WO2021153695A1

WO2021153695A1 - Retardation film manufacturing method

Info

Publication number: WO2021153695A1
Application number: PCT/JP2021/003102
Authority: WO
Inventors: 恭輔井上
Original assignee: 日本ゼオン株式会社
Priority date: 2020-01-30
Filing date: 2021-01-28
Publication date: 2021-08-05
Also published as: JPWO2021153695A1; KR20220127818A; TW202132087A; CN114868053A

Abstract

A retardation film manufacturing method comprises a step for making a resin film contact with a solvent to stretch the film. Said making the resin film contact with the solvent is preferably by immersing the resin film in the solvent. The resin film is preferably in a mode such as to be made from a resin having a positive intrinsic birefringence value.

Description

Manufacturing method of retardation film

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

Conventionally, a technique for manufacturing a retardation film has been proposed (see, for example, Patent Documents 1 and 2).

International Publication No. 2017/065222 (Corresponding Gazette: US Patent Application Publication No. 2020/292742) Japanese Unexamined Patent Publication No. 2016-212171

The retardation film has retardation in at least one of the in-plane direction and the thickness direction. As a method for obtaining such a retardation film, a method of heating a resin film to a glass transition temperature of Tg or higher of the resin and stretching the film is known (see, for example, Patent Document 1). However, when such a method is adopted, a device or equipment for heating the resin film is required, and there is a problem that the manufacturing equipment becomes large. There is also a problem that energy consumption is large.

An object of the present invention is to provide a method for manufacturing a retardation film that can simplify the manufacturing equipment.

The present inventor has made diligent studies to solve the above problems. As a result, the present inventor can develop the retardation in at least one of the in-plane direction and the thickness direction without heating the resin film by stretching the resin film in contact with the solvent. As a result, they have found that the above problems can be solved, and have completed the present invention.
That is, the present invention includes the following.

[1] A method for producing a retardation film.
A method for producing a retardation film, which comprises a step of bringing a resin film into contact with a solvent and stretching the film.
[2] The method for producing a retardation film according to [1], wherein the resin film and the solvent are brought into contact with each other 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 made of a resin having a positive natural birefringence value.
[4] The method for producing a retardation film according to any one of [1] to [3], wherein the resin film is made of a resin containing a polymer having crystallinity.
[5] The method for producing a retardation film according to [4], wherein the crystalline polymer is a hydride 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.

According to the present invention, it is possible to provide a method for manufacturing a retardation film that can simplify the manufacturing equipment.

FIG. 1 is a side view schematically showing an apparatus that can be used in step 1 of the method for manufacturing a retardation film according to the first embodiment. FIG. 2 is a plan view schematically showing a roll stretching machine that can be used in the method for producing a retardation film of Comparative Example 1.

Hereinafter, the present invention will be described in detail by showing embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily modified and implemented without departing from the scope of claims of the present invention and the equivalent scope thereof.

In the following description, the in-plane retardation Re of the film is a value represented by "Re = (nx-ny) x d" unless otherwise specified. Further, the birefringence in the in-plane direction of the film is a value represented by "(nx-ny)", and is therefore represented by "Re / d", unless otherwise specified. Further, the retardation Rth in the thickness direction of the film is a value represented by “Rth = [{(nx + ny) / 2} -nz] × d” unless otherwise specified. Further, the birefringence in the thickness direction of the film is a value represented by "[{(nx + ny) / 2} -nz]" unless otherwise specified, and is therefore represented by "Rth / d". Further, the NZ coefficient of the film is a value represented by "(nx-nz) / (nx-ny)", and is therefore represented by "0.5 + Rth / Re", unless otherwise specified. nx represents the refractive index in the direction perpendicular to the thickness direction of the film (in-plane direction) and in the direction in which the maximum refractive index is given. ny represents the refractive index in the in-plane direction of the film and orthogonal to the nx direction. nz represents the refractive index in the thickness direction of the film. d represents the thickness of the film. The measurement wavelength is 590 nm unless otherwise specified.

In the following description, a material having a positive intrinsic birefringence means a material in which the refractive index in the stretching direction is larger than the refractive index in the direction perpendicular to it, unless otherwise specified. Further, a material having a negative intrinsic birefringence means a material in which the refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular to the refractive index, unless otherwise specified. The value of the intrinsic birefringence can be calculated from the permittivity distribution.

In the following description, the diagonal direction of a long film indicates an in-plane direction of the film, which is neither parallel nor perpendicular to the width direction of the film, unless otherwise specified.

In the following description, the "long" film means a film having a length of 5 times or more, preferably 10 times or more, and specifically a roll. A film that has a length that allows it to be rolled up and stored or transported. There is no particular limitation on the upper limit of the length, but it is usually 100,000 times or less with respect to the width.

In the following description, the longitudinal direction of the long film is usually parallel to the film transport direction in the production line. Further, the MD direction (machine direction) is the transport direction of the film in the production line, and is usually parallel to the longitudinal direction of the long film. Further, the TD direction (transverse direction) is a direction parallel to the film surface, a direction perpendicular to the MD direction, and usually parallel to the width direction of a long film.

In the following description, the directions of elements "parallel", "vertical" and "orthogonal" include errors within a range that does not impair the effect of the present invention, for example, within a range of ± 5 °, unless otherwise specified. You may be.

[Overview 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 film.

The method for producing a retardation film of the present invention includes a step of bringing a resin film, which is a material of the retardation film, into contact with a solvent and stretching the film. Can be expressed. As a result, according to the present invention, since an apparatus for heating the resin film is not required, it is possible to provide a method for producing a retardation film that can simplify the production equipment.

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

[Overview of the method for producing a retardation film of the present embodiment]
In the present embodiment, a long resin film is prepared, and the roll 111 of the resin film is obtained by winding the masking film on the roll while adhering the masking film to the resin film. Next, as shown in FIG. 1, the masking film 12 is peeled off from the film 11 unwound from the roll 111 of the resin film, and the long resin film 15 is conveyed in the direction indicated by A1. The masking film 12 is wound around the roll 112 while being pressed by the

nip rolls

101A and 101B arranged at positions sandwiching the film 11 from the thickness direction.

Next, the resin film 15 is stretched while being brought into contact with the resin film 15 through a bathtub 102 filled with a solvent. In the present embodiment, the resin film 15 is moved in the film transport direction due to the difference in peripheral speed between the

nip rolls

101A and 101B arranged on the upstream side in the film transport direction and the

nip rolls

104A and 104B arranged on the downstream side in the film transport direction. Stretch. By stretching the resin film 15 while contacting it with a solvent, it is possible to develop retardation in at least one of the in-plane direction and the thickness direction of the film without heating the resin film. Therefore, the stretched film 10 thus obtained can be used as it is as a retardation film.

The stretched film 10 thus obtained is wound while adhering the masking film 13 unwound from the roll 113. As a result, the roll 110 of the 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 film. In the following description, the process may be referred to as "process 1".

[Step 1]
Step 1 is a step of bringing the resin film into contact with a solvent and stretching it. By bringing the resin film into contact with a solvent and stretching it, retardation can be developed in the resin film. The mechanism by which such an effect is obtained is presumed as follows. However, the technical scope of the present invention is not limited by the following mechanism.

When the resin film is brought into contact with a solvent, the solvent penetrates into the resin film. Due to the action of the infiltrated solvent, micro-Brownian motion occurs in the molecules of the polymer in the film, and the molecules of the polymer in the film are oriented. Here, the surface area of the resin film is large on the front surface and the back surface, which are the main surfaces. Therefore, as for the infiltration rate of the solvent, the infiltration rate in the thickness direction through the front surface or the back surface is high. Then, the orientation of the molecules of the polymer can proceed so that the molecules of the polymer are oriented in the thickness direction.
When the resin film in which the 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 is increased. As the degree of molecular orientation increases in this way, the birefringence of the film changes, which in turn increases the retardation.

Step 1 can be performed by the device 100 shown in FIG. The device 100 includes upstream nip rolls 101A and 101B arranged on the upstream side in the film transport direction, downstream nip rolls 104A and 104B arranged on the downstream side in the film transport direction, and a bathtub for bringing the resin film 15 into contact with a solvent. 102 is provided.

Step 1 includes a step 1A of bringing the resin film into contact with a solvent and a step 1B of stretching the resin film. This embodiment is an embodiment in which step 1A is performed while step 1B is performed. That is, the resin film is brought into contact with the solvent in the area of the path of the resin film in which tension is applied to the resin film due to stretching. However, the method for producing a retardation film of the present invention is not limited to this. The production method of the present invention includes a mode in which a part of the step 1B overlaps with the step 1A, for example, a mode in which the step 1B for stretching the resin film is started from the middle of the step 1A in which the resin film is brought into contact with the solvent. The production method of the present invention also includes an embodiment in which the step 1A of bringing the resin film into contact with the solvent is performed, and then the step 1B of stretching the resin film is performed with the resin adhered and / or impregnated with the solvent.

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

Examples of the contact method between the resin film and the solvent include a spray method of spraying the solvent on the resin film; a coating method of applying the solvent to the resin film; and a dipping method of immersing the resin film in the solvent. Of these methods, the dipping method is preferable from the viewpoint that retardation in the thickness direction can be easily expressed even when the resin film has a large thickness, and continuous contact can be easily performed. FIG. 1 shows a dipping method.

[Resin film]
The resin film is a film that is a material for producing a 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 natural birefringence value. A resin having a positive intrinsic birefringence value means a resin in which the refractive index in the stretching direction is larger than the refractive index in the direction perpendicular to the refractive index, unless otherwise specified. The value of the intrinsic birefringence can be calculated from the permittivity distribution.

Further, as the resin constituting the resin film, a resin containing a polymer having crystallinity is preferable. "Crystallinity polymer" refers to a polymer having a melting point Tm (ie, the melting point can be observed with a differential scanning calorimetry (DSC)). In the following description, a polymer having crystallization may be referred to as a "crystalline polymer". Further, a resin containing a crystalline polymer may be referred to as a "crystalline resin". This 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 natural birefringence value, and more preferably the resin is a resin containing a crystalline polymer.

[Crystalline polymer]
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 light weight of the obtained retardation film can be improved. The polymer containing an alicyclic structure represents a polymer containing an alicyclic structure in the molecule. The polymer containing such an alicyclic structure can be, for example, a polymer obtained 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 these, a cycloalkane structure is preferable because it is easy to obtain a retardation film having excellent properties such as thermal stability. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less. be. When the number of carbon atoms contained in one alicyclic structure is within the above range, mechanical strength, heat resistance, and moldability are highly balanced.

In the crystalline polymer containing an alicyclic structure, the ratio of the structural units containing the alicyclic structure to all the structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 70. Weight% or more. Heat resistance can be improved by increasing the proportion of structural units containing an alicyclic structure as described above. The ratio of structural units containing an alicyclic structure to all structural units may be 100% by weight or less. Further, in the crystalline polymer containing an alicyclic structure, the remainder other than the structural unit containing the alicyclic structure is not particularly limited and may be appropriately selected depending on the purpose of use.

Examples of the crystalline polymer containing an alicyclic structure include the following polymers (α) to (δ). Among these, the polymer (β) is preferable because it is easy to obtain a retardation film having excellent heat resistance.
Polymer (α): A ring-opening polymer of a cyclic olefin monomer having crystallinity.
Polymer (β): A hydride of the polymer (α) having crystallinity.
Polymer (γ): An addition polymer of a cyclic olefin monomer having crystallinity.
Polymer (δ): A hydride of the polymer (γ) that has crystallinity.

Specifically, the crystalline polymer containing an alicyclic structure includes a ring-opening polymer of dicyclopentadiene having crystallinity and a hydride of the ring-opening polymer of dicyclopentadiene. It is more preferable that it is present and has crystallinity. Of these, a hydride of a ring-opening polymer of dicyclopentadiene, which has crystallinity, is particularly preferable. Here, in the ring-opening polymer of dicyclopentadiene, the ratio of the structural unit derived from dicyclopentadiene to all the structural units is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more. More preferably, it refers to a polymer of 100% by weight.

The hydride of the ring-opening polymer of dicyclopentadiene preferably has a high proportion of racemic diad. Specifically, the proportion of the repeating unit racemic diad in the hydride 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 racemic diads indicates a high degree of syndiotactic stereoregularity. Therefore, the higher the proportion of racemic diad, the higher the melting point of the hydride of the ring-opening polymer of dicyclopentadiene tends to be.
The proportion of racemo diads can be determined based on ^{the 13 C-NMR spectral analysis described in Examples below.}

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

The melting point Tm of the crystalline polymer is preferably 200 ° C. or higher, more preferably 230 ° C. or higher, and preferably 290 ° C. or lower. By using a crystalline polymer having such a melting point Tm, it is possible to obtain a retardation film having a better balance between moldability and heat resistance.

Normally, the crystalline polymer has a glass transition temperature Tg. The specific glass transition temperature Tg of the crystalline polymer is not particularly limited, but is usually 80 ° C. or higher and usually 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.

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

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

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

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

As the crystalline polymer, one type may be used alone, or two or more types may be used in combination 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 more than the lower limit of the above range, the birefringence expression and heat resistance of the retardation film can be enhanced. The upper limit of the proportion of the crystalline polymer can be 100% by weight or less.

The crystalline resin may contain any component in addition to the crystalline polymer. Optional components include, for example, antioxidants such as phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants; light stabilizers such as hindered amine light stabilizers; petroleum waxes, Fishertroph waxes, etc. Waxes such as polyalkylene wax; sorbitol compounds, metal salts of organic phosphoric acid, metal salts of organic carboxylic acids, nucleating agents such as kaolin and talc; diaminostilben derivatives, coumarin derivatives, azole derivatives (eg, benzoxazole derivatives, etc. Fluorescent whitening agents such as benzotriazole derivatives, benzoimidazole derivatives, and benzothiazole derivatives), carbazole derivatives, pyridine derivatives, naphthalic acid derivatives, and imidazolone derivatives; benzophenone-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, benzotriazole-based UV absorbers such as UV absorbers; Inorganic fillers such as talc, silica, calcium carbonate, glass fibers; Colorants; Flame retardants; Flame retardant aids; Antistatic agents; Plastics; Near infrared absorbers; Lubricants; Fillers ; And any polymer other than the crystalline polymer, such as a soft polymer; and the like. As the arbitrary component, one kind may be used alone, or two or more kinds may be used in combination at an arbitrary ratio.

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. The specific crystallinity is preferably less than 10%, more preferably less than 5%, and particularly preferably less than 3%. If the crystallinity of the crystalline polymer contained in the resin film before contact with the solvent is low, many molecules of the crystalline polymer can be oriented in the thickness direction by contact with the solvent. The substrate can be adjusted.

The in-plane retardation Re of the resin film before performing 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. When the Re and Rth of the resin film before the step 1 are in the above ranges, the retardation can be easily adjusted in the resin film after the step 1.

The resin film before contact with the solvent preferably has a small solvent content, and more preferably does not contain the 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, and particularly preferably 0.1% or less, which is ideal. The target is 0.0%. Since the amount of the solvent contained in the resin film before the contact with the solvent is small, many polymer molecules can be oriented in the thickness direction by the contact with the solvent, so that the retardation can be adjusted in a wide range. It will be possible. The solvent content of the resin film can be measured by the density.

The thickness of the resin film is preferably set according to the thickness of the retardation film to be manufactured. Usually, contact with a solvent increases the thickness of the film. On the other hand, by stretching, the thickness of the film becomes smaller. Therefore, the thickness of the resin film may be set in consideration of the change in the thickness in the step 1 of contacting and stretching with the solvent.

It is preferable to use a long resin film as the resin film. As a result, the retardation film can be continuously produced by the roll-to-roll method, so that the productivity of the retardation film can be effectively increased.

There are no restrictions on the method of manufacturing the resin film. Since a resin film containing no solvent can be obtained, resin molding methods such as injection molding method, extrusion molding method, press molding method, inflation molding method, blow molding method, calendar molding method, casting molding method, and compression molding method can be used. preferable. Among these, the extrusion molding method is preferable because the thickness can be easily controlled.

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

In the present embodiment, a film roll is provided in step 1 by winding a masking film on a long resin film and winding it on a roll. Known masking films (for example, FF1025 and "FF1035" manufactured by Tredegar; "SAT116T", "SAT2038T-JSL" and "SAT4538T-JSL" manufactured by Sun A. Kaken Co., Ltd .; "NBO" manufactured by Fujimori Kogyo Co., Ltd. -0424 "," TFB-K001 "," TFB-K0421 "and" TFB-K202 ";" DT-2200-25 "and" K-6040 "manufactured by Hitachi Kasei Co., Ltd .;" 6010 # 75 "manufactured by Teraoka Seisakusho Co., Ltd. , "6010 # 100", "6011 # 75" and "6093 # 75").

[solvent]
In step 1A, as the solvent to be brought into 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; carbon disulfide; When the resin film is made of a resin containing a crystalline polymer, a hydrocarbon-based solvent is preferable as the solvent from the viewpoint that the crystalline polymer can be penetrated into the resin film without being dissolved. The solvent may be one type or two or more types.

The temperature of the solvent in contact with the resin film is arbitrary as long as the solvent can maintain the liquid state, and therefore can be set in the range above the melting point of the solvent and below the boiling point. In the present application, in particular, when the temperature of the solvent is set to room temperature (for example, 15 ° C. or higher and lower than 40 ° C., more preferably 18 ° C. or higher and lower than 35 ° C., further preferably 23 ° C. or higher and lower than 30 ° C.), or adjusted to a temperature range close to room temperature. Even in this case, good stretching can be performed. When heating the solvent, the temperature can be adjusted to a temperature higher than room temperature if necessary. However, even in that case, good stretching can be performed with simpler equipment as compared with the case where the temperature around the film conveyed at the time of stretching is heated in an oven in a general stretching device.

The time for contacting the resin film with the solvent is not particularly specified, but is preferably 1 second or longer, more preferably 3 seconds or longer, particularly preferably 5 seconds or longer, preferably 180 seconds or shorter, and more preferably 120 seconds. Hereinafter, it is particularly preferably 60 seconds or less. When the contact time is equal to or greater than the lower limit of the above range, the molecules contained in the resin film can be effectively oriented. On the other hand, the degree of molecular orientation tends not to change significantly even if the contact time is lengthened. Therefore, when the contact time is not more than the upper limit value of the above range, the productivity can be improved without impairing the quality of the retardation film.

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

In the manufacturing method of the present embodiment, the resin film is stretched by using a stretching machine that vertically stretches the resin film by the difference in peripheral speeds of a plurality of sets of rolls. The upstream nip rolls 101A and 101B and the downstream nip rolls 104A and 104B are rotationally driven by a driving means (not shown) so that the resin film 15 can be conveyed in the conveying direction A1. In the present embodiment, the peripheral speeds of the nip rolls 104A and 104B on the downstream side are set faster than the peripheral speeds of the nip rolls 101A and 101B on the upstream side. Therefore, there is a peripheral speed difference between the upstream nip rolls 101A and 101B and the downstream nip rolls 104A and 104B, and the resin film 15 can be continuously stretched in the transport direction (traveling direction) due to this peripheral speed difference. It has become. Further, the draw ratio of the resin film 15 can be adjusted by adjusting the peripheral speed difference.

In the production method of the present embodiment, since the resin film is stretched by contacting it with a solvent, it is possible to easily develop the retardation even if the resin film is stretched at a low stretching ratio. The draw 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 draw ratio is equal to or higher than the lower limit of the above range, the retardation can be effectively expressed in the resin film. When the draw ratio is not more than the upper limit of the above range, the 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, the retardation can be expressed without heating the resin film at the time of stretching, so that heating of the resin film at the time of stretching is not necessary, but at the time of stretching. The resin film may be heated. In this case, the resin film before stretching may be preheat-treated. When the resin film is heated during stretching, the stretching temperature is preferably Tg + 2 ° C. or higher, more preferably Tg + 2 ° C. or higher, particularly preferably Tg + 5 ° C. or higher, preferably Tg + 40 ° C. or lower, more preferably Tg + 35 ° C. or lower. Particularly preferably, it is Tg + 30 ° C. or lower. Here, Tg refers to the glass transition temperature of the polymer contained in the resin film 15.

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

[Effect of this embodiment]
In the method for producing a retardation film of the present embodiment, by contacting the resin film with a solvent and stretching the film, retardation is expressed in at least one of the in-plane direction and the thickness direction without heating the resin film. Can be made to. As a result, according to the present embodiment, since a heating device such as an oven for heating the resin film is not required, the production equipment for the retardation film can be simplified. Further, according to the present embodiment, since the contact between the resin film and the solvent and the stretching of the resin film are performed at the same time, the production efficiency of the retardation film can be improved.

[Arbitrary process]
The method for producing a retardation film of the present invention may include any step 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 and the solvent are brought into contact with each other. Examples of the method for removing the solvent from the resin film include drying and wiping.

When the solvent is removed from the resin film after contact with the solvent by drying, there is no limitation on the method, and it can be performed by 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 into the heating device for a predetermined time. The heating for removing the solvent can be performed at a relatively low temperature, unlike the heating when heating is performed at the time of stretching in a general stretching device, and can be performed without strict temperature control. Moreover, it can be completed in a relatively short time. Further, by appropriately selecting the type of solvent, it is possible to achieve drying by simply transporting the solvent at room temperature without performing a heating operation.

When removing the solvent by drying, the film may be tensioned. Drying in such a state is preferable because the uniformity of the optical properties of the film after being brought into contact with the solvent can be effectively increased. The magnitude of tension applied to the resin film and the direction of tension can be set in consideration of the material of the resin film and the like. When 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 pulled by the holder to apply tension. The holder may be one that can continuously hold the entire length of the side of the resin film, or one that can hold the resin film intermittently at intervals. For example, the sides 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 performing step 1. The stretching conditions such as the stretching direction, the stretching device, and the stretching ratio in the step are not particularly limited, and can be set in consideration of the intended use of the retardation film.

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

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

[The 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 10 nm or more, more preferably 30 nm or more, preferably 1000 nm or less, and more preferably 800 nm or less.

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

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

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 retardation Rth in the specific thickness direction of the retardation film is preferably −500 nm or more, more preferably −400 nm or more, preferably 300 nm or less, and more preferably 150 nm 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, and more preferably 8 or less. When a retardation film having an NZ coefficient range within the above range is provided in a display device, it is possible to improve display quality such as viewing angle, contrast, and image quality of the display device. The NZ coefficient of the retardation film can be arbitrarily set according to the use of the retardation film.

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

[Birerefringence of retardation film]
The retardation film usually has large birefringence in at least one of the in-plane direction and the thickness direction. Specifically, the retardation film is usually, 1.0 × ^{10 -3} or more in-plane direction of the birefringent Re / d, and, 1.0 × ^{10 -3} or more absolute value in the thickness direction of the birefringent It has at least one of | Rth / d |.

Specifically, the birefringence Re / d of the retardation film in the in-plane direction is usually 1.0 × 10 ^-3 or more, preferably 3.0 × 10 ^-3 or more, and particularly preferably 5.0 × 10 ^-3. That is all. There is no upper limit, for example, it may be 2.0 × 10 ^-2 or less, 1.5 × 10 ^-2 or less, or 1.0 × 10 ^-2 or less. However, when the absolute value | Rth / d | of the birefringence in the thickness direction of the retardation film is 1.0 × 10 ^-3 or more, the birefringence Re / d in the in-plane direction of the retardation film is in the above range. May be outside.

The absolute value | Rth / d | of birefringence in the thickness direction of the retardation film is usually 1.0 × 10 ^-3 or more, preferably 3.0 × 10 ^-3 or more, and particularly preferably 5.0 × 10 ^{It is -3} or more. There is no upper limit, for example, it may be 2.0 × 10 ^-2 or less, 1.5 × 10 ^-2 or less, or 1.0 × 10 ^-2 or less. However, when the birefringence Re / d in the in-plane direction of the retardation film is 1.0 × 10 ^-3 or more, the absolute value | Rth / d | of the birefringence in the thickness direction of the retardation film is in the above range. May be outside.

[Other characteristics of retardation film]
The haze of the retardation film is usually less than 1.0%, preferably less than 0.8%, more preferably less than 0.5%, ideally 0.0%. When the retardation film having a small haze is provided on the display device, the sharpness of the image displayed on the display device can be improved. The haze of the film can be measured using a haze meter (for example, "NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd.).

Since the retardation film is an optical film, it is preferable to have 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 400 nm to 700 nm using an ultraviolet-visible spectrometer.

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 handleability can be improved and the strength can be increased. Further, when the thickness d of the retardation film is not more than the upper limit value, it is easy to wind up the long retardation film.

In a retardation film produced by 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. The specific range of crystallinity is preferably 10% or more, more preferably 15% or more, and particularly preferably 30% or more.
The crystallinity of the crystalline polymer can be measured by X-ray diffraction.

[Solvent contained in retardation film]
Since 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 it, the retardation film produced by the production method may contain a solvent.

Upon contact with the solvent, all or part of the solvent incorporated into the resin film can enter the inside of the polymer contained in the resin constituting the film. Therefore, it is difficult to completely remove the solvent even if the solvent is dried above the boiling point. Therefore, the retardation film produced by a production method including a step of contacting with a solvent may contain a solvent.

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, and particularly preferably 0.1% by weight or less. Yes, it can exceed 0% by weight.

[Use of retardation film]
In the retardation film produced by the production method of the present invention, the resin film is brought into contact with a solvent and stretched to develop retardation in at least one of the in-plane direction and the thickness direction. Therefore, the retardation film obtained by the production method of the present invention can be used as a 1/2 wave plate, a 1/4 wave plate, or the like depending on its retardation value. A circularly polarizing plate using the retardation film produced by the production method of the present invention as either one or both of a 1/2 wave plate and a 1/4 wave plate can be used in a display device.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples shown below, and can be arbitrarily modified and implemented without departing from the scope of claims of the present invention and the equivalent scope thereof.

In the following explanation, "%" and "part" indicating the amount are based on weight unless otherwise specified. The operations described below were performed under normal temperature and pressure conditions unless otherwise specified. Further, in the following description, the measurement wavelengths of retardation and birefringence were 590 nm unless otherwise specified.

[Evaluation method]
(Method for measuring weight average molecular weight Mw and number average molecular weight Mn of polymer)
The weight average molecular weight Mw and the number average molecular weight Mn of the polymer were measured as polystyrene-equivalent values using a gel permeation chromatography (GPC) system (“HLC-8320” manufactured by Tosoh Corporation). At the time of measurement, an H type column (manufactured by Tosoh Corporation) was used as the column, and tetrahydrofuran was used as the solvent. The temperature at the time of measurement was 40 ° C.

(Measuring method of hydrogenation rate of polymer)
Hydrogenation rate of the polymer, o-dichlorobenzene -d ⁴ as solvent, at 145 ° ^C., as measured by 1 H-NMR measurement.

(Measuring method of 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 rapidly cooled with dry ice. Subsequently, using this polymer as a test piece, the glass transition temperature Tg and melting point Tm of the polymer were measured at a heating rate of 10 ° C./min (heating mode) using a differential scanning calorimeter (DSC). It was measured.

(Measuring method of the ratio of racemic diad of polymer)
The ratio of racemic diads in the polymer was measured as follows. Orthodichlorobenzene -d ⁴ as solvent, at 200 ° C., by applying the inverse-gated decoupling method, was ¹³ C-NMR measurement of the polymer. In ^{the results of this 13} C-NMR measurement, a signal of 43.35 ppm derived from meso-diad and a signal of 43.43 ppm derived from racemic diad were used with the peak of 127.5 ppm of ^{orthodichlorobenzene-d 4 as a reference shift.} Was identified. Based on the intensity ratios of these signals, the proportion of racemic diads in the polymer was determined.

(Method of measuring film thickness)
The thickness of the film was measured using a contact type thickness gauge (Code No. 543-390 manufactured by Mitutoyo Co., Ltd.).

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

[Manufacturing example 1. Production of crystalline resin containing hydride of ring-opening polymer of dicyclopentadiene]
The metal pressure resistant reactor was sufficiently dried and then replaced with nitrogen. In this metal pressure resistant reactor, 154.5 parts of cyclohexane, 42.8 parts of a 70% cyclohexane solution of dicyclopentadiene (endo content 99% or more) (30 parts as the amount of dicyclopentadiene), and 1- 1.9 parts of hexene was added and heated to 53 ° C.

0.014 parts of the tetrachlorotungsten phenylimide (tetrahydrofuran) complex was dissolved in 0.70 parts of toluene to prepare a solution. To this solution was added 0.061 part of a 19% concentration diethylaluminum ethoxide / n-hexane solution and stirred for 10 minutes to prepare a catalytic solution. This catalyst solution was added to a pressure resistant reactor to initiate a ring-opening polymerization reaction. Then, the reaction was carried out for 4 hours while maintaining 53 ° C. 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 8,750 and 28,100, respectively, and the molecular weight distribution (Mw / Mn) obtained from these is Was 3.21.

To 200 parts of the obtained solution of the ring-opening polymer of dicyclopentadiene, 0.037 parts of 1,2-ethanediol was added as a terminator, heated to 60 ° C., and stirred for 1 hour to stop the polymerization reaction. I let you. A part of a hydrotalcite-like compound (“Kyoward (registered trademark) 2000” manufactured by Kyowa Chemical Industry Co., Ltd.) was added thereto, and the mixture was heated to 60 ° C. and stirred for 1 hour. After that, 0.4 part of a filtration aid (Showa Chemical Industry Co., Ltd. "Radiolite (registered trademark) # 1500") was added, and a PP pleated cartridge filter (ADVANTEC Toyo Co., Ltd. "TCP-HX") was used as an adsorbent. The solution was filtered off.

To 200 parts of the filtered dicyclopentadiene ring-opening polymer solution (30 parts of polymer amount), 100 parts of cyclohexane was added, 0.0043 parts of chlorohydride carbonyltris (triphenylphosphine) ruthenium was added, and hydrogen was added. The hydrogenation reaction was carried out at a pressure of 6 MPa and 180 ° C. for 4 hours. As a result, a reaction solution containing a hydride of a ring-opening polymer of dicyclopentadiene was obtained. In this reaction solution, hydrides were precipitated to form a slurry solution.

The hydride contained in the reaction solution and the solution were separated using a centrifuge and dried under reduced pressure at 60 ° C. for 24 hours to obtain a hydride of a crystalline ring-opening polymer of dicyclopentadiene 28. I got 5 copies. The hydrogenation rate of this hydride was 99% or more, the glass transition temperature Tg was 93 ° C., the melting point (Tm) was 262 ° C., and the ratio of racemo diad was 89%.

100 parts of the hydride of the obtained ring-opening polymer of dicyclopentadiene is added with an antioxidant (tetrakis [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane. BASF Japan's "Irganox (registered trademark) 1010") After mixing 1.1 parts, a twin-screw extruder equipped with four die holes with an inner diameter of 3 mmΦ (product name "TEM-37B", manufactured by Toshiba Machine Co., Ltd.) ). A mixture of a hydride of a ring-opening polymer of dicyclopentadiene and an antioxidant was formed into a strand shape by hot melt extrusion molding, and then shredded with a strand cutter to obtain a pellet-shaped crystalline resin. This crystalline resin is a resin having a positive natural birefringence value.
The operating conditions of the twin-screw extruder are described below.
・ Barrel set temperature = 270 to 280 ° C
・ Die set temperature = 250 ℃
・ Screw rotation speed = 145 rpm

[Example 1]
(1-1) Production of Resin Film The pellet-shaped crystalline resin produced in Production Example 1 is molded using a heat-melt extrusion film molding machine equipped with a T-die, and a resin film having a width of about 600 mm is formed at a predetermined speed. A roll of the resin film was obtained by the method of winding the resin film on the roll. In this example, the line speed was adjusted so that the thickness of the resin film was 50 μm. When the film was wound on a roll, it was wound while being protected by a masking film (“FF1025” manufactured by Tredegar Co., Ltd.). When the Re, Rth and NZ coefficients of the resin film were measured, Re was 1.7 nm, Rth was 1.9 nm, and the NZ coefficient was 1.6.
The operating conditions of the film forming machine are described below.
-Barrel temperature setting = 280 ° C to 300 ° C
・ Die temperature = 270 ℃
・ Cast roll temperature = 80 ℃

(1-2) Step 1
Step 1 was performed by the following method using the apparatus shown in FIG. The film 11 was pulled out from the roll 111 of the resin film obtained in (1-1), the masking film 12 was continuously peeled off, and the resin film 15 was conveyed. The resin film 15 was brought into contact with a solvent and stretched (step 1). Specifically, the resin film 15 was immersed in toluene by passing the resin film 15 through a bathtub 102 filled with toluene as a solvent. The time for the resin film to be conveyed in the solvent (solvent contact time) was 5 seconds. The room temperature at this time was 25 ° C., and therefore the temperature of toluene in the bathtub 102 was also 25 ° C. The resin film 15 was stretched by providing a difference between the peripheral speeds Ps1 of the nip rolls 101A and 101B on the upstream side and the peripheral speeds Ps2 of the nip rolls 104A and 104B on the downstream side. Specifically, by setting the peripheral speed ratio (Ps2 / Ps1) of the two sets of nip rolls to 1.1, the film was stretched in the transport direction at a draw ratio of 1.1 times. The stretched film 10 obtained after performing step 1 was wound while being protected by a new masking film (“FF1025” manufactured by Tredegar) to obtain a roll 110 of the stretched film. When the Re, Rth, NZ coefficient and thickness of the stretched film were measured, Re was 56 nm, Rth was 324 nm, the NZ coefficient was −5.29, and the thickness was 57 μm.

[Example 2]
In Example 1 (1-2), the peripheral speed ratio (Ps2 / Ps1) of the two sets of nip rolls was set to 1.2, except that the film was stretched in the transport direction at a draw ratio of 1.2 times. The same operation as in (1-2) of Example 1 was carried out to obtain a roll of stretched film. When the Re, Rth, NZ coefficient and thickness of the stretched film were measured, Re was 265 nm, Rth was -295 nm, the NZ coefficient was −0.61, and the thickness was 56 μm.

[Example 3]
In Example 1 (1-2), except that the film was stretched at a draw ratio of 1.5 times in the transport direction by setting the peripheral speed ratio (Ps2 / Ps1) of the two sets of nip rolls to 1.5. The same operation as in (1-2) of Example 1 was carried out to obtain a roll of stretched film. When the Re, Rth, NZ coefficient and thickness of the stretched film were measured, Re was 650 nm, Rth was 65 nm, the NZ coefficient was 0.6, and the thickness was 47 μm.

[Example 4]
(4-1) Production of Resin Film In Example 1 (1-1), except that the line speed was adjusted and molding was performed so that the thickness of the resin film was 21 μm. The same operation as in 1-1) was carried out to obtain a roll of the resin film.

(4-2) Step 1
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 two sets of nip rolls were used. By setting the peripheral speed ratio (Ps2 / Ps1) of the film to 1.5, the same operation as in (1-2) of Example 1 was performed except that the film was stretched in the transport direction at a stretching ratio of 1.5 times. , A roll of stretched film was obtained. When the Re, Rth, NZ coefficient and thickness of the stretched film were measured, Re was 275 nm, Rth was 30 nm, the NZ coefficient was 0.61, and the thickness was 20 μm.

[Example 5]
In Example 1 (1-2), the contact between the resin film and the solvent is the same as in Example 1 except that the contact between the resin film and the solvent is performed by the following coating method instead of the method of passing the resin film through a bathtub filled with the solvent. The operation was carried out to obtain a roll of stretched film. When the Re, Rth, NZ coefficient and thickness of the stretched film were measured, Re was 62 nm, Rth was −62 nm, the NZ coefficient was −0.5, and the thickness was 51 μm.

(Applying method)
A coating device (reverse gravure method) was used instead of the bathtub 102, and toluene was coated on one surface of the resin film by the coating device. The coating amount of the solvent was 30 g / m ² (the coating amount immediately after coating).

[Comparative Example 1]
The film was pulled out from the roll of the film obtained in (1-1) of Example 1, the masking film was peeled from the film, and the resin film was conveyed. By passing the resin film through an oven heated to 110 ° C. so as to be heated in the oven for about 1 minute, free longitudinal uniaxial stretching was performed at a stretching temperature of 110 ° C. This free longitudinal uniaxial stretching was performed by the following method using the roll stretching machine shown in FIG.

The roll stretching machine 1 shown in FIG. 2 will be described. As shown in FIG. 2, the roll stretching machine 1 is a device for stretching the film 3 unwound from the film roll 2 in the longitudinal direction thereof. The roll stretching machine 1 includes an upstream roll 6A and a downstream roll 6B as nip rolls capable of transporting the film 3 in the longitudinal direction in order from the upstream in the transport direction. Here, the peripheral speed PsB of the downstream roll 6B is set to be faster than the peripheral speed PsA of the upstream roll 6A.

The resin film (corresponding to the film 3 in FIG. 2) was stretched using the roll stretching machine 1 as follows.
The film 3 was unwound from the film roll 2, and the film 3 was continuously supplied to the roll stretching machine 1. The roll stretching machine 1 conveyed the film 3 in the order of the upstream roll 6A and the downstream roll 6B. At this time, by setting the ratio (PsB / PsA) of the peripheral speed PsB of the downstream side roll 6B to the peripheral speed PsA of the upstream side roll 6A to 1.5, the film 3 is conveyed at a draw ratio of 1.5 times. Stretched in the direction (ie, longitudinal). Both ends of the stretched film in the width direction were trimmed with a trimming device (not shown) to obtain a long stretched film 4. This stretched film was wound while being protected by a new masking film (“FF1025” manufactured by Tredegar) to obtain a roll 5 of the stretched film. When the Re, Rth, NZ coefficient and thickness of the obtained stretched film were measured, Re was 75 nm, Rth was 38 nm, the NZ coefficient was 1.01, and the thickness was 40 μm.

The resin constituting the resin film used in Examples and Comparative Examples, the thickness of the resin film, the contact conditions with the solvent (solvent type, contact method, contact time), draw ratio and physical property values of the stretched film (Re, Rth, NZ coefficient, thickness) are shown in Table 1. For a comparative example, Table 1 shows the heating conditions (oven temperature) when the resin film is stretched. In Table 1, "crystalline COP" means a crystalline alicyclic structure-containing polymer. In Table 1, "immersion" means that the contact between the resin film and the solvent was performed by the method of immersing the resin film in the solvent, and "coating" means that the contact between the resin film and the solvent was performed. It means that the method was performed by applying a solvent to the resin film. In Table 1, the "stretched film" means a resin film after stretching.

As is clear from the results shown in Table 1, it can be seen that according to the method of the example, a film having retardation can be obtained even though the resin film is not heated during stretching. .. That is, according to the manufacturing method of the present invention, the retardation can be developed without heating the resin film, so that a heating device for the resin film is unnecessary and the manufacturing equipment can be simplified.

[Other Embodiments]
(1) In the above-described embodiments and examples, an example in which the resin film is freely stretched uniaxially in the film transport direction due to the difference in peripheral speed between the nip rolls on the upstream side and the downstream side in the transport direction is shown. (Device, stretching direction, etc.) are not limited to this. The stretching direction of the resin film may be an oblique direction or a film width direction. Further, 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.

1 ... Roll stretching machine 2 ... Resin film roll 3 ... Resin film 4 ... Stretched film 5 ... Stretched film roll 6A ... Upstream side roll 6B ... Downstream side roll 10 ... Stretched film 11 ... Film (masking film is attached to the resin film) Combined film)
12, 13 ... Masking film 15 ... Resin film 100 ...

Equipment

101A, 101B ... Upstream nip roll 102 ...

Bathtub

104A, 104B ... Downstream nip roll 110 ... Stretched film roll 111 ...

Resin film roll

112, 113 ... Masking film Roll

Claims

It is a method of manufacturing a retardation film.
A method for producing a retardation film, which comprises a step of bringing a resin film into contact with a solvent and stretching the film.
The method for producing a retardation film according to claim 1, wherein the resin film and the solvent are brought into contact with each other by immersing the resin film in the solvent.
The method for producing a retardation film according to claim 1 or 2, wherein the resin film is made of a resin having a positive natural birefringence value.
The method for producing a retardation film according to any one of claims 1 to 3, wherein the resin film is made of a resin containing a polymer having crystallinity.
The method for producing a retardation film according to claim 4, wherein the crystalline polymer is a hydride of a ring-opening polymer of dicyclopentadiene.
The method for producing a retardation film according to any one of claims 1 to 5, wherein the solvent is a hydrocarbon solvent.
The method for producing a retardation film according to any one of claims 1 to 6, wherein the stretching step is performed without heating the resin film.