Optical laminate and image display unit with optical laminate

Abstract

To provide an optical laminate that has end decoloration suppressed.SOLUTION: An optical laminate has: a cover glass of 7 to 50% in transmissivity at a wavelength of 243 nm; a first adhesive layer formed of a first adhesive composition as an ultraviolet-ray curable adhesive; a polarizer; a polarization plate including a protective layer laminated on at least one surface of the polarizer; and a second adhesive layer formed of a second adhesive composition, in this order.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical laminate and an image display device having the optical laminate.

Background Art

[0002] A polarizer is typically manufactured by dyeing a polyvinyl alcohol (PVA)-based resin film with a dichroic substance such as iodine (for example, Patent Documents 1 and 2). It is known that when a polarizer absorbs moisture, the iodine complex is destroyed and iodine elutes, resulting in a decrease in polarization degree and an increase in transmittance (decolorization). Since moisture enters from the end of the polarizing plate, decolorization tends to be significant at the end. In recent years, with the progress of thinning of image display devices that employ polarizers, a protective layer may be used only on one surface of the polarizer. In a polarizing plate having a protective layer only on one side, decolorization of the polarizer can be a more serious problem.

[0003] Polarizing plates are widely used in image display devices such as mobile phones and notebook personal computers to realize image display and / or improve the performance of the image display. In recent years, due to the rapid spread of smartphones and touch panel-type information processing devices, image display devices equipped with cameras have become widely used. Correspondingly, polarizing plates having through holes at positions corresponding to the camera unit have also come to be widely used. In such a polarizing plate having a through hole, there are various considerations in the through hole or its vicinity. In addition, in an image display device, a cover glass may be laminated on the outermost surface to impart surface hardness and impact resistance. Typically, in an image display device, the optical laminate and the cover glass are laminated via an adhesive composition. In an optical laminate in which a cover glass is laminated via an adhesive composition, excessive decolorization may occur at the end, which is different from the case of a polarizing plate alone (for example, a polarizing plate composed of a polarizer and a protective layer).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made to solve the above-described conventional problems, and its main object is to provide an optical laminate in which edge discoloration is suppressed.

Means for Solving the Problems

[0006] 1. The optical laminate according to an embodiment of the present invention includes a cover glass having a transmittance of 7% to 50% at a wavelength of 243 nm, a first adhesive layer composed of a first adhesive composition which is an ultraviolet curable adhesive, a polarizer, and a polarizing plate including a protective layer laminated on at least one surface of the polarizer, and a second adhesive layer composed of a second adhesive composition, in this order. 2. In the optical laminate according to 1 above, the polarizing plate has a through hole, and the through hole may be filled with the first adhesive composition. 3. In the optical laminate according to 1 or 2 above, the protective layer may be laminated only on the surface of the polarizer on the cover glass side. 4. In the optical laminate according to any one of 1 to 3 above, the first adhesive composition may include a base polymer having an amide skeleton and an acylphosphine oxide-based photopolymerization initiator. 5. In the optical laminate according to any one of 1 to 4 above, the cover glass contains a metal oxide of an alkaline earth metal. 6. In the optical laminate according to 5 above, the content of the metal oxide of the alkaline earth metal in the cover glass may be 2% by weight to 12% by weight. 7. In the optical laminate according to any one of 1 to 6 above, the thickness of the polarizer may be 15 μm or less. 8. In another aspect of the embodiment of the present invention, an image display device is provided. This image display device has the optical laminate described in any one of 1 to 7 above. 9. The image display device described in 8 above may have the optical laminate described in 2 above and may have a camera unit at a position corresponding to the through hole.

Effects of the Invention

[0007] According to the embodiment of the present invention, an optical laminate in which end discoloration is suppressed is provided even when a cover glass is laminated. The optical laminate of the embodiment of the present invention can suppress end discoloration even when placed under more severe conditions such as a humidification reliability evaluation test.

Brief Description of the Drawings

[0008]

Figure 1

Modes for Carrying Out the Invention

[0009] (Definitions of Terms and Symbols) The definitions of terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) “nx” is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and “nz” is the refractive index in the thickness direction. (2) In-Plane Phase Difference (Re) “Re(λ)” is the in-plane phase difference measured with light of wavelength λ nm at 23°C. For example, “Re(550)” is the in-plane phase difference measured with light of wavelength 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 the retardation in the thickness direction measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23°C. When the thickness of the layer (film) is d (nm), Rth(λ) is obtained by the formula: Rth(λ) = (nx - nz) × d. (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, "45°" means ±45°.

[0010] A. Overall configuration of the optical laminate FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 in the illustrated example has a cover glass 30, a first adhesive layer 20, a polarizing plate 10, and a second adhesive layer 40 in this order. Typically, the optical laminate 100 is laminated on a liquid crystal panel 200 via the second adhesive layer 40. The optical laminate 100 in the illustrated example has a through hole 15 that penetrates the polarizing plate 10 and the second adhesive layer 40. In the illustrated example, the through hole 15 is filled with a first adhesive composition that constitutes the first adhesive layer 20. In the illustrated example, the polarizing plate 10 has a polarizer 11 and protective layers 12 and 13 laminated on both surfaces of the polarizer 11. Either one of the protective layers 12 and 13 may be omitted. In one embodiment, the polarizing plate 10 has only the protective layer 12 laminated on the cover glass side of the polarizer 11. By omitting one of the protective layers, a thin optical laminate can be obtained. In a thin optical laminate, end discoloration may become prominent. However, according to the embodiment of the present invention, end discoloration can be suppressed even when one of the protective layers is omitted.

[0011] As described above, in one embodiment, the optical laminate has a through-hole. The through-hole is provided at any appropriate position according to the purpose. Typically, the through-hole is provided at or near the end of the optical laminate. With such a configuration, the influence on image display can be minimized. Only one through-hole may be provided, or a plurality of through-holes may be provided. For example, two or more through-holes may be provided. Even when the through-hole of the optical laminate according to the embodiment of the present invention is provided in the image display portion, excessive discoloration at the end can be suppressed, and a decrease in image display performance can be suppressed.

[0012] An optical functional layer (not shown) other than the polarizing plate 10 may be provided on the optical laminate. Examples of the optical functional layer include a retardation layer. The type, number, combination, arrangement position, and characteristics of the optical functional layer can be appropriately set according to the purpose. When the optical laminate has a retardation layer, the retardation layer can be disposed, for example, between the polarizing plate 10 and the second adhesive layer 40.

[0013] The thickness of the optical laminate 100 can be set to any appropriate value. The total thickness of the polarizing plate 10 and the second adhesive layer 40 is preferably 120 μm to 400 μm, more preferably 130 μm to 250 μm, and even more preferably 150 μm to 300 μm. If the total thickness of the polarizing plate 10 and the second adhesive layer 40 is within the above range, even in the case of an optical laminate having a through-hole, the filling of the adhesive composition into the through-hole can be facilitated. If the total thickness of the polarizing plate 10 and the second adhesive layer 40 is too thin, the handleability may decrease in the manufacturing process of the image display device.

[0014] The thickness of the polarizing plate 10 can be set to any appropriate value. The thickness of the polarizing plate is preferably 45 μm to 100 μm, more preferably 45 μm to 70 μm, and even more preferably 45 μm to 60 μm. As described above, when the optical laminate has a through-hole, the first adhesive layer can be provided so as to fill the through-hole. When trying to reduce the thickness of the first adhesive layer (and as a result, reduce the thickness of the obtained optical laminate), it may be necessary to make the depth of the through-hole shallower. Therefore, a polarizing plate with a small thickness as described above can be used. As a polarizing plate with such a thickness, typically, a polarizing plate in which a protective layer is laminated only on one side of the polarizer is known. In a polarizing plate in which a protective layer is laminated only on one side, decolorization of the polarizer may be more problematic than in a polarizing plate in which protective layers are laminated on both sides of the polarizer. According to the optical laminate of the embodiment of the present invention, even with a polarizing plate having such a thickness, end decolorization can be suppressed.

[0015] Hereinafter, the components of the optical laminate will be specifically described.

[0016] B. Cover glass The cover glass 30 has a transmittance of 7% to 50% at a wavelength of 243 nm. The transmittance of the cover glass at a wavelength of 243 nm is preferably 8% to 40%, more preferably 9% to 30%, and even more preferably 10% to 25%. If the transmittance at a wavelength of 243 nm is within the above range, an optical laminate with suppressed end decolorization is provided. When the transmittance at a wavelength of 243 nm exceeds 50%, there is a risk that the damage to the polarizing plate and the panel by sunlight will increase and the quality will deteriorate. The transmittance of the cover glass at a wavelength of 243 nm can be measured by a spectrophotometer (for example, product name: U-4100, manufactured by Hitachi High-Technologies Corporation). The cover glass only needs to have a transmittance of 7% to 50% at a wavelength of 243 nm, and one with any appropriate thickness can be used.

[0017] The cover glass typically contains silicon oxide (e.g., SiO2) and metal oxides such as aluminum oxide (Al2O3), boron oxide (B2O3), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), sodium oxide (Na2O), potassium oxide (K2O), iron oxide (Fe2O3), titanium oxide (TiO2), etc. Any appropriate metal oxide other than silicon oxide can be used according to the purpose. As the metal oxide other than silicon oxide, only one kind may be used, or two or more kinds may be combined.

[0018] The cover glass preferably has a magnesium element content of less than 0.5 atomic%, more preferably 0.4 atomic% or less, still more preferably 0.3 atomic% or less, and particularly preferably 0.1 atomic% or less. By the magnesium element content of the cover glass being within the above range, an optical laminate with suppressed edge discoloration can be provided. The cover glass may substantially contain no magnesium element (e.g., the element content is below the detection limit of the analyzer). The magnesium element content of the cover glass can be measured using an X-ray photoelectron analyzer (ESCA (e.g., manufactured by ULVAC-PHI, product name: Quantum 2000)).

[0019] In one embodiment, the cover glass preferably contains an alkaline earth metal metal oxide (hereinafter also referred to as an alkaline earth metal oxide). When containing an alkaline earth metal oxide, the durability of the cover glass is improved, and the devitrification temperature and viscosity during glass forming can be adjusted. Also, the thermal expansion coefficient of the cover glass can be adjusted. Examples of the alkaline earth metal metal oxide include MgO, CaO, and SrO. As the alkaline earth metal oxide, only one kind may be used, or two or more kinds may be used in combination.

[0020] The alkaline earth metal oxide is used in any appropriate content. The content of the alkaline earth metal oxide in the cover glass (for example, the total content of MgO, CaO, and SrO) is preferably 2% by weight to 12% by weight. When the content of the alkaline earth metal oxide exceeds 12% by weight, the ultraviolet transmittance may decrease due to an increase in the devitrification temperature during forming and an increase in the strain of the Si-O bonds contained in the glass.

[0021] In one embodiment, the content of MgO is preferably 10% by weight or less, and in one embodiment, it is preferably 0% by weight to 4% by weight. In one embodiment, the content of CaO is preferably 10% by weight or less, and in one embodiment, it is preferably 0% by weight to 9% by weight. In one embodiment, the content of SrO is preferably 15% by weight or less, and in one embodiment, it is preferably 0% by weight to 5% by weight. In embodiments containing an alkaline earth metal oxide, it may be used as long as the total content of the alkaline earth metal oxide falls within the above range. In this specification, a content of 0% by weight includes the case where the content is below the detection limit value by an analyzer.

[0022] The cover glass may further contain TiO2 and / or Fe2O3. It is known that by containing TiO2 or Fe2O3, the ultraviolet transmittance (for example, the transmittance in the deep ultraviolet region) can be adjusted. The total content of TiO2 and Fe2O3 is, for example, 0.0010% by weight or less. When the total content of TiO2 and Fe2O3 is too high, the ultraviolet transmittance tends to decrease.

[0023] C. Polarizing plate C-1. Polarizer A polarizer is typically composed of a resin film containing a dichroic substance (typically iodine). As the resin film, any appropriate resin film that can be used as a polarizer can be adopted. The resin film is typically a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

[0024] Specific examples of a polarizer composed of a single-layer resin film include those obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically uniaxial stretching). The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based resin film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. Also, it may be dyed after stretching. If necessary, the PVA-based resin film is subjected to a swelling treatment, a cross-linking treatment, a washing treatment, a drying treatment, etc. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only can the dirt on the surface of the PVA-based resin film and the blocking inhibitor be washed, but also the PVA-based resin film can be swollen to prevent uneven dyeing and the like.

[0025] As specific examples of the polarizer obtained using the laminate, there may be mentioned a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In the present embodiment, preferably, a PVA-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. The stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, the stretching may further include air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution, if necessary. In addition, in the present embodiment, preferably, the laminate is subjected to a drying shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. At the same time, by enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in the subsequent dyeing process or stretching process can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. Thereby, the optical properties of the polarizer obtained through treatment steps such as a dyeing treatment and an underwater stretching treatment, in which the laminate is immersed in a liquid, can be improved. Furthermore, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical properties can be improved.The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may be used as the protective layer of the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate, and any appropriate protective layer according to the purpose may be laminated on the peeled surface and used. Details of such a method for producing a polarizer are described, for example, in JP-A-2012-73580 (Patent No. 5414738) and Patent No. 6470455. The entire descriptions of these publications are incorporated herein by reference.

[0026] In one embodiment, the polarizer further contains boric acid. The boric acid content of the polarizer is preferably 10% by weight or more, more preferably 13% to 25% by weight. If the boric acid content of the polarizer is within such a range, due to the synergistic effect with the iodine content described later, the ease of curl adjustment during bonding can be maintained well, and while suppressing the curl during heating well, the appearance durability during heating can be improved. The boric acid content can be calculated, for example, by the neutralization method using the following formula as the amount of boric acid contained in the polarizer per unit weight.

Equation

[0027] The iodine content of the polarizer is preferably 2% by weight or more, more preferably 2% to 10% by weight. If the iodine content of the polarizer is within such a range, due to the synergistic effect with the above boric acid content, the ease of curl adjustment during bonding can be maintained well, and while suppressing the curl during heating well, the appearance durability during heating can be improved. In this specification, the "iodine content" means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, in the polarizer, iodine is iodine ions (I - ), iodine molecules (I2), polyiodine ions (I3 - , I5 -When present in the form of (etc.), the iodine content in this specification means the amount of iodine including all these forms. The iodine content can be calculated, for example, by the calibration curve method of X-ray fluorescence analysis. Note that polyiodide ions exist in a state where a PVA-iodine complex is formed in the polarizer. When such a complex is formed, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ion (PVA·I3 - ) has an absorption peak near 470 nm, and the complex of PVA and pentaiodide ion (PVA·I5 - ) has an absorption peak near 600 nm. As a result, polyiodide ions can absorb light in a wide range of visible light depending on their form. On the other hand, iodide ion (I - ) has an absorption peak near 230 nm and is not substantially involved in the absorption of visible light. Therefore, polyiodide ions existing in a complex state with PVA can mainly be involved in the absorption performance of the polarizer.

[0028] The polarizer preferably exhibits absorption dichroism at any wavelength in the wavelength range of 380 nm to 780 nm. The single transmittance Ts of the polarizer is preferably 40% to 48%, more preferably 41% to 46%. The degree of polarization P of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more. The above single transmittance is typically the Y value measured using an ultraviolet-visible spectrophotometer and corrected for visual sensitivity. The above degree of polarization is typically determined by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured using an ultraviolet-visible spectrophotometer and corrected for visual sensitivity. Degree of polarization (%) = {(Tp - Tc) / (Tp + Tc)} 1 / 2 ×100

[0029] The thickness of the polarizer can be set to any appropriate value. The thickness of the polarizer is, for example, preferably 15 μm or less, more preferably 1 μm to 12 μm, still more preferably 2 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0030] C-2. Protective Layer The protective layer is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, acetate-based resins, etc. Also, thermosetting resins or ultraviolet curable resins such as (meth)acrylic-based, urethane-based, (meth)acrylic urethane-based, epoxy-based, silicone-based resins, etc. can be mentioned. In addition to these, 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 for example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the above resin composition.

[0031] The outer protective layer (protective layer 12 in the illustrated example) may be subjected to surface treatments such as hard coat treatment, antireflection treatment, anti-sticking treatment, antiglare treatment, etc., as necessary.

[0032] The inner protective layer is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm and the retardation in the thickness direction Rth(550) is -10 nm to +10 nm.

[0033] The thickness of the protective layer can be any suitable thickness. The thickness of the protective layer is, for example, 15 μm to 45 μm, preferably 20 μm to 40 μm. When surface treatment is performed, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

[0034] The retardation layer is typically provided to impart antireflection properties to the polarizing plate, and when the retardation layer is a single layer, it can function as a λ / 4 plate. The retardation layer is preferably an alignment cured layer of a liquid crystal compound. The in-plane retardation Re(550) of the retardation layer is preferably more than 100 nm and less than 160 nm, more preferably 110 nm to 155 nm, and even more preferably less than 130 nm to 150 nm.

[0035] When the retardation layer is composed of a single layer, its thickness is preferably 0.5 μm to 7 μm, more preferably 1 μm to 5 μm. By using a liquid crystal compound, an in-plane retardation equivalent to that of a resin film can be achieved with a thickness much thinner than that of the resin film.

[0036] The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained optical laminate is used in an image display device, a very excellent reflected hue can be achieved.

[0037] The retardation layer may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes according to the wavelength of the measurement light. In one embodiment, the retardation layer exhibits an inverse dispersion wavelength characteristic. In this case, Re(450) / Re(550) of the retardation layer is preferably less than 1, more preferably 0.8 or more and less than 1, and further preferably 0.8 or more and 0.95 or less. Moreover, Re(550) / Re(650) of the retardation layer is preferably more than 1, more preferably more than 1 and 1.2 or less, and further preferably 1.01 to 1.15. With such a configuration, it is possible to realize very excellent antireflection properties.

[0038] The angle between the slow axis of the retardation layer and the absorption axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and further preferably about 45°. If the angle is in this range, by using a λ / 4 plate as the retardation layer as described above, an optical laminate having very good circular polarization properties (as a result, very good antireflection properties) can be obtained.

[0039] The retardation layer is preferably an alignment-solidified layer of a liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be significantly increased compared to non-liquid crystal materials, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be significantly reduced. As a result, a polarizing plate with a retardation layer can be further thinned. In this specification, the term "liquid crystal alignment-solidified layer" refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The term "alignment-solidified layer" is a concept that includes an alignment-solidified layer obtained by curing a liquid crystal monomer as described later.

[0040] The optical laminate 100 may further include another retardation layer. The another retardation layer may be a so-called positive C-plate showing a refractive index characteristic of nz > nx = ny. By using a positive C-plate as the another retardation layer, reflection in an oblique direction can be prevented well, and a wide viewing angle of the antireflection function can be achieved. In this case, the retardation Rth(550) in the thickness direction of the another retardation layer is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, still more preferably -90 nm to -200 nm, and particularly preferably -100 nm to -180 nm. Here, "nx = ny" includes not only the case where nx and ny are exactly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the another retardation layer can be less than 10 nm.

[0041] The another retardation layer having a refractive index characteristic of nz > nx = ny can be formed of any suitable material. The another retardation layer preferably comprises a film containing a liquid crystal material fixed in a homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the liquid crystal compounds and the method for forming the retardation layer described in paragraphs

[0020] to

[0028] of JP-A-2002-333642. In this case, the thickness of the another retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and still more preferably 0.5 μm to 5 μm.

[0042] D. The first adhesive layer The first adhesive layer is composed of a first adhesive composition which is an ultraviolet curable adhesive. Since the first adhesive layer is composed of an ultraviolet curable adhesive, the cover glass and the polarizing plate can be sufficiently adhered even when the thickness of the first adhesive layer is thin. The ultraviolet curable adhesive typically includes a base polymer and a photoinitiator. Any suitable ultraviolet curable adhesive can be used as the first adhesive composition.

[0043] The storage modulus of the first pressure-sensitive adhesive composition at 60 °C before curing is preferably 1.0×10 5 Pa or less, more preferably 1.0×10 3 Pa to 1.0×10 5 Pa, even more preferably 5.0×10 3 Pa to 8.0×10 4 Pa, and particularly preferably 7.5×10 3 Pa to 6.0×10 4 Pa. If the storage modulus of the first pressure-sensitive adhesive composition before curing is within such a range, the first pressure-sensitive adhesive composition exhibits appropriate deformation behavior (viscoelastic behavior), and even when the polarizing plate has a through-hole, it can flow well into the end of the through-hole, suppressing the gap between the pressure-sensitive adhesive layer and the through-hole. The storage modulus of the first pressure-sensitive adhesive composition at 60 °C after curing is preferably 5.0×10 3 Pa to 5.0×10 5 Pa, more preferably 7.5×10 3 Pa to 4.0×10 5 Pa, even more preferably 8.0×10 3 Pa to 3.0×10 5 Pa.

[0044] The total light transmittance of the first pressure-sensitive adhesive layer is preferably 85% or more, more preferably 90% or more. The haze value of the first pressure-sensitive adhesive layer is preferably 1.5% or less, more preferably 1.0% or less.

[0045] The thickness of the first pressure-sensitive adhesive layer can be set to any appropriate value. The thickness of the first pressure-sensitive adhesive layer is preferably 50 μm to 500 μm, more preferably 50 μm to 300 μm, even more preferably 75 μm to 200 μm.

[0046] D-1. Base Polymer As the base polymer of the first pressure-sensitive adhesive composition, any suitable polymer can be used. For example, (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy polymers, fluorine polymers, natural rubbers, rubber polymers such as synthetic rubbers, etc. may be mentioned. Preferably, a (meth)acrylic pressure-sensitive adhesive composition containing a (meth)acrylic polymer as the base polymer is used. This is because it has excellent optical transparency, exhibits pressure-sensitive adhesive properties such as appropriate wettability, cohesiveness, and adhesiveness, and is also excellent in weather resistance and heat resistance. In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0047] D-1-1. (Meth)acrylic base polymer (Meth)acrylic base polymers can be obtained by polymerizing any suitable monomer components. The acrylic base polymer preferably uses an amide group-containing monomer as the monomer component. By using an amide group-containing monomer as the monomer component, a base polymer having an amide backbone can be obtained. When the first pressure-sensitive adhesive composition contains an amide group-containing monomer and a base polymer having an amide backbone, the adhesion between the cover glass and the polarizing plate can be improved. Any suitable monomer can be used as the amide group-containing monomer. Examples of the amide group-containing monomer include acrylamide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam-based monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. Only one kind of amide group-containing monomer may be used, or two or more kinds may be used in combination.

[0048] (Meth)acrylic base polymers can be obtained by polymerizing any suitable monomer components. The acrylic base polymer preferably uses an amide group-containing monomer as the monomer component. By using an amide group-containing monomer as the monomer component, a base polymer having an amide backbone can be obtained. When the first pressure-sensitive adhesive composition contains an amide group-containing monomer and a base polymer having an amide backbone, the adhesion between the cover glass and the polarizing plate can be improved. Any suitable monomer can be used as the amide group-containing monomer. Examples of the amide group-containing monomer include acrylamide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam-based monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. Only one kind of amide group-containing monomer may be used, or two or more kinds may be used in combination.

[0049] The first pressure-sensitive adhesive composition contains an alkyl (meth)acrylate as a main monomer component. As the alkyl (meth)acrylate, an alkyl (meth)acrylate having an alkyl group with 1 to 20 carbon atoms is preferably used. The alkyl (meth)acrylate may have a linear alkyl group, a branched alkyl group, or a cyclic alkyl group. The amount of the alkyl (meth)acrylate relative to the total amount of the monomer components constituting the (meth)acrylic-based polymer is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 60% by weight or more. The alkyl (meth)acrylate is used, for example, such that the total of the monomer components is 100% by weight. From the viewpoint of setting the glass transition temperature (Tg) of the polymer chain within an appropriate range, the amount of the alkyl (meth)acrylate having a linear alkyl group with 4 to 10 carbon atoms relative to the total amount of the monomer components constituting the (meth)acrylic-based polymer is preferably 30% by weight or more, more preferably 40% by weight or more, and still more preferably 45% by weight or more.

[0050] (The (meth)acrylic-based polymer preferably further contains a monomer component having a crosslinkable functional group. Examples of the monomer component having a crosslinkable functional group include a hydroxyl group-containing monomer and a carboxyl group-containing monomer. When a crosslinked structure is introduced by an isocyanate crosslinking agent, the hydroxyl group becomes a reaction point with the isocyanate group, and when a crosslinked structure is introduced by an epoxy-based crosslinking agent, the carboxyl group becomes a reaction point with the epoxy group. Preferably, a hydroxyl group-containing monomer is used as the monomer component having a crosslinkable functional group, and a crosslinked structure can be introduced by an isocyanate-based crosslinking agent. With such a configuration, the crosslinkability of the base polymer can be enhanced, and a pressure-sensitive adhesive layer having high transparency can be formed. Furthermore, with such a configuration, a so-called acid-free pressure-sensitive adhesive can be realized.

[0051] The amount of the hydroxyl group-containing monomer relative to the total amount of the monomer components constituting the (meth)acrylic-based polymer is preferably 5% by weight to 30% by weight, more preferably 8% by weight to 25% by weight, and still more preferably 10% by weight to 20% by weight. If the amount of the hydroxyl group-containing monomer is within such a range, the crosslinking degree (gel fraction) can be increased with a small amount of a crosslinking agent, and as a result, the filling property and workability of the first adhesive composition before curing into through-holes can be enhanced.

[0052] The (meth)acrylic-based polymer may further contain any suitable monomer component according to the purpose. Specific examples include acid anhydride group-containing monomers, caprolactone adducts of (meth)acrylic acid, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, vinyl-based monomers such as vinyl acetate, vinyl propionate, styrene, and α-methylstyrene; cyano group-containing acrylic monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; and acrylic ester-based monomers such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl (meth)acrylate.

[0053] The (meth)acrylic-based polymer can be obtained by polymerizing the above monomer components by any suitable method. For example, solution polymerization, active energy ray polymerization such as UV polymerization, bulk polymerization, and various radical polymerizations such as emulsion polymerization can be mentioned. As the polymerization conditions, any suitable polymerization conditions can be adopted as long as the effects of the present invention are not impaired. When polymerizing the monomer components, any other suitable components other than the monomer components may be included. Examples of the other components include polymerization initiators, chain transfer agents, solvents, and the like. The content of these other components can be any suitable content as long as the effects of the present invention are not impaired.

[0054] As the polymerization initiator used for the polymerization of the base polymer, a thermal polymerization initiator, a photopolymerization initiator (photoinitiator), etc. can be adopted according to the type of polymerization reaction. The polymerization initiator may be only one kind, or two or more kinds.

[0055] In one embodiment, as the polymerization initiator, for example, an azo-based polymerization initiator, a peroxide-based polymerization initiator (e.g., dibenzoyl peroxide, tert-butyl permaleate, etc.), a redox-based polymerization initiator, etc. are used. Preferably, an azo-based polymerization initiator is used. By using an azo-based polymerization initiator, it is possible to prevent the decomposition products of the polymerization initiator from remaining in the (meth)acrylic-based base polymer as a part that causes the generation of heat-generated gas (outgas). Examples of the azo-based polymerization initiator include 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile (AMBN), 2,2'-azobis(2-methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid, etc.

[0056] In one embodiment, the first pressure-sensitive adhesive composition preferably contains a base polymer into which a crosslinked structure is introduced as the (meth)acrylic-based base polymer. The polymer in which a crosslinked structure is introduced into the (meth)acrylic-based base polymer can be obtained, for example, by the following methods: (1) after polymerizing a (meth)acrylic-based polymer having a functional group capable of reacting with a crosslinking agent, adding a crosslinking agent and reacting the (meth)acrylic-based polymer with the crosslinking agent; and (2) introducing a branched structure (crosslinked structure) into the polymer chain by including a polyfunctional compound in the polymerization components of the polymer. These may be used in combination.

[0057] Specific examples of the crosslinking agent in the method of reacting the base polymer of (1) above with a crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, metal chelate-based crosslinking agents, and the like. Among them, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred because they have high reactivity with the hydroxyl groups and carboxyl groups of the base polymer and it is easy to introduce a crosslinked structure. These crosslinking agents react with functional groups such as hydroxyl groups and carboxyl groups introduced into the base polymer to form a crosslinked structure. As described above, when an acid-free pressure-sensitive adhesive in which the base polymer does not contain a carboxyl group is employed, it is preferable to introduce a crosslinked structure with the hydroxyl groups in the base polymer and an isocyanate-based crosslinking agent.

[0058] The crosslinking agent can preferably be used in a proportion of 0.03 parts by weight to 0.5 parts by weight, more preferably 0.05 parts by weight to 0.3 parts by weight, still more preferably 0.06 parts by weight to 0.25 parts by weight, and particularly preferably 0.07 parts by weight to 0.2 parts by weight, based on 100 parts by weight of the base polymer. By setting the amount of the crosslinking agent used within such a range, the gel fraction can be set within the above desired range.

[0059] In the method of including a polyfunctional compound in the polymerization component of the base polymer of (2) above, the monomer components constituting the (meth)acrylic-based base polymer and the total amount of the polyfunctional compound for introducing a crosslinked structure may be reacted all at once, or polymerization may be carried out in multiple stages. As a method of carrying out polymerization in multiple stages, a monofunctional monomer constituting the (meth)acrylic-based base polymer is polymerized (prepolymerized) to prepare a partial polymer (prepolymer composition), and a polyfunctional compound such as a polyfunctional (meth)acrylate is added to the prepolymer composition, and the prepolymer composition and the polyfunctional monomer are polymerized (main polymerization). The prepolymer composition is a partial polymer containing a polymer with a low degree of polymerization and unreacted monomers.

[0060] By performing preliminary polymerization of the constituent components of a (meth)acrylic-based polymer, branch points (crosslinking points) formed by a polyfunctional compound can be uniformly introduced into the (meth)acrylic-based polymer. Further, after applying a mixture of a low molecular weight polymer or partial polymer and an unpolymerized monomer component (adhesive composition) onto a substrate, bulk polymerization can be carried out on the substrate to form an adhesive layer. Since a low polymerization composition such as a prepolymer composition has a low viscosity and excellent coatability, according to a method of performing bulk polymerization on a substrate after applying an adhesive composition which is a mixture of a prepolymer composition and a polyfunctional compound, the productivity of the adhesive layer can be improved and the thickness of the adhesive layer can be made uniform.

[0061] Examples of the polyfunctional compound used for introducing a crosslinked structure include compounds containing two or more polymerizable functional groups having an unsaturated double bond (ethylenically unsaturated groups) in one molecule. The polyfunctional compound is typically a photo-polymerizable polyfunctional compound. As the polyfunctional compound, polyfunctional (meth)acrylate is preferred because it is easily copolymerized with the monomer components of a (meth)acrylic-based polymer. Any suitable polyfunctional (meth)acrylate can be used as the polyfunctional (meth)acrylate. For example, 1,6-hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, and vinyl (meth)acrylate can be mentioned. When introducing a branched (crosslinked) structure by active energy ray polymerization (photo-polymerization), polyfunctional (meth)acrylate is preferred.

[0062] The molecular weight of the polyfunctional compound is preferably 1500 or less, more preferably 1000 or less. The lower limit of the molecular weight can be, for example, 500. The functional group equivalent (g / eq) of the polyfunctional compound is preferably 50 to 500, more preferably 70 to 300, and even more preferably 80 to 200. With such a configuration, the viscoelasticity of the first pressure-sensitive adhesive composition can be appropriately adjusted.

[0063] The polyfunctional compound can be preferably used in a proportion of 1 to 6 parts by weight, more preferably 2 to 5 parts by weight, and even more preferably 2.5 to 4 parts by weight based on 100 parts by weight of the base polymer. If the amount used is too small, the adhesion retention of the first pressure-sensitive adhesive composition (and as a result, the first pressure-sensitive adhesive layer) may be insufficient. If the amount used is too large, the formed first pressure-sensitive adhesive layer may become excessively hard and the impact resistance may be insufficient. Furthermore, the processability and / or processing dimensional stability of the first pressure-sensitive adhesive composition may be insufficient.

[0064] In one embodiment, the polyfunctional compound can preferably be a compound containing 3 or more photopolymerizable functional groups in one molecule, and more preferably a (meth)acrylate containing 3 or more photopolymerizable functional groups in one molecule. By using a trifunctional or higher photopolymerizable compound, the adhesion retention of the first pressure-sensitive adhesive composition (and as a result, the first pressure-sensitive adhesive layer) can be further enhanced. A bifunctional photopolymerizable compound and a trifunctional or higher photopolymerizable compound may be used in combination. The trifunctional or higher photopolymerizable compound can be preferably used in a proportion of 0.5 to 5 parts by weight, more preferably 1 to 4.5 parts by weight, and even more preferably 2 to 4 parts by weight based on 100 parts by weight of the base polymer.

[0065] In addition to the above-mentioned base polymer, crosslinking agent, and polyfunctional compound, the pressure-sensitive adhesive composition (the first pressure-sensitive adhesive composition) may contain a photopolymerization initiator, a silane coupling agent, and any appropriate additives according to the purpose.

[0066] Examples of the photoinitiator include acylphosphine oxide-based photoinitiators, alkylphenone-based photoinitiators, benzoin ether-based photoinitiators, acetophenone-based photoinitiators, α-ketol-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzoin-based photoinitiators, benzyl-based photoinitiators, benzophenone-based photoinitiators, ketal-based photoinitiators, and thioxanthone-based photoinitiators. Preferably, an acylphosphine oxide-based photoinitiator is used. By using an acylphosphine oxide-based photoinitiator as the photoinitiator, an ultraviolet curable pressure-sensitive adhesive composition excellent in internal curability can be provided even when the thickness of the pressure-sensitive adhesive layer is large due to the photobleaching effect that the absorption disappears after the photoreaction. In addition, since yellowing hardly occurs, a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer excellent in transparency can be provided. The photoinitiator may be used alone or in combination of two or more kinds.

[0067] Examples of acylphosphine oxide-based photoinitiators include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-n-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-t-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)cyclohexylphosphine oxide, bis(2,6-dimethoxybenzoyl)octylphosphine oxide, bis(2-methoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2-methoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dibutoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4-dimethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diisopropylphenylphosphine oxide, bis(2,4,(6-trimethylbenzoyl)-2-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-4-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,3,5,6-tetramethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4,6-trimethylbenzoyl-n-butylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dibutoxyphenylphosphine oxide, 1,10-bis[bis(2,4,6-trimethylbenzoyl)phosphine oxide]decane, tri(2-methylbenzoyl)phosphine oxide and the like can be mentioned.,

[0068] Examples of commercially available acylphosphine oxide-based photoinitiators include Omnirad 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM RESINS B.V.), Omnirad TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, manufactured by IG RESINS B.V.) and the like.,

[0069] The content of the photoinitiator in the first adhesive composition is preferably 0.01 part by weight to 5 parts by weight, more preferably 0.05 part by weight to 3 parts by weight, based on 100 parts by weight of the base polymer.,

[0070] As the silane coupling agent, any suitable silane coupling agent can be used. By using the silane coupling agent, the adhesive strength of the first adhesive composition can be adjusted. The content of the silane coupling agent in the adhesive composition is preferably 0.01 part by weight to 5 parts by weight, more preferably 0.03 part by weight to 2 parts by weight, based on 100 parts by weight of the base polymer.

[0071] As the additive, any suitable additive can be used. Specific examples of the additive include antioxidants, antistatic agents, rework improvers, colorants, pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, conductive agents, inorganic or organic fillers, metal powders, particulate matter, and foils. Also, within a controllable range, a redox system by adding a reducing agent may be adopted. The type, number, combination, blending amount, etc. of the additive can be appropriately set according to the purpose.

[0072] In one embodiment, the first adhesive composition contains an amide group-containing monomer as a monomer component, and an acylphosphine oxide-based photoinitiator is used as the photoinitiator. The first adhesive composition of this embodiment can further improve the adhesion between the cover glass and the polarizing plate. On the other hand, when used in a photochemical laminate including a polarizing plate having a through hole, excessive decolorization may occur at the end of the polarizing plate (especially at the end of the through hole). This excessive decolorization can occur due to a decrease in absorption (absorption by I5 - at high wavelengths), which is different from the decolorization of a normal polarizer. The optical laminate of the embodiment of the present invention uses a cover glass having a transmittance of 7% to 50% at a wavelength of 243 nm as the cover glass. By using it in combination with such a cover glass, end decolorization, particularly excessive decolorization at the end of the through hole of the polarizing plate having a through hole, can be prevented.

[0073] E. The second adhesive layer The second adhesive layer is typically used to bond the optical laminate to other components of an image display device such as a liquid crystal cell. Any suitable adhesive can be used as the adhesive composition for forming the second adhesive layer. Typically, an acrylic adhesive is used. For example, the properties of the adhesive can also be adjusted by adjusting the monomer composition of the base polymer.

[0074] The thickness of the second adhesive layer is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less. The thickness of the second adhesive layer can be, for example, 2 μm or more. If the thickness of the second adhesive layer is within such a range, it can contribute to thinning of the image display device. If the thickness of the second adhesive layer is within such a range, it becomes easier to fill the through-holes with the adhesive composition constituting the first adhesive layer. More specifically, since the depth of the through-holes becomes smaller, it becomes easier to be filled with the adhesive. As a result, the gap in the through-holes can be reduced.

[0075] F. Method for manufacturing an optical laminate The optical laminate according to the embodiment of the present invention is produced by any suitable manufacturing method. For example, a second adhesive composition is applied to one surface of a polarizing plate to form a second adhesive layer, and then a first adhesive composition is applied to the other surface of the polarizing plate to form a first adhesive layer, and then a cover glass is laminated on the polarizing plate via the first adhesive layer to obtain an optical laminate. The first adhesive layer and the second adhesive layer may be formed by transferring an adhesive layer formed on a release liner.

[0076] In one embodiment, the optical laminate has through-holes. In this embodiment, the first adhesive layer can be formed by applying the first adhesive layer and allowing the first adhesive composition to flow into the through-holes. Further, a cover glass on which the adhesive layer constituting the first adhesive layer is transferred may be bonded to the polarizing plate by, for example, vacuum lamination to produce an optical laminate.

[0077] G. Image display device The image display device according to an embodiment of the present invention includes the above optical laminate. In one embodiment, the optical laminate includes a polarizing plate having a through-hole. In one embodiment, this through-hole corresponds to the camera unit of the image display device. As described above, even when the optical laminate according to the embodiment of the present invention has a through-hole, excessive discoloration at the end can be prevented. In the image display device, the camera unit may be provided within the image display unit. According to the image display device of the embodiment of the present invention, even when there is a through-hole within the image display unit, an adverse effect on the display performance of the image display device can be prevented.

Example

[0078] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods for each characteristic in the examples are as follows.

[0079] (1) Thickness For a thickness of 10 μm or less, it was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). For a thickness exceeding 10 μm, it was measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). (2) Transmittance at a wavelength of 243 nm The transmittance at a wavelength of 243 nm of the cover glass used in the examples and comparative examples was measured using a spectrophotometer (manufactured by Hitachi High-Tech Science Corporation, product name: U-4100). The transmittance was measured in the thickness direction of the cover glass. (3) Element measurement of the cover glass The element content of the cover glass used in the examples and comparative examples was measured using an X-ray photoelectron analyzer (ESCA (manufactured by ULVAC, Inc., product name: Quantum 2000)). (4) Excessive discoloration The optical laminates obtained in the examples and comparative examples were placed under the conditions of 60 °C and 90% RH for 240 hours and subjected to a humidity reliability test. Then, for the portion 150 μm from the end of the through-hole of the optical laminate, the orthogonal transmittance at a wavelength of 505 nm and the orthogonal transmittance at a wavelength of 610 nm were measured using a spectrophotometer (manufactured by Hitachi High-Tech Sciences Corporation, product name: U-4100). When there was a decolorized portion where the orthogonal transmittance at a wavelength of 610 nm was greater than the orthogonal transmittance at a wavelength of 505 nm, it was considered that there was excessive decolorization. When there was no decolorized portion where the orthogonal transmittance at a wavelength of 610 nm around the end of the through-hole was greater than the orthogonal transmittance at a wavelength of 505 nm, it was considered that there was no excessive decolorization.

[0080] <Production Example 1: Preparation of the Adhesive Constituting the Second Adhesive Layer> A monomer mixture containing 99 parts by weight of butyl acrylate (BA) and 1 part by weight of 4-hydroxybutyl acrylate (4HBA) was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate with respect to 100 parts by weight of the monomer mixture (solid content), and nitrogen gas was introduced while gently stirring for nitrogen substitution. Then, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55 °C to prepare a solution of an acrylic polymer. With respect to 100 parts by weight of the solid content of the obtained acrylic polymer solution, 0.3 part by weight of benzoyl peroxide (manufactured by NOF Corporation, product name "Niper BMT 40SV") as a crosslinking agent, 0.2 part by weight of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "Takenate D110N"), 0.03 part by weight of a rework improver (manufactured by Kaneka Corporation, product name "Silyl SAT10"), 7 parts by weight of an antistatic agent (manufactured by Mitsubishi Materials Corporation, product name "LiTFSi30EA"), 0.3 part by weight of an antioxidant (manufactured by BASF Japan Ltd., product name "Irganox 1010", hindered phenol type), and 0.2 part by weight of a silane coupling agent (product name: A-100, manufactured by Soken Chemical & Engineering Co., Ltd., an acetylacetonyl group-containing silane coupling agent) were blended to obtain an adhesive composition A.

[0081] <Production Example 2: Production of the Adhesive Sheet B Having the First Adhesive Layer> In a 2 L female flask, 2-ethylhexyl acrylate (2EHA), 2-hydroxyethyl acrylate (HEA), and methacrylamide were added, and the mixture was diluted with a diluting solvent containing methyl ethyl ketone and ethyl acrylate and adjusted so that the total weight became 1110 parts by weight. Each material was added so as to have the composition ratio described in Table 1. The inside of the flask was purged with nitrogen at 0.5 MPa for 40 minutes, and then the azo polymerization initiator 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), which is a thermal initiator, was added. While maintaining the inside of the flask at 65 °C including the heat generated by the chemical reaction, stirring was carried out for two and a half hours. In order to react the remaining monomers, ADVN was further added as a chasing agent, and stirring was carried out at 80 °C for 2 hours. After stirring, the flask was cooled with water and taken out at the timing when the temperature reached 40 °C or lower to obtain a polymer dilution. To 100 parts by weight of the polymer dilution, 0.3 part by weight of a photopolymerization initiator (manufactured by IGM Resins, trade name: Omnirad 819) and 3 parts by weight of trimethylolpropane triacrylate (TMPTA) were added based on 100 parts by weight of the polymer in terms of solid content ratio to prepare an adhesive composition. The adhesive composition was coated on a release liner so that the thickness became 150 μm, and heated at 70 °C for 5 minutes and then at 130 °C for 2 minutes. Two of the same were prepared, and the two adhesive layers were bonded together to obtain an adhesive sheet B having an adhesive layer with a thickness of 200 μm.

[0082] <Production Example 3: Preparation of Adhesive Sheet C Having a First Adhesive Layer> An adhesive sheet C was obtained in the same manner as in Production Example 2 except that the composition ratio of the materials used for the synthesis of the base polymer was the same as that described in Table 1.

Table 1

[0083] <Example 1> 1. Preparation of Polarizer As a thermoplastic resin substrate, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) in a long shape and having a Tg of about 75 °C was used. One side of the resin substrate was subjected to corona treatment. 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Gohsei Chemical Industry Co., Ltd., trade name "Gosefimer Z410") at a ratio of 9:1 was mixed with 13 parts by weight of potassium iodide to prepare a PVA aqueous solution (coating solution). The above PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (lengthwise direction) between rolls with different peripheral speeds in an oven at 130°C (air-assisted stretching treatment). Subsequently, the laminate was immersed in an insolubilization bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment). Subsequently, the laminate was immersed in a dyeing bath at a liquid temperature of 30°C (an aqueous iodine solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer was 43% (dyeing treatment). Subsequently, the laminate was immersed in a crosslinking bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in an aqueous boric acid solution at a liquid temperature of 70°C (boric acid concentration: 4.0% by weight, potassium iodide: 5.0% by weight), uniaxial stretching was performed in the longitudinal direction (lengthwise direction) between rolls with different peripheral speeds so that the total stretching ratio was 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (washing treatment). Thereafter, while drying in an oven maintained at 90°C, the laminate was brought into contact with a SUS heating roll maintained at a surface temperature of 75°C for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminate due to the dry shrinkage treatment was 2%. In this way, a polarizer with a thickness of 5.0 μm was formed on the resin substrate.

[0084] 2. Production of Polarizing Plate An HC-TAC film was laminated on the surface of the polarizer of the resin substrate / first polarizer laminate obtained above via an ultraviolet curable adhesive. The HC-TAC film is a film in which a hard coat (HC) layer (thickness 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness 25 μm), and it was laminated so that the TAC film was on the polarizer side.

[0085] 3. Production of Polarizing Plate with Second Adhesive Layer Next, the resin substrate was peeled off, and a second adhesive layer (thickness 15 μm) was formed on the peeled surface using the adhesive composition A obtained in Production Example 1, to obtain a polarizing plate having a structure of outer protective layer (HC-TAC film) / polarizer / second adhesive layer. This polarizing plate was punched out into a size of 150 mm in length and 70 mm in width, and further, at a position where the distance from the center of the through hole to the short side was 5 mm, a through hole (diameter 3.8 mm) that penetrated integrally from the outer protective layer to the second adhesive layer was formed.

[0086] 4. Production of Optical Laminate A base polymer obtained by polymerizing a monomer composition containing acrylamide and an adhesive sheet A with a thickness of 150 μm formed of an adhesive composition containing a photopolymerization initiator (product name "Lucirin TPO") were obtained. The polarizing plate obtained in 2. above was laminated on one surface of a glass plate (corresponding to an image display cell) via the second adhesive layer. Next, one release liner of the adhesive sheet obtained in Production Example 2 was peeled off and laminated on a cover glass (manufactured by Nippon Electric Glass Co., Ltd., thickness 0.7 mm) with a roll laminator. Next, the other release liner of the adhesive sheet was peeled off, and it was brought into close contact with the outer protective layer side surface of the polarizing plate using a vacuum laminator and the through hole was filled with the adhesive sheet. The conditions for vacuum lamination were as follows: heating pressure bonding at 0.2 MPa and 60 °C (waiting time 90 seconds), and then vacuum lamination at 100 Pa for 10 seconds. Next, from the cover glass side, a metal halide lamp (300 mW / cm 2 ) with an integrated light amount of 3000 mJ / cm 2 ~3500 mJ / cm 2The obtained optical laminate was produced by irradiating ultraviolet rays to cure the pressure-sensitive adhesive sheet (first pressure-sensitive adhesive layer). The obtained optical laminate was subjected to the evaluations (4) to (6) above. The results are shown in Table 2.

[0087] <Examples 2 to 3 and Comparative Examples 1 to 3> An optical laminate was produced in the same manner as in Example 1 except that the cover glass described in Table 1 was used as the cover glass. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 2.

[0088] <Comparative Example 4> An optical laminate was produced in the same manner as in Comparative Example 3 except that the pressure-sensitive adhesive sheet B was used instead of the pressure-sensitive adhesive sheet A. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 2.

[0089] <Reference Example> An optical laminate was produced in the same manner as in Comparative Example 3 except that the pressure-sensitive adhesive sheet C was used instead of the pressure-sensitive adhesive sheet A. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 2.

[0090]

Table 2

[0091] <Evaluation> As is clear from Table 2, according to the examples of the present invention, excessive discoloration could be prevented in the peripheral portion of the through hole. Note that an optical laminate was produced in the same manner as in Comparative Examples 1 to 3 except that ultraviolet rays with an integrated light amount of 3000 mJ / cm 2 to 3500 mJ / cm 2 were not irradiated from the cover glass side with a metal halide lamp (300 mW / cm 2 ). When the produced optical laminate was subjected to the excessive discoloration evaluation, no excessive discoloration occurred. On the other hand, since the first pressure-sensitive adhesive layer was not cured, the cover glass and the polarizing plate could not be sufficiently adhered to each other as compared with the optical laminates obtained in the examples and the comparative examples, and it was difficult to maintain the laminated state, making it difficult to practically use in applications such as image display devices.

Industrial Applicability

[0092] The image display device of the present invention can be suitably used as an image display device having a through hole (for example, a through hole corresponding to a camera unit) typified by a smartphone, a tablet PC, or a smart watch.

Explanation of Reference Numerals

[0093] 10 Polarizing plate 11 Polarizer 12 Protective layer 13 Protective layer 15 Through hole 20 First adhesive layer 30 Cover glass 40 Second adhesive layer 100 Optical laminate 200 Liquid crystal panel

Claims

1. A cover glass having a transmittance of 7% to 50% at a wavelength of 243 nm, A first adhesive layer composed of a first adhesive composition which is an ultraviolet curable adhesive, A polarizing plate including a polarizer and a protective layer laminated on at least one surface of the polarizer, An optical laminate having, in this order, a second adhesive layer composed of a second adhesive composition.

2. The optical laminate according to claim 1, wherein the polarizing plate has a through hole, and the through hole is filled with the first adhesive composition.

3. The optical laminate according to claim 1, wherein the protective layer is laminated only on the surface of the polarizer on the cover glass side.

4. The optical laminate according to claim 1, wherein the first adhesive composition includes a base polymer having an amide skeleton and an acylphosphine oxide-based photopolymerization initiator.

5. The optical laminate according to claim 1, wherein the cover glass contains a metal oxide of an alkaline earth metal.

6. The optical laminate according to claim 5, wherein the content of the metal oxide of the alkaline earth metal in the cover glass is 2% by weight to 12% by weight.

7. The optical laminate according to claim 1, wherein the thickness of the polarizer is 15 μm or less.

8. An image display device having the optical laminate according to any one of claims 1 to 7.

9. An image display device having the optical laminate according to claim 2 and having a camera unit at a position corresponding to the through hole.

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