Circular polarizer

Abstract

To provide a circularly polarizing plate that exhibits sufficient antistatic performance, and that hardly causes deterioration in polarization characteristics under a moist heat environment and hardly causes corrosion of a metal electrode or the like provided in an image display element, and to provide an image display device including the circularly polarizing plate.SOLUTION: Provided are: a circularly polarizing plate comprising a linear polarizing plate, a first adhesive layer, a retardation layer structure comprising at least one retardation layer, and a second adhesive layer having a thickness of less than 150 μm in this order, where the linear polarizing plate comprises a linear polarizer which is a liquid crystal cured layer, the retardation layer is a liquid crystal cured layer, the first adhesive layer contains an antistatic agent, the second adhesive layer does not substantially contain an antistatic agent, and a content of the antistatic agent in the second adhesive layer measured after the circularly polarizing plate is stored under an environment of a temperature of 85°C and a relative humidity of 85% RH for 250 hours is 0.2% by mass or less in 100% by mass of the second adhesive layer; and an image display device including the circularly polarizing plate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a circular polarizing plate, and also to an image display device. [Background technology]

[0002] Patent Document 1 describes a laminate having a light-absorbing anisotropic film containing a dichroic dye and a predetermined transparent resin layer containing particles, wherein the transparent resin layer may have an adhesive layer containing an antistatic agent on the side opposite to the light-absorbing anisotropic film, and may further have a λ / 4 plate on the side opposite to the transparent resin layer of the adhesive layer. The same document also describes that by having a transparent resin layer, it is possible to suppress the decrease in optical performance due to the decrease in the degree of orientation of the dichroic substance when exposed to high temperatures and during the passage of moist heat. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2019 / 131949 [Overview of the project] [Problems that the invention aims to solve]

[0004] The use of antistatic agents in circular polarizers suppresses the generation of static electricity. Suppression of static electricity generation is desirable for image display elements. However, as described in Patent Document 1, antistatic agents can cause a decrease in the optical properties of linear polarizers in humid and hot environments. Furthermore, when circular polarizers are laminated on an image display element, antistatic agents may cause corrosion of metal electrodes and other components of the image display element.

[0005] The object of the present invention is to provide a circular polarizing plate that exhibits sufficient antistatic performance, is less prone to deterioration of polarization characteristics in a humid and hot environment, and is less likely to cause corrosion of metal electrodes and other components of an image display element, as well as an image display device including the circular polarizing plate.

Means for Solving the Problem

[0006] The present invention provides the following circular polarizing plate and image display device. [1] A circular polarizing plate including a linear polarizing plate, a first adhesive layer, a retardation layer structure including at least one retardation layer, and a second adhesive layer having a thickness of less than 150 μm in this order, wherein the linear polarizing plate includes a linear polarizer which is a liquid crystal cured layer, the retardation layer is a liquid crystal cured layer, the first adhesive layer contains an antistatic agent, and the second adhesive layer substantially does not contain an antistatic agent, the content of the antistatic agent in the second adhesive layer measured after storing the circular polarizing plate in an environment of a temperature of 85° C. and a relative humidity of 85% RH for 250 hours is 0.2% by mass or less in 100% by mass of the second adhesive layer, the circular polarizing plate. [2] The circular polarizing plate according to [1], wherein the total thickness of the first adhesive layer and the second adhesive layer is 150 μm or less. [3] The surface resistance value of the first adhesive layer at a temperature of 25° C. is 1.0×10 11 Ω / □ or less, the circular polarizing plate according to [1] or [2]. [4] The circular polarizing plate according to any one of [1] to [3], wherein the antistatic agent is an ionic compound. [5] The circular polarizing plate according to any one of [1] to [4], wherein the linear polarizer is a liquid crystal cured layer containing a cured product of a polymerizable liquid crystal compound and one or more dichroic dyes. [6] An image display device including the circular polarizing plate according to any one of [1] to [5].

Advantages of the Invention

[0007] A circular polarizing plate showing sufficient antistatic performance, in which the polarization characteristics are less likely to deteriorate in a humid heat environment, and a circular polarizing plate less likely to cause corrosion of a metal electrode or the like provided in an image display element, and an image display device including the circular polarizing plate can be provided.

Brief Description of the Drawings

[0008] [Figure 1] This is a schematic cross-sectional view showing an example of a circular polarizing plate according to the present invention. [Figure 2] This is a schematic cross-sectional view showing another example of a circular polarizing plate according to the present invention. [Figure 3] This is a schematic cross-sectional view showing yet another example of a circular polarizing plate according to the present invention. [Figure 4] This is a schematic cross-sectional view showing yet another example of a circular polarizing plate according to the present invention. [Figure 5] This is a schematic cross-sectional view showing an example of an image display device according to the present invention. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. All drawings below are provided to aid in understanding the present invention, and the size and shape of each component shown in the drawings do not necessarily correspond to the size and shape of the actual components.

[0010] <Circular polarizer> Figure 1 is a schematic cross-sectional view showing an example of a circular polarizer according to the present invention (hereinafter also simply referred to as "circular polarizer"). The circular polarizer according to the present invention comprises a linear polarizer 1, a first adhesive layer 10, a phase difference layer structure 2, and a second adhesive layer 20 in this order. The linear polarizer 1 and the first adhesive layer 10 are normally in contact, the first adhesive layer 10 and the phase difference layer structure 2 are normally in contact, and the phase difference layer structure 2 and the second adhesive layer 20 are normally in contact. Note that the term "circular polarizer" includes elliptic polarizers.

[0011] The circular polarizer according to the present invention is typically placed on the viewing side of the image display element. By arranging the circular polarizer in this way, it is possible to suppress internal reflected light that is emitted to the outside when ambient light incident on the image display element is reflected by metal electrodes or the like inside the element. In other words, the circular polarizer is suitable as an anti-reflective coating. The second adhesive layer 20 can be used for bonding with the image display element.

[0012] The first adhesive layer 10, which is placed between the linear polarizing plate 1 and the phase difference layer structure 2, contains an antistatic agent. On the other hand, the second adhesive layer 20, which is placed on the opposite side of the phase difference layer structure 2 from the first adhesive layer 10, does not substantially contain an antistatic agent.

[0013] According to the circular polarizer of the present invention, since the first adhesive layer 10 contains an antistatic agent, the generation of static electricity can be suppressed. Furthermore, with this circular polarizer, since the first adhesive layer 10, which is placed between the linear polarizer 1 and the phase difference layer structure 2, contains an antistatic agent, and the second adhesive layer 20 does not substantially contain an antistatic agent, compared to the case in which the second adhesive layer 20 substantially contains an antistatic agent, corrosion such as galvanic corrosion caused by contact between dissimilar metals, such as galvanic corrosion, is less likely to occur in metal electrodes and the like of image display elements in a humid and hot environment.

[0014] The following provides a more detailed explanation of circular polarizers. (1) Linear polarizing plate The linear polarizer plate 1 is equipped with a linear polarizer which is a liquid crystal cured layer. The linear polarizer has the function of selectively transmitting linearly polarized light in a certain direction from unpolarized light rays such as natural light. Examples of linear polarizers which are liquid crystal cured layers include cured products of polymerizable liquid crystal compounds and liquid crystal cured layers containing one or more dichroic dyes. Compared to linear polarizers which are polyvinyl alcohol films with iodine adsorbed and oriented, linear polarizers which are liquid crystal cured layers are less susceptible to the degradation of polarization characteristics of linear polarizers caused by antistatic agents in humid and hot environments.

[0015] The polymerizable liquid crystal compound used to form the linear polarizer, which is a liquid crystal curing layer, is a compound that has a polymerizable reactive group and exhibits liquid crystal properties. The polymerizable reactive group is a group that participates in the polymerization reaction, and is preferably a photopolymerizable reactive group. A photopolymerizable reactive group is a group that can participate in the polymerization reaction by active radicals or acids generated from a photopolymerization initiator. Examples of photopolymerizable reactive groups include vinyl groups, vinyloxy groups, 1-chlorovinyl groups, isopropenyl groups, 4-vinylphenyl groups, acryloyloxy groups, methacryloyloxy groups, oxyranyl groups, and oxetanyl groups. Among these, acryloyloxy groups, methacryloyloxy groups, vinyloxy groups, oxyranyl groups, and oxetanyl groups are preferred, and acryloyloxy groups are more preferred. The type of polymerizable liquid crystal compound is not particularly limited, and rod-shaped liquid crystal compounds, disc-shaped liquid crystal compounds, and mixtures thereof can be used. The liquid crystalline properties of polymerizable liquid crystal compounds can be either thermotropic or lyotropic, and when thermotropic liquid crystals are classified by their degree of order, they can be either nematic or smectic.

[0016] In the liquid crystal cured layer, the dichroic dye is dispersed and oriented within the cured polymerizable liquid crystal compound. The dichroic dye used in the linear polarizer, which is the liquid crystal cured layer, is preferably one having an absorption maximum wavelength in the range of 300 nm to 700 nm. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes, with azo dyes being preferred. Examples of azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stilbenazo dyes, with bisazo dyes and trisazo dyes being preferred. The dichroic dye may be used alone or in combination of two or more, with a combination of three or more being preferred. In particular, a combination of three or more azo dyes is more preferable. Some of the dichroic dyes may have reactive groups and may also be liquid crystalline.

[0017] A linear polarizer, which is a liquid crystal cured layer, can be formed, for example, by applying a linear polarizer-forming composition containing a polymerizable liquid crystal compound and a dichroic dye onto an alignment film formed on a substrate layer, and then polymerizing and curing the polymerizable liquid crystal compound. The thickness of the alignment film is, for example, 5 nm to 1 μm. Alternatively, a linear polarizer may be formed by applying the linear polarizer-forming composition onto a substrate layer to form a coating film, and then stretching this coating film together with the substrate layer. The substrate layer used to form the linear polarizer may be incorporated into a circular polarizer.

[0018] Examples of the base layer include thermoplastic resin films. Examples of thermoplastic resins constituting the thermoplastic resin film include cellulose resins such as triacetylcellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; polyamide resins such as nylon and aromatic polyamides; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; cyclic polyolefin resins having cyclo and norbornene structures (also called norbornene resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; and polyvinyl alcohol resins. Among these, the thermoplastic resin film is preferably a cyclic polyolefin resin film, a cellulose ester resin film, a polyester resin film, or a (meth)acrylic resin film. In this specification, "(meth)acrylic" means either acrylic or methacrylic. The "(meth)" in (meth)acrylate, etc., has the same meaning.

[0019] From the viewpoint of thinning, the thickness of the thermoplastic resin film is usually 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and still more preferably 30 μm or less, and is usually 1 μm or more, for example 5 μm or more or 20 μm or more.

[0020] A hard coat layer (HC layer) may be formed on the base layer. The hard coat layer may be formed on one side of the base layer or on both sides. By providing a hard coat layer, hardness and scratch resistance can be improved. When a linear polarizer is formed on the hard coat layer of a base layer having a hard coat layer, the hard coat layer may serve as a protective layer as described later.

[0021] Examples of linear polarizer-forming compositions containing polymerizable liquid crystal compounds and dichroic dyes, and methods for producing linear polarizers using these compositions, can be found in Japanese Patent Publication No. 2013-37353, Japanese Patent Publication No. 2013-33249, Japanese Patent Publication No. 2017-83843, and the like. In addition to polymerizable liquid crystal compounds and dichroic dyes, linear polarizer-forming compositions may further contain additives such as solvents, polymerization initiators, crosslinking agents, leveling agents, antioxidants, plasticizers, and sensitizers. These components may be used individually or in combination of two or more.

[0022] The polymerization initiator that may be contained in the linear polarizer forming composition is a compound that can initiate the polymerization reaction of a polymerizable liquid crystal compound, and a photopolymerizable initiator is preferred in that it can initiate the polymerization reaction under lower temperature conditions. Specifically, photopolymerization initiators that can generate active radicals or acids upon the action of light are mentioned, and among these, photopolymerization initiators that generate radicals upon the action of light are preferred. The content of the polymerization initiator is preferably 1 to 10 parts by mass, more preferably 3 to 8 parts by mass, per 100 parts by mass of the total amount of the polymerizable liquid crystal compound. Within this range, the reaction of the polymerizable groups proceeds sufficiently and the orientation state of the liquid crystal compound is easily stabilized.

[0023] The thickness of the linear polarizer, which is a liquid crystal curing layer, is usually 10 μm or less, preferably 0.5 μm to 8 μm, and more preferably 1 μm to 5 μm.

[0024] The luminous efficiency-corrected polarization degree Py of a linear polarizer is usually 95% or higher, preferably 97% or higher, more preferably 98% or higher, even more preferably 98.7% or higher, still more preferably 99.0% or higher, particularly preferably 99.4% or higher, and may also be 99.9% or higher. The luminous efficiency-corrected polarization degree Py of a linear polarizer may be 99.999% or lower or 99.99% or lower. The luminous efficiency-corrected polarization degree Py can be calculated by performing luminous efficiency correction on the obtained polarization degree using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) with a 2-degree field of view (C light source) as specified in "JIS Z 8701".

[0025] Increasing the luminous efficiency correction polarization degree Py of a linear polarizer is advantageous in enhancing the anti-reflective function of a circular polarizer. If the luminous efficiency correction polarization degree Py is less than 95%, the anti-reflective function may not be achieved.

[0026] The luminous efficiency-corrected single-unit transmittance Ty of a linear polarizer is usually 41% or higher, preferably 41.1% or higher, more preferably 41.2% or higher, and may also be 42% or higher, or 42.5% or higher. The luminous efficiency-corrected single-unit transmittance Ty of a linear polarizer is usually 50% or lower, and may also be 48% or lower, 46% or lower, 44% or lower, or 43% or lower. If the luminous efficiency-corrected single-unit transmittance Ty is excessively high, the luminous efficiency-corrected polarization degree Py may become too low, resulting in insufficient anti-reflective function of the circular polarizer. The luminous efficiency-corrected single-unit transmittance Ty can be calculated by using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) and performing luminous efficiency correction on the obtained transmittance using a 2-degree field of view (C light source) according to "JIS Z 8701".

[0027] The linear polarizer 1 may be a laminate of the above-described base layer and a linear polarizer which is a liquid crystal hardened layer. Alternatively, the base layer may be peeled off from the linear polarizer. The linear polarizer 1, which includes the linear polarizer which is a liquid crystal hardened layer, may or may not have an alignment film.

[0028] The linear polarizer 1 may have a protective layer to protect the linear polarizer. The protective layer can be placed on one or both sides of the linear polarizer. If protective layers are laminated on both sides of the linear polarizer, the two protective layers may be of the same type or different types. The protective layer may be, for example, an organic layer or an inorganic layer. The organic or inorganic layer may be, for example, a layer formed by coating. The organic layer may be a cured layer of a protective layer-forming composition (e.g., a (meth)acrylic resin composition, an epoxy resin composition, a polyimide resin composition, etc.), a water-soluble resin layer (e.g., a polyvinyl alcohol resin layer), etc. The curable protective layer-forming composition may be an active energy ray curable type or a thermosetting type. The inorganic layer may be formed from, for example, silicon oxide. When the protective layer is an organic layer, the protective layer may be called a hard coat layer (HC layer) or an overcoat layer (OC layer). The protective layer may be formed directly on the above-mentioned substrate layer or orientation film, or it may be formed directly on the linear polarizer.

[0029] Figure 2 is a schematic cross-sectional view showing another example of a circular polarizer. In the circular polarizer shown in Figure 2, the linear polarizer 1 includes a linear polarizer 1b, a protective layer (HC layer) 1a positioned on one side of the linear polarizer 1b, a protective layer (OC layer) 1c positioned on the other side of the linear polarizer 1b, and an alignment film 1d interposed between the protective layer (HC layer) 1a and the linear polarizer 1b.

[0030] When the protective layer is an organic layer, for example, an active energy ray curable protective layer-forming composition can be applied to the substrate layer or onto an alignment film formed on the substrate layer, and cured by irradiation with active energy to form a protective layer (e.g., an HC layer). The protective layer may be incorporated into the circular polarizer after the substrate layer has been peeled off and removed. Examples of methods for applying the protective layer-forming composition include spin coating. When the protective layer is an inorganic layer, it can be formed by methods such as sputtering or vapor deposition. The overcoat layer (OC layer) can be formed, for example, by directly applying it to the surface of a linear polarizer. The thickness of the protective layer is, for example, 0.1 μm to 10 μm, preferably 5 μm or less.

[0031] The protective layer may be a thermoplastic resin film. The thermoplastic resin films described above can be used. If the protective layer is a thermoplastic resin film, the thermoplastic resin film is laminated to the linear polarizer, for example, via a laminating layer described later. The laminating layer is preferably an adhesive layer. Alternatively, a linear polarizer may be formed on the protective layer. The circular polarizer preferably has at least one protective layer selected from the group consisting of a thermoplastic resin film and a cured layer on the side opposite to the first adhesive layer in the linear polarizer.

[0032] (2) Retardation layer structure As shown in Figure 2, the circular polarizer includes a phase difference layer structure 2, which includes at least one phase difference layer, i.e., a first phase difference layer 2a. The phase difference layer structure 2 may have only the first phase difference layer 2a, or it may be a laminated structure consisting of two or more phase difference layers. That is, the phase difference layer structure 2 may include one or more phase difference layers other than the first phase difference layer 2a (for example, a second phase difference layer 2b shown in Figure 2).

[0033] The first phase difference layer 2a is, for example, a λ / 4 layer. When the phase difference layer structure 2 includes two phase difference layers, possible combinations of phase difference layers, in order from the linear polarizer 1 side, include a combination of a λ / 4 layer and a positive C layer, a combination of a λ / 2 layer and a λ / 4 layer, and a combination of a positive C layer and a λ / 4 layer. A first bonding layer 2c can be used for lamination of the phase difference layers.

[0034] The λ / 4 layer has an in-plane phase difference value Re(550) at a wavelength of 550 nm that is typically in the range of 90 nm to 220 nm, preferably in the range of 100 nm to 200 nm. The λ / 2 layer has an in-plane phase difference value Re(550) at a wavelength of 550 nm that is preferably in the range of 200 nm to 300 nm. The positive C layer has a phase difference value Rth(550) in the thickness direction at a wavelength of 550 nm that is typically in the range of -170 nm to -10 nm, preferably in the range of -150 nm to -20 nm.

[0035] The phase difference layer structure 2 preferably has inverse wavelength dispersion, more preferably has a wavelength dispersion α of 0.95 or less, even more preferably has a wavelength dispersion α of 0.80 or more and 0.93 or less, even more preferably has a wavelength dispersion α of 0.80 or more and 0.90 or less, and particularly preferably has a wavelength dispersion α of 0.80 or more and 0.88 or less. Wavelength dispersion α is the ratio of the in-plane phase difference value Re(450) at a wavelength of 450 nm to the in-plane phase difference value Re(550) at a wavelength of 550 nm. Wavelength dispersion α=In-plane retardation value Re(450) / In-plane retardation value Re(550)

[0036] The first phase difference layer 2a and the other phase difference layers are liquid crystal cured layers. The liquid crystal cured layer is a cured product layer in which a polymerizable liquid crystal compound is polymerized and cured in an oriented state. The phase difference layer structure 2 includes one or more liquid crystal cured layers, and may include two or more layers. Using a liquid crystal cured layer as the phase difference layer, rather than a phase difference film formed by stretching or the like from the thermoplastic resin film described above, is advantageous because it can reduce the static electricity accumulated on the surface of the second adhesive layer 20, which is closest to the pixel display element when combined with the pixel display element, thereby providing the circular polarizer with sufficient antistatic performance.

[0037] Examples of polymerizable liquid crystal compounds include rod-shaped polymerizable liquid crystal compounds and disc-shaped polymerizable liquid crystal compounds. Either one of these may be used, or a mixture containing both may be used. When a rod-shaped polymerizable liquid crystal compound is oriented horizontally or vertically with respect to the substrate layer, the optical axis of the polymerizable liquid crystal compound coincides with the long axis direction of the polymerizable liquid crystal compound. When a disc-shaped polymerizable liquid crystal compound is oriented, the optical axis of the polymerizable liquid crystal compound is located in a direction perpendicular to the disc surface of the polymerizable liquid crystal compound.

[0038] For a liquid crystal cured layer formed by polymerizing a polymerizable liquid crystal compound to exhibit an in-plane phase difference, the polymerizable liquid crystal compound should be oriented in a suitable direction. When the polymerizable liquid crystal compound is rod-shaped, an in-plane phase difference is exhibited by oriented the optical axis of the polymerizable liquid crystal compound horizontally to the substrate layer plane, in which case the optical axis direction and the slow phase axis direction coincide. When the polymerizable liquid crystal compound is disc-shaped, an in-plane phase difference is exhibited by oriented the optical axis of the polymerizable liquid crystal compound horizontally to the substrate layer plane, in which case the optical axis and the slow phase axis are orthogonal. The orientation state of the polymerizable liquid crystal compound can be adjusted by the combination of the alignment film and the polymerizable liquid crystal compound.

[0039] A polymerizable liquid crystal compound is a compound having at least one polymerizable reactive group and possessing liquid crystalline properties. When two or more polymerizable liquid crystal compounds are used in combination, it is preferable that at least one of them has two or more polymerizable reactive groups in its molecule. A polymerizable reactive group is a group that participates in the polymerization reaction, and is preferably a photopolymerizable reactive group. A photopolymerizable reactive group is a group that can participate in the polymerization reaction by active radicals or acids generated from a photopolymerization initiator. Examples of photopolymerizable reactive groups are the same as those described above. The liquid crystalline properties of a polymerizable liquid crystal compound may be thermotropic or lyotropic, and if thermotropic liquid crystals are classified by their degree of order, they may be nematic or smectic.

[0040] The phase difference layer structure 2 may include an alignment film adjacent to the phase difference layer. The alignment film has an orientation restricting force that aligns the polymerizable liquid crystal compound in a desired direction. The alignment film may be a vertical alignment film in which the molecular axis of the polymerizable liquid crystal compound is oriented perpendicularly to the substrate layer, a horizontal alignment film in which the molecular axis of the polymerizable liquid crystal compound is oriented horizontally to the substrate layer, or a gradient alignment film in which the molecular axis of the polymerizable liquid crystal compound is oriented in a gradient relative to the substrate layer.

[0041] The thickness of the liquid crystal curing layer may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, 2 μm or more, and preferably 10 μm or less, 8 μm or less, or 5 μm or less. The thickness of the alignment film is, for example, 5 nm or more and 1 μm or less.

[0042] The liquid crystal curing layer can be formed by applying a liquid crystal layer forming composition containing a polymerizable liquid crystal compound onto a substrate layer, drying it, and polymerizing the polymerizable liquid crystal compound. The liquid crystal layer forming composition may also be applied onto an alignment film formed on the substrate layer. The material and thickness of the substrate layer may be the same as those of the thermoplastic resin film described above. The substrate layer may be incorporated into the phase difference layer structure 2 together with the phase difference layer, which is the liquid crystal curing layer, or the substrate layer may be peeled off and only the liquid crystal curing layer, or the liquid crystal curing layer and the alignment film, incorporated into the phase difference layer structure 2.

[0043] In the example of a circular polarizer shown in Figure 2, the phase difference layer structure 2 comprises a first phase difference layer 2a and a second phase difference layer 2b, which are bonded together by a first bonding layer 2c. However, the first bonding layer 2c and the second phase difference layer 2b may be omitted.

[0044] (3) First adhesive layer The first adhesive layer 10, which is interposed between the linear polarizing plate 1 and the phase difference layer structure 2 to bond the two together, is an antistatic adhesive layer containing an antistatic agent. The first adhesive layer 10 can be composed of an adhesive composition containing a base polymer and an antistatic agent. The adhesive layer may be, for example, a layer composed of an adhesive composition or a layer that has been treated in some way. An adhesive is also called a pressure-sensitive adhesive. In this specification, "adhesive" refers to an adhesive other than an adhesive (pressure-sensitive adhesive) and is clearly distinguished from an adhesive.

[0045] Examples of base polymers include (meth)acrylic resins, rubber resins, urethane resins, ester resins, silicone resins, and polyvinyl ether resins. Among these, (meth)acrylic resins, which have excellent transparency, weather resistance, and heat resistance, are preferred. The adhesive composition may be of the active energy ray curing type or thermosetting type.

[0046] As the (meth)acrylic resin, polymers or copolymers using one or more (meth)acrylic acid esters such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate as monomers are preferably used. It is preferable to copolymerize polar monomers into the (meth)acrylic resin. Examples of polar monomers include monomers having polar groups such as carboxyl groups, hydroxyl groups, amide groups, amino groups, and epoxy groups, such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0047] Examples of the antistatic agent include ionic compounds. An ionic compound is a compound having an inorganic cation or an organic cation and an inorganic anion or an organic anion. The first adhesive layer 10 may contain two or more kinds of ionic compounds.

[0048] Examples of the inorganic cation include, for example, alkali metal ions such as lithium cation [Li + , sodium cation [Na + , potassium cation [K + , etc., and alkaline earth metal ions such as beryllium cation [Be 2+ , magnesium cation [Mg 2+ , calcium cation [Ca 2+ , etc. Examples of the organic cation include, for example, imidazolium cation, pyridinium cation, pyrrolidinium cation, ammonium cation, sulfonium cation, phosphonium cation, etc. The organic cation component is preferably used because of its excellent compatibility with the base polymer.

[0049] Examples of the inorganic anion include, for example, chloride anion [Cl - , bromide anion [Br - , iodide anion [I - , tetrachloroaluminate anion [AlCl4 - , heptachlorodialuminate anion [Al2Cl7 - , tetrafluoroborate anion [BF4 - , hexafluorophosphate anion [PF6 - , perchlorate anion [ClO4 - , nitrate anion [NO3 - , hexafluoroarsenate anion [AsF6 - , hexafluoroantimonate anion [SbF6 - , hexafluoroniobate anion [NbF6 - , hexafluorotantalate anion [TaF6 -], dicyanamide anion [(CN)2N - Examples include:

[0050] Examples of organic anions include acetate anions [CH3COO - ], trifluoroacetate anion [CF3COO - ], methanesulfonate anion [CH3SO3 - ], trifluoromethanesulfonate anion [CF3SO3 - ], p-toluenesulfonate anion [p-CH3C6H4SO3 - ], bis(fluorosulfonyl)imido anion [(FSO2)2N - ], bis(trifluoromethanesulfonyl)imido anion [(CF3SO2)2N - ], Tris(trifluoromethanesulfonyl)methanide anion [(CF3SO2)3C - ], dimethyl phosphinate anion [(CH3)2POO - ], (poly)hydrofluorofluoride anion [F(HF) n - ] (n is approximately 1-3), thiocyan anion [SCN - ], perfluorobutanesulfonate anion [C4F9SO3 - ], bis(pentafluoroethanesulfonyl)imide anion [(C2F5SO2)2N - ], perfluorobutanoate anion [C3F7COO - ], (trifluoromethanesulfonyl)(trifluoromethanecarbonyl)imido anion [(CF3SO2)(CF3CO)N - ], perfluoropropane-1,3-disulfonate anion [ - O3S(CF2)3SO3 - ], carbonate anion [CO3 2- Examples include:

[0051] Among the anionic components described above, anionic components containing a fluorine atom are particularly preferred because they provide ionic compounds with excellent antistatic properties. Specifically, examples include bis(fluorosulfonyl)imide anions, hexafluorophosphate anions, or bis(trifluoromethanesulfonyl)imide anions.

[0052] Specific examples of ionic compounds can be appropriately selected from the above combinations of cationic and anionic components. Examples of ionic compounds having organic cations, classified by the structure of the organic cation, are as follows:

[0053] Pyridinium salts: N-hexylpyridinium hexafluorophosphate, N-octylpyridinium hexafluorophosphate, N-octyl-4-methylpyridinium hexafluorophosphate, N-butyl-4-methyllupyridinium hexafluorophosphate, N-decylpyridinium bis(fluorosulfonyl)imide, N-dodecylpyridinium bis(fluorosulfonyl)imide, N-tetradecylpyridinium bis(fluorosulfonyl)imide, N-Hexadecylpyridinium bis(fluorosulfonyl)imide, N-dodecyl-4-methylpyridinium bis(fluorosulfonyl)imide, N-tetradecyl-4-methylpyridinium bis(fluorosulfonyl)imide, N-Hexadecyl-4-methylpyridinium bis(fluorosulfonyl)imide, N-benzyl-2-methylpyridinium bis(fluorosulfonyl)imide, N-benzyl-4-methylpyridinium bis(fluorosulfonyl)imide N-Hexylpyridinium bis(trifluoromethanesulfonyl)imide N-octylpyridinium bis(trifluoromethanesulfonyl)imide, N-octyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide, N-butyl-4-methyllupyridinium bis(trifluoromethanesulfonyl)imide.

[0054] Imidazolium salt: 1-Ethyl-3-methylimidazolium hexafluorophosphate, 1-Ethyl-3-methylimidazolium p-toluenesulfonate, 1-Ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide 1-Butyl-3-methylimidazolium methanesulfonate, 1-Butyl-3-methylimidazolium bis(fluorosulfonyl)imide.

[0055] Pyrrolidinium salts: N-butyl-N-methylpyrrolidinium hexafluorophosphate, N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide.

[0056] Quaternary ammonium salts: Tetrabutylammonium hexafluorophosphate, Tetrabutylammonium p-toluenesulfonate, (2-hydroxyethyl)trimethylammonium bis(trifluoromethanesulfonyl)imide (2-hydroxyethyl)trimethylammonium dimethylphosphine.

[0057] Furthermore, examples of ionic compounds containing inorganic cations include the following: Lithium bromide, Lithium iodide, Lithium tetrafluoroborate, Lithium hexafluorophosphate, Lithium thiocyanate, Lithium perchlorate, Lithium trifluoromethanesulfonate, Lithium bis(fluorosulfonyl)imide, Lithium bis(trifluoromethanesulfonyl)imide, Lithium bis(pentafluoroethanesulfonyl)imide, Lithium tris(trifluoromethanesulfonyl)methanide, Lithium p-toluenesulfonate, Sodium hexafluorophosphate, Sodium bis(fluorosulfonyl)imide, Sodium bis(trifluoromethanesulfonyl)imide, Sodium p-toluenesulfonate, Potassium hexafluorophosphate, Potassium bis(fluorosulfonyl)imide, Potassium bis(trifluoromethanesulfonyl)imide, Potassium p-toluenesulfonate.

[0058] The ionic compound is preferably a solid at room temperature. Compared to using an ionic compound that is liquid at room temperature, the antistatic performance can be maintained for a longer period of time. From the viewpoint of such long-term stability of antistatic properties, the ionic compound is preferably a melting point of 30°C or higher, and more preferably 35°C or higher. On the other hand, if the melting point is too high, the compatibility with the base polymer will be poor, so the melting point is preferably 90°C or lower, more preferably 70°C or lower, and even more preferably less than 50°C.

[0059] The amount of antistatic agent is preferably such that the surface resistance value of the first adhesive layer 10 at a temperature of 25°C falls within the preferred range described later. Specifically, the amount is typically 0.2 parts by mass or more and 8 parts by mass or less, preferably 0.3 parts by mass or more and 5 parts by mass or less, more preferably 0.5 parts by mass or more and 5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of resin (base polymer) contained in the first adhesive layer 10. Having the ionic compound content within the above range is advantageous for achieving both sufficient antistatic performance and maintaining the durability of the adhesive layer.

[0060] The adhesive composition may further contain a crosslinking agent. Examples of crosslinking agents include metal ions with a valent or higher valency that form a metal carboxylate salt with a carboxyl group, polyamine compounds that form an amide bond with a carboxyl group, polyepoxy compounds or polyols that form an ester bond with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group. Among these, polyisocyanate compounds are preferred. The content of the crosslinking agent is usually 0.1 parts by mass or more and 1 part by mass or less per 100 parts by mass of resin (base polymer) contained in the first adhesive layer 10.

[0061] Active energy ray curable adhesive compositions have the property of curing upon irradiation with active energy rays such as ultraviolet rays or electron beams. They possess adhesive properties even before irradiation with active energy rays, allowing them to adhere to substrates such as films, and their adhesion strength can be adjusted by curing upon irradiation with active energy rays. Active energy ray curable adhesive compositions are preferably ultraviolet curable. Active energy ray curable adhesive compositions further contain active energy ray polymerizable compounds. If necessary, they may also contain photopolymerization initiators, photosensitizers, etc.

[0062] The adhesive composition constituting the first adhesive layer 10 may contain other components besides those mentioned above. Examples of other components include additives such as silane compounds, crosslinking catalysts, weather stabilizers, antioxidants, tackifiers, plasticizers, softeners, dyes, pigments, inorganic fillers, and light-scattering fine particles.

[0063] The thickness of the first adhesive layer 10 is, for example, 100 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. From the viewpoint of durability, the lower limit of the thickness of the adhesive layer is, for example, 1 μm or more, preferably 5 μm or more, and more preferably 10 μm or more. As will be described later, the total thickness of the first adhesive layer 10 and the second adhesive layer 20 is preferably 150 μm or less.

[0064] To impart sufficient antistatic performance to the circular polarizing plate, the surface resistance value of the first adhesive layer 10 at a temperature of 25°C is preferably 1.0 × 10⁻⁶. 11 It is less than or equal to Ω / □, and more preferably 8.0 × 10 10 It is less than or equal to Ω / □, and more preferably 6.0 × 10 10 The surface resistance is less than or equal to Ω / □. The surface resistance is measured by the method described in the Examples section.

[0065] (4)Second adhesive layer The circular polarizer includes a second adhesive layer 20 laminated on the side opposite to the viewing side (linear polarizer 1 side). The circular polarizer can be suitably applied to image display devices such as organic EL display devices. When applied to an image display device, the circular polarizer is positioned on the viewing side of the image display element such that the linear polarizer 1 side is the viewing side, that is, the phase difference layer structure 2 side is the image display element side. The second adhesive layer 20 can be used to bond the circular polarizer to the image display element.

[0066] The description of the first adhesive layer 10 is referenced for the adhesive composition constituting the second adhesive layer 20. However, the second adhesive layer 20 is substantially free of antistatic agents. Substantially free means that the amount of antistatic agent is 0.1 parts by mass or less per 100 parts by mass of resin (base polymer) contained in the second adhesive layer 20, and this amount is preferably 0.05 parts by mass or less, more preferably 0.01 parts by mass or less, and even more preferably 0 parts by mass. Because the second adhesive layer 20 is substantially free of antistatic agents, it is less likely to cause corrosion of metal electrodes and other components of the image display element in a humid and hot environment.

[0067] The thickness of the second adhesive layer 20 is less than 150 μm. By having a thickness within this range, sufficient antistatic performance of the circular polarizer can be ensured. The inventors have shown that even if the surface resistance value of the first adhesive layer 10 is the same, the antistatic performance of the circular polarizer changes depending on the thickness of the second adhesive layer 20. Furthermore, by having a thickness within the above range, the decrease in the polarization characteristics of the linear polarizer in a humid and hot environment can be suppressed. The inventors have shown that the decrease in the polarization characteristics of the linear polarizer is due to the migration of the dichroic dye to the outside of the linear polarizer through the layer adjacent to the linear polarizer, and that the amount of dichroic dye migration increases as the thickness of the second adhesive layer 20 increases. From the viewpoint of antistatic performance and suppression of the decrease in polarization degree, the thickness of the second adhesive layer 20 is preferably 145 μm or less, more preferably 130 μm or less, even more preferably 100 μm or less, and still more preferably 80 μm or less, and may be 50 μm or less or 40 μm or less.

[0068] From the viewpoint of durability, the thickness of the second adhesive layer 20 is, for example, 1 μm or more, preferably 5 μm or more, and more preferably 10 μm or more. This thickness is preferably greater than 5 μm, more preferably 8 μm or more, even more preferably 10 μm or more, and still more preferably 15 μm or more, in order to keep the content of the antistatic agent in the second adhesive layer 20, which will be measured after the humid heat test described later, within a predetermined range.

[0069] The inventors have shown that increasing the thickness of the first adhesive layer 10 also increases the amount of dichroic dye transferred. Therefore, the total thickness of the first adhesive layer 10 and the second adhesive layer 20 is preferably 150 μm or less. More preferably, the total thickness is 145 μm or less, even more preferably 120 μm or less, and still more preferably 100 μm or less. The total thickness is usually 20 μm or more, preferably 30 μm or more.

[0070] The circular polarizing plate according to the present invention has an antistatic agent content in the second adhesive layer 20 measured after a moist heat test, which is 0.2% by mass or less when the second adhesive layer 20 is considered to be 100% by mass. By having this content within this range, corrosion of metal electrodes and the like can be effectively suppressed. This content is the sum of the antistatic agent content that has migrated from the first adhesive layer 10 through the phase difference layer structure 2 to the second adhesive layer 20 by the moist heat test, and the antistatic agent content that was contained in the second adhesive layer before the moist heat test. This content is preferably 0.15% by mass or less, more preferably 0.10% by mass or less, even more preferably 0.05% by mass or less, and still more preferably 0.03% by mass or less.

[0071] The above-mentioned moist heat test refers to a test in which a circular polarizing plate is stored for 250 hours in an environment with a temperature of 85°C and a relative humidity of 85%RH. The content of the antistatic agent in the second adhesive layer 20 after the moist heat test is measured by the method described in the Examples section.

[0072] The amount of antistatic agent in the second adhesive layer 20 after the moist heat test can be controlled, for example, by adjusting the thickness of the second adhesive layer 20 within a range of less than 150 μm. Alternatively, an intervening layer can be provided between the phase difference layer structure 2 and the second adhesive layer 20 to suppress the migration of the antistatic agent to the second adhesive layer 20. This intervening layer may be, for example, a thin resin layer or resin film that is non-oriented and does not exhibit an in-plane phase difference value.

[0073] (5) Separation film As shown in Figure 3, the circular polarizer may include a separator film 21 to protect the outer surface of the second adhesive layer 20 (the surface opposite to the second phase difference layer 2b). The circular polarizer shown in Figure 3 has the same layer structure as the circular polarizer shown in Figure 2, except that it has a separator film 21. The separator film 21 is usually made of a thermoplastic resin film that has been treated with a release agent such as silicone or fluorine on one side, and the treated side is bonded to the second adhesive layer 20.

[0074] The thermoplastic resin constituting the separator film 21 is, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate. The thickness of the separator film 21 is, for example, 10 μm or more and 50 μm or less.

[0075] (6) Protective film As shown in Figure 4, the circular polarizer may include a protective film 30 laminated on the side facing the linear polarizer 1. The circular polarizer shown in Figure 4 has the same layer structure as the circular polarizer shown in Figure 3, except that it has a protective film 30. The protective film 30 is composed of, for example, a base film and an adhesive layer laminated thereon. The description of the adhesive layer is referenced from the description of the second adhesive layer 20 above. The resin constituting the base film can be a thermoplastic resin such as polyethylene resin such as polyethylene, polypropylene resin such as polypropylene, polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or polycarbonate resin. Preferably, it is a polyester resin such as polyethylene terephthalate.

[0076] (7) Laminate layer A circular polarizer may include a bonding layer for joining two layers (or films). Examples of bonding layers include a bonding layer for bonding a linear polarizer 1b to a protective layer, and a first bonding layer 2c for bonding a first phase difference layer 2a to a second phase difference layer 2b. The bonding layer is an adhesive layer composed of an adhesive composition or an adhesive layer composed of an adhesive composition. The composition of the adhesive layer is referenced from the description of the second adhesive layer 20 above. The thickness of the adhesive layer as a bonding layer is preferably 1 μm or more, may be 5 μm or more, and is usually 200 μm or less, for example, 150 μm or less or 100 μm or less.

[0077] Examples of adhesive compositions include water-based adhesives and active energy ray-curable adhesives. Examples of water-based adhesives include aqueous solutions of polyvinyl alcohol-based resins and water-based two-component urethane emulsion adhesives. Active energy ray-curable adhesives are adhesives that harden when irradiated with active energy rays such as ultraviolet light, and examples include adhesives containing polymerizable compounds and photopolymerization initiators, adhesives containing photoreactive resins, and adhesives containing binder resins and photoreactive crosslinking agents. Examples of polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth)acrylic monomers, and photocurable urethane monomers, and oligomers derived from these monomers. Examples of photopolymerization initiators include compounds containing substances that generate active species such as neutral radicals, anionic radicals, and cationic radicals when irradiated with active energy rays such as ultraviolet light.

[0078] The thickness of the bonding layer made of the adhesive composition may be, for example, 0.1 μm or more, preferably 0.5 μm or more, 1 μm or more, or 2 μm or more, and may be 100 μm or less, 50 μm or less, 25 μm or less, 15 μm or less, or 5 μm or less. The two opposing surfaces bonded via the bonding layer may be subjected to a surface activation treatment such as corona treatment, plasma treatment, or flame treatment beforehand.

[0079] <Image display device> The image display device according to the present invention (hereinafter also simply referred to as "image display device") includes a circular polarizer and an image display element according to the present invention. Examples of image display devices include organic electroluminescent (organic EL) display devices, inorganic electroluminescent (inorganic EL) display devices, liquid crystal display devices, and electroluminescent display devices, and an organic EL display device is preferred. In an organic EL display device, the circular polarizer functions as an anti-reflective film to suppress internally reflected light. The image display device may have a touch panel function, a blue light cut function, a viewing angle adjustment function, etc.

[0080] In an image display device, the circular polarizer is positioned on the viewing side of the image display element. The circular polarizer can be attached to the image display element using the second adhesive layer 20. The image display device can be used in mobile devices such as smartphones and tablets, televisions, digital photo frames, electronic signs, measuring instruments and gauges, office equipment, medical equipment, computer equipment, etc.

[0081] Figure 5 is a schematic cross-sectional view showing an example of an image display device according to the present invention. In Figure 5, the circular polarizer shown in Figure 2 is used as an example of a circular polarizer. The circular polarizer is bonded to the image display element 100 using its second adhesive layer 20.

[0082] On the side of the circular polarizing plate opposite to the second adhesive layer 20 (the outermost surface on the viewing side), a front plate 50 may be laminated via a second bonding layer 40. The description of the bonding layer described above is referenced for the second bonding layer 40.

[0083] (1)Front plate The front panel 50 constitutes the outermost surface on the viewing side of the image display device and can have the function of protecting the front (screen) of the image display device. The front panel 50 may also be called a window film. The material and thickness of the front panel 50 are not limited as long as it is a plate-like body that can transmit light, and it may consist of only one layer or two or more layers. Examples of the front panel 50 include a resin plate-like body (e.g., resin plate, resin sheet, resin film, etc.), a glass plate-like body (e.g., glass plate, glass film, etc.), and a touch sensor panel as described later. When the front panel 50 is provided on a circular polarizing plate, the front panel 50 is positioned on the viewing side of the circular polarizing plate.

[0084] The thickness of the front panel 50 is, for example, 30 μm or more and 500 μm or less, preferably 200 μm or less, and more preferably 100 μm or less.

[0085] Examples of resins that make up the resin plate-like body include thermoplastic resins such as triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, butyrylcellulose, acetylpropionylcellulose, polyester, polystyrene, polyamide, polyetherimide, poly(meth)acrylic, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyetherketone, polyetheretherketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These thermoplastic resins can be used individually or in mixtures of two or more. From the viewpoint of improving strength and transparency, the resin plate-like body is preferably a thermoplastic resin film formed from polyimide, polyamide, polyamideimide, etc.

[0086] From the viewpoint of hardness, the front panel 50 is preferably a film in which a hard coat layer (HC layer) is provided on at least one side of the base film. As the base film, a film made of the thermoplastic resin described above can be used. The hard coat layer may be formed on one side of the base film or on both sides. By providing a hard coat layer, a front panel with improved hardness and scratch resistance can be made. The hard coat layer is, for example, a cured layer of an ultraviolet-curable resin. Examples of ultraviolet-curable resins include (meth)acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, epoxy resins, etc. The hard coat layer may contain additives to improve its strength. The additives are not limited to inorganic fine particles, organic fine particles, or mixtures thereof.

[0087] If the front panel 50 is a glass plate, tempered glass for displays is preferably used. The thickness of the glass plate may be, for example, 10 μm to 1000 μm, or 10 μm to 800 μm. By using a glass plate, a front panel with excellent mechanical strength and surface hardness can be constructed.

[0088] The front plate 50 preferably has high rigidity, for example, a Young's modulus of 70 GPa or more, and may be 80 GPa or more. The Young's modulus of the front plate 50 is usually 100 GPa or less. The Young's modulus can be measured as follows: A sample of the front plate 60 measuring 110 mm on the long side and 10 mm on the short side is cut out using a super cutter. Next, the long side of the sample is clamped at both ends with the upper and lower grips of a tensile testing machine (Autograph AG-Xplus testing machine, manufactured by Shimadzu Corporation) with a gap of 5 cm between the grips, and the sample is pulled in the longitudinal direction at a tensile speed of 4 mm / min in an environment of 23°C and 55% relative humidity. The Young's modulus at 23°C and 55% relative humidity can be calculated from the slope of the straight line between 20 and 40 MPa in the resulting stress-strain curve.

[0089] (2) Image display element The image display element 100 includes an image display panel and may further include a touch sensor panel. Known panels can be used as the image display panel, such as organic EL panels. The organic EL display element is an image display element that includes an organic EL panel. When the image display element 100 includes an image display panel and a touch sensor panel, they are typically arranged in the order of touch sensor panel, then image display panel, from the circular polarizer side.

[0090] A touch sensor panel can use any sensor capable of detecting the touched position, and the detection method is not limited to resistive, capacitive, optical, ultrasonic, electromagnetically coupled, or surface acoustic wave methods. Among these, capacitive touch sensor panels are preferred due to their low cost, fast response speed, and thin-film capability.

[0091] The transparent conductive layer may be a transparent conductive layer made of a metal oxide such as ITO, or a metal layer made of a metal such as aluminum, copper, silver, gold, titanium, or an alloy thereof. The transparent electrode layer is formed by sputtering, printing, vapor deposition, etc. A photosensitive resist is formed on the transparent electrode layer, and then an electrode pattern layer is formed by photolithography. Negative-type or positive-type photosensitive resist is used as the photosensitive resist, and the photosensitive resist may remain or be removed after patterning. When forming the film by sputtering, a mask with the electrode pattern shape can be placed and sputtering performed to form the electrode pattern layer.

[0092] The separation layer is formed on a substrate such as glass and is a layer for separating the transparent conductive layer formed on the separation layer from the substrate together with the separation layer. The separation layer is preferably an inorganic layer or an organic layer. Examples of materials for forming the inorganic layer include silicon oxide. Examples of materials for forming the organic layer include (meth)acrylic resin compositions, epoxy resin compositions, polyimide resin compositions, etc. The separation layer can be formed by coating using a known coating method and curing by thermosetting, UV curing, or a combination thereof.

[0093] A protective layer may be provided in contact with the transparent conductive layer to protect it. The protective layer includes at least one of an organic insulating film and an inorganic insulating film, and these films can be formed by methods such as spin coating, sputtering, or vapor deposition.

[0094] The insulating layer can be formed from, for example, an inorganic insulating material such as silicon oxide, or a transparent organic material such as (meth)acrylic resin. The insulating layer can be formed by applying it using a known coating method, followed by thermosetting, UV curing, heat drying, vacuum drying, etc.

[0095] Examples of thermoplastic resin films for the touch sensor panel include triacetylcellulose, polyethylene terephthalate, cycloolefin polymer, polyethylene naphthalate, polyolefin, polycycloolefin, polycarbonate, polyethersulfone, polyarylate, polyimide, polyamide, polystyrene, and polynorbornene. Polyethylene terephthalate is preferably used because it is easy to construct a base film with the desired toughness. The thickness of the base film is preferably 50 μm or less, more preferably 30 μm or less, and usually 5 μm or more.

[0096] A touch sensor panel can be manufactured, for example, as follows. In the first method, a base film is first laminated onto a substrate via a bonding layer. A transparent conductive layer, patterned by photolithography, is formed on the base film. By applying heat, the substrate and the base film are separated to obtain a touch sensor panel consisting of the transparent conductive layer and the base film. The substrate is not particularly limited as long as it maintains flatness and has heat resistance, but a glass substrate is preferred.

[0097] In the second method, a separation layer is first formed on the substrate. If necessary, a protective layer is formed on the separation layer. The protective layer may be formed so as not to be formed in the area where the pad pattern layer is formed. A transparent conductive layer, patterned by photolithography, is formed on the separation layer (or protective layer). An insulating layer is formed on the transparent conductive layer so as to fill the electrode pattern layer. A protective film is laminated on the insulating layer, and the layers from the insulating layer to the separation layer are transferred to it to separate the substrate. By peeling off the protective film, a touch sensor panel having the insulating layer / transparent conductive layer / (protective layer) / separation layer in this order is obtained.

[0098] The thickness of the touch sensor panel including the base film is, for example, 5 μm to 2000 μm, or 5 μm to 100 μm. The thickness of the touch sensor panel without the base film is, for example, 0.5 μm to 10 μm, preferably 5 μm or less.

[0099] The circular polarizing plate according to the present invention has a high effect in suppressing corrosion of metal electrodes and the like in a humid and hot environment. Therefore, in an image display device in which the circular polarizing plate is laminated on an image display element, corrosion of the transparent conductive layer is less likely to occur even when the circular polarizing plate is in contact with the transparent conductive layer of the touch sensor panel, or even when the layer interposed between the circular polarizing plate and the transparent conductive layer of the touch sensor panel (e.g., a protective layer, a separation layer, etc.) is thin. [Examples]

[0100] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0101] [measurement] (1) Thickness of the layer The thickness of the adhesive layer was measured using a contact-type film thickness measuring device (Nikon Corporation's "MS-5C"). The linear polarizer, protective layer, phase difference layer, alignment layer, and adhesive layer were measured using a laser microscope (Olympus Corporation's "OLS4100").

[0102] (2) Content of antistatic agent in the second adhesive layer after the moist heat test A circular polarizing plate was cut into an optical laminate measuring 300 mm x 200 mm. An alkali-free glass plate was bonded to the protective layer (HC layer) using an adhesive layer, and a separator film was bonded to the second adhesive layer to obtain a test specimen. The obtained test specimen was subjected to a moist heat test, stored in an oven at 85°C and 85% RH for 250 hours. After the test, the separator film was peeled off, and a portion of the second adhesive layer was scraped off to obtain an adhesive sample. The weighed adhesive sample was dissolved in acetonitrile and filtered through a syringe filter. The obtained sample solution was measured by liquid chromatography (LC-MS, SIM mode), and the content (mass%) of the antistatic agent was determined by quantifying it from the peak area of ​​the antistatic agent, with the second adhesive layer being set to 100% by mass. The liquid chromatography measurement conditions were as follows.

[0103] [Measurement conditions for liquid chromatography] • Equipment: Agilent 1100 + 6310MS • Column: Kinetex 2.6u C18 100A (3.0mmφ × 75mm, 2.6μm) Mobile phase: A) H2O, B) Acetonitrile • Gradient: B) Concentration 10% - 30 min. - 100% (10 min.) ·Flow rate: 0.5mL / min. Oven temperature: 40℃ Detection: DAD 254nm (4nm, slit width: 8nm) • Quantitative method: Absolute testing method

[0104] (3) Surface resistance of the adhesive layer An adhesive layer with separator films laminated on both sides was cut to 100mm x 100mm. After peeling off one of the separator films, the surface resistance (Ω / □) of the adhesive layer at 25°C was measured using a resistance meter [product name "Hiresta-UP, model: MCP-HT450" manufactured by Mitsubishi Chemical Corporation].

[0105] (4) Measurement of single-unit transmittance and luminous-sensitivity corrected polarization The luminous efficiency-corrected polarization degree of the circular polarizer was measured by incidenting linearly polarized light from a prism onto the linear polarizer side of the circular polarizer and measuring it using a spectrophotometer with an integrating sphere (JASCO Corporation's "V7100"). MD transmittance and TD transmittance were determined in the wavelength range of 380 nm to 780 nm, and the single transmittance and polarization degree at each wavelength were calculated based on equations (A) and (B). Furthermore, luminous efficiency correction was performed using the 2-degree field of view (C light source) of JIS Z 8701 to determine the luminous efficiency-corrected polarization degree (Py). "MD transmittance" refers to the transmittance when the direction of polarization emitted from the Glan-Thompson prism is parallel to the transmission axis of the polarizer sample. In equations (A) and (B), "MD transmittance" is represented as "MD". Furthermore, "TD transmittance" is the transmittance when the direction of polarization emitted from the Grant-Thomson prism and the transmission axis of the polarizer sample are perpendicular, and in equations (A) and (B), "TD transmittance" is represented as "TD". Single element transmittance (%) = (MD + TD) / 2 Equation (A) Degree of polarization (%)={(MD-TD) / (MD+TD)}×100 Formula (B)

[0106] <Example 1> (1) Fabrication of linear polarizing plates A polyethylene terephthalate (PET) film (100 μm thick) was used as the base layer, and a protective layer (HC layer) forming composition was applied by bar coating. The film was then heated and dried in an 80°C drying oven for 3 minutes. The resulting dried film was then exposed to UV light using a UV irradiation device (SPOT CURE SP-7 manufactured by Ushio Inc.) at an exposure dose of 500 mJ / cm². 2 A protective layer (HC layer) was formed by irradiation with UV light (based on 365 nm). The thickness of the protective layer (HC layer) was 2.0 μm. In this way, a laminate consisting of a "substrate layer / protective layer (HC layer)" was obtained.

[0107] The composition for forming the protective layer (HC layer) was prepared by mixing 2.8 parts by mass of a dendrimer acrylate having 18 functional acrylic groups (Miramer SP1106, Miwon), 6.6 parts by mass of a urethane acrylate having 6 functional acrylic groups (Miramer PU-620D, Miwon), 0.5 parts by mass of a photopolymerization initiator (Irgacure-184, BASF), 0.1 parts by mass of a leveling agent (BYK-3530, BYK), and 90 parts by mass of methyl ethyl ketone (MEK).

[0108] A laminate consisting of a "substrate layer / protective layer (HC layer)" was subjected to one corona treatment on the protective layer (HC layer) side. The corona treatment conditions were an output of 0.3 kW and a processing speed of 3 m / min. Subsequently, an alignment film-forming composition was applied to the protective layer (HC layer) by bar coating and heated and dried in an 80°C drying oven for 1 minute. The resulting dried film was subjected to polarized UV irradiation treatment to form an alignment film. The polarized UV treatment involved transmitting light irradiated from the above UV irradiation device through a wire grid (UIS-27132## manufactured by Ushio Inc.) and measuring the integrated light amount at a wavelength of 365 nm to 100 mJ / cm². 2 The experiment was conducted under the following conditions. The thickness of the alignment film was 100 nm.

[0109] As the composition for forming the oriented film, a solution was used in which a polymer having a photoreactive group consisting of structural units represented by the following formula was dissolved in cyclopentanone at a concentration of 5% by mass. GPC measurement revealed that the polymer had a number-average molecular weight of 28200, an Mw / Mn ratio of 1.82, and a monomer content of 0.5%. [ka]

[0110] A linear polarizer-forming composition was applied to the formed alignment film by bar coating, heated and dried in a 120°C drying oven for 1 minute, and then cooled to room temperature. Using the above UV irradiation device, an integrated light intensity of 1200 mJ / cm² was applied. 2 A linear polarizer was formed by irradiating the dried film with ultraviolet light at a 365 nm reference. The thickness of the obtained linear polarizer was 1.8 μm. In this way, a laminate consisting of a "substrate layer / protective layer (HC layer) / alignment film / linear polarizer" was obtained.

[0111] The linear polarizer forming composition was prepared by mixing 75 parts by mass of a compound represented by formula (1-6) and 25 parts by mass of a compound represented by formula (1-7) as polymerizable liquid crystal compounds, 2.5 parts by mass each of azo dyes represented by formulas (2-1a), (2-1b), and (2-3a) as dichroic dyes, 6 parts by mass of 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one ("Irgacure 369" from BASF Japan) as a polymerization initiator, and 1.2 parts by mass of a polyacrylate compound ("BYK-361N" from BYK-Chemie) as a leveling agent with 400 parts by mass of toluene, and stirring the resulting mixture at 80°C for 1 hour. The compounds represented by formulas (1-6) and (1-7) were synthesized by the method described in Lub et al. Recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996). The azo dyes represented by formulas (2-1a), (2-1b), and (2-3a) are those described in the examples of Japanese Patent Application Publication No. 2013-101328.

[0112] [ka] [ka]

[0113] [ka] [ka] [ka]

[0114] A protective layer (OC layer) forming composition was applied to the formed linear polarizer by bar coating, and the coating was applied to a thickness of 1.0 μm after drying, and dried at a temperature of 80°C for 3 minutes. In this way, a laminate consisting of "base layer / protective layer (HC layer) / alignment film / linear polarizer / protective layer (OC layer)" was obtained. Immediately before use, the base layer was peeled off to obtain a linear polarizer consisting of "protective layer (HC layer) / alignment film / linear polarizer / protective layer (OC layer)".

[0115] The composition for forming the protective layer (OC layer) was prepared by mixing 3 parts by mass of polyvinyl alcohol resin powder (product name "KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization 18000) and 1.5 parts by mass of polyamide epoxy resin (crosslinking agent, product name "SR650(30)" manufactured by Sumika Chemtex Co., Ltd.) with 100 parts by mass of water.

[0116] (2) Fabrication of the phase difference layer structure A laminate A was fabricated that provided a phase difference of λ / 4, consisting of a cured layer of a nematic liquid crystal compound (first phase difference layer), a first alignment film, and a transparent substrate layer. The total thickness of the first phase difference layer and the first alignment film was 2 μm. The first phase difference layer was formed by coating a phase difference layer-forming composition containing a nematic liquid crystal compound onto the first alignment film formed on the transparent substrate layer, and then curing it.

[0117] Furthermore, a polyethylene terephthalate substrate with a thickness of 38 μm was used as a transparent substrate layer, and a composition for forming a vertically aligned film was coated on one side thereof to a thickness of 3 μm, resulting in a 20 mJ / cm² temperature. 2 A second orientation film was formed by irradiating it with polarized ultraviolet light. The composition for forming the vertical orientation film was a mixture of 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, dipentaerythritol triacrylate, and bis(2-vinyloxyethyl) ether in a mass ratio of 1:1:4:5, with 4% by mass of LUCIRIN® TPO added as a polymerization initiator.

[0118] Next, a phase difference layer forming composition containing a photopolymerizable nematic liquid crystal compound (Merck's "RMM28B") was applied to the formed second orientation film by die coating. The phase difference layer forming composition was prepared by mixing methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone (CHN) with a boiling point of 155°C in a mass ratio (MEK:MIBK:CHN) of 35:30:35, and then mixing the photopolymerizable nematic liquid crystal compound to a content of 1.5% by mass.

[0119] After coating the second alignment film with a composition for forming a phase difference layer, a drying treatment was performed at a drying temperature of 75°C for a drying time of 120 seconds. Subsequently, the liquid crystal compound was polymerized by ultraviolet (UV) irradiation to obtain a laminate B consisting of a second phase difference layer (positive C layer), a second alignment film, and a transparent substrate layer. The total thickness of the second phase difference layer and the second alignment film was 4 μm.

[0120] Laminate A and laminate B were bonded together using an ultraviolet-curing adhesive, with the phase difference layer surfaces (the surfaces opposite to the transparent substrate layer) of each laminate facing each other. The ultraviolet-curing adhesive was then cured by irradiation with ultraviolet light. The thickness of the adhesive after curing was 2 μm. In this way, a phase difference layer structure having the layer configuration of "transparent substrate layer / first orientation film / first phase difference layer / adhesive layer / second phase difference layer / second orientation film / transparent substrate layer" was fabricated.

[0121] (3) Preparation of the first adhesive layer A 20 μm thick adhesive layer was prepared as the first adhesive layer for bonding a linear polarizing plate and a phase difference layer structure, consisting of an adhesive composition having the following composition. On both sides of this adhesive layer, a separator film is laminated, with one side of a 38 μm thick polyethylene terephthalate film (base film) having been treated for release; one side is a heavy separator, and the other is a light separator. The surface resistance of the first adhesive layer at 25°C was measured according to the above method, and it was found to be 5.0 × 10⁻⁶. 10 It was Ω / □. [Composition of adhesive composition] • Base polymer: (meth)acrylic resin • Antistatic agent: N-octyl-4-methylpyridinium hexafluoride phosphorus, content: 3% by mass (relative to 100% by mass of base polymer)

[0122] (4) Preparation of the second adhesive layer A 15 μm thick second adhesive layer was prepared, consisting of an adhesive composition containing a (meth)acrylic resin as the base polymer and no antistatic agent. Separator films, each consisting of a 38 μm thick polyethylene terephthalate film (base film) with a release treatment on one side, were laminated on both sides of this adhesive layer; one side was a heavy separator, and the other a light separator. The surface resistance of the second adhesive layer at 25°C was measured according to the above method, yielding 1 × 10⁻⁶ 14 It was Ω / □ or greater.

[0123] (5) Fabrication of circular polarizing plates A light separator was peeled off from a first adhesive layer having separator films on both sides, and the exposed surface was bonded to the protective layer (OC layer) of the linear polarizing plate obtained in (1) above to obtain a laminate X. Both bonding surfaces were pre-treated with corona (output 0.3kW, speed 3m / min). Next, the heavy separator of the first adhesive layer was peeled off from laminate X, and the exposed surface was bonded to the surface exposed by peeling off the transparent substrate layer used to form the first phase difference layer from the phase difference layer structure obtained in (2) above to obtain a laminate Y. Both bonding surfaces were pre-treated with corona (output 0.3kW, speed 3m / min).

[0124] Next, the light separator was peeled off the second adhesive layer, which had separator films on both sides, and the exposed surface was bonded to the surface exposed by peeling off the transparent substrate layer used to form the second phase difference layer from the laminate Y, thereby obtaining a circular polarizing plate having the same layer structure as in Figure 3. Both bonded surfaces were pre-treated with corona (output 0.3kW, speed 3m / min). When the antistatic agent content in the second adhesive layer after the moist heat test was measured for the obtained circular polarizing plate according to the method described above, it was found to be 0.15% by mass out of 100% by mass of the second adhesive layer.

[0125] (6) Measurement and evaluation of ΔPy under humid heat conditions The following moist heat durability test was performed on the circular polarizer obtained in (5) above. First, the circular polarizer was cut into a 30mm x 30mm square. The heavy separator of the second adhesive layer was peeled off the cut circular polarizer and bonded to an alkali-free glass (Corning's "EAGLE XG") measuring 40mm x 40mm x 0.7mm thick via the second adhesive layer. Furthermore, the 40mm x 40mm x 0.7mm thick alkali-free glass (Corning's "EAGLE XG") was bonded to the protective layer (HC layer) of the circular polarizer via a (meth)acrylic resin-based adhesive layer (without antistatic agent), and the test specimen was prepared by autoclaving at a temperature of 50°C. The luminous efficiency-corrected polarization degree Py was measured on this test specimen according to the method described above.

[0126] Next, the test specimens were subjected to a moist heat endurance test, in which they were stored in an oven at a temperature of 85°C and a relative humidity of 85%RH for 168 hours. After the test, the luminous efficiency-corrected polarization degree Py was measured for the test specimens. The absolute value ΔPy of the difference in luminous efficiency-corrected polarization degree Py before and after the moist heat endurance test was calculated and evaluated according to the following criteria. The results are shown in Table 1. A: ΔPy is less than 5.5. B: ΔPy is 5.5 or greater.

[0127] (7) Measurement and evaluation of saturation voltage The circular polarizer obtained in (5) above was cut into a 40mm x 40mm square. The heavy separator of the second adhesive layer was peeled off from the cut circular polarizer. The cut circular polarizer was fixed to the voltage application section of an honest meter manufactured by Shishido Electric Co., Ltd., with the surface of the second adhesive layer exposed by the peeling off of the heavy separator facing it. The saturation band voltage of the surface of the second adhesive layer was measured with an applied voltage of +10kV in accordance with JIS L 1094 (voltage application method: high voltage DC corona discharge type), and evaluated according to the following criteria. The results are shown in Table 1. A: The saturation voltage is less than 1kV. B: The saturation voltage is 1kV or higher.

[0128] (8) Measurement and evaluation of metal corrosion A metal-layered glass substrate (manufactured by Geomatec) was prepared by forming a metallic aluminum layer approximately 500 nm thick on the alkali-free glass surface by sputtering. Next, the circular polarizer obtained in (5) above was cut to a size of 50 mm × 60 mm, the heavy separator of the second adhesive layer was peeled off from the cut circular polarizer, and the metallic aluminum layer side of the metal-layered glass substrate was bonded to the surface of the exposed second adhesive layer. Furthermore, a 50 mm × 60 mm × 0.7 mm thick alkali-free glass ("EAGLE XG" manufactured by Corning) was bonded to the protective layer (HC layer) of the circular polarizer via a (meth)acrylic resin-based adhesive layer (without antistatic agent) to obtain a test specimen. The obtained test specimen was subjected to a moist heat test by storing it in an oven at a temperature of 85°C and a relative humidity of 85% RH for 250 hours. After the test, the condition of the metal layer of the test specimen (the portion to which the second adhesive layer of the test specimen was bonded) was observed through a magnifying glass from the surface of the alkali-free glass on the protective layer (HC layer) side, while shining light from the back of the metal-layered glass substrate, and evaluated according to the following criteria. The results are shown in Table 1. The evaluation was based on the presence or absence of pitting corrosion (pores with a diameter of 0.1 mm or more that can transmit light) in the observed metal layer. A: No pitting. B: Pitting is present.

[0129] <Examples 2-4, Comparative Examples 1-2> A circular polarizing plate was prepared in the same manner as in Example 1, except that the thickness of the second adhesive layer was changed as shown in Table 1, and each evaluation was performed. The evaluation results are shown in Table 1. The content of the antistatic agent in the second adhesive layer after the moist heat test (per 100% by mass of the second adhesive layer) is shown in the "AS agent content of the second adhesive layer" column of Table 1.

[0130] <Comparative Example 3> A circular polarizing plate was fabricated in the same manner as in Example 1, except that a 23 μm thick phase difference film made of cyclic polyolefin resin was used instead of the phase difference layer structure, and the thickness of the second adhesive layer was changed as shown in Table 1. Each evaluation was then performed. The evaluation results are shown in Table 1. The content of the antistatic agent in the second adhesive layer after the moist heat test (per 100% by mass of the second adhesive layer) is shown in the "AS agent content in the second adhesive layer" column of Table 1.

[0131] [Table 1] [Explanation of symbols]

[0132] 1 Linear polarizer, 1a Protective layer (HC layer), 1b Linear polarizer, 1c Protective layer (OC layer), 1d Alignment film, 2 Phase difference layer structure, 2a First phase difference layer, 2b Second phase difference layer, 2c First bonding layer, 10 First adhesive layer, 20 Second adhesive layer, 21 Separating film, 30 Protective film, 40 Second bonding layer, 50 Front panel, 100 Image display element.

Claims

1. A circular polarizing plate comprising, in this order, a linear polarizing plate, a first adhesive layer, a phase difference layer structure including at least one phase difference layer, and a second adhesive layer having a thickness of more than 5 μm and less than 150 μm, The aforementioned linear polarizing plate includes a linear polarizer which is a liquid crystal hardened layer. The aforementioned phase difference layer is a liquid crystal curing layer, The first adhesive layer contains an antistatic agent, and the second adhesive layer substantially does not contain an antistatic agent. The antistatic agent comprises a compound having an organic cation and an inorganic anion or an organic anion. A circular polarizing plate in which the content of the antistatic agent in the second adhesive layer, measured after storing the circular polarizing plate in an environment of 85°C and 85% relative humidity for 250 hours, is 0.2% by mass or less of the second adhesive layer by mass.

2. The circular polarizing plate according to claim 1, wherein the total thickness of the first adhesive layer and the second adhesive layer is 150 μm or less.

3. The surface resistance of the first adhesive layer at a temperature of 25°C is 1.0 × 10⁻⁶. １１ A circular polarizer according to claim 1 or 2, wherein the Ω / □ is less than or equal to Ω.

4. The circular polarizer according to any one of claims 1 to 3, wherein the linear polarizer is a liquid crystal cured layer containing a cured polymerizable liquid crystal compound and one or more dichroic dyes.

5. An image display device comprising a circular polarizing plate according to any one of claims 1 to 4.

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