KR102278332B1 - Polarizing plate and display device - Google Patents

Abstract

The present invention includes a polarizer and a first protective film laminated on one side through a first adhesive layer, wherein the first protective film has a transmittance of 1 to 50% of the accumulated light in a wavelength region of 280 to 320 nm, , the first adhesive layer is made of a cured product of an ultraviolet curable adhesive containing a photosensitizer, the photosensitizer has an absorption band in at least a part of the wavelength region in the wavelength region of 280 to 380 nm, and more than 380 nm Provided are a polarizing plate having substantially no absorption band in a wavelength region, and a display device including the same.

Description

Polarizer and display device {POLARIZING PLATE AND DISPLAY DEVICE}

The present invention relates to a polarizing plate and a display device using the same, and more particularly, to a polarizing plate formed by bonding a protective film to at least one surface of the polarizer using an ultraviolet curable adhesive, and a display device using the same.

A polarizing plate is widely used for display apparatuses, such as a liquid crystal display device, especially in various mobile devices in recent years. As a polarizing plate, the thing of the structure which bonded together the protective film using the adhesive agent on the single side|surface or both surfaces of a polarizer is common.

Although water-based adhesives and UV-curable adhesives are known as the adhesive, a protective film with low moisture permeability is preferred from the viewpoint of water resistance of the polarizing plate, and accordingly, it is difficult to adhere with a water-based adhesive requiring drying (removal of moisture). In order to become a situation, an ultraviolet curable adhesive is used suitably in recent years [for example, Unexamined-Japanese-Patent No. 2013-142863 (patent document 1) and Unexamined-Japanese-Patent No. 2011-028234 (patent document 2)).

Patent Document 1: Japanese Patent Laid-Open No. 2013-142863 Patent Document 2: Japanese Patent Laid-Open No. 2011-028234

In addition to thickness reduction, various functionalities are calculated|required by the protective film used for the polarizing plate for mobile devices in many cases. In particular, this tendency is remarkable in high-end products represented by smartphones and the like.

For example, when it is set as a liquid crystal display device, it is calculated|required from a light resistance viewpoint to contain a ultraviolet absorber in the protective film arrange|positioned at the most visible side. In addition, the protective film disposed on the most visible side may be required to have retardation characteristics in order to ensure visibility when wearing sunglasses. Among them, a stretched film made of polyethylene terephthalate resin is suitably used from the viewpoint of low cost. is becoming

When the protective film is bonded to the polarizer with an ultraviolet curable adhesive, ultraviolet rays containing a wavelength region of 280 to 320 nm (hereinafter also referred to as “UVB region”), which is a general photosensitive wavelength region of the photopolymerization initiator contained in the ultraviolet curable adhesive, are emitted. It is usual to irradiate, thereby curing the adhesive layer. However, since the protective film containing a ultraviolet absorber absorbs most of ultraviolet rays, it is difficult to irradiate an ultraviolet-ray from the protective film side and harden an ultraviolet curable adhesive agent. In the case of a protective film made of a polyethylene terephthalate-based resin, the aromatic ring contained in the resin skeleton also substantially blocks ultraviolet rays, so it is difficult to cure the ultraviolet curable adhesive.

Moreover, today, with the spread of a touch panel etc., for antistatic, an antistatic agent may be added to the protective film arrange|positioned most on the visual recognition side, In this case, the transmittance|permeability of an ultraviolet-ray will fall further.

On the other hand, regarding the protective film arranged on the liquid crystal cell side when it is set as a liquid crystal display device, a negative retardation film has been requested|required by the spread of IPS mode, what stretched|stretched a polystyrene-type resin film, and liquid-crystal-coated retardation film is increasingly being used. Since the liquid crystal compound which forms the liquid-crystal layer of a liquid-crystal application type retardation film contains many aromatic rings in the frame|skeleton, it absorbs an ultraviolet-ray in most cases. Since the retardation film made of a polystyrene-based resin also contains an aromatic ring in the resin skeleton, it absorbs ultraviolet rays in the UVB region depending on the type of the polystyrene-based resin used.

As described above, it can be said that there is a growing demand for using a protective film disposed on the liquid crystal cell side of the polarizer and a protective film disposed on the opposite side of the polarizer, which hardly transmits ultraviolet rays in the UVB region, but at the same time, the protective film side The problem that it is difficult to harden the UV-curable adhesive by irradiating with UV light has surfaced. When insufficient curing of the UV-curable adhesive occurs, it can be seen that damage to the polarizer is caused under the durability test due to the residual of the curable compound (monomer), and in particular, yellowing of the polarizer under heat-resistant conditions or discoloration of the polarizer under moist heat conditions. raises the

As a means to solve the problem of insufficient curing of the UV-curable adhesive, Patent Document 1 proposes to contain an anthracene-based photosensitizer that exhibits maximum absorption in light of a wavelength longer than 380 nm in the UV-curable adhesive. have. However, since this photosensitizer has an absorption band even in the visible region, it absorbs blue and the polarizing plate takes on a yellow tone, or under an environment containing light around 400 nm (under sunlight, under fluorescent lamps, under mercury lamps, etc.) If the polarizing plate is left for a long time, it may cause problems such as gradually changing color. In addition, since the adhesive itself before curing has photosensitivity to light in the visible region, polymerization gradually proceeds and thickens even under a normal fluorescent lamp, etc. There is also a risk of causing a problem that the pot life is short.

Moreover, said patent document 2 describes that content of an anthracene type photosensitizer can be reduced by using together naphthalene type photosensitizer preparation together with an anthracene type photosensitizer. However, in the ultraviolet curable adhesive described in this patent document, the anthracene-based photosensitizer is an essential component for achieving sufficient curing, and even if the content can be reduced to some extent, the same problem as the ultraviolet curable adhesive described in Patent Document 1 can have another

The present invention has been made in view of the above, and its object is a polarizing plate in which a protective film is bonded to at least one side of a polarizer through an adhesive layer made of an ultraviolet curable adhesive, wherein the ultraviolet transmittance in the UVB region of the protective film is low However, it is an object to provide a polarizing plate in which the adhesive layer is sufficiently cured, and a display device including the same.

A further object of the present invention is to provide a polarizing plate that does not cause a problem such as a yellow tone or a color change gradually when placed in an environment containing light around 400 nm, and a display device having the same. .

As a result of intensive research to solve the above problems, the present inventors have found that when the protective film transmits ultraviolet rays in the UVB region even at a transmittance of only 1% of the accumulated light amount in the region, in order to ensure sufficient curing of the adhesive. Contrary to the prior art in which an anthracene-based photosensitizer exhibiting maximum absorption in light of a wavelength longer than 380 nm is an essential component, unexpectedly, only a photosensitizer having substantially no absorption band in the wavelength region exceeding 380 nm is contained. It has been found that, while sufficient curing can be realized with the above-mentioned problems, the above-described problems can be simultaneously solved by adding an anthracene-based photosensitizer having an absorption band in the visible region.

That is, the present invention provides the following polarizing plate and display device.

[1] It includes a polarizer and a first protective film laminated on one side through a first adhesive layer,

The first protective film has a transmittance of 1 to 50% of the accumulated light in a wavelength region of 280 to 320 nm,

The first adhesive layer is made of a cured product of an ultraviolet curable adhesive containing a photosensitizer,

The photosensitizer has an absorption band in at least a part of the wavelength region in a wavelength region of 280 to 380 nm, and substantially no absorption band in a wavelength region exceeding 380 nm.

[2] The polarizing plate according to [1], wherein the first protective film is a retardation film having a liquid crystal layer on a support film, or a retardation film made of a resin film containing an aromatic ring.

[3] The polarizing plate according to [1] or [2], further comprising a second protective film laminated on the other side of the polarizer through a second adhesive layer.

[4] The second protective film has a transmittance of 1 to 50% of the accumulated light in a wavelength region of 280 to 320 nm,

The second adhesive layer is made of a cured product of an ultraviolet curable adhesive containing a photosensitizer,

The polarizing plate according to [3], wherein the photosensitizer has an absorption band in at least a part of the wavelength region in a wavelength region of 280 to 380 nm, and substantially no absorption band in a wavelength region exceeding 380 nm.

[5] The polarizing plate according to [3] or [4], wherein the second protective film contains an ultraviolet absorber.

[6] The polarizing plate according to any one of [3] to [5], wherein the second protective film contains a polyethylene terephthalate-based resin or a (meth)acrylic-based resin.

[7] The polarizing plate according to any one of [1] to [6], wherein the photosensitizer is a naphthalene derivative.

[8] The polarizing plate according to any one of [1] to [7], wherein the polarizer has a thickness of 10 µm or less.

[9] A display device comprising the polarizing plate according to any one of [1] to [8].

According to the present invention, as a polarizing plate in which a protective film having a low ultraviolet transmittance in the UVB region is bonded to a polarizer through an adhesive layer made of a cured product of an ultraviolet curable adhesive, the adhesive layer is sufficiently cured and has a yellow tone It is possible to provide a polarizing plate that does not cause problems such as color change over time, and a display device having the same.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate which concerns on this invention.
It is a schematic sectional drawing which shows another example of the layer structure of the polarizing plate which concerns on this invention.
3 is a flowchart showing a preferred example of a method for manufacturing a polarizing plate according to the present invention.
It is a schematic sectional drawing which shows an example of the laminated constitution of the laminated|multilayer film obtained by the resin layer formation process.
It is a schematic sectional drawing which shows an example of the laminated constitution of the stretched film obtained by an extending process.
It is a schematic sectional drawing which shows an example of the laminated constitution of the light-polarizing laminated film obtained by a dyeing process.
It is a schematic sectional drawing which shows an example of the laminated constitution of the bonding film obtained by a 1st bonding process.
8 is an absorption spectrum of 1,4-diethoxynaphthalene.

<Polarizer>

(1) Layer composition of polarizing plate

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate which concerns on this invention. Like the polarizing plate 1 shown in FIG. 1 , the polarizing plate of the present invention includes a polarizer 5 and a first protective film 10 laminated through a first adhesive layer 15 on one side thereof. It may be a polarizing plate equipped with a film. The polarizing plate 1 may further have another optical function layer or an adhesive layer laminated on the first protective film 10 and/or the polarizer 5 .

In addition, the polarizing plate of the present invention, like the polarizing plate 2 shown in FIG. 2 , a polarizer 5 and a first protective film 10 laminated through a first adhesive layer 15 on one side thereof, and the other A polarizing plate provided with a double-sided protective film having a second protective film 20 laminated thereon via a second adhesive layer 25 may be used. The polarizing plate 2 may further have another optical function layer or an adhesive layer laminated on the first protective film 10 and/or the second protective film 20 .

In the polarizing plates 1 and 2, the first protective film 10 has a wavelength range of 280 to 320 nm (UVB), which is a general photosensitive wavelength range of the photopolymerization initiator contained in the ultraviolet curable adhesive forming the first adhesive layer 15. It is a film with a low transmittance|permeability of the area|region), specifically, the transmittance|permeability of the accumulated light amount in a UVB area|region is 50% or less (and 1% or more). The first adhesive layer 15 is a layer formed of an ultraviolet curable adhesive containing only a predetermined photosensitizer as a photosensitizer, and is specifically a cured product layer of the ultraviolet curable adhesive. A predetermined photosensitizer is a photosensitizer which has an absorption band in at least one part wavelength range in a wavelength range of 280-380 nm, and does not substantially have an absorption band in a wavelength range exceeding 380 nm.

Any film which can be used as a protective film for polarizers may be sufficient as the 2nd protective film 20 which the polarizing plate 2 provided with a double-sided protective film has, The 2nd adhesive bond layer 25 for bonding this also, the polarizer 5 ) and a layer made of any adhesive capable of bonding the second protective film 20 to each other. However, like the first protective film 10, the second protective film 20 has a transmittance of 50% or less in the UVB region, and the second protective film 20 is bonded to the polarizer 5 with an ultraviolet curable adhesive, and the second When the adhesive layer is cured by irradiating ultraviolet rays from the protective film 20 side, the UV-curable adhesive forming the second adhesive layer 25 is used as a photosensitizer as a photosensitizer similarly to the first adhesive layer 15 . It is preferable to contain only a photosensitizer.

(2) Polarizer

The polarizer 5 may be a uniaxially stretched polyvinyl alcohol-based resin layer (or film) in which a dichroic dye is adsorbed and oriented. The thickness of the polarizer 5 may be, for example, 30 µm or less, further 20 µm or less, but in particular, in a polarizing plate for mobile devices, from the viewpoint of thinning the polarizers 1 and 2, it is preferably 10 µm or less, and 8 µm or less more preferably. The thickness of the polarizer 5 is 2 micrometers or more normally.

As polyvinyl alcohol-type resin which comprises a polyvinyl alcohol-type resin layer, what saponified polyvinyl acetate-type resin can be used. As polyvinyl acetate-type resin, the copolymer of vinyl acetate and other monomer copolymerizable to this other than polyvinyl acetate which is a homopolymer of vinyl acetate is illustrated. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

What formed the said polyvinyl alcohol-type resin into a film comprises the polarizer 5. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and it can be formed by a known method, but it is easy to obtain a polarizer 5 having a small thickness, and the handling of the thin film polarizer 5 in the process is excellent. , It is preferable to apply a solution of a polyvinyl alcohol-based resin on a base film to form a film.

The degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, but preferably in the range of 90.0 to 99.5 mol%, more preferably in the range of 94.0 to 99.0 mol%. The water resistance and heat-and-moisture resistance of the polarizing plates 1 and 2 obtained as saponification degree is less than 80.0 mol% fall. When a saponification degree uses polyvinyl alcohol-type resin exceeding 99.5 mol%, a dyeing rate becomes slow, while productivity falls, the polarizer 5 which has sufficient polarization|polarized-light performance may not be obtained.

_{The degree of saponification refers to the ratio of the acetic acid group (acetoxy group: -OCOCH 3} ) contained in the polyvinyl acetate-based resin, which is a raw material of the polyvinyl alcohol-based resin, changed to a hydroxyl group by the saponification process as a unit ratio (mol%), the formula:

Saponification degree (mol%) = 100 x (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetic acid groups)

is defined as Saponification degree can be calculated|required based on JISK6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and therefore, the lower the proportion of acetic acid groups that inhibit crystallization.

The polyvinyl alcohol-based resin may be partially modified polyvinyl alcohol. For example, polyvinyl alcohol-type resin is olefins, such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; What modified|denatured with the alkyl ester of unsaturated carboxylic acid, acrylamide, etc. are mentioned. It is preferable that it is less than 30 mol%, and, as for the ratio of modification, it is more preferable that it is less than 10%. When modification|denaturation exceeding 30 mol% is performed, it becomes difficult to adsorb|suck a dichroic dye, and the polarizer 5 which has sufficient polarization|polarized-light performance cannot be obtained.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10000, more preferably 1500 to 8000, still more preferably 2000 to 5000. The average degree of polymerization of polyvinyl alcohol-type resin can also be calculated|required based on JISK6726 (1994).

The dichroic dye contained in the polarizer 5 (adsorption orientation) may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dye 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, and First Black. A dichroic dye may be used individually by 1 type, and may use 2 or more types together.

(3) 1st protective film

The first protective film 10 is formed of a light-transmitting (preferably optically transparent) thermoplastic resin such as a chain polyolefin-based resin (polypropylene-based resin, etc.) or a cyclic polyolefin-based resin (norbornene-based resin, etc.) polyolefin resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polyester-based resin; polycarbonate-based resin; (meth)acrylic resin; polystyrene-based resin; Or it may be a film made of a mixture or copolymer thereof. Among them, the first protective film 10 suitably used in the present invention is a protective film with low moisture permeability that is difficult to adhere with a water-based adhesive, such as polyolefin-based resin, polyester-based resin, (meth)acrylic-based resin, and polystyrene-based resin. It is a protective film which consists of resin etc.

In addition, in this specification, "(meth)acryl" means at least one selected from acryl and methacryl. The same is true when referring to "(meth)acryloyl" or "(meth)acrylate".

In addition, the first protective film 10 may be a protective film having an optical function such as a retardation film and a brightness improving film. For example, by stretching the film made of the thermoplastic resin (uniaxial stretching or biaxial stretching, etc.) or forming a liquid crystal layer or the like on the film, a retardation film to which an arbitrary retardation value is imparted can be obtained.

Examples of the chain polyolefin resin include a copolymer composed of two or more chain olefins other than a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin.

Cyclic polyolefin-type resin is a generic name of resin superposed|polymerized using cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and a chain olefin such as ethylene and propylene (typically a random copolymer) and unsaturated Graft polymers modified with carboxylic acids or derivatives thereof, and hydrides thereof. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers are preferably used as cyclic olefins.

Cellulose ester-based resins are esters of cellulose and fatty acids. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and the thing by which a part of hydroxyl group was modified by other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is especially preferable.

Polyester-type resin is resin which has an ester bond, and what consists of polycondensate of polyhydric carboxylic acid or its derivative(s), and polyhydric alcohol is common. As polyhydric carboxylic acid or its derivative(s), divalent dicarboxylic acid or its derivative(s) can be used, For example, terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalene dicarboxylic acid, etc. are mentioned. As polyhydric alcohol, dihydric diol can be used, For example, ethylene glycol, propanediol, butanediol, neopentyl glycol, cyclohexane dimethanol, etc. are mentioned.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, and polycyclohexane. dimethyl naphthalate.

The polycarbonate-based resin is composed of a polymer to which a monomer unit is bonded through a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate, a copolymer polycarbonate, or the like having a polymer skeleton modified.

(meth)acrylic-type resin is resin which uses the compound which has a (meth)acryloyl group as a main structural monomer. Specific examples of the (meth)acrylic resin include poly(meth)acrylic acid esters such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-(meth)acrylic acid ester copolymer; methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin, etc.); copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth) acrylate norbornyl copolymer, etc.) . _{Preferably, a polymer containing poly(meth)acrylic acid C 1-6} alkylester as a main component, such as poly(meth)methyl acrylate, is used, and more preferably, methyl methacrylate as a main component (50 to 100% by weight, Preferably 70 to 100% by weight) of a methyl methacrylate-based resin is used.

A surface treatment layer (coating layer) such as a hard coat layer, an anti-glare layer, an anti-reflection layer, an anti-static layer, and an anti-fouling layer may be formed on the surface opposite to the polarizer 5 of the first protective film 10 . The method of forming a surface treatment layer on the protective film surface is not specifically limited, A well-known method can be used.

Although it is preferable that the thickness of the 1st protective film 10 is thin from a viewpoint of thickness reduction of the polarizing plates 1 and 2, when it is too thin, intensity|strength will fall and workability will be inferior. Therefore, as for the thickness of the 1st protective film 10, 5-90 micrometers or less are preferable, More preferably, it is 5-60 micrometers, More preferably, it is 5-50 micrometers.

In the present invention, the first protective film 10 is a film having a low transmittance in the 280 to 320 nm region (UVB region), specifically, a film having a transmittance of the accumulated light amount of 50% or less in the UVB region. According to the present invention, as long as the transmittance is 1% or more, 30% or less, 20% or less, 10% or less, and even 5% or less, by irradiating ultraviolet rays including a UVB region from the first protective film 10 side The first adhesive layer 15 can be sufficiently cured. When the said transmittance|permeability is less than 1 %, an irradiated ultraviolet-ray hardly reaches an adhesive bond layer, and sufficient hardening cannot be obtained even if an ultraviolet curable adhesive contains a photosensitizer.

The degree of curing of the adhesive layer can be evaluated by, for example, a wet heat durability test. Although a specific test method is demonstrated in the term of an Example, if hardening is insufficient, discoloration or spot-like unevenness will arise in the polarizer 5 under a moist-heat endurance test.

The transmittance of the accumulated light amount in the UVB region of the first protective film 10 (the second protective film 20 is also the same) is obtained by the following method. The measuring device is not limited as long as it can be obtained by integrating the light intensity in the wavelength range of 280 to 320 nm, and for example, "UV Power Puck 2" sold by Electronic Instrumentation & Technology, Inc., etc. can be used. have.

The light from the light source (ultraviolet light source for curing the adhesive layer) is directly measured using the above measuring device, and the accumulated light amount (mJ/cm 2 ) in the UVB region is referred to as “standard accumulated light amount”. Next, the protective film to be measured is covered on the light-receiving part of the measuring device and fixed with a tape, and the measurement is performed again, and the accumulated light amount (mJ/cm 2 ) in the UVB region obtained is referred to as “the accumulated light amount beyond the protective film”. At this time, the transmittance of the accumulated light amount in the UVB region of the protective film is given by the following formula:

Transmittance (%) of accumulated light amount in UVB region = 100 x accumulated light amount beyond the protective film/standard accumulated light amount

saved as

In addition, in measuring the transmittance of this integrated light quantity, if the irradiation intensity of the light source is too weak, it may not be possible to measure normally. Therefore, it is preferable that the peak intensity of the light source is in the range of 150 to 250 mW/cm 2 . For the same reason, it is preferable that the standard accumulated light amount be in the range of 100 to 400 mJ/cm 2 .

The specific example of the 1st protective film 10 whose transmittance|permeability of the accumulated light amount in a UVB area|region is 1-50 % is given as follows.

[a] A protective film containing an ultraviolet absorber (including the case of a protective film having an optical function such as a retardation film and a luminance enhancing film. The following [b] and [c] are also the same);

[b] a protective film made of a resin containing an aromatic ring in a resin skeleton such as a polyester resin such as a polyethylene terephthalate resin, a polycarbonate resin, or a polystyrene resin;

[c] a protective film having a surface treatment layer as exemplified above;

[d] Retardation film having a liquid crystal layer on a support film.

As the ultraviolet absorber in [a], for example, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl) phenol], 2-(5-methyl-2-hydroxyphenyl)-2H-benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzo Triazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5 -Chloro-2H-benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chloro-2H-benzotriazole, 2-(3,5-di-t- benzotriazole-based ultraviolet absorbers such as amyl-2-hydroxyphenyl)-2H-benzotriazole and 2-(2'-hydroxy-5'-t-octylphenyl)-2H-benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone , 2-hydroxybenzophenone-based ultraviolet absorbers such as 2,2'-dihydroxy-4-methoxybenzophenone and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone; and a salicylic acid phenyl ester ultraviolet absorber such as p-t-butylphenyl salicylic acid ester and p-octylphenyl salicylic acid ester, and two or more types may be used as needed.

The support film in said [d] may be the film which consists of the above-mentioned thermoplastic resin. A liquid crystal layer is a layer which orientated, hardened and fixed the liquid crystal compound laminated|stacked on the support film through an orientation layer as needed. The liquid crystal compound may be a polymerizable liquid crystal compound containing a biphenyl group or a mesogenic group.

The polarizing plate (polarizing plate 1 with single-sided protective film and polarizing plate 2 with double-sided protective film) of the present invention may be a polarizing plate disposed on the front side (viewer side) when it is set as a liquid crystal display device, or on the back side ( The polarizing plate disposed on the backlight side) may be used, and the first protective film 10 is on the liquid crystal cell side of the polarizer 5 in any case where the polarizing plate of the present invention is either the polarizing plate on the front side or the back side. It may be a protective film laminated to, or a protective film laminated opposite to the liquid crystal cell.

When the first protective film 10 (especially in the polarizing plate 2 provided with the double-sided protective film) is a protective film laminated on the liquid crystal cell side of the polarizer 5, especially among the above [a] to [d] It may be a retardation film belonging to [b] or [d]. In addition, when the first protective film 10 is a protective film laminated on the opposite side of the liquid crystal cell of the polarizer 5 (eg, a protective film on the viewer side of the front-side polarizing plate), the above [a] to [d] Among them, in particular, it may be a protective film or retardation film belonging to the above [a] to [c].

(4) first adhesive layer

The first adhesive layer 15 is a cured product layer of an ultraviolet curable adhesive containing a photosensitizer. The thickness of the 1st adhesive bond layer 15 is about 0.001-5 micrometers normally, Preferably it is 0.01-2 micrometers, More preferably, it is 0.01-1 micrometer.

An ultraviolet curable adhesive agent contains a sclerosing|hardenable compound (polymerizable compound), a photoinitiator, and a photosensitizer. In the present invention, as the photosensitizer, a photosensitizer having an absorption band in at least a part of the wavelength region in a wavelength region of 280 to 380 nm and substantially not having an absorption band in a wavelength region exceeding 380 nm is used. Two or more types of photosensitizers may be used as long as such light absorption characteristics are exhibited.

One of the features of the present invention is the use of a photosensitizer having the above light absorption characteristics, but this is that the protective film transmits ultraviolet rays in the UVB region even at only 1% with the transmittance of the accumulated light amount in the UVB region. In this case, even if a photosensitizer having an absorption band on the longer wavelength side than 380 nm is not used, only a photosensitizer having an absorption band within a wavelength range of 280 to 380 nm is used, and the protective film is irradiated with ultraviolet rays from the side. It is based on the unexpected discovery of this inventor that the adhesive bond layer which consists of an ultraviolet curable adhesive agent can fully harden|cure. On the other hand, in the prior art, as in Patent Documents 1 and 2 described above, in order to sufficiently harden the adhesive layer by ultraviolet irradiation from the protective film side with low ultraviolet transmittance, an absorption band longer than 380 nm like an anthracene-based photosensitizer has an absorption band on the side. It has been thought that a photosensitizer having a

According to the present invention, in addition to being able to sufficiently harden the adhesive layer made of the ultraviolet curable adhesive by irradiation with ultraviolet rays from the protective film side, it is possible not to use a photosensitizer having an absorption band on the longer wavelength side than 380 nm. Because it absorbs blue, the polarizing plate (adhesive layer) has a yellow tone, or if the polarizing plate is left for a long time in an environment containing light around 400 nm, problems such as color change gradually can be solved, A polarizing plate having excellent light resistance can be provided.

In addition, according to the ultraviolet curable adhesive according to the present invention containing only a photosensitizer having an absorption band within a wavelength range of 280 to 380 nm as a photosensitizer, discoloration with time under external light, or when left for a long time under a fluorescent lamp or LED light It is also possible to prevent the progress of polymerization and thus thickening.

The photosensitizer used in the present invention may have an absorption band in at least a part of the wavelength region within the wavelength region of 280 to 380 nm, but a wavelength of 280 to 320 nm which is a general photosensitive wavelength region (absorption wavelength region) of the photopolymerization initiator used in combination. Since the region (UVB region) preferably overlaps the absorption band of the photosensitizer to some extent, the photosensitizer preferably has an absorption band within a wavelength region of at least 280 to 320 nm. In addition, since it is advantageous for the efficient use of light from a general ultraviolet light source irradiated to the adhesive layer through the first protective film 10 to have an absorption band on the wavelength side slightly longer than the wavelength region of 280 to 320 nm, the photosensitizer is It is preferable to have an absorption band in the wavelength range of 320 to 380 nm in addition to the wavelength range of 280 to 320 nm. In a preferred embodiment, the photosensitizer has a continuous absorption band over a wavelength of 320 nm in a wavelength region of 280 to 380 nm.

As mentioned above, the photosensitizer used for this invention does not have an absorption band substantially in the wavelength range exceeding 380 nm. "Substantially" means that the absorbance in the wavelength region exceeding 380 nm is less than 1/50 of the maximum absorbance exhibited by the sensitizer in the measurement by the absorber.

As a photosensitizer having the above light absorption characteristics, a naphthalene derivative can be suitably used, and specific examples thereof include 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, and 1,4- diethoxynaphthalene, 1,4-dibutoxynaphthalene, 1,4-dipropoxynaphthalene, and the like.

It is preferable that content of the photosensitizer in an ultraviolet curable adhesive agent is 0.1-10 weight part with respect to 100 weight part of sclerosing|hardenable compounds, It is more preferable that it is 0.3-5.0 weight part, It is more preferable that it is 0.5-3.0 weight part. If the amount of the sensitizer is too small, there is a possibility that the curing of the adhesive may be insufficient, and if the amount is too large, the photosensitizer does not completely dissolve, and the content of the curable compound and the photopolymerization initiator is relatively reduced, causing a problem in curing the adhesive layer and increasing the cost. It may cause problems such as

Examples of the curable compound contained in the ultraviolet curable adhesive include an epoxy compound cured by cationic polymerization (a compound having an average of one or more, preferably two or more epoxy groups in a molecule), and a (meth)acrylic compound cured by radical polymerization. compounds and the like can be used.

Examples of the epoxy compound that can be suitably used include a hydrogenated epoxy compound obtained by reacting epichlorohydrin with an alicyclic polyol obtained by subjecting an aromatic ring of an aromatic polyol to a hydrogenation reaction (glycidyl ether of an alicyclic polyol) ; aliphatic epoxy-based compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts; It contains an alicyclic epoxy-type compound which has one or more epoxy groups in a molecule|numerator. As the epoxy-based compound, the epoxy-based compound described in Patent Documents 1 and 2 can also be used.

Examples of the (meth)acrylic compound include (meth)acrylate monomers having at least one (meth)acryloyloxy group in the molecule; A (meth)acryloyloxy group-containing compound such as a (meth)acrylate oligomer obtained by reacting two or more functional group-containing compounds and having at least two (meth)acryloyloxy groups in the molecule is exemplified.

When a sclerosing|hardenable compound hardened|cured by cationic polymerization is included, an ultraviolet curable adhesive agent contains a photocationic polymerization initiator. As a photocationic polymerization initiator, For example, aromatic diazonium salt; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; an iron-allene complex, etc. are mentioned. Moreover, when an ultraviolet curable adhesive contains a radically polymerizable sclerosing|hardenable compound like a (meth)acrylic-type compound, it contains a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, xanthone, fluorenone, campaquinone, benzaldehyde, anthraquinone, and the like.

Content (total amount of photocationic polymerization initiator and photoradical polymerization initiator) of photoinitiator in ultraviolet curable adhesive is 0.5-20 weight part normally with respect to 100 weight part of sclerosing|hardenable compound, Preferably it is 1 weight part or more, More preferably preferably 15 parts by weight or less. When there are too few photoinitiators, hardening of an adhesive agent will become inadequate, and when too large, the ionic substance in hardened|cured material increases, the hygroscopicity of hardened|cured material may become high and durability of a polarizing plate may fall.

The ultraviolet curable adhesive, if necessary, a cationic polymerization accelerator such as oxetanes and polyols, an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, an antistatic agent, It may contain additives, such as a leveling agent and a solvent. As an additive, you may use what was illustrated by the said patent document 1 and 2 as needed.

(5) 2nd protective film

The second protective film 20 included in the polarizing plate 2 having a double-sided protective film may be a film made of the above-described thermoplastic resin, similarly to the first protective film 10, and may be optical such as a retardation film or a brightness enhancement film. The protective film which has a function together may be sufficient. Regarding the thickness of the surface treatment layer and the film that the second protective film 20 may have, the content described with respect to the first protective film 10 is cited. The 1st protective film 10 and the 2nd protective film 20 may be mutually the same kind of protective film, and a different kind of protective film may be sufficient as them. Among them, examples of the second protective film 20 suitably used in the present invention include a protective film with low moisture permeability that is difficult to adhere with a water-based adhesive, such as polyolefin-based resins, polyester-based resins, (meth)acrylic-based resins, It is a protective film which consists of polystyrene-type resin etc.

Similar to the first protective film 10 , the second protective film 20 may be a film having a transmittance of 1 to 50% of the amount of accumulated light in the UVB region. In this case, it is preferable to use the above-described ultraviolet curable adhesive containing a photosensitizer having a predetermined light absorption characteristic, similarly to the first adhesive layer 15 , for the second adhesive layer 25 . Regarding the transmittance of the accumulated light amount of the second protective film 20 and the measuring method thereof, the contents described for the first protective film 10 are cited.

Specific examples of the second protective film 20 having a transmittance of 1 to 50% of the accumulated light in the UVB region are the above [a] to [d] as in the first protective film 10 . In the polarizing plate 2 with a double-sided protective film, when the first protective film 10 is, for example, a protective film laminated on the liquid crystal cell side of the polarizer 5, the second protective film 20 is It is a protective film laminated on the opposite side of the liquid crystal cell, and in this case, the second protective film 20 may be, for example, a protective film or a retardation film belonging to [a] to [c]. Further, when the first protective film 10 is, for example, a protective film laminated on the opposite side to the liquid crystal cell of the polarizer 5 , the second protective film 20 is a protective film laminated on the liquid crystal cell side of the polarizer 5 . In this case, the second protective film 20 may be, for example, a retardation film belonging to [b] or [d].

(6) second adhesive layer

The second adhesive layer 25 is a layer for bonding the second protective film 20 to the polarizer 5 . The adhesive forming the second adhesive layer 25 is not particularly limited, and an active energy ray-curable adhesive that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, or an adhesive component in which an adhesive component is dissolved and dispersed in water. Although water-based adhesive may be sufficient, especially when the moisture permeability of the 2nd protective film 20 is low, an active energy ray-curable adhesive agent is used preferably, and an ultraviolet-curable adhesive agent is used more preferably.

When the transmittance of the accumulated light amount in the UVB region of the second protective film 20 is 1 to 50%, the second adhesive layer 25 is sufficiently cured by ultraviolet irradiation from the second protective film 20 side. As such, it is preferable to use the above-described ultraviolet curable adhesive containing a photosensitizer having a predetermined light absorption characteristic for the second adhesive layer 25, similarly to the first adhesive layer 15. Accordingly, since the second adhesive layer 25 also does not contain a photosensitizer having an absorption band on the longer wavelength side than 380 nm, the coloring of the polarizing plate caused by the second adhesive layer 25 and discoloration with time are reduced. can also be prevented.

Moreover, as a water-based adhesive agent, the adhesive agent which consists of polyvinyl alcohol-type resin aqueous solution, a water-system two-part type urethane type emulsion adhesive agent, etc. are mentioned. Especially, the aqueous adhesive agent which consists of polyvinyl alcohol-type resin aqueous solution is used suitably.

(7) adhesive layer

On the polarizer 5 in the polarizing plate 1 with a single-sided protective film shown in FIG. 1, or on the 1st protective film 10 in the polarizing plate 2 with a double-sided protective film shown in FIG. On the 2nd protective film 20, you may laminate|stack the adhesive layer for bonding a polarizing plate to another member (for example, the liquid crystal cell in the case of applying to a liquid crystal display device). The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is usually made of a (meth)acrylic resin, styrene-based resin, silicone-based resin, etc. as a base polymer, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. It consists of a pressure-sensitive adhesive composition. Moreover, it can also be set as the adhesive layer which contains microparticles|fine-particles and shows light-scattering property. The thickness of an adhesive layer is 1-40 micrometers normally, Preferably it is 3-25 micrometers.

(8) Other optical layers

The polarizing plates 1 and 2 may further include other optical layers laminated on the protective films 10 and 20 or the polarizer 5 . Examples of the other optical layer include a reflective polarizing film that transmits a certain kind of polarized light and reflects the polarized light exhibiting the opposite property; A film with an anti-glare function having an uneven shape on the surface; Film with surface anti-reflection function; a reflective film having a reflective function on the surface; a transflective film having both a reflective function and a transmissive function; A viewing angle compensation film etc. are mentioned.

<Method for producing a polarizing plate>

Since the polarizer 5 of a thin film is obtained easily, as for the polarizing plate of this invention, it is preferable to manufacture by the method shown in FIG. The manufacturing method of the polarizing plate shown in FIG. 3 is the following process:

(1) after coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the base film, and then drying to form a polyvinyl alcohol-based resin layer to obtain a laminated film, a resin layer forming step S10;

(2) Stretching step S20 of stretching a laminated film to obtain a stretched film;

(3) dyeing step S30 of obtaining a light-polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer;

(4) 1st bonding process S40 which bonds a protective film on the polarizer of a light-polarizing laminated film, and obtains a bonding film,

(5) Peeling process S50 which peels and removes a base film from a bonding film, and obtains the polarizing plate provided with a single-sided protective film

are included in this order.

When producing the polarizing plate 2 provided with a double-sided protective film as shown in FIG. 2, after peeling process S50, further

(6) 2nd bonding process S60 which bonds a protective film to the polarizer side of a polarizing plate with a single-sided protective film

includes

Hereinafter, each process is demonstrated, referring FIGS. 4-7. In addition, in resin layer formation process S10, although you may form a polyvinyl alcohol-type resin layer in both surfaces of a base film, the case where it mainly forms in single side|surface is demonstrated below.

(1) Resin layer forming step S10

Referring to FIG. 4 , this step is a step of forming the polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30 to obtain the laminated film 100 . This polyvinyl alcohol-type resin layer 6 is a layer used as the polarizer 5 through extending process S20 and dyeing process S30. The polyvinyl alcohol-type resin layer 6 can be formed by coating the coating liquid containing polyvinyl alcohol-type resin on the single side|surface or both surfaces of the base film 30, and drying a coating layer. The method of forming a polyvinyl alcohol-type resin layer by such coating is advantageous at the point that it is easy to obtain the polarizer 5 of a thin film.

The base film 30 may be composed of a thermoplastic resin, and among them, it is preferable to be composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such a thermoplastic resin include polyolefin-based resins such as chain polyolefin-based resins and cyclic polyolefin-based resins (such as norbornene-based resins); polyester-based resin; (meth)acrylic resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polycarbonate-based resin; polyvinyl alcohol-based resin; polyvinyl acetate-based resin; polyarylate-based resin; polystyrene-based resin; polyether sulfone-based resin; polysulfone-based resins; polyamide-based resin; polyimide-based resin; and mixtures and copolymers thereof.

The base film 30 may have a single-layer structure composed of one resin layer made of one or two or more types of thermoplastic resins, or a multilayer structure in which a plurality of resin layers made of one or more types of thermoplastic resins are laminated. The base film 30 is preferably composed of a resin that can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol-based resin layer 6 when stretching the laminated film 100 in the stretching step S20 to be described later. Do.

The base film 30 may contain additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments and colorants. Content of the thermoplastic resin in the base film 30 becomes like this. Preferably it is 50 to 100 weight%, More preferably, it is 50 to 99 weight%, More preferably, it is 60 to 98 weight%, Most preferably, it is 70 to 97 weight%. to be.

The thickness of the base film 30 is usually 1-500 µm in terms of workability such as strength and handleability, preferably 1-300 µm, more preferably 5-200 µm, still more preferably 5-150 µm. to be.

The coating liquid to be coated on the base film 30, Preferably it is a polyvinyl alcohol-type resin solution obtained by dissolving the powder of a polyvinyl alcohol-type resin in a good solvent (for example, water). Details of the polyvinyl alcohol-based resin are the same as described above. The coating liquid may contain additives, such as a plasticizer and surfactant, as needed.

A method of applying the coating solution to the base film 30 includes a wire bar coating method; roll coating methods such as reverse coating and gravure coating; die coat method; comma coat method; lip coat method; spin coating method; screen coating method; Fountain coating method; dipping method; It can select suitably from methods, such as a spray method.

The drying temperature and drying time of a coating layer (polyvinyl alcohol-type resin layer before drying) are set according to the kind of solvent contained in a coating liquid. The drying temperature is, for example, 50 to 200°C, preferably 60 to 150°C. When the solvent contains water, the drying temperature is preferably 80°C or higher.

The polyvinyl alcohol-type resin layer 6 may be provided only on one side of the base film 30, and may be provided on both surfaces. When formed on both sides, curling of the film that may occur during the manufacture of the light-polarizing laminated film 300 (refer to FIG. 6) can be suppressed, and two polarizing plates can be obtained from one light-polarizing laminated film 300 Therefore, it is advantageous also in terms of production efficiency of a polarizing plate.

It is preferable that it is 3-30 micrometers, and, as for the thickness of the polyvinyl alcohol-type resin layer 6 in the laminated|multilayer film 100, it is more preferable that it is 5-20 micrometers. In the case of the polyvinyl alcohol-based resin layer 6 having a thickness within this range, through the stretching step S20 and the dyeing step S30 described later, the dyeability of the dichroic dye is good, the polarization performance is excellent, and it is sufficiently thin (for example, a thickness of 10 The polarizer 5 (micrometer or less) can be obtained. When the thickness of the polyvinyl alcohol-type resin layer 6 is less than 3 micrometers, after extending|stretching, it becomes thin too much and there exists a tendency for dyeability to deteriorate.

Prior to the coating of the coating solution, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, at least the base film 30 on the side where the polyvinyl alcohol-based resin layer 6 is formed. Corona treatment, plasma treatment, flame (flame) treatment, etc. may be given to the surface of.

In addition, prior to the coating of the coating solution, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, a polyvinyl alcohol-based resin layer on the base film 30 through a primer layer or the like. (6) may be formed.

After coating the coating liquid for primer layer formation on the surface of the base film 30, a primer layer can be formed by drying. The coating liquid for primer layer formation contains the component which exhibits the adhesive force strong to some extent to both the base film 30 and the polyvinyl alcohol-type resin layer 6 . The coating liquid for forming a primer layer usually contains a resin component and a solvent that impart such adhesion. As a resin component, Preferably, the thermoplastic resin excellent in transparency, thermal stability, ductility, etc. is used, For example, (meth)acrylic-type resin, polyvinyl alcohol-type resin, etc. are mentioned. Especially, polyvinyl alcohol-type resin which provides favorable adhesive force is used preferably. More preferably, it is polyvinyl alcohol resin. As the solvent, a general organic solvent or aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer with a coating solution using water as a solvent.

In order to raise the intensity|strength of a primer layer, you may add a crosslinking agent to the coating liquid for primer layer formation. The crosslinking agent is appropriately selected from known ones of organic type and inorganic type according to the type of the thermoplastic resin to be used. Examples of the crosslinking agent include, for example, an epoxy-based, isocyanate-based, dialdehyde-based, metal-based (eg, metal salt, metal oxide, metal hydroxide, organometallic compound), and polymer-based crosslinking agent. When a polyvinyl alcohol-based resin is used as the resin component for forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde-based cross-linking agent, a metal chelate compound-based cross-linking agent, or the like is preferably used.

It is preferable that it is about 0.05-1 micrometer, and, as for the thickness of a primer layer, it is more preferable that it is 0.1-0.4 micrometer. When it becomes thinner than 0.05 micrometer, the adhesive force improvement effect of the base film 30 and the polyvinyl alcohol-type resin layer 6 is small, and when it becomes thicker than 1 micrometer, it is disadvantageous to thinning of a polarizing plate.

A method of applying the coating solution for forming a primer layer to the base film 30 may be the same as the coating solution for forming a polyvinyl alcohol-based resin layer. A primer layer is coated on the surface to which the coating liquid for polyvinyl alcohol-type resin layer formation is coated. The drying temperature of the coating layer which consists of the coating liquid for primer layer formation is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. When the solvent contains water, the drying temperature is preferably 80°C or higher.

(2) Stretching step S20

Referring to FIG. 5 , in this process, the laminated film 100 including the base film 30 and the polyvinyl alcohol-based resin layer 6 is stretched, and the stretched base film 30 ′ and the polyvinyl alcohol-based resin layer 6 are stretched. It is a process of obtaining the stretched film 200 which consists of the formation layer 6'. The stretching treatment is usually uniaxial stretching.

Although the draw ratio of the laminated|multilayer film 100 can be suitably selected according to the desired polarization characteristic, Preferably, it is more than 5 times and 17 times or less with respect to the original length of the laminated|multilayer film 100, More preferably, it exceeds 5 times. less than 8 times. Since the polyvinyl alcohol-type resin layer 6' is not fully orientated as a draw ratio is 5 times or less, the polarization degree of the polarizer 5 may not become high enough. On the other hand, when the draw ratio exceeds 17 times, breakage of the film tends to occur during stretching, the thickness of the stretched film 200 becomes thinner than necessary, and there is a risk that the workability and handleability in the subsequent step may decrease. have.

An extending|stretching process is not limited to extending|stretching by one stage, You can also perform it in multiple stages. In this case, all of the multistage extending|stretching process may be performed continuously before dyeing process S30, and the extending|stretching process after the 2nd stage may be performed simultaneously with the dyeing|staining process and/or crosslinking process in dyeing process S30. Thus, when performing an extending|stretching process in multiple stages, it is preferable to perform an extending|stretching process so that it may become a draw ratio exceeding 5 times in total of all the stages of an extending|stretching process.

The stretching treatment may be longitudinal stretching stretched in the film longitudinal direction (film conveyance direction), and transverse stretching or diagonal stretching stretching in the film width direction may be used. Examples of the longitudinal stretching method include inter-roll stretching, compression stretching, and stretching using a chuck (clip) to be stretched using rolls, and examples of the transverse stretching method include a tenter method. Although any of a wet type extending|stretching method and a dry type extending|stretching method can be employ|adopted for an extending|stretching process, it is preferable to use a dry extending|stretching method at the point which can select extending|stretching temperature from a wide range.

The stretching temperature is set above the temperature at which the polyvinyl alcohol-based resin layer 6 and the entire base film 30 exhibit fluidity enough to be stretched, preferably the phase transition temperature (melting point or glass transition temperature) of the base film 30 . ) in the range of -30°C to +30°C, more preferably in the range of -30°C to +5°C, and still more preferably in the range of -25°C to +0°C. When the base film 30 is formed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures indicated by the plurality of resin layers.

When the stretching temperature is lower than -30°C of the phase transition temperature, it is difficult to achieve high magnification stretching of more than 5 times, or the fluidity of the base film 30 is too low, so stretching treatment tends to be difficult. When extending|stretching temperature exceeds +30 degreeC of a phase transition temperature, there exists a tendency for the fluidity|liquidity of the base film 30 to become too large and extending|stretching becomes difficult. Since it is easy to achieve the high draw ratio exceeding 5 times, extending|stretching temperature is in the said range, More preferably, it is 120 degreeC or more.

As a heating method of the laminated|multilayer film 100 in an extending|stretching process, it is a zone heating method (For example, the method of heating in the same extending|stretching zone as the heating furnace adjusted to predetermined temperature by blowing hot air); In the case of stretching using a roll, a method of heating the roll itself; There is a heater heating method (a method in which an infrared heater, a halogen heater, a panel heater, etc. are installed above and below the laminated film 100 and heated by radiant heat) and the like. In the stretching method between rolls, the zone heating method is preferable from the viewpoint of uniformity of the stretching temperature.

Prior to extending|stretching process S20, you may provide the preheating process process of preheating the laminated|multilayer film 100. As a preheating method, the method similar to the heating method in an extending|stretching process can be used. It is preferable that it is the range of -50 degreeC of extending|stretching temperature, and, as for preheating temperature, it is more preferable that it is the range of -10 degreeC of extending|stretching temperature.

In addition, you may provide a heat setting treatment process after the extending process in extending process S20. A heat setting process is a process which heat-processes above the crystallization temperature, maintaining the edge part of the stretched film 200 in a tension state in the state clamped by the clip. Crystallization of the polyvinyl alcohol-type resin layer 6' is accelerated|stimulated by this heat setting process. It is preferable that it is the range of -0 degreeC - -80 degreeC of extending|stretching temperature, and, as for the temperature of a heat setting process, it is more preferable that it is the range of -0 degreeC - -50 degreeC of extending|stretching temperature.

(3) Dyeing process S30

Referring to FIG. 6 , this process is a process of dyeing the polyvinyl alcohol-based resin layer 6 ′ of the stretched film 200 with a dichroic dye and adsorbing and aligning it to obtain the polarizer 5 . Through this process, the light-polarizing laminated film 300 in which the polarizer 5 is laminated|stacked on one side or both surfaces of the base film 30' can be obtained.

A dyeing process can be performed by immersing the whole stretched film 200 in the solution (dyeing solution) containing a dichroic dye. As a dyeing solution, the solution which melt|dissolved the said dichroic dye in the solvent can be used. Although water is generally used as a solvent for a dyeing solution, an organic solvent compatible with water may further be added. It is preferable that it is 0.01 to 10 weight%, as for the density|concentration of the dichroic dye in a dyeing solution, it is more preferable that it is 0.02 to 7 weight%, It is more preferable that it is 0.025 to 5 weight%.

When using iodine as a dichroic dye, since dyeing efficiency can be improved further, it is preferable to further add iodide to the dyeing solution containing iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. It is preferable that the density|concentration of the iodide in a dyeing solution is 0.01 to 20 weight%. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100 by weight, more preferably in the range of 1:6 to 1:80, and 1:7 More preferably, it is in the range of -1:70. It is preferable to exist in the range of 10-60 degreeC, and, as for the temperature of a dyeing solution, it is more preferable to exist in the range of 20-40 degreeC.

Moreover, although dyeing process S30 may be performed before extending process S20, or these processes may be performed simultaneously, in order to orientate favorably the dichroic dye adsorbed to the polyvinyl alcohol-type resin layer, with respect to the laminated|multilayer film 100 It is preferable to perform dyeing process S30 after performing an extending|stretching process to a certain extent at least. That is, in addition to being able to provide the stretched film 200 obtained by performing the stretching treatment until it becomes the target magnification in the stretching step S20 to the dyeing step S30, in the stretching step S20, after stretching at a magnification lower than the target , You may perform an extending|stretching process until the total draw ratio becomes a target ratio during dyeing process S30. In the latter embodiment, 1) after stretching treatment at a magnification lower than the target in the stretching step S20, the stretching treatment is performed so that the total draw ratio becomes the target magnification during the dyeing treatment in the dyeing step S30. As described above, in the case of performing crosslinking treatment after dyeing treatment, 2) after performing the stretching treatment at a magnification lower than the target in the stretching step S20, during the dyeing treatment in the dyeing step S30, the total draw ratio does not reach the target magnification. The aspect etc. which extend process to the extent that it is not enough, and then perform an extending|stretching process during crosslinking process so that the final total draw ratio may become a target ratio, etc. are mentioned.

Dyeing process S30 may include the crosslinking treatment process implemented following the dyeing|staining process. A crosslinking process can be performed by immersing the dyed film in the solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, a conventionally known material can be used, and examples thereof include boric acid, boron compounds such as borax, glyoxal, glutaraldehyde, and the like. A crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

The crosslinking solution may specifically be a solution in which a crosslinking agent is dissolved in a solvent. As the solvent, for example, water can be used, and an organic solvent compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by weight, and more preferably in the range of 6 to 15% by weight.

The crosslinking solution may contain iodide. By addition of iodide, the polarization|polarized-light performance in the polarizer 5 plane can be made uniform more. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. It is preferable that it is 0.05 to 15 weight%, and, as for the density|concentration of the iodide in a crosslinking solution, it is more preferable that it is 0.5 to 8 weight%. It is preferable that the temperature of a crosslinking solution exists in the range of 10-90 degreeC.

In addition, a crosslinking process can also be performed simultaneously with a dyeing|staining process by mix|blending a crosslinking agent in a dyeing solution. Moreover, you may perform an extending|stretching process during a crosslinking process. The specific aspect of performing an extending|stretching process during a crosslinking process is as above-mentioned. Moreover, you may perform the process of immersing in a crosslinking solution twice or more using 2 or more types of crosslinking solutions from which a composition differs.

It is preferable to perform a washing|cleaning process and a drying process before 1st bonding process S40 mentioned later after dyeing process S30. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually in the range of 3 to 50°C, preferably 4 to 20°C. The immersion time in water is 2 to 300 second normally, Preferably it is 3 to 240 second. The washing process may be a combination of a water washing process and a washing process using an iodide solution.

As a drying process performed after a washing|cleaning process, arbitrary suitable methods, such as natural drying, air drying, and heat drying, are employable. For example, in the case of heat drying, the drying temperature is usually 20 to 95°C.

(4) 1st bonding process S40

Referring to FIG. 7 , in this process, on the polarizer 5 of the light-polarizing laminated film 300 , that is, on the side opposite to the base film 30 ′ side of the polarizer 5 through an adhesive layer. It is a process of obtaining the bonding film 400 by bonding a film. Although FIG. 7 shows an example of bonding the first protective film 10 through the first adhesive layer 15, in the case of manufacturing the polarizing plate 2 provided with the double-sided protective film, the second adhesive layer 25 The second protective film 20 may be bonded through the . The adhesive forming the first adhesive layer 15 or the second adhesive layer 25 is the same as described above.

Moreover, when the light-polarizing laminated|multilayer film 300 has the polarizer 5 on both surfaces of the base film 30', a protective film is respectively bonded on the polarizer 5 of both surfaces normally. In this case, the protective film of the same kind may be sufficient as these protective films, and a different kind of protective film may be sufficient as them.

When the bonding and bonding method of the protective film is described by taking the case of bonding the first protective film 10 using the above-described ultraviolet curable adhesive containing a photosensitizer having a predetermined light absorption characteristic, the first adhesive A first protective film 10 is laminated on the polarizer 5 through the UV-curable adhesive serving as the layer 15 , and then the adhesive layer is cured by irradiating UV rays. The irradiated ultraviolet light includes light in a wavelength region (UVB region) of 280 to 320 nm, and as a light source, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, A metal halide lamp etc. can be used.

Since the ultraviolet curable adhesive forming the first adhesive layer 15 contains the photosensitizer exhibiting the predetermined light absorption characteristics, even when irradiated with ultraviolet rays from the first protective film 10 side, the first adhesive layer ( 15) can be cured well. The second protective film 20 having a transmittance of 1 to 50% of the accumulated light in the UVB region is bonded in this step using the above-described ultraviolet curable adhesive containing a photosensitizer having a predetermined light absorption characteristic. The same is the case.

Referring to Figure 7, when the transmittance of the UVB region of the base film 30' is relatively high, it is also possible to cure the adhesive layer by irradiating ultraviolet rays from the base film 30' side, for example, Japanese Patent No. 4691205 Specification , as described in Japanese Patent No. 4979833, Japanese Patent No. 4751481, and Japanese Patent No. 4815544, a polyester-based resin such as polyethylene terephthalate resin may be used for the base film. In this case, since the ultraviolet transmittance of the base film 30' is also very low, the advantage of using the present invention is particularly great in this case.

Although the accumulated light amount of the irradiated ultraviolet light can be, for example, 10 to 10000 mJ/cm 2 , it has been found that it is advantageous for the ultraviolet curable adhesive layer to be sufficiently cured by tightening the accumulated light amount relatively low. In view of this point, it is preferable that the accumulated light amount be 500 mJ/cm 2 or less.

Since the amount of heat generated from the light source is also reduced by lowering the accumulated light amount of the ultraviolet ray to be irradiated, it can be suppressed that the bonding film 400 (and hence the polarizing plate) curls or deteriorates due to this heat. Moreover, damage to the polarizer 5 by ultraviolet irradiation can also be suppressed. That is, when a protective film with a low ultraviolet transmittance is adhered to the polarizer 5, the accumulated light amount of ultraviolet rays is conventionally increased so as to allow light to reach the adhesive layer, but it has been found that the polarizer 5 is damaged at the same time. It can be seen that the discoloration of the polarizer 5 in the wet heat endurance test of the polarizing plate is severe in the case where the accumulated light amount is large. If the amount of accumulated light can be made low, discoloration under such a wet heat endurance test can be effectively suppressed.

In bonding a protective film to the polarizer 5, in order to improve adhesiveness with the polarizer 5 on the surface of the polarizer 5 side of a protective film, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) Surface treatment (easy-adhesion treatment) such as treatment and saponification treatment can also be performed, and among these, plasma treatment, corona treatment or saponification treatment is preferably performed.

(5) Peeling step S50

This process is a process of peeling and removing the base film 30' from the bonding film 400. Through this step, a polarizing plate having a single-sided protective film as shown in Fig. 1 can be obtained. When the target polarizing plate is a polarizing plate having a single-sided protective film, the first protective film 10 is bonded in the first bonding step S40. do. When the light-polarizing laminated film 300 has the polarizer 5 on both surfaces of the base film 30' and the protective film is bonded to these both polarizers 5, by this peeling process S50, the light polarity of 1 sheet A polarizing plate with two single-sided protective films can be obtained from the laminated film 300 .

The method of peeling and removing the base film 30' is not specifically limited, It can peel by the method similar to the peeling process of the separator (peelable film) performed with a normal polarizing plate provided with an adhesive. After 1st bonding process S40, you may peel immediately as it is, and base film 30' may be wound up in roll shape once after 1st bonding process S40, and may peel, unwinding in a subsequent process.

(6) 2nd bonding process S60

In this process, on the polarizer 5 of the polarizing plate provided with a single-sided protective film, that is, on the surface opposite to the protective film bonded in 1st bonding process S40, a protective film is further bonded, and what is shown in FIG. It is a process of obtaining the polarizing plate 2 provided with the same double-sided protective film. When the 1st protective film 10 is bonded by 1st bonding process S40, when the 2nd protective film 20 is bonded by this process, and the 2nd protective film 20 is bonded by 1st bonding process S40 The first protective film 10 is bonded to each other in this step.

In the first bonding step S40, the first protective film 10 is bonded, and in this step, the UV-curable adhesive (adhesive for forming the second adhesive layer 25) containing a photosensitizer exhibiting a predetermined light absorption characteristic. ) to bond the second protective film 20 having a transmittance of 1 to 50% of the accumulated light in the UVB region, UV irradiation for curing the adhesive layer is usually performed from the second protective film side.

As mentioned above, although the method of manufacturing a polarizing plate by forming a polarizer with the polyvinyl alcohol-type resin layer coated on the base film was mentioned above, it is not limited to this, The 1st to the polarizer 5 which consists of a single (individual) film A polarizing plate may be manufactured by bonding the protective film 10 or the 1st and 2nd protective films 10 and 20 together.

The polarizer 5 which consists of a single (individual) film is, for example, the process of producing a polyvinyl alcohol-type resin film by well-known methods, such as a melt extrusion method and a solvent casting method; A process of uniaxially stretching a polyvinyl alcohol-type resin film; The process of dyeing a polyvinyl alcohol-type resin film with a dichroic dye, and adsorbing this; A step of treating the polyvinyl alcohol-based resin film to which the dichroic dye is adsorbed with an aqueous solution of boric acid; And it can manufacture by the method including the process of washing with water after treatment with boric acid aqueous solution. Uniaxial stretching can be performed before dyeing|staining of a dichroic dye, simultaneous with dyeing|staining, or after dyeing|staining. When performing uniaxial stretching after dyeing|staining, you may perform this uniaxial stretching before a boric-acid process or during a boric-acid process. Moreover, you may perform uniaxial stretching in these multiple steps.

When bonding both the 1st and 2nd protective films 10 and 20 and manufacturing the polarizing plate provided with a double-sided protective film WHEREIN: These protective films may be laminated|bonded sequentially through an adhesive bond layer, and may be bonded together. In the polarizing plate which bonds the 1st and 2nd protective films 10 and 20 with low ultraviolet transmittance using an ultraviolet curable adhesive agent WHEREIN: The merit of using this invention is large especially.

<Display device>

The polarizing plate of the present invention can be applied to a display device. This display device may include a display cell and the polarizing plate according to the present invention, which is disposed on at least one surface thereof. A typical example of a display device is a liquid crystal display device in which the display cell is a liquid crystal cell, but other display devices such as an organic EL device may be used. In a display device, although the polarizing plate which concerns on this invention should just be arrange|positioned on at least one surface of the cell for a display, it can also arrange|position on both surfaces. As a liquid crystal cell, the thing of a conventionally well-known type can be used.

Example

Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by these examples.

<Example 1>

(1) Preparation of base film

A homopolymer of propylene on both sides of a resin layer consisting of a random copolymer of propylene/ethylene containing about 5% by weight of ethylene units (“Sumitomo No Ren W151” manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 138° C.) ( Sumitomo Chemical Co., Ltd. "Sumitomo Novren FLX80E4", melting point Tm = 163 ° C.), a long base film having a three-layer structure arranged with a resin layer was produced by co-extrusion using a multi-layer extrusion molding machine. . The total thickness of the base film was 90 µm, and the thickness ratio (FLX80E4/W151/FLX80E4) of each layer was 3/4/3.

(2) Primer layer forming process

Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Kosei Chemicals Co., Ltd., average degree of polymerization 1100, saponification degree 99.5 mol%) was dissolved in hot water at 95° C., and a polyvinyl alcohol aqueous solution having a concentration of 3 wt. prepared The obtained aqueous solution was mixed with a crosslinking agent ("Sumirez Resin 650" manufactured by Taoka Chemical Industry Co., Ltd.) in a ratio of 5 parts by weight with respect to 6 parts by weight of polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Next, after corona treatment is performed on one side of the base film produced in (1) above, the coating solution for forming the primer layer is coated on the corona treated surface using a microgravure coater, and dried at 80 ° C. for 10 minutes. , a primer layer having a thickness of 0.2 µm was formed.

(3) Preparation of laminated film (resin layer formation process)

Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average degree of polymerization 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 8 wt%, This was used as the coating liquid for polyvinyl alcohol-type resin layer formation.

After coating the coating solution for forming a polyvinyl alcohol-based resin layer on the surface of the primer layer of the base film having the primer layer prepared in (2) using a lip coater, drying at 80° C. for 20 minutes, on the primer layer The polyvinyl alcohol-type resin layer was formed in it, and the laminated|multilayer film which consists of a base film/primer layer/polyvinyl alcohol-type resin layer was obtained.

(4) Preparation of stretched film (stretching process)

With respect to the laminated|multilayer film produced in said (3), 5.8 times free-end uniaxial stretching was performed at 160 degreeC using the longitudinal uniaxial stretching apparatus of a floating, and the stretched film was obtained. The thickness of the polyvinyl alcohol-type resin layer after extending|stretching was 6.2 micrometers.

(5) Preparation of light-polarizing laminated film (dyeing process)

The stretched film prepared in (4) above was immersed in an aqueous dyeing solution at 30° C. containing iodine and potassium iodide (0.6 parts by weight of iodine and 10 parts by weight of potassium iodide per 100 parts by weight of water) for about 180 seconds, After dyeing the vinyl alcohol-based resin layer, excess dyeing solution was washed away with 10°C pure water.

Then, it is immersed in a first aqueous crosslinking solution at 78°C containing boric acid (including 9.5 parts by weight of boric acid per 100 parts by weight of water) for 120 seconds, followed by a second aqueous crosslinking solution at 70°C containing boric acid and potassium iodide (water 9.5 parts by weight of boric acid per 100 parts by weight and 4 parts by weight of potassium iodide) was immersed for 60 seconds to perform crosslinking treatment. Then, the light-polarizing laminated film which consists of a base film/primer layer/polarizer was obtained by wash|cleaning for 10 second with 10 degreeC pure water, and finally drying at 40 degreeC for 300 second.

(6) Preparation of polarizing plate (1st bonding process, peeling process, 2nd bonding process)

"KR-70T" manufactured by ADEKA Co., Ltd. which is an ultraviolet curable adhesive containing a sclerosing|hardenable compound which is a cationically polymerizable epoxy compound, and a photocationic polymerization initiator was prepared. With respect to 100 weight part of this adhesive agent, 2.0 weight part of 1, 4- diethoxy naphthalene was mixed as a photosensitizer, and it was set as the photosensitizer containing ultraviolet curable adhesive agent. Fig. 8 shows the absorption spectrum of 1,4-diethoxynaphthalene measured using an absorbance spectrometer ("UV-2450" manufactured by Shimadzu Corporation). As illustrated, 1,4-diethoxynaphthalene has an absorption band in a wavelength region of 280 to 360 nm and does not have an absorption band in a wavelength region exceeding 380 nm.

On the bonding surface of the 25 µm-thick protective film A (a protective film made of polyethylene terephthalate and having a transmittance of 2% of the accumulated light in the UVB region) on the bonding surface, a microgravure coater was used to After coating the sensitizer containing ultraviolet curable adhesive agent, this was bonded to the polarizer surface of the light-polarizing laminated film produced in said (5) using the bonding roll. Then, using a high-pressure mercury lamp, the adhesive layer is cured by irradiating ultraviolet rays with a cumulative light amount of 150 mJ/cm 2 from the base film side, and the protective film A / adhesive layer / polarizer / primer layer / base film consisting of a layered structure The bonding film was obtained (1st bonding process). The thickness of the adhesive layer after curing was about 1 μm.

Next, the base film was peeled off from the obtained bonding film (peeling process). The base film peeled easily, and obtained the polarizing plate provided with the single-sided protective film which consists of a laminated constitution of protective film A/adhesive layer/polarizer/primer layer. The thickness of the polarizer was 6.7 μm.

Next, the bonding surface of a protective film B having a thickness of 21 µm (a retardation film having a transmittance of the accumulated light in the UVB region of 7%, formed by coating a liquid crystal compound on a cyclic polyolefin-based resin film) to which the bonding surface is corona-treated. After coating the UV curable adhesive containing the sensitizer on the surface using a microgravure coater, using a bonding roll, this was bonded to the surface opposite to the protective film A of a polarizing plate provided with a single-sided protective film. Then, using a high-pressure mercury lamp, the adhesive layer is cured by irradiating ultraviolet rays with a cumulative light amount of 150 mJ/cm 2 from the protective film B side, and the protective film A/adhesive layer/polarizer/primer layer/adhesive layer/protective film B The polarizing plate provided with the double-sided protective film which consists of the laminated constitution of was obtained (2nd bonding process). The thickness of the adhesive layer after curing was about 1 μm.

<Examples 2-3>

A polarizing plate provided with a double-sided protective film was produced in the same manner as in Example 1 except that the accumulated light amount of ultraviolet rays at the time of curing the adhesive layer on both sides was shown in Table 1.

<Example 4>

As a protective film to be bonded in the first bonding step, a protective film C (a protective film made of a cyclic polyolefin-based resin and containing a UV absorber, the transmittance of the accumulated light in the UVB region of 2%) instead of the protective film A. A polarizing plate provided with a double-sided protective film was produced in the same manner as in Example 1 except that it was used.

<Example 5>

In the 1st bonding process, ultraviolet-ray was irradiated from the protective film A side, and except not having implemented the 2nd bonding process, it carried out similarly to Example 1, and produced the polarizing plate with a single-sided protective film.

<Comparative Examples 1-4>

The UV curable adhesive "KR-70T" manufactured by ADEKA Co., Ltd. was used as an adhesive for bonding protective films without mixing with a photosensitizer, and the amount of accumulated UV light when curing the adhesive layers on both sides. Except having carried out like Table 1, it carried out similarly to Example 1, and produced the polarizing plate provided with a double-sided protective film.

<Comparative Examples 5-6>

Table 1 shows the amount of accumulated UV light when curing the adhesive layer and the UV-curable adhesive "KR-70T" manufactured by ADEKA Co., Ltd., used as an adhesive for bonding protective films without mixing with a photosensitizer. A polarizing plate provided with a single-sided protective film was produced in the same manner as in Example 5, except that it was carried out as described above.

The type of protective film used in each Example and Comparative Example and the transmittance of the accumulated light amount in the UVB region (referred to as “UVB transmittance” in Table 1), the accumulated light amount of the irradiated ultraviolet light (irradiation amount), and the photosensitizer in the adhesive Table 1 summarizes the presence or absence of (1,4-diethoxynaphthalene).

When the polarizing plates of Examples 1 to 5 were put into a sunshine carbon arc lamp type weatherability tester (SWOM) for 150 hours, problems such as yellowing did not occur. In addition, regarding pot life, when the sensitizer containing ultraviolet curable adhesive used in the Example was put under the environment of white LED lighting, and time-dependent change was observed until 48 hours, a viscosity change was not seen.

[Evaluation of curing degree of adhesive layer]

The degree of hardening of the adhesive bond layer was evaluated by the wet heat durability test shown below. When an adhesive bond layer is fully hardened|cured, discoloration (discoloration) of a polarizer is suppressed favorably in this test, but when hardening is inadequate, discoloration will arise or a spot-like nonuniformity will arise.

The polarizing plate obtained in Examples and Comparative Examples was chip-cut to a size of 4", and this was bonded to Corning glass using an adhesive layer. In a polarizing plate with a single-sided protective film, an adhesive layer was adhered to the polarizer surface. The obtained glass bonding sample was left for 48 hours in an environment of 80 ° C. temperature and 90% relative humidity.After that, a polarizing plate that had not been subjected to a wet heat endurance test was bonded to the surface opposite to the tested polarizing plate of Corning Glass in a cross-nickel relationship. , was observed on a backlight in a dark room, and the degree of discoloration was evaluated according to the following criteria: If Lv 5, it can be judged that the adhesive layer (adhesive layer on both sides in a polarizing plate with a double-sided protective film) is sufficiently cured. Table 1 shows.

Lv 1: Discoloration until the entire polarizer is almost transparent,

Lv 2: Discoloration until the polarizer is almost transparent in the shape of a spot,

Lv 3: The polarizer partially discolors,

Lv 4: It does not go to discoloration, but spots in the form of spots can be seen.

Lv 5: There is no discoloration at all.

1, 2: Polarizer;
5: Polarizer,
10: a first protective film;
15: a first adhesive layer;
20: a second protective film;
25: a second adhesive layer;
6: polyvinyl alcohol-based resin layer,
6': stretched polyvinyl alcohol-based resin layer,
30: base film,
30': stretched base film,
100: laminated film;
200: stretched film,
300: light-polarizing laminated film;
400: bonding film.

Claims (9)

It includes a polarizer and a first protective film laminated on one side thereof through a first adhesive layer,
The first protective film has a transmittance of 1 to 50% of the accumulated light in a wavelength region of 280 to 320 nm,
The first adhesive layer is made of a cured product of an ultraviolet curable adhesive containing a photosensitizer,
The photosensitizer has an absorption band in at least a part of the wavelength region in a wavelength region of 280 to 380 nm, and substantially no absorption band in a wavelength region exceeding 380 nm,
A polarizing plate having a thickness of 2 to 8 μm of the polarizer. The polarizing plate according to claim 1, wherein the first protective film is a retardation film having a liquid crystal layer on a support film, or a retardation film made of a resin film containing an aromatic ring. The polarizing plate of claim 1, further comprising a second protective film laminated on the other side of the polarizer through a second adhesive layer. The method according to claim 3, wherein the second protective film has a transmittance of 1 to 50% of the accumulated light in a wavelength range of 280 to 320 nm,
The second adhesive layer is made of a cured product of an ultraviolet curable adhesive containing a photosensitizer,
The photosensitizer has an absorption band in at least a part of a wavelength region in a wavelength region of 280 to 380 nm, and a polarizing plate that does not substantially have an absorption band in a wavelength region exceeding 380 nm. The polarizing plate according to claim 3, wherein the second protective film contains an ultraviolet absorber. The polarizing plate according to any one of claims 3 to 5, wherein the second protective film comprises a polyethylene terephthalate-based resin or a (meth)acrylic-based resin. The polarizing plate according to claim 1, wherein the photosensitizer is a naphthalene derivative. A display device comprising the polarizing plate according to claim 1 . delete

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