WO2017135239A1 - Optical laminate and image display device in which said optical laminate is used - Google Patents

Abstract

Provided is an optical laminate in which an electrically conductive layer is formed directly on a phase difference layer, the optical laminate being very thin, having an exceptional reflection-preventing function, and furthermore being capable of exhibiting exceptional display characteristics even when applied to a curved part of an image display device. This optical laminate is provided with a polarizer, a phase difference layer bonded to the polarizer, and an electrically conductive layer formed directly on the phase difference layer. The phase difference layer has an in-plane phase difference Re(550) of 100-180 nm, and satisfies the relationship Re(450)<Re(550)<Re(650), the glass transition temperature (Tg) being 150°C or higher, and the absolute value of the photo-elastic coefficient being 20×10^-12(m²/N) or lower. The angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizer is 35-55°.

Description

OPTICAL LAMINATE AND IMAGE DISPLAY DEVICE USING THE OPTICAL LAMINATE

The present invention relates to an optical laminate and an image display apparatus using the optical laminate.

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

Furthermore, in recent years, as represented by smartphones, the number of touch panel type input display devices in which an image display device also serves as a touch panel type input device is rapidly increasing. In particular, a so-called inner touch panel type input display device in which a touch sensor is incorporated between a display cell (for example, a liquid crystal cell or an organic EL cell) and a polarizing plate has been put into practical use. In such an inner touch panel type input display device, a transparent conductive layer functioning as a touch panel electrode is introduced by being laminated on a retardation film (typically a λ / 4 plate) as a conductive layer with an isotropic substrate. ing. From the viewpoint of reducing the thickness of the display device, it is desirable to form the transparent conductive layer directly on the retardation film. However, the optical properties of the retardation film are desired in a high-temperature environment during sputtering and subsequent treatment when forming the transparent conductive layer. This is because the base material for sputtering must be used because it is greatly deviated from the characteristics. Thus, a technique that can directly form a transparent conductive layer on a retardation film is strongly desired. Further, in order to cope with a flexible display, there is a demand for a circularly polarizing plate that does not impair display characteristics even when applied to a bent portion of a display.

Japanese Patent Laying-Open No. 2015-69158

The present invention has been made to solve the above-described conventional problems, and the object of the present invention is that the conductive layer is formed directly on the retardation layer, and is very thin and has an excellent antireflection function. It is another object of the present invention to provide an optical laminate that can realize excellent display characteristics even when applied to a bent portion of an image display device.

The optical layered body of the present invention includes a polarizer, a retardation layer, and a conductive layer directly formed on the retardation layer, and the retardation layer has an in-plane retardation Re (550) of 100 nm to 100 nm. 180 nm, the relationship of Re (450) <Re (550) <Re (650) is satisfied, the glass transition temperature (Tg) is 150 ° C. or higher, and the absolute value of the photoelastic coefficient is 20 × 10 6. ⁻¹² (m ² / N) or less, and the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is 35 ° to 55 °.
According to another aspect of the present invention, an image display device is provided. This image display device includes the optical layered body described above on the viewing side, and the polarizer of the optical layered body is disposed on the viewing side.

According to the embodiment of the present invention, a retardation film having a predetermined in-plane retardation, wavelength dependence of reverse dispersion, and having a predetermined glass transition temperature and photoelastic coefficient is used as a retardation layer. Thus, the conductive layer can be formed directly on the surface of the retardation layer, and desired optical characteristics of the retardation layer can be maintained despite the formation of such a conductive layer. As a result, it is possible to realize an optical laminate that is very thin and has an excellent antireflection function. Further, such an optical laminated body can realize excellent display characteristics even when applied to a bent portion of an image display device.

It is a schematic sectional drawing of the optical laminated body by one Embodiment of this invention.

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

(Definition of terms and symbols)
The definitions of terms and symbols in this specification 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 maximum (ie, the slow axis direction), and “ny” is the direction orthogonal to the slow axis in the plane (ie, the fast axis direction). “Nz” is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re (λ)” is the in-plane retardation of the film measured with light having a wavelength of λ nm at 23 ° C. For example, “Re (450)” is the in-plane retardation of the film measured with light having a wavelength of 450 nm at 23 ° C. Re (λ) is determined by the formula: Re = (nx−ny) × d, where d (nm) is the thickness of the film.
(3) Thickness direction retardation (Rth)
“Rth (λ)” is a retardation in the thickness direction of the film measured with light having a wavelength of λ nm at 23 ° C. For example, “Rth (450)” is the retardation in the thickness direction of the film measured with light having a wavelength of 450 nm at 23 ° C. Rth (λ) is determined by the formula: Rth = (nx−nz) × d, where d (nm) is the thickness of the film.
(4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re.
(5) Angle When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions.

A. FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical layered body 100 of the present embodiment includes a polarizer 10, a retardation layer 20, and a conductive layer 30 that is directly formed on the retardation layer 20. In practice, the optical laminate 100 may further include a protective layer 40 bonded to the opposite side of the retardation layer 20 of the polarizer 10 as in the illustrated example. Further, a protective layer (not shown) may be further provided between the polarizer 10 and the retardation layer 20. According to such a configuration, the optical laminate 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, a liquid crystal cell or an organic EL cell) and a polarizer. .

Each layer (each optical film) is bonded through any appropriate adhesive layer (typically, an adhesive layer or a pressure-sensitive adhesive layer). On the other hand, the conductive layer 30 is directly formed on the retardation layer 20 as described above. In this specification, “directly formed” means that the layers are laminated without interposing an adhesive layer. Typically, the conductive layer 30 can be formed on the surface of the retardation layer 20 by sputtering. In the illustrated example, the conductive layer 30 is formed on the opposite side of the retardation layer 20 from the polarizer 10 (lower side of the retardation layer), but between the retardation layer 20 and the polarizer 10 (of the retardation layer). (Upper side). Note that an index matching (IM) layer and / or a hard coat (HC) layer may be formed between the retardation layer and the conductive layer depending on the purpose (both not shown). In some cases, the conductive layer is formed directly on the IM layer or HC layer by sputtering. Such forms are also encompassed by "directly formed" forms. As the IM layer and the HC layer, configurations commonly used in the industry can be adopted, and thus detailed description thereof is omitted.

In the embodiment of the present invention, the retardation layer 20 is typically composed of a retardation film. Therefore, the retardation layer can also function as a protective layer (inner protective layer) for the polarizer. As a result, it can contribute to thinning of the optical laminate (as a result, an image display device). In addition, as above-mentioned, an inner side protective layer (inner side protective film) may be arrange | positioned between a polarizer and retardation layer as needed. The retardation layer has an in-plane retardation Re (550) of 100 nm to 180 nm and satisfies a relationship of Re (450) <Re (550) <Re (650). Further, the retardation layer has a glass transition temperature (Tg) of 150 ° C. or higher and an absolute value of a photoelastic coefficient of 20 × 10 ⁻¹² (m ² / N) or lower. With such a retardation layer, desired optical characteristics can be maintained even in a high-temperature environment in sputtering and post-processing accompanying it. Therefore, the conductive layer can be directly formed on the surface of the retardation layer by sputtering. As a result, the production efficiency is remarkably improved, and the adhesive layer for bonding the substrate for sputtering and the laminate of the conductive layer / substrate can be omitted, so that the optical laminate (as a result, This can contribute to further thinning of the image display device). Further, such an optical laminated body can realize excellent display characteristics even when applied to a bent portion of an image display device. More specifically, it is possible to suppress a change in color between the bent portion and the flat portion.

The angle formed between the slow axis of the retardation layer 20 and the absorption axis of the polarizer 10 is typically 35 ° to 55 °. If the angle is in such a range, by setting the in-plane retardation of the retardation layer in the above range, very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics) can be obtained. The optical laminated body which has can be obtained.

If necessary, an anti-blocking (AB) layer may be provided on the side of the conductive layer 30 opposite to the retardation layer 20 (outermost side of the optical laminate). The haze value of the AB layer is preferably 0.2% to 4%.

The total thickness of the optical laminate (for example, the total thickness of the protective layer / adhesive layer / polarizer / adhesive layer / protective layer / adhesive layer / retardation layer / conductive layer) is preferably 50 μm to 200 μm, more preferably 80 μm to 170 μm. According to the embodiment of the present invention, the conductive layer can be directly formed on the surface of the retardation layer, and the sputtering base material can be omitted, so that a remarkable reduction in thickness can be realized.

In one embodiment, the optical layered body of the present invention is elongated. The long optical laminate can be stored and / or transported, for example, wound in a roll.

The above embodiments may be combined as appropriate, the components in the above embodiments may be modified in a manner obvious in the art, and the configuration in the above embodiment may be replaced with an optically equivalent configuration.

Hereinafter, components of the optical laminate will be described.

B. Polarizer Any appropriate polarizer may be adopted as the polarizer 10. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and ethylene / vinyl acetate copolymer partially saponified films. In addition, there may be mentioned polyene-based oriented films such as those subjected to dyeing treatment and stretching treatment with dichroic substances such as iodine and dichroic dyes, PVA dehydrated products and polyvinyl chloride dehydrochlorinated products. Preferably, a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching is used because of excellent optical properties.

The dyeing with iodine is performed, for example, by immersing a PVA film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or may be performed while dyeing. Moreover, you may dye | stain after extending | stretching. If necessary, the PVA film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment and the like. For example, by immersing the PVA film in water and washing it before dyeing, not only can the surface of the PVA film be cleaned of dirt and anti-blocking agents, but the PVA film can be swollen to cause uneven staining. Can be prevented.

As a specific example of a polarizer obtained by using a laminate, a laminate of a resin substrate and a PVA resin layer (PVA resin film) laminated on the resin substrate, or a resin substrate and the resin Examples thereof include a polarizer obtained by using a laminate with a PVA resin layer applied and formed on a substrate. For example, a polarizer obtained by using a laminate of a resin base material and a PVA resin layer applied and formed on the resin base material may be obtained by, for example, applying a PVA resin solution to a resin base material and drying it. A PVA-based resin layer is formed thereon to obtain a laminate of a resin base material and a PVA-based resin layer; the laminate is stretched and dyed 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 and stretching. Furthermore, the stretching may further include, if necessary, stretching the laminate in the air at a high temperature (for example, 95 ° C. or higher) before stretching in the aqueous boric acid solution. The obtained resin base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer of the polarizer), and the resin base material is peeled from the resin base material / polarizer laminate. Any appropriate protective layer according to the purpose may be laminated on the release surface. Details of a method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. This publication is incorporated herein by reference in its entirety.

The thickness of the polarizer is preferably 15 μm or less, more preferably 1 μm to 12 μm, still more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 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. Furthermore, if the thickness of the polarizer is in such a range, it can contribute to the thinning of the optical laminate (as a result, the organic EL display device).

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

C. Retardation Layer The in-plane retardation Re (550) of the retardation layer 20 is 100 nm to 180 nm as described above, preferably 120 nm to 160 nm, and more preferably 135 nm to 155 nm. That is, the retardation layer can function as a so-called λ / 4 plate.

As described above, the retardation layer satisfies the relationship of Re (450) <Re (550) <Re (650). That is, the retardation layer shows the wavelength dependence of reverse dispersion in which the retardation value increases with the wavelength of the measurement light. Re (450) / Re (550) of the retardation layer is preferably 0.7 or more and less than 1.0, more preferably 0.8 or more and less than 1.0, and further preferably 0.8 or more and 0. .95, particularly preferably 0.8 or more and less than 0.9. Re (550) / Re (650) is preferably 0.8 or more and less than 1.0, and more preferably 0.8 to 0.97.

The retardation layer typically has a relationship of refractive index nx> ny and has a slow axis. The angle formed between the slow axis of the retardation layer 20 and the absorption axis of the polarizer 10 is 35 ° to 55 ° as described above, more preferably 38 ° to 52 °, and still more preferably 42 ° to 48. °, particularly preferably about 45 °. If the angle is in such a range, an optical laminate having very excellent circular polarization characteristics (as a result, very good antireflection characteristics) can be obtained by making the retardation layer a λ / 4 plate. Can be.

The retardation layer exhibits any suitable refractive index ellipsoid (refractive index characteristic) as long as it has a relationship of nx> ny. Preferably, the refractive index ellipsoid of the retardation layer exhibits a relationship of nx> ny ≧ nz or nx> nz> ny. 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 effects of the present invention are not impaired. The Nz coefficient of the retardation layer is preferably 0.2 to 2.0, more preferably 0.2 to 1.5, and still more preferably 0.2 to 1.0. By satisfying such a relationship, a very excellent reflection hue can be achieved when the optical layered body is used in an image display device.

The retardation layer has a glass transition temperature (Tg) of 150 ° C. or higher as described above. The lower limit of the glass transition temperature is more preferably 155 ° C or higher, further preferably 157 ° C or higher, still more preferably 160 ° C or higher, and particularly preferably 163 ° C or higher. On the other hand, the upper limit of the glass transition temperature is preferably 180 ° C. or lower, more preferably 175 ° C. or lower, and particularly preferably 170 ° C. or lower. If the glass transition temperature is too low, undesired changes in optical properties may occur in the high temperature environment of sputtering and the subsequent post-treatment. If the glass transition temperature is too high, the molding stability at the time of forming the retardation layer may deteriorate, and the transparency of the retardation layer may be impaired. The glass transition temperature is determined according to JIS K 7121 (1987).

The retardation layer has an absolute value of the photoelastic coefficient of 20 × 10 ⁻¹² (m ² / N) or less as described above, and preferably 1.0 × 10 ⁻¹² (m ² / N) to 15 × 10. ⁻¹² (m ² / N), more preferably 2.0 × 10 ⁻¹² (m ² / N) to 12 × 10 ⁻¹² (m ² / N). When the absolute value of the photoelastic coefficient is within such a range, a change in color before and after sputtering can be suppressed. Furthermore, when the optical laminate is applied to a bent portion of an image display device, excellent display characteristics can be realized also in the bent portion.

The thickness of the retardation layer can be set so as to function most appropriately as a λ / 4 plate. In other words, the thickness can be set so as to obtain a desired in-plane retardation. Specifically, the thickness is preferably 10 μm to 80 μm, more preferably 10 μm to 70 μm, still more preferably 20 μm to 65 μm, particularly preferably 20 μm to 60 μm, and most preferably 20 μm to 50 μm. is there.

The retardation layer is composed of a retardation film containing any appropriate resin that can satisfy the above-described characteristics. Examples of the resin forming the retardation film include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, and cellulose ester resins. Polycarbonate resin is preferable. Polycarbonate resin is relatively easy to synthesize a copolymer using a plurality of types of monomers, and molecular design for adjusting various physical property balances is possible. Moreover, heat resistance, stretchability, mechanical properties, etc. are relatively good. In the present invention, the polycarbonate resin is a generic term for resins having a carbonate bond in a structural unit, and includes, for example, a polyester carbonate resin. The polyester carbonate resin refers to a resin having a carbonate bond and an ester bond as structural units constituting the resin.

The polycarbonate resin used in the present invention preferably contains at least a structural unit represented by the following formula (1) or (2).

(In the formulas (1) and (2), R ¹ to R ³ are each independently a direct bond or an alkylene group having 1 to 4 carbon atoms which may have a substituent, and R ⁴ to R ⁹ Each independently has a hydrogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, an optionally substituted aryl group having 4 to 10 carbon atoms, or a substituent. An optionally substituted acyl group having 1 to 10 carbon atoms, an optionally substituted alkoxy group having 1 to 10 carbon atoms, an optionally substituted aryloxy group having 1 to 10 carbon atoms, An amino group which may have a substituent, a vinyl group having 1 to 10 carbon atoms which may have a substituent, an ethynyl group having 1 to 10 carbon atoms which may have a substituent, a substituent; A sulfur atom having a substituent, a silicon atom having a substituent, a halogen atom, a nitro group, or a cyano group. , R 4 ^~ R ⁹ are identical to one another or different, may form a ring with each other at least two neighboring groups of the R 4 ^~ R ^9.)

The above structural unit can efficiently exhibit reverse wavelength dispersion even if the content in the resin is small. In addition, the resin containing the structural unit has good heat resistance and high birefringence can be obtained by stretching. Therefore, the resin has characteristics suitable for the retardation layer used in the present invention.

The content of the structural unit represented by the formula (1) or (2) in the resin is such that all the structural units constituting the polycarbonate resin and the connection are obtained in order to obtain the optimum wavelength dispersion characteristic as a retardation film. When the total weight of the group is 100% by weight, the content is preferably 1% by weight or more and 50% by weight or less, more preferably 3% by weight or more and 40% by weight or less, and more preferably 5% by weight or more and 30% by weight. % Or less is particularly preferable.

Among the structural units represented by the formulas (1) and (2), preferred structures include structures having a skeleton specifically exemplified in the following [A] group.
[A]

Among the above [A] groups, the performance of the diester structural units (A1) and (A2) is high, and (A1) is particularly preferable. The specific diester structural unit is better in thermal stability than the structural unit derived from the dihydroxy compound represented by the formula (1), and good in optical characteristics such as reverse wavelength dispersion and photoelastic coefficient. Tend to show unique characteristics. In addition, when the polycarbonate resin which concerns on this invention contains the structural unit of a diester, such resin is called polyester carbonate resin.

The polycarbonate resin used in the present invention contains various structural units together with the structural unit represented by the above formula (1) or (2), so that various requirements are required for the retardation layer used in the present invention. Resins satisfying these physical properties can be designed. In order to impart high heat resistance, which is a particularly important physical property, it is preferable to contain a structural unit represented by the following formula (3).

(In formula (3), R ¹⁰ to R ¹⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group, an alkoxy group having 1 to 12 carbon atoms, or a halogen atom.)

The structural unit represented by the formula (3) is a component having a high glass transition temperature, and furthermore, despite the aromatic structure, it has a relatively low photoelastic coefficient and is required for the retardation layer used in the present invention. Satisfying the characteristics

The content of the structural unit represented by the formula (3) in the resin is 1% by weight or more when the total weight of all the structural units constituting the polycarbonate resin and the weight of the linking group is 100% by weight. 30 wt% or less, preferably 2 wt% or more and 20 wt% or less, more preferably 3 wt% or more and 15 wt% or less. Within this range, a resin excellent in processability can be obtained without imparting sufficient heat resistance while the resin does not become excessively brittle.

The structural unit represented by the formula (3) can be introduced into the resin by polymerizing a dihydroxy compound containing the structural unit. As the dihydroxy compound, 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane is used from the viewpoint of good physical properties and easy availability. It is particularly preferred.

The polycarbonate resin used in the present invention preferably further contains a structural unit represented by the following formula (4).

The structural unit represented by the above formula (4) has high birefringence when the resin is stretched and has a low photoelastic coefficient. Examples of the dihydroxy compound into which the structural unit represented by the formula (4) can be introduced include isosorbide (ISB), isomannide, and isoidet, which are in a stereoisomeric relationship, and among these, availability and polymerization reactivity In view of the above, it is most preferable to use ISB.

The polycarbonate resin used in the present invention may contain other structural units in addition to the structural units described above, depending on the required physical properties. Examples of monomers containing other structural units include aliphatic dihydroxy compounds, alicyclic dihydroxy compounds, dihydroxy compounds containing acetal rings, oxyalkylene glycols, dihydroxy compounds containing aromatic components, diester compounds, and the like. Can be mentioned. From the viewpoint of good balance of various physical properties and availability, 1,4-cyclohexanedimethanol (hereinafter sometimes abbreviated as CHDM), tricyclodecane dimethanol (hereinafter referred to as TCDDM). A dihydroxy compound such as spiroglycol (hereinafter sometimes abbreviated as SPG) is preferably used.

In the polycarbonate resin used in the present invention, a heat stabilizer, an antioxidant, a catalyst deactivator, an ultraviolet absorber, a light stabilizer, a release agent, a dye, Impact modifiers, antistatic agents, lubricants, lubricants, plasticizers, compatibilizers, nucleating agents, flame retardants, inorganic fillers, foaming agents and the like may be included.

The polycarbonate resin used in the present invention is an aromatic polycarbonate, aliphatic polycarbonate, aromatic polyester, aliphatic polyester, polyamide, polystyrene, polyolefin, acrylic, amorphous for the purpose of modifying properties such as mechanical properties and solvent resistance. It is good also as a polymer alloy formed by kneading | mixing with 1 type (s) or 2 or more types, such as synthetic resins, such as polyolefin, ABS, AS, polylactic acid, and polybutylene succinate, and rubber.

The additives and modifiers may be added to the resin used in the present invention simultaneously or in any order by a mixer such as a tumbler, V-type blender, nauter mixer, Banbury mixer, kneading roll, or extruder. Although it can manufacture by mixing, it is preferable to knead | mix by an extruder, especially a twin-screw extruder especially from a viewpoint of a dispersibility improvement.

The molecular weight of the polycarbonate resin used in the present invention can be represented by a reduced viscosity. The reduced viscosity is measured using a Ubbelohde viscometer tube at a temperature of 20.0 ° C. ± 0.1 ° C., using methylene chloride as a solvent, precisely preparing a polycarbonate resin concentration of 0.6 g / dL. The lower limit of the reduced viscosity is usually preferably 0.25 dL / g or more, more preferably 0.30 dL / g or more, and particularly preferably 0.32 dL / g or more. The upper limit of the reduced viscosity is usually preferably 0.50 dL / g or less, more preferably 0.45 dL / g or less, and particularly preferably 0.40 dL / g or less. If the reduced viscosity is less 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, the fluidity at the time of molding is lowered, and there may be a problem that productivity and moldability are lowered.

The polycarbonate resin used in the present invention preferably has a melt viscosity of 1000 Pa · s or more and 9000 Pa · s or less at a measurement temperature of 240 ° C. and a shear rate of 91.2 sec ⁻¹ . The lower limit of the melt viscosity is more preferably 2000 Pa · s or more, further preferably 2500 Pa · s or more, and particularly preferably 3000 Pa · s or more. The upper limit of the melt viscosity is more preferably 8000 Pa · s or less, further preferably 7000 Pa · s or less, still more preferably 6500 Pa · s or less, and particularly preferably 6000 Pa · s or less.

The retardation layer used in the present invention is required to have high heat resistance. Usually, the higher the heat resistance (glass transition temperature), the more the resin becomes brittle, but the above-described melt viscosity range is used. Thus, the resin can be melt processed while maintaining the minimum mechanical properties required during the processing of the resin.

The polycarbonate resin used in the present invention preferably has a refractive index of 1.49 or more and 1.56 or less at the sodium d line (589 nm). More preferably, the refractive index is 1.50 or more and 1.55 or less.

In order to impart optical characteristics required for the retardation layer used in the present invention, it is necessary to introduce an aromatic structure into the resin. However, the aromatic structure increases the refractive index and causes a decrease in the transmittance of the retardation layer. In general, an aromatic structure has a high photoelastic coefficient, and generally deteriorates optical characteristics. For the polycarbonate resin used in the present invention, it is preferable to select a structural unit that efficiently expresses the required characteristics, and to minimize the content of the aromatic structure in the resin.

The retardation layer used in the present invention is obtained by forming a film from the above polycarbonate resin and further stretching the film. Any appropriate molding method can be adopted as a method of forming a film from a polycarbonate resin. Specific examples include compression molding methods, transfer molding methods, injection molding methods, extrusion molding methods, blow molding methods, powder molding methods, FRP molding methods, cast coating methods (for example, casting methods), calendar molding methods, and hot presses. Law. Among them, an extrusion molding method or a cast coating method capable of increasing the smoothness of the obtained film and obtaining good optical uniformity is preferable. Since the cast coating method may cause a problem due to the residual solvent, the extrusion method, particularly the melt extrusion method using a T-die is particularly preferable from the viewpoint of film productivity and ease of subsequent stretching treatment. preferable. The molding conditions can be appropriately set according to the composition and type of the resin used, the properties desired for the retardation layer, and the like.

The thickness of the resin film (unstretched film) can be set to any appropriate value depending on the desired thickness of the obtained retardation film, the desired optical properties, the stretching conditions described later, and the like. The thickness is preferably 50 μm to 300 μm.

Any appropriate stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) may be employed 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 singly or simultaneously or sequentially. The stretching direction can also be performed in various directions and dimensions such as a length direction, a width direction, a thickness direction, and an oblique direction.

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

In one embodiment, the retardation film is produced by uniaxially stretching a resin film or uniaxially stretching a fixed end. As a specific example of the fixed end uniaxial stretching, there is a method of stretching in the width direction (lateral direction) while running the resin film in the longitudinal direction. The draw ratio is preferably 1.1 to 3.5 times.

In another embodiment, the retardation film can be produced by continuously stretching a long resin film obliquely in a direction at a predetermined angle with respect to the longitudinal direction. By adopting oblique stretching, a long stretched film having an orientation angle of a predetermined angle with respect to the longitudinal direction of the film (slow axis in the direction of the predetermined angle) is obtained. For example, with a polarizer Roll-to-roll is possible at the time of lamination, and the manufacturing process can be simplified. Furthermore, manufacturing efficiency can be remarkably improved by a synergistic effect that the conductive layer can be directly formed on the retardation layer (retardation film). The predetermined angle may be an angle formed between the absorption axis of the polarizer and the slow axis of the retardation layer in the optical layered body. As described above, the angle is preferably 35 ° to 55 °, more preferably 38 ° to 52 °, still more preferably 42 ° to 48 °, and particularly preferably about 45 °.

Examples of the stretching machine used for the oblique stretching include a tenter type stretching machine capable of adding feed forces, pulling forces, or pulling forces at different speeds in the lateral and / or longitudinal 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 a long resin film can be continuously stretched obliquely.

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

Examples of the oblique stretching method include, for example, JP-A-50-83482, JP-A-2-113920, JP-A-3-182701, JP-A-2000-9912, JP-A-2002-86554, Examples thereof include the method described in JP-A-2002-22944.

The stretching temperature of the film can vary depending on the in-plane retardation value and thickness desired for the retardation film, 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 + 30 ° C, more preferably Tg-15 ° C to Tg + 15 ° C, and most preferably Tg-10 ° C to Tg + 10 ° C. By stretching at such a temperature, a retardation film having appropriate characteristics in the present invention can be obtained. Tg is the glass transition temperature of the constituent material of the film.

D. Conductive Layer The conductive layer 30 is typically transparent (that is, the conductive layer is a transparent conductive layer). By forming a conductive layer on the opposite side of the retardation layer from the polarizer, the optical laminate is a so-called touch sensor in which a touch sensor is incorporated between a display cell (for example, a liquid crystal cell or an organic EL cell) and the polarizer. It can be applied to an inner touch panel type input display device.

The conductive layer can be patterned as needed. By conducting the patterning, a conductive portion and an insulating portion can be formed. As a result, an electrode can be formed. The electrode can function as a touch sensor electrode that senses contact with the touch panel. The pattern shape is preferably a pattern that works well as a touch panel (for example, a capacitive touch panel). Specific examples include the patterns described in JP2011-511357A, JP2010-164938A, JP2008-310550A, JP2003-511799A, and JP2010-541109A. It is done.

The total light transmittance of the conductive layer is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more.

The density of the conductive layer is preferably 1.0 g / cm ³ to 10.5 g / cm ³ , more preferably 1.3 g / cm ³ to 3.0 g / cm ³ .

The surface resistance value of the conductive layer is preferably 0.1Ω / □ to 1000Ω / □, more preferably 0.5Ω / □ to 500Ω / □, and further preferably 1Ω / □ to 250Ω / □.

A typical example of the conductive layer is a conductive layer containing a metal oxide. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Of these, indium-tin composite oxide (ITO) is preferable.

The thickness of the conductive layer is preferably 0.01 μm to 0.05 μm (10 nm to 50 nm), more preferably 0.01 μm to 0.03 μm (10 nm to 30 nm). If it is such a range, the conductive layer excellent in electroconductivity and light transmittance can be obtained.

E. Protective Layer The protective layer 40 is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based materials. And transparent resins such as polystyrene, polynorbornene, polyolefin, (meth) acryl, and acetate. Further, thermosetting resins such as (meth) acrylic, urethane-based, (meth) acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Further, a polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As a material for 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 nitrile group in the side chain For example, a resin composition having an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

As will be described later, the optical layered body of the present invention is typically disposed on the viewing side of the image display device, and the protective layer 40 is typically disposed on the viewing side. Therefore, the protective layer 40 may be subjected to surface treatment such as hard coat treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment as necessary. Further / or, if necessary, the protective layer 40 may be treated to improve visibility when viewed through polarized sunglasses (typically, an (elliptical) circular polarization function is imparted, an ultrahigh phase difference is provided. May be applied). By performing such processing, excellent visibility can be achieved even when the display screen is viewed through a polarizing lens such as polarized sunglasses. Therefore, the optical laminate can be suitably applied to an image display device that can be used outdoors.

The thickness of the protective layer is preferably 20 μm to 200 μm, more preferably 30 μm to 100 μm, and still more preferably 35 μm to 95 μm.

When an inner protective layer is provided, the inner protective layer is preferably optically isotropic. In this specification, “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 material and thickness of the inner protective layer are as described above for the protective layer 40.

F. Anti-blocking layer The anti-blocking layer typically has an uneven surface. The uneven surface may be a fine uneven surface or a surface having a flat portion and a raised portion. In one embodiment, the anti-blocking layer has an arithmetic average roughness Ra of the surface of preferably 50 nm or more. The uneven surface can be formed, for example, by allowing the resin composition forming the anti-blocking layer to contain fine particles and / or phase-separating the resin composition forming the anti-blocking layer.

Examples of the resin used in the resin composition include a thermosetting resin, a thermoplastic resin, an ultraviolet curable resin, an electron beam curable resin, and a two-component mixed resin. An ultraviolet curable resin is preferred. This is because the anti-blocking layer can be efficiently formed by a simple processing operation.

Any appropriate resin can be used as the ultraviolet curable resin. Specific examples include polyester resins, acrylic resins, urethane resins, amide resins, silicone resins, and epoxy resins. The ultraviolet curable resin includes an ultraviolet curable monomer, oligomer, and polymer. In the embodiment of the present invention, urethane (meth) acrylate can be suitably used as the ultraviolet curable resin.

As the urethane (meth) acrylate, those containing (meth) acrylic acid, (meth) acrylic acid ester, polyol and diisocyanate as constituent components may be used. For example, a hydroxy (meth) acrylate having at least one hydroxyl group is prepared using at least one monomer of (meth) acrylic acid and (meth) acrylic acid ester and a polyol, and the hydroxy (meth) acrylate is reacted with a diisocyanate. By making it, urethane (meth) acrylate can be manufactured. Urethane (meth) acrylate may be used individually by 1 type, and may use 2 or more types together.

As the fine particles, any appropriate fine particles can be used. The fine particles preferably have transparency. Examples of the material constituting such fine particles include metal oxide, glass, and resin. Specific examples include inorganic fine particles such as silica, alumina, titania, zirconia, and calcium oxide, and organic fine particles such as polymethyl methacrylate, polystyrene, polyurethane, acrylic resin, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate. And silicone-based particles. The fine particles may be used alone or in combination of two or more. Organic fine particles are preferable, and acrylic resin fine particles are more preferable. This is because the refractive index is appropriate.

The mode particle diameter of the fine particles can be appropriately set according to the anti-blocking property and haze of the anti-blocking layer. The mode particle diameter of the fine particles is within a range of ± 50% of the thickness of the anti-blocking layer, for example. In the present specification, “mode particle size” refers to a particle size showing a maximum value of particle distribution, and using a flow type particle image analyzer (product name “FPTA-3000S” manufactured by Sysmex), It is obtained by measuring under predetermined conditions (Sheath solution: ethyl acetate, measurement mode: HPF measurement, measurement method: total count). As a measurement sample, a dispersion liquid in which particles are diluted to 1.0% by weight with ethyl acetate and uniformly dispersed using an ultrasonic cleaner may be used.

The content of the fine particles is preferably 0.05 to 1.0 part by weight, more preferably 0.1 to 0.5 part by weight with respect to 100 parts by weight of the solid content of the resin composition. More preferably 0.1 to 0.2 parts by weight. When there is too little content of microparticles | fine-particles, antiblocking property may become inadequate. When there is too much content of microparticles | fine-particles, the haze of an antiblocking layer will become high and the visibility of an optical laminated body (eventually image display apparatus) may become inadequate.

The resin composition may further contain any appropriate additive depending on the purpose. Specific examples of the additive include a reactive diluent, a plasticizer, a surfactant, an antioxidant, an ultraviolet absorber, a leveling agent, a thixotropic agent, and an antistatic agent. The number, type, combination, addition amount, and the like of the additives can be appropriately set according to the purpose.

The anti-blocking layer can be typically formed by applying a resin composition to the surface of the substrate 30 and curing it. Any appropriate method can be adopted as a coating method. Specific examples of the coating method include a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, a die coating method, and an extrusion coating method.

The curing method can be appropriately selected according to the type of resin contained in the resin composition. For example, when an ultraviolet curable resin is used, the resin composition is appropriately cured by irradiating ultraviolet rays at an exposure amount of, for example, 150 mJ / cm ² or more, preferably 200 mJ / cm ² to 1000 mJ / cm ^2. A blocking layer can be formed.

The thickness of the anti-blocking layer is preferably 0.5 μm to 2.0 μm, more preferably 0.8 μm to 1.5 μm. With such a thickness, good antiblocking properties can be secured without adversely affecting the optical properties desired for the optical laminate.

As described above, the haze value of the anti-blocking layer is preferably 0.2% to 4%, more preferably 0.5% to 3%. If a haze value is such a range, it has the advantage that the blocking of films can be prevented, without losing visibility.

Details of the configuration, material, and forming method of the anti-blocking layer are described in, for example, JP-A-2015-115171, JP-A-2015-141684, JP-A-2015-120870, JP-A-2015-005272. Has been. These descriptions are incorporated herein by reference.

G. Image Display Device The optical layered body described in the items A to F can be applied to an image display device. Therefore, the present invention includes an image display device using such an optical laminate. Typical examples of the image display device include a liquid crystal display device and an organic EL display device. An image display device according to an embodiment of the present invention includes the optical layered body described in the items A to F on the viewing side. The optical layered body is disposed so that the conductive layer is on the display cell (for example, liquid crystal cell, organic EL cell) side (the polarizer is on the viewing side). The image display device is bendable (bendable) in one embodiment, and foldable (foldable) in another embodiment.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. In addition, the measuring method of each characteristic is as follows.

(1) Thickness The conductive layer was measured by an interference film thickness measurement method using MCPD2000 manufactured by Otsuka Electronics. The other films were measured using a digital micrometer (KC-351C manufactured by Anritsu).

(2) Retardation value of retardation layer Refractive indexes nx, ny and nz of retardation layers (retardation films) used in Examples and Comparative Examples are automatically determined from an automatic birefringence measuring device (manufactured by Oji Scientific Instruments Co., Ltd., automatic It was measured with a birefringence meter KOBRA-WPR. The measurement wavelength of the in-plane retardation Re was 450 nm and 550 nm, the measurement wavelength of the thickness direction retardation Rth was 550 nm, and the measurement temperature was 23 ° C.

(3-1) Reflected hue The optical laminate was mounted on the obtained organic EL display device substitute, and the reflected hue was measured using a spectrocolorimeter CM-2600d manufactured by Konica Minolta. If both a ^* and b ^{* have an} absolute value of 10 or less and the reflectance Y is 30% or less, “o”, and if at least one of a ^* , b ^* and the reflectance exceeds the range, “x”. did.
(3-2) Evaluation of bending portion color unevenness The color of the optical laminate mounted on the obtained curved surface display device substitute was visually observed, and “◯” indicates that the color change between the bending portion and the flat portion was small. A thing with a large color change was set to "x".

(4) Photoelastic coefficient The retardation films used in Examples and Comparative Examples were cut into a size of 20 mm × 100 mm to prepare a sample. This sample was measured with an ellipsometer (manufactured by JASCO Corporation, M-150) with light having a wavelength of 550 nm to obtain a photoelastic coefficient.

(5) Reduced viscosity A resin sample was dissolved in methylene chloride to prepare a resin solution having a concentration of 0.6 g / dL precisely. Measurement was performed at a temperature of 20.0 ° C. ± 0.1 ° C. using an Ubbelohde viscometer manufactured by Moriyu Rika Kogyo Co., Ltd., and a solvent passage time t ₀ and a solution passage time t were measured. The relative viscosity η _rel was obtained from the following equation (i) using the obtained values t ₀ and t, and the specific viscosity η _sp was obtained from the following equation (ii) using the obtained relative viscosity η _rel . .
η _rel = t / t ₀ (i)
η _sp = (η−η ₀ ) / η ₀ = η _rel −1 (ii)
Thereafter, the reduced viscosity η _sp / c was determined by dividing the obtained specific viscosity η _sp by the concentration c [g / dL].

(6) Glass transition temperature The glass transition temperature was measured using a differential scanning calorimeter DSC 6220 manufactured by SII Nanotechnology. About 10 mg of a resin sample was put in an aluminum pan manufactured by the same company and sealed, and the temperature was raised from 30 ° C. to 220 ° C. at a temperature rising rate of 20 ° C./min under a nitrogen stream of 50 mL / min. After maintaining the temperature for 3 minutes, it was cooled to 30 ° C. at a rate of 20 ° C./min. The temperature was maintained at 30 ° C. for 3 minutes, and the temperature was increased again to 220 ° C. at a rate of 20 ° C./min. From the DSC data obtained at the second temperature increase, a straight line obtained by extending the base line on the low temperature side to the high temperature side, and a tangent line drawn at a point where the slope of the step change portion of the glass transition becomes maximum The extrapolated glass transition start temperature, which is the temperature of the intersection point, was determined and used as the glass transition temperature.

(7) Melt viscosity The pellet-shaped resin sample was vacuum-dried at 90 ° C for 5 hours or more. Measurement was performed using a capillary rheometer manufactured by Toyo Seiki Seisakusho, using the dried pellets. The measurement temperature was 240 ° C., the melt viscosity was measured at a shear rate of 9.12 to 1824 sec ⁻¹ , and the value of the melt viscosity at 91.2 sec ⁻¹ was used. An orifice having a die diameter of φ1 mm × 10 mmL was used.

(8) Refractive index A rectangular test piece having a length of 40 mm and a width of 8 mm was cut out from an unstretched film produced in Examples and Comparative Examples described later to obtain a measurement sample. The refractive index n _D was measured with a multi-wavelength Abbe refractometer DR-M4 / 1550 manufactured by Atago Co., Ltd. using an interference filter of 589 nm (D line). The measurement was performed at 20 ° C. using monobromonaphthalene as the interfacial liquid.

(9) Total light transmittance Using the above unstretched film as a measurement sample, the total light transmittance was measured using a turbidimeter COH400 manufactured by Nippon Denshoku Industries Co., Ltd.

(Example of monomer synthesis)
[Synthesis Example 1] Synthesis of bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane (BPFM) The compound was synthesized by the method described in JP-A-2015-25111.
[Synthesis Example 2] Synthesis of 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane (SBI) The compound was synthesized by the method described in JP-A-2014-114281.

[Synthesis example and characteristic evaluation of polycarbonate resin]
Abbreviations and the like of compounds used in the following examples and comparative examples are as follows.
BPFM: bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane BCF: 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (manufactured by Osaka Gas Chemical Co., Ltd.)
BHEPF: 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (manufactured by Osaka Gas Chemical Co., Ltd.)
ISB: Isosorbide (Rocket Fleure, trade name: POLYSORB)
SBI: 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane SPG: Spiroglycol (manufactured by Mitsubishi Gas Chemical Co., Inc.)
・ PEG: Polyethylene glycol Number average molecular weight: 1000 (manufactured by Sanyo Chemical Co., Ltd.)
・ DPC: Diphenyl carbonate (Mitsubishi Chemical Corporation)

[Example 1]
(Production of retardation layer)
SBI 6.04 parts by weight (0.020 mol), ISB 59.58 parts by weight (0.408 mol), BPFM 34.96 parts by weight (0.055 mol), DPC 79.39 parts by weight (0.371 mol), and catalyst As a result, 7.53 × 10 ⁻⁴ parts by weight (4.27 × 10 ⁻⁶ mol) of calcium acetate monohydrate was charged into the reaction vessel, and the inside of the reaction apparatus was purged with nitrogen under reduced pressure. In a nitrogen atmosphere, the raw materials were dissolved while stirring at 150 ° C. for about 10 minutes. As the first step of the reaction, the temperature was raised to 220 ° C. over 30 minutes, and the reaction was performed at normal pressure for 60 minutes. Next, the pressure was reduced from normal pressure to 13.3 kPa over 90 minutes, maintained at 13.3 kPa for 30 minutes, and the generated phenol was extracted out of the reaction system. Next, as the second step of the reaction, the temperature of the heating medium was raised to 245 ° C. over 15 minutes, while the pressure was reduced to 0.10 kPa or less over 15 minutes, and the generated phenol was extracted out of the reaction system. After reaching a predetermined stirring torque, the reaction was stopped by restoring the pressure to normal pressure with nitrogen, the produced polyester carbonate resin was extruded into water, and the strand was cut to obtain pellets. The resulting resin had a reduced viscosity of 0.375 dL / g, a glass transition temperature of 165 ° C., a melt viscosity of 5070 Pa · s, a refractive index of 1.5454, and a photoelastic coefficient of 15 × 10 ⁻¹² m ² / N. It was.
Resin pellets that had been vacuum-dried at 100 ° C. for 5 hours or longer were used with a single die extruder (screw diameter 25 mm, cylinder set temperature: 255 ° C.) manufactured by Isuzu Chemical Industries, Ltd., and T-die (width 200 mm, set temperature: 250 ° C). The extruded film was rolled by a winder while being cooled by a chill roll (set temperature: 155 ° C.), and an unstretched film having a thickness of 100 μm was produced. The polycarbonate resin film obtained as described above was cut into a rectangular test piece of 120 mm × 150 mm with a safety razor, and stretched at a stretching temperature of 171 ° C. in the longitudinal direction with a batch-type biaxial stretching apparatus (Brookner) and a stretching speed. Uniaxial stretching was performed 1 × 2.4 times at 5 mm / sec.

As described above, a retardation film (thickness 64 μm) was obtained. The obtained retardation film had Re (550) of 147 nm and Rth (550) of 147 nm, and exhibited refractive index characteristics of nx> ny = nz. Moreover, Re (450) / Re (550) of the obtained retardation film was 0.81. The slow axis direction of the retardation film was 0 ° with respect to the longitudinal direction.

(Production of retardation layer / conductive layer laminate)
A transparent conductive layer (thickness 20 nm) made of an indium-tin composite oxide was formed on the surface of the retardation film (retardation layer) by sputtering to produce a retardation layer / conductive layer laminate. The specific procedure is as follows: 10% by weight oxidation in a vacuum atmosphere (0.40 Pa) with Ar and O ₂ (flow ratio Ar: O ₂ = 99.9: 0.1) introduced RF superimposed DC magnetron sputtering method (discharge voltage 150 V, RF frequency 13.56 MHz, DC, using a sintered body of tin and 90 wt% indium oxide as a target, setting the film temperature to 130 ° C., and setting the horizontal magnetic field to 100 mT. The ratio of RF power to power (RF power / DC power) was 0.8). The obtained transparent conductive layer was heated in a 150 ° C. hot air oven to perform a crystal conversion treatment.

(Production of polarizer)
At the same time, a long roll of polyvinyl alcohol (PVA) resin film (product name “PE3000”, manufactured by Kuraray Co., Ltd.) having a thickness of 30 μm is uniaxially stretched in the longitudinal direction so as to be 5.9 times in the longitudinal direction by a roll stretching machine. Swelling, dyeing, crosslinking, and washing treatment were performed, and finally a drying treatment was performed to produce a polarizer having a thickness of 12 μm.
Specifically, the swelling treatment was stretched 2.2 times while being treated with pure water at 20 ° C. Next, the dyeing treatment is performed in an aqueous solution at 30 ° C. in which the weight ratio of iodine and potassium iodide is 1: 7, the iodine concentration of which is adjusted so that the single transmittance of the obtained polarizer is 45.0%. The film was stretched 1.4 times. Furthermore, the crosslinking treatment employed a two-stage crosslinking treatment, and the first-stage crosslinking treatment was stretched 1.2 times while being treated in 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-stage crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. The cross-linking treatment at the second stage was stretched 1.6 times while being treated in 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 crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. In addition, the cleaning treatment was performed with an aqueous potassium iodide solution at 20 ° C. The potassium iodide content of the aqueous solution for the washing treatment was 2.6% by weight. Finally, the drying process was performed at 70 ° C. for 5 minutes to obtain a polarizer.

(Preparation of polarizing plate)
A TAC film was bonded to one side of the polarizer via a polyvinyl alcohol adhesive to obtain a polarizing plate having a protective layer / polarizer configuration.

(Production of optical laminate)
The polarizer surface of the polarizing plate obtained above and the retardation layer surface of the retardation layer / conductive layer laminate obtained above were bonded together via an acrylic pressure-sensitive adhesive. The retardation film was cut out so that the slow axis and the absorption axis of the polarizer form an angle of 45 degrees when bonded. The absorption axis of the polarizer was arranged so as to be parallel to the longitudinal direction. Thus, an optical layered body having a configuration of protective layer / polarizer / retardation layer / conductive layer was obtained.

(Production of image display device replacement)
An alternative to the organic EL display device was produced as follows. An aluminum vapor-deposited film (trade name “DMS vapor-deposited X-42”, thickness 50 μm) manufactured by Toray Film Processing Co., Ltd. was bonded to a glass plate with an adhesive to make an alternative to an organic EL display device. A pressure-sensitive adhesive layer is formed with an acrylic pressure-sensitive adhesive on the conductive layer side of the obtained optical laminate, cut into a size of 50 mm × 50 mm, and mounted on a substitute for an organic EL display device. It measured in the procedure of. At that time, as a control, the same applies to the mounted product using the optical laminate having the structure of the protective layer / polarizer / retardation layer produced in the same manner as above except that the conductive layer was not formed. The reflected hue was measured by the above procedure (3-1).

(Production of a curved surface display device replacement)
An alternative to the curved display device was produced as follows. The above-mentioned aluminum vapor deposition film “DMS vapor deposition X-42” is pasted with an adhesive on a tabletop name plate (made by Plus, L-shaped card stand, width dimension × depth dimension × height dimension 120 mm × 29 mm × 60 mm). It was replaced with a display device. An optical laminate having the structure of protective layer / polarizer / retardation layer produced in the same manner as above except that the conductive layer was not formed is bonded to the substitute with an acrylic adhesive and mounted. I got a product. In the optical laminate, the retardation film (retardation layer) was cut so that the slow axis and the absorption axis of the polarizer form an angle of 45 degrees. In addition, the optical layered body was disposed so that the slow axis of the retardation layer and the direction in which the bent portion extends were orthogonal to each other. The color of the bent part and the flat part in the mounted product was visually observed and evaluated according to the above criteria (3-2).

From the evaluation indicators (3-1) and (3-2) in the image display device substitute product and the bent display device substitute product, the ability index of the circularly polarizing plate that directly forms the spatter was used. The results are shown in Table 1.

[Example 2]
SBI 15.10 parts by weight (0.049 mol), ISB 42.27 parts by weight (0.289 mol), SPG 15.10 parts by weight (0.050 mol), BPFM 26.22 parts by weight (0.041 mol), DPC 75 Example 14 except that .14 parts by weight (0.351 mol) and calcium acetate monohydrate 2.05 × 10 ⁻³ parts by weight (1.16 × 10 ⁻⁵ mol) were used as the catalyst. Thus, a polyester carbonate resin was obtained. The resulting resin had a reduced viscosity of 0.334 dL / g, a glass transition temperature of 157 ° C., a melt viscosity of 3020 Pa · s, a refractive index of 1.5360, and a photoelastic coefficient of 12 × 10 ⁻¹² m ² / N. It was.

A retardation film in the same manner as in Example 1 except that the above polyester carbonate resin was used and uniaxial stretching was performed 1 × 2.4 times at a stretching temperature of 162 ° C. and a stretching speed of 5 mm / sec in the longitudinal direction. (Thickness 65 μm) was obtained. The obtained retardation film had Re (550) of 140 nm and Rth (550) of 140 nm, and exhibited refractive index characteristics of nx> ny = nz. Further, Re (450) / Re (550) of the obtained retardation film was 0.86. The slow axis direction of the retardation film was 0 ° with respect to the longitudinal direction.

[Comparative Example 1]
An optical laminate and an organic EL display device substitute were prepared in the same manner as in Example 1 except that a commercially available polycarbonate resin film (trade name “Pure Ace WR” manufactured by Teijin Limited) was used as the retardation layer. The obtained organic EL display device substitute was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
60.43 parts by weight (0.199 mol) of SPG, 32.20 parts by weight (0.085 mol) of BCF, 64.40 parts by weight (0.301 mol) of DPC, and 2.50 × 10 calcium acetate monohydrate as a catalyst ^A polycarbonate resin was obtained in the same manner as in Example 1 except that ⁻³ parts by weight (1.42 × 10 ⁻⁵ mol) was used and the final polymerization temperature was 260 ° C. The obtained resin has a reduced viscosity of 0.499 dL / g, a glass transition temperature of 135 ° C., a melt viscosity of 2940 Pa · s, a refractive index of 1.5334, and a photoelastic coefficient of 13 × 10 ⁻¹² m. ² / N. An optical laminate and an organic EL display device substitute were produced in the same manner as in Example 1 except that a film formed from this polycarbonate resin was used. The obtained organic EL display device substitute was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
The optical laminate and the organic EL display device were the same as in Example 1 except that a commercially available cycloolefin-based resin film (manufactured by ZEON Corporation, trade name “ZEONOR”, in-plane retardation 147 nm) was used as the retardation layer. An alternative was made. The obtained organic EL display device substitute was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
The retardation layer used in Comparative Example 1 was bonded to the polarizing plate used in Example 1 to obtain a circularly polarizing plate having a configuration of protective layer / polarizer / retardation layer. On the other hand, a commercially available cycloolefin resin film (manufactured by Zeon Corporation, trade name “ZEONOR”, in-plane retardation 3 nm) was used as a base material, and indium-tin was used on the surface of the base material in the same manner as in Example 1. A transparent conductive layer made of a complex oxide was formed by sputtering. An optical laminate having a constitution of protective layer / polarizer / retardation layer / conductive layer / base material, wherein the retardation layer surface of the circularly polarizing plate and the conductive layer surface of the laminate of the base material / conductive layer are bonded together with an acrylic adhesive. Got the body. An organic EL display device was produced in the same manner as in Example 1 except that this optical laminate was used. The obtained organic EL display device was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Evaluation]
As is clear from Table 1, by setting the Tg, photoelastic coefficient, and wavelength dependency of the retardation layer within a predetermined range, the desired optical characteristics can be obtained even when the conductive layer is directly formed on the surface by sputtering. Can be maintained. In Comparative Example 1 using the retardation layer having a large photoelastic coefficient, the color unevenness of the bent portion is poor. In Comparative Example 2 using a retardation layer having a low Tg, the reflection hue is poor due to the formation (sputtering) of the conductive layer. In Comparative Example 3 using a retardation layer having flat wavelength dispersion characteristics, the reflection hue is poor regardless of the presence or absence of a conductive layer (sputtering). In Comparative Example 4 in which the conductive layer was formed on the base material and the base material / conductive layer laminate was bonded, the thickness of the base material and the pressure-sensitive adhesive layer for bonding was increased. Furthermore, in Comparative Example 4, the color unevenness of the bent portion is defective.

The optical layered body of the present invention can be suitably used for an image display device (typically, a liquid crystal display device or an organic EL display device).

10 Polarizer 20 Retardation layer (retardation film)
30 conductive layer 40 protective layer 100 optical laminate

Claims (9)

1. A polarizer, a retardation layer, and a conductive layer formed directly on the retardation layer,
   The retardation layer has an in-plane retardation Re (550) of 100 nm to 180 nm, satisfies a relationship of Re (450) <Re (550) <Re (650), and has a glass transition temperature (Tg). Is 150 ° C. or more, and the absolute value of the photoelastic coefficient is 20 × 10 ⁻¹² (m ² / N) or less,
   The angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is 35 ° to 55 °.
   Optical laminate.
2. The optical laminate according to claim 1, wherein the retardation layer is composed of a polycarbonate resin containing at least a structural unit represented by the following formula (1) or (2):
   

   

   

   (In the formulas (1) and (2), R ¹ to R ³ are each independently a direct bond or an alkylene group having 1 to 4 carbon atoms which may have a substituent, and R ⁴ to R ⁹ Each independently has a hydrogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, an optionally substituted aryl group having 4 to 10 carbon atoms, or a substituent. An optionally substituted acyl group having 1 to 10 carbon atoms, an optionally substituted alkoxy group having 1 to 10 carbon atoms, an optionally substituted aryloxy group having 1 to 10 carbon atoms, An amino group which may have a substituent, a vinyl group having 1 to 10 carbon atoms which may have a substituent, an ethynyl group having 1 to 10 carbon atoms which may have a substituent, a substituent; A sulfur atom having a substituent, a silicon atom having a substituent, a halogen atom, a nitro group, or a cyano group. , R 4 ^~ R ⁹ are identical to one another or different, may form a ring with each other at least two neighboring groups of the R 4 ^~ R ^9.)
3. The optical layered body according to claim 1 or 2, wherein the retardation layer is composed of a polycarbonate resin containing at least a structural unit represented by the following formula (3):
   

   

   (In formula (3), R ¹⁰ to R ¹⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group, an alkoxy group having 1 to 12 carbon atoms, or a halogen atom.)
4. The optical laminate according to any one of claims 1 to 3, wherein the retardation layer is composed of a polycarbonate resin containing at least a structural unit represented by the following formula (4):
   

   
5. 5. The optical laminate according to claim 2, wherein the polycarbonate resin has a melt viscosity at a measurement temperature of 240 ° C. and a shear rate of 91.2 sec ⁻¹ of 3000 Pa · s or more and 7000 Pa · s or less. .
6. The optical laminate according to any one of claims 2 to 5, wherein the polycarbonate resin has a refractive index of 1.49 or more and 1.56 or less at a sodium d line (589 nm).
7. The optical laminate according to any one of claims 1 to 6, further comprising a protective layer bonded to the opposite side of the polarizer from the retardation layer.
8. The optical laminate according to any one of claims 1 to 7, further comprising a protective layer between the polarizer and the retardation layer.
9. An image display device comprising the optical laminate according to any one of claims 1 to 8 on the viewing side, wherein the polarizer of the optical laminate is disposed on the viewing side.
   
   

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