JP6994906B2 - Polarizer - Google Patents

Description

The present invention relates to a polarizing plate. Specifically, an active energy ray-curable composition containing a radically polymerizable silicone compound composed of polyorganosylsesquioxane and an acrylamide-based radically polymerizable compound directly formed on at least one surface of the polarizing element. The present invention relates to a polarizing plate provided with a protective film made of a cured product of.

Conventionally, in many polarizing plates constituting various image display devices, a protective layer is provided on one side or both sides of the polarizing element in order to protect the polarizing element and increase the mechanical strength of the polarizing plate. As such a protective layer, a protective film formed of triacetyl cellulose, cycloolefin, or the like, which is bonded to a polarizing element via an adhesive, is widely used. However, in recent years, the image display device has become thinner. Along with this, a polarizing plate having a thinned protective film formed by directly applying a curable composition onto a substituent and curing it has been developed. For example, in Patent Document 1, a curable resin composition containing a silicone resin containing polyorganosylsesquioxane having a cage-shaped structure as a main component and a radically polymerizable unsaturated compound is applied to one or both sides of a polarizing element. A polarizing plate having a protective film obtained by curing the mixture is described. Further, in Patent Document 2, a silicone-based composition containing a silicone compound having a polymerizable group and a boronic acid-based compound as a compound having a polymerizable group and a group capable of forming a bond with a polarizing element is directly applied to the polarizing element. Described is a polarizing plate provided with a polarizing element protective film obtained by curing.

International Publication No. 2010/095409 Pamphlet JP-A-2015-52710

However, in the polarizing plate as described in the above patent document, although the protective layer can be thinned, it is difficult to maintain sufficiently high mechanical strength due to the thinning, and the protective film is cracked. There was a problem that it became easier. In addition, the adhesion between the stator and the protective film may not be sufficient.

An object of the present invention is to provide a polarizing plate provided with a protective film having a thin protective layer, high mechanical strength, and excellent adhesion to a polarizing element. Another object of the present invention is to provide an active energy ray-curable composition capable of forming a thin protective film having excellent mechanical strength and adhesion to a polarizing element.

〔Ｒ^１は、水素原子またはメチル基であり、Ｒ^２およびＲ^３は、それぞれ独立して、水素原子、炭素数１～６のアルキル基またはＲ^２とＲ^３が一緒になって、それらが結合する窒素原子と共に、酸素原子を環構成員として有してもよい５員環若しくは６員環であり、該アルキル基に含まれる水素原子は、ヒドロキシル基またはアミノ基で置換されていてもよい〕
で表される化合物である、前記［１］～［４］のいずれかに記載の偏光板。
［６］前記（ｂ）（メタ）アクリルアミド系ラジカル重合性化合物が、Ｎ，Ｎ－ジメチル（メタ）アクリルアミド、Ｎ－ヒドロキシエチル（メタ）アクリルアミドおよびＮ，Ｎ－ジメチルアミノプロピル（メタ）アクリルアミドからなる群から選択される、前記［１］～［５］のいずれかに記載の偏光板。
［７］活性エネルギー線硬化性組成物が、活性エネルギー線硬化性組成物に含まれる全重合性化合物の総量に対して５～２５質量％の（ｂ）（メタ）アクリルアミド系ラジカル重合性化合物を含んでなる、前記［１］～［６］のいずれかに記載の偏光板。
［８］前記（ｃ）ウレタン系ラジカル重合性化合物が、２～６個のラジカル重合性基を含むウレタン系モノマー、または、２～６個のラジカル重合性基を含み、１０００～２００００の重量平均分子量を有するウレタン系オリゴマーである、前記［２］～［７］のいずれかに記載の偏光板。
［９］活性エネルギー線硬化性組成物が、活性エネルギー線硬化性組成物に含まれる全重合性化合物の総量に対して３～２０質量％の（ｃ）ウレタン系ラジカル重合性化合物を含んでなる、前記［２］～［８］のいずれかに記載の偏光板。
［１０］（ａ）ポリオルガノシルセスキオキサンから構成されるラジカル重合性シリコーン化合物、および
（ｂ）（メタ）アクリルアミド系ラジカル重合性化合物
を含んでなる活性エネルギー線硬化性組成物。 The present invention provides the following preferred embodiments.
[1] A polarizing plate including a polarizing element and a protective film directly formed on at least one surface of the polarizing element, wherein the protective film is formed.
A polarized product comprising (a) a radically polymerizable silicone compound composed of polyorganosylsesquioxane and (b) a cured product of an active energy ray-curable composition containing (b) a (meth) acrylamide radically polymerizable compound. Board.
[2] The polarizing plate according to the above [1], wherein the active energy ray-curable composition further contains (c) a urethane-based radically polymerizable compound.
[3] The polyorganosylsesquioxane constituting the (a) radically polymerizable silicone compound has a cage-like structure and has the following formula (1):
[RSiO _3/2 ] _n (1)
[In the formula, R is an organic functional group having a (meth) acryloyl group, and n is 8, 10 or 12].
The polarizing plate according to the above [1] or [2], which has a structural unit represented by.
[4] The active energy ray-curable composition comprises (a) a radically polymerizable silicone compound in an amount of 40 to 90% by mass based on the total amount of the total polymerizable compound contained in the active energy ray-curable composition. The polarizing plate according to any one of the above [1] to [3].
[5] The (b) (meth) acrylamide radically polymerizable compound has the following formula (2):

[R ¹ is a hydrogen atom or a methyl group, and R ² and R ³ are independently each of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or R ² and R ³ together, and they are combined. It is a 5-membered ring or a 6-membered ring which may have an oxygen atom as a ring member together with the nitrogen atom to be bonded, and the hydrogen atom contained in the alkyl group may be substituted with a hydroxyl group or an amino group. ]
The polarizing plate according to any one of the above [1] to [4], which is a compound represented by.
[6] The (b) (meth) acrylamide radically polymerizable compound comprises N, N-dimethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide and N, N-dimethylaminopropyl (meth) acrylamide. The polarizing plate according to any one of the above [1] to [5], which is selected from the group.
[7] The active energy ray-curable composition comprises 5 to 25% by mass of the (b) (meth) acrylamide radical polymerizable compound with respect to the total amount of the total polymerizable compound contained in the active energy ray-curable composition. The polarizing plate according to any one of the above [1] to [6], which comprises.
[8] The urethane-based radically polymerizable compound (c) contains a urethane-based monomer containing 2 to 6 radically polymerizable groups or 2 to 6 radically polymerizable groups, and has a weight average of 1000 to 20000. The polarizing plate according to any one of the above [2] to [7], which is a urethane-based oligomer having a molecular weight.
[9] The active energy ray-curable composition contains (c) a urethane-based radically polymerizable compound in an amount of 3 to 20% by mass based on the total amount of the total polymerizable compound contained in the active energy ray-curable composition. , The polarizing plate according to any one of the above [2] to [8].
[10] An active energy ray-curable composition comprising (a) a radically polymerizable silicone compound composed of polyorganosylsesquioxane and (b) a (meth) acrylamide radically polymerizable compound.

According to the present invention, it is possible to provide a polarizing plate provided with a thin protective film having high mechanical strength and excellent adhesion to a polarizing element. Further, it is possible to provide an active energy ray-curable composition capable of forming a thin protective film having excellent mechanical strength and adhesion of a stator.

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described here, and various modifications can be made without impairing the gist of the present invention.

<Polarizer>
〔Protective film〕
The polarizing plate of the present invention is a polarizing plate including a polarizing element and a protective film directly formed on at least one surface of the polarizing element. The protective film constituting the polarizing plate of the present invention has an active energy containing (a) a radically polymerizable silicone compound composed of polyorganosylsesquioxane and (b) a (meth) acrylamide radically polymerizable compound. It consists of a cured product of a radical curable composition. Here, the "protective film directly formed on at least one surface of the polarizing element" is an active energy ray containing the (a) radically polymerizable silicone compound and (b) (meth) acrylamide radically polymerizable compound. Obtained by forming a coating film by directly applying the curable composition to either one side or both sides of the polarizing element, and then polymerizing and curing the active energy ray-curable composition constituting the coating film. It means a film (layer) made of a cured product. In the present invention, the protective film is in a state of being directly laminated on the surface of the polarizing element, and the protective film is directly adhered to the polarizing element without the intervention of an adhesive layer or an adhesive layer. In the present invention, as compared with a protective film (protective layer) made of a conventional protective film that is bonded to the polarizing element via an adhesive or the like by forming the protective film directly on the surface of the polarizing element, the protective film is used. Not only is it possible to reduce the thickness of itself, but it is also advantageous in that the thickness of the entire polarizing plate can be reduced because the protective film is laminated on the polarizing element without interposing an adhesive layer or an adhesive layer.

In the present invention, the active energy ray-curable composition constituting the protective film contains (a) a radically polymerizable silicone compound composed of polyorganosylsesquioxane. By containing a radically polymerizable silicone compound composed of polyorganosylsesquioxane, it has high elastic modulus, surface hardness, and impact resistance, and is formed from triacetyl cellulose (TAC), which is widely used in conventional polarizing plates. It is possible to achieve a thinner protective film while having mechanical properties equal to or better than those of the protective film.
The silicone compound is a compound containing a Si—O bond, and in the present invention, “composed of polyorganosylsesquioxane” means that it is substantially composed of polyorganosylsesquioxane. Specifically, it means that 50% by mass or more of the total amount of the radically polymerizable silicone compound is polyorganosylsesquioxane.

Polyorganosylsesquioxane is a polysiloxane whose basic constituent unit is the T unit. In the present invention, examples of the structure of polyorganosylsesquioxane contained in the active energy ray-curable composition include polyorganosylsesquioxane having a random type, cage type or ladder type structure. In the present invention, only one type of polyorganosylsesquioxane may be used, or two or more types may be used in combination.

In the present invention, examples of the polymerizable group in the radically polymerizable silicone compound composed of polyorganosylsesquioxane include (meth) acryloyl group, vinyl group, styryl group and allyl group. Of these, a (meth) acryloyl group, a vinyl group or a styryl group is preferable, and a (meth) acryloyl group is more preferable. The number of polymerizable groups in the radically polymerizable silicone compound is not particularly limited, and may be one or a plurality. The (meth) acryloyl group means an acryloyl group or a methacryloyl group.

〔式中、Ｒ^１０は、水素原子またはメチル基を表し、ｍは１～３の整数を表す。〕
で表される官能基が挙げられる。 In the present invention, (a) the polyorganosylsesquioxane constituting the radically polymerizable silicone compound is preferably one having a cage-shaped structure, and in addition, the following formula (1):
[RSiO _3/2 ] _n (1)
[In the formula, R is an organic functional group having a (meth) acryloyl group, and n is 8, 10 or 12].
It is preferable that it has a structural unit represented by. In the formula (1), the organic functional group includes the following formula (3):

[In the formula, R ¹⁰ represents a hydrogen atom or a methyl group, and m represents an integer of 1 to 3. ]
Examples thereof include functional groups represented by.

In the present invention, since the mechanical strength, particularly the elastic modulus can be improved, (a) the polyorganosylsesquioxane constituting the radically polymerizable silicone compound includes a cage-shaped polyorganosylsesquioxane. Is preferable. As the cage-type polyorganosylsesquioxane, those having a polymerizable group in all the silicon atoms contained therein and having a controlled molecular weight distribution and molecular structure are preferable, but a part of the polymerizable group is an alkyl group, a phenyl group or the like. It may be replaced with. Further, it may have a complete polyhedral structure or a structure in which a part thereof is cleaved.

Specific examples of the cage-shaped polyorganosylsesquioxane include structures represented by the following formulas (4) to (6).

Further, a cleaved cage-shaped polyorganosylsesquioxane represented by the following formula (7): can also be preferably used.
(R ¹¹ SiO _3/2 ) _n1- (R ¹¹ (R ¹² ) ₂ SiO _1/2 ) _m1 (7)
In the formula, R ¹¹ represents an organic functional group having a (meth) acryloyl group. R ¹² represents a methyl group. The (n1 + m1) R ^11s may be the same or different from each other. As the organic functional group, an organic functional group represented by the above formula (3) is preferably mentioned. n1 indicates 8, 10, 12 or 14, and m1 indicates 0, 2, 4 or 6.

Specific examples of the cleaved cage-shaped polyorganosylsesquioxane represented by the above formula (7) include the following structures. In the following structure, "R ¹¹ " is referred to as "R ¹ " and "R ¹² " is referred to as "R ² ".

The polyorganosylsesquioxane may contain a non-cage-shaped polyorganosylsesquioxane, but the elastic modulus can be improved by containing the polyorganosylsesquioxane having a cage-shaped structure. Therefore, based on the total amount of polyorganosylsesquioxane, it is preferable to contain 50% by mass or more, more preferably 60% by mass or more, and 70% by mass or more of polyorganosylsesquioxane having a cage-shaped structure. Is even more preferable.

In the present invention, the active energy ray-curable composition is a radically polymerizable silicone compound composed of (a) polyorganosylsesquioxane with respect to the total amount of the total polymerizable compound contained in the active energy ray curable composition. Is preferably contained in an amount of 40 to 90% by mass, more preferably 45 to 85% by mass, and even more preferably 50 to 80% by mass. (A) When the content of the radically polymerizable silicone compound composed of polyorganosylsesquioxane is within the above range, a protective film having high elastic modulus and surface hardness and excellent mechanical properties can be obtained.

In the present invention, the active energy ray-curable composition constituting the protective film contains (b) (meth) acrylamide-based radically polymerizable compound. By containing the (meth) acrylamide-based radically polymerizable compound, the adhesion between the substituent and the protective film can be effectively improved. Further, for example, high adhesion between the polarizing element and the protective film can be ensured without subjecting the polarizing element to a surface treatment such as a silane coupling treatment, so that the number of steps required for manufacturing the polarizing plate is reduced. It is also advantageous in terms of productivity.

〔Ｒ^１は、水素原子またはメチル基であり、Ｒ^２およびＲ^３は、それぞれ独立して、水素原子、炭素数１～６のアルキル基またはＲ^２とＲ^３が一緒になって、それらが結合する窒素原子と共に、酸素原子を環構成員として有してもよい５員環若しくは６員環であり、該アルキル基に含まれる水素原子は、ヒドロキシル基またはアミノ基で置換されていてもよい〕
で表される化合物である
で表される化合物であることが好ましい。 In the present invention, the (b) (meth) acrylamide radically polymerizable compound is not particularly limited as long as it is a radically polymerizable compound having a (meth) acrylamide skeleton, but the following formula (2):

[R ¹ is a hydrogen atom or a methyl group, and R ² and R ³ are independently each of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or R ² and R ³ together, and they are combined. It is a 5-membered ring or a 6-membered ring which may have an oxygen atom as a ring member together with the nitrogen atom to be bonded, and the hydrogen atom contained in the alkyl group may be substituted with a hydroxyl group or an amino group. ]
It is preferable that it is a compound represented by.

Examples of the (meth) acrylamide-based radically polymerizable compound represented by the above formula (2) include N-methyl (meth) acrylamide, N-methylol (meth) acrylamide butyl ether, N-ethyl (meth) acrylamide, and N-. n-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-cyclopropyl (meth) acrylamide, diacetone (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methyl, N-ethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-methylol (meth) Acrylamide methyl ether, N-methylol (meth) acrylamide ethyl ether, N-methylol (meth) acrylamide propyl ether, N-butoxymethyl (meth) acrylamide, N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactum, and (Meta) Acrylamide morpholine and the like can be mentioned. Among them, a compound selected from the group consisting of N, N-dimethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N, N-dimethylaminopropyl (meth) acrylamide from the viewpoint of adhesion to a substituent. Is preferable. The "(meth) acrylamide radically polymerizable compound" means an acrylamide radically polymerizable compound or a methacrylamide radically polymerizable compound.

In the present invention, the active energy ray-curable composition contains 5 to 25% by mass of (b) (meth) acrylamide radical-polymerizable compound with respect to the total amount of the total polymerizable compound contained in the active energy ray-curable composition. It is preferably contained, more preferably 10 to 25% by mass, and even more preferably 10 to 20% by mass. (B) When the content of the (meth) acrylamide radically polymerizable compound is within the above range, a protective film having excellent adhesion to the polarizing element can be obtained.

In the present invention, the active energy ray-curable composition constituting the protective film preferably contains (c) a urethane-based radically polymerizable compound. By containing the urethane-based radically polymerizable compound, the toughness of the cured product of the curable composition can be increased and the impact resistance can be improved. It is also advantageous in that the handleability of the curable composition is improved and the processability is excellent.

In the present invention, the (c) urethane-based radically polymerizable compound is preferably a urethane-based monomer or a urethane-based oligomer containing 2 to 6 radically polymerizable groups. The urethane-based monomer and the urethane-based oligomer may be used alone or in combination.

The urethane-based oligomer is preferably an oligomer containing 2 to 6 radically polymerizable groups, having a urethane bond, and having a number weight average molecular weight of 1000 to 20000. When the number average molecular weight of the urethane-based oligomer is within the above range, it is possible to achieve both appropriate flexibility and surface hardness of the protective film. In the present invention, the weight average molecular weight of the urethane-based oligomer is more preferably 1500 to 15000, and even more preferably 2000 to 10000. The weight average molecular weight can be determined by gel permeation chromatography.

The urethane-based radically polymerizable compound can be prepared by a method conventionally known in the art. For example, it can be obtained by reacting a (meth) acrylic acid or a hydroxy (meth) acrylate obtained from a (meth) acrylic acid ester with a polyol with a diisocyanate. Urethane-based radically polymerizable compounds can be prepared.

Examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate and the like.

Examples of the polyol include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1, 6-hexanediol, 1,9-nonanediol, 1,10-decanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, neopentyl hydroxypivalate Glycol ester, tricyclodecanedimethylol, 1,4-cyclohexanediol, spiroglycol, hydrogenated bisphenol A, ethylene oxide-added bisphenol A, propylene oxide-added bisphenol A, trimethylolethane, trimethylolpropane, glycerin, 3-methylpentane -1,3,5-Triol, pentaerythritol, dipentaerythritol, tripentaerythritol, glucose and the like can be mentioned.

As the diisocyanate, for example, various aromatic, aliphatic or alicyclic diisocyanates can be used. Specific examples of the above diisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 4,4-diphenyldiisocyanate, 1,5-naphthalenedi isocyanate, and 3,3-dimethyl-4,4. -Diphenyldiisocyanate, xylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4-diphenylmethane diisocyanate, hydrogenated products thereof and the like can be mentioned.

In addition, a commercially available product may be used as the urethane-based radically polymerizable compound. For example, the product name "Shikou" series manufactured by Nippon Synthetic Chemical Industry Co., Ltd., the aliphatic urethane acrylate manufactured by Daicel Cytec Co., Ltd., etc. may be used. can.

In the present invention, the active energy ray-curable composition may contain (c) 3 to 20% by mass of the urethane-based radical polymerizable compound with respect to the total amount of the total polymerizable compound contained in the active energy ray-curable composition. It is preferably contained in an amount of 5 to 20% by mass, more preferably 5 to 15% by mass. (C) When the content of the urethane-based radically polymerizable compound is within the above range, a protective film having excellent impact resistance can be obtained.

In the present invention, the active energy ray-curable composition is a radically polymerizable silicone compound composed of (a) polyorganosylsesquioxane, (b) (meth) acrylamide radically polymerizable compound and (c) urethane-based. A radically polymerizable compound other than the radically polymerizable compound (hereinafter, also referred to as “(d) another radically polymerizable compound”) may be contained. (D) Examples of other radically polymerizable compounds include pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, trimethylolpropane acrylate, dimethylolpropane tetraacrylate, and ethoxylated isocyanuric acid triacrylate.

When the active energy ray-curable composition contains such other radically polymerizable compounds, the content thereof is 1 to 40 mass by mass with respect to the total amount of the total polymerizable compounds contained in the active energy ray-curable composition. %, More preferably 5 to 30% by mass.

The active energy ray-curable composition usually contains a radical polymerization initiator for initiating the polymerization of the radically polymerizable compound contained in the active energy ray curable composition. As the radical polymerization initiator, any known radical polymerization initiator may be used as long as it can initiate the polymerization of the radically polymerizable compound by irradiation with active energy rays. Specific examples thereof include an acetophenone-based initiator, a benzoin ether-based initiator, a benzophenone-based initiator, a thioxanthone-based initiator, and the like.

As the radical polymerization initiator, a commercially available product can be easily obtained, and for example, the trade name "IRGACURE" series manufactured by BASF Corporation can be used.

The content of the radical polymerization initiator in the active energy ray-curable composition is usually 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the total polymerizable compound contained in the active energy ray-curable composition. , Preferably 1 to 8 parts by mass. When the content of the radical polymerization initiator is in the above range, the active energy ray-curable composition can be sufficiently cured, and excellent adhesion between the protective film made of the obtained cured product and the substituent is ensured. be able to.

In the present invention, the active energy ray-curable composition can contain an additive generally used for the curable composition, if necessary. Examples of such additives include plasticizers, photosensitizers, leveling agents, antioxidants, stabilizers, flame retardants, viscosity modifiers, antifoaming agents, antistatic agents and the like.

In the polarizing plate of the present invention, the protective film is, for example, (a) a radically polymerizable silicone compound, (b) a (meth) acrylamide radically polymerizable compound, and, if necessary, (c) a urethane radically polymerizable compound. , (D) A curable composition obtained by mixing other polymerizable compounds, a radical polymerization initiator and an additive, is applied onto a polarizing element, and the curable composition is applied by irradiating with active energy rays. Can be formed by curing.

As the active energy rays to be irradiated, for example, visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, electron rays and the like can be used. Among them, ultraviolet light is preferable because it is easy to control the progress of the polymerization reaction and it is possible to use a photopolymerization apparatus widely used in the art.

Examples of the light source of the active energy ray include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a tungsten lamp, a gallium lamp, an excima laser, and a wavelength range. Examples thereof include LED light sources that emit light of 380 to 440 nm, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, and the like.

The integrated light amount expressed as the product of the irradiation intensity and the irradiation time on the active energy ray-curable composition is preferably set to be 500 to 10000 mJ / m ² , and more preferably 1000 to 8000 mJ / m ² . When the integrated light amount to the active energy ray-curable composition is within the above range, a sufficient amount of the active species derived from the polymerization initiator can be generated, the curing reaction can proceed more reliably, and the irradiation time can be extended. It does not become too long and can maintain good productivity. The curing of the active energy ray-curable composition by irradiation with active energy rays is preferably performed under conditions that do not deteriorate various functions of the polarizing plate such as the degree of polarization, the transmittance and the hue of the polarizing element.

In the polarizing plate of the present invention, the thickness of the protective film is not particularly limited, but it may be in the range of, for example, 1 to 100 μm because high mechanical properties can be maintained even with a thin film. It is preferably about 80 μm, more preferably 5 to 50 μm.

[Polarizer]
The polarizing element that can form the polarizing plate of the present invention is an optical film having a function of extracting linearly polarized light from incident natural light, for example, a polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented. Can be used.

The thickness of the splitter is usually 2 μm or more and 30 μm or less, preferably 25 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, and particularly preferably 7 μm or less. When a polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented is applied as a polarizing element, the polyvinyl alcohol-based resin alone may be stretched, or a solution of the polyvinyl alcohol-based resin may be applied to a substrate or the like. May be applied and dried, and then stretched together with the base material to remove the base material. When stretched together with a substrate, for example, a thin film polarizing element having a thickness of 7 μm or less can be easily produced. Examples of the base material include polyethylene terephthalate film, polycarbonate film, triacetyl cellulose film, norbornene film, polyester film, polystyrene film and the like.

As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides with ammonium groups and the like.

The saponification degree of the polyvinyl alcohol-based resin is usually 80 mol% or more, preferably 90 to 100 mol%, and more preferably 94 to 100 mol%. When the saponification degree is at least the above lower limit, the water resistance and moisture heat resistance of the obtained polarizing plate are good, and when the saponification degree is at least the above upper limit, the dyeing speed is high and efficient production can be achieved. A polarizing element having sufficient polarizing performance can be obtained.

The polyvinyl alcohol-based resin may be a partially modified modified polyvinyl alcohol, for example, olefin modification with ethylene, propylene or the like; unsaturated carboxylic acid modification with acrylic acid, methacrylic acid, crotonic acid or the like; unsaturated. Alkyl esters of carboxylic acids, those modified with acrylamide, etc. may be used. The modification rate of the polyvinyl alcohol-based resin is preferably less than 30 mol%, more preferably less than 10%. When the rate of denaturation is in the above range, the dichroic dye is easily adsorbed, and a polarizing element having sufficient polarizing performance can be obtained.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably about 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000. When the average degree of polymerization is at least the above lower limit, sufficient polarization performance can be obtained, and when the average degree of polymerization is at least the above upper limit, the solubility in a solvent is good and a polyvinyl alcohol-based resin film can be easily formed. can do.

As the polyvinyl alcohol-based resin, an appropriate commercially available product can be used. Suitable commercial products include, for example, "PVA124" and "PVA117" (both saponification degree: 98 to 99 mol%) and "Saponification degree: 95" (saponification degree: 95) manufactured by Kuraray Co., Ltd. under the trade names. ~ 96 mol%), "PVA617" (saponification degree: 94.5-95.5 mol%); "N-300" and "NH-18" (both saponification degree) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. : 98-99 mol%), "AH-22" (saponification degree: 97.5-98.5 mol%), "AH-26" (saponification degree: 97-98.8 mol%),; Japan "JC-33" (saponification degree: 99 mol% or more), "JF-17", "JF-17L" and "JF-20" (all saponification degree: 98-) manufactured by Vinegar Poval Co., Ltd. 99 mol%), "JM-26" (saponification degree: 95.5-97.5 mol%), "JM-33" (saponification degree: 93.5-95.5 mol%) and "JP-" 45 ”(saponification degree: 86.5 to 89.5 mol%) and the like can be mentioned.

The modulator is usually a step of uniaxially stretching such a polyvinyl alcohol-based resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye, and a dichroic dye. It is produced through a step of treating the adsorbed polyvinyl alcohol-based resin film with an aqueous boric acid solution and a step of washing with water after the treatment with the aqueous boric acid solution. By dyeing the polyvinyl alcohol-based resin film with the dichroic dye, the dichroic dye is contained in the polyvinyl alcohol-based resin film. When the polarizing element is produced by such a production method, the polarizing element becomes a stretched polyvinyl alcohol-based resin film containing a dichroic dye.

The uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing the dichroic dye, at the same time as dyeing, or after dyeing. If the uniaxial stretching is performed after staining, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. It is also possible to perform uniaxial stretching at these multiple stages. In uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched, or may be uniaxially stretched using a thermal roll. Further, the uniaxial stretching may be a dry stretching performed in the atmosphere, or may be a wet stretching performed in a state where the polyvinyl alcohol-based resin film is swollen using a solvent. The draw ratio is preferably 8 times or less, more preferably 7.5 times or less, still more preferably 7 times or less, from the viewpoint of suppressing deformation of the stator. Further, the draw ratio is usually 3 times or more from the viewpoint of expressing the function as a polarizing element. By setting the draw ratio within the above range, it is possible to suppress the deformation of the polarizing element over time.

As a method of dyeing the polyvinyl alcohol-based resin film with the dichroic dye, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye can be mentioned. As the dichroic dye, for example, iodine or a dichroic organic dye is used. Bicolor organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B. , Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue , Direct First Orange S, First Black and the like. As the dichroic dye, only one kind may be used alone, or two or more kinds may be used in combination. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

When iodine is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide for dyeing is usually adopted. The iodine content in this aqueous solution is usually 0.01 to 1 part by mass per 100 parts by mass of water, and the content of potassium iodide is usually 0.5 to 20 parts by mass per 100 parts by mass of water. .. When iodine is used as the dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C., and the immersion time (staining time) in this aqueous solution is usually 20 to 1800 seconds.
Before immersing the polyvinyl alcohol-based resin film in the aqueous solution containing iodine and potassium iodide, the film may be immersed in water in order to swell and facilitate dyeing. The temperature of the dipping treatment is usually 20 to 80 ° C., preferably 30 to 60 ° C., and the dipping time (staining time) is usually about 20 to 1800 seconds.

When a dichroic dye is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye and dyeing is usually adopted. The content of the dichroic dye in this aqueous solution is usually 1 × 10 ^-4 to 10 parts by mass, preferably 1 × 10 ^-3 to 1 part by mass, and more preferably 1 × 10 ⁻ per 100 parts by mass of water. ³ to 1 × ^10-2 parts by mass. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. When a dichroic dye is used as the dichroic dye, the temperature of the dye aqueous solution used for dyeing is usually 20 to 80 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 10 to 1800 seconds. be.

The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid aqueous solution. The amount of boric acid in the boric acid aqueous solution is usually 2 to 15 parts by mass, preferably 5 to 12 parts by mass per 100 parts by mass of water. When iodine is used as the dichroic dye, this boric acid aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid aqueous solution is usually 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass per 100 parts by mass of water. The immersion time in the boric acid aqueous solution is usually 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., and more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water in the washing treatment is usually 5 to 40 ° C., and the soaking time is usually 1 to 120 seconds. After washing with water, a drying treatment is performed to obtain a polarizing element. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually 30 to 100 ° C, preferably 40 to 95 ° C, and more preferably 50 to 90 ° C. The drying treatment time is usually 40 to 600 seconds, preferably 50 to 600 seconds, and more preferably 60 to 600 seconds.

As described above, a substituent can be obtained by subjecting the polyvinyl alcohol-based resin film to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment.

In the present invention, the adhesive surface between the polarizing element and the protective film may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, frame (flame) treatment, and keratinization treatment in order to improve the adhesiveness. However, since the protective film made of the cured product of the active energy ray-curable composition of the present invention has excellent adhesion to the polarizing element, the polarizing element and the protective film can be bonded to each other without the above treatment on the surface of the polarizing element. Sufficiently high adhesion can be ensured.

If necessary, the polarizing plate of the present invention may be further laminated with optical layers such as a retardation film, a viewing angle compensating film, and a luminance improving film. In the polarizing plate of the present invention, the optical layer can be formed by using a material known in the art.

The polarizing plate of the present invention can be produced by a known method. For example, it can be produced by applying an active energy ray-curable composition to a polarizing element and irradiating it with active energy rays to cure the curable composition to form a protective film. As a method for applying the active energy ray-curable composition, for example, known methods such as die coating, knife coating, and curtain coating can be adopted.

<Active energy ray-curable composition>
The present invention also relates to an active energy ray-curable composition. The active energy ray-curable composition of the present invention comprises (a) a radically polymerizable silicone composed of polyorganosylsesquioxane and (b) a (meth) acrylamide radically polymerizable compound. Further, it preferably further contains (c) a urethane-based radically polymerizable compound. The cured product produced by curing the active energy ray-curable composition of the present invention has excellent mechanical properties even if it is a thin film, and has excellent adhesion to a polarizing element. Therefore, for example, an image display measure. It can be suitably used as a material constituting a protective film (protective layer) of a polarizing plate used in an apparatus or the like. A thinner polarizing plate can be produced by using a cured product of the active energy ray-curable composition of the present invention instead of the protective film conventionally used for the polarizing plate.
Each component constituting the active energy ray-curable composition of the present invention containing the polymerizable compounds (a) to (c) is the same as each component constituting the protective film of the polarizing plate of the present invention. ..

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "%" and "part" in Examples and Comparative Examples represent "% by mass" or "parts by mass".

1. 1. Example 1
(1) Preparation of Polarizer A polyvinyl alcohol film with a thickness of 20 μm (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) was stretched about 5 times in the vertical uniaxial manner by dry stretching, and further maintained in a tense state. After soaking in pure water at 60 ° C. for 1 minute, it was immersed in an aqueous solution at 28 ° C. having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 for 60 seconds. Then, it was immersed in an aqueous solution at 72 ° C. having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 for 300 seconds. Subsequently, the cells were washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizing element having a thickness of 7 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

(2) Preparation of Active Energy Ray Curable Composition As the active energy ray curable resin composition, an ultraviolet curable resin composition composed of the following components was used.
A cage-type silsesquioxane composition having a polymerizable group containing a polymerization initiator (Nittetsu Sumikin Chemical Co., Ltd.) 80 parts by mass Urethane acrylate (Nippon Synthetic Chemical Co., Ltd. UV7000B) 5 parts by mass trimethylolpropane triacrylate (TMPTA) (Shin-Nakamura Chemical Industry Co., Ltd.) 5 parts by mass N, N-dimethylacrylamide (DMAA) (Tokyo Kasei Kogyo Co., Ltd.) 10 parts by mass

(3) Preparation of Polarizing Plate A cycloolefin-based resin film having a thickness of 13 μm was bonded to one side of the polarizing element using a water-based adhesive to obtain a one-sided protective film polarizing plate. An active energy ray-curable resin composition is applied to the polarizing surface of the obtained single-sided protective film polarizing plate to form a coating layer, and a cycloolefin-based resin film is laminated on the coating layer. The coating layer was cured by irradiating with an ultraviolet ray of 3200 mJ / m ² with a lamp to obtain a polarizing plate having a protective film directly formed on one side of the polarizing element.

(4) Preparation of Protective Film Single Layer An active energy ray-curable composition is applied onto a cycloolefin resin film to form a coating layer, and the coating layer is overlaid with a cycloolefin resin film without an H valve. The coating layer was cured by irradiating the coating layer with ultraviolet rays of 3200 mJ / m ² with an electrode UV lamp, and the cured film was peeled off from the cycloolefin resin film to obtain a protective film for evaluation.

(5) Evaluation of polarizing plate (protective film) <Adhesion>
For adhesion, the surface of the polarizing plate opposite to the one on which the cured resin layer was formed was attached to a glass plate via an adhesive layer having a thickness of about 20 μm, and then the surface of the cured resin layer was applied to JIS K 5400. The same Goban peeling test was carried out, and the evaluation was made based on the number of remaining Gobans in 100 Gobans.

<Elastic modulus>
For the elastic modulus, a single-layer protective film was subjected to a tensile test using a tensile tester (“Autograph AG-1” manufactured by Shimadzu Corporation) at a room temperature environment at a tensile speed of 1 mm / min, and the tensile strength of the film was obtained. The elastic modulus (MPa) was measured.

<Pencil hardness>
The pencil hardness was determined by a test method according to JIS K 5400 (1990) using pencils having different hardness in the polarizing plate on which the cured resin layer was formed.

<Mandrel test>
A test piece having a length of 120 mm and a width of 10 mm with the absorption axis direction of the polarizing film as the length direction was cut out from the film. A mandrel bending test was performed on this test piece using a bending resistance tester (cylindrical mandrel method) manufactured by TP Giken Co., Ltd., by winding it around a cylindrical mandrel and bending the test piece along its width direction. The minimum diameter of the mandrel at which the film was not cracked, chipped, cracked or broken was determined. The smaller the value of this minimum diameter, the better the toughness of the film, and the better the handleability and workability.

<Charpy impact test>
According to the method specified in JIS K7111-1, the obtained single cured resin layer was cut out in a vertical direction of 80 mm and a horizontal direction of 10 mm and measured, and the impact resistance of the cured resin layer was evaluated.

2. 2. Examples 2-4
Example 2
A polarizing plate was produced in the same manner as in Example 1 except that the thickness of the protective film was 40 μm. The obtained polarizing plate was evaluated by the same method as in Example 1.

Example 3
A polarizing plate was produced in the same manner as in Example 1 except that the urethane-based polymerizable compound was changed to the following. The obtained polarizing plate was evaluated by the same method as in Example 1.
Urethane acrylate (Nippon Synthetic Chemistry Co., Ltd. UV2000B) 5 parts by mass

Example 4
A polarizing plate was produced in the same manner as in Example 1 except that the composition ratio was changed to the following. The obtained polarizing plate was evaluated by the same method as in Example 1.
A cage-type silsesquioxane composition having a polymerizable group containing a polymerization initiator (Nittetsu Sumikin Chemical Co., Ltd.) 50 parts by mass Urethane acrylate (Nippon Synthetic Chemical Co., Ltd. UV7000B) 15 parts by mass Trimethylol propanetriacrylate (Shin Nakamura Chemical Industry Co., Ltd.) 15 parts by mass N, N-dimethylacrylamide (Tokyo Kasei Kogyo Co., Ltd.) 20 parts by mass

3. 3. Comparative Examples 1 to 4
Comparative Example 1
A polarizing plate was produced in the same manner as in Example 1 except that an ultraviolet curable resin composition composed of the following components was used as the active energy ray-curable resin composition. The obtained polarizing plate was evaluated by the same method as in Example 1.
Urethane Acrylate (Nippon Synthetic Chemical Co., Ltd. UV7000B) 50 parts by mass Trimethylolpropane Triacrylate (Shin Nakamura Chemical Industry Co., Ltd.) 30 parts by mass N, N-dimethylacrylamide (Tokyo Chemical Industry Co., Ltd.) 20 parts by mass Photopolymerization Initiator: Irgacure184 (BASF Co., Ltd.) 3 parts by mass

Comparative Example 2
A polarizing plate was produced in the same manner as in Example 1 except that an ultraviolet curable resin composition composed of the following components was used as the active energy ray-curable resin composition. The obtained polarizing plate was evaluated by the same method as in Example 1.
100 parts by mass of a cage-type silsesquioxane composition having a polymerizable group containing a polymerization initiator (Nippon Steel & Sumikin Chemical Co., Ltd.)

Comparative Example 3
A polarizing plate was produced in the same manner as in Example 1 except that an ultraviolet curable resin composition composed of the following components was used as the active energy ray-curable resin composition. The obtained polarizing plate was evaluated by the same method as in Example 1.
A cage-type silsesquioxane composition having a polymerizable group containing a polymerization initiator (Nittetsu Sumikin Chemical Co., Ltd.) 50 parts by mass Urethane acrylate (Nippon Synthetic Chemical Co., Ltd. UV7000B) 15 parts by mass Trimethylol propanetriacrylate (Shin-Nakamura Chemical Industry Co., Ltd.) 15 parts by mass 4-hydroxybutyl acrylate (HBA) (Tokyo Kasei Kogyo Co., Ltd.) 20 parts by mass

Comparative Example 4
A polarizing plate was produced in the same manner as in Example 1 except that an ultraviolet curable resin composition composed of the following components was used as the active energy ray-curable resin composition. The obtained polarizing plate was evaluated by the same method as in Example 1.
50 parts by mass of cage-type silsesquioxane composition having a polymerizable group containing a polymerization initiator (Nippon Steel & Sumikin Chemical Co., Ltd.) 50 parts by mass of trimethylolpropane triacrylate (Shin Nakamura Chemical Industry Co., Ltd.)

The composition of the active energy ray-curable resin composition used in each Example and Comparative Example is shown in Table 1, and the evaluation results are shown in Table 2, respectively.

Polyorganosilsesquioxane: A cage-type silsesquioxane composition having a polymerizable group containing a polymerization initiator (Nippon Steel & Sumikin Chemical Co., Ltd.)
UV-7000B: Urethane acrylate (Nippon Synthetic Chemistry Co., Ltd. UV7000B)
UV-2000B: Urethane acrylate (Nippon Synthetic Chemistry Co., Ltd. UV2000B)
TMPTA: Trimethylolpropane triacrylate (Shin Nakamura Chemical Industry Co., Ltd.)
HBA: 4-Hydroxybutyl acrylate (Tokyo Chemical Industry Co., Ltd.)
DMAA: N, N-dimethylacrylamide (DMAA) (Tokyo Chemical Industry Co., Ltd.)

Claims (6)

A polarizing plate including a polarizing element and a protective film directly formed on at least one surface of the polarizing element, wherein the protective film is:
It comprises a cured product of an active energy ray-curable composition containing (a) a radically polymerizable silicone compound composed of polyorganosylsesquioxane and (b) a (meth) acrylamide radically polymerizable compound.
The active energy ray-curable composition contains 5 to 25% by mass of the (b) (meth) acrylamide radical polymerizable compound based on the total amount of the total polymerizable compound contained in the active energy ray-curable composition. Become,
The (b) (meth) acrylamide radically polymerizable compound has the following formula (2):

[R ¹ is a hydrogen atom or a methyl group, and R ² and R ³ are independently hydrogen atoms or alkyl groups having 1 to 6 carbon atoms].
A polarizing plate, which is a compound represented by. The polarizing plate according to claim 1, wherein the active energy ray-curable composition further contains (c) a urethane-based radically polymerizable compound. The polyorganosylsesquioxane constituting the (a) radically polymerizable silicone compound has a cage-like structure and has the following formula (1):
[RSiO _3/2 ] _n (1)
[In the formula, R is an organic functional group having a (meth) acryloyl group, and n is 8, 10 or 12].
The polarizing plate according to claim 1 or 2, which has a structural unit represented by. Claim 1 in which the active energy ray-curable composition contains (a) a radically polymerizable silicone compound in an amount of 40 to 90% by mass based on the total amount of the total polymerizable compound contained in the active energy ray-curable composition. The polarizing plate according to any one of 3 to 3. The (c) urethane-based radically polymerizable compound contains a urethane-based monomer containing 2 to 6 radically polymerizable groups or 2 to 6 radically polymerizable groups, and has a weight average molecular weight of 1000 to 20000. The polarizing plate according to claim 2, which is a urethane-based oligomer. Claimed, wherein the active energy ray-curable composition contains (c) a urethane-based radically polymerizable compound in an amount of 3 to 20% by mass based on the total amount of the total polymerizable compound contained in the active energy ray-curable composition. The polarizing plate according to 2 or 5 .