to a polymer having an alicyclic structure in the molecule. Such an alicyclic structure-containing polymer may be, for example, a polymer obtained by a polymerization reaction using a cycloolefin as a monomer, or a hydrogenated product thereof.

As an alicyclic structure, a cycloalkane structure and a cycloalkene structure are mentioned, for example. Among them, a naphthenic structure is preferable in that it is easy to obtain a retardation film excellent in properties such as thermal stability. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, preferably 5 or more, and preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less . When the number of carbon atoms contained in one alicyclic structure is within the above range, mechanical strength, heat resistance and moldability can be highly balanced.

In the crystalline polymer containing an alicyclic structure, the ratio of the structural unit having an alicyclic structure to all the structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and more preferably 70% by weight or more Excellent. Heat resistance can be improved by increasing the ratio of the structural unit which has an alicyclic structure as mentioned above. The ratio of the structural unit having an alicyclic structure with respect to all the structural units must be 100% by weight or less. Moreover, in the crystalline polymer containing an alicyclic structure, the residue other than the structural unit having an alicyclic structure is not particularly limited, and can be appropriately selected according to the purpose of use.

As a crystalline polymer containing an alicyclic structure, the following polymer (α) - polymer (δ) are mentioned, for example. Among these, the polymer (β) is preferable in that it is easy to obtain a retardation film excellent in heat resistance. Polymer (α): A ring-opening polymer of a cycloolefin monomer and having crystallinity. Polymer (β): a hydride of polymer (α) and having crystallinity. Polymer (γ): An addition polymer of a cycloolefin monomer and having crystallinity. Polymer (δ): a hydride of polymer (γ) and having crystallinity.

Specifically, as a crystalline polymer containing an alicyclic structure, a ring-opening polymer of dicyclopentadiene having crystallinity and a hydrogenated product of a ring-opening polymer of dicyclopentadiene having crystallinity are compared. good. Among them, a hydrogenated product of a ring-opening polymer of dicyclopentadiene and having crystallinity is particularly preferred. Here, the so-called ring-opening polymer of dicyclopentadiene means that the ratio of structural units derived from dicyclopentadiene to all structural units is usually 50% by weight or more - preferably 70% by weight or more, and 90% by weight or more. More than % by weight is preferred, and 100% by weight is more preferred—the polymer.

It is preferable that the hydrogenated product of the ring-opening polymer of dicyclopentadiene has a high ratio of racemic diads. Specifically, the ratio of the racemic diad of the repeating unit in the hydrogenation of the ring-opening polymer of dicyclopentadiene is preferably 51% or more, more preferably 70% or more, and 85% or more for the best. A high ratio of racemic diads indicates high para-stereoisomerism. Accordingly, the higher the ratio of the racemic diad is, the higher the melting point of the hydrogenated product of the ring-opened polymer of dicyclopentadiene tends to be.

The ratio of the racemic diad can be determined based on the ¹³ C-NMR spectral analysis described in the examples to be described later.

As the above-mentioned polymer (α) to polymer (δ), a polymer obtained by the production method disclosed in International Patent Publication No. 2018/062067 can be used.

The melting point Tm of the crystalline polymer is preferably 200°C or higher, more preferably 230°C or higher, and more preferably 290°C or lower. By using a crystalline polymer having such a melting point Tm, a multilayer film having a better balance between moldability and heat resistance can be obtained.

Crystalline polymers generally have a glass transition temperature Tg. The specific glass transition temperature Tg of the crystalline polymer is not particularly limited, but is usually 85°C or higher and usually 170°C or lower.

The glass transition temperature Tg and melting point Tm of the polymer can be measured by the following methods. First, the polymer is melted by heating, and the melted polymer is rapidly cooled by dry ice. Next, using this polymer as a sample, a differential scanning calorimeter (DSC) was used to measure the glass transition temperature Tg and melting point Tm of the polymer at a heating rate of 10°C/min (heating mode).

The weight average molecular weight (Mw) of the crystalline polymer is preferably 1,000 or more, more preferably 2,000 or more, more preferably 1,000,000 or less, more preferably 500,000 or less. The crystalline polymer having such a weight average molecular weight is excellent in the balance between molding processability and heat resistance.

The molecular weight distribution (Mw/Mn) of the crystalline polymer is preferably 1.0 or more, more preferably 1.5 or more, more preferably 4.0 or less, more preferably 3.5 or less. Here, Mn represents the number average molecular weight. A crystalline polymer having such a molecular weight distribution is excellent in molding processability.

The weight-average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the polymer can be measured in terms of polystyrene values by gel permeation chromatography (GPC) using tetrahydrofuran as an eluent.

The degree of crystallinity of the crystalline polymer contained in the retardation film is not particularly limited, but is usually high to a certain degree or more. The specific crystallinity range is preferably 10% or more, preferably 15% or more, and particularly preferably 30% or more.

The crystallinity of the crystalline polymer can be measured by X-ray diffraction.

The crystalline polymer may be used alone or in combination of two or more at any ratio.

The proportion of the crystalline polymer in the crystalline resin (a) is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the ratio of a crystalline polymer is more than the said lower limit, the development property and heat resistance of the birefringence of a retardation film can be improved. The upper limit of the ratio of the crystalline polymer is 100% by weight or less.

The crystalline resin (a) must contain optional components in addition to the crystalline polymer. Examples of optional components include antioxidants such as phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants; light stabilizers such as hindered amine-based light stabilizers; petroleum-based waxes, Fischer-Tropsch waxes, polyalkylene waxes, and the like. Waxes; nucleating agents such as sorbitol compounds, metal salts of organic phosphoric acid, metal salts of organic carboxylic acids, kaolin and talc; diaminostilbene derivatives, coumarin derivatives, azole derivatives (such as benzene Fluorescence whitening such as oxazole derivatives, benzotriazole derivatives, benzimidazole derivatives and benzothiazole derivatives), carbazole derivatives, pyridine derivatives, naphthalenedicarboxylic acid derivatives and imidazolone derivatives UV absorbers such as benzophenone-based UV absorbers, salicylic acid-based UV absorbers, and benzotriazole-based UV absorbers; inorganic fillers such as talc, silica, calcium carbonate, and glass fiber; colorants; Flame retardants; flame retardant additives; antistatic agents; plasticizers; near-infrared absorbers; lubricants; fillers; and any polymers other than crystalline polymers such as soft polymers; etc. An arbitrary component may be used individually by 1 type, and may be used in combination of 2 or more types at arbitrary ratios.

[Organic solvent contained in crystalline resin (a)]

The crystalline resin (a) constituting the pA layer must contain an organic solvent. This organic solvent is usually incorporated into the film in the step (II) of the production method of the present invention.

All or part of the organic solvent incorporated in the film in step (II) may enter the interior of the polymer. Therefore, even if drying is performed above the boiling point of the organic solvent, it is difficult to easily and completely remove the solvent. Accordingly, the pA layer usually contains an organic solvent.

As the organic solvent, one that does not dissolve the crystalline polymer in the process of the production method of the present invention described later may be used. As a preferable organic solvent, hydrocarbon solvents, such as toluene, arcene, and decalin; ketones, such as methyl ethyl ketone; carbon disulfide, are mentioned, for example. One type of organic solvent may be used, or two or more types may be used.

The ratio (solvent content) of the organic solvent contained in the crystalline resin (a) to 100% by weight of the crystalline resin (a) is preferably 10% by weight or less, more preferably 5% by weight or less, and 0.1 The weight % or less is particularly preferred.

[Material constituting the pB layer]

The material (b) constituting the pB layer has negative intrinsic birefringence. Using a resin having a negative intrinsic birefringence as the material (b), combining it with a crystalline resin (a) having a positive intrinsic birefringence, a multilayer film satisfying the requirements of the present invention can be produced particularly easily.

Resins with negative intrinsic birefringence are generally thermoplastic resins, and include polymers with negative intrinsic birefringence. Examples of polymers with negative intrinsic birefringence include homopolymers and copolymers of styrene or styrene derivatives, and copolymers containing styrene or styrene derivatives and any monomer. Polystyrene polymers; polyacrylonitrile polymers; polymethyl methacrylate polymers; or multicomponent copolymers of these; and cellulose compounds such as cellulose esters. Moreover, as said arbitrary monomers which can be copolymerized with styrene or a styrene derivative, acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene are mentioned as a favorable thing, for example. Among them, polystyrene-based polymers and cellulose compounds are preferred. In addition, these polymers may be used individually by 1 type, and may be used in combination of 2 or more types in arbitrary ratios.

The ratio of the polymer in the resin having negative intrinsic birefringence is preferably 50% by weight to 100% by weight, preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. In the case where the proportion of the polymer is within the aforementioned range, the pB layer can be easily imparted with desired optical properties.

The material (b) preferably contains a plasticizer. By using a plasticizer, the glass transition temperature of the material (b) can be appropriately adjusted. As a plasticizer, a phthalate ester, a fatty acid ester, a phosphoric acid ester, an epoxy derivative, etc. are mentioned. Specific examples of the plasticizer include those described in Japanese Patent Laid-Open No. 2007-233114. Moreover, a plasticizer may be used individually by 1 type, and may be used in combination of 2 or more types in arbitrary ratios.

Among the plasticizers, phosphoric acid esters are preferable because they are easy to obtain and inexpensive. Examples of phosphoric acid esters include: trialkyl phosphates such as triethyl phosphate, tributyl phosphate, and trioctyl phosphate; halogen-containing trialkyl phosphates such as trichloroethyl phosphate; triphenyl phosphate, trimethyl phosphate ester, tris(cumyl phosphate), triaryl phosphate such as cresyl diphenyl phosphate; diaryl phosphate alkyl ester such as diphenyl phosphate octyl; tris(alkoxy phosphate) such as tris(butoxyethyl) phosphate Alkyl ester); etc.

When the material (b) contains a plasticizer, its amount is preferably 0.001% by weight or more, more preferably 0.005% by weight or more, and particularly preferably 0.1% by weight or more based on 100% by weight of the material (b). , and preferably 20 wt % or less, preferably 18 wt % or less, and particularly preferably 15 wt % or less. When the amount of the plasticizer is within the aforementioned range, since the glass transition temperature of the material (b) can be appropriately adjusted, desired optical properties can be easily imparted to the pB layer.

The material (b) may further include any components other than the polymer and the plasticizer in combination with the polymer and the plasticizer. As an arbitrary component, the same example as the arbitrary component which a crystalline resin (a) may contain is mentioned, for example. An arbitrary component may be used individually by 1 type, and may be used in combination of 2 or more types at arbitrary ratios.

The glass transition temperature of the material (b) is preferably 80°C or higher, more preferably 90°C or higher, more preferably 100°C or higher, more preferably 110°C or higher, and particularly preferably 120°C or higher. With the glass transition temperature of material (b) so high, the pB layer can easily be imparted with desired optical properties. The upper limit of the glass transition temperature of the material (b) is not particularly limited, but is usually 200° C. or lower.

[Optical film]

The optical film of the present invention is a uniaxial coextension of the aforementioned multilayer film of the present invention. That is, the film of the present invention is formed by extending the aforementioned multilayer film of the present invention to co-extension the pA layer and the pB layer. By such co-extension, all layers included in the multilayer film are extended with the same extension ratio and extension direction, and the molecules of the polymers included in these layers are oriented in a direction corresponding to the extension direction. Since the multilayer film has the specific requirements defined by the formulae (1) to (4), it is possible to easily obtain an optical film having optical properties that are difficult to obtain by ordinary retardation film production methods such as simple stretching of the resin for optical films. .

The optical film of the present invention includes a layer A composed of a crystalline resin (a) having a positive intrinsic birefringence, and a layer B composed of a material (b) having a negative intrinsic birefringence. The A layer has to be a layer body obtained as a result of the extension of the pA layer. The B layer has to be a layer body obtained as a result of the extension of the pB layer. Therefore, specific examples of the material constituting the A layer and the material constituting the B layer may be the same as those of the pA layer and the pB layer.

The optical film of the present invention satisfies the following formulae (5) and (6). Re(450)＜Re(550)＜Re(650) ・・・(5) Nz＜1 ・・・（6）

In a good form, the optical film of the present invention satisfies the following formula (7) or the following formula (8). Nz＜0 ・・・（7） 0＜Nz＜1・・・（8）

Re(450), Re(550) and Re(650) are the in-plane retardation of the optical film at a wavelength of 450 nm, the in-plane retardation of the optical film at a wavelength of 550 nm, and the in-plane retardation of the optical film at a wavelength of 650 nm, respectively Retardation, the NZ coefficient of Nz-based optical films.

The thin film satisfying the formula (5) is called a reverse wavelength dispersive thin film. The film satisfying the formula (5) can obtain the desired optical effect in a wide wavelength range. In addition, the film satisfying the formula (8) is called a three-dimensional retardation film. When the film satisfying the formula (8) is installed in a display device, it can exhibit effects such as reducing discoloration of the display surface when viewed from an oblique direction. Films satisfying both of the formulae (5) and (8) need to be produced by complicated processes in the prior art, but the optical film of the present invention is produced by using the multilayer film of the present invention having a specific structure. Easy to manufacture through its uniaxial extension. Furthermore, when the optical film of the present invention is a film satisfying the formulae (5) and (7), it can be easily converted into a film satisfying both the formulae (5) and (8) by further uniaxially extending the film. .

Regarding formula (1), the lower limit of Re(450)/Re(550) is not limited, but is preferably 0.60 or more, preferably 0.70 or more, and particularly preferably 0.75 or more.

The values of Re(450), Re(550) and Re(650) are adjusted to values suitable for the application of the optical film. In the case of using an optical film as the λ/4 wavelength plate, Re(550) is preferably 80 nm or more, preferably 100 nm or more, more preferably 120 nm or more, and preferably 180 nm or less, 160 nm or less is preferable, and 150 nm or less is more preferable.

In the case of using an optical film as the λ/2 wavelength plate, a good range of Re(550) is 275 nm or a value close to it, specifically 260-290 nm, 265-285 nm as better range.

Regarding the formula (8), Nz is larger than 0 and smaller than 1. The NZ coefficient of the retardation film is preferably 0.2 or more, more preferably 0.4 or more, more preferably 0.8 or less, and more preferably 0.6 or less.

The uniaxial coextension used to obtain the uniaxial coextension is defined as longitudinal uniaxial coextension, transverse uniaxial coextension, or oblique uniaxial coextension. The so-called longitudinal uniaxial extension refers to the extension along the longitudinal direction of the film, the so-called transverse uniaxial extension refers to the extension along the width direction of the film, and the so-called oblique uniaxial extension refers to the extension along the oblique direction of the film. , here, the so-called oblique direction refers to the direction that is perpendicular to the thickness direction and the angle between it and the width direction is neither 0° nor 90° (that is, the angle between the width direction exceeds 0° ° and less than 90°). Since the optical film of the present invention is an extension of the above-mentioned specific multilayer film, it can be made into a film satisfying the above-mentioned formulas (5) and (6), preferably the above-mentioned formulas (5) and (8), without Perform complex extensions such as biaxial extensions.

The optical film of the present invention can be made into a strip-shaped film. Efficient production of the optical film can be achieved by the optical film being an elongated film.

The optical film of the present invention may have one layer each of the A layer and the B layer. In addition, the multilayer film of the present invention may include two or more A layers, or two or more B layers. In a certain aspect, it is preferable that the optical film of this invention has one layer each of A layer and B layer from a viewpoint of efficiently carrying out the manufacturing method of an optical film. In another aspect, the optical film of the present invention preferably has one layer of A layer and two layers of B layer formed on both surfaces thereof. That is, the optical film of the present invention may be a film having a layer structure of (layer B)/(layer A)/(layer B). In the case of having such a layer structure, even if the thickness of the B layer of each layer is thin, an optical film having desired optical properties can be easily obtained, which is preferable.

In the case of having a plurality of A layers, the optical properties of the state "after overlapping them" may be determined as the optical properties of the A layers described above, and the overlapping is the same as that in the optical film. The same relationship is the same as the plane position relationship. In the same way, in the case of having a plurality of B layers, the optical characteristics of the state "after overlapping them" can be determined as the optical characteristics of the B layers mentioned above, and the overlapping is determined by the same as that in the optical film. Among these, the plane positional relationship is the same.

The optical film of the present invention may have an arbitrary layer body in addition to the A layer and the B layer. For example, an adhesive layer must be provided between the A layer and the B layer. However, in the optical film of the present invention, from the viewpoint of thinning the thickness and obtaining good optical properties, it is preferable that the A layer and the B layer are in direct contact with each other.

The thickness of the optical film of the present invention is not particularly limited, but can be formed into an optical film satisfying desired optical properties even if the thickness is thin. Specifically, the thickness of the optical film of the present invention is preferably 100 μm or less, more preferably 80 μm or less. The lower limit of the thickness of the optical film is not particularly limited, but may be set to, for example, 10 μm or more.

The respective thicknesses of the A layer and the B layer are appropriately adjusted so that desired optical properties can be obtained. The thickness of the A layer is preferably 10 μm or more, more preferably 20 μm or more, and on the other hand, preferably 100 μm or less, more preferably 80 μm or less. The thickness of the B layer is preferably 1 μm or more, more preferably 5 μm or more, and preferably 20 μm or less, more preferably 15 μm or less. When the optical film includes a plurality of A layers, the total thickness of these may be adjusted to the above-mentioned favorable range. Similarly, when the optical film includes a plurality of B layers, the total thickness of these should be adjusted to the above-mentioned favorable range.

[Production method of multilayer film and production method of optical film]

The multilayer film of the present invention can be produced by a production method including the following steps (I) to (II). And the optical film of this invention can be manufactured by the manufacturing method which includes the following process (III) in addition to the following processes (I)-(II). Step (I): A step of preparing the thin film oA made of the crystalline resin (a). Step (II): apply a liquid composition comprising a solvent and a material (b) having a negative intrinsic birefringence dissolved in the solvent on one side or both sides of the thin film oA, thereby forming a pB layer and making the thickness direction of the thin film oA The process of changing the birefringence of the pA layer to form a pA layer and obtaining a multi-layer thin film having a pA layer and a pB layer. Step (III): A step of uniaxially co-extending the multilayer film.

Hereinafter, such a production method will be described as the production method of the multilayer film of the present invention and the production method of the optical film of the present invention.

[Process (I)]

The step (I) can be performed by forming the crystalline resin (a) into the shape of a film. In addition, the step (I) can also be performed simply by obtaining a commercially available thin film. As a method of molding the crystalline resin (a) into the shape of a film, any molding method can be employed. From the viewpoint of production efficiency, it is preferable to form by melt extrusion. The thickness of the film oA is appropriately adjusted so that the thickness of the pA layer in the multilayer film of the product and the thickness of the A layer in the optical film becomes a desired thickness.

[Step (II): Liquid Composition]

In the step (II), a liquid composition containing a solvent and a material (b) is used. As an example of a solvent, the same thing as the example of the organic solvent which exists in the state which exists as the state contained in the crystalline resin (a) which comprises a pA layer mentioned above can be mentioned. More specifically, hydrocarbon solvents, such as toluene, arcene, and decalin; ketones, such as methyl ethyl ketone; and carbon disulfide are mentioned. From the viewpoint of exhibiting the effect of changing the oA of the film and dissolving the polymer having a negative intrinsic birefringence well, a ketone such as methyl ethyl ketone or a mixed solvent of a ketone and another solvent is particularly preferable. The type of the solvent contained in the liquid composition may be one type or two or more types.

As an example of the material (b), the same example as described above can also be given. That is, the liquid composition may contain, as the component (b), the polymer having a negative intrinsic birefringence as the constituent material and the example of the arbitrary components that may be contained in the other material (b), which are the same as those described above.

The ratio of the solvent and the material (b) in the liquid composition can be appropriately adjusted so that a desired thickness of the B layer can be formed and the degree of change in thin film oA can be set within a desired range. Specifically, the ratio of the polymer having negative intrinsic birefringence constituting the material (b) to the total of the solvent and the material (b) can be adjusted to a ratio of 1 to 50% by weight.

[Step (II): Coating]

In the step (II), the liquid composition is applied to one side or both sides of the thin film oA. The specific operation of coating is not particularly limited, but from the viewpoint of forming the B layer with a uniform desired thickness, an operation that can precisely control the coating thickness is preferable. Specifically, it is preferable to use a coating machine such as a die coater.

As a result of coating, the solvent, which is a component of the liquid composition, comes into contact with the surface of the oA layer. According to the findings of the present inventors, when the thin film of the crystalline resin (a) is used as the thin film oA, the birefringence in the thickness direction of the thin film oA can be changed by contacting the thin film oA with the solvent. As a result, in the obtained pA layer, nz(pA)>nx(pA)≧ny(pA) can be easily obtained, in which ordinary resins with positive intrinsic birefringence are formed by ordinary processes such as film forming and stretching. Optical properties that are difficult to obtain in the resulting film. In the step (II), the pB layer is formed on the surface of the thin film oA, and this change of the thin film oA can also be achieved. As a result, a generally difficult to obtain multilayer film having both a layer of a material whose intrinsic birefringence is positive and a layer of a material whose intrinsic birefringence is negative, and either of which has the optical properties of a positive C plate, can be easily produced. .

[Process (III)]

In the step (III), the multilayer film obtained in the step (II) is uniaxially coextensive. By such co-extension, the molecules of the polymers contained in the pA layer and the pB layer of the multilayer film are oriented in a direction corresponding to the direction of extension. Since the multilayer film goes through the step (II), as a result of the step (III), an optical film having optical properties that are difficult to obtain by a common retardation film manufacturing method such as simple stretching of a resin for an optical film can be easily obtained. The extending direction in the step (III) is not limited, and examples thereof include the longitudinal direction, the width direction, and the oblique direction.

When a film having optical properties equivalent to the optical film of the present invention is to be produced by a production method without the step (II), a complicated stretching step is usually required several times. In the case where optical properties are exhibited by stretching, since the conditions for stretching must be strictly controlled, the fact that there are many steps for stretching is rather disadvantageous from the viewpoint of manufacturing efficiency. On the other hand, in the production method of the present invention, since the optical film of the present invention can be obtained only by uniaxial stretching, it is advantageous from the viewpoint of production efficiency.

The stretching ratio is preferably 1.1 times or more, more preferably 1.2 times or more, more preferably 20.0 times or less, more preferably 10.0 times or less, more preferably 5.0 times or less, and particularly preferably 2.0 times or less. The specific stretching ratio is appropriately set to meet expectations according to factors such as the optical properties, thickness, and strength of the optical film to be a product. When the stretching ratio is equal to or greater than the aforementioned lower limit value, the birefringence can be greatly changed by stretching. In addition, when the stretching ratio is equal to or less than the above-mentioned upper limit value, the direction of the slow axis can be easily controlled, and the breakage of the film can be effectively suppressed.

The stretching temperature is preferably "Tg+5°C" or higher, preferably "Tg+10°C" or higher, and preferably "Tg+100°C" or lower, more preferably "Tg+90°C" or lower. Here, "Tg" represents the glass transition temperature of the crystalline polymer. When the stretching temperature is equal to or higher than the aforementioned lower limit value, the film can be sufficiently softened to uniformly stretch. Further, when the stretching temperature is equal to or lower than the above-mentioned upper limit value, since the solidification of the thin film due to the progress of crystallization of the crystalline polymer can be suppressed, the stretching can be smoothly performed, and the stretching can make a large Birefringence exhibits. Furthermore, the haze of the obtained multilayer film can generally be reduced to improve transparency.

Since the birefringence is changed by the step (III), the NZ coefficient can be adjusted. According to this, a thin film that satisfies the above-mentioned requirements such as the formula (7) or the formula (8) can be obtained by the stretching by the step (III). The obtained film can thus be utilized as the optical film of the present invention. Alternatively, the obtained film can be further arbitrarily processed to make the optical film of the present invention. As an example of an arbitrary process, the adjustment of birefringence by processes, such as a heat treatment in the state which maintains the extended size, and the relaxation process which reduces the extended size can be mentioned.

[Other process]

The method for producing the multilayer film of the present invention and the method for producing the optical film of the present invention may further include any steps combined with the steps described above. For example, after the step (II), a step of drying the solvent in the liquid composition may be included.

The method for producing an optical film of the present invention may include a preheating process for setting the temperature of the multilayer film to a stretching temperature or a temperature close to it before the step (III). Usually the preheat temperature is the same as the extension temperature, but it can be different. The preheating temperature is preferably T1-10°C or higher, preferably T1-5°C or higher, preferably T1+5°C or lower, preferably T1+2°C or lower, relative to the stretching temperature T1. The preheating time is optional, preferably 1 second or more, more preferably 5 seconds or more, and preferably 60 seconds or less, more preferably 30 seconds or less.

The elongated optical film obtained by the step (III) may be wound into a roll as required to obtain a film roll. Also, it may be cut into a desired shape such as a rectangle as needed.

[Application of Optical Film]

The optical film of the present invention can be used as a constituent element of an optical device such as a display device after being processed into a desired shape such as a rectangle as necessary. When the optical film of the present invention is used as a constituent element of a display device, display quality such as viewing angle, contrast, and image quality of an image displayed by the display device can be improved.

"Example"

The following examples are disclosed to specifically illustrate the present invention. However, the present invention is not limited to the embodiments shown below, and can be implemented with arbitrary changes without departing from the scope of the patent application of the present invention and the scope of its equivalents.

In the following description, "%" and "part" indicating the amount are based on weight unless otherwise noted. In addition, the operation described below was performed under the conditions of normal temperature and normal pressure unless otherwise noted.

In the following description, the free end uniaxial stretching of the film refers to uniaxial stretching performed in a state allowing shrinkage in a direction orthogonal to the stretching direction among the in-plane directions. On the other hand, uniaxial stretching in which the dimension in the direction orthogonal to the extending direction is fixed and does not allow shrinkage in the direction is referred to as fixed-end uniaxial stretching. Among the uniaxial stretching of the elongated film described below, the uniaxial stretching other than the uniaxial stretching at the free end in the longitudinal direction is the uniaxial stretching at the fixed end unless otherwise noted.

[Evaluation method]

(Measuring method of weight average molecular weight Mw and number average molecular weight Mn of polymer)

The weight-average molecular weight Mw and the number-average molecular weight Mn of the polymer were measured as polystyrene conversion values using a gel permeation chromatography (GPC) system (“HLC-8320” manufactured by Tosoh Corporation). In the measurement, an H-type column (manufactured by Tosoh Corporation) was used as a column, and tetrahydrofuran was used as a solvent. In addition, the temperature at the time of measurement was 40 degreeC.

(Measuring method of hydrogenation rate of polymer)

The hydrogenation rate of the polymer was measured by ¹ H-NMR measurement at 145° C. with o-dichlorobenzene-d ⁴ as a solvent.

(Measurement method of glass transition temperature Tg and melting point Tm)

The measurement of the glass transition temperature Tg and the melting point Tm of the polymer is carried out as follows. First, the polymer is melted by heating, and the melted polymer is rapidly cooled by dry ice. Next, using this polymer as a sample, a differential scanning calorimeter (DSC) was used to measure the glass transition temperature Tg and melting point Tm of the polymer at a heating rate (heating mode) of 10°C/min.

(Measuring method for the ratio of polymer racemic diads)

The measurement of the ratio of the polymer racemic diad is carried out as follows. The ¹³ C-NMR measurement of the polymer was carried out at 200 °C using an inverse-gated decoupling method with o-dichlorobenzene-d ⁴ as a solvent. In the results of this ¹³ C-NMR measurement, the 127.5 ppm peak of o-dichlorobenzene-d ⁴ was taken as the reference offset, and the 43.35 ppm signal originating from the meso diad was identified as the A signal of 43.43 ppm for the spin dyad. According to the intensity ratio of these signals, the ratio of the polymer racemic diad is obtained.

(Measuring method of optical properties of thin films)

The optical properties of the film (retardation Re in the in-plane direction, retardation Rth in the thickness direction, NZ coefficient, etc.) were measured using a phase difference meter (“AxoScan” manufactured by Axometrics). Measurement wavelength is measured at 590 nm unless otherwise noted.

The separation procedure in the case of separating each layer body of the thin film having the A layer (or pA layer) and the B layer (or pB layer) operates as follows. Attach the intermediary adhesive layer on the B layer (or pB layer) side of the film to the glass plate. After that, use a cutter to make a cut at the edge of the board, and peel the A layer (or pA layer) from the B layer (or pB layer). Optical properties were measured separately for each peeled A layer (or pA layer) and B layer (or pB layer) on the glass plate.

(Measuring method of thickness of thin film)

The thickness was measured at a plurality of locations at intervals of 5 cm in the width direction of the film using a caliper ("ID-C112BS" manufactured by Mitutoyo Corporation). The average thickness of the film is determined by calculating the average of these measurements.

(crystallinity)

The crystallinity (%) of the crystalline polymer was measured by X-ray diffraction.

(Bending Durability)

With respect to the thin film as a sample, a table-top durability tester (“DLDMLH-FS” manufactured by Yuasa System Co., Ltd.) was used to perform a no-load U-shaped expansion test of a planar body. In this test, the film was repeatedly folded under the conditions of a width of 50 mm, a bending radius of 1 mm, and a stretching speed of 80 times/min. After 1000 bending times, the apparatus was stopped, and the film was visually checked and evaluated according to the following evaluation criteria. "Good": Neither breakage of the film sheet, occurrence of cracks, or whitening could be seen. "Poor": Any of breakage of the film sheet, occurrence of cracks, and whitening were observed.

(Haze)

A film sheet was cut out from the center of the film in the width direction to obtain a square sample with a length of 50 mm and a width of 50 mm. For this sample, the haze was measured using a haze meter (“NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd.).

(Display quality improvement effect)

An elongated linear polarizing film having an absorption axis in the longitudinal direction is prepared. This linearly polarizing film was bonded to the optical film of the evaluation object. At the time of bonding, the angle was adjusted so that the absorption axis of the linear polarizing film and the absorption axis of the optical film formed an angle of 45°. This bonding is performed using an adhesive ("CS-9621" manufactured by Nitto Denko Corporation). Thereby, a circularly polarizing film was obtained.

The polarizing plate of the image display device (“Apple Watch” (registered trademark) of Apple Inc.) was peeled off, and the adhesive layer (Nitto Denko) was interposed between the display surface of the image display device and the surface of the optical film side of the circular polarizing film to be evaluated. Made "CS9621") fit. The display surface is set in the black display state (the state where the entire screen is displayed in black), and the display surface is observed from all directions of polar angle θ=0° (front direction) and polar angle θ=60° (oblique direction). The smaller the brightness and discoloration caused by the reflection of external light, the better the result. The results of observation were evaluated on the following criteria. "A": Brightness and discoloration are not visible. "B": Brightness and discoloration occurred to a visible extent. "C": Brightness and discoloration occurred severely.

[Production Example 1: Hydrogenated product of ring-opening polymer of dicyclopentadiene]

After the metal pressure-resistant reactor was sufficiently dried, nitrogen substitution was performed. This metal pressure-resistant reactor was charged with 154.5 parts of cyclohexane and 42.8 parts of a 70% concentration cyclohexane solution of dicyclopentadiene (with an endo-isomer content of 99% or more) (as the amount of dicyclopentadiene: 30 parts) and 1.8 parts of 1-hexene, heated to 53°C.

A solution was prepared by dissolving 0.014 part of phenylimide tetrachloride (tetrahydrofuran) tungsten complex in 0.70 part of toluene. To this solution, 0.061 part of a diethyl ethoxyaluminum/n-hexane solution with a concentration of 19% was added, and the mixture was stirred for 10 minutes to prepare a catalyst solution.

This catalyst solution was added to the mixture in the pressure-resistant reactor to initiate ring-opening polymerization. Then, it was made to react for 4 hours while maintaining 53 degreeC, and the solution of the ring-opening polymer of dicyclopentadiene was obtained.

The number average molecular weight (Mn) and weight average molecular weight (Mw) of the obtained ring-opened polymer of dicyclopentadiene were 8,830 and 29,800, respectively, and the molecular weight distribution (Mw/Mn) obtained from these was 3.37.

To 200 parts of the obtained solution of the ring-opening polymer of dicyclopentadiene was added 0.037 part of 1,2-ethylene glycol as a terminator, heated to 60° C., and stirred for 1 hour to terminate the polymerization reaction. To this, 1 part of a hydrotalcite-like compound ("KYOWAAD (registered trademark) 2000" manufactured by Kyowa Chemical Industry Co., Ltd.) was added, heated to 60°C, and stirred for 1 hour. Then, 0.4 part of a filter aid (“RADIOLITE (registered trademark) #1500” manufactured by Showa Chemical Industry Co., Ltd.) was added, and the adsorbent and the solution were separated by filtration using a PP pleated cartridge filter (“TCP-HX” manufactured by ADVANTEC Toyo Corporation).

Add 100 parts of cyclohexane to 200 parts of the solution of the ring-opening polymer of dicyclopentadiene after filtration (30 parts of polymer amount), add 0.0043 part of chlorohydrocarbonyl (triphenylphosphine) ruthenium, under a hydrogen pressure of 6 MPa and 180°C for 4 hours of hydrogenation. Thereby, the reaction liquid containing the hydrogenated product of the ring-opening polymer of dicyclopentadiene can be obtained. The hydride of the reaction solution was precipitated to form a slurry solution.

The hydrogenated product contained in the reaction solution was separated from the solution using a centrifugal separator, and dried under reduced pressure at 60° C. for 24 hours to obtain 28.5 parts of a hydrogenated product of a crystalline ring-opening polymer of dicyclopentadiene. The hydrogenation rate of this hydride is 99% or more, the glass transition temperature Tg is 97°C, the melting point Tm is 266°C, and the ratio of the racemic diad is 89%.

[Production Example 2: Particles of Crystalline Resin (a)]

Antioxidant (4{3-[3',5'-bis(tertiary butyl)-4'-hydroxyphenyl) was mixed with 100 parts of the hydrogenated product of the ring-opened polymer of dicyclopentadiene obtained in Production Example 1. ] Methylene propionate}methane; 1.1 parts of "Irganox (registered trademark) 1010" manufactured by BASF Japan) to obtain a crystalline resin (a).

The obtained crystalline resin (a) was put into a biaxial extruder (“TEM-37B” manufactured by Toshiba Machine Co., Ltd.) having four die holes with an inner diameter of 3 mm⌀. The resin is hot-melt extruded using a biaxial extruder to form a strand-shaped molded body. This molded body was finely cut with a strand cutter to obtain pellets of the crystalline resin (a). The operating conditions of the aforementioned biaxial extruder are as follows. ． Set temperature of barrel: 270℃～280℃ ． Mold setting temperature: 250℃ ． Screw revolutions: 145 rpm ． Feeder revolutions: 50 rpm

[Example 1]

(1-1. Process (I): Thin Film oA)

The pellets of the crystalline resin (a) obtained in Production Example 2 were dried at 100° C. for 5 hours. The dried granules are fed to a film former. The film forming machine is equipped with an extruder, a polymer tube, a polymer filter and a T-shaped die in sequence in the flow path of the resin, and the pellets put into the extruder are melted and extruded from the T-shaped mold through the flow path. A device in the shape of a film. A barrel temperature of 280°C to 290°C, a die temperature of 270°C, and a screw revolution of 30 rpm were set as the operating conditions of the film forming machine. Using this film forming machine, the molten crystalline resin (a) was extruded into a film with a width of 500 mm toward a rotating casting roll. The rotational speed of the casting roll at this time was set to 6 m/min. Then, the crystalline resin (a) is formed into an elongated film by cooling on a roll. Thereby, the thin film oA which consists of crystalline resin (a) is obtained. The thickness of the obtained thin film oA was 68 μm. The obtained film oA is wound on the core and recovered into a film roll.

The in-plane retardation Re(oA) of the thin film oA at a wavelength of 590 nm is 5 nm, the thickness direction retardation Rth(oA) is 5 nm, and the slow axis direction is the width direction relative to the longitudinal direction.

(1-2. Process (II): Multilayer Film)

A resin containing a styrene-maleic anhydride copolymer as a material with negative intrinsic birefringence (“Daylark D332” manufactured by NOVA Chemicals, glass transition temperature 130°C) was dissolved in methyl ethyl ketone to prepare a liquid composition. The concentration of the styrene-maleic anhydride copolymer in the liquid composition was 10% by weight.

The film oA obtained in (1-1) was pulled out from the film roll, and the liquid composition was applied on one surface thereof. After that, the liquid composition is dried. As a result, a layer of styrene-maleic anhydride copolymer (thickness: 10 μm) was formed as a pB layer, and the refractive index of the thin film oA in the thickness direction was changed to become a pA layer (thickness: 68 μm), and the obtained A multilayer film having a pA layer and a pB layer. The obtained multi-layer film is wound on the core and recovered into a film roll.

The pA layer and the pB layer of the multilayer film were peeled off, and the respective optical properties were measured to obtain Re, Rth, and NZ coefficients.

The in-plane retardation Re(pA) of the pA layer is 8 nm, the retardation Rth(pA) in the thickness direction is -42 nm, the birefringence Rth(pA)/d in the thickness direction is -0.6×10 ⁻³ , the NZ coefficient Nz (pA ) is -4.53.

The in-plane retardation Re(pB) of the pB layer is 1 nm, the retardation Rth(pB) in the thickness direction is -59 nm, the birefringence Rth(pA)/d in the thickness direction is -5.9×10 ⁻³ , the NZ coefficient Nz (pA ) is 2.50.

(1-3. Process (III): Optical Film)

The multilayer film obtained in (1-2) is drawn out from the film roll, and is continuously supplied to a tenter stretching machine. Then, the co-stretching of the multilayer film is performed by a tenter stretcher. The extending direction is defined as the width direction of the film. The stretching temperature was set at 145°C, and the stretching ratio was set at 1.15 times. As a result, an optical film including a layer A made of a crystalline resin (a) having a positive intrinsic birefringence and a layer B made of a material (b) having a negative intrinsic birefringence can be obtained.

Re(450), Re(550), and Re(650) of the optical film were measured to evaluate whether it was inverse wavelength dispersibility. Also, the NZ coefficient of the optical film at a wavelength of 590 nm was measured. Next, the bending durability, haze, and display quality improvement effect of the optical film were evaluated.

Next, the A layer and the B layer of the optical film were peeled off, and the respective thicknesses and optical properties were measured, and the Re, Rth, and NZ coefficients were obtained. And, the crystallinity of the A layer was measured.

[Example 2]

A multilayer film and an optical film were obtained and evaluated in the same manner as in Example 1 except for the following changes. ． In the co-stretching of the multilayer film of (1-3), the stretching of the film was uniaxially extending along the free end in the longitudinal direction, the stretching temperature was 140°C, and the stretching ratio was 1.20.

[Comparative Example 1]

(C1-1. Film)

Except for using pellets containing thermoplastic resin (“ZEONOR 1420” manufactured by Zeon Corporation, glass transition temperature 137°C) which is a normethylene polymer which is one of alicyclic structure-containing polymers in place of pellets of crystalline resin (a) , by the same operation as (1-1) of Example 1, a thin film with a thickness of 68 μm made of an amorphous resin was obtained. The in-plane retardation Re of this film at a wavelength of 590 nm is 3 nm, the thickness direction retardation Rth is 10 nm, and the slow axis direction is the width direction relative to the longitudinal direction.

(C1-2. Multilayer film and optical film)

A multilayer film and optical films and evaluated. However, the extension temperature was set at 135°C, and the extension ratio was set at 1.20 times.

In Comparative Example 1, most of the pA layer and the pB layer were peeled off at the stage before the step (III) after the end of the step (II), and there was a portion that could not be used for optical applications, and it was not possible to form an effective thin film. state, but able to extend. The evaluation of the optical film was performed with respect to the part where peeling did not generate|occur|produce.

The summary and results of the Examples and Comparative Examples are shown in Tables 1 to 2. In the respective items in the following table, the measurement objects are shown in parentheses. For example, the measurement results for pA layer, pB layer, A layer and B layer are respectively expressed as (pA), (pB), (A) and ( B). For optical properties, the measurement wavelength is shown in parentheses, for example, the measurement result at 590 nm is shown as (590nm). In addition, units are also indicated in parentheses.

"Table 1" Table 1 Example 1 Example 2 Comparative Example 1 Re(pA)(590nm)(nm) 8 8 3 Rth(pA)(590nm)(nm) −42 −42 10 Rth(pA)/d(590nm)(×10 ⁻³ ) −0.6 −0.6 0.1 Nz(pA)(590nm) −4.53 −4.53 8.1 nx(pA)(590nm) 1.5299 1.5299 1.5301 ny(pA)(590nm) 1.5297 1.5297 1.5300 nz(pA)(590nm) 1.5304 1.5304 1.5299 Re(pB)(590nm)(nm) 1 1 1 Rth(pB)(590nm)(nm) −59 −59 −59 Rth(pB)/d(590nm)(×10 ⁻³ ) −5.9 −5.9 −5.9 Nz(pB)(590nm) 2.50 2.50 2.50 nx(pB)(590nm) 1.5280 1.5280 1.5280 ny(pB)(590nm) 1.5280 1.5280 1.5280 nz(pB)(590nm) 1.5339 1.5339 1.5339 Extension temperature (℃) 145℃ 140℃ 135℃ Elongation ratio (times) 1.15 1.20 1.20 extension direction Width The long side Width extended form Fixed single axis free uniaxial Fixed single axis

"Table 2" Table 2 Example 1 Example 2 Comparative Example 1 A layer thickness (μm) 59 59 59 B layer thickness (μm) 8 8 8 Total thickness of layer A and layer B (μm) 67 67 67 Re(A)(450nm)(nm) 114 138 86 Re(A)(550nm)(nm) 113 136 80 Re(A)(650nm)(nm) 112 136 74 Rth(A)(450nm)(nm) −17.0 3.0 90 Rth(A)(550nm)(nm) −17.5 3.3 95 Rth(A)(650nm)(nm) −17.7 3.1 92 Re(A)(590nm)(nm) 111 136 80 Rth(A)(590nm)(nm) −19 3 93 Rth(A)/d(590nm)(×10 ⁻³ ) −0.3 0.1 1.6 Nz(A)(590nm) 0.33 0.52 1.66 A layer crystallinity (%) 42 42 — Re(B)(450nm)(nm) 66 82 70 Re(B)(550nm)(nm) 59 74 74 Re(B)(650nm)(nm) 56 70 82 Rth(B)(450nm)(nm) −73 −76 −76 Rth(B)(550nm)(nm) −68 −70 −70 Rth(B)(650nm)(nm) −65 −66 −66 Re(B)(590nm)(nm) 61 72 72 Rth(B)(590nm)(nm) −72 −70 −70 Rth/d(B)(590nm)(×10 ⁻³ ) −9.00 −8.75 −8.75 Nz(B)(590nm) −0.69 −0.47 −0.47 Whether Re450＜Re550＜Re650 Yes Yes no Optical film NZ coefficient −0.4 0.1 1.2 Bending Durability good good Difference haze HZ1.7 HZ2.0 Unable to measure due to peeling Visual evaluation B A C

As is apparent from the results of Examples and Comparative Examples, the optical film of the present invention produced on the basis of the multilayer film obtained by the production method of the present invention can exhibit good effects as a three-dimensional retardation film in a wide wavelength range, mechanical It has high strength, can be made into a thin film, can improve the display quality of the display device, and can be easily manufactured by uniaxial co-extension.

none.

none.

none.

Claims (11)

A multilayer film comprising a pA layer made of a crystalline resin with positive intrinsic birefringence (a) and a pB layer made of a material with negative intrinsic birefringence (b), wherein the pA layer satisfies The following formulae (1) to (2), the pB layer satisfies the following formulae (3) to (4): nz(pA)>nx(pA)≧ny(pA)・・・(1)nx(pA) －ny（pA）≦0.0003 Among them, nx(pA), ny(pA) and nz(pA) are the principal refractive indices of the pA layer, and nx(pB), ny(pB) and nz(pB) are the principal refractive indices of the pB layer. The multilayer film according to claim 1, which is a long strip film. The multilayer film of claim 1 or 2, wherein the aforementioned pA layer is in direct contact with the aforementioned pB layer. The multilayer film according to claim 1 or 2, wherein the thickness of the pB layer is 20 μm or less. An optical film, which is a uniaxial coextensive product of the multilayer film according to any one of Claims 1 to 4, and is provided with an A layer made of a crystalline resin (a) with positive intrinsic birefringence, and B-layer optical film made of material (b) with negative intrinsic birefringence, which satisfies the following formulas (5) and (6): Re(450)<Re(550)<Re(650)・・・(5) Nz<1 ・・・ (6) Re(450), Re(550) and Re(650) are the in-plane retardation of the aforementioned optical film at a wavelength of 450 nm, respectively, and the aforementioned optical film at a wavelength of 550 nm The in-plane retardation of and the in-plane retardation of the aforementioned optical film at a wavelength of 650 nm, Nz is the NZ coefficient of the aforementioned optical film. The optical film according to claim 5, which is an elongated film. The optical film according to claim 5 or 6, wherein the aforementioned uniaxial co-extension is longitudinal uniaxial co-extension, transverse uniaxial co-extension or oblique uniaxial co-extension. The optical film according to claim 5 or 6, wherein the thickness of the aforementioned layer B is 20 μm or less. The optical film according to claim 5 or 6, comprising one layer of the aforementioned A layer and two layers of the aforementioned B layer formed on both surfaces thereof. A method for producing a multilayer film, which is the method for producing a multilayer film according to any one of claims 1 to 4, comprising the step (I) of preparing a film oA made of a crystalline resin (a), and In step (II), a liquid composition comprising a solvent and a material (b) having a negative intrinsic birefringence dissolved in the solvent is applied to one or both sides of the thin film oA, thereby forming a pB layer and making the thin film oA The birefringence in the thickness direction is changed to form a pA layer, and a multilayer film having the aforementioned pA layer and the aforementioned pB layer is obtained. A method for producing an optical film, which is the method for producing an optical film according to any one of claims 5 to 9, comprising a step (I) of preparing a film oA made of a crystalline resin (a), step (II), a liquid composition comprising a solvent and a material (b) having a negative intrinsic birefringence dissolved in the solvent is applied to one or both sides of the thin film oA, thereby forming a pB layer and making the thin film oA The birefringence in the thickness direction is changed to form a pA layer to obtain a multilayer film including the pA layer and the pB layer, and in step (III), the multilayer film is uniaxially coextensive.