Foldable polarizer

Abstract

To provide a foldable polarizing plate arranged between an adhesive layer that is laminated adjacent to a window unit and a display module and including a thin-film hard layer, the thickness of which is 5 μm or less, with which breakage or cracking hardly occurs even when repeatedly bent, with the display module side as the center of bent.SOLUTION: Provided is a foldable polarizing plate arranged between an adhesive layer that is laminated adjacent to a window unit and a display module and including a thin-film hard layer, the thickness of which is 5 μm or less. With the thickness of the foldable polarizing plate being assumed to be 100%, the thin-film hard layer exists within only the range of 0% or more and 90% or less in a thickness direction from the outermost surface on the display module side of the foldable polarizing plate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a foldable polarizing plate and an image display device including the same. [Background technology]

[0002] As seen in the market in recent years, foldable smart devices have appeared, and the displays used therein may be required to be flexible. When a display is bent, bending stress and strain are applied to the components that make up the display, so the components that make up the display used in a foldable device need to be designed with materials that are specialized for that purpose. Patent Document 1 proposes a bendable circular polarizing plate that includes a polarizer and a retardation film as a component to be used in a bendable display device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-170221 Summary of the Invention [Problem to be solved by the invention]

[0004] A major challenge when designing polarizers specifically for foldable devices is the breakage and cracking that occurs when the display is bent. It is often difficult to apply polarizer designs for rigid displays to foldable devices as they are. Polarizers are laminated films made up of multiple functional films, and thin, hard layers in particular are prone to cracking when bent. This can cause light leakage from the panel, and cracks in the touch panel or light-emitting layer can make the display impossible.

[0005] The object of the present invention is to provide a foldable polarizing plate that includes a thin-film cured layer having a thickness of 5 μm or less, which is disposed between an adhesive layer laminated adjacent to a window unit and a display module, and which is less likely to break or crack even when repeatedly bent with the display module side as the bending center. Another object of the present invention is to provide a foldable polarizing plate that includes a thin film hardened layer having a thickness of 5 μm or less, in which a linear polarization layer and a retardation layer are laminated, and that is less likely to break or crack even when repeatedly bent with the retardation layer side as the bending center relative to the linear polarization layer. [Means for solving the problem]

[0006] The present invention provides the following foldable polarizing plate and image display device. [1] A foldable polarizing plate disposed between an adhesive layer laminated adjacent to a window unit and a display module, A thin hardened layer having a thickness of 5 μm or less is included, A foldable polarizing plate, wherein the thin film hardened layer is present only in a range of 0% to 90% in the thickness direction from the outermost surface of the foldable polarizing plate on the display module side, when the thickness of the foldable polarizing plate is 100%. [2] The Martens hardness of the thin film hardened layer at 23°C is 150N / mm 2 More than 800N / mm 2 The foldable polarizing plate according to [1], which is as follows: [3] The foldable polarizing plate according to [1] or [2], which has a thickness of 20 μm or more and 150 μm or less. [4] An image display device comprising the foldable polarizing plate according to any one of [1] to [3]. [5] A foldable polarizing plate in which a linear polarizing layer and a retardation layer are laminated, A thin hardened layer having a thickness of 5 μm or less is included, A foldable polarizer, wherein the thin film hardened layer is present only in a range of 0% to 90% in the thickness direction from the outermost surface of the foldable polarizer on the retardation layer side, based on the linear polarizing layer of the foldable polarizer, when the thickness of the foldable polarizer is 100%. [Effects of the Invention]

[0007] According to one aspect of the present invention, a foldable polarizing plate can be provided which includes a thin-film cured layer having a thickness of 5 μm or less, which is disposed between an adhesive layer laminated adjacent to a window unit and a display module, and which is less likely to break or crack even when repeatedly bent with the display module side as the bending center. According to another aspect of the present invention, there can be provided a foldable polarizing plate including a linear polarization layer and a retardation layer stacked together and including a thin film hardened layer having a thickness of 5 μm or less, which is less likely to break or crack even when repeatedly bent with the retardation layer side as the bending center relative to the linear polarization layer. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 10 is a schematic cross-sectional view showing an example of a configuration in which a foldable polarizing plate is arranged. [Figure 2] FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a foldable polarizing plate according to a first embodiment. [Figure 3] FIG. 4 is a schematic cross-sectional view showing another example of the layer structure of the foldable polarizing plate according to the first embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view showing yet another example of the layer structure of the foldable polarizing plate according to the first embodiment. [Figure 5] FIG. 4 is a schematic cross-sectional view showing another example of the layer structure of the foldable polarizing plate according to the first embodiment. [Figure 6] FIG. 10 is a schematic cross-sectional view showing an example of a layer structure of a foldable polarizing plate according to a second embodiment. [Figure 7] FIG. 10 is a schematic cross-sectional view showing another example of the layer structure of the foldable polarizing plate according to the second embodiment. [Figure 8] FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a laminate for a foldable image display device. [Figure 9] FIG. 2 is a schematic diagram for explaining a method for evaluating flex resistance. [Figure 10] FIG. 2 is a schematic diagram for explaining a method for measuring Martens hardness. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all of the drawings, the scales of the components are appropriately adjusted to make them easier to understand, and the scales of the components shown in the drawings do not necessarily match the scales of the actual components.

[0010] <Foldable polarizing plate> [First aspect] The foldable polarizer of the first embodiment includes a thin-film cured layer having a thickness of 5 μm or less, which is arranged between an adhesive layer laminated adjacent to a window unit and a display module, and the thin-film cured layer is present only in a range of 0% to 90% in the thickness direction from the outermost surface of the foldable polarizer on the display module side, when the thickness of the foldable polarizer is 100%.

[0011] The foldable polarizing plate 1 shown in FIG. 1 is disposed between an adhesive layer 3 laminated adjacent to a window unit 2 and a display module 4. Preferably, one surface of the foldable polarizing plate 1 is disposed in direct contact with the adhesive layer 3 laminated adjacent to the window unit 2, and the other surface is disposed in direct contact with the display module 4. The window unit 2 can be, for example, a front panel. The display module 4 can be, for example, a touch sensor panel or an image display element. The adhesive layer 3 can be one exemplified as an attachment layer, which will be described later.

[0012] In this specification, "foldable" refers to a foldable polarizer that can be bent along a bending axis, where the bending axis is the direction of the transmission axis of the linear polarizing layer in the foldable polarizer. The foldable polarizer 1 can be bent with the display module side facing inward. Bending includes a folding form in which a curved surface is formed at the bent portion. In the folding form, the bending radius of the inner surface of the fold is not particularly limited. Bending also includes a bending form in which the refraction angle of the inner surface is greater than 0° and less than 180°, and a folding form in which the refraction angle of the inner surface is close to zero or is 0°.

[0013] In this specification, the term "crack" refers to a crack observed in the thin film cured layer when the foldable polarizing plate is observed in a plan view using transmitted light through an optical microscope, and the term "crack" refers to a crack that has been caused by a crack in the thin film cured layer and continues to a layer other than the thin film cured layer. The crack and the crack can be observed according to the method described in the Examples section below.

[0014] When the foldable polarizing plate 1 is repeatedly bent along the bending axis with the display module surface facing inward so that the bending radius of the inner surface is 1.5 mm, cracks do not occur even after the number of bending cycles is preferably 50,000, and more preferably 80,000.

[0015] The foldable polarizing plate may be in a long or sheet-like shape. The foldable polarizing plate is preferably in a sheet-like shape. A sheet-like foldable polarizing plate can be obtained by cutting a long foldable polarizing plate. When the foldable polarizing plate is in a sheet-like shape, the planar shape of the foldable polarizing plate may be, for example, a square shape, preferably a square shape having long sides and short sides, more preferably a rectangle. When the planar shape of the foldable polarizing plate is rectangular, the length of the long side may be, for example, 10 mm or more and 1400 mm or less, preferably 50 mm or more and 600 mm or less. The length of the short side is, for example, 5 mm or more and 800 mm or less, preferably 30 mm or more and 500 mm or less, more preferably 50 mm or more and 300 mm or less. In this specification, planar view means viewing from the thickness direction of the layer.

[0016] When the foldable polarizing plate has a rectangular shape in plan view, the lengths of the sides of the layers constituting the foldable polarizing plate may be the same. The corners of the layers constituting the foldable polarizing plate may be rounded, or the edges may be notched or perforated.

[0017] The thickness of the foldable polarizer may be, for example, 20 μm or more and 150 μm or less, and preferably 25 μm or more and 130 μm or less. The thickness of the foldable polarizer is the thickness when the foldable polarizer is disposed between the adhesive layer laminated adjacent to the window unit and the display module. The foldable polarizer has an adhesive layer (described later) on the outermost surface on the display module side for bonding with the display module, and when the foldable polarizer has the adhesive layer when disposed between the adhesive layer laminated adjacent to the window unit and the display module, the thickness of the foldable polarizer includes the thickness of the adhesive layer. Even if the foldable polarizer has a separator film or a protective film before being disposed between the adhesive layer laminated adjacent to the window unit and the display module, when the foldable polarizer does not have the separator film or protective film when disposed between the adhesive layer laminated adjacent to the window unit and the display module, the thickness of the foldable polarizer does not include the thickness of the separator film or protective film.

[0018] The foldable polarizing plate can be used in an image display device. The image display device may be any type, such as a liquid crystal display device or an organic EL display device. The foldable polarizing plate can be disposed on the front side (viewing side) of the image display device, or on the back side. The foldable polarizing plate of the present invention is bendable, and is therefore suitable for a foldable image display device.

[0019] When the image display device is a liquid crystal display device, the foldable polarizer may be disposed as a polarizer including a polarizer disposed on the front side of the front or rear side of a liquid crystal cell. When the image display device is an organic electroluminescence (EL) display device, the foldable polarizer may be disposed on the front side as a circular polarizer disposed on the front side for the purpose of preventing reflection of external light.

[0020] When the foldable polarizing plate is a circular polarizing plate, the foldable polarizing plate can have anti-reflection properties. In an image display device, by providing a foldable polarizing plate having anti-reflection properties on the front side of the image display device, it is possible to suppress deterioration of visibility due to reflection of external light.

[0021] [Thin film hardened layer] Although not shown, the foldable polarizing plate 1 includes a thin-film cured layer having a thickness of 5 μm or less. The thin-film cured layer can be a layer containing a cured product of a curable resin. Examples of the thin-film cured layer include a cured resin layer formed on a polarizer protective layer that is a thermoplastic resin film, a coating protective layer, an adhesive layer for bonding the linear polarizing layer and the polarizer protective layer, a liquid crystal cured layer included in the retardation layer, and an adhesive layer for bonding the retardation layers together, all of which have a thickness of 5 μm or less. If the thickness of the thin-film cured layer exceeds 5 μm, the thin-film cured layer tends to be prone to breakage or cracks. Layers other than the thin-film cured layer will be described later.

[0022] The thickness of the thin film cured layer is preferably 4.5 μm or less, more preferably 4 μm or less. The thickness of the thin film cured layer 100 is usually 0.5 μm or more.

[0023] When the thickness of the foldable polarizing plate 1 is taken as 100%, the thin-film hardened layer is present only in a range T1 that is 0% to 90% in the thickness direction from the outermost surface of the foldable polarizing plate 1 on the display module 4 side. By having the thin-film hardened layer present only in the range T1, even when the foldable polarizing plate 1 is repeatedly bent with the display module 4 side facing inward, breakage or cracks tend to be less likely to occur.

[0024] When the thickness of the foldable polarizer 1 is taken as 100%, the thin film cured layer is preferably present only in a range of 0% to 90% in the thickness direction from the outermost surface of the foldable polarizer 1 on the display module 4 side, more preferably only in a range of 0% to 75%, and even more preferably only in a range of 0% to 60%.

[0025] The Martens hardness of the thin film hardened layer at a temperature of 23°C (hereinafter, for simplicity, simply referred to as Martens hardness) is, for example, 150 N / mm 2 More than 800N / mm 2 When the Martens hardness of the thin film hardened layer is within the above range, cracks tend to be less likely to occur. The Martens hardness can be measured according to the method described in the Examples section below.

[0026] The Martens hardness of the thin film hardened layer is preferably 150 N / mm 2 More than 700N / mm 2 Less than or equal to 150N / mm 2 More than 600N / mm 2 The following is the result.

[0027] The Martens hardness of the thin-film cured layer can be adjusted, for example, by adjusting the composition of the thin-film cured layer-forming composition used to form the thin-film cured layer. Examples of methods for adjusting the composition of the thin-film cured layer-forming composition include a method of adjusting the type and / or content of polymerizable monomers and additives that constitute the curable resin. Alternatively, a commercially available product having a predetermined Martens hardness can be selected and used.

[0028] The foldable polarizer may function as a linear polarizer including a polarizer protection layer and a linear polarizing layer, or as a circular polarizer including a linear polarizer and a retardation layer. The foldable polarizer 10 shown in FIG. 2 includes, in this order, a polarizer protection layer 100, a cured resin layer 101, an adhesive layer 102, a linear polarizing layer 103, a bonding layer 104, and a retardation layer 105 including a liquid crystal cured layer (not shown). The foldable polarizer 10 may further include layers other than the layers described above. Examples of such layers include a protective film and an adhesive layer.

[0029] [Polarizer protection layer] The polarizer protection layer 100 is a layer for protecting the linear polarizing layer 103, particularly the surface of the linear polarizing layer 103. The polarizer protection layer 100 can be disposed on one or both sides of the linear polarizing layer 103, either directly or via an adhesive layer alone. In this specification, the linear polarizing layer 103 on which the polarizer protection layer 100 is disposed may be referred to as a linear polarizing plate.

[0030] The polarizer protective layer 100 may be formed of, for example, a thermoplastic resin film or a coating protective layer. The foldable polarizer 10 may have the polarizer protective layer 100 on only one side of the linear polarizing layer 103, or may have the polarizer protective layer 100 on both sides. When the foldable polarizer 10 has polarizer protective layers on both sides of the linear polarizing layer 103, the polarizer protective layers 100 may be of the same type or different types. When the polarizer protective layer 100 is a thermoplastic resin film, the polarizer protective layer 100 may be attached to the linear polarizing layer 103 via an adhesive layer described below. When the polarizer protective layer 100 is a thermoplastic resin film, the polarizer protective layer 100 may include a cured resin layer 101 described below. The foldable polarizer 10 preferably includes a thermoplastic resin film.

[0031] [Thermoplastic resin film] A thermoplastic resin film that can be used as the polarizer protection layer 100 can be incorporated into the foldable polarizer 10 in a form in which it is attached to one or both sides of the linear polarizing layer 103 . The thermoplastic resin film may be, for example, a light-transmitting, preferably optically transparent, thermoplastic resin film. Examples include polyolefin resins such as linear polyolefin resins (polyethylene resins, polypropylene resins, polymethylpentene resins, etc.) and cyclic polyolefin resins (norbornene resins, etc.); cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate resins; ethylene-vinyl acetate resins; polystyrene resins; polyamide resins; polyetherimide resins; (meth)acrylic resins such as polymethyl (meth)acrylate resins; polyimide resins; polyethersulfone resins; polysulfone resins; polyvinyl chloride resins; polyvinylidene chloride resins; polyvinyl alcohol resins; polyvinyl acetal resins; polyether ketone resins; polyether ether ketone resins; polyethersulfone resins; polyamideimide resins, etc. The thermoplastic resins may be used alone or in combination. Among these, triacetyl cellulose-based resin films, cyclic polyolefin-based resin films, and (meth)acrylic-based resin films are preferred from the viewpoint of strength and light transmittance.

[0032] The thickness of the thermoplastic resin film may be, for example, 30 μm or less, preferably 25 μm or less from the viewpoint of thinning, and is usually 1 μm or more, preferably 5 μm or more, and more preferably 15 μm or more. The thermoplastic resin film may or may not have a retardation.

[0033] [Cured resin layer] The cured resin layer 101 is a layer containing a cured product of a curable resin. The cured resin layer 101 may be a layer having functions such as a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, an antifouling layer, or a conductive layer.

[0034] Examples of the curable resin include thermosetting resins and active energy ray-curable resins. A cured product of the curable resin can be formed from a cured resin layer-forming composition containing the curable resin. The cured resin layer-forming composition may be, for example, a thermosetting composition, a cationically curable composition, or a radically curable composition. The cured resin layer-forming composition may contain, for example, a polymerizable monomer, a polymerization initiator, an additive, a solvent, etc. Examples of the additive include a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a surfactant, etc.

[0035] When the cured resin layer 101 is a hard coat layer, it can easily improve the hardness and scratch resistance of the linear polarizing layer 103 or the polarizer protective layer 100. When the thermoplastic resin film has the cured resin layer 101 that is a hard coat layer, for example, a hard coat layer-forming composition is applied to the thermoplastic resin film that forms the polarizer protective layer 100, and cured to form a cured product of the hard coat layer-forming composition, thereby producing a thermoplastic resin film having a hard coat layer, which can then be attached to the linear polarizing layer 103 via the adhesive layer 102. A commercially available thermoplastic resin film having a cured resin layer can also be used as the polarizer protective layer 100.

[0036] The hard coat layer can be formed from a cured product of a hard coat layer-forming composition containing an active energy ray-curable resin. Examples of active energy ray-curable resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coat layer may contain an additive to improve strength. The additive is not limited, and examples include inorganic fine particles, organic fine particles, and mixtures thereof. The hard coat layer preferably contains an ultraviolet absorber.

[0037] The thickness of the cured resin layer 101 may be, for example, 5 μm or less, and is preferably 4 μm or less. The thickness of the thin cured layer 100 is usually 0.5 μm or more.

[0038] [Adhesive layer] The adhesive layer 102 used to bond the linearly polarizing layer 103 to the polarizer protective layer 100 (or the cured resin layer 101), which is a thermoplastic resin film, can be formed from an active energy ray-curable adhesive such as an ultraviolet-curable adhesive, an aqueous solution of a polyvinyl alcohol-based resin or an aqueous solution containing a crosslinking agent, or a water-based adhesive such as a urethane-based emulsion adhesive. When thermoplastic resin films are bonded to both sides of the linearly polarizing layer 103, the adhesives forming the two adhesive layers may be the same or different. For example, when thermoplastic resin films are bonded to both sides, one side may be bonded using an aqueous adhesive and the other side may be bonded using an active energy ray-curable adhesive. The ultraviolet-curable adhesive can be a mixture of a radically polymerizable (meth)acrylic compound and a photoradical polymerization initiator, or a mixture of a cationically polymerizable epoxy compound and a photocationic polymerization initiator. Alternatively, a cationically polymerizable epoxy compound and a radically polymerizable (meth)acrylic compound can be used in combination, and a photocationic polymerization initiator and a photoradical polymerization initiator can be used in combination as initiators. The thickness of the adhesive layer may be, for example, 0.1 μm or more and 5 μm or less.

[0039] When an active energy ray-curable adhesive is used, the adhesive is cured by irradiating it with active energy rays after lamination. The light source of the active energy rays is not particularly limited, but active energy rays (ultraviolet rays) having an emission distribution of wavelengths of 400 nm or less are preferred, and specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, etc. are preferably used.

[0040] In order to improve the adhesion between the linear polarization layer 103 and the polarizer protection layer 100 (or the cured resin layer 101), which is a thermoplastic resin film, one or both of the bonding surfaces may be subjected to a surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation treatment, primer coating treatment, or saponification treatment.

[0041] [Protective coating layer] The protective coating layer may be formed by applying and curing, for example, a cationically curable composition such as an epoxy resin or a radically curable composition such as a (meth)acrylate, or by applying and drying an aqueous solution of a polyvinyl alcohol-based resin or the like, and may contain, as necessary, a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, etc.

[0042] When the polarizer protective layer 100 is a coating protective layer, the thickness of the polarizer protective layer 100 may be, for example, 0.1 μm or more and 30 μm or less, and from the viewpoint of thinning, is preferably 0.5 μm or more and 20 μm or less, and more preferably 1 μm or more and 10 μm or less.

[0043] [Linear polarizing layer] The linear polarizing layer 103 can be a linear polarizer that absorbs linearly polarized light with a vibration plane parallel to its absorption axis and transmits linearly polarized light with a vibration plane perpendicular to the absorption axis (parallel to the transmission axis). Examples of the linear polarizing layer include a stretched film or stretched layer to which a dichroic dye is adsorbed. Specific examples of the dichroic dye include iodine and dichroic organic dyes. Examples of dichroic organic dyes include dichroic direct dyes made of disazo compounds such as CIDIRECT RED 39, and dichroic direct dyes made of compounds such as trisazo and tetrakisazo.

[0044] A linear polarizing layer that is a stretched film (hereinafter sometimes abbreviated as "stretched film") having a dichroic dye adsorbed thereon will be described. A stretched film having a dichroic dye adsorbed thereon can usually be produced by a process of uniaxially stretching a polyvinyl alcohol-based resin film, a process of dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye, a process of treating the polyvinyl alcohol-based resin film having the dichroic dye adsorbed thereon with a boric acid aqueous solution, and a process of washing with water after the treatment with the boric acid aqueous solution. The thickness of the linear polarizing layer that is a stretched film having a dichroic dye adsorbed thereon may be, for example, 2 μm or more and 40 μm or less.

[0045] Polyvinyl alcohol resins are obtained by saponifying polyvinyl acetate resins. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

[0046] The saponification degree of the polyvinyl alcohol resin is usually 85 mol% or more and 100 mol% or less, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The polymerization degree of the polyvinyl alcohol resin is usually 1,000 or more and 10,000 or less, preferably 1,500 or more and 5,000 or less.

[0047] Such a polyvinyl alcohol-based resin is formed into a film and used as a raw film for a stretched film. The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and the film can be formed by a known method. The thickness of the polyvinyl alcohol-based raw film may be, for example, 10 μm or more and 150 μm or less.

[0048] The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before or during the boric acid treatment. It is also possible to perform uniaxial stretching in these multiple stages. The uniaxial stretching may be performed uniaxially between rolls with different peripheral speeds, or may be performed uniaxially using a heated roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which the polyvinyl alcohol-based resin film is stretched in a swollen state using a solvent. The stretching ratio is usually about 3 to 8 times.

[0049] Dyeing of a polyvinyl alcohol-based resin film with a dichroic dye is carried out, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. Specific examples of the dichroic dye include iodine and dichroic organic dyes. Examples of dichroic organic dyes include dichroic direct dyes made of disazo compounds such as CIDIRECT RED 39, and dichroic direct dyes made of compounds such as trisazo and tetrakisazo. It is preferable to immerse the polyvinyl alcohol-based resin film in water before dyeing.

[0050] When iodine is used as the dichroic dye, a dyeing method is usually employed in which a polyvinyl alcohol resin film is immersed in an aqueous solution containing iodine and potassium iodide. The iodine content in this aqueous solution is usually 0.01 to 1 part by mass per 100 parts by mass of water. The potassium iodide content is usually 0.5 to 20 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is usually 20 to 40°C. The immersion time in this aqueous solution (dyeing time) is usually 20 to 1,800 seconds.

[0051] On the other hand, when a dichroic organic dye is used as the dichroic pigment, a method of dyeing a polyvinyl alcohol resin film by immersing it in an aqueous solution containing a water-soluble dichroic dye is usually adopted. The content of the dichroic organic dye in this aqueous solution is usually 1 × 10 per 100 parts by mass of water. -4 parts by mass or more and 10 parts by mass or less, preferably 1×10 -3 parts by mass or more and 1 part by mass or less, and more preferably 1×10 -3 Mass part or more 1×10 -2 The dichroic dye solution is usually at least 20°C and not more than 80°C. The immersion time in the solution (dyeing time) is usually at least 10 seconds and not more than 1,800 seconds.

[0052] The boric acid treatment after dyeing with a dichroic dye can usually be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid aqueous solution. The content of boric acid in this boric acid aqueous solution is usually 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic dye, the boric acid aqueous solution preferably contains potassium iodide. In this case, the content of potassium iodide is usually 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the boric acid aqueous solution is usually 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature for the boric acid treatment is usually 50°C or higher, preferably 50 to 85°C, and more preferably 60 to 80°C.

[0053] The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The washing can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water used in the washing is usually 5°C or higher and 40°C or lower. The immersion time is usually 1 second or higher and 120 seconds or lower.

[0054] After washing with water, the film is dried to obtain a stretched film having a dichroic dye adsorbed thereon. The drying process can be carried out using, for example, a hot air dryer or a far-infrared heater. The drying temperature is typically 30°C to 100°C, preferably 50°C to 80°C. The drying time is typically 60 to 600 seconds, preferably 120 to 600 seconds. The drying process reduces the moisture content of the stretched film having a dichroic dye adsorbed thereon to a practical level. The moisture content is typically 5 to 20% by mass, preferably 8 to 15% by mass. If the moisture content is less than 5% by mass, the stretched film having a dichroic dye adsorbed thereon loses its flexibility, and the stretched film having a dichroic dye adsorbed thereon may be damaged or broken after drying. If the moisture content exceeds 20% by mass, the thermal stability of the stretched film having a dichroic dye adsorbed thereon may be impaired.

[0055] Next, a linear polarizing layer that is a stretched layer having a dichroic dye adsorbed thereon (hereinafter, sometimes simply referred to as a "stretched layer") will be described. The stretched layer having a dichroic dye adsorbed thereon can usually be produced by a process of applying a coating liquid containing the polyvinyl alcohol-based resin to a substrate to obtain a laminated film, a process of uniaxially stretching the obtained laminated film, a process of dyeing the polyvinyl alcohol-based resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb it, a process of treating the film having the dichroic dye adsorbed thereon with a boric acid aqueous solution, and a process of washing with water after the treatment with the boric acid aqueous solution. Examples of the substrate include those exemplified in the description of the polarizer protective layer described below. The substrate may be peeled off from the stretched layer, and the substrate may serve as the polarizer protective layer. The thickness of the substrate may be, for example, 5 μm or more and 200 μm or less. When the substrate is incorporated into a foldable polarizing plate 10, the thickness of the substrate film is preferably 30 μm or less.

[0056] [Lamination layer] The bonding layer 104 for bonding the linear polarizing layer 103 and the retardation layer 105 together can usually be an adhesive layer made of a pressure-sensitive adhesive (hereinafter also referred to as an adhesive).

[0057] The thickness of the pressure-sensitive adhesive layer may be, for example, in the range of 1 μm to 50 μm, preferably 2 μm to 45 μm, more preferably 3 μm to 30 μm, and even more preferably 5 μm to 20 μm.

[0058] The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition whose main component is a resin such as a (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin. Among these, a pressure-sensitive adhesive composition whose base polymer is a (meth)acrylic resin is preferred from the viewpoints of transparency, weather resistance, heat resistance, and storage modulus. The pressure-sensitive adhesive composition may be an active energy ray-curable or heat-curable type.

[0059] The (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition is preferably a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, or an epoxy group, such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0060] The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Among these, polyisocyanate compounds are preferred.

[0061] The adhesive layer can be formed, for example, by dissolving or dispersing an adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, which is then directly applied to the target surface of the foldable polarizing plate to form an adhesive layer, or by forming an adhesive layer in sheet form on a release-treated separate film, which is then transferred to the target surface of the linear polarizing layer 103 or the retardation layer 105.

[0062] The separate film may be a film made of a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate, etc. Among these, a stretched film of polyethylene terephthalate is preferred.

[0063] The pressure-sensitive adhesive layer may contain optional components such as glass fibers, glass beads, resin beads, fillers made of metal powder or other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, and the like.

[0064] Examples of the antistatic agent include ionic compounds, conductive fine particles, and conductive polymers, with ionic compounds being preferred. The cationic component constituting the ionic compound may be an inorganic cation or an organic cation. Examples of organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations, phosphonium cations, piperidinium cations, and pyrrolidinium cations, and examples of inorganic cations include lithium ions and potassium ions. On the other hand, the anion component constituting the ionic compound may be either an inorganic anion or an organic anion, but an anion component containing a fluorine atom is preferred because it provides an ionic compound with excellent antistatic properties. As an anion component containing a fluorine atom, a hexafluorophosphate anion [(PF6 - )], bis(trifluoromethanesulfonyl)imide anion [(CF3SO2)2N - ] anion, bis(fluorosulfonyl)imide anion [(FSO2)2N - ] anions and the like.

[0065] [Phase difference layer] The retardation layer 105 can be disposed on the bending axis side when the foldable polarizing plate 10 is bent toward the display module side. The retardation layer 105 can be laminated on the linear polarizing layer 103 via an attachment layer 104. The retardation layer 105 can be a positive A layer such as a λ / 4 layer or a λ / 2 layer, or a positive C layer. The retardation layer 103 may be formed from a liquid crystal cured layer, or may be formed from a resin film exemplified as the material for the thermoplastic resin film described above. When the retardation layer 103 includes a liquid crystal cured layer, the retardation layer 103 may further include an adhesive layer, an alignment layer, and a substrate, which will be described later.

[0066] The retardation layer 105 preferably includes a λ / 4 layer, and more preferably includes a λ / 4 layer and at least one of a λ / 2 layer and a positive C layer. When the retardation layer 105 includes a λ / 2 layer, the λ / 2 layer and the λ / 4 layer can be laminated in this order from the linear polarizing layer 103 side. When the retardation layer 105 includes a positive C layer, the λ / 4 layer and the positive C layer may be laminated in this order from the linear polarizing layer 103 side, or the positive C layer and the λ / 4 layer may be laminated in this order from the linear polarizing layer 103 side.

[0067] The thickness of the retardation layer 105 may be, for example, 0.1 μm or more and 50 μm or less, preferably 1 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 15 μm or less.

[0068] The liquid crystal cured layer is a layer of a cured product formed by polymerizing a polymerizable liquid crystal compound. The liquid crystal cured layer may be formed by polymerizing polymerizable liquid crystal compounds with each other in a liquid crystal-oriented state. The polymerizable liquid crystal compounds may be oriented in-plane or vertically. When the polymerizable liquid crystal compounds are oriented in-plane, the liquid crystal cured layer becomes a positive A layer exhibiting in-plane retardation. When the polymerizable liquid crystal compounds are oriented vertically, the liquid crystal cured layer becomes a positive C layer exhibiting retardation in the thickness direction. The polymerizable liquid crystal compound is a compound that has a polymerizable group and can be in a liquid crystal state. The polymerizable groups of the polymerizable liquid crystal compound react with each other to polymerize the polymerizable liquid crystal compound, thereby hardening the polymerizable liquid crystal compound.

[0069] The retardation layer 105 may have one, two, or three or more liquid crystal cured layers. When the retardation layer 105 has two or more liquid crystal cured layers, the liquid crystal cured layers are usually laminated to each other via an adhesive layer. In addition to the liquid crystal cured layers and the adhesive layer that laminates them to each other, the retardation layer 105 may also include a substrate and / or an alignment layer for aligning the polymerizable liquid crystal compound when forming the liquid crystal cured layer. When the retardation layer 105 has a substrate, the substrate is usually removed when the retardation layer 105 is attached to the linear polarization layer 103.

[0070] Examples of adhesives used in the adhesive layer include active energy ray-curable adhesives such as ultraviolet-curable adhesives, aqueous solutions of polyvinyl alcohol resins or aqueous solutions containing crosslinking agents, and water-based adhesives such as urethane emulsion adhesives. When the retardation layer includes two or more adhesive layers, the adhesives may be the same or different. The thickness of the adhesive layer may be, for example, 0.1 μm or more and 5 μm or less.

[0071] The type of polymerizable liquid crystal compound is not particularly limited, but can be classified into rod-shaped (rod-shaped liquid crystal compounds) and discotic (discotic liquid crystal compounds) types based on their shape. Each type can further be divided into low-molecular-weight and high-molecular-weight types. Polymer generally refers to a compound with a degree of polymerization of 100 or more (see "Polymer Physics: Phase Transition Dynamics," by Masao Doi, p. 2, Iwanami Shoten, 1992). Any of the polymerizable liquid crystal compounds can be used in the present invention. Furthermore, two or more rod-shaped liquid crystal compounds, two or more discotic liquid crystal compounds, or a mixture of a rod-shaped liquid crystal compound and a discotic liquid crystal compound may also be used. For example, the rod-shaped liquid crystal compound described in claim 1 of JP-A-11-513019 can be suitably used. As the discotic liquid crystal compound, for example, those described in paragraphs

[0020] to

[0067] of JP-A No. 2007-108732 or paragraphs

[0013] to

[0108] of JP-A No. 2010-244038 can be suitably used.

[0072] Two or more types of polymerizable liquid crystal compounds may be used in combination. In this case, at least one type has two or more polymerizable groups in the molecule. That is, the layer formed by curing the polymerizable liquid crystal compound is preferably a layer formed by fixing a liquid crystal compound having a polymerizable group by polymerization. In this case, after forming the layer, it is no longer necessary for the compound to exhibit liquid crystallinity.

[0073] The polymerizable liquid crystal compound has a polymerizable group capable of undergoing a polymerization reaction. Examples of the polymerizable group include functional groups capable of undergoing an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a ring-polymerizable group. More specifically, examples of the polymerizable group include a (meth)acryloyl group, a vinyl group, a styryl group, and an allyl group. Among these, a (meth)acryloyl group is preferred. The term "(meth)acryloyl group" encompasses both a methacryloyl group and an acryloyl group.

[0074] The liquid crystallinity of the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, and when thermotropic liquid crystal is classified by the degree of order, it may be either nematic liquid crystal or smectic liquid crystal.

[0075] The liquid crystal cured layer can be formed, for example, by coating a composition containing a polymerizable liquid crystal compound (hereinafter also referred to as a retardation layer-forming composition) on an alignment layer and irradiating it with active energy rays. The retardation layer-forming composition may contain components other than the polymerizable liquid crystal compound. For example, the retardation layer-forming composition preferably contains a polymerization initiator. The polymerization initiator used may be, for example, a thermal polymerization initiator or a photopolymerization initiator, selected depending on the type of polymerization reaction. Examples of photopolymerization initiators include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, and combinations of triarylimidazole dimers and p-aminophenyl ketones. The amount of polymerization initiator used is preferably 0.01% by mass to 20% by mass, more preferably 0.5% by mass to 5% by mass, based on the total solids content of the coating liquid. The term "cured product" refers to a state in which the formed layer can exist independently without deformation or flow.

[0076] In addition, the retardation layer-forming composition may contain a polymerizable monomer in terms of the uniformity of the coating film and the strength of the film. Examples of the polymerizable monomer include radically polymerizable or cationic polymerizable compounds. Among them, polyfunctional radically polymerizable monomers are preferred.

[0077] The polymerizable monomer is preferably one that can be copolymerized with the polymerizable liquid crystal compound described above. The amount of the polymerizable monomer used is preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 30% by mass or less, based on the total mass of the polymerizable liquid crystal compound.

[0078] In addition, the retardation layer-forming composition may contain a surfactant in terms of the uniformity of the coating film and the strength of the film. Examples of the surfactant include conventionally known compounds. Among them, fluorine-based compounds are particularly preferred.

[0079] The retardation layer-forming composition may contain a solvent, and an organic solvent is preferably used. Examples of the organic solvent include amides (e.g., N,N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), alkyl halides (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane). Among these, alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

[0080] The retardation layer-forming composition may also contain various alignment agents, such as a vertical alignment promoter such as a polarizer interface-side vertical alignment agent or an air interface-side vertical alignment agent, and a horizontal alignment promoter such as a polarizer interface-side horizontal alignment agent or an air interface-side horizontal alignment agent. Furthermore, the retardation layer-forming composition may also contain an adhesion improver, a plasticizer, a polymer, etc., in addition to the above components.

[0081] The active energy rays include ultraviolet rays, visible light, electron beams, and X-rays, and are preferably ultraviolet rays. Examples of light sources for the active energy rays include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, halogen lamps, carbon arc lamps, tungsten lamps, gallium lamps, excimer lasers, LED light sources emitting light in the wavelength range of 380 to 440 nm, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

[0082] The irradiation intensity of ultraviolet light is usually 100 mW / cm for ultraviolet B waves (wavelength range 280 nm to 310 nm). 2 More than 3,000mW / cm 2The ultraviolet irradiation intensity is preferably an intensity in a wavelength region effective for activating a cationic polymerization initiator or a radical polymerization initiator. The ultraviolet irradiation time is usually from 0.1 seconds to 10 minutes, preferably from 0.1 seconds to 5 minutes, more preferably from 0.1 seconds to 3 minutes, and even more preferably from 0.1 seconds to 1 minute.

[0083] Ultraviolet light can be irradiated in one or more steps. The cumulative light dose at a wavelength of 365 nm is 700 mJ / cm2, depending on the polymerization initiator used. 2 It is preferable that the dose is 1,100 mJ / cm or more. 2 More preferably, it is 1,300 mJ / cm or more. 2 It is more preferable that the cumulative light amount is 2,000 mJ / cm or more. The above cumulative light amount is advantageous for increasing the polymerization rate of the polymerizable liquid crystal compound constituting the liquid crystal cured layer and improving heat resistance. The cumulative light amount at a wavelength of 365 nm is 2,000 mJ / cm. 2 It is preferable that the dose is 1,800 mJ / cm or less. 2 It is more preferable that the integrated light amount is set to the above value. If the integrated light amount is set to the above value, there is a risk that the cured liquid crystal layer will be colored.

[0084] The thickness of the cured liquid crystal layer is, for example, 0.5 μm or more and 5 μm or less. When the thickness of the cured liquid crystal layer is within the above range, sufficient durability can be obtained and it can contribute to the thinning of the foldable polarizing plate 10. The thickness of the cured liquid crystal layer can be adjusted so as to obtain the desired in-plane retardation value and thickness direction retardation value of the λ / 4 layer, λ / 2 layer, or positive C layer.

[0085] The retardation layer 105 may include a laminate of a plurality of retardation layers each having different retardation properties. Each retardation layer may be laminated using an adhesive, or a composition containing a polymerizable liquid crystal compound may be applied to the surface of an already formed retardation layer and then cured.

[0086] [Base material] The layer containing the cured product of the polymerizable liquid crystal compound can be formed, for example, on an alignment layer provided on a substrate. The substrate has the function of supporting the alignment layer and may be a substrate formed in a long length. This substrate functions as a releasable support and can support the liquid crystal cured layer and alignment layer for transfer. Furthermore, it is preferable that the surface of the substrate has sufficient adhesive strength to allow peeling. Examples of the substrate include a light-transmitting, preferably optically transparent, thermoplastic resin film. Examples of the thermoplastic resin film include those exemplified in the description of the polarizer protective layer above.

[0087] The substrate may be subjected to various anti-blocking treatments. Examples of anti-blocking treatments include an easy-adhesion treatment, a treatment for kneading a filler or the like, and an embossing (knurling) treatment. By subjecting the substrate to such anti-blocking treatments, it is possible to effectively prevent the substrates from sticking to each other when wound up, i.e., so-called blocking, and this tends to facilitate improvement in productivity.

[0088] [Alignment layer] The layer containing the cured product of the polymerizable liquid crystal compound is formed on the substrate via an alignment layer. That is, the substrate and the alignment layer are laminated in this order, and the layer containing the cured product of the polymerizable liquid crystal compound is laminated on the alignment layer.

[0089] The alignment layer is not limited to a vertical alignment layer, but may be an alignment layer that horizontally aligns the molecular axis of the polymerizable liquid crystal compound, or an alignment layer that tilts the molecular axis of the polymerizable liquid crystal compound. The alignment layer preferably has solvent resistance that prevents the polymerizable liquid crystal compound-containing composition from dissolving when applied, as described below, and heat resistance during heat treatment for removing the solvent or orienting the liquid crystal compound. Examples of alignment layers include alignment layers containing an orienting polymer, photo-alignment films, and groove alignment layers that form a concavo-convex pattern or multiple grooves on the surface to achieve alignment. The thickness of the alignment layer is typically in the range of 10 nm to 10,000 nm.

[0090] The alignment layer has a function of supporting the cured liquid crystal layer and may function as a releasable support. The alignment layer may be capable of supporting the cured liquid crystal layer for transfer and may have adhesive strength sufficient to allow its surface to be peeled off.

[0091] The resin used for the alignment layer is a resin obtained by polymerizing a polymerizable compound. The polymerizable compound is a compound having a polymerizable group, and is usually a non-liquid crystal polymerizable non-liquid crystal compound that does not become liquid crystal. The polymerizable groups of the polymerizable compound react with each other to polymerize the polymerizable compound, thereby forming a resin. Such a resin is used as an alignment layer for aligning a polymerizable liquid crystal compound during the formation of the liquid crystal cured layer, and is not particularly limited as long as it is a resin used as a material for a known alignment layer, as long as it is not contained in the liquid crystal cured layer. For example, a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth)acrylate monomer in the presence of a polymerization initiator can be used. Specific examples of (meth)acrylate monomers include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, urethane acrylate, etc. The resin may be one of these or a mixture of two or more of them. After the retardation layer is formed, the alignment layer can be peeled off and removed together with the substrate before or after the step of laminating the retardation layer with a linear polarizing layer or the like.

[0092] In addition, an alignment layer can be included in the cured liquid crystal layer for the purpose of improving peelability from the substrate and imparting film strength to the cured liquid crystal layer. When the cured liquid crystal layer includes an alignment layer, it is preferable to use a cured product obtained by curing a monofunctional or bifunctional (meth)acrylate monomer, imide monomer, or vinyl ether monomer as the resin used for the alignment layer. Examples of the monofunctional (meth)acrylate monomer include alkyl (meth)acrylates having 4 to 16 carbon atoms, β-carboxyalkyl (meth)acrylates having 2 to 14 carbon atoms, alkylated phenyl (meth)acrylates having 2 to 14 carbon atoms, methoxypolyethylene glycol (meth)acrylates, phenoxypolyethylene glycol (meth)acrylates, and isobornyl (meth)acrylates. Examples of bifunctional (meth)acrylate monomers include 1,3-butanediol di(meth)acrylate; 1,3-butanediol (meth)acrylate; 1,6-hexanediol di(meth)acrylate; ethylene glycol di(meth)acrylate; diethylene glycol di(meth)acrylate; neopentyl glycol di(meth)acrylate; triethylene glycol di(meth)acrylate; tetraethylene glycol di(meth)acrylate; polyethylene glycol diacrylate; bis(acryloyloxyethyl)ether of bisphenol A; ethoxylated bisphenol A di(meth)acrylate; propoxylated neopentyl glycol di(meth)acrylate; ethoxylated neopentyl glycol di(meth)acrylate, and 3-methylpentanediol di(meth)acrylate. Examples of imide resins obtained by curing imide monomers include polyamides and polyimides. The imide resin may be one of these, or a mixture of two or more of these. Furthermore, the resin forming the alignment layer may contain monomers other than monofunctional or bifunctional (meth)acrylate monomers, imide monomers, and vinyl ether monomers, and the content of monofunctional or bifunctional (meth)acrylate monomers, imide monomers, and vinyl ether monomers may be 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more, of the total monomers.

[0093] When an alignment layer is included in the retardation layer 105, the thickness of the alignment layer is usually in the range of 10 nm to 10,000 nm, and when the alignment of the retardation layer 105 is in-plane with respect to the film surface, the thickness of the alignment layer is preferably 10 nm to 1,000 nm, and when the alignment of the retardation layer 105 is perpendicular to the film surface, the thickness of the alignment layer is preferably 100 nm to 10,000 nm. When the thickness of the alignment layer is within the above range, it is possible to improve the peelability of the substrate and impart appropriate film strength.

[0094] [Other layers] The foldable polarizing plate 10 may further include at least one of an adhesive layer and a protective film, for example.

[0095] [Adhesive layer] The foldable polarizing plate 10 may have an adhesive layer disposed on the outermost surface on the retardation layer 105 side. The adhesive layer may be a layer for bonding a display module such as a touch sensor panel or an image display element to the foldable polarizing plate 10. The adhesive layer may generally be composed of an adhesive. As the adhesive, any conventionally known adhesive may be used without particular limitation, and adhesives having a base polymer such as an acrylic polymer, a urethane polymer, a silicone polymer, or a polyvinyl ether polymer may be used. In addition, active energy ray-curable adhesives, thermosetting adhesives, etc. may also be used.

[0096] [Protection film] The foldable polarizing plate 10 can include a protective film for protecting its surface, typically the surface of the cured resin layer 100. The protective film can be disposed on the outermost surface of the foldable polarizing plate 10. After the polarizing plate is attached to, for example, an image display element or other optical components, the protective film is peeled off and removed together with its adhesive layer.

[0097] The protective film is composed of, for example, a base film and a pressure-sensitive adhesive layer laminated thereon. The above description of the laminating layer applies to the pressure-sensitive adhesive layer. The resin constituting the base film can be, for example, a thermoplastic resin such as a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate-based resin. A polyester-based resin such as polyethylene terephthalate is preferred.

[0098] The thickness of the protective film is not particularly limited, but is preferably in the range of 20 μm to 200 μm, for example. When the thickness of the substrate is 20 μm or more, strength tends to be easily imparted to the foldable polarizing plate 10.

[0099] [Layer structure of foldable polarizer] Fig. 3 is a schematic cross-sectional view showing another example of the layer structure of a foldable polarizer. The foldable polarizer 20 shown in Fig. 3 includes, in this order, a polarizer protection layer 100, a cured resin layer 101, a first adhesive layer 102, a linear polarizer layer 103, an attachment layer 104, and a retardation layer 160. The retardation layer 160 includes a first liquid crystal cured layer 161, a second adhesive layer 162, and a second liquid crystal cured layer 163. At least one of the cured resin layer 101, the first adhesive layer 102, the first liquid crystal cured layer 161, the second adhesive layer 162, and the second liquid crystal cured layer 163 can be a thin film cured layer.

[0100] Fig. 4 is a schematic cross-sectional view showing yet another example of the layer structure of a foldable polarizer. The foldable polarizer 30 shown in Fig. 4 includes, in this order, a protection film 180, a polarizer protection layer 100, a cured resin layer 101, a first adhesive layer 102, a linear polarization layer 103, an attachment layer 104, and a retardation layer 160. The retardation layer 160 includes a first liquid crystal cured layer 161, a second adhesive layer 162, and a second liquid crystal cured layer 163. At least one of the cured resin layer 101, the first adhesive layer 102, the first liquid crystal cured layer 161, the second adhesive layer 162, and the second liquid crystal cured layer 163 can be a thin film cured layer.

[0101] Fig. 5 is a schematic cross-sectional view showing another example of the layer structure of a foldable polarizer. The foldable polarizer 40 shown in Fig. 5 includes, in this order, a polarizer protection layer 100, a cured resin layer 101, a first adhesive layer 102, a linear polarizer layer 103, an attachment layer 104, a retardation layer 160, and a pressure-sensitive adhesive layer 170. The retardation layer 160 includes a first liquid crystal cured layer 161, a second adhesive layer 162, and a second liquid crystal cured layer 163. At least one of the cured resin layer 101, the first adhesive layer 102, the first liquid crystal cured layer 161, the second adhesive layer 162, and the second liquid crystal cured layer 163 can be a thin film cured layer.

[0102] [Second aspect] The foldable polarizer according to the second embodiment is a foldable polarizer in which a linear polarizing layer and a retardation layer are laminated, and the thin-film rigid layer has a thickness of 5 μm or less, and the thin-film rigid layer is present only in a range of 0% to 90% in the thickness direction from the outermost surface on the retardation layer side of the linear polarizing layer of the foldable polarizer, when the thickness of the foldable polarizer is taken as 100%. The explanations for the shape, dimensions, thickness and uses of the foldable polarizer are the same as those for the first embodiment.

[0103] 6 includes a linear polarizing layer 6 and a retardation layer 7. The linear polarizing layer 6 and the retardation layer 7 are explained in the first embodiment.

[0104] The foldable polarizing plate 5 can be bent with the retardation layer 7 side facing inward relative to the linear polarizing layer 6. When the foldable polarizing plate 5 is repeatedly bent along the bending axis with the retardation layer 7 side facing inward relative to the linear polarizing layer 6 so that the bending radius of the inner surface is 1.5 mm, cracks do not occur even after the number of bendings is preferably 50,000 times, and more preferably 80,000 times.

[0105] [Thin film hardened layer] Although not shown in Fig. 6, the foldable polarizing plate 5 includes a thin-film cured layer having a thickness of 5 µm or less. The thin-film cured layer can be a layer containing a cured product of a curable resin. Examples and preferred ranges of the type, thickness, and Martens hardness of the thin-film cured layer are the same as those described in the first embodiment.

[0106] When the thickness of the foldable polarizer 5 is taken as 100%, the thin-film hardened layer is present only in a range T2 of 0% to 90% in the thickness direction from the outermost surface on the retardation layer 7 side with the linear polarization layer 6 of the foldable polarizer 5 as the reference. By the thin-film hardened layer being present only in the range T2, even when the foldable polarizer 5 is repeatedly bent with the retardation layer 7 side on the inside with the linear polarization layer 6 as the reference, breakage or cracks tend to be less likely to occur.

[0107] When the thickness of the foldable polarizer 5 is taken as 100%, the thin film cured layer is present preferably only in a range of 0% to 90% in the thickness direction from the outermost surface on the retardation layer 7 side of the linear polarizer layer 6 of the foldable polarizer 5, more preferably only in a range of 0% to 75%, and even more preferably only in a range of 0% to 60%.

[0108] Fig. 7 is a schematic cross-sectional view showing an example of the layer structure of a foldable polarizer according to the second embodiment of the present invention. The foldable polarizer 50 shown in Fig. 7 includes, in this order, a polarizer protection layer 200, a cured resin layer 201, an adhesive layer 202, a linear polarization layer 203, an attachment layer 204, and a retardation layer 205 including a liquid crystal cured layer (not shown). At least one of the cured resin layer 201, the adhesive layer 202, and the liquid crystal cured layer can be a thin film cured layer.

[0109] The foldable polarizing plate 50 may further include layers other than the above-described layers. Examples of such layers include a protective film, an adhesive layer, etc. The explanations for the first embodiment above apply to the polarizer protective layer 200, the cured resin layer 201, the adhesive layer 202, the linear polarizing layer 203, the bonding layer 204, the retardation layer 205, the protective film, and the adhesive layer in the second embodiment.

[0110] [Method of manufacturing foldable polarizing plates] When the foldable polarizing plate includes a polarizer protective layer and a retardation layer and includes a cured resin layer as the thin-film cured layer, the foldable polarizing plate can be manufactured by a method including a lamination step in which, for example, a polarizer protective layer, which is a thermoplastic resin film including a cured resin layer, and a linear polarizing layer are laminated via an adhesive layer, and then a retardation layer is laminated via an adhesive layer on the side opposite to the thin-film cured layer side of the linear polarizing layer. In the lamination step, when the layers are laminated via an adhesive layer, it is preferable to perform a surface activation treatment such as corona treatment on one or both of the lamination surfaces in order to improve adhesion. The cured resin layer, the linear polarizing layer, and the retardation layer can each be manufactured as described above.

[0111] The adhesive layer can be prepared as an adhesive sheet. The adhesive sheet can be produced by, for example, dissolving or dispersing an adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an adhesive solution, forming a layer of the adhesive into a sheet on a release film that has been subjected to a release treatment, and then laminating another release film on the adhesive layer. The layers can be laminated by a method in which the adhesive sheet from which one release film has been peeled is laminated to one layer, and then the other release film is peeled off and the other layer is laminated.

[0112] The adhesive liquid can be applied to the release film by a conventional coating technique using a die coater, comma coater, reverse roll coater, gravure coater, rod coater, wire bar coater, doctor blade coater, air doctor coater, or the like.

[0113] The release film is preferably composed of a plastic film and a release layer. Examples of the plastic film include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film, and polyolefin films such as polypropylene film. The release layer can be formed, for example, from a release layer-forming composition. The main component (resin) constituting the release layer-forming composition is not particularly limited, but examples include silicone resin, alkyd resin, acrylic resin, and long-chain alkyl resin.

[0114] <Image display device> The foldable polarizing plate of the present invention can be used in an image display device. An image display device is a device having an image display panel, and includes a light-emitting element or a light-emitting device as a light source. Examples of image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, inorganic electroluminescence (EL) display devices, and touch panel display devices. The foldable polarizing plate can be disposed on the viewing side of the image display panel. The foldable polarizing plate can be laminated on the image display device via, for example, an adhesive layer. The image display device can be a foldable image display device.

[0115] <Laminate for foldable image display device> The laminate for a foldable image display device may include a front panel on the viewing side of a foldable polarizing plate and a touch panel (described later) on the opposite side of the foldable polarizing plate from the front panel. The foldable image display device includes a laminate for a foldable image display device and an organic EL display panel, with the laminate for a foldable image display device disposed on the viewing side of the organic EL display panel and configured to be foldable. The laminate for a foldable image display device may include a foldable polarizing plate and either or both of a front panel and a touch panel. While the stacking order is arbitrary, the stacking order from the viewing side is preferably the front panel (window), foldable polarizing plate, touch panel, or front panel, touch panel, foldable polarizing plate. The presence of a foldable polarizing plate on the viewing side of the touch panel is preferable because it obscures the pattern on the touch panel and improves the visibility of the displayed image. Each component can be stacked using an adhesive or pressure-sensitive adhesive. Furthermore, a light-shielding pattern may be formed on at least one surface of any of the front panel, foldable polarizing plate, and touch panel.

[0116] [Front plate] A front panel may be disposed on the viewing side of the foldable polarizing plate. The front panel can be laminated to the foldable polarizing plate via an adhesive layer. Examples of the adhesive layer include the adhesive layer described above.

[0117] Examples of the front panel include glass and resin films with a hard coat layer on at least one side. Examples of glass that can be used include highly transparent glass and tempered glass. When using a particularly thin transparent surface material, chemically tempered glass is preferred. The thickness of the glass can be, for example, 20 μm or more and 5 mm or less.

[0118] A front panel comprising a hard coat layer on at least one surface of a resin film can be foldable, rather than rigid like conventional glass. The thickness of the hard coat layer is not particularly limited and may be, for example, 5 μm or more and 100 μm or less.

[0119] Resin films may be films formed from polymers such as cycloolefin derivatives having units of a monomer containing a cycloolefin such as norbornene or a polycyclic norbornene monomer, cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl ester cellulose, propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose), ethylene-vinyl acetate copolymers, polycycloolefins, polyesters, polystyrenes, polyamides, polyetherimides, polyacrylics, polyimides, polyamideimides, polyethersulfones, polysulfones, polyethylenes, polypropylenes, polymethylpentenes, polyvinyl chlorides, polyvinylidene chlorides, polyvinyl alcohols, polyvinyl acetals, polyetherketones, polyetheretherketones, polyethersulfones, polymethyl methacrylates, polyethylene terephthalates, polybutylene terephthalates, polyethylene naphthalates, polycarbonates, polyurethanes, and epoxy. Resin films may be unstretched, uniaxially, or biaxially stretched. These polymers may be used alone or in combination. Preferred resin films include polyamideimide or polyimide films, which are excellent in transparency and heat resistance, uniaxially or biaxially stretched polyester films, cycloolefin derivative films, polymethyl methacrylate films, and triacetyl cellulose and isobutyl ester cellulose films, which are excellent in transparency and heat resistance and can accommodate large film sizes. The thickness of the resin film may be 5 μm or more and 200 μm or less, preferably 20 μm or more and 100 μm or less.

[0120] [Shading pattern] The light-shielding pattern (bezel) can be formed on the display element side of the front panel. The light-shielding pattern can hide the wiring of the display device so that it is not visible to the user. The color and / or material of the light-shielding pattern are not particularly limited, and the pattern can be formed of a resin material having various colors such as black, white, gold, etc. In one embodiment, the thickness of the light-shielding pattern can be 2 μm to 50 μm, preferably 4 μm to 30 μm, and more preferably 6 μm to 15 μm. Furthermore, the light-shielding pattern can be shaped to prevent air bubbles from entering and the boundary from being visible due to a step between the light-shielding pattern and the display unit.

[0121] [Touch panel] Touch panels are used as input devices. Various types of touch sensors have been proposed for touch panels, including resistive, surface acoustic wave, infrared, electromagnetic induction, and capacitive touch sensors, and any of these may be used. Among these, capacitive touch sensors are preferred. A capacitive touch sensor is divided into an active area and an inactive area located outside the active area. The active area corresponds to the area where a screen is displayed (display area) on a display panel and senses a user's touch. The inactive area corresponds to the area where no screen is displayed (non-display area) on a display device. The touch panel may include a foldable substrate; a sensing pattern formed in the active area of the substrate; and sensing lines formed in the inactive area of the substrate for connecting to an external driving circuit via the sensing pattern and pad area. The foldable substrate may be made of the same material as the transparent substrate of the front panel.

[0122] The layer structure of a laminate for a foldable image display device will be described with reference to Fig. 8. A laminate for a foldable image display device 60 shown in Fig. 8 includes a foldable polarizing plate 40, a front plate 121 on the viewing side of the foldable polarizing plate 40 via an adhesive layer 122, and a touch panel 123 on the opposite side of the foldable polarizing plate 40 from the viewing side via an adhesive layer 170. The foldable polarizing plate 40 includes a polarizer protection layer 100, a cured resin layer 101, a first adhesive layer 102, a linear polarizing layer 103, an attachment layer 104, a retardation layer 160, and an adhesive layer 170, in this order. The retardation layer 160 includes a first liquid crystal cured layer 161, a second adhesive layer 162, and a second liquid crystal cured layer 163. At least one of the cured resin layer 101, the first adhesive layer 102, the first liquid crystal cured layer 161, the second adhesive layer 162, and the second liquid crystal cured layer 163 can be a thin film cured layer. [Example]

[0123] The present invention will be described in more detail below with reference to examples. In the examples, "%" and "parts" are by mass % and mass parts unless otherwise specified.

[0124] Layer Thickness The measurement was carried out using a contact type film thickness measuring device (Nikon Corporation "MH-15M").

[0125] [Bending resistance] The method for evaluating flex resistance is described below with reference to FIG. 9. The fabricated foldable polarizing plate was cut using a super cutter into a size of 10 mm short side x 100 mm long side, with the long side aligned with the absorption axis direction of the linear polarizer, to prepare test specimen 300. The short sides of test specimen 300 (or the test specimen from which the TAC film was removed when a TAC film was disposed on the retardation layer side) were fixed so that the surface facing the linear polarizer was in contact with two plate jigs 301 and 302 of a flex resistance tester (FIG. 9a). Kapton film tape (manufactured by DuPont Toray) 303 was used for fixing, and both ends of the test specimen were fixed 10 mm apart along the long side, with the distance L1 between the two plate jigs 301 and 302 being 53 mm. Next, when the bending radius of the test piece was set to R = 1.5 mm, the two plate jigs 301 and 302 were moved in the directions indicated by arrows A1 and A2, respectively, to continuously change the distance L2 between the jigs to 2R, and the fixed test piece was bent so that the absorption axis direction of the linear polarizer was perpendicular to the bending axis (Figure 9b). The bending speed was 60 rpm, and the number of flexions until cracks or breakage occurred in the film was measured.

[0126] [Martens hardness] The Martens hardness was measured using an ultra-microhardness tester (FISCHERSCOPE HM2000, manufactured by Fischer Instruments Inc.). As shown in Fig. 10, a single film 401 of each layer (the liquid crystal cured layer had no supporting layer) was electrostatically attached to soda glass 402, and the Martens hardness of each layer was measured at a temperature of 23°C. A Vickers indenter 403 was used to measure the indentation depth in the direction of arrow A3 at 0.2 µm, and the Martens hardness was calculated as the average value of n = 3 for each member by indentation measurement in accordance with ISO14577.

[0127] Example 1 A triacetyl cellulose (TAC) film and an acrylic resin film were attached to both sides of a linear polarizer (PVA, thickness 8 μm) in which iodine was adsorbed and aligned on a polyvinyl alcohol resin film, using water, and then dried to produce a double release paper PVA with a layer structure of TAC film / PVA / acrylic resin film. The acrylic resin film side of both release papers PVA was peeled off, and a UV absorber-containing hard coat (HC) layer (thickness 3 μm, Martens hardness 266.843 N / mm) was applied as a polarizer protective film. 2 The hard coat layer side of a cyclic olefin resin (COP) film (thickness 22 μm) having a water-based adhesive layer (thickness 0.1 μm, Martens hardness 522.611 N / mm 2 The laminated surfaces were subjected to corona treatment (780W x 1 pass).

[0128] Next, the TAC film of the resulting linear polarizer having a layer structure of COP film / UV absorber-containing HC layer / adhesive layer / PVA / TAC film was peeled off, and the PVA surface was subjected to corona treatment, and a pressure-sensitive adhesive layer (thickness 5 μm) with a separate film attached was attached thereto. A λ / 2 plate (thickness 2 μm, Martens hardness 239.038 N / mm) made by applying a polymerizable liquid crystal compound to a TAC film and curing it. 2 ) and λ / 4 plate (thickness 1 μm, Martens hardness 214.012 N / mm 2 ) and the liquid crystal surfaces of the LCD panel are connected by a UV-curable adhesive layer (thickness 2 μm, Martens hardness 175.665 N / mm 2 ) was bonded to prepare a retardation layer laminate.

[0129] The separate film of the adhesive layer attached to the linear polarizer was peeled off, and the TAC film on the λ / 2 plate side of the retardation layer laminate was peeled off. Then, corona treatment was performed on only the liquid crystal surface, and the adhesive layer was attached. A foldable polarizer (thickness excluding the TAC film: 43.1 μm) with a layer structure of COP film / UV absorber-containing HC layer / adhesive layer / PVA / adhesive layer / λ / 2 plate / adhesive layer / λ / 4 plate / TAC film was obtained. The evaluation results of bending resistance are shown in Table 1. In the obtained foldable polarizer, the hard coat layer, adhesive layer made of a water-based adhesive, λ / 2 plate, adhesive layer made of a UV-curable adhesive, and λ / 4 plate are thin-film cured layers, and the TAC film side is the display module side.

[0130] <Example 2> In Example 1, a UV absorber-containing hard coat (HC) layer (thickness: 3 μm, Martens hardness: 266.843 N / mm 2 ) was used instead of a hard coat (HC) layer (no UV absorber, thickness 2 μm, Martens hardness 280.775 N / mm 2 A foldable polarizing plate (thickness excluding the TAC film: 42.1 μm) having a layer structure of COP film / HC layer / adhesive layer / PVA / pressure-sensitive adhesive layer / λ / 2 plate / adhesive layer / λ / 4 plate / TAC film was obtained in the same manner as in Example 1, except that the 100% COP film was used. The results are shown in Table 1.

[0131] Example 3 In Example 1, a UV absorber-containing hard coat (HC) layer (thickness: 3 μm, Martens hardness: 266.843 N / mm 2 ) was used instead of a hard coat (HC) layer (no UV absorber, thickness 2 μm, Martens hardness 280.775 N / mm 2 A foldable polarizing plate (thickness 57.1 μm including adhesive layer) having a layer structure of COP film / HC layer / adhesive layer / PVA / adhesive layer / λ / 2 plate / adhesive layer / λ / 4 plate / adhesive layer was obtained in the same manner as in Example 1, except that a 15 μm adhesive layer (thickness 15 μm including adhesive layer) was used, and the TAC film was peeled off from the foldable polarizing plate and an adhesive layer (thickness 15 μm) was attached to the surface of the λ / 4 plate side. The results are shown in Table 1.

[0132] <Comparative Example 1> A foldable polarizing plate having a layer structure of UV absorber-containing hard coat (HC) layer / COP film / adhesive layer / PVA / pressure-sensitive adhesive layer / λ / 2 plate / adhesive layer / λ / 4 plate / TAC film was obtained in the same manner as in Example 1, except that PVA was attached via an adhesive layer to the COP film side of the polarizer protective film instead of the UV absorber-containing hard coat (HC) layer side of the polarizer protective film in Example 1. The results are shown in Table 1.

[0133] <Comparative Example 2> A foldable polarizing plate having a layer structure of HC layer / COP film / adhesive layer / PVA / pressure-sensitive adhesive layer / λ / 2 plate / adhesive layer / λ / 4 plate / TAC film was obtained in the same manner as in Example 1, except that PVA was attached via an adhesive layer to the COP film side of the polarizer protective film instead of the hard coat (HC) layer side of the polarizer protective film in Example 2. The results are shown in Table 1.

[0134] <Comparative Example 3> A foldable polarizing plate having a layer structure of HC layer / COP film / adhesive layer / PVA / pressure-sensitive adhesive layer / λ / 2 plate / adhesive layer / λ / 4 plate / adhesive layer was obtained in the same manner as in Example 1, except that PVA was attached via an adhesive layer to the COP film side of the polarizer protective film instead of the hard coat (HC) layer side of the polarizer protective film in Example 3. The results are shown in Table 1.

[0135] [Table 1] [Explanation of symbols]

[0136] 1,5,10,20,30,40,50 Foldable polarizer, 2 Window unit, 3,122 Adhesive layer, 4 Display module, 100,200 Polarizer protection layer, 101,201 Cured resin layer, 102,202 First adhesive layer, 6,103,203 Linear polarizing layer, 104,204 Bonding layer, 7,105,160,205 Retardation layer, 121 Front panel, 123 Touch panel, 161 First liquid crystal cured layer, 162 Second adhesive layer, 163 Second liquid crystal cured layer, 170 Adhesive layer, 180 Protective film, 300 Test piece, 301,302 Plate jig, 303 Kapton film tape, 401 Single film, 402 Soda glass, 403 Vickers indenter, L1, L2 Distance between jigs, T1, T2 range

Claims

1. A foldable polarizing plate having a polarizer protective layer, a thin film hardened layer having a thickness of 5 μm or less, a linear polarizing layer, and a retardation layer laminated in this order, the thin film cured layer is a layer containing a cured product of a curable resin, The Martens hardness of the thin hardened layer at 23°C is 150 N / mm ２ More than 800N / mm ２ is as follows: When the thickness of the foldable polarizer is 100%, the thin film rigid layer is present only in a range of 0% to 90% in the thickness direction from the outermost surface of the foldable polarizer on the retardation layer side, based on the linear polarizing layer; The retardation layer is a liquid crystal cured layer.

2. The foldable polarizing plate according to claim 1 , having a thickness of 20 μm or more and 150 μm or less.

3. The foldable polarizing plate according to claim 1 , which is bendable with the retardation layer side facing inward relative to the linear polarizing layer.

4. An image display device comprising the foldable polarizing plate according to any one of claims 1 to 3.

Images