JP2021173811A - Method of manufacturing retardation film - Google Patents

Abstract

To provide a method of manufacturing a retardation film with superior appearance and retardation expressibility.SOLUTION: A retardation film manufacturing method of the present invention comprises a first step of heating a resin film to obtain an intermediate film, and a second step of subjecting the intermediate film to stretch treatment.SELECTED DRAWING: None

Description

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

In recent years, an image display device in which a retardation film is provided on the viewing side has been widely used. In the production of the retardation film, typically, a resin film is extruded or coated to form a resin film, and the obtained resin film is stretched to obtain a retardation film. However, the conventional method for producing a retardation film has problems such as insufficient appearance of the obtained retardation film and insufficient expression of retardation.

Japanese Patent No. 3325560

The present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide a method for producing a retardation film having excellent appearance and phase difference expression.

The method for producing a retardation film of the present invention includes a first step of heating a resin film to obtain an intermediate film and a second step of applying a stretching treatment to the intermediate film.
In one embodiment, the intermediate film winding step is further included between the first step and the second step.
In one embodiment, the heating temperature of the first step is (Tg + 25 ° C.) / 2 or more.
In one embodiment, the heating temperature in the first step is Tg or more, and the increase in Re (550) of the intermediate film with respect to the resin film before heating is 10 nm or less.
In one embodiment, the heating time of the first step is 10 seconds to 180 seconds.
In one embodiment, the heating time of the first step is 30 seconds to 120 seconds.
In one embodiment, the heating temperature of the first step is higher than the stretching temperature of the second step.
In one embodiment, a step of adhering a shrinkable film to form a laminate is included between the first step and the second step.
In another embodiment, prior to the first step, a step of adhering the resin film to the shrinkable film to form a laminate, or a coating liquid in which the resin is dissolved or dispersed in a solvent is applied to the shrinkable film. The increase in Re (550) of the intermediate film with respect to the resin film before heating is 10 nm or less, including the step of coating.

According to the embodiment of the present invention, in the method for producing a retardation film, an appearance is obtained by including a first step of heating a resin film to obtain an intermediate film and a second step of applying a stretching treatment to the intermediate film. In addition, a retardation film having excellent retardation development can be realized.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
Definitions of terms and symbols herein are as follows.
(1) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and “ny” is the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advance axis direction). Is the refractive index of, and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
“Re (λ)” is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (550)" is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in the thickness direction (Rth)
“Rth (λ)” is a phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, "Rth (550)" is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is obtained by the formula: Rth (λ) = (nx−nz) × d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re.

A. Method for manufacturing a retardation film The method for manufacturing a retardation film in the present invention is a step of manufacturing a resin film, a step of heating the resin film to obtain an intermediate film (first step), and a step of stretching the intermediate film (second step). Step).

The method for producing the retardation film may further include a winding step of the intermediate film between the first step and the second step, if necessary.

In one embodiment, the method for producing a retardation film may further include a step of laminating the intermediate film and the shrinkable film between the first step and the second step. In another embodiment, in the method for producing a retardation film, a resin film may be adhered to a shrinkable film to form a laminate, and then the laminate may be heated to obtain an intermediate film. In yet another embodiment, in the method of producing a retardation film, a coating liquid in which a resin is dissolved in a solvent or dispersed is applied to a shrinkable film to form a laminate, and then the laminate is heated. An intermediate film may be obtained. Hereinafter, each step of the method for producing a retardation film will be described in detail.

B. Resin Film Fabrication The resin film can be made of any suitable resin. Examples of the resin forming the resin film include polycarbonate-based resin, cyclic olefin-based resin, cellulose-based resin, polyester-based resin, polyvinyl alcohol-based resin, polyamide-based resin, polyimide-based resin, polyether resin, and polystyrene-based resin. Examples include acrylic resins and polyester carbonate resins. Among these, a polycarbonate-based resin or a cyclic olefin-based resin can be preferably used.

As the polycarbonate-based resin, any suitable polycarbonate resin can be used as long as the effects of the present invention can be obtained. Preferably, the polycarbonate resin is selected from the group consisting of structural units derived from isosorbide dihydroxy compounds and alicyclic diols, alicyclic dimethanol, di, tri or polyethylene glycols, and alkylene glycols or spiroglycols. Includes structural units derived from at least one dihydroxy compound. More preferably, the polycarbonate resin contains a structural unit derived from an isosorbide dihydroxy compound, a structural unit derived from an alicyclic dimethanol and / or a structural unit derived from di, tri or polyethylene glycol. The polycarbonate resin may contain structural units derived from other dihydroxy compounds, if desired. Details of a method for producing a polycarbonate resin and a retardation film that can be suitably used in the present invention are described in, for example, International Publication No. 2011/062239, and the description is incorporated herein by reference. NS.

Cyclic olefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit. Examples include resins that are present. Specific examples include a ring-opening (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and an α-olefin such as ethylene and propylene (typically, a random copolymer). , And a grafted polymer obtained by modifying these with an unsaturated carboxylic acid and a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene-based monomers. Examples of the norbornene-based monomer include the monomers described in JP-A-2015-210459. Various products of the cyclic olefin resin are commercially available. Specific examples include Zeon Corporation's product names "Zeonex" and "Zeonoa", JSR's product name "Arton", TICONA's product name "Topus", and Mitsui Chemicals' product name. "APEL" can be mentioned.

Any suitable method can be adopted as the method for forming the resin film. For example, a melt extrusion method (for example, T die molding method), a cast coating method (for example, a casting method), a calender molding method, a hot pressing method, a co-extrusion method, a co-melt method, a multi-layer extrusion, an inflation molding method and the like can be mentioned. Be done. Preferably, a T-die molding method, a casting method and an inflation molding method are used.

The thickness of the resin film can be set to an arbitrary appropriate value according to desired optical characteristics, stretching conditions described later, and the like. It is preferably 30 μm to 300 μm, and more preferably 40 μm to 250 μm.

C. Step of heating the resin film to obtain an intermediate film (first step)
B. above. By heating the resin film obtained in 1 above, an intermediate film can be obtained. According to an embodiment of the present invention, a retardation film having excellent appearance and retardation is exhibited by heating the resin film under predetermined conditions as a separate step (that is, not preheating the stretching) before stretching. Can be obtained.

The heating temperature of the resin film in this step is preferably (Tg + 25 ° C.) / 2 or more, and more preferably Tg or more. If the heating temperature is in such a range, an intermediate film having a desired orientation state and / or Re (550) can be obtained. In one embodiment, the heating temperature of the first step is higher than the stretching temperature of the intermediate film.

The heating time of the resin film is preferably 10 seconds to 180 seconds, more preferably 30 seconds to 120 seconds. If the heating time is in such a range, an intermediate film having a desired orientation state and / or Re (550) can be obtained.

The Re (550) of the intermediate film obtained by this step is preferably 0 nm to 30 nm, more preferably 0 nm to 20 nm, and further preferably 0 nm to 10 nm. According to the present invention, by heating the resin film under the above heating conditions, an intermediate film having such Re (550) can be obtained. If the heating temperature is Tg or higher, Re (550) can be smaller.

The increase in Re (550) of the intermediate film with respect to the resin film before heating in this step is preferably 10 nm or less, more preferably 5 nm or less, and further preferably 3 nm or less. The smaller the increase in Re (550) of the intermediate film, the more preferable, and the lower limit thereof is preferably substantially 0 nm. According to the present invention, by heating the resin film under the above heating conditions, the amount of increase in Re (550) before and after heating can be reduced. If the heating temperature is Tg or higher, the amount of increase in Re (550) can be smaller.

This step is preferably performed under non-tension and low wind conditions. Examples of the non-tensioning process include a process of lining a process protective film against a resin film and a process of transporting the resin film by a tenter belt conveyor. Examples of the low wind power process include a process using an IR heater or the like. This is to prevent the resin film from being fanned by the air flow generated by the fan.

D. Winding process of intermediate film C.I. If necessary, the intermediate film obtained in (1) is wound around an axis orthogonal to the transport direction to form a roll body. The roll body may be subjected to the stretching step as it is, or may be stored for a predetermined time. When the roll is stored, the storage time is preferably 12 hours to 96 hours, more preferably 24 hours to 48 hours.

E. Intermediate film stretching step (second step)
In one embodiment, the retardation film is made by uniaxially stretching or fixed end uniaxially stretching the intermediate film. Specific examples of the fixed-end uniaxial stretching include a method of stretching the intermediate film in the width direction (lateral direction) while running the intermediate film in the longitudinal direction. The draw ratio is preferably 1.1 times to 3.5 times, more preferably 1.3 times to 2.0 times.

The stretching temperature of the intermediate film is preferably Tg-30 ° C to Tg + 30 ° C, more preferably Tg-20 ° C to Tg + 20 ° C, and even more preferably Tg-15 ° C to Tg + 15 ° C. By stretching at such a temperature, a retardation film having appropriate characteristics in the present invention can be obtained. Tg is the glass transition temperature of the constituent material of the film.

In this step, the above C.I. By stretching the intermediate film heated in, a so-called positive A plate (nx> ny = nz) or negative B plate (nx> ny> nz) can be obtained.

In another embodiment, the retardation film is made by continuously obliquely stretching the intermediate film in the direction of an angle θ with respect to the longitudinal direction. Examples of the stretching machine used for diagonal stretching include a tenter type stretching machine capable of applying a feeding force, a pulling force, or a pulling force at different speeds in the horizontal and / or vertical directions. The tenter type stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, but any suitable stretching machine can be used as long as the intermediate film can be continuously and diagonally stretched.

F. Embodiment F-1 using a shrinkable film. Embodiment in which a shrinkable film is used after the first step In one embodiment, the above-mentioned C.I. (First step) and E.I. A step of adhering the intermediate film and the shrinkable film to form a laminate is included between the (second step) and the (second step). The bonding of the intermediate film and the shrinkable film is carried out by the above-mentioned D. It may be performed before winding the intermediate film of the above, or after winding. By laminating the intermediate film and the shrinkable film and stretching the obtained laminate, a retardation film having a refractive index characteristic of nx>nz> ny can be obtained.

The shrinkage film preferably has a shrinkage ratio in the direction orthogonal to the stretching direction in the stretching step (second step) of the intermediate film, preferably in the range of 0.50 times to 0.99 times, more preferably. Is 0.60 times to 0.98 times, more preferably 0.75 times to 0.95 times.

The material for forming the shrinkable film is not particularly limited, but a thermoplastic resin is preferable because it is suitable for stretching treatment. Specifically, for example, acrylic resin, polyolefin resin such as polyethylene and polypropylene (PP), polyester resin such as polyethylene terephthalate (PET), polyamide, polycarbonate resin, norbornene resin, polystyrene, polyvinyl chloride, polyvinylidene chloride, etc. Examples thereof include cellulose resins such as triacetyl cellulose, polyethersulfone, polysulfone, polyimide, polyacrylic, acetate resin, polyarylate, polyvinyl alcohol, and mixtures thereof. Further, a liquid crystal polymer or the like can also be used. The shrinkable film is preferably a uniaxial or biaxial stretched film formed from one or more of the above-mentioned forming materials. As the shrinkable film, for example, a commercially available product may be used. Commercially available products include, for example, "Space Clean" manufactured by Toyo Spinning Co., Ltd., "Fancy Wrap" manufactured by Gunze Corporation, "Trefan" manufactured by Toray Industries, Inc., and "Lumirror" manufactured by Toray Industries, Inc. , "Arton" manufactured by JSR Corporation, "Zeonoa" manufactured by Zeon Corporation, and "Suntech" manufactured by Asahi Kasei Corporation.

The thickness of the shrinkable film is not particularly limited, but is, for example, in the range of 10 μm to 300 μm, preferably in the range of 20 μm to 200 μm, and more preferably in the range of 40 μm to 150 μm. The surface of the shrinkable film may be surface-treated for the purpose of improving the adhesion with the intermediate film. Examples of the surface treatment include chemical or physical treatments such as chromic acid treatment, ozone exposure, flame exposure, high-voltage exposure, and ionizing radiation treatment. Further, a primer layer may be formed on the surface of the shrinkable film by applying an undercoating agent (for example, an adhesive substance).

The method of adhering the shrinkable film to one side or both sides of the intermediate film is not particularly limited, but an acrylic type using a (meth) acrylic polymer as a base polymer between the intermediate film and the shrinkable film. A method of providing an adhesive layer and adhering is preferable from the viewpoint of excellent workability and economy.

C. above. The intermediate film obtained by heating in the above F.I. The laminate was subjected to bonding with the shrinkable film of the above E.I. By stretching as described in the above, a retardation film having a refractive index characteristic of nx> nz> ny can be obtained. The Nz coefficient of the obtained retardation film is preferably 0.3 to 0.9, and more preferably 0.4 to 0.8.

F-2. Embodiment F-2-1 in which a shrinkable film is used before the first step. Bonding Step of Resin Film and Shrinkable Film In another embodiment, the resin film may be adhered to the shrinkable film to form a laminate, and then the laminate may be heated to obtain an intermediate film. For details of the shrinkable film, refer to the above F-1. As described in. The step of adhering the resin film to the shrinkable film to form a laminate is described in F-1. It can be done in the same manner as.

F-2-2. Step of Applying Resin Solution to Shrinkable Film In another embodiment, an arbitrary suitable resin is dissolved in a solvent or a dispersed coating liquid is applied to the shrinkable film to form a laminate, and then the laminate is formed. The body may be heated to obtain an intermediate film. For details of the shrinkable film, refer to the above F-1. As described in.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows.

(1) Appearance The appearance of the retardation films obtained in Examples and Comparative Examples described later was visually evaluated. The evaluation contents were wrinkles and unevenness due to reflection and transmission, and wrinkles and unevenness when observed from the front and diagonally by sandwiching between orthogonal polarizing plates, and the evaluation criteria were set to 1 to 5 below.
1: No wrinkles or unevenness in reflection, transmission, and polarizing plate evaluation.
2: There are no wrinkles or unevenness in the reflection / transmission evaluation, and there are weak wrinkles / unevenness in the polarizing plate evaluation.
3: There are no wrinkles or unevenness in the reflection / transmission evaluation, and there are strong wrinkles / unevenness in the polarizing plate evaluation.
4: There are weak wrinkles and unevenness in the reflection and transmission evaluation.
5: There are strong wrinkles and unevenness in the reflection and transmission evaluation.
(2) Phase difference value Re (550) and Nz coefficient A 50 mm × 50 mm sample was cut out from the retardation film obtained in Examples and Comparative Examples described later and used as a measurement sample, and a surface was used using Axoscan manufactured by Axometrics. The internal phase difference Re (550) was measured. The measurement temperature was 23 ° C. Further, the phase difference Rth (550) in the thickness direction was measured, and the Nz coefficient was calculated.

An example of manufacturing a resin film is shown below.

[Manufacturing Example 1]
To 81.98 parts by mass of isosorbide (hereinafter sometimes abbreviated as "ISB"), 47.19 parts by mass of tricyclodecanedimethanol (hereinafter sometimes abbreviated as "TCDDM") and diphenyl carbonate (hereinafter "" 175.1 parts by mass (sometimes abbreviated as "DPC") and 0.979 parts by mass of a 0.2% by mass aqueous solution of cesium carbonate as a catalyst are put into the reaction vessel, and the first stage of the reaction is carried out under a nitrogen atmosphere. As an eye step, the heating tank temperature was heated to 150 ° C., and the raw materials were dissolved while stirring as necessary (about 15 minutes). Next, the pressure was changed from normal pressure to 13.3 kPa, and the generated phenol was extracted from the reaction vessel while raising the heating tank temperature to 190 ° C. in 1 hour. After holding the entire reaction vessel at 190 ° C. for 15 minutes, as the second step, the pressure inside the reaction vessel is set to 6.67 kPa, the heating tank temperature is raised to 230 ° C. in 15 minutes, and the generated phenol is generated. It was taken out of the reaction vessel. Since the stirring torque of the stirrer increased, the temperature was raised to 250 ° C. in 8 minutes, and the pressure in the reaction vessel was brought to 0.200 kPa or less in order to remove the generated phenol. After reaching a predetermined stirring torque, the reaction was terminated, and the produced reaction product was extruded into water to obtain pellets of a polycarbonate resin. After vacuum-drying the obtained polycarbonate resin at 80 ° C. for 5 hours, a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 ° C.), T-die (width 300 mm, set temperature: 250 ° C.), chill roll ( A polycarbonate resin film (1) having a thickness of 90 μm was produced using a film-forming device equipped with a set temperature (120 to 130 ° C.) and a winder. Tg was 130 ° C.

[Manufacturing Example 2]
Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with a stirring blade and a reflux condenser controlled at 100 ° C. Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane 29.60 parts by mass (0.046 mol), isosorbide (ISB) 29.21 parts by mass (0.200 mol), spiroglycol (SPG) 42 .28 parts by weight (0.139 mol), diphenyl carbonate (DPC) 63.77 parts by weight (0.298 mol) and calcium acetate monohydrate 1.19 × ^{10 -2} parts by weight as a catalyst (6.78 × 10 ^{- 5} mol) was charged. After substituting nitrogen under reduced pressure in the reactor, heating was performed with a heat medium, and stirring was started when the internal temperature reached 100 ° C. The internal temperature was brought to 220 ° C. 40 minutes after the start of the temperature rise, and the depressurization was started at the same time as controlling to maintain this temperature, and the temperature was adjusted to 13.3 kPa 90 minutes after reaching 220 ° C. The phenol vapor produced as a by-product of the polymerization reaction was guided to a reflux condenser at 100 ° C., the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the uncondensed phenol vapor was guided to a condenser at 45 ° C. for recovery. Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature rise and depressurization in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Then, the polymerization was allowed to proceed until the stirring power became a predetermined value. When the predetermined power was reached, nitrogen was introduced into the reactor to repressurize, the produced polyester carbonate-based resin was extruded into water, and the strands were cut to obtain pellets.
The obtained polyester carbonate-based resin (pellets) was vacuum-dried at 80 ° C. for 5 hours, and then a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 ° C.), T-die (width 200 mm, set temperature: 250). A long reverse-dispersed polycarbonate resin film (2) having a thickness of 130 μm was produced using a film-forming device equipped with a chill roll (set temperature: 120 to 130 ° C.) and a winder. Tg was 140 ° C.

[Manufacturing Example 3]
As the resin film (3), a commercially available cyclic olefin resin film (manufactured by Zeon Corporation, trade name "Zeonoa ZF14") was used. The thickness was 40 μm and the Tg was 136 ° C.

[Manufacturing Example 4]
As the resin film (4), a commercially available cyclic olefin resin film (manufactured by JSR Corporation, trade name “Arton (R5000)”) was used. The thickness was 130 μm and the Tg was 137 ° C.

[Example 1]
1. 1. Step of heating the resin film to obtain an intermediate film (first step)
The polycarbonate resin film (1) obtained in Production Example 1 was heated at 110 ° C. for 60 seconds using a tenter and an IR heater to obtain an intermediate film. The obtained intermediate film was subjected to the evaluation of (2) above. The value of Re (550) of the intermediate film after heating was 1 nm, and the increase of Re (550) was 0 nm.

2. Winding process of intermediate film 1. The intermediate film obtained in (1) was wound around an axis orthogonal to the transport direction to form a roll body. The roll was stored for 48 hours.

3. 3. Intermediate film stretching step (second step)
Above 2. The intermediate film wound in 1 was subjected to uniaxial stretching at a fixed end to obtain a retardation film. The stretching temperature was 145 ° C., and the stretching ratio was 1.5 times. The obtained retardation film was subjected to the evaluations (1) and (2) above. The results are shown in Table 1.

[Examples 2 to 8 and 17 to 30, and Comparative Examples 2 to 4 and 9 to 10]
Implementation except that the resin films of numbers (1) to (4) shown in Table 1 were used, and the heating conditions of the first step and the stretching conditions of the second step shown in Table 1 were adopted. A retardation film was produced in the same manner as in Example 1. The obtained retardation film was subjected to the evaluations (1) and (2) above. The results are shown in Table 1.

[Examples 9 to 16 and 31 to 44, and Comparative Examples 5 to 8 and 11 to 12]
Above 3. A shrinkable film having a thickness of 60 μm (manufactured by Toray Industries, Inc., trade name “Trefan BO2873”) was attached to one side of the intermediate film wound up in the above via an acrylic pressure-sensitive adhesive layer (thickness 15 μm). The intermediate film and the shrinkable film were bonded together, the resin films of numbers (1) to (4) shown in Table 1 were used, and the heating conditions of the first step shown in Table 1 and A retardation film was produced in the same manner as in Example 1 except that the stretching conditions of the second step were adopted.

<Evaluation>
It can be seen that the retardation film heated in the first step is superior in appearance and retardation development as compared with the retardation film not heated in the first step (Examples 1 and 2 and Comparative Examples). 1. Comparison between Examples 3 to 4 and Comparative Example 2, Examples 5 to 6 and Comparative Example 3, Comparison between Examples 7 to 8 and Comparative Example 4, and Examples 17 to 23 and Comparative Example 9 and Example 24. Comparison between ~ 30 and Comparative Example 10). Further, it can be seen that the same result is obtained even when the step of laminating with the shrinkable film is performed (Examples 9 to 10 and Comparative Example 5, Examples 11 to 12 and Comparative Example 6). Comparison of Examples 13 to 14 with Comparative Example 7, Examples 15 to 16 with Comparative Example 8, and Examples 31 to 37 with Comparative Example 11, and Examples 38 to 44 with Comparative Example 12).
Further, it can be seen that even if the heating temperature in the first step is Tg or less of the resin film, excellent appearance and phase difference development can be obtained by setting the heating time to 30 seconds or more (implementation). Examples 19, 26, 33 and 40). Further, it can be seen that when the heating temperature in the first step is a temperature equal to or higher than Tg of the resin film, excellent appearance and phase difference development can be obtained by setting the heating time to 10 seconds or longer (Example). 23, 30, 37 and 44).

The retardation film according to the embodiment of the present invention can be suitably used for an image display device.

Claims (9)

It has a first step of heating a resin film to obtain an intermediate film and a second step of applying a stretching treatment to the intermediate film.
A method for manufacturing a retardation film. An intermediate film winding step is further included between the first step and the second step.
The method for producing a retardation film according to claim 1. The heating temperature in the first step is (Tg + 25 ° C.) / 2 or more.
The method for producing a retardation film according to claim 1 or 2. The heating temperature in the first step is Tg or higher,
The increase in Re (550) of the intermediate film with respect to the resin film before heating is 10 nm or less.
The method for producing a retardation film according to claim 3. The heating time of the first step is 10 seconds to 180 seconds.
The method for producing a retardation film according to any one of claims 3 or 4. The heating time of the first step is 30 seconds to 120 seconds.
The method for producing a retardation film according to claim 5. The heating temperature of the first step is higher than the stretching temperature of the second step.
The method for producing a retardation film according to any one of claims 3 to 6. A step of adhering a shrinkable film to form a laminate is included between the first step and the second step.
The method for producing a retardation film according to any one of claims 1 to 7. Prior to the first step, a step of adhering the resin film to the shrinkable film to form a laminate, or a step of applying a coating liquid in which the resin is dissolved or dispersed in a solvent to the shrinkable film is included.
The increase in Re (550) of the intermediate film with respect to the resin film before heating is 10 nm or less.
The method for producing a retardation film according to any one of claims 1 to 7.