JP2013254072A - Polarizing plate, optical film, and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate that has a transparent protective film provided on at least one surface of a polarizer with an adhesive layer interposed therebetween, and satisfies durability under high temperature even when the adhesive layer is formed by irradiating an active energy ray curable adhesive containing a radical polymerizable compound with an active energy ray.SOLUTION: A polarizing plate is formed by making a transparent protective film to be adhered on at least one surface of a polarizer with an adhesive layer interposed therebetween. The polarizer is prepared by adsorbing and aligning a dichroic material, and is a polyvinyl alcohol film having the content rate of boric acid of 23 weight% or less; and the adhesive layer is formed by irradiating an active energy ray curable adhesive containing a radical polymerizable compound with an active energy ray.

Description

  The present invention relates to a polarizing plate in which a transparent protective film is provided on at least one surface of a polarizer via an adhesive formed of an active energy ray-curable adhesive. The polarizing plate can form an image display device such as a liquid crystal display device (LCD), an organic EL display device, a CRT, or a PDP alone or as an optical film in which the polarizing plate is laminated.

  Liquid crystal display devices are rapidly expanding in watches, mobile phones, PDAs, notebook computers, personal computer monitors, DVD players, TVs, and the like. The liquid crystal display device visualizes the polarization state by switching of the liquid crystal, and a polarizer is used from the display principle. In particular, in applications such as TVs, higher brightness, higher contrast, and wider viewing angles are required, and polarizing plates are also required to have higher transmittance, higher degree of polarization, and higher color reproducibility.

  As the polarizer, since it has a high transmittance and a high degree of polarization, for example, an iodine-based polarizer having a stretched structure by adsorbing iodine to polyvinyl alcohol (hereinafter also simply referred to as “PVA”) is most widely used. It is used. In general, a polarizing plate is used in which a transparent protective film is bonded to at least one surface of a polarizer with a so-called aqueous adhesive in which a polyvinyl alcohol-based material is dissolved in water (Patent Documents 1 to 4).

  When manufacturing a polarizing plate, when a water-based adhesive such as a polyvinyl alcohol-based adhesive is used (so-called wet lamination), a drying step is required after the polarizer and the transparent protective film are bonded together. . The said drying process is not preferable when improving the productivity of a polarizing plate. In particular, as represented by TV, in recent years, as the screen size of image display devices has increased, it has become very important to increase the size of the polarizing plate in terms of productivity and cost (yield and increase in number of products). . For the reasons described above, it is often proposed to use an active energy ray curable adhesive (particularly, an ultraviolet curable adhesive) instead of an aqueous adhesive in the production of a polarizing plate.

JP 2006-220732 A JP 2001-296427 A JP 2009-104062 A JP 2011-203641 A

  However, the polarizing plate obtained by laminating a polyvinyl alcohol polarizer and a transparent protective film using an active energy ray-curable adhesive undergoes significant dimensional changes under heating conditions and satisfies durability at high temperatures. It wasn't done. In other words, the polarizing plate obtained using the active energy ray-curable adhesive has a larger dimensional shrinkage ratio under high temperature conditions than the polarizing plate obtained using the aqueous adhesive. It was. Therefore, when a liquid crystal panel to which a polarizing plate obtained using an active energy ray-curable adhesive is bonded is used in a liquid crystal display device, for example, the polarizing plate contracts due to the heat of the backlight. There is a problem that a so-called light omission such as a black display appears white in a part of the entire screen becomes noticeable.

  The present invention is a polarizing plate in which a transparent protective film is provided on at least one surface of a polarizer via an adhesive layer, and the adhesive layer contains an active energy ray-curable adhesive containing a radical polymerizable compound An object of the present invention is to provide a polarizing plate that can satisfy durability at high temperatures even when it is formed by irradiating active energy rays.

  Another object of the present invention is to provide an optical film using the polarizing plate, and to provide an image display device such as a liquid crystal display device using the polarizing plate and the optical film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the polarizing plate shown below, and have completed the present invention.

That is, the present invention is a polarizing plate that a transparent protective film is bonded to at least one surface of a polarizer via an adhesive layer,
The polarizer is a polyvinyl alcohol film in which a dichroic substance is adsorbed and oriented, and a boron content is 23% by weight or less,
And the said adhesive bond layer is formed by irradiating an active energy ray to the active energy ray hardening-type adhesive agent containing a radically polymerizable compound, It is related with the polarizing plate characterized by the above-mentioned.

  In the polarizing plate, the adhesive layer preferably has a Tg of 60 ° C. or higher.

In the polarizing plate, the active energy ray-curable adhesive is an active energy ray-curable adhesive containing the radical polymerizable compounds (A), (B) and (C), and the total amount of the composition is 100% by weight. When
20 to 60% by weight of a radically polymerizable compound (A) having an SP value of 29.0 (kJ / m ³ ) ^1/2 or more and 32.0 or less (kJ / m ³ ) ^1/2 ,
10 to 30% by weight of the radically polymerizable compound (B) having an SP value of 18.0 (kJ / m ³ ) ^1/2 or more and less than 21.0 (kJ / m ³ ) ^1/2 , and an SP value of 21 0.0 (kJ / m ³ ) ^{1/2 to} 23.0 (kJ / m ³ ) 20 to 60% by weight of the radical polymerizable compound (C) that is ^1/2 or less,
It is preferable that each of the homopolymers of the radical polymerizable compounds (A), (B) and (C) has a glass transition temperature (Tg) of 60 ° C. or higher.

  In the polarizing plate, it is preferable that the radical polymerizable compound (A) in the active energy ray-curable adhesive is N-hydroxyethylacrylamide and / or N-methylolacrylamide. The radical polymerizable compound (B) in the active energy ray-curable adhesive is preferably tripropylene glycol diacrylate. Furthermore, it is preferable that the radical polymerizable compound (C) in the active energy ray-curable adhesive is acryloylmorpholine and / or N-methoxymethylacrylamide. According to these structures, the adhesiveness, durability, and water resistance of the adhesive layer can be improved in a balanced manner.

In the polarizing plate, the active energy ray-curable adhesive is a compound represented by the following general formula (1) as a photopolymerization initiator;
(Wherein R ¹ and R ² represent —H, —CH ₂ CH ₃ , —iPr or Cl, and R ¹ and R ² may be the same or different).

In the polarizing plate, the active energy ray-curable adhesive is a compound represented by the following general formula (2) in addition to the photopolymerization initiator of the general formula (1) as a photopolymerization initiator;
Wherein R ³ , R ⁴ and R ⁵ represent —H, —CH ₃ , —CH ₂ CH ₃ , —iPr or Cl, and R ³ , R ⁴ and R ⁵ may be the same or different. It is preferable to contain. By using together the photoinitiator of the said General formula (1) and General formula (2), reaction becomes highly efficient by these photosensitization reaction, and the adhesiveness of an adhesive bond layer improves especially.

  In the polarizing plate, the adhesive layer preferably has a thickness of 0.01 to 7 μm.

  The present invention also relates to an optical film in which at least one polarizing plate is laminated.

  Furthermore, the present invention relates to an image display device according to the present invention, wherein the polarizing plate and / or the optical film is used. In such an optical film and image display device, the polarizer of the polarizing plate and the transparent protective film are firmly bonded via the adhesive layer, and the durability and water resistance of the adhesive layer are excellent.

  When a water-based adhesive is used to bond a polyvinyl alcohol polarizer and a transparent protective film, the stress of the polarizer is relieved because the water-based adhesive gradually cures with drying in the drying process after bonding. In this state, a polarizing plate is produced. On the other hand, in the present invention, since the active energy linear adhesive is used, the curing speed is higher than that of the water-based adhesive, so that the adhesive is bonded to the transparent protective film while the stress on the polarizer is accumulated. Therefore, the thermal dimensional shrinkage, which is one of the durability evaluations as a polarizing plate, becomes larger when an active energy ray type adhesive is used than when an aqueous adhesive is used.

  In the polarizing plate of the present invention, the polarizer is controlled so that the boric acid content is as low as 23% by weight or less. Such a polarizer having a reduced boric acid content can exhibit a flexibility, that is, a molecular chain structure that is easy to relax stress. By using the polarizer, the polarizer has excellent dimensional durability under high temperature conditions. A board can be obtained. That is, the polarizing plate of the present invention uses a polarizer that is controlled so that the boric acid content is as low as 23% by weight or less. Therefore, active energy is applied to the bonding of the polarizer and the transparent protective film. Even when a wire curable adhesive is used, it is excellent in durability at high temperatures. Therefore, the polarizing plate of the present invention has a small dimensional shrinkage rate even under a high temperature condition of, for example, 60 ° C., and can suppress light leakage even when applied to a panel.

  In the polarizing plate of the present invention, a polarizer and a transparent protective film are bonded together with an adhesive layer, and an active energy ray-curable adhesive containing a radical polymerizable compound is used for the adhesive layer. . In cationic polymerization curing, moisture becomes an inhibitor of adhesion, and if there is moisture, adhesion failure occurs. For this reason, when an active energy ray-curable adhesive containing a cationic polymerizable compound is used, the moisture content of the polarizer to be used needs to be in a considerably low range (10% by weight or less). However, in order to reduce the moisture content of the polarizer, it is necessary to dry the polarizer, which reduces productivity. Moreover, when the moisture content of a polarizer is too low, when bonding with a transparent protective film, a polarizer will be easily damaged and point faults, such as a bubble, will increase. That is, from the viewpoint of producing a polarizing plate having a small number of defects and a good appearance, the active energy ray-curable adhesive containing a radical polymerizable compound is more active than the active energy ray curable adhesive containing a cationic polymerizable compound. Is also excellent.

  Moreover, in the polarizing plate of this invention, the composition which combined the radically polymerizable compound which has predetermined | prescribed SP value (solubility parameter) is suitable as said active energy ray hardening-type adhesive agent. In general, it can be said that substances having close SP values have high affinity. The polarizer has a high SP value (the SP value of the PVA polarizer is 32.8, for example), while the transparent protective film generally has a low SP value (the SP value is about 18 to 24). Therefore, for example, when the SP values of the radical polymerizable compounds are close to each other, the compatibility thereof increases, and when the SP values of the radical polymerizable compound and the polarizer in the active energy ray-curable adhesive are close, the adhesive is used. The adhesion between the layer and the polarizer is increased. Similarly, when the SP value of the radically polymerizable compound in the active energy ray-curable adhesive and the transparent protective film (triacetylcellulose film (TAC), acrylic film, cycloolefin film) is close, the adhesive layer and the transparent protective film Adhesion with the film increases. Based on these tendencies, in the active energy ray-curable adhesive, each SP value of at least three kinds of radical polymerizable compounds is designed within a specific range, and an optimal composition ratio is preferably used. it can.

  As described above, when the adhesive layer is formed of a cured product of an active energy ray-curable adhesive that has an SP value designed within a specific range and adjusted to an optimum composition ratio, the polarizer and the transparent protection An adhesive layer with improved adhesion to the film and improved durability and water resistance can be formed.

  The polarizing plate of the present invention has a transparent protective film via an adhesive layer formed by irradiating an active energy ray-curable adhesive containing a radical polymerizable compound on at least one surface of the polarizer with an active energy ray. Are pasted together.

  <Polarizer>

  As the polarizer, a polyvinyl alcohol film having a dichroic substance adsorbed and oriented and having a boron content of 23% by weight or less is used. As such a polyvinyl alcohol-based polarizer, a raw material polyvinyl alcohol-based film subjected to various steps and finally having a boric acid content controlled to 23% by weight or less is used.

  As the raw polyvinyl alcohol film, a film having translucency in the visible light region and capable of dispersing and adsorbing a dichroic substance such as iodine or a dichroic dye can be used without particular limitation. For example, a polyvinyl alcohol film conventionally used for a polarizer is preferably used. Examples of the material for the polyvinyl alcohol film include polyvinyl alcohol and derivatives thereof. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid and alkyl esters thereof, acrylamide and the like. Can be given. The degree of polymerization of polyvinyl alcohol is preferably about 100 to 10,000, and more preferably 1,000 to 10,000. A saponification degree of about 80 to 100 mol% is generally used. Usually, a polyvinyl alcohol film having a thickness of about 10 to 300 μm is used. Preferably it is 20-100 micrometers.

  In addition to the above, polyvinyl alcohol films include hydrophilic polymer films such as partially saponified ethylene / vinyl acetate copolymers, polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Etc.

  The polyvinyl alcohol film may contain additives such as a plasticizer and a surfactant. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol film.

  The polarizer is obtained, for example, by subjecting the polyvinyl alcohol film to a swelling process, a dyeing process, and a crosslinking process in this order. Each step is performed by immersing the polyvinyl alcohol film in the treatment bath according to each step. Moreover, in the manufacturing method of the said polarizer, it has an extending process in addition to the said process or with the said process.

  As the treatment liquid used in the swelling process, water, distilled water, or pure water is usually used. If the main component is water, the treatment liquid may contain a small amount of an additive such as an iodide compound and a surfactant as described below, alcohol, and the like. Further, when an iodide compound is contained in the treatment liquid, the iodide compound concentration is preferably about 0.1 to 10% by weight, more preferably 0.2 to 5% by weight. In addition to washing the surface of the polyvinyl alcohol film and the anti-blocking agent by the swelling step, there is also an effect of preventing unevenness such as uneven dyeing by swelling the polyvinyl alcohol film.

  The treatment temperature in the swelling step is usually preferably adjusted to about 20 to 45 ° C. Furthermore, it is preferable that it is 25-40 degreeC. In addition, if there is swelling unevenness, the portion becomes uneven coloring in the dyeing process, so that swelling unevenness is not generated. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.

  The dyeing step is performed by adsorbing and orienting iodine or a dichroic dye on the polyvinyl alcohol film. The dyeing process can be performed together with the stretching process. Dyeing is generally performed by immersing the film in a dyeing solution. As the staining solution, an iodine solution is generally used. As the iodine aqueous solution used as the iodine solution, an aqueous solution containing iodine ions with iodine and an iodide compound which is a dissolution aid is used. Examples of the iodide compound include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. are used. As the iodide compound, potassium iodide is preferred. The iodide compound used in the present invention is the same as described above when used in other steps.

  The iodine concentration in the iodine solution is about 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight. The iodide compound concentration is preferably about 0.1 to 10% by weight, more preferably 0.2 to 8% by weight. In iodine staining, the temperature of the iodine solution is usually about 20 to 50 ° C., preferably 25 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.

  The crosslinking step is performed by a boric acid treatment step using a boric acid treatment bath. In the treatment bath, boric acid is generally used in the form of an aqueous solution or a water-organic solvent mixed solution. Usually, an aqueous boric acid solution is used. The boric acid treatment step can be performed by one or more steps. Hereinafter, the case where a boric acid aqueous solution is used as the treatment bath will be described.

  In the boric acid treatment step, boric acid treatment is performed so that the boric acid content in the polyvinyl alcohol film in the finally obtained polarizer is 23% by weight or less from the viewpoint of high durability. On the other hand, if the boric acid content decreases, the durability under heating / humidification conditions is remarkably lowered. Therefore, the boric acid content is preferably 17% by weight or more.

  In the boric acid treatment step, the boric acid concentration of the boric acid aqueous solution is preferably 3% by weight or less, and preferably about 1 to 3% by weight. The boric acid aqueous solution or the like can contain an iodide compound such as potassium iodide. When the iodide compound is contained in the boric acid aqueous solution, the iodide compound concentration is about 0.1 to 10% by weight, and more preferably 0.2 to 5% by weight. The treatment temperature in the boric acid treatment step is usually 25 ° C. or higher, preferably 40 to 85 ° C., more preferably 50 to 70 ° C. The treatment time is usually about 5 to 800 seconds, preferably about 8 to 500 seconds. The boric acid content can be controlled by boric acid concentration, treatment temperature, and treatment time of the boric acid aqueous solution in the boric acid treatment step.

  The stretching step can be performed by performing a uniaxial stretching process. The stretching process can be performed together with the swelling process, the dyeing process, and the crosslinking process, or can be performed as a separate process from the process. The stretching is preferably performed so that the total stretching ratio is 5 to 7 times the original length of the polyvinyl alcohol film. The total draw ratio is further preferably 5.2 to 6.7 times, and more preferably 5.8 to 6.3 times. In addition, when a stretching process is accompanied in each process, the total stretching ratio refers to a cumulative stretching ratio including stretching in those processes.

  In the manufacturing method of the said polarizer, after performing the said swelling process, dyeing | staining process, and bridge | crosslinking process (an extending process is included), a washing | cleaning process can be given. Prior to the cleaning step, metal ion treatment can be performed in addition to the above steps. The metal ion treatment is performed by immersing a polyvinyl alcohol film in an aqueous solution containing a metal salt. Various metal ions are contained in the polyvinyl alcohol film by metal ion treatment.

  The washing step can be performed with water or an iodide-containing aqueous solution (treatment liquid). As the iodide in the iodide-containing aqueous solution, those described above can be used, and among them, for example, potassium iodide and sodium iodide are preferable. The remaining boric acid used in the crosslinking step can be washed away from the polyvinyl alcohol film by the washing step. When the aqueous solution is an aqueous potassium iodide solution, the concentration thereof is preferably in the range of 0.5 to 20% by weight, more preferably in the range of 1 to 15% by weight, and 1.5 to 7% by weight. Within the range is more preferable.

  Although the temperature of the said iodide containing aqueous solution is not specifically limited, Usually, the inside of the range of 15-40 degreeC is preferable, and the inside of the range which is 20-35 degreeC is more preferable. Further, the contact time with the polyvinyl alcohol film is not particularly limited, but is usually preferably in the range of 2 to 30 seconds, and more preferably in the range of 3 to 20 seconds.

  After performing each said process, a drying process is finally given and a polarizer is manufactured. As the drying step, an appropriate method such as natural drying, air drying, heat drying or the like can be used, but heat drying is usually preferably used. When performing heat drying, although heating temperature is not specifically limited, Usually, the inside of the range of 25-80 degreeC is preferable, The inside of the range of 30-70 degreeC is more preferable, The inside of the range of 30-60 degreeC is still more preferable. The drying time is preferably about 1 to 10 minutes.

  The polarizer preferably has a moisture content of 10 to 25% by weight, more preferably 10 to 20% by weight. Control of the moisture content within the above range is preferable from the viewpoint of few optical characteristics and appearance defects. When the moisture content of the polarizer is too low, it is liable to be damaged during lamination with the transparent protective film, which may cause appearance defects such as bubbles. Moreover, when the moisture content of a polarizer is too high, there exists a tendency for an optical characteristic to worsen.

  The moisture content of the polarizer may be adjusted by any appropriate method. For example, there is a method of controlling by adjusting the conditions of the drying process in the manufacturing process of the polarizer.

  The moisture content of the polarizer is measured by the following method. That is, the polarizer was cut out to a size of 100 × 100 mm, and the initial weight of this sample was measured. Subsequently, this sample was dried at 120 ° C. for 2 hours, the dry weight was measured, and the moisture content was measured by the following formula. Moisture content (% by weight) = {(initial weight−dry weight) / initial weight} × 100. The weight was measured three times, and the average value was used.

  The thickness of the polarizer is not particularly limited, but is generally about 80 μm or less. The thickness of the polarizer is usually preferably 15 to 35 μm.

  As the polarizer, a thin polarizer having a thickness of 10 μm or less can be used. From the viewpoint of thinning, the thickness is preferably 1 to 7 μm. Such a thin polarizer is preferable in that the thickness unevenness is small, the visibility is excellent, the dimensional change is small, the durability is excellent, and the thickness of the polarizing plate can be reduced.

<Transparent protective film>
As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, nylon and aromatic polyamides. Polyamide resin such as polyamide resin, polyimide resin, polyethylene, polypropylene, ethylene / propylene copolymer, cyclic olefin resin having cyclo or norbornene structure, (meth) acrylic resin, polyarylate resin, polystyrene resin, polyvinyl alcohol resin, And mixtures thereof. Among the resins, polycarbonate resins, cyclic polyolefin resins, and (meth) acrylic resins are preferable, and cyclic polyolefin resins and (meth) acrylic resins are particularly preferable. A transparent protective film is bonded to one side of the polarizer by an adhesive layer. On the other side, as a transparent protective film, (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, silicone A thermosetting resin such as a system or an ultraviolet curable resin can be used.

  The thickness of the transparent protective film can be appropriately determined, but is generally about 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm from the viewpoints of workability such as strength and handleability and thin layer properties. preferable. Furthermore, 20-200 micrometers is preferable and 30-80 micrometers is preferable.

  A specific example of the cyclic polyolefin resin is preferably a norbornene resin. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as the cyclic polyolefin resin. As specific examples, trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, product names “ARTON” manufactured by JSR Corporation, “TOPAS” manufactured by TICONA, and product names manufactured by Mitsui Chemicals, Inc. “APEL”.

  The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg is 115 ° C. or higher, the polarizing plate can be excellent in durability. Although the upper limit of Tg of the (meth) acrylic resin is not particularly limited, it is preferably 170 ° C. or lower from the viewpoint of moldability and the like. From the (meth) acrylic resin, a film having in-plane retardation (Re) and thickness direction retardation (Rth) of almost zero can be obtained.

  As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted as long as the effects of the present invention are not impaired. For example, poly (meth) acrylic acid ester 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.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, poly (meth) acrylate C1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

  Specific examples of (meth) acrylic resins include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

  Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in Japanese Patent No. 146084.

  The transparent protective film is provided on at least one side of the polarizer, but when provided on both sides, the transparent protective film made of the same polymer material may be used on the front and back, and the transparent protective film made of different polymer materials, etc. A protective film may be used.

  As the transparent protective film, a phase difference plate having a phase difference of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate functions also as a transparent protective film, so that the thickness can be reduced.

  Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm.

  In addition, the film which has the said phase difference can be separately bonded to the transparent protective film which does not have a phase difference, and the said function can be provided.

  A functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer or an antiglare layer can be provided on the surface of the transparent protective film to which the polarizer is not adhered. The functional layers such as the hard coat layer, antireflection layer, antisticking layer, diffusion layer and antiglare layer can be provided on the transparent protective film itself, and separately provided separately from the transparent protective film. You can also.

<Active energy ray-curable adhesive>
In the polarizing plate of the present invention, an active energy ray-curable adhesive containing a radical polymerizable compound is used for adhesion between the polarizer and the transparent protective film. The adhesive layer (cured product layer) formed by irradiating the active energy ray-curable adhesive with active energy rays has higher durability than the aqueous adhesive layer. The adhesive layer in the polarizing plate of the present invention preferably has a Tg of 60 ° C. or higher. In the polarizing plate of the present invention, when an active energy ray-curable adhesive having an adhesive layer having a high Tg of 60 ° C. or higher is used and the thickness of the adhesive layer is controlled within the above range, the adhesive layer is under high humidity and high temperature. The durability under the harsh environment can be satisfied.

  As described above, the radical polymerizable compound used for the active energy ray-curable adhesive is preferably selected so that the Tg of the adhesive layer formed thereby is 60 ° C. or higher, and more preferably 70 ° C. or higher. Preferably, it is 75 ° C. or higher, more preferably 100 ° C. or higher, and further preferably 120 ° C. or higher. On the other hand, if the Tg of the adhesive layer becomes too high, the flexibility of the polarizing plate is lowered. Therefore, the Tg of the adhesive layer is preferably 300 ° C. or lower, more preferably 240 ° C. or lower, and further preferably 180 ° C. or lower.

  Examples of the radical polymerizable compound include a compound having a (meth) acryloyl group and a compound having a vinyl group. These radically polymerizable compounds can be monofunctional or bifunctional or higher. As these radically polymerizable compounds, compounds having a (meth) acryloyl group are suitable. As the compound having a (meth) acryloyl group, an N-substituted amide monomer is preferably used. These monomers are preferable in terms of adhesiveness. The (meth) acryloyl group means an acryloyl group and / or a methacryloyl group. In the present invention, (meta) has the same meaning as described above.

The N-substituted amide monomer has the general formula (1): CH ₂ = C (R ¹ ) —CONR ² (R ³ ) (R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a hydroxyl group, mercapto Represents a linear or branched alkyl group having 1 to 4 carbon atoms which may have a group, an amino group or a quaternary ammonium group, and R ³ represents a hydrogen atom or a linear or branched chain having 1 to 4 carbon atoms Wherein R ² and R ³ are simultaneously a hydrogen atom, or R ² and R ³ are bonded to form a 5-membered ring or a 6-membered ring that may contain an oxygen atom. It is expressed by Examples of the linear or branched alkyl group having 1 to 4 carbon atoms for R ² or R ³ in the general formula (1) include a methyl group, an ethyl group, an isopropyl group, and a t-butyl group. Examples of the alkyl group having a hydroxyl group include a hydroxymethyl group and a hydroxyethyl group, and examples of the alkyl group having an amino group include an aminomethyl group and an aminoethyl group. Moreover, when R < ² >, R < ³ > couple | bonds together and forms the 5-membered ring or 6-membered ring which may contain an oxygen atom, it has a heterocyclic ring which has nitrogen. Examples of the heterocyclic ring include morpholine ring, piperidine ring, pyrrolidine ring, piperazine ring and the like.

  Specific examples of the N-substituted amide monomer include, for example, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropylacrylamide, N- Butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methylol-N-propane (meth) acrylamide, aminomethyl (meth) acrylamide, Examples include aminoethyl (meth) acrylamide, mercaptomethyl (meth) acrylamide, and mercaptoethyl (meth) acrylamide. Examples of the heterocycle-containing monomer having a heterocycle include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine and the like. These N-substituted amide monomers can be used singly or in combination of two or more.

  As the N-substituted amide monomer, N-hydroxyethylacrylamide, N-methylolacrylamide, N-isopropylacrylamide, and N-acryloylmorpholine are preferable. The N-substituted amide-based monomer exhibits good adhesion to a transparent protective film using a low moisture content polarizer or a material with low moisture permeability, but the exemplified monomers are particularly good. Shows adhesion. Of these, N-hydroxyethylacrylamide is preferred.

  The N-substituted amide monomers can be used singly or in combination of two or more. When two or more are combined, N-hydroxyethylacrylamide and N are used from the viewpoint of durability and adhesiveness. -A combination of acryloylmorpholine is preferred. Moreover, in the case of the said combination, it is preferable when obtaining the favorable adhesiveness that the ratio of N-hydroxyethyl acrylamide with respect to the total amount of N-hydroxyethyl acrylamide and N-acryloyl morpholine is 40 weight% or more. The proportion is more preferably 40 to 90% by weight, and further preferably 60 to 90% by weight.

  Moreover, as said radically polymerizable compound, in addition to the above, as a compound having a (meth) acryloyl group, for example, various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, And (meth) acrylate monomers. Among these, epoxy (meth) acrylates, particularly monofunctional (meth) acrylates having an aromatic ring and a hydroxy group are preferably used. These radically polymerizable compounds are used alone and in combination with the N-substituted amide monomer when an adhesive layer having a Tg of 60 ° C. or higher cannot be formed.

  As the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, various monofunctional (meth) acrylates having an aromatic ring and a hydroxy group can be used. The hydroxy group may exist as a substituent of the aromatic ring, but in the present invention, it exists as an organic group (bonded to a hydrocarbon group, particularly an alkylene group) that bonds the aromatic ring and the (meth) acrylate. Those that do are preferred.

  Examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include a reaction product of a monofunctional epoxy compound having an aromatic ring and (meth) acrylic acid. Examples of the monofunctional epoxy compound having an aromatic ring include phenyl glycidyl ether, t-butylphenyl glycidyl ether, and phenyl polyethylene glycol glycidyl ether. Specific examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include, for example, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy-3-t-butylphenoxypropyl (meth) Examples thereof include acrylate and 2-hydroxy-3-phenyl polyethylene glycol propyl (meth) acrylate.

  Moreover, a carboxyl group monomer is mention | raise | lifted as a compound which has a (meth) acryloyl group. A carboxyl group monomer is also preferable in terms of adhesiveness. Examples of the carboxyl group monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and the like. Of these, acrylic acid is preferred.

  In addition to the above, compounds having a (meth) acryloyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl. Alkyl (meth) acrylates having 1 to 12 carbon atoms such as (meth) acrylate and lauryl (meth) acrylate; (meth) acrylic acid alkoxyalkyl systems such as (meth) acrylic acid methoxyethyl and (meth) acrylic acid ethoxyethyl Monomer: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxy (meth) acrylate Octyl, (meth) acrylic acid 10-H Hydroxyl-containing monomers such as loxydecyl, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone addition of acrylic acid Products; sulfones such as styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid Acid group-containing monomers; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. (Meth) acrylamide; maleimide, N-cyclohexylmaleimide, N-phenylmaleimide, etc .; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate , (Meth) acrylic acid alkylaminoalkyl monomers such as (meth) acrylic acid t-butylaminoethyl, 3- (3-pyridinyl) propyl (meth) acrylate; N- (meth) acryloyloxymethylene succinimide and N- ( And nitrogen-containing monomers such as succinimide monomers such as (meth) acryloyl-6-oxyhexamethylene succinimide and N- (meth) acryloyl-8-oxyoctamethylene succinimide.

  As described above, as the radical polymerizable compound in the active energy ray-curable adhesive, an N-substituted amide monomer is used alone, or a monofunctional compound having an N-substituted amide monomer, an aromatic ring and a hydroxy group. It is preferable to use (meth) acrylate in combination. When these are used in combination, the proportion of the N-substituted amide monomer is 40% by weight or more, further 50% by weight or more, further 60% by weight or more, further 70% by weight or more, and further 80% by weight or more. Is preferable.

  As the radical polymerizable compound, a bifunctional or higher functional radical polymerizable compound can be used. The bifunctional or higher radical polymerizable compound is preferably a bifunctional or higher (meth) acrylate, particularly a bifunctional or higher epoxy (meth) acrylate. The bifunctional or higher functional epoxy (meth) acrylate is obtained by reacting a polyfunctional epoxy compound with (meth) acrylic acid. Various examples of the polyfunctional epoxy compound can be exemplified. Examples of the polyfunctional epoxy compound include aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins.

  Examples of the aromatic epoxy resin include bisphenol type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S; phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol Examples thereof include novolak-type epoxy resins such as novolak epoxy resins; glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol.

  Examples of the alicyclic epoxy resin include hydrogenated aromatic epoxy resins, cyclohexane-based, cyclohexylmethyl ester-based, cyclohexylmethyl ether-based, spiro-based, and tricyclodecane-based epoxy resins.

  Examples of the aliphatic epoxy resin include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. Examples include 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene. Polyethers of polyether polyols obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as glycol diglycidyl ether, ethylene glycol, propylene glycol, and glycerin Examples thereof include glycidyl ether.

  The epoxy equivalent of the epoxy resin is usually in the range of 30 to 3000 g / equivalent, preferably 50 to 1500 g / equivalent.

  The bifunctional or higher epoxy (meth) acrylate is preferably an epoxy (meth) acrylate of an aliphatic epoxy resin, particularly preferably an epoxy (meth) acrylate of a bifunctional aliphatic epoxy resin.

The active energy ray-curable adhesive used for the polarizing plate of the present invention has a SP value of 29.0 (kJ / m ³ ) ^1/2 or more and 32 as a radical polymerizable compound when the total amount of the composition is 100% by weight. 0.0 to less than (kJ / m ³ ) ^1/2 of the radical polymerizable compound (A) 20 to 60% by weight, SP value is 18.0 (kJ / m ³ ) ^{1/2 to} 21.0 (kJ / m ³ ) 10 to 30% by weight of the radically polymerizable compound (B) which is less than ^1/2 , and the SP value is 21.0 (kJ / m ³ ) ^1/2 or more and 23.0 (kJ / m ³ ) ¹ Those containing 20 to 60% by weight of the radically polymerizable compound (C) which is ^{/ 2} or less are preferred. In the present invention, the “composition total amount” means the total amount including various initiators and additives in addition to the radical polymerizable compound.

In the active energy ray-curable adhesive, the SP value of the radical polymerizable compound (A) is 29.0 (kJ / m ³ ) ^1/2 or more and 32.0 or less (kJ / m ³ ) ^1/2 , When the total amount of the composition is 100% by weight, the composition ratio is preferably 20 to 60% by weight. Such a radically polymerizable compound (A) has a high SP value and greatly contributes to, for example, an improvement in adhesion between a PVA polarizer (eg, SP value 32.8) and an adhesive layer. On the other hand, since the radically polymerizable compound (A) has an SP value relatively close to water (SP value 47.9), if the composition ratio of the radically polymerizable compound (A) in the composition is too large, There is concern about deterioration of the water resistance of the agent layer. Therefore, when the adhesiveness with a polarizer and water resistance are considered, it is preferable that the composition ratio of a radically polymerizable compound (A) shall be 20 to 60 weight%. In consideration of adhesiveness, the composition ratio of the radical polymerizable compound (A) is preferably 25% by weight or more, and more preferably 30% by weight or more. In consideration of water resistance, the composition ratio of the radical polymerizable compound (A) is preferably 55% by weight or less, and more preferably 50% by weight or less.

The SP value of the radically polymerizable compound (B) is 18.0 (kJ / m ³ ) ^1/2 or more and less than 21.0 (kJ / m ³ ) ^1/2 , and the composition ratio is 10 to 30% by weight. Preferably there is. Such radically polymerizable compound (B) has a low SP value, and is far away from water (SP value 47.9), which greatly contributes to improving the water resistance of the adhesive layer. The SP value of the radical polymerizable compound (B) is, for example, the SP value (for example, SP value 18.6) of a cyclic polyolefin resin (for example, trade name “ZEONOR” manufactured by Nippon Zeon Co., Ltd.) as a transparent protective film. Since it is near, it contributes to the improvement of adhesiveness with such a transparent protective film. In order to further improve the water resistance of the adhesive layer, the SP value of the radical polymerizable compound (B) is preferably less than 20.0 (kJ / m ³ ) ^1/2 . On the other hand, since the radically polymerizable compound (B) has a large SP value from the radically polymerizable compound (A), if the composition ratio is too large, the compatibility balance between the radically polymerizable compounds is lost. As the phase separation proceeds, there is a concern that the transparency of the adhesive layer may deteriorate. Therefore, when considering water resistance and transparency of the adhesive layer, it is important that the composition ratio of the radical polymerizable compound (B) is 10 to 30% by weight. In consideration of water resistance, the composition ratio of the radical polymerizable compound (B) is preferably 10% by weight or more, and more preferably 15% by weight or more. In consideration of the transparency of the adhesive layer, the composition ratio of the radical polymerizable compound (B) is preferably 25% by weight or less, more preferably 20% by weight or less, and its SP value is 19 0.0 (kJ / m ³ ) ^1/2 or more is preferable.

The SP value of the radical polymerizable compound (C) is 21.0 (kJ / m ³ ) ^1/2 or more and less than 23.0 (kJ / m ³ ) ^1/2 , and the composition ratio is 20 to 60% by weight. Preferably there is. As described above, the radically polymerizable compound (A) and the radically polymerizable compound (B) have a large SP value and are not compatible with each other. However, since the SP value of the radical polymerizable compound (C) is located between the SP value of the radical polymerizable compound (A) and the SP value of the radical polymerizable compound (B), the radical polymerizable compound (A) In addition to the radically polymerizable compound (B) and the radically polymerizable compound (C), the compatibility of the composition as a whole is improved in a well-balanced manner. Furthermore, the SP value of the radical polymerizable compound (C) is close to the SP value (for example, 23.3) of unsaponified triacetyl cellulose as a transparent protective film and the SP value (for example, 22.2) of an acrylic film, for example. It contributes to the improvement of adhesiveness with these transparent protective films. Therefore, in order to improve water resistance and adhesiveness in a well-balanced manner, the composition ratio of the radical polymerizable compound (C) is preferably 20 to 60% by weight. When considering the compatibility of the composition as a whole and the adhesion to the transparent protective film, the composition ratio of the radical polymerizable compound (C) is preferably 25% by weight or more, and more preferably 29% by weight or more. In consideration of water resistance, the composition ratio of the radical polymerizable compound (C) is preferably 55% by weight or less, and more preferably 50% by weight or less.

  Further, the glass transition temperature (Tg) of each of the radical polymerizable compounds (A), (B) and (C) is preferably 60 ° C. or higher, and the durability is particularly excellent. Generation of shock cracks can be prevented. Here, “heat shock crack” means, for example, a phenomenon in which when a polarizer contracts, it tears in the stretching direction, and in order to prevent this, it is polarized in a heat shock temperature range (−40 ° C. to 60 ° C.). It is important to suppress the expansion / contraction of the child. As described above, when the glass transition temperature (Tg) of each of the radical polymerizable compounds (A), (B) and (C) is 60 ° C. or higher, when the adhesive layer is formed, Tg also increases. As a result, a rapid change in elastic modulus of the adhesive layer in the heat shock temperature range can be suppressed, and the expansion / contraction force acting on the polarizer can be reduced, so that the occurrence of heat shock cracks can be prevented. .

  Here, the calculation method of the SP value (solubility parameter) in the present invention will be described below.

(Calculation method of solubility parameter (SP value))
In the present invention, the solubility parameter (SP value) of a radically polymerizable compound, a polarizer, various transparent protective films and the like is calculated by the Fedors calculation method ["Polymer Engineering &Sci." 14, Vol. 2 (1974), pages 148-154]

Where Δei is the evaporation energy at 25 ° C. belonging to the atom or group, and Δvi is the molar volume at 25 ° C.

  In the above formula, Δei and Δvi indicate constant numerical values given to i atoms and groups in the main molecule. Also, representative examples of numerical values of Δe and Δv given to atoms or groups are shown in Table 1 below.

The radical polymerizable compound (A) has a radical polymerizable group such as a (meth) acrylate group and has an SP value of 29.0 (kJ / m ³ ) ^1/2 or more and 32.0 or less (kJ / m ³ ) ^Any compound that is ^½ can be used without limitation. Specific examples of the radical polymerizable compound (A) include N-hydroxyethyl acrylamide (SP value 29.6), N-methylol acrylamide (SP value 31.5) and the like.

The radically polymerizable compound (B) has a radically polymerizable group such as a (meth) acrylate group and has an SP value of 18.0 (kJ / m ³ ) ^1/2 or more and 21.0 (kJ / m ³ ). ^Any compound that is less than ^½ can be used without limitation. Specific examples of the radically polymerizable compound (B) include, for example, tripropylene glycol diacrylate (SP value 19.0), 1,9-nonanediol diacrylate (SP value 19.2), and tricyclodecane dimethanol dimer. Acrylate (SP value 20.3), cyclic trimethylolpropane formal acrylate (SP value 19.1), dioxane glycol diacrylate (SP value 19.4), EO-modified diglycerin tetraacrylate (SP value 20.9), etc. Is mentioned. In addition, as a radically polymerizable compound (B), a commercial item can also be used conveniently, for example, Aronix M-220 (made by Toagosei Co., Ltd., SP value 19.0), light acrylate 1,9ND-A (Kyoeisha Chemical Co., Ltd.). Manufactured, SP value 19.2), light acrylate DGE-4A (manufactured by Kyoeisha Chemical Co., SP value 20.9), light acrylate DCP-A (manufactured by Kyoeisha Chemical Co., SP value 20.3), SR-531 (Sartomer) And SP-value 19.1), CD-536 (Sartomer, SP value 19.4), and the like.

The radical polymerizable compound (C) has a radical polymerizable group such as a (meth) acrylate group and has an SP value of 21.0 (kJ / m ³ ) ^1/2 or more and 23.0 (kJ / m ³ ). ^Any compound that is ^½ or less can be used without limitation. Specific examples of the radical polymerizable compound (C) include, for example, acryloylmorpholine (SP value 22.9), N-methoxymethylacrylamide (SP value 22.9), N-ethoxymethylacrylamide (SP value 22.3). Etc. In addition, as a radically polymerizable compound (C), a commercial item can also be used suitably, for example, ACMO (the Kojin company make, SP value 22.9), Wasmer 2MA (the Kasano Kosan company make, SP value 22.9). , Wasmer EMA (manufactured by Kasano Kosan Co., Ltd., SP value 22.3), Wasmer 3MA (manufactured by Kasano Kosan Co., Ltd., SP value 22.4), and the like.

  When the glass transition temperature (Tg) of each of the radical polymerizable compounds (A), (B), and (C) is 60 ° C. or higher, the Tg of the adhesive layer is increased and the durability is particularly excellent. It will be. As a result, for example, when an adhesive layer of a polarizer and a transparent protective film is used, occurrence of heat shock cracks in the polarizer can be prevented. Here, the Tg of the homopolymer of the radical polymerizable compound means Tg when the radical polymerizable compound is cured (polymerized) alone. A method for measuring Tg will be described later.

The active energy ray-curable adhesive according to the present invention contains radically polymerizable compounds (A), (B) and (C) in a total of 85 to 100 parts by weight, and further has an SP value of 23.0 (kJ / m). ³⁾ beyond ^1/2 29.0 ^(kJ / ^{m 3)} radically polymerizable compound is less than ^1/2 the (D) may contain 0 to 15 parts by weight. Specific examples of the radical polymerizable compound (D) include, for example, 4-hydroxybutyl acrylate (SP value 23.8), 2-hydroxyethyl acrylate (SP value 25.5), N-vinylcaprolactam (trade name V- CAP, manufactured by ISP, SP value 23.4), 2-hydroxypropyl acrylate (SP value 24.5), and the like.

  According to such a configuration, since the ratio of the radical polymerizable compounds (A), (B) and (C) in the adhesive composition can be sufficiently ensured, the adhesiveness of the adhesive layer is improved, and the durability and Water resistance can be further improved. In order to further improve the adhesion, durability and water resistance in a well-balanced manner, the radically polymerizable compounds (A), (B) and (C) are preferably contained in a total of 90 to 100 parts by weight, It is more preferable to contain parts by weight.

  When the active energy ray curable adhesive according to the present invention is used in an electron beam curable type, it is not particularly necessary to include a photopolymerization initiator in the composition. It is preferable to use an initiator, and it is particularly preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or more. A photopolymerization initiator that is highly sensitive to light of 380 nm or more will be described later.

In the active energy ray-curable adhesive according to the present invention, as a photopolymerization initiator, a compound represented by the following general formula (1);
(Wherein R ¹ and R ² represent —H, —CH ₂ CH ₃ , —iPr or Cl, and R ¹ and R ² may be the same or different), respectively, or a general formula ( It is preferable to use together the compound represented by 1) and a photopolymerization initiator that is highly sensitive to light of 380 nm or more, which will be described later. When the compound represented by the general formula (1) is used, the adhesiveness is excellent as compared with a case where a photopolymerization initiator having high sensitivity to light of 380 nm or more is used alone. Among the compounds represented by the general formula (1), diethylthioxanthone in which R ¹ and R ² are —CH ₂ CH ₃ is particularly preferable. The composition ratio of the compound represented by the general formula (1) in the composition is preferably 0.1 to 5.0% by weight when the total amount of the composition is 100% by weight, and preferably 0.5 to 4%. It is more preferably 0.0% by weight, and even more preferably 0.9 to 3.0% by weight.

  Since the photopolymerization initiator of the general formula (1) can initiate polymerization by light having a long wavelength that passes through a transparent protective film having UV absorption ability, the adhesive can be cured even through a UV absorbing film. Specifically, for example, even when a transparent protective film having UV absorbing ability is laminated on at least one surface of a polarizer, the adhesive composition can be cured if it contains a photopolymerization initiator of the general formula (1). is there.

  Moreover, it is preferable to add a polymerization initiation assistant as required. Examples of polymerization initiators include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, and the like. Among them, ethyl 4-dimethylaminobenzoate is particularly preferable. When a polymerization initiation assistant is used, the addition amount is usually 0 to 5% by weight, preferably 0 to 4% by weight, most preferably 0 to 3% by weight when the total amount of the composition is 100% by weight. .

  Moreover, a well-known photoinitiator can be used together as needed. Since the transparent protective film having UV absorbing ability does not transmit light of 380 nm or less, it is preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or more as the photopolymerization initiator. Specifically, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 2- (Dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine Oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole) 1-yl) -phenyl) titanium and the like.

In particular, as a photopolymerization initiator, in addition to the photopolymerization initiator of the general formula (1), a compound represented by the following general formula (2);
Wherein R ³ , R ⁴ and R ⁵ represent —H, —CH ₃ , —CH ₂ CH ₃ , —iPr or Cl, and R ³ , R ⁴ and R ⁵ may be the same or different. It is preferable to use it. As the compound represented by the general formula (2), 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (trade name: IRGACURE907 manufacturer: BASF) which is also a commercially available product is suitable. Can be used. In addition, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (trade name: IRGACURE369 manufacturer: BASF), 2- (dimethylamino) -2-[(4-methylphenyl) Methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone (trade name: IRGACURE379 manufacturer: BASF) is preferable because of its high sensitivity.

  Moreover, various additives can be mix | blended with the active energy ray hardening-type adhesive which concerns on this invention as another arbitrary component in the range which does not impair the objective and effect of this invention. Such additives include epoxy resin, polyamide, polyamideimide, polyurethane, polybutadiene, polychloroprene, polyether, polyester, styrene-butadiene block copolymer, petroleum resin, xylene resin, ketone resin, cellulose resin, fluorine-based oligomer, Polymers or oligomers such as silicone oligomers and polysulfide oligomers; polymerization inhibitors such as phenothiazine and 2,6-di-t-butyl-4-methylphenol; polymerization initiation aids; leveling agents; wettability improvers; Plasticizer; UV absorber; Silane coupling agent; Inorganic filler; Pigment;

  Among the above additives, the silane coupling agent acts on the polarizer surface and can impart further water resistance. When a silane coupling agent is used, the amount added is usually 0 to 10% by weight, preferably 0 to 5% by weight, most preferably 0 to 3% by weight when the total amount of the composition is 100% by weight. .

  As the silane coupling agent, an active energy ray-curable compound is preferably used, but the same water resistance can be imparted even if it is not active energy ray-curable.

  Specific examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycid as active energy ray-curable compounds. Xylpropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxy Examples thereof include silane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.

  Specific examples of silane coupling agents that are not active energy ray curable include N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2. (Aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, N -Phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3 -Mercaptopropylmethyldimethoxysilane, - mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanate propyltriethoxysilane, etc. imidazole silane.

  Preferable are 3-methacryloxypropyltrimethoxysilane and 3-acryloxypropyltrimethoxysilane.

  The active energy ray curable adhesive according to the present invention can be used in an electron beam curable type or an ultraviolet curable type.

  In the electron beam curable type, any appropriate condition can be adopted as the electron beam irradiation condition as long as the active energy ray curable adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably 5 kV to 300 kV, and more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. If the acceleration voltage exceeds 300 kV, the penetration force through the sample is too strong and damages the transparent protective film and the polarizer. There is a risk of giving. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the transparent protective film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

  Electron beam irradiation is usually performed in an inert gas, but if necessary, it may be performed in the atmosphere or under a condition in which a small amount of oxygen is introduced. Depending on the material of the transparent protective film, by appropriately introducing oxygen, the transparent protective film surface where the electron beam first hits can be obstructed to prevent oxygen damage and prevent damage to the transparent protective film. An electron beam can be irradiated efficiently.

  On the other hand, in the case of using a transparent protective film imparted with ultraviolet absorbing ability in the ultraviolet curable type, light having a wavelength shorter than about 380 nm is absorbed, so that light having a wavelength shorter than 380 nm does not reach the active energy ray curable adhesive. Therefore, it does not contribute to the polymerization reaction. Further, light having a wavelength shorter than 380 nm absorbed by the transparent protective film is converted into heat, and the transparent protective film itself generates heat, which causes defects such as curling and wrinkling of the polarizing plate. Therefore, when the ultraviolet curable type is adopted in the present invention, it is preferable to use an apparatus that does not emit light having a wavelength shorter than 380 nm as the ultraviolet ray generating apparatus, and more specifically, the integrated illuminance and wavelength in the wavelength range of 380 to 440 nm. The ratio with the integrated illuminance in the range of 250 to 370 nm is preferably 100: 0 to 100: 50, and more preferably 100: 0 to 100: 40. As the ultraviolet ray satisfying such a relationship of integrated illuminance, a gallium-filled metal halide lamp and an LED light source that emits light in the wavelength range of 380 to 440 nm are preferable. Alternatively, low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, incandescent lamp, xenon lamp, halogen lamp, carbon arc lamp, metal halide lamp, fluorescent lamp, tungsten lamp, gallium lamp, excimer laser or sunlight as the light source, It is also possible to use a light having a wavelength shorter than 380 nm by using a band pass filter.

  In the ultraviolet curable type, it is preferable to warm the active energy ray curable adhesive before irradiation with ultraviolet rays (heating before irradiation). In this case, it is preferable to warm to 40 ° C. or higher, and to 50 ° C. or higher. It is more preferable to warm. It is also preferable to heat the active energy ray-curable adhesive after irradiation with ultraviolet rays (heating after irradiation), in which case it is preferable to heat to 40 ° C. or higher, and more preferably to 50 ° C. or higher. preferable.

  The active energy ray-curable adhesive according to the present invention can be suitably used particularly when forming an adhesive layer that adheres a polarizer and a transparent protective film having a light transmittance of less than 5% at a wavelength of 365 nm. . Here, the active energy ray-curable adhesive according to the present invention irradiates ultraviolet rays through the transparent protective film having UV absorption ability by containing the photopolymerization initiator of the general formula (1) described above, The adhesive layer can be hardened. Therefore, an adhesive bond layer can be hardened also in the polarizing plate which laminated the transparent protective film which has UV absorption ability on at least one side of a polarizer. However, as a matter of course, the adhesive layer can be cured also in a polarizing plate on which a transparent protective film having no UV absorbing ability is laminated. In addition, the transparent protective film which has UV absorption ability means the transparent protective film whose transmittance | permeability with respect to light of 380 nm is less than 10%.

  Examples of the method for imparting UV absorbing ability to the transparent protective film include a method of containing an ultraviolet absorber in the transparent protective film and a method of laminating a surface treatment layer containing an ultraviolet absorber on the surface of the transparent protective film.

  Specific examples of the ultraviolet absorber include conventionally known oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. .

<Polarizing plate>
In the polarizing plate of the present invention, the active energy ray-curable adhesive is applied to the surface of the polarizer forming the adhesive layer and / or the surface of the transparent protective film forming the adhesive layer, and then at least one surface of the polarizer. A transparent protective film is bonded together, and then the active energy ray-curable adhesive is cured by irradiation with active energy rays to form an adhesive layer.

  The polarizer and the transparent protective film may be subjected to surface modification treatment before applying the active energy ray-curable adhesive. Specific examples of the treatment include corona treatment, plasma treatment, and saponification treatment.

  The coating method of the active energy ray-curable adhesive is appropriately selected depending on the viscosity of the composition and the target thickness. Examples of coating methods include reverse coaters, gravure coaters (direct, reverse and offset), bar reverse coaters, roll coaters, die coaters, bar coaters, rod coaters and the like. In addition, for coating, a method such as a dapping method can be appropriately used.

  Moreover, it is preferable to apply the active energy ray-curable adhesive so that the thickness of the adhesive layer is 0.01 to 7 μm. The thickness of the adhesive layer is more preferably 0.01 to 5 μm, further preferably 0.01 to 2 μm, and most preferably 0.01 to 1 μm. The thickness of the adhesive layer is preferably set to 0.01 μm or more from the viewpoint that the adhesive force itself obtains cohesive force to obtain adhesive strength. On the other hand, the thickness of the adhesive layer is preferably 7 μm or less from the viewpoint of durability of the polarizing plate.

  A polarizer and a transparent protective film are bonded together through the adhesive applied as described above. Bonding of the polarizer and the transparent protective film can be performed with a roll laminator or the like.

  After bonding a polarizer and a transparent protective film, an active energy ray (an electron beam, ultraviolet rays, etc.) is irradiated, an active energy ray hardening-type adhesive agent is hardened, and an adhesive bond layer is formed. The irradiation direction of active energy rays (electron beam, ultraviolet ray, etc.) can be irradiated from any appropriate direction. Preferably, it irradiates from the transparent protective film side. When irradiated from the polarizer side, the polarizer may be deteriorated by active energy rays (electron beams, ultraviolet rays, etc.).

  When the polarizing plate according to the present invention is produced in a continuous line, the line speed depends on the curing time of the adhesive, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and still more preferably 10 to 100 m / min. min. When the line speed is too low, productivity is poor, or damage to the transparent protective film is too great, and a polarizing plate that can withstand a durability test or the like cannot be produced. When the line speed is too high, the adhesive is not sufficiently cured, and the target adhesiveness may not be obtained.

  In the polarizing plate of the present invention, the polarizer and the transparent protective film are bonded via an adhesive layer formed by the cured layer of the active energy ray-curable adhesive, but the transparent protective film is bonded. An easy-adhesion layer can be provided between the agent layers. The easy adhesion layer can be formed of, for example, various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. These polymer resins can be used alone or in combination of two or more. Moreover, you may add another additive for formation of an easily bonding layer. Specifically, a stabilizer such as a tackifier, an ultraviolet absorber, an antioxidant, and a heat resistance stabilizer may be used.

  The easy adhesion layer is usually provided in advance on a transparent protective film, and the easy adhesion layer side of the transparent protective film and the polarizer are bonded together with an adhesive layer. The easy-adhesion layer is formed by coating and drying the material for forming the easy-adhesion layer on the transparent protective film by a known technique. The material for forming the easy-adhesion layer is usually adjusted as a solution diluted to an appropriate concentration in consideration of the thickness after drying and the smoothness of coating. The thickness of the easy adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and still more preferably 0.05 to 1 μm. Note that a plurality of easy-adhesion layers can be provided, but also in this case, the total thickness of the easy-adhesion layers is preferably in the above range.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  The optical film in which the optical layer is laminated on the polarizing plate can be formed by a method of laminating separately in the manufacturing process of a liquid crystal display device or the like. It is excellent in stability and assembly work, and has the advantage of improving the manufacturing process of a liquid crystal display device and the like. Appropriate bonding means such as an adhesive layer can be used for lamination. When adhering the above polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  An adhesive layer for adhering to other members such as a liquid crystal cell can be provided on the polarizing plate or the optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as an overlapping layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as adhesive layers, such as a different composition, a kind, and thickness, in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

  The exposed surface of the adhesive layer is temporarily covered with a separator for the purpose of preventing contamination until it is put into practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, an appropriate thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet, metal foil, or a laminate thereof, and a silicone-based or long sheet as necessary. Appropriate ones according to the prior art, such as those coated with an appropriate release agent such as a chain alkyl type, fluorine type or molybdenum sulfide, can be used.

  The polarizing plate or the optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply according to the former. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is arranged on one side or both sides of a liquid crystal cell, or a backlight or a reflecting plate used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, a single layer or a suitable layer such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Examples of the present invention will be described below, but the embodiments of the present invention are not limited thereto.

<Boric acid content>
About the obtained PVA-type polarizer, boric acid content was measured. The boric acid content was obtained by subjecting the polyvinyl alcohol film to be measured to heat drying at 120 ° C. for 2 hours, and then pulverizing to collect 2.0 g. To 2.0 g of the pulverized product, 500 ml of water was added and heated at 95 ° C. for 12 hours to completely dissolve the polyvinyl alcohol film in water to obtain an aqueous solution. A sample solution was prepared by adding 10 g of mannitol and 2 ml of BTB solution to this aqueous solution. To this sample solution, 0.1 mol / l sodium hydroxide was dropped until the neutralization point was reached, and the boric acid content (% by weight) in the polyvinyl alcohol film was calculated from the following formula from the amount dropped.
Boric acid content (%) of polarizer = C × V × Mw / M × 100
C: Concentration of sodium hydroxide aqueous solution (mol / l)
V: Amount of dripping sodium hydroxide aqueous solution (l)
Mw: Molecular weight of boric acid (g / mol)
M: Polarizer weight (g) after drying at 120 ° C. for 2 hours
Boric acid molecular weight: 61.84

Production Example 1
<Production of polarizer>
A polyvinyl alcohol film having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% and a thickness of 75 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Next, the film was dyed while being immersed in an aqueous solution of 0.3% concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) and stretched to 3.5 times. Then, it extended | stretched so that the total draw ratio might be 6 times in the boric-acid aqueous solution of 65 degreeC density | concentration 2.5%. After extending | stretching, it dried for 3 minutes in 40 degreeC oven, and obtained PVA-type polarizer 1 (SP value 32.8, thickness 23 micrometers). The boric acid concentration of the PVA polarizer 1 was 22% by weight and the moisture content was 14% by weight.

Production Examples 2 to 4
In Production Example 1, PVA polarizers 2 to 4 were obtained in the same manner as in Production Example 1 except that the concentration of the boric acid aqueous solution was changed as shown in Table 2. Table 2 shows the boric acid concentration, moisture content, and SP value of the PVA polarizers 2 to 4.

<Transparent protective film>
Thickness 40 [mu] m, moisture permeability ^60g / m 2 / 24h acrylic resin film (SP value 22.2).
Thickness 60 [mu] m, the moisture permeability 500g ^/ m 2 ^/ 24h triacetyl cellulose (TAC) film (SP value 23.3).

≪Water vapor permeability of transparent protective film≫
The moisture permeability was measured according to a moisture permeability test (cup method) of JIS Z0208. A sample cut to a diameter of 60 mm was set in a moisture permeable cup containing about 15 g of calcium chloride, and the temperature was 40 ° C. and the humidity was 90% R.D. H. The placed in a constant temperature machine, to determine the moisture permeability by measuring the weight increase of calcium chloride before and after allowing to stand for 24 hours ^{(g / m 2 / 24h)} .

<Active energy rays>
As an active energy ray, ultraviolet rays (gallium filled metal halide lamp) Irradiation device: Fusion UV Systems, Inc. Light HAMMER10 bulb: V bulb Peak illuminance: 1600 mW / cm ² , integrated irradiation amount 1000 / mJ / cm ² (wavelength 380 to 440 nm) )It was used. In addition, the illumination intensity of the ultraviolet-ray was measured using the Sola-Check system by Solatell.

<Preparation of active energy ray-curable adhesive>
As the radically polymerizable compound (A), 38.3 parts of N-hydroxyethylacrylamide (SP value 29.6, homopolymer Tg123 ° C., manufactured by Kojin Co., Ltd.),
19.1 parts tripropylene glycol diacrylate (trade name: Aronix M-220, SP value 19.0, homopolymer Tg 69 ° C., manufactured by Toagosei Co., Ltd.) as the radical polymerizable compound (B),
As the radical polymerizable compound (C), 38.3 parts of acryloylmorpholine (SP value 22.9, homopolymer Tg 150 ° C., manufactured by Kojin Co., Ltd.) and a photopolymerization initiator (trade name: KAYACURE DETX-S, diethyl) 1.4 parts of Thioxanthone (manufactured by Nippon Kayaku Co., Ltd.) were mixed and stirred at 50 ° C. for 1 hour to obtain an active energy ray-curable adhesive.

≪Tg: Glass transition temperature≫
Tg was measured under the following measurement conditions using a TA Instruments dynamic viscoelasticity measuring device RSAIII.
Sample size: width 10mm, length 30mm,
Clamp distance 20mm,
Measurement mode: Tensile, Frequency: 1 Hz, Temperature rising rate: 5 ° C./min Dynamic viscoelasticity was measured and adopted as the temperature Tg of tan δ peak top.

Example 1
<Preparation of polarizing plate>
After forming a 0.5 μm-thick urethane-based easy-adhesive layer on the acrylic resin film, the active energy ray-curable adhesive is applied to the easy-adhesive layer with an MCD coater (manufactured by Fuji Machine Co., Ltd.). (Cell shape: honeycomb, number of gravure roll lines: 1000 / inch, rotational speed 140% / vs. Line speed) was applied so that the thickness of the adhesive layer was 0.5 μm. Subsequently, the acrylic resin film provided with the urethane-based easy-adhesive layer and the triacetyl cellulose film were bonded to both surfaces of the polarizer by a roll machine via the adhesive. Then, it heated to 50 degreeC using IR heater from both sides of the acrylic resin film and triacetyl cellulose which were bonded together, and the said ultraviolet-ray was irradiated to both surfaces, and the active energy ray hardening-type adhesive agent was hardened. Furthermore, it dried with hot air at 70 degreeC for 3 minute (s), and the polarizing plate which has a transparent protective film on both surfaces of a polarizer was obtained. The line speed of bonding was 25 m / min. The Tg of the adhesive layer was 121 ° C.

Example 2 and Comparative Examples 1 and 2
A polarizing plate was obtained in the same manner as in Example 1, except that the type of PVA polarizer was changed as shown in Table 2 in Example 1.

Comparative Example 3
<Preparation of aqueous adhesive>
Polyvinyl alcohol-based resin containing acetoacetyl group (average polymerization degree: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) to 100 parts, Under temperature conditions, an aqueous solution dissolved in pure water and adjusted to a solid content concentration of 3.7% was prepared. An aqueous adhesive solution was prepared by adding 18 parts of an aqueous colloidal alumina solution (average particle size 15 nm, solid content concentration 10%, positive charge) to 100 parts of the aqueous solution.

<Preparation of polarizing plate>
A urethane-based easy-adhesive layer having a thickness of 0.3 μm was formed on the acrylic resin film. Next, the acrylic resin film (easily adhesive layer side) is bonded to both surfaces of the PVA polarizer 3 with a roll machine through the aqueous adhesive, and then dried at 70 ° C. for 3 minutes to obtain polarized light. I got a plate. The aqueous adhesive was dropped between the polarizer and the acrylic resin film so that the adhesive layer had a thickness of 150 nm.

Comparative Example 4
In Comparative Example 3, a polarizing plate was obtained in the same manner as in Comparative Example 3, except that the PVA polarizer 3 was changed to the PVA polarizer 4.

[Evaluation]
The following evaluation was performed about the polarizing plate obtained by the Example and the comparative example. The results are shown in Table 2.

[Heating dimensional shrinkage]
About the polarizing plate obtained in each example, the sample (polarizing plate) cut into the magnitude | size of 500 mm x 50 mm was prepared for the extending | stretching axis direction as a long side. The sample was put into a heating apparatus and left in an environment of 60 ° C. for 24 hours. Thereafter, the sample was taken out from the heating apparatus and allowed to stand at room temperature, and then the length of the sample in the direction of the stretching axis was measured using a 3DCNC image measuring machine manufactured by Mitutoyo Corporation. From the measured values before and after the charging to the heating device, the heating dimensional shrinkage was calculated based on the following formula.
Dimensional shrinkage (%) = {(L ₀ −L ₁ ) / L ₁ } × 100
L ₀ : Length of the initial sample in the direction of the stretching axis L ₁ : Length of the sample in the direction of the stretching axis after standing in a heating environment

[Checking for light loss]
A liquid crystal panel on which the polarizing plate produced in each example was bonded was mounted on a liquid crystal display device. The liquid crystal display device was put in a heating device and left in an environment of 60 ° C. for 24 hours. Thereafter, the liquid crystal display device was taken out from the heating device and allowed to stand at room temperature, and then the occurrence of light leakage of the liquid crystal display device was visually confirmed according to the following criteria. In addition, the liquid crystal display device takes out the liquid crystal panel from the liquid crystal television (47 type LX9500 manufactured by LG Electronics Co., Ltd.), and after replacing the polarizing plate of the liquid crystal panel with the polarizing plate produced in each example, The returned one was used.
○: No light loss.
X: There is light loss.

About Comparative Examples 3 and 4, since the water-system adhesive agent is used, a drying process is needed and it is not preferable when improving the productivity of a polarizing plate.

Claims (11)

It is a polarizing plate that a transparent protective film is bonded to at least one surface of a polarizer via an adhesive layer,
The polarizer is a polyvinyl alcohol film in which a dichroic substance is adsorbed and oriented, and the boric acid content is 23% by weight or less.
And the said adhesive bond layer is formed by irradiating an active energy ray to the active energy ray hardening-type adhesive agent containing a radically polymerizable compound, The polarizing plate characterized by the above-mentioned.   The polarizing plate according to claim 1, wherein Tg of the adhesive layer is 60 ° C. or more. The active energy ray-curable adhesive is an active energy ray-curable adhesive containing radical polymerizable compounds (A), (B) and (C), and the total amount of the composition is 100% by weight,
20 to 60% by weight of a radically polymerizable compound (A) having an SP value of 29.0 (kJ / m ³ ) ^1/2 or more and 32.0 or less (kJ / m ³ ) ^1/2 ,
10 to 30% by weight of the radically polymerizable compound (B) having an SP value of 18.0 (kJ / m ³ ) ^1/2 or more and less than 21.0 (kJ / m ³ ) ^1/2 , and an SP value of 21 0.0 (kJ / m ³ ) ^{1/2 to} 23.0 (kJ / m ³ ) 20 to 60% by weight of the radical polymerizable compound (C) that is ^1/2 or less,
The polarizing plate according to claim 1 or 2, wherein each of the homopolymers of the radical polymerizable compounds (A), (B) and (C) has a glass transition temperature (Tg) of 60 ° C or higher.   The polarizing plate according to claim 3, wherein the radical polymerizable compound (A) is N-hydroxyethylacrylamide and / or N-methylolacrylamide.   The polarizing plate according to claim 3 or 4, wherein the radical polymerizable compound (B) is tripropylene glycol diacrylate.   The polarizing plate according to claim 3, wherein the radically polymerizable compound (C) is acryloylmorpholine and / or N-methoxymethylacrylamide. The active energy ray-curable adhesive is a compound represented by the following general formula (1) as a photopolymerization initiator;
(Wherein R ¹ and R ² represent —H, —CH ₂ CH ₃ , —iPr or Cl, and R ¹ and R ² may be the same or different). The polarizing plate as described in. As a photopolymerization initiator, a compound represented by the following general formula (2);
Wherein R ³ , R ⁴ and R ⁵ represent —H, —CH ₃ , —CH ₂ CH ₃ , —iPr or Cl, and R ³ , R ⁴ and R ⁵ may be the same or different. The polarizing plate according to claim 7, which is contained.   The polarizing plate according to claim 1, wherein the adhesive layer has a thickness of 0.01 to 7 μm.   An optical film in which at least one polarizing plate according to claim 1 is laminated. An image display device comprising the polarizing plate according to claim 1 and / or the optical film according to claim 10.