JP7615993B2 - Multilayer optical film and method of making same - Google Patents

Description

The present invention relates to a multilayer optical film and a method for producing the same.

Conventionally, films for optical applications have generally been made of amorphous polymers. However, amorphous polymers tend to have poor solvent resistance. Therefore, it has been proposed to produce films with excellent solvent resistance by using resins containing a combination of amorphous polymers and crystalline polymers (e.g., Patent Documents 1 and 2). Multilayer optical films combining such films with other films have also been proposed (e.g., Patent Documents 3 and 4). In such multilayer optical films, by adopting layers containing crystalline polymers as layers constituting the surface layers, it is expected that the solvent resistance can be improved and the desired optical performance can be expressed by the core layer between them. The core layer can be, for example, a retardation layer having a retardation expressed by stretching.

JP 2002-249645 A JP 2007-016102 A Japanese Patent Application No. 3-230614 International Publication No. 2013/069666

The core layer that exerts optical performance is required to have a high glass transition temperature in order to enhance the heat resistance of the optical film when it is used. Such a core layer is required to be stretched at a relatively high temperature during the stretching process. However, when manufacturing an optical film using such a core layer with a high glass transition temperature together with a surface layer containing a crystalline polymer, it has been difficult to easily manufacture a high-quality product. For example, there is a high tendency for defects to occur, such as uneven thickness occurring on the cooling roll when the resin is formed into a film by melt extrusion, and breakage occurring when the unstretched film is subjected to the stretching process.

The object of the present invention is therefore to provide a multilayer optical film and a method for producing the same that have high heat resistance during use, high solvent resistance, and can be easily produced to high quality.

The present inventors have conducted studies to solve the above problems, and as a result, have found that the above problems can be solved by using a material that has specific properties in relation to a core layer as a material constituting a surface layer of a multilayer optical film, and have completed the present invention.
That is, the present invention includes the following.

[1] A multilayer optical film comprising a pair of B layers constituting surface layers on a front surface and a back surface, and an A layer located between the pair of B layers,
The layer A is a layer of a resin (a) containing an amorphous polymer (a) having no melting point,
The layer B is a layer of a resin (b) having a melting point, which contains a crystalline polymer (b1) having a melting point and an amorphous polymer (b2) having no melting point,
The resin (a) and the resin (b) satisfy the following formulas (1) to (3),
TgA-TgB≦20℃ (1)
110℃<TgB<140℃ (2)
180℃<TcB<235℃ (3)
In the formula, TgA is the glass transition temperature of resin (a), TgB is the glass transition temperature of resin (b), and TcB is the cold crystallization temperature of resin (b).
Multilayer optical films.
[2] The multilayer optical film according to [1], wherein the A layer and the B layer are in interlayer adhesion.
[3] The multilayer optical film according to [1] or [2], wherein each of the layers B has a thickness of 10 μm or less.
[4] The multilayer optical film according to any one of [1] to [3], having a haze of 1% or less.
[5] A method for producing the multilayer optical film according to any one of [1] to [4],
preparing the resin (a) and the resin (b);
A production method comprising a step of forming the resin (a) and the resin (b) to obtain a multilayer resin film.
[6] The method for producing a multilayer optical film according to [5], further comprising a step of stretching the multilayer resin film at a stretching temperature of TgA or higher.

The present invention provides a multilayer optical film and a method for producing the same that are highly heat-resistant during use, highly solvent-resistant, and easy to produce of high quality.

FIG. 1 is a side view diagrammatically illustrating a method for testing solvent resistance in the present examples. FIG. 2 is a perspective view that illustrates a method for testing interphase adhesion in the present examples.

The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be modified and implemented as desired without departing from the scope of the claims of the present invention and their equivalents.

In the following description, a "long" film refers to a film that is 5 times or more longer than its width, preferably 10 times or more longer, and specifically refers to a film that is long enough to be wound into a roll for storage or transportation. There is no particular upper limit to the length of the film, and it can be, for example, 100,000 times or less than its width.

In the following description, the in-plane retardation Re is a value expressed by Re = (nx - ny) x d, unless otherwise specified. Furthermore, the retardation in the thickness direction Rth is a value expressed by Rth = [{(nx + ny) / 2} - nz] x d, unless otherwise specified. Furthermore, the birefringence Δn is a value expressed by nx - ny, and therefore a value expressed by Re / d, unless otherwise specified. Here, nx represents the refractive index in the direction perpendicular to the thickness direction (in-plane direction) that gives the maximum refractive index. ny represents the refractive index in the in-plane direction that is perpendicular to the direction of nx. nz represents the refractive index in the thickness direction. d represents the thickness. The measurement wavelength is 590 nm, unless otherwise specified.

In the following description, unless otherwise specified, a polymer with positive intrinsic birefringence means a polymer whose refractive index in the stretching direction is greater than the refractive index in the direction perpendicular to the stretching direction. Also, a polymer with negative intrinsic birefringence means a polymer whose refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular to the stretching direction, unless otherwise specified.

[Multilayer Optical Films: Overview]
The multilayer optical film of the present invention comprises a pair of layers B constituting the front and back surface layers, and a layer A located therebetween. Here, when one surface of layer B that is the surface layer of the multilayer optical film is defined as the front surface, the other surface of the surface layers is defined as the back surface.
Layer A is a layer of resin (a) containing an amorphous polymer (a) having no melting point, and may be a layer consisting of resin (a) alone. Layer B is a layer of resin (b) having a melting point, containing a crystalline polymer (b1) having a melting point and an amorphous polymer (b2) having no melting point, and may be a layer consisting of resin (b) alone.

[Resin (b): Crystalline polymer (b1)]
As the crystalline polymer (b1), various crystalline polymers such as known ones can be used. In general, a crystalline polymer is a polymer having crystallinity. A polymer having crystallinity is: A crystalline polymer is a polymer that has a melting point. The melting point of a polymer can be measured by a differential scanning calorimeter (DSC). Therefore, a crystalline polymer is a polymer whose melting point can be observed by a differential scanning calorimeter (DSC). It is a combination.

The crystalline polymer (b1) may have a positive intrinsic birefringence or a negative intrinsic birefringence. Among them, a crystalline polymer having a positive intrinsic birefringence is preferred.

Examples of the crystalline polymer (b1) include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefins such as polyethylene (PE) and polypropylene (PP); and the like, but a cyclic olefin polymer is preferred. That is, the crystalline polymer (b1) is preferably a cyclic olefin polymer having a melting point. Hereinafter, a cyclic olefin polymer having a melting point may be referred to as a "cyclic olefin crystalline polymer."

The cyclic olefin crystalline polymer may have an alicyclic structure in its molecule. Such a cyclic olefin crystalline polymer may be, for example, a polymer or a hydrogenated product thereof that can be obtained by a polymerization reaction using a cyclic olefin as a monomer. When a resin (b) containing a cyclic olefin crystalline polymer is used, the mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability, and light weight of the multilayer optical film can be improved.

Examples of alicyclic structures include cycloalkane structures and cycloalkene structures. Among these, cycloalkane structures are preferred because they are more likely to produce multilayer optical films with excellent properties such as thermal stability. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, 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, the mechanical strength, heat resistance, and moldability are highly balanced.

In the cyclic olefin crystalline polymer, the ratio of structural units having an alicyclic structure to all structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 70% by weight or more. When the ratio of structural units having an alicyclic structure is high as described above, heat resistance can be improved. The ratio of structural units having an alicyclic structure to all structural units can be 100% by weight or less. In the cyclic olefin crystalline polymer, the remainder other than the structural units having an alicyclic structure is not particularly limited and can be appropriately selected depending on the purpose of use.

Examples of the cyclic olefin-based crystalline polymer include the following polymer (α) to polymer (δ). Among these, polymer (β) is preferred because it is easy to obtain a multilayer optical film having excellent heat resistance.
Polymer (α): A ring-opening polymer of a cyclic olefin monomer, which has crystallinity.
Polymer (β): A hydrogenated product of polymer (α) and has crystallinity.
Polymer (γ): An addition polymer of a cyclic olefin monomer, which has crystallinity.
Polymer (δ): A hydrogenated polymer (γ) having crystallinity.

Specifically, as the crystalline polymer containing an alicyclic structure, a ring-opening polymer of dicyclopentadiene having crystallinity and a hydrogenated ring-opening polymer of dicyclopentadiene having crystallinity are more preferable. Among them, a hydrogenated ring-opening polymer of dicyclopentadiene having crystallinity is particularly preferable. Here, a ring-opening polymer of dicyclopentadiene refers to a polymer in which 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, more preferably 90% by weight or more, and even more preferably 100% by weight.

The hydrogenated ring-opening polymer of dicyclopentadiene preferably has a high ratio of racemo dyads. Specifically, the ratio of racemo dyads in the repeating units of the hydrogenated ring-opening polymer of dicyclopentadiene is preferably 51% or more, more preferably 70% or more, and particularly preferably 85% or more. A high ratio of racemo dyads indicates high syndiotactic stereoregularity. Therefore, the higher the ratio of racemo dyads, the higher the melting point of the hydrogenated ring-opening polymer of dicyclopentadiene tends to be.
The ratio of the racemo dyads can be determined based on the ¹³ C-NMR spectrum analysis described in the Examples below.

As the above polymer (α) to polymer (δ), polymers obtained by the manufacturing method disclosed in WO 2018/062067 can be used.

The melting point Tmb1 of the crystalline polymer (b1) is preferably 200° C. or higher, more preferably 230° C. or higher, and preferably 290° C. or lower. When a crystalline polymer (b1) having such a melting point Tmb1 is used, a multilayer optical film with an even better balance between moldability and heat resistance can be obtained.

Typically, the crystalline polymer (b1) has a glass transition temperature Tgb1. The specific glass transition temperature Tgb1 of the crystalline polymer (b1) is not particularly limited, but is typically 85°C or higher and typically 170°C or lower.

The glass transition temperature and melting point of a polymer can be measured by the following method. First, the polymer is melted by heating, and the molten polymer is rapidly cooled with dry ice. Next, using this polymer as a test specimen, the glass transition temperature and melting point of the polymer can be measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C/min (heating mode).

The weight average molecular weight (Mw) of the crystalline polymer (b1) is preferably 1,000 or more, more preferably 2,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less. A crystalline polymer (b1) having such a weight average molecular weight has an excellent balance between moldability and heat resistance.

The molecular weight distribution (Mw/Mn) of the crystalline polymer (b1) is preferably 1.0 or more, more preferably 1.5 or more, and is preferably 4.0 or less, more preferably 3.5 or less. Here, Mn represents the number average molecular weight. The crystalline polymer (b1) having such a molecular weight distribution has excellent moldability.

The weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the polymer can be measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as the developing solvent. If the polymer does not dissolve in cyclohexane, the weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) can be measured in terms of polyisoprene using toluene as the solvent.

The crystalline polymer (b1) may be used alone or in any combination of two or more kinds in any ratio.

The amount of crystalline polymer (b1) contained in resin (b) is preferably 30% by weight or more, more preferably 35% by weight or more, particularly preferably 40% by weight or more, and is preferably 80% by weight or less, more preferably 75% by weight or less, particularly preferably 70% by weight or less, based on 100% by weight of resin (b). When the amount of crystalline polymer (b1) is within the above range, the solvent resistance, heat resistance, and flexibility of the multilayer optical film can be effectively improved.

The weight ratio Wa/Wb of the amount Wa of the crystalline polymer (b1) and the amount Wb of the amorphous polymer (b2) contained in the resin (b) is preferably within a specific range. Specifically, the weight ratio Wa/Wb is preferably greater than 30/70, more preferably greater than 35/65, particularly preferably greater than 40/60, and preferably less than 80/20, more preferably less than 75/25. By setting the weight ratio Wa/Wb to the lower limit or more, the resin (b) can be made to have a melting point. Furthermore, when the weight ratio Wa/Wb is within the above range, the solvent resistance, heat resistance, and flexibility of the multilayer optical film can be effectively improved.

The total amount of the crystalline polymer (b1) and the amorphous polymer (b2) contained in the resin (b) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 80% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, and particularly preferably 95% by weight to 100% by weight, based on 100% by weight of the resin (b).

[Resin (b): Amorphous polymer (b2)]
As the amorphous polymer (b2), various amorphous polymers such as known ones can be used. In general, an amorphous polymer is a polymer that does not have crystallinity. A polymer is a polymer that does not have a melting point. Thus, an amorphous polymer refers to a polymer whose melting point cannot be observed by differential scanning calorimetry (DSC).

The amorphous polymer (b2) may have positive intrinsic birefringence or may have negative intrinsic birefringence. Among these, an amorphous polymer having positive intrinsic birefringence is preferred.

As the amorphous polymer (b2), a cyclic olefin polymer is preferable. That is, the amorphous polymer (b2) is preferably a cyclic olefin polymer that does not have a melting point. Hereinafter, a cyclic olefin polymer that does not have a melting point may be referred to as a "cyclic olefin amorphous polymer." A cyclic olefin amorphous polymer has excellent mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability, and light weight.

A cyclic olefin-based amorphous polymer may have a cyclic structure in its molecule. Usually, the structural unit of a cyclic olefin-based amorphous polymer has an alicyclic structure. A cyclic olefin-based amorphous polymer may be a polymer having an alicyclic structure in the main chain, a polymer having an alicyclic structure in the side chain, a polymer having an alicyclic structure in the main chain and in the side chain, or a mixture of two or more of these in any ratio. Among these, it is preferable that the cyclic olefin-based amorphous polymer has an alicyclic structure in the main chain from the viewpoint of mechanical strength and heat resistance.

Examples of alicyclic structures include saturated alicyclic hydrocarbon (cycloalkane) structures and unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structures. Among these, from the viewpoints of mechanical strength and heat resistance, cycloalkane structures and cycloalkene structures are preferred, and cycloalkane structures are particularly preferred.

The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, 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 constituting the alicyclic structure is within this range, the mechanical strength, heat resistance, and moldability are highly balanced.

In cyclic olefin-based amorphous polymers, the ratio of structural units having an alicyclic structure to all structural units is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the ratio of structural units having an alicyclic structure to all structural units is within this range, the transparency and heat resistance are good.

Examples of cyclic olefin-based amorphous polymers include norbornene-based polymers, monocyclic cyclic olefin-based polymers, cyclic conjugated diene-based polymers, vinyl alicyclic hydrocarbon-based polymers, and hydrogenated versions of these polymers. Among these, norbornene-based polymers and hydrogenated versions thereof have good moldability.

Examples of norbornene-based polymers and their hydrogenated products include ring-opening polymers of monomers having a norbornene structure and their hydrogenated products; addition polymers of monomers having a norbornene structure and their hydrogenated products. Examples of ring-opening polymers of monomers having a norbornene structure include ring-opening homopolymers of one type of monomer having a norbornene structure, ring-opening copolymers of two or more types of monomers having a norbornene structure, and ring-opening copolymers of a monomer having a norbornene structure and other monomers that can be copolymerized therewith. Examples of addition polymers of monomers having a norbornene structure include addition homopolymers of one type of monomer having a norbornene structure, addition copolymers of two or more types of monomers having a norbornene structure, and addition copolymers of a monomer having a norbornene structure and other monomers that can be copolymerized therewith. Examples of these polymers include those disclosed in JP 2002-321302 A and WO 2017/145718 A. Among these, hydrogenated ring-opening polymers of monomers having a norbornene structure are particularly suitable from the standpoints of moldability, heat resistance, low moisture absorption, dimensional stability, and light weight.

Examples of monomers having a norbornene structure include bicyclo[2.2.1]hept-2-ene (common name: norbornene), tricyclo[4.3.0.1 ^2,5 ]deca-3,7-diene (common name: dicyclopentadiene), tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]dodec-3-ene (trivial name: tetracyclododecene), and other norbornene-based monomers not containing an aromatic ring structure; norbornene-based monomers having an aromatic substituent, such as 5-phenyl-2-norbornene, 5-(4-methylphenyl)-2-norbornene, 5-(1-naphthyl)-2-norbornene, and 9-(2-norbornen-5-yl)-carbazole; 1,4-methano-1,4,4a,4b,5,8,8a,9a-octahydrofluorene, 1,4-methano-1,4,4a,9a-tetrahydrofluorene (trivial name: meth norbornene-based monomers containing a norbornene ring structure and an aromatic ring structure in a condensed polycyclic structure, such as 1,4-methano-1,4,4a,9a-tetrahydrofluorene, 1,4-methano-1,4,4a,9a-tetrahydrodibenzofuran, 1,4-methano-1,4,4a,9a-tetrahydrocarbazole, 1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene, and 1,4-methano-1,4,4a,9,10,10a-hexahydrophenanthrene; as well as derivatives of these compounds (for example, those having a substituent on the ring).

Examples of the substituent include alkyl groups such as methyl, ethyl, propyl, and isopropyl groups; alkylidene groups; alkenyl groups; polar groups; and the like. Examples of the polar group include heteroatoms and atomic groups having heteroatoms. Examples of the heteroatom include oxygen atoms, nitrogen atoms, sulfur atoms, silicon atoms, and halogen atoms. Specific examples of the polar group include halogen groups such as fluoro, chloro, bromo, and iodine groups; carboxyl groups; carbonyloxycarbonyl groups; epoxy groups; hydroxy groups; oxy groups; alkoxy groups; ester groups; silanol groups; silyl groups; amino groups; nitrile groups; sulfone groups; cyano groups; amide groups; and imide groups. The number of the substituents may be one or more. The types of the two or more substituents may be the same or different. However, from the viewpoint of obtaining an amorphous resin with a low saturated water absorption rate and excellent moisture resistance, it is preferable that the norbornene monomer has a small amount of polar groups, and it is more preferable that the norbornene monomer has no polar groups.

Examples of cyclic olefin-based amorphous polymers by trade name include "ZEONEX" manufactured by Zeon Corporation; "ARTON" manufactured by JSR Corporation; "APEL" manufactured by Mitsui Chemicals, Inc.; and "TOPAS" manufactured by Polyplastics Co., Ltd.

The glass transition temperature Tgb2 of the amorphous polymer (b2) is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher, and is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower. When the glass transition temperature Tgb2 of the amorphous polymer (b2) is within the above range, both the solvent resistance and heat resistance of the multilayer optical film can be effectively improved. In addition, the stretching process can usually be carried out smoothly.

The weight average molecular weight (Mw) of the amorphous polymer (b2) is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, and is preferably 100,000 or less, more preferably 80,000 or less, particularly preferably 50,000 or less. When the weight average molecular weight is within the above range, the mechanical strength and moldability of the resin (b) are highly balanced.

The molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the amorphous polymer (b2) is preferably 1.2 or more, more preferably 1.5 or more, particularly preferably 1.8 or more, and is preferably 3.5 or less, more preferably 3.0 or less, particularly preferably 2.7 or less. When the molecular weight distribution is equal to or more than the lower limit of the above range, the productivity of the polymer can be increased and the production cost can be reduced. When the molecular weight distribution is equal to or less than the upper limit, the amount of low molecular weight components is reduced, thereby suppressing relaxation during exposure to high temperatures and improving the stability of the multilayer optical film.

The amorphous polymer (b2) may be used alone or in any combination of two or more kinds in any ratio.

The amount of amorphous polymer (b2) contained in resin (b) is preferably 20% by weight or more, more preferably 25% by weight or more, particularly preferably 30% by weight or more, and is preferably 70% by weight or less, more preferably 65% by weight or less, particularly preferably 60% by weight or less, based on 100% by weight of resin (b). When the amount of amorphous polymer (b2) is within the above range, both the solvent resistance and heat resistance of the multilayer optical film can be effectively increased.

The glass transition temperature Tgb2 of the amorphous polymer (b2) is preferably relatively higher than the glass transition temperature Tgb1 of the crystalline polymer (b1). Generally, crystalline polymers have low glass transition temperatures, while amorphous polymers have both high and low glass transition temperatures. By using an amorphous polymer (b2) with a high glass transition temperature Tgb2, the glass transition temperature TgB of the resin (b) as a whole can be set to the desired high temperature.

The absolute value |Tgb1-Tgb2| of the difference between the glass transition temperature Tgb1 of the crystalline polymer (b1) and the glass transition temperature Tgb2 of the amorphous polymer (b2) is preferably in a specific range. Specifically, the absolute value |Tgb1-Tgb2| is preferably 30°C or higher, more preferably 40°C or higher, particularly preferably 50°C or higher, and preferably 100°C or lower, more preferably 90°C or lower, particularly preferably 80°C or lower. When the absolute value |Tgb1-Tgb2| is equal to or higher than the lower limit, the glass transition temperature TgB of the resin (b) as a whole can be set to a desired high temperature. On the other hand, when the absolute value |Tgb1-Tgb2| is in the above range, the solvent resistance, heat resistance, and flexibility of the multilayer optical film can be effectively improved.

[Resin (b): optional component]
The resin (b) may further contain an optional component in combination with the crystalline polymer (b1) and the amorphous polymer (b2). 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 waxes, Fischer-Tropsch waxes, Waxes such as polyalkylene waxes; nucleating agents such as sorbitol compounds, metal salts of organic phosphoric acids, metal salts of organic carboxylic acids, kaolin and talc; diaminostilbene derivatives, coumarin derivatives, azole derivatives (e.g., benzoxazole derivatives, Fluorescent whitening agents such as benzotriazole derivatives, benzimidazole derivatives, and benzothiazole derivatives), carbazole derivatives, pyridine derivatives, naphthalic acid derivatives, and imidazolone derivatives; benzophenone-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, benzotriazole-based UV absorbers and other ultraviolet absorbing agents; colorants; flame retardants; flame retardant assistants; antistatic agents; plasticizers; near infrared absorbing agents; lubricants; inorganic fillers such as talc, silica, calcium carbonate, and glass fiber; etc. Examples include: The optional components may be used alone or in combination of two or more kinds in any ratio. The amount of the optional components may be appropriately determined within a range that does not significantly impair the effects of the present invention. The amount of any optional component can be, for example, in a range that maintains the total light transmittance of the multilayer optical film at 85% or greater.

[Characteristics of Resin (b)]
The resin (b) has a glass transition temperature TgB that satisfies the following formula (2).
110℃<TgB<140℃ (2)
Specifically, the glass transition temperature TgB of resin (b) is higher than 110°C, preferably higher than 115°C, particularly preferably 120°C or higher, and is lower than 140°C, preferably lower than 135°C, particularly preferably 130°C or lower.

The glass transition temperature TgB of resin (b) can be adjusted, for example, by adjusting the type and amount of crystalline polymer (b1) and the type and amount of amorphous polymer (b2).

The glass transition temperature TgB of resin (b) can be measured by the same method as that for measuring the glass transition temperature of the polymer described above.

The resin (b) has a cold crystallization temperature TcB that satisfies the following formula (3).
180℃<TcB<235℃ (3)
In detail, the cold crystallization temperature TcB of the resin (b) is higher than 180°C, preferably higher than 185°C, particularly preferably 190°C or higher, and is usually lower than 235°C, preferably lower than 230°C, particularly preferably lower than 225°C.

The cold crystallization temperature TcB of resin (b) can be adjusted, for example, by adjusting the type and amount of crystalline polymer (b1) and the type and amount of amorphous polymer (b2).

The cold crystallization temperature TcB of resin (b) can be measured by the following method. First, resin (b) is melted by heating, and the melted resin (b) is rapidly cooled with dry ice. Next, using this resin (b) as a test specimen, the cold crystallization temperature TcB of resin (b) can be measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C/min (heating mode). In this measurement method, the cold crystallization temperature TcB can be obtained as the temperature at the top of the exothermic peak during the heating process.

When resin (b) has a glass transition temperature TgB that satisfies the above-mentioned formula (2) and a cold crystallization temperature TcB that satisfies the above-mentioned formula (3), the resulting multilayer optical film can have high solvent resistance and can suppress the occurrence of defects in the manufacturing process of the multilayer film.

The absolute value of the difference between the glass transition temperature TgB of the resin (b) and the glass transition temperature Tgb1 of the crystalline polymer (b1), |TgB-Tgb1|, is preferably within a specific range. Specifically, the absolute value |TgB-Tgb1| is preferably 3°C or higher, more preferably 6°C or higher, particularly preferably 10°C or higher, and is preferably 45°C or lower, more preferably 40°C or lower, particularly preferably 35°C or lower. When the absolute value |TgB-Tgb1| is within the above range, both the solvent resistance and heat resistance of the multilayer optical film can be effectively increased.

The absolute value of the difference between the glass transition temperature TgB of the resin (b) and the glass transition temperature Tgb2 of the amorphous polymer (b2), |TgB-Tgb2|, is preferably within a specific range. Specifically, the absolute value |TgB-Tgb2| is preferably 20°C or higher, more preferably 25°C or higher, particularly preferably 30°C or higher, and is preferably 80°C or lower, more preferably 70°C or lower, particularly preferably 60°C or lower. When the absolute value |TgB-Tgb2| is within the above range, both the solvent resistance and heat resistance of the multilayer optical film can be effectively increased.

Resin (b) has a melting point Tmb. The melting point Tmb of resin (b) is preferably in the range of 200°C or higher, more preferably 230°C or higher, particularly preferably 240°C or higher, and preferably 290°C or lower. When resin (b) has a melting point Tmb in the above range, it is possible to effectively increase both the solvent resistance and heat resistance of the multilayer optical film.

The melting point Tmb of resin (b) can be measured, for example, by the same method as the method for measuring the melting point of the polymer described above.

[Layer B]
Resin (b) in layer B may be in a crystallized state because it contains crystalline polymer (b1). However, resin (b) that satisfies the desired requirements such as glass transition temperature TgB and is molded into the multilayer optical film of the present invention is often in an amorphous state in layer B. The presence or absence of crystallization can be determined by TEM observation under the conditions shown in the examples of the present application. If a spherulite structure or difference in contrast is found in the observed slice, it is determined to be in a crystallized state, and if not, it is determined to be in an amorphous state.

In the B layer, the resin (b) is often in an amorphous state, and the resin (b) in an amorphous state tends to exhibit low haze while also exhibiting low retardation. Therefore, from the viewpoint of exhibiting retardation in the multilayer optical film, it is preferable that the thickness of each of the B layers in the multilayer optical film is thin to a certain degree. The thickness of each B layer is preferably 10 μm or less, more preferably 9 μm or less. The lower limit of the thickness of the B layer is not particularly limited, but may be 3 μm or more from the viewpoint of effectively exhibiting solvent resistance.

[Resin (a): Amorphous polymer (a)]
Examples of the amorphous polymer (a) which is a component of the resin (a) constituting the layer A include the same as the examples of the amorphous polymer (b2) described above. In the multilayer optical film of the present invention, the amorphous polymer (a) and the amorphous polymer (b2) may be the same or different.

Resin (a) may contain optional components in addition to amorphous polymer (a). Examples of such optional components and the amounts thereof are the same as those for resin (b). Resin (a) does not have a melting point because it is mainly composed of amorphous polymer (a). The fact that it does not have a melting point can be confirmed by the fact that no melting point is observed using the method for measuring the melting point of a polymer described above.

The glass transition temperature TgA of the resin (a) and the glass transition temperature TgB of the resin (b) satisfy the following formula (1).
TgA-TgB≦20℃ (1)
The value of TgA-TgB is 20° C. or less, and preferably 15° C. or less. According to the findings of the present inventors, when the value of TgA-TgB is equal to or less than the upper limit, it becomes possible to easily produce a multilayer optical film in a high quality state. Specifically, it is possible to effectively suppress undesirable phenomena such as the occurrence of uneven thickness on a cooling roll when a resin is formed into a film by melt extrusion, and the occurrence of breakage when a film before stretching is subjected to a stretching step. Therefore, it is possible to realize a multilayer optical film that can be easily produced in a high quality state while enjoying the advantages of having a B layer as a surface layer, such as high solvent resistance.

The lower limit of the TgA-TgB value is not particularly limited, but it can usually be -10°C or higher, and preferably -5°C or higher. By having the TgA-TgB value be equal to or higher than this lower limit, it is possible to achieve both heat resistance and solvent resistance during use of the multilayer resin film.

The glass transition temperature TgA of the resin (a) itself is not particularly limited, but from the viewpoint of increasing the heat resistance when the multilayer optical film is used, it is preferable that the TgA is high. On the other hand, from the viewpoint of ease of handling, it is preferable that the TgA is lower to a certain degree. Specifically, the TgA is preferably 105°C or higher, more preferably 110°C or higher, and is preferably 145°C or lower, more preferably 140°C or lower. The glass transition temperature TgA of the resin (a) can be adjusted, for example, by appropriately selecting the type of crystalline polymer (a). The glass transition temperature TgA of the resin (a) can be measured by the same method as the method for measuring the glass transition temperature of the polymer described above.

[Layer A]
The thickness of the A layer is not particularly limited, but from the viewpoint of effectively expressing the retardation as a multilayer optical film, it is preferable that the thickness is at least a certain level. The lower limit of the thickness of the A layer is preferably 10 μm or more, more preferably 20 μm or more. On the other hand, from the viewpoint of thinning the device equipped with the multilayer optical film, the upper limit of the thickness of the A layer is preferably 160 μm or less, more preferably 150 μm or less.

[Properties of multilayer optical films]
The multilayer optical film of the present invention can have excellent solvent resistance, for example, the multilayer optical film can be a film that does not easily break even when n-hexane is dropped onto the bent portion in a bent state.

The multilayer optical film of the present invention can have excellent heat resistance by setting the glass transition temperature TgA of the resin (a) constituting the A layer within an appropriate range. This allows the multilayer optical film to suppress changes in retardation in high-temperature environments and increases in haze in high-temperature environments.

The multilayer optical film can easily exhibit high birefringence in the A layer. By combining the A layer and the B layer, the multilayer optical film can be made into a film that has high birefringence suitable for applications such as a retardation film, has excellent solvent resistance, and can be easily manufactured. The specific birefringence of the multilayer optical film is preferably 0.00200 or more, more preferably 0.00205 or more, and particularly preferably 0.00210 or more. There is no particular limit to the upper limit of the birefringence Δn, and it can be, for example, 0.01000 or less, 0.00800 or less, etc.

The multilayer optical film may have an in-plane retardation suitable for its application. For example, the in-plane retardation Re of the multilayer optical film at a measurement wavelength of 590 nm is preferably 30 nm or more, more preferably 40 nm or more, particularly preferably 50 nm or more, and is preferably 300 nm or less, more preferably 290 nm or less, particularly preferably 280 nm or less.

The multilayer optical film can have a thickness direction retardation suitable for its application. For example, the thickness direction retardation Rth of the multilayer optical film at a measurement wavelength of 590 nm is preferably 0 nm or more, more preferably 5 nm or more, particularly preferably 10 nm or more, and is preferably 300 nm or less, more preferably 250 nm or less, particularly preferably 200 nm or less.

The in-plane retardation and thickness direction retardation of the multilayer optical film can be measured using a phase difference meter (AxoScan OPMF-1 manufactured by AXOMETRICS).

It is preferable that the multilayer optical film has high transparency. The specific total light transmittance of the multilayer optical film is preferably 80% or more, more preferably 85% or more, and particularly preferably 88% or more. The total light transmittance of the film can be measured in the wavelength range of 400 nm to 700 nm using an ultraviolet-visible spectrometer.

It is preferred that the multilayer optical film has a small haze. The haze of the multilayer optical film is preferably 2.0% or less, more preferably 1.0% or less, particularly preferably 0.5% or less, and ideally 0.0%.

The multilayer optical film may be a sheet of film or a long film having a long shape.

The overall thickness of the multilayer optical film can be appropriately set depending on the application of the multilayer optical film, but it is usually desirable for the thickness to be thin in order to reduce the thickness of the device equipped with the multilayer optical film. The specific thickness of the multilayer optical film is preferably 10 μm or more, more preferably 20 μm or more, and is preferably 160 μm or less, more preferably 150 μm or less.

The ratio of the thickness of layer A to the total thickness of layer B in the multilayer optical film can be adjusted appropriately to obtain the desired optical performance and properties such as solvent resistance. Specifically, this ratio can be 5 to 25.

In the multilayer optical film, the layers A and B may be in direct contact with each other without the intervention of other layers such as an adhesive layer, and may be configured to be in close contact with each other. In particular, when the resin (a) contains an alicyclic structure-containing polymer as the amorphous polymer (a) and the resin (b) contains an alicyclic structure-containing polymer as one or both of the crystalline polymer (b1) and the amorphous polymer (b2), the affinity between them can be increased, and interlayer adhesion can be obtained without the intervention of other layers. The presence or absence of interlayer adhesion can be determined by a tear test under the conditions shown in the examples of this application. When peeling is not visible at the interface between the layers at the tear of the sample torn in the tear test, it can be determined that there is interlayer adhesion, and when peeling is visible at the interface between the layers, it can be determined that there is no interlayer adhesion.

[Method of manufacturing multilayer optical film]
The multilayer optical film of the present invention can be produced by a production method including the following steps (i) to (ii). Hereinafter, this production method will be described as a method for producing the multilayer optical film of the present invention. The method for producing the multilayer optical film of the present invention can also include the following step (iii) in addition to steps (i) to (ii).
Step (i): preparing resin (a) and resin (b).
Step (ii): A step of forming the resin (a) and the resin (b) to obtain a multilayer resin film.
Step (iii): A step of stretching the multilayer resin film at a stretching temperature of TgA or higher.

Step (i) can be carried out by synthesizing a polymer using the method for producing each of the polymers described above, and then mixing multiple polymers and optional components as necessary.

The molding method in step (ii) is not particularly limited, and various known molding methods can be used. Examples of molding methods include extrusion molding, solution casting, and inflation molding. Among these, extrusion molding and solution casting are preferred, and extrusion molding is particularly preferred.

In the molding by extrusion molding, resin (a) and resin (b) can be co-extruded. Specifically, resin (a) and resin (b) in a molten state are co-extruded and discharged from an extrusion molding device capable of co-extrusion molding of two kinds and three layers, to form a layered molten resin, which is then cooled to perform co-extrusion molding. The melt temperature at the time of discharge is preferably (TgA + 100) ° C or higher, more preferably (TgA + 110) ° C or higher, while it can be preferably (TgA + 180) ° C or lower, more preferably (TgA + 170) ° C or lower. The cooling body that the layered molten resin first comes into contact with is not particularly limited, but a cast roll is usually used. The cast roll temperature is preferably TgA - 15 ° C or higher, and preferably TgA + 5 ° C or lower.

Depending on the application, the multilayer resin film obtained in step (ii) can be used as it is as the multilayer optical film of the present invention as a product. On the other hand, when a film having a large phase difference is required as the multilayer optical film, step (iii) can be performed to impart a phase difference to the multilayer film. This stretching orients the polymer molecules in the resin film, so that a multilayer optical film having preferable optical properties can be obtained. The stretching temperature during this stretching is preferably TgA°C or higher, more preferably TgA+5°C or higher, while it can be preferably TgA+40°C or lower, more preferably TgA+30°C or lower. By performing the stretching within this temperature range, the desired phase difference can be easily imparted.

On the other hand, from the viewpoint of suppressing the promotion of crystallization of resin (b) in layer B and suppressing an increase in haze, the stretching temperature can be set within a certain range relative to the glass transition temperature TgB and cold crystallization temperature TcB of resin (b). Specifically, the stretching temperature is preferably TgB°C or higher, more preferably TgB+10°C or higher, and particularly preferably TgB+15°C or higher, while being preferably TcB-20°C or lower, more preferably TcB-25°C or lower, and particularly preferably TcB-30°C or lower.

The stretching ratio in step (iii) can be set according to the optical properties that the multilayer optical film should have. The specific stretching ratio is preferably greater than 1, more preferably 1.1 or more, particularly preferably 1.2 or more, and is preferably 5 or less, more preferably 4 or less, and particularly preferably 3 or less. When performing biaxial stretching, it is preferable that the overall stretching ratio, which is expressed as the product of the stretching ratio in one direction and the stretching ratio in the other direction, falls within the above range.

The stretching mode may be, for example, uniaxial stretching, in which stretching is performed in one direction, or biaxial stretching, in which stretching is performed in two non-parallel directions. The biaxial stretching may be simultaneous biaxial stretching, in which stretching is performed in two directions at the same time, or sequential biaxial stretching, in which stretching is performed in one direction and then in the other direction.

The method for producing a multilayer optical film may further include any step in combination with the above steps (i) to (iii). For example, the method for producing a multilayer optical film may include a step of preheating the resin film before stretching in step (iii). The preheating temperature is preferably at least "stretching temperature -40°C", more preferably at least "stretching temperature -30°C", and is preferably at most "stretching temperature +20°C", more preferably at most "stretching temperature +15°C".

Other examples of optional steps include trimming the multilayer optical film and subjecting the multilayer optical film to a surface treatment.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples shown below, and may be modified as desired without departing from the scope of the claims of the present invention and the scope of equivalents thereto.

In the following explanation, the "%" and "parts" used to indicate amounts are by weight unless otherwise specified. In addition, the operations described below were carried out in air at room temperature and normal pressure (23°C and 1 atm) unless otherwise specified.

[Evaluation method]
(Method of measuring weight average molecular weight Mw and number average molecular weight Mn of polymer)
The weight average molecular weight Mw and number average molecular weight Mn of the polymer were measured as polystyrene equivalent 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 the column, and tetrahydrofuran was used as the solvent. The temperature during the measurement was 40°C.

(Method of measuring hydrogenation rate of polymer)
The hydrogenation rate of the polymer was measured by ¹ H-NMR at 145° C. using orthodichlorobenzene-d4 as a solvent.

(Measuring methods of melting point, glass transition temperature and cold crystallization temperature)
The melting points, glass transition temperatures (TgA, TgB, etc.) of the resin and intermediates in the production process thereof, and the cold crystallization temperature TcB of the resin (b) were measured as follows.
First, a sample to be measured, such as a resin, was melted by heating, and the melted sample was quenched with dry ice. The glass transition temperature and cold crystallization temperature of the sample were then measured at a heating rate of 10°C/min (heating mode) using a differential scanning calorimeter (DSC). The cold crystallization temperature was determined by the value at the top of the exothermic peak during the heating process.

(Method for measuring the ratio of racemo-dyads in polymers)
The ratio of the racemo dyad in the polymer was measured as follows. The polymer was subjected to ¹³ C-NMR measurement by applying the inverse-gated decoupling method at 200°C using orthodichlorobenzene- _d4 as a solvent. In the results of this ¹³ C-NMR measurement, a signal at 43.35 ppm derived from the meso dyad and a signal at 43.43 ppm derived from the racemo dyad were identified, with the peak at 127.5 ppm of orthodichlorobenzene- _d4 as the reference shift. The ratio of the racemo dyad in the polymer was calculated based on the intensity ratio of these signals.

(Method of measuring film thickness)
The thickness of the entire film was measured using a contact thickness meter (Code No. 543-390, manufactured by MITUTOYO Corporation). The thickness of each layer was measured by cutting a cross section with a glass blade using a microtome and observing the cross section under a transmission microscope. When observation under a transmission microscope was difficult, a polarizing microscope was used to observe the cross section with two polarizing plates in crossed Nicols (black arrangement).

(Method of measuring Re, Rth, and Δn)
The in-plane retardation Re and the thickness direction retardation Rth of the film were measured using an "AxoScan OPMF-1" manufactured by AXOMETRICS. The measurement was performed at a wavelength of 590 nm. From the obtained Re value and the thickness value of the film measured separately, Δn was calculated according to the following formula.
Δn=Re[nm]/d[nm]

(Solvent resistance test)
The film to be evaluated was cut out to obtain a sample having dimensions of 5 cm x 2 cm in the longitudinal direction (the direction corresponding to the longitudinal direction of the long film before cutting) x width direction (the direction corresponding to the width direction of the long film before cutting).

The sample was bent so that the axial direction of bending (the cylindrical axial direction of the partially cylindrical shape created by bending a flat sample, the same applies below) was the width direction of the sample, and the longitudinal ends of the sample overlapped. The longitudinal ends were held with clips (commercially available double clips (binder clips)) and the sample was placed in the shape shown in Figure 1. In Figure 1, the sample 100 was held by clip 200 with its longitudinal ends 101 overlapping, resulting in the formation of a bent portion 102. The position of the clip 200 was adjusted so that the diameter of the bent portion 102 was 5 mm. Here, the diameter of the bent portion 102 is the length indicated by the arrow A1, which is the diameter of the bent portion in the direction Lh perpendicular to the extension direction Lv of the longitudinal end 101 of the sample 100.

Sample 100 was placed so that end 101 of sample 100 was on the bottom side and top 103 was on the top side, and one drop of n-hexane was dropped onto the position of top 103 using a dropper and held there for 30 seconds. Thereafter, sample 100 was removed from clip 200, and sample 100 was evaluated according to the following evaluation criteria.
Good: There are no cracks on the surface of the sample, or even if there are cracks, they do not penetrate through the thickness direction.
Poor: A crack exists that penetrates the sample in the thickness direction (including cases where the sample is broken).

(Evaluation of film-forming properties)
The thickness of the film to be evaluated was measured at 10 points at 3 cm intervals along the longitudinal direction (the direction corresponding to the longitudinal direction of the long film before cutting) using a contact thickness meter (manufactured by MITUTOYO Corporation, Code No. 543-390), and the difference between the maximum thickness and the minimum thickness was determined. When the difference between the maximum thickness and the minimum thickness is 3 μm or less, the film formability is judged to be good.

(Confirmation of crystallization)
TEM observation was performed under the following conditions, and when a spherulitic structure or difference in contrast was found in the observed slice, it was judged to be "crystallized."
Pretreatment: Cut the cross section using a room temperature microtome (diamond knife), feed the sample 50 nm, and after sectioning, stain with Ru vapor for 40 seconds and 2 minutes.
Six sections were observed.
TEM equipment: Hitachi HT7700.
Acceleration voltage: 100 kV.

(Interlayer adhesion)
The film to be evaluated was cut out to obtain a sample having dimensions of 150 cm x 50 cm in the longitudinal direction (the direction corresponding to the longitudinal direction of the long film before cutting) x width direction (the direction corresponding to the width direction of the long film before cutting).
A slit of 75±1 mm was made in the longitudinal direction of the sample with a cutter knife from one end in the longitudinal direction, the position of the slit being within a range of 25±1 mm from the end in the width direction of the sample.

A tear test was performed on the samples using a test stand (manufactured by Imada Co., Ltd., product name "Motorized Test Stand MX-500N-L550-E") and a force gauge (manufactured by Imada Co., Ltd., product name "ZP-5N") attached to it. As shown in Figure 2, the force gauge side gripper 310 and the test stand side gripper 320 each had a pair of flat gripping plates (311 and 312, and 321 and 322) and were shaped to grip the end of the sample with the inner gripping surfaces of the opposing plates. At the start of the measurement, the distance between the upper end of the test stand side gripper 320 and the lower end of the force gauge side gripper 310 was adjusted to 75 mm.

One end 410 of the sample 400 divided into two by the slit S was bent upward in an axial direction parallel to the sample width direction and held by the force gauge side holding tool 310. The other end 420 of the divided end of the sample 400 was bent downward in an axial direction parallel to the sample width direction and held by the measurement stand side holding tool 320. The length of each of the clamped ends was 30 mm. The ends 410 and 420 were located in the same vertical plane, and the positions of the holding tools 310 and 320 were adjusted so that their virtual center lines were aligned on the same line. The virtual center line of the end 410 is the center line of the sample in the width direction along the longitudinal direction of the sample at the part of the sample that is held in the hypothetical case where the sample is bent upward without being divided and held by the holding tool 310. The imaginary center line of the end 420 is the center line of the sample in the width direction along the longitudinal direction of the sample at the gripped portion of the sample when the sample is bent downward without being divided and gripped by the gripping tool 320.

While the gripping tool 320 was fixed, the gripping tool 310 was raised vertically upward at a moving speed of 200 mm/min to perform a tear test. After the sample was torn into two pieces, it was removed from the gripping tool and visually observed. If no peeling was visible at the interface between the layers at the tear in the sample, it was determined that there was interlayer adhesion, and if peeling was visible at the interface between the layers, it was determined that there was no interlayer adhesion.

(Haze Measurement)
The film was cut out to obtain a rectangular sample of 50 mm x 50 mm, and the haze of the sample was measured using NDH-7000 (manufactured by Nippon Denshoku Co., Ltd.) in accordance with JIS K7361-1997.

[Production Example 1: Production of Resin (b)]
A metallic pressure-resistant reactor was thoroughly dried and then purged with nitrogen. 154.5 parts of cyclohexane, 42.8 parts of a 70% cyclohexane solution of dicyclopentadiene (endo isomer content of 99% or more) (30 parts as the amount of dicyclopentadiene), and 1.9 parts of 1-hexene were added to the metallic pressure-resistant reactor, and the reactor was heated to 53°C.

0.014 parts of tetrachlorotungsten phenylimide (tetrahydrofuran) complex was dissolved in 0.70 parts of toluene to prepare a solution. 0.061 parts of a 19% diethylaluminum ethoxide/n-hexane solution was added to this solution and stirred for 10 minutes to prepare a catalyst solution. This catalyst solution was added to a pressure-resistant reactor to start the ring-opening polymerization reaction. The reaction was then continued for 4 hours while maintaining the temperature at 53°C to obtain a solution of a ring-opened polymer of dicyclopentadiene. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the obtained ring-opened polymer of dicyclopentadiene were 8,750 and 28,100, respectively, and the molecular weight distribution (Mw/Mn) calculated from these was 3.21.

0.037 parts of 1,2-ethanediol was added as a terminator to 200 parts of the resulting solution of ring-opened dicyclopentadiene polymer, and the mixture was heated to 60°C and stirred for 1 hour to terminate the polymerization reaction. 1 part of a hydrotalcite-like compound (Kyowa Chemical Industry Co., Ltd.'s "Kyoward (registered trademark) 2000") was added to the mixture, which was heated to 60°C and stirred for 1 hour. 0.4 parts of a filter aid (Showa Chemical Industry Co., Ltd.'s "Radiolite (registered trademark) #1500") was then added, and the adsorbent and solution were filtered using a PP pleated cartridge filter (Advantec Toyo Co., Ltd.'s "TCP-HX").

100 parts of cyclohexane was added to 200 parts of the filtered ring-opening polymer solution (polymer amount 30 parts), and 0.0043 parts of chlorohydridocarbonyltris(triphenylphosphine)ruthenium was added, and a hydrogenation reaction was carried out at a hydrogen pressure of 6 MPa and 180°C for 4 hours. As a result, a reaction liquid containing a hydrogenated product of the ring-opening polymer of dicyclopentadiene was obtained as the crystalline polymer (b1). The reaction liquid was a slurry solution in which the hydrogenated product had precipitated.

The hydride and the solution contained in the reaction liquid were separated using a centrifuge and dried under reduced pressure at 60°C for 24 hours to obtain 28.5 parts of a crystalline ring-opening polymer of dicyclopentadiene. The hydrogenation rate of this hydride was 99% or more, the glass transition temperature (Tg) was 93°C, the melting point (Tm) was 266°C, and the racemo-dyad ratio was 89%.

100 parts of the obtained hydrogenated ring-opening polymer of dicyclopentadiene was mixed with 1.1 parts of an antioxidant (tetrakis [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane; "Irganox (registered trademark) 1010" manufactured by BASF Japan Ltd.), and then the mixture was put into a twin-screw extruder (product name "TEM-37B", manufactured by Toshiba Machine Co., Ltd.) equipped with four die holes having an inner diameter of 3 mmΦ. The mixture of the hydrogenated ring-opening polymer of dicyclopentadiene and the antioxidant was molded into a strand shape by hot melt extrusion molding, and then chopped with a strand cutter to obtain a pellet-shaped crystalline resin (b1). The operating conditions of the twin-screw extruder were as follows. The glass transition temperature TgB and cold crystallization temperature TcB of the obtained crystalline resin (b1) were measured.
・Barrel temperature setting = 270-280℃
Die set temperature = 250°C
Screw rotation speed = 145 rpm

Thereafter, resin (b2) (ZEONEX790R; manufactured by Zeon Corporation, glass transition temperature 163°C, no melting point was observed) was prepared as the amorphous polymer (b2), and the resin was fed into a twin-screw kneading extruder (L/D = 41, φ25mm) with a weight feeder so that the weight ratio of crystalline resin (b1): amorphous resin (b2) was 45:55. The resin was formed into a strand shape by twin-screw kneading, and then chopped with a strand cutter to obtain a pellet-shaped crystalline resin (b-I). The operating conditions of the twin-screw extruder were as follows. The glass transition temperature TgB and cold crystallization temperature TcB of the obtained crystalline resin (b-I) were measured. The melting point of the crystalline resin (b-I) was 263°C.
・Barrel temperature setting = 275-280℃
Die set temperature = 275°C
Screw rotation speed = 200 rpm

[Production Example 2]
A pellet-shaped crystalline resin (b-II) was obtained by the same procedure as in Production Example 1, except that the ratio of the crystalline resin (b1) to the amorphous resin (b2) was changed to 35:65, and the glass transition temperature TgB and cold crystallization temperature TcB were measured. The melting point of the crystalline resin (b-II) was 263°C.

Example 1
(1-1. Step (1): Production of a multilayer resin film consisting of an amorphous resin (a) and a crystalline resin (b))
A double-flight type single-screw extruder (screw diameter D = 50 mm, ratio of screw length L to screw diameter D = 28) equipped with a leaf disk-shaped polymer filter with a mesh size of 3 μm was prepared. Amorphous resin (a) (ZEONEX690R; manufactured by Zeon Corporation; glass transition temperature 136 ° C., melting point not observed) was introduced into this single-screw extruder, melted, and fed to a single-layer die through a feed block for two-kind three-layer extrusion. "Two-kind three-layer" means that the number of layers contained in the film is three layers, and the types of resins forming those layers are two types. The introduction of resin (a) into the single-screw extruder was carried out through a hopper loaded in the single-screw extruder. The temperature of resin (a) at the extruder outlet was 280 ° C.

On the other hand, a single screw extruder (screw diameter D = 50 mm, ratio of screw length L to screw diameter D L/D = 30) equipped with a leaf disk-shaped polymer filter with a mesh size of 3 μm was prepared. The crystalline resin (b-I) produced in Production Example 1 was introduced into this single screw extruder, melted, and fed to the single layer die via a feed block. The temperature of the resin (b-I) at the extruder outlet was 280°C.

Then, resin (a) and resin (b-I) were extruded from the single-layer die in a molten state at 275°C to obtain a layered molten resin having three layers, in this order: a layer of resin (b-I), a layer of resin (a), and a layer of resin (b-I). The extruded layered molten resin was cast onto a cooling roll whose temperature was adjusted to 120°C, and edge pinning was performed on the roll. The resin was transported and cooled to obtain a long multilayer resin film.

The resulting multilayer resin film was a two-kind, three-layer film, including a B layer of resin (b-I), an A layer of resin (a), and a B layer of resin (b-I) in that order in the thickness direction. The total thickness of the multilayer resin film was 136 μm. Each of the B layers had a thickness of 8 μm, and the A layer had a thickness of 120 μm.

(1-2. Process (2): Heat stretching process)
The multilayer resin film obtained in (1-1) was cut into a rectangular film having dimensions of 130 mm x 130 mm. Each side of the rectangular film was parallel to the longitudinal direction or the transverse direction of the long multilayer resin film. The direction was.
A rectangular film was placed in a stretching machine (manufactured by Etoh Corporation), and each of the four sides was held by five clips, and the film was preheated at 150° C. Six minutes after the start of preheating, when the film temperature was stabilized, From this point on, the film temperature was maintained at 150° C., and the film was uniaxially stretched with fixed ends in the longitudinal direction (the direction corresponding to the longitudinal direction of the long film before being cut out). The stretching ratio was 3 times, and the stretching The speed was 7 mm/sec. Through this process, the multilayer resin film was heated and stretched to obtain a multilayer optical film.

The haze, Re, Rth, and thickness d of the obtained multilayer optical film were measured, Δn was calculated, and the interlayer adhesion, solvent resistance, film formability, and the presence or absence of crystallization were evaluated.

Example 2
A multilayer resin film and a multilayer optical film were obtained and evaluated by the same procedures as in Example 1, except for the following changes.
In step (1-1), resin (b-II) obtained in Production Example 2 was used in place of resin (b-I).
In order to obtain a retardation of about 250 nm after stretching, the rotation speed of the screw of the extruder was adjusted in step (1-1), and the thicknesses of each of the layers B/A/B before stretching were changed to those shown in Table 1.

Comparative Example 1
A multilayer resin film and a multilayer optical film were obtained and evaluated by the same procedures as in Example 1, except for the following changes.
In step (1-1), the crystalline resin (b1) used in Production Example 1 was used as it was, instead of the resin (bI), without being mixed with the resin (b2).
In order to obtain a retardation of about 250 nm after stretching, the rotation speed of the screw of the extruder was adjusted in step (1-1), and the thicknesses of each of the layers B/A/B before stretching were changed to those shown in Table 1.

Comparative Example 2
A multilayer resin film and a multilayer optical film were obtained and evaluated by the same procedures as in Example 1, except for the following changes.
In the step (1-1), as the amorphous resin (a), ZEONEX 790R (manufactured by Zeon Corporation; TgA = 163°C; the same as the resin (b2) used in Production Example 1) was used in place of ZEONEX 690R.
In order to obtain a retardation of about 250 nm after stretching, the rotation speed of the screw of the extruder was adjusted in step (1-1), and the thicknesses of each of the layers B/A/B before stretching were changed to those shown in Table 1.
The preheat and stretch temperature was changed to 165°C to match resin (a).

Comparative Example 3
Except for the following changes, the same procedures as in Example 1 were carried out to obtain and evaluate a single-layer film of layer A, which is the layer of resin (a), instead of the multilayer resin film, and an optical film obtained by stretching this film.
In step (1-1), resin (bI) was not supplied to the feed block, and only resin (a) was supplied.
In order to obtain a retardation after stretching of about 250 nm, the rotation speed of the screw of the extruder was adjusted in the step (1-1) and the thickness of the layer A before stretching was changed to the thickness shown in Table 1.

An overview and results of the examples and comparative examples are shown in Table 1.

As is clear from the above results, the multilayer optical film of the present invention, compared to the comparative example film, can be a high-quality optical film that has high solvent resistance due to layer B while also having desired physical properties such as low haze and low thickness unevenness.

100: Sample 101: End of sample in longitudinal direction 102: Bent portion of sample 103: Top of sample 200: Clip 310: Grip on force gauge side 311: Flat plate for gripping 312: Flat plate for gripping 320: Grip on measurement stand side 321: Flat plate for gripping 322: Flat plate for gripping 400: Sample 410: End of sample 420: End of sample A1: Diameter of bent portion Lh: Direction perpendicular to Lv Lv: Extension direction of end of sample in longitudinal direction S: Slit

Claims (6)

A multilayer optical film comprising a pair of B layers constituting surface layers on a front surface and a back surface, and an A layer located between the pair of B layers,
The layer A is a layer of a resin (a) containing an amorphous polymer (a) having no melting point,
The layer B is a layer of a resin (b) having a melting point, which contains a crystalline polymer (b1) having a melting point and an amorphous polymer (b2) having no melting point,
The resin (a) and the resin (b) satisfy the following formulas (1) to (3),
TgA-TgB≦20℃ (1)
110℃<TgB<140℃ (2)
180℃<TcB<235℃ (3)
In the formula, TgA is the glass transition temperature of resin (a), TgB is the glass transition temperature of resin (b), and TcB is the cold crystallization temperature of resin (b).
Multilayer optical films. The multilayer optical film according to claim 1, wherein the A layer and the B layer are in intimate contact with each other. The multilayer optical film according to claim 1 or 2, wherein each of the B layers has a thickness of 10 μm or less. The multilayer optical film according to any one of claims 1 to 3, having a haze of 1% or less. A method for producing the multilayer optical film according to any one of claims 1 to 4, comprising the steps of:
preparing the resin (a) and the resin (b);
A production method comprising a step of forming the resin (a) and the resin (b) to obtain a multilayer resin film. The method for producing a multilayer optical film according to claim 5 further comprises a step of stretching the multilayer resin film at a stretching temperature equal to or higher than TgA.

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