JP6904666B2 - Optical laminate - Google Patents

Description

The present invention relates to an optical laminate.

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 that these problems can be prevented by providing a circularly polarizing plate as an antireflection film on the visual recognition side (for example, Patent Document 1).

In recent years, there has been an increasing demand for flexible and flexible organic EL display devices. When a circularly polarizing plate is used in an organic EL display device having high flexibility, there is a problem that when the display device is bent, the circularly polarizing plate is cracked or broken, and the display characteristics are significantly deteriorated. In particular, this problem becomes remarkable in a foldable display device called foldable.

Japanese Unexamined Patent Publication No. 2006-171235

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is an optical lamination which is excellent in folding resistance and can be suitably applied to a bendable or foldable organic EL display device. To provide the body.

The optical laminate of the present invention includes a base material and a polarizer arranged on at least one side of the base material, and the delamination force between the base material and the polarizer is 0.5 N / 15 mm or more. After bending 100,000 times with a radius of curvature of 2 mm, there is no delamination between the base material / the polarizer, and there is no breakage or cracking of the polarizer.
In one embodiment, the optical laminate of the present invention has a tensile elastic modulus of 1.5 GPa or more at 25 ° C.
In one embodiment, the substrate and the polarizer are laminated via an adhesive layer.
In one embodiment, the optical laminate of the present invention is used as an antireflection film for an organic EL display device.
According to another aspect of the present invention, an organic EL display device is provided. This organic EL display device includes the above optical laminate.

According to the embodiment of the present invention, by providing the base material and the polarizer and setting the delamination force between the base material and the polarizer within a specific range, peeling and breaking are unlikely to occur even if bending is repeated. An optical laminate can be obtained. As described above, the optical laminate having excellent fold resistance can be suitably applied to a bendable or foldable organic EL display device.

It is the schematic sectional drawing of the optical laminated body by one Embodiment of this invention. It is the schematic sectional drawing of the optical laminated body by another embodiment of this invention. It is the schematic sectional drawing of the organic EL display device by one Embodiment of this invention. It is schematic cross-sectional view of the organic EL element used in the organic EL display device by one Embodiment of this invention. It is a figure explaining the folding resistance tester used for the folding resistance test of an Example and a comparative example.

Hereinafter, typical 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 the in-plane phase difference of the film measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (450)" is an in-plane phase difference of a film measured with light having a wavelength of 450 nm at 23 ° C. Re (λ) is obtained by the formula: Re = (nx−ny) × d, where d (nm) is the thickness of the film.
(3) Phase difference in the thickness direction (Rth)
“Rth (λ)” is the phase difference in the thickness direction of the film measured with light having a wavelength of 550 nm at 23 ° C. For example, "Rth (450)" is a phase difference in the thickness direction of a film measured with light having a wavelength of 450 nm at 23 ° C. Rth (λ) is obtained 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) Oriented solidified layer of liquid crystal compound The "aligned solidified layer" means a layer in which a liquid crystal compound is oriented in a predetermined direction in the layer and the oriented state is fixed. The "oriented solidified layer" is a concept including an oriented cured layer obtained by curing a liquid crystal monomer.
(6) Angle When referring to an angle in the present specification, the angle includes an angle in both clockwise and counterclockwise directions unless otherwise specified.

A. Overall Configuration of Optical Laminates FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 of the present embodiment includes a base material 10 and a polarizer 20 arranged on at least one side of the base material 10. The base material 10 is flexible. In one embodiment, the base material 10 has a function of substituting the cover glass of the organic EL display device as a surface protective layer, and also functions as a protective layer of the polarizer 20. As a result of substituting the cover glass, the optical laminate (as a result, the organic EL display device) can be made thinner. Preferably, the base material 10 and the polarizer 20 are laminated via an adhesive layer (not shown).

The delamination force between the base material and the polarizer is 0.5 N / 15 mm or more, preferably 1 N / 15 mm or more, more preferably 2 N / 15 mm or more, and further preferably 2.5 N / 15 mm or more. It is more preferably 3N / 15mm or more. The upper limit of the delamination force between the base material and the polarizer is, for example, 5N / 15 mm. The delamination force is the peeling force when the base material and the polarizer are peeled off under the conditions of a peeling angle of 90 ° and a peeling speed of 10 m / min by a tensile tester after fixing the optical laminate to a glass plate. Means power. The delamination force between the base material and the polarizer can be adjusted, for example, by the characteristics of the adhesive layer arranged between the base material and the polarizer.

In the present invention, the delamination force between the base material and the polarizer is set to a specific value or more as described above, and the base material and the polarizer are sufficiently brought into close contact with each other so that the polarizing element is bent when the optical laminate is bent. Can prevent breakage and cracking. More specifically, by preventing peeling of the polarizer when the optical laminate is bent, breakage and cracking of the polarizer caused by the peeling are prevented. The optical laminate of the present invention is less likely to peel and break even when bent repeatedly, and can be suitably applied to a bendable or foldable organic EL display device. In one embodiment, the delamination force between the substrate and the polarizer is 2N / 15 mm or more. Within such a range, the above effect becomes more remarkable, and even when the optical laminate is bent a plurality of times with a large bending ratio (for example, the radius of curvature of the bent portion is less than 2 mm), the polarizer is broken and cracked. Is prevented.

The optical laminate of the present invention has no delamination between the substrate and the polarizer after being bent 100,000 times with a radius of curvature of 2 mm, and there is no breakage or cracking of the polarizer. Here, the fact that there is no delamination between the substrate and the polarizer means that the area of the portion where the polarizer is detached from the substrate is 5% or less of the entire surface of the polarizer on the substrate side. .. The area of the portion where the polarizer is peeled off from the substrate is preferably 3% or less, more preferably 1% or less, based on the entire surface of the polarizer on the substrate side. Most preferably, the polarizer does not detach from the substrate at all. The bending is performed at a bending angle of 175 ° with a mandrel of 4 mmφ sandwiched (that is, the radius of curvature of the bent portion is 2 mm) with the base material side inside (details will be described later).

Preferably, the optical laminate of the present invention has no delamination between the substrate and the polarizer and no breakage or cracking of the polarizer after being bent 100,000 times with a radius of curvature of 1 mm. The bending is performed at a bending angle of 175 ° with a 2 mmφ mandrel sandwiched with the base material side inside.

FIG. 2 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention. The optical laminate 101 of the present embodiment further includes an optical compensation layer 30 on the side of the polarizer 20 opposite to the base material 10. In one embodiment, the laminate of the optical compensation layer 30 and the polarizer 20 functions as a circularly polarizing plate. A conductive layer (not shown) may be provided on the side of the optical compensation layer 30 opposite to the polarizer 20. By providing such a conductive layer, 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 (organic EL cell) and a polarizer. A print layer (not shown) may be formed on the peripheral edge of the optical laminate (more specifically, a position corresponding to the bezel of the organic EL display device). The printing layer may be formed on the polarizer 20 side of the base material 10 (substantially, the polarizer 20 side of the resin film 12), or may be formed on the side opposite to the polarizer 20 of the optical compensation layer 30. good. When the print layer is formed on the side opposite to the polarizer 20 of the optical compensation layer 30 and both the conductive layer and the print layer are formed, typically, between the optical compensation layer and the conductive layer. A print layer can be formed.

In one embodiment, the optical compensation layer is made of a retardation film. In this case, the retardation film can also function as a protective layer (inner protective layer) for the polarizer. As a result, it can contribute to further thinning of the optical laminate (as a result, the organic EL display device). If necessary, an inner protective layer (inner protective film) may be arranged between the polarizer and the retardation film.

In another embodiment, the optical compensation layer has a laminated structure of an oriented solidified layer of a liquid crystal compound (hereinafter, simply referred to as a liquid crystal oriented solidified layer). By using the liquid crystal compound, the difference between nx and ny of the obtained optical compensation layer can be made much larger than that of the non-liquid crystal material, so that the thickness of the optical compensation layer for obtaining a desired in-plane phase difference can be obtained. Can be made much smaller. As a result, it is possible to further reduce the thickness of the optical laminate (as a result, the organic EL display device).

When the optical laminate has a layer other than the polarizer and the base material, the delamination force between the layers is preferably equal to the delamination force between the base material and the polarizer. Specifically, the delamination force between each layer (for example, between the optical compensation layer / the polarizer, the optical compensation layer / the conductive layer, etc.) is preferably 0.5 N / 15 mm or more, and more preferably 1 N / 15 mm or more. It is more preferably 2N / 15mm or more, further preferably 2.5N / 15mm or more, and particularly 3N / 15mm or more.

Although not shown, the optical laminate of the present invention may further comprise any suitable other layer. Examples of other layers include an antireflection layer and an antifouling layer.

In one embodiment, the optical laminate of the present invention is elongated. The elongated optical laminate can be, for example, rolled into a roll for storage and / or transportation.

The total thickness of the optical laminate of the present invention is typically 30 μm to 300 μm, preferably 40 μm to 250 μm.

The tensile elastic modulus of the optical laminate of the present invention is preferably 1.5 GPa or more, more preferably 2.0 GPa or more, and further preferably 2.0 GPa to 10 GPa at 25 ° C. Within such a range, it is possible to obtain an optical laminate that is hard to break as a whole (that is, both the base material and the polarizer are hard to break). The tensile elastic modulus of the optical laminate can be set to a desired value, for example, by appropriately selecting the material constituting the base material. The tensile modulus can be measured according to JIS K 7127 (test piece: dumbbell test piece).

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

The optical laminate according to the embodiment of the present invention includes an image display device (for example, a liquid crystal display device, an organic EL display device), preferably a bendable image display device, and more preferably a bendable organic EL display device. More preferably, it is used for a foldable (foldable) organic EL display device. Hereinafter, for the sake of simplicity, a case where the optical laminate is applied to a bendable or foldable organic EL display device will be described, but it is obvious to those skilled in the art that the optical laminate can be similarly applied to a liquid crystal display device. Is.

Hereinafter, the components of the optical laminate will be described.

B. Substrate In one embodiment, the substrate comprises a hard coat layer and a resin film. In the optical laminate, the hard coat layer can be arranged on the surface of the resin film opposite to the polarizer. Depending on the structure of the resin film, the hard coat layer may be omitted, or hard coat layers may be formed on both sides of the resin film. The base material may be formed by directly laminating a resin film or a laminate of a hard coat layer and a resin film on a polarizing element, or may be formed by applying a coating liquid containing a resin, which will be described later, to a polarizing element. good.

B-1. Characteristics of Base Material The term "base material" in the description of the characteristics of the base material means a resin film when the resin film is used alone, and a laminate thereof when the hard coat layer and the resin film are included. ..

The substrate has a radius of curvature of 3 mm or less (for example, 3 mm, 2 mm, 1 mm) and has flexibility that allows it to bend preferably 200,000 times, more preferably 300,000 times, and even more preferably 500,000 times. When the base material has such flexibility, it is possible to realize an organic EL display device that can be bent or folded when the optical laminate is applied to the organic EL display device. When the substrate has a hard coat layer on one side of the resin film, the flexibility test is performed by bending with the hard coat layer inside. The flexibility of the base material can be measured by a folding resistance tester in which the chuck on one side repeatedly bends 180 ° across the mandrill.

The substrate preferably has resilience after bending. Restorability after bending means returning to the original state without leaving any creases after bending. The resilience after bending can be evaluated, for example, by the number of repetitions until a crease is formed after the base material (resin film or laminate) is repeatedly bent at a radius of curvature of 1 mm at 180 °. The base material preferably has a resilience of 10,000 times or more under the conditions.

The visible side surface (hard coat layer surface or resin film surface) of the base material preferably has a pencil hardness of 9H or more. Further, the visible surface has scratch resistance that does not cause scratches even if it is rubbed back and forth preferably 300 times, more preferably 500 times, and even more preferably 1000 times under a load of 1000 g. If the pencil hardness and scratch resistance are in such a range, the substrate can function well as a substitute for the cover glass. Pencil hardness can be measured according to JIS K 5400-5-4. Further, the scratch resistance can be evaluated in the state of scratches when the surface is reciprocated a predetermined number of times with a load of 1000 g of steel wool # 0000.

The light transmittance of the base material is preferably 91% or more, more preferably 93% or more, and further preferably 95% or more. The base material haze is preferably 0.5% or less, more preferably 0.4% or less, and further preferably 0.3% or less. When the light transmittance and / or haze of the base material is within such a range, good visibility can be realized when the optical laminate is applied to an organic EL display device.

B-2. Hard Coat Layer The hard coat layer may be made of any suitable material that can satisfy the properties described in item B-1 above. Specific examples of the constituent materials include a thermocurable resin, a thermoplastic resin, an active energy ray-curable resin (for example, an ultraviolet curable resin and an electron beam curable resin), and a two-component mixed resin. UV curable resin is preferable. This is because the hard coat layer can be efficiently formed by a simple processing operation. Examples of the ultraviolet curable resin include various resins such as polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based resins. These include UV curable monomers, oligomers, polymers and the like. An acrylic resin is preferable. The ultraviolet curable acrylic resin contains a monomer component and an oligomer component having preferably 2 or more, more preferably 3 to 6 ultraviolet polymerization functional groups. Typically, the ultraviolet curable resin contains a photopolymerization initiator. The curing method may be a radical polymerization method or a cationic polymerization method. In one embodiment, an organic-inorganic hybrid material in which silica particles, a cage-like silsesquioxane compound, or the like is blended with the constituent material may be used. A constituent material and a method for forming the hard coat layer are described in, for example, Japanese Patent Application Laid-Open No. 2011-237789. The description of this publication is incorporated herein by reference.

The hard coat layer may be formed by blending a slide ring material with the above-mentioned constituent materials. Good flexibility can be imparted by blending the slide ring material. Polyrotaxane is a typical example of the slide ring material. Polyrotaxane typically has a structure in which a cyclodextrin (CD) cyclic molecule slides on a linear polyethylene glycol (PEG) main chain. Both ends of the PEG backbone are modified with adamantaneamine to prevent shedding of the CD cyclic molecule. In the polyrotaxane used in the present invention, the CD cyclic molecule is chemically modified to impart an active energy ray-polymerizable group. When a slide ring material is used, a radically polymerizable monomer having a radically polymerizable group is preferably used as the hard coat layer constituent material. Examples of the radically polymerizable group include a (meth) acryloyl group and a (meth) acryloyloxy group. This is because it has excellent compatibility with polyrotaxane and various material selections are possible. When polyrotaxane (substantially the polymerizable group of the CD cyclic molecule) reacts with the active energy ray-curable component of the hard coat layer constituent material and cures, the hard coat layer whose cross-linking point is movable even after curing is formed. can get. As a result, the stress at the time of bending can be relaxed, and the bending durability is improved. Polyrotaxane and the curing mechanism are described in, for example, Japanese Patent Application Laid-Open No. 2015-155530. The description of this publication is incorporated herein by reference.

The hard coat layer may be formed by blending nanofibers and / or nanocrystals with the above-mentioned constituent materials. Typical examples of nanofibers include cellulose nanofibers, chitin nanofibers, and chitosan nanofibers. By blending these, a hard coat layer having excellent flexibility, pencil hardness, scratch resistance, and abrasion resistance can be obtained while maintaining excellent transparency. The nanofibers and / or nanocrystals (the total when used in combination) may be blended in a proportion of 0.1% to 40% by weight, preferably 0.1% by weight, based on the entire hardcoat layer. The nanofibers have an average fiber diameter of, for example, 1 nm to 100 nm, and an average fiber length of, for example, 10 nm to 1000 nm. The hard coat layer containing nanofibers is described in, for example, Japanese Patent Application Laid-Open No. 2012-131201 and Japanese Patent Application Laid-Open No. 2012-171171. The description of this publication is incorporated herein by reference.

The thickness of the hard coat layer is preferably 1 μm to 20 μm, more preferably 2 μm to 15 μm. If the thickness is too small, the hardness may be insufficient, or the effect of suppressing dimensional change due to bending or the like may be insufficient. Too much thickness can adversely affect flexibility and / or foldability.

B-3. Resin film The resin film can be made of any suitable material that can satisfy the properties described in item B-1 above. Specific examples of the constituent materials include polyethylene terephthalate resin, polyethylene naphthalate resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyamideimide resin, and polyolefin resin. Examples thereof include (meth) acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, polyarylate resins, polyphenylene sulfide resins and the like. These resins may be used alone or in combination of two or more. Preferred are polyarylate-based resins and / or polyimide-based resins. By using these resins, it is possible to obtain an optical laminate having an appropriate tensile elastic modulus (specifically, the tensile elastic modulus described in item A).

The resin film may contain fine particles in the above-mentioned constituent materials. More specifically, the resin film may be a so-called nanocomposite film in which nanometer-order fine particles are dispersed in the matrix of the constituent materials. With such a configuration, very good hardness and scratch resistance are imparted, so that the hard coat layer can be omitted. The average particle size of the fine particles is, for example, about 1 nm to 100 nm. The fine particles are typically composed of inorganic oxides. Preferably, the surface of the fine particles is modified with a predetermined functional group. Examples of the inorganic oxides constituting the fine particles include zirconium oxide, itria-added zirconium oxide, lead zirconate, strontium titanate, tin titanate, tin oxide, bismuth oxide, niobium oxide, tantalum oxide, potassium tantalate, and tungsten oxide. , Cerium oxide, lanthanum oxide, gallium oxide and the like, silica, alumina, titanium oxide, zirconium oxide, barium titanate and the like.

The thickness of the resin film is preferably 5 μm to 100 μm, more preferably 10 μm to 80 μm. With such a thickness, the balance between thinning, handleability, and mechanical strength is excellent.

C. Polarizer As the polarizer, 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 characteristics, 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 on the surface of the PVA-based film and the blocking inhibitor, 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 15 μm or less, more preferably 1 μm to 12 μm, further 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. Further, 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 of 380 nm to 780 nm. The simple substance transmittance of the polarizer is preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. 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. Optical compensation layer D-1. Optical Compensation Layer Consists of Phase Difference Film When the optical compensation layer is composed of a retardation film, the retardation film can function as a so-called λ / 4 plate. The in-plane retardation Re (550) of the retardation film is preferably 100 nm to 180 nm, more preferably 135 nm to 155 nm.

The retardation film preferably satisfies the relationship of Re (450) <Re (550) <Re (650). That is, it is preferable that the retardation film exhibits a wavelength dependence of inverse dispersion in which the retardation value increases according to the wavelength of the measurement light. The Re (450) / Re (550) of the retardation film is preferably 0.8 or more and less than 1.0, and more preferably 0.8 to 0.95. 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 film typically has a refractive index characteristic of nx> ny and has a slow phase axis. The angle formed by the slow axis of the retardation film and the absorption axis of the polarizer is preferably 35 ° to 55 °, more preferably 38 ° to 52 °, and even more preferably 42 ° to 48 °. , Particularly preferably about 45 °. If the angle is in such a range, by using a retardation film as a λ / 4 plate, an optical laminate having extremely excellent circularly polarized light characteristics (as a result, extremely excellent antireflection characteristics) can be obtained. Can be

The retardation film exhibits any suitable index of refraction ellipsoid as long as it has an nx> ny relationship. Preferably, the refractive index ellipsoid of the retardation film shows a relationship of nx> ny ≧ nz. 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 film is preferably 0.9 to 2, more preferably 0.9 to 1.5, and even more preferably 0.9 to 1.3. By satisfying such a relationship, a very excellent reflected hue can be achieved when the optical laminate is used in an organic EL display device.

The absolute value of the photoelastic coefficient of the retardation film is preferably 2 × 10 ^-12 (m ² / N) or more, and more preferably 10 × 10 ^-12 (m ² / N) to 100 × 10 ^{−. It is 12} (m ² / N), more preferably 20 × 10 ^-12 (m ² / N) to 40 × 10 ^-12 (m ² / N). If the absolute value of the photoelastic coefficient is within such a range, the flexibility of the organic EL display device can be maintained while ensuring a sufficient phase difference even with a small thickness, and the phase difference changes due to stress during bending. (As a result, the color change of the organic EL display device) can be further suppressed.

The thickness of the retardation film is preferably 1 μm to 70 μm, more preferably 1 μm to 20 μm, and further preferably 1 μm to 10 μm. Since the optical laminate of the present invention can use a film thinner than the conventional λ / 4 plate while maintaining the desired optical characteristics, the optical laminate (as a result, the organic EL display device) can be made thinner. Can contribute to.

The retardation film is made of any suitable resin that can satisfy the above properties. Examples of the resin forming the retardation film include a polycarbonate resin, a polyvinyl acetal resin, a cycloolefin resin, an acrylic resin, and a cellulose ester resin. A polycarbonate resin is preferable.

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 dihydroxy compound, a structural unit derived from an isosorbide 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 dihydroxy compounds, structural units derived from isosorbide 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.

The glass transition temperature of the polycarbonate resin is preferably 110 ° C. or higher and 250 ° C. or lower, more preferably 120 ° C. or higher and 230 ° 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 display device 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.

The retardation film can be obtained, for example, by stretching a film formed of the above-mentioned polycarbonate resin. As a method for forming a film from a polycarbonate-based 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 film, and the like.

The thickness of the resin film (unstretched film) can be set to an arbitrary appropriate value according to a desired thickness of the obtained retardation film, 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.

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.

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 a direction of a predetermined angle with respect to the longitudinal direction. By adopting oblique stretching, a long stretched film having an orientation angle (slow phase axis in the direction of a predetermined angle) at a predetermined angle with respect to the longitudinal direction of the film can be obtained, for example, with a polarizer. Roll-to-roll is possible during lamination, and the manufacturing process can be simplified. The predetermined angle may be an angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer in the optical laminate. 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 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 film having the desired in-plane retardation and having a slow phase axis in the desired direction (substantially long). (Phase difference film) can be obtained.

Examples of the method of diagonal stretching include JP-A-50-83482, JP-A-2-113920, JP-A-3-182701, JP-A-2000-9912, and JP-A-2002-86554. Examples thereof include the methods 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.

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. A commercially available film may be used as it is, or a commercially available film may be used after secondary processing (for example, stretching treatment or surface treatment) depending on the purpose.

D-2. Optical compensating layer composed of a laminated body of liquid crystal oriented solidified layers In one embodiment, the optical compensating layer composed of a laminated body of liquid crystal oriented solidified layers is a first liquid crystal oriented solidified layer and a second liquid crystal oriented solidified layer. It has a solidified layer. In the optical laminate, the optical compensation layer may have a first liquid crystal oriented solidified layer and a second liquid crystal oriented solidified layer in order from the side of the polarizer.

D-2-1. First Liquid Crystal Oriented Solidification Layer The first liquid crystal oriented solidified layer can function as a so-called λ / 2 plate. The first liquid crystal oriented solidified layer is a so-called λ / 2 plate, the second liquid crystal oriented solidified layer described later is a so-called λ / 4 plate, and these slow axes are oriented in a predetermined direction with respect to the absorption axis of the polarizer. By setting, an optical laminate having excellent circularly polarized light characteristics in a wide band can be obtained. The in-plane retardation Re (550) of the first liquid crystal oriented solidified layer is preferably 180 nm to 320 nm, more preferably 200 nm to 290 nm, and further preferably 230 nm to 280 nm.

The refractive index ellipsoid of the first liquid crystal oriented solidified layer typically shows a relationship of nx> ny = nz. The angle formed by the slow axis of the first liquid crystal oriented solidification layer and the absorption axis of the polarizer is preferably 10 ° to 20 °, more preferably 13 ° to 17 °, and even more preferably about 15 °. Is. If the angle formed by the slow axis of the first liquid crystal oriented solidified layer and the absorption axis of the polarizer is within such a range, the in-plane phase difference between the first liquid crystal oriented solidified layer and the second liquid crystal oriented solidified layer. Is set to a predetermined range, and the slow axis of the second liquid crystal oriented solidified layer is arranged at a predetermined angle as described later with respect to the absorption axis of the polarizer, so that the circularly polarized light is extremely excellent in a wide band. An optical laminate having properties (as a result, very good antireflection properties) can be obtained.

The thickness of the first liquid crystal oriented solidified layer is preferably 1 μm to 7 μm, and more preferably 1.5 μm to 2.5 μm. As described above, by using the liquid crystal compound, the difference between nx and ny of the obtained optical compensation layer can be made much larger than that of the non-liquid crystal material, so that a layer for obtaining a desired in-plane phase difference can be obtained. The thickness can be significantly reduced. Therefore, it is possible to realize an in-plane phase difference equivalent to that of the resin film with a thickness much thinner than that of the resin film.

In the present embodiment, the first liquid crystal oriented solidified layer is typically oriented with rod-shaped liquid crystal compounds arranged in a predetermined direction (homogeneous orientation). A slow-phase axis can be expressed in the orientation direction of the liquid crystal compound. Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) in which the liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal expression mechanism of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or cross-linking (that is, curing) the liquid crystal monomer. After the liquid crystal monomers are oriented, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the oriented state can be fixed. Here, the polymer is formed by polymerization, and the three-dimensional network structure is formed by cross-linking, but these are non-liquid crystal. Therefore, the formed first liquid crystal oriented solidified layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to a liquid crystal compound, for example. As a result, the first liquid crystal oriented solidified layer becomes an extremely stable layer that is not affected by temperature changes.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity differs depending on the type. Specifically, the temperature range is preferably 40 ° C. to 120 ° C., more preferably 50 ° C. to 100 ° C., and most preferably 60 ° C. to 90 ° C.

As the liquid crystal monomer, any suitable liquid crystal monomer can be adopted. For example, the polymerizable mesogen compounds described in Special Tables 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP02671712, DE19504224, DE4408171, GB2280445 and the like can be used. Specific examples of such a polymerizable mesogen compound include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

In the first liquid crystal alignment solidification layer, the surface of a predetermined base material is subjected to an orientation treatment, and a coating liquid containing a liquid crystal compound is applied to the surface to orient the liquid crystal compound in a direction corresponding to the orientation treatment. , Can be formed by fixing the orientation state. By using such an orientation treatment, the liquid crystal compound can be oriented in a predetermined direction with respect to the elongated direction of the elongated substrate, and as a result, the liquid crystal oriented solidified layer to be formed can be oriented in a predetermined direction. The slow axis can be expressed. For example, a liquid crystal oriented solidified layer having a slow phase axis in a direction of 15 ° with respect to the elongated direction can be formed on the elongated substrate. Even when it is desired that such a liquid crystal oriented solidified layer has a slow phase axis in an oblique direction, it can be laminated by using roll-to-roll, so that the productivity of the optical laminate is remarkably improved. Can improve. In one embodiment, the substrate is any suitable resin film and the oriented solidified layer formed on the substrate can be transferred to the surface of the polarizer. In another embodiment, the substrate can be an inner protective layer (inner protective film). In this case, the transfer step is omitted, and the lamination can be continuously performed by roll-to-roll from the formation of the oriented solidified layer.

As the orientation treatment, any appropriate orientation treatment can be adopted. Specific examples thereof include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of the mechanical orientation treatment include a rubbing treatment and a stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical alignment treatment include an orthorhombic deposition method and a photoalignment treatment. As the treatment conditions for various orientation treatments, any appropriate conditions can be adopted depending on the purpose.

The orientation of the liquid crystal compound is performed by treating at a temperature indicating the liquid crystal phase according to the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound takes a liquid crystal state, and the liquid crystal compound is oriented according to the orientation treatment direction of the surface of the base material.

In one embodiment, the orientation state is fixed by cooling the liquid crystal compound oriented as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the orientation state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the oriented solidified layer are described in JP-A-2006-163343. The description of this publication is incorporated herein by reference.

D-2-2. Second liquid crystal oriented solidified layer The second liquid crystal oriented solidified layer can function as a so-called λ / 4 plate. The second liquid crystal oriented solidified layer is a so-called λ / 4 plate, the first liquid crystal oriented solidified layer is a so-called λ / 2 plate as described above, and these slow axes are predetermined with respect to the absorption axis of the polarizer. By setting the direction, an optical laminate having excellent circularly polarized light characteristics in a wide band can be obtained. The in-plane retardation Re (550) of the second liquid crystal oriented solidified layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and further preferably 120 nm to 160 nm as described above.

The refractive index ellipsoid of the second liquid crystal oriented solidified layer typically shows a relationship of nx> ny = nz. The angle formed by the slow axis of the second liquid crystal oriented solidifying layer and the absorption axis of the polarizer is preferably 65 ° to 85 °, more preferably 72 ° to 78 °, and even more preferably 72 ° to 78 ° as described above. It is about 75 °. If the angle formed by the slow axis of the second liquid crystal oriented solidified layer and the absorption axis of the polarizer is within such a range, the in-plane phase difference between the first liquid crystal oriented solidified layer and the second liquid crystal oriented solidified layer. Is set to a predetermined range, and the slow axis of the first liquid crystal oriented solidified layer is arranged at a predetermined angle as described above with respect to the absorption axis of the polarizer, so that the circularly polarized light is extremely excellent in a wide band. An optical laminate having properties (as a result, very good antireflection properties) can be obtained.

The thickness of the second liquid crystal oriented solidified layer is preferably 0.5 μm to 2 μm, and more preferably 1 μm to 1.5 μm.

The constituent materials, properties, manufacturing method, etc. of the second liquid crystal oriented solidified layer are as described in Section D-2-1 above with respect to the first liquid crystal oriented solidified layer.

The angle formed by the slow axis of the first liquid crystal oriented solidified layer and the absorbing axis of the polarizer is about 15 °, and the angle formed by the slow axis of the second liquid crystal oriented solidified layer and the absorbing axis of the polarizer is about 15 °. Although the embodiment in which the temperature is about 75 ° has been described, the relationship between the axial angles may be reversed. Specifically, the angle formed by the slow axis of the first liquid crystal oriented solidified layer and the absorption axis of the polarizer is preferably 65 ° to 85 °, more preferably 72 ° to 78 °, and even more preferably about 75 °. In this case, the angle formed by the slow axis of the second liquid crystal oriented solidified layer and the absorption axis of the polarizer is preferably 10 ° to 20 °, more preferably 13 ° to 17 °. More preferably, it can be about 15 °.

E. Conductive layer The conductive layer (not shown) is typically transparent (ie, the conductive layer is a transparent conductive layer). By forming a conductive layer on the side opposite to the polarizer of the optical compensation layer, the optical laminate has a so-called inner touch panel type input display in which a touch sensor is incorporated between the display cell (organic EL cell) and the polarizer. Can be applied to the device.

The conductive layer may be used alone as a constituent layer of the optical laminate, or may be laminated on the optical compensation layer as a laminate with the base material (conductive layer with a base material). When composed of the conductive layer alone, the conductive layer can be transferred from the base material on which the conductive layer is formed to the optical compensation layer.

The conductive layer can be patterned if desired. 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. The shape of the pattern is preferably a pattern that operates well as a touch panel (for example, a capacitive touch panel). Specific examples include the patterns described in Japanese Patent Application Laid-Open No. 2011-511357, Japanese Patent Application Laid-Open No. 2010-164938, Japanese Patent Application Laid-Open No. 2008-310550, Japanese Patent Application Laid-Open No. 2003-511799, and Japanese Patent Application Laid-Open No. 2010-541109. Be 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. For example, by using the conductive nanowires described later, a transparent conductive layer having an opening can be formed, and a transparent conductive layer having high light transmittance can be obtained.

The density of the conductive layer is preferably ^{1.0g / cm 3 ~10.5g / cm 3} , more preferably from ^{1.3g / cm 3 ~3.0g / cm 3} .

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

Typical examples of the conductive layer include a conductive layer containing a metal oxide, a conductive layer containing conductive nanowires, and a conductive layer containing a metal mesh. Preferably, it is a conductive layer containing conductive nanowires or a conductive layer containing a metal mesh. This is because the conductive layer is excellent in bending resistance and the conductivity is not easily lost even if it is bent, so that a conductive layer that can be bent well can be formed.

The conductive layer containing the metal oxide is made of a metal on any suitable substrate 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 an oxide film. 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.

The conductive layer containing the conductive nanowires is formed by applying a dispersion liquid (conductive nanowire dispersion liquid) in which the conductive nanowires are dispersed in a solvent onto an arbitrary suitable base material, and then drying the coating layer. be able to. As the conductive nanowire, any suitable conductive nanowire can be used as long as the effect of the present invention can be obtained. The conductive nanowire is a conductive substance having a needle-like or thread-like shape and a diameter of nanometer size. The conductive nanowires may be linear or curved. The conductive layer containing the conductive nanowires has excellent bending resistance as described above. Further, in the conductive layer containing the conductive nanowires, the conductive nanowires form a gap between the conductive nanowires to form a mesh, so that a good electric conduction path can be formed even with a small amount of the conductive nanowires. , A conductive layer having a small electric resistance can be obtained. Further, since the conductive nanowires have a mesh shape, an opening can be formed in the gap between the meshes to obtain a conductive layer having high light transmittance. Examples of the conductive nanowires include metal nanowires made of metal, conductive nanowires containing carbon nanotubes, and the like.

The ratio (aspect ratio: L / d) of the thickness d to the length L of the conductive nanowire is preferably 10 to 100,000, more preferably 50 to 100,000, and further preferably 100 to 100,000. It is 10,000. When conductive nanowires having a large aspect ratio are used in this way, the conductive nanowires can intersect well, and a small amount of conductive nanowires can exhibit high conductivity. As a result, a conductive layer having high light transmittance can be obtained. In the present specification, the "thickness of the conductive nanowire" means the diameter of the conductive nanowire when the cross section is circular, and the minor diameter when the cross section of the conductive nanowire is elliptical. When it is a polygon, it means the longest diagonal line. The thickness and length of the conductive nanowires can be confirmed by a scanning electron microscope or a transmission electron microscope.

The thickness of the conductive nanowires is preferably less than 500 nm, more preferably less than 200 nm, still more preferably 1 nm to 100 nm, and particularly preferably 1 nm to 50 nm. Within such a range, a conductive layer having high light transmittance can be formed. The length of the conductive nanowires is preferably 2.5 μm to 1000 μm, more preferably 10 μm to 500 μm, and even more preferably 20 μm to 100 μm. Within such a range, a highly conductive conductive layer can be obtained.

As the metal constituting the conductive nanowire (metal nanowire), any suitable metal can be used as long as it is a highly conductive metal. Metal nanowires are preferably composed of one or more metals selected from the group consisting of gold, platinum, silver and copper. Of these, silver, copper or gold is preferable, and silver is more preferable, from the viewpoint of conductivity. Further, a material obtained by plating the metal (for example, gold plating) may be used.

As the carbon nanotube, any suitable carbon nanotube can be used. For example, so-called multi-walled carbon nanotubes, double-walled carbon nanotubes, single-walled carbon nanotubes and the like are used. Among them, single-walled carbon nanotubes are preferably used because of their high conductivity.

As the metal mesh, any suitable metal mesh can be used as long as the effects of the present invention can be obtained. For example, a metal wiring layer provided on a film base material in which a pattern is formed in a mesh pattern can be used.

Details of the conductive nanowires and the metal mesh are described in, for example, Japanese Patent Application Laid-Open No. 2014-113705 and Japanese Patent Application Laid-Open No. 2014-219667. The description of this publication is incorporated herein by reference.

The thickness of the conductive layer is preferably 0.01 μm to 10 μm, more preferably 0.05 μm to 3 μm, and even more preferably 0.1 μm to 1 μm. Within such a range, a conductive layer having excellent conductivity and light transmission can be obtained. When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 0.01 μm to 0.05 μm.

F. Printing layer As described above, the printing layer is formed at a position corresponding to the peripheral portion of the optical laminate, more specifically, the bezel of the organic EL display device in a plan view. As described above, the printed layer may be formed on the polarizer side of the base material (substantially, the polarizer side of the resin film), or may be formed on the side opposite to the polarizer of the optical compensation layer. good. The printing layer may be a design layer having a predetermined design, or may be a solid colored layer. The printing layer is preferably a solid colored layer, and more preferably a black colored layer. Since the non-display area can be concealed by forming the black colored layer at the position corresponding to the bezel, the optical laminate of the present embodiment can be used to realize an organic EL display device that does not use the bezel. Can be done. As a result, it is possible to provide an organic EL display device having an extremely excellent appearance with no step on the outermost surface. Further, when the print layer is formed on the optical compensation layer, the following advantages are obtained: That is, in such a configuration, the print layer is inevitably on the lower side of the polarizer (on the side of the organic EL display device). As a result, the reflected light at the interface of the print layer is reduced by the polarizer. Therefore, it is possible to realize an organic EL display device having an even better appearance.

The print layer can be formed by any suitable printing method with any suitable ink or paint. Specific examples of the printing method include gravure printing, offset printing, silk screen printing, and transfer printing from a transfer sheet.

The inks or paints used typically include binders, colorants, solvents and any suitable additives that may be used as needed. Examples of the binder include chlorinated polyolefins (for example, chlorinated polyethylene and chlorinated polypropylene), polyester resins, urethane resins, acrylic resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, and cellulose resins. .. The binder resin may be used alone or in combination of two or more. In one embodiment, the binder resin is a thermopolymerizable resin. Since the amount of the heat-polymerizable resin used is smaller than that of the photopolymerizable resin, the amount of the colorant used (colorant content in the colored layer) can be increased. As a result, especially when forming a black colored layer, it is possible to form a colored layer having a very small total light transmittance and excellent hiding power. In one embodiment, the binder resin is an acrylic resin, preferably an acrylic resin containing a polyfunctional monomer (for example, pentaerythritol triacrylate) as a copolymerization component. By using an acrylic resin containing a polyfunctional monomer as a copolymerization component, a colored layer having an appropriate elastic modulus can be formed, so that blocking can be satisfactorily prevented when the retardation film is formed into a roll shape. .. In addition, a step is also formed due to the thickness of the print layer, and the step can effectively function to prevent blocking.

As the colorant, any suitable colorant can be used depending on the purpose. Specific examples of colorants include inorganic pigments such as titanium white, zinc flower, carbon black, iron black, petal handle, chrome vermilion, ultramarine blue, cobalt blue, chrome yellow, and titanium yellow; phthalocyanine blue, induslen blue, and iso. Organic pigments or dyes such as indolinone yellow, benzidine yellow, quinacridone red, polyazo red, perylene red, aniline black; metal pigments composed of scaly foil pieces such as aluminum and brass; scales such as titanium dioxide coated mica and basic lead carbonate. Examples thereof include pearl luster pigments (pearl pigments) composed of shaped foil pieces. When forming a black colored layer, carbon black, iron black, and aniline black are preferably used. In this case, it is preferable to use a colorant in combination. This is because it can absorb visible light over a wide range and evenly to form a non-colored (ie, black) colored layer. For example, in addition to the colorants described above, azo compounds and / or quinone compounds can be used. In one embodiment, the colorant comprises carbon black as a main component and other colorants (eg, azo compounds and / or quinone compounds). According to such a configuration, it is possible to form a colored layer that is not colored and has excellent stability over time. When forming a black colored layer, the colorant can be used in a ratio of preferably 50 parts by weight to 200 parts by weight with respect to 100 parts by weight of the binder resin. In this case, the content ratio of carbon black in the colorant is preferably 80% to 100%. By using a colorant (particularly carbon black) at such a ratio, it is possible to form a colored layer having a very small total light transmittance and excellent stability over time.

The thickness of the print layer is preferably 3 μm to 5 μm. Further, the printed layer has a total light transmittance of preferably 0.01% or less, more preferably 0.008% or less at a thickness of 3 μm to 5 μm. When the total light transmittance is in such a range, the non-display area of the organic EL display device can be well concealed without using a bezel.

G. Inner protective layer (inner protective film)
When the inner protective layer (inner protective film) is provided, the inner protective film 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 inner protective film is preferably 20 μm to 200 μm, more preferably 30 μm to 100 μm, and further preferably 35 μm to 95 μm.

The inner protective film is formed of any suitable film as long as the desired properties are obtained. 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. , Polyester-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.

H. Adhesive layer or adhesive layer Any suitable adhesive layer or adhesive layer is used for laminating each layer constituting the optical laminate of the present invention.

Preferably, the substrate and the polarizer are laminated via an adhesive layer. By appropriately selecting the type, elastic modulus and / or thickness of the adhesive layer, the delamination force between the base material and the polarizer can be set to a desired value.

As the adhesive constituting the adhesive layer, any suitable form of adhesive can be adopted. Specific examples include water-based adhesives, solvent-based adhesives, emulsion-based adhesives, solvent-free adhesives, active energy ray-curable adhesives, and thermosetting adhesives. Examples of the active energy ray-curable adhesive include an electron beam-curable adhesive, an ultraviolet-curable adhesive, and a visible light-curable adhesive. A water-based adhesive and an active energy ray-curable adhesive can be preferably used. Specific examples of the water-based adhesive include isocyanate-based adhesives, polyvinyl alcohol-based adhesives (PVA-based adhesives), gelatin-based adhesives, vinyl-based latex-based adhesives, water-based polyurethanes, and water-based polyesters. Specific examples of the active energy ray-curable adhesive include (meth) acrylate-based adhesives. The (meth) acrylate means acrylate and / or methacrylate. Examples of the curable component in the (meth) acrylate-based adhesive include a compound having a (meth) acryloyl group and a compound having a vinyl group. Further, a compound having an epoxy group or an oxetanyl group can also be used as the cationic polymerization curable adhesive. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds can be used. Preferred epoxy compounds include compounds having at least two epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds) and at least one of them having at least two epoxy groups in the molecule. Examples thereof include a compound (alicyclic epoxy compound) formed between two adjacent carbon atoms constituting an alicyclic ring.

In one embodiment, a PVA-based adhesive is used as the adhesive constituting the adhesive layer. By using a PVA-based adhesive, it is possible to bond the materials together even when a material that does not transmit active energy rays is used. In another embodiment, an active energy ray-curable adhesive is used as the adhesive constituting the adhesive layer. If an active energy ray-curable adhesive is used, a sufficient delamination force can be obtained even for a material whose surface is hydrophobic and which cannot be adhered by a PVA adhesive.

The storage elastic modulus of the adhesive layer is preferably 1.0 × 10 ⁶ Pa or more, and more preferably 1.0 × 10 ⁷ Pa or more in the region of 70 ° C. or lower. The upper limit of the storage elastic modulus of the adhesive layer is, for example, 1.0 × 10 ¹⁰ Pa. The storage elastic modulus of the adhesive layer affects the polarizer cracks when the optical laminate is heat-cycled (-40 ° C to 80 ° C, etc.), and when the storage elastic modulus is low, the polarizer crack defect occurs. Cheap. The temperature range having a high storage elastic modulus is more preferably 80 ° C. or lower, still more preferably 90 ° C. or lower.

The thickness of the adhesive layer is typically 0.01 μm to 7 μm, preferably 0.01 μm to 5 μm.

The adhesive layer or the pressure-sensitive adhesive layer may be used for the lamination other than the lamination of the base material and the polarizer.

Examples of the adhesive constituting the adhesive layer include acrylic adhesive, rubber adhesive, vinyl alkyl ether adhesive, silicone adhesive, polyester adhesive, polyamide adhesive, urethane adhesive, and the like. Fluorine-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, and polyether-based pressure-sensitive adhesives can be mentioned. The pressure-sensitive adhesive may be used alone or in combination of two or more. An acrylic adhesive is preferably used from the viewpoint of transparency, processability, durability and the like.

The thickness of the pressure-sensitive adhesive layer is typically 10 μm to 250 μm, preferably 10 μm to 150 μm. The pressure-sensitive adhesive layer may be a single layer or may have a laminated structure.

The storage elastic modulus (G') of the pressure-sensitive adhesive layer is preferably 0.01 MPa to 1.00 MPa, more preferably 0.05 MPa to 0.50 MPa at 25 ° C. When the storage elastic modulus of the pressure-sensitive adhesive layer is within such a range, an optical laminate having extremely excellent flexibility can be obtained. As a result, a bendable or foldable organic EL display device can be realized.

I. Organic EL Display Device An organic EL display device will be described as an example of an image display device to which the optical laminate of the present invention can be applied. The optical laminate of the present invention can also be applied to a liquid crystal display device as described above. FIG. 3 is a schematic cross-sectional view of an organic EL display device according to one embodiment of the present invention. The organic EL display device 300 includes an organic EL element (organic EL display cell) 200 and an optical laminate 100 or 101 (preferably, an optical laminate 101) on the visual side of the organic EL element 200. The optical laminate is the optical laminate of the present invention described in the above items A to H. The optical laminate is laminated so that the optical compensation layer is on the organic EL element side (the base material is on the visual side). The optical laminate is not limited to the above-mentioned optical laminate 100 or 101, and may be an optical laminate according to yet another embodiment of the present invention (not shown). In one embodiment, the optical laminate 101 functions as an antireflection film.

The organic EL display device is preferably bendable. A bendable organic EL display device can be realized by combining the above-mentioned optical laminate of the present invention with a bendable organic EL element described later. More specifically, at least a part of the organic EL display device can be bent with a radius of curvature of preferably 10 mm or less, more preferably 8 mm or less. The organic EL display device can be bent at any suitable portion. For example, the organic EL display device may be bendable at the center like a foldable display device, or may be bendable at the edges from the viewpoint of maximizing the design and the display screen. good. Further, the organic EL display device may be bendable along the longitudinal direction thereof, or may be bendable along the lateral direction thereof. Needless to say, it is sufficient that a specific part of the organic EL display device can be bent (for example, a part or all of the four corners can be bent in an oblique direction) depending on the application.

When the optical compensation layer is composed of a retardation film, the slow axis direction of the retardation film is preferably 20 ° to 70 °, more preferably 30 ° to 60 ° with respect to the bending direction of the organic EL display device. The optical laminate can be arranged so as to be more preferably 40 ° to 50 °, particularly preferably in the vicinity of 45 °. When the optical compensation layer has a laminated structure of the first liquid crystal oriented solidified layer and the second liquid crystal oriented solidified layer, the slow axis direction of the first liquid crystal oriented solidified layer 31 is the bending direction of the organic EL display device. The optical laminate may be arranged so as to be preferably in the vicinity of 10 ° to 20 °, more preferably 11 ° to 19 °, further preferably 12 ° to 18 °, and particularly preferably in the vicinity of 15 °. In this case, the slow axis direction of the second liquid crystal oriented solidified layer is preferably 70 ° to 80 °, more preferably 71 ° to 79 °, still more preferably 72 ° to the bending direction of the organic EL display device. It is 78 °, particularly preferably around 75 °. Since the first liquid crystal oriented solidified layer and the second liquid crystal oriented solidified layer are very thin and are less affected by bending, the adjustment of the axial angle does not have to be as strict as in the case of the retardation film. In any of the embodiments, by adjusting the relationship between the slow axis direction of the optical compensation layer and the bending direction of the organic EL display device, a bendable organic EL display device in which color change due to bending is suppressed can be obtained. Can be done. In one embodiment, the bending direction of the organic EL display device (or organic EL element) is a longitudinal direction or a direction orthogonal to the longitudinal direction (short direction). In such an embodiment, if the absorption axis of the polarizer of the optical laminate is set orthogonally or parallel to the longitudinal direction (or the lateral direction), the optical compensation layer can be laminated when laminated on the organic EL element. It is not necessary to align the slow axis, but the absorption axis direction of the polarizer may be aligned. In this way, roll-to-roll manufacturing becomes possible.

J. Organic EL element As the organic EL element 200, any suitable organic EL element can be adopted as long as the effect of the present invention can be obtained. FIG. 4 is a schematic cross-sectional view illustrating one form of the organic EL device used in the present invention. The organic EL element 200 typically includes a substrate 210, a first electrode 220, an organic EL layer 230, a second electrode 240, and a sealing layer 250 covering them. The organic EL element 200 may further have any suitable layer, if desired. For example, a flattening layer (not shown) may be provided on the substrate, or an insulating layer (not shown) for preventing a short circuit may be provided between the first electrode and the second electrode.

The substrate 210 may be made of any suitable material as long as it can be bent with the predetermined radius of curvature. The substrate 210 is typically made of a flexible material. If a flexible substrate is used, in addition to the above-mentioned effects of the present invention, when a long optical laminate is used, an organic EL display device can be manufactured by a so-called roll-to-roll process, so that the cost is low. And mass production can be achieved. Further, the substrate 210 is preferably made of a material having a barrier property. Such a substrate can protect the organic EL layer 230 from oxygen and moisture. Specific examples of the material having the barrier property and the flexibility include thin glass having the flexibility property, a thermoplastic resin or a thermosetting resin film having the barrier property, an alloy, and a metal. 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. The thickness of the substrate is preferably 5 μm to 500 μm, more preferably 5 μm to 300 μm, and even more preferably 10 μm to 200 μm. With such a thickness, the organic EL display device can be bent with the predetermined radius of curvature, and the balance between flexibility, handleability, and mechanical strength is excellent. Further, the organic EL element can be suitably used for the roll-to-roll process.

The first electrode 220 can typically function as an anode. In this case, as the material constituting the first electrode, a material having a large work function is preferable from the viewpoint of facilitating hole injection. Specific examples of such materials include indium tin oxide (ITO), indium zinc oxide (IZO), indium tin oxide with silicon oxide added (ITSO), indium oxide containing tungsten oxide (IWO), and the like. Transparent conductive materials such as indium zinc oxide containing tungsten oxide (IWZO), indium oxide containing titanium oxide (ITIO), indium tin oxide containing titanium oxide (ITTIO), and indium tin oxide containing molybdenum (ITMO). Also included are metals such as gold, silver, platinum and their alloys.

The organic EL layer 230 is a laminate containing various organic thin films. In the illustrated example, the organic EL layer 230 is made of a hole-injecting organic material (for example, a triphenylamine derivative), and is provided with a hole injection layer 230a for improving the hole injection efficiency from the anode, for example, copper. A hole transport layer 230b composed of phthalocyanine and a luminescent organic substance (eg, anthracene, bis [N- (1-naphthyl) -N-phenyl] benzidine, N, N'-diphenyl-N-N-bis (1-). A light emitting layer 230c made of naphthyl) -1,1'-(biphenyl) -4,4'-diamine (NPB)), an electron transport layer 230d made of, for example, an 8-quinolinol aluminum complex, and an electron injectable material (eg, an electron injectable material). It is composed of a perylene derivative (lithium fluoride) and has an electron injection layer 230e provided for improving the electron injection efficiency from the cathode. The organic EL layer 230 is not limited to the illustrated example, and any suitable combination in which electrons and holes can recombine in the light emitting layer 230c to generate light can be adopted. The thickness of the organic EL layer 230 is preferably as thin as possible. This is because it is preferable to transmit the emitted light as much as possible. The organic EL layer 230 may be composed of an extremely thin laminate having, for example, 5 nm to 200 nm, preferably about 10 nm.

The second electrode 240 can typically function as a cathode. In this case, as the material constituting the second electrode, a material having a small work function is preferable from the viewpoint of facilitating electron injection and increasing luminous efficiency. Specific examples of such materials include aluminum, magnesium and alloys thereof.

The sealing layer 250 is made of any suitable material. The sealing layer 25 is preferably made of a material having excellent barrier properties and transparency. Typical examples of materials constituting the sealing layer include epoxy resin and polyurea. In one embodiment, the sealing layer 250 may be formed by applying an epoxy resin (typically, an epoxy resin adhesive) and attaching a barrier sheet on the epoxy resin.

The organic EL element 200 can preferably be continuously manufactured by a roll-to-roll process. The organic EL element 200 can be manufactured, for example, by a procedure according to the procedure described in Japanese Patent Application Laid-Open No. 2012-169236. The description of this publication is incorporated herein by reference. Further, the organic EL element 200 can be continuously laminated with the long optical laminate 100 by a roll-to-roll process to continuously manufacture the organic EL display device 300.

Details of the bendable 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. Further, in the examples, unless otherwise specified, "parts" and "%" are based on weight.

[Production Example 1] Preparation of Adhesives (Active Energy Ray Curable Adhesives) A to C Each component is mixed according to the formulation table shown in Table 1, stirred at 50 ° C. for 1 hour, and adhesives A to C (adhesives A to C). Active energy ray-curable adhesives A to C) were prepared. The numerical values in the table indicate the weight% when the total amount of the composition is 100% by weight. Each component used is as follows.
HEAA: Hydroxyethyl acrylamide, manufactured by Kojinsha;
M-220: ARONIX M-220 (M-220) (tripropylene glycol diacrylate), manufactured by Toa Synthetic Co., Ltd. ACMO: acryloyl morpholin, manufactured by Kojin Co., Ltd. AAEM: (2-acetoacetoxyethyl methacrylate), manufactured by Nippon Synthetic Chemical Co., Ltd. Light Acrylate 1,9ND-A: 1,9-Nanonediol Diacrylate, Kyoeisha Chemical Co., Ltd. UP-1190: ARUFON UP-1190, Toa Synthetic Co., Ltd. Nikalac MX-750LM: Nippon Carbide Industry Co., Ltd. IRG907: IRGACURE907 (2) -Methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one), BASF DETX-S: KAYACURE DETX-S (diethylthioxanthone), Nippon Kayaku Co., Ltd. CPI-100P: Triaryl Propylene carbonate solution containing sulfonium hexafluorophosphate as the main component and 50% active ingredient, manufactured by San Apro Co., Ltd.

In the examples and comparative examples using the adhesives A to C, the base material and the polarizer are laminated via the adhesive, and then the adhesive is cured by irradiating with ultraviolet rays to cure the adhesive layer. Was formed. For UV irradiation, gallium-filled metal halide lamp (Fusion UV Systems, Inc., trade name "Light HAMMER10", bulb: V bulb, peak illuminance: 1600 mW / cm ² , cumulative irradiation dose 1000 / mJ / cm ² (wavelength) 380 to 440 nm)) was used.

[Production Example 2] Preparation of Adhesive (PVA-based Adhesive) D Adhesive D (PVA-based adhesive D) was prepared according to the method described in JP-A-2008-15483.
In the example using the adhesive D, after laminating the base material and the polarizer via the adhesive, the adhesive was dried in an oven at 60 ° C. for 5 minutes to form an adhesive. ..

[Example 1]
A polyarylate (PAR) resin film having a thickness of 20 μm was used as a base material. The base material and a polarizer (manufactured according to the method described in Japanese Patent Application Laid-Open No. 2012-73580, having a thickness of 5 μm) were adhered to each other via the adhesive A to obtain an optical laminate.

[Example 2]
An optical laminate was obtained in the same manner as in Example 1 except that a polyimide (PI) resin film having a thickness of 20 μm was used instead of the polyarylate (PAR) resin film.

[Example 3]
An optical laminate was obtained in the same manner as in Example 1 except that the adhesive D was used instead of the adhesive A.

[Example 4]
Optical in the same manner as in Example 1 except that a 20 μm-thick triacetyl cellulose (TAC) film was used instead of the polyarylate (PAR) resin film and the adhesive D was used instead of the adhesive A. A laminate was obtained.

[Comparative Example 1]
An optical laminate was obtained in the same manner as in Example 1 except that the adhesive B was used instead of the adhesive A.

[Comparative Example 2]
An optical laminate was obtained in the same manner as in Example 1 except that the adhesive C was used instead of the adhesive A.

[evaluation]
The optical laminates obtained in Examples and Comparative Examples were subjected to the following evaluations (1) to (3). The results are shown in Table 2.

(1) Delamination force An optical laminate cut out to a predetermined size (length: 200 mm, width 15 mm; the direction parallel to the stretching direction of the polarizer is the length direction) was used as an evaluation sample.
At the end in the length direction of the optical laminate, a notch (length: 10 mm) was made between the base material and the adhesive layer with a cutter knife. Next, after fixing the optical laminate to the glass plate, the peeling force when the base material and the polarizer were peeled off was measured under the conditions of a peeling angle of 90 ° and a peeling speed of 10 m / min by a tensile tester. ..

(2) Fold resistance test A fold resistance tester manufactured by Imoto Seisakusho Co., Ltd. shown in Fig. 5 was used.
One end of the optical laminate 100 was fixed to a bendable jig A, and a predetermined load (100 g / 10 mm) was applied to the other end. By sandwiching a 4 mmφ mandrel B with the base material side inside (that is, the radius of curvature of the bent portion is 2 mm) and bending the jig A, the optical laminate is bent from a flat state to a bending angle X of 175 °. Was bent. As the mandrel, a mandrel whose surface was treated with fluorine-containing alumite (TUFRAM (registered trademark)) was used. Further, in order to reduce the influence of damage due to friction with the mandrel, the above test was carried out with a protective film (30 μm) attached to the surface of the optical laminate on the substrate side.
After performing the above bending 100,000 times (100,000 reciprocations of the jig), the presence or absence of breakage and cracks in the polarizer and the substrate was confirmed by visual inspection and microscopic observation.
In Table 2, when no breakage or crack was confirmed in both the base material and the polarizer, when no breakage or crack was confirmed in the polarizer (when breakage or crack was confirmed in the substrate). Is Δ, and the case where breakage or crack is confirmed in the polarizer is ×.

(3) Tension elastic modulus The tensile elastic modulus of the optical laminate was measured based on JIS K 7127.

The optical laminate of the present invention is suitably used for an organic EL display device, and may be particularly preferably used for a bendable or foldable organic EL display device.

10 Base material 20 Polarizer 30 Optical compensation layer (phase difference film)
100 Optical laminate 101 Optical laminate 200 Organic EL element 300 Organic EL display device

Claims (5)

An optical laminate for a bendable or foldable organic EL display device comprising a substrate and a polarizer arranged on at least one side of the substrate.
The base material is a surface protective layer of the organic EL display device and a protective layer of the polarizer.
The delamination force between the base material and the polarizer is 2N / 15mm to 5N / 15mm .
After bending 100,000 times using a 4 mmφ mandrel with the base material side inside, with a radius of curvature of 2 mm and a bending angle of 175 °, delamination between the base material and the polarizer occurs. without and, breaking and cracking of the polarizer is rather name
Further having a layer other than the polarizer and the substrate,
In all the layers constituting the optical laminate, the delamination force with the adjacent layer is 2N / 15mm to 5N / 15mm.
The tensile elastic modulus at 25 ° C. is 2.8 GPa or more.
Optical laminate. The optical laminate according to claim 1, wherein the base material and the polarizer are laminated via an adhesive layer. The storage elastic modulus of the adhesive layer is 70 ° C. in the following areas 1.0 × 10 6 ^Pa or more, the optical laminate according to claim 2. The optical laminate according to any one of claims 1 to 3 , which is used as an antireflection film for an organic EL display device. An organic EL display device comprising the optical laminate according to any one of claims 1 to 4.

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