JP6780930B2 - Optical laminate and image display device - Google Patents

Description

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

In recent years, with the spread of thin displays, displays (organic EL display devices) equipped with organic EL panels have been proposed. Since the organic EL panel has a highly reflective metal layer, problems such as reflection of external light and reflection of the background are likely to occur. Therefore, it is known that these problems can be prevented by providing a circular polarizing plate on the visual side. On the other hand, there is an increasing demand for a so-called inner touch panel type input display device in which a touch sensor is incorporated between a display cell (for example, an organic EL cell) and a polarizing plate. Since the distance between the image display cell and the touch sensor is short in the input display device having such a configuration, it is possible to give the user a natural feeling of input operation. Further, the input display device having the above configuration can reduce the influence of the reflected light caused by the conductive pattern formed on the touch sensor.

Generally, the touch sensor in the input display device having the above configuration includes a sensor film including a base material and a conductive layer formed on the base material. An isotropic base material is often used as the base material. If this isotropic base material is optically completely isotropic, the antireflection function of the circular polarizing plate is fully exhibited. However, in reality, due to the influence of the conductive layer forming step, the treatment for increasing the toughness of the base material, and the like, some anisotropy appears even in the base material intended for isotropic. As a result, even if the circular polarizing plate is arranged, there may be a problem that problems such as reflection of external light and reflection of the background are not solved.

Japanese Unexamined Patent Publication No. 2003-31239 JP-A-2002-372622 Japanese Patent No. 3325560 Japanese Unexamined Patent Publication No. 2003-036143

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide an optically anisotropic substrate (hereinafter, also referred to as an anisotropic substrate), but to have an antireflection function. It is an object of the present invention to provide an excellent optical laminate.

The optical laminate of the present invention comprises a polarizing plate including a polarizing element and a protective layer arranged on at least one side of the polarizing element, a first retardation layer, a second retardation layer, a conductive layer, and the like. The substrate is provided in this order, the in-plane retardation Re (550) of the substrate is larger than 0 nm, and the angle formed by the slow axis of the substrate and the slow axis of the second retardation layer is large. , -5 ° to 5 ° or 85 ° to 95 °.
In one embodiment, the angle formed by the absorption axis of the polarizer and the slow axis of the first retardation layer is 10 ° to 20 °, and the absorption axis and the second retardation layer have an angle of 10 ° to 20 °. The angle formed by the slow axis is 65 ° to 85 °.
In one embodiment, the first retardation layer and the second retardation layer are made of a cyclic olefin resin film.
In one embodiment, the first retardation layer and the second retardation layer are orientation-solidified layers of liquid crystal compounds.
According to another aspect of the present invention, an image display device is provided. This image display device includes the above optical laminate.

According to the present invention, by optimizing the slow axis angle of the anisotropic base material, it is possible to provide an optical laminate having an anisotropic base material and having an excellent antireflection function.

It is the schematic sectional drawing of the optical laminated body by one Embodiment of this invention. It is a graph which shows the result of an Example and a comparative example. It is a graph which shows the result of an Example and a comparative example.

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

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

A. Overall Configuration of 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 has a polarizing plate 11, a first retardation layer 12, a second retardation layer 13, a conductive layer 21, and a base material 22 in this order. The polarizing plate 11 includes a polarizer 1, a first protective layer 2 arranged on one side of the polarizer 1, and a second protective layer 3 arranged on the other side of the polarizer 1. .. Depending on the purpose, one of the first protective layer 2 and the second protective layer 3 may be omitted. For example, if the first retardation layer 12 can also function as a protective layer for the polarizer 1, the second protective layer 3 may be omitted. Each of the conductive layer 21 and the base material 22 may be a component of the optical laminate 100 as a single layer, or may be introduced into the optical laminate 100 as a laminate of the base material 22 and the conductive layer 21. The laminate of the base material 22 and the conductive layer 21 can function as, for example, the sensor film 20 of the touch sensor. For the sake of clarity, the ratio of the thickness of each layer in the drawing is different from the actual one. In addition, each layer constituting the optical laminate may be laminated via any suitable adhesive layer (adhesive layer or adhesive layer: not shown). On the other hand, the base material 22 may be closely laminated on the conductive layer 21. As used herein, the term "adhesive lamination" means that two layers are directly and fixedly laminated without interposing an adhesive layer (for example, an adhesive layer and an adhesive layer).

The laminate 10 of the polarizing plate 11 and the first retardation layer 12 and the second retardation layer 13 can function as a circular polarizing plate. Further, the base material 22 may be optically anisotropic. In the present invention, even if the anisotropic base material 22 is provided, the angle formed by the slow axis of the base material 22 and the second retardation layer 13 is within a specific range (as described later, from −5 ° to By setting the temperature to 5 ° or 85 ° to 95 °), the antireflection function of the circularly polarizing plate is fully exhibited, and an optical laminate capable of effectively preventing reflection of external light and reflection of the background is provided. Can be done. The base material 22 has an in-plane retardation (for example, the in-plane retardation Re (550) is greater than 0 nm and 10 nm or less). Details will be described later.

The total thickness of the optical laminate is preferably 220 μm or less, more preferably 40 μm to 180 μm.

The optical laminate may be long (for example, roll) or single-wafered.

Hereinafter, each layer and the optical film constituting the optical laminate will be described in more detail.

B. Polarizing plate B-1. Polarizer As the polarizer 1, 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 it 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. Moreover, you may dye after stretching. 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 it. 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 base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizer), and the resin base material is peeled off from the resin base material / 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 12 μm, and particularly preferably 5 μm to 12 μm.

The boric acid content of the polarizer is preferably 18% by weight or more, more preferably 18% by weight to 25% by weight. When the boric acid content of the polarizer is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the iodine content described later, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. The boric acid content can be calculated as the amount of boric acid contained in the polarizer per unit weight, for example, by using the following formula from the neutralization method.

The iodine content of the polarizer is preferably 2.1% by weight or more, more preferably 2.1% by weight to 3.5% by weight. When the iodine content of the polarizer is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the boric acid content described above, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. As used herein, the term "iodine content" means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, in the polarizer, iodine exists in the form of iodine ion (I ⁻ ), iodine molecule (I ₂ ), polyiodine ion (I ₃ ⁻ , I ₅ ⁻ ) and the like. Iodine content means the amount of iodine that includes all of these forms. The iodine content can be calculated, for example, by the calibration curve method of fluorescent X-ray analysis. The polyiodine ion exists in a state in which a PVA-iodine complex is formed in the polarizer. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, a complex of PVA and tri-iodide ion (PVA · _{I 3} ^-) has a light absorption peak around 470 nm, a complex of PVA and five iodide ion (PVA · _{I 5} ^-) is 600nm near Has an absorptive peak. As a result, polyiodine ions can absorb light in a wide range of visible light, depending on their morphology. On the other hand, iodine ion (I ⁻ ) has an absorption peak near 230 nm and is not substantially involved in the absorption of visible light. Therefore, polyiodine ions present in the form of a complex with PVA may be mainly involved in the absorption performance of the polarizer.

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

B-2. First Protective Layer The first protective layer 2 is formed of any suitable film that can be used as a protective layer for the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

As will be described later, the optical laminate of the present invention is typically arranged on the visible side of the image display device, and the first protective layer 2 is typically arranged on the visible side. Therefore, the first protective layer 2 may be subjected to surface treatment such as hard coating treatment, antireflection treatment, anti-sticking treatment, and anti-glare treatment, if necessary. Further / or, if necessary, the first protective layer 2 is provided with a process for improving visibility when visually recognizing through polarized sunglasses (typically, a (elliptical) circular polarization function is provided. (Giving an ultra-high phase difference) may be applied. By performing such processing, excellent visibility can be realized even when the display screen is visually recognized through a polarized lens such as polarized sunglasses. Therefore, the optical laminate can also be suitably applied to an image display device that can be used outdoors.

As the thickness of the first protective layer, any appropriate thickness can be adopted. The thickness of the first protective layer is, for example, 10 μm to 50 μm, preferably 15 μm to 40 μm. When the surface treatment is applied, the thickness of the first protective layer is a thickness including the thickness of the surface treatment layer.

B-3. Second Protective Layer The second protective layer 3 is also formed of any suitable film that can be used as a protective layer for the polarizer. The material that is the main component of the film is as described in Section B-2 above with respect to the first protective layer. The second protective layer 3 is preferably optically isotropic. In the present specification, "optically substantially 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. To say.

The thickness of the second protective layer is, for example, 15 μm to 35 μm, preferably 20 μm to 30 μm. The difference between the thickness of the first protective layer and the thickness of the second protective layer is preferably 15 μm or less, more preferably 10 μm or less. When the difference in thickness is within such a range, curl at the time of bonding can be satisfactorily suppressed. The thickness of the first protective layer and the thickness of the second protective layer may be the same, the first protective layer may be thicker, and the second protective layer may be thicker. .. Typically, the first protective layer is thicker than the second protective layer.

C. First retardation layer C-1. Properties of First Phase Difference Layer The first phase difference layer 12 may have any suitable optical and / or mechanical properties depending on the intended purpose. The first retardation layer 12 typically has a slow axis. In one embodiment, the angle formed by the slow axis of the first retardation layer 12 and the absorption axis of the polarizer 1 is preferably 10 ° to 20 °, more preferably 13 ° to 17 °. Yes, more preferably about 15 °. If the angle formed by the slow axis of the first retardation layer 12 and the absorption axis of the polarizer 1 is within such a range, the surfaces of the first retardation layer and the second retardation layer will be described later. By setting the inner phase difference to a predetermined range and arranging the slow axis of the second retardation layer at a predetermined angle with respect to the absorption axis of the polarizer, the circular polarization characteristics (excellent circular polarization characteristics) in a wide band are obtained. As a result, an optical laminate having very excellent antireflection properties) can be obtained.

The first retardation layer preferably has a refractive index characteristic of nx> ny ≧ nz. The in-plane retardation Re (550) of the first retardation layer is preferably 180 nm to 320 nm, more preferably 200 nm to 290 nm, and even more preferably 230 nm to 280 nm. 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 first retardation layer is preferably 0.1 to 3, more preferably 0.2 to 1.5, and even more preferably 0.3 to 1.3. By satisfying such a relationship, a very excellent reflected hue can be achieved when the obtained optical laminate is used in an image display device.

The first retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, and a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may be shown, or may show a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light. In this case, the retardation layer Re (450) / Re (550) is preferably 0.99 to 1.03, and Re (650) / Re (550) is preferably 0.98 to 1.02. is there. A first retardation layer showing flat wavelength dispersion characteristics and having a predetermined in-plane retardation characteristic and a second retardation layer showing flat wavelength dispersion characteristics and having a predetermined in-plane retardation characteristic are formed on a predetermined slow axis. By using them in combination at angles, it is possible to realize extremely excellent antireflection characteristics in a wide band.

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

C-2. First retardation layer made of a resin film When the first retardation layer is made of a resin film, the thickness thereof is preferably 40 μm or less, preferably 25 μm to 35 μm. If the thickness of the first retardation layer is in such a range, a desired in-plane retardation can be obtained.

The first retardation layer 12 may be made of any suitable resin film that can satisfy the above characteristics. Typical examples of such resins are cyclic olefin resins, polycarbonate resins, cellulose resins, polyester resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylics. Examples include based resins. When the first retardation layer is composed of a resin film exhibiting flat wavelength characteristics, a cyclic olefin resin can be preferably used.

Cyclic olefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin is mentioned. Specific examples include a ring-opening (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and an α-olefin such as ethylene and propylene (typically, a random copolymer). , And graft modified products obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene-based monomers. Examples of norbornene-based monomers include norbornene and its alkyl and / or alkylidene substitutions, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-. Polar group substituents such as these halogens such as 2-norbornene, 5-ethylidene-2-norbornene; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, alkyl and / or alkylidene substitutions thereof. The body and polar group substituents such as halogen, such as 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl -1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a , 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6 -Cyano-1,4: 5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4 , 4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydro Naphthalene and the like; tritetramers of cyclopentadiene, such as 4,9: 5,8-dimethano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoinden, 4,11 : 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentadianthracen and the like.

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

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

When the cyclic olefin resin is obtained by hydrogenating a ring-opening polymer of a norbornene monomer, the hydrogenation rate is preferably 90% or more, more preferably 95% or more. Most preferably, it is 99% or more. Within such a range, heat resistance and light deterioration are excellent.

A commercially available film may be used as the cyclic olefin resin film. Specific examples include Zeon Corporation's product names "Zeonex" and "Zeonoa", JSR's product name "Arton", TICONA's product name "Topus", and Mitsui Chemicals' product name. "APEL" can be mentioned.

The first retardation layer 12 is obtained, for example, by stretching a film formed from the cyclic olefin resin. As a method for forming a film from a cyclic olefin 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 enhanced and good optical uniformity can be obtained. The molding conditions can be appropriately set according to the composition and type of the resin used, the characteristics desired for the retardation layer, and the like. As described above, since many film products of the cyclic olefin resin are commercially available, the commercially available film may be subjected to the stretching treatment as it is.

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

Any suitable stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) can be adopted for the stretching. Specifically, various stretching methods such as free-end stretching, fixed-end stretching, free-end contraction, and fixed-end contraction can be used alone or simultaneously or sequentially. As for the stretching direction, it can be performed in various directions and dimensions such as a length direction, a width direction, a thickness direction, and an oblique direction. The stretching temperature is preferably Tg-30 ° C to Tg + 60 ° C, more preferably Tg-30 ° C to Tg + 50 ° C, and more preferably Tg-15 ° C to Tg + 30 with respect to the glass transition temperature (Tg) of the resin film. It is more preferably ° C.

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 axis in the direction of the angle) at a predetermined angle with respect to the longitudinal direction of the film can be obtained, and for example, laminated with a polarizer. At this time, roll-to-roll becomes possible, and the manufacturing process can be simplified. The angle may be an angle formed by the absorption axis of the polarizer and the slow axis of the first retardation layer in the optical laminate. As described above, the angle is preferably 10 ° to 20 °, more preferably 13 ° to 17 °, and even more preferably about 15 °.

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 lateral 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 first retardation layer (substantially, having the desired in-plane phase difference and having a slow phase axis in the desired direction). , Long retardation film) can be obtained.

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

C-3. The first retardation layer composed of the orientation-solidifying layer of the liquid crystal compound The first retardation layer 12 may be the orientation-solidification layer of the liquid crystal compound. By using the liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be made much larger than that of the non-liquid crystal material, so that the first phase difference for obtaining a desired in-plane phase difference can be obtained. The thickness of the layer can be significantly reduced. As a result, it is possible to further reduce the thickness of the optical laminate. When the first retardation layer 12 is composed of an oriented solidified layer of a liquid crystal compound, the thickness thereof is preferably 7 μm or less, more preferably 5 μm or less. By using the liquid crystal compound, 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.

As used herein, the term "oriented solidified layer" refers to a layer in which a liquid crystal compound is oriented in a predetermined direction within 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 as described later. In the present embodiment, the rod-shaped liquid crystal compounds are typically oriented in a state of being aligned in the slow-phase axial direction of the first retardation layer (homogeneous orientation). 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 retardation 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 retardation layer becomes an extremely stable retardation 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), EP666137 (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-Sillicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The alignment treatment of the liquid crystal compound is performed on the surface of a predetermined base material, and a coating liquid containing the liquid crystal compound is applied to the surface to orient the liquid crystal compound in a direction corresponding to the orientation treatment. It 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 retardation layer formed is delayed in the predetermined direction. The phase axis can be expressed. For example, a retardation layer having a slow phase axis in a direction of 15 ° with respect to the long direction can be formed on the long base material. Even when it is desired that such a retardation 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 be. 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 polarizing plate. In another embodiment, the substrate can be a second protective layer. In this case, the transfer step is omitted, and the stacking can be performed continuously from the formation of the oriented solidification layer (first retardation layer) by roll-to-roll, so that the productivity is further improved.

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 may 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 substrate surface.

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. Second retardation layer D-1. Properties of Second Phase Difference Layer The second phase difference layer 13 may have any suitable optical and / or mechanical properties depending on the intended purpose. The second retardation layer 13 typically has a slow axis. In one embodiment, the angle formed by the slow axis of the second retardation layer 13 and the absorption axis of the polarizer 1 is preferably 65 ° to 85 °, more preferably 72 ° to 78 °. Yes, more preferably about 75 °. The angle formed by the slow axis of the second retardation layer 13 and the slow axis of the first retardation layer 12 is preferably 52 ° to 68 °, more preferably 57 ° to 63 °. More preferably, it is about 60 °. If the angle formed by the slow axis of the second retardation layer 13 and the absorption axis of the polarizer 1 is within such a range, the in-plane retardation of the first retardation layer is within a predetermined range as described above. The slow axis of the first retardation layer is arranged at a predetermined angle with respect to the absorption axis of the polarizer, and the in-plane retardation of the second retardation layer is set to a predetermined range as described later. By setting, an optical laminate having very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics) can be obtained in a wide band.

The second retardation layer preferably shows a relationship in which the refractive index characteristic is nx> ny ≧ nz. The in-plane retardation Re (550) of the second retardation layer is preferably 80 nm to 200 nm, more preferably 100 nm to 180 nm, and even more preferably 110 nm to 170 nm.

Other characteristics of the second retardation layer are as described in Section C above with respect to the first retardation layer.

D-2. Second retardation layer made of a resin film When the second retardation layer is made of a resin film, the thickness thereof is preferably 40 μm or less, preferably 25 μm to 35 μm. If the thickness of the second retardation layer is in such a range, a desired in-plane retardation can be obtained. The material, characteristics, manufacturing method, etc. of the second retardation layer are as described in Section C-2 above with respect to the first retardation layer.

D-3. The second retardation layer composed of the orientation-solidifying layer of the liquid crystal compound The second retardation layer 13 may be the orientation-solidification layer of the liquid crystal compound in the same manner as the first retardation layer. When the second retardation layer 13 is composed of an oriented solidification layer of a liquid crystal compound, its thickness is preferably 7 μm or less, more preferably 5 μm or less. When the second retardation layer is composed of an orientation-solidified layer of a liquid crystal compound, its material, properties, manufacturing method and the like are as described in Section C-3 above with respect to the first retardation layer.

D-4. Combination of First Phase Difference Layer and Second Phase Difference Layer The first phase difference layer and the second phase difference layer can be used as any suitable combination. Specifically, the first retardation layer may be composed of a resin film and the second retardation layer may be composed of an orientation-solidifying layer of a liquid crystal compound; the first retardation layer may be an orientation-solidification of a liquid crystal compound. It may be composed of layers, and the second retardation layer may be composed of a resin film; both the first retardation layer and the second retardation layer may be composed of a resin film; the first position. Both the retardation layer and the second retardation layer may be composed of an orientation-solidified layer of a liquid crystal compound. Preferably, when the first retardation layer is made of a resin film, the second retardation layer is also made of a resin film; the first retardation layer is made of an oriented solidified layer of a liquid crystal compound. In some cases, the second retardation layer is also composed of an oriented solidified layer of the liquid crystal compound. When both the first retardation layer and the second retardation layer are made of a resin film, the first retardation layer and the second retardation layer may be the same, and have a detailed configuration. May be different. The same applies when both the first retardation layer and the second retardation layer are composed of an orientation-solidified layer of a liquid crystal compound.

E. Conductive layer The conductive layer is formed 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.). Can be formed by forming a film. After the film formation, heat treatment (for example, 100 ° C. to 200 ° C.) may be performed if necessary. The amorphous film can be crystallized by performing the heat treatment. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. The indium oxide may be doped with divalent metal ions or tetravalent metal ions. It is preferably an indium-based composite oxide, and more preferably an indium-tin composite oxide (ITO). The indium-based composite oxide has a feature of having a high transmittance (for example, 80% or more) in the visible light region (380 nm to 780 nm) and a low surface resistance value per unit area.

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

The surface resistance value of the conductive layer is preferably 300 Ω / □ or less, more preferably 150 Ω / □ or less, and further preferably 100 Ω / □ or less.

The conductive layer can be patterned if desired. By patterning, a conductive portion and an insulating portion can be formed. As the patterning method, any suitable method can be adopted. Specific examples of the patterning method include a wet etching method and a screen printing method.

F. Base material
The substrate has a slow axis. In the present invention, even if a base material having a slow axis, that is, an anisotropic base material is used, the antireflection function of the circular polarizing plate is sufficiently exhibited to effectively prevent reflection of external light and reflection of the background. It is possible to provide a possible optical laminate. Therefore, according to the present invention, it is not necessary to select the material constituting the base material with an emphasis on optical isotropic property as in the conventional case, and various materials can be selected according to desired characteristics. ..

Further, even if the base material is manufactured with the target of being optically isotropic (in-plane phase difference Re (550) is 0 nm), it inevitably has a slow axis. Good. When a conductive layer is formed by forming a film on the base material (that is, when the base material and the conductive layer are laminated by close contact lamination), a slow-phase shaft unnecessary for the base material due to heating in the film forming process or the like. May occur. The slow-phase axis generated in this way hinders the antireflection function of the circularly polarizing plate, and its direction is usually difficult to control, which also causes a decrease in production stability. In the present invention, the antireflection function of the circularly polarizing plate is sufficiently exhibited even in the base material having the slow axis. In such an invention, it is possible to allow the generation of a slow-phase axis to form a conductive layer, and it is possible to reduce restrictions on the conditions for forming a conductive layer.

The above effect is obtained by optimizing the angle between the slow axis of the base material and the slow axis of the second retardation layer. The present invention is particularly useful in that the antireflection function of the circularly polarizing plate is sufficiently exhibited regardless of the direction in which the slow axis of the base material is generated.

The angle formed by the slow axis of the base material and the slow axis of the second retardation layer is −5 ° to 5 ° or 85 ° to 95 °, preferably -3 ° to 3 ° or 87 ° to It is 93 °, more preferably -1 ° to 1 ° or 89 ° to 91 °, and particularly preferably 0 ° or 90 °. Within such a range, it is possible to provide an optical laminate in which the antireflection function of the circularly polarizing plate is fully exhibited and external light reflection, background reflection, and the like can be effectively prevented. In the present specification, the angle in the clockwise direction is defined as a positive angle and the angle in the counterclockwise direction is defined as a negative angle with respect to the slow axis of the base material.

The angle formed by the slow axis of the base material and the slow axis of the first retardation layer is 55 ° to 65 ° or 145 ° to 155 °, preferably 57 ° to 63 ° or 147 ° to 153 °. It is more preferably 59 ° to 61 ° or 149 ° to 151 °, and particularly preferably 60 ° or 150 °. Within such a range, it is possible to provide an optical laminate in which the antireflection function of the circularly polarizing plate is fully exhibited and external light reflection, background reflection, and the like can be effectively prevented.

The base material preferably has a refractive index characteristic of nx> ny ≧ nz. The in-plane retardation Re (550) of the substrate is larger than 0 nm. According to the present invention, it is possible to obtain an optical laminate in which the antireflection function of the circularly polarizing plate is sufficiently exhibited even if a base material having an in-plane retardation Re is used. In one embodiment, the in-plane retardation Re (550) of the substrate is 3 nm or more. In another embodiment, the in-plane retardation Re (550) of the substrate is 5 nm or more. The upper limit of the in-plane retardation Re (550) of the base material is, for example, 10 nm. When the in-plane retardation Re (550) of the base material is 10 nm or less (more preferably 8 nm or less, further preferably 6 nm or less), the antireflection function of the circularly polarizing plate becomes higher.

Any suitable resin film can be used as the base material. Specific examples of the constituent materials include cyclic olefin resins, polycarbonate resins, cellulosic resins, polyester resins, and acrylic resins.

The thickness of the base material is preferably 10 μm to 200 μm, more preferably 20 μm to 60 μm.

If necessary, a hard coat layer (not shown) may be provided between the conductive layer 21 and the base material 22. As the hard coat layer, a hard coat layer having an arbitrary appropriate structure can be used. The thickness of the hard coat layer is, for example, 0.5 μm to 2 μm. If the haze is acceptable, fine particles for reducing Newton's rings may be added to the hard coat layer. Further, if necessary, an anchor coat layer for enhancing the adhesion of the conductive layer and / or the reflectance is adjusted between the conductive layer 21 and the base material 22 (hard coat layer if present). A refractive index adjusting layer may be provided for this purpose. Any suitable configuration can be adopted as the anchor coat layer and the refractive index adjusting layer. The anchor coat layer and the refractive index adjusting layer can be thin layers of several nm to several tens of nm.

If necessary, another hard coat layer may be provided on the side of the base material 22 opposite to the conductive layer 21 (outermost side of the optical laminate). The hard coat layer typically contains a binder resin layer and spherical particles, and the spherical particles protrude from the binder resin layer to form convex portions. Details of such a hard coat layer are described in Japanese Patent Application Laid-Open No. 2013-145547, and the description of the publication is incorporated herein by reference.

G. Others The optical laminate according to the embodiment of the present invention may further include other layers. Practically, the surface of the base material 22 is provided with an adhesive layer (not shown) for sticking to the display cell. It is preferable that a release film is adhered to the surface of the pressure-sensitive adhesive layer until the optical laminate is used.

H. Image display device The optical laminate according to the above items A to G can be applied to an image display device. Therefore, the present invention includes an image display device using such an optical laminate. Typical examples of the image display device include a liquid crystal display device and an organic EL display device. The image display device according to the embodiment of the present invention includes the optical laminate according to the above items A to G on the visual side thereof. The optical laminate is laminated so that the conductive layer is on the display cell side (for example, the liquid crystal cell or the organic EL cell) (the polarizer is on the visual side). That is, the image display device according to the embodiment of the present invention can be a so-called inner touch panel type input display device in which a touch sensor is incorporated between a display cell (for example, a liquid crystal cell or an organic EL cell) and a polarizing plate. In this case, the touch sensor may be arranged between the conductive layer (or the conductive layer with a substrate) and the display cell. As for the configuration of the touch sensor, a configuration well known in the industry can be adopted, and detailed description thereof will be omitted.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

The reflection characteristics of the optical laminate having the configurations shown in Table 1 below were evaluated from the front hues a and b using an optical simulator (manufactured by Shintec, trade name "LCD Master V8").
A light source (D65 light source registered in "LCD Master V8") is arranged on the side opposite to the first retardation layer of the polarizing plate, and on the side opposite to the second retardation layer of the base material. , The reflector (idea-reflector registered in "LCD Master V8") is arranged.
Further, the front hues a and b were obtained with the same configuration as in Table 1 except that the base material was not included, and the results were used as a reference.
In this evaluation, as will be described later, the simulation is performed by changing the slow axis angle of the base material, and the reflection characteristics of the optical laminate are evaluated by comparison with the reference.

[Example 1]
The angle formed by the slow axis of the base material and the absorption axis of the polarizer of the polarizing plate was set to 75 °. That is, the angle formed by the slow axis of the base material and the slow axis of the second retardation layer was set to 0 °.

[Example 2]
The angle formed by the slow axis of the base material and the absorption axis of the polarizer of the polarizing plate was set to 165 °. That is, the angle formed by the slow axis of the base material and the slow axis of the second retardation layer was set to 90 °.

[Example 3]
The angle formed by the slow axis of the base material and the absorption axis of the polarizer of the polarizing plate was set to 70 °. That is, the angle formed by the slow axis of the base material and the slow axis of the second retardation layer was set to −5 °.

[Example 4]
The angle formed by the slow axis of the base material and the absorption axis of the polarizer of the polarizing plate was set to 80 °. That is, the angle formed by the slow axis of the base material and the slow axis of the second retardation layer was set to 5 °.

[Example 5]
The angle formed by the slow axis of the base material and the absorption axis of the polarizer of the polarizing plate was set to 160 °. That is, the angle formed by the slow axis of the base material and the slow axis of the second retardation layer was set to 85 °.

[Example 6]
The angle formed by the slow axis of the base material and the absorption axis of the polarizer of the polarizing plate was set to 170 °. That is, the angle formed by the slow axis of the base material and the slow axis of the second retardation layer was set to 95 °.

[Comparison example]
The angle formed by the slow axis of the base material and the absorption axis of the polarizer of the polarizing plate is changed within the range of 0 ° to 65 °, 85 ° to 155 °, and 175 ° to 180 °, and the reflection at each angle. The characteristics were evaluated.

FIG. 2 shows plots of front hues a and b for the results of Examples and Comparative Examples. Further, FIG. 3 shows graphs showing the axial angle dependence of Δab. In addition, Δab is calculated by Δab = {(front hue a-reference front hue a) ² + (front hue b-reference front hue b) ² } ^1/2 . The lower the Δab, the less the influence of the isotropic base material, and the better the antireflection property.

As is clear from FIGS. 2 and 3, the optical laminate of the present invention has an excellent antireflection function.

The optical laminate of the present invention is suitably used for image display devices such as liquid crystal display devices and organic EL display devices, and can be particularly preferably used as an antireflection film for organic EL display devices. Further, the optical laminate of the present invention can be suitably used for an inner touch panel type input display device.

1 Polarizer 2 First protective layer 3 Second protective layer 11 Polarizing plate 12 First retardation layer 13 Second retardation layer 21 Conductive layer 22 Base material 100 Optical laminate

Claims (4)

It has a polarizing plate including a polarizing element and a protective layer arranged on at least one side of the polarizing element, a first retardation layer, a second retardation layer, a conductive layer, and a base material in this order. ,
The in-plane retardation Re (550) of the base material is larger than 0 nm and 10 nm or less.
The angle formed by the slow axis of the base material and the slow axis of the second retardation layer is −5 ° to 5 ° or 85 ° to 95 °.
The angle formed by the absorption axis of the polarizer and the slow axis of the first retardation layer is 10 ° to 20 °, and the angle formed by the absorption axis and the slow axis of the second retardation layer. There Ri 65 ° ~85 ° der,
The in-plane retardation Re (550) of the first retardation layer is 180 nm to 320 nm.
The in-plane retardation Re (550) of the second retardation layer is 80 nm to 200 nm.
Optical laminate. The optical laminate according to claim 1, wherein the first retardation layer and the second retardation layer are made of a cyclic olefin resin film. The optical laminate according to claim 1, wherein the first retardation layer and the second retardation layer are orientation-solidified layers of liquid crystal compounds. An image display device comprising the optical laminate according to any one of claims 1 to 3 .