JP2021047229A - Laminated retardation film - Google Patents

Abstract

To provide a laminated retardation film in which occurrence of a crack is suppressed on a liquid crystal curing retardation layer even after cold-hot shock test is performed.SOLUTION: A laminated phase retardation film 100 comprises: a first liquid crystal curing retardation layer 10; a second liquid crystal curing retardation layer 30 laminated on one surface of the first liquid crystal curing retardation layer via a first adhesive layer 20; and a second adhesive layer 40 laminated on a surface of the first liquid crystal curing retardation layer opposite to the second liquid crystal curing retardation layer, wherein the second liquid crystal curing retardation layer has a higher piercing strength than that of the first liquid crystal curing retardation layer, and a storage elastic modulus of the second adhesive layer is 46000 Pa or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated retardation film, and further relates to a circular polarizing plate including the laminated retardation film, a laminated body for a flexible image display device, and an image display device.

Patent Document 1 proposes an optical laminate in which an adhesive layer is laminated on a retardation film obtained by curing a polymerizable liquid crystal compound, and a multilayer film composed of two or more retardation films is used as the retardation film. It is disclosed that it can be done.

Japanese Unexamined Patent Publication No. 2019-7002

The laminated retardation film including the retardation layer laminate in which two or more liquid crystal curing retardation layers are laminated and the pressure-sensitive adhesive layer is cooled to −40 ° C. for 30 minutes while being bonded to an inorganic glass plate. After holding, the liquid crystal curing retardation layer is subjected to a thermal shock test (hereinafter, also abbreviated as "cold thermal shock test") in which a test in which the operation of heating to 85 ° C. and holding for 30 minutes is one cycle is repeated for 300 cycles. May crack.

An object of the present invention is to provide a laminated retardation film in which cracks are suppressed in the liquid crystal cured retardation layer even after the thermal shock test is performed.

The present invention provides the following aspects [1] to [5].
[1] The first liquid crystal cured retardation layer and
A second liquid crystal cured retardation layer laminated on one surface of the first liquid crystal cured retardation layer via a first adhesive layer,
A laminated retardation film including a second adhesive layer laminated on a surface opposite to the second liquid crystal curing retardation layer of the first liquid crystal curing retardation layer.
The second liquid crystal cured retardation layer has a higher piercing strength than the first liquid crystal cured retardation layer.
A laminated retardation film having a storage elastic modulus of 46000 Pa or more in the second adhesive layer.
[2] The laminated retardation film according to [1], wherein a third adhesive layer is further laminated on the side of the second liquid crystal cured retardation layer.
[3] The laminated retardation film according to [2], wherein the storage elastic modulus of the second adhesive layer is equal to or higher than the storage elastic modulus of the third adhesive layer.
[4] A circular polarizing plate in which a linear polarizing plate is laminated on the second adhesive layer side of the laminated retardation film according to any one of [1] to [3].
[5] A laminate for a flexible image display device including the circular polarizing plate according to [4], a front plate and / or a touch sensor.
[6] An image display device including the circular polarizing plate according to [4].

According to the present invention, it is an object of the present invention to provide a laminated retardation film in which cracks are suppressed in the liquid crystal cured retardation layer even after the thermal shock test is performed.

It is the schematic sectional drawing which shows the laminated retardation film which concerns on one aspect of this invention. It is a schematic cross-sectional view which shows the circular polarizing plate which concerns on one aspect of this invention. It is a schematic sectional drawing which shows the laminated body for a flexible image display apparatus which concerns on one aspect of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the drawings below, the scale is appropriately adjusted to make it easier to understand each component, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Laminate retardation film>
FIG. 1 is a schematic cross-sectional view of a laminated retardation film according to an embodiment of the present invention. The laminated retardation film 100 shown in FIG. 1 includes a first liquid crystal curing retardation layer 10, a first adhesive layer 20, a second liquid crystal curing retardation layer 30, and a second adhesive layer 40 in this order. .. Hereinafter, the layer structure including the first liquid crystal cured retardation layer 10, the first adhesive layer 20, and the second liquid crystal cured retardation layer 30 is referred to as a retardation layer laminate 50.

In recent years, in circular polarizing plates and the like, a laminated retardation film including a retardation layer laminate in which two or more liquid crystal cured retardation layers are laminated is often used. However, it has been found that when a circularly polarizing plate having such a laminated retardation film is put into a thermal shock test, cracks tend to occur in the liquid crystal cured retardation layer.

As a result of the research by the present inventors, in a cold test environment, the liquid crystal cured retardation layer is cracked due to the stress that deforms the liquid crystal cured retardation layer due to the expansion or contraction of the polarizer. I found out that. As a result of further research, in a laminated retardation film including a retardation layer laminate in which two or more liquid crystal curing retardation layers are laminated, the storage elastic modulus is 46000 Pa or more on the liquid crystal curing retardation layer side having the lower puncture strength. It has been found that by laminating a certain adhesive layer, cracks in the liquid crystal cured retardation layer can be suppressed even when a thermal shock test is performed on a circular polarizing plate provided with such a laminated retardation film.

From the viewpoint of suppressing cracks in the liquid crystal cured retardation layer, the laminated retardation film 100 has a storage elastic modulus of 46,000 or more, preferably 50,000 Pa or more, and more preferably 100,000 Pa or more. The storage elastic modulus of the second adhesive layer 40 is usually less than 5000 MPa. The storage elastic modulus of the second adhesive layer 40 can be measured according to the measuring method described in the column of Examples described later.

Examples of the method for setting the storage elastic modulus of the second adhesive layer 40 to 46000 Pa or more include a method of selecting the type of the pressure-sensitive adhesive used for the second adhesive layer 40.

[Phase difference layer laminate]
The retardation layer laminate 50 includes a first liquid crystal curing retardation layer (hereinafter, also referred to as a first retardation layer) 10 and a second liquid crystal curing retardation layer (hereinafter, also referred to as a second retardation layer) 30. It is a retardation layer laminate laminated via the first adhesive layer 20. The retardation layer laminate 50 is preferably a retardation layer laminate in which the first retardation layer 10 and the second retardation layer 30 are laminated only via the first adhesive layer 20.

The second liquid crystal cured retardation layer 30 has a higher piercing strength than the first liquid crystal cured retardation layer 10. The puncture strength can be measured by the method described in the Examples section below. The second liquid crystal cured retardation layer 30 may have a puncture strength of, for example, 1 g or more higher than that of the first liquid crystal cured retardation layer 10, preferably 5 g or more, and more preferably 9 g or more from the viewpoint of crack suppression.
Examples of the method for increasing the puncture strength of the second liquid crystal cured retardation layer 30 to be higher than the puncture strength of the first liquid crystal cured retardation layer 10 include a method of selecting a polymerizable liquid crystal compound and a composition for forming a retardation layer layer. Examples thereof include a method of adjusting the composition of the substance, a method of adjusting the thickness of the liquid crystal cured retardation layer, and the like. For example, in the method of adjusting the thickness of the liquid crystal cured retardation layer, the piercing strength tends to increase as the thickness increases.

The retardation layer laminate 50 is a layer obtained by laminating a combination of at least two layers selected from a layer giving a phase difference of λ / 2, a layer giving a phase difference of λ / 4 and / or a positive C layer. Can be. Specific examples of the retardation layer laminate 50 include a laminate of a layer giving a phase difference of λ / 2 and a layer giving a phase difference of λ / 4, a layer giving a phase difference of λ / 4 and a positive C layer. And the laminate with. By laminating the retardation layer laminate 50 including the layer giving the phase difference of λ / 4 on the linear polarizing plate described later, the function as a circular polarizing plate is exhibited.

In the present specification, the "layer that gives a phase difference of λ / 4" is a retardation layer that converts linearly polarized light having a specific wavelength into circularly polarized light (or circularly polarized light is converted into linearly polarized light).
In the present specification, the "layer giving a phase difference of λ / 2" is a phase difference layer that converts the polarization direction of linearly polarized light having a specific wavelength by 90 °.
In the present specification, the “positive C layer” means the refractive index in the slow axis direction in the _{plane is n x} , the refractive index in the phase advance axis direction in the plane is n _y , and the refractive index in the thickness direction is n. _{When z} is set, it is a layer that satisfies the relationship of _{n z} > n _x = n _y. If the difference between _{the value of n x and} the value of n _{y is within 0.5% of the value of n y} , it can be substantially regarded as n _x = n _y, and it must be within 0.3%. Is more preferable.

In the retardation layer laminate 50, one of the first retardation layer 10 and the second retardation layer 30 functions as a layer that gives a phase difference of λ / 4, and the other is a layer that gives a retardation of λ / 2. It is preferable that either one of the first retardation layer 10 and the second retardation layer 30 functions as a layer giving a phase difference of λ / 4, and the other functions as a positive C layer. Therefore, the thicknesses of the first retardation layer 10 and the second retardation layer 20 and the materials constituting these layers are a layer giving a phase difference of λ / 4, a layer giving a phase difference of λ / 2, or a positive C. It can be adjusted so that a desired in-plane retardation value of the layer and a retardation value in the thickness direction can be obtained.

When the first retardation layer 10 functions as a layer that gives a phase difference of λ / 2 and the second retardation layer 30 functions as a layer that gives a phase difference of λ / 4, the thickness of the first retardation layer 10 is For example, it is 1 μm or more and 10 μm or less, and the thickness of the second retardation layer 30 is, for example, 1 μm or more and 10 μm or less. When the first retardation layer 10 functions as a layer that gives a retardation of λ / 4 and the second retardation layer 30 functions as a positive C layer, the thickness of the first retardation layer 10 is, for example, 1 μm or more and 10 μm or less. The thickness of the second retardation layer 30 is, for example, 1 μm or more and 10 μm or less.

[First retardation layer]
The first retardation layer 10 is composed of a layer containing a cured product of a polymerizable liquid crystal compound. It is more preferable that the first retardation layer 10 has a layer containing a cured product of the polymer polymerized in a state in which the polymerizable liquid crystal compound is oriented. The first retardation layer 10 may have an alignment layer and / or a base material described later, but the base material is usually peeled off when the laminated retardation film 100 is incorporated into the circular polarizing plate.

The first retardation layer 10 has a lower piercing strength than the second retardation layer 30. The puncture strength of the first retardation layer 10 may be, for example, less than 30 g, preferably 25 g or less, and more preferably 22 g or less. The puncture strength of the first retardation layer 10 is usually 5 g or more.

The polymerizable liquid crystal compound is a compound having a polymerizable group and can be in a liquid crystal state. The polymerizable liquid crystal compound is cured by reacting the polymerizable groups of the polymerizable liquid crystal compound with each other to polymerize the polymerizable liquid crystal compound.

(Base material)
The layer containing the cured product of the polymerizable liquid crystal compound can be formed, for example, on the alignment layer provided on the base material. The base material may be a long base material having a function of supporting the alignment layer. This base material functions as a releasable support and can support a retardation layer or an orientation layer for transfer. Further, it is preferable that the surface has an adhesive force that can be peeled off. The base material is a translucent, preferably optically transparent thermoplastic resin such as a chain polyolefin resin (polypropylene resin or the like) or a cyclic polyolefin resin (norbornen resin or the like). Polyolefin resin; Cellulosic resin such as triacetyl cellulose and diacetyl cellulose; Polyester resin such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resin; (Meta) acrylic resin such as methyl methacrylate resin; Polystyrene Resins; Polyvinyl chloride resins; Acrylonitrile, butadiene, styrene resins; Acrylonitrile, styrene resins; Polyvinyl acetate resins; Polyvinylidene chloride resins; Polyamide resins; Polyacetal resins; Modified polyphenylene ether resins; Polysulfones A film made of a resin; a polyether sulfone resin; a polyarylate resin; a polyamideimide resin; a polyimide resin; a maleimide resin or the like can be used.

The thickness of the base material is not particularly limited, but is preferably in the range of, for example, 20 μm or more and 200 μm or less. When the thickness of the base material is 20 μm or more, the strength tends to be easily imparted. The base material is usually peeled off when incorporated into the circular polarizing plate, but when the base material is incorporated into the circular polarizing plate, the thickness of the base material is preferably 30 μm or less.

The base material may be subjected to various blocking prevention treatments. Examples of the blocking prevention treatment include an easy-adhesion treatment, a treatment of kneading a filler and the like, an embossing treatment (knurling treatment) and the like. By applying such a blocking prevention treatment to the base material, it is possible to effectively prevent the base materials from sticking to each other when the base material is wound, so-called blocking, and the productivity tends to be improved easily. is there.

(Orientation layer)
A layer containing a cured product of the polymerizable liquid crystal compound is formed on the substrate via an orientation layer. That is, the base material and the alignment layer are laminated in this order, and the layer containing the cured product of the polymerizable liquid crystal compound is laminated on the alignment layer.

The alignment layer is not limited to the vertically oriented layer, and may be an oriented layer that horizontally aligns the molecular axis of the polymerizable liquid crystal compound, or may be an oriented layer that obliquely orients the molecular axis of the polymerizable liquid crystal compound. .. The alignment layer has solvent resistance that does not dissolve due to coating of a composition containing a polymerizable liquid crystal compound, which will be described later, and heat resistance in heat treatment for removing the solvent and aligning the liquid crystal compound. preferable. Examples of the alignment layer include an alignment layer containing an orientation polymer, a photoalignment film, and a grub alignment layer in which an uneven pattern or a plurality of grooves are formed and oriented on the surface. The thickness of the oriented layer is usually in the range of 10 nm or more and 10000 nm or less.

Further, the alignment layer has a function of supporting the liquid crystal layer and may function as a releasable support. A liquid crystal layer for transfer can be supported, and the surface thereof may have an adhesive force that can be peeled off.

As the resin used for the alignment layer, a resin obtained by polymerizing a polymerizable compound is used. The polymerizable compound is a compound having a polymerizable group, and is usually a non-liquid crystalline non-liquid crystal compound that does not become a liquid crystal state. The polymerizable groups of the polymerizable compound react with each other to polymerize the polymerizable compound, thereby forming a resin. Such a resin is a resin used as an alignment layer for orienting a polymerizable liquid crystal compound at the stage of forming the liquid crystal layer, and if it is not contained in the liquid crystal layer, it is used as a material for a known alignment layer. If there is no particular limitation, a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth) acrylate-based monomer under a polymerization initiator can be used. Specifically, examples of the (meth) acrylate-based monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, and trimethyl propantriacrylate. , Lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate. , Cyclohexyl methacrylate, methacrylic acid, urethane acrylate and the like can be exemplified. The resin may be one of these or a mixture of two or more.
The alignment layer can be peeled off together with the base material before and after the step of forming the retardation layer 30 and then laminating it with the linear polarizing plate 30 or the like.

Further, an orientation layer can be included in the liquid crystal layer for the purpose of improving the peelability from the base material and imparting film strength to the liquid crystal layer. When the liquid crystal layer contains an alignment layer, it is preferable to use a cured product obtained by curing a monofunctional or bifunctional (meth) acrylate-based monomer, an imide-based monomer, or a vinyl ether-based monomer as the resin used for the alignment layer.
Examples of the monofunctional (meth) acrylate-based monomer include alkyl (meth) acrylates having 4 to 16 carbon atoms, βcarboxyalkyl (meth) acrylates having 2 to 14 carbon atoms, and alkylated phenyl (meth) having 2 to 14 carbon atoms. Examples thereof include acrylates, methoxypolyethylene glycol (meth) acrylates, phenoxypolyethylene glycol (meth) acrylates and isobonyl (meth) acrylates.
Examples of the bifunctional (meth) acrylate-based monomer include 1,3-butanediol di (meth) acrylate; 1,3-butanediol (meth) acrylate; 1,6-hexanediol di (meth) acrylate; ethylene glycol di. (Meta) acrylate; Diethylene glycol di (meth) acrylate; Neopentyl glycol di (meth) acrylate; Triethylene glycol di (meth) acrylate; Tetraethylene glycol di (meth) acrylate; Polyethylene glycol diacrylate; Bisphenol A bis (acrylate) Loyloxyethyl) ether; ethoxylated bisphenol A di (meth) acrylate; propoxylated neopentyl glycol di (meth) acrylate; ethoxylated neopentyl glycol di (meth) acrylate, 3-methylpentanediol di (meth) acrylate, etc. Can be mentioned.
Examples of the imide-based resin obtained by curing the imide-based monomer include polyamide and polyimide. The imide-based resin may be one of these or a mixture of two or more.
Further, the resin forming the alignment layer may contain a monomer other than the monofunctional or bifunctional (meth) acrylate-based monomer, the imide-based monomer and the vinyl ether-based monomer, but the monofunctional or bifunctional (meth) The content ratio of the acrylate-based monomer, the imide-based monomer, and the vinyl ether-based monomer may be 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more in the total monomer. ..

When the alignment layer is included in the retardation layer 30, the thickness of the alignment layer is usually in the range of 10 nm or more and 10,000 nm or less, and when the orientation of the retardation layer 30 is in-plane orientation with respect to the film surface, the alignment layer of the alignment layer The thickness is preferably 10 nm or more and 1000 nm or less, and when the orientation of the retardation layer 30 is perpendicular to the film surface, it is preferably 100 nm or more and 10000 nm or less. When the thickness of the retardation layer 30 is within the above range, it is possible to improve the peelability of the base material and impart appropriate film strength.

(Polymerizable liquid crystal compound)
The type of the polymerizable liquid crystal compound is not particularly limited, but can be classified into a rod-shaped type (rod-shaped liquid crystal compound) and a disk-shaped type (disk-shaped liquid crystal compound, discotic liquid crystal compound) according to its shape. Further, there are a low molecular weight type and a high molecular weight type, respectively. The polymer generally refers to a polymer having a degree of polymerization of 100 or more (Polymer Physics / Phase Transition Dynamics, Masao Doi, 2 pages, Iwanami Shoten, 1992).

In this embodiment, any polymerizable liquid crystal compound can be used. Further, two or more kinds of rod-shaped liquid crystal compounds, two or more kinds of disk-shaped liquid crystal compounds, or a mixture of a rod-shaped liquid crystal compound and a disk-shaped liquid crystal compound may be used.

As the rod-shaped liquid crystal compound, for example, the compound described in claim 1 of JP-A-11-513019 can be preferably used. As the disk-shaped liquid crystal compound, for example, those described in paragraphs [0020] to [0067] of JP-A-2007-108732 or paragraphs [0013] to [0108] of JP-A-2010-244038 are preferably used. Can be used.

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

The polymerizable liquid crystal compound has a polymerizable group capable of carrying out a polymerization reaction. As the polymerizable group, for example, a functional group capable of an addition polymerization reaction such as a polymerizable ethylenically unsaturated group or a ring-polymerizable group is preferable. More specifically, examples of the polymerizable group include a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group. Among them, the (meth) acryloyl group is preferable. The (meth) acryloyl group is a concept that includes both a meta-acryloyl group and an acryloyl group.

The liquid crystal property of the polymerizable liquid crystal compound may be a thermotropic liquid crystal or a riotropic liquid crystal, and when the thermotropic liquid crystal is classified by order, it may be a nematic liquid crystal or a smectic liquid crystal.

As described later, the layer containing the cured product of the polymerizable liquid crystal compound is activated by applying a composition containing the polymerizable liquid crystal compound (hereinafter, also referred to as a composition for forming a retardation layer) onto, for example, an alignment layer. It can be formed by irradiating an energy ray. The composition for forming a retardation layer may contain components other than the above-mentioned polymerizable liquid crystal compound. For example, it is preferable that the composition for forming a retardation layer contains a polymerization initiator. As the polymerization initiator used, for example, a thermal polymerization initiator or a photopolymerization initiator is selected according to the type of the polymerization reaction. For example, examples of the photopolymerization initiator include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, and combinations of triarylimidazole dimers and p-aminophenyl ketones. The amount of the polymerization initiator used is preferably 0.01% by mass or more and 20% by mass or less, and 0.5% by mass or more and 5% by mass or less, based on the total solid content in the coating liquid. Is more preferable. The "cured product" refers to a state in which the formed layer alone can exist independently without being deformed or flowing.

Further, the composition for forming a retardation layer may contain a polymerizable monomer from the viewpoint of the uniformity of the coating film and the strength of the film. Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Among them, a polyfunctional radically polymerizable monomer is preferable.

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

Further, the composition for forming a retardation layer may contain a surfactant from the viewpoint of the uniformity of the coating film and the strength of the film. Examples of the surfactant include conventionally known compounds. Among them, fluorine-based compounds are particularly preferable.

Further, the composition for forming a retardation layer may contain a solvent, and an organic solvent is preferably used. Examples of the organic solvent include amide (eg, N, N-dimethylformamide), sulfoxide (eg, dimethyl sulfoxide), heterocyclic compound (eg, pyridine), hydrocarbon (eg, benzene, hexane), alkyl halide (eg, eg). , Chloroform, dichloromethane), esters (eg, methyl acetate, ethyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Among them, alkyl halides and ketones are preferable. Further, two or more kinds of organic solvents may be used in combination.

In addition, the composition for forming a retardation layer includes vertical alignment promoters such as a polarizer interface side vertical alignment agent and an air interface side vertical alignment agent, and a polarizer interface side horizontal alignment agent, an air interface side horizontal alignment agent, and the like. Various orienting agents such as the horizontal alignment accelerator of the above may be contained. Further, the composition for forming a retardation layer may contain an adhesion improver, a plasticizer, a polymer and the like in addition to the above components.

The active energy beam includes ultraviolet rays, visible light, electron beams, and X-rays, and is preferably ultraviolet rays. Examples of the light source of the active energy ray include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a tungsten lamp, a gallium lamp, an excima laser, and a wavelength range. Examples thereof include an LED light source that emits 380 to 440 nm, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp.

The irradiation intensity of ultraviolet light is usually the case of ultraviolet B wave (or wavelength range 280 nm 310 nm or less), 100 mW / cm ² or more 3,000 mW / cm ² or less. The ultraviolet irradiation intensity is preferably the intensity in the wavelength region effective for activating the cationic polymerization initiator or the radical polymerization initiator. The time for irradiating ultraviolet rays is usually 0.1 seconds or more and 10 minutes or less, preferably 0.1 seconds or more and 5 minutes or less, more preferably 0.1 seconds or more and 3 minutes or less, and further preferably 0. . 1 second or more and 1 minute or less.

Ultraviolet rays can be irradiated once or in a plurality of times. Depending on the polymerization initiator used, the accumulated amount of light at a wavelength of 365nm is preferably in a 700 mJ / cm ² or more, more preferably, to 1,100mJ / cm ² or more, 1,300mJ / cm ² or more and It is more preferable to do so. The integrated light intensity is advantageous for increasing the polymerization rate of the polymerizable liquid crystal compound constituting the liquid crystal layer 103 and improving the heat resistance. Integrated light intensity at a wavelength of 365nm is preferably in a 2,000 mJ / cm ² or less, and more preferably to 1,800mJ / cm ² or less. The integrated light intensity may cause coloring of the liquid crystal layer 103.

In the present embodiment, the thickness of the first retardation layer 10 is preferably 0.5 μm or more, and more preferably 1.0 μm or more. The thickness of the first retardation layer 10 is preferably 10 μm or less, and more preferably 5 μm or less. The above-mentioned upper limit value and lower limit value can be arbitrarily combined. When the thickness of the first retardation layer 10 is at least the lower limit value, durability tends to be easily obtained. When the thickness of the first retardation layer 10 is not more than the upper limit value, it can contribute to the thinning of the laminated retardation film 100. The thickness of the first retardation layer 10 is a desired in-plane retardation value of a layer giving a retardation of λ / 4, a layer giving a retardation of λ / 2, or a positive C layer, and a retardation value in the thickness direction. Can be adjusted to obtain.

[First adhesive layer]
The first adhesive layer is usually composed of an adhesive. Examples of the adhesive constituting the first adhesive layer include a water-based adhesive and an active energy ray-curable adhesive. Examples of the water-based adhesive include an adhesive in which a polyvinyl alcohol-based resin is dissolved and dispersed in water. Examples of the active energy ray-curable adhesive include adhesives containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. The storage elastic modulus, which is an index showing the hardness of the active energy ray-curable adhesive after curing, is often higher than the storage elastic modulus of the water-based adhesive. It is preferable to use an active energy ray-curable adhesive for the first adhesive layer.

The active energy ray-curable adhesive preferably contains one or both of a cationically polymerizable curable compound and a radically polymerizable curable compound because it exhibits good adhesiveness. The active energy ray-curable adhesive can further contain either or both of a cationic polymerization initiator for initiating the curing reaction of the curable compound and a radical polymerization initiator.

Examples of the cationically polymerizable curable compound include epoxy compounds (compounds having one or more epoxy groups in the molecule) and oxetane compounds (one or two or more oxetane rings in the molecule). Compounds having), or a combination thereof.

Examples of the radically polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule), radically polymerizable double bonds, and others. Vinyl compounds and combinations thereof can be mentioned.

Active energy ray-curable adhesives include cationic polymerization accelerators, ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow conditioners, plasticizers, and defoamers, as required. It can contain additives such as foaming agents, antistatic agents, leveling agents, and solvents.

In the retardation layer laminate, when the first retardation layer 10 and the second retardation layer 30 are bonded together using an adhesive, first, the adhesive is applied to the first retardation layer 10 and the second retardation layer 30. Apply to either one or both joint surfaces.

As a method of applying the adhesive to the joint surface, a usual coating technique using a die coater, a comma coater, a reverse roll coater, a gravure coater, a rod coater, a wire bar coater, a doctor blade coater, an air doctor coater, etc. Should be adopted.

The drying method when a water-based adhesive is used is not particularly limited, but for example, a method of drying using a hot air dryer or an infrared dryer can be adopted.

On the other hand, when an active energy ray-curable adhesive is used, the active energy ray-curable adhesive is cured by irradiating it with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. As the active energy ray, ultraviolet rays are preferable, and as a light source in this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used. it can.

The thickness of the first adhesive layer 20 is preferably 10 μm or less, and more preferably 5 μm or less. When the thickness of the first adhesive layer 20 is not more than the upper limit value, floating or peeling is unlikely to occur between the first retardation layer 10 and the second retardation layer 30.

[Second retardation layer]
The second retardation layer 30 is composed of a layer containing a cured product of a polymerizable liquid crystal compound. It is more preferable that the second retardation layer 30 has a layer containing a cured product of the polymer polymerized in a state in which the polymerizable liquid crystal compound is oriented. The second retardation layer 30 may have an alignment layer and / or a base material described later, but the base material is usually peeled off when the laminated retardation film 100 is incorporated into the circular polarizing plate.

The second retardation layer 30 has a higher piercing strength than the first retardation layer 10. The puncture strength of the second retardation layer 30 may be, for example, 25 g or more, preferably 27 g or more, and more preferably 30 g or more. The puncture strength of the second retardation layer 30 is usually 50 g or less.

As examples of the polymerizable liquid crystal compound, the alignment layer and the base material, the examples of the polymerizable liquid crystal compound, the alignment layer and the base material in the above description of the first retardation layer 10 are applied.

Examples of the method for producing the second retardation layer 30 and the composition for forming the retardation layer used therein include the production method in the above description of the first retardation layer 10 and the example of the composition for forming the retardation layer used therein. Applies.

The thickness of the second retardation layer 30 is preferably 0.5 μm or more, and more preferably 1.0 μm or more. The thickness of the second retardation layer 30 is preferably 10 μm or less, and more preferably 5 μm or less. The above-mentioned upper limit value and lower limit value can be arbitrarily combined. When the thickness of the second retardation layer 30 is at least the above lower limit value, durability tends to be easily obtained. When the thickness of the second retardation layer 30 is not more than the upper limit value, it tends to contribute to the thinning of the laminated retardation film 100. The thickness of the second retardation layer 30 is a desired in-plane retardation value of a layer giving a retardation of λ / 4, a layer giving a retardation of λ / 2, or a positive C layer, and a retardation value in the thickness direction. Can be adjusted to obtain.

[Second adhesive layer]
The second adhesive layer 40 can usually be a pressure-sensitive adhesive layer formed of a pressure-sensitive pressure-sensitive adhesive (hereinafter, also referred to as a pressure-sensitive adhesive). The pressure-sensitive adhesive layer preferably has a storage elastic modulus of 46000 Pa or more, more preferably 50,000 Pa or more, and further preferably 100,000 Pa or more. The storage elastic modulus of the pressure-sensitive adhesive layer is usually 50 MPa or less. The storage elastic modulus of the second adhesive layer 40 can be measured according to the measuring method described in the column of Examples described later. The storage elastic modulus of the second adhesive layer is preferably equal to or higher than the storage elastic modulus of the third adhesive layer, which will be described later, from the viewpoint of crack suppression.

The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition containing a resin as a main component, such as (meth) acrylic-based, rubber-based, urethane-based, ester-based, silicone-based, and polyvinyl ether-based. Among them, a pressure-sensitive adhesive composition using a (meth) acrylic resin as a base polymer is preferable from the viewpoint of transparency, weather resistance, heat resistance and storage elastic modulus. The pressure-sensitive adhesive composition may be an active energy ray-curable 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, and 2- (meth) acrylate. A polymer or copolymer containing one or more (meth) acrylic acid esters such as ethylhexyl as a monomer is preferably used. It is preferable that the base polymer is copolymerized with a polar monomer. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl (). Examples thereof include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as meth) acrylate.

The pressure-sensitive adhesive composition may contain only the above-mentioned base polymer, but usually further contains a cross-linking agent. The cross-linking agent is a divalent or higher metal ion that forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound that forms an amide bond with a carboxyl group; poly. Epoxy compounds and polyols that form an ester bond with a carboxyl group; polyisocyanate compounds that form an amide bond with a carboxyl group are exemplified. Of these, polyisocyanate compounds are preferable.

To form the pressure-sensitive adhesive layer, for example, the pressure-sensitive adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare a pressure-sensitive adhesive liquid, which is directly applied to the target surface of the laminate to provide a pressure-sensitive adhesive. A method of forming a layer, a method of forming an adhesive layer in a sheet shape on a separate film that has been subjected to a mold release treatment, and a method of transferring the adhesive layer to the target surface of the retardation layer laminate 50, or the like. Can be done.

The laminated retardation film 100 may include the above-mentioned separate film. The separate film can be a film made of a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate, or the like. Of these, a polyethylene terephthalate stretched film is preferable.

The pressure-sensitive adhesive layer contains optional components such as glass fibers, glass beads, resin beads, fillers composed of metal powder and other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antioxidants and the like. Can be done.

Examples of the antistatic agent include ionic compounds, conductive fine particles, conductive polymers, and the like, and ionic compounds are preferably used.
The cation component constituting the ionic compound may be an inorganic cation or an organic cation.
Examples of the organic cation include pyridinium cation, imidazolium cation, ammonium cation, sulfonium cation, phosphonium cation, piperidinium cation, pyrrolidinium cation and the like, and examples of the inorganic cation include lithium ion and potassium ion.
On the other hand, the anion component constituting the ionic compound may be an inorganic anion or an organic anion, but an anion component containing a fluorine atom is preferable because it provides an ionic compound having excellent antistatic performance. As anion components containing a fluorine atom, hexafluorophosphate anion [(PF ₆ ⁻ )], bis (trifluoromethanesulfonyl) imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ] anion, bis (fluorosulfonyl) imide anion [ (FSO ₂ ) ₂ N ⁻ ] anions and the like can be mentioned.

The thickness of the second adhesive layer 40 is determined according to its adhesive strength and the like, but may be, for example, in the range of 1 μm or more and 50 μm or less, preferably 2 μm or more and 45 μm or less, more preferably 3 μm or more and 40 μm or less, and further. It is preferably 5 μm or more and 35 μm or less.

[Other layers]
The laminated retardation film 100 may further have, for example, a third adhesive layer on the side of the second retardation layer 30. As the third adhesive layer, it can be usually a pressure-sensitive adhesive layer formed of a pressure-sensitive pressure-sensitive adhesive (hereinafter, also referred to as a pressure-sensitive adhesive).

As the pressure-sensitive adhesive used for the third adhesive layer, a conventionally known pressure-sensitive adhesive can be used without particular limitation, and a pressure-sensitive adhesive having a base polymer such as an acrylic polymer, a urethane-based polymer, a silicone-based polymer, or a polyvinyl ether-based polymer. Can be used. Further, it may be an active energy ray-curable pressure-sensitive adhesive, a thermosetting pressure-sensitive adhesive, or the like.

The storage elastic modulus of the third adhesive layer is preferably smaller than the storage elastic modulus of the second adhesive layer. The storage elastic modulus of the third adhesive layer is preferably smaller than the storage elastic modulus of the second adhesive layer by 20000 Pa or more, more preferably 60,000 Pa or more, and further preferably 90000 Pa or more. The third adhesive layer preferably has a storage elastic modulus of 10,000 Pa or more, and more preferably 20,000 Pa or more. The storage elastic modulus of the third adhesive layer is usually 50 MPa or less. The storage elastic modulus of the third adhesive layer can be measured according to the measuring method described in the column of Examples described later.

<Manufacturing method of laminated retardation film>
The laminated retardation film can be produced by a method including a step of laminating the first retardation layer and the second retardation layer via the first adhesive layer.

The liquid crystal cured retardation layer can be produced by applying a composition for forming a retardation layer containing a polymerizable liquid crystal compound on a base material and an alignment layer if present, and polymerizing the polymerizable liquid crystal compound. it can. The composition for forming a retardation layer further contains a solvent and a polymerization initiator, and may further contain a photosensitizer, a polymerization inhibitor, a leveling agent and the like. The base material and the alignment layer may be incorporated into the liquid crystal cured retardation layer, or may not be separated from the liquid crystal cured retardation layer and become a component of the circular polarizing plate.

The coating, drying and polymerization of the polymerizable liquid crystal compound of the composition for forming a retardation layer can be carried out by conventionally known coating methods, drying methods and polymerization methods.

For example, as a method for applying the composition for forming a retardation layer, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method and the like can be adopted.

The polymerization method of the polymerizable liquid crystal compound may be selected according to the type of the polymerizable group of the polymerizable liquid crystal compound. If the polymerizable group is a photopolymerizable group, it can be polymerized by a photopolymerization method. If the polymerizable group is a thermally polymerizable group, it can be polymerized by a thermal polymerization method. In the method for producing a laminated retardation film, a photopolymerization method is preferable. In the photopolymerization method, it is not always necessary to heat the transparent base material to a high temperature, so that a transparent base material having low heat resistance can be used. The photopolymerization method is carried out by irradiating a film made of a composition for forming a retardation layer containing a polymerizable liquid crystal compound with visible light or ultraviolet light. Ultraviolet light is preferable because it is easy to handle.

The first retardation layer and the second retardation layer can be bonded to each other via the first adhesive layer. The adhesive is applied to either one joint surface or both joint surfaces of the first phase difference layer 10 and the second retardation layer 30. The coating method, the drying method, and the polymerization method can be carried out as described in the above description of the first adhesive layer.

The second adhesive layer can be prepared as an adhesive sheet. The pressure-sensitive adhesive sheet is prepared by dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a pressure-sensitive adhesive solution, which is then subjected to a release treatment to form a layer of the pressure-sensitive adhesive on a release film. It can be produced by forming it into a sheet shape and laminating another release film on the pressure-sensitive adhesive layer. Each layer can be bonded by a method in which the pressure-sensitive adhesive sheet from which one release film has been peeled off is attached to one layer, then the other release film is peeled off, and the other layer is attached.

As a method of applying the adhesive liquid on the release film, a usual coating technique using a die coater, a comma coater, a reverse roll coater, a gravure coater, a rod coater, a wire bar coater, a doctor blade coater, an air doctor coater, etc. Should be adopted.

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

The thickness of the second adhesive layer can be adjusted according to the coating conditions of the pressure-sensitive adhesive liquid. In order to reduce the thickness of the pressure-sensitive adhesive layer, it is effective to reduce the coating thickness.

<Circular polarizing plate>
FIG. 2 is a schematic cross-sectional view of a circular polarizing plate according to another embodiment of the present invention. The circular polarizing plate 200 shown in FIG. 2 includes a laminated retardation film 100 and a linear polarizing plate 60 laminated via an adhesive layer 40 of the laminated retardation film 100. The linear polarizing plate 60 has a thermoplastic resin film 61, a polarizer 61, and a thermoplastic resin film 62. The circular polarizing plate 200 has a third adhesive layer 70 on the second retardation layer 30 side of the laminated retardation film 100.

By laminating the retardation layer laminate 50 including the layer giving the phase difference of λ / 4 on the linear polarizing plate 60 described later, the function as a circular polarizing plate is exhibited. The retardation layer laminate 50 can be laminated so that the slow axis of the retardation layer laminate 50 and the absorption axis of the polarizer 11 of the linear polarizing plate 60 are at a predetermined angle. The angle formed by the slow axis of the layer giving the phase difference of λ / 4 and the absorption axis of the polarizer 11 can be 45 ° ± 10 °.

[Linear polarizing plate]
The linear polarizing plate 60 has a polarizing element 62, and a thermoplastic resin film 61 and a thermoplastic resin film 63 on both sides of the polarizing element 62. Although the thermoplastic resin film 61 and the thermoplastic resin film 63 are arranged on both sides of the polarizer 62, the thermoplastic resin film may be provided only on one side of the polarizer 62. In FIG. 2, the thermoplastic resin film 61 and the thermoplastic resin film 63 may be the same type of thermoplastic resin film or different types of thermoplastic resin film. The linear polarizing plate 60 may further have a base material, an alignment film and a protective layer described later. Hereinafter, the thermoplastic resin film 61 and the thermoplastic resin film 63 may be collectively referred to as a thermoplastic resin film.

The thickness of the linear polarizing plate 60 is, for example, 2 μm or more and 100 μm or less, preferably 10 μm or more and 60 μm or less.

[Polarizer]
Examples of the polarizer 62 include a stretched film or a stretched layer on which a dye having absorption anisotropy is adsorbed, or a film coated with a dye having absorption anisotropy and cured. Examples of the dye having absorption anisotropy include a dichroic dye. Specifically, as the dichroic dye, iodine or a dichroic organic dye is used. For dichroic organic dyes, C.I. I. Included are dichroic direct dyes made of disuazo compounds such as DIRECT RED 39 and dichroic direct dyes made of compounds such as trisazo and tetrakisazo.

The film obtained by applying and curing a dye having absorption anisotropy is obtained by applying and curing a composition containing a dichroic dye having liquid crystal properties or a composition containing a dichroic dye and a polymerizable liquid crystal. Examples thereof include a film containing a cured product of a polymerizable liquid crystal compound such as a layer to be formed.

(1) Stretched film on which a dye having absorption anisotropy is adsorbed or a polarizer which is a stretched layer First, a stretched film on which a dye having absorption anisotropy is adsorbed (hereinafter, abbreviated as "stretched film" There is also), and the polarizer will be described. A stretched film on which a dye having absorption anisotropy is adsorbed is usually obtained by dyeing the polyvinyl alcohol-based resin film with a bicolor dye in a step of uniaxially stretching the polyvinyl alcohol-based resin film. It can be produced through a step of adsorbing, a step of treating a polyvinyl alcohol-based resin film on which a bicolor dye is adsorbed with an aqueous boric acid solution, and a step of washing with water after the treatment with the aqueous boric acid solution. A linear polarizing plate in which a thermoplastic resin film described later is bonded to one side or both sides of the polarizing element can be used. The thickness of this polarizer is preferably 2 μm or more and 40 μm or less.

The polyvinyl alcohol-based resin is obtained by saponifying a polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith is used. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less.

A film formed of such a polyvinyl alcohol-based resin is used as a raw film for a polarizer. The method for forming the film of the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method. The film thickness of the polyvinyl alcohol-based raw film can be, for example, about 10 to 150 μm.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with a dichroic dye, at the same time as dyeing, or after dyeing. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. It is also possible to perform uniaxial stretching at these multiple stages. In uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched, or thermal rolls may be used to uniaxially stretch the rolls. Further, the uniaxial stretching may be a dry stretching in which the stretching is performed in the atmosphere, or a wet stretching in which the polyvinyl alcohol-based resin film is swollen using a solvent. The draw ratio is usually about 3 to 8 times.

Dyeing of the polyvinyl alcohol-based resin film with a dichroic dye is performed, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. Specifically, as the dichroic dye, iodine or a dichroic organic dye is used. For dichroic organic dyes, C.I. I. Included are dichroic direct dyes made of disuazo compounds such as DIRECT RED 39 and dichroic direct dyes made of compounds such as trisazo and tetrakisazo. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

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

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye and dyeing is usually adopted. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ^-4 to 10 parts by mass, preferably 1 × 10 ^-3 to 1 part by mass, more preferably 1 × 10 -3 to 1 part by mass, per 100 parts by mass of water. 1 × 10 ^-3 to 1 × ^10-2 parts by mass. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dichroic dye aqueous solution used for dyeing is usually about 20 to 80 ° C. The immersion time (staining time) in this aqueous solution is usually about 10 to 1,800 seconds.

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

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water in the washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

After washing with water, a drying treatment is performed to obtain a polarizer. The drying process can be performed using, for example, a hot air dryer or a far-infrared heater. The temperature of the drying treatment is usually about 30 to 100 ° C, preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content of the polarizer is reduced to a practical level. The water content is usually about 5 to 20% by mass, preferably 8 to 15% by mass. If the moisture content is less than 5% by weight, the polarizer loses its flexibility and the polarizer may be damaged or broken after its drying. Further, if the water content exceeds 20% by mass, the thermal stability of the polarizer may deteriorate.

The thickness of the polarizer obtained by uniaxially stretching, dyeing with a dichroic dye, boric acid treatment, washing with water, and drying the polyvinyl alcohol-based resin film is preferably 5 to 40 μm.

Next, a polarizer which is a stretched layer (hereinafter, may be abbreviated as “stretched layer”) on which a dye having absorption anisotropy is adsorbed will be described. The stretched layer on which the dye having absorption anisotropy is adsorbed is usually subjected to a step of applying the coating liquid containing the polyvinyl alcohol-based resin on the base film, a step of uniaxially stretching the obtained laminated film, and uniaxially stretching. A step of dyeing the polyvinyl alcohol-based resin layer of the laminated film with a dichroic dye to adsorb the dichroic dye to form a polarizer, and treating the film on which the dichroic dye is adsorbed with an aqueous boric acid solution. It can be produced through a step of rinsing with water after treatment with an aqueous boric acid solution.

As an example of the base film, those exemplified in the description of the thermoplastic resin film described later are applied. The base film may be peeled off from the polarizer, and the base film may be either one of the thermoplastic resin films 61 and 63. The thickness of the base film may be, for example, 5 μm or more and 200 μm or less. When the base material is incorporated into the circular polarizing plate, the thickness of the base material is preferably 30 μm or less.

(2) Polarizer, which is a film coated with a dye having absorption anisotropy and cured. A polarizing element, which is a film coated with a dye having absorption anisotropy and cured, will be described. The film coated with the dye having absorption anisotropy and cured is obtained by applying a composition containing a dichroic dye having liquid crystal properties or a composition containing a dichroic dye and a liquid crystal compound to a substrate and curing the film. Examples thereof include the obtained film. The film may be used as a linear polarizing plate by peeling off the base material or together with the base material, or may be used as a linear polarizing plate in a configuration having a thermoplastic resin film on one side or both sides thereof.

As an example of the base material, those exemplified in the description of the thermoplastic resin film described later are applied. The base material may be peeled off from the polarizer, or the base material may be used as either one of the thermoplastic resin films 61 and 63. The thickness of the base material may be, for example, 5 μm or more and 200 μm or less. When the base material is incorporated into the circular polarizing plate, the thickness of the base material is preferably 30 μm or less. The substrate may have a hard coat layer, an antireflection layer, or an antistatic layer on at least one surface. The base material may have a hard coat layer, an antireflection layer, an antistatic layer, or the like formed only on the surface on the side where the polarizer is not formed. As the base material, the hard coat layer, the antireflection layer, the antistatic layer and the like may be formed only on the surface on the side where the polarizer is formed.

It is preferable that the film coated with the dye having absorption anisotropy and cured is thin, but if it is too thin, the strength is lowered and the processability tends to be inferior. The thickness of the film is usually 20 μm or less, preferably 5 μm or less, and more preferably 0.5 μm or more and 3 μm or less.

Specific examples of the film coated with the dye having absorption anisotropy and cured include those described in JP-A-2013-373353 and JP-A-2013-33249.

(Alignment film)
The alignment film can be arranged between the base material and a composition containing a dichroic dye having a liquid crystal property, or a layer of a cured product of the composition containing the dichroic dye and a liquid crystal compound. The alignment film has an orientation regulating force that aligns the liquid crystal layer formed on the liquid crystal layer in a desired direction. Examples of the alignment film include an orientation polymer layer formed of an alignment polymer, a photo-alignment polymer layer formed of a photo-alignment polymer, and a grub alignment film having an uneven pattern or a plurality of grubs (grooves) on the layer surface. Can be done. The thickness of the alignment film may be, for example, 10 nm or more and 500 nm or less, and preferably 10 nm or more and 200 nm or less.

The oriented polymer layer can be formed by applying a composition in which the oriented polymer is dissolved in a solvent to a substrate to remove the solvent, and if necessary, rubbing treatment. 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 condition of the orientation polymer and the rubbing conditions.

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

The grub alignment film is used, for example, in a method of forming a concavo-convex pattern by performing exposure, development, etc. through an exposure mask having a pattern-shaped slit on the surface of a photosensitive polyimide film, and is active on a plate-shaped master having a groove on the surface. A method of forming an uncured layer of an energy ray-curable resin, transferring this layer to a substrate and curing it, forming an uncured layer of an active energy ray-curable resin on the substrate, and making this layer uneven. It can be formed by a method of forming irregularities and hardening by pressing a roll-shaped master plate having the above.

(Protective layer)
The protective layer can be used to protect the surface of the polarizer 11. As the protective layer, a thermoplastic resin film exemplified as a material for the thermoplastic resin film described later may be used, or a coating type protective layer may be used. The coating type protective layer may be formed by applying a cationic curable composition such as an epoxy resin or a radical curable composition such as (meth) acrylate and curing it, and may be an aqueous solution of a polyvinyl alcohol-based resin or the like. It may be coated and dried, and if necessary, a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or a dye, an optical brightener, a dispersant, a heat stabilizer, and a light stabilizer. It may contain an agent, an antioxidant, an antioxidant, a lubricant, and the like.

The thickness of the protective layer may be, for example, 50 μm or less, preferably 35 μm or less, and more preferably 10 μm or less. The thickness of the protective layer may be, for example, 0.1 μm or more.

[Thermoplastic resin film]
The thermoplastic resin film can be incorporated into the linear polarizing plate in the form of being bonded to one side or both sides of the polarizer. The thermoplastic resin film may be, for example, a translucent, preferably optically transparent thermoplastic resin film, and examples thereof include chain polyolefin resins (polyethylene resin, polypropylene resin, poly). Methylpentene resin, etc.), Cyclic polyolefin resin (Norbornen resin, etc.) and other polyolefin resins; Triacetyl cellulose and other cellulose resins; Polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate and other polyester resins; Polycarbonate-based Resin; ethylene-vinyl acetate resin; polystyrene resin; polyamide resin; polyetherimide resin; (meth) acrylic resin such as polymethyl (meth) acrylate resin; polyimide resin; polyether sulfone resin; polysulfone type Resins; Polyvinyl chloride resin; Polyvinylidene chloride resin; Polypoly alcohol resin; Polypolyacetal resin; Polyether ketone resin; Polyether ether ketone resin; Polyether sulfone resin; Polyamideimide resin, etc. Be done. The thermoplastic resin can be used alone or in combination of two or more. Among them, a triacetyl cellulose-based resin film, a cyclic polyolefin-based resin film, and a (meth) acrylic-based resin film are preferable from the viewpoint of strength and translucency.

The thermoplastic resin film can function as a polarizer protective film or a retardation film. A surface treatment layer (coating layer) such as a hard coat layer, an antireflection layer, and an antistatic layer can also be formed on the surface of the thermoplastic resin film opposite to the polarizer.

By providing the hard coat layer on the thermoplastic resin film, it is possible to obtain a resin film having improved hardness and scratchability. The hard coat layer can be formed from a cured product of a composition for forming a hard coat layer containing an active energy ray-curable resin. Examples of the ultraviolet curable resin include acrylic resin, silicone resin, polyester resin, urethane resin, amide resin, epoxy resin and the like. The hard coat layer may contain additives to improve strength. Additives are not limited, and include inorganic fine particles, organic fine particles, or mixtures thereof.

The thickness of the thermoplastic resin film is preferably 30 μm or less, more preferably 25 μm or less, further preferably 20 μm or less, and usually 5 μm or more, preferably 15 μm or more, from the viewpoint of thinning. .. The thermoplastic resin film may or may not have a phase difference.

The adhesive used for bonding the polarizer and the thermoplastic resin film includes an active energy ray-curable adhesive such as an ultraviolet curable adhesive, an aqueous solution of a polyvinyl alcohol-based resin, or an aqueous solution containing a cross-linking agent. , Water-based adhesives such as urethane-based emulsion adhesives can be mentioned. When the thermoplastic resin films are bonded to both sides of the polarizer, the adhesives forming the two adhesive layers may be of the same type or different types. For example, when the thermoplastic resin film is bonded on both sides, one side may be bonded using a water-based adhesive and the other side may be bonded using an active energy ray-curable adhesive. The ultraviolet curable adhesive may be a mixture of a radically polymerizable (meth) acrylic compound and a photoradical polymerization initiator, a mixture of a cationically polymerizable epoxy compound and a photocationic polymerization initiator, and the like. Further, a cationically polymerizable epoxy compound and a radically polymerizable (meth) acrylic compound may be used in combination, and a photocationic polymerization initiator and a photoradical polymerization initiator may be used in combination as an initiator.

When an active energy ray-curable adhesive is used, the adhesive is cured by irradiating the active energy ray after bonding. The light source of the active energy ray is not particularly limited, but an active energy ray (ultraviolet ray) having an emission distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, and the like. A black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like is preferably used.

In order to improve the adhesiveness between the polarizer and the thermoplastic resin film, prior to the bonding between the polarizer and the thermoplastic resin film, the polarizing element and / or the bonded surface of the thermoplastic resin film is subjected to corona treatment and flame. Surface treatments such as treatment, plasma treatment, ultraviolet irradiation treatment, primer coating treatment, and saponification treatment may be performed.

[Manufacturing method of circularly polarizing plate]
The circular polarizing plate can be manufactured by a method including a step of laminating a linear polarizing plate and a laminated retardation film via an adhesive layer. When the layers are bonded to each other via the second adhesive layer, it is preferable to apply a surface activation treatment such as a corona treatment to one or both of the bonded surfaces in order to improve the adhesion. ..

When the polarizer is a stretched film or stretched layer on which a dye having absorption anisotropy is adsorbed, the method for producing a polarizer is a description of the stretched film or stretched layer on which a dye having absorption anisotropy is adsorbed. Can be manufactured as described in.

When the polarizer is a polarizer that is a film obtained by applying and curing the above-mentioned dye having absorption anisotropy, the polarizer can be formed on the substrate via an alignment film. The polarizer can be formed by applying a composition for forming a polarizer containing a dichroic dye and a polymerizable liquid crystal compound and curing the composition. The composition for forming a polarizer further contains, preferably, a polymerization initiator, a leveling agent, a solvent, a photosensitizer, a polymerization inhibitor, a leveling agent, etc., in addition to the above-mentioned dichroic dye and polymerizable liquid crystal compound. Can include.

The coating, drying and polymerization of the polymerizable liquid crystal compound of the composition for forming a polarizer can be carried out by conventionally known coating methods, drying methods and polymerization methods.

For example, as a method for applying the composition for forming a polarizer, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method and the like can be adopted.

The polymerization method of the polymerizable liquid crystal compound may be selected according to the type of the polymerizable group of the polymerizable liquid crystal compound. If the polymerizable group is a photopolymerizable group, it can be polymerized by a photopolymerization method. If the polymerizable group is a thermally polymerizable group, it can be polymerized by a thermal polymerization method. In the method for producing the liquid crystal cured retardation layer of the present embodiment, the photopolymerization method is preferable. In the photopolymerization method, it is not always necessary to heat the transparent base material to a high temperature, so that a transparent base material having low heat resistance can be used. The photopolymerization method is carried out by irradiating a film composed of a polarizer-forming composition or a retardation layer-forming composition containing a polymerizable liquid crystal compound with visible light or ultraviolet light. Ultraviolet light is preferable because it is easy to handle.

The adhesive layer can be prepared as an adhesive sheet. The pressure-sensitive adhesive sheet is prepared by dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a pressure-sensitive adhesive solution, which is then subjected to a release treatment to form a layer of the pressure-sensitive adhesive on a release film. It can be produced by forming it into a sheet shape and laminating another release film on the pressure-sensitive adhesive layer. Each layer can be bonded by a method in which the pressure-sensitive adhesive sheet from which one release film has been peeled off is attached to one layer, then the other release film is peeled off, and the other layer is attached.

As a method of applying the adhesive liquid on the release film, a usual coating technique using a die coater, a comma coater, a reverse roll coater, a gravure coater, a rod coater, a wire bar coater, a doctor blade coater, an air doctor coater, etc. Should be adopted.

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

The thickness of the adhesive layer can be adjusted according to the coating conditions of the adhesive liquid. In order to reduce the thickness of the pressure-sensitive adhesive layer, it is effective to reduce the coating thickness.

The circular polarizing plate can be manufactured by cutting a long-shaped film in which a linear polarizing plate and a liquid crystal cured retardation layer are bonded via an adhesive layer to a predetermined size. Further, the circular polarizing plate can also be manufactured by bonding a linear polarizing plate previously cut to a predetermined size and a liquid crystal cured retardation layer with an adhesive layer.

<Use of circularly polarizing plate>
The circular polarizing plate can be used in an image display device. The image display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, a touch panel display device, and an electroluminescent display device. ..

<Laminate for flexible image display device>
The image display device may be a flexible image display device. The flexible image display device is composed of a laminate for a flexible image display device and an organic EL display panel, and the laminate for the flexible image display device is arranged on the visual side with respect to the organic EL display panel and is configured to be bendable. There is. The laminated body for the flexible image display device may include the circular polarizing plate of the present invention, the front plate and / or the touch sensor, and the stacking order thereof is arbitrary, but the front plate (window) is viewed from the visual side. ), The circular polarizing plate of the present invention, or the touch sensor, or the front plate, the touch sensor, and the circular polarizing plate of the present invention are preferably laminated in this order. The presence of a circular polarizing plate on the visual side of the touch sensor is preferable because the pattern of the touch sensor is less likely to be visually recognized and the visibility of the displayed image is improved. Each member can be laminated using an adhesive, an adhesive, or the like. Further, a light-shielding pattern formed on at least one surface of any layer of the front plate, the circular polarizing plate, and the touch sensor can be provided.

[Front plate]
A front plate may be arranged on the visible side of the linear polarizing plate. The front plate can be laminated on the polarizing plate via the adhesive layer. Examples of the adhesive layer include the above-mentioned adhesive layer and adhesive layer.

Examples of the front plate include those having a hard coat layer on at least one surface of glass or a resin film. As the glass, for example, highly transparent glass or tempered glass can be used. Especially when a thin transparent surface material is used, chemically strengthened glass is preferable. The thickness of the glass can be, for example, 100 μm or more and 5 mm or less.

The front plate, which includes a hard coat layer on at least one surface of the resin film, can have a flexible property rather than being rigid like existing glass. The thickness of the hard coat layer is not particularly limited, and may be, for example, 5 μm or more and 100 μm or less.

Examples of the resin film include cycloolefin derivatives having a unit of a monomer containing cycloolefin such as norbornene or polycyclic norbornene-based monomer, and cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl ester cellulose). , Propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose) ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacrylic, polyimide, polyamideimide, polyethersulfone, polysulfone, polyethylene, Polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetate, polyether ketone, polyether ether ketone, polyether sulne, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate , Polyethylene, epoxy and other polymers may be used. As the resin film, an unstretched uniaxial or biaxially stretched film can be used. Each of these polymers can be used alone or in combination of two or more. As the resin film, a polyamideimide film or a polyimide film having excellent transparency and heat resistance, a uniaxial or biaxially stretched polyester film, a cycloolefin derivative film having excellent transparency and heat resistance and capable of adapting to a large size of the film. , Polymethylmethacrylate films and triacetylcellulose and isobutylester cellulose films that are transparent and not optically anisotropic are preferred. The thickness of the resin film may be 5 μm or more and 200 μm or less, preferably 20 μm or more and 100 μm or less.

[Shading pattern]
The light-shielding pattern (bezel) can be formed on the display element side of the front plate. The shading pattern can hide each wiring of the display device so that it cannot be seen by the user. The color and / or material of the light-shielding pattern is not particularly limited, and can be formed of a resin substance having various colors such as black, white, and gold. In one embodiment, the thickness of the light-shielding pattern may be 2 μm or more and 50 μm or less, preferably 4 μm or more and 30 μm or less, and more preferably 6 μm or more and 15 μm or less. Further, in order to suppress the mixing of air bubbles due to the step between the light-shielding pattern and the display unit and the visibility of the boundary portion, the light-shielding pattern can be given a shape.

[Touch sensor]
The touch sensor is used as an input means. As the touch sensor, various types such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and a capacitance method have been proposed, and any method may be used. Of these, the capacitance method is preferable. Capacitive touch sensor It is divided into an active region and an inactive region located outside the active region. The active area is an area corresponding to the area where the screen is displayed on the display panel (display unit), the area where the user's touch is sensed, and the inactive area is the area where the screen is not displayed on the display device (non-active area). This is the area corresponding to the display unit). The touch sensor is formed on a substrate having flexible characteristics; a sensing pattern formed in an active region of the substrate; and is formed in an inactive region of the substrate, and is connected to an external drive circuit via the sensing pattern and a pad portion. Each sensing line for can be included. As the substrate having flexible characteristics, the same material as the transparent substrate of the window can be used. A touch sensor substrate having a toughness of 2,000 MPa% or more is preferable from the viewpoint of suppressing cracks that may occur in the touch sensor. More preferably, the toughness is 2,000 MPa% to 30,000 MPa%. Here, toughness is defined as the lower area of the curve to the fracture point in the stress-strain curve obtained through the tensile test of the polymer material.

The layer structure of the laminated body for the flexible image display device will be described with reference to FIG. The laminated body 300 for a flexible image display device shown in FIG. 3 includes a laminated retardation film 100 and a linear polarizing plate 60 laminated on one of them. The laminated body 300 for a flexible image display device further includes a front plate 80 on the visible side of the linear polarizing plate 60 and a touch sensor 90 on the side opposite to the linear polarizing plate 60 of the laminated retardation film 100. The front plate 80 has a light-shielding pattern 81 on the surface on the side of the linear polarizing plate 60.

Hereinafter, the present invention will be described in more detail with reference to Examples.

<Cold impact test>
The long side dimension (the dimension of the side parallel to the slow axis direction of the first liquid crystal cured retardation layer) obtained in Examples and Comparative Examples is 130 mm, and the short side dimension (the dimension of the first liquid crystal cured retardation layer). A thermal shock test was performed on a circular polarizing plate having a (dimension of a side parallel to the phase-advancing axis direction) of 70 mm, and the absolute value of the amount of change in the dimensional difference and the absolute value of the amount of change in the reflected hue difference were obtained.
In the thermal shock test, a circular polarizing plate bonded to an inorganic glass plate via an adhesive layer on the liquid crystal curing retardation layer side is installed in a thermal shock test tank, cooled to -40 ° C, and then cooled at -40 ° C. After holding for 30 minutes, the cold test was repeated for 300 cycles, with the operation of heating to 85 ° C. and holding at 85 ° C. for 30 minutes as one cycle.
After the thermal shock test, the circular polarizing plate was observed with transmitted light with an optical microscope to confirm the presence or absence of cracks.

<Measurement method of piercing strength>
The composition for forming the retardation layer used for forming the first and second liquid crystal curing retardation layers described later was used as a base material so as to have the same thickness as the thickness of the first and second liquid crystal curing retardation layers described later. After coating and curing, the substrate was peeled off and measured as a single substance.
The puncture test was performed using a handy compression tester (KES-G5 needle penetration measurement specification, manufactured by Kato Tech Co., Ltd.) equipped with a needle having a tip diameter of 1 mmφ and 0.5R. The measurement was carried out in an environment of a temperature of 23 ± 3 ° C. and a piercing speed of 0.33 cm / sec. The piercing strength measured in the piercing test was the average value obtained by performing the piercing test on five test pieces. The piercing strength is determined by peeling the transparent base material from the laminate composed of the layer in which the retardation layer forming composition is cured, the alignment layer, and the transparent base material, and the layer in which the retardation layer forming composition is cured and the alignment layer. The measurement was carried out from the orientation layer side of the laminated body made of the above material through the alignment layer.

<Measurement method of storage elastic modulus>
The storage elastic modulus of the adhesive layer was measured by the following method.
A plurality of adhesive layers used in Examples and Comparative Examples were laminated so as to have a thickness of 0.2 mm. A cylinder having a diameter of 8 mm was punched out from the obtained pressure-sensitive adhesive layer, and this was used as a sample for measuring the storage elastic modulus. The storage elastic modulus (Pa) of the above sample was measured by a torsional shear method using a viscoelasticity measuring device (MCR300, manufactured by Physica) in accordance with JIS K7244-6 under the following conditions.
[Measurement condition]
Normal force FN: 1N
Strain γ: 1%
Frequency: 1Hz
Temperature: 25 ° C

<Linear polarizing plate>
[Preparation of polarizer]
A polyvinyl alcohol film having an average degree of polymerization of about 2400, a saponification degree of 99.9 mol%, and a thickness of 30 μm [trade name “VF-PE # 3000” of Kuraray Co., Ltd.] is immersed in pure water at 37 ° C. It was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.04 / 1.5 / 100 at 30 ° C. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 12 / 3.6 / 100 at 56.5 ° C. Subsequently, the mixture was washed with pure water at 10 ° C. and then dried at 85 ° C. to prepare a polarizer having a thickness of about 12 μm in which iodine was adsorbed and oriented on polyvinyl alcohol. The stretching was mainly carried out in the steps of iodine staining and boric acid treatment, and the total stretching ratio was 4.8 times.

[1st protective film]
A norbornene-based resin film having a thickness of 30 μm was used. One surface of this film is surface-treated so that the other surface serves as a bonding surface with a polarizer.

[Second protective film]
A triacetyl cellulose-based resin film having a thickness of 20 μm was used.

[Manufacturing of linear polarizing plate]
A polarizing plate was manufactured by sequentially adhering a first protective film, a polarizer, and a second protective film to the above-mentioned polarizing element via an aqueous adhesive. As the water-based adhesive, 3 parts of carboxy group-modified polyvinyl alcohol [trade name "KL-318" obtained from Kuraray Co., Ltd.] is dissolved in 100 parts of water, and polyamide epoxy, which is a water-soluble epoxy resin, is dissolved in the aqueous solution. Uses an epoxy adhesive containing 1.5 parts of a system additive [trade name "Smiley's Resin (registered trademark) 650 (30)" obtained from Taoka Chemical Industry Co., Ltd., an aqueous solution with a solid content concentration of 30%]. did.

<First liquid crystal cured retardation layer>
As the first liquid crystal cured retardation layer, a layer having a cured nematic liquid crystal compound, an alignment film, and a transparent substrate having a λ / 4 retardation was prepared. The total thickness of the cured layer of the nematic liquid crystal compound and the oriented layer was 2 μm. The cured layer of the nematic liquid crystal compound was formed by applying a composition for forming a retardation layer containing the nematic liquid crystal compound on an alignment film formed on a transparent substrate and curing the layer. Table 1 shows the measurement results of the piercing strength.

<Second liquid crystal cured retardation layer>
A polyethylene terephthalate base material having a thickness of 38 μm was used as a transparent base material, and one side thereof was coated with a composition for a vertically oriented layer so as to have a thickness of 3 μm, and an oriented layer was prepared by irradiating polarized ultraviolet rays of ^{20 mJ / cm 2.} .. The composition for the vertically oriented layer includes 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, dipentaerythritol triacrylate, and bis (2-vinyloxyethyl) ether in a ratio of 1: 1: 4: 5. A mixture was used in which LUCIRIN (registered trademark) TPO was added at a ratio of 4% as a polymerization initiator.

Next, a composition for forming a retardation layer containing a photopolymerizable nematic liquid crystal (manufactured by Merck & Co., Inc., RMM28B) was applied onto the formed alignment layer by die coating. Here, in the liquid crystal composition, as a solvent, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone (CHN) having a boiling point of 155 ° C. are mixed in a mass ratio (MEK: MIBK: CHN) of 35: A mixed solvent mixed at a ratio of 30:35 was used. Then, the composition for forming a retardation layer prepared so that the solid content was 1 to 1.5 g was applied onto the alignment layer so that the coating amount was 4 to 5 g (wet).

After applying the composition for forming a retardation layer on the oriented layer, the drying treatment was performed with a drying temperature of 75 ° C. and a drying time of 120 seconds. Then, the liquid crystal compound was polymerized by irradiation with ultraviolet rays (UV) to obtain a positive C layer composed of a cured layer of the photopolymerizable nematic liquid crystal compound, an alignment layer, and a transparent substrate. The total thickness of the cured layer of the photopolymerizable nematic liquid crystal compound and the oriented layer was 4 μm. Next, from the transparent substrate, the layer on which the photopolymerizable nematic liquid crystal compound was cured and the alignment layer were peeled off and obtained, and the layer on which the photopolymerizable nematic liquid crystal compound was cured and the alignment layer were laminated from the alignment layer side. The piercing strength of the compound was measured. Table 1 shows the measurement results of the piercing strength.

<Phase difference layer laminate>
The first liquid crystal curing retardation layer and the second liquid crystal curing retardation layer are used as the first adhesive layer by an ultraviolet curable adhesive, and the respective liquid crystal curing retardation layer surfaces (the surface opposite to the transparent substrate) are separated. It was pasted so that it would be the pasted surface. Then, the ultraviolet curable adhesive was cured by irradiating with ultraviolet rays. The thickness of the UV-curable adhesive after curing was 2 μm. In this way, a retardation layer laminate composed of two liquid crystal curing retardation layers, a first liquid crystal curing retardation layer and a second liquid crystal curing retardation layer, was produced.

<Second adhesive layer>
[Adhesive layer 1]
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 5 μm was laminated on the mold-release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm that had been subjected to a mold release treatment was used. The storage elastic modulus of the pressure-sensitive adhesive layer from which the release film was removed from the pressure-sensitive adhesive sheet was 125,000 Pa at 25 ° C.

[Adhesive layer 2]
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 17 μm was laminated on the mold-release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm that had been subjected to a mold release treatment was used. The storage elastic modulus of the pressure-sensitive adhesive layer from which the release film was removed from the pressure-sensitive adhesive sheet was 45,200 Pa at 25 ° C.

[Adhesive layer 3]
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 25 μm was laminated on the mold-release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm that had been subjected to a mold release treatment was used. The storage elastic modulus of the pressure-sensitive adhesive layer from which the release film was removed from the pressure-sensitive adhesive sheet was 25,500 Pa at 25 ° C.

[Adhesive layer 4]
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm was laminated on the mold-release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm that had been subjected to a mold release treatment was used. The storage elastic modulus of the pressure-sensitive adhesive layer from which the release film was removed from the pressure-sensitive adhesive sheet was 125,000 Pa at 25 ° C.

<Example 1>
The pressure-sensitive adhesive layer 1 was transferred to the side surface of the second protective film (triacetyl cellulose-based resin film) of the polarizing plate. The separate film laminated on the pressure-sensitive adhesive layer 1 was peeled off, and the transparent base material on the first liquid crystal cured retardation layer side of the retardation layer laminate composed of the above two liquid crystal cured retardation layers was laminated on the peeled surface. The transparent base material on the side opposite to the surface laminated on the polarizer in the liquid crystal cured retardation layer was peeled off. The pressure-sensitive adhesive layer 4 was laminated as a third adhesive layer on the exposed surface after peeling off the transparent base material. In this way, the first protective film, the polarizer, the second protective film, and the laminated retardation film [adhesive layer 1 (second adhesive layer) / first liquid crystal curing retardation layer (λ / 4 retardation) The circularly polarizing plate of Example 1 composed of the giving layer) / first adhesive layer / second liquid crystal curing retardation layer (positive C layer)] and the pressure-sensitive adhesive layer 4 (third adhesive layer) in this order. Made.
The obtained circular polarizing plate was cut into a size of 130 mm × 70 mm, and the pressure-sensitive adhesive layer 4 was attached to an inorganic glass plate to perform a thermal shock test. As shown in Table 2, no cracks were confirmed.

<Example 2>
A retardation layer laminate of Example 2 was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive layer 4 was replaced with the pressure-sensitive adhesive layer 3 in Example 1, and a thermal shock test was conducted. As shown in Table 2, no cracks were confirmed.

<Comparative example 1>
A retardation layer laminate of Comparative Example 1 was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive layer 1 was replaced with the pressure-sensitive adhesive layer 2 in Example 1, and a thermal shock test was conducted. It was confirmed that cracks having a length of 50 mm or more were generated in the slow-phase axial direction. The results are shown in Table 2.

10 1st retardation layer, 20 1st adhesive layer, 30 2nd retardation layer, 40 2nd adhesive layer, 50 retardation layer laminate, 60 linear polarizing plate, 61, 63 thermoplastic resin film, 62 polarized light Child, 70 third adhesive layer, 80 front plate, 81 light-shielding pattern, 90 touch sensor, 100 laminated retardation film, 200 circular polarizing plate, 300 laminated body for flexible image display device.

Claims (6)

The first liquid crystal curing retardation layer and
A second liquid crystal cured retardation layer laminated on one surface of the first liquid crystal cured retardation layer via a first adhesive layer,
A laminated retardation film including a second adhesive layer laminated on a surface opposite to the second liquid crystal curing retardation layer of the first liquid crystal curing retardation layer.
The second liquid crystal cured retardation layer has a higher piercing strength than the first liquid crystal cured retardation layer.
A laminated retardation film having a storage elastic modulus of 46000 Pa or more in the second adhesive layer. The laminated retardation film according to claim 1, wherein a third adhesive layer is further laminated on the side of the second liquid crystal cured retardation layer. The laminated retardation film according to claim 2, wherein the storage elastic modulus of the second adhesive layer is equal to or higher than the storage elastic modulus of the third adhesive layer. A circular polarizing plate in which a linear polarizing plate is laminated on the second adhesive layer side of the laminated retardation film according to any one of claims 1 to 3. A laminated body for a flexible image display device including the circular polarizing plate according to claim 4 and a front plate and / or a touch sensor. An image display device including the circular polarizing plate according to claim 4.

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