Method for manufacturing phase difference film

Abstract

The present invention provides a method for manufacturing a phase difference film, comprising the step of contacting a resin film with a solvent and stretching the resin film. Preferably, the resin film is contacted with the solvent by immersing the resin film in the solvent. In addition, the resin film is preferably made of a resin having a positive intrinsic birefringence value.

Description

Technical Field

[0001] The present invention relates to a method for producing a phase difference film. Background Art

[0002] Conventionally, techniques for producing retardation films have been proposed (see, for example, Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 065222 (Corresponding publication: U.S. Patent Application Publication No. 2020 / 292742)

[0006] Patent document 2: Japanese Patent Application Publication No. 2016-212171. Summary of the invention

[0007] Problem that the invention aims to solve

[0008] The phase difference film has a delay in at least one of the in-plane direction and the thickness direction. As a method for obtaining such a phase difference film, it is known to heat a resin film to above the glass transition temperature Tg of the above-mentioned resin and stretch it (see, for example, patent document 1). However, in the case of adopting such a method, a device or equipment for heating the resin film is required, and there is a problem of large-scale manufacturing equipment. In addition, there is also a problem of high energy consumption.

[0009] An object of the present invention is to provide a method for producing a retardation film that can simplify production equipment.

[0010] Solutions for solving problems

[0011] The present inventors have conducted intensive research to solve the above problems. As a result, the present inventors have found the following insights that can solve the above problems, and have completed the present invention: by contacting a resin film 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.

[0012] That is, the present invention includes the following contents.

[0013] [1] A method for manufacturing a phase difference film, comprising:

[0014] A step of bringing a resin film into contact with a solvent and stretching the resin film.

[0015] [2] The method for producing a phase difference film according to [1], wherein the resin film is brought into contact with the solvent by immersing the resin film in the solvent.

[0016] [3] The method for producing a retardation film according to [1] or [2], wherein the resin film is made of a resin having a positive intrinsic birefringence value.

[0017] [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 crystalline polymer.

[0018] [5] The method for producing a retardation film according to [4], wherein the crystalline polymer is a hydrogenated product of a ring-opening polymer of dicyclopentadiene.

[0019] [6] The method for producing a retardation film according to any one of [1] to [5], wherein the solvent is a hydrocarbon solvent.

[0020] [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.

[0021] Effects of the Invention

[0022] According to the present invention, it is possible to provide a method for producing a phase difference film capable of simplifying production equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a side view which schematically shows the apparatus which can be used for the process 1 of the manufacturing method of the retardation film of Embodiment 1.

[0024] Figure 2 It is a top view which schematically shows the roll stretching machine which can be used for the manufacturing method of the retardation film of Comparative Example 1. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below by showing embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily modified without departing from the scope of the claims of the present invention and their equivalents.

[0026] In the following description, unless otherwise specified, the in-plane retardation Re of the film is a value represented by "Re = (nx-ny) × d". In addition, 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". Furthermore, unless otherwise specified, the retardation Rth in the thickness direction of the film is a value represented by "Rth = [{(nx+ny) / 2}-nz] × d". In addition, 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". Furthermore, unless otherwise specified, the NZ coefficient of the film is a value represented by "(nx-nz) / (nx-ny)", and is therefore represented by "0.5+Rth / Re". nx represents the refractive index of the direction providing the maximum refractive index in the direction perpendicular to the thickness direction of the film (in-plane direction). Ny represents the refractive index in the direction orthogonal to the nx direction in the above-mentioned in-plane direction of the film. Nz represents the refractive index in the thickness direction of the film. D represents the thickness of the film. Unless otherwise specified, the measurement wavelength is 590 nm.

[0027] In the following description, unless otherwise specified, a material having positive intrinsic birefringence refers to a material having a refractive index in the stretching direction greater than a refractive index in the direction perpendicular thereto. In addition, unless otherwise specified, a material having negative intrinsic birefringence refers to a material having a refractive index in the stretching direction less than a refractive index in the direction perpendicular thereto. The value of intrinsic birefringence can be calculated based on the dielectric constant distribution.

[0028] In the following description, unless otherwise specified, the tilt direction of the long film means a direction in the plane of the film that is neither parallel nor perpendicular to the width direction of the film.

[0029] In the following description, a "long strip" of film refers to a film having a length of 5 times or more relative to the width, preferably 10 times or more, and specifically refers to a film having a length that can be rolled up for storage or transportation. The upper limit of the length is not particularly limited, and is usually 100,000 times or less relative to the width.

[0030] In the following description, the length direction of the long film is usually parallel to the conveying direction of the film on the manufacturing line. In addition, the MD direction (mashine direction, axial direction) is the conveying direction of the film on the manufacturing line, which is usually parallel to the length direction of the long film. Furthermore, the TD direction (transverse direction, transverse direction) is the direction parallel to the film surface and perpendicular to the above-mentioned MD direction, which is usually parallel to the width direction of the long film.

[0031] In the following description, unless otherwise specified, the directions of the elements "parallel", "perpendicular", and "orthogonal" may include errors within a range of, for example, ±5° within a range that does not impair the effects of the present invention.

[0032] [Overview of the method for producing the phase difference film of the present invention]

[0033] The method for producing a retardation film of the present invention includes the step of bringing a resin film into contact with a solvent and stretching the resin film.

[0034] In the method for manufacturing a phase difference film of the present invention, a process of bringing a resin film that is a material of the phase difference film into contact with a solvent and stretching the resin film is included. By including this process, retardation can be exhibited even without heating the resin film. As a result, according to the present invention, since a device for heating the resin film is not required, a method for manufacturing a phase difference film that can simplify manufacturing equipment can be provided.

[0035] [Implementation Method 1]

[0036] Below, reference Figure 1 , a method for producing a phase difference film according to Embodiment 1 of the present invention will be described in detail. Figure 1 This is a side view schematically showing an apparatus that can be used in the method for producing the retardation film of Embodiment 1.

[0037] [Overview of the method for producing a phase difference film according to the present embodiment]

[0038] In this embodiment, a long resin film is prepared, a masking film is attached to the resin film, and the resin film is rolled up to obtain a resin film roll 111. Figure 1 As shown, masking film 12 is peeled off from film 11 fed from resin film roll 111, and long resin film 15 is conveyed in direction A1. Masking film 12 is pressed by nip rolls 101A and 101B disposed at positions sandwiching film 11 in the thickness direction and wound into roll 112.

[0039] Next, the resin film 15 is stretched while passing through the bath 102 filled with a solvent and contacting the solvent. In this embodiment, the resin film 15 is stretched along the film conveying direction by the difference in peripheral speed between the nip rollers 101A and 101B arranged on the upstream side of the film conveying direction and the nip rollers 104A and 104B arranged on the downstream side of the film conveying direction. By contacting the resin film 15 with the solvent and stretching it, even without heating the resin film, retardation can be exhibited in at least one direction of the film's in-plane direction and thickness direction. Thus, the stretched film 10 obtained in this way can be used directly as a phase difference film.

[0040] The stretched film 10 thus obtained is wound up while being bonded to the masking film 13 fed from the roll 113. Thus, a stretched film roll 110 is obtained. The stretched film 10 and the masking film 13 are bonded together while being pressed by nip rolls 104A and 104B disposed at positions sandwiching the film in the thickness direction.

[0041] 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 may be referred to as "step 1".

[0042] [Process 1]

[0043] Step 1 is a step of contacting the resin film with a solvent and stretching it. By contacting the resin film with a solvent and stretching it, a delay can be manifested in the resin film. The mechanism for obtaining such an effect is speculated as follows. However, the technical scope of the present invention is not limited by the following mechanism.

[0044] When the resin film is brought into contact with a solvent, the solvent is immersed in the resin film. Due to the action of the immersed solvent, the molecules of the polymer in the film produce micro-Brownian motion, and the molecules of the polymer in the film are oriented. Here, in the surface area of ​​the resin film, the front and back surfaces, which are the main surfaces, are large. Therefore, with respect to the immersion speed of the solvent, the immersion speed in the thickness direction through the above-mentioned front or back surface is large. Thus, the orientation of the molecules of the above-mentioned polymer can be carried out in a manner that the molecules of the polymer are oriented in the thickness direction.

[0045] Furthermore, 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 becomes larger. As the degree of molecular orientation increases, the birefringence of the film changes, and the retardation increases.

[0046] Process 1 can be passed Figure 1 The apparatus 100 shown in the figure is performed. The apparatus 100 includes upstream nip rolls 101A and 101B arranged on the upstream side in the film conveying direction, downstream nip rolls 104A and 104B arranged on the downstream side in the film conveying direction, and a bath 102 for contacting the resin film 15 with a solvent.

[0047] Process 1 includes process 1A of contacting the resin film with a solvent and process 1B of stretching the resin film. The present embodiment is a method of performing process 1A during process 1B. That is, the resin film is contacted with the solvent in an area where tension is applied to the resin film by stretching in the path of the resin film. However, the method for manufacturing the phase difference film of the present invention is not limited to this. The manufacturing method of the present invention includes a method in which a portion of process 1B overlaps with process 1A, for example, a method in which process 1B of stretching the resin film is started from the middle of process 1A of contacting the resin film with a solvent. In addition, the manufacturing method of the present invention also includes the following method: after performing process 1A of contacting the resin film with a solvent, process 1B of stretching the resin film is performed in a state where the solvent is attached to and / or impregnated in the resin film.

[0048] [Process 1A]

[0049] Step 1A is a step of bringing the resin film into contact with a solvent.

[0050] Examples of the contact method between the resin film and the solvent include a spray method in which the solvent is sprayed onto the resin film; a coating method in which the solvent is applied onto the resin film; and an immersion method in which the resin film is immersed into the solvent. Among these methods, the immersion method is preferred because it is easy to show a delay in the thickness direction even when the thickness of the resin film is large and because continuous contact can be easily performed. Figure 1 The dipping method is shown in FIG.

[0051] [Resin film]

[0052] The resin film is a film that is a material for manufacturing a phase difference film, and can be composed of a resin. The resin constituting the resin film includes a polymer.

[0053] The resin constituting the resin film is preferably a resin having a positive intrinsic birefringence value. Unless otherwise specified, a resin having a positive intrinsic birefringence value refers to a resin whose refractive index in the stretching direction is greater than the refractive index in the direction perpendicular thereto. The intrinsic birefringence value can be calculated from the dielectric constant distribution.

[0054] In addition, as the resin constituting the resin film, a resin containing a crystalline polymer is preferred. "Crystallizable polymer" means a polymer having a melting point Tm (i.e., a melting point 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". In addition, a resin containing a crystalline polymer is sometimes referred to as a "crystalline resin". The crystalline resin is preferably a thermoplastic resin.

[0055] In the present invention, the resin film is preferably a film made of a resin having a positive intrinsic birefringence value, and more preferably the resin is a resin containing a crystalline polymer.

[0056] [Crystalline polymer]

[0057] The crystalline polymer preferably contains an alicyclic structure. By using a crystalline polymer containing an alicyclic structure, the mechanical properties, heat resistance, transparency, low hygroscopicity, dimensional stability and lightness of the obtained phase difference film can be improved. A polymer containing an alicyclic structure means a polymer containing an alicyclic structure in the molecule. Such a polymer containing an alicyclic structure can be, for example, a polymer or a hydride thereof that can be obtained by a polymerization reaction using a cyclic olefin as a monomer.

[0058] As the alicyclic structure, for example, a cycloalkane structure and a cycloolefin structure can be cited. Among them, from the aspect of easily obtaining a phase difference film with excellent characteristics such as thermal stability, a cycloalkane structure is preferred. The number of carbon atoms contained in one 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. By making the number of carbon atoms contained in one alicyclic structure within the above range, mechanical strength, heat resistance and formability can be highly balanced.

[0059] In the crystalline polymer containing an alicyclic structure, the ratio of the structural unit containing the alicyclic structure to the total structural unit 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 ratio of the structural unit containing the alicyclic structure as described above, the heat resistance can be improved. The ratio of the structural unit containing the alicyclic structure to the total structural unit can be 100% by weight or less. In addition, in the crystalline polymer containing an alicyclic structure, the remaining part other than the structural unit containing the alicyclic structure is not particularly limited and can be appropriately selected according to the purpose of use.

[0060] Examples of the crystalline polymer containing an alicyclic structure include the following polymers (α) to (δ). Among them, the polymer (β) is preferred because a retardation film having excellent heat resistance can be easily obtained.

[0061] Polymer (α): a ring-opening polymer of a cyclic olefin monomer having crystallinity.

[0062] Polymer (β): a hydrogenated product of the crystalline polymer (α).

[0063] Polymer (γ): an addition polymer of a cyclic olefin monomer having crystallinity.

[0064] Polymer (δ): A hydrogenated product of the crystalline polymer (γ).

[0065] Specifically, as the crystalline polymer containing an alicyclic structure, a ring-opening polymer of dicyclopentadiene having crystallinity and a hydrogenated product of a ring-opening polymer of dicyclopentadiene having crystallinity are more preferred. Among them, a hydrogenated product of a ring-opening polymer of dicyclopentadiene having crystallinity is particularly preferred. Here, the ring-opening polymer of dicyclopentadiene refers to a polymer in which the ratio of the structural unit derived from dicyclopentadiene to the total structural units is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, and further preferably 100% by weight.

[0066] The hydrogenated product of the ring-opening polymer of dicyclopentadiene preferably has a high proportion of syndiotactic diads. Specifically, the proportion of syndiotactic diads in the repeating units in the hydrogenated product of the ring-opening polymer of dicyclopentadiene is preferably 51% or more, more preferably 70% or more, and particularly preferably 85% or more. A high proportion of syndiotactic diads indicates high syndiotactic stereoregularity. Therefore, there is a tendency that the higher the proportion of syndiotactic diads, the higher the melting point of the hydrogenated product of the ring-opening polymer of dicyclopentadiene.

[0067] The ratio of the syndiotactic diad can be determined based on the following examples. 13 The results were confirmed by C-NMR spectral analysis.

[0068] As the polymers (α) to (δ), polymers obtained by the production method disclosed in International Publication No. 2018 / 062067 can be used.

[0069] The melting point Tm of the crystalline polymer is preferably 200° C. or higher, more preferably 230° C. or higher, and preferably 290° C. or lower. By using a crystalline polymer having such a melting point Tm, a retardation film having a better balance between moldability and heat resistance can be obtained.

[0070] Generally, a crystalline polymer has a glass transition temperature Tg. The specific glass transition temperature Tg of the crystalline polymer is not particularly limited, but is generally 80°C or higher and generally 170°C or lower. The glass transition temperature of the crystalline polymer is preferably 85°C or higher, more preferably 90°C or higher, preferably 150°C or lower, and more preferably 130°C or lower.

[0071] The glass transition temperature Tg and melting point Tm of a polymer can be measured by the following method. First, the polymer is melted by heating, and the melted polymer is quenched with dry ice. Next, the polymer can be used as a test body, and the glass transition temperature Tg and melting point Tm of the polymer can be measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min (heating mode).

[0072] The weight average molecular weight (Mw) of the crystalline polymer is preferably 1000 or more, more preferably 2000 or more, and preferably 1000000 or less, more preferably 500000 or less. A crystalline polymer having such a weight average molecular weight has an excellent balance between molding processability and heat resistance.

[0073] The molecular weight distribution (Mw / Mn) of the crystalline polymer is preferably 1.0 or more, more preferably 1.5 or more, and preferably 4.0 or less, more preferably 3.5 or less. Here, Mn represents the number average molecular weight. A crystalline polymer having such a molecular weight distribution has excellent molding processability.

[0074] The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer can be measured as polystyrene-equivalent values ​​by gel permeation chromatography (GPC) using tetrahydrofuran as a developing solvent.

[0075] The crystalline polymer may be used alone or in combination of two or more at any ratio.

[0076] The proportion of 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 proportion of crystalline polymer is above the lower limit of the above range, the birefringence and heat resistance of the phase difference film can be improved. The upper limit of the proportion of crystalline polymer can be 100% by weight or less.

[0077] In addition to the crystalline polymer, the crystalline resin may also contain any component. Examples of the optional component include antioxidants such as phenolic antioxidants, phosphorus antioxidants, and sulfur antioxidants; light stabilizers such as hindered amine light stabilizers; waxes such as petroleum 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., benzophenones ... Fluorescent whitening agents such as oxazole derivatives, benzotriazole derivatives, benzimidazole derivatives, and benzothiazole derivatives), carbazole derivatives, pyridine derivatives, naphthalene dicarboxylic acid derivatives, and imidazolide derivatives; UV absorbers such as benzophenone-based UV absorbers, salicylic acid-based UV absorbers, and benzotriazole-based UV absorbers; inorganic fillers such as talc, silica, calcium carbonate, and glass fiber; colorants; flame retardants; flame retardant aids; antistatic agents; plasticizers; near-infrared absorbers; lubricants; fillers; and any polymers other than crystalline polymers such as soft polymers. Any component may be used alone or in combination of two or more in any ratio.

[0078] When the resin contained in the resin film is a crystalline resin, the crystallinity of the crystalline polymer contained in the resin film before the step 1 is preferably small. Specifically, the crystallinity is preferably less than 10%, more preferably less than 5%, and particularly preferably less than 3%. When the crystallinity 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 contact with the solvent, so that the retardation can be adjusted in a wide range.

[0079] The retardation Re in the in-plane direction of the resin film before the step 1 is preferably 20 nm or less, more preferably 10 nm or less, and particularly preferably 0. The retardation Rth in the thickness direction of the resin film is preferably 20 nm or less, more preferably 10 nm or less, and particularly preferably 0. By making the Re and Rth of the resin film before the step 1 within the above ranges, it is easy to adjust the retardation in the resin film after the step 1.

[0080] The resin film before contact with the solvent preferably has a small content of 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 reducing the amount of solvent contained in the resin film before contact with the solvent, a large number of polymer molecules can be oriented in the thickness direction by contact with the solvent, so that the delay can be adjusted in a wide range. The solvent content of the resin film can be measured by density.

[0081] The thickness of the resin film is preferably set according to the thickness of the phase difference film to be manufactured. Usually, by contacting with a solvent, the thickness of the film becomes larger. On the other hand, by stretching, the thickness of the film becomes smaller. Therefore, the thickness of the resin film can also be set by considering the change of thickness in the step 1 of contacting with a solvent and stretching.

[0082] As the resin film, it is preferable to use a long resin film. Thereby, the phase difference film can be continuously manufactured by a roll-to-roll method, so the productivity of the phase difference film can be effectively improved.

[0083] The method for making the resin film is not limited. From the aspect of obtaining a resin film that does not contain a solvent, preferably resin molding methods such as injection molding, extrusion molding, compression molding, inflation molding, blow molding, calendering molding, injection molding, compression molding. Among them, from the aspect of easily controlling thickness, preferably extrusion molding.

[0084] For example, in the case of manufacturing a resin film made of a resin containing a crystalline polymer by an extrusion molding method, the manufacturing conditions are preferably as follows. The barrel temperature (molten resin temperature) is preferably above Tm, more preferably above "Tm+20°C", preferably below "Tm+100°C", and more preferably below "Tm+50°C". In addition, the cooling body that the molten resin extruded into a film first contacts is not particularly limited, but a casting roll is usually used. The casting roll temperature is preferably above "Tg-50°C", preferably below "Tg+70°C", and more preferably below "Tg+40°C". Furthermore, the cooling roll temperature is preferably above "Tg-70°C", more preferably above "Tg-50°C", preferably below "Tg+60°C", and more preferably below "Tg+30°C". In the case of manufacturing a resin film under such conditions, a raw material film with a thickness of 1μm to 1mm can be easily manufactured. Here, "Tm" represents the melting point of the crystalline polymer, and "Tg" represents the glass transition temperature of the crystalline polymer.

[0085] In the present embodiment, a masking film is bonded to a long resin film and wound into a roll, thereby providing it as a film roll to step 1. As the masking film, a known masking film (for example, FF1025 and FF1035 manufactured by Tredegar Co., Ltd.; SAT116T, SAT2038T-JSL, and SAT4538T-JSL manufactured by Sun A. Chemical Co., Ltd.; NBO-0424, TFB-K001, TFB-K0421, and TFB-K202 manufactured by Fujimori Industries; DT-2200-25 and K-6040 manufactured by Hitachi Chemical Co., Ltd.; 6010#75, 6010#100, 6011#75, and 6093#75 manufactured by Teraoka Manufacturing Co., Ltd.) can be used.

[0086] [Solvent]

[0087] In step 1A, as a solvent in contact with the resin film, a solvent that can penetrate into the resin film without dissolving the polymer contained in the resin film can be used. Examples of such a solvent include hydrocarbon solvents such as toluene, limonene, and decalin; and carbon disulfide. In the case where the resin film is made of a resin containing a crystalline polymer, a hydrocarbon solvent is preferably used as the solvent from the viewpoint of being able to penetrate into the resin film without dissolving the crystalline polymer. The solvent may be one type or two or more types.

[0088] The temperature of the solvent in contact with the resin film is any temperature within the range in which the solvent can maintain a liquid state, and therefore, can be set in a range above the melting point and below the boiling point of the solvent. In the present application, good stretching can be performed, especially when the temperature of the solvent is set to room temperature (for example, above 15°C and less than 40°C, more preferably above 18°C ​​and less than 35°C, and more preferably above 23°C and less than 30°C), or when adjusted to a temperature range close to room temperature. In the case of heating the solvent, the temperature can be adjusted to a temperature higher than room temperature as needed. However, even in this case, compared with the case in which an oven is used to heat the temperature around the film being transported during stretching in a conventional stretching device, good stretching can be performed with simpler equipment.

[0089] The time for the resin film to contact with the solvent is not particularly specified, preferably more than 1 second, more preferably more than 3 seconds, particularly preferably more than 5 seconds, preferably less than 180 seconds, more preferably less than 120 seconds, particularly preferably less than 60 seconds. By making the contact time more than the lower limit of the above range, the molecules contained in the resin film can be effectively oriented. On the other hand, there is a tendency that the degree of orientation of the molecules will not change significantly even if the contact time is long. Therefore, by making the contact time less than the upper limit of the above range, it is possible to improve productivity without damaging the quality of the phase difference film.

[0090] [Process 1B]

[0091] Step 1B is a step of stretching the resin film.

[0092] In the manufacturing method of the present embodiment, a stretching machine that performs longitudinal stretching through the circumferential speed difference of multiple groups of rollers is used to stretch the resin film. The nip rollers 101A and 101B on the upstream side and the nip rollers 104A and 104B on the downstream side are rotationally driven by a driving unit not shown in the figure, and the resin film 15 can be transported in the conveying direction A1. In the present embodiment, the circumferential speed of the nip rollers 104A and 104B on the downstream side is set to be faster than the circumferential speed of the nip rollers 101A and 101B on the upstream side. As a result, there is a circumferential speed difference between the upstream nip rollers 101A and 101B and the downstream nip rollers 104A and 104B, and through this circumferential speed difference, the resin film 15 can be continuously stretched in the conveying direction (travel direction). In addition, by adjusting the above-mentioned circumferential speed difference, the stretching ratio of the resin film 15 can be adjusted.

[0093] In the manufacturing method of the present embodiment, since the resin film is contacted with a solvent and stretched, even if it is stretched at a low stretch ratio, it is possible to easily show a delay. 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. By making the stretch ratio above the lower limit of the above range, it is possible to effectively show a delay in the resin film. By making the stretch ratio below the upper limit of the above range, it is possible to improve productivity without damaging the quality of the phase difference film obtained by the present invention.

[0094] According to the manufacturing method of this embodiment, since the delay can be manifested even if the resin film is not heated 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 can also be preheated. In the case of heating the resin film during stretching, the stretching temperature is preferably above Tg°C, more preferably above Tg+2°C, particularly preferably above Tg+5°C, preferably below Tg+40°C, more preferably below Tg+35°C, and particularly preferably below Tg+30°C. Here, Tg refers to the glass transition temperature of the polymer contained in the resin film 15.

[0095] The stretched film 10 obtained after the step 1 can be used as a retardation film as it is, or a film obtained by further steps (for example, further stretching step, etc.) can be used as a retardation film.

[0096] [Effects of this embodiment]

[0097] In the manufacturing method of the phase difference film of the present embodiment, by contacting the resin film with the solvent and stretching it, even if the resin film is not heated, it is possible to show a delay in at least one direction of the in-plane direction and the thickness direction. As a result, according to the present embodiment, a heating device such as an oven for heating the resin film is not required, so the manufacturing equipment of the phase difference film can be simplified. In addition, according to the present embodiment, since the contact between the resin film and the solvent and the stretching of the resin film are performed simultaneously, the production efficiency of the phase difference film can be improved.

[0098] [Optional process]

[0099] The method for producing the retardation film of the present invention may include the optional steps described below.

[0100] 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 the method for removing the solvent from the resin film include drying and wiping off.

[0101] When the solvent is removed from the resin film after contact with the solvent by drying, the method is not particularly limited, and can be carried out using a heating device such as an oven, for example. Specifically, the solvent can be removed by transporting the resin film after contact with the solvent in a heating device for a predetermined time. The heating for removing the solvent is different from the heating in the case of heating during stretching in a conventional stretching device, and can be carried out at a relatively low temperature, can be carried out without strict temperature control, and can be completed in a shorter time. In addition, by appropriately selecting the type of solvent, it is also possible to achieve drying by transporting at room temperature without performing a special heating operation.

[0102] When the solvent is removed by drying, it can be done while tension is applied to the film. Drying in such a state can effectively improve the uniformity of the optical properties of the film after contact with the solvent, so it is preferred. The magnitude of the tension applied to the resin film and the direction of the tension can be set in consideration of the material of the resin film, etc. In addition, when tension is applied to the resin film, for example, the resin film can be held by a suitable holder, and the resin film can be stretched and tension is applied by the holder. The holder can be a holder that can continuously hold the entire length of the edge of the resin film, or it can be a holder that can intermittently hold it with intervals. For example, the edge of the resin film can be intermittently held by a holder arranged at a specified interval.

[0103] The method for producing a retardation film of the present invention may include a step of further stretching the film obtained after 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 intended use of the retardation film.

[0104] Furthermore, when a long retardation film is produced, 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.

[0105] [Phase difference film]

[0106] Next, the retardation film obtained by the method for producing a retardation film of the present invention will be described.

[0107] [Retardation of Phase Difference Film]

[0108] The in-plane retardation Re value of the phase difference film can be set according to its application. The in-plane retardation Re value of the phase difference film is preferably 10 nm or more, more preferably 30 nm or more, and is preferably 1000 nm or less, more preferably 800 nm or less.

[0109] The specific in-plane retardation Re value of the phase difference film can be preferably 100 nm or more, more preferably 110 nm or more, particularly preferably 120 nm or more, and can be preferably 180 nm or less, more preferably 170 nm or less, particularly preferably 160 nm or less. In this case, the phase difference film can function as a quarter wave plate.

[0110] Furthermore, the specific in-plane retardation Re value of the phase difference film can be, for example, preferably 230 nm or more, more preferably 250 nm or more, particularly preferably 255 nm or more, and can be preferably 320 nm or less, more preferably 300 nm or less, particularly preferably 295 nm or less. In this case, the phase difference film can function as a 1 / 2 wave plate.

[0111] The value of the retardation Rth in the thickness direction of the retardation film can be set according to the application of the retardation film. The specific retardation Rth in the thickness direction of the retardation film is preferably -500 nm or more, more preferably -400 nm or more, preferably 300 nm or less, more preferably 150 nm or less.

[0112] [NZ coefficient of retardation film]

[0113] The NZ coefficient of the phase difference film is preferably greater than -10, more preferably greater than -8, preferably less than 10, more preferably less than 8. When a phase difference film having an NZ coefficient within the above range is provided in a display device, the display quality of the display device such as viewing angle, contrast, and image quality can be improved. The NZ coefficient of the phase difference film can be arbitrarily set according to the purpose of the phase difference film.

[0114] 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 using a retardation meter (for example, "AxoScan OPMF-1" manufactured by AxoMetrix).

[0115] [Birefringence of Phase Difference Film]

[0116] 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 generally has a 1.0×10 -3 The above in-plane birefringence Re / d and 1.0×10 -3 At least one of the absolute values ​​of birefringence |Rth / d| in the thickness direction described above.

[0117] Specifically, the birefringence Re / d in the in-plane direction of the retardation film is usually 1.0×10 -3 Above, preferably 3.0×10 -3Above, particularly preferably 5.0×10 -3 There is no upper limit, and it can be, for example, 2.0×10 -2 Below, 1.5×10 -2 Less than, or 1.0×10 -2 However, the absolute value of birefringence |Rth / d| in the thickness direction of the retardation film is 1.0×10 -3 In the above case, the birefringence Re / d in the in-plane direction of the retardation film may be outside the above range.

[0118] The absolute value of birefringence in the thickness direction of the retardation film |Rth / d| is usually 1.0×10 -3 Above, preferably 3.0×10 -3 Above, particularly preferably 5.0×10 -3 There is no upper limit, and it can be, for example, 2.0×10 -2 Below, 1.5×10 -2 Less than, or 1.0×10 -2 However, the birefringence Re / d in the in-plane direction of the retardation film is 1.0×10 -3 In the above case, the absolute value of birefringence |Rth / d| in the thickness direction of the retardation film may be outside the above range.

[0119] [Other characteristics of retardation film]

[0120] The haze of the phase difference film is usually less than 1.0%, preferably less than 0.8%, more preferably less than 0.5%, and ideally 0.0%. When a phase difference film with such a small haze is set in a display device, the clarity of the image displayed by the display device can be improved. The haze of the film can be measured using a haze meter (e.g., NDH5000 manufactured by Nippon Denshoku Industries).

[0121] Since the phase difference film is an optical film, it is preferably highly transparent. The specific total light transmittance of the phase difference film is preferably 80% or more, more preferably 85% or more, and particularly preferably 88% or more. The total light transmittance of the phase difference film can be measured using an ultraviolet visible spectrophotometer in the range of wavelengths of 400nm to 700nm.

[0122] The thickness d of the phase difference film can be appropriately set according to the purpose of the phase difference film. The specific thickness d of the phase difference 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 phase difference film is above the lower limit of the above range, the operability can be improved and the strength can be improved. In addition, when the thickness d of the phase difference film is below the upper limit, it is easy to wind the long strip of phase difference film.

[0123] In the retardation film produced using a resin film containing a crystalline polymer, the crystallinity of the crystalline polymer is not particularly limited, but is usually higher than a certain level, and the specific range of the crystallinity is preferably 10% or more, more preferably 15% or more, and particularly preferably 30% or more.

[0124] The degree of crystallinity of a crystalline polymer can be measured by X-ray diffraction.

[0125] [Solvent contained in phase difference film]

[0126] Since the method for producing a retardation film of the present invention includes the step of bringing a resin film into contact with a solvent and stretching the resin film, the retardation film produced by the production method can contain a solvent.

[0127] When in contact with a solvent, all or 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 solvent is dried above the boiling point, it is difficult to easily and completely remove the solvent. Therefore, the phase difference film manufactured in the manufacturing method including a step of contacting with a solvent can contain a solvent.

[0128] The ratio of the solvent contained in the retardation film to 100% by weight of the retardation film (solvent content) is preferably 10% by weight or less, more preferably 5% by weight or less, particularly preferably 0.1% by weight or less, and greater than 0% by weight.

[0129] [Application of retardation film]

[0130] The phase difference film manufactured in the manufacturing method of the present invention is delayed in at least one direction of the in-plane direction and the thickness direction by contacting the resin film with a solvent and stretching it. Therefore, the phase difference film obtained by the manufacturing method of the present invention can be used as a 1 / 2 wave plate or a 1 / 4 wave plate, etc. according to its retardation value. The circular polarizer using the phase difference film manufactured by the manufacturing method of the present invention as either or both of the 1 / 2 wave plate and the 1 / 4 wave plate can be used in a display device.

[0131] Example

[0132] The present invention will be described in detail below with reference to the following examples, but the present invention is not limited to the following examples and can be arbitrarily modified without departing from the scope of the claims and their equivalents.

[0133] In the following description, unless otherwise specified, "%" and "part" indicating an amount are weight-based. In addition, unless otherwise specified, the operations described below are performed under normal temperature and pressure. In addition, in the following description, unless otherwise specified, the measurement wavelength of retardation and birefringence is 590 nm.

[0134] [Evaluation method]

[0135] (Method for measuring weight average molecular weight Mw and number average molecular weight Mn of polymer)

[0136] The weight average molecular weight Mw and number average molecular weight Mn of the polymer were measured as polystyrene conversion values ​​using a gel permeation chromatography (GPC) system ("HLC-8320" manufactured by Tosoh Corporation). During the measurement, an H-type column (manufactured by Tosoh Corporation) was used as a column, and tetrahydrofuran was used as a solvent. In addition, the temperature during the measurement was 40°C.

[0137] (Method for measuring hydrogenation rate of polymer)

[0138] o-dichlorobenzene-d 4 As a solvent, at 145 ° C 1 The hydrogenation rate of the polymer was determined by H-NMR measurement.

[0139] [Measurement method of glass transition temperature Tg and melting point Tm]

[0140] The glass transition temperature Tg and melting point Tm of the polymer are measured as follows. First, the polymer is melted by heating, and the melted polymer is quenched with dry ice. Next, the polymer is used as a test body, and the glass transition temperature Tg and melting point Tm of the polymer are measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min (heating mode).

[0141] (Method for determining the ratio of syndiotactic diads in polymer)

[0142] The ratio of syndiotactic diads in the polymer was determined as follows. 4 As solvent, the polymer was decoupled at 200 °C using the inverse-gated decoupling method. 13 C-NMR measurement. 13 The results of C-NMR determination were based on o-dichlorobenzene-d 4The peak of 127.5 ppm was used as the reference shift, and a signal of 43.35 ppm derived from an isotactic diad and a signal of 43.43 ppm derived from a syndiotactic diad were confirmed. Based on the intensity ratio of these signals, the ratio of syndiotactic diads in the polymer was determined.

[0143] (Method for measuring film thickness)

[0144] The thickness of the film was measured using a contact thickness gauge (Code No. 543-390 manufactured by Mitutoyo Corporation).

[0145] (Method for measuring retardation and NZ coefficient)

[0146] The in-plane retardation Re, the retardation Rth in the thickness direction, and the NZ coefficient of the film were measured by Axo Scan OPMF-1 manufactured by Axo Metrix. At this time, the measurement was performed at a wavelength of 590 nm. In addition, the NZ coefficient was calculated based on the obtained in-plane retardation Re and the retardation Rth in the thickness direction.

[0147] [Production Example 1. Production of a crystalline resin comprising a hydrogenated ring-opening polymer of dicyclopentadiene]

[0148] After the metal pressure-resistant reactor was fully dried and purged with nitrogen, 154.5 parts of cyclohexane, 42.8 parts of a 70% cyclohexane solution of dicyclopentadiene (endomorph content of 99% or more) (30 parts based on the amount of dicyclopentadiene) and 1.9 parts of 1-hexene were added to the metal pressure-resistant reactor and heated to 53°C.

[0149] Dissolve 0.014 parts of tetrachlorotungsten benzimide (tetrahydrofuran) coordination compound in 0.70 parts of toluene to prepare a solution. Add 0.061 parts of 19% diethoxyethylaluminum / n-hexane solution to the solution and stir for 10 minutes to prepare a catalyst solution. Add the catalyst solution to a pressure-resistant reactor to initiate a ring-opening polymerization reaction. Then, maintain 53°C and react for 4 hours to obtain a solution of a ring-opening polymer of dicyclopentadiene. The number average molecular weight (Mn) and weight average molecular weight (Mw) of the obtained ring-opening polymer of dicyclopentadiene are 8750 and 28100, respectively, and the molecular weight distribution (Mw / Mn) is 3.21.

[0150] 0.037 parts of 1,2-ethylene glycol as a terminator was added to 200 parts of the obtained solution of the ring-opening polymer of dicyclopentadiene, 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 (manufactured by Kyowa Chemical Industry Co., Ltd., "Kyoward (registered trademark) 2000") was added thereto, and the mixture was heated to 60°C and stirred for 1 hour. Then, 0.4 parts of a filter aid (manufactured by Showa Chemical Industry Co., Ltd., "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 Co., Ltd., "TCP-HX").

[0151] 100 parts of cyclohexane and 0.0043 parts of carbonylchlorohydrotris(triphenylphosphine)ruthenium were added to 200 parts of the filtered solution of the ring-opening polymer of dicyclopentadiene (polymer amount: 30 parts), and a hydrogenation reaction was carried out at a hydrogen pressure of 6 MPa and 180° C. for 4 hours. Thus, a reaction solution containing a hydrogenated product of the ring-opening polymer of dicyclopentadiene was obtained. In the reaction solution, the hydrogenated product was precipitated to form a slurry solution.

[0152] The hydride contained in the reaction solution was separated from the solution using a centrifugal separator and dried under reduced pressure at 60°C for 24 hours to obtain 28.5 parts of a crystalline hydrogenated ring-opening polymer of dicyclopentadiene. The hydrogenation rate of the hydrogenated product was 99% or more, the glass transition temperature Tg was 93°C, the melting point (Tm) was 262°C, and the proportion of syndiotactic diads was 89%.

[0153] 1.1 parts of an antioxidant (tetrakis [methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate] methane, manufactured by BASF Japan, "Irganox (registered trademark) 1010") were mixed with 100 parts of the obtained hydrogenated ring-opening polymer of dicyclopentadiene, and then put into a twin-screw extruder (product name "TEM-37B", manufactured by Toshiba Machine Co., Ltd.) having four die holes with an inner diameter of 3 mm. After the mixture of the hydrogenated ring-opening polymer of dicyclopentadiene and the antioxidant was formed into a strand by hot melt extrusion molding, it was chopped in a wire cutter to obtain a crystalline resin in a particle shape. The crystalline resin is a resin with a positive intrinsic birefringence value.

[0154] The operating conditions of the twin-screw extruder are as follows.

[0155] ·Cylinder set temperature = 270 ~ 280 ℃

[0156] Die head set temperature = 250℃

[0157] Screw speed = 145 rpm

[0158] [Example 1]

[0159] (1-1) Production of resin film

[0160] The crystalline resin in the shape of particles manufactured in Manufacturing Example 1 was molded using a hot melt extrusion film molding machine with a T-die, and a roll of the resin film was obtained by winding a resin film of about 600 mm in width into a roll at a specified speed. In this example, the line speed was adjusted and the molding was performed in a manner such that the thickness of the resin film was 50 μm. In addition, when winding into a roll, it was protected and wound with a masking film ("FF1025" manufactured by Tredegar Co., Ltd.). With respect to the resin film, Re, Rth and NZ coefficient were measured, and the results showed that Re was 1.7 nm, Rth was 1.9 nm, and NZ coefficient was 1.6.

[0161] The operating conditions of the film forming machine are as follows.

[0162] ·Cylinder temperature setting = 280℃~300℃

[0163] Die temperature = 270°C

[0164] Casting roll temperature = 80°C

[0165] (1-2) Process 1

[0166] use Figure 1 The apparatus shown in the figure performs step 1 by the following method. The film 11 is pulled out from the roll 111 of the resin film obtained by (1-1), the masking film 12 is continuously peeled off and the resin film 15 is transported. The resin film 15 is brought into contact with a solvent and stretched (step 1). Specifically, the resin film 15 is passed through a bath 102 filled with toluene as a solvent, thereby immersing the resin film 15 in toluene. The time for the resin film to be transported in the solvent (solvent contact time) is 5 seconds. The room temperature at this time is 25°C, so the temperature of the toluene in the bath 102 is also 25°C. The resin film 15 is stretched by setting the difference between the circumferential speed Ps1 of the nip rollers 101A and 101B on the upstream side and the circumferential speed Ps2 of the nip rollers 104A and 104B on the downstream side. Specifically, by setting the circumferential speed ratio (Ps2 / Ps1) of the two sets of nip rollers to 1.1, the film is stretched at a stretching ratio of 1.1 times along the transport direction. The stretched film 10 obtained after the step 1 was protected with a new masking film ("FF1025" manufactured by Tredegar Co., Ltd.) and rolled up to obtain a stretched film roll 110. The Re, Rth, NZ coefficient and thickness of the stretched film were measured, and the results showed that Re was 56 nm, Rth was -324 nm, NZ coefficient was -5.29, and thickness was 57 μm.

[0167] [Example 2]

[0168] In (1-2) of Example 1, the same operation as in (1-2) of Example 1 was performed except that the peripheral speed ratio (Ps2 / Ps1) of the two sets of nip rollers was set to 1.2, thereby stretching the film at a stretching ratio of 1.2 in the conveying direction. A roll of a stretched film was obtained. Re, Rth, NZ coefficient and thickness of the stretched film were measured, and the results were Re of 265 nm, Rth of -295 nm, NZ coefficient of -0.61, and thickness of 56 μm.

[0169] [Example 3]

[0170] In (1-2) of Example 1, the same operation as in (1-2) of Example 1 was performed except that the peripheral speed ratio (Ps2 / Ps1) of the two sets of nip rollers was set to 1.5, thereby stretching the film at a stretching ratio of 1.5 times in the conveying direction. A roll of a stretched film was obtained. Re, Rth, NZ coefficient and thickness of the stretched film were measured, and the results were Re of 650 nm, Rth of 65 nm, NZ coefficient of 0.6, and thickness of 47 μm.

[0171] [Example 4]

[0172] (4-1) Production of resin film

[0173] A roll of a resin film was obtained by performing the same operation as in (1-1) of Example 1, except that the line speed was adjusted so that the thickness of the resin film was 21 μm.

[0174] (4-2) Process 1

[0175] In (1-2) of Example 1, 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 rollers was set to 1.5, so that the film was stretched at a stretching ratio of 1.5 times in the conveying direction. The same operation as in (1-2) of Example 1 was performed to obtain a roll of a stretched film. The Re, Rth, NZ coefficient and thickness of the stretched film were measured, and the results were Re of 275 nm, Rth of 30 nm, NZ coefficient of 0.61, and thickness of 20 μm.

[0176] [Example 5]

[0177] In (1-2) of Example 1, the same operation as in Example 1 was performed except that the following coating method was used instead of the method of passing the resin film through a bath filled with a solvent to contact the resin film with the solvent. The stretched film was measured for Re, Rth, NZ coefficient and thickness. The results were Re of 62 nm, Rth of -62 nm, NZ coefficient of -0.5, and thickness of 51 μm.

[0178] (Coating method)

[0179] A coating device (reverse gravure printing method) was used instead of the bath 102, and toluene was applied to one surface of the resin film using the coating device. The amount of solvent applied was set to 30 g / m 2 (Amount just applied).

[0180] [Comparative Example 1]

[0181] The film was unwound from the roll of the film obtained in (1-1) of Example 1, and the masking film was peeled off from the film to convey the resin film. The resin film was heated in an oven at 110° C. for about 1 minute and passed through the oven to be freely longitudinally uniaxially stretched at a stretching temperature of 110° C. Figure 2 The roll stretching machine shown here performs the free longitudinal uniaxial stretching by the following method.

[0182] right Figure 2 The roller stretching machine 1 shown in FIG. Figure 2 As shown, the roller stretching machine 1 is a device for stretching the film 3 fed from the film roll 2 in the longitudinal direction thereof. The roller stretching machine 1 has an upstream roller 6A and a downstream roller 6B in order from the upstream in the conveying direction as nip rollers capable of conveying the film 3 in the longitudinal direction. Here, the peripheral speed PsB of the downstream roller 6B is set faster than the peripheral speed PsA of the upstream roller 6A.

[0183] The resin film (with Figure 2 The stretching of the membrane 3 in FIG.

[0184] The film 3 is fed out from the film roll 2 and continuously supplied to the roller stretching machine 1. The roller stretching machine 1 conveys the film 3 in the order of the upstream roller 6A and the downstream roller 6B. At this time, by setting the ratio of the circumferential speed PsB of the downstream roller 6B to the circumferential speed PsA of the upstream roller 6A (PsB / PsA) to 1.5, the film 3 is stretched along the film conveying direction (i.e., the longitudinal direction) at a stretching ratio of 1.5 times. The ends of the stretched film in the width direction are trimmed by a trimming device not shown to obtain a long strip of stretched film 4. The stretched film is protected with a new masking film ("FF1025" manufactured by Tredegar Co., Ltd.) and wound to obtain a roll 5 of stretched film. Re, Rth, NZ coefficient and thickness of the obtained stretched film were measured, and the results showed that Re was 75nm, Rth was 38nm, NZ coefficient was 1.01, and thickness was 40μm.

[0185] The resin constituting the resin film used in the examples and comparative examples, the thickness of the resin film, the conditions for contact with the solvent (the type of solvent, the contact method, the contact time), the stretching ratio, and the physical properties of the stretched film (Re, Rth, NZ coefficient, thickness) are shown in Table 1. Regarding the comparative examples, the heating conditions (oven temperature) when stretching the resin film are shown in Table 1. In Table 1, "crystalline COP" refers to a crystalline alicyclic structure-containing polymer. In Table 1, "immersion" refers to contact between the resin film and the solvent by immersing the resin film in the solvent, and "coating" refers to contact between the resin film and the solvent by applying the solvent to the resin film. In Table 1, "stretched film" refers to the resin film after stretching.

[0186] [Table 1]

[0187] Table 1

[0188]

[0189] As shown in Table 1, according to the method of the embodiment, a film with retardation can be obtained regardless of whether the resin film is heated during stretching. That is, according to the manufacturing method of the present invention, retardation can be manifested even without heating the resin film, so a heating device for the resin film is not required, and the manufacturing equipment can be simplified.

[0190] [Other embodiments]

[0191] (1) In the above-mentioned embodiments and examples, an example of freely longitudinally uniaxially stretching the resin film along the film conveying direction by the difference in peripheral speed between the nip rollers on the upstream side and the downstream side in the conveying direction is shown, but the stretching method (device, stretching direction, etc.) of the resin film is not limited to this. The stretching direction of the resin film may be an inclined direction or a film width direction. In addition, the stretching direction may be two or more directions, in which case the stretching in the two or more directions may be performed simultaneously or sequentially.

[0192] Description of Reference Numerals

[0193] 1: Roller stretching machine

[0194] 2: Resin film roll

[0195] 3: Resin film

[0196] 4: Stretch film

[0197] 5: Roll of stretch film

[0198] 6A: Upstream roller

[0199] 6B: Downstream roller

[0200] 10: Stretch film

[0201] 11: Film (a film in which a masking film is bonded to a resin film)

[0202] 12, 13: Masking film

[0203] 15: Resin film

[0204] 100: Installation

[0205] 101A, 101B: Nip rollers on the upstream side

[0206] 102: Bathtub

[0207] 104A, 104B: Nip rollers on the downstream side

[0208] 110: Roll of stretch film

[0209] 111: Roll of resin film

[0210] 112, 113: Masking film roll

Claims

1. A method for manufacturing a phase difference film, comprising: A step of stretching a resin film composed of a resin containing a crystalline polymer while contacting the resin film with a solvent to orient molecules of the crystalline polymer in a thickness direction, The solvent is toluene, The crystalline polymer is a hydrogenated ring-opening polymer of dicyclopentadiene, The NZ coefficient of the retardation film is less than 0.61, The in-plane retardation Re of the phase difference film is 30 nm or more.

2. The method for producing a phase difference film according to claim 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 phase difference film according to claim 1 or 2, wherein: The resin film is made of a resin having a positive intrinsic birefringence value.

4. The method for producing a phase difference film according to claim 1 or 2, wherein: The step of stretching is performed without heating the resin film.

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