CN114868053A

CN114868053A - Method for producing retardation film

Info

Publication number: CN114868053A
Application number: CN202180007539.8A
Authority: CN
Inventors: 井上恭辅
Original assignee: Zeon Corp
Current assignee: Zeon Corp
Priority date: 2020-01-30
Filing date: 2021-01-28
Publication date: 2022-08-05
Also published as: WO2021153695A1; JPWO2021153695A1; TW202132087A; KR20220127818A

Abstract

The present invention provides a method for producing a retardation film, comprising a step of bringing a resin film into contact with a solvent and stretching the resin film. The contact between the resin film and the solvent is preferably performed by immersing the resin film in the solvent. Further, the resin film is preferably made of a resin having a positive intrinsic birefringence value.

Description

Method for producing retardation film

Technical Field

The present invention relates to a method for producing a retardation film.

Background

Conventionally, a technique for producing a retardation film has been proposed (see, for example, patent documents 1 to 2).

Documents of the prior art

Patent document

Patent document 1: international publication No. 2017/065222 (corresponding gazette: U.S. patent application publication No. 2020/292742)

Patent document 2: japanese patent laid-open publication No. 2016 and 212171.

Disclosure of Invention

Problems to be solved by the invention

The retardation film has retardation in at least one of an in-plane direction and a thickness direction. As a method for obtaining such a retardation film, a method of heating a film made of a resin to a temperature equal to or higher than the glass transition temperature Tg of the resin and stretching the film is known (see, for example, patent document 1). However, in the case of such a method, a device or equipment for heating the resin film is required, and there is a problem that the manufacturing equipment becomes large. Further, there is a problem that the consumption of energy is large.

The invention aims to provide a method for manufacturing a phase difference film, which can simplify manufacturing equipment.

Means for solving the problems

The present inventors have conducted intensive studies in order to solve the above problems. As a result, the present inventors have found the following finding that the above problems can be solved, and have completed the present invention: by bringing the resin film into contact with a solvent and stretching it, retardation can be exhibited in at least one of the in-plane direction and the thickness direction even without heating the resin film.

That is, the present invention includes the following.

[1] A method for manufacturing a retardation film, comprising:

and a step of bringing the resin film into contact with a solvent to stretch the resin film.

[2] The method for producing a retardation film according to [1], wherein the resin film is brought into contact with the solvent by immersing the resin film in the solvent,

[3] the method for producing a retardation film according to [1] or [2], wherein the resin film is composed of a resin having a positive intrinsic birefringence value.

[4] The method for producing a retardation film according to any one of [1] to [3], wherein the resin film is composed of a resin containing a polymer having crystallinity.

[5] The method for producing a retardation film according to [4], wherein the polymer having crystallinity is a hydrogenated product of a ring-opening polymer of dicyclopentadiene.

[6] The method for producing a retardation film according to any one of [1] to [5], wherein the solvent is a hydrocarbon solvent.

[7] The method for producing a retardation film according to any one of [1] to [6], wherein the stretching step is performed without heating the resin film.

Effects of the invention

According to the present invention, a method for manufacturing a retardation film, which can simplify manufacturing equipment, can be provided.

Drawings

Fig. 1 is a side view schematically showing an apparatus that can be used in step 1 of the method for producing a retardation film according to embodiment 1.

Fig. 2 is a plan view schematically showing a roll stretcher that can be used in the method for producing a retardation film of comparative example 1.

Detailed Description

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 described below, and may be modified and implemented as desired without departing from the scope and range of equivalents of the claims.

In the following description, the in-plane retardation Re of the film is a value represented by "Re ═ (nx-ny) × d", unless otherwise specified. Further, unless otherwise specified, the birefringence in the in-plane direction of the film is a value represented by "(nx-ny)" and is therefore represented by "Re/d". Further, unless otherwise specified, retardation Rth in the thickness direction of the film is a value represented by "Rth [ { (nx + ny)/2} -nz ] × d". Further, unless otherwise specified, the birefringence in the thickness direction of the film is a value represented by "[ { (nx + ny)/2} -nz ]", and is therefore represented by "Rth/d". Further, unless otherwise specified, the NZ coefficient of the film is represented by "(nx-NZ)/(nx-ny)", and thus is represented by "0.5 + Rth/Re". nx represents a refractive index of a direction providing the maximum refractive index among directions (in-plane directions) perpendicular to the film thickness direction. ny represents a refractive index in a direction orthogonal to the nx direction among the in-plane directions of the film. nz represents a refractive index in the thickness direction of the film. d represents the thickness of the film. Unless otherwise stated, the measurement wavelength was 590 nm.

In the following description, unless otherwise specified, a material having positive intrinsic birefringence means a material having a refractive index in the stretching direction larger than that in the direction perpendicular thereto. Unless otherwise stated, a material having negative intrinsic birefringence means a material having a refractive index in the stretching direction smaller than that in the direction perpendicular thereto. The value of intrinsic birefringence can be calculated from the dielectric constant distribution.

In the following description, unless otherwise specified, the oblique direction of a long film means a direction which is neither parallel nor perpendicular to the width direction of the film among the in-plane directions of the film.

In the following description, a "long film" is a film having a length of 5 times or more, preferably 10 times or more, with respect to the width, and more specifically, a film having a length of such a degree that it can be stored or transported by being wound in a roll. The upper limit of the length is not particularly limited, but is usually 10 ten thousand times or less as large as the width.

In the following description, the longitudinal direction of a long film is generally parallel to the film conveyance direction on a production line. The MD direction (axial direction) is a direction in which the film is conveyed on the production line, and is generally parallel to the longitudinal direction of the long film. Further, the TD direction (transverse direction) is a direction perpendicular to the MD direction among directions parallel to the film surface, and is generally parallel to the width direction of the long film.

In the following description, unless otherwise specified, the directions of the elements "parallel", "perpendicular", and "orthogonal" may include an error in the range of ± 5 °, for example, within a range not impairing the effect of the present invention.

[ outline of the method for producing a retardation film of the present invention ]

The method for producing a retardation film of the present invention includes a step of bringing a resin film into contact with a solvent and stretching the resin film.

The method for producing a retardation film of the present invention includes a step of bringing a resin film to be a material of the retardation film into contact with a solvent and stretching the resin film, and by including the step, retardation can be developed without heating the resin film. As a result, according to the present invention, since a device for heating the resin film is not required, it is possible to provide a method for manufacturing a retardation film, which can simplify the manufacturing equipment.

[ embodiment 1]

Hereinafter, a method for producing a retardation film according to embodiment 1 of the present invention will be specifically described with reference to fig. 1. Fig. 1 is a side view schematically showing an apparatus that can be used in the method for producing a retardation film according to embodiment 1.

[ outline of the method for producing a retardation film of the present embodiment ]

In the present embodiment, a long resin film is prepared, a masking film is bonded to the resin film, and the resin film is wound into a roll to obtain a roll 111 of the resin film. Next, as shown in fig. 1, the masking film 12 is peeled from the film 11 fed from the roll 111 of resin film, and the long resin film 15 is conveyed in the direction shown by a 1. The masking film 12 is pressed by nip

rollers

101A, 101B arranged at positions sandwiching the film 11 from the thickness direction and wound into a roll 112.

Next, the resin film 15 is stretched while passing the resin film 15 through the bath 102 filled with the solvent and contacting the solvent. In the present embodiment, the resin film 15 is stretched in the film conveying direction by a difference in peripheral speed between the nip rolls 101A and 101B disposed on the upstream side in the film conveying direction and the nip rolls 104A and 104B disposed on the downstream side in the film conveying direction. By bringing the resin film 15 into contact with a solvent and stretching it, retardation can be exhibited in at least one of the in-plane direction and the thickness direction of the film without heating the resin film. Thus, the stretched film 10 thus obtained can be used as a retardation film as it is.

The stretched film 10 thus obtained is wound while being bonded to the masking film 13 fed from the roll 113. Thereby, a roll 110 of stretched film is obtained. The stretched film 10 and the masking film 13 are bonded while being pressed by nip

rolls

104A and 104B arranged at positions sandwiching the film from the thickness direction.

The method for producing a retardation film of the present embodiment includes a step of bringing a resin film into contact with a solvent and stretching the resin film. In the following description, this step is sometimes referred to as "step 1".

[ Process 1]

Step 1 is a step of bringing a resin film into contact with a solvent and stretching the resin film. The retardation can be developed in the resin film by bringing the resin film into contact with a solvent and stretching the resin film. The mechanism for obtaining such an effect is presumed as follows. However, the technical scope of the present invention is not limited by the mechanism described below.

When the resin film is brought into contact with the solvent, the solvent is impregnated into the resin film. Molecules of the polymer in the film generate micro brownian motion by the action of the immersed solvent, and the molecules of the polymer in the film are oriented. Here, the surface area of the resin film is large on the front and back surfaces as main surfaces. Therefore, the solvent immersion speed is high in the thickness direction across the front surface or the back surface. Accordingly, the molecules of the polymer can be oriented in such a manner that the molecules of the polymer are oriented in the thickness direction.

When a resin film in which molecules are oriented in the thickness direction is stretched, the molecules in the film are oriented in the stretching direction, and the degree of orientation increases. As described above, when the degree of orientation of the molecules becomes large, the birefringence of the film changes, and the retardation becomes large.

Step 1 can be performed by the apparatus 100 shown in fig. 1. The apparatus 100 has upstream nip rolls 101A and 101B disposed on the upstream side in the film conveyance direction, downstream nip rolls 104A and 104B disposed on the downstream side in the film conveyance direction, and a bath 102 for bringing the resin film 15 into contact with a solvent.

Step 1 includes step 1A of bringing the resin film into contact with a solvent and step 1B of stretching the resin film. In the present embodiment, the step 1A is performed while the step 1B is performed. That is, the resin film is brought into contact with the solvent in a region where tension is applied to the resin film by stretching in the path of the resin film. However, the method for producing the retardation film of the present invention is not limited thereto. The production method of the present invention includes a mode in which a part of step 1B overlaps step 1A, for example, a mode of step 1B in which the resin film is stretched from the middle of step 1A in which the resin film is brought into contact with a solvent. The manufacturing method of the present invention further includes: after step 1A of bringing the resin film into contact with the solvent, step 1B of stretching the resin film is performed in a state where the resin film is attached to and/or impregnated with the solvent.

[ Process 1A ]

Step 1A is a step of bringing the resin film into contact with a solvent.

Examples of the method of contacting the resin film with the solvent include a spraying method in which the solvent is sprayed onto the resin film; a coating method of applying a solvent to a resin film; an immersion method in which the resin film is immersed in a solvent, and the like. Among these methods, the dipping method is preferable from the viewpoint that retardation in the thickness direction is easily developed even when the thickness of the resin film is large, and from the viewpoint that continuous contact can be easily performed. The dipping method is shown in fig. 1.

[ resin film ]

The resin film is a film to be a material for producing the retardation film, and may be made of a resin. The resin constituting the resin film contains a polymer.

The resin constituting the resin film is preferably a resin having a positive intrinsic birefringence value. Unless otherwise stated, a resin having a positive intrinsic birefringence value means a resin having a refractive index in the stretching direction that is greater than the refractive index in the direction perpendicular thereto. The value of intrinsic birefringence can be calculated from the dielectric constant distribution.

In addition, as the resin constituting the resin film, a resin containing a polymer having crystallinity is preferable. "Polymer having crystallinity" means a polymer having a melting point Tm (i.e., a melting point that can be observed using a Differential Scanning Calorimeter (DSC)). In the following description, a polymer having crystallinity is sometimes referred to as a "crystalline polymer". Further, a resin containing a crystalline polymer is sometimes referred to as a "crystalline resin". The crystalline resin is preferably a thermoplastic resin.

In the present invention, the resin film is preferably a film made of a resin having a positive intrinsic birefringence value, and more preferably a resin containing a crystalline polymer.

[ crystalline Polymer ]

The crystalline polymer preferably contains an alicyclic structure. By using the crystalline polymer containing an alicyclic structure, the obtained retardation film can be improved in mechanical properties, heat resistance, transparency, low hygroscopicity, dimensional stability, and light weight. The alicyclic structure-containing polymer means a polymer containing an alicyclic structure in a molecule. Such an alicyclic structure-containing polymer can be, for example, a polymer obtainable by a polymerization reaction using a cyclic olefin as a monomer or a hydride thereof.

Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure. Among them, a cycloalkane structure is preferable in terms of easy availability of a retardation film having excellent characteristics such as thermal stability. The number of carbon atoms included in 1 alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less. When the number of carbon atoms included in 1 alicyclic structure is within the above range, mechanical strength, heat resistance, and moldability can be highly balanced.

In the alicyclic structure-containing crystalline polymer, the proportion of the alicyclic structure-containing structural unit to the entire structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 70% by weight or more. By increasing the proportion of the alicyclic structure-containing structural unit as described above, heat resistance can be improved. The proportion of the alicyclic structure-containing structural unit to the total structural units can be 100% by weight or less. In addition, in the alicyclic structure-containing crystalline polymer, the remaining portion other than the alicyclic structure-containing structural unit is not particularly limited and can be appropriately selected depending on the purpose of use.

Examples of the alicyclic structure-containing crystalline polymer include the following polymers (α) to (δ). Among them, the polymer (β) is preferable because a retardation film having excellent heat resistance can be easily obtained.

Polymer (α): a ring-opened polymer of a cyclic olefin monomer having crystallinity.

Polymer (β): a hydride of the polymer (. alpha.) having crystallinity.

Polymer (γ): addition polymers of cyclic olefin monomers having crystallinity.

Polymer (δ): a hydride of the polymer (γ) having crystallinity.

Specifically, the crystalline polymer containing an alicyclic structure is more preferably a ring-opened polymer of dicyclopentadiene having crystallinity and a hydrogenated product of a ring-opened polymer of dicyclopentadiene having crystallinity. Among them, a hydrogenated product of a ring-opening polymer of dicyclopentadiene having crystallinity is particularly preferable. The ring-opened polymer of dicyclopentadiene is a polymer in which the proportion of the constituent unit derived from dicyclopentadiene is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, and still more preferably 100% by weight based on the total constituent units.

The hydride of the ring-opening polymer of dicyclopentadiene is preferably high in the proportion of syndiotactic diads. Specifically, the proportion of the syndiotactic diads in the repeating units in the hydrogenated product of the ring-opened polymer of dicyclopentadiene is preferably 51% or more, more preferably 70% or more, and particularly preferably 85% or more. A high proportion of syndiotactic dyads indicates a high syndiotacticity. Therefore, the higher the ratio of syndiotactic diads, the higher the melting point of the hydride of the ring-opening polymer of dicyclopentadiene tends to be.

The ratio of syndiotactic diad groups can be based on the description of the embodiments to be described later ¹³ And C-NMR spectral analysis.

As the polymers (α) to (δ), polymers obtained by the production method disclosed in international publication No. 2018/062067 can be used.

The crystalline polymer preferably has a melting point Tm of 200 ℃ or higher, more preferably 230 ℃ or higher, and preferably 290 ℃ or lower. By using a crystalline polymer having such a melting point Tm, a retardation film having a further excellent balance between moldability and heat resistance can be obtained.

Generally, crystalline polymers have a glass transition temperature Tg. The specific glass transition temperature Tg of the crystalline polymer is not particularly limited, but is usually 80 ℃ or higher, and usually 170 ℃ or lower. The glass transition temperature of the crystalline polymer is preferably 85 ℃ or higher, more preferably 90 ℃ or higher, preferably 150 ℃ or lower, and more preferably 130 ℃ or lower.

The glass transition temperature Tg and the melting point Tm of the polymer can be determined by the following methods. First, the polymer was melted by heating, and the melted polymer was quenched with dry ice. Next, using this polymer as a test sample, the glass transition temperature Tg and the melting point Tm of the polymer can be measured at a temperature increase rate (temperature increase mode) of 10 ℃/min using a Differential Scanning Calorimeter (DSC).

The weight average molecular weight (Mw) of the crystalline polymer is preferably 1000 or more, more preferably 2000 or more, preferably 1000000 or less, more preferably 500000 or less. The crystalline polymer having such a weight average molecular weight is excellent in the balance between moldability 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, preferably 4.0 or less, more preferably 3.5 or less. Here, Mn represents a number average molecular weight. The crystalline polymer having such a molecular weight distribution is excellent in moldability.

The weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn) of the polymer can be measured as polystyrene converted values by Gel Permeation Chromatography (GPC) using tetrahydrofuran as a developing solvent.

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

The proportion of the crystalline polymer in the crystalline resin 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 the crystalline polymer is not less than the lower limit of the above range, the appearance of birefringence and heat resistance of the retardation film can be improved. The upper limit of the proportion of the crystalline polymer may be 100% by weight or less.

The crystalline resin may contain an arbitrary component in addition to the crystalline polymer. Examples of the optional components include: antioxidants such as phenol antioxidants, phosphorus antioxidants, and sulfur antioxidants; light stabilizers such as hindered amine light stabilizers; waxes such as petroleum-based waxes, Fischer-Tropsch waxes, and 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. benzo

Fluorescent whitening agents such as azole derivatives, benzotriazole derivatives, benzimidazole derivatives, and benzothiazole derivatives), carbazole derivatives, pyridine derivatives, naphthalenedicarboxylic acid derivatives, and imidazolone derivatives; ultraviolet absorbers such as benzophenone-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers; inorganic fillers such as talc, silica, calcium carbonate, and glass fiber; a colorant; a flame retardant; a flame retardant aid; an antistatic agent; a plasticizer; a near infrared ray absorber; a lubricant; a filler; and any polymer other than the crystalline polymer, such as a soft polymer. Any of the components may be used alone, or two or more of them may be used in combination in any ratio.

When the resin contained in the resin film is a crystalline resin, the degree of crystallization of the crystalline polymer contained in the resin film before the step 1 is performed is preferably small. The specific degree of crystallization is preferably less than 10%, more preferably less than 5%, and particularly preferably less than 3%. When the crystallization degree of the crystalline polymer contained in the resin film before contact with the solvent is low, a large number of molecules of the crystalline polymer are oriented in the thickness direction by the contact with the solvent, so that retardation can be adjusted in a wide range.

The retardation Re in the in-plane direction of the resin film before the step 1 is performed is preferably 20nm or less, more preferably 10nm or less, and particularly preferably 0. The retardation Rth in the thickness direction of the resin film is preferably 20nm or less, more preferably 10nm or less, and particularly preferably 0. By making Re and Rth of the resin film before the step 1 in the above ranges, respectively, the retardation can be easily adjusted in the resin film after the step 1.

The resin film before being contacted with the solvent preferably has a small content of the solvent, and more preferably contains no solvent. The ratio of the solvent contained in the resin film to 100% by weight of the resin film (solvent content) is preferably 1% or less, more preferably 0.5% or less, particularly preferably 0.1% or less, and ideally 0.0%. By making the amount of the solvent contained in the resin film before contact with the solvent small, a large number of molecules of the polymer can be aligned in the thickness direction by contact with the solvent, so that retardation can be adjusted in a wide range. The solvent content of the resin film can be measured by density.

The thickness of the resin film is preferably set according to the thickness of the retardation film to be produced. Generally, the thickness of the film becomes large by contact with a solvent. On the other hand, by stretching, the thickness of the film becomes small. Therefore, the thickness of the resin film may be set in consideration of the change in thickness in step 1 of performing contact with a solvent and stretching.

As the resin film, a long resin film is preferably used. Thus, the retardation film can be continuously produced by a roll-to-roll method, and therefore, the productivity of the retardation film can be effectively improved.

The method for producing the resin film is not limited. From the viewpoint of obtaining a resin film containing no solvent, a resin molding method such as an injection molding method, an extrusion molding method, a press molding method, an inflation molding method, a blow molding method, a calendar molding method, an injection molding method, a compression molding method, or the like is preferable. Among them, extrusion molding is preferred in view of easy control of the thickness.

For example, in the case of producing a resin film made of a resin containing a crystalline polymer by an extrusion molding method, the production conditions thereof are preferably as follows. The cylinder temperature (molten resin temperature) is preferably Tm or more, more preferably "Tm +20 ℃ or more, preferably" Tm +100 ℃ or less, and more preferably "Tm +50 ℃ or less. The cooling body with which the molten resin extruded in a film shape first comes into contact is not particularly limited, but a casting roll is generally used. The casting roll temperature is preferably "Tg-50 ℃ or higher", preferably "Tg +70 ℃ or lower, and more preferably" Tg +40 ℃ or lower. Further, the chill roll temperature is preferably "Tg-70 ℃ or higher," more preferably "Tg-50 ℃ or higher," preferably "Tg +60 ℃ or lower, and more preferably" Tg +30 ℃ or lower. When a resin film is produced under such conditions, a raw material film having a thickness of 1 μm to 1mm can be easily produced. Here, "Tm" represents a melting point of the crystalline polymer, and "Tg" represents a glass transition temperature of the crystalline polymer.

In the present embodiment, a masking film is bonded to a long resin film and wound into a roll, thereby being supplied as a roll to step 1. Known mask films (for example, FF1025, FF1035, SAT116T, SAT2038T-JSL, and SAT4538T-JSL, both manufactured by Sun & Inc.; NBO-0424, TFB-K001, TFB-K0421, and TFB-K202, both manufactured by Sun chemical Co., Ltd.; DT-2200-25, and K-6040, both manufactured by Sun chemical Co., Ltd.; 6010#75, 6010#100, 6011#75, and 6093#75, both manufactured by Tekken Co., Ltd.) can be used as the mask film.

[ solvent ]

In step 1A, as the solvent that comes into contact with the resin film, a solvent that can be impregnated into the resin film without dissolving the polymer contained in the resin film can be used. Examples of such solvents include: hydrocarbon solvents such as toluene, limonene, and decalin; and (3) carbon disulfide. In the case where the resin film is made of a resin containing a crystalline polymer, from the viewpoint of being able to infiltrate into the resin film without dissolving the crystalline polymer, a hydrocarbon-based solvent is preferred as the solvent. The solvent may be one kind or two or more kinds.

The temperature of the solvent in contact with the resin film is set to any temperature within a range in which the solvent can be maintained in a liquid state, and therefore, can be set to a range of not less than the melting point of the solvent but not more than the boiling point. In the present application, particularly, when the temperature of the solvent is set to room temperature (for example, 15 ℃ or more and less than 40 ℃, more preferably 18 ℃ or more and less than 35 ℃, and further preferably 23 ℃ or more and less than 30 ℃), or when the temperature is adjusted to a temperature range close to room temperature, good stretching can be performed. When the solvent is heated, the temperature can be adjusted to a temperature higher than room temperature as needed. However, even in this case, it is possible to perform good stretching with a simpler apparatus than in the case where the temperature around the film conveyed during stretching is heated in an oven in a general stretching apparatus.

The time for which the resin film is in contact with the solvent is not particularly specified, and is preferably 1 second or more, more preferably 3 seconds or more, particularly preferably 5 seconds or more, preferably 180 seconds or less, more preferably 120 seconds or less, and particularly preferably 60 seconds or less. When the contact time is not less than the lower limit of the above range, the molecules contained in the resin film can be efficiently aligned. On the other hand, even if the contact time is long, the degree of orientation of the molecules tends not to change significantly. Therefore, by setting the contact time to be equal to or less than the upper limit of the above range, productivity can be improved without impairing the quality of the retardation film.

[ Process 1B ]

Step 1B is a step of stretching the resin film.

In the production method of the present embodiment, the resin film is stretched using a stretcher that performs longitudinal stretching by a circumferential speed difference between a plurality of sets of rollers. The upstream nip rolls 101A and 101B and the downstream nip rolls 104A and 104B are rotationally driven by a drive unit, not shown, and can convey the resin film 15 in the conveying direction a 1. In the present embodiment, the circumferential speeds of the downstream nip rolls 104A and 104B are set to be faster than the circumferential speeds of the upstream nip rolls 101A and 101B. Thus, there is a circumferential speed difference between the upstream nip rolls 101A, 101B and the downstream nip rolls 104A, 104B, and the resin film 15 can be continuously stretched in the conveying direction (traveling direction) by this circumferential speed difference. Further, by adjusting the circumferential speed difference, the stretching ratio of the resin film 15 can be adjusted.

In the production method of the present embodiment, the resin film is stretched by contacting it with a solvent, and therefore, even if the resin film is stretched at a low stretch ratio, retardation can be easily developed. The stretch ratio of the resin film in step 1 is preferably 1.05 or more, more preferably 1.1 or more, preferably 5.00 or less, and more preferably 3.00 or less. When the stretching ratio is not less than the lower limit of the above range, retardation can be effectively developed in the resin film. When the stretching ratio is not more than the upper limit of the above range, productivity can be improved without impairing the quality of the retardation film obtained by the present invention.

According to the production method of the present embodiment, since retardation can be exhibited without heating the resin film during stretching, it is not necessary to heat the resin film during stretching, and the resin film can be heated during stretching. In this case, the resin film before stretching may be subjected to a preheating treatment. When the resin film is heated during stretching, the stretching temperature is preferably Tg +2 ℃ or higher, more preferably Tg +5 ℃ or higher, preferably Tg +40 ℃ or lower, more preferably Tg +35 ℃ or lower, and particularly preferably Tg +30 ℃ or lower. Here, Tg means the glass transition temperature of the polymer included in the resin film 15.

The stretched film 10 obtained after the step 1 may be used as it is as a retardation film, or a film obtained by performing a further step (for example, a further stretching step) may be used as a retardation film.

[ Effect of the present embodiment ]

In the method for producing a retardation film of the present embodiment, the resin film is stretched by contacting the resin film with a solvent, whereby retardation can be exhibited in at least one of the in-plane direction and the thickness direction without heating the resin film. As a result, according to the present embodiment, a heating device such as an oven for heating the resin film is not required, and therefore, the apparatus for manufacturing the retardation film can be simplified. Further, according to the present embodiment, since the contact of the resin film with the solvent and the stretching of the resin film are performed simultaneously, the production efficiency of the retardation film can be improved.

[ optional Process ]

The method for producing a retardation film of the present invention may include any of the steps described below.

The method for producing a retardation film of the present invention may include a step of removing the solvent from the resin film after the resin film is brought into contact with the solvent. Examples of a method for removing the solvent from the resin film include drying, wiping, and the like.

When the solvent is removed from the resin film after contact with the solvent by drying, the method is not particularly limited, and the removal can be performed, for example, using a heating device such as an oven. Specifically, the resin film after contact with the solvent can be conveyed in a heating device for a predetermined time to remove the solvent. The heating for removing the solvent can be performed at a relatively low temperature, without strict temperature control, and can be completed in a short time, unlike the heating in the case of heating at the time of stretching in a general stretching apparatus. Further, by appropriately selecting the type of solvent, drying can be achieved by transporting the product at room temperature without particularly performing heating operation.

When the solvent is removed by drying, the removal may be performed in a state where tension is applied to the film. Drying in such a state is preferable because uniformity of optical properties of the film after contact with the solvent can be effectively improved. The magnitude and direction of the tension applied to the resin film can be set in consideration of the material of the resin film. In addition, in the case where tension is applied to the resin film, for example, the resin film may be held by an appropriate holder, and the resin film may be stretched and applied with tension by the holder. The holder may be a holder capable of continuously holding the entire length of the side of the resin film, or may be a holder capable of intermittently holding the resin film with a space. For example, the side of the resin film may be intermittently held by holders arranged at predetermined intervals.

The method for producing a retardation film of the present invention may include a step of further stretching the film obtained after the step 1. The stretching conditions such as the stretching direction, stretching device, and stretching ratio in this step are not particularly limited, and can be set in consideration of the application of the retardation film as an object.

In the case of producing a long retardation film, the method for producing a retardation film of the present invention may include a step of cutting the long retardation film into a desired shape.

[ retardation film ]

Next, a retardation film obtained by the method for producing a retardation film of the present invention will be described.

[ retardation of retardation film ]

The value of the in-plane retardation Re of the retardation film can be set according to the application. The value of the in-plane retardation Re of the retardation film is preferably 10nm or more, more preferably 30nm or more, preferably 1000nm or less, more preferably 800nm or less.

The specific value of the in-plane retardation Re of the retardation film may be, for example, preferably 100nm or more, more preferably 110nm or more, and particularly preferably 120nm or more, and may be preferably 180nm or less, more preferably 170nm or less, and particularly preferably 160nm or less. In this case, the retardation film can function as an 1/4 wave plate.

Further, a specific value of the in-plane retardation Re of the retardation film may be, for example, preferably 230nm or more, more preferably 250nm or more, particularly preferably 255nm or more, and may be preferably 320nm or less, more preferably 300nm or less, particularly preferably 295nm or less. In this case, the retardation film can function as an 1/2 wave plate.

The value of retardation Rth in the thickness direction of the retardation film can be set according to the application of the retardation film. The retardation Rth in the thickness direction of the retardation film is preferably-500 nm or more, more preferably-400 nm or more, preferably 300nm or less, and more preferably 150nm or less.

[ NZ coefficient of retardation film ]

The NZ coefficient of the retardation film is preferably-10 or more, more preferably-8 or more, preferably 10 or less, more preferably 8 or less. When a retardation film having an NZ coefficient within the above range is provided in a display device, the display device can improve display quality such as a viewing angle, a contrast, and an image quality. The NZ coefficient of the retardation film can be arbitrarily set according to the application of the retardation film.

The NZ coefficient of the retardation film can be calculated from the in-plane retardation Re and the retardation Rth in the thickness direction of the film. The in-plane retardation Re and the retardation Rth in the thickness direction of the film can be measured by using a phase difference meter (for example, "AxoSacan OPMF-1" manufactured by Acksomei).

[ birefringence of retardation film ]

The retardation film generally has a large birefringence in at least one of the in-plane direction and the thickness direction. Specifically, the retardation film usually has a thickness of 1.0 × 10 ^-3 The birefringence Re/d in the in-plane direction described above, and 1.0X 10 ^-3 At least one of the absolute values | Rth/d | of the birefringence in the thickness direction described above.

Specifically, the birefringence Re/d in the in-plane direction of the retardation film is usually 1.0X 10 ^-3 Above, preferably 3.0 × 10 ^-3 Above, particularly preferably 5.0X 10 ^-3 The above. The upper limit is not limited, and can be, for example, 2.0X 10 ^-2 1.5X 10 as follows ^-2 Below, or 1.0X 10 ^-2 The following. However, the absolute value of birefringence in the thickness direction of the retardation film, | Rth/d |, is 1.0X 10 ^-3 In the above case, the birefringence Re/d in the in-plane direction of the retardation film may be out of the above range.

Further, the absolute value of birefringence in the thickness direction of the retardation film, | Rth/d |, is usually 1.0X 10 ^-3 Above, preferably 3.0 × 10 ^-3 Above, particularly preferably 5.0X 10 ^-3 The above. The upper limit is not limited, and can be, for example, 2.0X 10 ^-2 1.5X 10 as follows ^-2 Below, or 1.0X 10 ^-2 The following. However, the birefringence Re/d in the in-plane direction of the retardation film was 1.0X 10 ^-3 In the above case, the absolute value | Rth/d | of the birefringence in the thickness direction of the retardation film may be out of the above range.

[ other characteristics of retardation film ]

The haze of the retardation film is generally less than 1.0%, preferably less than 0.8%, more preferably less than 0.5%, and desirably 0.0%. When a retardation film having such a small haze is provided in a display device, the sharpness of an image displayed by the display device can be improved. The haze of the film can be measured using a haze meter (for example, "NDH 5000" manufactured by japan electro-chromatic industries, ltd.).

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

The thickness d of the retardation film can be appropriately set according to the application of the retardation film. The specific thickness d of the retardation film is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 15 μm or more, preferably 200 μm or less, more preferably 100 μm or less, and particularly preferably 50 μm or less. When the thickness d of the retardation film is not less than the lower limit of the above range, the workability is improved and the strength can be improved. When the thickness d of the retardation film is not more than the upper limit, a long retardation film can be easily wound.

In the retardation film produced using the resin film containing a crystalline polymer, the degree of crystallization of the crystalline polymer is not particularly limited, and is usually higher than a certain degree. The specific crystallization degree is preferably 10% or more, more preferably 15% or more, and particularly preferably 30% or more.

The degree of crystallization of the crystalline polymer can be measured by an X-ray diffraction method.

[ solvent contained in retardation film ]

The method for producing a retardation film of the present invention includes a step of bringing a resin film into contact with a solvent and stretching the resin film, and therefore the retardation film produced by the production method can contain a solvent.

Upon contact with the solvent, all or a part of the solvent added to the resin film can enter the interior of the polymer contained in the resin constituting the film. Therefore, even if the drying is performed at a boiling point of the solvent or higher, it is difficult to easily remove the solvent completely. Therefore, the retardation film produced in the production method including the step of contacting with the solvent can include the solvent.

The ratio of the solvent contained in the retardation film to 100% by weight of the retardation film (solvent content) may be preferably 10% by weight or less, more preferably 5% by weight or less, particularly preferably 0.1% by weight or less and more than 0% by weight.

[ uses of retardation film ]

The retardation film produced in the production method of the present invention exhibits retardation in at least one of the in-plane direction and the thickness direction by bringing the resin film into contact with a solvent and stretching it. Therefore, the retardation film obtained by the production method of the present invention can be used as an 1/2-wave plate, a 1/4-wave plate, or the like, depending on the retardation value thereof. A circularly polarizing plate using the retardation film manufactured by the manufacturing method of the present invention as either one or both of the 1/2 wave plate and the 1/4 wave plate can be used for a display device.

Examples

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

In the following description, "%" and "part" representing amounts are based on weight unless otherwise specified. Unless otherwise stated, the operations described below were performed under normal temperature and normal pressure conditions. In the following description, the measurement wavelength of retardation and birefringence is 590nm unless otherwise specified.

[ evaluation method ]

(method of measuring the weight-average molecular weight Mw and number-average molecular weight Mn of the Polymer)

The weight average molecular weight Mw and the number average molecular weight Mn of the polymer were measured as polystyrene conversion values by using a Gel Permeation Chromatography (GPC) system ("HLC-8320" manufactured by Tosoh corporation). For the measurement, an H-type column (manufactured by Tosoh Co.) was used as a column, and tetrahydrofuran was used as a solvent. The temperature during the measurement was 40 ℃.

(method of measuring hydrogenation ratio of Polymer)

O-dichlorobenzene-d ⁴ As solvent, at 145 deg.C ¹ H-NMR measurement was carried out to determine the hydrogenation ratio of the polymer.

[ methods for measuring glass transition temperature Tg and melting Point Tm ]

The glass transition temperature Tg and the melting point Tm of the polymer were measured as follows. First, the polymer was melted by heating, and the melted polymer was quenched with dry ice. Next, using this polymer as a test body, the glass transition temperature Tg and the melting point Tm of the polymer were measured at a temperature increase rate (temperature increase mode) of 10 ℃/min using a Differential Scanning Calorimeter (DSC).

(method of measuring the proportion of syndiotactic diads in Polymer)

The ratio of syndiotactic diads in the polymer was determined as follows. O-dichlorobenzene-d ⁴ As solvent, the polymerization was carried out at 200 ℃ using the inverted-gated decoupling (inverted-gated decoupling) method ¹³ C-NMR measurement. According to the above ¹³ As a result of C-NMR measurement, o-dichlorobenzene-d was used ⁴ The peak at 127.5ppm was used as a reference shift, and 43.35ppm of a signal from the isotactic dyad and 43.43ppm of a signal from the syndiotactic dyad were observed. Based on the intensity ratio of these signals, the ratio of syndiotactic diads in the polymer was determined.

(method of measuring film thickness)

The thickness of the film was measured by using a contact type thickness meter (Code No. 543-.

(method of measuring delay and NZ coefficient)

The in-plane retardation Re, the retardation in the thickness direction Rth, and the NZ coefficient of the film were measured by Axo Scan OPMF-1 manufactured by Acksolmex. At this time, the measurement was performed at a wavelength of 590 nm. The NZ coefficient was calculated from the obtained in-plane retardation Re and the retardation in the thickness direction Rth.

Production example 1 production of crystalline resin containing hydrogenated Ring-opened Polymer of Dicyclopentadiene

After the metal pressure-resistant reactor was sufficiently dried, nitrogen substitution was performed. In the metal pressure resistant reactor, 154.5 parts of cyclohexane, 42.8 parts of a cyclohexane solution (30 parts by weight of dicyclopentadiene) having a concentration of dicyclopentadiene of 99% or more and 1.9 parts of 1-hexene were charged and heated to 53 ℃.

0.014 parts of a tungsten tetrachloride benzimide (tetrahydrofuran) complex was dissolved in 0.70 parts of toluene to prepare a solution. To the solution, 0.061 parts of a 19% strength diethoxyethylaluminum/n-hexane solution was added and stirred for 10 minutes to prepare a catalyst solution. The catalyst solution is added into a pressure-resistant reactor to initiate ring-opening polymerization. Then, 53 ℃ was maintained and allowed to react for 4 hours to obtain a solution of a ring-opened polymer of dicyclopentadiene. The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the obtained ring-opened polymer of dicyclopentadiene were 8750 and 28100, respectively, and the molecular weight distribution (Mw/Mn) was 3.21.

To 200 parts of the obtained solution of the ring-opened polymer of dicyclopentadiene, 0.037 part of 1, 2-ethanediol as a terminator was added, the mixture was heated to 60 ℃ and stirred for 1 hour to terminate the polymerization reaction. To this was added 1 part of a hydrotalcite-like compound (manufactured by Kyoward chemical industries, Ltd. "Kyoward (registered trademark) 2000") and the mixture was heated to 60 ℃ and stirred for 1 hour. Then, 0.4 part of a filter aid (manufactured by showa chemical industries, inc. "Radiolite (registered trademark) # 1500") was added, and the adsorbent and the solution were separated by filtration using a polypropylene pleated cartridge filter (manufactured by ADVANTEC toyo corporation, "TCP-HX").

100 parts of cyclohexane and 0.0043 part of ruthenium carbonyl chloride tris (triphenylphosphine) were added to 200 parts of the filtered solution of the ring-opened polymer of dicyclopentadiene (the amount of the polymer was 30 parts), and hydrogenation reaction was performed at a hydrogen pressure of 6MPa and 180 ℃ for 4 hours. Thereby, a reaction solution containing a hydride of the ring-opened polymer of dicyclopentadiene is obtained. In the reaction solution, a hydride precipitates to become a slurry solution.

The hydride contained in the reaction solution was separated from the solution by a centrifugal separator, and dried at 60 ℃ under reduced pressure for 24 hours to obtain 28.5 parts of a hydride of a ring-opened polymer of dicyclopentadiene having crystallinity. The hydrogenation rate of the hydride is 99% or more, the glass transition temperature Tg is 93 ℃, the melting point (Tm) is 262 ℃, and the proportion of the syndiotactic diad is 89%.

To 100 parts of the obtained hydrogenated product of the ring-opened polymer of dicyclopentadiene, 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 corporation, japan) was mixed, and then the mixture was charged into a biaxial extruder (product name "TEM-37B", manufactured by toshiba machines corporation) having 4 die holes with an inner diameter of 3mm Φ. After the mixture of the hydride of the ring-opening polymer of dicyclopentadiene and the antioxidant was formed into a strand shape by hot melt extrusion molding, it was cut up in a strand cutter to obtain a crystalline resin in a particle shape. The crystalline resin has a positive intrinsic birefringence value.

The operating conditions of the twin-screw extruder are as follows.

The set temperature of the cylinder is 270-280 DEG C

Die set temperature 250 deg.C

Screw speed 145rpm

[ example 1]

(1-1) production of resin film

The crystalline resin in the pellet shape produced in production example 1 was molded using a hot-melt extrusion film molding machine having a T-die, and a roll of the resin film was obtained by winding the resin film having a width of about 600mm at a predetermined speed into a roll. In this example, the linear velocity was adjusted so that the resin film had a thickness of 50 μm. Further, when wound into a roll, it is protected with a masking film ("FF 1025" by tedigar) and wound. As a result of measurement of Re, Rth and NZ coefficients for the resin film, Re was 1.7nm, Rth was 1.9nm and the NZ coefficient was 1.6.

The operating conditions of the film forming machine are as follows.

Setting the temperature of the cylinder to 280-300 DEG C

Die temperature 270 deg.C

Casting roll temperature 80 deg.C

(1-2) step 1

Step 1 was performed by the following method using the apparatus shown in fig. 1. The film 11 is drawn out from the roll 111 of the resin film obtained in (1-1), the masking film 12 is continuously peeled off, and the resin film 15 is conveyed. The resin film 15 is brought into contact with a solvent and stretched (step 1). Specifically, the resin film 15 is immersed in toluene by passing the resin film 15 through a bath 102 filled with toluene as a solvent. The time for the resin film to be carried in the solvent (solvent contact time) was 5 seconds. The room temperature at this time was 25 ℃, and therefore the temperature of toluene in the bath 102 was also 25 ℃. The resin film 15 is stretched by providing a difference between the circumferential speed Ps1 of the upstream nip rolls 101A and 101B and the circumferential speed Ps2 of the downstream nip rolls 104A and 104B. Specifically, the film was stretched at a stretch ratio of 1.1 times in the conveyance direction by setting the peripheral speed ratio (Ps2/Ps1) of the two sets of nip rolls to 1.1. The stretched film 10 obtained after the step 1 was protected with a new masking film ("FF 1025" manufactured by tedigai corporation) and wound up to obtain a roll 110 of the stretched film. As a result of measuring Re, Rth, NZ coefficient and thickness of the stretched film, Re was 56nm, Rth was-324 nm, NZ coefficient was-5.29 and thickness was 57 μm.

[ example 2]

A roll of a stretched film was obtained in the same manner as in (1-2) of example 1, except that the film was stretched in the carrying direction at a stretch ratio of 1.2 times by setting the peripheral speed ratio (Ps2/Ps1) of the two sets of nip rolls to 1.2 in (1-2) of example 1. As a result of measuring Re, Rth, NZ coefficient and thickness of the stretched film, Re was 265nm, Rth was-295 nm, NZ coefficient was-0.61 and thickness was 56 μm.

[ example 3]

A roll of a stretched film was obtained in the same manner as in (1-2) of example 1, except that the film was stretched in the carrying direction at a stretch ratio of 1.5 times by setting the peripheral speed ratio (Ps2/Ps1) of the two sets of nip rolls to 1.5 in (1-2) of example 1. As a result of measuring Re, Rth, NZ coefficient and thickness of the stretched film, Re was 650nm, Rth was 65nm, NZ coefficient was 0.6 and thickness was 47 μm.

[ example 4]

(4-1) production of resin film

A roll of the resin film was obtained in the same manner as in (1-1) in example 1 except that the linear velocity was adjusted and the resin film was molded so as to have a thickness of 21 μm in (1-1) in example 1.

(4-2) step 1

A roll of a stretched film was obtained in the same manner as in (1-2) of example 1, except that the roll of the resin film obtained in (4-1) was used instead of the roll of the resin film obtained in (1-1), and the peripheral speed ratio (Ps2/Ps1) of the two sets of nip rolls was set to 1.5, so that the film was stretched at a stretch ratio of 1.5 times in the transport direction. As a result of measuring Re, Rth, NZ coefficient and thickness of the stretched film, Re was 275nm, Rth was 30nm, NZ coefficient was 0.61 and thickness was 20 μm.

[ example 5]

A roll of a stretched film was obtained in the same manner as in example 1 except that the contact between the resin film and the solvent was performed in (1-2) of example 1 by the following coating method instead of passing the resin film through a bath filled with the solvent. As a result of measuring Re, Rth, NZ coefficient and thickness of the stretched film, Re was 62nm, Rth was-62 nm, NZ coefficient was-0.5 and thickness was 51 μm.

(coating method)

A coating apparatus (reverse gravure method) was used instead of the bath 102, and toluene was applied to one surface of the resin film by this coating apparatus. The amount of the solvent applied was set to 30g/m ² (amount of coating just applied).

Comparative example 1

The film was drawn out from the roll of the film obtained in (1-1) of example 1, and the masking film was peeled from the film and the resin film was conveyed. Free longitudinal uniaxial stretching was carried out at a stretching temperature of 110 ℃ by passing the resin film through an oven heated to 110 ℃ for about 1 minute. This free longitudinal uniaxial stretching was performed by the following method using a roll stretcher shown in fig. 2.

The roll stretcher 1 shown in fig. 2 will be explained. As shown in fig. 2, the roll stretcher 1 is a device for stretching a film 3 fed from a film roll 2 in the longitudinal direction thereof. The roll stretcher 1 has an upstream side roll 6A and a downstream side roll 6B as nip rolls capable of conveying the film 3 in the longitudinal direction in this order from the upstream side in the conveying direction. Here, the peripheral speed PsB of the downstream roller 6B is set to be faster than the peripheral speed PsA of the upstream roller 6A.

The resin film (corresponding to the film 3 in fig. 2) is stretched using the roll stretcher 1 described above in the following manner.

The film 3 is fed from the film roll 2, and the film 3 is continuously supplied to the roll stretcher 1. The roll stretcher 1 conveys the film 3 in the order of the upstream side roll 6A and the downstream side roll 6B. At this time, the film 3 was stretched in the film conveying direction (i.e., the longitudinal direction) at a stretch ratio of 1.5 times by setting the ratio (PsB/PsA) of the peripheral speed PsB of the downstream side roller 6B to the peripheral speed PsA of the upstream side roller 6A to 1.5. Both ends in the width direction of the stretched film are trimmed by a trimming device not shown, to obtain a long stretched film 4. The stretched film was protected with a new masking film ("FF 1025" manufactured by tedigar) and wound up to give a roll 5 of the stretched film. As a result of measuring Re, Rth, NZ coefficient and thickness of the obtained stretched film, Re was 75nm, Rth was 38nm, NZ coefficient was 1.01 and thickness was 40 μm.

The resins constituting the resin films, the thicknesses of the resin films, the conditions of contact with a solvent (the kind of solvent, the contact method, the contact time), the stretching ratios, and the physical properties (Re, Rth, NZ coefficient, thickness) of the stretched films used in the examples and comparative examples are shown in table 1. For the comparative examples, heating conditions (oven temperature) when the resin film was stretched are shown in table 1. In table 1, "crystalline COP" means a crystalline alicyclic structure-containing polymer. In table 1, "dipping" means that the contact of the resin film with the solvent is performed by a method of dipping the resin film into the solvent, and "coating" is that the contact of the resin film with the solvent is performed by a method of coating the solvent to the resin film. In table 1, "stretched film" refers to a resin film after stretching.

[ Table 1]

TABLE 1

As is clear from the results shown in table 1, according to the method of example, a film having retardation can be obtained regardless of whether or not the resin film is heated during stretching. That is, according to the manufacturing method of the present invention, since retardation can be exhibited without heating the resin film, a heating device for the resin film is not required, and the manufacturing equipment can be simplified.

[ other embodiments ]

(1) In the above embodiments and examples, the example in which the resin film is uniaxially stretched in the free longitudinal direction in the film conveying direction by the circumferential speed difference between the nip rolls on the upstream side and the downstream side in the conveying direction is shown, but the stretching method (apparatus, stretching direction, etc.) of the resin film is not limited thereto. The stretching direction of the resin film may be an oblique direction or a film width direction. The stretching direction may be two or more directions, and in this case, the stretching in two or more directions may be performed simultaneously or sequentially.

Description of the reference numerals

1: roller stretcher

2: roll of resin film

3: resin film

4: stretched film

5: roll of stretched film

6A: upstream side roller

6B: downstream side roller

10: stretched film

11: film (film having masking film attached to resin film)

12. 13: masking film

15: resin film

100: device for measuring the position of a moving object

101A, 101B: upstream-side nip roll

102: bath tub

104A, 104B: downstream nip roll

110: roll of stretched film

111: roll of resin film

112. 113: roll of masking film

Claims

1. A method for manufacturing a retardation film, comprising:

2. The method for producing a retardation film according to claim 1, wherein the contact of the resin film with the solvent is performed by immersing the resin film in the solvent.

3. The method for producing a retardation film according to claim 1 or 2, wherein the resin film is composed of a resin having a positive intrinsic birefringence value.

4. The method for producing a retardation film according to any one of claims 1 to 3, wherein the resin film is composed of a resin containing a polymer having crystallinity.

5. The method for producing a retardation film according to claim 4, wherein the polymer having crystallinity is a hydride of a ring-opening polymer of dicyclopentadiene.

6. The method for producing a retardation film according to any one of claims 1 to 5, wherein the solvent is a hydrocarbon solvent.

7. The method for producing a retardation film according to any one of claims 1 to 6, wherein the step of stretching the resin film is performed without heating the resin film.