KR20230006806A - circular polarizer - Google Patents

Abstract

An object of the present invention is to provide a circular polarizing plate having excellent flexibility and excellent bending resistance. The present invention is a circular polarizing plate having a polarizing layer comprising a linear polarization layer, and a retardation layer comprising a λ/4 retardation layer, a retardation layer bonding layer, and a positive C layer, wherein the retardation layer bonding layer is 1 GPa It has a modulus of elasticity of the above, and the circular polarizing plate has a crack strain of 15% or more. A circular polarizing plate is provided, which is the elongation rate (%) when a crack occurs in the circular polarizing plate.

Description

circular polarizer

The present invention relates to a circular polarizing plate, and particularly to a thin bending-resistant circular polarizing plate.

In order to solve problems such as reflection of external light or reflection of a background, a circularly polarizing plate is provided on the viewing surface of the organic EL display. A circular polarizing plate generally exhibits a circular polarizing function by laminating a λ/4 retardation layer on a linear polarizing layer. A positive C layer is bonded to the λ/4 retardation layer for the purpose of optical compensation, such as preventing coloring of reflected light when viewed obliquely.

In recent years, thin circular polarizing plates having excellent bending resistance are required for use in bendable organic EL displays. In the thin circular polarizing plate, a liquid crystal coating type is usually used as retardation layers such as λ/4 retardation layer and positive C layer. The phase difference layer of the liquid crystal coating type refers to a phase difference layer formed by applying a composition for forming a phase difference layer on an alignment layer and curing the coating film.

Patent Literature 1 describes a liquid crystal coating type elliptically polarizing plate having a polarizing layer, a λ/4 retardation layer, a homeotropic alignment liquid crystal cured layer, and a reinforcing layer. In this elliptically polarizing plate, mechanical strength is improved by introducing a reinforcing layer between the polarizing layer and the λ/4 retardation layer, and excellent processing properties such that problems such as waviness do not occur at the cut end surface when the liquid crystal cured film is cut are obtained. obtained (Examples 7 to 9, Comparative Example 2).

In Patent Document 2, a base material, a polarizing coating layer formed on one surface of the base material, a first adhesive layer formed on the polarizing coating layer, a first phase difference coating layer formed on the first adhesive layer, and a first phase difference coating layer formed on the first phase difference coating layer. It includes a second adhesive layer, a second retardation coating layer formed on the second adhesive layer, and a soft layer formed on the second retardation coating layer, and the soft layer has the formula:

[number 1]

[In the formula, the maximum stress represents the stress at the breaking point in the stress-strain graph, and the maximum strain represents the strain at the breaking point in the stress-strain graph.]

Described is a polarizing plate having crystal toughness defined by 1,000 to 40,000 MPa·%. In this circular polarizing plate, the crystal toughness of the soft layer corresponding to the reinforcing layer in Patent Literature 1 is specified as described above, and an appropriate film satisfying this is selected to give the circular polarizing plate flexibility.

Japanese Unexamined Patent Publication No. 2019-20725 Korean Patent Publication No. 10-1933765

When a circular polarizing plate provided with a liquid crystal coating type retardation layer is bent (eg, in-folding method) with a small bending radius (eg, a bending radius of 1 mm), the retardation layer is deteriorated in the bent portion. , there is a problem that it is easy to break.

Patent Literature 1 does not mention the improvement of the bending resistance of the polarizing plate. Further, in the circular polarizing plate described in Patent Document 2, a relatively rigid resin such as bifunctional urethane acrylate, triacetyl cellulose, or polyethylene terephthalate is used as a soft layer corresponding to the reinforcing layer, and flexible ( flexibility) is insufficient.

The present invention solves the problem of the conventional circular polarizing plate, and its object is to provide a circular polarizing plate having excellent flexibility and excellent bending resistance.

The present invention,

A circular polarizing plate having a polarization layer comprising a linear polarization layer and a retardation layer comprising a liquid crystal coating type retardation layer,

The circular polarizing plate has a crack strain of 15% or more,

The crack strain is the elongation rate when both ends of a circular polarizing plate having a length of 5 cm and a width of 10 mm are stretched at a rate of 4 mm / min in the longitudinal direction, and cracks occur in the circular polarizing plate ( %)sign,

A circular polarizing plate is provided.

In one aspect, the retardation layer includes a λ/4 retardation layer, a retardation layer bonding layer, and a positive C layer.

In one aspect, the said retardation layer bonding layer has an elastic modulus of 1 GPa or more.

In one aspect, the said retardation layer bonding layer has a thickness of 1-5 micrometers.

In one aspect, the positive C layer is a phase difference layer of a liquid crystal application type.

In one aspect, the retardation layer has a reinforcing layer on at least one surface thereof.

In one aspect, the reinforcing layer is formed on top of the retardation layer.

In one aspect, the reinforcing layer is formed below the retardation layer.

In one aspect, the reinforcing layer is formed above and below the retardation layer.

In one aspect, the said circularly polarizing plate has a thickness of 5-50 micrometers.

In one embodiment, the circular polarizing plate has a polarizing layer inside, and when the operation of bending and unfolding 180 degrees with a bending radius of 1 mm is repeatedly performed 300,000 times, cracks or fractures do not occur in the retardation layer. have flexibility.

According to the present invention, a circular polarizing plate having excellent flexibility and excellent bending resistance is provided. The circular polarizing plate of the present invention can be bent with a small bending radius such as, for example, a bending radius of 1 mm. Further, in the circular polarizing plate of the present invention, no cracks or fractures occur in the retardation layer when the operation of bending and unfolding by 180° with a bending radius of 1 mm with the polarizing layer facing inside is repeated 300,000 times.

1 is a cross-sectional view showing the structure of a circular polarizing plate according to an embodiment of the present invention.
2 is a cross-sectional view showing the structure of a circular polarizing plate according to another embodiment of the present invention.
3 is a cross-sectional view showing the structure of a circular polarizing plate according to another embodiment of the present invention.
4 is a cross-sectional view showing the structure of a circular polarizing plate according to another embodiment of the present invention.
5 is a cross-sectional view showing a method of static bending durability test (mandrel bending test) of the circular polarizing plate of the present invention. (a) shows the preparation phase of the test, and (b) shows it during the test.

1 is a cross-sectional view showing an example of the structure of a circular polarizing plate 100 according to the present invention. The circular polarizing plate 100 shown in FIG. 1 includes a polarizing layer 10, an adhesive agent layer 20, and a retardation layer 30 in this order from the polarizing layer side. The polarization layer 10 includes a linear polarization layer 12 . The retardation layer 30 includes a λ/4 retardation layer 31, a retardation layer bonding layer 32, and a positive C layer 33 in this order from the polarization layer side. A front plate may be further laminated on the polarizing layer 10 side of the circular polarizing plate 100 .

[Polarization layer 10]

In the embodiment of FIG. 1 , the polarization layer 10 includes a protective layer 11, a linear polarization layer 12, and an overcoat layer 13 in this order from the outside to be viewed.

(protective layer 11)

The protective layer 11 is provided on the linear polarization layer and has a function of protecting the linear polarization layer 12 . The material of the protective layer is not particularly limited, but examples thereof include cyclic polyolefin resins, triacetyl cellulose (TAC), cellulose acetate resins made of resins such as diacetyl cellulose, polyethylene terephthalate, and polyethylene. and resins known in the art such as polyester-based resins composed of resins such as naphthalate and polybutylene terephthalate, polycarbonate-based resins, (meth)acrylic-based resins, and polypropylene-based resins. The thickness of the protective layer is usually 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less, and usually 5 μm or more, preferably 20 μm or more, from the viewpoint of increasing flexibility. The protective layer may be a film, and the film-like protective layer may have a phase difference. When the protective layer is a film, the linear polarization layer and the protective layer can be laminated via an adhesive layer or an adhesive layer.

The protective layer 11 may be an overcoat layer described later, or may be an organic material layer or an inorganic material layer. The organic material layer or the inorganic material layer may be a layer formed by coating. The organic material layer may be formed using a composition for forming a protective layer, for example, a (meth)acrylic resin composition, an epoxy resin composition, a polyimide resin composition, or the like. The composition for forming a protective layer may be of an active energy ray curing type or a thermosetting type.

The inorganic material layer can be formed of, for example, silicon oxide. When the protective layer 11 is an organic material layer, the protective layer may be what is called a hard coating layer.

When the protective layer 11 is an organic material layer, the protective layer can be produced by, for example, applying an active energy ray-curable composition for forming a protective layer onto a base film and curing by irradiation with active energy. As for the base film, the description of the plate-shaped body made of resin of the front plate described later is applied. The base film is usually peeled off and removed. As a method of applying the composition for forming a protective layer, for example, a bar coating method, a spin coating method, and the like are exemplified. When the protective layer 11 is an inorganic material layer, the protective layer can be formed by, for example, sputtering or vapor deposition.

When the protective layer 11 is an organic material layer or an inorganic material layer, the thickness of the protective layer 11 may be, for example, 0.1 µm or more and 10 µm or less, and is preferably 0.5 µm or more and 5 µm or less.

(Linear polarization layer 12)

The linear polarization layer 12 is a layer having a function of selectively transmitting linearly polarized light in one direction, which is composed of unpolarized light rays such as natural light. The linearly polarizing layer 12 includes, for example, a cured product of a polymerizable liquid crystal compound and a dichroic dye, and the dichroic dye is dispersed and oriented in the cured product of the polymerizable liquid crystal compound. Compared with a linear polarization layer in which a dichroic dye such as iodine is adsorbed and oriented in a polyvinyl alcohol-based resin, such a linear polarization layer 12 has a small amount of shrinkage in a wet heat test, and thus a small dimensional change. Therefore, it can be suitably used for circular polarizing plates used under environments where moist heat durability is required.

A polymerizable liquid crystal compound is a compound that has a polymerizable reactive group and exhibits liquid crystallinity. The polymerizable reactive group is a group involved in the polymerization reaction, and is preferably a photopolymerizable reactive group. A photopolymerizable reactive group refers to a group capable of participating in a polymerization reaction by an active radical or an acid generated from a photopolymerization initiator. Examples of the photopolymerizable functional group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, and an oxetanyl group. . Among these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferable, and an acryloyloxy group is more preferable. The type of the polymerizable liquid crystal compound is not particularly limited, and rod-shaped liquid crystal compounds, disk-shaped liquid crystal compounds, and mixtures thereof can be used. The liquid crystal of the polymerizable liquid crystal compound may be a thermotropic liquid crystal or a lyotropic liquid crystal, and a nematic liquid crystal or a smectic liquid crystal may be used as a phase-order structure.

A dichroic dye refers to a dye having a property in which the absorbance in the direction of the major axis of the molecule and the absorbance in the direction of the minor axis of the molecule are different from each other. As the dichroic dye, it is preferable to have an absorption maximum wavelength (λMAX) in the range of 300 to 700 nm. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes. Among these, azo dyes are preferable. Examples of the azo dye include monoazo dye, bisazo dye, trisazo dye, tetrakisazo dye, and stilbenazo dye, and are preferably bisazo dye and trisazo dye. Although a dichroic dye may be used individually or may be used in combination of 2 or more types, it is preferable to use it in combination of 3 or more types. In particular, it is preferable to combine three or more types of azo compounds. A part of the dichroic dye may have a reactive group and may also have liquid crystallinity.

For the linear polarization layer 12, for example, a composition for forming a linear polarization layer containing a polymerizable liquid crystal compound and a dichroic dye is coated on an alignment layer formed on the protective layer 11, and the polymerizable liquid crystal It can be formed by polymerizing and curing a compound. Alternatively, the linear polarization layer 12 may be formed by applying a composition for forming a linear polarization layer onto the substrate layer to form a coating film, and stretching the coating film together with the substrate layer.

The alignment layer has an orientation regulating force that aligns the polymerizable liquid crystal compound in a desired direction. Examples of the orientation layer include an orientation polymer layer formed of an orientation polymer, an optical orientation polymer layer formed of an optical orientation polymer, and a groove orientation layer having a concave-convex pattern and a plurality of grooves on the surface of the layer. The thickness of the alignment layer is usually 10 to 500 nm, preferably 10 to 200 nm.

The orienting polymer layer can be formed by applying a composition obtained by dissolving an orienting polymer in a solvent to a substrate layer or a substrate layer for phase difference layer, removing the solvent, and performing a rubbing treatment if necessary. In this case, the orientation regulating force can be arbitrarily adjusted in the orientation polymer layer formed of the orientation polymer depending on the surface state of the orientation polymer and the rubbing conditions.

The photo-alignment polymer layer can be formed by applying a composition containing a polymer or monomer having a photoreactive group and a solvent to the substrate layer or the retardation layer substrate layer and irradiating with polarized light. In this case, the orientation regulating force can be arbitrarily adjusted in the photo-orientation polymer layer according to the polarized light irradiation conditions for the photo-orientation polymer.

For example, the groove alignment layer is a method of forming a concave-convex pattern by performing exposure, development, etc. through an exposure mask having a pattern-shaped slit on the surface of the photosensitive polyimide film, a plate-shaped master having grooves on the surface, and an active A method of forming an uncured layer of energy ray-curable resin, transferring this layer to a substrate layer or a substrate layer for retardation layer, and curing the layer; It can be formed by a method of forming a layer of , forming irregularities by pressing a roll-shaped disk having irregularities on the layer, and curing the layer.

As a composition for forming a linear polarization layer containing a polymerizable liquid crystal compound and a dichroic dye, and a method for producing a linear polarization layer using this composition, Japanese Unexamined Patent Publication No. 2013-37353, Japanese Unexamined Patent Publication No. 2013-33249, Japan What was described in Unexamined-Japanese-Patent No. 2017-83843 etc. is mentioned. The composition for forming a linear polarizing layer may further contain additives such as a solvent, a polymerization initiator, a crosslinking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer, in addition to the polymerizable liquid crystal compound and the dichroic dye. You may use these components individually or in combination of 2 or more types, respectively.

The thickness of the linear polarization layer 12 is, for example, 0.3 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 5 μm.

(over coating layer 13)

The overcoat layer 13 is provided for the purpose of protecting the linear polarization layer 12, suppressing migration of dichroic dyes in the linear polarization layer 12, and imparting barrier properties to oxygen and moisture. The overcoat layer 13 may be provided on both sides of the linear polarization layer 12 . The overcoat layer 13 can be formed by, for example, applying a material (composition) for forming the overcoat layer 13 to the surface of the linear polarization layer 12 .

The overcoat layer 13 preferably has excellent solvent resistance, transparency, mechanical strength, thermal stability, shielding properties, isotropy, and the like. As a material constituting the overcoat layer 13, a photocurable resin, a water-soluble polymer, etc. are mentioned, for example.

Examples of the photocurable resin include (meth)acrylic resins, urethane resins, (meth)acrylic urethane resins, epoxy resins, and silicone resins. Examples of the water-soluble polymer include poly(meth)acrylamide polymers; vinyl alcohol-based polymers such as polyvinyl alcohol, ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, and (meth)acrylic acid or its anhydride-vinyl alcohol copolymers; carboxyvinyl-based polymers; polyvinylpyrrolidone; All classification; sodium alginate; A polyethylene oxide type polymer etc. are mentioned.

The thickness of the overcoat layer 13 is, for example, 0.1 to 5 μm, preferably 0.3 to 4 μm, and more preferably 0.5 to 3 μm.

[adhesive adhesive layer 20]

In the embodiment of FIG. 1 , the adhesive agent layer 20 is a layer that bonds the polarization layer 10 and the retardation layer 30 together. The adhesive layer 20 is an adhesive layer or an adhesive layer. Moreover, an adhesive means the adhesive agent which has pressure-sensitive adhesiveness. It is preferable that the adhesive agent layer 20 is an adhesive layer.

When the pressure-sensitive adhesive layer 20 is a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is composed of, for example, a pressure-sensitive adhesive composition containing a resin such as (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether as a main component. . Among these, the adhesive composition which uses (meth)acrylic-type resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is preferable. The pressure-sensitive adhesive composition may be of an active energy ray curing type or a thermosetting type.

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

The pressure-sensitive adhesive composition may be composed of the base polymer alone, but usually further contains a crosslinking agent. Examples of the crosslinking agent include those that form a metal carboxylic acid salt with a carboxyl group as a divalent or higher metal ion; As a polyamine compound, what forms an amide bond with a carboxy group; Forming an ester bond with a carboxyl group as a polyepoxy compound or polyol; Examples of the polyisocyanate compound include those forming an amide bond with a carboxy group. Among these, polyisocyanate compounds are preferred.

The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by being irradiated with active energy rays such as ultraviolet rays or electron beams, and has adhesiveness even before active energy ray irradiation, so that it can adhere to adherends such as films. It is hardened by irradiation of active energy rays, and the adhesive force can be adjusted. It is preferable that the active energy ray curable adhesive composition is an ultraviolet curable type. As described above, the active energy ray-curable pressure-sensitive adhesive composition contains an active energy ray polymerizable compound in addition to the base polymer and the crosslinking agent. A photopolymerization initiator, a photosensitizer, and the like are also included as appropriate.

The pressure-sensitive adhesive composition includes fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, adhesiveness imparting agents, fillers (metal powder or other inorganic powders, etc.), antioxidants , additives such as ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, and photopolymerization initiators may be further included.

The pressure-sensitive adhesive layer can be formed by applying a diluted organic solvent solution of the pressure-sensitive adhesive composition onto a substrate and drying it. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the formed pressure-sensitive adhesive layer with an active energy ray.

The thickness of the pressure-sensitive adhesive layer is, for example, 0.1 to 30 µm, preferably 0.5 to 20 µm, and more preferably 1 to 10 µm.

When the adhesive layer 20 is an adhesive layer, the adhesive layer is formed of, for example, a water-based adhesive or an active energy ray curable adhesive.

Examples of the water-based adhesive include a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive composition, and the like, and a polyvinyl alcohol-based resin aqueous solution is preferable.

When the water-based adhesive contains a polyvinyl alcohol-based resin, the content of the polyvinyl alcohol-based resin is preferably 1 part by mass or more and 10 parts by mass or less, and preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of water. more preferable

A polyhydric aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, a zinc compound, or the like may be added as an additive to the water-based adhesive.

The water-based adhesive preferably contains a curable component such as a metal salt of glyoxylic acid, glyoxal, or a water-soluble epoxy resin and/or a crosslinking agent in order to improve adhesion. The metal salt of glyoxylic acid is preferably an alkali metal salt or an alkaline earth metal salt, and examples thereof include sodium glyoxylate, potassium glyoxylate, magnesium glyoxylate and calcium glyoxylate. As the water-soluble epoxy resin, epichlorohydrin is reacted with polyamideamine obtained by reaction of, for example, polyalkylene polyamines such as diethylenetriamine and triethylenetetramine with dicarboxylic acids such as adipic acid. The resulting polyamide polyamine epoxy resin can be preferably used.

An active energy ray-curable adhesive contains an active energy ray-curable compound. Examples of active energy ray-curable compounds include cationically polymerizable compounds and radically polymerizable compounds. When a cationically polymerizable compound or a radically polymerizable compound is included, an effect of increasing the hardness of the adhesive layer can be expected.

As a cationically polymerizable compound, an oxetane compound or an epoxy compound etc. are mentioned, for example. The content of the cationically polymerizable compound is preferably 10 parts by mass or more and 99 parts by mass or less, and more preferably 40 parts by mass or more and 99 parts by mass or less with respect to 100 parts by mass of the active energy ray-curable adhesive composition.

The active energy ray-curable adhesive may contain only one or two or more oxetane compounds. The active energy ray curing type adhesive may contain only 1 type of epoxy compound, or may contain 2 or more types of epoxy compounds.

Examples of the radically polymerizable compound include (meth)acrylic compounds and (meth)acrylamide compounds.

As a (meth)acrylic compound, a (meth)acrylate monomer having at least one (meth)acryloyloxy group in a molecule, a (meth)acrylate oligomer having at least two (meth)acryloyloxy groups in a molecule, and the like can be heard These may be used independently, respectively, and may use 2 or more types together.

Examples of (meth)acrylamide-based compounds include N-substituted (meth)acrylamide compounds. An N-substituted (meth)acrylamide compound is a (meth)acrylamide compound having a substituent at the N-position. A typical example of the substituent is an alkyl group. Substituents at the N-position may be bonded to each other to form a ring, and -CH ₂ - constituting this ring may be substituted with an oxygen atom. In addition, a substituent such as an alkyl group or an oxo group (=O) may be bonded to the carbon atoms constituting the ring. N-substituted (meth)acrylamide can generally be produced by reaction of (meth)acrylic acid or its chloride with a primary or secondary amine.

The content of the radical polymerizable compound is preferably 1 part by mass or more and 70 parts by mass or less, and more preferably 10 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the active energy ray curable adhesive.

The active energy ray-curable adhesive may contain only one or two or more radically polymerizable compounds.

The active energy ray curable adhesive may further contain a cationic polymerization initiator or a radical polymerization initiator. The active energy ray-curable adhesive may contain only one type of polymerization initiator, or may contain two or more types.

(other additives)

The active energy ray curing adhesive may also contain a photosensitizer, a solvent, a leveling agent, an antioxidant, a photostabilizer, an ultraviolet absorber, and the like.

The thickness of the adhesive layer is, for example, 0.1 to 5 μm, preferably 0.5 to 3 μm.

[Phase difference layer 30]

The retardation layer includes a liquid crystal coating type retardation layer. Since the liquid crystal coating type retardation layer is thin, cracks tend to occur easily when bent, but according to the present invention, cracks during bending can be prevented. 1, the retardation layer 30 includes a λ/4 retardation layer 31, a retardation layer bonding layer 32, and a positive C layer 33 in this order from the polarization layer 10 side do. In another embodiment, the retardation layer includes a λ/2 retardation layer, a retardation layer bonding layer, and a λ/4 retardation layer in this order from the polarization layer 10 side.

(λ/4 phase difference layer)

The λ/4 phase difference layer 31 has a function of imparting a phase difference of λ/4 to incident light.

The λ/4 retardation layer 31 may have, for example, an in-plane retardation value of 100 to 160 nm for light having a wavelength of 550 nm. The λ/4 retardation layer 31 contains a cured product of a polymerizable liquid crystal compound. The λ/4 phase difference layer 31 may have an orientation layer. As the polymerizable liquid crystal compound, a polymerizable liquid crystal compound used for the linear polarization layer 12 can be used, for example. The polymerizable liquid crystal compound forming the linear polarization layer 12 and the polymerizable liquid crystal compound forming the λ/4 retardation layer 31 may be of the same type or may be of different types.

The λ/4 retardation layer 31 is preferably a liquid crystal coating type retardation layer from the viewpoint of thinning.

The λ/4 retardation layer of the liquid crystal coating type can be formed by applying a composition for forming a retardation layer containing a polymerizable liquid crystal compound onto an alignment layer for a retardation layer, and polymerizing and curing the polymerizable liquid crystal compound.

The thickness of the λ/4 retardation layer 31 is, for example, 0.3 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 5 μm.

(Phase difference layer bonding layer 32)

The retardation layer bonding layer 32 is a layer bonding the λ/4 retardation layer 31 and the positive C layer 33, or a layer bonding the λ/2 retardation layer and the λ/4 retardation layer. The retardation layer bonding layer 32 is formed by the same method with the same material as the adhesive agent layer 20. The adhesive agent layer 20 is preferably an adhesive layer, and is more preferably formed of an active energy ray curable adhesive.

The thickness of the retardation layer bonding layer 32 is, for example, 0.1 to 30 μm, preferably 0.5 to 20 μm, more preferably 1 to 10 μm, still more preferably 1 to 5 μm or less. When the thickness of the retardation layer bonding layer 32 is less than 1 μm, the bending resistance of the obtained circular polarizing plate may be insufficient, and when it exceeds 30 μm, the flexibility of the obtained circular polarizing plate may be insufficient.

The modulus of elasticity of the retardation layer bonding layer is measured by the method described in Examples described later. The elastic modulus of the retardation layer bonding layer may be a value at a temperature of 25°C.

The elastic modulus of the retardation layer bonding layer 32 is 1 GPa or more, preferably 1.5 to 6 GPa, more preferably 2 to 5 GPa. When the modulus of elasticity of the retardation layer bonding layer 32 is less than 1 GPa, the resulting circular polarizing plate may have insufficient bending resistance. When the modulus of elasticity of the retardation layer bonding layer 32 is too large, the flexibility of the circular polarizing plate may become insufficient.

(Positive C layer 33)

The positive C layer 33 is a layer that compensates the optical function of the circular polarizing plate, such as preventing reflected light from appearing colored when the surface is viewed from an oblique direction. "Positive C" is the refractive index in the X-axis direction along the layer plane of the positive C layer n _x , the refractive index in the Y-axis direction orthogonal to the X-axis in the direction along the layer plane n _y , the refractive index in the layer thickness direction n _z , it refers to a property that satisfies the relationship of n _z > n _x ≒ n _y (optical axis: n _z direction).

The positive C layer 33 contains a cured product of a polymerizable liquid crystal compound. The positive C layer 33 may have an alignment layer. As the polymerizable liquid crystal compound, a polymerizable liquid crystal compound used for the linear polarization layer 12 can be used, for example. The polymerizable liquid crystal compound forming the linear polarization layer 12 and the polymerizable liquid crystal compound forming the positive C layer 33 may be of the same type or may be of different types. Examples of the polymerizable liquid crystal compound include discotic liquid crystal materials (discotic liquid crystal materials) and rod-like liquid crystal materials. Dispersibility can be controlled by changing the main chain and side chain, and the wavelength dispersion can also be adjusted. Since it is easy, it is more preferable to use a rod-shaped liquid crystal material.

From the viewpoint of thinning, the positive C layer 33 is preferably a liquid crystal coating type retardation layer.

The positive C layer of the liquid crystal coating type can be formed by applying a composition for forming a phase difference layer containing a polymerizable liquid crystal compound onto the alignment layer for a phase difference layer, and polymerizing and curing the polymerizable liquid crystal compound.

The thickness of the positive C layer 33 is, for example, 0.01 to 10 μm, preferably 0.1 to 8 μm, and more preferably 0.3 to 5 μm.

(λ/2 phase difference layer)

The λ/2 phase difference layer has a function of imparting a phase difference of λ/2 to incident light. The λ/2 retardation layer may have, for example, an in-plane retardation value of 200 to 350 nm for light having a wavelength of 550 nm. The λ/2 retardation layer may contain a cured product of a polymerizable liquid crystal compound. The λ/2 phase difference layer may have an orientation layer. As the polymerizable liquid crystal compound, for example, a polymerizable liquid crystal compound used for the λ/4 retardation layer can be used. The polymerizable liquid crystal compound forming the λ/4 retardation layer and the polymerizable liquid crystal compound forming the λ/2 retardation layer may be of the same type or may be of different types.

The λ/2 retardation layer is preferably a liquid crystal coating type retardation layer from the viewpoint of thinning. The λ/2 retardation layer of the liquid crystal application type can be formed by applying a composition for forming a retardation layer containing a polymerizable liquid crystal compound onto an alignment layer for a retardation layer, and polymerizing and curing the polymerizable liquid crystal compound.

The thickness of the λ/2 retardation layer is, for example, 0.3 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 5 μm.

[Manufacture of circular polarizing plate 100]

In the embodiment of FIG. 1 , the circular polarizing plate 100 can be manufactured, for example, by the following method. That is, the polarization layer 10 is obtained by forming the linear polarization layer 12 and the overcoat layer 13 on the protective layer 11 . A λ/4 retardation layer 31 is formed on a separately prepared substrate, and a positive C layer 33 is formed on a separately prepared substrate. Next, the λ/4 phase difference layer 31 and the positive C layer 33 are bonded using the adhesive agent for the phase difference layer bonding layer 32 to obtain the phase difference layer 30 .

After that, the base material on the side of the λ/4 retardation layer 31 is removed, and the adhesive agent for the adhesive layer 20 is used, and the λ of the overcoat layer 13 of the polarization layer 10 and the retardation layer 30 /4 retardation layer 31 is bonded to obtain circular polarizing plate 100.

[Other Embodiments]

2 to 4 are cross-sectional views showing the structure of a circular polarizing plate as another embodiment of the present invention. 2 to 4, the retardation layer 30 has a reinforcing layer on at least one surface thereof. In the circular polarizing plate 200 of FIG. 2 , the first reinforcing layer 41 is formed on top of the retardation layer 30 . In the circular polarizing plate 300 of FIG. 3 , the second reinforcing layer 42 is formed below the retardation layer 30 . In the circular polarizing plate 400 of FIG. 4 , the first reinforcing layer 41 is formed on the top of the retardation layer 30 and the second reinforcing layer 42 is formed on the bottom of the retardation layer 30 . The circularly polarizing plates of Figs. 2 to 4 exhibit more excellent bending resistance by having a reinforcing layer.

The reinforcing layer is formed of the same material as the adhesive layer 20 by the same method. The reinforcing layer is preferably formed using the active energy ray curable adhesive described above. For example, after forming the retardation layer 30 and before attaching it to the polarization layer 10, on the outer surface of the retardation layer 30, that is, the exposed surface of the λ/4 retardation layer 31, a first The first reinforcing layer 41 can be formed by applying an adhesive for the reinforcing layer 41 . In addition, after forming the retardation layer 30, the second reinforcing layer 42 is coated with an adhesive agent for the second reinforcing layer 42 on the inner side of the retardation layer 30, that is, the exposed surface of the positive C layer 33. (42) can be formed. If necessary, the adhesive may be cured by heating the adhesive or irradiating the adhesive with active energy rays.

The thickness of the reinforcing layer is, for example, 0.1 to 30 µm, preferably 0.3 to 10 µm, and more preferably 0.5 to 5 µm. When the thickness of the reinforcing layer is less than 0.1 μm, the bending resistance of the obtained circular polarizing plate may be insufficient, and when it exceeds 30 μm, the flexibility of the obtained circular polarizing plate may be insufficient.

The elastic modulus of the reinforcing layer is, for example, 1 GPa or more, preferably 1.5 to 6 GPa, and more preferably 2 to 5 GPa. When the modulus of elasticity of the reinforcing layer is less than 1 GPa, the bending resistance of the obtained circularly polarizing plate may be insufficient. If the modulus of elasticity of the reinforcing layer is too large, the flexibility of the circularly polarizing plate may become insufficient. The modulus of elasticity of the reinforcing layer is measured by the method described in Examples described later. The elastic modulus of the reinforcing layer may be a value at a temperature of 25°C.

[Circular polarizing plate]

The circular polarizing plate of the present invention has a thickness of 100 μm or less, preferably 5 to 50 μm, more preferably 10 to 30 μm, from the viewpoint of easily imparting excellent flexibility. When the thickness of the circularly polarizing plate exceeds 150 μm, flexibility may be insufficient.

The circular polarizing plate of the present invention has a crack strain of 15% or more, preferably 18% or more, more preferably 20% or more, still more preferably 26% or more, from the viewpoint of having excellent bending resistance. The upper limit of the crack strain is not particularly limited, but the crack strain may be, for example, 50% or less, or 35% or less. When the crack strain of the circularly polarizing plate is less than 15%, the bending resistance may be insufficient. Here, the crack strain refers to the limit elongation (%) at which cracks do not occur when the material is stretched in one direction under predetermined conditions. Crack strain measurement conditions are as described in Examples. Crack strain can be prepared by the material, thickness, etc. of the layer which comprises a circular polarizing plate. For example, crack strain can be increased by having a reinforcing layer in the retardation layer or by increasing the number of reinforcing layers. Moreover, crack strain can also be increased by heat-processing a circularly polarizing plate at 50-100 degreeC for 0.5-24 hours, for example.

(front panel)

A front plate (not shown in the drawings) is generally disposed above the protective layer 11 and constitutes the outermost side of the polarization layer 10 . The front plate is a plate-like layer having integrity and light transmission properties. The front plate may be composed of two or more layers. Examples of the front plate include a resin-made plate-like body (for example, a resin plate, a resin sheet, a resin film), a glass-made plate-like body (for example, a glass plate), and a laminate of a resin-made plate-like body and a glass-made plate-like body. sieve, and the like.

In the case where the front plate is a resin plate-shaped body, examples of the material include acrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; polyolefin resins such as polyethylene, polypropylene, polymethylpentene and polystyrene; cellulosic resins such as triacetyl cellulose, acetyl cellulose butyrate, propionyl cellulose, butyryl cellulose and acetyl propionyl cellulose; polyvinyl resins such as ethylene-vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol and polyvinyl acetal; sulfone-based resins such as polysulfone and polyethersulfone; ketone-based resins such as polyether ketone and polyether ether ketone; polyetherimide; polycarbonate-based resin; polyester-based resin; polyimide-based resin; polyamideimide-based resins; and polyamide-based resins. These polymers can be used individually or in mixture of 2 or more types. Among these, it is preferable to use a polycarbonate-based resin, a polyester-based resin, a polyimide-based resin, a polyamide-imide-based resin, or a polyamide-based resin from the viewpoint of improving strength and transparency.

The front plate may be a film made of the above resin, or may have a hard coat layer on at least one side of the film. The hard coat layer may be formed on the outer surface of the film or on both surfaces. By providing a hard coat layer, it can be set as a resin film with improved hardness and scratch resistance. The hard coat layer is, for example, a cured layer of an ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coat layer may contain additives in order to improve hardness. The additive is not particularly limited as long as it does not impair the light transmittance of the front plate, and inorganic fine particles, organic fine particles, or a mixture thereof may be used.

When the circular polarizing plate 100 is used for a display panel, the front plate may have a function as a window film in the display panel. The front plate may further have a function as a touch sensor, a blue light cut function, a viewing angle adjustment function, and the like.

The front plate has a thickness of, for example, 1 to 100 µm, preferably 10 to 70 µm, and more preferably 20 to 60 µm.

(rear plate)

A back plate (not shown in the drawings) may be laminated below the retardation layer 30 with an adhesive layer interposed therebetween. As the back plate, a plate-shaped body capable of transmitting light or a component used in a normal display device, or the like can be used.

The thickness of the back plate may be, for example, 5 µm to 2000 µm, preferably 10 µm to 1000 µm, and more preferably 15 µm to 500 µm.

The plate-like body used for the back plate may be composed of only one layer or may be composed of two or more layers, and those exemplified for the plate-like body described in the front plate can be used.

As a component used for the normal display device used for the back plate, a separator, a touch sensor panel, an organic EL display element, etc. are mentioned, for example. The lamination order of the components in the display device is, for example, front plate/circular polarizing plate/separator, front plate/circular polarizing plate/organic EL display element, front plate/circular polarizing plate/touch sensor panel/organic EL display element, front surface plate/touch sensor panel/circular polarizing plate/organic EL display element; and the like.

Example

Hereinafter, the present invention will be described in more detail by examples. The present invention is not limited to these examples. In this Example, unless otherwise specified, the unit "parts" of the ratio of materials to be blended is based on weight.

(a) Method for measuring layer thickness

The thickness of the layer constituting the circular polarizing plate was measured using a contact-type film thickness measuring device (manufactured by Nikon Corporation "MS-5C" (trade name)). However, the polarization layer and the orientation layer were measured using a laser microscope ("OLS3000" (trade name) manufactured by Olympus Corporation).

(b) Method for measuring elastic modulus (G')

In the case where the adhesive layer 20 and the reinforcing layer were adhesive layers, the adhesive layers were stacked so as to have a thickness of 150 μm, and samples were produced. The elastic modulus (G') measured the storage elastic modulus using a rheometer ("MCR-301" (trade name) manufactured by Anton Parr). The measurement conditions were a temperature of 25°C, a stress of 1%, and a frequency of 1 Hz.

Further, when the adhesive layer 20 and the reinforcing layer are adhesive layers other than the adhesive layer, a COP film (manufactured by Zeon Corporation, thickness 50 μm) is laminated on a coating film obtained by coating an adhesive composition on glass (thickness 1.0 mm). did. Then, with respect to the coating film, using an ultraviolet irradiation device (manufactured by Fusion UV Systems Inc., equipped with an H valve of an electrodeless ultraviolet lamp), the light irradiation intensity is 400 mW / cm 2 and the cumulative light amount at a wavelength of 280 to 320 nm Ultraviolet rays were irradiated so as to become 1500 mJ/cm 2 , and the adhesive composition was cured to obtain a laminated sheet having a layer structure of glass/adhesive layer/COP film. After peeling off the COP film from the laminated sheet, the exposed adhesive layer was measured for compressive modulus using a Nano Indenter (HM-500, manufactured by Fisher Instruments) under the conditions of a temperature of 25°C, a relative humidity of 50%, and a pressure of 1 mN. did For the indenter, a Berkovich triangular indenter was used.

<Production Example 1>

(Manufacture of polarization layer 10)

Preparation of composition for forming alignment layer

A solution in which a polymer having a photoreactive group represented by the following structural formula was dissolved in cyclopentanone at a concentration of 5% was prepared as a composition for forming an orientation layer (1).

[Tue 1]

Preparation of a composition for forming a linear polarization layer

Compound (1-1) and compound (1-2) represented by the following structures were used as polymerizable liquid crystal compounds. Compound (1-1) and compound (1-2) are described in Lub et al. Recl. Trav. Chim. It was synthesized by the method described in Pays-Bas, 115, 321-328 (1996).

·Compound (1-1)

[Tue 2]

·Compound (1-2)

[Tue 3]

Compound (2-1a), compound (2-1b), and compound (2-2) represented by the following structures were used as dichroic dyes.

·Compound (2-1a)

[Tuesday 4]

·Compound (2-1b)

[Tuesday 5]

·Compound (2-2)

[Tue 6]

The composition for forming a linear polarization layer is 75 parts of compound (1-1), 25 parts of compound (1-2), and the above formulas (2-1a), (2-1b) and (2-2) as dichroic dyes. 2.5 parts each of the appearing azo dye, 6 parts of 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure369, manufactured by BASF Corporation) as a polymerization initiator, and polyacrylic as a leveling agent It prepared by mixing 1.2 parts of rate compounds (BYK-361N, manufactured by BYK) with 400 parts of toluene as a solvent, and stirring the obtained mixture at 80 degreeC for 1 hour.

Preparation of a composition for forming an overcoat layer

The composition for forming an overcoat layer for forming an overcoat layer is 100 parts of water, 3 parts of polyvinyl alcohol resin powder (KL-318, manufactured by KURARAY CO., LTD, average degree of polymerization 18000), polyamide epoxy resin (SR650 (SR650 ( 30), manufactured by Sumika Chemtex Company, Limited) was prepared by mixing 1.5 parts.

Fabrication of the laminate

A triacetyl cellulose (TAC) film (KC2UA, manufactured by KONICA MINOLTA, INC., thickness: 25 μm) was used as the protective layer 11, and corona treatment was performed on this under conditions of an output of 0.3 kW and a processing speed of 3 m/min. did. Thereafter, the composition for forming an orientation layer prepared above (1) was applied to the corona-treated surface of the film by a bar coating method, and was heat-dried for 1 minute in a drying oven at a temperature of 80°C. The obtained film was passed through a wire grid (UIS-27132##, manufactured by Ushio Inc.) and irradiated with ultraviolet rays adjusted so that the cumulative light amount at a wavelength of 365 nm was 100 mJ/cm 2 to form an alignment layer having a thickness of 100 nm. got it Thereafter, the composition for forming a linear polarizing layer prepared above was applied to the alignment layer obtained by the bar coating method, and the film was heated and dried in a drying oven at a temperature of 120° C. for 1 minute and cooled to room temperature. This was irradiated with ultraviolet rays adjusted so that the amount of integrated light at a wavelength of 365 nm was 1200 mJ/cm 2 to form a linear polarization layer 12 having a thickness of 2.0 μm. On the formed linear polarizing layer, the above-prepared composition for forming an overcoat layer was applied by a bar coating method to a thickness after drying of 1.0 μm, and dried at a temperature of 80° C. for 3 minutes. With this procedure, the polarization layer 10 having the protective layer 11 (thickness of 25 μm), the linear polarization layer 12 (thickness of 2.0 μm), and the overcoat layer 13 (thickness of 1.0 μm) in this order was formed. manufactured

<Production Example 2>

(Preparation of pressure-sensitive adhesive for adhesive layer 20)

An acrylic resin was obtained by reacting 70 parts of butyl acrylate, 20 parts of methyl acrylate, 2.0 parts of acrylic acid, and 0.2 part of a radical polymerization initiator (2,2'-azobisisobutyronitrile) at 55°C while stirring in a nitrogen atmosphere. After that, 100 parts of the acrylic resin, 1.0 part of a crosslinking agent (“Colonate L” manufactured by TOSOH CORPORATION), and 0.5 part of a silane coupling agent (“X-12-981” manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed, Ethyl acetate was added so that the solid content concentration might be 10%, and an adhesive composition was obtained. The obtained adhesive composition was applied to the release-treated surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) subjected to release treatment using an applicator so that the thickness after drying was 5 μm. The coating layer was dried at 100°C for 1 minute to obtain a pressure-sensitive adhesive layer for the adhesive agent layer 20 with PET film.

Thereafter, another polyethylene terephthalate (PET) film (thickness: 38 μm) subjected to the release treatment was bonded to this pressure-sensitive adhesive layer, and cured for 7 days under conditions of a temperature of 23° C. and a relative humidity of 50% RH. The pressure-sensitive adhesive layer for the adhesive layer 20 had an elastic modulus (storage elastic modulus) of 0.7 MPa.

The PET film serving as the substrate was appropriately peeled off in the process of manufacturing the circular polarizing plate.

<Production Example 3>

(Manufacture of retardation layer 30)

Preparation of composition for forming λ/4 retardation layer 31

The composition for forming the λ/4 phase difference layer 31 for forming the λ/4 phase difference layer 31 was prepared by mixing each component shown below and stirring the obtained mixture at 80°C for 1 hour.

A compound represented by the following structural formula: 80 parts

[Tue 7]

A compound represented by the following structural formula: 20 parts

[Tue 8]

Polymerization initiator (Irgacure369, manufactured by BASF Corporation): 6 parts Leveling agent (BYK-361N, polyacrylate compound, manufactured by BYK): 0.1 part Solvent (cyclopentanone): 400 parts

Fabrication of λ/4 retardation layer 31

On a base material of a polyethylene terephthalate (PET) film (thickness: 100 μm), the composition for forming an orientation layer (1) was applied by a bar coating method, and then heated and dried in a drying oven at a temperature of 80° C. for 1 minute. Polarized UV irradiation treatment was performed on the obtained coating film to form an alignment layer. The polarization UV treatment was performed using a UV irradiation device (SPOT CURE SP-7, manufactured by Ushio Inc.) under conditions such that the amount of integrated light at a wavelength of 365 nm was 100 mJ/cm 2 . In addition, the polarization direction of polarized light UV was set to be 45° with respect to the absorption axis of the linearly polarized layer.

Next, on the formed alignment layer, the composition for forming a λ/4 phase difference layer was applied by a bar coating method, and after heating and drying in a drying oven at a temperature of 120° C. for 1 minute, it was cooled to room temperature. The obtained coating film was irradiated with ultraviolet rays adjusted so that the amount of integrated light at a wavelength of 365 nm was 1000 mJ/cm 2 to form a λ/4 retardation layer having a thickness of 2.0 μm, thereby obtaining a λ/4 retardation layer 31 with a PET film. . This λ/4 retardation layer exhibited reverse wavelength dispersion.

Fabrication of positive C layer 33

Polymerization was performed by mixing 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, dipentaerythritol triacrylate, and bis(2-vinyloxyethyl) ether at a ratio of 1:1:4:5 A composition for forming an alignment layer (2) was prepared by adding LUCIRIN TPO as an initiator at a rate of 4%.

As a composition for forming a positive C layer, a photopolymerizable nematic liquid crystal compound (manufactured by Merck, RMM28B) and a solvent were prepared and produced so that the solid content would be 1 to 1.5 g. The solvent is a mixed solvent obtained by mixing methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone (CHN) at a mass ratio (MEK: MIBK: CHN) of 35:30:35. used

A polyethylene terephthalate (PET) film having a thickness of 38 μm was prepared as a base material. The composition for forming an orientation layer (2) was applied to one side of the base material so as to have a film thickness of 3 μm, and ultraviolet rays were irradiated at 200 mJ/cm 2 to prepare an orientation layer.

On the alignment layer, a composition for forming a positive C layer was applied by die coating.

The coating amount was 4 to 5 g (wet). The coating film was dried at a drying temperature of 75°C and a drying time of 120 seconds. Thereafter, the coating film was irradiated with ultraviolet (UV) light to polymerize the polymerizable liquid crystal compound. When the thickness of the obtained coating film was measured with a laser microscope (LEXT, manufactured by Olympus Corporation), it was 4 µm in total with the orientation layer.

Combination of phase difference layer

70 parts of 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (trade name: CEL2021P, manufactured by Daicel Corporation), a photocationic curable resin, neopentyl glycol diglycidyl ether (EX-211, Nagase Chemtex Corporation) 20 parts, 2-ethylhexylglycidyl ether (EX-121, manufactured by Nagase Chemtex Corporation) 10 parts, photocationic polymerization initiator (CPI-100, manufactured by San-Apro Ltd.) 2.25 parts, photocationic polymerization After mixing the sensitizer in a compounding ratio of 2 parts of 1,4-diethoxynaphthalene, it was degassed to prepare an adhesive for phase difference layer bonding layer which is a photocurable adhesive. The photocationic polymerization initiator was mixed as a 50% propylene carbonate solution.

On the λ/4 retardation layer side of the λ/4 retardation layer 31 with the PET film and on the positive C layer side of the positive C layer 33 with the PET film, under conditions of an output of 0.3 kW and a processing speed of 3 m/min, Corona treatment was performed once. Between the λ/4 retardation layer 31 and the positive C layer 33, the adhesive for retardation layer bonding layer was applied to a thickness of 1.5 μm, and bonded with a nip roll. From the PET film substrate side of the positive C layer 33 of the bonded retardation layer 30, ultraviolet rays adjusted so that the amount of integrated light at a wavelength of 365 nm was 300 mJ / cm 2 were irradiated, and the retardation layer bonding layer was cured with ultraviolet rays. In this procedure, the retardation layer 30 provided with the λ/4 retardation layer 31, the retardation layer bonding layer 32, and the positive C layer 33 in this order was manufactured. The cured retardation layer bonding layer had an elastic modulus (compressive elastic modulus) of 2.4 GPa. The PET film serving as the substrate was appropriately peeled off in the process of manufacturing the circular polarizing plate.

<Example 1>

Manufacture of circular polarizing plate 200 shown in FIG. 2

1. Perform corona treatment (condition: output 0.3 kW, processing speed 3 m / min) on the surface of the overcoat layer 13 side of the polarizing layer 10 obtained in Production Example 1, and the adhesive agent layer obtained in Production Example 2 (20 Corona treatment was performed on the surface of the pressure-sensitive adhesive layer for ), and the corona-treated surfaces were bonded together.

2. Corona treatment was performed on the surface of the retardation layer 30 obtained in Production Example 3 on the side of the λ/4 phase difference layer 31, and this and a cycloolefin polymer (COP) film (thickness: 23 μm) were prepared in Production Example 3 It laminated|stacked with the nip roll through the adhesive for retardation layer bonding layers obtained in (thickness 1-2 micrometers). Thereafter, ultraviolet rays were irradiated from the side of the COP film adjusted so that the amount of integrated light at a wavelength of 365 nm was 300 mJ/cm 2 , and a first reinforcing layer 41 having a thickness of 1.5 μm was obtained. The COP film was peeled and removed after forming the first reinforcing layer 41 .

3. Corona treatment is performed on the surface of the adhesive agent of the bonded body obtained in Procedure 1, corona treatment is performed on the surface of the first reinforcing layer 41 formed in Procedure 2, and the corona treated surfaces are bonded to each other to form phase difference layer 30 A circularly polarizing plate 200 having a first reinforcing layer 41 on top was obtained.

<Example 2>

Manufacture of the circular polarizing plate 300 shown in FIG. 3

1. Perform corona treatment on the surface of the polarizing layer 10 obtained in Production Example 1 on the overcoating layer 13 side, corona treatment on the surface of the pressure-sensitive adhesive layer for the adhesive layer 20 obtained in Production Example 2, and corona The treated surfaces bonded together.

2. Corona treatment is performed on the surface of the adhesive layer for the adhesive layer 20 of the obtained bonding body, corona treatment is performed on the surface of the λ / 4 phase difference layer side of the phase difference layer 30 obtained in Production Example 3, and corona treatment The noodles were bonded together.

3. What corona treated the surface of the positive C layer side of the obtained bonding body, and the COP film (thickness 23 micrometers) prepared separately, through the adhesive for retardation layer bonding layers obtained in manufacture example 3 (thickness 1.5 micrometers), nip Laminated in rolls. Then, from the COP film side, ultraviolet rays adjusted so that the amount of integrated light at a wavelength of 365 nm is 300 mJ / cm 2, the COP film is removed, and the circular polarizing plate having the second reinforcing layer 42 under the retardation layer ( 300) was obtained.

<Example 3>

Manufacture of the circular polarizing plate 400 shown in FIG. 4

Corona treatment was performed on the surface on the positive C layer side of the circular polarizing plate 200 obtained in Example 1. Next, this and the separately prepared COP film (thickness: 23 μm) were laminated with a nip roll through the adhesive for phase difference layer bonding layer (thickness: 1.5 μm) obtained in Production Example 3. Thereafter, from the COP film side, ultraviolet rays adjusted so that the cumulative light amount at a wavelength of 365 nm is 300 mJ / cm 2, the COP film is removed, and the first reinforcing layer 41 is formed on top of the retardation layer 30, A circularly polarizing plate 400 having a second reinforcing layer 42 under the retardation layer 30 was obtained.

<Example 4>

Manufacture of the circular polarizing plate 100 shown in FIG. 1

A circular polarizing plate 100 was obtained in the same manner as in Procedures 1 and 2 of Example 2. This circular polarizing plate was further cured at 80°C for 1 hour.

<Comparative Example 1>

On the λ/4 retardation layer side of the λ/4 retardation layer 31 with PET film obtained in Production Example 3 and on the positive C layer side of the positive C layer 33 with PET film, the output was 0.3 kW and the processing speed was 3 m/min. Corona treatment was performed under the conditions of Between the λ/4 phase difference layer 31 and the positive C layer 33, the adhesive layer for the adhesive adhesive layer 20 obtained in Production Example 2 was disposed, and both were bonded together. In this procedure, a retardation layer comprising a λ/4 retardation layer (thickness of 2.0 μm), a retardation layer bonding layer (thickness of 5 μm), and a positive C layer (thickness of 450 nm) in this order was produced. The PET film serving as the substrate was appropriately peeled off in the process of manufacturing the circular polarizing plate.

A circularly polarizing plate was obtained in the same manner as in Procedures 1 and 2 of Example 2, except that the retardation layer was used instead of the retardation layer 30 obtained in Production Example 3. Although the structure of the obtained circular polarizing plate is the same as that of Example 4, it differs in that the elastic modulus (storage elastic modulus) of the retardation layer bonding layer is 0.0007 GPa.

<Comparative Example 2>

Instead of the PET film, the positive C layer was formed on the TAC film in the same manner as in Production Example 3 except for using the TAC film used also as the protective layer.

A circularly polarizing plate was obtained in the same manner as in Comparative Example 1 except for using the obtained positive C layer with TAC film. Thus, a circular polarizing plate having a TAC film (thickness of 25 μm) as a reinforcing layer under the retardation layer was obtained.

<Measurement of crack strain>

Each circular polarizing plate was cut into a size of 5 cm length x 10 mm width to prepare a sample. Using UTM (Universal Testing Machine, "Autograph AG-X" (product name) manufactured by Shimadzu Corporation), both ends of the prepared sample were held with clips, and the sample surface was visually observed while being pulled at a speed of 4 mm/min in the longitudinal direction. Observed. The elongation when a crack occurred in the sample was recorded as crack strain (%). For example, since the length of the sample when a crack occurred in Example 1 was 6.25 cm, the crack strain was calculated as 100 x (6.25 - 5)/5 = 25%.

<Dynamic bending resistance test>

The dynamic bending test was conducted under room temperature conditions (temperature: 25°C, humidity: 50%). On the protective layer of the circular polarizer prepared in Examples and Comparative Examples, a polyimide-based polymer resin film (front plate, thickness 40 μm) having a hard coating layer (10 μm thick) on one side was bonded, and on the positive C layer Then, two polyimide films (both back plates and thicknesses of 38 µm and tensile modulus of elasticity of 5 GPa or more) were double bonded to each other to obtain a laminate for a bending test. For pasting of the film, a pressure-sensitive adhesive layer (thickness: 25 μm) prepared in the same manner as in Production Example 2 was used except that the amount of the crosslinking agent was changed to 3.0 parts.

The obtained laminate for bending test is installed in a flat state (uncurved state) in a dynamic bending tester ("STS-VRT-500" (product name) manufactured by Science Town) so that the front plate layer side is on the inside (infolding method). ) 180°, and then returned to the original flat state. The bending radius was 1.0 mm under room temperature conditions.

What performed the operation of bending and returning flat was counted as one bending frequency, and this operation was repeated. The bending speed was 60 rpm. The number of bends when cracks (cracks or breaks) occurred in the lowermost retardation layer in the region bent by the bending operation was recorded in Table 1 as the limiting number of bends.

<Static bending durability test>

5 is a cross-sectional view showing a static bending durability test (mandrel bending test) method of the circular polarizing plate of the present invention. First, the laminate for the bending test was cut into a test piece of 1 cm x 10 cm. The laminated body 52 for the bending test cut on the test plate 51 was placed so that the front plate side was the upper side, and an iron bar 53 having a diameter of 3 mm was placed thereon (Fig. 5(a)). The test plate 51 and the laminated body 52 for the bending test were folded 180° by hand with the iron bar 53 interposed therebetween and fixed (Fig. 5(b)). Then, the laminated body 52 for a bending test in a folded state was placed under high temperature and high humidity conditions (temperature 60°C, humidity 90%).

Static bending durability was evaluated as follows based on the case where cracks occurred in the lowest layer retardation layer among the layers constituting the circular polarizing plate in the region bent by the bending operation. The results are shown in Table 1.

A: Cracks did not occur when 30 days had elapsed.

B: Cracks were generated when 30 days had elapsed.

C: When 20 days passed, cracks were generated.

D: Cracks were generated when 10 days had elapsed.

[Table 1]

*In Example 4, curing was performed at 80°C for 1 hour.

From Table 1, it can be seen that the circular polarizing plate of the present invention having a high crack strain has excellent bending resistance. Among them, a circular polarizing plate having reinforcing layers above and below the retardation layer had particularly excellent bending resistance.

10: polarization layer
11: protective layer
12: linear polarization layer
13: over coating layer
20: adhesive layer
30: phase difference layer
31: λ/4 phase difference layer
32: phase difference layer bonding layer
33: positive C layer
41: first reinforcing layer
42: second reinforcing layer
51: Trial
52: laminate for bending test
53: iron bar
100, 200, 300, 400: circular polarizer

Claims (11)

A circular polarizing plate having a polarization layer comprising a linear polarization layer and a retardation layer comprising a liquid crystal coating type retardation layer,
The circular polarizing plate has a crack strain of 15% or more,
The crack strain is an elongation (%) when both ends of a circular polarizing plate having a length of 5 cm and a width of 10 mm are pulled at a rate of 4 mm / min in the longitudinal direction, and cracks occur in the circular polarizing plate. According to claim 1,
The said retardation layer is a circular polarizing plate which consists of a λ/4 retardation layer, a retardation layer bonding layer, and a positive C layer. According to claim 2,
The said retardation layer bonding layer has an elastic modulus of 1 GPa or more, The circularly polarizing plate. According to claim 2 or 3,
The said retardation layer bonding layer has a thickness of 1-5 micrometers, circularly polarizing plate. According to any one of claims 2 to 4,
The positive C layer is a liquid crystal coating type retardation layer, a circular polarizing plate. According to any one of claims 1 to 5,
The circular polarizing plate, wherein the retardation layer has a reinforcing layer on at least one side thereof. According to claim 6,
The reinforcing layer is formed on top of the retardation layer, the circular polarizing plate. According to claim 6,
The reinforcing layer is formed under the retardation layer, the circular polarizing plate. According to claim 6,
The reinforcing layer is formed on top and bottom of the retardation layer, the circular polarizing plate. According to any one of claims 1 to 9,
A circularly polarizing plate having a thickness of 5 to 50 μm. According to any one of claims 1 to 10,
A circular polarizing plate having bending resistance in which cracks or fractures do not occur in the retardation layer when the polarizing layer is turned inside out and bent by 180° with a bending radius of 1 mm and then stretched repeatedly 300,000 times.

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