KR101938413B1 - Optical film and flexible display device including the same - Google Patents

Abstract

The optical film of the embodiments of the present invention includes a polarizer and a retardation layer laminated on one side of the polarizer and including a half-wave retardation layer and a quarter-wave retardation layer. The absorption axis of the polarizer is orthogonal on the same plane as the folding axis, and the quarter wave phase slow axis of the half wave phase retardation half wave retardation layer and the quarter wave retardation layer of half wave retardation are disposed between the absorption axis and the folding axis. The axial and axial design of the polarizer and phase difference layer can improve the bending and reflection reducing properties.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film and a flexible display device including the optical film.

The present invention relates to an optical film and a flexible display device including the optical film. More particularly, the present invention relates to an optical film including a polarizer and a flexible display device including the optical film.

2. Description of the Related Art [0002] Recently, a variety of devices, such as a liquid crystal display device, a plasma display panel device, an electro luminescent display device, an organic light-emitting diode display device, Display devices are being developed to meet various demands such as thinning and lightening.

Since the external light is reflected or scattered on the image display surface of the display device when external light is present in the display device, the original image displayed on the display device is not easily seen. Therefore, an optical film including a retardation film and a polarizer can be incorporated into the display device for improving image or image quality.

2. Description of the Related Art In recent years, a flexible display device capable of folding or bending has been developed while the display device is applied to a portable device such as a mobile phone, a PDA, a notebook computer, and the like. In this case, the optical film is also folded together during the folding or bending operation, and when the optical film having relatively poor folding durability is damaged, the desired polarization and antireflection effect may not be realized. In addition, the folding or bending may disturb the optical designs (for example, various optical axis arrangements) set in manufacturing the optical film, resulting in discoloration or the like.

For example, Korean Patent Laid-Open Publication No. 2013-0110204 discloses a polarizing plate for realizing an image with high contrast. The optical film design according to the above-described flexible characteristic is not considered.

Korean Patent Publication No. 10-2013-0110204

An object of the present invention is to provide an optical film excellent in folding and optical reliability.

An object of the present invention is to provide a flexible display device including an optical film excellent in folding and optical reliability.

1. polarizer; And a retardation layer laminated on one surface of the polarizer and including a half-wave retardation layer and a quarter-wave retardation layer,

The absorption axis of the polarizer is orthogonal on the same plane as the folding axis, and the half-wave retardation axis of the half-wave retardation and the quarter-wave retardation axis of the quarter wave retardation layer are the same among the regions divided by the absorption axis and the folding axis Is disposed in the region.

2. The polarizer of claim 1, wherein the polarizer is divided into a first quadrant, a second quadrant, a third quadrant and a fourth quadrant in which the same plane is sequentially arranged in a counterclockwise direction by an absorption axis and a folding axis of the polarizer,

The slow axis of the half-wave retardation layer and the slow axis of the quarter-wave retardation layer are disposed in the second quadrant and the fourth quadrant.

3. The method of claim 2, wherein a first inclination angle formed by the slow axis of the half-wave retardation layer in a counterclockwise direction from the folding axis portion between the first quadrant and the second quadrant is defined,

And a second inclination angle formed by the slow axis of the quarter wave retardation layer in a counterclockwise direction from the folding axis portion between the first quadrant and the second quadrant is defined.

4. The optical film as in 3 above, wherein the second inclination angle is larger than the first inclination angle.

5. The optical film of claim 4, wherein the first inclination angle is about 7 to 30 ^degrees and the second inclination angle is about 65 to 85 ^degrees .

6. The optical film as in 1 above, wherein the half-wave retardation layer and the quarter-wave retardation layer are sequentially disposed from the polarizer.

7. The optical film according to 6 above, further comprising a protective film formed on at least one of the upper surface or the lower surface of the polarizer.

8. The optical film as in 1 above, wherein the polarizer comprises a stretched polyvinyl alcohol resin.

9. The optical film of claim 8, wherein the folding axis is orthogonal to the stretching direction of the polarizer.

10. A flexible display device comprising the optical film of any one of claims 1 to 9.

According to the embodiments of the present invention, it is possible to arrange the absorption axis of the polarizer perpendicularly to the folding axis of the optical film to prevent distortion in the polarization direction upon folding or bending, and to suppress mechanical damage in the polarizer.

In addition, the half-wave retardation film and the quadruple-wavelength retardation film are disposed between the absorption axis of the polarizer and the folding axis of the optical film, so that discoloration caused by axial disturbance due to folding can be suppressed.

1 is a schematic cross-sectional view of an optical film according to exemplary embodiments;
2 is a plan view showing the axial orientation in an optical film according to exemplary embodiments;
3 is a schematic diagram illustrating a window stack and a flexible display device in accordance with exemplary embodiments.
Figs. 4 and 5 are plan views showing the axial orientation in the optical film according to the comparative examples. Fig.

According to embodiments of the present invention, an optical film is provided that includes a polarizer having an absorption axis perpendicular to the folding axis, and has excellent flexible characteristics and optical reliability. Further, a flexible display including the optical film is provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Should not be construed as limiting

1 is a schematic cross-sectional view illustrating an optical film according to exemplary embodiments.

1, the optical film 50 may include a quarter wavelength (λ / 4) retardation layer 110, a half wavelength (λ / 2) retardation layer 120 and a polarizer 130 which are sequentially stacked have.

The quartic wave-length retardation layer 110 and the half-wave retardation layer 120 each output a phase delay of 1/4 and 1/2 with respect to the component that vibrates the incident light? In the slow axis direction. Thus, reflection of light incident from the outside of the display device can be suppressed.

The term " slow axis " used in the present application means an optical axis having a phase difference generated in the retardation layer.

The quarter wavelength retardation layer 110 and the half-wave retardation layer 120 may be formed of, for example, a film type or a liquid crystal coating layer. The film type retardation layer can be obtained, for example, by orienting the polymer film in the uniaxial direction, the biaxial direction, or other suitable method of the present invention. For example, the polymer film may be formed of any one selected from the group consisting of a cyclic polymeric olefin (COP), a polycarbonate, a polyester, a polysulfone, a polyether sulfone, a polystyrene, a polyolefin, a polyvinyl alcohol, a cellulose acetate, Methacrylate-based, polyvinyl chloride-based, polyacrylate-based, and polyamide-based polymers.

The liquid crystal coating layer type retardation layer can be produced through the use of a reactive liquid crystal composition comprising a nematic or a smectic liquid crystal material. For example, the reactive liquid crystal composition can be prepared by coating on a substrate, orienting the liquid crystal composition in a plane orientation, and exposing it to heat or ultraviolet light to induce polymerization.

The quarter wavelength retardation layer 110 and the half wavelength retardation layer 120 may have reverse wavelength dispersion, flat wavelength dispersion, or regular wavelength dispersion.

For example, the value of Ro (450 nm) / Ro (550 nm) may range from about 0.7 or more to less than 0.99 when the quaternary wavelength retardation layer 110 and the half wavelength retardation layer 120 have reverse wavelength dispersion properties. For example, the value of Ro (450 nm) / Ro (550 nm) may range from about 0.99 to less than 1.01 when the quarter wavelength retardation layer 110 and the half wavelength retardation layer 120 have flat wavelength dispersibility. For example, the value of Ro (450 nm) / Ro (550 nm) may range from about 1.01 to 2 when the quarter wavelength retardation layer 110 and the half wavelength retardation layer 120 have a regular wavelength dispersibility.

For example, the polarizer 130 may be a film in which a dichroic dye is adsorbed and oriented on a stretched polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin can be obtained by saponifying a polyvinyl acetate-based resin.

Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, or copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with the vinyl acetate include an acrylamide monomer having a small unsaturated carboxylic acid type, an unsaturated sulfonic acid type, an olefin type, a vinyl ether type, and an ammonium group.

The polyvinyl alcohol resin may be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of saponification of the polyvinyl alcohol-based resin may be 85 to 100 mol%, preferably 98 mol% or more. The polymerization degree of the polyvinyl alcohol-based resin may be about 1,000 to 10,000, and preferably 1,500 to 5,000.

The above-mentioned polyvinyl alcohol-based resin film can be used as the original film of the polarizer 130. The thickness of the original film may be, for example, 10 to 150 mu m.

In some embodiments, the polarizer 130 may include a process of uniaxially stretching a polyvinyl alcohol-based film continuously in an aqueous solution, a process of dyeing and adsorbing with a dichroic dye, a process of treating with an aqueous solution of boric acid, ≪ / RTI >

A protective film may be formed on at least one surface of the polarizer 130. In some embodiments, the first protective film 142 and the second protective film 144 may be formed on the bottom and top surfaces of the polarizer 130, respectively. 1, the polarizing plate 150 can be defined by the protective films 142 and 144 bonded on the bottom and top surfaces of the polarizer 130 and the polarizer 130. As shown in FIG.

The protective films 142 and 144 may include a resin film excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropic properties. For example, the protective films 142 and 144 may be acrylic resin films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Polyester based resin films such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and polybutylene terephthalate; Cellulose-based resin films such as diacetylcellulose and triacetylcellulose; A polyolefin-based resin having a polyethylene, polypropylene, cyclo- or norbornene structure, and a polyolefin-based resin film such as an ethylene-propylene copolymer.

In some embodiments, the protective films 142 and 144 may be attached to the polarizer 130 via a point-adhesive layer. For example, the pressure-sensitive adhesive layer may be formed by coating a photocurable pressure-sensitive adhesive composition on the adherend surface of the polarizer 130 or the protective films 142 and 144 and attaching the pressure-sensitive adhesive composition to each other, .

The photocurable adhesive composition may include a photopolymerizable compound, a photopolymerization initiator, and a solvent.

The photopolymerizable compound may include a photo-radical polymerizable compound or a photo-cationic polymerizable compound. Preferably, the photo-radical polymerizable compound or photo-cationic polymerizable compound may be used together.

Examples of the photopolymerization initiator include photo radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin and benzoin alkyl ether; And / or a photocationic polymerization initiator such as an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodo aluminum salt, a benzoin sulfonic acid ester compound and the like.

The primer treatment, the plasma treatment, the corona treatment, and the saponification (alkali) surface treatment may be performed on the adhered surface of the polarizer 130 and / or the protective films 142 and 144 in order to improve the adhesion through the viscous adhesive layer have.

In some embodiments, the polarizing plate 150 and the half-wave retardation layer 120 may also be bonded via a point-adhesive layer.

1, the half-wave retardation layer 120 and the quadrature-wavelength retardation layer 120 are sequentially arranged below the polarizer 150. However, depending on the application to which the optical film 50 is applied and the optical properties to be implemented, The order may change.

In some embodiments, the optical film 50 may further include a substrate on the top surface of the polarizer 150 or below the retardation layer (e.g., the quarter wavelength retardation layer 110). The cage may be, for example, selected from the group consisting of a cyclic olefin polymer (COP), polyethylene terephthalate (PET), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyphenylene sulfide (PAS), cellulose triacetate (TAC), polycarbonate (PC), cyclic olefin copolymer (COC), polyarylate, polyallylate, polyimide (PI), cellulose acetate propionate And a transparent resin film such as polymethyl methacrylate (PMMA).

2 is a plan view showing the axial orientation in an optical film according to exemplary embodiments;

2 shows the absorption axis 70 of the polarizer 130 or the polarizer 150 shown in Fig. 1, the retardation axis of the half-wave retardation layer 120 (Fig. 80) (hereinafter, abbreviated as a half-wave phase slow axis) and a slow axis 90 (hereinafter, abbreviated as a quarter wave phase slow axis) of the quarter wave retardation layer 110 are projected in the same plane have.

Referring to Fig. 2, the plane can be divided into four quadrants by the polarizer absorption axis 70 and the folding axis 60 of the optical film 50. Fig. As shown in FIG. 1, the quadrants may be divided into a first quadrant A, a second quadrant B, a third quadrant C, and a fourth quadrant D arranged counterclockwise.

According to exemplary embodiments, the polarizer absorption axis 70 and the folding axis 60 may be substantially coplanar with each other. The term "orthogonal" as used in the present application is used not only in mathematical orthogonality but also in a range that permits an error that can be derived from the manufacturing process of the optical film 50. [ For example, "orthogonal " may encompass a range of ± 5 ^o or ± 10 ^o .

The folding shaft 60 may correspond to a reference or guide axis on which the folding or bending of the flexible display device into which the optical film 50 is inserted is performed. For example, the flexible display device may be bent with respect to a line parallel to the folding axis 60. The polarizer absorption axis 70 may be, for example, the stretching direction of the polyvinyl alcohol-based film described above. In this case, the folding axis 60 may substantially correspond to the transmission axis of the polarizer 130.

As the polarizer absorption axis 70 is arranged orthogonal to the folding axis 60, when the optical film 50 is folded or bent with the folding axis 60 as a reference line, the bending stress is directed in the direction of the polarizer absorption axis 70 Can be dispersed in parallel. Therefore, mechanical defects such as cracks in the polarizer 130 due to the bending stress can be reduced. In addition, discoloration due to disturbance of optical characteristics can be suppressed by the bending stress.

According to exemplary embodiments, the half-wave ground axle 80 and the quarter wave ground axle 90 may be disposed between the folding axis 60 and the polarizer absorption axis 70. In some embodiments, the half-wave ground axle 80 and the quarter wave geomagnetic axis 90 may be disposed in the same one of the areas divided by the folding axis 60 and the polarizer absorption axis 70.

2, the half-wave ground axle 80 and the quadrant wave ground axes 90 are arranged in a second quadrant B defined by the folding axis 60 and the polarizer absorption axis 70. For example, And the fourth quadrant (D).

The first inclination angle [theta] 1 can be defined by the folding axis 60 and the half-wave ground axis 80. [ For example, the first inclination angle? 1 is defined as a counterclockwise angle formed by the half-wave ground shaft 80 and the folding axis 60 portion between the first quadrant A and the second quadrant B .

The second inclination angle [theta] 2 may be defined by the folding axis 60 and the quadrant wave slow axis 90. [ For example, the second inclination angle [theta] 2 is defined as a counterclockwise angle formed by the quadrant wave slow axis 90 and the portion of the folding axis 60 between the first quadrant A and the second quadrant B .

According to exemplary embodiments, the second inclination angle [theta] 2 may be larger than the first inclination angle [theta] 1. Thus, the half-wave ground shaft 80 and the quarter-wave ground shaft 90 are sequentially arranged counterclockwise from the folding shaft 60 portion between the first quadrant A and the second quadrant B .

In some embodiments, the first inclination angle (θ1) may be about 7 to 30 ^o range, and the second inclination angle (θ2) may be about 65 to 85 ^o range.

Preferably, the first inclination angle (θ1) may be about 17.5 ^o, the may be a second inclined angle (θ2) is about 77.5 ^o. The angle values or ranges described above should be interpreted as including mathematical or process errors, and may include, for example, errors in the range of +/- 1 ^o or +/- 2 ^o .

As described above, the half-wave retardation axis 80 and the quadrant wave retardation axis 90 can be sequentially arranged in a state in which the polarizer absorption axis 70 is arranged to be orthogonal to the folding axis 60. Accordingly, it is possible to realize a desired antireflection characteristic in a state in which the discoloration phenomenon is suppressed while ensuring crack resistance even in a bending or folding operation.

3 is a schematic diagram illustrating a window stack and a flexible display device in accordance with exemplary embodiments. The window laminate 250 may include a window substrate 230, an optical film 210, and a touch sensor 200.

The window substrate 230 includes, for example, a hard coating film, and in one embodiment, a light shielding pattern 235 may be formed on the peripheral portion of one side of the window substrate 230. The light-shielding pattern 235 may include, for example, a color printing pattern, and may have a single layer or a multi-layer structure. The bezel portion or the non-display region of the image display apparatus can be defined by the shielding pattern 235. [

The optical film 210 may include a polarizer, a half-wave retardation layer, and a quarter-wave retardation layer so as to have an orientation of the axes according to the above-described exemplary embodiments. The optical film 210 may be directly bonded to the one side of the window substrate 230 or may be attached through the first adhesive layer 220.

The touch sensor 200 may be included in the window laminate 230 in the form of a film or a panel. In one embodiment, the touch sensor 200 may be coupled to the optical film 210 via a second point-of-use adhesive layer 225.

3, the window substrate 230, the optical film 210, and the touch sensor 200 may be disposed in this order from the viewer side of the user. In this case, since the sensing electrodes of the touch sensor 200 are disposed under the optical film 210, the phenomenon of pattern visibility can be more effectively prevented. In one embodiment, the window substrate 230, the touch sensor 200, and the optical film 210 may be disposed in this order from the viewer's side.

The image display device may include the above-described window stack 250 coupled to the display panel 360 and the display panel 360.

The display panel 360 includes a pixel electrode 310, a pixel defining layer 320, a display layer 330, an opposite electrode 340, and an encapsulation layer 350 disposed on the panel substrate 300 .

The panel substrate 300 may comprise, for example, a soluble resin material such as polyimide, whereby a flexible display device capable of being folded as indicated by the arrows may be implemented.

On the panel substrate 300, a pixel circuit including a thin film transistor (TFT) is formed, and an insulating film covering the pixel circuit can be formed. The pixel electrode 310 may be electrically connected to the drain electrode of the TFT, for example, on the insulating film.

The pixel defining layer 320 may be formed on the insulating layer to define the pixel region by exposing the pixel electrode 310. The display layer 330 may be formed on the pixel electrode 310, and may include a liquid crystal layer or an organic light emitting layer, for example.

The counter electrode 340 may be disposed on the pixel defining layer 320 and the display layer 330. The counter electrode 340 may be provided, for example, as a common electrode or a cathode of an image display apparatus. An encapsulation layer 350 for protecting the display panel 360 may be laminated on the counter electrode 340.

In some embodiments, the display panel 360 and the window laminate 250 may be bonded via the lacquer layer 260.

The optical film 210 can be applied to, for example, a circularly polarizing plate, an anti-reflection film, or the like of the flexible display device. A highly reliable flexible display device capable of realizing a desired high resolution image can be realized by reducing the external light reflection and discoloration phenomenon through the above-described axial orientation design.

Hereinafter, exemplary embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the present invention is not limited to the accompanying claims, It will be apparent to those skilled in the art that various changes and modifications can be made in the embodiments within the scope of the claims, and such variations and modifications are within the scope of the appended claims.

Production of Polarizer

(PE60, KURARAY) having a degree of saponification of 99.9% or more was immersed in water (deionized water) at 30 DEG C for 2 minutes and swelled. Then, 1.25 mM / L of iodine and 1.25 wt% of potassium iodide, And dipped in a dyeing solution at 30 占 폚 containing 0.0005% by weight for 4 minutes. Specifically, in the swelling and dyeing steps, the stretching was performed at a stretching ratio of 1.3 times and 1.4 times, respectively, and the stretching ratio to the dyeing bath was 1.82 times.

Subsequently, it was immersed (crosslinked first) for 30 seconds in an aqueous solution for crosslinking at 50 DEG C containing 10% by weight of potassium iodide and 3.7% by weight of boric acid, and stretched at a draw ratio of 2, while being crosslinked. Thereafter, the resultant was immersed in a crosslinking aqueous solution at 50 DEG C containing 10 wt% of potassium iodide and 3.7 wt% of boric acid for 20 seconds (second crosslinking), and was stretched at a draw ratio of 1.5 times while being crosslinked (the accumulation of the first crosslinking and the second crosslinking The stretching ratio is 3 times). The total cumulative stretching ratio of the swelling, dyeing and crosslinking steps was adjusted to be 5.46 times. The crosslinked polyvinyl alcohol film was dried in an oven at 70 DEG C for 4 minutes to prepare a polarizer. A protective film was attached to one surface of the polarizer to prepare a polarizing plate.

Example

A coating type half-wave retardation layer and a coating type quarter-wave retardation layer were formed sequentially (within a thickness of 2 탆) using a liquid crystal composition (manufactured by Fuji Film Co., Ltd., trade name: QL) on the polarizing plate prepared as described above. The arrangement of the half-wave ground axes and the quadruple wave ground axes was arranged as shown in Fig. The prepared optical film was cut so that the absorption axis (stretching direction) of the polarizing plate was 0 ^° , and the absorption axis of the polarizing plate was aligned perpendicular to the folding axis.

Comparative Example 1

An optical film was produced in the same manner as in Example, except that the orientation of the absorption axis, half-wave slow axis and quadrupole slow axis of the polarizing plate was changed as shown in Fig.

Comparative Example 2

An optical film was produced in the same manner as in Example, except that the orientation of the absorption axis, half-wave slow axis and quadrupole slow axis of the polarizing plate was changed as shown in Fig.

The specific angles of the axis alignments in the examples and comparative examples are as shown in Table 1.

Experimental Example

(1) Evaluation of bending durability

The optical films of the examples and comparative examples were evaluated for crack occurrence after performing a bending test of 1R (curvature radius) at 60 ° C and 93% relative humidity using a folding evaluation equipment (CFT-720C, COVOTECH) Table 1 shows the following.

○: No crack occurred

×: occurrence of crack (number of folding at which cracking occurs)

(2) Evaluation of discoloration

After the optical films of the examples and comparative examples were folded about the folding axis, a reflection layer (Al-Foil) was bonded to the lower part of the optical film to confirm discoloration. The results are shown in Table 1 below.

○: no discoloration occurred

X: Discoloration observation (number of times of folding in which cracks occur)

Folding side and absorption axis angle First inclination angle
(? 1) Second inclination angle
(? 2) Crack evaluation Discoloration evaluation Example
(Fig. 2) 90 ^o 17.5 ^o 77.5 ^o ○ ○ Comparative Example 1
(Figure 4) 135 ^o 62.5 ^o 122.5 ^o ×
(1,200 times) ×
(Reddish) Comparative Example 2
(Fig. 5) 45 ^o 152.5 ^o 32.5 ^o ×
(1,200 times) ×
(Bluish)

Referring to Table 1, it can be seen that the absorption axis and the folding axis of the polarizing plate are arranged vertically to improve the crack resistance. Further, in the comparative examples, blue or red shifts were observed together as the arrangement of the slow axis was distorted from the Examples.

50: Optical film 110: Half wavelength retardation layer
120: quarter wavelength retardation layer 130: polarizer
142: first protective film 144: second protective film
150: polarizer

Claims (9)

A polarizer; And
And a retardation layer laminated on one side of the polarizer and including a half-wave retardation layer and a quarter-wave retardation layer,
The absorption axis of the polarizer is orthogonal on the same plane as the folding axis and the slow axis of the half wave retardation layer and the slow axis of the quarter wave retardation layer are arranged in the same one of the areas divided by the absorption axis and the folding axis And,
A second quadrant, a third quadrant and a fourth quadrant in which the same plane is sequentially arranged in a counterclockwise direction by an absorption axis and a folding axis of the polarizer,
The slow axis of the half-wave retardation layer and the slow axis of the quarter-wave retardation layer are disposed in the second quadrant and the fourth quadrant.
delete The method of claim 1, wherein a first inclination angle formed by the slow axis of the half-wave retardation layer is defined in a counterclockwise direction from the folding axis portion between the first quadrant and the second quadrant,
And a second inclination angle formed by the slow axis of the quarter wave retardation layer in a counterclockwise direction from the folding axis portion between the first quadrant and the second quadrant is defined.
The optical film according to claim 3, wherein the second inclination angle is larger than the first inclination angle.
5. The optical film according to claim 4, wherein the first inclination angle is 7 to 30 ^degrees and the second inclination angle is 65 to 85 ^degrees .
The optical film according to claim 1, wherein the half-wave retardation layer and the quarter-wave retardation layer are sequentially disposed from the polarizer.
The optical film according to claim 6, further comprising a protective film formed on at least one of the upper surface or the lower surface of the polarizer.
The optical film of claim 1, wherein the polarizer comprises a stretched polyvinyl alcohol resin.
A flexible display device comprising an optical film according to any one of claims 1 to 7.

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