CN112088325A - Polarizing plate and display device - Google Patents

Abstract

The present invention provides a circularly polarizing plate comprising a polarizing plate, a phase difference film and an adhesive layer, wherein the polarizing plate comprises a polarizer having a thickness of 15 [ mu ] m or less, the phase difference film comprises a phase difference layer having positive birefringence, the adhesive layer is formed from an adhesive composition, the gel fraction of the adhesive layer is 60 to 99 wt%, the adhesive composition comprises 0.01 to 5 parts by weight of a crosslinking agent (B) per 100 parts by weight of an acrylic resin (A), the acrylic resin (A) is a copolymer of 80 to 96 parts by weight of an alkyl (meth) acrylate, 3 to 15% by weight of a monomer having a ring (an aromatic ring or an aliphatic ring) and 0.1 to 5% by weight of a monomer having a polar functional group, and has a weight average molecular weight of 100 to 200 ten thousand and a molecular weight distribution of 3 to 7.

Description

Polarizing plate and display device

Technical Field

The invention relates to a polarizing plate and a display device.

Background

In recent years, image display devices typified by organic electroluminescence (hereinafter also referred to as organic EL) display devices have rapidly spread. An organic EL display device is equipped with a circularly polarizing plate having a polarizer and a retardation film (λ/4 plate). By disposing the circularly polarizing plate, reflection of outside light can be prevented and visibility of a screen can be improved.

With the rise of organic EL display devices, the desire for thinning of image display devices has become strong. Along with this, further thinning of the circularly polarizing plate is also required. The circularly polarizing plate generally includes a polarizing plate (a polarizing plate including a linear polarizer) and a retardation film. In addition, in view of the fact that the retardation film can be made thin, it has been studied to change the conventional retardation film formed from a resin film to a retardation film formed from a liquid crystal compound, for example, to a retardation film formed by polymerizing and curing a polymerizable liquid crystal compound (for example, see patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-54093

Disclosure of Invention

Problems to be solved by the invention

However, when the circularly polarizing plate is placed in a high-temperature environment, the color tone of the circularly polarizing plate may be changed from the initial state to blue or red. Such a problem may occur particularly in a circularly polarizing plate including a retardation film formed of a polymerizable liquid crystal compound, and for example, when the circularly polarizing plate is rectangular, the color tone of the circularly polarizing plate near 4 edges may be observed to be blue or red, respectively.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a circularly polarizing plate having a retardation film, in which a polarizing plate having a specific structure and a specific protective film are used, and in which an in-plane change in color tone is small even after the circularly polarizing plate is left in a high-temperature environment.

Means for solving the problems

The present invention provides a circularly polarizing plate represented by the following [1 ].

[1] A circularly polarizing plate having a protective film on one surface of a polarizer and a retardation film on the other surface thereof via an adhesive layer,

the thickness of the polarizing plate is 15 μm or less,

the retardation film comprises a retardation layer having positive birefringence,

the adhesive layer is formed from an adhesive composition containing 0.01-5 parts by weight of a crosslinking agent (B) per 100 parts by weight of an acrylic resin (A),

the acrylic resin (A) is a copolymer of a monomer mixture comprising a weight average molecular weight Mw of 100 to 200 ten thousand and a molecular weight distribution represented by the ratio Mw/Mn of the weight average molecular weight Mw to the number average molecular weight Mn of 3 to 7,

(A-1) 80 to 96% by weight of an alkyl (meth) acrylate represented by the following formula (I):

[ solution 1]

(in the formula, R₁Represents a hydrogen atom or a methyl group, R₂Represents an alkyl group having 1 to 14 carbon atoms optionally substituted with an alkoxy group having 1 to 10 carbon atoms);

(A-2) 3 to 15% by weight of an unsaturated monomer having 1 olefinic double bond and at least 1 aromatic or aliphatic ring in the molecule; and

(A-3) 0.1 to 5% by weight of an unsaturated monomer having a polar functional group.

Further, the circularly polarizing plate of the present invention is provided with the following [2] to [6] as a preferred embodiment.

[2] The circularly polarizing plate according to [1], wherein the (A-2) is an unsaturated monomer which is an aromatic ring-containing (meth) acrylic compound represented by the following formula (II):

[ solution 2]

(in the formula, R₃Represents a hydrogen atom or a methyl group, n is an integer of 1 to 8, R₄Represents a hydrogen atom, an alkyl group, an aralkyl group or an aryl group).

[3] The circularly polarizing plate according to [1] or [2], wherein the (A-3) is an unsaturated monomer having 1 or more polar functional groups selected from a free carboxyl group, a hydroxyl group, an amino group and an epoxy ring.

[4] The circularly polarizing plate according to any one of [1] to [3], wherein the (B) contains a crosslinking agent which is an isocyanate compound.

[5] The circularly polarizing plate according to any one of [1] to [4], wherein the adhesive composition further contains 0.03 to 1 part by weight of (C) a silane compound per 100 parts by weight of the acrylic resin.

[6] The circularly polarizing plate according to any one of [1] to [4], wherein the retardation layer is a layer obtained by polymerizing a polymerizable liquid crystal compound.

The present invention also provides the following [7] as a use of any one of the circularly polarizing plates.

[7] A display device in which the circularly polarizing plate according to any one of [1] to [6] is laminated on a display element.

Effects of the invention

According to the present invention, it is possible to provide a display device which has a small in-plane change in color tone, particularly in reflection color tone, even after being placed in a high-temperature environment, and which can provide a circularly polarizing plate suitable as a member of the display device.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a layer structure of a circularly polarizing plate.

Fig. 2 is a schematic cross-sectional view showing an example of a layer structure of the organic EL display device.

Fig. 3 is a plan view of a sample for evaluation.

Detailed Description

< definition of terms and symbols >

The terms and symbols in the present specification are defined as follows.

(1) Refractive index (nx, ny, nz)

"nx" is a refractive index in a direction in which the in-plane refractive index is maximized (i.e., the slow axis direction), "ny" is a direction orthogonal to the slow axis direction in the plane, and "nz" is a refractive index in the thickness direction.

(2) Phase difference value in plane

The in-plane phase difference (Re [ lambda ]) means the in-plane phase difference of the film at 23 ℃ and a wavelength [ lambda ] (nm). When the film thickness is d (nm), Re [ λ ] can be obtained by using (nx-ny) × d.

(3) Phase difference value in thickness direction

The retardation value in the thickness direction (Rth [ lambda ]) means the retardation value in the thickness direction of the film at 23 ℃ and a wavelength lambda (nm). When the thickness of the film is d (nm), Rth [ λ ] can be obtained by using Rth [ λ ] (nx + ny)/2-nz) × d.

(4) The negative birefringence means that a slow axis is developed in a direction perpendicular to the stretching direction of the resin film.

(5) The positive birefringence means that a slow axis is developed in a direction parallel to the stretching direction of the resin (retardation) film.

(6) Non-oriented film

The non-oriented film used in the present invention is a film having a phase difference Re [590] in the plane of the film at a wavelength of 590nm of 10nm or less. Further, when the retardation value Rth [590] in the thickness direction satisfies 15nm or less, the color change in the heat resistance test can be remarkably suppressed, and therefore, it is preferable.

< circular polarizing plate >

The circularly polarizing plate of the present invention is a circularly polarizing plate comprising a polarizing plate having a protective film on one surface of a polarizer and a retardation film on the other surface thereof, wherein the polarizer has a thickness of 15 [ mu ] m or less, the retardation film comprises a retardation layer having positive birefringence, and the adhesive layer is formed from a specific adhesive composition. The polarizing plate and the retardation film may be laminated via an adhesive layer, for example. Examples of the adhesive layer include an adhesive layer and an adhesive layer described later. An example of the layer structure of the circularly polarizing plate of the present invention will be described below with reference to fig. 1. In fig. 1, an adhesive layer for bonding the polarizing plate 10 and the protective film to each other is not shown. Further, since the effects of the present invention can be further enjoyed, it is preferable that the retardation film includes a layer obtained by polymerizing (curing) a polymerizable liquid crystal compound (hereinafter, such a retardation film is referred to as a "liquid crystal cured film").

The circularly polarizing plate 100 shown in fig. 1(a) has a structure in which a protective film 11 is laminated on one surface of a polarizer 10 and a retardation film 20 is laminated on the other surface via an adhesive layer 13. Although not shown, an adhesive layer may be provided between the polarizing plate 10 and the protective film 11. In the circularly polarizing plate of the present invention, the retardation film 20 may have, for example, as shown in fig. 1(b), a retardation film 20 (circularly polarizing plate 101) composed of a layer in which a liquid crystal cured film 21 and a liquid crystal cured film 22 are laminated via an adhesive layer 15. Either one of the liquid crystal cured film 21 and the liquid crystal cured film 22 may be replaced with, for example, a retardation film obtained by stretching a polycarbonate resin film. The circularly polarizing plate 100 has an adhesive layer 14 on the side of the retardation film 2 opposite to the polarizing plate 1, and the circularly polarizing plate 101 has an adhesive layer 14 on the side of the retardation film 20 opposite to the polarizing plate 1. The pressure-sensitive adhesive layer 14 is used for bonding to a display panel such as an organic EL display device.

As shown in fig. 1(a) and (b), in the circularly polarizing plate of the present invention, the retardation film may have 1 retardation layer or 2 retardation layers. The retardation film may have 3 or more retardation layers in a range where the circularly polarizing plate does not become extremely thick. In addition, in the case of having a liquid crystal cured film constituting the retardation film 20, the liquid crystal cured film may have an alignment film for aligning the polymerizable liquid crystal compound in the production stage thereof.

The circularly polarizing plate of the present invention may have layers other than those illustrated in fig. 1 and 2. Examples of the circularly polarizing plate that may further include a layer include a front panel and a light-shielding pattern. The front panel may be disposed on the opposite side of the polarizing plate from the side on which the retardation film is laminated.

The light shielding pattern may be formed on a face of the front panel on the polarizing plate side. The light-shielding pattern is formed in a frame (non-display region) of the image display device, and the wiring of the image display device can be prevented from being viewed by a user.

The shape of the main surface of the circularly polarizing plate may be substantially rectangular. Here, the main surface refers to a surface having the largest area corresponding to the display surface. The substantially rectangular shape means that at least 1 of the 4 corners (corners) may be cut out to form an obtuse angle or may be formed into an arc shape, or a portion of an end surface perpendicular to the main surface may have a recessed portion (notch) recessed in the in-plane direction, or a portion of the main surface may have a hole portion hollowed out in a shape such as a circle, an ellipse, a polygon, or a combination thereof.

The size of the circularly polarizing plate is not particularly limited. The size can be selected according to the type and size of the display surface of the display device used after the circular polarizing plate is bonded. When the circularly polarizing plate is substantially rectangular, the length of the long side is preferably 6cm or more and 35cm or less, more preferably 10cm or more and 30cm or less, and the length of the short side is preferably 5cm or more and 30cm or less, more preferably 6cm or more and 25cm or less.

< polarizing plate >

In the circularly polarizing plate of the present invention, the polarizing plate is a laminate comprising a polarizer and a protective film attached to one surface of the polarizer. The circularly polarizing plate 100 and the circularly polarizing plate 101 shown in fig. 1(a) and (b) include a protective film 11 on one surface of a polarizer 10. The protective film provided in the polarizing plate may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, a light diffusion layer, an antireflection layer, a low refractive index layer, an antistatic layer, and an antifouling layer, which will be described later. The polarizing plate and the protective film may be laminated via an adhesive layer or an adhesive layer, for example. The members provided in the polarizing plate are described below.

(1) Polarizing plate

The polarizing plate may be an absorption-type polarizing plate having a property of absorbing linearly polarized light having a vibration plane parallel to the absorption axis thereof and transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to the transmission axis). As the polarizing plate, a polarizing plate in which a uniaxially stretched polyvinyl alcohol resin film is allowed to adsorb a dichroic dye and is oriented can be suitably used. Such a polarizing plate can be used, for example, by a method including a step of uniaxially stretching a polyvinyl alcohol resin film (stretching treatment); a step of dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye (dyeing treatment); a step of treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with a crosslinking agent liquid such as an aqueous boric acid solution (crosslinking treatment); and a step of washing with water after the crosslinking treatment.

As the polyvinyl alcohol resin, a resin obtained by saponifying a polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other copolymerizable monomers. Specific examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

In the present specification, "(meth) acrylic acid (Japanese text: (メタ) アクリル)" means at least one member selected from acrylic acids and methacrylic acids. The same applies to "(meth) acryloyl group", "(meth) acrylate", and the like.

The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polyvinyl alcohol resin has an average polymerization degree of usually 1000 to 10000, preferably 1500 to 5000. The average polymerization degree of the polyvinyl alcohol resin can be determined in accordance with JIS K6726.

A film (polyvinyl alcohol resin film) obtained by forming such a polyvinyl alcohol resin film can be used as a raw material (raw material film) of a polarizing plate (polarizing plate). The method for forming the film from the polyvinyl alcohol resin is not particularly limited, and a known method can be used. The thickness of the polyvinyl alcohol resin film is not particularly limited, but in order to set the thickness of the polarizing plate to 15 μm or less, the thickness of the polyvinyl alcohol resin film before uniaxial stretching is preferably 5 to 35 μm, and more preferably 20 μm or less. As described in the above background art, it is desired to further reduce the thickness of the circularly polarizing plate, and therefore, it is also preferable to reduce the thickness of the polarizing plate and the polarizer included in the circularly polarizing plate.

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing treatment of the dichroic dye. In the case where the uniaxial stretching is performed after the dyeing treatment, the uniaxial stretching may be performed before or during the crosslinking treatment. In addition, uniaxial stretching may be performed in a plurality of stages of these.

In the case of uniaxial stretching, the stretching may be performed uniaxially between rolls having different peripheral speeds, or may be performed uniaxially using a heat roll. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state where the polyvinyl alcohol resin film is swollen with a solvent or water. The draw ratio is usually 3 to 8 times.

As a method for dyeing (dyeing treatment) a polyvinyl alcohol resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye is employed.

Iodine or a dichroic organic dye is used as the dichroic dye. The polyvinyl alcohol resin film is preferably subjected to an immersion treatment in water before the dyeing treatment.

As the crosslinking treatment after the dyeing treatment with the dichroic dye, a method of immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid is generally employed. In the case of using iodine as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide.

In the circularly polarizing plate of the present invention, the thickness of the polarizer is 15 μm or less, more preferably 13 μm or less, still more preferably 10 μm or less, and still more preferably 8 μm or less. The thickness of the polarizing plate is usually 2 μm or more, preferably 3 μm or more. According to the studies of the present inventors, it was clarified that the change in the color tone of the circularly polarizing plate is caused by the change in the retardation value of the retardation film. It is clarified that the change in the retardation value of the retardation film is caused by the stress when the polarizing plate is subjected to dimensional shrinkage in the circularly polarizing plate placed in a high-temperature environment. Therefore, from the viewpoint of reducing the influence of shrinkage of the polarizing plate, it is effective to prevent the change in color tone, particularly reflection color tone, by setting the thickness of the polarizing plate to 15 μm or less.

As the polarizing plate, for example, a polarizing plate in which a dichroic dye is aligned in a cured film obtained by polymerizing a liquid crystal compound can be used as described in japanese patent application laid-open No. 2016-170368. As the dichroic dye, a dichroic dye having absorption in a wavelength range of 380 to 800nm can be used, and an organic dye is preferably used. Examples of the dichroic dye include azo compounds.

The liquid crystal compound is a liquid crystal compound that can be polymerized in a state where alignment occurs, and may have a polymerizable group in a molecule. Further, as described in WO2011/024891, the polarizing plate may be formed of a dichroic dye having liquid crystallinity. The same applies to a liquid crystal cured film as a retardation film, but the polymerizable liquid crystal compound is polymerized and cured, and means that the polymerizable liquid crystal compound is polymerized three-dimensionally to become a solid substance insoluble or hardly soluble in a solvent or the like.

The contraction force of the polarizing plate is preferably 2.0N/2mm or less, more preferably 1.8N/2mm or less, and still more preferably 1.5N/2mm or less. The method for measuring the shrinkage force of the polarizing plate was the method described in the examples described later.

(2) Protective film

The circularly polarizing plate of the present invention has a polarizing plate having a protective film on one surface of a polarizer.

The protective film (protective film to be bonded to a polarizing plate) included in the polarizing plate may be a transparent (preferably optically transparent) polyolefin resin including a thermoplastic resin, for example, a chain polyolefin resin or a cyclic polyolefin resin; cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins such as methyl methacrylate resins; a polystyrene-based resin; a polyvinyl chloride resin; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins; polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; modified polyphenylene ether resin; a polysulfone-based resin; a polyether sulfone-based resin; a polyarylate-based resin; a polyamide imide resin; a polyimide-based resin; a film of maleimide resin or the like.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resins (polyethylene resins that are homopolymers of ethylene, and copolymers mainly composed of polymerized units derived from ethylene), polypropylene resins (polypropylene resins that are homopolymers of propylene, and copolymers mainly composed of polymerized units derived from propylene), and copolymers containing 2 or more kinds of chain olefins.

The cyclic polyolefin resin is a general term for resins obtained by polymerizing a cyclic olefin as a polymerization unit, and examples thereof include those described in Japanese patent application laid-open Nos. H1-240517, H3-14882, and H3-122137. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene (typically random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids and derivatives thereof, and hydrogenated products of these. Among these, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.

The polyester resin is a resin having an ester bond in the main chain, and is generally a polycondensate of a polycarboxylic acid or a derivative thereof and a polyol. As the polycarboxylic acid or a derivative thereof, a 2-membered dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalenedicarboxylate and the like. Examples of the polyol that can be used include 2-membered diols such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol. A typical example of the polyester resin is polyethylene terephthalate which is a condensation product of terephthalic acid and ethylene glycol.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example, poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymers; methyl methacrylate-acrylate- (meth) acrylic acidAn acid copolymer; methyl (meth) acrylate-styrene copolymers (MS resins and the like); copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylic acid norbornyl ester copolymer, etc.). Preferably, a poly (meth) acrylic acid C such as poly (methyl (meth) acrylate) is used_1-6The polymer containing an alkyl ester as a main component is preferably a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

The (meth) acrylic resin may be a (meth) acrylic resin having a lactone ring structure or a glutarimide structure. The (meth) acrylic resin having a lactone ring structure or a glutarimide structure is excellent in heat resistance. More preferably a (meth) acrylic resin having a glutarimide structure. When a (meth) acrylic resin having a glutarimide structure is used, a (meth) acrylic resin film having low moisture permeability and small retardation and ultraviolet transmittance can be obtained as described above. (meth) acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are described in, for example, Japanese patent application laid-open Nos. 2006-. These descriptions are incorporated herein by reference.

The glutarimide resin preferably contains a polymerized unit represented by the following general formula (1) (hereinafter also referred to as a glutarimide unit) and a polymerized unit represented by the following general formula (2) (hereinafter also referred to as a (meth) acrylate unit).

[ solution 3]

In the formula (1), R¹⁰And R²⁰Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R³⁰The group is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a group containing an aromatic ring having 5 to 15 carbon atoms. In the formula (2), R⁴⁰And R⁵⁰Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R⁶⁰The group is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a group containing an aromatic ring having 5 to 15 carbon atoms.

The glutarimide resin may further contain a polymerized unit represented by the following general formula (3) (hereinafter also referred to as an aromatic vinyl unit) as needed.

[ solution 4]

In the formula (3), R⁷Is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R⁸Is an aryl group having 6 to 10 carbon atoms.

In the general formula (1), R is preferably¹And R²Each independently being a hydrogen atom or a methyl group, R³Is a hydrogen atom, a methyl group, a butyl group, or a cyclohexyl group. In the general formula (1), R is more preferably¹Is methyl, R²Is a hydrogen atom, R³Is methyl.

The glutarimide resin may contain only a single type of glutarimide unit, or may contain R in the above general formula (1)¹、R²And R³A plurality of different categories.

The glutarimide unit may be formed by imidizing a (meth) acrylate unit represented by the general formula (2). Alternatively, the glutarimide unit may be prepared by reacting an acid anhydride such as maleic anhydride or a half ester of such an acid anhydride with a linear or branched alcohol having 1 to 20 carbon atoms; and α, β -ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, itaconic anhydride, crotonic acid, fumaric acid, and citraconic acid.

In the general formula (2), R is preferable⁴And R⁵Each independently being a hydrogen atom or a methyl group, R⁶Is a hydrogen atom or a methyl group, more preferably R⁴Is a hydrogen atom, R⁵Is methyl, R⁶Is methyl.

The glutarimide resin may contain only a single type as the (meth) acrylate unit, or may contain R in the above general formula (2)⁴、R⁵And R⁶A plurality of different categories.

In the above glutarimide resin, the aromatic vinyl unit represented by the above general formula (3) may preferably contain a polymerized unit derived from styrene, α -methylstyrene, or the like, and more preferably contains a polymerized unit derived from styrene. By having such an aromatic vinyl unit, the positive birefringence of the glutarimide structure can be reduced, and a (meth) acrylic resin film having a lower retardation value can be obtained.

The glutarimide resin may contain only a single type of aromatic vinyl unit, or may contain R⁷And R⁸A plurality of different categories.

The content of the glutarimide units in the glutarimide resin, for example, is preferably dependent on R³And the like. The content of the glutarimide unit is preferably 1 to 80% by weight, more preferably 1 to 70% by weight, still more preferably 1 to 60% by weight, and particularly preferably 1 to 50% by weight, based on the weight of the glutarimide resin. When the content of the glutarimide unit is in such a range, a (meth) acrylic resin film having a low retardation and excellent heat resistance can be obtained.

The content of the aromatic vinyl unit in the glutarimide resin may be appropriately set according to the purpose and the desired characteristics. The content of the aromatic vinyl unit may be 0 depending on the use. When the aromatic vinyl unit is contained, the content thereof is preferably 10 to 80% by weight, more preferably 20 to 80% by weight, further preferably 20 to 60% by weight, and particularly preferably 20 to 50% by weight, based on the total weight of the glutarimide units of the glutarimide resin. When the content of the aromatic vinyl unit is in such a range, a (meth) acrylic resin film having a low phase difference and excellent heat resistance and mechanical strength can be obtained.

The glutarimide resin may further contain a glutarimide unit, a (meth) acrylate unit, and a structural unit other than the aromatic vinyl unit, if necessary. Examples of the other structural units include structural units derived from nitrile monomers such as acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide and N-cyclohexylmaleimide. These other structural units may be directly copolymerized in the above-mentioned glutarimide resin or may be graft-copolymerized.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, there may be mentioned copolymers having a plurality of kinds of polymerization units constituting these cellulose ester resins, and resins in which a part of the hydroxyl groups is modified with other substituent groups. Among them, cellulose triacetate (triacetyl cellulose) is particularly preferable.

Polycarbonate-based resins are engineering plastics containing a polymer in which monomer units are bonded via carbonate groups.

The protective film may contain any suitable additive according to the purpose. Examples of the additives include stabilizers such as hindered phenol-based, phosphorus-based, and sulfur-based antioxidants, light-resistant stabilizers, ultraviolet absorbers, weather-resistant stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; a near infrared ray absorber; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic fillers, inorganic fillers; a resin modifier; a plasticizer; a lubricant; a retardation reducing agent, etc. The kind, combination, content and the like of the additives to be contained can be appropriately set according to the purpose and the desired characteristics.

The method for producing the protective film is not particularly limited. Here, the production of the protective film will be briefly described by taking a (meth) acrylic resin film as an example. For example, the (meth) acrylic resin, the ultraviolet absorber, and other polymers and additives used as needed may be sufficiently mixed by any appropriate mixing method to prepare a thermoplastic resin composition in advance, and then the thermoplastic resin composition may be subjected to film molding. Alternatively, the (meth) acrylic resin, the ultraviolet absorber, and other polymers and additives used as needed may be prepared into different solutions, and then mixed to prepare a uniform mixed solution, followed by film-forming.

In the production of the thermoplastic resin composition, the above-mentioned film materials are premixed by an arbitrary appropriate mixer such as a universal mixer, and the resulting mixture is extruded and kneaded. In this case, the mixer used for extrusion kneading is not particularly limited, and any appropriate mixer such as a single-screw extruder, a twin-screw extruder, and a pressure kneader can be used.

Examples of the film forming method include any appropriate film forming method such as a solution casting method, a melt extrusion method, a rolling method, and a compression forming method. Among them, the melt extrusion method is preferable. Since the melt extrusion method does not use a solvent, the production cost and the burden on the global environment and the work environment due to the solvent can be reduced.

Examples of the melt extrusion method include a T-die method and a blow molding method.

The molding temperature is preferably 150 to 350 ℃, more preferably 200 to 300 ℃, and may be selected within an appropriate range depending on the type of resin (thermoplastic resin) used for film molding, the type of additive used together, and the like.

In the case of film formation by the T-die method, a T-die may be attached to a tip portion of a known single-screw extruder or twin-screw extruder, and a film extruded in a film shape may be wound to obtain a roll-shaped film. In this case, the temperature of the winding roll may be appropriately adjusted to apply stretching in the extrusion direction, thereby performing uniaxial stretching. Further, simultaneous biaxial stretching, sequential biaxial stretching, or the like may be performed by stretching the film in a direction perpendicular to the extrusion direction.

The (meth) acrylic resin film may be any of an unstretched film and a stretched film. In the case of the stretched film, the stretched film may be any of a uniaxially stretched film and a biaxially stretched film. In the case of the biaxially stretched film, the film may be either a simultaneously biaxially stretched film or a sequentially biaxially stretched film.

Hereinafter, the case of stretching the (meth) acrylic resin film will be described. The stretching temperature is preferably in the vicinity of the glass transition temperature of the thermoplastic resin composition as a film raw material, more specifically preferably in the range of (glass transition temperature-30 ℃) to (glass transition temperature +30 ℃), still more preferably in the range of (glass transition temperature-20 ℃) to (glass transition temperature +20 ℃). If the stretching temperature is less than (glass transition temperature-30 ℃), the haze of the obtained film becomes large, or the film may crack or break, and a predetermined stretching ratio may not be obtained. On the other hand, if the stretching temperature is higher than (glass transition temperature +30 ℃), the resulting film tends to have large thickness unevenness, or to have insufficient mechanical properties such as elongation, tear propagation strength (japanese original: strength for index grain reinforced distribution), and flex fatigue resistance (japanese original: flex fatigue resistance ). Further, there is a tendency that troubles such as adhesion of the film to the roller are easily caused.

The stretching ratio is preferably 1.1 to 3 times, and more preferably 1.3 to 2.5 times.

When the stretching ratio is within such a range, mechanical properties such as elongation, tear propagation strength, and rolling fatigue resistance of the film can be significantly improved. As a result, a film having small thickness unevenness, substantially zero birefringence (and thus a small retardation value), and a small haze can be produced.

The (meth) acrylic resin film may be subjected to a heat treatment (annealing) or the like after the stretching treatment in order to stabilize the optical isotropy and mechanical properties. The heat treatment conditions may be any appropriate conditions.

It is also useful to control the phase difference value of the protective film to a value suitable for an image display device such as an organic EL display device or a liquid crystal display device. For example, in an in-plane switching (IPS) mode liquid crystal display device, a film having a substantially zero retardation value is preferably used as the protective film. The phase difference value being substantially zero means that the in-plane phase difference value Re (550) at a wavelength of 550nm is 10nm or less and the absolute value of the thickness-direction phase difference value Rth at a wavelength of 550nm is 10nm or less. The absolute value of the retardation value Rth in the thickness direction at a wavelength of 480 to 750nm is preferably 15nm or less. In order to improve the visibility of the screen when the user wears polarized sunglasses or the like, the in-plane phase difference value Re (550) at a wavelength of 550nm may be set to 70 to 140 nm.

For example, the protective film may be subjected to stretching and/or shrinking processing to provide an appropriate retardation depending on the mode of the liquid crystal display device. For example, a film of a single layer or a multilayer structure may also be used as the protective film for the purpose of compensating the viewing angle.

The thickness of the protective film is usually 1 to 100 μm, but from the viewpoint of strength and workability, it is preferably 5 to 60 μm, more preferably 10 to 55 μm, and still more preferably 15 to 40 μm.

As described above, the protective film may be a film having a surface treatment layer (coating layer) on its outer surface (the surface opposite to the polarizing plate). The thickness of the protective film includes the thickness of the surface treatment layer.

As described above, although not shown in fig. 1 and the like, the protective film may be bonded to the polarizing plate via an adhesive layer or an adhesive layer, for example. As the adhesive for forming the adhesive layer, an aqueous adhesive, an active energy ray-curable adhesive, or a thermosetting adhesive can be used, and an aqueous adhesive or an active energy ray-curable adhesive is preferable. The pressure-sensitive adhesive layer may be the one described later.

Examples of the aqueous adhesive include an adhesive containing a polyvinyl alcohol resin aqueous solution, an aqueous two-part type urethane emulsion adhesive, and the like. Among them, an aqueous adhesive containing an aqueous solution of a polyvinyl alcohol resin is suitable. The polyvinyl alcohol resin used in the adhesive may be a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate as a homopolymer of vinyl acetate, a polyvinyl alcohol copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, or a modified polyvinyl alcohol polymer obtained by partially modifying hydroxyl groups of the above. The polyvinyl alcohol-based water-based adhesive may contain a crosslinking agent such as an aldehyde compound (e.g., glyoxal), an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, and a polyvalent metal salt.

When an aqueous adhesive is used, it is preferable to perform a drying step for removing water contained in the aqueous adhesive after the polarizing plate and the protective film are bonded. After the drying step, a curing step of curing at a temperature of 20 to 45 ℃ may be provided, for example.

The active energy ray-curable adhesive is an adhesive containing a curable compound that is cured by irradiation with an active energy ray such as ultraviolet ray, visible light, electron beam, or X-ray, and is preferably an ultraviolet ray-curable adhesive.

The curable compound may be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having 1 or 2 or more epoxy groups in a molecule), an oxetane compound (a compound having 1 or 2 or more oxetane rings in a molecule), and a combination thereof. Examples of the radically polymerizable curable compound include a (meth) acrylic compound (a compound having 1 or 2 or more (meth) acryloyloxy groups in the molecule), another vinyl compound having a radically polymerizable double bond, and a combination thereof. The cationically polymerizable curable compound and the radically polymerizable curable compound may be used in combination. The active energy ray-curable adhesive usually further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.

When the polarizing plate and the protective film are bonded, at least one of the bonding surfaces may be subjected to a surface activation treatment in order to improve the adhesiveness. Examples of the surface activation treatment include dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.); a wet treatment such as an ultrasonic treatment, a saponification treatment, and an anchor coating treatment using a solvent such as water or acetone. These surface activation treatments may be performed individually or in combination of 2 or more.

< retardation film >

The circularly polarizing plate of the present invention has a retardation film provided with a retardation layer having positive birefringence. As described above, the retardation layer preferably has a layer formed of a liquid crystal cured film. In the present specification, the liquid crystal cured film as the retardation layer includes a layer for imparting a retardation of λ/2, a layer (positive a layer) for imparting a retardation of λ/4, a positive C layer, and the like. Further, as described above, the retardation film may include an alignment film. The alignment film will be described later.

Next, the liquid crystal cured film will be explained. The liquid crystal cured film is a film having a layer obtained by curing a polymerizable liquid crystal compound, and is formed, for example, by providing an alignment film on a substrate in advance. The substrate has a function of supporting the alignment film, and may be a long substrate. The substrate functions as a releasable support and can support a phase difference layer for transfer. Further, a substrate having an adhesive force of a degree that can be peeled off on the surface thereof is preferable. The substrate may be a resin film exemplified as a material of the protective film.

The thickness of the substrate is not particularly limited, and is preferably in the range of, for example, 20 μm or more and 200 μm or less. The strength can be imparted when the thickness of the base material is 20 μm or more. On the other hand, when the thickness is 200 μm or less, increase of machining chips and abrasion of the cutting blade can be suppressed when the base material is cut into individual pieces.

The base material may be subjected to various anti-blocking treatments. Examples of the anti-blocking treatment include an easy adhesion treatment, a treatment in which a filler is added, and an embossing (knurling treatment). By applying such anti-blocking treatment to the base material, sticking, so-called blocking, between the base materials when the base material is wound can be effectively prevented. By the anti-blocking treatment of the base material, a liquid crystal cured film can be produced with high productivity.

When the liquid crystal cured film has a layer obtained by curing a polymerizable liquid crystal compound, the layer is formed on a substrate with an alignment film interposed therebetween. That is, an alignment film is laminated on a substrate, and a layer obtained by curing a polymerizable liquid crystal compound is laminated on the alignment film.

The alignment film is a film for aligning the molecular axis of the polymerizable liquid crystal compound in a specific direction, and may be not only a vertical alignment film but also an alignment film in which the molecular axis of the polymerizable liquid crystal compound is horizontally aligned, or an alignment film in which the molecular axis of the polymerizable liquid crystal compound is obliquely aligned. The alignment film is preferably one having solvent resistance that does not dissolve by coating of a composition containing a polymerizable liquid crystal compound described later or the like, and having heat resistance for use in heat treatment for removing the solvent or aligning the liquid crystal compound. Examples of the alignment film include an alignment film containing an alignment polymer, a photo-alignment film, and a groove alignment film in which a concave-convex pattern and a plurality of grooves are formed on the surface thereof and the grooves are aligned. The thickness of the alignment film is usually in the range of 10nm to 10000nm, preferably 10nm to 1000nm, more preferably 500nm or less, and still more preferably 10nm to 200 nm. When the retardation film includes an alignment film, the puncture elastic modulus is likely to be increased by increasing the thickness of the alignment film. By setting the thickness of the alignment film to the above range, appropriate rigidity and toughness can be imparted to the polymerizable liquid crystal compound, and high film strength can be imparted.

The resin used for the alignment film is not particularly limited as long as it is a known resin used as a material of the alignment film, and a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth) acrylate monomer with a polymerization initiator, or the like can be used. Specifically, examples of the (meth) acrylate monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol mono-phenyl ether acrylate, tetraethylene glycol mono-phenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and urethane acrylate. The resin may be a mixture of 1 or 2 or more of them.

The type of the polymerizable liquid crystal compound used in the present embodiment is not particularly limited, but the polymerizable liquid crystal compound can be classified into a rod-like type (rod-like liquid crystal compound) and a discotic type (discotic liquid crystal compound ) according to its shape. Further, there are low molecular type and high molecular type, respectively. The term "polymer" generally means a substance having a polymerization degree of 100 or more (physical-phase-transfer-of-polymer ダイナミクス (kinetics of physical-phase transfer), native-well, page 2, Shibo Shigaku, 1992).

In the formation of the retardation layer of the retardation film of the circularly polarizing plate of the present invention, any polymerizable liquid crystal compound may be used. In addition, 2 or more kinds of rod-like liquid crystal compounds, 2 or more kinds of discotic liquid crystal compounds, or a mixture of rod-like liquid crystal compounds and discotic liquid crystal compounds may be used.

As the rod-like liquid crystal compound, for example, the rod-like liquid crystal compounds described in claim 1 of Japanese patent application laid-open No. 11-513019 or paragraphs [0026] to [0098] of Japanese patent application laid-open No. 2005-289980 can be suitably used. As the discotic liquid crystal compound, for example, discotic liquid crystal compounds described in paragraphs [0020] to [0067] of Japanese patent laid-open No. 2007-108732 or paragraphs [0013] to [0108] of Japanese patent laid-open No. 2010-244038 can be suitably used.

The polymerizable liquid crystal compound may be used in combination of 2 or more. In this case, at least 1 of the 2 or more polymerizable liquid crystal compounds has 2 or more polymerizable groups in the molecule. As described above, the liquid crystal cured film is fixedly formed by curing the polymerizable liquid crystal compound through three-dimensional crosslinking. In this case, after the liquid crystal cured film is formed, it is not necessary for the polymer (cured product) of the polymerizable liquid crystal compound contained in the liquid crystal cured film to exhibit liquid crystallinity.

As the polymerizable group of the polymerizable liquid crystal compound, for example, a functional group capable of undergoing an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a cyclopolymerizable 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, (meth) acryloyl groups are preferable. As described above, the (meth) acryloyl group is a concept including both a methacryloyl group and an acryloyl group.

As described later, the liquid crystal cured film can be formed by, for example, applying a composition containing a polymerizable liquid crystal compound onto an alignment film and irradiating the composition with active energy rays. The composition may contain components other than the polymerizable liquid crystal compound. For example, in the composition, a polymerization initiator is preferably contained. The polymerization initiator used may be selected, for example, from thermal polymerization initiators and photopolymerization initiators, depending on the form of the polymerization reaction. The photopolymerization initiator is preferably used for polymerizing the polymerizable liquid crystal compound by irradiation with active energy rays, particularly ultraviolet irradiation. Examples of the photopolymerization initiator include α -carbonyl compounds, acyloin ethers, α -hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, combinations of triarylimidazole dimers and p-aminophenyl ketones, and the like. The amount of the polymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total weight of all solid components in the composition.

The composition may contain a polymerizable monomer in terms of uniformity of the coating film and strength of the film. Examples of the polymerizable monomer include a radical polymerizable or cation polymerizable compound, and an appropriate polymerizable monomer is selected according to the kind of the polymerizable liquid crystal compound used. Among them, polyfunctional radical polymerizable monomers are preferable.

As the polymerizable monomer, a polymerizable monomer copolymerizable with the polymerizable liquid crystal compound is preferable. The amount of the polymerizable monomer used is preferably 1 to 50% by weight, more preferably 2 to 30% by weight, based on the total weight of the polymerizable liquid crystal compound.

In addition, the composition may contain a surfactant in terms of uniformity of a coating film and strength of the film. Examples of the surfactant include conventionally known compounds. Among them, fluorine compounds are particularly preferable.

In addition, a solvent may be contained in the composition, and in this case, an organic solvent is preferably used. Examples of the organic solvent include an amide solvent (e.g., N-dimethylformamide), a sulfoxide solvent (e.g., dimethylsulfoxide), a heterocyclic compound solvent (e.g., pyridine), a hydrocarbon solvent (e.g., benzene, hexane), a haloalkane solvent (e.g., chloroform, dichloromethane), an ester solvent (e.g., methyl acetate, ethyl acetate, butyl acetate), a ketone solvent (e.g., acetone, methyl ethyl ketone), and an ether solvent (e.g., tetrahydrofuran, 1, 2-dimethoxyethane). Among them, halogenated alkyl solvents and ketone solvents are preferable. In addition, 2 or more organic solvents may be used in combination.

The composition may contain various alignment agents such as a vertical alignment promoter such as a polarizing plate interface side vertical alignment agent and an air interface side vertical alignment agent, and a horizontal alignment promoter such as a polarizing plate interface side horizontal alignment agent and an air interface side horizontal alignment agent. In addition to the above components, the composition may further contain an adhesion improver, a plasticizer, a polymer, and the like.

The active energy ray includes ultraviolet ray, visible light, electron beam, and X-ray, preferably ultraviolet ray. 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 excimer laser, an LED light source emitting light having a wavelength range of 380 to 440nm, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp.

When ultraviolet rays are used as the active energy rays, the irradiation intensity is usually 10 to 3000mW/cm in the ultraviolet B wave (wavelength region of 280 to 320nm)². The ultraviolet irradiation intensity is preferably an intensity in a wavelength region effective for activation of the cationic polymerization initiator or the radical polymerization initiator. The time for ultraviolet irradiation is usually 0.1 second to 10 minutes, preferably 0.1 second to 5 minutes, more preferably 0.1 second to 3 minutes, and still more preferably 0.1 second to 1 minute.

The ultraviolet rays may be irradiated 1 time or in a plurality of times. Although it depends also on the polymerization initiator used in the composition, the cumulative light amount at a wavelength of 365nm is preferably set to 700mJ/cm²More preferably 1100mJ/cm²It is more preferable to set the concentration to 1300mJ/cm²The above. The accumulated light amount is advantageous for increasing the polymerization rate of the polymerizable liquid crystal compound constituting the retardation film and improving the heat resistance of the retardation film. The cumulative light amount at a wavelength of 365nm is preferably set to 2000mJ/cm²More preferably 1800mJ/cm²The following. If the accumulated light amount is too high, the retardation film may be colored.

In the circularly polarizing plate of the present invention, the thickness of the retardation layer is preferably 0.5 μm or more. The thickness of the retardation layer is preferably 10 μm or less, and more preferably 5 μm or less. When the thickness of the retardation layer is not less than the lower limit, sufficient durability can be obtained. If the thickness of the retardation layer is not more than the upper limit, it can contribute to making the circularly polarizing plate thinner. The thickness of the retardation layer can be adjusted so as to obtain a desired in-plane retardation value and a thickness-direction retardation value of the layer giving a retardation of λ/4, the layer giving a retardation of λ/2, or the positive C layer.

In the retardation film of the circularly polarizing plate of the present invention, the retardation layer preferably has a liquid crystal cured film, and the liquid crystal cured film may be a liquid crystal cured film including 1 layer of a layer obtained by curing a polymerizable liquid crystal compound, or may be a liquid crystal cured film including 2 or more layers of a layer obtained by curing a polymerizable liquid crystal compound. When the retardation layer includes 2 layers obtained by curing a polymerizable liquid crystal compound, the 2 layers are preferably a combination of a layer giving a retardation of λ/4 and a positive C layer, or a combination of a layer giving a retardation of λ/4 and a layer giving a retardation of λ/2. When the retardation layer includes 2 cured layers of the polymerizable liquid crystal compound, the retardation film can be produced by preparing each cured layer of the polymerizable liquid crystal compound on the alignment film and laminating the two layers via an adhesive layer and an adhesive layer. After laminating the two, the substrate and the alignment film can be peeled off. The thickness of the retardation film is preferably 3 to 30 μm, and more preferably 5 to 25 μm.

The optical elasticity coefficient of the phase difference film is preferably 3-100 x 10^－13Pa^－1More preferably 5 to 70X 10^－13Pa^－1More preferably 15 to 60X 10^－13Pa^－1More preferably 20 to 60X 10^－13Pa^－1。

The photoelastic coefficient is a value measured by the method described in the examples described below.

< adhesive layer >

The circularly polarizing plate of the present invention includes an adhesive layer for laminating the polarizing plate and the retardation film or bonding the circularly polarizing plate to a display device such as a display panel. In the following, the pressure-sensitive adhesive layer 13 for bonding the polarizing plate 1 and the retardation film 20 to each other will be described first.

The adhesive layer contains a (meth) acrylic resin (base polymer) formed from an adhesive composition containing each monomer described below. The thickness of the adhesive layer 13 is preferably 3 to 30 μm, and more preferably 3 to 25 μm.

In the present invention, the adhesive layer 13 of the circularly polarizing plate 100 shown in fig. 1(a) or 101 shown in fig. 1(b) is formed of an adhesive composition in which a predetermined amount of a crosslinking agent is blended with an acrylic resin, which is the above-mentioned specific copolymer, and the weight average molecular weight Mw and the molecular weight distribution Mw/Mn determined by the ratio of the weight average molecular weight to the number average molecular weight Mn are within a predetermined range, and the gel fraction is set to 60 to 99% by weight. These weight average molecular weight Mw and molecular weight distribution Mw/Mn can be determined by a Gel Permeation Chromatography (GPC) method. The conditions for the GPC method may be set to appropriate conditions according to the type of the acrylic resin to be measured. Hereinafter, an adhesive composition for forming an appropriate adhesive layer will be described.

First, each component constituting the adhesive composition will be described. In addition, in accordance with the above-mentioned expression, the acrylic resin referred to herein is referred to as "acrylic resin (a)" and the crosslinking agent referred to herein is referred to as "crosslinking agent (B)". The alkyl (meth) acrylate represented by the above-mentioned (A-1) which is derived from the acrylic resin (A) may be referred to as "alkyl (meth) acrylate (A-1)", and the unsaturated monomers represented by (A-2) and (A-3) may be referred to as "unsaturated monomer (A-2)" and "unsaturated monomer (A-3)".

(1) Acrylic resin (A)

The acrylic resin (a) used in the adhesive composition for forming the adhesive layer 13 of the circularly polarizing plate of the present invention is a resin containing a polymerized unit derived from an alkyl (meth) acrylate represented by the formula (I) as a main component, and further containing a polymerized unit derived from a monomer having an aromatic ring and a polymerized unit derived from a monomer having a polar functional group in addition to the polymerized unit derived from the alkyl (meth) acrylate.

In the formula (I) which becomes a main polymerization unit of the acrylic resin (A), R₁Is a hydrogen atom or a methyl group, R₂Is an alkyl group having 1 to 14 carbon atoms. With R₂The hydrogen atom in each group of the alkyl group may be substituted by an alkoxy group having 1 to 10 carbon atoms.

Illustrative of R in the alkyl (meth) acrylate (A-1) represented by the formula (I)₂Alkyl (meth) acrylates which are unsubstituted alkyl groups. Examples of the alkyl (meth) acrylate (a-1) include linear alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, n-octyl acrylate, and lauryl acrylate; branched alkyl acrylates such as isobutyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate; linear alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, and lauryl methacrylate; branched alkyl methacrylates such as isobutyl methacrylate, 2-ethylhexyl methacrylate, and isooctyl methacrylate.

Among them, n-butyl acrylate is preferred, and specifically, n-butyl acrylate among the alkyl (meth) acrylates (A-1) derived from the whole polymerization units constituting the acrylic resin (A) is preferably made to be 50% by weight or more, and satisfies the regulation concerning the alkyl (meth) acrylate (A-1).

As R₂The alkyl (meth) acrylate represented by the formula (I) when it is an alkoxyalkyl group, which is an alkyl group substituted with an alkoxy group, specifically includes 2-methoxyethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl methacrylate, ethoxymethyl methacrylate, and the like.

These alkyl (meth) acrylates can be used alone or in combination of two or more different alkyl (meth) acrylates to produce the acrylic resin (a).

As the unsaturated monomer (a-2) having 1 olefinic double bond and at least 1 aromatic ring or aliphatic ring in the molecule, an unsaturated monomer having a (meth) acryloyl group as a group containing an olefinic double bond is preferable. The aromatic ring may be any of aromatic rings composed of only carbon atoms and heteroaromatic rings containing a hetero element other than carbon, but in the case of an aromatic ring composed of only carbon atoms, an unsaturated monomer which is easily available from the market can be used as the unsaturated monomer (a-2), and therefore, this is preferable. In addition, by using such an aromatic ring-containing unsaturated monomer (a-2), the adhesive exhibits a retardation in a direction perpendicular to the stress applied thereto with the shrinkage of the polarizing plate in a high temperature environment, whereas the retardation film exhibits a retardation in a direction parallel to the stress applied thereto with the shrinkage of the polarizing plate. This makes it possible to cancel out the change in retardation of the retardation film caused by the shrinkage of the polarizing plate by the adhesive layer.

This makes it possible to reduce the in-plane variation in color tone, particularly in reflection color tone, even when the film is left in a high-temperature environment. Examples of the unsaturated monomer (a-2) [ aromatic ring-containing acrylic compound ] having 1 olefinic double bond and at least 1 aromatic ring in the molecule include benzyl (meth) acrylate, neopentyl glycol benzoate (meth) acrylate, and the like, and a preferable compound is an aromatic ring-containing (meth) acrylic compound represented by the above formula (II) having a (meth) acryloyl group.

In addition, the same effect can be obtained by using a compound in which an aromatic ring is replaced with an aliphatic ring in the unsaturated monomer (A-2). Examples of the unsaturated monomer having 1 olefinic double bond and at least 1 aliphatic ring in the molecule (aliphatic ring-containing (meth) acrylic compound) include cyclohexyl methacrylate and cyclohexyl acrylate.

As the unsaturated monomer (a-2), an aromatic ring-containing monomer having an aromatic ring is preferable, and among the aromatic ring-containing monomers, an aromatic ring-containing (meth) acrylic compound represented by the following formula (II) is particularly preferable.

[ solution 5]

(in the formula, R₃Represents a hydrogen atom or a methyl group, n is an integer of 1 to 8, R₄Represents a hydrogen atom, an alkyl group, an aralkyl group or an aryl group. )

In the formula (II) representing the aromatic ring-containing (meth) acrylic compound, in R₄When the alkyl group is used, the number of carbon atoms may be about 1 to 9, and R is₄In the case of an aralkyl group, the number of carbon atoms is about 7 to 11, and R is₄When the aryl group is used, the number of carbon atoms may be about 6 to 10. Examples of the alkyl group having 1 to 9 carbon atoms include a methyl group, a butyl group, and a nonyl group. Examples of the aralkyl group having 7 to 11 carbon atoms include a benzyl group, a phenethyl group, a naphthylmethyl group and the like. Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, a naphthyl group and the like.

Specific examples of the aromatic ring-containing (meth) acrylic compound represented by the formula (II) include 2-phenoxyethyl (meth) acrylate, 2- (2-phenoxyethoxy) ethyl (meth) acrylate, ethylene oxide-modified nonylphenol (meth) acrylate, and 2- (o-phenylphenoxy) ethyl (meth) acrylate. These aromatic ring-containing monomers may be used alone or in combination of two or more different monomers. Among them, 2-phenoxyethyl (meth) acrylate [ in said formula (II), R₄Compound of 1 ═ H, n ═ or 2- (o-phenylphenoxy) ethyl (meth) acrylate [ in the formula (II), R is₄O-phenyl, n-1. Such an aromatic ring-containing (meth) acrylic compound is preferably used as one of the unsaturated monomers (a-2) from which the structural unit constituting the acrylic resin (a) is derived.

The polar functional group of the unsaturated monomer (A-3) is a free carboxyl group, a hydroxyl group, an amino group, a heterocyclic group represented by an epoxy ring, or the like. The unsaturated monomer (A-3) is preferably a (meth) acrylic compound having a polar functional group. Specific examples thereof include unsaturated monomers having a free carboxyl group such as acrylic acid, methacrylic acid, and β -carboxyethyl acrylate; unsaturated monomers having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-or 3-chloro-2-hydroxypropyl (meth) acrylate, and diethylene glycol mono (meth) acrylate; unsaturated monomers having a heterocyclic group such as acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, 3, 4-epoxycyclohexylmethyl (meth) acrylate, glycidyl (meth) acrylate, and 2, 5-dihydrofuran; unsaturated monomers having an amino group different from a heterocyclic ring, such as N, N-dimethylaminoethyl (meth) acrylate, and the like. The polar functional group is preferably a free carboxyl, hydroxyl, amino or epoxy ring. These unsaturated monomers (A-3) as polar functional group-containing monomers may be used alone or in different plural kinds for producing the acrylic resin (A).

Among them, an unsaturated monomer having a hydroxyl group is preferably used as one of the polar functional group-containing monomers (a-3) constituting the acrylic resin (a). In addition, it is also effective to use another unsaturated monomer having a polar functional group, for example, an unsaturated monomer having a free carboxyl group, in addition to the unsaturated monomer having a hydroxyl group.

In the acrylic resin (A), the structural unit derived from the alkyl (meth) acrylate (A-1) represented by the formula (I) is 80 to 96% by weight, preferably 82% by weight or more, and more preferably 94% by weight or less. The structural unit derived from the aromatic ring-containing monomer (A-2) is 3 to 15% by weight, preferably 5% by weight or more, more preferably 7% by weight or more, particularly preferably 8% by weight or more, and further preferably 13% by weight or less, more preferably 11% by weight or less, and particularly preferably 10% by weight or less. The structural unit derived from the polar functional group-containing monomer (A-3) is 0.1 to 5% by weight, preferably 0.5% by weight or more, and more preferably 3% by weight or less.

The acrylic resin (a) used in the present invention may contain polymerized units derived from monomers other than the above-mentioned alkyl (meth) acrylate (a-1) represented by the formula (I), unsaturated monomer (a-2) [ aromatic ring-containing (meth) acrylic compound and/or aliphatic ring-containing (meth) acrylic compound ], and unsaturated monomer (a-3) [ polar functional group-containing monomer ]. Examples thereof include a structural unit derived from a styrene monomer, a structural unit derived from a vinyl monomer, a structural unit derived from a monomer having a plurality of (meth) acryloyl groups in the molecule, and the like.

Specific examples of the styrene-based monomer include, in addition to styrene, alkylstyrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene; and nitrostyrene, acetylstyrene, methoxystyrene, divinylbenzene, and the like.

Specific examples of the vinyl monomer include vinyl esters of fatty acids such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, and vinyl laurate; vinyl halides such as vinyl chloride and vinyl bromide; vinylidene halides such as vinylidene chloride; nitrogen-containing aromatic vinyl compounds such as vinylpyridine, vinylpyrrolidone, and vinylcarbazole; conjugated diene monomers such as butadiene, isoprene, and chloroprene; and acrylonitrile, methacrylonitrile, and the like.

Specific examples of the monomer having a plurality of (meth) acryloyl groups in a molecule include monomers having 2 (meth) acryloyl groups in a molecule, such as 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and tripropylene glycol di (meth) acrylate; a monomer having 3 (meth) acryloyl groups in the molecule, such as trimethylolpropane tri (meth) acrylate.

The monomers other than the alkyl (meth) acrylate (A-1), the unsaturated monomer (A-2) and the unsaturated monomer (A-3) as described above may be used individually or in combination of 2 or more. In the acrylic resin (a) used in the binder, the polymerized units derived from monomers other than the alkyl (meth) acrylate (a-1), the unsaturated monomer (a-2) and the unsaturated monomer (a-3) are contained in a proportion of usually 0 to 20 parts by weight, preferably 0 to 10 parts by weight, based on the total weight of the acrylic resin (a).

The resin component constituting the pressure-sensitive adhesive composition may be a resin component containing the acrylic resin (a) alone as described above, or may be a resin component containing a resin other than the acrylic resin (a). The resin other than the acrylic resin (a) is also preferably an acrylic resin. An acrylic resin other than the acrylic resin (a), for example, an acrylic resin having a structural unit derived from an alkyl (meth) acrylate of the formula (I) and containing no polar functional group, or the like may be used in combination. The acrylic resin (a) containing polymerized units derived from each of the alkyl (meth) acrylate (a-1), the unsaturated monomer (a-2), and the unsaturated monomer (a-3) represented by the formula (I) is preferably 80% by weight or more, more preferably 90% by weight or more, based on the total weight of the resin components.

The acrylic resin (a) has a weight average molecular weight Mw in the range of 100 to 200 ten thousand in terms of standard polystyrene based on Gel Permeation Chromatography (GPC). When the weight average molecular weight in terms of standard polystyrene is 100 ten thousand or more, the adhesiveness under high temperature and high humidity is improved, the possibility of occurrence of lifting and peeling between the liquid crystal cell and the pressure-sensitive adhesive layer tends to be reduced, and the reworkability tends to be improved, which is preferable. Further, when the weight average molecular weight is 200 ten thousand or less, the adhesive layer preferably changes so as to follow the dimensional change even if the size of the polarizing plate attached to the adhesive layer changes, and therefore there is no difference between the brightness at the peripheral portion of the liquid crystal cell and the brightness at the central portion, and white leakage and color unevenness tend to be suppressed.

The molecular weight distribution represented by the ratio Mw/Mn of the weight average molecular weight Mw to the number average molecular weight Mn is in the range of 3 to 7. When the molecular weight distribution Mw/Mn is set to be in the range of 3 to 7, the heat resistance of the obtained adhesive layer is improved, and when the circularly polarizing plate of the present invention is applied to a liquid crystal panel or a liquid crystal display device, defects such as white spots are favorably prevented from occurring even when the circularly polarizing plate is exposed to high temperatures.

In order to achieve the adhesion, the glass transition temperature of the acrylic resin (A) is preferably in the range of-10 to-60 ℃. The glass transition temperature can be generally measured by a differential scanning calorimeter.

The acrylic resin (a) can be produced by various known methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. In the production of the acrylic resin (a), a polymerization initiator is generally used. About 0.001 to 5 parts by weight of a polymerization initiator is used based on 100 parts by weight of the total of all monomers used for producing the acrylic resin (A).

As the polymerization initiator, a thermal polymerization initiator, a photopolymerization initiator, or the like is used. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone and the like. Examples of the thermal polymerization initiator include azo compounds such as 2, 2 ' -azobisisobutyronitrile, 2 ' -azobis (2-methylbutyronitrile), 1 ' -azobis (cyclohexane-1-carbonitrile), 2 ' -azobis (2, 4-dimethylvaleronitrile), 2 ' -azobis (2, 4-dimethyl-4-methoxyvaleronitrile), dimethyl-2, 2 ' -azobis (2-methylpropionate), and 2, 2 ' -azobis (2-hydroxymethylpropionitrile); organic peroxides such as lauryl peroxide, t-butyl hydroperoxide, benzoyl peroxide, t-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, and (3, 5, 5-trimethylhexanoyl) peroxide; inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide. Further, a redox initiator using a peroxide and a reducing agent in combination, and the like can be used as a polymerization initiator.

Among the above-mentioned methods, the solution polymerization method is preferable as the method for producing the acrylic resin (a). The solution polymerization method is explained by taking a specific example, and there is a method of mixing a desired monomer and an organic solvent (polymerization solvent), adding a thermal polymerization initiator under a nitrogen atmosphere, and stirring at about 40 to 90 ℃, preferably about 60 to 80 ℃ for about 3 to 10 hours. In addition, in order to control the reaction, the monomer and the thermal polymerization initiator may be continuously or intermittently added during the polymerization, or may be added in a state of being dissolved in an organic solvent. Here, as the polymerization solvent, for example, aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; aliphatic alcohols such as propanol and isopropanol; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and the like.

(2) Crosslinking agent (B)

The acrylic resin (a) is mixed with a crosslinking agent (B) to prepare an adhesive composition. The crosslinking agent (B) is a compound having at least 2 functional groups in the molecule that can crosslink with the polymerized units derived from the unsaturated monomer (a-3) in particular in the acrylic resin (a), and specific examples thereof include isocyanate compounds, epoxy compounds, metal chelate compounds, aziridine compounds, and the like.

The isocyanate-based compound is a compound having at least 2 isocyanate groups (-NCO) in the molecule, and examples thereof include toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and the like. In addition, adducts obtained by reacting a polyol such as glycerin or trimethylolpropane with these isocyanate compounds, and products obtained by converting the isocyanate compounds into dimers, trimers, and the like can also be used as crosslinking agents used in adhesives. 2 or more kinds of isocyanate compounds may be used in combination.

The epoxy compound has at least 2 epoxy groups in the molecule, and examples thereof include bisphenol a type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N-diglycidylaniline, N '-tetraglycidyl-m-xylylenediamine, 1, 3-bis (N, N' -diglycidylaminomethyl) cyclohexane, and the like. 2 or more epoxy compounds may be used in combination.

Examples of the metal chelate compound include compounds prepared by complexing acetylacetone and ethyl acetoacetate with a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

The aziridine-based compound is a compound having a skeleton of at least 2 3-membered rings containing 1 nitrogen atom and 2 carbon atoms, also referred to as ethyleneimine, in the molecule, and examples thereof include diphenylmethane-4, 4' -bis (aziridine-1-carboxamide), toluene-2, 4-bis (aziridine-1-carboxamide), triethylenemelamine, isophthaloylbis-1- (2-methylaziridine), tri-1-aziridinyloxyphosphine oxide, hexamethylene-1, 6-bis (aziridine-1-carboxamide), trimethylolpropane tri- β -aziridinylpropionate, tetramethylolmethane tri- β -aziridinylpropionate, and the like.

Among these crosslinking agents, isocyanate compounds, particularly xylylene diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, adducts obtained by reacting these isocyanate compounds with polyhydric alcohols such as glycerin and trimethylolpropane, dimers and trimers of these isocyanate compounds, and mixtures of these isocyanate compounds are preferably used. When the unsaturated monomer (a-3) has a polar functional group selected from a free carboxyl group, a hydroxyl group, an amino group and an epoxy ring, it is particularly preferable to use an isocyanate compound as at least one of the crosslinking agents (B). Examples of suitable isocyanate compounds include toluene diisocyanate, an adduct obtained by reacting toluene diisocyanate with a polyol, a dimer of toluene diisocyanate, and a trimer of toluene diisocyanate, and hexamethylene diisocyanate, an adduct obtained by reacting hexamethylene diisocyanate with a polyol, a dimer of hexamethylene diisocyanate, and a trimer of hexamethylene diisocyanate.

The crosslinking agent (B) is added in a proportion of 0.01-5 parts by weight relative to 100 parts by weight of the acrylic resin (A). The amount of the crosslinking agent (B) is preferably about 0.1 to 5 parts by weight, more preferably about 0.2 to 3 parts by weight, based on 100 parts by weight of the acrylic resin (A). When the amount of the crosslinking agent (B) is 0.01 parts by weight or more, particularly 0.1 parts by weight or more, based on 100 parts by weight of the acrylic resin (a), the durability of the pressure-sensitive adhesive layer tends to be improved, and therefore, it is preferable, and when it is 5 parts by weight or less, so-called white spots are not noticeable.

(3) Other ingredients constituting the adhesive composition

In the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, in order to improve the adhesiveness of the pressure-sensitive adhesive layer itself, it is preferable to contain the silane-based compound (C), and it is particularly preferable to contain the silane-based compound (C) in the acrylic resin (a) before the crosslinking agent is blended.

Examples of the silane-based compound (C) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2-glycidoxypropyl, 3-glycidoxypropyldimethoxymethylsilane, 3-glycidoxypropylethoxydimethylsilane and the like. 2 or more kinds of the silane-based compound (C) can be used.

The silane compound (C) may be a silicone oligomer type silane compound. When the silicone oligomer is represented as a (monomer) - (monomer) copolymer, examples thereof include the following.

Mercaptopropyl-containing copolymers such as 3-mercaptopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-mercaptopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-mercaptopropyltriethoxysilane-tetramethoxysilane copolymer, and 3-mercaptopropyltriethoxysilane-tetraethoxysilane copolymer;

mercaptomethyl group-containing copolymers such as mercaptomethyltrimethoxysilane-tetramethoxysilane copolymer, mercaptomethyltrimethoxysilane-tetraethoxysilane copolymer, mercaptomethyltriethoxysilane-tetramethoxysilane copolymer, and mercaptomethyltriethoxysilane-tetraethoxysilane copolymer;

methacryloxypropyl-containing copolymers such as 3-methacryloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-methacryloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-methacryloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-methacryloxypropyltriethoxysilane-tetraethoxysilane copolymer, 3-methacryloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-methacryloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-methacryloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-methacryloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;

acryloxypropyl-containing copolymers such as 3-acryloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-acryloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-acryloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-acryloxypropyltriethoxysilane-tetraethoxysilane copolymer, 3-acryloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-acryloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-acryloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-acryloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;

vinyl group-containing copolymers such as vinyltrimethoxysilane-tetramethoxysilane copolymer, vinyltrimethoxysilane-tetraethoxysilane copolymer, vinyltriethoxysilane-tetramethoxysilane copolymer, vinyltriethoxysilane-tetraethoxysilane copolymer, vinylmethyldimethoxysilane-tetramethoxysilane copolymer, vinylmethyldimethoxysilane-tetraethoxysilane copolymer, vinylmethyldiethoxysilane-tetramethoxysilane copolymer, and vinylmethyldiethoxysilane-tetraethoxysilane copolymer;

examples of the amino group-containing copolymer include copolymers containing an amino group such as a 3-aminopropyltrimethoxysilane-tetramethoxysilane copolymer, a 3-aminopropyltrimethoxysilane-tetraethoxysilane copolymer, a 3-aminopropyltriethoxysilane-tetramethoxysilane copolymer, a 3-aminopropyltriethoxysilane-tetraethoxysilane copolymer, a 3-aminopropylmethyldimethoxysilane-tetramethoxysilane copolymer, a 3-aminopropylmethyldimethoxysilane-tetraethoxysilane copolymer, a 3-aminopropylmethyldiethoxysilane-tetramethoxysilane copolymer, and a 3-aminopropylmethyldiethoxysilane-tetraethoxysilane copolymer.

These silane-based compounds (C) are liquid in many cases. The amount of the silane compound (C) to be incorporated in the pressure-sensitive adhesive composition is usually about 0.01 to 10 parts by weight, preferably 0.03 to 1 part by weight, based on 100 parts by weight of the nonvolatile content of the acrylic resin (a) (the total amount of 2 or more types of the acrylic resin (a)) in the pressure-sensitive adhesive composition. It is preferable that the amount of the silane compound is 0.01 parts by weight or more, particularly 0.03 parts by weight or more, based on 100 parts by weight of the nonvolatile component of the acrylic resin (a), because the adhesion is improved. Further, it is preferable that the amount is 10 parts by weight or less, particularly 1 part by weight or less, because bleeding of the silane compound from the pressure-sensitive adhesive layer tends to be suppressed.

The pressure-sensitive adhesive composition described above may further contain a crosslinking catalyst, a weather-resistant stabilizer, a tackifier, a plasticizer, a softener, a dye, a pigment, an inorganic filler, an antistatic agent, a resin (for example, a resin other than the acrylic resin (a)), and the like. It is also useful to form a harder pressure-sensitive adhesive layer by blending an ultraviolet-curable compound in the pressure-sensitive adhesive composition and irradiating ultraviolet rays after the pressure-sensitive adhesive layer is formed to cure the mixture. In addition, when a crosslinking catalyst is added to the adhesive together with the crosslinking agent composition, the adhesive layer can be prepared by aging in a short time, and in the circularly polarizing plate of the present invention, the occurrence of lifting or peeling between the polarizing plate and the adhesive layer and the occurrence of foaming in the adhesive layer can be suppressed, and the reworkability is further improved. Examples of the crosslinking catalyst include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamino resins, and melamine resins. When an isocyanate compound is used as the crosslinking agent (B), an amine compound is suitable as the crosslinking catalyst.

These components constituting the pressure-sensitive adhesive composition may be mixed with the acrylic resin (a) and the crosslinking agent (B) as essential components in a state of being dissolved in a solvent as necessary to prepare a pressure-sensitive adhesive composition. It can be applied to a suitable substrate and dried to form an adhesive layer.

< gel fraction of adhesive layer >

As described earlier in the present invention, the gel fraction of the adhesive layer is set to 60 to 99 wt%. The gel fraction of the pressure-sensitive adhesive layer is preferably 60% by weight or more because the durability of the pressure-sensitive adhesive layer is improved. Further, it is preferable that the gel fraction is 99% by weight or less because the production is easy. The gel fraction here is a value measured in accordance with the following (I) to (IV).

(I) An adhesive layer having an area of about 8cm × about 8cm was attached to a metal mesh made of SUS 304 (its weight was set to Wm) of about 10cm × about 10 cm.

(II) the weight of the adherend obtained in the above (I) was weighed to obtain Ws, and then folded 4 times so as to wrap the adhesive layer and fixed with a stapler (stapler), and then weighed to obtain Wb.

(III) A glass container was charged with the stapler-fixed net of (II) above, and after dipping with 60mL of ethyl acetate, the glass container was stored at room temperature for 3 days.

(IV) the net was taken out of the glass container, dried at 120 ℃ for 24 hours, weighed, and the gel fraction was calculated based on the following formula, assuming the weight as Wa.

Gel fraction (% by weight) [ (Wa- (Wb-Ws) -Wm }/(Ws-Wm) ]. times.100

The gel fraction of the pressure-sensitive adhesive layer can be adjusted by, for example, the type of the acrylic resin (a) and the type and amount of the crosslinking agent (B) contained in the pressure-sensitive adhesive composition. Specifically, since the gel fraction increases with an increase in the amount of the polymerized unit derived from the unsaturated monomer (a-3) in the acrylic resin (a) or an increase in the amount of the crosslinking agent (B) in the pressure-sensitive adhesive composition, the gel fraction can be adjusted by using the amount of the polymerized unit having a polar functional group and/or the crosslinking agent (B) such as the polymerized unit derived from the unsaturated monomer (a-3) constituting the acrylic resin (a). The amount of the polymerization unit derived from the unsaturated monomer (a-3) in the acrylic resin (a) may be selected and adjusted from the range of 0.1 to 5% by weight so that the gel fraction is in the above range by combining with other components constituting the acrylic resin (a) and by combining with the kind and amount of the crosslinking agent (B). On the other hand, the amount of the crosslinking agent (B) is preferably selected from the range of about 0.1 to 5 parts by weight in accordance with the kind of the acrylic resin, relative to 100 parts by weight of the nonvolatile component of the acrylic resin constituting the pressure-sensitive adhesive layer (the total amount in the case of using 2 or more kinds of the acrylic resin (a)).

Although the pressure-sensitive adhesive layer 13 for bonding the polarizing plate 1 and the retardation film 20 has been described above, a pressure-sensitive adhesive composition containing the acrylic resin (a) and the crosslinking agent (B) may be used for forming the pressure-sensitive adhesive layer 14 for bonding the display panel and the circularly polarizing plate of the present invention.

In the formation of the pressure-sensitive adhesive layer 14, a pressure-sensitive adhesive composition other than the pressure-sensitive adhesive composition containing the acrylic resin (a) and the crosslinking agent (B) may be used. Here, a case where a conventionally known adhesive layer can be applied to the adhesive layer 14, including a conventionally known adhesive layer, will be briefly described.

The pressure-sensitive adhesive layer 14 can be formed using a pressure-sensitive adhesive composition containing a resin such as a (meth) acrylic resin, a rubber resin, a urethane resin, an ester resin, a silicone resin, or a polyvinyl ether resin as a main component. Among them, from the viewpoint of obtaining an adhesive layer excellent in transparency, weather resistance, heat resistance, and the like, an adhesive composition containing a (meth) acrylic resin as a base polymer is suitable. The adhesive composition may be an active energy ray-curable adhesive composition or a thermosetting adhesive composition. The thickness of the adhesive layer 14 is the same as that of the adhesive layer 13, and is preferably 3 to 30 μm, more preferably 3 to 25 μm.

As the (meth) acrylic resin (base polymer) suitable for use in the adhesive composition, for example, a polymer or copolymer containing 1 or 2 or more kinds of (meth) acrylic acid esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate as monomers can be suitably used.

It is preferred to copolymerize the polar monomer with the base polymer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The adhesive composition may comprise only the base polymer, but typically also contains a crosslinking agent. Examples of the crosslinking agent include a crosslinking agent which is a metal ion having a valence of 2 or more and forms a metal carboxylate salt with a carboxyl group; a crosslinking agent which is a polyamine compound and forms an amide bond with a carboxyl group; a crosslinking agent which is a polyepoxy compound or a polyol and forms an ester bond between the polyepoxy compound or the polyol and a carboxyl group; a crosslinking agent which is a polyisocyanate compound and forms an amide bond between the polyisocyanate compound and a carboxyl group. Among them, polyisocyanate compounds are preferable.

The above description has been made of a suitable layer structure and a structure of each layer of the circularly polarizing plate of the present invention. Next, a display device including the circularly polarizing plate of the present invention will be described.

< front panel >

The front panel is arranged on the visible side of the display device. The front panel may be laminated to the polarizing plate via an adhesive layer. Examples of the adhesive layer include the aforementioned adhesive layer and adhesive layer. Fig. 2(a) and (b) show cross-sectional structures of display devices including the circularly polarizing plates of fig. 1(a) and (b). The front panel 4 may be laminated on the protective film 11 of the polarizing plate 1 via an adhesive layer 16. Fig. 2(c) and (d) show cross-sectional structures of display devices including the circularly polarizing plates of fig. 1(c) and (d) in the same manner as (a) and the like.

The front plate may be any of a glass plate and a resin film, and at least one surface thereof may include a hard coat layer. As the glass plate, for example, a glass plate made of high-transmittance glass or tempered glass can be used. When a particularly thin transparent surface material is used, a glass plate which is chemically strengthened is preferable. The thickness of the glass plate may be, for example, 100 μm to 5 mm.

In the case where the front panel is a resin film, it may not be as rigid as a glass plate but may have a flexible characteristic. When a resin film is used as the front panel, the resin film preferably has a hard coat layer, and the thickness of the hard coat layer is not particularly limited, and may be, for example, 5 to 100 μm.

The resin film may be a resin film made of a cycloolefin derivative having a unit of a cycloolefin-containing monomer such as a norbornene or polycyclic norbornene-based monomer, cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose), an ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacrylic acid, polyimide, polyamideimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene terephthalate, polyvinyl acetate, films made of polymers such as polycarbonate, polyurethane, and epoxy resin. The resin film may be an unstretched, uniaxially stretched or biaxially stretched film. These polymers may be used alone or in combination of 2 or more. As the resin film, a polyamideimide film or a polyimide film excellent in transparency and heat resistance, a uniaxially or biaxially stretched polyester film, a cycloolefin derivative film excellent in transparency and heat resistance and capable of coping with the increase in size of the film, a polymethyl methacrylate film, and a triacetyl cellulose and isobutyl cellulose film exhibiting transparency and having no optical anisotropy are preferable. The thickness of the resin film may be 5 to 200 μm, preferably 20 to 100 μm.

In the resin film having a hard coat layer, the hard coat layer may be formed by curing a hard coat composition containing a reactive material that forms a crosslinked structure by irradiation with light or thermal energy. The hard coat layer can be formed by curing a hard coat composition containing both a photocurable (meth) acrylate monomer or oligomer and a photocurable epoxy monomer or oligomer. The photocurable (meth) acrylate monomer may include 1 or more selected from epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate. The epoxy (meth) acrylate can be obtained by reacting a carboxylic acid having a (meth) acryloyl group with an epoxy compound.

The hard coating composition may further include one or more selected from a solvent, a photoinitiator, and an additive. The additive may include one or more selected from inorganic nanoparticles, a leveling agent, and a stabilizer. In addition, as each component generally used in the art, for example, an antioxidant, a UV absorber, a surfactant, a lubricant, an antifouling agent, and the like may be further included.

The circularly polarizing plate of the present invention having the front panel 4 bonded to the display panel 3 via the adhesive layer 16 as described above is further bonded to the display panel 3 via the adhesive layer 14, thereby constituting a display device. When the display device is a liquid crystal display device, the display panel is a liquid crystal panel, and when the display device is an organic EL display device, the display panel is an organic EL display panel including organic EL light emitting elements. Note that the same adhesive layer as the adhesive layer 14 may be used for the adhesive layer 16.

< light-shielding pattern >

The light shielding pattern may be provided as at least a portion of a bezel or a housing of the front panel or the display device to which the front panel is applied. The light blocking pattern may be formed on the display element side of the front panel. The light-shielding pattern can hide the wirings of the display device from the user. The color and/or material of the light-shielding pattern is not particularly limited, and may be formed using a resin substance having various colors such as black, white, gold, and the like. In one embodiment, the thickness of the light-shielding pattern may be in the range of 2 to 50 μm, preferably 4 to 30 μm, and more preferably 6 to 15 μm. In addition, in order to suppress the mixing of bubbles due to a difference in height between the light shielding pattern and the display portion and the visibility of the boundary portion, a shape may be given to the light shielding pattern.

Method for manufacturing circular polarizing plate

A method for manufacturing a circularly polarizing plate will be described with reference to a circularly polarizing plate 100 shown in fig. 1 (a). The circularly polarizing plate 100 can be manufactured by laminating the polarizing plate 1 and the phase difference film 2 via the adhesive layer 13.

The polarizing plate 1 can be manufactured by laminating the polarizer 10 and the protective film 11 with an adhesive layer interposed therebetween. The polarizing plate may be manufactured by preparing a long member, cutting the long member into a predetermined shape after the long member is bonded by a roll-to-roll method, or may be bonded after the long member is cut into a predetermined shape. After the protective film 11 is bonded to the polarizing plate 10, a heating step and a humidity conditioning step may be provided. An appropriate sacrificial film (conceivably: concession フィルム) may be attached to the surface of the polarizing plate 10 opposite to the surface to which the protective film 11 is attached.

As described above, the retardation film 20 preferably has a retardation layer including a liquid crystal cured film obtained by polymerizing and curing a polymerizable liquid crystal compound. Here, the production of a retardation film having a layer including a liquid crystal cured film is shown simply. The retardation film 20 can be produced, for example, as follows. An alignment film is formed on a substrate, and a coating liquid containing a polymerizable liquid crystal compound is applied to the alignment film. The polymerizable liquid crystal compound is cured by irradiation with an active energy ray in a state where the polymerizable liquid crystal compound is aligned. The pressure-sensitive adhesive layer 14 formed on the release film is laminated on the layer obtained by curing the polymerizable liquid crystal compound. Then, the substrate and/or the alignment film is peeled.

Then, on the protective film 12, the adhesive layer 13 formed on the release film is laminated. The retardation film 20 may be manufactured by preparing a long member, cutting each member into a predetermined shape after bonding each member by a roll-to-roll method, or may be manufactured by cutting each member into a predetermined shape and bonding each member.

Thereafter, the release film laminated on the pressure-sensitive adhesive layer 13 is peeled off, and the retardation film 20 is bonded to the polarizing plate 1 via the pressure-sensitive adhesive layer 13, whereby the circularly polarizing plate 100 can be produced.

< use >)

The circularly polarizing plate can be used in various display devices. The display device is a device having a display element, and includes a light-emitting element or a light-emitting device as a light-emitting source. Examples of the display device include a liquid crystal display device, an organic EL display device, an inorganic electroluminescence (hereinafter also referred to as an inorganic EL) display device, an electron emission display device (for example, a field emission display device (also referred to as an FED) or a surface field emission display device (also referred to as an SED)), electronic paper (using electronic ink, a display device of an electrophoretic element), a plasma display device, a projection type display device (for example, a grating light valve (also referred to as GLV) display device, a display device having a digital micromirror device (also referred to as DMD), a piezoelectric ceramic display, and the like.

In fig. 2(a) and (b), the organic EL display devices 104 and 105 have a layer structure in which a circularly polarizing plate is laminated on the organic EL display element 3 via the adhesive layer 14 laminated on the retardation film 20. Hereinafter, the organic EL is sometimes referred to as an "OLED".

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, the parts and% indicating the contents or amounts used are based on the weight unless otherwise specified. The measurement of each physical property in the following examples was performed by the following method.

(1) Method for measuring film thickness

The measurement was carried out using MH-15M as a digital micrometer manufactured by Nikon K.K.

(2) Method for measuring phase difference value

The measurement was carried out using a phase difference measuring apparatus KOBRA-WPR (manufactured by Okinson instruments Co., Ltd.).

(3) Method for measuring reflection color tone

The reflection color tones (a, b) were measured using a spectrocolorimeter (trade name: CM-2600 d, manufactured by Konica Minolta Japan). The reflection color tone is a value obtained when the light source is D65, and is measured by the SCI method (including regular reflection light).

(4) Method for measuring photoelastic coefficient

A phase difference value (23 ℃/wavelength 550nm) at the center of a sample was measured while applying stress (0.5N to 8N) to both ends of the sample (1.5 cm. times.6 cm in size) with the use of a phase difference measuring device KOBRA-WPR (manufactured by Okinson instruments Co., Ltd.), and the value was calculated from the slope of a function of the stress and the phase difference value. In the present specification, a sample having positive birefringence is described as a positive value, and a sample having negative birefringence is described as a negative value. For a sample for measuring the photoelastic coefficient of a retardation film, a laminate comprising a retardation film, an adhesive a described below, and a protective film C described below was prepared, and a sample obtained by cutting out a sample for measurement such that the slow axis of the laminate was parallel to the long side of the sample for measurement was used. The photoelastic coefficient of the retardation film was measured while applying stress to both short sides of the measurement sample. In the lamination of the samples, the lamination surfaces were subjected to corona treatment before lamination.

(5) Method for measuring shrinkage force of polarizing plate

The polarizing plate was cut into pieces of 2mm in width by 50mm in length by a super cutter manufactured by Amaranthus sonchifolius, Ltd, so that the absorption axis direction of the polarizing plate was a long axis. The obtained polarizing film in the form of a strip was used as a shrinkage force measuring sample. The shrinkage force measurement sample was mounted on a thermomechanical analyzer ("TMA/6100" manufactured by hitachi High-Tech Science) with a distance between chucks of 10mm, and the temperature in the sample chamber was increased from 20 ℃ to 80 ℃ for 1 minute after the test piece was left in the chamber at a temperature of 20 ℃/55% relative humidity, and the temperature in the sample chamber after the temperature increase was maintained at 80 ℃. After the temperature was raised and left to stand for 4 hours, the shrinkage force in the longitudinal direction of the measurement sample was measured at 80 ℃. In this measurement, a probe made of SUS was used as a jig with a static load of 0 mN.

Production example 1 production of polarizing film

A polyvinyl alcohol film having a thickness of 20 μm (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) was uniaxially stretched by dry stretching to about 4 times, and then immersed in pure water at 40 ℃ for 40 seconds while being kept in a stretched state, and then immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.052/5.7/100 at 28 ℃ for 30 seconds to be dyed. Thereafter, the plate was immersed at 70 ℃ for 120 seconds in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 11.0/6.2/100. Subsequently, the substrate was washed with pure water at 8 ℃ for 15 seconds, dried at 60 ℃ for 50 seconds while being held under a tension of 300N, and then dried at 75 ℃ for 20 seconds, to obtain an absorption-type polarizing plate having a thickness of 8 μm, in which iodine was adsorbed and oriented on a polyvinyl alcohol film. The resultant polarizing plate had a shrinkage force of 1.5N/2 mm.

Production example 2 production of retardation film

5 parts (weight-average molecular weight: 30000) of a photo-alignment material having the following structure (Me represents a methyl group) and 95 parts of cyclopentanone (solvent) were mixed, and the resulting mixture was stirred at 80 ℃ for 1 hour to obtain an alignment film-forming composition.

[ solution 6]

The following polymerizable liquid crystal compound a and polymerizable liquid crystal compound B were mixed at a ratio of 90: 10, 1.0 part of a leveling agent (type F-556; manufactured by DIC) and 6 parts of 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) -1-butanone (trade name Irgacure 369(Irg369), manufactured by BASF Japan K.K.) as a polymerization initiator were added to the mixture.

Subsequently, N-methyl-2-pyrrolidone (NMP) was added so that the solid content concentration became 13%, and the mixture was stirred at 80 ℃ for 1 hour to obtain a composition for forming a liquid crystal cured film.

The polymerizable liquid crystal compound a is produced by the method described in japanese patent application laid-open No. 2010-31223. The polymerizable liquid crystal compound B is produced according to the method described in Japanese patent laid-open No. 2009-173893. The respective molecular structures are given below.

[ polymerizable liquid Crystal Compound A ]

[ solution 7]

[ polymerizable liquid Crystal Compound B ]

[ solution 8]

[ production of a laminate comprising a substrate, an alignment film, and a layer obtained by curing a liquid Crystal Compound ]

A50 μm-thick cycloolefin film (trade name "ZF-14-50" manufactured by Zeon, Japan) as a base material was subjected to corona treatment, and then an alignment film forming composition was applied by a bar coater, dried at 80 ℃ for 1 minute, and then irradiated with polarized UV light at a wavelength of 313nm at a cumulative light amount of 100mJ/cm using a polarized UV irradiation apparatus (trade name "SPOT CURE SP-9" manufactured by Ushio Motor, Ltd.)²Under conditions of polarized UV exposure at an axial angle of 45 °. Next, the composition for forming an oriented liquid crystal cured film was applied to an oriented film using a bar coater, dried at 120 ℃ for 1 minute, and then dried using a high pressure mercury lamp [ trade name of Ushio motor (ltd.): "Unicure VB-15201 BY-A" ], and ultraviolet rays (cumulative light quantity at a wavelength of 365nm under a nitrogen atmosphere: 500 mJ/cm)²) Thus, a layer obtained by curing the liquid crystal compound was formed, and a laminate comprising the substrate, the alignment film, and the layer obtained by curing the liquid crystal compound was obtained.

The in-plane retardation value Re (λ) of the layer obtained by curing the liquid crystal compound produced by the above method was measured after being bonded to glass via an adhesive, and the cycloolefin film as a substrate was peeled off. The phase difference Re (. lamda.) at each wavelength was measured to find that Re (450)

＝121nm，Re(550)＝142nm，Re (650) ═ 146nm, Re (450)/Re (550) ═ 0.85, and Re (650)/Re (550) ═ 1.03. The photoelastic coefficient of the resulting retardation film was 53.9X 10^－13Pa^－1。

[ preparation of protective film ]

And (3) protecting the film A:

a film having a hard coat layer of 3 μm thickness was formed on a stretched film of 25 μm thickness made of norbornene-based resin [ product name "COP 25 ST-HC" manufactured by Japan paper-making Co., Ltd ]

And (3) a protective film B:

a triacetyl cellulose film having a positive birefringence and a thickness of 20 μm (trade name "ZRG 20 SL" manufactured by Fuji film Co., Ltd.). The protective film B had an in-plane retardation Re of 1.1nm and a retardation Rth of 1.3nm in the thickness direction at a wavelength of 590 nm. Photoelastic coefficient of 94X 10^－13Pa^－1。

[ preparation of adhesive A ]

To the aqueous solution, 3 parts by weight of carboxyl-modified polyvinyl alcohol [ trade name "KL-318" obtained from Kuraray corporation ] was dissolved per 100 parts by weight of water, and 1.5 parts by weight of a polyamide epoxy additive [ trade name "Sumirez Resin (registered trademark) 650 (30)" obtained from takaki chemical industries co., ltd., a 30% solid content aqueous solution ] as a water-soluble epoxy Resin was added to prepare an adhesive a.

[ preparation of adhesive B ]

The photocurable adhesive B was prepared by mixing the following cationically curable components a1 to a3 and a cationic polymerization initiator, mixing the following cationic polymerization initiator and a sensitizer, and defoaming the mixture. The following compounding amounts are based on the solid content.

Cationic curable component a1(70 parts):

3', 4' -epoxycyclohexanecarboxylic acid 3', 4' -epoxycyclohexylmethyl ester (trade name: CEL2021P, manufactured by Daicel K.K.)

Cationic curable component a2(20 parts):

neopentyl glycol diglycidyl ether (trade name: EX-211, manufactured by Nagase ChemteX)

Cationic curable component a3(10 parts):

2-ethylhexyl glycidyl ether (trade name: EX-121, manufactured by Nagase ChemteX)

Cationic polymerization initiator (2.25 parts (amount of solid component)):

trade name: CPI-100 (manufactured by San-Apro Co., Ltd.) in 50% propylene carbonate solution

Sensitizer (2 parts):

1, 4-diethoxynaphthalenes

[ preparation of adhesive layer A ]

Adhesive layer a:

sheet-like adhesive having a thickness of 5 μm (NCF # L2 manufactured by Lintec corporation)

[ preparation of adhesive layer B ]

In the following examples, the weight average molecular weight was measured by arranging 4 "TSKgel XL" manufactured by Tosoh corporation and 5 "Shodex GPC KF-802" 1 manufactured by Showa Denko K.K.K.K. in total in a GPC apparatus as columns in series, using tetrahydrofuran as an eluent, under the conditions of a sample concentration of 5mg/mL, a sample introduction amount of 100. mu.L, a temperature of 40 ℃ and a flow rate of 1 mL/min, in terms of standard polystyrene.

Polymerization example 1 production example of acrylic resin (A) as the main component of pressure-sensitive adhesive composition

A reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer was charged with 81.8 parts of ethyl acetate, 93.4 parts of n-butyl acrylate as the alkyl (meth) acrylate (A-1), 5.0 parts of 2-phenoxyethyl acrylate as the unsaturated monomer (A-2), 1.0 part of 2-hydroxyethyl acrylate as the unsaturated monomer (A-3) and 0.6 part of acrylic acid, and the internal temperature was raised to 55 ℃ while the air in the reaction vessel was replaced with nitrogen gas to exclude oxygen. Thereafter, a solution prepared by dissolving 0.14 parts of azobisisobutyronitrile as a polymerization initiator in 10 parts of ethyl acetate was added in total. After 1 hour of the addition of the polymerization initiator (polymerization initiator solution), ethyl acetate was continuously added into the reaction vessel at an addition rate of 17.3 parts/hour so that the concentration of the acrylic resin as a product became 35%, and the temperature was maintained at an internal temperature of 54 to 56 ℃ for 12 hours, and finally ethyl acetate was added to adjust the concentration of the acrylic resin to 20%. The weight average molecular weight Mw of the acrylic resin (A) was 1650000 in terms of polystyrene equivalent by GPC, and Mw/Mn was 4.3. This was referred to as acrylic resin a. The acrylic resin a had 5% structural units derived from 2-phenoxyethyl acrylate as an aromatic ring-containing monomer, 1% structural units derived from 2-hydroxyethyl acrylate as a hydroxyl group-containing monomer, and 0.6% structural units derived from acrylic acid as a carboxyl group-containing monomer.

< crosslinking agent >

Coronate L: an ethyl acetate solution of a trimethylolpropane adduct of toluene diisocyanate (solid content concentration 75%) was obtained from Japanese polyurethane (Co., Ltd.).

< silane-based Compound >

KBM-403: glycidoxypropyltrimethoxysilane (liquid) was obtained from shin-Etsu chemical industry.

A pressure-sensitive adhesive composition was prepared by mixing 0.5 parts of the above silane-based compound (KBM-403) and 0.5 parts of a crosslinking agent (Coronate L) with 100 parts of the solid content of the acrylic resin a (20% ethyl acetate solution) obtained in polymerization example 1, and adding ethyl acetate so that the solid content concentration was 13%. The obtained adhesive composition was applied to a release-treated surface of a polyethylene terephthalate film (trade name "PET 3811", available from linetec corporation, and referred to as a spacer) subjected to release treatment using a coater so that the thickness after drying was 20 μm, and dried at 90 ℃ for 1 minute, to prepare a sheet-like adhesive B. The gel fraction of the resulting sheet-like adhesive B was 83%.

[ preparation of reflecting plate ]

As the reflector, a non-lighting panel of an OLED device (Samsung Electronics co., ltd. trade name: Galaxy-Tab S8.4) was prepared.

Production example 2 production of polarizing plate with protective film on one surface

Adhesive a was applied to one surface of the polarizing film obtained in production example 1, and protective film a was attached. In this case, the protective film a was bonded so that the stretching direction was 45 degrees with respect to the absorption axis of the polarizing plate. Thereafter, the resulting film was dried to obtain a polarizing plate with a protective film on one surface.

[ example 1]

A retardation film was bonded to the polarizing plate side with the protective film on one surface obtained in production example 2 via an adhesive a. Here, the retardation film was attached so that the slow axis of the retardation film was 45 ° counterclockwise with respect to the absorption axis of the polarizing film. The adhesive B was further bonded to the side of the retardation film opposite to the side of the adhesive layer a to obtain a circularly polarizing plate with an adhesive. In the lamination of these materials, the lamination surfaces of the respective materials are subjected to corona treatment.

The obtained circularly polarizing plate was cut into 140mm × 70mm so that the absorption axis of the polarizing film was 45 ° counterclockwise with respect to the long side. The circularly polarizing plate was bonded to alkali-free glass (Eagle XG, manufactured by Corning) by peeling off the acrylic adhesive exposed by the release film.

[ evaluation of color tone before and after Heat resistance test ]

The obtained evaluation sample was put into an oven at 80 ℃ for 168hr, and the evaluation sample was placed on a reflecting plate to measure the reflection color tone. The measurement points are points shown in fig. 3. The 9 dots shown in fig. 3 are dots in a region inside 5mm with respect to the end of the circularly polarizing plate, and the short side direction is positioned at intervals of about 30mm and the long side direction is positioned at intervals of about 65 mm.

As the evaluation of the uniformity in the plane, when the a and b of each measurement point are plotted in the color coordinates, the evaluation is performed with the distance between the 2 points with the largest distance. That is, the evaluation result was set to the value between 2 points where the following formula is the maximum.

Δa＊b＊＝〔(Δa＊)²+(Δb＊)²〕^1/2

Delta a and Delta b represent the difference between a and b between arbitrary 2 points.

The visibility evaluation was evaluated at 4 levels of a to D described below. The evaluation results are shown in table 1.

A: no thermal unevenness was observed at 0.8. DELTA.a.bb.ANGELM.

B: thermal inhomogeneities can be observed very slightly with a < 0.8 < Deltaa < b < 1.0.

C: 1.0 < Deltaa < Bb < 1.8, thermal unevenness can be slightly observed.

D: thermal inhomogeneities can be observed clearly in < 1.8 < Deltaa b.

[ Table 1]

Industrial applicability

According to the present invention, a circularly polarizing plate provided with a retardation film, which is useful because the change in color tone is small before and after the circularly polarizing plate is placed in a high-temperature environment, can be provided. In particular, when a circularly polarizing plate having a retardation film including a layer obtained by curing a polymerizable liquid crystal compound is placed in a high-temperature environment, in-plane variations in color tone, particularly in reflection color tone, of the circularly polarizing plate are likely to occur, but according to the present invention, even a circularly polarizing plate having a retardation film including a layer obtained by curing a polymerizable liquid crystal compound can sufficiently suppress variations in color tone when placed in a high-temperature environment.

Therefore, the circularly polarizing plate of the present invention can be effectively used for display devices, particularly organic EL display devices and inorganic EL display devices.

Description of the reference numerals

1 polarizing plate, 20 retardation film, 3 display panel (display element), 4 front panel, 5 dot, 10 polarizer (polarizing film), 11 protective film, 13, 14, 16 adhesive layer, 15 adhesive layer, 21, 22 liquid crystal cured film (layer obtained by curing polymerizable liquid crystal compound), 100, 101 circularly polarizing plate, 104, 105 display device.

Claims (7)

1. A circularly polarizing plate is provided,

a circularly polarizing plate having a protective film on one surface of a polarizing plate and a retardation film on the other surface via an adhesive layer,

the thickness of the polarizing plate is 15 μm or less,

the retardation film comprises a retardation layer having positive birefringence,

the adhesive layer is formed of an adhesive composition and has a gel fraction of 60 to 99 wt%,

the adhesive composition contains 0.01 to 5 parts by weight of a B crosslinking agent per 100 parts by weight of an A acrylic resin,

the A acrylic resin is a copolymer of a monomer mixture containing a component in which the weight average molecular weight Mw of the A acrylic resin is in the range of 100 to 200 ten thousand, the molecular weight distribution represented by the ratio Mw/Mn of the weight average molecular weight Mw to the number average molecular weight Mn is in the range of 3 to 7,

a-1: 80 to 96 wt% of an alkyl (meth) acrylate represented by the following formula (I),

in the formula (I), R₁Represents a hydrogen atom or a methyl group, R₂Represents an alkyl group having 1 to 14 carbon atoms optionally substituted with an alkoxy group having 1 to 10 carbon atoms;

a-2: 3 to 15 wt.% of an unsaturated monomer having 1 olefinic double bond and at least 1 aromatic ring or aliphatic ring in the molecule; and

a-3: 0.1 to 5% by weight of an unsaturated monomer having a polar functional group.

2. The circularly polarizing plate of claim 1,

a-2 is a (meth) acrylic compound containing an aromatic ring represented by the following formula (II),

in the formula (II), R₃Represents a hydrogen atom or a methyl group, n is an integer of 1 to 8, R₄Represents a hydrogen atom, an alkyl group, an aralkyl group or an aryl group.

3. The circularly polarizing plate of claim 1 or 2,

a-3 is an unsaturated monomer having 1 or more polar functional groups selected from a free carboxyl group, a hydroxyl group, an amino group and an epoxy ring.

4. The circularly polarizing plate according to any one of claims 1 to 3,

the B contains a crosslinking agent which is an isocyanate compound.

5. The circularly polarizing plate according to any one of claims 1 to 4,

the adhesive composition further contains 0.03 to 1 part by weight of a C silane compound per 100 parts by weight of the acrylic resin.

6. The circularly polarizing plate according to any one of claims 1 to 5,

the retardation layer is a layer obtained by polymerizing a polymerizable liquid crystal compound.

7. A display device comprising a display element and the circularly polarizing plate according to any one of claims 1 to 6 laminated thereon.

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