JPWO2020070962A1 - Polarizer - Google Patents

Abstract

To provide a polarizing plate containing a polarizer having a high iodine content and in which the amount of change in transmittance and edge color loss are remarkably suppressed in a high-temperature and high-humidity environment. The polarizing plate of the present invention has a polarizer, a protective film, and an adhesive layer. The polarizer is made of a polyvinyl alcohol-based resin film containing iodine, has a thickness of 5 μm or less, and has an iodine content of 12.5% by weight or more. Pressure-sensitive adhesive layer is disposed adjacent to the polarizer, the moisture permeability is not more than 300g ^/ m 2 ^/ 24hr.

Description

The present invention relates to a polarizing plate.

A polarizer is used in an image display device such as a liquid crystal display device. The polarizer is typically produced by dyeing a polyvinyl alcohol (PVA) -based resin film with a dichroic substance such as iodine (for example, Patent Documents 1 and 2). In recent years, there has been an increasing demand for thinner image display devices. Therefore, the polarizer is also required to be thinner. However, since the amount of iodine incorporated into the PVA-based resin film in the dyeing process is limited, if the polarizer is simply thinned, the ratio of iodine to PVA does not change, and the PVA-based resin film becomes thin. The iodine content is also reduced by the amount. As a result, the transmittance of the polarizer increases and the polarization characteristics deteriorate. Therefore, there is a demand for a polarizer having a higher iodine content than before. However, the polarizer having a higher iodine content has a durability problem that the optical characteristics are remarkably deteriorated in a high temperature and high humidity environment. More specifically, in a polarizer, the polarization performance at the end may be lost in a high temperature and high humidity environment, and a phenomenon of so-called edge color loss may occur.

Japanese Patent No. 5048120 Japanese Unexamined Patent Publication No. 2013-156391

The present invention has been made to solve the above problems, and its main purpose is to include a polarizing element having a high iodine content, and to significantly change the transmittance and color loss at the edges in a high temperature and high humidity environment. The purpose is to provide a suppressed polarizing plate.

The polarizing plate of the present invention has a polarizer, a protective film, and an adhesive layer. The polarizer is made of a polyvinyl alcohol-based resin film containing iodine, has a thickness of 5 μm or less, and has an iodine content of 12.5% by weight or more. Adhesive layer is disposed adjacent to the polarizer, the moisture permeability is not more than 300g ^/ m 2 ^/ 24hr.
In one embodiment, the polarizing plate has a transmittance change of less than 2.5% and an edge color loss of 800 μm or less after being held at 60 ° C. and 90% RH for 500 hours. Is.
In one embodiment, the pressure-sensitive adhesive layer is composed of an active energy ray-crosslinked rubber-based pressure-sensitive adhesive composition containing polyisobutylene.

According to the present invention, by arranging the pressure-sensitive adhesive layer having a predetermined moisture permeability adjacent to the polarizer, the iodine content is significantly higher than that of the conventional polarizing element (typically, the iodine content). (12.5% by weight or more) can also be used to obtain a polarizing plate in which a change in transmittance and edge color loss in a high temperature and high humidity environment are remarkably suppressed.

It is the schematic sectional drawing of the polarizing plate by one Embodiment of this invention. It is a schematic diagram for demonstrating the calculation of the edge color loss amount.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Overall Configuration of Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 100 of the illustrated example has a polarizing element 10, a protective film 20 arranged on at least one side of the polarizing element 10, and an adhesive layer 30 arranged on the opposite side of the polarizing element 10 from the protective film 20. .. By arranging the polarizer and the pressure-sensitive adhesive layer adjacent to each other (without interposing another layer or film) as shown in the illustrated example, the barrier function of the pressure-sensitive adhesive layer deformed in a high-temperature and high-humidity environment is good. Can be demonstrated. The barrier function of the adhesive layer will be described later. In the embodiment of the present invention, the polarizer is composed of a PVA-based resin film containing iodine, the thickness thereof is 5 μm or less, and the iodine content thereof is 12.5% by weight or more. Further, in the embodiment of the present invention, the moisture permeability of the adhesive layer is not more than 300g ^/ m 2 ^/ 24hr. That is, the pressure-sensitive adhesive layer has a barrier function. As used herein, the term "having a barrier function" means controlling the amount of oxygen and / or water vapor permeating into the polarizer to substantially block the polarizer from them. When the polarizer contains a high concentration of iodine and its thickness is very thin, the stability of iodine is likely to be significantly reduced due to the intrusion of water in a high temperature and high humidity environment. Therefore, by using the adhesive layer having a specific moisture permeability as described above and arranging it adjacent to the polarizer, a polarizing plate capable of maintaining excellent optical characteristics even in a high temperature and high humidity environment can be obtained. Can be done. More specifically, it is possible to obtain a polarizing plate in which the change in transmittance and the color loss at the edges are remarkably suppressed.

The polarizing plate according to the embodiment of the present invention has a transmittance change amount of preferably less than 2.5%, more preferably less than 2.0% after being held in a 60 ° C. and 90% RH environment for 500 hours. , More preferably less than 1.7%. The lower limit of the amount of change in transmittance is preferably zero, and in one embodiment it is 0.1%. Further, the polarizing plate according to the embodiment of the present invention has an edge color loss amount of preferably 800 μm or less, more preferably 700 μm or less, and further preferably 700 μm or less after being held in an environment of 60 ° C. and 90% RH for 500 hours. Is 500 μm or less, particularly preferably 400 μm or less, and most preferably 300 μm or less. The lower limit of the amount of edge color loss is preferably zero, and in one embodiment it is 10 μm. The amount of color loss at the end can be calculated as follows: A test piece of a predetermined size having two sides facing each other in the absorption axis direction and the direction orthogonal to the absorption axis is cut out from the polarizing plate. The absorption axis direction typically corresponds to the stretching direction in the production of the polarizer. The stretching direction may correspond to, for example, the elongated direction (conveying direction (MD direction)) or the width direction (TD direction) of the polarizing plate. Next, the test piece is attached to a glass plate via the adhesive layer of the test piece, and this is left in an oven at 60 ° C. and 90% RH for 500 hours to heat and humidify. When the test piece after heat and humidification is placed in the state of a standard polarizing plate and cross Nicol, the state of color loss at the end of the test piece after heat and humidification is examined with a microscope. Specifically, the size of color loss (color loss amount: μm) from the end of the test piece (polarizing plate or polarizer) is measured. As shown in FIG. 2, the length of the region where the color is removed from the corner of the test piece is defined as the amount of color loss at the end. The decolorized region has extremely low polarization characteristics and does not substantially function as a polarizing plate. Therefore, the smaller the amount of color loss, the more preferable. The transmittance (typically, the single transmittance) and the amount of color loss at the end are substantially the characteristics of the polarizer, but the components other than the polarizer in the polarizing plate are the transmittance and the amount of color loss at the end. Since it does not substantially affect the amount, the transmittance and the amount of color loss at the edge of the polarizer are substantially the same as the transmittance and the amount of color loss at the edge of the polarizing plate.

As described above, the polarizing plate according to the embodiment of the present invention has a small amount of color loss at the edges in a high temperature and high humidity environment. The suppression of such edge color loss will be described. First, the polarizer in the present invention has an iodine content of 12.5% by weight or more. In addition, in this specification, "iodine content" means the amount of all iodine contained in a polarizer (PVA-based resin film). More specifically, iodine may be present in the polarizer in the form of ^{I −} , I ₂ , I ₃ ⁻ , I ₅ ^{− and the like.} The iodine content in the present specification means the iodine content including all of these forms. The iodine content can be measured by the method described in Examples. Specifically, it can be calculated by the following formula from the fluorescent X-ray intensity (kcps) by the fluorescent X-ray analysis and the thickness (μm) of the film (polarizer).
(Iodine content) = 18.2 x (fluorescent X-ray intensity) / (film thickness)
The fluorescent X-ray intensity per unit thickness of the polarizer is, for example, 0.50 kcps / μm or more, preferably 0.65 kcps / μm or more. If the fluorescent X-ray intensity per unit thickness is in the above range, even a thin polarizing element having a polarizer of 5 μm or less contains sufficient iodine to function as a polarizer.
The high iodine content in the polarizer means that even a small amount of water vapor invades reduces the stability of iodine, and in particular, iodine existing in the form of _{I 2} , I ₃ ⁻ , I ₅ ^{−, etc. is destroyed.} This means that it will typically be in the I ^{− state.} Iodine in the I ⁻ state does not absorb light in the visible light region, so that the polarization function is impaired. If this situation affects the entire polarizing plate, the transmittance of the polarizing plate changes. On the other hand, since the invasion of water vapor typically occurs from the end of the polarizing plate, the polarization characteristics deteriorate in the form of color loss at the end of the polarizing plate.
Further, the thickness of the polarizer in the present invention is 5 μm or less as described above. Since the polarizer in the present invention is very thin as compared with the conventional polarizer obtained by stretching a PVA film, there is little invasion of moisture from the polarizer end, which causes iodine to be destroyed in high temperature and high humidity. .. As a result, in a thin polarizing element having a thickness of 5 μm or less, the invasion of water from the adhesive adjacent to the polarizer becomes dominant and iodine in the polarizer is destroyed. According to the embodiment of the present invention, the pressure-sensitive adhesive layer is controlled to function as a barrier layer, and the amount of water vapor permeating into the polarizer is controlled to substantially protect the polarizer from water vapor. Becomes possible. As a result, color loss at the edges is remarkably suppressed. Therefore, it is critical that the polarizing element has a thickness equal to or less than a predetermined value (thin polarizing element), and by using such a thin polarizing element, the pressure-sensitive adhesive layer can be used without separately providing a barrier layer. The end face of the polarizer can be protected from oxygen and / or water vapor. Further, by adjusting the constituent material and / or the property of the pressure-sensitive adhesive layer, the end face of the polarizer can be covered better.

The polarizing plate according to the embodiment of the present invention may be arranged on the viewing side of the display panel, may be arranged on the side opposite to the viewing side, and a pair of polarizing plates according to the embodiment of the present invention are arranged on both sides. May be good.

B. Polarizer B-1. Structure of Polarizer As described above, the polarizer 10 is composed of a PVA-based resin film containing iodine. The polarizer may contain an iron element, a sulfur element, a zinc element, a boron element, a potassium element and the like. These elements can be contained in the polarizer due to the method for producing the polarizer described later. Only one of these elements may be contained, or two or more of these elements may be contained.

As the PVA-based resin forming the PVA-based resin film, any suitable resin can be adopted. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be mentioned. Polyvinyl alcohol is obtained by saponification of polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. .. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the intended purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 5000, and more preferably 1500 to 4500. The average degree of polymerization can be determined according to JIS K 6726-1994.

As mentioned above, the polarizer contains iodine. The polarizer is substantially a PVA-based resin film in which iodine is adsorption-oriented. The iodine content of the polarizer is 12.5% by weight or more, preferably 14% by weight or more, more preferably 16% by weight or more, still more preferably 20% by weight or more, as described above. The iodine content is, for example, 60% by weight or less. The iodine content can be, for example, 12.5% by weight to 30.0% by weight. The boric acid content of the polarizer is, for example, 5.0% by weight to 25% by weight.

As mentioned above, the polarizer may contain an element of iron. When the polarizer contains an iron element, the humidification durability of the polarizer can be improved. Polarizers with a high iodine content may have problems with humidification durability in high temperature humidified environments such as 65 ° C. and 90% RH. Is preferable. The iron content of the polarizer is preferably 500 ppm or more, more preferably 750 ppm or more. When the iron content of the polarizer is in the above range, the humidification durability of the polarizer can be improved. The iron content of the polarizer can be, for example, 10000 ppm or less. In the case of a polarizer having a thickness of 5 μm or less, the iron content of the polarizer is within the above range, so that a polarizer having good transmittance and degree of polarization and excellent humidification durability can be obtained. Can be done. The iron content of the polarizer can be measured by ICP-MS.

The thickness of the PVA-based resin film (polarizer) is 5 μm or less, preferably 2.5 μm or less, more preferably 2 μm or less, and further preferably 1.5 μm or less as described above. On the other hand, the thickness of the PVA-based resin film is preferably 0.6 μm or more, more preferably 1.0 μm or more.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizer is preferably 35.0% to 46.0%, more preferably 38.0% to 43.0%. The degree of polarization of the polarizer is preferably 99.0% or more, more preferably 99.9% or more. According to the present invention, such excellent optical characteristics (excellent balance between simple substance transmittance and degree of polarization) and excellent durability (which can maintain such excellent optical characteristics even in a high temperature and high humidity environment). It is possible to achieve both.

B-2. Method for Producing Polarizer A polarizer can be produced, for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step, a cross-linking step, a stretching step, a washing step, and a drying step. In one embodiment, the PVA-based resin film may be a PVA-based resin layer formed on a substrate. The laminate of the base material and the resin layer can be obtained, for example, by a method of applying the coating liquid containing the PVA-based resin to the base material, a method of laminating a PVA-based resin film on the base material, or the like. As the base material, any suitable resin base material can be used, and for example, a thermoplastic resin base material can be used. Each step is performed at an arbitrary appropriate timing. Further, if necessary, any step other than the dyeing step may be omitted, a plurality of steps may be performed at the same time, and each step may be performed a plurality of times. Hereinafter, each step will be described.

B-2-1. Swelling step The swelling step is usually performed before the dyeing step. The swelling step may be performed together with the dyeing step in the same immersion bath. The swelling step is performed, for example, by immersing a PVA-based resin film in a swelling bath. As the swelling bath, any suitable liquid can be used, and for example, water such as distilled water or pure water is used. The swelling bath may contain any suitable other ingredients other than water. Examples of other components include solvents such as alcohol, additives such as surfactants, and iodides. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. And so on. Preferably, potassium iodide is used. The temperature of the swelling bath is, for example, 20 ° C to 45 ° C. The immersion time is, for example, 10 seconds to 300 seconds.

B-2-2. Stretching Step In the stretching step, the PVA-based resin film is stretched at an arbitrary appropriate stretching ratio according to the desired performance and thickness. The stretching method may be uniaxial stretching or biaxial stretching. Typically, the PVA-based resin film is uniaxially stretched 3 to 7 times the original length. The stretching direction may be the longitudinal direction of the film (MD direction) or the width direction of the film (TD direction). The stretching method may be dry stretching, wet stretching, or a combination of these. Further, the PVA-based resin film may be stretched when performing a crosslinking step, a swelling step, a dyeing step, or the like. The stretching direction may correspond to the absorption axis direction of the obtained polarizer.

B-2-3. Dyeing Step In the dyeing step, the PVA-based resin film is dyed with a dyeing solution containing a dichroic substance. The dichroic substance is typically iodine. In one embodiment, the staining solution comprises an oxidizing agent for polyiodine ions, iodide and iodine ions. As the oxidizing agent, for example, an ionic compound composed of a cation and an anion is used. As the ionic compound, preferably, an ionic compound in which the standard electrode potential of either anion or cation is larger than the standard electrode potential of iodine ion is used.

The content of iodide contained in the dyeing solution is preferably 1 part by weight to 40 parts by weight, and more preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. As the iodide, those exemplified in the above swelling step can be used. Potassium iodide is preferred.

When an ionic compound composed of a cation and an anion is used as the oxidizing agent, the standard electrode potential of the anion or cation is preferably larger than the standard electrode potential of iodine ion (0.536V). The standard electrode potential of the anion or cation is preferably 0.55 V or higher, more preferably 0.60 V or higher. This is because it can function suitably as an oxidizing agent. The standard electrode potential of the anion or cation is, for example, 2.00 V or less.

Examples of the anion or cation include Fe ³⁺ (0.771V), Ag ⁺ (0.7991V), Ag ²⁺ (1.980V), Au ⁺ (1.83V), Au ³⁺ (1.52V), Co. ^{3+ (1.92V), Cu 2+ (} 0.559V), Mn 3+ (1.5V), Pt 2+ (1.188V) such _{^{cations, Br 3- (1.0503V), ClO}} 3 - (0.622V _{^{), ClO 2 - (0.681V)}} , ClO - (0.890V), Cr 2 O 7 2- (1.36V), NO 3 - (0.835V, 0.94V, 0.9557V), MnO 4 ⁻ (0.56V) and other anions can be mentioned. It is preferably a trivalent iron ion (Fe ³⁺ ). The trivalent iron ion is present in the dyeing solution as a divalent iron ion after oxidizing the iodine ion. The trivalent iron ion and the divalent iron ion can be incorporated into the PVA-based resin film in the dyeing step. These iron ions have the effect of dehydrating PVA. Therefore, it is possible to suppress the action of polyiodine ions coming out of the PVA-based resin film in the subsequent steps. As a result, it is possible to provide a polarizer having improved humidification durability. In the present specification, the standard electrode potential refers to a value in an aqueous solution having a standard pressure of 1 atm and 25 ° C. The standard electrode potential in an aqueous solution having a standard pressure of 1 atm and 25 ° C. is described in, for example, Maruzen Publishing Co., Ltd., edited by the Electrochemical Society, 6th Edition, Electrochemical Handbook. In this specification, the values described in the above electrochemical manual are used.

As the oxidizing agent, any suitable compound can be used as long as it is an ionic compound in which an electrode reaction at a desired standard electrode potential occurs in the dyeing solution. ^{For example, compounds containing Fe 3+} as a cation such as ferric sulfate, ferric chloride and ferric nitrate, compounds containing MnO ₄ ^{− as anions such as potassium permanganate, and Cu 2+} such as copper chloride and copper sulfate. Examples thereof include compounds containing the above as a cation. Since ^{it contains Fe 3+} , it is preferable to use at least one compound selected from the group consisting of ferric sulfate, ferric chloride, and ferric nitrate. Only one kind of oxidizing agent may be used, or two or more kinds may be used in combination.

The content of the oxidizing agent in the dyeing solution is preferably 0.1 parts by weight to 10 parts by weight, and more preferably 0.5 parts by weight to 4 parts by weight with respect to 100 parts by weight of the solvent. The content of the oxidizing agent in the dyeing solution can be determined according to the content of iodide contained in the dyeing solution.

The molar ratio of iodide to the oxidizing agent can be set to any suitable value, for example, 2/1 to 50/1, preferably 10/1 to 50/1. When the molar ratio of iodide to the oxidizing agent is within the above range, the oxidizing agent can sufficiently function as an oxidizing agent for iodine ions.

As the solvent of the dyeing solution, any suitable solvent can be used, and water is usually used.

The staining solution may contain any other suitable compound other than the iodide and the oxidizing agent. For example, the staining solution may further contain iodine. When the dyeing solution further contains iodine, the iodine content in the dyeing solution is, for example, 1 part by weight or less with respect to 100 parts by weight of the solvent. When the dyeing solution does not contain an oxidizing agent, the iodine content is, for example, 1 part by weight to 10 parts by weight with respect to 100 parts by weight of the solvent.

Examples of the dyeing method include a method of immersing the PVA-based resin film in the dyeing solution, a method of applying the dyeing solution to the PVA-based resin film, a method of spraying the dyeing solution onto the PVA-based resin film, and the like. .. Since it can be dyed well, it is preferably a method of immersing a PVA-based resin film in a dyeing solution.

The liquid temperature at the time of dyeing the dyeing solution can be set to any appropriate value, for example, 20 ° C. to 50 ° C. When the PVA-based resin film is immersed in the dyeing solution, the immersion time is, for example, 1 second to 1 minute.

B-2-4. Cross-linking step In the cross-linking step, a boron compound is usually used as a cross-linking agent. Examples of the boron compound include boric acid and borax. Preferably, it is boric acid. In the cross-linking step, the boron compound is usually used in the form of an aqueous solution.

When an aqueous boric acid solution is used, the boric acid concentration of the aqueous boric acid solution is, for example, 0.5% by weight to 15% by weight, preferably 1% by weight to 5% by weight. The boric acid aqueous solution may further contain an iodide such as potassium iodide and a zinc compound such as zinc sulfate and zinc chloride.

The cross-linking step can be performed by any suitable method. For example, a method of immersing a PVA-based resin film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to a PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound onto a PVA-based resin film can be mentioned. Be done. It is preferable to immerse in an aqueous solution containing a boron compound.

The temperature of the solution used for crosslinking is, for example, 25 ° C. or higher, preferably 30 ° C. to 85 ° C., and more preferably 40 ° C. to 70 ° C. The immersion time is, for example, 5 seconds to 800 seconds, preferably 8 seconds to 500 seconds.

B-2-5. Cleaning step The cleaning step is performed using water or an aqueous solution containing the above-mentioned iodide. Typically, this is done by immersing a PVA-based resin film in an aqueous potassium iodide solution. The temperature of the aqueous solution in the washing step is, for example, 5 ° C to 50 ° C. The immersion time is, for example, 1 second to 300 seconds.

B-2-6. Drying Step The drying step can be carried out by any suitable method. For example, natural drying, blast drying, vacuum drying, heat drying and the like can be mentioned, and heat drying is preferably used. When heat drying is performed, the heating temperature is, for example, 30 ° C. to 100 ° C. The drying time is, for example, 10 seconds to 10 minutes.

C. Protective film The protective film 20 is composed of any suitable film that can be used as a protective film for the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polysulfone-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

In the embodiment of the present invention, the resin base material used in the production of the polarizing plate may be used as it is as the protective film.

If necessary, the protective film may be subjected to surface treatment such as hard coating treatment, antireflection treatment, anti-sticking treatment, and anti-glare treatment. Further, a brightness improving film such as a reflective polarizer may be used as the protective film.

As the thickness of the protective film, any appropriate thickness can be adopted as long as the effects of the present invention can be obtained. The thickness of the protective film is, for example, 20 μm to 60 μm. When the surface treatment is applied, the thickness of the protective film is the thickness including the thickness of the surface treatment layer.

D. Adhesive layer D-1. 40 ° C. Characteristics adhesive layer of the pressure-sensitive adhesive layer, a water vapor transmission rate of at 90% RH conditions (moisture permeability), for example 300 g ^/ m and a 2/24 hr or less, preferably be less than 100g ^/ m 2 ^/ 24hr , more preferably not more than ^50g / m 2 / 24hr, more preferably not more than ^25g / m 2 / 24hr. The lower limit of the moisture permeability, for example, 0.01g ^/ m 2 ^/ 24hr, and preferably below the detection limit. When the moisture permeability of the pressure-sensitive adhesive layer is within such a range, the pressure-sensitive adhesive layer can be well protected from moisture and oxygen in the air by arranging the pressure-sensitive adhesive layer preferably adjacent to the polarizer. As a result, the optical characteristics of the polarizing plate can be maintained even in a high temperature and high humidity environment, and the durability of the polarizing plate can be improved. More specifically, it is possible to obtain a polarizing plate in which color loss in the absorption axis direction is remarkably suppressed in a high temperature and high humidity environment. The moisture permeability can be measured according to JIS Z0208.

The gel fraction of the pressure-sensitive adhesive layer is preferably 10% to 98%, more preferably 25% to 98%, still more preferably 45% to 90%, and particularly preferably 60% to 85%. be. When the gel fraction is in such a range, both durability and adhesive strength can be achieved.

The thickness of the pressure-sensitive adhesive layer is, for example, 10 μm to 100 μm, preferably 15 μm to 70 μm, and more preferably 20 μm to 55 μm. With such a thickness, a desired moisture permeability can be achieved.

D-2. Constituent Material of Adhesive Layer The adhesive layer may be composed of any suitable material as long as the above-mentioned properties can be satisfied. The constituent material is typically a rubber-based pressure-sensitive adhesive composition, and more specifically, an active energy ray-crosslinked rubber-based pressure-sensitive adhesive composition containing polyisobutylene. Hereinafter, the constituent components of the rubber-based pressure-sensitive adhesive composition will be described.

D-2-1. Polyisobutylene and other polymer components Polyisobutylene is a homopolymer of isobutylene, and for example, a commercially available product such as OPPANOL manufactured by BASF can be used. In the embodiment of the present invention, since polyisobutylene containing no double bond in the main chain is used, a pressure-sensitive adhesive layer having excellent weather resistance can be formed.

The weight average molecular weight (Mw) of polyisobutylene is preferably 100,000 or more, more preferably 300,000 or more, still more preferably 600,000 or more, and particularly preferably 700,000 or more. On the other hand, the weight average molecular weight is preferably 5 million or less, more preferably 3 million or less, and further preferably 2 million or less. By setting the weight average molecular weight of polyisobutylene to 100,000 or more, a rubber-based pressure-sensitive adhesive composition having more excellent durability during high-temperature storage can be obtained.

The content of polyisobutylene in the rubber-based pressure-sensitive adhesive composition is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight, based on the total solid content of the rubber-based pressure-sensitive adhesive composition. % Or more, particularly preferably 80% by weight or more, particularly preferably 85% by weight or more, and most preferably 90% by weight or more. On the other hand, the content of polyisobutylene is preferably 99% by weight or less, and more preferably 98% by weight or less. When the content of polyisobutylene is in such a range, a pressure-sensitive adhesive layer having a desired moisture permeability can be formed.

The rubber-based pressure-sensitive adhesive composition may contain a polymer component (typically, a polymer or an elastomer) other than polyisobutylene, depending on the purpose and desired properties. Specific examples include copolymers of isobutylene and normal butylene, copolymers of isobutylene and isoprene (for example, butyl rubbers such as regular butyl rubber, chlorinated butyl rubber, brominated butyl rubber, and partially crosslinked butyl rubber), and sulfides thereof. Isobutylene-based polymers such as substances and modified products (for example, those modified with functional groups such as hydroxyl group, carboxyl group, amino group, epoxy group); styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene -Sterene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-propylene-styrene block copolymer (separates of SEPS, SIS), styrene-ethylene-propylene block Styrene-based heat such as copolymers (SEP, hydrogenated styrene-isoprene block copolymer), styrene-isobutylene-styrene block copolymers (SIBS), styrene-based block copolymers such as styrene-butadiene rubber (SBR), etc. Plastic elastomers; butyl rubber (IIR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), EPR (binary ethylene-propylene rubber), EPT (ternary ethylene-propylene rubber), acrylic rubber, urethane rubber, Polyurethane-based thermoplastic elastomers; Polyester-based thermoplastic elastomers; Blend-based thermoplastic elastomers such as polymer blends of polypropylene and EPT (ternary ethylene-propylene rubber) can be mentioned. The content of such a polymer component is preferably 10 parts by weight or less with respect to 100 parts by weight of polyisobutylene.

D-2-2. Hydrogen Extraction Type Photopolymerization Initiator A hydrogen extraction type photopolymerization initiator extracts hydrogen from polyisobutylene by irradiating it with active energy rays without cleaving the initiator itself to generate a reaction point, and the reaction point is used. , Initiates the cross-linking reaction of polyisobutylene.

Examples of the hydrogen abstraction type photopolymerization initiator include acetophenone, benzophenone, methyl-4-phenylbenzophenone o-benzoylbenzoate, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4,4'-dimethoxybenzophenone, 4,4. '-Dichlorobenzophenone, 4,4'-dimethylbenzophenone, 4-benzoyl-4'-methyl-diphenylsulfide, acrylicized benzophenone, 3,3', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, Benzophenone compounds such as 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone; 4, Aminobenzophenone compounds such as 4'-bis (dimethylamino) benzophenone, 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacrydone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, camphor Kinones and the like; aromatic ketone compounds such as acetonafton and 1-hydroxycyclohexylphenyl ketone; aromatic aldehydes such as terephthalaldehyde, and quinone-based aromatic compounds such as methylanthraquinone can be mentioned. These may be used alone or in combination of two or more. Among these, benzophenone compounds are preferable, and benzophenone is more preferable, from the viewpoint of reactivity.

The content of the hydrogen abstraction type photopolymerization initiator is preferably 0.001 part by weight to 10 parts by weight, more preferably 0.005 part by weight to 10 parts by weight, based on 100 parts by weight of polyisobutylene. More preferably, it is 0.01 parts by weight to 10 parts by weight. When the content of the hydrogen abstraction type photopolymerization initiator is in such a range, the crosslinking reaction can proceed to the desired density.

D-2-3. Polyfunctional Radical Polymerizable Compound The rubber-based pressure-sensitive adhesive composition may further contain a polyfunctional radical polymerizable compound. The polyfunctional radically polymerizable compound can function as a cross-linking agent for polyisobutylene.

A polyfunctional radically polymerizable compound is a compound having at least two radically polymerizable functional groups having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group. Specific examples of the polyfunctional radical polymerizable compound include tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol. Di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 2-ethyl-2-butylpropanediol di (meth) acrylate, bisphenol A di (meth) acrylate, bisphenol A ethylene oxide adduct di (meth) acrylate ) Acrylate, bisphenol A propylene oxide adduct Di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, neopentyl glycol di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, dioxane glycol Di (meth) acrylate, trimethylolpropantri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, EO Examples thereof include esterified products of (meth) acrylic acid and polyhydric alcohol such as modified diglycerin tetra (meth) acrylate, and 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene. These may be used alone or in combination of two or more. Among these, esterified products of (meth) acrylic acid and polyhydric alcohol are preferable from the viewpoint of compatibility with polyisobutylene, and bifunctional (meth) acrylates and (meth) acryloyl groups having two (meth) acryloyl groups are preferable. A trifunctional (meth) acrylate having three or more of the above is more preferable, and tricyclodecanedimethanol di (meth) acrylate and trimethylolpropane tri (meth) acrylate are particularly preferable.

The content of the polyfunctional radically polymerizable compound is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and further preferably 10 parts by weight or less with respect to 100 parts by weight of polyisobutylene. On the other hand, the content of the polyfunctional radically polymerizable compound is preferably 0.1 part by weight or more, more preferably 0.5 part by weight or more, still more preferably 1 part by weight, based on 100 parts by weight of polyisobutylene. It is more than a part. When the content of the polyfunctional radically polymerizable compound is in such a range, a pressure-sensitive adhesive layer having excellent durability can be formed.

The molecular weight of the polyfunctional radically polymerizable compound is, for example, 1000 or less, preferably 500 or less.

D-2-4. Adhesive Adhesive The rubber-based adhesive composition may further contain a tackifier. By containing the tackifier, it is possible to form a pressure-sensitive adhesive layer having high adhesiveness to an adherend (for example, a polarizer or a protective film) and high durability even in a high temperature environment. can. Specific examples of the tackifier include a tackifier containing a terpene skeleton, a tackifier containing a rosin skeleton, and hydrogenated products thereof.

Examples of the tackifier containing a terpene skeleton include terpene polymers such as α-pinene polymer, β-pinene polymer, and dipentene polymer, and terpene polymers modified (phenolic modification, styrene modification, aromatic modification). , Hydrogen addition modification, hydrocarbon modification, etc.) Modified terpene resin and the like. Examples of the modified terpene resin include a terpene phenol resin, a styrene modified terpene resin, an aromatic modified terpene resin, and a hydrogenated terpene resin (hydrogenated terpene resin). Here, the hydrogenated terpene resin includes a hydride of a terpene polymer and a hydrogenated product of another modified terpene resin and a terpene phenol resin. Among these, a hydrogenated terpene phenol resin is preferable from the viewpoint of compatibility with the rubber-based pressure-sensitive adhesive composition and adhesive properties.

Examples of the tackifier containing a rosin skeleton include a rosin resin, a polymerized rosin resin, a hydrogenated rosin resin, a rosin ester resin, a hydrogenated rosin ester resin, and a rosin phenol resin. Specifically, unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, hydrogenated, disproportionated, polymerized, and other chemically modified modified rosins, and derivatives thereof. Can be used.

When the tackifier is a hydrogenated additive, it may be a partially hydrogenated partially hydrogenated additive, or a completely hydrogenated additive in which all the double bonds in the compound are hydrogenated. You may. Completely hydrogenated additives are preferred from the standpoint of adhesive properties, weather resistance and hue.

The tackifier preferably contains a cyclohexanol skeleton from the viewpoint of tack property. Although the detailed principle is unknown, it is considered that the cyclohexanol skeleton has a better balance of compatibility with the base polymer polyisobutylene than the phenol skeleton. As the tackifier containing a cyclohexanol skeleton, for example, a hydrogenated product such as a terpenephenol resin or a rosinphenol resin is preferable, and a completely hydrogenated additive such as a terpenephenol resin or a rosinphenol resin is more preferable.

The softening point (softening temperature) of the tackifier is preferably 80 ° C. or higher, more preferably 100 ° C. or higher. On the other hand, the softening point of the tackifier is preferably 200 ° C. or lower, more preferably 180 ° C. or lower. When the softening point of the pressure-sensitive adhesive is within such a range, it is possible to obtain a pressure-sensitive adhesive composition that can maintain the pressure-sensitive properties even at a high temperature and does not cause problems such as whitening. The softening point of the tackifier resin is defined as a value measured by the softening point test method (ring ball method) specified in any of JIS K5902 and JIS K2207.

The weight average molecular weight (Mw) of the tackifier is preferably 50,000 or less, more preferably 30,000 or less, still more preferably 10,000 or less, particularly preferably 8,000 or less, and particularly preferably 5,000. It is as follows. On the other hand, the weight average molecular weight of the tackifier is preferably 500 or more, more preferably 1000 or more, and further preferably 2000 or more. When the weight average molecular weight of the tackifier is in such a range, the compatibility with polyisobutylene is good, and problems such as whitening can be suppressed.

The amount of the tackifier added is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 20 parts by weight or less with respect to 100 parts by weight of polyisobutylene. On the other hand, the amount of the tackifier added is preferably 0.1 part by weight or more, more preferably 1 part by weight or more, and further preferably 5 parts by weight or more. When the content of the tackifier is in such a range, the desired tack property can be realized.

The rubber-based pressure-sensitive adhesive composition may contain a pressure-sensitive adhesive other than the above-mentioned pressure-sensitive adhesive. Examples of the tackifier include petroleum resin-based tackifiers. Examples of the petroleum-based tackifier include aromatic petroleum resins, aliphatic petroleum resins, alicyclic petroleum resins (aliphatic cyclic petroleum resins), aliphatic / aromatic petroleum resins, and aliphatic / alicyclic petroleum resins. Examples thereof include group-based petroleum resins, hydrogenated petroleum resins, kumaron-based resins, and kumaron-inden-based resins. The petroleum resin-based tackifier can be used at a ratio of, for example, 30 parts by weight or less with respect to 100 parts by weight of polyisobutylene.

D-2-5. Other Additives The rubber-based pressure-sensitive adhesive composition may contain any suitable additive other than the above. Specific examples of the additive include a diluent (for example, an organic solvent such as toluene, xylene, n-heptane, and dimethyl ether), a softening agent, a cross-linking agent (for example, a polyisocyanate, an epoxy compound, and an alkyl etherified melamine compound), and a filling. Examples thereof include agents, anti-aging agents, ultraviolet absorbers, anti-static agents, and rework improvers. The type, combination, addition amount, and the like of the additives added to the rubber-based pressure-sensitive adhesive composition can be appropriately set according to the purpose. The content (total amount) of the additive in the rubber-based pressure-sensitive adhesive composition is preferably 30% by weight or less, more preferably 20% by weight or less, and further preferably 10% by weight or less.

D-3. Formation of a pressure-sensitive adhesive layer The pressure-sensitive adhesive layer can be formed by irradiating a rubber-based pressure-sensitive adhesive composition with active energy rays to crosslink polyisobutylene. The specific procedure is as follows.

In one embodiment, the pressure-sensitive adhesive layer can be formed directly on the surface of the polarizer or protective film. In this case, first, the rubber-based pressure-sensitive adhesive composition is applied to the polarizer surface of the laminate of the protective film 20 / polarizer 10. As the coating method, any suitable method can be adopted. Specific examples include roll coats, kiss roll coats, gravure coats, reverse coats, roll brushes, spray coats, dip roll coats, bar coats, knife coats, air knife coats, curtain coats, lip coats, die coaters, and other extrusion coats. The law can be mentioned.

The coating layer is then dried, if necessary. By drying, volatile components (eg, diluents) in the coating layer can be removed. The drying temperature can be appropriately set according to the purpose, the drying time, and the like. The drying temperature is, for example, 30 ° C. to 90 ° C., preferably 60 ° C. to 80 ° C. The drying time can be appropriately set according to the purpose, the drying temperature, and the like. The drying time is, for example, 5 seconds to 20 minutes, preferably 30 seconds to 10 minutes, and more preferably 1 minute to 8 minutes.

Next, if necessary, the dried coating layer is irradiated with active energy rays. Examples of the active energy ray include visible light, ultraviolet light, and electron beam. Ultraviolet rays are preferred. The ultraviolet irradiation conditions can be set to any appropriate conditions according to the composition of the rubber-based pressure-sensitive adhesive composition, the desired properties of the pressure-sensitive adhesive layer, and the like. For example, the irradiation integrated light quantity of ultraviolet rays is preferably ^{100mJ / cm 2 ~2000mJ / cm 2} .

In another embodiment, the pressure-sensitive adhesive layer may be formed on any suitable support and then transferred to the polarizer surface. A typical example of the support is a separator. The procedure for forming the adhesive on the support is as described above.

As described above, the pressure-sensitive adhesive layer can be formed.

E. Applications of Polarizing Plate The polarizing plate according to the embodiment of the present invention is suitably used for an image display device. Examples of the image display device include a liquid crystal display device, an organic electroluminescence (EL) display device, and a quantum dot display device.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" are based on weight.

(1) Thickness The thickness of the polarizer was measured using a spectroscopic film thickness meter (manufactured by Otsuka Electronics Co., Ltd., trade name "MCPD-3000"). The thickness of the components other than the polarizer in the polarizing plate was measured using a digital micrometer (KC-351C manufactured by Anritsu Corporation).
(2) Moisture Permeability Using the pressure-sensitive adhesive compositions prepared in Examples and Comparative Examples, a pressure-sensitive adhesive sheet having a thickness of 50 μm was formed according to the method described in Examples. One of the release liners of the adhesive sheet is peeled off to expose the adhesive surface, and the adhesive sheet is attached to a triacetyl cellulose film (TAC film, thickness: 25 μm, manufactured by Konica Minolta Co., Ltd.) through the adhesive surface, and is 10 cmΦ. It was cut out in the shape of a circle. Finally, the other release liner was peeled off to obtain a measurement sample. The moisture permeability (water vapor permeability) of the obtained measurement sample was measured by a moisture permeability test method (cup method, according to JIS Z 0208). The measurement conditions were as follows. In addition, a constant temperature and humidity chamber was used for the measurement.
Measurement temperature: 40 ° C
Relative humidity: 92%
Measurement time: 24 hours (3) Iodine content Fluorescent X-ray analyzer (manufactured by Rigaku Co., Ltd., trade name "ZSX-PRIMUS II") was measured for the polarizers of the laminates obtained in Examples, Comparative Examples and Reference Examples. The fluorescent X-ray intensity (kcps) was measured using a diameter (diameter: ψ20 mm). The iodine content (% by weight) was determined from the obtained fluorescent X-ray intensity and the thickness of the polarizer using the following formula.
(Iodine content) = 18.2 x (fluorescent X-ray intensity) / (polarizer thickness)
The coefficient for calculating the iodine content differs depending on the measuring device, but the coefficient can be obtained by using an appropriate calibration curve.
(4) Amount of color loss at the edges From the polarizing plates obtained in Examples and Comparative Examples, test pieces (50 mm × 50 mm) having two sides opposite to each other in the direction orthogonal to the stretching direction and the stretching direction were cut out. The test piece is attached to non-alkali glass via the adhesive layer of the test piece, left in an oven at 60 ° C. and 90% RH for 500 hours to heat and humidify, and placed in the state of a standard polarizing plate and cross Nicol. The state of color loss at the end of the polarizer after heating and humidification was examined with a microscope. Specifically, the magnitude of color loss (color loss amount: μm) from the end of the polarizer was measured. An MX61L manufactured by Olympus was used as a microscope, and the amount of color loss was measured from an image taken at a magnification of 10 times. As shown in FIG. 2, the amount of color loss from the corners of the test piece was measured.
(5) Humidification reliability For the test piece bonded to the non-alkali glass prepared in (4) above, a single polarizing plate was used using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). The transmittance (Ts) was measured. The Ts is a Y value measured by the JIS Z 8701 2 degree field of view (C light source) and corrected for luminosity factor. In addition, when the protective film for the polarizer is provided with functions that affect the transmittance such as reflection characteristics, light scattering, and hue adjustment, only the polarizer was measured. After that, the test piece was left in an oven at 60 ° C. and 90% RH for 500 hours to heat and humidify, and Ts measurement was performed in the same manner as described above to determine the amount of change in transmittance ΔTs = (Ts _{0 -Ts 500} ). Note that Ts ₀ is the single transmittance before heating and humidification, and Ts ₅₀₀ is the single transmittance after heating and humidification.

[Manufacturing Example 1]
100 parts by weight of polyisobutylene (trade name: OPPANOL B80, Mw: about 750,000, manufactured by BASF) and tricyclodecanedimethanol diacrylate (trade name: NK ester A-DCP, 2) as a polyfunctional radically polymerizable compound. A toluene solution (adhesive) containing 5 parts by weight of functional acrylate, molecular weight: 304, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., and 1 part of benzophenone (manufactured by Wako Pure Chemical Industries, Ltd.), which is a hydrogen abstraction type photopolymerization initiator. The solution) was adjusted so that the solid content was 15% by weight, and a rubber-based pressure-sensitive adhesive composition (solution) was prepared. The obtained rubber-based pressure-sensitive adhesive composition (solution) is applied to the peel-treated surface of a separator (a polyester film having a thickness of 38 μm with one side peeled with silicone, trade name “Diafoil MRF”, manufactured by Mitsubishi Plastics Co., Ltd.). To form a coating layer. Next, the coating layer was dried at 80 ° C. for 3 minutes to form a rubber-based pressure-sensitive adhesive layer having a thickness of 25 μm. Next, ultraviolet rays were irradiated from the pressure-sensitive adhesive layer side at room temperature to crosslink polyisobutylene. The ultraviolet irradiation had a light intensity of 1000 mJ / cm ² in the UVA region. In this way, a pressure-sensitive adhesive sheet of a separator / pressure-sensitive adhesive layer (thickness 25 μm) was obtained. Moisture permeability of the adhesive layer was ^24g / m 2 / 24hr.

[Example 1]
As the thermoplastic resin base material, an amorphous isophthalic acid copolymer polyethylene terephthalate (IPA copolymer PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ° C. was used. One side of the base material is corona-treated, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6) are applied to the corona-treated surface. %, Degree of polymerization of 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z200") in a ratio of 9: 1 is applied and dried at 25 ° C. to a thickness of 11 μm. A PVA-based resin layer was formed to prepare a laminate.
The obtained laminate was stretched 4.5 times in the air at 140 ° C. in a direction orthogonal to the longitudinal direction of the laminate using a tenter stretching machine (stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds.
Next, the laminate was added to a staining solution at 30 ° C. (an aqueous solution in which 6.0 parts by weight of potassium iodide and 0.8 parts by weight of ferric sulfate n hydrate were added to 100 parts by weight of water) for 30 seconds. Soaked and stained.
Next, it was immersed in a cross-linked bath at a liquid temperature of 60 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 35 seconds. ..
Then, the laminate was immersed in a washing bath at a liquid temperature of 25 ° C. (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) for 10 seconds.
Then, it was dried in an oven at 60 ° C. for 60 seconds to obtain a laminate 1 having a PVA-based resin layer (polarizer) having a thickness of 2.5 μm. The pressure-sensitive adhesive layer was transferred from the pressure-sensitive adhesive sheet of Production Example 1 to the surface of the polarizer to obtain a polarizing plate of Example 1. The obtained polarizing plate was subjected to the evaluations (3) to (5) above. The results are shown in Table 1.

[Example 2]
A PVA-based resin layer having a thickness of 7 μm was formed to prepare a laminate, and 15.0 parts by weight of potassium iodide and 2.0 parts by weight of ferric sulfate n-hydrate were added to 100 parts by weight of water as a staining solution. A polarizing plate of Example 2 having a PVA-based resin layer (polarizer) having a thickness of 1.5 μm was obtained in the same manner as in Example 1 except that the aqueous solution was prepared by adding the above. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

[Example 3]
The thickness was 1 in the same manner as in Example 2 except that the staining solution was an aqueous solution prepared by adding 3.8 parts by weight of potassium iodide and 0.5 parts by weight of ferric sulfate n hydrate to 100 parts by weight of water. A polarizing plate of Example 3 having a PVA-based resin layer (polarizer) of .5 μm was obtained. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

[Example 4]
A PVA-based resin layer having a thickness of 6 μm was formed to prepare a laminate, and the staining solution was an aqueous solution obtained by adding 12.0 parts by weight of potassium iodide and 1.0 part by weight of solid iodine to 100 parts by weight of water. A polarizing plate of Example 4 having a PVA-based resin layer (polarizer) having a thickness of 1.2 μm was obtained in the same manner as in Example 1 except for the above. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

[Example 5]
In the same manner as in Example 1, a PVA-based resin layer having a thickness of 11 μm was formed on a thermoplastic resin base material to prepare a laminated body.
The obtained laminate was uniaxially stretched at the free end 2.0 times in the longitudinal direction between rolls having different peripheral speeds in an oven at 115 ° C.
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 30 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds.
Next, the laminate was added to a staining solution at 30 ° C. (an aqueous solution in which 4.5 parts by weight of potassium iodide and 0.6 parts by weight of ferric sulfate n-hydrate were added to 100 parts by weight of water) for 30 seconds. Soaked and stained.
Then, it was immersed in a cross-linked bath at a liquid temperature of 30 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds.
Then, the laminate is immersed in an aqueous solution of boric acid at a liquid temperature of 70 ° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water). Uniaxial stretching was performed 2.7 times in the longitudinal direction between rolls having different speeds.
Then, the laminate was immersed in a washing bath having a liquid temperature of 30 ° C. (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) for 10 seconds, and then 60 with warm air at 60 ° C. Allowed to dry for seconds.
In this way, a laminate 5 having a PVA-based resin layer (polarizer) having a thickness of 5 μm was obtained on the resin substrate. The pressure-sensitive adhesive layer was transferred from the pressure-sensitive adhesive sheet of Production Example 1 to the surface of the polarizer to obtain a polarizing plate of Example 5. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

[Comparative Example 1]
Ordinary acrylic pressure-sensitive adhesive except for forming an adhesive layer by using a (thickness 25 [mu] m, moisture permeability 1400g / m 2 / ^24hr) in the same manner as in Example 1 to obtain a polarizing plate of Comparative Example 1. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

[Comparative Example 2]
Ordinary acrylic pressure-sensitive adhesive except for forming an adhesive layer by using a (thickness 25 [mu] m, moisture permeability 1400g / m 2 / ^24hr) in the same manner as in Example 2 to obtain a polarizing plate of Comparative Example 2. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

[Reference example 1]
A PVA-based resin layer having a thickness of 5.0 μm was obtained in the same manner as in Example 5 except that the dyeing solution was an aqueous solution prepared by adding 0.4 parts by weight of iodine and 3.0 parts by weight of potassium iodide to 100 parts by weight of water. A laminate 6 having (polarizer) was obtained. The pressure-sensitive adhesive layer was transferred from the pressure-sensitive adhesive sheet of Production Example 1 to the surface of the polarizer to obtain a polarizing plate of Reference Example 1. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

[Reference example 2]
Ordinary acrylic pressure-sensitive adhesive except for forming an adhesive layer by using a (thickness 25 [mu] m, moisture permeability 1400g / m 2 / ^24hr) in the same manner as in Reference Example 1 to obtain a polarizing plate of Example 2. The obtained polarizing plate was subjected to the same evaluation as in Examples. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, a pressure-sensitive (more specifically, low-moisture) pressure-sensitive adhesive layer is placed adjacent to a polarizer with a very high iodine content and a very thin thickness. As a result, it can be seen that the change in transmittance and the color loss at the edges are remarkably suppressed in a high temperature and high humidity environment. Furthermore, as is clear from the reference examples, it can be seen that the examples of the present invention solve the problems peculiar to the thin polarizer having a very high iodine content.

The polarizing plate of the present invention is suitably used for an image display device. Examples of the image display device include a liquid crystal display device, an organic electroluminescence (EL) display device, and a quantum dot display device. Such image display devices are suitably used for televisions, mobile phones, personal digital assistants, digital cameras, video cameras, portable game machines, car navigation systems, copiers, printers, fax machines, clocks, microwave ovens, and the like.

10 Polarizer 20 Protective film 30 Adhesive layer 100 Polarizing plate

Claims (3)

It has a polarizer, a protective film, and an adhesive layer.
The polarizer is composed of a polyvinyl alcohol-based resin film containing iodine, has a thickness of 5 μm or less, and has an iodine content of 12.5% by weight or more.
Adhesive layer is disposed adjacent to the polarizer, the moisture permeability is not more than 300g ^/ m 2 ^/ 24hr,
Polarizer. The polarizing plate according to claim 1, wherein the amount of change in transmittance after holding for 500 hours in an environment of 60 ° C. and 90% RH is less than 2.5%, and the amount of color loss at the edges is 800 μm or less. The polarizing plate according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is composed of an active energy ray-crosslinked rubber-based pressure-sensitive adhesive composition containing polyisobutylene.

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