JP6920047B2 - Circularly polarizing plate and flexible image display device using it - Google Patents

Description

The present invention relates to a circularly polarizing plate and a flexible image display device using the circularly polarizing plate.

In recent years, there are increasing opportunities for smart devices such as smartphones and display devices such as digital signage and window displays to be used under strong external light. Along with this, problems such as external light reflection by the display device itself or a touch panel unit used for the display device, a glass substrate, a reflector such as a metal wiring, and reflection of the background have arisen. In particular, an organic electroluminescence (EL) display device that has been put into practical use in recent years tends to cause problems such as reflection of external light and reflection of a background because it has a highly reflective metal layer. Therefore, it is known to prevent these problems by providing a circularly polarizing plate having a retardation film (typically a λ / 4 plate) as an antireflection film on the visual recognition side.

By the way, with regard to organic EL display devices, practical application of organic EL display devices having a flexible or bendable (foldable) configuration is being promoted by taking advantage of features not found in liquid crystal display devices. However, the use of conventional circularly polarizing plates has the problem that undesired bending and / or warpage occurs in the organic EL display device.

Japanese Unexamined Patent Publication No. 2010-139548 Japanese Unexamined Patent Publication No. 2003-207640 Japanese Unexamined Patent Publication No. 2004-226842 Patent No. 3815790 Japanese Unexamined Patent Publication No. 2014-170221

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to reduce curl due to both state change and aging, and when applied to a flexible image display device, the image display device. It is an object of the present invention to provide a circularly polarizing plate capable of suppressing undesired bending and warping.

The circularly polarizing plate of the present invention has a first protective layer, a polarizer, a second protective layer, and a retardation layer having an in-plane retardation Re (550) of 80 nm to 200 nm in this order. The moisture permeability of the second protective layer at 40 ° C. and 92% relative humidity is less than ^{160 g / m 2 / 24H.} This circularly polarizing plate is used in a flexible image display device.
In one embodiment, the second protective layer is omitted and the retardation layer also serves as the protection layer for the polarizer, and the moisture permeability of the retardation layer at 40 ° C. and 92% relative humidity is 160 g / m. It is less than ^{2 / 24H.}
In one embodiment, the angle θ formed by the absorption axis of the polarizer and the slow axis of the retardation layer is 35 ° to 55 °.
In one embodiment, the circularly polarizing plate further has a hard coat layer on the outside of the first protective layer.
In one embodiment, the circularly polarizing plate further has an adhesive layer on the outermost side of the retardation layer side, and a release liner is temporarily attached to the surface of the adhesive layer.
In one embodiment, the circularly polarizing plate has a surface protective film temporarily attached to the outermost surface on the side of the first protective layer.
In one embodiment, the circularly polarizing plate is provided with the release liner and the surface protective film temporarily attached; the release liner is peeled off and the surface protective film is temporarily attached; and the surface protective film is temporarily attached. In each state where the release liner and the surface protective film have been peeled off, the curl amount is within ± 6 mm when placed in an environment of 25 ° C. ± 5 ° C. and a relative humidity of 55% ± 10% for 72 hours. ..
According to another aspect of the present invention, a flexible image display device is provided. This image display device includes the above-mentioned circularly polarizing plate.

According to the present invention, the state change (typically, peeling of the surface protective film and / or peeling of the release liner) is performed by optimizing the moisture permeability of the layer adjacent to the display cell side of the polarizing element in the circularly polarizing plate. ) And the change with time can realize a circularly polarizing plate having a small curl. As a result, when the circularly polarizing plate is applied to a flexible image display device, undesired bending and warpage of the image display device can be satisfactorily suppressed.

It is a schematic cross-sectional view of the circularly polarizing plate according to one Embodiment of this invention.

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. Overall Configuration of Circular Polarizing Plate The circularly polarizing plate according to the embodiment of the present invention can be typically used in a flexible image display device (typically, an organic EL display device). FIG. 1 is a schematic cross-sectional view of a circularly polarizing plate according to one embodiment of the present invention. The circularly polarizing plate 100 of the present embodiment has a first protective layer 11, a polarizer 20, a second protective layer 12, and a retardation layer 30 in this order. In the circularly polarizing plate 100, typically, the first protective layer 11 is on the viewing side, and the retardation layer 30 is on the display cell side of the image display device. The in-plane retardation Re (550) of the retardation layer 30 is 80 nm to 200 nm. The retardation layer 30 typically functions as a so-called λ / 4 plate. The angle θ formed by the absorption axis of the polarizer 20 and the slow axis of the retardation layer 30 is typically 35 ° to 55 °, preferably 38 ° to 52 °, and more preferably 42 ° to 42 °. It is 48 °, more preferably about 45 °.

In one embodiment, the circularly polarizing plate 100 may further have a hard coat layer 40 on the outside of the first protective layer 11 as shown in the illustrated example. In one embodiment, the circularly polarizing plate 100 may further have another retardation layer (not shown). The optical characteristics (for example, in-plane phase difference, thickness direction phase difference, Nz coefficient, refractive index characteristic), number, combination, arrangement position, and the like of another retardation layer can be appropriately set according to the purpose. In one embodiment, the circularly polarizing plate 100 may further have a conductive layer or an isotropic base material with a conductive layer (neither shown). In this case, the circular polarizing plate can be applied to a so-called inner touch panel type input display device in which a touch sensor is incorporated between a display cell (for example, an organic EL cell) and the polarizing plate.

Practically, the circularly polarizing plate 100 may further have the pressure-sensitive adhesive layer 50 on the outermost side on the retardation layer 30 side as shown in the illustrated example. Since the pressure-sensitive adhesive layer is provided in advance, it can be easily attached to another optical member (for example, a display cell of an image display device). In this case, it is preferable that the release liner 60 is temporarily attached to the surface of the pressure-sensitive adhesive layer 50 to protect the pressure-sensitive adhesive layer 50 until the circularly polarizing plate is used. Further, practically, the circularly polarizing plate 100 may have a surface protective film 70 temporarily attached to the outermost side on the first protective layer 11 side as shown in the illustrated example. The term "surface protective film" as used herein means a film that temporarily protects the circularly polarizing plate during work, and is a protective layer for a polarizing element such as the first protective layer 11 and the second protective layer 12. It is different from (polarizer protective film).

The layers or optical films that make up the circularly polarizing plate are laminated via any suitable adhesive layer (adhesive layer or adhesive layer). A typical example of the adhesive constituting the adhesive layer is a polyvinyl alcohol-based adhesive. A typical example of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive.

In the present invention, the moisture permeability of the second protective layer 12 at 40 ° C. and 92% relative humidity is ^{less than 160 g / m 2} / 24H. In one embodiment of the present invention, the second protective layer 12 is omitted, and the retardation layer 30 can also serve as the protective layer for the polarizer 20. In this case, the moisture permeability of the retardation layer 30 at 40 ° C. and a relative humidity of 92% may be less than ^{160 g / m 2 / 24H.} That is, according to the embodiment of the present invention, the state change (typically, peeling of the surface protective film and / or release liner) is performed by optimizing the moisture permeability of the layer adjacent to the display cell side of the polarizer 20. A circularly polarizing plate having a small curl can be realized by both the peeling) and the change with time. As a result, when the circularly polarizing plate is applied to a flexible image display device, undesired bending and warpage of the image display device can be satisfactorily suppressed. That is, the embodiment of the present invention solves the problem clarified only when a circularly polarizing plate is applied to a flexible (or foldable) image display device. This is because the moisture permeability of the film is affected by both the properties of the constituent material of the film itself and the film thickness, while maintaining the desired optical properties for the layer (film) adjacent to the display cell side of the polarizer. It is an unexpectedly excellent effect obtained by repeating trial and error for optimizing the material and thickness. The moisture permeability can be measured according to JIS Z 0208 (cup method).

The circularly polarizing plate according to the embodiment of the present invention has (i) a state in which the release liner 60 and the surface protective film 70 are temporarily attached; (ii) a state in which the release liner 60 is peeled off and the surface protective film 70 is temporarily attached. In addition, in each state in which the (iii) release liner 60 and the surface protective film 70 have been peeled off, the environment is 25 ° C. ± 5 ° C. and the relative humidity is 55% ± 10% (typically, a clean room environment). The curl amount when left in the lower) for 72 hours is preferably within ± 6 mm, more preferably within ± 5 mm, and further preferably within ± 4 mm. In particular, the circularly polarizing plate according to the embodiment of the present invention is characterized in that the amount of curl due to the change with time in the state (iii) is small. That is, curl control in the states (i) and (ii) has been conventionally performed, and in the conventional rigid image display device, curl control in these states is sufficient. On the other hand, it has been found that by setting the curl amount due to the change with time in the state (iii) within the above range, bending and warping of the flexible (or foldable) image display device itself can be satisfactorily suppressed. By optimizing the moisture permeability of the layer adjacent to the display cell side of the polarizer as described above, it is possible to control the amount of curl due to the change with time in the state (iii).

The above embodiments may be combined as appropriate, and the components of the above embodiments may be modified in the art. Further, the components in the above embodiment may be replaced with optically equivalent configurations.

Hereinafter, each component of the circularly polarizing plate will be described in more detail.

B. First Protective Layer The first protective layer 11 is formed of any suitable film that can be used as a protective layer for the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

As the thickness of the first protective layer, any appropriate thickness can be adopted as long as the effects of the present invention can be obtained. The thickness of the first protective layer is, for example, 5 μm to 70 μm, preferably 15 μm to 50 μm. When the surface treatment described later is applied, the thickness of the first protective layer is a thickness including the thickness of the surface treatment layer.

The circularly polarizing plate of the present invention is typically arranged on the visible side of an image display device, and the first protective layer 11 is typically arranged on the visible side. Therefore, the first protective layer 11 may be subjected to any appropriate surface treatment depending on the purpose. In one embodiment, a hard coat treatment is performed and the hard coat layer 40 can be provided as described above. Examples of the material constituting the hard coat layer include an acrylic resin (acrylate, urethane acrylate) and an ultraviolet curable resin containing an epoxy resin as a main component. In the hard coat layer, a solution containing a monomer or oligomer of such an ultraviolet curable resin and, if necessary, a photopolymerization initiator and a leveling agent is applied to the first protective layer and dried, and the dried coating is applied. It can be formed by irradiating the layer with light (typically ultraviolet light) and curing it. Other specific examples of the surface treatment include antireflection treatment, anti-sticking treatment, and anti-glare treatment. Further / or, if necessary, the first protective layer 11 is provided with a process for improving visibility when visually recognizing through polarized sunglasses (typically, a (elliptical) circularly polarized light function is imparted. (Giving an ultra-high phase difference) may be applied. By performing such a process, excellent visibility can be realized even when the display screen is visually recognized through a polarized lens such as polarized sunglasses. Therefore, the circularly polarizing plate can be suitably applied to an image display device that can be used outdoors.

C. Polarizer As the polarizer 20, any suitable polarizer can be adopted. For example, the resin film forming the polarizer may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer system partially saponified film. Examples thereof include those which have been dyed and stretched with a bicolor substance such as iodine or a bicolor dye, and polyene-based oriented films such as a dehydrated product of PVA and a dehydrogenated product of polyvinyl chloride. Preferably, since the PVA-based film is excellent in optical properties, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is used.

The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment or while dyeing. Alternatively, it may be stretched and then dyed. If necessary, the PVA-based film is subjected to a swelling treatment, a cross-linking treatment, a washing treatment, a drying treatment and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible not only to clean the dirt and blocking inhibitor on the surface of the PVA-based film, but also to swell the PVA-based film to prevent uneven dyeing. Can be prevented.

Specific examples of the polarizer obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and the resin. Examples thereof include a polarizer obtained by using a laminate with a PVA-based resin layer coated and formed on a base material. The polarizer obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the resin base material. It is produced by forming a PVA-based resin layer on the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further include, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous solution. The obtained resin substrate / polarizer laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), and the resin substrate is peeled off from the resin substrate / polarizer laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of the method for producing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.

The thickness of the polarizer is preferably 25 μm or less, more preferably 1 μm to 22 μm, further preferably 1 μm to 12 μm, and particularly preferably 3 μm to 12 μm. When the thickness of the polarizer is in such a range, curling during heating can be satisfactorily suppressed, and good appearance durability during heating can be obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizer is 43.0% to 46.0%, preferably 44.5% to 46.0%, as described above. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

D. Second Protective Layer The second protective layer 12 has a moisture permeability of ^{less than 160 g / m 2} / 24H as described above at 40 ° C. and a relative humidity of 92%, preferably 155 g / m ² / 24H or less, and more. It is preferably 150 g / m ² / 24H or less. By setting the moisture permeability in such a range, as described above, a circularly polarizing plate having a small curl due to both state change (typically peeling of the surface protective film and / or peeling of the release liner) and aging. Can be realized. The lower limit of the moisture permeability of the second protective layer is, for example, 10 g / m ² / 24H.

The second protective layer is formed of any suitable film that can be used as a protective layer for the polarizer as long as it can have the above-mentioned moisture permeability. A typical example of the material for forming the second protective layer is an acrylic resin. In one embodiment, as the acrylic resin, a (meth) acrylic resin having a glutarimide structure is used. Examples of the (meth) acrylic resin having a glutarimide structure include JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, JP-A-2006-328334, and JP-A-2006. -337491, JP-A-2006-337492, JP-A-2006-337493, JP-A-2006-337569, JP-A-2007-009182, JP-A-2009-161744, JP-A-2010-284840 It is described in the publication. These statements are incorporated herein by reference.

In another embodiment, as the acrylic resin, a (meth) acrylic resin having a lactone ring structure is used. Examples of the (meth) acrylic resin having a lactone ring structure include JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, and JP-A-2005. It is described in Japanese Patent Application Laid-Open No. -146084. These statements are incorporated herein by reference.

The (meth) acrylic resin has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. This is because it can be excellent in durability. The upper limit of Tg of the (meth) acrylic resin is not particularly limited, but is preferably 170 ° C. or lower from the viewpoint of moldability and the like.

The (meth) acrylic resin has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1000 to 20000000, more preferably 5000 to 1000000, still more preferably 1000 to 500000, and particularly preferably 50000 to 500000. Is.

The second protective layer 12 is preferably optically isotropic. As used herein, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. say.

The thickness of the second protective layer is, for example, 15 μm to 35 μm, preferably 15 μm to 25 μm. With such a thickness, the above-mentioned moisture permeability can be realized while maintaining the desired optical characteristics as the protective layer inside (display cell side) of the polarizer.

E. Phase Difference Layer The phase difference layer 30 may have any suitable optical and / or mechanical properties depending on the intended purpose. The retardation layer 30 typically has a slow axis. As described above, the angle θ formed by the slow axis of the retardation layer 30 and the absorption axis of the polarizer 11 is typically 35 ° to 55 °, preferably 38 ° to 52 °, more preferably. Is 42 ° to 48 °, more preferably about 45 °. When the angle θ is in such a range, the retardation layer 30 has a λ / 4 plate as described later, so that it has very excellent circularly polarized light characteristics (as a result, very excellent antireflection characteristics). A circularly polarizing plate can be obtained.

The retardation layer 30 preferably has a refractive index characteristic of nx> ny ≧ nz. The retardation layer is typically provided to impart antireflection characteristics to the polarizing plate, and can function as a λ / 4 plate. The in-plane retardation Re (550) of the retardation layer is 80 nm to 200 nm, preferably 100 nm to 180 nm, and more preferably 110 nm to 170 nm as described above. Here, "ny = nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, ny <nz may be satisfied as long as the effect of the present invention is not impaired.

The Nz coefficient of the retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. .. By satisfying such a relationship, a very excellent reflected hue can be achieved when the obtained circularly polarizing plate is used in an image display device.

The retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, or may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It is also possible to exhibit a flat wavelength dispersion characteristic in which the phase difference value hardly changes depending on the wavelength of the measurement light. In one embodiment, the retardation layer exhibits inverse dispersion wavelength characteristics. In this case, the Re (450) / Re (550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection characteristics can be realized. In another embodiment, the retardation layer exhibits flat wavelength dispersion characteristics. In this case, Re (450) / Re (550) of the retardation layer is preferably 0.99 to 1.03, and Re (650) / Re (550) is preferably 0.98 to 1.02. be.

In the retardation layer, the absolute value of the photoelastic coefficient is preferably 2 × 10 ^-11 m ² / N or less, more preferably 2.0 × 10 ^-13 m ² / N to 1.5 ^{× 10 -11} m ² /. N, more preferably includes a resin of ^{1.0 × 10 -12 m 2 /N~1.2×10 -11} m 2 / N. When the absolute value of the photoelastic coefficient is in such a range, a phase difference change is unlikely to occur when a shrinkage stress occurs during heating. As a result, thermal unevenness of the obtained image display device can be satisfactorily prevented.

When the second protective layer 12 is omitted as described above and the retardation layer 30 also serves as the protective layer for the polarizer 20, the retardation layer has a moisture permeability of 160 g / m as described above at 40 ° C. and 92% relative humidity. ^{It is less than 2} / 24H, preferably 120 g / m ² / 24H or less, and more preferably 100 g / m ² / 24H or less. By setting the moisture permeability in such a range, as described above, a circularly polarizing plate having a small curl due to both state change (typically peeling of the surface protective film and / or peeling of the release liner) and aging. Can be realized. The lower limit of the moisture permeability of the retardation layer is, for example, 10 g / m ² / 24H.

The thickness of the retardation layer is preferably 60 μm or less, preferably 30 μm to 58 μm. With such a thickness, the above-mentioned moisture permeability can be realized while maintaining the desired optical characteristics as a λ / 4 plate imparting a circularly polarized light function.

The retardation layer 30 may be made of any suitable resin film that can satisfy the above characteristics. Typical examples of such resins are cyclic olefin resins, polycarbonate resins, cellulose resins, polyester resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylics. Examples include based resins. When the retardation layer is composed of a resin film exhibiting inverse dispersion wavelength characteristics, a polycarbonate resin can be preferably used, and when the retardation layer is composed of a resin film exhibiting flat wavelength dispersion characteristics, a cyclic olefin resin is preferably used. Can be used.

As the polycarbonate resin, any suitable polycarbonate resin can be used as long as the effects of the present invention can be obtained. Preferably, the polycarbonate resin comprises a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, an alicyclic diol, an alicyclic dimethanol, di, tri or polyethylene glycol, and an alkylene. Includes structural units derived from at least one dihydroxy compound selected from the group consisting of glycols or spiroglycols. Preferably, the polycarbonate resin is derived from a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, a structural unit derived from an alicyclic dimethanol, and / or di, tri or polyethylene glycol. Includes structural units; more preferably structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, and structural units derived from di, tri or polyethylene glycol. The polycarbonate resin may contain structural units derived from other dihydroxy compounds, if desired. Details of the polycarbonate resin that can be suitably used in the present invention are described in, for example, JP-A-2014-10291 and JP-A-2014-26266, and the description is incorporated herein by reference. NS.

（上記一般式（１）および上記一般式（２）中、Ｒ_５およびＲ_６はそれぞれ独立に、直接結合、置換若しくは無置換の炭素数１〜４のアルキレン基（好ましくは、主鎖上の炭素数が２〜３であるアルキレン基）である。Ｒ_７は、直接結合、置換若しくは無置換の炭素数１〜４のアルキレン基（好ましくは、主鎖上の炭素数が１〜２であるアルキレン基）である。Ｒ_８〜Ｒ_１３はそれぞれ独立に、水素原子、置換若しくは無置換の炭素数１〜１０（好ましくは１〜４、より好ましくは１〜２）のアルキル基、置換若しくは無置換の炭素数４〜１０（好ましくは４〜８、より好ましくは４〜７）のアリール基、置換若しくは無置換の炭素数１〜１０（好ましくは１〜４、より好ましくは１〜２）のアシル基、置換若しくは無置換の炭素数１〜１０（好ましくは１〜４、より好ましくは１〜２）のアルコキシ基、置換若しくは無置換の炭素数１〜１０（好ましくは１〜４、より好ましくは１〜２）のアリールオキシ基、置換若しくは無置換の炭素数１〜１０（好ましくは１〜４、より好ましくは１〜２）のアシルオキシ基、置換若しくは無置換のアミノ基、置換若しくは無置換の炭素数１〜１０（好ましくは１〜４）のビニル基、置換若しくは無置換の炭素数１〜１０（好ましくは１〜４）のエチニル基、置換基を有する硫黄原子、置換基を有するケイ素原子、ハロゲン原子、ニトロ基、またはシアノ基である。Ｒ_８〜Ｒ_１３のうち隣接する少なくとも２つの基が互いに結合して環を形成していてもよい。） In one embodiment, a polycarbonate resin containing an oligofluorene structural unit can be used. Examples of the polycarbonate-based resin containing an oligofluorene structural unit include a resin containing a structural unit represented by the following general formula (1) and / or a structural unit represented by the following general formula (2).

(In the general formula (1) and the above general formula (2), R ₅ and R ₆ are independently bonded, substituted or unsubstituted alkylene groups having 1 to 4 carbon atoms (preferably on the main chain). An alkylene group having 2 to 3 carbon atoms). R ₇ is a directly bonded, substituted or unsubstituted alkylene group having 1 to 4 carbon atoms (preferably having 1 to 2 carbon atoms on the main chain). (Alkylene groups). R _{8 to} R ₁₃ are independently hydrogen atoms, substituted or unsubstituted alkyl groups having 1 to 10 carbon atoms (preferably 1 to 4, more preferably 1 to 2), substituted or unsubstituted. Substituted aryl groups having 4 to 10 carbon atoms (preferably 4 to 8, more preferably 4 to 7), substituted or unsubstituted carbon atoms 1 to 10 (preferably 1 to 4, more preferably 1 to 2). Acrylic group, substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms (preferably 1 to 4, more preferably 1-2), substituted or unsubstituted carbon number 1 to 10 (preferably 1 to 4, more preferably). 1 to 2) aryloxy group, substituted or unsubstituted acyloxy group having 1 to 10 carbon atoms (preferably 1 to 4, more preferably 1-2), substituted or unsubstituted amino group, substituted or unsubstituted Vinyl group having 1 to 10 carbon atoms (preferably 1 to 4), ethynyl group having 1 to 10 (preferably 1 to 4) carbon atoms substituted or unsubstituted, sulfur atom having a substituent, silicon having a substituent. It is an atom, a halogen atom, a nitro group, or a cyano group. At _{least two adjacent groups of R 8 to} R ₁₃ may be bonded to each other to form a ring.)

In one embodiment, the fluorene ring contained in the oligofluorene structural unit has a configuration in which all of _{R 8 to} R _{13 are hydrogen atoms, or R 8} and / or R ₁₃ is a halogen atom and an acyl group. , A nitro group, a cyano group, and a sulfo group, and R _{9 to} R ₁₂ are hydrogen atoms.

Details of the polycarbonate-based resin containing the oligofluorene structural unit are described in, for example, Japanese Patent Application Laid-Open No. 2015-212816. The description of the patent document is incorporated herein by reference.

The glass transition temperature of the polycarbonate resin is preferably 110 ° C. or higher and 150 ° C. or lower, more preferably 120 ° C. or higher and 140 ° C. or lower. If the glass transition temperature is excessively low, the heat resistance tends to deteriorate, dimensional changes may occur after film molding, and the image quality of the obtained organic EL panel may be deteriorated. If the glass transition temperature is excessively high, the molding stability during film molding may be deteriorated, and the transparency of the film may be impaired. The glass transition temperature is determined according to JIS K 7121 (1987).

The molecular weight of the polycarbonate resin can be expressed by the reducing viscosity. The reduced viscosity is measured by using methylene chloride as a solvent, precisely adjusting the polycarbonate concentration to 0.6 g / dL, and using an Ubbelohde viscous tube at a temperature of 20.0 ° C. ± 0.1 ° C. The lower limit of the reduction viscosity is usually preferably 0.30 dL / g, more preferably 0.35 dL / g or more. The upper limit of the reduction viscosity is usually preferably 1.20 dL / g, more preferably 1.00 dL / g, and further preferably 0.80 dL / g. If the reduced viscosity is smaller than the lower limit, there may be a problem that the mechanical strength of the molded product is reduced. On the other hand, if the reduced viscosity is larger than the upper limit value, the fluidity at the time of molding is lowered, and there may be a problem that the productivity and the moldability are lowered.

A commercially available film may be used as the polycarbonate resin film. Specific examples of commercially available products include the product names "Pure Ace WR-S", "Pure Ace WR-W", "Pure Ace WR-M" manufactured by Teijin Limited, and the product name "NRF" manufactured by Nitto Denko. Be done.

Cyclic olefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit. Resin is mentioned. 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 or propylene (typically, a random copolymer). , And graft modified products obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene-based monomers. Norbornene-based monomers include, for example, norbornene and its alkyl and / or alkylidene substitutions, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-. Polar group substituents such as these halogens such as 2-norbornene, 5-ethylidene-2-norbornene; dicyclopentadiene, 2,3-dihydrodicyclopentadiene and the like; dimethanooctahydronaphthalene, alkyl and / or alkylidene substitutions thereof. The body and polar group substituents such as halogen, such as 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl -1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a , 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6 -Cyano-1,4: 5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4 , 4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydro Naphthalene, etc .; 3-4 weights of cyclopentadiene, eg, 4,9: 5,8-dimethano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoinden, 4,11 : 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentadianthracene and the like.

In the present invention, other cycloolefins capable of ring-opening polymerization can be used in combination as long as the object of the present invention is not impaired. Specific examples of such cycloolefins include compounds having one reactive double bond, such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

The cyclic olefin resin preferably has a number average molecular weight (Mn) of 25,000 to 200,000, more preferably 30,000 to 100, measured by a gel permeation chromatography (GPC) method using a toluene solvent. 000, most preferably 40,000 to 80,000. When the number average molecular weight is in the above range, it is possible to obtain a product having excellent mechanical strength, good solubility, moldability, and operability of casting.

A commercially available film may be used as the cyclic olefin resin film. 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.

The retardation layer 30 is obtained, for example, by stretching a film formed of the above resin. As a method for forming a film from a resin, any suitable molding processing method can be adopted. Specific examples include a compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, a blow molding method, a powder molding method, an FRP molding method, a cast coating method (for example, a casting method), a calendar molding method, and a hot press. Law etc. can be mentioned. Extrusion molding method or cast coating method is preferable. This is because the smoothness of the obtained film can be improved and good optical uniformity can be obtained. The molding conditions can be appropriately set according to the composition and type of the resin used, the characteristics desired for the retardation layer, and the like. As described above, since many film products of the polycarbonate resin or the cyclic olefin resin are commercially available, the commercially available film may be subjected to the stretching treatment as it is.

The thickness of the resin film (unstretched film) can be set to an arbitrary appropriate value according to a desired thickness of the retardation layer, desired optical characteristics, stretching conditions described later, and the like. It is preferably 50 μm to 300 μm.

Any suitable stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) can be adopted for the stretching. Specifically, various stretching methods such as free-end stretching, fixed-end stretching, free-end contraction, and fixed-end contraction can be used alone or simultaneously or sequentially. As for the stretching direction, it can be performed in various directions and dimensions such as a length direction, a width direction, a thickness direction, and an oblique direction.

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

In another embodiment, the retardation film can be made by continuously obliquely stretching a long resin film in the direction of the above angle θ with respect to the longitudinal direction. By adopting oblique stretching, a long stretched film having an orientation angle of an angle θ with respect to the longitudinal direction of the film (a slow axis in the direction of the angle θ) can be obtained. Roll-to-roll is possible, and the manufacturing process can be simplified. The angle θ can be an angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer in the circular polarizing plate. As described above, the angle θ is typically 35 ° to 55 °, preferably 38 ° to 52 °, more preferably 42 ° to 48 °, and even more preferably about 45 °.

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 long resin film can be continuously and diagonally stretched.

By appropriately controlling the left and right velocities in the stretching machine, a retardation layer having the desired in-plane phase difference and having a slow phase axis in the desired direction (substantially long). (Phase difference film) can be obtained.

The stretching temperature of the film can change depending on the in-plane retardation value and thickness desired for the retardation layer, the type of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the stretching temperature is preferably Tg-30 ° C to Tg + 60 ° C, more preferably Tg-15 ° C to Tg + 55 ° C, and most preferably Tg-10 ° C to Tg + 50 ° C. By stretching at such a temperature, a first retardation layer having appropriate characteristics in the present invention can be obtained. Tg is the glass transition temperature of the constituent material of the film.

By appropriately selecting the stretching method and stretching conditions, a retardation film having the desired optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient) can be obtained.

F. Conductive layer or isotropic base material with conductive layer The conductive layer is an arbitrary suitable base material by any suitable film forming method (for example, vacuum deposition method, sputtering method, CVD method, ion plating method, spray method, etc.). It can be formed by forming a metal oxide film on top of it. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimon composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Of these, indium-tin composite oxide (ITO) is preferable.

When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm.

The conductive layer may be transferred from the base material to the retardation layer to form a constituent layer of a circularly polarizing plate by itself, and may be laminated on the retardation layer as a laminate with the base material (base material with a conductive layer). May be done. Preferably, the substrate is optically isotropic, and therefore the conductive layer can be used in a circularly polarizing plate as an isotropic substrate with a conductive layer.

As the optically isotropic base material (isotropic base material), any suitable isotropic base material can be adopted. Examples of the material constituting the isotropic base material include a material having a resin having no conjugate system such as a norbornene resin and an olefin resin as a main skeleton, and an acrylic resin having a cyclic structure such as a lactone ring and a glutarimide ring. Examples include the material contained in the main chain. When such a material is used, when an isotropic base material is formed, the expression of the phase difference due to the orientation of the molecular chains can be suppressed to be small. The thickness of the isotropic base material is preferably 50 μm or less, more preferably 35 μm or less. The lower limit of the thickness of the isotropic base material is, for example, 20 μm.

The conductive layer and / or the conductive layer of the isotropic base material with the conductive layer can be patterned, if necessary. By patterning, a conductive portion and an insulating portion can be formed. As a result, electrodes can be formed. The electrode can function as a touch sensor electrode that senses contact with the touch panel. As the patterning method, any suitable method can be adopted. Specific examples of the patterning method include a wet etching method and a screen printing method.

G. Image Display Device The circularly polarizing plate according to the above items A to F can be applied to a flexible image display device. Therefore, the present invention includes a flexible image display device using such a circularly polarizing plate. A typical example of a flexible image display device is an organic EL display device. The flexible image display device according to the embodiment of the present invention includes the circularly polarizing plate according to the above items A to F on the visible side thereof. The circularly polarizing plates are laminated so that the retardation layer is on the display cell side (for example, the organic EL cell) side (the polarizer is on the visual recognition side).

A flexible organic EL display device can be realized, for example, by configuring the substrate of the organic EL cell with a flexible or foldable material. Typical examples of such materials include flexible thin glass, thermoplastic or thermosetting resin films, alloys, and metals. Examples of the thermoplastic resin or the thermosetting resin include polyester resin, polyimide resin, epoxy resin, polyurethane resin, polystyrene resin, polyolefin resin, polyamide resin, polycarbonate resin, silicone resin, and fluorine. Examples thereof include based resins and acrylonitrile-butadiene-styrene copolymer resins. Examples of the alloy include stainless steel, 36 alloy, and 42 alloy. Examples of the metal include copper, nickel, iron, aluminum and titanium.

Since the configuration of the organic EL display device is well known in the industry, detailed description thereof will be omitted. Details of the flexible or foldable organic EL display device are described in, for example, Japanese Patent No. 4601463 or Japanese Patent No. 4707996. These statements are incorporated herein by reference.

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) Thickness Measured using a digital micrometer (KC-351C manufactured by Anritsu Co., Ltd.).
(2) Phase difference value of the retardation layer The refractive indexes nx, ny and nz of the retardation layer used in Examples and Comparative Examples are measured by an automatic birefringence measuring device (manufactured by Oji Measuring Instruments Co., Ltd., automatic birefringence meter KOBRA-). It was measured by WPR). The measurement wavelengths of the in-plane retardation Re were 450 nm and 550 nm, the measurement wavelength of the thickness direction retardation Rth was 550 nm, and the measurement temperature was 23 ° C.
(3) Moisture Permeability The film constituting the second protective layer or the retardation layer was measured according to JIS Z 0208 (cup method).
(4) Curl amount With respect to the circularly polarizing plates obtained in Examples and Comparative Examples, (i) a state in which the release liner and the surface protective film are temporarily attached; (ii) the release liner is peeled off and the surface protective film is temporarily attached. Placed in a clean room (relative humidity 55% ± 10%) environment at 25 ° C ± 5 ° C for 72 hours in each state with the (iii) release liner and surface protective film peeled off. The amount of curl was measured. Specifically, a circularly polarizing plate is placed on a base on which static electricity is not generated so that the central portion thereof is in contact with the pedestal, and the warp of the circularly polarizing plate after 72 hours is measured with a steel metal scale at the four corners. The highest amount of warpage was taken as the amount of curl. Further, the case where the circularly polarizing plate warps toward the first protective layer side (hard coat layer side) is defined as “plus”, and the case where it warps toward the second protective layer side (adhesive layer side) is defined as “minus”. When the curl amount was within ± 6 mm, it was regarded as “good”, and when it exceeded 6 mm, it was regarded as “bad”.

[Reference Example 1: Fabrication of Polarizing Plate]
A long roll of a 60 μm-thick polyvinyl alcohol (PVA) resin film (manufactured by Kuraray Co., Ltd., product name “PE6000”) is uniaxially stretched in the long direction by a roll stretching machine so as to be 5.9 times in the long direction. At the same time, swelling, dyeing, cross-linking, and washing treatment were performed at the same time, and finally drying treatment was performed to prepare a polarizer 1 having a thickness of 22 μm.
Specifically, the swelling treatment was carried out by stretching 2.2 times while treating with pure water at 20 ° C. Next, the dyeing treatment was carried out in an aqueous solution at 30 ° C. in which the weight ratio of iodine and potassium iodide was adjusted so that the simple substance transmittance of the obtained polarizer was 45.0% and the weight ratio was 1: 7. However, it was stretched 1.4 times. Further, the cross-linking treatment adopted a two-step cross-linking treatment, and the first-step cross-linking treatment was carried out 1.2 times while being treated with an aqueous solution in which boric acid and potassium iodide were dissolved at 40 ° C. The boric acid content of the aqueous solution of the first-step cross-linking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. The second-step cross-linking treatment was carried out 1.6 times while treating with an aqueous solution in which boric acid and potassium iodide were dissolved at 65 ° C. The boric acid content of the aqueous solution of the second step cross-linking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. The washing treatment was carried out with an aqueous potassium iodide solution at 20 ° C. The potassium iodide content of the aqueous solution of the washing treatment was set to 2.6% by weight. Finally, the drying treatment was carried out at 70 ° C. for 5 minutes to obtain a polarizer 1.
A methacrylic resin film having a glutarimide ring structure (thickness: 20 μm, corresponding to the second protective layer) and a TAC film were hard-coated on both sides of the obtained polarizing element 1 via a polyvinyl alcohol-based adhesive. An HC-TAC film (thickness: 47 μm, corresponding to the first protective layer) having a hard coat (HC) layer formed by the treatment is bonded to each other, and the first protective layer / polarizer 1 / second A polarizing plate 1 having a protective layer structure was obtained.
A methacrylic resin film having a glutarimide ring structure was produced as follows. A methacrylic resin pellet having a glutarimide ring structure was dried at 100.5 kPa at 100 ° C. for 12 hours, and extruded from a T-die at a die temperature of 270 ° C. using a single-screw extruder to form a film. The obtained film is stretched in the transport direction (MD) in an atmosphere 10 ° C. higher than the glass transition temperature Tg of the resin, and then the glass transition of the resin is carried out in the direction orthogonal to the transport direction (TD). It was stretched in an atmosphere 7 ° C. higher than the temperature Tg. The resulting film was substantially optically isotropic.

[Reference Example 2: Fabrication of Polarizing Plate]
A long roll of a polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name "PE3000") having a thickness of 30 μm is uniaxially stretched in the long direction by a roll stretching machine so as to be 5.9 times in the long direction. At the same time, swelling, dyeing, cross-linking, and washing treatment were performed, and finally drying treatment was performed to prepare a polarizer 2 having a thickness of 12 μm. An HC-PC film (thickness: 25 μm, thickness: 25 μm,) having a hard coat (HC) layer formed on one side of the obtained polarizing element 2 by a hard coat treatment on one side of a polycarbonate resin film via a polyvinyl alcohol-based adhesive. (Corresponding to the first protective layer) was laminated to obtain a polarizing plate 2 having the structure of the first protective layer / polarizer 2.

[Reference Example 3: Fabrication of Polarizing Plate]
A TAC film manufactured by Konica Minolta Co., Ltd. (product name: KC2UA, thickness: 25 μm, corresponding to the second protective layer) on both sides of the polarizing element 2 obtained in Reference Example 2 via a polyvinyl alcohol-based adhesive. And an HC-TAC film (thickness: 32 μm, corresponding to the first protective layer) having a hard coat (HC) layer formed by a hard coat treatment on one side of the TAC film is bonded to the first protective layer. A polarizing plate 3 having a layer / polarizer 2 / second protective layer configuration was obtained.

[Reference Example 4: Fabrication of Polarizing Plate]
Similar to Reference Example 1 except that a TAC film (product name: KC2CT1, thickness: 20 μm) manufactured by Konica Minolta Co., Ltd. was used as the second protective layer. A polarizing plate 4 having a protective layer structure was obtained.

[Reference Example 5: Fabrication of Polarizing Plate]
A long roll of a 60 μm-thick polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name “PE6000”) is uniaxially stretched in the long direction by a roll stretching machine so as to be 5.9 times in the long direction. At the same time, swelling, dyeing, cross-linking, and washing treatment were performed, and finally drying treatment was performed to prepare a polarizer 3 having a thickness of 23 μm. A low-reflection TAC film having a hard coat (HC) layer formed on one side of the obtained polarizing element 3 by a low-reflection hard coat treatment on one side of the TAC film via a polyvinyl alcohol-based adhesive (thickness: 71 μm, Corresponding to the first protective layer; manufactured by Dainippon Printing Co., Ltd., product name "DSG-03HL") was bonded to obtain a polarizing plate 5 having the configuration of the first protective layer / polarizer 3.

[Reference Example 6: Fabrication of a retardation film constituting a retardation layer]
1. 1. Preparation of Polycarbonate Resin Film Isosorbide (ISB) 26.2 parts by mass, 9,9- [4- (2-hydroxyethoxy) phenyl] fluorene (BHEPF) 100.5 parts by mass, 1,4-cyclohexanedimethanol (1,4-cyclohexanedimethanol) 10.7 parts by mass of 4-CHDM), 105.1 parts by mass of diphenyl carbonate (DPC), and 0.591 parts by mass of cesium carbonate (0.2 mass% aqueous solution) as a catalyst were added to the reaction vessel to create a nitrogen atmosphere. Below, as the first step of the reaction, the heat medium temperature of the reaction vessel was set to 150 ° C., and the raw materials were dissolved with stirring as necessary (about 15 minutes).
Next, the pressure inside the reaction vessel was changed from normal pressure to 13.3 kPa, and the temperature of the heat medium of the reaction vessel was raised to 190 ° C. in 1 hour, and the generated phenol was extracted from the reaction vessel.
After maintaining the temperature inside the reaction vessel at 190 ° C. for 15 minutes, as the second step, the pressure inside the reaction vessel was set to 6.67 kPa, and the heat medium temperature of the reaction vessel was raised to 230 ° C. in 15 minutes. The generated phenol was extracted from 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 reduced to 0.200 kPa or less in order to remove the generated phenol. After reaching the predetermined stirring torque, the reaction is terminated, the produced reaction product is extruded into water, and then pelletized, and BHEPF / ISB / 1,4-CHDM = 47.4 mol% / 37.1 mol%. / 15.5 mol% polycarbonate resin was obtained.
The glass transition temperature of the obtained polycarbonate resin was 136.6 ° C., and the reducing viscosity was 0.395 dL / g.
After vacuum-drying the obtained polycarbonate resin at 80 ° C. for 5 hours, a single-screw extruder (manufactured by Isuzu Kakoki Co., Ltd., screw diameter 25 mm, cylinder set temperature: 220 ° C.), T-die (width 200 mm, set temperature: 220). A polycarbonate resin film having a thickness of 120 μm was produced using a film-forming device equipped with a chill roll (set temperature: 120 to 130 ° C.) and a winder.

2. Preparation of Phase Difference Film The obtained polycarbonate resin film was transversely stretched using a tenter stretching machine to obtain a retardation film having a thickness of 50 μm. At that time, the stretching ratio was 250%, and the stretching temperature was 137 to 139 ° C.
The obtained retardation film has a Re (550) of 137 to 147 nm, a Re (450) / Re (550) of 0.89, an Nz coefficient of 1.21, and an orientation angle (slow-phase axis). The direction) was 90 ° with respect to the long direction. This retardation film was used as the retardation layer 1.

[Reference Example 7: Fabrication of a retardation film constituting a retardation layer]
A retardation film having a thickness of 55 μm was obtained in the same manner as in Reference Example 6 except that a polycarbonate resin film having a thickness of 140 μm was produced. The Re (550) of the obtained retardation film is 147 nm, Re (450) / Re (550) is 0.89, the Nz coefficient is 1.21, and the orientation angle (direction of the slow phase axis). Was 90 ° with respect to the longitudinal direction. This retardation film was used as the retardation layer 2.

[Reference Example 8: Fabrication of a retardation film constituting a retardation layer]
1. 1. Preparation of Polycarbonate Resin Film Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] 38.06 parts by weight (0.059 mol) of methane and isosorbide (manufactured by Rocket Foil, trade name "POLYSORB") 53. 73 parts by weight (0.368 mol), 1,4-cyclohexanedimethanol (cis, trans mixture, manufactured by SK Chemical Co., Ltd.) 9.64 parts by weight (0.067 mol), diphenyl carbonate (manufactured by Mitsubishi Chemical Co., Ltd.) 81. 28 parts by weight (0.379 ^{mol) and 3.83 × 10 -4} parts by weight (2.17 × 10 ^-6 mol) of calcium acetate monohydrate as a catalyst were put into the reaction vessel, and the inside of the reaction apparatus was charged. It was replaced with reduced pressure nitrogen. The raw materials were dissolved with stirring at 150 ° C. for about 10 minutes in a nitrogen atmosphere. As the first step of the reaction, the temperature was raised to 220 ° C. over 30 minutes, and the reaction was carried out at normal pressure for 60 minutes. Next, the pressure was reduced from normal pressure to 13.3 kPa over 90 minutes, held at 13.3 kPa for 30 minutes, and the generated phenol was extracted from the reaction system. Next, as the second step of the reaction, the temperature of the heat medium was raised to 240 ° C. over 15 minutes, the pressure was reduced to 0.10 kPa or less over 15 minutes, and the generated phenol was extracted from the reaction system. After reaching a predetermined stirring torque, the pressure was restored to normal pressure with nitrogen to stop the reaction, the produced polyester carbonate was extruded into water, and the strands were cut to obtain polycarbonate resin pellets.
2. Preparation of Phase Difference Film A film composed of the above polycarbonate resin pellets was obliquely stretched to obtain a retardation film having a thickness of 58 μm. At that time, the stretching direction was set to 45 ° with respect to the longitudinal direction of the film. Further, the draw ratio was adjusted to 2 to 3 times so that the retardation film exhibited a retardation of λ / 4. The stretching temperature was 148 ° C. (that is, Tg + 5 ° C. of the unstretched modified polycarbonate film). The obtained retardation film has a Re (550) of 141 nm, a Re (450) / Re (550) of 0.83, an Nz coefficient of 1.1, and a photoelastic coefficient of 16 × ^10-12. It was Pa, and the orientation angle (direction of the slow axis) was 45 ° with respect to the long direction. This retardation film was used as the retardation layer 3.

[Example 1]
The second protective layer surface of the polarizing plate 1 and the retardation layer 1 are attached via an acrylic pressure-sensitive adhesive so that the angle between the absorption axis of the polarizing element and the slow axis of the retardation layer is 45 °. Together, a circularly polarizing plate 1 was obtained. An acrylic pressure-sensitive adhesive layer (thickness 15 μm) was provided on the retardation layer surface of the obtained circularly polarizing plate 1, and a release liner was temporarily attached to the surface of the pressure-sensitive adhesive layer. Further, a surface protective film was temporarily attached to the surface of the first protective layer. As the protective film, a PET film having a thickness of 38 μm coated with an adhesive having a thickness of 10 μm was used. The moisture permeability of the second protective layer at 40 ° C. and 92% relative humidity was 150 g / m ² / 24H. The obtained circularly polarizing plate 1 was used for evaluation of the curl amount in (4) above. The results are shown in Table 1. Further, the organic EL cell was taken out from a flexible organic EL display device (manufactured by Samsung, trade name "Galaxy S6 Edge"). On the other hand, the release liner was peeled off from the circularly polarizing plate 1, and the circularly polarizing plate 1 was attached to the organic EL cell via the pressure-sensitive adhesive layer. Further, the surface protective film was peeled off from the circularly polarizing plate attached to the organic EL cell. The organic EL cell to which the circularly polarizing plate 1 was attached was left to stand for 72 hours under the conditions of 23 ° C. and 55% RH, and then the presence or absence of warpage was visually observed. As a result, neither warpage nor bending was observed.

[Example 2]
The polarizing element surface of the polarizing plate 2 and the retardation layer 2 are bonded together via a PVA-based adhesive so that the angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer is 45 °. A circularly polarizing plate 2 was obtained. An acrylic pressure-sensitive adhesive layer (thickness 15 μm) was provided on the retardation layer surface of the obtained circularly polarizing plate 2, and a release liner was temporarily attached to the surface of the pressure-sensitive adhesive layer. Further, a surface protective film was temporarily attached to the surface of the first protective layer. The moisture permeability of the retardation layer at 40 ° C. and 92% relative humidity was 70 g / m ² / 24H. The obtained circularly polarizing plate 2 was used for evaluation of the curl amount in (4) above. The results are shown in Table 1. Further, the obtained circularly polarizing plate 2 was attached to an organic EL cell in the same manner as in Example 1 and subjected to the same evaluation as in Example 1. As a result, neither warpage nor bending was observed.

[Example 3]
The polarizing element surface of the polarizing plate 5 and the retardation layer 3 are bonded together via a PVA-based adhesive so that the angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer is 45 °. A circularly polarizing plate 5 was obtained. An acrylic pressure-sensitive adhesive layer (thickness 20 μm) was provided on the retardation layer surface of the obtained circularly polarizing plate 5, and a release liner was temporarily attached to the surface of the pressure-sensitive adhesive layer. Further, a surface protective film was temporarily attached to the surface of the first protective layer. The moisture permeability of the retardation layer at 40 ° C. and 92% relative humidity was 80 g / m ² / 24H. The obtained circularly polarizing plate 5 was used for evaluation of the curl amount in (4) above. The results are shown in Table 1. Further, the obtained circularly polarizing plate 5 was attached to an organic EL cell in the same manner as in Example 1 and subjected to the same evaluation as in Example 1. As a result, neither warpage nor bending was observed.

[Comparative Example 1]
The polarizing element surface of the polarizing plate 3 and the retardation layer 1 are bonded to each other via an acrylic pressure-sensitive adhesive so that the angle between the absorption axis of the polarizer and the slow axis of the retardation layer is 45 °. A circularly polarizing plate 3 was obtained. An acrylic pressure-sensitive adhesive layer (thickness 15 μm) was provided on the retardation layer surface of the obtained circularly polarizing plate 3, and a release liner was temporarily attached to the surface of the pressure-sensitive adhesive layer. Further, a surface protective film was temporarily attached to the surface of the first protective layer. The moisture permeability of the second protective layer at 40 ° C. and a relative humidity of 92% was 1000 g / m ² / 24H. The obtained circularly polarizing plate 3 was used for evaluation of the curl amount in (4) above. The results are shown in Table 1. Further, the obtained circularly polarizing plate 3 was attached to an organic EL cell in the same manner as in Example 1 and subjected to the same evaluation as in Example 1. As a result, warpage was observed.

[Comparative Example 2]
The polarizing element surface of the polarizing plate 4 and the retardation layer 1 are bonded to each other via an acrylic pressure-sensitive adhesive so that the angle between the absorption axis of the polarizer and the slow axis of the retardation layer is 45 °. A circularly polarizing plate 4 was obtained. An acrylic pressure-sensitive adhesive layer (thickness 15 μm) was provided on the retardation layer surface of the obtained circularly polarizing plate 4, and a release liner was temporarily attached to the surface of the pressure-sensitive adhesive layer. Further, a surface protective film was temporarily attached to the surface of the first protective layer. The moisture permeability of the second protective layer at 40 ° C. and 92% relative humidity was 1500 g / m ² / 24H. The obtained circularly polarizing plate 4 was used for evaluation of the curl amount in (4) above. The results are shown in Table 1. Further, the obtained circularly polarizing plate 4 was attached to an organic EL cell in the same manner as in Example 1 and subjected to the same evaluation as in Example 1. As a result, warpage was observed.

<Evaluation>
As is clear from Table 1, it can be seen that the circularly polarizing plate of the embodiment of the present invention has a small amount of curl due to aging with the release liner and the surface protective film peeled off. As a result, it was confirmed that when applied to a flexible image display device, bending and warpage of the image display device itself can be satisfactorily suppressed.

The circularly polarizing plate of the present invention is suitably used for a flexible image display device (for example, an organic EL display device).

11 First protective layer 12 Second protective layer 20 Polarizer 30 Phase difference layer 40 Hard coat layer 50 Adhesive layer 70 Surface protective film 100 circular polarizing plate

Claims (5)

It has a first protective layer, a polarizer, a second protective layer, and a retardation layer having an in-plane retardation Re (550) of 80 nm to 200 nm in this order.
^{The second protective layer has a moisture permeability of less than 160 g / m 2} / 24H at 40 ° C. and a relative humidity of 92%.
An adhesive layer is further provided on the outermost side of the retardation layer side, and a release liner is temporarily attached to the surface of the adhesive layer.
A surface protective film is temporarily attached to the outermost surface on the first protective layer side.
A state in which the release liner and the surface protective film are temporarily attached; a state in which the release liner is peeled off and the surface protective film is temporarily attached; and a state in which the release liner and the surface protective film are peeled off. In each of these states, the curl amount is within ± 6 mm when placed in an environment of 25 ° C. ± 5 ° C. and relative humidity of 55% ± 10% for 72 hours.
Used in flexible image display devices,
Circularly polarized light. The second protective layer is omitted, and the retardation layer also serves as a protective layer for the polarizer, and the moisture permeability of the retardation layer at 40 ° C. and 92% relative humidity is less than ^{160 g / m 2 / 24H.} The circularly polarizing plate according to claim 1. The circularly polarizing plate according to claim 1 or 2, wherein the angle θ formed by the absorption axis of the polarizer and the slow axis of the retardation layer is 35 ° to 55 °. The circularly polarizing plate according to any one of claims 1 to 3, further comprising a hard coat layer on the outside of the first protective layer. A flexible image display device comprising the circularly polarizing plate according to any one of claims 1 to 4.

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